To Explore The Role Of Nrf2 Pathway In The Treatment Mechanism Of Acupuncture Combined Exercise On Chronic Myofascial Pain Syndrome

ObjectiveMyofascial pain syndrome(MPS)is the most common chronic musculoskeletal pain disorder.Myofascial trigger points(MTrPs)are the most important clinical features of MPS and the key treatment points of MPs.Related studies have confirmed that local inflammation is an important pathological feature of MTrPs.Previous studies have shown that the local inflammatory environment in MTrPs can stimulate nociceptors in MTrPs and cause peripheral and central nerve sensitization,which can lead to the decrease of pain threshold.Thesignaling pathway is related to NF-κB.Nuclear transcription factor E2 related factor 2(Nrf2)is a key nuclear transcription factor in cellular oxidative stress and anti-inflammatory response,and It can inhibit the effect of NF-κB/p65.When the cells are stable,Keap1 can combine with Nrf2 to inhibit Nrf2 translocation and thus inhibit its effect.As an effective treatment for MPs,exercise therapy and acupuncture can raise the pain threshold to a certain extent.Therefore,this study intends to establish the MPS rat model first,then to observe the changes of local morphology and pain threshold by exercise intervention and acupuncture intervention,and at last,to detect the expression of Nrf2 Keap1 and NF in MTrPs cells by immune(or fluorescent)histochemical technique,so as to explore the possible mechanism of Nrf2 in the improvement of MPS model rats by exercise therapy and acupuncture therapy.Methods17 male SD rats,with an average age of 6 weeks and average weight of220～260g,after one week of adaptation,were randomly divided into 4 groups:normal control group(group A),MPS model group(group B),MPS model exercise group(Group C),MPS model acupuncture group(Group D),MPS model acupuncture combined exercise group(Group E).The rat model of MPS was established by blunt hitting the left posterior gastrocnemius muscle and downhill running for 8weeks.After 4 weeks of rest,2 rats were randomly selected from the control group and the model group for histomorphological observation.After the model was successfully established,group C,D and E were treated with exercise or acupuncture intervention for 2 weeks.Acupuncture intervention:filiform needle direct puncture MTrPs,local needle retention for 30 min,one time/day;Exercise intervention: uphill running with a slope of 6 °,a running speed of 15m/min and 60 minutes/ day.Acupuncture combined with exercise intervention:exercise intervention in the morning and acupuncture intervention in the afternoon.The intervention was to stop for two days after 5consecutive days of intervention.The next day after the experimental intervention,the pain threshold measurement and muscle bone ultrasound examination were carried out in each group,and the local tissues of MTrPs were taken on the same day.Then the morphological changes of tissues were observed by HE staining technique,the changes of NF-κB were detected by immunohistochemical technique,and the changes of Nrf2 and Keap1 were detected by immunofluorescence histochemical technique.Rusults(1)Pain threshold:the pain threshold in group B,group D and group E was significantly lower than that in group A(P<0.05),but there was no significant difference between group C and group A(P>0.05).After corresponding intervention,the pain threshold of MPS model rats in each intervention group changed in varying degrees.Compared with group B,and the pain threshold was significantly increased by exercise intervention and significantly reduced by exercise combined with acupuncture intervention(P<0.05);Acupuncture intervention increased the pain threshold of MPS rats,but there was no significant difference(P>0.05);In addition,the pain threshold in group C and group D was significantly higher than that in group E(P<0.05).(2)The expression of NF-κB in MTrPs cells:the expression of NF-κB in group B,group C,group D and group E was significantly higher than that in the control group(P<0.05);Compared with the model group B,the expression of NF-κB in both group C and group D decreased after(P<0.05),but no obvious changes in group E(P>0.05).(3)The expression of Nrf2-Keap1 in MTrPs cells:No expression of Nrf2 were found in skeletal muscle of normal group and in MTrPs cells of model group.The expression of Keap1 in MTrPs cells in group B was significantly lower than that in group A.Compared with the model group B,the expression of Keap1 in group C,group D and group E increased significantly(P<0.05),and the expression of Keap1 in group D was significantly higher than that in group D.ConclusionsExercise and acupuncture intervention can increase pain threshold in MTrPs,especially exercise,but acupuncture combined with exercise had a negative effect on pain threshold.The mechanism of exercise and acupuncture intervention on pain threshold may be associated with the local inflammatory response,but not the Nrf2 pathway.