Inhibitors of Tyrosine Kinase Signaling Cascade Attenuated Antigen Challenge of Guinea-Pig Airways In Vitro

Abstract

Activation of nontransmembrane protein tyrosine kinases (PTKs), phosphatidylinositol 3-kinase (PI3K), and mitogen-activated protein kinase (MAPK) has been shown to be responsible for high-affinity Fc receptor (Fcepsilon RI)-mediated mast cell degranulation. Effects of inhibitors of the PTK signaling cascade on ovalbumin (OA)-induced anaphylactic contraction of isolated guinea-pig bronchi and release of histamine and peptidoleukotrienes from chopped lung preparations were studied. Genistein (30 microM) and tyrphostin 47 (50 microM), two PTK inhibitors, as well as LY294002 (10 microM), a selective PI3K inhibitor, significantly reduced (p < 0.05) peak anaphylactic bronchial contraction and facilitated relaxation of the contracted bronchi. PD 098059 (30 microM), a selective MAPK kinase inhibitor, failed to suppress OA-induced peak bronchial contraction, but facilitated the relaxation of the contracted bronchi (p < 0.05). At the same concentrations, none of these inhibitors showed any inhibitory effects on histamine-, leukotriene D(4) (LTD(4))- or KCl-induced bronchial contraction. On the other hand, these inhibitors significantly prevented (p < 0.05) OA-induced release of both histamine and peptidoleukotrienes from chopped lung preparations. In addition, combined PD 098059 and LY294002 treatment markedly (p < 0.05) suppressed the peak anaphylactic bronchial contraction and facilitated relaxation of the contracted bronchi. The combination of these two inhibitors further inhibited the release of peptidoleukotrienes from chopped lung preparations. Taken together, our data show that inhibition of tyrosine kinase signaling cascade can markedly attenuate anaphylactic contraction of airways, probably via inhibition of mast cell degranulation, and that inhibitors of this signaling cascade may have therapeutic potential for the treatment of asthma.

An anti-inflammatory role for a phosphoinositide 3-kinase inhibitor LY294002 in a mouse asthma model

“…Walker et al [14] described the crystal structure of PI3Kg with LY294002, showing that the morpholino group of LY294002 is absolutely required for binding and selectivity. Our present findings confirm our previous in vitro anti-inflammatory data [15,16] that inhibition of PI3K by LY294002 could attenuate OVA-induced pulmonary inflammation, release of Th2 cytokines into the airway, airway mucus production, and AHR in sensitized mice.…”

“…Our laboratory has recently demonstrated that LY294002, a PI3K inhibitor [13,14], significantly inhibited antigen-induced anaphylactic contraction of bronchial rings and release of histamine and peptidoleukotrienes from chopped lung preparations from sensitized guinea pigs [15], and thrombin-induced airway smooth muscle cell proliferation [16]. The purpose of the present study was to extend our recent in vitro findings of anti-inflammatory effects of LY294002 to an in vivo mouse asthma model.…”

Intracellular signaling pathways in IgE-dependent mast cell activation

“…Recently it has also been reported that they can markedly attenuate antigen-induced acute bronchoconstriction and airway hyperresponsiveness to inhaled methacholine in a guinea pig model of asthma [89]. Similar observations of Syk-selective inhibition have been published [75,89]. Piceatannol, a Syk-selective inhibitor, significantly diminished antigen-induced bronchial smooth muscle contraction and release of histamine and leukotrienes from lung fragments isolated from sensitized guinea pigs [75].…”

“…Genistein inhibits PTK activity through competitive inhibition at the ATP-binding domain of the kinase, whereas tyrphostin acts by competitive inhibition at the substrate site of the kinase [2]. Recently it has also been reported that they can markedly attenuate antigen-induced acute bronchoconstriction and airway hyperresponsiveness to inhaled methacholine in a guinea pig model of asthma [89]. Similar observations of Syk-selective inhibition have been published [75,89].…”

“…PD 098059, a selective MAPK kinase inhibitor, and UO126, a potent and selective MEK1/2 blocker, are known to inhibit FcεRI-mediated signal transduction and airway hyperresponsiveness in mouse and rat models of asthma [19,89]. Using LY294002, a highly specific inhibitor of PI3K, a significant suppression of antigen-induced inflammatory cell influx and cytokine production has been shown [18].…”