MiR-106a-5p in extracellular vesicles derived from alveolar epithelial cells mediates cognitive dysfunction induced by chronic intermittent hypoxia in mice through MAPK signaling pathway

Obstructive sleep apnea (OSA), characterized by chronic intermittent hypoxia (CIH), is frequently associated with cognitive dysfunction. However, the underlying peripheral-central interplay mechanism remains to be elucidated. Recent years have witnessed the proposal of the “lung-brain axis (LBA)” concept, suggesting that lung tissue can remotely regulate brain function via extracellular vesicles (EVs). This investigation aims to determine whether EVs derived from alveolar epithelial cells (AEC-EVs) mediate CIH-induced cognitive impairment and to delineate the associated molecular mechanisms. Mice were exposed to CIH to model obstructive sleep apnea. EVs were isolated from brain tissue and MLE-12 cells via ultracentrifugation. CIH-AEC-EVs were administered to normal mice via tail vein injection; cognitive function was assessed using behavioral tests (Open Field, Y-Maze, Novel Object Recognition). In vitro, BV-2 cells were treated with CIH-AEC-EVs, and their polarization status was evaluated by Flow Cytometry (FCM), Quantitative Real-Time PCR (qPCR), Western Blotting (WB), and Immunofluorescence (IF). Key miRNAs and their target genes were screened and validated using miRNA sequencing, bioinformatics analysis, and dual-luciferase reporter assays. Finally, functional rescue experiments were performed using a miR-106a-5p inhibitor and a MAPK inhibitor to validate the functional outcomes both in vivo and in vitro. CIH-exposed mice exhibited cognitive impairment, hippocampal neuronal apoptosis, and increased M1 polarization of microglia. CIH markedly increased the abundance of alveolar-epithelial-cell-derived EVs (AEC-EVs) and microglial EVs in the brain, whereas neuron-derived EVs remained unchanged. CIH-AEC-EVs traversed the blood-brain barrier (BBB), were taken up by microglia, and induced M1 polarization while suppressing M2 polarization. Mechanistically, miR-106a-5p were enriched in CIH-AEC-EVs, which directly targeted DUSP2 mRNA, thereby relieving DUSP2-mediated suppression of ERK/MAPK signaling and facilitating M1 polarization. Administration of a miR-106a-5p antagonist or a MAPK inhibitor significantly reversed the aforementioned pathological alterations and ameliorated cognitive function. Through the lung-brain axis, CIH enhances the transfer of miR-106a-5p-loaded AEC-EVs to the hippocampus, where they downregulate DUSP2 and activate the MAPK signaling pathway. This alteration results in an M1/M2 microglial imbalance, which contributes to cognitive dysfunction. Targeted suppression of AEC-EVs secretion or the miR-106a-5p/DUSP2 axis may provide a potential non-invasive therapeutic strategy for addressing cognitive impairments associated with OSA. The alveolar epithelial cells of patients with chronic intermittent hypoxia secrete a large number of miR-106a-5p EVs through the lung brain axis, which act on brain tissue, leading to increased polarization of microglia M1 and neuronal cell apoptosis. 1. This study reveals that chronic intermittent hypoxia (CIH) mediates the lung-brain axis via alveolar epithelial cell-derived EVs (AEC-EVs), remotely regulating microglial polarization in the central nervous system and ultimately leading to cognitive dysfunction. 2. The study identifies that miR-106a-5p, highly enriched within AEC-EVs, drives M1 polarization and suppresses M2 polarization in microglia by targeting and inhibiting DUSP2, consequently activating the MAPK signaling pathway. 3. This research distinguishes, for the first time, the functional disparity between AEC-EVs and microglia-derived EVs under CIH conditions, demonstrating that the former predominantly drives neuroinflammation, while the latter may exert compensatory protective effects potentially via M2 polarization. 4.This study proposes non-invasive strategies targeting either AEC-EVs or the miR-106a-5p/DUSP2-MAPK axis, offering novel perspectives for the prevention and treatment of OSA-associated cognitive impairment.