Irisin Ameliorates Oxidative Stress-induced Apoptosis In Experimental Traumatic Brain Injury Through Nrf2 Pathway

Objective: Irisin has antioxidant,anti-inflammatory and anti-apoptotic effects on various diseases,such as type 2 diabetes,obesity,myocardial injury,and even neurodegenerative diseases and cerebral infarction.The protective effect of irisin on brain injury It is increasingly recognized,but its specific mechanism remains to be discovered.Oxidative stress is one of the main manifestations of the pathophysiology of TBI,and irisin plays a key role in reducing inflammation,reducing oxidative stress and reducing apoptosis,as well as reducing damaged mitochondrial function,but it has no effect on traumatic brain injury(TBI)The mechanism of treatment is not fully understood.The purpose of this study was to investigate whether irisin exerts a neuroprotective function in a TBI model,and through which pathways it reduces oxidative stress-induced apoptosis,and what role Nrf2-related pathways play in it..Methods: Male C57BL/6J wild mice(20–25 g,6–8w)were randomly divided into 5 groups: sham operation group,sham operation+irisin group,TBI group,TBI+vehicle group and TBI+irisin group.To induce TBI using the controlled cortical impingement(CCI)injury model,mice were anesthetized by intraperitoneal injection of 1.5%pentobarbital sodium 50 mg/kg after fasting for 8 hours before surgery but with free access to water.Then,the mouse’s skull skin was sterilized,and the top of the right side of the skull was incised to expose the junction of the sagittal and coronal sutures.Next,scrape the periosteum,and drill a bone window with a diameter of4 mm at 2 mm from the sagittal and coronal sutures.Then the mice were fixed on the base of the CCI electronic craniocerebral injury instrument and received a moderate TBI impact of 150 ms with the parameters set at a speed of 3.5 m/s and a depth of 1 mm.Operation.Then,the bone fragments and skin are sutured.Finally,mice were housed in individual cages under ventilation and natural light.Then the sham + irisin group,TBI + vehicle group and TBI + irisin group were given irisin(0.5 μg/g body weight)or vehicle by intraperitoneal injection.Brain samples were collected for analysis 24 hours after neurological examination assessment after TBI.We conducted neurological evaluation through water maze and grasping test;measured the water content of the brain by dry and wet weight method to observe the degree of cerebral edema in brain tissue;observed damaged nerve cells and apoptosis by nylon staining+ TUNEL staining Cell index;measure the content of malondialdehyde(MDA)and the activity of SOD and GPx through the kit to clarify the degree of oxidative stress in brain tissue;then analyze the levels of apoptosis-related factors and proteins by Western bot and immunohistochemical staining Changes in Nrf2-related factors and assessment of the extent of neuronal damage.Results: Irisin significantly improved TBI-induced secondary brain injury,including neurological deficit and neuronal apoptosis.Compared with the control group,the group treated with irisin had higher neurological function scores,demonstrating the potential value of irisin in restoring neurological function;the irisin+TBI group had lower brain water content than the TBI group,demonstrating the potential value of irisin in restoring neurological function.Irisin reduced the degree of brain tissue edema after TBI;in addition,after nylon staining,the apoptosis of brain tissue treated with irisin was less,and the anti-apoptotic effect of irisin can be concluded;in addition,irisin also reduced TBI The level of MDA in the hindbrain tissue increased the activity of SOD and GPx,and it can be seen that irisin has the effect of attenuating oxidative stress;in Western blot and immunohistochemistry,the brain tissue after irisin treatment Brain tissue,higher expression level of Nrf2 in brain tissue and higher expression level of Nrf2 pathway-related downstream factors including NQO-1,HO-1,reduced expression level of cleaved caspase-3,proved irisin’s anti-cellular Apoptosis is accomplished by activating the Nrf2 signaling pathway,thereby reducing oxidative stress.Conclusion: This study shows that irisin has a neuroprotective effect by alleviating oxidative stress and apoptosis after TBI,and irisin can attenuate oxidative stress by enhancing the expression and activity of antioxidant enzymes in the brain tissue of mice after TBI.reaction.In addition,experimental data showed that irisin exerted anti-apoptotic and neuroprotective effects after TBI in mice by activating the Nrf2 pathway and its downstream factors including NQO-1 and HO-1 against oxidative stress.However,we still need further studies to elucidate the underlying mechanism between the Nrf2 pathway and apoptosis after irisin administration...