Soluble biglycan induces the production of ICAM-1 and MCP-1 in human aortic valve interstitial cells through TLR2/4 and the ERK1/2 pathway

Exploring molecular profiles of calcification in aortic vascular smooth muscle cells and aortic valvular interstitial cells

Cardiovascular calcification can occur in vascular and valvular structures and is commonly associated with calcium deposition and tissue mineralization leading to stiffness and dysfunction. Patients with chronic kidney disease and associated hyperphosphatemia have an elevated risk for coronary artery calcification (CAC) and calcific aortic valve disease (CAVD). However, there is mounting evidence to suggest that the susceptibility and pathobiology of calcification in these two cardiovascular structures may be different, yet clinically they are similarly treated. To better understand diversity in molecular and cellular processes that underlie hyperphosphatemia-induced calcification in vascular and valvular structures, we exposed aortic vascular smooth muscle cells (AVSMCs) and aortic valve interstitial cells (AVICs) to high (2.5 mM) phosphate (Ph) conditions in vitro, and examined cell-specific responses. To further identify hyperphosphatemic-specific responses, parallel studies were performed using osteogenic media (OM) as an alternative calcific stimulus. Consistent with clinical observations made by others, we show that AVSMCs are more susceptible to calcification than AVICs. In addition, bulk RNA-sequencing reveals that AVSMCs and AVICs activate robust ossification-programs in response to high phosphate or OM treatments, however, the signaling pathways, cellular processes and osteogenic-associated markers involved are cell- and treatment-specific. For example, compared to VSMCs, VIC-mediated calcification involves biological processes related to osteo-chondro differentiation and down regulation of 'actin cytoskeleton'-related genes, that are not observed in VSMCs. Furthermore, hyperphosphatemic-induced calcification in AVICs and AVSMCs is independent of P13K signaling, which plays a role in OM-treated cells. Together, this study provides a wealth of information suggesting that the pathogenesis of cardiovascular calcifications is significantly more diverse than previously appreciated.

Influence of Aortic Valve Stenosis and Wall Shear Stress on Platelets Function

Aortic valve stenosis (AS) is a common heart valve disease in the elderly population, and its pathogenesis remains an interesting area of research. The degeneration of the aortic valve leaflets gradually progresses to valve sclerosis. The advanced phase is marked by the presence of extracellular fibrosis and calcification. Turbulent, accelerated blood flow generated by the stenotic valve causes excessive damage to the aortic wall. Elevated shear stress due to AS leads to the degradation of high-molecular weight multimers of von Willebrand factor, which may involve bleeding in the mucosal tissues. Conversely, elevated shear stress has been associated with the release of thrombin and the activation of platelets, even in individuals with acquired von Willebrand syndrome. Moreover, turbulent blood flow in the aorta may activate the endothelium and promote platelet adhesion and activation on the aortic valve surface. Platelets release a wide range of mediators, including lysophosphatidic acid, which have pro-osteogenic effects in AS. All of these interactions result in blood coagulation, fibrinolysis, and the hemostatic process. This review summarizes the current knowledge on high shear stress-induced hemostatic disorders, the influence of AS on platelets and antiplatelet therapy.

Recombinant IL-37 Exerts an Anti-inflammatory Effect on Human Aortic Valve Interstitial Cells through Extracellular and Intracellular Actions

Calcific aortic valve disease (CAVD) is a chronic inflammatory disease with slow progression that involves soluble extracellular matrix (ECM) proteins. Previously, we found that recombinant interleukin (IL)-37 suppresses aortic valve interstitial cells (AVIC) inflammatory response through the interaction with IL-18 receptor α-chain (IL-18Rα) on the cell surface. Endogenous IL-37 can be retained in the cytoplasm or released into extracellular spaces. It remains unknown whether recombinant IL-37 exerts the anti-inflammatory effect through intracellular action. Here, we found that recombinant IL-37 suppressed AVIC inflammatory response to soluble ECM proteins. Interestingly, recombinant IL-37 was internalized by human AVICs in an IL-18Rα-independent fashion. Blocking endocytic pathways reduced the internalization and anti-inflammatory potency of recombinant IL-37. Overexpression of IL-37 in human AVICs suppressed soluble ECM proteins-induced NF-κB activation and the production of ICAM-1 and VCAM-1. However, IL-37D20A (mutant IL-37 lacking nucleus-targeting sequences) overexpression had no such effect, and the inflammatory response to soluble ECM proteins was essentially intact in AVICs from transgenic mice expressing IL-37D20A. Together, recombinant IL-37 can be internalized by human AVICs through endocytosis. Intracellular IL-37 exerts an anti-inflammatory effect through a nucleus-targeting mechanism. This study highlights the potent anti-inflammatory effect of recombinant IL-37 in both extracellular and intracellular compartments through distinct mechanisms.

Identification of key genes involved in calcific aortic valve disease based on integrated bioinformatics analysis

The calcific aortic valve disease (CAVD) develops as an aortic valve sclerosis and progresses to an advanced form of stenosis. In many biological fields, bioinformatics becomes a fundamental component. The key mechanisms involved in CAVD are discovered with the use of bioinformatics to investigate gene function and pathways. We downloaded the original data (GSE51472) from the Gene Expression Omnibus (GEO) database (http://www.ncbi.nlm.nih.gov/geo/). After standardization, 2978 differentially expressed genes (DEGs) were identified from the data sets GSE51472 containing samples from normal, calcified, and sclerotic aortic valves. Analysis of DEGs based on the series test of clusters (STCs) revealed the two most significant patterns. Based on the result of the STC, the functional enrichment analysis of gene ontology (GO) was conducted to investigate the molecular function (MF), biological process (BP), and cell compound (CC) of the DEGs. With a p value of 0.01, DEGs associated with "chronic inflammation," "T-cell receptor complexes," and "antigen binding" had the highest significance within BP, CC, and MF. DEG enrichment in signaling pathways was analyzed using KEGG pathway enrichment. Using a p < 0.05 level of significance, the most enriched biological pathways related to CAVD were "Chemokine signaling pathway," "Cytokine-cytokine receptor interaction," "Tuberculosis," "PI3K-Akt signaling pathway," and "Transcriptional misregulation in cancer." Finally, the construction of gene co-expression networks and pathway networks illustrated the pathogensis of CAVD. TLR2, CD86, and TYROBP were identified as hub genes for the development of CAVD. Moreover, "MAPK signaling pathway," "Apoptosis," and "Pathways in cancer" were regarded as the core pathways among the samples of normal, sclerotic and calcified aortic valve samples.

TNF-α Inhibitors in Combination with MTX Reduce Circulating Levels of Heparan Sulfate/Heparin and Endothelial Dysfunction Biomarkers (sVCAM-1, MCP-1, MMP-9 and ADMA) in Women with Rheumatoid Arthritis

Sulfated glycosaminoglycans (sGAGs) are likely to play an important role in the development and progression of rheumatoid arthritis (RA)-associated atherosclerosis. The present study investigated the effect of anti-tumor necrosis factor-α (anti-TNF-α) therapy in combination with methotrexate on plasma sGAG levels and serum markers of endothelial dysfunction. Among sGAG types, plasma chondroitin/dermatan sulfate (CS/DS) and heparan sulfate/heparin (HS/H) were characterized using electrophoretic fractionation. Serum levels of soluble vascular cell adhesion molecule-1 (sVCAM-1), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase-9 (MMP-9) and asymmetric dimethylarginine (ADMA) were measured by immunoassays. The measurements were carried out four times: at baseline and after 3, 9 and 15 months of anti-TNF-α therapy. All analyzed parameters, excluding ADMA, were significantly elevated in patients with RA before the implementation of biological therapy compared to healthy subjects. Performed anti-TNF-α treatment led to a successive decrease in HS/H levels toward normal values, without any effect on CS/DS levels in female RA patients. The treatment was also effective at lowering the serum levels of sVCAM-1, MCP-1, MMP-9 and ADMA. Moreover, a significant positive correlation was found between the circulating HS/H and the 28 joint disease activity score based on the erythrocyte sedimentation rate (DAS28-ESR, r = 0.408; p <0.05), MCP-1 (r = 0.398; p <0.05) and ADMA (r = 0.396; p <0.05) in patients before the first dose of TNF-α inhibitor. In conclusion, a beneficial effect of anti-TNF-α therapy on cell-surface heparan sulfate proteoglycans (HSPGs)/HS turnover and endothelial dysfunction was observed in this study. This was manifested by a decrease in blood HS/H levels and markers of endothelial activation, respectively. Moreover, the decrease in the concentration of HS/H in the blood of patients during treatment, progressing with the decline in disease activity, indicates that the plasma HS/H profile may be useful for monitoring the efficacy of anti-TNF-α treatment in patients with RA.

Proteoglycans in Toll-like receptor responses and innate immunity

The extracellular matrix (ECM) is an active and dynamic feature of tissues that not only provides gross structure but also plays key roles in cellular responses. The ever-changing microenvironment responds dynamically to cellular and external signals, and in turn influences cell fate, tissue development, and response to environmental injury or microbial invasion. It is therefore paramount to understand how the ECM components interact with each other, the environment and cells, and how they mediate their effects. Among the ECM components that have recently garnered increased attention, proteoglycans (PGs) deserve special note. Recent evidence strongly suggests that they play a crucial role both in health maintenance and disease development. In particular, proteoglycans dictate whether homeostasis or cell death will result from a given injury, by triggering and modulating activation of the innate immune system, via a conserved array of receptors that recognize exogenous (infectious) or endogenous (tissue damage) molecular patterns. Innate immune activation by proteoglycans has important implications for the understanding of cell-matrix interactions in health and disease. In this review, we will summarize the current state of knowledge of innate immune signaling by proteoglycans, discuss the implications, and explore future directions to define progress in this area of extracellular matrix biology.

Monocytes augment inflammatory responses in human aortic valve interstitial cells via β2-integrin/ICAM-1-mediated signaling

OBJECTIVE

Inflammatory infiltration in aortic valves promotes calcific aortic valve disease (CAVD) progression. While soluble extracellular matrix (ECM) proteins induce inflammatory responses in aortic valve interstitial cells (AVICs), the impact of monocytes on AVIC inflammatory responses is unknown. We tested the hypothesis that monocytes enhance AVIC inflammatory responses to soluble ECM protein in this study.

METHODS

Human AVICs isolated from normal aortic valves were cocultured with monocytes and stimulated with soluble ECM protein (matrilin-2). ICAM-1 and IL-6 productions were assessed. YAP and NF-κB phosphorylation were analyzed. Recombinant CD18, neutralizing antibodies against β₂-integrin or ICAM-1, and inhibitor of YAP or NF-κB were applied.

RESULTS

AVIC expression of ICAM-1 and IL-6 was markedly enhanced by the presence of monocytes, although matrilin-2 did not affect monocyte production of ICAM-1 or IL-6. Matrilin-2 up-regulated the expression of monocyte β₂-integrin and AVIC ICAM-1, leading to monocyte-AVIC adhesion. Neutralizing β₂-integrin or ICAM-1 in coculture suppressed monocyte adhesion to AVICs and the expression of ICAM-1 and IL-6. Recombinant CD18 enhanced the matrilin-2-induced ICAM-1 and IL-6 expression in AVIC monoculture. Further, stimulation of coculture with matrilin-2 induced greater YAP and NF-κB phosphorylation. Inhibiting either YAP or NF-κB markedly suppressed the inflammatory response to matrilin-2 in coculture.

CONCLUSION

Monocyte β₂-integrin interacts with AVIC ICAM-1 to augment AVIC inflammatory responses to soluble matrilin-2 through enhancing the activation of YAP and NF-κB signaling pathways. Infiltrated monocytes may promote valvular inflammation through cell-cell interaction with AVICs to enhance their sensitivity to damage-associated molecular patterns.

Identification of Hub Biomarkers and Immune-Related Pathways Participating in the Progression of Antineutrophil Cytoplasmic Antibody-Associated Glomerulonephritis

Background

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic autoimmune disease that generally induces the progression of rapidly progressive glomerulonephritis (GN). The purpose of this study was to identify key biomarkers and immune-related pathways involved in the progression of ANCA-associated GN (ANCA-GN) and their relationship with immune cell infiltration.

Methods

Gene microarray data were downloaded from the Gene Expression Omnibus (GEO). Hub markers for ANCA-GN were mined based on differential expression analysis, weighted gene co-expression network analysis (WGCNA) and lasso regression, followed by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Set Enrichment Analysis (GSEA) of the differential genes. The infiltration levels of 28 immune cells in the expression profile and their relationship to hub gene markers were analysed using single-sample GSEA (ssGSEA). In addition, the accuracy of the hub markers in diagnosing ANCA-GN was subsequently evaluated using the receiver operating characteristic curve (ROC).

Results

A total of 651 differential genes were screened. Twelve co-expression modules were obtained via WGCNA; of which, one hub module (black module) had the highest correlation with ANCA-GN. A total of 66 intersecting genes were acquired by combining differential genes. Five hub genes were subsequently obtained by lasso analysis as potential biomarkers for ANCA-GN. The immune infiltration results revealed the most significant relationship among monocytes, CD4⁺ T cells and CD8⁺ T cells. ROC curve analysis demonstrated a prime diagnostic value of the five hub genes. According to the functional enrichment analysis of the differential genes, hub genes were mainly enhanced in immune- and inflammation-related pathways.

Conclusion

B cells and monocytes were closely associated with the pathogenesis of ANCA-GN. Hub genes (CYP3A5, SLC12A3, BGN, TAPBP and TMEM184B) may be involved in the progression of ANCA-GN through immune-related signal pathways.

Macrophage ICAM-1 functions as a regulator of phagocytosis in LPS induced endotoxemia

OBJECTIVE

Intracellular adhesion molecule-1 (ICAM-1), a transmembrane glycoprotein belonging to the immunoglobulin superfamily, plays a critical role in mediating cell-cell interaction and outside-in cell signaling during the immune response. ICAM-1 is expressed on the cell surface of several cell types including endothelial cells, epithelial cells, leucocytes, fibroblasts, and neutrophils. Despite ICAM-1 has been detected on macrophage, little is known about the function and mechanism of macrophage ICAM-1.

METHODS

To investigate the role of lipopolysaccharide (LPS) in ICAM-1 regulation, both the protein and cell surface expression of ICAM-1 were measured. The phagocytosis of macrophage was evaluated by flow cytometry and Confocal microscopy. Small interfering RNA and neutralizing antibody of ICAM-1 were used to assess the effect of ICAM-1 on macrophage phagocytosis. TLR4 gene knockout mouse and cytoplasmic and mitochondrial ROS scavenger were used for the regulation of ICAM-1 expression. ROS was determined using flow cytometry.

RESULTS

In this study, we reported that macrophage can be stimulated to increase both the protein and cell surface expression of ICAM-1 by LPS. Macrophage ICAM-1 expression was correlated with enhanced macrophage phagocytosis. We found that using ICAM-1 neutralizing antibody or ICAM-1 silencing to attenuate the function or expression of ICAM-1 could decrease LPS-induced macrophage phagocytosis. Furthermore, we found that knocking out of TLR4 led to inhibited cytoplasmic and mitochondrial ROS production, which in turn, attenuated ICAM-1 expression at both the protein and cell surface levels.

CONCLUSION

This study demonstrates that the mechanism of ICAM-1-mediated macrophage phagocytosis is depending on TLR4-mediated ROS production and provides significant light on macrophage ICAM-1 in endotoxemia.

Monocytes enhance the inflammatory response to TLR2 stimulation in aortic valve interstitial cells through paracrine up-regulation of TLR2 level

Background and Objectives: Chronic valvular inflammation associated with monocyte infiltration promotes calcific aortic valve disease (CAVD) progression. Further, innate immunity in aortic valve interstitial cells (AVICs), mediated by Toll-like receptors (TLRs), up-regulates cellular inflammatory, fibrogenic and osteogenic activities. Currently, the pro-inflammatory communication between monocytes and AVICs and the underlying mechanism are unclear. We hypothesized that monocytes up-regulate AVIC inflammatory activity. This study sought to characterize the interaction between monocytes and AVICs and to elucidate the mechanism underlying cell-to-cell communication.

Methods and Results: AVICs, monocytes and co-cultures were exposed to a low concentration of TLR2 activator Pam3CSK4 (0.03 µg/ml). The TLR2 activator at this dose induced a marked increase in AVIC production of ICAM-1 and VCAM-1 only when co-cultured with monocytes. Adding conditioned medium from Pam3CSK4-treated monocytes (Pam3 CM, containing 0.1 µg/ml of Pam3CSK4) to AVIC culture (30% vol/vol; diluting Pam3CSK4 to 0.03 µg/ml) greatly increased the expression of adhesion molecules while adding conditioned medium from untreated monocytes (control CM) had no effect. Inhibition or knockdown of TLR2 in AVICs markedly reduced ICAM-1 and VCAM-1 expression induced by Pam3 CM. Further, Pam3 CM increased TLR2 levels in AVICs. Multiplex-ELISA analysis of Pam3 CM identified greater levels of TNF-α. Neutralization of TNF-α abolished the effect of Pam3 CM on AVIC TLR2 levels, resulting in marked attenuation of its potency in the induction of adhesion molecule expression.

Conclusions: This study demonstrates that activated monocytes use paracrine signaling to sensitize AVICs for inflammatory responses to a low level of TLR2 activator. The mechanism of sensitization involves up-regulation of AVIC TLR2 levels by TNF-α from monocytes. Infiltrated monocytes in aortic valve tissue may exacerbate valvular inflammation by rendering AVICs hypersensitive to TLR2 activators.

Mechanistic Roles of Matrilin-2 and Klotho in Modulating the Inflammatory Activity of Human Aortic Valve Cells

BACKGROUND

Calcific aortic valve disease (CAVD) is a chronic inflammatory disease. Soluble extracellular matrix (ECM) proteins can act as damage-associated molecular patterns and may induce valvular inflammation. Matrilin-2 is an ECM protein and has been found to elevate the pro-osteogenic activity in human aortic valve interstitial cells (AVICs). Klotho, an anti-aging protein, appears to have anti-inflammatory properties. The effect of matrilin-2 and Klotho on AVIC inflammatory responses remains unclear.

METHODS AND RESULTS

Isolated human AVICs were exposed to matrilin-2. Soluble matrilin-2 induced the production of ICAM-1, MCP-1, and IL-6. It also induced protein kinase R (PKR) activation via Toll-like receptor (TLR) 2 and 4. Pretreatment with PKR inhibitors inhibited NF-κB activation and inflammatory mediator production induced by matrilin-2. Further, recombinant Klotho suppressed PKR and NF-κB activation and markedly reduced the production of inflammatory mediators in human AVICs exposed to matrilin-2.

CONCLUSIONS

This study revealed that soluble matrilin-2 upregulates AVIC inflammatory activity via activation of the TLR-PKR-NF-κB pathway and that Klotho is potent to suppress AVIC inflammatory responses to a soluble ECM protein through inhibiting PKR. These novel findings indicate that soluble matrilin-2 may accelerate the progression of CAVD by inducing valvular inflammation and that Klotho has the potential to suppress valvular inflammation.

Overexpression of Biglycan is Associated with Resistance to Rapamycin in Human WERI-Rb-1 Retinoblastoma Cells by Inducing the Activation of the Phosphatidylinositol 3-Kinases (PI3K)/Akt/Nuclear Factor kappa B (NF-κB) Signaling Pathway

Background

Biglycan (BGN) is an extracellular matrix (ECM) protein that regulates the growth of epithelial cells. The mammalian target of rapamycin (mTOR) inhibitor, rapamycin, is a treatment for advanced retinoblastoma. This study aimed to investigate the effects of expression of BGN on the response of human WERI-Rb-1 retinoblastoma cells to rapamycin and to investigate the associated signaling pathways.

Material/Methods

BGN gene expression was induced in human WERI-Rb-1 retinoblastoma cells, which were incubated with rapamycin at doses of 0, 5, 10, 20, 30, and 50 μg/ml. Cells were treated with the PI3K/Akt pathway inhibitor, LY294002. The MTT assay determined the rate of cell inhibition. Real-time polymerase chain reaction (RT-PCR) was performed to measure BGN gene expression using RT²-PCR. Western blot detected the protein levels of BGN, p-PI3K, p-Akt, nuclear NF-κB, and p65.

Results

Rapamycin impaired cell growth, induced cell apoptosis, and suppressed the expression levels of p-PI3K, p-Akt, nuclear NF-κB, and p65. Overexpression of the BGN gene restored growth potential and inhibited apoptosis and was associated with the activation of the PI3K/Akt-mediated NF-κB pathway. In cells that overexpressed BGN, inhibition of the PI3K/Akt pathway by LY294002 increased the sensitivity of human WERI-Rb-1 retinoblastoma cells to rapamycin.

Conclusions

Overexpression of BGN induced rapamycin resistance in WERI-Rb-1 retinoblastoma cells by activating PI3K/Akt/NF-κB signaling.

Development of calcific aortic valve disease: Do we know enough for new clinical trials?

Calcific aortic valve disease (CAVD), previously thought to represent a passive degeneration of the valvular extracellular matrix (VECM), is now regarded as an intricate multistage disorder with sequential yet intertangled and interacting underlying processes. Endothelial dysfunction and injury, initiated by disturbed blood flow and metabolic disorders, lead to the deposition of low-density lipoprotein cholesterol in the VECM further provoking macrophage infiltration, oxidative stress, and release of pro-inflammatory cytokines. Such changes in the valvular homeostasis induce differentiation of normally quiescent valvular interstitial cells (VICs) into synthetically active myofibroblasts producing excessive quantities of the VECM and proteins responsible for its remodeling. As a result of constantly ongoing degradation and re-deposition, VECM becomes disorganised and rigid, additionally potentiating myofibroblastic differentiation of VICs and worsening adaptation of the valve to the blood flow. Moreover, disrupted and excessively vascularised VECM is susceptible to the dystrophic calcification caused by calcium and phosphate precipitating on damaged collagen fibers and concurrently accompanied by osteogenic differentiation of VICs. Being combined, passive calcification and biomineralisation synergistically induce ossification of the aortic valve ultimately resulting in its mechanical incompetence requiring surgical replacement. Unfortunately, multiple attempts have failed to find an efficient conservative treatment of CAVD; however, therapeutic regimens and clinical settings have also been far from the optimal. In this review, we focused on interactions and transitions between aforementioned mechanisms demarcating ascending stages of CAVD, suggesting a predisposing condition (bicuspid aortic valve) and drug combination (lipid-lowering drugs combined with angiotensin II antagonists and cytokine inhibitors) for the further testing in both preclinical and clinical trials.

MicroRNA-214 promotes the calcification of human aortic valve interstitial cells through the acceleration of inflammatory reactions with activated MyD88/NF-κB signaling

Calcific aortic valve disease (CAVD) is a complex active process involving in endothelial injury, lipid infiltration, chronic inflammation, matrix remodeling, cell differentiation, progressive bone formation, and new angiogenesis. The excess inflammatory responses induced by aortic valve interstitial cells (AVICs) are one of the common pathogeneses of this disease. Although many microRNAs (miRs) have been identified to play crucial roles in the calcification process of the aortic valve, numerous miRs are still waiting to be explored. In this study, we explored the functional role of miR-214 in the inflammatory reaction and calcification of human AVICs and its underlying molecular mechanism. Alizarin red staining was used to determine the number of calcified nodules. The protein levels of ICAM-1, IL-6, IL-8, and MCP-1 detected by enzyme-linked immunosorbent assay (ELISA) were used to assess the inflammatory reaction of AVICs; expression levels of RUNX2, Msx2, and BMP2 were used to evaluate AVICs osteoblast differentiation. Results showed that the expression levels of TLR4, MyD88, NF-κB, and miR-214 were up-regulated in the blood and aortic valve tissue samples of patients with CAVD when compared with normal individuals. Knockdown of miR-214 in AVICs inhibited the secretion of IL-6, IL-8, ICAM-1, and MCP-1, while this effect was repressed when lipopolysaccharide (LPS) was added to AVICs. LPS also enhanced the effects of miR-214 in promoting the secretion of pro-inflammatory factors. Besides, up-regulation of miR-214 promoted the protein expression of MyD88 and NF-κB but had no influence on TLR4, and miR-214 could directly combine with MyD88 protein. Up-regulation of MyD88 facilitated the secretion of pro-inflammatory factors and increased calcified nodules number and accelerated the expression of RUNX2, Msx2, and BMP2. Moreover, promotion of the expressions of pro-inflammatory factors and "osteoblast-like" cell markers induced by miR-214 overexpression was abolished when MyD88 was down-regulated in AVICs. In conclusion, this study revealed that miR-214 promoted calcification by facilitating inflammatory reaction through MyD88/NF-κB signaling pathway in AVICs.

Biglycan, a Nitric Oxide-Downregulated Proteoglycan, Prevents Nitric Oxide-Induced Neuronal Cell Apoptosis via Targeting Erk1/2 and p38 Signaling Pathways

Nitric oxide (NO), a gaseous signaling molecule, induces apoptosis and mediates neurodegenerative diseases and brain injury. Biglycan (BGN), a member of the small leucine-rich proteoglycan family, was demonstrated to exert anti-apoptosis function in various disease models. However, little is known about the effect of BGN on NO-induced neurotoxicity. Here, for the first time, we reported that BGN protects against NO-induced apoptosis in human neuroblastoma SH-EP1 cells. This is supported by the finding that sodium nitroprusside (SNP), a NO donor, triggered downregulation of BGN in SH-EP1 cells, and over-expression of BGN strikingly attenuated NO-induced nuclear fragmentation and apoptosis of neuronal cells. More importantly, BGN remarkably blocked NO-induced phosphorylation of Erk1/2 and p38 signaling, but not JNK MAPK pathway in neuronal cells. Furthermore, inhibiting Erk1/2 by U0126 or p38 by SB203580 partially protected against NO-induced cell death. Conversely, downregulation of BGN by siRNA aggravated NO-induced neuronal cell death, which was not attenuated by U0126 or SB203580. These findings indicated that BGN, downregulated by NO, prevents NO-induced neuronal cell apoptosis via targeting Erk1/2 and p38 signaling pathways. Our results strongly suggest that BGN could be explored for the prevention of NO-induced neurodegenerative disorders.

Simvastatin reduces the TLR4-induced inflammatory response in human aortic valve interstitial cells

BACKGROUND

Calcific aortic stenosis is a chronic inflammatory disease. Proinflammatory stimulation via toll-like receptor 4 (TLR4) causes the aortic valve interstitial cell (AVIC) to undergo phenotypic change. The AVIC first assumes an inflammatory phenotype characterized by the production of inflammatory mediators such as intercellular adhesion molecule-1 (ICAM-1), interleukin-8 (IL-8), and monocyte chemoattractant protein-1 (MCP-1). This change has been linked with an osteogenic phenotypic response. Statins have recently been shown to have anti-inflammatory properties. We therefore hypothesized that statins may have an anti-inflammatory effect on human AVICs by downregulation of TLR4-stimulated inflammatory responses. Our purposes were (1) to determine the effect of simvastatin on TLR4-induced expression of inflammatory mediators in human AVICs and (2) to determine the mechanism(s) through which simvastatin exert this effect.

MATERIALS AND METHODS

Human AVICs were isolated from the explanted hearts of four patients undergoing cardiac transplantation. Cells were treated with simvastatin (50 μM) for 1 h before stimulation with TLR4 agonist lipopolysaccharide (LPS, 0.2 μg/mL). Immunoblotting (IB) was used to analyze cell lysates for ICAM-1 expression, and enzyme-linked immunosorbent assay was used to detect IL-8 and MCP-1 in cell culture media. Likewise, lysates were analyzed for TLR4 and nuclear factor-kappa B activation (IB). After simvastatin treatment, lysates were analyzed for TLR4 levels (IB). Statistics were by analysis of variance (P < 0.05).

RESULTS

Simvastatin reduced TLR4-induced ICAM-1, IL-8, and MCP-1 expression in AVICs. Simvastatin down-regulated TLR4 levels and suppressed TLR4-induced phosphorylation of nuclear factor-kappa B.

CONCLUSIONS

These data demonstrate the potential of a medical therapy (simvastatin) to impact the pathogenesis of aortic stenosis.

Biglycan promotes the chemotherapy resistance of colon cancer by activating NF-κB signal transduction

Biglycan (BGN) is overexpressed in cancer stem cells of colon cancer and induces the activation of NF-κB pathway which contributes to the chemotherapy resistance of diverse cancer types. Therefore, we hypothesized that the overexpression of BGN also promoted the development of multiple drug resistance (MDR) in colon cancer via NF-κB pathway. The expression of BGN was bilaterally modulated in colon cancer cell lines HT-29 and SW-480 and the effect of treatments on the cell proliferation and resistance to 5-FU was assessed. Moreover, the role of NF-κB signaling in the BGN-mediated formation of MDR was further investigated by subjecting BGN-overexpressed SW-480 cells to the co-treatment of chemo-agents and NF-κB inhibitor, PDTC. The inhibition of BGN expression decreased the proliferation potential of HT-29 cells while the induction of BGN expression increased the potential of SW-480 cells. BGN knockdown increased HT-29 cells' sensitivity to 5-FU, represented by the lower colony number and higher apoptotic rate. To the contrary, BGN overexpression promoted the resistance of SW-480 cells to 5-FU. The effect of BGN modulation on colon cancer cells was associated with the changes in apoptosis and NF-κB pathways: BGN inhibition increased the expressions of pro-apoptosis indicators and suppressed NF-κB pathway activity while BGN overexpression had the opposite effect. It was also found that the BGN-mediated formation of MDR was impaired when NF-κB pathway was blocked. Findings outlined in the current study showed that BGN contributed to the formation of chemotherapy resistance in colon cancer cells by activating NF-κB signaling.

Toll-Like Receptors, Inflammation, and Calcific Aortic Valve Disease

Inflammation, the primary response of innate immunity, is essential to initiate the calcification process underlying calcific aortic valve disease (CAVD), the most prevalent valvulopathy in Western countries. The pathogenesis of CAVD is multifactorial and includes inflammation, hemodynamic factors, fibrosis, and active calcification. In the development of CAVD, both innate and adaptive immune responses are activated, and accumulating evidences show the central role of inflammation in the initiation and propagation phases of the disease, being the function of Toll-like receptors (TLR) particularly relevant. These receptors act as sentinels of the innate immune system by recognizing pattern molecules from both pathogens and host-derived molecules released after tissue damage. TLR mediate inflammation via NF-κB routes within and beyond the immune system, and play a crucial role in the control of infection and the maintenance of tissue homeostasis. This review outlines the current notions about the association between TLR signaling and the ensuing development of inflammation and fibrocalcific remodeling in the pathogenesis of CAVD. Recent data provide new insights into the inflammatory and osteogenic responses underlying the disease and further support the hypothesis that inflammation plays a mechanistic role in the initiation and progression of CAVD. These findings make TLR signaling a potential target for therapeutic intervention in CAVD.

The proteoglycan biglycan mediates inflammatory response by activating TLR-4 in human chondrocytes: Inhibition by specific siRNA and high polymerized Hyaluronan

Cartilage degeneration are hallmarks of wear, tear, mechanical and inflammatory damage of the joint cartilage. Tissue degradation as well as compromising the integrity and function of the organ, produces different intermediates, directly able to stimulate further inflammatory effect, therefore, amplifying the inflammation response. Biglycan is a soluble component of the extracellular matrix that is released during tissue injury. It has been reported that released biglycan is an endogenous ligand for TLR-2/4 in some cell type. We studied the role of biglycan in an experimental model of biglycan-induced inflammatory response in human chondrocytes and the effect of high polymerized HA on reducing its activity. Exposition of chondrocytes to LPS generated cell injury, including high levels of biglycan. Chondrocyte treatment with biglycan produces a high mRNA expression of several detrimental inflammation mediators such as IL-1β, IL-6, MMP-13, and IL-17, as well as NF-kB and TLR-4 activation. Administration of high polymerized HA to chondrocytes exposed to biglycan was able to attenuate the inflammatory response by decreasing the expression of the inflammatory mediators. Involvement of the TLR-4 in the mediation of the biglycan action was confirmed using a specific silent agent (siRNA). Taken together, these data could be used to develop new anti-inflammatory approaches.

Lysophosphatidylcholine activates the Akt pathway to upregulate extracellular matrix protein production in human aortic valve cells

BACKGROUND

Overproduction of extracellular matrix (ECM) protein by aortic valve interstitial cells (AVICs) plays an important role in valvular sclerosis (thickening) associated with the early pathobiology of aortic stenosis. Accumulation of oxidized low-density lipoprotein (oxLDL) is observed in sclerotic aortic valve and may have a mechanistic role in valvular disease progression. Lysophosphatidylcholine (LysoPC) is a component of oxLDL and has multiple biological activities. This study was to test the hypothesis that oxLDL and LysoPC upregulate ECM protein production in human AVICs.

METHODS AND RESULTS

AVICs were isolated from normal human aortic valves. Cells were treated with oxLDL (40 μg/mL) or LysoPC (40 μmol/L). Immunoblotting was applied to analyze ECM proteins (collagens I and III and biglycan) in cell lysate and Picrosirius red staining was used to examine collagen deposition. Both oxLDL and LysoPC upregulated the production of biglycan and collagen I. The upregulation of ECM proteins by LysoPC was preceded by the phosphorylation of Akt and ERK1/2. Inhibition of Akt markedly reduced the effect of LysoPC on ECM protein production and collagen deposition. However, inhibition of ERK1/2 had no effect.

CONCLUSIONS

LysoPC upregulates the production of biglycan and collagen I in human AVICs and may mediate the effect of oxLDL on ECM protein production. The Akt pathway appears to be critical in mediating the effect of LysoPC. oxLDL accumulation and generation of LysoPC in the aortic valve tissue may contribute to the mechanism of valvular sclerosis associated with the development and progression of aortic stenosis.

ADAMTS5 Deficiency in Calcified Aortic Valves Is Associated With Elevated Pro-Osteogenic Activity in Valvular Interstitial Cells

OBJECTIVE

Extracellular matrix proteinases are implicated in the pathogenesis of calcific aortic valve disease. The ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5) enzyme is secreted, matrix-associated metalloendopeptidase, capable of degrading extracellular matrix proteins, particularly matrilin 2. We sought to determine the role of the ADAMTS5/matrilin 2 axis in mediating the phenotype transition of valvular interstitial cells (VICs) associated with calcific aortic valve disease.

APPROACH AND RESULTS

Levels of ADAMTS5, matrilin 2, and α-SMA (α-smooth muscle actin) were evaluated in calcified and normal human aortic valve tissues and VICs. Calcified aortic valves have reduced levels of ADAMTS5 and higher levels of matrilin 2 and α-SMA. Treatment of normal VICs with soluble matrilin 2 caused an increase in α-SMA level through Toll-like receptors 2 and 4, which was accompanied by upregulation of runt-related transcription factor 2 and alkaline phosphatase. In addition, ADAMTS5 knockdown in normal VICs enhanced the effect of matrilin 2. Matrilin 2 activated nuclear factor (NF) κB and NF of activated T cells complex 1 and induced the interaction of these 2 NFs. Inhibition of either NF-κB or NF of activated T cells complex 1 suppressed matrilin 2's effect on VIC phenotype change. Knockdown of α-SMA reduced and overexpression of α-SMA enhanced the expression of pro-osteogenic factors and calcium deposit formation in human VICs.

CONCLUSIONS

Matrilin 2 induces myofibroblastic transition and elevates pro-osteogenic activity in human VICs via activation of NF-κB and NF of activated T cells complex 1. Myofibroblastic transition in human VICs is an important mechanism of elevating the pro-osteogenic activity. Matrilin 2 accumulation associated with relative ADAMTS5 deficiency may contribute to the mechanism underlying calcific aortic valve disease progression.

Soluble TLR2 and 4 concentrations in cerebrospinal fluid in HIV/SIV-related neuropathological conditions

HIV in the central nervous system (CNS) mainly infects microglial cells which are known to express toll-like receptors (TLRs). This paper aimed to study the role of soluble TLR2 (sTLR2), sTLR4, and other inflammatory markers in cerebrospinal fluid (CSF) in HIV/Simian immunodeficiency virus (SIV)-related neurological sequelae. We determined sTLR2 and sTLR4 levels in CSF and serum/plasma of SIV-infected rhesus macaques with and without neurological sequelae, as well as in HIV-infected patients with and without cognitive impairments and Alzheimer's disease (AD) patients and matched controls. CSF cytokines and chemokines levels were analyzed in macaques as markers of neuroinflammation, while neopterin and S100B CSF concentrations were measured in HIV-infected patients as microglial and astrocyte marker, respectively. We found detectable levels of sTLR2 and sTLR4 in CSF of macaques and humans. Furthermore, CSF sTLR2 and sTLR4 concentrations were higher in SIV-infected macaques with neurological sequelae compared to those without neurological complications (p = 0.0003 and p = 0.0006, respectively). CSF IL-8 and monocyte chemoattractant protein-1 (MCP-1) levels were elevated in macaques with neurological sequelae, and a positive correlation was found between CSF levels of sTLR2/4 and IL-8 and MCP-1. Also in humans, elevated CSF sTLR4 levels were found in HIV-infected patients with cognitive impairments compared to HIV-infected patients with normal cognition (p = 0.019). Unlike CSF S100B levels, neopterin correlated positively with sTLR2 and sTLR4. No difference was found in plasma and CSF sTLR2 and sTLR4 levels between AD patients and control subjects (p = 0.26). In conclusion, CSF sTLR2 and sTLR4 may play a role in HIV/SIV-related neuroinflammation and subsequent neuropathology.

Biological roles of glycans

Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural and physical roles in biological systems. Targeted microbial binding to host glycans has also been studied for decades. But such biological roles can only explain some of the remarkable complexity and organismal diversity of glycans in nature. Reviewing the subject about two decades ago, one could find very few clear-cut instances of glycan-recognition-specific biological roles of glycans that were of intrinsic value to the organism expressing them. In striking contrast there is now a profusion of examples, such that this updated review cannot be comprehensive. Instead, a historical overview is presented, broad principles outlined and a few examples cited, representing diverse types of roles, mediated by various glycan classes, in different evolutionary lineages. What remains unchanged is the fact that while all theories regarding biological roles of glycans are supported by compelling evidence, exceptions to each can be found. In retrospect, this is not surprising. Complex and diverse glycans appear to be ubiquitous to all cells in nature, and essential to all life forms. Thus, >3 billion years of evolution consistently generated organisms that use these molecules for many key biological roles, even while sometimes coopting them for minor functions. In this respect, glycans are no different from other major macromolecular building blocks of life (nucleic acids, proteins and lipids), simply more rapidly evolving and complex. It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences.

Innate and Adaptive Immunity in Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD) is the most common heart valve disorder. CAVD is a chronic process characterized by a pathologic mineralization of valve leaflets. Ectopic mineralization of the aortic valve involves complex relationships with immunity. Studies have highlighted that both innate and adaptive immunity play a role in the development of CAVD. In this regard, accumulating evidence indicates that fibrocalcific remodelling of the aortic valve is associated with activation of the NF-κB pathway. The expression of TNF-α and IL-6 is increased in human mineralized aortic valves and promotes an osteogenic program as well as the mineralization of valve interstitial cells (VICs), the main cellular component of the aortic valve. Different factors, including oxidized lipid species, activate the innate immune response through the Toll-like receptors. Moreover, VICs express 5-lipoxygenase and therefore produce leukotrienes, which may amplify the inflammatory response in the aortic valve. More recently, studies have emphasized that an adaptive immune response is triggered during CAVD. Herein, we are reviewing the link between the immune response and the development of CAVD and we have tried, whenever possible, to keep a translational approach.

Expression of Toll-Like Receptors in Chronic Histiocytic Intervillositis of the Placenta

Chronic histiocytic intervillositis of the placenta (CHI) shows monocytic/histiocytic infiltration of the intervillous space. Placental malaria has a CHI-like histopathology and induces an aberrant expression of Toll-like receptors (TLR) 3, 7-9. We hypothesized that, similar to placental malaria, CHI could be associated with increased TLR expression. TLR1-10 and other inflammation-associated factors were analyzed by real-time PCR and immunohistochemistry. A total of 31 formalin-fixed and paraffin-embedded placenta samples were evaluated: CHI (n = 9), and for control purposes, villitis of unknown etiology (VUE, n = 8) and placentas without inflammation (n = 14). CHI shows increased expression of monocytic TLR1, a receptor which is involved in bacterial lipopolysaccharide (LPS)-induced inflammation. This could indicate a TLR1-mediated immune mechanism in the placenta (e.g. triggered by transient, clinically inapparent maternal bacteraemia) which leads to massive monocytic/histiocytic accumulation in the intervillous space. The increased expression of TLR1 with no increased expression of TLR3 and TLR7-9 is different from that in malaria.

Serum toll-like receptors are potential biomarkers of radiation pneumonia in locally advanced NSCLC

OBJECTIVE

Toll-like receptors (TLRs) are highly or lowly expressed in a wide variety of tumors and exhibit either pro-tumor or anti-tumor activities. In the present study, we investigate whether there are relationships between the expressions of TLRs and the occurrence of radiation pneumonia in advanced NSCLC patients treated with radiotherapy.

MATERIALS AND METHODS

76 patients diagnosed with NSCLC and 50 healthy controls were recruited from Oct 2012 to Jan 2014. The expressions of serum TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR8, and TLR9 were detected by ELISA techniques. Fisher exact test, χ(2) test, ROC working curve and Cox regression model were applied to analyze all data.

RESULTS

serum TLR1, TLR2, TLR4, and TLR9 exhibited a relative high expression level in NSCLC patients compared with healthy controls. Importantly, pre-neutrophil granulocyte ratio was associated with the expression of TLR1, TLR2, and TLR4. Moreover, the patients with high ratio of neutrophil granulocyte significantly increased the occurrence of fever in comparison to normal neutrophil ratio in NSCLC patients during the course of radiotherapy. We further evaluated the containing of TLRs when patients had temperatures and found serum TLR1, TLR2 and TLR4 were over-expressed. Finally, 26 of 76 patients were diagnosed with different stages of radiation induced pneumonia; as a result, the contents of TLR1 and TLR4 before radiotherapy were identified as independent significances with pneumonia occurrence.

CONCLUSIONS

The pretreatment levels of TLR1 and TLR4 have the predictive value to be clinically potential biomarkers of pneumonia risk in locally advanced NSCLC.