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A7258 - Androgen Receptor Signaling and Intracellular Calcium Regulation in Human Airway Smooth Muscle Cells
Author Block: R. Katragadda1, N. A. Borkar1, M. A. Thompson2, C. M. Pabelick2, Y. Prakash2, S. Venkatachalem1; 1Department of Pharmaceutical Sciences, North Dakota State University, Fargo, ND, United States, 2Department of Anesthesiology and Perioperative Medicine, Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States.
Rationale: Bronchial asthma is characterized by chronic inflammation, airway hyperreactivity and importantly remodeling, both of which involve altered structure and function of airway smooth muscle (ASM). Asthma prevalence is higher in adult women than men raising the question of whether estrogens are detrimental or testosterone (TES) is “protective”. Animal studies using tracheal, vascular and urinary bladder smooth muscle have demonstrated non-genomic relaxation of contracted tissue and decreased intracellular calcium [Ca2+]i following exposure to TES, 5α-Dihydrotestosterone (5α-DHT) and other endogenous androgens. However, the role of androgen receptor (AR) signaling in asthma or genomic mechanisms of androgen action in [Ca2+]i regulation in human ASM are unknown. We aimed to establish the significance of AR signaling in human ASM and to study the effect of androgen agonists on [Ca2+]i regulation in the presence of inflammation with the hypothesis that TES is protective. Methods: Human ASM cells were enzymatically dissociated from tissue obtained incidental to lung surgery at Mayo Clinic (IRB approved) and grown in a 95% air/ 5% CO2 humidified incubator using DMEM F/12. AR mRNA and protein expression after treatment with vehicle and inflammatory cytokines, TNFα (20ng/mL) or IL-13 (50ng/mL) for 24h were measured. ASM cells treated with TNFα or IL-13 in the presence vs. absence of TES (10nM) or 5α-DHT (10nM) for 24h were assessed for [Ca2+]i responses to 10µM histamine under both physiological (2mM Ca2+) and zero extracellular Ca2+ in HBSS using Fluo3 and Biotek LionheartFX Imager. Results: Basal expression of AR in human ASM was higher in cells derived from male patients compared to females. However, expression was significantly upregulated in asthmatic females. Treatment with TNFα or IL-13 significantly increased AR expression and these effects were more pronounced with TNFα. TNFα and IL-13 significantly increased [Ca2+]i compared to vehicle. 24h treatment with TES or 5α-DHT significantly reduced cytokine-induced [Ca2+]i increases. Less pronounced effect was observed in the absence of extracellular [Ca2+]. Conclusion: Androgen receptor expression is increased in asthma and androgen agonists have receptor-mediated genomic effects in decreasing [Ca2+]i in inflamed human ASM, especially via plasma membrane associated calcium regulatory pathways. Thus targeting of ARs may be a novel approach to reducing airway hyperreactivity in airway inflammation.