CD14 major role during lipopolysaccharide-induced inflammation in chick embryo cardiomyocytes

CD14 is a surface differentiation antigen that functions as a receptor for bacterial lipopolysaccharide. The cellular signaling events that lead to lipopolysaccharide-induced production of inflammatory mediators are the primary cause of myocardial dysfunction observed in sepsis. Here, we evaluated the role of CD14 in chick embryo cardiomyocytes stimulated with lipopolysaccharide. CD14 expression was detected by confocal laser microscopy observation and by immunoblotting analysis. Moreover, we provided evidence for CD14-dependent functional responses of lipopolysaccharide-stimulated cardiomyocytes in terms of tumor necrosis factor (TNF)-α and nitric oxide (NO) production. Attenuated TNF-α and NO secretion, following anti-CD14 treatment of cardiomyocytes, suggested a role for this receptor in lipopolysaccharide-mediated cell responses. We also evidenced that labeled lipopolysaccharide was internalized and localized next to the Golgi complex, at the level of lysosomes, and in the perinuclear zone. The intracytoplasmatic transport seems to depend on the contractile apparatus, because cell pretreatment with cytochalasin D prevented lipopolysaccharide internalization and reduced both TNF-α and NO release. Lipopolysaccharide internalization was dependent on CD14 receptor, since anti-CD14 pre-treatment prevented endotoxin uptake by cardiomyocytes. Results demonstrated: (1) CD14 is expressed on the surface membrane of cardiomyocytes; (2) CD14 is involved in cytoskeletal dependent lipopolysaccharide internalization at specific cytoplasmatic locations; (3) CD14 plays a role in lipopolysaccharide-mediated responses by cardiomyocytes after lipopolysaccharide internalization.