The Role And Mechanism Of SIRT2 Mediated NF-?B Deacetylation In Experimental Traumatic Brain Injury

Background:Sirtuin 2(SIRT2)is a member of the Sirtuin family of NAD~+-dependent protein deacetylases.In recent years,SIRT2 inhibition has emerged as a promising treatment for neurodegenerative diseases.However,to date,there is no evidence of a specific role for SIRT2 in traumatic brain injury(TBI).We investigated the effects of SIRT2 inhibition on experimental TBI using the controlled cortical impact(CCI)injury model.Methods:Adult male C57Bl/6 mice underwent CCI or sham surgery.A selective brain-permeable SIRT2 inhibitor,AK-7,was administrated 30 min before injury.The volume of the brain edema lesion was calculated from T2-weighted images(T2WIs)obtained by magnetic resonance imaging(MRI),and water content of the brain was further quantified using the wet-dry method at 1 day and 3 days after injury.Blood–brain barrier(BBB)integrity was evaluated by Evans Blue(EB)dye extravasation and assessment of the degradation of the tight junction protein.Inflammatory responses,including microglia/macrophage activation,cytokine production,and NF-?B signaling pathway activation,were also evaluated following TBI.To determine the effects of SIRT2 inhibition on behavioral changes after injury,AK-7 was administered twice daily in a subset of mice for up to 7 days.To validate the effects of SIRT2 inhibition in TBI,SIRT2 knock out(KO)mice were enrolled,in vivo and in vitro TBI induced neural cell death and neurobehavioral deficits were assessed.Results:The volume of the brain edema lesion and the water content of the brain were significantly increased in mice treated with AK-7(20 mg/kg),compared to the vehicle group,following TBI(p<0.05 at 1 day and p<0.05 at 3 days,respectively).Furthermore,AK-7 administration greatly worsened neurobehavioral deficits on days3 and 7 after CCI.BBB disruption and matrix metalloproteinasese(MMP)-9 activity increased following SIRT2 inhibition.AK-7 treatment increased TBI-induced microglial activation both in vivo and in vitro.A multiplex array revealed a large increase in inflammatory cytokine production in the treated group.Mechanistically,SIRT2 inhibition increased both K310 acetylation and nuclear translocation of NF-?B p65,leading to enhanced NF-?B activation and upregulation of its target genes,including aquaporin 4(AQP4),MMP-9,and pro-inflammatory cytokines.SIRT2 KO increased the level of LDH release caused by stretch induced neuron injury and CCI induced neural cell apoptosis,compared with WT group.Conclusion:The SIRT2 inhibitor AK-7 exacerbates TBI by increasing NF-?B p65acetylation and activation.SIRT2 KO Our findings provide additional evidence of an anti-inflammatory effect of SIRT2 and demonstrate its role in neuroprotection.