Gut Flora Mediates the Rapid Tolerance of Electroacupuncture on Ischemic Stroke by Activating Melatonin Receptor through Regulating Indole-3-Propionic Acid

Electroacupuncture (EA) is commonly used to treat cerebrovascular diseases. This study aimed to clarify the mechanisms of action of treatments of cerebral ischemic stroke from the perspective of gut microecology. We used a mouse model and cell cultures to investigate the effects of EA on the intestinal microflora in mice models of middle cerebral artery occlusion (MCAO) and the mechanisms underlying the antioxidant activities of metabolites. Fecal microbiota transplantation (FMT) was used to validate the roles of gut microbiota. Metabolomic analysis was performed to characterize the metabolic profile differences between the mice in the EA + MCAO and MCAO groups. Gavaging with feces relieved brain damage in mice that received EA (EA mice) more than in mice that did not (non-EA [NEA] mice). The gut microbial composition and metabolic profiles of the EA and NEA mice were different. In particular, the microbiota from the mice in the EA or EA-FMT groups generated more indole-3-propionic acid (IPA) than the microbiota from the mice in the MCAO or NEA-FMT groups. We confirmed that IPA binds to specific melatonin receptors (MTRs) in target cells and exerts antioxidant effects by adding MTR inhibitors or knocking out the MTR1 gene in vivo and in the oxygen and glucose deprivation/reperfusion models of N2a cell experiments. EA can prevent ischemic stroke by improving the composition of intestinal microbiota in MCAO mice. Moreover, this study reveals a new mechanism of intestinal flora regulation of stroke that differs from inflammation/immunity, namely gut microbiota regulates stroke by affecting IPA levels.