Changes in aortic reactivity associated with the loss of equilibrative nucleoside transporter 1 (ENT1) in mice

Abstract

Slc29a1 encodes for equilibrative nucleoside transporter subtype 1 (ENT1), the primary mechanism of adenosine transfer across cell membranes. Previous studies showed that tissues isolated from Slc29a1-null mice are relatively resistant to injury caused by vascular ischemia-reperfusion. To determine if there are similar changes in the microvasculature, and investigate underlying mechanism, we examined aortas isolated from wildtype and Slc29a1-null mice. Aorta macrostructure and gene expression were examined histologically and by qPCR, respectively. Wire myography was used to assess the contractile properties of isolated thoracic aortic rings and their response to adenosine under both normoxic and hypoxic conditions. In vivo haemodynamic parameters were assessed using the tail-cuff method. Slc29a1-null mice had significantly (P<0.05) increased plasma adenosine (2.75-fold) and lower blood pressure (~15% ↓) than wild-type mice. Aortas from Slc29a1-null mice were stiffer with a smaller circumference (11% ↓), and had an enhanced contractile response to KCl and receptor-mediated stimuli. Blockade of ENT1 with nitrobenzylthioinosine significantly enhanced (by ~3.5-fold) the response of aorta from wild-type mice to phenylephrine, but had minimal effect on aortas from Slc29a1-null mice. Adenosine enhanced phenylephrine-mediated constriction in the wild-type tissue under both normoxic (11.7-fold) and hypoxic (3.6-fold) conditions, but had no effect on the Slc29a1-null aortic aorta. In conclusion, aortas from Slc29a1-null mice respond to hypoxic insult in a manner comparable to wild-type tissues that have been pharmacologically preconditioned with adenosine. These data also support a role for ENT1 in the regulation of the protective effects of adenosine on contractile function in elastic conduit arteries such as thoracic aorta.

Discovery of rare variants associated with blood pressure regulation through meta-analysis of 1.3 million individuals

“…The minor allele is associated with both decreased SBP and DBP ( Table 1 ), and the SNV has been shown to affect the function of the encoded protein, equilibrative nucleoside transporter (ENT1) 44 . Best et al 45 showed that loss of function of ENT1 caused an (~2.75-fold) increase in plasma adenosine and (~15%) lower BP in mice. Drugs, including dipyridamole and S-(4-Nitrobenzyl)-6-thioinosine (NBTI, NBMPR), are currently used as ENT1 inhibitors for their anti-cancer, anti-cardio, and neuro-protective properties, and our results provide the genetic evidence to indicate that ENT1 inhibition might lower BP in humans.…”

Deletion of murine slc29a4 modifies vascular responses to adenosine and 5‐hydroxytryptamine in a sexually dimorphic manner

“…We thus hypothesized that, if ENT4 was playing a significant role in the regulation of 5‐HT and/or adenosine levels in the vasculature, then changes in ENT4 activity would have a significant impact on vascular regulation by these agents. In particular, loss/inhibition of ENT4 is anticipated to lead to increases in extracellular adenosine, as has been seen in ENT1‐null mice (Best, Bone, Vilas, Gros, & Hammond, 2018; Warraich et al, 2013), and extracellular 5‐HT, as has been reported for SERT‐null mice (Li, 2006), and thereby increase their vascular activities via enhanced stimulation of their respective extracellular receptors. We tested this hypothesis by examining the vascular reactivity of the slc29a4 ‐null (ENT4‐KO) mouse.…”