Effect of acute ethanol exposure on cultured fetal rat hepatocytes: relation to mitochondrial function

Cellular Bioenergetics: Experimental Evidence for Alcohol-induced Adaptations

At-risk alcohol use is associated with multisystemic effects and end-organ injury, and significantly contributes to global health burden. Several alcohol-mediated mechanisms have been identified, with bioenergetic maladaptation gaining credence as an underlying pathophysiological mechanism contributing to cellular injury. This evidence-based review focuses on the current knowledge of alcohol-induced bioenergetic adaptations in metabolically active tissues: liver, cardiac and skeletal muscle, pancreas, and brain. Alcohol metabolism itself significantly interferes with bioenergetic pathways in tissues, particularly the liver. Alcohol decreases states of respiration in the electron transport chain, and activity and expression of respiratory complexes, with a net effect to decrease ATP content. In addition, alcohol dysregulates major metabolic pathways, including glycolysis, the tricarboxylic acid cycle, and fatty acid oxidation. These bioenergetic alterations are influenced by alcohol-mediated changes in mitochondrial morphology, biogenesis, and dynamics. The review highlights similarities and differences in bioenergetic adaptations according to tissue type, pattern of (acute vs. chronic) alcohol use, and energy substrate availability. The compromised bioenergetics synergizes with other critical pathophysiological mechanisms, including increased oxidative stress and accelerates cellular dysfunction, promoting senescence, programmed cell death, and end-organ injury.

Fetal alcohol spectrum disorders model alters the functionality of glutamatergic neurotransmission in adult zebrafish

Fetal alcohol spectrum disorders (FASD) describe a wide range of ethanol-induced developmental disabilities, including craniofacial dysmorphology, and neurochemical and behavioral impairments. Zebrafish has become a popular animal model to evaluate the long-lasting effects of, both, severe and milder forms of FASD, including alterations to neurotransmission. Glutamate is one of the most affected neurotransmitter systems in ethanol-induced developmental disabilities. Therefore, the aim of the present study was to evaluate the functionality of the glutamatergic neurotransmitter system in an adult zebrafish FASD model. Zebrafish larvae (24 h post-fertilization) were exposed to ethanol (0.1 %, 0.25 %, 0.5 %, and 1%) for 2 h. After 4 months, the animals were euthanized and their brains were removed. The following variables were measured: glutamate uptake, glutamate binding, glutamine synthetase activity, Na+/K + ATPase activity, and high-resolution respirometry. Embryonic ethanol exposure reduced Na+-dependent glutamate uptake in the zebrafish brain. This reduction was positively modulated by ceftriaxone treatment, a beta-lactam antibiotic that promotes the expression of the glutamate transporter EAAT2. Moreover, the 0.5 % and 1% ethanol groups demonstrated reduced glutamate binding to brain membranes and decreased Na+/K + ATPase activity in adulthood. In addition, ethanol reduced glutamine synthetase activity in the 1% EtOH group. Embryonic ethanol exposure did not alter the immunocontent of the glutamate vesicular transporter VGLUT2 and the mitochondrial energetic metabolism of the brain in adulthood. Our results suggest that embryonic ethanol exposure may cause significant alterations in glutamatergic neurotransmission in the adult zebrafish brain.

Fetal Cerebral Artery Mitochondrion as Target of Prenatal Alcohol Exposure

Prenatal alcohol exposure results in an array of developmental abnormalities known as fetal alcohol spectrum disorders (FASDs). Despite the high prevalence of FASDs, therapeutic interventions against accidental or intended exposure of developing fetuses to alcohol are limited. This review outlines current knowledge about mitochondria in cerebral blood vessels as a potential target for anti-FASDs intervention. First, it describes the multifaceted role of mitochondria in maintaining the cerebral artery diameter as shown in adult tissue. Second, current literature on alcohol-driven damage of mitochondrial morphology and function in several fetal tissues, including liver, heart, and brain is summarized. The functional consequences of alcohol exposure in these organs include morphological enlargement of mitochondria, increased oxidative stress, and alteration of cellular respiration. These studies point to a tissue-specific effect of alcohol on mitochondrial function and a particular vulnerability of fetal mitochondria to alcohol exposure when compared to adult counterparts. Third, recent work from our group describing persistent changes in fetal baboon cerebral artery proteome following three episodes of prenatal alcohol exposure is reviewed. In conclusion, the consequences of prenatal alcohol exposure on cerebral artery mitochondria constitute an open field of investigation and, eventually, a point of therapeutic intervention against FASDs.

Alcohol Teratogenesis: Mechanisms of Damage and Strategies for Intervention

There are multiple mechanisms by which alcohol can damage the developing brain, but the type of damage induced will depend on the amount and developmental timing of exposure, along with other maternal and genetic factors. This article reviews current perspectives on how ethanol can produce neuroteratogenic effects by its interactions with molecular regulators of brain development. The current evidence suggests that alcohol produces many of its damaging effects by exerting specific actions on molecules that regulate key developmental processes (e.g., L1 cell adhesion molecule, alcohol dehydrogenase, catalase), interfering with the early development of midline serotonergic neurons and disrupting their regulatory-signaling function for other target brain structures, interfering with trophic factors that regulate neurogenesis and cell survival, or inducing excessive cell death via oxidative stress or activation of caspase-3 proteases. The current understanding of pathogenesis mechanisms suggests several strategic approaches to develop rational molecular prevention. However, the development of behavioral and biologic treatments for alcohol-affected children is crucial because it is unlikely that effective delivery of preventative interventions can realistically be achieved in ways to prevent prenatal damage in at-risk pregnancies. Toward that end, behavioral training that promotes experience-dependent neuroplasticity has been effective in a rat model of cerebellar damage induced by alcohol exposure during the period of brain development that is comparable to that of the human third trimester.

Iron-mediated effect of alcohol on hepatocyte differentiation in HepaRG cells

The development of alcoholic liver diseases depends on the ability of hepatocyte to proliferate and differentiate in the case of alcohol-induced injury. Our previous work showed an inhibitory effect of alcohol on hepatocyte proliferation. However, the effect of alcohol on hepatocyte differentiation has not yet been precisely characterized. In the present study, we evaluated the effect of alcohol on hepatocyte differentiation in relationship with changes of iron metabolism in HepaRG cells. This unique bipotent human cell line can differentiate into hepatocytes and biliary epithelial cells, paralleling liver development. Results showed that alcohol reduced cell viability, total protein level and enhanced hepatic enzymes leakage in differentiated HepaRG cells. Moreover, it caused cell enlargement, decreased number of hepatocyte and expression of C/EBPα as well as bile canaliculi F-actin. Alcohol increased expression of hepatic cell-specific markers and alcohol-metabolizing enzymes (ADH2, CYP2E1). This was associated with a lipid peroxidation and an iron excess expressed by an increase in total iron content, ferritin level, iron uptake as well as an overexpression of genes involved in iron transport and storage. Alcohol-induced hepatoxicity was amplified by exogenous iron via exceeding iron overload. Taken together, our data demonstrate that in differentiated hepatocytes, alcohol reduces proliferation while increasing expression of hepatic cell-specific markers. Moreover, iron overload could be one of the underlying mechanisms of effect of alcohol on the whole differentiation process of hepatocytes.

Sulforaphane inhibits mitochondrial permeability transition and oxidative stress

Exposure of mitochondria to oxidative stress and elevated Ca(2+) promotes opening of the mitochondrial permeability transition pore (PTP), resulting in membrane depolarization, uncoupling of oxidative phosphorylation, and potentially cell death. This study tested the hypothesis that treatment of rats with sulforaphane (SFP), an activator of the Nrf2 pathway of antioxidant gene expression, increases the resistance of liver mitochondria to redox-regulated PTP opening and elevates mitochondrial levels of antioxidants. Rats were injected with SFP or drug vehicle and liver mitochondria were isolated 40h later. Respiring mitochondria actively accumulated added Ca(2+), which was then released through PTP opening induced by agents that either cause an oxidized shift in the mitochondrial redox state or directly oxidize protein thiol groups. SFP treatment of rats inhibited the rate of pro-oxidant-induced mitochondrial Ca(2+) release and increased expression of the glutathione peroxidase/reductase system, thioredoxin, and malic enzyme. These results are the first to demonstrate that SFP treatment of animals increases liver mitochondrial antioxidant defenses and inhibits redox-sensitive PTP opening. This novel form of preconditioning could protect against a variety of pathologies that include oxidative stress and mitochondrial dysfunction in their etiologies.

Genetic influence on dysmorphogenesis in embryos from different rat strains exposed to ethanol in vivo and in vitro

BACKGROUND

The aim was to investigate the susceptibility of embryos from 2 rat strains (U and H) to a 48 hours ethanol exposure in early pregnancy, both in vivo and in vitro.

METHODS

The embryos were studied on gestational days 9 to 11. We used 1 ethanol dose in vivo (6 g/kg x 2), 3 different ethanol concentrations in vitro (88 mM, 132 mM, 176 mM) and also attempted to diminish the teratogenic effect in vitro by supplying the antioxidant N-acetylcysteine (NAC, 0.5 mM) to the culture medium.

RESULTS

The U embryos were more damaged by ethanol than the H embryos, both in vivo and in vitro. NAC addition diminished, but failed to completely normalize, the embryonic maldevelopment. Ethanol increased the Bax/Bcl-2 ratio in the U embryos both in vivo and in vitro, but not in the H embryos. Furthermore, ethanol caused increased Caspase-3 immunostaining in U embryos, but not in H embryos. Ethanol exposure in vivo did not alter CuZnSOD and MnSOD mRNA levels in U and H embryos. In vitro, however, the ethanol-exposed U embryos increased their CuZnSOD and MnSOD mRNA levels, whereas the CuZnSOD mRNA was unchanged and MnSOD mRNA decreased in the H embryos, in neither strain did NAC exert any effect. The U embryos increased catalase gene expression in response to ethanol in vivo, but decreased catalase mRNA levels in vitro, changes normalized by NAC. The H embryos did not alter catalase mRNA levels in vivo, but increased gene expression in vitro, with no NAC effect. Ethanol affected the gene expression of the other ROS scavenging enzymes and the developmental genes studied - Bmp-4, Ret, Shh, Pax-6 - similarly in the 2 strains.

CONCLUSIONS

The findings support a role for genetic predisposition, oxidative stress, and apoptosis in ethanol teratogenicity, and suggest that the teratogenic predisposition of the more susceptible U rats may reside, at least in part, in the regulation of the ROS scavenging enzymes in the U embryos.

In Vivo Dysfunction of the Term Alveolar Macrophage After in Utero Ethanol Exposure

BACKGROUND

The effects of in utero alcohol exposure on the immune function of the newborn remain under investigation. Fetal ethanol (ETOH) exposure increases oxidative stress in the developing lung, in part due to decreased availability of the antioxidant glutathione (GSH). We have previously shown that in utero ETOH impairs alveolar macrophage phagocytosis and viability in the premature pup, while maintaining GSH availability with maternal supplementation of S-adenosyl-methionine (SAM) during ETOH ingestion improves macrophage function and viability. We hypothesized that dysfunction of the neonatal alveolar macrophage exposed to ETOH in utero would persist at term gestation.

METHODS

Using a guinea-pig model of fetal ETOH exposure, timed-pregnant guinea-pigs were pair-fed ETOH+/-the GSH precursor SAM and the diet continued until spontaneous delivery. Term alveolar macrophages were evaluated using fluorescent microscopy for phagocytosis and apoptosis after in vitro incubation with Staphalococcus aureus. Using an in vivo model of intranasal Staph. aureus inoculation, the in vivo function of the term alveolar macrophage was also investigated using confocal fluorescent analysis.

RESULTS

In utero ETOH exposure increased oxidant stress in the alveolar macrophage and decreased phagocytosis and viability in vitro and in vivo. Confocal analysis of phagocytosis in vivo demonstrated a marked impairment of internalization of the bacteria by the ETOH-exposed alveolar macrophage. The addition of SAM during maternal ETOH ingestion prevented loss of alveolar macrophage function and viability in vitro and in vivo.

CONCLUSIONS

In utero ETOH exposure impairs alveolar macrophage function and viability in vitro and in vivo even at term gestation. The ETOH-induced changes in macrophage function and viability can be ablated with maternal SAM supplementation. Further investigations are required to identify the mechanisms of ETOH-induced derangement of phagocytosis in the neonatal alveolar macrophage and the clinical ramifications of altered immune function after in utero alcohol exposure for the newborn.

Ethanol-Induced Fetal Dysmorphogenesis in the Mouse Is Diminished by High Antioxidative Capacity of the Mother

Intrauterine exposure to ethanol causes embryonic and fetal maldevelopment. Oxidative stress in mother and offspring has been suggested to be part of the teratogenic mechanism of ethanol. Here we aimed to assess the importance of maternal and fetal antioxidative capability for the risk of dysmorphogenesis in the offspring. We used male and female mice with different levels of superoxide dismutase (SOD) activity-wild-type (WT) mice, mice with a targeted SOD mutation (KO, decreased CuZnSOD mRNA), and mice transgenic for SOD (TG, increased CuZnSOD mRNA). Female WT, KO (heterozygous), and TG (heterozygous) mice were given drinking water containing 20% ethanol before and throughout gestation. Non-ethanol-exposed WT, KO, and TG mice served as controls. The female mice were mated with males with identical genotype, and the pregnancy was interrupted on gestational day 18 when the offspring was evaluated and genotyped. Fetal hepatic isoprostane (8-epi-PGF(2alpha)) levels were measured to assess the degree of fetal oxidative stress. Exposure to 20% ethanol decreased fetal weight by 9-13% in the three groups. Ethanol exposure roughly doubled the rates of maldeveloped WT and KO offspring but did not affect TG offspring. The fetal hepatic levels of 8-epi-PGF(2alpha) were increased in the ethanol-exposed WT and KO mice but not in ethanol-exposed TG mice. Ethanol exposure preferentially damaged WT fetuses in pregnant KO mice, whereas no such effect was found in the litters of ethanol-consuming TG mice. Administration of ethanol to pregnant mice disturbs embryogenesis by oxidative stress, and the adverse effects are more pronounced in offspring of mice with low antioxidative capacity.

Ethanol feeding enhances age-related deterioration of the rat hepatic mitochondrion

Chronic ethanol feeding damages the hepatic mitochondrion by increasing mitochondrial DNA (mtDNA) oxidation, lowering mtDNA yields and impairing mitochondrial respiration. These effects are also seen during aging. By employing a 21-day chronic feeding regimen, we investigated the effects of ethanol consumption on mtDNA content and mitochondrial respiration in 2-, 12-, and 24-mo-old male rats. Aging resulted in decreased mtDNA content, increased mtDNA damage (as indicated by inhibition of Taq polymerase progression), and a decline in state 3 respiration; effects that were further exacerbated by ethanol feeding. Additionally, ethanol consumption caused an increase in the levels of citrate synthase while not impacting mitochondrial protein content. In conclusion, ethanol and aging combine to cause deterioration in the structural and functional integrity of the hepatic mitochondrion. The additive effects of aging and ethanol feeding may have serious consequences for hepatic energy metabolism in aged animals, and their detrimental combination may serve as one of the molecular mechanisms underlying the progression of alcoholic liver disease.

Fetal alcohol exposure impairs alveolar macrophage function via decreased glutathione availability

Immature function of the alveolar macrophage increases the risk of pulmonary infections in premature newborns. In utero alcohol increases fetal systemic oxidative stress. Because the premature lung is deficient in glutathione (GSH), we hypothesized that chronic in utero alcohol (ethanol) exposure exacerbates the oxidative stress within the developing lung, thereby impairing alveolar macrophage function. Additionally, we evaluated the effects of in vivo and in vitro GSH availability on ethanol-exposed macrophage function. Using a guinea pig model of chronic in utero ethanol exposure, fetal epithelial lining fluid (ELF) and alveolar macrophage GSH were decreased with increased markers of oxidative stress. Ethanol-exposed macrophage exhibited impaired phagocytosis and increased apoptosis compared with gestational control. When the GSH precursor S-adenosyl-methionine (SAM) was added to the maternal drinking water containing ethanol, fetal ELF and macrophage GSH were maintained and ELF oxidative stress diminished. In vivo maternal SAM therapy maintained macrophage phagocytosis and decreased apoptosis. In vitro GSH supplements also improved phagocytosis and viability in both premature and ethanol-exposed macrophage. This suggested that in utero ethanol impaired premature macrophage function and viability via decreased GSH availability. Furthermore, GSH supplementation during and after ethanol exposure improved fetal macrophage function and viability. These results add a new dimension to the detrimental effects of fetal alcohol exposure on the developing alveolar macrophage, raising the possibility of GSH therapy to augment premature alveolar macrophage function.

Effect of a single dose of ethanol on developing skeletal muscle of chick embryos

Fetal alcohol syndrome is a condition occurring in some children of mothers who have consumed alcohol during pregnancy. Many of these affected children show retarded physical growth in the postnatal period despite adequate nutrition. On the basis of findings from studies with animals, it has been proposed that this is due to allometric retardation of growth of skeletal muscle, although the exact reasons for this are not known. The aim of the current study was to examine the structural changes in skeletal muscle in fetal alcohol syndrome in an attempt to understand the mechanisms of growth retardation in fetal alcohol syndrome. Chick embryos were exposed to single doses of 5%, 10%, and 15% ethanol, and the effects on the general growth and development, as well as on the skeletal muscle, of these chicks were studied. There was a significant retardation in crown rump length, head circumference, and body weight in ethanol-exposed chicks when these parameters were compared with findings for appropriate control groups. This retardation was associated with significant and proportionate reductions in the weights of skeletal muscles. Microscopic examination of skeletal muscle showed areas of neutrophil infiltration and necrosis, suggestive of muscle damage, in chicks exposed to 10% and 15% ethanol. Thus, findings of the current study demonstrate the direct toxic effects of a single dose of ethanol on developing embryos in general and skeletal muscle in particular. The pathologic changes seen in skeletal muscle could account for the failure in postnatal growth in fetal alcohol syndrome.

Ethanol differentially modulates the expression and activity of cell cycle regulatory proteins in rat aortic smooth muscle cells

The aim of this study was to determine the effect of ethanol on cell cycle events during the G(1) and S phases in cultured vascular smooth muscle cells (VSMC). Flow cytometric analysis for the DNA content in rat aortic VSMC indicated that following ethanol treatment, the cell population in the G(0)/G(1) phase increased; 57.8+/-1.6% vs. 72.3+/-1.2%, concomitant with a decrease in cells in the S phase; 12.7+/-1.4% vs. 3.67+/-0.6%, for control vs. ethanol, respectively. Western blot analysis on VSMC lysates demonstrated that ethanol (10-160 mmol/l) dose-dependently inhibited serum-induced retinoblastoma (pRb) hyperphosphorylation. While having no effect on Cdk2 protein expression, ethanol dose-dependently decreased (IC(50) approximately 60 mmol/l) Cdk2 activity, assessed by histone H1 phosphorylation. Furthermore, ethanol induced the expression of the cyclin-dependent kinase (Cdk) inhibitor p21(waf1/cip1), and inhibited the induction of cyclin A. These data demonstrate that modulation of the expression and activity of key cell cycle regulatory molecules may be a mechanism by which ethanol inhibits VSMC proliferation. These actions of ethanol may be relevant to its cardiovascular protective effect in vivo.

Fetoprotectivity of the flavanolignan compound siliphos against ethanol-induced toxicity

Of the three flavanolignans that are found in silymarin (Silybum marianum [L.] Gaertn.), silybin is thought to be the primary therapeutic constituent. To test the capacity of silybin to protect the rat fetus from toxic effects of maternally ingested EtOH we did the following: Adult female rats were assigned to one of four groups; EtOH, EtOH/silybin, pair-fed control, and chow fed control. Silybin was orally administered as Siliphos(R), which is one part silybin to two parts phosphatidylcholine. All groups except the chow-fed control were maintained on a liquid diet throughout pregnancy. On day 21 of pregnancy the rats were killed and the fetuses removed. Gamma glutamyl transpeptidase (GGTP) activity and glutathione (GSH) levels were determined for liver and brain tissue for both the fetuses and the dams. Maternal and fetal GGTP activity in the EtOH rats was significantly higher than that of pair-fed controls, whereas the GGTP activity observed in the Siliphos(R)/EtOH rats was not elevated. Fetal mortality rates in the EtOH rats significantly exceeded those of all three other groups.

Formation of malondialdehyde adducts in livers of rats exposed to ethanol: role in ethanol-mediated inhibition of cytochrome c oxidase

BACKGROUND

Previous studies in our laboratory demonstrated that short-term ethanol consumption by maternal rats increased the hepatic levels of 4-hydroxynonenal (HNE) in both the adult and the fetus. Additionally, HNE inhibited cytochrome c oxidase (COX) by forming adducts with the enzyme subunits. The present study examined modification of COX by another major aldehydic lipid peroxidation product, malondialdehyde (MDA), and its role in COX inhibition by ethanol.

METHODS AND RESULTS

It is demonstrated in vitro that MDA inhibits the activity of purified COX while forming adducts with the enzyme. Compared with HNE, MDA is a more potent inhibitor of COX. Overnight incubation at room temperature caused an 80% decrease in COX activity by MDA versus a 67% decrease by HNE. MDA produced marked inhibition of COX activity at physiologically relevant concentrations, e.g., 43% inhibition at 10 microM. Although our previous studies documented that HNE formed adducts primarily with subunit IV of COX via histidine residues, the current report showed that MDA forms adducts with both subunit IV and subunit V via lysine residues. Furthermore, both aldehydes induce carbonyl formation in subunit IV. The in vivo role of MDA in the impairment of COX by ethanol is assessed in both adult and fetal liver after maternal ethanol consumption.

CONCLUSIONS

The results showed that: (1) there are significant increases in MDA levels in liver homogenate as well as mitochondria in both adult and fetal livers after ethanol exposure; (2) these MDA levels are in the nanomole/mg protein range, in contrast to picomole/mg protein range of HNE in identical setting; and (3) ethanol-induced production of MDA is accompanied by enhanced formation of MDA adducts with COX. These findings suggest that MDA may play at least as equally an important role as HNE in ethanol-induced inhibition of COX.

Ethanol potentiates tumor necrosis factor-alpha cytotoxicity in hepatoma cells and primary rat hepatocytes by promoting induction of the mitochondrial permeability transition

In the present study, tumor necrosis factor-alpha (TNF-alpha) cytotoxicity is shown to be potentiated by ethanol exposure in vitro in the human hepatoma cell line, HepG2, and in rat primary hepatocytes. Exposure of HepG2 cells and primary hepatocytes for 48 hours to concentrations of ethanol ranging between 50 and 100 mmol/L significantly increased TNF-alpha cytotoxicity compared with cells treated with TNF-alpha alone. The cell killing was associated with, and dependent on, the development of the mitochondrial permeability transition (MPT). Two inhibitors of MPT pore opening, cyclosporin A and bongkrekic acid, prevented TNF-alpha cytotoxicity in the presence of ethanol. In addition to inhibiting cell death caused by TNF-alpha, blockade of MPT pore opening prevented mitochondrial depolarization, cytochrome c redistribution from the mitochondria to the cytosol, caspase 3 activation, and oligonucleosomal DNA fragmentation. Unlike the potentiation of TNF-alpha cytotoxicity by the translational inhibitor cycloheximide, ethanol promoted TNF-alpha-induced cell killing by a mechanism that was independent of caspase-8 activity. HepG2 cells overexpressing cytochrome-P4502E1 were even more sensitized by ethanol to induction of the MPT by TNF-alpha and the resultant cytotoxicity than wild-type HepG2 cells. In addition, primary hepatocytes isolated from chronically ethanol-fed rats showed enhanced susceptibility to TNF-alpha cytotoxicity compared with their isocalorically matched controls. Again as with the HepG2 cells, inhibiting MPT pore opening prevented the cytotoxicity of TNF-alpha in the primary hepatocytes isolated from ethanol-fed animals.

Formation of 4-hydroxynonenal adducts with cytochrome c oxidase in rats following short-term ethanol intake

This study addresses the role of the lipid peroxidation product, 4-hydroxynonenal (HNE), in ethanol-related damage of cytochrome c oxidase (COX) in vivo. It utilizes an animal model with acute ethanol exposure in which HNE levels in liver mitochondria are strikingly increased. Pregnant female Sprague-Dawley rats were administered 5 doses of ethanol (4 gm/kg, po at 12-hour intervals) beginning on day 17 of gestation and were sacrificed on day 19. Controls were pair-fed and received dextrose isocaloric to ethanol. Mitochondria were isolated from maternal and fetal livers and COX activities were measured spectrophotometrically. Compared with the pair-fed controls, COX activity was decreased with exposure to ethanol by 25% in maternal rats and 43% in fetal rats (P<.05). Western Blot with an HNE-Histidine antibody showed enhanced formation of HNE adducts with COX from ethanol-exposed rats, which was more pronounced in fetal than in adult livers. The HNE adducts were mainly with subunit IV of COX. The cause and effect relationship between HNE adduct formation and COX inhibition was examined in vitro by incubating purified COX with HNE. COX inhibition was accompanied by concentration-dependent HNE adduct formation that was consistent with those found in in vivo ethanol-exposed samples. These results suggest that the ethanol-related decreases in COX activity found in liver mitochondria could be attributable to HNE adduct formation with the enzyme complex. This could be an important mechanism by which modification of proteins occur in in vivo oxidative stress.

Cytotoxicity of short-chain alcohols

Ethanol and other short-chain alcohols elicit a number of cellular responses that are potentially cytotoxic and, to some extent, independent of cell type. Aberrations in phospholipid and fatty acid metabolism, changes in the cellular redox state, disruptions of the energy state, and increased production of reactive oxygen metabolites have been implicated in cellular damage resulting from acute or chronic exposure to short-chain alcohols. Resulting disruptions of intracellular signaling cascades through interference with the synthesis of phosphatidic acid, decreases in phosphorylation potential and lipid peroxidation are mechanisms by which solvent alcohols can affect the rate of cell proliferation and, consequently, cell number. Nonoxidative metabolism of short-chain alcohols, including phospholipase D-mediated synthesis of alcohol phospholipids, and the synthesis of fatty acid alcohol esters are additional mechanisms by which alcohols can affect membrane structure and compromise cell function.

Protective effects of the flavonoid mixture, silymarin, on fetal rat brain and liver

We investigated the possibility that the flavonoid mixture, silymarin (SY), administered as the compound Silymarin Phytosome (PHYTO), could protect the fetus from maternally ingested EtOH. Seventy-six female rats were randomly assigned to one of seven groups: pair-fed control; chow fed control; EtOH; and four groups receiving EtOH and PHYTO in varying dosages. All groups except the chow-fed control were maintained on a liquid diet. On day 1 of pregnancy the dams began the treatment protocol. On day 21 of pregnancy the rats were sacrificed and the fetuses removed. Gamma glutamyl transpeptidase (GGTP) activity was determined for liver and brain tissue from both the fetuses and the dams. GGTP activity in the EtOH/silymarin treatment groups did not differ significantly from that observed for the pair-fed control group. The observed GGTP activity levels for the EtOH-only group were significantly higher than those attained by the pair-fed control group. Although GGTP activity did not vary significantly with the quantity of PHYTO administered, as PHYTO dose was increased, GGTP activity decreased.

An ethanol-sensitive variant of the PC12 neuronal cell line: sensitivity to alcohol is associated with increased cell adhesion and decreased glucose accumulation

A stable variant of the PC12 cell line (PC12.4) has been isolated on the basis of its cell adhesive properties and morphological characteristics. Cells from the PC12.4 subline differ from the parental cell line in that they readily adhere to untreated plastic surfaces and grow individually rather than aggregated in large clusters. When compared to the PC12.1 cell line (original phenotype), PC12.4 cells were found to have a more rapid growth rate (24 h vs. 40 h doubling time) and higher production of lactate but lower glucose metabolism as judged by the accumulation of 3H-2-deoxyglucose. Western blot analyses also revealed differences between PC12.1 and PC12.4 cells with respect to the expression of glucose transporters (GLUTs) and the subcellular distribution of the heat shock protein (Hsp) Hsp60. We have reported here that PC12.4 cells were far more sensitive to growth inhibition by ethanol when compared with PC12.1 cells and appeared to be more dependent upon glutamine and serum for cell growth. The cytostatic effects of ethanol were most pronounced when the cells were cultured in medium with low concentrations of serum and glutamine. Thus, there appears to be an interplay between energy metabolism in the cell and the response to ethanol.

Antioxidant transport by the human placenta

We investigated the transfer of three antioxidants - melatonin, S-adenosyl methionine (SAM) and various forms of vitamin E - across the term, normal human placenta. The transport technique involved the single, isolated placental cotyledon system in vitro. Melatonin crossed the placental rapidly, equally to the freely diffusible marker, antipyrine. There was no biotransformation of the agent. SAM was transferred slowly, similarly to passively transported L-glucose as a marker. There was a breakdown of SAM to at least one other derivative; the process appeared to be nonenzymatic. Vitamin E was transferred slowly, at a rate only 10% of L-glucose. The natural RRR (nonracemic) form of vitamin E was transported best. Free vitamin, rather than the acetate seems to be transferred best, a finding that will require further study.

Inhibition of cytochrome c oxidase activity by 4-hydroxynonenal (HNE). Role of HNE adduct formation with the enzyme subunits

The role of 4-hydroxynonenal (HNE), a major lipid peroxidation product, in oxidative damage to mitochondrial cytochrome c oxidase (COX) was examined. Oxidative stress was induced in mitochondria isolated from livers of male Sprague-Dawley rats by tert-butylhydroperoxide (t-BHP). COX activity was inhibited, with a concomitant increase in endogenous HNE level in mitochondria. COX activity was also inhibited following incubation of mitochondria with 50-450 microM HNE. Blocking HNE degradation intensified COX inhibition by HNE and by t-BHP-induced oxidative stress, the latter accompanied by a simultaneous increase in endogenous HNE production. On the other hand, COX inhibition by HNE was markedly reduced by potentiating HNE degradation via enhancing conjugation of HNE with reduced glutathione (GSH). Incubation of purified COX with 10-400 microM HNE resulted in HNE adduct formation with specific subunits of COX, correlated with inhibition of the enzyme activity. These data suggest that HNE may inhibit mitochondrial COX by forming adducts with the enzyme, and that this could be one mechanism underlying mitochondrial damage caused by oxidative stress. The findings also illustrate a role for GSH in protecting mitochondria from the deleterious effects of HNE.

Prenatal exposure to ethanol in rats: effects on liver energy level and antioxidant status in mothers, fetuses, and newborns

The fetal alcohol syndrome is a clinical condition that affects newborns from alcoholic mothers. It is not clear, however, whether ethanol consumption during gestation can affect liver functions of fetuses and newborns. In this study, we aimed to assess the effects of ethanol administration on body weight, liver energy level, and antioxidant status of mothers, fetuses, and newborns. Pregnant rats were exposed to ethanol during the third week of gestation. Body weight, survival, and liver concentration of gluthatione (GSH) and adenosintriphosphate (ATP) were measured. No differences were observed in body weight or in liver ATP and GSH between mothers exposed to ethanol and control animals. Conversely, fetuses from rats exposed to ethanol showed a marked decrease in GSH, ATP, and body weight when compared to those from control rats. Newborns exposed prenatally to ethanol were no different from those born to control mothers. This study suggests that an amount of ethanol that is not sufficient to determine a significant effect on mothers can, nevertheless, cause a marked decrease in growth and in liver antioxidant and energy status in fetuses. These parameters, however, return to control value one week after ethanol discontinuation.

Comparative study of the damage produced by acute ethanol and acetaldehyde treatment in a human fetal hepatic cell line

The effects of acute ethanol and acetaldehyde treatment on cell proliferation, cell adhesion capacity, neutral red incorporation into lysosomes, glutathione content, protein sulfhydryl compounds, lipid peroxidation, inner mitochondrial membrane integrity (MTT test), lactate dehydrogenase activity (LDH) and ultrastructural alterations were investigated in a human fetal hepatic cell line (WRL-68 cells). WRL-68 cells were used, due to the fact that, although this cell line expresses some hepatic characteristics, it does not express alcohol dehydrogenase or cytochrome P450 activity, so it could be a good model to study the effect of the toxic agents per se. Cells were exposed during 120 min with 200 mM ethanol or 10 mM acetaldehyde. Under these conditions, cells presented 100% viability and no morphological alteration was observed by light microscopy. Acetaldehyde-treated cells reduced their proliferative capacity drastically while the ethanol-treated ones presented no difference with control cells. Cell adhesion to substrate, measured as time required to adhere to the substrate and time required to detach from the substrate, was diminished in acetaldehyde WRL-68-treated cells. Cytotoxicity measures as neutral red and MTT test showed that acetaldehyde-treated cells presented more damage than ethanol-treated ones. Cellular respiratory capacity was compromised by acetaldehyde treatment due to 40% less oxygen consumption than control cells. Lipid peroxidation values, measured as malondialdehyde production, were higher in ethanol-treated WRL-68 cells (127%) than in acetaldehyde-treated ones (60%) to control cell values. Lactate dehydrogenase activity (LDH) in extracellular media of ethanol-treated cells presented the highest values. GSH content was reduced 95% and thiol protein content was diminished severely in acetaldehyde-treated cells. Transmission electron microscopy showed more ultrastructural alterations in cells treated with acetaldehyde. The results indicate that acetaldehyde, like ethanol, produced damage at cellular level, although more damage could be observed in acetaldehyde WRL-68-treated cells.

Ethanol-induced oxidative stress and enzymatic defenses in cultured fetal rat hepatocytes

Previously, we have documented an ethanol (E)-induced oxidative stress (OS) in cultured fetal rat hepatocytes (FRH). The cause of this is uncertain, but an inhibition of key antioxidant enzymes could be a/the factor. OS was also observed in fetal liver (FL) during in utero E exposure, but not in maternal liver, a difference that might be related to selectively lower enzymatic defenses in the fetus. Here, we record effects of E on activities of catalase (Cat), superoxide dismutase (Cu, Zn SOD and Mn SOD), glutathione peroxidase (GPX), and glutathione-S-transferase (GST) in FRH isolated from 20-day-old fetuses and exposed to E (2 mg/ml) for up to 24 h and we compare these to adult rat liver data. E treatment decreased fetal liver reduced glutathione (GSH) pools by 23% (p < 0.05) and increased malondialdehyde (MDA) by 14% (p < 0.05) within 24 h of E exposure. E caused an increase in fetal liver Cat by 18%, 32%, and 47% by 3, 6, and 24 h of E, respectively (p < 0.05). A 24-h E exposure increased Cu, Zn SOD by 22% (p < 0.05) and Mn SOD by 21% (p < 0.05). A 24 h E treatment increased GPX by 18% (p < 0.05) and GST by 17% (p < 0.05). Cat in whole FL was 26% of adult (p < 0.05) whereas Cu, Zn SOD and Mn SOD in whole FL were 12% and 11% of adult levels (p < 0.05). GPX and GST in FL were 11% and 28% of adult values (p < 0.05). It is concluded that in FRH, E-induced OS is not caused by impaired activities of these enzymes, but their low basal activities (vs. adult) may predispose the fetus to OS.

In utero ethanol exposure elicits oxidative stress in the rat fetus

Prior studies in our laboratory have shown that exposure of cultured fetal rat hepatocytes to ethanol (E) blocks epidermal growth factor-dependent replication and that this is paralleled by cell membrane damage, mitochondrial dysfunction, membrane lipid peroxidation (LP), and enhanced generation of reactive oxygen species. These measures of E-mediated oxidative stress (OS) were mitigated by treatment with antioxidants, and cell replication could be normalized by maintaining cell glutathione (GSH) pools. We have now extended these studies to an in vivo model. Rats were administered E (4 g/kg, po) at 12-hr intervals on days 17 and 18 of gestation and killed on day 19, 1 hr following a final dose of E (a total of 5 doses). Fetal and maternal brain and liver were assayed for signs of OS. The 2-day in utero E exposure increased membrane LP in fetal brain as evidenced by increased malondialdehyde (MDA) levels from 1.76 +/- 0.12 SE (nMol/mg protein) to 2.00 +/- 0.08 (p < 0.05) and conjugated dienes from 0.230 +/- 0.006 SE (OD223/mg lipid) to 0.282 +/- 0.006 (p < 0.05). In fetal liver, MDA levels increased from 2.39 +/- 0.08 SE (nMol/mg protein) to 2.87 +/- 0.08 (p < 0.05), whereas dienes differed significantly only between ad libitum controls and the E and pair-fed control groups (p < 0.05). E decreased GSH levels in fetal brain by 19%, from 19.88 +/- 0.72 to 16.13 +/- 1.06 (nMol/mg protein) (p < 0.05). A 10% decrease in GSH was seen in fetal liver (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)