Reversal of ethanol-induced hepatic steatosis and lipid peroxidation by taurine: a study in rats

Taurine and liver diseases: a focus on the heterogeneous protective properties of taurine

Taurine (2-aminoethylsulfonic acid) has many physiological and pharmacological functions in most tissues. It is abundantly maintained in the liver by both endogenous biosynthesis and exogenous transport, but is decreased in liver diseases. In the hepatic lobule, there are heterogeneous differences in metabolism between the pericentral (PC) and periportal regions, and the distributions of the biosynthesis capacity and specific taurine transporter expression are predominantly in the PC region. In cases of depletion of hepatic taurine level, serious liver damages were observed in the PC region. Taurine has protective effects against xenobiotics-induced liver damages in the PC region, but not xenobiotics-induced PP region damages. The xenobiotics that injure the PC region are mainly catabolized by NADPH-dependent cytochrome P450 2E1 that is also predominantly expressed in the PC region. Taurine treatment seems to be a useful agent for CYP2E1-related liver diseases with predominant damages in the PC region.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Anti-lipid peroxidation effects of taurine ganbo in rats with alcoholic liver disease

AIM: To observe the protective and therapeutic effects and anti-lipid peroxidation effects of taurine ganbo in rats with alcoholic liver disease.

METHODS: A rat model of alcoholic liver disease was established by intragastric infusion of alcohol. Seventy-five male Wistar rats were randomly divided into five groups: normal control group, model group, low-dose taurine ganbo group, middle-dose taurine ganbo group, and high-dose taurine ganbo group. The model group was given dehydrated alcohol (500 mL/L) once a day for 8 weeks. The three taurine ganbo groups were treated as the model group and additionally given taurine ganbo once a day for 8 weeks. The normal control group was given equal volumes of distilled water for the same duration. After treatment, all the rats were killed. Serum alanine aminotransferase (ALT), aspartate amino transferase (AST), triglyceride (TG), total cholesterol (T-CHO), glucose (GLU), and circulating IgG against malondialdehyde-modified human serum albumin (MDA-HSA) were measured. Hepatic pathological changes were observed.

RESULTS: The levels of serum ALT, AST, TG, T-CHO, and GLU were significantly higher in the model group than in the normal control group, the middle- and high-dose taurine ganbo groups (all P < 0.0). The levels of serum ALT, AST and GLU in the low-dose taurine ganbo group were lower than those in the model group (63.67 U/L ± 6.89 U/L vs 81.53 U/L ± 22.85 U/L, 131.2 U/L ± 11.63 U/L vs 156.47 U/L ± 32.23 U/L, and 6.38 mmol/L ± 0.66 mmol/L vs 6.86 mmol/L ± 0.67 mmol/L, respectively; all P < 0.01 or 0.05). The level of circulating IgG against MDA-HSA in the model group was higher than those in the normal control group and the middle- and high-dose taurine ganbo groups (all P < 0.01). Compared to the normal control group, the model group had a much heavier lipid accumulation (P < 0.01). The hepatic pathological changes were milder in the middle- and high-dose groups than in the model group (both P < 0.05).

CONCLUSION: Taurine ganbo can attenuate alcohol-mediated increase in serum ALT, AST, TG and T-CHO levels and exert anti-lipid peroxidation effects in rats with alcoholic liver disease.

Oxidative stress in viral and alcoholic hepatitis

Liver damage ranges from acute hepatitis to hepatocellular carcinoma, through apoptosis, necrosis, inflammation, immune response, fibrosis, ischemia, altered gene expression and regeneration, all processes that involve hepatocyte, Kupffer, stellate, and endothelial cells. Reactive oxygen and nitrogen species (ROS, RNS) play a crucial role in the induction and in the progression of liver disease, independently from its etiology. They are involved in the transcription and activation of a large series of cytokines and growth factors that, in turn, can contribute to further production of ROS and RNS. The main sources of free radicals are represented by hepatocyte mitochondria and cytochrome p450 enzymes, by endotoxin-activated macrophages (Kupffer cells), and by neutrophils. The consequent alteration of cellular redox state is potentiated by the correlated decrease of antioxidant and energetic reserves. Indices of free radical-mediated damage, such as the increase of malondialdehyde, 4-hydroxynonenal, protein-adducts, peroxynitrite, nitrotyrosine, etc., and/or decrease of glutathione, vitamin E, vitamin C, selenium, etc., have been documented in patients with viral or alcoholic liver disease. These markers may contribute to the monitoring the degree of liver damage, the response to antiviral therapies and to the design of new therapeutic strategies. In fact, increasing attention is now paid to a possible "redox gene therapy." By enhancing the antioxidant ability of hepatocytes, through transgene vectors, one could counteract oxidative/nitrosative stress and, in this way, contribute to blocking the progression of liver disease.

Homocysteine and alcoholism

Chronic alcohol consumption can induce alterations in the function and morphology of most if not all brain systems and structures. However, the exact mechanism of brain damage in alcoholics remains unknown. Partial recovery of brain function with abstinence suggests that a proportion of the deficits must be functional in origin (i.e. plastic changes of nerve cells) while neuronal loss from selected brain regions indicates permanent and irreversible damage. There is growing evidence that chronic alcoholism is associated with a derangement in the sulfur amino acid metabolism. Recently, it has been shown that excitatory amino acid (EAA) neurotransmitters and homocysteine levels are elevated in patients who underwent withdrawal from alcohol. Furthermore, it has been found that homocysteine induces neuronal cell damage by stimulating NMDA receptors as well as by producing free radicals. Homocysteine neurotoxicity via overstimulation of N-methyl-D-aspartate receptors may contribute to the pathogenesis of both brain shrinkage and withdrawal seizures linked to alcoholism.