Prenatal Alcohol Exposure Affects Galactosyltransferase Activity and Glycoconjugates in the Golgi Apparatus of Fetal Rat Hepatocytes

Abstract

been clearly demonstrated in experimental animals, 4,5 in Prenatal exposure to alcohol affects the morphologiwhich important alterations in the ultrastructure of various cal, structural, and functional features of the Golgi appatissues and organs, including the liver, were found to be inratus (GA), thus altering the glycosylation process in feduced by prenatal exposure to ethanol. 6 We have previously tal hepatocytes. To elucidate the cellular mechanisms demonstrated that prenatal exposure to ethanol induces seunderlying these alterations, we have studied the effect vere morphological alterations in newborn rat hepatocytes, of alcohol exposure in utero on the activity of liver galacincluding an increase in the hepatocyte and mitochondrial tosyltransferase, an enzyme involved in the glycosylavolume, 7,8 alterations in the morphology of mitochondria 7,8 tion process, and on the hepatic glycoprotein sugar comand in the characteristics of the lateral plasma membrane of position. For this, livers from 21-day-old fetuses obtained hepatocytes, 9 a decrease in the activities of several phosphafrom control and ethanol-fed rats were used. Galactosyltransferase (GT) activity was determined in isolated GA tases known to be markers of different cell components, 10 and cis and trans fractions. Colloidal gold-labeled lectin cy-increases in the peroxisomal catalase. 11 tochemistry was used to analyze sugar residues in hepaHowever, one of the most striking changes induced by ethatocytes at the subcellular level. Finally, the integrity of nol in the developing hepatocyte is a morphological disorganithe GA after alcohol treatment was assessed by electron zation of the Golgi apparatus (GA), which is accompanied by microscopy and by evaluating the distribution of the alterations in the cytochemical properties of both the cis and Golgi b-COP, a protein involved in vesicular trafficking. trans sides of this organelle, 10,12 suggesting a functional imPrenatal alcohol exposure induces a significant increase pairment of this cell organelle. Indeed, we have shown that in both liver weight and total protein content in the prenatal ethanol exposure to alcohol induces a decrease in trans Golgi. Moreover, this treatment decreases the ac-the synthesis of proteins in the hepatocyte, as well as an tivity of galactosyltransferase, increases a-L-Fuc resi-alteration in the process of glycosylation and/or transport of dues, and reduces the number of a-Man, GlcNAc(b1,4,Gl-secretory glycoproteins, 13 processes that depend on the GA cNAc) 1,2 , GalNAca1,3GalNAc, a-GalNAc, and a-Gal integrity. It is known that the terminal glycosylation of most residues. Alcohol exposure also causes the Golgi cister-secretory proteins occurs in this cell component. The comnae to disappear in about 30% of the hepatocytes, and pleted glycoproteins are then packaged into secretory vesicles reduces 75% the number of anti-Golgi b-COP protein and sorted from the trans-Golgi network to the final destinabinding sites. Our results suggest that the decrease in tions. 14-16 Theref...

Ethanol Exposure Affects Glial Fibrillary Acidic Protein Gene Expression and Transcription During Rat Brain Development

“…In our studies, the offspring of chronic ethanol-fed mothers showed several hormonal alterations during development (Esquifino et al, 1986;Portolés et al, 1988). Using this animal model, we have reproduced in the rat (Guerri et al, 1984;Sanchis et al, 1986Sanchis et al, , 1987Guerri, 1987;Renau-Piqueras et al, 1997) many alterations observed in children with fetal alcohol syndrome (Clarren and Smith, 1978) who were born of alcoholic mothers.…”

Ethanol impairs monosaccharide uptake and glycosylation in cultured rat astrocytes

“…Previous data demonstrate that ethanol-induced changes in the glycoconjugate moieties may easily be due to alterations in the activity of glycosyltranferases and/or glycosidases including galactosyltransferase, sialyltranferase, N-acetylglucosaminyltransferase and sialidase (Guasch et al 1992;Rosenberg and Noble 1994;Renau-Piqueras et al 1997;Ghosh et al 1998;Lakshman et al 1999 II in accordance with the increase in glycoprotein binding to GNA suggesting that alcohol induces an accumulation of N-glycans of high Man and hybrid type sugar chains as well as an alteration in the synthesis of complex oligosaccharides. In fact, the inhibition of Man II results in the synthesis of glycoproteins with glucose-containing high Man structures, or various high-Man or hybrid chains (Hughes and Feeney 1986;Elbein 1991;Herscovics 1999).…”

Protein Traffic Is an Intracellular Target in Alcohol Toxicity

“…Thus, prenatal alcohol exposure has been reported to induce a striking disorganization of the GA cisternae in about 40% hepatocytes, where the cytochemical activity of several trans-GA markers, including thiamine pyrophosphatase or acid phosphatase, considerably lowered [47]. In addition, these cells displayed a significant reduction in galactosyltransferase activity [48]. Lectin cytochemistry and lectin blotting have also demonstrated that prenatal alcohol exposure results in alterations in the oligosaccharide chain composition of glycoproteins, thus inducing glycoprotein microheterogeneity [44,48].…”

“…In addition, these cells displayed a significant reduction in galactosyltransferase activity [48]. Lectin cytochemistry and lectin blotting have also demonstrated that prenatal alcohol exposure results in alterations in the oligosaccharide chain composition of glycoproteins, thus inducing glycoprotein microheterogeneity [44,48]. It is interesting to note that this effect differed in adult and neonatal rat hepatocytes, suggesting that the carbohydrate moiety of some glycoproteins in neonatal hepatocytes differs from that in adult livers [44].…”