Expression of dysfunctional connexin40 in vascular endothelium enhances myogenic constriction and reduces artery distensibility

Abstract

Mutant forms of connexin40 (Cx40) are known to exist in the human population and increase the risk of cardiovascular diseases such as atrial fibrillation. We hypothesised that the existence of dysfunctional Cx40 proteins amongst the native Cx40 population in the vascular endothelium may also impair arterial function. To this end, we created a new transgenic mouse strain expressing a mutant Cx40 (Cx40T202S) specifically in the endothelium; leaving native Cx40 expression intact. The ability of this mutation to impair gap junction function was tested in Xenopus Oocytes and mouse coronary endothelial cells while its effect on arterial function was tested in isolated small mesenteric arteries using pressure myography. Cell coupling studies found that Cx40T202S could form electrically but not chemically patent gap junctions. Analysis of the myogenic response of arteries from Cx40T202S mice revealed increased sensitivity to intraluminal pressure compared to wild type (P<0.05). This effect coincided with a loss of basally activated endothelium dependent hyperpolarisation (EDH) while nitric oxide remained intact. Examination of passive arterial properties showed Cx40T202S arteries were significantly stiffer than wild type (P<0.05). We conclude that the presence of a mutant Cx40 in the vascular endothelium is sufficient to prevent basal EDH, and increase both myogenic sensitivity and arterial stiffness.