Amphiphilic amine-N-oxides with aliphatic alkyl chain act as efficient superoxide dismutase mimics, antioxidants and lipid peroxidation blockers in yeast

Hydrogen peroxide and superoxide anion production during acetic acid-induced yeast programmed cell death

Hydrogen peroxide production in yeast cells undergoing programmed cell death in response to acetic acid occurred in the majority of live cells 15 min after death induction and was no longer detectable after 60 min. Superoxide anion production was found later, 60 and 90 min after death induction when cells viability was 60 and 30%, respectively. In cells protected from death due to acid stress adaptation neither hydrogen peroxide nor superoxide anion could be observed after acetic acid treatment. The early production of hydrogen peroxide in cells in which survival was 100% could play a major role in acetic acid-induced programmed cell death signaling. Superoxide anion is assumed to be generated in cells already en route to acetic acid-induced programmed cell death.

Assaying the antioxidant and radical scavenging properties of aliphatic mono- and di-N-oxides in superoxide dismutase-deficient yeast and in a chemiluminescence test

The antioxidative action of amphiphilic mono-(alkanoylamino) ethyldimethylamine-N-oxides (EDA), di-N-oxides 1,1-bis {[2-(N,N-dimethylamino)ethyl]amido}alkane-di-N-oxides (MEDA) and 1,1-bis {[3-(N,N-dimethylamino)propyl]amido}alkane-di-N-oxides (MPDA) with a 12- and 14-membered acyl chain against tert-butylhydroperoxide (TBHP)-produced peroxyl and paraquat (PQ)-generated superoxide radicals was determined in superoxide dismutase-deficient mutants of Saccharomyces cerevisiae, and, in parallel, in a chemical assay based on chemiluminescence changes caused in a luminol system by peroxyl radicals generated from the azo-compound 2,2'-azobis(2-amidinopropane dihydrochloride) (AAPH). At 30 micromol/L, the shorter-chain compounds did not affect strain survival while longer-chain ones, in some cases, lowered the survival of sod2 and sod1 sod2 cells. Whether nontoxic or medium-toxic, all N-oxides protected the sod strains against the toxic effect of PQ and TBHP, the protection being stronger with the di-N-oxides. The survival was lowered only by 14-MPDA in the TBHP-exposed sod2 mutant. Membrane lipids isolated from all strains were protected against TBHP-induced peroxidation by both mono- and di-N-oxides, the protection being dependent on the alkyl chain length. Mono-N-oxides were again less active than di-N-oxides with the same alkyl chains, the antiperoxidative activity being also dependent on lipids isolated from the individual mutants. In the chemiluminescence assay, the IC50 value of the N-oxides for scavenging of radicals generated from AAPH generally decreased (i.e. the scavenging efficiency increased) with increasing chain length and was the highest in MEDA.