Fe(II)-induced DNA damage in α-synuclein-transfected human dopaminergic BE(2)-M17 neuroblastoma cells: Detection by the Comet assay

Lewy bodies in the brains of patients with Parkinson's disease (PD) contain aggregates of α-synuclein (α-syn). Missense mutations (A53T or A30P) in the gene encoding α-syn are responsible for rare, inherited forms of PD. In this study, we explored the susceptibility of untransfected human dopaminergic BE(2)-M17 neuroblastoma cells, cells transfected with vector only, or cells transfected with wild-type α-syn, A30P α-syn or A53T α-syn to Fe(II)-induced DNA damage in the form of single-strand breaks (SSBs). DNA SSBs were detected following 2-h treatments with various concentrations of Fe(II) (0.01-100.0 μm), using the alkaline single cell-gel electrophoresis ('Comet') assay and quantified by measuring comet tail length (CTL) (μm). Fe(II) treatment induced significant increases in CTL in cells transfected with A30P α-syn or A53T α-syn, even at the lowest concentrations of Fe(II) tested. In comparison, untransfected cells, vector control cells or cells transfected with wild-type α-syn exhibited increases in SSBs only when exposed to concentrations of 1.0 μm FE(II) and above. Even when exposed to higher concentrations (10.0-100.0 μm) of Fe(II), untransfected cells, vector control cells or cells transfected with wild-type α-syn were less susceptible to DNA-damage induction than cells transfected with A30P α-syn or A53T α-syn. Incorporation of DNA-repair inhibitors, hydroxyurea and cytosine arabinoside, enhanced the sensitivity of DNA damage detection. Susceptibility to Fe(II)-induced DNA damage appeared to be dependent on α-syn status because cells transfected with wild-type α-syn or A53T α-syn were equally susceptible to the damaging effects of the mitochondrial respiratory chain inhibitor rotenone. Overall, our data are suggestive of an enhanced susceptibility to the toxic effects of Fe(II) in neuroblastoma cells transfected with mutant α-syn associated with inherited forms of PD.