Ginsenoside retinoblastoma 1 (Rb1) suppresses NO production and inducible nitric oxide synthase (iNOS) expression by inhibiting nuclear factor B (NF-B) activation in SW1353 chondrosarcoma cells

Ginseng (Panax ginseng C.A. Mey) is commonly used to treat osteoarthritis (OA) in Chinese traditional medicine (TCM). In this study, we investigated whether ginsenoside retinoblastoma 1 (Rb1), an active component of ginseng, could regulate NO production in chondrocytes and its potential mechanisms of action. SW1353 cells were stimulated with IL-1β in the presence of different concentrations of ginsenoside Rb1. NO concentration was assessed by the Griess reaction. Expression of iNOS, degradation of IBα and nuclear translocation of NF-κB p65 were determined by Western blot. DNA binding activity of NF-κB complex was evaluated with Trans AM™ kit for p65. We found that ginsenoside Rb1 significantly decreased the NO production and iNOS protein expression in a concentration-dependent manner. Ginsenoside Rb1 markedly decreased the IκBα degradation and nuclear p65 levels, as well as inhibited the DNA binding activity of NF-κB complex. These results suggest that ginsenoside Rb1 inhibits IL-1β-induced NO production through downregulation of NF-κB-dependent iNOS expression in chondrocytes, and reveals potential mechanisms explaining the benefits of ginseng for OA treatment in TCM.   Key words: Ginsenoside, retinoblastoma 1 (Rb1), NO, inducible nitric oxide synthase (iNOS), nuclear factor κB (NF-κB), chondrocyte, osteoarthritis.