Interleukin 13 increases contractility of murine tracheal smooth muscle by a phosphoinositide 3-kinase p110delta-dependent mechanism

The Th2 cytokine interleukin (IL) 13 can elicit a number of responses consistent with a key role in the pathogenesis of asthma. We have used pharmacological and genetic approaches to demonstrate the role of signaling via the class I phosphoinositide 3-kinase p110delta isoform in IL-13-induced hyper-responsiveness of murine tracheal smooth muscle contractility in vitro. IL-13 treatment of tracheal tissue is associated with an early activation of phosphoinositide 3-kinase (PI3K), as assessed by phosphorylation of Akt. Tracheal smooth muscle contractility is enhanced by overnight incubation with IL-13, resulting in increased maximal contractions (E(max)) to carbachol (CCh) and KCl. Inhibition of PI3K by the non-isoform-selective inhibitors wortmannin or 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002), or the selective inhibitor of the PI3K p110delta isoform 2-(6-aminopurin-9-ylmethyl)-5-methyl-3-O-tolyl-3H-quinazolin-4-one (IC87114), prevented IL-13-induced hyper-responsiveness. Consistent with a role for PI3K p110delta in IL-13-induced hyper-responsiveness, IL-13 was unable to induce hyper-responsiveness in tissues from mice expressing the catalytically inactive form of p110delta (p110delta(D910A)). These data indicate that IL-13 contributes to tracheal smooth muscle hyper-responsiveness via the PI3K p110delta isoform. In addition to previously reported effects on airway inflammation, inhibition of PI3K p110delta may be a useful target for the treatment of asthma by preventing IL-13-induced airway smooth muscle hyper-responsiveness.

Phosphoinositide 3-kinase signalling in lung disease: leucocytes and beyond

The family of lipid kinases termed phosphoinositide-3-kinase (PI3K) is known to contribute at multiple levels to innate and adaptive immune responses, and is hence an attractive target for drug discovery in inflammatory and autoimmune disease, including respiratory diseases. The development of isoform-selective pharmacological inhibitors, targeted gene manipulation and short interfering RNA (siRNA) target validation have facilitated a better understanding of the role that each member of this family of kinases plays in the physiology and pathology of the respiratory system. In this review, we will evaluate the evidence for the roles of specific PI3K isoforms in the lung and airways, and discuss their potential as targets for novel drug therapies.

Leukocyte navigation mechanisms as targets in airway diseases

Respiratory diseases, including asthma and chronic obstructive pulmonary disease, are among the most significant diseases in terms of their disabling effects and healthcare burden. A characteristic feature of almost all respiratory diseases is the accumulation and activation of inflammatory leukocytes in the lung or airway. Recent advances in the understanding of the molecules and intracellular signalling events controlling these processes are now translating to new therapeutic entities. In this article, the process of leukocyte accumulation is summarized, together with the preclinical and clinical evidence supporting the utility of the individual components of this process as targets for disease therapy.

Possible activation of the NO-cyclic GMP-protein kinase G-K+ channels pathway by gabapentin on the formalin test

The effect of modulators of the nitric oxide-cyclic GMP-protein kinase G-K+ channels pathway on the local peripheral antinociceptive action induced by gabapentin was assessed in the rat 1% formalin test. Local peripheral administration of gabapentin produced a dose-dependent antinociception in the second phase of the test. Gabapentin-induced antinociception was due to a local action as its administration in the contralateral paw was ineffective. Local peripheral pretreatment of the paws with NG-L-nitro-arginine methyl ester (L-NAME, a nitric oxide synthesis inhibitor), 1H-(1,2,4)-oxadiazolo(4,2-a)quinoxalin-1-one (ODQ, a soluble guanylyl cyclase inhibitor) and KT-5823 (a protein kinase G inhibitor) dose-dependently reduced gabapentin-induced antinociception. Likewise, glibenclamide or tolbutamide (ATP-sensitive K+ channel inhibitors), 4-aminopyridine or tetraethylammonium (non-selective inward rectifier K+ channel inhibitors) or charybdotoxin (large-conductance Ca2+-activated-K+ channel blocker), but not apamin (small-conductance Ca2+-activated-K+ channel blocker) or naloxone (opioid receptor antagonist), reduced the antinociception induced by gabapentin. Our data suggest that gabapentin could activate the nitric oxide-cyclic GMP-protein kinase G-K+ channels pathway in order to produce its peripheral antinociceptive effect in the rat 1% formalin test.