Liqun Ma

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 PPAR-γ inhibits PDGF-induced proliferation of mouse renal fibroblasts

Recent studies have shown that activation of peroxisome proliferators activated receptor-γ (PPAR-γ) ameliorates renal interstitial fibrosis (RIF) in animal model. Yet, the underlying molecular mechanisms remain still largely unknown. Here, we investigated the hypothesis that activation of PPAR-γ regulates renal remodeling by modulating proliferation of primary cultured renal fibroblasts. In our present study, platelet-derived growth factor-AA (PDGF-AA), a key isoform of PDGF superfamily as mitogen in RIF, was applied to stimulate renal fibroblasts, the selective inhibitor or sequence specific siRNA of PI3K, skp2 or PPAR-γ was used to investigate the involvement of above molecular mediators in PDGF-AA-induced cell proliferation. Our results demonstrate that PDGF-AA induced proliferation of renal fibroblasts by activating PI3K/AKT signaling and resultant skp2 production. Pre-stimulation of cells with rosiglitazone or adenovirus carrying PPAR-γ cDNA (AdPPAR-γ) blocked PDGF-AA-stimulated cell proliferation, this effect was particularly coupled to PPAR-γ inhibition of AKT phosphorylation and skp2 expression. Inhibition of PPAR-γ by GW9662 restored the suppression of activated PPAR-γ on phosphorylation of AKT and subsequent skp2 production. Our results indicate that activation of PI3K/AKT signaling and resultant skp2 generation mediated PDGF-induced proliferation of renal fibroblasts. Activation of PPAR-γ inhibited cell proliferation by inhibition of AKT phosphorylation and its down-streams.

Premature senescence and cellular phenotype transformation of mesangial cells induced by TGF-B1

Abstract Background: Transforming growth factor-β1 (TGF-β1) is a polypeptide member of the transforming growth factor β superfamily of cytokines and performs many cellular functions. Its overexpression may lead to renal fibrosis. Aim: This study planed to investigate the effects of TGF-β1 on the cell cycle and phenotype of mesangial cells. Methods: Rat mesangial cells were cultured together with different concentrations (0, 1, 2, 5, and 10 ng/mL) of TGF-β1 for specified times from 0 min to 72 h. 0 ng/mL TGF-β1 and 0 min served as controls. Cell cycles were assessed by flow cytometry and α-smooth muscle actin expression (α-SMA) protein expression by western blot analysis. All data were presented as Mean ± SD. Statistical analysis was performed by using one-way analysis of variance and correlation analysis. Results were considered significant at p < 0.05. Results: After 15 min of co-culture with different concentrations of TGF-β1, the percentage of mesangial cells in G0/G1 phase was significantly elevated compared to the control (p < 0.05). 12 h co-culture induced cell hyperplasia, 24 h co-culture obvious up-regulation of α-SMA (p < 0.01) and one or two cells’ myofibroblast phenotype transition, and 36 h co-culture several cells’ phenotype transition. Correlation analysis prompted that the TGF-β1-induced premature aging was time-dependent (p < 0.01). Conclusion: TGF-β1 may induce mesangial cells’ premature senescence and myofibroblast-like phenotype transformation time-dependently, which may contribute to the development of early stage of glomerulosclerosis.

Uremic anorexia and gastrointestinal motility dysfunction correlate with the changes of ghrelin system in hypothalamus.

Ghrelin can act as a signal for meal initiation and play a role in the regulation of gastrointestinal (GI) motility via hypothalamic circuit. This study investigated the correlation between changes of hypothalamic ghrelin system and GI motility dysfunction and anorexia in rats with chronic renal failure (CRF).

Citrate Attenuates Adenine-Induced Chronic Renal Failure in Rats by Modulating the Th17/Treg Cell Balance.

Citrate is commonly used as an anticoagulant in hemodialysis for chronic renal failure (CRF) and for the regulation of the immune dysfunction in CRF patients. The objective of this study was to investigate the effect of citrate on the balance of T helper 17 (Th17) and regulatory T (Treg) cells in CRF. The levels of blood urea nitrogen (BUN) and serum creatinine (Scr) were significantly increased in the CRF model group compared to the control group, and were decreased in the citrate-treated groups. Citrate treatment inhibited the viability of Th17 cells while elevating the viability of Treg cells in CRF rats. Moreover, Th17-related cytokines significantly decreased while the Treg-related cytokines significantly increased with citrate treatment. Moreover, citrate had a negative influence on the deviation of Th17/Treg cells in CRF rats. Therefore, our study suggests that citrate had an anti-inflammatory effect on CRF through the modulation of the Th17/Treg balance.

Chronic Renal Failure Impacts the Expression of Ghrelin and Its Receptor in Hypothalamus and Hippocampus

Background/Aims: Ghrelin plays a central role in the regulation of gastrointestinal (GI) motility. This study aimed to investigate the expression of ghrelin and growth hormone secretagogue receptor (GHSR) in the central nervous system of rats with chronic renal failure (CRF). Methods: Sprague-Dawley rats (male, 180 ± 20 g, n = 24) were treated by 5/6 nephrectomy to construct CRF model. As their plasma creatinine concentration and blood urea nitrogen were maintained more than double the normal level for 2 weeks, they were killed for assessing the expression of ghrelin and GHSR in hypothalamus and hippocampus using immunohistochemistry and real-time polymerase chain reaction (RT-PCR). The rats (male, 180 ± 20 g, n = 24) treated by Sham operation served as a control. One-way analysis of variance and Student–Newman–Keuls q test were used to analyze group difference and a p-value of <0.05 was considered as statistically significant. Results: Compared with the controls, the ghrelin and GHSR expression was obviously increased in the hippocampus (p < 0.05) but decreased in the hypothalamus of rats with CRF (p < 0.05). Conclusions: CRF was found to impact the expression of ghrelin and GHSR in hypothalamus and hippocampus. This might be associated with the CRF-induced GI motility dysfunction.

Uremic anorexia and ghrelin expression in the amygdala

BACKGROUND/AIMS Ghrelin can act as a signal for mealtime hunger and meal initiation. Amygdala is indispensable in appetitive behavior motivated by learned emotions. This study was to investigate the alteration of ghrelin in the amygdala of rats with chronic renal failure (CRF) and its relation with uremic anorexia. METHODS SD rats were randomly classified into CRF group and control group (n=16 per group). The CRF model was constructed using 5/6 nephrectomy. When plasma creatinine (PCr) and blood urea nitrogen (BUN) in the CRF group were twice more than the normal level, food intake (g/24h) was measured and then all rats were killed for detection of ghrelin protein expression in the amygdala using immunohistochemical analysis and mRNA expression using RT-PCT. Statistics was conducted with one-way analysis of variance, Student-Newman-Keuls-q test and correlation analysis. RESULTS By the 8th week after the surgery, the BUN and PCr of CRF rats exceeded double the normal level, and their food intake was obviously decreased compared with the controls (P<0.05). The protein and mRNA expression of ghrelin in the amygdala of CRF group were significantly reduced, and there was a positive correlation between this reduction and the decrease in food intake (P<0.05). CONCLUSION The reduction of amygdalas ghrelin in CRF rats may be associated with uremic anorexia.