Macrophage-stimulating protein differently affects human alveolar macrophages from smoker and non-smoker patients: evaluation of respiratory burst, cytokine release and NF-κB pathway

1. Macrophage activation is a key feature of inflammatory reactions occurring during bacterial infections, immune responses and tissue injury. We previously demonstrated that human macrophages of different origin express the tyrosine kinase receptor recepteur d'origine nantaise, the human receptor for MSP (RON) and produce superoxide anion (O(2)(−)) when challenged with macrophage-stimulating protein (MSP), the endogenous ligand for RON. 2. This study was aimed to evaluate the role of MSP in alveolar macrophages (AM) isolated from healthy volunteers and patients with interstitial lung diseases (sarcoidosis, idiopathic pulmonary fibrosis), either smokers or non-smokers, by evaluating the respiratory burst, cytokine release and nuclear factor-kappa B (NF-κB) activation. MSP effects were compared with those induced by known AM stimuli, for example, phorbol myristate acetate, N-formyl-methionyl-leucyl-phenylalanine, lipopolysaccharide. 3. MSP evokes O(2)(−) production, cytokine release and NF-κB activation in a concentration-dependent manner. By evaluating the respiratory burst, we demonstrate a significantly increased O(2)(−) production in AM from healthy smokers or smokers with pulmonary fibrosis, as compared to non-smokers, thus suggesting MSP as an enhancer of cigarette smoke toxicity. 4. Besides inducing interleukin-1 beta (IL-1β) and interleukin-10 (IL-10) production, MSP triggers an enhanced tumor necrosis factor-alpha release, especially in healthy and pulmonary fibrosis smokers. On the contrary, MSP-induced IL-10 release is higher in AM from healthy non-smokers. 5. MSP activates the transcription factor NF-κB; this effect is more potent in healthy and fibrosis smokers (2.5-fold increase in p50 subunit translocation). This effect is receptor-mediated, as it is prevented by a monoclonal anti-human MSP antibody. 6. The higher effectiveness of MSP in AM from healthy smokers and patients with pulmonary fibrosis is suggestive of its role in these clinical conditions

Expression of functional NK(1) receptors in human alveolar macrophages: superoxide anion production, cytokine release and involvement of NF-κB pathway

1. Substance P (SP) is deeply involved in lung pathophysiology and plays a key role in the modulation of inflammatory-immune processes. We previously demonstrated that SP activates guinea-pig alveolar macrophages (AMs) and human monocytes, but a careful examination of its effects on human AMs is still scarce. 2. This study was undertaken to establish the role of SP in human AM isolated from healthy smokers and non-smokers, by evaluating the presence of tachykinin NK(1) receptors (NK-1R) and SP's ability to induce superoxide anion (O(2)(−)) production and cytokine release, as well as activation of the nuclear factor-κB (NF-κB) pathway. 3. By Western blot analysis and immunofluorescence, we demonstrate that authentic NK-1R are present on human AMs, a three-fold enhanced expression being observed in healthy smokers. These NK-1R are functional, as SP and NK(1) agonists dose-dependently induce O(2)(−) production and cytokine release. In AMs from healthy smokers, SP evokes an enhanced respiratory burst and a significantly increased release of tumor necrosis factor-α as compared to healthy non-smokers, but has inconsistent effects on IL-10 release. The NK(1) selective antagonist CP 96,345 ((2S,3S)-cis-2-diphenylmethyl-N[(2-methoxyphenyl)-methyl]-1-azabicyclo-octan-3-amine)) competitively antagonized SP-induced effects. 4. SP activates the transcription factor NF-κB, a three-fold increased nuclear translocation being observed in AMs from healthy smokers. This effect is receptor-mediated, as it is reproduced by the NK(1) selective agonist [Sar(9)Met(O(2))(11)]SP and reverted by CP 96,345. 5. These results clearly indicate that human AMs possess functional NK-1R on their surface, which are upregulated in healthy smokers, providing new insights on the mechanisms involved in tobacco smoke toxicity