Chronic administration of ethanol with high vitamin A supplementation in a liquid diet to rats does not cause liver fibrosis. 1. Morphological observations

All trans retinoic acid modulates TNF-α and CYP2E1 pathways and enhances regression of ethanol-induced fibrosis markers in hepatocytes and HSCs in abstaining rodent model

Context: Our previous studies showed that all trans retinoic acid (ATRA) ameliorates alcohol-induced toxicity. Hence, we evaluated the efficacy of ATRA and abstention in the regression of alcohol-induced hepatotoxicity. Materials and methods: After ethanol administration to rats for 90 days, the regression of alcohol-induced toxicity was studied by supplementing ATRA at a dose of 100 μg/kg body weight for 30 days. It was also compared with animals in abstention. Results and discussion: Ethanol administration enhanced oxidative stress, activated HSCs and increased collagen deposition. All these alterations were reversed to a certain extent by ATRA supplementation. Conclusions: ATRA had better efficacy than just abstention in reducing ethanol-induced toxicity. The mechanism might be downregulation of CYP2E1, leading to reduced oxidative stress in the hepatocytes and thus impeding NFκB activation, cytokine production, activation of HSC and resulting in the reduction of inflammation and remodelling of fibrosis by modulating MMP and TIMP.

The adverse effects of alcohol on vitamin A metabolism

The objective of this review is to explore the relationship between alcohol and the metabolism of the essential micronutrient, vitamin A; as well as the impact this interaction has on alcohol-induced disease in adults. Depleted hepatic vitamin A content has been reported in human alcoholics, an observation that has been confirmed in animal models of chronic alcohol consumption. Indeed, alcohol consumption has been associated with declines in hepatic levels of retinol (vitamin A), as well as retinyl ester and retinoic acid; collectively referred to as retinoids. Through the use of animal models, the complex interplay between alcohol metabolism and vitamin A homeostasis has been studied; the reviewed research supports the notion that chronic alcohol consumption precipitates a decline in hepatic retinoid levels through increased breakdown, as well as increased export to extra-hepatic tissues. While the precise biochemical mechanisms governing alcohol's effect remain to be elucidated, its profound effect on hepatic retinoid status is irrefutable. In addition to a review of the literature related to studies on tissue retinoid levels and the metabolic interactions between alcohol and retinoids, the significance of altered hepatic retinoid metabolism in the context of alcoholic liver disease is also considered.

The effect of vitamin A on CCl4-induced hepatic injuries in rats: a histochemical, immunohistochemical and ultrastructural study

In this study, we aimed to investigate the effect of vitamin A on the transformation of the Ito cells to fibrogenic form and suppression of the development of fibrosis. Carbon tetrachloride intoxication was performed on rats for 2, 8, 12 or 20 weeks and 5x10(4) IU vitamin A (as retinol palmitate) was injected subcutaneously once every 4 weeks. Ito cells were detected by gold chloride impregnation, as well as desmin and alpha-smooth muscle actin (alpha-SMA) immunohistochemistry. Additionally, all groups were examined ultrastructurally. The number of Ito cells that were labelled positively with gold impregnation decreased in the fibrotic groups; however, alpha-SMA and desmin immunopositive Ito cells increased. The samples from animals that were treated with vitamin A showed an increase in labelling with gold impregnation but a decrease in alpha-SMA immunopositivity. The data showed that vitamin A can prevent hepatic injury, by suppressing the transformation of Ito cells to fibrogenic form. We conclude that vitamin A has potential for the treatment of hepatic fibrotic diseases. Alpha-SMA immunohistochemistry was found to be more informative than desmin immunohistochemistry for monitoring liver fibrosis.

Role of vitamin A in liver fibrosis

The relationship between vitamin A and liver fibrosis was studied with a CCl4-induced fibrosis model in rats. Depending on the time of administration, vitamin A can potentiate or reduce fibrosis: when present during CCl4-treatment parenchymal cell damage and fibrosis were enhanced, whereas vitamin A post-treatment strongly reduced fibrosis. Enhanced fibrosis was also found in rats with low hepatic retinoid levels. Administration of beta-carotene during CCl4-treatment reduced several signs of fibrosis. The notion that liver retinoids play an important role in hepatic fibrogenesis is discussed.

Beta-carotene (provitamin A) decreases the severity of CCl4-induced hepatic inflammation and fibrosis in rats

Earlier data from experiments in rats have shown that administration of retinyl esters (vitamin A) strongly influences the effects of CCl4 on the liver. The accumulation of collagen was inhibited, but an increase in CCl4-toxicity with high mortality was observed. The present study was conducted to examine the effects of beta-carotene (provitamin A) on CCl4-related general and hepatic toxicity in rats. Oral administration of beta-carotene during CCl4-treatment resulted, biochemically, in a significantly lower increase in the hydroxyproline liver content and, histopathologically, in less severe liver fibrosis as compared with the liver of rats not treated with beta-carotene. The study also showed that beta-carotene administration could prevent the long-term loss of retinoids from the CCl4-injured liver. No significant toxic effects of beta-carotene, as previously found with retinyl esters (vitamin A), were observed. This experimental study suggests that beta-carotene has the therapeutic potential to decrease the severity of liver fibrosis without marked toxicity.

Alcohol in combination with malnutrition causes increased liver fibrosis in rats

Rats were malnourished for 12 months with a highly inadequate fat-rich, calorie-sufficient but otherwise poly-deficient liquid diet composed of mashed potatoes with mayonnaise, comparable with the nutritional intake of many chronic alcoholics. When alcohol was incorporated into this diet, administered as whisky in drinking water available ad libitum, the livers of all eight rats showed increased fibrosis and cirrhosis as compared to the livers of the eight non-alcohol-treated, isocalorically fed, paired control rats. Alcohol-treated rats developed fibrosis and cirrhosis on a dietary fat content of 38% of total caloric intake and low blood alcohol levels, ranging from 50 to 126 mg/dl, due to gradual intake over the day and to low absolute intake (mean 11.9 +/- 0.6 g/kg per day). None of the rats died spontaneously. Malnutrition is likely to be an important factor in the development of the fibrosis of alcoholic liver disease, and this rat model may be used to study aspects of the pathogenesis.

Inhibition of hepatic fibrogenesis: a review of pharmacologic candidates

Therapeutic attempts with anti-fibrotic drugs are still at an experimental stage. The clinical efficacies of most agents listed in Table II have not been proved. Some potential agents, such as colchicine, analogues of PGE, gamma-interferon, inhibitors of prolyl hydroxylase, malotilate, and PUL, must be further evaluated in controlled clinical trials. In addition, almost all anti-fibrotic agents, except HOE 077, are neither liver-nor fibrosis-specific. Some site-directed (targeted) drug delivery systems, drug-loaded vesicle carrier systems, like liposomes and erythrocyte ghosts, which selectively affect the extracellular matrix-producing cells, may improve efficacy and reduce adverse effects if they can be carriers for anti-fibrotic agents. Developments in biochemistry, immunohistochemistry, and molecular biology have considerably advanced our understanding of pathogenic mechanisms of hepatic fibrosis. With the development of available pathologic and serologic markers for ongoing fibrogenesis, experimental and clinical anti-fibrotic trials have become more active. Some therapeutic strategies have chosen targets for interference in collagen metabolism. In vivo inhibition of Ito cell activation has been a focus for the anti-fibrotic studies (70). In the present review an update of pharmacologic intervention in the process of metabolic pathways of collagen, the main extracellular matrices in both interstitium and basement membrane, has been summarized. Several drugs or biochemical agents that act on different steps of collagen synthesis, crosslinking, and breakdown are listed and discussed briefly. Moreover, agents that inhibit other matrix components are also involved in the review.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of malnutrition in chronic alcoholism: role of gastric emptying

Epidemiological studies reveal that chronic alcoholics exhibiting liver disease are generally malnourished. Experimental studies unequivocally demonstrate that incidence of malnutrition cannot be avoided in animals fed liquid diets containing high concentrations of alcohol. Furthermore, ingestion of additional amounts of macronutrients by such chronically alcoholic animals prevents or regresses alcohol-induced adverse effects despite a continuous intake of high amounts of alcohol. It is thus apparent that high amounts of alcohol intake and malnutrition are necessary factors to produce adverse effects in chronic alcoholism. The mechanism by which malnutrition manifests in chronic alcoholism is, however, not clear. Recent studies have demonstrated, a) an inverse relationship between alcohol and non-alcohol energy intake and its impact on alcohol-induced effects in chronically alcoholic rats, b) a synergism between malnutrition and high doses of alcohol intake in the induction of alcoholemia, and c) that chronic alcoholemia significantly prolongs the delay in gastric emptying. Data obtained from these studies enable us to hypothesize that abnormal prolongation of gastric emptying in alcoholics with chronic alcoholemia may play a major role in the initiation of macronutrient deficiencies leading eventually to the induction of malnutrition.

Vitamin A deficiency potentiates carbon tetrachloride-induced liver fibrosis in rats

Earlier studies have shown that retinoid administration suppresses the generation of hepatic fibrosis and stimulates its regression in normal (i.e., vitamin A-sufficient) carbon tetrachloride-treated rats. This study focuses on the possible role of a marginal or deficient vitamin A status on carbon tetrachloride-induced fibrosis. This experimental study in rats shows that vitamin A status, reflected by hepatic retinoid content (retinol and retinyl esters), modulates the development of hepatic fibrosis induced by carbon tetrachloride. In rats with low hepatic retinoid levels (12 +/- 0.9 micrograms/gm liver), carbon tetrachloride-induced liver fibrosis was more pronounced than in rats with sufficient hepatic retinoid levels (1,065 +/- 327 micrograms/gm liver). Enhanced liver fibrogenesis was confirmed both morphologically and by a higher hydroxyproline content of the liver. It was associated with a reduced liver weight and the development of parenchymal regeneration nodules. Furthermore, carbon tetrachloride treatment itself reduced the hepatic retinoid content in rats independently of the liver vitamin A status before treatment and increased serum retinol levels in vitamin A-sufficient rats. The results show that the vitamin A status of the liver plays an important role in hepatic fibrogenesis. Low hepatic vitamin A levels, which can be the result not only of low dietary intake but also of interference with vitamin A metabolism by agents such as ethanol and carbon tetrachloride, may be a risk factor for the development of liver fibrosis. We suggest that retinoids modulate collagen synthesis and deposition irrespective of the degree of hepatocellular necrosis induced by carbon tetrachloride.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in hepatic collagen produced by chronic intoxication of rats with ethanol

It was decided to study the effect of chronic intoxication of rats with ethanol on collagen content in the liver, its solubility, and molecular polymorphism. It was found that treatment of rats with 10% ethanol instead of drinking water for 6 months resulted in a 50% increase of collagen content in livers of the investigated animals. Significant changes in quantitative relationships between types I, III, and V collagens were observed. Proportional amounts of type III and V collagens were higher and type I collagen was lower in comparison to those in control rat liver.

Chronic administration of ethanol with high vitamin A supplementation in a liquid diet to rats does not cause liver fibrosis. 2. Biochemical observations

The inability of the 'ethanol/high vitamin A Lieber-DeCarli diet' to induce liver fibrosis in two different rat strains was further evaluated by determining changes in parameters of liver cell damage and of retinoid and lipid metabolism. In the ethanol/vitamin A-treated group, slight but constant hepatic cell damage, as indicated by elevated alanine aminotransferase, aspartate aminotransferase and glutamate dehydrogenase activities in blood, was already observed at 6 months and maintained until the time of death at 16 months. Serum gamma-glutamyl transaminase activities were not raised. Moderate parenchymal liver cell damage was not accompanied by fibrosis. Hypertriglyceridemia or hypercholesterolemia were observed at 6-16 months of chronic alcohol administration. This response was strain dependent. In ethanol-treated rats of both strains, total liver retinoids and serum retinol concentrations were not altered. Therefore, the hypothesis that interaction between alcohol and retinoids is a major factor in the pathogenesis of alcoholic liver disease, needs to be reconsidered.