Modified Natural Porcine Surfactant Inhibits Superoxide Anions and Proinflammatory Mediators Released by Resting and Stimulated Human Monocytes

Abstract

Pulmonary surfactant has a potential role in modulating inflammation in normal and injured lungs. In lung injury, monocytes become activated and participate in lung inflammation. We therefore, investigated the proinflammatory functions of stimulated human blood monocytes after an overnight preincubation period with modified natural porcine surfactant (Curosurf) (500-1000 micrograms/mL). Monocytes were stimulated either with phorbol myristate acetate (PMA), bacterial extract OM-85, lipopolysaccharide (LPS), or Ca2+ ionophore A23187. The present study shows that Curosurf significantly inhibits: 1) the production of superoxide anions stimulated with OM-85 (1 mg/mL, 30 min), but not with PMA (100 ng/mL, 30 min); 2) the release of cyclooxygenase metabolites prostaglandin E2 and thromboxane B2 stimulated with OM-85 (1 mg/mL, overnight); 3) the release of lipoxygenase metabolite leukotriene C4 stimulated with A23187 (10 microM, 10 min); 4) the release of the cytokine TNF-alpha stimulated overnight with either OM-85 (1 mg/mL) or LPS (10 micrograms/mL)) in a dose-dependent fashion. In addition, Curosurf decreases the spontaneous adherence of monocytes to plastic culture wells in a dose-dependent fashion. Experiments performed with staurosporine, an inhibitor of protein kinase C (PKC) indicate that, in contrast with PMA, the production of superoxide anions stimulated by OM-85 is not related to PKC activation. Consequently, we propose that the mechanism involved in the suppressive effects of Curosurf is PKC-independent. In summary, the present study provides experimental evidence that favors the anti-inflammatory role of modified natural porcine surfactant (Curosurf) in human monocytes in vitro.

Surfactant lipids regulate LPS-induced interleukin-8 production in A549 lung epithelial cells by inhibiting translocation of TLR4 into lipid raft domains

“…Second, they suggest that these surfactant phospholipid components act by disrupting the translocation of TLRs into membrane lipid raft microdomains. Moreover, these results support the idea that under normal conditions, pulmonary surfactant, and particularly the lipid components, plays an immunoregulatory role, preventing excessive infl ammatory responses in the delicate gas-exchanging regions of the lung (32)(33)(34)(35)(36)46 ).…”

“…Although the major physiologic function of pulmonary surfactant is to confer mechanical stability to the alveoli and the small airways (22)(23)(24), there is growing evidence that pulmonary surfactant also has a potential role in modulating infl ammation in normal and injured lungs (25)(26)(27)(28)(29)(30). Our previous work ( 31,32 ) and that of others (33)(34)(35)(36) have shown that surfactant lipids modulate the release of oxidative and infl ammatory mediators from infl ammatory cells. However, the potential role of surfactant in modulating infl ammatory responses from lung epithelial cells, which synthesize and secrete surfactant components, and the mechanisms by which surfactant lipids affect the immune response are poorly understood.…”

Molecular composition of the alveolar lining fluid in the aging lung

“…The rest of the lipids are charged phospholipids, cholesterol, acylglycerols, and free fatty acids (Veldhuizen et al 1998). Surfactant lipids modulate the release of oxidative and inflammatory mediators from inflammatory cells (Hayakawa et al 1992;Tonks et al 2001;Walti et al 1997), and alterations in their composition lead to lung surfactant dysfunction (Reid et al 2005) including a decrease in SP-A function (Yu and Possmayer 1996). Alterations in surfactant phospholipid profiles have been directly related to cases of chronic obstructive pulmonary disease (COPD) (Lusuardi et al 1992), a disease prevalent in older people (Taffet et al 2014).…”

Surfactant Modulates Intracellular Signaling of the Adhesion Receptor L-Selectin

“…Inhibition of LPS-induced release of tumor necrosis factor-␣, the anti-inflammatory IL-1 receptor antagonist, and other proinflammatory cytokines (such as IL-1, IL-6, and IL-8) in monocytes by different surfactant preparations underscores the immunomodulatory role of surfactant (20,21,23,38). Production of superoxide anions and release of prostaglandin E 2 and thromboxane B 2 in monocytes by a bacterial extract were significantly inhibited by Curosurf (22). The molecular mechanisms in the surfactant-induced inhibition of bactericidal functions of monocytes comprise intracellular signaling pathways involving protein kinases (39).…”

“…For studying the influence of surfactant on L-selectin-induced signaling events, Curosurf (500 g/mL) or Exosurf (1 g/mL), reflecting the amount of dipalmitoyl phosphatidylcholine in the preparation, were added in all experiments to the cells 30 min before cell stimulation. These concentrations were in the same range of the concentration of synthetic surfactant (20,21) or natural porcine surfactant (22,23), respectively, used previously in experiments studying the modulating effects of surfactant on immune function, e.g. cytokine synthesis, synthesis of superoxide anions, and activation of transcription factors.…”