Cigarette Smoke and Estrogen Signaling in Human Airway Smooth Muscle

Abstract

Aims: Cigarette smoke (CS) in active smokers and second-hand smoke exposure exacerbate respiratory disorders such as asthma and chronic bronchitis. While women are known to experience a more asthmatic response to CS than emphysema in men, there is limited information on the mechanisms of CS-induced airway dysfunction. We hypothesize that CS interferes with a normal (protective) bronchodilatory role of estrogens, thus worsening airway contractility. Methods: We tested effects of cigarette smoke extract (CSE) on 17β-estradiol (E₂) signaling in enzymatically-dissociated bronchial airway smooth muscle (ASM) obtained from lung samples of non-smoking female patients undergoing thoracic surgery. Results: In fura-2 loaded ASM cells, CSE increased intracellular calcium ([Ca²⁺]_i) responses to 10µM histamine. Acute exposure to physiological concentrations of E₂ decreased [Ca²⁺]_i responses. However, in 24h exposed CSE cells, although expression of estrogen receptors was increased, the effect of E₂ on [Ca²⁺]_i was blunted. Acute E₂ exposure also decreased store-operated Ca²⁺ entry and inhibited stromal interaction molecule 1 (STIM1) phosphorylation: effects blunted by CSE. Acute exposure to E₂ increased cAMP, but less so in 24h CSE-exposed cells. 24h CSE exposure increased S-nitrosylation of ERα. Furthermore, 24h CSE-exposed bronchial rings showed increased bronchoconstrictor agonist responses that were not reduced as effectively by E₂ compared to non-CSE controls. Conclusion: These data suggest that CS induces dysregulation of estrogen signaling in ASM, which could contribute to increased airway contractility in women exposed to CS.