[Electroacupuncture intervention increases testosterone level of aged rats by activating ERK/Nrf2/HO-1 signaling of Leydig cells].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on anti-oxidant function of Leydig cells in aged rats with low testosterone, so as to reveal its underlying mechanism of anti-aging of male reproduction. METHODS: Eighteen 20 months old SD rats were divided into aged control, medication and EA groups(n=6 in each group), and other 6 young male SD rats (2 months of age) were used as the youth control group. The rats of the youth and the aged control groups received subcutaneous injection of 0.9% normal saline (7 mg·kg-1·3 d-1) for 8 weeks, and those of the medication group received abdominal subcutaneous injection of Testosterone Propionate (7 mg·kg-1·3 d-1) for 8 weeks. EA (2 Hz/100 Hz, 1 mA) was applied to bilateral "Shenshu" (BL23) and "Guanyuan" (CV4) for 15 min, once daily for 8 weeks except the weekends. The levels of serum total testosterone (TT) and free testosterone (FT) were determined by enzyme linked immune sorbent assay (ELISA), the immunoactivity of phosphorylated extracellular signal-regulated protein kinase (p-ERK) was detected by immunohistochemistry, and the expression levels of ERK, p-ERK, nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) proteins in the testis tissues were determined by Western blot. RESULTS: Before and after the treatment, the levels of serum TT and FT in the aged control group were significantly lower than those of the youth control group (P<0.01). After the treatment, the serum TT and FT contents in the EA and medication groups were obviously higher than those in the aged control group (P<0.01). Compared with the youth control group, the expression levels of ERK, p-ERK, Nrf2 and HO-1 proteins were significantly down-regulated in the aged control group (P<0.01), while in comparison with the aged control group, the expression levels of ERK, p-ERK, Nrf2 and HO-1 proteins were significantly up-regulated in the medication and EA groups (P<0.01). The therapeutic effect of EA was notably superior to that of medication in up-regulating the immunoactivity of p-ERK, and the expression levels of ERK, p-ERK, Nrf2 and HO-1 proteins (P<0.01). No significant differences were found between the EA and medication groups in the increased levels of serum TT and FT after the intervention (P>0.05). CONCLUSION: EA intervention may increase testosterone level of the aged rats, which may be related to its effects in triggering ERK /Nrf2 /HO-1 signaling (anti-oxidative stress signal pathway) in the testis.