Disparate regulation of LPS-induced MAPK signaling and IL-12p40 expression between different myeloid cell types with and without HIV infection.
Studies from our laboratory and those of others have implicated lipopolysaccharide (LPS)-induced MAPK signaling as an important pathway in the regulation of cytokine expression. In this article, the regulation of IL-12 expression in two different human myeloid cell populations was evaluated. In primary monocytes, the inhibition of p38 enhanced IL-12 production, whereas it downregulated IL-12 production in THP-1 cells. The role of MAPK signaling in transcription factor binding to the IL-12p40 promoter was subsequently determined. In primary monocytes, ERK and p38 inhibition increased binding of AP-1 and Sp1, respectively, to the IL-12p40 promoter, while JNK inhibition increased NF-kappaB, AP-1, and Sp1 binding. In THP-1 cells, p38, ERK, and JNK inhibition increased NF-kappaB and Sp1 binding to the IL-12p40 promoter, while inhibiting AP-1 binding. In monocytes, mutations in the NF-kappaB, AP-1, Sp1, or Ets-2 binding sites resulted in complete inhibition of LPS-stimulated IL-12p40 promoter activity using a luciferase-based assay. In contrast, promoter activity was abrogated in THP-1 cells only when the Sp1 or Ets-2 binding sites were mutated. Transcription factor binding to the IL-12p40 promoter following in-vitro HIV infection demonstrated several differences between monocytes and THP-1 cells. Infection with HIV produced an increase in NF-kappaB, AP-1, and Sp1 binding in primary monocytes. In contrast, binding of Ets-2 was dramatically impaired following HIV infection of monocytes, but was unaffected in THP-1 cells. These data clearly show that although LPS induces IL-12p40 expression in primary monocytes and THP-1 cells, the signaling pathways involved and the effect of HIV infection differ and can have disparate effects in these two cell types.
Boucher
Jonathan G
JG
Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.
Parato
Kelley A
KA
Frappier
Fiona
F
Fairman
Peter
P
Busca
Aurelia
A
Saxena
Mansi
M
Blahoianu
Maria A
MA
Ma
Wei
W
Gajanayaka
Niranjala
N
Parks
Robin J
RJ
Kumar
Ashok
A
Angel
Jonathan B
JB
D002460:Cell Line; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D015658:HIV Infections / Q000276:immunology*; D006801:Humans; D053762:Interleukin-12 Subunit p40 / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000276:immunology*; D020935:MAP Kinase Signaling System; D022423:Myeloid Cells / Q000276:immunology*; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D050787:Proto-Oncogene Protein c-ets-2 / Q000378:metabolism; D015398:Signal Transduction; D016329:Sp1 Transcription Factor / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism
D053762:Interleukin-12 Subunit p40; D008070:Lipopolysaccharides; D016328:NF-kappa B; D050787:Proto-Oncogene Protein c-ets-2; D016329:Sp1 Transcription Factor; D018808:Transcription Factor AP-1; D004247:DNA