| The neurochemistry of hydrogen peroxide (H2O2) in living systems has received increased attention owing to its contributions as a marker for oxidative stress and damage events associated with neurodegeneration. H2O2 is a major reactive oxygen species (ROS) in living organisms, yet its production, accumulation and trafficking within neuronal cells is poorly understood. Using the H2O2 selective optical probe Peroxyfluor-1 (PF1), we determined its ability to operate within neuronal cell lines (RN46A-B14 and SKNSH) and primary cortical neurons.;In collaboration with Professor Bryan K Yamamoto at the BU Medical Campus, we used PF1 to study the role of H2O2 in serotonin (5-HT) neurons in the presence of the well-known neurotoxin and drug of abuse, 3,4methylenedioxymethamphetamine (MDMA). We found that MDMA creates the pro-oxidant environment to non-enzymatically hydroxylate L-tyrosine in the 5-HT cell line RN46A-B14. Dopamine (DA) is formed by endogenous amino acid decarboxylase (AADC) and is further metabolized by monoamine oxidase B (MAO-B) to produce H2O2 as a by-product.;Next, we investigated oxidative stress in a dopaminergic cell line (SKNSH). We found significant increases in H2O2 formation upon treatment with the current drug therapy for Parkinson's disease (PD), L-3,4 dihydroxyphenylalanine (L-dopa). L-dopa results in the AADC conversion of L-dopa to DA in the brain. A replenishment of DA in the surviving neurons temporarily alleviates symptoms of the disease; however, the therapy is not curative, and dopaminergic cells continue to die in PD patients receiving L-dopa. The proposed mechanism for L-dopa induced cell death is by autoxidation into ROS and toxic quinones. We found that resveratrol and flavonoid antioxidants reduced L-dopa-induced H2O2 formation and cytotoxicity.;We also synthesized boronate polyphenols that resemble the antioxidant scaffolds with which we had great success as neuroprotectants. We envisioned that placing a boronate ester functionality on the antioxidant backbone would increase solubility, cell permeability and decrease H2O2-induced cell death in SKNSH cells. Of the boronate coumarins, stilbenes and flavones we synthesized, we found that 7-boronatecoumarin and to a lesser extent (E)-3,5-dihydroxy, 4'-boronatestilbene were water soluble, cell permeable and preserved SKNSH cell viability in the presence of H2O2. |
