Influence of electroacupuncture on ghrelin and the phosphoinositide 3-kinase/protein kinase B/endothelial nitric oxide synthase signaling pathway in spontaneously hypertensive rats

Objective To investigate the influence of electroacupuncture(EA)on ghrelin and the phosphoinositide 3-kinase/protein kinase B/endothelial nitric oxide synthase(PI3K/Akt/eNOS)signaling pathway in spontaneously hypertensive rats(SHRs).Methods Eight Wistar-Kyoto rats were used as the healthy blood pressure(BP)control(normal group),and 32 SHRs were randomized into model group,EA group,EA plus ghrelin group(EA+G group),and EA plus PF04628935 group(a potent ghrelin receptor blocker;EA+P group)using a random number table.Rats in the normal group and model group did not receive treatment,but were immobilized for 20 min per day,5 times a week,for 4 continuous weeks.SHRs in the EA group,EA+G group and EA+P group were immobilized and given EA treatment in 20 min sessions,5 times per week,for 4 weeks.Additionally,1 h before EA,SHRs in the EA+G group and EA+P group were intraperitoneally injected with ghrelin or PF04628935,respectively,for 4 weeks.The tail-cuff method was used to measure BP.After the 4-week intervention,the rats were sacrificed by cervical dislocation,and pathological morphology of the abdominal aorta was observed using hematoxylin-eosin(HE)staining.Enzyme-linked immunosorbent assay(ELISA)was used to detect the levels of ghrelin,nitric oxide(NO),endothelin-1(ET-1)and thromboxane A2(TXA2)in the serum.Isolated thoracic aortic ring experiment was performed to evaluate vasorelaxation.Western blot was used to measure the expression of PI3K,Akt,phosphorylated Akt(p-Akt)and eNOS proteins in the abdominal aorta.Further,quantitative real-time polymerase chain reaction(qRT-PCR)was conducted to measure the relative levels of mRNA expression for PI3K,Akt and eNOS in the abdominal aorta.Results EA significantly reduced the systolic BP(SBP)and diastolic BP(DBP)(P<0.05).HE staining showed that EA improved the morphology of the vascular endothelium to some extent.Results of ELISA indicated that higher concentrations of ghrelin and NO,and lower concentrations of ET-1 and TXA2 were present in the EA group(P<0.05).The isolated thoracic aortic ring experiment demonstrated that the vasodilation capacity of the thoracic aorta increased in the EA group.Results of Western blot and qRT-PCR showed that EA increased the abundance of PI3K,p-Akt/Akt and eNOS proteins,as well as expression levels of PI3K,Akt and eNOS mRNAs(P<0.05).In the EA+G group,SBP and DBP decreased(P<0.05),ghrelin concentrations increased(P<0.05),and the concentrations of ET-1 and TXA2 decreased(P<0.05),relative to the EA group.In addition,the levels of PI3K and eNOS proteins,the p-Akt/Akt ratio,and the expression of PI3K,Akt and eNOS mRNAs increased significantly in the EA+G group(P<0.05),while PF04628935 reversed these effects.Conclusion EA effectively reduced BP and protected the vascular endothelium,and these effects may be linked to promoting the release of ghrelin and activation of the PI3K/Akt/eNOS signaling pathway.