Search

Representative H&E images of Ahnak-/- and WT lungs in embryonic day 18.5 and postnatal day 1.

AHNAK is known to be a tumor suppressor in breast cancer due to its ability to activate the TGFβ signaling pathway. However, the role of AHNAK in lung tumor development and progression remains unknown. Here, the Ahnak gene was disrupted to determine its effect on lung tumorigenesis and the mechanism by which it triggers lung tumor development was investigated. First, AHNAK protein expression was determined to be decreased in human lung adenocarcinomas compared with matched nonneoplastic lung tissues. Then, Ahnak−/− mice were used to investigate the role of AHNAK in pulmonary tumorigenesis. Ahnak−/− mice showed increased lung volume and thicker alveolar walls with type II pneumocyte hyperplasia. Most importantly, approximately 20% of aged Ahnak−/− mice developed lung tumors, and Ahnak−/− mice were more susceptible to urethane-induced pulmonary carcinogenesis than wild-type mice. Mechanistically, Ahnak deficiency promotes the cell growth of lung epithelial cells by suppressing the TGFβ signaling pathway. In addition, increased numbers of M2-like alveolar macrophages (AM) were observed in Ahnak−/− lungs, and the depletion of AMs in Ahnak−/− lungs alleviated lung hyperplastic lesions, suggesting that M2-like AMs promoted the progression of lung hyperplastic lesions in Ahnak-null mice. Collectively, AHNAK suppresses type II pneumocyte proliferation and inhibits tumor-promoting M2 alternative activation of macrophages in mouse lung tissue. These results suggest that AHNAK functions as a novel tumor suppressor in lung cancer.Implications: The tumor suppressor function of AHNAK, in murine lungs, occurs by suppressing alveolar epithelial cell proliferation and modulating lung microenvironment. Mol Cancer Res; 16(8); 1287–98. ©2018 AACR.

Supplementary figure legends

Supplementary Figure S1: Interaction between NoxO1 and Grb2 Supplementary Figure S2: Interaction domains between NoxO1 and Grb2 Supplementary Figure S3: Stability of Nox1 and NoxA1 Supplementary Figure S4: Target of ubiquitination is not p47phox Supplementary Figure S5: PKC-dependent NoxO1 phosphorylation Supplementary Figure S6: Subcellular localization of NoxO1 and NoxA1 Supplementary Figure S7: Effect of NoxO1 on Erk activation

The generation of reactive oxygen species (ROS) is required for proper cell signaling, but must be tightly regulated to minimize deleterious oxidizing effects. Activation of the NADPH oxidases (Nox) triggers ROS production and, thus, regulatory mechanisms exist to properly control Nox activity. In this study, we report a novel mechanism in which Nox1 activity is regulated through the proteasomal degradation of Nox organizer 1 (NoxO1). We found that through the interaction between NoxO1 and growth receptor–bound protein 2 (Grb2), the Casitas B–lineage lymphoma (Cbl) E3 ligase was recruited, leading to decreased NoxO1 stability and a subsequent reduction in ROS generation upon epidermal growth factor (EGF) stimulation. Additionally, we show that EGF-mediated phosphorylation of NoxO1 induced its release from Grb2 and facilitated its association with Nox activator 1 (NoxA1) to stimulate ROS production. Consistently, overexpression of Grb2 resulted in decreased Nox1 activity, whereas knockdown of Grb2 led to increased Nox1 activity in response to EGF. CRISPR/Cas9-mediated NoxO1 knockout in human colon cancer cells abrogated anchorage-independent growth on soft agar and tumor-forming ability in athymic nude mice. Moreover, the expression and stability of NoxO1 were significantly increased in human colon cancer tissues compared with normal colon. Taken together, these results support a model whereby Nox1 activity and ROS generation are regulated by Grb2/Cbl-mediated proteolysis of NoxO1 in response to EGF, providing new insight into the processes by which excessive ROS production may promote oncogenic signaling to drive colorectal tumorigenesis. Cancer Res; 76(4); 855–65. ©2016 AACR.

Supplementary Materials and Methods

Supplementary Figure S1: Interaction between NoxO1 and Grb2 Supplementary Figure S2: Interaction domains between NoxO1 and Grb2 Supplementary Figure S3: Stability of Nox1 and NoxA1 Supplementary Figure S4: Target of ubiquitination is not p47phox Supplementary Figure S5: PKC-dependent NoxO1 phosphorylation Supplementary Figure S6: Subcellular localization of NoxO1 and NoxA1 Supplementary Figure S7: Effect of NoxO1 on Erkactivation

Reactive oxygen species (ROS) play important roles as second messengers in a wide array of cellular processes including differentiation of stem cells. We identified Nox4 as the major ROS-generating enzyme whose expression is induced during differentiation of embryoid body (EB) into cells of all three germ layers. The role of Nox4 was examined using induced pluripotent stem cells (iPSCs) generated from Nox4 knockout (Nox4−/−) mouse. Differentiation markers showed significantly reduced expression levels consistent with the importance of Nox4-generated ROS during this process. From transcriptomic analyses, we found insulin-like growth factor 2 (IGF2), a member of a gene family extensively involved in embryonic development, as one of the most down-regulated genes in Nox4−/− cells. Indeed, addition of IGF2 to culture partly restored the differentiation competence of Nox4−/− iPSCs. Our results reveal an important signaling axis mediated by ROS in control of crucial events during differentiation of pluripotent stem cells. Graphical Abstract

The AHNAK nucleoprotein has been determined to exert an anti-obesity effect in adipose tissue and further inhibit adipogenic differentiation. In this study, we examined the role of AHNAK in regulating hepatic lipid metabolism to prevent diet-induced fatty liver. Ahnak KO mice have reportedly exhibited reduced fat accumulation in the liver and decreased serum triglyceride (TG) levels when provided with either a normal chow diet or a high-fat diet (HFD). Gene expression profiling was used to identify novel factors that could be modulated by genetic manipulation of the Ahnak gene. The results revealed that fibroblast growth factor 21 (FGF21) was markedly increased in the livers of Ahnak KO mice compared with WT mice fed a HFD. Ahnak knockdown in hepatocytes reportedly prevented excessive lipid accumulation induced by palmitate treatment and was associated with increased secretion of FGF21 and the expression of genes involved in fatty acid oxidation, which are primarily downstream of PPARα. These results indicate that pronounced obesity and hepatic steatosis are attenuated in HFD-fed Ahnak KO mice. This may be attributed, in part, to the induction of FGF21 and regulation of lipid metabolism, which are considered to be involved in increased fatty acid oxidation and reduced lipogenesis in the liver. These findings suggest that targeting AHNAK may have beneficial implications in preventing or treating hepatic steatosis., Liver disease: A potential treatment for nonalcoholic fatty liver A protein that modulates lipid accumulation could be a target for controlling nonalcoholic fatty liver disease (NAFLD). The AHNAK protein regulates fat cell development, and mice lacking AHNAK are less susceptible to obesity after being fed a HFD. South Korean researchers led by Je Kyung Seong of Seoul National University and Yun Soo Bae of Ewha Womans University, Seoul, have identified a mechanism by which AHNAK inhibition prevents lipid accumulation in NAFLD. The authors profiled gene expression in AHNAK-deficient mice, and noted a striking increase in levels of a signaling protein called FGF21 in the liver. This elevated FGF21 was in turn linked to increased breakdown and reduced production of fatty acids. Therapeutic interventions that inhibit AHNAK could help control NAFLD, a hard-to-treat condition that can ultimately lead to cirrhosis and liver failure.

Several recent studies have reported that reactive oxygen species (ROS), superoxide anion and hydrogen peroxide (H2O2), play important roles in various cellular signaling networks. NADPH oxidase (Nox) isozymes have been shown to mediate receptor-mediated ROS generation for physiological signaling processes involved in cell growth, differentiation, apoptosis, and fibrosis. Detectable intracellular levels of ROS can be induced by the electron leakage from mitochondrial respiratory chain as well as by activation of cytochrome p450, glucose oxidase and xanthine oxidase, leading to oxidative stress. The up-regulation and the hyper-activation of NADPH oxidases (Nox) also likely contribute to oxidative stress in pathophysiologic stages. Elevation of the renal ROS level through hyperglycemia-mediated Nox activation results in the oxidative stress which induces a damage to kidney tissues, causing to diabetic nephropathy (DN). Nox inhibitors are currently being developed as the therapeutics of DN. In this review, we summarize Nox-mediated ROS generation and development of Nox inhibitors for therapeutics of DN treatment.

Oxidative stress can cause generation of uncontrolled reactive oxygen species (ROS) and lead to cytotoxic damage to cells and tissues. Recently, it has been shown that transient ROS generation can serve as a secondary messenger in receptor-mediated cell signaling. Although excessive levels of ROS are harmful, moderated levels of ROS are essential for normal physiological function. Therefore, regulating cellular ROS levels should be an important concept for development of novel therapeutics for treating diseases. The overexpression and hyperactivation of NADPH oxidase (Nox) can induce high levels of ROS, which are strongly associated with diabetic nephropathy. This review discusses the theoretical basis for development of the Nox inhibitor as a regulator of ROS homeostasis to provide emerging therapeutic opportunities for diabetic nephropathy.

Summary: Cytosolic proteins are required for regulation of NADPH (nicotinamide adenine dinucleotide phosphate) oxidase (Nox) isozymes. Here we show that Src homology 3 (SH3) domain-containing YSC84-like 1 (SH3YL1), as a Nox4 cytosolic regulator, mediates lipopolysaccharide (LPS)-induced H2O2 generation, leading to acute kidney injury. The SH3YL1, Ysc84p/Lsb4p, Lsb3p, and plant FYVE proteins (SYLF) region and SH3 domain of SH3YL1 contribute to formation of a complex with Nox4-p22phox. Interaction of p22phox with SH3YL1 is triggered by LPS, and the complex induces H2O2 generation and pro-inflammatory cytokine expression in mouse tubular epithelial cells. After LPS injection, SH3YL1 knockout mice show lower levels of acute kidney injury biomarkers, decreased secretion of pro-inflammatory cytokines, decreased infiltration of macrophages, and reduced tubular damage compared with wild-type (WT) mice. The results strongly suggest that SH3YL1 is involved in renal failure in LPS-induced acute kidney injury (AKI) mice. We demonstrate that formation of a ternary complex of p22phox-SH3YL1-Nox4, leading to H2O2 generation, induces severe renal failure in the LPS-induced AKI model.

Chemosensitization of cancer cells with small molecules may improve the therapeutic index of antitumoral agents by making tumor cells sensitive to the drug regimen and thus overcome the treatment resistance and side effects of single therapy. Cell membrane lipid rafts are known to transduce various signaling events in cell proliferation. Sensitizing cancer cells may cause modulation of membrane lipid rafts which may potentially be used in improving anticancer drug response. Cedrol, a natural sesquiterpene alcohol, was used to treat human leukemia K562 and colon cancer HT-29 cell lines, and effects were observed. Cedrol decreased the cell viability by inducing apoptosis in both cell lines by activation of pro-apoptosis protein BID and inhibition of anti-apoptosis proteins Bcl-XL, Bcl-2, and XIAP. Cedrol activated the caspase-9-dependent mitochondrial intrinsic pathway of apoptosis. Furthermore, cedrol inhibited the levels of pAKT, pERK, and pmTOR proteins as well as nuclear and cytoplasmic levels of the p65 subunit of NF-κB. Cedrol caused redistribution of cholesterol and sphingomyelin contents from membrane lipid raft, which was confirmed by a combined additive effect with methyl-β-cyclodextrin (lipid raft-disrupting agent). Lipid raft destabilization by cedrol led to the increased production of ceramides and inhibition of membrane-bound NADPH oxidase 2 enzyme activity. Cholesterol/sphingomyelin-redistributing abilities of cedrol appear as a novel mechanism of growth inhibition of cancer cells. Cedrol can be classified as a natural lipid raft-disrupting agent with possibilities to be used in general studies involving membrane lipid raft modifications.

Despite numerous studies on the molecular switches governing the conversion of stemness to differentiation in embryonic stem cells (ESCs), little is known about the involvement of the retromer complex. Under neural differentiation conditions, Vps26a deficiency (Vps26a-/-) or knockdown suppressed the loss of stemness and subsequent neurogenesis from ESCs or embryonic carcinoma cells, respectively, as evidenced by the long-lasting expression of stemness markers and the slow appearance of neuronal differentiation markers. Interestingly, relatively low reactive oxygen species (ROS) levels were generated during differentiation of Vps26a-/- ESCs, and treatment with an antioxidant or inhibitor of NADPH oxidase (Nox), a family of ROS-generating enzymes, led to restoration of stemness in wild-type cells to the level of Vps26a-/- cells during neurogenesis. Importantly, a novel interaction between Vps26a and Nox4 linked to the activation of ERK1/2 depended highly on ROS levels during neurogenesis, which were strongly suppressed in differentiating Vps26a-/- ESCs. Moreover, inhibition of phosphorylated ERK1/2 (pERK1/2) resulted in decreased ROS and Nox4 levels, indicating the mutual dependency between pERK1/2 and Nox4-derived ROS during neurogenesis. These results suggest that Vps26a regulates stemness by actively cooperating with the Nox4/ROS/ERK1/2 cascade during neurogenesis. Our findings have important implications for understanding the regulation of stemness via crosstalk between the retromer molecule and redox signaling, and may contribute to the development of ESC-based therapeutic strategies for the mass production of target cells.

Reactive oxygen species (ROS) derived from NADPH oxidase (Nox) has been shown to activate ADP-ribosyl cyclase (ARC), which produces the Ca2+ mobilizing second messenger, cyclic ADP-ribose (cADPR). In the present study, we examined how ROS activates cluster of differentiation (CD)38, a mammalian prototype of ARC. CD38 exists in type II and III forms with opposing membrane orientation. This study showed the coexpression of type II and III CD38 in lymphokine-activated killer (LAK) cells. The catalytic site of the constitutively active type II CD38 faces the outside of the cell or the inside of early endosomes (EEs), whereas the basally inactive type III CD38 faces the cytosol. Type III CD38 interacted with Nox4/phosphorylated-p22phox (p-p22phox) in EEs of LAK cells upon IL-8 treatment. H2O2 derived from Nox4 activated type III CD38 by forming a disulfide bond between Cys164 and Cys177, resulting in increased cADPR formation. Our study identified the mechanism by which type III CD38 is activated in an immune cell (LAK), in which H2O2 generated by Nox4 oxidizes and activates type III CD38 to generate cADPR. These findings provide a novel model of cross-talk between ROS and Ca2+ signaling.-Park, D.-R., Nam, T.-S., Kim, Y.-W., Bae, Y. S., Kim, U.-H. Oxidative activation of type III CD38 by NADPH oxidase-derived hydrogen peroxide in Ca2+ signaling.

Previously, we reported a molecular mechanism by which Ahnak potentiates transforming growth factor-β (TGFβ) signaling during cell growth. Here, we show that Ahnak induces epithelial-mesenchymal transition (EMT) in response to TGFβ. EMT phenotypes, including altered in cell morphology, and expression patterns of various EMT marker genes were detected in HaCaT keratinocytes transfected with Ahnak-specific siRNA. Knockdown of Ahnak expression in HaCaT keratinocytes resulted in attenuated cell migration and invasion. We found that Ahnak activates TGFβ signaling via Smad3 phosphorylation, leading to enhanced Smad3 transcriptional activity. To validate function of Ahnak in EMT of B16F10 cells having high metastatic and tumorigenic properties, we established B16F10 cells with stable knockdown of Ahnak. N-cadherin expression and Smad3 phosphorylation were significantly decreased in B16F10-shAhnak cells, compared to B16F10-shControl cells after treatment of TGFβ. Moreover, TGFβ failed to induce cell migration and cell invasion in B16F10-shAhnak cells. To determine whether Ahnak regulates the metastatic activity of B16F10 cells, we established a lung metastasis model in C57BL/6 mice via tail vein injection of B16F10-shAhnak cells. Lung metastasis was significantly suppressed in mice injected with B16F10-shAhnak cells, compared to those injected with B16F10-shControl cells. Taken together, we propose that TGFβ-Ahnak signaling axis regulates EMT during tumor metastasis.

AHNAK is known to be a tumor suppressor in breast cancer due to its ability to activate the TGFβ signaling pathway. However, the role of AHNAK in lung tumor development and progression remains unknown. Here, the Ahnak gene was disrupted to determine its effect on lung tumorigenesis and the mechanism by which it triggers lung tumor development was investigated. First, AHNAK protein expression was determined to be decreased in human lung adenocarcinomas compared with matched nonneoplastic lung tissues. Then, Ahnak−/− mice were used to investigate the role of AHNAK in pulmonary tumorigenesis. Ahnak−/− mice showed increased lung volume and thicker alveolar walls with type II pneumocyte hyperplasia. Most importantly, approximately 20% of aged Ahnak−/− mice developed lung tumors, and Ahnak−/− mice were more susceptible to urethane-induced pulmonary carcinogenesis than wild-type mice. Mechanistically, Ahnak deficiency promotes the cell growth of lung epithelial cells by suppressing the TGFβ signaling pathway. In addition, increased numbers of M2-like alveolar macrophages (AM) were observed in Ahnak−/− lungs, and the depletion of AMs in Ahnak−/− lungs alleviated lung hyperplastic lesions, suggesting that M2-like AMs promoted the progression of lung hyperplastic lesions in Ahnak-null mice. Collectively, AHNAK suppresses type II pneumocyte proliferation and inhibits tumor-promoting M2 alternative activation of macrophages in mouse lung tissue. These results suggest that AHNAK functions as a novel tumor suppressor in lung cancer. Implications: The tumor suppressor function of AHNAK, in murine lungs, occurs by suppressing alveolar epithelial cell proliferation and modulating lung microenvironment. Mol Cancer Res; 16(8); 1287–98. ©2018 AACR.

Apolipoprotein A-I binding protein (AIBP) reduces lipid raft abundance by augmenting the removal of excess cholesterol from the plasma membrane. Here, we report that AIBP prevents and reverses processes associated with neuroinflammatory-mediated spinal nociceptive processing. The mechanism involves AIBP binding to Toll-like receptor-4 (TLR4) and increased binding of AIBP to activated microglia, which mediates selective regulation of lipid rafts in inflammatory cells. AIBP-mediated lipid raft reductions downregulate LPS-induced TLR4 dimerization, inflammatory signaling, and expression of cytokines in microglia. In mice, intrathecal injections of AIBP reduce spinal myeloid cell lipid rafts, TLR4 dimerization, neuroinflammation, and glial activation. Intrathecal AIBP reverses established allodynia in mice in which pain states were induced by the chemotherapeutic cisplatin, intraplantar formalin, or intrathecal LPS, all of which are pro-nociceptive interventions known to be regulated by TLR4 signaling. These findings demonstrate a mechanism by which AIBP regulates neuroinflammation and suggest the therapeutic potential of AIBP in treating preexisting pain states.

In a previous study, the specific NOX1/2/4 inhibitor Ewha-18278 was confirmed as a possible treatment for osteoporosis both in vitro and in vivo. Here, we investigated the pharmacokinetics (PK) of the compound by intravenous (IV) and oral administrations to rats. Dimethyl sulfoxide (DMSO)-based and diazepam injection-based formulations were used to dissolve the compound. In the latter formulation applicable to humans, the changes in PK parameters were monitored at two different concentrations (1 mg/mL and 2 mg/mL). The area under the plasma concentration-time curve from zero time to infinity (AUCinf) of Ewha-18278 was highest in the DMSO-based formulation (2 mg/mL). Also, the concentration was increased 1.6-fold at the low concentration of the diazepam injection-based formulation compared to the high concentration. There was no statistical significance in the AUCinf of the compound between DMSO-based formulation (2 mg/mL) and diazepam injection-based formulation (1 mg/mL). These results suggest that Ewha-18278 can be delivered to humans by both IV and oral routes. In addition, the diazepam injection-based formulation of Ewha-18278 appears to be a suitable candidate for dosage development for future toxicity test and clinical trial.

The generation of reactive oxygen species (ROS) is required for proper cell signaling, but must be tightly regulated to minimize deleterious oxidizing effects. Activation of the NADPH oxidases (Nox) triggers ROS production and, thus, regulatory mechanisms exist to properly control Nox activity. In this study, we report a novel mechanism in which Nox1 activity is regulated through the proteasomal degradation of Nox organizer 1 (NoxO1). We found that through the interaction between NoxO1 and growth receptor–bound protein 2 (Grb2), the Casitas B–lineage lymphoma (Cbl) E3 ligase was recruited, leading to decreased NoxO1 stability and a subsequent reduction in ROS generation upon epidermal growth factor (EGF) stimulation. Additionally, we show that EGF-mediated phosphorylation of NoxO1 induced its release from Grb2 and facilitated its association with Nox activator 1 (NoxA1) to stimulate ROS production. Consistently, overexpression of Grb2 resulted in decreased Nox1 activity, whereas knockdown of Grb2 led to increased Nox1 activity in response to EGF. CRISPR/Cas9-mediated NoxO1 knockout in human colon cancer cells abrogated anchorage-independent growth on soft agar and tumor-forming ability in athymic nude mice. Moreover, the expression and stability of NoxO1 were significantly increased in human colon cancer tissues compared with normal colon. Taken together, these results support a model whereby Nox1 activity and ROS generation are regulated by Grb2/Cbl-mediated proteolysis of NoxO1 in response to EGF, providing new insight into the processes by which excessive ROS production may promote oncogenic signaling to drive colorectal tumorigenesis. Cancer Res; 76(4); 855–65. ©2016 AACR.

Objective Previous reports have indicated that Ahnak-deficient mice were protected from high-fat diet-induced obesity. However, the molecular mechanism in which Ahnak mediates adipocyte differentiation and high-fat diet-induced obesity is unclear. Methods Adipocytes from Ahnak knockout (Ahnak−/−) mice and knockdown of Ahnak in C3H10T1/2 were used to investigate the function of Ahnak in adipocyte differentiation. Ahnak-induced adipocyte differentiation was analyzed by Oil Red O staining. Results Adipocytes from Ahnak−/− mice were smaller than those from wild-type mice. Silencing of Ahnak in C3H10T1/2 and adipose tissue-derived mesenchymal stem cells (ADSCs) from Ahnak−/− mice showed severely impaired adipocyte differentiation. Down-regulation of Ahnak in C3H10T1/2 cells and ADSCs from Ahnak−/− mice attenuated the phosphorylation and nuclear localization of Smad1 in response to BMP2, whereas Ahnak overexpression in 3T3-L1 cells significantly increased Smad1 activation. Because PPARγ is a well-known transcriptional factor in adipocyte differentiation, the PPARγ expression in Ahnak-mediated adipocyte differentiation was investigated. Transfection of C3H10T1/2 cells with Ahnak siRNA resulted in reduced PPARγ expression apparently through inhibited binding of Smad1 to the Smad1-binding site in the PPARγ promoter. These results suggest that Ahnak regulates adipogenesis by regulating Smad1-dependent PPARγ expression. Conclusions A molecular mechanism was proposed in which Ahnak regulates adipocyte differentiation through Smad1 activation.

We have previously reported that Ahnak-mediated TGFβ signaling leads to down-regulation of c-Myc expression. Here, we show that inhibition of Ahnak can promote generation of induced pluripotent stem cells (iPSC) via up-regulation of endogenous c-Myc. Consistent with the c-Myc inhibitory role of Ahnak, mouse embryonic fibroblasts from Ahnak-deficient mouse (Ahnak(-/-) MEF) show an increased level of c-Myc expression compared with wild type MEF. Generation of iPSC with just three of the four Yamanaka factors, Oct4, Sox2, and Klf4 (hereafter 3F), was significantly enhanced in Ahnak(-/-) MEF. Similar results were obtained when Ahnak-specific shRNA was applied to wild type MEF. Of note, expressionof Ahnak was significantly induced during the formation of embryoid bodies from embryonic stem cells, suggesting that Ahnak-mediated c-Myc inhibition is involved in embryoid body formation and the initial differentiation of pluripotent stem cells. The iPSC from 3F-infected Ahnak(-/-) MEF cells (Ahnak(-/-)-iPSC-3F) showed expression of all stem cell markers examined and the capability to form three primary germ layers. Moreover, injection of Ahnak(-/-)-iPSC-3F into athymic nude mice led to development of teratoma containing tissues from all three primary germ layers, indicating that iPSC from Ahnak(-/-) MEF are bona fide pluripotent stem cells. Taken together, these data provide evidence for a new role for Ahnak in cell fate determination during development and suggest that manipulation of Ahnak and the associated signaling pathway may provide a means to regulate iPSC generation.

We report that phytosphingosine, a sphingolipid found in many organisms and implicated in cellular signaling, promotes megakaryocytic differentiation of myeloid leukemia cells. Specifically, phytosphingosine induced several hallmark changes associated with megakaryopoiesis from K562 and HEL cells including cell cycle arrest, cell size increase and polyploidization. We also confirmed that cell type specific markers of megakaryocytes, CD41a and CD42b are induced by phytosphingosine. Phospholipids with highly similar structures were unable to induce similar changes, indicating that the activity of phytosphingosine is highly specific. Although phytosphingosine is known to activate p38 mitogen-activated protein kinase (MAPK)-mediated apoptosis, the signaling mechanisms involved in megakaryopoiesis appear to be distinct. In sum, we present another model for dissecting molecular details of megakaryocytic differentiation which in large part remains obscure. [BMB Reports 2015; 48(12): 691-695]

// Guideock Kwon 1, * , Md Jamal Uddin 1, * , Gayoung Lee 1 , Songling Jiang 1 , Ahreum Cho 1 , Jung Hwa Lee 1 , Sae Rom Lee 2 , Yun Soo Bae 2 , Sung Hwan Moon 3 , Soo Jin Lee 3 , Dae Ryong Cha 4 and Hunjoo Ha 1 1 Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul, Korea 2 Department of Life Science, Ewha Womans University, Seoul, Korea 3 Aptabio Therapeutics Inc, Yongin-si, Korea 4 Department of Internal Medicine, Division of Nephrology, Korea University, Seoul, Korea * These authors contributed equally to this work Correspondence to: Hunjoo Ha, email: hha@ewha.ac.kr Keywords: APX-115, diabetic kidney disease, mitochondria and peroxisome, oxidative stress, pan-Nox inhibitor Received: March 24, 2017 Accepted: June 05, 2017 Published: June 16, 2017 ABSTRACT NADPH oxidase (Nox)-derived reactive oxygen species (ROS) are increasingly recognized as a key factor in inflammation and extracellular matrix accumulation in diabetic kidney disease. APX-115 (3-phenyl-1-(pyridin-2-yl)-4-propyl-1-5-hydroxypyrazol HCl) is a novel orally active pan-Nox inhibitor. The objective of this study was to compare the protective effect of APX-115 with a renin-angiotensin system inhibitor (losartan), the standard treatment against kidney injury in diabetic patients, on streptozotocin (STZ)-induced diabetic kidney injury. Diabetes was induced by intraperitoneal injection of STZ at 50 mg/kg/day for 5 days in C57BL/6J mice. APX-115 (60 mg/kg/day) or losartan (1.5 mg/kg/day) was administered orally to diabetic mice for 12 weeks. APX-115 effectively prevented kidney injury such as albuminuria, glomerular hypertrophy, tubular injury, podocyte injury, fibrosis, and inflammation as well as oxidative stress in diabetic mice, similar to losartan. In addition, both APX-115 and losartan treatment effectively inhibited mitochondrial and peroxisomal dysfunction associated with lipid accumulation. Our data suggest that APX-115, a pan-Nox inhibitor, may become a novel therapeutic agent against diabetic kidney disease by maintaining peroxisomal and mitochondrial fitness.

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox) are an important family of catalytic enzymes that generate reactive oxygen species (ROS), which mediate the regulation of diverse cellular functions. Although phagocyte Nox2/gp91phox is closely associated with the activation of host innate immune responses, the roles of Nox family protein during Toxoplasma gondii (T. gondii) infection have not been fully investigated. Here, we found that T. gondii-mediated ROS production was required for the upregulation of macrophage migration inhibitory factor (MIF) mRNA and protein levels via activation of mitogen-activated protein kinase and nuclear factor-κB signaling in macrophages. Interestingly, MIF knockdown led to a significant increase in the survival of intracellular T. gondii in bone marrow-derived macrophages (BMDMs). Moreover, Nox4 deficiency, but not Nox2/gp91phox and the cytosolic subunit p47phox, resulted in enhanced survival of the intracellular T. gondii RH strain and impaired expression of T. gondii-mediated MIF in BMDMs. Additionally, Nox4-deficient mice showed increased susceptibility to virulent RH strain infection and increased cyst burden in brain tissues and low levels of MIF expression following infection with the avirulent ME49 strain. Collectively, our findings indicate that Nox4-mediated ROS generation plays a central role in MIF production and resistance to T. gondii infection.

The function of reactive oxygen species (ROS) as second messengers in cell differentiation has been demonstrated only for a limited number of cell types. Here, we used a well-established protocol for BMP2-induced neuronal differentiation of neural crest stem cells (NCSCs) to examine the function of BMP2-induced ROS during the process. We first show that BMP2 indeed induces ROS generation in NCSCs and that blocking ROS generation by pretreatment of cells with diphenyleneiodonium (DPI) as NADPH oxidase (Nox) inhibitor inhibits neuronal differentiation. Among the ROS-generating Nox isozymes, only Nox4 was expressed at a detectable level in NCSCs. Nox4 appears to be critical for survival of NCSCs at least in vitro as down-regulation by RNA interference led to apoptotic response from NCSCs. Interestingly, development of neural crest-derived peripheral neural structures in Nox4−/− mouse appears to be grossly normal, although Nox4−/− embryos were born at a sub-Mendelian ratio and showed delayed over-all development. Specifically, cranial and dorsal root ganglia, derived from NCSCs, were clearly present in Nox4−/− embryo at embryonic days (E) 9.5 and 10.5. These results suggest that Nox4-mediated ROS generation likely plays important role in fate determination and differentiation of NCSCs, but other Nox isozymes play redundant function during embryogenesis.

Testosterone is an endocrine hormone with functions in reproductive organs, anabolic events, and skin homeostasis. We report here that GPRC6A serves as a sensor and mediator of the rapid action of testosterone in epidermal keratinocytes. The silencing of GPRC6A inhibited testosterone-induced intracellular calcium ([Ca(2+)]i) mobilization and H2O2 generation. These results indicated that a testosterone-GPRC6A complex is required for activation of Gq protein, IP3 generation, and [Ca(2+)]i mobilization, leading to Duox1 activation. H2O2 generation by testosterone stimulated the apoptosis of keratinocytes through the activation of caspase-3. The application of testosterone into three-dimensional skin equivalents increased the apoptosis of keratinocytes between the granular and stratified corneum layers. These results support an understanding of the molecular mechanism of testosterone-dependent apoptosis in which testosterone stimulates H2O2 generation through the activation of Duox1.

2-(Trimethylammonium) ethyl (R)-3-methoxy-3-oxo-2-stearamidopropyl phosphate [(R)-TEMOSPho], a derivative of an organic chemical identified from a natural product library, promotes highly efficient megakaryopoiesis. Here, we show that (R)-TEMOSPho blocks osteoclast maturation from progenitor cells of hematopoietic origin, as well as blocking the resorptive function of mature osteoclasts. The inhibitory effect of (R)-TEMOSPho on osteoclasts was due to a disruption of the actin cytoskeleton, resulting from impaired downstream signaling of c-Fms, a receptor for macrophage-colony stimulating factor linked to c-Cbl, phosphoinositol-3-kinase (PI3K), Vav3, and Rac1. In addition, (R)-TEMOSPho blocked inflammation-induced bone destruction by reducing the numbers of osteoclasts produced in mice. Thus, (R)-TEMOSPho may represent a promising new class of antiresorptive drugs for the treatment of bone loss associated with increased osteoclast maturation and activity.

Midazolam is a widely used anesthetic of the benzodiazepine class that has shown cytotoxicity and apoptosis-inducing activity in neuronal cells and lymphocytes. This study aims to evaluate the effect of midazolam on growth of K562 human leukemia cells and HT29 colon cancer cells. The in vivo effect of midazolam was investigated in BALB/c-nu mice bearing K562 and HT29 cells human tumor xenografts. The results show that midazolam decreased the viability of K562 and HT29 cells by inducing apoptosis and S phase cell-cycle arrest in a concentration-dependent manner. Midazolam activated caspase-9, capspase-3 and PARP indicating induction of the mitochondrial intrinsic pathway of apoptosis. Midazolam lowered mitochondrial membrane potential and increased apoptotic DNA fragmentation. Midazolam showed reactive oxygen species (ROS) scavenging activity through inhibition of NADPH oxidase 2 (Nox2) enzyme activity in K562 cells. Midazolam caused inhibition of pERK1/2 signaling which led to inhibition of the anti-apoptotic proteins Bcl-XL and XIAP and phosphorylation activation of the pro-apoptotic protein Bid. Midazolam inhibited growth of HT29 tumors in xenograft mice. Collectively our results demonstrate that midazolam caused growth inhibition of cancer cells via activation of the mitochondrial intrinsic pathway of apoptosis and inhibited HT29 tumor growth in xenograft mice. The mechanism underlying these effects of midazolam might be suppression of ROS production leading to modulation of apoptosis and growth regulatory proteins. These findings present possible clinical implications of midazolam as an anesthetic to relieve pain during in vivo anticancer drug delivery and to enhance anticancer efficacy through its ROS-scavenging and pro-apoptotic properties.

Aims NADPH oxidase (Nox) isozymes that generate intracellular reactive oxygen species (ROS) and Toll-like receptor 2 (TLR2), an inflammatory mediator, are both involved in the development of atherosclerotic lesions. To identify the molecular connection between TLR2 and Nox isozymes in vascular remodelling, we analysed generation of ROS and pro-inflammatory cytokines in aortic smooth muscle cells from Nox1-deficient mice in response to the synthetic triacylated lipoprotein Pam3CSK, a TLR2 agonist. Methods and results We showed that TLR2 signalling stimulates progression of the pro-inflammatory phenotype in mouse aortic smooth muscle cells (MASMCs) through activation of Nox1. We demonstrated the interaction of TLR2 with Nox1 using yeast two-hybrid and co-immunoprecipitation assays. MASMCs from Nox1-deficient mice failed to generate of ROS in response to Pam3CSK4, indicating that Nox1 is essential for TLR2-dependent production of ROS. We also found that Pam3CSK4 stimulated migration of MASMCs from wild-type mice in a Transwell system, but MASMCs from Nox1-deficient mice failed to show this response. Wild-type MASMCs produced matrix metalloprotease 2 in response to Pam3CSK4, whereas Nox1-deficient MASMCs failed to generate this protease. Moreover, stimulation of MASMCs with Pam3CSK4 resulted in increased expression of the pro-inflammatory cytokine macrophage inflammatory protein 2 in a Nox1-dependent manner, leading to enhanced monocyte-endothelial cell adhesion and trans-endothelial migration of U937 cells. Conclusion These data suggest that Nox1 plays an important role in TLR2-mediated intracellular H2O2 generation, activation of matrix metalloprotease 2, and secretion of pro-inflammatory cytokines, which in turn stimulate MASMC migration and vascular remodelling.

Recent studies have suggested that renal Nox is important in the progression of diabetic nephropathy. Therefore, we investigated the effect of a novel pan-NOX-inhibitor, APX-115, on diabetic nephropathy in type 2 diabetic mice. Eight- week-old db/m and db/db mice were treated with APX-115 for 12 weeks. APX-115 was administered by oral gavage at a dose of 60 mg/kg per day. To compare the effects of APX-115 with a dual Nox1/Nox4 inhibitor, db/db mice were treated with GKT137831 according to the same protocol. APX-115 significantly improved insulin resistance in diabetic mice, similar to GKT137831. Oxidative stress as measured by plasma 8-isoprostane level was decreased in the APX-115 group compared with diabetic controls. All lipid profiles, both in plasma and tissues improved with Nox inhibition. APX-115 treatment decreased Nox1, Nox2, and Nox4 protein expression in the kidney. APX-115 decreased urinary albumin excretion and preserved creatinine level. In diabetic kidneys, APX-115 significantly improved mesangial expansion, but GKT137831 did not. In addition, F4/80 infiltration in the adipose tissue and kidney decreased with APX-115 treatment. We also found that TGF-β stimulated ROS generation in primary mouse mesangial cells (pMMCs) from wild-type, Nox1 KO, and Duox1 KO mice, but did not induce Nox activity in pMMCs from Nox2 knockout (KO), Nox4 KO, or Duox2 KO mice. These results indicate that activating Nox2, Nox4, or Duox2 in pMMCs is essential for TGF-β-mediated ROS generation. Our findings suggest that APX-115 may be as effective or may provide better protection than the dual Nox1/Nox4 inhibitor, and pan-Nox inhibition with APX-115 might be a promising therapy for diabetic nephropathy.

It is widely accepted that bacterial infection-mediated inflammation facilitates development of atherosclerosis by activating toll-like receptor (TLR) signaling system. We reasoned that NADPH oxidases (Nox), required for TLR-mediated inflammatory response, are involved in atherogenesis. Here, we show that the activation of Nox4 through TLR5 regulates the inflammation of the endothelium and in atherogenesis. Flagellin-induced interaction between the COOH region of Nox4 and the TIR domain of TLR5 led to H2O2 generation, which in turn promoted the secretion of pro-inflammatory cytokines including IL-8, as well as the expression of ICAM-1 in human aortic endothelial cells (HAECs). Knockdown of the Nox4 in HAECs resulted in attenuated expressions of IL-8 and ICAM-1 leading to a reduction in the adhesion and trans-endothelial migration of monocytes. Challenge of recombinant FliC (rFliC) to the ApoE KO mice with high-fat diet (HFD) resulted in significantly increased atherosclerotic plaque sizes compared to the saline-injected mice. However, an injection of rFliC into the Nox4ApoE DKO mice with HFDs failed to generate atherosclerotic plaque, suggesting that Nox4 deficiency resulted in significant protections against rFliC-mediated atherogenesis. We conclude that TLR5-dependent Nox4 activation and subsequent H2O2 generation play critical roles for the development of atherosclerosis.

Osteoclast cells (OCs) are differentiated from bone marrow-derived macrophages (BMMs) by activation of receptor activator of nuclear factor κB (NF-κB) ligand (RANKL). Activation of NADPH oxidase (Nox) isozymes is involved in RANKL-dependent OC differentiation, implicating Nox isozymes as therapeutic targets for treatment of osteoporosis. Here, we show that a novel pyrazole derivative, Ewha-18278 has high inhibitory potency on Nox isozymes. Blocking the activity of Nox with Ewha-18278 inhibited the responses of BMMs to RANKL, including reactive oxygen species (ROS) generation, activation of mitogen-activated protein (MAP) kinases and NF-κB, and OC differentiation. To evaluate the anti-osteoporotic function of Ewha-18278, the derivative was applied to estrogen-deficient ovariectomized (OVX) ddY mice. Oral administration of Ewha-18278 (10 mg/kg/daily, 4 weeks) into the mice recovered bone mineral density, trabecular bone volume, trabecular bone length, number and thickness, compared to control OVX ddY mice. Moreover, treatment of OVX ddY mice with Ewha-18278 increased bone strength by increasing cortical bone thickness. We provide that Ewha-18278 displayed Nox inhibition and blocked the RANKL-dependent cell signaling cascade leading to reduced differentiation of OCs. Our results implicate Ewha-18278 as a novel therapeutic agent for the treatment of osteoporosis.

In adipose tissue, agonists of the β3-adrenergic receptor (ADRB3) regulate lipolysis, lipid oxidation, and thermogenesis. The deficiency in the thermogenesis induced by neuroblast differentiation-associated protein AHNAK in white adipose tissue (WAT) of mice fed a high-fat diet suggests that AHNAK may stimulate energy expenditure via development of beige fat. Here, we report that AHNAK deficiency promoted browning and thermogenic gene expression in WAT but not in brown adipose tissue of mice stimulated with the ADRB3 agonist CL-316243. Consistent with the increased thermogenesis, Ahnak−/− mice exhibited an increase in energy expenditure, accompanied by elevated mitochondrial biogenesis in WAT depots in response to CL-316243. Additionally, AHNAK-deficient WAT contained more eosinophils and higher levels of type 2 cytokines (IL-4/IL-13) to promote browning of WAT in response to CL-316243. This was associated with enhanced sympathetic tone in the WAT via upregulation of adrb3 and tyrosine hydroxylase (TH) in response to β-adrenergic activation. CL-316243 activated PKA signalling and enhanced lipolysis, as evidenced by increased phosphorylation of hormone-sensitive lipase and release of free glycerol in Ahnak−/− mice compared to wild-type mice. Overall, these findings suggest an important role of AHNAK in the regulation of thermogenesis and lipolysis in WAT via β-adrenergic signalling.

Spleen tyrosine kinase (SYK) is the best known for its involvement in immune receptor signalling, mediated by binding of SYK tandem Src-homology 2 domains to tandem phosphotyrosine in immunoreceptor tyrosine-based activation motifs (ITAMs). ITAM adaptors or ITAM-containing receptor tails mediate signalling from B- and T-cell receptors, Fc receptors and many C-type lectins, including dectin-1. Recent data point to constitutive binding of SYK to the cytoplasmic domain of toll-like receptor-4 (TLR4). This SYK-TLR4 binding increases upon TLR4 dimerization and phosphorylation, and SYK plays a prominent role in TLR4 signalling in response to LPS in neutrophils and monocytes. SYK also plays an important role in TLR4-mediated macrophage responses to minimally oxidized low-density lipoprotein (mmLDL), which is a form of oxidized LDL relevant to development of human atherosclerosis. Interestingly, mmLDL-induced effects in macrophages, which occur via TLR4, are predominantly MyD88 independent. This unmasks the role of the SYK branch of TLR4 signalling, which mediates modest cytokine release via activation of AP-1 transcription and robust reactive oxygen species generation and cytoskeletal rearrangements. The latter results in extensive membrane ruffling and macropinocytosis, leading to lipoprotein uptake and foam cell formation, a hallmark of atherosclerotic lesions. Because inhibitors of SYK activity, such as fostamatinib, are in advanced clinical trials for rheumatoid arthritis and other autoimmune diseases, understanding the role of SYK in signalling via TLR4 is of immediate importance. This signalling pathway seems to be particularly important in TLR4 activation by host-derived, damage-associated molecular pattern ligands, such as mmLDL, relevant to development of atherosclerosis and other chronic inflammatory diseases.

Reactive oxygen species (ROS) including superoxide anion and hydrogen peroxide (H(2)O(2)) are thought to be byproducts of aerobic respiration with damaging effects on DNA, protein, and lipid. A growing body of evidence indicates, however, that ROS are involved in the maintenance of redox homeostasis and various cellular signaling pathways. ROS are generated from diverse sources including mitochondrial respiratory chain, enzymatic activation of cytochrome p450, and NADPH oxidases further suggesting involvement in a complex array of cellular processes. This review summarizes the production and function of ROS. In particular, how cytosolic and membrane proteins regulate ROS generation for intracellular redox signaling will be detailed.

Although mutations in the insulin receptor have been causally implicated with leprechaunism, the full pathophysiology of the syndrome cannot be accounted for by malfunction of this gene alone. We sought to characterize a connection between Wnt-mediated cell signaling and the production of reactive oxygen species (ROS) which revealed a novel mechanistic basis for understanding the pathogenesis of leprechaunism. To identify candidate genes involved in this process, a PCR-based subtractive hybridization was performed. Candidate genes were examined for interaction with the Wnt signaling pathway and ROS generation. We found that Dickkopf 1 (Dkk1), a Wnt inhibitor, is overexpressed in skin fibroblast cells derived from three leprechaunism patients and that the cells showed an impaired response to Wnt2 in terms of beta-catenin-Tcf activation. Knockdown of Dkk1 in the patient cell lines rescued Wnt2-mediated Tcf activation. Concerted action of Wnt2 and knockdown of Dkk1 resulted in enhanced Nox4 expression and PDGF-induced ROS generation compared to parental patient cells. Furthermore, we found that NFATc2 was activated in response to Wnt2 stimulation and directly activates Nox4 expression. These data show a crosstalk between Wnt and ROS pathways which in turn provides new mechanistic insights at the molecular level into the pathogenesis of leprechaunism.