Modulation by protein kinase C of the enhanced responsiveness to tachykinins in ovalbumin-sensitized guinea pig alveolar macrophages

As previously reported, alveolar macrophages (AMs) from ovalbumin- sensitized guinea pigs present an enhanced responsiveness to tachykinins but not to N-formylmethionyl-leucyl-phenylalanine (fMLP). We have investigated the biochemical mechanisms underlying this varied responsiveness to tachykinins. The protein kinase C (PKC) activator phorbol 12-myristate 13- acetate (PMA) induced a larger superoxide anion (O₂/^-) production in AMs from sensitized guinea pigs, as did tachykinins. Pretreatment of AMs with pertussis toxin abolished tachykinin-evoked respiratory burst, had no effect on PMA-evoked O₂^- production and strongly inhibited fMLP-evoked one, with no appreciable variation between control or sensitized AMs. Staurosporine and its derivative cgp 41251, significantly decreased PMA- and tachykinin- evoked O₂/^- production in both populations, being more potent in control AMs, but exerted little effects against fMLP. Pretreatment of AMs with PMA significantly inhibited fMLP-, PMA- and tachykinin-evoked O₂/^- production in both control and sensitized AMs. fMLP, substance P (SP), neurokinin A (NKA) and the NK₂ agonist [β-Ala⁸]-NKA(4-10) dose-dependently increased [³H] phorbor 12, 13 dibutyrate (PDBu) binding to control and sensitized AMs. While fMLP exerted similar effects in both populations, dose-response curves for SP, NKA and the NK₂ receptor agonist were shifted leftwards (1, 4 and 3 orders of magnitude, respectively) in sensitized AMs. These results indicate a possible PKC involvement in the enhanced responsiveness to tachykinins in actively sensitized AMs.