Pterin-6-carboxylic Acid Induces Oxidative Stress-Mediated Cytotoxicity, Genotoxicity, and Chromosomal Instability in Mammalian Cells

Objective: Pterin-6-carboxylic acid (PCA) is a photoactive oxidative pterin derivative with potential biological reactivity; however, its cellular toxicological profile remains insufficiently characterized. This study investigated the cytotoxic, oxidative, genotoxic, and clonogenic effects of PCA in HaCaT, A375, and CHO-K1 cell lines. Methods: A comprehensive multi-endpoint approach, including MTT cell viability assay, intracellular ROS measurement, alkaline comet assay, cytokinesis-block micronucleus assay, clonogenic survival assay, and caspase-3/7 activity analysis, was employed to define the mechanistic toxicological profile of PCA. Results: PCA exposure induced a significant and concentration-dependent reduction in cell viability across all models. Intracellular ROS levels were markedly elevated, indicating pronounced oxidative stress and disruption of redox homeostasis. Comet assay analysis demonstrated significant DNA strand breaks in a dose-dependent manner, confirming genotoxic potential. In addition, PCA significantly reduced clonogenic survival, indicating long-term proliferative impairment. Micronucleus formation was also significantly increased, suggesting chromosomal instability and both clastogenic and/or aneugenic effects. Conclusions: Collectively, these findings demonstrate that PCA induces multi-level cellular toxicity primarily mediated by oxidative stress. The consistent sensitivity pattern (A375 > CHO-K1 > HaCaT) suggests enhanced vulnerability of melanoma cells to redox imbalance. These results position oxidative stress as a central mechanism underlying PCA-induced cytotoxic and genotoxic responses.