Abstract:

AIM: To investigate the role of Kv7 channels in nicotine-induced enhancement of pulmonary arterial tension in mice. METHODS: Mice were anesthetized, and lung tissues were quickly removed and placed in 4 ℃ Krebs–Henseleit (K-H) buffer. Pulmonary arteries were dissected under a microscope and cut into rings approximately 2 mm in length. Effect of nicotine on isolated pulmonary artery tension under agonist prestimulation: pulmonary artery rings with a basal tension >2 mN were precontracted with norepinephrine (NE) or phenylephrine (PE) to reach a plateau. Different concentrations of nicotine (10^?11-10^?5 mol/L) were then added, and changes in tension were recorded. The half-maximal effective concentration (EC₅₀) was calculated and used as the optimal intervention concentration for subsequent experiments. Detection of intracellular Ca²⁺ in pulmonary artery smooth muscle cells (PASMCs): fresh PASMCs were isolated from mouse pulmonary arteries using enzymatic digestion and incubated in Ca²-free HBSS solution. Cells were stained with the Ca²⁺-sensitive fluorescent probe Fluo-4 AM, stimulated with EC₅₀ nicotine, and fluorescence intensity before and after stimulation was recorded to evaluate changes in intracellular Ca²⁺ concentration. Effect of incubation time on nicotine-induced pulmonary arterial tension: pulmonary artery rings were incubated with EC₅₀ nicotine for 0, 6, 12, and 24 h, respectively, followed by NE or PE stimulation. The contractile responses at different incubation times were compared. Effect of nicotine incubation on Kv7 channel function: Pulmonary artery rings were incubated with EC₅₀ nicotine for 24 h, then treated with the Kv7 channel inhibitor XE991 (10^?8-10^?5 mol/L). The induced contractions were recorded to assess Kv7 channel activity. RESULTS: After mild prestimulation with NE or PE, nicotine induced concentration-dependent contractions of mouse pulmonary arteries (P<0.01), with an EC₅₀ of 10^?8 mol/L. Nicotine stimulation at 10^?8 mol/L significantly increased intracellular Ca²⁺ levels in PASMCs (P<0.01). Nicotine (10^?8 mol/L) incubation for 0, 6, 12, and 24 h progressively enhanced NE- and PE-induced contractions, with the 24 h group showing the most pronounced effect (P<0.01), which was selected as the optimal intervention duration. Compared with the control group, nicotine (10^?8 mol/L, 24 h) incubation significantly attenuated XE991-induced pulmonary artery contraction (P<0.01). CONCLUSION: Nicotine increases pulmonary arterial tension in mice, and the underlying mechanism may be related to the inhibition of Kv7 channels.

Key words: nicotine, pulmonary artery, vascular tension, Kv7 channel