Accumulation of inhibitory kappaB-alpha as a mechanism contributing to the anti-inflammatory effects of surfactant protein-A.
The collectin surfactant protein (SP)-A has been implicated in multiple immunoregulatory functions of innate pulmonary host defense via modulating immune responses both in vitro and in vivo. The aim of the present study was to investigate mechanisms responsible for the anti-inflammatory effects of human (hu) SP-A on the inhibitory kappaB (IkappaB)/nuclear factor (NF)-kappaB signaling pathway in alveolar macrophages (AMs). Initial CD25 expression analysis by flow cytometry of CD14/hu Toll-like receptor 4-transfected Chinese hamster ovary reporter cells demonstrated that SP-A alone does not induce any NF-kappaB-dependent CD25 expression in these cells. In AMs, SP-A pretreatment caused a marked inhibition of lipopolysaccharide (LPS)-induced NF-kappaB activation independent of the LPS chemotype used as determined by electrophoretic mobility shift assay. Western blot analysis revealed that SP-A by itself increased the protein expression of IkappaB-alpha, the predominant regulator for rapidly induced NF-kappaB, in a dose- and time-dependent manner without enhancing IkappaB-alpha messenger RNA as determined by reverse transcription-polymerase chain reaction. SP-A did not interfere with LPS-induced serine(32) phosphorylation of IkappaB-alpha but significantly enhanced IkappaB-alpha abundance under LPS-coupled conditions. The data suggest that anti-inflammatory effects of SP-A on LPS-challenged AMs are associated with a SP-A-mediated direct modulation of the IkappaB-alpha turnover in these cells.
Wu
Yingda
Y
Department of Immunochemistry and Biochemical Microbiology, Research Center Borstel, Parkallee 22, 23845 Borstel, Germany.
Adam
Stefanie
S
Hamann
Lutz
L
Heine
Holger
H
Ulmer
Artur J
AJ
Buwitt-Beckmann
Ute
U
Stamme
Cordula
C
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism*; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D037662:Pulmonary Surfactant-Associated Protein A / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000378:metabolism; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
D000893:Anti-Inflammatory Agents; D020672:I-kappa B Proteins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606206:Nfkbia protein, rat; D037662:Pulmonary Surfactant-Associated Protein A; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D000072000:NF-KappaB Inhibitor alpha; D010768:Phosphoserine