Bp5250 inhibits vascular endothelial growth factor-induced angiogenesis and HIF-1α expression on endothelial cells

Angiogenesis plays a critical role in many physiological and pathological phenomena. A number of anti-angiogenesis drugs have been used in the clinical treatment of diseases such as malignant tumors and macular degeneration. Vascular endothelial growth factor (VEGF), the major pro-angiogenesis factor, is known to stimulate various steps of endothelial angiogenic activity, such as proliferation, migration, and differentiation into vessel-like tubes. In this study, we tested the effects of bp5250 on the angiogenesis of human umbilical endothelial cells (HUVECs). Bp5250 suppressed VEGF-induced endothelial cell proliferation by triggering apoptosis, and reduced endothelial cell migration toward VEGF. Bp5250 also decreased VEGF-stimulated tube formation and rat aortic ring sprouting on Matrigel in a concentration-dependent manner. In the VEGF-activated signaling pathways, bp5250 decreased the phosphorylation of ERK, p38, PI3K-AKT, Src, and FAK and also reduced the activation of the cytoskeleton-associated Rho family, all in a concentration-dependent manner. Bp5250 also attenuated the hypoxia-inducible factor-1α (HIF-1α) and VEGF-stimulated mRNA expression of HUVECs under the hypoxic condition. In vivo, angiogenesis was restrained by a daily intraperitoneal administration of bp5250 in a dose-dependent manner (1–3 mg/kg/d) in the Matrigel plug implantation assay. These results indicate that bp5250 is a potential candidate for developing anti-angiogenic agents.     

TiO₂ nanoparticles induce dysfunction and activation of human endothelial cells

Nanoparticles can reach the blood and cause inflammation, suggesting that nanoparticles-endothelial cells interactions may be pathogenically relevant. We evaluated the effect of titanium dioxide nanoparticles (TiO?) on proliferation, death, and responses related with inflammatory processes such as monocytic adhesion and expression of adhesion molecules (E- and P-selectins, ICAM-1, VCAM-1, and PECAM-1) and with inflammatory molecules (tissue factor, angiotensin-II, VEGF, and oxidized LDL receptor-1) on human umbilical vein endothelial cells (HUVEC). We also evaluated the production of reactive oxygen species, nitric oxide production, and NF-κB pathway activation. Aggregates of TiO? of 300 nm or smaller and individual nanoparticles internalized into HUVEC inhibited proliferation strongly and induced apoptotic and necrotic death starting at 5 μg/cm2. Besides, TiO? induced activation of HUVEC through an increase in adhesion and in expression of adhesion molecules and other molecules involved with the inflammatory process. These effects were associated with oxidative stress and NF-κB pathway activation. In conclusion, TiO? induced HUVEC activation, inhibition of cell proliferation with increased cell death, and oxidative stress.     

Oxidized low-density lipoproteins induce apoptosis in aortic and endocardial endothelial cells

目的：研究氧化型低密度脂蛋白（ｏｘＬＤＬ）诱导血管和心内膜内皮细胞凋亡．方法：用超速离心法分离健康人血浆低密度脂蛋白（ＬＤＬ），以ＣｕＳＯ４１０μｍｏｌ·Ｌ－１氧化．观察ｏｘＬＤＬ对培养新生小牛主动脉内皮细胞及心内膜细胞的损伤作用．琼脂糖凝胶电泳和Ｈｏｅｃｈｓｔ３３２５８荧光密度法定性与定量分析ＤＮＡ降解．结果：ｏｘＬＤＬ诱导血管内皮细胞及心内膜细胞典型凋亡形态学改变，ＤＮＡ降解呈时间和剂量依赖性．环己米特和硫酸葡聚糖对此作用无影响．ＢＨＴ２０μｍｏｌ·Ｌ－１可取消ＤＮＡ降解．溶血性磷脂酰胆碱５０μｍｏｌ·Ｌ－１无诱导凋亡作用．ｏｘＬＤＬ诱导的ＤＮＡ降解可被依他酸取消．结论：ｏｘＬＤＬ诱导血管内皮细胞及心内膜细胞凋亡．     

Biomarkers of inflammation and endothelial function: the holy grail of experimental and clinical medicine?

Drug induced vasculitides in humans are relatively rare diseases, resembling drug-induced vasculitis in rodents and primary idiopathic vasculitis. Because of their exquisite inflammatory nature, vascular lesions in these conditions release a large amount of bioactive molecules and activate multiple cell types, including endothelial cells, neutrophils, monocytes and T-lymphocytes, all of which might be in principle used as biomarkers of the underlying disease. Although each vasculitis may have specific features, the potential biomarkers released remain largely non-specific, raising the question of whether they represent a useful clinical tool. Low specificity, short half-lives and analytical weaknesses are all issues that must be resolved before such biomarkers can be routinely used as diagnostic tools in vasculitis. Further investigation of biomarkers in animal models may be key to a better understanding of their potential usefulness (graphical abstract figure).     

Oxidized low-density lipoprotein and β-glycerophosphate synergistically induce endothelial progenitor cell ossification

Aim:

To investigate the ability of ox-LDL to induce ossification of endothelial progenitor cells (EPCs) in vitro and explored whether oxidative stress, especially hypoxia inducible factor-1α (HIF-1α) and reactive oxygen species (ROS), participate in the ossific process.

Methods:

Rat bone marrow-derived endothelial progenitor cells (BMEPCs) were cultured in endothelial growth medium supplemented with VEGF (40 ng/mL) and bFGF (10 ng/mL). The cells were treated with oxidized low-density lipoprotein (ox-LDL, 5 μg/mL) and/or β-glycerophosphate (β-GP, 10 mmol/L). Calcium content and Von Kossa staining were used as the measures of calcium deposition. Ossific gene expression was determined using RT-PCR. The expression of osteocalcin (OCN) was detected with immunofluorescence. Alkaline phosphatase (ALP) activity was analyzed using colorimetric assay. Intercellular reactive oxygen species (ROS) were measured with flow cytometry.

Results:

BMEPCs exhibited a spindle-like shape. The percentage of cells that expressed the cell markers of EPCs CD34, CD133 and kinase insert domain-containing receptor (KDR) were 46.2%±5.8%, 23.5%±4.0% and 74.3%±8.8%, respectively. Among the total cells, 78.3%±4.2% were stained with endothelial-specific fluorescence. Treatment of BMEPCs with ox-LDL significantly promoted calcium deposition, which was further significantly enhanced by co-treatment with β-GP. The same treatments significantly increased the gene expression of core-binding factor a-1 (cbfa-1) and OCN, while decreased the gene expression of osteoprotegerin (OPG). The treatments also significantly enhanced the activity of ALP, but did not affect the number of OCN⁺ cells. Furthermore, the treatments significantly increased ROS and activated the hypoxia inducible factor-1α (HIF-1α). In all these effects, ox-LDL acted synergistically with β-GP.

Conclusion:

Ox-LDL and β-GP synergistically induce ossification of BMEPCs, in which an oxidizing mechanism is involved.     

Curcumin attenuates endothelial cell fibrosis through inhibiting endothelial–interstitial transformation

Curcumin (Cur) has various pharmacological activities, including anti-inflammatory, antiapoptotic and anticancer effects. However, there is no report on the effect of Cur on endothelial cell fibrosis. This study was designed to investigate the effect and mechanism of Cur on endothelial cell fibrosis. An endothelial cell fibrosis model was established by using transforming growth factor (TGF) induction. Proliferation assays, qRT-PCR, western blotting and immunostaining were performed to investigate the effects and mechanism of Cur on endothelial cell fibrosis. We found that in human umbilical vein endothelial cells (HUVECs), TGF-β1 treatment significantly decreased the expression of nuclear factor erythroid-2-related factor 2 (NRF-2), dimethylarginine dimethylaminohydrolase-1 (DDAH1), and VE-cadherin, the secretion of cellular nitric oxide (NO) and the activity of nitrous oxide synthase (NOS), while asymmetric dimethylarginine (ADMA) and the release of inflammatory factors were elevated. Immunofluorescence showed decreased CD31 and increased α-smooth muscle actin (α-SMA). Overexpression of NRF-2 significantly attenuated the effects of TGF-β1, while downregulation of DDAH1 potently counteracted the effect of NRF-2. In addition, ADMA treatment resulted in similar results to those of TGF-β1, and Cur significantly attenuated the effect of TGF-β1, accompanied by increased VE-cadherin, DDAH1 and NRF-2 and decreased matrix metalloproteinase-9 (MMP-9) and extracellular regulated protein kinases 1/2 (ERK1/2) phosphorylation. The NRF-2 inhibitor ML385 had the opposite effect as that of Cur. These results demonstrated that Cur inhibits TGF-β1-induced endothelial-to-mesenchymal transition (EndMT) by stimulating DDAH1 expression via the NRF-2 pathway, thus attenuating endothelial cell fibrosis.     

Comparative analysis of nanosystems’ effects on human endothelial and monocytic cell functions

Abstract

The objective of our work was to investigate the effects of different types of nanoparticles on endothelial (HUVEC) and monocytic cell functions. We prepared and tested 14 different nanosystems comprising liposomes, lipid nanoparticles, polymer, and iron oxide nanoparticles. Some of the tested nanosystems contained targeting, therapeutic, or contrast agent(s). The effect of particles (0–400 µg/mL) on endothelial-monocytic cell interactions in response to TNF-α was investigated using an arterial bifurcation model and dynamic monocyte adhesion assay. Spontaneous HUVEC migration (0–100 µg/mL nanoparticles) and chemotaxis of monocytic cells towards MCP-1 in presence of particles (0–400 µg/mL) were determined using a barrier assay and a modified Boyden chamber assay, respectively. Lipid nanoparticles dose-dependently reduced monocytic cell chemotaxis and adhesion to activated HUVECs. Liposomal nanoparticles had little effect on cell migration, but one formulation induced monocytic cell recruitment by HUVECs under non-uniform shear stress by about 50%. Fucoidan-coated polymer nanoparticles (25–50 µg/mL) inhibited HUVEC migration and monocytic cell chemotaxis, and had a suppressive effect on monocytic cell recruitment under non-uniform shear stress. No significant effects of iron oxide nanoparticles on monocytic cell recruitment were observed except lauric acid and human albumin-coated particles which increased endothelial-monocytic interactions by 60–70%. Some of the iron oxide nanoparticles inhibited HUVEC migration and monocytic cell chemotaxis. These nanoparticle-induced effects are of importance for vascular cell biology and function and must be considered before the potential clinical use of some of the analyzed nanosystems in cardiovascular applications.     

Interaction of vascular endothelial cells with leukocytes, platelets and cancer cells in inflammation, thrombosis and cancer growth and metastasis

Adhesion and migration of mammalian cells are of crucial importance in a number of biological events, such as fertilization, embryogenesis, pattern, tissue and organ formation, and in a variety of physiological and pathological processes, including lymphocyte trafficking, leukocyte recruitment, hemostasis, wound healing, tumor angiogenesis and cancer metastasis. All these     

Arsenic modulates heme oxygenase-1, interleukin-6, and vascular endothelial growth factor expression in endothelial cells: roles of ROS, NF-κB, and MAPK pathways

Chronic arsenic exposure has been linked to an increased risk of vascular diseases. To clarify the molecular mechanisms through which arsenic causes injuries to blood vessels, we analyzed the effects of arsenic trioxide on the cytotoxicity, intracellular reactive oxygen species (ROS), the expression of related genes, and signaling pathways involved in the SVEC4-10 mouse endothelial cells. Arsenic dose-dependently caused SVEC4-10 cell death, which is completely inhibited by α-lipoic acid (LA), a thioreductant, but partially ameliorated by Tiron, a potent superoxide scavenger. The mRNA levels of heme oxygenase-1 (HO-1), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and vascular endothelial growth factor (VEGF) were significantly increased by arsenic. The up-regulation of these can be blocked by LA instead of Tiron, suggesting ROS is not important in their increase. HO-1 competitive inhibitor zinc protoporphyrin improved the cytotoxicity of arsenic in an inverted-U dose-response curve, indicating the biphasic hormetic effect of HO-1. HO-1 siRNA decreased VEGF expression in response to arsenic. Arsenic exposure also enhanced NF-E2-related factor 2 (Nrf2) expression and increased activation of nuclear factor-κB (NF-κB). NF-κB inhibitor Bay 11-7082 reduced arsenic-mediated expression of HO-1 and IL-6. Selective blocking of the MAPK pathways with p38 inhibitor SB203580 significantly decreased arsenic-induced HO-1 and VEGF expression, while JNKs inhibitor SP600125 increased IL-6 expression. These results suggest that in arsenic-treated SVEC4-10 cells, HO-1 expression is mediated through Nrf2-, NF-κB-, and p38 MAPK-dependent signaling pathways and serves as an upstream regulator of VEGF. IL-6 expression is regulated by NF-κB and JNKs. In conclusion, oxidative stress may be associated with arsenic-induced cytotoxicity and endothelial gene up-regulation, but signaling transduction dominates the direct effects of ROS.     

β1-Adrenoceptor stimulation suppresses endothelial IKCa-channel hyperpolarization and associated dilatation in resistance arteries

Background and Purpose

In small arteries, small conductance Ca²⁺-activated K⁺ channels (SK_Ca) and intermediate conductance Ca²⁺-activated K⁺ channels (IK_Ca) restricted to the vascular endothelium generate hyperpolarization that underpins the NO- and PGI₂-independent, endothelium-derived hyperpolarizing factor response that is the predominate endothelial mechanism for vasodilatation. As neuronal IK_Ca channels can be negatively regulated by PKA, we investigated whether β-adrenoceptor stimulation, which signals through cAMP/PKA, might influence endothelial cell hyperpolarization and as a result modify the associated vasodilatation.

Experimental Approach

Rat isolated small mesenteric arteries were pressurized to measure vasodilatation and endothelial cell [Ca²⁺]_i, mounted in a wire myograph to measure smooth muscle membrane potential or dispersed into endothelial cell sheets for membrane potential recording.

Key Results

Intraluminal perfusion of β-adrenoceptor agonists inhibited endothelium-dependent dilatation to ACh (1 nM–10 μM) without modifying the associated changes in endothelial cell [Ca²⁺]_i. The inhibitory effect of β-adrenoceptor agonists was mimicked by direct activation of adenylyl cyclase with forskolin, blocked by the β-adrenoceptor antagonists propranolol (non-selective), atenolol (β₁) or the PKA inhibitor KT-5720, but remained unaffected by ICI 118 551 (β₂) or glibenclamide (ATP-sensitive K⁺ channels channel blocker). Endothelium-dependent hyperpolarization to ACh was also inhibited by β-adrenoceptor stimulation in both intact arteries and in endothelial cells sheets. Blocking IK_Ca {with 1 μM 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34)}, but not SK_Ca (50 nM apamin) channels prevented β-adrenoceptor agonists from suppressing either hyperpolarization or vasodilatation to ACh.

Conclusions and Implications

In resistance arteries, endothelial cell β₁-adrenoceptors link to inhibit endothelium-dependent hyperpolarization and the resulting vasodilatation to ACh. This effect appears to reflect inhibition of endothelial IK_Ca channels and may be one consequence of raised circulating catecholamines.     

TiO2 nanoparticles induce endothelial cell activation in a pneumocyte–endothelial co-culture model

The effects of particulate matter (PM) on endothelial cells have been evaluated in vitro by exposing isolated endothelial cells to different types of PM. Although some of the findings from these experiments have been corroborated by in vivo studies, an in vitro model that assesses the interaction among different cell types is necessary to achieve more realistic assays. We developed an in vitro model that mimics the alveolar–capillary interface, and we challenged the model using TiO₂ nanoparticles (TiO₂-NPs). Human umbilical endothelial cells (HUVECs) were cultured on the basolateral side of a membrane and pneumocytes (A549) on the apical side. Confluent co-cultures were exposed on the apical side to 10 μg/cm² of TiO₂-NPs or 10 ng/mL of TNFα for 24 h. Unexposed cultures were used as negative controls. We evaluated monocyte adhesion to HUVECs, adhesion molecule expression, nitric oxide concentration and proinflammatory cytokine release. The TiO₂-NPs added to the pneumocytes induced a 3- to 4-fold increase in monocyte adhesion to the HUVECs and significant increases in the expression of adhesion molecules (4-fold for P-selectin at 8 h, and about 8- and 10-fold for E-selectin, ICAM-1, VCAM-1 and PECAM-1 at 24 h). Nitric oxide production also increased significantly (2-fold). These results indicate that exposing pneumocytes to TiO₂-NPs causes endothelial cell activation.     

Enhanced serelaxin signalling in co‐cultures of human primary endothelial and smooth muscle cells

Background and Purpose

In the phase III clinical trial, RELAX‐AHF, serelaxin caused rapid and long‐lasting haemodynamic changes. However, the cellular mechanisms involved are unclear in humans.

Experimental Approach

This study examined the effects of serelaxin in co‐cultures of human primary endothelial cells (ECs) and smooth muscle cells (SMCs) on cAMP and cGMP signalling.

Key Results

Stimulation of HUVECs or human coronary artery endothelial cells (HCAECs) with serelaxin, concentration‐dependently increased cGMP accumulation in co‐cultured SMCs to a greater extent than in monocultures of either cell type. This was not observed in human umbilical artery endothelial cells (HUAECs) that do not express the relaxin receptor, RXFP1. Treatment of ECs with l‐N^G‐nitro arginine (NOARG; 30 μM, 30 min) inhibited serelaxin‐mediated (30 nM) cGMP accumulation in HUVECs, HCAECs and co‐cultured SMCs. In HCAECs, but not HUVECs, pre‐incubation with indomethacin (30 μM, 30 min) also inhibited cGMP accumulation in SMCs. Pre‐incubation of SMCs with the guanylate cyclase inhibitor ODQ (1 μM, 30 min) had no effect on serelaxin‐mediated (30 nM) cGMP accumulation in HUVECs and HCAECs but inhibited cGMP accumulation in SMCs. Serelaxin stimulation of HCAECs, but not HUVECs, increased cAMP accumulation concentration‐dependently in SMCs. Pre‐incubation of HCAECs with indomethacin, but not l‐NOARG, abolished cAMP accumulation in co‐cultured SMCs, suggesting involvement of prostanoids.

Conclusions and Implications

In co‐cultures, treatment of ECs with serelaxin caused marked cGMP accumulation in SMCs and with HCAEC also cAMP accumulation. Responses involved EC‐derived NO and with HCAEC prostanoid production. Thus, serelaxin differentially modulates vascular tone in different vascular beds.

Abbreviations

AHF

acute heart failure

DEA

diethylamine NONOate

ECs

endothelial cells

HCAEC

human coronary artery endothelial cell

HUAEC

human umbilical artery endothelial cell

HUASMC

human umbilical artery smooth muscle cell

HUVSMC

human umbilical vein smooth muscle cell

l‐NOARG

l‐N^G‐nitro arginine

SMCs

smooth muscle cells

     

Inhibition of γ-irradiation induced adhesion molecules and NO production by alginate in human endothelial cells

Inflammation is a frequent radiation-induced reaction following therapeutic irradiation. Treatment of human umbilical endothelial cells (HUVEC) with gamma-irradiation (gammaIR) induces the expression of adhesion proteins such as intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin. Since the upregulation of these proteins on endothelial cell surface has been known to be associated with inflammation, interfering with the expression of adhesion molecules is an important therapeutic target. In the present study, we demonstrate that high mannuronic acid-containing alginate (HMA) inhibits gammaIR induced expression of ICAM-1, VCAM-1, and E-selectin on HUVEC in a dose dependent manner. HMA also inhibited gammaIR induced production of Nitric oxide (NO). These data suggest that HMA has therapeutic potential for the treatment of various inflammatory disorder associated with an increase of endothelial leukocyte adhesion molecules.     

Submaximal PPARγ activation and endothelial dysfunction: new perspectives for the management of cardiovascular disorders

PPARγ activation plays an important role in glucose metabolism by enhancing insulin sensitization. PPARγ is a primary target for thiazolidinedione-structured insulin sensitizers like pioglitazone and rosiglitazone employed for the treatment of type 2 diabetes mellitus. Additionally, PPARγ activation inhibits adhesion cascades and detrimental vascular inflammatory events. Importantly, activation of PPARγ plays a distinctive role in regulating the physiology and expression of endothelial nitric oxide synthase (eNOS) in the endothelium, resulting in enhanced generation of vascular nitric oxide. The PPARγ activation-mediated vascular anti-inflammatory and direct endothelial functional regulatory actions could, therefore, be beneficial in improving the vascular function in patients with atherosclerosis and hypertension with or without diabetes mellitus. Despite the disappointing cardiac side effect profile of rosiglitazone-like PPARγ full agonists, the therapeutic potential of novel pharmacological agents targeting PPARγ submaximally cannot be ruled out. This review discusses the potential regulatory role of PPARγ on eNOS expression and activation in improving the function of vascular endothelium. We argue that partial/submaximal activation of PPARγ could be a major target for vascular endothelial functional improvement. Interestingly, newly synthesized partial agonists of PPARγ such as balaglitazone, MBX-102, MK-0533, PAR-1622, PAM-1616, KR-62776 and SPPARγM5 are devoid of or have a reduced tendency to cause the adverse effects associated with full agonists of PPARγ. We propose that the vascular protective properties of pharmacological agents, which submaximally activate PPARγ, should be investigated. Moreover, the therapeutic opportunities of agents that submaximally activate PPARγ in preventing vascular endothelial dysfunction (VED) and VED-associated cardiovascular disorders are discussed.     

Therapeutic use of stem and endothelial progenitor cells in acute renal injury: ça ira

Acute renal failure (ARF) seriously worsens prognosis of hospitalized patients. The dysfunction and apoptosis/necrosis of tubular epithelial cells is of key importance for the pathophysiological consequences of the syndrome. ARF also affects the structure and function of the renal endothelium because these cells undergo an early swelling with narrowing of the vascular lumen, resulting in prolonged renal hypoperfusion. The dysfunctional renal epithelium and endothelium have remarkable capacity to recover. With the growing knowledge in the field of stem cell research, these regenerative mechanisms become more and more elucidated. Recent data suggest that bone marrow derived mesenchymal stem cells can ameliorate ARF through both paracrine effects and repair of injured microvasculature by providing endothelial progenitor cells. Evidence for resident adult renal stem cells is also now emerging.     

17β-estradiol-linked nitro-L-arginine as simultaneous inducer of apoptosis in melanoma and tumor-angiogenic vascular endothelial cells

Aggressive melanoma is commonly associated with rapid angiogenic growth in tumor mass, tumor cells acquiring apoptosis resistance, inhibition of cellular differentiation etc. Designing a single anticancer molecule which will target all these factors simultaneously is challenging. In the pretext of inciting anticancer effect through inhibiting nitric oxide synthase (NOS) via estrogen receptors (ER) in ER-expressing skin cancer cells, we developed an estrogen-linked L-nitro-arginine molecule (ESAr) for inciting anticancer effect in melanoma cells. ESAr showed specific anticancer effect through diminishing aggressiveness and metastatic behavior in melanoma cells and tumor. In comparison, ESAr showed significantly higher antiproliferative effect than parent molecule L-nitroarginine methyl ester (L-NAME, a NOS inhibitor) through induction of prominent apoptosis in melanoma cells. ESAr-pretreated aggressive melanoma cells could not form tumor possibly because of transformation/differentiation into epithelial-type cells. Furthermore, its antiangiogenic effect was demonstrated through ESAr-induced antiproliferation in HUVEC cells and apoptosis-induction in tumor-associated vascular endothelial cells, thereby significantly restricting severe growth in melanoma tumor. The targeting moiety, estrogen, at the therapeutic concentration of ESAr has apparently no effect in tumor-growth reduction. Albeit, no specific NOS-inhibition was observed, but ESAr could simultaneously induce these three cancer-specific antiaggressiveness factors, which the parent molecule could not induce. Our data rationalize and establish a new use of estrogen as a ligand for potentially targeting multiple cellular factors for treating aggressive cancers.     

Immunosuppressor FK506 increases endoglin and activin receptor-like kinase 1 expression and modulates transforming growth factor-β1 signaling in endothelial cells

Hereditary hemorrhagic telangiectasia (HHT), or Rendu-Osler-Weber syndrome, is an autosomal-dominant vascular disease. The clinical manifestations are epistaxis, mucocutaneous and gastrointestinal telangiectases, and arteriovenous malformations in internal organs. Patients show severe epistaxis, and/or gastrointestinal bleeding, both of which notably interfere with their quality of life. There are two predominant types of HHT caused by mutations in endoglin (ENG) and ACVRL1/activin receptor-like kinase 1 (ALK1) genes, named HHT1 and HHT2, respectively. ENG and ALK1 code for proteins involved in the transforming growth factor (TGF)-β1 signaling pathway, and it is widely accepted that HHT pathogenicity results from haploinsufficiency. No cure for HHT has been found, so identification of drugs able to increase the expression of these genes is essential when proposing new therapies. We report the efficacy of tacrolimus (FK506) in increasing ENG and ALK1 expression. The rationale comes from a case report of a patient with HHT who received a liver transplantation after hepatic failure due to a liver arteriovenous malformation. The liver was transplanted, and the immunosuppressor FK506 was used to prevent the rejection. After the first month of FK506 treatment, the internal and external telangiectases, epistaxes, and anemia disappeared. Here, we find that the immunosuppressor FK506 increases the protein and mRNA expression of ENG and ALK1 in cultured endothelial cells and enhances the TGF-β1/ALK1 signaling pathway and endothelial cell functions like tubulogenesis and migration. These results suggest that the mechanism of action of FK506 involves a partial correction of endoglin and ALK1 haploinsufficiency and may therefore be an interesting drug for use in patients with HHT who undergo transplantation.