These findings indicate that patients with NMS present different purinergic profiles and that responses to HUT and ATP are correlated with these profiles.
The function of A2AR of patients with VVS was preserved since their stimulation by Adonis led to cAMP production with an EC50 comparable with those in controls. However, their affinity was lower than those of controls. Our results suggest that A2AR are implicated in the physiopathology of VVS.
In patients with unexplained syncope, a significant association between high incidence of syncopal episodes, positive HUT, and the presence of the CC variant in the adenosine A(2A) receptor gene was elicited.
Some ligand–receptor couples involve spare receptors, which are apparent when a maximal response is achieved with only a small fraction of the receptor population occupied. This situation favours cross-reactions with low-affinity ligands, which may be detrimental for cell signaling. In the case of the adenosine A2A receptors (A2AR), which have an immunosuppressive effect on lymphocytes through cAMP production, the presence of spare A2AR remains to be established. We examined the situation using patients over-expressing lymphocyte A2AR and an agonist-like mAb to A2AR. We found that maximal mAb binding and functional response varied among the patients whereas the dissociation constant and half-maximal effective concentration had similar mean values (0.19 and 0.18 μM, respectively). Lymphocyte A2AR expression was correlated to plasma adenosine level and A2AR occupation but not to A2AR response. These results are consistent with a lack of a reserve of functional A2AR on human lymphocytes as a general rule and suggest that the amount and functional state of the expressed A2AR determine the maximal level of the lymphocyte response to adenosine.
The synthesis of new C-6 1,2,3-triazole adenosine derivatives via microwave assisted 1,3-dipolar cycloaddition as key step is described. The binding on membranes of cells that over express A(1) adenosine receptors (A(1)AR) was also evaluated. Among them, four compounds increased cAMP production, in a dose-dependent manner acting as antagonists of the A(1)AR, while two compounds act as agonists.
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