Electroacupuncture Intervention Enhances Splenic Natural Killer Cell Activity via Inhibiting Phosphorylation of ERK 5in the Hypothalamus of Surgically Traumatized Rats

Objective To observe the effect of electroacupuncture(EA)on cytotoxic activity of splenic natural killer(NK)cells after surgical trauma via extracellular signal-regulated kinase(ERK)5pathway in the rats' hypothalamus,so as to explore its mechanism underlying improving immune disorders after surgery.Methods Sprague-Dawley rats were randomly divided into the following 6groups:control,trauma model,EA,sham EA,4nmol-BIX 02188(an inhibitor for ERK 5catalytic activity)and 20nmol-BIX 02188(n=6rats per group).The surgical trauma model was established by making a longitudinal incision(6cm in length)along the median line of the back to expose the spinal column and another longitudinal incision along the abdominal median line.EA(2Hz/15 Hz,1-2mA)was applied to bilateral"Zusanli"(ST 36)for 30 min immediately after surgery.For rats of the BIX groups,intra-lateral ventricular microinjection of BIX 02188(10μL,4nmol or 20 nmol,or saline for control rats)was conducted 30 min before the surgery.The expression level and protein of phosphorylated ERK 5(p-ERK 5)and corticotropin-releasing factor(CRF)protein were measured by immunohistochemistry and Western blot,respectively.The cytotoxicity of splenic NK cells and the expression of splenic Perforin and Granzyme-B genes were measured by lactate dehydrogenase(LDH)release assay and real-time PCR,respectively.Results In comparison with the control group,hypothalamic p-ERK 5immunoactivity,p-ERK5 protein and CRF protein expression levels were significantly up-regulated in the model group(P<0.01,P<0.05),while splenic NK cell cytotoxicity and Perforin mRNA and Granzyme-B mRNA expression levels were notably down-regulated in the model group(P<0.05,P<0.01).Following EA and administration of ERK 5antagonist,the increased expression levels of p-ERK 5immunoactivity in the EA group,and p-ERK 5and CRF proteins in both EA and 20nmol-BIX 02188 groups were obviously down-regulated(P<0.05,P<0.01),without changes in the sham EA and 4nmol-BIX 02188groups(P>0.05)except the increased p-ERK 5protein in the 4nmol-BIX 02188 group.In addition,the down-regulated NK cell activity,Perforin mRNA and Granzyme-B mRNA expression levels were significantly reversed in the EA and 20nmol-BIX 02188groups(P<0.05,P<0.01).No significant differences were found between the EA group and 20nmol-BIX 02188 group in down-regulating hypothalamic p-ERK 5and CRF protein expression and up-regulating splenic NK cytotoxicity and Perforin and Granzyme-B gene expression(P>0.05).Conclusion EA can promote the cytotoxicity of splenic NK cells in surgical trauma rats,which may be closely associated with its functions in down-regulating trauma-induced activation of ERK 5pathway and production of CRF in the hypothalamus.