MicroRNA-138-5p Regulates Hippocampal Neuroinflammation and Cognitive Impairment by NLRP3/Caspase-1 Signaling Pathway in Rats

Xiaojin Feng,1,2 Jialing Hu,1 Fenfang Zhan,1 Deqiang Luo,3 Fuzhou Hua,1,2 Guohai Xu1,2 1Department of Anesthesiology, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, 330006, People’s Republic of China; 2Key Laboratory of Anesthesiology of Jiangxi Province, Nanchang, Jiangxi 330006, People’s Republic of China; 3Department of Intensive Care Unit, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, 330006, People’s Republic of ChinaCorrespondence: Guohai Xu; Fuzhou HuaDepartment of Anesthesiology, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, 330006, People’s Republic of ChinaTel +86-791-86299131Email xuguohai1@sina.com; 415134607@qq.comPurpose: Neuroinflammation is an essential causative factor in the pathogenesis and progression of cognitive impairment. The present study aims to evaluate the critical role of microRNA-138-5p (miR-138-5p) in hippocampal neuroinflammation and cognitive impairment through the NLRP3/caspase-1 signaling pathway in rats.Material and Methods: We established the cognitive impairment rat model and RM (Rat microglia) microglial cellular inflammation model by intracerebroventricular (icv) injection or stimulation of lipopolysaccharide (LPS). Morris water maze (MWM) and Y-maze tests were performed to assess the cognitive behaviors. Quantitative real-time polymerase chain reaction (qRT-PCR), Enzyme-linked immune-sorbent assay (ELISA) and Western blot analysis were utilized to evaluate mRNA or protein expression. Bioinformatic analysis and dual-luciferase reporter gene assay were performed to verify the targeting relationship between NLRP3 and miR-138-5p. Besides, Hematoxylin and eosin (H&E) staining and immunohistochemistry were applied to observe the neuronal morphology and detect the positive cells of the hippocampus, respectively.Results: Compared to the control groups, LPS-treated rats exhibited significantly impaired learning and memory in MWM and Y-maze tests. The expression of NLRP3, caspase-1 and pro-inflammation cytokines (IL-1β and IL-18) were upregulated, while miR-138-5p was downregulated both in rat hippocampus and RM cells treated with LPS. MiR-138-5p is downregulated in microarray data of cognitive impairment animals and could directly target the 3ʹ-UTR of NLRP3. Furthermore, upregulation of miR-138-5p improved impaired cognitive functions, while inhibited hippocampal neuroinflammation demonstrated by decreased expression of NLRP3/caspase-1 axis, pro-inflammation cytokines and microglial activation. This study demonstrates for the first time that miR-138-5p suppresses the hippocampal NLRP3/caspase-1 signaling pathway activation in cognition impaired rats.Conclusion: The low expression of miR-138-5p after LPS administration may contribute to the activation of the NLRP3/caspase-1 pathway, leading to hippocampal neuroinflammation and cognitive impairment in rat models. These findings indicate a promising therapeutic avenue for cognitive disorders.Keywords: microRNA-138-5p, NLRP3/caspase-1, neuroinflammation, cognitive impairment, microglial activation