Sleep apnea is associated with testosterone dysregulation as well as increased risk of developing neurodegenerative diseases, such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). A rodent model of the hypoxic events of sleep apnea, chronic intermittent hypoxia (CIH), has been previously documented to impair cognitive function and elevate oxidative stress in male rats, while simultaneously decreasing testosterone. Therefore, androgens may modulate neuronal function under CIH. To investigate the role of androgens during CIH, male rats were assigned to one of four hormone groups: 1) gonadally intact, 2) gonadectomized (GDX), 3) GDX + testosterone (T) supplemented, or 4) GDX + dihydrotestosterone (DHT) supplemented. Each group was exposed to either normal room air or CIH exposure for one week, followed by memory and motor task assessments. Brain regions associated with AD and PD (entorhinal cortex, dorsal hippocampus, and substantia nigra) were examined for oxidative stress and inflammatory markers, key characteristics of AD and PD. Gonadally intact rats exhibited elevated oxidative stress due to CIH, but no significant memory and motor impairments. GDX increased memory impairments, regardless of CIH exposure. T preserved memory function and prevented detrimental CIH-induced changes. In contrast, DHT was not protective, as evidenced by exacerbated oxidative stress under CIH. Further, CIH induced significant spatial memory impairment in rats administered DHT. These results indicate androgens can have both neuroprotective and detrimental effects under CIH, which may have clinical relevance for men with untreated sleep apnea.

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Fast, nongenomic androgen actions have been described in various cell types, including neurons. However, the receptor mediating this cell membrane–initiated rapid signaling remains unknown. This study found a putative androgen receptor splice variant in a dopaminergic N27 cell line and in several brain regions (substantia nigra pars compacta, entorhinal cortex, and hippocampus) from gonadally intact and gonadectomized (young and middle-aged) male rats. This putative splice variant protein has a molecular weight of 45 kDa and lacks an N-terminal domain, indicating it is homologous to the human AR45 splice variant. Interestingly, AR45 was highly expressed in all brain regions examined. In dopaminergic neurons, AR45 is localized to plasma membrane lipid rafts, a microdomain involved in cellular signaling. Further, AR45 protein interacts with membrane-associated G proteins Gαq and Gαo. Neither age nor hormone levels altered AR45 expression in dopaminergic neurons. These results provide the first evidence of AR45 protein expression in the brain, specifically plasma membrane lipid rafts. AR45 presence in lipid rafts indicates that it may function as a membrane androgen receptor to mediate fast, nongenomic androgen actions.

Sleep apnea is a common sleep disorder characterized by intermittent periods of low blood oxygen levels. The risk for sleep apnea increases with age and is more prevalent in men than women. A common comorbidity of sleep apnea includes male sexual dysfunction, but it is not clear if a causal relationship exists between sleep apnea and sexual dysfunction. Possible mechanisms that link these two disorders include oxidative stress and testosterone. Oxidative stress is elevated in clinical patients with sleep apnea and in rodents exposed to chronic intermittent hypoxia (CIH), an animal model for apnea-induced hypopnea. Further, oxidative stress levels increase with age. Therefore, age may play a role in sleep apnea-induced sexual dysfunction and oxidative stress generation. To investigate this relationship, we exposed gonadally intact 3 (young) and 12 (middle-aged) month old male F344/BN F1 hybrid male rats to 8 days of CIH, and then examined male sexual function. Plasma was used to assess circulating oxidative stress and hormone levels. Middle-aged male rats had lower testosterone levels with increased sexual dysfunction and oxidative stress, independent of CIH. However, CIH decreased testosterone levels and increased sexual dysfunction and oxidative stress only in young gonadally intact male rats, but not in gonadectomized young rats with physiological testosterone replacement. In sum, CIH had a greater impact on younger gonadally intact animals, with respect to sexual behaviors, testosterone, and oxidative stress. Our data indicate CIH mimics the effects of aging on male sexual behavior in young gonadally intact male rats.

A common characteristic of several neurodegenerative disorders is oxidative stress (OS). Many neurodegenerative disorders are more prevalent in men and postmenopausal women compared to premenopausal women, indicating the possible involvement of androgens (men > postmenopausal women > premenopausal women) in neurodegeneration. Our lab found testosterone can have either neuroprotective or neurodamaging effects depending on the presence of OS in the cellular environment. We have shown testosterone via a non‐genomic mechanism exacerbates OS damage in neurons. Indeed, our lab was the first to discover the presence of the androgen receptor (AR) splice variant, AR45, in the brain. Subcellular localization of AR45 is in the lipid rafts of the plasma membrane in several brain regions affected by neurodegenerative disorders (eg. substantia nigra, hippocampus). We found testosterone can initiate signaling cascades via this membrane associated AR (mAR), leading to increased OS. However, the mechanism for OS generation is unknown. NADPH Oxidase 1 and 2 (NOX 1/2) are major OS generators, and potential targets for androgen‐induced OS and cell death. Based on our studies showing protein‐protein interactions between NOX1/2, AR45, and Gαq, we hypothesize testosterone increases OS by activating mAR complexed with NOX 1/2, initiating IP3 signaling. Using an immortalized neuronal cell line (N27 cells), we exposed cells to hydrogen peroxide (H2O2) prior to testosterone (100 nM) or DHT‐BSA (500nM). Inhibitors were used to examine G protein, androgen receptor, IP3 and NOX1/2 signaling. Cell viability and OS were quantified. In addition to in vitro experiments, we examined the effects of NOX 1/2 on DHT exacerbation of chronic intermittent hypoxia, CIH (AHI=10) induced OS by treating adult male Long Evans rats with the NOX1/2 inhibitor, apocynin (4mg/kg). Classical AR antagonists did not block testosterone's negative effects, indicating the classical AR does not mediate these effects. Since AR antagonists do not block mAR, we used an AR protein degrader, ASC‐J9 (5uM). Unlike AR antagonists, the AR degrader blocked testosterone's negative effects. Next, we examined signaling cascades associated with proteins complexed with mAR‐AR45, such as NOX1/2 and Gαq. To block NOX actions, we used apocynin (10 uM), a nonspecific NOX inhibitor. Apocynin did not alter H2O2‐induced cell loss, indicating H2O2 increases OS via a non‐NOX mechanism. However, apocynin completely blocked testosterone induced cell loss and OS, suggesting the involvement of NOX1/2. Consistent with our in vitro data, apocynin also decreased OS generation in DHT‐treated rats exposed to the oxidative stressor, CIH, during sleep phase for 7 days. Inhibition of Gαq or G protein activation did not alter testosterone's negative effects on cell viability. However, inhibition of IP3 receptor blocked these effects. Interestingly, NOX can influence IP3 receptor mediated signaling, indicating that testosterone may activate IP3 signaling via the mAR‐NOX complex and not the mAR‐ Gαq complex l...