J Nutr Biochem. 2021 Jul 02. pii: S0955-2863(21)00232-1. [Epub ahead of print] 108812
It has been widely reported that cancer, along with its treatment regimens, cause severe toxicity in the host. A suitable agent having chemopreventive properties as well as capabilities of ameliorating tumor- and drug-induced toxicities is of imminent need. Pomegranate has been projected as an excellent anti-tumor, anti-inflammatory and anti-oxidant agent. In this study, for the first time, we delineated the exact signaling cascade by which dietary supplementation of pomegranate fruit extract (PFE) protects tumor-bearing mice from tumor-induced hepatotoxicity. Increased activities of serum Alanine transaminase (ALT), Aspartate transaminase (AST), Lactate dehydrogenase (LDH) and Alkaline phosphatase (ALP), as well as histological studies confirmed the establishment of a state of hepatic dysfunction in tumor-bearers. Further investigations revealed that increased hepatic reactive oxygen species (ROS) content and glutathione (GSH) depletion initiated apoptosis in these hepatocytes as we observed an alteration in the apoptotic proteins. PFE supplementation in tumor-bearing mice, on the other hand, differentially modulated redox-sensitive transcription factors Nrf2 and NF-κB, ultimately decreasing tumor-induced hepatic oxidative damage and cell death. siRNA-mediated inhibition of Nrf2 and NF-κB completely abolished the hepato-protective activities of PFE while pre-treatment of tumor-conditioned hepatocytes with N-acetyl cysteine (NAC) augmented the cyto-protective properties of PFE. The present study clearly identified Nrf2/NF-κB/GSH axis as the key factor behind the hepatoprotective potential of PFE. These findings would add to the existing knowledge about cancer chemoprevention by dietary polyphenols and might lead to the application of pomegranate polyphenols as supplement to escalate the effectiveness of cancer therapy by protecting normal cells from cancer related toxicities.
Keywords: ALP, Alkaline phosphatase; ALT, Alanine transaminase; ARE-Antioxidant response element; AST, Aspartate transaminase; Apoptosis. Abbreviations: ROS, Reactive oxygen species; Bax- Bcl-2-associated X; Bcl-2 -B-cell lymphoma 2; CAT, Catalase; Cancer; DHE, Dihydroethidium; EAC, Erhlich's ascites carcinoma; GPx, Glutathione peroxidase; GR, Glutathione reductase; GSH, Glutathione; GSSG, Glutathione disulfide; GST, Glutathione S-transferase; HO 1, Heme oxygenase 1; Hepatotoxicity; Inflammation; IκB, Inhibitor of κB; Keap1, Kelch-like ECH-associated protein 1; LDH, Lactate dehydrogenase; NAC- N-acetyl cysteine; NF-κB; NF-κB, Nuclear factor kappa light-chain-enhancer of activated B cells; NQO 1, NAD(P)H Quinone oxidoreductase 1; Nrf2; Nrf2, Nuclear factor (erythroid-derived 2)-like 2; PFE, Pomegranate fruit extract; PMS, Post-mitochondrial supernatant; Pomegranate; Reactive Oxygen Species; SAPK/JNK, Stress activated protein Kinase/c-Jun N-terminal kinases; SOD, Superoxide dismutase; TNF-α, Tumor necrosis factor alpha