Tetrandrine down-regulates ERK/NF-κB signaling and inhibits activation of mesangial cells.

OBJECTIVES: Tetrandrine (TET), a bisbenzylisoquinoline alkaloid isolated from Stephania tetrandra S. Moore of the Menispermaceae, possesses anti-inflammatory activity. We examined the effect of tetrandrine on interleukin-1β (IL-1β)-provoked inflammatory response in mesangial cells.
MATERIALS AND METHODS: Primary rat mesangial cells (PRMCs) were treated with IL-1β to induce inflammation to resemble glomerulonephritis. Cell viability, morphology and NO production were evaluated. Western blotting was applied for expression of matrix metalloproteinase-9 (MMP-9), inducible NO synthase (iNOS), extracellular signal-regulated kinase (ERK) and NF-κB-related molecules. Electrophoretic mobility shift assay was performed to examine the DNA-binding activity of NF-κB.
RESULTS: TET, at concentrations up to 10 μg/ml, had no significant effect on viability of PRMCs. At non-toxic concentrations, TET inhibited expression of phosphorylated ERK as well as phosphorylated IKK, enhanced degradation of IκBα and reduced the DNA-binding activity of NF-κB in IL-1β-primed PRMCs, suggesting an inhibitory effect on ERK/NF-κB signaling. TET attenuated the IL-1β-provoked expression of iNOS and release of NO. Moreover, both the protein expression and gelatinase activity of MMP-9, but not MMP-2, were markedly suppressed by TET. SIGNIFICANCE: TET down-regulated ERK/NF-κB signaling and inhibited the expression of inflammatory mediators NO and MMP-9. Since these mediators appear to activate mesangial cells, TET may play an important role in prevention of glomerulonephritis.