Trained immunity: A link between risk factors and cardiovascular disease.

Cardiovascular diseases are significant contributors to human mortality, closely associated with inflammation. With the changing living conditions and the extension of human lifespan, greater attention has been directed towards understanding the impact of early, long-term events on the development of cardiovascular events. Lifestyle factors such as stress, unhealthy diet and physical inactivity can increase the risk of cardiovascular diseases. Interestingly, even if the risk factors are addressed later, their influence may persist. Recently, the concept of trained innate immunity (TRIM), defined as sustained alterations in the function of innate immunocyte that promote a more robust response to downstream stimuli, has been proposed to be involved in cardiovascular diseases. It is hypothesized that TRIM may serve as a mediator bridging the impacts of aforementioned risk factors. This review aims to elucidate the role of TRIM in cardiovascular diseases and highlight its significance in uncovering new mechanisms and therapeutic targets.

Defective VWF secretion due to expression of MYH9-RD E1841K mutant in endothelial cells disrupts hemostasis.

Mutations in MYH9, the gene encoding the heavy chain of nonmuscle myosin IIa (NMII-A), cause MYH9-related disease (MYH9-RD), which is an autosomal-dominant thrombocytopenia with bleeding tendency. Previously, we showed that NMII-A in endothelial cells (ECs) is critical for hemostasis via regulating von Willebrand factor (VWF) release from Weibel-Palade bodies (WPBs). The aim of this study was to determine the role of the expression of MYH9 mutants in ECs in the pathogenesis of the MYH9-RD bleeding symptom. First, we expressed the 5 most common NMII-A mutants in ECs and found that E1841K mutant-expressing ECs secreted less VWF than the controls in response to a cyclic adenosine monophosphate (cAMP) signaling agonist. Then, we generated 2 knockin mouse lines, 1 with Myh9 E1841K in ECs and the other in megakaryocytes. Endothelium-specific E1841K mice exhibited impaired cAMP-induced VWF release and a prolonged bleeding time with normal platelets, whereas megakaryocyte-specific E1841K mice exhibited macrothrombocytopenia and a prolonged bleeding time with normal VWF release. Finally, we presented mechanistic findings that E1841K mutation not only interferes with S1943 phosphorylation and impairs the peripheral distribution of Rab27a-positive WPBs in Ecs under quiescent condition but also interferes with S1916 phosphorylation by disrupting the interaction with zyxin and CKIIα and reduces actin framework formation around WPBs and subsequent VWF secretion under the stimulation by a cAMP agonist. Altogether, our results suggest that impaired cAMP-induced endothelial VWF secretion by E1841K mutant expression may contribute to the MYH9-RD bleeding phenotype.

Zyxin Mediates Vascular Repair via Endothelial Migration Promoted by Forskolin in Mice.

Background and Purpose: Endothelial repair upon vascular injury is critical for the protection of vessel integrity and prevention of the development of vascular disorders, but the underlying mechanisms remain poorly understood. In this study, we investigated the role of zyxin and its associated cyclic adenosine monophosphate (cAMP) signaling in the regulation of re-endothelialization after vascular injury. Experimental Approach: In zyxin-/- and wild-type mice, wire injury of the carotid artery was carried out, followed by Evans blue staining, to evaluate the re-endothelialization. Mice with endothelium-specific zyxin knockout were used to further determine its role. An in vitro wound-healing assay was performed in primary human endothelial cells (ECs) expressing zyxin-specific short-hairpin RNAs (shRNAs) or scrambled controls by measuring cell migration and proliferation. The effects of the cAMP signaling agonist forskolin were assessed. Key Results: The re-endothelialization of the injured carotid artery was impaired in zyxin-deficient mice, whereas the rate of cell proliferation was comparable with that in wild-type controls. Furthermore, endothelium-specific deletion of zyxin led to similar phenotypes. Knockdown of zyxin by shRNAs in primary human ECs significantly reduced cell migration in the wound-healing assay. Notably, forskolin enhanced endothelial migration in a dose-dependent manner, and this was dependent on zyxin through its interaction with vasodilator-stimulated phosphoprotein. In addition, forskolin promoted the re-endothelialization of the injured carotid artery, and this was compromised by zyxin deficiency. Conclusion and Implications: This study reveals zyxin as a new player in endothelial repair, which is promoted by forskolin, after vascular injury. Thus, zyxin-mediated signaling might be a potential treatment target for diseases involving vascular injury.

Zyxin regulates endothelial von Willebrand factor secretion by reorganizing actin filaments around exocytic granules.

Endothelial exocytosis of Weibel-Palade body (WPB) is one of the first lines of defence against vascular injury. However, the mechanisms that control WPB exocytosis in the final stages (including the docking, priming and fusion of granules) are poorly understood. Here we show that the focal adhesion protein zyxin is crucial in this process. Zyxin downregulation inhibits the secretion of von Willebrand factor (VWF), the most abundant cargo in WPBs, from human primary endothelial cells (ECs) induced by cAMP agonists. Zyxin-deficient mice exhibit impaired epinephrine-stimulated VWF release, prolonged bleeding time and thrombosis, largely due to defective endothelial secretion of VWF. Using live-cell super-resolution microscopy, we visualize previously unappreciated reorganization of pre-existing actin filaments around WPBs before fusion, dependent on zyxin and an interaction with the actin crosslinker α-actinin. Our findings identify zyxin as a physiological regulator of endothelial exocytosis through reorganizing local actin network in the final stage of exocytosis.