Preventive Electroacupuncture Alleviates Oxidative Stress and Inflammation via Keap1/Nrf2/HO-1 Pathway in Rats with Cyclophosphamide-Induced Premature Ovarian Insufficiency

Abstract

Electroacupuncture (EA) is a popular therapeutic therapy for premature ovarian insufficiency (POI). However, little has been known about the underlying processes of EA therapy. To investigate the benefit of EA and reveal the mechanism, thirty SD female rats were allocated into the control, model, sham, EA, and GnRHa groups at random. Vaginal smears were used to monitor the rats’ estrous cycle. Serum liver and renal function (ALT, AST, BUN, and Cr), sex hormone (FSH, E2, and AMH), oxidative stress markers (SOD, GSH, and MDA), and inflammatory cytokine (IL6, IL1β, and TNFα) levels were measured by enzyme-linked immunosorbent assay (ELISA). Their ovary morphology was observed by hematoxylin-eosin staining. Transmission electron microscope was used to remark the ultrastructure of the granulocytes. Protein and gene expressions of Keap1/Nrf2/HO-1 pathway were detected by western blot and RT-PCR. Compared with the model group, in the EA group, the levels of serum sex hormones recovered to normal levels. Moreover, it reduced oxidative stress in rats, as demonstrated by increased SOD and GSH levels and decreased MDA levels. Meanwhile, Keap1 mRNA and protein expression dropped considerably in the EA group, while the mRNA and protein expressions of Nrf2 and HO-1 increased. We found that preventive EA might rescue rats with CTX-induced ovarian dysfunction. The anti-inflammatory and antioxidative stress properties of EA, which elevated the Keap1/Nrf2/HO-1 signaling pathway, might be the underlying mechanism. Furthermore, as compared to GnRHa, electroacupuncture did not raise the burden of the liver (ALT and AST) or the kidney (BUN and Cr). Electroacupuncture has a meaningful impact and a sufficient level of safety, making it useful for therapeutic setting in POI.

Premature ovarian insufficiency: a review on the role of oxidative stress and the application of antioxidants

“…In parallel with the activation of oxidative damage, Nrf2 and its cytoplasmic binding protein cooperate with Keap1 to bind to the antioxidant response element (ARE) in the target gene promoter and promote the transcription of the antioxidant gene heme oxygenase-1 (HO-1), thereby regulating the redox state of the cell to maintain cellular homeostasis (96). Chen Y et al also verified this conclusion that ovarian tissues of POI model rats suffered from oxidative damage and the expression of Keap-1 protein was increased in ovarian tissues, while the expression of Nrf2/HO-1 protein was decreased (97). Several studies have demonstrated that Keap1-Nrf2-ARE pathway-related drugs treat age-related eye diseases through anti-OS (98).…”

Role of nuclear factor erythroid 2-related factor 2 (Nrf2) in female and male fertility

“…POI is a disorder characterized by a lack of ovarian sex hormones and a decrease in residual follicles following ovarian dysfunction in women under 40 years of age and is associated with hypogonadism, oligo/amenorrhea, and subfertility/infertility [ 77 , 83 ]. Recent studies have shown that in POI mouse model, the GSH- and SOD-related activity of ovarian oxidation markers decreases, while the expression of MDA increases [ 84 ]. These findings indicate the role of oxidative stress as one of the underlying etiology of POI [ 85 ].…”

“…This increase in Nrf2 mRNA expression along with a significant decrease in Nrf2 protein expression ultimately leads to the depletion of ovarian reserves [ 89 ]. In addition, the expression of Keap-1 protein in ovarian tissue increases, while the expression of downstream proteins of Nrf2, including GCLC, HO-1, and NQO1, decreases [ 84 , 87 ]. Therefore, by inhibiting the Nrf2/Keap1 signaling pathway, the antioxidant capacity is weakened in the POI [ 90 ].…”

Role of the Nrf2 Signaling Pathway in Ovarian Aging: Potential Mechanism and Protective Strategies

“…Electroacupuncture (EA) is a popular therapy for POI in China. EA activates the Keap1/Nrf2/HO-1 signaling pathway and rescues CTX-induced ovarian dysfunction, which includes a disturbed motility cycle, decreased AMH and E 2 hormone levels, and an increased atretic follicle number [97].…”