Abstract
Tumor necrosis factor-alpha (TNFalpha) critically regulates several cellular functions during monocyte/macrophage differentiation. We therefore investigated during the phorbol ester (phorbol 12-myristate 13-acetate (PMA))-induced monocyte/macrophage differentiation of the human HL-60 leukemia cells, if TNFalpha contributed to plasminogen activator inhibitor type-1 (PAI-1) synthesis that is initiated by a protein kinase Cbeta-extracellular signal-regulated kinase 2-dependent pathway (Lopez, S., Peiretti, F., Morange, P., Laouar, A., Fossat, C., Bonardo, B., Huberman, E., Juhan-Vague, I., and Nalbone, G. (1999) Thromb. Haemostasis 81, 415-422). Following PMA treatment, the level of TNFalpha mRNA strongly increased and appeared earlier than PAI-1 mRNA. An anti-TNFalpha antibody significantly inhibited the PMA-induced PAI-1 mRNA and protein levels. The recombinant human TNFalpha, which is inactive on native HL-60 cells in terms of PAI-1 synthesis, optimally potentiates it once HL-60 cells are committed into the differentiation process. The use of 1) the HL-525 cell line, a clone issued from HL-60 cells rendered resistant to PMA-induced differentiation, and 2) the transforming growth factorbeta-1/vitamin D3 differentiative mixture confirmed the relationships between the induction of differentiation and the potency of TNFalpha to up-regulate PAI-1 synthesis. In conclusion, we showed that during the induction of monocyte/macrophage differentiation, TNFalpha and PAI-1 gene expressions are activated and that synthesized TNFalpha up-regulates and prolongs, in an autocrine manner, the synthesis of PAI-1.
Highlights
The expression of PAI-1,1 a major inhibitor of fibrinolysis, is enhanced in atherosclerotic plaque [1,2,3,4,5] and co-localizes, in part, with macrophages [2, 4, 6] that are central cell types in atherosclerosis
Its effect on PAI-1 in leukocytes appears linked to their differentiated stage because 1) TNF␣ is inactive on monocytic progenitors [22, 29] and 2) mature macrophages produce more PAI-1 than monocytes isolated from circulation [7, 8]
We show that an excess of anti-TNF␣ dramatically reduced the phorbol 12-myristate 13-acetate (PMA)-induced synthesis of PAI-1, observed at the mRNA level, 4 h after PMA stimulation
Summary
The expression of PAI-1,1 a major inhibitor of fibrinolysis, is enhanced in atherosclerotic plaque [1,2,3,4,5] and co-localizes, in part, with macrophages [2, 4, 6] that are central cell types in atherosclerosis. The Up-regulating Effect of TNF␣ on PAI-1 Synthesis Is Linked to the Induction of Differentiation rhTNF␣ Activates PAI-1 Synthesis in PMA-treated HL-60 Cells—rhTNF␣ did not induce any changes in the accumulation of PAI-1 antigen from native HL-60 cells, which did not exceed 1 ng/106 cells (Fig. 2B) at 24 h. Anti-TNF␣ reduced the level of PAI-1 mRNA in RA ϩ PMA-treated HL-525 cells but, the inhibitory effect could not be firmly detected before 9 h (Fig. 7A).
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