Inhibition of ERK1/2 by silymarin in mouse mesangial cells.

The present study aimed to show that pro-inflammatory cytokines [tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, and interleukin (IL)-1 beta] synergistically induce the production of nitric oxide (NO) production in mouse mesangial cells, which play an important role in inflammatory glomerular injury. We also found that co-treatment with cytokines at low doses (TNF-alpha; 5 ng/ml, IFN-gamma; 5 ng/ml, and IL-1 beta; 1.25 U/ml) synergistically induced NO production, whereas treatment with each cytokine alone did not increase NO production at doses up to 100 ng/ml or 50 U/ml. Silymarin, a polyphenolic flavonoid isolated from milk thistle (Silybum marianum), attenuates cytokine mixture (INF-alpha, IFN-gamma, and IL-1 beta-induced NO production. Western blot and RT-PCR analyses showed that silymarin inhibits inducible nitric oxide synthase (iNOS) expression in a dose-dependent manner. Silymarin also inhibited extracellular signal-regulated protein kinase-1 and -2 (ERK1/2) phosphorylation. Collectively, we have demonstrated that silymarin inhibits NO production in mouse mesangial cells, and may act as a useful anti-inflammatory agent.