Connexin 43 Plays a Role in Pulmonary Vascular Reactivity in Mice

Abstract

Pulmonary arterial hypertension (PAH) is a chronic condition characterized by vascular remodeling and increased vaso-reactivity. PAH is more common in females than in males (~3:1). Connexin (Cx)43 has been shown to be involved in cellular communication within the pulmonary vasculature. Therefore, we investigated the role of Cx43 in pulmonary vascular reactivity using Cx43 heterozygous (Cx43+/−) mice and 37,43Gap27, which is a pharmacological inhibitor of Cx37 and Cx43. Contraction and relaxation responses were studied in intra-lobar pulmonary arteries (IPAs) derived from normoxic mice and hypoxic mice using wire myography. IPAs from male Cx43+/− mice displayed a small but significant increase in the contractile response to endothelin-1 (but not 5-hydroxytryptamine) under both normoxic and hypoxic conditions. There was no difference in the contractile response to endothelin-1 (ET-1) or 5-hydroxytryptamine (5-HT) in IPAs derived from female Cx43+/−mice compared to wildtype mice. Relaxation responses to methacholine (MCh) were attenuated in IPAs from male and female Cx43+/− mice or by pre-incubation of IPAs with 37,43Gap27. Nω-Nitro-L-arginine methyl ester (l-NAME) fully inhibited MCh-induced relaxation. In conclusion, Cx43 is involved in nitric oxide (NO)-induced pulmonary vascular relaxation and plays a gender-specific and agonist-specific role in pulmonary vascular contractility. Therefore, reduced Cx43 signaling may contribute to pulmonary vascular dysfunction.

Connexin-43 is a promising target for pulmonary hypertension due to hypoxaemic lung disease

“…PA vasoreactivity to ET-1 was increased in Cx43 +/− mice compared to Cx43 +/+ mice, under both N and CH conditions (figure 6a), whereas PA vasoreactivity to 5-HT was identical in all groups of mice (figure 6b). Such results are consistent with those observed by HTET et al [11] in Cx43 +/− C57BL6 mice. Such a role for Cx43 on PA vasoreactivity to ET-1 may explain why, despite PA remodelling and inflammation being absent, right-ventricular systolic pressure and Fulton index remained high in Cx43 +/− mice with CH-PH compared to Cx43 +/+ mice with CH-PH.…”

“…Collectively, these results indicate that Cx43 plays an important role in PA vasoreactivity, under both physiological and pathophysiological conditions (N and CH-PH, respectively), as already shown in rat and C57BL6 mouse pulmonary circulation [7,8,11].…”

“…For instance, we observed similar Cx43 expression under N and CH conditions and similar Cx37 and Cx40 mRNA levels in Cx43 +/+ versus Cx43 +/− mice independent of the conditions tested in both PAs and hearts (supplementary figures S6 and S11), indicating that Cx43 knock-down was not compensated by variations in expression of Cx with a homology close to Cx43 and expressed in PAs of mice. However, HTET et al [11] demonstrated 1) a decrease in Cx43 mRNA expression in PAs from both Cx43 +/+ and Cx43 +/− mice with CH-PH compared to N mice; and 2) a decrease in Cx37 and Cx40 mRNA expression in N Cx43 +/− mice compared to N Cx43 +/+ mice. It should be noted however that they used a C57BL6 mouse strain whereas we used a CD1 mouse strain.…”

“…Gap junctions are clusters of intercellular channels composed of various structural proteins (connexins (Cx)) also essential for spreading cellular signalling [7,8]. Our group and others have previously shown that Cx37, Cx40 and Cx43 are expressed in rat, mouse and human PAs and such expression is modified in experimental models of PH as well as in patients with IPAH; however, disparities have been observed between the different studies [8][9][10][11][12][13][14]. Interestingly, Cx43 is known to be involved in tone regulation, cell proliferation and inflammatory infiltration in vessels, which are the main hallmarks of PH [7,8,10,[15][16][17].…”

Connexin 43 plays a role in proliferation and migration of pulmonary arterial fibroblasts in response to hypoxia

“…10 Mice deficient in Cx43 show reduced pulmonary vascular relaxation, and pharmacological inhibition of Cx43 also reduces pulmonary vascular relaxation. 11 In addition, Cx43 can mediate 5-HT signalling between rat PAECs and rat PASMCs (rPASMCs). 12 Transfer of 5-HT between these cell types was inhibited by the non-specific gap junction blocker, carbenoxolone or by siRNA knockdown of Cx43, but not by the serotonin transporter inhibitor fluoxetine.…”