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Biomedical subjects

G Szabo

Publications and source records attributed to G Szabo.

At least 55 records · Page 3Linked to original sources
PubMed1998

Monocytes, alcohol use, and altered immunity.

The immunomodulatory capacity of acute, moderate alcohol consumption was investigated in this study in nonalcoholic volunteers after 2 ml of vodka/kg body weight of alcohol consumption. There was a significant, transient increase in interleukin-12 and interferon-gamma (IFNgamma) levels in whole blood samples collected 4 hr after alcohol consumption in response to an ex vivo bacterial challenge with lipopolysaccharide (p < 0.02). However, decreased IFNgamma levels were produced by mononuclear cells collected later after alcohol consumption (16 hr), suggesting that acute alcohol consumption has a biphasic effect on IFNgamma inducibility. Furthermore, isolated blood monocytes collected 16 hr after alcohol consumption showed significantly decreased IL-1beta production in response to subsequent bacterial stimulation, implying that in vivo alcohol consumption affects monocyte-derived inflammatory cytokine production. These results demonstrate that even acute, moderate alcohol consumption has a modulating capacity on immune functions that may contribute to decreased immunity and host defense.

Adult↗
PubMed1998

Five-year 224-patient prospective histological study of clinical applications using a synthetic bone alloplast.

Clinical and histologic evaluations of a synthetic bone were performed in 224 patients in a well monitored environment. This material (Bioplant HTR, Bioplant Inc., South Norwalk, CT) was used to obliterate cysts, treat periodontal defects, correct jawbone contours and deficiencies, and gain sufficient support for the placement of dental implants in maxillary subantral augmentation. Implants were positioned either at the time of the synthetic bone graft or after the new supporting tissue was formed. Evidence of new bone formation between the synthetic granules and host tissue was observed during histological examinations. After the material was placed, tissue that could strengthen and augment the inferior wall of the maxillary sinus formed in 3 months. This was observed both clinically and radiographically. After 8 to 12 months, this tissue provided sufficient hard tissue support for the placement of dental implants. This clinical study reconfirmed the applicability of a synthetic bone for bone replacement and augmentation in oral and maxillofacial surgery. No complications caused by infection, inflammation, or rejection of the implanted graft material were observed.

Adult↗
PubMed1998

Regulation of monocyte interleukin-12 production by acute alcohol: a role for inhibition by interleukin-10.

Acute ethanol treatment results in decreased antigen presentation capacity (Th1-type immunity) and elevated interleukin IL-10 (Th2 cytokine) production in human monocytes. Monocytes can contribute to both Th1 (IL-12) and Th2 (IL-10) immune responses via production of IL-12 and IL-10, respectively. Thus, we tested the hypothesis that acute alcohol treatment might affect Th1/Th2 immune balance by altering monocyte production of IL-12 and IL-10. Neither acute ethanol treatment alone (25 to 100 mM) nor its combination with a bacterial challenge Staphylococcal enterotoxin B (SEB) induced IL-12 production in isolated blood monocytes. In contrast, the same physiological alcohol concentrations increased monocyte IL-10 levels, suggesting that ethanol can induce a dysbalance of monocyte-derived mediator production at the expense of Th1 cytokines. However, we found that monocyte activation with interferon-gamma (IFN-gamma) can prevent the preferential IL-10 induction by ethanol. IFN-gamma (100 units/ml) inhibited monocyte IL-10 production whether induced by 1 microg/ml of lipopolysaccharide (p < 0.01), 1 microg/ml of SEB (p < 0.02), or a combination of bacterial stimulation + ethanol (lipopolysaccharide: p < 0.01). Furthermore, decreased IL-10 was concomitant to an increase in IL-12 production in IFN-gamma-treated monocytes. Moreover, acute ethanol treatment augmented IL-12 production in IFN-gamma-treated monocytes in response to SEB stimulation (25 mM ethanol, p < 0.01; 100 mM ethanol, p < 0.01). Experiments with anti-IL-10 neutralizing antibody show that ethanol may prevent monocyte IL-12 induction via IL-10. These results suggest that inhibition of ethanol-induced IL-10 production by IFN-gamma treatment is permissive for IL-12 induction by alcohol stimulation in monocytes. Thus, our results imply that the presence or absence of IFN-gamma is critical in determining the effect of acute ethanol treatment on monocyte IL-12 versus IL-10 induction.

Adult↗
PubMed1997

Anion, cation, and zwitterion selectivity of phospholemman channel molecules.

Phospholemman (PLM), a 72-amino acid membrane protein with a single transmembrane domain, forms taurine-selective ion channels in lipid bilayers. Because taurine forms zwitterions, a taurine-selective channel might have binding sites for both anions and cations. Here we show that PLM channels indeed allow fluxes of both cations and anions, making instantaneous and voltage-dependent transitions among conformations with drastically different ion selectivity characteristics. This surprising and novel ion channel behavior offers a molecular explanation for selective taurine flux across cell membranes and may explain why molecules in the phospholemman family can induce cation- or anion-selective conductances when expressed in Xenopus oocytes.

Animals↗
PubMed1997

Alcohol's contribution to compromised immunity.

Alcoholics frequently suffer from infectious diseases and have increased rates of some cancers, indicating that alcohol impairs the immune system, which protects the body against this type of damage. Alcohol interferes with the functions of many of the cells and molecules that are part of the immune system. For example, alcohol inhibits the functions of the cells that ingest and destroy invading microorganisms (i.e., neutrophils, monocytes, and macrophages). Both acute and chronic alcohol exposure also alter the production of signaling molecules that help coordinate the immune response (i.e., cytokines). Finally, alcohol adversely affects the functions of the cells that mediate the immune response against specific microorganisms and long-term immunity (i.e., T cells and B cells). As a result, alcoholics have an increased susceptibility to diseases caused by bacterial infections, such as tuberculosis and pneumonia. Alcoholics also may be more susceptible to infections from the virus that causes AIDS. In addition, alcohol intoxication can exacerbate the immune suppression that occurs after traumatic injuries.

Alcohol Drinking↗
PubMed1997

Alcohol-induced regulation of nuclear regulatory factor-kappa beta in human monocytes.

Acute ethanol exposure has the capacity to modulate immune functions, particularly, to down regulate monocyte production of inflammatory cytokines. However, the intracellular mechanisms for these effects of ethanol are yet to be understood. Considering that nuclear regulatory factor-kappa beta (NF-kappa B)/Rel is a common regulatory element of the promoter region of the inflammatory cytokine genes, herein, we tested the hypothesis that acute ethanol affects NF-kappa B activation in human monocytes. Adherence-isolated monocytes showed constitutive DNA binding activity of NF-kappa B. A clinically relevant dose (25 mM) of acute ethanol treatment in vitro increased NF-kappa B binding activity in monocytes with a preferential induction of the inhibitory, p50/p50, NF-kappa B/Rel homodimer, and resulted in no induction of the p65/p50 heterodimer. In contrast, lipopolysaccharide stimulation primarily induced the p65/p50 heterodimer that has been shown to result in gene activation. Thus, such unique activation of the inhibitory p50/p50 homodimer by acute ethanol treatment may result in inhibition rather than activation of NF-kappa B-regulated inflammatory cytokine genes. Consequently, these results suggest that physiologically relevant concentrations of ethanol may affect production of inflammatory cytokines, such as tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6 by disrupting NF-kappa B signaling in monocytes.

Adolescent↗
PubMed1996

Chondrocyte matrix metalloproteinase-8. Human articular chondrocytes express neutrophil collagenase.

This study confirms that normal human articular chondrocytes express neutrophil collagenase or matrix metalloproteinase-8 (MMP-8), a gene product previously thought to be expressed exclusively by neutrophil leukocytes. Both MMP-8 protein and mRNA were present in articular cartilages collected from normal human donors. Cartilage extracts were assayed by immunoblotting and by analysis of enzymatic activity on gelatin-substrate gels. Latent MMP-8 extracted from cartilage has a molecular mass of 55 kDa; active MMP-8 was identified at 46 and 42 kDa. In the absence of a reducing agent, MMP-8 migrated in a high molecular mass complex above 200 kDa. Northern blotting results demonstrated the expression of MMP-8 in chondrocytes, which could be up-regulated by stimulation with interleukin-1 beta. In addition, reverse transcription-polymerase chain reaction using nested primers and in situ hybridization revealed the presence of MMP-8 mRNA in chondrocytes. The presence of both MMP-8 protein and message in cartilage supports the concept that neutrophil collagenase could be the enzyme described as "aggrecanase".

Blotting, Northern↗
PubMed1996

Human monocyte IL-10 production is increased by acute ethanol treatment.

Immune alterations after acute ethanol treatment are characterized by abnormal monocyte mediator production and antigen presentation capacity. Here, we tested the hypothesis that some of the regulatory effects of ethanol on monocyte functions are mediated by elevated M phi IL-10 production. Physiologically relevant in vitro doses of ethanol (25-100 mM) resulted in significantly increased IL-10 secretion by normal blood monocytes after 18 h stimulation. We found that monocyte IL-10 production induced by either ethanol or LPS increased at 10 h, maximized at 18 h and decreased by 40 h post-stimulation. Furthermore, ethanol significantly augmented LPS-induced monocyte IL-10 secretion at 18 h. Data also show that ethanol-induced changes in monocyte IL-10 mRNA levels mirror those seen at the protein levels. Greater IL-10 levels and IL-10 induction by LPS in adherent compared to non-adherent M phi imply that adherence is an important co-stimulator for IL-10 production in human M phi. We further showed that cyclooxygenase inhibitor treatment augments M phi IL-10 production suggesting that elevated PGE2 (and cAMP) is not necessary for IL-10 induction by ethanol or LPS in isolated M phi. Finally, our data demonstrate that ethanol-induced elevated M phi IL-10 contributes to the decreased M phi TNF-alpha production seen after acute ethanol treatment. However, observation of an ethanol-induced decrease in TNF-alpha mRNA as early as 1.5 h after stimulation indicate that ethanol has an additional, IL-10 independent, effect on M phi TNF-alpha production. These results suggest that elevated monocyte-derived IL-10 can contribute to the monocyte as well as other immune abnormalities after acute ethanol uptake.

Alcoholic Intoxication↗
PubMed1996

Regulation of human monocyte functions by acute ethanol treatment: decreased tumor necrosis factor-alpha, interleukin-1 beta and elevated interleukin-10, and transforming growth factor-beta production.

We and others have previously shown that even acute ethanol exposure has the capacity to modulate immune functions, particularly monocyte functions. Herein, we tested the hypothesis that acute ethanol treatment inhibits inflammatory, while increasing inhibitory cytokine production in human blood monocytes that, in turn, could contribute to the overall immune abnormalities seen after alcohol use. Our data show that in vitro treatment of blood monocytes with a physiologically relevant dose of alcohol (25 mM) results in significantly decreased induction of tumor necrosis factor-alpha (TNF alpha) and interleukin (IL)-1 beta by bacterial stimulation of either Gram-positive [staphylococcal enterotoxin B (SEB), 1 microgram/ml of SEB] or Gram-negative [lipopolysaccharide (LPS), 1 microgram/ml of LPS] origin both at the protein and mRNA levels. In contrast, acute ethanol treatment induces monocyte production of mediators with immunoinhibitory potential, including transforming growth factor-beta and IL-10. We further show that ethanol not only induces monocyte/macrophage (Mø) IL-10 and transforming growth factor-beta, but even augments bacterial (both LPS and SEB) stimulation-induced production of both of these cytokines. IL-10 is a potent inhibitor of Mø TNF alpha production. We found that ethanol-induced elevation in Mø IL-10 levels contributes to the decreased Mø TNF alpha production to bacterial challenge in ethanol-exposed Mø. However, mRNA levels for TNF alpha are downregulated as early as 1.5 hr after ethanol treatment, suggesting that ethanol likely has an IL-10 independent, direct effect on early signaling events of TNF alpha induction.

Adult↗
PubMed1996

A voltage-operable current is involved in Ca2+ entry in human lymphocytes whereas ICRAC has no apparent role.

Presently, it is thought that a non-voltage-gated current is responsible for activation-induced Ca2+ entry in nonelectrically excitable cells such as lymphocytes. However, it has also been proposed that the pathway instead involves a second messenger-regulated Ca2+ channel that is voltage operable, where "voltage operable" is defined as an intrinsic property of the channel protein(s) rather than a requirement of normal gating. To evaluate the contribution of these currents to activation-induced Ca2+ influx, each was examined with respect to its ability to account for Ca2+ influx as reported by Ca(2+)-sensitive dyes. We identified a set of reagents, nordihydroguaiaretic acid and various calmodulin inhibitors, that inhibits Ca2+ entry and blocks the voltage-operable current but leaves the non-voltage-gated current unaltered. Further-more, nordihydroguaiaretic acid inhibited Ca(2+)-dependent proliferation of mitogen-activated human peripheral blood mononuclear cells or Jurkat T cells and specifically blocked Ca(2+)-dependent interleukin 2 production by Jurkat T cells to a degree similar to the immunosuppressant drug cyclosporin A. We also identified compounds, amiloride and Mn2+, that block the non-voltage-gated current but have no effect on either the voltage-operable current or Ca2+ entry. Correspondingly, amiloride had no effect on Ca(2+)-dependent proliferation of Jurkat cells. These observations imply that blockade of the non-voltage-gated current does not block either Ca2+ entry or Ca(2+)-dependent lymphocyte proliferation, whereas blockade of the voltage-operable current does. The data suggest that the voltage-operable current may be a mediator of activation-induced Ca2+ entry in lymphocytes.

Amiloride↗
PubMed1996

Effects of volatile anesthetics on the G protein-regulated muscarinic potassium channel.

The muscarinic-activated K+ channel K(ACh), a prototype of channels regulated by neuroendocrine agonists via G proteins, was used to investigate the mode of action of isoflurane and halothane on G protein-coupled signal transduction processes. The evolution of the muscarinic current I(K(ACh)) was characterized through rapid agonist application and washout. At physiologically relevant concentrations, halothane and isoflurane reduced the rate of I(K(ACh)) activation without comparable effects on deactivation. Furthermore, both anesthetics reduced or eliminated the spontaneous decay (rapid desensitization) typical of the muscarinic response. In contrast to these similarities of anesthetic action on the time course of the response, the magnitude of I(K(ACh)) was slowly reduced by isoflurane but rapidly augmented by halothane. Neither halothane nor isoflurane altered the conductance of single I(K(ACh)) channels, indicating that these volatile anesthetics act on channel open-close kinetics. The reduced I(K(ACh)) activation rates suggest that impaired receptor/G protein interactions are induced by both anesthetics. For halothane, the increased amplitude of the response, also seen for I(K(ACh)) activated in a receptor-independent manner by guanosine-5'-O-(3-thio)triphosphate, suggests a direct action on the channel. Alteration of signal transduction processes by halothane and isoflurane may underlie some anesthetic actions of these compounds as well as secondary effects on the cardiovascular system.

Anesthetics, Inhalation↗
PubMed1995

Unitary anion currents through phospholemman channel molecules.

Phospholemman (PLM) is a 72-amino-acid peptide with a single transmembrane domain, the expression of which induces chloride currents in Xenopus oocytes. It has remained unknown whether PLM is an ion channel or acts as a channel regulator. Here we show, by measuring unitary anion currents across planar phospholipid bilayers to which immunoaffinity-purified recombinant PLM was added, that it does indeed form ion channels. Excised patches of oocytes expressing PLM had similar currents. Of the ions tested, the sulphonic amino acid taurine was the most permeant, and expression of PLM increased fluxes of radiolabelled taurine in oocytes. Phospholemman is the smallest protein in cell membranes known to form an ion channel and the taurine selectivity suggests that it is involved in cell volume regulation.

Animals↗
PubMed1995

Functional expression of an epitope-tagged G protein-coupled K+ channel (GIRK1).

An epitope-tagged form of an inwardly rectifying and G protein-coupled K+ channel (GIRK1-cp) was expressed at high levels in transfected mammalian cells. Immunoblot analysis of transfected human embryonic kidney cells (HEK293) and mouse insulinoma cells (beta TC3) revealed several GIRK1-cp polypeptides, including the major 59-kDa band, corresponding to the predicted mass of the GIRK1 polypeptide plus the epitope tag. Immunohistochemical staining using two anti-tag antibodies showed abundant immunoreactive material, which was predominantly concentrated in the perinuclear area in both transfected cell types. While functional GIRK1-cp message was present in poly(A)+ RNA prepared from HEK293 cells expressing GIRK1-cp protein, appropriate K+ currents could not be detected. In contrast, whole cell recordings made directly from transfected beta TC3 cells expressing GIRK1-cp revealed inwardly rectifying, pertussis toxin-sensitive currents activated by norepinephrine and galanin. Single channel recordings in excised patches of beta TC3 cells expressing GIRK1-cp showed rectifying K+ currents when activated by 50 microM guanosine 5'-O-(thiotriphosphate), with a slope conductance of 39.1 +/- 1.0 picosiemens. This is the first report of stable heterologous expression of a functional G protein-coupled K+ channel in mammalian cells. The activity of an epitope-tagged channel in insulinoma cells demonstrates the utility of this system for further biochemical and biophysical analyses of G protein-K+ channel interactions.

Animals↗
PubMed1995

Membrane depolarization prevents cell invasion by Bordetella pertussis adenylate cyclase toxin.

Adenylate cyclase toxin from Bordetella pertussis is a 177-kDa calmodulin-activated enzyme that has the ability to enter eukaryotic cells and convert endogenous ATP into cAMP. Little is known, however, about the mechanism of cell entry. We now demonstrate that intoxication of cardiac myocytes by adenylate cyclase toxin is driven and controlled by the electrical potential across the plasma membrane. The steepness of the voltage dependence of intoxication is comparable with that previously observed for the activation of K+ and Na+ channels of excitable membranes. The voltage-sensitive process is downstream from toxin binding to the cell surface and appears to correspond to the translocation of the catalytic domain across the membrane.

Adenylate Cyclase Toxin↗
PubMed1995

Anesthetics reduce the magnitude of the membrane dipole potential. Measurements in lipid vesicles using voltage-sensitive spin probes.

Lipid membranes possess a large internal dipole potential that greatly exceeds the magnitude of typical transmembrane or surface potentials. The volatile general anesthetics, halothane, isoflurane and enflurane were tested by the use of positively and negatively charged hydrophobic ion spin labels in lipid bilayer vesicles for their ability to modulate the membrane dipole potential. These anesthetics decreased the binding of negatively charged hydrophobic ion spin probes based on trinitrophenol, but increased the binding of positively charged hydrophobic ion probes based on triphenylalkylphosphoniums. They also enhanced the transit rates for both hydrophobic anions and cations; however, translocation rates were enhanced to a greater extent for the cation probes compared to the anion probes. The changes in binding constant for cations versus anions could be accurately accounted for using a simple model for the free energy profile for hydrophobic ions across membranes, and indicate that these anesthetics decrease the membrane dipole potential. From a fit of the experimental data to this model, anesthetics could promote a decrease in the dipole potential in two ways. First, anesthetics appear to modify the effective dipole moment in the membrane interface and may accomplish this by orienting their molecular dipole antiparallel to the intrinsic dipoles at the interface. Second, they modify the membrane dielectric constant, leading to a decrease in the field across the interface. At equivalent membrane concentrations, isoflurane, enflurane, and halothane produced similar changes in the dipole potential and decreased the dipole potential as much as 65 mV at a membrane mole fraction of 0.20.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1995

Inhibition of superantigen-induced T cell proliferation and monocyte IL-1 beta, TNF-alpha, and IL-6 production by acute ethanol treatment.

Alcohol use has been shown to decrease monocyte antigen presentation capacity and inflammatory cytokine production, thereby increasing susceptibility to infections. Here, we demonstrate that in vitro acute treatment of normal monocytes with pharmacological doses of ethanol can decrease superantigen [Staphylococcus enterotoxins B (SEB) and A (SEA)]-induced T cell proliferation. Furthermore, ethanol treatment (25-100 mM) significantly inhibited SEA- or SEB-induced production of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and IL-6 in monocytes. Ethanol-induced down-regulation of monocyte TNF-alpha, IL-1 beta, and IL-6 occurred at both the protein and mRNA levels. Additional data suggest that ethanol can decrease IL-1 beta mRNA stability. Furthermore, experiments using cycloheximide indicate that de novo protein synthesis is required for the inhibitory effect of ethanol on SEB-induced IL-1 beta mRNA production. Finally, ethanol treatment decreased HLA-DR expression in monocytes, suggesting that ethanol treatment can compromise monocyte stimulation by down-regulating the SEB-binding capacity of monocytes. These results suggest that acute ethanol treatment can interfere with monocyte activation by SEB at multiple steps. Consequently, decreased superantigen-induced polyclonal T cell activation and inflammatory monokine production would contribute to an impaired immune response to bacterial challenge with superantigens after acute alcohol intake.

Adult↗
PubMed1995

Cardiocirculatory effects of acutely increased intracranial pressure and subsequent brain death.

Hemodynamic instability and functional impairment of the donor heart are currently reported problems in organ transplantation. Actual shortage of potential donor hearts continues to raise controversial discussion about adequate donor management with regard to graft quality. In an experimental open chest model, physiopathologic effects of acutely induced, irreversible intracranial hypertension (AIIHT) were investigated in situ with respect to hemodynamics, cardiac pump and muscle function, and hormonal parameters. Acutely induced irreversible intracranial hypertension was induced by rapid inflation of a subdural balloon catheter in 10 anesthetized dogs, four animals serving as controls. The observation period in both groups was 300 min. Cardiocirculatory stability was maintained by continuous crystalloid volume substitution without the use of inotropic or pressor agents. After AIIHT, three characteristic hemodynamic response phases have been observed: 1) The "acute hyperdynamic phase" lasting up to 15 min with marked increases of heart rate (HR), left ventricular pressure (LVP), cardiac output (CO) and myocardial contractility indices, 2) At the end of the "early restabilization phase", (60 min), these parameters returned close to control levels, except HR (+50%) and systemic vascular resistance (SVR) (-40%), 3) During the "late restabilization phase", filling pressures, LVP and CO remained within control limits at low SVR, contractility indices showed a decreasing tendency. All assessed plasmatic hormones (Catecholamines, triiodothyronine (T3), thyroxine (T4), adrenocorticotropic hormone (ACTH), cortisol and anti-diuretic hormone (ADH) showed a continuous fall to levels significantly below control over the phases of restabilization. Acutely induced irreversible intracranial hypertension leads to multifactorial hemodynamic and hormonal changes. At low SVR, cardiac pump function was preserved exclusively by continuous volume substitution, while myocardial contractility indicated a slight decrease. From this observed hemodynamic and functional state within the donor organism, no reliable prediction on graft functional capacity can be made.

Animals↗