Interacting hepatic PAI-1/tPA gene regulatory pathways influence impaired fibrinolysis severity in obesity
Ze Zheng, … , José A. López, Ira Tabas
Ze Zheng, … , José A. López, Ira Tabas
Published July 13, 2020
Citation Information: J Clin Invest. 2020;130(8):4348-4359. https://doi.org/10.1172/JCI135919.
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Interacting hepatic PAI-1/tPA gene regulatory pathways influence impaired fibrinolysis severity in obesity

Abstract

Fibrinolysis is initiated by tissue-type plasminogen activator (tPA) and inhibited by plasminogen activator inhibitor 1 (PAI-1). In obese humans, plasma PAI-1 and tPA proteins are increased, but PAI-1 dominates, leading to reduced fibrinolysis and thrombosis. To understand tPA–PAI-1 regulation in obesity, we focused on hepatocytes, a functionally important source of tPA and PAI-1 that sense obesity-induced metabolic stress. We showed that obese mice, like humans, had reduced fibrinolysis and increased plasma PAI-1 and tPA, due largely to their increased hepatocyte expression. A decrease in the PAI-1 (SERPINE1) gene corepressor Rev-Erbα increased PAI-1, which then increased the tPA gene PLAT via a PAI-1/LRP1/PKA/p-CREB1 pathway. This pathway was partially counterbalanced by increased DACH1, a PLAT-negative regulator. We focused on the PAI-1/PLAT pathway, which mitigates the reduction in fibrinolysis in obesity. Thus, silencing hepatocyte PAI-1, CREB1, or tPA in obese mice lowered plasma tPA and further impaired fibrinolysis. The PAI-1/PLAT pathway was present in primary human hepatocytes, and associations among PAI-1, tPA, and PLAT in livers from obese and lean humans were consistent with these findings. Knowledge of PAI-1 and tPA regulation in hepatocytes in obesity may suggest therapeutic strategies for improving fibrinolysis and lowering the risk of thrombosis in this setting.

Authors

Ze Zheng, Keiko Nakamura, Shana Gershbaum, Xiaobo Wang, Sherry Thomas, Marc Bessler, Beth Schrope, Abraham Krikhely, Rui-Ming Liu, Lale Ozcan, José A. López, Ira Tabas

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Figure 7

PAI-1 induces hepatic tPA expression through an LRP1/p-CREB1/PKA pathway.

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PAI-1 induces hepatic tPA expression through an LRP1/p-CREB1/PKA pathway...
(A) Human primary hepatocytes transfected with si-LRP1 or scrambled control were treated for 8 hours with 1 μg rPAI-1/mL culture medium and then assayed for phosphorylated and total CREB1 and LRP1 and PLAT mRNA. (B) Human primary hepatocytes treated for 8 hours with 1 μg/mL WT rPAI-1 (WT) or a mutant rPAI-1 (Mut) with enzymatic activity, but lacking the LRP1-interacting heparin-binding domain, were assayed for p-CREB1 and total CREB1 and PLAT mRNA. For A and B, results are represented as mean ± SEM. n = 3 sets of cells/group. *P < 0.05; **P < 0.01, 1-way ANOVA followed by Tukey’s test. (C) Lean mice were injected intravenously with 100 μg WT or mutant rPAI-1 or vehicle control. After 90 minutes, livers were assayed for p-CREB1 and total CREB1 and Plat mRNA. n = 5 mice/group. *P < 0.05, 1-way ANOVA followed by Tukey’s test. (D) Human primary hepatocytes were treated for 4 hours with 10 μM of PKA inhibitor H89 and then treated 4 hours with 1 μg rPAI-1/mL. Cells were then assayed for p-CREB1 and total CREB1 and PLAT mRNA. n = 3 sets of cells/group. *P < 0.05, 1-way ANOVA followed by Tukey’s test. (E) Summary schematic. Red font and arrows depict pathways that contribute to impaired fibrinolysis in obesity, and pathway in green depicts the compensatory PAI/tPA pathway. The 2 pathways that contribute to impaired fibrinolysis are increased SERPINE1 due to decreased Rev-Erbα and partial suppression of PLAT due to increased DACH1, which represses the PLAT inducer ATF6. The compensatory pathway is mediated by an increase in the PLAT inducer p-CREB1 downstream of a PAI-1/LRP1/PKA signaling cascade. See text for details.