Cigarette smoke extraxt influences intracellular calcium concentration in A549 cells

Cigarette smoking is a major risk factor for pulmonary diseases, including chronic obstructive pulmonary disease (COPD) and cancer. Cigarette smoke is reported to contain over 4,000 chemical compounds. Therefore, it needs to study the effects of cigarette smoke extract (CSE) administration on intracellular calcium concentration. In this study, we investigated how CSE influences intracellular calcium concentration in human lung adenocarcinoma A549 cells. The CSE concentrations used (0.4, 2, 3%) did not influence cell viability. However, at these CSE concentrations, calcium influx transient receptor potential vanilloid 4 (TRPV4) and transient receptor potential vanilloid 6 (TRPV6) proteins significantly increased, whereas calcium efflux sodium-calcium exchanger (NCX1) and plasma membrane Ca²⁺ ATPase (PMCA1) proteins significantly decreased from those of the control cells. The 3% CSE treatment produced an intracellular calcium concentration higher than that of the control treatment through methods of co-transfection of pGP-CMV-GCaMP6f/CMV-R-GECO1.2 and Rhod-4 Assay. CSE induced concentration-dependent increments in hypoxia-inducible factor (HIF)-1α and HIF-2α protein levels. Moreover, phosphorylation of ERK and Akt was induced by CSE treatment. Also, mitochondrial marker B-cell lymphoma 2 (Bcl-2) protein level decreased and Bcl-2-associated X (Bax) protein level increased following CSE treatment. Also, endoplasmic reticulum (ER) stress markers BiP, CHOP, p-SAPK, and p-eIF2α levels were increased by CSE treatment. These results suggest that CSE may increase the concentration of intracellular calcium, thus increasing mitochondrial and ER stress.