Thrombin induces a temporal biphasic vascular response through the differential phosphorylation of endothelial nitric oxide synthase via protease-activated receptor-1 and protein kinase C.

Endothelial nitric oxide synthase (eNOS) is a critical regulatory enzyme that controls vascular tone via the production of nitric oxide. Although thrombin also modulates vascular tone predominantly via the activation of protease-activated receptors (PARs), the time course and mechanisms involved in how thrombin controls eNOS enzymatic activity are unknown. eNOS enzymatic activity is enhanced by the phosphorylation of eNOS-Ser1177 and reduced by the phosphorylation of eNOS-Thr495. In this study, we hypothesized that thrombin regulates vascular tone through the differential phosphorylation of eNOS. Using rat descending aorta, we show that thrombin modulates vascular tone in an eNOS-dependent manner via activated PAR-1. We also show that thrombin causes a temporal biphasic response. Protein kinase C (PKC) is associated with second phase of thrombin-induced response. Western blot analysis demonstrated thrombin phosphorylated eNOS-Ser1177 and eNOS-Thr495 in human umbilical vein endothelial cells. A PKC inhibitor suppressed the thrombin-induced phosphorylation of eNOS-Thr495, but not that of eNOS-Ser1177. Our results suggest that thrombin induces a temporal biphasic vascular response through the differential phosphorylation of eNOS via activated PAR-1. Thrombin causes transient vasorelaxation by the phosphorylation of eNOS-Ser1177, and subsequent attenuation of vasorelaxation by the phosphorylation of eNOS-Thr495 via PKC, leading to the modulation of vascular tone.

Endothelial Notch signaling directly regulates the small GTPase RND1 to facilitate Notch suppression of endothelial migration.

To control sprouting angiogenesis, endothelial Notch signaling suppresses tip cell formation, migration, and proliferation while promoting barrier formation. Each of these responses may be regulated by distinct Notch-regulated effectors. Notch activity is highly dynamic in sprouting endothelial cells, while constitutive Notch signaling drives homeostatic endothelial polarization, indicating the need for both rapid and constitutive Notch targets. In contrast to previous screens that focus on genes regulated by constitutively active Notch, we characterized the dynamic response to Notch. We examined transcriptional changes from 1.5 to 6 h after Notch signal activation via ligand-specific or EGTA induction in cultured primary human endothelial cells and neonatal mouse brain. In each combination of endothelial type and Notch manipulation, transcriptomic analysis identified distinct but overlapping sets of rapidly regulated genes and revealed many novel Notch target genes. Among the novel Notch-regulated signaling pathways identified were effectors in GPCR signaling, notably, the constitutively active GTPase RND1. In endothelial cells, RND1 was shown to be a novel direct Notch transcriptional target and required for Notch control of sprouting angiogenesis, endothelial migration, and Ras activity. We conclude that RND1 is directly regulated by endothelial Notch signaling in a rapid fashion in order to suppress endothelial migration.

Paeoniflorin alleviates NG-nitro-L-arginine methyl ester (L-NAME)-induced gestational hypertension and upregulates silent information regulator 2 related enzyme 1 (SIRT1) to reduce H2O2-induced endothelial cell damage.

Pregnancy-induced hypertension (PIH) is a leading cause of maternal mortality. Paeoniflorin has been reported to alleviate hypertension, thus relieving the injury of target organ. This study aimed to investigate the role of paeoniflorin in PIH development by regulating SIRT1 in rats. The mean arterial pressure (MAP), urine protein and histopathological damage of placenta in gestational hypertension rats were, respectively, detected by noninvasive tail-artery pressure measuring instrument, BCA method and H&E staining. The viability of human umbilical vein endothelial cells (HUVECs) treated with paeoniflorin or/and H2O2 was observed by CCK-8 assay. SIRT1 protein expression in HUVECs treated with paeoniflorin or/and H2O2 was analyzed by Western blot. Tunel assay, wound healing assay and tube formation assay were used to detect the apoptosis, migration and tube formation of HUVECs administrated with paeoniflorin or/and H2O2 or/and EX527 (SIRT1 inhibitor). As a result, MAP, urine protein and histopathological damage of placenta were enhanced in PIH rats, which were then alleviated by paeoniflorin. Paeoniflorin decreased the levels of sFlt-1, PlGF and VEGF in serum and placental tissues of gestational hypertension rats as well as the inflammatory response and oxidative stress. In addition, paeoniflorin promoted the expressions of SIRT1 and NO/eNOS and inhibited the production of iNOS in gestational hypertension rats to improve vascular endothelial cell injury. However, SIRT1 inhibition could suppress the protective effects of paeoniflorin on endothelial dysfunction of H2O2-induced HUVECs. In conclusion, paeoniflorin could improve gestational hypertension development by upregulating SIRT1.

MiR-221-3p targets HIPK2 to promote diabetic wound healing.

Diabetic foot ulcer is a severe complication of diabetes and is prone to being a chronic non-healing wound. We previously demonstrated that endothelial progenitor cell-derived exosomes, which contain miR-221-3p, alleviate diabetic ulcers. Here, to explore the mechanisms underlying this wound healing, we investigated the potential angiogenic effects of miR-221-3p in vitro using cultured human umbilical vein endothelial cells (HUVECs) and in vivo using a streptozotocin-induced mouse model of diabetes. We found that miR-221-3p promoted HUVEC viability, migration, and capillary-like tube formation. HUVECs cultured in high glucose showed up-regulated expression of homeodomain-interacting protein kinase 2 (HIPK2), a predicted target of miR-221-3p that may decrease angiogenesis. Knockdown of HIPK2 enhanced high glucose-suppressed HUVEC viability, migration, and tube formation, counteracting the effects of high glucose. Using a dual luciferase reporter assay, we found that HIPK2 was indeed a direct target of miR-221-3p. Subcutaneous injection of miR-221-3p agomir into diabetic mice promoted wound healing and suppressed HIPK2 expression in wound margin tissue. These findings indicate that HIPK2, as a direct target of miR-221-3p, contributes to the regulatory role of miR-221-3p in diabetic wound healing and may be a novel therapeutic target for diabetic foot ulcer.

Overexpression of sFlt-1 represses ox-LDL-induced injury of HUVECs by activating autophagy via PI3K/AKT/mTOR pathway.

Soluble fms-like tyrosine kinase-1 (sFlt-1), a circulating antiangiogenic protein, is involved in the pathogenesis of atherosclerosis (AS), and the underlying mechanism is still unclear. Here, we attempted to investigate the mechanism of action of sFlt-1 in AS. Human umbilical vein endothelial cells (HUVECs) were treated with oxidized low density lipoprotein (ox-LDL) to induce cell injury. ox-LDL treatment increased LC3-II/LC3-I ratio, Beclin-1 expression and GFP-LC3 puncta in HUVECs, suggesting that ox-LDL may induce autophagic flux impairment in HUVECs. ox-LDL-treated HUVECs displayed a decrease of sFlt-1 levels. Moreover, ox-LDL treatment reduced cell proliferation and elevated apoptosis in HUVECs, which was abrogated by sFlt-1 overexpression. Up-regulation of sFlt-1 repressed the activity of PI3K/AKT/mTOR signaling pathway and enhanced autophagy in HUVECs following ox-LDL treatment. Additionally, sFlt-1 overexpression-mediated increase of autophagy in ox-LDL-treated HUVECs was abolished by 3-methyladenine (autophagy inhibitor). 3-methyladenine abrogated the impact of sFlt-1 overexpression on proliferation and apoptosis in ox-LDL-treated HUVECs. This work confirmed that overexpression of sFlt-1 activated autophagy by repressing PI3K/Akt/mTOR signaling pathway, and thus alleviated ox-LDL-induced injury of HUVECs. Therefore, this study suggests that sFlt-1 may be a potential target for AS treatment.

Rutaecarpine Prevents High Glucose-Induced Endothelial Cell Senescence Through Transient Receptor Potential Vanilloid Subtype 1/ SIRT1 Pathway.

ABSTRACT: SIRT1 functions as a longevity factor to counteract vascular aging induced by high glucose. Our previous study revealed that rutaecarpine, the natural agonist of transient receptor potential vanilloid subtype 1 (TRPV1), prevented high glucose-induced endothelial dysfunction. The present study aims to evaluate the effects of rutaecarpine on endothelial cell senescence induced by high glucose, and focus on the regulatory effect on SIRT1 expression. In cultured human umbilical vein endothelial cell (HUVEC), exposure to 33 mM high glucose for 72 hours induced cellular senescence, demonstrated as cell cycle arrest at G0/G1 phase, decreased cell viability, and increased number of senescence-associated ß-galactosidase positive senescence cells and ROS production, which were effectively attenuated by treatment with rutaecarpine (0.3, 1, and 3 µM). Furthermore, rutaecarpine upregulated longevity protein SIRT1 expression in HUVECs, accompanied by decreased level of senescence marker p21. In addition, rutaecarpine increased intracellular calcium level in HUVECs, and pretreatment with TRPV1 antagonist capsazepine, intracellular Ca2+ chelator BAPTA-AM or CaM antagonist W-7 abolished the effects of rutaecarpine on SIRT1 expression. In summary, this study shows that rutaecarpine upregulates SIRT1 expression and prevents high glucose-induced endothelial cell senescence, which is related to activation of TRPV1/[Ca2+]i/CaM signal pathway. Our findings provide evidence that rutaecarpine may be a promising candidate with a novel mechanism in prevention vascular aging in diabetes.

PGC1α Regulates the Endothelial Response to Fluid Shear Stress via Telomerase Reverse Transcriptase Control of Heme Oxygenase-1.

OBJECTIVE: Fluid shear stress (FSS) is known to mediate multiple phenotypic changes in the endothelium. Laminar FSS (undisturbed flow) is known to promote endothelial alignment to flow, which is key to stabilizing the endothelium and rendering it resistant to atherosclerosis and thrombosis. The molecular pathways responsible for endothelial responses to FSS are only partially understood. In this study, we determine the role of PGC1α (peroxisome proliferator gamma coactivator-1α)-TERT (telomerase reverse transcriptase)-HMOX1 (heme oxygenase-1) during shear stress in vitro and in vivo. Approach and Results: Here, we have identified PGC1α as a flow-responsive gene required for endothelial flow alignment in vitro and in vivo. Compared with oscillatory FSS (disturbed flow) or static conditions, laminar FSS (undisturbed flow) showed increased PGC1α expression and its transcriptional coactivation. PGC1α was required for laminar FSS-induced expression of TERT in vitro and in vivo via its association with ERRα(estrogen-related receptor alpha) and KLF (Kruppel-like factor)-4 on the TERT promoter. We found that TERT inhibition attenuated endothelial flow alignment, elongation, and nuclear polarization in response to laminar FSS in vitro and in vivo. Among the flow-responsive genes sensitive to TERT status, HMOX1 was required for endothelial alignment to laminar FSS. CONCLUSIONS: These data suggest an important role for a PGC1α-TERT-HMOX1 axis in the endothelial stabilization response to laminar FSS.

The RNA helicase Ddx21 controls Vegfc-driven developmental lymphangiogenesis by balancing endothelial cell ribosome biogenesis and p53 function.

The development of a functional vasculature requires the coordinated control of cell fate, lineage differentiation and network growth. Cellular proliferation is spatiotemporally regulated in developing vessels, but how this is orchestrated in different lineages is unknown. Here, using a zebrafish genetic screen for lymphatic-deficient mutants, we uncover a mutant for the RNA helicase Ddx21. Ddx21 cell-autonomously regulates lymphatic vessel development. An established regulator of ribosomal RNA synthesis and ribosome biogenesis, Ddx21 is enriched in sprouting venous endothelial cells in response to Vegfc-Flt4 signalling. Ddx21 function is essential for Vegfc-Flt4-driven endothelial cell proliferation. In the absence of Ddx21, endothelial cells show reduced ribosome biogenesis, p53 and p21 upregulation and cell cycle arrest that blocks lymphangiogenesis. Thus, Ddx21 coordinates the lymphatic endothelial cell response to Vegfc-Flt4 signalling by balancing ribosome biogenesis and p53 function. This mechanism may be targetable in diseases of excessive lymphangiogenesis such as cancer metastasis or lymphatic malformation.

Preliminary Evidence for IL-10-Induced ACE2 mRNA Expression in Lung-Derived and Endothelial Cells: Implications for SARS-Cov-2 ARDS Pathogenesis.

Angiotensin-converting enzyme 2 (ACE2) is a receptor for the spike protein of SARS-COV-2 that allows viral binding and entry and is expressed on the surface of several pulmonary and non-pulmonary cell types, with induction of a "cytokine storm" upon binding. Other cell types present the receptor and can be infected, including cardiac, renal, intestinal, and endothelial cells. High ACE2 levels protect from inflammation. Despite the relevance of ACE2 levels in COVID-19 pathogenesis, experimental studies to comprehensively address the question of ACE2 regulations are still limited. A relevant observation from the clinic is that, besides the pro-inflammatory cytokines, such as IL-6 and IL-1ß, the anti-inflammatory cytokine IL-10 is also elevated in worse prognosis patients. This could represent somehow a "danger signal", an alarmin from the host organism, given the immuno-regulatory properties of the cytokine. Here, we investigated whether IL-10 could increase ACE2 expression in the lung-derived Calu-3 cell line. We provided preliminary evidence of ACE2 mRNA increase in cells of lung origin in vitro, following IL-10 treatment. Endothelial cell infection by SARS-COV-2 is associated with vasculitis, thromboembolism, and disseminated intravascular coagulation. We confirmed ACE2 expression enhancement by IL-10 treatment also on endothelial cells. The sartans (olmesartan and losartan) showed non-statistically significant ACE2 modulation in Calu-3 and endothelial cells, as compared to untreated control cells. We observed that the antidiabetic biguanide metformin, a putative anti-inflammatory agent, also upregulates ACE2 expression in Calu-3 and endothelial cells. We hypothesized that IL-10 could be a danger signal, and its elevation could possibly represent a feedback mechanism fighting inflammation. Although further confirmatory studies are required, inducing IL-10 upregulation could be clinically relevant in COVID-19-associated acute respiratory distress syndrome (ARDS) and vasculitis, by reinforcing ACE2 levels.

Human urinary kininogenase reduces the endothelial injury by inhibiting Pyk2/MCU pathway.

The injury of endothelial cells is one of the initiating factors in restenosis after endovascular treatment. Human urinary kallidinogenase (HUK) is a tissue kallikrein which is used for ischemia-reperfusion injury treatment. Studies have shown that HUK may be a potential therapeutic agent to prevent stenosis after vascular injury, however, the precise mechanisms have not been fully established. This study is to investigate whether HUK can protect endothelial cells after balloon injury or H2O2-induced endothelial cell damage through the proline-rich tyrosine kinase 2 (Pyk2)/mitochondrial calcium uniporter (MCU) pathway. Intimal hyperplasia, a decrease of pinocytotic vesicles and cell apoptosis were found in the common carotid artery balloon injury and H2O2-induced endothelial cell damage, Pyk2/MCU was also up-regulated in such pathological process. HUK could prevent these injuries partially via the bradykinin B2 receptor by inhibiting Pyk2/MCU pathway, which prevented the mitochondrial damage, maintained calcium balance, and eventually inhibited cell apoptosis. Furthermore, MCU expression was not markedly increased if Pyk2 was suppressed by shRNA technique in the H2O2 treatment group, and cell viability was significantly better than H2O2-treated only. In short, our results indicate that the Pyk2/MCU pathway is involved in endothelial injury induced by balloon injury or H2O2-induced endothelial cell damage. HUK plays an protective role by inhibiting the Pyk2/MCU pathway in the endothelial injury.

The molecular pathway triggered by zirconia in endothelial cells involves epigenetic control.

The requirement to achieve natural looking restorations is one of the most challenging aspects in dentistry. Although zirconia has provided new opportunities for achieving superior aesthetics and physicochemical outcomes, very little has been achieved for its cellular and molecular performance, especially considering angiogenesis and osteogenesis. As angiogenesis is a secondary event and concomitant to osteogenesis, an indirect effect of dental implant on endothelial cells could be the release of active molecules such as those already reported affecting osteoblasts. To better address this issue, we challenged human endothelial cells (HUVECs) with zirconia-conditioned medium up to 72 h to allow analysis specific gene expression and protein pattern of mediators of epigenetic machinery in full. Our data shows involvement of zirconia in triggering intracellular signaling through MAPK-ERK activation, leading the signal to activate histone deacetylase HDAC6 likely with concomitant well-modulated DNA methylation profile by DNMTs and TETs. These signaling pathways seem to culminate in cytoskeleton rearrangement of endothelial cells, an important prerequisite to cell migration expected in angiogenesis. Collectively, this study demonstrates for the first time epigenetic-related molecular mechanism involved in endothelial cells responding to zirconia, revealing a repertoire of signaling molecules capable of executing the reprogramming process of gene expression, which are necessary to drive cell proliferation, migration, and consequently angiogenesis. This set of data can further studies using gene editing approaches to better elucidate functional roles.

Liraglutide Improves Endothelial Function via the mTOR Signaling Pathway.

BACKGROUND: Mammalian target of rapamycin (mTOR) is crucial for endothelial function. This study is aimed at assessing whether the glucagon-like peptide-1 (GLP-1) analogue liraglutide has a protective effect on endothelial function via the mTOR signaling pathway. METHODS: Human umbilical vein endothelial cells (HUVECs) were administered liraglutide (100 nM) for 0, 10, 30, 60, 720, and 1440 minutes, respectively. Then, the expression and phosphorylation levels of mTOR, mTOR-Raptor complex (mTORC1), and mTOR-Rictor complex (mTORC2) were determined by Western blot and immunoprecipitation, while mTORC1 and mTORC2 expression was blocked by siRNA-Raptor and siRNA-Rictor, respectively. Akt phosphorylation was detected by Western blot. HUVECs were then incubated with liraglutide in the absence or presence of Akt inhibitor IV. Nitric oxide (NO) release was assessed by the nitrate reductase method. Phosphorylated endothelial nitric oxide synthase (eNOS), human telomerase reverse transcriptase (hTERT), and apoptosis-related effectors were assessed for protein levels by Western blot. Telomerase activity was evaluated by ELISA. RESULTS: Sustained mTOR phosphorylation, mTORC2 formation, and mTORC2-dependent Akt phosphorylation were induced by liraglutide. In addition, eNOS phosphorylation, NO production, nuclear hTERT accumulation, and nuclear telomerase activity were enhanced by mTORC2-mediated Akt activation. Liraglutide also showed an antiapoptotic effect by upregulating antiapoptotic proteins and downregulating proapoptotic proteins in an mTORC2-Akt activation-dependent manner. CONCLUSION: Liraglutide significantly improves endothelial function, at least partially via the mTORC2/Akt signaling pathway.

Palladium (II) complex and thalidomide intercept angiogenic signaling via targeting FAK/Src and Erk/Akt/PLCγ dependent autophagy pathways in human umbilical vein endothelial cells.

The current study assessed the effects of the thalidomide and palladium (II) saccharinate complex of terpyridine on the suppression of angiogenesis-mediated cell proliferation. The viability was assessed after treatment with palladium (II) complex (1.56-100 µM) and thalidomide (0.1-400 µM) alone by using ATP assay for 48 h. Palladium (II) complex was found to inhibit growth statistically significant in a dose-dependent manner in HUVECs and promoted PARP-1 cleavage through the production of ROS. On the other hand, thalidomide did not cause any significant change in cell viability. Moreover, cell death was observed to be manifested as late apoptosis due to Annexin V/SYTOX staining after palladium (II) complex treatment however, thalidomide did not demonstrate similar results. Thalidomide and palladium (II) complex also suppressed HUVEC migration and capillary-like structure tube formation in vitro in a time-dependent manner. Palladium (II) complex (5 mg/ml) treatment showed a strong antiangiogenic effect similar to positive control thalidomide (5 mg/ml) and successfully disrupted the vasculature and reduced the thickness of the vessels compared to control (agar). Furthermore, suppression of autophagy enhanced the cell death and anti-angiogenic effect of thalidomide and palladium (II) complex. We also showed that being treated with thalidomide and palladium (II) complex inhibited phosphorylation of the signaling regulators downstream of the VEGFR2. These results provide evidence for the regulation of endothelial cell functions that are relevant to angiogenesis through the suppression of the FAK/Src/Akt/ERK1/2 signaling pathway. Our results also indicate that PLC-γ1 phosphorylation leads to activation of p-Akt and p-Erk1/2 which cause stimulation on cell proliferation at lower doses. Hence, we demonstrated that palladium (II) and thalidomide can induce cell death via the Erk/Akt/PLCγ signaling pathway and that this pathway might be a novel mechanism.

N-3-oxododecanoyl homoserine lactone exacerbates endothelial cell death by inducing receptor-interacting protein kinase 1-dependent apoptosis.

Endothelial dysfunction is associated with the initiation of sepsis-associated organ failure. Bacterial quorum-sensing molecules act as pathogen-associated molecular patterns; however, the effects of quorum-sensing molecules on endothelial cells remain less understood. This study investigated the molecular mechanisms of quorum-sensing molecule-induced cell death and their interaction with lipopolysaccharide (LPS) in human umbilical vein endothelial cells. Endothelial cells were treated with N-3-oxododecanoyl homoserine lactone (3OC12-HSL) and LPS derived from Pseudomonas aeruginosa. Treatment with 3OC12-HSL reduced cell viability in a dose-dependent manner, and cotreatment with 3OC12-HSL and LPS enhanced cell death. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling assay revealed an increase in apoptotic cell death following 3OC12-HSL treatment; furthermore, cotreatment with 3OC12-HSL and LPS enhanced apoptosis. Western blotting revealed that treatment with 3OC12-HSL activated the receptor-interacting protein kinase 1 (RIPK1) pathway, leading to an increase in the levels of cleaved caspase 8 and 3. In addition, we found that treatment with necrostatin-1, an RIPK1 inhibitor, reduced cell death and ameliorated the activation of the RIPK1-dependent apoptotic pathway in 3OC12-HSL-treated cells. In conclusion, 3OC12-HSL induced endothelial cell apoptosis via the activation of the RIPK1 pathway, independent of LPS toxicity. Inhibition of RIPK1 may act as a therapeutic option for preserving endothelial cell integrity in patients with sepsis by disrupting the mechanism by which quorum-sensing molecules mediate their toxicity.

The Protective Effect of Tetrahydroxystilbene Glucoside on High Glucose-Induced Injury in Human Umbilical Vein Endothelial Cells through the PI3K/Akt/eNOS Pathway and Regulation of Bcl-2/Bax.

Endothelial dysfunction plays a central role in the patho-genesis of diabetic vascular complications. 2,3,5,4'-tetra-hydroxystilbene-2-O-ß-D-glucoside (TSG), an active component extracted from the roots of Polygonum multiflorum Thunb, has been shown to have strong antioxidant and antiapoptotic activities. In the present study, we investigated the protective effect of TSG on apoptosis induced by high glucose in human umbilical vein endothelial cells (HUVECs) and the possible mechanisms. Our data demonstrated that TSG significantly reversed the high glucose-induced decrease in cell viability, suppressed high glucose-induced generation of intracellular reactive oxygen species (ROS), the activity of caspase-3, and decreased the percentage of apoptotic cells in a dose-dependent manner. In addition, we found that TSG not only increased the expression of Bcl-2, while decreasing Bax expression, but also activated phosphorylation of Akt and endothelial nitric oxide synthase (eNOS) with subsequent nitric oxide production and ultimately reduced high glucose-induced apoptosis. However, the antiapoptotic effects of TSG were abrogated by pretreatment of the cells with PI3K inhibitor (LY294002) or eNOS inhibitor NG-L-nitro-arginine methyl ester, respectively. These results suggest that TSG inhibits high glucose-induced apoptosis in HUVECs through inhibition of ROS production, activation of the PI3K/Akt/eNOS pathway, and upregulation of the Bcl-2/Bax ratio, and thus may demonstrate significant potential for preventing diabetic cardiovascular complications.

mTOR Inhibition Promotes Pneumonitis through Inducing Endothelial Contraction and Hyperpermeability.

Compromised endothelial-cell (EC) barrier function is a hallmark of inflammatory diseases. mTOR inhibitors, widely applied as clinical therapies, cause pneumonitis through mechanisms that are not yet fully understood. This study aimed to elucidate the EC mechanisms underlying the pathogenesis of pneumonitis caused by mTOR inhibition (mTORi). Mice with EC-specific deletion of mTOR complex components (Mtor, Rptor or Rictor) were administered LPS to induce pulmonary injury. Cultured ECs were treated with pharmacologic inhibitors, siRNA, or overexpression plasmids. EC barrier function was evaluated in vivo with Evans blue assay and in vitro by measurement of transendothelial electrical resistance and albumin flux. mTORi increased basal and TNFα-induced EC permeability, which was caused by myosin light chain (MLC) phosphorylation-dependent cell contraction. Inactivation of mTOR kinase activity by mTORi triggered PKCδ/p38/NF-κB signaling that significantly upregulated TNFα-induced MLCK (MLC kinase) expression, whereas Raptor promoted the phosphorylation of PKCα/MYPT1 independently of its interaction with mTOR, leading to suppression of MLCP (MLC phosphatase) activity. EC-specific deficiency in mTOR, Raptor or Rictor aggravated lung inflammation in LPS-treated mice. These findings reveal that mTORi induces PKC-dependent endothelial MLC phosphorylation, contraction, and hyperpermeability that promote pneumonitis.

Proteinase 3 contributes to endothelial dysfunction in an experimental model of sepsis.

In sepsis-induced inflammation, polymorphonuclear neutrophils (PMNs) contribute to vascular dysfunction. The serine proteases proteinase 3 (PR3) and human leukocyte elastase (HLE) are abundant in PMNs and are released upon degranulation. While HLE's role in inflammation-induced endothelial dysfunction is well studied, PR3's role is largely uninvestigated. We hypothesized that PR3, similarly to HLE, contributes to vascular barrier dysfunction in sepsis. Plasma PR3 and HLE concentrations and their leukocyte mRNA levels were measured by ELISA and qPCR, respectively, in sepsis patients and controls. Exogenous PR3 or HLE was applied to human umbilical vein endothelial cells (HUVECs) and HUVEC dysfunction was assessed by FITC-dextran permeability and electrical resistance. Both PR3 and HLE protein and mRNA levels were significantly increased in sepsis patients (P < 0.0001 and P < 0.05, respectively). Additionally, each enzyme independently increased HUVEC monolayer FITC-dextran permeability (P < 0.01), and decreased electrical resistance in a time- and dose-dependent manner (P < 0.001), an effect that could be ameliorated by novel treatment with carbon monoxide-releasing molecule 3 (CORM-3). The serine protease PR3, in addition to HLE, lead to vascular dysfunction and increased endothelial permeability, a hallmark pathological consequence of sepsis-induced inflammation. CORMs may offer a new strategy to reduce serine protease-induced vascular dysfunction.

METTL3 Regulates Angiogenesis by Modulating let-7e-5p and miRNA-18a-5p Expression in Endothelial Cells.

[Figure: see text].

MicroRNA-200b-3p promotes endothelial cell apoptosis by targeting HDAC4 in atherosclerosis.

BACKGROUND: Epicardial adipose tissue (EAT) shares the same microcirculation with coronary arteries through coronary arteries branches, and contributes to the development of atherosclerosis. MicroRNAs (miRNAs) are involved in the formation of atherosclerosis. However, the alteration of miRNA profile in EAT during atherosclerosis is still uncovered. METHODS: The miRNA expression profiles of EAT from non-coronary atherosclerosis disease (CON, n = 3) and coronary atherosclerosis disease (CAD, n = 5) patients was performed to detect the differentially expressed miRNA. Then the expression levels of miRNA in other CON (n = 5) and CAD (n = 16) samples were confirmed by realtime-PCR. miR-200b-3p mimic was used to overexpress the miRNA in HUVECs. The apoptosis of HUVECs cells was induced by H2O2 and ox-LDL, and detected by Annexin V/PI Staining, Caspase 3/7 activity and the expression of BCL-2 and BAX. RESULTS: 250 miRNAs were differentially expressed in EAT from CAD patients, which were associated with metabolism, extracellular matrix and inflammation process. Among the top 20 up-regulated miRNAs, the expression levels of miR-200 family members (hsa-miR-200b/c-3p, miR-141-3p and miR-429), which were rich in endothelial cells, were increased in EAT from CAD patients significantly. Upregulation of miR-200 family members was dependent on the oxidative stress. The overexpression of miR-200b-3p could promote endothelial cells apoptosis under oxidative stress by targeting HDAC4 inhibition. CONCLUSIONS: Our study suggests that EAT derived miR-200b-3p promoted oxidative stress induced endothelial cells damage by targeting HDAC4, which may provide a new and promising therapeutic target for AS.

Depletion of Arg/Abl2 improves endothelial cell adhesion and prevents vascular leak during inflammation.

Endothelial barrier disruption and vascular leak importantly contribute to organ dysfunction and mortality during inflammatory conditions like sepsis and acute respiratory distress syndrome. We identified the kinase Arg/Abl2 as a mediator of endothelial barrier disruption, but the role of Arg in endothelial monolayer regulation and its relevance in vivo remain poorly understood. Here we show that depletion of Arg in endothelial cells results in the activation of both RhoA and Rac1, increased cell spreading and elongation, redistribution of integrin-dependent cell-matrix adhesions to the cell periphery, and improved adhesion to the extracellular matrix. We further show that Arg is activated in the endothelium during inflammation, both in murine lungs exposed to barrier-disruptive agents, and in pulmonary microvessels of septic patients. Importantly, Arg-depleted endothelial cells were less sensitive to barrier-disruptive agents. Despite the formation of F-actin stress fibers and myosin light chain phosphorylation, Arg depletion diminished adherens junction disruption and intercellular gap formation, by reducing the disassembly of cell-matrix adhesions and cell retraction. In vivo, genetic deletion of Arg diminished vascular leak in the skin and lungs, in the presence of a normal immune response. Together, our data indicate that Arg is a central and non-redundant regulator of endothelial barrier integrity, which contributes to cell retraction and gap formation by increasing the dynamics of adherens junctions and cell-matrix adhesions in a Rho GTPase-dependent fashion. Therapeutic inhibition of Arg may provide a suitable strategy for the treatment of a variety of clinical conditions characterized by vascular leak.