Molecular mechanism of the interaction between Megalocytivirus-induced virus-mock basement membrane (VMBM) and lymphatic endothelial cells

IMPORTANCE

Viruses are able to mimic the physiological or pathological mechanism of the host to favor their infection and replication. Virus-mock basement membrane (VMBM) is a Megalocytivirus-induced extracellular structure formed on the surface of infected cells and structurally and functionally mimics the basement membrane of the host. VMBM provides specific support for lymphatic endothelial cells (LECs) rather than blood endothelial cells to adhere to the surface of infected cells, which constitutes a unique phenomenon of Megalocytivirus infection. Here, the structure of VMBM and the interactions between VMBM components and LECs have been analyzed at the molecular level. The regulatory effect of VMBM components on the proliferation and migration of LECs has also been explored. This study helps to understand the mechanism of LEC-specific attachment to VMBM and to address the issue of where the LECs come from in the context of Megalocytivirus infection.

Formation of the glomerular microvasculature is regulated by VEGFR-3

Microvascular dysfunction is a key driver of kidney disease. Pathophysiological changes in the kidney vasculature are regulated by vascular endothelial growth factor receptors (VEGFRs), supporting them as potential therapeutic targets. The tyrosine kinase receptor VEGFR-3, encoded by FLT4 and activated by the ligands VEGF-C and VEGF-D, is best known for its role in lymphangiogenesis. Therapeutically targeting VEGFR-3 to modulate lymphangiogenesis has been proposed as a strategy to treat kidney disease. However, outside the lymphatics, VEGFR-3 is also expressed in blood vascular endothelial cells in several tissues including the kidney. Here, we show that Vegfr-3 is expressed in fenestrated microvascular beds within the developing and adult mouse kidney, which include the glomerular capillary loops. We found that expression levels of VEGFR-3 are dynamic during glomerular capillary loop development, with the highest expression observed during endothelial cell migration into the S-shaped glomerular body. We developed a conditional knockout mouse model for Vegfr-3 and found that loss of Vegfr-3 resulted in a striking glomerular phenotype characterized by aneurysmal dilation of capillary loops, absence of mesangial structure, abnormal interendothelial cell junctions, and poor attachment between glomerular endothelial cells and the basement membrane. In addition, we demonstrated that expression of the VEGFR-3 ligand VEGF-C by podocytes and mesangial cells is dispensable for glomerular development. Instead, VEGFR-3 in glomerular endothelial cells attenuates VEGFR-2 phosphorylation. Together, the results of our study support a VEGF-C-independent functional role for VEGFR-3 in the kidney microvasculature outside of lymphatic vessels, which has implications for clinical therapies that target this receptor.NEW & NOTEWORTHY Targeting VEGFR-3 in kidney lymphatics has been proposed as a method to treat kidney disease. However, expression of VEGFR-3 is not lymphatic-specific. We demonstrated developmental expression of VEGFR-3 in glomerular endothelial cells, with loss of Vegfr-3 leading to malformation of glomerular capillary loops. Furthermore, we showed that VEGFR-3 attenuates VEGFR-2 activity in glomerular endothelial cells independent of paracrine VEGF-C signaling. Together, these data provide valuable information for therapeutic development targeting these pathways.

VEGFR3 tyrosine kinase inhibition aggravates cisplatin nephrotoxicity

Expansion of renal lymphatic networks, or lymphangiogenesis (LA), is well recognized during development and is now being implicated in kidney diseases. Although LA is associated with multiple pathological conditions, very little is known about its role in acute kidney injury. The purpose of this study was to evaluate the role of LA in a model of cisplatin-induced nephrotoxicity. LA is predominately regulated by vascular endothelial growth factor (VEGF)-C and VEGF-D, ligands that exert their function through their cognate receptor VEGF receptor 3 (VEGFR3). We demonstrated that use of MAZ51, a selective VEGFR3 inhibitor, caused significantly worse structural and functional kidney damage in cisplatin nephrotoxicity. Apoptotic cell death and inflammation were also increased in MAZ51-treated animals compared with vehicle-treated animals following cisplatin administration. Notably, MAZ51 caused significant upregulation of intrarenal phospho-NF-κB, phospho-JNK, and IL-6. Cisplatin nephrotoxicity is associated with vascular congestion due to endothelial dysfunction. Using three-dimensional tissue cytometry, a novel approach to explore lymphatics in the kidney, we detected significant vascular autofluorescence attributed to erythrocytes in cisplatin alone-treated animals. Interestingly, no such congestion was detected in MAZ51-treated animals. We found increased renal vascular damage in MAZ51-treated animals, whereby MAZ51 caused a modest decrease in the endothelial markers endomucin and von Willebrand factor, with a modest increase in VEGFR2. Our findings identify a protective role for de novo LA in cisplatin nephrotoxicity and provide a rationale for the development of therapeutic approaches targeting LA. Our study also suggests off-target effects of MAZ51 on the vasculature in the setting of cisplatin nephrotoxicity.NEW & NOTEWORTHY Little is known about injury-associated LA in the kidney and its role in the pathophysiology of acute kidney injury (AKI). Observed exacerbation of cisplatin-induced AKI after LA inhibition was accompanied by increased medullary damage and cell death in the kidney. LA inhibition also upregulated compensatory expression of LA regulatory proteins, including JNK and NF-κB. These data support the premise that LA is induced during AKI and lymphatic expansion is a protective mechanism in cisplatin nephrotoxicity.

Expression levels of VEGF-C and VEGFR-3 in renal cell carcinoma and their association with lymph node metastasis

Renal cell carcinoma (RCC) is the most common form of kidney cancer. Vascular endothelial growth factor-C (VEGF-C) and its receptor, VEGFR-3, are involved in lymphangiogenesis. The aim of the present study was to investigate the expression levels of VEGF-C and VEGFR-3 in RCC, and their association with lymphatic vessel density (LVD) and lymph node metastasis. The mRNA expression levels of VEGF-C in 40 RCC tissues and 10 normal renal tissues were determined by reverse transcription-semiquantitative PCR. The differential expression of VEGF-C and VEGFR-3 was examined by immunohistochemistry. Using an anti-D2-40 antibody as a lymphatic marker, the morphology and structure of lymphatic vessels in tissues was examined, and the LVD was calculated. VEGF-C mRNA expression in RCC tissues was higher than that in normal renal tissues, and VEGF-C mRNA expression in the lymph node metastasis group was higher than that in the non-lymph node metastasis group. The positive expression rate of VEGF-C and VEGFR-3 in RCC tissues was significantly higher than that in normal renal tissues. VEGF-C expression in the lymph node metastasis group was significantly higher than that in the non-lymph node metastasis group, and the positive expression of VEGF-C was associated with the clinical staging of RCC. In addition, there was a correlation between VEGF-C and VEGFR-3 expression in tumor cells. The LVD around the tumor was higher than that in the center of the tumor tissues and normal renal tissues, and it was closely associated with lymphatic invasion and lymph node metastasis. Overall, the current findings demonstrated that the VEGF-C/VEGFR-3 signaling pathway promoted lymphangiogenesis around the tumor and provided an approach for tumor lymphatic invasion and lymph node metastasis. Therefore, VEGFC and VEGFR-3 expression may serve an important role in the initiation and development of RCC.

[Research on influence mechanism of G protein coupled receptor kinase interacting protein 1 on differentiation of bone marrow mesenchymal stem cells into endothelial cells]

Objective

To investigate the mechanism of G protein coupled receptor kinase interacting protein 1 (GIT1) affecting angiogenesis by comparing the differentiation of bone marrow mesenchymal stem cells (BMSCs) differentiated into endothelial cells between GIT1 wild type mice and GIT1 gene knockout mice.

Methods

Male and female GIT1 heterozygous mice were paired breeding, and the genotypic identification of newborn mice were detected by PCR. The 2nd generation BMSCs isolated from GIT1 wild type mice or GIT1 gene knockout mice were divided into 4 groups, including wild type control group (group A), wild type experimental group (group A1), GIT1 knockout control group (group B), and GIT1 knockout experimental group (group B1). The cells of groups A1 and B1 were cultured with the endothelial induction medium and the cells of groups A and B with normal cluture medium. The expressions of vascular endothelial growth factor receptor 2 (VEGFR-2), VEGFR-3, and phospho-VEGFR-2 (pVEGFR-2), and pVEGFR-3 proteins were detected by Western blot. The endothelial cell markers [von Willebrand factor (vWF), platelet-endothelial cell adhesion molecule 1 (PECAM-1), and vascular endothelial cadherin (VE-Cadherin)] were detected by flow cytometry. The 2nd generation BMSCs of GIT1 wild type mice were divided into 4 groups according to the different culture media: group Ⅰ, primary cell culture medium; group Ⅱ, cell culture medium containing SAR131675 (VEGFR-3 blocker); group Ⅲ, endothelial induction medium; group Ⅳ, endothelial induction medium containing SAR131675. The endothelial cell markers (vWF, PECAM-1, and VE-Cadherin) in 4 groups were also detected by flow cytometry.

Results

Western blot results showed that there was no obviously difference in protein expressions of VEGFR-2 and pVEGFR-2 between groups; and the expressions of VEGFR-3 and pVEGFR-3 proteins in group A1 were obviously higher than those in groups A, B, and B1. The flow cytometry results showed that the expressions of vWF, PECAM-1, and VE-Cadherin were significantly higher in group A1 than in groups A, B, and B1 ( P<0.05), and in group B1 than in groups A and B ( P<0.05); but no significant difference was found between groups A and B ( P>0.05). In the VEGFR-3 blocked experiment, the flow cytometry results showed that the expressions of vWF, PECAM-1, and VE-Cadherin were significantly higher in group Ⅲ than in groupsⅠ, Ⅱ, and Ⅳ, and in group Ⅳ than in groups Ⅰ and Ⅱ ( P<0.05); but no significant difference was found between groups Ⅰ and Ⅱ ( P>0.05).

Conclusion

GIT1 mediates BMSCs of mice differentiation into endothelial cells via VEGFR-3, thereby affecting the angiogenesis.

Serum vascular endothelial growth factor receptor 3 as a potential biomarker in psoriasis

To discover novel biomarkers of psoriasis, a target-specific antibody array screening of serum samples from psoriasis patients was initially performed. The results revealed that vascular endothelial growth factor receptor 3 (VEGFR-3) was significantly elevated in the sera of psoriasis patients, compared to healthy controls. Next, ELISA validation studies in a larger cohort of psoriasis patients (N = 73) were conducted, which confirmed that serum VEGFR-3 was indeed significantly increased in patients with psoriasis compared to healthy controls (P < 0.001). Furthermore, receiver operating characteristic curve analysis demonstrated that serum VEGFR-3 exhibited potential in distinguishing healthy controls from psoriasis patients: area under the curve = 0.85, P < 0.001. In addition, serum levels of VEGFR-3 were correlated with Psoriasis Area Severity Index scores (R = 0.32, P = 0.008) in psoriasis patients. Interestingly, serum VEGFR-3 levels were significantly elevated in psoriatic arthritis compared to non-psoriatic arthritis (P = 0.026). A pilot longitudinal study demonstrated that serum levels of VEGFR-3 could reflect disease progression in psoriasis. Collectively, serum VEGFR-3 may have a clinical value in monitoring disease activity of psoriasis.

The optimum marker for the detection of lymphatic vessels

Podoplanin, lymphatic vessel endothelial hyaluronic acid receptor-1, prospero-related homeobox-1 and vascular endothelial growth factor receptor 3 have been demonstrated to have crucial roles in the development of the lymphatic system and lymphangiogenesis process by combining with their corresponding receptors. Thus, the four markers have been widely used in labelling lymphatic vessels for the detection of lymphangiogenesis and lymphatic vessel invasion. Numerous authors have aimed to identify the roles of these four markers in the lymphatic system and the mechanisms have been partly clarified at the molecular level. The aim of the present review was to comprehensively clarify the characteristics and latent action modes of the four markers in order to determine which is the best one for the detection of lymphangiogenesis and lymphatic vessel invasion.

VEGFR-3 blocking deteriorates inflammation with impaired lymphatic function and different changes in lymphatic vessels in acute and chronic colitis

BACKGROUND

Recent studies show inflammation-associated lymphangiogenesis (IAL) induced by vascular endothelial growth factor receptor 3 (VEGFR-3) pathway has a close relationship with chronic intestinal inflammation, and antilymphatic signaling pathways may repress IAL. However, whether the biologic function of lymphatic vessel is the same in severe acute intestinal inflammation still remain unknown.

METHODS

C57BL/6 mice were administered with 5% of dextran sodium sulfate (DSS) in drinking water for 7 days to establish severe acute colitis (SAC) model. Chronic colitis (CC) model was established by three cycles of 2% DSS for 5 days following water for 5 days. Mice were treated with VEGFR-3 antibody once daily in SAC group, or once every 3 days in CC group. The colon inflammation, submucosal edema, lymphatic vessel (LV) density, LV size, lymph flow, cytokines and immune cells infiltration were detected.

RESULTS

Both acute and chronic colitis resulted in a significant aggravation of colon inflammation in anti-VEGFR-3-treated mice, compared with PBS-treated colitis mice. Meanwhile, this was accompanied with decreased lymph drainage, increased submucosal edema, inflammatory cells infiltration and cytokines levels. In acute intestinal inflammation, significantly distorted and enlarged lymphatics were found but the LV number remained unchanged; not only significantly distorted and enlarged lymphatics but reduced LV number were found in chronic colitis.

CONCLUSION

Blocking VEGFR-3 in acute and chronic colitis leads to deterioration of colon inflammation with impaired lymphatic function and different changes in LVs. In the therapy targeting VEGF-C/VEGFR-3 pathway for lymphangiogenesis, the phrase and severity of intestinal inflammation should be taken into account.

Lymphatic endothelial differentiation in pulmonary lymphangioleiomyomatosis cells

Pulmonary lymphangioleiomyomatosis (LAM) is a rare, low-grade neoplasm affecting almost exclusively women of childbearing age. LAM belongs to the family of perivascular epithelioid cell tumors, characterized by spindle and epithelioid cells with smooth muscle and melanocytic differentiation. LAM cells infiltrate the lungs, producing multiple, bilateral lesions rich in lymphatic channels and forming cysts, leading to respiratory insufficiency. Here we used antibodies against four lymphatic endothelial markers-podoplanin (detected by D2-40), prospero homeobox 1 (PROX1), vascular endothelial growth factor receptor 3 (VEGFR-3), and lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1)-to determine whether LAM cells show lymphatic differentiation. Twelve of 12 diagnostic biopsy specimens (early-stage LAM) and 19 of 19 explants (late-stage LAM) showed immunopositivity for D2-40 in most neoplastic cells. PROX1, VEGFR-3, and LYVE1 immunoreactivity varied from scarce in the early stage to abundant in the late stage. Lymphatic endothelial, smooth muscle, and melanocytic markers were partially co-localized. These findings indicate that lymphatic endothelial differentiation is a feature of LAM and provide evidence of a previously unidentified third lineage of differentiation in this neoplasm. This study has implications for the histological diagnosis of LAM, the origin of the neoplastic cells, and potential future treatment with drugs targeting lymphangiogenesis.

Cannabidiol inhibits growth and induces programmed cell death in kaposi sarcoma-associated herpesvirus-infected endothelium

Kaposi sarcoma is the most common neoplasm caused by Kaposi sarcoma-associated herpesvirus (KSHV). It is prevalent among the elderly in the Mediterranean, inhabitants of sub-Saharan Africa, and immunocompromised individuals such as organ transplant recipients and AIDS patients. Current treatments for Kaposi sarcoma can inhibit tumor growth but are not able to eliminate KSHV from the host. When the host's immune system weakens, KSHV begins to replicate again, and active tumor growth ensues. New therapeutic approaches are needed. Cannabidiol (CBD), a plant-derived cannabinoid, exhibits promising antitumor effects without inducing psychoactive side effects. CBD is emerging as a novel therapeutic for various disorders, including cancer. In this study, we investigated the effects of CBD both on the infection of endothelial cells (ECs) by KSHV and on the growth and apoptosis of KSHV-infected ECs, an in vitro model for the transformation of normal endothelium to Kaposi sarcoma. While CBD did not affect the efficiency with which KSHV infected ECs, it reduced proliferation and induced apoptosis in those infected by the virus. CBD inhibited the expression of KSHV viral G protein-coupled receptor (vGPCR), its agonist, the chemokine growth-regulated protein α (GRO-α), vascular endothelial growth factor receptor 3 (VEGFR-3), and the VEGFR-3 ligand, vascular endothelial growth factor C (VEGF-C). This suggests a potential mechanism by which CBD exerts its effects on KSHV-infected endothelium and supports the further examination of CBD as a novel targeted agent for the treatment of Kaposi sarcoma.