Over-expression of a cardiac-specific human dopamine D5 receptor mutation in mice causes a dilated cardiomyopathy through ROS over-generation by NADPH oxidase activation and Nrf2 degradation

Dilated cardiomyopathy (DCM) is a severe disorder caused by medications or genetic mutations. D(5) dopamine receptor (D5R) gene knockout (D5(-/-)) mice have cardiac hypertrophy and high blood pressure. To investigate the role and mechanism by which the D5R regulates cardiac function, we generated cardiac-specific human D5R F173L(hD5(F173L)-TG) and cardiac-specific human D5R wild-type (hD5(WT)-TG) transgenic mice, and H9c2 cells stably expressing hD5(F173L) and hD5(WT). We found that cardiac-specific hD5(F173L)-TG mice, relative to hD5(WT)-TG mice, presented with DCM and increased cardiac expression of cardiac injury markers, NADPH oxidase activity, Nrf2 degradation, and activated ERK1/2/JNK pathway. H9c2-hD5(F173L) cells also had an increase in NADPH oxidase activity, Nrf2 degradation, and phospho-JNK (p-JNK) expression. A Nrf2 inhibitor also increased p-JNK expression in H9c2-hD5(F173L) cells but not in H9c2-hD5(WT) cells. We suggest that the D5R may play an important role in the preservation of normal heart function by inhibiting the production of reactive oxygen species, via inhibition of NADPH oxidase, Nrf2 degradation, and ERK1/2/JNK pathways.