The 1976C>T polymorphism in the adenosine A2A receptor gene does not affect the vasodilator response to adenosine in humans in vivo

“No-Reflow” Phenomenon: A Contemporary Review

Primary percutaneous angioplasty (pPCI), represents the reperfusion strategy of choice for patients with STEMI according to current international guidelines of the European Society of Cardiology. Coronary no-reflow is characterized by angiographic evidence of slow or no anterograde epicardial flow, resulting in inadequate myocardial perfusion in the absence of evidence of mechanical vessel obstruction. No reflow (NR) is related to a functional and structural alteration of the coronary microcirculation and we can list four main pathophysiological mechanisms: distal atherothrombotic embolization, ischemic damage, reperfusion injury, and individual susceptibility to microvascular damage. This review will provide a contemporary overview of the pathogenesis, diagnosis, and treatment of NR.

Impact of the Polymorphism rs5751876 of the Purinergic Receptor ADORA2A on Periprocedural Myocardial Infarction in Patients Undergoing Percutaneous Coronary Intervention

Aim: Periprocedural myocardial infarction (PMI), a severe complication of Percutaneous Coronary Intervention (PCI) procedures, has a negative prognostic effect, both at short and long-term follow-up. So far, adenosine's role in preventing PMI has shown contrasting results. A genetic variant of ADORA2A receptor, 1976 C > T, has been suggested as a potential determinant of the interindividual response to adenosine, thus conditioning its potential benefits on PMI. In our study, we investigated whether the ADORA2A 1976 C > T polymorphism is associated with PMI occurrence in patients undergoing coronary stenting.

Methods: The study included consecutive patients undergoing PCI at the Azienda Ospedaliera-Universitaria “Maggiore della Carità,” Novara, Italy, between January 2010 and January 2016. Their genetic status was assessed using polymerase chain reaction (PCR) and restriction-fragment-length-polymorphism technique. Myonecrosis biomarkers were measured at intervals from 6 to 48 hours. PMI was defined as CKMB increased 3 times over the Upper Limit of Normal (ULN), or 50% of pre-PCI value; periprocedural myonecrosis was defined as troponin I increased 3 times over the ULN or by 50% of the baseline value.

Results: We included 1,104 patients undergoing PCI, 863 (78.2%) of whom carried the ADORA2A T-allele. No difference was found for the main demographic, clinical features, or biochemistry parameters. However, C-carriers had lower statin therapy use (p = 0.008) and lower HDL-cholesterol levels (p = 0.01). Homozygous C/C patients had more frequent multivessel disease (p = 0.03), longer lesions (p = 0.01) and Type C lesions (p = 0.01), thus requiring more complex procedures. After correction for baseline confounding factors at multivariate analysis, there was no difference in myocardial necrosis according to the ADORA2A genotype (p = 0.40). In contrast, PMI tended to increase in the homozygous C/C population (p = 0.06), but this trend was attenuated at multivariate analysis after correction for baseline confounding factors (C/C: OR[95%CI]= 1.52 [0.88–2.6], p = 0.14).

Conclusions: Our study showed that the polymorphism rs5751876 of the ADORA2A receptor is associated with a higher prevalence of complex coronary lesions and multivessel disease. However, it does not significantly influence the occurrence of periprocedural MI or myonecrosis.

Relationship between adenosine A2a receptor polymorphism rs5751876 and fractional flow reserve during percutaneous coronary intervention

Fractional flow reserve (FFR) assessed during adenosine-induced maximal hyperemia has emerged as a useful tool for the guidance of percutaneous coronary interventions (PCI). However, interindividual variability in the response to adenosine has been claimed as a major limitation to the use of adenosine for the measurement of FFR, carrying the risk of underestimating the severity of coronary stenoses, with potential negative prognostic consequences. Genetic variants of the adenosine receptor A2a (ADORA2A gene), located in the coronary circulation, have been involved in the modulation of the hyperemic response to adenosine. However, no study has so far evaluated the impact of the single nucleotide polymorphism rs5751876 of ADORA2A on the measurement of FFR in patients undergoing percutaneous coronary intervention that was, therefore, the aim of our study. We included patients undergoing coronary angiography and FFR assessment for intermediate (40-70%) coronary lesions. FFR measurement was performed by pressure-recording guidewire (Prime Wire, Volcano), after induction of hyperemia with intracoronary boli of adenosine (from 60 to 1440 μg, with dose doubling at each step). Restriction fragment length polymorphism (RFLP) analysis was performed to assess the presence of rs5751876 C>T polymorphism of ADORA2a receptor. We included 204 patients undergoing FFR measurement of 231 coronary lesions. A total of 134 patients carried the polymorphism (T allele), of whom 41 (30.6%) in homozygosis (T/T).Main clinical and angiographic features did not differ according to ADORA2A genotype. The rs5751876 C>T polymorphism did not affect mean FFR values (p = 0.91), the percentage of positive FFR (p = 0.54) and the duration of maximal hyperemia. However, the time to recovery to baseline FFR values was more prolonged among the T-allele carriers as compared to wild-type patients (p = 0.04). Based on these results, in patients with intermediate coronary stenoses undergoing FFR assessment with adenosine, the polymorphism rs5751876 of ADORA2A does not affect the peak hyperemic response to adenosine and the results of FFR. However, a more prolonged effect of adenosine was observed in T-carriers.

Adenosine A2A receptor gene polymorphisms (ADORA2A) are associated with maximal concentric contraction pain

Objectives

To test associations of adenosine A2A receptor gene (ADORA2A) polymorphisms with maximal concentric contraction pain, caffeine-induced perceptual changes, and responses to mild eccentric injury.

Design

Targeted candidate gene association study.

Methods

ADORA2A (rs5751876) was genotyped in 26 adults. Pain of a maximal elbow flexor contraction was assessed. Participants performed 18 eccentric actions of the elbow flexors. Arm volume was measured before and 24- and 48-h post-injury. At 24- and 48-h post-injury, caffeine or placebo capsules were given using a randomized cross-over design and effort and pain were assessed.

Results

Maximal concentric contraction pain was higher for the CC compared to the CT/TT group (effect size d = 0.89) and lower for the TT compared to the CT/CC group (d = 0.62). There were moderate sized differences between CC and TT/CT groups for post-injury exertion and arm volume 24-h post injury.

Conclusions

ADORA2A polymorphisms are moderately associated with muscle pain during maximal contractions in uninjured muscle.

Adenosine 2A receptor modulates inflammation and phenotype in experimental abdominal aortic aneurysms

Activation of the adenosine 2A receptor (A2AR) reduces inflammation in models of acute injury but contribution in development of chronic abdominal aortic aneurysms (AAAs) is unknown. Elastase perfusion to induce AAA formation in A2AR-knockout (A2ARKO) and C57BL6/J wild-type (WT) mice resulted in nearly 100% larger aneurysms in A2ARKO compared to WT at d 14 (P<0.05), with evidence of greater elastin fragmentation, more immune cell infiltration, and increased matrix metallatoproteinase (MMP) 9 expression (P<0.05). Separately, exogenous A2AR antagonism in elastase-perfused WT mice also resulted in larger aneurysms (P<0.05), while A2AR agonism limited aortic dilatation (P<0.05). Activated Thy-1.2(+) T lymphocytes from WT mice treated in vitro with A2AR antagonist increased cytokine production, and treatment with A2AR agonist decreased cytokine production (P<0.05 for all). Primary activated CD4(+) T lymphocytes from A2ARKO mice exhibited greater chemotaxis (P<0.05). A2AR antagonist increased chemotaxis of activated CD4(+) cells from WT mice in vitro, and A2AR agonist reduced this effect (P<0.05). A2AR activation attenuates AAA formation partly by inhibiting immune cell recruitment and reducing elastin fragmentation. These findings support augmenting A2AR signaling as a putative target for limiting aneurysm formation.