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Emerging studies show that circRNA catenin beta 1 (circCTNNB1) plays a critical role in cancer. However, the expression and function of circCTNNB1 in cerebral ischemia/reperfusion injury (IRI) have not been reported. The present study discovered that circCTNNB1 and scavenger receptor class B type 1 (SRB1) expression levels were significantly down-regulated in mouse astrocytes (mAS) treated with oxygen glucose deprivation and reperfusion (OGD/R), and similar results were observed in a mouse middle cerebral artery occlusion model. Overexpression of circCTNNB1 alleviated cell apoptosis, oxidative stress and the inflammatory response induced by OGD/R

Scavenger receptor class B type 1 (SR-B1) promotes atheroprotection through its role in HDL metabolism and reverse cholesterol transport in the liver. However, evidence indicates that SR-B1 may impact atherosclerosis through nonhepatic mechanisms.Recent studies have brought to light various mechanisms by which SR-B1 affects lesional macrophage function and protects against atherosclerosis. Efferocytosis is efficient in early atherosclerotic lesions. At this stage, and beyond its role in cholesterol efflux, SR-B1 promotes free cholesterol-induced apoptosis of macrophages through its control of apoptosis inhibitor of macrophage (AIM). At more advanced stages, macrophage SR-B1 binds and mediates the removal of apoptotic cells. SR-B1 also participates in the induction of autophagy which limits necrotic core formation and increases plaque stability.These studies shed new light on the atheroprotective role of SR-B1 by emphasizing its essential contribution in macrophages during atherogenesis as a function of lesion stages. These new findings suggest that macrophage SR-B1 is a therapeutic target in cardiovascular disease.

The global propagation of SARS-CoV-2 leads to an unprecedented public health emergency. Despite that the lungs are the primary organ targeted by COVID-19, systemic endothelial inflammation and dysfunction is observed particularly in patients with severe COVID-19, manifested by elevated endothelial injury markers, endotheliitis, and coagulopathy. Here, we review the clinical characteristics of COVID-19 associated endothelial dysfunction; and the likely pathological mechanisms underlying the disease including direct cell entry or indirect immune overreactions after SARS-CoV-2 infection. In addition, we discuss potential biomarkers that might indicate the disease severity, particularly related to the abnormal development of thrombosis that is a fatal vascular complication of severe COVID-19. Furthermore, we summarize clinical trials targeting the direct and indirect pathological pathways after SARS-CoV-2 infection to prevent or inhibit the virus induced endothelial disorders., Graphical abstract Unlabelled Image

RNA alternative splicing (AS) expands the regulatory potential of eukaryotic genomes. The mechanisms regulating liver-specific AS profiles and their contribution to liver function are poorly understood. Here, we identify a key role for the splicing factor RNA-binding Fox protein 2 (RBFOX2) in maintaining cholesterol homeostasis in a lipogenic environment in the liver. Using enhanced individual-nucleotide-resolution ultra-violet cross-linking and immunoprecipitation, we identify physiologically relevant targets of RBFOX2 in mouse liver, including the scavenger receptor class B type I (Scarb1). RBFOX2 function is decreased in the liver in diet-induced obesity, causing a Scarb1 isoform switch and alteration of hepatocyte lipid homeostasis. Our findings demonstrate that specific AS programmes actively maintain liver physiology, and underlie the lipotoxic effects of obesogenic diets when dysregulated. Splice-switching oligonucleotides targeting this network alleviate obesity-induced inflammation in the liver and promote an anti-atherogenic lipoprotein profile in the blood, underscoring the potential of isoform-specific RNA therapeutics for treating metabolism-associated diseases.

OBJECTIVE: To investigate the role of adipocyte Pcpe2 in SR-BI-mediated HDL-C uptake and contributions to adipose lipid storage. APPROACH AND RESULTS: Pcpe2, a glycoprotein devoid of intrinsic proteolytic activity, is believed to participate in extracellular protein-protein interactions, supporting SR-BI-mediated HDL-C uptake. In published studies, Pcpe2 deficiency increased the development of atherosclerosis by reducing SR-BI-mediated HDL-C catabolism, but the biological impact of this deficiency on adipocyte SR-BI-mediated HDL-C uptake is unknown. Differentiated cells from Ldlr(−/−)/Pcpe2(−/−) (Pcpe2(−/−)) and Ldlr(−/−) (control) mouse adipose tissue showed elevated SR-BI protein levels, but significantly reduced HDL-C uptake. SR-BI-mediated HDL-C uptake was restored by pre-incubation of cells with exogenous Pcpe2. In diet-fed mice lacking Pcpe2, significant reductions in visceral, subcutaneous and brown adipose tissue mass were observed, despite elevations in plasma triglyceride and cholesterol concentrations. Significant positive correlations exist between adipose mass and Pcpe2 expression in both mice and humans. CONCLUSIONS: Overall, these findings reveal a novel and unexpected function for Pcpe2 in modulating SR-BI expression and function as it relates to adipose tissue expansion and cholesterol balance in both mice and humans.

Background and Objectives: Visceral obesity is associated with chronic low-grade inflammation that predisposes to metabolic syndrome. Indeed, infiltration of adipose tissue with immune–inflammatory cells, including ‘classical’ inflammatory M1 and anti-inflammatory ‘alternative’ M2 macrophages, causes the release of a variety of bioactive molecules, resulting in the metabolic complications of obesity. This study examined the relative expression of macrophage phenotypic surface markers, cholesterol efflux proteins, scavenger receptors, and adenosine receptors in human circulating peripheral blood mononuclear cells (PBMCs), isolated from patients with type 2 diabetes mellitus (T2DM), with the aim to phenotypically characterize and identify biomarkers for these ill-defined cells. Materials and Methodology: PBMCs were isolated from four groups of adults: Normal-weight non-diabetic, obese non-diabetic, newly diagnosed with T2DM, and T2DM on metformin. The mRNA expression levels of macrophage phenotypic surface markers (interleukin-12 (IL-12), C-X-C motif chemokine ligand 10 (CXCL10), C-C motif chemokine ligand 17 (CCL17), and C-C motif receptor 7 (CCR7)), cholesterol efflux proteins (ATP-binding cassette transporter-1 (ABCA1), ATP binding cassette subfamily G member 1 (ABCG1), and sterol 27-hydroxylase (CYP27A)), scavenger receptors (scavenger receptor-A (SR-A), C-X-C motif ligand 16 (CXCL16), and lectin-like oxidized LDL receptor-1 (LOX-1)), and adenosine receptors (adenosine A2A receptor (A2AR) and adenosine A3 receptor (A3R)) were measured using qRT-PCR. Results: In PBMCs from T2DM patients, the expression of IL-12, CCR7, ABCA1, and SR-A1 was increased, whereas the expression of CXCL10, CCL17, ABCG1,27-hydroxylase, LOX-1, A2AR and A3R was decreased. On the other hand, treatment with the antidiabetic drug, metformin, reduced the expression of IL-12 and increased the expression of 27-hydroxylase, LOX-1, CXCL16 and A2AR. Conclusions: PBMCs in the circulation of patients with T2DM express phenotypic markers that are different from those typically present in adipose tissue M1 and M2 macrophages and could be representative of metabolically activated macrophages (MMe)-like cells. Our findings suggest that metformin alters phenotypic markers of MMe-like cells in circulation.

The dysregulation of cholesterol metabolism is a high-risk factor for non-alcoholic fatty liver disease (NAFLD), dyslipidemia, and atherosclerosis (AS). Cholesterol transport maintains whole-body cholesterol homeostasis. Low-density apolipoprotein receptor (LDLR) mediates cholesterol uptake in cells and plays an important role in the primary route of circulatory cholesterol clearance in liver cells. Caveolins 1 is an integral membrane protein and shuttle between the cytoplasm and cell membrane. Caveolins 1 not only plays a role in promoting cholesterol absorption in cells but also in the transport of cellular cholesterol efflux by interacting with the ATP-binding cassette transporter A1 (ABCA1) and scavenger receptor class B type I (SR-BI). These proteins, which are associated with reverse cholesterol transport (RCT), are potential therapeutic targets for NAFLD and AS. Many studies have indicated that natural products have lipid-lowering effects. Moreover, natural molecules, derived from natural products, have the potential to be developed into novel drugs. However, the mechanisms underlying the regulation of cholesterol transport by natural molecules have not yet been adequately investigated. In this review, we briefly describe the process of cholesterol transport and summarize the mechanisms by which molecules regulate cholesterol transport. This article provides an overview of recent studies and focuses on the potential therapeutic effects of natural molecules; however, further high-quality studies are needed to firmly establish the clinical efficacies of natural molecules.

Rationale: Coronary artery disease (CAD) is a pervasive and critical health care problem. Elevated high-density lipoprotein-associated cholesterol (HDL-C) is associated with improved atherosclerotic cardiovascular disease outcomes on a population level, but clinical trials aimed at HDL-C elevation have not succeeded in improving atherosclerotic cardiovascular disease event risk. Nevertheless, human variants in the HDL receptor, encoded by SCARB1 , are associated with dyslipidemia, suggesting that HDL metabolism, not HDL-C, is a suitable target for therapy. However, variants in SCARB1 have never been directly attributed to CAD by Mendelian inheritance. Objective: To determine if compound heterozygous variants in SCARB1 cause disease in 2 brothers with severe, early-onset CAD. Methods and Results: Using whole exome sequencing, we have identified rare, compound heterozygous variants in SCARB1 that segregate with severe, premature CAD, following patterns of Mendelian inheritance. Using induced pluripotent stem cell–derived hepatocyte-like cells from the proband, we discovered the maternal variant (c.754_755delinsC) to be the first identified SCARB1 null allele, characterized by the absence of RNA and protein expression. Further, we demonstrate that the variant on the paternal allele (c.956G>T [p.G319V]) results in decreased cholesterol uptake, decreased SR-BI:HDL binding, and increased affinity for SR-BI dimerization. Finally, we generated a p.G319V knock-in mouse model that displays nearly 100% homozygous lethality and elevated plasma cholesterol in heterozygous animals, confirming pathogenicity of this variant. Conclusions: In summary, our data provide the first molecular mechanism to show the Mendelian inheritance of CAD as a result of human SCARB1 variants. The rarity of these variants supports pathogenicity in this family. Furthermore, SR-BI p.G319V, which has previously been reported benign in the context of heterozygosity, was uniquely presented alongside a null allele, demonstrating the disease-contributing capability of loss-of-function SCARB1 variants within the population.

To investigate the influences ofMouse RAW264.7 cells were induced in foam cells and identification of the foamed by oil-red O staining. The RAW264.7 macrophage origin foam cells were dealt with APS with distinct contents (0, 10, 20, 50, or 100 mg/L). The mRNA and protein expressions of SR-BI and LXRMacrophages were differentiated into foam cells 48 h after ox-LDL induction. In contrast to the control part, the mRNA and protein expressions of SR-BI and LXRAPS could promote intracellular cholesterol efflux by up-regulating the expressions of SR-BI and LXR

Both clear cell renal carcinoma (ccRCC) and clear cell carcinoma of the ovary (CCOC) have a clear cytoplasmic morphological feature, hence it is difficult to identify metastatic ccRCC and CCOC by morphology alone. At present, there are no effective immunohistochemical markers to distinguish between these two tumors. Studies have shown that the clear cytoplasm of ccRCC is mainly caused by cholesterol-rich lipids in the cytoplasm, while that of CCOC is due to the accumulation of cytoplasmic glycogen. Objective: to hypothesize that the scavenger receptor class B-type 1 (SR-B1) protein responsible for HDL cholesterol uptake may be differentially expressed in ccRCC and CCOC, and high CD10 expression in the renal tubular epithelium may assist in distinguishing between ccRCC and CCOC. Methods: effective immunohistochemical markers were applied in 90 cases of renal clear cell carcinoma and 31 cases of ovarian cancer to distinguish between the two types of tumors.Result: SR-B1 and CD10 expression is significantly higher in ccRCC than CCOC. Both SR-B1 and CD10 exhibited focal weak-medium intensity staining in CCOC, and their staining extent and intensity were significantly lower than ccRCC. The sensitivity and specificity of SR-B1 for identifying ccRCC were 74.4% and 83.9%, respectively. The sensitivity and specificity of CD10 for identifying CCOC were 93.3% and 80.6%, respectively. The combined SR-B1( +) CD10( +) immunoprofile supports the diagnosis of ccRCC with a specificity of 93.5%. The combined SR-B1(-) CD10(-) immunoprofile supports the diagnosis of CCOC with a specificity of 93.3%. Conclusions: our findings demonstrate that the combination of SR-B1 and CD10 immunoprofiling is a valuable tool for differential diagnosis of ccRCC and CCOC.

Activating transcription factor (ATF)3 is known to have an anti-inflammatory function, yet the role of hepatic ATF3 in lipoprotein metabolism or atherosclerosis remains unknown. Here we show that overexpression of human ATF3 in hepatocytes reduces the development of atherosclerosis in Western-diet-fed Ldlr-/- or Apoe-/- mice, whereas hepatocyte-specific ablation of Atf3 has the opposite effect. We further show that hepatic ATF3 expression is inhibited by hydrocortisone. Mechanistically, hepatocyte ATF3 enhances high-density lipoprotein (HDL) uptake, inhibits intestinal fat and cholesterol absorption and promotes macrophage reverse cholesterol transport by inducing scavenger receptor group B type 1 (SR-BI) and repressing cholesterol 12α-hydroxylase (CYP8B1) in the liver through its interaction with p53 and hepatocyte nuclear factor 4α, respectively. Our data demonstrate that hepatocyte ATF3 is a key regulator of HDL and bile acid metabolism and atherosclerosis.

The current limited understanding of HCV entry mechanisms hinders the development of specific antiviral drug screening techniques and vaccine assessment. HCV subtypes and cellular surface proteins both can affect virus tropism. Human factors such as low-density lipoprotein receptor (hLDLR), CD81 (hCD81), scavenger receptor class B type I (hSR-BI), claudin 1 (hCLDN1), and occludin (hOCLN) assist HCV entry into hepatocytes. Here, we studied the importance of five human proteins in the process of cell culture-derived (HCVcc) and serum-derived (HCV-sd) HCV entry using constructed humanized mouse hepatocytes and mouse models. We determined that unlike hLDLR, hSR-BI was an indispensable factor for 1b genotype HCV adsorption. Furthermore, this attachment can be completely prevented by treatment with a monoclonal antibody targeting hSR-BI. Our data support the idea that SR-BI is an essential factor in HCV infection, particularly during the initial HCV particle-binding step. This novel finding will facilitate the development of antiviral drugs and vaccines. Keywords: hepatitis C virus; virus internalization; model construction; hSR-BI.

Cholesterol has long been suspected of influencing hair biology, with dysregulated homeostasis implicated in several disorders of hair growth and cycling. Cholesterol transport proteins play a vital role in the control of cellular cholesterol levels and compartmentalisation. This research aimed to determine the cellular localisation, transport capability and regulatory control of cholesterol transport proteins across the hair cycle. Immunofluorescence microscopy in human hair follicle sections revealed differential expression of ATP-binding cassette (ABC) transporters across the hair cycle. Cholesterol transporter expression (ABCA1, ABCG1, ABCA5 and SCARB1) reduced as hair follicles transitioned from growth to regression. Staining for free cholesterol (filipin) revealed prominent cholesterol striations within the basement membrane of the hair bulb. Liver X receptor agonism demonstrated active regulation of ABCA1 and ABCG1, but not ABCA5 or SCARB1 in human hair follicles and primary keratinocytes. These results demonstrate the capacity of human hair follicles for cholesterol transport and trafficking. Future studies examining the role of cholesterol transport across the hair cycle may shed light on the role of lipid homeostasis in human hair disorders. Supplementary Information The online version contains supplementary material available at 10.1007/s00418-020-01957-8.

Importance: Despite the availability of a vaccine against the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), humans will have to live with this virus and the after-effects of the coronavirus disease 2019 (COVID-19) infection for a long time. Cholesterol plays an important role in the infection and prognosis of SARS-CoV-2, and the study of its mechanism is of great significance not only for the treatment of COVID-19 but also for research on generic antiviral drugs. Observations: Cholesterol promotes the development of atherosclerosis by activating NLR family pyrin domain containing 3 (NLRP3), and the resulting inflammatory environment indirectly contributes to COVID-19 infection and subsequent deterioration. In in vitro studies, membrane cholesterol increased the number of viral entry sites on the host cell membrane and the number of angiotensin-converting enzyme 2 (ACE2) receptors in the membrane fusion site. Previous studies have shown that the fusion protein of the virus interacts with cholesterol, and the spike protein of SARS-CoV-2 also requires cholesterol to enter the host cells. Cholesterol in blood interacts with the spike protein to promote the entry of spike cells, wherein the scavenger receptor class B type 1 (SR-B1) plays an important role. Because of the cardiovascular protective effects of lipid-lowering therapy and the additional anti-inflammatory effects of lipid-lowering drugs, it is currently recommended to continue lipid-lowering therapy for patients with COVID-19, but the safety of extremely low LDL-C is questionable. Conclusions and Relevance: Cholesterol can indirectly increase the susceptibility of patients to SARS-CoV-2 and increase the risk of death from COVID-19, which are mediated by NLRP3 and atherosclerotic plaques, respectively. Cholesterol present in the host cell membrane, virus, and blood may also directly participate in the virus cell entry process, but the specific mechanism still needs further study. Patients with COVID-19 are recommended to continue lipid-lowering therapy.

We hypothesised that synthetic HDL nanoparticles carrying a gemcitabine prodrug and apolipoprotein A-II (sHDLGemA2) would target scavenger receptor-B1 (SR-B1) to preferentially and safely deliver gemcitabine into pancreatic ductal adenocarcinoma (PDAC). We designed, manufactured and characterised sHDLGemA2 nanoparticles sized ~130 nm, incorporating 20 mol% of a gemcitabine prodrug within the lipid bilayer, which strengthens on adding ApoA-II. We measured their ability to inhibit growth in cell lines and cell-derived and patient-derived murine PDAC xenografts. Fluorescent-labelled sHDLGemA2 delivered gemcitabine inside xenografts. Xenograft levels of active gemcitabine after sHDLGemA2 were similar to levels after high-dose free gemcitabine. Growth inhibition in mice receiving 4.5 mg gemcitabine/kg/d, carried in sHDLGemA2, was equivalent to inhibition after high-dose (75 mg/kg/d) free gemcitabine, and greater than inhibition after low-dose (4.5 mg/kg/d) free gemcitabine. sHDLGemA2 slowed growth in semi-resistant cells and a resistant human xenograft. sHDLGemA2 targeted xenografts more effectively than sHDLGemA1. SR-B1 was over-expressed in PDAC cells and xenografts. Targeting by ApoA-II was suppressed by anti-SR-B1. Because sHDLGemA2 provided only ~6% of the free gemcitabine dose for an equivalent response, patient side effects can be greatly reduced, and the sHDLGemA2 concept should be developed through clinical trials.

Background: Emerging studies have indicated that circular RNAs (circRNAs) play important roles in the development of many tumors. CircRNA-scavenger receptor class B member 1 (Circ-SCARB1) was consistently reported as an elevated circRNA in RCC tissues. This study focused on examining the biological function and molecular mechanism of circSCARB1 in RCC progression. Methods: Expressions of Circ-SCARB1, microRNA (miR)-510-5p, and syndecan 3 (SDC3) were detected using a quantitative real-time polymerase chain reaction (RT-PCR) and/or western blot. Cell proliferation and apoptosis were measured by 3-(4, 5)-dimethylthiahiazo (-z-y1)-3, 5-diphenytetrazoliumromide and flow cytometry, respectively. Cell migration and invasion were measured using Transwell assays. The interaction between miR-510-5p and Circ-SCARB1 or SDC3 was verified using dual-luciferase reporter assays. Results: Circ-SCARB1 was elevated in 30 pairs of RCC tissues and multiple RCC cell lines. Knockdown of Circ-SCARB1 inhibited cell proliferation, migration, and invasion while inducing cell apoptosis. MiR-510-5p was confirmed to be a target of Circ-SCARB1; inhibition of cell progression by silencing Circ-SCARB1 was mediated by a direct interaction between Circ-SCARB1 and miR-510-5p. SDC3 was verified to be a gene target of miR-510-5p; transfection of miR-510-5p mimic not only suppressed the expression of SDC3 but also the cell proliferation and an SDC3 cotransfection partially restored cell proliferation. Additionally, the genetic knockdown of Circ- SCARB1 reduced the expression SDC3, and the addition of anti-miR-510-5p could partially reelevate SDC3 expression. Conclusion: Circ-SCARB1 promotes RCC progression via sequestering miR-510-5p and indirectly up-regulating SDC3 expression. This provides a novel perspective for the pathogenesis of RCC and potential therapeutic targets for the treatment of RCC.

High-density lipoprotein (HDL) metabolism is facilitated in part by scavenger receptor class B, type 1 (SR-B1) that mediates HDL uptake into cells. Higher levels of HDL have been associated with protection in other diseases, however, its role in prostate cancer is not definitive. SR-B1 is up-regulated in prostate cancer tissue, suggesting a possible role of this receptor in tumor progression. Here, we report that knockout (KO) of SR-B1 in both human and mouse prostate cancer cell lines through CRISPR/Cas9-mediated genome editing reduces HDL uptake into the prostate cancer cells and reduces their proliferation in response to HDL. In vivo studies using syngeneic SR-B1 WT (SR-B1(+/+)) and SR-B1 KO (SR-B1(−/−)) prostate cancer cells in WT and apolipoprotein-AI KO (apoA1-KO) C57BL/6J mice revealed that WT hosts, containing higher levels of total and HDL-cholesterol, grew larger tumors than apoA1-KO hosts with lower levels of total and HDL-cholesterol. Furthermore, SR-B1(−/−) prostate cancer cells formed smaller tumors in WT hosts than SR-B1(+/+) cells in the same host model. Increased tumor volume was overall associated with reduced survival. We conclude that knocking out SR-B1 in prostate cancer tumors reduces HDL-associated increases in prostate cancer cell proliferation and disease progression.

Atherosclerosis is the pathological basis of most cardiovascular diseases. Reverse cholesterol transport (RCT) is a main mechanism of cholesterol homeostasis and involves the direct transport of high-density lipoprotein (HDL) cholesteryl ester by selective cholesterol uptake. Hepatic scavenger receptor class B member 1 (SR-BI) overexpression can effectively promote RCT and reduce atherosclerosis. SR-BI may be an important target for prevention or treatment of atherosclerotic disease. In our study, we inserted human SR-BI mRNA 3' untranslated region (3'UTR) downstream of the luciferase reporter gene, to establish a high-throughput screening model based on stably transfected HepG2 cells and to screen small-molecule compounds that can significantly enhance the mRNA stability of the SR-BI gene. Through multiple screenings of 25 755 compounds, the top five active compounds that have similar structures were obtained, with a positive rate of 0.19%. The five positive compounds could enhance the SR-BI expression and uptake of DiI-HDL in the hepatocyte HepG2. E238B-63 could also effectively extend the half-life of SR-BI mRNA and enhance the SR-BI mRNA and protein level and the uptake of DiI-HDL in hepatocytes in a time-dependent and dose-dependent manner. The structure-activity relationship analysis showed that the structure N-(3-hydroxy-2-pyridyl) carboxamide is possibly the key pharmacophore of the active compound, providing reference for acquiring candidate compounds with better activity. The positive small molecular compounds obtained in this study might become new drug candidates or lead compounds for the treatment of cardiovascular diseases and contribute to the further study of the posttranscriptional regulation mechanism of the SR-BI gene.

Objective The aim of this study was to determine whether downstream [peroxisome proliferator-activated-receptor alpha (PPARα) and the G-protein coupled receptor, GPR119] and upstream (a fatty acid translocase, CD36) signaling targets of N-oleoylethanolamide (OEA) were necessary for weight loss, metabolic improvements, and diet preference following vertical sleeve gastrectomy (VSG). Summary background data OEA is an anorectic N-acylethanolamine produced from dietary fats within the intestinal lumen that can modulate lipid metabolism, insulin secretion, and energy expenditure by activating targets such as PPARα and GPR119. Methods Diet-induced obese mice, including wild-type or whole body knockout (KO) of PPARα, GPR119, and CD36, were stratified to either VSG or sham surgery before body weight, body composition, diet preference, and glucose and lipid metabolic endpoints were assessed. Results We found increased duodenal production of OEA and expression of both GPR119 and CD36 were upregulated in wild-type mice after VSG. However, weight loss and glucose tolerance were improved in response to VSG in PPARαKO, GPR119KO, and CD36KO mice. In fact, VSG corrected hepatic triglyceride dysregulation in CD36KO mice, and circulating triglyceride and cholesterol levels in PPARαKO mice. Lastly, we found PPARα-mediated signaling contributes to macronutrient preference independent of VSG, while removal of CD36 signaling blunts the VSG-induced shift toward carbohydrate preference. Conclusions In the search for more effective and less invasive therapies to help reverse the global acceleration of obesity and obesity-related disease OEA is a promising candidate; however, our data indicate that it is not an underlying mechanism of the effectiveness of VSG.

The presence of antiendothelial cell antibodies (AECAs) has been documented in Takayasu arteritis (TAK), a chronic granulomatous vasculitis. Here, we identify cell-surface autoantigens using an expression cloning system. A cDNA library of endothelial cells is retrovirally transfected into a rat myeloma cell line from which AECA-positive clones are sorted with flow cytometry. Four distinct AECA-positive clones are isolated, and endothelial protein C receptor (EPCR) and scavenger receptor class B type 1 (SR-BI) are identified as endothelial autoantigens. Autoantibodies against EPCR and SR-BI are detected in 34.6% and 36.5% of cases, respectively, with minimal overlap (3.8%). Autoantibodies against EPCR are also detected in ulcerative colitis, the frequent comorbidity of TAK. In mechanistic studies, EPCR and SR-BI function as negative regulators of endothelial activation. EPCR has also an effect on human T cells and impair Th17 differentiation. Autoantibodies against EPCR and SR-BI block the functions of their targets, thereby promoting pro-inflammatory phenotype., Autoantibodies against endothelium have been recognized in Takayasu arteritis (TAK). Here the authors identify endothelial protein C receptor and scavenger receptor class B type 1 as major autoantigens in TAK, and find autoantibodies inhibit the negative regulation of endothelial activation.

Cholesterol efflux is the first and rate-limiting step of reverse cholesterol transport (RCT) from peripheric cells to the liver. The involvement of high-density lipoprotein (HDL) in RCT determines the atheroprotective properties of HDL. Cholesterol efflux from different membrane pools includes both passive and energy-dependent processes. The first type of route consists of cholesterol desorption from the cell membrane into the unstirred layer adjacent to the cell surface and diffusion in the water phase. Moreover, the selective uptake and facilitated diffusion of cholesterol and cholesteryl ester molecules through the hydrophobic tunnel in the scavenger receptor BI molecule does not require energy consumption. The second type of route includes active cholesterol export by the ATP-binding cassette transporters A1 (ABCA1) and G1 (ABCG1). Several cholesterol acceptors specifically bind cholesterol and phospholipid molecules, and cholesterol binding to the albumin molecule, which acts as a shuttle, significantly increases cholesterol movement between acceptors and red blood cells, thus functioning as a sink for cholesterol. Cholesterol and phospholipid molecules effluxed from macrophages by ABCA1 are accepted exclusively by the lipid-free apolipoprotein apoA-I, which is the major protein moiety of HDL, whereas those effluxed by ABCG1 are accepted by HDL. ABCA1- and ABCG1-mediated cholesterol transport, together with cholesterol diffusion, largely determine cholesterol turnover at the physiological level of intracellular cholesterol. However, at cholesterol overload, ABCA1-mediated efflux prevails over other routes. The exchange of apoA-I between lipid-free and lipid-associated states and the synergism of nascent and mature HDL contribute to cholesterol efflux efficiency. Moreover, extracellular cholesterol deposits and microvesicles may be involved in RCT.

Scavenger receptor class B type I (SR-BI) protein is an integral membrane glycoprotein. SR-BI is emerging as a multifunctional protein, which regulates autophagy, efferocytosis, cell survival and inflammation. It is well known that SR-BI plays a critical role in lipoprotein metabolism by mediating cholesteryl esters selective uptake and the bi-directional flux of free cholesterol. Recently, SR-BI has also been identified as a potential marker for cancer diagnosis, prognosis, or even a treatment target. Natural products are a promising source for the discovery of new drug leads. Multiple natural products were identified to regulate SR-BI protein expression. There are still a number of challenges in modulating SR-BI expression in cancer and in using natural products for modulation of such protein expression. In this review, our purpose is to discuss the relationship between SR-BI protein and cancer, and the molecular mechanisms regulating SR-BI expression, as well as to provide an overview of natural products that regulate SR-BI expression.

Circular RNAs (circRNAs) exhibit essential regulation in the malignant development of clear cell renal cell carcinoma (ccRCC). The aims of this study were to investigate the role and mechanism of circ_0003146 in the biologic behaviors of ccRCC. RNA level analysis was performed through reverse transcription-quantitative PCR assay. Cell proliferation was measured by EdU assay and cell counting kit-8 assay. The protein expression was analyzed using a western blot. Flow cytometry and caspase 3 activity assay were used to assess cell apoptosis. Cell migration and invasion were evaluated via wound healing assay and transwell assay. Circ_0003146 function in vivo was determined by xenograft tumor assay. Dual-luciferase reporter assay was applied for target relation analysis. Circ_0003146 upregulation was detected in ccRCC tissues and cells. Downregulation of circ_0003146 induced inhibition of proliferation, migration, invasion and EMT but the promotion of apoptosis in ccRCC cells. Tumor growth in vivo was inhibited after knockdown of circ_0003146. Circ_0003146 directly interacted with miR-1272, and the miR-1272 sponging effect was responsible for the function of circ_0003146. Scavenger receptor class B type 1 (SCARB1) was a target of miR-1272, and circ_0003146 regulated SCARB1 level by absorbing miR-1272. The regulation of circ_0003146 in ccRCC progression was achieved by upregulating SCARB1 in part. The current findings demonstrated that circ_0003146 contributed to the malignant progression of ccRCC via inducing SCARB1 upregulation by targeting miR-1272.

Purpose of Review As both a cholesterol acceptor and carrier in the reverse cholesterol transport (RCT) pathway, high-density lipoprotein (HDL) is putatively atheroprotective. However, current pharmacological therapies to increase plasma HDL cholesterol (HDL-c) concentration have paradoxically failed to prevent or reduce atherosclerosis and cardiovascular disease (CVD). Given that free cholesterol (FC) transfer between surfaces of lipoproteins and cells is reversible, excess plasma FC can be transferred to the cells of peripheral tissue sites resulting in atherosclerosis. Here, we summarize potential mechanisms contributing to this paradox and highlight the role of excess free cholesterol (FC) bioavailability in atherosclerosis vs. atheroprotection. Recent Findings Recent findings have established a complex relationship between HDL-c concentration and atherosclerosis. Systemic scavenger receptor class B type 1 (SR-B1) knock out (KO) mice exhibit with increased diet-induced atherosclerosis despite having an elevated plasma HDL-c concentration compared to wild type (WT) mice. The greater bioavailability of HDL-FC in SR-B1 vs. WT mice is associated with a higher FC content in multiple cell types and tissue sites. These results suggest that dysfunctional HDL with high FC bioavailability is atheroprone despite high HDL-c concentration. Summary Past oversimplification of HDL-c involvement in cholesterol transport has led to the failures in HDL targeted therapy. Evidence suggests that FC-mediated functionality of HDL is of higher importance than its quantity; as a result, deciphering the regulatory mechanisms by which HDL-FC bioavailability can induce atherosclerosis can have far-reaching clinical implications.

Phytosterol serum concentrations are under tight genetic control. The relationship between phytosterols and coronary artery disease (CAD) is controversially discussed. We perform a genome-wide meta-analysis of 32 phytosterol traits reflecting resorption, cholesterol synthesis and esterification in six studies with up to 9758 subjects and detect ten independent genome-wide significant SNPs at seven genomic loci. We confirm previously established associations at ABCG5/8 and ABO and demonstrate an extended locus heterogeneity at ABCG5/8 with different functional mechanisms. New loci comprise HMGCR, NPC1L1, PNLIPRP2, SCARB1 and APOE. Based on these results, we perform Mendelian Randomization analyses (MR) revealing a risk-increasing causal relationship of sitosterol serum concentrations and CAD, which is partly mediated by cholesterol. Here we report that phytosterols are polygenic traits. MR add evidence of both, direct and indirect causal effects of sitosterol on CAD., Physterols are cholesterol homologs derived from plants, which are found in humans through consumption of plant products. Here the authors have performed a genome-wide meta-analysis of 32 serum phytosterol traits, with evidence suggesting causality between sitosterol and coronary artery disease.

(1) Background: The myristoylated pre-S1 peptide (Myr47) synthesized to mimic pre-S1 domain (2-48) in large (L) surface protein of hepatitis B virus (HBV) prevents HBV infection to hepatocytes by binding to sodium taurocholate cotransporting polypeptide (NTCP). We previously demonstrated that yeast-derived nanoparticles containing L protein (bio-nanocapsules: BNCs) bind scavenger receptor class B type 1 (SR-B1). In this study, we examined the binding of Mry47 to SR-B1. (2) Methods: The binding and endocytosis of fluorescence-labeled Myr47 to SR-B1 (and its mutants)-green fluorescence protein (GFP) fusion proteins expressed in HEK293T cells were analyzed using flow cytometry and laser scanning microscopy (LSM). Various ligand-binding properties were compared between SR-B1-GFP and NTCP-GFP. Furthermore, the binding of biotinylated Myr47 to SR-B1-GFP expressed on HEK293T cells was analyzed via pull-down assays using a crosslinker and streptavidin-conjugated beads. (3) Conclusions: SR-B1 bound not only Myr47 but also its myristoylated analog and BNCs, but failed to bind a peptide without myristoylation. However, NTCP only bound Myr47 among the ligands tested. Studies using SR-B1 mutants suggested that both BNCs and Myr47 bind to similar sites of SR-B1. Crosslinking studies indicated that Myr47 binds preferentially SR-B1 multimer than monomer in both HEK293T and HepG2 cells.

HDL is endowed with several metabolic, vascular, and immunoinflammatory protective functions. Among them, a key property is to promote reverse cholesterol transport from cells back to the liver. The aim of this study was to estimate the association of scavenger receptor class B type I (SR-BI)- and ATP binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux (the two major routes for cholesterol efflux to HDL) with the presence, extent, and severity of coronary artery disease (CAD), vascular wall remodelling processes, coronary plaque characteristics, and the incidence of myocardial infarction in the different subgroups of patients from the CAPIRE study. Patients (n = 525) from the CAPIRE study were divided into two groups: low-risk factors (RF), with 0–1 RF (n = 263), and multiple-RF, with ≥2 RFs; within each group, subjects were classified as no-CAD or CAD based on the segment involvement score (SIS) evaluated by coronary computed tomography angiography (SIS = 0 and SIS > 5, respectively). SR-BI- and ABCA1-mediated cholesterol efflux were measured using the plasma of all patients. SR-BI-mediated cholesterol efflux was significantly reduced in patients with CAD in both the low-RF and multiple-RF groups, whereas ABCA1-mediated cholesterol efflux was similar among all groups. In CAD patients, multivariable analysis showed that SR-BI-mediated cholesterol efflux th percentile predicted cardiovascular outcome (odds ratio 4.1; 95% CI: 1.3–13.7; p = .019), whereas ABCA-1-mediated cholesterol efflux and HDL-C levels significantly did not. Despite this finding, reduced SR-BI-mediated cholesterol efflux was not associated with changes in high-risk plaque features or changes in the prevalence of elevated total, non-calcified, and low-attenuation plaque volume. SR-BI-mediated cholesterol efflux capacity is lower in patients with diffuse coronary atherosclerosis. In addition, a lower SR-BI-mediated cholesterol efflux capacity is associated with the worst clinical outcomes in patients with CAD, independently of atherosclerotic plaque features. Key MessagesIncreased cholesterol efflux capacity, an estimate of HDL function, is associated with a reduced CVD risk, regardless of HDL-C levels.HDL-C levels are significantly lower in patients with CAD.Lower SR-BI-mediated cholesterol efflux capacity is observed in patients with diffuse coronary atherosclerosis and is associated with the worst clinical outcomes in patients with CAD, independently of atherosclerotic plaque features. Increased cholesterol efflux capacity, an estimate of HDL function, is associated with a reduced CVD risk, regardless of HDL-C levels. HDL-C levels are significantly lower in patients with CAD. Lower SR-BI-mediated cholesterol efflux capacity is observed in patients with diffuse coronary atherosclerosis and is associated with the worst clinical outcomes in patients with CAD, independently of atherosclerotic plaque features.

Since the pioneering discoveries, by the Nobel laureates Jules Hoffmann and Bruce Beutler, that Toll and Toll-like receptors can sense pathogenic microorganisms and initiate, in vertebrates and invertebrates, innate immune responses against microbial infections, many other families of pattern recognition receptors (PRRs) have been described. One of such receptor clusters is composed by, if not all, at least several members of the scavenger receptor cysteine-rich (SRCR) superfamily. Many SRCR proteins are plasma membrane receptors of immune cells; however, a small subset consists of secreted receptors that are therefore in circulation. We here describe the first characterization of biological and functional roles of the circulating human protein SSC4D, one of the least scrutinized members of the family. Within leukocyte populations, SSC4D was found to be expressed by monocytes/macrophages, neutrophils, and B cells, but its production was particularly evident in epithelial cells of several organs and tissues, namely, in the kidney, thyroid, lung, placenta, intestinal tract, and liver. Similar to other SRCR proteins, SSC4D shows the capacity of physically binding to different species of bacteria, and this opsonization can increase the phagocytic capacity of monocytes. Importantly, we have uncovered the capacity of SSC4D of binding to several protozoan parasites, a singular feature seldom described for PRRs in general and here demonstrated for the first time for an SRCR family member. Overall, our study is pioneer in assigning a PRR role to SSC4D.

The scavenger receptor class B type 1 (SR-BI, SCARB1), which is a high-density lipoprotein (HDL) receptor that mediates selective cholesteryl ester uptake, plays an important role in reverse cholesterol transport. This study investigated the distribution of polymorphic variants of the SR-BI gene in patients with coronary heart disease (CHD) with a history of early myocardial infarction (MI) at an early age and their effects on their serum lipid levels.SR-BI rs5888(TC), rs4238001(CT), and rs10846744(GC) were analyzed in 100 male patients with CHD with a history of MI (MI+) who were younger than 50 years and 89 male control subjects without MI history (MI-) using real-time polymerase chain reaction (PCR) and mutant-allele-specific PCR techniques.SR-BI rs4238001 common-CC genotype was found to be more frequent in patients with MI+ than in control subjects (MI-; odds ratio 4.046, p0.001). The rs10846744 rare-C allele showed a significant association with increased total cholesterol (p=0.014) and triglyceride (p=0.009) levels in the MI+ CHD group. Logistic regression analysis confirmed that there may be an association between the rs4238001-CC genotype (p=0.002), smoking (p=0.026), and MI+ CHD in the presence of other risk factors associated with CHD, whereas haplotype analysis confirmed that patients with MI+ CHD (rs5888-C, rs10846744-G, and rs4238001-C alleles) and CCC (rs5888-C, rs10846744-C, and rs4238001-C alleles) haplotypes were highly frequent (p0.01 and p=0.027, respectively).These results indicated that SR-BI gene variants show different distribution in patients with MI+ CHD compared with that in MI- control subjects, and these variants may have effects in favor of dyslipidemia.

International audience; High-density lipoproteins (HDLs) display endothelial protective effects. We tested the role of SR-BI, an HDL receptor expressed by endothelial cells, in the neuroprotective effects of HDLs using an experimental model of acute ischemic stroke. After transient intraluminal middle cerebral artery occlusion (tMCAO), control and endothelial SR-BI deficient mice were intravenously injected by HDLs or saline. Infarct volume and blood-brain barrier (BBB) breakdown were assessed 24 h post tMCAO. The potential of HDLs and the role of SR-BI to maintain the BBB integrity was assessed by using a human cellular model of BBB (hCMEC/D3 cell line) subjected to oxygen-glucose deprivation (OGD). HDL therapy limited the infarct volume and the BBB leakage in control mice relative to saline injection. Interestingly, these neuroprotective effects were thwarted by the deletion of SR-BI in endothelial cells and preserved in mice deficient for SR-BI in myeloid cells. In vitro studies revealed that HDLs can preserve the integrity of the BBB in OGD conditions, and that this effect was reduced by the SR-BI inhibitor, BLT-1. The protection of BBB integrity plays a pivotal role in HDL therapy of acute ischemic stroke. Our results show that this effect is partially mediated by the HDL receptor, SR-BI expressed by endothelial cells.

Objective: ApoM enriches S1P (sphingosine-1-phosphate) within HDL (high-density lipoproteins) and facilitates the activation of the S1P 1 (S1P receptor type 1) by S1P, thereby preserving endothelial barrier function. Many protective functions exerted by HDL in extravascular tissues raise the question of how S1P regulates transendothelial HDL transport. Approach and Results: HDL were isolated from plasma of wild-type mice, Apom knockout mice, human apoM transgenic mice or humans and radioiodinated to trace its binding, association, and transport by bovine or human aortic endothelial cells. We also compared the transport of fluorescently-labeled HDL or Evans Blue, which labels albumin, from the tail vein into the peritoneal cavity of apoE-haploinsufficient mice with (apoE-haploinsufficient mice with endothelium-specific knockin of S1P 1 ) or without (control mice, ie, apoE-haploinsufficient mice without endothelium-specific knockin of S1P 1 ) endothelium-specific knockin of S1P 1 . The binding, association, and transport of HDL from Apom knockout mice and human apoM-depleted HDL by bovine aortic endothelial cells was significantly lower than that of HDL from wild-type mice and human apoM-containing HDL, respectively. The binding, uptake, and transport of 125 I-HDL by human aortic endothelial cells was increased by an S1P 1 agonist but decreased by an S1P 1 inhibitor. Silencing of SR-BI (scavenger receptor BI) abrogated the stimulation of 125 I-HDL transport by the S1P 1 agonist. Compared with control mice, that is, apoE-haploinsufficient mice without endothelium-specific knockin of S1P 1 , apoE-haploinsufficient mice with endothelium-specific knockin of S1P 1 showed decreased transport of Evans Blue but increased transport of HDL from blood into the peritoneal cavity and SR-BI expression in the aortal endothelium. Conclusions: ApoM and S1P 1 promote transendothelial HDL transport. Their opposite effect on transendothelial transport of albumin and HDL indicates that HDL passes endothelial barriers by specific mechanisms rather than passive filtration.

Hyperlipidemia is a potent risk factor for the development of cardiovascular diseases. The reverse cholesterol transport (RCT) process has been shown to alleviate hyperlipidemia and protect against cardiovascular diseases. Recently, rosmarinic acid was reported to exhibit lipid-lowering effects. However, the underlying mechanism is still unclear. This study aims to investigate whether rosmarinic acid lowers lipids by modulating the RCT process in high-fat diet (HFD)-induced hyperlipidemic C57BL/6J mice. Our results indicated that rosmarinic acid treatment significantly decreased body weight, blood glucose, and plasma total cholesterol and triglyceride levels in HFD-fed mice. Rosmarinic acid increased the expression levels of cholesterol uptake-associated receptors in liver tissues, including scavenger receptor B type 1 (SR-B1) and low-density lipoprotein receptor (LDL-R). Furthermore, rosmarinic acid treatment notably increased the expression of cholesterol excretion molecules, ATP-binding cassette G5 (ABCG5) and G8 (ABCG8) transporters, and cholesterol 7 alpha-hydroxylase A1 (CYP7A1) as well as markedly reduced cholesterol and triglyceride levels in liver tissues. In addition, rosmarinic acid facilitated fatty acid oxidation through AMP-activated protein kinase (AMPK)-mediated carnitine palmitoyltransferase 1A (CPT1A) induction. In conclusion, rosmarinic acid exhibited a lipid-lowering effect by modulating the expression of RCT-related proteins and lipid metabolism-associated molecules, confirming its potential for the prevention or treatment of hyperlipidemia-derived diseases.

Recent studies suggest an anti-inflammatory protective role for class B scavenger receptor BI (SR-BI) in endotoxin-induced inflammation and sepsis. Other data, including ours, provide evidence for an alternative role of SR-BI, facilitating bacterial and endotoxin uptake and contributing to inflammation and bacterial infection. Enhanced endotoxin susceptibility of SR-BI-deficient mice due to their anti-inflammatory glucocorticoid deficiency complicates the understanding of SR-BI's role in endotoxemia/sepsis, calling for the use of alternative models. In this study, using human SR-BI (hSR-BI) and hSR-BII transgenic mice, we found that SR-BI and, to a lesser extent, its splicing variant SR-BII protect against LPS-induced lung damage. At 20 h after intratracheal LPS instillation, the extent of pulmonary inflammation and vascular leakage was significantly lower in hSR-BI and hSR-BII transgenic mice than in wild-type mice. Higher bronchoalveolar lavage fluid (BALF) inflammatory cell count and protein content and lung tissue neutrophil infiltration found in wild-type mice were associated with markedly (2 to 3 times) increased proinflammatory cytokine production compared to these parameters in transgenic mice following LPS administration. The markedly lower endotoxin levels detected in BALF of transgenic versus wild-type mice and the significantly increased BODIPY-LPS uptake observed in lungs of hSR-BI and hSR-BII mice 20 h after the i.t. LPS injection suggest that hSR-BI- and hSR-BII-mediated enhanced LPS clearance in the airways could represent the mechanism of their protective role against LPS-induced acute lung injury.

Aims Dysfunctional innate immune function and inflammation contributes to the pathogenesis of obesity-associated hypertension, in which macrophage infiltration in the perivascular adipose tissue (PVAT) plays a key role. However, the mechanisms behind it are not well understood. Class A1 scavenger receptor (SR-A1) is one of the major pattern recognition receptors in modulating macrophage activity, and here, we aimed to investigate its role in obesity-associated hypertension. Methods and results Both diet-induced and genetic obesity were generated in mice. Deficiency in SR-A1 aggravated the obesity-induced blood pressure (BP) elevation and endothelial dysfunction in mice. The BP-elevating effect of SR-A1 deficiency was blocked by the down-regulation of vascular endothelial growth factor B (VEGF-B) in obese mice. Overexpression of VEGF-B raised BP in the obese mice but not in normal mice. Administration of fucoidan, a ligand of SR-A1, lowered BP, and VEGF-B levels in Sr-a1+/+ but not in Sr-a1−/− obese mice. Conclusion These results reveal a new link between PVAT and vascular biology in obesity orchestrated by the SR-A1/VEGF-B axis in macrophages. SR-A1 and VEGF-B may be promising therapeutic targets in the treatment of obesity-associated hypertension.

Background Scavenger receptor class B type 1 (SR-BI) encoded by SCARB1 gene serves as a multifunctional HDL receptor, facilitating the uptake of cholesteryl esters from HDL to the liver. Recent studies have identified the association between the P376L missense mutation of the SCARB1 gene with increased serum HDL-Cholesterol level. However, the contribution of this variant to the development of cardiovascular disease (CVD) remains unclear. Objective We have investigated the association between the P376L polymorphism with the properties of HDL and CVD outcomes in a population sample recruited as part of the Mashhad-Stroke and Heart-Atherosclerotic-Disorders (MASHAD) cohort. Methods Six hundred and fifteen individuals who had a median follow-up period of 7 years were recruited as part of the MASHAD cohort. Anthropometric, biochemical parameters and HDL lipid peroxidation (HDLox) were assessed. Genotyping was performed using TaqMan-real-time-PCR based method. The association of P376L-rs74830766 with cardiovascular-risk-factors and CVD events were evaluated. Results Carriers of the P376L variant were significantly more likely than non-carriers to develop CVD using multivariate analyses adjusted for traditional CVD risk factors defined as: age, sex, BMI, presence of diabetes, or hypertension, positive smoking habit, and total cholesterol (OR: 3.75, 95%CI: 1.76–7.98, p = 0.001). In an adjusted model, there was a two fold increase in cardiovascular endpoints among individuals who were heterozygous for the P376L variant (hazard ratio, 2.08; 95% CI, 1.12-to 3.84, p = 0.02). Although there was no association between the presence of the P376L variant and HDL-C level, serum HDLox, measured as dysfunctional HDL, was 13% higher among carriers of the P376L variant than non-carriers. Conclusion We have found that carriers of the P376L variant possessed higher HDLox and were at increased risk of CVD in a representative population-based cohort, as compared to non-carriers.

Cholesterol homeostasis is of central importance for life. Therefore, cells have developed a divergent set of pathways to meet their cholesterol needs. In this review, we focus on the direct transfer of cholesterol from lipoprotein particles to the cell membrane. More molecular details on the transfer of lipoprotein-derived lipids were gained by recent studies using phospholipid bilayers. While amphiphilic lipids are transferred right after contact of the lipoprotein particle with the membrane, the transfer of core lipids is restricted. Amphiphilic lipid transfer gains special importance in genetic diseases impairing lipoprotein metabolism like familial hypercholesterolemia. Taken together, these data indicate that there is a constant exchange of amphiphilic lipids between lipoprotein particles and the cell membrane.

Benzyl butyl phthalate (BBP) is a widely used plasticizer and has raised public health concerns. Here, we report the effects of BBP on the testis development during rat puberty. BBP (0, 10, 100 or 1000 mg/kg) was gavaged to 35-day-old male Sprague Dawley rats for 21 days. The serum testosterone levels, Leydig cell number, the expressions of Leydig and Sertoli cell genes and proteins were measured. The in vitro effects on steroidogenesis and gene expression in immature Leydig cells were observed. BBP significantly increased serum testosterone level at 10 mg/kg but lowered its level at 1000 mg/kg without affecting serum luteinizing hormone and follicle-stimulating hormone levels. BBP increased Leydig cell number at all doses but inhibited steroidogenic capacity per Leydig cell at 1000 mg/kg. BBP significantly increased the ratio of phosphos-AKT2 (pAKT2)/AKT2, and phosphos-ERK1/2 (pERK1/2)/ERK1/2 in the testis. Mono-benzyl phthalate (the metabolite of BBP) inhibited steroidogenesis but BBP did not affect androgen production in immature Leydig cells in vitro. In conclusion, BBP non-linearly regulates Leydig cell development by increasing Leydig cell number but inhibiting steroidogenesis.

Objective: Determine the impact of CETP (cholesteryl ester transfer protein) on the route of cholesterol elimination in mice. Approach and Results: We adapted our protocol for biliary cholesterol secretion with published methods for measuring transintestinal cholesterol elimination. Bile was diverted and biliary lipid secretion maintained by infusion of bile acid. The proximal small bowel was perfused with bile acid micelles. In high-fat, high-cholesterol–fed mice, the presence of a CETP transgene increased biliary cholesterol secretion at the expense of transintestinal cholesterol elimination. The increase in biliary cholesterol secretion was not associated with increases in hepatic SR-BI (scavenger receptor BI) or ABCG5 (ATP-binding cassette G5) ABCG8. The decline in intestinal cholesterol secretion was associated with an increase in intestinal Niemann-Pick disease, type C1, gene-like 1 mRNA. Finally, we followed the delivery of HDL (high-density lipoprotein) or LDL (low-density lipoprotein) cholesteryl esters (CE) from plasma to bile and intestinal perfusates. HDL-CE favored the biliary pathway. Following high-fat feeding, the presence of CETP directed HDL-CE away from the bile and towards the intestine. The presence of CETP increased LDL-CE delivery to bile, whereas the appearance of LDL-CE in intestinal perfusate was near the lower limit of detection. Conclusions: Biliary and intestinal cholesterol secretion can be simultaneously measured in mice and used as a model to examine factors that alter cholesterol elimination. Plasma factors, such as CETP, alter the route of cholesterol elimination from the body. Intestinal and biliary cholesterol secretion rates are independent of transhepatic or transintestinal delivery of HDL-CE, whereas LDL-CE was eliminated almost exclusively in the hepatobiliary pathway.

Farnesoid X receptor (FXR) agonists play important regulatory roles in bile acid, lipid and glucose metabolism in vitro and in vivo. Thus, FXR agonists exhibit potential therapeutic effects on metabolism-related diseases that are associated with extrahepatic manifestations induced by hepatitis C virus (HCV) infection. This study investigated the effect and mechanism of FXR agonist GW4064 against HCV in vitro to explore the potential application of FXR agonists. Results showed that GW4064 and other FXR agonists have potent antiviral activity against HCV in Huh7.5 cells. GW4064 down-regulated the expression of scavenger receptor class B type I protein via FXR and thereby indirectly inhibited HCV entry into cells, leading to interruption of HCV life cycle. GW4064 also exhibited synergistic anti-HCV effect with known direct-acting antiviral agents (DAAs) used in the clinic and remained sensitive to DAA-resistant HCV mutations. Therefore, FXR agonists are also a kind of antiviral agent, and might be helpful in treatment of HCV-induced hepatic and extrahepatic manifestations.

The bile acid (BA) nuclear receptor, farnesoid X receptor (FXR/NR1H4), maintains metabolic homeostasis by transcriptional control of numerous genes, including an intestinal hormone, fibroblast growth factor-19 (FGF19; FGF15 in mice). Besides activation by BAs, the gene-regulatory function of FXR is also modulated by hormone or nutrient signaling–induced post-translational modifications. Recently, phosphorylation at Tyr-67 by the FGF15/19 signaling–activated nonreceptor tyrosine kinase Src was shown to be important for FXR function in BA homeostasis. Here, we examined the role of this FXR phosphorylation in cholesterol regulation. In both hepatic FXR-knockout and FXR-knockdown mice, reconstitution of FXR expression up-regulated cholesterol transport genes for its biliary excretion, including scavenger receptor class B member 1 (Scarb1) and ABC subfamily G member 8 (Abcg5/8), decreased hepatic and plasma cholesterol levels, and increased biliary and fecal cholesterol levels. Of note, these sterol-lowering effects were blunted by substitution of Phe for Tyr-67 in FXR. Moreover, consistent with Src's role in phosphorylating FXR, Src knockdown impaired cholesterol regulation in mice. In hypercholesterolemic apolipoprotein E–deficient mice, expression of FXR, but not Y67F-FXR, ameliorated atherosclerosis, whereas Src down-regulation exacerbated it. Feeding or treatment with an FXR agonist induced Abcg5/8 and Scarb1 expression in WT, but not FGF15-knockout, mice. Furthermore, FGF19 treatment increased occupancy of FXR at Abcg5/8 and Scarb1, expression of these genes, and cholesterol efflux from hepatocytes. These FGF19-mediated effects were blunted by the Y67F-FXR substitution or Src down-regulation or inhibition. We conclude that phosphorylation of hepatic FXR by FGF15/19-induced Src maintains cholesterol homeostasis and protects against atherosclerosis.

Atherosclerosis, which underlies life-threatening cardiovascular disorders such as myocardial infarction and stroke1, is initiated by passage of low-density lipoprotein (LDL) cholesterol into the artery wall and its engulfment by macrophages, which leads to foam cell formation and lesion development2,3. It is unclear how circulating LDL enters the artery wall to instigate atherosclerosis. Here we show in mice that scavenger receptor class B type 1 (SR-B1) in endothelial cells mediates the delivery of LDL into arteries and its accumulation by artery wall macrophages, thereby promoting atherosclerosis. LDL particles are colocalized with SR-B1 in endothelial cell intracellular vesicles in vivo, and transcytosis of LDL across endothelial monolayers requires its direct binding to SR-B1 and an eight-amino-acid cytoplasmic domain of the receptor that recruits the guanine nucleotide exchange factor dedicator of cytokinesis 4 (DOCK4)4. DOCK4 promotes internalization of SR-B1 and transport of LDL by coupling the binding of LDL to SR-B1 with activation of RAC1. The expression of SR-B1 and DOCK4 is increased in atherosclerosis-prone regions of the mouse aorta before lesion formation, and in human atherosclerotic arteries when compared with normal arteries. These findings challenge the long-held concept that atherogenesis involves passive movement of LDL across a compromised endothelial barrier. Interventions that inhibit the endothelial delivery of LDL into artery walls may represent a new therapeutic category in the battle against cardiovascular disease. The SR-B1 receptor partners with DOCK4 and RAC1 to drive the uptake and transcytosis of LDL in endothelial cells, thereby promoting atherosclerosis in mice.

Hyperlipidemia-associated lipid disorders are considered the cause of atherosclerotic cardiovascular disease. Reverse cholesterol transport (RCT) is a mechanism by which excess peripheral cholesterol is transported to the liver and further converted into bile acid for excretion from the body in feces, which contributes to reducing hyperlipidemia as well as cardiovascular disease. We previously found that the recombinant humanized IgG1 antibody promotes macrophages to engulf lipids and increases cholesterol efflux to high-density lipoprotein (HDL) through ATP-binding cassette sub-family A1 (ABCA1), one of the key proteins related to RCT. In the present study, we explored other RCT related proteins expression on hepatocytes, including scavenger receptor class B type I (SR-BI), apolipoprotein A-I (ApoA-I), and apolipoprotein A-II (ApoA-II), and its modulation mechanism involved. We confirmed that the recombinant humanized IgG1 antibody selectively activated ERK1/2 to upregulate SR-BI, ApoA-I, and ApoA-II expression in mice liver and human hepatocellular carcinoma cell lines HepG2 cells. The rate-limiting enzymes of bile acid synthesis, including cholesterol 7α-hydroxylase (CYP7A1) and sterol 27-hydroxylase (CYP27A1), exhibited a significant increase when treated with the recombinant humanized IgG1 antibody, as well as increased excretion of bile acids in feces. Besides, abolishment or mutation of peroxisome proliferator-activated receptor α (PPARα)/RXR binding site on SR-BI promoter eliminated SR-BI reporter gene luciferase activity even in the presence of the recombinant humanized IgG1 antibody. Knock down the neonatal Fc receptor (FcRn) on hepatocytes impaired the effect of recombinant humanized IgG1 antibody on activation of ERK1/2, as well as upregulation of SR-BI, ApoA-I, and ApoA-II expression. In conclusion, one of the mechanisms on the recombinant humanized IgG1 antibody attenuates hyperlipidemia in ApoE−/− mice model fed with high-fat-diet might be through reinforcement of liver RCT function in an FcRn-ERK1/2-PPARα dependent manner.

During reverse cholesterol transport, high-density lipoprotein (HDL) carries excess cholesterol from peripheral cells to the liver for excretion in bile. The first and last steps of this pathway involve the HDL receptor, scavenger receptor BI (SR-BI). While the mechanism of SR-BI-mediated cholesterol transport has not yet been established, it has long been suspected that cholesterol traverses through a hydrophobic tunnel in SR-BI's extracellular domain. Confirmation of a hydrophobic tunnel is hindered by the lack of a full-length SR-BI structure. Part of SR-BI's structure has been resolved, encompassing residues 405 to 475, which includes the C-terminal transmembrane domain and its adjacent extracellular region. Within the extracellular segment is an amphipathic helix (residues 427-436, referred to as AH(427-436)) that showed increased protection from solvent in NMR-based studies. Homology models predict that hydrophobic residues in AH(427-436) line a core cavity in SR-BI's extracellular region that may facilitate cholesterol transport. Therefore, we hypothesized that hydrophobic residues in AH(427-436) are required for HDL cholesterol transport. Here, we tested this hypothesis by mutating individual residues along AH(427-436) to a charged residue (aspartic acid), transiently transfecting COS-7 cells with plasmids encoding wild-type and mutant SR-BI, and performing functional analyses. We found that mutating hydrophobic, but not hydrophilic, residues in AH(427-436) impaired SR-BI bidirectional cholesterol transport. Mutating phenylalanine-430 was particularly detrimental to SR-BI's functions, suggesting that this residue may facilitate important interactions for cholesterol delivery within the hydrophobic tunnel. Our results support the hypothesis that a hydrophobic tunnel within SR-BI mediates cholesterol transport.

Background Midazolam is a neurological drug with diverse functions, including sedation, hypnosis, decreased anxiety, anterograde amnesia, brain-mediated muscle relaxation, and anticonvulsant activity. Since it is frequently used in children and adolescents for extended periods of time, there is a risk that it may affect their pubertal development. Here, we report a potential effect of the drug on the development of Leydig cells (LCs), the testosterone (T)-producing cells in the testis. Methods Stem LCs (SLCs), isolated from adult rat testes by a magnetic-activated cell sorting technique, were induced to differentiate into LCs in vitro for 3 weeks. Midazolam (0.1–30 μM) was added to the culture medium, and the effects on LC development were assayed. Results Midazolam has dose-dependent effects on SLC differentiation. At low concentrations (0.1–5 μM), the drug can mildly increase SLC differentiation (increased T production), while at higher concentrations (15–30 μM), it inhibits LC development (decreased T production). T increases at lower levels may be due to upregulations of scavenger receptor class b Member 1 (SCARB1) and cytochrome P450 17A1 (CYP17A1), while T reductions at higher levels of midazolam could be due to changes in multiple steroidogenic proteins. The uneven changes in steroidogenic pathway proteins, especially reductions in CYP17A1 at high midazolam levels, also result in an accumulation of progesterone. In addition to changes in T, increases in progesterone could have additional impacts on male reproduction. The loss in steroidogenic proteins at high midazolam levels may be mediated in part by the inactivation of protein kinase B/cAMP response element-binding protein (AKT/CREB) signaling pathway. Conclusion Midazolam has the potential to affect adult Leydig cell (ALC) development at concentrations comparable with the blood serum levels in human patients. Further studies are needed to test the effects on human cells.

Objective: Overall and atherosclerosis-associated mortality is elevated in humans with very high HDL (high-density lipoprotein) cholesterol concentrations. Mice with a deficiency of the HDL receptor, Scarb1 (scavenger receptor class B type 1), are a robust model of this phenotype and exhibit several additional pathologies. We hypothesized that the previously reported high plasma concentration of free cholesterol (FC)–rich HDL in Scarb1 −/ − mice produces a state of high HDL-FC bioavailability that increases whole-body FC and dysfunction in multiple tissue sites. Approach and Results: The higher mol% FC in Scarb1 −/− versus WT (wild type) HDL (41.1 versus 16.0 mol%) affords greater FC bioavailability for transfer to multiple sites. Plasma clearance of autologous HDL-FC mass was faster in WT versus Scarb1 −/− mice. FC influx from Scarb1 −/− HDL to LDL (low-density lipoprotein) and J774 macrophages was greater (≈4×) than that from WT HDL, whereas FC efflux capacity was similar. The higher mol% FC of ovaries, erythrocytes, heart, and macrophages of Scarb1 −/− versus WT mice is associated with previously reported female infertility, impaired cell maturation, cardiac dysfunction, and atherosclerosis. The FC contents of other tissues were similar in the two genotypes, and these tissues were not associated with any overt pathology. In addition to the differences between WT versus Scarb1 −/− mice, there were many sex-dependent differences in tissue-lipid composition and plasma FC clearance rates. Conclusions: Higher HDL-FC bioavailability among Scarb1 −/− versus WT mice drives increased FC content of multiple cell sites and is a potential biomarker that is mechanistically linked to multiple pathologies.