| PurposeThe NLRP3 inflammasome is a multiprotein complex that regulates the innate immune inflammatory response by activating caspase-1 and up-regulating IL-1β and IL-18.Fluoxetine has been shown to have anti-inflammatory properties in many disease models,yet its role and mechanism in early brain injury following subarachnoid hemorrhage(SAH)is unclear.This study explored the role of NLRP3 inflammasome and caspase-1 activation in early brain injury following SAH and the possible mechanism of fluoxetine on NLRP3 inflammasome and caspase-1 activation.MethodsAdult male Sprague-Dawley rats weighing 300-320 g were selected and SAH models were made by intravascular puncture.N-Ac-Tyr-Val-Ala-Asp-Chloromethyl ketone(AC-YVAD-CMK)was injected intraperitoneally 1 hour after SAH(5 mg/kg).Fluoxetine was injected intravenously 6 h after SAH.3-Methyladenine(3-MA)was intracerebroventricularly injected 20 min before SAH.SAH score,neurological function score,brain water content,propidium iodide(PI)staining,western blot,immunofluorescence staining and transmission electron microscopy were used for detection and evaluation.ResultsExpression of caspase-1 increased and peaked at 24 h after SAH.Caspase activation was along with the increased necrotic cells,which occurred mainly in neurons.Necrotic cell death of microglias and astrocytes were also found.Administration of AC-YVAD-CMK,a caspase-1 inhibitor,reduced the expression of IL-1β and IL-18 and the number of PI-positive cells,attenuated brain edema,and improved neurological function,which was also observed in fluoxetine-treated rats.Furthermore,fluoxetine treatment significantly decreased the expression of NLRP3 and cleaved caspase-1 and upregulated the expression of beclin-1,a marker for autophagy.Finally,the effects of fluoxetine in NLRP3 inflammasome activation were reversed by additional 3-MA administration.ConclusionTogether,our present study indicated that NLRP3 inflammasome and caspase-1 activation played a deleterious role in early brain injury and fluoxetine mitigated NLRP3 inflammasome and caspase-1 activation through autophagy activation after SAH,providing a potential therapeutic agent for SAH treatment. |
