Shanxi University of Chinese Medicine，Jinzhong 030619，China
Objective To detect the toxicity of water-eluted fraction from Siegesbeckiae Herba （SWEF） at different concentrations against MRC-5 human embryonic lung fibroblasts and its impacts on the expression of α7 nicotinic acetylcholine receptor （α7nAChR） and inflammatory factors， so as to figure out the active components responsible for toxicity and efficacy.Method The toxicities of SWEF at 1， 6， 10， 20， and 50 g·L-1 against MRC-5 cells were determined by cell counting kit-8 （CCK-8） assay combined with flow cytometry and Trypan blue staining. The changes in α7nAChR expression and inflammatory factor levels before and after α7nAChR gene silencing were detected to reveal the pharmacodynamic effect of SWEF on MRC-5 cells.Result SWEF （≥6 g·L-1） obviously inhibited the viability of MRC-5 cells （P<0.01） and promoted their apoptosis and necrosis （P<0.01）， with the half-maximal inhibitory concentration （IC50） being 6.03 g·L-1. The determination of α7nAChR expression and inflammatory factor levels in MRC-5 cells showed that SWEF contained α7nAChR agonist-like substance， which enhanced α7nAChR mRNA and protein expression （P<0.05， P<0.01） and decreased the inflammatory factor levels （P<0.05， P<0.01）. SWEF down-regulated the inflammatory factors possibly by re-regulating α7nAChR mRNA expression， exhibiting a negative correlation between them （P<0.01）.Conclusion SWEF （≥6 g·L-1） is highly toxic to MRC-5 cells. Pharmacodynamic studies have confirmed that α7nAChR agonist-like substance contained in SWEF was responsible for the elevated α7nAChR expression and reduced inflammatory cytokines. It is inferred that excessive α7nAChR agonist-like substance may trigger the toxicity of Siegesbeckiae Herba.
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