17-18-epoxy-5-8-11-14-eicosatetraenoic-acid and Pneumonia

Protein kinase C variants (PKCs) have been involved in the control of airway smooth muscle (ASM) tone, and abnormalities in PKC-dependent signaling have been associated with respiratory diseases such as asthma. In this study, the role of atypical PKCζ in airway hyperresponsiveness was investigated, using an in-vitro model of TNFα-treated human bronchi and an in vivo guinea pig model of chronic asthma. Our results demonstrated that PKCζ-specific inhibition produced a significant increase in isoproterenol sensitivity in TNFα-treated bronchi and ovalbumin (OVA)-sensitized guinea pig bronchi. The role of epoxy-eicosanoids, known to exert anti-inflammatory effects in lung, on PKCζ expression and activity in these models was evaluated. An enhanced PKCζ protein expression was delineated in TNFα-treated bronchi when compared with control (untreated) and epoxy-eicosanoid-treated bronchi. Measurements of Ca(2+) sensitivity, performed in TNFα-treated bronchi, demonstrated that treatment with myristoylated (Myr) PKCζ peptide inhibitor resulted in significant reductions of pCa-induced tension. Epoxy-eicosanoid treatments had similar effects on Ca(2+) sensitivity in TNFα-treated bronchi. In control and epoxy-eicosanoid-treated bronchi, the phosphorylated forms of p38MAPK and CPI-17 were significantly decreased compared with the TNFα-treated bronchi. An enhanced expression of PKCζ was ascertained in our in-vivo model of allergic asthma. Hence an increased Ca(2+) sensitivity could be explained by the phosphorylation of p38-MAPK, which in turn leads to phosphorylation and activation of the CPI-17 regulatory protein. This process was reversed upon treatment with the Myr-PKCζ-peptide inhibitor. The present data provide relevant evidence regarding the role of PKCζ in human and rodent models of airways inflammation.

Topics: Adrenergic beta-2 Receptor Agonists; Animals; Arachidonic Acids; Asthma; Biomechanical Phenomena; Bronchi; Bronchial Hyperreactivity; Bronchodilator Agents; Calcium; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Guinea Pigs; Humans; Intracellular Signaling Peptides and Proteins; Male; Muscle Contraction; Muscle Proteins; Muscle Relaxation; Muscle, Smooth; Ovalbumin; p38 Mitogen-Activated Protein Kinases; Phosphoprotein Phosphatases; Phosphorylation; Pneumonia; Protein Kinase C; Protein Kinase Inhibitors; Tissue Culture Techniques; Tumor Necrosis Factor-alpha; Up-Regulation

This study sought to assess putative pathways involved in the anti-inflammatory effects of 17,18-epoxyeicosatetraenoic acid (17,18-EpETE), as measured by a decrease in the contractile reactivity and Ca(2+) sensitivity of TNF-α-pretreated human bronchi. Tension measurements performed in the presence of 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), a soluble epoxide hydrolase (sEH)-specific inhibitor, demonstrated that 17,18-EpETE reduced the reactivity of TNF-α-pretreated tissues. The overexpression of sEH detected in patients with asthma and TNF-α-treated bronchi contributed to the maintenance of hyperresponsiveness in our models, which involved intracellular proinflammatory cascades. The inhibition of peroxisome proliferator-activated receptor (PPAR)γ by GW9662 abolished 17,18-EpETE + AUDA-mediated anti-inflammatory effects by inducing IκBα degradation and cytokine synthesis, indicating that PPARγ is a molecular target of epoxy-eicosanoids. Western blot analysis revealed that 17,18-EpETE pretreatment reversed the phosphorylation of p38 mitogen-activated protein kinase (p38-MAPK) induced by TNF-α in human bronchi. The Ca(2+) sensitivity of human bronchial explants was also quantified on β-escin permeabilized preparations. The presence of SB203580, a p38-MAPK inhibitor, reversed the effect induced by epoxy-eicosanoid in the presence of AUDA on TNF-α-triggered Ca(2+) hypersensitivity by increasing the phosphorylation level of PKC Potentiated Inhibitor Protein-17 (CPI-17) regulatory protein. Moreover, PPARγ ligands, such as rosiglitazone and 17,18-EpETE, decreased the expression of CPI-17, both at the mRNA and protein levels, whereas this effect was countered by GW9662 treatment in TNF-α-treated bronchi. These results demonstrate that 17,18-EpETE is a potent regulator of human lung inflammation and concomitant hyperresponsiveness, and may represent a valuable asset against critical inflammatory bronchial disorder.

Topics: 8,11,14-Eicosatrienoic Acid; Anti-Inflammatory Agents; Arachidonic Acids; Bronchi; Calcium; Cyclooxygenase 2; Epoxide Hydrolases; Humans; Intracellular Signaling Peptides and Proteins; Lung; Models, Biological; Muscle Proteins; Myosin-Light-Chain Phosphatase; p38 Mitogen-Activated Protein Kinases; Phosphoprotein Phosphatases; Phosphorylation; Pneumonia; PPAR gamma; Protein Kinase Inhibitors; Solubility; Tumor Necrosis Factor-alpha