The extracellular matrix protein matrilin-2 induces post-burn inflammatory responses as an endogenous danger signal

Kinetics of Inflammatory Mediators in the Immune Response to Burn Injury: Systematic Review and Meta-Analysis of Animal Studies

Burns are often accompanied by a dysfunctional immune response, which can lead to systemic inflammation, shock, and excessive scarring. The objective of this study was to provide insight into inflammatory pathways associated with burn-related complications. Because detailed information on the various inflammatory mediators is scattered over individual studies, we systematically reviewed animal experimental data for all reported inflammatory mediators. Meta-analyses of 352 studies revealed a strong increase in cytokines, chemokines, and growth factors, particularly 19 mediators in blood and 12 in burn tissue. Temporal kinetics showed long-lasting surges of proinflammatory cytokines in blood and burn tissue. Significant time-dependent effects were seen for IL-1β, IL-6, TGF-β1, and CCL2. The response of anti-inflammatory mediators was limited. Burn technique had a profound impact on systemic response levels. Large burn size and scalds further increased systemic, but not local inflammation. Animal characteristics greatly affected inflammation, for example, IL-1β, IL-6, and TNF-α levels were highest in young, male rats. Time-dependent effects and dissimilarities in response demonstrate the importance of appropriate study design. Collectively, this review presents a general overview of the burn-induced immune response exposing inflammatory pathways that could be targeted through immunotherapy for burn patients and provides guidance for experimental set-ups to advance burn research.

Low expression of TGF-β2 and matrilin2 in human aqueous humour with acute primary angle closure

Primary angle-closure glaucoma (PACG) is the leading cause of irreversible blindness in the world. Angle closure induced by pupil block and secondary iris synechia is the fundamental pathology of the PACG. The molecular mechanisms of angle closure have not yet been clearly illustrated. This study was designed to investigate the protein difference in the aqueous humour and explore new biomarker of the PACG. Aqueous humour (AH) was collected from patients with acute primary angle closure (APAC) and cataract (n = 10 in APAC group) and patients with cataract only (n = 10 in control group). Samples were pooled and measured using label-free proteome technology. Then, the differentially expressed proteins (DEPs) were verified by ELISA using independent AH samples (n = 20 each group). More than 400 proteins were revealed in both groups through proteomics. Comparing the two groups, there were 91DEPs. These proteins participate in biological activities such as inflammation, fibrosis, nerve growth and degeneration and metabolism. We found that the expression of transforming growth factor-β2 and matrilin2 was downregulated in the APAC group. The two proteins are related to inflammation and extracellular matrix formation, which might be involved in angle closure. This study characterized DEPs in AH of the APAC and found a downregulated protein matrilin2.

Plasma Proteomics Unveil Novel Immune Signatures and Biomarkers upon SARS-CoV-2 Infection

Several elements have an impact on COVID-19, including comorbidities, age and sex. To determine the protein profile changes in peripheral blood caused by a SARS-CoV-2 infection, a proximity extension assay was used to quantify 1387 proteins in plasma samples among 28 Finnish patients with COVID-19 with and without comorbidities and their controls. Key immune signatures, including CD4 and CD28, were changed in patients with comorbidities. Importantly, several unreported elevated proteins in patients with COVID-19, such as RBP2 and BST2, which show anti-microbial activity, along with proteins involved in extracellular matrix remodeling, including MATN2 and COL6A3, were identified. RNF41 was downregulated in patients compared to healthy controls. Our study demonstrates that SARS-CoV-2 infection causes distinct plasma protein changes in the presence of comorbidities despite the interpatient heterogeneity, and several novel potential biomarkers associated with a SARS-CoV-2 infection alone and in the presence of comorbidities were identified. Protein changes linked to the generation of SARS-CoV-2-specific antibodies, long-term effects and potential association with post-COVID-19 condition were revealed. Further study to characterize the identified plasma protein changes from larger cohorts with more diverse ethnicities of patients with COVID-19 combined with functional studies will facilitate the identification of novel diagnostic, prognostic biomarkers and potential therapeutic targets for patients with COVID-19.

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.

A genome-wide association meta-analysis identifies new eosinophilic esophagitis loci

BACKGROUND

Eosinophilic esophagitis (EoE) is a chronic inflammatory disorder of the esophagus marked by eosinophilic infiltration. Cumulative evidence indicates that the risk of EoE involves the complex interplay of both genetic and environmental factors. Because only a few genetic loci have been identified in EoE, the genetic underpinning of EoE remains largely elusive.

OBJECTIVE

We sought to identify genetic loci associated with EoE.

METHODS

Four EoE cohorts were genotyped using the Illumina single nucleotide polymorphism array platform, totaling 1,930 cases and 13,634 controls of European ancestry. Genotype imputation was performed with the Michigan Imputation Server using the Trans-Omics for Precision Medicine reference panel including whole-genome sequencing data from more than 100,000 individuals. Meta-analysis was conducted to identify potential novel genetic loci associated with EoE.

RESULTS

Our study identified 11 new genome-wide significant loci, of which 6 are common variant loci, including 5q31.1 (rs2106984, P = 4.16 × 10^-8; odds ratio [OR], 1.26, RAD50), 15q22.2 (rs2279293, P = 1.23 × 10^-10; OR, 0.69, RORA), and 15q23 (rs56062135, P = 2.91 × 10^-11; OR, 1.29, SMAD3), which have been previously associated with allergic conditions. Interestingly, a low-frequency synonymous mutation within the MATN2 gene was identified as the most significant single nucleotide polymorphism at the 8q22.1 locus. We also identified 5 sex-specific loci in the EoE cases, including an inflammatory bowel disease-associated locus at 9p24.1 (rs62541556, P = 4.4 × 10^-8; OR, 1.11, JAK2).

CONCLUSIONS

Our findings demonstrate shared genetic underpinnings between EoE and other immune-mediated diseases and provide novel candidate genes for therapeutic target identification and prioritization.

Damage-Associated Molecular Patterns and the Systemic Immune Consequences of Severe Thermal Injury

Thermal injury is often associated with a proinflammatory state resulting in serious complications. After a burn, the innate immune system is activated with subsequent immune cell infiltration and cytokine production. Although the innate immune response is typically beneficial, an excessive activation leads to cytokine storms, multiple organ failure, and even death. This overwhelming immune response is regulated by damage-associated molecular patterns (DAMPs). DAMPs are endogenous molecules that are actively secreted by immune cells or passively released by dead or dying cells that can bind to pathogen recognition receptors in immune and nonimmune cells. Recent studies involving animal models along with human studies have drawn great attention to the possible pathological role of DAMPs as an immune consequence of thermal injury. In this review, we outline DAMPs and their function in thermal injury, shedding light on the mechanism of sterile inflammation during tissue injury and identifying new immune targets for treating thermal injury.

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.