The cystathionine β-synthase/hydrogen sulfide pathway contributes to microglia-mediated neuroinflammation following cerebral ischemia.

The mechanisms underlying neuroinflammation following cerebral ischemia remain unclear. Hydrogen sulfide (HS), a newly identified gasotransmitter, has been reported to regulate inflammation. In the current study, we investigated whether the endogenous HS production pathway contributed to microglia-mediated neuroinflammation following stroke. We used a mouse middle cerebral artery occlusion (MCAO) model and an in vitro cellular model to mimic ischemia-induced microglial neuroinflammation. Expression of the HS synthase cystathionine β-synthase (CBS) and HS synthetic activity were rapidly decreased in the ischemic brain tissue following MCAO. Consistently, when cultured microglia were polarized toward a pro-inflammatory phenotype with conditioned medium collected from neurons that had been subjected to oxygen-glucose deprivation (OGD neuron CM), they displayed reduced CBS expression and HS production. Enhancing HS bioavailability either by overexpressing CBS or by supplementing with exogenous HS donors promoted a shift in microglial polarization from ischemia-induced pro-inflammatory phenotypes toward anti-inflammatory phenotypes. Mechanistically, microglia that were exposed to OGD neuron CM displayed reduced activation of AMP-activated protein kinase (AMPK), which was rescued by overexpressing CBS or by supplementing with HS donors. Moreover, the promoting effects of HS donors on microglial anti-inflammatory polarization were abolished by an AMPK inhibitor or CaMKKβ inhibitor. Our results suggested that reduced CBS-HS-AMPK cascade activity contributed to microglia-mediated neuroinflammation following stroke. Targeting the CBS-HS pathway is a promising therapeutic approach for ischemic stroke.