A classical perspective of cardiovascular risk does not adequately account for all of the cardiovascular events associated with obesity and diabetes. The combination of hypertriglyceridemia, glucose intolerance and inflammation is linked with increased production of the primary inhibitor of endogenous thrombolysis, plasminogen activator inhibitor-1 (PAI-1). Recent data suggest that PAI-1 contributes directly to the complications of obesity, including type 2 diabetes, coronary arterial thrombi, and may even influence the accumulation of visceral fat. Therefore, direct inhibition of PAI-1 might not only provide a new therapeutic strategy for reducing cardiovascular risk, but may also have beneficial effects on obesity and insulin resistance.
"Through inhibition of uPA/tPA, PAI-1 inhibits the plasminogen-to-plasmin conversion and plasmin-dependent matrix metalloproteinase (MMP) activation. Non-physiologic levels (both decreased and increased) of this secreted serine protease inhibitor are associated with a wide variety of human diseases such as obesity, insulin resistance, diabetes, cardiovascular diseases, abnormal bleeding, emphysema, thrombosis, atherosclerosis, cancer, impairment of wound healing and multi-organ fibrosis , , . Numerous studies demonstrated that in injury-induced fibrotic tissues, the level of PAI-1 is significantly elevated and plays an important role in fibrogenesis via suppression of the proteolytic degradation of extracellular matrix proteins . "
[Show abstract][Hide abstract] ABSTRACT: Fibrosis is defined as an abnormal matrix remodeling due to excessive synthesis and accumulation of extracellular matrix proteins in tissues during wound healing or in response to chemical, mechanical and immunological stresses. At present, there is no effective therapy for organ fibrosis. Previous studies demonstrated that aged plasminogen activator inhibitor-1(PAI-1) knockout mice develop spontaneously cardiac-selective fibrosis without affecting any other organs. We hypothesized that differential expressions of profibrotic and antifibrotic genes in PAI-1 knockout hearts and unaffected organs lead to cardiac selective fibrosis. In order to address this prediction, we have used a genome-wide gene expression profiling of transcripts derived from aged PAI-1 knockout hearts and kidneys. The variations of global gene expression profiling were compared within four groups: wildtype heart vs. knockout heart; wildtype kidney vs. knockout kidney; knockout heart vs. knockout kidney and wildtype heart vs. wildtype kidney. Analysis of illumina-based microarray data revealed that several genes involved in different biological processes such as immune system processing, response to stress, cytokine signaling, cell proliferation, adhesion, migration, matrix organization and transcriptional regulation were affected in hearts and kidneys by the absence of PAI-1, a potent inhibitor of urokinase and tissue-type plasminogen activator. Importantly, the expressions of a number of genes, involved in profibrotic pathways including Ankrd1, Pi16, Egr1, Scx, Timp1, Timp2, Klf6, Loxl1 and Klotho, were deregulated in PAI-1 knockout hearts compared to wildtype hearts and PAI-1 knockout kidneys. While the levels of Ankrd1, Pi16 and Timp1 proteins were elevated during EndMT, the level of Timp4 protein was decreased. To our knowledge, this is the first comprehensive report on the influence of PAI-1 on global gene expression profiling in the heart and kidney and its implication in fibrogenesis and several other biological processes. The significance of these observations in the light of heart-specific profibrotic signaling and fibrogenesis are discussed.
PLoS ONE 05/2013; 8(5):e63825. DOI:10.1371/journal.pone.0063825 · 3.23 Impact Factor
"PAI-1 promoted microglial migration via the LRP1/JAK/STAT1 axis, and inhibited microglial phagocytosis of zymosan particles. Extensive studies have been conducted for PAI-1 in cardiovascular diseases, obesity, and diabetes [103-107], but little is known about its role in inflammatory diseases of the brain. Our results suggest PAI-1 as a potential therapeutic target to control microglial migration and phagocytosis under pathological conditions in the CNS. "
[Show abstract][Hide abstract] ABSTRACT: Plasminogen activator inhibitor type 1 (PAI-1) is the primary inhibitor of urokinase type plasminogen activators (uPA) and tissue type plasminogen activators (tPA), which mediate fibrinolysis. PAI-1 is also involved in the innate immunity by regulating cell migration and phagocytosis. However, little is known about the role of PAI-1 in the central nervous system.
In this study, we identified PAI-1 in the culture medium of mouse mixed glial cells by liquid chromatography and tandem mass spectrometry. Secretion of PAI-1 from glial cultures was detected by ELISA and western blotting analysis. Cell migration was evaluated by in vitro scratch-wound healing assay or Boyden chamber assay and an in vivo stab wound injury model. Phagocytic activity was measured by uptake of zymosan particles.
The levels of PAI-1 mRNA and protein expression were increased by lipopolysaccharide and interferon-γ stimulation in both microglia and astrocytes. PAI-1 promoted the migration of microglial cells in culture via the low-density lipoprotein receptor-related protein (LRP) 1/Janus kinase (JAK)/signal transducer and activator of transcription (STAT)1 axis. PAI-1 also increased microglial migration in vivo when injected into mouse brain. PAI-1-mediated microglial migration was independent of protease inhibition, because an R346A mutant of PAI-1 with impaired PA inhibitory activity also promoted microglial migration. Moreover, PAI-1 was able to modulate microglial phagocytic activity. PAI-1 inhibited microglial engulfment of zymosan particles in a vitronectin- and Toll-like receptor 2/6-dependent manner.
Our results indicate that glia-derived PAI-1 may regulate microglial migration and phagocytosis in an autocrine or paracrine manner. This may have important implications in the regulation of brain microglial activities in health and disease.
Journal of Neuroinflammation 06/2012; 9(1):149. DOI:10.1186/1742-2094-9-149 · 5.41 Impact Factor
"Among the endothelium-dependent vasodilators studied in rats, bradykinin is a particularly potent releaser of t-PA, suggesting an important role for bradykinin in the initiation of fibrinolysis (Smith et al. 1985). The physiological inhibitor of t-PA, the serine protease inhibitor plasminogen activator inhibitor-1, is also synthesized in endothelial cells as well as liver and adipose tissue (van Mourik et al. 1984; De Taeye et al. 2005). "
[Show abstract][Hide abstract] ABSTRACT: The endothelium, although only a single layer of cells lining the vascular and lymphatic systems, contributes in multiple ways to vascular homeostasis. Subsequent to the 1980 report by Robert Furchgott and John Zawadzki, there has been a phenomenal increase in our knowledge concerning the signalling molecules and pathways that regulate endothelial - vascular smooth muscle communication. It is now recognised that the endothelium is not only an important source of nitric oxide (NO), but also numerous other signalling molecules, including the putative endothelium-derived hyperpolarizing factor (EDHF), prostacyclin (PGI(2)), and hydrogen peroxide (H(2)O(2)), which have both vasodilator and vasoconstrictor properties. In addition, the endothelium, either via transferred chemical mediators, such as NO and PGI(2), and (or) low-resistance electrical coupling through myoendothelial gap junctions, modulates flow-mediated vasodilatation as well as influencing mitogenic activity, platelet aggregation, and neutrophil adhesion. Disruption of endothelial function is an early indicator of the development of vascular disease, and thus an important area for further research and identification of potentially new therapeutic targets. This review focuses on the signalling pathways that regulate endothelial - vascular smooth muscle communication and the mechanisms that initiate endothelial dysfunction, particularly with respect to diabetic vascular disease.
Canadian Journal of Physiology and Pharmacology 05/2012; 90(6):713-38. DOI:10.1139/y2012-073 · 1.77 Impact Factor
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