Study Of The Effects Of Immune Response And Mechanism Induced By Cadmium Exposure In Mouse Spleen Cells

Cadmium(Cd)is one of the toxic heavy metals and widely distributed in polluted water,air and soil.It can be enriched in organisms with a long half-life and is not easy to be discharged,causing adverse reactions in the body.In recent years,studies on the physiological toxicity caused by Cd pollution have focused on renal toxicity and liver toxicity,and the potential threat to the body’s immune function has also been highly concerned.Previous studies in our laboratory showed that Cd inhibited the expression of immune factors by promoting autophagy degradation of Toll-like receptor 9 under Con A activation and Cd promoted the expression of inflammatory cytokines by inhibiting the autophagy degradation of Toll-like receptor 4 under Lipopolysaccharide activation.In addition,the oxidative stress and Ca2+ signal may be involved in Cd-induced immonotoxicity.Hoever,the underlying mechanism remains unclear.To clarify the mechanism of abnormal immune response induced by Cd exposure under the two different activation conditions,we construct the transcriptome of mice spleen after Cd exposure.Through the transcriptomic GO and KEGG enrichment analysis,it indicated that oxidative stress,Ca2+ signal and lysosomal pathway may be involved in Cd modulated immune response.Preliminary results suggest that oxidative stress is a major factor contributes to B cell immunotoxicity induced by Cd.The results in this study showed that Cd exposure caused oxidative stress in primary mouse spleen cells.Reactive oxygen species scavenger agent TCP inhibited the promotion of Cd to LPS-induced inflammatory response and reversed the inhibition of Cd by Con A immune response.Cd exposure also induces elevated cytoplasmic Ca2+ levels,which contributes to oxidative stress and vice verse.The results in this study showed that under LPS treated,Cd exposure inhibited the expression of Cadmium regulated intracelluar Ca2+transporter(CRICT)and Sarco(endo)plasmic reticulum Ca2+ ATPase 2(SERCA2),increased of Ca2+ content in the endoplasmic reticulum(ER),and inhibited intracellular free Ca2+ level.Under Con A activation,Cd exposure promoted the expression of CRICT and SERCA2,reduced the content of Ca2+ in ER,and increased of intracellular free Ca2+ level.Under LPS-activated conditions,Ca2+ chelator BAPTA could reverse the effect of Cd exposure on cytokine expression,while the SERCA2 inhibitor thapsigargin(TG)could not.BAPTA could not reverse Cd suppressed cytokine expression under Con A activation,but could restored by TG treatment.Studies have shown that the absorption of Ca2+ by lysosomes can affect its acidic environment.The results in this study showed that Cd exposure inhibited lysosomal acidity under LPS activation.Under Con A activation condition,Cd exposure promoted lysosomal acidification.In addition,BAPTA could reverse Cd up-regulated of lysosomal pH under LPS condition,but could not reverse the down-regulation of lysosomal pH under Con A activation condition.TG could not reverse the effect of Cd up-regulated of lysosomal pH under LPS condition,but it reversed the down-regulation of lysosomal pH under Con A activation condition.In conclusion,under Con A and LPS treated,Cd exposure can induce oxidative stress and regulate the expression difference of intracellular calcium transporters CRICT and SERCA2,causing in different intracellular Ca2+ distribution,promoting or disrupting lysosomal acidity,which contribute to abnormal immune response of spleen cells.Oxidative stress,Ca2+ homeostasis and lysosomal acidity may be the main pathways mediated immune response to Cd exposure of spleen cells.