Microvascular Endothelial Cell Injury Research Articles

Effect of penehyclidine hydrochloride on β-arrestin-1 expression in lipopolysaccharide-induced human pulmonary microvascular endothelial cells

β-arrestins are expressed proteins that were first described, and are well-known, as negative regulators of G protein-coupled receptor signaling. Penehyclidine hydrochloride (PHC) is a new anti-cholinergic drug that can inhibit biomembrane lipid peroxidation, and decrease cytokines and oxyradicals. However, to date, no reports on the effects of PHC on β-arrestin-1 in cells have been published. The aim of this study was to investigate the effect of PHC on β-arrestin-1 expression in lipopolysaccharide (LPS)-induced human pulmonary microvascular endothelial cells (HPMEC). Cultured HPMEC were pretreated with PHC, followed by LPS treatment. Muscarinic receptor mRNAs were assayed by real-time quantitative PCR. Cell viability was assayed by the methyl thiazolyl tetrazolium (MTT) conversion test. The dose and time effects of PHC on β-arrestin-1 expression in LPS-induced HPMEC were determined by Western blot analysis. Cell malondialdehyde (MDA) level and superoxide dismutase (SOD) activity were measured. It was found that the M3 receptor was the one most highly expressed, and was activated 5 min after LPS challenge. Furthermore, 2 μg/mL PHC significantly upregulated expression of β-arrestin-1 within 10 to 15 min. Compared with the control group, MDA levels in cells were remarkably increased and SOD activities were significantly decreased in LPS pretreated cells, while PHC markedly decreased MDA levels and increased SOD activities. We conclude that PHC attenuated ROS injury by upregulating β-arrestin-1 expression, thereby implicating a mechanism by which PHC may exert its protective effects against LPS-induced pulmonary microvascular endothelial cell injury.

8-C N-ethyl-2-pyrrolidinone substituted flavan-3-ols as the marker compounds of Chinese dark teas formed in the post-fermentation process provide significant antioxidative activity

Phytochemical investigation of the aqueous extract of pu-erh tea afforded eight novel 8-C N-ethyl-2-pyrrolidinone substituted flavan-3-ols (puerins I–VIII) by 1H, 13C, two-dimensional nuclear magnetic resonance (NMR) and high-performance liquid chromatography with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD–ESI/MS) analysis. Comparative chemical analysis of green tea, black tea and Chinese dark teas confirmed that these compounds were the marker compounds of Chinese dark teas. Furthermore, fungal fermentation was indispensable for the biosynthesis of these novel compounds. Through single fungal fermentation, it was proved that catechins and theanine were the precursors of puerins I–VIII. HPLC-DAD-ESI/MS analysis elucidated the biosynthetic pathway for puerins I–VIII. Puerins I–IV have potential protective effects for the human micro-vascular endothelial cells (HMEC) injury induced by hydrogen dioxide compared to other tea polyphenols. 8-C N-ethyl-2-pyrrolidinone substituted flavan-3-ols could be used in the quality control and authentication of Chinese dark teas.

Stretch in Brain Microvascular Endothelial Cells (cEND) as an <em>In Vitro</em> Traumatic Brain Injury Model of the Blood Brain Barrier

Due to the high mortality incident brought about by traumatic brain injury (TBI), methods that would enable one to better understand the underlying mechanisms involved in it are useful for treatment. There are both in vivo and in vitro methods available for this purpose. In vivo models can mimic actual head injury as it occurs during TBI. However, in vivo techniques may not be exploited for studies at the cell physiology level. Hence, in vitro methods are more advantageous for this purpose since they provide easier access to the cells and the extracellular environment for manipulation. Our protocol presents an in vitro model of TBI using stretch injury in brain microvascular endothelial cells. It utilizes pressure applied to the cells cultured in flexible-bottomed wells. The pressure applied may easily be controlled and can produce injury that ranges from low to severe. The murine brain microvascular endothelial cells (cEND) generated in our laboratory is a well-suited model for the blood brain barrier (BBB) thus providing an advantage to other systems that employ a similar technique. In addition, due to the simplicity of the method, experimental set-ups are easily duplicated. Thus, this model can be used in studying the cellular and molecular mechanisms involved in TBI at the BBB.

Stretch in Brain Microvascular Endothelial Cells (cEND) as an <em>In Vitro</em> Traumatic Brain Injury Model of the Blood Brain Barrier

Due to the high mortality incident brought about by traumatic brain injury (TBI), methods that would enable one to better understand the underlying mechanisms involved in it are useful for treatment. There are both in vivo and in vitro methods available for this purpose. In vivo models can mimic actual head injury as it occurs during TBI. However, in vivo techniques may not be exploited for studies at the cell physiology level. Hence, in vitro methods are more advantageous for this purpose since they provide easier access to the cells and the extracellular environment for manipulation.Our protocol presents an in vitro model of TBI using stretch injury in brain microvascular endothelial cells. It utilizes pressure applied to the cells cultured in flexible-bottomed wells. The pressure applied may easily be controlled and can produce injury that ranges from low to severe. The murine brain microvascular endothelial cells (cEND) generated in our laboratory is a well-suited model for the blood brain barrier (BBB) thus providing an advantage to other systems that employ a similar technique. In addition, due to the simplicity of the method, experimental set-ups are easily duplicated. Thus, this model can be used in studying the cellular and molecular mechanisms involved in TBI at the BBB.

Involvement of the FoxO3a pathway in the ischemia/reperfusion injury of cardiac microvascular endothelial cells

FoxO3a, a member of the forkhead transcription factors, has been demonstrated to be involved in myocardial ischemia/reperfusion (I/R) injury. Cardiac microvascular endothelial cells (CMECs) are some of the predominant cells damaged immediately after myocardial I/R injury. Despite the importance of injured CMECs in an ischemic heart, little is known about the involvement of FoxO3a in regulating CMECs injury. Thus, we used rat CMECs following simulated I/R to examine FoxO3a activation and signaling in relation to survival, the cell cycle and apoptosis in CMECs. We found that Akt negatively regulates activation of the FoxO3a pathway by phosphorylating FoxO3a in CMECs as demonstrated with an Akt inhibitor and activator. Upon I/R injury, the FoxO3a pathway was significantly activated in CMECs, which was accompanied by Akt deactivation. In parallel, the I/R of CMECs induced G1-phase arrest through p27Kip1 up-regulation and significant activation of caspase-3. Accordingly, inhibition of the FoxO3a pathway by IGF-1, an Akt activator, could significantly block the I/R-enhanced activation of p27Kip1 and caspase-3 in CMECs. Collectively, our results indicate that the FoxO3a pathway is involved in the I/R injury of CMECs at least in part through the regulation of cell cycle arrest and apoptosis, suggesting that the FoxO3a pathway may be a novel therapeutic target that protects against microvascular endothelial damage in ischemic hearts.

Vagal Efferent Fiber Stimulation Ameliorates Pulmonary Microvascular Endothelial Cell Injury by Downregulating Inflammatory Responses

Electrical stimulation of the vagus nerve may have positive effects on many inflammatory diseases. This study determined the beneficial effects of vagus nerve stimulation and the mechanisms by which it attenuates lipopolysaccharide (LPS)-induced acute lung injury (ALI). Rats were intraperitoneally injected with 10 mg/kg LPS to induce ALI. The results showed that vagus nerve stimulation could improve lung injury, as evidenced by remarkable reductions in lung edema (wet-to-dry weight ratio), neutrophil infiltration (myeloperoxidase activity), and pulmonary permeability [total number of cells and protein concentrations in bronchoalveolar lavage fluid (BALF)]. In addition, vagus nerve stimulation not only decreased the expressions of Src-suppressed C kinase substrate and E-selectin proteins in lung tissue but also effectively attenuated the concentrations of the proinflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6 in BALF. These suggest that vagus nerve stimulation is a suitable treatment for LPS-induced ALI and indicate that it helps ameliorate pulmonary microvascular endothelial cell injury by downregulating inflammatory responses.

Intermedin protects against ischaemia and reperfusion injury in human ventricular cardiomyocytes: receptor subtype involvement

Purpose: Early reperfusion following myocardial infarction is essential but results in ischaemia/reperfusion (I/R) injury, whereby myocardial cells die largely due to oxidative stress. Intermedin (IMD; adrenomedullin-2), a novel peptide related to adrenomedullin (AM), is up-regulated in cardiovascular disease and is protective against I/R injury in rodent hearts and human coronary microvascular endothelial cells and cardiac non-myocytes. Protection is dependent on calcitonin receptor-like receptor (CRLR) signalling in association with one of three receptor activity-modifying proteins (RAMPs). IMD has yet to be investigated in human cardiomyocytes for a cardioprotective role. Aims: To identify if IMD and its receptor components are expressed in human ventricular cardiomyocytes; to investigate whether IMD protects these cells against simulated I/R injury and if so, determine receptor subtype involvement. Methods: Left ventricular adult human cardiomyocytes (HCM) were subjected to normoxia or simulated ischaemia for 4 h or I/R (3 h normoxia followed by 1 h reperfusion) all in the absence or presence of IMD. Cell viability was assessed using Trypan blue dye exclusion and oxidative damage by commercial Oxyblot assay. mRNA expression and protein distribution of IMD, AM, CRLR and RAMPs1-3 were assessed by Quantitative Real-Time PCR and indirect immunofluorescence microscopy, respectively. The silencing of the peptides or their receptor components using siRNA knock-down was employed to determine endogenous peptide and receptor subtype involvement in protection against I/R. Results: IMD, AM and their receptor component mRNAs were expressed in HCM; RAMP2 was the most abundant RAMP, while IMD was less abundantly expressed than AM. Ischaemia or I/R reduced the HCM cell count by 40% and 60% respectively (p<0.05 for both). IMD (10-9 mol.L-1) protected against the deleterious effects of ischaemia and I/R injury (∼20% salvaged for both conditions, p<0.05), with preservation of cell structure when examined by phase contrast microscopy and decreased oxidative stress noted on Oxyblot (p<0.001 vs. non-IMD counterpart for ischaemia or I/R). Protection was greatest when IMD was given during reperfusion (p<0.001) and was abolished by silencing CRLR (p<0.05) and RAMP2 (p<0.001). However, silencing endogenous IMD and/or AM expression did not augment extent of I/R injury in HCM. Conclusion: Exogenous IMD is protective against I/R in HCM, attributed to AM1 receptor subtype involvement. IMD administration during cardiac reperfusion could improve levels of morbidity and mortality in patients following myocardial infarction.

Hypoxic preconditioning protects microvascular endothelial cells against hypoxia/reoxygenation injury by attenuating endoplasmic reticulum stress

Endothelial cells (ECs) are directly exposed to hypoxia and contribute to injury during myocardial ischemia/reperfusion. Hypoxic preconditioning (HPC) protects ECs against hypoxia injury. This study aimed to explore whether HPC attenuates hypoxia/reoxygenation (H/R) injury by suppressing excessive endoplasmic reticulum stress (ERS) in cultured microvascular ECs (MVECs) from rat heart. MVECs injury was measured by lactate dehydrogenase (LDH) leakage, cytoskeleton destruction, and apoptosis. Expression of glucose regulating protein 78 (GRP78) and C/EBP homologous protein (CHOP), activation of caspase-12 (pro-apoptosis factors) and phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) were detected by western blot analysis. HPC attenuated H/R-induced LDH leakage, cytoskeleton destruction, and cell apoptosis, as shown by flow cytometry, Bax/Bcl-2 ratio, caspase-3 activation and terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling. HPC suppressed H/R-induced ERS, as shown by a decrease in expression of GRP78 and CHOP, and caspase-12 activation. HPC enhanced p38 MAPK phosphorylation but decreased that of protein kinase R-like ER kinase (PERK, upstream regulator of CHOP). SB202190 (an inhibitor of p38 MAPK) abolished HPC-induced cytoprotection, downregulation of GRP78 and CHOP, and activation of caspase-12, as well as PERK phosphorylation. HPC may protect MVECs against H/R injury by suppressing CHOP-dependent apoptosis through p38 MAPK mediated downregulation of PERK activation.

The role of platelet in mouse pulmonary microvascular endothelial cell injury induced by lipopolysaccharide-activated neutrophil in vitro

Objective To investigate the role of platelet in mouse pulmonary microvascular endothelial cell (PMVEC) injury caused by lipopolysaccharide( LPS)-activated neutrophil.Methods PMVECs were obtained from pathogen-free C3H/HeN mice of both sexes aged 6-8 weeks weighing 18-25 g according to the method described by Lim YC et al.Platelets and neutrophils were isolated from mouse blood by twice centrifugation and denaity gradient centrifugation respectively.PMVECs were seeded into twelve- or six-well plates ( 1 or 2 ml/well) after 2-5 passages and were randomly divided into 4 groups (n =31 each): group LPS; group platelets (group P);group neutrophils (group N) and group platelets + neutrophils (group PN).Each well contained about 5 × 107/ml platelets and/or 5 × 105/ml neutrophils respectively.PMVECs were incubated with LPS1 μg/ml at 37 ℃ in a 5％ CO2 humidified atmosphere for 1,6,12,18 and 24 h respectively in all 4 groups.The cells were examined with phase contrast microscope for morphological changes and survival condition.Viability rate,apoptotic rate and activation rate of PMVECs were detected by flow cytometry at each time points.Results There was no significant difference in morphology and number of endothelial cells (ECs) among the 4 groups,while the number of activated ECs was significantly increased but the number of living cells decreased in group PN compared with group LPS.The activation rate of ECs was significantly higher after being incubated with LPS for 6-12 h in groups P and N than in group LPS.The viability rate was significantly lower,while the apoptotic rate and activation rate were significantly higher after ECs were incubated with LPS in group PN than in groups LPS,P and N.Conclusion Platelets play a decisive role in mouse PMVEC injury induced by LPS activated neutrophils. Key words: Blood platelets; Neutrophils; Lipopolysaccharides; Lung; Capillaries; Endothelium , vascular

Effects of diazoxide pretreatment on the expression of hypoxia- inducible factor-1α mRNA and p53 mRNA in rat myocardial microvascular endothelial cells exposed to hypoxia-reoxygenation

Objective To investigate the effects of diazoxide pretreatment on the expression of hypoxia-inducible factor-1α (HIF-1α) mRNA and p53 mRNA in rat myocardial microvascular endothelial cells exposed to hypoxia-reoxygenation (H/R).Methods The SD rat myocardial microvascular endothelial cells were cultured. The cells were seeded in 96-well plates ( 100 μl/hole) or in 6 cm diameter dishes (2 ml/dish) with the density of 1 ×106/ml and randomly divided into 4 groups ( n = 24 each): normal control group (group C), H/R group, H/R +diazoxide pretreatment group (group DZ) and H/R + diazoxide pretreatment + mitochondrial ATP-sensitive potassium channel blocker 5-hydroxydecanoate (5-HD) group (group DZ + 5-HD). The cells were exposed to 2 h hypoxia followed by 2 h reoxygenation. Diazoxide 100 μmol/L and diazoxide 100 μmol/L + 5-HD 100 μmol/L were added to the culture medium 2 h before hypoxia in DZ and DZ + 5-HD groups respectively. The cell vitality, apoptotic rate and expression of HIF-1α mRNA and p53 mRNA were detected at the end of reoxygenation. Results Compared with group C, the cell vitality was significantly decreased, apoptotic rate increased and the expression of HIF- 1α mRNA and p53 mRNA up-regulated in H/R group ( P ＜ 0.01). Compared with group H/R, the cell vitality was significantly increased, apoptotic rate decreased, the expression of HIF-1α mRNA up-regulated and the expression of p53 mRNA down-regulated in group DZ ( P ＜ 0.05 or 0.01 ). 5-HD could inhibit diazoxide pretreatment-induced changes mentioned above (P ＜ 0.05 ). Conclusion Diazoxide pretreatment can reduce H/R injury in rat myocardial microvascular endothelial cells through up-regulating the expression of HIF-1α and down-regulating the expression of p53, and the mechanism is related to activation of mitochondrial ATP-sensitive potassium channels. Key words: Dazoxide; Heart; Endothelium, vascular; Oxygen; Cell hpoxia; Hypoxia-inducible factor 1, alpha subunit; Tumor suppressor protein p53

Protection from lipopolysaccharide-induced pulmonary microvascular endothelial cell injury by activation of hedgehog signaling pathway

Pulmonary microvascular endothelial cells (PMVECs) are critically involved in the pathogenesis of acute lung injury. Hedgehog signaling pathway plays a fundamental role in embryonic development as well as adult morphogenesis and carcinogenesis. As the priming protein of hedgehog signaling pathway, sonic hedgehog (Shh) may recently be advantage for decreasing endothelial injury and promoting the repair of endothelial barrier function. To investigate the expression and role of hedgehog signal pathway in PMVECs injured by lipopolysaccharide (LPS), cells were divided into six groups: control group, LPS group, rhShh group, LPS+rhShh group, rhShh+cyclopamine group, and LPS+rhShh+cyclopamine group. Real time RT-PCR and Western blotting were used to detect the mRNA and protein expression of hedgehog signal molecules including Shh, Patched-1 (Ptc-1) and Gli1 in nucleus. The activity of PMVECs was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In this study, we found that Shh, Ptch1, and Gli1 were expressed in rat PMVECs and their expression decreased when cells were treated by LPS. In the other hand, LPS inhibited the activity of rat PMVECs and caused the cells injury. Activation of Hedgehog signaling pathway by Shh could elevate the activity of PMVECs with pretreatment by LPS. Therefore, hedgehog signaling pathway should play a protective role on injury PMVECs by LPS.

Effects of diazoxide pretreatment on the expression of NF-kB mRNA and fractalkine mRNA in rat myocardial microvascular endothelial cells exposed to hypoxia-reoxygenation

Objective To investigate the effects of diazoxide pretreatment on the expression of NF-κB mRNA and fractalkine （FKN） mRNA in rat myocardial microvascular endothelial cells exposed to hypoxia-reoxygenation （H/R）. Methods The SD rat myocardial microvascular endothelial cells were cultured. The cells were seeded in 96-well plates （100μl/hole） or in 6 cm diameter dishes （2 ml/dish） with the density of 1 × 106/ml and randomly divided into4 groups （n = 24 each）： Ⅰ normal control group （group C）, Ⅱ H/R group, Ⅲ diazoxide pretreatment group （group DZ）, Ⅳ diazoxide pretreatment ＋ mitochondrial ATP-sensitive potassium channel blocker 5-hydroxydecanoate （5-HD） group （group DZ ＋ 5-HD）. The cells were exposed to 2 h hypoxia followed by 2 h reoxygenation. Diazoxide 100 μmol/L and diazoxide 100 μmol/L ＋ 5-HD 100μmol/L were added to the cultured medium 2 h before hypoxia in group DZ and DZ ＋ 5-HD respectively. The cell vitality, apoptotic rate and expression of NF-κB mRNA and FKN mRNA were detected at end of reoxygenation. Results Compared with group C, the cell vitality was significantly decreased, apoptotic rate increased and the expression of NF-κB mRNA and FKN mRNA up-regulated in H/R group. Compared with group H/R, the cell vitality was significantly increased,apoptotic rate decreased and the expression of NF-κB mRNA and FKN mRNA down-regulated in group DZ. 5-HD could inhibit diazoxide pretreatment-induced changes mentioned above. Conclusion Diazoxide pretreatment can reduce H/R injury in rat myocardial microvascular endothelial cells through down-regulating the expression of NFκB and FKN, and the mechanism is related to activation of mitochondrial ATP-sensitive potassium channels. Key words: Dazoxide; Heart; Endothelium,vascular; Oxygen; Cell hpoxia; NF-kappa B; Chemokine CX3CL1

Blood–brain barrier breakdown and repair by Src after thrombin‐induced injury

Thrombin mediates the life-threatening cerebral edema that occurs after intracerebral hemorrhage. Therefore, we examined the mechanisms of thrombin-induced injury to the blood-brain barrier (BBB) and subsequent mechanisms of BBB repair. Intracerebroventricular injection of thrombin (20U) was used to model intraventricular hemorrhage in adult rats. Thrombin reduced brain microvascular endothelial cell (BMVEC) and perivascular astrocyte immunoreactivity-indicating either cell injury or death-and functionally disrupted the BBB as measured by increased water content and extravasation of sodium fluorescein and Evans blue dyes 24 hours later. Administration of nonspecific Src family kinase inhibitor (PP2) immediately after thrombin injections blocked brain edema and BBB disruption. At 7 to 14 days after thrombin injections, newborn endothelial cells and astrocytes were observed around cerebral vessels at the time when BBB permeability and cerebral water content resolved. Delayed administration of PP2 on days 2 through 6 after thrombin injections prevented resolution of the edema and abnormal BBB permeability. Thrombin, via its protease-activated receptors, is postulated to activate Src kinase phosphorylation of molecules that acutely injure the BBB and produce edema. Thus, acute administration of Src antagonists blocks edema. In contrast, Src blockade for 2 to 6 days after thrombin injections is postulated to prevent resolution of edema and abnormal BBB permeability in part because Src kinase proto-oncogene members stimulate proliferation of newborn BMVECs and perivascular astrocytes in the neurovascular niche that repair the damaged BBB. Thus, Src kinases not only mediate acute BBB injury but also mediate chronic BBB repair after thrombin-induced injury.

Peritubular capillary preservation with COMP-angiopoietin-1 decreases ischemia-reperfusion-induced acute kidney injury

Ischemia followed by reperfusion induces microvascular endothelial cell injury, leading to the loss of functions such as regulation of vascular tone, tissue perfusion, permeability, and inflammation in kidney. Improvement of this endothelial dysfunction could be a good approach to treating ischemia-reperfusion-induced renal injury. Cartilage oligomeric matrix protein-angiopoietin-1 (COMP-Ang1) is a variant of native angiogenic factor angiopoietin-1 engineered to have higher activity. We evaluated the protective effect of COMP-Ang1 in an ischemia-reperfusion renal injury model. COMP-Ang1 preserved renal peritubular capillaries after ischemia-reperfusion injury without recruiting pericytes. Pretreatment with COMP-Ang1 attenuated the increase of blood urea nitrogen and serum creatinine levels after ischemia-reperfusion. In addition, the morphological examination indicated less tubular injury in mice pretreated with COMP-Ang1 than in those treated with the vehicle. COMP-Ang1 treatment reduced the increase in the number of Gr-1-positive neutrophils or ER-HR3-positive macrophages infiltrating kidneys, increased phosphorylation of Akt, and preserved renal tissue perfusion flow and microvascular permeability. Furthermore, COMP-Ang1 decreased renal interstitial fibrosis 30 days after the ischemia-reperfusion injury. In conclusion, COMP-Ang1 can be a possible endothelial cell-targeted therapy for preventing ischemia-reperfusion-induced acute kidney injury.

Advances in understanding of pathogenesis of aHUS and HELLP

Both atypical haemolytic uraemic syndrome (aHUS) and the HELLP syndrome (haemolytic anaemia, elevated liver enzymes, and low platelets) are thrombotic microangiopathies characterized by microvascular endothelial activation, cell injury and thrombosis. aHUS is a disease of complement dysregulation, specifically a gain of function of the alternative pathway, due to mutations in complement regulatory proteins and activating components. Recently, the same complement mutation identified in multiple patients with aHUS was found in a patient with the HELLP syndrome. The pathogeneses of both diseases are reviewed focusing on the role of the complement system and how its dysfunction could result in a thrombotic microangiopathy in the kidney in the case of aHUS and in the liver in the case of the HELLP syndrome.

Human neutrophil–pulmonary microvascular endothelial cell interactions in vitro: Differential effects of nitric oxide vs. peroxynitrite

Sepsis-induced acute lung injury is characterized by activation and injury of pulmonary microvascular endothelial cells (PMVEC), increased neutrophil–PMVEC adhesion and migration, and trans-PMVEC high-protein edema. Inducible NO synthase (iNOS) inhibits septic murine neutrophil migration in vivo and in vitro. The effects of NO in human neutrophil–PMVEC interactions are not known. We isolated human PMVEC using magnetic bead-bound anti-PECAM antibody. Confluent PMVEC at passage 3–4 were co-cultured with human neutrophils for assessment of neutrophil–PMVEC adhesion, and trans-PMVEC neutrophil migration and Evans-Blue dye-labeled albumin leak. Two NO donors (spermine-NONOate, S-nitroso- N-acetylpenicillamine) attenuated both cytomix-enhanced neutrophil–PMVEC adhesion by 64 ± 14% ( p < 0.01) and 32 ± 3% ( p < 0.05), respectively, and cytomix-induced trans-PMVEC neutrophil migration by 85 ± 16% ( p < 0.01) and 43 ± 5% ( p < 0.01), respectively. Correspondingly, iNOS inhibition with 1400W enhanced cytomix-stimulated neutrophil migration by 52 ± 3% ( p < 0.01), but had no effect on neutrophil–PMVEC adhesion. Conversely, a peroxynitrite donor (SIN-1) increased both neutrophil–PMVEC adhesion (38 ± 2% vs. 14 ± 1% control, p < 0.01) and trans-PMVEC neutrophil migration; with both effects were completely inhibited by scavenging of NO, superoxide, or peroxynitrite ( p < 0.05 for each). Scavenging of peroxynitrite also eliminated cytomix-induced neutrophil adhesion and migration. Blocking CD18-dependent neutrophil adhesion prevented cytomix-stimulated trans-PMVEC EB-albumin leak ( p < 0.05), while inhibiting neutrophil migration paradoxically enhanced cytomix-stimulated EB-albumin leak (11 ± 1% vs. 7 ± 0.5%, p < 0.01). FMLP-induced neutrophil migration had no effect on trans-PMVEC EB-albumin leak. In summary, we report differential effects, including the inhibitory action of NO and stimulatory effect of ONOO − on human neutrophil–PMVEC adhesion and trans-PMVEC migration under cytomix stimulation. Moreover, neutrophil–PMVEC adhesion, but not trans-PMVEC migration, contributes to human PMVEC barrier dysfunction.

Prevention of lipopolysaccharide-induced injury by 3,5-dicaffeoylquinic acid in endothelial cells

To investigate the effect of 3,5-dicaffeoylquinic acid (3,5-diCQA) on lipopolysaccharide (LPS)-induced injury in human dermal microvascular endothelial cells (HMEC-1). The anti-oxidant effect was detected using the malondialdehyde (MDA) assay in a rat liver microsome model of lipid peroxidation. Cell viability was analyzed using the 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide assay. Cell lipid peroxide injury was measured by lactate dehydrogenase (LDH) release. Apoptotic cells were detected by flow cytometry, and confirmed by DNA fragmentation analysis. Caspase-3 activity was measured using a specific assay kit. The level of intracellular reactive oxygen species (ROS) was determined by flow cytometry with a 2,7-dichlorodihydro-fluorescein diacetate fluorescence probe. The exposure of microsomes to ascorbate-Fe2+ resulted in lipoperoxidation according to an increase in the level of MDA. MDA formation decreased in a dose-dependent manner on treatment with 5, 10, or 50 micromol/L 3,5-diCQA. Treatment with LPS for 16 h resulted in a 60% decrease in cell viability and an increase in LDH release from 47.6% to 61.5%. DNA laddering was observed by agarose gel electrophoresis. The level of apoptotic cells peaked at 27% after treatment with LPS for 12 h. Following treatment with LPS for 12 h, intracellular ROS and caspase-3 activity increased. Pretreatment with 3,5-diCQA at 5, 10, or 50 micromol/L for 1 h attenuated LPS-mediated endothelial cell injury. The anti-apoptotic action of 3,5-diCQA was partially dependent on its capacity for anti-oxidation and the suppression of caspase-3 activity. 3,5-diCQA displays anti-oxidative and anti-apoptotic activity in HMEC-1 due to scavenging of intracellular ROS induced by LPS, and the suppression of caspase-3 activity.

Interference with TRALI‐causing anti‐HLA DR alloantibody induction of human pulmonary microvascular endothelial cell injury by purified soluble HLA DR

Antibodies to human leucocyte antigens (HLA) and human polymorphonuclear neutrophil (PMN) antigens are considered etiologic agents of transfusion-related acute lung injury (TRALI). The aim of this study was to clarify the role of anti-HLA DR antibodies in the pathophysiology of TRALI and the ability of purified soluble HLA DR (psHLA DR) to inhibit the release of cytokines in an in vitro model. A coculture of human pulmonary microvascular endothelial cells (HMVEC) and monocytes in the presence of serum containing anti-HLA DR alloantibodies previously associated with cases of TRALI was used as an in vitro TRALI model. The release of leukotriene B(4) (LTB(4)) and tumour necrosis factor-alpha (TNF-alpha), the apoptosis of HMVECs were measured. The release of LTB(4) and TNF-alpha and apoptosis of HMVECs were observed in the model. The addition of psHLA DR markedly reduced the release of LTB(4) and TNF-alpha and inhibited apoptosis of HMVECs. These results support the critical role of anti-HLA DR alloantibodies in the pathogenesis of TRALI and suggest that the soluble HLA DR could inhibit TRALI development caused by anti-HLA DR alloantibodies.

Inducible NO synthase (iNOS) in human neutrophils but not pulmonary microvascular endothelial cells (PMVEC) mediates septic protein leak in vitro

Sepsis-induced acute lung injury (ALI) is characterized by injury of the pulmonary microvascular endothelial cells (PMVEC) leading to high-protein pulmonary edema. Inducible NO synthase (iNOS) mediates trans-PMVEC protein leak in septic mice in vivo and in murine PMVEC under septic conditions in vitro, but the role of iNOS in human PMVEC protein leak has not been addressed. We hypothesized that iNOS in human neutrophils, but not human PMVEC, mediates septic trans-PMVEC protein leak in vitro. We isolated human PMVEC from lung tissue using magnetic bead-bound anti-PECAM antibody and assessed Evans blue albumin leak across human PMVEC monolayers under septic conditions in the presence/absence of human neutrophils. PMVEC were used at passages 3–4, seeded on 3 μm Transwell inserts and grown to confluence. Cytomix-stimulated trans-PMVEC albumin leak was not attenuated by pre-treatment with 1400 W, a selective iNOS inhibitor, or l-NAME, a non-selective NOS inhibitor. In neutrophil-PMVEC co-culture, basal unstimulated trans-EB-albumin leak was 0.6 ± 0.3%, which was increased by cytomix stimulation to 11.5 ± 4.4%, p < 0.01. Cytomix-stimulated EB-albumin leak in neutrophil-PMVEC co-cultures was inhibited by pre-treatment with 1400 W (3.8 ± 1.0%, p < 0.05) or l-NAME (4.0 ± 1.1%, p < 0.05). Pre-treatment of neutrophil-PMVEC co-cultures with PEG-SOD (superoxide scavenger) and FeTPPS (peroxynitrite scavenger) also significantly attenuated neutrophil-dependent cytomix-stimulated leak (4.7 ± 3.0%, p < 0.05; 0.5 ± 1.0%, p < 0.01, respectively). In conclusion, trans-human PMVEC albumin leak under septic conditions is dependent on iNOS activity specifically in neutrophils, but not in PMVEC themselves. Septic neutrophil-dependent trans-PMVEC albumin leak may be mediated by peroxynitrite.

Association of Complement with Microvascular Endothelial Cell Injury in Thrombotic Microangiopathy In Vivo and in In Vitro Model Systems.

We have previously shown that plasma from patients with idiopathic as well as HIV and thienopyridine-linked TTP induces apoptosis of microvascular endothelial cells (MVEC) in vitro, with specific sparing of large vessel and pulmonary MVEC, consistent with the clinical syndrome. This correlates with in vivo measures of apoptosis in splenic tissue of TTP patients. We found that osteoprotegrin (OPG), an inhibitor of multiple inducers of MVEC apoptosis, could block TTP plasma-mediated MVEC injury. Utilizing OPG affinity-binding columns and MS-TOFI analysis of column eluates, we subsequently identified complement (C) components and C-regulatory factors as potentially involved in TTP plasma-mediated EC injury. Building on the observation that familial TTP syndromes have been linked to genetic deficiencies of the C-regulatory factors Factor H and MCP, and three cases of sporadic HUS in children have been accompanied by autoantibodies to factor H, we hypothesized that the C-system plays an important role in TTP-induced MVEC injury, facilitated by autoantibody-mediated suppression of C-regulatory proteins. To evaluate the role of the complement system we looked at:IFA staining of splenic tissue from TTP patients versus controls for C-components in conjunction with CD34+ indentification of MVEC.ELISA-based assays of complement activation/deposition on MVEC exposed to TTP vs. control plasma.Ability of anti-C agents to block TTP plasma-mediated MVEC apoptosis.DNA microarray analysis of TTP plasma MVEC exposed to TTP vs. control plasma.ELISA-based search for autoantibodies against C-regulatory proteins in TTP plasma.IFA staining demonstrated increased deposition of C-components on MVEC in vivo on splenic tissue of TTP vs. control patients (4/5 TTP, 0/3 control). Increased C-activation was demonstrated on MVEC exposed to plasmas of TTP patients in vitro as evidenced by decreased C3b (p=0.002) and C4d (p=0.0002) deposition. Microarray data revealed increased expression of C-regulatory factors in resistant vs. susceptible MVEC exposed to TTP plasma. C-inhibtion resulted in prevention of TTP-plasma induced MVEC apoptosis by annexin-V staining (P<0.02). The search for autoantibodies against five C-regulatory components: CD46 (MCP), CD55 (DAF), CD59, Factor H, and Factor I by ELISA assay is currently ongoing. In conclusion, the clinical expression of thrombotic microangiopathy likely requires a double-hit of endothelial cell injury and autoantibodies against proteins vital to hemostasis and/or MVEC survival. In some patients this may involve autoantibodies to ADAMTS13; in others, C-system activation and inhibition of C-regulation by C-regulatory protein autoantibodies may be involved. Inhibition of the C-system may be a feasible clinical approach in some patients with thrombotic microangiopathies.