title: Surfactant protein A (SP-A)-tacrolimus complexes have a greater anti-inflammatory effect than either SP-A or tacrolimus alone on human macrophage-like U937 cells.
abstract: Intratracheal administration of immunosuppressive agents to the lung is a novel treatment after lung transplantation. Nanoparticles of tacrolimus (FK506) might interact with human SP-A, which is the most abundant lipoprotein in the alveolar fluid. This study was undertaken to determine whether the formation of FK506/SP-A complexes interferes with FK506 immunosuppressive actions on stimulated human macrophage-like U937 cells. We found that SP-A was avidly bound to FK506 (K(d) = 35 ± 4nM), as determined by solid phase-binding assays and dynamic light scattering. Free FK506, at concentrations ≤ 1 μM, had no effect on the inflammatory response of LPS-stimulated U937 macrophages. However, coincubation of FK506 and SP-A, at concentrations where each component alone did not affect LPS-stimulated macrophage response, significantly inhibited LPS-induced NF-κB activation and TNF-alpha secretion. Free FK506, but not FK506/SP-A, functioned as substrate for the efflux transporter P-glycoprotein. FK506 bound to SP-A was delivered to macrophages by endocytosis, since several endocytosis inhibitors blocked FK506/SP-A anti-inflammatory effects. This process depended partly on SP-A binding to its receptor, SP-R210. These results indicate that FK506/SP-A complexes have a greater anti-inflammatory effect than either FK506 or SP-A alone and suggest that SP-A strengthened FK506 anti-inflammatory activity by facilitating FK506 entrance into the cell, overcoming P-glycoprotein.
authors.affiliation: Departamento de Bioquímica & Biología Molecular & CIBER Enfermedades Respiratorias, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Almudena
authors.initials: A
authors.lastname: López-Sánchez
authors.forename: Alejandra
authors.initials: A
authors.lastname: Sáenz
authors.forename: Cristina
authors.initials: C
authors.lastname: Casals
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004705:Endocytosis / Q000187:drug effects; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D011485:Protein Binding; D037662:Pulmonary Surfactant-Associated Protein A / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000378:metabolism; D016559:Tacrolimus / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D020298:U937 Cells
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000894:Anti-Inflammatory Agents, Non-Steroidal; D007166:Immunosuppressive Agents; D008070:Lipopolysaccharides; D037662:Pulmonary Surfactant-Associated Protein A; D011956:Receptors, Cell Surface; C482199:lipopolysaccharide, E coli O55-B5; C067774:surfactant protein A receptor; D016559:Tacrolimus