Triptolide inhibits COX-2 expression via NF-kappa B pathway in astrocytes

Previous investigations have showed that triptolide possessed potent anti-inflammatory and immunosuppressive properties. In the present study, we examined the protective effects of triptolide on the inflammatory response induced by bacterial lipopolysaccharide (LPS) both in vivo and in vitro. Intrahippocampal injection of LPS (4 μg) in rats significantly increased the immunoreactivity of glial fibrillary acid protein (GFAP) and cyclooxygenase-2 (COX-2) in the injected region, which was reduced by pretreatment with triptolide (10-50 μg/kg) for 5 d. In the cultured human differentiated A172 astroglial cells, LPS (1 mg/L) increased the expression of COX-2 mRNA and protein, the production of prostaglandin E₂ (PGE₂) and the DNA binding activity of NF-kappa B, which were markedly attenuated by pretreatment with triptolide (0.2-5 μg/L) for 1 h. These results suggested that the protective effect of triptolide on neuroinflammation is mediated by decreasing COX-2 expression, at least partly, via the inhibition of NF-kappa B signaling pathway.