Protein Tyrosine Phosphatases Regulate Asthma Development in a Murine Asthma Model 1 Philippe Pouliot,* † Pierre Camateros, † Danuta Radzioch, † Bart N. Lambrecht, ‡ and Martin Olivier 2 * † Allergic asthma is a chronic inflammatory disease characterized by Th2-type inflammation. Although the cellular interactions are now well studied, the intracellular signaling involved in asthma development is still a developing field. Protein tyrosine kinases are one focus of such research and their inhibition shows improvement of asthmatic features. Interestingly, very little attention was given to protein tyrosine phosphatases (PTPs), the counterparts to protein tyrosine kinases, in the development of asthma. Previous studies from our laboratory showed that pharmacological inhibition of PTPs induced a transient Th1 response in the spleen. Therefore, we hypothesized that modulation of PTPs could influence asthma development. To assess PTP functions, we used the PTP inhibitor bis-peroxovanadium bpV(phen) in a murine model of asthma during either allergen sensitization or challenge. Inhibition of PTPs during allergen sensitization resulted in the reduction of key features of allergic asthma: serum IgE levels, lung tissue inflammation, eosinophilia, and airway hyperresponsiveness. Of utmost interest, PTP inhibition at allergen challenge resulted in a very similar improvement of asthmatic features. Of further importance, we observed that bpV(phen) treatment modulated cytokine expression in the spleen and, more specifically, favored Th1 cytokines while inhibiting Th2 cyto- kines. Collectively, we show for the first time that intact activity of PTPs is required for a complete induction of asthma in a mouse model. This clearly suggests that PTPs have a pivotal regulatory role in the development of asthmatic diseases, which opens the possibility of new therapeutic avenues. The Journal of Immunology, 2009, 182: 1334 –1340. A llergic asthma is a chronic inflammatory disease char- acterized by sustained Th2-type immune response (1). Development of this disease relies on the sensitization to an allergen and subsequently on the IgE-mediated response to that allergen (2). Mast cell degranulation following allergen recogni- tion by membrane-bound IgEs leads to bronchoconstriction and recruitment of inflammatory cells. Recruited eosinophils and Th2 cells further promote the allergic inflammation and favor tissue damage, which can lead to lung remodeling (2). Although the var- ious cell interactions leading to asthma development are now bet- ter understood, little is known regarding the intracellular events regulating cellular responses involved in asthma. The importance of intracellular signaling in cell regulation is indisputable: alterations in signaling pathways can result in severe dysfunction of the immune response. Of the events involved in the transmission of a signal from the membrane to the nucleus, ty- rosine phosphorylation is a critical step that is often obligatory for numerous cell receptors related to immunity (3– 6). For example, tyrosine phosphorylation in the TCR complex is the first detectable event occurring after receptor ligation (5, 6). Consequently, the regulation of tyrosine phosphorylation must be tightly regulated and this is achieved by a balance between the protein tyrosine kinases (PTKs), 3 which add a phosphate group, and the protein tyrosine phosphatases (PTPs), which remove it (7, 8). In addition to its role in TCR signaling, tyrosine phosphorylation is also crit- ical to other receptors such as IL-4, IL-5, IL-13, and IFN- recep- tors (9) as well as the FcR1 receptor (10), which all exert a potent role in the modulation of immune response. Since PTKs were char- acterized 10 years before PTPs (11–13), their role in asthma de- velopment is now better understood (14) and previous studies show that inhibition of various PTKs successfully reduced asth- matic symptoms in animal models (reviewed in Ref. 14). In contrast, very little is known about the role of PTPs in asthma. Upon allergen challenge, phosphatase and tensin homolog (PTEN) protein expression was shown to be down-regulated, which favors development of the disease in a murine model (15). Conversely, overexpression of PTEN by an adenoviral vector re- duced asthma development. The PTP Src homology 2 domain- containing phosphatase (SHP) 1 was also shown to play a role in asthma development: if SHP-1 activity is reduced (as in Ptpn6 me/+ mice), investigators noted an exacerbated development of asthma (16). However, there are no reports regarding the pharmacological modulation of PTPs in asthma. We previously reported (17, 18) that PTP inhibitors of the peroxovanadium class alone or in com- bination with various stimuli (e.g., IFN-) can significantly aug- ment signaling pathways and transcriptional events, which result in the promotion of specific cellular functions. In mouse experiments, i.p. injections of the peroxovanadium PTP inhibitor bpV(phen) *Department of Microbiology and Immunology, McGill University, Montreal, Que- bec, Canada; † Centre for the Study of Host Resistance, The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada; and ‡ Department of Respiratory Diseases, University Hospital Ghent, Ghent, Belgium Received for publication June 19, 2008. Accepted for publication November 16, 2008. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Funding was provided by the Canadian Institute of Health Research through an operating grant (to M.O.). P.P. is the recipient of a Canada Graduate Scholarships- Doctoral Award from the Canadian Institute of Health Research. 2 Address correspondence and reprint requests to Dr. Martin Olivier, Department of Microbiology and Immunology, McGill University, Lyman Duff Medical Building (Room 610), 3775 University Street, Montreal, Quebec, Canada H9S 3W6. E-mail address: martin.olivier@mcgill.ca 3 Abbreviations used in this paper: PTK, protein tyrosine kinase; PTP, protein ty- rosine phosphatase; PTEN, phosphatase and tensin homolog; SHP, Src homology 2 domain-containing phosphatase; AHR, airway hyperresponsiveness; BALf, bron- choalveolar lavage fluid; DAPI, 4',6-diamidino-2-phenylindole; Penh, enhanced pause; pNPP, p-nitrophenyl phosphate; pV, bpV(phen); Sal, saline. 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