Influence of Val16Ala SOD2 polymorphism on the in-vitro effect of clomiphene citrate in oxidative metabolism

Abstract

This study investigated the in-vitro antioxidant properties of the ovulation induction drug, clomiphene citrate, and assessed whether its effects are influenced by the Val16Ala polymorphism in the SOD2 gene, which encodes manganese superoxide dismutase enzyme. The investigation involved an in-vitro experimental protocol testing the effect of different concentrations of clomiphene citrate on antioxidant capacity, reactive oxygen species (ROS) production and peripheral blood mononuclear cell (PBMC) culture viability. A total of 58 healthy adult women were genotyped for the Val16Ala SOD2 polymorphism, and blood samples were collected to perform in-vitro experiments. ROS production and cytotoxicity assays were performed on blood and PBMC from carriers of different Val16Ala SOD2 genotypes. Clomiphene citrate exhibited antioxidant capacity and effects and decreased ROS production. The AA genotype displayed a more responsive antioxidant effect with clomiphene citrate treatment than other genotypes. AA and AV PBMC showed an increase in viability following treatment with 10 μmol/l clomiphene citrate when compared with control groups. The results suggest that clomiphene citrate exhibits antioxidant activity similar to that observed with other selective oestrogen receptor modulators, and the intensity of the effect appears to be SOD2 polymorphism dependent. This study was performed to investigate whether clomiphene citrate, a drug broadly used to evaluate reproductive function in women, presents antioxidant effects and if these effects could be influenced by genetic variation in the women. We found evidence that clomiphene citrate has some antioxidant properties similar to those observed with other selective oestrogen receptor modulators such as tamoxifen. As the antioxidant enzyme manganese superoxide dismutase (SOD2) is considered a key molecule involved in female reproductive metabolism, we also tested if a functional SOD2 gene polymorphism (Val16Ala) could influence the in-vitro antioxidant clomiphene citrate response. Significant differences of the clomiphene citrate antioxidant effect on PBMC with different Val16Ala SOD genotypes were observed in this study. Based on these results, we could speculate that alterations in SOD2 activity caused by the Val16Ala polymorphism can result in differential responses to drugs such as clomiphene citrate. In assisted reproduction clinics, clomiphene citrate is commonly used to induce ovulation, especially in patients with polycystic ovary syndrome. However, some women have clomiphene citrate resistance and either ovulation is not triggered by the drug or ovulation is induced but the pregnancy still fails. The causes of no effect of clomiphene citrate remain unclear and we cannot discard the influence of genetic effects including the Val16Ala SOD2 polymorphism. Therefore, it is important to perform complementary investigations considering the potential pharmacogenetic influence of Val16Ala SOD2 polymorphism on the treatment of polycystic ovary syndrome or in ovulation to elucidate this question.