Interleukin-6-induced JAK2/STAT3 signaling pathway in endothelial cells is suppressed by hemodynamic flow

Effects of Sodium Nitroprusside on Lipopolysaccharide-Induced Inflammation and Disruption of Blood-Brain Barrier

In various neurodegenerative conditions, inflammation plays a significant role in disrupting the blood-brain barrier (BBB), contributing to disease progression. Nitric oxide (NO) emerges as a central regulator of vascular function, with a dual role in inflammation, acting as both a pro- and anti-inflammatory molecule. This study investigates the effects of the NO donor sodium nitroprusside (SNP) in protecting the BBB from lipopolysaccharide (LPS)-induced inflammation, using bEnd.3 endothelial cells as a model system. Additionally, Raw 264.7 macrophages were employed to assess the effects of LPS and SNP on their adhesion to a bEnd.3 cell monolayer. Our results show that LPS treatment induces oxidative stress, activates the JAK2/STAT3 pathway, and increases pro-inflammatory markers. SNP administration effectively mitigates ROS production and IL-6 expression, suggesting a potential anti-inflammatory role. However, SNP did not significantly alter the adhesion of Raw 264.7 cells to bEnd.3 cells induced by LPS, probably because it did not have any effect on ICAM-1 expression, although it reduced VCAM expression. Moreover, SNP did not prevent BBB disruption. This research provides new insights into the role of NO in BBB disruption induced by inflammation.

Biomarkers in Peripartum Cardiomyopathy-What We Know and What Is Still to Be Found

Peripartum cardiomyopathy (PPCM) is a form of heart failure, often severe, that occurs in previously healthy women at the end of their pregnancy or in the first few months after delivery. In PPCM, the recovery of heart function reaches 45-50%. However, the all-cause mortality in long-term observation remains high, reaching 20% irrespective of recovery status. The incidence of PPCM is increasing globally; therefore, effort is required to clarify the pathophysiological background of the disease, as well as to discover specific diagnostic and prognostic biomarkers. The etiology of the disease remains unclear, including oxidative stress; inflammation; hormonal disturbances; endothelial, microcirculatory, cardiomyocyte and extracellular matrix dysfunction; fibrosis; and genetic mutations. Currently, antiangiogenic 16-kDa prolactin (PRL), cleaved from standard 23-kDa PRL in the case of unbalanced oxidative stress, is recognized as the main trigger of the disease. In addition, 16-kDa PRL causes damage to cardiomyocytes, acting via microRNA-146a secreted from endothelial cells as a cause of the NF-κβ pathway. Bromocriptine, which inhibits the secretion of PRL from the pituitary gland, is now the only specific treatment for PPCM. Many different phenotypes of the disease, as well as cases of non-responders to bromocriptine treatment, indicate other pathophysiological pathways that need further investigation. Biomarkers in PPCM are not well established. There is a deficiency in specific diagnostic biomarkers. Pro-brain-type natriuretic peptide (BNP) and N-terminal BNP are the best, however unspecific, diagnostic biomarkers of heart failure at the moment. Therefore, more efforts should be engaged in investigating more specific biomolecules of a diagnostic and prognostic manner such as 16-kDa PRL, galectin-3, myeloperoxidase, or soluble Fms-like tyrosine kinase-1/placental growth factor ratio. In this review, we present the current state of knowledge and future directions of exploring PPCM pathophysiology, including microRNA and heat shock proteins, which may improve diagnosis, treatment monitoring, and the development of specific treatment strategies, and consequently improve patients' prognosis and outcome.

Upregulation of PTPN1 aggravates endotoxemia-induced cardiac dysfunction through inhibiting mitophagy

OBJECTIVES

To investigate the role of protein tyrosine phosphatase non-receptor type 1 (PTPN1) in mitophagy during sepsis and its underlying mechanisms and determine the therapeutic potential of PTPN1 inhibitors in endotoxemia-induced cardiac dysfunction.

METHODS

A mouse model of endotoxemia was established by administering an intraperitoneal injection of lipopolysaccharide (LPS). The therapeutic effect of targeting PTPN1 was evaluated using its inhibitor Claramine (CLA). Mitochondrial structure and function as well as the expression of mitophagy-related proteins were evaluated. Rat H9c2 cardiomyocytes were exposed to mouse RAW264.7 macrophage-derived conditioned medium. Cryptotanshinone, a specific p-STAT3 (Y705) inhibitor, was used to confirm the role of STAT3 in PTPN1-mediated mitophagy following LPS exposure. Electrophoretic mobility shift and dual luciferase reporter assays were performed to discern the mechanisms by which STAT3 regulated the expression of PINK1 and PRKN.

RESULTS

CLA alleviated LPS-induced myocardial damage, cardiac dysfunction, and mitochondrial injury and dysfunction in the mouse heart. PTPN1 upregulation exacerbated LPS-induced mitochondrial injury and dysfunction in H9c2 cardiomyocytes, but inhibited LPS-induced mitophagy. LPS promoted the interaction between PTPN1 and STAT3 and reduced STAT3 phosphorylation at Tyr705 (Y705), which was required to inhibit mitophagy by PTPN1. Upon LPS stimulation, PTPN1 negatively regulated the transcription of PINK1 and PRKN through dephosphorylation of STAT3 at Y705. STAT3 regulated the transcription of PINK1 and PRKN by binding to STAT3-responsive elements in their promoters.

CONCLUSION

PTPN1 upregulation aggravates endotoxemia-induced cardiac dysfunction by impeding mitophagy through dephosphorylation of STAT3 at Y705 and negative regulation of PINK1 and PRKN transcription.

LINC00926 is involved in hypoxia-induced vascular endothelial cell dysfunction via miR-3194-5p regulating JAK1/STAT3 signaling pathway

Vascular endothelial cell (VEC) dysfunction is associated with the development of coronary heart disease (CHD). Long intergenic non-protein coding RNA 926 (LINC00926), a kind of long noncoding RNA (lncRNA), has been found to be abnormally expressed in CHD patients. However, the biological role of LINC00926 has not been reported. In our research, we intended to explore the regulatory mechanism of LINC00926 in hypoxia-exposed HUVEC cells (HUVECs). In our in vitro study, HUVECs were exposed under hypoxic conditions (5% O2) for 24 h. RT-qPCR and Western blotting assay were used to detect the mRNA and protein levels. CCK-8 assay, flow cytometry, transwell assay and in vitro angiogenesis assay were performed to measure cell proliferation, apoptosis, migration and tube formation, respectively. Bioinformatics analysis was applied to predict the target of LINC00926 and miR-3194-5p, which was verified by dual-luciferase reporter assays. The results showed that LINC00926 was highly expressed in CHD patients and hypoxia-exposed HUVECs. LINC00926 overexpression suppressed cell proliferation, migration and tube formation and increased cell apoptosis. MiR-3194-5p was a target of LINC00926 and can target binding to JAK1 3'UTR. LINC00926 could up-regulate JAK1 and p-STAT3 levels via miR-3194-5p. In addition, overexpressed LINC00926 suppressed cell proliferation, migration and tube formation and increased cell apoptosis via miR-3194-5p/JAK1/STAT3 axis. In summary, LINC00926 aggravated endothelial cell dysfunction via miR-3194-5p regulating JAK1/STAT3 signaling pathway in hypoxia-exposed HUVECs.

Neuroprotective effect of meglumine cyclic adenylate against ischemia/reperfusion injury via STAT3-Ser727 phosphorylation

OBJECTIVES

Ischemia/reperfusion can induce neuronal apoptosis in the brain and lead to function deficits. The activation of cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) is neuroprotective against transient cerebral ischemia. The neuroprotective mechanisms of PKA mainly involve the regulation of gene transcription via the PKA/CREB pathway. The present study aims to investigate the neuroprotective effect of meglumine cyclic adenylate, an activator of PKA, under a rat model of global cerebral ischemia/reperfusion and to reveal the underlying mechanism involving signal transducer and activator of transcription 3 (STAT3)-Ser727 phosphorylation and mitochondrion modulation.

MATERIALS AND METHODS

Male Sprague-Dawley rats were subjected to 15 min global cerebral ischemia, and meglumine cyclic adenylate was treated through tail intravenous injection 30 min before ischemia. Cresyl violet staining was used to evaluate neuron injury at 5 d of reperfusion. Western blotting was used to detect p-Ser⁷²⁷-STAT3, total STAT3, cytochrome c (Cyt c) and active caspase-3 in the tissues of hippocampal CA1 region at 6 h of reperfusion. STAT3-S727A was overexpressed in HT22 cells to reveal the significance of STAT3-Ser727 phosphorylation in the neuroprotective effect of meglumine cyclic adenylate.

RESULTS

Pretreatment with meglumine cyclic adenylate not only significantly ameliorated neuron loss in CA1 region after global cerebral ischemia but also enhanced STAT3-Ser727 phosphorylation, increased mitochondrial STAT3, and decreased cytosolic Cyt c and active caspase-3. Overexpression of STAT3-S727A in HT22 cells eliminated meglumine cyclic adenylate-induced increase of p-Ser⁷²⁷-STAT3, mitochondrial STAT3, cytosolic Cyt c and active caspase-3.

CONCLUSION

Meglumine cyclic adenylate protects neurons against ischemia/reperfusion injury via promoting p-Ser⁷²⁷-STAT3-associated mitochondrion modulation and inhibiting apoptosis pathway.

Requirement for STAT3 and its target, TFCP2L1, in self-renewal of naïve pluripotent stem cells in vivo and in vitro

We previously demonstrated gradual loss of epiblast during diapause in embryos lacking components of the LIF/IL6 receptor. Here, we explore the requirement for the downstream signalling transducer andactivator of transcription STAT3 and its target, TFCP2L1, in maintenance of naïve pluripotency. Unlike conventional markers, such as NANOG, which remains high in epiblast until implantation, both STAT3 and TFCP2L1 proteins decline during blastocyst expansion, but intensify in the embryonic region after induction of diapause, as observed visually and confirmed using our image-analysis pipeline, consistent with our previous transcriptional expression data. Embryos lacking STAT3 or TFCP2L1 underwent catastrophic loss of most of the inner cell mass during the first few days of diapause, indicating involvement of signals in addition to LIF/IL6 for sustaining naïve pluripotency in vivo. By blocking MEK/ERK signalling from the morula stage, we could derive embryonic stem cells with high efficiency from STAT3 null embryos, but not those lacking TFCP2L1, suggesting a hitherto unknown additional role for this essential STAT3 target in transition from embryo to embryonic stem cells in vitro. This article has an associated First Person interview with the first author of the paper.

Growth Hormone-Releasing Hormone in Endothelial Inflammation

The discovery of hypothalamic hormones propelled exciting advances in pharmacotherapy and improved life quality worldwide. Growth hormone-releasing hormone (GHRH) is a crucial element in homeostasis maintenance, and regulates the release of growth hormone from the anterior pituitary gland. Accumulating evidence suggests that this neuropeptide can also promote malignancies, as well as inflammation. Our review is focused on the role of that 44 - amino acid peptide (GHRH) and its antagonists in inflammation and vascular function, summarizing recent findings in the corresponding field. Preclinical studies demonstrate the protective role of GHRH antagonists against endothelial barrier dysfunction, suggesting that the development of those peptides may lead to new therapies against pathologies related to vascular remodeling (eg, sepsis, acute respiratory distress syndrome). Targeted therapies for those diseases do not exist.

Study on Mechanism of Invigorating Qi and Promoting Blood Circulation in Treatment of Angiogenesis after Myocardial Infarction Using Network Pharmacology

Objective

This article aims to explore the impact and mechanism of invigorating qi and promoting blood circulation (IQPBC) on angiogenesis after myocardial infarction (AMI) by using network pharmacology approach.

Methods

First, IQPBC was searched on the traditional Chinese medicine systems pharmacology database and analysis platform (TCMSP), and the main active ingredients and targets of IQPBC were screened and obtained. Second, by virtue of GeneCards and Online Mendelian Inheritance in Man (OMIM) databases, the targets related to AMI are screened and then obtained. Then, the intersection targets between IQPBC and AMI can be obtained by using online tool Venny 2.1.0. Third, based on the STRING database, the interaction of target proteins is established and some key targets can be analyzed and obtained. Finally, the IQPBC-AMI interaction network is constructed by using Cytoscape, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses are executed by DAVID and OmicShare databases.

Results

143 intersection targets between IQPBC and AMI are obtained. Besides, key active ingredients, namely, quercetin, tanshinone, kaempferol, and luteolin, are shown. Furthermore, AKT1, VEGFA, STAT3, HIF-1α, and other 10 key targets are obtained. A total of 752 enrichment results are acquired by using GO analysis. KEGG pathway enrichment analysis shows 241 signaling pathways, focusing on cancer, fluid shear stress and atherosclerosis, and TNF and PI3K/AKT signaling pathways.

Conclusion

This article studies the potential targets and signaling pathways of IQPBC drugs acting on AMI via the network pharmacology approach, which better illustrates the effect and mechanism, and provides some good ideas for the following mechanism research studies.

Y705 and S727 are required for the mitochondrial import and transcriptional activities of STAT3, and for regulation of stem cell proliferation

The STAT3 transcription factor, acting both in the nucleus and mitochondria, maintains embryonic stem cell pluripotency and promotes their proliferation. In this work, using zebrafish, we determined in vivo that mitochondrial STAT3 regulates mtDNA transcription in embryonic and larval stem cell niches and that this activity affects their proliferation rates. As a result, we demonstrated that import of STAT3 inside mitochondria requires Y705 phosphorylation by Jak, whereas its mitochondrial transcriptional activity, as well as its effect on proliferation, depends on the MAPK target S727. These data were confirmed using mouse embryonic stem cells: although the Y705-mutated STAT3 cannot enter mitochondria, the S727 mutation does not affect import into the organelle and is responsible for STAT3-dependent mitochondrial transcription. Surprisingly, STAT3-dependent increase of mitochondrial transcription appears to be independent from STAT3 binding to STAT3-responsive elements. Finally, loss-of-function experiments, with chemical inhibition of the JAK/STAT3 pathway or genetic ablation of stat3 gene, demonstrated that STAT3 is also required for cell proliferation in the intestine of zebrafish.

Summary: Mitochondrial import of STAT3 requires Y705 phosphorylation by Jak, whereas STAT3 mitochondrial transcriptional activity and its effect on proliferation depend on the MAPK target S727.

The JAK-STAT pathway: an emerging target for cardiovascular disease in rheumatoid arthritis and myeloproliferative neoplasms

Inflammation contributes centrally to cardiovascular diseases, and anti-inflammatory treatments can reduce cardiovascular events. The JAK-STAT pathway is an emerging target in inflammation, mainly in rheumatoid arthritis (RA) and chronic myeloproliferative neoplasms (MPNs), disorders that heighten cardiovascular risk. The aim of this study was to review the international literature on the relationship between dysregulation of the JAK-STAT pathway in RA/MPNs and cardiovascular risk and on the potential cardiovascular effects of JAK-STAT inhibitors. The JAK-STAT pathway sustains inflammatory and thrombotic events in autoimmune disorders such as RA and MPNs. Here, an imbalance exists between pro- and anti-inflammatory cytokines [increased levels of interleukin (IL)-6, IL-1-β, tumour necrosis factor-α, decreased levels of IL-10] and the over-expression of some prothrombotic proteins, such as protein kinase Cε, on the surface of activated platelets. This pathway also operates in atherosclerotic cardiovascular disease. JAK-STAT inhibitors may reduce cardiovascular events and related deaths in such conditions, but the potential of these agents requires more studies, especially with regard to cardiovascular safety, and particularly for potential prothrombotic effects. JAK-STAT inhibitors merit consideration to curb heightened cardiovascular risk in patients with RA and MPNs, with rigorous assessment of the potential benefits and risks.

Expression, regulation and clinical significance of B7-H3 on neutrophils in human gastric cancer

Neutrophils are conspicuous components of gastric cancer (GC) tumors, increasing with tumor progression and poor patient survival. However, the phenotype, regulation and clinical relevance of neutrophils in human GC are presently unknown. Most intratumoral neutrophils showed an activated CD54⁺ phenotype and expressed high level B7-H3. Tumor tissue culture supernatants from GC patients induced the expression of CD54 and B7-H3 on neutrophils in time-dependent and dose-dependent manners. Locally enriched CD54⁺ neutrophils and B7-H3⁺ neutrophils positively correlated with increased granulocyte-macrophage colony stimulating factor (GM-CSF) detection ex vivo; and in vitro GM-CSF induced the expression of CD54 and B7-H3 on neutrophils in both time-dependent and dose-dependent manners. Furthermore, GC tumor-derived GM-CSF activated neutrophils and induced neutrophil B7-H3 expression via JAK-STAT3 signaling pathway activation. Finally, intratumoral B7-H3⁺ neutrophils increased with tumor progression and independently predicted reduced overall survival. Collectively, these results suggest B7-H3⁺ neutrophils to be potential biomarkers in GC.

Overlapping and distinct biological effects of IL-6 classic and trans-signaling in vascular endothelial cells

IL-6 affects tissue protective/reparative and inflammatory properties of vascular endothelial cells (ECs). This cytokine can signal to cells through classic and trans-signaling mechanisms, which are differentiated based on the expression of IL-6 receptor (IL-6R) on the surface of target cells. The biological effects of these IL-6-signaling mechanisms are distinct and have implications for vascular pathologies. We have directly compared IL-6 classic and trans-signaling in ECs. Human ECs expressed IL-6R in culture and in situ in coronary arteries from heart transplants. Stimulation of human ECs with IL-6, to model classic signaling, triggered the activation of phosphatidylinositol 3-kinase (PI3K)-Akt and ERK1/2 signaling pathways, whereas stimulation with IL-6 + sIL-6R, to model trans-signaling, triggered activation of STAT3, PI3K-Akt, and ERK1/2 pathways. IL-6 classic signaling reduced persistent injury of ECs in an allograft model of vascular rejection and inhibited cell death induced by growth factor withdrawal. When inflammatory effects were examined, IL-6 classic signaling did not induce ICAM or CCL2 expression but was sufficient to induce secretion of CXCL8 and support transmigration of neutrophil-like cells. IL-6 trans-signaling induced all inflammatory effects studied. Our findings show that IL-6 classic and trans-signaling have overlapping but distinct properties in controlling EC survival and inflammatory activation. This has implications for understanding the effects of IL-6 receptor-blocking therapies as well as for vascular responses in inflammatory and immune conditions.

Granulocyte-Macrophage Colony-Stimulating Factor-Activated Neutrophils Express B7-H4 That Correlates with Gastric Cancer Progression and Poor Patient Survival

Neutrophils are prominent components of gastric cancer (GC) tumors and exhibit distinct phenotypes in GC environment. However, the phenotype, regulation, and clinical relevance of neutrophils in human GC are presently unknown. Here, immunohistochemistry, real-time PCR, and flow cytometry analyses were performed to examine levels and phenotype of neutrophils in samples from 41 patients with GC, and also isolated, stimulated, and/or cultured neutrophils for in vitro regulation assays. Finally, we performed Kaplan-Meier plots for overall survival by using the log-rank test to evaluate the clinical relevance of neutrophils and their subsets. In our study, neutrophils in tumor tissues were significantly higher than those in nontumor tissues and were positively associated with tumor progression but negatively correlated with GC patient survival. Most intratumoral neutrophils showed an activated CD54⁺ phenotype and expressed high-level immunosuppressive molecule B7-H4. Tumor tissue culture supernatants from GC patients induced neutrophils to express CD54 and B7-H4 in both time-dependent and dose-dependent manners. Locally enriched CD54⁺ neutrophils and B7-H4⁺ neutrophils positively correlated with increased granulocyte-macrophage colony-stimulating factor (GM-CSF) detection ex vivo, and in vitro GM-CSF induced the expression of CD54 and B7-H4 on neutrophils in a time-dependent and dose-dependent manner. Moreover, GC tumor-derived GM-CSF activated neutrophils and induced neutrophil B7-H4 expression via Janus kinase (JAK)-signal transducer and activator of transcription 3 (STAT3) signaling pathway activation. Furthermore, higher intratumoral B7-H4⁺ neutrophil percentage/number was found in GC patients with advanced tumor node metastasis stage and reduced overall survival following surgery. Our results illuminate a novel regulating mechanism of B7-H4 expression on tumor-activated neutrophils in GC, suggesting that functional inhibition of these novel GM-CSF-B7-H4 pathways may be a suitable therapeutic strategy to treat the immune tolerance feature of GC.

Deficiency in BDNF/TrkB Neurotrophic Activity Stimulates δ-Secretase by Upregulating C/EBPβ in Alzheimer's Disease

BDNF/TrkB neurotrophic signaling regulates neuronal development, differentiation, and survival, and deficient BDNF/TrkB activity underlies neurodegeneration in Alzheimer’s disease (AD). However, exactly how BDNF/TrkB participates in AD pathology remains unclear. Here, we show that deprivation of BDNF/TrkB increases inflammatory cytokines and activates the JAK2/STAT3 pathway, resulting in the upregulation of transcription factor C/EBPβ. This, in turn, results in increased expression of δ-secretase, leading to both APP and Tau fragmentation by δ-secretase and neuronal loss, which can be blocked by expression of STAT3 Y705F, knockdown of C/EBPβ, or the δ-secretase enzymatic-dead C189S mutant. Inhibition of this pathological cascade can also rescue impaired synaptic plasticity and cognitive dysfunctions. Importantly, reduction in BDNF/TrkB neurotrophic signaling is inversely coupled with an increase in JAK2/STAT3, C/EBPβ, and δ-secretase escalation in human AD brains. Therefore, our findings provide a mechanistic link between BDNF/TrkB reduction, C/EBPβ upregulation, δ-secretase activity, and Aβ and Tau alterations in murine brains.

Deficient BDNF/TrkB activity underlies AD pathogenesis. Wang et al. report that deprivation of BDNF/TrkB increases inflammatory cytokines and activates the JAK2/STAT3 pathway, resulting in the upregulation of C/EBPβ/AEP signaling. Reduction of BDNF is inversely coupled with the aforementioned pathway in AD brains. Inhibition of JAK2/STAT3/C/EBPβ/AEP prevents BDNF-depletion-mediated pathology.

Bone interface modulates drug resistance in breast cancer bone metastasis

Metastatic breast cancer cells on arriving at bone site interact with the bone cells to influence their growth, proliferation, and chemoresistance. There are currently no effective therapeutics available in the clinic for bone metastases. Many existing anti-cancer therapeutics are ineffective at the metastatic bone site due to a lack of accurate models of breast cancer bone metastasis for drug screening. Here, we report the development of an effective in vitro model using osteogenically differentiated human mesenchymal stem cells (MSCs) and human breast cancer cells on 3D nanoclay scaffolds as a testbed for screening drugs. Our results demonstrate that breast cancer cells grown in 3D bone-mimetic scaffolds exhibited altered physiological and biochemical properties, including tumoroids formation, elevated levels of cytokine such as IL-6, and its downstream effector-mediated inhibition of apoptosis and upregulation of multidrug transporters proteins, leading to drug resistance against paclitaxel. Most importantly, Signal Transducer and Activator of Transcription 3 (STAT3), a potential biomarker for chemoresistance in many cancers, was activated in the 3D breast cancer bone metastasis model. Thus, our data suggest that 3D bone-mimetic nanoclay scaffolds-based in vitro tumor model is a promising testbed for screening new therapeutics for breast cancer bone metastasis where bone interface governs drug resistance in breast cancer cells.

Iron promotes breast cancer cell migration via IL-6/JAK2/STAT3 signaling pathways in a paracrine or autocrine IL-6-rich inflammatory environment

Iron overload can act as catalyst for the formation of free radicals, which may promote oxidant-mediated breast carcinogenesis. However, the association between iron and breast cancer has not been comprehensively elucidated. In this study, we found that iron overload upregulated the inflammatory cytokine interleukin-6 (IL-6) expression to activate Janus Kinases 2/Signal Transducer and Activator of Transcription 3 (JAK2/STAT3) signaling in triple negative breast cancer (TNBC) MDA-MB-231 cell lines, resulting in epithelial-mesenchymal transition (EMT) and cancer cell migration, but it had no effects on the estrogen receptor (ER)-positive breast cancer MCF-7 cells. However, in the presence of exogenous IL-6, iron overload could also dramatically induce an autocrine IL-6 loop in ER-positive MCF-7 cells to active IL-6/JAK2/STAT3 signaling, resulting in enhanced EMT and cell motility. In vivo animal studies also identified that iron overload promoted the progression of low metastatic breast cancer tumorigenicity and lung metastasis following the addition of exogenous IL-6. This study suggested that iron overload could result in inducible IL-6 expression leading to promote malignant transformation of breast cancer cells in an paracrine or autocrine IL-6-rich inflammatory environment. Anti-inflammation and iron depletion therapy would be an effective therapeutic/preventive strategy for suppressing breast cancer progression.

Global Transcriptional Profiling Reveals Novel Autocrine Functions of Interleukin 6 in Human Vascular Endothelial Cells

Background

Interleukin 6 (IL6) is a multifunctional cytokine produced by various cells, including vascular endothelial cells. IL6 has both pro- and non-/anti-inflammatory functions, and the response to IL6 is dependent on whether it acts via the membrane-bound IL6 receptor α (IL6Rα) (classic signaling) or the soluble form of the receptor (transsignaling). As human endothelial cells produce IL6 and at the same time express IL6Rα, we hypothesized that IL6 may have autocrine functions.

Methods

Knockdown of IL6 in cultured human endothelial cells was performed using siRNA. Knockdown efficiency was evaluated using ELISA. RNA sequencing was employed to characterize the transcriptional consequence of IL6 knockdown, and Ingenuity Pathway Analysis was used to further explore the functional roles of IL6.

Results

Knockdown of IL6 in cultured endothelial cells resulted in a 84-92% reduction in the release of IL6. Knockdown of IL6 resulted in dramatic changes in transcriptional pattern; knockdown of IL6 in the absence of soluble IL6Rα (sIL6Rα) led to differential regulation of 1915 genes, and knockdown of IL6 in the presence of sIL6Rα led to differential regulation of 1967 genes (fold change 1.5, false discovery rate < 0.05). Pathway analysis revealed that the autocrine functions of IL6 in human endothelial cells are mainly related to basal cellular functions such as regulation of cell cycle, signaling, and cellular movement. Furthermore, we found that knockdown of IL6 activates functions related to adhesion, binding, and interaction of endothelial cells, which seem to be mediated mainly via STAT3.

Conclusion

In this study, a large number of novel genes that are under autocrine regulation by IL6 in human endothelial cells were identified. Overall, our data indicate that IL6 acts in an autocrine manner to regulate basal cellular functions, such as cell cycle regulation, signaling, and cellular movement, and suggests that the autocrine functions of IL6 in human endothelial cells are mediated via IL6 classic signaling.

MiR-599 regulates LPS-mediated apoptosis and inflammatory responses through the JAK2/STAT3 signalling pathway via targeting ROCK1 in human umbilical vein endothelial cells

MicroRNA plays an integral role in the development of atherosclerosis. Our study aimed to investigate the roles of miR-599 in lipopolysaccharide (LPS)-induced endothelial damage in human umbilical vein endothelial cells (HUVECs). HUVECs were transfected with a miR-599 mimic and negative control, and then exposed to LPS. The expression of miR-599 was detected by quantitative real time-polymerase chain reaction (RT-qPCR). Cell viability was analyzed by CCK-8 assay and trypan blue exclusion assay; the formation of DNA fragments was tested by Cell Death Detection ELISA Plus kit; the incidence of apoptosis was detected by flow cytometry; the expression of p53 and cleaved-caspase 3 (c-caspase 3) was evaluated by western blot. Moreover, the mRNA levels and concentrations of tumour necrosis factor (TNF)-α, interleukin (IL)-6, ICAM-1 and VCAM-1 were assayed by RT-qPCR and ELISA. The results showed that overexpression of miR-599 increased cell viability, reduced DNA fragments, the incidence of apoptosis, as well as the protein levels of p53 and c-caspase 3 in the presence of LPS. TNF-α, IL-6, ICAM-1 and VCAM-1 mRNA levels and concentrations were also decreased upon miR-599 upregulation. In addition, the dual luciferase reporter assay demonstrated that ROCK1 is a direct target of miR-599. MiR-599 overexpression inhibited ROCK1 expression. Induced expression of ROCK1 reversed the roles of miR-599 in apoptosis and inflammation. The gain function of miR-599 function inhibited activation of the JAK2/STAT3 signalling pathway, which was abrogated by overexpression of ROCK1. Taken together, our results indicate that miR-599 attenuates LPS-caused cell apoptosis and inflammatory responses through the JAK2/STAT3 signalling pathway via targeting ROCK1.

Genetic Predisposition to High-Altitude Pulmonary Edema

Background: Exaggerated pulmonary arterial hypertension (PAH) is a hallmark of high-altitude pulmonary edema (HAPE). The objective of this study was therefore to investigate genetic predisposition to HAPE by analyzing PAH candidate genes in a HAPE-susceptible (HAPE-S) family and in unrelated HAPE-S mountaineers. Materials and Methods: Eight family members and 64 mountaineers were clinically and genetically assessed using a PAH-specific gene panel for 42 genes by next-generation sequencing. Results: Two otherwise healthy family members, who developed re-entry HAPE at 3640 m during childhood, carried a likely pathogenic missense mutation (c.1198T>G p.Cys400Gly) in the Janus Kinase 2 (JAK2) gene. One of them progressed to a mild form of PAH at the age of 23 years. In two of the 64 HAPE-S mountaineers likely pathogenic variants have been detected, one missense mutation in the Cytochrome P1B1 gene, and a deletion in the Histidine-Rich Glycoprotein (HRG) gene. Conclusions: This is the first study identifying an inherited missense mutation of a gene related to PAH in a family with re-entry HAPE showing a progression to borderline PAH in the index patient. Likely pathogenic variants in 3.1% of HAPE-S mountaineers suggest a genetic predisposition in some individuals that might be linked to PAH signaling pathways.

Inhibition of JAK2/STAT3 and activation of caspase‑9/3 are involved in KYS05090S‑induced apoptosis in ovarian cancer cells

To overcome the poor prognosis of patients with ovarian cancer, attempting to target ovarian cancer with effective antitumor compounds has been conducted for numerous years. Although the 3,4‑dihydroquinazoline derivative KYS05090S was known to exert antitumor effects in A549 and ovarian cancer cells by inhibition of T‑type Ca2+ channels, the complete underlying antitumor mechanism of this compound remains unclear. Thus, in the present study, the potential apoptotic mechanism of KYS05090S was elucidated in SKOV3 and OVCAR3 ovarian cancer cells. KYS05090S exerted significant cytotoxicity in SKOV3 and OVCAR3 ovarian cancer cells, and also increased the number of apoptotic bodies, and the number of terminal deoxynucleotidyl transferase dUTP nick end labeling positive cells and the sub‑G1 population as a feature of apoptosis. Consistently, KYS05090S induced cleavage of poly(ADP‑ribose) polymerase and caspase‑9/3 in ovarian cancer cells. Notably, KYS05090S attenuated the expression of anti‑apoptotic proteins, including cyclin D1 and B‑cell lymphoma‑2 (Bcl‑2), and reduced the phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) in ovarian cancer cells. Additionally, KYS05090S blocked the nuclear translocation of STAT3 and suppressed the signaling of JAK2/STAT3 in interleukin‑6‑treated SKOV3 cells, as a STAT3 activator. Overall, these observations indicated that inhibition of JAK2/STAT3 signaling and activation of caspase‑9/3 are critically involved in the effects of KYS05090S on apoptosis in ovarian cancer types, and the compound may be beneficial as a potent antitumor agent.

Ang-(1-7) protects HUVECs from high glucose-induced injury and inflammation via inhibition of the JAK2/STAT3 pathway

Angiotensin (Ang)‑1‑7, which is catalyzed by angiotensin‑converting enzyme 2 (ACE2) from angiotensin‑II (Ang‑II), exerts multiple biological and pharmacological effects, including cardioprotective effects and endothelial protection. The Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway has been demonstrated to be involved in diabetes‑associated cardiovascular complications. The present study hypothesized that Ang‑(1‑7) protects against high glucose (HG)‑induced endothelial cell injury and inflammation by inhibiting the JAK2/STAT3 pathway in human umbilical vein endothelial cells (HUVECs). HUVECs were treated with 40 mmol/l glucose (HG) for 24 h to establish a model of HG‑induced endothelial cell injury and inflammation. Protein expression levels of p‑JAK2, t‑JAK2, p‑STAT3, t‑STAT3, NOX‑4, eNOS and cleaved caspase‑3 were tested by western blotting. CCK‑8 assay was performed to assess cell viability of HUVECs. Apoptotic cell death was analyzed by Hoechst 33258 staining. Mitochondrial membrane potential (MMP) was obtained using JC‑1. Superoxide dismutase (SOD) activity was tested by SOD assay kit. Interleukin (IL)‑1β, IL‑10, IL‑12 and TNF‑α levels in culture media were tested by ELISA. The findings demonstrated that exposure of HUVECs to HG for 24 h induced injury and inflammation. This injury and inflammation were significantly ameliorated by pre‑treatment of cells with either Ang‑(1‑7) or AG490, an inhibitor of the JAK2/STAT3 pathway, prior to exposure of the cells to HG. Exposure of the cells to HG also increased the phosphorylation of JAK2/STAT3 (p‑JAK2 and p‑STAT3). Increased activation of the JAK2/STAT3 pathway was attenuated by pre‑treatment with Ang‑(1‑7). To the best of our knowledge, the findings from the present study provided the first evidence that Ang‑(1‑7) protects against HG‑induced injury and inflammation by inhibiting activation of the JAK2/STAT3 pathway in HUVECs.

Laminar shear stress promotes mitochondrial homeostasis in endothelial cells

Vascular endothelial cells (ECs) are constantly subjected to flow-induced shear stress that is crucial for endothelial functions. Laminar shear stress (LSS) exerts atheroprotection to ECs. Mitochondrial homeostasis is essential for cellular survival. However, the effects of LSS on mitochondrial homeostasis in ECs remain unclear. Mitochondrial homeostasis in ECs exposed to LSS was examined. Cultured human umbilical vein ECs were subjected to LSS (12 dynes/cm² ) generated by a parallel-plate flow chamber system. ECs subjected to LSS demonstrated an increment of mitochondria in tubular form coupled with the increase of fusion proteins (Mfn2, OPA1) and the decrease of fission protein (Fis1). An increase of both long- and short- OPA1 along with a higher protease YME1L level were observed. LSS triggered a rapid phosphorylation on S637 but a decrease on S616 of fission-controlled protein Drp1. Consistently, Drp1 translocation to mitochondria was decreased in sheared ECs, suggesting that LSS promotes mitochondrial fusion. Enhanced mitochondrial biogenesis in sheared ECs was shown by the increase of mitochondrial mass and its regulatory proeins (PGC1α, TFAM, Nrf1). LSS enhances the expression of mitochondrial antioxidant enzymes and improves mitochondrial functions indicated by the increase of mitochondrial membrane potential (ΔΨm) and ATP generation. TNFα treatment decreased mitochondrial tubular network and its functions in ECs. LSS mitigated TNFα-induced mitochondrial impairments in ECs. Our results clearly indicate that LSS promotes mitochondrial homeostasis and attenuates inflammation-induced mitochondrial impairments in ECs. Our results provide novel insights into the manner of mitochondrial dynamics and functions modulated by LSS that contribute to endothelial integrity.

Angiogenic gene signature in human pancreatic cancer correlates with TGF-beta and inflammatory transcriptomes

Pancreatic ductal adenocarcinomas (PDACs) are hypovascular, but overexpress pro-angiogenic factors and exhibit regions of microvasculature. Using RNA-seq data from The Cancer Genome Atlas (TCGA), we previously reported that ∼12% of PDACs have an angiogenesis gene signature with increased expression of multiple pro-angiogenic genes. By analyzing the recently expanded TCGA dataset, we now report that this signature is present in ∼35% of PDACs but that it is mostly distinct from an angiogenesis signature present in pancreatic neuroendocrine tumors (PNETs). These PDACs exhibit a transcriptome that reflects active TGF-β signaling, and up-regulation of several pro-inflammatory genes, and many members of JAK signaling pathways. Moreover, expression of SMAD4 and HDAC9 correlates with endothelial cell abundance in PDAC tissues. Concomitantly targeting the TGF-β type I receptor (TβRI) kinase with SB505124 and JAK1-2 with ruxolitinib suppresses JAK1 phosphorylation and blocks proliferative cross-talk between human pancreatic cancer cells (PCCs) and human endothelial cells (ECs), and these anti-proliferative effects were mimicked by JAK1 silencing in ECs. By contrast, either inhibitor alone does not suppress their enhanced proliferation in 3D co-cultures. These findings suggest that targeting both TGF-β and JAK1 signaling could be explored therapeutically in the 35% of PDAC patients whose cancers exhibit an angiogenesis gene signature.

Eudesmane-type sesquiterpenoids from Salvia plebeia inhibit IL-6-induced STAT3 activation

Seven eudesmane-type sesquiterpenoid lactones and the known plebeiolide C were isolated from an ethanol-soluble extract of the aerial parts of Salvia plebeia R. Br. Their structures were determined via NMR and MS, and their absolute configurations were elucidated using ECD, and X-ray crystallographic analysis, as well as the modified Mosher ester method. All isolates were evaluated for their inhibitory effects on IL6-induced STAT3 promoter activation in stably transfected Hep3B cells. Of these isolates, eudebeiolide D exhibited an inhibitory effect with the IC50 value of 1.1 μM.

MicroRNA-mediated mechanisms of the cellular stress response in atherosclerosis

Atherosclerosis is characterised by the accumulation of lipid-laden macrophages in atherosclerotic lesions and occurs preferentially at arterial branching points, which are prone to inflammation during hyperlipidaemic stress. The increased susceptibility at branching sites of arteries is attributable to poor adaptation of arterial endothelial cells to disturbed blood flow. In the past 5 years, several studies have provided mechanistic insights into the regulatory roles of microRNAs (miRNAs) in inflammatory activation, proliferation, and regeneration of endothelial cells during this maladaptive process. The intercellular transfer of vesicle-bound miRNAs contributes to arterial homeostasis, and the combinatorial effect of multiple miRNAs controls the unresolved inflammation orchestrated by macrophages in atherosclerotic lesions. In this Review, we highlight the miRNA-dependent regulation of the endothelial phenotype and the proliferative reserve that occurs in response to altered haemodynamic conditions as a prerequisite for atherogenic inflammation. In particular, we discuss the regulation of transcriptional modules by miRNAs and the protective role of complementary strand pairs, which encompasses remote miRNA signalling. In addition, we review the roles of miRNA tandems and describe the relevance of RNA target selection and competition to the behaviour of lesional macrophages. Elucidating miRNA-mediated regulatory mechanisms can aid the development of novel diagnostic and therapeutic strategies for atherosclerosis.

Shear-induced endothelial mechanotransduction: the interplay between reactive oxygen species (ROS) and nitric oxide (NO) and the pathophysiological implications

Hemodynamic shear stress, the blood flow-generated frictional force acting on the vascular endothelial cells, is essential for endothelial homeostasis under normal physiological conditions. Mechanosensors on endothelial cells detect shear stress and transduce it into biochemical signals to trigger vascular adaptive responses. Among the various shear-induced signaling molecules, reactive oxygen species (ROS) and nitric oxide (NO) have been implicated in vascular homeostasis and diseases. In this review, we explore the molecular, cellular, and vascular processes arising from shear-induced signaling (mechanotransduction) with emphasis on the roles of ROS and NO, and also discuss the mechanisms that may lead to excessive vascular remodeling and thus drive pathobiologic processes responsible for atherosclerosis. Current evidence suggests that NADPH oxidase is one of main cellular sources of ROS generation in endothelial cells under flow condition. Flow patterns and magnitude of shear determine the amount of ROS produced by endothelial cells, usually an irregular flow pattern (disturbed or oscillatory) producing higher levels of ROS than a regular flow pattern (steady or pulsatile). ROS production is closely linked to NO generation and elevated levels of ROS lead to low NO bioavailability, as is often observed in endothelial cells exposed to irregular flow. The low NO bioavailability is partly caused by the reaction of ROS with NO to form peroxynitrite, a key molecule which may initiate many pro-atherogenic events. This differential production of ROS and RNS (reactive nitrogen species) under various flow patterns and conditions modulates endothelial gene expression and thus results in differential vascular responses. Moreover, ROS/RNS are able to promote specific post-translational modifications in regulatory proteins (including S-glutathionylation, S-nitrosylation and tyrosine nitration), which constitute chemical signals that are relevant in cardiovascular pathophysiology. Overall, the dynamic interplay between local hemodynamic milieu and the resulting oxidative and S-nitrosative modification of regulatory proteins is important for ensuing vascular homeostasis. Based on available evidence, it is proposed that a regular flow pattern produces lower levels of ROS and higher NO bioavailability, creating an anti-atherogenic environment. On the other hand, an irregular flow pattern results in higher levels of ROS and yet lower NO bioavailability, thus triggering pro-atherogenic effects.

STAT3 oligonucleotide inhibits tumor angiogenesis in preclinical models of squamous cell carcinoma

PURPOSE

Signal transducer and activator of transcription 3 (STAT3) has shown to play a critical role in head and neck squamous cell carcinoma (HNSCC) and we have recently completed clinical trials of STAT3 decoy oligonucleotide in patients with recurrent or metastatic HNSCC. However, there is limited understanding of the role of STAT3 in modulating other aspects of tumorigenesis such as angiogenesis. In this study, we aimed to examine the effects of STAT3 decoy oligonucleotide on tumor angiogenesis.

EXPERIMENTAL DESIGN

A STAT3 decoy oligonucleotide and small interfering RNA (siRNA) were used to inhibit STAT3 in endothelial cells in vitro and in vivo. The biochemical effects of STAT3 inhibition were examined in conjunction with the consequences on proliferation, migration, apoptotic staining, and tubule formation. Additionally, we assessed the effects of STAT3 inhibition on tumor angiogenesis using murine xenograft models.

RESULTS

STAT3 decoy oligonucleotide decreased proliferation, induces apoptosis, decreased migration, and decreased tubule formation of endothelial cells in vitro. The STAT3 decoy oligonucleotide also inhibited tumor angiogenesis in murine tumor xenografts. Lastly, our data suggest that the antiangiogenic effects of STAT3 decoy oligonucleotide were mediatedthrough the inhibition of both STAT3 and STAT1.

CONCLUSIONS

The STAT3 decoy oligonucleotidewas found to be an effective antiangiogenic agent, which is likely to contribute to the overall antitumor effects of this agent in solid tumors.Taken together with the previously demonstrated antitumor activity of this agent, STAT3 decoy oligonucleotide represents a promising single agent approach to targeting both the tumor and vascular compartments in various malignancies.

Inhibition of microRNA-92a prevents endothelial dysfunction and atherosclerosis in mice

RATIONALE FOR STUDY

MicroRNAs (miRNAs) are small noncoding RNAs that regulate protein expression at post-transcriptional level. We hypothesized that a specific pool of endothelial miRNAs could be selectively regulated by flow conditions and inflammatory signals, and as such be involved in the development of atherosclerosis.

OBJECTIVE

To identify miRNAs, called atheromiRs, which are selectively regulated by shear stress and oxidized low-density lipoproteins (oxLDL), and to determine their role in atherogenesis.

METHODS AND RESULTS

Large-scale miRNA profiling in HUVECs identified miR-92a as an atheromiR candidate, whose expression is preferentially upregulated by the combination of low shear stress (SS) and atherogenic oxLDL. Ex vivo analysis of atheroprone and atheroprotected areas of mouse arteries and human atherosclerotic plaques demonstrated the preferential expression of miR-92a in atheroprone low SS regions. In Ldlr(-/-) mice, miR-92a expression was markedly enhanced by hypercholesterolemia, in particular in atheroprone areas of the aorta. Assessment of endothelial inflammation in gain- and loss-of-function experiments targeting miR-92a expression revealed that miR-92a regulated endothelial cell activation by oxLDL, more specifically under low SS conditions, which was associated with modulation of Kruppel-like factor 2 (KLF2), Kruppel-like factor 4 (KLF4), and suppressor of cytokine signaling 5. miR-92a expression was regulated by signal transducer and activator of transcription 3 in SS- and oxLDL-dependent manner. Furthermore, specific in vivo blockade of miR-92a expression in Ldlr(-/-) mice reduced endothelial inflammation and altered the development of atherosclerosis, decreasing plaque size and promoting a more stable lesion phenotype.

CONCLUSIONS

Upregulation of miR-92a by oxLDL in atheroprone areas promotes endothelial activation and the development of atherosclerotic lesions. Therefore, miR-92a antagomir seems as a new atheroprotective therapeutic strategy.

Hepatitis C virus core protein stimulates fibrogenesis in hepatic stellate cells involving the obese receptor

Hepatitis C virus core protein (HCVcp), which is secreted by infected cells, is reported as an immunomodulator in immune cells. However, the effects of HCVcp on hepatic stellate cells (HSCs), the key cells in liver fibrosis, still remain unclear. In this study, we investigated the effects of HCVcp on obese receptor (ObR) related downstream signaling pathways and fibrogenic gene expression in HSCs. LX-2, a human HSC line, was incubated with HCVcp. Inhibitors and short interfering RNAs were used to interrogate the mechanisms of HCVcp action on HSCs. HCVcp (20-100 ng/ml) concentration-dependently stimulated α-smooth muscle actin (α-SMA) protein expression and mRNA expression of α-SMA, procollagen α2(I) and TGF-β1 genes, with a plateau of 220% of controls at 100 ng/ml. HCVcp induced mRNA and protein expression of ObR. Blocking of Ob-Rb with a neutralizing antibody inhibited phosphorylation of signal transducer and activator of transcription 3 (STAT3) and AMPKα stimulated by HCVcp. Furthermore, knockdown of Ob-Rb down-regulated HCVcp-induced STAT3, AKT, and AMPKα phosphorylation, and reversed HCVcp-suppressed mRNA expression of matrix metalloproteinase (MMP)-1, peroxisome proliferator-activated receptor (PPAR)γ and sterol regulatory element binding protein-1c (SREBP-1c) genes. AMPKα signaling blockade reversed HCVcp-suppressed SREBP-1c mRNA expression. HCVcp stimulated reactive oxygen species formation and gp91(phox) (a component of NADPH oxidase) protein expression, together with AKT phosphorylation, leading to suppression of PPARγ and SREBP-1c genes. Our results provide a new finding that HCVcp induced ObR-dependent Janus Kinase (JAK) 2-STAT3, AMPKα, and AKT signaling pathways and modulated downstream fibrogenetic gene expression in HSCs.

Cytokines are systemic effectors of lymphatic function in acute inflammation

The response of the lymphatic system to inflammatory insult and infection is not completely understood. Using a near-infrared fluorescence (NIRF) imaging system to noninvasively document propulsive function, we noted the short-term cessation of murine lymphatic propulsion as early as 4h following LPS injection. Notably, the effects were systemic, displaying bilateral lymphatic pumping cessation after a unilateral insult. Furthermore, IL-1β, TNF-α, and IL-6, cytokines that were found to be elevated in serum during lymphatic pumping cessation, were shown separately to acutely and systemically decrease lymphatic pulsing frequency and velocity following intradermal administration. Surprisingly, marked lymphatic vessel dilation and leakiness were noted in limbs contralateral to IL-1β intradermal administration, but not in ipsilateral limbs. The effects of IL-1β on lymphatic pumping were abated by pre-treatment with an inhibitor of inducible nitric oxide synthase, L-NIL (N-iminoethyl-L-lysine). The results suggest that lymphatic propulsion is systemically impaired within 4h of acute inflammatory insult, and that some cytokines are major effectors of lymphatic pumping cessation through nitric oxide-mediated mechanisms. These findings may help in understanding the actions of cytokines as mediators of lymphatic function in inflammatory and infectious states.

Suppression of JAK2/STAT3 signaling reduces end-to-end arterial anastomosis induced cell proliferation in common carotid arteries of rats

BACKGROUND

JAK2/STAT3 pathway was reported to play an essential role in the neointima formation after vascular intima injury. However, little is known regarding this pathway to the whole layer injury after end-to-end arterial anastomosis (AA). Here, we investigated the role of JAK2/STAT3 pathway in common carotid arterial (CCA) anastomosis-induced cell proliferation, phenotypic change of vascular smooth muscle cells (VSMCs) and re-endothelialization.

METHODS

CCAs of adult male Wistar rats were resected at 3, 7, 14, and 30 days after end-to-end CCA anastomosis. Activation of JAK2/STAT3 pathway was detected by Western blotting and Immunofluorescence, and expression of proliferating cell nuclear antigen (PCNA) was detected by Q-PCR and Western blotting. Under the treatment with AG490 (a JAK2 inhibitor), protein levels of JAK2, STAT3 and PCNA, morphological changes of artery, phenotypic change of VSMCs, and re-endothelialization were measured by Western blotting, H&E, Q-PCR, and Evans blue staining respectively.

RESULTS

The protein levels of p-JAK2, p-STAT3, and PCNA were up-regulated, peaked on the 7(th) day in the vessel wall after AA. AG490 down-regulated the levels of p-JAK2, p-STAT3, and PCNA on the 7(th)-day-group, resulting in reduced vessel wall proliferation on the 7(th) and 14(th) day after AA. Besides, AG490 switched the phenotypic change of VSMCs after AA representing inhibited mRNA levels of synthetic phase markers (osteopoitin and SMemb) and up-regulated contractile phase markers (ASMA, SM2 and SM22α). Furthermore, AG490 did not affect the re-endothelialization process on all indicated time points after AA (the 3(rd), 7(th), 14(th), and 30(th) day).

CONCLUSION

Our study indicated that JAK2/STAT3 signaling pathway played an important role on cell proliferation of the injured vessel wall, and probably a promising target for the exploration of drugs increasing the patency or reducing the vascular narrowness after AA.

The many faces of interleukin-6: the role of IL-6 in inflammation, vasculopathy, and fibrosis in systemic sclerosis

Interleukin-6 is currently attracting significant interest as a potential therapeutic target in systemic sclerosis (SSc). In this paper, the biology of interleukin-6 is reviewed, and the evidence for interleukin-6 dysregulation in SSc is explored. The role of inteleukin-6 classical and trans signalling pathways in SSc relevant phenomena such as chronic inflammation, autoimmunity, endothelial cell dysfunction, and fibrogenesis is discussed. The existing evidence that interventions designed to block interleukin-6 signalling are of therapeutic relevance in SSc is evaluated.

Effects of cold exposure and shear stress on endothelial nitric oxide synthase activation

Endothelial nitric oxide synthase (eNOS) is the primary enzyme that produces nitric oxide (NO), which plays an important role in blood vessel relaxation. eNOS activation is stimulated by various mechanical forces, such as shear stress. Several studies have shown that local cooling of the human finger causes strong vasoconstriction, followed after several minutes by cold-induced vasodilation (CIVD). However, the role played by endothelial cells (ECs) in blood vessel regulation in respond to cold temperatures is not fully understood. In this study, we found that low temperature alone does not significantly increase or decrease eNOS activation in ECs. We further found that the combination of shear stress with temperature change leads to a significant increase in eNOS activation at 37°C and 28°C, and a decrease at 4°C. These results show that ECs play an important role in blood vessel regulation under shear stress and low temperature.

Effects of disturbed flow on vascular endothelium: pathophysiological basis and clinical perspectives

Vascular endothelial cells (ECs) are exposed to hemodynamic forces, which modulate EC functions and vascular biology/pathobiology in health and disease. The flow patterns and hemodynamic forces are not uniform in the vascular system. In straight parts of the arterial tree, blood flow is generally laminar and wall shear stress is high and directed; in branches and curvatures, blood flow is disturbed with nonuniform and irregular distribution of low wall shear stress. Sustained laminar flow with high shear stress upregulates expressions of EC genes and proteins that are protective against atherosclerosis, whereas disturbed flow with associated reciprocating, low shear stress generally upregulates the EC genes and proteins that promote atherogenesis. These findings have led to the concept that the disturbed flow pattern in branch points and curvatures causes the preferential localization of atherosclerotic lesions. Disturbed flow also results in postsurgical neointimal hyperplasia and contributes to pathophysiology of clinical conditions such as in-stent restenosis, vein bypass graft failure, and transplant vasculopathy, as well as aortic valve calcification. In the venous system, disturbed flow resulting from reflux, outflow obstruction, and/or stasis leads to venous inflammation and thrombosis, and hence the development of chronic venous diseases. Understanding of the effects of disturbed flow on ECs can provide mechanistic insights into the role of complex flow patterns in pathogenesis of vascular diseases and can help to elucidate the phenotypic and functional differences between quiescent (nonatherogenic/nonthrombogenic) and activated (atherogenic/thrombogenic) ECs. This review summarizes the current knowledge on the role of disturbed flow in EC physiology and pathophysiology, as well as its clinical implications. Such information can contribute to our understanding of the etiology of lesion development in vascular niches with disturbed flow and help to generate new approaches for therapeutic interventions.

Progressive endothelial cell damage in an inflammatory model of pulmonary hypertension

Monocrotaline (MCT)-induces progressive disruption of endothelial cell membrane and caveolin-1 leading to pulmonary arterial hypertension (PAH). Treatment instituted early rescues caveolin-1 and attenuates PAH. To test the hypothesis that the poor response to therapy in established PAH is due to progressive deregulation of multiple signaling pathways, the authors investigated time-dependent changes in the expression of caveolin-1, gp130, PY-STAT3, Bcl-xL, and the molecules involved in NO signaling pathway (endothelial nitric oxide synthase [eNOS], heat sock protein 90 [HSP90], Akt, soluble guanylate cyclase [sGC] alpha1 and beta1 subunits). PAH and right ventricular hypertrophy (RVH) were observed at 2 and 3 weeks. Progressive loss of endothelial caveolin-1 and sGC (alpha1, beta1), PY-STAT3 activation, and Bcl-xL expression were observed at 1 to 3 weeks post-MCT. The expression of gp130 increased at 48 hours and 1 week, with a subsequent loss at 2 and 3 weeks. The expression of eNOS increased at 48 hours and 1 week post-MCT, with a significant loss at 3 weeks. The expression of HSP90 and Akt decreased at 2 and 3 weeks post-MCT concomitant with PAH. Thus, MCT induces progressive loss of membrane and cytosolic proteins, resulting in the activation of proliferative and antiapoptotic factors, and deregulation of NO signaling leading to PAH. An attractive therapeutic approach to treat PAH may be an attempt to rescue endothelial cell membrane integrity.

Functional analyses reveal the greater potency of preadipocytes compared with adipocytes as endothelial cell activator under normoxia, hypoxia, and TNFalpha exposure

Obesity is associated with a state of chronic low-grade inflammation. Immune cells accumulate in white adipose tissue (WAT). The vascular endothelium plays an interactive role in these infiltration and inflammatory processes. Mature and hypertrophic adipocytes are considered as the major adipogenic cell type secreting proinflammatory cytokines in WAT. In contrast, the proinflammatory capacity of preadipocytes and their role in endothelial cell activation have been neglected so far. To gain new insights into this molecular and cellular cross-talk, we examined the proinflammatory expression and secretion of normoxia, hypoxia, and TNFalpha-treated human preadipocytes and adipocytes (SGBS cells) and their impact on human microvascular endothelial cell (HMEC-1) function. In this study, stimulation of HMEC-1 with conditioned media (CM) from preadipocytes increased endothelial ICAM-1 expression and monocyte adhesion but not adipocyte-CM. After hypoxia and TNFalpha stimulation of SGBS cells, adipocyte-CM induced and preadipocyte-CM enhanced the monocyte adhesion. Concordantly, the expression of proinflammatory adipokines was considerably higher in preadipocytes than in adipocytes. SGBS-CM upregulated the phosphorylation of three MAPK pathways, STAT1/3, and c-Jun in HMEC-1, whereas the NF-kappaB pathway was not affected. Inhibitor experiments showed that monocyte/endothelial cell-cell adhesion and endothelial ICAM-1 expression was JNK and JAK-1/STAT1/3 pathway dependent and revealed IL-6 as a major mediator in CM increasing monocyte/endothelial cell-cell adhesion via the STAT1/3 pathway. Our study shows that preadipocytes rather than adipocytes operate as potent activators of endothelial cells. This can be enhanced in preadipocytes and induced in adipocytes by TNFalpha and hypoxia in a manner similar to what may occur in WAT in the etiology of obesity.

Flow-Mediated Signaling Modulates Endothelial Cell Phenotype

The focal development of atherosclerosis in the vascular tree may be explained in part by the local nature of blood flow. Bifurcations and branching points, prone to early atherogenesis, experience disturbed and oscillatory flow, whereas straight vascular regions, resistant to atherosclerosis, are exposed to steady laminar flow. A large number of studies suggest that the antiatherosclerotic effects of laminar flow are in part due to the ability of flow to modulate endothelial cell phenotype. Under steady laminar flow, endothelial cells generate molecules that promote a vasoactive, anticoagulant, anti-inflammatory, and growth-inhibitory surface. In contrast, disturbed flow induces a proliferative, prothrombotic, and adhesive phenotype. Endothelial cells are able to sense the variations of flow via mechanosensitive cell surface proteins and to transduce these signals via intracellular pathways to transcription factors in the nucleus leading to phenotypic changes. This review summarizes the "outside-in" signaling events initiated by flow that modulate endothelial cell phenotype.

Induction of the cytoprotective enzyme heme oxygenase-1 by statins is enhanced in vascular endothelium exposed to laminar shear stress and impaired by disturbed flow

In addition to cholesterol-lowering properties, statins exhibit lipid-independent immunomodulatory, anti-inflammatory actions. However, high concentrations are typically required to induce these effects in vitro, raising questions concerning therapeutic relevance. We present evidence that endothelial cell sensitivity to statins depends upon shear stress. Using heme oxygenase-1 expression as a model, we demonstrate differential heme oxygenase-1 induction by atorvastatin in atheroresistant compared with atheroprone sites of the murine aorta. In vitro, exposure of human endothelial cells to laminar shear stress significantly reduced the statin concentration required to induce heme oxygenase-1 and protect against H(2)O(2)-mediated injury. Synergy was observed between laminar shear stress and atorvastatin, resulting in optimal expression of heme oxygenase-1 and resistance to oxidative stress, a response inhibited by heme oxygenase-1 small interfering RNA. Moreover, treatment of laminar shear stress-exposed endothelial cells resulted in a significant fall in intracellular cholesterol. Mechanistically, synergy required Akt phosphorylation, activation of Kruppel-like factor 2, NF-E2-related factor-2 (Nrf2), increased nitric-oxide synthase activity, and enhanced HO-1 mRNA stability. In contrast, heme oxygenase-1 induction by atorvastatin in endothelial cells exposed to oscillatory flow was markedly attenuated. We have identified a novel relationship between laminar shear stress and statins, demonstrating that atorvastatin-mediated heme oxygenase-1-dependent antioxidant effects are laminar shear stress-dependent, proving the principle that biomechanical signaling contributes significantly to endothelial responsiveness to pharmacological agents. Our findings suggest statin pleiotropy may be suboptimal at disturbed flow atherosusceptible sites, emphasizing the need for more specific therapeutic agents, such as those targeting Kruppel-like factor 2 or Nrf2.

Shear flow increases S-nitrosylation of proteins in endothelial cells

AIMS

Endothelial cells (ECs) constantly exposed to shear flow increase nitric oxide production via the activation of endothelial nitric oxide synthase. Nitric oxide-mediated S-nitrosylation has recently been identified as an important post-translational modification that may alter signalling and/or protein function. S-nitrosylation of endothelial proteins after shear flow treatment has not been fully explored. In this study, the CyDye switch method was utilized to examine S-nitrosylated proteins in ECs after exposure to shear flow.

METHODS AND RESULTS

Human umbilical vein ECs were subjected to shear flow for 30 min, and S-nitrosylated proteins were detected by the CyDye switch method. In principle, free thiols in proteins become blocked by alkylation, the S-nitrosylated bond is reduced by ascorbate, and then CyDye labels proteins. Proteins that separately labelled with Cy3 or Cy5 were mixed and subjected to two-dimensional gel electrophoresis for further analysis. More than 100 S-nitrosoproteins were detected in static and shear-treated ECs. Among these, 12 major proteins of heterogeneous function showed a significant increase in S-nitrosylation following shear flow. The S-nitrosylated residues in tropomyosin and vimentin, which were localized in the hydrophobic motif of each protein, were identified as Cys170 and Cys328, respectively.

CONCLUSION

Post-translational S-nitrosylation of proteins in ECs can be detected by a reliable CyDye switch method. This flow-induced S-nitrosylation of endothelial proteins may be essential for the adaptation and remodelling of ECs under flow conditions.

Interleukin-6 modulates the expression of the bone morphogenic protein receptor type II through a novel STAT3-microRNA cluster 17/92 pathway

Dysregulated expression of bone morphogenetic protein receptor type II (BMPR2) is a pathogenetic hallmark of pulmonary hypertension. Downregulation of BMPR2 protein but not mRNA has been observed in multiple animal models mimicking the disease, indicating a posttranscriptional mechanism of regulation. Because microRNAs (miRNAs) regulate gene expression mainly through inhibition of target gene translation, we hypothesized that miRNAs may play a role in the modulation of BMPR2. Performing a computational algorithm on the BMPR2 gene, several miRNAs encoded by the miRNA cluster 17/92 (miR-17/92) were retrieved as potential regulators. Ectopic overexpression of miR-17/92 resulted in a strong reduction of the BMPR2 protein, and a reporter gene system showed that BMPR2 is directly targeted by miR-17-5p and miR-20a. By stimulation experiments, we found that the miR-17/92 cluster is modulated by interleukin (IL)-6, a cytokine involved in the pathogenesis of pulmonary hypertension. Because IL-6 signaling is mainly mediated by STAT3 (signal transducer and activator of transcription 3), the expression of STAT3 was knocked down by small interfering RNA, which abolished the IL-6-mediated expression of miR-17/92. Consistent with these data, we found a highly conserved STAT3-binding site in the promoter region of the miR-17/92 gene (C13orf25). Promoter studies confirmed that IL-6 enhances transcription of C13orf25 through this distinct region. Finally, we showed that persistent activation of STAT3 leads to repressed protein expression of BMPR2. Taken together, we describe here a novel STAT3-miR-17/92-BMPR2 pathway, thus providing a mechanistic explanation for the loss of BMPR2 in the development of pulmonary hypertension.

Regulation of shear-induced nuclear translocation of the Nrf2 transcription factor in endothelial cells

Background

Vascular endothelial cells (ECs) constantly experience fluid shear stresses generated by blood flow. Laminar flow is known to produce atheroprotective effects on ECs. Nrf2 is a transcription factor that is essential for the antioxidant response element (ARE)-mediated induction of genes such as heme-oxygenase 1 (HO-1). We previously showed that fluid shear stress increases intracellular reactive oxygen species (ROS) in ECs. Moreover, oxidants are known to stimulate Nrf2. We thus examined the regulation of Nrf2 in cultured human ECs by shear stress.

Results

Exposure of human umbilical vein endothelial cells (HUVECs) to laminar shear stress (12 dyne/cm²) induced Nrf2 nuclear translocation, which was inhibited by a phosphatidylinositol 3-kinase (PI3K) inhibitor, a protein kinase C (PKC) inhibitor, and an antioxidant agent N-acetyl cysteine (NAC), but not by other protein kinase inhibitors. Therefore, PI3K, PKC, and ROS are involved in the signaling pathway that leads to the shear-induced nuclear translocation of Nrf2. We also found that shear stress increased the ARE-binding activity of Nrf2 and the downstream expression of HO-1.

Conclusion

Our data suggest that the atheroprotective effect of laminar flow is partially attributed to Nrf2 activation which results in ARE-mediated gene transcriptions, such as HO-1 expression, that are beneficial to the cardiovascular system.

Acute hypoxia enhances proteins' S-nitrosylation in endothelial cells

Hypoxia-induced responses are frequently encountered during cardiovascular injuries. Hypoxia triggers intracellular reactive oxygen species/nitric oxide (NO) imbalance. Recent studies indicate that NO-mediated S-nitrosylation (S-NO) of cysteine residue is a key posttranslational modification of proteins. We demonstrated that acute hypoxia to endothelial cells (ECs) transiently increased the NO levels via endothelial NO synthase (eNOS) activation. A modified biotin-switch method coupled with Western blot on 2-dimensional electrophoresis (2-DE) demonstrated that at least 11 major proteins have significant increase in S-NO after acute hypoxia. Mass analysis by CapLC/Q-TOF identified those as Ras-GTPase-activating protein, protein disulfide-isomerase, human elongation factor-1-delta, tyrosine 3/tryptophan 5-monooxygenase activating protein, and several cytoskeleton proteins. The S-nitrosylated cysteine residue on tropomyosin (Cys 170) and beta-actin (Cys 285) was further verified with the trypsic peptides analyzed by MASCOT search program. Further understanding of the functional relevance of these S-nitrosylated proteins may provide a molecular basis for treating ischemia-induced vascular disorders.

Nitroalkenes suppress lipopolysaccharide-induced signal transducer and activator of transcription signaling in macrophages: a critical role of mitogen-activated protein kinase phosphatase 1

Nitration products of unsaturated fatty acids are formed via NO-dependent oxidative reactions and appear to be a new class of endogenous antiinflammatory mediators. Nitroalkene derivatives of nitrated linoleic acid (LNO(2)) and nitrated oleic acid (OA-NO(2)) alleviate inflammatory responses in macrophages, but the underlying mechanisms remain to be fully defined. Herein we report that LNO(2) and OA-NO(2) suppress proinflammatory signal transducer and activator of transcription (STAT) signaling in macrophages. In RAW264.7 cells, a murine macrophage cell line, LNO(2) and OA-NO(2) inhibited the lipopolysaccharide (LPS)-induced STAT1 phosphorylation and the STAT1-dependent transcriptional activity, thereby suppressing expression of its target gene such as iNOS and MCP-1. The nitroalkene-mediated inhibition of STAT1 activity was not affected by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (a NO scavenger), GW9662 (a peroxisome proliferator-activated receptor-gamma-specific antagonist) or glutathione (an antioxidant), suggesting an underlying mechanism independent of NO, peroxisome proliferator-activated receptor-gamma, or thio-nitralkylation. In contrast, LNO(2) or OA-NO(2) alone up-regulated both mRNA and protein levels of MAPK phosphatase 1 (MKP-1) and strongly augmented the LPS-induced MKP-1 protein expression. Knockdown of MKP-1 by MKP-1 small interfering RNA enhanced the LPS-induced STAT1 phosphorylation, suggesting that MKP-1 acts as a negative regulator for LPS-induced STAT signaling. In addition, the nitroalkene-mediated inhibitory effects on STAT1 phosphorylation, iNOS expression, and MCP-1 secretion were also largely attenuated by the MKP-1 small interfering RNA approach. Taken together, our data demonstrate that nitroalkenes inhibit proinflammatory STAT signaling through inducting MKP-1 in macrophages.

Sequential activation of JAKs, STATs and xanthine dehydrogenase/oxidase by hypoxia in lung microvascular endothelial cells

Xanthine dehydrogenase/oxidase (XDH/XO) is associated with various pathological conditions related to the endothelial injury. However, the molecular mechanism underlying the activation of XDH/XO by hypoxia remains largely unknown. In this report, we determined whether the Janus kinases (JAKs) and signal transducers and activators of transcription (STATs) signaling pathway is involved in hypoxia-induced activation of XDH/XO in primary cultures of lung microvascular endothelial cells (LMVEC). We found that hypoxia significantly increased interleukin 6 (IL6) production in a time-dependent manner in LMVEC. Hypoxia also markedly augmented phosphorylation/activation of JAKs (JAK1, JAK2 and JAK3) and the JAK downstream effectors STATs (STAT3 and STAT5). Hypoxia-induced activation of STAT3 was blocked by IL6 antibodies, the JAK inhibitor AG490 and the suppressor of cytokine signaling 3 (SOCS3), implying that hypoxia-promoted IL6 secretion activates the JAK/STAT pathway in LMVEC. Phosphorylation and DNA-binding activity of STAT3 were also inhibited by the p38 MAPK inhibitor SB203580 and the phosphatidylinositol 3-kinase inhibitor LY294002, suggesting that multiple signaling pathways involved in STAT activation by hypoxia. Importantly, hypoxia promoted XDH/XO activation in LMVEC, which was markedly reversed by inhibiting the JAK-STAT pathway using IL6 antibodies, AG490 and SOCS3. These data demonstrated that JAKs, STATs and XDH/XO were sequentially activated by hypoxia. These data provide the first evidence indicating that the JAK-STAT pathway is involved in hypoxia-mediated XDH/XO activation in LMVEC.

Pulmonary Artery Hypertension

Pulmonary artery hypertension (PAH) is a sequela of a number of disparate diseases, often with a fatal consequence. Endothelial dysfunction is considered to be an early event during the development of PAH. Impaired availability of bioactive nitric oxide (NO) is a key underlying feature in most forms of clinical and experimental PAH. NO, generated by catalytic activity of endothelial NO synthase (eNOS) on l-arginine, modulates vascular function and structure. For optimal activation, eNOS is targeted to caveolae, the flask-shaped invaginations found on the surface of plasmalemmal membrane of a variety of cells, including endothelial cells. Caveolin-1, the major coat protein of caveolae, regulates eNOS activity. Evidence is accumulating to suggest that caveolin-1 may play a significant role in the pathogenesis of PAH. This review is intended to summarize recent findings indicating a role for caveolin-1 and caveolin-1/eNOS interrelationship in PAH.

Mechanisms of induction of endothelial cell E-selectin expression by smooth muscle cells and its inhibition by shear stress

E-selectin is a major adhesion molecule expressed by endothelial cells (ECs), which are exposed to shear stress and neighboring smooth muscle cells (SMCs). We investigated the mechanisms underlying the modulation of EC E-selectin expression by SMCs and shear stress. SMC coculture induced rapid and sustained increases in expression of E-selectin and phosphorylation of interleukin-1 (IL-1) receptor-associated kinase glycoprotein-130, as well as the downstream mitogen-activated protein kinases (MAPKs) and Akt. By using specific inhibitors, dominant-negative mutants, and small interfering RNA, we demonstrated that activations of c-Jun-NH(2)-terminal kinase (JNK) and p38 of the MAPK pathways are critical for the coculture-induced E-selectin expression. Gel shifting and chromatin immunoprecipitation assays showed that SMC coculture increased the nuclear factor-kappaB (NF-kappaB)-promoter binding activity in ECs; inhibition of NF-kappaB activation by p65-antisense, lactacystin, and N-acetyl-cysteine blocked the coculture-induced E-selectin promoter activity. Protein arrays and blocking assays using neutralizing antibodies demonstrated that IL-1beta and IL-6 produced by EC/SMC cocultures are major contributors to the coculture induction of EC signaling and E-selectin expression. Preshearing of ECs at 12 dynes/cm(2) inhibited the coculture-induced EC signaling and E-selectin expression. Our findings have elucidated the molecular mechanisms underlying the SMC induction of EC E-selectin expression and the shear stress protection against this SMC induction.