Human microvascular endothelial cells from different fetal organs demonstrate organ-specific CAM expression

Transcriptional Regulation of Drug Metabolizing CYP Enzymes by Proinflammatory Wnt5A Signaling in Human Coronary Artery Endothelial Cells

Downregulation of drug metabolizing enzymes and transporters by proinflammatory mediators in hepatocytes, enterocytes and renal tubular epithelium is an established mechanism affecting pharmacokinetics. Emerging evidences indicate that vascular endothelial cell expression of drug metabolizing enzymes and transporters may regulate pharmacokinetic pathways in heart to modulate local drug bioavailability and toxicity. However, whether inflammation regulates pharmacokinetic pathways in human cardiac vascular endothelial cells remains largely unknown. The lipid modified protein Wnt5A is emerging as a critical mediator of proinflammatory responses and disease severity in sepsis, hypertension and COVID-19. In the present study, we employed transcriptome profiling and gene ontology analyses to investigate the regulation of expression of drug metabolizing enzymes and transporters by Wnt5A in human coronary artery endothelial cells. Our study shows for the first time that Wnt5A induces the gene expression of CYP1A1 and CYP1B1 enzymes involved in phase I metabolism of a broad spectrum of drugs including chloroquine (the controversial drug for COVID-19) that is known to cause toxicity in myocardium. Further, the upregulation of CYP1A1 and CYP1B1 expression is preserved even during inflammatory crosstalk between Wnt5A and the prototypic proinflammatory IL-1β in human coronary artery endothelial cells. These findings stimulate further studies to test the critical roles of vascular endothelial cell CYP1A1 and CYP1B1, and the potential of vascular-targeted therapy with CYP1A1/CYP1B1 inhibitors in modulating myocardial pharmacokinetics in Wnt5A-associated inflammatory and cardiovascular diseases.

Tissue-specific endothelial cell heterogeneity contributes to unequal inflammatory responses

Endothelial cells (EC) coordinate vascular homeostasis and inflammation. In organ transplantation, EC are a direct alloimmune target. We posited that tissue specific heterogeneity of vascular EC may partly underlie the disparate organ-specific alloimmune risk. We examined the vascular endothelial response to inflammation across six primary endothelial beds from four major transplanted organs: the heart, lung, kidney and liver. First, we reanalyzed a public dataset of cardiac allograft rejection and found that endothelial inflammatory response genes were elevated in human cardiac allograft biopsies undergoing rejection compared with stable grafts. Next, the inducible inflammatory phenotypes of EC from heart, lung, kidney, and liver were characterized in vitro, focused on expression of adhesion molecules and chemokines, and recruitment of allogeneic peripheral blood mononuclear immune cells. Large vessel cardiac EC most highly upregulated VCAM-1, particularly compared with hepatic EC, supported greater leukocyte adhesion and had distinct chemokine profiles after stimulation with cytokines and complement. Differentially expressed gene candidates that are known regulators of cytokine signaling and inflammatory programming were verified in publicly available datasets of organ-specific endothelial transcriptomes. In summary, differential baseline expression of immune regulating genes may contribute to differential vascular inflammatory responses depending on organ.

Endothelial to Mesenchymal Transition Represents a Key Link in the Interaction between Inflammation and Endothelial Dysfunction

Endothelial cells that line the inner walls of blood vessels are in direct contact with blood and display remarkable heterogeneity in their response to exogenous stimuli. These ECs have unique location-dependent properties determined by the corresponding vascular beds and play an important role in regulating the homeostasis of the vascular system. Evidence suggests that vascular endothelial cells exposed to various environments undergo dynamic phenotypic switching, a key biological program in the context of endothelial heterogeneity, but that might result in EC dysfunction and, in turn, cause a variety of human diseases. Emerging studies show the importance of endothelial to mesenchymal transition (EndMT) in endothelial dysfunction during inflammation. EndMT is a complex biological process in which ECs lose their endothelial characteristics, acquire mesenchymal phenotypes, and express mesenchymal cell markers, such as alpha smooth muscle actin and fibroblast-specific protein 1. EndMT is induced by inflammatory responses, leading to pathological states, including tissue fibrosis, pulmonary arterial hypertension, and atherosclerosis, via dysfunction of the vascular system. Although the mechanisms associated with inflammation-induced EndMT have been identified, unraveling the specific role of this phenotypic switching in vascular dysfunction remains a challenge. Here, we review the current understanding on the interactions between inflammatory processes, EndMT, and endothelial dysfunction, with a focus on the mechanisms that regulate essential signaling pathways. Identification of such mechanisms will guide future research and could provide novel therapeutic targets for the treatment of vascular diseases.

Comparison of apoptosis in human primary pulmonary endothelial cells and a brain microvascular endothelial cell line co-cultured with Plasmodium falciparum field isolates

BACKGROUND

Plasmodium falciparum infection can progress unpredictably to severe forms including respiratory distress and cerebral malaria. The mechanisms underlying the variable natural course of malaria remain elusive.

METHODS

The cerebral microvascular endothelial cells-D3 and lung endothelial cells both from human were cultured separately and challenged with P. falciparum field isolates taken directly from malaria patients or 3D7 strain (in vitro maintained culture). The capacity of these P. falciparum isolates to induce endothelial cell apoptosis via cytoadherence or not was then assessed.

RESULTS

Overall, 27 P. falciparum isolates were collected from patients with uncomplicated malaria (n = 25) or severe malaria (n = 2). About half the isolates (n = 17) were able to bind brain endothelial cells (12 isolates, 44%) or lung endothelial cells (17 isolates, 63%) or both (12 isolates, 44%). Sixteen (59%) of the 27 isolates were apoptogenic for brain and/or lung endothelial cells. The apoptosis stimulus could be cytoadherence, direct cell-cell contact without cytoadherence, or diffusible soluble factors. While some of the apoptogenic isolates used two stimuli (direct contact with or without cytoadherence, plus soluble factors) to induce apoptosis, others used only one. Among the 16 apoptogenic isolates, eight specifically targeted brain endothelial cells, one lung endothelial cells, and seven both.

CONCLUSION

These results indicate that the brain microvascular cell line was more susceptible to apoptosis triggered by P. falciparum than the primary pulmonary endothelial cells and may have relevance to host-parasite interaction.

The zebrafish ventricle: A hub of cardiac endothelial cells for in vitro cell behavior studies

Despite our increasing understanding of zebrafish heart development and regeneration, there is limited information about the distribution of endothelial cells (ECs) in the adult zebrafish heart. Here, we investigate and compare the distribution of cardiac ECs (cECs) in adult mouse and zebrafish ventricles. Surprisingly, we find that (i) active coronary vessel growth is present in adult zebrafish, (ii) ~37 and ~39% of cells in the zebrafish heart are ECs and cardiomyocytes, respectively, a composition similar to that seen in mouse. However, we find that in zebrafish, ~36% of the ventricular tissue is covered with ECs, i.e., a substantially larger proportion than in mouse. Capitalising on the high abundance of cECs in zebrafish, we established a protocol to isolate them with high purity using fluorescent transgenic lines. Our approach eliminates side-effects due to antibody utilisation. Moreover, the isolated cECs maintained a high proliferation index even after three passages and were amenable to pharmacological treatments to study cEC migration in vitro. Such primary cultures will be a useful tool for supplementary in vitro studies on the accumulating zebrafish mutant lines as well as the screening of small molecule libraries on cardiac specific endothelial cells.

Culture media-based selection of endothelial cells, pericytes, and perivascular-resident macrophage-like melanocytes from the young mouse vestibular system

The vestibular blood-labyrinth barrier (BLB) is comprised of perivascular-resident macrophage-like melanocytes (PVM/Ms) and pericytes (PCs), in addition to endothelial cells (ECs) and basement membrane (BM), and bears strong resemblance to the cochlear BLB in the stria vascularis. Over the past few decades, in vitro cell-based models have been widely used in blood-brain barrier (BBB) and blood-retina barrier (BRB) research, and have proved to be powerful tools for studying cell-cell interactions in their respective organs. Study of both the vestibular and strial BLB has been limited by the unavailability of primary culture cells from these barriers. To better understand how barrier component cells interact in the vestibular system to control BLB function, we developed a novel culture medium-based method for obtaining EC, PC, and PVM/M primary cells from tiny explants of the semicircular canal, sacculus, utriculus, and ampullae tissue of young mouse ears at post-natal age 8-12 d. Each phenotype is grown in a specific culture medium which selectively supports the phenotype in a mixed population of vestibular cell types. The unwanted phenotypes do not survive passaging. The protocol does not require additional equipment or special enzyme treatment. The harvesting process takes less than 2 h. Primary cell types are generated within 7-10 d. The primary culture ECs, PCs, and PVM/M shave consistent phenotypes more than 90% pure after two passages (∼ 3 weeks). The highly purified primary cell lines can be used for studying cell-cell interactions, barrier permeability, and angiogenesis.

Distribution of CD10-positive epithelial and mesenchymal cells in human mid-term fetuses: a comparison with CD34 expression

CD10, a marker of immature B lymphocytes, is expressed in the developing epithelium of mammary glands, hair follicles, and renal tubules of human fetuses. To assess mesenchymal and stromal expression of CD10, we performed immunohistochemical assays in whole body sections from eight fetuses of gestational ages 15-20 weeks. In addition to expression in urinary tract and intestinal epithelium, CD10 was strongly expressed at both gestational ages in fibrous tissues surrounding the airways from the larynx to lung alveoli, in the periosteum and ossification center, and in the glans of external genitalia. CD10 was not expressed, however, in other cavernous tissues. These findings suggest that mesenchymal, in addition to epithelial cells at specific sites, are likely to express CD10. The glomeruli, alveoli, and glans are all end products of budding or outgrowth processes in the epithelium or skin. However, in contrast to the CD34 marker of stromal stem cells, CD10 was not expressed in vascular progenitor cells and in differentiated vascular endothelium. The alternating pattern of CD10 and CD34 expression suggests that these factors play different roles in cellular differentiation and proliferation of the kidneys, airway and external genitalia.

Isolation and expansion of human and mouse brain microvascular endothelial cells

Brain microvascular endothelial cells (BMVECs) have an important role in the constitution of the blood-brain barrier (BBB). The BBB is involved in the disease processes of a number of neurological disorders in which its permeability increases. Isolation of BMVECs could elucidate the mechanism involved in these processes. This protocol describes how to isolate and expand human and mouse BMVECs. The procedure covers brain-tissue dissociation, digestion and cell selection. Cells are selected on the basis of time-responsive differential adhesiveness to a collagen type I-precoated surface. The protocol also describes immunophenotypic characterization, cord formation and functional assays to confirm that these cells in endothelial proliferation medium (EndoPM) have an endothelial origin. The entire technique requires ∼7 h of active time. Endothelial cell clusters are readily visible after 48 h, and expansion of BMVECs occurs over the course of ∼60 d.

Human and mouse brain-derived endothelial cells require high levels of growth factors medium for their isolation, in vitro maintenance and survival

Background

Brain microvascular endothelial cells (BMVECs) constitute the primary limitation for passage of ions and molecules from the blood into the brain through the blood brain barrier. Numerous multi-step procedures for isolating and culturing BMVECs have been described. However, each one demonstrates major limitations in purity of culture and/or low proliferation rate. Our goal was to study the efficiency of our pending patent medium, Endothelial Proliferation Medium (EndoPM), on the isolation and purification of human and murine BMVECs.

Methods

BMVECs, cultured in EndoPM were compared to those cultured in a commercial medium EBM. Cultures were characterized by flow cytometric analysis, lineage differentiation, the ability to form tube-like structure, immunofluorescence, molecular analyses and also in an in vivo model assay. Moreover permeability was assayed by monitoring the passage of Dextran-FITC through a tight monolayer of BMVECs grown to confluence in Boyden chambers. One way Anova two-tailed test was utilized for all statistical analyses.

Results

The properties of ECs in human and murine BMVECs is confirmed by the expression of endothelial markers (CD31, CD105, CD146, Tie-2 and vWF), of representative proangiogenic genes (ICAM1, VCAM1 and integrin ITGAV), of considerable tube-forming ability, with low-density lipoprotein uptake, eNOS and GLUT-1 expression. Furthermore cells are able to express markers of the junctional architecture as VE-cadherin, β-catenin and Claudin-5 and greatly reduce dextran permeability as barrier functional test. Moreover BMVECs spontaneously organize in vascular-like structures and maintain the expression of endothelial markers in an in vivo xenograft model assay. The significant effect of EndoPM is confirmed by the study of proliferation index, survival index and the behaviour of BMVECs and fibroblasts in co-culture conditions.

Conclusion

Herein we describe a simple and reproducible method for the isolation and expansion of human and mouse BMVECs, based on a newly formulated medium (EndoPM) with optimized concentration of growth factors (EGF, FGF-2 and Bovine Brain Extract-BBE). This procedure should facilitate the isolation and expansion of human and mouse BMVECs with extended lifetime, good viability and purity. This approach may provide an effective strategy to aid phenotypical and functional studies of brain vessels under physiological and pathological conditions.

Relationship between birth weight and retinal microvasculature in newborn infants

OBJECTIVE

The purposes of this study were to determine the normal retinal microvasculature measurements in human infants who are born at term and to determine whether birth weight influences measurements of retinal microvasculature.

STUDY DESIGN

Retinal arteriole and venule measurements were obtained in a cohort of 24 infants who were born at term. Digital images of both the retinas were obtained using a digital retinal camera after pupillary dilation.

RESULT

In all, 24 newborn infants born at term (12 females and 12 males) were analyzed in this study. The measured retinal arteriole diameters were from 66.8 to 147.8 μm (mean, 94.2±19.6 μm), and the venule diameters were from 102.0 to 167.8 μm (mean, 135.2±19.1 μm). Seven babies in the sample had low birth weight (LBW), while 17 babies were born with normal weight. Babies with lower birth weights had larger arteriole (113.1±17.9 μm vs 86.4±14.4 μm; P=0.0009) and venule diameters (151.7±14.9 μm vs 128.4±16.9 μm; P=0.0040).

CONCLUSION

Retinal venules and arterioles in LBW babies are larger compared with those of normal-birth-weight babies. We postulate that the difference observed in our study was due to in utero pathophysiological changes that occurred in the cerebral circulation of growth-restricted fetuses.

DLK1(PREF1) is a negative regulator of adipogenesis in CD105⁺/CD90⁺/CD34⁺/CD31⁻/FABP4⁻ adipose-derived stromal cells from subcutaneous abdominal fat pats of adult women

The main physiological function of adipose-derived stromal/progenitor cells (ASC) is to differentiate into adipocytes. ASC are most likely localized at perivascular sites in adipose tissues and retain the capacity to differentiate into multiple cell types. Although cell surface markers for ASC have been described, there is no complete consensus on the antigen expression pattern that will precisely define these cells. DLK1(PREF1) is an established marker for mouse adipocyte progenitors which inhibits adipogenesis. This suggests that DLK1(PREF1) could be a useful marker to characterize human ASC. The DLK1(PREF1) status of human ASC is however unknown. In the present study we isolated ASC from the heterogeneous stromal vascular fraction of subcutaneous abdominal fat pats of adult women. These cells were selected by their plastic adherence and expanded to passage 5. The ASC were characterized as relatively homogenous cell population with the capacity to differentiate in vitro into adipocytes, chondrocytes, and osteoblasts and the immunophenotype CD105⁺/CD90⁺/CD34⁺/CD31⁻/FABP4⁻. The ASC were positive for DLK1(PREF1) which was well expressed in proliferating and density arrested cells but downregulated in the course of adipogenic differentiation. To investigate whether DLK1(PREF1) plays a role in the regulation of adipogenesis in these cells RNAi-mediated knockdown experiments were conducted. Knockdown of DLK1(PREF1) in differentiating ASC resulted in a significant increase of the expression of the adipogenic key regulator PPARγ2 and of the terminal adipogenic differentiation marker FABP4. We conclude that DLK1(PREF1) is well expressed in human ASC and acts as a negative regulator of adipogenesis. Moreover, DLK1(PREF1) could be a functional marker contributing to the characterization of human ASC.

CD34-positive primitive vessels and other structures in human fetuses: an immunohistochemical study

CONCLUSION

CD34-positive mesenchymal tissues are likely to play a critical role in the pattern formation of laryngeal and pharyngeal walls. In the ear, nose, and throat regions, a future clinical relevance may be found in their use for muscle repair and regeneration.

OBJECTIVES

CD34 is a well-known marker of progenitor cells of blood vessels and stromal tissues. Thus, CD34-positive cells have recently been used clinically in the field of vascular and orthopedic biotechnology because of their capacity to assist regeneration of injured tissues. However, to our knowledge, the in situ distribution of CD34-positive cells has not yet been described in the human fetus, with the exception of a few organs. The purpose of this study was to describe the location of CD34-positive cells in the head and neck regions.

METHODS

Immunohistochemistry for CD34 was carried out using seven human fetuses (12 and 15 weeks of gestation).

RESULTS

CD34-positive structures showed a vessel-like appearance and were regularly arrayed along the nasal, oral, pharyngeal, and laryngeal mucosal epithelia, whereas in the laryngeal and pharyngeal striated muscles they were distributed diffusely as fibrous tissues such as the fascia and perimysium.

CD34-positive developing vessels and other structures in human fetuses: an immunohistochemical study

CD34 is a well-known marker of progenitor cells of blood vessels and stromal tissues. Thus, CD34-positive cells have recently been used clinically in the field of vascular and orthopedic biotechnology because of their capacity to assist regeneration of injured tissues. However, to our knowledge, the in situ distribution of CD34-positive cells has not yet been described in the human fetus, with the exception of a few organs. In the present study, we conducted immunohistochemistry for CD34 using 12 human fetuses (9-15 weeks of gestation). CD34-positive structures showed a vessel-like appearance and were regularly arrayed in the viscera, nerves and lymph nodes, whereas in the body wall and extremities, they were distributed diffusely as fibrous tissues, such as the fascia and perimysium. The myocardium was also divided and bundled by CD34-positive fibrous tissues. In striated muscles, limited examples of CD34 expression were found in the tongue and extraocular muscles in which only vessels were positive. Lymphatic vessels were negative for CD34. In addition to their contribution to vascular development in any part of the body, CD34-positive mesenchymal tissues seem to play a critical role in the pattern formation of skeletal muscle, synovial tissue and other muscle/tendon-associated tissues in human fetuses.

In vitro assays for endothelial cell functions related to angiogenesis: proliferation, motility, tubular differentiation, and proteolysis

This chapter covers the breakdown of the process of angiogenesis into simple assays to measure discrete endothelial cell functions. The techniques described are suitable for studying stimulators or inhibitors of angiogenesis and determining which aspect of the process is modulated. The procedures outlined are robust and straightforward but cannot cover the complexity of the angiogenic process as a whole, incorporating as it does myriad positive and negative signals, three-dimensional interactions with host tissues and many accessory cells, including fibroblasts, macrophages, pericytes, and platelets. The extent to which in vitro assays predict responses in vivo (e.g., wound healing, tumor angiogenesis, or surrogate techniques such as Matrigel plugs, sponge implants, corneal assays, etc.) remains to be determined.

Validity of a patient-derived system of tissue-specific human endothelial cells: interleukin-6 as a surrogate marker in the coronary system

The aim of our study was to evaluate the relevance of tissue- and species-specific endothelial cells (EC) to study EC-dependent mechanisms in inflammatory-mediated tissue injury. We established an isolation protocol for highly purified EC (pEC) preparations of different origin and compared EC-specific inflammatory responses. Fluorescence-activated cell separation was used to obtain pEC cultures from different human arterial (coronary artery, internal thoracic artery) and venous (umbilical vein, saphenous vein) vessels. All pEC were analyzed for growth kinetics, morphology, release of cytokines/chemokines, and expression of E-selectin. For all different EC cultures, purities of ≥99% were reproducibly achieved. The EC isolation did not affect EC growth, morphology, and function. However, characterization of pEC from different vessel materials revealed an intrinsic, tissue-specific functional heterogeneity of EC cultures. Despite an arterial and venous difference in the secretion of IL-8 and monocyte chemoattractant protein-1, especially EC from coronary arteries produced significantly more IL-6 compared with other EC types, independent of age, gender, and disease of the cell donors. In contrast, the expression of E-selectin was not affected. We conclude that the proposed isolation protocol allows the generation of a pEC bank, enabling us to study tissue-specific aspects at the level of the endothelium.

Phenotypic Heterogeneity of the Endothelium

Endothelial cells, which form the inner cellular lining of blood vessels and lymphatics, display remarkable heterogeneity in structure and function. This is the first of a 2-part review focused on phenotypic heterogeneity of blood vessel endothelium. This review provides an historical perspective of our understanding of endothelial heterogeneity, discusses the scope of phenotypic diversity across the vascular tree, and addresses proximate and evolutionary mechanisms of endothelial cell heterogeneity. The overall goal is to underscore the importance of phenotypic heterogeneity as a core property of the endothelium.

Protective effects of transcription factor HESR1 on retinal vasculature

HESR1 is a basic helix-loop-helix transcription factors regulated by the Notch signaling pathway in vertebrate and Drosophila embryos, and is related to the HES/Hairy/E (sp1) family. HESR1 is a downstream target of Notch in endothelial cells and could be an effector of Notch signaling in these cells. HESR1 is necessary for the induction of a tubular network and for continued maintenance of mature and quiescent blood vessels. To examine the role of HESR1 in retinal neovascularization, we transfected retinal vascular endothelial cells (HRCECs) with the HESR1 gene and studied its effects on the expression of angiogenic factors, on the proliferation and migration of endothelial cells, and on the formation of tube-like structures (TLSs). Overexpression of HESR1 downregulated VEGFR-2 expression, upregulated occludin expression, inhibited the migration and proliferation of HRCECs, and inhibited the formation of TLSs. Thus, HESR1 plays a key role in the finely tuned network of molecules involved in the regulation of retinal vascular homeostasis. HESR1 seems to inhibit the vessel-promoting effects of VEGF, shift endothelial cells from a proliferative state to a quiescent state, and restore normal vessel structures. Expression of the HESR1 gene in retinal vascular endothelial cells may protect retinal blood vessels and may be useful in the treatment of diseases involving damage to the retinal vasculature, including diabetic retinopathy, age-related macular degeneration, and retinal vein occlusion.

Susceptibility of brain microvascular endothelial cells to advanced glycation end products-induced tissue factor upregulation is associated with intracellular reactive oxygen species

There is accumulating evidence that advanced glycation end products (AGEs) are relevant to the formation of vascular complications in diabetes mellitus. The aim of this study was to investigate whether AGEs have a significant effect on tissue factor (TF) expression in brain microvascular endothelial cells compared with that in other arterial endothelial cells. Cultured bovine brain microvascular endothelial cells (BBMECs) and aortic endothelial cells (BAECs) were incubated in medium containing glyceraldehyde-derived AGE (glycer-AGE). TF mRNA expression, protein expression, and activity were measured at multiple time points after glycer-AGE incubation. Participation of reactive oxygen species (ROS) in the effect of glycer-AGE on TF expression was investigated by treatment with a free radical scavenger, edaravone, and intracellular ROS measurements with dihydroethidium (DHE). Basic TF mRNA expression was greater in BBMECs than in BAECs. Glycer-AGE significantly upregulated TF mRNA expression in both cells, and the upregulation was more prominent in BBMECs than in BAECs. TF protein expression and activity were also upregulated with a pattern of being greater in BBMECs than in BAECs. Edaravone significantly attenuated the AGE-induced upregulation of TF mRNA expression, protein expression, and activity. Intracellular ROS levels measured with DHE-stained fluorescent intensity were significantly upregulated by glycer-AGE with a pattern of being greater in BBMECs than in BAECs. AGE-induced ROS upregulation was attenuated by edaravone like AGE-induced TF upregulation. These results suggest that brain microvascular endothelial cells are more susceptible to AGE-induced TF upregulation than aortic endothelial cells, and that this susceptibility is associated with levels of intracellular ROS.

Mechanisms of endothelial cell guidance and vascular patterning in the developing mouse retina

The appropriate guidance and patterning of vessels during vascular development is critical for proper tissue function. The loss of these guidance mechanisms can lead to abnormal vascularization and a number of pathological conditions. The molecular basis of endothelial cell guidance and subsequent tissue specific vascular patterning remains largely unknown in spite of its clinical relevance and biological importance. In this regard, retinal vascular development offers many advantages for studying endothelial cell guidance and the mechanisms by which characteristic vascular patterns are formed. In this review, we will provide an overview of the known mechanisms that mediate vascular patterning during mouse retinal development, synthesizing these data to formulate a model of how growth factors, cellular adhesion molecules, and vascular-associated cells mediate directed endothelial cell migration and appropriate vascular remodeling. Finally, we will discuss the many aspects of retinal vascular development that remain unknown and cite evidence that many of these gaps may be addressed by further studying the guidance cues shared by vascular and neuronal elements in the retina and other parts of the central nervous system.

Croix B, Kinzler KW, Huso DL. Tumor endothelial marker 1 (Tem1) functions in the growth and progression of abdominal tumors

Tumor endothelial marker 1 (Tem1; endosialin) is the prototypical member of a family of genes expressed in the stroma of tumors. To assess the functional role of Tem1, we disrupted the Tem1 gene in mice by targeted homologous recombination. Tem1(-/-) mice were healthy, their wound healing was normal, and tumors grew normally when implanted in s.c. sites. However, there was a striking reduction in tumor growth, invasiveness, and metastasis after transplantation of tumors to abdominal sites in mice without functional Tem1 genes. These data indicate that the stroma can control tumor aggressiveness and that this control varies with anatomic site. Therefore, they have significant implications for the mechanisms underlying tumor invasiveness and for models that evaluate this process.

Albumin leak across human pulmonary microvascular vs. umbilical vein endothelial cells under septic conditions

Human pulmonary microvascular endothelial cell (HPMVEC) injury is central to the pathophysiology of human lung injury. However, septic HPMVEC barrier dysfunction and the contribution of neutrophils have not been directly addressed in vitro. Instead, human EC responses are often extrapolated from studies of human umbilical vein EC (HUVEC). We hypothesized that HUVEC was not a good model for investigating HPMVEC barrier function under septic conditions. HPMVEC was isolated from lung tissue resected from lung cancer patients using magnetic bead-bound anti-PECAM-1 antibody. In confluent monolayers in 3-mum cell-culture inserts, we assessed trans-EC Evans-Blue (EB)-conjugated albumin leak under basal, unstimulated conditions and following stimulation with either lipopolysaccharide or a mixture of equal concentrations of TNF-alpha, IL-1beta and IFN-gamma (cytomix). Basal EB-albumin leak was significantly lower across HPMVEC than HUVEC (0.64 +/- 0.06% vs. 1.13 +/- 0.10%, respectively, P < 0.001). Lipopolysaccharide and cytomix increased leak across both HPMVEC and HUVEC in a dose-dependent manner, with a similar increase relative to basal leak in both cell types. The presence of neutrophils markedly and dose-dependently enhanced cytomix-induced EB-albumin leak across HPMVEC (P < 0.01), but had no effect on EB-albumin leak across HUVEC. Both cytomix and lipopolysaccharide-induced albumin leak was not associated with a loss of cell viability. In conclusion, HPMVEC barrier dysfunction under septic conditions is dramatically enhanced by neutrophil presence, and HUVEC is not a suitable model for studying HPMVEC septic barrier responses. The direct study of HPMVEC septic responses will lead to a better understanding of human lung injury.

Anti-inflammatory effect of docosahexaenoic acid on cytokine-induced adhesion molecule expression in human retinal vascular endothelial cells

PURPOSE

Docosahexaenoic acid (DHA(22:6n3)), the principal n3-polyunsaturated fatty acid (PUFA) in the retina, has been shown to have a pronounced anti-inflammatory effect in numerous in vivo and in vitro studies. Despite the importance of vascular inflammation in diabetic retinopathy, the anti-inflammatory role of DHA(22:6n3) in cytokine-stimulated human retinal vascular endothelial cells (hRVECs) has not been addressed.

METHODS

Cytokine-induced expression of cell adhesion molecules (CAMs) was assessed by Western blot. The effect of DHA(22:6n3) on cytokine-induced nuclear factor (NF)-kappaB signaling was analyzed by Western blot analysis and electrophoretic mobility shift assay (EMSA).

RESULTS

Stimulation of hRVECs with VEGF(165), TNFalpha, or IL-1beta for 6 to 24 hours caused significant induction of intracellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 expression. Pretreatment of the cells with 100 microM of BSA-bound DHA(22:6n3) for 24 hours remarkably inhibited cytokine-induced CAM expression. IL-1beta, TNFalpha, and VEGF(165) induced nuclear translocation and binding of p65 and p50 NF-kappaB isoforms to the VCAM-1 promoter. DHA(22:6n3) pretreatment inhibited cytokine-induced NF-kappaB binding by 25% to 40%. Moreover, DHA(22:6n3) diminished IL-1beta induced phosphorylation of the inhibitor of nuclear factor (NF)-kappaB (I-kappaBalpha), thus preventing its degradation.

CONCLUSIONS

IL-1beta, TNFalpha, and VEGF(165) induced CAM expression in hRVECs through activation of the NF-kappaB pathway. DHA(22:6n3) inhibited cytokine induced CAM expression through suppression of NF-kappaB nuclear translocation and upstream I-kappaBalpha phosphorylation and degradation. DHA(22:6n3) could be an important anti-inflammatory agent in the face of increased cytokine production and CAM expression in the diabetic retina.