Roles of Rho/ROCK and MLCK in TNF-alpha-induced changes in endothelial morphology and permeability

Hopping the Hurdle: Strategies to Enhance the Molecular Delivery to the Brain through the Blood-Brain Barrier

Modern medicine has allowed for many advances in neurological and neurodegenerative disease (ND). However, the number of patients suffering from brain diseases is ever increasing and the treatment of brain diseases remains an issue, as drug efficacy is dramatically reduced due to the existence of the unique vascular structure, namely the blood-brain barrier (BBB). Several approaches to enhance drug delivery to the brain have been investigated but many have proven to be unsuccessful due to limited transport or damage induced in the BBB. Alternative approaches to enhance molecular delivery to the brain have been revealed in recent studies through the existence of molecular delivery pathways that regulate the passage of peripheral molecules. In this review, we present recent advancements of the basic research for these delivery pathways as well as examples of promising ventures to overcome the molecular hurdles that will enhance therapeutic interventions in the brain and potentially save the lives of millions of patients.

Effects of hazelnut protein isolate-induced food allergy on the gut microenvironment in a BALB/c mouse model

Hazelnuts are reported as among the nuts that cause severe allergic reactions. However, few systematic studies exist on the changes in the gut microenvironment following hazelnut allergy. This study focused on the effects of hazelnut allergy on the duodenum, jejunum, ileum and colon microenvironment in vivo. We established a hazelnut protein isolate (HPI)-allergic mouse model, which was distinguished by the visible allergy symptoms, dropped temperatures and enhanced allergic inflammatory factor levels in serum, such as HPI-specific immunoglobulin E (sIgE), sIgG2a, interleukin-4, histamine, mouse mast cell protease-1, TNF-α, monocyte chemotactic protein-1 and lipopolysaccharide. For HPI sensitized mice, aggravated mast cell degranulation, severe morphologic damage and inflammatory cell infiltration were observed in the duodenum, jejunum, ileum, and colon, while goblet cell numbers were reduced in the duodenum, jejunum and ileum. Secretory IgA of the jejunum and tight junctions of the duodenum and jejunum were decreased significantly after HPI sensitization. There was no remarkable difference in the pH values of small intestinal contents, but the pH values of colonic contents were elevated, which was due to the decreased short-chain fatty acids (mainly acetate, propionate and butyrate) in the colon. The antioxidant capacity of both large and small intestinal contents declined after HPI sensitization, as evidenced by the increased malondialdehyde and decreased superoxide dismutase activity. HPI sensitization induced gut microbiota dysbiosis with decreased α diversity and altered β diversity in colonic contents. Spearman correlation analysis indicated that the increased characteristic genera, namely Bacteroides, Lactobacillus, Alloprevotella, Erysipelatoclostridium, Parabacteroides, and Helicobacter, played potentially synergistic roles in promoting allergy and gut microenvironment dysregulation.

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.

Junctional integrity and directional mobility of lymphatic endothelial cell monolayers are disrupted by saturated fatty acids

The lymphatic circulation regulates transfer of tissue fluid and immune cells toward the venous circulation. While obesity impairs lymphatic vessel function, the contribution of lymphatic endothelial cells (LEC) to metabolic disease phenotypes is poorly understood. LEC of lymphatic microvessels are in direct contact with the interstitial fluid, whose composition changes during the development of obesity, markedly by increases in saturated fatty acids. Palmitate, the most prevalent saturated fatty acid in lymph and blood, is detrimental to metabolism and function of diverse tissues, but its impact on LEC function is relatively unknown. Here, palmitate (but not its unsaturated counterpart palmitoleate) destabilized adherens junctions in human microvascular LEC in culture, visualized as changes in VE-cadherin, α-catenin, and β-catenin localization. Detachment of these proteins from cortical actin filaments was associated with abundant actomyosin stress fibers. The effects were Rho-associated protein kinase (ROCK)- and myosin-dependent, as inhibition with Y27632 or blebbistatin, respectively, prevented stress fiber accumulation and preserved junctions. Without functional junctions, palmitate-treated LEC failed to directionally migrate to close wounds in two dimensions and failed to form endothelial tubes in three dimensions. A reorganization of the lymphatic endothelial actin cytoskeleton may contribute to lymphatic dysfunction in obesity and could be considered as a therapeutic target.

"Non-cytotoxic" doses of metal-organic framework nanoparticles increase endothelial permeability by inducing actin reorganization

Cytotoxicity of nanoparticles is routinely characterized by biochemical assays such as cell viability and membrane integrity assays. However, these approaches overlook cellular biophysical properties including changes in the actin cytoskeleton, cell stiffness, and cell morphology, particularly when cells are exposed to "non-cytotoxic" doses of nanoparticles. Zeolitic imidazolate framework-8 nanoparticles (ZIF-8 NPs), a member of metal-organic framework family, has received increasing interest in various fields such as environmental and biomedical sciences. ZIF-8 NPs may enter the blood circulation system after unintended oral and inhalational exposure or intended intravenous injection for diagnostic and therapeutic applications, yet the effect of ZIF-8 NPs on vascular endothelial cells is not well understood. Here, the biophysical impact of "non-cytotoxic" dose ZIF-8 NPs on human aortic endothelial cells (HAECs) is investigated. We demonstrate that "non-cytotoxic" doses of ZIF-8 NPs, pre-defined by a series of biochemical assays, can increase the endothelial permeability of HAEC monolayers by causing cell junction disruption and intercellular gap formation, which can be attributed to actin reorganization within adjacent HAECs. Nanomechanical atomic force microscopy and super resolution fluorescence microscopy further confirm that "non-cytotoxic" doses of ZIF-8 NPs change the actin structure and cell morphology of HAECs at the single cell level. Finally, the underlying mechanism of actin reorganization induced by the "non-cytotoxic" dose ZIF-8 NPs is elucidated. Together, this study indicates that the "non-cytotoxic" doses of ZIF-8 NPs, intentionally or unintentionally introduced into blood circulation, may still pose a threat to human health, considering increased endothelial permeability is essential to the progression of a variety of diseases. From a broad view of cytotoxicity evaluation, it is important to consider the biophysical properties of cells, since they can serve as novel and more sensitive markers to assess nanomaterial's cytotoxicity.

Endothelial progenitor cells in the host defense response

Extensive injury of endothelial cells in blood vasculature, especially in the microcirculatory system, frequently occurs in hosts suffering from sepsis and the accompanied systemic inflammation. Pathological factors, including toxic components derived from invading microbes, oxidative stress associated with tissue ischemia/reperfusion, and vessel active mediators generated during the inflammatory response, are known to play important roles in mediating endothelial injury. Collapse of microcirculation and tissue edema developed from the failure of endothelial barrier function in vital organ systems, including the lung, brain, and kidney, are detrimental, which often predict fatal outcomes. The host body possesses a substantial capacity for maintaining vascular homeostasis and repairing endothelial damage. Bone marrow and vascular wall niches house endothelial progenitor cells (EPCs). In response to septic challenges, EPCs in their niche environment are rapidly activated for proliferation and angiogenic differentiation. In the meantime, release of EPCs from their niches into the blood stream and homing of these vascular precursors to tissue sites of injury are markedly increased. The recruited EPCs actively participate in host defense against endothelial injury and repair of damage in blood vasculature via direct differentiation into endothelial cells for re-endothelialization as well as production of vessel active mediators to exert paracrine and autocrine effects on angiogenesis/vasculogenesis. In recent years, investigations on significance of EPCs in host defense and molecular signaling mechanisms underlying regulation of the EPC response have achieved substantial progress, which promotes exploration of vascular precursor cell-based approaches for effective prevention and treatment of sepsis-induced vascular injury as well as vital organ system failure.

TNF-α and IL-1β Modulate Blood-Brain Barrier Permeability and Decrease Amyloid-β Peptide Efflux in a Human Blood-Brain Barrier Model

The blood-brain barrier (BBB) is a selective barrier and a functional gatekeeper for the central nervous system (CNS), essential for maintaining brain homeostasis. The BBB is composed of specialized brain endothelial cells (BECs) lining the brain capillaries. The tight junctions formed by BECs regulate paracellular transport, whereas transcellular transport is regulated by specialized transporters, pumps and receptors. Cytokine-induced neuroinflammation, such as the tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), appear to play a role in BBB dysfunction and contribute to the progression of Alzheimer’s disease (AD) by contributing to amyloid-β (Aβ) peptide accumulation. Here, we investigated whether TNF-α and IL-1β modulate the permeability of the BBB and alter Aβ peptide transport across BECs. We used a human BBB in vitro model based on the use of brain-like endothelial cells (BLECs) obtained from endothelial cells derived from CD34+ stem cells cocultivated with brain pericytes. We demonstrated that TNF-α and IL-1β differentially induced changes in BLECs’ permeability by inducing alterations in the organization of junctional complexes as well as in transcelluar trafficking. Further, TNF-α and IL-1β act directly on BLECs by decreasing LRP1 and BCRP protein expression as well as the specific efflux of Aβ peptide. These results provide mechanisms by which CNS inflammation might modulate BBB permeability and promote Aβ peptide accumulation. A future therapeutic intervention targeting vascular inflammation at the BBB may have the therapeutic potential to slow down the progression of AD.

In vivo dissection of Rhoa function in vascular development using zebrafish

The small monomeric GTPase RHOA acts as a master regulator of signal transduction cascades by activating effectors of cellular signaling, including the Rho-associated protein kinases ROCK1/2. Previous in vitro cell culture studies suggest that RHOA can regulate many critical aspects of vascular endothelial cell (EC) biology, including focal adhesion, stress fiber formation, and angiogenesis. However, the specific in vivo roles of RHOA during vascular development and homeostasis are still not well understood. In this study, we examine the in vivo functions of RHOA in regulating vascular development and integrity in zebrafish. We use zebrafish RHOA-ortholog (rhoaa) mutants, transgenic embryos expressing wild type, dominant negative, or constitutively active forms of rhoaa in ECs, pharmacological inhibitors of RHOA and ROCK1/2, and Rock1 and Rock2a/b dgRNP-injected zebrafish embryos to study the in vivo consequences of RHOA gain- and loss-of-function in the vascular endothelium. Our findings document roles for RHOA in vascular integrity, developmental angiogenesis, and vascular morphogenesis in vivo, showing that either too much or too little RHOA activity leads to vascular dysfunction.

Membrane curvature and PS localize coagulation proteins to filopodia and retraction fibers of endothelial cells

Prior reports indicate that the convex membrane curvature of phosphatidylserine (PS)-containing vesicles enhances formation of binding sites for factor Va and lactadherin. Yet, the relationship of convex curvature to localization of these proteins on cells remains unknown. We developed a membrane topology model, using phospholipid bilayers supported by nano-etched silica substrates, to further explore the relationship between curvature and localization of coagulation proteins. Ridge convexity corresponded to maximal curvature of physiologic membranes (radii of 10 or 30 nm) and the troughs had a variable concave curvature. The benchmark PS probe lactadherin exhibited strong differential binding to the ridges, on membranes with 4% to 15% PS. Factor Va, with a PS-binding motif homologous to lactadherin, also bound selectively to the ridges. Bound factor Va supported coincident binding of factor Xa, localizing prothrombinase complexes to the ridges. Endothelial cells responded to prothrombotic stressors and stimuli (staurosporine, tumor necrosis factor-α [TNF- α]) by retracting cell margins and forming filaments and filopodia. These had a high positive curvature similar to supported membrane ridges and selectively bound lactadherin. Likewise, the retraction filaments and filopodia bound factor Va and supported assembly of prothrombinase, whereas the cell body did not. The perfusion of plasma over TNF-α-stimulated endothelia in culture dishes and engineered 3-dimensional microvessels led to fibrin deposition at cell margins, inhibited by lactadherin, without clotting of bulk plasma. Our results indicate that stressed or stimulated endothelial cells support prothrombinase activity localized to convex topological features at cell margins. These findings may relate to perivascular fibrin deposition in sepsis and inflammation.

Human endothelial cells display a rapid tensional stress increase in response to tumor necrosis factor-α

Endothelial cells form the inner layer of blood vessels, making them the first barrier between the blood and interstitial tissues; thus endothelial cells play a crucial role in inflammation. In the inflammatory response, one important element is the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α). While other pro-inflammatory agents like thrombin and histamine induce acute but transient changes in endothelial cells, which have been well studied biologically as well as mechanically, TNF-α is primarily known for its sustained effects on permeability and leukocyte recruitment. These functions are associated with transcriptional changes that take place on the timescale of hours and days. Here, we investigated the early mechanical action of TNF-α and show that even just 4 min after TNF-α was added onto human umbilical vein endothelial cell monolayers, there was a striking rise in mechanical substrate traction force and internal monolayer tension. These traction forces act primarily at the boundary of the monolayer, as was to be expected. This increased internal monolayer tension may, in addition to TNF-α’s other well-studied biochemical responses, provide a mechanical signal for the cells to prepare to recruit leukocytes.

Brain-derived neurotrophic factor regulates LYN kinase-mediated myosin light chain kinase activation to modulate nonmuscle myosin II activity in hippocampal neurons

Myosins belong to a large superfamily of actin-dependent molecular motors. Nonmuscle myosin II (NM II) is involved in the morphology and function of neurons, but little is known about how NM II activity is regulated. Brain-derived neurotrophic factor (BDNF) is a prevalent neurotrophic factor in the brain that encourages growth and differentiation of neurons and synapses. In this study, we report that BDNF upregulates the phosphorylation of myosin regulatory light chain (MLC2), to increases the activity of NM II. The role of BDNF on modulating the phosphorylation of MLC2 was validated by using Western blotting in primary cultured hippocampal neurons. This result was confirmed by injecting BDNF into the dorsal hippocampus of mice and detecting the phosphorylation level of MLC2 by Western blotting. We further perform coimmunoprecipitation assay to confirm that this process depends on the activation of the LYN kinase through binding with tyrosine kinase receptor B, the receptor of BDNF, in a kinase activity-dependent manner. LYN kinase subsequently phosphorylates MLCK, further promoting the phosphorylation of MLC2. Taken together, our results suggest a new molecular mechanism by which BDNF regulates MLC2 activity, which provides a new perspective for further understanding the functional regulation of NM II in the nervous system.

Experimental Models to Study the Pathogenesis of Malaria-Associated Acute Respiratory Distress Syndrome

Malaria-associated acute respiratory distress syndrome (MA-ARDS) is increasingly gaining recognition as a severe malaria complication because of poor prognostic outcomes, high lethality rate, and limited therapeutic interventions. Unfortunately, invasive clinical studies are challenging to conduct and yields insufficient mechanistic insights. These limitations have led to the development of suitable MA-ARDS experimental mouse models. In patients and mice, MA-ARDS is characterized by edematous lung, along with marked infiltration of inflammatory cells and damage of the alveolar-capillary barriers. Although, the pathogenic pathways have yet to be fully understood, the use of different experimental mouse models is fundamental in the identification of mediators of pulmonary vascular damage. In this review, we discuss the current knowledge on endothelial activation, leukocyte recruitment, leukocyte induced-endothelial dysfunction, and other important findings, to better understand the pathogenesis pathways leading to endothelial pulmonary barrier lesions and increased vascular permeability. We also discuss how the advances in imaging techniques can contribute to a better understanding of the lung lesions induced during MA-ARDS, and how it could aid to monitor MA-ARDS severity.

STAT3-YAP/TAZ signaling in endothelial cells promotes tumor angiogenesis

[Figure: see text].

Effects of Dietary Zinc Sources on Growth Performance and Gut Health of Weaned Piglets

The present study aimed to investigate the effects of dietary zinc sources on the growth performance and gut health of weaned piglets. In total, 96 Duroc × Landrace × Yorkshire (DLY) weaned piglets with an initial average body weight of 8.81±0.42kg were divided into four groups, with six replicates per treatment and four pigs per replicate. The dietary treatment groups were as follows: (1) control group, basal diet; (2) zinc sulphate (ZnSO4) group, basal diet +100mg/kg ZnSO4; (3) glycine zinc (Gly-Zn) group, basal diet +100mg/kg Gly-Zn and (4) zinc lactate group, and basal diet +100mg/kg zinc lactate. The whole trial lasted for 28days. Decreased F/G was noted in the Gly-Zn and zinc lactate groups (p<0.05). The zinc lactate group had a lower diarrhea rate than the control group (p<0.05). Moreover, the ZnSO4, Gly-Zn, and zinc lactate groups had significantly higher apparent total tract digestibility of dry matter (DM), crude protein (CP), ether extract (EE), crude ash, and zinc than the control group (p<0.05). The Gly-Zn and zinc lactate groups had higher jejunal villus height and a higher villus height:crypt depth ratio than the control group (p<0.05). In addition, the ZnSO4, Gly-Zn and zinc lactate groups had a significantly lower mRNA expression level of jejunal ZRT/IRT-like protein 4 (ZIP4) and higher mRNA expression level of jejunal interleukin-1β (IL-1β) than the control group (p<0.05). The mRNA expression level of jejunal zinc transporter 2 (ZNT2) was higher and that of jejunal Bcl-2-associated X protein (Bax) was lower in the Gly-Zn and zinc lactate groups than in the control group (p<0.05). Moreover, the zinc lactate group had a higher count of Lactobacillus spp. in the cecal digesta and higher mRNA expression levels of jejunal occludin and mucin 2 (MUC2) than the control group (p<0.05). In conclusion, dietary supplementation with 100mg/kg ZnSO4, Gly-Zn, or zinc lactate could improve the growth performance and gut barrier function of weaned piglets. Dietary supplementation with organic zinc, particularly zinc lactate, had the best effect.

Endothelial Dysfunction through Oxidatively Generated Epigenetic Mark in Respiratory Viral Infections

The bronchial vascular endothelial network plays important roles in pulmonary pathology during respiratory viral infections, including respiratory syncytial virus (RSV), influenza A(H1N1) and importantly SARS-Cov-2. All of these infections can be severe and even lethal in patients with underlying risk factors.A major obstacle in disease prevention is the lack of appropriate efficacious vaccine(s) due to continuous changes in the encoding capacity of the viral genome, exuberant responsiveness of the host immune system and lack of effective antiviral drugs. Current management of these severe respiratory viral infections is limited to supportive clinical care. The primary cause of morbidity and mortality is respiratory failure, partially due to endothelial pulmonary complications, including edema. The latter is induced by the loss of alveolar epithelium integrity and by pathological changes in the endothelial vascular network that regulates blood flow, blood fluidity, exchange of fluids, electrolytes, various macromolecules and responses to signals triggered by oxygenation, and controls trafficking of leukocyte immune cells. This overview outlines the latest understanding of the implications of pulmonary vascular endothelium involvement in respiratory distress syndrome secondary to viral infections. In addition, the roles of infection-induced cytokines, growth factors, and epigenetic reprogramming in endothelial permeability, as well as emerging treatment options to decrease disease burden, are discussed.

Loss of Endothelial Barrier Function in the Inflammatory Setting: Indication for a Cytokine-Mediated Post-Transcriptional Mechanism by Virtue of Upregulation of miRNAs miR-29a-3p, miR-29b-3p, and miR-155-5p

Dysfunction of the endothelial barrier plays a central role in the pathogenesis of both acute and chronic inflammatory processes such as sepsis or atherosclerosis. Due to attenuation of endothelial cell contacts, there is an increased transfer of blood proteins and fluid into the surrounding tissue, which relates to edema formation and distribution disorders. However, the mechanisms underlying these responses are not fully understood. In this study, we used human endothelial cells to mimic the loss of barrier function in an inflammatory milieu. We found that a weakened endothelial barrier after cytokine stimulation was accompanied by a significantly changed transcriptome. Apparent was a depletion of mRNAs encoding cell adhesion molecules. Furthermore, we found that cytokine treatment of endothelial cells induced upregulation of miR-29a-3p, miR-29b-3p, and miR-155-5p. miRNAs are known to negatively affect stability and translational efficiency of target mRNAs. Remarkably, miR-29a-3p, miR-29b-3p, and miR-155-5p have already been described to target the mRNAs of central tight and adherent junction proteins including F11 receptor, claudin 1, β-catenin, p120-catenin, and eplin. This taken together points to the existence of a posttranscriptional mechanism for expression inhibition of central adhesion proteins, which is triggered by inflammatory cytokines and mediated by miR-29a-3p, miR-29b-3p, and miR-155-5p.

Effect of bound water content on cell adhesion strength to water-insoluble polymers

Adhesion of cells on biomaterials plays an essential role in modulating cellular functions. Although hydration of biomaterials occurs under biological conditions, it is challenging to systematically evaluate the correlation of hydrated water content in biomaterials with the cell adhesion strength. In this report, we investigated the effect of bound water content on the adhesion strength of cells on poly(2-methoxyethyl acrylate) (PMEA) analogue substrates. Water-insoluble PMEA analogues were synthesized to fabricate substrates with a systemically controlled bound water content. To assess the surface properties of their substrates, contact angle measurement, atomic force microscopy (AFM), and fluorescence measurement were conducted. To reflect the effect of bound water of PMEA analogues, the relationship between the bound water content and cell adhesion behavior was evaluated under serum-free condition. From the single cell force spectrometry (SCFS) and microscopic analysis, it revealed that the increment of bound water content on the substrates decreased cell adhesion strength and cell spreading on the substrates. The bound water content exhibited a good correlation with adhesion strength, spreading area, circularity, and aspect ratio of cells. Our findings indicate that the bound water content could contribute to the development of a novel biomaterial and evaluation of cell behaviors on biomaterials. STATEMENT OF SIGNIFICANCE: For coordinating cell functions, such as growth, mobility, and differentiation, modulating the adhesion strength between cells and their environments is important. Although the hydration to biomaterials has been reported to be closely related to a antifouling property, the effect of hydration water on the cell adhesion behavior is not well understood. We present the first demonstration of essential relationship between cell adhesion strength and hydrated water on a biomaterials surface using the water-insoluble polymers with different hydrated water content. The results reveal that the hydrated water content of polymer substrates strong correlation with adhesion strength of cells. Collectively, the hydrated water content of the biomaterials will be a predominant factor affecting the cell adhesion strength and behavior.

mTOR Inhibition Promotes Pneumonitis Through Inducing Endothelial Contraction and Hyperpermeability

Compromised endothelial (EC) barrier function is a hallmark of inflammatory diseases. Mammalian target of rapamycin (mTOR) inhibitors, widely applied as clinical therapies, cause pneumonitis through mechanisms not yet fully understood. This study aimed to elucidate the EC mechanisms underlying the pathogenesis of pneumonitis caused by mTOR inhibition (mTORi). Mice with EC-specific deletion of mTOR complex components (Mtor, Rptor or Rictor) were administered LPS to induce pulmonary injury. Cultured EC were treated with pharmacological inhibitors, small interfering RNA or overexpression-plasmids. EC barrier function was evaluated in vivo with Evan's blue assay and in vitro by measurement of transendothelial electrical resistance and albumin flux. mTORi increased basal and TNFα-induced EC permeability, which was caused by myosin light chain (MLC) phosphorylation-dependent cell contraction. Inactivation of mTOR kinase activity by mTORi triggered PKCδ/p38/NF-κB signaling that significantly upregulated TNFα-induced MLC kinase (MLCK) expression, while Raptor promoted the phosphorylation of PKCα/MYPT1 independent of its interaction with mTOR, leading to suppression of MLC phosphatase (MLCP) activity. EC-specific deficiency in mTOR, Raptor or Rictor aggravated lung inflammation in LPS-treated mice. These findings reveal that mTORi induces PKC-dependent endothelial MLC phosphorylation, contraction and hyperpermeability that promote pneumonitis.

Molecular Dambusters: What Is Behind Hyperpermeability in Bradykinin-Mediated Angioedema?

In the last few decades, a substantial body of evidence underlined the pivotal role of bradykinin in certain types of angioedema. The formation and breakdown of bradykinin has been studied thoroughly; however, numerous questions remained open regarding the triggering, course, and termination of angioedema attacks. Recently, it became clear that vascular endothelial cells have an integrative role in the regulation of vessel permeability. Apart from bradykinin, a great number of factors of different origin, structure, and mechanism of action are capable of modifying the integrity of vascular endothelium, and thus, may participate in the regulation of angioedema formation. Our aim in this review is to describe the most important permeability factors and the molecular mechanisms how they act on endothelial cells. Based on endothelial cell function, we also attempt to explain some of the challenging findings regarding bradykinin-mediated angioedema, where the function of bradykinin itself cannot account for the pathophysiology. By deciphering the complex scenario of vascular permeability regulation and edema formation, we may gain better scientific tools to be able to predict and treat not only bradykinin-mediated but other types of angioedema as well.

The Inflammation Network in the Pathogenesis of Erectile Dysfunction: Attractive Potential Therapeutic Targets

BACKGROUND

Erectile dysfunction (ED) is an evolving health problem in the aging male population. Chronic low-grade inflammation is a critical component of ED pathogenesis and a probable intermediate stage of endothelial dysfunction, especially in metabolic diseases, with the inclusion of obesity, metabolic syndrome, and diabetes.

OBJECTIVE

This review will present an overview of preclinical and clinical data regarding common inflammatory mechanisms involved in the pathogenesis of ED associated with metabolic diseases and the effect of antiinflammatory drugs on ED.

METHODS

A literature search of existing pre-clinical and clinical studies was performed on databases [Pubmed (MEDLINE), Scopus, and Embase] from January 2000 to October 2019.

RESULTS

Low-grade inflammation is a possible pathological role in endothelial dysfunction as a consequence of ED and other related metabolic diseases. Increased inflammation and endothelial/prothrombotic markers can be associated with the presence and degree of ED. Pharmacological therapy and modification of lifestyle and risk factors may have a significant role in the recovery of erectile response through reduction of inflammatory marker levels.

CONCLUSION

Inflammation is the least common denominator in the pathology of ED and metabolic disorders. The inflammatory process of ED includes a shift in the complex interactions of cytokines, chemokines, and adhesion molecules. These data have established that anti-inflammatory agents could be used as a therapeutic opportunity in the prevention and treatment of ED. Further research on inflammation-related mechanisms underlying ED and the effect of therapeutic strategies aimed at reducing inflammation is required for a better understanding of the pathogenesis and successful management of ED.

Effects of ROCK Inhibitors on Apoptosis of Corneal Endothelial Cells in CMV-Positive Posner-Schlossman Syndrome Patients

Purpose

To examine the role of aqueous tumor necrosis factor α (TNF-α)–RhoA–Rho kinase (ROCK) signaling in cytomegalovirus (CMV)-induced apoptosis and the barrier function of cultured human corneal endothelial cells (hCECs) in CMV-positive Posner–Schlossman syndrome (CMV+/PSS) patients.

Methods

Aqueous levels of TNF-α, IL-8, IL-10, and several other cytokines in 19 CMV+/PSS patients and 20 healthy control subjects were quantitated using a multiplex assay. The expression of active RhoA in hCECs post-CMV infection was determined using western blotting (WB). The expression levels of TNF-α and nuclear factor kappa B (NF-κB) in CMV-infected hCECs were examined by immunocytochemistry (ICC) and WB with and without ROCK inhibitors. The apoptotic rate and barrier integrity in CMV-infected hCECs were also examined.

Results

The expression levels of TNF-α, monocyte chemoattractant protein-1 (MCP-1), IL-8, and IL-10 were upregulated in the aqueous humor of CMV+/PSS patients, and among these upregulated cytokines aqueous TNF-α was negatively correlated with the number of corneal endothelial cells. In CMV-infected hCECs, upregulation of TNF-α and NF-κB was determined by WB and ICC. In hCECs, CMV infection induced apoptosis and significantly impaired cell–cell contacts, effects that were attenuated by treatment with a ROCK inhibitor.

Conclusions

Aqueous TNF-α was upregulated in CMV+/PSS patients, which may have triggered corneal endothelial cell loss. Modulation of TNF-α, including its downstream Rho–ROCK signaling, could serve as a novel treatment modality for corneal endothelial cell loss in CMV+/PSS patients.

Significance of vagus nerve function in terms of pathogenesis of psychosocial disorders

The vagus nerve (VN) belongs to the parasympathetic nervous system, which is well known to be involved in the regulation of the functions of organs in the body. The neurotransmitter acetylcholine, released from the cholinergic system including VN, has been known to play an anti-inflammatory role through the efferent pathways in regulating peripheral inflammatory responses profoundly involved in the pathogenesis of diseases. In contrast, anatomically, it connects the central nervous system (CNS) and peripheral organs, including the heart and gastrointestinal (GI) tract. Therefore, it has been recently reported that the VN also plays an important role in the pathogenesis of psychological disorders since it confers varied signals from the GI tract to the CNS, and alteration of microbiota residing in GI definitely influences the condition of neuropsychiatric disorders. Furthermore, the CNS includes microglia, a neuroinflammatory effector in the brain, which is also influenced by the VN to modulate its inflammatory status. Based on significant findings of the VN, the VN stimulation (VNS) has recently drawn attention from many scientific fields. VNS was initially applied to patients with refractory epilepsy, followed by patients with refractory depression. Subsequently, VNS was also attempted to be introduced to other diseases. However, against whichever disease, central or peripheral, detailed underlying mechanisms of VNS involved in neuropsychiatric disorders as well as VNS target molecules in the GI tract and the CNS remains to be studied. In this review, we discuss the mechanisms and predicted responsible factors of VNS in terms of neuropsychiatric disorders.

Towards the development of a human in vitro model of the blood-brain barrier for virus-associated acute encephalopathy: assessment of the time- and concentration-dependent effects of TNF-α on paracellular tightness

The pathogenesis of virus-associated acute encephalopathy (VAE) involves brain edema caused by disruption of the blood-brain barrier (BBB). We aimed to develop an in vitro VAE model using an in vitro BBB model, to evaluate the dynamics of vascular dysfunction caused by tumor necrosis factor (TNF)-α. A co-culture model, consisting of Transwell®-grown human brain microvascular endothelial cells and pericytes, was treated with serially diluted TNF-α. Transendothelial electrical resistance (TER) was measured using cellZscope®. A permeability assay, using fluorescein isothiocyanate-conjugated sodium or dextran, was performed. Changes in claudin-5 localization and expression after TNF-α treatment were observed using immunofluorescence staining and western blot analysis. The TER decreased and permeability increased after TNF-α treatment; recovery time was dependent on TNF-α concentration. Claudin-5 was delocalized after TNF-α treatment and recovered in a TNF-α concentration-dependent manner. The expression of claudin-5 decreased 24 h after the TNF-α treatment and completely recovered 48 h after TNF-α treatment. Claudin-5 delocalization was likely associated with vascular hyperpermeability. To conclude, we evaluated vascular endothelial cell permeability and injury in VAE using an in vitro BBB model treated with TNF-α. This system can be useful for developing novel therapeutic strategies for VAE and designing treatments that target vascular permeability.

Myosin light chain kinase mediates intestinal barrier dysfunction following simulated microgravity based on proteomic strategy

Microgravity induces injury of intestinal barrier. However, the underlying mechanism remains unclear. The present study aimed to investigate the pathological change of intestinal mucosa induced by long term simulated microgravity and to explore its etiological mechanism using a proteomic approach. The well accepted tail-suspended rat model was used to simulate microgravity. The damage of rat small intestine was evaluated via histological and molecular test, and a label-free comparative proteomic strategy was used to determine the molecular mechanism. Simulated microgravity for 21 days damaged intestine barrier with decreased numbers of the goblet cells, large intercellular space, and down-regulated adhesion molecules, accompanied by increased intestinal permeability. Proteomic analysis identified 416 differentially expressed proteins and showed simulated microgravity dramatically down-regulated the adhesion molecules and deteriorated several pathways for metabolism, focal adhesion, and regulation of actin cytoskeleton. Western-blot analysis confirmed that myosin regulatory light chain (MLC) 12B was significantly down-regulated, while rho-associated protein kinase, myosin light chain kinase (MLCK), and phosphorylated MLC were dramatically up-regulated. Taken together, these data reveal that down-regulation of adhesion molecules and MLCK dependent up-regulation MLC phosphorylation mediate intestinal barrier dysfunction during simulated microgravity injury. Our results also indicate that regulation of epithelial MLCK is a potential target for the therapeutic treatment of microgravity injury.

Occludin regulation of blood-brain barrier and potential therapeutic target in ischemic stroke

Occludin is a key structural component of the blood–brain barrier (BBB) that has recently become an important focus of research in BBB damages. Many studies have demonstrated that occludin could regulate the integrity and permeability of the BBB. The function of BBB depends on the level of occludin protein expression in brain endothelial cells. Moreover, occludin may serve as a potential biomarker for hemorrhage transformation after acute ischemic stroke. In this review, we summarize the role of occludin in BBB integrity and the regulatory mechanisms of occludin in the permeability of BBB after ischemic stroke. Multiple factors have been found to regulate occludin protein functions in maintaining BBB permeability, such as Matrix metalloproteinas-mediated cleavage, phosphorylation, ubiquitination, and related inflammatory factors. In addition, various signaling pathways participate in regulating the occludin expression, including nuclear factor-kappa B, mitogen-activated protein kinase, protein kinase c, RhoK, and ERK1/2. Emerging therapeutic interventions for ischemic stroke targeting occludin are described, including normobaric hyperoxia, Chinese medicine, chemical drugs, genes, steroid hormones, small molecular peptides, and other therapies. Since occludin has been shown to play a critical role in regulating BBB integrity, further preclinical studies will help evaluate and validate occludin as a viable therapeutic target for ischemic stroke.

The vascular endothelium: the cornerstone of organ dysfunction in severe SARS-CoV-2 infection

In severe SARS-CoV-2 infections, emerging data including recent histopathological studies have emphasized the crucial role of endothelial cells (ECs) in vascular dysfunction, immunothrombosis, and inflammation.Histopathological studies have evidenced direct viral infection of ECs, endotheliitis with diffuse endothelial inflammation, and micro- and macrovascular thrombosis both in the venous and arterial circulations. Venous thrombotic events, particularly pulmonary embolism, with elevated D-dimer and coagulation activation are highly prevalent in COVID-19 patients. The pro-inflammatory cytokine storm, with elevated levels of interleukin-6 (IL-6), IL-2 receptor, and tumor necrosis factor-α, could also participate in endothelial dysfunction and leukocyte recruitment in the microvasculature. COVID-19-induced endotheliitis may explain the systemic impaired microcirculatory function in different organs in COVID-19 patients. Ongoing trials directly and indirectly target COVID-19-related endothelial dysfunctions: i.e., a virus-cell entry using recombinant angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS-2) blockade, coagulation activation, and immunomodulatory therapies, such as anti-IL-6 strategies. Studies focusing on endothelial dysfunction in COVID-19 patients are warranted as to decipher their precise role in severe SARS-CoV-2 infection and organ dysfunction and to identify targets for further interventions.

CX3CL1 Induces Vertebral Microvascular Barrier Dysfunction via the Src/P115-RhoGEF/ROCK Signaling Pathway

Trans-endothelial migration (TEM) of cancer cells is a critical step in metastasis. Micro-vascular barrier disruptions of distant organs play important roles in tumor cells TEM. The spine is a preferred site for multiple cancer cell metastases. Our previous study found that vertebral spongy bone was rich in CX3CL1 and that CX3CL1 can attract fractalkine receptor-expressing tumor cells to the spine. In the present study, we determined whether CX3CL1 was involved in vertebral micro-vascular barrier disruption and promoted tumor cell TEM after circulating tumor cells were arrested in the vertebral micro-vasculature. We examined the role of CX3CL1 in the barrier function of vertebral micro-vascular endothelial cells (VMECs) and explored the molecular mechanisms of CX3CL1-induced VMEC barrier disruption. Our results demonstrated that CX3CL1 led to F-actin formation and ZO-1 disruption in VMECs and induced the vertebral micro-vascular barrier disruption. Importantly, we found that the activation of the Src/P115-RhoGEF/ROCK signaling pathway plays an important role in CX3CL1-induced VMEC stress fiber formation, ZO-1 disruption and then vertebral micro-vascular barrier hyper-permeability. Inhibiting Src/P115-RhoGEF/ROCK signaling in VMECs effectively blocked CX3CL1-induced vertebral vascular endothelial dysfunction and subsequent tumor cell TEM. The results of this study and our previous study indicate that in addition to its chemotaxis, CX3CL1 plays a critical role in regulating vertebral micro-vascular barrier function and tumor cell TEM. CX3CL1 induced VMECs stress fiber formation, ZO-1 disruption and then vascular endothelial hyperpermeability via activation of the Src/P115-RhoGEF/ROCK signaling pathway. The inhibition of the Src/P115-RhoGEF/ROCK signaling pathway in VMECs effectively blocked tumor cells TEMs in vertebral spongy bone and maybe a potential therapeutic strategy for spine metastases in the future.

miR-144-mediated Inhibition of ROCK1 Protects against LPS-induced Lung Endothelial Hyperpermeability

Dysfunctional endothelial cell (EC) barrier and increased lung vascular permeability is a cardinal feature of acute lung injury and sepsis that may result in a pathophysiological condition characterized by alveolar flooding, pulmonary edema, and subsequent hypoxemia. In lung ECs, activation of Rho-associated kinase-1 (ROCK1) phosphorylates myosin light chain (MLC)-associated phosphatase at its inhibitory site, which favors phosphorylation of MLC, stress fiber formation, and hyperpermeability during acute lung injury. The role of microRNA-144 (miR-144) has been well investigated in many human diseases, including cardiac ischemia/reperfusion-induced injury, lung cancer, and lung viral infection; however, its role in pulmonary EC barrier regulation remains obscure. Here, we investigated the miR-144-mediated mechanism in the protection of endothelial barrier function in an LPS-induced lung injury model. By using transendothelial electrical resistance and transwell permeability assay to examine in vitro permeability and immunofluorescence microscopy to determine barrier integrity, we showed that ectopic expression of miR-144 effectively blocked lung EC barrier disruption and hyperpermeability in response to proinflammatory agents. Furthermore, using a gain-and-loss-of-function strategy, overexpression of miR-144 significantly decreased ROCK1 expression. Concomitantly, miR-144 inhibits ROCK1-mediated phosphorylation of MLC phosphatase^Thr853 and thus phosphorylation of MLC^Thr18/Ser19 to counteract stress fiber formation in LPS-activated EC. Finally, in LPS-challenged mice, intranasal delivery of miR-144 mimic via liposomes attenuated endotoxemia-induced increases in lung wet/dry ratio, vascular permeability, and inflammation. In conclusion, these data suggest that miR-144-attenuated activation of inflammatory ROCK1/MLC pathway in vascular ECs is a promising therapeutic strategy to counter inflammatory lung injury.

Immune Consequences of Endothelial Cells' Activation and Dysfunction During Sepsis

The vascular endothelium provides a direct interface between circulating blood cells and parenchymal cells. Thus, it has a key role in vasomotor tone regulation, primary hemostasis, vascular barrier, and immunity. In the case of systemic inflammation, endothelial cell (EC) activation initiates a powerful innate immune response to eliminate the pathogen. In some specific conditions, ECs may also contribute to the activation of adaptive immunity and the recruitment of antigen-specific lymphocytes. However, the loss of EC functions or an exaggerated activation of ECs during sepsis can lead to multiorgan failure.

Cerebral Cavernous Malformation Proteins in Barrier Maintenance and Regulation

Cerebral cavernous malformation (CCM) is a disease characterized by mulberry shaped clusters of dilated microvessels, primarily in the central nervous system. Such lesions can cause seizures, headaches, and stroke from brain bleeding. Loss-of-function germline and somatic mutations of a group of genes, called CCM genes, have been attributed to disease pathogenesis. In this review, we discuss the impact of CCM gene encoded proteins on cellular signaling, barrier function of endothelium and epithelium, and their contribution to CCM and potentially other diseases.

Egr1 Knockdown Combined with an ACE Inhibitor Ameliorates Diabetic Kidney Disease in Mice: Blockade of Compensatory Renin Increase

BACKGROUND

Increased compensatory intrarenal renin diminishes the efficacy of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in the treatment of diabetic kidney disease (DKD). Early growth response-1 (Egr1) is a crucial transcriptional factor in the progress of DKD and is a potential transcription factor of intrarenal renin according to bioinformatic analysis. However, whether inhibition of Egr1 can suppress compensatory renin increase in DKD is unclear.

METHODS

We generated a high-fat diet (HFD)/streptozotocin (STZ)-induced diabetic mouse model. The mice were treated with either enalapril (an ACEI) or enalapril combined with a shEgr1 plasmid, and age-matched DKD mice were used as controls. Urine microalbumin, urinary renin and kidney TGF-β1 were determined by enzyme-linked immunosorbent assay (ELISA). Hematoxylin and eosin (H&E) and Masson staining were used to determine renal pathological changes. Egr1, renin, TNF-α, and FN were measured by real-time quantitative PCR, Western blot, and immunohistochemistry. The SV40-MES13 murine mesangial cell line was transfected with pENTER-Egr1 plasmid and siEgr1.

RESULTS

Our results showed that enalapril increased the renin level of urinary and renal in DKD mice, while shEgr1 attenuated this effect. In addition, enalapril treatment reduced the levels of urinary microalbumin, TNF-α, TGF-β1 and FN, and alleviated the pathological changes, while shEgr1 strengthened these effects. The protein and mRNA expression of renin in the SV40 MES13 cells was upregulated and downregulated following overexpression and silence of Egr1, respectively.

CONCLUSION

Silence of Egr1 could alleviate renal injury in DKD by downregulating intrarenal renin.

Endothelial tight junctions and their regulatory signaling pathways in vascular homeostasis and disease

Endothelial tight junctions (TJs) regulate the transport of water, ions, and molecules through the paracellular pathway, serving as an important barrier in blood vessels and maintaining vascular homeostasis. In endothelial cells (ECs), TJs are highly dynamic structures that respond to multiple external stimuli and pathological conditions. Alterations in the expression, distribution, and structure of endothelial TJs may lead to many related vascular diseases and pathologies. In this review, we provide an overview of the assessment methods used to evaluate endothelial TJ barrier function both in vitro and in vivo and describe the composition of endothelial TJs in diverse vascular systems and ECs. More importantly, the direct phosphorylation and dephosphorylation of TJ proteins by intracellular kinases and phosphatases, as well as the signaling pathways involved in the regulation of TJs, including and the protein kinase C (PKC), PKA, PKG, Ras homolog gene family member A (RhoA), mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K)/Akt, and Wnt/β-catenin pathways, are discussed. With great advances in this area, targeting endothelial TJs may provide novel treatment for TJ-related vascular pathologies.

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.

Ursolic Acid Improves Intestinal Damage and Bacterial Dysbiosis in Liver Fibrosis Mice

Liver fibrosis is a reversible process of extracellular matrix deposition or scar formation after liver injury. Intestinal damage and bacterial dysbiosis are important concomitant intestinal changes in liver fibrosis and may in turn accelerate the progression of liver fibrosis through the gut-liver axis. RhoA, an important factor in the regulation of the cytoskeleton, plays an important role in intestinal damage. We investigated the effects of ursolic acid (UA), a traditional Chinese medicine with anti-fibrotic effects, on intestinal damage and bacterial disorder through the RhoA pathway. UA treatment reduced intestinal damage by inhibiting the inflammatory factor TNF-α and increasing the expression of tight junction proteins and antibacterial peptides to protect the intestinal barrier. Moreover, the corrective effect of UA on bacterial dysbiosis was also confirmed by sequencing of the 16S rRNA gene. Potential beneficial bacteria, such as the phylum Firmicutes and the genera Lactobacillus and Bifidobacterium, were increased in the UA group compared to the CCl₄ group. In liver fibrosis mice with RhoA inhibition via injection of adeno-associated virus, the liver fibrosis, intestinal damage, and flora disturbances were improved. Moreover, UA inhibited the expression of RhoA pathway components. In conclusion, UA improves intestinal damage and bacterial dysbiosis partly via the RhoA pathway. This may be a potential mechanism by which UA exerts its anti-fibrotic effects and provides effective theoretical support for the future use of UA in clinical practice.

Functional inhibition of F11 receptor (F11R/junctional adhesion molecule-A/JAM-A) activity by a F11R-derived peptide in breast cancer and its microenvironment

Purpose

To examine the involvement of the F11R/JAM-A protein in breast cancer metastasis, we utilized the F11R/JAM-A antagonistic peptide 4D (P4D) in experiments of transendothelial migration (TEM) of breast cancer cells.

Methods

Experiments were conducted in the mouse 4T1 breast cancer model utilizing the human mammary epithelial cell and endothelial cell lines. The levels of soluble F11R/JAM-A (sJAM-A) in the murine plasmas were measured by ELISA. Levels of F11R/JAM-A mRNA and protein in cell lines were assessed by qRT-PCR and Western blot, respectively. Cell surface expression of F11R/JAM-A was demonstrated by flow cytometry. Functional tests included the TEM of breast cancer cells and adhesion of breast cancer cells to the endothelium. The endothelial permeability was studied by fluorescent tracer assay and by the Real-Time Cell Analysis (RTCA).

Results

The tumor inducers Tβ4 and TGF-β1 reduced the levels of sJAM-A in murine plasma, and reduced the F11R/JAM-A protein levels in the human microvascular endothelial cell line HMEC-1. The adhesion and TEM measured between breast cancer cells and inflamed or Tβ4-treated endothelium were inhibited by P4D. The presence of P4D did not destabilize the pre-existing tight junctions in the endothelial monolayer. The barrier-protecting effect of P4D was stronger than that of forskolin, when a booster dose of P4D was applied to the inflamed endothelium.

Conclusions

F11R/JAM-A protein can be considered as a novel target in the treatment of breast cancer metastasis. In vivo and clinical studies are needed to further investigate the effectiveness of F11R/JAM-A-derived peptide as a possible anti-metastatic drug.

Electronic supplementary material

The online version of this article (10.1007/s10549-019-05471-x) contains supplementary material, which is available to authorized users.

The E3 Ubiquitin Ligase MARCH8 Regulates TNF-α-Induced Apoptosis in Hippocampal Neurons by Targeting Myosin Light Chain 2 for Degradation

Tumor necrosis factor-α (TNF-α) is an important inflammatory cytokine that plays a key role in neuronal damage. Elevated expression of TNF-α is associated with numerous neurodegenerative diseases including Alzheimer's Disease and Parkinson's Disease. However, the specific mechanism of the signaling events that trigger TNF-α-mediated neurotoxicity remain unknown. In this study, we report that intracerebroventricular injection of TNF-α in rat hippocampal neurons down-regulates MLC2 and up-regulates MARCH8, an essential light chain and regulatory myosin light chain of NM Myosin II, respectively. MARCH8 overexpression attenuates the degradation of MLC2 by promoting its ubiquitination and degradation. Inhibition of MARCH8 by siRNA blocks caspase-3 activation and apoptosis signaling, suggesting that TNF-α-induced apoptosis of neurons is partially dependent on the accumulation of MARCH8 and the ubiquitination of MLC2. Taken together, our data not only clarify the function of MARCH8 in TNF-α-induced neurotoxicity, but also demonstrates that TNF-α promotes the MARCH8-MLC2 mediated apoptosis of hippocampal neurons. Anat Rec, 302:2271-2278, 2019. © 2019 American Association for Anatomy.

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.

TNF-α promotes human antibody-mediated complement-dependent cytotoxicity of porcine endothelial cells through downregulating P38-mediated Occludin expression

Background

The major limitation of organ transplantation is the shortage of available organs. Xenotransplantation is considered to be an effective way to resolve the problem. Immune rejection is a major hurdle for the successful survival of pig xenografts in primate recipients. Cytokines play important roles in inflammation and many diseases including allotransplantation, however, their roles in xenotransplantation have been less well investigated.

Methods

We assessed the role of several cytokines in xenotransplantation using an in vitro model of human antibody-mediated complement-dependent cytotoxicity (CDC). Porcine aortic endothelial cells (PAECs) and porcine iliac endothelial cells (PIECs) were selected as target cells. The complement regulators (CD46, CD55 and CD59) and junction protein genes were assessed by real-time PCR, flow cytometry, or western-blotting assay. Flow cytometry assay was also used to evaluate C3 and C5b-9 deposition, as well as the extent of human IgM and IgG binding to PIECs. Gene silencing was used to reduce genes expression in PIECs. Gene overexpression was mediated by adenovirus or retrovirus.

Results

Recombinant human TNF-α increased the cytotoxicity of PAECs and PIECs in a human antibody-mediated CDC model. Unexpectedly, we found that the expression of complement regulators (CD46, CD55 and CD59) increased in PIECs exposed to human TNF-α. Human TNF-α did not modify C3 or C5b-9 deposition on PIECs. The extent of human IgM and IgG binding to PIECs was not affected by human TNF-α. Human TNF-α decreased the expression of Occludin in PIECs. Gene silencing and overexpression assay suggested that Occludin was required for human TNF-α-mediated cytotoxicity of PIECs in this model. P38 gene silencing or inhibition of P38 signaling pathway with a specific inhibitor, SB203580, inhibited the reduction of Occludin expression induced by TNF-α, and suppressed TNF-α-augmented cytotoxicity of PIECs.

Conclusion

Our data suggest that human TNF-α increases the cytotoxicity of porcine endothelial cells in a human antibody-mediated CDC model by downregulating P38-dependent Occludin expression. Pharmacologic blockade of TNF-α is likely to increase xenograft survival in pig-to-primate organ xenotransplantation.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0386-7) contains supplementary material, which is available to authorized users.

The Rho Kinase Isoforms ROCK1 and ROCK2 Each Contribute to the Development of Experimental Pulmonary Fibrosis

Pulmonary fibrosis is thought to result from dysregulated wound repair after repetitive lung injury. Many cellular responses to injury involve rearrangements of the actin cytoskeleton mediated by the two isoforms of the Rho-associated coiled-coil-forming protein kinase (ROCK), ROCK1 and ROCK2. In addition, profibrotic mediators such as transforming growth factor-β, thrombin, and lysophosphatidic acid act through receptors that activate ROCK. Inhibition of ROCK activation may be a potent therapeutic strategy for human pulmonary fibrosis. Pharmacological inhibition of ROCK using nonselective ROCK inhibitors has been shown to prevent fibrosis in animal models; however, the specific roles of each ROCK isoform are poorly understood. Furthermore, the pleiotropic effects of this kinase have raised concerns about on-target adverse effects of ROCK inhibition such as hypotension. Selective inhibition of one isoform might be a better-tolerated strategy. In the present study, we used a genetic approach to determine the roles of ROCK1 and ROCK2 in a mouse model of bleomycin-induced pulmonary fibrosis. Using ROCK1- or ROCK2-haploinsufficient mice, we found that reduced expression of either ROCK1 or ROCK2 was sufficient to protect them from bleomycin-induced pulmonary fibrosis. In addition, we found that both isoforms contribute to the profibrotic responses of epithelial cells, endothelial cells, and fibroblasts. Interestingly, ROCK1- and ROCK2-haploinsufficient mice exhibited similar protection from bleomycin-induced vascular leak, myofibroblast differentiation, and fibrosis; however, ROCK1-haploinsufficient mice demonstrated greater attenuation of epithelial cell apoptosis. These findings suggest that selective inhibition of either ROCK isoform has the potential to be an effective therapeutic strategy for pulmonary fibrosis.

Fibronectin inhibitor pUR4 attenuates tumor necrosis factor α-induced endothelial hyperpermeability by modulating β1 integrin activation

BACKGROUND

The blood-spinal cord barrier (BSCB) is composed of a monolayer of endothelium linked with tight junctions and extracellular matrix (ECM)-rich basement membranes and is surrounded by astrocyte foot processes. Endothelial permeability is regulated by interaction between endothelial cells and ECM proteins. Fibronectin (FN) is a principal ECM component of microvessels. Excessive FN deposition disrupts cell-cell adhesion in fibroblasts through β1 integrin ligation. To determine whether excessive FN deposition contributes to the disruption of endothelial integrity, we used an in vitro model of the endothelial monolayer to investigate whether the FN inhibitor pUR4 prevents FN deposition into the subendothelial matrix and attenuates endothelial leakage.

METHODS

To correlate the effects of excessive FN accumulation in microvessels on BSCB disruption, spinal nerve ligation-which induces BSCB leakage-was applied, and FN expression in the spinal cord was evaluated through immunohistochemistry and immunoblotting. To elucidate the effects by which pUR4 modulates endothelial permeability, brain-derived endothelial (bEND.3) cells treated with tumor necrosis factor (TNF)-α were used to mimic a leaky BSCB. A bEND.3 monolayer was preincubated with pUR4 before TNF-α treatment. The transendothelial electrical resistance (TEER) measurement and transendothelial permeability assay were applied to assess the endothelial integrity of the bEND.3 monolayer. Immunofluorescence analysis and immunoblotting were performed to evaluate the inhibitory effects of pUR4 on TNF-α-induced FN deposition. To determine the mechanisms underlying pUR4-mediated endothelial permeability, cell morphology, stress fiber formation, myosin light chain (MLC) phosphorylation, and β1 integrin-mediated signaling were evaluated through immunofluorescence analysis and immunoblotting.

RESULTS

Excessive FN was accumulated in the microvessels of the spinal cord after spinal nerve ligation; moreover, pUR4 inhibited TNF-α-induced FN deposition in the bEND.3 monolayer and maintained intact TEER and endothelial permeability. Furthermore, pUR4 reduced cell morphology alteration, actin stress fiber formation, and MLC phosphorylation, thereby attenuating paracellular gap formation. Moreover, pUR4 reduced β1 integrin activation and downstream signaling.

CONCLUSIONS

pUR4 reduces TNF-α-induced β1 integrin activation by depleting ECM FN, leading to a decrease in endothelial hyperpermeability and maintenance of monolayer integrity. These findings suggest therapeutic benefits of pUR4 in pathological vascular leakage treatment.

MicroRNA-92a promotes vascular smooth muscle cell proliferation and migration through the ROCK/MLCK signalling pathway

To identify the interaction between known regulators of atherosclerosis, microRNA-92a (miR-92a), Rho-associated coiled-coil-forming kinase (ROCK) and myosin light chain kinase (MLCK), we examined their expressions during proliferation and migration of platelet-derived growth factor-BB (PDGF-BB)-regulated vascular smooth muscle cells (VSMCs), both in vivo and in vitro. During the formation of atherosclerosis plaque in mice, a parallel increase in expression levels of MLCK and miR-92a was observed while miR-92a expression was reduced in ML-7 (an inhibitor of MLCK) treated mice and in MLCK-deficient VSMCs. In vitro results indicated that both MLCK and miR-92a shared the same signalling pathway. Transfection of miR-92a mimic partially restored the effect of MLCK's deficiency and antagonized the effect of Y27632 (an inhibitor of ROCK) on the down-regulation of VSMCs activities. ML-7 increased the expression of Kruppel-like factor 4 (KLF4, a target of miR-92a), and siRNA-KLF4 increased VSMCs' activity level. Consistently, inhibition of either MLCK or ROCK enhanced the KLF4 expression. Moreover, we observed that ROCK/MLCK up-regulated miR-92a expression in VSMCs through signal transducer and activator of transcription 3 (STAT3) activation. In conclusion, the activation of ROCK/STAT3 and/or MLCK/STAT3 may up-regulate miR-92a expression, which subsequently inhibits KLF4 expression and promotes PDGF-BB-mediated proliferation and migration of VSMCs. This new downstream node in the ROCK/MLCK signalling pathway may offer a potential intervention target for treatment of atherosclerosis.

Tetramethylpyrazine alleviates LPS-induced inflammatory injury in HUVECs by inhibiting Rho/ROCK pathway

Endothelial dysfunction plays an important role in the pathogenesis of acute lung injury (ALI). Tetramethylpyrazine (TMP) has been reported to attenuate harmful changes in ALI rats. However, the effects of TMP on endothelial cell injury and its underlying mechanisms remain unknown. In this study, human umbilical vein endothelial cells (HUVECs) induced by lipopolysaccharide (LPS) was used as an inflammatory injury model, also served as LPS group. HUVECs pretreated with TMP for 2 h before induced by LPS was served as LPS + TMP group. Untreated HUVECs was served as control group. After incubation with LPS for 12 h, cell viability and morphology, cell apoptosis rate, CD31-positive endothelial microparticles (EMPs) release, proinflammatory cytokines secretion, and ROCK II expression were evaluated. Compared with LPS group, TMP pretreatment improved cell viability and morphology. Besides, cell apoptosis rate, CD31-positive EMPs amount, TNF-α and IL-1β concentrates, and ROCK II mRNA and protein levels in LPS + TMP group were significantly decreased when compared with LPS group. To further confirm the mechanism, HUVECs in all the above groups were pretreated with Y27632 (ROCK II inhibitor) for 30 min before grouping, then treated as above. No significant differences in cell apoptosis rate, CD31-positive EMPs amount, and ROCK II expression between Y27632 + LPS group and Y27632 + LPS + TMP group were found. To sum up, our study found that TMP alleviated LPS-induced inflammatory injury in HUVECs by inhibiting Rho/ROCK pathway.

Label-Free Multi Parameter Optical Interrogation of Endothelial Activation in Single Cells using a Lab on a Disc Platform

Cellular activation and inflammation leading to endothelial dysfunction is associated with cardiovascular disease (CVD). We investigated whether a single cell label-free multi parameter optical interrogation system can detect endothelial cell and endothelial progenitor cell (EPC) activation in vitro and ex vivo, respectively. Cultured human endothelial cells were exposed to increasing concentrations of tumour necrosis factor alpha (TNF-α) or lipopolysaccharide (LPS) before endothelial activation was validated using fluorescence-activated cell sorting (FACS) analysis of inflammatory marker expression (PECAM-1, E-selectin and ICAM-1). A centrifugal microfluidic system and V-cup array was used to capture individual cells before optical measurement of light scattering, immunocytofluorescence, auto-fluorescence (AF) and cell morphology was determined. In vitro, TNF-α promoted specific changes to the refractive index and cell morphology of individual cells concomitant with enhanced photon activity of fluorescently labelled inflammatory markers and increased auto-fluorescence (AF) intensity at three different wavelengths, an effect blocked by inhibition of downstream signalling with Iκβ. Ex vivo, there was a significant increase in EPC number and AF intensity of individual EPCs from CVD patients concomitant with enhanced PECAM-1 expression when compared to normal controls. This novel label-free 'lab on a disc' (LoaD) platform can successfully detect endothelial activation in response to inflammatory stimuli in vitro and ex vivo.

The Robo4-TRAF7 complex suppresses endothelial hyperpermeability in inflammation

Roundabout guidance receptor 4 (Robo4) is an endothelial cell-specific receptor that stabilizes the vasculature in pathological angiogenesis. Although Robo4 has been shown to suppress vascular hyperpermeability induced by vascular endothelial growth factor (VEGF) in angiogenesis, the role of Robo4 in inflammation is poorly understood. In this study, we investigated the role of Robo4 in vascular hyperpermeability during inflammation. Endotoxemia models using Robo4 ^-/- mice showed increased mortality and vascular leakage. In endothelial cells, Robo4 suppressed tumor necrosis factor α (TNFα)-induced hyperpermeability by stabilizing VE-cadherin at cell junctions, and deletion assays revealed that the C-terminus of Robo4 was involved in this suppression. Through binding and localization assays, we demonstrated that in endothelial cells, Robo4 binds to TNF receptor-associated factor 7 (TRAF7) through interaction with the C-terminus of Robo4. Gain- and loss-of-function studies of TRAF7 with or without Robo4 expression showed that TRAF7 is required for Robo4-mediated suppression of hyperpermeability. Taken together, our results demonstrate that the Robo4-TRAF7 complex is a novel negative regulator of inflammatory hyperpermeability. We propose this complex as a potential future target for protection against inflammatory diseases.

Leaky brain in neurological and psychiatric disorders: Drivers and consequences

BACKGROUND

The blood-brain barrier acts as a highly regulated interface; its dysfunction may exacerbate, and perhaps initiate, neurological and neuropsychiatric disorders.

METHODS

In this narrative review, focussing on redox, inflammatory and mitochondrial pathways and their effects on the blood-brain barrier, a model is proposed detailing mechanisms which might explain how increases in blood-brain barrier permeability occur and can be maintained with increasing inflammatory and oxidative and nitrosative stress being the initial drivers.

RESULTS

Peripheral inflammation, which is causatively implicated in the pathogenesis of major psychiatric disorders, is associated with elevated peripheral pro-inflammatory cytokines, which in turn cause increased blood-brain barrier permeability. Reactive oxygen species, such as superoxide radicals and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide and peroxynitrite, play essential roles in normal brain capillary endothelial cell functioning; however, chronically elevated oxidative and nitrosative stress can lead to mitochondrial dysfunction and damage to the blood-brain barrier. Activated microglia, redox control of which is mediated by nitric oxide synthases and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, secrete neurotoxic molecules such as reactive oxygen species, nitric oxide, prostaglandin, cyclooxygenase-2, quinolinic acid, several chemokines (including monocyte chemoattractant protein-1 [MCP-1], C-X-C motif chemokine ligand 1 [CXCL-1] and macrophage inflammatory protein 1α [MIP-1α]) and the pro-inflammatory cytokines interleukin-6, tumour necrosis factor-α and interleukin-1β, which can exert a detrimental effect on blood-brain barrier integrity and function. Similarly, reactive astrocytes produce neurotoxic molecules such as prostaglandin E2 and pro-inflammatory cytokines, which can cause a 'leaky brain'.

CONCLUSION

Chronic inflammatory and oxidative and nitrosative stress is associated with the development of a 'leaky gut'. The following evidence-based approaches, which address the leaky gut and blood-brain barrier dysfunction, are suggested as potential therapeutic interventions for neurological and neuropsychiatric disorders: melatonin, statins, probiotics containing Bifidobacteria and Lactobacilli, N-acetylcysteine, and prebiotics containing fructo-oligosaccharides and galacto-oligosaccharides.

RhoA/ROCK-2 Pathway Inhibition and Tight Junction Protein Upregulation by Catalpol Suppresses Lipopolysaccaride-Induced Disruption of Blood-Brain Barrier Permeability

Lipopolysaccaride (LPS) directly or indirectly injures brain microvascular endothelial cells (BMECs) and damages the intercellular tight junction that gives rise to altered blood-brain barrier (BBB) permeability. Catalpol plays a protective role in LPS-induced injury, but whether catalpol protects against LPS-caused damage of BBB permeability and the underlying mechanism remain to be delineated. Prophylactic protection with catalpol (5 mg/kg, i.v.) consecutively for three days reversed the LPS-induced damage of BBB by decreased Evans Blue (EB) leakage and restored tight junctions in C57 mice. Besides, catalpol co-administrated with LPS increased BMECs survival, decreased their endothelin-1, TNF-Α and IL-6 secretion, improved transmembrane electrical resistance in a time-dependent manner, and in addition increased the fluorescein sodium permeability coefficient of BMECs. Also, transmission electron microscopy showed catalpol protective effects on tight junctions. Fluorescence staining displayed that catalpol reversed the rearrangement of the cytoskeleton protein F-actin and upregulated the tight junction protein of claudin-5 and ZO-1, which have been further demonstrated by the mRNA and protein expression levels of ZO-1, ZO-2, ZO-3, claudin-5, and occludin. Moreover, catalpol concurrently downregulated the mRNA and protein levels of RhoA, and ROCK2, the critical proteins in the RhoA/ROCK2 signaling pathway. This study thus indicated that catalpol, via inhibition of the RhoA/ROCK2 signaling pathway, reverses the disaggregation of cytoskeleton actin in BMECs and prevents down-regulation of junctional proteins, such as claudin-5, occludin, and ZO-1, and decreases endothelin-1 and inflammatory cytokine secretion, eventually alleviating the increase in LPS-induced BBB permeability.

Regulation of connexin 43 expression in human gingival fibroblasts

AIMS

Abundance of connexin 43 (Cx43), a transmembrane protein that forms hemichannels (HCs) and gap junctions (GJs), is dynamically regulated in human gingival fibroblasts (GFBLs) during wound healing. This may be important for fast and scarless gingival wound healing as Cx43 is involved in key cell functions important during this process. Our aim was to uncover the factors that regulate Cx43 expression and abundance in GFBLs. We hypothesized that cytokines and growth factors released during wound healing coordinately regulate Cx43 abundance in GFBLs.

RESULTS

TGF-β1, -β2, -β3, PGE2 and IL-1β significantly upregulated, while TNF-α and IFN-γ downregulated Cx43 in cultured GFBLs. TGF-β1, -β2, -β3, IL-1β and IFN-γ modulated Cx43 abundance at both mRNA and protein levels, while TNF-α and PGE2 regulated only Cx43 protein abundance, suggesting involvement of distinct transcriptional/post-transcriptional and translational/post-translational mechanisms, respectively. TGF-β1-induced upregulation of Cx43 was mediated by TGFβRI (ALK5) and SMAD2/3 signaling, and this was potently suppressed by PGE2, IL-1β, TNF-α and IFN-γ that inhibited SMAD2/3 phosphorylation.

CONCLUSION

Regulation of Cx43 abundance in GFBLs involves transcriptional/post-transcriptional and translational/post-translational mechanisms that are distinctly modulated by an interplay between TGF-β isoforms and PGE2, IL-1β, TNF-α and IFN-γ.