Nicotine-Induced Airway Smooth Muscle Cell Proliferation Involves TRPC6-Dependent Calcium Influx Via α7 nAChR

Abstract

Background/Aims: The proliferation of human bronchial smooth muscle cells (HBSMCs) is a key pathophysiological component of airway remodeling in chronic obstructive pulmonary disease (COPD) for which pharmacotherapy is limited, and only slight improvements in survival have been achieved in recent decades. Cigarette smoke is a well-recognized risk factor for COPD; however, the pathogenesis of cigarette smoke-induced COPD remains incompletely understood. This study aimed to investigate the mechanisms by which nicotine affects HBSMC proliferation. Methods: Cell viability was assessed with a CCK-8 assay. Proliferation was measured by cell counting and EdU immunostaining. Fluorescence calcium imaging was performed to measure intracellular Ca²⁺ concentration ([Ca²⁺]_i). Results: The results showed that nicotine promotes HBSMC proliferation, which is accompanied by elevated store-operated calcium entry (SOCE), receptor-operated calcium entry (ROCE) and basal [Ca²⁺]_i in HBSMCs. Moreover, we also confirmed that canonical transient receptor potential protein 6 (TRPC6) and α7 nicotinic acetylcholine receptor (α7 nAChR) are involved in nicotine-induced upregulation of cell proliferation. Furthermore, we verified that activation of the PI3K/Akt signaling pathway plays a pivotal role in nicotine-enhanced proliferation and calcium influx in HBSMCs. Inhibition of α7 nAChR significantly decreased Akt phosphorylation levels, and LY294002 inhibited the protein expression levels of TRPC6. Conclusion: Herein, these data provide compelling evidence that calcium entry via the α7 nAChR-PI3K/Akt-TRPC6 signaling pathway plays an important role in the physiological regulation of airway smooth muscle cell proliferation, representing an important target for augmenting airway remodeling.

Acute pulmonary effects of aerosolized nicotine

“…Our results on nicotine-induced death of airway epithelial cells as well as alveolar epithelial cells further support its toxic effects and are also consistent with a report on colonic epithelial cells (19). Long-term exposure to millimolar concentrations of nicotine results in a steady increase of intracellular calcium, which may also lead to cell damage (35). Taken together, these studies suggest that inhaled nicotine at doses commonly found in e-cigs can cause systemic inflammation, barrier disruption, cell death, and pulmonary edema (Fig.…”

MicroRNA-142 Inhibits Proliferation and Promotes Apoptosis in Airway Smooth Muscle Cells During Airway Remodeling in Asthmatic Rats via the Inhibition of TGF-β -Dependent EGFR Signaling Pathway

“…Airway remodeling is defined as the deposition of collagen and associated structural changes in an asthmatic airway, including smooth-muscle hypertrophy and cell hyperplasia [17,18]. Because airway remodeling represents a significant social and economic burden, asthma has become an important health challenge in developed countries [19].…”

Core Role of TRPC6 Channels in Regulating Airway Re-modelling in Chronic Obstructive Pulmonary Disease

“…Nicotine, a well-believed major component of cigarette smoking extract, has been demonstrated plays an essential role in developing enhanced airway contraction and airway smooth muscle cell proliferation. Nicotine elevated [Ca 2+ ] i in rat airway smooth muscle cells via activating and up-regulating α7 nAChR in ASMCs 33 34 . Therefore, mapping the molecular mechanisms for nicotine induced alterations in bronchial smooth muscle cells may offer clues into COPD pathogenesis and treatment.…”