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Increasing evidence suggests that dysregulation of brain insulin/insulin receptor (InsR) and insulin signaling cascade are associated with the pathogenesis of Alzheimer's disease (AD). Our group has designed and synthesized a series of multi-target iron chelating, brain permeable compounds for AD. One leading multi-target compound, M30 possesses the neuroprotective N-propargyl moiety of the anti-Parkinsonian, monoamine oxidase (MAO)-B inhibitor, rasagiline (Azilect®) and the antioxidant-iron chelating moiety of an 8-hydroxyquinoline derivative of the iron chelator, VK28. Positive outcomes for the behavioral/cognitive and neuroprotective effects of M30 were recently obtained in preclinical experimental studies, regarding pathological aspects relevant to ageing and AD. We report that chronic treatment with M30 (1 and 5 mg/kg p.o; three times a week for 9 months) significantly elevated cortical insulin and InsR transcript and protein expression, respectively and increased the phosphorylated form of glycogen synthase kinase-3β in the frontal cortex of amyloid precursor protein (APP) and presenilin 1 (PS1) double transgenic mice. In addition, M30 treatment upregulated the levels of hypoxia-inducible factor (HIF)-1α and expression of its target genes involved in glycolysis including, aldolase A, enolase-1 and glucose transporter-1 (Glut-1), in the frontal cortex of APP/PS1 mice. Treatment with M30 also lead to an increase in the hepatic protein expression levels of InsR and Glut-1 and lowered the increase in blood glucose levels following glucose tolerance test. The present findings indicate that the multifunctional iron chelating drug, M30 regulates major brain glucose metabolism parameters and thus, might be beneficial for AD, in which impaired neuronal insulin signaling and Glut expression have been implicated.

Increasing evidence suggests that oxidative stress (OS)-induced pancreatic ␤-cell impairments is involved in diabetes and diabetic complications. Our group has recently synthesized two multifunctional nontoxic, lipophilic, ironchelating drugs, 5-{N-methyl-N-propargylaminomethyl}-8-hydroxyquinoline (M30) and 5-{4-propargylpiperazin-1-ylmethyl}-8-hydroxyquinoline (HLA20), for the treatment of various OS-mediated pathogeneses. These compounds contain the N-propargylamine cytoprotective moiety of the antiparkinsonian drug rasagiline (Azilect) and the ironcomplexing component 8-hydroxyquinoline. The aim of this research was to evaluate the protective effect of the multifunctional iron-chelating drugs on rat insulin-producing pancreatic ␤-cells (INS-1E and RINm) against OS-induced cytotoxicity. We found that M30 and HLA20 markedly and dose-dependently inhibited H 2 O 2 -induced cytotoxicity, associated with decreased intracellular reactive oxygen species formation and increased catalase activity. In accordance, the catalase inhibitor 3-amino-1,2,4-triazol blocked the protective action of M30 against H 2 O 2 -induced damage. Both compounds significantly increased the levels of the iron-responsive protein transferrin receptor indicating their iron-chelating effect. Further mechanistic studies showed that M30 and HLA20 attenuated H 2 O 2 -induced mitochondrial membrane potential loss, decreased the release of cytochrome c into the cytoplasm, and inhibited the activation of caspase-3, suggesting that these drugs may produce cytoprotective effects via the preservation of mitochondrial function. These results indicate that the novel drugs, M30 and HLA20 display significant cytoprotective activity against OS-induced cytotoxicity in insulin producing ␤-cells, which might be of therapeutic use in the treatment of diabetes mellitus.

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