Tumor Necrosis Factor α Activates the Human Plasminogen Activator Inhibitor-1 Gene through a Distal Nuclear Factor κB Site

Abstract

Plasminogen activator inhibitor-1 (PAI-1) is the major inhibitor of plasminogen activation and likely plays important roles in coronary thrombosis and arteriosclerosis. Tumor necrosis factor-␣ (TNF␣) is one of many recognized physiological regulators of PAI-1 expression and may contribute to elevated plasma PAI-1 levels in sepsis and obesity. Although TNF␣ is a potent inducer of PAI-1 expression in vitro and in vivo, the precise location of the TNF␣ response site in the PAI-1 promoter has yet to be determined. Transient transfection studies using luciferase reporter constructs containing PAI-1 promoter sequence up to 6.4 kb failed to detect a response to TNF␣. Moreover, TNF␣ failed to induce expression of enhanced green fluorescent protein under the control of a 2.9-kb human PAI-1 promoter in transgenic mice, although endogenous murine PAI-1 was strongly induced. These data suggested that the TNF␣ response element in the PAI-1 gene is remote from the proximal promoter region. In this study, seven candidate regulatory regions were identified using cross-species sequence homology analysis as well as DNase I-hypersensitive site analysis. We identified a 5 distal TNF␣-responsive enhancer of the PAI-1 gene located 15 kb upstream of the transcription start site containing a conserved NFBbinding site that mediates the response to TNF␣. This newly recognized site is fully capable of binding NFB subunits p50 and p65, whereas overexpression of the NFB inhibitor IB prevents TNF␣-induced activation of this enhancer element.Plasminogen activator inhibitor 1 (PAI-1), 1 a member of the serine protease inhibitor (serpin) family, was isolated 20 years ago and was identified as the primary inhibitor of fibrinolysis by rapidly binding and inactivating both tissue-type plasminogen activator (PA) and urokinase-type PA (1, 2). Subsequently, it has been shown that PAI-1 is involved in many other physiological functions, including ovulation, embryogenesis, angiogenesis, metastasis, and arteriosclerosis through its interactions with PAs, the urokinase-type PA receptor, and vitronectin (3-8).Under normal conditions, PAI-1 is present in plasma at low concentrations. High levels of PAI-1 are observed in a variety of clinical settings, including type 2 diabetes mellitus (9), obesity (3, 10), cancer (4, 11), and infection (12)(13)(14). In addition, increased PAI-1 levels are associated with an increased risk of type 2 diabetes (15), myocardial infarction (16), and stroke (17). In severe sepsis, increased plasma PAI-1 levels are associated with poor prognosis (18) and appear to predict the development of septic shock in meningococcemia (19).Active PAI-1 is conformationally unstable and has a short half-life in circulation (20). Furthermore, except in platelets, which contain large quantity of predominately latent PAI-1, there is no storage pool of PAI-1 in cells (21). As a result, transcriptional control of PAI-1 is a pivotal mechanism in determining tissue and plasma PAI-1 content. Accordingly, the molecular regulation of PAI-1 expression ha...

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“…Hence, TNFα is a strong against for PAI-1 regulation, contributing to various diseases. Likewise, similar to our results Hou et al [43] and Plomgaard et al [44] reported that TNFα but not cytokine IL-6 regulates PAI-1 expression in the sub-cutaneous adipose tissue. This confirms the key role of TNFα in the observed effects.…”

Ubiquitin-specific Protease 20 Regulates the Reciprocal Functions of β-Arrestin2 in Toll-like Receptor 4-promoted Nuclear Factor κB (NFκB) Activation

“…In response to LPS, bone marrow-derived macrophages from ␤arr2 Ϫ/Ϫ mice show more IKK activity than WT macrophages (6), but they show equivalent LPS-induced secretion of the NFB-dependent gene products TNF and IL-6 (11). Although ␤arr2 appears to reduce secretion of TNF and IL-6 from fibroblast-like synoviocytes (13), it has no effect on the secretion of the NFB-dependent gene products (52)(53)(54) hyaluronan and plasminogen activator inhibitor-1 from lung fibroblasts (15). However, in SMCs, ␤arr2 augments TLR4-dependent IB degradation and inflammation-associated SMC proliferation (Fig.…”

Inflammatory Stress and Idiosyncratic Hepatotoxicity: Hints from Animal Models

“…The transcriptional induction of PAI-1 is mediated through an Sp1 element, hypoxiaresponsive element, and/or Sma-and Mad-related protein 3/4 (SMAD 3/4) binding sites in the PAI-1-promoter (Fink et al, 2002;Hou et al, 2004). Up-regulation of PAI-1 is associated with disseminated intravascular coagulation and other thrombotic diseases (Padró et al, 1995(Padró et al, , 1997.…”