PON1 increases cellular DNA damage by lactone substrates.

Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated enzyme that by hydrolysing exogenous and endogenous substrates can provide protection against substrate induced toxicity. To investigate the extent to which PON1 provides protection against lactone induced DNA damage, DNA damage was measured in HepG2 cells using the neutral Comet assay following lactone treatment in the presence and absence of exogenous recombinant PON1 (rPON1). Low dose lactones (10 mM) caused little or no damage while high doses (100 mM) induced DNA damage in the following order of potency: α-angelica lactone > γ-butyrolactone ~ γ-hexalactone > γ-heptalactone ~ γ-octaclactone ~ γ-furanone ~ γ-valerolactone > γ-decalactone.

L-β-N-methylamino-l-alanine (BMAA) nitrosation generates a cytotoxic DNA damaging alkylating agent: An unexplored mechanism for neurodegenerative disease.

Background: L-β-N-methylamino-l-alanine (BMAA) is a non-proteinic amino acid, that is neurotoxic in vitro and in animals, and is implicated in the causation of amyotrophic lateral sclerosis and parkinsonism-dementia complex (ALS-PDC) on Guam. Given that natural amino acids can be N-nitrosated to form toxic alkylating agents and the structural similarity of BMAA to other amino acids, our hypothesis was that N-nitrosation of BMAA might result in a toxic alkylating agent, providing a novel mechanistic hypothesis for BMAA action.

Findings: We have chemically nitrosated BMAA with sodium nitrite to produce nitrosated BMAA (N-BMAA) which was shown to react with the alkyl-trapping agent, 4-(p-nitrobenzyl)pyridine, cause DNA strand breaks in vitro and was toxic to the human neuroblastoma cell line SH-SY5Y under conditions in which BMAA itself was minimally toxic.