The Therapeutic Effect Of Vagus Nerve Stimulation On Skeletal Muscle Ischemia-reperfusion Injury And Its Underlying Mechanisms

Background and objective: Skeletal muscle ischemia-reperfusion injury(SMIRI)is a common pathophysiological phenomenon in clinical practice.Due to the complexities of its underlying mechanisms,there is few effective treatment for SMIRI.Vagus nerve stimulation(VNS)has been known to improve ischemia-reperfusion injury in multiple organs.Present study aimed to demonstrate the protective effects of VNS against SMIRI and further explore the potential mechanisms.Methods: Male Sprague-Dawley rats were randomly divided into 3 groups: the Control,SMIR,and SMIR+VNS groups.The SMIR model was induced by occlusion of the left femoral artery for 2.5 hours followed by reperfusion for 2 hours.The vagal nerve trunk was separated as the stimulating target,and VNS was performed during the whole IR process.The intensity of VNS was optimized in each rat to obtain a 10% reduction in the heart rate relative to the value before stimulation.After the experiment,the blood sample and left gastrocnemius muscle tissues were collected.The damage of skeletal muscle was observed by the histopathology changes in skeletal muscle and the serum levels of creatine kinase(CK)and lactate dehydrogenase(LDH).Terminal deoxynucleotidyl transferase d UTP nick end labeling(TUNEL)staining was used to detect skeletal muscle cell apoptosis among the three groups.Mechanism study:Western blot and q RT-PCR were used to detect the expression of interleukin 1 beta(IL-1β),interleukin 6(IL-6)and tumor necrosis factor alpha(TNF-α)in skeletal muscle.The level of myeloperoxidase(MPO)activity in serum,malondialdehyde(MDA)and superoxide dismutase(SOD)activity in skeletal muscle and serum were measured to assess the intensity of oxidative stress.And the expression of vascular cell adhesion molecule-1(VCAM-1),intercellular adhesion molecule-1(ICAM-1)and endothelial nitric oxide synthase(e NOS)in skeletal muscle tissue were measured by western blot to reflect the vascular endothelial function.Result: Compared with the Control group,severe skeletal muscle cell degeneration,necrosis,sarcoplasmic dissolution,neutrophil infiltration,increased serum CK,LDH levels and higher percentage of TUNEL-positive cells were observed in the SMIR group.While these changes were significantly alleviated in the SMIR+VNS group.(p<0.05 for all)Mechanism study: the expression of inflammatory factor IL-1、IL-6、TNF-α were significantly increased;the level of MPO activity in serum was significantly increased;the level of MDA was increased and the SOD activity was decreased in tissue and serum;the expression of indicators of vascular endothelial function,ICAM-1 and VCAM-1 were significantly increase while the expression of e NOS was deceased in the SMIR group compared to the Control group.All these changes were significantly alleviated in the SMIR+VNS group.(p<0.05 for all)Conclusion: VNS could protect against SMIR injury by suppressing excessive inflammation,alleviating oxidative stress,and preserving vascular endothelial dysfunction.