Bacteria and endotoxin enhance basophil histamine release and potentiation is abolished by carbohydrates

Histamine regulates the inflammatory response of the tunicate Styela plicata

Histamine is stored inside hemocytes of the tunicate Styela plicata (Chordata, Tunicata, Ascidiacea), but no evidence on its role in the regulation of the immune response of this species has been reported. We examined whether histamine participated in the regulation of inflammation and host defense in S. plicata. The presence of histamine inside S. plicata hemocytes was confirmed by flow cytometry, and histamine release was detected by ELISA, after in vitro hemocyte stimulation with different PAMPs. In vitro hemocyte treatment with histamine, or specific histamine-receptor agonists, reduced their phagocytic ability. Injection of histamine into the tunic recruited hemocytes to the site of injection. Systemic injection of histamine, or the histamine-releasing agent compound 48/80, decreased the phagocytic ability of hemocytes. Histamine promoted the constriction of tunic hemolymph vessels in vivo, having a direct effect on vasoconstriction in tunic explants. These results provide for the first time clear evidence for the involvement of histamine in the regulation of inflammation and host defense in tunicates.

The effects of various doses of bacterial lipopolysaccharide on the expression of CD63 and the release of histamine by basophils of atopic and non-atopic patients

OBJECTIVE

We tested the effect of various doses of bacterial lipopolysaccharide (LPS, endotoxin) on the expression of CD63 and the in vitro release of histamine by basophils stimulated with ragweed allergen in patients with or without ragweed and mite allergies.

METHODS

The peripheral blood of 11 patients with ragweed allergy, 10 patients with mite allergy and 14 control patients was incubated with ragweed allergen extract following pretreatment with varying doses of LPS. The expression of CD63 in basophils was measured by flow cytometry, and the release of histamine was determined by ELISA.

RESULTS

In the samples of patients with ragweed allergy that were exposed to specific allergen, only high doses of LPS significantly elevated the expression of CD63 (200 ng/ml; 1,000 EU/ml) and the release of histamine (2,000 ng/ml; 10,000 EU/ml). There was no effect of LPS in any other cases.

CONCLUSIONS

Bacterial LPS (endotoxin) concentrations higher than 200 ng/ml (1,000 EU/ml), which rarely occurs in nature, could only activate the basophils from atopic patients whilst in the presence of the specific allergen. Thus, the restoration of the urban, "microbe-poor" milieu with endotoxin (as LPS) can be a promising and harmless approach for allergy prevention.

Toll-like receptor (TLR)2 and TLR4 in human peripheral blood granulocytes: a critical role for monocytes in leukocyte lipopolysaccharide responses

Leukocyte responsiveness to LPS is dependent upon CD14 and receptors of the Toll-like receptor (TLR) family. Neutrophils respond to LPS, but conflicting data exist regarding LPS responses of eosinophils and basophils, and expression of TLRs at the protein level in these granulocyte lineages has not been fully described. We examined the expression of TLR2, TLR4, and CD14 and found that monocytes expressed relatively high levels of cell surface TLR2, TLR4, and CD14, while neutrophils also expressed all three molecules, but at low levels. In contrast, basophils expressed TLR2 and TLR4 but not CD14, while eosinophils expressed none of these proteins. Tested in a range of functional assays including L-selectin shedding, CD11b up-regulation, IL-8 mRNA generation, and cell survival, neutrophils responded to LPS, but eosinophils and basophils did not. In contrast to previous data, we found, using monocyte depletion by negative magnetic selection, that neutrophil responses to LPS were heavily dependent upon the presence of a very low level of monocytes, and neutrophil survival induced by LPS at 22 h was monocyte dependent. We conclude that LPS has little role in the regulation of peripheral blood eosinophil and basophil function, and that, even in neutrophils, monocytes orchestrate many previously observed leukocyte LPS response patterns.

Staphylococcus aureus superantigens and airway disease

Twenty-five percent of the population are permanent carriers of Staphylococcus aureus, possibly producing a variety of toxins with superantigenic properties. Staphylococcal superantigens are a group of high- molecular-weight pyrogenic proteins that have in common an extremely potent stimulatory activity for T-lymphocytes, macrophages, mast cells, eosinophils, and epithelial cells. The role of staphylococcal superantigens in atopic dermatitis has recently been recognized, and new evidence suggests that similar mechanisms may also be relevant in airway disease. This circumstantial evidence is currently limited to rhinitis, sinusitis, and possibly asthma, but may, if supported, open a new understanding of pathomechanisms and therapeutic targets.

Endotoxin-stimulated innate immunity: A contributing factor for asthma

Exposure to airborne endotoxin in infancy may protect against asthma by promoting enhanced T(H)1 response and tolerance to allergens. On the other hand, later in life, it adversely affects patients with asthma. Endotoxin binding to receptors on macrophages and other cells generates IL-12, which inhibits IgE responses. It also generates cytokines like IL-1, TNF-alpha, and IL-8, which cause inflammation. These signal transduction pathways resemble those leading to the generation of cytokines, such as IL-4, IL-13, and IL-5, which are responsible for the inflammation of IgE-mediated allergic disease. The main difference seems to be that endotoxin recruits neutrophils, but IgE recruits eosinophils, and the details of the tissue injury from these granulocytes differ. Sources of airborne endotoxin include many agricultural dusts, aerosols from contaminated water in many industrial plants, contaminated heating and air-conditioning systems, mist-generating humidifiers, and damp or water-damaged homes. Acute inhalation of high concentrations of endotoxin can cause fever, cough, and dyspnea. Chronic inhalation of lesser amounts causes chronic bronchitis and emphysema and is associated with airway hyperresponsiveness. Airborne endotoxin adversely affects patients with asthma in 3 ways: (1) by increasing the severity of the airway inflammation; (2) by increasing the susceptibility to rhinovirus-induced colds; and (3) by causing chronic bronchitis and emphysema with development of irreversible airway obstruction after chronic exposure of adults. The most effective management is mitigating exposure. The potential of drug treatments requires further clinical investigation.

[The role of infection in asthma]

Since the first decades of the twentieth century, some authors have believed bacterial respiratory infection to be an important triggering factor in bronchial asthma, drawing attention to an asthmatic response to infection. In this context, already in 1995, we presented a study on nasal secretion cultures and the relationship between IgE and sensitization to allergens. There was a statistically significant association between patients with sensitization to Dermatophagoides, elevated IgE levels and Staphylococcus Aureus positive cultures. Following the studies by Norn, we performed a study in 40 children, aged 2-14 years, and observed that these children with sensitization to mites and positive culture released higher histamine levels than did children with negative cultures and controls. The differences were statistically significant. In agreement with other authors, we also found that the presence of both S. aureus and D. pteronyssinus favored antigen specific histamine release. In the last few years, when the increase in the prevalence of bronchial asthma began to be studied, the role of infection, among other factors, in favoring this increase began to be examined. Using the methodology of the ISAAC project, we distributed a parallel questionnaire containing questions on triggering and contributing factors among which was respiratory infection. We found that there was an association between having three of more episodes of bronchitis in the previous year, accompanied by fever and with a duration of more than 7 days and having asthma at some time (OR: 29.09). This association was even higher in patients with wheezing in the previous 12 months (OR: 43.26) and was also associated with the need to present to the emergency department (OR: 30.65). From these results we conclude that respiratory infection is an aggravating factor in asthma, as we already know. For several years, several authors have studied how non-nosocomial respiratory infections can directly modulate Th1/Th2 response. In order to obtain our own results, we studied serum interleukin 4 (IL4) and interferon-gamma (IFN-gamma) in 42 children aged 3-17 years. The most frequent IL-4 values expressed in ng/ml were between 0.25-0.40, with little variation in the sample, which did not permit correlation among variables. Concerning IFN-gamma, we found values between < 5 and 605 pg/ml. In children undergoing antigen-specific immunotherapy, we observed mean IFN-gamma values of 115.86 pg/ml, while children not undergoing immunotherapy and those who had been administered this treatment for less than 1 year, had a mean of 66.06 pg/ml. These differences were statistically significant (p = 0.035), thus revealing a Th1 response to immunotherapy. These differences were not statistically significant when children who had been administered immunotherapy for less than 1 year were included. When we studied children with bacterial immunotherapy and grouped them in the same way, we found that the mean IFN-gamma of the children undergoing immunotherapy for more than 1 year was 56.4 pg/ml compared with 101.75 pg/ml in those without immunotherapy. This difference was statistically significant (p = 0.034). We are able to conclude that bacterial immunotherapy modifies Th1 response, inhibiting it in children with higher susceptibility to infection. In view of these preliminary results, it would be interesting to continue to study interleukins in order to determine the modification of these substances by immunotherapy in a prospective study and with a sample selected in relation to immunotherapy and not other parameters, since those we have studied have shown no relationship.

Microorganism-induced or enhanced mediator release: a possible mechanism in organic dust related diseases

Bacteria were found to trigger mediator release, including histamine, leukotriene B4, and prostaglandin D2. Furthermore, histamine release caused by allergens as well as by nonimmunological reactions was enhanced by bacteria, endotoxins, and spores from molds. Mediator release and its enhancement play a crucial role for bronchoconstriction and inflammatory events in the airways. These effects of allergens, microorganisms, and other noxious agents in dusts may, therefore, in concert be responsible for the symptoms in organic dust related diseases.

Helicobacter pylori potentiates histamine release from serosal rat mast cells in vitro

Helicobacter pylori seems to be involved in the etiology of peptic ulcer and chronic gastritis. Histamine is fundamental in gastric secretion modulation, and some features of H. pylori-associated gastritis (edema, vasodilatation, inflammatory cell infiltration) are typical of the histamine-mediated response. This in vitro study has been undertaken as a preliminary step, in order to find a possible link between H. pylori and histamine release. H. pylori isolated from gastric biopsies has been tested as whole washed bacterium, whole formalin-killed bacterium, and crude cell wall preparation with serosal mast cells obtained by density gradient centrifugation or elutriation from peritoneal and pleural washings of male Wistar albino rats. Histamine release was assayed fluorimetrically. No significant histamine release was obtained by testing the various bacterial preparations alone with mast cells. On the contrary, whole washed cells, whole formalin-killed cells and crude cell walls from H. pylori have been found to potentiate compound 48/80 or calcium ionophore A23187-induced histamine release. Crude cell walls showed the highest activity, whereas filtered supernatants from broth cultures constantly appeared inactive. The enhancement in histamine release differed between the different strains. The present in vitro study, which shows the potentiating effect of H. pylori on histamine release, may prove interesting; however, at present, clinical implications cannot be inferred and further studies as well as in vivo demonstrations are needed.