A2B adenosine receptor activity is reduced in neutrophils from patients with systemic sclerosis

We conducted the present study to investigate protein expression and functioning of A(2A) and A(2B) adenosine receptors (ARs) in neutrophils of patients affected by systemic sclerosis (SSc). The presence of A(2A) and A(2B) ARs was assessed by immunoblotting using specific antibodies. Equilibrium A(2A) and A(2B) ARs binding parameters were evaluated by radioligand binding assay. Functional studies were conducted to investigate coupling of the A(2B) AR to the adenylyl cyclase pathway. This is the first report of the use of Western blot analysis to confirm the presence of A(2A) and A(2B) ARs in human neutrophils. No significant changes in A(2A) AR binding parameters or expression levels were detected between SSc patients and healthy control individuals. A significant decrease (65%) in the maximum density of A(2B) AR binding sites occurred in SSc neutrophils, whereas no changes in the affinity constant values were found. Moreover, a decrease in A(2B) AR mediated adenylyl cyclase activity was observed in patients with SSc. Our findings demonstrate the occurrence of selective alterations in A2B AR density and signalling in SSc.