Melatonin Alleviates Lipopolysaccharide-compromised Integrity Of Blood-brain Barrier Through Activating AMP-activated Protein Kinase In Old Mice

Blood-brain barrier(BBB)dysfunction is considered to be an early event in the pathogenesis of a variety of neurological diseases in old patients,and this could occur in old people even when facing common stress.However,the mechanism remains to be defined.In this study,we tested the hypothesis that decreased melatonin levels may account for the BBB disruption in old mice challenged with lipopolysaccharide(LPS),which imitated the common stress of sepsis.Objective:We used intraperitoneal injection of LPS to creat the sepsis model,which LPS to cause blood-brain barrier damage in older mice,and to give melatonin by long-term intraperitoneal injection(7 days).To investigate the role of melatonin in LPS-induced blood-brain barrier injury.Methods:Mice(24-28 months of age)received melatonin(10mg/kg/day,intraperitoneally,i.p.)or saline for one week before exposing to LPS(1 mg/kg,i.p.).Evan's blue dye(EB)and immunoglobulin G(IgG)leakage were used to assess BBB permeability.Immunostaining and Western blot were used to detect protein expression and distribution.Results:1.Our results showed that LPS significantly increased BBB permeability in old mice accompanied by the degradation of tight junction proteins claudin-5 and occludin;2.LPS is through the inhibition of AMP-activated protein kinase(AMPK)phosphorylation activation and increased gp91phox protein expression degradation of tight junction proteins claudin-5 and occludin;3.Administration of melatonin for one week significantly decreased LPS-induced BBB disruption,AMPK suppression,and gp91phox up regulation.4.Activation of AMPK with metformin significantly inhibited LPS-induced gp91phox up regulation in endothelial cells.Conclusions:Taken together,our findings demonstrate that melatonin alleviates LPS-induced BBB disruption through activating AMPK and inhibiting gp91phox up regulation in old mice.