title: Preadipocyte apoptosis is prevented by macrophage-conditioned medium in a PDGF-dependent manner.
abstract: Obesity is associated with macrophage accumulation and inflammation in adipose tissue. Macrophage-secreted factors have been reported to inhibit the differentiation of preadipocytes into adipocytes and to modulate adipogenic extracellular matrix gene expression. To enlarge our understanding of macrophages and the scope of their interactions with preadipocytes, we investigated their effect on preadipocyte survival. Acute exposure of 3T3-L1 preadipocytes to J774A.1 macrophage-conditioned medium (MacCM) stimulated platelet-derived growth factor receptor (PDGFR) tyrosine phosphorylation by 4.1-fold. There were significant increases in the phosphocontent of downstream PDGFR targets Akt and ERK1/2 (5.3-fold and 2.4-fold, respectively) that were inhibited by PDGF immunoneutralization or by the selective PDGFR inhibitor imatinib. Serum-free J774A.1-MacCM or RAW264.7-MacCM completely prevented 3T3-L1 preadipocyte apoptosis normally induced by serum deprivation. Addition of PDGF alone to serum-free control medium was sufficient to prevent 3T3-L1 preadipocyte apoptosis. Inhibition of PDGFR activation by MacCM, either by addition of imatinib or by PDGF immunodepletion of MacCM, effectively disrupted the prosurvival effect. In summary, our data indicate that MacCM promotes preadipocyte survival in a PDGF-dependent manner.
authors.affiliation: Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: André Sd
authors.initials: AS
authors.lastname: Molgat
authors.forename: Annemarie
authors.initials: A
authors.lastname: Gagnon
authors.forename: Alexander
authors.initials: A
authors.lastname: Sorisky
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides; D002470:Cell Survival; D017077:Culture Media, Conditioned / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D019899:Paracrine Communication; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D017479:Receptors, Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D013552:Swine; D013997:Time Factors
chemical_list: D001549:Benzamides; D017077:Culture Media, Conditioned; D010879:Piperazines; D010982:Platelet-Derived Growth Factor; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D017479:Receptors, Platelet-Derived Growth Factor; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3