Combination of phenolic compounds with arachidonic acid induces "futile thiol pumping" and oxidative stress in epidermal human keratinocytes.
Shvedova-AA; Tyurina-YY; Tyurin-VA; Jeffries-B; Kommineni-C; Castranova-V; Kagan-VE
Toxicologist 1999 Mar; 48(1-S):205
In human epidermis, active metabolism of arachidonic acid to prostaglandins is regulated by prostaglandin H synthase (PHS) which is also known to catalyze xenobiotic biotransformation. In particular, peroxidase activity of PHS may catalyze one-electron oxidation of phenolic compounds to their phenoxyl radicals. The phenoxyl radical may attack intracellular thiols to regenerate the phenolic compound that may repeatedly undergo peroxidase-catalyzed oxidation. This thiol-supported redox-cycling of phenolic compounds (i.e., "futile thiol pumping") has been demonstrated in keratinocytes exposed to acetaminophen (Mason et al., 1989). In the present work, we tested whether redox-cycling of phenolic compounds can induce peroxidation of membrane phospholipids and deplete antioxidants in keratinocytes. We used a fluorescence HPLC assay for quantitation of membrane phospholipids metabolically prelabelled with oxidation-sensitive natural fluorescent fatty acid, cis-parinaric acid (PnA). We found that a combination of phenol/arachidpnic acid or cresol/rachidonic acid caused a pronounced oxidation of major phospholipids: phosphatidytcholine, phosphatidylethanolamine, and phosphatidylserine in keratinocytes. Exposure to phenol (cresol) + arachidonic acid decreased total antioxidant reserves in keratinocytes as measured by luminol-enhanced chemiluminescence in the presence of a water-soluble azo-initiator, AAPH. Measurements with a thiol-reagent, ThioGlo-1 showed that phenol (cresol) + arachidonic acid depleted GSH and oxidized protein sulfuydryls in keratinocytes. Electron microscopy revealed characteristic apoptotic nuclear fragmentation in keratinocytes exposed to a combination of phenolic compounds with arachidonic acid. These results suggest that peroxidase activity of PHS may be involved in phenol (cresol)-induced "futile thiol pumping" in human epidermal keratinocytes.
Statistical-analysis; Exposure-assessment; Epidemiology; Phenolic-compounds; Phenolic-acids; Phenols; Thiols; Skin-disorders; Skin-exposure; Skin-sensitivity; Skin-tests
The Toxicologist. Society of Toxicology 38th Annual Meeting, March 14-18, 1999, New Orleans, Louisiana