Effects Of Indole-3-propionic Acid On Intestinal Barrier Dysfunction And Neuroinflammation After Ischemic Stroke And Its Mechanism

Background:Researches shown that a local neuroinflammatory cascade is induced after acute ischemic stroke,which greatly influences its outcomes.Growing evidence marked the gut microbiota and its metabolites as environmental factor is important for ischemic stroke outcomes.However,the role of microbial indole derivatives in ischemic stroke remains largely unknown.Here,we evaluated the effects and the underlying mechanism of Indole-3-propionic acid(IP A)in a mouse model of acute middle cerebral artery occlusion(MCAO).Methods:The mice were divided into Sham,MCAO and MCAO+IPA.We collected blood samples and evaluated serum indole derivatives levels using ultra-performance liquid chromatography with tandem mass spectrometry(UPLC-MS)in male C57BL/6 mice undergoing Sham or MCAO surgery.Intragastric IPA administration(400 μg/20 g/d)was performed in MCAO mice.For detecting intestinal barrier function,gut microbiome dysbiosis was analyzed by 16S rRNA gene sequencing,the integrity of the small intestinal epithelial barrier function was assessed by Immunohistochemistry staining and Western Blotting,and intestinal regulatory cells(Tregs)and Th17 cells numbers are analyzed by flow cytometry.Then,local neuroinflammatory responses,immune cell activation,cell apoptosis,neurological impairment,and cerebral infarction were analyzed by Western blotting,quantitative real-time polymerase chain reaction,histo-immunofluorescence,etc.Finally,Tregs of gut-derived and astrocytes of Oxygen glucose deprivation(OGD)were co-cultured to explore the direct connection.Results:We found that serum IPA levels in MCAO mice were significantly lower than those in the Sham.IPA reshaped the microbial community composition to resemble that in the control group,with an increase of beneficial bacteria and a decrease of harmful bacteria.IPA increased intestinal epithelial barrier integrity and positively regulated intestinal immune to enhance intestinal barrier function.And IPA regulated the intestine and central nervous system immune imbalance and reactive astrogliosis to inhibit neuroinflammation,which alleviated neurological dysfunction and infarction.In addition,IPA mediated the anti-inflammatory effect of intestinal Tregs that inhibited A1 astrocyte activation after reoxygenation of OGD.Conclusion:The content of IPA decreased after stroke,IPA reshape the structure of the intestinal microbiome to alleviate the intestinal dysbiosis,and IPA improve stroke outcomes by enhancing intestinal barrier function and inhabiting neuroinflammation.It shows that IPA as a potential treatment option for ischemic stroke,which could provide the experimental data reference of microbiome metabolism-based treatments for ischemic stroke.