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 [beta-Ala8]-NKA(4-10) dose-dependently increased [3H] phorbol 12, 13 dibutyrate (PDBu) binding to control and sensitized AMs. While fMLP exerted similar effects in both populations, dose-response curves for SP1 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.

Tachykinin activation of human alveolar macrophages in tobacco smoke and sarcoidosis: a phenotypical and functional study.

Substance P (SP) and neurokinin A (NKA), which exert bronchoconstrictor effects on human airways, are known to interact with inflammatory and immune cells, including monocyte macrophages. We have evaluated the effects of SP, NKA and the NK2 selective agonist [beta-Ala8]-NKA(4-10) on alveolar macrophages (AM) isolated from 4 healthy smokers and 4 non-smoker active pulmonary sarcoid patients. An accumulation of activated mononuclear phagocytes, as well as elevated angiotensin-converting enzyme (ACE) activity, has been evidenced in both clinical conditions. The phenotype of AMs in the studied subjects was characterized by an elevated expression of CD68+, HLA-DR+ and CD14+, CD14+ being significantly less in sarcoidosis as compared to smokers. SP, NKA and the NK2 selective agonist evoked superoxide anion (O2-) production in AMs obtained from sarcoid patients or healthy smokers. While SP acted in a non-dose-dependent manner in both conditions, NKA and [beta-Ala8]-NKA(4-10) evoked a dose-dependent respiratory burst (ED50 = 0.25 and 0.26 nM, respectively) in smokers, but not in sarcoidosis. The more marked phenotypical expression correlated well with the ability of NK2 receptors to activate AMs in smoker subjects.

In vivo antiviral effects of pidotimod.

The effect of pretreatment with pidotimod ((R)-3-[(S)- (5-oxo-2-pyrrolidinyl)-carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) was evaluated in mice infected with two challenging doses of three different viruses. Mengovirus, Herpes simplex, influenza virus were used. The mice were treated 15 days before the virus challenge. The antiviral effect of pidotimod was evaluated as difference in survival time versus control groups challenged with viruses but not pretreated with pidotimod. In groups pretreated and challenged with the lower dose of each virus strain a statistically significant increase in survival time was observed. On the basis of the known effects of pidotimod on immune system, this effect is due to an immunostimulating effect of this drug.