Monoamine oxidase in end-stage heart failure associated with dilated and ischemic cardiomyopaties: a comparison between left and right ventricles.

Dilated (DCM) and ischemic (IHD) cardiomyopathies are the most common causes of heart failure, which is characterized by a progressive remodeling and dysfunction. Reactive species (ROS) contributed to each of these abnormalities. Among the multiple source of ROS, the monoamine oxidases (MAOs), that catalyze oxidative deamination of catecholamines and biogenic amines. generating hydrogen peroxide (H2O2) and aldehyde, may play an important role in the maladaptive evolution towards failure. At homeostatic conditions, the amount of aldehydes and H2O2 are regulated by aldehyde dehydrogenase (ALDH) and catalase (CAT) activities, respectively, both rescuing enzymes of the heart. Possibly, different levels of such enzymes might be present in DMC and IHD failing hearts and they may be proposed as discriminating markers of the two cardiomyopathies. Therefore, we investigated the enzymatic activities of MAO-A and MAO-B, of cytosolic and mitochondrial ALDH and of CAT and the amount of carbonylated proteins and malondialdehyde (MDA), indirect markers of oxidative stress, in right (RV) and left ventricles (LV) from end-stage failing hearts secondary to IHD and DMC.Both MAO isoforms, with a prevalence of MAO-A, were observed in failing hearts. Nevertheless, we reported a significant increase in total MAO activity in IHD compared to DCM. In DMC specimens MAO-A was preferentially active in LV compared to RV, in concomitance with a higher level of CAT activity and a lower level of MDA amount, suggesting a role for CAT in scavenging MAO-derived H2O2. Our results indicate that the evaluation of MAO activity, in particular MAO-A, might help to discriminate between IHD and DCM associated with heart failure.