Antioxidant/Oxidant Status and Cardiac Function in Bradykinin B1- and B2-Receptor Null Mice

Abstract

Kinin-vasoactive peptides activate two G-protein-coupled receptors (R), B(1)R (inducible) and B(2)R (constitutive). Their complex role in cardiovascular diseases could be related to differential actions on oxidative stress. This study investigated impacts of B(1)R or B(2)R gene deletion in mice on the cardiac function and plasma antioxidant and oxidant status. Echocardiography-Doppler was performed in B(1)R (B(1)R(-/-)) and B(2)R (B(2)R(-/-)) deficient and wild type (WT) adult male mice. No functional alteration was observed in B(2)R(-/-) hearts. B(1)R(-/-) mice had significantly lowered fractional shortening and increased isovolumetric contraction time. The diastolic E and A waves velocity ratio was similar in all mice groups. Thus B(1)R(-/-) mice provide a model of moderate systolic dysfunction, whereas B(2)R(-/-) mice displayed a normal cardiac phenotype. Plasma antioxidant capacity (ORAC) was significantly decreased in both B(1)R(-/-) and B(2)R(-/-) mice whereas the vitamin C levels were decreased in B(2)R(-/-) mice only. Plasma ascorbyl free radical was significantly higher in B(1)R(-/-) compared to WT and B(2)R(-/-) mice. Therefore, the oxidative stress index, ascorbyl free radical to vitamin C ratio, was increased in both B(1)R(-/-) and B(2)R(-/-) mice. Hence, B(1)R and B(2)R deficiency are associated with increased oxidative stress, but there is a differential imbalance between free radical production and antioxidant defense. The interrelationship between the differential B(1)R and B(2)R roles in oxidative stress and cardiovascular diseases remain to be investigated.