Ethanol inhibits veratridine-stimulated sodium uptake in synaptosomes

The effects of ethanol and pentobarbital on voltage-sensitive sodium channels in whole brain (rat) synaptosomes were studied using isotopic flux measurements. Incubation of synaptosomes with ethanol or pentobarbital $\text{in}$$\text{vitro}$ inhibited veratridine-stimulated ²²Na⁺ uptake. The effect of ethanol is dose-dependent, occurs at sublethal, pharmacologically relevant concentrations and is fully reversible. These results suggest that ethanol and pentobarbital directly interfere with sodium channel function in nervous tissue. Alterations in sodium channel function may be a possible mechanism for the central nervous system (CNS) depressant action of ethanol and related compounds.     

Transport of L-arginine and nitric oxide formation in human platelets.

The results of the present study show that human platelets take up l-arginine by two transport systems which are compatible with the systems y+ and y+L. These Na+independent transporters have been distinguished by treating platelets with N-ethylmaleimide that blocks selectively system y+. System y+, that accounts for 30-40% of the total transport, is characterized by low affinity for l-arginine, is unaffected by l-leucine, is sensitive to changes of membrane potential and to trans-stimulation. The other component of l-arginine transport identified with the system y+L (approximately 60-70% of the total flux) shows high affinity for l-arginine, is insensitive to N-ethylmaleimide treatment, unaffected by changes in membrane potential, sensitive to trans-stimulation and inhibited by l-leucine in the presence of Na+. Moreover a strict correlation between l-arginine transport and nitric oxide (NO) production in whole cells was found. N-ethylmaleimide and l-leucine decreased NO production as well as cGMP elevation, and the effect on NO and cGMP were closely related. It is likely that the l-arginine transport systems y+ and y+L are both involved in supplying substrate for NO production and regulation in human platelets.     

Hypoxia inhibits amino acid uptake in human lung fibroblasts.

Hypoxia and amino acid deprivation downregulate expression of extracellular matrix genes in lung fibroblasts. We examined the effect of hypoxia on amino acid uptake and protein formation in human lung fibroblasts. Low O(2) tension (0% O(2)) suppressed incorporation of [(3)H]proline into type I collagen without affecting [(35)S]methionine labeling of other proteins. Initial decreases in intracellular [(3)H]proline incorporation occurred after 2 h of exposure to 0% O(2), with maximal suppression of intracellular [(3)H]proline levels at 6 h of treatment. Hypoxia significantly inhibited the uptake of radiolabeled proline, 2-aminoisobutyric acid (AIB), and 2-(methylamino)isobutyric acid (methyl-AIB) while inducing minor decreases in leucine transport. Neither cycloheximide nor indomethacin abrogated hypoxia-related suppression of methyl-AIB uptake. Efflux studies demonstrated that hypoxia inhibited methyl-AIB transport in a bidirectional fashion. The downregulation of amino acid transport was not due to a toxic effect; function recovered on return to standard O(2) conditions. Kinetic analysis of AIB transport revealed a 10-fold increase in K(m) accompanied by a small increase in maximal transport velocity among cells exposed to 0% O(2). These data indicate that low O(2) tension regulates the system A transporter by decreasing transporter substrate affinity.     

Vanadate enhances insulin-receptor binding in gestational diabetic human placenta

Although vanadium is found abundantly in animal and plant kingdoms its biological effects are not clear. Vanadate compounds have been shown to normalize blood glucose levels in streptozotocin treated rats, enhance glucose oxidation and improve the sensitivity to insulin by enhanced receptor binding in rat adipocytes. The aim of the present study was to investigate the effect of vanadate, at high (0–8 mmol l^?1) and low (0–1·0 mmol l^?1) physiological concentrations, on [¹²⁵I]-insulin binding in the placenta of three groups of pateints, namely from normal (N) controls, gestational diabetics (GDM) and women with risk factors in their medical history for developing diabetes mellitus (RF). Vanadate at low concentrations (0·2–0·6 mmol l^?1) enhanced the maximal binding 2-fold in GDM placenta but only increased (up to 1·2-fold) the binding slightly at high cncentrations (5 mmol l^?1). However with placenta from normal or women at risk, vanadate increased the [¹²⁵I]-insulin binding up to 1·2-fold both at low and high concentrations. Thus it appears that vanadate augements insulin binding in the placenta from women with gestational diabetes mellitus.     

Ethanol inhibits ligand-activated Ca2+ channels in human B lymphocytes.

Ethanol reportedly is immunosuppressive, interfering with lymphocyte proliferation. To investigate the basis for this immunosuppression, the effects of acute treatment with ethanol were studied on Ca2+ mobilization in tonsillar B lymphocytes and the human lymphoblastoid B-cell line, Ramos. The level of intracellular Ca2+ was monitored in cells loaded with the fluorescent dye indo-1 following stimulation with either anti-IgM antibody or platelet activating factor. The effect of ethanol was also examined on the induction of the early proto-oncogene c-fos in these cells. Ethanol inhibited ligand-activated Ca2+ mobilization due to transmembrane influx but not intracellular store release, in a dose- and time-dependent manner. This inhibition was not due to the inability of anti-IgM to bind to its surface receptor nor to membrane depolarization induced by ethanol. Ethanol also inhibited the Ca2(+)-dependent induction by anti-IgM of c-fos in these cells. The inhibitory effects of ethanol on ligand-activated Ca2+ channels and subsequent induction of c-fos may provide the basis for its immunosuppressive action.     

Ethanol inhibits human and hamster sperm penetration of eggs

The effect of alcohol on the fertilizing ability of both human and hamster spermatozoa was examined by an in vitro fertilization assay using hamster ova. Spermatozoa were incubated in capacitating media for 3 hr (hamster sperm) and 4 hr (human sperm). Hamster ova were inseminated with preincubated sperm and were examined after 2 to 3 hr. Ethanol was added to the capacitating media at concentrations of 25, 50, 100, 200, and 400 mg%. Fertilization of zona-free hamster eggs by human spermatozoa was reduced from 49.6% in no alcohol to 16.7% in 400 mg% ethanol. Fertilization of hamster eggs by hamster sperm revealed a reduction from 63.6% to 33.7% in cumulus-intact eggs and from 65.8% to 10.8% in cumulus-free eggs in the presence of ethanol at 400 mg%. Hamster sperm acrosome reaction was reduced from 47% to 12%. When these hamster sperm with reduced acrosome reaction were placed with zona-free hamster eggs, the 100% fertilization rate was not reduced; however, the fertilization index, which reflects the number of swelling sperm heads per egg, was reduced from 8.5 to 1.8. This suggests that as little as 12% of the sperm with an acrosome reaction is sufficient to fertilize 100% of the zona-free eggs. If ethanol was added to the insemination media only, there was no inhibition of fertilization by human sperm or hamster sperm that had been previously capacitated in an ethanol-free media. Removal of the ethanol from the preincubated sperm produced fertilization at control levels; thus the inhibitory effect is reversible. These results indicate that ethanol may affect fertilization by an inhibition of the capacitation and/or acrosome reaction process.     

Mechanism of zinc uptake by microvilli isolated from human term placenta.

The mechanism of zinc (Zn) uptake by microvillous membrane vesicles prepared from human term placenta has been studied. The uptake was complex, with two processes being identified. In the first process, uptake was rapid, reaching equilibrium within 2 min, and was temperature dependent, with a Q10 of 1.5. Equilibrium Zn levels were sensitive to osmotic pressure, with Zn binding at infinite osmolarity being 69% iso-osmotic value. The uptake was saturable, with a Vmax of 58 +/- 2 nmol/mg protein/min and an apparent Kt of 128 +/- 13 microM. Uptake was inhibited by increasing extravesicular K+ concentration, dropping from 0.91 +/- 0.03 nmol/mg/min at 0 extravesicular K+ to 0.47 +/- 0.03 at an extravesicular K+ concentration of 150 mM ([Zn] = 1.0 microM). In the presence of both valinomycin, an electrogenic ionophore, and nigericin, an electroneutral exchanger, an outwardly directed K+ gradient stimulated Zn uptake. Similarly, preloading vesicles with Zn and imposing an inward gradient resulted in a temperature dependent efflux of Zn. The data suggest that there is a K+ dependent Zn transporter in vesicle membranes, and we suggest that the evidence is biased in favour of a Zn/K+ exchanger rather than Zn being dependent on the membrane potential.     

Ethanol enhances the formation of endogenously and exogenously derived adducts in rat hepatic DNA

To investigate the role of ethanol in chemically-induced carcinogenesis, we exposed Wistar rats to ethanol, either as an acute dose or for prolonged periods in a liquid diet and looked for effects on endogenously and exogenously derived DNA adducts. Changes in the cytochrome P450 protein (CYP 2E1) and its catalytic demethylase activity were also followed in order to provide a sequence of relatively well understood changes that are associated with free radical production and, therefore, potentially capable of affecting DNA.The exocyclic DNA adducts, ethenodeoxyadenosine (varepsilondA) and ethenodeoxycytidine (varepsilondC), known to arise from oxidative stress and lipid peroxidation (LPO) sources, were detected in the liver DNA of Wistar rats at background concentrations of 4-6 (varepsilondA) and 25-35 (varepsilondC) adducts per 10(9) parent bases. When rats were given either an acute dose of ethanol (5g/kg, i.g.) or exposed for 1 week to ethanol in a liquid diet (5%, w/v), etheno adduct levels were increased approximately 2-fold and this was statistically significant for varepsilondC (P<0.05 and P<0.02, respectively) for the two separate treatments.In N-nitrosodimethylamine (NDMA)-treated rats, acute ethanol treatment significantly increased the level of O(6)-methylguanine (O(6)-MeG) in hepatic DNA and this was paralleled by a decrease in O(6)-alkylguanine DNA alkyltransferase (ATase) activity; immunohistochemistry confirmed this increase of O(6)-MeG in both hepatic and renal nuclei. When rats were given ethanol in the diet and treated with NDMA, O(6)-MeG levels in hepatic DNA increased at 1 week which coincided with the peak of CYP 2E1-dependent NDMA-demethylase activity. Single cell gel electrophoresis of liver cells showed that after 1 week of exposure to ethanol, there was a small but significant increase in the frequency of DNA strand breaks induced by NDMA (P<0.05); after 4 weeks the increase was 1.4-fold (P<0.01).Our results indicate that exposures to ethanol, which resulted in blood ethanol concentrations similar to those seen in chronic alcoholics and increased levels of expression of the CYP 2E1 protein can exacerbate the DNA damaging effects of endogenous and exogenous alkylating agents. These observations provide indications of possible mechanisms for the carcinogenic or co-carcinogenic action of ethanol.     

L-arginine uptake and L-phosphoarginine synthesis in Trypanosoma cruzi

A very specific L-arginine transporter showing high affinity has been characterized in Trypanosoma cruzi epimastigotes. Uptake was found to be dependent on L-arginine concentration and it was saturable. Values for maximum velocity and Km ranged between 48.1-57.5 pmol.min-1 per 3 x 10(7) cells and between 4.2-5.5 microM, respectively. The calculated activation energy and Q10 were 31.1 KJ.mol-1, and 1.7, respectively. Uptake velocity significantly increased when cells were preincubated in the absence of L-arginine. Cells retained the labeled amino acid independently of the presence or absence of exogenous L-arginine. The specificity of L-arginine uptake was demonstrated by competition assays in the presence of 80-fold molar excess of natural amino acids and several L-arginine derivatives. The highest levels of inhibition were caused by L-homoarginine, D-arginine, L-canavanine, L-ornithine, and L-citrulline. L-arginine uptake by T. cruzi epimastigotes was not affected by the presence of potassium or sodium ions in the incubation mixture or by pH changes in the range between 5.5-8.5. The major product of L-arginine uptake was characterized as phosphoarginine. Moreover, arginine kinase activity was detected in soluble extracts from T. cruzi epimastigotes.     

Selective stimulation of L-arginine uptake contributes to shear stress-induced formation of nitric oxide

The aim of this study was to investigate the kinetics of L-arginine transport mechanisms and the role of extracellular L-arginine in nitric oxide formation during shear stress activation of endothelial cells. Porcine aortic endothelial cells were grown to confluence and were exposed to various amounts of shear stress for 40 min. Formation of nitric oxide was monitored by measuring elevation of endothelial cGMP. Activity of amino acid transport systems was determined by measuring the uptake of L-[3H]leucine (L system) and L-[3H]arginine (y+) under resting and shear stress condition. Shear stress-mediated nitric oxide formation critically depended on the presence of extracellular L-arginine, which increased shear stress-induced cGMP increases in a concentration dependent manner (EC50=123 microM). In addition, shear stress increased L-arginine uptake, while the transport capacity for neutral amino acids (L system) remained unchanged under shear stress conditions. Analysis of the kinetics of the uptake of L-arginine under resting and shear stress conditions indicate that shear stress increased velocity of the high affinity, low capacity transport (y+) without affecting affinity of this system. These data suggest that shear stress selectively activates uptake of L-arginine in endothelial cells and that the uptake of L-arginine might be important for shear stress-mediated nitric oxide formation.     

Immunoactive products of human placenta. I. An immunoregulatory factor obtained from explant cultures of human placenta inhibits CTL generation and cytotoxic effector activity

Supernatants were prepared from short-duration explant cultures of term human placentas obtained after cesarean delivery. These supernatants inhibited murine and human mixed lymphocyte reactions, as well as CTL generation. The effects were reversed by an excess of IL-2-containing medium. Similarly, the material inhibited human natural killer cytotoxicity against K 562 targets. The material was subjected to gel-filtration chromatography on an ACA 44 or Bio-Gel A15m column. The apparent MW of the MLR-CML material was about 60-70 kDa, whereas the NK inhibiting activity was eluted in high-MW components (greater than 200 kDa) as well as in the 50-kDa range. The relevance of this material in local immunoregulation during human pregnancy is discussed.     

Ethanol stimulates bile acid formation in primary human hepatocytes

The conversion of cholesterol to bile acids is a key pathway for elimination of cholesterol from the body, thereby reducing the risk of arteriosclerosis. Moderate consumption of ethanol has been shown to have preventive effects on cardiovascular disease and decrease the risk of gallstone formation. In the present study primary human hepatocytes were used to investigate if ethanol affected bile acid synthesis. Hepatocytes were prepared from donor liver (n = 11) and treated with ethanol, 7.7 or 50 mM, for 24 h. mRNA levels for enzymes in bile acid synthesis pathways were studied and bile acid synthesis was analyzed. Treatment with 7.7 mM ethanol increased cholic acid synthesis by 20% and treatment with 50 mM ethanol up-regulated cholic acid formation by 60%. The synthesis of cholic acid increased more than that of chenodeoxycholic acid, indicating that the classical pathway for bile acid synthesis was up-regulated. Increased bile acid levels in the cells treated with ethanol were seen after approximately 20 h. mRNA expression of CYP7A1, CYP27A1, and CYP8B1 in the hepatocytes was not affected by alcohol exposure.     

Ethanol inhibits mitogen-induced calcium mobilization in mouse splenocytes.

Ethanol inhibited the mitogen-induced initial increase in cytoplasmic free-calcium [Ca2+]i in mouse splenocytes. This effect was concentration-dependent, reversible, and observed at pharmacologically relevant concentrations (24-166mM). Other short-chain alcohols such as propanol, butanol, and pentanol also inhibited this mitogen-induced increase in [Ca2+]i. The potencies of these alcohols to produce this effect were highly correlated (r = 0.98, p less than 0.001) with their membrane/buffer partition coefficients. Analysis of mouse splenocyte subpopulations demonstrated that this effect was manifest in both B and T lymphocytes. Within T lymphocyte subpopulations, both CD4+ and CD8+ T cells were affected. These results suggest that the inhibition of [Ca2+]i increase may be an early event mediating ethanol-induced immunosuppression and that this may be a predisposing factor to infection and malignancies associated with alcoholism.     

Ethanol inhibits phosphatidylcholine and phosphatidylethanolamine biosynthesis in human leukemic monocyte-like U937 cells

The effect of ethanol (ETOH) on the incorporation of [¹⁴C]oleic acid (18:1) into lipid in human monocyte-like U937 cells was investigated. With increasing time of exposure to ETOH, the percentage of the label distributed into neutral lipid (NL) declined from 35 per cent (3 h) to 10 per cent (24 h) accompanied by increased incorporation into phospholipid (PL). [¹⁴C] 18 : 1 was preferentially incorporated into triglyceride (TG) and phosphatidylcholine (PC), comprising over 65 per cent and 50 per cent of the label associated with NL and PL, respectively. Low concentrations of ETOH (⩽ 1·0 per cent; v/v) had no effect. At concentrations greater than 1·5 per cent, there was enhanced incorporation into TG and diacylglycerol (DAG) in a 24-h incubation period, while at 16 h the label in phosphatidylethanolamine (PE) was decreased. The effect of ETOH on the CDP-choline or ethanolamine pathway was examined by monitoring the incorporation of [³H]choline or [¹⁴C]ethanolamine into PC or PE, respectively. At low concentrations ETOH had no effect on either choline uptake or the incorporation into PC. Higher concentrations (≥ 1·5 per cent) for 3 and 6 h resulted in a slightly decreased choline uptake, and the reduction (40–50 per cent) of incorporation into PC suggests that the CDP-choline pathway was inhibited. There was a similar inhibition of the incorporation of [¹⁴C]ethanolamine into PE. When the cells were incubated for 3 h in the presence of 2 per cent ETOH and with labelled 18 : 1 and PL-base, the ratios of incorporation (base/18 : 1) into PC and PE fractions decreased, indicating that the major inhibition lay in blockage of the availability of the base moiety for PL formation. Analysis of the distribution of the label into metabolites revealed that ETOH inhibited the conversion of [¹⁴C] ethanolamine into [¹⁴C]phosphorylethanolamine. The reduction in incorporation was not due to the enhanced breakdown of base-labelled PL. Our results indicate that ETOH has an inhibitory effect on the CDP-choline or ethanolamine pathway.     

Ethanol inhibits IgE-induced degranulation and cytokine production in cultured mouse and human mast cells

Activated mast cells (MC) can produce a wide variety of potent inflammatory mediators. Excessive alcohol consumption is known to lead to immune deficiency and propensity for pneumonias in particular. As MCs are important in the first line of defence of mucosal membranes we have studied the effect of ethanol (EtOH) on several MC functions. EtOH attenuated dose dependently IgE-induced degranulation of mouse bone marrow derived mast cells (mBMMC) as reflected by the release of granule associated beta-hexosaminidase (beta-hex). A mean of 26 +/- 7% inhibition of beta-hex release was observed in the presence of 5/1000 (86 mM) EtOH and nearly complete inhibition in the presence of 20/1000 (344 mM) ethanol. The IgE-induced degranulation of mBMMC cultured with EtOH for seven days was inhibited to a similar degree as the degranulation of mBMMC exposed to EtOH for only one hour. Inclusion of 5/1000 (86 mM) ethanol in the medium reduced tumour necrosis factor (TNF)-alpha and interleukin (IL)-8 production in human mast cell line (HMC-1) cells by 55 +/- 7% and 19 +/- 5%, respectively, and the presence of 20/1000 (344 mM) ethanol inhibited the expression 81 +/- 12% and 59 +/- 14% respectively. These results suggest that, in contrast to previous assumption, ethanol inhibits several critical MC functions at least in vitro. This inhibition of mediator, and cytokine release in particular, could contribute to the immune deficiency associated with chronic alcohol consumption.     

L-arginine enhances aerobic exercise capacity in association with augmented nitric oxide production.

We tested whether supplementation with L-arginine can augment aerobic capacity, particularly in conditions where endothelium-derived nitric oxide (EDNO) activity is reduced. Eight-week-old wild-type (E(+)) and apolipoprotein E-deficient mice (E(-)) were divided into six groups; two groups (LE(+) and LE(-)) were given L-arginine (6% in drinking water), two were given D-arginine (DE(+) and DE(-)), and two control groups (NE(+) and NE(-)) received no arginine supplementation. At 12-16 wk of age, the mice were treadmill tested, and urine was collected after exercise for determination of EDNO production. NE(-) mice demonstrated a reduced aerobic capacity compared with NE(+) controls [maximal oxygen uptake (VO(2 max)) of NE(-) = 110 +/- 2 (SE) vs. NE(+) = 122 +/- 3 ml O(2). min(-1). kg(-1), P < 0.001]. This decline in aerobic capacity was associated with a diminished postexercise urinary nitrate excretion. Mice given L-arginine demonstrated an increase in postexercise urinary nitrate excretion and aerobic capacity in both groups (VO(2 max) of LE(-) = 120 +/- 1 ml O(2). min(-1). kg(-1), P < 0.05 vs. NE(-); VO(2 max) of LE(+) = 133 +/- 4 ml O(2). min(-1). kg(-1), P < 0.01 vs. NE(+)). Mice administered D-arginine demonstrated an intermediate increase in aerobic capacity in both groups. We conclude that administration of L-arginine restores exercise-induced EDNO synthesis and normalizes aerobic capacity in hypercholesterolemic mice. In normal mice, L-arginine enhances exercise-induced EDNO synthesis and aerobic capacity.     

Recombinant human interferon-gamma inhibits formation of human osteoclast-like cells

Interferon-gamma (IFN-gamma) inhibits osteoclastic bone resorption in vitro, but the mechanism responsible for this inhibition is unknown. We have used a long-term human marrow culture system that forms multinucleated cells (MNC) with osteoclast characteristics to test the effect of recombinant human IFN-gamma on MNC formation. The addition of 1,25-dihydroxy-vitamin D3 (1,25D3) at 10(-8) M to these cultures significantly increased both MNC formation and the number of nuclei per MNC. IFN-gamma at 100 U/ml strongly inhibited both of these effects of 1,25D3 in this system. IFN-gamma significantly inhibited MNC formation at very low concentrations (4 U/ml), with 10 U/ml inhibiting 1,25D3-stimulated MNC formation by 50%. In contrast, 100 U/ml of IFN-gamma were required to inhibit the growth of granulocyte-macrophage colony-forming cells, the probable progenitor for MNC, by 50%. Treatment of cultures with IFN-gamma for only the first or last week of culture significantly inhibited MNC formation stimulated by 1,25D3. Autoradiographic studies with [3H]thymidine showed that IFN-gamma did not inhibit proliferation of precursors for MNC. Additionally, IFN-gamma inhibited MNC formation stimulated by parathyroid hormone or interleukin 1. These results suggest that IFN-gamma inhibits MNC formation, and that IFN-gamma inhibits bone resorption in part by inhibiting osteoclast formation.     

In vivo and in vitro evidence for ACh-stimulated L-arginine uptake

Whereas L-arginine is clearly recognized as the precursor for nitric oxide synthesis, and its entry into endothelial cells via system y(+) transport is established, few data exist regarding the acute regulation of this transport process. We specifically investigated the effect of ACh and isoprenaline (Iso) on L-arginine uptake in the human forearm and in cultured bovine aortic endothelial cells (BAEC). Sixteen healthy males were studied. During a steady-state intra-arterial infusion of [(3)H]L-arginine (100 nCi/min), the effects of ACh (9.25 and 37 microg/min), Iso (25-50 and 200 microg/min), and sodium nitroprusside (SNP) (1-2 and 8 microg/min) on forearm plasma flow (FPF), L-[(3)H]arginine uptake, and L-[(3)H]citrulline release were determined. In parallel experiments, the effects of ACh, Iso, and SNP on L-[(3)H]arginine uptake were studied in BAEC. L-Arginine uptake was inversely related to FPF (r = -0.50; P < 0.005). At a similar FPF (ACh 56.82 +/- 9.25, Iso 58.49 +/- 5.56, SNP 57.92 +/- 4.96 ml/min; P = ns), intra-arterial ACh significantly increased forearm uptake of L-[(3)H]arginine (54,655 +/- 8,018 dpm/min), compared with that observed with either Iso (40,517.23 +/- 6,841 dpm/min; P = 0.01) or SNP (36,816 +/- 4,650 dpm/min; P = 0.011). This was associated with increased ACh-induced L-[(3)H]citrulline release compared with Iso and SNP (P = 0.046). Similarly, in BAEC, ACh significantly increased L-[(3)H]arginine uptake compared with control, Iso, or SNP (ACh 12.0 x 10(7) +/- 1.83 x 10(7) vs. control 6.67 x 10(7) +/- 1.16 x 10(7) vs. Iso 7.35 x 10(7) +/- 1.63 x 10(7) vs. SNP 6.01 x 10(7) +/- 1.11 x 10(7) fmol.min(-1).mg(-1) at 300 micromol/l L-arginine; P = 0.043). Taken together, these data indicate that ACh stimulates L-arginine uptake in cultured endothelial cells and in human forearm circulation, indicating the potential for acute modulation of endothelial L-arginine uptake.