A Small-Molecule, Tight-binding Inhibitor of the Integrin α₄β₁ Blocks Antigen-induced Airway Responses and Inflammation in Experimental Asthma in Sheep

Abstract

The leukocyte integrin very late antigen-4 (alpha(4)beta(1), CD49d/CD29) is an adhesion receptor that plays an important role in allergic inflammation and contributes to antigen-induced late responses (LAR) and airway hyperresponsiveness (AHR). In this study, we show that single doses of a new small-molecule, tight-binding inhibitor of alpha(4), BIO-1211, whether given by aerosol or intravenously, either before or 1.5 h after antigen challenge blocks allergen- induced LAR and post-antigen-induced AHR in allergic sheep. Multiple treatments with doses of BIO-1211 that were ineffective when given singly, were protective. BIO-1211 also provided dose-dependent inhibition of the early airway response (EAR) to antigen. In conjunction with the functional protection against the antigen-induced LAR and AHR, sheep treated with BIO-1211 before challenge showed significantly reduced: (1) numbers of eosinophils in bronchoalveolar lavage (BAL), (2) BAL levels of the inflammatory marker tissue kallikrein, and (3) numbers of inflammatory cells (lymphocytes, eosinophils, metachromatic staining cells, and neutrophils) in bronchial biopsies obtained after challenge when compared with corresponding biopsies after vehicle treatment. More importantly, we show for the first time that an inhibitor of alpha(4) was able to reverse post-antigen-induced AHR, thereby decreasing the time of recovery from the normal period of > 9 d to 3 d. Our results show that effective inhibition of antigen-induced airway responses can be achieved with single doses of a potent small-molecule inhibitor of alpha(4) and that such agents may be used therapeutically, as well as prophylactically, to alleviate allergen- induced inflammatory events. These data provide further support and extend the evidence for the role of alpha(4) integrins in the pathophysiologic events that follow airway antigen challenge.

Pulmonary Eosinophilia in a Murine Model of Allergic Inflammation Is Attenuated by Small Molecule α4β1 Antagonists

“…This interaction has been proposed to result in cell activation, such as the mast cell (Ra et al, 1994), and may explain the efficacy of ␣4␤1 antagonism in early phase response to antigen challenge as has been reported in rats (Hojo et al, 1998) and sheep (Abraham et al, 1997(Abraham et al, , 2000. In our studies, intratracheal instillation of CP-609643 at a dose that significantly attenuated eosinophil infiltration failed to affect levels of the mediators known to be important in the recruitment of these cells, including TNF-␣, eotaxin, and IL-4.…”

“…and suggests that factors other than in vitro activity contribute to in vivo efficacy in this model. In contrast, BIO1211 was efficacious when delivered by aerosol or intravenous routes in an allergic sheep model of asthma using inflammatory cell influx and airway hyperresponsiveness as endpoints (Abraham et al, 2000).…”

“…Two small molecule ␣4␤1 antagonists have been evaluated in the allergic sheep model following aerosol administration. Efficacy was reported for both the CS-1 ligand mimic phenylacetyl-L-leucyl-L-aspartyl-L-phenylalanyl-D-prolineamide (Abraham et al, 1997) and BIO1211 (Abraham et al, 2000) as measured by modification of antigen-induced alterations in cell infiltration and pulmonary function.…”

Airway Responses to Aerosolized Brevetoxins in an Animal Model of Asthma

“…Thus, if the sensitivity to inhaled toxin is related to the inflammatory state of the lung, then similar responses between unchallenged allergic sheep and nonallergic sheep might occur, as seen in the present study. This explanation, although speculative, is based on our observations that the response to PbTx-3 is significantly enhanced in allergic sheep after antigen challenge (our unpublished observations) when the airways are visibly inflamed (27,28). It is important, however, that the nonallergic animals responded to the toxin because it mimics what occurs with natural exposures (11,12) and indicates that the airway responses reported here are not due to the allergic status of the animals.…”

Unique and redundant roles of α4 and β2 integrins in kinetics of recruitment of lymphoid vs myeloid cell subsets to the inflamed peritoneum revealed by studies of genetically deficient mice

“…However, results of antibody studies vary with the animal model used or the route of antibody administration, and off-target effects can not be excluded [10][11][12][13][14]. To avoid the ambiguity of antibody-based studies and to carry out long-term observations, mouse models with genetically modified integrin genes have been generated [15][16][17].…”