Effect of atorvastatin on plasminogen activator inhibitor type-1 synthesis in human monocytes/macrophages.

The fibrinolytic inhibitor plasminogen activator inhibitor type 1 (PAI-1) plays a role in the development of atherothrombosis and is produced by macrophages that infiltrate the atherosclerotic vessel wall. Because statins are effective in reducing atherosclerosis, we investigated if they modulate the synthesis of PAI-1 in human monocytes/macrophages. To this end, we studied the effect of atorvastatin in different models of monocyte/macrophage differentiation, such as differentiated human promyelocytic cell line HL-60 and human peripheral blood monocyte-derived macrophages. HL-60 cells were differentiated along monocyte lineage by phorbol myristate acetate (PMA) or a mixture of transforming growth factor-beta type 1 (TGF-beta1)/1alpha,25-dihydroxyvitamin D3 (D3). In these conditions, PAI-1 synthesis was strongly induced and atorvastatin upregulated this synthesis, especially during TGF-beta1/D3-induced differentiation. Recombinant human tumor necrosis factor-alpha (TNF-alpha) strongly upregulated PAI-1 synthesis in PMA- or TGF-beta1/D3-differentiated cells, and the potentiating effect of atorvastatin was of the same order as in the absence of TNF-alpha. Mevalonate reversed the enhancing effect of atorvastatin. In mature human monocyte-derived macrophages, atorvastatin, alone or in combination with TNF-alpha, TGF-beta1, or PMA, did not exert any significant effect on PAI-1 synthesis. Basal production of urokinase (uPA), which was below detection limits in HL-60 cells and very low in human monocyte-derived macrophages, was not altered by atorvastatin. These results show that atorvastatin upregulates PAI-1 synthesis during the early stages of monocyte/macrophage differentiation, but has no effect on PAI-1 and uPA synthesis in mature human monocyte-derived macrophages. Atorvastatin did not significantly interact with the upregulating action of TNF-alpha on PAI-1 synthesis during differentiation.

Inhibition of p70(S6) kinase during transforming growth factor-beta 1/vitamin D(3)-induced monocyte differentiation of HL-60 cells allows tumor necrosis factor-alpha to stimulate plasminogen activator inhibitor-1 synthesis.

We investigated intracellular mechanisms involved in the up-regulation of plasminogen activator inhibitor I (PAI-1) synthesis by human recombinant tumor necrosis factor-alpha (TNF) during monocyte differentiation of HL-60 cells triggered by the transforming growth factor-beta1/vitamin D(3) (TGF/D3) mixture. TGF/D3-treated cells expressed surface monocytic markers and produced noticeable amounts of PAI-1 but stopped to proliferate. A reduced p70 S6 kinase (p70(S6K)) phosphorylation was also observed and, in this situation, TNF dramatically enhanced PAI-1 synthesis. Similarly, TNF significantly up-regulated PAI-1 synthesis when p70(S6K) phosphorylation was inhibited by rapamycin. This phenomenon was not due to a general decrease in protein synthesis but involved the activation of gene transcription rather than PAI-1 mRNA stabilization. The level of the transcriptional regulator factor E2F1, a repressor of PAI-1 gene expression, was shown to be down-modulated in TGF/D3- as well as in rapamycin-treated cells. Furthermore, the apoptotic effect of TNF in HL-60 cells appeared to be prevented by the addition of either TGF/D3 or rapamycin. In conclusion, these results indicate that inhibition of p70(S6K) phosphorylation during TGF/D3-induced monocyte differentiation of HL-60 cells is a determinant factor that allows TNF to exert its up-regulating effect on PAI-1 synthesis while protecting cells from apoptosis.