CD36 regulates macrophage and endothelial cell activation and multinucleate giant cell formation in anti neutrophil cytoplasm antibody vasculitis.

OBJECTIVE: To investigate CD36 in ANCA-associated vasculitis (AAV), a condition characterized by monocyte/macrophage activation and vascular damage. METHODS: CD36 expression was assessed in AAV patients and healthy controls (HC). The impact of palmitic acid (PA) stimulation on multinucleate giant cell (MNGC) formation, macrophage, and endothelial cell activation, with or without CD36 knockdown, was examined. RESULTS: CD36 was overexpressed on AAV patients' monocytes compared to HC, regardless of disease activity. AAV patients exhibited elevated soluble CD36 levels in serum and plasma and PR3-ANCA patients' monocytes demonstrated increased MNGC formation following PA stimulation compared to HC. PA stimulation of macrophages or endothelial cells resulted in heightened CD36 expression, cell activation, increased macrophage migration inhibitory factor (MIF) production, and c-Myc expression, with attenuation upon CD36 knockdown. CONCLUSION: CD36 participates in macrophage and endothelial cell activation and MNGC formation, features of AAV pathogenesis. AAV treatment may involve targeting CD36 or MIF.

Six-hour time-restricted feeding inhibits lung cancer progression and reshapes circadian metabolism.

BACKGROUND: Accumulating evidence has suggested an oncogenic effect of diurnal disruption on cancer progression. To test whether targeting circadian rhythm by dietary strategy suppressed lung cancer progression, we adopted 6-h time-restricted feeding (TRF) paradigm to elucidate whether and how TRF impacts lung cancer progression. METHODS: This study used multiple lung cancer cell lines, two xenograft mouse models, and a chemical-treated mouse lung cancer model. Stable TIM-knockdown and TIM-overexpressing A549 cells were constructed. Cancer behaviors in vitro were determined by colony formation, EdU proliferation, wound healing, transwell migration, flow cytometer, and CCK8 assays. Immunofluorescence, pathology examinations, and targeted metabolomics were also used in tumor cells and tissues. mCherry-GFP-LC3 plasmid was used to detect autophagic flux. RESULTS: We found for the first time that compared to normal ad libitum feeding, 6-h TRF inhibited lung cancer progression and reprogrammed the rhythms of metabolites or genes involved in glycolysis and the circadian rhythm in tumors. After TRF intervention, only timeless (TIM) gene among five lung cancer-associated clock genes was found to consistently align rhythm of tumor cells to that of tumor tissues. Further, we demonstrated that the anti-tumor effect upon TRF was partially mediated by the rhythmic downregulation of the TIM and the subsequent activation of autophagy. Combining TRF with TIM inhibition further enhanced the anti-tumor effect, comparable to treatment efficacy of chemotherapy in xenograft model. CONCLUSIONS: Six-hour TRF inhibits lung cancer progression and reshapes circadian metabolism, which is partially mediated by the rhythmic downregulation of the TIM and the subsequent upregulation of autophagy.

[Deletion of CD36 gene ameliorates glucose metabolism abnormality induced by high-fat diet and promotes liver lipid accumulation].

This study aimed to investigate the effects and the underlying mechanism of CD36 gene on glucose and lipid metabolism disorder induced by high-fat diet in mice. Wild type (WT) mice and systemic CD36 knockout (CD36-/-) mice were fed with high-fat diet for 14 weeks (n = 12). Mice were intraperitoneally injected with glucose (1 g/kg) or insulin (5 units/kg) to perform glucose tolerance test (GTT) or insulin tolerance test (ITT). Liver lipid deposition was observed by HE staining, and the contents of total triglyceride (TG), free fatty acid (FFA), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the serum were determined by automatic biochemical analyzer. Real-time PCR and Western blot were used to detect insulin signaling pathways in liver and muscle tissues of mice. The mRNA levels of genes encoding phosphoenolpyruvate carboxykinase (PEPCK) in primary hepatocytes of mice were detected by real-time PCR, and glucose detection kit was used to detect gluconeogenesis. Co-immunoprecipitation (Co-IP) and ELISA were used to detect insulin receptor ß (IRß) tyrosine phosphorylation in mouse muscle. Real-time PCR and immunofluorescence staining (IF) were used to detect the expression and location of glucose transporter 4 (GLUT4) in muscle of mice. After high-fat diet feeding, serum FFA, TG, AST and ALT levels of CD36-/- mice were significantly higher than WT mice (P < 0.05). The appearance of CD36-/- mouse liver presented fatty degeneration, and HE staining results showed increased lipid accumulation in the liver, suggesting that CD36 knockout promoted the occurrence of fatty liver. However, CD36-/- mice showed decreased fasting glucose levels, increased glucose tolerance, and decreased insulin tolerance compared with WT mice (P < 0.05), suggesting that CD36 knockout protects against the abnormal glucose metabolism induced by high-fat diet. Compared with WT mice, there was no significant difference in insulin signaling pathway in CD36-/- mouse liver, and there were no significant differences in PEPCK expression and gluconeogenesis between the two groups of primary hepatocytes. In muscle tissue, Co-IP and ELISA experiments showed that the phosphorylation level of IRß tyrosine was significantly increased in CD36-/- mice compared with that in WT mice. Besides, the levels of p-AKT in CD36-/- mouse muscle were significantly increased (P < 0.05). At the same time, IF experiment indicated that GLUT4 localization in cell membrane was enhanced in the muscle of CD36-/- mice, indicating that insulin sensitivity and glucose utilization ability were enhanced in CD36-/- mouse muscle. The results suggested that deletion of CD36 gene increased lipid accumulation in liver of mice with high-fat diet, but had no significant effect on liver gluconeogenesis. CD36 deficiency improves the abnormal glucose metabolism in mice with high-fat diet mainly through improving insulin sensitivity of muscle tissue and promoting GLUT4-mediated glucose utilization.

[Lipopolysaccharide inhibits lipophagy in HepG2 cells via activating mTOR pathway].

This study aimed to investigate the effect of lipopolysaccharide (LPS) on lipophagy in hepatocytes and the underlying mechanism. Human hepatoma cell line HepG2 was cultured in vitro, treated with 0.1 mmol/L palmitic acid (PA), and then divided into control group (0 µg/mL LPS), LPS group (10 µg/mL LPS), LPS+DMSO group and LPS+RAPA (rapamycin, 10 µmol/L) group. Lipid accumulation in hepatocytes was observed by oil red O staining. The autophagic flux of the cells was assessed using confocal laser scanning microscope after being transfected with autophagy double-labeled adenovirus (mRFP-GFP-LC3). The level of intracellular lipophagy was visualized by the colocalization of lipid droplets (BODIPY 493/503 staining) and lysosomes (lysosome marker, lysosomal associated membrane protein 1, LAMP1). The expression levels of mammalian target of rapamycin (mTOR), phosphorylated mTOR (p-mTOR), ribosome protein subunit 6 kinase 1 (S6K1), p-S6K1, LC3II/I and P62 protein were examined by Western blot. The results showed that the number of red lipid droplets stained with oil red O was significantly increased in LPS group compared with that in control group (P < 0.001). Moreover, in LPS group, the number of autophagosomes was increased, while the number of autophagolysosomes and the colocalization rate of LAMP1 and BODIPY were significantly decreased (P < 0.05). Meanwhile, the ratios of p-mTOR/mTOR and p-S6K1/S6K1, the ratio of LC3II/LC3I and the protein expression of P62 were significantly increased (P < 0.05) in LPS group. Furthermore, compared with LPS+DMSO group, RAPA treatment obviously reduced the number of lipid droplets and autophagosomes, and raised the number of autophagolysosomes and the colocalization rate of LAMP1 and BODIPY (P < 0.05). In conclusion, the results demonstrate that LPS inhibits lipophagy in HepG2 cells via activating mTOR signaling pathway, thereby aggravating intracellular lipid accumulation.

(Pro)renin Receptor Inhibition Reprograms Hepatic Lipid Metabolism and Protects Mice From Diet-Induced Obesity and Hepatosteatosis.

RATIONALE: An elevated level of plasma LDL (low-density lipoprotein) is an established risk factor for cardiovascular disease. Recently, we reported that the (pro)renin receptor ([P]RR) regulates LDL metabolism in vitro via the LDLR (LDL receptor) and SORT1 (sortilin-1), independently of the renin-angiotensin system. OBJECTIVES: To investigate the physiological role of (P)RR in lipid metabolism in vivo. METHODS AND RESULTS: We used N-acetylgalactosamine modified antisense oligonucleotides to specifically inhibit hepatic (P)RR expression in C57BL/6 mice and studied the consequences this has on lipid metabolism. In line with our earlier report, hepatic (P)RR silencing increased plasma LDL-C (LDL cholesterol). Unexpectedly, this also resulted in markedly reduced plasma triglycerides in a SORT1-independent manner in C57BL/6 mice fed a normal- or high-fat diet. In LDLR-deficient mice, hepatic (P)RR inhibition reduced both plasma cholesterol and triglycerides, in a diet-independent manner. Mechanistically, we found that (P)RR inhibition decreased protein abundance of ACC (acetyl-CoA carboxylase) and PDH (pyruvate dehydrogenase). This alteration reprograms hepatic metabolism, leading to reduced lipid synthesis and increased fatty acid oxidation. As a result, hepatic (P)RR inhibition attenuated diet-induced obesity and hepatosteatosis. CONCLUSIONS: Collectively, our study suggests that (P)RR plays a key role in energy homeostasis and regulation of plasma lipids by integrating hepatic glucose and lipid metabolism.

Gut microbiota dysbiosis-induced activation of the intrarenal renin-angiotensin system is involved in kidney injuries in rat diabetic nephropathy.

Some studies have shown that gut microbiota along with its metabolites is closely associated with diabetic mellitus (DM). In this study we explored the relationship between gut microbiota and kidney injuries of early diabetic nephropathy (DN) and its underlying mechanisms. Male SD rats were intraperitoneally injected with streptozotocin to induce DM. DM rats were orally administered compound broad-spectrum antibiotics for 8 weeks. After the rats were sacrificed, their blood, urine, feces, and renal tissues were harvested for analyses. We found that compared with the control rats, DM rats had abnormal intestinal microflora, increased plasma acetate levels, increased proteinuria, thickened glomerular basement membrane, and podocyte foot process effacement in the kidneys. Furthermore, the protein levels of angiotensin II, angiotensin-converting enzyme, and angiotensin II type 1 receptor in the kidneys of DM rats were significantly increased. Administration of broad-spectrum antibiotics in DM rats not only completely killed most intestinal microflora, but also significantly lowered the plasma acetate levels, inhibited intrarenal RAS activation, and attenuated kidney damage. Finally, we showed that plasma acetate levels were positively correlated with intrarenal angiotensin II protein expression (r = 0.969, P < 0.001). In conclusion, excessive acetate produced by disturbed gut microbiota might be involved in the kidney injuries of early DN through activating intrarenal RAS.

Ablation of cytochrome P450 omega-hydroxylase 4A14 gene attenuates hepatic steatosis and fibrosis.

Nonalcoholic fatty liver disease (NAFLD) is characterized by simple hepatic steatosis (SS), nonalcoholic steatohepatitis (NASH), hepatic fibrosis, and cirrhosis. Dysregulated fatty acid metabolism in the liver plays a critical role in the pathogenesis of NAFLD. Cytochrome P450 omega-hydroxylase 4A14 (CYP4A14) is a homolog of human CYP4A hydroxylase that catalyzes omega-hydroxylation of medium-chain fatty acids and arachidonic acid in mice. The goal of this study was to determine the role of CYP4A14 in the development and the progression of NAFLD. Here, we showed that hepatic CYP4A expression was up-regulated in the livers of patients and three murine models of NAFLD. Adenovirus-mediated overexpression of CYP4A14 in the livers of C57BL/6 mice resulted in a fatty liver phenotype with a significant increase in hepatic fatty acid translocase (FAT/CD36) expression. In contrast, CYP4A14 gene-deficient mice fed a high-fat diet or a methionine and choline-deficient (MCD) diet exhibited attenuated liver lipid accumulation and reduced hepatic FAT/CD36 expression. In addition, hepatic inflammation and fibrosis was markedly ameliorated in MCD diet-fed CYP4A14-deficient mice. Collectively, CYP4A14 plays an important role in the pathogenesis of both SS and NASH and may represent a potential therapeutic target for the treatment of NAFLD.

C1q/tumor necrosis factor-related protein-3 improves renal fibrosis via inhibiting notch signaling pathways.

C1q/tumor necrosis factor-related protein-3 (CTRP3) has been extensively reported as an important role involved in antifibrosis, antiapoptosis, and anti-inflammation. However, the role of CTRP3 involved in renal fibrosis remains unclear. Our current study explored the role of CTRP3 in renal fibrosis and its underlying mechanisms by using serums and renal biopsy specimens from renal fibrosis patients and control subjects, rats models with the surgery of unilateral ureteral obstruction (UUO) and human renal proximal tubular epithelial cells (HRPTEpiCs). We found that circulating levels of CTRP3 had no significant difference between renal fibrosis patients and healthy subjects; however, renal CTRP3 expression was markedly downregulated in the fibrotic region with an abundant expression of collagen-I. In UUO rat models, circulating levels of CTRP3 have not changed with the prolonged obstruction of the kidney; renal CTRP3 expression was decreased with the severity of renal fibrosis; adenovirus-mediated CTRP3 treatment inhibited renal interstitial fibrosis. In vitro experiments revealed that CTRP3 attenuates TGF-ß1 induced tubular epithelial cells fibrotic changes; CTRP3 knockdown facilitates the expression of fibrotic markers in TGF-ß1-induced HRPTEpiCs; recombinant CTRP3 or adenovirus-mediated CTRP3 overexpression significantly inhibited the Notch signaling pathway-associated factors, and knockdown of CTRP3 increased TGF-ß1-mediated activation of the Notch signaling pathways. Collectively, our current study found that CTRP3 could improve renal fibrosis, to some extent, through inhibiting the Notch pathway.

Platelet microparticles contribute to aortic vascular endothelial injury in diabetes via the mTORC1 pathway.

Platelet microparticles (PMPs) are closely associated with diabetic macrovascular complications. The present study aimed to investigate the effects of PMPs in diabetes on aortic vascular endothelial injury and to explore the underlying mechanisms. Peritoneal injection of streptozotocin was used to generate a diabetic rat model in vivo, and human umbilical vein endothelial cells (HUVECs) treated with PMPs were used in vitro. PMP levels in the circulation and aorta tissues were time-dependently increased in streptozotocin-induced diabetic rats at weeks 4, 8, and 12 (P < 0.05). Aspirin significantly inhibited the PMP levels at each time point (P < 0.05). In diabetic rats, the endothelial nitric oxide levels were decreased significantly combined with increased endothelial permeability. PMPs were internalized by HUVECs and primarily accumulated around the nuclei. PMPs inhibited endothelial nitric oxide levels to about 50% and caused approximately twofold increase in reactive oxygen species production. Furthermore, PMPs significantly decreased the endothelial glycocalyx area and expression levels of glypican-1 and occludin (P < 0.05). Interestingly, the PMP-induced endothelial injuries were prevented by raptor siRNA and rapamycin. In conclusion, increased PMPs levels contribute to aortic vascular endothelial injuries in diabetes through activating the mTORC1 pathway.

Lipid Metabolism Disorder and Renal Fibrosis.

Since the lipid nephrotoxicity hypothesis was proposed in 1982, increasing evidence has supported the hypothesis that lipid abnormalities contributed to the progression of glomerulosclerosis. In this chapter, we will discuss the general promises of the original hypothesis, focusing especially on the role of lipids and metabolic inflammation accompanying CKD in renal fibrosis and potential new strategies of prevention.

Palmitic Acid-Induced Podocyte Apoptosis via the Reactive Oxygen Species-Dependent Mitochondrial Pathway.

BACKGROUND/AIMS: Chronic kidney disease (CKD) is often accompanied by hyperlipidemia, which accelerates progression of the disease. Podocyte injury can lead to dysfunction of the glomerular filtration barrier, which is associated with proteinuria, a risk marker for the progression of CKD. Our previous studies demonstrated that palmitic acid (PA) can induce podocyte apoptosis; however, the underlying mechanisms are unclear. In the present study, we investigated the specific molecular mechanisms of PA-induced apoptosis in cultured podocytes. METHODS: We cultured mouse podocytes and treated them with PA. Then, cell viability was measured using the Cell Counting Kit-8 colorimetric assay, lipid uptake was assessed by Oil Red O staining and boron-dipyrromethene staining, apoptosis was measured by flow cytometry, mitochondrial injury was assessed by JC-1 staining and transmission electron microscopy, and mitochondrial production of reactive oxygen species (ROS) was evaluated by fluorescence microscopy using the MitoSOX Red reagent. The effects of PA on the mitochondria-mediated caspase activation pathway were investigated by examining the expression of caspase-8, cleaved caspase-9, cleaved caspase-3, cleaved poly (ADP-ribose) polymerase (PARP), B-cell lymphoma 2 (Bcl-2), Bax, Bid, cytochrome c, and Fas-associated protein with death domain (FADD) using western blotting. The translocation of Bax and cytochrome c were detected by immunofluorescence. RESULTS: PA treatment significantly increased lipid accumulation and induced podocyte apoptosis. We investigated whether the two primary apoptosis signaling pathways (death receptor-mediated pathway and mitochondria-mediated pathway) were involved in the execution of PA-induced podocyte apoptosis, and found that the levels of FADD, caspase-8, and Bid did not significantly change during this process. Meanwhile, PA treatment induced an increase in Bax protein expression and a decrease in Bcl-2 protein expression, with Bax translocation to the mitochondria. Furthermore, PA treatment induced mitochondrial impairment, and triggered the release of cytochrome c from the mitochondria to cytosol, with a concomitant dose-dependent increase in the levels of cleaved caspase-9, cleaved caspase-3, and PARP. Meanwhile, PA treatment increased mitochondrial production of ROS, and the mitochondria-targeted antioxidant mitoTEMPO significantly ameliorated PA-induced podocyte apoptosis. CONCLUSION: Our findings indicated that PA induced caspase-dependent podocyte apoptosis through the mitochondrial pathway, and mitochondrial ROS production participated in this process, thus potentially contributing to podocyte injury.

Berberine Protects Against Palmitate-Induced Apoptosis in Tubular Epithelial Cells by Promoting Fatty Acid Oxidation.

BACKGROUND Increased lipid accumulation in renal tubular epithelial cells (TECs) contributes to their injury and dysfunction and progression of tubulointerstitial fibrosis. Berberine (BBR), a natural plant alkaloid isolated from traditional medicine herbs, is effective in lowing serum lipid, and has a protective effect on chronic kidney disease (CKD) with dyslipidemia, including diabetic nephropathy. The aim of this study was to investigate the effect of BBR on palmitate (PA)-induced lipid accumulation and apoptosis in TECs. MATERIAL AND METHODS Human kidney proximal tubular epithelial cell line (HK-2) cells were treated with PA, BBR, and/or palmitoyltransferase 1A (CPT1A) inhibitor Etomoxir. Intracellular lipid content was assessed by Oil Red O and Nile Red staining. Cell apoptosis rate was evaluated by flow cytometry assay. The expression of apoptosis-related protein cleaved-caspase3 and fatty acid oxidation (FAO)-regulating proteins, including CPT1A, peroxisome proliferator-activated receptor α (PPARα), and PPARγ co-activator-1α (PGC1α), was measured by Western blot analysis and immunofluorescence. RESULTS In the present study, PA treatment increased intracellular lipid deposition accompanied by elevated apoptosis in TECs compared with control group, whereas the protein expression of CPT1A, PPARα, and PGC1α, did not correspondingly increase in TECs. BBR significantly up-regulated the protein expression of CPT1A, PPARα, and PGC1α in TECs treated with or without PA, and reversed PA-induced intracellular lipid accumulation and apoptosis. Moreover, the CPT1A inhibitor Etomoxir counteracted the protective effect of BBR in TECs. CONCLUSIONS These in vitro findings suggest that PA can induce intracellular lipid accumulation and apoptosis in TECs, and the mechanism may be associated with inducing defective FAO, whereas BBR can protect TECs against PA-induced intracellular lipid accumulation and apoptosis by promoting FAO.

Long-chain fatty acid activates hepatocytes through CD36 mediated oxidative stress.

BACKGROUND: Accumulating evidence suggests that activated hepatocytes are involved in the deposition of the excess extracellular matrix during liver fibrosis via the epithelial to mesenchymal transition. Lipid accumulation in hepatocytes are implicated in the pathogenesis of chronic liver injury. CD36 is known to mediate long-chain fatty acid (LCFA) uptake and lipid metabolism. However, it is unclear whether LCFA directly promotes hepatocyte activation and the involved mechanisms have not been fully clarified. METHODS: Mice were fed with a high fat diet (HFD) and normal hepatocyte cells (Chang liver cells) were treated with palmitic acid (PA) in vivo and in vitro. Real-time polymerase chain reaction (RT-PCR) and western blotting were used to examine the gene and protein expression of molecules involved in hepatic fibrogenesis and hepatocyte activation. CD36 was knocked down by transfecting CD36 siRNA into hepatocyte cells. Hydrogen peroxide (H2O2) and reactive oxygen species (ROS) levels were detected using commercial kits. RESULTS: HFD induced a profibrogenic response and up-regulated CD36 expression in vivo. Analogously, PA increased lipid accumulation and induced human hepatocyte activation in vitro, which was also accompanied by increased CD36 expression. Interestingly, knockdown of CD36 resulted in a reduction of hepatocyte lipid deposition and decreased expression of Acta2 (34% decrease), Vimentin (29% decrease), Desmin (60% decrease), and TGF-ß signaling pathway related genes. In addition, HFD and PA increased the production of H2O2 in vivo (48% increase) and in vitro (385% increase), and the antioxidant, NAC, ameliorated PA-induced hepatocyte activation. Furthermore, silencing of CD36 in vitro markedly attenuated PA-induced oxidative stress (H2O2: 41% decrease; ROS: 39% decrease), and the anti-activation effects of CD36 knockdown could be abolished by pretreatment with H2O2. CONCLUSIONS: Our study demonstrated that LCFA facilitates hepatocyte activation by up-regulating oxidative stress through CD36, which could be an important mechanism in the development of hepatic fibrosis.

Liver X receptor α induces 17ß-hydroxysteroid dehydrogenase-13 expression through SREBP-1c.

Liver X receptors, including LXRα and LXRß, are known to be master regulators of liver lipid metabolism. Activation of LXRα increases hepatic lipid storage in lipid droplets (LDs). 17ß-Hydroxysteroid dehydrogenase-13 (17ß-HSD13), a recently identified liver-specific LD-associated protein, has been reported to be involved in the development of nonalcoholic fatty liver disease. However, little is known about its transcriptional regulation. In the present study, we aimed at determining whether 17ß-HSD13 gene transcription is controlled by LXRs. We found that treatment with T0901317, a nonspecific LXR agonist, increased both 17ß-HSD13 mRNA and protein levels in cultured hepatocytes. It also significantly upregulated hepatic 17ß-HSD13 expression in wild-type (WT) and LXRß-/- mice but not in LXRα-/- mice. Basal expression of 17ß-HSD13 in the livers of LXRα-/- mice was lower than that in the livers of WT and LXRß-/- mice. Moreover, induction of hepatic 17ß-HSD13 expression by T0901317 was almost completely abolished in SREBP-1c-/- mice. Bioinformatics analysis revealed a consensus sterol regulatory element (SRE)-binding site in the promoter region of the 17ß-HSD13 gene. A 17ß-HSD13 gene promoter-driven luciferase reporter and ChIP assays further confirmed that the 17ß-HSD13 gene was under direct control of SREBP-1c. Collectively, these findings demonstrate that LXRα activation induces 17ß-HSD13 expression in a SREBP-1c-dependent manner. 17ß-HSD13 may be involved in the development of LXRα-mediated fatty liver.

Endotoxin Tolerance Inhibits Degradation of Tumor Necrosis Factor Receptor-Associated Factor 3 by Suppressing Pellino 1 Expression and the K48 Ubiquitin Ligase Activity of Cellular Inhibitor of Apoptosis Protein 2.

Pellino 1 positively regulates Toll-like receptor 4 signaling by regulating tumor necrosis factor receptor-associated factor 3 (TRAF3) degradation and is suppressed with the induction of endotoxin tolerance. However, the role of TRAF3 in endotoxin tolerance is largely unknown. In this study, we found that lipopolysaccharide (LPS) stimulation decreased TARF3 protein expression in mouse Kupffer cells (KCs) and liver tissues, whereas endotoxin tolerization abrogated this effect. Degradative TRAF3 K48-linked ubiquitination and the cytoplasmic translocation of the MYD88-associated multiprotein complex were significantly inhibited in tolerized KCs, which led to markedly impaired activation of MYD88-dependent JNK and p38 and downregulation of inflammatory cytokines. TRAF3 ablation failed to induce a fully endotoxin-tolerant state in RAW264.7 cells. Pellino 1 knockdown in Raw264.7 cells did not impair induction of cIAP2 in response to LPS but inhibited the K63-linked ubiquitination of cellular inhibitor of apoptosis protein 2 (cIAP2) and K48-linked ubiquitination of TRAF3 protein. We also found upregulation of Pellino 1 and downregulation of TRAF3 in liver tissues of patients with cholangitis. Our findings reveal a novel mechanism that endotoxin tolerance reprograms mitogen-activated protein kinase signaling by suppressing Pellino 1-mediated K63-linked ubiquitination of cIAP2, K48-linked ubiquitination, and degradation of TRAF3.

MicroRNA-101 overexpression by IL-6 and TNF-α inhibits cholesterol efflux by suppressing ATP-binding cassette transporter A1 expression.

BACKGROUND: MicroRNAs play key roles in regulating cholesterol homeostasis. Here, we investigated the role of microRNA-101 (miR-101) in regulating ATP-binding cassette transporter A1 (ABCA1) expression and cholesterol efflux under non-inflammatory and inflammatory conditions in human THP-1-derived macrophages and HepG2 hepatoblastoma cells. METHODS: The cell lines were transfected with one of four lentiviral vectors: miR-101, miR-101 control, anti-miR-101, or anti-miR-101 control. A luciferase reporter assay was used to examine miR-101 binding to the 3' untranslated region (UTR) of ABCA1. Western blotting was conducted to assess ABCA1 protein expression. Cells were loaded with BODIPY-cholesterol and stained with oil red O to assess cholesterol efflux. RESULTS: The luciferase activity assay revealed that wild-type miR-101 binding at site 2 significantly repressed ABCA1 3' UTR activity, suggesting that miR-101 directly targets the ABCA1 mRNA at site 2. In both cell lines, Western blotting revealed that miR-101 expression negatively regulates ABCA1 protein expression and significantly suppresses cholesterol efflux to ApoA1 under both low-density lipoprotein (LDL) and non-LDL conditions, which was confirmed by pronounced lipid inclusions visible by oil red O staining. In HepG2 cells, both IL-6 and TNF-α treatments produced significant miR-101 overexpression; however, in THP-1-derived macrophages, only IL-6 treatment produced significant miR-101 overexpression. Anti-mir-101 transfection under both IL-6 and TNF-α treatment conditions led to ABCA1 upregulation, indicating that miR-101 expression represses ABCA1 expression under inflammatory conditions. CONCLUSIONS: miR-101 promotes intracellular cholesterol retention under inflammatory conditions through suppressing ABCA1 expression and suggests that the miR-101-ABCA1 axis may play an intermediary role in the development of NAFLD and vascular atherosclerosis.

A genomic association study revealing subphenotypes of childhood steroid-sensitive nephrotic syndrome in a larger genomic sequencing cohort.

Dissecting the genetic components that contribute to the two main subphenotypes of steroid-sensitive nephrotic syndrome (SSNS) using genome-wide association studies (GWAS) strategy is important for understanding the disease. We conducted a multicenter cohort study (360 patients and 1835 controls) combined with a GWAS strategy to identify susceptibility variants associated with the following two subphenotypes of SSNS: steroid-sensitive nephrotic syndrome without relapse (SSNSWR, 181 patients) and steroid-dependent/frequent relapse nephrotic syndrome (SDNS/FRNS, 179 patients). The distribution of two single-nucleotide polymorphisms (SNPs) in ANKRD36 and ALPG was significant between SSNSWR and healthy controls, and that of two SNPs in GAD1 and HLA-DQA1 was significant between SDNS/FRNS and healthy controls. Interestingly, rs1047989 in HLA-DQA1 was a candidate locus for SDNS/FRNS but not for SSNSWR. No significant SNPs were observed between SSNSWR and SDNS/FRNS. Meanwhile, chromosome 2:171713702 in GAD1 was associated with a greater steroid dose (>0.75 mg/kg/d) upon relapse to first remission in patients with SDNS/FRNS (odds ratio = 3.14; 95% confidence interval, 0.97-9.87; P = 0.034). rs117014418 in APOL4 was significantly associated with a decrease in eGFR of greater than 20% compared with the baseline in SDNS/FRNS patients (P = 0.0001). Protein-protein intersection network construction suggested that HLA-DQA1 and HLA-DQB1 function together through GSDMA. Thus, SSNSWR belongs to non-HLA region-dependent nephropathy, and the HLA-DQA/DQB region is likely strongly associated with disease relapse, especially in SDNS/FRNS. The study provides a novel approach for the GWAS strategy of SSNS and contributes to our understanding of the pathological mechanisms of SSNSWR and SDNS/FRNS.

Interaction of RAS activation and lipid disorders accelerates the progression of glomerulosclerosis.

BACKGROUND: The activation of the renin-angiotensin system (RAS) and lipid disorders are major risk factors in progressive chronic kidney disease. This study aimed to investigate the potential synergistic mechanisms of RAS activation and lipid disorders that contribute to glomerulosclerosis. MATERIALS AND METHODS: Human renal mesangial cells (HMCs) were treated with 10(-7) mol/L angiotensin II (Ang II) or with 30 µg/ml cholesterol and 1 µg/ml 25-hydroxycholesterol (lipid loading) for 24 hours. Lipid accumulation in the cells was evaluated by Oil Red O staining and intracellular cholesterol quantitative assays. The gene and protein expression of molecules in the low-density lipoprotein receptor (LDLr) pathway, the RAS family, and the extracellular matrix were examined by real-time polymerase chain reaction and Western blotting. The translocation of sterol regulatory element-binding protein (SREBP) cleavage activating protein (SCAP), which escorts SREBP-2 from the endoplasmic reticulum (ER) to the Golgi, was examined by immunofluorescent staining. RESULTS: Ang II increased lipid droplet accumulation in HMCs. Further analysis revealed that Ang II increased the mRNA and protein expression of LDLr, SCAP, and SREBP-2. This increase was correlated with an enhanced translocation of the SCAP/SREBP-2 complex from the ER to the Golgi in HMCs that was induced by Ang II, thereby activating LDLr gene transcription. Interestingly, lipid loading increased the mRNA and protein expression of angiotensinogen, Ang II, renin, angiotensin-converting enzyme, angiotensin II type 1 receptor, and type 2 receptor in HMCs with increased mRNA and protein expression of collagen I, α-smooth muscle actin, and fibronectin. CONCLUSIONS: This study demonstrates that the interaction of RAS activation and lipid disorders accelerates the progression of glomerulosclerosis.

Activation of renin-angiotensin system is involved in dyslipidemia-mediated renal injuries in apolipoprotein E knockout mice and HK-2 cells.

BACKGROUND: Dyslipidemia and activation of renin-angiotensin system (RAS) contribute to the progression of chronic kidney disease (CKD). This study investigated possible synergistic effects of intrarenal RAS activation with hyperlipidemia in renal injuries. METHODS: Apolipoprotein knockout mice were fed with normal chow diet (control) or high fat diet (HF group) for eight weeks. Human proximal tubular epithelial cell line (HK-2) was treated without (control) or with cholesterol (30 µg/ml) plus 25-hydroxycholesterol (1 µg/ml) (lipid group) for 24 hours. The plasma lipid profile and RAS components were determined by clinical biochemistry assay and radiommunoassay, respectively. Collagen deposition in kidneys was evaluated by Masson-staining. The gene and protein expressions of molecules involved in RAS components and biomarkers of epithelial mesenchymal transition (EMT) were examined by real-time PCR, immunochemical staining, and Western blot. RESULTS: The mice fed with high-fat diet showed significant hyperlipidemia with collagen deposition in renal tubular interstitium compared to controls. The plasma levels of renin, angiotensin I, and angiotensin II were no difference in two groups. However, the kidneys of HF group showed up-regulated RAS components, which were positively associated with increased plasma levels of triglyceride, total cholesterol, and LDL. These effects were further confirmed by in vitro studies. Lipid loading induced HK-2 cells underwent EMT, which was closely associated with the increased expressions of intracellular RAS components. CONCLUSIONS: Local RAS activation was involved in hyperlipidemia-mediated renal injuries, suggesting that there are synergistic effects resulting from RAS activation with hyperlipidemia that accelerates the progression of CKD.

[Effect of inflammatory stress on hepatic cholesterol accumulation and hepatic fibrosis in C57BL/6J mice].

OBJECTIVE: To investigate whether inflammatory stress exacerbates hepatic cholesterol accumulation and liver fibrosis using a C57BL/6J mouse model of chronic inflammation. METHODS: Twelve male C57BL/6J mice were given a high-fat diet (15.0% fat, 1.25% cholesterol, 0.5% cholic acid) and randomly assigned to the normal control group (n=6; subcutaneously injected with 0.5 mL of isotonic saline, every other day for 14 weeks) or the chronic inflammation model group (n=6; subcutaneously injected with of 0.5 mL of 10% casein, every other day for 14 weeks). At the end of week 14, the animals were sacrificed and blood was collected from the left ventricle for serological analysis of inflammatory markers and lipid profile, including serum amyloid A (SAA), interleukin-6 (IL-6), total cholesterol (TC) and free cholesterol (FC), low-density lipoprotein (LDL), and high-density lipoprotein (HDL)). Extracted liver tissues were divided for use in histological analysis (lipid accumulation and fibrosis evaluated by Oil Red O, Sirius red and Masson's trichrome staining) and quantitative fluorescence real-time PCR (to measure b-actin normalized expression of TNF-a MCP1, SREBP-2, LDLr, HMGCoA-r, ATF-6, GRP78, BMP-7, TGF-b, and collagens type I and type IV). Comparisons between groups were made by the two-samples t-test or Satterthwaite t-approximation test, collagen type I and type IV. RESULTS: Compared to the normal control group, the inflammation model group showed elevated serum IL-6 (12.55+/-4.75 vs. 32.41+/-7.42 pg/mL, P less than 0.01), reduced serum TC (14.82+/-1.56 vs. 10.62+/-0.48 mmol/L, P less than 0.01), up-regulated hepatic TNF-a mRNA expression (1.05+/-0.35 vs. 2.12+/-0.72, P less than 0.01), and elevated hepatic TC (12.10+/-2.57 vs. 23.21+/-8.75 mmol/L, P less than 0.05). In addition, the inflammation group showed abnormal lipid deposition, and increased and thickened reticular fibers. The livers of the inflammation group also showed up-regulated mRNA expression of SREBP-2 (normal control: 1.01+/-0.19 vs. 2.63+/-0.13, P less than 0.05), GRP78 (1.07+/-0.47 vs. 2.21+/-0.99, P less than 0.05), TGF-b (1.01+/-0.14 vs. 1.38+/-0.28, P less than 0.05), and collagen type I (1.02+/-0.27 vs. 1.71+/-0.51, P less than 0.05) and down-regulation of BMP-7 (1.01+/-0.15 vs. 0.55+/-0.25, P less than 0.01). CONCLUSION: Activation of the inflammatory system exacerbates hepatic cholesterol accumulation and hepatic fibrosis in C57BL/6J mice.