Airways exposure of bacterial superantigen SEB enhances bone marrow eosinophil population and facilitates its egress to blood and lung tissue.

BACKGROUND: Differentiation of bone marrow eosinophils (BM-EO) and its trafficking to peripheral blood and respiratory mucosa are a hallmark of inflammatory diseases. Staphylococcal enterotoxin B (SEB) has been shown to aggravate airways eosinophilic inflammation. This study aimed to investigate the effects of mouse airways SEB exposure on BM-EO population, as well as its adhesive properties and release of cytokines/chemokines that orchestrate BM-EO trafficking to lungs. METHODS: Male BALB/c mice were intranasally exposed to SEB (1 µg), and at 4, 16, 24 and 48 h thereafter, bone marrow (BM), circulating blood and bronchoalveolar lavage (BAL) fluid were collected. Levels of cytokines/chemokines and expressions of VLA-4 and CCR3 in BM were evaluated. Adhesion of BM to ICAM-1 and VCAM-1 were also evaluated. RESULTS: SEB exposure promoted a marked eosinophil influx to BAL at 16 and 24 h after exposure, which was accompanied by significant increases in counts of immature (16 h) and mature (4 to 48 h) forms of eosinophil in BM, along with blood eosinophilia (16 h). In BM, higher levels of eotaxin, IL-5, IL-4, IL-3 and IL-7 were detected at 16 to 48 h. SEB also significantly increased CCR3 expression and calcium levels in BM-EO, and enhanced the cell adhesion to ICAM-1 (24 h) and ICAM-1 (48 h). CONCLUSION: Airways SEB exposure increases the number of eosinophils in BM by mechanisms involving a network of cytokine and chemokine release, facilitating the BM-EO adhesion to ICAM-1 and VCAM-1 to gain access to the peripheral blood and lung tissues.

Airway exposure to Staphylococcal enterotoxin type B (SEB) enhances the number and activity of bone marrow neutrophils via the release of multiple cytokines.

BACKGROUND: The lung infections by Staphylococcus aureus are strongly associated with its ability to produce enterotoxins. However, little is known about the mechanisms underlying trafficking of bone marrow (BM) neutrophils during airway inflammation induced by Staphylococcal enterotoxin B (SEB). We therefore aimed to investigate the effects of mouse airways SEB exposure on BM neutrophil counts and its adhesive properties as well as on the release of cytokines/chemokines that orchestrate BM neutrophils trafficking to lung tissue. METHODS: Male BALB/c mice were intranasally exposed to SEB (1 µg), and at 4, 16 and 24 h thereafter, BM, circulating blood, bronchoalveolar lavage (BAL) fluid and lung tissue were collected. BM neutrophils adhesion, MAC-1 and LFA1-α expressions (by flow cytometry) as well as measurement of cytokine and/or chemokines levels were assayed after SEB-airway exposure. RESULTS: Prior exposure to SEB promoted a marked influx of neutrophils to BAL and lung tissue, which was accompanied by increased counts of BM immature neutrophils and blood neutrophilia. BM neutrophil expressions of LFA1-α and MAC-1 were unchanged by SEB exposure whereas a significant enhancement of adhesion properties to VCAM-1 was observed. The early phase of airway SEB exposure was accompanied by high levels of GM-CSF, G-CSF, IFN-γ, TNF-α and KC/CXCL1, while the latter phase by the equilibrated actions of SDF1-α and MIP-2. CONCLUSION: Mouse airways exposure to SEB induces BM cytokines/chemokines release and their integrated actions enhance the adhesion of BM neutrophils leading to acute lung injury.

Staphylococcal enterotoxin A regulates bone marrow granulocyte trafficking during pulmonary inflammatory disease in mice.

Pulmonary neutrophil infiltration produced by Staphylococcal enterotoxin A (SEA) airway exposure is accompanied by marked granulocyte accumulation in bone marrow (BM). Therefore, the aim of this study was to investigate the mechanisms of BM cell accumulation, and trafficking to circulating blood and lung tissue after SEA airway exposure. Male BALB/C mice were intranasally exposed to SEA (1µg), and at 4, 12 and 24h thereafter, BM, circulating blood, bronchoalveolar lavage (BAL) fluid and lung tissue were collected. Adhesion of BM granulocytes and flow cytometry for MAC-1, LFA1-α and VLA-4 and cytokine and/or chemokine levels were assayed after SEA-airway exposure. Prior exposure to SEA promoted a marked PMN influx to BAL and lung tissue, which was accompanied by increased counts of immature and/or mature neutrophils and eosinophils in BM, along with blood neutrophilia. Airway exposure to SEA enhanced BM neutrophil MAC-1 expression, and adhesion to VCAM-1 and/or ICAM-1-coated plates. Elevated levels of GM-CSF, G-CSF, INF-γ, TNF-α, KC/CXCL-1 and SDF-1α were detected in BM after SEA exposure. SEA exposure increased production of eosinopoietic cytokines (eotaxin and IL-5) and BM eosinophil VLA-4 expression, but it failed to affect eosinophil adhesion to VCAM-1 and ICAM-1. In conclusion, BM neutrophil accumulation after SEA exposure takes place by integrated action of cytokines and/or chemokines, enhancing the adhesive responses of BM neutrophils and its trafficking to lung tissues, leading to acute lung injury. BM eosinophil accumulation in SEA-induced acute lung injury may occur via increased eosinopoietic cytokines and VLA-4 expression.

Regional dissociation of paradigm-specific synapse remodeling during memory consolidation in the adult rat dentate gyrus.

Arising from studies on the amnesia that follows site-specific physical or chemical lesions, the acquisition and consolidation of certain behavioral tasks has been demonstrated to be associated with different hippocampal subregions. Although not absolute, spatial learning is reliant on the dorsal region of the hippocampus, whereas avoidance- and fear-conditioning tasks appear to be dependent on its more ventral aspects. Thus, if learning-associated synapse remodeling is a true feature of memory consolidation it must also follow these regional dissociations. We therefore determined if the learning-associated increases in synapse density that occur in the mid-molecular layer of the dentate gyrus at the 6-h post-training time and the frequency of polysialylated cells at the infragranular zone that occur at the 12-h post-training time were dissociated to specific hippocampal subregions following training in either a massed water maze task or light-dark passive avoidance response. Synapse remodeling was found to occur only in the dorsal hippocampus following spatial learning. We could not, however, discern any regional dissociation of neural remodeling following avoidance conditioning. These results point to strong associations between learning and specific groups of novel synapses during consolidation of spatial learning and avoidance conditioning paradigms.

Inflammatory responses induced in mice by lectin from Talisia esculenta seeds.

A novel lectin from Talisia esculenta seeds (TEL) has recently been purified and characterized. In this study we investigated the proinflammatory activity of TEL in mice using both the air-pouch and peritoneal cavity as well as paw oedema models. TEL (10-40 microg) induced significant neutrophil and mononuclear cell recruitment when injected into either mouse air-pouch or peritoneal cavity. The neutrophil accumulation into the air-pouch was dose- and time-dependent with a maximal response at 16 h, returning to control levels at 72 h whereas maximal mononuclear cell accumulation was observed at 24 h after TEL injection. The same profile of neutrophil accumulation was observed when this lectin was injected into mouse peritoneal cavity, although the maximal mononuclear cell recruitment was observed 48 h after TEL injection. Additionally, TEL (12.5-200 microg/paw) caused a dose-dependent mice paw, as evaluated at 4 h after the lectin injection. D-mannose, better than D-glucose, significantly inhibited TEL-induced neutrophil migration into the peritoneal cavity or air-pouch. D-galactose had no effect on TEL-induced neutrophil migration in either cavity studied. On the other hand, D-mannose slightly inhibited the TEL-induced paw oedema, whereas neither D-glucose nor D-galactose affected this phenomenon. In conclusion, our data show that TEL induces neutrophil and mononuclear cell accumulation by a mechanism related to their specific sugar-binding properties.

Mouse macrophages release a neutrophil chemotactic mediator following stimulation by staphylococcal enterotoxin type A.

OBJECTIVE AND DESIGN: To examine the role of macrophages in the neutrophil migration induced by staphylococcal enterotoxin type A (SEA) in mice. MATERIALS AND METHODS: Peritoneal macrophages were harvested from male Swiss mice pre-treated with thioglycollate. After adhering to plastic tissue culture dishes, the cells were washed and incubated with RPMI or SEA (0.62-2.5 microg/ml) and washed again prior to further incubation with RPMI alone. The medium was then collected, sterilized and assayed for promigratory activity in the mouse peritoneal cavity. RESULTS: Mouse macrophage monolayers stimulated with SEA secreted a thermolabile neutrophil chemotactic component (MNCC-SEA) with a molecular mass >100 kDa (by ultrafiltration). This release was dose- and time-dependent and was inhibited by dexamethasone but not by indomethacin or BW755C. Dexamethasone, indomethacin, BWA4C, BW755C, BN52021, cimetidine and SR48968 had no effect on the neutrophil migration induced by MNCC-SEA while capsaicin and SR 140333 reduced this phenomenon. CONCLUSIONS: Macrophages play a key role in the neutrophil recruitment induced by SEA probably by releasing an MNCC-SEA that presumably induces neutrophil migration via a mechanism mediated by substance P.

Involvement of nitric oxide on the peritoneal neutrophil influx induced by staphylococcal enterotoxin B in mouse.

In this study, the role of nitric oxide (NO) on neutrophil migration induced by staphylococcal enterotoxin B (SEB) in the mouse peritoneal cavity was investigated. The NO synthase inhibitors L-NAME and aminoguanidine, as well as dexamethasone, markedly reduced SEB-induced neutrophil influx. In mice with an increased population of peritoneal macrophages, the inhibition of SEB-induced neutrophil influx by these agents was significantly lower. The in vivo treatment with aminoguanidine inhibited only the iNOS activity, whereas L-NAME inhibited both the cNOS and iNOS activities. In conclusion, NO modulates the neutrophil migration in response to SEB through the activity of an iNOS isoform.

Role of nitric oxide on the increased vascular permeability and neutrophil accumulation induced by staphylococcal enterotoxin B into the mouse paw.

The role of nitric oxide (NO) on the increase in vascular permeability and neutrophil migration induced by staphylococcal enterotoxin B (SEB; 25 microgram/paw) in the mouse was investigated in this study. The NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) [but not its inactive enantiomer N(omega)-nitro-D-arginine methyl ester (D-NAME)], given intravenously (25-100 micromol/kg) or subplantarly (0.25-1.0 micromol/paw), reduced SEB-induced paw oedema significantly. A similar response was observed with aminoguanidine, given either intravenously (200-600 micromol/kg) or subplantarly (2 micromol/paw). In contrast to paw oedema, the plasma exudation in response to SEB was not affected by the subplantar injection of L-NAME or aminoguanidine. The inhibition of oedema and plasma exudation by systemic treatment with L-NAME or aminoguanidine was reversed by co-injection of the vasodilator iloprost (0.3 nmol/paw). Subplantar injection of SEB (25 microgram/paw) increased by 69% the myeloperoxidase (MPO) activity of SEB-treated paws, indicating the presence of neutrophils. Intravenous (12.5-50 micromol/kg) or subplantar (0.125-0.5 micromol/paw) administration of L-NAME (but not of its inactive enantiomer, D-NAME) largely reduced the MPO activity in SEB-treated paws. Similarly, intravenous (200-600 micromol/kg) or subplantar (2 micromol/paw) administration of aminoguanidine significantly reduced the MPO values of the SEB-injected paws. The vasodilator iloprost (0.3 nmol/paw) completely reversed the inhibition by L-NAME or aminoguanidine of the MPO activity in SEB-injected paws. Our results show that the increased vascular permeability and neutrophil accumulation in response to subplantar injection of SEB in the mouse are inhibited by L-NAME and aminoguanidine by mechanisms probably involving reduction of local microvascular blood flow.

The hind paw edema produced by staphylococcal enterotoxin B in female mice is modulated by sex hormones.

This paper describes the involvement of sex hormones in the edematogenic response produced by staphylococcal enterotoxin B (SEB) in the mouse hindpaw. Both the paw weight variation and the protein exudate produced by the intraplantar administration of SEB (12.5 micrograms/paw) to intact, randomly cycling female (IRCF) mice were significantly attenuated when the animals were ovariectomized (OVX). The attenuation of SEB-induced paw swelling produced by OVX was not reversed by estradiol (OE2) reposition. Thus, 4 h after the injection of SEB the increase in paw weight in OVX-mice treated with OE2 (10 micrograms/kg in corn oil) was 15.0 +/- 0.9 mg, while the exudation corresponded to 2.1 +/- 0.3 micrograms of Evans blue dye/g of tissue. Neither of these values differed significantly from those obtained 4 h after the intraplantar injection of SEB (12.5 micrograms/paw) in non-treated OVX-mice (paw swelling, 14.0 +/- 0.8 mg; dye exudation, 2.0 +/- 0.3 micrograms/g, N = 6). Pretreating IRCF mice once a day for three days with human chorionic gonadotrophin (40 IU/kg, i.m.) reduced the paw edema produced by the toxin, thus indicating an involvement of gonadotrophins in this event. A pronounced decrease in paw weight variation (about 45%) and dye exudation (61%) was detected when IRCF mice were previously treated every 72 h with three injections of OE2 (10 micrograms/kg in corn oil, i.m.). Similar situations were also seen when the animals were pretreated at 72 h intervals with three injections of testosterone (10 mg/kg in corn oil, i.m.). We conclude that the paw edema induced by SEB in female mice is hormonally regulated. Our results also indicate that the HPA-immune axis is involved in this phenomenon.

Role of frontal cortex in social odor discrimination and scent-marking in female golden hamsters (Mesocricetus auratus).

Orbital/agranular insular (ORB/AI) cortex has been implicated in traditional olfactory learning tasks and social behavior but its precise role in discriminating-learning social odors is not known. Female golden hamsters received aspiration lesions of ORB/AI or dorsomedial (DM) frontal cortex and were tested for their ability to (a) discriminate between odors of individual males in a habituation-discrimination task, (b) show preferences for male over female odors, and (c) scent-mark in response to male odors. Lesioned females readily discriminated between scents of individual males. Neither lesion altered female preferences for male odors. Females with DM lesions showed increased levels of scent marking to male odors, but those with ORB/AI cortex lesions did not differ from controls. Thus, ORB/AI cortex does not appear to be critical for discrimination of odors of individuals or sex or for scent-marking responses based on these discriminations.

Neutrophil migration induced by staphylococcal enterotoxin type A in mice: a pharmacological analysis.

Staphylococcal enterotoxin type A induced marked neutrophil migration into the mouse peritoneal cavity and was dependent on the number of resident macrophages. This migratory response was dose- (16-64 microg of staphylococcal enterotoxin type A/cavity) and time-dependent, peaking at 12 h and disappearing after 72 h. Dexamethasone (0.5 mg/kg) inhibited the neutrophil migration induced by staphylococcal enterotoxin type A (32 microg; 42% inhibition). A similar response was observed with the platelet-activating factor-acether receptor antagonist, BN 52021 (ginkgolide B, 3-(1,1-dimethylethyl)-hexahydro-1,4-7b-trihydroxy-8-methyl-9H-1,7alph a (epoxymethano-1H,6alphaH-cyclopenta (c) furo (2,3-b) furo (3', 2': 3,4) cyclopenta (1,2-d) furan-5, 9, 12 (4H)-trione); 10 mg/kg; 57% inhibition), the histamine H2 receptor antagonist, cimetidine (2 mg/kg; 31% inhibition), the lipoxygenase inhibitor, BWA4C (N-(3-phenoxycinnamyl) acetohydroxamic acid); 10 mg/kg; 73% inhibition), and capsaicin (trans-8-methyl-N-vanillyl-6-nonamide), a sensory C-fiber neuropeptide depletor. In contrast, indomethacin (5 mg/kg) had no effect on staphylococcal enterotoxin type A-induced chemotaxis. We conclude that the peritonitis induced by staphylococcal enterotoxin type A in mice is macrophage-dependent. The mechanism whereby staphylococcal enterotoxin type A stimulates macrophages to induce neutrophil recruitment remains to be elucidated.

The pharmacological profile of mouse hind paw inflammation induced by staphylococcal enterotoxin type A.

OBJECTIVE AND DESIGN: The present paper examines the possible pharmacological mediators involved in mouse hind paw inflammation induced by staphylococcal enterotoxin type A (SEA). MATERIALS AND METHODS: The edema and the Evans blue exudation were measured in male Swiss mice (20-25 g) using methods described by Levy and Griswold, respectively. RESULTS: SEA (32 micrograms/paw) produced a biphasic, long-lasting, dose- and time-dependent edematogenic response. The acute phase edema was pronounced while the chronic edema was of a low intensity. Exudate was the principal component of the edema. The edematogenic effect of SEA appears to involve cyclooxygenase products and was dose-dependently reduced by pretreating the mice with dexamethasone, indomethacin, BW755C, WEB2086, capsaicin, diphenhydramine or cimetidine. CONCLUSIONS: These results demonstrate that SEA-induced mouse hind paw inflammation is a useful model for studying SEA-mediated enterotoxemia and may be sufficiently sensitive to differentiate between the effects of SEA and those of SE type B (SEB).