Tenascin-C is increased in atherothrombotic stroke patients and has an anti-inflammatory effect in the human carotid artery

Biology of Tenascin C and its Role in Physiology and Pathology

Tenascin-C (TNC) is a multimodular extracellular matrix (ECM) protein hexameric with several molecular forms (180-250 kDa) produced by alternative splicing at the pre-mRNA level and protein modifications. The molecular phylogeny indicates that the amino acid sequence of TNC is a well-conserved protein among vertebrates. TNC has binding partners, including fibronectin, collagen, fibrillin-2, periostin, proteoglycans, and pathogens. Various transcription factors and intracellular regulators tightly regulate TNC expression. TNC plays an essential role in cell proliferation and migration. Unlike embryonic tissues, TNC protein is distributed over a few tissues in adults. However, higher TNC expression is observed in inflammation, wound healing, cancer, and other pathological conditions. It is widely expressed in a variety of human malignancies and is recognized as a pivotal factor in cancer progression and metastasis. Moreover, TNC increases both pro-and anti-inflammatory signaling pathways. It has been identified as an essential factor in tissue injuries such as damaged skeletal muscle, heart disease, and kidney fibrosis. This multimodular hexameric glycoprotein modulates both innate and adaptive immune responses regulating the expression of numerous cytokines. Moreover, TNC is an important regulatory molecule that affects the onset and progression of neuronal disorders through many signaling pathways. We provide a comprehensive overview of the structural and expression properties of TNC and its potential functions in physiological and pathological conditions.

Tenascin-C induction exacerbates post-stroke brain damage

The role of tenascin-C (TNC) in ischemic stroke pathology is not known despite its prognostic association with cerebrovascular diseases. Here, we investigated the effect of TNC knockdown on post-stroke brain damage and its putative mechanism of action in adult mice of both sexes. Male and female C57BL/6 mice were subjected to transient middle cerebral artery occlusion and injected (i.v.) with either TNC siRNA or a negative (non-targeting) siRNA at 5 min after reperfusion. Motor function (beam walk and rotarod tests) was assessed between days 1 and 14 of reperfusion. Infarct volume (T2-MRI), BBB damage (T1-MRI with contrast), and inflammatory markers were measured at 3 days of reperfusion. The TNC siRNA treated cohort showed significantly curtailed post-stroke TNC protein expression, motor dysfunction, infarction, BBB damage, and inflammation compared to the sex-matched negative siRNA treated cohort. These results demonstrate that the induction of TNC during the acute period after stroke might be a mediator of post-ischemic inflammation and secondary brain damage independent of sex.

Pleiotropic Role of Tenascin-C in Central Nervous System Diseases: From Basic to Clinical Applications

The extracellular matrix is composed of a variety of macromolecular substances secreted by cells, which form a complex network that supports and connects tissue structures, regulates the morphogenesis of tissues, and maintains the physiological activities of cells. Tenascin-C, a secreted extracellular matrix glycoprotein, is abundantly expressed after exposure to pathological stimuli. It plays an important regulatory role in brain tumors, vascular diseases, and neurodegenerative diseases by mediating inflammatory responses, inducing brain damage, and promoting cell proliferation, migration, and angiogenesis through multiple signaling pathways. Therefore, tenascin-C may become a potential therapeutic target for intracranial diseases. Here, we review and discuss the latest literature regarding tenascin-C, and we comprehensively explain the role and clinical significance of tenascin-C in intracranial diseases.

Immunomodulatory role of the extracellular matrix protein tenascin-C in neuroinflammation

The extracellular matrix (ECM) consists of a dynamic network of various macromolecules that are synthesized and released by surrounding cells into the intercellular space. Glycoproteins, proteoglycans and fibrillar proteins are main components of the ECM. In addition to general functions such as structure and stability, the ECM controls several cellular signaling pathways. In this context, ECM molecules have a profound influence on intracellular signaling as receptor-, adhesion- and adaptor-proteins. Due to its various functions, the ECM is essential in the healthy organism, but also under pathological conditions. ECM constituents are part of the glial scar, which is formed in several neurodegenerative diseases that are accompanied by the activation and infiltration of glia as well as immune cells. Remodeling of the ECM modulates the release of pro- and anti-inflammatory cytokines affecting the fate of immune, glial and neuronal cells. Tenascin-C is an ECM glycoprotein that is expressed during embryonic central nervous system (CNS) development. In adults it is present at lower levels but reappears under pathological conditions such as in brain tumors, following injury and in neurodegenerative disorders and is highly associated with glial reactivity as well as scar formation. As a key modulator of the immune response during neurodegeneration in the CNS, tenascin-C is highlighted in this mini-review.

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.

Correlation of tenascin-C concentrations in serum with outcome of traumatic brain injury in humans

BACKGROUND

Tenascin-C, a matricellular protein, is involved in brain injury. However, change of tenascin-C concentrations in peripheral blood remains unknown after traumatic brain injury (TBI).

METHODS

Serum tenascin-C concentrations were measured in 100 healthy controls, 108 severe TBI patients, 79 moderate TBI patients and 32 mild TBI patients.

RESULTS

Serum tenascin-C concentrations of patients were significantly higher than those of controls. Tenascin-C concentrations negatively correlated with Glasgow Coma Scale (GCS) scores in all patients (r=-0.658, P<0.001). In severe TBI patients, tenascin-C in serum significantly discriminated patients at risk of 6-month mortality (area under curve, 0.821; 95% confidence interval, 0.735-0.888) and poor outcome (Glasgow Outcome Scale score of 1-3) (area under curve, 0.833; 95% confidence interval, 0.749-0.898) and emerged as an independent predictor for 6-month mortality (odds ratio, 1.114; 95% confidence interval, 1.008-1.233; P=0.005), overall survival (hazard ratio, 1.085; 95% confidence interval, 1.010-1.166; P=0.003) and unfavorable outcome (odds ratio, 1.049; 95% confidence interval, 1.014-1.076; P=0.001). By receiver-operating characteristic analysis, serum tenascin-C concentrations had similar prognostic value compared with GCS scores.

CONCLUSIONS

Enhanced serum tenascin-C concentrations are closely related to trauma severity and clinical outcomes, substantializing tenascin-C as a potential prognostic biomarker after TBI.

Involvement of Angiotensin II Type 1 and 2 Receptors in Gelatinase Regulation in Human Carotid Atheroma in vitro

AIM

Matrix metalloproteinases (MMPs), angiotensin II (AII) and its receptors are implicated in atherosclerotic plaque instability, however the roles of the two receptor subtypes, ATR1 and ATR2, in MMP regulation remain uncertain. In this study, we investigated the effect of ATR1 and ATR2 blockade on the expression and activity of MMP-2, MMP-3 and MMP-9, in human carotid atheroma.

METHODS

Atheroma samples (n=36) were obtained from patients undergoing carotid endarterectomy. The effects of ATR1 (irbesartan), ATR2 (PD123319) and combined ATR1 and ATR2 blockade on the expression and activity of the MMPs and the expression of tissue inhibitors of metalloproteinases (TIMPs) were investigated in explant culture experiments. Paired atheroma samples were incubated with the intervention or media control for 4 days. Protein levels (MMP-2, MMP-3, MMP-9, TIMP-1, TIMP-2, TIMP-4, ATR1 and ATR2) were determined by ELISA. Overall gelatinase activity and specific activation were measured by chromogenic activity assays and zymography, respectively.

RESULTS

ATR1 blockade, but not ATR2 blockade significantly reduced TIMP-1, TIMP-2 and TIMP-4 expression in atheroma supernatant. Combined ATR1 and ATR2 blockade significantly reduced MMP-2, MMP-3 and MMP-9 expression. MMP-2 and MMP-9 relative activation, and overall MMP-9 catalytic capacity were significantly increased by ATR1 blockade.

CONCLUSIONS

Our findings suggest that ATR1 blockade reduces TIMP expression and increases gelatinase activity in human carotid atheroma.

Altering 5-hydroxymethylcytosine modification impacts ischemic brain injury

Epigenetic modifications such as cytosine methylation and histone modification are linked to the pathology of ischemic brain injury. Recent research has implicated 5-hydroxymethylcytosine (5hmC), a DNA base derived from 5-methylcytosine (5mC) via oxidation by ten-eleven translocation (Tet) enzymes, in DNA methylation-related plasticity. Here we show that 5hmC abundance was increased after ischemic injury, and Tet2 was responsible for this increase; furthermore, inhibiting Tet2 expression abolished the increase of 5hmC caused by ischemic injury. The decrease in 5hmC modifications from inhibiting Tet2 activity was accompanied by increased infarct volume after ischemic injury. Genome-wide profiling of 5hmC revealed differentially hydroxymethylated regions (DhMRs) associated with ischemic injury, and DhMRs were enriched among the genes involved in cell junction, neuronal morphogenesis and neurodevelopment. In particular, we found that 5hmC modifications at the promoter region of brain-derived neurotrophic factor (BDNF) increased, which was accompanied by increased BDNF mRNA, whereas the inhibition of Tet2 reduced BDNF mRNA and protein expression. Finally, we show that the abundance of 5hmC in blood samples from patients with acute ischemic stroke was also significantly increased. Together, these data suggest that 5hmC modification could serve as both a potential biomarker and a therapeutic target for the treatment of ischemic stroke.

ATF3 Inhibits Tenascin-C-induced Foam Cell Formation in LPS-Stimulated THP-1 Macrophages by Suppressing TLR-4

AIM

Efficiently inhibiting the formation of macrophage foam cells is indispensable for mitigating and treating atherosclerosis. Tenascin-C (TN-C) plays an important role in promoting atherosclerosis; therefore, it is essential to inhibit foam cell formation associated with TN-C for controlling atherosclerosis. Activating transcription factor 3 (ATF3) is one of the factors involved in regulating the complex process of foam cell formation. This study aimed to explore the role of TN-C and ATF3 in LPS-stimulated THP-1-derived macrophages.

METHODS

RT-PCR was used for evaluating the expression of TN-C in LPS-stimulated THP-1 macrophages. Further, exogenous TN-C was introduced and incubated with cultured THP-1 macrophages to confirm the effect of TN-C on LPS-stimulated THP-1 macrophages. ATF3-modified THP-1 macrophages were constructed and verified by western blot. High performance liquid chromatography (HPLC) assay and Oil red O staining were applied for detecting cholesteryl ester/total cholesterol (CE/TC) and lipid formation in THP-1 macrophages.

RESULTS

The expression of TN-C was determined to be upregulated in LPS-stimulated THP-1 macrophages in a dose- and time-dependent manner. HPLC assay and Oil red O staining confirmed that TN-C can enhance LPS-induced THP-1 macrophage foam cell formation. Moreover, ATF3 can act as a negative regulatory factor for inhibiting TN-C-induced foam cell formation by suppressing TLR-4 in LPS-stimulated THP-1 macrophages.

CONCLUSION

ATF3 can inhibit TN-C-induced foam cell formation in LPS-stimulated THP-1 macrophages by suppressing TLR-4. It may be a useful molecular target to control TN-C-induced foam cell formation in atherosclerosis.

Taurine, a major amino acid of oyster, enhances linear bone growth in a mouse model of protein malnutrition

Oysters (Oys) contain various beneficial components, such as, antioxidants and amino acids. However, the effects of Oys or taurine (Tau), a major amino acid in Oys on bone growth have not been determined. In the present study, we evaluated the effects of Oys or Tau on linear bone growth in a mouse model of protein malnutrition. To make the protein malnutrition in a mouse, we used a low protein diet. Growth plate thickness was increased by Oys or Tau. Bone volume/tissue volume, trabecular thickness, trabecular number, connection density, and total porosity were also improved by Oys or Tau. Oys or Tau increased insulin-like growth factor-1 (IGF-1) levels in serum, liver, and tibia-growth plate. Phosphorylations of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 5 (STAT5) were increased by Oys and by Tau. These findings show that Oys or Tau may increase growth plate thickness by elevating IGF-1 levels and by promoting the phosphorylations of JAK2-STAT5, and suggest that Oys or Tau are growth-promoting substances of potential use in the food and pharmaceutical industries.