Ascorbic acid regulates <i>in vitro</i> and <i>in vivo</i> toxicogenetic effects of hydroxyurea on eukaryotic cells

Hydroxyurea (HU) exerts unique and diverse biological effects as an anti-leukemic agent, irradiation sensitizer, and HbS inducer in patients with sickle cell anemia. Herein, we assessed the potential toxicogenic and/or oxidant effects of hydroxyurea associated with ascorbic acid by <i>in vivo</i> examinations in <i>Allium cepa</i> and human cancer cells and systemically on mice tissues. Growing <i>A. cepa</i> roots and HCT-116 colorectal tumor cells were examined after HU and HU plus ascorbic acid exposure. DNA damage and antioxidant enzymatic activity were quantified in peripheral blood mononuclear cells (PBMC), bone marrow leukocytes and livers of mice after 7 day-HU treatment (7.5, 15 and 30 mg/kg/day) and Vitamin C 2 μM. Hydroxyurea presented toxic effects on meristematic <i>Allium cepa</i> cells, causing chromosomal abnormalities and reduction of mitotic index, killed HCT-116 colorectal carcinoma cells and induced DNA injuries upon mice cells (hepatocytes, bone marrow leukocytes and PBMC). Simultaneously, hydroxyurea decreased levels of CAT and GSH activities and expand lipid peroxidation. All these biochemical and physiological changes were ameliorated when associated with ascorbic acid, indicating it restored antioxidant enzymes, decreased MDA levels, removed peroxides and, consequently, presented cytoprotection against HU-provoked cellular damage in normal cells. On the other hand, antioxidants compounds may interfere on effectiveness of HU during anticancer chemotherapies.