Involvement of Protein Kinase C-γ in IL-1β-Induced Cyclooxygenase-2 Expression in Human Pulmonary Epithelial Cells
- Chien-Huang Lin1,
- Sheng-Yuan Sheu2,
- Horng-Mo Lee1,
- Yuan-Soon Ho1,
- Wen-Sen Lee2,
- Wun-Chang Ko2 and
- Joen-Rong Sheu2
- 1Graduate Institutes of Biomedical Technology (C.-H.L., H.-M.L., Y.-S.H.) and 2Medical Sciences (S.-Y.S., W.-S.L., W.-C.K., J.-R.S.), Taipei Medical College, Taipei, Taiwan
Abstract
The signaling pathway of protein kinase C (PKC) is known to play a role in mediating the action of various cytokines. Here we examined the signal transduction pathway of PKC activation and the role of PKC isoforms in interleukin-1β (IL-1β)-mediated cyclooxygenase-2 (COX-2) expression in human pulmonary epithelial cell line (A549). The tyrosine kinase inhibitors (genistein and tyrphostin AG126) and phosphatidylcholine-phospholipase C inhibitor (D-609) prevented IL-1β-induced prostaglandin E2 (PGE2) release and COX-2 expression, whereas U-73122 (a phosphatidylinositol-phospholipase C inhibitor) and propranolol (a phosphatidate phosphohydrolase inhibitor) had no effect. The PKC inhibitors (Go 6976 and Ro 31–8220) and NF-κB inhibitor, pyrrolidine dithiocarbamate, also attenuated IL-1β-induced PGE2release and COX-2 expression. Western blot analysis using PKC isoenzyme-specific antibodies indicated that A549 cells expressed PKC-α, -γ, -ι, -λ, -ζ, and -μ. IL-1β caused the translocation of PKC-γ but not other isoforms from cytosol to the membrane fraction. Moreover, the translocation of PKC-γ was inhibited by genistein or D-609, but not by U-73122. IL-1β caused the translocation of p65 NF-κB from cytosol to the nucleus as well as the degradation of IκB-α in cytosol. Furthermore, the translocation of p65 NF-κB was inhibited by genistein, Go 6976, Ro 31–8220, or pyrrolidine dithiocarbamate. These results indicate that in human pulmonary epithelial cells, IL-1β might activate phosphatidylcholine-phospholipase C through an upstream tyrosine phosphorylation to elicit PKC activation, which in turn initiates NF-κB activation, and finally induces COX-2 expression and PGE2 release. Of the PKC isoforms present in A549 cells, only activation of PKC-γ is involved in regulating IL-1β-induced responses.
Footnotes
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Send reprint requests to: Chien-Huang Lin, Ph.D., Institute of Biomedical Technology, Taipei Medical College, 250 Wu-Hsing St., Taipei 110, Taiwan. E-mail: chlin{at}tmc.edu.tw
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This work was supported by the National Science Council of the Republic of China Research Grants NSC87–2314-B-038–052 and NSC88–2314-B-038–131.
- Abbreviations:
- COX
- cyclooxygenase
- IL-1β
- interleukin-1β
- PGE2
- prostaglandin E2
- PC-PLC
- phosphatidylcholine-phospholipase C
- PI-PLC
- phosphatidylinositol-phospholipase C
- DAG
- diacylglycerol
- PKC
- protein kinase C
- PDTC
- pyrrolidine dithiocarbamate
- DMEM
- Dulbecco's modified Eagle's medium
- FCS
- fetal calf serum
- DTT
- dithiothreitol
- PMSF
- phenylmethylsulfonyl fluoride
- NP-40
- Nonident P-40
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- Received May 24, 1999.
- Accepted October 10, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
