Black currant anthocyanins abrogate oxidative stress through Nrf2- mediated antioxidant mechanisms in a rat model of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC), considered to be one of the most lethal cancers with almost > 1 million deaths reported annually worldwide, remains a devastating disease with no known effective cure. Hence, chemopreventive strategies come into play, offering an effective and safe mode of treatment, ideal to ward off potential cancer risks and mortality. A major predisposing condition, pertinent to the development and progression of HCC is oxidative stress. We previously reported a striking chemopreventive effect of anthocyanin-rich black currant skin extract (BCSE) against diethylnitrosamine (DENA)-initiated hepatocarcinogenesis in rats. The current study aims to elucidate the underlying antioxidant mechanisms of black currant anthocyanins implicated in the previously observed chemopreventive effects against experimental hepatocarcinogenesis. Dietary BCSE (100 and 500 mg/kg) administered four weeks before and 18 weeks after DENA challenge decreased abnormal lipid peroxidation, protein oxidation, and expression of inducible nitric oxide synthase (iNOS) and 3-nitrotyrosine (3-NT) in a dose-responsive fashion. Mechanistic studies revealed that BCSE upregulated the gene expression of a number of hepatic antioxidant and carcinogen detoxifying enzymes, such as NAD(P)H:quinone oxidoreductase, glutathione S-transferase, and uridine diphosphate-glucuronosyltransferase isoenzymes, in DENA-initiated animals. Protein and mRNA expressions of nuclear factor E2-related factor 2 (Nrf2) were substantially elevated with BCSE treatment, providing a direct evidence of a coordinated activation of the Nrf2-regulated antioxidant pathway, which led to the upregulation of a variety of housekeeping genes. The results of our study provide substantial evidence that black currant bioactive anthocyanins exert chemopreventive actions against DENA-inflicted hepatocarcinogenesis by attenuating oxidative stress through activation of Nrf2 signaling pathway.

Resveratrol suppresses oxidative stress and inflammatory response in diethylnitrosamine-initiated rat hepatocarcinogenesis.

Hepatocellular carcinoma (HCC), one of the most frequent and deadliest cancers, has been increasing considerably in the United States. In the absence of a proven effective therapy for HCC, novel chemopreventive strategies are urgently needed to lower the current morbidity and mortality of HCC. Recently, we have reported that resveratrol, a compound present in grapes and red wine, significantly prevents diethylnitrosamine (DENA)-induced liver tumorigenesis in rats, although the mechanism of action is not completely understood. In the present study, we have examined the underlying mechanisms of resveratrol chemoprevention of hepatocarcinogenesis by investigating the effects of resveratrol on oxidative damage and inflammatory markers during DENA-initiated rat liver carcinogenesis. There was a significant increase in hepatic lipid peroxidation and protein oxidation in carcinogen control animals compared with their normal counterparts at the end of the study (20 weeks). Elevated expressions of inducible nitric oxide synthase and 3-nitrotyrosine were noticed in the livers of the same animals. Dietary resveratrol (50-300 mg/kg) administered throughout the study reversed all the aforementioned markers in a dose-responsive fashion in rats challenged with DENA. Resveratrol also elevated the protein and mRNA expression of hepatic nuclear factor E2-related factor 2 (Nrf2). Results of the present investigation provide evidence that attenuation of oxidative stress and suppression of inflammatory response mediated by Nrf2 could be implicated, at least in part, in the chemopreventive effects of this dietary agent against chemically induced hepatic tumorigenesis in rats. The outcome of this study may benefit the development of resveratrol in the prevention and intervention of human HCC.

Suppression of the inflammatory cascade is implicated in resveratrol chemoprevention of experimental hepatocarcinogenesis.

PURPOSE: Resveratrol, present in grapes and red wine, has been found to prevent diethylnitrosamine (DENA)-initiated rat liver tumorigenesis, though the chemopreventive mechanisms are not completely elucidated. The current study was designed to explore whether the antiinflammatory properties of resveratrol play a role in its antihepatocarcinogenic action. METHODS: Liver samples were harvested from a 20-week chemopreventive study in which resveratrol (50, 100 and 300 mg/kg) was shown to inhibit DENA-induced hepatocyte nodules in Sprague-Dawley rats in a dose-responsive manner. Hepatic preneoplastic and inflammatory markers, namely heat shock protein (HSP70), cyclooxygenase-2 (COX-2) and nuclear factor-kappaB (NF-kappaB), were studied using immunohistochemical as well as Western blot techniques. RESULTS: Resveratrol dose-dependently suppressed DENA-induced increased expressions of hepatic HSP70 and COX-2. Resveratrol also attenuated the DENA-mediated translocation of NF-kappaB p65 from the cytosol to the nucleus with stabilization of inhibitory kappaB. CONCLUSION: The present findings indicate that resveratrol exerts chemoprevention of hepatocarcinogenesis possibly through antiinflammatory effects during DENA-evoked rat liver carcinogenesis by suppressing elevated levels of HSP70, COX-2 as well as NF-kappaB. These beneficial effects combined with an excellent safety profile encourage the development of resveratrol for chemoprevention and intervention of human HCC that remains a devastating disease.

Structure-based design of a thiazolidinedione which targets the mitochondrial protein mitoNEET.

Several PPAR-gamma agonists containing a thiazolidinedione moiety (referred to as glitazones) have been proposed to be neuroprotective and appear to alter mitochondrial function. Recently, a search for mitochondrial proteins that bind pioglitazone identified a novel protein, mitoNEET, which was later shown to regulate the oxidative capacity of the mitochondria. This identified an alternative target for the glitazones suggesting a possible new drug target for the treatment of neurodegenerative diseases. Molecular docking studies employing the reported crystal structure revealed five possible binding pockets on mitoNEET. We focused on two sites based on their physical characteristics. Using binding information gained from the analysis of two glitazones docked in these pockets, we designed and synthesized a ligand (NL-1) that would preferentially bind to site 1. Based on [(3)H]-binding data of the glitazones and comparisons to computer generated K(i)s, we were able to predict that site 1 was likely the target of the glitazones. NL-1 uncoupled isolated mitochondrial complex I respiration with an IC(50) of 2.4 microM and inhibited state III respiration up to 45%. To investigate the ability of NL-1 to block rotenone initiated free radicals from complex I, we found it was able to protect the human neuronal cell line SH-SY5Y against rotenone induced cell death. These data demonstrate that mitoNEET is a viable target for the design and synthesis of novel therapeutic agents aimed at altering mitochondrial function.