Antibacterial agents based on the cyclic D,L-alpha-peptide architecture

The rapid emergence of bacterial infections that are resistant to many drugs underscores the need for new therapeutic agents. Here we report that six- and eight-residue cyclic d,l-alpha-peptides act preferentially on Gram-positive and/or Gram-negative bacterial membranes compared to mammalian cells, increase membrane permeability, collapse transmembrane ion potentials, and cause rapid cell death. The effectiveness of this class of materials as selective antibacterial agents is highlighted by the high efficacy observed against lethal methicillin-resistant Staphylococcus aureus infections in mice. Cyclic d,l-alpha-peptides are proteolytically stable, easy to synthesize, and can be derived from a potentially vast membrane-active sequence space. The unique abiotic structure of the cyclic peptides and their quick bactericidal action may also contribute to limit temporal acquirement of drug resistant bacteria. The low molecular weight d,l-alpha-peptides offer an attractive complement to the current arsenal of naturally derived antibiotics, and hold considerable potential in combating a variety of existing and emerging infectious diseases.

Biochemical, electrophysiological and neurohormonal studies with B-20991, a selective 5-HT1A receptor agonist

Different receptor subtypes mediate the effects produced by serotonin (5-HT) in mammals. Besides their proved anxiolytic action, agonists of the 5-HT1A receptor subtype show prospects as antidepressants or neuroprotective agents in case of ischemia. In order to better define the pharmacological profile and determine the selectivity for the 5-HT receptor type, the properties of the new 5-HT1A receptor agonist 2[[4-(o-methoxyphenyl)piperazin-1-yl]-methyl]-1.3-dioxoperhydroimidazo[1.5-a]pyridine (B-20991), an arylpiperazine derivative, have now been further studied. B-20991 was found to antagonize the forskolin-induced increase of cAMP synthesis in a HeLa cell line transfected with the human 5-HT1A in a process sensitive to the selective blocker N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinyl-cyclohexanecarboxamide maleate (WAY 100635). Additionally, B-20991 showed a dose-dependent inhibition of the spontaneous on-going activity of serotonin (5-HT) neurons in the dorsal raphe nucleus in rats, an effect that was reversed by treatment with WAY 100635. This, together with the fact that the hypothermia induced by B-20991 in mice was also antagonized by WAY 100635, suggests that the new compound acts upon somatodendritic 5-HT1A receptors. Additional activation of 5-HT1A postsynaptic receptors was indicated by the increase of corticosterone plasma levels induced by B-20991 in the rat. These results demonstrate that B-20991 is a selective 5-HT1A receptor agonist acting both pre- and postsynaptically, which represents an useful pharmacological tool to study 5-HT1A-receptor-mediated effects.

Inhibition of endotoxin-induced macrophage chemokine production by vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide in vitro and in vivo

Inflammatory chemokines recruit various populations of immune cells that initiate and maintain the inflammatory response against foreign Ags. Although such a response is necessary for the elimination of the Ag, the inflammation has to be eventually resolved in a healthy organism. Neuropeptides such as vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP), released after antigenic stimulation, contribute to the termination of an inflammatory response primarily by inhibiting the production of proinflammatory cytokines. Here we investigated the effects of VIP and PACAP on chemokine production. We report that VIP and PACAP inhibit the expression of the macrophage-derived CXC chemokines macrophage inflammatory protein-2 and KC (IL-8), and of the CC chemokines MIP-1alpha, MIP-1beta, monocyte chemoattractant protein 1, and RANTES in vivo and in vitro. The inhibition of chemokine gene expression correlates with an inhibitory effect of VIP/PACAP on NF-kappaB binding and transactivating activity. The VIP/PACAP inhibition of both chemokine production and of NF-kappaB binding and transactivating activity is mediated through the specific VIP receptor VPAC1, and involves both cAMP-dependent and -independent intracellular pathways. In an in vivo model of acute peritonitis, the inhibition of chemokine production by VIP/PACAP leads to a significant reduction in the recruitment of polymorphonuclear cells, macrophages, and lymphocytes into the peritoneal cavity. These findings support the proposed role of VIP and PACAP as key endogenous anti-inflammatory agents and describe a novel mechanism, i.e., the inhibition of the production of macrophage-derived chemokines.

Bacterial colonization of endotracheal tubes in intubated neonates

OBJECTIVE

To obtain in vivo bacterial colonization profiles on endotracheal tubes at different sites in the neonatal airway in an attempt to better characterize one potential element of chondritis.

DESIGN

A case series in which cultures were obtained from calculated segments of 33 endotracheal tubes immediately following extubation. This allowed for sampling at specific levels of the airway corresponding to the trachea, the subglottis, and the oropharynx. Data collected included gender, race, duration of intubation, use of antibiotic therapy, comorbidities, gestational age at birth and extubation, crown-rump length, weight, radiographic distance from tube tip to carina, and culture results.

SETTING

Newborn intensive care unit at a tertiary care medical center.

PATIENTS

Twenty-nine neonates intubated for longer than 24 hours (range, 24 hours to 15 days).

MAIN OUTCOME MEASURES

Bacterial and fungal cultures obtained from 3 endotracheal tube segments for each extubation.

RESULTS

A statistically significant difference (P < .05) was found in colonization rates between patients intubated for less than 4 days and those intubated for longer periods. No significant difference was noted in bacterial profile between the 3 sites.

CONCLUSIONS

Data demonstrate that bacterial colonization of an indwelling object in the neonatal airway increases with the duration of intubation. Furthermore, 4 days seems to represent a critical period in the formation of such colonization (possibly in the form of a biofilm). These bacteria may contribute to the chondritis known to precede the development of subglottic stenosis. Further studies are indicated to suggest ways to interrupt this process and reduce the incidence of airway injury.

Immunogenicity of recombinant class 1 protein from Neisseria meningitidis refolded into phospholipid vesicles and detergent

The possibility of eliciting bactericidal antibodies against a recombinant class 1 protein (P1) from Neisseria meningitidis, joined to the first 45 amino acids of the neisserial LpdA protein (PM82), was examined. P1 was produced in Escherichia coli as intracellular inclusion bodies, from which it was purified and reconstituted by (a) inclusion into phospholipid vesicles and detergent and (b) refolding in 0.1% SDS. When Balb/c mice were immunised, high titres of subtype-specific bactericidal antibodies against P1 were obtained in both cases. These results suggest that in spite of being a denaturing agent, it is possible to use SDS to reconstitute the P1 protein in a conformation that exposes the immunodominat regions.

Vasoactive intestinal peptide prevents experimental arthritis by downregulating both autoimmune and inflammatory components of the disease

Rheumatoid arthritis (RA) is a chronic and debilitating autoimmune disease of unknown etiology, characterized by chronic inflammation in the joints and subsequent destruction of the cartilage and bone. We describe here a new strategy for the treatment of arthritis: administration of the neuropeptide vasoactive intestinal peptide (VIP). Treatment with VIP significantly reduced incidence and severity of arthritis in an experimental model, completely abrogating joint swelling and destruction of cartilage and bone. The therapeutic effect of VIP was associated with downregulation of both inflammatory and autoimmune components of the disease. Our data indicate VIP as a viable candidate for the development of treatments for RA.

Cutting edge: is vasoactive intestinal peptide a type 2 cytokine?

A component of the chemical language shared by the immune and nervous system is the expression of neuropeptides by immune cells. Vasoactive intestinal peptide (VIP) was shown to be produced by T lymphocytes. Here we investigate whether T cell subsets differentially express VIP. Our studies indicate that, upon specific Ag stimulation, Th2 and T2 cells, but not Th1 and T1 cells derived from TCR transgenic (Tg) mice, express VIP mRNA and protein, and secrete VIP. Following immunization with the specific Ag, significant levels of VIP are present in the serum of syngeneic, non-Tg hosts that receive Th2, but not Th1 Tg cells. Th2 Tg cells recovered from the non-Tg hosts immunized with the specific Ag, but not with an irrelevant Ag, express intracellular VIP. Because VIP is produced by Ag-stimulated type 2 T cells, and differentially affects Th1 and Th2 cells, could VIP be viewed as a type 2 cytokine?

VIP and PACAP inhibit activation induced apoptosis in T lymphocytes

Apoptosis in T and B lymphocytes is a major element controlling the immune response. Activation induced cell death (AICD) in T cells is a main mechanism for maintaining peripheral tolerance and for limiting an ongoing immune response. AICD is initiated by antigen reengagement of the T cell receptor (TCR), and mediated through Fas/Fas ligand (FasL) interactions. VIP and PACAP are two multifunctional neuropeptides present in the lymphoid microenvironment that act primarily as anti-inflammatory agents. In this study we report on the role of VIP and PACAP on T cell AICD, and on the mechanisms involved. VIP and PACAP inhibit AICD in vivo and in vitro, in peripheral T cells and T cell hybridomas. The effect is dose dependent and is mediated through the specific receptors VPAC1 and VPAC2. The inhibition of AICD is achieved through reduction in FasL expression at protein and mRNA level. By affecting FasL expression, VIP and PACAP may play a physiological role in both the generation of memory T cells and the inhibition of FasL-mediated T cell cytotoxicity.

Receptors and transcriptional factors involved in the anti-inflammatory activity of VIP and PACAP

VIP and PACAP modulate the function of inflammatory cells through specific receptors. VIP/PACAP inhibit the production of TNF alpha, IL-6, IL-12, and nitric oxide (NO), and stimulate IL-10 in peritoneal macrophages and Raw 264.7 cells. Here we report on the specific VIP/PACAP receptors, transduction pathways, and transcriptional factors involved in the regulation of these macrophage factors by VIP and PACAP. Both neuropeptides inhibit IL-6 production mainly through PAC1 binding, PKC activation, and the subsequent shedding of the LPS receptor CD14 in macrophages. However, the effects on TNF alpha, IL-10, IL-12, and NO are mostly mediated through the constitutively expressed VPAC1 receptor, although the inducible expressed VPAC2 may also participate. VIP/PACAP binding to VPAC1 induces both a cAMP-dependent and a cAMP-independent pathways that regulate cytokine and NO production at the transcriptional level. VIP/PACAP inhibit TNF alpha through reduction in NFkB binding and changes in the composition of CRE-binding complexes; they inhibit IL-12 through reduction in NFkB binding and changes in the composition of the ets-2 complexes. VIP/PACAP inhibit iNOS expression through reduction in NFkB and IRF-1 binding, and augment IL-10 by increasing CREB-binding. Whereas the inhibition of IRF-1 and CRE-binding complexes seems to be mediated through the cAMP-dependent pathway, VIP/PACAP inhibition of NFkB nuclear translocation is mediated through a reduction in IkB alpha degradation mediated by the cAMP-independent pathway. This study provides new evidence for the understanding of the molecular mechanism by means of which VIP and PACAP attenuate the inflammatory response.

Modification of wheat rDNA loci by rye B chromosomes: a chromatin organization model

The rDNA loci, and their associated NORs, on chromosomes 1B and 6B of the hexaploid wheat cv. Lindström have been used as a chromatin marker to investigate the functional basis of the phenotype effects of introgressed supernumerary B chromosomes (Bs) of rye. The rye Bs themselves lack genes, other than those which determine their mitotic drive mechanism, and the way in which they can modulate characters determined by the A chromosome background has always been a puzzle. An isogenic line of Lindström plants carrying different numbers of Bs was used as the experimental system to see how different doses of Bs (from 0 to 6) affected the activity of the wheat NORs and the organization of their rDNA loci at interphase. Silver staining on metaphase chromosomes was used to evaluate the previous activity of the NORs, and to reveal variations in their size; and the pTa71 FISH probe from wheat was used to visualize structural modifications to the interphase rDNA loci. A single B had no measurable effect, but, as the B-number increased, there were significant changes in the physical dimensions of the metaphase NORs, reflecting reduced levels of their activity earlier in the cell cycle, and also in the condensation patterns of the interphase rDNA loci. In addition, the higher B-numbers caused a size heteromorphism between the homologous NORs. A model is discussed which interprets the phenotypic effects of Bs generically, in nucleotypic terms, based of their being 'genetically inert' but 'chromosomally active'.

[The usefulness of sucralfate in postoperative improvement of children's tonsillectomy]

INTRODUCTION

Sucralfate is an effective agent in the treatment of peptic ulcer, mixing up the fibrinous exudate of duodenal ulcer to form a protective barrier promoting its healing. Similarly the deprived muscle in the tonsillar bed results protected and consequently bring down the post-surgical morbidity.

OBJECTIVE

The aim of this study has been to ascertain the suitability of sucralfate in alleviating symptoms after tonsil's removal.

MATERIAL AND METHODS

205 children were included in the study and randomly postoperative treated with sucralfate. A lot of different parameters were controlled afterwards such as days with pain, taken of analgesics, return to normal diet, fever, bloody saliva, halitosis or vomits.

RESULTS

There was a significant association between the use of sucralfate and less days with sore throat, less pain and analgesia required.

CONCLUSIONS

The use of sucralfate means and efficient measure in order to alleviate the pain and postoperative discomfort associated with tonsils removal, being a cheap drug and without having topical after-effects.

VIP and PACAP induce shift to a Th2 response by upregulating B7.2 expression

VIP and PACAP, two structurally related neuropeptides produced within the lymphoid microenvironment, modulate several immunological functions. Although primarily anti-inflammatory in nature, VIP and PACAP also affect resting macrophages. In this study, we report on the role of VIP and PACAP on macrophage B7 expression and costimulatory function for antigen-primed CD4+ T cells, and on the macrophage-induced regulation of Th1/Th2 differentiation in vitro and in vivo. VIP and PACAP upregulate B7.2, but not B7.1, MHC class II, or ICAM-1 expression, and activate macrophages to stimulate the proliferation of naïve T cells in response to soluble anti-CD3 or allogeneic stimulation. The stimulatory effect is mediated through the specific receptor VPAC1, and involves the cAMP/PKA pathway as second messengers. The enhancement in B7.2 expression occurs at both mRNA and protein levels, and correlates with the VIP/PACAP induced upregulation of the costimulatory activity of macrophages for antigen-primed CD4+ T cells. VIP/PACAP-treated macrophages gain the ability to induce Th2-type cytokines such as IL-4 and IL-5, and to reduce Th1-type cytokines such as IFN gamma and IL-2. In vivo administration of VIP or PACAP in antigen-immunized mice reduces the numbers of IFN gamma-secreting cells, enhances the numbers of IL-4-secreting cells, and affects the pattern of antigen-specific Ig isotypes. The preferential differentiation into Th2 effector cells induced by VIP/PACAP-treated macrophages is mediated through the upregulation of B7.2 expression. Since Th1-dominated responses are associated with some autoimmune diseases and inflammatory reactions typical of cell-mediated immunity, the VIP/PACAP inhibition of Th1 development may represent an additional mechanism for the general anti-inflammatory activity of the two neuropeptides.

Cryptococcus neoformans in bird excreta in the city zoo of Cali, Colombia

The presence of Cryptococcus neoformans was studied in bird excreta and in the air circulating in and around bird cages in the City Zoo of Cali, Colombia, between August 1994 and April 1995, using a sunflower seed agar culture medium for fungus isolation. A total of 380 samples was studied, 110 from droppings and 270 from Petri dishes placed inside (148) and outside (122) the cages. C. neoformans var neoformans was found in only two cases, one from bird excreta (0.9%) and the other from air inside a cage (0.7%). The former positive sample was collected from the cracks of a dead tree where two crested caracaras (Polyborus plancus) roosted; the feces were dry, accumulated, and with a pH of 6. The other positive sample was found inside the cage of these birds; however, samples taken in a dispersion study at 0.5, 1, 5 and 10 m around this cage were all negative. It appears that this low isolation rate is due to adequate cleaning and disinfection procedures used in the city zoo of Cali.

Inhibitory neuropeptide receptors on macrophages

The immune response, both in innate and adaptive immunity, is controlled at several levels, including signaling from the central nervous system. Neuropeptides released within the lymphoid organs modulate the immune response, either as stimulators or inhibitors. The subject of this review is the description of macrophage-expressed receptors of inhibitory neuropeptides. We describe the inhibitory effects on macrophage function for several neuropeptides, the receptors that mediate those activities, and the molecular mechanisms initiated by some of these receptors in terms of transduction pathways and transcriptional factors.

Mapping of monoclonal antibodies specific to P64k: A common antigen of several isolates of Neisseria meningitidis

P64k is a minor outer membrane protein from Neisseria meningitidis. This protein has been produced at high levels in Escherichia coli. We generated a group of monoclonal antibodies (mAbs) against recombinant P64k, which recognise four non-overlapping epitopes, as shown using competition assays with biotinylated mAbs. The P64k sequences involved in mAbs binding were mapped with synthetic overlapping peptides derived from the P64k protein, and located in the previously determined three-dimensional structure of the protein. These antibodies were also characterised by whole-cell ELISA and bactericidal tests against N. meningitidis. Only two of the recognised epitopes were exposed on the bacterial surface, and none of the mAbs showed bactericidal activity. The relationship between these results and the structural data on the epitopes bound by the mAbs is discussed.Key words: Neisseria meningitidis, P64k, monoclonal antibodies, epitope mapping.

Mapping of monoclonal antibodies specific to P64k: a common antigen of several isolates of Neisseria meningitidis

P64k is a minor outer membrane protein from Neisseria meningitidis. This protein has been produced at high levels in Escherichia coli. We generated a group of monoclonal antibodies (mAbs) against recombinant P64k, which recognise four non-overlapping epitopes, as shown using competition assays with biotinylated mAbs. The P64k sequences involved in mAbs binding were mapped with synthetic overlapping peptides derived from the P64k protein, and located in the previously determined three-dimensional structure of the protein. These antibodies were also characterised by whole-cell ELISA and bactericidal tests against N. meningitidis. Only two of the recognised epitopes were exposed on the bacterial surface, and none of the mAbs showed bactericidal activity. The relationship between these results and the structural data on the epitopes bound by the mAbs is discussed.

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit expression of Fas ligand in activated T lymphocytes by regulating c-Myc, NF-kappa B, NF-AT, and early growth factors 2/3

Activation-induced cell death in T cells, a major mechanism for limiting an ongoing immune response, is initiated by Ag reengagement and mediated through Fas/Fas ligand interactions. Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP), two multifunctional neuropeptides, modulate innate and adaptive immunity. We reported previously that VIP/PACAP protect T cells from activation-induced cell death through down-regulation of Fas ligand (FasL). In this study, we investigate the molecular mechanisms involved in the protective effect of VIP and PACAP. VIP/PACAP reduce in a dose-dependent manner anti-CD3-induced apoptosis in 2B4.11 T cell hybridomas. The protective effect is mediated through the specific type 2 VIP receptor, and the cAMP/protein kinase A pathway. A functional study demonstrates that VIP/PACAP inhibit activation-induced FasL expression. VIP/PACAP inhibit the expression and/or DNA-binding activity of several transcriptional factors involved in FasL expression, i.e., c-myc, NF-kappaB, NF-ATp, and early growth factors (Egr) 2/3. The inhibition of NF-kappaB binding is due to the stabilization of I-kappaB (inhibitory protein that dissociates from NF-kappaB), through the inhibition of I-kappaB kinase alpha activity. Subsequently, p65 nuclear translocation is significantly reduced. The inhibition in NF-ATp binding results from a calcineurin-independent reduction in NF-ATp nuclear translocation. VIP/PACAP inhibit the expression of Egr2 and 3, but not of Egr1. The effects on the transcriptional factors are mediated through type 2 VIP receptor with cAMP as secondary messenger.

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit nuclear factor-kappa B-dependent gene activation at multiple levels in the human monocytic cell line THP-1

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) suppress monocyte/macrophage production of proinflammatory agents. The transcription factor NF-kappa B regulates the transcription of most agents. VIP/PACAP inhibit NF-kappa B transactivation in the lipopolysaccharide-stimulated human monocytic cell line THP-1 at multiple levels. First, VIP/PACAP inhibit p65 nuclear translocation and NF-kappa B DNA binding by stabilizing the inhibitor I kappa B alpha. Second, VIP/PACAP induce phosphorylation of the CRE-binding protein (CREB) and its binding to the CREB-binding protein (CBP). This results in a decrease in p65.CBP complexes, which further reduces NF-kappa B transactivation. Third, VIP and PACAP reduce the phosphorylation of the TATA box-binding protein (TBP), resulting in a reduction in TBP binding to both p65 and the TATA box. All these effects are mediated through the specific receptor VPAC1. The cAMP/cAMP-dependent protein kinase pathway mediates the effects on CBP and TBP, whereas a cAMP-independent pathway is the major transducer for the effects on p65 nuclear translocation. Since NF-kappaB represents a focal point for various stimuli and induces the expression of many proinflammatory genes, its targeting by VIP and PACAP positions them as important anti-inflammatory agents. The VIP/PACAP inhibition of NF-kappa B at various levels and through different transduction pathways could offer a significant advantage over other anti-inflammatory agents.

Mining association rules with improved semantics in medical databases

The discovery of new knowledge by mining medical databases is crucial in order to make an effective use of stored data, enhancing patient management tasks. One of the main objectives of data mining methods is to provide a clear and understandable description of patterns held in data. We introduce a new approach to find association rules among quantitative values in relational databases. The semantics of such rules are improved by introducing imprecise terms in both the antecedent and the consequent, as these terms are the most commonly used in human conversation and reasoning. The terms are modeled by means of fuzzy sets defined in the appropriate domains. However, the mining task is performed on the precise data. These "fuzzy association rules" are more informative than rules relating precise values. We also introduce a new measure of accuracy, based on Shortliffe and Buchanan's certainty factors [Shortliffe E, Buchanan B. Math Biosci 1975;23:351-79]. Also, the semantics of the usual measure of usefulness of an association rule, called support are discussed and some new criteria are introduced. Our new measures have been shown to be more understandable and appropriate than ordinary ones. Several experiments on large medical databases show that our new approach can provide useful knowledge with better semantics in this field.

Immunology of VIP: a review and therapeutical perspectives

Vasoactive intestinal peptide (VIP) is a neuropeptide with a broad distribution in the body that exerts very important pleiotropic functions in several systems. The present work reviews the immunology of VIP. Being daring, this neuropeptide could be included in the group of cytokines since it is produced and secreted by different immunocompetent cells in response to various immune signals, plays a broad spectrum of immunological functions, and exerts them, in a paracrine and/or autocrine way, through three different specific receptors. Although VIP has been classically considered as an immunodepressant agent, and its main described role has been as an anti-inflammatory factor, several evidences suggest that a better way to see this peptide is as a modulator of the homeostasis of the immune system. In the last decade, the pharmacology of VIP has spectacularly grown, and VIP itself, as well as more stable VIP-derived agents, have been used or proposed as efficient therapeutical treatments of several disorders, specially inflammatory and autoimmune diseases, such as septic shock, rheumatoid arthritis, multiple sclerosis, Crohn's disease and autoimmune diabetes. A broad field of perspectives is actually open, and further investigations will help us to definitively understand the immunology of this very important peptide.

Neuropeptides as modulators of macrophage functions. Regulation of cytokine production and antigen presentation by VIP and PACAP

Vasoactive intestinal peptide (VIP) and the structurally related neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP), present in the microenvironment of lymphoid organs, modulate the function of inflammatory cells through specific receptors. VIP and PACAP inhibit the production of pro-inflammatory agents and stimulate the production of anti-inflammatory cytokines in activated macrophages. The effect is mediated through specific receptors and involves shedding of the CD14 lipopolysaccharide (LPS) receptor and the transcriptional regulation of cytokine genes through effects on de novo expression or nuclear translocation of NFkappaB, cAMP-element binding protein (CREB), c-Jun, and interferon regulatory factor 1 (IRF-1). The in vivo administration of VIP/PACAP results in a similar pattern of cytokine modulation which, presumably, mediates the protective effect of VIP/PACAP in a high-endotoxic murine model for septic shock. VIP/PACAP reduce the expression of the costimulatory B7.1/B7.2 molecules and the subsequent stimulatory activity for T helper (Th) cells in stimulated macrophages. In contrast, in unstimulated macrophages, VIP/PACAP induce specific B7.2 expression and promote Th2 cell differentiation. We propose that VIP/PACAP act as endogenous factors that regulate immune homeostasis and that the physiological consequences of VIP/PACAP presence in the immune microenvironment depend on the timing of the neuropeptide release and the activation stage of the neighboring immune cells.

A real-coded genetic algorithm for training recurrent neural networks

The use of Recurrent Neural Networks is not as extensive as Feedforward Neural Networks. Training algorithms for Recurrent Neural Networks, based on the error gradient, are very unstable in their search for a minimum and require much computational time when the number of neurons is high. The problems surrounding the application of these methods have driven us to develop new training tools. In this paper, we present a Real-Coded Genetic Algorithm that uses the appropriate operators for this encoding type to train Recurrent Neural Networks. We describe the algorithm and we also experimentally compare our Genetic Algorithm with the Real-Time Recurrent Learning algorithm to perform the fuzzy grammatical inference.

VIP and PACAP inhibit Fas ligand-mediated bystander lysis by CD4(+) T cells

FasL/Fas-mediated lysis represents the major cytotoxic mechanism for CD4(+) effectors, with important consequences for immune cell homeostasis. Upon stimulation by specific antigen-presenting cells (APCs), CD4(+) effectors can lyse the cognate APCs (direct targets) and neighboring innocent bystanders. Previously we showed that the neuropeptides VIP and PACAP prevent FasL expression and activation-induced cell death in T cells. In this study we investigated the effects of VIP and PACAP on FasL expression and subsequent direct and bystander lysis by CD4(+) effectors generated in vivo. VIP/PACAP inhibit FasL expression in allogeneic effectors, and reduce Fas-mediated cytotoxicity against specific allotargets and syngeneic bystanders. VIP/PACAP also inhibit FasL expression in antigen-specific CD4(+) effectors, and reduce their cytotoxic activity against both the stimulatory APC, and syngeneic or allogeneic bystanders. Since bystander lysis is involved in the pathogenesis of several autoimmune and inflammatory diseases, the identification of regulatory factors that limit this process is highly significant.

Anti-inflammatory properties of the type 1 and type 2 vasoactive intestinal peptide receptors: role in lethal endotoxic shock

Vasoactive intestinal peptide (VIP) is a neuropeptide that can modulate several immune aspects. Previous reports showed that VIP attenuates the deleterious consequences of septic shock by inhibiting the production of pro-inflammatory agents and stimulating the production of anti-inflammatory cytokines in activated macrophages. In this study, by using selective VIP agonists, we investigated the differential involvement of the VIP receptors in the anti-inflammatory role of VIP. Both the type 1 VIP receptor (VPAC1) agonist, [K(15), R(16), L(27)] VIP 1-7-GRF 8-27, and the type 2 VIP receptor (VPAC2) agonist, Ro25-1553, protected mice from lethal endotoxemia by inhibiting the macrophage-derived pro-inflammatory mediators IL-6, TNF-alpha, IL-12 and NO, and by stimulating the production of the anti-inflammatory cytokine IL-10. In addition, both VIP and VPAC1 agonist, but not the VPAC2 agonist, reduced in vitro and in vivo the expression of the co-stimulatory B7. 1/B7.2 molecules, and the subsequent stimulatory activity for T helper cells in stimulated macrophages. The higher effectiveness of the VPAC1 agonist compared with the VPAC2 agonist suggests that VPAC1 is the major mediator of the anti-inflammatory action of VIP. Since VIP and the two agonists appear to affect multiple cytokines and inflammatory factors, they might provide a more efficient therapeutical alternative to the use of specific cytokine antibodies or antagonists.

Vasoactive intestinal peptide and pituitary adenylate cyclase activating polypeptide inhibit the MEKK1/MEK4/JNK signaling pathway in LPS-stimulated macrophages

The vasoactive intestinal peptide (VIP) and the pituitary adenylate cyclase activating polypeptide (PACAP), two immunomodulatory neuropeptides that affect both innate and acquired immunity, downregulate TNFalpha expression in LPS-stimulated peritoneal macrophages and Raw 264.7 cells. We showed previously that VIP/PACAP change the composition of the CRE-binding complex in the TNFalpha promoter from highc-Jun/(low)CREB, characteristic for LPS-stimulated macrophages, to lowc-Jun/(high)CREB, characteristic for the unstimulated cells. In the present study we examined the effects of VIP/PACAP on the MEKK1/MEK4/JNK transduction pathway, and on the subsequent changes in Jun family members. Our studies indicate that VIP/PACAP inhibit MEKK1 activity, and the subsequent phosphorylation of MEK4, JNK, and c-Jun. Treatment with VIP or PACAP results in a decrease in AP-1 binding, and a marked change in the composition of the AP-1 complexes from c-Jun/c-Fos to JunB/c-Fos. Western blots confirm that VIP stimulates JunB production in LPS-stimulated macrophages. Both the inhibition of the MEKK1/MEK4/JNK pathway, leading to the reduction in phosphorylated c-Jun, and the stimulation of JunB, are mediated through the specific VPAC1 receptor and the cAMP/PKA pathway. The VIP/PACAP interference with the stress-induced SAPK/JNK pathway in stimulated macrophages may represent a significant element in the regulation of the inflammatory response by the endogenous neuropeptides.

TNF-alpha dependent production of inducible nitric oxide is involved in PGE(1) protection against acute liver injury

BACKGROUND

Tumour necrosis factor alpha (TNF-alpha) and nitric oxide modulate damage in several experimental models of liver injury. We have previously shown that protection against D-galactosamine (D-GalN) induced liver injury by prostaglandin E(1) (PGE(1)) was accompanied by an increase in TNF-alpha and nitrite/nitrate in serum.

AIMS

The aim of the present study was to evaluate the role of TNF-alpha and nitric oxide during protection by PGE(1) of liver damage induced by D-GalN.

METHODS

Liver injury was induced in male Wistar rats by intraperitoneal injection of 1 g/kg of D-GalN. PGE(1) was administered 30 minutes before D-GalN. Inducible nitric oxide synthase (iNOS) was inhibited by methylisothiourea (MT), and TNF-alpha concentration in serum was lowered by administration of anti-TNF-alpha antibodies. Liver injury was evaluated by alanine aminotransferase activity in serum, and histological examination and DNA fragmentation in liver. TNF-alpha and nitrite/nitrate concentrations were determined in serum. Expression of TNF-alpha and iNOS was also assessed in liver sections.

RESULTS

PGE(1) decreased liver injury and increased TNF-alpha and nitrite/nitrate concentrations in serum of rats treated with D-GalN. PGE(1) protection was related to enhanced expression of TNF-alpha and iNOS in hepatocytes. Administration of anti-TNF-alpha antibodies or MT blocked the protection by PGE(1) of liver injury induced by D-GalN.

CONCLUSIONS

This study suggests that prior administration of PGE(1) to D-GalN treated animals enhanced expression of TNF-alpha and iNOS in hepatocytes, and that this was causally related to protection by PGE(1) against D-GalN induced liver injury.

Inhibition of IFN-gamma-induced janus kinase-1-STAT1 activation in macrophages by vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide

The vasoactive intestinal peptide (VIP) and the pituitary adenylate cyclase-activating polypeptide (PACAP), two immunomodulatory neuropeptides that affect both innate and acquired immunity, down-regulate IL-12 p40 and inducible NO synthase expression in LPS/IFN-gamma-stimulated macrophages. We showed previously that VIP/PACAP inhibit NF-kappaB nuclear translocation through the stabilization of IkappaB and reduce IFN regulatory factor-1 (IRF-1) binding to the regulatory elements found in the IL-12 p40 and inducible NO synthase promoters. In this paper we studied the molecular mechanisms involved in the VIP/PACAP regulation of IRF-1 transactivating activity. Our studies indicate that the inhibition in IRF-1 binding correlates with a reduction in IRF-1 protein and mRNA in IFN-gamma-treated Raw 264.7 macrophages. In agreement with the described Janus kinase (Jak)1/Jak2/STAT1/IRF-1 activation pathway, VIP/PACAP inhibit Jak1/Jak2, STAT1 phosphorylation, and the binding of STAT1 to the GAS sequence motif in the IRF-1 promoter. The effects of VIP/PACAP are mediated through the specific VIP/PACAP receptor-1 and the cAMP/protein kinase A (PKA) transduction pathway, but not through the induction of suppressor of cytokine signaling-1 or suppressor of cytokine signaling-3. Because IFN-gamma is a major stimulator of innate immune responses in vivo, the down-regulation of IFN-gamma-induced gene expression by VIP and PACAP could represent a significant element in the regulation of the inflammatory response by endogenous neuropeptides.

Vasoactive intestinal peptide (VIP) inhibits TGF-beta1 production in murine macrophages

Vasoactive intestinal peptide (VIP) and the structurally related neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP), produced and/or released in the lymphoid microenvironment act primarily as macrophage- and T cell-deactivating agents. In the present study we investigate the effect of VIP and PACAP on the production of TGF-beta1 in the macrophage cell line Raw 264.7 and in peritoneal macrophages. The two neuropeptides do not affect the baseline TGF-beta1 production by unstimulated macrophages, but reduce dramatically TGF-beta1 production by LPS-stimulated macrophages. The effects are mediated through the specific receptors VPAC1, VPAC2, and PAC1. The effect of VIP is mediated primarily through the cAMP pathway, whereas PACAP activates both the cAMP and the protein kinase C pathway. VIP reduces the TGF-beta1 steady-state mRNA levels in both peritoneal macrophages and Raw 264.7 cells treated with LPS. A similar effect is observed upon the in vivo administration of VIP. This report adds VIP and PACAP to the only other neuropeptide, substance P, known to regulate TGF-beta1 production in immune cells.

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit T cell-mediated cytotoxicity by inhibiting Fas ligand expression

We reported recently that the neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) protect CD4+ T cells against Ag-induced apoptosis by down-regulating the expression of Fas ligand (FasL). Because the cytotoxic activity of CD8+ CTLs is mediated through two mechanisms, which involve the perforin/granzyme and the FasL/Fas pathways, in this study we investigated the effects of VIP/PACAP on the generation and activity of allogeneic CTLs, of CD8+ T1 and T2 effector cells and of alloreactive peritoneal exudate cytotoxic T cells (PEL) generated in vivo. VIP/PACAP did not affect perforin/granzyme-mediated cytotoxicity, perforin gene expression, or granzyme B enzymatic activity, but drastically inhibited FasL/Fas-mediated cytotoxicity against allogeneic or syngeneic Fas-bearing targets. VIP/PACAP inhibit CTL generation, but not the activity of competent CTLs. The inhibition is associated with a profound down-regulation of FasL expression, and these effects are mediated through both VPAC1 and VPAC2 receptors. VIP/PACAP inhibit the FasL/Fas-mediated cytotoxicity of T1 effectors and do not affect T2 cytotoxicity, which is entirely perforin/granzyme mediated. Similar effects were observed in vivo. Both the FasL/Fas-mediated cytotoxicity and FasL expression of cytotoxic allogeneic PELs generated in vivo in the presence of VIP or PACAP were significantly reduced. We conclude that, similar to their effect on CD4+ T cells, the two structurally related neuropeptides inhibit FasL expression in CD8+ cytotoxic T cells and the subsequent lysis of Fas-bearing target cells.

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit antigen-induced apoptosis of mature T lymphocytes by inhibiting Fas ligand expression

Apoptosis in T and B lymphocytes is a major element controlling the immune response. The Ag-induced cell death (AICD) in T cells is a main mechanism for maintaining peripheral tolerance and for limiting an ongoing immune response. AICD is initiated by Ag re-engagement of the TCR and is mediated through Fas/Fas ligand (FasL) interactions. Vasoactive intestinal peptide (VIP) and the structurally related pituitary adenylate cyclase-activating polypeptide (PACAP) are two multifunctional neuropeptides present in the lymphoid microenvironment that act primarily as anti-inflammatory agents. In the present study we investigated whether VIP and PACAP affect AICD in mature peripheral T cells and T cell hybridomas. VIP and PACAP reduce in a dose-dependent manner anti-CD3-induced apoptosis in Con A/IL-2-preactivated peripheral T cells and the murine T hybridomas 2B4.11 and A1.1. A functional study demonstrates that the inhibition of AICD is achieved through the inhibition of activation-induced FasL expression at protein and mRNA levels. VIP/PACAP-mediated inhibition of both AICD and FasL expression is mediated through the specific receptors VPAC1 and VPAC2. Of obvious biological significance is the fact that VIP and PACAP prevent Ag-induced clonal deletion of CD4+ T cells, but not that of CD8+ T cells. By affecting FasL expression, VIP and PACAP may play a physiological role in both the generation of memory T cells and the inhibition of FasL-mediated T cell cytotoxicity.