Deuterium-Enriched Water Increases the Cytotoxicity of Cyclooxygenase Inhibitors in Hep-G2 Hepatocellular Carcinoma Cells; Involvement of MAPK Pathway and Apoptosis

Background: One of the most prevalent forms of liver cancer globally is the hepatocellular carcinoma (HCC). Increasing evidence from both clinical settings and experimental studies indicates that cyclooxygenase (COX) enzymes could play a role in the formation of different types of cancer, including HCC. Deuterium-enriched water (DEW) and deuterium-depleted water (DDW) are involved in both the treatment and prevention of cancer. Employing a blend of COX inhibitors in conjunction with DDW/DEW might serve as a promising strategy to enhance the efficacy of both therapies in HCC. Methods: The cytotoxicity of celecoxib and indomethacin, examined both individually and in combination with DDW and DEW, was assessed. To explore their antiproliferative effects, Hep G2 cells were treated with the drugs and various concentrations of deuterium in the forms of DDW or DEW, while cell viability was evaluated through the MTT assay. Furthermore, the levels of COX-2, MAPK pathway proteins, the anti-apoptotic protein Bcl2, the pro-apoptotic protein Bax, and the activity of caspase-3 were investigated using SDS-polyacrylamide gel (SDS-PAGE) and western blot techniques. Results: The simultaneous administration of indomethacin or celecoxib alongside DEW significantly improved the cytotoxic effects and induced apoptosis in Hep G2 cells. The combination of DEWs with celecoxib or indomethacin enhanced the antiproliferative impact of the drug by about 20%–60% and 15%–45%, respectively. This improvement was linked to the activation of p38 and JNK MAPKs, along with a reduction in the pro-survival proteins Bcl-2, COX-2, and ERK1/2. Additionally, the simultaneous treatment led to the activation of caspase-3, an important mediator of apoptosis, and suppressed poly ADP-ribose polymerase (PARP). Conclusion: The pairing of DEW with NSAIDs can influence the primary cellular signaling pathways, acting as a tactic in cancer chemotherapy.