Oxidative stress in tardive dyskinesia: Genetic association study and meta-analysis of NADPH quinine oxidoreductase 1 (NQO1) and Superoxide dismutase 2 (SOD2, MnSOD) genes

Introduction: Tardive dyskinesia (TD) is a potentially irreversible side effect of antipsychotic medication treatment that occurs in approximately 25% of chronically treated schizophrenia patients. Oxidative stress has been one of the proposed mechanisms influencing TD risk. Pae et al. (2004) originally reported a significant association between TD and the NADPH quinine oxidoreductase 1 (NQO1) gene Pro187Ser (C609T, rs1800566) polymorphism in Korean schizophrenia patients; however, subsequent studies have not consistently replicated these findings. Similarly, Hori et al. (2000) reported an association between TD and the Manganese superoxide dismutase SOD2 (MnSOD) gene Ala9Val (rs4880) polymorphism in a Japanese sample, but most research groups failed to replicate their positive findings. Aims: We investigated the role of the NQO1 polymorphism Pro187Ser and SOD2 (Ala9Val) in a group of well-characterized schizophrenia patients (N = 223) assessed for TD. We also performed a meta-analysis of all the previously published TD studies, including data from our sample, on these polymorphisms, Pro187Ser (N = 5 studies) and Ala9Val (N = 9 studies). Results: We did not observe a significant association of the Pro187Ser or Ala9Val polymorphism with TD occurrence or AIMS scores in our Caucasian and African American samples when analyzed independently. Meta-analysis did not reveal a significant association of the Pro187Ser/Ala9Val alleles or genotypes with TD occurrence. Conclusions: Neither the NQO1 Pro187Ser nor the SOD2 Ala9Val appear to play a major role in TD risk, although additional polymorphisms should be tested before the role of NQO1 and SOD2 in TD can be completely excluded.