Activated alveolar macrophages express the insulin-like growth factor-I receptor.
Alveolar macrophages (AM) recovered from the lower respiratory tract of individuals with interstitial lung disease (ILD) proliferate at a 2- to 15-fold increased rate (P.B. Bitterman et al. 1984. J. Clin. Invest. 74:460-469). Normal AM stimulated with immune complexes or asbestos release platelet-derived growth factor and insulin-like growth factor-I (IGF-I), and AM activated in vivo in ILD release these growth factors. We evaluated normal unstimulated and activated AM for the receptor for IGF-I to determine if macrophage IGF-I could be involved in the enhanced macrophage proliferation. Although normal AM did not have specific 125I-labeled recombinant IGF-I binding, AM activated by chrysotile asbestos or lipopolysaccharide in vitro or from individuals with ILD had detectable binding that could be inhibited by an anti-IGF-I receptor monoclonal antibody in a dose-dependent fashion. Autoradiography with 125I-labeled recombinant IGF-I revealed binding to the IGF-I receptor on the surface of activated AM, and the percentage of labeled cells was reduced with anti-IGF-I receptor monoclonal antibody or excess unlabeled recombinant IGF-I. Hybridization of total AM RNA to a 32P-labeled IGF-I receptor riboprobe using solution hybridization demonstrated IGF-I receptor mRNA transcripts in AM from an individual with asbestosis, consistent with active expression of the IGF-I receptor gene. In the context of the known role of IGF-I as a growth factor for many cells, these data are consistent with the concept that IGF-I and its receptor may play an important role in the proliferation of AM in the inflamed lower respiratory tract.
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Department of Medicine, Bellevue Hospital, New York University Medical Center, New York 10016.
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D000328:Adult; D000911:Antibodies, Monoclonal; D001194:Asbestos / Q000494:pharmacology; D017632:Asbestos, Serpentine; D015870:Gene Expression; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D011658:Pulmonary Fibrosis / Q000235:genetics / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017451:Receptors, Somatomedin; D011994:Recombinant Proteins / Q000378:metabolism
D000911:Antibodies, Monoclonal; D017632:Asbestos, Serpentine; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D011994:Recombinant Proteins; D001194:Asbestos; D007334:Insulin-Like Growth Factor I