Soluble biglycan as a biomarker of inflammatory renal diseases

Paracrine regulations of IFN-γ secreting CD4 + T cells by lumican and biglycan are protective in allergic contact dermatitis

The extracellular matrix (ECM) is known to regulate innate immune cells but its role in T cell functions is poorly understood. Here, we show a protective role for ECM proteoglycans, lumican and biglycan in hapten-induced contact dermatitis that is achieved through limiting proinflammatory CD4 + T cells. Lumican and biglycan-null mice develop significant inflammation with greater numbers of CD4 + T cells in hapten-challenged ear pinnae, while their draining lymph nodes show increased T-bet-STAT1 signaling, Th1 commitment, and IFN-γ secreting CD4 + T cell proliferation. Wild type mouse lymph node fibroblastic reticular cells secrete lumican, biglycan and decorin, a related proteoglycan, while none are expressed by naive or activated T cells. In vitro , lumican and biglycan co-localize with LFA-1 on T cell surfaces, and all three proteoglycans suppress LFA-1 mediated T cell activation. Overall, this study elucidates a novel paracrine regulation of Th1 cells by ECM proteoglycans to limit inflammation and tissue damage.

Soluble Proteoglycans and Proteoglycan Fragments as Biomarkers of Pathological Extracellular Matrix Remodeling

Proteoglycans and their proteolytic fragments diffuse into biological fluids such as plasma, serum, urine, or synovial fluid, where they can be detected by antibodies or mass-spectrometry. Neopeptides generated by the proteolysis of proteoglycans are recognized by specific neoepitope antibodies and can act as a proxy for the activity of certain proteases. Proteoglycan and proteoglycan fragments can be potentially used as prognostic, diagnostic, or theragnostic biomarkers for several diseases characterized by dysregulated extracellular matrix remodeling such as osteoarthritis, rheumatoid arthritis, atherosclerosis, thoracic aortic aneurysms, central nervous system disorders, viral infections, and cancer. Here, we review the main mechanisms accounting for the presence of soluble proteoglycans and their fragments in biological fluids, their potential application as diagnostic, prognostic, or theragnostic biomarkers, and highlight challenges and opportunities ahead of their clinical translation.

Evaluation of a proteomic signature coupled with the kidney failure risk equation in predicting end stage kidney disease in a chronic kidney disease cohort

BACKGROUND

The early identification of patients at high-risk for end-stage renal disease (ESRD) is essential for providing optimal care and implementing targeted prevention strategies. While the Kidney Failure Risk Equation (KFRE) offers a more accurate prediction of ESRD risk compared to static eGFR-based thresholds, it does not provide insights into the patient-specific biological mechanisms that drive ESRD. This study focused on evaluating the effectiveness of KFRE in a UK-based advanced chronic kidney disease (CKD) cohort and investigating whether the integration of a proteomic signature could enhance 5-year ESRD prediction.

METHODS

Using the Salford Kidney Study biobank, a UK-based prospective cohort of over 3000 non-dialysis CKD patients, 433 patients met our inclusion criteria: a minimum of four eGFR measurements over a two-year period and a linear eGFR trajectory. Plasma samples were obtained and analysed for novel proteomic signals using SWATH-Mass-Spectrometry. The 4-variable UK-calibrated KFRE was calculated for each patient based on their baseline clinical characteristics. Boruta machine learning algorithm was used for the selection of proteins most contributing to differentiation between patient groups. Logistic regression was employed for estimation of ESRD prediction by (1) proteomic features; (2) KFRE; and (3) proteomic features alongside KFRE.

RESULTS

SWATH maps with 943 quantified proteins were generated and investigated in tandem with available clinical data to identify potential progression biomarkers. We identified a set of proteins (SPTA1, MYL6 and C6) that, when used alongside the 4-variable UK-KFRE, improved the prediction of 5-year risk of ESRD (AUC = 0.75 vs AUC = 0.70). Functional enrichment analysis revealed Rho GTPases and regulation of the actin cytoskeleton pathways to be statistically significant, inferring their role in kidney function and the pathogenesis of renal disease.

CONCLUSIONS

Proteins SPTA1, MYL6 and C6, when used alongside the 4-variable UK-KFRE achieve an improved performance when predicting a 5-year risk of ESRD. Specific pathways implicated in the pathogenesis of podocyte dysfunction were also identified, which could serve as potential therapeutic targets. The findings of our study carry implications for comprehending the involvement of the Rho family GTPases in the pathophysiology of kidney disease, advancing our understanding of the proteomic factors influencing susceptibility to renal damage.

Control of tissue homeostasis by the extracellular matrix: Synthetic heparan sulfate as a promising therapeutic for periodontal health and bone regeneration

Proteoglycans are core proteins associated with carbohydrate/sugar moieties that are highly variable in disaccharide composition, which dictates their function. These carbohydrates are named glycosaminoglycans, and they can be attached to proteoglycans or found free in tissues or on cell surfaces. Glycosaminoglycans such as hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin/heparan sulfate have multiple functions including involvement in inflammation, immunity and connective tissue structure, and integrity. Heparan sulfate is a highly sulfated polysaccharide that is abundant in the periodontium including alveolar bone. Recent evidence supports the contention that heparan sulfate is an important player in modulating interactions between damage associated molecular patterns and inflammatory receptors expressed by various cell types. The structure of heparan sulfate is reported to dictate its function, thus, the utilization of a homogenous and structurally defined heparan sulfate polysaccharide for modulation of cell function offers therapeutic potential. Recently, a chemoenzymatic approach was developed to allow production of many structurally defined heparan sulfate carbohydrates. These oligosaccharides have been studied in various pathological inflammatory conditions to better understand their function and their potential application in promoting tissue homeostasis. We have observed that specific size and sulfation patterns can modulate inflammation and promote tissue maintenance including an anabolic effect in alveolar bone. Thus, new evidence provides a strong impetus to explore heparan sulfate as a potential novel therapeutic agent to treat periodontitis, support alveolar bone maintenance, and promote bone formation.

Global impact of proteoglycan science on human diseases

In this comprehensive review, we will dissect the impact of research on proteoglycans focusing on recent developments involved in their synthesis, degradation, and interactions, while critically assessing their usefulness in various biological processes. The emerging roles of proteoglycans in global infections, specifically the SARS-CoV-2 pandemic, and their rising functions in regenerative medicine and biomaterial science have significantly affected our current view of proteoglycans and related compounds. The roles of proteoglycans in cancer biology and their potential use as a next-generation protein-based adjuvant therapy to combat cancer is also emerging as a constructive and potentially beneficial therapeutic strategy. We will discuss the role of proteoglycans in selected and emerging areas of proteoglycan science, such as neurodegenerative diseases, autophagy, angiogenesis, cancer, infections and their impact on mammalian diseases.

Involvement of small leucine-rich proteoglycans and telocytes in thin and thick human endometrium: immunohistochemical and ultrastructural examination

Thin endometrium, defined as an endometrial thickness of less than 7 mm during the late follicular phase, is a common cause of frequent cancelation of embryo transfers or recurrent implantation failure during assisted reproductive treatment. Small proteoglycans regulate intracellular signaling cascades by bridging other matrix molecules and tissue elements, affecting cell proliferation, adhesion, migration, and cytokine concentration. The aim of the study is to investigate the role of small leucine-rich proteoglycans in the pathogenesis of thin and thick human endometrium and their differences from normal endometrium in terms of fine structure properties. Normal, thin, and thick endometrial samples were collected, and small leucine-rich proteoglycans (SLRPs), decorin, lumican, biglycan, and fibromodulin immunoreactivities were comparatively analyzed immunohistochemically. The data were compared statistically. Moreover, ultrastructural differences among the groups were evaluated by transmission electron microscopy. The immunoreactivities of decorin, lumican, and biglycan were higher in the thin endometrial glandular epithelium and stroma compared to the normal and thick endometrium (p < .001). Fibromodulin immunoreactivity was also higher in the thin endometrial glandular epithelium than in the normal and thick endometrium (p < .001). However, there was no statistical difference in the stroma among the groups. Ultrastructural features were not profoundly different among cases. Telocytes, however, were not seen in the thin endometrium in contrast to normal and thin endometrial tissues. These findings suggest a possible role of changes in proteoglycan levels in the pathogenesis of thin endometrium.

Molecular cues for immune cells from small leucine-rich repeat proteoglycans in their extracellular matrix-associated and free forms

In this review we highlight emerging immune regulatory functions of lumican, keratocan, fibromodulin, biglycan and decorin, which are members of the small leucine-rich proteoglycans (SLRP) of the extracellular matrix (ECM). These SLRPs have been studied extensively as collagen-fibril regulatory structural components of the skin, cornea, bone and cartilage in homeostasis. However, SLRPs released from a remodeling ECM, or synthesized by activated fibroblasts and immune cells contribute to an ECM-free pool in tissues and circulation, that may have a significant, but poorly understood foot print in inflammation and disease. Their molecular interactions and the signaling networks they influence also require investigations. Here we present studies on the leucine-rich repeat (LRR) motifs of SLRP core proteins, their evolutionary and functional relationships with other LRR pathogen recognition receptors, such as the toll-like receptors (TLRs) to bring some molecular clarity in the immune regulatory functions of SLRPs. We discuss molecular interactions of fragments and intact SLRPs, and how some of these interactions are likely modulated by glycosaminoglycan side chains. We integrate findings on molecular interactions of these SLRPs together with what is known about their presence in circulation and lymph nodes (LN), which are important sites of immune cell regulation. Recent bulk and single cell RNA sequencing studies have identified subsets of stromal reticular cells that express these SLRPs within LNs. An understanding of the cellular source, molecular interactions and signaling consequences will lead to a fundamental understanding of how SLRPs modulate immune responses, and to therapeutic tools based on these SLRPs in the future.

XBP1 Modulates the Aging Cardiorenal System by Regulating Oxidative Stress

X-box binding protein 1 (XBP1) is a unique basic-region leucine zipper (bZIP) transcription factor. Over recent years, the powerful biological functions of XBP1 in oxidative stress have been gradually revealed. When the redox balance remains undisturbed, oxidative stress plays a role in physiological adaptations and signal transduction. However, during the aging process, increased cellular senescence and reduced levels of endogenous antioxidants cause an oxidative imbalance in the cardiorenal system. Recent studies from our laboratory and others have indicated that these age-related cardiorenal diseases caused by oxidative stress are guided and controlled by a versatile network composed of diversified XBP1 pathways. In this review, we describe the mechanisms that link XBP1 and oxidative stress in a range of cardiorenal disorders, including mitochondrial instability, inflammation, and alterations in neurohumoral drive. Furthermore, we propose that differing degrees of XBP1 activation may cause beneficial or harmful effects in the cardiorenal system. Gaining a comprehensive understanding of how XBP1 exerts influence on the aging cardiorenal system by regulating oxidative stress will enhance our ability to provide new directions and strategies for cardiovascular and renal safety outcomes.

An integrated organoid omics map extends modeling potential of kidney disease

Kidney organoids are a promising model to study kidney disease, but their use is constrained by limited knowledge of their functional protein expression profile. Here, we define the organoid proteome and transcriptome trajectories over culture duration and upon exposure to TNFα, a cytokine stressor. Older organoids increase deposition of extracellular matrix but decrease expression of glomerular proteins. Single cell transcriptome integration reveals that most proteome changes localize to podocytes, tubular and stromal cells. TNFα treatment of organoids results in 322 differentially expressed proteins, including cytokines and complement components. Transcript expression of these 322 proteins is significantly higher in individuals with poorer clinical outcomes in proteinuric kidney disease. Key TNFα-associated protein (C3 and VCAM1) expression is increased in both human tubular and organoid kidney cell populations, highlighting the potential for organoids to advance biomarker development. By integrating kidney organoid omic layers, incorporating a disease-relevant cytokine stressor and comparing with human data, we provide crucial evidence for the functional relevance of the kidney organoid model to human kidney disease.

Identification of the core genes in Randall's plaque of kidney stone and immune infiltration with WGCNA network

Background: Randall's plaque is regarded as the precursor lesion of lithiasis. However, traditional bioinformatic analysis is limited and ignores the relationship with immune response. To investigate the underlying calculi formation mechanism, we introduced innovative algorithms to expand our understanding of kidney stone disease. Methods: We downloaded the GSE73680 series matrix from the Gene Expression Omnibus (GEO) related to CaOx formation and excluded one patient, GSE116860. In the RStudio (R version 4.1.1) platform, the differentially expressed genes (DEGs) were identified with the limma package for GO/KEGG/GSEA analysis in the clusterProfiler package. Furthermore, high-correlated gene co-expression modules were confirmed by the WGCNA package to establish a protein-protein interaction (PPI) network. Finally, the CaOx samples were processed by the CIBERSORT algorithm to anchor the key immune cells group and verified in the validation series matrix GSE117518. Results: The study identified 840 upregulated and 1065 downregulated genes. The GO/KEGG results revealed fiber-related or adhesion-related terms and several pathways in addition to various diseases identified from the DO analysis. Moreover, WGCNA selected highly correlated modules to construct a PPI network. Finally, 16 types of immune cells are thought to participate in urolithiasis pathology and are related to hub genes in the PPI network that are proven significant in the validation series matrix GSE117518. Conclusion: Randall's plaque may relate to genes DCN, LUM, and P4HA2 and M2 macrophages and resting mast immune cells. These findings could serve as potential biomarkers and provide new research directions.

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.

The Involvement of Alarmins in the Pathogenesis of Sjögren's Syndrome

Sjögren’s syndrome (SS) is a chronic autoimmune disease that affects exocrine glands, primarily the salivary and lachrymal glands. It is characterized by lymphoplasmacytic infiltration of the glandular tissues, ultimately leading to their dysfunction and destruction. Besides classic dry eyes and dry mouth defined as sicca syndrome, patients affected by the disease also typically display symptoms such as fatigue, pain and in more than 50% of cases, systemic manifestations such as arthritis, interstitial lung involvement, neurological involvement and an increased risk of lymphoma. The pathophysiological mechanisms underlying SS still remain elusive. The crucial role of innate immunity has been advocated in recent years regarding the pathogenesis of pSS, especially in the initiation and progression toward autoimmunity. Alarmins are endogenous molecules that belong to the large family of damage associated molecular pattern (DAMP). Alarmins are rapidly released, ensuing cell injury and interacting with pattern recognition receptors (PRR) such as toll-like receptors (TLR) to recruit and activate cells of the innate immune system and to promote adaptive immunity responses. This review highlights the current knowledge of various alarmins and their role in the pathogenesis of pSS.

The role of biglycan in the healthy and thoracic aneurysmal aorta

The class I small leucine-rich proteoglycan biglycan is a crucial structural extracellular matrix component that interacts with a wide range of extracellular matrix molecules. In addition, biglycan is involved in sequestering growth factors such as TGF-β and BMPs and thereby regulating pathway activity. Biglycan consists of a 42-kDa core protein linked to two glycosaminoglycan side chains and both are involved in protein interactions. Biglycan is encoded by the BGN gene located on the X-chromosome and is expressed in various tissues, including vascular tissue, skin, brain, kidney lung, the immune system and the musculoskeletal system. Although an increasing amount of data on the biological function of biglycan in the vasculature has been produced, its role in thoracic aortic aneurysms is still not fully elucidated. This review focusses on the role of biglycan in the healthy thoracic aorta and the development of thoracic aortic aneurysm and dissections in both mice and humans.

Biglycan Promotes Cancer Stem Cell Properties, NFκB Signaling and Metastatic Potential in Breast Cancer Cells

Simple Summary

Breast cancer stem cells (BCSCs) are a small sub-population of cells within tumors with high metastatic potential. We identified biglycan (BGN) as a prospective molecular target in BCSCs that regulates the aggressive phenotypes of these cells. These findings establish a foundation for the development of therapeutics against BGN to eliminate BCSCs and prevent metastatic breast cancer.

Abstract

It is a major challenge to treat metastasis due to the presence of heterogenous BCSCs. Therefore, it is important to identify new molecular targets and their underlying molecular mechanisms in various BCSCs to improve treatment of breast cancer metastasis. Here, we performed RNA sequencing on two distinct co-existing BCSC populations, ALDH⁺ and CD29^hi CD61⁺ from PyMT mammary tumor cells and detected upregulation of biglycan (BGN) in these BCSCs. Genetic depletion of BGN reduced BCSC proportions and tumorsphere formation. Furthermore, BCSC associated aggressive traits such as migration and invasion were significantly reduced by depletion of BGN. Glycolytic and mitochondrial metabolic assays also revealed that BCSCs exhibited decreased metabolism upon loss of BGN. BCSCs showed decreased activation of the NFκB transcription factor, p65, and phospho-IκB levels upon BGN ablation, indicating regulation of NFκB pathway by BGN. To further support our data, we also characterized CD24⁻/CD44⁺ BCSCs from human luminal MCF-7 breast cancer cells. These CD24⁻/CD44⁺ BCSCs similarly exhibited reduced tumorigenic phenotypes, metabolism and attenuation of NFκB pathway after knockdown of BGN. Finally, loss of BGN in ALDH⁺ and CD29^hi CD61⁺ BCSCs showed decreased metastatic potential, suggesting BGN serves as an important therapeutic target in BCSCs for treating metastasis of breast cancer.

Damage associated molecular patterns in necrotic femoral head inhibit osteogenesis and promote fibrogenesis of mesenchymal stem cells

In Legg-Calvé-Perthes disease (LCPD), a loss of blood supply to the juvenile femoral head leads to extensive cell death and release of damage-associated molecular patterns (DAMPs). Over time chronic inflammatory repair process is observed with impaired bone regeneration. Increased fibrous tissue and adipose tissue are seen in the marrow space with decreased osteogenesis in a piglet model of LCPD, suggesting inhibition of osteoblastic differentiation and stimulation of fibroblastic and adipogenic differentiation of mesenchymal stem cell (MSC) during the healing process. Little is known about the DAMPs present in the necrotic femoral head and their effects on MSC differentiation. The purpose of this study was to characterize the DAMPs present in the femoral head following ischemic osteonecrosis and to determine their effects on MSC differentiation. Necrotic femoral heads were flushed with saline at 48 h, 2 weeks and 4 weeks following the induction of ischemic osteonecrosis in piglets to obtain necrotic bone fluid (NBF). Western blot analysis of the NBF revealed the presence of prototypic DAMP, high mobility group box 1 (HMGB1), and other previously described DAMPs: biglycan, 4-hydroxynonenal (4-HNE), and receptor activator of NF-κB ligand (RANKL). ELISA of the NBF revealed increasing levels of inflammatory cytokines IL1β, IL6 and TNFα with the temporal progression of osteonecrosis. To determine the effects of NBF on MSC differentiation, we cultured primary porcine MSCs with NBF obtained by in vivo necrotic bone flushing method. NBF inhibited osteoblastic differentiation of MSCs with significantly decreased OSX expression (p = 0.008) and Von Kossa/Alizarin Red staining for mineralization. NBF also significantly increased the expression of proliferation markers Ki67 (p = 0.03) and PCNA (p < 0.0001), and fibrogenic markers Vimentin (p = 0.02) and Fibronectin (p = 0.04). Additionally, NBF treated MSC cells showed significantly elevated RANKL/OPG secretion ratio (p = 0.003) and increased expression of inflammatory cytokines IL1β (p = 0.006) and IL6 (p < 0.0001). To specifically assess the role of DAMPs in promoting the fibrogenesis, we treated porcine fibroblasts with artificial NBF produced by bone freeze-thaw method. We found increased fibroblastic cell proliferation in an NBF dose-dependent manner. Lastly, we studied the effect of HMGB1, a prototypic DAMP, and found that HMGB1 partially contributes to MSC proliferation and fibrogenesis. In summary, our findings show that DAMPs and the inflammatory cytokines present in the necrotic femoral head inhibit osteogenesis and promote fibrogenesis of MSCs, potentially contributing to impaired bone regeneration following ischemic osteonecrosis as observed in LCPD.

Inhibition of the renin-angiotensin system causes concentric hypertrophy of renal arterioles in mice and humans

Inhibitors of the renin-angiotensin system (RAS) are widely used to treat hypertension. Using mice harboring fluorescent cell lineage tracers, single-cell RNA-Seq, and long-term inhibition of RAS in both mice and humans, we found that deletion of renin or inhibition of the RAS leads to concentric thickening of the intrarenal arteries and arterioles. This severe disease was caused by the multiclonal expansion and transformation of renin cells from a classical endocrine phenotype to a matrix-secretory phenotype: the cells surrounded the vessel walls and induced the accumulation of adjacent smooth muscle cells and extracellular matrix, resulting in blood flow obstruction, focal ischemia, and fibrosis. Ablation of the renin cells via conditional deletion of β1 integrin prevented arteriolar hypertrophy, indicating that renin cells are responsible for vascular disease. Given these findings, prospective morphological studies in humans are necessary to determine the extent of renal vascular damage caused by the widespread use of inhibitors of the RAS.

The Role of Decorin and Biglycan Signaling in Tumorigenesis

The complex and adaptive nature of malignant neoplasm constitute a major challenge for the development of effective anti-oncogenic therapies. Emerging evidence has uncovered the pivotal functions exerted by the small leucine-rich proteoglycans, decorin and biglycan, in affecting tumor growth and progression. In their soluble forms, decorin and biglycan act as powerful signaling molecules. By receptor-mediated signal transduction, both proteoglycans modulate key processes vital for tumor initiation and progression, such as autophagy, inflammation, cell-cycle, apoptosis, and angiogenesis. Despite of their structural homology, these two proteoglycans interact with distinct cell surface receptors and thus modulate distinct signaling pathways that ultimately affect cancer development. In this review, we summarize growing evidence for the complex roles of decorin and biglycan signaling in tumor biology and address potential novel therapeutic implications.

Plasma Levels of Decorin Increased in Patients during the Progression of Breast Cancer

Decorin (DCN), an extracellular matrix proteoglycan found in tumor surrounding tissues, is a natural inhibitor of tumor cell proliferation and invasion. We conducted a cross-sectional observation study to evaluate the association of the pathological stage with the levels of DCN in plasma or tumor surrounding tissue. Among 118 patients who underwent breast surgery, 35 were designated as carcinoma in situ (Stage 0), 39 were Stage I, and 44 were Stage II or III. The stromal expression of DCN was quantified using a semiquantitative digital image analysis after immunohistochemical staining. The concentration of DCN was evaluated with a specific ELISA. As we have previously shown, stromal DCN expression was attenuated in the patients with Stage I, whereas stromal and plasma DCN was elevated paradoxically in those with Stage II/III. The elevated plasma DCN is an independent predictive factor of Stage II/III by the multivariate logistic regression analysis. The plasma level of DCN was negatively correlated with stromal DCN expression only in patients with advanced disease (Stage II/III). The plasma level of DCN could become a useful biomarker for patients in the advanced stages. Extensive studies and further assessments are warranted for evaluating the prognostic significance and tumor characteristics to understand the clinical significances of stromal and systemic DCN.

Biglycan: an emerging small leucine-rich proteoglycan (SLRP) marker and its clinicopathological significance

Extracellular matrix (ECM) plays an important role in the structural organization of tissue and delivery of external cues to the cell. Biglycan, a class I small leucine-rich proteoglycans (SLRP), is a key component of the ECM that participates in scaffolding the collagen fibrils and mediates cell signaling. Dysregulation of biglycan expression can result in wide range of clinical conditions such as metabolic disorder, inflammatory disorder, musculoskeletal defects and malignancies. In this review, we aim to update our current understanding regarding the link between altered expression of biglycan and different clinicopathological states. Biglycan interacts with toll like receptors (TLR)-2 and TLR-4 on the immune cells which initiates inflammation and aggravates inflammatory disorders. ECM unbound soluble biglycan acts as a DAMP (danger associated molecular pattern) resulting in sterile inflammation. Dysregulation of biglycan expression is also observed in inflammatory metabolic conditions such as atherosclerosis and obesity. In cancer, high-biglycan expression facilitates tumor growth, invasion and metastasis which is associated with poor clinical outcome. As a pivotal structural component of the ECM, biglycan strengthens the musculoskeletal system and its absence is associated with musculoskeletal defects. Thus, SLRP biglycan is a potential marker which is significantly altered in different clinicopathological states.

Matrix lumican endocytosed by immune cells controls receptor ligand trafficking to promote TLR4 and restrict TLR9 in sepsis

Infections and inflammation are profoundly influenced by the extracellular matrix (ECM), but their molecular underpinnings are ill defined. Here, we demonstrate that lumican, an ECM protein normally associated with collagens, is elevated in sepsis patients' blood, while lumican-null mice resolve polymicrobial sepsis poorly, with reduced bacterial clearance and greater body weight loss. Secreted by activated fibroblasts, lumican promotes Toll-like receptor (TLR) 4 response to bacterial lipopolysaccharides (LPS) but restricts nucleic acid-specific TLR9 in macrophages and dendritic cells. The underlying mechanism involves lumican attachment to the common TLR coreceptor CD14 and caveolin 1 (Cav1) in lipid rafts on immune cell surfaces via two epitopes, which may be cryptic in collagen-associated lumican. The Cav1 binding epitope alone is sufficient for cell surface enrichment of Cav1, while both are required for lumican to increase cell surface TLR4, CD14, and proinflammatory cytokines in response to LPS. Endocytosed lumican colocalizes with TLR4 and LPS and promotes endosomal induction of type I interferons. Lumican-null macrophages show elevated TLR9 in signal-permissive endolysosomes and increased response, while wild types show lumican colocalization with CpG DNA but not TLR9, consistent with a ligand sequestering, restrictive role for lumican in TLR9 signaling. In vitro, lumican competes with CD14 to bind CpG DNA; biglycan, a lumican paralog, also binds CpG DNA and suppresses TLR9 response. Thus, lumican and other ECM proteins, synthesized de novo or released from collagen association during ECM remodeling, may be internalized by immune cells to regulate their transcriptional programs and effector responses that may be harnessed in future therapeutics.

Biglycan, tumor endothelial cell secreting proteoglycan, as possible biomarker for lung cancer

OBJECTIVES

In lung cancer, surgery remains the most curative treatment and limited resection is beneficial for patients with low cardiopulmonary function and low malignancy tumors. However, there are no biomarkers of low malignancy to select candidates for limited resection without compromising the outcome of treatments. Recently we identified biglycan (BGN) as a tumor endothelial cell (TEC) marker that is associated with tumor progression in various cancers. In this study, we analyzed the association between BGN expression in TECs in lung cancer and cancer progression in patients.

MATERIALS AND METHODS

First, we performed immunohistochemistry of BGN with resected lung tumor tissues of 155 patients who had undergone thoracic surgery and analyzed the correlation between BGN-positive vessel density in primary lung tumors and clinicopathological factors. Second, we measured the BGN levels in preoperative serum of other 46 patients with lung cancer by ELISA, and analyzed the correlation between BGN expression in tumor tissues and blood BGN levels.

RESULTS

High BGN expression in the TECs was significantly associated with T factor, and was a significant negative predictor. BGN levels in preoperative serum of 46 patients with lung cancer was significantly correlated with BGN expression in the TECs. Preoperative serum BGN level was significantly lower in healthy volunteers and less invasive adenocarcinoma than in invasive adenocarcinoma and other lung carcinomas. These results suggest that low BGN level in preoperative serum in patients with lung cancer might indicate low malignancy.

CONCLUSIONS

BGN can be a potential biomarker for lung cancer.

Use of amnion-derived cellular cytokine solution for the treatment of gingivitis: A 2-week safety, dose-ranging, proof-of-principle randomized trial

Background

A 6‐week Phase I clinical trial was performed to primarily evaluate the safety and secondarily determine the preliminary efficacy of a novel biological solution, ST266, comprised of a mixture of cytokines, growth factors, nucleic acids, and lipids secreted by cultured amnion‐derived multipotent progenitor cells on gingival inflammation.

Methods

Fifty‐four adults with gingivitis/periodontitis were randomly assigned to 1X ST266 or diluted 0.3X ST266 or saline topically applied on facial/lingual gingiva (20 µL/tooth). Safety was assessed through oral soft/hard tissue exam, adverse events, and routine laboratory tests. Efficacy was assessed by modified gingival index (MGI), bleeding on probing, plaque index, probing depth (PD), and clinical attachment level (CAL). Assessments were performed on day 0, 8, 12, and 42. ST266 and saline applied daily starting at day 0 through day 12 except weekend days. Plasma was analyzed for safety and proinflammatory cytokines, interleukin (IL)‐1β, IL‐6, tumor necrosis factor‐alpha, and interferon gamma. Gingival crevicular fluid (GCF) was analyzed for the same cytokines. Subgingival plaque was primarily analyzed by checkerboard DNA‐DNA hybridization. Comparisons with saline were modeled through a generalized estimating equations method adjusting for baseline.

Results

No safety concern was found related to ST266. Statistically significant reduction in MGI was noted at day 42 by 1X ST266 compared with saline (P = 0.044). PD and CAL were reduced by both doses of ST266 at day 42 (P <0.01) and by 1X ST266 at day 12 (P <0.05). GCF IL‐1β and IL‐6 levels were reduced by both doses of ST266 at day 12 (P <0.05, P <0.01, respectively). IL‐6 was also significantly reduced in plasma of both ST266 groups (P <0.05). Significant reductions in red complex bacteria were detected in both ST266 doses.

Conclusions

In this “first in human oral cavity” study, topical ST266 was safe and effective in reducing gingival inflammation in 6 weeks. Longitudinal studies with large sample sizes are warranted to assess the therapeutic value of this novel host modulatory compound in the treatment of periodontal diseases.

The Damage-Associated Molecular Patterns (DAMPs) as Potential Targets to Treat Osteoarthritis: Perspectives From a Review of the Literature

During the osteoarthritis (OA) process, activation of immune systems, whether innate or adaptive, is strongly associated with low-grade systemic inflammation. This process is initiated and driven in the synovial membrane, especially by synovium cells, themselves previously activated by damage-associated molecular patterns (DAMPs) released during cartilage degradation. These fragments exert their biological activities through pattern recognition receptors (PRRs) that, as a consequence, induce the activation of signaling pathways and beyond the release of inflammatory mediators, the latter contributing to the vicious cycle between cartilage and synovial membrane. The primary endpoint of this review is to provide the reader with an overview of these many molecules categorized as DAMPs and the contribution of the latter to the pathophysiology of OA. We will also discuss the different strategies to control their effects. We are convinced that a better understanding of DAMPs, their receptors, and associated pathological mechanisms represents a decisive issue for degenerative joint diseases such as OA.

Extracellular Matrix Remodeling in Chronic Liver Disease

PURPOSE OF THE REVIEW

This review aims to summarize the current knowledge of the extracellular matrix remodeling during hepatic fibrosis. We discuss the diverse interactions of the extracellular matrix with hepatic cells and the surrounding matrix in liver fibrosis, with the focus on the molecular pathways and the mechanisms that regulate extracellular matrix remodeling.

RECENT FINDINGS

The extracellular matrix not only provides structure and support for the cells, but also controls cell behavior by providing adhesion signals and by acting as a reservoir of growth factors and cytokines.

SUMMARY

Hepatic fibrosis is characterized by an excessive accumulation of extracellular matrix. During fibrogenesis, the natural remodeling process of the extracellular matrix varies, resulting in the excessive accumulation of its components, mainly collagens. Signals released by the extracellular matrix induce the activation of hepatic stellate cells, which are the major source of extracellular matrix and most abundant myofibroblasts in the liver.

GRAPHICAL ABSTRACT

Communications via the Small Leucine-rich Proteoglycans: Molecular Specificity in Inflammation and Autoimmune Diseases

Inflammation is a highly regulated biological response of the immune system that is triggered by assaulting pathogens or endogenous alarmins. It is now well established that some soluble extracellular matrix constituents, such as small leucine-rich proteoglycans (SLRPs), can act as danger signals and trigger aseptic inflammation by interacting with innate immune receptors. SLRP inflammatory signaling cascade goes far beyond its canonical function. By choosing specific innate immune receptors, coreceptors, and adaptor molecules, SLRPs promote a switch between pro- and anti-inflammatory signaling, thereby determining disease resolution or chronification. Moreover, by orchestrating signaling through various receptors, SLRPs fine-tune inflammation and, despite their structural homology, regulate inflammatory processes in a molecule-specific manner. Hence, the overarching theme of this review is to highlight the molecular and functional specificity of biglycan-, decorin-, lumican-, and fibromodulin-mediated signaling in inflammatory and autoimmune diseases.

Immunomodulatory Role of the Extracellular Matrix Within the Liver Disease Microenvironment

Chronic liver disease when accompanied by underlying fibrosis, is characterized by an accumulation of extracellular matrix (ECM) proteins and chronic inflammation. Although traditionally considered as a passive and largely architectural structure, the ECM is now being recognized as a source of potent damage-associated molecular pattern (DAMP)s with immune-active peptides and domains. In parallel, the ECM anchors a range of cytokines, chemokines and growth factors, all of which are capable of modulating immune responses. A growing body of evidence shows that ECM proteins themselves are capable of modulating immunity either directly via ligation with immune cell receptors including integrins and TLRs, or indirectly through release of immunoactive molecules such as cytokines which are stored within the ECM structure. Notably, ECM deposition and remodeling during injury and fibrosis can result in release or formation of ECM-DAMPs within the tissue, which can promote local inflammatory immune response and chemotactic immune cell recruitment and inflammation. It is well described that the ECM and immune response are interlinked and mutually participate in driving fibrosis, although their precise interactions in the context of chronic liver disease are poorly understood. This review aims to describe the known pro-/anti-inflammatory and fibrogenic properties of ECM proteins and DAMPs, with particular reference to the immunomodulatory properties of the ECM in the context of chronic liver disease. Finally, we discuss the importance of developing novel biotechnological platforms based on decellularized ECM-scaffolds, which provide opportunities to directly explore liver ECM-immune cell interactions in greater detail.

The Yin and Yang of Alarmins in Regulation of Acute Kidney Injury

Acute kidney injury (AKI) is a major clinical burden affecting 20 to 50% of hospitalized and intensive care patients. Irrespective of the initiating factors, the immune system plays a major role in amplifying the disease pathogenesis with certain immune cells contributing to renal damage, whereas others offer protection and facilitate recovery. Alarmins are small molecules and proteins that include granulysins, high-mobility group box 1 protein, interleukin (IL)-1α, IL-16, IL-33, heat shock proteins, the Ca++ binding S100 proteins, adenosine triphosphate, and uric acid. Alarmins are mostly intracellular molecules, and their release to the extracellular milieu signals cellular stress or damage, generally leading to the recruitment of the cells of the immune system. Early studies indicated a pro-inflammatory role for the alarmins by contributing to immune-system dysregulation and worsening of AKI. However, recent developments demonstrate anti-inflammatory mechanisms of certain alarmins or alarmin-sensing receptors, which may participate in the prevention, resolution, and repair of AKI. This dual function of alarmins is intriguing and has confounded the role of alarmins in AKI. In this study, we review the contribution of various alarmins to the pathogenesis of AKI in experimental and clinical studies. We also analyze the approaches for the therapeutic utilization of alarmins for AKI.

Proteoglycans in Obesity-Associated Metabolic Dysfunction and Meta-Inflammation

Proteoglycans are a specific subset of glycoproteins found at the cell surface and in the extracellular matrix, where they interact with a plethora of proteins involved in metabolic homeostasis and meta-inflammation. Over the last decade, new insights have emerged on the mechanism and biological significance of these interactions in the context of diet-induced disorders such as obesity and type-2 diabetes. Complications of energy metabolism drive most diet-induced metabolic disorders, which results in low-grade chronic inflammation, thereby affecting proper function of many vital organs involved in energy homeostasis, such as the brain, liver, kidney, heart and adipose tissue. Here, we discuss how heparan, chondroitin and keratan sulfate proteoglycans modulate obesity-induced metabolic dysfunction and low-grade inflammation that impact the initiation and progression of obesity-associated morbidities.

Danger matrix molecules orchestrate CD14/CD44 signaling in cancer development

The tumor matrix together with inflammation and autophagy are crucial regulators of cancer development. Embedded in the tumor stroma are numerous proteoglycans which, in their soluble form, act as danger-associated molecular patterns (DAMPs). By interacting with innate immune receptors, the Toll-like receptors (TLRs), DAMPs autonomously trigger aseptic inflammation and can regulate autophagy. Biglycan, a known danger proteoglycan, can regulate the cross-talk between inflammation and autophagy by evoking a switch between pro-inflammatory CD14 and pro-autophagic CD44 co-receptors for TLRs. Thus, these novel mechanistic insights provide some explanation for the plethora of reports indicating that the same matrix-derived DAMP acts either as a promoter or suppressor of tumor growth. In this review we will summarize and critically discuss the role of the matrix-derived DAMPs biglycan, hyaluronan, and versican in regulating the TLR-, CD14- and CD44-signaling dialogue between inflammation and autophagy with particular emphasis on cancer development.

Complexity of matrix phenotypes

The extracellular matrix is engaged in an ever-evolving and elegant ballet of dynamic reciprocity that directly and bi-directionally regulates cell behavior. Homeostatic and pathophysiological changes in cell-matrix signaling cascades manifest as complex matrix phenotypes. Indeed, the extracellular matrix can be implicated in virtually every known human disease, thus, making it the most critical and dynamic "organ" in the human body. The overall goal of this Special Issue is to provide an accurate and inclusive functional definition that addresses the inherent complexity of matrix phenotypes. This goal is summarily achieved via a corpus of expertly written articles, reviews and original research, focused at answering this question empirically and fundamentally via state-of-the-art methods and research strategies.

Celastrol Induces Necroptosis and Ameliorates Inflammation via Targeting Biglycan in Human Gastric Carcinoma

Celastrol, a triterpene isolated from the root of traditional Chinese medicine Thunder of God Vine, possesses anti-cancer and anti-inflammatory activity to treat rheumatoid disease or as health product. Necroptosis is considered as a new approach to overcome chemotherapeutics resistance. However, whether celastrol exerts necroptosis leading to gastric cancer cell death is still unclear. Here, for the first time we showed that celastrol induced necroptosis in HGC27 and AGS gastric cancer cell lines. More importantly, celastrol down-regulated biglycan (BGN) protein, which is critical for gastric cancer migration and invasion. Furthermore, celastrol activated receptor-interacting protein 1 and 3 (RIP1 and RIP3) and subsequently promoted the translation of mixed-lineage kinase domain-like (MLKL) from cytoplasm to plasma membrane, leading to necroptosis of gastric cancer cell, which was blocked by over-expression BGN. In addition, celastrol suppressed the release of pro-inflammatory cytokines TNF-α and IL-8 in HGC27 and AGS cells, which was reversed by over-expression BGN. Taken together, we identified celastrol as a necroptosis inducer, activated RIP1/RIP3/MLKL pathway and suppressed the level of pro-inflammatory cytokines by down-regulating BGN in HGC-27 and AGS cells, which supported the feasibility of celastrol in gastric cancer therapy.

Sequencing and Combination of Systemic Therapy in Metastatic Renal Cell Carcinoma

CONTEXT

Introduction of additional new agents targeting the vascular endothelial growth factor receptor (VEGFR) and immune checkpoint inhibitors (ICIs) has completely modified the systemic treatment of metastatic renal cell carcinoma (mRCC) during the last years.

OBJECTIVE

A comprehensive (nonsystematic) review to determine the suggested sequence or combinations for the systemic treatment of mRCC.

EVIDENCE ACQUISITION

PubMed and abstracts from main conferences up to December 2018 were reviewed to retrieve the current evidence for treatment of mRCC. Search terms included renal cell carcinoma, systemic therapy, targeted therapy (TT), and immunotherapy.

EVIDENCE SYNTHESIS

Marked advances in the treatment of mRCC have been made with novel VEGFR tyrosine kinase inhibitors and multiple ICIs that have been included in the current treatment paradigm of mRCC. Remarkable advance has been made with the combination of double checkpoint blockade. The combination of ipilimumab and nivolumab compared with sunitinib has shown to increase the overall survival in the intermediate- and poor-risk patients based on the International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) model.

CONCLUSIONS

Double checkpoint blockade with ipilimumab and nivolumab has reported overall survival benefit in IMDC intermediate- and poor-risk patients, providing a durable response for a subset of patients. VEGF inhibitors remain the standard of care for favorable-risk patients in the first line. In the immediate future, more consolidated data on combination of VEGF-TT plus ICIs may show similar robust benefit with different safety profiles.

PATIENT SUMMARY

Multiple drugs and sequences are now accepted as effective treatment for metastatic renal cell carcinoma (mRCC). Combination of immune checkpoint inhibitors has shown to increase the overall survival in treatment-naïve mRCC patients. Combinations of immunotherapy and antiangiogenics may be another option in the near future. Outcomes of the first line will determine the sequence, although the best sequence has yet to be defined.

Identification of Key Genes and Candidated Pathways in Human Autosomal Dominant Polycystic Kidney Disease by Bioinformatics Analysis

Background/Aims: Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic form of kidney disease. High-throughput microarray analysis has been applied for elucidating key genes and pathways associated with ADPKD. Most genetic profiling data from ADPKD patients have been uploaded to public databases but not thoroughly analyzed. This study integrated 2 human microarray profile datasets to elucidate the potential pathways and protein-protein interactions (PPIs) involved in ADPKD via bioinformatics analysis in order to identify possible therapeutic targets. Methods: The kidney tissue microarray data of ADPKD patients and normal individuals were searched and obtained from NCBI Gene Expression Omnibus. Differentially expressed genes (DEGs) were identified, and enriched pathways and central node genes were elucidated using related websites and software according to bioinformatics analysis protocols. Seven DEGs were validated between polycystic kidney disease and control kidney samples by quantitative real-time polymerase chain reaction. Results: Two original human microarray datasets, GSE7869 and GSE35831, were integrated and thoroughly analyzed. In total, 6,422 and 1,152 DEGs were extracted from GSE7869 and GSE35831, respectively, and of these, 561 DEGs were consistent between the databases (291 upregulated genes and 270 downregulated genes). From 421 nodes, 34 central node genes were obtained from a PPI network complex of DEGs. Two significant modules were selected from the PPI network complex by using Cytotype MCODE. Most of the identified genes are involved in protein binding, extracellular region or space, platelet degranulation, mitochondrion, and metabolic pathways. Conclusions: The DEGs and related enriched pathways in ADPKD identified through this integrated bioinformatics analysis provide insights into the molecular mechanisms of ADPKD and potential therapeutic strategies. Specifically, abnormal decorin expression in different stages of ADPKD may represent a new therapeutic target in ADPKD, and regulation of metabolism and mitochondrial function in ADPKD may become a focus of future research.

Biglycan evokes autophagy in macrophages via a novel CD44/Toll-like receptor 4 signaling axis in ischemia/reperfusion injury

Biglycan, a small leucine-rich proteoglycan, acts as a danger signal and is classically thought to promote macrophage recruitment via Toll-like receptors (TLR) 2 and 4. We have recently shown that biglycan signaling through TLR 2/4 and the CD14 co-receptor regulates inflammation, suggesting that TLR co-receptors may determine whether biglycan-TLR signaling is pro- or anti-inflammatory. Here, we sought to identify other co-receptors and characterize their impact on biglycan-TLR signaling. We found a marked increase in the number of autophagic macrophages in mice stably overexpressing soluble biglycan. In vitro, stimulation of murine macrophages with biglycan triggered autophagosome formation and enhanced the flux of autophagy markers. Soluble biglycan also promoted autophagy in human peripheral blood macrophages. Using macrophages from mice lacking TLR2 and/or TLR4, CD14, or CD44, we demonstrated that the pro-autophagy signal required TLR4 interaction with CD44, a receptor involved in adhesion, migration, lymphocyte activation, and angiogenesis. In vivo, transient overexpression of circulating biglycan at the onset of renal ischemia/reperfusion injury (IRI) enhanced M1 macrophage recruitment into the kidneys of Cd44^+/+ and Cd44^-/- mice but not Cd14^-/- mice. The biglycan-CD44 interaction increased M1 autophagy and the number of renal M2 macrophages and reduced tubular damage following IRI. Thus, CD44 is a novel signaling co-receptor for biglycan, an interaction that is required for TLR4-CD44-dependent pro-autophagic activity in macrophages. Interfering with the interaction between biglycan and specific TLR co-receptors could represent a promising therapeutic intervention to curtail kidney inflammation and damage.

HMGB1 and repair: focus on the heart

High-mobility group box 1 (HMGB1) is one of the most abundant proteins in eukaryotes and the best characterized damage-associated molecular pattern (DAMP). The biological activities of HMGB1 depend on its subcellular location, context and post-translational modifications. Inside the nucleus, HMGB1 is engaged in many DNA events such as DNA repair, transcription regulation and genome stability; in the cytoplasm, its main function is to regulate the autophagic flux while in the extracellular environment, it possesses more complicated functions and it is involved in a large variety of different processes such as inflammation, migration, invasion, proliferation, differentiation and tissue regeneration. Due to this pleiotropy, the role of HMGB1 has been vastly investigated in various pathological diseases and a large number of studies have explored its function in cardiovascular pathologies. However, in this contest, the precise mechanism of action of HMGB1 and its therapeutic potential are still very controversial since is debated whether HMGB1 is involved in tissue damage or plays a role in tissue repair and regeneration. The main focus of this review is to provide an overview of the effects of HMGB1 in different ischemic heart diseases and to discuss its functions in these pathological conditions.

Anti-tumor responses to hypofractionated radiation in mice grafted with triple negative breast cancer is associated with decorin induction in peritumoral muscles

Triple negative breast cancer (TNBC) is the most lethal one for all types of breast cancer. Though radiotherapy is an efficient treatment, long-term survival rate of TNBC patients is still suboptimal. Hyprofractionated radiotherapy, an improved radiotherapy, has made an inspiring result in clinic. However, the mechanism underlying TNBC treated with hyprofractionated radiotherapy is not clear. Decorin (DCN) is a small poteoglycan of matrix which has an inhibitory effect on the breast cancer and is secreted by muscle under certain conditions. In this study, we demonstrated that peritumoral muscles secrete more DCN at higher dose irradiation than that at conventional irradiation dose in TNBC tumor-bearing mice. Thus, it indicates that DCN secreted from peritumoral muscle may be one of the reasons why hyprofractionated radiotherapy could inhibit the growth of TNBC more effectively. Moreover, we also indicated that the up-regulated DCN attenuated lung metastasis of TNBC. In conclusion, we demonstrated that hypofractionated radiation promotes the secretion of DCN in peritumoral muscle, thus enhancing the inhibitory effect on TNBC, which might help to optimize the strategy of radiotherapy for TNBC patients in the future.

Decoding fibrosis: Mechanisms and translational aspects

Fibrosis, a complex process of abnormal tissue healing which inevitably leads to loss of physiological organ structure and function, is a worldwide leading cause of death. Despite a large body of research over the last two decades, antifibrotic approaches are mainly limited to organ replacement therapy generating high costs of medical care. In this translational issue, a unique group of basic and clinical researchers provide meaningful answers to a desperate call of society for effective antifibrotic treatments. Fortunately, a plethora of novel fibrogenic factors and biomarkers has been identified. Noninvasive diagnostic methods and drug delivery systems have been recently developed for the management of fibrosis. Consequently, a large number of exciting clinical trials addressing comprehensive, organ and stage-specific mechanisms of fibrogenesis are ongoing. By critically addressing previously unsuccessful and novel promising therapeutic strategies, we aim to spread hope for future treatments of the various forms of organ fibrosis.

Targeting renal fibrosis: Mechanisms and drug delivery systems

Renal fibrosis is the common outcome of many chronic kidney diseases (CKD) independent of the underlying etiology. Despite a host of promising experimental data, currently available strategies only ameliorate or delay the progression of CKD but do not reverse fibrosis. One of the major impediments of translating novel antifibrotic strategies from bench to bedside is due to the intricacies of the drug delivery process. In this review, we briefly describe mechanisms of renal fibrosis and methods of drug transfer into the kidney. Various tools used in gene therapy to administer nucleic acids in vivo are discussed. Furthermore, we review the modes of action of protein- or peptide-based drugs with target-specific antibodies and cytokines incorporated in hydrogels. Additionally, we assess an intriguing new method to deliver drugs specifically to tubular epithelial cells via conjugation with ligands binding to the megalin receptor. Finally, plant-derived compounds with antifibrotic properties are also summarized.

Small Leucine-Rich Proteoglycans in Renal Inflammation: Two Sides of the Coin

It is now well-established that members of the small leucine-rich proteoglycan (SLRP) family act in their soluble form, released proteolytically from the extracellular matrix (ECM), as danger-associated molecular patterns (DAMPs). By interacting with Toll-like receptors (TLRs) and the inflammasome, the two SLRPs, biglycan and decorin, autonomously trigger sterile inflammation. Recent data indicate that these SLRPs, besides their conventional role as pro-inflammatory DAMPs, additionally trigger anti-inflammatory signaling pathways to tightly control inflammation. This is brought about by selective employment of TLRs, their co-receptors, various adaptor molecules, and through crosstalk between SLRP-, reactive oxygen species (ROS)-, and sphingolipid-signaling. In this review, the complexity of SLRP signaling in immune and kidney resident cells and its relevance for renal inflammation is discussed. We propose that the dichotomy in SLRP signaling (pro- and anti-inflammatory) allows for fine-tuning the inflammatory response, which is decisive for the outcome of inflammatory kidney diseases.

Danger-Associated Molecular Patterns Derived From the Extracellular Matrix Provide Temporal Control of Innate Immunity

It is evident that components of the extracellular matrix (ECM) act as danger-associated molecular patterns (DAMPs) through direct interactions with pattern recognition receptors (PRRs) including Toll-like receptors (TLRs) and inflammasomes. Through these interactions, ECM-derived DAMPs autonomously trigger sterile inflammation or prolong pathogen-induced responses through the production of proinflammatory mediators and the recruitment of leukocytes to sites of injury and infection. Recent research, however, suggests that ECM-derived DAMPs are additionally involved in the resolution and fine-tuning of inflammation by orchestrating the production of anti-inflammatory mediators that are required for the resolution of tissue inflammation and the transition to acquired immunity. Thus, in this review, we discuss the current knowledge of the interplay between ECM-derived DAMPs and the innate immune signaling pathways that are activated to provide temporal control of innate immunity.

Urothelial cancer proteomics provides both prognostic and functional information

Traditionally, bladder cancer has been classified based on histology features. Recently, some works have proposed a molecular classification of invasive bladder tumors. To determine whether proteomics can define molecular subtypes of  muscle invasive urothelial cancer (MIUC) and allow evaluating the status of biological processes and its clinical value. 58 MIUC patients who underwent curative surgical resection at our institution between 2006 and 2012 were included. Proteome was evaluated by high-throughput proteomics in routinely archive FFPE tumor tissue. New molecular subgroups were defined. Functional structure and individual proteins prognostic value were evaluated and correlated with clinicopathologic parameters. 1,453 proteins were quantified, leading to two MIUC molecular subgroups. A protein-based functional structure was defined, including several nodes with specific biological activity. The functional structure showed differences between subtypes in metabolism, focal adhesion, RNA and splicing nodes. Focal adhesion node has prognostic value in the whole population. A 6-protein prognostic signature, associated with higher risk of relapse (5 year DFS 70% versus 20%) was defined. Additionally, we identified two MIUC subtypes groups. Prognostic information provided by pathologic characteristics is not enough to understand MIUC behavior. Proteomics analysis may enhance our understanding of prognostic and classification. These findings can lead to improving diagnosis and treatment selection in these patients.

Signaling at the Crossroads: Matrix-Derived Proteoglycan and Reactive Oxygen Species Signaling

SIGNIFICANCE

Proteoglycans (PGs), besides their structural contribution, have emerged as dynamic components that mediate a multitude of cellular events. The various roles of PGs are attributed to their structure, spatial localization, and ability to act as ligands and receptors. Reactive oxygen species (ROS) are small mediators that are generated in physiological and pathological conditions. Besides their reactivity and ability to induce oxidative stress, a growing body of data suggests that ROS signaling is more relevant than direct radical damage in development of human pathologies. Recent Advances: Cell surface transmembrane PGs (syndecans, cluster of differentiation 44) represent receptors in diverse and complex transduction networks, which involve redox signaling with implications in cancer, fibrosis, renal dysfunction, or Alzheimer's disease. Through NADPH oxidase (NOX)-dependent ROS, the extracellular PG, hyaluronan is involved in osteoclastogenesis and cancer. The ROS sources, NOX1 and NOX4, increase biglycan-induced inflammation, while NOX2 is a negative regulator.

CRITICAL ISSUES

The complexity of the mechanisms that bring ROS into the light of PG biology might be the foundation of a new research area with significant promise for understanding health and disease. Important aspects need to be investigated in PG/ROS signaling: the discovery of specific targets of ROS, the precise ROS-induced chemical modifications of these targets, and the study of their pathological relevance.

FUTURE DIRECTIONS

As we become more and more aware of the interactions between PG and ROS signaling underlying intracellular communication and cell fate decisions, it is quite conceivable that this field will allow to identify new therapeutic targets.-Antioxid. Redox Signal. 27, 855-873.