Connexin43 mediates NF-κB signalling activation induced by high glucose in GMCs: involvement of c-Src.

BACKGROUND: Nuclear factor kappa-B (NF-κB) signalling plays an important role in diabetic nephropathy. Altered expression of connexin43 (Cx43) has been found in kidneys of diabetic animals. The aim of the current study was to investigate the role of Cx43 in the activation of NF-κB induced by high glucose in glomerular mesangial cells (GMCs) and to determine whether c-Src is involved in this process. RESULTS: We found that downregulation of Cx43 expression induced by high glucose activated NF-κB in GMCs. Orverexpression of Cx43 attenuated NF-κB p65 nuclear translocation induced by high glucose. High glucose inhibited the interaction between Cx43 and c-Src, and enhanced the interaction between c-Src and IκB-α. PP2, a c-Src inhibitor, also inhibited the tyrosine phosphorylation of IκB-α and NF-κB p65 nuclear translocation induced by high glucose. Furthermore, overexpression of Cx43 or inhibition of c-Src attenuated the upregulation of intercellular adhesion molecule-1 (ICAM-1), transforming growth factor-beta 1 (TGF-ß1) and fibronectin (FN) expression induced by high glucose. CONCLUSIONS: In conclusion, downregulation of Cx43 in GMCs induced by high glucose activates c-Src, which in turn promotes interaction between c-Src and IκB-α and contributes to NF-κB activation in GMCs, leading to renal inflammation.

Dibutyltin (DBT) inhibits in vitro androgen biosynthesis of rat immature Leydig cells.

Dibutyltin (DBT) is an organotine widely applied in stabilizing plastics and de-worm poultry agents. But the effects of DBT on immature Leydig cells remain elusive. Thus, the present study aims to investigate whether in vitro exposure to DBT affects immature Leydig cell function of androgen production and delineate the underlying mechanisms. 35 days old rat immature Leydig cells were isolated and exposed to DBT at different concentrations (0, 0.1, 0.5, and 1 µM). It was found that 0.5 and 1 µM DBT lowered androgen production from immature Leydig cells under basal conditions. DBT at 1 µM lowered androgen production from immature Leydig cells under the stimulations from luteinizing hormone or 8-Br-cAMP. DBT at 1 µM lowered 22R-hydroxycholesterol and pregnenolone-mediated androgen production from immature Leydig cells. DBT at 0.1, 0.5, and 1 µM down-regulated the mRNA expression levels of Lhcgr, Star, Cyp11a1, Hsd3b1, and Nr5a1. Further investigation found that DBT at 1 µM directly inhibited CYP11A1 and 3ß-HSD1 enzyme activities. In conclusion, this study told us that in vitro exposure to DBT inhibited androgen biosynthesis in immature Leydig cells by selectively interfering with the expressions and enzyme activities of CYP11A1 and 3ß-HSD1.

Berberine ameliorates experimental diabetes-induced renal inflammation and fibronectin by inhibiting the activation of RhoA/ROCK signaling.

The accumulation of glomerular extracellular matrix proteins, especially fibronectin (FN), is a critical pathological characteristic of diabetic renal fibrosis. Inflammation mediated by nuclear factor-κB (NF-κB) plays a critical role in the pathogenesis of diabetic nephropathy (DN). RhoA/ROCK signaling is responsible for FN accumulation and NF-κB activation. Berberine (BBR) treatment significantly inhibited renal inflammation and thus improved renal damage in diabetes. Here, we study whether BBR inhibits FN accumulation and NF-κB activation by inhibiting RhoA/ROCK signaling and the underlying mechanisms involved. Results showed that BBR effectively inhibited RhoA/ROCK signaling activation in diabetic rat kidneys and high glucose-induced glomerular mesangial cells (GMCs) and simultaneously down-regulated NF-κB activity, which was accompanied by reduced intercellular adhesionmolecule-1, transforming growth factor-beta 1 and FN overproduction. Furthermore, we observed that BBR abrogated high glucose-mediated reactive oxygen species generation in GMCs. BBR and N-acetylcysteine inhibited RhoA/ROCK signaling activation in high glucose-exposed GMCs. Collectively, our data suggest that the renoprotective effect of BBR on DN partly depends on RhoA/ROCK inhibition. The anti-oxidative stress effect of BBR is responsible for RhoA/ROCK inhibition in DN.

Activation of RhoA/ROCK regulates NF-κB signaling pathway in experimental diabetic nephropathy.

Both RhoA/ROCK and NF-κB signaling pathways play important roles in the pathogenesis of diabetic nephropathy (DN). However, it remains unknown whether and how RhoA/ROCK regulates NF-κB signaling in diabetic kidneys. In cultured glomerular mesangial cells (GMCs), the high glucose-activated NF-κB nuclear translocation and DNA binding activity were attenuated by ROCK inhibitor Y27632 or dominant-negative RhoA mutant, indicating that RhoA/ROCK signaling regulates high glucose-activated NF-κB pathway. Furthermore, NF-κB-regulated inflammatory factors ICAM-1 and TGF-ß1 were markedly increased in high glucose-treated GMCs, leading to accumulation of fibronectin (FN), an important component of extracellular matrix (ECM), This effect was also effectively attenuated by Y27632 or dominant-negative RhoA mutant. In STZ-induced diabetic rats, treatment with ROCK inhibitor fasudil suppressed the RhoA/ROCK activation and NF-κB nuclear translocation, and significantly reduced the renal FN, ICAM-1 and TGF-ß1 protein levels. Thus, the RhoA/ROCK pathway may regulate NF-κB to upregulate inflammatory genes and mediate the development of DN.