Chlamydia pneumoniae infection promotes monocyte transendothelial migration by increasing vascular endothelial cell permeability via the tyrosine phosphorylation of VE-cadherin

iRHOM2 regulates inflammation and endothelial barrier permeability via CX3CL1

Acute lung injury (ALI) is associated with increased lung inflammation and lung permeability. The present study aimed to determine the role of inactive rhomboid-like protein 2 (iRHOM2) in ALI in lipopolysaccharide (LPS)-induced pulmonary microvascular endothelial cell model. Human pulmonary microvascular endothelial cells (HPMVECs) were transfected with small interfering RNA targeting iRHOM2 and C-X3-C motif chemokine ligand 1 (CX3CL1) overexpression plasmids and treated with LPS. Cell viability was detected using a Cell Counting Kit-8 assay, while levels of TNFα, IL-1β, IL-6 and p65 were measured by reverse transcription-quantitative PCR and western blotting. Apoptosis levels were measured using a TUNEL assay. Endothelial barrier permeability was detected, followed by analysis of zonula occludens-1, vascular endothelial-cadherin and occludin by immunofluorescence staining or western blotting. The interaction of iRHOM2 and CX3CL1 was analyzed using an immune-coprecipitation assay. Through bioinformatics analysis, it was found that CX3CL1 was upregulated in the LPS group compared with the control. Kyoto Encyclopedia of Genes and Genomes pathway analysis demonstrated that the TNF signaling pathway affected by iRHOM2 and cytokine-cytokine receptor interaction, including CX3CL1, served a key role in ALI. HPMVECs treated with LPS exhibited a decrease in cell viability and an increase in inflammation, apoptosis and endothelial barrier permeability, while these effects were reversed by iRHOM2 silencing. However, CX3CL1 overexpression inhibited the effects of iRHOM2 silencing on LPS-treated HPMVECs. The present study demonstrated a novel role of iRHOM2 as a regulator that affects inflammation, apoptosis and endothelial barrier permeability; this was associated with CX3CL1.

Low-Dose X-Ray Increases Paracellular Permeability of Human Renal Glomerular Endothelial Cells

Objective

Glomerular endothelium functions as a filtration barrier of metabolites in the kidney. Although X-ray irradiation modulated the permeability of the vascular endothelium, the response of human renal glomerular endothelial cells (HRGECs) to low-dose X-ray irradiation has not been investigated. We evaluated the impacts of low-dose X-ray irradiation on HRGECs and revealed the underlying mechanism.

Methods

HRGECs were exposed to X-ray with doses of 0, 0.1, 0.5, 1.0, and 2.0 Gy. The proliferation, viability, and apoptosis of HRGECs were examined by MTT assay, trypan blue staining assay, and TUNEL staining, respectively. The paracellular permeability was assessed by paracellular permeability assay. The expression of VE-cadherin was investigated via immunofluorescence assay. Western blot and qRT-PCR detected the expression levels of VE-cadherin and CLDN5. Besides, the expression levels of pVE-cadherin (pY658), TGF-β, TGF-βRI, Src, p-Src, Smad2, p-Smad2, Smad3, p-Smad3, SNAIL, SLUG, and apoptosis-related proteins were tested by Western blot.

Results

The proliferation, viability, and apoptosis of HRGECs were not affected by low-dose (<2.0 Gy) X-ray irradiation. X-ray irradiation dose-dependently reduced the level of VE-cadherin, and VE-cadherin and CLDN5 levels were reduced with X-ray irradiation. The levels of pY658, p-Src, p-Smad2, and p-Smad3 were upregulated with the increase in X-ray dose. Besides, the paracellular permeability of HRGECs was increased by even low-dose (<2.0 Gy) X-ray irradiation. Therefore, low-dose X-ray irradiation reduced the cumulative content of VE-cadherin and increased the level of pY658 via activation of the TGF-β signaling pathway.

Conclusion

Even though low-dose X-ray exposure had no impact on proliferation, viability, and apoptosis of HRGECs, it increased the paracellular permeability by deterioration and downregulation of VE-cadherin through stimulating the TGF-β signaling pathway. This study built the framework for kidney response to low-dose irradiation exposure.

VE-cadherin N-glycosylation modified by N-acetylglucosaminyltransferase V regulates VE-cadherin-β-catenin interaction and monocyte adhesion

NEW FINDINGS

What is the central question of this study? Inflammation-induced monocyte adhesion is the initiator of most vascular diseases. The underlying mechanisms that mediate monocyte adhesion remain to be clarified fully. What is the main finding and its importance? N-acetylglucosaminyltransferase V (GnT-V)-mediated N-glycosylation of VE-cadherin regulates the dissociation of the VE-cadherin-β-catenin complex to modulate monocyte adhesion, but GnT-V overexpression cannot rescue monocyte adhesion induced by interleukin-1β. This study clarified the molecular mechanism of VE-cadherin in regulating the monocyte adhesion process.

ABSTRACT

Monocyte adhesion is a crucial step in the initial stage of atherosclerosis, and dysfunction of VE-cadherin has been reported to be involved in this process. Our group previously found that VE-cadherin and its binding protein, β-catenin, were modified by sialylation, and the levels of sialylation were decreased in pro-inflammatory cytokine-treated human umbilical vein EA.hy926 cells. In this study, we confirmed that the sugar chains of VE-cadherin were modified by N-acetylglucosaminyltransferase V (GnT-V). We showed that the levels of GnT-V and β1,6-N-acetylglucosamine on the VE-cadherin were reduced in the presence of interleukin-1β, whereas the level of monocyte transendothelial migration was increased. Moreover, the interaction between VE-cadherin and β-catenin was increased, accompanied by an increased accumulation of degradative VE-cadherin and cytoplasmic β-catenin, indicating impairment of cell-cell junctions after interleukin-1β treatment. Furthermore, GnT-V short hairpin RNA and overexpression analysis confirmed that glycosylation of VE-cadherin was modified by GnT-V in EA.hy926 cells, which contributed to the monocyte-endothelial adhesion process. Taken together, these results suggest that the function of VE-cadherin in facilitating monocyte adhesion might result from the decreasing GnT-V expression and disorder of GnT-V-catalysed N-glycosylation. Our study clarified the molecular mechanism of VE-cadherin in regulation of the monocyte adhesion process and provided new insights into the post-transcriptional modifications of VE-cadherin.

An In Vitro Model of Diabetic Retinal Vascular Endothelial Dysfunction and Neuroretinal Degeneration

BACKGROUND

Diabetic retinopathy (DR) is a leading cause of blindness in working-age populations. Proper in vitro DR models are crucial for exploring pathophysiology and identifying novel therapeutic targets. This study establishes a rational in vitro diabetic retinal neuronal-endothelial dysfunction model and a comprehensive downstream validation system.

METHODS

Human retinal vascular endothelial cells (HRMECs) and retinal ganglion cells (RGCs) were treated with different glucose concentrations with mannitol as matched osmotic controls. Cell proliferation and viability were evaluated by the Cell Counting Kit-8. Cell migration was measured using a transwell migration assay. Cell sprouting was assessed by a tube formation assay. The VEGF expression was assessed by ELISA. RGCs were labeled by neurons and RGC markers TUJ1 and BRN3A for quantitative and morphological analysis. Apoptosis was detected using PI/Hoechst staining and TUNEL assay and quantified by ImageJ.

RESULTS

Cell proliferation and migration in HRMECs were significantly higher in the 25 mM glucose-treated group (p < 0.001) but lower in the 50 mM and 100 mM groups (p < 0.001). The permeability and the apoptotic index in HRMECs were statistically higher in the 25 mM, 50 mM, and 100 mM groups (p < 0.05). The tube formation assay found that all the parameters were significantly higher in the 25 mM and 50 mM groups (p < 0.001) concomitant with the elevated VEGFA expression in HRMECs (p = 0.016). Cell viability was significantly lower in the 50 mM, 100 mM, and 150 mM groups in RGCs (p _50mM = 0.013, p _100mM = 0.019, and p _150mM = 0.002). Apoptosis was significantly elevated, but the proportion of RGCs with neurite extension was significantly lower in the 50 mM, 100 mM, and 150 mM groups (p _50mM < 0.001, p _100mM < 0.001, and p _150mM < 0.001).

CONCLUSIONS

We have optimized glucose concentrations to model diabetic retinal endothelial (25-50 mM) or neuronal (50-100 mM) dysfunction in vitro, which have a wide range of downstream applications.

TM4SF19 aggravates LPS-induced attenuation of vascular endothelial cell adherens junctions by suppressing VE-cadherin expression

Atherosclerosis is a chronic vascular inflammatory disease that initially starts from an arterial intima lesion and endothelial barrier dysfunction. The purpose of this study was to investigate the role of TM4SF19, a recently identified member of the transmembrane 4L six superfamily, in vascular endothelial cell adherens junctions. We found TM4SF19 expression was significantly increased in atherosclerotic plaques and sera of patients with coronary heart disease (CHD) compared with healthy people by immunohistochemistry and ELISA. In vitro, human umbilical vein endothelial cells (HUVECs) were stimulated by lipopolysaccharides (LPS). TM4SF19 and VE-cadherin expression as well as cell adherens junctions were assessed. Additionally, LPS could upregulate TM4SF19 expression and downregulate VE-cadherin expression in HUVECs in a concentration dependent manner. Overexpression of TM4SF19 substantially aggravated LPS-induced reduction of VE-cadherin expression and attenuation of vascular endothelial cell adherens junctions. However, both the decreased VE-cadherin expression and weakened cell adherens junctions induced by LPS could be dramatically reversed when the expression of TM4SF19 was depressed. This study is the first to reveal the effect of TM4SF19 on endothelial cell adherens junctions. Meanwhile, our results also provide novel therapeutic strategies for atherosclerotic diseases.

Toxoplasma gondii Dysregulates Barrier Function and Mechanotransduction Signaling in Human Endothelial Cells

Toxoplasma gondii can infect and replicate in vascular endothelial cells prior to entering host tissues. However, little is known about the molecular interactions at the parasite-endothelial cell interface. We demonstrate that T. gondii infection of primary human umbilical vein endothelial cells (HUVEC) altered cell morphology and dysregulated barrier function, increasing permeability to low-molecular-weight polymers. T. gondii disrupted vascular endothelial cadherin (VE-cadherin) and β-catenin localization to the cell periphery and reduced VE-cadherin protein expression. Notably, T. gondii infection led to reorganization of the host cytoskeleton by reducing filamentous actin (F-actin) stress fiber abundance under static and microfluidic shear stress conditions and by reducing planar cell polarity. RNA sequencing (RNA-Seq) comparing genome-wide transcriptional profiles of infected to uninfected endothelial cells revealed changes in gene expression associated with cell-cell adhesion, extracellular matrix reorganization, and cytokine-mediated signaling. In particular, genes downstream of Hippo signaling and the biomechanical sensor and transcriptional coactivator Yes-associated protein (YAP) were downregulated in infected endothelial cells. Interestingly, T. gondii infection activated Hippo signaling by increasing phosphorylation of LATS1, leading to cytoplasmic retention of YAP, and reducing YAP target gene expression. These findings suggest that T. gondii infection triggers Hippo signaling and YAP nuclear export, leading to an altered transcriptional profile of infected endothelial cells.IMPORTANCE Toxoplasma gondii is a foodborne parasite that infects virtually all warm-blooded animals and can cause severe disease in individuals with compromised or weakened immune systems. During dissemination in its infected hosts, T. gondii breaches endothelial barriers to enter tissues and establish the chronic infections underlying the most severe manifestations of toxoplasmosis. The research presented here examines how T. gondii infection of primary human endothelial cells induces changes in cell morphology, barrier function, gene expression, and mechanotransduction signaling under static conditions and under the physiological conditions of shear stress found in the bloodstream. Understanding the molecular interactions occurring at the interface between endothelial cells and T. gondii may provide insights into processes linked to parasite dissemination and pathogenesis.

Exosomal Thrombospondin-1 Disrupts the Integrity of Endothelial Intercellular Junctions to Facilitate Breast Cancer Cell Metastasis

Transendothelial migration of malignant cells plays an essential role in tumor progression and metastasis. The present study revealed that treating human umbilical vein endothelial cells (HUVECs) with exosomes derived from metastatic breast cancer cells increased the number of cancer cells migrating through the endothelial cell layer and impaired the tube formation of HUVECs. Furthermore, the expression of intercellular junction proteins, including vascular endothelial cadherin (VE-cadherin) and zona occluden-1 (ZO-1), was reduced significantly in HUVECs treated with carcinoma-derived exosomes. Proteomic analyses revealed that thrombospondin-1 (TSP1) was highly expressed in breast cancer cell MDA-MB-231-derived exosomes. Treating HUVECs with TSP1-enriched exosomes similarly promoted the transendothelial migration of malignant cells and decreased the expression of intercellular junction proteins. TSP1-down regulation abolished the effects of exosomes on HUVECs. The migration of breast cancer cells was markedly increased in a zebrafish in vivo model injected with TSP1-overexpressing breast cancer cells. Taken together, these results suggest that carcinoma-derived exosomal TSP1 facilitated the transendothelial migration of breast cancer cells via disrupting the intercellular integrity of endothelial cells.

A renewed tool kit to explore Chlamydia pathogenesis: from molecular genetics to new infection models

Chlamydia trachomatis is the most prevalent sexually transmitted bacterial pathogen and the leading cause of preventable blindness in the developing world. C. trachomatis invades the epithelium of the conjunctiva and genital tract and replicates within an intracellular membrane-bound compartment termed the inclusion. To invade and replicate in mammalian cells, Chlamydia remodels epithelial surfaces by reorganizing the cytoskeleton and cell–cell adhesions, reprograms membrane trafficking, and modulates cell signaling to dampen innate immune responses. If the infection ascends to the upper female genital tract, it can result in pelvic inflammatory disease and tissue scarring. C. trachomatis infections are associated with infertility, ectopic pregnancies, the fibrotic disorder endometriosis, and potentially cancers of the cervix and uterus. Unfortunately, the molecular mechanisms by which this clinically important human pathogen subverts host cellular functions and causes disease have remained relatively poorly understood because of the dearth of molecular genetic tools to study Chlamydiae and limitations of both in vivo and in vitro infection models. In this review, we discuss recent advances in the experimental molecular tool kit available to dissect C. trachomatis infections with a special focus on Chlamydia-induced epithelial barrier disruption by regulating the structure, function, and dynamics of epithelial cell–cell junctions.

Effect of melatonin on EGF- and VEGF-induced monolayer permeability of HUVECs

Melatonin is a natural hormone involved in the regulation of circadian rhythm, immunity, and cardiovascular function. In the present study, we focused on the mechanism of melatonin in the regulation of vascular permeability. We found that melatonin could inhibit both VEGF- and EGF-induced monolayer permeability of human umbilical vein endothelial cells (HUVECs) and change the tyrosine phosphorylation of vascular-endothelial (VE-)cadherin, which was related to endothelial barrier function. In addition, phospho-AKT (Ser⁴⁷³) and phospho-ERK(1/2) played significant roles in the regulation of VE-cadherin phosphorylation. Both the phosphatidylinositol 3-kinase/AKT inhibitor LY49002 and MEK/ERK inhibitor U0126 could inhibit the permeability of HUVECs, but with different effects on tyrosine phosphorylation of VE-cadherin. Melatonin can influence the two growth factor-induced phosphorylation of AKT (Ser⁴⁷³) but not ERK(1/2). Our results show that melatonin can inhibit growth factor-induced monolayer permeability of HUVECs by influencing the phosphorylation of AKT and VE-cadherin. Melatonin can be a potential treatment for diseases associated with abnormal vascular permeability. NEW & NOTEWORTHY We found that melatonin could inhibit both EGF- and VEGF-induced monolayer permeability of human umbilical vein endothelial cells, which is related to phosphorylation of vascular-endothelial cadherin. Blockade of phosphatidylinositol 3-kinase/AKT and MEK/ERK pathways could inhibit the permeability of human umbilical vein endothelial cells, and phosphorylation of AKT (Ser⁴⁷³) might be a critical event in the changing of monolayer permeability and likely has cross-talk with the MEK/ERK pathway.