Protective Potential of Hormone Replacement Therapy in Post-Menopausal Women

Purpose: Menopause is the cessation of a woman’s menstrual cycle, generally diagnosed after 12 months of amenorrhea. Due to hormonal changes, women often undergo physical and behavioral changes: including hot flashes, mood lability, and sleep disturbances. The first line of treatment for menopausal symptoms is hormonal replacement therapy (HRT). HRT use does have risks, such as cardiovascular disease and breast cancer. Younger postmenopausal women had reduced risks compared to older postmenopausal women. Aging is linked with oxidative stress (OS), and thus OS may be a mediating factor in HRT risk. Previously, we showed HRT given prior to OS insult is neuroprotective. If given after OS insult, HRT is neurotoxic in dopaminergic neurons. Therefore, we will determine if OS and HRT interactions is a general phenomenon applicable to all cell types or specific to neurons. Further, we will determine if either the estrogen receptor or the androgen receptor mediate OS and HRT interactions. Materials and Methods: We utilized 1RB3AN27 (N27) neuronal cells derived from female fetal mesencephalic tissue, human embryonic kidney cells (HEK), and C6 glial cells. Cells were grown in their preferred media supplemented with L-glutamine, penicillin-streptomycin and fetal bovine serum. Prior to experimentation, media was switched to charcoal stripped serum to remove hormones. To model post-menopause, hormone-deficient cells were exposed to OS using hydrogen peroxide (H2O2). Three different HRTs were examined: testosterone, 17-beta estradiol, and membrane impermeable dihydrotestosterone (DHT-BSA). An estrogen receptor inhibitor (ICI-182,780) and androgen receptor degrader will be included to explore the hormonal pathways. Cell viability was assessed with MTT assays. Results: Testosterone, estradiol, and DHT-BSA had different effects, which were dependent on the presence of OS. Both testosterone and estradiol were protective when given prior to OS, but DHT-BSA was not protective. Conversely, all HRTs given after OS exacerbated OS-induced cell loss. Conclusion: Based on our results, HRT's protective effects against subsequent OS damage is predominantly due to estrogen hormonal pathways. Activation of androgen pathways may not be neuroprotective and could be damaging. Currently, post-menopausal women are mainly using estradiol-based HRT. However, an increasing trend for off-label use of testosterone-based HRTs has been noted in post-menopausal women to improve libido.