Enzymatic Study of Methionine Sulfoxide Reductase A, some other Enzymes Associated with Neural Pathways and Oxidative Stress in Down Syndrome Patients in Mosul City

Down syndrome (DS) is a genetic disorder that arises when a third chromosome 21 is found in either some or all cells of the body contributing to complex conditions involving intellectual disability and learning inability. Oxidative stress (OS) has been correlated, which plays an important role in rapid aging, how antioxidants utilize in treating cognitive defect, oxidative damage of biomolecules in DS, also disruption of some neurotransmitter levels in the neurons has been observed. This study was conducted to measure in serum of (50) DS individuals against (25) of control group, Methionine Sulfoxide Reductase (MsrA), Senescence Marker Protein-30(SMP-30), Thioredoxin (TRX), glutamate decarboxylase 67 (GAD67), Serotonin N-acetyltransferase (AANAT), Catechol O-Methyl Transferase (COMT), Methionine S-Adenosyl Transferase (MAT), monoamine oxidase A (MAOA) in addition to peroxynitrite (ONOO-) and malondialdehyde (MDA). Decreased levels of the activity of MsrA, SMP-30 was observed while GAD67, AANAT, TRX and peroxynitrite show significantly higher levels in DS comparing with control group. There is no alteration COMT, MAT, MAOA and MDA. Significant positive correlation between MsrA, peroxynitrite and MAT, without relation with GAD67, AANAT in which (ONOO-) may trigger MsrA that will provide the substrate for MAT. Therefor the higher oxidative stress, represented by lower antioxidants activities related to senescence, may indicate acceleration of aging in patients. Additionally, elevation of TRX may indicate oxidative damage to macromolecules. -Aminobutyric acid (GABA) neuron and N-acetyl-serotonin may be affected by the higher concentration of GAD67 and AANAT, respectively.