Studies on the interaction of IL-8 with human plasma alpha 2-macroglobulin: evidence for the presence of IL-8 complexed to alpha 2-macroglobulin in lung fluids of patients with adult respiratory distress syndrome.
alpha 2-Macroglobulin (alpha 2m) is a major plasma proteinase inhibitor, as well as a carrier and regulator of the function of many cytokines. IL-8 is a potent neutrophil attractant and activator, and it plays an important role in the pathogenesis of adult respiratory distress syndrome (ARDS). The concentration of both IL-8 and alpha 2m is increased in lung fluids from patients with ARDS. Therefore, interaction of IL-8 with human alpha 2m was studied. Mixtures of native and methylamine-treated alpha 2m (fast alpha 2m) with 125I-labeled IL-8 were analyzed using nonreducing gel electrophoresis. 125I-labeled IL-8 exclusively bound to fast alpha 2m, and the binding could be inhibited by unlabeled IL-8. Analysis of the IL-8-alpha 2m interaction using SDS-PAGE gels indicated that the binding was mainly noncovalent. The affinity of the binding of alpha 2m to IL-8 was measured using an equilibrium dialysis technique, and Kd was 30 nM. Bioassays revealed that fast alpha 2m did not affect IL-8-induced neutrophil degranulation or chemotaxis. However, it protected IL-8 from proteolytic degradation. In addition, IL-8 complexed to alpha 2m was detected in lung fluids from patients with ARDS. alpha 2m may therefore modulate IL-8 function in the lung.
Kurdowska
A
A
Department of Biochemistry, University of Texas Health Center, Tyler 75710, USA.
Carr
F K
FK
Stevens
M D
MD
Baughman
R P
RP
Martin
T R
TR
D015703:Antigens, CD / Q000032:analysis; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology*; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D004347:Drug Interactions; D010450:Endopeptidases; D006801:Humans; D006868:Hydrolysis; D016209:Interleukin-8 / Q000378:metabolism*; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D017551:Microdialysis; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D011971:Receptors, Immunologic / Q000032:analysis; D018123:Receptors, Interleukin / Q000032:analysis; D023062:Receptors, Interleukin-8A; D012128:Respiratory Distress Syndrome / Q000097:blood* / Q000276:immunology* / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000378:metabolism*
D015703:Antigens, CD; D016209:Interleukin-8; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D018123:Receptors, Interleukin; D023062:Receptors, Interleukin-8A; D000511:alpha-Macroglobulins; D009240:N-Formylmethionine Leucyl-Phenylalanine; D010450:Endopeptidases