Caffeine-associated reduction in patent ductus arteriosus is mediated in part by adenosine receptor antagonism

Persistent patency of the ductus arteriosus (PDA) is less frequent among infants treated with caffeine for apnea of prematurity. Caffeine acts to inhibit A₁, A₂, and A₃ adenosine receptors (ARs). Adenosine is typically vasodilatory, and serum adenosine levels are elevated in preterm newborns, suggesting a potential mechanism for caffeine-associated reduction in PDA. We hypothesized that caffeine has an indirect vasoconstrictive effect on the ductus by antagonizing specific ARs. The expression of AR subtypes in the mouse ductus was analyzed by RT-PCR on days 15, 17, 19 (full term) of gestation, and postnatal day 1. Pressure myography was used to examine responses of the isolated ductus to adenosine, caffeine (citrate or base), or preincubation with either caffeine or adenosine. AR immuno-localization and adenosine-mediated cyclic AMP (cAMP) generation were evaluated in human ductus smooth muscle cells (SMCs). A₁AR, A_2AAR, A_2BAR, and A₃AR were present and developmentally regulated in the mouse ductus. Adenosine promoted ductus dilation under fetal and newborn O₂ conditions. Caffeine had little or no effect on ductus tone with concentrations spanning the therapeutic range and failed to augment O₂-induced or cyclooxygenase inhibitor-stimulated ductus constriction. However, pretreatment with caffeine or selective A₁AR and A_2AAR antagonists prevented adenosine-induced ductus dilation. Caffeine also blocked adenosine-stimulated cAMP release in human ductus SMCs. In conclusion, caffeine did not induce direct ductus constriction ex vivo. However, caffeine exposure prevented adenosine-induced ductus relaxation, suggesting the inhibition of an endogenous vasodilator as a mechanism for the reduction in PDA.NEW & NOTEWORTHY Caffeine is a respiratory stimulant and one of the most commonly prescribed drugs in the NICU. Primarily used to reduce apnea of prematurity, additional therapeutic benefits have been noted, including decreasing the incidence of patent ductus arteriosus. Using mouse and human ductus models, we have identified a mechanism by which caffeine can promote ductus constriction by inhibiting adenosine-mediated vasodilation.