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

Abstract

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. 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. 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). 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.