Glymphatic improves inflammation and apoptosis after cerebral ischemia-reperfusion injury in mice through ERK signaling pathway

Abstract

Background The acute inhibition of glymphatic after stroke has been shown to aggravate post-stroke inflammation and apoptosis; however, the related mechanisms remain ambiguous. This study aimed to assess the specific mechanism of inflammation and apoptosis after cerebral ischemia-reperfusion (I/R) injury by improving glymphatic dysfunction. Materials and Methods Ischemic stroke was induced using the mice middle cerebral artery occlusion (MCAO) model. The C57/BL6 mice were randomly divided into three groups as follows: sham operation, Ischemia-reperfusion (I/R) 48 hours, and N-(1,3,4-thiadiazol-2-yl) pyridine-3-carboxamide dihydrochloride (TGN-020) + I/R 48 hours treatment. Neurological examination, TTC, fluorescence tracer, western blot, and immunofluorescence staining were performed in all mice in sequence. The glymphatic function in the cortex surrounding cerebral infarction was determined using tracer, glial fibrillary acid protein (GFAP), aquaporin-4 (AQP4) co-staining, and beta-amyloid precursor protein (APP) staining, differential genes were detected using RNA-seq. Iba-1, IL-1β, TNF-α, cleaved caspase 3, and tunel staining were used to verify inflammation and apoptosis after TGN-020 treatment. Results Compared with I/R group, the degree of neurological deficit was alleviated in TGN-020 group. TGN-020 alleviated glymphatic dysfunction by improving astrocyte proliferation and reducing tracer accumulation in the peri-infarct area. RNA-seq showed that the differentially expressed genes were mainly involved in the activation of astrocytes and microglia, and involved in the ERK pathway. RNA-seq was verified by western blot and immunofluorescence. Conclusions The inflammation of astrocytes and microglia after cerebral ischemia-reperfusion (I/R) is closely related to the glymphatic system. The improvement of glymphatic function may play a neuroprotective role after cerebral I/R by inhibiting inflammation through ERK pathway.

Astrocyte aquaporin mediates a tonic water efflux maintaining brain homeostasis

“…Additionally, pro-inflammatory cytokines and chemokines during the immunological maladaptation could also contribute to shape astrocyte functions including aquaporin-mediated water transport (Lucchinetti et al, 2014, Mireles-Ramirez et al, 2022. Recent data show that TGN-020 targeting of AQP4 mitigates the inflammation during ischemia-reperfusion injury, by enhancing glymphatic amyloid clearance and inhibiting the ERK 1/2 pathway (Li et al, 2023), suggesting that in pathological conditions, multiple factors could be recruited by astrocyte aquaporin targeting.…”