Identification of LPS-Activated Endothelial Subpopulations With Distinct Inflammatory Phenotypes and Regulatory Signaling Mechanisms

E-selectin in vascular pathophysiology

Selectins are a group of Ca2+-dependent, transmembrane type I glycoproteins which attract cell adhesion and migration. E-selectin is exclusively expressed in endothelial cells, and its expression is strongly enhanced upon activation by pro-inflammatory cytokines. The interaction of E-selectin with its ligands on circulating leukocytes captures and slows them down, further facilitating integrin activation, firm adhesion to endothelial cells and transmigration to tissues. Oxidative stress induces endothelial cell injury, leading to aberrant expression of E-selectin. In addition, the elevated level of E-selectin is positively related to high risk of inflammation. Dysregulation of E-selectin has been found in several pathological conditions including acute kidney injury (AKI), pulmonary diseases, hepatic pathology, Venous thromboembolism (VTE). Deletion of the E-selectin gene in mice somewhat ameliorates these complications. In this review, we describe the mechanisms regulating E-selectin expression, the interaction of E-selectin with its ligands, the E-selectin physiological and pathophysiological roles, and the therapeutical potential of targeting E-selectin.

HIV-Associated Hypertension: Risks, Mechanisms, and Knowledge Gaps

HIV type 1 (HIV-1) is the causative agent of AIDS. Since the start of the epidemic, HIV/AIDS has been responsible for ≈40 million deaths. Additionally, an estimated 39 million people are currently infected with the virus. HIV-1 primarily infects immune cells, such as CD4+ (cluster of differentiation 4+) T lymphocytes (T cells), and as a consequence, the number of CD4+ T cells progressively declines in people living with HIV. Within a span of ≈10 years, HIV-1 infection leads to the systemic failure of the immune system and progression to AIDS. Fortunately, potent antiviral therapy effectively controls HIV-1 infection and prevents AIDS-related deaths. The efficacy of the current antiviral therapy regimens has transformed the outcome of HIV/AIDS from a death sentence to a chronic disease with a prolonged lifespan of people living with HIV. However, antiviral therapy is not curative, is challenged by virus resistance, can be toxic, and, most importantly, requires lifelong adherence. Furthermore, the improved lifespan has resulted in an increased incidence of non-AIDS-related morbidities in people living with HIV including cardiovascular diseases, renal disease, liver disease, bone disease, cancer, and neurological conditions. In this review, we summarize the current state of knowledge of the cardiovascular comorbidities associated with HIV-1 infection, with a particular focus on hypertension. We also discuss the potential mechanisms known to drive HIV-1-associated hypertension and the knowledge gaps in our understanding of this comorbid condition. Finally, we suggest several directions of future research to better understand the factors, pathways, and mechanisms underlying HIV-1-associated hypertension in the post-antiviral therapy era.

Unveiling the Silent Intruder: H. pylori's Hidden Link to Ischemic Heart Disease

Cardiovascular disease is the leading cause of death. In addition to the well-known risk factors associated with cardiovascular disease, such as age, diabetes mellitus, smoking, hypertension, and obesity, there has been a growing concern regarding cardiac complications stemming from the Gram-negative bacteria Helicobacter pylori. While H. pylori is most commonly associated with chronic gastritis, peptic ulcer disease, gastric adenocarcinoma, and gastric lymphoma, it has also been implicated in extra gastric manifestations, encompassing cardiac, neurologic, ocular, and dermatologic issues. Key virulent factors for coronary artery disease include the vacuolating cytotoxin gene A and the cytotoxin-associated gene A. The most likely pathogenic mechanism of the relationship between H. pylori and coronary artery disease is initiating a chronic inflammatory process associated with infection and the modifications of classic risk factors. These alterations lead to the creation of prothrombotic and procoagulant environments. Here, we review the cardiac manifestations of H. pylori and the underlying pathophysiological mechanisms.

Alterations in the diversity, composition and function of the gut microbiota in Uyghur individuals with sarcopenia

BACKGROUND

Research on the gut microbiota has emerged as a new direction for understanding pathophysiologic changes in diseases associated with aging, such as sarcopenia. Several studies have shown that there are differences in the gut microbiota between individuals with sarcopenia and without sarcopenia. However, these differences are not consistent across regions and ethnic groups, and additional research is needed.

METHODS

In this study, we collected fresh fecal samples from 31 Uyghur individuals with sarcopenia and 31 healthy controls. We used 16S rRNA sequencing to obtain fecal base sequences and analyzed the diversity, composition and function of the gut microbiota.

RESULTS

There was no significant difference in alpha diversity between the sarcopenia group and the healthy control group (P > 0.05). There was a significant difference in beta diversity between the groups (P < 0.05). In the sarcopenia group, the abundances of Alloprevotella, un_f_Prevotellaceae, Anaerovibrio, Prevotellaceae_NK3B31_group, Mitsuokella, Prevotella and Allisonella were lower than those in the heathy control group, and the abundances of Flavobacteriales, Flavobacteriaceae, Catenibacterium, Romboutsia, Erysipelotrichaceae_UCG-003, GCA-900066575, Lachnospiraceae_FCS020_group, and un_f_Flavobacteriaceae were higher than those in the heathy control group. Linear discriminant analysis effect size (LEfSe) revealed that the microbial species in the control group that were significantly different from those in the sarcopenia group were concentrated in the genus Alloprevotella, while the species in the sarcopenia group were concentrated in the genus Catenibacterium. Functional prediction analysis revealed that D-alanine, glycine, serine, and threonine metabolism and transcription machinery, among others, were enriched in the sarcopenia group, which indicated that metabolic pathways related to amino acid metabolism and nutrient transport may be regulated to varying degrees in the pathophysiological context of sarcopenia.

CONCLUSIONS

There were significant differences in the composition and function of the gut microbiota between Xinjiang Uyghur sarcopenia individuals and healthy individuals. These findings might aid in the development of probiotics or microbial-based therapies for sarcopenia in Uyhur individuals.

Viral uptake and pathophysiology of the lung endothelial cells in age-associated severe SARS-CoV-2 infection models

Thrombosis is the major cause of death in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and the pathology of vascular endothelial cells (ECs) has received much attention. Although there is evidence of the infection of ECs in human autopsy tissues, their detailed pathophysiology remains unclear due to the lack of animal model to study it. We used a mouse-adapted SARS-CoV-2 virus strain in young and mid-aged mice. Only mid-aged mice developed fatal pneumonia with thrombosis. Pulmonary ECs were isolated from these infected mice and RNA-Seq was performed. The pulmonary EC transcriptome revealed that significantly higher levels of viral genes were detected in ECs from mid-aged mice with upregulation of viral response genes such as DDX58 and IRF7. In addition, the thrombogenesis-related genes encoding PLAT, PF4, F3 PAI-1, and P-selectin were upregulated. In addition, the inflammation-related molecules such as CXCL2 and CXCL10 were upregulated in the mid-aged ECs upon viral infection. Our mouse model demonstrated that SARS-CoV-2 virus entry into aged vascular ECs upregulated thrombogenesis and inflammation-related genes and led to fatal pneumonia with thrombosis. Current results of EC transcriptome showed that EC uptake virus and become thrombogenic by activating neutrophils and platelets in the aged mice, suggesting age-associated EC response as a novel finding in human severe COVID-19.

Differentiation-inducing factor-1 reduces lipopolysaccharide-induced vascular cell adhesion molecule-1 by suppressing mTORC1-S6K signaling in vascular endothelial cells

AIMS

Differentiation-inducing factor-1 (DIF-1), a compound in Dictyostelium discoideum, exhibits anti-cancer effects by inhibiting cell proliferation and motility of various mammalian cancer cells in vitro and in vivo. In addition, DIF-1 suppresses lung colony formation in a mouse model, thus impeding cancer metastasis. However, the precise mechanism underlying its anti-metastatic effect remains unclear. In the present study, we aim to elucidate this mechanism by investigating the adhesion of circulating tumor cells to blood vessels using in vitro and in vivo systems.

MAIN METHODS

Melanoma cells (1.0 × 105 cells) were injected into the tail vein of 8-week-old male C57BL/6 mice after administration of DIF-1 (300 mg/kg per day) and/or lipopolysaccharide (LPS: 2.5 mg/kg per day). To investigate cell adhesion and molecular mechanisms, cell adhesion assay, western blotting, immunofluorescence staining, and flow cytometry were performed.

KEY FINDINGS

Intragastric administration of DIF-1 suppressed lung colony formation. DIF-1 also substantially inhibited the adhesion of cancer cells to human umbilical vein endothelial cells. Notably, DIF-1 did not affect the expression level of adhesion-related proteins in cancer cells, but it did decrease the expression of vascular cell adhesion molecule-1 (VCAM-1) in human umbilical vein endothelial cells by suppressing its mRNA-to-protein translation through inhibition of mTORC1-p70 S6 kinase signaling.

SIGNIFICANCE

DIF-1 reduced tumor cell adhesion to blood vessels by inhibiting mTORC1-S6K signaling and decreasing the expression of adhesion molecule VCAM-1 on vascular endothelial cells. These findings highlight the potential of DIF-1 as a promising compound for the development of anti-cancer drugs with anti-metastatic properties.

MC3/SAINT-O-Somes, a novel liposomal delivery system for efficient and safe delivery of siRNA into endothelial cells

Increased understanding of chronic inflammatory diseases and the role of endothelial cell (EC) activation herein, have urged interest in sophisticated strategies to therapeutically intervene in activated EC to treat these diseases. Liposome-mediated delivery of therapeutic siRNA in inflammation-activated EC is such a strategy. In this study, we describe the design and characterisation of two liposomal siRNA delivery systems formulated with the cationic MC3 lipid or MC3/SAINT mixed lipids, referred to as MC3-O-Somes (MOS) and MC3/SAINT-O-Somes (MSS). The two formulations showed comparable physicochemical properties, except for better siRNA encapsulation efficiency in the MSS formulation. Antibody-mediated VCAM-1 targeting (AbVCAM-1) increased the association of the targeted MOS and MSS with activated EC, although the targeted MOS showed a significantly higher VCAM-1 specific association than the targeted MSS. AbVCAM-1 MSS containing RelA siRNA achieved significant downregulation of RelA expression, while AbVCAM-1 MOS containing RelA siRNA did not downregulate RelA expression in activated EC. Additionally, AbVCAM-1 MSS containing RelA siRNA showed low cytotoxicity in EC and at the same time prohibited endothelial inflammatory activation by reducing expression of cell adhesion molecules. The AbVCAM-1 MSS formulation is a novel siRNA delivery system based on a combination of the cationic lipids MC3 and SAINT, that shows good physicochemical characteristics, enhanced endothelial cell association, improved transfection activity, low toxicity and significant anti-inflammatory effect, thereby complying with the requirements for future in vivo investigations.

Mechanism of XiJiaQi in the treatment of chronic heart failure: Integrated analysis by pharmacoinformatics, molecular dynamics simulation, and SPR validation

OBJECTIVE

Chronic heart failure (CHF) is a complicated clinical syndrome with a high mortality rate. XiJiaQi (XJQ) is a traditional Chinese medicine used in the clinical treatment of CHF, but its bioactive components and their modes of action remain unknown. This study was designed to unravel the molecular mechanism of XJQ in the treatment of CHF using multiple computer-assisted and experimental methods.

METHODS

Pharmacoinformatics-based methods were used to explore the active components and targets of XJQ in the treatment of CHF. ADMETlab was then utilized to evaluate the pharmacokinetic and toxicological properties of core components. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were to explore the underlying mechanism of XJQ treatment. Molecular docking, surface plasmon resonance (SPR), and molecular dynamics (MD) were employed to evaluate the binding of active components to putative targets.

RESULTS

Astragaloside IV, formononetin, kirenol, darutoside, periplocin and periplocymarin were identified as core XJQ-related components, and IL6 and STAT3 were identified as core XJQ targets. ADME/T results indicated that periplocin and periplocymarin may have potential toxicity. GO and KEGG pathway analyses revealed that XJQ mainly intervenes in inflammation, apoptosis, diabetes, and atherosclerosis-related biological pathways. Molecular docking and SPR revealed that formononetin had a high affinity with IL6 and STAT3. Furthermore, MD simulation confirmed that formononetin could firmly bind to the site 2 region of IL6 and the DNA binding domain of STAT3.

CONCLUSION

This study provides a mechanistic rationale for the clinical application of XJQ. Modulation of STAT3 and IL-6 by XJQ can impact CHF, further guiding research efforts into the molecular underpinnings of CHF.

Bacterial lipopolysaccharide-induced endothelial activation and dysfunction: a new predictive and therapeutic paradigm for sepsis

BACKGROUND

Lipopolysaccharide, a highly potent endotoxin responsible for severe sepsis, is the major constituent of the outer membrane of gram-negative bacteria. Endothelial cells participate in both innate and adaptive immune responses as the first cell types to detect lipopolysaccharide or other foreign debris in the bloodstream. Endothelial cells are able to recognize the presence of LPS and recruit specific adaptor proteins to the membrane domains of TLR4, thereby initiating an intracellular signaling cascade. However, lipopolysaccharide binding to endothelial cells induces endothelial activation and even damage, manifested by the expression of proinflammatory cytokines and adhesion molecules that lead to sepsis.

MAIN FINDINGS

LPS is involved in both local and systemic inflammation, activating both innate and adaptive immunity. Translocation of lipopolysaccharide into the circulation causes endotoxemia. Endothelial dysfunction, including exaggerated inflammation, coagulopathy and vascular leakage, may play a central role in the dysregulated host response and pathogenesis of sepsis. By discussing the many strategies used to treat sepsis, this review attempts to provide an overview of how lipopolysaccharide induces the ever more complex syndrome of sepsis and the potential for the development of novel sepsis therapeutics.

CONCLUSIONS

To reduce patient morbidity and mortality, preservation of endothelial function would be central to the management of sepsis.

Reduced Tie2 in Microvascular Endothelial Cells Is Associated with Organ-Specific Adhesion Molecule Expression in Murine Health and Endotoxemia

Endothelial cells (ECs) in the microvasculature in organs are active participants in the pathophysiology of sepsis. Tyrosine protein kinase receptor Tie2 (Tek; Tunica interna Endothelial cell Kinase) is thought to play a role in their inflammatory response, yet data are inconclusive. We investigated acute endotoxemia-induced changes in the expression of Tie2 and inflammation-associated endothelial adhesion molecules E-selectin and VCAM-1 (vascular cell adhesion molecule-1) in kidneys and lungs in inducible, EC-specific Tie2 knockout mice. The extent of Tie2 knockout in healthy mice differed between microvascular beds, with low to absent expression in arterioles in kidneys and in capillaries in lungs. In kidneys, Tie2 mRNA dropped more than 70% upon challenge with lipopolysaccharide (LPS) in both genotypes, with no change in protein. In renal arterioles, tamoxifen-induced Tie2 knockout was associated with higher VCAM-1 protein expression in healthy conditions. This did not increase further upon challenge of mice with LPS, in contrast to the increased expression occurring in control mice. Also, in lungs, Tie2 mRNA levels dropped within 4 h after LPS challenge in both genotypes, while Tie2 protein levels did not change. In alveolar capillaries, where tamoxifen-induced Tie2 knockout did not affect the basal expression of either adhesion molecule, a 4-fold higher E-selectin protein expression was observed after exposure to LPS compared to controls. The here-revealed heterogeneous effects of absence of Tie2 in ECs in kidney and lung microvasculature in health and in response to acute inflammatory activation calls for further in vivo investigations into the role of Tie2 in EC behavior.

The Role of Palmitic Acid in the Co-Toxicity of Bacterial Metabolites to Endothelial Cells

Introduction

Metabolic endotoxemia most often results from obesity and is accompanied by an increase in the permeability of the intestinal epithelial barrier, allowing co-absorption of bacterial metabolites and diet-derived fatty acids into the bloodstream. A high-fat diet (HFD) leading to obesity is a significant extrinsic factor in developing vascular atherosclerosis. In this study, we evaluated the effects of palmitic acid (PA) as a representative of long-chain saturated fatty acids (LCSFA) commonly present in HFDs, along with endotoxin (LPS; lipopolysaccharide) and uremic toxin indoxyl sulfate (IS), on human vascular endothelial cells (HUVECs).

Methods

HUVECs viability was measured based on tetrazolium salt metabolism, and cell morphology was assessed with fluorescein-phalloidin staining of cells' actin cytoskeleton. The effects of simultaneous treatment of endothelial cells with PA, LPS, and IS on nitro-oxidative stress in vascular cells were evaluated quantitatively with fluorescent probes. The expression of vascular cell adhesion molecule VCAM-1, E-selectin, and occludin, an essential tight junction protein, in HUVECs treated with these metabolites was evaluated in Western blot.

Results

PA, combined with LPS and IS, did not influence HUVECs viability but induced stress on actin fibers and focal adhesion complexes. Moreover, PA combined with LPS significantly enhanced reactive oxygen species (ROS) production in HUVECs but decreased nitric oxide (NO) generation. PA also considerably increased the expression of VCAM-1 and E-selectin in HUVECs treated with LPS or IS but decreased occludin expression.

Conclusion

Palmitic acid enhances the toxic effect of metabolic endotoxemia on the vascular endothelium.

Serum amyloid A and interleukin -1β facilitate LDL transcytosis across endothelial cells and atherosclerosis via NF-κB/caveolin-1/cavin-1 pathway

BACKGROUND AND AIMS

Inflammatory molecules play important roles in atherosclerosis. We aimed to illustrate the roles of serum amyloid A (SAA), and interleukin (IL)-1β in low density lipoproteins (LDL) transcytosis and atherosclerosis.

METHODS

Effects of SAA and IL-1β on transcytosis of LDL were measured by an in vitro LDL transcytosis model. NF-κB/caveolin-1/cavin-1 pathway activation was investigated by Western blots and ELISA. Effects of SAA and IL-1β on the retention of LDL in aorta of C57BL/6J mice were detected by IVIS spectrum. Effects of SAA and IL-1β on atherosclerosis in Apoe-/- mice were examined by Oil Red O staining.

RESULTS

SAA and IL-1β stimulated LDL transcytosis across endothelial cells (ECs), which was accompanied by an increase in LDL uptake by ECs. SAA and IL-1β enhanced the activity of nuclear factor (NF)-κB, consequently facilitating an up-regulation of proteins involved in caveolae formation, including caveolin-1 and cavin-1, along with an assembly of NLRP3 inflammasome. Furthermore, SAA- and IL-1β-induced effects were blocked by NF-κB subunit p65 siRNA. Meanwhile, SAA- and IL-1β-induced LDL transcytosis were effectively blocked by caveolin-1 siRNA or cavin-1 siRNA. Interestingly, SAA and IL-1β facilitated LDL entering into the aorta of C57BL/6J mice. In Apoe-/- mice, SAA and IL-1β increased the areas of lipid-rich atherosclerotic lesions in the both ascending and root of aorta. Furthermore, a significant increase in the NLRP3 inflammasome, accompanied by accumulation of cavin-1 and caveolin-1, was observed in the aortic endothelium of Apoe-/- mice.

CONCLUSIONS

SAA and IL-1β accelerated LDL transcytosis via the NF-κB/caveolin-1/cavin-1 axis.

Microbiome analysis of Brazilian women cervix reveals specific bacterial abundance correlation to RIG-like receptor gene expression

The relationship among microbiome, immunity and cervical cancer has been targeted by several studies, yet many questions remain unanswered. We characterized herein the virome and bacteriome from cervical samples and correlated these findings with innate immunity gene expression in a Brazilian convenience sample of HPV-infected (HPV+) and uninfected (HPV-) women. For this purpose, innate immune gene expression data were correlated to metagenomic information. Correlation analysis showed that interferon (IFN) is able to differentially modulate pattern recognition receptors (PRRs) expression based on HPV status. Virome analysis indicated that HPV infection correlates to the presence of Anellovirus (AV) and seven complete HPV genomes were assembled. Bacteriome results unveiled that vaginal community state types (CST) distribution was independent of HPV or AV status, although bacterial phyla distribution differed between groups. Furthermore, TLR3 and IFNαR2 levels were higher in the Lactobacillus no iners-dominated mucosa and we detected correlations among RIG-like receptors (RLR) associated genes and abundance of specific anaerobic bacteria. Collectively, our data show an intriguing connection between HPV and AV infections that could foster cervical cancer development. Besides that, TLR3 and IFNαR2 seem to create a protective milieu in healthy cervical mucosa (L. no iners-dominated), and RLRs, known to recognize viral RNA, were correlated to anaerobic bacteria suggesting that they might be related to dysbiosis.

The role of 14-3-3 in the progression of vascular inflammation induced by lipopolysaccharide

OBJECTIVE

To explore the role of 14-3-3 protein and the Hippo and yes-associated protein 1 (YAP) signaling pathway in lipopolysaccharide (LPS)-induced vascular inflammation.

METHODS

Human umbilical vein endothelial cells (HUVECs) and C57B6 mice were treated with LPS to establish cell and animal models of vascular inflammation. Lentiviral transfection, Western blot, qPCR, immunofluorescence, immunohistochemistry, co-immunoprecipitation, and enzyme-linked immunosorbent assays were used to measure inflammatory factors and expression of 14-3-3 protein and phosphorylation of YAP at S127. HUVECs and C57B6 mice were pretreated with a YAP inhibitor, Verteporfin, to observe changes in YAP expression and downstream vascular inflammation.

RESULTS

LPS induced acute and chronic inflammatory responses in HUVECs and mice and upregulated the expression of several inflammatory factors. LPS also induced expression of 14-3-3 protein and phosphorylation of YAP at S127 in response to acute vascular inflammation and downregulated these markers in response to chronic vascular inflammation. Verteporfin reduced these LPS-induced effects on vascular inflammation.

CONCLUSION

In chronic vascular inflammation, 14-3-3 protein is downregulated, which promotes inflammation by increasing Hippo/YAP nuclear translocation.

Transcriptional drifts associated with environmental changes in endothelial cells

Environmental cues, such as physical forces and heterotypic cell interactions play a critical role in cell function, yet their collective contributions to transcriptional changes are unclear. Focusing on human endothelial cells, we performed broad individual sample analysis to identify transcriptional drifts associated with environmental changes that were independent of genetic background. Global gene expression profiling by RNA sequencing and protein expression by liquid chromatography-mass spectrometry directed proteomics distinguished endothelial cells in vivo from genetically matched culture (in vitro) samples. Over 43% of the transcriptome was significantly changed by the in vitro environment. Subjecting cultured cells to long-term shear stress significantly rescued the expression of approximately 17% of genes. Inclusion of heterotypic interactions by co-culture of endothelial cells with smooth muscle cells normalized approximately 9% of the original in vivo signature. We also identified novel flow dependent genes, as well as genes that necessitate heterotypic cell interactions to mimic the in vivo transcriptome. Our findings highlight specific genes and pathways that rely on contextual information for adequate expression from those that are agnostic of such environmental cues.

Disseminated intravascular coagulation phenotype is regulated by the TRPM7 channel during sepsis

BACKGROUND

Sepsis is an uncontrolled inflammatory response against a systemic infection that results in elevated mortality, mainly induced by bacterial products known as endotoxins, producing endotoxemia. Disseminated intravascular coagulation (DIC) is frequently observed in septic patients and is associated with organ failure and death. Sepsis activates endothelial cells (ECs), promoting a prothrombotic phenotype contributing to DIC. Ion channel-mediated calcium permeability participates in coagulation. The transient reception potential melastatin 7 (TRPM7) non-selective divalent cation channel that also contains an α-kinase domain, which is permeable to divalent cations including Ca²⁺, regulates endotoxin-stimulated calcium permeability in ECs and is associated with increased mortality in septic patients. However, whether endothelial TRPM7 mediates endotoxemia-induced coagulation is not known. Therefore, our aim was to examine if TRPM7 mediates coagulation during endotoxemia.

RESULTS

The results showed that TRPM7 regulated endotoxin-induced platelet and neutrophil adhesion to ECs, dependent on the TRPM7 ion channel activity and by the α-kinase function. Endotoxic animals showed that TRPM7 mediated neutrophil rolling on blood vessels and intravascular coagulation. TRPM7 mediated the increased expression of the adhesion proteins, von Willebrand factor (vWF), intercellular adhesion molecule 1 (ICAM-1), and P-selectin, which were also mediated by the TRPM7 α-kinase function. Notably, endotoxin-induced expression of vWF, ICAM-1 and P-selectin were required for endotoxin-induced platelet and neutrophil adhesion to ECs. Endotoxemic rats showed increased endothelial TRPM7 expression associated with a procoagulant phenotype, liver and kidney dysfunction, increased death events and an increased relative risk of death. Interestingly, circulating ECs (CECs) from septic shock patients (SSPs) showed increased TRPM7 expression associated with increased DIC scores and decreased survival times. Additionally, SSPs with a high expression of TRPM7 in CECs showed increased mortality and relative risk of death. Notably, CECs from SSPs showed significant results from the AUROC analyses for predicting mortality in SSPs that were better than the Acute Physiology and Chronic Health Evaluation II (APACHE II) and the Sequential Organ Failure Assessment (SOFA) scores.

CONCLUSIONS

Our study demonstrates that sepsis-induced DIC is mediated by TRPM7 in ECs. TRPM7 ion channel activity and α-kinase function are required by DIC-mediated sepsis-induced organ dysfunction and its expression are associated with increased mortality during sepsis. TRPM7 appears as a new prognostic biomarker to predict mortality associated to DIC in SSPs, and as a novel target for drug development against DIC during infectious inflammatory diseases.

Endothelial Toll-like receptor 4 is required for microglia activation in the murine retina after systemic lipopolysaccharide exposure

BACKGROUND

Clustering of microglia around the vasculature has been reported in the retina and the brain after systemic administration of lipopolysaccharides (LPS) in mice. LPS acts via activation of Toll-like receptor 4 (TRL4), which is expressed in several cell types including microglia, monocytes and vascular endothelial cells. The purpose of this study was to investigate the effect of systemic LPS in the pigmented mouse retina and the involvement of endothelial TLR4 in LPS-induced retinal microglia activation.

METHODS

C57BL/6J, conditional knockout mice that lack Tlr4 expression selectively on endothelial cells (Tek^Cre-posTlr4^loxP/loxP) and Tek^Cre-negTlr4^loxP/loxP mice were used. The mice were injected with 1 mg/kg LPS via the tail vein once per day for a total of 4 days. Prior to initiation of LPS injections and approximately 5 h after the last injection, in vivo imaging using fluorescein angiography and spectral-domain optical coherence tomography was performed. Immunohistochemistry, flow cytometry, electroretinography and transmission electron microscopy were utilized to investigate the role of endothelial TLR4 in LPS-induced microglia activation and retinal function.

RESULTS

Activation of microglia, infiltration of monocyte-derived macrophages, impaired ribbon synapse organization and retinal dysfunction were observed after the LPS exposure in C57BL/6J and Tek^Cre-negTlr4^loxP/loxP mice. None of these effects were observed in the retinas of conditional Tlr4 knockout mice after the LPS challenge.

CONCLUSIONS

The findings of the present study suggest that systemic LPS exposure can have detrimental effects in the healthy retina and that TLR4 expressed on endothelial cells is essential for retinal microglia activation and retinal dysfunction upon systemic LPS challenge. This important finding provides new insights into the role of microglia-endothelial cell interaction in inflammatory retinal disease.

Role of Gut Microbiota and Oxidative Stress in the Progression of Transplant-Related Complications following Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT), also known as bone marrow transplantation, has curative potential for various hematologic malignancies but is associated with risks such as graft-versus-host disease (GvHD), severe bloodstream infection, viral pneumonia, idiopathic pneumonia syndrome (IPS), lung fibrosis, and sinusoidal obstruction syndrome (SOS), which severely deteriorate clinical outcomes and limit the wide application of HSCT. Recent research has provided important insights into the effects of gut microbiota and oxidative stress (OS) on HSCT complications. Therefore, based on recent studies, we describe intestinal dysbiosis and OS in patients with HSCT and review recent molecular findings underlying the causal relationships of gut microbiota, OS, and transplant-related complications, focusing particularly on the involvement of gut microbiota-mediated OS in postengraftment complications. Also, we discuss the use of antioxidative and anti-inflammatory probiotics to manipulate gut microbiota and OS, which have been associated with promising effects in improving HSCT outcomes.

Establishment and application of a high-throughput screening model for cell adhesion inhibitors

The cell adhesion between leukocytes and endothelial cells plays an important balanced role in the pathophysiological function, while excessive adhesion caused by etiological agents is associated with the occurrence and development of many acute and chronic diseases. Cell adhesion inhibitors have been shown to have a potential therapeutic effect on these diseases, therefore, efficient and specific inhibitors against cell adhesion are highly desirable. Here, using lipopolysaccharide-induced human umbilical vein endothelial cells (HUVECs) and calcein-AM-labeled human monocytic cell THP-1, we established a high-throughput screening model for cell adhesion inhibitors with excellent model evaluation parameters. Using the drug repurposing strategy, we screened out lifitegrast, a potent cell adhesion inhibitor, which inhibited cell adhesion between HUVEC and THP-1 cells by directly interrupting the adhesion interaction between HUVEC and THP-1 cells and showed a strong therapeutic effect on the mouse acute liver injury induced by poly (I:C)/D-GalN. Therefore, the screening model is suitable for screening and validating cell adhesion inhibitors, which will promote the research and development of inhibitors for the treatment of diseases caused by excessive cell adhesion.

Histone Citrullination Mediates a Protective Role in Endothelium and Modulates Inflammation

NETosis is a key host immune process against a pathogenic infection during innate immune activation, consisting of a neutrophil "explosion" and, consequently, NET formation, containing mainly DNA, histones, and other nuclear proteins. During sepsis, an exacerbated immune host response to an infection occurs, activating the innate immunity and NETosis events, which requires histone H3 citrullination. Our group compared the circulating histone levels with those citrullinated H3 levels in plasma samples of septic patients. In addition, we demonstrated that citrullinated histones were less cytotoxic for endothelial cells than histones without this post-translational modification. Citrullinated histones did not affect cell viability and did not activate oxidative stress. Nevertheless, citrullinated histones induced an inflammatory response, as well as regulatory endothelial mechanisms. Furthermore, septic patients showed elevated levels of circulating citrullinated histone H3, indicating that the histone citrullination is produced during the first stages of sepsis, probably due to the NETosis process.

TLR2 axis on peripheral blood mononuclear cells regulates inflammatory responses to non-infectious immature dengue virus particles

Severe dengue virus (DENV) infection is characterized by exacerbated inflammatory responses that lead to endothelial dysfunction and plasma leakage. We have recently demonstrated that Toll-like receptor 2 (TLR2) on blood monocytes senses DENV infection leading to endothelial activation. Here, we report that non-infectious immature DENV particles, which are released in large numbers by DENV-infected cells, drive endothelial activation via the TLR2 axis. We show that fully immature DENV particles induce a rapid, within 6 hours post-infection, inflammatory response in PBMCs. Furthermore, pharmacological blocking of TLR2/TLR6/CD14 and/or NF-kB prior to exposure of PBMCs to immature DENV reduces the initial production of inter alia TNF-α and IL-1β by monocytes and prevents endothelial activation. However, prolonged TLR2 block induces TNF-α production and leads to exacerbated endothelial activation, indicating that TLR2-mediated responses play an important role not only in the initiation but also the resolution of inflammation. Altogether, these data indicate that the maturation status of the virus has the potential to influence the kinetics and extent of inflammatory responses during DENV infection.

Lipopolysaccharide affects energy metabolism and elevates nicotinamide N-methyltransferase level in human aortic endothelial cells (HAEC)

This study aimed to investigate the putative role of nicotinamide N-methyltransferase in the metabolic response of human aortic endothelial cells. This enzyme catalyses S-adenosylmethionine-mediated methylation of nicotinamide to methylnicotinamide. This reaction is accompanied by the reduction of the intracellular nicotinamide and S-adenosylmethionine content. This may affect NAD⁺ synthesis and various processes of methylation, including epigenetic modifications of chromatin. Particularly high activity of nicotinamide N-methyltransferase is detected in liver, many neoplasms as well as in various cells in stressful conditions. The elevated nicotinamide N-methyltransferase content was also found in endothelial cells treated with statins. Although the exogenous methylnicotinamide has been postulated to induce a vasodilatory response, the specific metabolic role of nicotinamide N-methyltransferase in vascular endothelium is still unclear. Treatment of endothelial cells with bacterial lipopolysaccharide evokes several metabolic and functional consequences which built a multifaceted physiological response of endothelium to bacterial infection. Among the spectrum of biochemical changes substantially elevated protein level of nicotinamide N-methyltransferase was particularly intriguing. Here it has been shown that silencing of the nicotinamide N-methyltransferase gene influences several changes which are observed in cells treated with lipopolysaccharide. They include altered energy metabolism and rearrangement of the mitochondrial network. A complete explanation of the mechanisms behind the protective consequences of the nicotinamide N-methyltransferase deficiency in cells treated with lipopolysaccharide needs further investigation.

Endothelial Cells as a Key Cell Type for Innate Immunity: A Focused Review on RIG-I Signaling Pathway

The vascular endothelium consists of a highly heterogeneous monolayer of endothelial cells (ECs) which are the primary target for bacterial and viral infections due to EC’s constant and close contact with the bloodstream. Emerging evidence has shown that ECs are a key cell type for innate immunity. Like macrophages, ECs serve as sentinels when sensing invading pathogens or microbial infection caused by viruses and bacteria. It remains elusive how ECs senses danger signals, transduce the signal and fulfil immune functions. Retinoic acid-inducible gene-I (RIG-I, gene name also known as DDX58) is an important member of RIG-I-like receptor (RLR) family that functions as an important pathogen recognition receptor (PRR) to execute immune surveillance and confer host antiviral response. Recent studies have demonstrated that virus infection, dsRNA, dsDNA, interferons, LPS, and 25-hydroxycholesterol (25-HC) can increase RIG-1 expression in ECs and propagate anti-viral response. Of translational significance, RIG-I activation can be inhibited by Panax notoginseng saponins, endogenous PPARγ ligand 15-PGJ2, tryptanthrin and 2-animopurine. Considering the pivotal role of inflammation and innate immunity in regulating endothelial dysfunction and atherosclerosis, here we provided a concise review of the role of RIG-I in endothelial cell function and highlight future direction to elucidate the potential role of RIG-I in regulating cardiovascular diseases as well as virus infectious disease, including COVID-19. Furthered understanding of RIG-I-mediated signaling pathways is important to control disorders associated with altered immunity and inflammation in ECs.

Immune Regulator Retinoic Acid-Inducible Gene I (RIG-I) in the Pathogenesis of Cardiovascular Disease

Retinoic acid-inducible gene I (RIG-I) is a cytosolic pattern recognition receptor that contains two CARD domains, an RNA helicase domain, and a C-terminal domain. RIG-I initiates antiviral innate immunity by recognizing exogenous viral RNAs/DNAs. However, some studies have reported that RIG-I activation leads to damage in various organs and tissues in diverse circumstances. Recent studies have shown that RIG-I is involved in cancer, lupus nephritis, immunoglobulin A nephropathy, Crohn’s disease, and atherosclerosis. These reports indicate that RIG-I not only participates in antiviral signaling pathways but also exerts an influence on non-viral infectious diseases. RIG-I is widely expressed in immune and non-immune cells including smooth muscle cells, endothelial cells, and cardiomyocytes. A succinct overview of RIG-I and its signaling pathways, with respect to the cardiovascular system, will aid in the development of novel therapeutics for cardiovascular diseases. In this review, we summarize the structure, activation, signaling pathways, and role of RIG-I in cardiovascular diseases.

Unlocking the Untapped Potential of Endothelial Kinase and Phosphatase Involvement in Sepsis for Drug Treatment Design

Sepsis is a devastating clinical condition that can lead to multiple organ failure and death. Despite advancements in our understanding of molecular mechanisms underlying sepsis and sepsis-associated multiple organ failure, no effective therapeutic treatment to directly counteract it has yet been established. The endothelium is considered to play an important role in sepsis. This review highlights a number of signal transduction pathways involved in endothelial inflammatory activation and dysregulated endothelial barrier function in response to sepsis conditions. Within these pathways – NF-κB, Rac1/RhoA GTPases, AP-1, APC/S1P, Angpt/Tie2, and VEGF/VEGFR2 – we focus on the role of kinases and phosphatases as potential druggable targets for therapeutic intervention. Animal studies and clinical trials that have been conducted for this purpose are discussed, highlighting reasons why they might not have resulted in the expected outcomes, and which lessons can be learned from this. Lastly, opportunities and challenges that sepsis and sepsis-associated multiple organ failure research are currently facing are presented, including recommendations on improved experimental design to increase the translational power of preclinical research to the clinic.

Vascular Protective Effect and Its Possible Mechanism of Action on Selected Active Phytocompounds: A Review

Vascular endothelial dysfunction is characterized by an imbalance of vasodilation and vasoconstriction, deficiency of nitric oxide (NO) bioavailability and elevated reactive oxygen species (ROS), and proinflammatory factors. This dysfunction is a key to the early pathological development of major cardiovascular diseases including hypertension, atherosclerosis, and diabetes. Therefore, modulation of the vascular endothelium is considered an important therapeutic strategy to maintain the health of the cardiovascular system. Epidemiological studies have shown that regular consumption of medicinal plants, fruits, and vegetables promotes vascular health, lowering the risk of cardiovascular diseases. This is mainly attributed to the phytochemical compounds contained in these resources. Various databases, including Google Scholar, MEDLINE, PubMed, and the Directory of Open Access Journals, were searched to identify studies demonstrating the vascular protective effects of phytochemical compounds. The literature had revealed abundant data on phytochemical compounds protecting and improving the vascular system. Of the numerous compounds reported, curcumin, resveratrol, cyanidin-3-glucoside, berberine, epigallocatechin-3-gallate, and quercetin are discussed in this review to provide recent information on their vascular protective mechanisms in vivo and in vitro. Phytochemical compounds are promising therapeutic agents for vascular dysfunction due to their antioxidative mechanisms. However, future human studies will be necessary to confirm the clinical effects of these vascular protective mechanisms.

A human pluripotent stem cell-based model of SARS-CoV-2 infection reveals an ACE2-independent inflammatory activation of vascular endothelial cells through TLR4

To date, the direct causative mechanism of SARS-CoV-2-induced endotheliitis remains unclear. Here, we report that human ECs barely express surface ACE2, and ECs express less intracellular ACE2 than non-ECs of the lungs. We ectopically expressed ACE2 in hESC-ECs to model SARS-CoV-2 infection. ACE2-deficient ECs are resistant to the infection but are more activated than ACE2-expressing ones. The virus directly induces endothelial activation by increasing monocyte adhesion, NO production, and enhanced phosphorylation of p38 mitogen-associated protein kinase (MAPK), NF-κB, and eNOS in ACE2-expressing and -deficient ECs. ACE2-deficient ECs respond to SARS-CoV-2 through TLR4 as treatment with its antagonist inhibits p38 MAPK/NF-κB/ interleukin-1β (IL-1β) activation after viral exposure. Genome-wide, single-cell RNA-seq analyses further confirm activation of the TLR4/MAPK14/RELA/IL-1β axis in circulating ECs of mild and severe COVID-19 patients. Circulating ECs could serve as biomarkers for indicating patients with endotheliitis. Together, our findings support a direct role for SARS-CoV-2 in mediating endothelial inflammation in an ACE2-dependent or -independent manner.

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The majority of adult and fetal ECs rarely express surface ACE2

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ACE2 is dispensable for SARS-CoV-2-mediated endothelial activation

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SARS-CoV-2 directly induces endothelial inflammation through TLR4 activation

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ScRNA-seq reveals TLR4 pathway activation in circulating ECs of COVID-19 patients

Renal microvascular endothelial cell responses in sepsis-induced acute kidney injury

Microvascular endothelial cells in the kidney have been a neglected cell type in sepsis-induced acute kidney injury (sepsis-AKI) research; yet, they offer tremendous potential as pharmacological targets. As endothelial cells in distinct cortical microvascular segments are highly heterogeneous, this Review focuses on endothelial cells in their anatomical niche. In animal models of sepsis-AKI, reduced glomerular blood flow has been attributed to inhibition of endothelial nitric oxide synthase activation in arterioles and glomeruli, whereas decreased cortex peritubular capillary perfusion is associated with epithelial redox stress. Elevated systemic levels of vascular endothelial growth factor, reduced levels of circulating sphingosine 1-phosphate and loss of components of the glycocalyx from glomerular endothelial cells lead to increased microvascular permeability. Although coagulation disbalance occurs in all microvascular segments, the molecules involved differ between segments. Induction of the expression of adhesion molecules and leukocyte recruitment also occurs in a heterogeneous manner. Evidence of similar endothelial cell responses has been found in kidney and blood samples from patients with sepsis. Comprehensive studies are needed to investigate the relationships between segment-specific changes in the microvasculature and kidney function loss in sepsis-AKI. The application of omics technologies to kidney tissues from animals and patients will be key in identifying these relationships and in developing novel therapeutics for sepsis.

Uncovering emergent phenotypes in endothelial cells by clustering of surrogates of cardiovascular risk factors

Endothelial dysfunction (ED) is a hallmark of atherosclerosis and is influenced by well-defined risk factors, including hypoxia, dyslipidemia, inflammation, and oscillatory flow. However, the individual and combined contributions to the molecular underpinnings of ED remain elusive. We used global gene expression in human coronary artery endothelial cells to identify gene pathways and cellular processes in response to chemical hypoxia, oxidized lipids, IL-1β induced inflammation, oscillatory flow, and these combined stimuli. We found that clustering of the surrogate risk factors differed from the sum of the individual insults that gave rise to emergent phenotypes such as cell proliferation. We validated these observations in samples of human coronary artery atherosclerotic plaques analyzed using single-cell RNA sequencing. Our findings suggest a hierarchical interaction between surrogates of CV risk factors and the advent of emergent phenotypes in response to combined stimulation in endothelial cells that may influence ED.

[Effect of Ketone Body β-Hydroxybutyrate to Attenuate Inflammation-Induced Mitochondrial Oxidative Stress in Vascular Endothelial Cells]

OBJECTIVE

To investigate the regulatory function and mechanism of β-hydroxybutyrate (β-OHB), a ketone body, on the mitochondrial oxidative stress of inflammatory human umbilical vein endothelial cells (HUVECs).

METHODS

Lipopolysaccharide (LPS) and adenosine triphosphate (ATP) were used to induce macrophages to release proinflammatory factors, and the culture supernatant was collected as a macrophage-conditioned medium (MCM) to culture HUVECs. A total of 7 groups of cells were used in the study: ①control group, or normal cultured HUVECs; ②MCM group, or the MCM-cultured HUVECs; groups ③ to ⑦ were all HUVECs co-cultured with different reagents, including ③MCM+β-OHB group, ④MCM+N-acetylcysteine (NAC) group, ⑤MCM+β-OHB+NAC group, ⑥MCM+β-OHB+histone deacetylase agonist ITSA1 group, and ⑦MCM+β-OHB+histone deacetylase inhibitor Entinostat group. MitoSOX immunofluorescence staining was conducted to analyzes the mitochondrial superoxide levels, real-time fluorescent quantitative polymerase chain reaction (RT-qPCR) was performed to examine the mRNA expression of antioxidant genes, and Seahorse mitochondrial energy analyzer was used to measure mitochondrial aerobic respiration capacity.

RESULTS

Compared with the control group, mitochondrial superoxide production was significantly increased in the MCM cultured HUVECs cells, while β-OHB treatment significantly inhibited mitochondrial superoxide production, which was accompanied by an increase in the mRNA expression of antioxidant genes, and significant increase in the basal mitochondrial oxygen consumption rate and respiratory reserve capacity. NAC treatment did not further enhance the protective effect of β-OHB on mitochondrial functions. In addition, ITSA1 treatment could completely offset the antioxidant and mitochondrial protective effects of β-OHB, and these stated effects were still maintained after Entinostat treatment.

CONCLUSION

The ketone body β-OHB attenuates the mitochondrial oxidative stress of vascular endothelial cells through activating the antioxidant pathway and inhibiting histone deacetylase activity.

Comparison of Selenium Nanoparticles and Sodium Selenite on the Alleviation of Early Atherosclerosis by Inhibiting Endothelial Dysfunction and Inflammation in Apolipoprotein E-Deficient Mice

Atherosclerosis and related cardiovascular diseases represent the greatest threats to human health, worldwide. Previous animal studies showed that selenium nanoparticles (SeNPs) and Na₂SeO₃ might have anti-atherosclerotic activity, but the underlying mechanisms are poorly elucidated. This study compared the anti-atherosclerotic activity of SeNPs stabilized with chitosan (CS-SeNPs) and Na₂SeO₃ and the related mechanism in a high-fat-diet-fed apolipoprotein E-deficient mouse model of atherosclerosis. The results showed that oral administration of both CS-SeNPs and Na₂SeO₃ (40 μg Se/kg/day) for 10 weeks significantly reduced atherosclerotic lesions in mouse aortae. Mechanistically, CS-SeNPs and Na₂SeO₃ not only alleviated vascular endothelial dysfunction, as evidenced by the increase of serum nitric oxide level and the decrease of aortic adhesion molecule expression, but also vascular inflammation, as evidenced by the decrease of macrophage recruitment as well as the expression of proinflammatory molecules. Importantly, these results were replicated within in-vivo experiments on the cultured human endothelial cell line EA.hy926. Overall, CS-SeNPs had a comparable effect with Na₂SeO₃ but might have more potential in atherosclerosis prevention due to its lower toxicity. Together, these results provide more insights into the mechanisms of selenium against atherosclerosis and further highlight the potential of selenium supplementation as a therapeutic strategy for atherosclerosis.

Pitavastatin stimulates retinal angiogenesis via HMG-CoA reductase-independent activation of RhoA-mediated pathways and focal adhesion

BACKGROUND

Excessive angiogenesis of the retina is a key component of irreversible causes of blindness in many ocular diseases. Pitavastatin is a cholesterol-lowering drug used to reduce the risk of cardiovascular diseases. Various studies have shown the effects of pitavastatin on angiogenesis but the conclusions are contradictory. The effects of pitavastatin on retinal angiogenesis have not been revealed. This study investigated the effects of pitavastatin at clinically relevant concentrations on retinal angiogenesis and its underlying mechanisms using retinal microvascular endothelial cells (RMECs).

METHODS

The effects of pitavastatin on retinal angiogenesis were determined using in vitro model of retinal angiogenesis, endothelial cell migration, adhesion, proliferation, and apoptosis assays. The mechanism studies were conducted using immunoblotting and stress fiber staining.

RESULTS

Pitavastatin stimulated capillary network formation of RMECs in a similar manner as vascular endothelial growth factor (VEGF) and lipopolysaccharide (LPS). Pitavastatin also increased RMEC migration, adhesion to Matrigel, growth, and survival. The combination of pitavastatin with VEGF or LPS was more effective than VEGF or LPS alone in stimulating biological activities of RMECs, suggesting that pitavastatin can enhance the stimulatory effects of VEGF and LPS on retinal angiogenesis. Pitavastatin acted on RMECs in a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase-independent manner. In contrast, pitavastatin activated pro-angiogenic microenvironment via promoting the secretion of VEGF and stimulated retinal angiogenesis via multiple mechanisms including activation of RhoA-mediated pathways, induction of focal adhesion complex formation, and activation of ERK pathway.

CONCLUSION

Our work provides a preclinical evidence on the pro-angiogenic effect of pitavastatin in retina via multiple mechanisms that are irrelevant to mevalonate pathway.

Early modifications of the gut microbiome in children with hepatic sinusoidal obstruction syndrome after hematopoietic stem cell transplantation

Hepatic sinusoidal obstruction syndrome (SOS/VOD) represents a dramatic complication of hematopoietic stem cell transplantation (HSCT), particularly in children. Recent evidence has suggested a role for the gut microbiome (GM) in the context of HSCT and its related complications, but no data are available on the relationship between GM and SOS/VOD. Here, we conducted a retrospective case–control study in allo-HSCT pediatric patients developing or not SOS/VOD and profiled their GM over time, from before the transplant up to 72 days after. A rich and diverse GM before HSCT was found to be associated with a reduced likelihood of developing SOS/VOD. Furthermore, prior to transplant, patients not developing SOS/VOD showed an enrichment in some typically health-associated commensals, such as Bacteroides, Ruminococcaceae and Lachnospiraceae. Their levels remained overall higher until post-transplant. This high-diversity configuration resembles that described in other studies for other HSCT-related complications, including graft-versus-host disease, potentially representing a common protective GM feature against HSCT complications.

LCZ696 ameliorates lipopolysaccharide-induced endothelial injury

Lipopolysaccharide (LPS)-induced endothelial dysfunction plays an important role in the pathogenesis of cardiovascular diseases. LCZ696, the dual-acting angiotensin receptor blocker, and neprilysin inhibitor has been used for the treatment of heart failure with reduced ejection fraction. Recent work suggests that LCZ696 therapy might have an anti-inflammatory effect in cardiovascular tissue. In the current study, we show that LCZ696 attenuates LPS-induced oxidative stress by reducing the production of intracellular reactive oxygen species (ROS) and the measurements of malonyl dialdehyde (MDA) level in human umbilical vascular endothelial cells (HUVECs). LCZ696 inhibits LPS-induced expressions and secretions of the pro-inflammatory cytokines, interleukin-6 (IL-6), interleukin-1α (IL-1α), and tumor necrosis factor β (TNF-β) as well as the chemokines, monocyte chemotactic protein 1 (MCP-1), and chemokine (C-X-C motif) ligand 1 protein (CXCL1). Additionally, we found that LCZ696 reduces LPS-induced expressions of vascular cell adhesion molecule 1 (VCAM-1) and P-selectin and the attachment of U937 monocytes to HUVECs. Mechanistically, LCZ696 prevents LPS-induced activation of the TLR4/Myd88 pathway and nuclear translocation of nuclear factor kappa-B (NF-κB) p65 factor. Based on these findings, we conclude that LCZ696 is capable of ameliorating LPS-induced endothelial dysfunction via anti-inflammatory properties.

Machine-perfused donor kidneys as a source of human renal endothelial cells

Renal endothelial cells (ECs) play crucial roles in vasorelaxation, ultrafiltration, and selective transport of electrolytes and water, but also in leakage of the glomerular filtration barrier and inflammatory processes like complement activation and leukocyte recruitment. In addition, they are target cells for both cellular and antibody-mediated rejection in the transplanted kidney. To study the molecular and cellular processes underlying EC behavior in renal disease, well-characterized primary renal ECs are indispensible. In this report, we describe a straightforward procedure to isolate ECs from the perfusion fluid of human donor kidneys by a combination of negative selection of monocytes/macrophages, positive selection by CD31 Dynabeads, and propagation in endothelium-specific culture medium. Thus, we isolated and propagated renal ECs from 102 donor kidneys, representative of all blood groups and major human leukocyte antigen (HLA) class I and II antigens. The obtained ECs were positive for CD31 and von Willebrand factor, expressed other endothelial markers such as CD34, VEGF receptor-2, TIE2, and plasmalemmal vesicle associated protein-1 to a variable extent, and were negative for the monocyte marker CD14 and lymphatic endothelial marker podoplanin. HLA class II was either constitutively expressed or could be induced by interferon-γ. Furthermore, as a proof of principle, we showed the diagnostic value of this renal endothelial biobank in renal endothelium-specific cross-matching tests for HLA antibodies.NEW & NOTEWORTHY We describe a new and widely accessible approach to obtain human primary renal endothelial cells in a standardized fashion, by isolating from the perfusate of machine-perfused donor kidneys. Characterization of the cells showed a mixed population originating from different compartments of the kidney. As a proof of principle, we demonstrated a possible diagnostic application in an endothelium-specific cross-match. Next to transplantation, we foresee further applications in the field renal endothelial research.

ERK1/2 Has Divergent Roles in LPS-Induced Microvascular Endothelial Cell Cytokine Production and Permeability

ABSTRACT

Endothelial cells play a major role in inflammatory responses to infection and sterile injury. Endothelial cells express Toll-like receptor 4 (TLR4) and are activated by LPS to express inflammatory cytokines/chemokines, and to undergo functional changes, including increased permeability. The extracellular signal-regulated kinase 1/2 (ERK1/2) mediates pro-inflammatory signaling in monocytes and macrophages, but the role of ERK1/2 in LPS-induced activation of microvascular endothelial cells has not been defined. We therefore studied the role of ERK1/2 in LPS-induced inflammatory activation and permeability of primary human lung microvascular endothelial cells (HMVEC). Inhibition of ERK1/2 augmented LPS-induced IL-6 and vascular cell adhesion protein (VCAM-1) production by HMVEC. ERK1/2 siRNA knockdown also augmented IL-6 production by LPS-treated HMVEC. Conversely, ERK1/2 inhibition abrogated permeability and restored cell-cell junctions of LPS-treated HMVEC. Consistent with the previously described pro-inflammatory role for ERK1/2 in leukocytes, inhibition of ERK1/2 reduced LPS-induced cytokine/chemokine production by primary human monocytes. Our study identifies a complex role for ERK1/2 in TLR4-activation of HMVEC, independent of myeloid differentiation primary response gene (MyD88) and TIR domain-containing adaptor inducing IFN-β (TRIF) signaling pathways. The activation of ERK1/2 limits LPS-induced IL-6 production by HMVEC, while at the same time promoting HMVEC permeability. Conversely, ERK1/2 activation promotes IL-6 production by human monocytes. Our results suggest that ERK1/2 may play an important role in the nuanced regulation of endothelial cell inflammation and vascular permeability in sepsis and injury.

Link between microbiota and hypertension: Focus on LPS/TLR4 pathway in endothelial dysfunction and vascular inflammation, and therapeutic implication of probiotics

High blood pressure (BP) presents a significant public health challenge. Recent findings suggest that altered microbiota can exert a hypertensive effect on the host. One of the possible mechanisms involved is the chronic translocation of its components, mainly lipopolysaccharides (LPS) into systemic circulation leading to metabolic endotoxemia. In animal models, LPS has been commonly used to induce endothelial dysfunction and vascular inflammation. In human studies, plasma LPS concentration has been positively correlated with hypertension, however, the mechanistic link has not been fully elucidated. It is hypothesised here that the LPS-induced direct alterations to the vascular endothelium and resulting hypertension are possible targets for probiotic intervention. The methodology of this review involved a systematic search of the literature with critical appraisal of papers. Three tranches of search were performed: 1) existing review papers; 2) primary mechanistic animal, in vitro and human studies; and 3) primary intervention studies. A total of 70 peer-reviewed papers were included across the three tranches and critically appraised using SIGN50 for human studies and the ARRIVE guidelines for animal studies. The extracted information was coded into key themes and summarized in a narrative analysis. Results highlight the role of LPS in the activation of endothelial toll-like receptor 4 (TLR4) initiating a cascade of interrelated signalling pathways including: 1) Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase/ Reactive oxygen species (ROS)/ Endothelial nitric oxide synthase (eNOS) pathway leading to endothelial dysfunction; and 2) Mitogen-Activated Protein Kinase (MAPK) and Nuclear factor kappa B (NF-κB) pathways leading to vascular inflammation. Findings from animal intervention studies suggest an improvement in vasorelaxation, vascular inflammation and hypertension following probiotic supplementation, which was mediated by downregulation of LPS-induced pathways. Randomised controlled trials (RCTs) and systematic reviews provided some evidence for the anti-inflammatory effect of probiotics with statistically significant antihypertensive effect in clinical samples and may offer a viable intervention for the management of hypertension.

Toll-Like Receptors in Acute Kidney Injury

Acute kidney injury (AKI) is an important health problem, affecting 13.3 million individuals/year. It is associated with increased mortality, mainly in low- and middle-income countries, where renal replacement therapy is limited. Moreover, survivors show adverse long-term outcomes, including increased risk of developing recurrent AKI bouts, cardiovascular events, and chronic kidney disease. However, there are no specific treatments to decrease the adverse consequences of AKI. Epidemiological and preclinical studies show the pathological role of inflammation in AKI, not only at the acute phase but also in the progression to chronic kidney disease. Toll-like receptors (TLRs) are key regulators of the inflammatory response and have been associated to many cellular processes activated during AKI. For that reason, a number of anti-inflammatory agents targeting TLRs have been analyzed in preclinical studies to decrease renal damage during AKI. In this review, we updated recent knowledge about the role of TLRs, mainly TLR4, in the initiation and development of AKI as well as novel compounds targeting these molecules to diminish kidney injury associated to this pathological condition.

Extratubular Polymerized Uromodulin Induces Leukocyte Recruitment and Inflammation In Vivo

Uromodulin (UMOD) is produced and secreted by tubular epithelial cells. Secreted UMOD polymerizes (pUMOD) in the tubular lumen, where it regulates salt transport and protects the kidney from bacteria and stone formation. Under various pathological conditions, pUMOD accumulates within the tubular lumen and reaches extratubular sites where it may interact with renal interstitial cells. Here, we investigated the potential of extratubular pUMOD to act as a damage associated molecular pattern (DAMP) molecule thereby creating local inflammation. We found that intrascrotal and intraperitoneal injection of pUMOD induced leukocyte recruitment in vivo and led to TNF-α secretion by F4/80 positive macrophages. Additionally, pUMOD directly affected vascular permeability and increased neutrophil extravasation independent of macrophage-released TNF-α. Interestingly, pUMOD displayed no chemotactic properties on neutrophils, did not directly activate β2 integrins and did not upregulate adhesion molecules on endothelial cells. In obstructed neonatal murine kidneys, we observed extratubular UMOD accumulation in the renal interstitium with tubular atrophy and leukocyte infiltrates. Finally, we found extratubular UMOD deposits associated with peritubular leukocyte infiltration in kidneys from patients with inflammatory kidney diseases. Taken together, we identified extratubular pUMOD as a strong inducer of leukocyte recruitment, underlining its critical role in mounting an inflammatory response in various kidneys pathologies.

Pharmacological inhibition of focal adhesion kinase 1 (FAK1) and anaplastic lymphoma kinase (ALK) identified via kinome profile analysis attenuates lipopolysaccharide-induced endothelial inflammatory activation

Sepsis is a life-threatening condition often leading to multiple organ failure for which currently no pharmacological treatment is available. Endothelial cells (EC) are among the first cells to respond to pathogens and inflammatory mediators in sepsis and might be a sentinel target to prevent the occurrence of multiple organ failure. Lipopolysaccharide (LPS) is a Gram-negative bacterial component that induces endothelial expression of inflammatory adhesion molecules, cytokines, and chemokines. This expression is regulated by a network of kinases, the result of which in vivo enables leukocytes to transmigrate from the blood into the underlying tissue, causing organ damage. We hypothesised that besides the known kinase pathways, other kinases are involved in the regulation of EC in response to LPS, and that these can be pharmacologically targeted to inhibit cell activation. Using kinome profiling, we identified 58 tyrosine kinases (TKs) that were active in human umbilical vein endothelial cells (HUVEC) at various timepoints after stimulation with LPS. These included AXL tyrosine kinase (Axl), focal adhesion kinase 1 (FAK1), and anaplastic lymphoma kinase (ALK). Using siRNA-based gene knock down, we confirmed that these three TKs mediate LPS-induced endothelial inflammatory activation. Pharmacological inhibition with FAK1 inhibitor FAK14 attenuated LPS-induced endothelial inflammatory activation and leukocyte adhesion partly via blockade of NF-κB activity. Administration of FAK14 after EC exposure to LPS also resulted in inhibition of inflammatory molecule expression. In contrast, inhibition of ALK with FDA-approved inhibitor Ceritinib attenuated LPS-induced endothelial inflammatory activation via a pathway that was independent of NF-κB signalling while it did not affect leukocyte adhesion. Furthermore, Ceritinib administration after start of EC exposure to LPS did not inhibit inflammatory activation. Combined FAK1 and ALK inhibition attenuated LPS-induced endothelial activation in an additive manner, without affecting leukocyte adhesion. Summarising, our findings suggest the involvement of FAK1 and ALK in mediating LPS-induced inflammatory activation of EC. Since pharmacological inhibition of FAK1 attenuated endothelial inflammatory activation after the cells were exposed to LPS, FAK1 represents a promising target for follow up studies.

Loss of HMBOX1 promotes LPS-induced apoptosis and inhibits LPS-induced autophagy of vascular endothelial cells in mouse

Our previous study revealed that Homeobox containing 1 (HMBOX1), essential for the survival of vascular endothelial cells (VECs), was involved in the progression of atherosclerosis. Knockdown of HMBOX1 promoted apoptosis and inhibited autophagy through regulating intracellular free zinc level in cultured VECs. In current study, in order to investigate the roles of HMBOX1 in vivo and in endothelium, we generated a knockout (KO) mouse for HMBOX1 by using transcription activator-like effector nucleases (TALENs) technology. Herein, we reported that the protein level of HMBOX1 was gradually increased during mouse development. The HMBOX1 KO mouse was viable and fertile. There existed no differences in apoptosis and autophagy of aortic endothelial cells between wild type and KO mouse. Whereas, loss of HMBOX1 promoted apoptosis and inhibited autophagy of aortic endothelial cells under lipopolysaccharide (LPS) stimulation in mouse. We also demonstrated that HMBOX1 deletion had no influence on the secretion of inflammatory cytokines TNF-α and IL-6. Moreover, overexpression or knockdown of HMBOX1 failed to regulate multiple pro-apoptotic genes expression in vitro. In conclusion, HMBOX1 participated in the functional maintenance of mouse aortic endothelial cells, the aortic endothelial cells of HMBOX1 KO mouse showed increased apoptosis and decreased autophagy with LPS treatment.

Lipopolysaccharide-Induced Vascular Inflammation Model on Microfluidic Chip

Inflammation is the initiation of defense of our body against harmful stimuli. Lipopolysaccharide (LPS), originating from outer membrane of Gram-negative bacteria, causes inflammation in the animal’s body and can develop several diseases. In order to study the inflammatory response to LPS of blood vessels in vitro, 2D models have been mainly used previously. In this study, a microfluidic device was used to investigate independent inflammatory response of endothelial cells by LPS and interaction of inflamed blood vessel with monocytic THP-1 cells. Firstly, the diffusion of LPS across the collagen gel into blood vessel was simulated using COMSOL. Then, inflammatory response to LPS in engineered blood vessel was confirmed by the expression of Intercellular Adhesion Molecule 1 (ICAM-1) and VE-cadherin of blood vessel, and THP-1 cell adhesion and migration assay. Upregulation of ICAM-1 and downregulation of VE-cadherin in an LPS-treated condition was observed compared to normal condition. In the THP-1 cell adhesion and migration assay, the number of adhered and trans-endothelial migrated THP-1 cells were not different between conditions. However, migration distance of THP-1 was longer in the LPS treatment condition. In conclusion, we recapitulated the inflammatory response of blood vessels and the interaction of THP-1 cells with blood vessels due to the diffusion of LPS.

Gene Expression Profile of Isolated Dermal Vascular Endothelial Cells in Keloids

Wound healing is a complex biological process, and imbalances of various substances in the wound environment may prolong healing and lead to excessive scarring. Keloid is abnormal proliferation of scar tissue beyond the original wound margins with excessive deposition of extracellular matrix (ECM) and chronic inflammation. Despite numerous previous research efforts, the pathogenesis of keloid remains unknown. Vascular endothelial cells (VECs) are a major type of inductive cell in inflammation and fibrosis. Despite several studies on vascular morphology in keloid formation, there has been no functional analysis of the role of VECs. In the present study, we isolated living VECs from keloid tissues and investigated gene expression patterns using microarray analysis. We obtained 5 keloid tissue samples and 6 normal skin samples from patients without keloid. Immediately after excision, tissue samples were gently minced and living cells were isolated. Magnetic-activated cell sorting of VECs was performed by negative selection of fibroblasts and CD45⁺ cells and by positive selection of CD31⁺cells. After RNA extraction, gene expression analysis was performed to compare VECs isolated from keloid tissue (KVECs) with VECs from normal skin (NVECs). After cell isolation, the percentage of CD31⁺ cells as measured by flow cytometry ranged from 81.8%–98.6%. Principal component analysis was used to identify distinct molecular phenotypes in KVECs versus NVECs and these were divided into two subgroups. In total, 15 genes were upregulated, and 3 genes were downregulated in KVECs compared with NVECs using the t-test (< 0.05). Quantitative RT-PCR and immunohistochemistry showed 16-fold and 11-fold overexpression of SERPINA3 and LAMC2, respectively. SERPINA3 encodes the serine protease inhibitor, α1-antichymotripsin. Laminin γ2-Chain (LAMC2) is a subunit of laminin-5 that induces retraction of vascular endothelial cells and enhances vascular permeability. This is the first report of VEC isolation and gene expression analysis in keloid tissue. Our data suggest that SERPINA3 and LAMC2 upregulation in KVECs may contribute to the development of fibrosis and prolonged inflammation in keloid. Further functional investigation of these genes will help clarify the mechanisms of abnormal scar tissue proliferation.

Three-dimensional tissue engineering-based Dentin/Pulp tissue analogue as advanced biocompatibility evaluation tool of dental restorative materials

OBJECTIVE

Two-dimensional (2D) in vitro models have been extensively utilized for cytotoxicity assessment of dental materials, but with certain limitations in terms of direct in vitro-in vivo extrapolation (IVIVE). Three-dimensional (3D) models seem more appropriate, recapitulating the structure of human tissues. This study established a 3D dentin/pulp analogue, as advanced cytotoxicity assessment tool of dental restorative materials (DentCytoTool).

METHODS

DentCytoTool comprised two compartments: the upper, representing the dentin component, with a layer of odontoblast-like cells expanded on microporous membrane of a cell culture insert and covered by a treated dentin matrix; and the lower, representing a pulp analogue, incorporating HUVEC/SCAP co-cultures into collagen I/fibrin hydrogels. Representative resinous monomers (HEMA: 1-8mM; TEGDMA: 0.5-5mM) and bacterial components (LPS: 1μg/ml) were applied into the construct. Cytotoxicity was assessed by MTT and LDH assays, live/dead staining and real-time PCR for odontogenesis- and angiogenesis-related markers.

RESULTS

DentCytoTool supported cell viability and promoted capillary-like network formation inside the pulp analogue. LPS induced expression of odontogenesis-related markers (RUNX2, ALP, DSPP) without compromising viability of the odontoblast-like cells, while co-treatment with LPS and resin monomers induced cytotoxic effects (live/dead staining, MTT and LDH assays) in cells of both upper and lower compartments and reduced expression angiogenesis-related markers (VEGF, VEGFR2, ANGPT-1, Tie-2, PECAM-1) in a concentration- and time- dependent manner. LPS treatment aggravated TEGDMA-induced and -in certain concentrations (2-4mM)- HEMA-induced cytotoxicity.

SIGNIFICANCE

DentCytoTool represents a promising tissue-engineering-based cytotoxicity assessment tool, providing more insight into the mechanistic aspects of interactions of dental materials to the dentin/pulp complex.