|Ph.D Student||Ben-Ari Shunit|
|Subject||Novel Multi-Functional Neuroprotective and Neurorestorative|
Iron Chelator-Monoamine Oxidase Inhibitor Drugs
for Neurodegenerative Diseases
|Department||Department of Medicine||Supervisor||Professor Emeritus Moussa Youdim|
|Full Thesis text|
Iron-dependent oxidative stress, elevated levels of iron and of monoamine oxidase (MAO)-B activity, and depletion of antioxidants in the brain may be major pathogenic factors in Parkinson’s disease (PD) and related neurodegenerative diseases. Therefore, we have developed several novel multi-functional brain permeable iron chelators-MAO inhibitors, for prevention and treatment of PD. These potential drugs were synthesized as hybrid molecules containing brain permeable VK28-derived iron-chelator moiety, and N-propargylamine-derived MAO-inhibitor moiety. Based on previous in-vitro screening, in the present study, selected drugs were further investigated. Initially, we characterized several molecules ex-vivo, to select the drug most potent both as iron chelator and MAO inhibitor. The multi-functional molecule M30, displaying IC50 values of 9.22±0.22μM for iron-induced lipid peroxidation, and 0.037±0.02μM and 0.057±0.01μM for MAO-A and B, respectively, was selected for further investigation. We have shown that M30 (1,2.5, or 5mg/kg, i.p.) is a brain permeable, irreversible MAO-A/B inhibitor and that this drug potently inhibits MAO-A/B in the brain, but not in the liver or small intestine, an effect shown following a single and chronic drug administration, intraperitoneously or orally. In the rat model, M30 was shown to induce only limited tyramine-induced blood pressure potentiation, increasing pressor-response by 2-fold, vs. a 12.5-fold increase potentiated by MAO-A/B inhibitor, tranylcypromine, suggesting that M30 would not lead to the "cheese effect", characterized by life threatening hypertension, common to non-selective MAO-A/B inhibitors. M30 was examined for its ability to prevent neurotoxicty in the N-methy-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinsonism. In this paradigm, M30 was shown to completely protect against MPTP-induced loss of striatal dopamine (DA) and tyrosine-hydroxylase (TH) activity, and led to decreased DA metabolism (0.072±0.003), as compared to control and MPTP-treated mice (0.131±0.007). Since at diagnosis most PD patients lose 50-75% of the dopaminergic neurons in their substantia nigra pars compacta (SNpc), we examined the effect of M30 on a pre-existing lesion induced by MPTP. In this neurorescue paradigm, M30 orally administered to mice for 14 days (2.5 mg/kg/day) following MPTP was shown to significantly elevate striatal DA levels, reduce its metabolism, and elevate TH protein levels (from 25.86±5.10% to 68.35±10.67% of control) and activity (from 7.52±0.98 to 16.33±2.92 pmol/mg protein/min). Importantly, M30 elevated MPTP-reduced TH (from 62.8±4.1% to 84.2±5.9% of control) and transferrin receptor (from 31.3±2.6% to 80.4±7.6% of control) cell count in the SNpc. Taken together, the results of this study imply that M30 may clearly be of clinical importance for the treatment of PD.