The Role And Mechanism Of Silymarin Prevents NLRP3 Inflammasome Activation And Protects Against Intracerebral Hemorrhage

Background and objectiveIntracerebral hemorrhage(ICH)is linked with increased mortality and morbidity and represents about 20% among the different types of strokes.Primary injury usually occurs within few hours after bleeding,resulting in brain edema and hematoma in the adjacent tissues.As the result of secondary injury,neurological function declines in most of the cases.Red blood cell(RBC)lysis and hemin mediated toxic effects play a major role in ICH injury through release of iron and ROS production.The plant derived antioxidant silymarin,is shown to offer protection against various diseases through its potential antioxidant activity.Apart from its role against oxidative stress,silymarin exerts its neuroprotection through inhibiting inflammatory activation and apoptotic cell death.Since,inflammatory activation is an important mechanism in ICH injury,we focused on evaluating whether silymarin might offer protective role by regulating oxidative stress and NLRP3 inflammasome activation.MethodsThe ICH model was performed using unilateral intrastriatial infusion of 0.04 units of collagenase type VII-S in C57BL/6 male mice aged 8–10 weeks.Silymarin was injected intraperitoneally(200 mg/kg)30 mins post-ICH induction.Analysis of serum interleukin levels.Tissues were fixed with formaldehyde for histopathological studies.Estimate the ROS content and lipid peroxide content in the tissue homogenate.The tissue homogenate was assessed for antioxidant enzyme activities.The serum was analyzed for levels of TNF-?,IL-6,IL-8 by ELISA.The brain tissue was analyzed for expression levels of NLRP3,IL-1?,caspase-1,Nrf-2 and HO-1 by Western blot.ResultsSilymarin showed dose-dependent protective effect by decreasing ICH induced oxidative stress.Significant increase(p < 0.001)in ROS and lipid peroxide content followed by ICH injury compared to sham mice.Treatment with silymarin decreased(p < 0.001)the oxidative stress markers compared to ICH group.Significant decline in antioxidant enzyme activities including SOD,CAT,GST and GSH compared to sham group.There was significant increase in antioxidant status post ICH injury +silymarin treatment group.Significant increase in expressions of NLRP3,IL-1? and caspase-1 expressions were observed post ICH injury compared to sham group.The NLRP3 mediated inflammatory responses were down-regulated during silymarin treatment post ICH injury compared to ICH group.ICH-induced inflammatory cytokine expressions were significantly down-regulated during silymarin treatment post ICH injury.Significant decline in nuclear Nrf-2 levels in ICH group compared to sham group.Treatment with silymarin,post ICH injury increased Nrf-2expression compared to ICH group.There was concomitant increase in cytosolic accumulation of Nrf-2 in the ICH group.Further,silymarin also increased the Heme oxygenase-1(HO-1)expressions post ICH injury compared to ICH group.ConclusionICH injury mediated significant levels of oxidative stress and inflammasome activation.However,silymarin protected against ICH injury induced inflammation by regulating oxidative stress,NLRP3 and Nrf-2 expressions.Our study shows insights on the neuroprotective role of silymarin through Nrf-2/HO-1 signaling.