Human Brain Microvascular Endothelial Cells Migration Research Articles

CircRNA-PTPN4 mediated regulation of FOXO3 and ZO-1 expression: implications for blood–brain barrier integrity and cognitive function in uremic encephalopathy

Uremic encephalopathy (UE) poses a significant challenge in neurology, leading to the need to investigate the involvement of non-coding RNA (ncRNA) in its development. This study employed ncRNA-seq and RNA-seq approaches to identify fundamental ncRNAs, specifically circRNA and miRNA, in the pathogenesis of UE using a mouse model. In vitro and in vivo experiments were conducted to explore the circRNA-PTPN4/miR-301a-3p/FOXO3 axis and its effects on blood–brain barrier (BBB) function and cognitive abilities. The research revealed that circRNA-PTPN4 binds to and inhibits miR-301a-3p, leading to an increase in FOXO3 expression. This upregulation results in alterations in the transcriptional regulation of ZO-1, affecting the permeability of human brain microvascular endothelial cells (HBMECs). The axis also influences the growth, proliferation, and migration of HBMECs. Mice with UE exhibited cognitive deficits, which were reversed by overexpression of circRNA-PTPN4, whereas silencing FOXO3 exacerbated these deficits. Furthermore, the uremic mice showed neuronal loss, inflammation, and dysfunction in the BBB, with the expression of circRNA-PTPN4 demonstrating therapeutic effects. In conclusion, circRNA-PTPN4 plays a role in promoting FOXO3 expression by sequestering miR-301a-3p, ultimately leading to the upregulation of ZO-1 expression and restoration of BBB function in mice with UE. This process contributes to the restoration of cognitive abilities.Graphical 1. The circRNA-PTPN4/miR-301a-3p/FOXO3 axis is identified as a key regulator of blood–brain barrier integrity and cognitive function in uremic encephalopathy.2. circRNA-PTPN4 sequestration of miR-301a-3p enhances FOXO3 expression, leading to upregulation of ZO-1 and improved endothelial permeability.3. Overexpression of circRNA-PTPN4 in uremic mice restores cognitive abilities and reduces neuronal loss and inflammatory infiltration.

The synthetic cannabinoid 5F-MDMB-PICA enhances the metabolic activity and angiogenesis in human brain microvascular endothelial cells by upregulation of VEGF, ANG-1, and ANG-2.

Brain angiogenesis, the formation of new blood vessels from existing brain vasculature, has been previously associated with neural plasticity and addictive behaviors related to substances. Synthetic cannabinoids (SCs) have become increasingly popular due to their ability to mimic the effects of cannabis, offering high potency and easy accessibility. In the current study, we reveal that the SC 5F-MDMB-PICA, the most common SC in the United States in 2019, increases cell metabolic activity and promotes angiogenesis in human brain microvascular endothelial cells (HBMECs). First, we performed an MTT assay to evaluate the effects of 5F-MDMB-PICA treatment at various concentrations (0.0001μM, 0.001μM, 0.01μM, 0.1μM, and 1μM) on HBMECs metabolic activity. The results demonstrated higher concentrations of the SC improved cell metabolic activity. Furthermore, 5F-MDMB-PICA treatment enhanced tube formation and migration of HBMECs in a dosage-dependent manner. Additionally, the mRNA, secreted protein, and intracellular protein levels of vascular endothelial growth factor, angiopoietin-1, and angiopoietin-2, which are involved in the regulation of angiogenesis, as well as the protein levels of cannabinoid receptor type-1, were all increased following treatment with 5F-MDMB-PICA. Notably, the phosphorylation levels at Serine 9 residue of glycogen synthase kinase-3β were also increased in the 5F-MDMB-PICA treated HBMECs. Collectively, our findings demonstrate that 5F-MDMB-PICA can enhance angiogenesis in HBMECs, suggesting the significant role of angiogenesis in the response to SCs. Manipulating this interaction may pave the way for innovative treatments targeting SC addiction and angiogenesis-related conditions.

Circvrk1 downregulation attenuates brain microvascular endothelial cell damage induced by oxygen-glucose deprivation through modulating the miR-150-5p/MLLT1 axis.

The pivotal regulatory role of circular RNAs (circRNAs) in ischemic stroke (IS) has been expounded. The study aimed to probe the exact role and underlying mechanism of circVRK1 in oxygen-glucose deprivation (OGD)-induced human brain microvascular endothelial cells (HBMECs) injury. HBMECs challenged by OGD were used as in vitro models of IS. Quantitative real-time PCR was used to examine the levels of circVRK1, vaccinia-related kinase 1 (VRK1), miR-150-5p and MLLT1 mRNA. Cell viability, migration angiogenesis ability and death were evaluated by Cell counting kit-8 assay, transwell assay, wound-healing assay, tube formation assay and flow cytometry analysis. All the protein levels were monitored by western blot assay. Enzyme-linked immunosorbent assay was conducted for examining cell oxidative stress. Dual-luciferase reporter assay, RIP assay and RNA pull-down assay were performed to verify the combination between miR-150-5p and circVRK1 or MLLT1. CircVRK1 was upregulated in OGD-treated HBMECs. CircVRK1 knockdown alleviated OGD-caused effects on HBMECs migration, angiogenesis, death, inflammatory response and oxidative stress. Furthermore, circVRK1 could sponge miR-150-5p, and miR-150-5p silencing also mitigated the impact of circVRK1 deficiency on OGD-evoked injury. Besides, MLLT1 acted as a molecular target of miR-150-5p, and the protective influence of miR-150-5p on OGD-induced cell damage was overturned by MLLT1 introduction. CircVRK1 knockdown weakened OGD-evoked injury in HBMECs through modulating miR-150-5p/MLLT1 pathway, and this might supply new insights and probable targets for IS treatment.

Epstein-Barr virus infection modulates blood-brain barrier cells and its co-infection with Plasmodium falciparum induces RBC adhesion.

Plasmodium falciparum infection-mediated Epstein-Barr virus (EBV) reactivation is well established in malaria-endemic countries. We hypothesize that, during malaria onset, the reactivated EBV can infect human brain microvascular endothelial cells (HBECs). This may cause severe cerebral manifestations. We infected HBECs with EBV in vitro. The subsequent gene expression pattern of EBV, inflammatory and endothelial markers was analysed using qRT-PCR. Further, a wound-healing assay for cells maintaining blood-brain barrier (BBB) integrity was performed to investigate the effect of EBV-infected HBECs secretions. The RBC adhesion assay was conducted to assess RBC attachment onto HBECs during EBV and P. falciparum mono- and co-infection. Our experiments revealed that EBV infection of HBECs significantly elevated several inflammatory (TNFα, CCL2) and endothelial (integrin β3, PECAM, VEGFA, VWF, claudin-5, cx37) markers. The EBV-infected HBECs secretion significantly reduced migration of HBECs, glial and neuronal cells. Additionally, EBV-P. falciparum co-infection significantly (P<0.05) enhanced RBC adhesion to HBECs compared to mono-infection scenarios. Conclusively, the EBV infection of HBECs led to endothelial activation and modulated the BBB microenvironment. The EBV-P. falciparum co-infection scenario increased RBC adhesion on ECs which is a hallmark of cerebral malaria. Together with malaria, EBV infection can aid in exacerbation of cerebral malaria pathology.

Glioblastoma Factors Increase the Migration of Human Brain Endothelial Cells In Vitro by Increasing MMP-9/CXCR4 Levels

Glioblastoma (GB) is the most aggressive type of tumor in the central nervous system and is characterized by resistance to therapy and abundant vasculature. Tumor vessels contribute to the growth of GB, and the tumor microenvironment is thought to influence tumor vessels. We evaluated the molecular communication between human GB cells and human brain microvascular endothelial cells (HBMEC) in vitro. We investigated whether GB-conditioned media (GB-CM) influenced HBMEC proliferation and migration, as well as the levels of MMP-9, CXCL12, CXCR4, CXCR7, VEGFs, VEGFR-2, and WNT5a in HBMEC. Although HBMEC proliferation was not modified, increased HBMEC migration was detected after GB-CM treatment. Furthermore, treatment of HBMEC with GB-CM resulted in increased levels of MMP-9 and CXCR4. The levels of WNT5a, VEGFs and VEGFR-2 were not affected. GB-secreted factors lead to increased endothelial cell migration and to increased levels of MMP-9 and CXCR4.

Fibroblast growth factor 21 enhances angiogenesis and wound healing of human brain microvascular endothelial cells by activating PPARγ

Angiogenesis of brain microvascular endothelial cells (BMECs) is required in the functional restoration of brain injury, such as traumatic brain injury (TBI) and ischemic stroke. Fibroblast growth factor 21 (FGF21) is an angiogenic molecule that functions through the formation of the FGF21/FGFR1/β-klotho complex but does not cause carcinogenic events. The current study was to determine whether recombinant human FGF21 (rhFGF21) could promote angiogenesis and scratch wound healing of human brain microvascular endothelial cells (HBMECs) and the possible underlying mechanism. rhFGF21 promoted angiogenesis and migration of HBMECs. The FGFR1 inhibitor PD173074 was applied to demonstrate that rhFGF21 functions through the formation of FGF21/FGFR1/β-klotho complexes. In addition, the specific PPARγ inhibitor GW9662 and PPARγ activator rosiglitazone were applied to determine that the role of rhFGF21 in increasing angiogenesis is through the PPARγ pathway. In addition, we revealed that the effect of rhFGF21 acts partially through upregulating eNOS expression. In conclusion, our study provides novel evidence that rhFGF21 can enhance the angiogenesis and migration of HBMECs through the formation of the FGF21/FGFR1/β-klotho complex via PPARγ activation and eNOS upregulation, indicating that FGF21 is a potential therapeutic angiogenic agent for the treatment of human brain injury.

YKL-40 can promote angiogenesis in sporadic cerebral cavernous malformation (CCM)

The factors affecting the formation of sporadic CCMs remain unclear. A cDNA microarray was used to identify characteristic gene expression patterns in sporadic CCMs. Transcription level of YKL-40 was confirmed by reverse transcription-polymerase chain reaction (RT-PCR). The location and expression were revealed by immunochemistry, immunofluorescence staining and level of YKL-40 was quantified by Western blotting. Alterations to endothelial function following the up or down regulation of gene expression was assessed by Transwell assays, cell counting kit-8 assays and capillary-like tube formation assays in human brain microvascular endothelial cells (HBMECs) in vitro. We generated a murine model by stereotaxically injecting HBMECs with expressing amounts of YKL-40 into the brain. cDNA microarray and RT-PCR results revealed that the transcription level of YKL-40 was ≥140-fold higher in sporadic CCMs in healthy controls. Histological staining revealed excessive YKL-40 expression in the CCM endothelium. Western blotting results analysis showed that YKL-40 protein expression was significantly higher in CCM endothelium (P < 0.05). YKL-40 over-expressing HBMECs showed increased cell proliferation, migration and tube formation ability compared with the control group, whereas downregulating of YKL-40 inhibited the proliferation, migration of HBMECs and capillary-like tube formation (P < 0.05). In animals, increased of YKL-40 was associated with abnormal vascular lesions that were similar to CCMs. YKL-40 is over-expressed in the CCM endothelium and acts as an angiogenic factor that promotes the pathogenesis of sporadic CCMs. YKL-40 may therefore represent a potential therapeutic target in the treatment of sporadic CCM.

The Role of Matrix Metalloproteinase-3 in the Doxycycline Attenuation of Intracranial Venous Hypertension-Induced Angiogenesis.

The molecular mechanism of brain arteriovenous malformation (BAVM) is largely unknown. Intracranial venous hypertension (VH) may enhance focal angiogenesis and promote BAVM development and progression. A rat VH model effectively simulates the hemodynamic microenvironment of this disease. To explore the effect of doxycycline in VH-related angiogenesis, as well as the role of matrix metalloproteinase-3 (MMP-3) and other molecular factors. A rat VH model was generated by common carotid artery and distal external jugular vein anastomosis. Microvessel density (MVD) in the perisinus area and expression of MMP-3/2/9, VEGF, TIMP-1, TGF-β, and HIF-1α were examined, with and without daily doxycycline treatment for 4 wk. The effects of doxycycline were verified in Vitro using human brain microvascular endothelial cells (HBMECs). MMP-3 overexpression or knockdown in HBMECs was used to confirm the role of MMP-3 in cell functions. MVD in the perisinus cortex was greatly increased after VH. Doxycycline decreased MVD, suppressed MMP-3 overexpression, and reduced VEGF, TGF-β, and TIMP-1 levels compared with the controls (P < .05). In Vitro, doxycycline decreased HBMEC migration, tube formation, and the mRNA, protein, and enzymatic activity levels of MMP-3. MMP-3 overexpression in HBMECs promoted migration, while knockdown of MMP-3 significantly attenuated proliferation, migration, and tube formation (P < .05). Our findings indicate that MMP-3 plays an important role in VH-related angiogenesis and the promotion of vascular remodeling. Suppression of MMP-3 overexpression by doxycycline may provide a potential strategy for inhibiting BAVM development.

Cilostazol에 의한 뇌혈관내피세포의 세포이동 증진 효과연구

Cilostazol is known to be a selective inhibitor of phosphodiesterase III and is generally used to treat stroke. Our previous findings showed that cilostazol enhanced capillary density through angiogenesis after focal cerebral ischemia. Angiogenesis is an important physiological process for promoting revascularization to overcome tissue ischemia. It is a multistep process consisting of endothelial cell proliferation, migration, and tubular structure formation. Here, we examined the modulatory effect of cilostazol at each step of the angiogenic mechanism by using human brain microvascular endothelial cells (HBMECs). We found that cilostazol increased the migration of HBMECs in a dose-dependent manner. However, it did not enhance HBMEC proliferation and capillary-like tube formation. We used a cDNA microarray to analyze the mechanisms of cilostazol in cell migration. We picked five candidate genes that were potentially related to cell migration, and we confirmed the gene expression levels by real-time PCR. The genes phosphoserine aminotransferase 1 (PSAT1) and CCAAT/enhancer binding protein β (C/EBPβ) were up-regulated. The genes tissue factor pathway inhibitor 2 (TFPI2), retinoic acid receptor responder 1 (RARRES1), and RARRES3 were down-regulated. Our observations suggest that cilostazol can promote angiogenesis by promoting endothelial migration. Understanding the cilostazol-modulated regulatory mechanisms in brain endothelial cells may help stimulate blood vessel formation for the treatment of ischemic diseases.

Abstract 3364: Adaptive mechanisms upon LRP1 repression: Impact on sphingosine-1-phosphate-mediated signalling and migration of brain endothelial cells

Abstract Switches in the sphingolipid metabolism have recently been associated with oncogenic transformation, and a role for the low density lipoprotein receptor related protein (LRP1) in the sphingosine-1-phosphate (S1P) proangiogenic signalling inferred. Although S1P is a key determinant of blood-brain barrier (BBB) permeability, the interdependent signalling crosstalk with LRP1 in brain endothelial cells (EC) remains unclear. Here, we tested whether any adaptive LRP1/S1P interdependence mechanisms are required in a SV40-immortalized human brain microvascular EC (HBMEC) model which closely mimics the brain tumor endothelium phenotype. Transient LRP1 silencing and stable LRP1-/- HBMEC were generated and increased expression of CCAAT/enhancer binding protein β (C/EBPβ), a transcription factor which regulates the transcription of all five S1P receptors members, was observed upon stable but not transient LRP1 repression. Migration of EC isolated from Lrp1(EC)-/- mice and of stable LRP1-/- HBMEC became unresponsive to S1P, in part explained by altered ERK and p38 MAPK pathways, whereas it remained unaltered in transient in vitro LRP1 repression. Adaptive diminished expressions of S1P1, S1P3, and S1P5, and increased S1P2 were observed in stable LRP1-/- HBMEC and in brain EC isolated from Lrp1(EC)-/- mice. Finally, gene silencing strategies highlighted the need for S1P3 for proper S1P-mediated HBMEC migration. Collectively, our study highlights an unexpected adaptive transcriptional crosstalk between LRP1 and specific S1P receptors which accounts for S1P signalling in brain EC. Targeting of the LRP1/S1P signalling axis at the BBB may thus be considered in future therapeutic strategies. Citation Format: Amélie Vézina, Cyndia Charfi, Alain Zgheib, Borhane Annabi. Adaptive mechanisms upon LRP1 repression: Impact on sphingosine-1-phosphate-mediated signalling and migration of brain endothelial cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3364.

Olive oil compounds inhibit the paracrine regulation of TNF-α-induced endothelial cell migration through reduced glioblastoma cell cyclooxygenase-2 expression

The established causal relationship between the chronic inflammatory microenvironment, tumor development and cancer recurrence has provided leads for developing novel preventive strategies. Accumulating experimental, clinical and epidemiological data has provided support for the chemopreventive properties of olive oil compounds traditionally found within the Mediterranean diet. In this study, we investigated whether tyrosol (Tyr), hydroxytyrosol, oleuropein and oleic acid (OA), four compounds contained in extra virgin olive oil, can prevent tumor necrosis factor (TNF)-α-induced expression of cyclooxygenase (COX)-2 (an inflammation biomarker) in a human glioblastoma cell (U-87 MG) model. We found that Tyr and OA significantly inhibited TNF-α-induced COX-2 gene and protein expression, as well as PGE2 secretion. Both compounds also inhibited TNF-α-induced JNK and ERK phosphorylation, whereas only Tyr inhibited TNF-α-induced NF-κB phosphorylation. Paracrine-regulated migration of human brain microvascular endothelial cells (HBMECs) was assessed using growth factor-enriched conditioned media (CM) isolated from U-87 MG cells. We found that while PGE2 triggered HBMEC migration, the CM isolated from U-87 MG cells, where either COX-2 or NF-κB had been silenced or had been treated with Tyr or OA, exhibited decreased chemotactic properties. These observations demonstrate that olive oil compounds inhibit the effect of the chronic inflammatory microenvironment on glioblastoma progression through TNF-α actions and may be useful in cancer chemoprevention.

ET-40 * ONCOLYTIC VIRUS INDUCED HMGB1 SECRETION AND ITS IMPACT ON TUMOR ANGIOGENESIS

Glioblastoma multiforme (GBM) is a difficult-to-treat, and the most aggressive of primary brain tumors. Survival is less than 2 years despite aggressive therapy. Oncolytic virus (OV) therapy has shown tremendous benefits in the treatment of GBM and other tumors. This benefit is limited by host antiviral immune responses that enhance OV clearance and tumor progression. In this study, using both in-vivo and in-vitro models of GBM, we have tested the role of High mobility group box 1 (HMGB1) in OV therapy. HMGB1 is a nuclear protein that binds and regulates transcription factors. Extracellular HMGB1 functions as damage associated molecular pattern (DAMP), it mediates the inflammatory response upon binding to inflammation mediators, such as receptor of advanced glycated end product (RAGE), toll-like receptors (TLRs) 2, 4, and 9. Here, we report that; 1) HSV1716 infection induced significant secretion of HMGB1 in human glioma cell lines and glioma neurosphere cells alone or when co-cultured with microglia. 2) Measurement of HMGB1 in serum of mice with intracranial tumors revealed an increase in serum HMGB1 levels after virus treatment. 3) HSV1716 infection enhanced human brain microvascular endothelial cells (HBMEC) migration towards infected cells, which was blocked by HMGB1 blocking antibodies. 4) HMGB1 both directly enhanced HBMEC migration and induced production of VEGF by microglia cells co-cultured with glioma cells. 5) Pharmacologic inhibitor of HMGB1 (Garbexate (100uM)), and anti-HMGB1 polyclonal blocking antibody blocked HSV1716 induced HMGB1 secretion of VEGF in vitro and in vivo. Our findings suggest that OV therapy with HSV1716 activates proangiogenic pathway by induction of HMGB1, and that tumor microenvironment contributes to it proangiogenic property. Thus we conclude that OV therapy that target HMGB1 secretion and angiogenic axis may improve virotherapy of HSV1716, and other oncolytic herpes simplex virus in tumors.

The effect of a rock inhibitor ama0428 in a model of wet age‐related macular degeneration

AbstractPurpose Rho kinase (ROCK) is associated with VEGF‐driven angiogenesis and is involved in inflammation and fibrosis. Therefore, the effect of a locally acting ROCK inhibitor, AMA0428, was studied in wet age‐related macular degeneration (AMD).Methods The effect of AMA0428 on human brain microvascular endothelial cells (HBMEC), human brain vascular pericytes (HBVP) and human tenon fibroblasts (HTF) was determined by measuring cell viability (WST‐1), apoptosis (caspase 3/7) and 2 migration assays (scratch and under‐agarose) The in vivo response was investigated using a laser‐induced choroidal neovascularization (CNV) mouse model. Intravitreal injections were given on day 0, 4, 10 and 20 with AMA0428, murine anti‐VEGFR Ab (DC101) or placebo. Outcome was assessed by analysis of inflammation (CD45), angiogenesis (FITC‐dextran), vessel leakage (Texas Red‐conjugated Dextran and FITC‐labeled lectin) and fibrosis (Collagen I).Results AMA0428 dose‐dependently reduced proliferation and VEGF‐induced migration of HBMEC and HTF. No significant effect was seen on HBVP proliferation; however, migration and pericyte recruitment were increased. There was no apoptosis induction. AMA0428 significantly reduced CNV and vessel leakage 2 weeks after lasering, comparable to DC101. In addition, AMA0428 inhibited inflammation on day 5 by 20% and collagen deposition on day 30 by 39% while DC101 had no effect on inflammation nor fibrosis.Conclusion Our data suggest that targeting ROCK with AMA0428 not only reduces neoangiogenesis, but also blocks inflammation and fibrosis (contrary to anti‐VEGF). These results point to a potential therapeutic benefit of ROCK inhibition in wet AMD.

Inhibition of Tubulogenesis and of Carcinogen‐mediated Signaling in Brain Endothelial Cells Highlight the Antiangiogenic Properties of a Mumbaistatin Analog

A better understanding of the metabolic adaptations of the vascular endothelial cells (EC) that mediate tumor vascularization would help the development of new drugs and therapies. Novel roles in cell survival and metabolic adaptation to hypoxia have been ascribed to the microsomal glucose-6-phosphate translocase (G6PT). While antitumorigenic properties of G6PT inhibitors such as chlorogenic acid (CHL) have been documented, those of the G6PT inhibitor and semi-synthetic analog AD4-015 of the polyketide mumbaistatin are not understood. In the present study, we evaluated the in vitro antiangiogenic impact of AD4-015 on human brain microvascular endothelial cells (HBMEC), which play an essential role as structural and functional components in tumor angiogenesis. We found that in vitro HBMEC migration and tubulogenesis were reduced by AD4-015 but not by CHL. The mumbaistatin analog significantly inhibited the phorbol 12-myristate 13-acetate (PMA)-induced matrix-metalloproteinase (MMP)-9 secretion and gene expression as assessed by zymography and RT-PCR. PMA-mediated cell signaling leading to cyclooxygenase (COX)-2 expression and IkappaB downregulation was also inhibited, further confirming AD4-015 as a cell signaling inhibitor in tumor promoting conditions. G6PT functions may therefore account for the metabolic flexibility that enables EC-mediated neovascularization. This process could be specifically targeted within the vasculature of developing brain tumors by G6PT inhibitors.

Propranolol adrenergic blockade inhibits human brain endothelial cells tubulogenesis and matrix metalloproteinase-9 secretion

In recent clinical observation, the growth of endothelial tumors, such as hemangiomas of infancy, was repressed by the non-selective β-adrenergic antagonist propranolol possibly through targeting of the vascular endothelial compartment. As human brain microvascular endothelial cells (HBMEC) play an essential role as structural and functional components in tumor angiogenesis, we assessed whether propranolol could target HBMEC's in vitro angiogenic properties. We found that biopsies from human glioblastoma as well as from experimental brain tumor-associated vasculature expressed high levels of the β2-adrenergic receptor, suggesting adrenergic adaptative processes could take place during tumor vascularization. We observed that in vitro tubulogenesis was significantly reduced by propranolol when HBMEC were seeded on Matrigel. Propranolol, as much as 100 μM, did not reduce cell viability and did not alter HBMEC migration as assessed with Boyden chambers. Secretion of the key angiogenic and extracellular matrix degrading enzymes MMP-2 and MMP-9 was assessed by zymography. Propranolol significantly reduced MMP-9 secretion upon treatment with the tumor-promoting agent phorbol 12-myristate 13-acetate, while secretion of MMP-2 remained unaffected. This was correlated with a decrease in MMP-9 gene expression which is, in part, explained by a decrease in the nucleocytoplasmic export of the mRNA stabilizing factor HuR. Our data are therefore indicative of a selective role for propranolol in inhibiting MMP-9 secretion and HBMEC tubulogenesis which could potentially add to propranolol's anti-angiogenic properties.

The diet‐derived sulforaphane inhibits matrix metalloproteinase‐9‐activated human brain microvascular endothelial cell migration and tubulogenesis

Human brain microvascular endothelial cells (HBMECs) play an essential role as structural and functional components of the blood-brain barrier (BBB). While disruption of the BBB by the brain tumor-secreted matrix metalloproteinase-9 (MMP-9) favors tumor invasion, the role and regulation of MMP-9 secretion by HBMEC themselves in response to carcinogens or brain tumor-derived growth factors has received little attention. Our study delineates a unique brain endothelial phenotype in that MMP-9 secretion is increased upon phorbol 12-myristate 13-acetate (PMA) treatment of HBMEC. Sulforaphane (SFN), an isothiocyanate present in broccoli which exhibits chemopreventive properties, selectively inhibited the secretion of MMP-9 but not that of MMP-2. The decrease in MMP-9 gene expression correlated with a decrease in the expression of the mRNA stabilizing factor HuR protein triggered by SFN. PMA-induced HBMEC migration was also antagonized by SFN. Silencing of the MMP-9 gene inhibited PMA-induced MMP-9 secretion, cell migration, and in vitro tubulogenesis on Matrigel. While SFN inhibited the chemoattractive abilities of brain tumor-derived growth factors, it failed to inhibit PMA-induced tubulogenesis. Our data are indicative of a selective role for SFN to inhibit MMP-9-activated, but not basal, HBMEC migration, and tubulogenesis whose actions could add to SFN's antitumor properties.

The response to brain tumor-derived growth factors is altered in radioresistant human brain endothelial cells

Introduction: Radioresistant brain tumor vasculature is thought to hamper the efficiency of adjuvant cancer therapies. However, little is known regarding the signalling pathways involved in the angiogenic response to brain tumor-derived growth factors in irradiated human brain microvascular endothelial cells (HBMEC). The goal of this study is to assess the effect of ionizing radiation (IR) on HBMEC survival, migration and tubulogenesis. Methods: HBMEC were cultured and irradiated at sublethal single doses. Cell survival was assessed by nuclear cell counting and flow cytometry. HBMEC migration in response to brain tumor-derived growth factors (U-87 GF) and tubulogenesis were assayed using modified Boyden chambers and Matrigel, respectively. Results: We observed that single administration of 3-10 Gy IR doses only reduced cell survival by 30%. Radioresistant HBMEC overexpressed RhoA, a small GTPase protein regulating cellular adhesion and migration, and Rho-kinase (ROK), a serine-threonine protein kinase and one of RhoA’s major targets. HBMEC migration was induced by vascular endothelial growth factor (VEGF), but even more so in response to sphingosine-1-phosphate (S1P) and to U-87 GF. Following IR exposure, HBMEC basal migration increased more than two-fold, whereas the response to S1P and to U-87 GF was significantly diminished. Similarly, the inhibitor of ROK Y-27632 decreased HBMEC migration in response to S1P and U-87 GF. Overexpression of RhoA decreased tubulogenesis, an effect also observed in irradiated HBMEC. Conclusion: Our results suggest that radioresistant HBMEC migration response to tumor-secreted growth factors and tubulogenesis are altered following IR. The RhoA/ROK signalling pathway is involved in the IR-altered angiogenic functions and may represent a potential molecular target for enhancing the impact of radiotherapy on tumor-associated endothelial cells.

HIV-1 Tat Mediated Effects on Focal Adhesion Assembly and Permeability in Brain Microvascular Endothelial Cells.

The blood-brain barrier (BBB) is a network formed mainly by brain microvascular endothelial cells. The integrity of the BBB is critical for brain function. Breakdown of the BBB is commonly seen in AIDS patients with HIV-1-associated dementia (HAD), despite the lack of productive HIV-infection of the brain endothelium. The processes by which HIV causes these pathological conditions are not well understood. Here, we characterized the molecular mechanisms by which Tat mediates its pathogenic effects in-vitro on primary human brain microvascular endothelial cells (HBMECs). Tat treatment of HBMECs stimulated cytoskeletal organization and increased focal adhesion sites as compared to control cells or cells treated with heat-inactivated Tat. Pretreatment with Tat antibodies or with the specific inhibitor SU-1498, which interferes with VEGFR-2 (Flk-1/KDR) receptor phosphorylation, blocked the ability of Tat to stimulate focal adhesion assembly and the migration of HBMECs. Focal adhesion kinase (FAK) was tyrosine-phosphorylated by Tat and found to be an important component of focal adhesion sites. Inhibition of FAK by the dominant-interfering mutant form FRNK (FAK-related non-kinase) significantly blocked HBMEC migration and disrupted focal adhesions upon Tat activation. Furthermore, HIV-Tat induced permeability changes in HBMECs in a time dependent manner. Tat also impaired BBB permeability as observed in HIV-1 Tat transgenic mice. These studies define a mechanism for HIV-1 Tat in focal adhesion complex assembly in HBMECs, via activation of FAK, leading to cytoskeletal reorganization and permeability changes.

HIV-1 Tat-Mediated Effects on Focal Adhesion Assembly and Permeability in Brain Microvascular Endothelial Cells

The blood-brain barrier (BBB) is a network formed mainly by brain microvascular endothelial cells (BMECs). The integrity of the BBB is critical for brain function. Breakdown of the BBB is commonly seen in AIDS patients with HIV-1-associated dementia despite the lack of productive HIV infection of the brain endothelium. The processes by which HIV causes these pathological conditions are not well understood. In this study we characterized the molecular mechanisms by which Tat mediates its pathogenic effects in vitro on primary human BMECs (HBMECs). Tat treatment of HBMECs stimulated cytoskeletal organization and increased focal adhesion sites compared with control cells or cells treated with heat-inactivated Tat. Pretreatment with Tat Abs or with the specific inhibitor SU-1498, which interferes with vascular endothelial growth factor receptor type 2 (Flk-1/KDR) phosphorylation, blocked the ability of Tat to stimulate focal adhesion assembly and the migration of HBMECs. Focal adhesion kinase (FAK) was tyrosine-phosphorylated by Tat and was found to be an important component of focal adhesion sites. Inhibition of FAK by the dominant interfering mutant form, FAK-related nonkinase, significantly blocked HBMEC migration and disrupted focal adhesions upon Tat activation. Furthermore, HIV-Tat induced permeability changes in HBMECs in a time-dependent manner. Tat also impaired BBB permeability, as observed in HIV-1 Tat transgenic mice. These studies define a mechanism for HIV-1 Tat in focal adhesion complex assembly in HBMECs via activation of FAK, leading to cytoskeletal reorganization and permeability changes.