Human umbilical vein and dermal microvascular endothelial cells show heterogeneity in response to PKC activation

Trained Immunity and Reactivity of Macrophages and Endothelial Cells

Innate immune cells can develop exacerbated immunologic response and long-term inflammatory phenotype following brief exposure to endogenous or exogenous insults, which leads to an altered response towards a second challenge after the return to a nonactivated state. This phenomenon is known as trained immunity (TI). TI is not only important for host defense and vaccine response but also for chronic inflammations such as cardiovascular and metabolic diseases such as atherosclerosis. TI can occur in innate immune cells such as monocytes/macrophages, natural killer cells, endothelial cells (ECs), and nonimmune cells, such as fibroblast. In this brief review, we analyze the significance of TI in ECs, which are also considered as innate immune cells in addition to macrophages. TI can be induced by a variety of stimuli, including lipopolysaccharides, BCG (bacillus Calmette-Guerin), and oxLDL (oxidized low-density lipoprotein), which are defined as risk factors for cardiovascular and metabolic diseases. Furthermore, TI in ECs is functional for inflammation effectiveness and transition to chronic inflammation. Rewiring of cellular metabolism of the trained cells takes place during induction of TI, including increased glycolysis, glutaminolysis, increased accumulation of tricarboxylic acid cycle metabolites and acetyl-coenzyme A production, as well as increased mevalonate synthesis. Subsequently, this leads to epigenetic remodeling, resulting in important changes in chromatin architecture that enables increased gene transcription and enhanced proinflammatory immune response. However, TI pathways and inflammatory pathways are separated to ensure memory stays when inflammation undergoes resolution. Additionally, reactive oxygen species play context-dependent roles in TI. Therefore, TI plays significant roles in EC and macrophage pathology and chronic inflammation. However, further characterization of TI in ECs and macrophages would provide novel insights into cardiovascular disease pathogenesis and new therapeutic targets. Graphic Abstract: A graphic abstract is available for this article.

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.

Reduced interstitial cells of Cajal and increased intraepithelial lymphocytes are associated with development of small intestinal bacterial overgrowth in post-infectious IBS mouse model

OBJECTIVE

Intestinal dysmotility and immune activation are likely involved in the pathogenesis of small intestinal bacteria overgrowth (SIBO) in irritable bowel syndrome (IBS). We aimed at investigating the role of interstitial cells of Cajal (ICC) and intestinal inflammation in the development of SIBO using a post-infectious IBS (PI-IBS) mouse model.

MATERIALS AND METHODS

NIH mice were randomly infected with Trichinella spiralis. Visceral sensitivity and stool pattern were assessed at 8-weeks post-infection (PI). Intestinal bacteria counts from jejunum and ileum were measured by quantitative real-time PCR to evaluate the presence of SIBO. ICC density, intraepithelial lymphocytes (IELs) counts, and intestinal cytokine levels (IL1-β, IL-6, toll-like receptor-4 (TLR-4), IL-10) in the ileum were examined.

RESULTS

PI-IBS mice demonstrated increased visceral sensitivity compared with the control group. One-third of the PI-IBS mice developed SIBO (SIBO+/PI-IBS) and was more likely to have abnormal stool form compared with SIBO negative PI-IBS (SIBO-/PI-IBS) mice but without difference in visceral sensitivity. SIBO+/PI-IBS mice had decreased ICC density and increased IELs counts in the ileum compared with SIBO-/PI-IBS mice. No difference in inflammatory cytokine expression levels were detected among the groups except for increased TLR-4 in PI-IBS mice compared with the control group.

CONCLUSIONS

Development of SIBO in PI-IBS mice was associated with reduced ICC density and increased IELs counts in the ileum. Our findings support the role of intestinal dysmotility and inflammation in the pathogenesis of SIBO in IBS and may provide potential therapeutic targets.

Soluble mediators produced by the crosstalk between microvascular endothelial cells and dengue-infected primary dermal fibroblasts inhibit dengue virus replication and increase leukocyte transmigration

When dengue virus (DENV)-infected mosquitoes use their proboscis to probe into human skin during blood feeding, both saliva and virus are released. During this process, cells from the epidermis and dermis layers of the skin, along with small blood vessels, may get exposed to or infected with DENV. In these microenvironments of the skin, the presence of DENV initiates a complex interplay among the DENV-infected and non-infected neighboring cells at the initial bite site. Previous studies suggested that DENV-infected human dermal fibroblasts (HDFs) participate in the immune response against DENV by secreting soluble mediators of innate immunity. In the present study, we investigated whether DENV-infected HDFs activate human dermal microvascular endothelial cells (HDMECs) in co-cultures. Our results suggest that co-cultures of DENV-infected HDFs and HDMECs elicit soluble mediators that are sufficient to reduce viral replication, activate HDMECs, and induce leukocyte migration through HDMEC monolayers. These effects were partly dependent on HDF donor and DENV serotype, which may provide novel insights into the natural variation in host susceptibility to DENV disease.

Pain management in patients with inflammatory bowel disease: translational approaches from bench to bedside

Abdominal pain is a common symptom in patients with inflammatory bowel disease (IBD) that negatively affects quality of life and can lead to increased health-seeking behavior. Although abdominal pain has been traditionally attributed to inflammation, there is growing literature demonstrating the existence of functional abdominal pain in patients with IBD, of which there are a variety of potential causes. Thus, when approaching a patient with IBD who has abdominal pain, in addition to IBD-related complications (e.g., inflammation/stricture), it is important to screen for related contributors, including peripheral factors (visceral hypersensitivity, bacterial overgrowth, and bowel dysmotility) and centrally mediated neurobiological and psychosocial underpinnings. These central factors include psychological symptoms/diagnoses, sleep disturbance, and stress. Opioid-induced hyperalgesia (e.g., narcotic bowel syndrome) is also growing in recognition as a potential central source of abdominal pain. This review draws from clinical studies and animal models of colitis and abdominal pain to consider how knowledge of these potential etiologies can be used to individualize treatment of abdominal pain in patients with IBD, including consideration of potential novel treatment modalities for the future. Accurate assessment of the source(s) of pain in patients with IBD can help guide appropriate diagnostic workup and use of disease-modifying therapy.

Non-contact high-frequency ultrasound microbeam stimulation for studying mechanotransduction in human umbilical vein endothelial cells

We describe how contactless high-frequency ultrasound microbeam stimulation (HFUMS) is capable of eliciting cytoplasmic calcium (Ca(2+)) elevation in human umbilical vein endothelial cells. The cellular mechanotransduction process, which includes cell sensing and adaptation to the mechanical micro-environment, has been studied extensively in recent years. A variety of tools for mechanical stimulation have been developed to produce cellular responses. We developed a novel tool, a highly focused ultrasound microbeam, for non-contact cell stimulation at a microscale. This tool, at 200 MHz, was applied to human umbilical vein endothelial cells to investigate its potential to elicit an elevation in cytoplasmic Ca(2+) levels. It was found that the response was dose dependent, and moreover, extracellular Ca(2+) and cytoplasmic Ca(2+) stores were involved in the Ca(2+) elevation. These results suggest that high-frequency ultrasound microbeam stimulation is potentially a novel non-contact tool for studying cellular mechanotransduction if the acoustic pressures at such high frequencies can be quantified.

Heterogenic endothelial responses to inflammation: role for differential N-glycosylation and vascular bed of origin

BACKGROUND

Endothelial cell responses during inflammation are heterogeneous and key for selectivity in how leukocytes hone in on specific sites and why vascular diseases are highly bed specific. However, mechanisms for this specificity remain unclear.

METHODS AND RESULTS

Here, we exposed human endothelial cells isolated from 5 systemic arterial beds from 1 donor (to overcome donor-to-donor genetic/epigenetic differences), the umbilical vein, and pulmonary microvasculature to TNF-α, LPS, and IL-1β and assessed acute (ERK1/2 and p65) and chronic (ICAM-1, VCAM-1 total and surface expression) signaling responses and assessed changes in surface N-glycans and monocyte adhesion. Significant diversity in responses was evident by disparate changes in ERK1/2 and p65 NF-κB phosphorylation, which varied up to 5-fold between different cells and in temporal and magnitude differences in ICAM-1 and VCAM-1 expression (maximal VCAM-1 induction typically being observed by 4 hours, whereas ICAM-1 expression was increased further at 24 hours relative to 4 hours). N-glycan profiles both basally and with stimulation were also bed specific, with hypoglycosylated N-glycans correlating with increased THP-1 monocyte adhesion. Differences in surface N-glycan expression tracked with dynamic up- or downregulation of α-mannosidase activity during inflammation.

CONCLUSIONS

These results demonstrate a critical role for the vascular bed of origin in controlling endothelial responses and function to inflammatory stimuli and suggest that bed-specific expression of N-linked sugars may provide a signature for select leukocyte recruitment.

Mechanisms of motility change on trinitrobenzenesulfonic Acid-induced colonic inflammation in mice

Ulcerative colitis is an inflammatory bowel disease (IBD) characterized by recurrent episodes of colonic inflammation and tissue degeneration in human or animal models. The contractile force generated by the smooth muscle is significantly attenuated, resulting in altered motility leading to diarrhea or constipation in IBD. The aim of this study is to clarify the altered contractility of circular and longitudinal smooth muscle layers in proximal colon of trinitrobenzen sulfonic acid (TNBS)-induced colitis mouse. Colitis was induced by direct injection of TNBS (120 mg/kg, 50% ethanol) in proximal colon of ICR mouse using a 30 G needle anesthetized with ketamin (50 mg/kg), whereas animals in the control group were injected of 50% ethanol alone. In TNBS-induced colitis, the wall of the proximal colon is diffusely thickened with loss of haustration, and showed mucosal and mucular edema with inflammatory infiltration. The colonic inflammation is significantly induced the reduction of colonic contractile activity including spontaneous contractile activity, depolarization-induced contractility, and muscarinic acetylcholine receptor-mediated contractile response in circular muscle layer compared to the longitudinal muscle layer. The inward rectification of currents, especially, important to Ca(2+) and Na(+) influx-induced depolarization and contraction, was markedly reduced in the TNBS-induced colitis compared to the control. The muscarinic acetylcholine-mediated contractile responses were significantly attenuated in the circular and longitudinal smooth muscle strips induced by the reduction of membrane expression of canonical transient receptor potential (TRPC) channel isoforms from the proximal colon of the TNBS-induced colitis mouse than the control.

Upcyte® microvascular endothelial cells repopulate decellularized scaffold

A general problem in tissue engineering is the poor and insufficient blood supply to guarantee tissue cell survival as well as physiological tissue function. To address this limitation, we have developed an in vitro vascularization model in which a decellularized porcine small bowl segment, representing a capillary network within a collagen matrix (biological vascularized scaffold [BioVaSc]), is reseeded with microvascular endothelial cells (mvECs). However, since the supply of mvECs is limited, in general, and as these cells rapidly dedifferentiate, we have applied a novel technology, which allows the generation of large batches of quasi-primary cells with the ability to proliferate, whilst maintaining their differentiated functionality. These so called upcyte mvECs grew for an additional 15 population doublings (PDs) compared to primary cells. Upcyte mvECs retained endothelial characteristics, such as von Willebrandt Factor (vWF), CD31 and endothelial nitric oxide synthase (eNOS) expression, as well as positive Ulex europaeus agglutinin I staining. Upcyte mvECs also retained biological functionality such as tube formation, cell migration, and low density lipoprotein (LDL) uptake, which were still evident after PD27. Initial experiments using MTT and Live/Dead staining indicate that upcyte mvECs repopulate the BioVaSc Scaffold. As with conventional cultures, these cells also express key endothelial molecules (vWF, CD31, and eNOS) in a custom-made bioreactor system even after a prolonged period of 14 days. The combination of upcyte mvECs and the BioVaSc represents a novel and promising approach toward vascularizing bioreactor models which can better reflect organs, such as the liver.

The effects of 5-HT4 receptor agonist, mosapride citrate, on visceral hypersensitivity in a rat model

BACKGROUND AND AIMS

Mosapride citrate is known to affect gastric motility. However, whether mosapride citrate has any effect on visceral pain in the colon or rectum is not certain. The aim of this study was to assess the effects of mosapride citrate on visceral pain in a rat visceral hypersensitivity model.

METHODS

The perception of visceral pain was evaluated by the visceromotor response to colorectal distension observed on electromyographs of the abdominal musculature in urethane-anesthetized rats. Visceral hypersensitivity was induced by the intrarectal instillation of 4% acetic acid or 1.5% zymosan. Mosapride citrate was administered intraperitoneally 3 h later. VMRs to CRD were recorded prior to the instillation of acetic acid or zymosan and before and after mosapride citrate treatment.

RESULTS

The intracolonic instillation of acetic acid resulted in a significant increase in VMRs of the abdominal muscles to CRD, compared with the pretreatment state (174 ± 24%, P < 0.05). The intracolonic instillation of zymosan resulted in a significant increase in VMRs of the abdominal muscles to CRD, compared with the pretreatment state (144 ± 9%, P < 0.05). Intraperitoneal injection of mosapride citrate resulted in a significant reduction in the VMRs to CRD in an acetic acid-induced visceral hypersensitivity rat model (61 ± 9%, P < 0.05). The intraperitoneal injection of mosapride citrate also resulted in a significant reduction in the VMRs to CRD in a zymosan-induced visceral hypersensitivity rat model (67 ± 9%, P < 0.05).

CONCLUSIONS

Mosapride citrate diminished visceral pain in rats.

The Ras activator RasGRP3 mediates diabetes-induced embryonic defects and affects endothelial cell migration

RATIONALE

Fetuses that develop in diabetic mothers have a higher incidence of birth defects that include cardiovascular defects, but the signaling pathways that mediate these developmental effects are poorly understood. It is reasonable to hypothesize that diabetic maternal effects are mediated by 1 or more pathways activated downstream of aberrant glucose metabolism, because poorly controlled maternal glucose levels correlate with the frequency and severity of the defects.

OBJECTIVE

We investigated whether RasGRP3 (Ras guanyl-releasing protein 3), a Ras activator expressed in developing blood vessels, mediates diabetes-induced vascular developmental defects. RasGRP3 is activated by diacylglycerol, and diacylglycerol is overproduced by aberrant glucose metabolism in diabetic individuals. We also investigated the effects of overactivation and loss of function for RasGRP3 in primary endothelial cells and developing vessels.

METHODS AND RESULTS

Analysis of mouse embryos from diabetic mothers showed that diabetes-induced developmental defects were dramatically attenuated in embryos that lacked Rasgrp3 function. Endothelial cells that expressed activated RasGRP3 had elevated Ras-ERK signaling and perturbed migration, whereas endothelial cells that lacked Rasgrp3 function had attenuated Ras-ERK signaling and did not migrate in response to endothelin-1. Developing blood vessels exhibited endothelin-stimulated vessel dysmorphogenesis that required Rasgrp3 function.

CONCLUSIONS

These findings provide the first evidence that RasGRP3 contributes to developmental defects found in embryos that develop in a diabetic environment. The results also elucidate RasGRP3-mediated signaling in endothelial cells and identify endothelin-1 as an upstream input and Ras/MEK/ERK as a downstream effector pathway. RasGRP3 may be a novel therapeutic target for the fetal complications of diabetes.

Crohn's disease: ultrastructure of interstitial cells in colonic myenteric plexus

The role of the interstitial cells of Cajal (ICC) in chronic inflammatory bowel disease, i.e., ulcerative colitis (UC) and Crohn's disease (CD), remains unclear. Ultrastructural alterations in ICC in the colonic myenteric plexus (ICC-MP) have been reported previously in UC, but descriptions of ICC-MP and other interstitial cells in the myenteric region of the colon are lacking for CD. In the present study, we characterized the ultrastructure of interstitial cells, nerves, and glial cells in the myenteric region in Crohn's colitis (CC). In comparison with controls, varicosities of the myenteric bundles were dilated and appeared to be empty. Lipid droplets and lipofuscin-bodies were prominent in glial cells and neurons. ICC-MP were scanty but, as in controls, had caveolae, prominent intermediate filaments, cytoplasmic dense bodies, and membrane-associated dense bands with a patchy basal lamina. ICC-MP were similar in the various colonic regions. ICC-MP in CC showed no signs of degeneration or cytological changes. As in controls, fibroblast-like cells had abundant coated vesicles but lacked prominent intermediate filaments and caveolae. Macrophages also appeared as in controls. In comparison with ICC-MP in UC, the cytology of ICC-MP in CC were thus undisturbed. The ultrastructural differences between UC and CC might reflect pathophysiological differences of importance for understanding pathogenetic differences between CD and UC.

Ulcerative colitis: ultrastructure of interstitial cells in myenteric plexus

Interstitial cells of Cajal (ICC) are key regulatory cells in the gut. In the colon of patients with severe ulcerative colitis (UC), myenteric ICC had myoid ultrastructural features and were in close contact with nerve terminals. In all patients as opposed to controls, some ICC profiles showed degenerative changes, such as lipid droplets and irregular vacuoles. Nerve terminals often appeared swollen and empty. Glial cells, muscle cells, and fibroblast-like cells (FLC) showed no alterations. FLC enclosed macrophages (MLC), which were in close contact with naked axon terminals. The organization and cytological changes may be of pathophysiological significance in patients with UC.

Crohn's disease of the colon: ultrastructural changes in submuscular interstitial cells of Cajal

Interstitial cells of Cajal (ICC) at the submuscular border of the human colon (ICC-SMP) are the proposed pacemaker cells of the musculature. In patients with Crohn's disease (CD) of the colon, ICC-SMP showed characteristic cytological changes from controls. The changes comprised secondary lysosomes in connection with lipid droplets and cytoplasmic vacuoles or multiple empty, confluent and often outbulging vacuoles merging with cisterns of granular endoplasmic reticulum and clusters of glycogen granules. These changes were most pronounced in patients with macroscopical mucosal inflammation but were also demonstrable in uninvolved colonic segments. Relationships of ICC to other cells were undisturbed. The changes were selective to ICC-SMP, as glial cells, muscle cells and fibroblast-like cells at the submuscular border showed no cytological alterations compared with controls. Varicosities of the submuscular plexus were often empty and dilated. Fibroblast-like cells selectively encased macrophages and mast cells. The cytological changes in ICC-SMP in CD are thus similar to changes seen in ulcerative colitis and may be of pathophysiological significance with regard to the motility and sensory disturbances seen in patients with CD.

Ca2+-activated K+ current in freshly isolated c-Kit positive cells in guinea-pig stomach

This study was designed to isolate Ca2+-activated K+ current (I(KCa)) and elucidate its physiological significance in freshly isolated interstitial cells of Cajal (ICCs) of guinea-pig stomach. Single ICC was freshly isolated by enzymatically dissociating from myenteric border of gastric antrum free of circular muscles, and conventional whole-cell voltage clamp technique including immunohistochemical techniques were employed to characterize the cells: In myenteric border of gastric antrum, ICC-MY (ICCs from myenteric border) were detected by immunohistochemical reactivity, and single ICC-MY which has many branches was immunohistochemically c-Kit positive. Under K+-rich and 0.1 mM ethylene glycol-bis (2-aminoethyl ether)-N,N,N',N'-tetraacetic acid pipette solution, ICC produced spontaneous inward current (-256 +/- 92.2 pA). When step-depolarizing pulse from -80 to +80 mV was applied at holding potential (V(h)) of -80 mV, voltage-dependent outward currents were recorded with superimposed spontaneous transient outward currents (STOCs). Both STOCs and outward currents were reversibly affected by tetraethylammonium chloride (TEA) and iberiotoxin (IbTX); 2 mM TEA and 200 nM IbTX completely abolished STOCs and significantly inhibited outward K+ current over the whole potential range tested for current/voltage (I/V) relationship. In addition, TEA delayed repolarization phase of spontaneous inward current. The present results indicate the presence of I(KCa) in a single ICC, and it might be involved in regulation of repolarizing phase of spontaneous inward current in guinea-pig stomach.

Downregulation of CPI-17 contributes to dysfunctional motility in chronic intestinal inflammation model mice and ulcerative colitis patients

BACKGROUND

Chronic intestinal inflammation is frequently accompanied by motility disorders. We previously reported that proinflammatory cytokines, such as tumor necrosis factor alpha and interleukin (IL)-1beta downregulate CPI-17, an endogenous inhibitor of serine/threonine protein phosphatase in smooth-muscle cells, which results in the inhibition of myosin light chain phosphorylation and contractility. However, its clinical relevance has not been clarified.

METHODS

The present study examined the changes in CPI-17 expression in chronic intestinal inflammation using smooth-muscle tissues from IL-10 knockout mice and from patients with ulcerative colitis (UC).

RESULTS

The IL-10 knockout mice developed spontaneous and chronic colitis accompanied by immune cell infiltration, submucosal fibrosis, and thickening of the muscularis externa. The expression of alpha-smooth muscle actin protein in the smooth-muscle layer did not change, whereas that of CPI-17 protein was decreased by about 40% compared with healthy wild-type controls. Consistent with this observation, smooth-muscle contractile force and myosin light chain phosphorylation induced by a muscarinic agonist were reduced in the knockout mice. Moreover, we observed that CPI-17 protein expression was decreased in smooth-muscle tissues from patients with UC compared with controls.

CONCLUSIONS

CPI-17 downregulation might contribute to the decreased motor function in chronic inflammatory bowel diseases.

The anti-tumor agent, ingenol-3-angelate (PEP005), promotes the recruitment of cytotoxic neutrophils by activation of vascular endothelial cells in a PKC-delta dependent manner

The modes of action of the novel anti-skin tumor agent ingenol-3-angelate (PEP005) are incompletely understood. Crucially, the cytotoxic functions of neutrophils recruited to the tumor in response to topical application of PEP005 are necessary for effective ablation of the treated lesion. Here, we investigated the hypothesis that the phorbol ester-like properties of PEP005 and its ability to activate PKC could directly activate endothelial cells (EC) so that they support the recruitment of neutrophils. Exposure of EC to PEP005 induced mRNA and/or protein for E-selectin, ICAM-1 and IL-8 in a dose dependent manner, while in a flow based adhesion assay, PEP005 treated EC supported the recruitment of neutrophils at levels comparable to EC stimulated with TNF-alpha. Neutrophil adhesion was inhibited by antibody against E-selectin but not P-selectin. Activation of EC was inhibited by the PKC inhibitor bisindolylmaleimide-1 and confocal immuno-fluorescent studies demonstrated translocation of PKC-delta from the cytosol to the peri-nuclear membrane in response to PEP005. Importantly, the knock down of PKC-delta using siRNA completely abolished neutrophil recruitment to EC subsequently treated with PEP005. Thus, we describe a novel route by which the anti-tumor agent PEP005 regulates the recruitment of cytotoxic leukocytes by directly activating EC in a PKC-delta dependent manner.

Soluble ICAM-1 and VCAM-1 as markers of endothelial activation

Activated endothelium releases the soluble adhesion molecules vascular cell adhesion molecule-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1). Measurement of fluid-phase adhesion molecules is therefore used to quantify endothelial activation, but it is unclear which is the better marker. The aims of the study were to compare the relationships between mRNA, surface and total expression and released VCAM-1 and ICAM-1 in endothelial cell cultures during activation, and to compare human umbilical vein endothelial cells (HUVEC) with the microvascular cell line HMEC-1. sVCAM-1 better represented mRNA and surface expression changes in HUVEC undergoing endotoxin stimulation than did sICAM-1. Very little VCAM-1 was released from endotoxin-stimulated HMEC-1, and sICAM-1 seemed a better activation marker for these cells. During incubation of HUVEC in media with glucose concentrations of 5.6, 10.6 or 20.6 mM, VCAM-1 was released to the media in a dose-dependent way without changes in surface expression. ICAM-1 was not influenced by the glucose concentration. There are situations when VCAM-1 concentrations in the media do not mirror the surface expression on HUVEC in culture, indicating that measurements of soluble adhesion molecules may not necessarily be representative of the conditions on the cell surface. Endothelium from different locations showed varying responses with respect to VCAM-1 and ICAM-1 liberation upon endotoxin stimulation. Thus, both sVCAM-1 and sICAM-1 should be quantified in clinical studies of endothelial activation until their characteristics are better clarified.

Interstitial Cells of Cajal and their Role in Veterinary Gastrointestinal Pathologies

This study highlights the importance of interstitial cells of Cajal (ICs) in gastrointestinal disease. Human research is already considering IC pathologies but in veterinary research IC pathologies are rarely studied. Nevertheless, recent studies of ICs show a growing interest in the pathophysiology of gastrointestinal diseases and emphasize the consideration of this cell type in the pathophysiology of veterinary gastrointestinal malfunctions.

The Chinese herbal preparation Qing Yi Tang (QYT) improves intestinal myoelectrical activity and increases intestinal transit during acute pancreatitis in rodents

The aim was to investigate alterations of intestinal motility in models of acute pancreatitis and to investigate the effects of the Chinese herbal preparation Qing Yi Tang (QYT) on these alterations. Upper gastrointestinal transit was evaluated in mice following induction of mild acute pancreatitis (MAP) using caerulein. Myoelectrical activity was recorded in rats after induction of severe acute pancreatitis (SAP) using sodium deoxycholate (SDOC). The contractility of jejunum segments was evaluated in the presence of SDOC, lipopolysaccharide (LPS) and trypsin. QYT accelerated the transit in MAP mice in a concentration dependent manner. Slow wave activity of smooth muscle in rat stomach and jejunum remained unchanged following SAP, but the spiking activity was significantly decreased, with bursts of 7.2 +/- 2.6/10 min compared with 47.9 +/- 13.2/10 min without SAP (p < 0.01). QYT reversed this decrease. Additionally, the amplitudes of slow waves and spikes were enhanced by QYT in SAP rats. The tension and amplitude of spontaneous contractile activity was reduced by SDOC and LPS and increased by trypsin. Gastrointestinal (GI) transit is altered by SAP but not by MAP. The Chinese herbal preparation QYT improves disturbed motility in AP by stimulating myoelectrical activity and accelerating GI transit.

Enteric ganglioneuritis and abnormal interstitial cells of Cajal: features of inflammatory bowel disease

BACKGROUND

An increased prevalence of irritable bowel syndrome (IBS) and disturbances in cardiac and blood pressure reflexes have been described in patients with Crohn's disease (CD) and ulcerative colitis (UC). These features could be due to abnormalities in the gastrointestinal neurotransmission. The aims of this study were to examine whether histopathologic changes in the enteric nervous system correlate with disturbances in cardiac and blood pressure reflexes and the occurrence of IBS- and dyspepsia-like symptoms in these patients.

METHODS

Thirty patients with CD and UC with bowel resection were examined by deep-breathing and orthostatic tests. The resection specimens were evaluated histologically regarding visceral neuro- or myopathy. All medical records were studied for treatment and clinical course.

RESULTS

Ganglioneuritis was observed in 11 of 19 patients with CD and in 5 of 11 with UC. Only patients with CD had ganglioneuritis in the small intestine. Moreover, in CD the interstitial cells of Cajal (ICCs) in the small bowel showed atrophy and vacuolar degeneration, along with a reduced number of cells (P = 0.005). In UC the colonic ICCs were hyperplastic (P = 0.05) without signs of degeneration. The indices of deep-breathing and orthostatic tests were impaired, except in CD with ganglioneuritis, who showed normal test values. There were no correlations between histopathologic alterations versus IBS and dyspepsia.

CONCLUSIONS

Visceral ganglioneuritis and pathologic ICCs were observed in patients with CD and UC. However, these histopathologic abnormalities could not be related to the clinical or autonomic features of the disease.

A role for endothelial selectins in allergic and nonallergic inflammatory disease

BACKGROUND

Several studies indicate that selectin-mediated leukocyte migration may depend on the types of initiating inflammatory stimuli or on the vascular beds involved in the inflammatory response. Thus, targeting selectin interactions to treat inflammation may have variable effects depending on the site and origin of the inflammatory response.

OBJECTIVE

To address whether selectin-mediated leukocyte recruitment is stimulus or tissue dependent.

METHODS

We examined pulmonary and cutaneous allergic inflammatory responses and silica-induced nonallergic lung inflammation and fibrosis in wild-type and P- and E-selectin-deficient (P/E-/-) double knockout mice. Allergen-sensitized wild-type and P/E-/- double knockout mice were challenged either intradermally or via the airways to induce allergic responses in the skin or lung, respectively. Other animals were subjected to intranasal silica administration to induce a nonallergic lung inflammatory/fibrotic response.

RESULTS

The P/E-/- mice exhibited significantly reduced allergic inflammation in the skin and lung. Allergic late-phase ear swelling and allergic lung airway hyperresponsiveness were also significantly attenuated in the P/E-/- mice compared with identically treated wild-type animals. In contrast, pulmonary inflammation and fibrosis induced by intranasal administration of silica particles resulted in a more severe phenotype in the P/E-/- mice.

CONCLUSIONS

Selectin interactions drive allergic inflammation in the lung and skin. Silica-induced pulmonary inflammation and fibrosis, however, was more pronounced in the absence of selectin interactions, suggesting that selectin-mediated leukocyte migration may depend on the types of initiating inflammatory stimuli.

Double-tether extraction from human umbilical vein and dermal microvascular endothelial cells

Multiple tethers are very likely extracted when leukocytes roll on the endothelium under high shear stress. Endothelial cells have been predicted to contribute more significantly to simultaneous tethers and thus to the overall rolling stabilization. We therefore extracted and quantified double tethers from endothelial cells with the micropipette aspiration technique. We show that the constitutive parameters (threshold force (F0) and effective viscosity (etaeff)) for double-tether extraction are twice those for single-tether extraction and are remarkably similar for human neonatal (F0=105+/-5 pN; etaeff=1.0+/-0.1 pN.s/microm) and adult (F0=118+/-13 pN; etaeff=1.3+/-0.2 pN.s/microm) dermal microvascular, and human umbilical vein (F0=99+/-3 pN; etaeff=1.0+/-0.1 pN.s/microm) endothelial cells. Additionally, these parameters are also independent of surface receptor type, cytokine stimulation, and attachment state of the endothelial cell. We also introduce a novel correlation between the cell-substrate contact stress and gap width, with which we can predict the apparent cell-substrate separation range to be 0.01-0.1 microm during leukocyte rolling. With a biomechanical model of leukocyte rolling, we calculate the force history on the receptor-ligand bond during tether extraction and predict maximum stabilization for the double simultaneous tether extraction case.

Intestinal dysmotility in inflammatory bowel disease: mechanisms of the reduced activity of smooth muscle contraction

Inflammation suppresses intestinal motility, which secondarily induces abnormal growth of intestinal flora. Disturbance of this flora plays a role in the pathogenesis of mucosal inflammation, which in turn aggravates the intestinal dysmotility. Therefore, it is important to know the mechanism of alteration in motor function in the inflamed intestine. Recent studies have shown molecular mechanisms responsible for the motility disorder in the inflamed gut. These include an increase in the activity of myosin light-chain phosphatase and an alteration of ion channel activity in smooth muscle cells.

NK2 Receptor-Mediated Spontaneous Phasic Contractions in Normal and Ulcerative Colitis Human Sigmoid Colon

Human colonic circular muscle produces spontaneous phasic contractions that are reduced in ulcerative colitis. How the spontaneous phasic contractions develop and why they decrease in ulcerative colitis are not known. We found that spontaneous phasic contractions of normal sigmoid circular muscle strips were significantly reduced by 90-min incubation with tetrodotoxin (10(-5) M), which blocked neurokinin A release in basal conditions and in response to electrical stimulation. In addition, spontaneous contraction of human sigmoid colon was significantly decreased by the NK2 receptor antagonists MEN10376 (Asp-Tyr-D-Trp-Val-D-Trp-D-Trp-Lys-NH2) and NK2ra (Bz-Ala-Ala-D-Trp-Phe-D-pro-Pro-Nle-NH2) but not by atropine or by the NK1 antagonist FK888 (N2-[(4R)-4-hydroxyl-1-(1-methyl-1H-indol-3-yl)carbonyl-l-prolyl]-N-methyl-N-phenylmethyl-3-(2-naphthyl)-l-alaninamide), suggesting that NK2 receptors are involved in their development. The spontaneous phasic contractions were abolished by thapsigargin and cyclopiazonic acid and significantly decreased by the protein kinase C inhibitor chelerythrine and by the calmodulin inhibitor CGS9343B (1,3-dihydro-1-[1-[(4-methyl-4H,6H-pyrrolo[1,2-a]-[4,1]-benzoxazepin-4-yl)methyl]-4-piperidinyl]-2H-benzimidazol-2-one (1:1) maleate), suggesting that spontaneous phasic contractions may be mediated by Ca2+ release from intracellular stores and by a protein kinase C- and calmodulin-dependent pathway. In strips from patients with ulcerative colitis, spontaneous contractions were significantly reduced, and this reduction was partially restored by the hydrogen peroxide scavenger catalase. Neurokinin A release, however, was not affected. We conclude that spontaneous phasic contractions of human sigmoid circular smooth muscle may be mediated by activation of NK2 receptors, calcium release from intracellular stores, and activation of calmodulin and protein kinase C. In ulcerative colitis patients, spontaneous phasic contractions are decreased, and this decrease may be in part due to overproduction of hydrogen peroxide affecting sigmoid circular muscle.

The response of VEGF-stimulated endothelial cells to angiostatic molecules is substrate-dependent

Background

The microenvironment surrounding cells can exert multiple effects on their biological responses. In particular the extracellular matrix surrounding cells can profoundly influence their behavior. It has been shown that the extracellular matrix composition in tumors is vastly different than that found in normal tissue with increased amounts of certain matrices such as collagen I. It has been previously demonstrated that VEGF stimulation of endothelial cells growing on type I collagen results in the induction of bcl-2 expression and enhanced endothelial cell survival. We sought to investigate whether this increased endothelial cell survival resulted in the failure of angiostatic molecules to inhibit angiogenesis.

Results

We now demonstrate that VEGF-induced survival on collagen I impairs the ability of three known angiostatic molecules, TSP-1, IP-10 and endostatin to inhibit endothelial cell proliferation. Apoptosis of endothelial cells, growing on collagen I, induced by TSP-1 and IP-10 was also inhibited following VEGF stimulation. In contrast, endostatin induced apoptosis in these same cells. Further analysis determined that endostatin did not decrease the expression of bcl-2 nor did it increase activation of caspase-3 in the presence of VEGF. Alternatively, it appeared that in the presence of VEGF, endostatin induced the activation of caspase-8 in endothelial cells grown on collagen I. Furthermore, only endostatin had the ability to inhibit VEGF-induced sprout formation in collagen I gels.

Conclusion

These data suggest that TSP-1, IP-10 and endostatin inhibit endothelial cells via different mechanisms and that only endostatin is effective in inhibiting angiogenic activities in the presence of collagen I. Our results suggest that the efficacy of angiostatic treatments may be impaired depending on the context of the extracellular matrix within the tumor environment and thus could impede the efficacy of angiostatic therapies.

Characterization of functional and morphological changes in a rat model of colitis induced by Trichinella spiralis

We intended to characterize the effect of inflammation on the spontaneous colonic motility pattern and the role of iNOS in its disruption in colitis. Colitis was induced by an intracolonic enema of T. spiralis larvae. Animals were studied 2-30 days postinfection (PI). Standard H&E and iNOS staining was performed on colonic sections. Altered stool consistency was found from day 1 to day 21 PI; leukocytosis peaked on days 6-21 PI. Edema and cell infiltration were found in mucosa and submucosa (days 2-14 PI). Contractility displayed a disorganized pattern with decreased high-amplitude, low-frequency (HALF) contractions. A progressive fading of spontaneous activity was observed and was partly restored in strips devoid of submucosa. iNOS immunoreactivity increased in epithelial and infiltrating cells (days 2-14 PI). In this model of colonic inflammation, the decrease in spontaneous contractility, which might be caused by NO generated from mucosal and submucosal iNOS, bears some traits with changes observed in ulcerative colitis and might thus be useful to study the dismotility observed in this human disease.

Dengue virus infection of human microvascular endothelial cells from different vascular beds promotes both common and specific functional changes

Dengue shock syndrome (DSS), the major life threatening outcome of severe dengue disease, which occurs in some patients in the course of dengue infection, is the consequence of plasma leakage in the microvascular territories. Data from clinical and in vitro studies suggest that an inadequate immunological response is partly responsible for the pathophysiology of DSS, but few is known concerning the consequences of direct infection of endothelial cells by dengue virus per se. In this study, an attempt was made to study the response of two microvascular human cell lines originating, respectively, from liver and dermis to infection by a dengue type 2 virus, by analyzing the virus-induced modulation of functional markers. It is shown that the two microvascular cell lines exhibit both common and specific behaviors upon infection. In particular, LSEC and HMEC-1 replicate efficiently the low-passage virus and respond to infection by over-producing inflammatory mediators involved in the cross talk with circulating immune cells. However, direct infection modulates differently the cell surface expression of molecules critically involved in the interactions between endothelial and inflammatory cells. ICAM-1 and HLA-I are up regulated as a consequence of infection in LSEC whereas direct infection results in downregulation of ICAM-1 in HMEC-1. The present results show that infection of human microvascular cells by unadapted dengue virus results in both common and specific activation patterns depending likely on the tissue origin of the cells, thus suggesting that endothelia from different territories may contribute differently to the pathophysiological events in the course of dengue infection.

Cyclosporin A differentially inhibits multiple steps in VEGF induced angiogenesis in human microvascular endothelial cells through altered intracellular signaling

The immunosuppressive agent cyclosporin A (CsA), a calcineurin inhibitor which blocks T cell activation has provided the pharmacologic foundation for organ transplantation. CsA exerts additional effects on non-immune cell populations and may adversely effect microvascular endothelial cells, contributing to chronic rejection, a long-term clinical complication and significant cause of mortality in solid-organ transplants, including patients with small bowel allografts. Growth of new blood vessels, or angiogenesis, is a critical homeostatic mechanism in organs and tissues, and regulates vascular populations in response to physiologic requirements. We hypothesized that CsA would inhibit the angiogenic capacity of human gut microvessels. Primary cultures of human intestinal microvascular endothelial cells (HIMEC) were used to evaluate CsA's effect on four in vitro measures of angiogenesis, including endothelial stress fiber assembly, migration, proliferation and tube formation, in response to the endothelial growth factor VEGF. We characterized the effect of CsA on intracellular signaling mechanisms following VEGF stimulation. CsA affected all VEGF induced angiogenic events assessed in HIMEC. CsA differentially inhibited signaling pathways which mediated distinct steps of the angiogenic process. CsA blocked VEGF induced nuclear translocation of the transcription factor NFAT, activation of p44/42 MAPK, and partially inhibited JNK and p38 MAPK. CsA differentially affected signaling cascades in a dose dependent fashion and completely blocked expression of COX-2, which was integrally linked to HIMEC angiogenesis. These data suggest that CsA inhibits the ability of microvascular endothelial cells to undergo angiogenesis, impairing vascular homeostatic mechanisms and contributing to the vasculopathy associated with chronic rejection.

Mucosal angiogenesis regulation by CXCR4 and its ligand CXCL12 expressed by human intestinal microvascular endothelial cells

Mice genetically deficient in the chemokine receptor CXCR4 or its ligand stromal cell-derived factor (SDF)-1/CXCL12 die perinatally with marked defects in vascularization of the gastrointestinal tract. The aim of this study was to define the expression and angiogenic functions of microvascular CXCR4 and SDF-1/CXCL12 in the human intestinal tract. Studies of human colonic mucosa in vivo and primary cultures of human intestinal microvascular endothelial cells (HIMEC) in vitro showed that the intestinal microvasculature expresses CXCR4 and its cognate ligand SDF-1/CXCL12. Moreover, SDF-1/CXCL12 stimulation of HIMEC triggers CXCR4-linked G proteins, phosphorylates ERK1/2, and activates proliferative and chemotactic responses. Pharmacological studies indicate SDF-1/CXCL12 evokes HIMEC chemotaxis via activation of ERK1/2 and phosphoinositide 3-kinase signaling pathways. Consistent with chemotaxis and proliferation, endothelial tube formation was inhibited by neutralizing CXCR4 or SDF-1/CXCL12 antibodies, as well as the ERK1/2 inhibitor PD-98059. Taken together, these data demonstrate an important mechanistic role for CXCR4 and SDF-1/CXCL12 in regulating angiogenesis within the human intestinal mucosa.

The bHLH TAL-1/SCL regulates endothelial cell migration and morphogenesis

The basic helix-loop-helix tal-1 gene (or scl), known for its fundamental role in embryonic and adult hematopoiesis in vertebrates, is also required for embryonic vascular remodeling. In adults, TAL-1 protein is undetectable in quiescent endothelium but it is present in newly formed vessels including tumoral vasculature, indicating its involvement in angiogenesis. Here, we demonstrate that TAL-1 expression is tightly regulated during in vitro angiogenesis: it is low during the initial step of migration and is upregulated during formation of capillary-like structures. We investigated whether ectopic expression of either wild-type TAL-1 or a dominant-negative mutant lacking the DNA-binding domain (Delta-bas) modulates the activity of human primary endothelial cells in the angiogenic processes of migration, proliferation and cell morphogenesis. Overexpression of either wild-type or Delta-bas TAL-1 affected chemotactic migration of primary endothelial cells without modifying their proliferative properties. Ectopic expression of wild-type TAL-1 accelerated the formation of capillary-like structures in vitro and, in vivo, enhanced vascularisation in mice (Matrigel implants) associated with a general enlargement of capillary lumens. Importantly, transduction of the mutant Delta-bas completely impaired in vitro angiogenesis and strongly inhibited vascularisation in mice. Taken together, our data show that TAL-1 modulates the angiogenic response of endothelial cells by stimulating cell morphogenesis and by influencing their behavior in migration. This study highlights the importance of TAL-1 regulation in postnatal vascular remodeling and provides the first physiological evidence that links TAL-1 activity to endothelial cell morphogenic processes.

Isolation and characterization of human esophageal microvascular endothelial cells: mechanisms of inflammatory activation

Gastroesophageal reflux disease is the most common malady of the esophagus, affecting 7% of the United States population. Histological assessment demonstrates classic inflammatory mechanisms including selective leukocyte recruitment and hemorrhage, suggesting a prominent role for the microvasculature. We isolated and characterized human esophageal microvascular endothelial cells (EC) (HEMEC), examined inflammatory activation in response to cytokines, LPS, and acidic pH exposure, and identified signaling pathways that underlie activation. HEMEC displayed characteristic morphological and phenotypic features including acetylated LDL uptake. TNF-alpha/LPS activation of HEMEC resulted in upregulation of the cell adhesion molecules (CAM) ICAM-1, VCAM-1, E-selectin, and mucosal addressin CAM-1 (MAdCAM-1), increased IL-8 production, and enhanced leukocyte binding. Both acid and TNF-alpha/LPS activation lead to activation of SAPK/JNK in HEMEC that was linked to VCAM-1 expression and U-937 leukocyte adhesion. Expression of constitutive inducible nitric oxide synthase in HEMEC was in marked contrast to intestinal microvascular endothelial cells. In this study, we demonstrate that HEMECs are phenotypically and functionally distinct from lower gut-derived endothelial cells and will facilitate understanding of inflammatory mechanisms in esophageal inflammation.

Inhibition of angiogenesis by non-toxic doses of temozolomide

It is well established that certain chemotherapeutic agents have potent antiangiogenic properties which may be part of their antitumor activity. Temozolomide (TMZ) is a lipophilic methylating agent used in the therapy of malignant melanoma and other tumors. We sought to determine whether TMZ is capable of inhibiting angiogenesis or influencing endothelial function. We used the in vivo chorioallantoic membrane (CAM) assay, and HUVEC-based in vitro Matrigel, adhesion and proliferation assays to determine the antiangiogenic effects of different doses of TMZ. In the CAM assay, angiogenesis was significantly inhibited by 5 microM TMZ, a concentration also found to be effective in interfering with in vitro angiogenesis as measured by the Matrigel assay. For the inhibition of basic fibroblast growth factor (bFGF)-, vascular endothelial growth factor (VEGF)- or beta-phorbol 12-myristate-13-acetate (PMA)-induced endothelial cell proliferation or endothelial cell adhesion to fibronectin, TMZ concentrations of at least 25 microM were necessary, indicating that bFGF-, VEGF- or protein kinase C-mediated pathways may not primarily be involved in the observed antiangiogenic effect. Thus, we could demonstrate that TMZ inhibits angiogenesis at low, non-toxic doses that correspond to the plasma concentrations achieved by an oral application of 20 mg/m2 every 8 h. This 'metronomic' scheduling has already been used in phase I studies and has produced antitumor effects. Therefore, the antitumor activity of TMZ may, at least in part, be due to its antiangiogenic properties. The precise mechanism of its antiangiogenic action remains to be elucidated.

Different mechanisms of adhesion molecule expression in human dermal microvascular endothelial cells by xanthoma tissue-mediated and copper-mediated oxidized low density lipoproteins

BACKGROUND

Oxidation of low density lipoprotein (LDL) has been implicated in infiltration of foam cells derived from circulating monocytes. Monocyte adhesion to endothelial cells and migration into dermis are essential steps for infiltration of foam cells.

OBJECTIVE

We investigated the role of adhesion molecules contributing to the process of monocyte adhesion to human dermal microvascular endothelial cells (HDMEC). Special attention was paid to the signal transduction for adhesion molecule expression induced by two distinct types of oxidized LDL.

METHODS

HDMEC were incubated with xanthoma tissue-modified LDL (x-LDL), a model of extravasated LDL oxidized in xanthoma lesions, or Cu(2+)-treated LDL (Cu-LDL), a model of oxidized LDL. Adhesion of U937 cells, a human monocytic leukemia cell line, to HDMEC and expression of endothelial cell adhesion molecules on HDMEC were examined. Signal transduction pathways for the adhesion molecule expression were evaluated by employing specific inhibitors.

RESULTS

x-LDL induced adhesion of U937 cells to HDMEC through vascular cell adhesion molecule-1 (VCAM-1) and E-selectin by activating tyrosine kinase pathway. Cu-LDL up-regulated the adhesion through not only VCAM-1 and E-selectin but also intercellular cell adhesion molecule-1 (ICAM-1) by activating G(i) protein pathway.

CONCLUSION

Extravasated and oxidized LDL in xanthoma lesions contributes to foam cell recruitment by activating tyrosine kinase pathway and inducing adhesion of monocytes to HDMEC through VCAM-1 and E-selectin. Cu-LDL, on the other hand, activates G(i) protein pathway and induces the adhesion through ICAM-1, VCAM-1 and E-selectin.

Endothelial cell heterogeneity

OBJECTIVE

To review recent advances in the field of endothelial cell heterogeneity, and to apply this knowledge to an understanding of site-specific vasculopathy, including acute lung injury.

DATA SOURCES AND STUDY SELECTION

Published research and review articles in the English language related to endothelial cell biology and endothelial cell heterogeneity.

DATA EXTRACTION AND SYNTHESIS

The results of published studies have been used to provide a perspective of endothelial cell phenotypes in health and disease.

CONCLUSIONS

The structure and function of endothelial cells are differentially regulated in space and time. Far from being a giant monopoly of homogeneous cells, the endothelium represents a consortium of smaller enterprises of cells located within blood vessels of different tissues. Although united in certain functions, each enterprise is uniquely adapted to meet the demands of the underlying tissue. The endothelium may also vary in its response to pathophysiologic stimuli and therefore contribute to the focal nature of vasculopathic disease states. In acute lung injury, the unique properties of the endothelium may conspire with systemic imbalances to localize pathology to the pulmonary vasculature.

Angiogenic effects of interleukin 8 (CXCL8) in human intestinal microvascular endothelial cells are mediated by CXCR2

Angiogenesis plays a critical role in metastasis and tumor growth. Human tumors, including colorectal adenocarcinoma, secrete angiogenic factors, inducing proliferation and chemotaxis of microvascular endothelial cells, eventually leading to tumor neovascularization. The chemokine interleukin 8 (IL-8; CXCL8) exerts potent angiogenic properties on endothelial cells through interaction with its cognate receptors CXCR1 and CXCR2. As CXCR1 and CXCR2 expression is differentially regulated in tissue-specific endothelial cells and effects of IL-8 on intestinal endothelial cells are not defined, we characterized the potential IL-8-induced angiogenic mechanisms in primary cultures of human intestinal microvascular endothelial cells (HIMEC) and IL-8 receptor expression in human intestinal microvessels. CXCR1 and CXCR2 expression on HIMEC were defined using reverse transcriptase-PCR, immunohistochemistry, flow cytometry, and Western blot analysis. IL-8-induced downstream signaling events were assessed using immunoblot analysis and immunofluorescence. The angiogenic effects of IL-8 on HIMEC were determined using proliferation and chemotaxis assays. HIMEC responded to IL-8 with rapid stress fiber assembly, chemotaxis, enhanced proliferation, and phosphorylation of extracellular signal-regulated protein kinase 1/2 (ERK 1/2). HIMEC express CXCR2, but not CXCR1. Neutralizing antibodies to CXCR2 diminished IL-8-induced chemotaxis and stress fiber assembly. Specific inhibitors of ERK 1/2 and phosphoinositide 3-kinase abrogated endothelial tube formation and IL-8-induced chemotaxis in HIMEC. IL-8 elicits angiogenic responses in microvascular endothelial cells isolated from human intestine by engaging CXCR2. We confirmed tissue expression of CXCR2 in human intestinal microvessels. Supported by the notion that malignant colonic epithelial cells overexpress IL-8, CXCR2 blockade may be a novel target for anti-angiogenic therapy in colorectal adenocarcinoma.

Protein kinase C modulates pulmonary endothelial permeability: a paradigm for acute lung injury

The intracellular serine/threonine kinase protein kinase C (PKC) has an important role in the genesis of pulmonary edema. This review discusses the PKC-mediated mechanisms that participate in the pulmonary endothelial response to agents involved in lung injury characteristic of the respiratory distress syndrome. Thus the paradigms of PKC-induced lung injury are discussed within the context of pulmonary transvascular fluid exchange. We focus on the signal transduction pathways that are modulated by PKC and their effect on lung endothelial permeability. Specifically, alpha-thrombin, tumor necrosis factor (TNF)-alpha, and reactive oxygen species are discussed because of their well-established roles in both human and experimental lung injury. We conclude that PKC, most likely PKC-alpha, is a primary supporter for lung endothelial injury in response to alpha-thrombin, TNF-alpha, and reactive oxygen species.

Inflammation inhibits muscarinic signaling in in vivo canine colonic circular smooth muscle cells

We investigated the effects of experimental colitis on the muscarinic signaling properties and contractile behavior of canine colonic circular smooth muscle. The hypotheses that inflammation 1) inhibits in vivo muscarinic receptor mediated contractions, and 2) alters receptor density or receptor-binding affinities were tested. Muscarine was infused close-intra-arterially in seven conscious dogs during normal and experimental colitis states. Colonic circular muscle contractions were recorded via surgically attached strain gauge transducers. Muscarine stimulated phasic contractions in a dose-dependent manner, whereas colitis was inhibited. The inhibitory concentration 50% dose of M(3) receptor inhibitor was several times lower than that of M(1), M(2), and M(4) inhibitors during normal and colitis. However, inflammation induced a significant leftward shift in the circular muscle inhibitory dose-response curve of M(2) inhibitor. Muscarinic receptor density and binding analyses in isolated circular muscle cells was done in normal and colitis states. Inflammation significantly decreased maximum binding from 4082 fmol/mg to 2708 fmol/mg, whereas affinity constant remained unaffected. The conclusions were that 1) spontaneous and muscarine-activated in vivo phasic contractile activity of colonic circular muscle cells is primarily mediated by M(3) receptors; 2) inflammation was associated with a shift in M(2) receptor potency, due chiefly to a decrease in receptor density; and 3) this inhibitory effect was seen in normal and inflamed states, suggesting the importance of M(2) receptor. These findings suggest that changes in muscarinic response during colitis may contribute to the abnormal motility seen with inflammatory bowel disease.

Cytokine regulation of E-selectin in rat CNS microvascular endothelial cells: differential response of CNS and non-CNS vessels

We have compared the induced expression of E-selectin in primary cultures of rat brain microvascular endothelial cells (EC), pericytes and in non-CNS microvascular endothelium stimulated with the cytokines, IL-1beta (20 ng/ml), and tumor necrosis factor (TNF)-alpha (75 ng/ml). Expression was studied at both the protein and mRNA levels. Fluorescence in-situ hybridization (FISH) was used to examine de novo synthesis of E-selectin mRNA. Laser cytometric analysis was used as a novel approach to the quantitaion of FISH. In-situ hybridization was performed using two PCR-generated probes. The first probe (517 bp) spanned the lectin and epidermal growth factor (EGF)-like domain. The second probe (562 bp) spanned the CR3, 4, and 6 domains. E-selectin-specific mRNA was localized to the perinuclear regions of the EC. Both cytokines, IL-1beta and TNF-alpha significantly increased E-selectin gene expression in CNS EC but not pericytes. IL-1beta induced higher E-selectin mRNA levels than TNF-alpha. The maximum number of mRNA-positive cells was observed after stimulation for 4--6 h. Surface protein expression was sustained for up to 48 h following addition of cytokine. This was in contrast to the transient expression in non-CNS EC indicating that pure primary CNS EC display slightly different kinetics of E-selectin expression than non-CNS EC.

Shear-induced changes in endothelin-1 secretion of microvascular endothelial cells

Human glomerular microvascular endothelial cell (HGMEC) culture monolayers were maintained in static culture as controls or subjected to steady laminar shear stress of 0.5, 1.0, or 1.5 N/m2. Over 25 h of shear, the cumulative secretion of ET-1 was 705.4 pg/cm2 in the control, 820.7 pg/cm2 at 0.5 N/m2, 1063.2 pg/cm2 at 1.0 N/m2, and 644.7 pg/cm2 at 1.5 N/m2. The average ET-1 secretion rate for the HGMEC monolayers exposed to 0.5, 1.0, or 1.5 N/m2 of shear stress was 32.83 +/- 2.01 pg/cm2 x h, 42.53 +/- 3.74 pg/cm2 x h, and 25.79 +/- 1.29 pg/cm2 x h, respectively. The average ET-1 secretion rate of the static controls was 28.22 +/- 3.11 pg/cm2 x h. The results showed that low shear stress (0.5 N/m2) elevated and high shear stress (1.5 N/m2) suppressed secretion of ET-1, while an intermediate level of shear stress (1.0 N/m2) led to the maximum secretion of ET-1, and furthermore, ET-1 secretion varied with the duration of shear in a nonlinear fashion, and the logistic equations may be used to describe relationship between the duration of shear and the ET-1 secretion. The major secretion period of ET-1 occurred between 5.3 and 22.3 h, with the peak secretion rate occurring at approximately 10.7-15.2 h. Our findings showed also that the major secretion period and peak secretion rate of HGMECs varied with the level of shear stress. Thus, the response of cultured human microvascular endothelial cells to shear stress differed from that of large-vessel endothelial cell cultures in terms of ET-1 secretion. In addition to the level of shear stress, the duration of shear is an important determinant in ET-1 secretion. Consequently, the heterogeneity of vascular endothelial cells and the duration of shear should both be considered in future research on the secretion of vascular endothelial cell cultures.

Studies on single-cell adhesion probability between lymphocytes and endothelial cells with micropipette technique

An in vitro model with micropipette technique was used to investigate single-cell adhesion probability between lymphocytes and endothelial cells. The basal adhesion probability between lymphocytes and endothelial cells was low and was significantly increased when either lymphocytes were activated by phytohemagglutinin (PHA) or endothelial cells were stimulated by tumor necrosis factor. The adhesion probability of lymphocytes to human umbilical vein endothelial cells was similar to that of lymphocytes to human brain microvascular endothelial cells (HB-MVEC). However, lymphocyte adhesion probability was higher in HB-MVEC than in mouse brain microvascular endothelial cells (MB-MVEC) under both resting and activated conditions. Furthermore, lymphocytes preincubated with monoclonal antibodies to lymphocyte function-associated antigen-1 (LFA-1) or HB-MVEC preincubated with monoclonal antibodies to intercellular adhesion molecule 1 (ICAM-1) significantly down-regulated the adhesion probability between lymphocytes and endothelial cells, indicating that the adhesion probability is related to the expression of LFA-1 on lymphocytes and to the expression of ICAM-1 on endothelial cells. Lymphocytes isolated from patients with cerebral stroke exhibited increased adhesion probability to HB-MVEC as compared with lymphocytes from healthy donors. Preincubation of lymphocytes with tetramethylpyrazine (TMP), an extract from a Chinese traditional herb, effectively inhibited the adhesion probability to HB-MVEC, suggesting that TMP has a potential therapeutic value. These results indicate that the micropipette technique is a useful model for investigating single-cell adhesion probability between lymphocytes and endothelial cells in vitro.

Alterations of neurokinin receptors and interstitial cells of Cajal during and after jejunal inflammation induced by Nippostrongylus brasiliensis in the rat

Substance P (SP) and its receptors NK1 and NK2 are widely expressed in the intestinal wall by neurones, interstitial cells of Cajal (ICC) and smooth muscle cells. Changes in SP and/or its NK receptors have been documented during experimental inflammation in animals or inflammatory bowel diseases in humans, but the data concern the acute phase of the inflammatory process. We determined immunohistochemically whether NK receptors and SP were altered in the muscle coat during jejunal inflammation induced by the nematode Nippostrongylus brasiliensis and whether these alterations persisted when inflammation had spontaneously resolved 30 days postinfection. An ultrastructural analysis was also conducted on ICC, nerves and muscle. At day 14, when inflammation peaked, there was a reduction in NK1 receptors in myenteric neurones and in SP-immunoreactive nerve endings. There were also ultrastructural anomalies in synaptic vesicles and NK2 receptor loss in the circular muscle layer. The SP decrease persisted at day 30, whereas neurones and circular muscle cells re-expressed NK1 and NK2 receptors, respectively. The ICC at the deep muscular plexus, located near to the inflammatory site, underwent alterations leading to their complete loss at day 30. These morphological changes are probably associated with impairment in tachykinergic control of jejunal functions leading to the alterations of motility and sensitivity to distension already described in these animals.

Deficiency of interstitial cells of Cajal in the small intestine of patients with Crohn's disease

OBJECTIVE

Interstitial cells of Cajal are critical for the generation of electrical slow waves that regulate the phasic contractile activity of the tunica muscularis of the GI tract. Under certain pathophysiological conditions loss of interstitial cells of Cajal may play a role in the generation of certain motility disorders. The aim of the present study was to determine if there is an abnormality in the density or distribution of interstitial cells of Cajal from patients with Crohn's disease.

METHODS

Small intestines from control subjects and patients with Crohn's disease were examined using immunohistochemistry and antibodies against the Kit receptor, which is expressed in interstitial cells of Cajal within the tunica muscularis of the GI tract. The density and distribution of interstitial cells of Cajal were assessed in the longitudinal and circular muscle layers and in the myenteric and deep muscular plexus regions of Crohn's and control tissues.

RESULTS

Tissues from Crohn's disease patients showed an almost complete abolition of interstitial cells of Cajal within the longitudinal and circular muscle layers and a significant reduction in numbers at the level of the myenteric and deep muscular plexuses.

CONCLUSIONS

In tissues from Crohn's disease patients, the density of interstitial cells of Cajal was reduced throughout the tunica muscularis in comparison to control small intestines. The disturbance of intestinal motility that occurs in patients with Crohn's disease may be a consequence of the loss of or defects in specific populations of interstitial cells of Cajal within the tunica muscularis.

Intestinal fibrosis in human and experimental inflammatory bowel disease

Fibrosis is a serious complication of Crohn disease for which there is no effective therapy. It is unclear why fibrosis, particularly fibrosis of the mucosal layer, develops in Crohn disease and not in ulcerative colitis. Smooth muscle cells, subepithelial myofibroblasts, and fibroblasts have traditionally been considered mediators of fibrosis, but new information points to a role of interstitial cells of Cajal and mast cells. Recent evidence about the role of each of these cell types in fibrosis in Crohn disease or other inflammatory bowel diseases is described. Hypothetical models to describe how altered function of these cells could underlie fibrosis of the mucosa or submucosal layers are presented. Fibrosis is not well characterized in any animal model of inflammatory bowel disease. The merits of several animal models for defining the mechanisms of inflammation-induced intestinal fibrosis are reviewed.

Griseofulvin has a potential to modulate the expression of cell adhesion molecules on leukocytes and vascular endothelial cells

Griseofulvin has been used as an antifungal drug for many years, but it has recently been shown effective for several inflammatory skin diseases. We therefore investigated its putative immunomodulatory roles by flow cytometric analysis of cell adhesion molecules on human leukocytes and human vascular endothelial cells. Griseofulvin downregulated L-selectin expression on neutrophils, but not on lymphocytes, in a dose-dependent manner. Griseofulvin did not affect CD11b/CD18 expression on neutrophils. On human dermal microvascular endothelial cells (HDMEC), griseofulvin inhibited the expression of TNF alpha-induced VCAM-1 dose-dependently, and this inhibition was fully reversible. Similarly, griseofulvin inhibited the induction of VCAM-1 expression on both TNF alpha- and IL-1 alpha-stimulated human umbilical vein endothelial cells (HUVEC). In addition, it partially inhibited the induction of E-selectin expression, whereas it had a marginal effect on ICAM-1 expression. Reverse transcription-polymerase chain reaction of TNF alpha-stimulated HDMEC showed inhibition of VCAM-1, but not ICAM-1 gene transcription. These results indicate potent immunomodulatory properties of griseofulvin, which may be associated with its feature as a microtubule antagonist.

Ischemic preconditioning upregulates vascular endothelial growth factor mRNA expression and neovascularization via nuclear translocation of protein kinase C epsilon in the rat ischemic myocardium

Ischemic preconditioning (IP) exerts cardioprotection through protein kinase C (PKC) activation, whereas myocardial ischemia enhances vascular endothelial growth factor (VEGF) mRNA expression. However, the IP effect or the involvement of PKC on the VEGF expression is unknown in myocardial infarction. We investigated whether IP enhances VEGF gene expression and angiogenesis through PKC activation in the in vivo myocardial infarction model. Sprague-Dawley rats were assigned into the following 3 groups: the sham group; the IP group, which underwent 3 cycles of 3 minutes of ischemia and 5 minutes of reperfusion (IP procedure); and the non-IP group. The latter 2 groups were subsequently subjected to left anterior descending coronary artery occlusion. To examine the involvement of PKC, the PKC inhibitor chelerythrine (5 mg/kg) or bisindolylmaleimide (1 mg/kg) was injected intravenously before the IP procedures. PKCepsilon was translocated to the nucleus after 10 minutes of ischemia after the IP procedure but was not translocated in the non-IP and the sham groups. VEGF mRNA expression 3 hours after infarction was significantly higher in the IP group than in the non-IP and the sham groups. Capillary density in the infarction was significantly higher, whereas the infarct size was smaller in the IP group than in the non-IP group at 3 days of infarction. Chelerythrine but not bisindolylmaleimide blocked all of the IP effects on the nuclear translocation of PKCepsilon, enhancement of VEGF mRNA expression and angiogenesis, and infarct size limitation. These results show that IP may enhance VEGF gene expression and angiogenesis through nuclear translocation of PKCepsilon in the infarcted myocardium.

Anti-endothelial cell antibodies from patients with thrombotic thrombocytopenic purpura specifically activate small vessel endothelial cells

Thrombotic thrombocytopenic purpura (TTP) is an uncommon disease of an unknown etiology, characterized by consumptive thrombocytopenia, microangiopathic hemolytic anemia, fever and acute thrombotic complications, especially within the cerebral circulation. Although anti-endothelial cell antibodies (AECA) have occasionally been shown to be present in TTP, their role in the pathogenesis of the disease has never been ascertained. In the current study we demonstrated the pathogenic activity of affinity-purified anti-endothelial cell F(ab)2 antibodies (AECA/TTP) from four consecutive patients with active TTP. These AECA/TTP bound to and activated only microvascular endothelial cells (EC) and not large vessel EC. The specificity of AECA/TTP binding to microvascular EC was confirmed by competition assay employing membranes derived from small and large vessels EC. Activation included enhanced IL-6 and von Willebrand factor release from the EC followed by increased expression of adhesion molecules P-selectin, E-selectin and vascular cell adhesion molecule-1 on the EC, as evaluated by ELISA. Increased expression of adhesion molecules was followed by an increase in monocyte adhesion to EC. The level of soluble thrombomodulin (TM) also increased in the culture medium of activated microvascular EC upon exposure to AECA/TTP antibodies and was directly correlated to a decrease in cell-associated TM. Our data suggest that AECA/TTP directed against microvascular EC could play a pathogenic role in the development of endothelial injury in TTP that leads to thrombosis.

Induction of endothelial cell decay-accelerating factor by vascular endothelial growth factor: a mechanism for cytoprotection against complement-mediated injury during inflammatory angiogenesis

OBJECTIVE

Decay-accelerating factor (DAF) is a widely expressed, multifunctional cell surface protein involved in complement regulation and cell signaling. Previous studies have demonstrated that endothelial cell (EC) DAF is up-regulated by tumor necrosis factor alpha and inhibits complement binding. Because vascular endothelial growth factor (VEGF) is cytoprotective to endothelium and is expressed at sites of chronic inflammation, we hypothesized that VEGF may induce DAF expression during inflammatory angiogenesis.

METHODS

Human umbilical vein and dermal microvascular EC were isolated using routine procedures, and the regulation and function of DAF, as well as other complement-regulatory proteins (membrane cofactor protein and CD59), were analyzed following stimulation with VEGF.

RESULTS

Incubation of large- or small-vessel EC with VEGF led to increased expression of DAF, with maximal expression after 48-72 hours of stimulation. This effect depended on the activation of protein kinase C (PKC) and required increased steady-state messenger RNA levels and de novo protein synthesis. Although VEGF-induced EC proliferation was inhibited by both p38 and p42/44 mitogen-activated protein kinase (MAPK) antagonists, DAF up-regulation in response to VEGF was only sensitive to inhibition of p38 MAPK. VEGF-stimulated EC showed a 60% reduction in C3 deposition following complement activation, and this resulted in a marked reduction in complement-mediated EC lysis. These protective effects were abolished by anti-DAF monoclonal antibody 1H4.

CONCLUSION

This study confirms the importance of PKC for the regulation of DAF expression by EC and reveals VEGF to be a physiologic agonist for this pathway. The up-regulation of DAF expression by VEGF may represent an important mechanism for the protection of EC from complement-mediated injury during angiogenesis in inflammatory rheumatic diseases.