Delta-tocotrienol enhances the antitumor effects of interferon alpha through ROS and Erk/MAPK signaling pathways in hepatocellular carcinoma cells

The complexity of hepatocellular carcinoma (HCC) signaling and the failure of pharmacological therapeutics reveal the significance of establishing new anti-cancer strategies. Interferon alpha (IFN α) has been used as adjuvant therapy for reducing HCC recurrence and improving survival. Delta-tocotrienol (δ-tocotrienol), a natural unsaturated isoform of vitamin E, is a promising candidate for cancer treatment. In this study, we evaluated whether the combination of δ-tocotrienol with IFN α displays significant advantages in the treatment of HCC cells. Results showed that the combination significantly decreased cell viability, migration and invasion of HCC cells compared to single therapies. Combining δ-tocotrienol and IFN α enhanced the decrease in proliferating cell nuclear antigen (PCNA) and matrix metalloproteinases MMP-7 and MMP-9. The combination also produced an enhancement of apoptosis together with increased Bax/Bcl-xL ratio and ROS generation. δ-tocotrienol induced Notch1 activation and changes in Erk and p38 MAPK signaling status. Blocking experiments confirmed that ROS and Erk are involved, at least in part, in the anticancer effects of the combined treatment. In conclusion, the combination of δ-tocotrienol with IFN α therapy showed promising results for HCC cells treatment, which makes the combination of cytokine-based immunotherapy with natural products a potential strategy against liver cancer.

Interferon-alpha2b (IFN-alpha2b)-induced apoptosis is mediated by p38 MAPK in hepatocytes from rat preneoplastic liver via activation of NADPH oxidase

It is still unclear how Interferon-alfa (IFN-alpha) acts on preventing the appearance of hepatocarcinogenesis. We have demonstrated that IFN-alpha2b induces hepatocytic transforming growth factor-beta1 (TGF-beta(1)) production and secretion by inducing reactive oxygen species (ROS) formation through the activation of NADPH oxidase. This TGF-beta(1), alters antioxidant defences and induces programmed cell death. Since it was demonstrated that IFN-alpha induces apoptosis through the activation of p38 mitogen-activated protein kinase (p38 MAPK), this study was aimed to assess the role of this kinase in the IFN-alpha2b-induced apoptosis in rat liver preneoplasia; and to further evaluate the participation of NADPH oxidase. p38 MAPK pathway was activated during the IFN-alpha2b-induced apoptosis in rat liver preneoplasia. This activation was accompanied with phosphorylation of different transcription factors, depending on the time of IFN-alpha2b stimulus. Our data suggest that NADPH oxidase is activated by IFN-alpha2b through p38 MAPK. p38 MAPK-induced activation of NADPH oxidase is accomplished by a two-step pathway: first, ROS-independent and second ROS- and TGF-beta(1)-dependent.

Biliary Secretory Function in Rats Chronically Intoxicated with Aluminum

The effects of a chronic aluminum (Al) exposure on biliary secretory function, with special emphasis on hepatic handling of non-bile salt organic anions, was investigated. Male Wistar rats received, intraperitoneally, either 27 mg/kg body weight of Al, as Al hydroxide [Al (+) rats], or the vehicle saline [Al (-) rats] three times a week for 3 months. Serum and hepatic Al levels were increased by the treatment (approximately 9- and 4-fold, respectively). This was associated with enhanced malondialdehyde formation (+110%) and a reduction in GSH content (-17%) and in the activity of the antioxidant enzymes catalase (-84%) and GSH peroxidase (-46%). Bile flow (-23%) and the biliary output of bile salts (-39%), cholesterol (-43%), and proteins (-38%) also decreased. Compartmental analysis of the plasma decay of the model organic anion bromosulphophthalein revealed that sinusoidal uptake and canalicular excretion of the dye were significantly decreased in Al (+) rats (-53 and -43%, respectively). Expression of multidrug resistance-associated protein 2 (Mrp2), the main, multispecific transporter involved in the canalicular excretion of organic anions, was also decreased (-40%), which was associated with a significant decrease in the cumulative biliary excretion of the Mrp2 substrate, dinitrophenyl-S-glutathione (-50%). These results show that chronic Al exposure leads to oxidative stress, cholestasis, and impairment of the hepatic handling of organic anions by decreasing both sinusoidal uptake and canalicular excretion. The alteration of the latter process seems to be causally related to impairment of Mrp2 expression. We have addressed some possible mechanisms involved in these deleterious effects.