Pre-exposure to Staphylococcal enterotoxin A exacerbates the pulmonary allergic eosinophil recruitment in rats Nadia S. Mariano a , Glaucia C. de Mello a , Tatiane Ferreira a , André Schenka a , Enilton A. Camargo a , Gilberto de Nucci a , Ivani A. DeSouza a,b , Edson Antunes a, ⁎ a Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas (Sao Paulo), Brazil b Department of Biology and Physiology, Faculty of Medicine of Jundiái (FMJ), Jundiaí (São Paulo), Brazil abstract article info Article history: Received 1 July 2009 Received in revised form 25 August 2009 Accepted 24 September 2009 Keywords: Staphylococcal enterotoxins Lung inflammation Eosinophils Eotaxin Bone marrow Gram-positive Staphylococcus aureus releases classical enterotoxins which aggravates allergic airway diseases. However, little is known about the mechanisms underlying the cell influx exacerbation in asthmatic individuals under exposure to Staphylococcal enterotoxins. We therefore aimed to investigate the effects of airways exposure to Staphylococcal enterotoxin A (SEA) to pulmonary leukocyte recruitment in rats sensitized and challenged with ovalbumin (OVA). Rats were exposed to SEA at 4 h prior to OVA challenge or at 4 h post-OVA challenge. Bronchoalveolar lavage (BAL) fluid, bone marrow and lung tissue were obtained at 24 h after OVA challenge. Pre-exposure to SEA markedly enhanced the eosinophil counts in both BAL fluid and pulmonary tissue in OVA-challenged rats, whereas neutrophil and mononuclear cell counts remained unchanged. In bone marrow, pre-exposure to SEA alone significantly increased the number of eosinophils, and that was further increased in OVA-challenged rats. Exposure to SEA post-OVA challenge did not affect the number of eosinophils, neutrophils and mononuclear cells in BAL fluid. Pre-exposure to the endotoxin lipopolyssacharide (LPS) in OVA-challenged animals rather enhanced the neutrophil number in BAL fluid. In rats pre-exposed to SEA and OVA-challenged, a marked elevation in the levels of TNF-α and eotaxin (but not of IL-10) in BAL fluid was observed. The eotaxin levels increased by about of 3-fold in alveolar macrophages treated with SEA in vitro. In conclusion, airways pre- exposure to SEA causes a selective increase in eosinophil number in BAL fluid and bone marrow of OVA- challenged rats by mechanisms involving enhancement of TNF-α and eotaxin synthesis. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Staphylococcus aureus is a gram-positive bacterium that produces and secretes the so-called staphylococcal enterotoxins, which are a family of structurally related heat-stable 25 to 30 kDa proteins. These enterotoxins comprise several serological types, namely the classical types A to E, and the newly characterized types G to Q [1]. Two novel genes coding for enterotoxins types S and T have been recently described [2]. Among the Staphylococcal enterotoxins, toxins A and B can be easily obtained in relatively large amounts and purity [3], and therefore has been used to a great extent in experimental investiga- tions. In addition to the well-known ability to cause food poisoning [4], Staphylococcal enterotoxins often lead to multiorgan dysfunction [5] that may be a consequence of the release of several inflammatory mediators such as cytokines (IL-1, IL-2, IL-6, IL-8, IFN-γ, TNF-α), mast cell-derived amines (histamine and 5-hydroxytriptamine), neuropep- tides (substance P), lipid mediators (PGE 2 and PAF), amongst others [6–12]. Moreover, Staphylococcal enterotoxins are considered proto- typical superantigens, which interacts with the outside of the MHC molecule and V-beta chain of T-cell-receptor without the need for internalization, processing, or presentation within the confines of a major histocompatibility complex [13]. S. aureus, which often asymptomatically colonize the upper respiratory tract, has been associated with allergic diseases. A correlation between levels of IgE antibodies to staphylococcal enter- otoxins and the severity of eosinophilic inflammation in upper airway disease has been found [14–16]. Polyvalent sensitization with Staphy- lococcal enterotoxins A and B has been associated with increased IgE reactivity leading to exacerbation of allergic responses in humans [17]. However, little is known about the mechanisms underlying such pulmonary inflammatory exacerbation in asthmatic individuals under exposure to Staphylococcal enterotoxins. An experimental study showed that mice cutaneous sensitization with Staphylococcal entero- toxin B cause allergic skin inflammation and increased serum IgE levels [18]. Later, nasal and bronchial exposure to Staphylococcal enterotoxin B was shown to enhance the allergic pulmonary eosinophilic inflamma- tion in ovalbumin (OVA)-sensitized mice, which was associated with increased mRNA expression of IL-5, IL-4, IFN-γ, IL-12 p40, eotaxin-1 and TGF-β as well as IgE titers in the serum [19]. However, no studies exist International Immunopharmacology 10 (2010) 43–49 ⁎ Corresponding author. Department of Pharmacology, Faculty of Medical Sciences, P.O. Box 6111, UNICAMP, 13084-971, Campinas, SP, Brazil. Tel.: +55 19 35219555; fax: +55 19 32892968. E-mail addresses: edson.antunes@uol.com.br, antunes@fcm.unicamp.br (E. Antunes). 1567-5769/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.intimp.2009.09.017 Contents lists available at ScienceDirect International Immunopharmacology journal homepage: www.elsevier.com/locate/intimp