Nogo-B receptor increases glycolysis and the paclitaxel resistance of estrogen receptor-positive breast cancer via the HIF-1α-dependent pathway.

Chemotherapy can improve the prognosis and overall survival of breast cancer patients, but chemoresistance continues a major problem in clinical. Most breast cancer is estrogen receptor (ER) positive but responds less to neoadjuvant or adjuvant chemotherapy than ER-negative breast cancer. The Nogo-B receptor (NgBR) increases the chemoresistance of ER-positive breast cancer by facilitating oncogene signaling pathways. Here, we further investigated the potential role of NgBR as a novel target to overcome glycolysis-dependent paclitaxel resistance in ER-positive breast cancer. NgBR knockdown inhibited glycolysis and promoted paclitaxel-induced apoptosis by attenuating HIF-1α expression in ER-positive breast cancer cells via NgBR-mediated estrogen receptor alpha (ERα)/hypoxia-inducible factor-1 alpha (HIF-1α) and nuclear factor-kappa B subunit (NF-κB)/HIF-1α signaling pathways. A ChIP assay further confirmed that NgBR overexpression not only facilitates ERα binding to HIF-1α and GLUT1 genes but also promotes HIF-1α binding to GLUT1, HK2, and LDHA genes, which further promotes glycolysis and induces paclitaxel resistance. In conclusion, our study suggests that NgBR expression is essential for maintaining the metabolism and paclitaxel resistance of ER-positive breast cancer, and the NgBR can be a new therapeutic target for improving chemoresistance in ER-positive breast cancer.

NOGOB receptor deficiency increases cerebrovascular permeability and hemorrhage via impairing histone acetylation-mediated CCM1/2 expression.

The loss function of cerebral cavernous malformation (CCM) genes leads to most CCM lesions characterized by enlarged leaking vascular lesions in the brain. Although we previously showed that NOGOB receptor (NGBR) knockout in endothelial cells (ECs) results in cerebrovascular lesions in the mouse embryo, the molecular mechanism by which NGBR regulates CCM1/2 expression has not been elucidated. Here, we show that genetic depletion of Ngbr in ECs at both postnatal and adult stages results in CCM1/2 expression deficiency and cerebrovascular lesions such as enlarged vessels, blood-brain-barrier hyperpermeability, and cerebral hemorrhage. To reveal the molecular mechanism, we used RNA-sequencing analysis to examine changes in the transcriptome. Surprisingly, we found that the acetyltransferase HBO1 and histone acetylation were downregulated in NGBR-deficient ECs. The mechanistic studies elucidated that NGBR is required for maintaining the expression of CCM1/2 in ECs via HBO1-mediated histone acetylation. ChIP-qPCR data further demonstrated that loss of NGBR impairs the binding of HBO1 and acetylated histone H4K5 and H4K12 on the promotor of the CCM1 and CCM2 genes. Our findings on epigenetic regulation of CCM1 and CCM2 that is modulated by NGBR and HBO1-mediated histone H4 acetylation provide a perspective on the pathogenesis of sporadic CCMs.

NGBR is required to ameliorate type 2 diabetes in mice by enhancing insulin sensitivity.

The reduction of insulin resistance or improvement of insulin sensitivity is the most effective treatment for type 2 diabetes (T2D). We previously reported that Nogo-B receptor (NGBR), encoded by the NUS1 gene, is required for attenuating hepatic lipogenesis by blocking nuclear translocation of liver X receptor alpha, suggesting its important role in regulating hepatic lipid metabolism. Herein, we demonstrate that NGBR expression was decreased in the liver of obesity-associated T2D patients and db/db mice. NGBR knockout in mouse hepatocytes resulted in increased blood glucose, insulin resistance, and beta-cell loss. High-fat diet (HFD)/streptozotocin (STZ)-treated mice presented the T2D phenotype by showing increased nonesterified fatty acid (NEFA) and triglyceride (TG) in the liver and plasma and increased insulin resistance and beta-cell loss. AAV-mediated NGBR overexpression in the liver reduced NEFA and TG in the liver and circulation and improved liver functions. Consequently, HFD/STZ-treated mice with hepatic NGBR overexpression had increased insulin sensitivity and reduced beta-cell loss. Mechanistically, NGBR overexpression restored insulin signaling of AMPKα1-dependent phosphorylation of AKT and GSK3ß. NGBR overexpression also reduced expression of endoplasmic reticulum stress-associated genes in the liver and skeletal muscle to improve insulin sensitivity. Together, our results reveal that NGBR is required to ameliorate T2D in mice, providing new insight into the role of hepatic NGBR in insulin sensitivity and T2D treatment.

Nogo-B receptor is required for stabilizing TGF-ß type I receptor and promotes the TGF-ß1-induced epithelial-to-mesenchymal transition of non-small cell lung cancer.

Background and Objective: Metastasis is the leading cause of death in patients with advanced non-small cell lung cancer (NSCLC), and epithelial-mesenchymal transition (EMT) is a crucial event in the metastasis of NSCLC. Our previous works demonstrated that NgBR promoted EMT in NSCLC. However, the molecular mechanism was unclear. Methods: TGF-ß1 was used to induce EMT process of NSCLC cells. The biological functions of NgBR in promoting TGF-ß1-induced NSCLC metastasis were studied by gain- and loss-of-function assays both in vitro and in vivo. The underlying mechanisms were studied using molecular biology assays. Results: We found that knockdown of NgBR inhibited TGF-ß1-induced cell migration and invasion in NSCLC cells. In contrast, NgBR overexpression promoted TGF-ß1-induced EMT of A549 cells. Mechanically, we found that knockdown of NgBR facilitated ubiquitination and degradation of TßRI, leading to downregulation of TßRI expression in NSCLC cells. Moreover, we confirmed a positive correlation between NgBR and TßRI in NSCLC tissues. Conclusions: Our findings provide a novel role of NgBR in modulating TGF-ß1-induced EMT and propose NgBR as a new therapeutic target for treating NSCLC patients.

Reduced Nogo expression inhibits diet-induced metabolic disorders by regulating ChREBP and insulin activity.

BACKGROUND & AIMS: Chronic overconsumption of a high-carbohydrate diet leads to steatosis and its associated metabolic disorder and, eventually, to non-alcoholic fatty liver disease. Carbohydrate-responsive element binding protein (ChREBP) and insulin regulate de novo lipogenesis from glucose. Herein, we studied the effect of reticulon-4 (Nogo) expression on diet-induced metabolic disorders in mice. METHODS: Nogo-deficient (Nogo-/-) and littermate control [wild-type (WT)] mice were fed a high-glucose or high-fructose diet (HGD/HFrD) to induce metabolic disorders. The effects of Nogo small interfering (si) RNA (siRNA) on HFrD-induced metabolic disorders were investigated in C57BL/6J mice. RESULTS: HGD/HFrD induced steatosis and its associated metabolic disorders in WT mice by activating ChREBP and impairing insulin sensitivity. They also activated Nogo-B expression, which in turn inhibited insulin activity. In response to HGD/HFrD feeding, Nogo deficiency enhanced insulin sensitivity and energy metabolism to reduce the expression of ChREBP and lipogenic molecules, activated AMP-activated catalytic subunit α, peroxisome proliferator activated receptor α and fibroblast growth factor 21, and reduced endoplasmic reticulum (ER) stress and inflammation, thereby blocking HGD/HFrD-induced hepatic lipid accumulation, insulin resistance and other metabolic disorders. Injection of Nogo siRNA protected C57BL/6J mice against HFrD-induced metabolic disorders by ameliorating insulin sensitivity, ChREBP activity, ER stress and inflammation. CONCLUSIONS: Our study identified Nogo as an important mediator of insulin sensitivity and ChREBP activity. Reduction of Nogo expression is a potential strategy for the treatment of high-carbohydrate diet-induced metabolic complications. LAY SUMMARY: Nogo deficiency blocks high-carbohydrate diet-induced glucose intolerance and insulin resistance, while increasing glucose/lipid utilisation and energy expenditure. Thus, reduction of Nogo expression protects against high-carbohydrate diet-induced body-weight gain, hepatic lipid accumulation and the associated metabolic disorders, indicating that approaches inhibiting Nogo expression can be applied for the treatment of diseases associated with metabolic disorders.

Rosiglitazone alleviates intrahepatic cholestasis induced by α-naphthylisothiocyanate in mice: The role of circulating 15-deoxy-Δ12,14 -PGJ2 and Nogo.

BACKGROUND AND PURPOSE: Intrahepatic cholestasis is mainly caused by dysfunction of bile secretion and has limited effective treatment. Rosiglitazone is a synthetic agonist of PPARγ, whose endogenous agonist is 15-deoxy-Δ12,14 -PGJ2 (15d-PGJ2 ). Reticulon 4B (Nogo-B) is the detectable Nogo protein family member in the liver and secreted into circulation. Here, we determined if rosiglitazone can alleviate intrahepatic cholestasis in mice. EXPERIMENTAL APPROACH: Wild-type, hepatocyte-specific PPARγ or Nogo-B knockout mice received intragastric administration of α-naphthylisothiocyanate (ANIT) and/or rosiglitazone, followed by determination of intrahepatic cholestasis and the involved mechanisms. Serum samples from primary biliary cholangitis (PBC) patients and non-PBC controls were analysed for cholestasis-related parameters. KEY RESULTS: Rosiglitazone prevented wild type, but not hepatocyte-specific PPARγ deficient mice from developing ANIT-induced intrahepatic cholestasis by increasing expression of bile homeostatic proteins, reducing hepatic necrosis, and correcting abnormal serum parameters and enterohepatic circulation of bile. Nogo-B knockout provided protection similar to that of rosiglitazone treatment. ANIT-induced intrahepatic cholestasis decreased 15d-PGJ2 but increased Nogo-B in serum, and both were corrected by rosiglitazone. Nogo-B deficiency in the liver increased 15d-PGJ2 production, thereby activating expression of PPARγ and bile homeostatic proteins. Rosiglitazone and Nogo-B deficiency also alleviated cholestasis-associated dyslipidemia. In addition, rosiglitazone reduced symptoms of established intrahepatic cholestasis in mice. In serum from PBC patients, the decreased 15d-PGJ2 and increased Nogo-B levels were significantly correlated with classical cholestatic markers. CONCLUSIONS AND IMPLICATIONS: Levels of 15d-PGJ2 and Nogo are important biomarkers for intrahepatic cholestasis. Synthetic agonists of PPARγ could be used for treatment of intrahepatic cholestasis and cholestasis-associated dyslipidemia.

Epigenetically Down-Regulated Acetyltransferase PCAF Increases the Resistance of Colorectal Cancer to 5-Fluorouracil.

Only 10%-20% of colorectal cancer (CRC) patients observe effective responses to 5-fluorouracil (5-FU) based chemo-treatment. We used real-time PCR array and Western blot analysis to examine the expression alteration of acetyltransferases and deacetylases in 5-FU resistant CRC cell lines as compared to their respective parental CRC cell lines. Unlike other acetyltransferases and deacetylases, we found that the expression of acetyltransferase P300/CBP-associated factor (PCAF) is consistently decreased in three 5-FU resistant CRC cell lines. Similarly, knockdown of PCAF in HCT116 CRC parental cell line also increases the resistance to 5-FU and attenuates 5-FU-induced apoptosis. Mechanistically, we demonstrated that increased binding of trimethylated histone H3K27 in the promoter region of PCAF attenuated its transcription in 5-FU resistant HCT116/5-FU cells. Decreased PCAF impairs the acetylation of p53 and attenuates the p53-dependent transcription of p21, which results in the increased cyclin D1 and phosphorylation of Retinoblastoma 1. Conversely, overexpression of PCAF in CRC cell lines increases p21 and their susceptibility to 5-FU in vitro and in vivo. However, knockdown of p21 abolishes the beneficial effects of PCAF overexpression on increasing the sensitivity of HCT116/5-FU cells to 5-FU. Also, the reduced intensity of PCAF immunostaining was observed in the precancerous lesion, and microarray data from the public database further demonstrated the association between PCAF down-regulation and poor survival outcome. Our data suggest that PCAF-mediated p53 acetylation is an essential regulatory mechanism for increasing the susceptibility of CRC to 5-FU.

Sema3E/PlexinD1 signaling inhibits postischemic angiogenesis by regulating endothelial DLL4 and filopodia formation in a rat model of ischemic stroke.

Angiogenesis is a crucial defense response to hypoxia that regulates the process of raising the promise of long-term neurologic recovery during the management of stroke. A high expression of antiangiogenic factors leads to the loss of neovascularization capacity in pathologic conditions. We have previously documented an impairment of the cerebral vessel perfusion and neovascularization in the cortex neighboring the stroke-induced lesion, which was accompanied by an activation of semaphorin 3E (Sema3E)/PlexinD1 after ischemic stroke. In this study, we employed micro-optical sectioning tomography to fully investigate the details of the vascular pattern, including the capillaries. We found that after transient middle cerebral artery occlusion, inhibiting PlexinD1 signaling led to an organized recovery of the vascular network in the ischemic area. We then further explored the possible mechanisms. In vivo, Sema3E substantially decreased dynamic delta-like 4 (DLL4) expression. In cultured brain microvascular endothelial cells, Sema3E down-regulated DLL4 expression via inhibiting Ras-related C3 botulinum toxin substrate 1-induced JNK phosphorylation. At the microcosmic level, Sema3E/PlexinD1 signaling promoted F-actin disassembly and focal adhesion reduction by activating the small guanosine triphosphatase Ras homolog family member J by releasing RhoGEF Tuba from direct binding to PlexinD1, thus mediating endothelial cell motility and filopodia retraction. Our study reveals that Sema3E/PlexinD1 signaling, which suppressed endothelial DLL4 expression, cell motility, and filopodia formation, is expected to be a novel druggable target for angiogenesis during poststroke progression.-Zhou, Y.-F., Chen, A.-Q., Wu, J.-H., Mao, L., Xia, Y.-P., Jin, H.-J., He, Q.-W., Miao, Q. R., Yue, Z.-Y., Liu, X.-L., Huang, M., Li, Y.-N., Hu, B. Sema3E/PlexinD1 signaling inhibits postischemic angiogenesis by regulating endothelial DLL4 and filopodia formation in a rat model of ischemic stroke.

Gd-Metallofullerenol nanoparticles cause intracellular accumulation of PDGFR-α and morphology alteration of fibroblasts.

Gadolinium-metallofullerenols (Gd@C82(OH)22) are a promising agent for cancer therapy and have shown beneficial effects in regulating the tumor microenvironment with low toxicity. However, the underlying mechanism by which Gd@C82(OH)22 interacts with fibroblasts remains unclear. In order to explore the critical role that activated fibroblasts play in tumorigenesis and fibrosis, we investigated the regulatory effect of Gd@C82(OH)22 in fibroblast activation and oncogenic transformation, and found that the PDGFR-α is an essential molecule in modulating the morphology and functional changes in fibroblasts after Gd@C82(OH)22 treatment. Apart from increasing the PDGFR-α protein level, Gd@C82(OH)22 nanoparticles also significantly increased the protein level of Rab5, which is required for regulating PDGFR-α endosomal recycling. The Rab5-mediated recycling of PDGFR-α maybe attributed to the Gd@C82(OH)22 regulated inhibition of fibroblast activation. Overall, our work demonstrated that Gd@C82(OH)22 nanoparticles can attenuate the PDGF-stimulated phosphorylation of PDGFR-α in fibroblasts and suppress the fibroblast activation by interrupting endosomal recycling. These findings may be contributed to the collagen accumulation for encaging cancer.

Nogo-B receptor increases the resistance to tamoxifen in estrogen receptor-positive breast cancer cells.

BACKGROUNDS: Tamoxifen is typically used to treat patients with estrogen receptor alpha (ERα)-positive breast cancer. However, 30% of these patients gain acquired resistance to tamoxifen during or after tamoxifen treatment. As a Ras modulator, Nogo-B receptor (NgBR) is required for tumorigenesis through the signaling crosstalk with epidermal growth factor (EGF) receptor (EGFR)-mediated pathways. NgBR is highly expressed in many types of cancer cells and regulates the sensitivity of hepatocellular carcinoma to chemotherapy. In this study, we found the expression of NgBR is increased in tamoxifen-resistant ERα-positive breast cancer cells. METHODS: Tamoxifen-resistant ERα-positive MCF-7 and T47D breast cancer cell lines were established by culturing with gradually increased concentration of 4-hydroxytamoxifen (4-OHT). The effects of NgBR on tamoxifen resistance was determined by depleting NgBR in these cell lines using previously validated small interfering RNA (siRNA). The effects of 4-OHT on cell viability and apoptosis were determined using well-accepted methods such as clonogenic survival assay and Annexin V/propidium iodide staining. The alteration of EGF-stimulated signaling and gene expression was determined by western blot analysis and real-time PCR, respectively. RESULTS: NgBR knockdown with siRNA attenuates EGF-induced phosphorylation of ERα and restores the sensitivity to tamoxifen in ERα-positive breast cancer cells. Mechanistically, our data demonstrated that NgBR knockdown increases the protein levels of p53 and decreases survivin, which is an apoptosis inhibitor. CONCLUSIONS: These results suggested that NgBR is a potential therapeutic target for increasing the sensitivity of ERα-positive breast cancer to tamoxifen.

Sema3E/PlexinD1 inhibition is a therapeutic strategy for improving cerebral perfusion and restoring functional loss after stroke in aged rats.

Brain tissue survival and functional recovery after ischemic stroke greatly depend on cerebral vessel perfusion and functional collateral circulation in the ischemic area. Semaphorin 3E (Sema3E), one of the class 3 secreted semaphorins, has been demonstrated to be a critical regulator in embryonic and postnatal vascular formation via binding to its receptor PlexinD1. However, whether Sema3E/PlexinD1 signaling is involved in poststroke neovascularization remains unknown. To determine the contribution of Sema3E/PlexinD1 signaling to poststroke recovery, aged rats (18 months) were subjected to a transient middle cerebral artery occlusion. We found that depletion of Sema3E/PlexinD1 signaling with lentivirus-mediated PlexinD1-specific-shRNA improves tissue survival and functional outcome. Sema3E/PlexinD1 inhibition not only increases cortical perfusion but also ameliorates blood-brain barrier damage, as determined by positron emission tomography and magnetic resonance imaging. Mechanistically, we demonstrated that Sema3E suppresses endothelial cell proliferation and angiogenic capacity. More importantly, Sema3E/PlexinD1 signaling inhibits recruitment of pericytes by decreasing production of platelet derived growth factor-BB in endothelial cells. Overall, our study revealed that inhibition of Sema3E/PlexinD1 signaling in the ischemic penumbra, which increases both endothelial angiogenic capacity and recruitment of pericytes, contributed to functional neovascularization and blood-brain barrier integrity in the aged rats. Our findings imply that Sema3E/PlexinD1 signaling is a novel therapeutic target for improving brain tissue survival and functional recovery after ischemic stroke.

Delivery of small interfering RNA against Nogo-B receptor via tumor-acidity responsive nanoparticles for tumor vessel normalization and metastasis suppression.

Nogo-B receptor (NgBR) plays fundamental roles in regulating angiogenesis, vascular development, and the epithelial-mesenchymal transition (EMT) of cancer cells. However, the therapeutic effect of NgBR blockade on tumor vasculature and malignancy is unknown, investigations on which requires an adequate delivery system for small interfering RNA against NgBR (NgBR siRNA). Here a surface charge switchable polymeric nanoparticle that was sensitive to the slightly acidic tumor microenvironment was developed for steady delivery of NgBR siRNA to tumor tissues. The nanoformulation was constructed by conjugating 2, 3-dimethylmaleic anhydride (DMMA) molecules to the surface amines of micelles formed by cationic co-polymer poly(lactic-co-glycolic acid)2-poly(ethylenimine) and subsequent absorption of NgBR siRNAs. The nanoparticles remained negatively charged in physiological condition and smartly converted to positive surface charge due to tumor-acidity-activated shedding of DMMA. The charge conversion facilitated cellular uptake of siRNAs and in turn efficiently depleted the expression of NgBR in tumor-bearing tissues. Silencing of NgBR suppressed endothelial cell migration and tubule formation, and reverted the EMT process of breast cancer cells. Delivery of the nanoformulation to mice bearing orthotopic breast carcinoma showed no effect on tumor growth, but led to remarkable decrease of distant metastasis by normalizing tumor vessels and suppressing the EMT of breast cancer cells. This study demonstrated that NgBR is a promising therapeutic target in abnormal tumor vasculature and aggressive cancer cells, and the tumor-responsive nanoparticle with the feature of charge transformation offers great potential for tumor-specific delivery of gene therapeutics.

Nogo-B receptor promotes epithelial-mesenchymal transition in non-small cell lung cancer cells through the Ras/ERK/Snail1 pathway.

Nogo-B receptor (NgBR) is a specific receptor of Nogo-B that regulates vascular remodeling and angiogenesis. Previously, we found that NgBR promotes the membrane translocation and activation of Ras in breast cancer cells and enhances the chemoresistance of hepatocellular carcinoma cells to 5-fluorouracil. However, the role of NgBR in lung cancer has not yet been elucidated. In the present study, we found that NgBR knockdown inhibited epithelial-mesenchymal transition (EMT) in non-small cell lung cancer (NSCLC) cells in vitro and metastasis of NSCLC cells in vivo. In contrast, NgBR overexpression promoted EMT in and lung metastasis of NSCLC cells. At the molecular level, NgBR modulated the expression of EMT-related proteins and enhanced the protein expression of Snail1, a crucial transcription factor that represses epithelial cell protein marker E-cadherin. Moreover, we found that NgBR overexpression promoted the membrane localization of Ras and activation of downstream MEK/ERK signaling pathway and that NgBR knockdown by using a specific shRNA inversely affected the expression of EMT-related proteins in NSCLC cells. Thus, our results provide novel insights on the regulatory role of NgBR in the metastasis of NSCLC that should be investigated further for developing a therapeutic strategy for treating patients with NSCLC.

Nogo-B receptor increases the resistance of estrogen receptor positive breast cancer to paclitaxel.

Intrinsic or acquired chemoresistance is a hurdle in oncology. Only 7%-16% of estrogen receptor α (ERα) positive breast cancer cases achieve a pathological complete response (pCR) after neo-adjuvant chemotherapy. Nogo-B receptor (NgBR) is a cell surface receptor that binds farnesylated Ras and promotes Ras translocation to the plasma membrane. Here, we demonstrate NgBR as a potential therapeutic target for ERα positive breast cancer patients to attenuate paclitaxel resistance. NgBR knockdown enhanced paclitaxel-induced cell apoptosis by modulating expression of p53 and survivin in ERα positive breast cancer cells via NgBR-mediated PI3K/Akt and MAPK/ERK signaling pathways. NgBR knockdown attenuated either 17ß-estradiol or epidermal growth factor stimulated phosphorylation of ERα at Serine 118 residue. The ChIP-PCR assay further demonstrated that NgBR knockdown decreased ERα binding to the estrogen response element (ERE) of the ERα target gene and increased the binding of p53 to the promoter region of survivin to attenuate survivin transcription. In summary, our data suggest that NgBR expression is essential to promoting ERα positive breast cancer cell resistance to paclitaxel. Findings from this study implicate a novel therapeutic target for treating ERα positive breast cancer in neo-adjuvant/adjuvant chemotherapy.

Precision design of nanomedicines to restore gemcitabine chemosensitivity for personalized pancreatic ductal adenocarcinoma treatment.

Low chemosensitivity considerably restricts the therapeutic efficacy of gemcitabine (GEM) in pancreatic cancer treatment. Using immunohistochemical evaluation, we investigated that decreased expression of human equilibrative nucleoside transporter-1 (hENT1, which is the major GEM transporter across cell membranes) and increased expression of ribonucleotide reductase subunit 2 (RRM2, which decreases the cytotoxicity of GEM) was associated with low GEM chemosensitivity. To solve these problems, we employed a nanomedicine-based formulation of cationic liposomes for co-delivery of GEM along with siRNA targeting RRM2. Due to the specific endocytic uptake mechanism of nanocarriers and gene-silencing effect of RRM2 siRNA, this nanomedicine formulation significantly increased GEM chemosensitivity in tumor models of genetically engineered Panc1 cells with low hENT1 or high RRM2 expression. Moreover, in a series of patient-derived cancer cells, we demonstrated that the therapeutic benefits of the nanomedicine formulations were associated with the expression levels of hENT1 and RRM2. In summary, we found that the essential factors of GEM chemosensitivity were the expression levels of hENT1 and RRM2, and synthesized nanoformulations can overcome these problems. This unique design of nanomedicine not only provides a universal platform to enhance chemosensitivity but also contributes to the precision design and personalized treatment in nanomedicine.

Activation of hepatic Nogo-B receptor expression-A new anti-liver steatosis mechanism of statins.

Deficiency of hepatic Nogo-B receptor (NgBR) expression activates liver X receptor α (LXRα) in an adenosine monophosphate-activated protein kinase α (AMPKα)-dependent manner, thereby inducing severe hepatic lipid accumulation and hypertriglyceridemia. Statins have been demonstrated non-cholesterol lowering effects including anti-nonalcoholic fatty liver disease (NAFLD). Herein, we investigated if the anti-NAFLD function of statins depends on activation of NgBR expression. In vivo, atorvastatin protected apoE deficient or NgBR floxed, but not hepatic NgBR deficient mice, against Western diet (WD)-increased triglyceride levels in liver and serum. In vitro, statins reduced lipid accumulation in nonsilencing small hairpin RNA-transfected (shNSi), but not in NgBR small hairpin RNA-transfected (shNgBRi) HepG2 cells. Inhibition of cellular lipid accumulation by atorvastatin is related to activation of AMPKα, and inactivation of LXRα and lipogenic genes. Statin also inhibited expression of oxysterol producing enzymes. Associated with changes of hepatic lipid levels by WD or atorvastatin, NgBR expression was inversely regulated. At cellular levels, statins increased NgBR mRNA and protein expression, and NgBR protein stability. In contrast to reduced cellular cholesterol levels by statin or ß-cyclodextrin, increased cellular cholesterol levels decreased NgBR expression suggesting cholesterol or its synthesis intermediates inhibit NgBR expression. Indeed, mevalonate, geranylgeraniol or geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate or farnesol, blocked atorvastatin-induced NgBR expression. Furthermore, we determined that induction of hepatic NgBR expression by atorvastatin mainly depended on inactivation of extracellular signal-regulated kinases 1/2 (ERK1/2) and protein kinase B (Akt). Taken together, our study demonstrates that statins inhibit NAFLD mainly through activation of NgBR expression.

Activation of Adiponectin Receptor Regulates Proprotein Convertase Subtilisin/Kexin Type 9 Expression and Inhibits Lesions in ApoE-Deficient Mice.

OBJECTIVE: The reduced adiponectin levels are associated with atherosclerosis. Adiponectin exerts its functions by activating adiponectin receptor (AdipoR). Proprotein convertase subtilisin kexin type 9 (PCSK9) degrades LDLR protein (low-density lipoprotein receptor) to increase serum LDL-cholesterol levels. PCSK9 expression can be regulated by PPARγ (peroxisome proliferator-activated receptor γ) or SREBP2 (sterol regulatory element-binding protein 2). The effects of AdipoR agonists on PCSK9 and LDLR expression, serum lipid profiles, and atherosclerosis remain unknown. APPROACH AND RESULTS: At cellular levels, AdipoR agonists (ADP355 and AdipoRon) induced PCSK9 transcription/expression that solely depended on activation of PPAR-responsive element in the PCSK9 promoter. AdipoR agonists induced PPARγ expression; thus, the AdipoR agonist-activated PCSK9 expression/production was impaired in PPARγ deficient hepatocytes. Meanwhile, AdipoR agonists transcriptionally activated LDLR expression by activating SRE in the LDLR promoter. Moreover, AMP-activated protein kinase α (AMPKα) was involved in AdipoR agonist-activated PCSK9 expression. In wild-type mice, ADP355 increased PCSK9 and LDLR expression and serum PCSK9 levels, which was associated with activation of PPARγ, AMPKα and SREBP2 and reduction of LDL-cholesterol levels. In contrast, ADP355 reduced PCSK9 expression/secretion in apoE-deficient (apoE-/-) mice, but it still activated hepatic LDLR, PPARγ, AMPKα, and SREBP2. More importantly, ADP355 inhibited lesions in en face aortas and sinus lesions in aortic root in apoE-/- mice with amelioration of lipid profiles. CONCLUSIONS: Our study demonstrates that AdipoR activation by agonists regulated PCSK9 expression differently in wild-type and apoE-/- mice. However, ADP355 activated hepatic LDLR expression and ameliorated lipid metabolism in both types of mice and inhibited atherosclerosis in apoE-/- mice.