Hirudin alleviates acute ischemic stroke by inhibiting NLRP3 inflammasome-mediated neuroinflammation: In vivo and in vitro approaches

Acute ischemic stroke is a severe condition that a vessel supplying blood to the brain is abruptly blocked mostly due to cerebral thrombosis and embolism. There is a dearth of the effective prevention and early intervention strategies. NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated neuroinflammation plays a crucial role in the pathophysiology of ischemic stroke. Hirudin is a secretion from the salivary glands of the leech Hirudo medicinalis and has a role in regulating inflammation. In this study, hirudin with a dose of 10-40 mg/kg was given to middle cerebral artery occlusion/reperfusion mice. Hirudin markedly constrained cerebral infarct area in a dose-dependent manner, and significantly improved locomotor disability at 40 mg/kg dose. Similar to MCC950, a selective NLRP3 inflammasome inhibitor, hirudin inhibited M1 polarization and promoted M2 polarization. It also strikingly suppressed the ischemia-induced overexpression of NLRP3 and its downstream components, caspase-1, apoptosis-associated speck-like protein (ASC), and interleukin-1β (IL-1β). Hirudin and MCC950 equivalently protected viability and death of BV-2 microglia cells against oxygen-glucose deprivation/reperfusion (OGD/R), an in vitro cell model of brain ischemia. Both agents had similar effects in normalizing the OGD/R-evoked aberrant microglial profiles and NLRP3 pathway dysregulation as observed in the mice. These results demonstrated anti-ischemic effects of hirudin and its association with the inhibition of microglial NLRP3 inflammasome-mediated neuroinflammation. Hirudin is a promising agent for the early intervention of acute ischemic stroke.