Clovamide and rosmarinic acid induce neuroprotective effects in in vitro models of neuronal death

Background and purpose: Phenolic compounds exert cytoprotective effects; our purpose was to investigate whether the isosteric polyphenolic compounds clovamide and rosmarinic acid are neuroprotective. Experimental approach: Three in vitro models of neuronal death were selected: (i) differentiated SH-SY5Y human neuroblastoma cells exposed to tert-butylhydroperoxide (t-BOOH), for oxidative stress; (ii) differentiated SK-N-BE(2) human neuroblastoma cells treated with L-glutamate, for excitotoxicity; and (iii) differentiated SH-SY5Y human neuroblastoma cells exposed to oxygen-glucose deprivation/reoxygenation, for ischaemia-reperfusion. Cell death was evaluated by lactate dehydrogenase measurements in the cell media, while the mechanisms underlying the effects by measuring: (i) t-BOOH-induced glutathione depletion and increase in lipoperoxidation; and (ii) L-glutamate-induced intracellular Ca2+ overload (fura-2 method) and inducible gene expression (c-fos, c-jun), by reverse transcriptase-PCR. The ability of compounds to modulate nuclear factor-kB and peroxisome proliferator-activated receptor-g activation was evaluated by Western blot in SH-SY5Y cells not exposed to harmful stimuli. Key results: Both clovamide and rosmarinic acid (10-100 mmol-L-1) significantly protected neurons against insults with similar potencies and efficacies. The EC50 values were in the low micromolar range (0.9-3.7 mmol-L-1), while the maximal effects ranged from 40% to-60% protection from cell death over untreated control at 100 mmol-L-1. These effects are mediated by the prevention of oxidative stress, intracellular Ca2+ overload and c-fos expression. In addition, rosmarinic acids inhibited nuclear factor-kB translocation and increased peroxisome proliferator-activated receptor-g expression in SH-SY5Y cells not exposed to harmful stimuli. Conclusion and implications: Clovamide and rosmarinic acid are neuroprotective compounds of potential use at the nutritional/pharmaceutical interface.