RhoA/ROCK inhibition attenuates endothelin-1-induced elevated glomerular permeability to albumin, inflammation, and fibrosis

Endothelin-1 (ET-1) contributes to the development of kidney diseases. However, the underlying molecular mechanism is largely undefined. Here we sought to investigate the potential role of ET-1 receptors, ET_A and ET_B in the regulation of increased glomerular permeability and underlying signaling pathways post-ET-1 infusion. Male Sprague-Dawley rats were infused with ET-1 (2 pmol/kg per minute, i.v.) for four weeks, and the effect on glomerular permeability to albumin (P_alb) and albuminuria was measured. The selective ROCK-1/2 inhibitor, Y-27632, was administered to a separate group of rats to determine its effect on ET-1-induced P_alb and albuminuria. The role of ET_A and ET_B receptors in regulating RhoA/ROCK activity was determined by incubating isolated glomeruli from normal rats with ET-1 and with selective ET_A and ET_B receptor antagonists. ET-1 infusion for four weeks significantly elevated P_alb and albuminuria. Y-27632 significantly reduced the elevation of P_alb and albuminuria. The activities of both RhoA and ROCK-1/2 were increased by ET-1 infusion. Selective ET_B receptor antagonism had no effect on the elevated activity of both RhoA and ROCK-1/2 enzymes. Selective ET_A receptor and combined ET_A/ET_B receptors blockade restored the activity of RhoA and ROCK-1/2 to normal levels. In addition, chronic ET-1 infusion increased the levels of glomerular inflammatory and fibrotic markers. These effects were all attenuated in rats following ROCK-1/2 inhibition. These observations suggest that ET-1 contributes to increased albuminuria, inflammation, and fibrosis by modulating the activity of the ET_A-RhoA/ROCK-1/2 pathway. Selective ET_A receptor blockade may represent a potential therapeutic strategy to limit glomerular injury and albuminuria in kidney disease.

Ginsenoside Rg1 attenuates glomerular fibrosis by inhibiting CD36/TRPC6/NFAT2 signaling in type 2 diabetes mellitus mice

ETHNOPHARMACOLOGICAL RELEVANCE

Ginsenoside Rg1 (Rg1) is one of the main active components in Panax ginseng C. A. Meyer (ginseng), which has been widely used to delay senescence or improve health conditions for more than 2000 years. Increasing studies have revealed that Rg1 could regulate cell proliferation and differentiation, as well as anti-inflammatory and anti-apoptotic effects, and might have protective effects on many chronic kidney diseases.

AIM OF THE STUDY

Diabetic nephropathy (DN) is one of the most dangerous microvascular complications of diabetes and is the leading cause of end-stage renal disease worldwide. However, the role and mechanism of Rg1 against high-glucose and high-fat-induced glomerular fibrosis in DN are not clear. This study aimed to investigate the protective effect of Rg1 on DN and its possible mechanism.

MATERIALS AND METHODS

The type 2 diabetes mellitus (T2DM) mice models were established with a high-fat diet (HFD) combined with an intraperitoneal injection of streptozotocin (STZ). Urine protein and serum biochemical indexes were detected by corresponding kits. The kidney was stained with H&E, PAS, and Masson to observe the pathological morphology, glycogen deposition, and fibrosis. The expression of CD36 and p-PLC in the kidney cortex was detected by IHC. The expressions of FN and COL4 were detected by IF. Western blot and PCR were performed to examine protein and mRNA expressions of kidney fibrosis and TRPC6/NFAT2-related pathways in DN mice. Calcium imaging was used to examine the effect of Rg1 on [Ca²⁺]_i in PA + HG-induced human mesangial cells (HMCs). Visualization of the interaction between Rg1 and CD36 was detected by molecular docking.

RESULTS

Rg1 treatment for 8 weeks could prominently decrease urinary protein, serum creatinine, and urea nitrogen and downgrade blood lipid levels and renal lipid accumulation in T2DM mice. The pathological results indicated that Rg1 treatment attenuated renal pathological injury and glomerular fibrosis. The further results demonstrated that Rg1 treatment remarkably decreased the expressions of CD36, TRPC6, p-PLC, CN, NFAT2, TGF-β, p-Smad2/3, COL4, and FN in renal tissues from T2DM mice. Calcium imaging results found that Rg1 downgraded the base levels of [Ca²⁺]_i and ΔRatioF340/F380 after BAPTA and CaCl₂ treatment. Molecular docking results showed that Rg1 could interact with CD36 with a good affinity.

CONCLUSION

These results revealed that Rg1 could ameliorate renal lipid accumulation, pathological damage, and glomerular fibrosis in T2DM mice. The mechanism may be involved in reducing the overexpression of CD36 and inhibiting the TRPC6/NFAT2 signaling pathway in renal tissues of T2DM mice.

Mesenchymal stem cells modified with angiotensin-converting enzyme 2 are superior for amelioration of glomerular fibrosis in diabetic nephropathy

AIMS

This study aimed to detect the effect of angiotensin-converting enzyme (ACE) 2-modified mesenchymal stem cells (MSCs) on glomerular fibrosis in vitro and in vivo and investigate the underlying molecular mechanism.

METHODS

MSCs transduced with the ACE2 gene (MSCs-ACE2) were cocultured with glomerular mesangial cells (GMCs) following Ang II stimulation. MSCs-ACE2 were transplanted into streptozotocin-induced diabetic rats. Physical, biochemical and morphological parameters were measured, and fibrotic indicators and renin-angiotensin system (RAS) components in GMCs and kidney tissues were assessed.

RESULTS

The transduction efficiency of MSCs was as high as 85%. The modified MSCs secreted soluble ACE2 protein into the culture medium. After transplantation into rats with diabetes, MSCs-ACE2 targeted injured kidneys and enhanced local expression of ACE2. Compared with MSC treatment alone, MSC-ACE2 treatment was superior in reducing albuminuria and improving glomerulosclerosis. In vitro and in vivo, MSCs-ACE2 were more beneficial than MSCs alone in decreasing Ang II and increasing Ang1-7, thereby inhibiting the detrimental effects of Ang II accumulation by downregulating collagen I and fibronectin (FN) expression and inhibiting the transforming growth factor (TGF-β)/Smad pathway.

CONCLUSIONS

MSCs modified with ACE2 therapy have additional benefits to the progression of diabetic nephropathy (DN) by inhibiting renal RAS activation and reducing glomerular fibrosis.

DNA double-strand breaks induced intractable glomerular fibrosis in renal allografts

BACKGROUNDS

The relationship between DNA damage and glomerular fibrosis in renal allografts remains unclear.

METHODS

We examined renal allograft specimens from 35 patients in which DNA double-strand breaks (DSBs) and glomerular fibrosis were detected by phospho-histone H2A.X (γ-H2AX) expression and collagen (COL) types III, IV, and VI accumulation. We also examined the in vitro relationship between DNA damage and COL accumulation by mitomycin C (MMc)-induced DNA damage in human glomerular endothelial cells (HRGEc).

RESULTS

The γ-H2AX and COL type VI, which mainly accumulated in the subendothelial and mesangial regions, were positively correlated with the duration of the post-renal transplant (RT) period. In multiple regression analysis, the duration of the post-RT period and cg in the Banff '07 classification were identified as a significant predictor of COL type VI accumulation and γ-H2AX expression in the glomerular capillaries. In addition, the γ-H2AX-positive area was also identified as a predictor of glomerular accumulation of COL type VI. COL type VI was detected in the cytoplasm of the HRGEc, which was secreted into the supernatant after MMc stimulation with γ-H2AX expression. The number of γ-H2AX (-)/COL type VI (+) cells was inversely associated with the number of γ-H2AX (+)/COL type VI (-) cells during 24-h MMc treatment.

CONCLUSIONS

Our findings suggest that the long-term RT induces DSBs and HRGEc-secreted COL type VI accumulation in the glomerular capillaries, which might progress to intractable glomerular fibrosis.