Bacterial lipopolysaccharide activates NF-kappaB through toll-like receptor 4 (TLR-4) in cultured human dermal endothelial cells. Differential expression of TLR-4 and TLR-2 in endothelial cells

Pathophysiology of Sepsis

Sepsis is a condition of life-threatening organ dysfunction caused by a dysregulated host response to infection. It is the result of a series of exaggerated physiologic responses that lead to simultaneous hyper- and hypoinflammatory states. In the hyperinflammatory phase, there is an exuberant release of cytokines, commonly referred to as a cytokine storm. The immune-suppressive phase is characterized by counterregulatory attempts to achieve homeostasis that sometimes "overshoot", leaving the host in a state of immunosuppression, thus predisposing to recurrent nosocomial and secondary infections. The aging population with comorbidities faces higher risks of immune dysfunction and inflammation. Thus, the number of sepsis survivors that develop subsequent infections is predicted to rise substantially in the next few decades. Understanding sepsis-induced immune dysregulation may enhance surveillance and outcomes. This review is intended to describe the pathophysiology of sepsis and its effects on the immune system.

Associations between Toll-like receptor 4 Asp299Gly polymorphism and susceptibility to intracranial aneurysm among male and female patients within the North Indian population

OBJECTIVES

Intracranial aneurysms (IA), often remain asymptomatic until they get ruptured, invariably leads to subarachnoid hemorrhage (SAH), and is influenced by both genetic and environmental factors. Recent studies indicated inflammation as a key player in IA development. This study delves into genetic variations within inflammatory pathways, focusing on TLR4-mediated cytokine release as potential IA biomarkers.

METHODS

Eighty IA patients and eighty healthy controls from North India participated, and demographic and clinical data were analyzed, including gender-stratified comparisons of TLR4 Asp299Gly genotype and TLR4 expression. Histological and molecular analyses of blood and brain tissue were done using SEM imaging, qPCR, and western blot.

RESULTS

Our result revealed elevated TLR4 expression in IA patients, with SEM imaging indicating intracerebral damage. TLR4 Asp299Gly heterozygote genotype was less prevalent in IA patients, suggesting a protective effect against IA development. Moreover, TNF-α levels were significantly higher in IA patients, indicating an inflammatory response. Further, TNF-α expression was downregulated in heterozygous patients, suggesting TLR4 Asp299Gly gene polymorphism affects the activation of TNF-α expression. Gender-based analysis between control and aneurysm cases showed a decrease in TLR4 Asp299Gly heterozygote genotype with heightened TLR4 expression and neurological deficits in IA female patients compared to males.

CONCLUSIONS

This study highlights the association between TLR4 Asp299Gly genotype and IA susceptibility in North Indian populations, linking increased TLR4 expression to IA pathogenesis. Gender-specific disparities in TLR4 genotype and expression underscore the need for personalized treatment strategies, with TLR4 signaling modulation emerging as a promising therapeutic avenue warranting further investigation.

PCSK9 in T-cell function and the immune response

Proprotein convertase subtilisin/kexin type 9 (PCSK9) was first reported in 2003 and confirmed to be strongly associated with familial hypercholesterolemia. Small-molecule inhibitors targeting PCSK9 provide an effective and safe method for managing hypercholesterolemia and reducing the cardiovascular risk. In recent years, increasing evidence has indicated other important roles for PCSK9 in inflammation, tumors, and even immune regulation. PCSK9 might be an attractive regulator of T-cell activation and expansion. It might mediate inflammation and regulate other types of immune cells. In this review, we summarize the current advances in the field of PCSK9 and provide a narrative of the biological processes associated with PCSK9. The relationships between PCSK9 and different T cells were investigated in depth. Finally, the signaling pathways associated with PCSK9 and the immune response are also summarized in this review.

Macrophage activation syndrome in Sepsis: from pathogenesis to clinical management

BACKGROUND

Sepsis represents a significant global health and hygiene challenge. Excessive activation of macrophages in sepsis can result in certain patients displaying characteristics akin to those observed in Macrophage Activation Syndrome (MAS). MAS represents a grave immune system disorder characterized by persistent and severe inflammation within the body. In the context of sepsis, MAS presents atypically, leading some researchers to refer to it as Macrophage Activation-Like Syndrome (MALS). However, there are currently no effective treatment measures for this situation. The purpose of this article is to explore potential treatment methods for sepsis-associated MALS.

OBJECTIVE

The objective of this review is to synthesize the specific pathophysiological mechanisms and treatment strategies of MAS to investigate potential therapeutic approaches for sepsis-associated MALS.

METHOD

We searched major databases (including PubMed, Web of Science, and Google Scholar etc.) for literature encompassing macrophage activation syndrome and sepsis up to Mar 2024 and combined with studies found in the reference lists of the included studies.

CONCLUSION

We have synthesized the underlying pathophysiological mechanism of MALS in sepsis, and then summarized the diagnostic criteria and the effects of various treatment modalities utilized in patients with MAS or MALS. In both scenarios, heterogeneous treatment responses resulting from identical treatment approaches were observed. The determination of whether the patient is genuinely experiencing MALS significantly impacts the ultimate outcomes of therapeutic efficacy. In order to tackle this concern, additional clinical trials and research endeavors are imperative.

Challenges in tendon-bone healing: emphasizing inflammatory modulation mechanisms and treatment

Tendons are fibrous connective tissues that transmit force from muscles to bones. Despite their ability to withstand various loads, tendons are susceptible to significant damage. The healing process of tendons and ligaments connected to bone surfaces after injury presents a clinical challenge due to the intricate structure, composition, cellular populations, and mechanics of the interface. Inflammation plays a pivotal role in tendon healing, creating an inflammatory microenvironment through cytokines and immune cells that aid in debris clearance, tendon cell proliferation, and collagen fiber formation. However, uncontrolled inflammation can lead to tissue damage, and adhesions, and impede proper tendon healing, culminating in scar tissue formation. Therefore, precise regulation of inflammation is crucial. This review offers insights into the impact of inflammation on tendon-bone healing and its underlying mechanisms. Understanding the inflammatory microenvironment, cellular interactions, and extracellular matrix dynamics is essential for promoting optimal healing of tendon-bone injuries. The roles of fibroblasts, inflammatory cytokines, chemokines, and growth factors in promoting healing, inhibiting scar formation, and facilitating tissue regeneration are discussed, highlighting the necessity of balancing the suppression of detrimental inflammatory responses with the promotion of beneficial aspects to enhance tendon healing outcomes. Additionally, the review explores the significant implications and translational potential of targeted inflammatory modulation therapies in refining strategies for tendon-bone healing treatments.

Psilocin, the Psychoactive Metabolite of Psilocybin, Modulates Select Neuroimmune Functions of Microglial Cells in a 5-HT2 Receptor-Dependent Manner

Neuroinflammation that is caused by microglia, the main immune cells of the brain, contributes to neurodegenerative diseases. Psychedelics, including psilocybin and lysergic acid diethylamide (LSD), possess certain anti-inflammatory properties and, therefore, should be considered as drug candidates for treating neuroinflammatory pathologies. When ingested, psilocybin is rapidly dephosphorylated to yield psilocin, which crosses the blood-brain barrier and exerts psychotropic activity by interacting with the 5-hydroxytryptamine 2A receptors (5-HT2ARs) on neurons. Since microglia express all three 5-HT2R isoforms, we hypothesized that, by interacting with these receptors, psilocin beneficially modulates select neuroimmune functions of microglia. We used microglia-like cell lines to demonstrate that psilocin, at non-toxic concentrations, did not affect the secretion of tumor necrosis factor (TNF) by immune-stimulated microglial cells, but significantly inhibited their phagocytic activity, the release of reactive oxygen species (ROS), and nitric oxide (NO) production. The inhibitory activity of psilocin on the latter two functions was similar to that of two selective 5-HT2R agonists, namely, 25I-NBOH and Ro60-0175. The role of this subfamily of receptors was further demonstrated by the application of 5-HT2R antagonists cyproheptadine and risperidone. Psilocin should be considered a novel drug candidate that might be effective in treating neuroimmune disorders, such as neurodegenerative diseases, where reactive microglia are significant contributors.

The roles of SFKs in the regulation of proinflammatory cytokines and NLRP3 in familial mediterranean fever patients

Familial Mediterranean Fever (FMF) is caused by mutations in pyrin, a protein produced in innate immune cells that regulates the development of interleukin (IL)-1β by interacting with caspase-1 and other components of inflammasomes. Although overexpression of proinflammatory cytokines have been observed in FMF patients, no studies have been conducted on the role of Src family kinases (SFKs). The purpose of this study was to examine the impact of SFKs on the modulation of IL-1β, IL-6, IL-8, TNF-α, and NLRP3 inflammasome in patients with FMF. The study included 20 FMF patients and 20 controls. Peripheral blood mononuclear cells (PBMCs) were isolated by density gradient centrifugation. Protein expression levels of SFKs members were measured by western blot. The effect of lipopolysaccharide-induced (LPS) activation and PP2- induced inhibition of SFKs on NLRP3 and IL-1β, IL 6, IL-8, TNF-α were examined by western blot and flow cytometry respectively. Patients with FMF have considerably greater levels of Lck expression. In addition, patients had a substantially greater basal level of NLRP3 than the control group (*p = 0.016). Most importantly, the levels of IL-1 β were elevated with LPS stimulation and reduced with PP2 inhibition in FMF patients. These results suggest that SFKs are effective in regulation of IL-1 β in FMF patients.

Effect of human umbilical cord blood-mesenchymal stem cells on cisplatin-induced nephrotoxicity in rats

BACKGROUND

Cisplatin-containing regimen is an effective treatment for several malignancies. However, cisplatin is an important cause of nephrotoxicity. So, many trials were performed to transplant stem cells systemically or locally to control cisplatin-induced nephrotoxicity. Stem cell therapeutic effect may be dependent on the regulation of inflammation and oxidant stress.

AIM

To investigate the effect of human umbilical cord blood-mesenchymal stem cells (hUCB-MSCs) on the histological structure, the oxidant stress, and the inflammatory gene expression in an experimental model of cisplatin-induced nephrotoxicity in rats.

METHOD

The rats were divided into 6 equal groups (each of 10 rats): Group I included normal rats that received no treatment. Group II included healthy rats that received IV hUCB-MSCs. Group III included untreated cisplatin-induced nephrotoxic rats. Group IV included cisplatin-induced nephrotoxic rats that received magnesium (Mg) injections after injury. Group V was injected with hUCB-MSCs after injury. Group VI received both Mg and hUCB-MSCs after injury. In tissue homogenates, reduced glutathione (GSH), superoxide dismutase (SOD), and malondialdehyde (MDA) activities were measured. Quantitative real-time-polymerase chain reaction (qRT-PCR) was performed to assess iNOS, TLR4, and NF-kB gene expression. Hematoxylin and eosin (H&E) staining was performed to study the histological structure of the kidney. Immunohistochemical staining of iNOS and NF-κB was performed, as well.

RESULTS

Disturbed kidney functions, oxidative status, and histological structure were seen in the rats that received cisplatin. Treated groups showed improvements in kidney functions, oxidative status, and histological structure, particularly in the combined treatment group.

CONCLUSION

In the cisplatin-induced nephrotoxicity model, hUCB-MSCs could improve the functional and morphological kidney structure by modulation of oxidative and inflammatory status.

Commonly disrupted pathways in brain and kidney in a pig model of systemic endotoxemia

Sepsis is a life-threatening state that arises due to a hyperactive inflammatory response stimulated by infection and rarely other insults (e.g., non-infections tissue injury). Although changes in several proinflammatory cytokines and signals are documented in humans and small animal models, far less is known about responses within affected tissues of large animal models. We sought to understand the changes that occur during the initial stages of inflammation by administering intravenous lipopolysaccharide (LPS) to Yorkshire pigs and assessing transcriptomic alterations in the brain, kidney, and whole blood. Robust transcriptional alterations were found in the brain, with upregulated responses enriched in inflammatory pathways and downregulated responses enriched in tight junction and blood vessel functions. Comparison of the inflammatory response in the pig brain to a similar mouse model demonstrated some overlapping changes but also numerous differences, including oppositely dysregulated genes between species. Substantial changes also occurred in the kidneys following LPS with several enriched upregulated pathways (cytokines, lipids, unfolded protein response, etc.) and downregulated gene sets (tube morphogenesis, glomerulus development, GTPase signal transduction, etc.). We also found significant dysregulation of genes in whole blood that fell into several gene ontology categories (cytokines, cell cycle, neutrophil degranulation, etc.). We observed a strong correlation between the brain and kidney responses, with significantly shared upregulated pathways (cytokine signaling, cell death, VEGFA pathways) and downregulated pathways (vasculature and RAC1 GTPases). In summary, we have identified a core set of shared genes and pathways in a pig model of systemic inflammation.

Anti-inflammatory potential of ulvan

Green seaweeds are a widespread group of marine macroalgae that could be regarded as biorenewable source of valuable compounds, in particular sulfated polysaccharides like ulvans with interesting biological properties. Among them, anti-inflammatory activity represents an interesting target, since ulvans could potentially avoid side effects of conventional therapies. However, a great variability in ulvan content, composition, structure and properties occurs depending on seaweed specie and growth and processing conditions. All these aspects should be carefully considered in order to have reproducible and well characterized products. This review presents some concise ideas on ulvan composition and general concepts on inflammation mechanisms. Then, the main focus is on the importance of adequate selection of extraction, depolymerization and purification technologies followed by an updated survey on anti-inflammatory properties of ulvans through modulation of different signaling pathways. The potential application in a number of diseases, with special emphasis on inflammaging, gut microbiota dysbiosis, wound repair, and metabolic diseases is also discussed. This multidisciplinary overview tries to present the potential of ulvans considering not only mechanistic, but also processing and applications aspects, trusting that it can aid in the development and application of this widely available and renewable resource as an efficient and versatile anti-inflammatory agent.

Suberosin Alleviates Sepsis-Induced Lung Injury in A Rat Model of Cecal Ligation and Puncture

BACKGROUND/AIMS

Sepsis is one of the major problems encountered in intensive care units, causing organ damage and increasing mortality. Suberosin (SBR) is a type of coumarin with antioxidant and anti-inflammatory activities. The goal of this study is to explore the protective effects of SBR on the lungs in a rat model of sepsis.

METHODS

Male Wistar rats were utilized in this study. A cecal ligation and puncture (CLP) model was applied to induce sepsis. Rats were separated into six groups with nine animals in each group, including healthy control, SBR, CLP, and CLP + SBR (5, 10, and 20 mg/kg) groups. Superoxide dismutase (SOD), glutathione (GSH) enzyme activities, and malondialdehyde (MDA) level were measured via enzyme-linked immunosorbent assay (ELISA). The messenger RNA (mRNA) expressions of tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β) were evaluated by real-time polymerase chain reaction (RT-PCR). Histopathological changes in the lungs were investigated with hematoxylin and eosin (H&E).

RESULTS

MDA levels and GSH and SOD enzyme activities were negatively affected in the CLP group, but SBR treatment ameliorated these oxidative stress parameters in the SBR1-3 groups (p< 0.05). The mRNA expressions of TNF-α and IL-1β were increased in the CLP group, and SBR treatment decreased those expression levels in a dose-dependent manner (p < 0.05). Organ damage and necrosis were seen in the CLP group and were alleviated in the SBR3 group. Immunohistochemical (IHC) analysis of lung tissues demonstrated decreased TNF-α and IL-1β immunopositivity in the SBR1-3 groups (p< 0.05).

CONCLUSIONS

SBR ameliorated sepsis-related lung injury in a dose-dependent manner. This compound has significant potential as a future agent in the treatment of sepsis.

The Journey Through the Pathogenesis and Treatment of Venous Thromboembolism in Inflammatory Bowel Diseases: A Narrative Review

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders of the gastrointestinal tract including Crohn's disease and ulcerative colitis, which may result in several extraintestinal complications (∼20-30% of cases), such as increased risk of venous thromboembolism (VTE). The main pathophysiological mechanism of VTE is an inflammation-induced hypercoagulable state, and recent data have shown that endothelial dysregulation due to gut and systemic inflammation may also lead to a prothrombotic state. Several prothrombotic alterations have been described, such as the activation of the coagulation system, platelet abnormalities, and dysregulation of fibrinolysis. Furthermore, the dysregulation of the gut microbiome seems to play a vital role in increasing systemic inflammation and thus inducing a procoagulant state. Our review aims to examine the main correlations between IBD and VTE, the underlying pathophysiology, and current therapeutic options.

Mast cell-mediated immune regulation in health and disease

Mast cells are important components of the immune system, and they perform pro-inflammatory as well as anti-inflammatory roles in the complex process of immune regulation in health and disease. Because of their strategic perivascular localization, sensitivity and adaptability to the microenvironment, and ability to release a variety of preformed and newly synthesized effector molecules, mast cells perform unique functions in almost all organs. Additionally, Mast cells express a wide range of surface and cytoplasmic receptors which enable them to respond to a variety of cytokines, chemicals, and pathogens. The mast cell's role as a cellular interface between external and internal environments as well as between vasculature and tissues is critical for protection and repair. Mast cell interactions with different immune and nonimmune cells through secreted inflammatory mediators may also turn in favor of disease promoting agents. First and forefront, mast cells are well recognized for their multifaceted functions in allergic diseases. Reciprocal communication between mast cells and endothelial cells in the presence of bacterial toxins in chronic/sub-clinical infections induce persistent vascular inflammation. We have shown that mast cell proteases and histamine induce endothelial inflammatory responses that are synergistically amplified by bacterial toxins. Mast cells have been shown to exacerbate vascular changes in normal states as well as in chronic or subclinical infections, particularly among cigarette smokers. Furthermore, a potential role of mast cells in SARS-CoV-2-induced dysfunction of the capillary-alveolar interface adds to the growing understanding of mast cells in viral infections. The interaction between mast cells and microglial cells in the brain further highlights their significance in neuroinflammation. This review highlights the significant role of mast cells as the interface that acts as sensor and early responder through interactions with cells in systemic organs and the nervous system.

End-stage kidney disease: a never healing wound leading to another never healing wound, renal cancer

BACKGROUND

End-stage kidney disease and acquired cystic kidney disease are the final stages of chronic kidney disease, leading to loss of kidney function and frequent development of tumours. It has been suggested that an inflammatory microenvironment may be responsible for the progressive kidney remodelling and cancer development.

METHODS

Our aim was to analyse gene expression suggested to be involved in the remodelling of kidneys in end-stage kidney disease, and in the development of preneoplastic lesions and tumours. Immunohistochemistry was employed to assess the cellular localisation of different genes involved in these pathways on representative tissue sections.

RESULTS

Cellular (αSMA positive naïve activated fibroblasts, endothelial cells, macrophages) and non-cellular components (cytokines IL6, TGFβ, IL1β, CSF2, fibronectin, laminin, and matrix modifier proteases MMP9 and MMP12) of the inflammatory microenvironment were expressed in the kidneys of patients with end-stage kidney disease. IL6 and FN1 expressing naïve activated fibroblasts and recruited inflammatory cells were the most abundant cellular components of the inflammatory microenvironment.

CONCLUSION

The progressive inflammatory and fibrotic processes in end-stage kidney disease have features recalling those of  a never healing wound and may explain the frequent development of kidney cancer.

Impact of Enzymatically Extracted High Molecular Weight Fucoidan on Lipopolysaccharide-Induced Endothelial Activation and Leukocyte Adhesion

The endothelial cell lining creates an interface between circulating blood and adjoining tissue and forms one of the most critical barriers and targets for therapeutical intervention. Recent studies suggest that fucoidans, sulfated and fucose-rich polysaccharides from brown seaweed, show multiple promising biological effects, including anti-inflammatory properties. However, their biological activity is determined by chemical characteristics such as molecular weight, sulfation degree, and molecular structure, which vary depending on the source, species, and harvesting and isolation method. In this study, we investigated the impact of high molecular weight (HMW) fucoidan extract on endothelial cell activation and interaction with primary monocytes (MNCs) in lipopolysaccharide (LPS)-induced inflammation. Gentle enzyme-assisted extraction combined with fractionation by ion exchange chromatography resulted in well-defined and pure fucoidan fractions. FE_F3, with a molecular weight ranging from 110 to 800 kDa and a sulfate content of 39%, was chosen for further investigation of its anti-inflammatory potential. We observed that along with higher purity of fucoidan fractions, the inflammatory response in endothelial mono- and co-cultures with MNCs was reduced in a dose-dependent manner when testing two different concentrations. This was demonstrated by a decrease in IL-6 and ICAM-1 on gene and protein levels and a reduced gene expression of TLR-4, GSK3β and NF-kB. Expression of selectins and, consequently, the adhesion of monocytes to the endothelial monolayer was reduced after fucoidan treatment. These data indicate that the anti-inflammatory effect of fucoidans increases with their purity and suggest that fucoidans might be useful in limiting the inflammatory response of endothelial cells in cases of LPS-induced bacterial infection.

NQO1 alleviates renal fibrosis by inhibiting the TLR4/NF-κB and TGF-β/Smad signaling pathways in diabetic nephropathy

OBJECTIVE

Diabetic nephropathy (DN) is one of the main complications of diabetes, and inflammation and fibrosis play an important role in its progression. NAD(P)H: quinone oxidoreductase 1 (NQO1) protects cells from oxidative stress and damage caused by toxic quinones. In the present study, we aimed to investigate the protective effects of NQO1 against diabetes-induced renal inflammation and fibrosis and the underlying mechanisms.

METHODS

In vivo, the kidneys of type 2 diabetes model db/db mice were infected with adeno-associated virus vectors to induce NQO1 overexpression. In vitro, human renal tubular epithelial (HK-2) cells transfected with NQO1 pcDNA3.1(+) were cultured under high-glucose (HG) conditions. Gene and protein expression was assessed by quantitative real-time PCR, Western blotting, immunofluorescence, and immunohistochemical staining. Mitochondrial reactive oxygen species (ROS) were detected with MitoSOX Red.

RESULT

Our study revealed that the expression of NQO1 was markedly downregulated and that Toll-like receptor (TLR)4 and TGF-β1 expression was upregulated in vivo and in vitro under diabetic conditions. Overexpression of NQO1 suppressed proinflammatory cytokine (IL-6, TNF-α, MCP-1) secretion, extracellular matrix (ECM) (collagen IV, fibronectin) accumulation and epithelial-mesenchymal transition (EMT) (α-SMA, E-cadherin) in the db/db mouse kidneys and HG-cultured HK-2 cells. Furthermore, NQO1 overexpression ameliorated HG-induced TLR4/NF-κB and TGF-β/Smad pathways activation. Mechanistic studies demonstrated that a TLR4 inhibitor (TAK-242) suppressed the TLR4/NF-κB signaling pathway, proinflammatory cytokine secretion, EMT and ECM-related protein expression in HG-exposed HK-2 cells. In addition, we found that the antioxidants N-acetylcysteine (NAC) and tempol increased the expression of NQO1 and decreased the expression of TLR4, TGF-β1, Nox1, and Nox4 and ROS production in HK-2 cells cultured under HG conditions.

CONCLUSIONS

These data suggest that NQO1 alleviates diabetes-induced renal inflammation and fibrosis by regulating the TLR4/NF-κB and TGF-β/Smad signaling pathways.

Bacterial extracellular vesicles repress the vascular protective factor RNase1 in human lung endothelial cells

BACKGROUND

Sepsis is one of the leading causes of death worldwide and characterized by blood stream infections associated with a dysregulated host response and endothelial cell (EC) dysfunction. Ribonuclease 1 (RNase1) acts as a protective factor of vascular homeostasis and is known to be repressed by massive and persistent inflammation, associated to the development of vascular pathologies. Bacterial extracellular vesicles (bEVs) are released upon infection and may interact with ECs to mediate EC barrier dysfunction. Here, we investigated the impact of bEVs of sepsis-related pathogens on human EC RNase1 regulation.

METHODS

bEVs from sepsis-associated bacteria were isolated via ultrafiltration and size exclusion chromatography and used for stimulation of human lung microvascular ECs combined with and without signaling pathway inhibitor treatments.

RESULTS

bEVs from Escherichia coli, Klebsiella pneumoniae and Salmonella enterica serovar Typhimurium significantly reduced RNase1 mRNA and protein expression and activated ECs, while TLR2-inducing bEVs from Streptococcus pneumoniae did not. These effects were mediated via LPS-dependent TLR4 signaling cascades as they could be blocked by Polymyxin B. Additionally, LPS-free ClearColi™ had no impact on RNase1. Further characterization of TLR4 downstream pathways involving NF-кB and p38, as well as JAK1/STAT1 signaling, revealed that RNase1 mRNA regulation is mediated via a p38-dependent mechanism.

CONCLUSION

Blood stream bEVs from gram-negative, sepsis-associated bacteria reduce the vascular protective factor RNase1, opening new avenues for therapeutical intervention of EC dysfunction via promotion of RNase1 integrity. Video Abstract.

Pseudomonas stutzeri PM101005 inhaled with atmospheric particulate matter induces lung damage through inflammatory responses

Atmospheric particulate matter (PM) contains a mixture of chemical and biological elements that pose threat to human health by increasing susceptibility to respiratory diseases. Although the identification of the microorganisms composing the PM has been assessed, their immunological impacts are still questionable. Here, we examined the mechanisms responsible for the pathogenicity of Pseudomonas stutzeri PM101005 (PMPS), a bacterium isolated from fine dust, in lung epithelial cells, alveolar cells, and macrophages. Relative to its comparative strain Pseudomonas stutzeri (PS), infections with PMPS induced higher production of inflammatory cytokines and chemokines, mediated by the activation of NF-κB and MAPK signaling pathways. Additionally, with three-dimensional (3D) airway spheroids which mimic the human bronchial epithelium, we confirmed that PMPS infections lead to relatively higher induction of pro-inflammatory cytokines than PM infections. Consistent results were observed in murine models as the infections with PMPS provoked greater inflammatory responses than the infections with PS. These PMPS-induced responses were mediated by the signaling pathways of the Toll-like receptors (TLRs), which regulated PMPS infection and played an important role in the expression of the antibiotic peptide β-defensin 3 (BD3) that suppressed PMPS proliferation. Moreover, PM pretreatment enhanced inflammatory responses and tissue damage of PMPS, while reducing BD3 expression. Overall, these results indicate that PM-isolated PMPS induce TLR-mediated inflammatory responses in lung tissues, and contributes to the understanding of the etiology of PM-induced respiratory damage.

Endothelial Activation and Microcirculatory Disorders in Sepsis

The vascular endothelium is crucial for the maintenance of vascular homeostasis. Moreover, in sepsis, endothelial cells can acquire new properties and actively participate in the host's response. If endothelial activation is mostly necessary and efficient in eliminating a pathogen, an exaggerated and maladaptive reaction leads to severe microcirculatory damage. The microcirculatory disorders in sepsis are well known to be associated with poor outcome. Better recognition of microcirculatory alteration is therefore essential to identify patients with the worse outcomes and to guide therapeutic interventions. In this review, we will discuss the main features of endothelial activation and dysfunction in sepsis, its assessment at the bedside, and the main advances in microcirculatory resuscitation.

Elevated Expression of TLR2 in Aging Hearts Exacerbates Cardiac Inflammatory Response and Adverse Remodeling Following Ischemia and Reperfusion Injury

This study tested the hypothesis that Toll-like receptor 2 (TLR2) augments the inflammatory responses and adverse remodeling in aging hearts to exacerbate myocardial injury and cardiac dysfunction.

Methods

Old (20-22 months old) and adult (4-6 months old) mice of C57BL/6 wild-type and TLR2 knockout (KO) were subjected to coronary artery ligation (30 minutes) and reperfusion (3 or 14 days). Left ventricle function was assessed using a pressure-volume microcatheter. Cardiac infarct size was determined by histology. Levels of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), matrix metalloproteinase 9 (MMP 9), and collagen I in non-ischemic myocardium were assessed by immunoblotting. Monocyte chemoattractant protein-1 (MCP-1), keratinocyte chemoattractant (KC), and interleukin-6 (IL-6) levels in ischemic and non-ischemic myocardium were measured by enzyme-linked immunosorbent assay (ELISA). TLR2 expression in the myocardium of untreated wild type mice was also measured by immunoblotting.

Results

Higher levels of MCP-1, KC, IL-6 were induced in both ischemic and non-ischemic myocardium of old wild type mice at day 3 and 14 following ischemia/reperfusion (I/R) than those of adult wild type mice. The hyper-inflammatory responses to I/R in aging hearts were associated with elevated levels of myocardial TLR2. TLR2 KO markedly down-regulated the expression of MCP-1, KC, IL-6, ICAM-1 and VCAM-1 in aging hearts at day 3 and 14 following I/R. The down-regulated inflammatory activity in aging TLR2 KO hearts was associated with attenuated production of MMP 9 and collagen I at day 14 and resulted in reduced infarct size and improved cardiac function.

Conclusion

Elevated expression of myocardial TLR2 contributes to the mechanism by which aging exacerbates the inflammatory responses, adverse remodeling and cardiac dysfunction following myocardial I/R in aging.

Quantum dots bind nanosheet to promote nanomaterial stability and resist endotoxin-induced fibrosis and PM2.5-induced pneumonia

Endotoxin lipopolysaccharide (LPS) is a harmful substance commonly found in various environments that causes lung fibrosis. Exposure to PM2.5 also increases the risk of respiratory diseases. Through sulfur-carbon bonds and the edge S effect, GOQDs were used to bind in single-layer molybdenum disulfide (SLMoS2) nanosheets to synthesize SLMoS2@GOQDs heterojunction structures. GOQDs doping greatly increased the water solubility and stabilized of SLMoS2. SLMoS2@GOQDs with catalase-like activity protected cells from ultrastructural and cytomembrane damage and apoptosis induced by LPS. Moreover, the doping of GOQDs enhanced the escape of SLMoS2@GOQDs from cellular uptake and suppressed the release of Mo ions. Nanosheet-cell interface interactions that were regulated by quantum dots supported these positive effects. Immunofluorescence analysis and cell imaging confirmed that the nanomaterial protected against cell injury by regulating the canonical Wnt/β-catenin pathway and the secretion of relevant cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Moreover, SLMoS2@GOQDs also mitigated pneumonia caused by PM2.5 in vivo. Collectively, our findings not only provide a simple and effective approach to control lung diseases (caused by LPS or PM2.5), but also reveal the potential value of heterojunction materials in the fields of toxicology and human health, boosting the application of nanotechnology in the fields of ecotoxicology and environmental safety.

Inflammatory Microenvironment of Skin Wounds

Wound healing is a dynamic and highly regulated process that can be separated into three overlapping and interdependent phases: inflammation, proliferation, and remodelling. This review focuses on the inflammation stage, as it is the key stage of wound healing and plays a vital role in the local immune response and determines the progression of wound healing. Inflammatory cells, the main effector cells of the inflammatory response, have been widely studied, but little attention has been paid to the immunomodulatory effects of wound healing in non-inflammatory cells and the extracellular matrix. In this review, we attempt to deepen our understanding of the wound-healing microenvironment in the inflammatory stage by focusing on the interactions between cells and the extracellular matrix, as well as their role in regulating the immune response during the inflammatory stage. We hope our findings will provide new ideas for promoting tissue regeneration through immune regulation.

Cysteine Peptidase Cathepsin X as a Therapeutic Target for Simultaneous TLR3/4-mediated Microglia Activation

Microglia are resident macrophages in the central nervous system that are involved in immune responses driven by Toll-like receptors (TLRs). Microglia-mediated inflammation can lead to central nervous system disorders, and more than one TLR might be involved in these pathological processes. The cysteine peptidase cathepsin X has been recognized as a pathogenic factor for inflammation-induced neurodegeneration. Here, we hypothesized that simultaneous TLR3 and TLR4 activation induces synergized microglia responses and that these phenotype changes affect cathepsin X expression and activity. Murine microglia BV2 cells and primary murine microglia were exposed to the TLR3 ligand polyinosinic-polycytidylic acid (poly(I:C)) and the TLR4 ligand lipopolysaccharide (LPS), individually and simultaneously. TLR3 and TLR4 co-activation resulted in increased inflammatory responses compared to individual TLR activation, where poly(I:C) and LPS induced distinct patterns of proinflammatory factors together with different patterns of cathepsin X expression and activity. TLR co-activation decreased intracellular cathepsin X activity and increased cathepsin X localization at the plasma membrane with concomitant increased extracellular cathepsin X protein levels and activity. Inhibition of cathepsin X in BV2 cells by AMS36, cathepsin X inhibitor, significantly reduced the poly(I:C)- and LPS-induced production of proinflammatory cytokines as well as apoptosis. Additionally, inhibiting the TLR3 and TLR4 common signaling pathway, PI3K, with LY294002 reduced the inflammatory responses of the poly(I:C)- and LPS-activated microglia and recovered cathepsin X activity. We here provide evidence that microglial cathepsin X strengthens microglia activation and leads to subsequent inflammation-induced neurodegeneration. As such, cathepsin X represents a therapeutic target for treating neurodegenerative diseases related to excess inflammation.

Reperfusion Cardiac Injury: Receptors and the Signaling Mechanisms

It has been documented that Ca2+ overload and increased production of reactive oxygen species play a significant role in reperfusion injury (RI) of cardiomyocytes. Ischemia/reperfusion induces cell death as a result of necrosis, necroptosis, apoptosis, and possibly autophagy, pyroptosis and ferroptosis. It has also been demonstrated that the NLRP3 inflammasome is involved in RI of the heart. An increase in adrenergic system activity during the restoration of coronary perfusion negatively affected cardiac resistance to RI. Toll-like receptors are involved in RI of the heart. Angiotensin II and endothelin-1 aggravated ischemic/reperfusion injury of the heart. Activation of neutrophils, monocytes, CD4+ T-cells and platelets contributes to cardiac ischemia/reperfusion injury. Our review outlines the role of these factors in reperfusion cardiac injury.

Evaluation of blood cell viability rate, gene expression, and O-GlcNAcylation profiles as indicative signatures for fungal stimulation of salmonid cell models

Fungal diseases of fish are a significant economic problem in aquaculture. Using high-throughput expression analysis, we identified potential transcript markers in primary head kidney and secondary embryonic cells from salmonid fish after stimulation with the inactivated fungi Mucor hiemalis and Fusarium aveneacium and with purified fungal molecular patterns. The transcript levels of most of the 45 selected genes were altered in head-kidney cells after 24 h of stimulation with fungal antigens. Stimulation with the inactivated fungus M. hiemalis induced the most pronounced transcriptional changes, including the pathogen receptor-encoding genes CLEC18A and TLR22, the cytokine-encoding genes IL6 and TNF, and the gene encoding the antimicrobial peptide LEAP2. In parallel, we analyzed the total GlcNAcylation status of embryonic salmonid cells with or without stimulation with inactivated fungi. O-GlcNAcylation modulates gene expression, intracellular protein, and signal activity, but we detected no significant differences after a 3-h stimulation. A pathway analysis tool identified the "apoptosis of leukocytes" based on the expression profile 24 h after fungal stimulation. Fluorescence microscopy combined with flow cytometry revealed apoptosis in 50 % of head-kidney leukocytes after 3 h stimulation with M. hiemalis, but this level decreased by > 5% after 24 h of stimulation. The number of apoptotic cells significantly increased in all blood cells after a 3-h stimulation with fungal molecular patterns compared to unstimulated controls. This in vitro approach identified transcript-based parameters that were strongly modulated by fungal infections of salmonid fish.

Responses of increasingly complex intestinal epithelium in vitro models to bacterial toll-like receptor agonists

The intestine fulfills roles in the uptake of nutrients and water regulation and acts as a gatekeeper for the intestinal microbiome. For the latter, the intestinal gut barrier system is able to respond to a broad range of bacterial antigens, generally through Toll-like receptor (TLR) signaling pathways. To test the capacity of various in vitro intestinal models, we studied IL-8 secretion, as a marker of pro-inflammatory response through the TLR pathway, in a Caco-2 monoculture, Caco-2/HT29-MTX di-culture, Caco-2/HT29-MTX/HMVEC-d tri-culture and in a HT29-p monoculture in response to exposure to various TLR agonists. Twenty-one-day-old differentiated cells in Transwells were exposed to Pam3CSK4 (TLR1/2), lipopolysaccharide (TLR4), single-stranded RNA (TLR7/8), Poly(i:C) (TLR3) and flagellin (TLR5) for 24 h. In all systems IL-8 secretion was increased in response to flagellin exposure, with HT29-p cells also responding to Poly(I:C) exposure. All other agonists did not induce an IL-8 response in the tested in vitro models, indicating that the specific TLRs are either not present or not functional in these models. This highlights the need for careful selection of in vitro models when studying intestinal immune responses and the need for improved in vitro models that better recapitulate intestinal immune responses.

Venous and arterial thromboembolism in patients with inflammatory bowel diseases

The risk of thromboembolism (TE) is increased in patients with inflammatory bowel disease (IBD), mainly due to an increased risk of venous TE (VTE). The risk of arterial TE (ATE) is less pronounced, but an increased risk of cardiovascular diseases needs to be addressed in IBD patients. IBD predisposes to arterial and venous thrombosis through similar prothrombotic mechanisms, including triggering activation of coagulation, in part mediated by impairment of the intestinal barrier and released bacterial components. VTE in IBD has clinical specificities, i.e., an earlier first episode in life, high rates during both active and remission stages, higher recurrence rates, and poor prognosis. The increased likelihood of VTE in IBD patients may be related to surgery, the use of medications such as corticosteroids or tofacitinib, whereas infliximab is antithrombotic. Long-term complications of VTE can include post-thrombotic syndrome and high recurrence rate during post-hospital discharge. A global clot lysis assay may be useful in identifying patients with IBD who are at risk for TE. Many VTEs occur in IBD outpatients; therefore, outpatient prophylaxis in high-risk patients is recommended. It is crucial to continue focusing on prevention and adequate treatment of VTE in patients with IBD.

A novel polysaccharide obtained from Siraitia grosvenorii alleviates inflammatory responses in a diabetic nephropathy mouse model via the TLR4-NF-κB pathway

The inflammatory and antioxidant effects of a novel Siraitia grosvenorii polysaccharide (SGP-1-1) were investigated in an inflammation-suppressed diabetic nephropathy (DN) mouse model, and the underlying molecular mechanisms of inflammation and oxidative stress in SGP-1-1-treated mouse models were elucidated. The results demonstrated that DN mouse models treated with SGP-1-1 (50, 100, and 200 mg kg^-1 d^-1) exhibited good inflammation-modulating activity. In addition, histopathological analysis showed that glomerular atrophy, severe glomerular thylakoid hyperplasia, tubular endothelial detachment, basement membrane exposure, cytoplasmic infiltration with inflammatory cells, and interstitial oedema were all alleviated in DN mice after treatment with SGP-1-1. Metabolomics analysis based on UPLC-Q-TOF/MS revealed that a close relationship between the occurrence of DN and the potential 39 biomarkers, especially, leukotriene E3 and arachidonic acid,of which the main invloved metabolic pathways may beglycerophospholipid metabolism, arachidonic acid metabolism and primary bile acid biosynthesis. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot analysis results demonstrated that SGP-1-1 downregulates mRNA and the protein expression of the G protein-coupled cell membrane receptor TLR4 and its downstream protein kinase (NF-κB p65). This, resulted in the inhibition of the TLR4-NF-κB pathway in the peritoneum of DN mice by regulating inflammation, while stimulating the production of superoxide dismutase (SOD) and reducing the production of cytokine (IL-6, TNF-α) and malondialdehyde (MDA).

Any Role of High-Dose Vitamin C for Septic Shock in 2021?

While the use of vitamin C as a therapeutic agent has been investigated since the 1950s, there has been substantial recent interest in the role of vitamin C supplementation in critical illness and particularly, sepsis and septic shock. Humans cannot synthesize vitamin C and rely on exogenous intake to maintain a plasma concentration of approximately 70 to 80 μmol/L. Vitamin C, in healthy humans, is involved with antioxidant function, wound healing, endothelial function, and catecholamine synthesis. Its function in the human body informs the theoretical basis for why vitamin C supplementation may be beneficial in sepsis/septic shock.Critically ill patients can be vitamin C deficient due to low dietary intake, increased metabolic demands, inefficient recycling of vitamin C metabolites, and loss due to renal replacement therapy. Intravenous supplementation is required to achieve supraphysiologic serum levels of vitamin C. While some clinical studies of intravenous vitamin C supplementation in sepsis have shown improvements in secondary outcome measures, none of the randomized clinical trials have shown differences between vitamin C supplementation and standard of care and/or placebo in the primary outcome measures of the trials. There are some ongoing studies of high-dose vitamin C administration in patients with sepsis and coronavirus disease 2019; the majority of evidence so far does not support the routine supplementation of vitamin C in patients with sepsis or septic shock.

Implications for the role of lipopolysaccharide in the development of atherosclerosis

Mounting scientific evidence over decades has established that atherosclerosis is a chronic inflammatory disorder. Among the potentially critical sources of vascular inflammation during atherosclerosis are the components of pathogenic bacteria, especially lipopolysaccharide (LPS). Toll-like receptor (TLR)-4, expressed on different inflammatory cells involved with the recognition of bacterial LPS, has been recognized to have mutations that are prevalent in a number of ethnic groups. Such mutations have been associated with a decreased risk of atherosclerosis. In addition, epidemiological investigations have proposed that LPS confers a risk factor for the development of atherosclerosis. Gram-negative bacteria are the major source of LPS in an individual's serum, which may be generated during subclinical infections. The major cell receptors on inflammatory cells involved in the pathogenesis of atherosclerosis, like macrophages, monocytes, and dendritic cells (DCs), are CD14, MD-2, and LPS binding protein (LBP). These receptors have been blamed for the development of atherosclerosis through dysregulated activation following LPS recognition. Lipoproteins may also play a role in modulating the LPS-induced inflammatory events during atherosclerosis development. In this review article, we attempt to clarify the role of LPS in the initiation and progression of atherosclerotic lesion development.

Rosiglitazone alleviates lipopolysaccharide-induced inflammation in RAW264.7 cells via inhibition of NF-κB and in a PPARγ-dependent manner

Rosiglitazone is a synthetic peroxisome proliferator-activated receptor (PPAR)γ agonist widely used for the treatment of type 2 diabetes. Recent studies have demonstrated that rosiglitazone displays anti-inflammatory effects. The present study aimed to investigate whether rosiglitazone alleviates decreases in RAW264.7 cell viability resulting from lipopolysaccharide (LPS)-induced inflammation, as well as exploring the underlying mechanism. A macrophage inflammatory injury model was established by treating RAW264.7 cells with 100 ng/ml LPS. Cells were divided into LPS and rosiglitazone groups with different concentrations. Cell viability was assessed by performing an MTT assay. The expression of inflammatory cytokines was detected by conducting enzyme-linked immunosorbent assays and reverse transcription-quantitative PCR. Nitric oxidesecretion was assessed using the Griess reagent system. The expression levels of key nuclear factor-κB pathway-associated proteins were detected via western blotting. Rosiglitazone alleviated LPS-induced decrease in RAW264.7 cell viability and inhibited inflammatory cytokine expression in a concentration-dependent manner. Rosiglitazone significantly inhibited LPS-induced upregulation of p65 phosphorylation levels and downregulated IκBα expression levels. However, rosiglitazone-mediated inhibitory effects were reversed by PPARγ knockdown. The results of the present study demonstrated that rosiglitazone significantly inhibited LPS-induced inflammatory responses in RAW264.7 macrophage cells, which was dependent on PPARγ activation and NF-κB suppression.

Flavonoids and cellular stress: a complex interplay affecting human health

Flavonoid consumption has beneficial effects on human health, however, clinical evidence remains often inconclusive due to high interindividual variability. Although this high interindividual variability has been consistently observed in flavonoid research, the potential underlying reasons are still poorly studied. Especially the knowledge on the impact of health status on flavonoid responsiveness is limited and merits more investigation. Here, we aim to highlight the bidirectional interplay between flavonoids and cellular stress. First, the state-of-the-art concerning inflammatory stress and mitochondrial dysfunction is reviewed and a comprehensive overview of recent in vitro studies investigating the impact of flavonoids on cellular stress, induced by tumor necrosis factor α, lipopolysaccharide and mitochondrial stressors, is given. Second, we critically discuss the influence of cellular stress on flavonoid uptake, accumulation, metabolism and cell responses, which has, to our knowledge, never been extensively reviewed before. Next, we advocate the innovative insight that stratification of the general population based on health status can reveal subpopulations that benefit more from flavonoid consumption. Finally, suggestions are given for the development of future cell models that simulate the physiological micro-environment, including interindividual variability, since more mechanistic research is needed to establish scientific-based personalized food recommendations for specific subpopulations.

miR-489-3p inhibits TLR4/NF-κB signaling to prevent inflammation in psoriasis

Psoriasis is a chronic inflammatory skin disease whose etiology has not yet been determined. MicroRNAs (miRs) regulate the early stages of psoriasis and are targets for therapeutic intervention. The present study aimed to investigate the functional role of miR-489-3p in psoriasis. The present study first assessed the expression levels of miR-489-3p and Toll-like receptor (TLR)4 mRNA using reverse transcription-quantitative PCR, and also detected the protein expression levels of TLR4 and NF-κB via western blot analysis. TargetScan and miRDB target gene prediction tools were used to confirm the regulation of Toll-like receptor (TLR)4 by miR-489-3p. Moreover, a Cell Counting Kit (CCK)-8 assay was conducted to evaluate cell viability, while cell cycle and colony formation assays were performed to evaluate cell proliferation. Human keratinocytes (HaCaT) were co-transfected with TLR4-small interfering RNA and miR-489-3p-inhibitor plasmids, and analysis of cell proliferation and inflammatory cytokine secretion was performed using CCK-8 assay and ELISA. It was found that miR-489-3p expression was downregulated in patients with psoriasis. Bioinformatics analysis identified that TLR4 was a direct target of miR-489-3p. This was confirmed via luciferase reporter assays in HaCaT cells. The overexpression of miR-489-3p inhibited the TLR4/NF-κB signaling pathway and reduced cell proliferation. TLR4 silencing alleviated the effects of miR-489-3p, and enhanced cell proliferation and inflammatory cytokine secretion. Taken together, these data suggested that miR-489-3p may be a key effector of psoriasis, which promotes inflammatory responses by direct targeting of TLR4. miR-489-3p therefore represents a promising prognostic biomarker and therapeutic target for psoriasis treatment.

In Vivo Imaging of Local Inflammation: Monitoring LPS-Induced CD80/CD86 Upregulation by PET

PURPOSE

The co-stimulatory molecules CD80 and CD86 are upregulated on activated antigen-presenting cells (APC). We investigated whether local APC activation, induced by subcutaneous (s.c.) inoculation of lipopolysaccharides (LPS), can be imaged by positron emission tomography (PET) with CD80/CD86-targeting 64Cu-labelled abatacept.

PROCEDURES

Mice were inoculated s.c. with extracellular-matrix gel containing either LPS or vehicle (PBS). Immune cell populations were analysed by flow cytometry and marker expression by RT-qPCR. 64Cu-NODAGA-abatacept distribution was analysed using PET/CT and ex vivo biodistribution.

RESULTS

The number of CD80+ and CD86+ immune cells at the LPS inoculation site significantly increased a few days after inoculation. CD68 and CD86 expression were higher at the LPS than the PBS inoculation site, and CD80 was only increased at the LPS inoculation site. CTLA-4 was highest 10 days after LPS inoculation, when CD80/CD86 decreased again. A few days after inoculation, 64Cu-NODAGA-abatacept distribution to the inoculation site was significantly higher for LPS than PBS (4.2-fold). Co-administration of unlabelled abatacept or human immunoglobulin reduced tracer uptake. The latter reduced the number of CD86+ immune cells at the LPS inoculation site.

CONCLUSIONS

CD80 and CD86 are upregulated in an LPS-induced local inflammation, indicating invasion of activated APCs. 64Cu-NODAGA-abatacept PET allowed following APC activation over time.

Sterile inflammation in the pathogenesis of maturation failure of arteriovenous fistula

Chronic kidney disease is a widespread terminal illness that afflicts millions of people across the world. Hemodialysis is the predominant therapeutic management strategy for kidney failure and involves the external filtration of metabolic waste within the circulation. This process requires an arteriovenous fistula (AVF) for vascular access. However, AVF maturation failures are significant obstacles in establishing long-term vascular access for hemodialysis. Appropriate stimulation, activation, and proliferation of smooth muscle cells, proper endothelial cell orientation, adequate structural changes in the ECM, and the release of anti-inflammatory markers are associated with maturation. AVFs often fail to mature due to inadequate tissue repair and remodeling, leading to neointimal hyperplasia lesions. The transdifferentiation of myofibroblasts and sterile inflammation are possibly involved in AVF maturation failures; however, limited data is available in this regard. The present article critically reviews the interplay of various damage-associated molecular patterns (DAMPs) and the downstream sterile inflammatory signaling with a focus on the NLRP3 inflammasome. Improved knowledge concerning AVF maturation pathways can be unveiled by investigating the novel DAMPs and the mediators of sterile inflammation in vascular remodeling that would open improved therapeutic opportunities in the management of AVF maturation failures and its associated complications.

Outdoor Atmospheric Microbial Diversity Is Associated With Urban Landscape Structure and Differs From Indoor-Transit Systems as Revealed by Mobile Monitoring and Three-Dimensional Spatial Analysis

Microbes are abundant inhabitants of the near-surface atmosphere in urban areas. The distribution of microbial communities may benefit or hinder human wellbeing and ecosystem function. Surveys of airborne microbial diversity are uncommon in both natural and built environments and those that investigate diversity are stationary in the city, thus missing continuous exposure to microbes that covary with three-dimensional urban structure. Individuals in cities are generally mobile and would be exposed to diverse urban structures outdoors and within indoor-transit systems in a day. We used mobile monitoring of microbial diversity and geographic information system spatial analysis, across Philadelphia, Pennsylvania, USA in outdoor and indoor-transit (subways and train cars) environments. This study identifies to the role of the three-dimensional urban landscape in structuring atmospheric microbiomes and employs mobile monitoring over ~1,920 kilometers to measure continuous biodiversity. We found more diverse communities outdoors that significantly differ from indoor-transit air in microbial community structure, function, likely source environment, and potentially pathogenic fraction of the community. Variation in the structure of the urban landscape was associated with diversity and function of the near-surface atmospheric microbiome in outdoor samples.

Immune Cell Number, Phenotype, and Function in the Elderly with Sepsis

Sepsis is a form of life-threatening organ dysfunction caused by dysregulated host responses to an infection that can be partly attributed to immune dysfunction. Although sepsis affects patients of all ages, elderly individuals display increased susceptibility and mortality. This is partly due to immunosenescence, a decline in normal immune system function associated with physiological aging that affects almost all cell types in the innate and adaptive immune systems. In elderly patients with sepsis, these alterations in immune cells such as endothelial cells, neutrophils, monocytes, macrophages, natural killer cells, dendritic cells, T lymphocytes, and B lymphocytes, are largely responsible for their poor prognosis and increased mortality. Here, we review recent studies investigating the events affecting both innate and adaptive immune cells in elderly mice and patients with sepsis, including alterations in their number, phenotype, and function, to shed light on possible new therapeutic strategies.

Effects of both Pro- and Synbiotics in Liver Surgery and Transplantation with Special Focus on the Gut-Liver Axis-A Systematic Review and Meta-Analysis

The gut-liver axis is of upmost importance for the development of infections after surgery. Further bacterial translocation due to surgery-related dysbiosis is associated with limited detoxification function of the liver compromising outcome of surgical therapy. After liver surgery, about 30% of patients develop a bacterial infection, with the risk of bacteremia or even sepsis-associated liver failure and mortality in >40%. The potential benefit of pro-/synbiotics given before surgery is still under debate. Thus, a systematic literature search on trials comparing patients with or without supplementation and outcome after liver resection or transplantation was performed. Our search strategy revealed 12 relevant studies on perioperative administration of pro-/synbiotics in liver surgery. The pro-/synbiotic combinations and concentrations as well as administration timeframes differed between studies. Five studies were performed in liver transplantation and 7 in liver resection. All studies but one reported lower infection rates (pooled RR: 0.46, 95% CI: 0.31-0.67) with pro-/synbiotics. Liver function was assessed after LT/LR in 3 and 5 studies, respectively. Pro-/synbiotics improved function in 1/3 and 2/5 studies, respectively. Concluding, perioperative pro-/synbiotics clearly reduce infection after liver surgery. However, standard protocols with both well-defined probiotic strain preparations and administration timeframes are pending.

Mesenchymal Stem Cells Attenuate Lipopolysaccharide-Induced Inflammatory Response in Human Uterine Smooth Muscle Cells

Objective  The aim of this study was to determine if mesenchymal stem cells (MSCs) would suppress the inflammatory response in human uterine cells in an in vitro lipopolysaccharide (LPS)-based preterm birth (PTB) model. Study Design  Cocultures of human uterine smooth muscle cells (HUtSMCs) and MSCs were exposed to 5 μg/mL LPS for 4 hours and further challenged with 1 μg/mL LPS for a subsequent 24 hours. Key elements of the parturition cascade regulated by toll-like receptors (TLRs) through activation of mitogen-activated protein kinases (MAPKs) were quantified in culture supernatant as biomarkers of MSC modulation. Results  Coculture with MSCs significantly attenuated TLR-4, p-JNK, and p- extracellular signal-regulated kinase 1/2 (ERK1/2) protein levels compared with HUtSMCs monoculture ( p  = 0.05). In addition, coculture was associated with significant inhibition of proinflammatory cytokines interleukin (IL)-6 and IL-8 ( p  = 0.0001) and increased production of anti-inflammatory cytokines IL-10 and transforming growth factor (TGF)-β1 ( p  = 0.0001). Conclusion  MSCs appear to play a role in significantly attenuating LPS-mediated inflammation via alteration of down-stream MAPKs. MSCs may represent a novel, cell-based therapy in women with increased risk of inflammatory-mediated preterm birth.

Vascular Endothelial Cells and Innate Immunity

In addition to the roles of endothelial cells (ECs) in physiological processes, ECs actively participate in both innate and adaptive immune responses. We previously reported that, in comparison to macrophages, a prototypic innate immune cell type, ECs have many innate immune functions that macrophages carry out, including cytokine secretion, phagocytic function, antigen presentation, pathogen-associated molecular patterns-, and danger-associated molecular patterns-sensing, proinflammatory, immune-enhancing, anti-inflammatory, immunosuppression, migration, heterogeneity, and plasticity. In this highlight, we introduce recent advances published in both ATVB and many other journals: (1) several significant characters classify ECs as novel immune cells not only in infections and allograft transplantation but also in metabolic diseases; (2) several new receptor systems including conditional danger-associated molecular pattern receptors, nonpattern receptors, and homeostasis associated molecular patterns receptors contribute to innate immune functions of ECs; (3) immunometabolism and innate immune memory determine the innate immune functions of ECs; (4) a great induction of the immune checkpoint receptors in ECs during inflammations suggests the immune tolerogenic functions of ECs; and (5) association of immune checkpoint inhibitors with cardiovascular adverse events and cardio-oncology indicates the potential contributions of ECs as innate immune cells.

The p38-interacting protein p38IP suppresses TCR and LPS signaling by targeting TAK1

Negative regulation of immunoreceptor signaling is required for preventing hyperimmune activation and maintaining immune homeostasis. The roles of p38IP in immunoreceptor signaling remain unclear. Here, we show that p38IP suppresses T-cell receptor (TCR)/LPS-activated NF-κB and p38 by targeting TAK1 kinase and that p38IP protein levels are downregulated in human PBMCs from rheumatoid arthritis (RA) patients, inversely correlating with the enhanced activity of NF-κB and p38. Mechanistically, p38IP interacts with TAK1 to disassemble the TAK1-TAB (TAK1-binding protein) complex. p38IP overexpression decreases TCR-induced binding of K63-linked polyubiquitin (polyUb) chains to TAK1 but increases that to TAB2, and p38IP knockdown shows the opposite effects, indicating unanchored K63-linked polyUb chain transfer from TAB2 to TAK1. p38IP dynamically interacts with TAK1 upon stimulation, because of the polyUb chain transfer and the higher binding affinity of TAK1 and p38IP for polyUb-bound TAB2 and TAK1, respectively. Moreover, p38IP scaffolds the deubiquitinase USP4 to deubiquitinate TAK1 once TAK1 is activated. These findings reveal a novel role and the mechanisms of p38IP in controlling TCR/LPS signaling and suggest that p38IP might participate in RA pathogenesis.

Overexpression of Toll-Like Receptor 4 Affects Autophagy, Oxidative Stress, and Inflammatory Responses in Monocytes of Transgenic Sheep

Toll-like receptor 4 (TLR4) is a critical pattern recognition receptor that plays a critical role in the host innate immune system’s recognition of Gram-negative bacteria. Since it is the lipopolysaccharide (LPS) receptor, it links the activated inflammatory response with autophagy and oxidative stress. Autophagy, or type II programmed cell death, was reported to have defensive functions in response to the production of inflammatory cytokines and oxidative stress. To explore the relationship between autophagy, inflammation, and oxidative stress, a TLR4-enriched transgenic (Tg) animal model (sheep) was generated. Autophagy activity in the Tg blood monocytes was significantly higher than in the wild-type animal under LPS stress, and it returned to normal after transfection of TLR4 siRNA. Pretreatment with 3-methyladenine (3-MA) inhibited autophagy and enhanced oxidative stress and the production of TNF-α. The LPS-induced reactive oxygen species (ROS) level was markedly increased in the Tg group at an early stage before quickly returning to normal values. In addition, suppressing ROS production by N-acetyl-L-cysteine down-regulated the number of intracellular autophagosomes and the expression of Beclin-1, ATG5, and cytokines IL-1β, IL-6, and TNF-α. Further mechanistic investigation suggested that the TLR4-associated p38 mitogen-activated protein kinase (MAPK) signaling pathway was involved in autophagy and oxidative stress. P38 MAPK promotes intracellular autophagy, ROS production, and inflammatory response. Moreover, TLR4 over-expression suppressed oxidative stress and the production of inflammatory cytokines and increased autophagy activity in vivo. Taken together, our results showed that LPS induced autophagy, which was related to TLR4-mediated ROS production through the p38 MAPK signaling pathway. In addition, our study also provided a novel transgenic animal model to analyze the effects of TLR4 on autophagy, oxidative stress, and inflammatory responses.

OTUD4 alleviates hepatic ischemia-reperfusion injury by suppressing the K63-linked ubiquitination of TRAF6

Hepatic ischemia-reperfusion (IR) injury can cause serious liver damage, leading to liver dysfunction after liver surgery, which is associated with NF-κB-mediated inflammation. The K63-linked auto-polyubiquitination of tumor necrosis factor receptor-associated factor 6 (TRAF6) is essential for the activation of NF-κB. Here, we found that OTU domain-containing protein 4 (OTUD4), a deubiquitinating enzyme (DUB), interacts with TRAF6 and decreases the K63 auto-polyubiquitination of TRAF6. In addition, the data showed that NF-κB activation was impaired and inflammatory factor levels were reduced after overexpressing OTUD4 in a hypoxia/reoxygenation (HR) model and a hepatic IR model. Additionally, the liver inflammatory response and tissue damage were ameliorated in mice overexpressing OTUD4.Taken together, these results show that OTUD4 can negatively regulate NF-κB activation by suppressing the K63-linked ubiquitination of TRAF6, thus alleviating hepatic ischemia-reperfusion injury.

Leukocyte-Released Mediators in Response to Both Bacterial and Fungal Infections Trigger IFN Pathways, Independent of IL-1 and TNF-α, in Endothelial Cells

In sepsis, dysregulated immune responses to infections cause damage to the host. Previous studies have attempted to capture pathogen-induced leukocyte responses. However, the impact of mediators released after pathogen-leukocyte interaction on endothelial cells, and how endothelial cell responses vary depending on the pathogen-type is lacking. Here, we comprehensively characterized the transcriptomic responses of human leukocytes and endothelial cells to Gram negative-bacteria, Gram positive-bacteria, and fungi. We showed that whole pathogen lysates induced strong activation of leukocytes but not endothelial cells. Interestingly, the common response of leukocytes to various pathogens converges on endothelial activation. By exposing endothelial cells to leukocyte-released mediators, we observed a strong activation of endothelial cells at both transcription and protein levels. By adding IL-1RA and TNF-α antibody in leukocyte-released mediators before exposing to endothelial cells, we identified specific roles for IL-1 and TNF-α in driving the most, but not all, endothelial activation. We also showed for the first time, activation of interferon response by endothelial cells in response to leukocyte-released mediators, independently from IL-1 and TNF-α pathways. Our study therefore, not only provides pathogen-dependent transcriptional changes in leukocytes and endothelial cells during infections, but also reveals a role for IFN, together with IL1 and TNFα signaling, in mediating leukocyte-endothelial interaction in infections.

Imaging the Vascular Bone Marrow Niche During Inflammatory Stress

RATIONALE

Inflammatory stress induced by exposure to bacterial lipopolysaccharide causes hematopoietic stem cell expansion in the bone marrow niche, generating a cellular immune response. As an integral component of the hematopoietic stem cell niche, the bone marrow vasculature regulates the production and release of blood leukocytes, which protect the host against infection but also fuel inflammatory diseases.

OBJECTIVE

We aimed to develop imaging tools to explore vascular changes in the bone marrow niche during acute inflammation.

METHODS AND RESULTS

Using the TLR (Toll-like receptor) ligand lipopolysaccharide as a prototypical danger signal, we applied multiparametric, multimodality and multiscale imaging to characterize how the bone marrow vasculature adapts when hematopoiesis boosts leukocyte supply. In response to lipopolysaccharide, ex vivo flow cytometry and histology showed vascular changes to the bone marrow niche. Specifically, proliferating endothelial cells gave rise to new vasculature in the bone marrow during hypoxic conditions. We studied these vascular changes with complementary intravital microscopy and positron emission tomography/magnetic resonance imaging. Fluorescence and positron emission tomography integrin αVβ3 imaging signal increased during lipopolysaccharide-induced vascular remodeling. Vascular leakiness, quantified by albumin-based in vivo microscopy and magnetic resonance imaging, rose when neutrophils departed and hematopoietic stem and progenitor cells proliferated more vigorously.

CONCLUSIONS

Introducing a tool set to image bone marrow either with cellular resolution or noninvasively within the entire skeleton, this work sheds light on angiogenic responses that accompany emergency hematopoiesis. Understanding and monitoring bone marrow vasculature may provide a key to unlock therapeutic targets regulating systemic inflammation.

Effects of Levosimendan on Inflammation and Oxidative Stress Pathways in a Lipopolysaccharide-Stimulated Human Endothelial Cell Model

Levosimendan is a myocardial Ca²⁺ sensitizer and opener of ATP-dependent potassium channels with inotropic, vasodilating, and cardioprotective properties. It was originally developed for the treatment of acute decompensated heart failure, but its complex mechanism of action means that it could also play a role in organ protection in response to infection. Using an in vitro approach, we explored whether levosimendan administration influenced cell responses to lipopolysaccharide (LPS). Primary human umbilical vein endothelial cells were stimulated with 1 µg/ml LPS from Escherichia coli (E. coli). Cells were treated with levosimendan at 0, 0.1, 1, or 10 µM 3 hr later. Samples were taken 24 hr after treatment to measure cell necrosis, apoptosis, pro-inflammatory mediators (interleukin 6 [IL-6] and toll-like receptor 4 [TLR4]), and oxidative stress (total reactive oxygen species/reactive nitrogen species [ROS/RNS]). Levosimendan at 1 and 10 µM protected against LPS-induced endothelial cell death and reduced TLR4 expression (p < .05). All doses reduced levels of IL-6 and ROS/RNS (p < .05). Findings suggest that levosimendan may exert protective effects against endothelial cell death in this model via attenuation of inflammation and oxidative stress pathways. Future studies might explore the potential beneficial role of levosimendan in modulating molecular mechanisms triggered by infections.