Therapeutic Effects of FK506 on IgA Nephropathy Rat.

BACKGROUND/AIMS: FK506 is an immunosuppressive drug and a calcineurin inhibitor that has been widely used in kidney disease in recent years. FK506 shows a wide range of biological and pharmaceutical effects; however, the mechanism of its anti- proliferative effect has not been well elucidated. An IgA nephropathy (IgAN) model was used to generate a mesangial cell proliferation model. This study aims to examine the effect of FK506 on IgAN rats and the underlying mechanisms. METHODS: Hematuria, proteinuria and renal function were measured. To observe the pathological conditions, we performed HE (hematoxylin - eosin) and PAS (periodic acid - schiff) staining. Transcription and protein expression levels were detected by qRT - PCR (quantitative real-time polymerase chain reaction) and Wb (western blotting). The location and semi-quantitative expression levels of TRPCs, CaN (Calcineurin) and α-SMA were examined by IHC (Immunohistochemical staining). RESULTS: We found that FK506 could improve hematuria, proteinuria and renal function, especially in the HF (high-dose FK506) groups. Renal pathological changes were ameliorated in the treatment groups. FK506 could significantly decrease TRPCs, CaN, phosphorylation of ERK1/2 and α-SMA expression. CONCLUSION: Taken together, these results suggest that the therapeutic effect of FK506 on IgAN might be partially associated with the down-regulated expression of TRPC channels, CaN and phosphorylation of ERK1/2.

Uremia-caused changes of ghrelin system in hippocampus may be associated with impaired cognitive function of hippocampus.

PURPOSE: Hippocampus plays an important role in spatial learning and memory. Ghrelin, a brain-gut peptide, participates in the mnestic functions of hippocampus through its receptor growth hormone secretagogue receptor (GHS-R) distributed in hippocampus. This study was to investigate whether there was a correlation between the changes of ghrelin system in hippocampus and the spatial cognitive impairment caused by chronic renal failure (CRF). METHODS: Sprague-Dawley rats (male, 180 ± 10 g, 7-8 weeks old) were randomly classified into CRF group and control group (n = 18 per group). The CRF model was constructed by 5/6 nephrectomy and the controls treated with sham operation. By the 8th week after the surgery, the spatial cognitive function of rats was assessed by Morris water-maze test (MWM), the protein expression of ghrelin and GHS-R in the hippocampus by immunohistochemistry, and the mRNA expression by real-time PCR. Statistical analysis was performed using ANOVA, Student-Newman-Keuls-q test and Pearson correlation analysis, and P < 0.05 was considered significant. RESULTS: Compared with the controls, the time spent in "platform" quadrant (TSPQ) of rats with CRF was decreased, but the escape latency (EL) was increased significantly in MWM, and meanwhile the protein and mRNA expression of ghrelin and GHS-R in hippocampus was also increased significantly (P < 0.05 or P < 0.01). Correlation analysis suggested that the TSPQ was negatively but the EL was positively correlated with the mRNA expression of ghrelin and GHS-R (P < 0.01). CONCLUSION: The CRF-caused changes of ghrelin system in hippocampus might be correlated with the CRF-caused cognitive function impairment.

Sirt1 is essential for resveratrol enhancement of hypoxia-induced autophagy in the type 2 diabetic nephropathy rat.

Type 2 diabetic nephropathy (DN) is a serious end-stage kidney disease worldwide. Multiple studies demonstrate that resveratrol (RSV) has a beneficial effect on DN. However, whether RSV-induced improvement in kidney function in diabetes is due to the regulation of autophagy remains unclear. Here, we investigated the mechanisms underlying RSV-mediated protection against DN in diabetic rats, with a special focus on the role of NAD-dependent deacetylase sirtuin 1 (Sirt1) in regulating autophagy. We found that long-term RSV treatment in rats promoted Sirt1 expression and improved related metabolic levels in the diabetic kidney. Our study showed that, in cultured NRK-52E cells, Sirt1 knockdown inhibited the autophagy levels of proteins Atg7, Atg5, and LC3 and impaired the RSV amelioration of dysfunctional autophagy under hypoxic condition. Furthermore, exposed to 1% O2 over time induced autophagy dysfunction and apoptosis in NRK-52E cells, which could be improved by RSV treatment. Our data highlight the role of the Sirt1-mediated pathway in the effects of RSV on autophagy in vivo and in vitro, suggesting RSV could be a potential new therapy for type 2 DN.

Activation of AMPK by metformin inhibits TGF-ß-induced collagen production in mouse renal fibroblasts.

AIMS: To clarify whether activation of adenosine monophosphate-activated protein kinase (AMPK) by metformin inhibits transforming growth factor beta (TGF-ß)-induced collagen production in primary cultured mouse renal fibroblasts and further to address the molecular mechanisms. MAIN METHODS: Primary cultured mouse renal fibroblasts were stimulated with TGF-ß1 and the sequence specific siRNA of Smad3 or connective tissue growth factor (CTGF) was applied to investigate the involvement of these molecular mediators in TGF-ß1-induced collagen type I production. Cells were pre-incubated with AMPK agonist metformin or co-incubated with AMPK agonist metformin and AMPK inhibitor Compound C before TGF-ß1 stimulation to clarify whether activation of AMPK inhibition of TGF-ß1-induced renal fibroblast collagen type I expression. KEY FINDINGS: Our results demonstrate that TGF-ß1 time- and dose-dependently induced renal fibroblast collagen type I production; TGF-ß1 also stimulated Smad3-dependent CTGF expression and caused collagen type I generation; this effect was blocked by knockdown of Smad3 or CTGF. Activation of AMPK by metformin reduced TGF-ß1-induced collagen type I production by suppression of Smad3-driven CTGF expression. SIGNIFICANCE: This study suggests that activation of AMPK might be a novel strategy for the treatment of chronic kidney disease (CKD) partially by inhibition of renal interstitial fibrosis (RIF).