Neuroprotective and MAOB inhibitory effects of a series of caffeine-8-thioglycolic acid amides

Abstract

The effects of new derivatives of caffeine-8-thioglycolic acid (100 μM) on isolated rat brain synaptosomes, human neuroblastoma cell line SH-SY5Y and human recombinant MAOB enzyme (hMAOB) (1 μM) were evaluated. Most of the compounds, administered alone, didn’t show statistically significant neurotoxic effects on SH-SY5Y, when compared to the control (non-treated cells). Of all studied structures JTA-2Ox, JTA-11, JTA-12 and JTA-13 decreased cell viability. In combination with 6-hydroxydopamine (6-OHDA) (100 μM), only JTA-1 and JTA-2 revealed neuroprotective effects, stronger than those of caffeine. All compounds administered alone revealed, neurotoxic effects on synaptosomes, as compared to nontreated synaptosomes. JTA-1, JTA-2 and JTA-3 showed lowest neurotoxic effects and were investigated in a model of 6-OHDA-induced oxidative stress. In this model of neurotoxicity, only JTA-1 and JTA-2 showed statistically significant neuroprotective effect, by preserving the synaptosomal viability and the level of reduced glutathione. Inhibition of hMAOB, was revealed by JTA-1 and JTA-2. They inhibited the enzyme by 23% and 25% respectively, thus approaching the selegiline activity, which was 42%. The possible mechanisms of neuroprotection of JTA-1 and JTA-2 might be a result from the inhibition of hMAOB, which catalyze the production of neurotoxic p-quinone from 6-OHDA.