Tacrolimus and cyclosporine A inhibit allostimulatory capacity and cytokine production of human myeloid dendritic cells

Myeloid dendritic cells (DCs) are pivotal in the recognition of alloantigens and, therefore, in the induction of allograft rejection. Induction of alloreactive T cell proliferation by myeloid DCs depends on the maturation of DCs, the expression of costimulatory molecules, and the cytokine environment. This study investigated the effects of tacrolimus and cyclosporine A (CsA) on DC maturation and allostimulatory capacity. Myeloid DCs were propagated from normal blood monocytes with interleukin (IL) 4 and GM-CSF for 7 days in the presence or absence of tacrolimus (FK506; 10 nM) or CsA (1 microg/mL). Exposure of DCs during maturation to tacrolimus or CsA resulted in no significant change in the expression of DC phenotypic markers, including CD80, CD86, and HLA Class I and II antigens determined by flow cytometry. T cell proliferation in one-way, mixed-leukocyte reaction experiments revealed a decreased allostimulatory capacity of DCs that matured in the presence of tacrolimus or CsA compared with untreated controls (P<0.02). Production of inflammatory cytokines, tumor necrosis factor alpha (P<0.04) and IL-12 (P<0.04) in response to lipopolysaccharide (1 microg/mL) or staphylococcal enterotoxin B (1 microg/mL) induction was significantly reduced in DCs exposed to tacrolimus or CsA during maturation. In contrast, production of the immuninhibitory cytokine IL-10 was not decreased in tacrolimus- or CsA-treated DCs. These results suggest that tacrolimus and CsA inhibit the allostimulatory capacity of in vitro-generated myeloid DCs without significant effects on DC phenotypic maturation. Decreased production of IL-12 and tumor necrosis factor alpha, but not of IL-10, is likely to contribute to the impaired accessory-cell function of tacrolimus- and CsA-treated DCs. Thus, tacrolimus and CsA can inhibit recognition of alloantigens by decreasing the accessory-cell capacity of monocyte-derived myeloid DCs.

Interferon alpha and alcohol augment nuclear regulatory factor-kappaB activation in HepG2 cells, and interferon alpha increases pro-inflammatory cytokine production

BACKGROUND

The mechanisms for decreased therapeutic response to IFNalpha in chronic hepatitis C patients with alcohol are unknown. We investigated the hypothesis that IFNalpha and alcohol regulate cells both in the liver parenchyma and the immune system.

METHODS

We used the hepatocellular carcinoma cells (HepG2) to determine if IFNalpha (500-10,000 U/ml) or ethanol (25-100 mM) modulates NF-kB activation alone or in combination with TNFalpha (0.1-20 microg/ml) as determined in electromobility gel shift assays. IkB levels were evaluated in the cytoplasmic extracts by western blot. Monocytes from normal donors were activated with LPS (1 microg/ml) in combination with IFNalpha or ethanol overnight and TNFalpha, IL-6, and IL-12 were measured in the supernatants.

RESULTS

In HepG2 cells, both IFNalpha and acute alcohol treatment induced NF-kappaB activation and augmented TNFalpha-induced NF-kappaB binding. Pretreatment of HepG2 cells with IFNalpha resulted in the highest levels of NF-kappaB activation in response to TNFalpha or TNFalpha plus ethanol stimulation. Supershift experiments confirmed that the NF-kappaB dimer induced by TNFalpha and its combination with IFNalpha or ethanol contains RelA (p65) and involves rapid degradation of IkappaBalpha. Experiments using the proteasome inhibitor, MG132, revealed that augmentation of NF-kappaB by ethanol and IFNalpha is mediated via the proteasome pathway. We show that in normal monocytes, IFNalpha augments LPS-induced production of the inflammatory cytokines TNFalpha, IL-6, and IL-12 (p < 0.06) without further modulation by acute alcohol treatment.

CONCLUSIONS

These results suggest that IFNalpha can increase HepG2 cell sensitivity to TNFalpha and ethanol-mediated activation. Augmentation of monocyte inflammatory cytokines, particularly of IL-12 production, by IFNalpha could be a key element of the antiviral response in chronic HCV. These results support the hypothesis that the therapeutic benefits of IFNalpha likely involve activation of both immune and parenchymal cells in the liver.

Vertical bias in dendritic trees of non-pyramidal neocortical neurons expressing GAD67-GFP in vitro

The neocortical neuropil has a strong vertical (orthogonal to pia) orientation, constraining the intracortical flow of information and forming the basis for the functional parcellation of the cortex into semi-independent vertical columns or 'modules'. Apical dendrites of excitatory pyramidal neurons are a major component of this vertical neuropil, but the extent to which inhibitory, GABAergic neurons conform to this structural and functional design is less well documented. We used a gene gun to transfect organotypic slice cultures of mouse and rat neocortex with the enhanced green fluorescent protein (eGFP) gene driven by the promoter for glutamic acid decarboxylase 67 (GAD67), an enzyme expressed exclusively in GABAergic cells. Many GAD67-GFP expressing cells were highly fluorescent, and their dendritic morphologies and axonal patterns, revealed in minute detail, were characteristic of GABAergic neurons. We traced 150 GFP-expressing neurons from confocal image stacks, and estimated the degree of vertical bias in their dendritic trees using a novel computational metric. Over 70% of the neurons in our sample had dendritic trees with a highly significant vertical bias. We conclude that GABAergic neurons make an important contribution to the vertical neocortical neuropil, and are likely to integrate synaptic inputs from axons terminating within their own module.

Branching annihilating random walk on random regular graphs

The branching annihilating random walk is studied on a random graph whose sites have a uniform number of neighbors (z). The Monte Carlo simulations in agreement with the generalized mean-field analysis indicate that the concentration decreases linearly with the branching rate for z>/=4, while the coefficient of the linear term becomes zero if z=3. These properties are described by a modified mean-field theory taking explicitly into consideration the probability of mutual annihilation of the parent and its offspring particles using the returning features of a single walker on the same graph.

Management of recurrent hepatitis C after liver transplantation: a concise review

Recurrent hepatitis C infection and subsequent graft failure are increasingly recognized problems after orthotopic liver transplantation. Although many prospective therapeutic, controlled trials in primary hepatitis C disease have been reported, large-scale studies are yet to be performed in patients with posttransplant recurrent hepatitis C after liver transplantation. In this review, we summarize the current literature on the therapeutic approaches for recurrent hepatitis C and discuss the results of published studies on therapy with ribavirin or interferon (IFN) alone and on combination therapy with IFN plus ribavirin. Further, we discuss results of prophylactic approaches to the problem of recurrent hepatitis C after transplant. Finally, we discuss additional aspects of anti-hepatitis C virus therapy after liver transplantation.

Variable absorption of carbidopa affects both peripheral and central levodopa metabolism

Carbidopa (CD), a competitive inhibitor of aromatic l-amino acid decarboxylase that does not cross the blood-brain barrier, is routinely administered with levodopa (LD) to patients with Parkinson disease (PD) to reduce the peripheral decarboxylation of LD to dopamine. Using a stable isotope-labeled form of LD, the authors examined in 9 PD patients the effects of variable CD absorption on peripheral and central LD metabolism. Subjects were administered orally 50 mg of CD followed in 1 hour by a slow bolus intravenous infusion of 150 mg stable isotope-labeled LD (ring 1',2',3',4',5',6'-13C). Eight patients underwent a lumbar puncture 6 hours following the infusion. Blood and cerebrospinal fluid (CSF) samples were analyzed for labeled and unlabeled metabolites using a combination of high-performance liquid chromatography and mass spectrometry. When patients were divided into "slow" and "rapid" CD absorption groups, significantly greater peripheral LD decarboxylation (as measured by area under the curve [AUC]-labeled serum HVA) was noted in the poor absorbers (p = 0.05, Mann-Whitney U test). Elimination half-lives for serum LD did not differ between groups, suggesting a further capacity for decarboxylation inhibition in the "rapid" absorbers. A significant correlation between AUC serum CD and percent-labeled HVA in CSF was found for all patients (R = 0.786, p = 0.02). "Rapid" as compared to "slow" CD absorbers had significantly more percent-labeled CSF HVA (60 vs. 49, p = 0.02, Mann-Whitney U test), indicating greater central-labeled DA production in the better CD absorbers. The data suggest that peripheral aromatic l-amino acid decarboxylase activity is not saturated at CD doses used in current practice. The authors believe that future studies to better examine a dose dependence of CD on peripheral LD decarboxylation and LD brain uptake are warranted.

A lumped parameter model of left ventricular filling-pressure waveforms

Assessment of left-ventricular function and quantification of valve stenosis are important in clinical practice as well as in physiological research. This paper describes a mathematical model of diastolic ventricular filling and flow across the mitral valve. The model primarily consists of a system of three first-order, non-linear ordinary differential equations. The equations are solved in MATLAB using the ode45 command. The model generates pressure versus time waveforms for the atrium and ventricle, and flow versus time waveforms for mitral valve flow. Comparisons between model outputs and in-vivo data collected in two porcine experiments show excellent agreement.

Acceptance of an ABO-incompatible mismatched (AB(+) to O(+)) liver allograft with the use of daclizumab and mycophenolate mofetil

Liver allograft survival rates of 50% to 60% are reported in blood group A, group B, group O (ABO)-incompatible mismatched grafts even when aggressive immunosuppressive protocols, including plasmapheresis, OKT(3), cyclophosphamide, cyclosporine, prostaglandin E(1), and steroids, are used. A 59-year-old woman, blood type O(+), required emergency retransplantation posttransplantation day 2 because of primary nonfunction of the liver allograft. A blood type AB(+) allograft was used. Induction immunosuppressive therapy included tacrolimus, mycophenolate mofetil, OKT(3) (muromonab-CD(3)), steroids, and prostaglandin E(1). In addition, plasmapheresis was performed daily for 9 days. OKT(3) and prostaglandin E(1) were also discontinued postoperative day 9. Biopsy-proven acute cellular rejection was diagnosed postoperative day 12 and was treated with double-dose OKT(3) (10 mg) for another 6 days. On the day OKT(3) was discontinued, daclizumab, 60 mg, was administered intravenously. This dose was repeated every 2 weeks for a total of 5 doses. At 1-year follow-up, the patient is doing very well with normal liver function. We are unaware of previous reports of the use of daclizumab and mycophenolate mofetil as part of an immunosuppressive protocol aimed to induce acceptance of ABO-incompatible mismatched liver allografts. Based on our experience with this case, it seems that mycophenolate mofetil is an adequate replacement for cyclophosphamide. We also believe daclizumab provided adequate protection at a critical time. Further experience with both these drugs is required to establish their role in ABO-incompatible mismatched liver allografts.

Spatial evolutionary prisoner's dilemma game with three strategies and external constraints

The emergency of mutual cooperation is studied in a spatially extended evolutionary prisoner's dilemma game in which the players are located on the sites of cubic lattices for dimensions d=1, 2, and 3. Each player can choose one of the three following strategies: cooperation (C), defection (D) or "tit for tat" (T). During the evolutionary process the randomly chosen players adopt one of their neighboring strategies if the chosen neighbor has a higher payoff. Moreover, an external constraint imposes that the players always cooperate with probability p. The stationary state phase diagram is computed by both using generalized mean-field approximations and Monte Carlo simulations. Nonequilibrium second-order phase transitions associated with the extinction of one of the possible strategies are found and the corresponding critical exponents belong to the directed percolation universality class. It is shown that externally forcing the collaboration does not always produce the desired result.

Vascular tracheobronchial compression syndromes-- experience in surgical treatment and literature review

Between January 1988 and December 1997 a total of 22 patients (age: 8 days-46 years) were operated for vascular airway compression syndromes with respiratory insufficiency. Vascular anomalies in tracheal compression were double aortic arch in 7 patients, (2 previously operated elsewhere), right aortic arch + left ligamentum arteriosum in 1, and pulmonary artery sling in 3. Three of these patients had secondary long-segment tracheomalacia. Compression of trachea and a main bronchus existed in 2 patients with right aortic arch + left ligamentum. Isolated main bronchus obstruction was present in 9 patients (abnormal insertion of ligamentum arteriosum in 1, status post (s.p.) previous operation for PDA in 4, s. p. surgery for coarctation in 1, right aortic arch + left ligamentum arteriosum in 2, and right lung aplasia + left ligamentum in 1). 3 of these cases had secondary long-segment bronchomalacia. All patients had a complex respiratory anamnesis [long-term intubation in 7, s.p. tracheostomy in 2 (over 3 months - 3 years), and progressive respiratory insufficiency in 13). In tracheal compression, surgical correction included transsection of the underlying ring or sling components (with additional anterior aortic arch translocation in 5 patients resection-reimplantation of left pulmonary artery in 3, segmental tracheal resection in 1, and external tracheal suspension in 2). In the 2 cases with compression of the trachea and a main bronchus, aortic "extension" by a prosthetic tube was necessary. In isolated main bronchus obstruction, surgical decompression basically consisted of transsection of the ligamentum arteriosum or resection of its scarry remnant forming the "corner point" of a compression between aorta and pulmonary artery. In 3 patients with secondary long-segment malacia, additional external bronchus suspension was performed. Effective decompression and re-expansion of the airway segment concerned was achieved, and was demonstrated by intraoperative endoscopy in all patients. There were 3 postoperative deaths (sepsis 2; massive, irreversible edema of the tracheal mucosa 1). Of the 19 surviving patients 16 could be extubated between the 1st and 17th (mean = 7.5) postoperative day. In 1 case the preoperative long-term tracheostomy had to be left in place for inoperable additional laryngeal stricture. 2 patients had to be reoperated (segmental cervical tracheal resection after 5 months for primary long-term intubation-related subglottic stenosis in 1, esophageal decompression for residual dysphagia after 57 months related to a traction phenomenon at the right descending aorta in the other), both with gratifying results. In all other patients clinical, endoscopic, and radiographic examinations (follow-up = 2 months - 6 years) demonstrate good results.

Refolded outer membrane protein A of Escherichia coli forms ion channels with two conductance states in planar lipid bilayers

Outer membrane protein A (OmpA), a major structural protein of the outer membrane of Escherichia coli, consists of an N-terminal 8-stranded beta-barrel transmembrane domain and a C-terminal periplasmic domain. OmpA has served as an excellent model for studying the mechanism of insertion, folding, and assembly of constitutive integral membrane proteins in vivo and in vitro. The function of OmpA is currently not well understood. Particularly, the question whether or not OmpA forms an ion channel and/or nonspecific pore for uncharged larger solutes, as some other porins do, has been controversial. We have incorporated detergent-purified OmpA into planar lipid bilayers and studied its permeability to ions by single channel conductance measurements. In 1 M KCl, OmpA formed small (50-80 pS) and large (260-320 pS) channels. These two conductance states were interconvertible, presumably corresponding to two different conformations of OmpA in the membrane. The smaller channels are associated with the N-terminal transmembrane domain, whereas both domains are required to form the larger channels. The two channel activities provide a new functional assay for the refolding in vitro of the two respective domains of OmpA. Wild-type and five single tryptophan mutants of urea-denatured OmpA are shown to refold into functional channels in lipid bilayers.

A dominant negative mutant of Helicobacter pylori vacuolating toxin (VacA) inhibits VacA-induced cell vacuolation

Most Helicobacter pylori strains secrete a toxin (VacA) that causes structural and functional alterations in epithelial cells and is thought to play an important role in the pathogenesis of H. pylori-associated gastroduodenal diseases. The amino acid sequence, ultrastructural morphology, and cellular effects of VacA are unrelated to those of any other known bacterial protein toxin, and the VacA mechanism of action remains poorly understood. To analyze the functional role of a unique strongly hydrophobic region near the VacA amino terminus, we constructed an H. pylori strain that produced a mutant VacA protein (VacA-(Delta6-27)) in which this hydrophobic segment was deleted. VacA-(Delta6-27) was secreted by H. pylori, oligomerized properly, and formed two-dimensional lipid-bound crystals with structural features that were indistinguishable from those of wild-type VacA. However, VacA-(Delta6-27) formed ion-conductive channels in planar lipid bilayers significantly more slowly than did wild-type VacA, and the mutant channels were less anion-selective. Mixtures of wild-type VacA and VacA-(Delta6-27) formed membrane channels with properties intermediate between those formed by either isolated species. VacA-(Delta6-27) did not exhibit any detectable defects in binding or uptake by HeLa cells, but this mutant toxin failed to induce cell vacuolation. Moreover, when an equimolar mixture of purified VacA-(Delta6-27) and purified wild-type VacA were added simultaneously to HeLa cells, the mutant toxin exhibited a dominant negative effect, completely inhibiting the vacuolating activity of wild-type VacA. A dominant negative effect also was observed when HeLa cells were co-transfected with plasmids encoding wild-type and mutant toxins. We propose a model in which the dominant negative effects of VacA-(Delta6-27) result from protein-protein interactions between the mutant and wild-type VacA proteins, thereby resulting in the formation of mixed oligomers with defective functional activity.

Inhibition of lipopolysaccharide-mediated NFkappaB activation by ethanol in human monocytes

Alcohol use is typically associated with impaired immunity and increased host susceptibility to infection, partially due to decreased inflammatory response. Acute ethanol exposure has been shown to down-regulate monocyte production of inflammatory cytokines. Activation of the pluripotent transcription factor NFkappaB is a pivotal step in the induction of inflammatory cytokines, chemokines and growth factors. Therefore, we hypothesized that alcohol may alter NFkappaB activation, thus providing a mechanism for the decreased inflammatory cytokine production by monocytes after acute alcohol treatment. We show here for the first time that alcohol inhibits lipopolysaccharide (LPS)-induced NFkappaB activation in human monocytes by decreasing DNA binding of the p65/p50 heterodimer as seen in electrophoretic mobility shift and supershift assays. We also demonstrate that alcohol prevents LPS-induced nuclear translocation of p65 and to a lesser extent that of the p50 subunits. NFkappaB activation is regulated via phosphorylation and proteolytic degradation of IkappaB. Thus, we investigated the effect of acute ethanol treatment on IkappaB in human monocytes. Alcohol did not prevent LPS-induced IkappaBalpha degradation but decreased the levels of phospho-specific IkappaBalpha (Ser32). Finally, for the first time we show that de novo protein synthesis is necessary to bring about the ethanol-mediated inhibition of LPS-induced NFkappaB activation. Consequently, these results suggest that physiologically relevant concentrations of alcohol interfere with NFkappaB activation and thereby may affect the regulation of NFkappaB-controlled gene activation.

Consequences of alcohol consumption on host defence

This communication reviews recent literature and summarizes current views on the immunomodulatory effects of acute and chronic alcohol consumption. Chronic and even acute, moderate alcohol use can increase host susceptibility to infections caused by bacterial and viral pathogens. Impaired host defence after alcohol exposure appears to be linked to a combination of decreased inflammatory response, altered cytokine production, and abnormal reactive oxygen intermediate generation. Furthermore, cellular immunity, particularly antigen-specific immune response, is impaired by both acute and chronic alcohol use. Although T lymphocyte functions can be directly affected by ethanol, decreased antigen presenting cell function appears to be a key element in the ethanol-induced decrease in cell-mediated immunity. In addition, a preferential induction of Th2 vs Th1 immune response has been suggested, based on the increased immunoglobulin levels seen in chronic alcoholics. The effects of chronic and acute alcohol consumption in humans, animal models and in vitro systems on host defence and immunity are discussed in the context of the functional abnormalities of T and B lymphocytes, natural killer cells and monocytes/macrophages resulting in the altered immune response seen after alcohol use.

Palmitoylation of the recombinant human A1 adenosine receptor: enhanced proteolysis of palmitoylation-deficient mutant receptors

Palmitoylation of the recombinant human A(1) adenosine receptor (A(1)AR) expressed in HEK-293 cells is demonstrated by showing that hexahistidine (His(6))/Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys (FLAG) (H/F) A(1)ARs, purified to homogeneity from cells metabolically labelled with [(3)H]palmitate, incorporate tritium into a 38-42 kDa receptor glycoprotein. The amount of palmitoylation is not affected by incubation of cells with the A(1)AR-selective agonist N(6)-cyclopentyladenosine (CPA). A(1)AR palmitoylation is abolished by treatment with neutral hydroxylamine or by mutation of Cys-309 to Ala (C(309)-->A). Based on Western blotting and pulse-chase experiments with [(35)S]methionine, at least 90% of wild-type receptors are palmitoylated and turn over with a t1/2 of 6.4 h. Of the C(309)-->A mutated receptors, 40% appear to turn over like wild-type receptors, with a t1/2 of 7.1 h, and 60% appear to be rapidly cleaved to form a 25 kDa receptor fragment that turns over with a t1/2 of 0.8 h. In HEK-293 cell lines expressing similar numbers of wild-type or C(309)-->A mutant A(1)Rs, there is little difference in the kinetics of CPA-induced receptor internalization (1 h), down-regulation (24 h), inhibition of forskolin-stimulated cAMP accumulation, or activation of co-transfected G-protein-activated inward rectifier K(+)/cardiac inward rectifying K(+) (GIRK1/CIR K(+)) channels. Also unaffected by palmitoylation is guanosine 5'-[gamma-thio]-triphosphate ([S]GTP)-sensitive binding to membranes by the agonist (125)I-labelled aminobenzyladenosine. The results suggest that palmitoylation has little effect on receptor-effector coupling, agonist-induced internalization or down-regulation. We speculate that palmitoylation may divert newly synthesized A(1)ARs from a pathway leading to rapid degradation.