Plasma A2AR Measurement Can Help Physicians Identify Patients Suspected of Coronary Chronic Syndrome: A Pilot Study.

The evaluation of suspected coronary artery disease (CAD) in the medical community is challenging. Patients with suspected coronary chronic syndrome (CCS) are referred by the medical community to be assessed by specialists for the performance of noninvasive tests that have high rates of false positives and false negatives. While troponins are the gold standard for evaluate myocardial injuries, there is no biomarker to assess myocardial ischemia in patient populations with negative electrocardiography or without an increase in troponin level. A2A adenosine receptors control the coronary blood flow through its vasodilating properties. It has been shown that patients with CAD have a lower A2AR expression on peripheral blood mononuclear cells, suggesting a link between A2AR production and the severity of CAD. Herein, we present a new and innovative method of inhibition ELISA for A2AR in the plasma of patients who permit the evaluation of the amount of soluble A2AR. For this analysis, the total study sample was 54, including 31 patients with CAD with stenosis > 50% and a significant fractional flow reserve (FFR < 0.8) (Group 1) and 23 patients with normal or non-obstructive coronary arteries (stenosis < 50% and nonsignificant FFR > 0.8) (Group 2). The % inhibition (which is linked to the presence of soluble receptors) with the plasma of patients with FFR < 0.8 was significantly lower than that of patients with FFR > 0.8 (median [range]: 68% [20.7−86.9] vs. 83% [67−88.4]; p < 0.001). The ROC curve indicated a good sensitivity/specificity ratio with a cut off of 72.5% and an area under the curve of 0.87. In conclusion, a rapid ELISA to assess soluble A2AR in the plasma shows promise to screen patients suspected of having CAD.

Homocysteine concentration and adenosine A2A receptor production by peripheral blood mononuclear cells in coronary artery disease patients.

Hyperhomocysteinemia is associated with coronary artery disease (CAD). The mechanistic aspects of this relationship are unclear. In CAD patients, homocysteine (HCy) concentration correlates with plasma level of adenosine that controls the coronary circulation via the activation of adenosine A2A receptors (A2A R). We addressed in CAD patients the relationship between HCy and A2A R production, and in cellulo the effect of HCy on A2A R function. 46 patients with CAD and 20 control healthy subjects were included. We evaluated A2A R production by peripheral blood mononuclear cells using Western blotting. We studied in cellulo (CEM human T cells) the effect of HCy on A2A R production as well as on basal and stimulated cAMP production following A2A R activation by an agonist-like monoclonal antibody. HCy concentration was higher in CAD patients vs controls (median, range: 16.6 [7-45] vs 8 [5-12] µM, P < 0.001). A2A R production was lower in patients vs controls (1.1[0.62-1.6] vs 1.53[0.7-1.9] arbitrary units, P < 0.001). We observed a negative correlation between HCy concentration and A2A R production (r = -0.43; P < 0.0001), with decreased A2A R production above 25 µM HCy. In cellulo, HCy inhibited A2A R production, as well as basal and stimulated cAMP production. In conclusion, HCy is negatively associated with A2A R production in CAD patients, as well as with A2A R and cAMP production in cellulo. The decrease in A2A R production and function, which is known to hamper coronary blood flow and promote inflammation, may support CAD pathogenesis.

Altered muscle membrane potential and redox status differentiates two subgroups of patients with chronic fatigue syndrome.

BACKGROUND: In myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), altered membrane excitability often occurs in exercising muscles demonstrating muscle dysfunction regardless of any psychiatric disorder. Increased oxidative stress is also present in many ME/CFS patients and could affect the membrane excitability of resting muscles. METHODS: Seventy-two patients were examined at rest, during an incremental cycling exercise and during a 10-min post-exercise recovery period. All patients had at least four criteria leading to a diagnosis of ME/CFS. To explore muscle membrane excitability, M-waves were recorded during exercise (rectus femoris (RF) muscle) and at rest (flexor digitorum longus (FDL) muscle). Two plasma markers of oxidative stress (thiobarbituric acid reactive substance (TBARS) and oxidation-reduction potential (ORP)) were measured. Plasma potassium (K+) concentration was also measured at rest and at the end of exercise to explore K+ outflow. RESULTS: Thirty-nine patients had marked M-wave alterations in both the RF and FDL muscles during and after exercise while the resting values of plasma TBARS and ORP were increased and exercise-induced K+ outflow was decreased. In contrast, 33 other patients with a diagnosis of ME/CFS had no M-wave alterations and had lower baseline levels of TBARS and ORP. M-wave changes were inversely proportional to TBARS and ORP levels. CONCLUSIONS: Resting muscles of ME/CFS patients have altered muscle membrane excitability. However, our data reveal heterogeneity in some major biomarkers in ME/CFS patients. Measurement of ORP may help to improve the diagnosis of ME/CFS. Trial registration Ethics Committee "Ouest II" of Angers (May 17, 2019) RCB ID: number 2019-A00611-56.

Pharmacological profile of adenosine A2A receptors in patients with lower extremity peripheral artery disease and associated coronary artery disease: A pilot study.

BACKGROUND: Altered blood flow occurs in patients with low extremity peripheral artery disease (LE-PAD). LE-PAD is mostly associated with coronary artery disease (CAD). Adenosine is an endogenous nucleoside that affects both coronary and limb artery blood flow, mostly via the adenosine A2A receptor (A2AR). We evaluated A2AR expression and function in peripheral blood mononuclear cells (PBMCs) and the femoral artery tissues of patients with LE-PAD. METHODS: Artery tissues and PBMCs were sampled in 24 patients with intermittent claudication, and compared with PBMCs in 24 healthy subjects. Expression and function of A2AR was studied, using a A2AR monoclonal antibody with agonist properties, allowing determination of A2AR affinity (KD) and cAMP production (ie.EC50). RESULTS: A2AR expression on PBMCs was lower in patients than controls (median1.3 [range 0.6-1.8] vs 1.75 [1.45-2.1] arbitrary units; P < 0.01), and correlated with A2AR expression in artery tissues (Pearson's r = 0.71; P < 0.01). Basal and maximally stimulated cAMP production of PBMCs was lower in patients vs controls: 172 [90-310] vs 244 [110-380] pg/106 cells (P < 0.05) and 375 [160-659] vs 670 [410-980] pg/106 cells (P < 0.05), respectively. A high KD/EC50 ratio, characteristic of spare receptors, was observed in CAD with inducible-myocardial-ischemia. CONCLUSION: A2AR expression in the arteries of patients, correlated with their expression in PBMCs. A2AR expression was lower in patients than in controls. A single blood sample (for measurement of A2AR expression on PBMCs) may help to screen patients with LE-PAD, whereas the presence of spare receptors may help with risk stratification before vascular surgery in CAD patients with high risk of myocardial ischemia.