Study The Molecular Mechanism Of Lipopolysaccharide-induced Inflammatory Response Enhaced By Cadmium Exposure In Mice

Cadmium(Cd)is the most serious heavy metal pollution element in China,and its toxicity has been widely studied.However,the study of the effects of cadmium exposure on immune response and inflammation is not clear,and the mechanism of its effect on immune response is also unclear.Therefore,this paper mainly studies the effect of cadmium on the immune response of primary cultured cells from the spleen of mice under the condition of immune activation,and clarifies the underlying mechanism in the promotion of the inflammatory response by cadmium.Previous studies in our laboratory have found that cadmium can affect autophagy and Toll-like receptor(TLR)signaling pathway in a Concanavalin A(ConA)immune activation model,thereby inhibiting immune activation.Compared with ConA,LPS is a more extensively used immune activator.Therefore,LPS is selected to study the effect and molecular mechanism of cadmium on LPS activation inflammation.We measured the expression of inflammatory factors TNF-α and IFN-γ as immune change indicators,which can be activated by LPS,,and found that cadmium exposure can promote the inflammation induced by LPS in primary cultured spleen cells.Under the conditions of LPS activation,primary spleen cells of BALB/c mice were treated with cadmium.Western blotting showed that the expression of LC3B-II and p62 protein increased,indicating that cadmium inhibited the process of autophagy,further using m RFP-GFP-LC3 transfected mouse spleen cells and found that green fluorescence increased in the cadmium-treated group under the activation of LPS,and the spots turned yellow,indicating that the autophagosome and lysosome could not fused,so cadmium exposure inhibited autophagy flux.Treatment of cells with the Rapamycin to increase cell autophagy,the inflammatory promotion effect by cadmium exposure was reduced.These results indicate that the promotion of immune inflammatory response by cadmium exposure may be mediated by the inhibition of autophagy.In order to further explore the role of autophagy in immune inflammation and the relevance to Toll-like receptor 4(TLR4),which is the target of LPS,we used autophagy regulators to modulate autophagy and detect changes in TLR4 protein and its downstream pathway.The results showed that cadmium promoted the expression of TLR4 protein,and the phosphorylation levels of key proteins P-IκBα and P-p65 in its downstream signaling pathway were also up-regulated.At the same time,autophagy inducers can reduce the effects of cadmium.Real-time fluorescence quantitative PCR showed no change in the TLR4 m RNA.However,the half-life of TLR4 protein was prolonged by cadmium,which indicated that cadmium could inhibit the degradation of TLR4 Protein.In this study,four metal ions of copper,zinc,manganese and nickel were used to study their effects on inflammation induced by LPS.It was found thatcopper,manganese and nickel promoted the inflammation induced by LPS,which indicates immunotoxicity of heavy metals shares common pathways.In summary,under the condition of LPS activation,cadmium slows down the degradation of TLR4 protein by inhibiting autophagy,resulting in increased immune inflammation.This conclusion lays the foundation for finding the target of heavy metal cadmium on the immune system in the future,and also provides a theoretical basis for the prevention and treatment of cadmium and other heavy metals’ immunotoxicity.