Green tea polyphenol (-)-epigallocatechin-3-gallate restores Nrf2 activity and ameliorates crescentic glomerulonephritis.

Crescentic glomerulonephritis (GN) is the most severe form of GN and is associated with significant morbidity and mortality despite aggressive immunotherapy with steroids, cytotoxic drugs, and plasmapheresis. We examined the therapeutic efficacy of the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG, 50 mg/kg BW/day x3 weeks), a potent anti-inflammatory and anti-oxidant agent, on experimental crescentic GN induced in 129/svJ mice by administration of rabbit anti-mouse glomerular basement membrane sera. Routine histology and key molecules involved in inflammatory and redox signaling were studied. EGCG treatment significantly reduced mortality, decreased proteinuria and serum creatinine, and markedly improved renal histology when compared with vehicle-treated mice. The improvements in renal function and histology were accompanied by the restoration of Nrf2 signaling (which was impaired in vehicle-treated mice) as shown by increased nuclear translocation of Nrf2 and cytoplasmic glutamate cysteine ligase catalytic subunit, glutamate cysteine ligase modifier subunit, and glutathione peroxidase. EGCG-treated mice also showed reduction in p-Akt, p-JNK, p-ERK1/2 and p-P38 as well as restoration of PPARγ and SIRT1 levels. Lower dose of EGCG (25 mg/kg BW/day x2 weeks) treatment also significantly decreased proteinuria and serum creatinine, and markedly improved renal histology when compared with vehicle-treated mice. Thus, our data illustrate the efficacy of EGCG in reversing the progression of crescentic GN in mice by targeting multiple signaling and inflammatory pathways as well as countering oxidative stress.

Resveratrol attenuates early diabetic nephropathy by down-regulating glutathione s-transferases Mu in diabetic rats.

Diabetic nephropathy (DN) is the major cause of end-stage renal disease. Resveratrol has been shown to ameliorate hyperglycemia in diabetic rats. However, the effects of resveratrol on DN remain unknown. The aim of the present study is to investigate the effects of resveratrol on early-stage DN. Diabetes was induced by streptozotocin injection in male Wistar rats. The diabetic rats were treated with resveratrol at a dose of 20 mg/kg body weight for 8 weeks. Plasma glucose, creatinine, kidney/body weight ratio, and 24-h urinary protein were determined. The renal pathological changes were examined with periodic acid Schiff staining, and renal mesangial cells were cultured in high glucose concentrations with indicated concentrations of resveratrol (2.5, 5.0, and 10.0 µmol/L). The proliferation of mesangial cells was evaluated by methylthiazoletetrazolium assay. Expressions of glutathione S-transferases Mu (GSTM) and nuclear factor erythroid 2-related factor 2 (Nrf2) were detected by western blot, and apoptosis was analyzed using a flow cytometer. Resveratrol reduced plasma glucose, creatinine, and urinary protein excretion, and attenuated renal hypertrophy. Moreover, resveratrol also reduced the expression of GSTM in diabetic rats. In vitro, resveratrol inhibited the proliferation of mesangial cells caused by high glucose and down-regulated GSTM and Nrf2 expressions in a dose-dependent manner. These findings suggest that resveratrol help prevent the progression of DN. The renoprotection by resveratrol is in part mediated through the inhibition of high glucose-induced rat mesangial cell proliferation and downregulation of GSTM expression.