title: The protein phosphatase inhibitor calyculin A stimulates chemokine production by human synovial cells.
abstract: Cultured human synovial fibroblasts express mRNA for the chemotactic cytokines (chemokines) interleukin-8 (IL-8), monocyte chemotactic protein 1 (MCP-1) and regulated upon activation normal T-cell expressed and presumably secreted (RANTES), when stimulated with IL-1 or tumour necrosis factor alpha (TNF alpha). Calyculin A, a potent type 1/2A protein serine/threonine phosphatase inhibitor, was used to examine the role of protein phosphatases in the regulation of chemokine gene expression. Calyculin A (1 nM) mimicked IL-1 by inducing IL-8 and MCP-1 mRNA expression in synovial cells. IL-8 mRNA was induced over a similar time period (1-6 h) in response to IL-1 or calyculin A, whereas MCP-1 mRNA was induced more rapidly (1-2 h) by calyculin A than by IL-1 (4-6 h). Expression of RANTES mRNA occurred in response to TNF alpha, but could not be induced by stimulation with calyculin A alone. These results suggest that inhibition of protein phosphatase type 1/2A may have a differential role in the regulation of the expression of each of the chemokine genes. Synovial fibroblasts also secreted IL-8 and IL-6 peptide when stimulated with either IL-1/TNF alpha or calyculin A. The amount of IL-8 and IL-6 peptide produced in response to calyculin A was significantly increased above that produced by untreated synovial cells, though it was much less than the amount induced by IL-1 or TNF alpha. Calyculin A also acted synergistically with IL-1 or TNF alpha to cause a 2-fold potentiation of IL-1- or TNF alpha-induced IL-8 mRNA and peptide and RANTES mRNA expression. These results suggest that although inhibition of a protein phosphatase may be able to regulate the magnitude of IL-1-induced chemokine gene expression, the IL-1 signal transduction pathway involves components in addition to phosphatase inhibition, possibly including the activation of a protein kinase, the action of which may be opposed by a protein phosphatase inhibited by calyculin A.
authors.affiliation: Department of Pharmacology, University of Bath, Claverton Down, U.K.
authors.forename: N J
authors.initials: NJ
authors.lastname: Jordan
authors.forename: M L
authors.initials: ML
authors.lastname: Watson
authors.forename: J
authors.initials: J
authors.lastname: Westwick
mesh_terms: D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics; D018946:Chemokine CCL5 / Q000096:biosynthesis; D016207:Cytokines / Q000096:biosynthesis*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004988:Ethers, Cyclic / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6 / Q000096:biosynthesis; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics; D008387:Marine Toxins; D019319:Okadaic Acid; D010080:Oxazoles / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D012333:RNA, Messenger / Q000378:metabolism; D013583:Synovial Membrane / Q000166:cytology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D018932:Chemokine CCL2; D018946:Chemokine CCL5; D016207:Cytokines; D004791:Enzyme Inhibitors; D004988:Ethers, Cyclic; D007375:Interleukin-1; D015850:Interleukin-6; D016209:Interleukin-8; D008387:Marine Toxins; D010080:Oxazoles; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D019319:Okadaic Acid; C059041:calyculin A; D010749:Phosphoprotein Phosphatases