Shamsuddin Khwaja

Elevated plasma levels of hyaluronic acid indicate endothelial cell dysfunction in the initial stages of alcoholic liver disease in the rat

BACKGROUND/AIMS We used the intragastric feeding rat model for alcoholic liver disease to evaluate the relationship between morphologic and functional indicators of endothelial cell dysfunction. METHODS Twelve groups of rats (4-5 rats/group) were fed the following diets: saturated fat and dextrose (SD), saturated fat and ethanol (SE), corn oil and dextrose (CD), corn oil and ethanol (CE). Four of the 12 groups were sacrificed at 2 weeks, four groups at 4 weeks and remaining four groups at 8 weeks. The following were evaluated at sacrifice: pathologic changes in the liver, endothelial cell proliferation using a monoclonal antibody to proliferating cell nuclear antigen, factor VIII-related antigen staining of endothelial cells in liver, plasma endotoxin, hyaluronan and prostaglandin F2 alpha. RESULTS Only CE rats at 4 and 8 weeks showed pathologic changes. The plasma levels of HA were significantly higher in the CE groups compared to the other groups at all time intervals studied. In the CE rats, a significant correlation was obtained between plasma endotoxin and hyaluronan (r = 0.84, p < 0.01). Endotoxin levels also correlated significantly with the number of G1/S arrested hepatic sinusoidal endothelial cell (r = 0.61, p < 0.05). A role for prostaglandin F2 alpha, in causing endothelial dysfunction, was suggested by a significant correlation between plasma hyaluronan and prostaglandin F2 alpha levels (r = 0.95, p < 0.01). Positive factor VIII related antigen staining of hepatic endothelial cells was seen in rats with high plasma hyaluronan levels. CONCLUSION We propose that endotoxin, mediating part of its effect through prostaglandin F2 alpha, plays a role in hepatic sinusoidal endothelial cell G1/S arrest. This morphologic change, associated with increased plasma hyaluronan levels, precedes capillarization in this model of alcoholic liver injury.

Plasma endothelin levels in chronic ethanol fed rats: relationship to pathologic liver injury

We used the intragastric feeding rat model for alcohol liver disease to investigate the relationship between endothelin and pathologic liver injury. Rats were fed the following diets for periods of 1, 2 and 4 weeks: corn oil plus ethanol (CE), corn oil plus dextrose (CD) and saturated fat plus ethanol (SE). Plasma endothelin levels were significantly higher in the CE group compared to the other groups at all time periods studied. The CE animals, also, developed pathologic liver injury which is in contrast to the SE and CD animals which showed no pathologic changes. We propose that endothelin, because of its powerful vasoconstrictive effects, leads to a reduction in hepatic blood flow which is important in the pathogenesis of alcoholic liver disease.

Thromboxane inhibitors attenuate pathological changes in alcoholic liver disease in the rat

BACKGROUND & AIMS Thromboxane levels correlate with severity of liver injury in rats given alcohol. The aim of this study was to evaluate the effect of thromboxane inhibitors on pathological changes in experimental alcoholic liver disease. METHODS Male Wistar rats were given a liquid diet and ethanol intragastrically for 1 month. The thromboxane inhibitors tested were a thromboxane receptor antagonist (TXRA) and a thromboxane synthase inhibitor (TXSI). Pathological changes, liver and plasma thromboxane levels, 6-ketoprostaglandin F1 alpha levels, lipid peroxidation, and messenger RNA levels for tumor necrosis factor (TNF)-alpha and transforming growth factor (TGF) beta were evaluated. RESULTS Treatment with thromboxane inhibitors prevented necrosis and inflammation. In the TXSI-treated group, fatty liver was also decreased. Ethanol administration led to a 3-4-fold increase in liver thromboxane levels; a reduction in thromboxane levels and lipid peroxidation was seen in the TXSI group. In all treatment groups, TNF-alpha and TGF-beta messenger RNA levels were decreased. CONCLUSIONS The prevention of necroinflammatory changes in thromboxane-treated groups is related to a decrease in TNF-alpha levels. Inhibition of TGF-beta expression may also prevent fibrosis in ethanol-treated rats.

Decreased prostacyclin production by liver non-parenchymal cells precedes liver injury in experimental alcoholic liver disease

We used the intragastric feeding rat model for alcoholic liver disease to investigate the relationship between prostacyclin and liver injury. Rats were fed the following diets for periods ranging from 1 to 8 weeks: corn oil plus ethanol (CO+E), corn oil plus dextrose (CO+D), saturated fat plus ethanol (SF+E) and saturated fat plus dextrose (SF+D). Prostacyclin production (assessed by 6-ketoprostaglandin F1 alpha) by liver non-parenchymal cells decreased steadily over the 8 week period in animals fed CO+E (liver injury present) whereas in animals fed SF+E (no liver injury) there was no change in prostacyclin production. Plasma levels of 6-ketoprostaglandin F1 alpha were also significantly lower in the CO+E group compared to the other groups studied. We propose that decreased prostacyclin production by liver non-parenchymal cells may contribute to the hepatotoxic effect of ethanol.

Eicosanoid production in experimental alcoholic liver disease is related to vitamin E levels and lipid peroxidation

We investigated the association between vitamin E, lipid peroxidation and eicosanoid production in experimental alcoholic liver injury. We used the intragastric feeding rat model in which animals were fed corn oil and ethanol (CO+E) and corn oil and dextrose (CO+D) for 2 and 4 week periods. At sacrifice, we measured plasma levels of alpha-tocopherol, 8-isoprostane, thromboxane B2(TXB2) and 6-ketoprostaglandin F1α(6-KetoPGF1α). Animals fed CO+E had significantly lower concentrations of α-tocopherol and higher concentrations of 8 isoprostane at both 2 and 4 weeks. a significant inverse correlation was seen between α-tocopherol concentrations and the TXB2: PGF1α ratio (r=0.72, p<0.01). A positive correlation was seen between the TXB2: PGF1α ratio and 8 isoprostane levels (r=0.84, p<0.001). These results suggest that vitamin E depletion and enhanced lipid peroxidation may affect eicosanoid metabolism in experimental alcoholic liver disease in such a way so as to increase the thromboxane to prostacyclin ration.