Potentiation of GPR68 alleviates post-ischemia BBB dysfunction and brain edema in mice

Ischemia-reperfusion can increase blood-brain barrier (BBB) permeability and extravasation of peripheral molecules. Further damage to BBB results in blood vessel rupture and hemorrhagic transformation (HT). Associated with these processes, brain edema is common. In previous studies, we and others have shown that Ogerin, a small molecule positive modulator of the acid-sensitive GPR68- reduces ischemic brain injury. Here, we asked whether Ogerin attenuates post-ischemia BBB leakage, HT, or edema. To determine HT and edema, we first analyzed the 2,3,5-triphenyltetrazolium chloride (TTC) images from a previous study. In male mice, Ogerin administration reduced both HT severity and brain edema. Ogerin had no significant effect in GPR68-/- mice. Ipsilateral brain tissue exhibited increased mouse IgG and reduced ZO-1 and NeuN, and Ogerin showed a trend of increasing Claudin-5 clustering at cerebral microvessels. In female animals, Ogerin significantly reduced post-stroke edema while showed a trend of reducing HT severity. Combining TTC staining and a sensitive and quantitative fluorescent approach to detect Evans Blue, we examined BBB permeability and brain injury at 72 h. Ogerin reduced brain infarct, edema, and Evans Blue extravasation on day 3 after reperfusion. These results suggest that GPR68 activation may protect against post-tMCAO BBB hyperpermeability, alleviate HT, and reduce brain edema. These findings, together with the earlier observations on brain injury, suggest that pharmacological potentiation of GPR68 is a promising therapeutic intervention for improving post-ischemia outcomes.