Anti-Inflammatory molecular mechanisms of Bo-Ye-Niu- Pi-Xiao (<i>Cynanchum taiwanianum</i> Yamazaki)

Abstract

Bo-Ye-Niu-Pi-Xiao, Cynanchum taiwanianum Yamazaki (family: Asclepiadaceae) is a well-known and popular herb; its rhizome has been used as a folk medicine in Taiwan. Many therapeutic effects of C. taiwanianum Yamaz. had been studied; however, there is still no anti-inflammatory effect and mechanism of C. taiwanianum Yamaz. reported. Besides, it is well-known that the phosphorylation of I kappa B-alpha (IκBα) to phospho-IκBα (p-IκBα) is a decisive step in the nuclear factor kappa B (NF-κB) activation pathway. In addition, the induction of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) by cytokines, such as interleukin-1β (IL-1β), is well known to be partly mediated by NF- κB. Hence, the objective of this study was to evaluate the activity and distinguish the mechanism of anti-inflammation of C. taiwanianum Yamaz. rhizome on rat kidney cell line NRK-52E induced by IL-1β. In the present study, we investigated the anti-inflammatory effect and potential mechanism of C. taiwanianum Yamaz. rhizome ethanolic extract (CTEE) in IL-1β-induced NRK-52E cells. Production of nitric oxide (NO) and prostaglandin E2 (PGE₂) by enzyme linked immunosorbent assay. The messenger ribonucleic acid (mRNA) and protein expression of iNOS and COX-2, phosphorylation of IκBα, and activation of NF-κB was executed by reverse transcription-polymerase chain reaction and Western blotting. Results show that the CTEE significantly (P < 0.05) inhibited NO and PGE₂ production and also significantly (P < 0.05) attenuated protein and mRNA expression of iNOS and COX-2 in IL-1β-induced NRK-52E cells without obvious cytotoxic effects. Furthermore, the CTEE suppressed the NF-κB nuclear translocation, in terms of inhibition of IκBα phosphorylation. The results provided evidence for its folkloric uses and suggest that the anti-inflammatory activities of CTEE may result from the inhibition of inflammatory mediators, such as NO and PGE₂ and an upstream suppression of NF-κB-dependent mechanism might be involved.

Key words: Cynanchum taiwanianum Yamazaki, anti-inflammatory, cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS).