The Effects And Mechanism Of Chronic Restraint Stress On Adaptive Immune

BackgroundStress is an essential adaptive response of body to the stimuli of various internal or external factor.However,in recent years,chronic long-term stress has caused most psychological and physical problems for people,and brought very serious adverse effects to people’s life and work.Current studies have shown that chronic stress promotes the release of glucocorticoids and catecholamines by activating hypothalamic-pituitary-adrenal(HPA)axis and sympathetic nervous system(SNS)that further promotes the secretion of anti-inflammatory cytokines interleukin-4(IL-4)and IL-10 and inhibits the releasing of pro-inflammatory cytokines interferon-γ(IFN-γ),tumor necrosis factor-α(TNF-α),IL-1 and IL-12,leading to changes of the immune system function.CD4+ helper T(Th)cells are a type of immune cells that play an important role in the adaptive immune response,mainly divided into Th1,Th2,Th17,follicular T helper cells(Tfh),regulatory T cells(Treg)and other subtypes.Th1 and Th17 cells play a pro-inflammatory role by respectively secreting IFN-γ,IL-17 and as well as other cytokines.Th2 and Treg cells play an anti-inflammatory role by respectively secreting IL-4,IL-10,transforming growth factor-β(TGF-β)and as well as other cytokines.Tfh cells could promote the formation of germinal centers,induce the differentiation and maturation of plasma cells and induce the class switching of antibodies.The PD-1(programmed cell death protein-1)/PD-L1(programmed death-ligand 1)pathway could suppress the immune response by inhibiting the proliferation and activation of effector T cells and promoting the proliferation and differentiation of Treg cells.Long-term chronic stress can increase the risk of infection,cardiovascular disease and cancer by suppressing the immune response.However,how chronic stress affects the differentiation and function of adaptive immune cells is still unclear.Therefore,elucidating the impact of chronic stress on the adaptive immune cells may provide new ideas and theoretical basis for the prevention and treatment of chronic inflammatory diseases and tumors.ObjectiveInvestigating the effect and mechanism of chronic restraint stress on adaptive immune cells.MethodC57BL/6 mice were used to establish a chronic restraint stress model(CRS)for 62 days,and normal untreated C57BL/6J mice were used as the blank control group(CTL).The behavioral changes were assessed by open field test(OFT),tail suspension test(TST),elevated plus maze test(EPM)and forced swim test(FST).The weight of mice was measured once a week.The spleen,neck draining lymph nodes and peripheral blood of mice in each group were extracted,and the differentiation of Treg,Th17,Th1,Th2,Tfh cells and plasma cells were analyzed by flow cytometry.The levels of TNF-α,IL-1β and IL-10 in serum were tested by enzyme linked immunosorbent assay(ELISA).The m RNA levels of PD-1 and PD-L1 in spleen were detected by quantitative real-time PCR(q PCR).Result1.Chronic restraint stress induced weight loss and stress-like behaviorThe weight of CRS group was decresed from the first week and significantly lower than that in CTL group from the second week.The central zone duration and total distance moved in OFT,duration of the mobility state in TST and duration of self-grooming of CRS group were significantly reduced compared with that in CTL group.The duration of the mobility state in OFT of CRS group was also decreased,but had no significance.2.Chronic restraint stress promoted the differentiation of Treg cell and expression of IL-10Compared with CTL group,the frequency of Treg cells in spleen,neck draining lymph nodes and peripheral blood of the mice in CRS group were significantly increased.The serum IL-10 was also significantly increased,compared with that of CTL group.3.Chronic restraint stress reduced the frequency of Th1 and Th17 cells,but did not affect the frequency of Th2 cellsCompared with CTL group,the frequency of Th17 cells in spleen of CRS group were significantly decreased.the frequency of Th17 cells in neck draining lymph nodes and peripheral blood were also decreased but had no significant difference.The frequency of Th1 cells in peripheral blood of the mice in CRS group were lower than CTL group,but there was no change in spleen.The frequency of Th2 cells of CRS group did not change.4.Chronic restraint stress reduced the frequency of Tfh and plasma cellsCompared with CTL group,the frequency of Tfh cells in the spleen of CRS group were significantly decreased,but there was no change in the neck draining lymph nodes.The frequency of plasma cells of CRS group were significantly decreased in the spleen and neck draining lymph nodes compared with that of CTL group.5.Chronic restraint stress inhibited the expression of pro-inflammatory cytokinesCompared with CTL group,the expression of IL-1β of CRS group in the serum was significantly decreased.The expression of TNF-α of CRS group in the serum was also lower than that in CTL group.6.Chronic restraint stress promoted the expression of PD-1 and PD-L1Compared with CTL group,the m RNA levels of PD-1 in the spleen of CRS group were significantly increased.The m RNA levels of PD-L1 in the spleen of the mice in CRS group were higher than that in CTL group without significant difference.ConclusionChronic restraint stress can promote the proliferation and differentiation of Treg cells and reduce the frequency of pro-inflammatory adaptive immune cells such as Th1,Th17,Tfh and plasma cells via activation of PD-1/PD-L1 pathway.