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Epigenetic regulation, which is characterized by reversible and heritable genetic alterations without changing DNA sequences, has recently been increasingly studied in diseases. Histone variant regulation is an essential component of epigenetic regulation. The substitution of canonical histones by histone variants profoundly alters the local chromatin structure and modulates DNA accessibility to regulatory factors, thereby exerting a pivotal influence on gene regulation and DNA damage repair. Histone H2A variants, mainly including H2A.Z, H2A.B, macroH2A, and H2A.X, are the most abundant identified variants among all histone variants with the greatest sequence diversity. Harboring varied chromatin occupancy and structures, histone H2A variants perform distinct functions in gene transcription and DNA damage repair. They are implicated in multiple pathophysiological mechanisms and the emergence of different illnesses. Cancer, embryonic development abnormalities, neurological diseases, metabolic diseases, and heart diseases have all been linked to histone H2A variant alterations. This review focuses on the functions of H2A histone variants in mammals, including H2A.Z, H2A.B, macroH2A, and H2A.X, and their current roles in various diseases.

Abstract Autophagy of endoplasmic reticulum (ER-phagy) selectively removes damaged ER through autophagy-lysosome pathway, acting as an adaptive mechanism to alleviate ER stress and restore ER homeostasis. However, the role and precise mechanism of ER-phagy in tubular injury of diabetic kidney disease (DKD) remain obscure. In the present study, we demonstrated that ER-phagy of renal tubular cells was severely impaired in streptozocin (STZ)-induced diabetic mice, with a decreased expression of phosphofurin acidic cluster sorting protein 2 (PACS-2), a membrane trafficking protein which was involved in autophagy, and a reduction of family with sequence similarity 134 member B (FAM134B), one ER-phagy receptor. These changes were further aggravated in mice with proximal tubule specific knockout of Pacs-2 gene. In vitro, transfection of HK-2 cells with PACS-2 overexpression plasmid partially improved the impairment of ER-phagy and the reduction of FAM134B, both of which were induced in high glucose ambience; while the effect was blocked by FAM134B siRNA. Mechanistically, PACS-2 interacted with and promoted the nuclear translocation of transcription factor EB (TFEB), which was reported to activate the expression of FAM134B. Collectively, these data unveiled that PACS-2 deficiency aggravates renal tubular injury in DKD via inhibiting ER-phagy through TFEB/FAM134B pathway.

Renal interstitial fibrosis (RIF) is a classic pathophysiological process of chronic kidney disease (CKD). However, the mechanisms underlying RIF remain unclear. The present study found that a novel circular RNA, cirInpp5b, might be involved in RIF by high-throughput sequencing. Subsequent experiments revealed that circInpp5b was reduced in UUO mouse kidney tissues and TGF-β1-treated proximal tubular cells. The overexpression of circInpp5b inhibited RIF in UUO mice and prevented extracellular matrix (ECM) deposition in TGF-β1-treated proximal tubular cells. Furthermore, overexpression of circInpp5b down-regulated the protein level of DDX1. Mechanistically, circInpp5b bound to the DDX1 protein and promoted its lysosomal degradation. Collectively, the findings of our study demonstrate that circInpp5b ameliorates RIF by binding to the DDX1 protein and promoting its lysosomal degradation.

Abstract Background Renal interstitial fibrosis (RIF) is a common pathway to end-stage renal disease regardless of the initial etiology. Currently, the molecular mechanisms for RIF remains not fully elucidated. Nuclear receptor subfamily 4 group A member 1(Nr4a1), a member of the NR4A subfamily of nuclear receptors, is a ligand-activated transcription factor. The role of Nr4a1 in RIF remains largely unknown. Methods In this study, we determined the role and action mechanism of Nr4a1 in RIF. We used unilateral ureteral obstruction (UUO) mice and transforming growth factor (TGF)-β1-treated human renal proximal tubular epithelial cells (HK-2 cells) as in vivo and in vitro models of RIF. A specific Nr4a1 agonist Cytosporone B (Csn-B) was applied to activate Nr4a1 both in vivo and in vitro, and Nr4a1 small interfering RNA was applied in vitro. Renal pathological changes were evaluated by hematoxylin and eosin and Masson staining, and the expression of fibrotic proteins including fibronectin (Fn) and collagen-I (Col-I), and phosphorylated p38 MAPK was measure by immunohistochemical staining and western blot analysis. Results The results showed that Nr4a1 was upregulated in UUO mouse kidneys, and was positively correlated with the degree of interstitial kidney injury and the levels of fibrotic proteins. Csn-B treatment aggravated UUO-induced renal interstitial fibrosis, and induced p38 MAPK phosphorylation. In vitro, TGF-β induced Nr4a1 expression, and Nr4a1 downregulation prevented TGF-β1-induced expression of Fn and Col-I and the activation of p38 MAPK. Csn-B induced fibrotic proteins expression and p38 MAPK phosphorylation, and moreover Csn-B induced fibrotic proteins expression was abrogated by treatment with p38 MAPK inhibitor SB203580. We provided further evidence that Csn-B treatment promoted cytoplasmic accumulation of Nr4a1. Conclusion The findings in the present study indicate that Nr4a1 promotes renal fibrosis potentially through activating p38 MAPK kinase.

AbstractBackground Severe renal impairment is a common complication of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and is associated with poor prognosis and shorter survival. It is urgent to find effective treatments to improve the prognosis of AAV patients. This study was designed to assess the efficacy and safety of protein A immunoadsorption (PAIA) and therapeutic plasma exchange (TPE) for AAV with severe renal involvement.Methods A total of 48 AAV patients with renal involvement admitted to the Second Xiangya Hospital from January 2018 to February 2021 were selected. Clinical data, myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA), remission at 6 months, and outcomes were evaluated. The primary outcomes of interest were death and renal survival as defined by the occurrence of end-stage renal disease (ESRD).Results PAIA was effective in the removal of MPO-ANCA and IgG, and showed superior over TPE in the clearance of MPO-ANCA within 1 month after treatment. After a median follow-up of 14.5 months, PAIA therapy showed an advantage in reducing mortality over TPE. There was no difference in the development of ESRD between the two groups. Multivariate Cox regression analysis indicated that higher serum creatinine (SCr) and lower haemoglobin level were independent risks of ESRD. Age > 60, lower serum albumin (ALB), and failure to achieve remission at 6 months were independent risks of death.Conclusions PAIA treatment reduces MPO-ANCA and IgG as well as mortality in AAV patients, and may be beneficial for severe AAV in clinical practice. Higher SCr, lower serum ALB or haemoglobin levels, age > 60, and failure to achieve remission at 6 months independently predict the ESRD or death of AAV patients with severe renal involvement.KEY MESSAGESCompared with therapeutic plasma exchange, protein A immunoadsorption treatment eliminates myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA) and IgG better and reduces mortality in ANCA-associated vasculitis (AAV) patients with severe renal involvement.Higher serum creatinine, lower serum albumin or haemoglobin levels, age > 60, and failure to achieve remission at 6 months independently predict the end-stage renal disease (ESRD) or death of AAV patients with severe renal involvement.

AbstractObjective Bowman’s capsule rupture (BCR) is a glomerular pathological change, but it is still not well recognized in immunoglobulin A vasculitis nephritis (IgAV-N). The Oxford MEST-C score is a classification for IgA nephropathy; however, its clinical correlation and prognostic value in adult patients with IgAV-N are unclear.Methods A retrospective study of 145 adult patients with IgAV-N diagnosed by renal biopsy was conducted. Clinical manifestations, pathological changes and the prognosis of IgAV-N patients were compared depending on the presence or absence of BCR, International Study of Kidney Disease in Children (ISKDC) classification and MEST-C score. The primary endpoint events were end-stage renal disease, renal replacement therapy and all-cause death.Results In total, 51 of 145 (35.17%) patients with IgAV-N presented with BCR. Patients with BCR had more proteinuria, lower serum albumin, and more crescents. Compared with IgAV-N patients with crescents only, 51/100 patients with crescents combined with BCR had a higher proportion of crescents in all glomeruli (15.79% vs. 9.09%; p = 0.003). Patients with higher ISKDC grades had more severe clinical presentation, but it did not reflect the prognosis. However, the MEST-C score not only reflected clinical manifestations but also predicted prognosis (p

Abstract Background Septic acute kidney injury (S-AKI) is the leading form of acute kidney failure among hospitalized patients, and the inflammatory response is involved in this process. 4-octyl itaconate (4-OI) is a multi-target itaconate derivative with potent anti-inflammatory action. However, it remains elusive whether and how 4-OI contributes to the regulation of S-AKI. Methods We employed a lipopolysaccharide (LPS)-induced AKI murine model and explored the potential renoprotective effect of 4-OI in vivo. In vitro experiments, BUMPT cells, a murine renal tubular cell line, were conducted to examine the effects of 4-OI on inflammation, oxidative stress, and mitophagy. Moreover, STAT3 plasmid was transfected in BUMPT cells to investigate the role of STAT3 signaling in the 4-OI-administrated state. Results We demonstrate that 4-OI protects against S-AKI through suppressing inflammation and oxidative stress and enhancing mitophagy. 4-OI significantly reduced the levels of Scr, BUN, Ngal as well as the tubular injury in LPS-induced AKI mice. 4-OI restrained inflammation by reducing macrophage infiltration and suppressing the expression of IL-1β and NLRP3 in the septic kidney. 4-OI also reduced ROS levels, as well as cleaved caspase-3 and boosted antioxidants such as HO-1, and NQO1 in mice. In addition, the 4-OI treatment significantly promoted mitophagy. Mechanistically, 4-OI activated Nrf2 signaling and suppressed phosphorylated STAT3 in vivo and vitro. Molecular docking revealed the binding affinity of 4-OI towards STAT3. ML385, a specific Nrf2 inhibitor, partially repressed the anti-inflammatory and anti-oxidative effects of 4-OI and partially restricted the mitophagy induced by 4-OI in vivo and in vitro. Transfected with STAT3 plasmid partially suppressed mitophagy and the anti-inflammatory effect provoked by 4-OI in vitro. Conclusion These data suggest that 4-OI ameliorates LPS-induced AKI by suppressing inflammation and oxidative stress and enhancing mitophagy through the overactivation of the Nrf2 signaling pathway, and inactivation of STAT3. Our study identifies 4-OI as a promising pharmacologic for S-AKI.

Abstract Background Lipid accumulation in tubular cells plays a key role in diabetic kidney disease (DKD). Targeting lipid metabolism disorders has clinical value in delaying the progression of DKD, but the precise mechanism by which molecules mediate lipid-related kidney injury remains unclear. Phosphofurin acidic cluster sorting protein 2 (PACS-2) is a multifunctional sorting protein that plays a role in lipid metabolism. This study determined the role of PACS-2 in lipid-related kidney injury in DKD. Methods Diabetes was induced by a high-fat diet combined with intraperitoneal injections of streptozotocin (HFD/STZ) in proximal tubule-specific knockout of Pacs-2 mice (PT-Pacs-2 −/− mice) and the control mice (Pacs-2 fl/fl mice). Transcriptomic analysis was performed between Pacs-2 fl/fl mice and PT-Pacs-2 −/− mice. Results Diabetic PT-Pacs-2 −/− mice developed more severe tubule injury and proteinuria compared to diabetic Pacs-2 fl/fl mice, which accompanied with increasing lipid synthesis, uptake and decreasing cholesterol efflux as well as lipid accumulation in tubules of the kidney. Furthermore, transcriptome analysis showed that the mRNA level of sterol O-acyltransferase 1 (Soat1) was up-regulated in the kidney of control PT-Pacs-2 −/− mice. Transfection of HK2 cells with PACS-2 siRNA under high glucose plus palmitic acid (HGPA) condition aggravated lipid deposition and increased the expression of SOAT1 and sterol regulatory element-binding proteins (SREBPs), while the effect was blocked partially in that of co-transfection of SOAT1 siRNA. Conclusions PACS-2 has a protective role against lipid-related kidney injury in DKD through SOAT1/SREBPs signaling.

Abstract Objectives Conventional glucocorticoid (GC) treatment poses significant risks for opportunistic infections due to its suppressive impact on CD4+ T cells. This study aimed to explore the mechanisms by which GCs modulate the functionality of CD4+ T cells during infection. Methods We consistently measured FOXP3, inflammatory cytokines and phospho‐S6 ribosomal protein levels in CD4+ T cells from patients undergoing conventional GC treatment. Using Foxp3EGFP animals, we investigated the dynamic activation of the mechanistic target of rapamycin complex 1 (mTORC1) pathway and its correlation with the immunoregulatory function of CD4+ T cells under the influence of GCs. Results GCs dynamically altered the expression pattern of FOXP3 in CD4+ T cells, promoting their acquisition of an active T regulatory (Treg) cell phenotype upon stimulation. Mechanistically, GCs undermined the kinetics of the mTORC1 pathway, which was closely correlated with phenotype conversion and functional properties of CD4+ T cells. Dynamic activation of the mTORC1 signaling modified the GC‐dampened immunoregulatory capacity of CD4+ T cells by phenotypically and functionally bolstering the FOXP3+ Treg cells. Interventions targeting the mTORC1 pathway effectively modulated the GC‐dampened immunoregulatory capacity of CD4+ T cells. Conclusion These findings highlight a novel mTORC1‐mediated mechanism underlying CD4+ T cell immunity in the context of conventional GC treatment.

Abstract Both endoplasmic reticulum (ER) stress and autophagy have been implicated in chronic kidney injury and renal fibrosis. However, the relationship and regulatory mechanisms between ER stress and autophagy under this condition remain largely unknown. In this study, we first established a mouse model of ER stress-induced chronic kidney injury by 2 weekly injections of a low dose of tunicamycin (TM), a classical ER stress inducer. This model showed the induction of ER stress, autophagy, fibrosis and apoptosis in kidney tissues. In vitro, TM also induced ER stress, autophagy, fibrosis and apoptosis in HK-2 human kidney proximal tubular cells and BUMPT-306 mouse kidney proximal tubular cells. In these cells, autophagy inhibitor suppressed TM-induced fibrotic changes and apoptosis, suggesting an involvement of autophagy in ER stress-associated chronic kidney injury. PERK inhibitor ameliorated autophagy, fibrotic protein expression and apoptosis in TM-treated cells, indicating a role of the PERK/eIF2α pathway in autophagy activation during ER stress. Similar results were shown in TGF-β1-treated HK-2 cells. Interestingly, in both TM- or TGF-β1-treated kidney proximal tubular cells, inhibition of autophagy exaggerated ER stress, suggesting that autophagy induced by ER stress provides a negative feedback mechanism to reduce the stress. Together, these results unveil a reciprocal regulation between ER stress and autophagy in chronic kidney injury and fibrosis.

Chronic inflammation contributes to maladaptive kidney repair, but its regulation is unclear. Here, we report that sirtuin 1 (SIRT1) is downregulated after repeated low-dose cisplatin (RLDC) injury, and this downregulation leads to p65 acetylation and consequent NF-κB activation resulting in a persistent inflammatory response. RLDC induced the down-regulation of SIRT1 and activation of NF-κB, which were accompanied by chronic tubular damage, tubulointerstitial inflammation, and fibrosis in mice. Inhibition of NF-κB suppressed the production of pro-inflammatory cytokines and fibrotic phenotypes in RLDC-treated renal tubular cells. SIRT1 activation by its agonists markedly reduced the acetylation of p65 (a key component of NF-κB), resulting in the attenuation of the inflammatory and fibrotic responses. Conversely, knockdown of SIRT1 exacerbated these cellular changes. At the upstream, p53 was activated after RLDC treatment to repress SIRT1, resulting in p65 acetylation, NF-κB activation and transcription of inflammatory cytokines. In mice, SIRT1 agonists attenuated RLDC-induced chronic inflammation, tissue damage, and renal fibrosis. Together, these results unveil the p53/SIRT1/NF-κB signaling axis in maladaptive kidney repair following RLDC treatment, where p53 represses SIRT1 to increase p65 acetylation for NF-κB activation, leading to chronic renal inflammation.

BackgroundIgA nephropathy (IgAN) is the most common primary glomerular disease and the leading cause of the end-stage renal disease in the world. The pathogenesis of IgAN has not been well elucidated, and yet treatment is limited. High-throughput microarray has been applied for elucidating molecular biomarkers and potential mechanisms involved in IgAN. This study aimed to identify the potential key genes and therapeutics associated with IgAN using integrative bioinformatics and transcriptome-based computational drug repurposing approach.MethodsThree datasets of mRNA expression profile were obtained from the gene expression omnibus database and differentially expressed genes (DEGs) between IgAN glomeruli and normal tissue were identified by integrated analysis. Gene ontology and pathway enrichment analyses of the DEGs were performed by R software, and protein-protein interaction networks were constructed using the STRING online search tool. External dataset and immunohistochemical assessment of kidney biopsy specimens were used for hub gene validation. Potential compounds for IgAN therapy were obtained by Connectivity Map (CMap) analysis and preliminarily verified in vitro. Stimulated human mesangial cells were collected for cell proliferation and cell cycle analysis using cell counting kit 8 and flow cytometry, respectively.Results134 DEGs genes were differentially expressed across kidney transcriptomic data from IgAN patients and healthy living donors. Enrichment analysis showed that the glomerular compartments underwent a wide range of interesting pathological changes during kidney injury, focused on anion transmembrane transporter activity and protein digestion and absorption mostly. Hub genes (ITGB2, FCER1G, CSF1R) were identified and verified to be significantly upregulated in IgAN patients, and associated with severity of renal lesions. Computational drug repurposing with the CMap identified tetrandrine as a candidate treatment to reverse IgAN hub gene expression. Tetrandrine administration significantly reversed mesangial cell proliferation and cell cycle transition.ConclusionThe identification of DEGs and related therapeutic strategies of IgAN through this integrated bioinformatics analysis provides a valuable resource of therapeutic targets and agents of IgAN. Especially, our findings suggest that tetrandrine might be beneficial for IgAN, which deserves future research.

Autophagy, a highly conserved catabolic pathway in eukaryotic cells, contributes to the maintenance of the homeostasis and function of the kidney. Upon acute kidney injury (AKI), autophagy is activated in renal tubular cells to act as an intrinsic protective mechanism. However, the role of autophagy in the development of chronic kidney pathologies including renal fibrosis after AKI remains unclear. In this study, we detected a persistent autophagy activation in mouse kidneys after nephrotoxicity of repeated low dose cisplatin (RLDC) treatment. 3-methyladenine (3-MA) and chloroquine (CQ), respective inhibitors of autophagy at the initiation and degradation stages, blocked autophagic flux and improved kidney repair in post-RLDC mice, as indicated by kidney weight, renal function, and less interstitial fibrosis. In vitro, RLDC induced a pro-fibrotic phenotype in renal tubular cells, including the production and secretion of pro-fibrotic cytokines. Notably, autophagy inhibitors blocked RLDC-induced secretion of pro-fibrotic cytokines in these cells. Together, the results indicate that persistent autophagy after AKI induces pro-fibrotic cytokines in renal tubular cells, promoting renal fibrosis and chronic kidney disease.

Background: Immunoglobulin A nephropathy (IgAN) is the most common primary glomerular disease and poses a global major public health burden. The preparation of Tripterygium wilfordii Hook F (TwHF) is widely applied for treating patients with Immunoglobulin A nephropathy in China, while the molecular mechanisms remain unclear. This study aimed to verify the therapeutic mechanism of TwHF on IgAN by undertaking a holistic network pharmacology strategy in combination with in vitro and in vivo experiments.Methods: TwHF active ingredients and their targets were obtained via the Traditional Chinese Medicine Systems Pharmacology Database. The collection of IgAN-related target genes was collected from GeneCards and OMIM. TwHF-IgAN common targets were integrated and visualized by Cytoscape. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to determine the predominant molecular mechanisms and pathways of TwHF on the treatment of IgAN. The protein-protein interaction network was constructed by the STRING online search tool, and hub genes were identified using R software. The expression of hub gene and related signaling were evaluated in TwHF-treated mice through immunohistochemistry and western blot and further validated in human mesangial cells (HMCs). In addition, Cell counting kit 8 (CCK8) and flow cytometry were used to detect the effects of TwHF on cell proliferation and cell cycle of mesangial cells.Results: A total of 51 active ingredients were screened from TwHF and 61 overlapping targets related to IgAN were considered potential therapeutic targets, GO functions and KEGG analyses demonstrated that these genes were primarily associated with DNA-binding transcription factor binding, lipid and atherosclerosis pathway. Genes with higher degrees including AKT1, CXCL8, MMP9, PTGS2, CASP3, JUN are hub genes of TwHF against IgAN. Verification of hub gene JUN both in vitro and in vivo showed that TwHF significantly attenuated JUN phosphorylation in the kidneys of IgAN mice and aIgA1-activated HMCs, meanwhile suppressing HMCs proliferation and arresting G1-S cell cycle progression.Conclusion: Our research strengthened the mechanisms of TwHF in treating IgAN, inhibition of JUN activation may play a pivotal role in TwHF in alleviating IgAN renal injury.

Background: Skeletal dysplasias (SDs) are a heterogeneous group of genetic disorders that primarily affect bone and cartilage. This study aims to identify the genetic causes for fetal SDs, and evaluates the diagnostic yield of prenatal whole-exome sequencing (WES) for this disorder.Methods: WES was performed on 38 fetuses with sonographically identified SDs and normal results of karyotype and single nucleotide polymorphism (SNP) analysis. Candidate variants were selected by bioinformatics analysis, and verified by Sanger sequencing.Results: WES revealed pathogenic or likely pathogenic variants associated with SDs in 65.79% (25/38) of fetuses, variants of uncertain significance (VUS) in SDs-related genes in 10.53% (4/38) cases, and incidental findings in 31.58% (12/38) fetuses. The SDs-associated variants identified in the present study affected 10 genes, and 35.71% (10/28) of the variants were novel.Conclusion: WES has a high diagnostic rate for prenatal SDs, which improves pregnancy management, prenatal counseling and recurrence risk assessment for future pregnancies. The newly identified variants expanded mutation spectrum of this disorder.

Cornelia de Lange syndrome (CdLS) is a genetic disorder characterized by multisystemic malformations. Mutation in the NIPBL gene accounts for nearly 60% of the cases. This study reports the clinical and genetic findings of three cases of CdLS from unrelated Chinese families. Clinically, all the three cases were classified as classic CdLS based on the cardinal (distinctive facial features and limb malformations) and suggestive (developmental delay, growth retardation, microcephaly, hirsutism, etc.) manifestations. SNP array detected a novel de novo heterozygous microdeletion of 0.2 Mb [arr[GRCh37]5p13.2(36848530_37052821) × 1] that spans the first 43 exons of NIPBL in the fetus with nuchal translucency thickening in case 1. Whole-exome sequencing in family trios plus Sanger sequencing validation identified a de novo heterozygous NIPBL c.5566G>A (p.R1856G) mutation in the fetus with intrauterine growth retardation in case 2 and a novel de novo heterozygous NIPBL c.448dupA (p.S150Kfs*23) mutation in the proband (an 8-month-old girl) in case 3. The cases presented in this study may serve as references for increasing our understanding of the mutation spectrum of NIPBL in association with CdLS.

Renal fibrosis is the final common pathway to chronic kidney diseases regardless of etiology. Parkinson disease protein 7 (PARK7) is a multifunctional protein involved in various cellular processes, but its pathophysiological role in kidneys remain largely unknown. Here, we have determined the role of PARK7 in renal fibrosis and have further elucidated the underlying mechanisms by using the in vivo mouse model of unilateral ureteric obstruction (UUO) and the in vitro model of transforming growth factor-b (TGFB1) treatment of cultured kidney proximal tubular cells. PARK7 decreased markedly in atrophic kidney tubules in UUO mice, and Park7 deficiency aggravated UUO-induced renal fibrosis, tubular cell apoptosis, ROS production and inflammation. In vitro, TGFB1 treatment induced fibrotic changes in renal tubular cells, which was accompanied by alterations of PARK7. Park7 knockdown exacerbated TGFB1-induced fibrotic changes, cell apoptosis and ROS production, whereas Park7 overexpression or treatment with ND-13 (a PARK7-derived peptide) attenuated these TGFB1-induced changes. Mechanistically, PARK7 translocated into the nucleus of renal tubular cells following TGFB1 treatment or UUO, where it induced the expression of SOD2, an antioxidant enzyme. Taken together, these results indicate that PARK7 protects against chronic kidney injury and renal fibrosis by inducing SOD2 to reduce oxidative stress in tubular cells.

Background: Acute kidney injury (AKI) may lead to the development of chronic kidney disease (CKD), i.e. AKI-CKD transition, but the underlying mechanism remains largely unclear. Endoplasmic reticulum (ER) stress is characterized by the accumulation of unfolded or misfolded proteins in ER resulting in a cellular stress response. The role of ER stress in AKI-CKD transition remains unknown. Methods: In this study, we examined ER stress in the mouse model of AKI-CKD transition after unilateral renal ischemia-reperfusion injury (uIR). To determine the role of ER stress in AKI-CKD transition, we tested the effects of two chemical chaperones: Tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA). Findings: uIR led to the induction of ER stress in kidneys, as indicated by increased expression of UPR molecules CHOP (C/EBP homologous protein) and BiP(binding immunoglobulin protein; also called GRP78–78 kDa glucose­regulated protein). Given at 3 days after uIR, both TUDCA and 4-PBA blocked ER stress in post-ischemic kidneys. Notably, both chemicals promoted renal recovery and suppressed tubulointerstitial injury as manifested by the reduction of tubular atrophy, renal fibrosis and myofibroblast activation. Inhibition of ER stress further attenuated renal tubular epithelial cell apoptosis, inflammation and autophagy in post-ischemic kidneys. Interpretation: These findings suggest that ER stress contributes critically to the development of chronic kidney pathologies and CKD following AKI, and inhibition of ER stress may represent a potential therapeutic strategy to impede AKI-CKD transition. Keywords: ER stress, AKI-CKD transition, Renal ischemia-reperfusion, Fibrosis, Apoptosis, Autophagy

Abstract Background Split hand/foot malformation (SHFM) is a congenital limb developmental disorder, which impairs the fine activities of hand/foot in the affected individuals seriously. SHFM is commonly inherited as an autosomal dominant disease with incomplete penetrance. Chromosomal aberrations such as copy number variations and translocations have been linked to SHFM. This study aimed to identify the genetic cause for three patients with bilateral hand and foot malformation in a Chinese family. Methods Karyotyping, single‐nucleotide polymorphism (SNP) array, whole exome sequencing, whole genome sequencing, and Sanger sequencing were applied to identify the pathogenic variant. Results Karyotyping revealed that the three patients had balanced reciprocal translocation, 46, XX, t(3;15) (q29;q22). SNP array identified no pathogenic copy number variation in the proband. Trio‐WES (fetus–mother–father) sequencing results revealed no pathogenic variants in the genes related to SHFM. Whole‐genome low‐coverage mate‐pair sequencing (WGL‐MPS), breakpoint PCR, and Sanger sequencing identified the breakpoints disrupting TP63 in the patients, but not in healthy family members. Conclusion This study firstly reports that a translocation breakpoint disrupting TP63 contributes to the SHFM in a Chinese family, which expands our knowledge of genetic risk and counseling underlying SHFM. It provides a basis for genetic counseling and prenatal diagnosis (preimplantation genetic diagnosis) for this family.

Sepsis is the major cause of acute kidney injury (AKI) associated with high mortality rates. Mitochondrial dysfunction contributes to the pathophysiology of septic AKI. Mitophagy is an important mitochondrial quality control mechanism that selectively eliminates damaged mitochondria, but its role and regulation in septic AKI remain largely unknown. Here, we demonstrate the induction of mitophagy in mouse models of septic AKI induced by lipopolysaccharide (LPS) treatment or by cecal ligation and puncture. Mitophagy was also induced in cultured proximal tubular epithelial cells exposed to LPS. Induction of mitophagy under these experimental setting was suppressed by pink1 or park2 knockout, indicating the role of the PINK1/PARK2 pathway of mitophagy in septic AKI. In addition, sepsis induced more severe kidney injury and cell apoptosis in pink1 or park2 knockout mice than in wild-type mice, suggesting a beneficial role of mitophagy in septic AKI. Furthermore, in cultured renal tubular cells treated with LPS, knockdown of pink1 or park2 inhibited mitochondrial accumulation of the autophagy adaptor optineurin (OPTN) and silencing Optn inhibited LPS-induced mitophagy. Taken together, these findings suggest that the PINK1/PARK2 pathway of mitophagy plays an important role in mitochondrial quality control, tubular cell survival, and renal function in septic AKI.

Autophagy is a conserved, multistep pathway that degrades and recycles dysfunctional organelles and macromolecules to maintain cellular homeostasis. Mammalian target of rapamycin (mTOR) and adenosine-monophosphate activated-protein kinase (AMPK) are major negative and positive regulators of autophagy, respectively. In cisplatin-induced acute kidney injury (AKI) or nephrotoxicity, autophagy is rapidly induced in renal tubular epithelial cells and acts as a cytoprotective mechanism for cell survival. Both mTOR and AMPK have been implicated in the regulation of autophagy in cisplatin-induced AKI. Targeting mTOR and/or AMPK may offer effective strategies for kidney protection during cisplatin-mediated chemotherapy.

Sepsis is the leading cause of acute kidney injury (AKI). However, the pathogenesis of septic AKI remains largely unclear. Here, we demonstrate a significant decrease of microRNA-376b (miR-376b) in renal tubular cells in mice with septic AKI. Urinary miR-376b in these mice was also dramatically decreased. Patients with sepsis with AKI also had significantly lower urinary miR-376b than patients with sepsis without AKI, supporting its diagnostic value for septic AKI. LPS treatment of renal tubular cells led to the activation of NF-κB, and inhibition of NF-κB prevented a decrease of miR-376b. ChIP assay further verified NF-κB binding to the miR-376b gene promoter upon LPS treatment. Functionally, miR-376b mimics exaggerated tubular cell death, kidney injury, and intrarenal production of inflammatory cytokines, while inhibiting miR-376b afforded protective effects in septic mice. Interestingly, miR-376b suppressed the expression of NF-κB inhibitor ζ (NFKBIZ) in both in vitro and in vivo models of septic AKI. Luciferase microRNA target reporter assay further verified NFKBIZ as a direct target of miR-376b. Collectively, these results illustrate the NF-κB/miR-376b/NFKBIZ negative feedback loop that regulates intrarenal inflammation and tubular damage in septic AKI. Moreover, urinary miR-376b is a potential biomarker for the diagnosis of AKI in patients with sepsis.

Abstract Background This study aimed to define the molecular basis for 12 prenatal cases of Cri‐du‐chat syndrome (CdCS) and the potential genotyping‐phenotyping association. Methods Karyotyping and single nucleotide polymorphism array analyses for copy number variants were performed. Results Nine cases had 5p terminal deletions and three had 5p interstitial deletions, and these cases had variable deletion sizes with partial overlapping. Phenotypically, besides intrauterine growth restriction (IUGR) and brain as well as heart abnormalities, hypospadias, and lung dysplasia were observed. Potential genetic causes for specific phenotypes in these cases were identified. Conclusion This study defined the molecular bases for the patients of CdCS, which is important for genetic counseling for these families. The findings of present study expand the clinical features of CdCS in the fetal period, and provided important information for further refining the genotypic–phenotypic correlations for this syndrome.

Introduction Metabolomics has emerged as a valuable tool to discover novel biomarkers and study the pathophysiology of diabetic nephropathy (DN). However, the effect of postoperative acute kidney injury (AKI) on diabetes mellitus (DM) to chronic DN progression has not been evaluated from the perspective of metabolomics. Methods A group of type 2 diabetes mellitus (T2DM) inpatients, who underwent off-pump coronary artery bypass grafting (CABG), were enrolled in our study. According to whether postoperative AKI occurred, patients were grouped in either the AKI group (AKI, n = 44) or the non-AKI group (NAKI, n = 44). Urine samples were collected from these patients before and 24 h after operation. Six patients from the AKI group and six patients from the NAKI group were chosen as the pilot cohort for untargeted metabolomics analysis, with the goal of identifying postoperative AKI-related metabolites. To understand the possible role of these metabolites in the chronic development of renal injury among T2DM patients, trans-4-hydroxy-L-proline and azelaic acid were quantified by targeted metabolomics analysis among 38 NAKI patients, 38 AKI patients, 46 early DN patients (DN-micro group), and 34 overt DN patients (DN-macro group). Results Untargeted metabolomics screened 61 statistically distinguishable metabolites in postoperative urine samples, compared with preoperative urine samples. Via Venn diagram analysis, nine of 61 were postoperative AKI-related metabolites, including trans-4-hydroxy-L-proline, uridine triphosphate, p-aminobenzoate, caffeic acid, adrenochrome, δ-valerolactam, L-norleucine, 5′-deoxy-5′-(methylthio) adenosine, and azelaic acid. By targeted metabolomics analysis, the level of trans-4-hydroxy-L-proline increased gradually from the NAKI group to the AKI, DN-micro, and DN-macro groups. For azelaic acid, the highest level was found in the NAKI and DN-micro groups, followed by the DN-macro group. The AKI group exhibited the lowest level of azelaic acid. Conclusions The detection of urinary trans-4-hydroxy-L-proline after AKI could be treated as an early warning of chronic DN progression and might be linked to renal fibrosis. Urinary azelaic acid can be used to monitor renal function noninvasively in DM and DN patients. Our results identified markers of AKI on DM and the chronic progression of DN. In addition, the progression of DN was associated with AKI-like episodes occurring in DM.

NLRP3/IL-1β activation via thioredoxin (TRX)/thioredoxin-interacting protein (TXNIP) following mitochondria ROS (mtROS) overproduction plays a key role in inflammation. However, the involvement of this process in tubular damage in the kidneys of patients with diabetic nephropathy (DN) is unclear. Here, we demonstrated that mtROS overproduction is accompanied by decreases in TRX expression and TXNIP up-regulation. In addition, we discovered that mtROS overproduction is also associated with increases in NLRP3/IL-1β and TGF-β expression in the kidneys of patients with DN and db/db mice. We reversed these changes in db/db mice by administering a peritoneal injection of MitoQ, an antioxidant targeting mtROS. Similar results were observed in human tubular HK-2 cells subjected to high-glucose (HG) conditions and treated with MitoQ. Treating HK-2 cells with MitoQ suppressed the dissociation of TRX from TXNIP and subsequently blocked the interaction between TXNIP and NLRP3, leading to the inhibition of NLRP3 inflammasome activation and IL-1β maturation. The effects of MitoQ were enhanced by pretreatment with TXNIP siRNA and abolished by pretreatment with monosodium urate (MSU) and TRX siRNA in vitro. These results suggest that mitochondrial ROS-TXNIP/NLRP3/IL-1β axis activation is responsible for tubular oxidative injury, which can be ameliorated by MitoQ via the inhibition of mtROS overproduction. Keywords: Diabetic nephropathy, Mitochondria, Reactive oxygen species (ROS), TRX/TXNIP, NLRP3 inflammasome, MitoQ

Mitochondria play a crucial role in tubular injury in diabetic kidney disease (DKD). MitoQ is a mitochondria-targeted antioxidant that exerts protective effects in diabetic mice, but the mechanism underlying these effects is not clear. We demonstrated that mitochondrial abnormalities, such as defective mitophagy, mitochondrial reactive oxygen species (ROS) overexpression and mitochondrial fragmentation, occurred in the tubular cells of db/db mice, accompanied by reduced PINK and Parkin expression and increased apoptosis. These changes were partially reversed following an intraperitoneal injection of mitoQ. High glucose (HG) also induces deficient mitophagy, mitochondrial dysfunction and apoptosis in HK-2 cells, changes that were reversed by mitoQ. Moreover, mitoQ restored the expression, activity and translocation of HG-induced NF-E2-related factor 2 (Nrf2) and inhibited the expression of Kelch-like ECH-associated protein (Keap1), as well as the interaction between Nrf2 and Keap1. The reduced PINK and Parkin expression noted in HK-2 cells subjected to HG exposure was partially restored by mitoQ. This effect was abolished by Nrf2 siRNA and augmented by Keap1 siRNA. Transfection with Nrf2 siRNA or PINK siRNA in HK-2 cells exposed to HG conditions partially blocked the effects of mitoQ on mitophagy and tubular damage. These results suggest that mitoQ exerts beneficial effects on tubular injury in DKD via mitophagy and that mitochondrial quality control is mediated by Nrf2/PINK. Keywords: Mitoq, Diabetic kidney disease, Mitophagy, Tubular

Acute kidney injury (AKI) is a major kidney disease characterized by rapid decline of renal function. Besides its acute consequence of high mortality, AKI has recently been recognized as an independent risk factor for chronic kidney disease (CKD). Maladaptive or incomplete repair of renal tubules after severe or episodic AKI leads to renal fibrosis and, eventually, CKD. Recent studies highlight a key role of mitochondrial pathology in AKI development and abnormal kidney repair after AKI. As such, timely elimination of damaged mitochondria in renal tubular cells represents an important quality control mechanism for cell homeostasis and survival during kidney injury and repair. Mitophagy is a selective form of autophagy that selectively removes redundant or damaged mitochondria. Here, we summarize our recent understanding on the molecular mechanisms of mitophagy, discuss the role of mitophagy in AKI development and kidney repair after AKI, and present future research directions and therapeutic potential.

Acute kidney injury (AKI) is a major kidney disease characterized by an abrupt loss of renal function. Accumulating evidence indicates that incomplete or maladaptive repair after AKI can result in kidney fibrosis and the development and progression of chronic kidney disease (CKD). Hypoxia, a condition of insufficient supply of oxygen to cells and tissues, occurs in both acute and chronic kidney diseases under a variety of clinical and experimental conditions. Hypoxia-inducible factors (HIFs) are the “master” transcription factors responsible for gene expression in hypoxia. Recent researches demonstrate that HIFs play an important role in kidney injury and repair by regulating HIF target genes, including microRNAs. However, there are controversies regarding the pathological roles of HIFs in kidney injury and repair. In this review, we describe the regulation, expression, and functions of HIFs, and their target genes and related functions. We also discuss the involvement of HIFs in AKI and kidney repair, presenting HIFs as effective therapeutic targets.

The pathogenesis of chronic kidney disease (CKD) is complex and apparently multifactorial. Hypoxia or decrease in oxygen supply in kidney tissues has been implicated in CKD. Hypoxia inducible factors (HIF) are a small family of transcription factors that are mainly responsive to hypoxia and mediate hypoxic response. HIF plays a critical role in renal fibrosis during CKD through the modulation of gene transcription, crosstalk with multiple signaling pathways, epithelial-mesenchymal transition, and epigenetic regulation. Moreover, HIF also contributes to the development of various pathological conditions associated with CKD, such as anemia, inflammation, aberrant angiogenesis, and vascular calcification. Treatments targeting HIF and related signaling pathways for CKD therapy are being developed with promising clinical benefits, especially for anemia. This review presents an updated analysis of hypoxia response, HIF, and their associated signaling network involved in the pathogenesis of CKD.

Fragile X associated tremor/ataxia syndrome (FXTAS) is a late onset neurodegenerative disorder caused by aberrant expansion of CGG repeats in 5' UTR of FMR1 gene. The elevated mRNA confers a toxic gain-of-function thought to be the critical event of pathogenesis. Expressing rCGG90 repeats of the human FMR1 5'UTR in Drosophila is sufficient to induce neurodegeneration. Rapamycin has been demonstrated to attenuate neurotoxicity by inducing autophagy in various animal models of neurodegenerative diseases. Surprisingly, we observed rapamycin exacerbated rCGG90-induced neurodegenerative phenotypes through an autophagy-independent mechanism. CGG90 expression levels of FXTAS flies exposed to rapamycin presented no significant differences. We further demonstrated that activation of the mammalian target of rapamycin (mTOR) signaling could suppress neurodegeneration of FXTAS. These findings indicate that rapamycin will exacerbate neurodegeneration, and that enhancing autophagy is insufficient to alleviate neurotoxicity in FXTAS. Moreover, these results suggest mTOR and its downstream molecules as new therapeutic targets for FXTAS by showing significant protection against neurodegeneration.

Mutations in Connexin-31 (Cx31) are associated with multiple human diseases including erythrokeratodermia variabilis (EKV). The molecular action of Cx31 pathogenic mutants remains largely elusive. We report here that expression of EKV pathogenic mutant Cx31R42P induces cell death with necrotic characteristics. Inhibition of hemichannel activity by a connexin hemichannel inhibitor or high extracellular calcium suppresses Cx31R42P-induced cell death. Expression of Cx31R42P induces ER stress resulting in reactive oxygen species (ROS) production, in turn, to regulate gating of Cx31R42P hemichannels and Cx31R42P induced cell death. Moreover, Cx31R42P hemichannels play an important role in mediating ATP release from the cell. In contrast, no hemichannel activity was detected with cells expressing wildtype Cx31. Together, the results suggest that Cx31R42P forms constitutively active hemichannels to promote necrotic cell death. The Cx31R42P active hemichannels are likely resulted by an ER stress mediated ROS overproduction. The study identifies a mechanism of EKV pathogenesis induced by a Cx31 mutant and provides a new avenue for potential treatment strategy of the disease.

Autophagy, a highly conserved catabolic pathway in eukaryotic cells, contributes to the maintenance of the homeostasis and function of the kidney. Upon acute kidney injury (AKI), autophagy is activated in renal tubular cells to act as an intrinsic protective mechanism. However, the role of autophagy in the development of chronic kidney pathologies including renal fibrosis after AKI remains unclear. In this study, we detected a persistent autophagy activation in mouse kidneys after nephrotoxicity of repeated low dose cisplatin (RLDC) treatment. 3-methyladenine (3-MA) and chloroquine (CQ), respective inhibitors of autophagy at the initiation and degradation stages, blocked autophagic flux and improved kidney repair in post-RLDC mice, as indicated by kidney weight, renal function, and less interstitial fibrosis. In vitro, RLDC induced a pro-fibrotic phenotype in renal tubular cells, including the production and secretion of pro-fibrotic cytokines. Notably, autophagy inhibitors blocked RLDC-induced secretion of pro-fibrotic cytokines in these cells. Together, the results indicate that persistent autophagy after AKI induces pro-fibrotic cytokines in renal tubular cells, promoting renal fibrosis and chronic kidney disease. [ABSTRACT FROM AUTHOR]