TREM1: A positive regulator for inflammatory response via NF-κB pathway in A549 cells infected with Mycoplasma pneumoniae

TREM1: Activation, signaling, cancer and therapy

Triggering receptor expressed on myeloid cells 1 (TREM1) is a cell surface receptor expressed on neutrophils, monocytes and some tissue macrophages, where it functions as an immunoregulator that controls myeloid cell responses. The activation of TREM1 is suggested to be an upregulation-based, ligands-induced and structural multimerization-mediated process, in which damage- and pathogen-associated molecular patterns play important roles. Activated TREM1 initiates an array of downstream signaling pathways that ultimately result in the production of pro-inflammatory cytokines and chemokines, whereby it functions as an amplifier of inflammation and is implicated in the pathogenesis of many inflammation-associated diseases. Over the past decade, there has been growing evidence for the involvement of TREM1 overactivation in tumor stroma inflammation and cancer progression. Indeed, it was shown that TREM1 promotes tumor progression, immunosuppression, and resistance to therapy by activating tumor-infiltrating myeloid cells. TREM1-deficiency or blockade provide protection against tumors and reverse the resistance to anti-PD-1/PD-L1 therapy and arginine-deprivation therapy in preclinical models. Here, we first review the structure, activation modes and signaling pathways of TREM1 and emphasize the role of soluble TREM1 as a biomarker of infection and cancer. We then focus on the role of TREM1 in cancer and systematically summarize its expression patterns, upregulation mechanisms and functions in tumor development and progression. Lastly, we discuss the therapeutic prospects of TREM1 inhibition, via effective pharmacological inhibitors, in treating cancer and other diseases.

Bioactivity and mechanism of action of sanguinarine and its derivatives in the past 10 years

Sanguinarine is a quaternary ammonium benzophenanthine alkaloid found in traditional herbs such as Chelidonium, Corydalis, Sanguinarum, and Borovula. It has been proven to possess broad-spectrum biological activities, such as antitumor, anti-inflammatory, antiosteoporosis, neuroprotective, and antipathogenic microorganism activities. In this paper, recent progress on the biological activity and mechanism of action of sanguinarine and its derivatives over the past ten years is reviewed. The results showed that the biological activities of hematarginine and its derivatives are related mainly to the JAK/STAT, PI3K/Akt/mTOR, NF-κB, TGF-β, MAPK and Wnt/β-catenin signaling pathways. The limitations of using sanguinarine in clinical application are also discussed, and the research prospects of this subject are outlined. In general, sanguinarine, a natural medicine, has many pharmacological effects, but its toxicity and safety in clinical application still need to be further studied. This review provides useful information for the development of sanguinarine-based bioactive agents.

The Clinical Value of Systemic Immune Inflammation Index (SII) in Predicting the Severity of Hospitalized Children with Mycoplasma Pneumoniae Pneumonia: A Retrospective Study

Objective

The Systemic Immune Inflammation Index (SII), as a novel inflammation biomarker that comprehensively reflects the inflammatory and immune status of the body, has not been reported in studies on Mycoplasma pneumoniae pneumonia (MPP) in children. This study aims to investigate whether SII can serve as an effective indicator for evaluating the condition of MPP.

Methods

This study recruited a total of 304 hospitalized patients with mycoplasma pneumoniae pneumonia (MPP), including 78 patients with severe MPP (SMPP) and 226 patients with non-SMPP. Univariate analysis using chi-square test, t-test, and Mann-Whitney U-test was conducted to analyze the clinical data of the patients. Logistic regression analysis was employed to identify the main risk factors for SMPP. Receiver operating characteristic curves were plotted to evaluate the potential of using neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and systemic immune response index (SIRI) to predict the severity of MPP.

Results

The ROC curve results show that patients with SII values ≥ 699.00 are more likely to develop severe MPP (sensitivity=0.876, specificity=0.987, AUC=0.940), and the predictive value of SII is significantly better than that of NLR, PLR, and SIRI. The results of multivariate logistic regression analysis indicate that SII can serve as a major risk factor for distinguishing non-SMPP from SMPP.

Conclusion

This study suggests that SII may be an effective indicator for predicting the severity of MPP in children. SII is more sensitive and specific than NLR, PLR, and SIRI in evaluating the condition of MPP.

Microglia TREM1-mediated neuroinflammation contributes to central sensitization via the NF-κB pathway in a chronic migraine model

BACKGROUND

Neuroinflammation, mediated by the activation of microglia, contributes to central sensitization, which is associated with the development of chronic migraine (CM). TREM1 receptors amplify the inflammatory response. However, their relationship to CM is unclear. Thus, this study endeavoured to elucidate the exact role of TREM1 in CM.

METHODS

Nitroglycerin (NTG) was repeatedly administered intraperitoneally to establish the CM model. Mechanical and thermal sensitivities were assessed using von Frey filaments and hot plate assays. Using Western blotting, TREM1, NF-κB pathway, NLRP3 inflammasome components, and proinflammatory cytokines were all detected. Immunofluorescence was used to examine the cellular distribution of TREM1 and NLRP3, the number of microglia, immunoreactivity, and morphological changes. We examined the effects of TREM1 antagonists (LR12) and NF-κB inhibitors (PDTC) on pain behaviour, as well as the production of c-fos and CGRP. Additionally, we investigated whether LR12 and PDTC affect the activation of microglia and the NLRP3 inflammasome. We synthesized siRNA and TREM1-overexpressing plasmids to transfect BV2 cells treated with LPS and normal BV2 cells and treated TREM1-overexpressing BV2 cells with PDTC. The NF-κB pathway, NLRP3 inflammasome components, and proinflammatory cytokines were quantified using Western blotting.

RESULTS

Following NTG administration, the expression of TREM1 was significantly upregulated and exclusively localized in microglia in the TNC, and was well co-localized with NLRP3. Furthermore, activation of the classical NF-κB pathway was observed. Pre-treatment with LR12 and PDTC effectively attenuated mechanical hypersensitivity, suppressed the expression of c-fos and CGRP, and inhibited NF-κB activity in CM mice. Additionally, inhibition of TREM1 and NF-κB activity mitigated NTG-induced microglia and NLRP3 activation, as well as proinflammatory cytokines production. In vitro, knockdown of TREM1 resulted in attenuated activation of the NF-κB pathway following lipopolysaccharide (LPS) treatment and reduced expression of NLRP3 inflammasome components as well as proinflammatory cytokines. After TREM1 overexpression, the NF-κB pathway was activated, NLRP3 inflammasome components and proinflammatory cytokines were upregulated, and PDTC reversed this phenomenon.

CONCLUSIONS

Our findings suggest that TREM1 regulates microglia and NLRP3 activation via the NF-κB pathway, thereby contributing to central sensitization and implicating its involvement in chronic migraine pathogenesis.

Activation of toll-like receptor 4/nuclear factor-kappa B signaling by triggering a receptor expressed on myeloid cells 1 promotes alveolar macrophage M1 polarization and exacerbates septic acute lung injury

BACKGROUND

Septic acute lung injury (ALI) is a life-threatening condition commonly occurring in the intensive care unit. Inflammation is considered as the basic pathological response of septic ALI. Triggering receptor expressed on myeloid cells 1 (TREM1) is a member of the immunoglobulin superfamily receptors that regulates the inflammatory response. However, the role of TREM1 in septic ALI has not yet been reported.

METHODS

Cell viability was tested using the MTT assay. TdT-mediated dUTP nick end labeling assay and flow cytometry were used for apoptosis. The level of protein was detected using western blot analysis. The levels of tumor necrosis factor-α and interleukin-1β were assessed using enzyme-linked immunosorbent assay. The lactate dehydrogenase content was assessed using the assay kit. Myeloperoxidase activity was determined using an assay. Histology of lung tissue was further analyzed through hematoxylin-eosin staining.

RESULTS

We found that TREM1 knockdown by transfection with si-TREM1 inhibited lipopolysaccharide (LPS)-induced cell apoptosis of alveolar macrophage cell line MH-S. The LPS stimulation caused M1 polarization of MH-S cells, which could be reversed by TREM1 knockdown. In vivo assays proved that si-TREM1 injection improved lung injury and inflammation of cecal ligation and puncture-induced ALI in mice. In addition, TREM1 knockdown suppressed the activation of toll-like receptor 4/nuclear factor-kappa B signaling, implying the involvement of TLR4 in the effects of TREM1 in response to LPS stimulation.

CONCLUSIONS

This study examined the proinflammatory role of TREM1 in septic ALI and its regulatory effect on alveolar macrophage polarization. These results suggest that TREM1 could potentially serve as a therapeutic target in the prevention and treatment of ALI.

Soluble TREM-1 plasma levels are associated with acute kidney injury, acute atrial fibrillation and prolonged ICU stay after cardiac surgery- a proof-concept study

Background

Cardiopulmonary bypass (CPB) during cardiac surgery leads to deleterious systemic inflammation. We hypothesized that TREM-1, a myeloid receptor shed after activation, drives systemic inflammation during CPB.

Methods

Prospective observational bi-centric study. Blood analysis (flow cytometry and ELISA) before and at H2 and H24 after CPB. Inclusion of adult patients who underwent elective cardiac surgery with CPB.

Results

TREM-1 expression on neutrophils decreased between H0 and H2 while soluble (s)TREM-1 plasma levels increased. sTREM-1 levels increased at H2 and at H24 (p < 0.001). IL-6, IL-8, G-CSF and TNF-α, but not IL-1β, significantly increased at H2 compared to H0 (p < 0.001), but dropped at H24. Principal component analysis showed a close relationship between sTREM-1 and IL-8. Three patterns of patients were identified: Profile 1 with high baseline sTREM-1 levels and high increase and profile 2/3 with low/moderate baseline sTREM-1 levels and no/moderate increase overtime. Profile 1 patients developed more severe organ failure after CPB, with higher norepinephrine dose, higher SOFA score and more frequently acute kidney injury at both H24 and H48. Acute atrial fibrillation was also more frequent in profile 1 patients at H24 (80% vs. 19.4%, p = 0.001). After adjustment on age and duration of CPB, H0, H2 and H24 sTREM-1 levels remained associated with prolonged ICU and hospital length of stay.

Conclusions

Baseline sTREM-1 levels as well as early kinetics after cardiac surgery identified patients at high risk of post-operative complications and prolonged length of stay.

sTREM-1 and TNF-α levels are associated with the clinical outcome of leprosy patients

Leprosy reaction (LR) and physical disability (PD) are the most significant clinical complications of leprosy. Herein, we assessed the circulating serum-sTREM-1 and TNF-α levels and their genetic polymorphisms in leprosy. Serum-sTREM-1 and TNF-α levels were measured in leprosy patients (LP) before treatment (n = 51) and from their household contacts (HHCs; n = 25). DNA samples were genotyped using TREM-1 rs2234246 and TNF-α rs1800629-SNP in 210 LPs and 168 endemic controls. The circulating sTREM-1 and TNF-α levels are higher in the multibacillary form. The ROC curve of the serum-sTREM-1 levels was able to differentiate LR from non-LR and PD from non-PD. Similarly, LPs with serum-sTREM-1 levels >210 pg/ml have 3-fold and 6-fold higher chances of presenting with LR and PD, respectively. Genotypes CC+CT of the TREM-1 were associated with leprosy. Taken together, our analyses indicated that sTREM-1 and TNF-α play an important role in the pathogenesis of leprosy and provide promising biomarkers to assist in the diagnosis of leprosy complications.

Interaction between alveolar macrophages and epithelial cells during Mycoplasma pneumoniae infection

Mycoplasma pneumoniae, as one of the most common pathogens, usually causes upper respiratory tract infections and pneumonia in humans and animals. It accounts for 10% to 40% of community-acquired pneumonia in children. The alveolar epithelial cells (AECs) are the first barrier against pathogen infections, triggering innate immune responses by recruiting and activating immune cells when pathogens invade into the lung. Alveolar macrophages (AMs) are the most plentiful innate immune cells in the lung, and are the first to initiate immune responses with pathogens invasion. The cross-talk between the alveolar epithelium and macrophages is necessary to maintain physiological homeostasis and to eradicate invaded pathogen by regulating immune responses during Mycoplasma pneumoniae infections. This review summarizes the communications between alveolar macrophages and epithelial cells during Mycoplasma pneumoniae infections, including cytokines-medicated communications, signal transduction by extracellular vesicles, surfactant associated proteins-medicated signal transmission and establishment of intercellular gap junction channels.

Association between genetic variants in TREM1, CXCL10, IL4, CXCL8 and TLR7 genes with the occurrence of congenital Zika syndrome and severe microcephaly

Congenital Zika syndrome (CZS) is a cluster of malformations induced by Zika virus (ZIKV) infection and the underline mechanisms involved in its occurrence are yet not fully understood. Along with epidemiological and environmental factors, the genetic host factors are suggested as important to the CZS occurrence and development, however, few studies have evaluated this. This study enrolled a total of 245 individuals in a case-control association study compound a cohort of high specific interest constituted by 75 mothers who had delivered CZS infants, their 76 infants, and 47 mothers that had delivered healthy infants, and their 47 infants. Sixteen single-nucleotide polymorphisms on TREM1, CXCL10, IL4, CXCL8, TLR3, TLR7, IFNR1, CXCR1, IL10, CCR2 and CCR5 genes were genotyped to investigate their association as risk factors to CZS. The results show an association between C allele at TREM1 rs2234246 and C allele at IL4 rs224325 in mothers infected with ZIKV during pregnancy, with the increased susceptibility to CZS occurrence in their infants and the SNP CXCL8 rs4073 and the G allele at CXCL10 rs4508917 with presence of CZS microcephaly in the infants. Furthermore, the T allele at CXCL8 rs4073 and TRL7 rs179008 SNPs were associated with the severity of microcephaly in children with CZS. These results suggest that these polymorphisms in genes of innate immune responses addressed here are associated to increased risk of occurrence and severity of CZS in pregnant mothers infected with ZIKV and their CZS infants.

Reserve of Wnt/β-catenin Signaling Alleviates Mycoplasma pneumoniae P1-C-induced Inflammation in airway epithelial cells and lungs of mice

Mycoplasma pneumoniae (M. pneumoniae) is the most common pathogen of respiratory tract infections in both children and adults. M. pneumoniae P1 adhesin plays an important role in the pathogenesis of M. pneumoniae infection by mediating the attachment of pathogen to host cells. The inoculation of C-terminal residuals of P1 (P1-C) showed a protective role from M. pneumoniae infection. Accumulated evidence suggests that the Wnt/β-Catenin signaling is implicated in regulation of inflammatory responses to bacterial infections. However, mechanisms underlying the regulatory roles of Wnt signaling in host cells in response to M. pneumoniae infections are incompletely understood. In the present study, the impact and molecular mechanism of Wnt/β-catenin signaling in immune responses induced by M. pneumoniae P1-C were investigated. The results demonstrated that the P1-C could activate Wnt/β-catenin and Toll-like receptor (TLR) signaling in primary mouse airway epithelial cells cultured in an air-liquid interface (ALI) state. Interestingly, the inhibition of Wnt/β-catenin signaling by an adenovirus-mediated Wnt inhibitor Dickkopf-1 (Dkk1) gene transduction alleviated the P1-C induced inflammation fibrosis in mouse lung, accompanied by the reduced expression of epithelial mesenchymal transition (EMT) markers. Mechanistical analysis further demonstrated that the Dkk1 could suppress the expression of JAK2/STAT1-STAT3 and Caspase3, 8/Bax signaling in mouse lung tissues. In vitro study further revealed that XAV939, a small molecule of Wnt/β-catenin inhibitor, inhibited the P1-C-activated TLR4/MyD88 signaling and cytokine productions in primary mouse airway ALI epithelial cells. This study thus provides an insight into the function of Wnt/β-catenin signaling in regulation of the pathogenesis of M. pneumoniae infection, suggesting that targeting Wnt/β-catenin signaling by gene transduction of Dkk1, or pharmacological molecules of inhibitor may be a promised approach that worthy of further investigation in the treatment of M. pneumoniae pneumonia.

Knockdown of triggering receptor expressed on myeloid cells 1 (TREM1) inhibits endoplasmic reticulum stress and reduces extracellular matrix degradation and the apoptosis of human nucleus pulposus cells

According to the linear model of microarray data analysis, triggering receptor expressed on myeloid cells 1 (TREM1) has been shown to have a significantly different expression profile between intervertebral disc degeneration (IDD) samples and associated control samples. The purpose of the present study was to explore the probable role and underlying mechanism of TREM1 in IDD. To accomplish this, an in vitro model of IDD was established by using IL-1β to stimulate human nucleus pulposus cells (NPCs). After the level of TREM1 had been determined, its functions in terms of the viability of the NPCs, extracellular matrix (ECM) degradation, inflammation, apoptosis and endoplasmic reticulum stress (ERS) were assessed. The downstream target of TREM1 was predicted to be Toll-like receptor-4 (TLR-4) and its roles were then studied, incorporating experiments featuring an ERS agonist. IL-1β was found to elevate the level of TREM1 in NPCs. TREM1 knockdown reversed the observed effects of IL-1β on cell viability, ECM degradation, inflammation, apoptosis of NPCs, ERS and TLR4/NF-κB signaling. Subsequently, the TLR4 and ERS agonists were found to reverse the effect of TREM1 knockdown on NPCs, indicating that the TLR4/NF-κB signaling pathway and ERS were responsible for mediating the regulation of TREM1. In conclusion, the present study showed that TREM1 knockdown blocked the TLR4/NF-κB signaling pathway, inhibited ERS and reduced the levels of ECM degradation and apoptosis of NPCs induced by IL-1β.

Combination of azithromycin and methylprednisolone alleviates Mycoplasma pneumoniae induced pneumonia by regulating miR‑499a‑5p/STAT3 axis

Mycoplasma pneumoniae (M. pneumoniae) is a contributing factor to community-acquired pneumonia in children. The present study sought to explain the underlying mechanism of azithromycin (AZM) combined with methylprednisolone (MP) in the treatment of M. pneumoniae infection. Peripheral blood samples were obtained from patients with M. pneumoniae and healthy volunteers for analysis. A549 cells were infected with M. pneumoniae to construct an in vitro cell model with M. pneumoniae, followed by treatment with AZM and MP. Cell Counting Kit-8 and TUNEL assays were conducted to detect cell viability and apoptosis. RT-qPCR was employed to measure the expression levels of microRNA (miR)-499a-5p and STAT3. Western blotting was performed to measure the expression of STAT3 and apoptosis-related proteins. Luciferase report assay was performed to verify the binding site between miR-499a-5p and STAT3. The production of inflammatory cytokines was determined using ELISA kits. The results exhibited the downregulated miR-499a-5p and dysregulated inflammatory cytokines in peripheral blood of patients and M. pneumoniae-infected A549 cells. AZM and MP treatment alone or combined significantly inhibited inflammatory response, cell viability loss and promoted apoptosis in A549 cells infected with M. pneumoniae, which was partly reversed by inhibition of miR-499a-5p. Furthermore, miR-499a-5p could negatively regulate its direct target STAT3. In addition, STAT3 is also regulated by AZM and MP. Collectively, the present results suggested that combination treatment of AZM and MP could inhibit M. pneumoniae infection-induced inflammation, cell viability loss and promoted apoptosis partly by regulating miR-499a-5p/STAT3 axis.

D-dimer: The Risk Factor of Children's Severe Mycoplasma Pneumoniae Pneumonia

OBJECTIVE

Mycoplasma Pneumoniae (MP) is an important cause of community-acquired pneumonia in children, which can cause serious consequences. There has been some research into predicting Severe Mycoplasma Pneumoniae Pneumonia (SMPP) primarily focused on pre-treatment time by macrolide, pre-hospital course, CRP and LDH et.al. while seldom reporting on concoagulation status. We designed this retrospective study to compare the difference between SMPP and Non-severe MPP (NSMPP) with an attempt to find the risk factors, with a special focus on concoagulation status.

METHOD

We performed a retrospective study of 786 MPP patients who were hospitalized from January 1, 2016 to December 31, 2018, age ranging from 28 days to 18 years old. All patients were divided into SMPP group and NSMPP group. A univariate analysis was conducted between both groups. The factors with statistical differences were included in logistic regression analysis to summarize the predictors of SMPP. Next, the predictive value of each risk factor was calculated from the receiver operating characteristic curve (ROC curve). Patients who had D-dimer records were divided into the elevated D-dimer group (D-dimer > 308ug/L) and the control group (D-dimer ≤ 308ug/L), and the clinical manifestations were compared.

RESULTS

There was no significant difference in gender, age, pre-treatment time by macrolide, the white blood cell counts (WBC), Fibrinogen (FIB), Activated Partial Prothrombin Time (APTT), Prothrombin Time (PT) and Thrombin Time (TT) between SMPP and NSMPP. Compared with NSMPP, the pre-hospital course of SMPP was longer (P < 0.05), the neutrophil ratio (N%), platelet Count (PLT), C-reactive Protein (CRP), Lactate Dehydrogenase (LDH) and D-dimer were significantly higher (P < 0.01). The binary logistic regression analysis showed that the N%, PLT, CRP, LDH and D-dimer were the key predictors for SMPP, the N% > 67%, OR = 3.233, PLT > 445 × 10⁹ /L, OR = 2.589, LDH > 354U/L, OR = 4.335 and D-dimer level > 403 ug/L, OR = 7.316. The D-dimer possessed the best predictive value. The incidence of complications such as pleural effusion, myocardial and liver damage of MPP was higher in the elevated D-dimer group than that in the control group (P < 0.05).

CONCLUSION

The N%, PLT, CRP, LDH and D-dimer were risk factors for SMPP. D-dimer was the best predictor among them. MPP patients with D-dimer > 308ug/L had more complications such as pleural effusion, myocardial and liver damage. More attention should be given in the treatment for this group.

A single-cell transcriptome of mesenchymal stromal cells to fabricate bioactive hydroxyapatite materials for bone regeneration

The osteogenic microenvironment of bone-repairing materials plays a key role in accelerating bone regeneration but remains incompletely defined, which significantly limits the application of such bioactive materials. Here, the transcriptional landscapes of different osteogenic microenvironments, including three-dimensional (3D) hydroxyapatite (HA) scaffolds and osteogenic medium (OM), for mesenchymal stromal cells (MSCs) in vitro were mapped at single-cell resolution. Our findings suggested that an osteogenic process reminiscent of endochondral ossification occurred in HA scaffolds through sequential activation of osteogenic-related signaling pathways, along with inflammation and angiogenesis, but inhibition of adipogenesis and fibrosis. Moreover, we revealed the mechanism during OM-mediated osteogenesis involves the ZBTB16 and WNT signaling pathways. Heterogeneity of MSCs was also demonstrated. In vitro ossification of LRRC75A⁺ MSCs was shown to have better utilization of WNT-related ossification process, and PCDH10⁺ MSCs with superiority in hydroxyapatite-related osteogenic process. These findings provided further understanding of the cellular activity modulated by OM conditions and HA scaffolds, providing new insights for the improvement of osteogenic biomaterials. This atlas provides a blueprint for research on MSC heterogeneity and the osteogenic microenvironment of HA scaffolds and a database reference for the application of bioactive materials for bone regeneration.

Conditioned Media of Adipose-Derived Stem Cells Suppresses Sidestream Cigarette Smoke Extract Induced Cell Death and Epithelial-Mesenchymal Transition in Lung Epithelial Cells

The role of the epithelial-mesenchymal transition (EMT) in lung epithelial cells is increasingly being recognized as a key stage in the development of COPD, fibrosis, and lung cancers, which are all highly associated with cigarette smoking and with exposure to second-hand smoke. Using the exposure of human lung cancer epithelial A549 cells and non-cancerous Beas-2B cells to sidestream cigarette smoke extract (CSE) as a model, we studied the protective effects of adipose-derived stem cell-conditioned medium (ADSC-CM) against CSE-induced cell death and EMT. CSE dose-dependently induced cell death, decreased epithelial markers, and increased the expression of mesenchymal markers. Upstream regulator analysis of differentially expressed genes after CSE exposure revealed similar pathways as those observed in typical EMT induced by TGF-β1. CSE-induced cell death was clearly attenuated by ADSC-CM but not by other control media, such as a pass-through fraction of ADSC-CM or A549-CM. ADSC-CM effectively inhibited CSE-induced EMT and was able to reverse the gradual loss of epithelial marker expression associated with TGF-β1 treatment. CSE or TGF-β1 enhanced the speed of A549 migration by 2- to 3-fold, and ADSC-CM was effective in blocking the cell migration induced by either agent. Future work will build on the results of this in vitro study by defining the molecular mechanisms through which ADSC-CM protects lung epithelial cells from EMT induced by toxicants in second-hand smoke.

Epidemic dropsy toxin, sanguinarine chloride, stimulates sucrose-sensitive hemolysis and breakdown of membrane phospholipid asymmetry in human erythrocytes

Sanguinarine (SGN) is a benzophenathridine alkaloid extracted from Sanguinaria canadensis plant. SGN is incriminated in epidemic dropsy (ED) characterized by multiple-organ failure and anemia. Nevertheless, how SGN leads to anemia of ED remains poorly understood. This study was thus initiated to investigate the interaction of SGN with human red blood cells (RBCs) and to delineate associated molecular mechanisms. Heparin- and EDTA-anticoagulated blood was collected from healthy participants and whole blood was analyzed for a complete blood count, while isolated RBCs were examined for hemolytic and eryptotic markers following exposure to 1-100 μM SGN for 24 h at 37 °C. Calcium was measured by Fluo4/AM, hemolysis by hemoglobin leakage, membrane scrambling by Annexin V-FITC, cell size by forward scatter (FSC), cell granularity by side scatter (SSC), and oxidative stress by H₂DCFDA. SGN led to increased Fluo4 fluorescence and dose-dependent hemolysis which was not ameliorated by exclusion of extracellular Ca²⁺ but was nevertheless sensitive to hyperosmotic conditions and to the presence of aspirin. SGN also caused significant increase in Annexin V-positive cells, decreased FSC and SSC values, and elevated DCF fluorescence. Moreover, significantly reduced lymphocyte and basophil percentages along with selective toxicity to platelets was noted. Collectively, SGN possesses sucrose- and cyclooxygenase-sensitive hemolytic potential and elicits eryptosis characterized by Ca²⁺ accumulation, phosphatidylserine externalization, morphological alterations including cell shrinkage and loss of granularity, and oxidative stress. In conclusion, this report reveals a novel activity of SGN against human RBCs and informs prospective policies in ED prevention and management.

Shengxian decoction decreases doxorubicin‑induced cardiac apoptosis by regulating the TREM1/NF‑κB signaling pathway

Shengxian decoction (SXT) is a traditional Chinese medicine that is clinically used for treating cardiovascular diseases. It is known for its beneficial effect on cardiomyocyte injuries, some of which can be induced by anticancer agents including doxorubicin (DOX). To determine the molecular mechanisms involved in the cardioprotective effects of SXT, DOX‑induced H9c2 cells were analyzed for apoptosis and expression levels of apoptosis biomarkers. Cell viability and apoptosis were measured by CCK‑8 and flow cytometry. Triggering receptors expressed on myeloid cells 1 (TREM1), cleaved caspase‑3, survivin and NF‑κBp65 expression levels were measured by reverse transcription‑quantitative PCR and/or western blotting. A total of 30 adult male Sprague‑Dawley rats were randomly allocated into five groups (n=6 each); control group receiving 0.9% saline, 1 DOX group receiving 2.5 mg/kg of DOX and 3 DOX + SXT groups, receiving a DOX dose equivalent to the DOX‑only group and either 0.4, 0.8 or 1.6 g/kg of SXT. It was found that DOX increased apoptosis and NF‑κB activation of H9c2 cells by increasing TREM1 expression and that SXT inhibited apoptosis and NF‑κB activation of H9c2 cells induced by DOX or Trem1 overexpression. SXT also significantly reversed DOX‑induced cardiotoxicity in rats. The results suggested that the protective effects of SXT against DOX‑induced apoptosis may be attributed to its downregulation of TREM1.

Regulatory mechanisms of neutrophil migration from the circulation to the airspace

The neutrophil, a short-lived effector leukocyte of the innate immune system best known for its proteases and other degradative cargo, has unique, reciprocal physiological interactions with the lung. During health, large numbers of ‘marginated’ neutrophils reside within the pulmonary vasculature, where they patrol the endothelial surface for pathogens and complete their life cycle. Upon respiratory infection, rapid and sustained recruitment of neutrophils through the endothelial barrier, across the extravascular pulmonary interstitium, and again through the respiratory epithelium into the airspace lumen, is required for pathogen killing. Overexuberant neutrophil trafficking to the lung, however, causes bystander tissue injury and underlies several acute and chronic lung diseases. Due in part to the unique architecture of the lung’s capillary network, the neutrophil follows a microanatomic passage into the distal airspace unlike that observed in other end-organs that it infiltrates. Several of the regulatory mechanisms underlying the stepwise recruitment of circulating neutrophils to the infected lung have been defined over the past few decades; however, fundamental questions remain. In this article, we provide an updated review and perspective on emerging roles for the neutrophil in lung biology, on the molecular mechanisms that control the trafficking of neutrophils to the lung, and on past and ongoing efforts to design therapeutics to intervene upon pulmonary neutrophilia in lung disease.

TREM-1 isoforms in bacterial infections: to immune modulation and beyond

The triggering receptor expressed on myeloid cells 1 (TREM-1) is an innate immunity receptor associated with the amplification of inflammation in sterile and non-sterile inflammatory disorders. Since its first description, the two isoforms of the receptor, membrane and soluble (mTREM-1 and sTREM-1, respectively) have been largely explored in the immunopathogenesis of several bacterial diseases and sepsis. The role of the receptor in these scenarios seems to be at least partly dependent on the source/type of bacteria, host and context. As uncontrolled inflammation is a result of several bacterial infections, the inhibition of the receptor has been considered as a promising approach to treat such conditions. Further, sTREM-1 has been explored as a biomarker for diagnosis and/or prognosis of several bacterial diseases. Therefore, this review aims to provide an updated insight into how the receptor influences and is influenced by bacterial infections, highlighting the advances regarding the use/manipulation of TREM-1 isoforms in biomedical research and clinical practice.

Extracellular CIRP Induces Inflammation in Alveolar Type II Cells via TREM-1

Extracellular cold-inducible RNA-binding protein (eCIRP) induces acute lung injury (ALI) in sepsis. Triggering receptor expressed on myeloid cells-1 (TREM-1) serves as a receptor for eCIRP to induce inflammation in macrophages and neutrophils. The effect of eCIRP on alveolar epithelial cells (AECs) remains unknown. We hypothesize that eCIRP induces inflammation in AECs through TREM-1. AECs were isolated from C57BL/6 mice and freshly isolated AECs were characterized as alveolar type II (ATII) cells by staining AECs with EpCAM, surfactant protein-C (SP-C), and T1 alpha (T1α) antibodies. AECs were stimulated with recombinant murine (rm) CIRP and assessed for TREM-1 by flow cytometry. ATII cells from WT and TREM-1^-/- mice were stimulated with rmCIRP and assessed for interleukin-6 (IL-6) and chemokine (C-X-C motif) ligand 2 (CXCL2) in the culture supernatants. ATII cells from WT mice were pretreated with vehicle (PBS), M3 (TREM-1 antagonist), and LP17 (TREM-1 antagonist) and then after stimulating the cells with rmCIRP, IL-6 and CXCL2 levels in the culture supernatants were assessed. All of the freshly isolated AECs were ATII cells as they expressed EpCAM and SP-C, but not T1α (ATI cells marker). Treatment of ATII cells with rmCIRP significantly increased TREM-1 expression by 56% compared to PBS-treated ATII cells. Stimulation of WT ATII cells with rmCIRP increased IL-6 and CXCL2 expression, while the expression of IL-6 and CXCL2 in TREM-1^-/- ATII cells were reduced by 14 and 23%, respectively. Pretreatment of ATII cells with M3 and LP17 significantly decreased the expression of IL-6 by 30 and 47%, respectively, and CXCL2 by 27 and 34%, respectively, compared to vehicle treated ATII cells after stimulation with rmCIRP. Thus, eCIRP induces inflammation in ATII cells via TREM-1 which implicates a novel pathophysiology of eCIRP-induced ALI and directs a possible therapeutic approach targeting eCIRP-TREM-1 interaction to attenuate ALI.

miR-143-3p impacts on pulmonary inflammatory factors and cell apoptosis in mice with mycoplasmal pneumonia by regulating TLR4/MyD88/NF-κB pathway

miR-143-3p is correlated with inflammatory pain responses, such as hsa-miR-143-3p expression reduction in fibromyalgia. The present study aimed to explore the effects of miR-143-3p and Toll-like receptor (TLR) 4/myeloid differentiation factor 88 (MyD88)/NF-κB signaling pathway on pulmonary inflammatory factors levels and alveolar epithelial cell apoptosis in mycoplasmal pneumonia mice. Twenty mice were selected as normal group. The 120 successfully modeled Mycoplasma pneumoniae (MP) infection mice were randomly divided into model group (without any treatment), negative control (NC) group (injected with NC mimic), miR-143-3p mimic group (injected with miR-143-3p mimic), miR-143-3p inhibitor group (injected with miR-143-3p inhibitor), TAK-242 group (treatment with TAK-242), and miR-143-3p inhibitor + TAK-242 group (treatment with miR-143-3p inhibitor + TAK-242). Compared with model group, model mice had up-regulated miR-143-3p expression and decreased MyD88 and p-NF-κB p50 protein expressions (all P<0.05); Model mice treated with miR-143-3p mimic and TAK-242 had reduced interleukin (IL)-2 and tumor necrosis factor (TNF)-α contents and protein expressions of MyD88, p-NF-κB p50, increased IL-10 content, fewer alveolar epithelial cell apoptosis, lower Bax expression and higher Bcl-2 expression (all P<0.05); however, mice with miR-143-3p inhibitor treatment showed opposite trends in terms of above indicators. The exacerbation of mycoplasmal pneumonia caused by miR-143-3p inhibitor was partly improved by miR-143-3p inhibitor + TAK-242 combination treatment (all P<0.05). Therefore, up-regulation of miR-143-3p expression may ameliorate pulmonary inflammatory factors levels and reduce alveolar epithelial cell apoptosis in mycoplasmal pneumonia mice by inhibiting TLR4/MyD88/NF-κB signaling pathway.

Astragalus polysaccharides attenuate pulmonary fibrosis by inhibiting the epithelial-mesenchymal transition and NF-κB pathway activation

Astragalus polysaccharides (APS), the active ingredients isolated from the plant Astragalus, have been reported to have numerous biological activities, including anti‑inflammatory and antitumor activities. However, the effect of APS on pulmonary fibrosis (PF) remains unknown. The present study aimed to evaluate the protective effect of APS against PF and to explore its underlying mechanisms by using in vivo and in vitro models. A mouse in vivo model of bleomycin‑induced PF and an in vitro model of transforming growth factor β1 (TGF‑β1)‑stimulated human lung epithelial A549 cells were established. Histopathologic examination and collagen deposition were investigated by hematoxylin and eosin staining and Masson staining, and by detecting the hydroxyproline content. The expression of related genes was analyzed by western blotting, reverse transcription‑quantitative (RT‑q) PCR, immunofluorescence and immunohistochemistry. The results from the in vivo mouse model demonstrated that treatment with APS could ameliorate collagen deposition and reduce fibrotic area and hydroxyproline content in the matrix. Furthermore, APS significantly inhibited the epithelial‑mesenchymal transition (EMT), as evidenced by an increased level of E‑cadherin and a decreased expression of vimentin and alpha smooth muscle actin. Furthermore, APS treatment significantly decreased TGF‑β1‑induced EMT and NF‑κB pathway activation in vitro. The results from the present study provided new insights on PF regression via the anti‑fibrotic effects of APS.

Human Islet Response to Selected Type 1 Diabetes-Associated Bacteria: A Transcriptome-Based Study

Type 1 diabetes (T1D) is a chronic autoimmune disease that results from destruction of pancreatic β-cells. T1D subjects were recently shown to harbor distinct intestinal microbiome profiles. Based on these findings, the role of gut bacteria in T1D is being intensively investigated. The mechanism connecting intestinal microbial homeostasis with the development of T1D is unknown. Specific gut bacteria such as Bacteroides dorei (BD) and Ruminococcus gnavus (RG) show markedly increased abundance prior to the development of autoimmunity. One hypothesis is that these bacteria might traverse the damaged gut barrier, and their constituents elicit a response from human islets that causes metabolic abnormalities and inflammation. We have tested this hypothesis by exposing human islets to BD and RG in vitro, after which RNA-Seq analysis was performed. The bacteria altered expression of many islet genes. The commonly upregulated genes by these bacteria were cytokines, chemokines and enzymes, suggesting a significant effect of gut bacteria on islet antimicrobial and biosynthetic pathways. Additionally, each bacteria displayed a unique set of differentially expressed genes (DEGs). Ingenuity pathway analysis of DEGs revealed that top activated pathways and diseases included TREM1 signaling and inflammatory response, illustrating the ability of bacteria to induce islet inflammation. The increased levels of selected factors were confirmed using immunoblotting and ELISA methods. Our data demonstrate that islets produce a complex anti-bacterial response. The response includes both symbiotic and pathogenic aspects. Both oxidative damage and leukocyte recruitment factors were prominent, which could induce beta cell damage and subsequent autoimmunity.