The Neuroprotective Role And Mechanism Of Inhibition Sur1 In Experimental Traumatic Brain Injury Induced Injury

Objective: Sulfonylurea receptor 1(Sur1)belongs to the ATPbinding cassette transporter(ABC)protein family.Sur1 could act as a regulator in KATP through combination with Kir6.1/Kcnj8.Sur1 also associates with an ATP and calcium sensitive nonselective cation channel to form Sur1-regulated NCCa-ATP channels.Recent studies indicate that Sur1-regulated NCCa-ATP channels play an important role in central nervous system(CNS)impairments.Western blot analysis had shown the expression of Sur1 upregulated significantly after CNS injury.Blocking Sur1 with glibenclamide which is one of sulfonylureas,would alleviate brain injury.However,the role and mechanism of Sur1 on traumatic brain injury(TBI)remains unclear although the protective effects had been observed in inhibition of Sur1 with glibenclamide following TBI.The present study was to investigate inhibition Sur1 with glibenclamide would benefit via alleviating traumatic injury induced apoptosis in endothelial,and inhibition neuroinflammation.Methods: In the present study,130 adult male C57BL/6 mice were exposed to a controlled cortical impact(CCI)injury and then received glibenclamide treatment.T2-weighted images obtained by magnetic resonance imaging was applied to calculate the volume of the brain edema lesion,and the water content of the brain was further quantified at 1 day and 3 day after CCI.Blood brain barrier(BBB)integrity was evaluated by Evnas Blue dye extravasation and assessment of degradation of the tight junction protein.Inflammatory responses were also evaluated following CCI.Western Blot analysis was used to evaluate expression of aquaporin 4.In order to asses the effects of inhibition of Sur1 on neuroethology,glibenclamide intraperitoneal injection was applied in mice after CCI(10μg).Mechanical stretch injury treated b End.3 cells and LPS treated BV2 cells were used to investigate the underline molecular biological mechanisms.In b End.3 cells,Sur1 si RNA interference was applied to detect apoptotic protein levels following mechanical stretch injury.In additionapoptotic cells and mitochondrial membrane potential were detected by flow cytometer,apoptosis-related protein levels and phosphorylation levels of JNK/c-jun signal pathway were quantified.On BV2 cells,expression of inflammatory factors were evaluated by quantitative PCR after LPS-treatment,expression of COX2,i NOS and phosphorylation levels of p38/MAPK were detected by Western Blot analysis.The effectiveness of p38/MAPK inhibitor and glibenclamide on expression of inflammatory mediators in LPS-treated BV2 cell were also compared.Results: The volume of the brain edema lesion and water content of the brain were significantly decreased in mice treated with glibenclamide,compared to the vehicle group,following CCI(p < 0.05 at 1day and 3 day).Furthermore,glibenclamide administration greatly improved neurobehavioral assessment from day 7 after CCI.BBB disruption and expression of cytokines decreased after Sur1 inhibition.Glibenclamide treatment decreased CCI-induced microglial activation both in vivo and in vitro.In b End.3 cells,Sur1 si RNA interference significantly decreased TUNEL positive cells(p < 0.05)and protein levels of cleaved caspase 3(p < 0.01).Mechanistically,glibenclamide relieve the decrease of mitochondrial membrane potential and tight junction protein levels in b End.3 cells after mechanical stretch injury,furthermore,glibenclamide promoted anti-apoptotic protein levels and suppressed pro-apoptotic protein levels following injury.Phosphorylation levels of JNK/c-jun signal pathway were decreased with treatment of glibenclamide in b End.3 cells following stretch injury which indicated that the JNK/c-jun signal pathway may be potentially regulated by Sur1.Sur1 inhibition alleviated expression of inflammatory cytokines,COX2 and i NOS,DHE positive cells were also significantly reduced in LPS-treated BV2 cell(p < 0.05).Phosphorylation levels of p38/MAPK signal pathway were decreased with treatment of glibenclamide in LPS-exposed BV2 cells.Moreover,comparison with glibenclamide and p38/MAPK inhibitor suggested that the p38/MAPK signal pathway may be potentially regulated by Sur1.Conclusions: The integrity of BBB was prevented and inflammation was reduced after Sur1 inhibition in CCI mice,brain edema alleviation and neurological functional recovery improvement were also observed.Sur1 inhibitor-glibenclamide would relief trauma-induced endothelial apoptosis and alleviate microglia activation which may potentially protect against traumatic brain injury.Therefore,Sur1 is a promising therapeutic target in the TBI therapy.