Oxidation and generation of hydrogen peroxide by thiol compounds in commonly used cell culture media

Many studies have examined the effects of thiol compounds upon cells in culture (e.g., upon signal transduction and regulation of gene expression), but few have considered how thiols can interact with cell culture media. A wide range of thiols (cysteine, GSH, N-acetylcysteine, gamma-glutamylcysteine, cysteinylglycine, cysteamine, homocysteine) were found to interact with three commonly used cell culture media (RPMI, MEM, DMEM) to generate hydrogen peroxide with complex concentration-dependencies. Thiols added to these media rapidly disappeared, although less H(2)O(2) was generated on a molar basis than the amount of thiol lost. Studies on cellular effects of thiols, especially those on redox regulation of gene expression or protein function, need to take into account that thiols are rapidly lost, and that their oxidation generates H(2)O(2), which can have multiple concentration-dependent effects on cell metabolism.