Hydroxysafflor Yellow A Can Improve Depressive Behavior By Inhibiting Hippocampal Inflammation And Oxidative Stress Through Regulating HPA Axis

Background and Objective:Depression is a psychological disease with significant and lasting depressive mood as the core symptom.It causes patients to have severe limitation of psychosocial function,lower quality of life and increased risk of suicidal behavior.According to WHO statistics,it has become the second leading cause of disability in the world,causing a huge burden on patients,families and society.There is a hypothesis that depression is a chronic inflammation caused by stressors,and that the hypothalamic-pituitary-adrenal axis plays an important role in the development of depression.However,the exact mechanism of depression is still unclear.The chronic unpredictable mild stimulus model is currently the most commonly used,most reliable,and most effective murine model of depression.At present,psychotherapy and drug therapy are effective methods for the treatment of depression,but there are still many patients with poor trerapeutical effect.Hydroxysafflor yellow A(HSYA)is the main active ingredients of safflower,which has the effects of antioxidant,anti-inflammatory,anticoagulant and neuroprotection.Some studies have also suggested that safflower and its extracts have antidepressant effects,but the role and mechanism of HSYA,the main active ingredient of safflower,in depression is still unclear.However,the role and effect of HSYA in depression are not clear.In this study,Wistar male rats were used to establish chronic unpredictable mild stress(CUMS)model to study the relationship between depression and hypothalamic–pituitary–adrenal(HPA)axis,proinflammatory factors,oxidative stress level,the expression levels of Toll-like receptor 4/ nuclear factor kappa-B((TLR4/NF-κB)pathway and the effect and related mechanism of HSYA on CUMS model rats.Methods:1.In this study,we use Wistar male rats to establish the CUMS model,and then the core symptoms of depression in the model rats were tested by behavioral methods such as the open field test,the forced swim test and sucrose preference test.The levels of adreno-cortico-tropic-hormone(ACTH),corticotropin releasing hormone(CRH),cortisol(CORT)in serum were measured by ELISA method.The levels of tumor necrosis factor α(TNF-α),Interleukin-6(IL-6),Interleukin-1β(IL-1β),malondialdehyde(MDA),superoxide dismutase(SOD)and glutathione peroxidase(GSH-Px)and the reactive oxygen species(ROS)activity in hippocampus were detected by ELISA method.The levels of TNF-α,IL-6 and IL-1β were detected by q RT-PCR technology.Finally,Western blot was used to study the levels of TLR4 and p-p65 in hippocampus of CUMS rats.2.To study the effect of HSYA on depressive behavior in CUMS model and related mechanisms.The CUMS model was established for 5 weeks,then 15 mg/kg,30 mg/kg and 60 mg/kg of HSYA were injected intraperitoneally to the CUMS model rats for 1 week,and the control group rats were given the same dose of normal saline every day.Then,behavioral methods such as open field test,the forced swim test and sucrose preference test were used to evaluate the depressive behavior of animals.The levels of ACTH,CRH and CORT in serum and TNF-α,IL-6,IL-1β,MDA,SOD,GSH-Px in hippocampus of four groups rats were measured by ELISA,and the activity of ROS was detected.The levels of TNF-α,IL-6 and IL-1β in serum were studied by q RT-PCR technology.Finally,Western blot was used to study the levels of TLR4 and p-p65 in CUMS rats.Results:1.We used Wistar male rats to establish the classic CUMS model,and then evaluated it by behavioral methods such as open field test,the forced swim test and sucrose preference test.We found that CUMS model rats had less open field exercise,increased forced swimming immobility time and decreased sucrose preference index compared with Sham rats.Further study found that the HPA axis of CUMS model rats was hyperactivated.The levels of pro-inflammatory cytokines(TNF-α、IL-6 and IL-1β)and oxidative stress in hippocampus of CUMS model were increased.Then the expression levels of TLR4 / NF-κB pathway were up-regulated.2.Intraperitoneal injection of HSYA at different doses of 15mg/kg,30mg/kg and60mg/kg for one week can improve the depressive behavior of CUMS model rats in a dose-dependent manner.Further study found that HSYA could reduce the activation of HPA axis,the level of inflammatory response and oxidative stress in hippocampus of CUMS model rats in a dose-dependent manner.Finally,Western blot showed that HSYA could reverse the up-regulated protein expression level of TLR4/NF-κB pathway in hippocampus of CUMS model rats in a dose-dependent manner.Conclusion:HSYA may improve depressive behavior by inhibiting the HPA axis and regulating the TLR4/NF-κB pathway to suppress hippocampal inflammatory response and oxidative stress,providing a new strategy for the treatment of depression.