Release Of Chemical Mediators Research Articles

Muscarinic receptor subtypes in neuronal and non‐neuronal cholinergic function

1 Muscarinic M1-M5 receptors mediate the metabotropic actions of acetylcholine in the nervous system. A growing body of data indicate they also mediate autocrine functions of the molecule. The availability of novel and selective muscarinic agonists and antagonists, as well as in vivo gene disruption techniques, has clarified the roles of muscarinic receptors in mediating both functions of acetylcholine. 2 Selective M1 agonists or mixed M1 agonists/M2 antagonists may provide an approach to the treatment of cognitive disorders, while M3 antagonism, or mixed M2/M3 antagonists, are approved for the treatment of contractility disorders including overactive bladder and chronic obstructive pulmonary disease. Preclinical data suggest that selective agonism of the M4 receptor will provide novel anti-nociceptive agents, while therapeutics-based upon agonism or antagonism of the muscarinic M5 receptor have yet to be reported. 3 The autocrine functions of muscarinic receptors broadly fall into two areas - control of cell growth or proliferation and mediation of the release of chemical mediators from epithelial cells, ultimately causing muscle relaxation. The former particularly are involved in embryological development, oncogenesis, keratinocyte function and immune responsiveness. The latter regulate contractility of smooth muscle in the vasculature, airways and urinary bladder. 4 Most attention has focused on muscarinic M1 or M3 receptors which mediate lymphocyte immunoresponsiveness, cell migration and release of smooth muscle relaxant factors. Muscarinic M4 receptors are implicated in the regulation of keratinocyte adhesion and M2 receptors in stem cell proliferation and development. Little data are available concerning the M5 receptor, partly due to the difficulties in defining the subtype pharmacologically. 5 The autocrine functions of acetylcholine, like those in the nervous system, involve activation of several muscarinic receptor subtypes. Consequently, the role of these subtypes in autocrine, as well neuronal cholinergic systems, significantly expands their importance in physiology and pathophysiology.

Challenge exposure of sheep immunized with live vaccine and culture supernatant of Mannheimia haemolytica A1: Effects of revaccination

Vaccination against Mannheimia haemolytica is a routine procedure in sheep farming, being repeatedly performed on the recommendations of commercial veterinary manufacturers or due to outbreaks of respiratory disease. However, the consequences of repeat vaccination after a short period, using live vaccines or culture supernatant (CS), have not been established, and its benefits are unknown. This study aims to evaluate, in a challenge exposure, the effects of revaccinating sheep with this type of biological product. Thus, 20 mixed-breed, 6–9-month-old sheep were divided into four groups, with five animals in each. Animals in group I were inoculated subcutaneously with 2 ml of a 1 × 10 9 CFU/ml suspension of bacteria in the exponential growth phase. Group II was inoculated with the same bacterial concentration but in the stationary phase. Animals in group III were inoculated with 3 ml of CS and group IV with saline solution, as control. Each group was immunized again 14 days later, following the same guidelines. On day 21, they were intranasally exposed to parainfluenza-3 virus (PI-3). On day 27, they were challenged with a transthoracic injection of live M. haemolytica (2 × 10 9 CFU/ml). In this experiment, the levels of agglutinating and antileukotoxin antibodies were evaluated through indirect hemagglutination and toxin neutralization assays. During the first 24 h post-challenge, four animals in group I died, three in group II and two in group III, even though they had developed significant levels of agglutinating and antileukotoxin antibodies. Only one animal from the control group died. Thus, contrary to the development of improved protection due to continuous immunizations with live bacteria or CS, a negative effect was observed. This can be explained as the result of a hypersensitivity type III reaction, due to the significant decrease in agglutinating antibodies observed shortly after the challenge, indicating the formation of immune complex, which triggered the release of chemical mediators of inflammation that, finally, promoted edema and pulmonary congestion.

Peripheral 5-HT 2A receptor antagonism attenuates primary thermal hyperalgesia and secondary mechanical allodynia after thermal injury in rats

Inflammation or injury of peripheral tissue causes release of chemical mediators, including 5-hydroxytryptamine (5-HT), which is involved in the facilitation of nociceptive transmission and the induction of hyperalgesia. The present study examined the effect of a selective 5-HT 2A receptor antagonist, sarpogrelate, on hyperalgesia and allodynia induced by thermal injury in rats. Mild thermal injury to the hindpaw produces thermal hyperalgesia in the injured area (primary thermal hyperalgesia) and mechanical allodynia in sites adjacent to the primary area (secondary mechanical allodynia). Mechanical allodynia was assessed by paw withdrawal thresholds using von Frey filaments, and thermal hyperalgesia was assessed by paw withdrawal latencies upon exposure to a radiant heat source. Intraperitoneal administration (30–100 mg/kg) or local injection (30–300 μg) of sarpogrelate 10 min prior to thermal injury attenuated secondary mechanical allodynia in a dose-dependent manner. Intraperitoneal administration (3–100 mg/kg) or local injection (30–300 μg) of sarpogrelate 10 min prior to thermal injury attenuated primary thermal hyperalgesia in a dose-dependent manner. Intraplantar injection of sarpogrelate (300 μg) to the contralateral hindpaw had no effect on primary thermal hyperalgesia or secondary mechanical allodynia in the ipsilateral paw. The tissue concentration of 5-HT was measured using microdialysis. Concentrations of 5-HT increased after thermal injury in both primary and secondary areas, and the increase was not attenuated by pretreatment with sarpogrelate (100 mg/kg, i.p.). These data suggest that 5-HT released in peripheral tissues after thermal injury sensitizes primary afferent neurons and produces mechanical allodynia and thermal hyperalgesia via peripheral 5-HT 2A receptors.

Effects of Salmeterol Xinafoate and Fluticasone Propionate on Immunological Activation of Human Cultured Mast Cells

The clinical efficacy of combination therapy comprising a long acting beta(2)-agonist (LABA) and corticosteroid is widely recognized for the treatment of adult asthma. Here we examine the effect of salmeterol xinafoate (SX) and fluticasone propionate (FP) alone and in combination on the immunological activation of human cultured mast cells (HCMC)in vitro. HCMC were passively sensitized with IgE antibody and then activated by challenging with anti-IgE antibody. The effect of drugs on the activation of mast cells was examined by measuring the amount of released chemical mediators (histamine, leukotrienes (LT) and prostaglandin D(2) (PGD(2))) and granulocyte macrophage colony stimulating factor (GM-CSF). The release of each chemical mediator was inhibited by 10-9-10-8M SX but not by 10-10-10-7M FP. The production of GM-CSF was inhibited by a concentration of 10-8M in both drugs and the inhibition was augmented by combined treatment with 10-11M of each drug. The immunological release of chemical mediators (histamine, LT, PGD(2)) from HCMC was inhibited by SX but not by FP. SX and FP inhibited the production of GM-CSF by HCMC and both drug showed synergistic inhibition in the production of GM-CSF.

3-O-(2,3-Dimethylbutanoyl)-13-O-decanoylingenol from Euphorbia kansui Suppresses IgE-Mediated Mast Cell Activation

Aggregation of the high affinity receptor for IgE (FcepsilonRI) on mast cells by antigen and IgE complex induces release of chemical mediators, leading to acute allergic inflammation. We recently found that 3-O-(2,3-dimethylbutanoyl)-13-O-decanoylingenol (DBDI), purified from the Euphorbia kansui L., inhibits degranulation in rat basophilic leukemia 2H3 cells upon aggregation of the FcepsilonRI. In the present study, we demonstrated that the DBDI significantly inhibits release of beta-hexosaminidase, synthesis of eicosanoids, and mobilization of intracellular Ca(2+) in the bone marrow-derived mouse mast cells stimulated with IgE and antigen. Furthermore, we revealed that phosphorylation of Syk, phospholipase C-gamma(2), and extracellular signal-related kinase 1/2 is significantly suppressed in the DBDI-treated mast cells. These findings suggest that the DBDI may have a therapeutic potential for allergic diseases by inhibiting intracellular signaling pathways for activation and chemical mediator release in mast cells.

Aminophilline suppress the release of chemical mediators in treatment of acute asthma

The control of airway inflammation is crucial for management of asthma. Theophylline has been demonstrated to have an anti-inflammatory effect as a long-term-medication for asthma in various studies. In the present study we attempted to clarify if aminophylline, a theophylline derivative, could act as an anti-inflammatory agent as well as a bronchodilator in the treatment for acute asthma exacerbations. Patients are initially treated either with an intravenous infusion of aminophylline or with inhalation of salbutamol. Pro-inflammatory mediators such as eosinophil cationic protein (ECP), histamine, serotonin, thromboxane B2, leukotriene C4 were measured before and one hour after the initial treatment. Clinical parameters such as peak expiratory flow (PEF) and SpO2 were also checked during the studies. Significant improvements of PEF and SpO2 with both aminophylline and salbutamol treatment were seen. Furthermore, significant decreases of ECP, histamine, and serotonin were observed with aminophylline but not with salbutamol. Suppressing the release of pro-inflammatory mediators may play a role, at least in part, in the beneficial effects of aminophylline in the treatment of acute exacerbations in asthma. Additionally, this study indicated that treatment with aminophylline is at least as beneficial as nebulized salbutamol in the restoration of lung function.

Effects of Fexofenadine Hydrochloride in a Guinea Pig Model of Antigen-Induced Rhinitis

Allergic rhinitis is an inflammatory disease of the nasal mucosa, induced by histamine, leukotrienes, and other substances released from mast cells. Fexofenadine hydrochloride, the active metabolite of terfenadine, is a novel, nonsedating antiallergic drug having H₁ receptor antagonistic activity. Fexofenadine is effective for the treatment of allergic rhinitis. However, its mechanism of action in attenuating nasal congestion has not yet been elucidated. Therefore, we first examined the effects of fexofenadine on a guinea pig model of antigen-induced rhinitis. We also evaluated the effects of mepyramine, zafirlukast and ramatroban in this model; these drugs are an H₁ receptor antagonist, a selective leukotriene antagonist and a selective thromboxane antagonist, respectively. Rhinitis was induced by ovalbumin (OVA) instillation into the nasal cavity of animals that had been sensitized by two earlier OVA injections (s.c. and i.p.). The nasal airway resistance was measured for 45 min after the challenge. Fexofenadine hydrochloride (20 mg/kg) and terfenadine (20 mg/kg) administered orally 70 min prior to the challenge significantly inhibited (fexofenadine, p < 0.001, terfenadine, p < 0.05) the increase in nasal airway resistance. Ramatroban (30 mg/kg) administered orally 60 min prior to the challenge also significantly inhibited (p < 0.05) the increase in nasal airway resistance. In contrast, mepyramine (3 mg/kg i.v.) and zafirlukast (3 mg/kg p.o.) failed to reduce the increase in nasal airway resistance. These results suggest that thromboxane may be involved in the increase in the nasal airway resistance in this model. Accordingly, fexofenadine may reduce the increase in nasal airway resistance by inhibiting the release of chemical mediators, including thromboxane, that are involved in the increase in nasal airway resistance in this model.

Role of the FcϵRI β-chain ITAM as a signal regulator for mast cell activation with monomeric IgE

The beta-chain of the high-affinity receptor for IgE (FcepsilonRI) plays a crucial role for amplification of the intracellular signaling in mast cells upon FcepsilonRI cross-linking by IgE*antigen complexes (IgE*Ag). Some monomeric IgE as well as IgE*Ag stimulate FcepsilonRI-signaling pathways, leading to cell activation, whereas the biological functions of the beta-chain in the monomeric IgE-mediated mast cell signaling and responses are largely unknown. In the present study, FcepsilonRI is reconstituted with either wild-type beta-chain or mutated beta-chain immunoreceptor tyrosine-based activation motif (ITAM) employing retrovirus-mediated gene transfer into the FcepsilonRI beta-chain-/- mast cells. We demonstrated that the transfectants with mutated beta-chain ITAM stimulated with monomeric IgE sufficiently produce inflammatory cytokines, although degranulation, intracellular Ca(2+) mobilization and leukotriene C(4) synthesis are significantly reduced. Furthermore, analyses of molecular mechanisms of the signaling revealed that the expression of cytokine genes and activation of extracellular signal-regulated kinase 1/2 and protein kinase C were significantly delayed in the beta-chain ITAM mutant cells stimulated with monomeric IgE, suggesting that the beta-chain ITAM regulates kinetics of gene transcriptions and signaling pathways for cytokine production. These findings for the first time revealed the unique functions of the beta-chain ITAM in both chemical mediator release and cytokine production of mast cells upon monomeric IgE stimulation.

Involvement of the jaw bones in systemic mastocytosis

Systemic mastocytosis is characterised by proliferation of mast cells and infiltration of organs. Severe bony pain may result from release of chemical mediators from mast cells and affected patients are at an increased risk of anaphylaxis. Traditional analgesics such as non-steroidal anti-inflammatory agents and opioids are contraindicated. Diagnosis is based on presentation, biopsy of bone marrow, and magnetic resonance imaging of the affected area. In the head and neck, the disease may present as facial pain, localised osteomyelitis, oral sinus formation, and oral ulceration. Treatment is with histamine antagonists and bisphosphonates to control symptoms. An adrenaline pen is provided for use in case of anaphylaxis.

The discovery of cromolyn sodium and its effect on research and practice in allergy and immunology

The discovery of cromolyn sodium and its effect on research and practice in allergy and immunology

クロモグリク酸ナトリウムの遅発性ぜん息反応に対する抑制効果

Disodium cromoglycate (DSCG) is a widely used anti-asthmatic drug with few side effects. One of the mechanisms by which DSCG suppresses asthma is prevention of anaphylactic release of chemical mediators from mast cells. However, it has also been reported that DSCG attenuates late asthmatic response and airway hyperresponsiveness, the induction mechanisms of which can not be explained simply by release of chemical mediators from mast cells. Mechanisms of anti-inflammatory effects of DSCG other than its mast-cell stabilising effect have been unclear. In this study, we evaluated effects of DSCG on early and late asthmatic response in guinea pig. Guinea pigs were alternately sensitized and challenged by exposure to mists of ovalbumin+Al(OH)3 and ovalbumin, respectively. DSCG administered intratracheally before the fifth challenge dose-dependently inhibited late asthmatic response, but early asthmatic response was not affected. Interestingly, DSCG at 2 mg/kg potently suppressed increases in cysteinyl leukotrienes and thromboxane A2 in the lung during late asthmatic response. Eosinophilia was slightly reduced by DSCG. The inhibitory effect of DSCG on late asthmatic response is apparently due to inhibition of release of arachidonic acid metabolites.

Coumarin and Flavone Derivatives from Estragon and Thyme as Inhibitors of Chemical Mediator Release from RBL-2H3 Cells

Estragon and thyme extracts showed potent inhibitory activities against chemical mediator release from rat basophilic leukemia RBL-2H3 cells. 7-Methoxycoumarin was isolated from estragon, and 5,4'-dihydroxy-6,7,3'-trimethoxyflavone, 5,4'-dihydroxy-6,7,8,3'-tetramethoxyflavone, 5-hydroxy-6,7,8,3',4'-pentamethoxyflavone and luteolin were isolated from thyme as active components. Structure-activity relationship studies among the active isolates and their related compounds indicated that the oxygen-containing functional group at the 7-position of the coumarin structure was advantageous for the inhibitory activity and that methylation of the hydroxyl group at the 4'-position of the flavone structure was disadvantageous. It was also found that coumarin derivatives inhibited an earlier step than intracellular calcium release and proteinkinase C activation, while flavones inhibited a later step or both earlier and later steps.

Control of bladder function by peripheral nerves: avenues for novel drug targets

The micturition reflex involves afferent nerve activation when the bladder is sufficiently full and subsequent controlled firing of parasympathetic efferent nerves to contract the detrusor muscle as part of the voiding mechanism. Alteration of the sensitivity of afferent activation or loss of control over transmitter release could lead to sensory- or motor-activated incontinence, respectively. The control mechanisms that regulate these 2 activities remain poorly understood. Current opinion is that the sensation of bladder fullness is relayed by afferent nerves in the mucosal layer, which are activated by the release of chemical mediators, such as adenosine triphosphate (ATP), from the urothelium when it is stretched as the bladder fills. This hypothesis supports the concept that other chemical signals that affect bladder sensation (eg, changes in urine composition and agents such as capsaicin) can modulate the sensitivity of the basic system. It has also been proposed that a layer of myofibroblasts immediately below the basal lamina of the urothelium acts as a variable gain regulator of the sensory process between ATP release and afferent excitation. These myofibroblasts are functionally connected to form an electrical syncytium, make close contact with nerves, and respond by generating electrical responses and transient increases in intracellular Ca2+ when exposed to ATP. On the efferent side, using a guinea pig detrusor model, possible modulators of transmitter release have been investigated, including adenosine (the breakdown product of the neurotransmitter ATP). Adenosine reduces the force of nerve-mediated contractions by acting predominantly at presynaptic sites at the nerve–muscle junction via a subtype of an adenosine receptor—the A1 receptor. An additional effect, possibly via A2 receptors, is also present on the detrusor muscle itself. These actions of adenosine are less evident in human detrusor muscle but remain a potential modulatory target. In summary, the cellular and molecular regulation of bladder fullness sensation and efferent transmitter release are becoming better understood and represent potential drug targets for the management of detrusor overactivity.

Differential Effects of .BETA.2-Adrenoceptor Desensitization on the IgE-Dependent Release of Chemical Mediators from Cultured Human Mast Cells

In the present study, we examined the inhibitory effects of the beta2-adrenoceptor agonists isoproterenol, salbutamol, fenoterol, and clenbuterol, on the release of chemical mediators from cultured human mast cells after prolonged treatment with the agonists. Although preincubation of sensitized mast cells for 10 min with beta2-adrenoceptor agonists potently inhibited mediator release, prolongation of the preincubation period up to 240 min attenuated the inhibition. The attenuation of histamine release inhibition was potent when compared with that of prostaglandin D2 (PGD2) and cysteinyl leukotriene (LT) release inhibition. In contrast, forskolin inhibited mediator release and the inhibition increased gradually in proportion to the preincubation period. The reduced inhibition by the beta2-adrenoceptor agonists was compensated for by simultaneous treatment with cholera toxin. The beta2-adrenoceptor agonists elevated intracellular cAMP levels after 10-min incubation and the elevated levels were almost comparable to those after 240-min incubation. Forskolin elevated the intracellular cAMP levels more potently after incubation for 240 min than after 10 min. When mast cells were incubated for 3 d with the beta2-adrenoceptor agonists, similar attenuation of mediator release inhibition was observed. Elevation of intracellular cAMP levels was also attenuated, although beta2-adrenoceptor mRNA expression was potentiated. The present results collectively indicate that the attenuation of mediator release inhibition by beta2-adrenoceptor agonists under the present experimental conditions involves uncoupling between beta2-adrenoceptors and Gs proteins. Furthermore, the beta2-adrenoceptor desensitization causes differential attenuating effects on the inhibition of histamine, PGD2, and LT release, suggesting that downstream events involved in each inhibitory pathway have different sensitivity to receptor desensitization.

THE ELEMENTAL ANALYSIS OF IgE-SENSITIZED RBL-2H3 CELLS USING IN-AIR MICRO-PIXE

Rat basophilic leukaemia cells (RBL-2H3) were analyzed by in air micro-PIXE analysis to investigate the relationship between the distribution of elements and histamine release in immune system. RBL-2H3 cells were sensitized with monoclonal immunoglobuline E ( IgE ) and stimulated with antigen. In the stimulated cells, it is understood that the level of Ca 2+ increases in cytoplasm and then the degranulation or the release of chemical mediators occur. In this study, stimulated RBL-2H3 cells with antigen and control cells were analyzed. After the stimulation, the Na in the cells was increased. Moreover some stimulated cells showed the characteristic distribution of sulfur that is not accompany with the distribution of phosphorus. In the same measurement, the aggregations of Na , Ca , Fe , and Zn were observed.

Inhibitory effect of zinc on beta-hexosaminidase release from RBL-2H3 cells by synthetic chemicals

The effects of foods and chemicals related to food hygiene on degranulation were evaluated using a method for assaying the enzyme activity of beta-hexosaminidase as an index of chemical mediator release from RBL-2H3 cells in vitro. Using a previously developed assay system, we had found a large number of inhibitors and promoters of degranulation of RBL-2H3 cells. In the present study, we examined the inhibitory effect of zinc chloride on the degranulation (beta-hexosaminidase release) from RBL-2H3 cells with or without antigen in the presence of the degranulation-promotive chemicals, namely, 4 food additives, 7 pesticides and 2 veterinary drugs. These promotive chemicals were classified into two types on the basis of inhibitory profile by zinc chloride: 1) those which showed marked degranulation-inhibitory action when the cells were stimulated with antigen, such as butylhydroxyanisole, dibutylhydroxytoluene, EPN, cis- and trans-permethrin, prothiofos, pyridaben, terbufos, 2) those which showed marked degranulation-inhibitory action whether the cells were stimulated with antigen or not, such as butyl p-hydroxybenzoate, o-phenylphenol, bitertanol, salinomycin. In conclusion, zinc had a dramatic inhibitory effect on enhanced degranulation induced by synthetic chemicals in vitro.

Flavonoids as Potential Anti-Allergic Substances

Progress in the management of allergic diseases including asthma, pollen diseases and atopic dermatitis has recently improved patients quality of life. In addition to steroids, which are powerful inhibitors of allergic inflammation, other anti-allergic compounds, humanized anti-IgE antibody and cytokine modulators have been developed. However, the world-wide prevalence of allergic diseases has been increased during the last two decades, making early intervention to prevent the development of such diseases essential. Through analysis of the clinical evaluation of one kind of traditional remedy in patients with atopic dermatitis, flavonoids were shown to possess significant anti-allergic activity. Among the twenty kinds of flavonoids examined, fisetin, luteolin, apigenin, quercetin and kaempferol inhibited not only the release of chemical mediators but also the production of T-helper (Th)-2 type cytokines (Interleukin (IL)-4, IL-5 and IL-13) by basophils. These flavonoids inhibit expression of these cytokines through their inhibitory effect on the activation of several calcium-calmodulin dependent kinases. Administration of either persimmon leaf extract, which is rich in flavonoids, or its major ingredient astragalin (a glycoside of kaempferol), in atopic dermatitis-model mice (NC / Nga) prevented the onset of dermatitis and showed a substantial ameliorative effect even in mice with open dermatitis. Moreover, a double-blind, randomized, placebo-controlled trial of flavonoid in patients with atopic dermatitis showed a significant effect. These results indicate the possibility that flavonoids, which are contained in vegetables, fruits and tea, may constitute a complementary and alternative medicine for allergic patients and may act as a prophylactic substance against the development of allergic diseases. Keywords: flavonoid, allergy, mast cells/basophils, prevention, complementary and alternative medicine

Anti-Allergic Action of Glucocorticoids: Comparison with Immunosuppressive and Anti-Inflammatory Effects

Glucocorticoid (GC) exhibits immunosuppressive and anti-inflammatory effects by suppressing the nuclear factor functions on T cells and monocytes / macrophages. GC exerts its effects by binding cytosolic GC receptor (GR) and antagonizes the transcription factors including AP-1, NF-κB and STATs, in both transcriptional regulation and upstream cross-talk with signaling molecules, resulting in the inhibition of target gene expression such as cytokines and other proteins, followed by the suppression of T cell activation and the production of inflammatory mediators. In addition, in anti-allergic actions of GC, one of the most important targets is mast cell. GC specifically inhibits the release of chemical mediators from mast cells. It also suppresses survival and activation of mast cells, at least in partial, overlapping with the suppressive mechanisms of T cell activation and monocytes / macrophages functions, by inhibiting the production of growth factors and inflammatory mediators, and suppressing the transcriptional induction of Th2-type cytokines, such as IL-4, -5, -10, -13 and TNF-α, chemokines and adhesion molecules, resulting in the suppression of immediate- and late-phase of allergic inflammation and remodeling. In this issue, we summarize the molecular mechanisms of GC to regulate the transcription factors, molecules regulated by GC and its action on the immune system in contrast with other agents, and also discuss the specific molecular targets of a possible drug design for allergy learned from the variable immunosuppressive and anti-inflammatory actions of GC. Keywords: Glucocorticoid, Immunosuppression, Inflammation, Allergy, Mast cell, Transcription factor, Signal transduction

In-vitro anti-inflammatory and immunomodulatory effects of grepafloxacin in zymogen A- or Staphylococcus aureus-stimulated human THP-1 monocytes.

The effects of grepafloxacin on the release of cytokines, chemical mediators, hydrolytic enzyme activities, and lipoxygenation in zymogen A- or Staphylococcus aureus-stimulated human THP-1 monocytes were evaluated. Initially, consistent with stimulation of phagocytic mechanisms of the monocytes, increases in cyclic adenosine monophosphate (cAMP) release, nitric oxide [NO] release, and hydrogen peroxide [H(2)O(2)] release, with a small decrease in cellular pH, occurred within 2 h. Enzymatic activities associated with oxygen burst of phagocytic cells (e.g., protein kinase C and nicotinamide adenine dinucleotide phosphate, reduced (NADPH) oxidase) were elevated, suggesting that monocytes attempted to destroy the invading organism through an innate phagocytic cidal immunologic mechanism. After 1-2 h of exposure to grepafloxacin, the oxygen burst and the release of proinflammatory cytokines and chemical mediators were suppressed. After 4 h, suppression of n-acetyl glucosaminidase (NAG) and cathepsin D activities and lipid peroxidation occurred, suppressing the pathogen-induced spread of infection and inflammation. Release of tumor necrosis factor (TNFalpha), interleukin (IL)-1, IL-6, and IL-8 was inhibited by grepafloxacin in a concentration-dependent manner, suggesting a reduction in the acute-phase inflammatory responses initiated by cytokine release from monocytes. Later, S. aureus were killed through inhibition of DNA synthesis, consistent with a bacteriostatic effect. Drug action against invading organisms appears to occur through multiple processes. Modulation of the innate immune system occurs within the first hour, causing the activation of cytokines, chemical mediators, and hydrolytic enzymes. A second phase between 2-4 h appears to involve the suppression of cellular components involved in inflammation and the spread of the infection. The third response, an apparent bacteriostatic inhibition of DNA synthesis, causes bacterial death.

Neuroimmune interactions in guinea pig stomach and small intestine.

Enteric neuroimmune interactions in gastrointestinal hypersensitivity responses involve antigen detection by mast cells, mast cell degranulation, release of chemical mediators, and modulatory actions of the mediators on the enteric nervous system (ENS). Electrophysiological methods were used to investigate electrical and synaptic behavior of neurons in the stomach and small intestine during exposure to beta-lactoglobulin in guinea pigs sensitized to cow's milk. Application of beta-lactoglobulin to sensitized preparations depolarized the membrane potential and increased neuronal excitability in small intestinal neurons but not in gastric neurons. Effects on membrane potential and excitability in the small intestine were suppressed by the mast cell stabilizing drug ketotifen, the histamine H(2) receptor antagonist cimetidine, the cyclooxygenase inhibitor piroxicam, and the 5-lipoxygenase inhibitor caffeic acid. Unlike small intestinal ganglion cells, gastric myenteric neurons did not respond to histamine applied exogenously. Antigenic exposure suppressed noradrenergic inhibitory neurotransmission in the small intestinal submucosal plexus. The histamine H(3) receptor antagonist thioperamide and piroxicam, but not caffeic acid, prevented the allergic suppression of noradrenergic inhibitory neurotransmission. Antigenic stimulation of neuronal excitability and suppression of synaptic transmission occurred only in milk-sensitized animals. Results suggest that signaling between mast cells and the ENS underlies intestinal, but not gastric, anaphylactic responses associated with food allergies. Histamine, prostaglandins, and leukotrienes are paracrine signals in the communication pathway from mast cells to the small intestinal ENS.