Angiopoietin-like protein 4 promotes hyperlipidemia-induced renal injury by down-regulating the expression of ACTN4.

OBJECTIVE: The molecular mechanism of in hyperlipidemia-induced renal injury has not been elucidated. Angiogenin-like protein 4 (ANGPTL4) is a key regulator of lipid metabolism. The role of ANGPTL4 hyperlipidemia-induced renal injury has not been reported. METHODS: Wild type C57 mice and gene angptl4 knockout mice were fed with 60% high fat diet or normal diet respectively. The serum lipid, urinary albumin and renal pathology were tested at the 9th, 13th, 17th and 21st week with high fat diet. RESULTS: Elevated blood lipids in the wild-type mice with high-fat diet were found at 9th week. At the 17th week, the level of urinary albumin in high-fat fed wild type mice were significantly higher than which with normal diet, correspondingly, segmental fusion of podocyte foot process in kidney could be observed in these hyperlipidemia mice. IHC showed that the expression of ANGPTL4 in glomeruli of high-fat fed wild type mice began significant elevated since the 9th week. When given high fat diet, compared to the wild type, the gene angptl4 knockout mice showed significantly alleviated the levels of hyperlipidemia, proteinuria and effacement of podocyte foot process. Finally, the expression of ACTN4 showed remarkably lower in glomeruli podocyte of wild type mice fed high fat diet than that of wild type mice with normal diet at each time-point (P < 0.01). Differently, the expression of ACTN4 in gene angptl4 knockout mice did not happen significantly weaken when given the same dose of high fat diet. CONCLUSION: ANGPTL4 could play a role in hyperlipidemic-induced renal injury via down-regulating the expression of ACTN4 in kidney podocyte.

Brahma-related gene-1 promotes tubular senescence and renal fibrosis through Wnt/ß-catenin/autophagy axis.

Although accelerated cellular senescence is closely related to the progression of chronic kidney disease (CKD) and renal fibrosis, the underlying mechanisms remain largely unknown. Here, we reported that tubular aberrant expression of Brahma-related gene 1 (BRG1), an enzymatic subunit of the SWItch/Sucrose Non-Fermentable complex, is critically involved in tubular senescence and renal fibrosis. BRG1 was significantly up-regulated in the kidneys, predominantly in tubular epithelial cells, of both CKD patients and unilateral ureteral obstruction (UUO) mice. In vivo, shRNA-mediated knockdown of BRG1 significantly ameliorated renal fibrosis, improved tubular senescence, and inhibited UUO-induced activation of Wnt/ß-catenin pathway. In mouse renal tubular epithelial cells (mTECs) and primary renal tubular cells, inhibition of BRG1 diminished transforming growth factor-ß1 (TGF-ß1)-induced cellular senescence and fibrotic responses. Correspondingly, ectopic expression of BRG1 in mTECs or normal kidneys increased p16INK4a, p19ARF, and p21 expression and senescence-associated ß-galactosidase (SA-ß-gal) activity, indicating accelerated tubular senescence. Additionally, BRG1-mediated pro-fibrotic responses were largely abolished by small interfering RNA (siRNA)-mediated p16INK4a silencing in vitro or continuous senolytic treatment with ABT-263 in vivo. Moreover, BRG1 activated the Wnt/ß-catenin pathway, which further inhibited autophagy. Pharmacologic inhibition of the Wnt/ß-catenin pathway (ICG-001) or rapamycin (RAPA)-mediated activation of autophagy effectively blocked BRG1-induced tubular senescence and fibrotic responses, while bafilomycin A1 (Baf A1)-mediated inhibition of autophagy abolished the effects of ICG-001. Further, BRG1 altered the secretome of senescent tubular cells, which promoted proliferation and activation of fibroblasts. Taken together, our results indicate that BRG1 induces tubular senescence by inhibiting autophagy via the Wnt/ß-catenin pathway, which ultimately contributes to the development of renal fibrosis.

circRNA_010383 Acts as a Sponge for miR-135a, and Its Downregulated Expression Contributes to Renal Fibrosis in Diabetic Nephropathy.

Diabetic nephropathy (DN), a vascular complication of diabetes, is the leading cause of death in patients with diabetes. The contribution of aberrantly expressed circular RNAs (circRNAs) to DN in vivo is poorly understood. Integrated comparative circRNA microarray profiling was used to examine the expression of circRNAs in diabetic kidney of db/db mice. We found that circRNA_010383 expression was markedly downregulated in diabetic kidneys, mesangial cells, and tubular epithelial cells cultured in high-glucose conditions. circRNA_010383 colocalized with miRNA-135a (miR-135a) and inhibited miR-135a function by directly binding to miR-135a. In vitro, the knockdown of circRNA_010383 promoted the accumulation of extracellular matrix (ECM) proteins and downregulated the expression of transient receptor potential cation channel, subfamily C, member 1 (TRPC1), which is a target protein of miR-135a. Furthermore, circRNA_010383 overexpression effectively inhibited the high-glucose-induced accumulation of ECM and increased TRPC1 levels in vitro. More importantly, the kidney target of circRNA_010383 overexpression inhibited proteinuria and renal fibrosis in db/db mice. Mechanistically, we identified that a loss of circRNA_010383 promoted proteinuria and renal fibrosis in DN by acting as a sponge for miR-135a. This study reveals that circRNA_010383 may be a novel therapeutic target for DN in the future.

circRNA_010383 Acts as a Sponge for miR-135a and its Downregulated Expression Contributes to Renal Fibrosis in Diabetic Nephropathy.

Diabetic nephropathy (DN), a vascular complication of diabetes mellitus, is the leading cause of death in diabetic patients. The contribution of aberrantly expressed circRNAs to diabetic nephropathy in vivo is poorly understood. Integrated comparative circRNA microarray profiling was used to examine the expression of circRNAs in diabetic kidney of db/db mice. We found that circRNA_010383 expression was markedly downregulated in diabetic kidneys, mesangial cells and tubular epithelial cells cultured in high-glucose conditions. circRNA_010383 colocalized with microRNA-135a (miR-135a) and inhibited miR-135a function by directly binding to miR-135a. In vitro, the knockdown of circRNA_010383 promoted the accumulation of extracellular matrix (ECM) proteins and downregulated the expression of transient receptor potential cation channel, subfamily C, member (TRPC1), which is a target protein of miR-135a. Furthermore, circRNA_010383 overexpression effectively inhibited the high-glucose-induced accumulation of ECM and increased TRPC1 levels in vitro More importantly, the kidney-target of circRNA_010383 overexpression inhibited proteinuria and renal fibrosis in db/db mice. Mechanistically, we identified that a loss of circRNA_010383 promoted proteinuria and renal fibrosis in DN by acting as a sponge for miRNA-135a. This study reveals that circRNA_010383 may be a novel therapeutic target for DN in the future.

FOXO3a accumulation and activation accelerate oxidative stress-induced podocyte injury.

Podocyte injury is the primary cause of glomerular injury in diabetic nephropathy (DN). Advanced oxidation protein products (AOPPs), the triggers and markers of oxidative stress in DN, have been linked to podocyte damage. However, the underlying mechanism is not yet clear. Here, we investigated the potential role of FOXO3a, a key transcription factor in the response to stress, in mediating AOPPs-induced podocyte injury. We found that FOXO3a expression was increased in the glomeruli of kidney biopsies from patients with DN and it was positively correlated with proteinuria. The serum from patients with DN significantly increased FOXO3a and its downstream genes FasL and Bim, thereby inducing the high level of cleaved caspase3 and the loss of nephrin and podocin expressions in podocytes. Blockade of AOPPs signaling by a neutralizing antibody against the receptor of advanced glycation end products (αRAGE) abolished the effect of DN serum on podocytes, confirming the pathogenic role of AOPPs in DN serum. Downregulation of FOXO3a decreased AOPPs-induced podocyte apoptosis and restored the levels of podocyte markers nephrin and podocin, and upregulation of FOXO3a exacerbated these changes in podocytes after AOPPs treatment. Furthermore, FOXO3a specifically activated proapoptotic genes in podocytes only in the presence of AOPPs. Mechanistically, AOPPs increased the FOXO3a protein levels by inhibiting their autophagic degradation in a ROS/mTOR-dependent manner. Moreover AOPPs activated the accumulated FOXO3a by maintaining FOXO3a in the nucleus, and this process was dependent on ROS-mediated AKT signaling deactivation. These studies suggest that FOXO3a plays a critical role in mediating AOPPs-induced podocyte injury and reveal a new mechanistic linkage of oxidative stress, FOXO3a activation and podocyte injury in DN.

Correction: Micheliolide ameliorates renal fibrosis by suppressing the Mtdh/BMP/MAPK pathway.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Parthenolide, an NF-κB inhibitor, alleviates peritoneal fibrosis by suppressing the TGF-ß/Smad pathway.

Transforming growth factor (TGF)-ß/Smad signalling plays a central role in the pathogenesis of peritoneal fibrosis related to peritoneal dialysis (PD). Parthenolide (PTL), a naturally occurring phytochemical, is isolated from the shoots of feverfew (Tanacetum parthenium) and displays analgesia, anti-inflammation and anticancer activities. In this study, we examined the therapeutic potential of PTL on PD-related peritoneal fibrosis induced by daily intraperitoneal injection of 4.25% dextrose-containing PD fluid (PDF) in vivo and TGF-ß1-induced epithelial-mesenchymal transition (EMT) in vitro. PTL was administered daily before PDF injection or after 14 days of PDF injection. Both PTL treatments showed a protective effect on peritoneal fibrosis and prevented peritoneal dysfunction. Similarly, PTL suppressed the expression of fibrotic markers (fibronectin and collagen I) and restored the expression of the epithelial marker (E-cadherin) in TGF-ß1-treated HMrSV5 cells. Furthermore, PTL inhibited TGF-ß1-induced Smad2 and Smad3 phosphorylation and nuclear translocation but did not influence Smad1/5/9 phosphorylation or activate other downstream signalling pathways of TGF-ß1, including AKT, extracellular signal-regulated kinase (ERK) or p38. In conclusion, PTL treatment may represent an effective and novel therapy for PD-associated peritoneal fibrosis by suppressing the TGF-ß/Smad pathway.

Micheliolide ameliorates diabetic kidney disease by inhibiting Mtdh-mediated renal inflammation in type 2 diabetic db/db mice.

Diabetic kidney disease (DKD) is the principal cause of end-stage renal disease worldwide and few treatments are available. Because immunomodulators are pivotal to DKD pathophysiology, anti-inflammatory agents may be useful for treating DKD. This study was conducted to investigate the effect of micheliolide (MCL), a novel guaianolide sesquiterpene lactone with well-known anti-inflammatory effects, on DKD. Treatment with dimethylaminomicheliolide (DMAMCL), the pro-drug of MCL currently under clinical trial in oncology, protected the kidneys against proteinuria, renal failure, histopathological injury, and inflammation in db/db mice. This effect was associated with metadherin (Mtdh) downregulation. We observed aberrant upregulation of Mtdh in the kidneys of db/db mice and high-glucose (HG)-induced mouse tubular epithelial cells (mTECs). Downregulation of Mtdh obviously inhibited nuclear factor-κB signaling activation and suppressed its downstream inflammatory cytokines, such as monocyte chemotactic peptide-1, interleukin-1ß, tumor necrosis factor-α, and interleukin-6 in HG-induced mTECs, which was similar to the effect of MCL. Mtdh overexpression largely reversed the anti-inflammatory role of MCL. Moreover, MCL downregulated Mtdh by both inhibiting the transcription level and promoting ubiquitin-mediated degradation. These findings suggest that DMAMCL is a promising anti-inflammatory agent useful for preventing renal injury in DKD by inhibiting Mtdh-mediated renal inflammation.

MicroRNA-145 promotes the epithelial-mesenchymal transition in peritoneal dialysis-associated fibrosis by suppressing fibroblast growth factor 10.

Peritoneal fibrosis is a common complication of long-term peritoneal dialysis (PD) and the principal cause of ultrafiltration failure during PD. The initial and reversible step in PD-associated peritoneal fibrosis is the epithelial-mesenchymal transition (EMT). Although the mechanisms in the EMT have been the focus of many studies, only limited information is currently available concerning microRNA (miRNA) regulation in peritoneal fibrosis. In this study, we aimed to characterize the roles of microRNA-145 (miR-145) and fibroblast growth factor 10 (FGF10) in peritoneal fibrosis. After inducing EMT with transforming growth factor-ß1 (TGF-ß1) in vitro, we found that miR-145 is significantly up-regulated, whereas FGF10 is markedly down-regulated, suggesting a close link between miR-145 and FGF10 in peritoneal fibrosis, further confirmed in luciferase reporter experiments. Furthermore, in human peritoneal mesothelial cells (i.e. HMrSV5 cells), miR-145 mimics induced EMT, whereas miR-145 inhibition suppressed EMT, and we also observed that miR-145 suppressed FGF10 expression. In vivo, we found that the exogenous delivery of an miR-145 expression plasmid both blocked FGF10 and intensified the EMT, whereas miR-145 inhibition promoted the expression of FGF10 and reversed the EMT. In conclusion, miR-145 promotes the EMT during the development of peritoneal fibrosis by suppressing FGF10 activity, suggesting that miR-145 represents a potential therapeutic target for managing peritoneal fibrosis.

Micheliolide ameliorates renal fibrosis by suppressing the Mtdh/BMP/MAPK pathway.

Micheliolide (MCL), derived from parthenolide (PTL), is known for its antioxidant and anti-inflammatory effects and has multiple roles in inflammatory diseases and tumours. To investigate its effect on renal disease, we intragastrically administrated DMAMCL, a dimethylamino Michael adduct of MCL for in vivo use, in two renal fibrosis models-the unilateral ureteral occlusion (UUO) model and an ischaemia-reperfusion injury (IRI) model and used MCL in combination with transforming growth factor beta 1 (TGF-ß1) on mouse tubular epithelial cells (mTEC) in vitro. The expression of fibrotic markers (fibronectin and α-SMA) was remarkably reduced, while the expression of the epithelial marker E-cadherin was restored after DMAMCL treatment both in the UUO and IRI mice. MCL function in TGF-ß1-induced epithelial-mesenchymal transition (EMT) in mTEC was consistent with the in vivo results. Metadherin (Mtdh) was activated in the fibrotic condition, suggesting that it might be involved in fibrogenesis. Interestingly, we found that while Mtdh was upregulated in the fibrotic condition, DMAMCL/MCL could suppress its expression. The overexpression of Mtdh exerted a pro-fibrotic effect by modulating the BMP/MAPK pathway in mTECs, and MCL could specifically reverse this effect. In conclusion, DMAMCL/MCL treatment represents a novel and effective therapy for renal fibrosis by suppressing the Mtdh/BMP/MAPK pathway.

Dimethylaminomicheliolide ameliorates peritoneal fibrosis through the activation of autophagy.

Peritoneal fibrosis (PF) is a major cause of ultrafiltration failure in patients receiving long-term peritoneal dialysis (PD), and effective prevention and treatment strategies are urgently needed. The dimethylamino Michael adduct of a natural product-derived micheliolide (MCL), dimethylaminomicheliolide (DMAMCL), is a new lead compound with the advantages of high stability, low toxicity, and sustainable release of MCL. This study aimed to investigate the protective effect of DMAMCL against PD-related PF and the mechanisms involved. In this study, we found that DMAMCL significantly decreased PD-induced extracellular matrix (ECM) deposition in a mouse model of PD, and that delayed DMAMCL administration halted the progression of PF in an established PD model. In addition, rapamycin administration induced autophagy and significantly ameliorated PF. The protective effect of DMAMCL against PF was weakened when co-administered with DMAMCL and 3-methyladenine. Inducing autophagy by rapamycin decreased transforming growth factor-ß1-induced ECM accumulation in vitro. MCL promoted autophagy and inhibited ECM deposition. The anti-fibrotic effect of MCL was eliminated when knocking down ATG7 by siRNA. Taken together, DMAMCL might prevent against PF through activating autophagy. The anti-fibrotic effect of DMAMCL may be a new candidate for the treatment in patients with PD-related PF. KEY MESSAGES: Dimethylaminomicheliolide, the pro-drug of micheliolide, protects against peritoneal fibrosis in a mouse peritoneal dialysis model. Micheliolide inhibits TGF-ß1-induced extracellular matrix accumulation in vitro. Autophagy plays a protective role against peritoneal fibrosis. The antifibrogenic effect of dimethylaminomicheliolide may be due to the activation of autophagy.

Micheliolide alleviates hepatic steatosis in db/db mice by inhibiting inflammation and promoting autophagy via PPAR-γ-mediated NF-кB and AMPK/mTOR signaling.

The anti-inflammatory, immunomodulatory, and anticancer effects of micheliolide (MCL) isolated from Michelia champaca were previously reported, but its role and underlying mechanisms in relieving liver steatosis remain unclear. Herein, we investigated the effects of MCL on hepatic steatosis using a db/db mouse model and lipid mixture (LM)-induced AML12 and LO2 cells. The body and liver weights, food consumption, lipid content and liver aminotransferase levels in serum, the lipid content and inflammatory cytokine levels in liver tissue, and the extent of hepatic steatosis in db/db mice were increased compared with those in db/m mice, and these increases were reversed by MCL treatment. Similarly, MCL also attenuated the inflammatory responses and lipid accumulation in LM-treated AML12 and L02 cells by upregulating PPAR-γ and decreasing p-IкBα and p-NF-κB/p65, thereby inhibiting the NF-κB pathway and reducing lipotoxicity. Furthermore, MCL administration increased LC3B, Atg7 and Beclin-1 expression and the LC3B-II/I ratio in db/db mouse livers and LM-treated AML12 and L02 cells, and these MCL-induced increases were mediated by the activation of PPAR-γ and p-AMPK and inhibition of p-mTOR and induce autophagy. These effects were blocked by PPAR-γ and AMPK inhibitors. Our findings suggest that MCL ameliorates liver steatosis by upregulating PPAR-γ expression, thereby inhibiting NF-κB-mediated inflammation and activating AMPK/mTOR-dependent autophagy.

Irbesartan ameliorates hyperlipidemia and liver steatosis in type 2 diabetic db/db mice via stimulating PPAR-γ, AMPK/Akt/mTOR signaling and autophagy.

Irbesartan (Irb), a unique subset of angiotensin II receptor blockers (ARBs) with PPAR-γ activation function, has been reported to play a role in renal dysfunction, glucose metabolism, and abnormal lipid profile in diabetic animal models and humans. However, the underlying mechanisms that improve hyperlipidemia and liver steatosis are unclear. This study investigated the effects of Irb on lipid metabolism and hepatic steatosis using the spontaneous type 2 diabetic db/db mouse model. The results demonstrated body and liver weight, food consumption, lipid content in serum and liver tissue, and liver dysfunction as well as hepatic steatosis were increased in db/db mice compared with db/m mice, whereas the increases were reversed by Irb treatment. Moreover, Irb administration resulted in an increase in LC3BII as well as the LC3BII/I ratio through activating PPAR-γ and p-AMPK and inhibiting p-Akt and p-mTOR, thereby inducing autophagy in the db/db mouse liver. Therefore, our findings suggest that Irb can ameliorate hyperlipidemia and liver steatosis by upregulating the expression of PPAR-γ, activating the AMPK/Akt/mTOR signaling pathway and inducing liver autophagy.

Metadherin facilitates podocyte apoptosis in diabetic nephropathy.

Apoptosis, one of the major causes of podocyte loss, has been reported to have a vital role in diabetic nephropathy (DN) pathogenesis, and understanding the mechanisms underlying the regulation of podocyte apoptosis is crucial. Metadherin (MTDH) is an important oncogene, which is overexpressed in most cancers and responsible for apoptosis, metastasis, and poor patient survival. Here we show that the expression levels of Mtdh and phosphorylated p38 mitogen-activated protein kinase (MAPK) are significantly increased, whereas those of the microRNA-30 family members (miR-30s) are considerably reduced in the glomeruli of DN rat model and in high glucose (HG)-induced conditionally immortalized mouse podocytes (MPC5). These levels are positively correlated with podocyte apoptosis rate. The inhibition of Mtdh expression, using small interfering RNA, but not Mtdh overexpression, was shown to inhibit HG-induced MPC5 apoptosis and p38 MAPK pathway, and Bax and cleaved caspase 3 expression. This was shown to be similar to the effects of p38 MAPK inhibitor (SB203580). Furthermore, luciferase assay results demonstrated that Mtdh represents the target of miR-30s. Transient transfection experiments, using miR-30 microRNA (miRNA) inhibitors, led to the increase in Mtdh expression and induced the apoptosis of MPC5, whereas the treatment with miR-30 miRNA mimics led to the reduction in Mtdh expression and apoptosis of HG-induced MPC5 cells in comparison with their respective controls. Our results demonstrate that Mtdh is a potent modulator of podocyte apoptosis, and that it represents the target of miR-30 miRNAs, facilitating podocyte apoptosis through the activation of HG-induced p38 MAPK-dependent pathway.

[Irbesartan ameliorates cardiac inflammation in type 2 diabetic db/db mice].

OBJECTIVE: To investigate the protective effects of irbesartan against cardiac inflammation associated with diabetes and obesity in the db/db mouse model of type 2 diabetes and explore the underlying mechanisms. METHODS: Twenty- four 10-week-old diabetic db/db mice were equally randomized into irbesartan treatment (50 mg/kg per day) group and model group, using 12 nondiabetic littermates (db/+) as the controls, The mice were treated with irbesartan or saline vehicle for 16 consecutive weeks, after which the heart pathology was observed and the heart weight, body weight, and serum levels of fasting blood glucose (FBG), total cholesterol(TC), and triglycerides(TG) were measured. The expression of nuclear factor-kappaB (NF-κB) p65 in the myocardium was assessed with immunohistochemistry, the protein levels of P-IκBα ,IκBα and ß-actin were analyzed with Western blotting, and the pro-inflammatory cytokines IL-6 and TNF-α mRNA were detected using quantitative real-time PCR (qPCR). RESULTS: Compared with db/+ mice, the saline-treated db/db mice developed obesity, hyperglycemia and hyperlipidemia (P<0.01). Histopathological examination of the heart tissue revealed inflammatory cell infiltration, increased myocardial interstitium and disorders of myocardial fiber arrangement. The diabetic mice showed increased P-IαBα and decreased IκBα protein levels, enhanced activity and expression of NF-κB in the hearts, and increased mRNA expression of IL-6 and TNF-α in the myocardium. These abnormalities were all associated with increased inflammatory response. Treatment with irbesartan improved the heart architecture and attenuated high glucose-induced inflammation in the diabetic mice. CONCLUSION: Treatment with irbesartan attenuates cardiac inflammation in type 2 diabetic db/db mice, and this effect was probably associated with the suppression of cardiac angiotensin II and NF-κB signaling pathway.