Oxidatively-induced DNA damage has previously been associated with
bipolar disorder. More recently, impairments in DNA repair mechanisms have also been reported. We aimed to investigate oxidatively-induced DNA lesions and expression of
DNA glycosylases involved in base excision repair in euthymic patients with
bipolar disorder compared to healthy individuals.
DNA base lesions including both base and
nucleoside modifications were measured using gas chromatography-tandem mass spectrometry and liquid chromatography-tandem mass spectrometry with
isotope-dilution in
DNA samples isolated from leukocytes of euthymic patients with
bipolar disorder (n = 32) and healthy individuals (n = 51). The expression of
DNA repair enzymes OGG1 and NEIL1 were measured using quantitative real-time polymerase chain reaction. The levels of
malondialdehyde were measured using high performance liquid chromatography. Seven
DNA base lesions in
DNA of leukocytes of patients and healthy individuals were identified and quantified. Three of them had significantly elevated levels in bipolar patients when compared to healthy individuals. No elevation of lipid peroxidation marker
malondialdehyde was observed. The level of OGG1 expression was significantly reduced in bipolar patients compared to healthy individuals, whereas the two groups exhibited similar levels of NEIL1 expression. Our results suggest that oxidatively-induced DNA damage occurs and base excision repair capacity may be decreased in bipolar patients when compared to healthy individuals. Measurement of oxidatively-induced
DNA base lesions and the expression of
DNA repair enzymes may be of great importance for large scale basic research and clinical studies of
bipolar disorder.