Inhibition of the arachidonic acid pathway prevents induction of IL-8 mRNA by phorbol ester and changes the release of IL-8 from HL 60 cells: Differential inhibition of induced expression of IL-8, TNF-α, IL-1α, and IL-1β
✍ Scribed by R. W. Meier; G. Niklaus; B. Dewald; M. F. Fey; A. Tobler
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 1004 KB
- Volume
- 165
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
The promyelocytic HL 60 cell line can be used as an in vitro model system to study hematopoetic cell differentiation and inflammatory events. We studied the signal transduction pathway of induced interleukin (IL)-8 expression and compared it with those of tumor necrosis factor alpha (TNF-a), IL-l a, and IL-1 j3. The differentiation of HL 60 cells to macrophage-like cells by PMA resulted in a rapid and marked induction of these inflammatory cytokines. The up-regulation occurred in the absence of ongoing protein synthesis, but cycloheximide-sensitive gene products modulated their induction kinetics. Staurosporine, a potent inhibitor of protein kinases, strongly inhibited their gene expression. Phosphorylation may not act directly on latent transcription factors, since bromophenacyl bromide, an inhibitor for the release of arachidonic acid from phorbol-12 myristate 13acetate (PMA)-stimulated HL 60 cells, markedly depressed the induced mRNAs for IL-8, TNF-a, and IL-la and -j3. Similarly, 5,8,11,14 eicosatetraynoic acid (ETYA), another inhibitor of the arachidonic acid pathway, blocked the induction of transcripts for TNF-a, and both IL-1 genes in phorbol ester-stimulated HL 60 cells. In contrast, ETYA increased the induced IL-8 RNA levels and stimulated the release for IL-8. Also, ketoconazole, an inhibitor of 5-lipoxygenase and indomethacin, an inhibitor of cyclooxygenases did not block the induction of IL-8 mRNA. However, the release of IL-8 protein was regulated by indomethacin and ketoconazole. Our results indicate that arachidonic acid metabolites are mediators in the signal transduction pathway of IL-8 expression and that the involved second messengers are different from those which are important for the induction of TNF-a and IL-1 j3 expression. o 199s wilcy-Liss, Inc.
Tumor-promoting phorbol diesters such as phorbol 12-myristate 13-acetate (PMA) induce HL 60 cells t o differentiate along the monocytic pathway (Rovera et al., 1979;Huberman and Callahan, 1979). They induce changes in the cellular phenotype l i k e growth inhibition, increased cell adherence, and cause positive staining for alpha-naphthyl-acetate esterase (Rovera e t al., 1979;Huberman and Callahan, 1979;Lotem and Sachs, 1979). During this cell differentiation process modulation o f gene expression has been described, for example the regulation of myeloperoxidase (MPO) a t the transcriptional level (Tobler et al., 1988; Meier e t al., 1991, 1992) and of c-fms at t h e post-transcriptional level (Sariban et al., 1985). Furthermore, protein phosphorylation on serinelthreonine (Feuerstein and Cooper, 1983; Kreutter et al., 1985) and tyrosine residues 8 1995 WILEY-LISS, INC. (Evans et al., 1990; Katagiri et al., 1991), induction of protein tyrosine phosphatases (Taetle e t al., 1991), and up-regulation o f cytokine expression (Horiguchi et al., 1989) were demonstrated.
PMA activates the calcium-and phospholipid-dependent protein kinase C (Castagna et al., 1982). Activa-