Tumor necrosis factor disrupts claudin-5 endothelial tight junction barriers in two distinct NF-κB-dependent phases

TNF Induces Laminin-332-Encoding Genes in Endothelial Cells and Laminin-332 Promotes an Atherogenic Endothelial Phenotype

Laminins are essential components of the basement membranes, expressed in a tissue- and cell-specific manner under physiological conditions. During inflammatory circumstances, such as atherosclerosis, alterations in laminin composition within vessels have been observed. Our study aimed to assess the influence of tumor necrosis factor-alpha (TNF), a proinflammatory cytokine abundantly found in atherosclerotic lesions, on endothelial laminin gene expression and the effects of laminin-332 (LN332) on endothelial cells' behavior. We also evaluated the expression of LN332-encoding genes in human carotid atherosclerotic plaques. Our findings demonstrate that TNF induces upregulation of LAMB3 and LAMC2, which, along with LAMA3, encode the LN332 isoform. Endothelial cells cultured on recombinant LN332 exhibit decreased claudin-5 expression and display a loosely connected phenotype, with an elevated expression of chemokines and leukocyte adhesion molecules, enhancing their attractiveness and adhesion to leukocytes in vitro. Furthermore, LAMB3 and LAMC2 are upregulated in human carotid plaques and show a positive correlation with TNF expression. In summary, TNF stimulates the expression of LN332-encoding genes in human endothelial cells and LN332 promotes an endothelial phenotype characterized by compromised junctional integrity and increased leukocyte interaction. These findings highlight the importance of basement membrane proteins for endothelial integrity and the potential role of LN332 in atherosclerosis.

Vascular leak in sepsis: physiological basis and potential therapeutic advances

Sepsis is a life-threatening condition characterised by endothelial barrier dysfunction and impairment of normal microcirculatory function, resulting in a state of hypoperfusion and tissue oedema. No specific pharmacological therapies are currently used to attenuate microvascular injury. Given the prominent role of endothelial breakdown and microcirculatory dysfunction in sepsis, there is a need for effective strategies to protect the endothelium. In this review we will discuss key mechanisms and putative therapeutic agents relevant to endothelial barrier function.

Effect of L-4-Thiazolylalanine (Protinol™) on skin barrier strength and skin protection

OBJECTIVES

Skin barrier properties are critical for maintaining epidermal water content, protecting from environmental factors and providing the first line of defense against pathogens. In this study, we investigated the non-proteinogenic amino acid L-4-Thiazolylalanine (L4) as a potential active ingredient in skin protection and barrier strength.

METHODS

L4 on wound healing, anti-inflammatory and anti-oxidant properties were evaluated using monolayers and 3D skin equivalents. The transepithelial electrical resistance (TEER) value was used in vitro as a strong indicator of barrier strength and integrity. Clinical L4 efficacy was assessed for the evaluation of the skin barrier integrity and soothing benefits.

RESULTS

In vitro treatments of L4 show beneficial effects in wound closure mechanism, and we demonstrate that L4 anti-oxidant benefits with markedly increased HSP70 and decreased reactive oxygen species production induced by UVs exposure. Barrier strength and integrity were significantly improved by L4, confirmed clinically by an increase in 12R-lipoxygenase enzymatic activity in the stratum corneum. In addition, soothing benefits of L4 have been shown clinically with the decrease in redness after methyl nicotinate application on the inner arm and the significant reduction of the erythema and the skin desquamation on the scalp.

CONCLUSION

L4 delivered multiple skin benefits by strengthening the skin barrier, accelerating the skin repair process as well as soothing the skin and the scalp with anti-inflammaging effects. The observed efficacy validates L4 as a desirable skincare ingredient for topical treatment.

Differential Expression of Serum Proinflammatory Cytokine TNF-α and Genetic Determinants of TNF-α, CYP2C19*17, miR-423 Genes and Their Effect on Coronary Artery Disease Predisposition and Progression

Coronary artery disease (CAD) is the leading cause of death and hospitalization worldwide and represents a problem for public health systems everywhere. In Saudi Arabia, the prevalence of CAD is estimated to be 5.5%. Risk factors for CAD include older age, male gender, obesity, high blood pressure, smoking, diabetes, hyperlipidemia, and genetic factors. Reducing the risk factors in susceptible individuals will decrease the prevalence of CAD. Genome wide association studies have helped to reveal the association of many loci with diseases like CAD. In this study, we examined the link between single nucleotide variations (SNVs) of TNF-α-rs1800629 G>A, CYP2C19*17 (rs12248560) C>T, and miR-423 rs6505162 C>A and the expression of TNF-α with CAD. We used the mutation specific PCR, ARMS-PCR, and ELISA. The results showed that the A allele of the TNF-α rs1800629 G>A SNP is linked to CAD with odd ratio (OR) (95% CI) = 2.10, p-value = 0.0013. The T allele of the CYP2C19*17 (rs12248560) C>T is linked to CAD with OR (95% CI) = 2.02, p-value = 0.003. In addition, the A allele of the miR-423 rs6505162 C>A SNV is linked to CAD with OR (95% CI) = 1.49, p-value = 0.036. The ELISA results indicated that the TNF-α serum levels are significantly increased in CAD patients compared to healthy controls. We conclude the TNF-α rs1800629 G>A, CYP2C19*17, and miR-423 rs6505162 C>A are potential genetic loci for CAD in the Saudi population. These findings require further verification in future studies. After being verified, our results might be utilized in genetic testing to identify individuals that are susceptible to CAD and, therefore, for whom reducing modifiable risk factors (e.g., poor diet, diabetes, obesity, and smoking) would result in prevention or delay of CAD.

TNF-α evokes blood-brain barrier dysfunction through activation of Rho-kinase and neurokinin 1 receptor

Ischaemic stroke, accompanied by neuroinflammation, impairs blood-brain barrier (BBB) integrity through a complex mechanism involving activation of both RhoA/Rho kinase/myosin light chain-2 and neurokinin 1 receptor (NK1R). Using an in vitro model of human BBB composed of brain microvascular endothelial cells (BMEC), astrocytes and pericytes, this study examined the potential contributions of these elements to BBB damage induced by elevated availability of pro-inflammatory cytokine, TNF-α. Treatment of human BMECs with TNF-α significantly enhanced RhoA activity and the protein expressions of Rho kinase and phosphorylated Ser19MLC-2 while decreasing that of NK1R. Pharmacological inhibition of Rho kinase by Y-27632 and NK1R by CP96345 neutralised the disruptive effects of TNF-α on BBB integrity and function as ascertained by reversal of decreases in transendothelial electrical resistance and increases in paracellular flux of low molecular weight permeability marker, sodium fluorescein, respectively. Suppression of RhoA activation, mitigation of actin stress fibre formation and restoration of plasma membrane localisation of tight junction protein zonula occludens-1 appeared to contribute to the barrier-protective effects of both Y-27632 and CP96345. Attenuation of TNF-α-mediated increases in NK1R protein expression in BMEC by Y-27632 suggests that RhoA/Rho kinase pathway acts upstream to NK1R. In conclusion, specific inhibition of Rho kinase in cerebrovascular conditions, accompanied by excessive release of pro-inflammatory cytokine TNF-α, helps preserve endothelial cell morphology and inter-endothelial cell barrier formation and may serve as an important therapeutic target.

Bortezomib Increased Vascular Permeability by Decreasing Cell-Cell Junction Molecules in Human Pulmonary Microvascular Endothelial Cells

Bortezomib (BTZ), a chemotherapeutic drug used to treat multiple myeloma, induces life-threatening side effects, including severe pulmonary toxicity. However, the mechanisms underlying these effects remain unclear. The objectives of this study were to (1) investigate whether BTZ influences vascular permeability and (2) clarify the effect of BTZ on the expression of molecules associated with cell-cell junctions using human pulmonary microvascular endothelial cells in vitro. Clinically relevant concentrations of BTZ induced limited cytotoxicity and increased the permeability of human pulmonary microvascular endothelial cell monolayers. BTZ decreased the protein expression of claudin-5, occludin, and VE-cadherin but not that of ZO-1 and β-catenin. Additionally, BTZ decreased the mRNA expression of claudin-5, occludin, ZO-1, VE-cadherin, and β-catenin. Our results suggest that BTZ increases the vascular permeability of the pulmonary microvascular endothelium by downregulating cell-cell junction molecules, particularly claudin-5, occludin, and VE-cadherin.

Pro-inflammatory role of Wnt/β-catenin signaling in endothelial dysfunction

Background

Endothelial dysfunction is a critical component of both atherosclerotic plaque formation and saphenous vein graft failure. Crosstalk between the pro-inflammatory TNF-α-NFκB signaling axis and the canonical Wnt/β-catenin signaling pathway potentially plays an important role in regulating endothelial dysfunction, though the exact nature of this is not defined.

Results

In this study, cultured endothelial cells were challenged with TNF-α and the potential of a Wnt/β-catenin signaling inhibitor, iCRT-14, in reversing the adverse effects of TNF-α on endothelial physiology was evaluated. Treatment with iCRT-14 lowered nuclear and total NFκB protein levels, as well as expression of NFκB target genes, IL-8 and MCP-1. Inhibition of β-catenin activity with iCRT-14 suppressed TNF-α-induced monocyte adhesion and decreased VCAM-1 protein levels. Treatment with iCRT-14 also restored endothelial barrier function and increased levels of ZO-1 and focal adhesion-associated phospho-paxillin (Tyr118). Interestingly, inhibition of β-catenin with iCRT-14 enhanced platelet adhesion in cultured TNF-α-stimulated endothelial cells and in an ex vivo human saphenous vein model, most likely via elevating levels of membrane-tethered vWF. Wound healing was moderately retarded by iCRT-14; hence, inhibition of Wnt/β-catenin signaling may interfere with re-endothelialisation in grafted saphenous vein conduits.

Conclusion

Inhibition of the Wnt/β-catenin signaling pathway with iCRT-14 significantly recovered normal endothelial function by decreasing inflammatory cytokine production, monocyte adhesion and endothelial permeability. However, treatment of cultured endothelial cells with iCRT-14 also exerted a pro-coagulatory and moderate anti-wound healing effect: these factors may affect the suitability of Wnt/β-catenin inhibition as a therapy for atherosclerosis and vein graft failure.

Neutrophil, neutrophil extracellular traps and endothelial cell dysfunction in sepsis

Sepsis is a persistent systemic inflammatory condition involving multiple organ failures resulting from a dysregulated immune response to infection, and one of the hallmarks of sepsis is endothelial dysfunction. During its progression, neutrophils are the first line of innate immune defence against infection. Aside from traditional mechanisms, such as phagocytosis or the release of inflammatory cytokines, reactive oxygen species and other antibacterial substances, activated neutrophils also release web-like structures composed of tangled decondensed DNA, histone, myeloperoxidase and other granules called neutrophil extracellular traps (NETs), which can efficiently ensnare bacteria in the circulation. In contrast, excessive neutrophil activation and NET release may induce endothelial cells to shift toward a pro-inflammatory and pro-coagulant phenotype. Furthermore, neutrophils and NETs can degrade glycocalyx on the endothelial cell surface and increase endothelium permeability. Consequently, the endothelial barrier collapses, contributing to impaired microcirculatory blood flow, tissue hypoperfusion and life-threatening organ failure in the late phase of sepsis.

Lipedema Research-Quo Vadis?

When studying the current literature, one might get the impression that lipedema is a "modern" disease, with increasing incidence and augmenting prevalence throughout Western countries during the last decade. However, a quick look into older textbooks shows that disproportionate accumulation of fat in female bodies has long been known without being recognized as an independent disease. Nevertheless, it was not until 1940 that Allen and Hines described a "syndrome characterized by fat legs and orthostatic edema" in a seminal publication. The mere awareness that people who have lipedema are not just overweight but suffer from a yet poorly defined pathological condition, may be considered a decisive leap forward in the understanding of lipedema. A number of comprehensive publications have since dealt with the clinical presentation of lipedema and have provided the first clues towards the potential pathological mechanisms underlying its initiation and progression. Nevertheless, despite all effort that has been undertaken to unravel lipedema pathology, many questions have remained unanswered. What can be deduced with certainty from all experimental and medical evidence available so far is that lipedema is neither a cosmetic problem nor is it a problem of lifestyle but should be accepted as a serious disease with yet undetermined genetic background, which makes women's lives unbearable from both a physical and psychological point of view. To date, results from clinical inspections have led to the categorization of various types and stages of lipedema, describing how the extremities are affected and evaluating its progression, as demonstrated by skin alterations, adipose tissue volume increase and physical and everyday-behavioral impediments. There is accumulating evidence showing that advanced stages of lipedema are usually accompanied by excessive weight or obesity. Thus, it is not unreasonable to assume that the progression of lipedema is largely driven by weight gain and the pathological alterations associated with it. Similarly, secondary lymphedema is frequently found in lipedema patients at advanced stages. Needless to say, both conditions considerably blur the clinical presentation of lipedema, making diagnosis difficult and scientific research challenging. The present literature review will focus on lipedema research, based on evidence fromex vivo and in vitro data, which has accumulated throughout the last few decades. We will also open the discussion as to whether the currently used categorization of lipedema stages is still sufficient and up-to-date for the accurate description of this enigmatic disease, whose name, strangely enough, does not match its pathologic correlate.

Loss of SOX18/CLAUDIN5 disrupts the pulmonary endothelial barrier in ventilator-induced lung injury

Mechanical strain contributes to ventilator-induced lung injury (VILI) through multi-factorial and complex mechanisms that remain unresolved. Prevailing evidence suggests that the loss of pulmonary endothelial tight junctions (TJs) plays a critical role. TJs are dynamically regulated by physiologic and hemodynamic forces to stabilize the endothelial barrier. The transcription factor sex-determining region Y-box (SOX)-18 is important in regulating blood vessel development and vascular permeability through its ability to regulate the transcription of Claudin-5, an endothelial TJ protein. Previously, we demonstrated that SOX18 expression is increased by shear stress in the pulmonary endothelium. Therefore, in this study, we investigated how mechanical strain mediated through cyclic stretch affects the SOX18/Claudin-5 regulatory axis. Our data demonstrate that SOX18 and Claudin-5 are downregulated in human lung microvascular endothelial cells (HLMVEC) exposed to cyclic stretch and the mouse lung exposed to high tidal mechanical ventilation. Overexpression of SOX18 reduced the loss of Claudin-5 expression in HLMVEC with cyclic stretch and preserved endothelial barrier function. Additionally, overexpression of Claudin-5 in HLMVEC ameliorated barrier dysfunction in HLMVEC exposed to cyclic stretch, although SOX18 expression was not enhanced. Finally, we found that the targeted overexpression of SOX18 in the pulmonary vasculature preserved Claudin-5 expression in the lungs of mice exposed to HTV. This, in turn reduced lung vascular leak, attenuated inflammatory lung injury, and preserved lung function. Together, these data suggest that enhancing SOX18 expression may prove a useful therapy to treat patients with ventilator-induced lung injury.

Phenotypic and Transcriptional Changes of Pulmonary Immune Responses in Dogs Following Canine Distemper Virus Infection

Canine distemper virus (CDV), a morbillivirus within the family Paramyxoviridae, is a highly contagious infectious agent causing a multisystemic, devastating disease in a broad range of host species, characterized by severe immunosuppression, encephalitis and pneumonia. The present study aimed at investigating pulmonary immune responses of CDV-infected dogs in situ using immunohistochemistry and whole transcriptome analyses by bulk RNA sequencing. Spatiotemporal analysis of phenotypic changes revealed pulmonary immune responses primarily driven by MHC-II⁺, Iba-1⁺ and CD204⁺ innate immune cells during acute and subacute infection phases, which paralleled pathologic lesion development and coincided with high viral loads in CDV-infected lungs. CD20⁺ B cell numbers initially declined, followed by lymphoid repopulation in the advanced disease phase. Transcriptome analysis demonstrated an increased expression of transcripts related to innate immunity, antiviral defense mechanisms, type I interferon responses and regulation of cell death in the lung of CDV-infected dogs. Molecular analyses also revealed disturbed cytokine responses with a pro-inflammatory M1 macrophage polarization and impaired mucociliary defense in CDV-infected lungs. The exploratory study provides detailed data on CDV-related pulmonary immune responses, expanding the list of immunologic parameters potentially leading to viral elimination and virus-induced pulmonary immunopathology in canine distemper.

The Effect of TNF-α on CHD and the Relationship between TNF-α Antagonist and CHD in Rheumatoid Arthritis: A Systematic Review

Tumor necrosis factor-alpha (TNF-α) plays an important role in coronary heart disease (CHD), a chronic inflammatory process. Meanwhile, this pro-inflammatory factor is also involved in the pathogenesis of autoimmune diseases such as rheumatoid arthritis (RA). Patients with RA correspond to a higher risk of CHD. TNF-α antagonist, one of the main treatments for RA, may reduce the risk of CHD in patients with RA. This review summarizes the pathogenesis of TNF-α in CHD and discusses the relationship between TNF-α antagonist and CHD in patients with RA.

Comprehensive overview of COVID-19-related respiratory failure: focus on cellular interactions

The pandemic outbreak of coronavirus disease 2019 (COVID-19) has created health challenges in all parts of the world. Understanding the entry mechanism of this virus into host cells is essential for effective treatment of COVID-19 disease. This virus can bind to various cell surface molecules or receptors, such as angiotensin-converting enzyme 2 (ACE2), to gain cell entry. Respiratory failure and pulmonary edema are the most important causes of mortality from COVID-19 infections. Cytokines, especially proinflammatory cytokines, are the main mediators of these complications. For normal respiratory function, a healthy air-blood barrier and sufficient blood flow to the lungs are required. In this review, we first discuss airway epithelial cells, airway stem cells, and the expression of COVID-19 receptors in the airway epithelium. Then, we discuss the suggested molecular mechanisms of endothelial dysfunction and blood vessel damage in COVID-19. Coagulopathy can be caused by platelet activation leading to clots, which restrict blood flow to the lungs and lead to respiratory failure. Finally, we present an overview of the effects of immune and non-immune cells and cytokines in COVID-19-related respiratory failure.

Schizophrenia Hypothesis: Autonomic Nervous System Dysregulation of Fetal and Adult Immune Tolerance

The autonomic nervous system can control immune cell activation via both sympathetic adrenergic and parasympathetic cholinergic nerve release of norepinephrine and acetylcholine. The hypothesis put forward in this paper suggests that autonomic nervous system dysfunction leads to dysregulation of immune tolerance mechanisms in brain-resident and peripheral immune cells leading to excessive production of pro-inflammatory cytokines such as Tumor Necrosis Factor alpha (TNF-α). Inactivation of Glycogen Synthase Kinase-3β (GSK3β) is a process that takes place in macrophages and microglia when a toll-like receptor 4 (TLR4) ligand binds to the TLR4 receptor. When Damage-Associated Molecular Patterns (DAMPS) and Pathogen-Associated Molecular Patterns (PAMPS) bind to TLR4s, the phosphatidylinositol-3-kinase (PI3K)-protein kinase B (Akt) pathway should be activated, leading to inactivation of GSK3β. This switches the macrophage from producing pro-inflammatory cytokines to anti-inflammatory cytokines. Acetylcholine activation of the α7 subunit of the nicotinic acetylcholine receptor (α7 nAChR) on the cell surface of immune cells leads to PI3K/Akt pathway activation and can control immune cell polarization. Dysregulation of this pathway due to dysfunction of the prenatal autonomic nervous system could lead to impaired fetal immune tolerance mechanisms and a greater vulnerability to Maternal Immune Activation (MIA) resulting in neurodevelopmental abnormalities. It could also lead to the adult schizophrenia patient’s immune system being more vulnerable to chronic stress-induced DAMP release. If a schizophrenia patient experiences chronic stress, an increased production of pro-inflammatory cytokines such as TNF-α could cause significant damage. TNF-α could increase the permeability of the intestinal and blood brain barrier, resulting in lipopolysaccharide (LPS) and TNF-α translocation to the brain and consequent increases in glutamate release. MIA has been found to reduce Glutamic Acid Decarboxylase mRNA expression, resulting in reduced Gamma-aminobutyric acid (GABA) synthesis, which combined with an increase of glutamate release could result in an imbalance of glutamate and GABA neurotransmitters. Schizophrenia could be a “two-hit” illness comprised of a genetic “hit” of autonomic nervous system dysfunction and an environmental hit of MIA. This combination of factors could lead to neurotransmitter imbalance and the development of psychotic symptoms.

ArhGEF12 activates Rap1A and not RhoA in human dermal microvascular endothelial cells to reduce tumor necrosis factor-induced leak

Overwhelming inflammation in the setting of acute critical illness induces capillary leak resulting in hypovolemia, edema, tissue dysoxia, organ failure and even death. The tight junction (TJ)-dependent capillary barrier is regulated by small GTPases, but the specific regulatory molecules most active in this vascular segment under such circumstances are not well described. We set out to identify GTPase regulatory molecules specific to endothelial cells (EC) that form TJs. Transcriptional profiling of confluent monolayers of TJ-forming human dermal microvascular ECs (HDMECs) and adherens junction only forming-human umbilical vein EC (HUVECs) demonstrate ARHGEF12 is basally expressed at higher levels and is only downregulated in HDMECs by junction-disrupting tumor necrosis factor (TNF). HDMECs depleted of ArhGEF12 by siRNA demonstrate a significantly exacerbated TNF-induced decrease in trans-endothelial electrical resistance and disruption of TJ continuous staining. ArhGEF12 is established as a RhoA-GEF in HUVECs and its knock down would be expected to reduce RhoA activity and barrier disruption. Pulldown of active GEFs from HDMECs depleted of ArhGEF12 and treated with TNF show decreased GTP-bound Rap1A after four hours but increased GTP-bound RhoA after 12 h. In cell-free assays, ArhGEF12 immunoprecipitated from HDMECs is able to activate both Rap1A and RhoA, but not act on Rap2A-C, RhoB-C, or even Rap1B which shares 95% sequence identity with Rap1A. We conclude that in TJ-forming HDMECs, ArhGEF12 selectively activates Rap1A to limit capillary barrier disruption in a mechanism independent of cAMP-mediated Epac1 activation.

Cell-Crossing Functional Network Driven by microRNA-125a Regulates Endothelial Permeability and Monocyte Trafficking in Acute Inflammation

Opening of the endothelial barrier and targeted infiltration of leukocytes into the affected tissue are hallmarks of the inflammatory response. The molecular mechanisms regulating these processes are still widely elusive. In this study, we elucidate a novel regulatory network, in which miR-125a acts as a central hub that regulates and synchronizes both endothelial barrier permeability and monocyte migration. We found that inflammatory stimulation of endothelial cells induces miR-125a expression, which consecutively inhibits a regulatory network consisting of the two adhesion molecules VE-Cadherin (CDH5) and Claudin-5 (CLDN5), two regulatory tyrosine phosphatases (PTPN1, PPP1CA) and the transcription factor ETS1 eventually leading to the opening of the endothelial barrier. Moreover, under the influence of miR-125a, endothelial expression of the chemokine CCL2, the most predominant ligand for the monocytic chemokine receptor CCR2, was strongly enhanced. In monocytes, on the other hand, we detected markedly repressed expression levels of miR-125a upon inflammatory stimulation. This induced a forced expression of its direct target gene CCR2, entailing a strongly enhanced monocyte chemotaxis. Collectively, cell-type-specific differential expression of miR-125a forms a synergistic functional network controlling monocyte trafficking across the endothelial barrier towards the site of inflammation. In addition to the known mechanism of miRNAs being shuttled between cells via extracellular vesicles, our study uncovers a novel dimension of miRNA function: One miRNA, although disparately regulated in the cells involved, directs a biologic process in a synergistic and mutually reinforcing manner. These findings provide important new insights into the regulation of the inflammatory cascade and may be of great use for future clinical applications.

Protective Effects of Alternanthera sessilis Ethanolic Extract against TNF-α or H2O2-Induced Endothelial Activation in Human Aortic Endothelial Cells

Activation of the endothelium has been shown to contribute to the early stage of vascular diseases such as atherosclerosis and hypertension. In endothelial activation, excess reactive oxygen species (ROS) production and increased expression of cell adhesion molecules cause an increase in vascular permeability. Alternanthera sessilis (L.) R. Br. is an edible traditional herbal plant, which has previously been shown to possess antioxidant and anti-inflammatory effects. However, the effect of A. sessilis on the activation of human aortic endothelial cells (HAECs) remains unknown. This study aimed to investigate the effects of A. sessilis on endothelial permeability, vascular cell adhesion-1 (VCAM-1) expression, production of ROS and hydrogen peroxide (H₂O₂), and superoxide dismutase (SOD) and catalase (CAT) activities. The viability of HAECs was first determined using the MTT viability assay. The effect of A. sessilis on endothelial permeability was examined using the FITC-dextran permeability assay. Besides, enzyme-linked immunosorbent assay (ELISA) was done to assess soluble VCAM-1 (sVCAM-1) expression. The production of ROS and H₂O₂ was studied using 2′,7′-dichlorodihydrofluorescein diacetate (H₂-DCFDA) and Amplex Red fluorescent dyes, respectively. SOD and CAT activities were also measured using commercial kits. Our results showed that 25–200 μg/mL of A. sessilis ethanolic extract did not cause significant death in HAECs. A. sessilis at 200 μg/mL significantly inhibited TNF-α-induced hyperpermeability of HAECs. However, A. sessilis did not reduce increased VCAM-1 expression induced by TNF-α. A. sessilis also significantly reduced TNF-α-induced increased ROS production, but not H₂O₂ production. Furthermore, 100 μM of H₂O₂ decreased both SOD and CAT activities in HAECs at 2 h. A. sessilis ethanolic extract dramatically increased both reduced SOD and CAT activities caused by H₂O₂. The liquid chromatography-mass spectrometry (LC-MS) analysis of A. sessilis ethanolic extract demonstrated the presence of arachidonic acid, azadirachtin, astaxanthin, flavanole base + 3O, 2Prenyl, and vicenin 2, while the gas chromatography-mass spectrometry (GC-MS) analysis showed that the extract contains 1,3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one, 3-deoxy-d-mannoic lactone, 4-pyrrolidinobenzaldehyde, and n-hexadecanoic acid. In conclusion, our findings suggest that A. sessilis ethanolic extract protects against endothelial hyperpermeability and oxidative stress elicited by pro-inflammatory or prooxidant stimulus. This study reveals a therapeutic potential of A. sessilis in preventing endothelial activation, which is a key event in early atherosclerosis.

TNFα-mediated necroptosis in brain endothelial cells as a potential mechanism of increased seizure susceptibility in mice following systemic inflammation

BACKGROUND

Systemic inflammation is a potent contributor to increased seizure susceptibility. However, information regarding the effects of systemic inflammation on cerebral vascular integrity that influence neuron excitability is scarce. Necroptosis is closely associated with inflammation in various neurological diseases. In this study, necroptosis was hypothesized to be involved in the mechanism underlying sepsis-associated neuronal excitability in the cerebrovascular components (e.g., endothelia cells).

METHODS

Lipopolysaccharide (LPS) was used to induce systemic inflammation. Kainic acid intraperitoneal injection was used to measure the susceptibility of the mice to seizure. The pharmacological inhibitors C87 and GSK872 were used to block the signaling of TNFα receptors and necroptosis. In order to determine the features of the sepsis-associated response in the cerebral vasculature and CNS, brain tissues of mice were obtained for assays of the necroptosis-related protein expression, and for immunofluorescence staining to identify morphological changes in the endothelia and glia. In addition, microdialysis assay was used to assess the changes in extracellular potassium and glutamate levels in the brain.

RESULTS

Some noteworthy findings, such as increased seizure susceptibility and brain endothelial necroptosis, Kir4.1 dysfunction, and microglia activation were observed in mice following LPS injection. C87 treatment, a TNFα receptor inhibitor, showed considerable attenuation of increased kainic acid-induced seizure susceptibility, endothelial cell necroptosis, microglia activation and restoration of Kir4.1 protein expression in LPS-treated mice. Treatment with GSK872, a RIP3 inhibitor, such as C87, showed similar effects on these changes following LPS injection.

CONCLUSIONS

The findings of this study showed that TNFα-mediated necroptosis induced cerebrovascular endothelial damage, neuroinflammation and astrocyte Kir4.1 dysregulation, which may coalesce to contribute to the increased seizure susceptibility in LPS-treated mice. Pharmacologic inhibition targeting this necroptosis pathway may provide a promising therapeutic approach to the reduction of sepsis-associated brain endothelia cell injury, astrocyte ion channel dysfunction, and subsequent neuronal excitability.

Xuebijing Injection Ameliorates H2S-Induced Acute Respiratory Distress Syndrome by Promoting Claudin-5 Expression

OBJECTIVE

To investigate the protective effects and underlying mechanisms of Xuebijing Injection (XBJ) on the lung endothelial barrier in hydrogen sulfide (H₂S)-induced acute respiratory distress syndrome (ARDS).

METHODS

Sprague-Dawley rats were exposed to H₂S (300 ppm) to establish ARDS model, while human pulmonary microvascular endothelial cells (HPMECs) were incubated with NaHS (a H₂S donor, 500 µmol/L) to establish cell model. H₂S and XBJ were concurrently administered to the rat and cell models. Lung hematoxylin and eosin staining, immunohistochemistry, transmission electron microscopy and wet/dry ratio measurement were used to confirm ARDS induced by H₂S in vivo. The expression levels of claudin-5, phosphorylated protein kinase B (p-AKT)/t-AKT and p-forkhead box transcription factor O1 (FoxO1)/t-FoxO1 in vivo and in vitro were also assessed. Paracellular permeability and transepithelial electrical resistance (TEER) were measured to evaluate endothelial barrier function in the cell model.

RESULTS

The morphological investigation showed that XBJ attenuated H₂S-induced ARDS in rats. XBJ significantly ameliorated both the reduction in TEER and the increased paracellular permeability observed in NaHS-treated HPMECs (P<0.05). The protective effects of XBJ were blocked by LY294002, a phosphatidylinositol 3-kinase (PI3K)/AKT/FoxO1 pathway antagonist (P<0.05). Furthermore, XBJ promoted the expression of claudin-5 and increased the levels of p-AKT and p-FoxO1 in vivo and in vitro (P<0.05).

CONCLUSIONS

XBJ ameliorated H₂S-induced ARDS by promoting claudin-5 expression via the PI3K/AKT/FoxO1 signaling pathway.

ClbG in Avian Pathogenic Escherichia coli Contributes to Meningitis Development in a Mouse Model

Colibactin is a complex secondary metabolite that leads to genotoxicity that interferes with the eukaryotic cell cycle. It plays an important role in many diseases, including neonatal mouse sepsis and meningitis. Avian pathogenic Escherichia coli (APEC) is responsible for several diseases in the poultry industry and may threaten human health due to its potential zoonosis. In this study, we confirmed that clbG was necessary for the APEC XM strain to produce colibactin. The deletion of clbG on APEC XM contributed to lowered γH2AX expression, no megalocytosis, and no cell cycle arrest in vitro. None of the 4-week Institute of Cancer Research mice infected with the APEC XM ΔclbG contracted meningitis or displayed weakened clinical symptoms. Fewer histopathological lesions were observed in the APEC XM ΔclbG group. The bacterial colonization of tissues and the relative expression of cytokines (IL-1β, IL-6, and TNF-α) in the brains decreased significantly in the APEC XM ΔclbG group compared to those in the APEC XM group. The tight junction proteins (claudin-5, occludin, and ZO-1) were not significantly destroyed in APEC XM ΔclbG group in vivo and in vitro. In conclusion, clbG is necessary for the synthesis of the genotoxin colibactin and affects the development of APEC meningitis in mice.

Rho-Proteins and Downstream Pathways as Potential Targets in Sepsis and Septic Shock: What Have We Learned from Basic Research

Sepsis and septic shock are associated with acute and sustained impairment in the function of the cardiovascular system, kidneys, lungs, liver, and brain, among others. Despite the significant advances in prevention and treatment, sepsis and septic shock sepsis remain global health problems with elevated mortality rates. Rho proteins can interact with a considerable number of targets, directly affecting cellular contractility, actin filament assembly and growing, cell motility and migration, cytoskeleton rearrangement, and actin polymerization, physiological functions that are intensively impaired during inflammatory conditions, such as the one that occurs in sepsis. In the last few decades, Rho proteins and their downstream pathways have been investigated in sepsis-associated experimental models. The most frequently used experimental design included the exposure to bacterial lipopolysaccharide (LPS), in both in vitro and in vivo approaches, but experiments using the cecal ligation and puncture (CLP) model of sepsis have also been performed. The findings described in this review indicate that Rho proteins, mainly RhoA and Rac1, are associated with the development of crucial sepsis-associated dysfunction in different systems and cells, including the endothelium, vessels, and heart. Notably, the data found in the literature suggest that either the inhibition or activation of Rho proteins and associated pathways might be desirable in sepsis and septic shock, accordingly with the cellular system evaluated. This review included the main findings, relevance, and limitations of the current knowledge connecting Rho proteins and sepsis-associated experimental models.

Tumor necrosis factor-induced ArhGEF10 selectively activates RhoB contributing to human microvascular endothelial cell tight junction disruption

Capillary endothelial cells (ECs) maintain a semi-permeable barrier between the blood and tissue by forming inter-EC tight junctions (TJs), regulating selective transport of fluid and solutes. Overwhelming inflammation, as occurs in sepsis, disrupts these TJs, leading to leakage of fluid, proteins, and small molecules into the tissues. Mechanistically, disruption of capillary barrier function is mediated by small Rho-GTPases, such as RhoA, -B, and -C, which are activated by guanine nucleotide exchange factors (GEFs) and disrupted by GTPase-activating factors (GAPs). We previously reported that a mutation in a specific RhoB GAP (p190BRhoGAP) underlays a hereditary capillary leak syndrome. Tumor necrosis factor (TNF) treatment disrupts TJs in cultured human microvascular ECs, a model of capillary leak. This response requires new gene transcription and involves increased RhoB activation. However, the specific GEF that activates RhoB in capillary ECs remains unknown. Transcriptional profiling of cultured tight junction-forming human dermal microvascular endothelial cells (HDMECs) revealed that 17 GEFs were significantly induced by TNF. The function of each candidate GEF was assessed by short interfering RNA depletion and trans-endothelial electrical resistance screening. Knockown of ArhGEF10 reduced the TNF-induced loss of barrier which was phenocopied by RhoB or dual ArhGEF10/RhoB knockdown. ArhGEF10 knockdown also reduced the extent of TNF-induced RhoB activation and disruption at tight junctions. In a cell-free assay, immunoisolated ArhGEF10 selectively catalyzed nucleotide exchange to activate RhoB, but not RhoA or RhoC. We conclude ArhGEF10 is a TNF-induced RhoB-selective GEF that mediates TJ disruption and barrier loss in human capillary endothelial cells.

The Mechanism behind Influenza Virus Cytokine Storm

Influenza viruses are still a serious threat to human health. Cytokines are essential for cell-to-cell communication and viral clearance in the immune system, but excessive cytokines can cause serious immune pathology. Deaths caused by severe influenza are usually related to cytokine storms. The recent literature has described the mechanism behind the cytokine-storm network and how it can exacerbate host pathological damage. Biological factors such as sex, age, and obesity may cause biological differences between different individuals, which affects cytokine storms induced by the influenza virus. In this review, we summarize the mechanism behind influenza virus cytokine storms and the differences in cytokine storms of different ages and sexes, and in obesity.

Epithelial Barrier Integrity Profiling: Combined Approach Using Cellular Junctional Complex Imaging and Transepithelial Electrical Resistance

A core aspect of epithelial cell function is barrier integrity. A loss of barrier integrity is a feature of a number of respiratory diseases, including asthma, allergic rhinitis, and chronic obstructive pulmonary disease. Restoration of barrier integrity is a target for respiratory disease drug discovery. Traditional methods for assessing barrier integrity have their limitations. Transepithelial electrical resistance (TEER) and dextran permeability methods can give poor in vitro assay robustness. Traditional junctional complex imaging approaches are labor-intensive and tend to be qualitative but not quantitative. To provide a robust and quantitative assessment of barrier integrity, high-content imaging of junctional complexes was combined with TEER. A scalable immunofluorescent high-content imaging technique, with automated quantification of junctional complex proteins zonula occludens-1 and occludin, was established in 3D pseudostratified primary human bronchial epithelial cells cultured at an air-liquid interface. Ionic permeability was measured using TEER on the same culture wells.The improvements to current technologies include the design of a novel 24-well holder to enable scalable in situ confocal cell imaging without Transwell membrane excision, the development of image analysis pipelines to quantify in-focus junctional complex structures in each plane of a Z stack, and the enhancement of the TEER data analysis process to enable statistical evaluation of treatment effects on barrier integrity. This novel approach was validated by demonstrating measurable changes in barrier integrity in cells grown under conditions known to perturb epithelial cell function.

Targeting tumour necrosis factor to ameliorate viral pneumonia

Pneumonia is a serious complication associated with inflammation of the lungs due to infection with viral pathogens. Seasonal and pandemic influenza viruses, variola virus (agent of smallpox) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; agent of COVID-19) are some leading examples. Viral pneumonia is triggered by excessive inflammation associated with dysregulated cytokine production, termed 'cytokine storm'. Several cytokines have been implicated but tumour necrosis factor (TNF) plays a critical role in driving lung inflammation, severe lung pathology and death. Despite this, the exact role TNF plays in the aetiology and pathogenesis of virus infection-induced respiratory complications is not well understood. In this review, we discuss the pathological and immunomodulatory roles of TNF in contributing to immunopathology and resolution of lung inflammation, respectively, in mouse models of influenza- and smallpox (mousepox)-induced pneumonia. We review studies that have investigated dampening of inflammation on the outcome of severe influenza and orthopoxvirus infections. Most studies on the influenza model have evaluated the efficacy of treatment with anti-inflammatory drugs, including anti-TNF agents, in animal models on the day of viral infection. We question the merits of those studies as they are not transferable to the clinic given that individuals generally present at a hospital only after the onset of disease symptoms and not on the day of infection. We propose that research should be directed at determining whether dampening lung inflammation after the onset of disease symptoms will reduce morbidity and mortality. Such a treatment strategy will be more relevant clinically.

S-1-propenylcysteine improves TNF-α-induced vascular endothelial barrier dysfunction by suppressing the GEF-H1/RhoA/Rac pathway

Background

Vascular endothelial barrier function is maintained by cell-to-cell junctional proteins and contributes to vascular homeostasis. Various risk factors such as inflammation disrupt barrier function through down-regulation of these proteins and promote vascular diseases such as atherosclerosis. Previous studies have demonstrated that aged garlic extract (AGE) and its sulfur-containing constituents exert the protective effects against several vascular diseases such as atherosclerosis. In this study, we examined whether AGE and its sulfur-containing constituents improve the endothelial barrier dysfunction elicited by a pro-inflammatory cytokine, Tumor-necrosis factor-α (TNF-α), and explored their mode of action on TNF-α signaling pathway.

Methods

Human umbilical vein endothelial cells (HUVECs) were treated with test substances in the presence of TNF-α for various time periods. The endothelial permeability was measured by using a transwell permeability assay. The localization of cell-to-cell junctional proteins and actin cytoskeletons were visualized by immunostaining. RhoA and Rac activities were assessed by using GTP-binding protein pulldown assay. Gene and protein expression levels of signaling molecules were analyzed by real-time PCR and western blotting, respectively.

Results

We found that AGE and its major sulfur-containing constituent, S-1-propenylcysteine (S1PC), reduced hyperpermeability elicited by TNF-α in HUVECs. In addition, S1PC inhibited TNF-α-induced production of myosin light chain (MLC) kinase and inactivation of MLC phosphatase through the suppression of the Rac and RhoA signaling pathways, respectively, which resulted in the dephosphorylation of MLC2, a key factor of actin remodeling. Moreover, S1PC inhibited the phosphorylation and activation of guanine nucleotide exchange factor-H1 (GEF-H1), a common upstream key molecule and activator of Rac and RhoA. These effects of S1PC were accompanied by its ability to prevent the disruption of junctional proteins on the cell–cell contact regions and the increase of actin stress fibers induced by TNF-α.

Conclusions

The present study suggested that AGE and its major constituent, S1PC, improve endothelial barrier disruption through the protection of junctional proteins on plasma membrane.

The effects of sepsis on endothelium and clinical implications

ABSTRACT

Sepsis accounts for nearly 700 000 deaths in Europe annually and is caused by an overwhelming host response to infection resulting in organ failure. The endothelium is an active contributor to sepsis and as such represents a major target for therapy. During sepsis, endothelial cells amplify the immune response and activate the coagulation system. They are both a target and source of inflammation and serve as a link between local and systemic immune responses. In response to cytokines produced by immune cells, the endothelium expresses adhesion molecules and produces vasoactive compounds, inflammatory cytokines, and chemoattractants, thus switching from an anticoagulant to procoagulant state. These responses contribute to local control of infection, but systemic activation can lead to microvascular thrombosis, capillary permeability, hypotension, tissue hypoxia, and ultimately tissue damage. This review focuses on the role of the endothelium in leucocyte adhesion and transmigration as well as production of reactive oxygen and nitrogen species, microRNAs and cytokines, formation of signalling microparticles, and disseminated intravascular coagulation. We also discuss alterations in endothelial permeability and apoptosis. Finally, we review the diagnostic potential of endothelial markers and endothelial pathways as therapeutic targets for this devastating disease.

Tight Junction Modulating Bioprobes for Drug Delivery System to the Brain: A Review

The blood-brain barrier (BBB), which is composed of endothelial cells, pericytes, astrocytes, and neurons, separates the brain extracellular fluid from the circulating blood, and maintains the homeostasis of the central nervous system (CNS). The BBB endothelial cells have well-developed tight junctions (TJs) and express specific polarized transport systems to tightly control the paracellular movements of solutes, ions, and water. There are two types of TJs: bicellular TJs (bTJs), which is a structure at the contact of two cells, and tricellular TJs (tTJs), which is a structure at the contact of three cells. Claudin-5 and angulin-1 are important components of bTJs and tTJs in the brain, respectively. Here, we review TJ-modulating bioprobes that enable drug delivery to the brain across the BBB, focusing on claudin-5 and angulin-1.

Angiopoietin Level Trajectories in Toddlers With Severe Sepsis and Septic Shock and Their Effect on Capillary Endothelium

OBJECTIVE

Angiopoietins are postulated diagnostic biomarkers in children and adults with severe sepsis and septic shock. The diagnostic value of angiopoietins in children less than 5 years old has not been established, nor has their effect on permeability in the capillary microvasculature. We aim to determine if levels of angiopoietin-1 or -2 (angpt-1, -2) are diagnostic for severe sepsis/shock in young children and whether they affect the permeability of cultured human dermal microvascular endothelial cells (HDMEC).

DESIGN

Prospective observational study of children < 5 years old. Patients were classified as non-systemic inflammatory response syndrome (SIRS), SIRS/sepsis and severe sepsis/septic shock.

SETTING

Tertiary care pediatric hospitals.

PATIENTS

Critically ill children.

INTERVENTIONS

None.

MEASUREMENTS

Plasma angpt-1 and -2 levels were measured with enzyme-linked immunoassays. Expression of angpt-2 in endothelial cells was assessed with quantitative polymerase chain reaction. Permeability changes in cultured HDMECs were assessed with transendothelial electrical resistance measurements.

RESULTS

Angpt-1 levels were significantly higher in younger children compared with levels found in previous study of older children across disease severity (all P < 0.001). Angpt-2 was significantly higher in this cohort with severe sepsis/septic shock compared with children without SIRS and SIRS/sepsis (all P < 0.003). Angpt-2/1 ratio was also elevated in children with severe sepsis/septic shock but an order of magnitude less than older children (P < 0.02, P = 0.002). Angpt-1 and -2 did not affect basal HDMEC permeability or modulate leak in isolation or in the presence of tumor necrosis factor (TNF).

CONCLUSIONS

Angpt-2 levels and the angpt-2/1 ratio are appropriate diagnostic biomarkers of severe sepsis/septic shock in children less than 5 years old. Neither angpt-1 nor -2 affects basal HDMEC permeability alone or modulates TNF induced capillary leak.

Pericytes enable effective angiogenesis in the presence of proinflammatory signals

Angiogenesis frequently occurs in the context of acute or persistent inflammation. The complex interplay of proinflammatory and proangiogenic cues is only partially understood. Using an experimental model, permitting exposure of developing blood vessel sprouts to multiple combinations of diverse biochemical stimuli and juxtacrine cell interactions, we present evidence that a proinflammatory cytokine, tumor necrosis factor (TNF), can have both proangiogenic and antiangiogenic effects, depending on the dose and the presence of pericytes. In particular, we find that pericytes can rescue and enhance angiogenesis in the presence of otherwise-inhibitory high TNF doses. This sharp switch from proangiogenic to antiangiogenic effect of TNF observed with an escalating dose of this cytokine, as well as the effect of pericytes, are explained by a mathematical model trained on the biochemical data. Furthermore, this model was predictive of the effects of diverse combinations of proinflammatory and antiinflammatory cues, and variable pericyte coverage. The mechanism supports the effect of TNF and pericytes as modulating signaling networks impinging on Notch signaling and specification of the Tip and Stalk phenotypes. This integrative analysis elucidates the plasticity of the angiogenic morphogenesis in the presence of diverse and potentially conflicting cues, with immediate implications for many physiological and pathological settings.

Blocking connexin43 hemichannels protects mice against tumour necrosis factor-induced inflammatory shock

Upon intravenous injection of tumour necrosis factor (TNF) in mice, a systemic inflammatory response syndrome (SIRS) is initiated, characterized by an acute cytokine storm and induction of vascular hyperpermeability. Connexin43 hemichannels have been implicated in various pathological conditions, e.g. ischemia and inflammation, and can lead to detrimental cellular outcomes. Here, we explored whether targeting connexin43 hemichannels could alleviate TNF-induced endothelial barrier dysfunction and lethality in SIRS. Therefore, we verified whether administration of connexin43-targeting-peptides affected survival, body temperature and vascular permeability in vivo. In vitro, TNF-effects on connexin43 hemichannel function were investigated by single-channel studies and Ca²⁺-imaging. Blocking connexin43 hemichannels with TAT-Gap19 protected mice against TNF-induced mortality, hypothermia and vascular leakage, while enhancing connexin43 hemichannel function with TAT-CT9 provoked opposite sensitizing effects. In vitro patch-clamp studies revealed that TNF acutely activated connexin43 hemichannel opening in endothelial cells, which was promoted by CT9, and inhibited by Gap19 and intracellular Ca²⁺-buffering. In vivo experiments aimed at buffering intracellular Ca²⁺, and pharmacologically targeting Ca²⁺/calmodulin-dependent protein kinase-II, a known modulator of endothelial barrier integrity, demonstrated their involvement in permeability alterations. Our results demonstrate significant benefits of inhibiting connexin43 hemichannels to counteract TNF-induced SIRS-associated vascular permeability and lethality.

Prominin-1 Modulates Rho/ROCK-Mediated Membrane Morphology and Calcium-Dependent Intracellular Chloride Flux

Membrane morphology is an important structural determinant as it reflects cellular functions. The pentaspan membrane protein Prominin-1 (Prom1/CD133) is known to be localised to protrusions and plays a pivotal role in migration and the determination of cellular morphology; however, the underlying mechanism of its action have been elusive. Here, we performed molecular characterisation of Prom1, focussing primarily on its effects on cell morphology. Overexpression of Prom1 in RPE-1 cells triggers multiple, long, cholesterol-enriched fibres, independently of actin and microtubule polymerisation. A five amino acid stretch located at the carboxyl cytosolic region is essential for fibre formation. The small GTPase Rho and its downstream Rho-associated coiled-coil-containing protein kinase (ROCK) are also essential for this process, and active Rho colocalises with Prom1 at the site of initialisation of fibre formation. In mouse embryonic fibroblast (MEF) cells we show that Prom1 is required for chloride ion efflux induced by calcium ion uptake, and demonstrate that fibre formation is closely associated with chloride efflux activity. Collectively, these findings suggest that Prom1 affects cell morphology and contributes to chloride conductance.

Post-treatment With Qing-Ying-Tang, a Compound Chinese Medicine Relives Lipopolysaccharide-Induced Cerebral Microcirculation Disturbance in Mice

Objective: Lipopolysaccharide (LPS) causes microvascular dysfunction, which is a key episode in the pathogenesis of endotoxemia. This work aimed to investigate the effect of Qing-Ying-Tang (QYT), a compound Chinese medicine in cerebral microcirculation disturbance and brain damage induced by LPS.

Methods: Male C57/BL6 mice were continuously transfused with LPS (7.5 mg/kg/h) through the left femoral vein for 2 h. QYT (14.3 g/kg) was given orally 2 h after LPS administration. The dynamics of cerebral microcirculation were evaluated by intravital microscopy. Brain tissue edema was assessed by brain water content and Evans Blue leakage. Cytokines in plasma and brain were evaluated by flow cytometry. Confocal microscopy and Western blot were applied to detect the expression of junction and adhesion proteins, and signaling proteins concerned in mouse brain tissue.

Results: Post-treatment with QYT significantly ameliorated LPS-induced leukocyte adhesion to microvascular wall and albumin leakage from cerebral venules and brain tissue edema, attenuated the increase of MCP-1, MIP-1α, IL-1α, IL-6, and VCAM-1 in brain tissue and the activation of NF-κB and expression of MMP-9 in brain. QYT ameliorated the downregulation of claudin-5, occludin, JAM-1, ZO-1, collagen IV as well as the expression and phosphorylation of VE-cadherin in mouse brain.

Conclusions: This study demonstrated that QYT protected cerebral microvascular barrier from disruption after LPS by acting on the transcellular pathway mediated by caveolae and paracellular pathway mediated by junction proteins. This result suggests QYT as a potential strategy to deal with endotoxemia.

Passing the Vascular Barrier: Endothelial Signaling Processes Controlling Extravasation

A central function of the vascular endothelium is to serve as a barrier between the blood and the surrounding tissue of the body. At the same time, solutes and cells have to pass the endothelium to leave or to enter the bloodstream to maintain homeostasis. Under pathological conditions, for example, inflammation, permeability for fluid and cells is largely increased in the affected area, thereby facilitating host defense. To appropriately function as a regulated permeability filter, the endothelium uses various mechanisms to allow solutes and cells to pass the endothelial layer. These include transcellular and paracellular pathways of which the latter requires remodeling of intercellular junctions for its regulation. This review provides an overview on endothelial barrier regulation and focuses on the endothelial signaling mechanisms controlling the opening and closing of paracellular pathways for solutes and cells such as leukocytes and metastasizing tumor cells.

Mesenchymal stem cells decrease blood-brain barrier permeability in rats with severe acute pancreatitis

Background

Impairment of the blood–brain barrier (BBB) could result in secondary cerebral edema and life-threatening pancreatic encephalopathy in patients with severe acute pancreatitis (SAP). Mesenchymal stem cells (MSCs) have been widely adopted in clinical research because of their pleiotropic functions. The aim of this study was to investigate the impact of MSCs on BBB permeability in SAP and the potential mechanisms driving these effects.

Methods

Sprague-Dawley rats were randomly assigned to the control, SAP and SAP+MSCs groups. Pancreatic impairment was assessed. The serum levels of amylase, TNF-α and IL-10, expression levels of claudin-5, Bax, Bcl-2 and MMP-9, and the BBB permeability were measured. Endothelial cell apoptosis was evaluated.

Results

SAP rats showed BBB impairment with increased permeability and secondary cerebral edema, which was confirmed using the Evans blue assay and the calculation of the brain dry/wet ratio. Treatment with MSCs decreased the serum levels of amylase and TNF-α, increased the serum levels of IL-10, attenuated the apoptosis of brain microvascular endothelial cells, upregulated claudin-5 expression and downregulated MMP-9 expression. This treatment attenuated the increased BBB permeability in SAP rats.

Conclusions

MSCs attenuated the impairment of the BBB and decreased its permeability, producing protective effects in SAP rats.

Electronic supplementary material

The online version of this article (10.1186/s11658-019-0167-8) contains supplementary material, which is available to authorized users.

FAK and Pyk2 activity promote TNF-α and IL-1β-mediated pro-inflammatory gene expression and vascular inflammation

Protein tyrosine kinase (PTK) activity has been implicated in pro-inflammatory gene expression following tumor necrosis factor-α (TNF-α) or interkeukin-1β (IL-1β) stimulation. However, the identity of responsible PTK(s) in cytokine signaling have not been elucidated. To evaluate which PTK is critical to promote the cytokine-induced inflammatory cell adhesion molecule (CAM) expression including VCAM-1, ICAM-1, and E-selectin in human aortic endothelial cells (HAoECs), we have tested pharmacological inhibitors of major PTKs: Src and the focal adhesion kinase (FAK) family kinases - FAK and proline-rich tyrosine kinase (Pyk2). We found that a dual inhibitor of FAK/Pyk2 (PF-271) most effectively reduced all three CAMs upon TNF-α or IL-1β stimulation compared to FAK or Src specific inhibitors (PF-228 or Dasatinib), which inhibited only VCAM-1 expression. In vitro inflammation assays showed PF-271 reduced monocyte attachment and transmigration on HAoECs. Furthermore, FAK/Pyk2 activity was not limited to CAM expression but was also required for expression of various pro-inflammatory molecules including MCP-1 and IP-10. Both TNF-α and IL-1β signaling requires FAK/Pyk2 activity to activate ERK and JNK MAPKs leading to inflammatory gene expression. Knockdown of either FAK or Pyk2 reduced TNF-α-stimulated ERK and JNK activation and CAM expression, suggesting that activation of ERK or JNK is specific through FAK and Pyk2. Finally, FAK/Pyk2 activity is required for VCAM-1 expression and macrophage recruitment to the vessel wall in a carotid ligation model in ApoE-/- mice. Our findings define critical roles of FAK/Pyk2 in mediating inflammatory cytokine signaling and implicate FAK/Pyk2 inhibitors as potential therapeutic agents to treat vascular inflammatory disease such as atherosclerosis.

The cerebral endothelial cell as a key regulator of inflammatory processes in sterile inflammation

Cerebral endothelial cells accomplish numerous tasks connected to the maintenance of homeostasis of the central nervous system. They create a barrier between the central nervous system and peripheral blood and regulate mechanotransduction, vascular permeability, rheology, thrombogenesis, and leukocyte adhesion. In pathophysiological conditions (e.g., stroke or ischemia-reperfusion injury) the endothelial functions are impaired, leading to increased vascular permeability, vascular inflammation, leukocyte-endothelium interactions, and transendothelial migration, driving CNS inflammation and neuronal destruction. This review describes the current knowledge on the regulatory roles of endothelial cells in neuroinflammatory processes.

Blast exposure elicits blood-brain barrier disruption and repair mediated by tight junction integrity and nitric oxide dependent processes

Mild blast-induced traumatic brain injury (TBI) is associated with blood-brain barrier (BBB) disruption. However, the mechanisms whereby blast disrupts BBB integrity are not well understood. To address this issue BBB permeability to peripherally injected ¹⁴C-sucrose and ^99mTc-albumin was quantified in ten brain regions at time points ranging from 0.25 to 72 hours. In mice, repetitive (2X) blast provoked BBB permeability to ¹⁴C-sucrose that persisted in specific brain regions from 0.25 to 72 hours. However, ^99mTc-albumin revealed biphasic BBB disruption (open-closed-open) over the same interval, which was most pronounced in frontal cortex and hippocampus. This indicates that blast initiates interacting BBB disruption and reparative processes in specific brain regions. Further investigation of delayed (72 hour) BBB disruption revealed that claudin-5 (CLD5) expression was disrupted specifically in the hippocampus, but not in dorsal striatum, a brain region that showed no blast-induced BBB permeability to sucrose or albumin. In addition, we found that delayed BBB permeability and disrupted CLD5 expression were blocked by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). These data argue that latent nitric oxide-dependent signaling pathways initiate processes that result in delayed BBB disruption, which are manifested in a brain-region specific manner.

Sera From Children After Cardiopulmonary Bypass Reduces Permeability of Capillary Endothelial Cell Barriers

OBJECTIVES

Children undergoing cardiopulmonary bypass develop clinically impactful capillary leak of unclear etiology. A widely held hypothesis that exposure of circulating cells to the cardiopulmonary bypass circuit induces the release of inflammatory mediators that act to disrupt intercellular junctions of capillary endothelial cells inducing paracellular capillary leak either directly or through new gene expression.

DESIGN

Cohort study.

SETTING

Tertiary pediatric hospital.

PATIENTS

Twenty children undergoing surgery with cardiopulmonary bypass for congenital heart disease. Serum was collected before cardiopulmonary bypass, 2 hours after cardiopulmonary bypass, and 18 hours after cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We analyzed the effects of 10% patient sera on the "function, structure, and gene expression" of cultured human dermal and pulmonary microvascular endothelial cells. Changes in barrier "function" were measured using transendothelial electrical resistance. Associations between changes in transendothelial electrical resistance and subject characteristics were analyzed using linear mixed effects model with area under the resistance curve as outcome. Changes in junctional "structure" were assessed by analyzing the organization of the endothelial cell junctional proteins claudin-5 and VE-cadherin using immunofluorescence microscopy. Changes in inflammatory "gene expression" were measured using real-time quantitative reverse transcription-polymerase chain reaction. All serum samples induced a transient, 120-minute increase in transendothelial electrical resistance followed by persistent loss of barrier function. Unexpectedly, sera collected postcardiopulmonary bypass-induced significantly less loss of barrier function in both dermal and pulmonary capillary endothelial cell compared with precardiopulmonary bypass sera. Consistent with the transendothelial electrical resistance results, claudin-5 and vascular endothelial-cadherin junctional staining showed less disruption in cultures treated with postcardiopulmonary bypass sera. Expression of genes commonly associated with inflammation was largely unaffected by patient sera.

CONCLUSIONS

Contrary to the hypothesis, sera taken from children after cardiopulmonary bypass induces less capillary barrier disruption relative to sera taken from children before cardiopulmonary bypass, and none of the sera induced significant changes in expression of inflammatory genes.

Interleukin-10 attenuates impairment of the blood-brain barrier in a severe acute pancreatitis rat model

Background

Impairment of the blood-brain barrier (BBB) in severe acute pancreatitis (SAP) could result in life-threatening pancreatic encephalopathy. Interleukin-10 (IL-10) is a classical cytokine that is well-known for its strong immunoregulatory and anti-inflammatory abilities. However, whether and how IL-10 protects the BBB in SAP are still unclear.

Methods

This study includes in vivo experiments using a SAP rat model and in vitro experiments using an in vitro BBB model consisting of a monolayer of brain microvascular endothelial cells (BMECs). The study groups are divided into the control, SAP (in vivo)/TNF-α (in vitro), IL-10 treatment, IL-10 + signal transducer and activator of transcription 3 (STAT3) inhibitor S3I-201 treatment groups. Pancreatic pathological scores, serum amylase, serum TNF-α levels and BBB permeability by Evan’s blue assay in SAP rat models were evaluated. BMEC apoptosis in SAP rats or induced by TNF-αin vitro was detected by terminal-deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) and flow cytometry, separately. Expression levels of claudin-5 and proteins involved in the STAT3 signaling pathway were measured by Western blotting. Location and changes of junctional structure of claudin-5 on BMECs were assessed by immunohistochemistry and immunofluorescence.

Results

In vivo, IL-10 alleviated the severity of inflammation, attenuated the increased BBB permeability in SAP rat models by reducing BMEC apoptosis via the STAT3 pathway and ameliorated the down-regulation of claudin-5 expression in BMECs; in vitro, IL-10 improved BBB integrity against TNF-α by attenuating BMEC apoptosis via the STAT3 pathway, the impairment of tight junction structure and the down-regulation of claudin-5 expression in BMECs.

Conclusions

IL-10 improves BBB properties in SAP by attenuating the down-regulation of claudin-5 expression and the impairment of tight junctions and by STAT3 pathway-mediated anti-apoptotic effects on BMECs.

The Cullin-3-Rbx1-KCTD10 complex controls endothelial barrier function via K63 ubiquitination of RhoB

The RhoA GTPase controls endothelial cell migration, adhesion, and barrier formation but the role of RhoB is unclear. Kovačević et al. now discover that RhoB is ubiquitinated by the CUL3–Rbx1–KCTD10 complex and that this is a prerequisite for lysosomal degradation of RhoB and the maintenance of endothelial barrier integrity. 

RhoGTPases control endothelial cell (EC) migration, adhesion, and barrier formation. Whereas the relevance of RhoA for endothelial barrier function is widely accepted, the role of the RhoA homologue RhoB is poorly defined. RhoB and RhoA are 85% identical, but RhoB’s subcellular localization and half-life are uniquely different. Here, we studied the role of ubiquitination for the function and stability of RhoB in primary human ECs. We show that the K63 polyubiquitination at lysine 162 and 181 of RhoB targets the protein to lysosomes. Moreover, we identified the RING E3 ligase complex Cullin-3–Rbx1–KCTD10 as key modulator of endothelial barrier integrity via its regulation of the ubiquitination, localization, and activity of RhoB. In conclusion, our data show that ubiquitination controls the subcellular localization and lysosomal degradation of RhoB and thereby regulates the stability of the endothelial barrier through control of RhoB-mediated EC contraction.

Interleukin-6 promotes a sustained loss of endothelial barrier function via Janus kinase-mediated STAT3 phosphorylation and de novo protein synthesis

Vascular leakage is a hallmark of the inflammatory response. Acute changes in endothelial permeability are due to posttranslational changes in intercellular adhesion and cytoskeleton proteins. However, little is known about the mechanisms leading to long-term changes in vascular permeability. Here, we show that interleukin-6 (IL-6) promotes an increase in endothelial monolayer permeability that lasts over 24 h and demonstrate that activation of Src and MEK/ERK pathways is required only for short-term increases in permeability, being dispensable after 2 h. In contrast, Janus kinase (JAK)-mediated STAT3 phosphorylation at Y705 (but not S727) and de novo synthesis of RNA and proteins are required for the sustained permeability increases. Loss of junctional localization of VE-cadherin and ZO-1 is evident several hours after the maximal IL-6 response, thus suggesting that these events are a consequence of IL-6 signaling, but not a cause of the increased permeability. Understanding the mechanisms involved in sustaining vascular permeability may prove crucial to allow us to directly target vascular leakage and minimize tissue damage, thus reducing the rates of mortality and chronic sequelae of excessive edema. Targeting endothelial-specific mechanisms regulating barrier function could provide a new therapeutic strategy to prevent vascular leakage while maintaining the immune response and other beneficial aspects of the inflammatory response that are required for bacterial clearance and tissue repair.

Mind the gap: mechanisms regulating the endothelial barrier

The endothelial barrier consists of intercellular contacts localized in the cleft between endothelial cells, which is covered by the glycocalyx in a sievelike manner. Both types of barrier-forming junctions, i.e. the adherens junction (AJ) serving mechanical anchorage and mechanotransduction and the tight junction (TJ) sealing the intercellular space to limit paracellular permeability, are tethered to the actin cytoskeleton. Under resting conditions, the endothelium thereby builds a selective layer controlling the exchange of fluid and solutes with the surrounding tissue. However, in the situation of an inflammatory response such as in anaphylaxis or sepsis intercellular contacts disintegrate in post-capillary venules leading to intercellular gap formation. The resulting oedema can cause shock and multi-organ failure. Therefore, maintenance as well as coordinated opening and closure of interendothelial junctions is tightly regulated. The two principle underlying mechanisms comprise spatiotemporal activity control of the small GTPases Rac1 and RhoA and the balance of the phosphorylation state of AJ proteins. In the resting state, junctional Rac1 and RhoA activity is enhanced by junctional components, actin-binding proteins, cAMP signalling and extracellular cues such as sphingosine-1-phosphate (S1P) and angiopoietin-1 (Ang-1). In addition, phosphorylation of AJ components is prevented by junction-associated phosphatases including vascular endothelial protein tyrosine phosphatase (VE-PTP). In contrast, inflammatory mediators inhibiting cAMP/Rac1 signalling cause strong activation of RhoA and induce AJ phosphorylation finally leading to endocytosis and cleavage of VE-cadherin. This results in dissolution of TJs the outcome of which is endothelial barrier breakdown.

A p190BRhoGAP mutation and prolonged RhoB activation in fatal systemic capillary leak syndrome

Pierce et al. describe a pediatric patient with a fatal systemic capillary leak syndrome (Clarkson’s disease). They identify a point mutation in p190BRhoGAP and show that patient-derived microvascular endothelial cells show prolonged activation RhoB that correlates with impaired barrier recovery after treatment with TNF compared with control cultures.

We describe a fatal case of pediatric systemic capillary leak (Clarkson’s disease) associated with a point mutation in p190BRhoGAP. Dermal microvascular endothelial cells (ECs) isolated from this patient form monolayers with similar levels and distribution of junctional proteins and transendothelial electrical resistance compared with normal human dermal microvascular ECs. However, patient-derived ECs demonstrate a greater increase in permeability and impaired recovery of barrier function in response to tumor necrosis factor (TNF) compared with normal donor EC cultures. TNF transiently activates RhoB in ECs coincident with developing leak, and inactivation of RhoB correlates with barrier recovery. The mutation in p190BRhoGAP impairs RhoB inactivation, and the mutant phenotype of patient-derived ECs is replicated by siRNA knockdown of p190BRhoGAP in normal ECs. These data suggest a previously unknown function for p190BRhoGAP in control of capillary EC barrier function that may also be important in acquired systemic capillary leak associated with critical illness in humans.

Endothelial cell-cell adhesion and signaling

Endothelial cells line blood vessels and provide a dynamic interface between the blood and tissues. They remodel to allow leukocytes, fluid and small molecules to enter tissues during inflammation and infections. Here we compare the signaling networks that contribute to endothelial permeability and leukocyte transendothelial migration, focusing particularly on signals mediated by small GTPases that regulate cell adhesion and the actin cytoskeleton. Rho and Rap GTPase signaling is important for both processes, but they differ in that signals are activated locally under leukocytes, whereas endothelial permeability is a wider event that affects the whole cell. Some molecules play a unique role in one of the two processes, and could therefore be targeted to selectively alter either endothelial permeability or leukocyte transendothelial migration.

Effect of toll-like receptor 3 agonist poly I:C on intestinal mucosa and epithelial barrier function in mouse models of acute colitis

AIM

To investigate potential effects of poly I:C on mucosal injury and epithelial barrier disruption in dextran sulfate sodium (DSS)-induced acute colitis.

METHODS

Thirty C57BL/6 mice were given either regular drinking water (control group) or 2% (w/v) DSS drinking water (model and poly I:C groups) ad libitum for 7 d. Poly I:C was administrated subcutaneously (20 μg/mouse) 2 h prior to DSS induction in mice of the poly I:C group. Severity of colitis was evaluated by disease activity index, body weight, colon length, histology and myeloperoxidase (MPO) activity, as well as the production of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin 17 (IL-17) and interferon-γ (IFN-γ). Intestinal permeability was analyzed by the fluorescein isothiocyanate labeled-dextran (FITC-D) method. Ultrastructural features of the colon tissue were observed under electron microscopy. Expressions of tight junction (TJ) proteins, including zo-1, occludin and claudin-1, were measured by immunohistochemistry/immunofluorescence, Western blot and real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

DSS caused significant damage to the colon tissue in the model group. Administration of poly I:C dramatically protected against DSS-induced colitis, as demonstrated by less body weight loss, lower disease activity index score, longer colon length, colonic MPO activity, and improved macroscopic and histological scores. It also ameliorated DSS-induced ultrastructural changes of the colon epithelium, as observed under scanning electron microscopy, as well as FITC-D permeability. The mRNA and protein expressions of TJ protein, zo-1, occludin and claudin-1 were also found to be significantly enhanced in the poly I:C group, as determined by immunohistochemistry/immunofluorescence, Western blot and RT-qPCR. By contrast, poly I:C pretreatment markedly reversed the DSS-induced up-regulated expressions of the inflammatory cytokines TNF-α, IL-17 and IFN-γ.

CONCLUSION

Our study suggested that poly I:C may protect against DSS-induced colitis through maintaining integrity of the epithelial barrier and regulating innate immune responses, which may shed light on the therapeutic potential of poly I:C in human colitis.

Measurement of Cellular Behavior by Electrochemical Impedance Sensing

There is a great demand for label-free in vitro assays in a high-throughput context, in order to measure cell viability and analyze cellular functions like cell migration or cell differentiation under noninvasive conditions. Here, we describe impedance measurement to quantify dynamic changes on cell morphology in real time. In order to monitor physiological changes, cells are grown in tissue culture vessels where gold electrodes are incorporated at the bottom. An alternating current signal of several kHz is applied to the electrodes and the resulting voltage is measured to calculate the cellular impedance. Since impedance is closely related to the area of the electrodes covered by the growing cells, parameters such as cell number, size of the cells attached to the electrodes, and cell-cell and cell-substrate/extracellular matrix interactions contribute to the overall impedance values.

IL-17 Promotes Neutrophil-Mediated Immunity by Activating Microvascular Pericytes and Not Endothelium

A classical hallmark of acute inflammation is neutrophil infiltration of tissues, a multistep process that involves sequential cell-cell interactions of circulating leukocytes with IL-1- or TNF-activated microvascular endothelial cells (ECs) and pericytes (PCs) that form the wall of the postcapillary venules. The initial infiltrating cells accumulate perivascularly in close proximity to PCs. IL-17, a proinflammatory cytokine that acts on target cells via a heterodimeric receptor formed by IL-17RA and IL-17RC subunits, also promotes neutrophilic inflammation but its effects on vascular cells are less clear. We report that both cultured human ECs and PCs strongly express IL-17RC and, although neither cell type expresses much IL-17RA, PCs express significantly more than ECs. IL-17, alone or synergistically with TNF, significantly alters inflammatory gene expression in cultured human PCs but not ECs. RNA sequencing analysis identifies many IL-17-induced transcripts in PCs encoding proteins known to stimulate neutrophil-mediated immunity. Conditioned media from IL-17-activated PCs, but not ECs, induce pertussis toxin-sensitive neutrophil polarization, likely mediated by PC-secreted chemokines, and they also stimulate neutrophil production of proinflammatory molecules, including TNF, IL-1α, IL-1β, and IL-8. Furthermore, IL-17-activated PCs, but not ECs, can prolong neutrophil survival by producing G-CSF and GM-CSF, delaying the mitochondrial outer membrane permeabilization and caspase-9 activation. Importantly, neutrophils exhibit enhanced phagocytic capacity after activation by conditioned media from IL-17-treated PCs. We conclude that PCs, not ECs, are the major target of IL-17 within the microvessel wall and that IL-17-activated PCs can modulate neutrophil functions within the perivascular tissue space.