Possible role of free radical intermediates in hepatotoxicity of hydrazine derivatives

Light-induced disruption of an acyl hydrazone link as a novel strategy for drug release and activation: isoniazid as a proof-of-concept case

Photocleavage of an acyl hydrazone bridge was achieved by conjugating isoniazid to a ruthenium(ii) metal complex through the generation of singlet oxygen, which released and activated the anti-tuberculosis pro-drug isoniazid.

Liver Transplantation for Alcoholic Liver Disease and Hepatocellular Carcinoma

Hepatocellular carcinoma is one of the main important causes of cancer-related death and its mortality is increasingly worldwide. In Europe, alcohol abuse accounts for approximately half of all liver cancer cases and it will become the leading cause of hepatocellular carcinoma in the next future with the sharp decline of chronic viral hepatitis. The pathophysiology of alcohol-induced carcinogenesis involves acetaldehyde catabolism, oxidative stress and chronic liver inflammation. Genetic background plays also a significant role and specific patterns of gene mutations in alcohol-related hepatocellular carcinoma have been characterized. Survival is higher in patients who undergo specific surveillance programmes than in patients who do not. However, patients with alcohol cirrhosis present a significantly greater risk of liver decompensation than those with cirrhosis due to other aetiologies. Furthermore, the adherence to screening program can be suboptimal. Liver transplant for patients with Milan-in hepatocellular carcinoma represents the best possible treatment in case of tumour recurrence/progression despite loco-regional or surgical treatments. Long-term result after liver transplantation for alcohol related liver disease is good. However, cardiovascular disease and de novo malignancies can significantly hamper patients' survival and should be carefully considered by transplant team. In this review, we have focused on the evolution of alcohol-related hepatocellular carcinoma epidemiology and risk factors as well as on liver transplantation in alcoholic patients with and without hepatocellular carcinoma.

Recent insights into the biological functions of liver fatty acid binding protein 1

Over four decades have passed since liver fatty acid binding protein (FABP)1 was first isolated. There are few protein families for which most of the complete tertiary structures, binding properties, and tissue occurrences are described in such detail and yet new functions are being uncovered for this protein. FABP1 is known to be critical for fatty acid uptake and intracellular transport and also has an important role in regulating lipid metabolism and cellular signaling pathways. FABP1 is an important endogenous cytoprotectant, minimizing hepatocyte oxidative damage and interfering with ischemia-reperfusion and other hepatic injuries. The protein may be targeted for metabolic activation through the cross-talk among many transcriptional factors and their activating ligands. Deficiency or malfunction of FABP1 has been reported in several diseases. FABP1 also influences cell proliferation during liver regeneration and may be considered as a prognostic factor for hepatic surgery. FABP1 binds and modulates the action of many molecules such as fatty acids, heme, and other metalloporphyrins. The ability to bind heme is another cytoprotective property and one that deserves closer investigation. The role of FABP1 in substrate availability and in protection from oxidative stress suggests that FABP1 plays a pivotal role during intracellular bacterial/viral infections by reducing inflammation and the adverse effects of starvation (energy deficiency).

Mechanisms of alcohol-induced hepatocellular carcinoma

Chronic alcohol abuse is a major risk factor for hepatocellular carcinoma (HCC), the third leading cause of cancer deaths worldwide. Alcohol can also function synergistically with other risk factors to cause HCC. Hence, alcohol consumption is a major factor affecting hepatic carcinogenesis in millions and the cause of a substantial public health burden. Chronic alcohol consumption interferes with several host anti-tumor mechanisms, thereby facilitating hepatocyte proliferation and tumorigenesis. This review summarizes the major mechanisms of alcohol-induced HCC. These include pathways of ethanol metabolism, alcohol-induced oxidative stress and hypomethylation of DNA, and interplay of alcohol with iron elevation, retinoid metabolism, the immune system, inflammatory pathways, and neoangiogenesis. The relevance of each pathway in affecting HCC transformation is a topic of intense investigation. Ongoing research will enhance our insight into the alcohol-induced occurrence of HCC and offer hope in developing better therapeutics.

Activation of alkylhydrazines to free radical intermediates by ethanol-inducible cytochrome P-4502E1 (CYP2E1)

Electron spin resonance (EPR) spectroscopy analysis using the spin trapping agent 4-pyridyl-1-oxide-t-butyl nitrone (4-POBN) was used to measure the formation of free radical intermediates during NADPH-dependent oxidation of 1-methyl-, 1-ethyl-, and 1-isopropylhydrazine in rat liver microsomes and in reconstituted enzyme systems. The experiments in microsomes revealed that the specific activation of the hydrazines, as measured by the EPR signal intensities, was about two-fold higher, when expressed per nmol of P-450, in microsomes from rats treated with ethanol (EtOH) as compared to membranes isolated from either phenobarbital (PB)-, beta-naphthoflavone (beta-NF)-treated or control rats. Furthermore, kinetic experiments revealed that EtOH-microsomes had an apparent affinity for 1-ethylhydrazine about one order of magnitude higher than PB-microsomes. In reconstituted vesicular systems composed of phospholipids, NADPH cytochrome P-450 reductase and P-450, the intensities of EPR signals produced by the formation of the methyl-, ethyl- and isopropyl-free radicals, were 3- to 5-fold more intense in membrane vesicles containing ethanol-inducible CYP2E1 than phenobarbital-inducible CYP2B1. By contrast, CYP1A2, CYP2B4 and CYP2C4 were inefficient catalysts of radical formation. Desferrioxamine, catalase and superoxide dismutase did not influence the extent of ethyl radicals formed in EtOH-microsomes, indicating that hydroxyl radicals are not involved in the CYP2E1-dependent activation of 1-ethylhydrazine. Addition of cytochrome b5, an efficient donor of the second electron to P-450 and hence an inhibitor of the formation of the oxy-cytochrome P-450 complex, increased to be consistent with the results, did not influence the amount of ethyl radicals trapped. In liver microsomes from untreated rats selective substrates of CYP2E1, such as diethyl-dithiocarbamate and p-nitrophenol, as well as anti-CYP2E1-IgG, inhibited the free radical formation from 1-ethylhydrazine by about 60%. The anti-CYP2E1 IgG used significantly inhibited ethyl radical production also in human liver microsomes incubated with 1-ethylhydrazine and 4-POBN. Taken together, these results indicate that CYP2E1, as compared to other rat liver cytochromes P-450, is an efficient catalyst of transformation of alkylhydrazines to free radical intermediates, a finding that might be of importance in the development of the toxicity of these compounds.