Chemoprotective Activity of D-Ribose-L-Cysteine (Riboceine) against the Cytotoxic effects of Methotrexate and Docetaxel on Normal and Cancer Cell Lines

Abstract

ABSTRACT Background: Methotrexate (MET) and docetaxel (DOC) are chemotherapeutic agents used for the treatment of breast and prostate cancers, respectively. Their action results in the generation of reactive oxygen species (ROS). Excessive ROS consume cellular antioxidants such as glutathione (GSH) that leads to oxidative stress in both normal and cancer cells. Riboceine (RIB), a GSH-enhancer diet supplement, has been shown to protect against oxidative stress. However, there is a dearth of information on the protective effects of RIB on normal and cancer cells during chemotherapy. Aim: This study sought to determine the chemoprotective effects of RIB against the cytotoxic effects of DOC and MET on normal and cancer cells Methodology: The effects of increasing concentrations of MET and DOC and their combination with RIB or N-acetylcysteine (NAC, positive control) on the cell viability of normal human prostate cell (PNT-2), human prostate cancer cell (PC3) and human breast cancer cell (MCF-7) lines were determined using the resazurin assay. Also, the effects of these agents and their combinations on the GSH content and ROS level of the normal and cancer cell lines were measured using O-phthalaldehyde (OPA) and dichlorofluorescein diacetate (DCFDA) assays, respectively. RESULTS MET and DOC dose-dependently decreased (p<0.05) the viability of PNT-2 cell (IC50 = 0.552 and 0.524 μM, respectively) and PC3 cell (IC50 = 0.338 and 0.320 μM, respectively) lines. RIB and NAC significantly reduced (p<0.05) the cytotoxic effect of MET and DOC on PNT-2 cell line (IC50 > 10 μM). On the other hand, RIB and NAC had no significant effect on the cytotoxicity of MET and DOC on PC3 cell line. MET and DOC significantly decreased (p<0.05) GSH content and significantly increased (p<0.05) ROS level of both normal and cancer cell lines when compared to untreated cells. Similarly, RIB and NAC significantly

increased (p<0.05) GSH content and decreased (p<0.05) ROS level in both normal and cancer cell line, in the presence of MET and DOC. CONCLUSION: The current study suggests that RIB protected the normal cells PNT-2 against the cytotoxic effects of MET and DOC. RIB and NAC also protected MCF-7 but not PC3 cell lines against the cytotoxic effects of MET and DOC. The protective effect of RIB was associated with an increase in GSH content and a decrease in ROS level in both normal and cancer cell lines. The effect of RIB was similar but less pronounced than the effect of NAC, the standard drug. Further studies should be conducted to confirm these findings at the molecular and in vivo levels. Also, other antioxidant defences such as catalase, superoxide dismutase and peroxidase should be investigated.