Absence of T lymphocyte-derived cytokines fails to diminish macrophage 12/15-lipoxygenase expression in vivo.
IL-4 and IL-13 are the only known activators of 15-lipoxygenase (LO) expression in cultured macrophages. To determine whether these lymphocyte-derived cytokines regulate 15-LO expression in vivo, the abundance of the murine homologue (12/15-LO) was assessed in peritoneal macrophages from immune-deficient strains of mice. Macrophages were harvested from recombinase activator gene (RAG)-2-/- mice that do not develop mature lymphocytes and cannot secrete activation-dependent cytokines. Unexpectedly, 12/15-LO protein and activity were significantly increased in peritoneal macrophages from RAG-2-/- mice compared with strain-matched controls. This increase was related to phenotypic differences between cells from RAG-2+/+ and RAG-2-/- mice. After 3 h in culture, RAG-2+/+ macrophages were of two distinct sizes, with only the larger cells immunostaining for 12/15-LO. However, all RAG-2-/- cells were distributed in the large size range, and all were immunoreactive for the enzyme. The activation of 12/15-LO expression appears to be related to prolonged residence within the peritoneum, since there were fewer resident peritoneal macrophages in RAG-2-/- than in RAG-2+/+ mice, and newly recruited macrophages elicited by the administration of Sephacryl to RAG-2-/- mice did not immunostain for 12/15-LO. To determine whether 12/15-LO expression was due to IL-4 or IL-13 from nonlymphoid cells, the abundance of the enzyme was quantified in peritoneal macrophages from STAT6-/-mice that have attenuated responses to both cytokines. STAT6 deficiency did not influence the abundance of the protein in macrophages. Therefore, neither IL-4 nor IL-13 secretion is a requirement for macrophage 15-LO expression in vivo.
Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
S M
SM
Sendobry
J A
JA
Cornicelli
K
K
Welch
M J
MJ
Grusby
A
A
Daugherty
D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000096:biosynthesis* / Q000187:drug effects / Q000378:metabolism; D001093:Arachidonate 15-Lipoxygenase / Q000096:biosynthesis* / Q000187:drug effects / Q000378:metabolism; D002465:Cell Movement / Q000235:genetics / Q000276:immunology; D016207:Cytokines / Q000172:deficiency* / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D017353:Gene Deletion; D016130:Immunophenotyping; D018793:Interleukin-13 / Q000494:pharmacology; D015847:Interleukin-4 / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D051379:Mice; D018345:Mice, Knockout; D050800:STAT6 Transcription Factor; D013045:Species Specificity; D013601:T-Lymphocytes / Q000378:metabolism*; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics
D016207:Cytokines; D004268:DNA-Binding Proteins; D018793:Interleukin-13; C499308:Rag2 protein, mouse; D050800:STAT6 Transcription Factor; C494100:Stat6 protein, mouse; D015534:Trans-Activators; C064655:V(D)J recombination activating protein 2; D015847:Interleukin-4; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase