Impact of NA-1 on Pericyte-Driven Vasoconstriction and Its Role in No-Reflow During Cerebral Ischemia-Reperfusion.

BACKGROUND: The no-reflow phenomenon in the ischemic brain following arterial recanalization leads to poor prognosis. Previous studies suggest that the clinically proven NA-1 drug, with disruption of PSD95 in the neuronal terminals alongside the cerebral microvasculature, may inhibit pericytic contraction of microvessels by reducing endothelin-1 secretion. METHODS: A 1.5-h tMCAO model using Balb/c mice was employed. In vivo two-photon imaging and immunofluorescence staining were employed to assess the constriction effect of pericytes on capillaries. The impact of NR2B9c/NA-1 administration (intravenously infused at a dose of 10 μmol/kg) on pericyte constriction was evaluated through immunofluorescent staining of brain sections. Additionally, The effect of NA-1 on cerebral perfusion was assessed using laser speckle blood flow monitoring, whole brain slice perfusion, and high-magnification capillary imaging. Enzyme-linked immunosorbent Assay (ELISA) was conducted to determine changes in quantitative ONOO(-) and endothelin-1 (ET-1) content after tat-NA-1 administration. Lastly, microtubule-associated protein 2 (MAP2) staining and behavioral scores were used to evaluate the effects of NA-1 on infarct size and behavioral deficits. RESULTS: In vivo two-photon imaging and immunofluorescence staining revealed that pericyte constriction following ischemia and recanalization resulted in a decreased diameter of capillaries, particularly at the soma and adjacent areas. Notably, capillary obstruction was localized near pericytes. After administration of NA-1, the immunofluorescence staining section showed that the diameter of capillaries at pericytes' soma and in the adjacent parts increased. The ELISA results indicated a reduction in ONOO(-) and ET-1 levels. Additionally, MAP2 staining revealed a decrease in infarct size, while behavioral scores showed improvements in deficits. This effect of NA-1 was counteracted notably when added ET-1. CONCLUSION: NA-1 inhibits pericyte constriction following ischemia-reperfusion by reducing ET-1 levels. It improves capillary no-reflow in mice, enhances cerebral perfusion, decreases infarct size, and mitigates behavioral deficits.