Beneficial drugs for liver diseases

Liver diseases are a major problem of worldwide proportions. However, the number of drugs actually used successfully in humans is very small. In this review some of the most promising/studied drugs utilized for liver diseases were chosen and analysed critically from the basic to the clinical point of view. Antiviral agents are not discussed because excellent reviews have appeared on this topic. The compounds/preparations described herein are, alphabetically: colchicine, corticosteroids, curcumin, glycyrrhizin, interferons (for their antifibrotic properties), Liv 52, nitric oxide, resveratrol, silymarin, sulfoadenosylmethionine, and thalidomide. Colchicine and corticosteroids have been studied extensively in animals and humans; most clinical studies suggest that these compounds are not useful in the treatment of liver diseases. Glycyrrhizin is an herbal medicine with several components that has interesting hepatoprotective properties in patients with subacute liver failure but deserves more prospective controlled trials. Interferon has shown interesting antifibrotic properties in animals and humans; prospective studies on their antifibrotic/fibrolytic activity are required. Curcumin, resveratrol and thalidomide are very attractive newly discovered protective and curative compounds on experimental hepatic diseases. Their mechanism of action is associated with the ability to down-regulate NF-kappaB and to decrease pronecrotic and profibrotic cytokines. Unfortunately, clinical studies are lacking. Sulfoadenosylmethionine and silymarin are also promising drugs utilized mainly in cholestasis but the benefits can be expanded if more controlled trials are performed. The future is to carry out controlled prospective double-blind multicenter studies with the newly discovered drugs with proven beneficial effects on animals. Fundamental hepatobiology should also be encouraged.

A method to induce manganese accumulation in the brain of the cirrhotic rat and its evaluation

Cirrhotic patients tend to accumulate manganese in their brain, especially in basal ganglia. Manganese is a well-known neurotoxic metal, however, its effect in a condition such as liver damage has not been explored deeply due to the lack of a suitable experimental model. A method to induce manganese accumulation in the brain of the cirrhotic rat is described. Cirrhosis was induced by obstruction of biliary duct and simultaneous treatment with manganese in the drinking water (0.5 or 1 mg/ml) during 4 weeks. Metal brain accumulation was low in sham-operated rats with both of the Mn concentrations used. In contrast, manganese treatment to bile obstructed rats resulted in fourfold and eightfold metal increments in the 0.5 and 1 mg/ml Mn2+ concentrations, respectively. This method is useful to induce brain manganese deposition and to study its consequences.

Hepatic basolateral plasma high-affinity Ca2+-ATPase is inhibited by nitric oxide and peroxynitrite anion

The aim of the present work was to study the effect of nitric oxide (NO) and peroxynitrite radicals on basolateral liver plasma membrane activity of high-affinity Ca2+-ATPase. Basolateral membranes were isolated by ultracentrifugation in sucrose gradients and characterized enzymatically. Basolateral membranes were incubated with S-nitroso-N-acetyl-penicillamine (SNAP, an NO donor) or 3-morpholinosydnonimine (SIN-1, a peroxynitrite donor). The liberation of NO or peroxynitrite was monitored by measuring in the medium. Calcium ATPase activity decreased by NO and peroxynitrite in a concentration-dependent manner. It is likely that both compounds inhibit ATPase activity by oxidation of thiol groups of the enzyme. Our results suggest that NO may exert part of its cytotoxic properties by inhibiting the calcium ATPase activity. Inhibition of calcium ATPase may result in Ca2+ accumulation, which in turn may be useful as an intracellular signal.

Striatal manganese accumulation induces changes in dopamine metabolism in the cirrhotic rat

Manganese (Mn) is an essential metal that, in excess, causes an extrapyramidal syndrome consisting in tremor, rigidity and akinesia. Recently, Mn was found to accumulate in brains of cirrhotic patients who also present motor abnormalities. Manganese alters dopaminergic transmission promoting an increase in the turnover of dopamine (DA). In this study, we studied the changes in dopamine and its main metabolite homovanillic acid (HVA) to evaluate DA turnover following administration of manganese to bile-duct obstructed rats. Some groups of rats were treated with manganese chloride in two concentrations: 0.5 and 1 mg/ml of Mn2+ in their drinking water. Four weeks after surgery and treatment with manganese, striatal Mn, DA and HVA were assessed. Marked increases (P<0.05) of striatal manganese content were observed in cirrhotic rats treated and untreated with manganese, these augments were dependent on the Mn concentration in water. Striatal contents of DA in cirrhotic rats diminished by 30% (P<0.05), administration of 0.5 mg/ml of manganese in drinking water to these rats returned dopamine to the basal level and 1 mg/ml of manganese increased dopamine content by 27%. The relationship of Mn content and DA turnover (HVA:DA) in the same animal showed a positive and statically significant correlation (P<0.05), with differences in slope for sham (b1=0.1528) and cirrhotic rats (b1=0.0174). These results suggest that manganese brain accumulation observed in liver failure could be a key element to understand dopamine metabolism in cirrhotic condition of humans.

Nitric oxide and inducible nitric oxide synthase expression are downregulated in acute cholestasis in the rat accompanied by liver ischemia

Hepatic blood flow decreases under cholestasis and there is evidence that NO regulates liver microvascular perfusion. Thus, the aim of the present study was to evaluate NO synthesis in cholestasis. Cholestasis was induced by bile-duct ligation (BDL) in male Wistar rats. Bilirubins and enzyme activities were measured in serum. Lipid peroxidation, GSH, GSSG and glycogen were determined in liver. Histopathological analysis was performed. Serum NO2- + NO3- concentration was measured by the Gries reaction. iNOS immunoblot analysis was carried out using an iNOS polyclonal antibody. After 7 days of BDL lipid peroxidation increased while GSH/GSSG ratio decreased. Serum NO2- + NO3- and liver iNOS protein were reduced, accompanied by ischemia as revealed by the histopathological analysis. GSH upregulates NO synthesis by increasing iNOS mRNA levels and iNOS activity, thus the reduction of GSH/GSSG ratio may be responsible for the downregulation of iNOS protein and NO synthesis, which in turn may explain the observed ischemia and the decreased hepatic blood perfusion in cholestasis reported by others.

Hepatic basolateral plasma high-affinity Ca2+-ATPase is inhibited by nitric oxide and peroxynitrite anion

The aim of the present work was to study the effect of nitric oxide (NO) and peroxynitrite radicals on basolateral liver plasma membrane activity of high-affinity Ca2+-ATPase. Basolateral membranes were isolated by ultracentrifugation in sucrose gradients and characterized enzymatically. Basolateral membranes were incubated with S-nitroso-N-acetyl-penicillamine (SNAP, an NO donor) or 3-morpholinosydnonimine (SIN-1, a peroxynitrite donor). The liberation of NO or peroxynitrite was monitored by measuring in the medium. Calcium ATPase activity decreased by NO and peroxynitrite in a concentration-dependent manner. It is likely that both compounds inhibit ATPase activity by oxidation of thiol groups of the enzyme. Our results suggest that NO may exert part of its cytotoxic properties by inhibiting the calcium ATPase activity. Inhibition of calcium ATPase may result in Ca2+ accumulation, which in turn may be useful as an intracellular signal.