Study On The Effect And Mechanism Of Triiodothyronine In Inflammation And Apoptosis Induced By Silica In Macrophage

Silica is one of the most common occupational harmful factors in China.After inhalation of silica,it enters the lungs through the respiratory tract.Macrophages act as the first barrier of the body’s protection and are stimulated by silica,thus starting a series of immune defense reactions.Triiodothyronine(T3)is an endocrine hormone that can regulate the body’s innate immune response.Thyroid hormone receptor alpha(TRα)serves as the nuclear receptor for triiodothyronine,which is mainly associated with triiodothyronine to play a biological role in anti-oxidation,anti-inflammatory and antiapoptosis.However,in the current study,the regulatory role and mechanism of triiodothyronine in oxidative stress,inflammatory response,and apoptosis caused by silica have not been reported.Objective: To study the effect and mechanism of triiodothyronine(T3)on oxidative stress,inflammatory response and apoptosis induced by silica in macrophages.Methods: The silica is standard European quartz(DQ12),with a particle size of 1μm.The experimental cells are macrophages differentiated by PMA-induced THP-1.In the first part of the experiment,the dose grouping used 0(control),50,100,200,and 400μg/ml silica to treat macrophages for 24 h.In the second part of the experiment,while treating with 400μg/ml silica,which were given doses(0,5,10,20,40 n M)of the T3 supplementation group and the thyroid hormone receptor alpha(TRα)silencing group(specifically blocking the T3/TRα signal pathway),as well as the blank control group and the T3(40n M)control group.Finally,the cell viability was measured by Cell counting kit-8 reagent,LDH of supernatant was measured by lactate dehydrogenase kit,reactive oxygen species and superoxide dismutase levels were measured by ROS and SOD kits,and inflammatory test was detected by ELISA.The mitochondrial membrane potential and apoptosis rate were measured by flow cytometry,and the level of apoptosis factors Caspase-3 and Cytochrome c was determined by immunofluorescence.Results: 1.The oxidative damage,inflammation and apoptosis induced by silica in macrophages.After exposure to silica,the cell viability of macrophages decreased with the increase in the concentration and time of silica in comparison with the control group(P <0.05),LDH,ROS,IL-1β,IL-6,TNF-α,Caspase-3 and Cytochrome c increased with the increase in concentration of silica(P <0.05),SOD and MMP decreased with the increase of silica concentration(P <0.05).Thus,the results showed that silica caused oxidative stress,increased level of inflammatory response and initiation of apoptosis.2.T3/TRα inhibited oxidative damage and inflammatory response caused by silica in macrophages.After supplementing the doses of T3,compared with the silica-exposed group,the cell viability increased(P <0.05),the LDH and ROS decreased(P <0.05),and the SOD increased(P <0.05).In the inflammatory reaction,the expression levels of inflammatory factors of IL-1β,IL-6,and TNF-α decreased after T3 treatment compared with the silica-exposed group(P <0.05).In addition,compared with the sh RNA of control group,in the TRα-knockdown group,cell viability decreased(P <0.05),LDH and ROS increased(P <0.05),SOD decreased(P <0.05),IL-1β,IL-6,and TNF-α increased(P <0.05).Thus,the results showed that T3 supplementation inhibited the oxidative stress and inflammatory response caused by silica.After blocking the T3/TRα pathway,the oxidative stress and inflammatory response increased.3.T3/TRα inhibited apoptosis caused by silica.After supplementing with doses of T3,compared with the silica group,after T3 treatment,the apoptosis rate decreased(P <0.05),the mitochondrial membrane potential increased(P <0.05),and the expression of Caspase-3 and Cytochrome c decreased(P <0.05),the results showed that supplementation of T3 inhibited the occurrence of apoptosis.In addition,compared with the sh RNA of control group,the apoptosis rate increased in the TRα-knockdown group(P <0.05),the membrane potential decreased(P <0.05),and expression of Caspase-3 and Cytochrome c increased(P <0.05).The results showed that after specifically blocking the T3/TRα pathway,the level of apoptosis increased.Conclusions: Silica can reduce macrophage viability,induce oxidative stress and inflammatory response,and initiate apoptosis.Administration of exogenous T3 can significantly inhibit the macrophage damage and inflammatory response caused by silica,and down-regulate the apoptosis process;specifically blocking the T3/TRα pathway can significantly inhibit the biological role of T3 in the silica-macrophage model.