LOX-1 deletion improves neutrophil responses, enhances bacterial clearance, and reduces lung injury in a murine polymicrobial sepsis model

Detailed phenotyping reveals diverse and highly skewed neutrophil subsets in both the blood and airways during active tuberculosis infection

Introduction

Neutrophils play a complex and important role in the immunopathology of TB. Data suggest they are protective during early infection but become a main driver of immunopathology if infection progresses to active disease. Neutrophils are now recognized to exist in functionally diverse states, but little work has been done on how neutrophil states or subsets are skewed in TB disease.

Methods

To address this, we carried out comprehensive phenotyping by flow cytometry of neutrophils in the blood and airways of individuals with active pulmonary TB with and without HIV co-infection recruited in Durban, South Africa.

Results

Active TB was associated with a profound skewing of neutrophils in the blood toward phenotypes associated with activation and apoptosis, reduced phagocytosis, reverse transmigration, and immune regulation. This skewing was also apparently in airway neutrophils, particularly the regulatory subsets expressing PDL-1 and LOX-1. HIV co-infection did not impact neutrophil subsets in the blood but was associated with a phenotypic change in the airways and a reduction in key neutrophil functional proteins cathelicidin and arginase 1.

Discussion

Active TB is associated with profound skewing of blood and airway neutrophils and suggests multiple mechanisms by which neutrophils may exacerbate the immunopathology of TB. These data indicate potential avenues for reducing neutrophil-mediated lung pathology at the point of diagnosis.

Sepsis in elderly patients: the role of neutrophils in pathophysiology and therapy

Sepsis is among the most important causes of mortality, particularly within the elderly population. Sepsis prevalence is on the rise due to different factors, including increasing average population age and the concomitant rise in the prevalence of frailty and chronic morbidities. Recent investigations have unveiled a "trimodal" trajectory for sepsis-related mortality, with the ultimate zenith occurring from 60 to 90 days until several years after the original insult. This prolonged temporal course ostensibly emanates from the sustained perturbation of immune responses, persevering beyond the phase of clinical convalescence. This phenomenon is particularly associated with the aging immune system, characterized by a broad dysregulation commonly known as "inflammaging." Inflammaging associates with a chronic low-grade activation of the innate immune system preventing an appropriate response to infective agents. Notably, during the initial phases of sepsis, neutrophils-essential in combating pathogens-may exhibit compromised activity. Paradoxically, an overly zealous neutrophilic reaction has been observed to underlie multi-organ dysfunction during the later stages of sepsis. Given this scenario, discovering treatments that can enhance neutrophil activity during the early phases of sepsis while curbing their overactivity in the later phases could prove beneficial in fighting pathogens and reducing the detrimental effects caused by an overactive immune system. This narrative review delves into the potential key role of neutrophils in the pathological process of sepsis, focusing on how the aging process impacts their functions, and highlighting possible targets for developing immune-modulatory therapies. Additionally, the review includes tables that outline the principal potential targets for immunomodulating agents.

New insight into arginine and tryptophan metabolism in macrophage activation during tuberculosis

Arginine and tryptophan are pivotal in orchestrating cytokine-driven macrophage polarization and immune activation. Specifically, interferon-gamma (IFN-γ) stimulates inducible nitric oxide synthase (iNOS) expression), leading to the conversion of arginine into citrulline and nitric oxide (NO), while Interleukin-4 (IL4) promotes arginase activation, shifting arginine metabolism toward ornithine. Concomitantly, IFN-γ triggers indoleamine 2,3-dioxygenase 1 (IDO1) and Interleukin-4 induced 1 (IL4i1), resulting in the conversion of tryptophan into kynurenine and indole-3-pyruvic acid. These metabolic pathways are tightly regulated by NAD+-dependent sirtuin proteins, with Sirt2 and Sirt5 playing integral roles. In this review, we present novel insights that augment our understanding of the metabolic pathways of arginine and tryptophan following Mycobacterium tuberculosis infection, particularly their relevance in macrophage responses. Additionally, we discuss arginine methylation and demethylation and the role of Sirt2 and Sirt5 in regulating tryptophan metabolism and arginine metabolism, potentially driving macrophage polarization.

Role of Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 in Inflammation and Pathogen-Associated Interactions

BACKGROUND

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is known as a major receptor for oxidized low-density lipoproteins (oxLDL) and plays a significant role in the genesis of atherosclerosis. Recent research has shown its involvement in cancer, ischemic stroke, and diabetes. LOX-1 is a C-type lectin receptor and is involved in the activation of immune cells and inflammatory processes. It may further interact with pathogens, suggesting a role in infections or the host's response.

SUMMARY

This review compiles the current knowledge of potential implications of LOX-1 in inflammatory processes and in host-pathogen interactions with a particular emphasis on its regulatory role in immune responses. Also discussed are genomic and structural variations found in LOX-1 homologs across different species as well as potential involvements of LOX-1 in inflammatory processes from the angle of different cell types and organ-specific interactions.

KEY MESSAGES

The results presented reveal both similar and different structures in human and murine LOX-1 and provide clues as to the possible origins of different modes of interaction. These descriptions raise concerns about the suitability, particularly of mouse models, that are often used in the analysis of its functionality in humans. Further research should also aim to better understand the mostly unknown binding and interaction mechanisms between LOX-1 and different pathogens. This pursuit will not only enhance our understanding of LOX-1 involvement in inflammatory processes but also identify potential targets for immunomodulatory approaches.

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

Innate immune responses in pneumonia

The lungs are an immunologically unique environment; they are exposed to innumerable pathogens and particulate matter daily. Appropriate clearance of pathogens and response to pollutants is required to prevent overwhelming infection, while preventing tissue damage and maintaining efficient gas exchange. Broadly, the innate immune system is the collection of immediate, intrinsic immune responses to pathogen or tissue injury. In this review, we will examine the innate immune responses of the lung, with a particular focus on their role in pneumonia. We will discuss the anatomic barriers and antimicrobial proteins of the lung, pathogen and injury recognition, and the role of leukocytes (macrophages, neutrophils, and innate lymphocytes) and lung stromal cells in innate immunity. Throughout the review, we will focus on new findings in innate immunity as well as features that are unique to the lung.

Lectin-like oxidized low-density lipoprotein receptor 1 attenuates pneumonia-induced lung injury

Identifying host factors that contribute to pneumonia incidence and severity are of utmost importance to guiding the development of more effective therapies. Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1, encoded by OLR1) is a scavenger receptor known to promote vascular injury and inflammation, but whether and how LOX-1 functions in the lung are unknown. Here, we provide evidence of substantial accumulation of LOX-1 in the lungs of patients with acute respiratory distress syndrome and in mice with pneumonia. Unlike previously described injurious contributions of LOX-1, we found that LOX-1 is uniquely protective in the pulmonary airspaces, limiting proteinaceous edema and inflammation. We also identified alveolar macrophages and recruited neutrophils as 2 prominent sites of LOX-1 expression in the lungs, whereby macrophages are capable of further induction during pneumonia and neutrophils exhibit a rapid, but heterogenous, elevation of LOX-1 in the infected lung. Blockade of LOX-1 led to dysregulated immune signaling in alveolar macrophages, marked by alterations in activation markers and a concomitant elevation of inflammatory gene networks. However, bone marrow chimeras also suggested a prominent role for neutrophils in LOX-1-mediated lung protection, further supported by LOX-1+ neutrophils exhibiting transcriptional changes consistent with reparative processes. Taken together, this work establishes LOX-1 as a tissue-protective factor in the lungs during pneumonia, possibly mediated by its influence on immune signaling in alveolar macrophages and LOX-1+ airspace neutrophils.

The Impact of Cytokines on Neutrophils' Phagocytosis and NET Formation during Sepsis-A Review

Sepsis is an overwhelming inflammatory response to infection, resulting in multiple-organ injury. Neutrophils are crucial immune cells involved in innate response to pathogens and their migration and effector functions, such as phagocytosis and neutrophil extracellular trap (NET) formation, are dependent on cytokine presence and their concentration. In the course of sepsis, recruitment and migration of neutrophils to infectious foci gradually becomes impaired, thus leading to loss of a crucial arm of the innate immune response to infection. Our review briefly describes the sepsis course, the importance of neutrophils during sepsis, and explains dependence between cytokines and their activation. Moreover, we, for the first time, summarize the impact of cytokines on phagocytosis and NET formation. We highlight and discuss the importance of cytokines in modulation of both processes and emphasize the direction of further investigations.

Knockdown of lectin-like oxidized low-density lipoprotein-1 ameliorates alcoholic cardiomyopathy via inactivating the p38 mitogen-activated protein kinase pathway

LOX-1 triggers myocardial fibrosis, but its roles and mechanisms in alcoholic cardiomyopathy and the involvement of the downstream signaling pathways had not been fully reported. We planned to explore how LOX-1 facilitated myocardial fibrosis in alcoholic cardiomyopathy. The in vitro and in vivo alcoholic cardiomyopathy model was established by alcohol treatment to rats' cardiac fibroblasts and rats, respectively. Masson staining was conducted to observe the collagen deposition and the IHC assay was executed to evaluate the contents of collagen I and III in vitro and in vivo. The cardiac tissues were also observed under TEM and the cardiac function of rats was evaluated using UCG. The expression levels of LOX-1 and P38MAPK in cardiac fibroblasts and tissues at both mRNA and protein levels were analyzed by RT-qPCR and western blot, respectively. Alcohol treatment could trigger collagen deposition, cell hypertrophy, fibrotic changes and increased the expression levels of LOX-1 and P38MAPK both in vivo and in vitro. It also deteriorated the cardiac function of rats in vivo. Overexpression of LOX-1 in vitro could aggravate the fibrotic changes while knockdown of LOX-1 ameliorated the fibrotic effects of alcohol treatment both in vitro and in vivo such as reduction of collagen deposition, relief of cell hypertrophy and inactivation of the P38MAPK signaling pathway. We concluded that knockdown of LOX-1 exerted anti-fibrotic effects via inhibiting P38MAPK signaling in alcoholic cardiomyopathy both in vitro and in vivo. Our findings highlighted that LOX-1 could become a potential therapeutic target in the treatment of alcoholic cardiomyopathy.

The amniotic fluid proteome changes with gestational age in normal pregnancy: a cross-sectional study

The cell-free transcriptome in amniotic fluid (AF) has been shown to be informative of physiologic and pathologic processes in pregnancy; however, the change in AF proteome with gestational age has mostly been studied by targeted approaches. The objective of this study was to describe the gestational age-dependent changes in the AF proteome during normal pregnancy by using an omics platform. The abundance of 1310 proteins was measured on a high-throughput aptamer-based proteomics platform in AF samples collected from women during midtrimester (16-24 weeks of gestation, n = 15) and at term without labor (37-42 weeks of gestation, n = 13). Only pregnancies without obstetrical complications were included in the study. Almost 25% (320) of AF proteins significantly changed in abundance between the midtrimester and term gestation. Of these, 154 (48.1%) proteins increased, and 166 (51.9%) decreased in abundance at term compared to midtrimester. Tissue-specific signatures of the trachea, salivary glands, brain regions, and immune system were increased while those of the gestational tissues (uterus, placenta, and ovary), cardiac myocytes, and fetal liver were decreased at term compared to midtrimester. The changes in AF protein abundance were correlated with those previously reported in the cell-free AF transcriptome. Intersecting gestational age-modulated AF proteins and their corresponding mRNAs previously reported in the maternal blood identified neutrophil-related protein/mRNA pairs that were modulated in the same direction. The first study to utilize an aptamer-based assay to profile the AF proteome modulation with gestational age, it reveals that almost one-quarter of the proteins are modulated as gestation advances, which is more than twice the fraction of altered plasma proteins (~ 10%). The results reported herein have implications for future studies focused on discovering biomarkers to predict, monitor, and diagnose obstetrical diseases.

Using RNA-Seq to Investigate Immune-Metabolism Features in Immunocompromised Patients With Sepsis

Objective: Sepsis is life threatening and leads to complex inflammation in patients with immunocompromised conditions, such as cancer, and receiving immunosuppressants for autoimmune diseases and organ transplant recipients. Increasing evidence has shown that RNA-Sequencing (RNA-Seq) can be used to define subendotype in patients with sepsis; therefore, we aim to use RNA-Seq to identify transcriptomic features among immunocompromised patients with sepsis.

Methods: We enrolled patients who were admitted to medical intensive care units (ICUs) for sepsis at a tertiary referral centre in central Taiwan. Whole blood on day-1 and day-8 was obtained for RNA-Seq. We used Gene Set Enrichment Analysis (GSEA) to identify the enriched pathway of day-8/day-1 differentially expressed genes and MiXCR to determine the diversity of T cell repertoire.

Results: A total of 18 immunocompromised subjects with sepsis and 18 sequential organ failure assessment (SOFA) score-matched immunocompetent control subjects were enrolled. The ventilator-day, ICU-stay, and hospital-day were similar between the two groups, whereas the hospital mortality was higher in immunocompromised patients than those in immunocompetent patients (50.0 vs. 5.6%, p < 0.01). We found that the top day-8/day-1 upregulated genes in the immunocompetent group were mainly innate immunity and inflammation relevant genes, namely, PRSS33, HDC, ALOX15, FCER1A, and OLR1, whereas a blunted day-8/day-1 dynamic transcriptome was found among immunocompromised patients with septic. Functional pathway analyses of day-8/day-1 differentially expressed genes identified the upregulated functional biogenesis and T cell-associated pathways in immunocompetent patients recovered from sepsis, whereas merely downregulated metabolism-associated pathways were found in immunocompromised patients with septic. Moreover, we used MiXCR to identify a higher diversity of T cell receptor (TCR) in immunocompetent patients both on day-1 and on day-8 than those in immunocompromised patients.

Conclusions: Using RNA-Seq, we found compromised T cell function, altered metabolic signalling, and decreased T cell diversity among immunocompromised patients with septic, and more mechanistic studies are warranted to elucidate the underlying mechanism.

Scavenger receptors in host defense: from functional aspects to mode of action

Scavenger receptors belong to a superfamily of proteins that are structurally heterogeneous and encompass the miscellaneous group of transmembrane proteins and soluble secretory extracellular domain. They are functionally diverse as they are involved in various disorders and biological pathways and their major function in innate immunity and homeostasis. Numerous scavenger receptors have been discovered so far and are apportioned in various classes (A-L). Scavenger receptors are documented as pattern recognition receptors and known to act in coordination with other co-receptors such as Toll-like receptors in generating the immune responses against a repertoire of ligands such as microbial pathogens, non-self, intracellular and modified self-molecules through various diverse mechanisms like adhesion, endocytosis and phagocytosis etc. Unlike, most of the scavenger receptors discussed below have both membrane and soluble forms that participate in scavenging; the role of a potential scavenging receptor Angiotensin-Converting Enzyme-2 has also been discussed whereby only its soluble form might participate in preventing the pathogen entry and replication, unlike its membrane-bound form. This review majorly gives an insight on the functional aspect of scavenger receptors in host defence and describes their mode of action extensively in various immune pathways involved with each receptor type. Video abstract.

LOX-1-Expressing Immature Neutrophils Identify Critically-Ill COVID-19 Patients at Risk of Thrombotic Complications

Background

Lymphopenia and the neutrophil/lymphocyte ratio may have prognostic value in COVID-19 severity.

Objective

We investigated neutrophil subsets and functions in blood and bronchoalveolar lavage (BAL) of COVID-19 patients on the basis of patients’ clinical characteristics.

Methods

We used a multiparametric cytometry profiling based to mature and immature neutrophil markers in 146 critical or severe COVID-19 patients.

Results

The Discovery study (38 patients, first pandemic wave) showed that 80% of Intensive Care Unit (ICU) patients develop strong myelemia with CD10⁻CD64⁺ immature neutrophils (ImNs). Cellular profiling revealed three distinct neutrophil subsets expressing either the lectin‐like oxidized low‐density lipoprotein receptor‐1 (LOX‐1), the interleukin-3 receptor alpha (CD123), or programmed death-ligand 1 (PD-L1) overrepresented in ICU patients compared to non-ICU patients. The proportion of LOX-1- or CD123-expressing ImNs is positively correlated with clinical severity, cytokine storm (IL-1β, IL-6, IL-8, TNFα), acute respiratory distress syndrome (ARDS), and thrombosis. BALs of patients with ARDS were highly enriched in LOX-1-expressing ImN subsets and in antimicrobial neutrophil factors. A validation study (118 patients, second pandemic wave) confirmed and strengthened the association of the proportion of ImN subsets with disease severity, invasive ventilation, and death. Only high proportions of LOX-1-expressing ImNs remained strongly associated with a high risk of severe thrombosis independently of the plasma antimicrobial neutrophil factors, suggesting an independent association of ImN markers with their functions.

Conclusion

LOX-1-expressing ImNs may help identifying COVID-19 patients at high risk of severity and thrombosis complications.

Critical role of oxidized LDL receptor-1 in intravascular thrombosis in a severe influenza mouse model

Although coagulation abnormalities, including microvascular thrombosis, are thought to contribute to tissue injury and single- or multiple-organ dysfunction in severe influenza, the detailed mechanisms have yet been clarified. This study evaluated influenza-associated abnormal blood coagulation utilizing a severe influenza mouse model. After infecting C57BL/6 male mice with intranasal applications of 500 plaque-forming units of influenza virus A/Puerto Rico/8/34 (H1N1; PR8), an elevated serum level of prothrombin fragment 1 + 2, an indicator for activated thrombin generation, was observed. Also, an increased gene expression of oxidized low-density lipoprotein (LDL) receptor-1 (Olr1), a key molecule in endothelial dysfunction in the progression of atherosclerosis, was detected in the aorta of infected mice. Body weight decrease, serum levels of cytokines and chemokines, viral load, and inflammation in the lungs of infected animals were similar between wild-type and Olr1 knockout (KO) mice. In contrast, the elevation of prothrombin fragment 1 + 2 levels in the sera and intravascular thrombosis in the lungs by PR8 virus infection were not induced in KO mice. Collectively, the results indicated that OLR1 is a critical host factor in intravascular thrombosis as a pathogeny of severe influenza. Thus, OLR1 is a promising novel therapeutic target for thrombosis during severe influenza.

Lipid and Lipoprotein Dysregulation in Sepsis: Clinical and Mechanistic Insights into Chronic Critical Illness

In addition to their well-characterized roles in metabolism, lipids and lipoproteins have pleiotropic effects on the innate immune system. These undergo clinically relevant alterations during sepsis and acute inflammatory responses. High-density lipoprotein (HDL) plays an important role in regulating the immune response by clearing bacterial toxins, supporting corticosteroid release, decreasing platelet aggregation, inhibiting endothelial cell apoptosis, reducing the monocyte inflammatory response, and inhibiting expression of endothelial cell adhesion molecules. It undergoes quantitative as well as qualitative changes which can be measured using the HDL inflammatory index (HII). Pro-inflammatory, or dysfunctional HDL (dysHDL) lacks the ability to perform these functions, and we have also found it to independently predict adverse outcomes and organ failure in sepsis. Another important class of lipids known as specialized pro-resolving mediators (SPMs) positively affect the escalation and resolution of inflammation in a temporal fashion. These undergo phenotypic changes in sepsis and differ significantly between survivors and non-survivors. Certain subsets of sepsis survivors go on to have perilous post-hospitalization courses where this inflammation continues in a low grade fashion. This is associated with immunosuppression in a syndrome of persistent inflammation, immunosuppression, and catabolism syndrome (PICS). The continuous release of tissue damage-related patterns and viral reactivation secondary to immunosuppression feed this chronic cycle of inflammation. Animal data indicate that dysregulation of endogenous lipids and SPMs play important roles in this process. Lipids and their associated pathways have been the target of many clinical trials in recent years which have not shown mortality benefit. These results are limited by patient heterogeneity and poor animal models. Considerations of sepsis phenotypes and novel biomarkers in future trials are important factors to be considered in future research. Further characterization of lipid dysregulation and chronic inflammation during sepsis will aid mortality risk stratification, detection of sepsis, and inform individualized pharmacologic therapies.

Sensing Tissue Damage by Myeloid C-Type Lectin Receptors

After both sterile and infectious insults, damage is inflicted on tissues leading to accidental or programmed cell death. In addition, events of programmed cell death also take place under homeostatic conditions, such as in embryo development or in the turnover of hematopoietic cells. Mammalian tissues are seeded with myeloid immune cells, which harbor a plethora of receptors that allow the detection of cell death, modulating immune responses. The myeloid C-type lectin receptors (CLRs) are one of the most prominent families of receptors involved in tailoring immunity after sensing dead cells. In this chapter, we will cover a diversity of signals arising from different forms of cell death and how they are recognized by myeloid CLRs. We will also explore how myeloid cells develop their sentinel function, exploring how some of these CLRs identify cell death and the type of responses triggered thereof. In particular, we will focus on DNGR-1 (CLEC9A), Mincle (CLEC4E), CLL-1 (CLEC12A), LOX-1 (OLR1), CD301 (CLEC10A) and DEC-205 (LY75) as paradigmatic death-sensing CLRs expressed by myeloid cells. The molecular processes triggered after cell death recognition by myeloid CLRs contribute to the regulation of immune responses in pathologies associated with tissue damage, such as infection, autoimmunity and cancer. A better understanding of these processes may help to improve the current approaches for therapeutic intervention.

Matrix Metalloproteinase 9 is Regulated by LOX-1 and erk1/2 Pathway in Dental Peri-Implantitis

BACKGROUND AND OBJECTIVE

Dental peri-implantitis, which can be caused by several different microbial factors, is characterized by inflammatory lesions of the surrounding hard and soft tissues of an oral implant. Matrix Metalloproteinase 9 (MMP9) is thought to be involved in the pathogenesis of peri-implantitis. However, the regulatory mechanism of MMP9 in peri-implantitis has not been fully elucidated. In this study, we tried to evaluate the regulatory mechanism of MMP9 in peri-implantitis.

METHODS

We collected Peri-Implant Crevicular Fluid (PICF) from ten healthy implants and ten periimplantitis patients and compared their expression level of MMP9. We also cultured macrophages from the peripheral blood of healthy volunteers infected by Porphyromonas gingivalis to reveal the regulatory mechanism of MMP9 in peri-implantitis. Western blot, immunofluorescence staining and quantitative Polymerase Chain Reaction (RT-PCR) were used to better characterize the mechanism of MMP9.

RESULTS

The expression of MMP9 was up-regulated in peri-implantitis patient PICF and P. gingivalis infected human macrophages. LOX-1, not dectin-1, was found to mediate MMP9 expression in human macrophages with P. gingivalis infection. Expression of Erk1/2 was responsible for infection-induced MMP9 expression. Finally, use of a broad-spectrum metalloproteinase inhibitor impaired LOX-1 expression in infected macrophages.

CONCLUSION

Our results demonstrate that MMP9 is involved in dental peri-implantitis and is regulated by LOX-1 and Erk1/2. This LOX-1/MMP9 signaling pathway may represent a potential drug target for peri-implantitis.

Intestinal Lipid Metabolism Genes Regulated by miRNAs

MicroRNAs (miRNAs) crucial roles in translation repression and post-transcriptional adjustments contribute to regulate intestinal lipid metabolism. Even though their actions in different metabolic tissues have been elucidated, their intestinal activity is yet unclear. We aimed to investigate intestinal miRNA-regulated lipid metabolism-related genes, by creating an intestinal-specific Dicer1 knockout (Int-Dicer1 KO) mouse model, with a depletion of microRNAs in enterocytes. The levels of 83 cholesterol and lipoprotein metabolism-related genes were assessed in the intestinal mucosa of Int-Dicer1 KO and Wild Type C57BL/6 (WT) littermates mice at baseline and 2 h after an oral lipid challenge. Among the 18 genes selected for further validation, Hmgcs2, Acat1 and Olr1 were found to be strong candidates to be modulated by miRNAs in enterocytes and intestinal organoids. Moreover, we report that intestinal miRNAs contribute to the regulation of intestinal epithelial differentiation. Twenty-nine common miRNAs found in the intestines were analyzed for their potential to target any of the three candidate genes found and validated by miRNA-transfection assays in Caco-2 cells. MiR-31-5p, miR-99b-5p, miR-200a-5p, miR-200b-5p and miR-425-5p are major regulators of these lipid metabolism-related genes. Our data provide new evidence on the potential of intestinal miRNAs as therapeutic targets in lipid metabolism-associated pathologies.

Regulation of LOX-1 on adhesion molecules and neutrophil infiltration in mouse Aspergillus fumigatus keratitis

AIM

To determine whether lectin-like ox-LDL receptor (LOX-1) regulates adhesion molecules expression and neutrophil infiltration in Aspergillus fumigatus (A. fumigatus) keratitis of C57BL/6 mice.

METHODS

C57BL/6 mice were pretreated with a neutralizing antibody to LOX-1 (5 µg/5 µL) or control nonspecific IgG (5 µg/5 µL), LOX-1 inhibitor Poly-I (2 µg/5 µL) or PBS by subconjunctival injection. Fungal keratitis (FK) mouse models of C57BL/6 mice were established by scraping corneal central epithelium, smearing A. fumigatus on the corneal surface and covering the eye with contact lenses. The corneal response to infection was assessed via clinical score. The mRNA levels of the adhesion molecules intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), P-selectin and E-selectin were tested in control and infected corneas by reverse transcription-polymerase chain reaction (RT-PCR). The protein levels of ICAM-1 were evaluated by immunofluorescence (IF) and Western blot. Neutrophils were extracted from the abdominal cavity of C57BL/6 mice followed by pretreatment using antibody to LOX-1 (10 µg/mL) or control nonspecific IgG (10 µg/mL), the Poly-I (4 µg/mL) or PBS. The cells were then stimulated with A. fumigatus and tested mRNA and protein levels of lymphocyte function-associated antigen-1 (LFA-1) using RT-PCR and Western blot. IF and myeloperoxidase (MPO) assays were used to assess neutrophil infiltration in mice corneas.

RESULTS

Pretreatment of LOX-1 antibody or the Poly-I reduced the degree of inflammation of cornea and decreased the clinical FK score compared with pretreatment of IgG or PBS (both P<0.01). And these pretreatment also displayed an obvious decline in the mRNA levels of ICAM-1, VCAM-1, P-selectin, E-selectin and LFA-1 expression compared with control groups (all P<0.01). Furthermore, pretreated with LOX-1 antibody or Poly-I, the protein levels of ICAM-1 and LFA-1 also decreased compared with control groups (all P<0.05). Neutrophil infiltration in the cornea was significantly reduced after pretreatment of LOX-1 antibody or Poly-I compared with control groups by IF and MPO assays (both P<0.01).

CONCLUSION

Inhibition of LOX-1 can decrease the expression of adhesion molecules and reduce neutrophil infiltration in A. fumigatus infected corneas of C57BL/6 mice.

Isoflavone-mediated radioprotection involves regulation of early endothelial cell death and inflammatory signaling in Radiation-Induced lung injury

Purpose: Vascular damage and inflammation are limiting toxic effects of lung cancer radiotherapy, which lead to pneumonitis and pulmonary fibrosis. We have demonstrated that soy isoflavones (SIF) mitigate these toxic effects at late time points after radiation. However, the process by which SIF impacts the onset of radiation-induced inflammation remains to be elucidated. We have now investigated early events of radiation-induced inflammation and identified cellular and molecular signaling patterns by endothelial cells that could be modified by SIF to control vascular damage and the initiation of lung inflammation.Materials and methods: Histopathological, cellular and molecular studies were performed on mouse lungs from C57Bl/6 mice treated with 10 Gy of thoracic radiation (XRT) in conjunction with daily oral SIF treatment given prior and after radiation. Parallel studies were performed in-vitro using EA.hy926 endothelial cell line with SIF and radiation. Immunohistochemistry, western blots analysis, and flow cytometry were performed on lung tissue or EA.hy926 cells to analyze endothelial cells, their patterns of cell death or survival, and signaling molecules involved in inflammatory events.Results: Histopathological differences in inflammatory infiltrates and vascular injury in lungs, including vascular endothelial cells, were observed with SIF treatment at early time points post-XRT. XRT-induced expression of proinflammatory adhesion molecule ICAM-1 cells was reduced by SIF in-vitro and in-vivo in endothelial cells. Molecular changes in endothelial cells with SIF treatment in conjunction with XRT included increased DNA damage, reduced cell viability and cyclin B1, and inhibition of nuclear translocation of NF-κB. Analysis of cell death showed that SIF treatment promoted apoptotic endothelial cell death and decreased XRT-induced type III cell death. In-vitro molecular studies indicated that SIF + XRT increased apoptotic caspase-9 activation and production of IFNβ while reducing the release of inflammatory HMGB-1 and IL-1α, the cleavage of pyroptotic gasdermin D, and the release of active IL-1β, which are all events associated with type III cell death.Conclusions: SIF + XRT caused changes in patterns of endothelial cell death and survival, proinflammatory molecule release, and adhesion molecule expression at early time points post-XRT associated with early reduction of immune cell recruitment. These findings suggest that SIF could mediate its radioprotective effects in irradiated lungs by limiting excessive immune cell homing via vascular endothelium into damaged lung tissue and curtailing the overall inflammatory response to radiation.

LOX-1 is involved in TLR2 induced RANKL regulation in peri-implantitis

PURPOSE

To explore whether receptor activator of nuclear factor kappa-B ligand (RANKL) is involved in the nosogenesis of peri-implantitis and to reveal the regulatory mechanism in Porphyromonas gingivalis induced RANKL production.

METHODS

Therefore, we collected peri-implant crevicular fluid (PICF) and gingival tissues from healthy implants and peri-implantitis patients. The expression of RANKL in samples was tested by ELISA, Western blot and immunofluorescence staining. The production of RANKL in THP-1 macrophages stimulated with P. gingivalis was detected by qRT-PCR and Western blot. Then macrophages were pre-treated with neutralizing antibodies of Toll-like receptor 2 (TLR2) or lectin-type oxidized LDL receptor 1 (LOX-1) and inhibitors of TLR2, LOX-1 or Erk1/2 before P. gingivalis stimulation to evaluate the roles of TLR2, LOX-1 and Erk1/2 in RANKL production by qRT-PCR and Western blot.

RESULTS

The protein level of RANKL was higher in PICF of peri-implantitis patients than healthy implants. We observed increased RANKL expression in P. gingivalis infected macrophages compared to controls. RANKL induced by P. gingivalis stimulation was mediated by TLR2 and Erk1/2 signaling pathway in THP-1 macrophages. LOX-1 is involved in TLR2 induced RANKL expression.

CONCLUSION

RANKL was involved in peri-implantitis, and regulated by TLR2, LOX-1 and Erk1/2 signaling against P. gingivalis infection. As the novel inflammation pathway triggers, TLR2 and LOX-1 which mediate RANKL production seems to be potential drug targets of peri-implantitis.

Wnt5a is involved in LOX-1 and TLR4 induced host inflammatory response in peri-implantitis

BACKGROUND AND OBJECTIVE

Peri-implantitis is a plaque-associated pathological condition occurring in tissues around dental implants, characterized by inflammation in the peri-implant mucosa and subsequent progressive loss of supporting bone. Wnt5a is the activating ligand of the non-canonical Wnt signaling pathways and plays important roles in leukocyte infiltration and cytokine/ chemokine production in inflammatory disorders. Previous studies showed that Wnt5a was significantly up-regulated in gingival tissues of chronic and aggressive periodontitis. However, the roles and the regulatory mechanisms of Wnt5a in peri-implantitis are not well known.

METHODS

The expression of Wnt5a in gingival tissues collected from 8 healthy implant patients and 8 peri-implantitis patients was analyzed by Western blotting and immunofluorescence. Porphyromonas gingivalis infected macrophages isolated from the peripheral blood of healthy volunteers were used as an in vitro cellular model of peri-implantitis. Using neutralizing antibodies, inhibitors and siRNA, the production and roles of Wnt5a in peri-implantitis were assessed by immunofluorescence, quantitative polymerase chain reaction (RT-PCR) and Western blotting. Unpaired two-tailed Student's t test was used to compare qRT-PCR and Western blotting results. P ≤ .05 was considered statistically significant.

RESULTS

Wnt5a was highly expressed in the gingival tissues of peri-implantitis patients. Compared to controls, Wnt5a increased in P gingivalis infected macrophages. Wnt5a production in response to P gingivalis infection was dependent on LOX-1 and TLR4. Compared to controls, Wnt5a knockdown impaired IL-1β, MCP-1, and MMP2 production induced by P gingivalis infection.

CONCLUSION

Our results indicate that Wnt5a is involved in LOX-1 and TLR4 induced inflammatory signature via inflammatory cytokines production in response to P gingivalis infection. These findings demonstrate that Wnt5a maybe an important component of the host immune response in peri-implantitis.

ATF4 Involvement in TLR4 and LOX-1-Induced Host Inflammatory Response to Aspergillus fumigatus Keratitis

Purpose

Activating transcription factor 4 (ATF4) is induced by various stressors. Here, we investigated the expression of ATF4 in the host inflammatory response to Aspergillus fumigatus (A. fumigatus) keratitis.

Methods

A. fumigatus keratitis mouse models developed by intrastromal injection as well as corneal epithelium scratching were examined daily with a slit lamp microscope for corneal opacification and ulceration. Subsequent in vitro experimentation was carried out in human corneal epithelial cells (HCECs) as well as THP-1 macrophages infected with A. fumigatus. Inhibitors, including CLI-095, Poly (I), SCH772984, and SP600125, were used to assess the role of proteins like toll-like receptor 4 (TLR4), lectin-type oxidized LDL receptor 1 (LOX-1), extracellular signal-regulated kinases (ERK1/2), and c-Jun N-terminal kinase (JNK) in ATF4 expression as a response to A. fumigatus infection. This assessment was made in both mouse models and HCECs using western blot.

Results

Compared to the controls, ATF4 was increased in corneas from two kinds of A. fumigatus keratitis models at 3 days after infection. ATF4 expression was upregulated with A. fumigatus conidia both in HCECs and THP-1 macrophages 16 hours after stimulation. Furthermore, ATF4 expression in response to A. fumigatus infection was shown to be dependent on TLR4 and LOX-1 expression, and ERK1/2 and JNK contributed to the expression of ATF4 in response to A. fumigatus.

Conclusion

Our results clearly indicate that ATF4 was involved in the host antifungal immune response to A. fumigatus keratitis; expression was found to be dependent on TLR4, LOX-1 expression, and MAPKs pathway.

Fenretinide Inhibits Neutrophil Recruitment and IL-1β Production in Aspergillus fumigatus Keratitis

Purpose:

Fungal keratitis is a major cause of corneal ulcers, resulting in significant visual impairment and blindness. Fenretinide, a derivative of vitamin A, has been shown to suppress inflammation in a multitude of diseases. In this study, we aimed to characterize the effect of fenretinide in Aspergillus fumigatus keratitis of the eye in a mouse model.

Methods:

In vivo and in vitro experiments were performed in mouse models and THP-1 macrophage cell cultures infected with A. fumigatus, respectively. Experimental subjects were first pretreated with fenretinide, and then the effect of the compound was assessed with clinical evaluation, neutrophil staining, myeloperoxidase assay, quantitative polymerase chain reaction (qRT-PCR), and western blot.

Results:

We confirmed that fenretinide contributed to protection of corneal transparency during early mouse A. fumigatus keratitis by reducing neutrophil recruitment, decreasing myeloperoxidase (MPO) levels and increasing apoptosis. Compared with controls, fenretinide impaired proinflammatory cytokine interleukin 1 beta (IL-1β) production in response to A. fumigatus exposure with contributions by lectin-type oxidized LDL receptor 1 (LOX-1) and c-Jun N-terminal kinase (JNK).

Conclusions:

Together, these findings demonstrate that fenretinide may suppress inflammation through reduced neutrophil recruitment and inflammatory cytokine production in A. fumigatus keratitis.

Wnt5a contributes to dectin-1 and LOX-1 induced host inflammatory response signature in Aspergillus fumigatus keratitis

Fungal keratitis causes devastating corneal ulcers which can result in significant visual impairment and even blindness. As a ligand that activates the non-canonical Wnt signaling pathways, Wnt5a triggers the production of important inflammatory chemokines and the chemotactic migration of neutrophils. In this study we aimed to characterize the role of Wnt5a production, in situ, in vivo and in vitro in response to fungal keratitis. Wnt5a expression in corneas of Aspergillus fumigatus (A. fumigatus) keratitis patients was determined by quantitative polymerase chain reaction (qRT-PCR) and immunofluorescence. In vivo and in vitro experiments were then performed in mouse models and THP-1 macrophages cell cultures infected with A. fumigatus, respectively. C57BL/6 mice were pretreated with siRNAs or neutralizing antibodies for dectin-1, LOX-1 and Wnt5a, or inhibitors of erk1/2 and JNK. Changes in Wnt5a expression were assessed by clinical evaluation, qRT-PCR, immunofluorescence, western blot and bioluminescence imaging system image acquisition. We confirmed that corneal Wnt5a expression increased with A. fumigatus keratitis in patients and a murine model. Wnt5a production was dependent on dectin-1 and LOX-1 expression with contributions by Erk1/2 and JNK pathways. Additionally, Wnt5a knockdown revealed decreased levels of MPO, lower neutrophil recruitment, and a higher fungal load in mouse models. Compared with controls, Wnt5a knockdown impaired pro-inflammatory cytokine IL-1β production in response to A. fumigatus exposure. Wnt5a also produces dectin-1 and LOX-1 induced inflammatory signature via effective neutrophil recruitment and inflammatory cytokine production in response to A. fumigatus keratitis. These findings demonstrate that Wnt5a is a critical component of the antifungal immune response.

CEBPE-Mutant Specific Granule Deficiency Correlates With Aberrant Granule Organization and Substantial Proteome Alterations in Neutrophils

Specific granule deficiency (SGD) is a rare disorder characterized by abnormal neutrophils evidenced by reduced granules, absence of granule proteins, and atypical bilobed nuclei. Mutations in CCAAT/enhancer-binding protein-ε (CEBPE) are one molecular etiology of the disease. Although C/EBPε has been studied extensively, the impact of CEBPE mutations on neutrophil biology remains elusive. Here, we identified two SGD patients bearing a previously described heterozygous mutation (p.Val218Ala) in CEBPE. We took this rare opportunity to characterize SGD neutrophils in terms of granule distribution and protein content. Granules of patient neutrophils were clustered and polarized, suggesting that not only absence of specific granules but also defects affecting other granules contribute to the phenotype. Our analysis showed that remaining granules displayed mixed protein content and lacked several glycoepitopes. To further elucidate the impact of mutant CEBPE, we performed detailed proteomic analysis of SGD neutrophils. Beside an absence of several granule proteins in patient cells, we observed increased expression of members of the linker of nucleoskeleton and cytoskeleton complex (nesprin-2, vimentin, and lamin-B2), which control nuclear shape. This suggests that absence of these proteins in healthy individuals might be responsible for segmented shapes of neutrophilic nuclei. We further show that the heterozygous mutation p.Val218Ala in CEBPE causes SGD through prevention of nuclear localization of the protein product. In conclusion, we uncover that absence of nuclear C/EBPε impacts on spatiotemporal expression and subsequent distribution of several granule proteins and further on expression of proteins controlling nuclear shape.

LOX-1 is involved in IL-1β production and extracellular matrix breakdown in dental peri-implantitis

PURPOSE

To explore whether lectin-type oxidized LDL receptor 1 (LOX-1), interleukin 1 beta (IL-1β), matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9) are involved in the nosogenesis of human dental peri-implantitis and determine the role of LOX-1 in IL-1β, MMP2 and MMP9 production in response to Porphyromonas gingivalis.

METHODS

Peri-implant crevicular fluid (PICF) was collected from ten patients with healthy implants and ten patients with peri-implantitis. The LOX-1 protein in PICF was detected by Western-blot, and the expression of LOX-1 in superficial gingiva of peri-implantitis patients was detected by immunofluorescence staining. The IL-1β, MMP2 and MMP9 proteins in PICF were detected by enzyme-linked immunosorbent assay (ELISA). THP-1 macrophages were pretreated with neutralizing antibody (LOX-1) and inhibitors (LOX-1 and c-Jun N-terminal kinase, JNK) to evaluate the role of LOX-1 and JNK in IL-1β production, as well as the role of LOX-1 in MMP2 and MMP9 production in response to P. gingivalis by quantitative polymerase chain reaction (RT-PCR) and Western-blot.

RESULTS

LOX-1, IL-1β, MMP2 and MMP9 increased in PICF of peri-implantitis patients and in THP-1 macrophages on P. gingivalis stimulation. IL-1β, MMP2 and MMP9 production in response to P. gingivalis in THP-1 macrophages was dependent on LOX-1. JNK was responsible for LOX-1 induced IL-1β production as a result of P. gingivalis infection.

CONCLUSION

LOX-1 is involved in IL-1β production and extracellular matrix breakdown is a novel inflammatory pathway trigger and potential drug target in human dental peri-implantitis.

An interaction map of circulating metabolites, immune gene networks, and their genetic regulation

BACKGROUND

Immunometabolism plays a central role in many cardiometabolic diseases. However, a robust map of immune-related gene networks in circulating human cells, their interactions with metabolites, and their genetic control is still lacking. Here, we integrate blood transcriptomic, metabolomic, and genomic profiles from two population-based cohorts (total N = 2168), including a subset of individuals with matched multi-omic data at 7-year follow-up.

RESULTS

We identify topologically replicable gene networks enriched for diverse immune functions including cytotoxicity, viral response, B cell, platelet, neutrophil, and mast cell/basophil activity. These immune gene modules show complex patterns of association with 158 circulating metabolites, including lipoprotein subclasses, lipids, fatty acids, amino acids, small molecules, and CRP. Genome-wide scans for module expression quantitative trait loci (mQTLs) reveal five modules with mQTLs that have both cis and trans effects. The strongest mQTL is in ARHGEF3 (rs1354034) and affects a module enriched for platelet function, independent of platelet counts. Modules of mast cell/basophil and neutrophil function show temporally stable metabolite associations over 7-year follow-up, providing evidence that these modules and their constituent gene products may play central roles in metabolic inflammation. Furthermore, the strongest mQTL in ARHGEF3 also displays clear temporal stability, supporting widespread trans effects at this locus.

CONCLUSIONS

This study provides a detailed map of natural variation at the blood immunometabolic interface and its genetic basis, and may facilitate subsequent studies to explain inter-individual variation in cardiometabolic disease.

Involvement of epithelial-mesenchymal transition afforded by activation of LOX-1/ TGF-β1/KLF6 signaling pathway in diabetic pulmonary fibrosis

BACKGROUND AND OBJECTIVE

Diabetic pulmonary fibrosis is a severe disease that increases mortality risk of diabetes. However, the molecular mechanisms leading to pulmonary fibrosis in diabetes are poorly understood. This study investigated the roles of epithelial-mesenchymal transition (EMT) and the associated molecular mechanisms in streptozotocin (STZ)-induced rat pulmonary fibrosis.

METHODS

The rat model of diabetic pulmonary fibrosis was established by intraperitoneal injection of a single dose of STZ (35 mg/kg). Typical lesions of diabetic pulmonary fibrosis were observed 8 weeks after STZ injection by hematoxylin-eosin (HE) and Masson staining. Human bronchial epithelial cells (HBECs) and A549 cells were treated by high glucose. Gene or protein expression was measured by real-time PCR, Western blot, immunohistochemistry or immunofluorescence. The knockdown of lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) or transforming growth factor-β1 (TGF-β1) was conducted by siRNA.

RESULTS

Activation of EMT was observed in lung tissues of STZ-induced diabetic rats, exhibiting a loss in the epithelial cell marker E-cadherin and an increase in the mesenchymal marker Vimentin. The protein and mRNA levels of LOX-1, TGF-β1 and krüppel-like factor 6 (KLF6) in the lung tissues were increased. Incubation of HBECs and A549 cells with high glucose activated EMT and induced an increase in LOX-1, TGF-β1 and KLF-6 expression. LOX-1 siRNA inhibited high glucose-induced EMT in HBECs and A549 cells, which correlated with the reduction of TGF-β1. TGF-β1 siRNA decreased the expression of LOX-1 and KLF6.

CONCLUSIONS

EMT was involved in the pathological process of diabetic pulmonary fibrosis, which was activated by LOX-1/TGF-β1/KLF6 signaling pathway.

Neutrophil dysregulation during sepsis: an overview and update

Sepsis remains a leading cause of death worldwide, despite advances in critical care, and understanding of the pathophysiology and treatment strategies. No specific therapy or drugs are available for sepsis. Neutrophils play a critical role in controlling infection under normal conditions, and it is suggested that their migration and antimicrobial activity are impaired during sepsis which contribute to the dysregulation of immune responses. Recent studies further demonstrated that interruption or reversal of the impaired migration and antimicrobial function of neutrophils improves the outcome of sepsis in animal models. In this review, we provide an overview of the associated mediators and signal pathways involved which govern the survival, migration and antimicrobial function of neutrophils in sepsis, and discuss the potential of neutrophils as a target to specifically diagnose and/or predict the outcome of sepsis.

Deletion of Nlrp3 Augments Survival during Polymicrobial Sepsis by Decreasing Autophagy and Enhancing Phagocytosis

NLRP3 inflammasome is a critical player in innate immunity. Neutrophil recruitment to tissues and effective neutrophil function are critical innate immune mechanisms for bacterial clearance. However, the role of NLRP3 in neutrophil-dependent bacterial clearance in polymicrobial sepsis is unclear. In this study, we evaluated the role of NLRP3 in polymicrobial sepsis induced by cecal ligation and puncture (CLP). Our results showed protection from death in NLRP3-deficient (Nlrp3^-/-) and NLRP3 inhibitor-treated wild-type (C57BL/6) mice. Nlrp3^-/- and NLRP3 inhibitor-treated mice displayed lower bacterial load but no impairment in neutrophil recruitment to peritoneum. However, neutrophil depletion abrogated protection from death in Nlrp3^-/- mice in response to CLP. Intriguingly, following CLP, Nlrp3^-/- peritoneal cells (primarily neutrophils) demonstrate decreased autophagy, augmented phagocytosis, and enhanced scavenger receptor (macrophage receptor with collagenous structure) and mannose-binding leptin expression. These findings enhance our understanding of the critical role of NLRP3 in modulating autophagy and phagocytosis in neutrophils and suggest that therapies should be targeted to modulate autophagy and phagocytosis in neutrophils to control bacterial burden in tissues during CLP-induced polymicrobial sepsis.

Association of the LOX-1 rs1050283 Polymorphism with Risk for Atherosclerotic Cerebral Infarction and its Effect on sLOX-1 and LOX-1 Expression in a Chinese Population

AIMS

The interaction between lectin-like oxidized low density lipoprotein (LDL) receptor-1 (LOX-1) and oxidized LDL (ox-LDL) has been viewed as an important pathogenic factor for cardiovascular diseases. This study aimed to explore the association of a functional polymorphism rs1050283 in the 3'-untranslated region of the LOX-1 gene with atherosclerotic cerebral infarction (ACI) susceptibility, and we also investigated the effects of the rs1050283 polymorphism on LOX-1 expression and serum levels of sLOX-1 in patients with ACI.

METHODS

A case-controlled study was performed in 526 patients with ACI and 640 healthy controls. Genotyping was performed by DNA sequencing method. Real-time PCR and Western blotting were used to determine the level of LOX-1 expression. Serum levels of sLOX-1 were quantified using ELISA according to the manufacturer's instruction.

RESULTS

The results of the present study showed that the frequency of rs1050283 T allele was significantly higher in patients with ACI than in healthy controls. We also found that the rs1050283 polymorphism T allele was associated with increased LOX-1 expression at mRNA and protein levels in patients with ACI. Furthermore, we also observed that among patients with ACI, those with the rs1050283 T allele showed an increased serum level of sLOX-1.

CONCLUSION

Our research demonstrated that the rs1050283 T allele of LOX-1 is strongly associated with an increased risk for ACI in a Chinese population, which also affects levels of LOX-1 and sLOX-1.

The role of LOX-1 on innate immunity against Aspergillus keratitis in mice

AIM

To explore the effects of lectin-like ox-LDL receptor (LOX-1) on innate immunity against Aspergillus fumigatus (A. fumigatus ) in mice cornea.

METHODS

The mRNA levels of LOX-1 were tested in normal and A. fumigatus infected corneas of C57BL/6 and BALB/c mice. The expression of LOX-1, pro-inflammatory cytokines TNF-α, CXCL1 and IL-6, anti-inflammatory cytokines IL-10, and matrix metalloproteinase 9 (MMP9) were tested with treatment with LOX-1 neutralizing antibody or control IgG in A. fumigatus infected corneas of C57BL/6. Macrophages and neutrophils were extracted from susceptible C57BL/6 mice, and pretreated with LOX-1 neutralizing antibody or IgG, then stimulated with A. fumigatus. The mRNA levels of LOX-1, TNF-α, CXCL1, IL-6, IL-10 and MMP9 were evaluated by polymerase chain reaction.

RESULTS

The expression of LOX-1 was significantly increased in C57BL/6 mice corneas after A. fumigatus infection compared with BABL/c mice. After treatment with LOX-1 neutralizing antibody, the expression of LOX-1, TNF-α, CXCL1, IL-6, MMP9 and IL-10 in C57BL/6 corneas were significantly decreased compared with treatment with control IgG; the expression of LOX-1, CXCL1, IL-6 and IL-10 were significantly decreased in macrophages, while TNF-α and MMP9 expressions had no change; LOX-1, TNF-α, CXCL1, IL-6, MMP9 and IL-10 expressions were significantly decreased in neutrophils.

CONCLUSION

The expression of LOX-1 can affect the expression of pro-inflammatory and anti-inflammatory cytokines in fungal infected corneas, macrophages and neutrophils of C57BL/6. LOX-1 inhibition rebalances the inflammatory response of fungal keratitis in mice.

Exploring host-pathogen interactions through genome wide protein microarray analysis

During bacterial pathogenesis extensive contacts between the human and the bacterial extracellular proteomes take place. The identification of novel host-pathogen interactions by standard methods using a case-by-case approach is laborious and time consuming. To overcome this limitation, we took advantage of large libraries of human and bacterial recombinant proteins. We applied a large-scale protein microarray-based screening on two important human pathogens using two different approaches: (I) 75 human extracellular proteins were tested on 159 spotted Staphylococcus aureus recombinant proteins and (II) Neisseria meningitidis adhesin (NadA), an important vaccine component against serogroup B meningococcus, was screened against ≈2300 spotted human recombinant proteins. The approach presented here allowed the identification of the interaction between the S. aureus immune evasion protein FLIPr (formyl-peptide receptor like-1 inhibitory protein) and the human complement component C1q, key players of the offense-defense fighting; and of the interaction between meningococcal NadA and human LOX-1 (low-density oxidized lipoprotein receptor), an endothelial receptor. The novel interactions between bacterial and human extracellular proteins here presented might provide a better understanding of the molecular events underlying S. aureus and N. meningitidis pathogenesis.

Paradoxical Roles of the Neutrophil in Sepsis: Protective and Deleterious

Sepsis, an overwhelming inflammatory response syndrome secondary to infection, is one of the costliest and deadliest medical conditions worldwide. Neutrophils are classically considered to be essential players in the host defense against invading pathogens. However, several investigations have shown that impairment of neutrophil migration to the site of infection, also referred to as neutrophil paralysis, occurs during severe sepsis, resulting in an inability of the host to contain and eliminate the infection. On the other hand, the neutrophil antibacterial arsenal contributes to tissue damage and the development of organ dysfunction during sepsis. In this review, we provide an overview of the main events in which neutrophils play a beneficial or deleterious role in the outcome of sepsis.

Inhibitory effects of Mycoepoxydiene on macrophage foam cell formation and atherosclerosis in ApoE-deficient mice

Background

Mycoepoxydiene (MED) is a polyketide that can be isolated from a marine fungus and is associated with various activities, including antitumor and anti-inflammatory functions. However, its effects on atherosclerosis remain unknown. Macrophage-derived foam cells play crucial roles in the initiation and progression of atherosclerotic plaques. In this study, we investigated the effects of MED on oxidized low-density lipoprotein (ox-LDL)-induced macrophage foam cell formation and activation, and on high fat diet (HFD)-induced atherosclerosis in ApoE-deficient (ApoE^−/−) mice.

Results

Our findings show that MED could significantly inhibit ox-LDL-induced macrophage foam cell formation and suppress the expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), which is a receptor for ox-LDL. Additionally, MED could significantly inhibit the secretion of proinflammatory cytokines, such as tumor necrosis factor (TNF-α), interleukin (IL)-6, and IL-1β. Mechanistically, MED inhibited NF-κB activation by blocking IκB-α degradation and reducing NF-κB DNA binding activity. Moreover, MED dramatically reduced the occurrence of HFD-induced atherosclerotic lesions in ApoE^−/− mice.

Conclusions

Our study shows that MED can inhibit macrophage foam cell formation and activation by inhibiting NF-κB activation, thereby protecting ApoE^−/− mice from HFD-induced atherosclerosis. Our findings suggest that MED might be a potential lead compound for the development of antiatherosclerotic therapeutics.

Electronic supplementary material

The online version of this article (doi:10.1186/s13578-015-0017-y) contains supplementary material, which is available to authorized users.

Scavenger receptor structure and function in health and disease

Scavenger receptors (SRs) are a ‘superfamily’ of membrane-bound receptors that were initially thought to bind and internalize modified low-density lipoprotein (LDL), though it is currently known to bind to a variety of ligands including endogenous proteins and pathogens. New family of SRs and their properties have been identified in recent years, and have now been classified into 10 eukaryote families, defined as Classes A-J. These receptors are classified according to their sequences, although in each class they are further classified based in the variations of the sequence. Their ability to bind a range of ligands is reflected on the biological functions such as clearance of modified lipoproteins and pathogens. SR members regulate pathophysiological states including atherosclerosis, pathogen infections, immune surveillance, and cancer. Here, we review our current understanding of SR structure and function implicated in health and disease.

Impact of dietary plane of energy during the dry period on lipoprotein parameters in the transition period in dairy cattle

The high energy demands of dairy cows during the transition period from late gestation into early lactation can place them at an increased risk for the development of metabolic and infectious diseases. Modification of the dry period diet has been investigated as a preventive means to minimize the detrimental aspects of metabolic shifts during the transition period. Studies investigating the impact of dry period diet on lipid parameters during the transition period have largely focused on markers of lipolysis and ketogenesis. Total cholesterol declines during the periparturient period and increases in early lactation. The impact total energy in the dry period diet has on the ability of the cow to maintain total serum cholesterol, as well as its natural high-density lipoprotein-rich status, during this metabolically challenging window is not clear. The impact of lipoproteins on inflammation and immune function may have a clinical impact on the cow's ability to ward off production-related diseases. In this study, we hypothesized that the provision of adequate, but not excessive, total metabolizable energy, would better allow the cow to maintain total cholesterol and a higher relative proportion of HDL throughout the transition period. Cows were allocated to one of three dry period dietary treatment groups following a randomized block design. Total serum triglycerides, cholesterol and lipoprotein fractions were measured on a weekly basis from approximately 7 weeks pre-calving to 6 weeks post-calving. The cows on the high energy diet maintained total serum cholesterol as compared to the cows provided a lower energy diet, but there was no significant increase in the LDL fraction of lipoproteins between diet treatment groups.

Key role for scavenger receptor B-I in the integrative physiology of host defense during bacterial pneumonia

Scavenger receptor B-I (SR-BI) is a multirecognition receptor that regulates cholesterol trafficking and cardiovascular inflammation. Although it is expressed by neutrophils (PMNs) and lung-resident cells, no role for SR-BI has been defined in pulmonary immunity. Herein, we report that, compared with SR-BI(+/+) counterparts, SR-BI(-/-) mice suffer markedly increased mortality during bacterial pneumonia associated with higher bacterial burden in the lung and blood, deficient induction of the stress glucocorticoid corticosterone, higher serum cytokines, and increased organ injury. SR-BI(-/-) mice had significantly increased PMN recruitment and cytokine production in the infected airspace. This was associated with defective hematopoietic cell-dependent clearance of lipopolysaccharide from the airspace and increased cytokine production by SR-BI(-/-) macrophages. Corticosterone replacement normalized alveolar neutrophilia but not alveolar cytokines, bacterial burden, or mortality, suggesting that adrenal insufficiency derepresses PMN trafficking to the SR-BI(-/-) airway in a cytokine-independent manner. Despite enhanced alveolar neutrophilia, SR-BI(-/-) mice displayed impaired phagocytic killing. Bone marrow chimeras revealed this defect to be independent of the dyslipidemia and adrenal insufficiency of SR-BI(-/-) mice. During infection, SR-BI(-/-) PMNs displayed deficient oxidant production and CD11b externalization, and increased surface L-selectin, suggesting defective activation. Taken together, SR-BI coordinates several steps in the integrated neutrophilic host defense response to pneumonia.

Sirt1 restrains lung inflammasome activation in a murine model of sepsis

Excessive inflammation is a major cause of organ damage during sepsis. The elderly are highly susceptible to sepsis-induced organ injury. Sirt1 expression is reduced during aging. In the present study, we investigated the role of Sirt1, a histone deacetylase, in controlling inflammatory responses in a murine sepsis model induced by cecal ligation and puncture (CLP). We examined lung inflammatory signaling in inducible Sirt1 knockout (Sirt1(-/-)) mice and wild-type littermates (Sirt1(+/+)) after CLP. Our results demonstrated that Sirt1 deficiency led to severe lung inflammatory injury. To further investigate molecular mechanisms of Sirt1 regulation of lung inflammatory responses in sepsis, we conducted a series of experiments to assess lung inflammasome activation after CLP. We detected increased lung inflammatory signaling including NF-κB, signal transducer and activator of transcription 3, and ERK1/2 activation in Sirt1(-/-) mice after CLP. Furthermore, inflammasome activity was increased in Sirt1(-/-) mice after CLP, as demonstrated by increased IL-1β and caspase-7 cleavage and activation. Aggravated inflammasome activation in Sirt1(-/-) mice was associated with the increased production of lung proinflammatory mediators, including ICAM-1 and high-mobility group box 1, and further disruption of tight junctions and adherens junctions, as demonstrated by dramatic reduction of lung claudin-1 and vascular endothelial-cadherin expression, which was associated with the upregulation of matrix metallopeptidase 9 expression. In summary, our results suggest that Sirt1 suppresses acute lung inflammation during sepsis by controlling inflammasome activation pathway.

MicroRNA-147b regulates vascular endothelial barrier function by targeting ADAM15 expression

A disintegrin and metalloproteinase15 (ADAM15) has been shown to be upregulated and mediate endothelial hyperpermeability during inflammation and sepsis. This molecule contains multiple functional domains with the ability to modulate diverse cellular processes including cell adhesion, extracellular matrix degradation, and ectodomain shedding of transmembrane proteins. These characteristics make ADAM15 an attractive therapeutic target in various diseases. The lack of pharmacological inhibitors specific to ADAM15 prompted our efforts to identify biological or molecular tools to alter its expression for further studying its function and therapeutic implications. The goal of this study was to determine if ADAM15-targeting microRNAs altered ADAM15-induced endothelial barrier dysfunction during septic challenge by bacterial lipopolysaccharide (LPS). An in silico analysis followed by luciferase reporter assay in human vascular endothelial cells identified miR-147b with the ability to target the 3′ UTR of ADAM15. Transfection with a miR-147b mimic led to decreased total, as well as cell surface expression of ADAM15 in endothelial cells, while miR-147b antagomir produced an opposite effect. Functionally, LPS-induced endothelial barrier dysfunction, evidenced by a reduction in transendothelial electric resistance and increase in albumin flux across endothelial monolayers, was attenuated in cells treated with miR-147b mimics. In contrast, miR-147b antagomir exerted a permeability-increasing effect in vascular endothelial cells similar to that caused by LPS. Taken together, these data suggest the potential role of miR147b in regulating endothelial barrier function by targeting ADAM15 expression.

TRAIL induces neutrophil apoptosis and dampens sepsis-induced organ injury in murine colon ascendens stent peritonitis

TNF-related apoptosis inducing ligand (TRAIL) influences several inflammatory reactions by partially still unknown mechanisms. TRAIL is produced and expressed by several cells of the immune system. Murine Colon Ascendens Stent Peritonitis (CASP) represents a hyperinflammatory model of diffuse peritonitis. As we have shown previously, TRAIL strongly improves survival in murine CASP. This is accompanied by a significantly reduced infiltration of neutrophils in the associated lymphoid tissue. Additionally, it is known that TRAIL induces apoptosis in neutrophils and acceleration of neutrophil apoptosis enhances resolution of inflammatory reactions. In this study, we investigated the correlation of the protective effect of TRAIL in sepsis and its influence on neutrophils. We found that neutrophils infiltrating the lymphoid organs express the TRAIL-receptor DR5 at high density. Furthermore, we demonstrated that TRAIL-treatment enhances apoptosis of neutrophils in the spleen, lung and liver and decreases organ injury during sepsis. To further examine a role for neutrophils in TRAIL-mediated protection in CASP, we have depleted neutrophils 24 hours prior to CASP. In these depleted mice, administration of TRAIL was ineffective. We conclude that TRAIL induces apoptosis in tissue-infiltrating neutrophils thereby protecting organs from sepsis-induced injury.

Chaperonin-containing TCP-1 complex directly binds to the cytoplasmic domain of the LOX-1 receptor

Lectin-like oxidized low-density lipoprotein receptor (LOX-1) is a scavenger receptor that binds oxidized low-density lipoprotein (OxLDL) and has a role in atherosclerosis development. The N-terminus intracellular region (cytoplasmic domain) of LOX-1 mediates receptor internalization and trafficking, potentially through intracellular protein interactions. Using affinity isolation, we identified 6 of the 8 components of the chaperonin-containing TCP-1 (CCT) complex bound to LOX-1 cytoplasmic domain, which we verified by coimmunoprecipitation and immunostaining in human umbilical vein endothelial cells. We found that the interaction between CCT and LOX-1 is direct and ATP-dependent and that OxLDL suppressed this interaction. Understanding the association between LOX-1 and the CCT complex may facilitate the design of novel therapies for cardiovascular disease.

Apolipoprotein E-deficient mice are susceptible to the development of acute lung injury

BACKGROUND

Apolipoprotein E (apoE) has been shown to play a pivotal role in the development of cardiovascular disease, attributable to its function in lipid trafficking and immune modulating properties; however, its role in modulating inflammation in the setting of acute lung injury (ALI) is unknown.

OBJECTIVE

To determine whether apoE-deficient mice (apoE-/-) are more susceptible to ALI compared to wild-type (WT) animals.

METHODS

Two independent models of ALI were employed. Firstly, WT and apoE-/- mice were randomized to acid aspiration (50 μl of 0.1 N hydrochloric acid) followed by 4 h of mechanical ventilation. Secondly, WT and apoE-/- mice were randomized to 72 h of hyperoxia exposure or room air. Thereafter, the intrinsic responses of WT and apoE-/- mice were assessed using the isolated perfused mouse lung (IPML) setup. Finally, based on elevated levels of oxidized low-density lipoprotein (oxLDL) in apoE-/-, the effect of oxLDL on lung endothelial permeability and inflammation was assessed.

RESULTS

In both in vivo models, apoE-/- mice demonstrated greater increases in lung lavage protein levels, neutrophil counts, and cytokine expression (p < 0.05) compared to WT mice. Experiments utilizing the IPML setup demonstrated no differences in intrinsic lung responses to injury between apoE-/- and WT mice, suggesting the presence of a circulating factor as being responsible for the in vivo observations. Finally, the exposure of lung endothelial cells to oxLDL resulted in increased monolayer permeability and IL-6 release compared to native (nonoxidized) LDL.

CONCLUSIONS

Our findings demonstrate a susceptibility of apoE-/- animals to ALI that may occur, in part, due to elevated levels of oxLDL.

Oxidized LDL and LOX-1 in experimental sepsis

Oxidized low-density lipoproteins (oxLDL) and the lectin-like oxLDL receptor-1 (LOX-1) are upregulated in inflammation. Because of the importance of inflammation and capillary leakage in the impairment of the microcirculation, which in turn contributes to the development of sepsis and multiorgan failure, the role of oxidized LDL and LOX-1 as players of intestinal inflammation is of great interest. In fact, the blockade of LOX-1 during experimental endotoxemia was effective in reducing leukocyte activation. There are several mechanisms by which oxLDL can participate in local and systemic inflammation, including cell proliferation, apoptosis, capillary perfusion, leukocyte-endothelial cell interactions, and endothelial activation. This review highlights the evidence relating oxLDL and LOX-1 to proinflammatory disease mechanisms. We also indicate situations when oxLDL, because of exposure time, dose, or degree of oxidization, is involved in disease resolution. Modulation of LOX-1 response could be utilized for the treatment of local and systemic inflammation, but the successful use of this target requires further understanding of its broad effects.