Protopine attenuates inflammation stimulated by carrageenan and LPS via the MAPK/NF-κB pathway

We investigated the anti-inflammatory activity of protopine (PTP) and sought to determine its mechanism of action in LPS-stimulated BV2 cells and a carrageenan (CA)-induced mouse model. Treatment with PTP (5, 10, and 20 mu M) significantly suppresses the secretion of NO and PGE(2) in a concentration-dependent manner without affecting cell viability by downregulating iNOS and COX-2 expression in LPS-induced BV2 cells. PTP also attenuates the production of pro-inflammatory chemokines, such as MCP-1, and cytokines, including TNF-alpha, IL-1 beta and IL-6, and augments the expression of the anti-inflammatory cytokine IL-10. In addition, PTP suppresses the nuclear translocation of NF-kappa B by hindering the degradation of I kappa B and downregulating the expression of mitogen-activated protein kinases (MAPKs), including p38, ERK1/2 and JNK protein. Furthermore, PTP treatment significantly suppresses CA-induced paw oedema in mice compared to that seen in untreated mice. Expression of iNOS and COX-2 proteins is also abrogated by PTP (50 mg/kg) treatment in CA-induced mice. PTP treatment also abolishes I kappa B phosphorylation, which hinders the activation of NF-kappa B. Collectively, these results suggest PTP has potential for attenuating CA- and LPS-induced inflammatory symptoms through modulation of MAPKs/NF-kappa B signaling cascades.