Recent work has revealed an essential involvement of soluble CD40L (sCD40L) in inflammation and vascular disease. Activated platelets are the major source of sCD40L, which has been implicated in platelet and leukocyte activation, although its exact functional impact on leukocyte-platelet interactions and the underlying mechanisms remain undefined. We aimed to determine the impact and the mechanisms of sCD40L on neutrophils. We studied neutrophil interactions with activated, surface-adherent platelets as a model for leukocyte recruitment to the sites of injury. Our data show that CD40L contributes to neutrophil firm adhesion to and transmigration across activated surface-adherent platelets, possibly through two potential mechanisms. One involves the direct interaction of ligand-receptor (CD40L-CD40), i.e., platelet surface CD40L interaction with neutrophil CD40; another involves an indirect mechanism, i.e. soluble CD40L stimulates activation of the leukocyte-specific β2 integrin Mac-1 in neutrophils and thereby further promotes neutrophil adhesion and migration. Activation of the integrin Mac-1 is known to be critical for mediating neutrophil adhesion and migration. sCD40L activated Mac-1 in neutrophils and enhanced neutrophil-platelet interactions in wild-type neutrophils, but failed to elicit such responses in CD40-deficient neutrophils. Furthermore, our data show that the protein kinase C zeta (PKCζ) is critically required for sCD40L-induced Mac-1 activation and neutrophil adhesive function. sCD40L strongly stimulated the focal clustering of Mac-1 (CD11b) and the colocalization of Mac-1 with PKCζ in wild-type neutrophils, but had minimal effect in CD40-deficient neutrophils. Blocking PKCζ completely inhibited sCD40L-induced neutrophil firm adhesion. Moreover, sCD40L strongly stimulates neutrophil oxidative burst via CD40-dependent activation of PI3K/NF-KB, but independent of Mac-1 and PKCζ. These findings may contribute to a better understanding of the underlying mechanisms by which sCD40L/CD40 pathway contributes to inflammation and vascular diseases.
One of the global socioeconomic phenomena occurred during the last decades is the increased prevalence of obesity, with direct consequence on the risk of developing thrombotic disorders. As the physiological inhibitor of tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA), plasminogen activator inhibitor-1 (PAI-1) is well known for its role in fibrinolysis. More and more evidences have shown that PAI-1 involves in physiopathologic mechanisms of many diseases and metabolic disorder. Increased serum level of PAI-1 has been observed in obesity and it also contributes to the development of adipose tissue and then has effects on obesity. Meantime, obesity affects also the PAI-1 levels. These evidences indicate the complicated interaction between PAI-1 and obesity. Many clinic studies have confirmed that obesity relates to the stroke outcome although there are many contradictory results. Simultaneously, correlation is found between plasma PAI-1 and thrombotic cerebrovascular diseases. This article reviews contemporary knowledge regarding the complex interplay of obesity, PAI-1 and stroke.
BackgroundExcessive angiogenesis is a key feature of vulnerable atherosclerotic plaques, and is considered an independent predictor of cardiovascular risk. CD137 signaling has previously been shown to be involved in atherosclerosis. However, the possible role of CD137 signaling in regulating angiogenesis has not been reported.Methods and ResultsApolipoprotein E‐deficient (ApoE−/−) mice were used as the in vivo model of atherosclerosis. Masson and immunohistochemical analysis of atherosclerotic plaques and Matrigel plug assay were used to evaluate the angiogenesis. Human umbilical vein endothelial cells and mouse brain microvascular endothelial cells were used as in vitro and ex vivo models to study how CD137 signaling affects angiogenesis. Matrigel tube formation assay, mouse aortic ring angiogenesis assay, and migration and proliferation assay were employed to assess angiogenesis. Western blot was used to detect protein expression. We found increased neovessel formation in atherosclerotic plaques of ApoE−/− mice treated with agonist anti‐CD137 antibody. Activation of CD137 signaling induced angiogenesis, endothelial proliferation, and endothelial cell migration. CD137 signaling activates the pro‐angiogenic Smad1/5 pathway, induces the phosphorylation of Smad1/5 and nuclear translocation of p‐Smad1/5, which in turn promotes the expression and translocation of NFATc1. Blocking CD137 signaling with inhibitory anti‐CD137 antibody could inhibit this activation and attenuated agonist anti‐CD137 antibody‐induced angiogenesis.ConclusionsThese findings suggest that CD137 signaling is a new regulator of angiogenesis by modulating the Smad1/5‐NFATc1 pathway.
Nuclear factor of activated T cells (NFAT) was first identified as a transcription factor about 3 decades ago and was not well studied until the development of immunosuppressant. Numerous studies confirm that calcineurin/NFAT signaling is very important in the development of vasculature and cardiovascular system during embryogenesis and is involved in the development of vascular diseases such as hypertension, atherosclerosis and restenosis. Recent studies demonstrated that NFAT proteins also regulate immune response and vascular cells in the pulmonary microenvironment. In this review, we will discuss how different NFAT isoforms contribute to pulmonary vascular remodeling and potential new therapeutic targets for treating pulmonary arterial hypertension.
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