Nicotine Induced Pulmonary Artery Myogenic Abnormalities in C57BL / 6J Mice by Up-Regulating Cx43 Expression: An Experimental Study

Objective To investigate the mechanism of action of connexin 43 (Cx43) in nicotine-induced pulmonary artery myogenic abnormalities in C57BL/6J mice.

Methods The tested C57BL/6J mice were randomly divided into blank control group (n = 12, normal drinking and food intake), 0.003 mg/kg nicotine group n = 12, intraperitoneal injection of nicotine at a dose of 0.003 mg/(kg ·d), 0.03 mg/kg nicotine group n = 12, intraperitoneal injection of nicotine at a dose of 0.03 mg/(kg ·d), and 0.3 mg/kg nicotine group (n = 12, intraperitoneal injection of nicotine at a dose of 0.3 mg/kg ·d), with an intervention time of 24 weeks. Microvascular tension test was used to determine the contractile response of isolated mouse pulmonary arteries to different concentrations of KCl (20, 28, 39, 55, 77 and 108 mmol/L) and U46619 (3×10^-8, 10^-7, 3×10^-7, 10^-6 and 3×10^-6 mol/L), and the vasodilation to different concentrations of SNP (10^-8, 3×10^-8, 10^-7, 3×10^-7 and 10^-6 mol/L) and pinacidil (10^-8, 3×10^-8, 10^-7, 3×10^-7 and 10^-6 mol/L) in each group. Hematoxylin-eosin staining was used to observe the pulmonary artery remodeling of mice in each group. Immunofluorescence assay was used to measure the expression level of Cx43 in the pulmonary arteries of mice in each group. Reverse transcription polymerase chain reaction (RT-PCR) and Western blot were used to measure the mRNA and protein expression levels of Cx43 in the pulmonary arteries of mice.

Results The results of in vitro vascular tension measurement showed that compared with the blank control group, after 24 weeks of intervention, the isolated pulmonary arteries of C57BL/6J mice in the 0.003, 0.03, and 0.3 mg/kg nicotine groups showed different degrees of enhancement in the maximal contractile response to different concentrations of KCl and U46619 (P < 0.05), as wella different degrees of weakening in the maximal vasodilation to different concentrations of SNP and pinacidil (P < 0.05).In addition, compared with the blank control group, the 0.003, 0.03 and 0.3 mg/kg nicotine groups had concentration-dependent increases in the degree of pulmonary artery remodeling, significantly higher Cx43 protein expression according to the immunofluorescence assay results, and significantly higher mRNA and protein expression of Cx43 according to the RT-PCR and Western blot results (P < 0.05).

Conclusion Nicotine can cause pulmonary artery myogenic abnormalities in C57BL/6J mice, and its mechanism may be related to the up-regulation of Cx43 expression.