ADAM15 deficiency attenuates pulmonary hyperpermeability and acute lung injury in lipopolysaccharide-treated mice

ADAM15 is a disintegrin and metalloprotease recently implicated in cancer and chronic immune disorders. We have recently characterized ADAM15 as a mediator of endothelial barrier dysfunction. Whether this molecule contributes to acute inflammation has not been evaluated. The purpose of this study was to investigate the role of ADAM15 in mediating pulmonary microvascular leakage during acute inflammatory injury. Immunofluorescent staining and Western blotting revealed that the endothelium was the main source of ADAM15 in lung tissue. In a mouse model of acute lung injury induced by lipopolysaccharide (LPS), upregulation of ADAM15 was observed in association with pulmonary edema and neutrophil infiltration. The LPS-induced inflammatory injury, as demonstrated by bronchoalveolar lavage neutrophil count, lung wet-to-dry weight ratio, and myeloperoxidase activity, was significantly attenuated in Adam15(-/-) mice. Studies with primary cell culture demonstrated abundant ADAM15 expression in endothelial cells (ECs) of mouse lung but not in neutrophils. Deficiency of ADAM15 in ECs had no obvious effect on basal permeability but significantly attenuated hyperpermeability response to LPS as evidenced by albumin flux assay and measurements of transendothelial electrical resistance, respectively. ADAM15 deficiency also reduced neutrophil chemotactic transmigration across endothelial barriers in the presence or absence of formyl-methionyl-leucyl-phenylalanine (fMLP). Rescue expression of ADAM15 in Adam15(-/-) ECs restored neutrophil transendothelial migration. These data indicate that ADAM15 upregulation contributes to inflammatory lung injury by promoting endothelial hyperpermeability and neutrophil transmigration.

A disintegrin and metalloproteinase 15 contributes to atherosclerosis by mediating endothelial barrier dysfunction via Src family kinase activity

OBJECTIVE

Endothelium dysfunction is an initiating factor in atherosclerosis. A disintegrin and metalloproteinase 15 (ADAM 15) is a multidomain metalloprotease recently identified as a regulator of endothelial permeability. However, whether and how ADAM15 contributes to atherosclerosis remains unknown.

METHODS AND RESULTS

Genetic ablation of ADAM15 in apolipoprotein E-deficient mice led to a significant reduction in aortic atherosclerotic lesion size (by 52%), plaque macrophage infiltration (by 69%), and smooth muscle cell deposition (by 82%). In vitro studies implicated endothelial-derived ADAM15 in barrier dysfunction and monocyte transmigration across mouse aortic and human umbilical vein endothelial cell monolayers. This role of ADAM15 depended on intact functioning of the cytoplasmic domain, as evidenced in experiments with site-directed mutagenesis targeting the metalloprotease active site (E349A), the disintegrin domain (Arginine-Glycine-Aspartic acid→Threonine-Aspartic acid-Aspartic acid), or the cytoplasmic tail. Further investigations revealed that ADAM15-induced barrier dysfunction was concomitant with dissociation of endothelial adherens junctions (vascular endothelial [VE]-cadherin/γ-catenin), an effect that was sensitive to Src family kinase inhibition. Through small interfering RNA-mediated knockdown of distinct Src family kinase members, c-Src and c-Yes were identified as important mediators of these junctional effects of ADAM15.

CONCLUSIONS

These results suggest that endothelial cell-derived ADAM15, signaling through c-Src and c-Yes, contributes to atherosclerotic lesion development by disrupting adherens junction integrity and promoting monocyte transmigration.

Myosin light chain kinase signaling in endothelial barrier dysfunction

Microvascular barrier dysfunction is a serious problem that occurs in many inflammatory conditions, including sepsis, trauma, ischemia-reperfusion injury, cardiovascular disease, and diabetes. Barrier dysfunction permits extravasation of serum components into the surrounding tissue, leading to edema formation and organ failure. The basis for microvascular barrier dysfunction is hyperpermeability at endothelial cell-cell junctions. Endothelial hyperpermeability is increased by actomyosin contractile activity in response to phosphorylation of myosin light chain by myosin light chain kinase (MLCK). MLCK-dependent endothelial hyperpermeability occurs in response to inflammatory mediators (e.g., activated neutrophils, thrombin, histamine, tumor necrosis factor alpha, etc.), through multiple cell signaling pathways and signaling molecules (e.g., Ca(++) , protein kinase C, Src kinase, nitric oxide synthase, etc.). Other signaling molecules protect against MLCK-dependent hyperpermeability (e.g., sphingosine-1-phosphate or cAMP). In addition, individual MLCK isoforms play specific roles in endothelial barrier dysfunction, suggesting that isoform-specific inhibitors could be useful for treating inflammatory disorders and preventing multiple organ failure. Because endothelial barrier dysfunction depends upon signaling through MLCK in many instances, MLCK-dependent signaling comprises multiple potential therapeutic targets for preventing edema formation and multiple organ failure. The following review is a discussion of MLCK-dependent mechanisms and cell signaling events that mediate endothelial hyperpermeability.

Aerobic degradation of tetrabromobisphenol-A by microbes in river sediment

This study investigated the aerobic degradation of tetrabromobisphenol-A (TBBPA) and changes in the microbial community in river sediment from southern Taiwan. Aerobic degradation rate constants (k(1)) and half-lives (t(1/2)) for TBBPA (50 μg g(-1)) ranged from 0.053 to 0.077 d(-1) and 9.0 to 13.1 d, respectively. The degradation of TBBPA (50 μg g(-1)) was enhanced by adding yeast extract (5 mg L(-1)), sodium chloride (10 ppt), cellulose (0.96 mg L(-1)), humic acid (0.5 g L(-1)), brij 30 (55 μM), brij 35 (91 μM), rhamnolipid (130 mg L(-1)), or surfactin (43 mg L(-1)), with rhamnolipid yielding a higher TBBPA degradation than the other additives. For different toxic chemicals in the sediment, the results showed the high-to-low order of degradation rates were bisphenol-A (BPA) (50 μg g(-1))>nonylphenol (NP) (50 μg g(-1))>4,4'-dibrominated diphenyl ether (BDE-15) (50 μg g(-1))>TBBPA (50 μg g(-1))>2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE-209) (50 μg g(-1)). The addition of various treatments changed the microbial community in river sediments. The results also showed that Bacillus pumilus and Rhodococcus ruber were the dominant bacteria in the process of TBBPA degradation in the river sediments.

Interleukin-1β-induced barrier dysfunction is signaled through PKC-θ in human brain microvascular endothelium

Blood-brain barrier dysfunction is a serious consequence of inflammatory brain diseases, cerebral infections, and trauma. The proinflammatory cytokine interleukin (IL)-1β is central to neuroinflammation and contributes to brain microvascular leakage and edema formation. Although it is well known that IL-1β exposure directly induces hyperpermeability in brain microvascular endothelium, the molecular mechanisms mediating this response are not completely understood. In the present study, we found that exposure of the human brain microvascular endothelium to IL-1β triggered activation of novel PKC isoforms δ, μ, and θ, followed by decreased transendothelial electrical resistance (TER). The IL-1β-induced decrease in TER was prevented by small hairpin RNA silencing of PKC-θ or by treatment with the isoform-selective PKC inhibitor Gö6976 but not by PKC inhibitors that are selective for all PKC isoforms other than PKC-θ. Decreased TER coincided with increased phosphorylation of regulatory myosin light chain and with increased proapoptotic signaling indicated by decreased uptake of mitotracker red in response to IL-1β treatment. However, neither of these observed effects were prevented by Gö6976 treatment, indicating lack of causality with respect to decreased TER. Instead, our data indicated that the mechanism of decreased TER involves PKC-θ-dependent phosphorylation of the tight junction protein zona occludens (ZO)-1. Because IL-1β is a central inflammatory mediator, our interpretation is that inhibition of PKC-θ or inhibition of ZO-1 phosphorylation could be viable strategies for preventing blood-brain barrier dysfunction under a variety of neuroinflammatory conditions.

Neutrophil transmigration, focal adhesion kinase and endothelial barrier function

Neutrophil activation is an essential component of innate immune defense against infection and injury. In response to inflammatory stimulation, circulating neutrophils undergo a series of dynamic and metabolic changes characterized by β2-intergrin mediated adhesion to microvascular endothelium and subsequent transendothelial migration. During this process, neutrophils release granular contents containing digestive enzymes and produce cytotoxic agents such as reactive oxygen species and cytokines. These products target endothelial barriers inducing phosphorylation-triggered junction dissociation, actin stress fiber formation, and actomyosin contraction, manifest as paracellular hyperpermeability. Endothelial cell-matrix focal adhesions play an integral role in this process by providing structural support for endothelial conformational changes that facilitate neutrophil transmigration, as well as by recruiting intracellular molecules that constitute the hyperpermeability signaling cascades. As a central connector of the complex signaling network, focal adhesion kinase (FAK) is activated following neutrophil adhesion, and further mediates the reorganization of endothelial integrin-matrix attachments in a pattern coordinating with cytoskeleton contraction and junction opening. In this review, we present recent experimental evidence supporting the importance of FAK in neutrophil-dependent regulation of endothelial permeability. The discussion focuses on the mechanisms by which neutrophils activate FAK and its downstream effects on endothelial barriers.

Serum metalloproteinases MMP-2, MMP-9, and metalloproteinase tissue inhibitors in patients are associated with arteriovenous fistula maturation

OBJECTIVE

Many vascular surgeons construct arteriovenous fistulas (AVFs) for hemodialysis access as the primary choice access. A significant number of AVFs fail to mature, however, leading to patient frustration and repeated operations. Metalloproteinase (MMP) activity, particularly MMP-2 and MMP-9, may be important for AVF maturation. We therefore sought to identify whether serum MMP levels could serve as a biomarker for predicting future successful AVF maturation.

METHODS

Blood was collected from patients with chronic renal insufficiency at the time of surgery for long-term hemodialysis access. Serum was separated from whole blood and ultracentrifuged at 1000g for 10 minutes. Serum aliquots were frozen at -80°C until used for analysis. Enzyme-linked immunosorbent assay was used to assay levels of MMP-2, MMP-9, and tissue inhibitor of metalloproteinase type 2 (TIMP-2), and TIMP type 4 (TIMP-4). Clinical end points were used to divide patients into failed and matured AVF groups. Successful maturation was considered in patients who had specific duplex findings or 1 month of successful two-needle cannulation hemodialysis. MMP/TIMP ratios were calculated as an index of the MMP axis activity because MMP activity parallels alterations in TIMP levels.

RESULTS

Of 20 enrolled patients, AVF maturation was successful in 13 and failed in 7. Serum levels of MMP-2/TIMP-2 were significantly higher in patients with matured AVFs vs levels in those that failed (P = .003). Similarly, a trend toward increased serum levels of MMP-9/TIMP-4 was found in patients with successful AVF (P = .06).

CONCLUSIONS

MMP-2 and TIMP-2 levels were different among patients whose AVF matured vs those who did not. Further follow-up studies to determine the predictability of AVF maturation using relative patient serum levels of MMP-2 and TIMP-2 should be performed.

Nonmuscle myosin light-chain kinase deficiency attenuates atherosclerosis in apolipoprotein E-deficient mice via reduced endothelial barrier dysfunction and monocyte migration

BACKGROUND

Endothelial dysfunction and monocyte migration are key events in the pathogenesis of atherosclerosis. Nonmuscle myosin light-chain kinase (nmMLCK), the predominant MLCK isoform in endothelial cells, has been shown to contribute to vascular inflammation by altering endothelial barrier function. However, its impact on atherogenesis remains unknown.

METHODS AND RESULTS

We investigated the role of nmMLCK in the development of atherosclerotic lesions in apolipoprotein E-deficient (apoE(-/-)) mice fed an atherogenic diet for 12 weeks. Histopathological examination demonstrated that nmMLCK deficiency (apoE(-/-)nmmlck(-/-)) reduced the size of aortic lesions by 53%, lipid contents by 44%, and macrophage deposition by 40%. Western blotting and reverse-transcription polymerase chain reaction revealed the expression of nmMLCK in aortic endothelial cells and peripheral blood monocytes. Measurements of transendothelial electric resistance indicated that nmMLCK deficiency attenuated endothelial barrier dysfunction caused by thrombin, oxidized low-density lipoprotein, and tumor necrosis factor α. In monocytes, nmMLCK deficiency reduced their migration in response to the chemokine monocyte chemoattractant protein-1. Further mechanistic studies showed that nmMLCK acted through both myosin light chain phosphorylation-coupled and -uncoupled pathways; the latter involved Rous sacracoma virus homolog genes-encoded tyrosine kinases (Src) signaling. Moreover, depletion of Src via gene silencing, site-specific mutagenesis, or pharmacological inhibition of Src greatly attenuated nmMLCK-dependent endothelial barrier dysfunction and monocyte migration.

CONCLUSIONS

Nonmuscle myosin light-chain kinase contributes to atherosclerosis by regulating endothelial barrier function and monocyte migration via mechanisms involving not only kinase-mediated MLC phosphorylation but also Src activation.

Vein tissue expression of matrix metalloproteinase as biomarker for hemodialysis arteriovenous fistula maturation

Failure of arteriovenous fistula (AVF) maturation is attributed to impaired vein remodeling. The purpose of this study is to identify whether vein matrix metalloproteinase (MMP) expression and activity is associated with AVF maturation. Patients with renal insufficiency undergoing surgery had their vein segments harvested and snap-frozen at time of AVF construction. Expression of MMP-2, MMP-9, membrane type-1 MMP (MT1-MMP), tissue inhibitor of metallopreoteinases type 2 (TIMP-2), and TIMP-4 were measured using zymography and Western blotting techniques. Of 14 patients enrolled, 9 had successful maturation and 5 had failure of AVF maturation. Significantly higher levels of MT1-MMP (an MMP-2 activator; P = .01), TIMP-2 (an MMP-2 inhibitor; P = .03), MMP-2 latent (P = .02), and MMP-2 total (P = .03) were associated with AVF maturation. There was a trend toward higher levels of TIMP-4 in the successful group (P = .18). These data demonstrate a positive relationship between MMP-2 expression in veins and AVF maturation. MMP-2 could serve as a potential preoperative marker to predict maturation.

Tissue inhibitor of metalloproteinase-2 regulates matrix metalloproteinase-2-mediated endothelial barrier dysfunction and breast cancer cell transmigration through lung microvascular endothelial cells

Matrix metalloproteinases (MMP) have been implicated in multiple stages of cancer metastasis. Tissue inhibitor of metalloproteinase-2 (TIMP-2) plays an important role in regulating MMP-2 activity. By forming a ternary complex with pro-MMP-2 and its activator MMP-14 on the cell surface, TIMP-2 can either initiate or restrain the cleavage and subsequent activation of MMP-2. Our recent work has shown that breast cancer cell adhesion to vascular endothelial cells activates endothelial MMP-2, promoting tumor cell transendothelial migration (TEM(E)). However, the mechanism of MMP-2 regulation during TEM(E) remains unclear. In the current study, we present evidence that MMP-14 is expressed in both invasive breast cancer cells (MDA-MB-231 and MDA-MB-436) and lung microvascular endothelial cells (HBMVEC-L), whereas TIMP-2 is exclusively expressed and released from the cancer cells. The tumor cell-derived TIMP-2 was further identified as a major determinant of endothelial MMP-2 activity during tumor cell transmigration in the presence of MMP-14. This response was associated with endothelial barrier dysfunction because coculture of MDA-MB-231 or MDA-MB-436 with HBMVEC-L caused a significant decrease in transendothelial electrical resistance concomitantly with endothelial cell-cell junction disruption and tumor cell transmigration. Knockdown of TIMP-2 or inhibition of TIMP-2/MMP-14 attenuated MMP-2-dependent transendothelial electrical resistance response and TEM(E). These findings suggest a novel interactive role of breast cancer cells and vascular endothelial cells in regulating the TIMP-2/MMP-14/MMP-2 pathway during tumor metastasis.

Myosin light chain kinase in microvascular endothelial barrier function

Microvascular barrier dysfunction is implicated in the initiation and progression of inflammation, posttraumatic complications, sepsis, ischaemia-reperfusion injury, atherosclerosis, and diabetes. Under physiological conditions, a precise equilibrium between endothelial cell-cell adhesion and actin-myosin-based centripetal tension tightly controls the semi-permeability of microvascular barriers. Myosin light chain kinase (MLCK) plays an important role in maintaining the equilibrium by phosphorylating myosin light chain (MLC), thereby inducing actomyosin contractility and weakening endothelial cell-cell adhesion. MLCK is activated by numerous physiological factors and inflammatory or angiogenic mediators, causing vascular hyperpermeability. In this review, we discuss experimental evidence supporting the crucial role of MLCK in the hyperpermeability response to key cell signalling events during inflammation. At the cellular level, in vitro studies of cultured endothelial monolayers treated with MLCK inhibitors or transfected with specific inhibiting peptides have demonstrated that induction of endothelial MLCK activity is necessary for hyperpermeability. Ex vivo studies of live microvessels, enabled by development of the isolated, perfused venule method, support the importance of MLCK in endothelial permeability regulation in an environment that more closely resembles in vivo tissues. Finally, the role of MLCK in vascular hyperpermeability has been confirmed with in vivo studies of animal disease models and the use of transgenic MLCK210 knockout mice. These approaches provide a more complete view of the role of MLCK in vascular barrier dysfunction.

ADAM15 regulates endothelial permeability and neutrophil migration via Src/ERK1/2 signalling

AIMS

Endothelial barrier dysfunction is a key event in the pathogenesis of vascular diseases associated with inflammation. ADAM (a disintegrin and metalloprotease) 15 has been shown to contribute to the development of vascular inflammation. However, its role in regulating endothelial barrier function is unknown. The aim of this study was to examine the effect of ADAM15 on endothelial permeability and its underlying mechanisms.

METHODS AND RESULTS

By measuring albumin transendothelial flux and transendothelial electric resistance in cultured human umbilical vein endothelial cell monolayers, we found that depletion of ADAM15 expression via siRNA decreased endothelial permeability and attenuated thrombin-induced barrier dysfunction. In contrast, endothelial cells overexpressing either wild-type or catalytically dead mutant ADAM15 displayed a higher basal permeability and augmented hyperpermeability in response to thrombin. In addition, ADAM15 knockdown inhibited whereas ADAM15 overexpression promoted neutrophil transendothelial migration. Further molecular assays revealed that ADAM15 did not cleave vascular endothelial-cadherin or cause its degradation. However, overexpression of ADAM15 promoted extracellular signal-regulated kinase (ERK)1/2 phosphorylation in both non-stimulated and thrombin-stimulated endothelial cells in a protease activity-independent manner. Pharmacological inhibition of Src kinase or ERK activation reversed ADAM15-induced hyperpermeability and neutrophil transmigration.

CONCLUSION

The data provide evidence for a novel function of ADAM15 in regulating endothelial barrier properties. The mechanisms of ADAM15-induced hyperpermeability involve Src/ERK1/2 signalling independent of junction molecule shedding.

Endothelial contractile cytoskeleton and microvascular permeability

Microvascular barrier dysfunction represents a significant problem in clinical conditions associated with trauma, burn, sepsis, acute respiratory distress syndrome, ischemia-reperfusion injury, and diabetic retinopathy. An important cellular mechanism underlying microvascular leakage is the generation of contractile force from the endothelial cytoskeleton, which counteracts cell-cell and cell-matrix adhesions leading to paracellular hyperpermeability. In this review, we present recent experimental evidence supporting the critical role of MLCK-activated, RhoA/ROCK-regulated contractile cytoskeleton in endothelial permeability response to inflammatory and thrombotic stimuli arising from thermal injury, activated neutrophils, vascular endothelial growth factor, and fibrinogen degradation products. Further understanding the molecular basis of microvascular barrier structure and function would contribute to the development of novel therapeutic targets for treating circulatory disorders and vascular injury.

Biodegradation of phthalate esters in compost-amended soil

In this study, we investigated the biodegradation of the phthalate acid esters (PAEs) di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) in compost and compost-amended soil. DBP (50 mg kg(-1)) and DEHP (50 mg kg(-1)) were added to the two types of compost (straw and animal manure) and subsequently added to the soil; they were tested as a single compound and in combination. Optimal PAE degradation in soil was at pH 7 and 30 degrees C. The degradation of PAE was enhanced when DBP and DEHP were simultaneously present in the soil. The addition of either of the two types of compost individually also improved the rate of PAE degradation. Compost samples were separated into fractions with various particle size ranges, which spanned from 0.1-0.45 to 500-2000 microm. We observed that the compost fractions with smaller particle sizes demonstrated higher PAE degradation rates. When the different compost fractions were added to soil, however, compost particle size had no significant effect on the rate of PAE degradation.

Fibrinogen-gamma C-terminal fragments induce endothelial barrier dysfunction and microvascular leak via integrin-mediated and RhoA-dependent mechanism

OBJECTIVES

The purposes of this study were to characterize the direct effect of the C-terminal fragment of fibrinogen gamma chain (gammaC) on microvascular endothelial permeability and to examine its molecular mechanism of action.

METHODS AND RESULTS

Intravital microscopy was performed to measure albumin extravasation in intact mesenteric microvasculature, followed by quantification of hydraulic conductivity in single perfused microvessels. Transendothelial electric resistance was measured in microvascular endothelial cells in combination with immunoblotting and immunocytochemistry. The results show that gammaC induced time- and concentration-dependent increases in protein transvascular flux and water permeability and decreases in endothelial barrier function, coupled with Rho GTPase activation, myosin light chain phosphorylation, and stress fiber formation. Depletion of RhoA via siRNA knockdown or pharmacological inhibition of RhoA signaling attenuated gammaC-induced barrier dysfunction. Imaging analyses demonstrated binding of gammaC to endothelial cells; the interaction was inhibited during blockage of the alphavbeta3 integrin. Furthermore, in vivo experiments showed that the microvascular leak response to gammaC was attenuated in integrin beta3(-/-) animals.

CONCLUSION

Fibrinogen-gamma C terminus directly interacts with the microvascular endothelium causing fluid and protein leak. The endothelial response to gammaC involves an integrin receptor-mediated RhoA-dependent signaling pathway that leads to paracellular hyperpermeability.

Toll-like receptor 4 contributes to microvascular inflammation and barrier dysfunction in thermal injury

Systemic and microvascular inflammation plays a key role in the development of multiple organ failure after infection, sepsis, and traumatic injury. Toll-like receptors (TLRs) regulate host responses to pathogens and sterile, injury-associated inflammatory responses. We investigated whether TLR-4 contributes to microvascular dysfunction during thermal injury in vivo in anesthetized wild-type or TLR-4 (-/-) mice receiving either a 25% total body surface area full-thickness scald burn or sham treatment on the dorsal skin. Using intravital microscopy, we assessed the hemodynamics and leukocyte dynamics in the mesenteric microvasculature as representative of the splanchnic microcirculation at a site remote from the burn wound. The transvascular flux of fluorescein isothiocyanate-albumin across mesenteric venules was measured as an indicator of microvascular permeability. Furthermore, cultured microvascular endothelial cell models were used to evaluate the endothelial-specific mechanisms involved in TLR-4-mediated barrier dysfunction. The results showed significantly elevated microvascular permeability in wild-type mice after burn, whereas this response was markedly attenuated in TLR-4 (-/-) mice. Burn injury also increased leukocyte adhesion in mesenteric venules of wild-type mice, and a blunted leukocyte response was seen in the TLR-4 mice. Treatment of endothelial cell monolayers with burn plasma induced a rapid reduction in the transendothelial electrical resistance measured by electric cell-substrate impedance sensing, indicative of endothelial cell-cell adhesive barrier dysfunction. Reducing expression of TLR-4 with siRNA treatment attenuated this response. Taken together, these data indicate that TLR-4 plays an important role in microvascular leakage and leukocyte adhesion under the inflammatory condition associated with nonseptic thermal injury.

Counter regulatory effects of PKCbetaII and PKCdelta on coronary endothelial permeability

OBJECTIVE

The aim of this study was to examine the endothelial distribution and activity of selected PKC isoforms in coronary vessels with respect to their functional impact on endothelial permeability under the experimental conditions relevant to diabetes.

METHODS AND RESULTS

En face immunohistochemistry demonstrated a significant increase of PKC(betaII) and decrease of PKCdelta expression in coronary arterial endothelium of Zucker diabetic rats. To test whether changes in PKC expression alter endothelial barrier properties, we measured the transcellular electric resistance in human coronary microvascular endothelial monolayers and found that either PKC(betaII) overexpression or PKCdelta inhibition disrupted the cell-cell adhesive barrier. Three-dimensional fluorescence microscopy revealed that hyperpermeability was caused by altered PKC activity in association with distinct translocation of PKC(betaII) to the cell-cell junction and PKCdelta localization to the cytosol. Further analyses in fractionated endothelial lysates confirmed the differential redistribution of these isozymes. Additionally, FRET analysis of PKC subcellular dynamics demonstrated a high PKC(betaII) activity at the cell surface and junction, whereas PKCdelta activity is concentrated in intracellular membrane organelles.

CONCLUSIONS

Taken together, these data suggest that PKC(betaII) and PKCdelta counter-regulate coronary endothelial barrier properties by targeting distinctive subcellular sites. Imbalanced PKC(betaII)/PKCdelta expression and activity may contribute to endothelial hyperpermeability and coronary dysfunction in diabetes.

VE-cadherin and beta-catenin binding dynamics during histamine-induced endothelial hyperpermeability

Beta-catenin plays an important role in the regulation of vascular endothelial cell-cell adhesions and barrier function by linking the VE-cadherin junction complex to the cytoskeleton. The purpose of this study was to evaluate the effect of beta-catenin and VE-cadherin interactions on endothelial permeability during inflammatory stimulation by histamine. We first assessed the ability of a beta-catenin binding polypeptide known as inhibitor of beta-catenin and T cell factor (ICAT) to compete beta-catenin binding to VE-cadherin in vitro. We then overexpressed recombinant FLAG-ICAT in human umbilical vein endothelial cells (HUVECs) to study its impact on endothelial barrier function controlled by cell-cell adhesions. The binding of beta-catenin to VE-cadherin was quantified before and after stimulation with histamine along with measurements of transendothelial electrical resistance (TER) and apparent permeability to albumin (P(a)) under the same conditions. The results showed that ICAT bound to beta-catenin and competitively inhibited binding of the VE-cadherin cytoplasmic domain to beta-catenin in a concentration-dependent manner. Overexpression of FLAG-ICAT in endothelial cell monolayers did not affect their basal permeability properties, as indicated by unaltered TER and P(a); however, the magnitude and duration of histamine-induced decreases in TER were significantly augmented. Likewise, the increase in P(a) in the presence of histamine was exacerbated. Overexpression of FLAG-ICAT also significantly decreased the level of beta-catenin-associated VE-cadherin following histamine stimulation. Taken together, these data suggest that inflammatory agents like histamine cause a transient and reversible disruption of binding between beta-catenin and VE-cadherin, during which endothelial permeability is elevated.

Anaerobic degradation of phenanthrene and pyrene in mangrove sediment

This study investigated the anaerobic degradation of the polycyclic aromatic hydrocarbons (PAHs) phenanthrene and pyrene in mangrove sediment from Taiwan. The anaerobic degradation of PAH was enhanced by the addition of acetate, lactate, pyruvate, sodium chloride, cellulose, or zero-valent iron. However, it was inhibited by the addition of humic acid, di-(2-ethylhexyl) phthalate (DEHP), nonylphenol, or heavy metals. Of the microorganism strains isolated from the sediment samples, we found that strain MSA3 (Clostridium pascui), expressed the best ability to biodegrade PAH. The inoculation of sediment with the strain MSA3 could enhance PAH degradation.

VEGF-C alters barrier function of cultured lymphatic endothelial cells through a VEGFR-3-dependent mechanism

BACKGROUND

The lymphatic endothelium is an important semi-permeable barrier separating lymph from the interstitial space. However, there is currently a limited understanding of the lymphatic endothelial barrier and the mechanisms of lymph formation. The objectives of this study were to investigate the potential active role of lymphatic endothelial cells in barrier regulation, and to test whether the endothelial cell agonists VEGF-A and VEGF-C can alter lymphatic endothelial barrier function.

METHODS AND RESULTS

Cultured adult human dermal microlymphatic endothelial cells (HMLEC-d) and human umbilical vein endothelial cells (HUVEC) were respectively used as models of lymphatic and vascular endothelium. Transendothelial electrical resistance (TER) of endothelial monolayers served as an index of barrier function. Cells were treated with VEGF-A, VEGF-C, or the VEGFR-3 selective mutant VEGF-C156S. MAZ51 was used to inhibit VEGFR-3 signaling. The results show that while VEGF-A causes a time-dependent decrease in TER in HUVEC, there is no response in HMLEC-d. In contrast, VEGF-C and VEGF-C156S cause a similar decrease in TER in HMLEC-d that is not observed in HUVEC. These results corresponded to the protein expression of VEGFR-2 and VEGFR-3 in these cell types, determined by Western blotting. In addition, the VEGF-C- and VEGF-C156S-induced TER changes were inhibited by MAZ51.

CONCLUSIONS

The results indicate differential responses of the lymphatic and vascular endothelial barriers to VEGF-A and VEGF-C. Furthermore, our data suggest that VEGF-C alters lymphatic endothelial function through a mechanism involving VEGFR-3.

Biodegradation of four phthalate esters in sludge

This study investigated the effects of ultrasonic pretreatment and various treatments on the aerobic degradation of four phthalic acid esters (PAEs) such as diethyl phthalate (DEP), benzyl butyl phthalate (BBP), di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl)phthalate (DEHP) in sludge. The effect on PAE degradation of treating sludge with a 20 min sonication period at a power level of 0.1 W ml(-1) was evaluated. The degradation rates of the four PAEs were DBP>BBP>DEP>DEHP. Degradation rate constants (k(1)) and half-lives (t(1/2)) for the four PAEs (50 mg kg(-1)) ranged from 0.182 to 0.379 day(-1) and 1.8 to 3.8 days, respectively. The optimal pH for PAE degradation in sludge was 7.0 at 30 degrees C. PAE degradation was enhanced by the addition of yeast extract, brij 30 or brij 35 and inhibited by the addition of hydrogen peroxide. Our results show that a combination of ultrasonic pretreatment and biodegradation can effectively remove PAE from sludge.

Microvascular permeability in diabetes and insulin resistance

Microvascular barrier injury has been implicated in the initiation and progress of end organ complications of diabetic mellitus. Plasma leakage and fluid retention are seen in various tissues of diabetic patients or animals at the early stages of the disease before structural microangiopathy can be detected. Clinical and experimental evidence suggests that hyperglycemia, often accompanied with insulin deficiency or insulin resistance, causes impaired autoregulation and increased permeability in microvessels. Multiple molecular pathways have been identified as contributors to the altered fluid homeostasis, including increased polyol flux that promotes oxidative stress, advanced glycation that leads to carbonyl stress, and excessive glucose metabolism that results in protein kinase C activation. These abnormal metabolic activities are associated with the production of pro-inflammatory cytokines and growth factors, which can stimulate an array of signaling reactions and structural changes at the endothelial barrier and ultimately cause microvascular leakage. Interventions that manipulate these metabolic and inflammatory pathways have demonstrated efficacy in delaying the progress of diabetic microvascular complications; however, their direct effects and mechanisms of action on the microcirculation remain elusive. A deeper understanding of the molecular basis of diabetes-induced endothelial barrier dysfunction will provide a framework for the development of new therapeutic targets to treat this chronic and debilitating disease process.

A role for endothelial-derived matrix metalloproteinase-2 in breast cancer cell transmigration across the endothelial-basement membrane barrier

Invasive cancer cells utilize matrix metalloproteinases (MMPs) to degrade the extracellular matrix and basement membrane in the process of metastasis. Among multiple members of the MMP family, the gelatinase MMP-2 has been implicated in the development and dissemination of malignancies. However, the cellular source of MMP-2 and its effect on metastatic extravasation have not been well characterized. The objective of this study was to test the hypothesis that active MMP-2 derived from endothelial cells facilitated the transmigration of breast cancer cells across the microvascular barrier. Gelatin zymography was used to assess latent and active MMP-2 production in conditioned media from MDA-MB-231 human breast cancer cells, human lung microvascular endothelial cells (HLMVEC) and co-culture of these two cells. Transmigrated cancer cells were measured during MMP-2 knockdown with siRNA and pharmacological inhibition of MMP activity with OA-HY. The results showed consistent MMP-2 secretion by the HLMVECs, whereas a low level production was seen in the MDA-MB-231 cells. Inhibition of MMP-2 expression or activity in HLMVECs significantly attenuated the transmigration of MDA-MB-231 cells across an endothelial monolayer barrier grown on a reconstituted basement membrane. The data provide evidence supporting a potential role for the endothelial production of MMPs in promoting cancer cell extravasation. We suggest that the interaction between malignant cells and peritumoral benign tissues including the vascular endothelium may serve as an important mechanism in the regulation of tumor invasion and metastasis.

Vascular endothelial growth factor-C stimulates the lymphatic pump by a VEGF receptor-3-dependent mechanism

Vascular endothelial growth factor (VEGF)-C plays an important role in lymphangiogenesis; however, functional responses of lymphatic vessels to VEGF-C have not been characterized. We tested the hypothesis that VEGF-C-induced activation of VEGF receptor (VEGFR)-3 increases lymphatic pump output. We examined the in vivo pump activity of rat mesenteric collecting lymphatics using intravital microscopy during basal conditions and during treatment with 1 nM recombinant VEGF-C, the selective VEGFR-3 agonist VEGF-Cys156Ser mutation (C156S; 1 nM), or 0.1 nM VEGF-A. Their specific responses were also analyzed during selective inhibition of VEGFR-3 with MAZ-51. Contraction frequency, end-diastolic diameter, end-systolic diameter, stroke volume index, pump flow index, and ejection fraction were evaluated. We also assessed arteriolar diameter and microvascular extravasation of FITC-albumin. The results show that both VEGF-C and VEGF-C156S significantly increased contraction frequency, end-diastolic diameter, stroke volume index, and pump flow index in a time-dependent manner. VEGF-A caused a different response characterized by a significantly increased stroke volume after 30 min of treatment. MAZ-51 (5 μM) caused tonic constriction and decreased contraction frequency. In addition, 0.5 and 5 μM MAZ-51 attenuated VEGF-C- and VEGF-C156S-induced lymphatic pump activation. VEGF-A caused vasodilation of arterioles, whereas VEGF-C and VEGF-C156S did not significantly alter arteriolar diameter. Also, VEGF-A and VEGF-C caused increased microvascular permeability, whereas VEGF-C156S did not. Our results demonstrate that VEGF-C increases lymphatic pumping through VEGFR-3. Furthermore, changes in microvascular hemodynamics are not required for VEGFR-3-mediated changes in lymphatic pump activity.

VapC-1 of nontypeable Haemophilus influenzae is a ribonuclease

Nontypeable Haemophilus influenzae (NTHi) organisms are obligate parasites of the human upper respiratory tract that can exist as commensals or pathogens. Toxin-antitoxin (TA) loci are highly conserved gene pairs that encode both a toxin and antitoxin moiety. Seven TA gene families have been identified to date, and NTHi carries two alleles of the vapBC family. Here, we have characterized the function of one of the NTHi alleles, vapBC-1. The gene pair is transcribed as an operon in two NTHi clinical isolates, and promoter fusions display an inverse relationship to culture density. The antitoxin VapB-1 forms homomultimers both in vitro and in vivo. The expression of the toxin VapC-1 conferred growth inhibition to an Escherichia coli expression strain and was successfully purified only when cloned in tandem with its cognate antitoxin. Using total RNA isolated from both E. coli and NTHi, we show for the first time that VapC-1 is an RNase that is active on free RNA but does not degrade DNA in vitro. Preincubation of the purified toxin and antitoxin together results in the formation of a protein complex that abrogates the activity of the toxin. We conclude that the NTHi vapBC-1 gene pair functions as a classical TA locus and that the induction of VapC-1 RNase activity leads to growth inhibition via the mechanism of mRNA cleavage.

Biodegradation of nonylphenol in soil

We investigated the effects of various factors (brij 30, brij 35, yeast extract, hydrogen peroxide and compost) on the aerobic degradation of nonylphenol (NP) in soil and characterized the structure of the microbial community in that soil. Residues of NP were measured using gas chromatography-mass spectrometry (GC-MS) and a change of microbial communities was demonstrated using denaturing gradient gel electrophoresis (DGGE). The results showed that Taichung sandy clay loam had higher NP degradation rate than Kaoshiung silty clay. The addition of compost, yeast extract (0.5 mg/l), brij 30 (55 microM), or brij 35 (91 microM) enhanced NP degradation, while the addition of hydrogen peroxide (1.0 mg/l) inhibited its degradation. We also found that the addition of various substrates changed the microbial community in the soils. Cytophaga sp. and Ochrobactrum sp. were constantly dominant bacteria under various conditions in the soil.

Rho and ROCK signaling in VEGF-induced microvascular endothelial hyperpermeability

OBJECTIVES

Vascular endothelial growth factor (VEGF) plays an important role in the regulation of microvascular permeability under various physiological and pathological conditions. The authors tested the hypothesis that the small GTPase Rho and its downstream effector ROCK (Rho-associated coiled-coil-containing protein kinase) mediate VEGF-induced increases in venular permeability. They also investigated myosin light chain (MLC) phosphorylation and actin polymerization, two well-characterized targets of the Rho-ROCK pathway that are implicated in the regulation of endothelial barrier function.

METHODS

The apparent permeability coefficient of albumin (P(a)) was measured in intact isolated porcine coronary venules and in cultured coronary venular endothelial cell (CVEC) monolayers. RhoA activation was determined using a Rhotekin-agarose pull down assay. MLC phosphorylation was evaluated by immunoblotting with phospho-specific antibodies, and endothelial cellular F-actin was viewed using fluorescence microscopy.

RESULTS

VEGF increased P(a) in both isolated coronary venules and CVEC monolayers. The hyperpermeability response occurred in a similar time course to that of Rho activation, MLC phosphorylation, and actin stress fiber formation. Selective blockage of ROCK with Y27632 dose-dependently inhibited VEGF-induced venular hyperpermeability. Moreover, inhibition of either Rho with exoenzyme C3 or ROCK with Y-27632 attenuated VEGF-induced increases in permeability, MLC phosphorylation, and actin-stress fiber formation in CVEC monolayers.

CONCLUSIONS

Collectively, these findings suggest that the Rho-ROCK signal pathway contributes to VEGF-induced hyperpermeability. Myosin light-chain phosphorylation and actin stress fiber formation occur concomitantly with the increase in permeability upon VEGF stimulation.

Plasma glucose levels and diabetes are independent predictors for mortality and morbidity in patients with SARS

AIMS

To investigate the relationships between a known history of diabetes and ambient fasting plasma glucose (FPG) levels with death and morbidity rates in patients with severe acute respiratory syndrome (SARS).

METHODS

In this retrospective analysis, the clinical and biochemical characteristics of 135 patients who had died from SARS, 385 survivors of SARS and 19 patients with non-SARS pneumonia were compared.

RESULTS

All patients were treated according to a predefined protocol. Before steroid treatment, the mean FPG level was significantly higher in the SARS group (deceased vs. survivors vs. non-SARS pneumonia group: 9.7 +/- 5.2 vs. 6.5 +/- 3.0 vs. 5.1 +/- 1.0 mmol/l, P < 0.01). In the SARS group, the percentage of patients with a known history of diabetes was significantly higher in the deceased patients than in the survivors (21.5% vs. 3.9%, P < 0.01). Among patients with no known history of diabetes and before commencement of steroid therapy, those who had hypoxaemia (SaO(2) < 93%) had higher FPG levels than those who did not have hypoxia in both the survivor (8.7 +/- 4.9 vs. 6.3 +/- 2.1 mmol/l, P < 0.001) and deceased (9.8 +/- 4.8 vs. 7.2 +/- 1.5 mmol/l, P < 0.001) groups. A known history of diabetes [odds ratio (OR) 3.0, 95% confidence interval (CI) 1.4, 6.3; P = 0.005] and FPG > or = 7.0 mmol/l before steroid treatment (OR 3.3, 95% CI 1.4, 7.7, P = 0.006) were independent predictors of death. During the course of the illness, FPG levels were negatively associated with SaO(2) (beta =-0.682 +/- 0.305, P = 0.025, general estimation equation model) in SARS patients. Survival analysis showed that FPG was independently associated with an increased hazard ratio (HR) of mortality (HR = 1.1, 95% CI 1.0, 1.1, P = 0.001) and hypoxia (HR = 1.1, 95% CI 1.0, 1.1, P = 0.002) after controlling for age and gender.

CONCLUSIONS

A known history of diabetes and ambient hyperglycaemia were independent predictors for death and morbidity in SARS patients. Metabolic control may improve the prognosis of SARS patients.

Involvement of ROCK-mediated endothelial tension development in neutrophil-stimulated microvascular leakage

Neutrophil-induced coronary microvascular barrier dysfunction is an important pathophysiological event in heart disease. Currently, the precise cellular and molecular mechanisms of neutrophil-induced microvascular leakage are not clear. The aim of this study was to test the hypothesis that rho kinase (ROCK) increases coronary venular permeability in association with elevated endothelial tension. We assessed permeability to albumin (P(a)) in isolated porcine coronary venules and in coronary venular endothelial cell (CVEC) monolayers. Endothelial barrier function was also evaluated by measuring transendothelial electrical resistance (TER) of CVEC monolayers. In parallel, we measured isometric tension of CVECs grown on collagen gels. Transference of constitutively active (ca)-ROCK protein into isolated coronary venules or CVEC monolayers caused a significant increase in P(a) and decreased TER in CVECs. The ROCK inhibitor Y-27632 blocked the ca-ROCK-induced changes. C5a-activated neutrophils (10(6)/ml) also significantly elevated venular P(a), which was dose-dependently inhibited by Y-27632 and a structurally distinct ROCK inhibitor, H-1152. In CVEC monolayers, activated neutrophils increased permeability with a concomitant elevation in isometric tension, both of which were inhibited by Y-27632 or H-1152. Treatment with ca-ROCK also significantly increased CVEC monolayer permeability and isometric tension, coupled with actin polymerization and elevated phosphorylation of myosin regulatory light chain on Thr18/Ser19. The data suggest that during neutrophil activation, ROCK promotes microvascular leakage in association with actin-myosin-mediated tension development in endothelial cells.

Biodegradation of nonylphenol in sewage sludge

We investigated the effects of various factors on the aerobic degradation of nonylphenol (NP) in sewage sludge. NP (5 mg/kg) degradation rate constants (k1) calculated were 0.148 and 0.224 day(-1) for the batch experiment and the bioreactor experiment, respectively, and half-lives (t(1/2)) were 4.7 and 3.1 days, respectively. The optimal pH value for NP degradation in sludge was 7.0 and the degradation rate was enhanced when the temperature was increased and when yeast extract (5 mg/l) and surfactants such as brij 30 or brij 35 (55 or 91 microM) were added. The addition of aluminum sulfate (200 mg/l) and hydrogen peroxide (1 mg/l) inhibited NP degradation within 28 days of incubation. Of the microorganism strains isolated from the sludge samples, we found that strain CT7 (identified as Bacillus sphaericus) manifested the best degrading ability.

Focal adhesion kinase in neutrophil-induced microvascular hyperpermeability

OBJECTIVE

Recent experimental evidence indicates an essential role of focal adhesion kinase (FAK) in mediating endothelial adhesion, contraction, and migration under physical stress and chemical stimulation. However, the functional impact of FAK on microvascular barrier property during inflammation has not been revealed. The aim of this study was to explore the potential contribution of FAK to neutrophil-dependent microvascular hyperpermeability.

METHODS

The apparent permeability coefficient of albumin was measured in intact, isolated porcine coronary venules during stimulation by C5a-activated neutrophils. In parallel, the transendothelial flux of albumin was quantified in cultured venular endothelial cell monolayers exposed to C5a-activated neutrophils. Western blotting and immunocytochemistry were performed to assess FAK tyrosine phosphorylation and distribution in endothelial cells, respectively. To specify the signaling effect of FAK on neutrophil-elicited endothelial hyperpermeability, FAK-related nonkinase (FRNK) was expressed, purified, and directly transfected into the endothelium of venules, and the permeability response to neutrophils was measured during inhibition of FAK.

RESULTS

C5a-activated neutrophils induced a time- and concentration-dependent increase in venular permeability. Transfection of venules with FRNK did not alter the basal barrier function but greatly attenuated neutrophil-induced hyperpermeability in a dose-related manner. A similar permeability response to neutrophils was observed in venular endothelial cell monolayers, which was diminished after FRNK transfection. In addition, Western blot analysis showed that activated neutrophils caused a concentration-dependent increase in FAK tyrosine phosphorylation with a time course correlating with that of venular hyperpermeability. Transfection of FRNK blocked neutrophil-evoked FAK tyrosine phosphorylation. Furthermore, immunofluorescence microscopy revealed a significant morphological change of FAK from a punctuated, dot-like pattern under normal conditions to an elongated, dash-like staining that aligned with the longitudinal axis of cells upon neutrophil stimulation.

CONCLUSION

The results suggest that focal adhesion kinase significantly contributes to the endothelial hyperpermeability response to neutrophil activation. Phosphorylation of FAK may play an important signaling role in the regulation of microvascular barrier function during inflammation.

Histamine effects on endothelial cell fibronectin interaction studied by atomic force microscopy

Atomic force microscopy was used to investigate the cellular response to histamine, one of the major inflammatory mediators that cause endothelial hyperpermeability and vascular leakage. AFM probes were labeled with fibronectin and used to measure binding strength between alpha5beta1 integrin and fibronectin by quantifying the force required to break single fibronectin-integrin bonds. The cytoskeletal changes, binding probability, and adhesion force before and after histamine treatment on endothelial cells were monitored. Cell topography measurements indicated that histamine induces cell shrinkage. Local cell stiffness and binding probability increased twofold after histamine treatment. The force necessary to rupture single alpha5beta1-fibronectin bond increased from 34.0 +/- 0.5 pN in control cells to 39 +/- 1 pN after histamine treatment. Experiments were also conducted to confirm the specificity of the alpha5beta1-fibronectin interaction. In the presence of soluble GRGDdSP the probability of adhesion events decreased >50% whereas the adhesion force between alpha5beta1 and fibronectin remained unchanged. These data indicate that extracellular matrix-integrin interactions play an important role in the endothelial cell response to changes of external chemical mediators. These changes can be recorded as direct measurements on live endothelial cells by using atomic force microscopy.