Effects of maternal ethanol intake during pregnancy on fetal and maternal liver enzyme systems in Wistar rats

Changes in the enterocyte cytoskeleton in newborn rats exposed to ethanol in utero

BACKGROUND

Cytoskeletal changes after longterm exposure to ethanol have been described in a number of cell types in adult rat and humans. These changes can play a key part in the impairment of nutrient assimilation and postnatal growth retardation after prenatal damage of the intestinal epithelium produced by ethanol intake.

AIMS

To determine, in the newborn rat, which cytoskeletal proteins are affected by longterm ethanol exposure in utero and to what extent.

ANIMALS

The offspring of two experimental groups of female Wistar rats: ethanol treated group receiving up to 25% (w/v) of ethanol in the drinking fluid and control group receiving water as drinking fluid.

METHODS

Single and double electron microscopy immunolocalisation and label density estimation of cytoskeletal proteins on sections of proximal small intestine incubated with monoclonal antibodies against actin, alpha-tubulin, cytokeratin (polypeptides 1, 5, 6, 7, 8, 10, 11, and 18), and with a polyclonal antibody anti-beta 1,4-galactosyl transferase as trans golgi (TG) or trans golgi network (TGN) marker, or both. SDS-PAGE technique was also performed on cytoskeletal enriched fractions from small intestine. Western blotting analysis was carried out by incubation with the same antibodies used for immunolocalisation.

RESULTS

Intestinal epithelium of newborn rats from the ethanol treated group showed an overexpression of cytoskeletal polypeptides ranging from 39 to 54 kDa, affecting actin and some cytokeratins, but not tubulin. Furthermore, a cytokeratin related polypeptide of 28-29 kDa was identified together with an increase in free ubiquitin in the same group. It was noteworthy that actin and cytokeratin were abnormally located in the TG or the TGN, or both.

CONCLUSIONS

Longterm exposure to ethanol in utero causes severe dysfunction in the cytoskeleton of the developing intestinal epithelium. Actin and cytokeratins, which are involved in cytoskeleton anchoring to plasma membrane and cell adhesion, are particularly affected, showing overexpression, impaired proteolysis, and mislocalisation.

Molecular modeling studies on the urease active site and the enzyme-catalyzed urea hydrolysis

These studies are an attempt to gain better insight into the pharmacophore requirements of urease. On the basis of published information on this enzyme (EXAFS, amino acid sequence, essential groups at the active site) a hypothetical nickel-tripeptide complex, as preliminary substitute for the urease active site was modeled using computer-aided molecular modeling techniques. The results suggest two alternative docking modes of urea and reaction intermediates, corresponding to two different reaction mechanisms. Both binding modes are compatible with the docking of known potent inhibitors such as selected hydroxamic acids and phosphorodiamides. The results can be used to help in the design of new potential inhibitors of urease.