Tenascin-C deficiency in apo E-/- mouse increases eotaxin levels: implications for atherosclerosis

Bioactive TNIIIA2 Sequence in Tenascin-C Is Responsible for Macrophage Foam Cell Transformation; Potential of FNIII14 Peptide Derived from Fibronectin in Suppression of Atherosclerotic Plaque Formation

One of the extracellular matrix proteins, tenascin-C (TN-C), is known to be upregulated in age-related inflammatory diseases such as cancer and cardiovascular diseases. Expression of this molecule is frequently detected, especially in the macrophage-rich areas of atherosclerotic lesions; however, the role of TN-C in mechanisms underlying the progression of atherosclerosis remains obscure. Previously, we found a hidden bioactive sequence termed TNIIIA2 in the TN-C molecule and reported that the exposure of this sequence would be carried out through limited digestion of TN-C by inflammatory proteases. Thus, we hypothesized that some pro-atherosclerotic phenotypes might be elicited from macrophages when they were stimulated by TNIIIA2. In this study, TNIIIA2 showed the ability to accelerate intracellular lipid accumulation in macrophages. In this experimental condition, an elevation of phagocytic activity was observed, accompanied by a decrease in the expression of transporters responsible for lipid efflux. All these observations were mediated through the induction of excessive β1-integrin activation, which is a characteristic property of the TNIIIA2 sequence. Finally, we demonstrated that the injection of a drug that targets TNIIIA2's bioactivity could rescue mice from atherosclerotic plaque expansion. From these observations, it was shown that TN-C works as a pro-atherosclerotic molecule through an internal TNIIIA2 sequence. The possible advantages of clinical strategies targeting TNIIIA2 are also indicated.

The role of TNC in atherosclerosis and drug development opportunities

Tenascin C (TNC), a rich glycoprotein of the extracellular matrix, exhibits a pro-atherosclerosis or anti-atherosclerosis effect depending on its location. TNC, especially its C domain/isoform (TNC-C), is strongly overexpressed in atherosclerotic plaque active areas but virtually undetectable in most normal adult tissues, suggesting that TNC is a promising delivery vector target for atherosclerosis-targeted drugs. Many delivery vectors were investigated by recognizing TNC-C, including G11, G11-iRGD, TN11, PL1, and PL3. F16 and FNLM were also investigated by recognizing TNC-A1 and TNC, respectively. Notably, iRGD was undergoing clinical trials. PL1 not only recognizes TNC-C but also the extra domain-B (EDB) of fibronectin (FN), which is also a promising delivery vector for atherosclerosis-targeted drugs, and several conjugate agents are undergoing clinical trials. The F16-conjugate agent F16IL2 is undergoing clinical trials. Therefore, G11-iRGD, PL1, and F16 have great development value. Furthermore, ATN-RNA and IMA950 were investigated in clinical trials as therapeutic drugs and vaccines by targeting TNC, respectively. Therefore, targeting TNC could greatly improve the success rate of atherosclerosis-targeted drugs and/or specific drug development. This review discussed the role of TNC in atherosclerosis, atherosclerosis-targeted drug delivery vectors, and agent development to provide knowledge for drug development targeting TNC.

Matricellular proteins in atherosclerosis development

The extracellular matrix (ECM) is an intricate network composed of various multi-domain macromolecules like collagen, proteoglycans, and fibronectin, etc., that form a structurally stable composite, contributing to the mechanical properties of tissue. However, matricellular proteins are non-structural, secretory extracellular matrix proteins, which modulate various cellular functions via interacting with cell surface receptors, proteases, hormones, and cell-matrix. They play essential roles in maintaining tissue homeostasis by regulating cell differentiation, proliferation, adhesion, migration, and several signal transduction pathways. Matricellular proteins display a broad functionality regulated by their multiple structural domains and their ability to interact with different extracellular substrates and/or cell surface receptors. The expression of these proteins is low in adults, however, gets upregulated following injuries, inflammation, and during tumor growth. The marked elevation in the expression of these proteins during atherosclerosis suggests a positive association between their expression and atherosclerotic lesion formation. The role of matricellular proteins in atherosclerosis development has remained an area of research interest in the last two decades and studies revealed these proteins as important players in governing vascular function, remodeling, and plaque formation. Despite extensive research, many aspects of the matrix protein biology in atherosclerosis are still unknown and future studies are required to investigate whether targeting pathways stimulated by these proteins represent viable therapeutic approaches for patients with atherosclerotic vascular diseases. This review summarizes the characteristics of distinct matricellular proteins, discusses the available literature on the involvement of matrix proteins in the pathogenesis of atherosclerosis and suggests new avenues for future research.

The Roles of Tenascins in Cardiovascular, Inflammatory, and Heritable Connective Tissue Diseases

Tenascins are a family of multifunctional extracellular matrix (ECM) glycoproteins with time- and tissue specific expression patterns during development, tissue homeostasis, and diseases. There are four family members (tenascin-C, -R, -X, -W) in vertebrates. Among them, tenascin-X (TNX) and tenascin-C (TNC) play important roles in human pathologies. TNX is expressed widely in loose connective tissues. TNX contributes to the stability and maintenance of the collagen network, and its absence causes classical-like Ehlers-Danlos syndrome (clEDS), a heritable connective tissue disorder. In contrast, TNC is specifically and transiently expressed upon pathological conditions such as inflammation, fibrosis, and cancer. There is growing evidence that TNC is involved in inflammatory processes with proinflammatory or anti-inflammatory activity in a context-dependent manner. In this review, we summarize the roles of these two tenascins, TNX and TNC, in cardiovascular and inflammatory diseases and in clEDS, and we discuss the functional consequences of the expression of these tenascins for tissue homeostasis.

Expression of Nik-related kinase in smooth muscle cells attenuates vascular inflammation and intimal hyperplasia

Inflammation of the vascular microenvironment modulates distinct types of vascular cells, and plays important roles in promoting atherosclerosis, stenosis/restenosis, and vascular-related diseases. Nik-related kinase (Nrk), a member of the Ste20-type kinase family, has been reported to be selectively expressed in embryonic skeletal muscle. However, whether Nrk is expressed in adult vascular smooth muscle, and if it influences intimal hyperplasia is unclear. Here, we found that Nrk is abundantly expressed in cultured vascular smooth muscle cells (VSMC) and mouse arterial intima. Treatment of mouse VSMCs with lipopolysaccharide (LPS) or platelet-derived growth factor significantly reduced Nrk expression. In addition, expression of Nrk was significantly reduced in regions of neointimal formation caused by guide-wire carotid artery injuries in mice, as well as in human atherosclerotic tissues, when compared to normal vessels. We identified that expression of matrix metalloproteinases (MMP3, MMP8 and MMP12) and inflammatory cytokines/chemokines (CCL6, CCL8, CCL11, CXCL1, CXCL3, CXCL5 and CXCL9) are synergistically induced by Nrk siRNA in LPS-treated mouse VSMCs. Moreover, we found that resveratrol significantly impaired LPS- and Nrk siRNA-induced expression of MMP3, CCL8, CCL11, CXCL3 and CXCL5. These results suggested that Nrk may play important roles in regulating pathological progression of atherosclerosis or neointimal- hyperplasia-related vascular diseases.

Multiple Roles of Tenascins in Homeostasis and Pathophysiology of Aorta

Tenascins are a family of large extracellular matrix (ECM) glycoproteins. Four family members (tenascin-C, -R, -X, and -W) have been identified to date. Each member consists of the same types of structural domains and exhibits time- and tissue-specific expression patterns, suggesting their specific roles in embryonic development and tissue remodeling. Among them, the significant involvement of tenascin-C (TNC) and tenascin-X (TNX) in the progression of vascular diseases has been examined in detail. TNC is strongly up-regulated under pathological conditions, induced by a number of inflammatory mediators and mechanical stress. TNC has diverse functions, particularly in the regulation of inflammatory responses. Recent studies suggest that TNC is involved in the pathophysiology of aneurysmal and dissecting lesions, in part by protecting the vascular wall from destructive mechanical stress. TNX is strongly expressed in vascular walls, and its distribution is often reciprocal to that of TNC. TNX is involved in the stability and maintenance of the collagen network and elastin fibers. A deficiency in TNX results in a form of Ehlers–Danlos syndrome (EDS). Although their exact roles in vascular diseases have not yet been elucidated, TNC and TNX are now being recognized as promising biomarkers for diagnosis and risk stratification of vascular diseases.

Investigating cell-type specific functions of tenascin-C

The extracellular matrix molecule tenascin-C (TNC) has received a lot of attention since its discovery 30 years ago because of its multiple roles in tissue repair, and in pathologies such as chronic inflammation, fibrosis, and cancer. Mouse models with high or no TNC expression have enabled the validation of key roles for TNC in immunity and angiogenesis. In parallel, many approaches including primary cell or organ cultures have shed light on the cellular and molecular mechanisms by which TNC exerts its multiple actions in vivo. Here, we will describe assays that investigate its antiadhesive properties and that measure the effect of TNC on the actin cytoskeleton, cell survival, proliferation, and migration. We will also describe assays to assess the impact of TNC on endothelial and immune cells in cell and organ culture, and to compare the responses of fibroblasts from normal and diseased tissues.

Tenascin-c renders a proangiogenic phenotype in macrophage via annexin II

Tenascin-c is an extracellular matrix glycoprotein, the expression of which relates to the progression of atherosclerosis, myocardial infarction and heart failure. Annexin II acts as a cell surface receptor of tenascin-c. This study aimed to delineate the role of tenascin-c and annexin II in macrophages presented in atherosclerotic plaque. Animal models with atherosclerotic lesions were established using ApoE-KO mice fed with high-cholesterol diet. The expression of tenascin-c and annexin II in atherosclerotic lesions was determined by qRT-PCR, Western blot and immunohistochemistry analysis. Raw 264.7 macrophages and human primary macrophages were exposed to 5, 10 and 15 μg/ml tenascin-c for 12 hrs. Cell migration as well as the proangiogenic ability of macrophages was examined. Additionally, annexin II expression was delineated in raw 264.7 macrophages under normal condition (20% O₂ ) for 12 hrs or hypoxic condition (1% O₂ ) for 6-12 hrs. The expression of tenascin-c and annexin II was markedly augmented in lesion aorta. Tenascin-c positively regulated macrophage migration, which was dependent on the expression of annexin II in macrophages. VEGF release from macrophages and endothelial tube induction by macrophage were boosted by tenascin-c and attenuated by annexin II blocking. Furthermore, tenascin-c activated Akt/NF-κB and ERK signalling through annexin II. Lastly, hypoxia conditioning remarkably facilitates annexin II expression in macrophages through hypoxia-inducible factor (HIF)-1α but not HIF-2α. In conclusion, tenascin-c promoted macrophage migration and VEGF expression through annexin II, the expression of which was modulated by HIF-1α.

Oxidized LDL activated eosinophil polarize macrophage phenotype from M2 to M1 through activation of CD36 scavenger receptor

BACKGROUND AND AIMS

Inflammation, particularly innate immunity, plays an important role in cardiovascular diseases. The aim of this study was to investigate whether atherogenic determinants such as oxidized LDL modulate the phenotype of eosinophils.

METHODS

Cultured eosinophils were treated with oxidized LDL and the expression of selective inflammatory and anti-inflammatory cytokines was determined. In addition, the eosinophil receptor and signaling that mediate these events were identified.

RESULTS

Treatment of cultured eosinophils with oxidized LDL (Ox-LDL) specifically induced the expression of IFNα and IFNβ without affecting expression of other proinflammatory cytokines, such as TNFα, IL-1β, and IL-6. In macrophages, Ox-LDL downregulated expression of both IFNα and IFNβ, suggesting that the effect of Ox-LDL on the expression of type I interferons is specific to eosinophils. Furthermore, we noted that eosinophils constitutively expressed IL-4 and IL-13, and Ox-LDL markedly downregulated their expression. Analysis of Ox-LDL signaling revealed that eosinophils constitutively expressed SRB2, CD36, and CD68 scavenger receptors, and Ox-LDL markedly induced the expression of CD36. Further analysis of CD36 signaling by siRNA and neutralizing antibodies showed that the induction of type I IFN by Ox-LDL is mediated by CD36 signaling whereas downregulation of IL-4 is independent of CD36 activation. We further showed that peritoneal macrophages treated with condition medium collected from Ox-LDL treated eosinophils markedly induced the expression of M1 markers such as iNOS, IL6, SOSC3 and TNFα whereas the condition medium from non-treated eosinophils significantly induced expression of M2 markers like ARG1 and CCL24.

CONCLUSIONS

Our data suggest that an atherogenic condition could activate eosinophils and modulate the phenotype of macrophages (from M2 to M1 phenotype), in part, through the CD36 receptor signaling.

Tenascin-C in development and disease of blood vessels

Tenascin-C (TNC) is an extracellular glycoprotein categorized as a matricellular protein. It is highly expressed during embryonic development, wound healing, inflammation, and cancer invasion, and has a wide range of effects on cell response in tissue morphogenesis and remodeling including the cardiovascular system. In the heart, TNC is sparsely detected in normal adults but transiently expressed at restricted sites during embryonic development and in response to injury, playing an important role in myocardial remodeling. Although TNC in the vascular system appears more complex than in the heart, the expression of TNC in normal adult blood vessels is generally low. During embryonic development, vascular smooth muscle cells highly express TNC on maturation of the vascular wall, which is controlled in a way that depends on the embryonic site of cell origin. Strong expression of TNC is also linked with several pathological conditions such as cerebral vasospasm, intimal hyperplasia, pulmonary artery hypertension, and aortic aneurysm/ dissection. TNC synthesized by smooth muscle cells in response to developmental and environmental cues regulates cell responses such as proliferation, migration, differentiation, and survival in an autocrine/paracrine fashion and in a context-dependent manner. Thus, TNC can be a key molecule in controlling cellular activity in adaptation during normal vascular development as well as tissue remodeling in pathological conditions.

Diagnostic potential of differentially expressed Homer1, IL-1β, and TNF-α in coronary artery disease

Increasing evidences suggest that inflammation plays an important role in the pathogenesis of coronary artery disease (CAD). Numerous inflammatory cytokines and related genes mediate adverse cardiovascular events in patients with CAD, such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and Homer in the present study. The study was carried out on 163 CAD patients at different stages and 68 controls. The gene expression of Homer1, Homer2, Homer3, IL-1β, and TNF-α in the peripheral blood leukocytes were measured by real-time polymerase chain reaction. The mRNA levels of Homer1, IL-1β, and TNF-α in CAD patients were significantly higher than those in the control group, but not Homer2 and Homer3. However, there was no considerable difference in the mRNA levels of Homer1, IL-1β, and TNF-α among AMI, UAP, and SAP three subgroups of CAD. The receiver operating characteristic (ROC) curves showed that Homer1 had a better diagnostic value for UAP patients compared with IL-1β and TNF-α. Like IL-1β and TNF-α, Homer1 may also be an important participant of atherosclerotic plaque development and eventually rupture. The results of the present study may provide an important basis for diagnosing CAD patients, and provide new therapeutic targets for CAD.

Carotid intima-media thickness is predicted by combined eotaxin levels and severity of hepatic steatosis at ultrasonography in obese patients with Nonalcoholic Fatty Liver Disease

BACKGROUND

Non-Alcoholic Fatty Liver Disease (NAFLD) is a distinct coronary artery disease (CAD) risk factor. The atherosclerotic process predisposing to CAD includes altered lipid profile and inflammatory processes. The available evidence suggests that increased circulating levels of eotaxin, an eosinophil chemoattractant cytokine implicated in allergic responses, are detected in the serum of patients with CAD. Relationships were sought between serum eotaxin on the one hand, and intima-media thickness--an early predictor of the atherosclerotic process, hepatic steatosis, arterial blood pressure values, as well as inflammation/immune markers and angiogenetic factors--on the other.

METHODS

Eighty obese patients with NAFLD, diagnosed at ultrasonography, without evident cytolysis, formed our study population. Anthropometric measures, metabolic profile, serum concentrations of interleukin-1β, C-reactive protein, interleukin-6, fibrinogen, ferritin, TNF-α, spleen size, vascular endothelial growth factor, platelet-derived growth factor-BB and heat shock protein-70 were evaluated.

RESULTS

Serum eotaxin concentrations were distinctly associated with TNF α, IL-6, IL-1β, VEGF and PDGF-BB levels but not with CRP, fibrinogen, heat shock protein-70 or spleen size. Among the metabolic and anthropometric parameters, a significant predictive power emerged when comparing eotaxin to insulin resistance, expressed as HOMA. NAFLD was distinctly associated with HOMA (P = 0.0005). Intima-media thickness was well predicted by both eotaxin levels and severity of NAFLD at ultrasonography, although no relation was detected between these last two variables.

DISCUSSION AND CONCLUSION

A role for insulin resistance in mediating the interplay between eotaxin and other inflammation/immune parameters could be evidenced in the induction/maintenance of atherosclerosis of obese patients with NAFLD.