Critical Role of Protein Kinase C (PKC) in the Onset of Airway Hypersensitivity in Ova-Sensitized Guinea Pig Model of Asthma

Background and Objectives: Protein kinase C (PKC) activation plays an important role in activation of T-lymphocytes in asthma. Airway hypersensitivity is one of the main characteristic features of asthma, the mechanism of onset of which is not clearly understood. Therefore, the objective was to elucidate the role of PKC in etiopathogenesis of airway hypersensitivity in asthma. Methods: Male guinea pigs (n = 30) were sensitized with ovalbumin and day of initial allergen-specific immune response determined by intradermal test, airway hypersensitivity, BALF cytology and lung histopathology. Total PKC activity, PKC isoenzymes and phosphoinositides were assessed in airway smooth muscles (ASM) and peripheral blood lymphocytes. Results: Intradermal test revealed that day 9 was the earliest time of allergen-specific response and onset of airway hypersensitivity to ovalbumin. It was associated with significant increase in total and differential (lymphocytes and eosinophils) BALF counts and grade I peribronchiolar chronic lymphocytic inflammation in lung. On day 14, grade II infiltration of lymphocytes and eosinophils with onset ofstructural remodelingofproximal and distal airways was seen. Total PKC activity, expression of PKCα, PKCe and phosphoinositides increased significantly in ASM and lymphocytes on day 9 and were maximum on day 14. There was no change in PKC-τ expression. Conclusions: Activation of PKC, particularly PKCα and PKCe, mediated signal transduction pathway plays a critical role in lymphocyte infiltration and onset of airway hypersensitivity, airway remodeling and asthma pathophysiology. The present study is the first one on the mechanism of the etiopathogenesis of the disease, which shows a direct evidence of the role of PKC mediated pathway in the initiation and onset of airway hypersensitivity in ovalbumin sensitized guinea pig model.