The Protection Of Uric Acid In Reducing TLR4/NF-?B Activation Through The Inhibition Of HMGB1 Acetylation In Ischemia-reperfusion

Objective:Inflammation plays an important role in cerebral ischemia-reperfusion injury.In our previous studies,we have found that appropriate concentration of uric acid(uric acid,UA)played a role of antioxidant,which could reduce inflammation and prevented severe neurons damage.However,it is not clear that the protective mechanism of UA in inflammation in cerebral ischemic reperfusion injury.This study investigated the protective mechanism of UA in the model of ischemia-reperfusion injury in vitro.Methods : Mouse hippocampal neurons(HT22 cells)were used to construct oxygen-glucose deprivation-reperfusion(Oxygen-glucose deprivation reperfusion,OGD/R)model in vitro.Mouse hippocampal neurons were divided into six groups: the control,OGD,OGD/R,OGD/R+HMGB1 si RNA,OGD/R+ uric acid,and OGD/R+ uric acid + HMGB1 groups.The expression of HMGB1,TLR4,NF-?B-p65 and phosphorylated NF-?B-p65(p-NF-?B-p65)was detected by Western blotting.At the same time,microenzyme reaction colorimetric method of tetramethylazolium salt(MTT)was used to evaluate cell viability,while apoptosis was detected by flow cytometry.In addition,the levels of interleukin-6(IL-6),interleukin-1 ?(IL-1 ?)and tumor necrosis factor-?(TNF-?)in the culture medium were determined by ELISA.Results:On the base of above experiments,the results were as follows:(1)After OGD/R,cell viability was increased and apoptosis was decreased in the presence of HMGB1 si RNA and uric acid;But the opposite findings in the presence of HMGB1 protein after OGD/R.(2)Uric acid and HMGB1 si RNA inhibited HMGB1 acetylation to prevent its transport from the nucleus to the cytoplasm.(3)The expression of HMGB1 downstream proteins(TLR4,NF--?B-p65 and p-NF-?B-p65)and the levels of inflammatory factors(IL-6?IL-1??TNF-?)in the presence of HMGB1 si RNA and uric acid was lower than those in the presence of HMGB1 protein after OGD or OGD/R.Conclusions : These data indicated that UA may inhibit intracellular HMGB1 acetylation to prevent its transport from the nucleus to the cytoplasm.Therefore,it reduced the activation of TLR4/NF-?B pathway and then reduced the level of inflammatory factors(IL-6?IL-1??TNF-?)to prevent severe neurons damage.It also suggested that uric acid can be used as a potential therapeutic target in ischemic stroke.