Amphiregulin may be a new biomarker of classically activated macrophages

LPS-induced extracellular AREG triggers macrophage pyroptosis through the EGFR/TLR4 signaling pathway

Amphiregulin (AREG), a member of the EGF family, exists as a transmembrane protein anchored to the cell surface. In response to external stimuli, its extracellular domain is released into the extracellular matrix through paracrine or autocrine signaling. However, its role in septic macrophage pyroptosis remains poorly understood. This study aims to investigate the role of extracellular AREG in septic macrophages, mice, and patients. We found that high expression of extracellular AREG was regulated by RPLP1 at the translation level, which increased the expression of IL-6, CCL2, and CCL3 protein, as well as Caspase 1, IL-1β, and Nlrp3 mRNA expression, resulting in macrophage pyroptosis. Mechanistically, macrophage pyroptosis was aggravated by extracellular AREG pretreatment, which was triggered by extracellular AREG and ATP (adenosine 5'-triphosphate). The AREG-neutralizing antibody reduced LPS-induced epidermal growth factor receptor (EGFR) activation, TLR4 expression, and pyroptosis. Extracellular AREG-induced macrophage pyroptosis decreased with EGFR and NF-κB inhibition, as well as TLR4 and Myd88 knockout. Additionally, DTT-pretreated extracellular AREG suppressed macrophage pyroptosis. In vivo, extracellular AREG attenuates systemic inflammation infiltration and delays survival in a septic mouse model. Furthermore, extracellular AREG mediates sepsis in humans, and genes involved in the AREG-mediated pyroptosis signaling pathway were highly expressed in patients with severe sepsis compared with those with general or moderate sepsis. Overall, LPS-induced extracellular AREG aggravated or triggered macrophage pyroptosis through the EGFR/TLR4/Myd88/NF-κB signaling pathway, providing promising treatment strategies for sepsis.

Single-cell analysis reveals the loss of FABP4-positive proliferating valvular endothelial cells relates to functional mitral regurgitation

BACKGROUND

Functional mitral regurgitation (MR) is a common form of mitral valve dysfunction that often persists even after surgical intervention, requiring reoperation in some cases. To advance our understanding of the pathogenesis of functional MR, it is crucial to characterize the cellular composition of the mitral valve leaflet and identify molecular changes in each cell subtype within the mitral valves of MR patients. Therefore, we aimed to comprehensively examine the cellular and molecular components of mitral valves in patients with MR.

METHODS

We conducted a single-cell RNA sequencing (scRNA-seq) analysis of mitral valve leaflets extracted from six patients who underwent heart transplantation. The cohort comprised three individuals with moderate-to-severe functional MR (MR group) and three non-diseased controls (NC group). Bioinformatics was applied to identify cell types, delineate cell functions, and explore cellular developmental trajectories and interactions. Key findings from the scRNA-seq analysis were validated using pathological staining to visualize key markers in the mitral valve leaflets. Additionally, in vitro experiments with human primary valvular endothelial cells were conducted to further support our results.

RESULTS

Our study revealed that valve interstitial cells are critical for adaptive valve remodelling, as they secrete extracellular matrix proteins and promote fibrosis. We discovered an abnormal decrease in a subpopulation of FABP4 (fatty acid binding protein 4)-positive proliferating valvular endothelial cells. The trajectory analysis identifies this subcluster as the origin of VECs. Immunohistochemistry on the expanded cohort showed a reduction of FABP4-positive VECs in patients with functional MR. Intervention experiments with primary cells indicated that FABP4 promotes proliferation and migration in mitral valve VECs and enhances TGFβ-induced differentiation.

CONCLUSIONS

Our study presented a comprehensive assessment of the mitral valve cellular landscape of patients with MR and sheds light on the molecular changes occurring in human mitral valves during functional MR. We found a notable reduction in the proliferating endothelial cell subpopulation of valve leaflets, and FABP4 was identified as one of their markers. Therefore, FABP4 positive VECs served as proliferating endothelial cells relates to functional mitral regurgitation. These VECs exhibited high proliferative and differentiative properties. Their reduction was associated with the occurrence of functional MR.

Mediators of monocyte chemotaxis and matrix remodeling are associated with mortality and pulmonary fibroproliferation in patients with severe COVID-19

Acute respiratory distress syndrome (ARDS) has a fibroproliferative phase that may be followed by pulmonary fibrosis. Pulmonary fibrosis following COVID-19 pneumonia has been described at autopsy and following lung transplantation. We hypothesized that protein mediators of tissue remodeling and monocyte chemotaxis are elevated in the plasma and endotracheal aspirates of critically ill patients with COVID-19 who subsequently develop features of pulmonary fibroproliferation. We enrolled COVID-19 patients admitted to the ICU with hypoxemic respiratory failure. (n = 195). Plasma was collected within 24h of ICU admission and at 7d. In mechanically ventilated patients, endotracheal aspirates (ETA) were collected. Protein concentrations were measured by immunoassay. We tested for associations between protein concentrations and respiratory outcomes using logistic regression adjusting for age, sex, treatment with steroids, and APACHE III score. In a subset of patients who had CT scans during hospitalization (n = 75), we tested for associations between protein concentrations and radiographic features of fibroproliferation. Among the entire cohort, plasma IL-6, TNF-α, CCL2, and Amphiregulin levels were significantly associated with in-hospital mortality. In addition, higher plasma concentrations of CCL2, IL-6, TNF-α, Amphiregulin, and CXCL12 were associated with fewer ventilator-free days. We identified 20/75 patients (26%) with features of fibroproliferation. Within 24h of ICU admission, no measured plasma proteins were associated with a fibroproliferative response. However, when measured 96h-128h after admission, Amphiregulin was elevated in those that developed fibroproliferation. ETAs were not correlated with plasma measurements and did not show any association with mortality, ventilator-free days (VFDs), or fibroproliferative response. This cohort study identifies proteins of tissue remodeling and monocyte recruitment are associated with in-hospital mortality, fewer VFDs, and radiographic fibroproliferative response. Measuring changes in these proteins over time may allow for early identification of patients with severe COVID-19 at risk for fibroproliferation.

Multiomic analysis of monocyte-derived alveolar macrophages in idiopathic pulmonary fibrosis

BACKGROUND

Monocyte-derived alveolar macrophages (Mo_AMs) are increasingly recognised as potential pathogenic factors for idiopathic pulmonary fibrosis (IPF). While scRNAseq analysis has proven valuable in the transcriptome profiling of Mo_AMs, the integration analysis of multi-omics may provide additional dimensions of understanding of these cellular populations.

METHODS

We performed multi-omics analysis on 116 scRNAseq, 119 bulkseq and five scATACseq lung tissue samples from IPF. We built a large-scale IPF scRNAseq atlas and conducted the Monocle 2/3 as well as the Cellchat to explore the developmental path and intercellular communication on Mo_AMs. We also reported the difference in metabolisms, tissue repair and phagocytosis between Mo_AMs and tissue-resident alveolar macrophages (TRMs). To determine whether Mo_AMs affected pulmonary function, we projected clinical phenotypes (FVC%pred) from the bulkseq dataset onto the scRNAseq atlas. Finally, we used scATATCseq to uncover the upstream regulatory mechanisms and determine key drivers in Mo_AMs.

RESULTS

We identified three Mo_AMs clusters and the trajectory analysis further validated the origin of these clusters. Moreover, via the Cellchat analysis, the CXCL12/CXCR4 axis was found to be involved in the molecular basis of reciprocal interactions between Mo_AMs and fibroblasts through the activation of the ERK pathway in Mo_AMs. SPP1_RecMacs (RecMacs, recruited macrophages) were higher in the low-FVC group than in the high-FVC group. Specifically, compared with TRMs, the functions of lipid and energetic metabolism as well as tissue repair were higher in Mo_AMs than TRMs. But, TRMs may have higher level of phagocytosis than TRMs. SPIB (PU.1), JUNB, JUND, BACH2, FOSL2, and SMARCC1 showed stronger association with open chromatin of Mo_AMs than TRMs. Significant upregulated expression and deep chromatin accessibility of APOE were observed in both SPP1_RecMacs and TRMs.

CONCLUSION

Through trajectory analysis, it was confirmed that SPP1_RecMacs derived from Monocytes. Besides, Mo_AMs may influence FVC% pred and aggravate pulmonary fibrosis through the communication with fibroblasts. Furthermore, distinctive transcriptional regulators between Mo_AMs and TRMs implied that they may depend on different upstream regulatory mechanisms. Overall, this work provides a global overview of how Mo_AMs govern IPF and also helps determine better approaches and intervention therapies.

Single-cell RNA sequencing analysis of vestibular schwannoma reveals functionally distinct macrophage subsets

BACKGROUND

Vestibular schwannomas (VSs) remain a challenge due to their anatomical location and propensity to growth. Macrophages are present in VS but their roles in VS pathogenesis remains unknown.

OBJECTIVES

The objective was to assess phenotypic and functional profile of macrophages in VS with single-cell RNA sequencing (scRNAseq).

METHODS

scRNAseq was carried out in three VS samples to examine characteristics of macrophages in the tumour. RT-qPCR was carried out on 10 VS samples for CD14, CD68 and CD163 and a panel of macrophage-associated molecules.

RESULTS

scRNAseq revealed macrophages to be a major constituent of VS microenvironment with three distinct subclusters based on gene expression. The subclusters were also defined by expression of CD163, CD68 and IL-1β. AREG and PLAUR were expressed in the CD68+CD163+IL-1β+ subcluster, PLCG2 and NCKAP5 were expressed in CD68+CD163+IL-1β- subcluster and AUTS2 and SPP1 were expressed in the CD68+CD163-IL-1β+ subcluster. RT-qPCR showed expression of several macrophage markers in VS of which CD14, ALOX15, Interleukin-1β, INHBA and Colony Stimulating Factor-1R were found to have a high correlation with tumour volume.

CONCLUSIONS

Macrophages form an important component of VS stroma. scRNAseq reveals three distinct subsets of macrophages in the VS tissue which may have differing roles in the pathogenesis of VS.

Amphiregulin in infectious diseases: Role, mechanism, and potential therapeutic targets

Amphiregulin (AREG) serves as a ligand for the epidermal growth factor receptor (EGFR) and is involved in vital biological functions, including inflammatory responses, tissue regeneration, and immune system function. Upon interaction with the EGFR, AREG initiates a series of signaling cascades necessary for several physiological activities, such as metabolism, cell cycle regulation, and cellular proliferation. Recent findings have provided evidence for the substantial role of AREG in maintaining the equilibrium of homeostasis in damaged tissues and preserving epithelial cell structure in the context of viral infections affecting the lungs. The development of resistance to influenza virus infection depends on the presence of type 1 cytokine responses. Following the eradication of the pathogen, the lungs are subsequently colonized by several cell types that are linked with type 2 immune responses. These cells contribute to the process of repairing and resolving the tissue injury and inflammation caused by infections. Following influenza infection, the activation of AREG promotes the regeneration of bronchial epithelial cells, enhancing the tissue's structural integrity and increasing the survival rate of infected mice. In the same manner, mice afflicted with influenza experience rapid mortality due to a subsequent bacterial infection in the pulmonary region when both bacterial and viral infections manifest concurrently inside the same host. The involvement of AREG in bacterial infections has been demonstrated. The gene AREG experiences increased transcriptional activity inside host cells in response to bacterial infections caused by pathogens such as Escherichia coli and Neisseria gonorrhea. In addition, AREG has been extensively studied as a mitogenic stimulus in epithelial cell layers. Consequently, it is regarded as a prospective contender that might potentially contribute to the observed epithelial cell reactions in helminth infection. Consistent with this finding, mice that lack the AREG gene exhibit a delay in the eradication of the intestinal parasite Trichuris muris. The observed delay is associated with a reduction in the proliferation rate of colonic epithelial cells compared to the infected animals in the control group. The aforementioned findings indicate that AREG plays a pivotal role in facilitating the activation of defensive mechanisms inside the epithelial cells of the intestinal tissue. The precise cellular sources of AREG in this specific context have not yet been determined. However, it is evident that the increased proliferation of the epithelial cell layer in infected mice is reliant on CD4+ T cells. The significance of this finding lies in its demonstration of the crucial role played by the interaction between immunological and epithelial cells in regulating the AREG-EGFR pathway. Additional research is necessary to delve into the cellular origins and signaling mechanisms that govern the synthesis of AREG and its tissue-protective properties, independent of infection.

Sex disparities in non-small cell lung cancer: mechanistic insights from a cRaf transgenic disease model

BACKGROUND

Women are at greater risk of developing non-small cell lung cancer (NSCLC), yet the underlying causes remain unclear.

METHODS

We performed whole genome scans in lung tumours of cRaf transgenic mice and identified miRNA, transcription factor and hormone receptor dependent gene regulations. We confirmed hormone receptors by immunohistochemistry and constructed regulatory gene networks by considering experimentally validated miRNA-gene and transcription factor-miRNA/gene targets. Bioinformatics, genomic foot-printing and gene enrichment analysis established sex-specific circuits of lung tumour growth. Translational research involved a large cohort of NSCLC patients. We evaluated commonalities in sex-specific NSCLC gene regulations between mice and humans and determined their prognostic value in Kaplan-Meier survival statistics and COX proportional hazard regression analysis.

FINDINGS

Overexpression of the cRaf kinase elicited an extraordinary 8-fold increase in tumour growth among females, and nearly 70% of the 112 differentially expressed genes (DEGs) were female specific. We identified oncogenes, oncomirs, tumour suppressors, cell cycle regulators and MAPK/EGFR signalling molecules, which prompted sex-based differences in NSCLC, and we deciphered a regulatory gene-network, which protected males from accelerated tumour growth. Strikingly, 41% of DEGs are targets of hormone receptors, and the majority (85%) are oestrogen receptor (ER) dependent. We confirmed the role of ER in a large cohort of NSCLC patients and validated 40% of DEGs induced by cRaf in clinical tumour samples.

INTERPRETATION

We report the molecular wiring that prompted sex disparities in tumour growth. This allowed us to propose the development of molecular targeted therapies by jointly blocking ER, CDK1 and arginase 2 in NSCLC.

FUNDING

We gratefully acknowledge the financial support of the Lower Saxony Ministry of Culture and Sciences and Volkswagen Foundation, Germany to JB (25A.5-7251-99-3/00) and of the Chinese Scholarship Council to SZ (202008080022). This publication is funded by the Deutsche Forschungsgemeinschaft (DFG) as part of the "Open Access Publikationskosten" program.

Mediators of monocyte chemotaxis and matrix remodeling are associated with the development of fibrosis in patients with COVID-19

Acute respiratory distress syndrome (ARDS) has a fibroproliferative phase that may be followed by pulmonary fibrosis. This has been described in patients with COVID-19 pneumonia, but the underlying mechanisms have not been completely defined. We hypothesized that protein mediators of tissue remodeling and monocyte chemotaxis are elevated in the plasma and endotracheal aspirates of critically ill patients with COVID-19 who subsequently develop radiographic fibrosis. We enrolled COVID-19 patients admitted to the ICU who had hypoxemic respiratory failure, were hospitalized and alive for at least 10 days, and had chest imaging done during hospitalization ( n = 119). Plasma was collected within 24h of ICU admission and at 7d. In mechanically ventilated patients, endotracheal aspirates (ETA) were collected at 24h and 48-96h. Protein concentrations were measured by immunoassay. We tested for associations between protein concentrations and radiographic evidence of fibrosis using logistic regression adjusting for age, sex, and APACHE score. We identified 39 patients (33%) with features of fibrosis. Within 24h of ICU admission, plasma proteins related to tissue remodeling (MMP-9, Amphiregulin) and monocyte chemotaxis (CCL-2/MCP-1, CCL-13/MCP-4) were associated with the subsequent development of fibrosis whereas markers of inflammation (IL-6, TNF-α) were not. After 1 week, plasma MMP-9 increased in patients without fibrosis. In ETAs, only CCL-2/MCP-1 was associated with fibrosis at the later timepoint. This cohort study identifies proteins of tissue remodeling and monocyte recruitment that may identify early fibrotic remodeling following COVID-19. Measuring changes in these proteins over time may allow for early detection of fibrosis in patients with COVID-19.

Collagen-Derived Dipeptides and Amino Acids Have Immunomodulatory Effects in M1-Differentiated RAW264.7 Cells and PBMC

A number of food components, such as polyphenols and phytonutrients, have immunomodulatory effects. Collagen has various bioactivities, such as antioxidative effects, the promotion of wound healing, and relieving symptoms of bone/joint disease. Collagen is digested into dipeptides and amino acids in the gastrointestinal tract and subsequently absorbed. However, the difference in immunomodulatory effects between collagen-derived dipeptides and amino acids is unknown. To investigate such differences, we incubated M1 macrophages or peripheral blood mononuclear cells (PBMC) with collagen-derived dipeptides (hydroxyproline-glycine (Hyp-Gly) and proline-hydroxyproline (Pro-Hyp)) and amino acids (proline (Pro), hydroxyproline (Hyp), and glycine (Gly)). We first investigated the dose dependency of Hyp-Gly on cytokine secretion. Hyp-Gly modulates cytokine secretion from M1 macrophages at 100 µM, but not at 10 µM and 1 µM. We then compared immunomodulatory effects between dipeptides and mixtures of amino acids on M1 macrophages and PBMC. There was, however, no difference in cytokine secretion between dipeptides and their respective amino acids. We conclude that collagen-derived dipeptides and amino acids have immunomodulatory effects on M1-differentiated RAW264.7 cells and PBMC and that there is no difference in the immunomodulatory effects between dipeptides and amino acids.

The Underexplored Landscape of Hypoxia-Inducible Factor 2 Alpha and Potential Roles in Tumor Macrophages: A Review

Low tissue oxygenation, termed hypoxia, is a characteristic of solid tumors with negative consequences. Tumor-associated macrophages (TAMs) accumulate in hypoxic tumor regions and correlate with worse outcomes in cancer patients across several tumor types. Thus, the molecular mechanism in which macrophages respond to low oxygen tension has been increasingly investigated in the last decade. Hypoxia stabilizes a group of hypoxia-inducible transcription factors (HIFs) reported to drive transcriptional programs involved in cell survival, metabolism, and angiogenesis. Though both tumor macrophage HIF-1α and HIF-2α correlate with unfavorable tumor microenvironments, most research focuses on HIF-1α as the master regulator of hypoxia signaling, because HIF-1α expression was originally identified in several cancer types and correlates with worse outcome in cancer patients. The relative contribution of each HIFα subunit to cell phenotypes is poorly understood especially in TAMs. Once thought to have overlapping roles, recent investigation of macrophage HIF-2α has demonstrated a diverse function from HIF-1α. Little work has been published on the differential role of hypoxia-dependent macrophage HIF-2α when compared to HIF-1α in the context of tumor biology. This review highlights cellular HIF-2α functions and emphasizes the gap in research investigating oxygen-dependent functions of tumor macrophage HIF-2α.

Mesenchymal Stem Cell Derived Extracellular Vesicles: Promising Nanomedicine for Cutaneous Wound Treatment

A skin wound represents a rupture caused by external damage or the existence of underlying pathological conditions. Sometimes, skin wound healing processes may place a heavy burden on patients, families, and society. Wound healing processes mainly consist of several continuous, dynamic, but overlapping stages, namely, the coagulation stage, inflammation stage, proliferation stage, and remodeling stage. Bacterial infection, excessive inflammation, impaired angiogenesis, and scar formation constitute the four significant factors impeding the recovery efficacy of skin wounds. This encourages scientists to develop multifunctional nanomedicines to meet challenging needs. As we know, mesenchymal stem cells (MSCs) have been widely explored for wound repair owing to their unique capability for self-renewal and multipotency. However, problems including immune concerns and legal restrictions should be properly resolved before MSC-based therapeutics are safely and widely used in clinics. Besides, maintaining the high viability/proliferation capability of MSCs during administration processes and therapy procedures is also one of the biggest technical bottlenecks. Extracellular vesicles (EVs) are cell-derived nanovesicles, that not only possess the basic characteristics and functions of their corresponding maternal cells but also contain several outstanding advantages including abundant sources, excellent biocompatibility, and convenient administration routes. Furthermore, the membrane surface and cavity are easy to flexibly modify to meet versatile application needs. Recently, MSC-derived EVs have emerged as promising therapeutics for skin wound repair. However, current reviews are too broad and rarely focused on the specific roles of EVs in the different stages of wound recovery. Therefore, it is quite necessary to demonstrate the significance of stem cell-derived EVs in promoting wound healing from several specific aspects. Here, this review primarily tries to provide critical comments on current advances in EVs derived from MSCs for wound repair, particularly elaborating on their impressive roles in effectively eliminating infections, inhibiting inflammation, promoting angiogenesis, and reducing scar formation. Last but not least, current limitations and future prospects of EVs derived from MSCs in the areas of wound repair are also objectively analyzed.

Aurantiamide promotes M2 polarization of microglial cells to improve the cognitive ability of mice with Alzheimer's disease

This work aimed to investigate the effect of aurantiamide (Aur) in promoting the M2 polarization of microglial cells to improve the cognitive ability of mice with Alzheimer's disease (AD). The M2 polarization of BV2 cells was induced by interleukin-4 (IL-4) treatment.Aur promoted the M2 polarization of BV2 cells, and up-regulated the expression of CD206 and SOCS3. In the meantime, it increased TGF-β1, Arg-1 and IL-10 levels, and promoted the polarization of JAK1-STAT6. Treatment with STAT6 inhibitor antagonized the effect of Aur. Besides, the cognitive ability of AD mice was improved after Aur treatment, meanwhile, the expression of CD206 was up-regulated, while that of IBA-1 was down-regulated. Aur promotes the M2 polarization of microglial cells to improve the cognitive ability of AD mice, and such effect is related to the STAT6 signal.

Macrophage-intrinsic DUOX1 contributes to type 2 inflammation and mucus metaplasia during allergic airway disease

The NADPH oxidase DUOX1 contributes to epithelial production of alarmins, including interleukin (IL)-33, in response to injurious triggers such as airborne protease allergens, and mediates development of mucus metaplasia and airway remodeling in chronic allergic airways diseases. DUOX1 is also expressed in non-epithelial lung cell types, including macrophages that play an important role in airway remodeling during chronic lung disease. We therefore conditionally deleted DUOX1 in either lung epithelial or monocyte/macrophage lineages to address its cell-specific actions in innate airway responses to acute airway challenge with house dust mite (HDM) allergen, and in chronic HDM-driven allergic airway inflammation. As expected, acute responses to airway challenge with HDM, as well as type 2 inflammation and related features of airway remodeling during chronic HDM-induced allergic inflammation, were largely driven by DUOX1 with the respiratory epithelium. However, in the context of chronic HDM-driven inflammation, DUOX1 deletion in macrophages also significantly impaired type 2 cytokine production and indices of mucus metaplasia. Further studies revealed a contribution of macrophage-intrinsic DUOX1 in macrophage recruitment upon chronic HDM challenge, as well as features of macrophage activation that impact on type 2 inflammation and remodeling.

Transcriptional and Histochemical Signatures of Bone Marrow Mononuclear Cell-Mediated Resolution of Synovitis

Osteoarthritis (OA) may result from impaired ability of synovial macrophages to resolve joint inflammation. Increasing macrophage counts in inflamed joints through injection with bone marrow mononuclear cells (BMNC) induces lasting resolution of synovial inflammation. To uncover mechanisms by which BMNC may affect resolution, in this study, differential transcriptional signatures of BMNC in response to normal (SF) and inflamed synovial fluid (ISF) were analyzed. We demonstrate the temporal behavior of co-expressed gene networks associated with traits from related in vivo and in vitro studies. We also identified activated and inhibited signaling pathways and upstream regulators, further determining their protein expression in the synovium of inflamed joints treated with BMNC or DPBS controls. BMNC responded to ISF with an early pro-inflammatory response characterized by a short spike in the expression of a NF-ƙB- and mitogen-related gene network. This response was associated with sustained increased expression of two gene networks comprising known drivers of resolution (IL-10, IGF-1, PPARG, isoprenoid biosynthesis). These networks were common to SF and ISF, but more highly expressed in ISF. Most highly activated pathways in ISF included the mevalonate pathway and PPAR-γ signaling, with pro-resolving functional annotations that improve mitochondrial metabolism and deactivate NF-ƙB signaling. Lower expression of mevalonate kinase and phospho-PPARγ in synovium from inflamed joints treated with BMNC, and equivalent IL-1β staining between BMNC- and DPBS-treated joints, associates with accomplished resolution in BMNC-treated joints and emphasize the intricate balance of pro- and anti-inflammatory mechanisms required for resolution. Combined, our data suggest that BMNC-mediated resolution is characterized by constitutively expressed homeostatic mechanisms, whose expression are enhanced following inflammatory stimulus. These mechanisms translate into macrophage proliferation optimizing their capacity to counteract inflammatory damage and improving their general and mitochondrial metabolism to endure oxidative stress while driving tissue repair. Such effect is largely achieved through the synthesis of several lipids that mediate recovery of homeostasis. Our study reveals candidate mechanisms by which BMNC provide lasting improvement in patients with OA and suggests further investigation on the effects of PPAR-γ signaling enhancement for the treatment of arthritic conditions.

Gene expression signatures identify paediatric patients with multiple organ dysfunction who require advanced life support in the intensive care unit

BACKGROUND

Multiple organ dysfunction syndrome (MODS) occurs in the setting of a variety of pathologies including infection and trauma. Some patients decompensate and require Veno-Arterial extra corporeal membrane oxygenation (ECMO) as a palliating manoeuvre for recovery of cardiopulmonary function. The molecular mechanisms driving progression from MODS to cardiopulmonary collapse remain incompletely understood, and no biomarkers have been defined to identify those MODS patients at highest risk for progression to requiring ECMO support.

METHODS

Whole blood RNA-seq profiling was performed for 23 MODS patients at three time points during their ICU stay (at diagnosis of MODS, 72 hours after, and 8 days later), as well as four healthy controls undergoing routine sedation. Of the 23 MODS patients, six required ECMO support (ECMO patients). The predictive power of conventional demographic and clinical features was quantified for differentiating the MODS and ECMO patients. We then compared the performance of markers derived from transcriptomic profiling including [1] transcriptomically imputed leukocyte subtype distribution, [2] relevant published gene signatures and [3] a novel differential gene expression signature computed from our data set. The predictive power of our novel gene expression signature was then validated using independently published datasets.

FINDING

None of the five demographic characteristics and 14 clinical features, including The Paediatric Logistic Organ Dysfunction (PELOD) score, could predict deterioration of MODS to ECMO at baseline. From previously published sepsis signatures, only the signatures positively associated with patient's mortality could differentiate ECMO patients from MODS patients, when applied to our transcriptomic dataset (P-value ranges from 0.01 to 0.04, Student's test). Deconvolution of bulk RNA-Seq samples suggested that lower neutrophil counts were associated with increased risk of progression from MODS to ECMO (P-value = 0.03, logistic regression, OR=2.82 [95% CI 0.63 - 12.45]). A total of 30 genes were differentially expressed between ECMO and MODS patients at baseline (log2 fold change ≥ 1 or ≤ -1 with false discovery rate ≤ 0.01). These genes are involved in protein maintenance and epigenetic-related processes. Further univariate analysis of these 30 genes suggested a signature of seven DE genes associated with ECMO (OR > 3.0, P-value ≤ 0.05, logistic regression). Notably, this contains a set of histone marker genes, including H1F0, HIST2H3C, HIST1H2AI, HIST1H4, HIST1H2BL and HIST1H1B, that were highly expressed in ECMO. A risk score derived from expression of these genes differentiated ECMO and MODS patients in our dataset (AUC = 0.91, 95% CI 0.79-1.00, P-value = 7e-04, logistic regression) as well as validation dataset (AUC= 0.73, 95% CI 0.53-0.93, P-value = 2e-02, logistic regression).

INTERPRETATION

This study demonstrates that transcriptomic features can serve as indicators of severity that could be superior to traditional methods of ascertaining acuity in MODS patients. Analysis of expression of signatures identified in this study could help clinicians in the diagnosis and prognostication of MODS patients after arrival to the Hospital.

Prenatal smoke exposure dysregulates lung epithelial cell differentiation in mouse offspring: role for AREG-induced EGFR signaling

Prenatal smoke exposure is a risk factor for impaired lung development in children. Recent studies have indicated that amphiregulin (AREG), which is a ligand of the epidermal growth factor receptor (EGFR), has a regulatory role in airway epithelial cell differentiation. In this study, we investigated the effect of prenatal smoke exposure on lung epithelial cell differentiation and linked this with AREG-EGFR signaling in 1-day-old mouse offspring. Bronchial and alveolar epithelial cell differentiations were assessed by immunohistochemistry. Areg, epidermal growth factor (Egf), and mRNA expressions of specific markers for bronchial and alveolar epithelial cells were assessed by RT-qPCR. The results in neonatal lungs were validated in an AREG-treated three-dimensional mouse lung organoid model. We found that prenatal smoke exposure reduced the number of ciliated cells and the expression of the cilia-related transcription factor Foxj1, whereas it resulted in higher expression of mucus-related transcription factors Spdef and Foxm1 in the lung. Moreover, prenatally smoke-exposed offspring had higher numbers of alveolar epithelial type II cells (AECII) and lower expression of the AECI-related Pdpn and Gramd2 markers. This was accompanied by higher expression of Areg and lower expression of Egf in prenatally smoke-exposed offspring. In bronchial organoids, AREG treatment resulted in fewer ciliated cells and more basal cells when compared with non-treated bronchiolar organoids. In alveolar organoids, AREG treatment led to more AECII cells than non-treated AECII cells. Taken together, the observed impaired bronchial and alveolar cell development in prenatally smoke-exposed neonatal offspring may be induced by increased AREG-EGFR signaling.

Macrophages in the pancreas: Villains by circumstances, not necessarily by actions

Introduction

Mounting evidence suggest that macrophages play crucial roles in disease and tissue regeneration. However, despite much efforts during the past decade, our knowledge about the extent of macrophages' contribution to adult pancreatic regeneration after injury or during pancreatic disease progression is still limited. Nevertheless, it is generally accepted that some macrophage features that normally would contribute to healing and regeneration may be detrimental in pancreatic cancer. Altogether, the current literature contains conflicting reports on whether macrophages act as friends or foe in these conditions.

Methods and Results

In this review, we briefly review the origins of tissue resident and infiltrating macrophages and the importance of cellular crosstalking between macrophages and other resident cells in tissue regeneration. The primary objective of this review is to summarize our knowledge of the distinct roles of tissue resident and infiltrating macrophages, the impact of M1 and M2 macrophage phenotypes, and emerging evidence on macrophage crosstalking in pancreatic injury, regeneration, and disease.

Conclusion

Macrophages are involved with various stages of pancreatic cancer development, pancreatitis, and diabetes. Elucidating their role in these conditions will aid the development of targeted therapeutic treatments.

Cytotoxic effects of dental prosthesis grinding dust on RAW264.7 cells

Respiratory diseases, including pulmonary fibrosis, silicosis, and allergic pneumonia, can be caused by long-term exposure to dental prosthesis grinding dust. The extent of the toxicity and pathogenicity of exposure to PMMA dust, Vitallium dust, and dentin porcelain dust differs. The dust from grinding dental prosthesis made of these three materials was characterized in terms of morphology, particle size, and elemental composition. The adverse effects of different concentrations of grinding dust (50, 150, 300, 450, and 600 μg ml-l) on RAW264.7 macrophages were evaluated, including changes in cell morphology and the production of lactate dehydrogenase (LDH) and reactive oxygen species (ROS). The dust particles released by grinding dental prosthesis made of these materials had different morphologies, particle sizes, and elemental compositions. They also induced varying degrees of cytotoxicity in RAW264.7 macrophages. A possible cytotoxicity mechanism is the induction of lipid peroxidation and plasma membrane damage as the dust particles penetrate cells. Therefore, clinicians who regularly work with these materials should wear the appropriate personal protection equipment to minimize exposure and reduce the health risks caused by these particulates.

Amphiregulin inhibits TNF-α-induced alveolar epithelial cell death through EGFR signaling pathway

BACKGROUND

We previously observed that amphiregulin (Areg), a ligand of epithelial growth factor receptor (EGFR), was highly expressed in lipopolysaccharide (LPS)-induced acute lung injury (ALI) lung tissues mainly by the classically activated (M1) alveolar macrophages (AMs). Areg also plays a protective role in LPS-induced injury in lung tissues and alveolar epithelial cells (AECs). However, whether Areg is co-expressed with tumor necrosis factor (TNF)-α in ALI lung tissues, and can directly inhibit TNF-α-induced AEC injury remains unclear.

METHODS

We first detected the kinetic expressions of Areg and TNF-α in LPS-stimulated lung tissues and M1 AMs and then identified the role of exogenous recombinant Areg (rmAreg) in the injured lung tissues. The effect of Areg on TNF-α-induced apoptosis in MLE-12 cells, a kind of AECs, was examined by terminal deoxynucleotidyl transferase dUTP nick end labeling staining. The activation of the EGFR-AKT pathway and caspase-3, -8, and -9 were detected by Western blotting. The EGFR knockdown by small interfering RNA was used to assess the role of EGFR in Areg functions.

RESULTS

Areg production occurred in close parallel with TNF-α expression in M1 AMs and ALI lung tissues, and rmAreg attenuated LPS-induced ALI in mice. TNF-α stimulation induced significant apoptosis in MLE-12 cells, but this apoptosis was inhibited under rmAreg treatment. Moreover, rmAreg enhanced the activation of EGFR and AKT, and reduced the expressions of cleaved caspase-3, -8, and -9 in ALI lung tissues and TNF-α-challenged MLE-12 cells. However, the EGFR knockdown significantly inhibited the Areg-induced improvement in apoptosis, enhancement of EGFR and AKT activation, and reduction of cleaved caspase-3, -8, and -9 expressions.

CONCLUSIONS

Areg and TNF-α were synchronously produced by ALI lung tissues and M1 AMs, and Areg directly inhibited the TNF-induced apoptosis and transduction of caspase death signals in AECs via the EGFR pathway.

Are Liver Pericytes Just Precursors of Myofibroblasts in Hepatic Diseases? Insights from the Crosstalk between Perivascular and Inflammatory Cells in Liver Injury and Repair

Cirrhosis, a late form of liver disease, is characterized by extensive scarring due to exacerbated secretion of extracellular matrix proteins by myofibroblasts that develop during this process. These myofibroblasts arise mainly from hepatic stellate cells (HSCs), liver-specific pericytes that become activated at the onset of liver injury. Consequently, HSCs tend to be viewed mainly as myofibroblast precursors in a fibrotic process driven by inflammation. Here, the molecular interactions between liver pericytes and inflammatory cells such as macrophages and neutrophils at the first moments after injury and during the healing process are brought into focus. Data on HSCs and pericytes from other tissues indicate that these cells are able to sense pathogen- and damage-associated molecular patterns and have an important proinflammatory role in the initial stages of liver injury. On the other hand, further data suggest that as the healing process evolves, activated HSCs play a role in skewing the initial proinflammatory (M1) macrophage polarization by contributing to the emergence of alternatively activated, pro-regenerative (M2-like) macrophages. Finally, data suggesting that some HSCs activated during liver injury could behave as hepatic progenitor or stem cells will be discussed.

Role of Epidermal Growth Factor Receptor (EGFR) and Its Ligands in Kidney Inflammation and Damage

Chronic kidney disease (CKD) is characterized by persistent inflammation and progressive fibrosis, ultimately leading to end-stage renal disease. Although many studies have investigated the factors involved in the progressive deterioration of renal function, current therapeutic strategies only delay disease progression, leaving an unmet need for effective therapeutic interventions that target the cause behind the inflammatory process and could slow down or reverse the development and progression of CKD. Epidermal growth factor receptor (EGFR) (ERBB1), a membrane tyrosine kinase receptor expressed in the kidney, is activated after renal damage, and preclinical studies have evidenced its potential as a therapeutic target in CKD therapy. To date, seven official EGFR ligands have been described, including epidermal growth factor (EGF) (canonical ligand), transforming growth factor-α, heparin-binding epidermal growth factor, amphiregulin, betacellulin, epiregulin, and epigen. Recently, the connective tissue growth factor (CTGF/CCN2) has been described as a novel EGFR ligand. The direct activation of EGFR by its ligands can exert different cellular responses, depending on the specific ligand, tissue, and pathological condition. Among all EGFR ligands, CTGF/CCN2 is of special relevance in CKD. This growth factor, by binding to EGFR and downstream signaling pathway activation, regulates renal inflammation, cell growth, and fibrosis. EGFR can also be “transactivated” by extracellular stimuli, including several key factors involved in renal disease, such as angiotensin II, transforming growth factor beta (TGFB), and other cytokines, including members of the tumor necrosis factor superfamily, showing another important mechanism involved in renal pathology. The aim of this review is to summarize the contribution of EGFR pathway activation in experimental kidney damage, with special attention to the regulation of the inflammatory response and the role of some EGFR ligands in this process. Better insights in EGFR signaling in renal disease could improve our current knowledge of renal pathology contributing to therapeutic strategies for CKD development and progression.

Serum proteome mapping of EGF transgenic mice reveal mechanistic biomarkers of lung cancer precursor lesions with clinical significance for human adenocarcinomas

Atypical adenomatous hyperplasia (AAH) of the lung is a pre-invasive lesion (PL) with high risk of progression to lung cancer (LC). However, the pathways involved are uncertain. We searched for novel mechanistic biomarkers of AAH in an EGF transgenic disease model of lung cancer. Disease regulated proteins were validated by Western immunoblotting and immunohistochemistry (IHC) of control and morphologically altered respiratory epithelium. Translational work involved clinical resection material. Collectively, 68 unique serum proteins were identified by 2DE-MALDI-TOF mass spectrometry and 13 reached statistical significance (p < 0.05). EGF, amphiregulin and the EGFR endosomal sorting protein VPS28 were induced up to 5-fold while IHC confirmed strong induction of these proteins. Furthermore, ApoA1, α-2-macroglobulin, and vitamin-D binding protein were nearly 6- and 2-fold upregulated in AAH; however, ApoA1 was oppositely regulated in LC to evidence disease stage dependent regulation of this tumour suppressor. Conversely, plasminogen and transthyretin were highly significantly repressed by 3- and 20-fold. IHC confirmed induced ApoA1, Fetuin-B and transthyretin expression to influence calcification, inflammation and tumour-infiltrating macrophages. Moreover, serum ApoA4, ApoH and ApoM were 2-, 2- and 6-fold repressed; however tissue ApoM and sphingosine-1-phosphate receptor expression was markedly induced to suggest a critical role of sphingosine-1-phosphate signalling in PL and malignant transformation. Finally, a comparison of three different LC models revealed common and unique serum biomarkers mechanistically linked to EGFR, cMyc and cRaf signalling. Their validation by IHC on clinical resection material established relevance for distinct human lung pathologies. In conclusion, we identified mechanistic biomarker candidates recommended for in-depth clinical evaluation.

Trefoil Factor 2 Promotes Type 2 Immunity and Lung Repair through Intrinsic Roles in Hematopoietic and Nonhematopoietic Cells

Trefoil factors (TFFs) are small secreted proteins that regulate tissue integrity and repair at mucosal surfaces, particularly in the gastrointestinal tract. However, their relative contribution(s) to controlling baseline lung function or the extent of infection-induced lung injury are unknown issues. With the use of irradiation bone marrow chimeras, we found that TFF2 produced from both hematopoietic- and nonhematopoietic-derived cells is essential for host protection, proliferation of alveolar type 2 cells, and restoration of pulmonary gas exchange after infection with the hookworm parasite Nippostrongylus brasiliensis. In the absence of TFF2, lung epithelia were unable to proliferate and expressed reduced lung mRNA transcript levels for type 2 response-inducing IL-25 and IL-33 after infectious injury. Strikingly, even in the absence of infection or irradiation, TFF2 deficiency compromised lung structure and function, as characterized by distended alveoli and reduced blood oxygen levels relative to wild-type control mice. Taken together, we show a previously unappreciated role for TFF2, produced by either hematopoietic or nonhematopoietic sources, as a pro-proliferative factor for lung epithelial cells under steady-state and infectious injury conditions.

The EGFR-ADAM17 Axis in Chronic Obstructive Pulmonary Disease and Cystic Fibrosis Lung Pathology

Chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF) share molecular mechanisms that cause the pathological symptoms they have in common. Here, we review evidence suggesting that hyperactivity of the EGFR/ADAM17 axis plays a role in the development of chronic lung disease in both CF and COPD. The ubiquitous transmembrane protease A disintegrin and metalloprotease 17 (ADAM17) forms a functional unit with the EGF receptor (EGFR), in a feedback loop interaction labeled the ADAM17/EGFR axis. In airway epithelial cells, ADAM17 sheds multiple soluble signaling proteins by proteolysis, including EGFR ligands such as amphiregulin (AREG), and proinflammatory mediators such as the interleukin 6 coreceptor (IL-6R). This activity can be enhanced by injury, toxins, and receptor-mediated external triggers. In addition to intracellular kinases, the extracellular glutathione-dependent redox potential controls ADAM17 shedding. Thus, the epithelial ADAM17/EGFR axis serves as a receptor of incoming luminal stress signals, relaying these to neighboring and underlying cells, which plays an important role in the resolution of lung injury and inflammation. We review evidence that congenital CFTR deficiency in CF and reduced CFTR activity in chronic COPD may cause enhanced ADAM17/EGFR signaling through a defect in glutathione secretion. In future studies, these complex interactions and the options for pharmaceutical interventions will be further investigated.

5-Azacytidine engages an IRE1α-EGFR-ERK1/2 signaling pathway that stabilizes the LDL receptor mRNA

Hepatic low-density lipoprotein receptor (LDLR) is the primary conduit for the clearance of plasma LDL-cholesterol and increasing its expression represents a central goal for treating cardiovascular disease. However, LDLR mRNA is unstable and undergoes rapid turnover mainly due to the three AU-rich elements (ARE) in its proximal 3'-untranslated region (3'-UTR). Herein, our data revealed that 5-azacytidine (5-AzaC), an antimetabolite used in the treatment of myelodysplastic syndrome, stabilizes the LDLR mRNA through a previously unrecognized signaling pathway resulting in a strong increase of its protein level in human hepatocytes in culture. 5-AzaC caused a sustained activation of the inositol-requiring enzyme 1α (IRE1α) kinase domain and c-Jun N-terminal kinase (JNK) independently of endoplasmic reticulum stress. This resulted in activation of the epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase1/2 (ERK1/2) that, in turn, stabilized LDLR mRNA. Systematic mutation of the AREs (ARE1-3) in the LDLR 3'UTR and expression of each mutant coupled to a luciferase reporter in Huh7 cells demonstrated that ARE1 is required for rapid LDLR mRNA decay and 5-AzaC-induced mRNA stabilization via the IRE1α-EGFR-ERK1/2 signaling cascade. The characterization of this pathway will help to reveal potential targets to enhance plasma LDL clearance and novel cholesterol-lowering therapeutic strategies.

Bone Marrow CD11c+ Cell-Derived Amphiregulin Promotes Pulmonary Fibrosis

Amphiregulin (AREG), an epidermal growth factor receptor ligand, is implicated in tissue repair and fibrosis, but its cellular source and role in regeneration versus fibrosis remain unclear. In this study, we hypothesize that AREG induced in bone marrow-derived CD11c(+) cells is essential for pulmonary fibrosis. Thus, the objectives were to evaluate the importance and role of AREG in pulmonary fibrosis, identify the cellular source of AREG induction, and analyze its regulation of fibroblast function and activation. The results showed that lung AREG expression was significantly induced in bleomycin-induced pulmonary fibrosis. AREG deficiency in knockout mice significantly diminished pulmonary fibrosis. Analysis of AREG expression in major lung cell types revealed induction in fibrotic lungs predominantly occurred in CD11c(+) cells. Moreover, depletion of bone marrow-derived CD11c(+) cells suppressed both induction of lung AREG expression and pulmonary fibrosis. Conversely, adoptive transfer of bone marrow-derived CD11c(+) cells from bleomycin-treated donor mice exacerbated pulmonary fibrosis, but not if the donor cells were made AREG deficient prior to transfer. CD11c(+) cell-conditioned media or coculture stimulated fibroblast proliferation, activation, and myofibroblast differentiation in an AREG-dependent manner. Furthermore, recombinant AREG induced telomerase reverse transcriptase, which appeared to be essential for the proliferative effect. Finally, AREG significantly enhanced fibroblast motility, which was associated with increased expression of α6 integrin. These findings suggested that induced AREG specifically in recruited bone marrow-derived CD11c(+) cells promoted bleomycin-induced pulmonary fibrosis by activation of fibroblast telomerase reverse transcriptase-dependent proliferation, motility, and indirectly, myofibroblast differentiation.