Mechanism of fluoxetine downregulation of circMap2k1 to alleviate neurological function after ischemic stroke

Abstract Background Ischemic stroke (IS) is known for its high incidence, disability and mortality, and there is an urgent need to investigate the pathophysiological mechanisms and develop novel treatment strategies. We aimed to investigate the mechanisms of the novel circMap2k1/miR-135b-5p/Pidd1 axis in the treatment of IS progression with fluoxetine. Methods The middle cerebral artery occlusion (MCAO) model was established, followed by fluoxetine treatment and injecting adeno-associated viruses (AAV)-sh-ctr and AAV-sh-circMap2k1 into bilateral hippocampal tissues of rats. Then cerebral infarction area, weight, Longa score, and neurological injury were evaluated. Dual-luciferase reporter gene assay was employed to confirm the binding between miR-135b-5p and Pidd1. ELISA was performed to measure the concentrations of inflammatory factors TNF-α, IL-6, and IL-1β in the plasma. Finally, we verified the role of circMap2k1 in cellular experiments by overexpression of circMap2k1. Cell viability was assessed using CCK-8 assay, while apoptosis was measured by flow cytometry. Results Knockdown of circMap2k1 enhanced the therapeutic effect of fluoxetine on IS injury (cerebral infarction area, weight, and Longa score) in rats. Then knockdown of circMap2k1 enhanced the protective effect of fluoxetine on neurological injury after IS in rats. Dual-luciferase reporter gene assay confirmed the targeting of miR-135b-5p to Pidd1. Additionally, fluoxetine deactivated the adsorption of miR-135b-5p by downregulating circMap2k1, and miR-135b-5p further exerts its inhibitory effect on Pidd1, and finally attenuares the inflammatory response caused by microglial polarization after IS. Cell experiments revealed that overexpression of circMap2k1 repressed cell viability and promoted cell apoptosis. Conclusions Fluoxetine downregulated circMap2k1 to ameliorate neurological injury and inflammatory responses induced by microglia polarization after IS.