Comparison between Monoamine Oxidase A and B: role and effect in human diseases: A review

MAOs are isoenzymes that occur in two isoforms Monoamine oxidases A and B. They are flavoproteins found in mitochondria and their role is to catalyze the oxidative deamination of monoamine neurotransmitters to their corresponding aldehydes. Both MAOs play a major role in the human body as they contribute to many illnesses. MAO plays an essential role in both peripheral; and central nervous system through affecting the levels of MAO neurotransmitters. MAO-A is generally concentrated in dopaminergic and norepinephrinergic neurons. Contrary to MAO-B, which is predominantly concentrated in serotoninergic neurons. By-product of MAOs which are aldehyde, ammonia, and H2O2 (which is considered reactive oxygen species) that is toxic at high concentration or it may lead to the generation of free Radicals. Free radicals considered as a starting signal in the generation of cancers. Also, MAO inhibition showed to decrease pressure overload and heart failure. This action is mainly related to the prevention of oxidative stress mainly (H2O2) apoptosis in cardiac muscle and improved bioavailability of Norepinephrine. MAO-A plays a totally different role from MAO—B in renal carcinoma. Ranging from Alzheimer disease, depression to cardiac myopathy, diabetes, kidney diseases, and cancers, MAO-A participates differently from MAO-B in these diseases. Therefore it is necessary to study their separate effect in human diseases and the consequences of their inhibition. In this review, we compare between MAO-A and MAO-B effect from many aspects that includes heart failure, renal carcinoma, breast cancer, esophageal cancer, prostate cancer, bladder cancer, glioma and diabetes. And finally, the role of MAO inhibitors and their effects also have been discussed.