Thiopental Does Not Produce Hyperalgesia: A Laboratory Study Using Two Human Experimental Pain Models.

Objective: Past investigations assessing the effects of thiopental on pain are conflicting. Although several studies demonstrate hyperalgesia as a result of barbiturate administration, others show analgesia. Our objective was to assess the effects of an infusion of the GABAA agonist thiopental, compared with placebo, in healthy participants on two subjective experimental pain paradigms: noxious electrical stimulation and intradermal capsaicin.

Effect of Intravenous Ethanol on Capsaicin-Induced Hyperalgesia in Human Subjects.

Background: The objective of this study was to assess ethanol's (EtOH's) effects on capsaicin-induced hyperalgesia in healthy participants. Specifically, we investigated the change in area of capsaicin-induced hyperalgesia following 3 interventions: intravenous EtOH at 2 targeted breath alcohol concentrations (BrAC), or placebo.

Methods: Eighteen participants participated in 3 test days in a randomized order.

Significant association between rare IPO11-HTR1A variants and attention deficit hyperactivity disorder in Caucasians.

We comprehensively examined the rare variants in the IPO11-HTR1A region to explore their roles in neuropsychiatric disorders. Five hundred seventy-three to 1,181 rare SNPs in subjects of European descent and 1,234-2,529 SNPs in subjects of African descent (0 < minor allele frequency (MAF) < 0.05) were analyzed in a total of 49,268 subjects in 21 independent cohorts with 11 different neuropsychiatric disorders.

Accumulation of proteins bearing atypical isoaspartyl residues in livers of alcohol-fed rats is prevented by betaine administration: effects on protein-L-isoaspartyl methyltransferase activity.

Background/aims: Protein-L-isoaspartyl methyltransferase (PIMT) is a methyltransferase that plays a crucial role in the repair of damaged proteins. In this study, we investigated whether ethanol exposure causes an accumulation of modified proteins bearing atypical isoaspartyl residues that may be related to impaired PIMT activity. We further sought to determine whether betaine administration could prevent the accumulation of these types of damaged proteins.

Betaine attenuates alcoholic steatosis by restoring phosphatidylcholine generation via the phosphatidylethanolamine methyltransferase pathway.

Background/aims: Previous studies in our laboratory implicated ethanol-induced decreases in hepatocellular S-adenosylmethionine to S-adenosylhomocysteine (SAM:SAH) ratios in lowering the activity of phosphatidylethanolamine methyltransferase (PEMT), which is associated with the generation of steatosis. Further in vitro studies showed that betaine supplementation could correct these alterations in the ratio as well as attenuate alcoholic steatosis. Therefore, we sought to determine whether the protective effect of betaine is via its effect on PEMT activity.

Role of elevated S-adenosylhomocysteine in rat hepatocyte apoptosis: protection by betaine.

Previous studies from our laboratory have shown that ethanol consumption results in an increase in hepatocellular S-adenosylhomocysteine levels. Because S-adenosylhomocysteine is a potent inhibitor of methylation reactions, we propose that increased intracellular S-adenosylhomocysteine levels could be a major contributor to ethanol-induced pathologies. To test this hypothesis, hepatocytes isolated from rat livers were grown on collagen-coated plates in Williams' medium E containing 5% FCS and exposed to varying concentrations of adenosine in order to increase intracellular S-adenosylhomocysteine levels.

A comparison of the effects of betaine and S-adenosylmethionine on ethanol-induced changes in methionine metabolism and steatosis in rat hepatocytes.

Previous studies showed that chronic ethanol administration alters methionine metabolism in the liver, resulting in increased intracellular S-adenosylhomocysteine (SAH) levels and increased homocysteine release into the plasma. We showed further that these changes appear to be reversed by betaine administration. This study compared the effects of betaine and S-adenosylmethionine (SAM), another methylating agent, on ethanol-induced changes of methionine metabolism and hepatic steatosis.

Dangerous byproducts of alcohol breakdown--focus on adducts.

Alcohol breakdown in the liver results in the generation of the reactive molecule acetaldehyde and, as a byproduct, highly reactive oxygen-containing molecules known as oxygen radicals. Both acetaldehyde and oxygen radicals can interact with proteins and other complex molecules in the cell, forming hybrid compounds called adducts. Other adducts are formed with aldehyde molecules, which are produced through the interaction of oxygen radicals with lipids in the cells.

Transforming growth factor-beta induces contraction of activated hepatic stellate cells.

Background/aims: Transforming growth factor-beta (TGF-beta) is a cytokine produced in abundance during liver injury. Recognizing the prominent roles that hepatic stellate cells (HSCs) and TGF-beta play in portal hypertension and fibrogenesis, respectively, we sought to evaluate the effect of TGF-beta on the contractility of activated HSCs.

Methods: Spontaneous immortalized cell lines of HSC origin were used in this study.

Betaine lowers elevated s-adenosylhomocysteine levels in hepatocytes from ethanol-fed rats.

Previous studies showed that chronic ethanol administration inhibits methionine synthase activity, resulting in impaired homocysteine remethylation to form methionine. This defect in homocysteine remethylation was shown to increase plasma homocysteine and to interfere with the production of hepatic S-adenosylmethionine (SAM) in ethanol-fed rats. These changes were shown to be reversed by the administration of betaine, an alternative methylating agent.

Effect of malondialdehyde-acetaldehyde-protein adducts on the protein kinase C-dependent secretion of urokinase-type plasminogen activator in hepatic stellate cells.

Previous studies from our laboratory have shown that malondialdehyde-acetaldehyde-protein adducts (MAA adducts) are formed in hepatocytes of ethanol-fed rats and directly influence the hepatic stellate cells (HSCs) to induce their secretion of chemokines and to up-regulate their expression of adhesion molecules. Since protein kinase C (PKC) is known to play a major role in many diverse intracellular signal transduction processes, we investigated whether MAA adducts influence the function of HSCs via a PKC-dependent pathway. HSCs in culture were exposed to MAA adducts, and PKC activity was determined.

Role of malondialdehyde-acetaldehyde adducts in liver injury.

Malondialdehyde and acetaldehyde react together with proteins in a synergistic manner and form hybrid protein adducts, designated as MAA adducts. MAA-protein adducts are composed of two major products whose structures and mechanism of formation have been elucidated. MAA adduct formation, especially in the liver, has been demonstrated in vivo during ethanol consumption.

Expression and cytoskeletal association of integrin subunits is selectively increased in rat perivenous hepatocytes after chronic ethanol administration.

Background: For normal function and survival, hepatocytes require proper cell-extracellular matrix (ECM) contacts mediated by integrin receptors and focal adhesions. Previous studies have shown that chronic ethanol consumption selectively impairs perivenous (PV) hepatocyte attachment and spreading on various ECM substrates but increases expression of the beta1 integrin subunit, the common beta subunit for two major hepatocyte-ECM receptors, alpha1beta1 and alpha5beta1 integrins. This study examined the effects of ethanol treatment on the expression and cytoskeletal distribution of alpha1, alpha5, and beta1 integrin subunits, the epidermal growth factor receptor (EGF-R), and the cytoskeletal proteins focal adhesion kinase, paxillin, vinculin, and actin in periportal and PV hepatocytes.

Malondialdehyde-acetaldehyde-protein adducts increase secretion of chemokines by rat hepatic stellate cells.

Findings obtained from our recent studies have demonstrated that malondialdehyde, a product of lipid peroxidation, and acetaldehyde can react together with proteins in a synergistic manner and form hybrid protein conjugates, which have been designated as malondialdehyde-acetaldehyde (MAA)-protein adducts. These adducts have been detected in livers of ethanol-fed rats and are immunogenic because significant increases in circulating antibody titers against MAA-adducted proteins have been observed in ethanol-fed rats and more recently in human alcoholics. Although immunological factors may tend to perpetuate liver injury, little is known about the direct functional consequences of MAA-adducted proteins on the different cellular populations of the liver.

Chronic ethanol consumption increases homocysteine accumulation in hepatocytes.

Results of previous studies have shown that chronic ethanol administration impairs methionine synthetase activity and decreases S-adenosylmethionine levels in the liver, indicating interference with homocysteine remethylation. The purpose of the present study was to investigate the effects of chronic ethanol feeding on the accumulation of homocysteine (Hcy), a potentially toxic agent. The research was divided into two experiments.

Ethanol feeding selectively impairs the spreading of rat perivenous hepatocytes on extracellular matrix substrates.

Background: Hepatocytes require attachment and subsequent spreading on an extracellular matrix for their proper growth, function and survival. Our previous studies have shown that ethanol feeding selectively impairs perivenule hepatocyte attachment to various extracellular matrices. This study was undertaken to determine whether zonal differences in hepatocyte spreading in response to ethanol feeding occurs and to ascertain the influence of ethanol consumption on the zonal expression of the beta1 subunit of integrins, which are the major surface receptors responsible for matrix binding and subsequent interactions.

Betaine effects on hepatic methionine metabolism elicited by short-term ethanol feeding.

Previous studies in this laboratory have shown that feeding of ethanol to rats produces prompt inhibition of methionine synthetase (MS) as well as a subsequent increase in activity of betaine homocysteine methyltransferase (BHMT). Further studies have shown that supplemental dietary betaine enhanced methionine metabolism and S-adenosylmethionine (SAM) generation in control and ethanol-fed rats. Because MS and BHMT are both involved in the formation of SAM, this study was conducted to determine early effects of ethanol on hepatic SAM levels and the influence of betaine supplementation on parameters of methionine metabolism during the early periods of MS inhibition and enhanced BHMT activity.

Betaine, ethanol, and the liver: a review.

Two of the most important biochemical hepatic pathways in the liver are those that synthesize methionine and S-adenosylmethionine (SAM) through the methylation of homocysteine. This article reviews some recent findings in this laboratory, which demonstrate that ethanol feeding to rats impairs one of these pathways involving the enzyme methionine synthetase (MS), but by way of compensation increases the activity of the enzyme betaine:homocysteine methyl transferase (BHMT), which catalyzes the second pathway in methionine and SAM biosynthesis. It has been shown that despite the inhibition of MS, the enhanced BHMT pathway utilizes hepatic betaine pools to maintain levels of SAM.

Acetaldehyde and malondialdehyde react together to generate distinct protein adducts in the liver during long-term ethanol administration.

Acetaldehyde and the lipid peroxidation-derived aldehyde malondialdehyde (MDA), are reactive compounds that are generated during ethanol metabolism in the liver, and both aldehydes have been shown to be capable of binding to proteins and forming stable adducts. Because similar concentrations of MDA and acetaldehyde can coexist in the liver during ethanol oxidation, protein adduct formation in the presence of both of these aldehydes was studied under both in vitro and in vivo conditions. When proteins were incubated in the presence of both MDA and acetaldehyde, MDA caused a marked and concentration-dependent increase in the stable binding of acetaldehyde to proteins.