Myosin light chain kinase signaling in endothelial barrier dysfunction

Oligomeric Tau-induced oxidative damage and functional alterations in cerebral endothelial cells: Role of RhoA/ROCK signaling pathway

Despite of yet unknown mechanism, microvascular deposition of oligomeric Tau (oTau) has been implicated in alteration of the Blood-Brain Barrier (BBB) function in Alzheimer's disease (AD) brains. In this study, we employed an in vitro BBB model using primary mouse cerebral endothelial cells (CECs) to investigate the mechanism underlying the effects of oTau on BBB function. We found that exposing CECs to oTau induced oxidative stress through NADPH oxidase, increased oxidative damage to proteins, decreased proteasome activity, and expressions of tight junction (TJ) proteins including occludin, zonula occludens-1 (ZO-1) and claudin-5. These effects were suppressed by the pretreatment with Fasudil, a RhoA/ROCK signaling inhibitor. Consistent with the biochemical alterations, we found that exposing the basolateral side of CECs to oTau in the BBB model disrupted the integrity of the BBB, as indicated by an increase in FITC-dextran transport across the model, and a decrease in trans endothelial electrical resistance (TEER). oTau also increased the transmigration of peripheral blood mononuclear cells (PBMCs) in the BBB model. These functional alterations in the BBB induced by oTau were also suppressed by Fasudil. Taken together, our findings suggest that targeting the RhoA/ROCK pathway can be a potential therapeutic strategy to maintain BBB function in AD.

β-Caryophyllene promotes the survival of random skin flaps by upregulating the PI3K/AKT signaling pathway

BACKGROUND

Flap transplantation is a widely used plastic repair technique in surgical procedures, aimed at addressing skin defects resulting from diverse wounds and diseases. However, due to the insufficient blood supply after flap surgery, the occurrence of ischemia-reperfusion injury, and an excessive sterile inflammatory response, flaps frequently develop complications (e.g., partial or complete ischemic necrosis). These complications have adverse effects on wound healing and repair. β-Caryophyllene (BCP) is a bicyclic sesquiterpene that is widely present in plants. It mitigates oxidative stress and inflammatory responses, demonstrates neuroprotective and analgesic properties, and serves a protective function in organs or tissues subjected to ischemia-reperfusion injury. However, no study has confirmed whether BCP can be used in the field of flap transplantation to improve the flap survival rate.

METHODS

To assess the impact of BCP on random flap survival, we constructed a modified McFarlane random flap model on the rat. After 7 consecutive days of gavage with different doses of BCP, we measured the survival area ratio, angiogenesis, blood perfusion, tissue inflammation level, apoptosis-related protein levels, and the PI3K/AKT signaling pathway expression of the random flap.

RESULTS

BCP treatment increased the survival area of the flap in a dose-dependent manner after random flap transplantation in rats. BCP mainly promoted the formation of tissue blood vessels, improved flap blood perfusion, limited the local inflammatory response, and reduced apoptosis. In addition, we demonstrated that BCP works primarily by promoting the PI3K/AKT signaling expression while enhancing the phosphorylation of AKT. Administration of wortmannin, a selective inhibitor of PI3K, eliminated the effects of BCP.

CONCLUSION

BCP can promote the survival of random flaps by upregulating the PI3K/AKT signaling pathway, increasing tissue blood perfusion, and limiting the inflammatory response and apoptosis.

Action and therapeutic targets of myosin light chain kinase, an important cardiovascular signaling mechanism

The global incidence of cardiac diseases is increasing, imposing a substantial socioeconomic burden on healthcare systems. The pathogenesis of cardiovascular disease is complex and not fully understood, and the physiological function of the heart is inextricably linked to well-regulated cardiac muscle movement. Myosin light chain kinase (MLCK) is essential for myocardial contraction and diastole, cardiac electrophysiological homeostasis, vasoconstriction of vascular nerves and blood pressure regulation. In this sense, MLCK appears to be an attractive therapeutic target for cardiac diseases. MLCK participates in myocardial cell movement and migration through diverse pathways, including regulation of calcium homeostasis, activation of myosin light chain phosphorylation, and stimulation of vascular smooth muscle cell contraction or relaxation. Recently, phosphorylation of myosin light chains has been shown to be closely associated with the activation of myocardial exercise signaling, and MLCK mediates systolic and diastolic functions of the heart through the interaction of myosin thick filaments and actin thin filaments. It works by upholding the integrity of the cytoskeleton, modifying the conformation of the myosin head, and modulating innervation. MLCK governs vasoconstriction and diastolic function and is associated with the activation of adrenergic and sympathetic nervous systems, extracellular transport, endothelial permeability, and the regulation of nitric oxide and angiotensin II. Additionally, MLCK plays a crucial role in the process of cardiac aging. Multiple natural products/phytochemicals and chemical compounds, such as quercetin, cyclosporin, and ML-7 hydrochloride, have been shown to regulate cardiomyocyte MLCK. The MLCK-modifying capacity of these compounds should be considered in designing novel therapeutic agents. This review summarizes the mechanism of action of MLCK in the cardiovascular system and the therapeutic potential of reported chemical compounds in cardiac diseases by modifying MLCK processes.

Targeting 5-Hydroxytryptamine Receptor 1A in the Portal Vein to Decrease Portal Hypertension

BACKGROUNDS & AIMS

Portal hypertension (PH) is one of the most frequent complications of chronic liver disease. The peripheral 5-hydroxytryptamine (5-HT) level was increased in cirrhotic patients. We aimed to elucidate the function and mechanism of 5-HT receptor 1A (HTR1A) in the portal vein (PV) on PH.

METHODS

PH models were induced by thioacetamide injection, bile duct ligation, or partial PV ligation. HTR1A expression was detected using real-time polymerase chain reaction, in situ hybridization, and immunofluorescence staining. In situ intraportal infusion was used to assess the effects of 5-HT, the HTR1A agonist 8-OH-DPAT, and the HTR1A antagonist WAY-100635 on portal pressure (PP). Htr1a-knockout (Htr1a-/-) rats and vascular smooth muscle cell (VSMC)-specific Htr1a-knockout (Htr1aΔVSMC) mice were used to confirm the regulatory role of HTR1A on PP.

RESULTS

HTR1A expression was significantly increased in the hypertensive PV of PH model rats and cirrhotic patients. Additionally, 8-OH-DPAT increased, but WAY-100635 decreased, the PP in rats without affecting liver fibrosis and systemic hemodynamics. Furthermore, 5-HT or 8-OH-DPAT directly induced the contraction of isolated PVs. Genetic deletion of Htr1a in rats and VSMC-specific Htr1a knockout in mice prevented the development of PH. Moreover, 5-HT triggered adenosine 3',5'-cyclic monophosphate pathway-mediated PV smooth muscle cell contraction via HTR1A in the PV. We also confirmed alverine as an HTR1A antagonist and demonstrated its capacity to decrease PP in rats with thioacetamide-, bile duct ligation-, and partial PV ligation-induced PH.

CONCLUSIONS

Our findings reveal that 5-HT promotes PH by inducing the contraction of the PV and identify HTR1A as a promising therapeutic target for attenuating PH. As an HTR1A antagonist, alverine is expected to become a candidate for clinical PH treatment.

Hydrogen sulfide improves endothelial barrier function by modulating the ubiquitination degradation of KLF4 through TRAF7 S-sulfhydration in diabetic aorta

Anomalous vascular endothelium significantly contributes to various cardiovascular diseases. VE-cadherin plays a vital role in governing the endothelial barrier. Krüppel-like factor 4(KLF4), as a transcription factor, which binds the VE-cadherin promoter and enhances its transcription. Tumor necrosis factor receptor-associated factor 7 (TRAF7) is an E3 ubiquitin ligase that has been shown to modulate the degradation of KLF4. H2S can covalently modify cysteine residues on proteins through S-sulfhydration, thereby influencing the structure and functionality of the target protein. However, the role of S-sulfhydration on endothelial barrier integrity remains to be comprehensively elucidated. This study aims to investigate whether protein S-sulfhydration in the endothelium regulates endothelial integrity and its underlying mechanism. In this study, we observed that protein S-sulfhydration was reduced in the endothelium during diabetes and TRAF7 was the main target. Overexpression of TRAF7-Cys327 mutant could mitigate the endothelial barrier damage by weakening TRAF7 interaction with KLF4 and reducing ubiquitination degradation of KLF4. In conclusion, our research demonstrates that H2S plays a pivotal role in regulating S-sulfhydration of TRAF7 at Cys327. This regulation effectively inhibits the ubiquitin-mediated degradation of KLF4, resulting in an upregulation of VE-cadherin levels. This molecular mechanism contributes to the prevention of endothelial barrier damage.

Trifluoperazine regulates blood-brain barrier permeability via the MLCK/p-MLC pathway to promote ischemic stroke recovery

Blood-brain barrier (BBB) disruption following ischemic stroke (IS) can induce significant aftereffects. Elevated calmodulin (CaM) expression following stroke causes calcium overload-a key contributor to BBB collapse. Trifluoperazine (TFP), a CaM inhibitor, reduces CaM overexpression following IS. However, it remains unclear whether TFP participates in BBB repair after IS. We administered TFP to mice subjected to middle cerebral artery occlusion (MCAO) and bEnd.3 cells subjected to oxygen-glucose deprivation (OGD). TFP treatment in MCAO mice reduced cerebral CaM expression and infarct size and decreased BBB permeability. OGD-treated bEnd.3 cells showed significantly increased CaM protein levels and reduced tight junction (TJ) protein levels; these changes were reversed by TFP treatment. Our results found that TFP administration in mice inhibited actin contraction following cerebral ischemia-reperfusion by suppressing the MLCK/p-MLC pathway, thereby attenuating cell retraction, improving TJ protein integrity, and reducing BBB permeability. Consequently, this treatment may promote neurological function recovery after IS.

Ageratina adenophora causes intestinal integrity damage in goats via the activation of the MLCK/ROCK signaling pathway

As a global toxin invasive species, the whole herb of Ageratina adenophora (A. adenophora) contains various sesquiterpenes, which can cause various degrees of toxic reactions characterized by inflammatory damage when ingested by animals. Current studies on the toxicity of A. adenophora have focused on parenchymatous organs such as the liver and spleen, but few studies have been conducted on the intestine as the organ that is first exposed to A. adenophora and digests and absorbs its toxic components. In this study, after feeding goats with 40 % A. adenophora herb powder for 90 d, we found that the intestinal structure of goats showed pathological changes characterized, and the damage to the small intestinal segments was more severe than that of the large intestine. The MLCK/ROCK signaling pathway was activated, the cytoskeleton underwent centripetal contraction, the composition of tight junctions between intestinal epithelial cells was altered table, Occludin, Claudin-1 and Zonula occluden (ZO-1) amount was decreased, and the intestinal mechanical barrier was disrupted. The intestinal damage markers diamine oxidase (DAO) and D-lactate (D-LA) levels were elevated. In addition, we also found that intestinal bacteria translocate and enter the portal vein to colonize the liver and mesenteric lymph nodes. The expression of intestinal pro-inflammatory factors and anti-inflammatory factors was changed, the intestinal immune function was disrupted. The present study is the first to analyze the mechanism of poisoning of A. adenophora from the intestinal tract in compound-gastric animals.

Fibrinogen in mice cerebral microvessels induces blood-brain barrier dysregulation with aging via a dynamin-related protein 1-dependent pathway

We previously reported evidence that oxidative stress during aging leads to adverse protein profile changes of brain cortical microvessels (MVs: end arterioles, capillaries, and venules) that affect mRNA/protein stability, basement membrane integrity, and ATP synthesis capacity in mice. As an extension of our previous study, we also found that proteins which comprise the blood-brain barrier (BBB) and regulate mitochondrial quality control were also significantly decreased in the mice's cortical MVs with aging. Interestingly, the neuroinflammatory protein fibrinogen (Fgn) was increased in mice brain MVs, which corresponds with clinical reports indicating that the plasma Fgn concentration increased progressively with aging. In this study, protein-protein interaction network analysis indicated that high expression of Fgn is linked with downregulated expression of both BBB- and mitochondrial fission/fusion-related proteins in mice cortical MVs with aging. To investigate the mechanism of Fgn action, we observed that 2 mg/mL or higher concentration of human plasma Fgn changed cell morphology, induced cytotoxicity, and increased BBB permeability in primary human brain microvascular endothelial cells (HBMECs). The BBB tight junction proteins were significantly decreased with increasing concentration of human plasma Fgn in primary HBMECs. Similarly, the expression of phosphorylated dynamin-related protein 1 (pDRP1) and other mitochondrial fission/fusion-related proteins were also significantly reduced in Fgn-treated HBMECs. Interestingly, DRP1 knockdown by shRNA(h) resulted in the reduction of both BBB- and mitochondrial fission/fusion-related proteins in HBMECs. Our results suggest that elevated Fgn downregulates DRP1, leading to mitochondrial-dependent endothelial and BBB dysfunction in the brain microvasculature.

Endothelial Cell Calcium Influx Mediates Trauma-induced Endothelial Permeability

OBJECTIVE

We aimed to investigate if ex vivo plasma from injured patients causes endothelial calcium (Ca2+) influx as a mechanism of trauma-induced endothelial permeability.

SUMMARY BACKGROUND DATA

Endothelial permeability after trauma contributes to post-injury organ dysfunction. While the mechanisms remain unclear, emerging evidence suggests intracellular Ca2+ signaling may play a role.

METHODS

Ex vivo plasma from injured patients with "Low Injury/Low Shock" (injury severity score [ISS]<15, base excess [BE])≥-6mEq/L) and "High Injury/High Shock" (ISS≥15, BE<-6mEq/L) were used to treat endothelial cells. Experimental conditions included Ca2+ removal from the extracellular buffer, cyclopiazonic acid pre-treatment to deplete intracellular Ca2+ stores, and GSK2193874 pre-treatment to block the TRPV4 Ca2+ channel. Live cell fluorescence microscopy and ECIS were used to assess cytosolic Ca2+ increases and permeability, respectively. Western blot and live cell actin staining were used to assess myosin light chain (MLC) phosphorylation and actomyosin contraction.

RESULTS

Compared to Low Injury/Low Shock plasma, High Injury/High Shock induced greater cytosolic Ca2+ increase. Cytosolic Ca2+ increase, MLC phosphorylation, and actin cytoskeletal contraction were lower without extracellular Ca2+ present. High Injury/High Shock plasma did not induce endothelial permeability without extracellular Ca2+ present. TRPV4 inhibition lowered trauma plasma-induced endothelial Ca2+ influx and permeability.

CONCLUSIONS

This study illuminates a novel mechanism of post-injury endotheliopathy involving Ca2+ influx via the TRPV4 channel. TRPV4 inhibition mitigates trauma-induced endothelial permeability. Moreover, widespread endothelial Ca2+ influx may contribute to trauma-induced hypocalcemia. This study provides the mechanistic basis for the development of Ca2+-targeted therapies and interventions in the care of severely injured patients.

Inhibition of UTX/KDM6A improves recovery of spinal cord injury by attenuating BSCB permeability and macrophage infiltration through the MLCK/p-MLC pathway

Spinal cord injury (SCI) can prompt an immediate disruption to the blood-spinal cord barrier (BSCB). Restoring the integrity of this barrier is vital for the recovery of neurological function post-SCI. The UTX protein, a histone demethylase, has been shown in previous research to promote vascular regeneration and neurological recovery in mice with SCI. However, it is unclear whether UTX knockout could facilitate the recovery of the BSCB by reducing its permeability. In this study, we systematically studied BSCB disruption and permeability at different time points after SCI and found that conditional UTX deletion in endothelial cells (ECs) can reduce BSCB permeability, decrease inflammatory cell infiltration and ROS production, and improve neurological function recovery after SCI. Subsequently, we used RNA sequencing and ChIP-qPCR to confirm that conditional UTX knockout in ECs can down-regulate expression of myosin light chain kinase (MLCK), which specifically mediates myosin light chain (MLC) phosphorylation and is involved in actin contraction, cell retraction, and tight junctions (TJs) protein integrity. Moreover, we found that MLCK overexpression can increase the ratio of p-MLC/MLC, further break TJs, and exacerbate BSCB deterioration. Overall, our findings indicate that UTX knockout could inhibit the MLCK/p-MLC pathway, resulting in decreased BSCB permeability, and ultimately promoting neurological recovery in mice. These results suggest that UTX is a promising new target for treating SCI.

Targeted Delivery of RGD-CD146+CD271+ Human Umbilical Cord Mesenchymal Stem Cell-Derived Exosomes Promotes Blood-Spinal Cord Barrier Repair after Spinal Cord Injury

Spinal cord injury (SCI) disrupts the blood-spinal cord barrier (BSCB), potentially exacerbating nerve damage and emphasizing the criticality of preserving the BSCB integrity during SCI treatment. This study explores an alternative therapeutic approach for SCI by identifying a subpopulation of exosomes with stable BSCB function and achieving a specific targeted delivery. Specific subpopulations of CD146+CD271+ umbilical cord mesenchymal stem cells (UCMSCs) were isolated, from which engineered exosomes (RGD-CD146+CD271+ UCMSC-Exos) with targeted neovascularization function were obtained through gene transfection. In vivo and in vitro experiments were performed to explore the targeting and therapeutic effects of RGD-CD146+CD271+ UCMSC-Exos and the potential mechanisms underlying BSCB stabilization and neural function recovery. The results demonstrated that RGD-CD146+CD271+ UCMSC-Exos exhibited physical and chemical properties similar to those of regular exosomes. Notably, following intranasal administration, RGD-CD146+CD271+ UCMSC-Exos exhibited enhanced aggregation at the SCI center and demonstrated the specific targeting of neovascular endothelial cells. In the SCI model, intranasal administration of RGD-CD146+CD271+ UCMSC-Exos reduced Evans blue dye leakage, increased tight junction protein expression, and improved neurological function recovery. In vitro testing revealed that RGD-CD146+CD271+ UCMSC-Exos treatment significantly reduced the permeability of bEnd.3 cells subjected to oxygen-glucose deprivation, thereby restoring the integrity of tight junctions. Moreover, further exploration of the molecular mechanism underlying BSCB stabilization by CD146+CD271+ UCMSC-Exos identified the crucial role of the miR-501-5p/MLCK axis in this process. In conclusion, targeted delivery of RGD-CD146+CD271+ UCMSC-Exos presents a promising and effective treatment option for SCI.

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.

Lipocalin 10 is essential for protection against inflammation-triggered vascular leakage by activating LDL receptor-related protein 2-slingshot homologue 1 signalling pathway

AIMS

Systemic inflammation occurs commonly during many human disease settings and increases vascular permeability, leading to organ failure, and lethal outcomes. Lipocalin 10 (Lcn10), a poorly characterized member of the lipocalin family, is remarkably altered in the cardiovascular system of human patients with inflammatory conditions. Nonetheless, whether Lcn10 regulates inflammation-induced endothelial permeability remains unknown.

METHODS AND RESULTS

Systemic inflammation models were induced using mice by injection of endotoxin lipopolysaccharide (LPS) or caecal ligation and puncture (CLP) surgery. We observed that the expression of Lcn10 was dynamically altered only in endothelial cells (ECs), but not in either fibroblasts or cardiomyocytes isolated from mouse hearts following the LPS challenge or CLP surgery. Using in vitro gain- and loss-of-function approaches and an in vivo global knockout mouse model, we discovered that Lcn10 negatively regulated endothelial permeability upon inflammatory stimuli. Loss of Lcn10 augmented vascular leakage, leading to severe organ damage and higher mortality following LPS challenge, compared to wild-type controls. By contrast, overexpression of Lcn10 in ECs displayed opposite effects. A mechanistic analysis revealed that both endogenous and exogenous elevation of Lcn10 in ECs could activate slingshot homologue 1 (Ssh1)-Cofilin signalling cascade, a key axis known to control actin filament dynamics. Accordingly, a reduced formation of stress fibre and increased generation of cortical actin band were exhibited in Lcn10-ECs, when compared to controls upon endotoxin insults. Furthermore, we identified that Lcn10 interacted with LDL receptor-related protein 2 (LRP2) in ECs, which acted as an upstream factor of the Ssh1-Confilin signalling. Finally, injection of recombinant Lcn10 protein into endotoxic mice showed therapeutic effects against inflammation-induced vascular leakage.

CONCLUSION

This study identifies Lcn10 as a novel regulator of EC function and illustrates a new link in the Lcn10-LRP2-Ssh1 axis to controlling endothelial barrier integrity. Our findings may provide novel strategies for the treatment of inflammation-related diseases.

Substance P reversibly compromises the integrity and function of blood-brain barrier

BACKGROUND

Substance P (SP) plays a role in vasodilatation and tissue integrity through its receptor, neurokinin 1 (NK1R). However, its specific effect on blood-brain barrier (BBB) remains unknown.

METHODS

The impact of SP on the integrity/function of human BBB model in vitro, composed of brain microvascular endothelial cells (BMECs), astrocytes and pericytes, was assessed by measurements of transendothelial electrical resistance and paracellular flux of sodium fluorescein (NaF), respectively in the absence/presence of specific inhibitors targeting NK1R (CP96345), Rho-associated protein kinase (ROCK; Y27632) and nitric oxide synthase (NOS; N(G)-nitro-L-arginine methyl ester). Sodium nitroprusside (SNP), a NO donor, was employed as a positive control. The levels of tight junction proteins, zonula occludens-1, occludin and claudin-5 alongside RhoA/ROCK/myosin regulatory light chain-2 (MLC2) and extracellular signal‑regulated protein kinase (Erk1/2) proteins were detected by western analyses. Subcellular localisations of F-actin and tight junction proteins were visualized by immunocytochemistry. Flow cytometry was used to detect transient calcium release.

RESULTS

Exposure to SP increased RhoA, ROCK2 and phosphorylated serine-19 MLC2 protein levels and Erk1/2 phosphorylation in BMECs which were abolished by CP96345. These increases were independent of the changes in intracellular calcium availability. SP perturbed BBB in a time-dependent fashion through induction of stress fibres. Changes in tight junction protein dissolution or relocalisation were not involved in SP-mediated BBB breakdown. Inhibition of NOS, ROCK and NK1R mitigated the effect of SP on BBB characteristics and stress fibre formation.

CONCLUSION

SP promoted a reversible decline in BBB integrity independent of tight junction proteins expression or localisation.

Low-dose albumin-coated gold nanorods induce intercellular gaps on vascular endothelium by causing the contraction of cytoskeletal actin

Cytotoxicity of nanoparticles, typically evaluated by biochemical-based assays, often overlook the cellular biophysical properties such as cell morphology and cytoskeletal actin, which could serve as more sensitive indicators for cytotoxicity. Here, we demonstrate that low-dose albumin-coated gold nanorods (HSA@AuNRs), although being considered noncytotoxic in multiple biochemical assays, can induce intercellular gaps and enhance the paracellular permeability between human aortic endothelial cells (HAECs). The formation of intercellular gaps can be attributed to the changed cell morphology and cytoskeletal actin structures, as validated at the monolayer and single cell levels using fluorescence staining, atomic force microscopy, and super-resolution imaging. Molecular mechanistic study shows the caveolae-mediated endocytosis of HSA@AuNRs induces the calcium influx and activates actomyosin contraction in HAECs. Considering the important roles of endothelial integrity/dysfunction in various physiological/pathological conditions, this work suggests a potential adverse effect of albumin-coated gold nanorods on the cardiovascular system. On the other hand, this work also offers a feasible way to modulate the endothelial permeability, thus promoting drug and nanoparticle delivery across the endothelium.

Overview of blood-brain barrier dysfunction in methamphetamine abuse

Methamphetamine (METH) is one of the psychostimulants most widely abused in the world. METH abuse can lead to severe neurotoxicity. The blood-brain barrier (BBB) is a natural barrier separating the central nervous system (CNS) from the peripheral blood circulation, which can limit or regulate the exchange of toxic substances, molecules, ions, etc., to maintain the homeostasis of CNS. Long-term or high dose abuse of METH can cause structural or functional abnormalities of the BBB and increase the risk of neurodegenerative diseases. In this review, we discussed the mechanisms of METH-induced BBB dysfunction, summarized the risk factors that could exacerbate METH-induced BBB dysfunction, and introduced some potential therapeutic agents. It would provide an important basis and direction for the prevention and treatment of BBB dysfunction induced by METH.

MYOSIN LIGHT CHAIN KINASE DELETION WORSENS LUNG PERMEABILITY AND INCREASES MORTALITY IN PNEUMONIA-INDUCED SEPSIS

ABSTRACT

Increased epithelial permeability in sepsis is mediated via disruptions in tight junctions, which are closely associated with the perijunctional actin-myosin ring. Genetic deletion of myosin light chain kinase (MLCK) reverses sepsis-induced intestinal hyperpermeability and improves survival in a murine model of intra-abdominal sepsis. In an attempt to determine the generalizability of these findings, this study measured the impact of MLCK deletion on survival and potential associated mechanisms following pneumonia-induced sepsis. MLCK -/- and wild-type mice underwent intratracheal injection of Pseudomonas aeruginosa . Unexpectedly, survival was significantly worse in MLCK -/- mice than wild-type mice. This was associated with increased permeability to Evans blue dye in bronchoalveolar lavage fluid but not in tissue homogenate, suggesting increased alveolar epithelial leak. In addition, bacterial burden was increased in bronchoalveolar lavage fluid. Cytokine array using whole-lung homogenate demonstrated increases in multiple proinflammatory and anti-inflammatory cytokines in knockout mice. These local pulmonary changes were associated with systemic inflammation with increased serum levels of IL-6 and IL-10 and a marked increase in bacteremia in MLCK -/- mice. Increased numbers of both bulk and memory CD4 + T cells were identified in the spleens of knockout mice, with increased early and late activation. These results demonstrate that genetic deletion of MLCK unexpectedly increases mortality in pulmonary sepsis, associated with worsened alveolar epithelial leak and both local and systemic inflammation. This suggests that caution is required in targeting MLCK for therapeutic gain in sepsis.

Dachaihu decoction inhibits hypernutrition-induced liver metastasis from colorectal cancer by maintaining the gut vascular barrier

Background

Colorectal cancer (CRC) is the third most common malignancy and the second deadliest cancer worldwide. Metastasis to the liver, the most common metastatic site in CRC, is the leading cause of death in patients with CRC. Hyperlipidemia, which is common in patients with CRC, promotes CRC progression and metastasis. Hyperlipidemia is commonly observed in obese patients and is often induced by hypernutrition. The underlying mechanism of hypernutrition-induced hyperlipidemia in promoting CRC liver metastasis remains unclear, and there is an unmet need for effective and low-cost treatments for patients with CRC.

Methods

A mouse cecum orthotopic CRC model combined with high-fat diet (HFD) feeding, was established to mimic liver metastasis in CRC in obese patients. The effects of Dachaihu decoction (DCHD), a traditional herbal medicine used to treat inflammation and nonalcoholic fatty liver disease, and of the conventional prescription medicine obeticholic acid (OCA) were evaluated. HFD-induced obesity, hyperlipidemia, and CRC liver metastasis were assessed, along with the histology and pathology of the liver and intestine and the expression of metabolic genes in these tissues. The effects of DCHD and OCA on HFD-induced outcomes were evaluated, and human umbilical vein endothelial cells (HUVECs) treated with bile acids (BAs) and DCHD were used to study the underlying mechanisms in vitro.

Results

HFD-mediated obesity and hyperlipidemia promoted CRC metastasis, accompanied by disruption of the gut vascular barrier (GVB) and altered bile acid (BA) metabolism. DCHD decreased HFD-induced hyperlipidemia and liver metastasis in CRC, improving overall survival. Those effects of DCHD were equivalent to or better than those of OCA. DCHD regulated the expression of genes of BA metabolism and tight junctions (TJ) to prevent HFD-induced disruption of the GVB. In HUVECs, DCHD prevented the increases in intracellular Ca2+ and accumulation of reactive oxygen species induced by primary conjugated BAs, assisting in the maintenance of redox homeostasis and preventing the downregulation of TJ proteins, thereby maintaining the integrity of the endothelial barrier.

Conclusions

The data provide a link between hypernutrition and GVB disruption, which contributes to high liver metastasis in patients with CRC. DCHD may represent a novel therapy in CRC, and targeting abnormal lipid metabolism could be a promising therapeutic strategy for avoiding hypernutrition-associated CRC metastasis.

Research progress of mechanisms for tight junction damage on blood-brain barrier inflammation

Inflammation in the central nervous system (CNS) contributes to disease pathologies by disrupting the integrity of the blood-brain barrier (BBB). Tight junctions (TJ) are a key component of the BBB. Following hypoxic-ischaemic or mechanical injury to the brain, inflammatory mediators are released such as cytokines, chemokines, and growth factors. Simultaneously, matrix metalloproteinases (MMPs) are released which can degrade TJ proteins. Subsequently, the function and morphology of the BBB are disrupted, which allows immune cells an opportunity to enter into the brain parenchyma. This review summarises the information on the role of TJ protein families in the BBB and provides a comprehensive summary of the mechanisms whereby inflammation breaks down the BBB by increasing degradation of TJ proteins.

A Drug Screening Reveals Minocycline Hydrochloride as a Therapeutic Option to Prevent Breast Cancer Cells Extravasation across the Blood-Brain Barrier

Among breast cancer (BC) patients, 15-25% develop BC brain metastases (BCBM), a severe condition due to the limited therapeutic options, which points to the need for preventive strategies. We aimed to find a drug able to boost blood-brain barrier (BBB) properties and prevent BC cells (BCCs) extravasation, among PI3K, HSP90, and EGFR inhibitors and approved drugs. We used BCCs (4T1) and BBB endothelial cells (b.End5) to identify molecules with toxicity to 4T1 cells and safe for b.End5 cells. Moreover, we used those cells in mixed cultures to perform a high-throughput microscopy screening of drugs' ability to ameliorate BBB properties and prevent BCCs adhesion and migration across the endothelium, as well as to analyse miRNAs expression and release profiles. KW-2478, buparlisib, and minocycline hydrochloride (MH) promoted maximal expression of the junctional protein β-catenin and induced 4T1 cells nucleus changes. Buparlisib and MH further decreased 4T1 adhesion. MH was the most promising in preventing 4T1 migration and BBB disruption, tumour and endothelial cytoskeleton-associated proteins modifications, and miRNA deregulation. Our data revealed MH's ability to improve BBB properties, while compromising BCCs viability and interaction with BBB endothelial cells, besides restoring miRNAs' homeostasis, paving the way for MH repurposing for BCBM prevention.

Mannose ameliorates experimental colitis by protecting intestinal barrier integrity

Metabolite alteration has been associated with the pathogenesis of inflammatory bowel disease (IBD), including colitis. Mannose, a natural bioactive monosaccharide that is involved in metabolism and synthesis of glycoproteins, exhibits anti-inflammatory and anti-oxidative activities. We show here that the circulating level of mannose is increased in patients with IBD and mice with experimental colitis. Mannose treatment attenuates intestinal barrier damage in two mouse colitis models, dextran sodium sulfate (DSS)-induced colitis and spontaneous colitis in IL-10-deficient mice. We demonstrate that mannose treatment enhanced lysosomal integrity and limited the release of cathepsin B, preventing mitochondrial dysfunction and myosin light chain kinase (MLCK)-induced tight junction disruption in the context of intestinal epithelial damage. Mannose exerts a synergistic therapeutic effect with mesalamine on mouse colitis. Cumulatively, the results indicate that mannose supplementation may be an optional approach to the treatment of colitis and other diseases associated with intestinal barrier dysfunction.

Lymphoedema conditions disrupt endothelial barrier function in vitro

Lymphatic vessel contractions generate net antegrade pulsatile lymph flow. By contrast, impaired lymphatic vessels are often associated with lymphoedema and altered lymph flow. The effect of lymphoedema on the lymph flow field and endothelium is not completely known. Here, we characterized the lymphatic flow field of a platelet-specific receptor C-type lectin-like receptor 2 (CLEC2) deficient lymphoedema mouse model. In regions of lymphoedema, collecting vessels were significantly distended, vessel contractility was greatly diminished and pulsatile lymph flow was replaced by quasi-steady flow. In vitro exposure of human dermal lymphatic endothelial cells (LECs) to lymphoedema-like quasi-steady flow conditions increased intercellular gap formation and permeability in comparison to normal pulsatile lymph flow. In the absence of flow, LECs exposed to steady pressure (SP) increased intercellular gap formation in contrast with pulsatile pressure (PP). The absence of pulsatility in steady fluid flow and SP conditions without flow-induced upregulation of myosin light chain (MLCs) regulatory subunits 9 and 12B mRNA expression and phosphorylation of MLCs, in contrast with pulsatile flow and PP without flow. These studies reveal that the loss of pulsatility, which can occur with lymphoedema, causes LEC contraction and an increase in intercellular gap formation mediated by MLC phosphorylation.

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

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

Tetrastigma hemsleyanum Diels et Gilg ameliorates lipopolysaccharide induced sepsis via repairing the intestinal mucosal barrier

OBJECTIVE

Sepsis causes excessive systemic inflammation and leads to multiple organ dysfunction syndrome (MODS). The intestine plays a key role in the occurrence and development of sepsis. Tetrastigma hemsleyanum Diels et Gilg (San ye qing, SYQ), a precious Chinese medicine, has been widely used for centuries due to its high traditional value, such as a remarkable anti-inflammatory effect. However, the role of SYQ in intestinal permeability during the development of sepsis needs to be discovered.

METHODS

Mice were intraperitoneally injected with lipopolysaccharide (LPS) to simulate intestinal mucosal barrier function damage in sepsis. Pathological section, inflammatory cytokines, tight junctions, cell apoptosis, and intestinal flora were detected to evaluate the protective effect of SYQ on intestinal mucosal barrier injury in LPS-induced septic mice.

RESULTS

The results showed that SYQ treatment obviously attenuated LPS-induced intestinal injury and reduced the production of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and interleukin 6 (IL-6). Besides, SYQ also up-regulated the expressions of tight junctions, including Zonula occludens 1 (ZO-1), Claudin-5, and Occludin along with a decreased in the levels of myosin light chain kinase (MLCK) and myosin light chain (MLC). In addition, SYQ down-regulated the expression of Bax/Bcl2 as well as that of cleaved caspase-3 to prevent the cells from undergoing apoptosis. Further, SYQ restored the diversity of the intestinal flora, increased the abundance of Firmicutes, and decreased the abundance of Bacteroidota.

CONCLUSIONS

The study indicated that SYQ exerted its protective effect on intestinal mucosal barrier injury in LPS-induced septic mice by reducing inflammatory response, improving the tight junction protein expression, inhibiting cell apoptosis, and adjusting the intestinal flora structure.

Oxidative Stress: Meeting Multiple Targets in Pathogenesis of Vascular Endothelial Dysfunction

Vascular endothelium is the innermost lining of blood vessels, which maintains vasoconstriction and vasodilation. Loss of vascular tone is a hallmark for cardiovascular disorders. Though there are numerous factors, such as over activation of renin angiotensin aldosterone system, kinases, growth factors, etc. play crucial role in induction and progression of vascular abrasion. Interestingly, dysregulation of these pathways either enhances the intensity of oxidative stress, or these pathways are affected by oxidative stress. Thus, oxidative stress has been considered a key culprit in the progression of vascular endothelial dysfunction. Oxidative stress induced by reactive oxygen and nitrogen species causes abnormal gene expression, alteration in signal transduction, and the activation of pathways leading to induction and progression of vascular injury. In addition, numerous antioxidants have been noted to possess promising therapeutic potential in preventing the development of vascular endothelial dysfunction. Therefore, we have focused on current perspectives in oxidative stress signalling to evaluate common biological processes whereby oxidative stress plays a crucial role in the progression of vascular endothelial dysfunction.

Endothelial Cell Plasma Membrane Biomechanics Mediates Effects of Pro-Inflammatory Factors on Endothelial Mechanosensors: Vicious Circle Formation in Atherogenic Inflammation

Chronic low-grade vascular inflammation and endothelial dysfunction significantly contribute to the pathogenesis of cardiovascular diseases. In endothelial cells (ECs), anti-inflammatory or pro-inflammatory signaling can be induced by different patterns of the fluid shear stress (SS) exerted by blood flow on ECs. Laminar blood flow with high magnitude is anti-inflammatory, while disturbed flow and laminar flow with low magnitude is pro-inflammatory. Endothelial mechanosensors are the key upstream signaling proteins in SS-induced pro- and anti-inflammatory responses. Being transmembrane proteins, mechanosensors, not only experience fluid SS but also become regulated by the biomechanical properties of the lipid bilayer and the cytoskeleton. We review the apparent effects of pro-inflammatory factors (hypoxia, oxidative stress, hypercholesterolemia, and cytokines) on the biomechanics of the lipid bilayer and the cytoskeleton. An analysis of the available data suggests that the formation of a vicious circle may occur, in which pro-inflammatory cytokines enhance and attenuate SS-induced pro-inflammatory and anti-inflammatory signaling, respectively.

Axis specification: Breaking symmetry with a myosin patch in the egg

Drosophila anterior-posterior axis specification occurs in the oocyte, but the initial symmetry break has been unclear. A new study reveals that a posterior domain of cortical myosin is induced with unique post-translational modification and dynamics and that this domain recruits downstream posterior determinants.

Proinflammatory mediators, TNFα, IFNγ, and thrombin, directly induce lymphatic capillary tube regression

In this work, we sought to investigate the direct effects of proinflammatory mediators on lymphatic endothelial cell (LEC) capillaries and whether they might induce regression. Our laboratory has developed novel in-vitro, serum-free, lymphatic tubulogenesis assay models whereby human LEC tube networks readily form in either three-dimensional collagen or fibrin matrices. These systems were initially conceptualized in the hopes of better understanding the influence of proinflammatory mediators on LEC capillaries. In this work, we have screened and identified proinflammatory mediators that cause regression of LEC tube networks, the most potent of which is TNFα (tumor necrosis factor alpha), followed by IFNγ (interferon gamma) and thrombin. When these mediators were combined, even greater and more rapid lymphatic capillary regression occurred. Surprisingly, IL-1β (interleukin-1 beta), one of the most potent and pathologic cytokines known, had no regressive effect on these tube networks. Finally, we identified new pharmacological drug combinations capable of rescuing LEC capillaries from regression in response to the potent combination of TNFα, IFNγ, and thrombin. We speculate that protecting lymphatic capillaries from regression may be an important step toward mitigating a wide variety of acute and chronic disease states, as lymphatics are believed to clear both proinflammatory cells and mediators from inflamed and damaged tissue beds. Overall, these studies identify key proinflammatory mediators, including TNFα, IFNγ, and thrombin, that induce regression of LEC tube networks, as well as identify potential therapeutic agents to diminish LEC capillary regression responses.

Aortic intimal resident macrophages are essential for maintenance of the non-thrombogenic intravascular state

Leukocytes and endothelial cells frequently cooperate to resolve inflammatory events. In most cases, these interactions are transient in nature and triggered by immunological insults. Here, we report that in areas of disturbed blood flow, aortic endothelial cells permanently and intimately associate with a population of specialized macrophages that are recruited at birth from the closing ductus arteriosus and share the luminal surface with the endothelium becoming interwoven in the tunica intima. Anatomical changes that affect hemodynamics, like in patent ductus arteriosus, alter macrophage seeding to coincide with regions of disturbed flow. Aortic resident macrophages expand in situ via direct cell renewal. Induced-depletion of intimal macrophages led to thrombin-mediated endothelial cell contraction, progressive fibrin accumulation and formation of microthrombi that, once dislodged, caused blockade of vessels in several organs. Together the findings revealed that intravascular resident macrophages are essential to regulate thrombin activity and clear fibrin deposits in regions of disturbed blood flow.

IL-1β and the Intestinal Epithelial Tight Junction Barrier

The intestinal epithelial tight junction (TJ) barrier controls the paracellular permeation of contents from the intestinal lumen into the intestinal tissue and systemic circulation. A defective intestinal TJ barrier has been implicated as an important pathogenic factor in inflammatory diseases of the gut including Crohn's disease, ulcerative colitis, necrotizing enterocolitis, and celiac disease. Previous studies have shown that pro-inflammatory cytokines, which are produced during intestinal inflammation, including interleukin-1β (IL-1β), tumor necrosis factor-α, and interferon-γ, have important intestinal TJ barrier-modulating actions. Recent studies have shown that the IL-1β-induced increase in intestinal TJ permeability is an important contributing factor of intestinal inflammation. The IL-1β-induced increase in intestinal TJ permeability is mediated by regulatory signaling pathways and activation of nuclear transcription factor nuclear factor-κB, myosin light chain kinase gene activation, and post-transcriptional occludin gene modulation by microRNA and contributes to the intestinal inflammatory process. In this review, the regulatory role of IL-1β on intestinal TJ barrier, the intracellular mechanisms that mediate the IL-1β modulation of intestinal TJ permeability, and the potential therapeutic targeting of the TJ barrier are discussed.

Rho GTPase signalling networks in cancer cell transendothelial migration

Rho GTPases are small signalling G-proteins that are central regulators of cytoskeleton dynamics, and thereby regulate many cellular processes, including the shape, adhesion and migration of cells. As such, Rho GTPases are also essential for the invasive behaviour of cancer cells, and thus involved in several steps of the metastatic cascade, including the extravasation of cancer cells. Extravasation, the process by which cancer cells leave the circulation by transmigrating through the endothelium that lines capillary walls, is an essential step for metastasis towards distant organs. During extravasation, Rho GTPase signalling networks not only regulate the transmigration of cancer cells but also regulate the interactions between cancer and endothelial cells and are involved in the disruption of the endothelial barrier function, ultimately allowing cancer cells to extravasate into the underlying tissue and potentially form metastases. Thus, targeting Rho GTPase signalling networks in cancer may be an effective approach to inhibit extravasation and metastasis. In this review, the complex process of cancer cell extravasation will be discussed in detail. Additionally, the roles and regulation of Rho GTPase signalling networks during cancer cell extravasation will be discussed, both from a cancer cell and endothelial cell point of view.

The wHole Story About Fenestrations in LSEC

The porosity of liver sinusoidal endothelial cells (LSEC) ensures bidirectional passive transport of lipoproteins, drugs and solutes between the liver capillaries and the liver parenchyma. This porosity is realized via fenestrations - transcellular pores with diameters in the range of 50-300 nm - typically grouped together in sieve plates. Aging and several liver disorders severely reduce LSEC porosity, decreasing their filtration properties. Over the years, a variety of drugs, stimulants, and toxins have been investigated in the context of altered diameter or frequency of fenestrations. In fact, any change in the porosity, connected with the change in number and/or size of fenestrations is reflected in the overall liver-vascular system crosstalk. Recently, several commonly used medicines have been proposed to have a beneficial effect on LSEC re-fenestration in aging. These findings may be important for the aging populations of the world. In this review we collate the literature on medicines, recreational drugs, hormones and laboratory tools (including toxins) where the effect LSEC morphology was quantitatively analyzed. Moreover, different experimental models of liver pathology are discussed in the context of fenestrations. The second part of this review covers the cellular mechanisms of action to enable physicians and researchers to predict the effect of newly developed drugs on LSEC porosity. To achieve this, we discuss four existing hypotheses of regulation of fenestrations. Finally, we provide a summary of the cellular mechanisms which are demonstrated to tune the porosity of LSEC.

Acute myocardial injury secondary to severe acute liver failure: A retrospective analysis supported by animal data

To investigate whether acute liver failure (ALF) leads to secondary acute myocardial injury, 100 ALF patients that were retrospectively identified in a single center based on ICD 10 codes and 8 rats from an experimental study that died early after bile duct ligation (BDL) were examined. Creatine kinase (CK), creatine kinase-MB isoenzyme (CKMB) and cardiac troponin-I (cTnI) were analyzed as markers of myocardial injury. For histological analysis, hematoxylin-eosin (HE), elastic Van Gieson (EVG), CD41 and myeloperoxidase were used to stain rat hearts. Major adverse cardiac events (MACEs) were a critical factor for mortality (p = 0.037) in human ALF. Deceased patients exhibited higher levels of CKMB than survivors (p = 0.023). CKMB was a predictor of mortality in ALF (p = 0.013). Animals that died early after BDL exhibited increased cTnI, CKMB, tumor necrosis factor α (TNFα) and interleukin-6 (IL-6) levels compared to controls (cTnI: p = 0.011, CKMB: p = 0.008, TNFα: p = 0.003, IL-6: p = 0.006). These animals showed perivascular lesions and wavy fibers, microthrombi and neutrophilic infiltration in the heart. MACEs are decisive for mortality in human ALF, and elevated CKMB values indicate that this might be due to structural myocardial damage. Accordingly, CKMB was found to have predictive value for mortality in ALF. The results are substantiated by data from a rat BDL model demonstrating diffuse myocardial injury.

Ethanol-induced lymphatic endothelial cell permeability via MAP-kinase regulation

Chronic alcohol alters the immune system enhancing the susceptibility to inflammation, bacterial, and viral infections in alcohol users. We have shown that alcohol causes increased permeability of mesenteric lymphatic vessels in alcohol-fed rats. The mechanisms of alcohol-induced lymphatic leakage are unknown. Endothelial cell monolayer permeability is controlled by junctional proteins complexes called tight junctions (TJ) and adherens junctions (AJ), and each can be regulated by MAPK activation. We hypothesize that ethanol induces lymphatic endothelial cell (LEC) permeability via disruption of LEC TJ through MAPK activation. An in vitro model of rat LECs was used. Ethanol-supplemented medium was added at concentrations of 0, 25, and 50 mM to confluent cells. Resistance-based barrier function, transwell permeability, cell viability, TJ, AJ, and MAPK protein activity, TJ and AJ gene expressions, and the role of p38 MAPK in barrier function regulation were measured. Ethanol increased the permeability of LECs compared to controls that was not associated with decreased cell viability. LECs treated with 50 mM ethanol showed an increase in phosphorylated levels of p38. No significant changes in TJ and AJ gene or protein expressions were observed after ethanol treatment. p38 inhibition prevented ethanol-induced increases in permeability. These findings suggest that p38 may play a role in the regulation of ethanol-induced LEC permeability, but altered permeability may not be associated with decreased TJ or AJ protein expression. Further investigation into junctional protein localization is needed to better understand the effects of ethanol on lymphatic endothelial cell-to-cell contacts and hyperpermeability.

Behind Brain Metastases Formation: Cellular and Molecular Alterations and Blood-Brain Barrier Disruption

Breast cancer (BC) brain metastases is a life-threatening condition to which accounts the poor understanding of BC cells' (BCCs) extravasation into the brain, precluding the development of preventive strategies. Thus, we aimed to unravel the players involved in the interaction between BCCs and blood-brain barrier (BBB) endothelial cells underlying BBB alterations and the transendothelial migration of malignant cells. We used brain microvascular endothelial cells (BMECs) as a BBB in vitro model, under conditions mimicking shear stress to improve in vivo-like BBB features. Mixed cultures were performed by the addition of fluorescently labelled BCCs to distinguish individual cell populations. BCC-BMEC interaction compromised BBB integrity, as revealed by junctional proteins (β-catenin and zonula occludens-1) disruption and caveolae (caveolin-1) increase, reflecting paracellular and transcellular hyperpermeability, respectively. Both BMECs and BCCs presented alterations in the expression pattern of connexin 43, suggesting the involvement of the gap junction protein. Myosin light chain kinase and phosphorylated myosin light chain were upregulated, revealing the involvement of the endothelial cytoskeleton in the extravasation process. β4-Integrin and focal adhesion kinase were colocalised in malignant cells, reflecting molecular interaction. Moreover, BCCs exhibited invadopodia, attesting migratory properties. Collectively, hub players involved in BC brain metastases formation were unveiled, disclosing possible therapeutic targets for metastases prevention.

Potential Mechanisms Mediating the Protective Effects of Tricholoma matsutake-Derived Peptides in Mitigating DSS-Induced Colitis

Intestinal barrier dysfunction and inflammatory cytokine secretion play crucial roles in inflammatory bowel disease (IBD). Herein, we investigated the protective effects of Tricholoma matsutake-derived peptides SDIKHFPF and SDLKHFPF against dextran sulfate sodium-induced colitis. Both peptides alleviated colitis signs, including diarrhea, weight loss, bloody stools, colon shortening, and histopathological changes, while reducing mucus destruction, goblet cell exhaustion, and intestinal permeability. SDIKHFPF and SDLKHFPF protected the barrier function by promoting the expression of tight junction (TJ) zonula occludens-1 and occludin within the colon, as well as attenuating colonic inflammation through myeloperoxidase and pro-inflammatory cytokine suppression. Western blotting indicated that the peptides suppressed myosin light chain kinase (MLCK) and nuclear factor kappa B (NF-κB) levels, inhibiting MLC phosphorylation. SDLKHFPF was more potent than SDIKHFPF. These findings suggest that peptide SDLKHFPF mitigates colitis by regulating TJ protein expression and pro-inflammatory cytokine production via NF-κB/MLCK/p-MLC signaling, improving the barrier function.

Homophilic and heterophilic cadherin bond rupture forces in homo- or hetero-cellular systems measured by AFM-based single-cell force spectroscopy

Cadherins enable intercellular adherens junctions to withstand tensile forces in tissues, e.g. generated by intracellular actomyosin contraction. In-vitro single molecule force spectroscopy experiments can reveal cadherin–cadherin extracellular region binding dynamics such as bond formation and strength. However, characterization of cadherin-presenting cell homophilic and heterophilic binding in the proteins’ native conformational and functional states in living cells has rarely been done. Here, we used atomic force microscopy (AFM) based single-cell force spectroscopy (SCFS) to measure rupture forces of homophilic and heterophilic bond formation of N- (neural), OB- (osteoblast) and E- (epithelial) cadherins in living fibroblast and epithelial cells in homo- and hetero-cellular arrangements, i.e., between cells and cadherins of the same and different types. In addition, we used indirect immunofluorescence labelling to study and correlate the expression of these cadherins in intercellular adherens junctions. We showed that N/N and E/E-cadherin homophilic binding events are stronger than N/OB heterophilic binding events. Disassembly of intracellular actin filaments affects the cadherin bond rupture forces suggesting a contribution of actin filaments in cadherin extracellular binding. Inactivation of myosin did not affect the cadherin rupture force in both homo- and hetero-cellular arrangements, but particularly strengthened the N/OB heterophilic bond and reinforced the other cadherins’ homophilic bonds.

Phosphorylated‑myosin light chain mediates the destruction of small intestinal epithelial tight junctions in mice with acute liver failure

Tight junction dysregulation and epithelial damage contribute to intestinal barrier loss in patients with acute liver failure (ALF); however, the regulatory mechanisms of these processes remain poorly understood. The aim of the present study was to investigate the changes of intestinal tight junction and intestinal mucosa in mice with ALF and their mechanisms. In the present study, ALF was induced in mice through an intraperitoneal injection of D-galactosamine and lipopolysaccharide (D-GalN/LPS), and the morphological changes of the liver or small intestine were analyzed using hematoxylin and eosin staining, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The intestinal tissues and isolated serum were analyzed using western blotting, immunofluorescence staining and ELISA. D-GalN/LPS-induced mice exhibited signs of hepatocyte necrosis, alongside inflammatory cell infiltration into the liver tissue and partial microvilli detachment in the small intestinal mucosa. TEM demonstrated that the intestinal epithelial tight junctions were impaired, whereas SEM micrographs revealed the presence of abnormal microvilli in D-GalN/LPS-induced mice. In addition, the expression levels of phosphorylated (p)-myosin light chain (MLC), MLC kinase (MLCK) and Rho-associated kinase (ROCK) were significantly increased in the D-GalN/LPS-induced mice compared with those in the control mice, whereas the subsequent inhibition of MLCK or ROCK significantly reduced p-MLC expression levels. Conversely, the expression levels of occludin and zonula occludens-1 (ZO-1) were significantly decreased in the D-GalN/LPS-induced mice, and the inhibition of MLCK or ROCK significantly increased occludin and ZO-1 protein expression levels compared with those in the control group. Changes in the serum levels of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 were similar to the trend observed in p-MLC expression levels. In conclusion, the findings of the present study suggested that in a D-GalN/LPS-induced ALF model, TNF-α and IL-6 signaling may increase MLCK and ROCK expression levels, further mediate phosphorylation of MLC, which may result in tight junction dysregulation and intestinal barrier dysfunction.

Activating Sphingosine-1-phospahte signaling in endothelial cells increases myosin light chain phosphorylation to decrease endothelial permeability thereby inhibiting cancer metastasis

Targeting the metastatic process to prevent disease dissemination in cancer remains challenging. One step in the metastatic cascade involves cancer cells transiting through the vascular endothelium after inflammation has increased the permeability of this cellular layer. Reducing inflammation-mediated gaps in the vascular endothelium could potentially be used to retard metastasis. This study describes the development of a novel ASR396-containing nanoparticle designed to activate the Sphingosine-1-Phosphate Receptor 1 (S1PR1) in order to tighten the junctions between the endothelial cells lining the vascular endothelium thereby inhibiting metastasis. ASR396 was derived from the S1PR1 agonist SEW2871 through chemical modification enabling the new compound to be loaded into a nanoliposome. ASR396 retained S1PR1 binding activity and the nanoliposomal formulation (nanoASR396) made it systemically bioavailable upon intravenous injection. Studies conducted in microvessels demonstrated that nanoASR396 significantly attenuated inflammatory mediator-induced permeability increase through the S1PR1 activation. Similarly, nanoASR396 inhibited gap formation mediated by inflammatory agents on an endothelial cell monolayer by decreasing levels of phosphorylated myosin light chain protein thereby inhibiting cellular contractility. In animal models, nanoASR396 inhibited lung metastasis by up to 80%, indicating its potential for retarding melanoma metastasis. Thus, a novel bioavailable nanoparticle-based S1PR1 agonist has been developed to negate the effects of inflammatory mediators on the vascular endothelium in order to reduce the metastatic dissemination of cancer cells.

BAFF Blockade Attenuates Inflammatory Responses and Intestinal Barrier Dysfunction in a Murine Endotoxemia Model

B cell-activating factor (BAFF) production is increased in septic patients. However, the specific role of BAFF in sepsis remains unknown. This study was designed to investigate the expression and function of BAFF in an experimental endotoxemia model and to identify the potential mechanisms. We established an endotoxemia mouse (6–8 weeks, 20–22 g) model by administering 30 mg/kg lipopolysaccharide (LPS). BAFF levels in the circulating system and organ tissues were measured 4 and 8 h after LPS injection. Survival rates in the endotoxemia mice were monitored for 72 h after BAFF blockade. The effects of BAFF blockade on systemic and local inflammation, organ injuries, and intestinal barrier function were also evaluated 4 h after LPS treatment. BAFF production was systemically and locally elevated after LPS challenge. BAFF blockade improved the survival rate, systemic inflammation, and multi-organ injuries. Moreover, BAFF blockade attenuated both intestinal inflammation and impaired intestinal permeability. BAFF blockade upregulated ZO-1 and occludin protein levels via the NF-κB/MLCK/MLC signaling pathway. These results suggested that BAFF blockade protects against lethal endotoxemia at least partially by alleviating inflammation, multi-organ injuries, and improving intestinal barrier function and provides a novel focus for further research on sepsis and experimental evidence for clinical therapy.

Luminespib counteracts the Kifunensine-induced lung endothelial barrier dysfunction

Unfolded protein response (UPR) suppression by Kifunensine has been associated with lung hyperpermeability, the hallmark of Acute Respiratory Distress Syndrome. The present study investigates the effects of the heat shock protein 90 inhibitor Luminespib (AUY-922) towards the Kifunensine-triggered lung endothelial dysfunction. Our results indicate that the UPR inducer Luminespib counteracts the effects of Kifunensine in both human and bovine lung endothelial cells. Hence, we suggest that UPR manipulation may serve as a promising therapeutic strategy against potentially lethal respiratory disorders, including the ARDS related to COVID-19.

Chromogranin A (CGA)-derived polypeptide (CGA47-66) inhibits TNF-α-induced vascular endothelial hyper-permeability through SOC-related Ca2+ signaling

CGA_1-78 (Vasostatin-1, VS-1) a N-terminal Chromogranin A (CGA)-derived peptide, has been shown to have a protective effect against TNF-α-induced impairment of endothelial cell integrity. However, the mechanisms of this effect have not yet been clarified. CGA_47-66 (Chromofungin, CHR) is an important bioactive fragment of CGA_1-78. The present study aims to explore the protective effects of CHR on the vascular endothelial cell barrier response to TNF-α and its related Ca²⁺ signaling mechanisms. EA.hy926 cells were used as a vascular endothelial culture model. The synthetic peptides CHR and CGA_4-16 were assessed for their ability to suppress TNF-α-induced EA.hy926 cells hyper-permeability through Transwell® and TEER assays. Changes in [Ca²⁺]_i were measured through confocal laser scanning microscopy. SOC channel currents (Isoc) were measured via patch-clamp analysis. RT-PCR and western blot were used to analyze mRNA and protein expression of the transient receptor potential channels TRPC1 and TRPC4, respectively. FITC and rhodamine-phalloidin fluorescence were used to assess cell morphology and the distribution of MyPT-1 and F-actin. Compared to untreated cells, TNF-α increased the permeability of EA.hy926 cells that was inhibited by pre-treatment with CHR (10-1000 nM) in concentration-dependent manner, and the effect was most obvious at 100 nM, but CGA_4-16 (100 nM) had no effect. TNF-α treatment increased the phosphorylation of MyPT-1 and stress fiber formation. CHR (10-1000 nM) pretreatment inhibited the cytoskeletal rearrangements and increased [Ca²⁺]_i in response to TNF-α treatment. CHR also reduced TRPC1 expression following TNF-α induction. Similar to SOC inhibitor 2-APB, CHR suppressed IP₃ mediated SOC activation. These findings suggest that CHR inhibits TNF-α-induced Ca²⁺ influx and protects the barrier function of vascular endothelial cells, and that these effects are related to the inhibition of SOC and Ca²⁺ signaling by CHR.

The tight junction protein cingulin regulates the vascular response to burn injury in a mouse model

Edema formation due to the collapse of physiological barriers and the associated delayed healing process is still a central problem in the treatment of burn injuries. In healthy individuals, tight junctions form a barrier to fluid and small molecules. Cingulin is a cytoplasmic component of tight junctions and is involved in the regulation of the paracellular barrier. Endothelial specific cingulin knock-out mice provide new insight into the influence of tight junction proteins on edema formation and angiogenesis during wound healing. Knock-out mice lacking the head domain of cingulin in endothelial cells (Cgn^ΔEC) were created by breeding Cgn^fl/fl mice with Tie1-cre mice. Using a no-touch hot air jet a burn trauma was induced on the ear of the mouse. Over a period of 12 days microcirculatory parameters such as edema formation, angiogenesis and leukocyte-endothelial interactions were visualized using intravital fluorescence microscopy. At baseline, Cgn^ΔEC mice surprisingly showed significantly less tracer extravasation compared to Cgn^fl/fl littermates, whereas, after burn injury, edema was consistently higher in Cgn^ΔEC mice. Non-perfused area after wounding was increased, but there was no difference in vessel diameters, contraction or dilation of arteries in Cgn^ΔEC mice. Moreover, cingulin knock-out did not cause a difference in leukocyte adhesion after burn injury. In summary, cingulin limits non-perfused area after burn injury and maintains the paracellular barrier of blood vessels. Since edema formation with serious systemic effects is a central problem of burn wounds, understanding the importance of tight junction proteins might help to find new treatment strategies for burn wounds.

PDE3 Inhibition Reduces Epithelial Mast Cell Numbers in Allergic Airway Inflammation and Attenuates Degranulation of Basophils and Mast Cells

Epithelial mast cells are generally present in the airways of patients with allergic asthma that are inadequately controlled. Airway mast cells (MCs) are critically involved in allergic airway inflammation and contribute directly to the main symptoms of allergic patients. Phosphodiesterase 3 (PDE3) tailors signaling of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which are critical intracellular second messenger molecules in various signaling pathways. This paper investigates the pathophysiological role and disease-modifying effects of PDE3 in mouse bone marrow-derived MCs (bmMCs), human LAD2- and HMC1 mast cell lines, human blood basophils, and peripheral blood-derived primary human MCs (HuMCs). In a chronic house dust mite (HDM)-driven allergic airway inflammation mouse model, we observed that PDE3 deficiency or PDE3 inhibition (PDE3i) therapy reduced the numbers of epithelial MCs, when compared to control mice. Mouse bone marrow-derived MCs (bmMCs) and the human HMC1 and LAD2 cell lines predominantly expressed PDE3B and PDE4A. BmMCs from Pde3^−/− mice showed reduced loss of the degranulation marker CD107b compared with wild-type BmMCs, when stimulated in an immunoglobulin E (IgE)-dependent manner. Following both IgE-mediated and substance P-mediated activation, PDE3i-pretreated basophils, LAD2 cells, and HuMCs, showed less degranulation than diluent controls, as measured by surface CD63 expression. MCs lacking PDE3 or treated with the PDE3i enoximone exhibited a lower calcium flux upon stimulation with ionomycine. In conclusion PDE3 plays a critical role in basophil and mast cell degranulation and therefore its inhibition may be a treatment option in allergic disease.

MicroRNA and mRNA analysis of angiotensin II-induced renal artery endothelial cell dysfunction

Continuous activation of angiotensin II (Ang II) induces renal vascular endothelial dysfunction, inflammation and oxidative stress, all of which may contribute to renal damage. MicroRNAs (miRs/miRNAs) play a crucial regulatory role in the pathogenesis of hypertensive nephropathy (HN). The present study aimed to assess the differential expression profiles of potential candidate genes involved in Ang II-induced rat renal artery endothelial cell (RRAEC) dysfunction and explore their possible functions. In the present study, the changes in energy metabolism and autophagy function in RRAECs were evaluated using the Seahorse XF Glycolysis Stress Test and dansylcadaverine/transmission electron microscopy following exposure to Ang II. Subsequently, mRNA-miRNA sequencing experiments were performed to determine the differential expression profiles of mRNAs and miRNAs. Integrated bioinformatics analysis was applied to further explore the molecular mechanisms of Ang II on endothelial injury induced by Ang II. The present data supported the notion that Ang II upregulated glycolysis levels and promoted autophagy activation in RRAECs. The sequencing data demonstrated that 443 mRNAs and 58 miRNAs were differentially expressed (DE) in response to Ang II exposure, where 66 mRNAs and 55 miRNAs were upregulated, while 377 mRNAs and 3 miRNAs were downregulated (fold change >1.5 or <0.67; P<0.05). Functional analysis indicated that DE mRNA and DE miRNA target genes were mainly associated with cell metabolism (metabolic pathways), differentiation (Th1 and Th2 cell differentiation), autophagy (autophagy-animal and autophagy-other) and repair (RNA-repair). To the best of the authors' knowledge, this is the first report on mRNA-miRNA integrated profiles of Ang II-induced RRAECs. The present results provided evidence suggesting that the miRNA-mediated effect on the ‘mTOR signaling pathway’ might play a role in Ang II-induced RRAEC injury by driving glycolysis and autophagy activation. Targeting miRNAs and their associated pathways may provide valuable insight into the clinical management of HN and may improve patient outcome.

The fibroblast-derived protein PI16 controls neuropathic pain

Chronic pain is a major clinical problem of which the mechanisms are incompletely understood. Here, we describe the concept that PI16, a protein of unknown function mainly produced by fibroblasts, controls neuropathic pain. The spared nerve injury (SNI) model of neuropathic pain increases PI16 protein levels in fibroblasts in dorsal root ganglia (DRG) meninges and in the epi/perineurium of the sciatic nerve. We did not detect PI16 expression in neurons or glia in spinal cord, DRG, and nerve. Mice deficient in PI16 are protected against neuropathic pain. In vitro, PI16 promotes transendothelial leukocyte migration. In vivo, Pi16 ^-/- mice show reduced endothelial barrier permeability, lower leukocyte infiltration and reduced activation of the endothelial barrier regulator MLCK, and reduced phosphorylation of its substrate MLC2 in response to SNI. In summary, our findings support a model in which PI16 promotes neuropathic pain by mediating a cross-talk between fibroblasts and the endothelial barrier leading to barrier opening, cellular influx, and increased pain. Its key role in neuropathic pain and its limited cellular and tissue distribution makes PI16 an attractive target for pain management.

Principle and design of pseudo-natural products

Natural products (NPs) are a significant source of inspiration towards the discovery of new bioactive compounds based on novel molecular scaffolds. However, there are currently only a small number of guiding synthetic strategies available to generate novel NP-inspired scaffolds, limiting both the number and types of compounds accessible. In this Perspective, we discuss a design approach for the preparation of biologically relevant small-molecule libraries, harnessing the unprecedented combination of NP-derived fragments as an overarching strategy for the synthesis of new bioactive compounds. These novel 'pseudo-natural product' classes retain the biological relevance of NPs, yet exhibit structures and bioactivities not accessible to nature or through the use of existing design strategies. We also analyse selected pseudo-NP libraries using chemoinformatic tools, to assess their molecular shape diversity and properties. To facilitate the exploration of biologically relevant chemical space, we identify design principles and connectivity patterns that would provide access to unprecedented pseudo-NP classes, offering new opportunities for bioactive small-molecule discovery.