Paeoniflorin protects RAW 264.7 macrophages from LPS-induced cytotoxicity and genotoxicity

LPS is one of the major constituents of the outer membrane of Gram-negative bacteria. LPS-induced activation of macrophage results in the nitrite (NO) production and the secretion of a pro-inflammatory mediator such as PGE(2). Excessive NO reacts with the superoxide anion to generate a selective oxidant and nitrating agent, peroxynitrite, which interacts with biological molecules and damages the cell membranes of them, being able to result in the cell death. We evaluated the protective effects of paeoniflorin (PF) against LPS-induced toxicity by measuring its dose-dependent effects on cell viability in MTT assay, NO production in NO assay, PGE(2) production in prostaglandin E(2) (PGE(2)) assay, and DNA damage in comet assay in LPS-treated RAW 264.7 macrophages. In the comet assay, we also analyzed tail length, tail DNA, and tail moment as the markers of DNA strand breaks. PF-treatment significantly protected RAW 264.7 macrophages against LPS-induced toxicity with the increase of viable cells, the decrease of NO and PGE(2), and the repair of DNA damage.