The Brain And Intestinal Protective Effects And Potential Underlying Mechanisms Of Ghrelin Following Experimental Intracerebral Hemorrhage

Objective: Ghrelin,a 28 amino-acid brain-gut peptide,has been proven to exert brain and gastrointestinal protection in different kinds of neurological diseases,such as ischemic stroke,subarachnoid hemorrhage(SAH),spinal cord injury(SCI),and traumatic brain injury(TBI);however,its role and the potential molecular mechanisms in intracerebral hemorrhage(ICH)-induced secondary brain injury and intestinal barrier dysfunction are still unknown.In the current study,using an autologous blood mouse model of ICH,we aimed to determine whether ghrelin could attenuate secondary brain injury and intestinal barrier dysfunction after ICH in mice,and if so,attempted to clarify the underlying mechanisms.Methods: Stereotactically intrastriatal infusion of autologous blood was performed to mimic ICH.Ghrelin was given intraperitoneally immediately following ICH and again 1 h later.Neurobehavioral deficits and brain water content on days 1 and 3 after ICH were measured.The perihematomal cell death,NLRP3 inflammasome activation,microglia activation,neutrophil infiltration,pro-inflammatory mediators expression,oxidative stress,and Nrf2/ARE antioxidative signaling pathway were detected in the perihematomal regions on day 3 after ICH.The mucosal injury,intestinal permeability,intestinal tight junction proteins expression,ICAM-1 expression,translocation of intestinal endotoxin were measured on day 1 after ICH.The survival rate and body weight loss were observed during the 14 days after ICH.Nrf2 knockout(KO)mice were applied to determine the role of ghrelin-mediated Nrf2 antioxidative pathway in NLRP3 inflammasome inhibition.Results: Our results demonstrate that ghrelin attenuated neurological deficits,decreased brain water content,reduced perihematomal cell death,inhibited NLRP3 inflammasome activation,suppressed microglia activation,reduced neutrophil infiltration,downregulated pro-inflammatory mediators expression,suppressed oxidative stress,activated Nrf2/ARE antioxidative signaling pathway after ICH.However,ghrelin failed to suppress oxidative stress and inhibite NLRP3 inflammasome activation after ICH in Nrf2 knockout mice.Also,our results showed that ghrelin alleviated intestinal mucosal injury,decreased intestinal permeability,upregulated intestinal tight junction proteins expression,downregulated intestinal ICAM-1 expression,inhibited intestinal endotoxin translocation,improved survival rate,and improve the nutritional status after ICH.Conclusions: Together,our data suggested that ghrelin inhibited NLRP3 inflammasome activation by scavenging ROS generation via the Nrf2/ARE antioxidative pathway,thus reducing inflammatory response,thereby attenuating secondary brain injury after ICH.Meanwhile,our data also showed that ghrelin reduced intestinal mucosal injury and improved intestinal barrier function post-ICH,thus improving the nutritional status.