Granulocytopoietic activity of satphylococcal enterotoxin type A (SEA) and B (SEB) in mice: a possible mechanism to explain the exacerbation of pulmonary allergic granulocyte recruitment induced by these toxins.

I A Desouza1,2, W Takeshita1, GC Mello0,2, D Squebola-Cola2, E Antunes2. 1Faculty of Medicine of Jundiaí, Biology and Physiology, Brazil, 2Faculty of Medical Science - State University of Campinas - UNICAMP, Pharmacology, Brazil

The staphylococcal enterotoxins (SEs) are proteins produced and secreted by the gram-positive bacterium Staphylococcus aureus, and are responsible for the most pathological conditions associated with S. aureus infections, including pulmonary infections in hospitalar environment. Clinical evidences have shown a strong association between Staphylococcus aureus infections and exacerbation of bronchial asthma. However, few studies have attempted to evaluate the mechanisms involved on the exacerbation of allergic cell pulmonary infiltration induced by prior expousure to SEA and SEB. The aim of this study was investigated if the mechanisms whereby SEA and SEB cause exacerbation of allergic pulmonary inflammation are correlated with changes on granulocytopoese and citokines/chemokines production on mice bone marrow (BM). Male BALB/C mice were intransally instilled with SEA or SEB (0.3-1 μg). Broncoalveolar lavage (BAL) and BM were examined (4 to 48 h post-SEs instillation). Mice intranasally instilation with SEA significantly increases the eosinophil (at 4 h) and neutrophil (at 16 h) recruitment to BAL accompanied by the increase number of immature and mature forms of granulocytes on BM. A marked eosinophilia and neutrophilia was observed at 16 h and 24 h post-SEB to BAL fluid which was also correlated with BM increase on immature and mature forms of granulocytes. We also evaluated the levels of cytokines (GM-CSF, IL-5 e IL-4) and chemokines (eotaxin and KC/CXCL1) on the BM supernatant from mice submitted to airways exposition of SEs. Our results showed that both SEs are able to induced increase levels of eotaxin at 16 h when compared with control group (Control: 59.7±7.8; SEA: 146.1±14.6 and SEB: 322.8±77.6 pg of eotaxin/mg of protein). A similar results was observed for the levels of the granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 after SEA or SEB instilation (Control: 4.78±1.0; SEA: 10.3±1.4; SEB: 47.5±13.3 pg of GM-CSF/mg of protein; Control:16.4±3.5; SEA: 29.6±3.79; SEB: 49.5±13.8 pg of IL-4/mg of protein). However, while SEB induced increased levels of IL-5 at 16 h (Control: 52.6±8.8; SEB: 266.6±103.0 pg of IL-5/mg of protein) in mice BM the instilation of SEA induced a marked reduction on the levels of this cytokine (17.7±2.8 pg of IL-5/mg of protein). In addition the levels of the chemokine KC/CXCL1 was increased at 4 h after SEA (Control: 23.4±5.16; .SEA: 54.0±8.0 pg of KC/CXCL1/mg of protein) and 16 h after SEB (67.2±12.5 pg of KC/CXCL1/mg of protein). In conlcusion our study shows that SEA and SEB have granulocytopoietic activity probably by their ability to mediate inflammatory cytokine/chemokine release which display a major role on the production and trafficking of granulocytes (neutrophil/eosinophil) from mice BM to pulmonary inflammatory site. Taken in consideration the high number of clinical infections induced by Staphylococcus aureus, and their connection with allergic respiratory diseases (through SEs release and actions) the findings from this study, showing the effects of these toxins in mice BM can be useful to provide advancement to explain the allergic respiratory disease exacerbation after gram-positive bacterial exposition in human and animal experimental models. Financial Support: Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP: 2009/16522-0).