MicroRNA-7 Attenuates Secondary Brain Injury Following Experimental Intracerebral Hemorrhage via Inhibition of NLRP3.

BACKGROUND AND PURPOSE: The pathophysiological mechanisms underlying brain injury resulting from intracerebral hemorrhage (ICH) remain incompletely elucidated, and efficacious therapeutic interventions to enhance the prognosis of ICH patients are currently lacking. Previous research indicates that MicroRNA-7 (miR-7) can suppress the expression of Nod-like receptor protein 3 (NLRP3), thereby modulating neuroinflammation in Parkinson's disease pathogenesis. However, the potential regulatory effects miR-7 on NLRP3 inflammasome after ICH are yet to be established. This study aims to ascertain whether miR-7 mitigates secondary brain injury following experimental ICH by inhibiting NLRP3 and to investigate the underlying mechanisms.

METHODS: An ICH model was established by stereotaxically injecting 100 μL of autologous blood into the right basal ganglia of Sprague-Dawley (SD) rats. Subsequently, these rats were allocated into three groups: sham, ICH + Vehicle, and ICH + miR-7, each comprising 18 animals. Twelve hours post-modeling, rats received intraventricular injections of 10 μL physiological saline, 10 μL phosphate, and 10 μL phosphate-buffered saline solution containing 0.5 nmol of miR-7 mimics, respectively. Neurological function was assessed on day three post-modeling, followed by euthanasia for brain tissue collection. Brain water content was determined using the dry-wet weight method. The expression of inflammatory cytokines in cerebral tissues surrounding the hematoma was analyzed through immunohistochemistry and Western blot assays. These cytokines were re-evaluated using Reverse Transcription-Polymerase Chain Reaction (RT-PCR). Moreover, bioinformatics tools were employed to predict miR-7's binding to NLRP3. A wild-type luciferase reporter gene vector and a corresponding mutant vector were constructed, followed by transfection of miR-7 mimics into HEK293T cells to assess luciferase activity.

RESULTS: Our study demonstrates that the administration of miR-7 mimics markedly reduced neurological function scores and attenuated brain edema in rats following ICH. A significant upregulation of NLRP3 expression in microglia/macrophage adjacent to the hematoma was observed, substantially reduced after the treatment with miR-7 mimics. Furthermore, this intervention ameliorated neurodegenerative changes and effectively decreased the protein and mRNA levels of pro-inflammatory cytokines, namely TNF-α, IL-1β, IL-6, and Caspase1, in the cerebral tissues proximate to the hematomas. In addition, miR-7 mimics distinctly inhibited the luciferase activity associated with the wild-type reporter gene, an effect not mirrored in its mutant variant.

CONCLUSIONS: The miR-7 suppressed NLRP3 expression in microglia/macrophage to reduce the production of inflammatory cytokines, leading to conducting certain neuroprotection post-ICH in rats.