Synergistic effects of cyclic strain and Th1-like cytokines on tenascin-C production by rheumatic aortic valve interstitial cells

IgG2 rules: N-acetyl-β-D-glucosamine-specific IgG2 and Th17/Th1 cooperation may promote the pathogenesis of acute rheumatic heart disease and be a biomarker of the autoimmune sequelae of Streptococcus pyogenes

Antecedent group A streptococcal pharyngitis is a well-established cause of acute rheumatic fever (ARF) where rheumatic valvular heart disease (RHD) and Sydenham chorea (SC) are major manifestations. In ARF, crossreactive antibodies and T cells respond to streptococcal antigens, group A carbohydrate, N-acetyl-β-D-glucosamine (GlcNAc), and M protein, respectively, and through molecular mimicry target heart and brain tissues. In this translational human study, we further address our hypothesis regarding specific pathogenic humoral and cellular immune mechanisms leading to streptococcal sequelae in a small pilot study. The aims of the study were to (1) better understand specific mechanisms of pathogenesis in ARF, (2) identify a potential early biomarker of ARF, (3) determine immunoglobulin G (IgG) subclasses directed against GlcNAc, the immunodominant epitope of the group A carbohydrate, by reaction of ARF serum IgG with GlcNAc, M protein, and human neuronal cells (SK-N-SH), and (4) determine IgG subclasses deposited on heart tissues from RHD. In 10 pediatric patients with RHD and 6 pediatric patients with SC, the serum IgG2 subclass reacted significantly with GlcNAc, and distinguished ARF from 7 pediatric patients with uncomplicated pharyngitis. Three pediatric patients who demonstrated only polymigrating arthritis, a major manifestation of ARF and part of the Jones criteria for diagnosis, lacked the elevated IgG2 subclass GlcNAc-specific reactivity. In SC, the GlcNAc-specific IgG2 subclass in cerebrospinal fluid (CSF) selectively targeted human neuronal cells as well as GlcNAc in the ELISA. In rheumatic carditis, the IgG2 subclass preferentially and strongly deposited in valve tissues (n = 4) despite elevated concentrations of IgG1 and IgG3 in RHD sera as detected by ELISA to group A streptococcal M protein. Although our human study of ARF includes a very small limited sample set, our novel research findings suggest a strong IgG2 autoantibody response against GlcNAc in RHD and SC, which targeted heart valves and neuronal cells. Cardiac IgG2 deposition was identified with an associated IL-17A/IFN-γ cooperative signature in RHD tissue which displayed both IgG2 deposition and cellular infiltrates demonstrating these cytokines simultaneously. GlcNAc-specific IgG2 may be an important autoantibody in initial stages of the pathogenesis of group A streptococcal sequelae, and future studies will determine if it can serve as a biomarker for risk of RHD and SC or early diagnosis of ARF.

Interference with the expression of S1PR1 or STAT3 attenuates valvular damage due to rheumatic heart disease

Rheumatic heart disease (RHD) affects numerous individuals annually; however, its pathogenesis remains unclear. The sphingosine 1‑phosphate receptor 1 (S1PR1) and signal transducer and activator of transcription 3 (STAT3) have recently been shown to be involved in valvular damage via the promotion of the differentiation of T helper 17 (Th17) cells during the development of RHD‑induced valvular damage. The present study investigated whether altering the expression of S1PR1 or STAT3 attenuates valvular damage due to RHD. Inactivated group A streptococcus (GAS) was used to establish a rat model of RHD. Recombinant adeno‑associated viral vectors carrying an S1PR1 overexpression sequence were used to overexpress S1PR1. STAT3 small interfering RNA (STAT3‑siRNA) was used to inhibit STAT3 expression. Reverse transcription‑quantitative PCR (RT‑qPCR) was performed to detect the mRNA expression of S1PR1, STAT3, collagen type III α1 chain (Col3a1) and fibroblast‑specific protein 1. Western blotting (WB) and immunohistochemistry were used to detect the levels of S1PR1, STAT3, phosphorylated (p‑) STAT3, and retinoic acid‑related orphan receptor γT (RORγt) proteins. Enzyme‑linked immunosorbent assays (ELISAs) and immunohistochemistry were used to detect the levels of interleukin (IL)‑6 and IL‑17. Hematoxylin and eosin (H&E) staining and Sirius Red staining were performed to evaluate the degree of inflammation and fibrosis in the valvular tissues. S1PR1 expression was decreased in the valvular tissues of the rats with RHD. The levels of IL‑6, IL‑17 and p‑STAT3 in the rats with RHD were increased. The degree of valvular inflammation and fibrosis in the rats with RHD was also increased. The overexpression of S1PR1 and the inhibition of STAT3 reduced the total p‑STAT3 level, resulting in decreased levels of IL‑6, IL‑17 and RORγt, and a reduced degree of valvular inflammation and fibrosis. These results suggest that the expression of S1PR1 and STAT3 may be involved in valvular tissue damage due to RHD. Thus, strategies designed to interfere with the expression of S1PR1 or STAT3 may affect the expression of Th17 cell‑related cytokines and may thus attenuate valvular damage due to RHD.

Signalling pathways implicated in the pathogenesis of rheumatic heart disease (Review)

Rheumatic heart disease (RHD) is frequently encountered in underdeveloped areas and primarily affects patients under the age of 40 years old. The pathogenesis of RHD has yet to be fully elucidated and surgical treatment remains the only option, which is expensive and technically demanding for patients in less developed areas. Signalling pathways are crucial for the occurrence and development of several diseases, and researchers worldwide have made progress in elucidating the signalling pathways associated with the pathogenesis of RHD. The aim of the present review was to discuss 6 signalling pathways implicated in the pathogenesis of RHD, summarize the methods and progress of these studies and propose future research directions. Important information on the pathogenesis of RHD according to the current progress of signalling pathway studies was also summarized, in the hope that this review may serve as a reference for future research on the signalling pathways involved in the pathogenesis of RHD.

Rheumatic Heart Disease and Myxomatous Degeneration: Differences and Similarities of Valve Damage Resulting from Autoimmune Reactions and Matrix Disorganization

Autoimmune inflammatory reactions leading to rheumatic fever (RF) and rheumatic heart disease (RHD) result from untreated Streptococcus pyogenes throat infections in individuals who exhibit genetic susceptibility. Immune effector mechanisms have been described that lead to heart tissue damage culminating in mitral and aortic valve dysfunctions. In myxomatous valve degeneration (MXD), the mitral valve is also damaged due to non-inflammatory mechanisms. Both diseases are characterized by structural valve disarray and a previous proteomic analysis of them has disclosed a distinct profile of matrix/structural proteins differentially expressed. Given their relevance in organizing valve tissue, we quantitatively evaluated the expression of vimentin, collagen VI, lumican, and vitronectin as well as performed immunohistochemical analysis of their distribution in valve tissue lesions of patients in both diseases. We identified abundant expression of two isoforms of vimentin (45 kDa, 42 kDa) with reduced expression of the full-size protein (54 kDa) in RHD valves. We also found increased vitronectin expression, reduced collagen VI expression and similar lumican expression between RHD and MXD valves. Immunohistochemical analysis indicated disrupted patterns of these proteins in myxomatous degeneration valves and disorganized distribution in rheumatic heart disease valves that correlated with clinical manifestations such as valve regurgitation or stenosis. Confocal microscopy analysis revealed a diverse pattern of distribution of collagen VI and lumican into RHD and MXD valves. Altogether, these results demonstrated distinct patterns of altered valve expression and tissue distribution/organization of structural/matrix proteins that play important pathophysiological roles in both valve diseases.

Temporal expression of tenascin-C and type I collagen in response to gonadotropins in the immature rat ovary

Ovarian morphogenesis and physiology in mammals take place in the context of hormones, paracrine factors and extracellular matrix molecules. Both fibrillar type I collagen and the multidomain tenascin-C are matrix molecules capable of modulating the behavior of both normal and neoplastic cells in many organs. Therefore, the objective of this qualitative study was to simultaneously examine the distribution of both tenascin-C and type I collagen in ovarian follicles and corpora lutea induced to develop in response to gonadotropin treatments. In preantral follicles both matrix proteins were present in the focimatrix, theca externa and the interstitium. Equine gonadotropin induced the appearance of both proteins in the theca interna. Subsequent to administration with human chorionic gonadotropin, tenascin-C appearance in the thecal capillaries preceded type I collagen expression. Tenascin-C was also observed in the capillaries of functional and regressing corpora lutea, while type I collagen was predominantly present in the interstitium and tunica albuginea. Western blots showed both an increase in and degradation of tenascin-C in the regressing corpora lutea. The ovarian surface epithelium also showed immunoreactivity for both tenascin-C and type I collagen. The study reveals that tenascin-C and type I collagen may participate in the morphogenesis of ovarian follicles, and in the formation and regression of corpora lutea.

Revisiting the matricellular concept

The concept of a matricellular protein was first proposed by Paul Bornstein in the mid-1990s to account for the non-lethal phenotypes of mice with inactivated genes encoding thrombospondin-1, tenascin-C, or SPARC. It was also recognized that these extracellular matrix proteins were primarily counter or de-adhesive. This review reappraises the matricellular concept after nearly two decades of continuous investigation. The expanded matricellular family as well as the diverse and often unexpected functions, cellular location, and interacting partners/receptors of matricellular proteins are considered. Development of therapeutic strategies that target matricellular proteins are discussed in the context of pathology and regenerative medicine.

Polymethoxy flavones do not exert an inducing effect on the biosynthesis and secretion of insulin by pancreatic β-cells

Polymethoxylated flavones (PMFs), which are compounds characteristic of citrus plants, possess a wide range of biological properties, particularly affecting glucose and lipid metabolism. However, the mechanism underlying the antidiabetic activity of PMFs has not been fully elucidated. In this study, we aimed to investigate the potential effect of PMFs on the biosynthesis and secretion of insulin, which are crucial in diabetes. We investigated whether PMFs are able to induce insulin secretion by pancreatic β-cells and observed that different concentrations (12.5, 25, 37.5 and 50 μg/ml) of PMFs exerted no effect on insulin synthesis and secretion in INS-1 cells, regardless of the glucose levels. To the best of our knowledge, this is the first study to demonstrate that the regulation of glucose and lipid metabolism by PMFs is not mediated by directly affecting insulin synthesis or secretion. Therefore, further studies are required to elucidate the role of PMFs in diabetes.

mTOR signal transduction pathways contribute to TN-C FNIII A1 overexpression by mechanical stress in osteosarcoma cells

Osteosarcoma is the most common primary malignant bone tumor with a very poor prognosis. Treating osteosarcoma remains a challenge due to its high transitivity. Tenascin-C, with large molecular weight variants including different combinations of its alternative spliced FNIII repeats, is specifically over expressed in tumor tissues. This study examined the expression of Tenascin-C FNIIIA1 in osteosarcoma tissues, and estimated the effect of mechanical stimulation on A1 expression in MG-63 cells. Through immunohistochemical analysis, we found that the A1 protein was expressed at a higher level in osteosarcoma tissues than in adjacent normal tissues. By cell migration assay, we observed that there was a significant correlation between A1 expression and MG-63 cell migra-tion. The relation is that Tenascin-C FNIIIA1 can promote MG-63 cell migration. According to our further study into the effect of mechanical stimulation on A1 expression in MG-63 cells, the mRNA and protein levels of A1 were significantly up-regulated under mechanical stress with the mTOR molecule proving indispensable. Meanwhile, 4E-BP1 and S6K1 (downstream molecule of mTOR) are necessary for A1 normal expression in MG-63 cells whether or not mechanical stress has been encountered. We found that Tenascin-C FNIIIA1 is over-expressed in osteosar-coma tissues and can promote MG-63 cell migration. Furthermore, mechanical stress can facilitate MG-63 cell migration though facilitating A1 overexpression with the necessary molecules (mTOR, 4E-BP1 and S6K1). In con-clusion, high expression of A1 may promote the meta-stasis of osteosarcoma by facilitating MG-63 cell migration. Tenascin-C FNIIIA1 could be used as an indicator in metastatic osteosarcoma patients.

Serum tenascin-C: a novel biomarker for diagnosis and predicting prognosis of rheumatic carditis?

BACKGROUND

Tenascin-C (TnC) is an extracellular matrix glycoprotein that has a major role in tissue remodeling.

OBJECTIVE

To evaluate the serum TnC level in acute rheumatic fever (ARF) and chronic rheumatic heart disease (CRHD) during childhood.

METHODS

Twenty-five patients with ARF, 25 patients with CRHD and 20 control subjects were included in the study. The TnC levels were analyzed using the enzyme-linked immunosorbent assay method in the ARF group.

RESULTS

The TnC levels were lower in the acute carditis group compared with the control group (p < 0.001). The cut-off level was estimated as 2.08 ng/ml for diagnosing carditis with 93.3% sensitivity and 95% specificity. On second analysis, prominent decrease was detected in valve insufficiency patients with markedly elevated TnC levels. In the CRHD group, TnC level was significantly lower in cases with severe valve insufficiency (p < 0.001).

CONCLUSIONS

Serum TnC level can be used as a new biochemical marker for diagnosis and predicting the prognosis of rheumatic carditis.

An investigation of tenascin-C levels in rheumatic mitral stenosis and their response to percutaneous mitral balloon valvuloplasty

OBJECTIVE

The purpose of this study was to evaluate the tenascin-C levels in severe rheumatic mitral stenosis before and after percutaneous mitral balloon valvuloplasty (PMBV).

SUBJECTS AND METHODS

Forty patients with severe mitral stenosis requiring PMBV and 20 age-matched healthy subjects were included in the study. The mitral valve areas, mitral gradients and systolic pulmonary artery pressure (sPAP) were measured by echocardiography. The sPAP values and mitral gradients were also measured by catheterization before and after PMBV. The blood tenascin-C levels were measured before PMBV and 1 month after the procedure.

RESULTS

The echocardiographic mean mitral gradients had a significant decrease after PMBV (11.7 ± 2.8 vs. 5.6 ± 1.7 mm Hg; p < 0.001) and also those of catheterization (13.9 ± 4.4 vs. 4.0 ± 2.4 mm Hg; p < 0.001). Mitral valve areas increased significantly after PMBV (from 1.1 ± 0.1 to 1.8 ± 0.2 cm(2), p < 0.001). Tenascin-C levels decreased significantly in patients after PMBV (from 15.0 ± 3.8 to 10.9 ± 3.1 ng/ml; p < 0.001). Tenascin-C levels were higher in patients with mitral stenosis before PMBV than in healthy subjects (15.0 ± 3.8 and 9.4 ± 2.9 ng/ml; p < 0.001, respectively). There were no significant differences between patients with mitral stenosis after PMBV and healthy subjects (10.9 ± 3.1 and 9.4 ± 2.9 ng/ml; p = 0.09, respectively). There was a significant positive correlation between tenascin-C levels and sPAP (r = 0.508, p < 0.001). In multivariant analysis, tenascin-C predicted mitral stenosis (p = 0.004, OR: 2.31).

CONCLUSIONS

Tenascin-C was an independent predictor for rheumatic mitral stenosis.

Tenascin-C produced by oxidized LDL-stimulated macrophages increases foam cell formation through Toll-like receptor-4

Atherosclerosis is a chronic inflammatory disease in which both innate and adaptive immunity are involved. Although there have been major advances in the involvement of toll-like receptor 4 (TLR4) and CD36 in the initiation and development of this disease, detailed mechanisms remain unknown. Here, we show that tenascin-C (TN-C) can stimulate foam cell formation and this can be inhibited by a TLR4-blocking antibody or CD36 gene silencing. Our results identify TN-C-TLR4 activation as a common molecular mechanism in oxLDL-stimulated foam cell formation and atherosclerosis. In addition, CD36 is the major scavenger receptor responsible for the TN-C-mediated foam cell formation. Taken together, we have identified that TNC produced by oxLDL-stimulated macrophages increases foam cell formation through TLR4 and scavenger receptor CD36.

Advances in tenascin-C biology

Tenascin-C is an extracellular matrix glycoprotein that is specifically and transiently expressed upon tissue injury. Upon tissue damage, tenascin-C plays a multitude of different roles that mediate both inflammatory and fibrotic processes to enable effective tissue repair. In the last decade, emerging evidence has demonstrated a vital role for tenascin-C in cardiac and arterial injury, tumor angiogenesis and metastasis, as well as in modulating stem cell behavior. Here we highlight the molecular mechanisms by which tenascin-C mediates these effects and discuss the implications of mis-regulated tenascin-C expression in driving disease pathology.

Attenuated expression of tenascin-C in ovalbumin-challenged STAT4-/- mice

Background

Asthma leads to structural changes in the airways, including the modification of extracellular matrix proteins such as tenascin-C. The role of tenascin-C is unclear, but it might act as an early initiator of airway wall remodelling, as its expression is increased in the mouse and human airways during allergic inflammation. In this study, we examined whether Th1 or Th2 cells are important regulators of tenascin-C in experimental allergic asthma utilizing mice with impaired Th1 (STAT4-/-) or Th2 (STAT6-/-) immunity.

Methods

Balb/c wildtype (WT), STAT4-/- and STAT6-/- mice were sensitized with intraperitoneally injected ovalbumin (OVA) followed by OVA or PBS airway challenge. Airway hyperreactivity (AHR) was measured and samples were collected. Real time PCR and immunohistochemistry were used to study cytokines and differences in the expression of tenascin-C. Tenascin-C expression was measured in human fibroblasts after treatment with TNF-α and IFN-γ in vitro.

Results

OVA-challenged WT mice showed allergic inflammation and AHR in the airways along with increased expression of TNF-α, IFN-γ, IL-4 and tenascin-C in the lungs. OVA-challenged STAT4-/- mice exhibited elevated AHR and pulmonary eosinophilia. The mRNA expression of TNF-α and IFN-γ was low, but the expression of IL-4 was significantly elevated in these mice. OVA-challenged STAT6-/- mice had neither AHR nor pulmonary eosinophilia, but had increased expression of mRNA for TNF-α, IFN-γ and IL-4. The expression of tenascin-C in the lungs of OVA-challenged STAT4-/- mice was weaker than in those of OVA-challenged WT and STAT6-/- mice suggesting that TNF-α and IFN-γ may regulate tenascin-C expression in vivo. The stimulation of human fibroblasts with TNF-α and IFN-γ induced the expression of tenascin-C confirming our in vivo findings.

Conclusions

Expression of tenascin-C is significantly attenuated in the airways of STAT4-/- mice, which may be due to the impaired secretion of TNF-α and IFN-γ in these mice.