Interleukin-6 upregulates expression of KDR and stimulates proliferation of human cerebrovascular smooth muscle cells

Role of inflammatory mediators in intracranial aneurysms: A review

The formation, growth, and rupture of intracranial aneurysms (IAs) involve hemodynamics, blood pressure, external stimuli, and a series of hormonal changes. In addition, inflammatory response causes the release of a series of inflammatory mediators, such as IL, TNF-α, MCP-1, and MMPs, which directly or indirectly promote the development process of IA. However, the specific role of these inflammatory mediators in the pathophysiological process of IA remains unclear. Recently, several anti-inflammatory, lipid-lowering, hormone-regulating drugs have been found to have a potentially protective effect on reducing IA formation and rupture in the population. These therapeutic mechanisms have not been fully elucidated, but we can look for potential therapeutic targets that may interfere with the formation and breakdown of IA by studying the relevant inflammatory response and the mechanism of IA formation and rupture involved in inflammatory mediators.

Preliminary Mechanism of Glial Maturation Factor β on Pulmonary Vascular Remodeling in Pulmonary Arterial Hypertension

Recent evidence suggests that glia maturation factor β (GMFβ) is important in the pathogenesis of pulmonary arterial hpertension (PAH), but the underlying mechanism is unknown. To clarify whether GMFβ can be involved in pulmonary vascular remodeling and to explore the role of the IL-6-STAT3 pathway in this process, the expression of GMFβ in PAH rats is examined and the expression of downstream molecules including periostin (POSTN) and interleukin-6 (IL-6) is measured using real-time quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. The location and expression of POSTN is also tested in PAH rats using immunofluorescence. It is proved that GMFβ is upregulated in the lungs of PAH rats. Knockout GMFβ alleviated the MCT-PAH by reducing right ventricular systolic pressure (RVSP), mean pulmonary arterial pressure (mPAP), and pulmonary vascular remodeling. Moreover, the inflammation of the pulmonary vasculature is ameliorated in PAH rats with GMFβ absent. In addition, the IL-6-STAT3 signaling pathway is activated in PAH; knockout GMFβ reduced POSTN and IL-6 production by inhibiting the IL-6-STAT3 signaling pathway. Taken together, these findings suggest that knockout GMFβ ameliorates PAH in rats by inhibiting the IL-6-STAT3 signaling pathway.

Understanding the pathogenesis of brain arteriovenous malformation: genetic variations, epigenetics, signaling pathways, and immune inflammation

Brain arteriovenous malformation (BAVM) is a rare but serious cerebrovascular disease whose pathogenesis has not been fully elucidated. Studies have found that epigenetic regulation, genetic variation and their signaling pathways, immune inflammation, may be the cause of BAVM the main reason. This review comprehensively analyzes the key pathways and inflammatory factors related to BAVMs, and explores their interplay with epigenetic regulation and genetics. Studies have found that epigenetic regulation such as DNA methylation, non-coding RNAs and m6A RNA modification can regulate endothelial cell proliferation, apoptosis, migration and damage repair of vascular malformations through different target gene pathways. Gene defects such as KRAS, ACVRL1 and EPHB4 lead to a disordered vascular environment, which may promote abnormal proliferation of blood vessels through ERK, NOTCH, mTOR, Wnt and other pathways. PDGF-B and PDGFR-β were responsible for the recruitment of vascular adventitial cells and smooth muscle cells in the extracellular matrix environment of blood vessels, and played an important role in the pathological process of BAVM. Recent single-cell sequencing data revealed the diversity of various cell types within BAVM, as well as the heterogeneous expression of vascular-associated antigens, while neutrophils, macrophages and cytokines such as IL-6, IL-1, TNF-α, and IL-17A in BAVM tissue were significantly increased. Currently, there are no specific drugs targeting BAVMs, and biomarkers for BAVM formation, bleeding, and recurrence are lacking clinically. Therefore, further studies on molecular biological mechanisms will help to gain insight into the pathogenesis of BAVM and develop potential therapeutic strategies.

Passive smoking may be associated with bleeding of cerebral arteriovenous malformation in non-smoking women: a retrospective analysis

BACKGROUND

Smoking has been considered to be a risk factor for cardiovascular disease, cancer, depression and other diseases in previous reports, and active smoking is considered to be a risk factor for hemorrhagic stroke. In addition, a retrospective study showed that male smokers were at increased risk of bleeding from arteriovenous malformation (AVM), compared with non-smokers. However, the effect of passive smoking on rupturing of cerebral AVM in non-smoking women has not been addressed.

OBJECTIVE

This study aimed to assess the impact of tobacco exposure on AVM bleeding risk in non-smoking women.

METHODS

A total of 393 non-smoking women diagnosed with AVM were included. They were divided into a bleeding group (205 women) and a non-bleeding group (188 women). We conducted univariate and multivariate analysis on these two groups. In univariate analysis, risk factors that might be related to AVM bleeding were analyzed. In multivariate analysis, the relationship between passive smoking and AVM rupture was analyzed by correcting confounding factors.

RESULTS

Multivariate analysis showed that the proportion of passive smoking was statistically different between the bleeding group and the non-bleeding group (OR = 1.609; CI = 1.031-2.509; p = 0.036).

CONCLUSION

Passive smoking may increase the risk of AVM bleeding in non-smoking women. This increased risk may be related to the inflammatory response, vascular wall damage, hemodynamic disorders, changes in atherosclerosis and changes in gene expression caused by passive smoking.

CircRNA-miRNA interactions in atherogenesis

Atherosclerosis is the major cause of coronary artery disease (CAD) which includes unstable angina, myocardial infarction, and heart failure. The onset of atherogenesis, a process of atherosclerotic lesion formation in the intima of arteries, is driven by lipid accumulation, a vicious cycle of reactive oxygen species (ROS)-induced oxidative stress and inflammatory reactions leading to endothelial cell (EC) dysfunction, vascular smooth muscle cell (VSMC) activation, and foam cell formation which further fuel plaque formation and destabilization. In recent years, there is a surge in the number of publications reporting the involvement of circular RNAs (circRNAs) in the pathogenesis of cardiovascular diseases, cancers, and metabolic syndromes. These studies have advanced our understanding on the biological functions of circRNAs. One of the most common mechanism of action of circRNAs reported is the sponging of microRNAs (miRNAs) by binding to the miRNAs response element (MRE), thereby indirectly increases the transcription of their target messenger RNAs (mRNAs). Individual networks of circRNA-miRNA-mRNA associated with atherogenesis have been extensively reported, however, there is a need to connect these findings for a complete overview. This review aims to provide an update on atherogenesis-related circRNAs and analyze the circRNA-miRNA-mRNA interactions in atherogenesis. The atherogenic mechanisms and clinical relevance of each atherogenesis-related circRNA were systematically discussed for better understanding of the knowledge gap in this area.

Circular RNA circLIFR regulates the proliferation, migration, invasion and apoptosis of human vascular smooth muscle cells via the miR-1299/KDR axis

Dysfunction of vascular smooth muscle cells (VSMCs) plays a critical role in the development of intracranial aneurysm (IA). Here, we explored the detailed role and mechanism of circular RNA (circRNA) LIF receptor subunit alpha (circLIFR, circ_0072309) in human umbilical artery smooth muscle cells (HUASMCs). CircLIFR, microRNA (miR)-1299 and kinase insert domain receptor (KDR) expression levels were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot assays. Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8) and 5-Ethynyl-2'-Deoxyuridine (EdU) assays. Cell migration was gauged by wound-healing and transwell assays. Cell invasion and apoptosis were detected by transwell assay and flow cytometry, respectively. Direct relationship between miR-1299 and circLIFR or KDR was verified by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. CircLIFR and KDR were down-regulated and miR-1299 was up-regulated in the artery wall tissues and ASMCs of IA patients. Enforced expression of circLIFR enhanced HUASMC proliferation, migration, invasion, and impeded apoptosis. Mechanistically, circLIFR directly targeted miR-1299, and miR-1299 was a downstream mediator of circLIFR in regulating the proliferation, migration, invasion and apoptosis of HUASMCs. KDR was identified as a direct and functional target of miR-1299 in HUASMCs. Furthermore, circLIFR was a post-transcriptional regulator of KDR expression through miR-1299. Our findings suggest that circLIFR, an underexpressed circRNA in IA, can regulate the proliferation, migration, invasion and apoptosis of HUASMCs depending on the miR-1299/KDR axis.

Molecular Signature of Brain Arteriovenous Malformation Hemorrhage: A Systematic Review

BACKGROUND

The mechanisms of brain arteriovenous malformation (bAVM) development, formation, and progress are still poorly understood. By gaining more knowledge about the molecular signature of bAVM in relation to hemorrhage, we might be able to find biomarkers associated with this serious complication, which can function as a goal for further research and can be a potential target for gene therapy.

AIMS

To provide a comprehensive overview of the molecular signature of bAVM-related hemorrhage We conducted a systematic review, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, of articles published in Embase, Medline, Cochrane central, Scopus, and Chinese databases (CNKI, Wanfang).

SUMMARY OF REVIEW

Our search identified 3944 articles, of which 3108 remained after removal of duplicates. After title, abstract, and full-text screening, 31 articles were included for analysis. The results show an overview of molecular characteristics. Several genetic polymorphisms are identified that increase the risk of bAVM rupture by increasing the expression of certain inflammatory cytokines (interleukin [IL]-6, IL-17A, IL-1β, and tumor necrosis factor-α), NOTCH pathways, matrix metalloproteinase-9, and vascular endothelial growth factor-α.

CONCLUSIONS

Several molecular factors are associated with the risk of bAVM-related hemorrhage. These factors are associated with increased inflammation on the cellular level and changes in the endothelium leading to instability of the vessel wall. Further investigation of these biomarkers regarding hemorrhage rates, together with their relationship with noninvasive diagnostic methods, should be a goal of future studies to improve the patient specific risk estimation and future treatment options.

Neurovascular inflammation in the pathogenesis of brain arteriovenous malformations

Brain arteriovenous malformations (bAVM) arise as congenital or sporadic focal lesions with a significant risk for intracerebral hemorrhage (ICH). A wide range of interindividual differences is present in the onset, progression, and severity of bAVM. A growing body of gene expression and polymorphism-based research studies support the involvement of localized inflammation in bAVM disease progression and rupture. In this review article, we analyze the altered responses of neural, vascular, and immune cell types that contribute to the inflammatory process, which exacerbates the pathophysiological progression of vascular dysmorphogenesis in bAVM lesions. The cumulative effect of inflammation in bAVM development is orchestrated by various genetic moderators and inflammatory mediators. We also discuss the potential therapies for the treatment of brain AVM by targeting the inflammatory processes and mediators. Elucidating the precise role of inflammation in the bAVM growth and hemorrhage would open novel avenues for noninvasive and effectual causal therapy that may complement the current therapeutic strategies.

The impact of preradiosurgery embolization on intracranial arteriovenous malformations: a matched cohort analysis based on de novo lesion volume

OBJECTIVE

The benefits and risks of pre-stereotactic radiosurgery (SRS) embolization have been reported in different studies. The goal of this study was to compare the long-term outcome of arteriovenous malformations (AVMs) treated with and without pre-SRS embolization.

METHODS

A database including 1159 patients with AVMs who underwent SRS was reviewed. The embolized group was selected by including AVMs with pre-SRS embolization, maximal diameter > 30 mm, and estimated volume > 8 ml. The nonembolized group was defined as AVMs treated by SRS alone with matched de novo nidus volume. Outcomes including incidences of favorable clinical outcome (obliteration without hemorrhage, cyst formation, worsening, or new seizures), obliteration, adverse effects, and angioarchitectural complexity were evaluated.

RESULTS

The study cohort comprised 17 patients in the embolized group (median AVM volume 17.0 ml) and 35 patients in the nonembolized group (median AVM volume 13.1 ml). The rates of obliteration (embolized cohort: 33%, 44%, and 56%; nonembolized cohort: 32%, 47%, and 47% at 4, 6, and 10 years, respectively) and favorable outcome were comparable between the 2 groups. However, the embolized group had a significantly higher incidence of repeat SRS (41% vs 23%, p = 0.012) and total procedures (median number of procedures 4 vs 1, p < 0.001), even with a significantly higher margin dose delivered at the first SRS (23 Gy vs 17 Gy, p < 0.001). The median angioarchitectural complexity score was reduced from 7 to 5 after embolization. Collateral flow and neovascularization were more frequently observed in the embolized nonobliterated AVMs.

CONCLUSIONS

Both embolization plus SRS and SRS alone were effective therapies for moderately large (8-39 ml) AVMs. Even with a significantly higher prescription dose at the time of initial SRS, the embolized group still required more procedures to reach final obliteration. The presence of collateral flow and neovascularization could be risk factors for a failure to obliterate following treatment.

Is smoking a risk factor for bleeding in adult men with cerebral arteriovenous malformations? A single-center regression study from China

OBJECTIVE

To assess whether smoking increases the risk of bleeding in patients with cerebral arteriovenous malformations (CAVM).

MATERIAL AND METHODS

According to our research plan, 385 CAVM patients admitted to Beijing Tiantan Hospital from December 2015 to January 2018 were included in this study, including 210 bleeding patients and 175 non-bleeding patients. We divided patients into three subgroups of current smokers, ex-smokers (those who quit smoking for one year or more) and non-smokers. The relationship between smoking and the risk of CAVM rupture was assessed by univariate and multivariate regression analysis.

RESULTS

Multivariate regression analysis showed that there was a statistically significant difference between current smoker and non-smoker (OR = 1.87, p = 0.019). Among the covariates of the multivariate regression analysis, the location, combined with blood flow-related intracranial aneurysms and size were related to the risk of CAVM bleeding.

CONCLUSION

Current smoking may increase the risk of CAVM bleeding; however, there was no significant correlation between ex-smoking and CAVM bleeding.

Mechanistic regulation of SPHK1 expression and translocation by EMAP II in pulmonary smooth muscle cells

Phosphorylation of sphingosine by sphingosine kinase 1 (SPHK1) produces the bioactive sphingolipid sphingosine-1-phosphate (S1P), a microvascular and immuno-modulator associated with vascular remodeling in pulmonary arterial hypertension (PAH). The low intracellular concentration of S1P is under tight spatial-temporal control. Molecular mechanisms that mediate S1P burden and S1P regulation of vascular remodeling are poorly understood. Similarities between two early response pro-inflammatory cytokine gene transcript activation profiles, S1P and Endothelial Monocyte Activating Polypeptide II (EMAP II), suggested a strategic link between their signaling pathways. We determined that EMAP II triggers a bimodal phosphorylation, transcriptional regulation and membrane translocation of SPHK1 through a common upstream process in both macrophages and pulmonary artery smooth muscle cells (PASMCs). EMAP II initiates a dual function of ERK1/2: phosphorylation of SPHK1 and regulation of the transcription factor EGR1 that induces expression of SPHK1. Activated ERK1/2 induces a bimodal phosphorylation of SPHK1 which reciprocally increases S1P levels. This identified common upstream signaling mechanism between a protein and a bioactive lipid initiates cell specific downstream signaling representing a multifactorial mechanism that contributes to inflammation and PASMC proliferation which are cardinal histopathological phenotypes of PAH.

Decreased expression of circ_0020397 in intracranial aneurysms may be contributing to decreased vascular smooth muscle cell proliferation via increased expression of miR-138 and subsequent decreased KDR expression

Dysfunction of vascular smooth muscle cells (VSMCs) mediates intracranial aneurysm (IA). KDR is reported to alleviate IA progression via promoting VSMC proliferation, while the upstream regulators are still unclear. Arterial wall tissues at the aneurysm site from 12 patients were obtained. The real-time PCR result indicated that circRNA_0020397 was down-regulated, but miR-138 was up-regulated in artery wall tissues and cells of IA. Overexpressed circRNA_0020397 promoted proliferation of human umbilical artery SMCs. MiR-138 negatively regulated KDR via binding with 3'UTR of KDR mRNA. The expression of circRNA_0020397 was negatively correlated with miR-138. In conclusion, our findings demonstrated that decreased expression of circRNA_0020397 in IA may contribute to the decreased VSMC proliferation via increasing miR-138 expression and subsequently decreasing KDR expression.

Interleukin-6 in pulmonary artery hypertension

Interleukin (IL)-6 is a pleiotropic cytokine, playing an important role in various pathological conditions, such as inflammatory, infectious, and neoplastic disorders. The casual relationship between IL-6 levels and development of pulmonary artery hypertension (PAH) has been elusive. Based on comprehensive retrieval of pertinent literature of recent two decades, this article aims to give an overview of the impact of IL-6 on PAH development in view of both clinical and experimental aspects. Results showed that IL-6 was overexpressed in all types of PAH in both human and animal models. The elevated IL-6 levels were closely related to right ventricular (RV) dysfunction and predicted poor prognosis and mortality of PAH patients. Several IL-6-regulated signaling pathways including transforming growth factor (TGF)-β/bone morphogenetic protein signaling pathway are involved in PAH development. IL-6 antagonizing agents are effective in ameliorating the symptoms and improving the RV function of PAH patients.

Evaluation of flow-modulation approaches in ventricular assist devices using an in-vitro endothelial cell culture model

BACKGROUND

Continuous-flow ventricular assist devices (CF-VADs) produce non-physiologic flow with diminished pulsatility, which is a major risk factor for development of adverse events, including gastrointestinal (GI) bleeding and arteriovenous malformations (AVMs). Introduction of artificial pulsatility by modulating CF-VAD flow has been suggested as a potential solution. However, the levels of pulsatility and frequency of CF-VAD modulation necessary to prevent adverse events are currently unknown and need to be evaluated.

METHODS

The purpose of this study was to use human aortic endothelial cells (HAECs) cultured within an endothelial cell culture model (ECCM) to: (i) identify and validate biomarkers to determine the effects of pulsatility; and (ii) conclude whether introduction of artificial pulsatility using flow-modulation approaches can mitigate changes in endothelial cells seen with diminished pulsatile flow. Nuclear factor erythroid 2-related factor 2 (Nrf-2)-regulated anti-oxidant genes and proteins and the endothelial nitric oxide synthase/endothelin-1 (eNOS/ET-1) signaling pathway are known to be differentially regulated in response to changes in pulsatility.

RESULTS

Comparison of HAECs cultured within the ECCM (normal pulsatile vs CF-VAD) with aortic wall samples from patients (normal pulsatile [n = 5] vs CF-VADs [n = 5]) confirmed that both the Nrf-2-activated anti-oxidant response and eNOS/ET-1 signaling pathways were differentially regulated in response to diminished pulsatility. Evaluation of 2 specific CF-VAD flow-modulation protocols to introduce artificial pulsatility, synchronous (SYN, 80 cycles/min, pulse pressure 20 mm Hg) and asynchronous (ASYN, 40 cycles/min, pulse pressure 45 mm Hg), suggested that both increased expression of Nrf-2-regulated anti-oxidant genes and proteins along with changes in levels of eNOS and ET-1 can potentially be minimized with ASYN and, to a lesser extent, with SYN.

CONCLUSIONS

HAECs cultured within the ECCM can be used as an accurate model of large vessels in patients to identify biomarkers and select appropriate flow-modulation protocols. Pressure amplitude may have a greater effect in normalizing anti-oxidant response compared with frequency of modulation.

Bazedoxifene, a selective estrogen receptor modulator, reduces cerebral aneurysm rupture in Ovariectomized rats

Background

Estrogen deficiency is thought to be responsible for the higher frequency of aneurysmal subarachnoid hemorrhage in post- than premenopausal women. Estrogen replacement therapy appears to reduce this risk but is associated with significant side effects. We tested our hypothesis that bazedoxifene, a clinically used selective estrogen receptor (ER) modulator with fewer estrogenic side effects, reduces cerebral aneurysm rupture in a new model of ovariectomized rats.

Methods

Ten-week-old female Sprague-Dawley rats were subjected to ovariectomy, hemodynamic changes, and hypertension to induce aneurysms (ovariectomized aneurysm rats) and treated with vehicle or with 0.3 or 1.0 mg/kg/day bazedoxifene. They were compared with sham-ovariectomized rats subjected to hypertension and hemodynamic changes (HT rats). The vasoprotective effects of bazedoxifene and the mechanisms underlying its efficacy were analyzed.

Results

During 12 weeks of observation, the incidence of aneurysm rupture was 52% in ovariectomized rats. With no effect on the blood pressure, treatment with 0.3 or 1.0 mg/kg/day bazedoxifene lowered this rate to 11 and 17%, almost the same as in HT rats (17%). In ovariectomized rats, the mRNA level of ERα, ERβ, and the tissue inhibitor of metalloproteinase-2 was downregulated in the cerebral artery prone to rupture at 5 weeks after aneurysm induction; the mRNA level of interleukin-1β and the matrix metalloproteinase-9 was upregulated. In HT rats, bazedoxifene restored the mRNA level of ERα and ERβ and decreased the level of interleukin-1β and matrix metalloproteinase-9. These findings suggest that bazedoxifene was protective against aneurysmal rupture by alleviating the vascular inflammation and degradation exacerbated by the decrease in ERα and ERβ.

Conclusions

Our observation that bazedoxifene decreased the incidence of aneurysmal rupture in ovariectomized rats warrants further studies to validate this response in humans.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-0966-7) contains supplementary material, which is available to authorized users.

MicroRNA-137 and microRNA-195* inhibit vasculogenesis in brain arteriovenous malformations

OBJECTIVE

Brain arteriovenous malformations (AVMs) are the most common cause of nontraumatic intracerebral hemorrhage in young adults. The genesis of brain AVM remains enigmatic. We investigated microRNA (miRNA) expression and its contribution to the pathogenesis of brain AVMs.

METHODS

We used a large-scale miRNA analysis of 16 samples including AVMs, hemangioblastoma, and controls to identify a distinct AVM miRNA signature. AVM smooth muscle cells (AVMSMCs) were isolated and identified by flow cytometry and immunohistochemistry, and candidate miRNAs were then tested in these cells. Migration, tube formation, and CCK-8-induced proliferation assays were used to test the effect of the miRNAs on phenotypic properties of AVMSMCs. A quantitative proteomics approach was used to identify protein expression changes in AVMSMCs treated with miRNA mimics.

RESULTS

A distinct AVM miRNA signature comprising a large portion of lowly expressed miRNAs was identified. Among these miRNAs, miR-137 and miR-195* levels were significantly decreased in AVMs and constituent AVMSMCs. Experimentally elevating the level of these microRNAs inhibited AVMSMC migration, tube formation, and survival in vitro and the formation of vascular rings in vivo. Proteomics showed the protein expression signature of AVMSMCs and identified downstream proteins regulated by miR-137 and miR-195* that were key signaling proteins involved in vessel development.

INTERPRETATION

Our results indicate that miR-137 and miR-195* act as vasculogenic suppressors in AVMs by altering phenotypic properties of AVMSMCs, and that the absence of miR-137 and miR-195* expression leads to abnormal vasculogenesis. Ann Neurol 2017;82:371-384.

Hyperhomocysteinemia induced by excessive methionine intake promotes rupture of cerebral aneurysms in ovariectomized rats

Background

Hyperhomocysteinemia (HHcy) is associated with inflammation and a rise in the expression of matrix metalloproteinase-9 (MMP-9) in the vascular wall. However, the role of HHcy in the growth and rupture of cerebral aneurysms remains unclear.

Methods

Thirteen-week-old female Sprague-Dawley rats were subject to bilateral ovariectomy and ligation of the right common carotid artery and fed an 8 % high-salt diet to induce cerebral aneurysms. Two weeks later, they underwent ligation of the bilateral posterior renal arteries. They were divided into two groups and methionine (MET) was or was not added to their drinking water. In another set of experiments, the role of folic acid (FA) against cerebral aneurysms was assessed.

Results

During a 12-week observation period, subarachnoid hemorrhage due to aneurysm rupture was observed at the anterior communicating artery (AcomA) or the posterior half of the circle of Willis. HHcy induced by excessive MET intake significantly increased the incidence of ruptured aneurysms at 6–8 weeks. At the AcomA of rats treated with MET, we observed the promotion of aneurysmal growth and infiltration by M1 macrophages. Furthermore, the mRNA level of MMP-9, the ratio of MMP-9 to the tissue inhibitor of metalloproteinase-2, and the level of interleukin-6 were higher in these rats. Treatment with FA abolished the effect of MET, suggesting that the inflammatory response and vascular degradation at the AcomA is attributable to HHcy due to excessive MET intake.

Conclusions

We first demonstrate that in hypertensive ovariectomized rats, HHcy induced by excessive MET intake may be associated with the propensity of the aneurysm wall to rupture.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0634-3) contains supplementary material, which is available to authorized users.

Thiamylal sodium increased inflammation and the proliferation of vascular smooth muscle cells

Background

Thiamylal sodium is a common anesthetic barbiturate prepared in alkaline solution for clinical use. There is no previously reported study on the effects of barbiturates on the inflammation and proliferation of vascular smooth muscle cells (VSMCs). Here, we examined the effects of clinical-grade thiamylal sodium solution (TSS) on the inflammation and proliferation of rat VSMCs.

Methods

Expression levels of interleukin (IL)-1α, IL-1β, IL-6, and toll-like receptors in rat VSMCs were detected by quantitative reverse transcription-polymerase chain reaction and microarray analyses. The production of IL-6 by cultured VSMCs or ex vivo-cultured rat aortic segments was detected in supernatants by enzyme-linked immunosorbent assay. VSMC proliferation and viability were determined by the water-soluble tetrazolium-1 assay and trypan blue staining, respectively.

Results

TSS increased expression of IL-1α, IL-6, and TLR4 in VSMCs in a dose-dependent manner, and reduced IL-1β expression. Ex vivo TSS stimulation of rat aorta also increased IL-6. Low concentrations of TSS enhanced VSMC proliferation, while high concentrations reduced both cell proliferation and viability. Expression of IL-1 receptor antagonist, which regulates cell proliferation, was not increased by TSS stimulation. Exposure of cells to the TSS additive, sodium carbonate, resulted in significant upregulation of IL-1α and IL-6 mRNA levels, to a greater extent than TSS.

Conclusions

TSS-induced proinflammatory cytokine production by VSMCs is caused by sodium carbonate. However, pure thiamylal sodium has an anti-inflammatory effect in VSMCs. TSS exposure to VSMCs may promote vascular inflammation, leading to the progression of atherosclerosis or in-stent restenosis, resulting in vessel bypass graft failure.

Age-dependent expression of VEGFR2 in deep brain arteries in small vessel disease, CADASIL, and healthy brains

Vascular myocytes are central to brain aging. Small vessel disease (SVD; arteriolosclerosis) is a widespread cause of lacunar stroke and vascular dementia and is characterized by fibrosis and depletion of vascular myocytes in small penetrating arteries. Vascular endothelial growth factor (VEGF) is associated with brain aging, and Immunolabeling for vascular endothelial growth factor receptor 2 (VEGFR2) is a potent determinant of cell fate. Here, we tested whether VEGFR2 in vascular myocytes is associated with older age and SVD in human brain. Immunolabeling for VEGFR2 in deep gray matter was assessed in older people with or without moderate-severe SVD or in younger people without brain pathology or with a monogenic form of SVD (Cerebral Autosomal-Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy). All cases were without Alzheimer's disease pathology. Myocyte VEGFR2 was associated with increasing age (p = 0.0026) but not with SVD pathology or with sclerotic index or blood vessel density. We conclude that VEGFR2 is consistently expressed in small artery myocytes of older people and may mediate effects of VEGF on brain vascular aging.

Biology of cerebral arteriovenous malformations with a focus on inflammation

Cerebral arteriovenous malformations (AVMs) entail a significant risk of intracerebral hemorrhage owing to the direct shunting of arterial blood into the venous vasculature without the dissipation of the arterial blood pressure. The mechanisms involved in the growth, progression and rupture of AVMs are not clearly understood, but a number of studies point to inflammation as a major contributor to their pathogenesis. The upregulation of proinflammatory cytokines induces the overexpression of cell adhesion molecules in AVM endothelial cells, resulting in enhanced recruitment of leukocytes. The increased leukocyte-derived release of metalloproteinase-9 is known to damage AVM walls and lead to rupture. Inflammation is also involved in altering the AVM angioarchitecture via the upregulation of angiogenic factors that affect endothelial cell proliferation, migration and apoptosis. The effects of inflammation on AVM pathogenesis are potentiated by certain single-nucleotide polymorphisms in the genes of proinflammatory cytokines, increasing their protein levels in the AVM tissue. Furthermore, studies on metalloproteinase-9 inhibitors and on the involvement of Notch signaling in AVMs provide promising data for a potential basis for pharmacological treatment of AVMs. Potential therapeutic targets and areas requiring further investigation are highlighted.

Inhibition of vascular endothelial growth factor receptor under hypoxia causes severe, human-like pulmonary arterial hypertension in mice: potential roles of interleukin-6 and endothelin

AIMS

Severe pulmonary arterial hypertension (PAH) is an incurable disease whose exact mechanisms remain unknown. However, growing evidence highlights the role of inflammation and endothelin (ET) signaling. The lack of reliable models makes it difficult to investigate the pathophysiology of this disease. Our aim was therefore to develop a mouse model of severe PAH closely mimicking the human condition to explore the role of interleukin-6 (IL-6), and ET signaling in advanced PAH progression.

MAIN METHODS

Young male SV129 mice received vascular endothelial growth factor receptor inhibitor (SU5416) three times a week and were exposed to hypoxia (10% O2) for three weeks. Molecular analysis and histological assessment were examined using real-time PCR, Western blot and immunostaining, respectively.

KEY FINDINGS

The developed murine model presented important characteristics of severe PAH in human: concentric neointimal wall thickening, plexogenic lesions, recruitment of macrophages, and distal arteriolar wall muscularization. We detected an increase of IL-6 production and a stronger macrophage recruitment in adventitia of remodeled arterioles developing plexogenic lesions. Moreover, ET-1 and ET receptor A were up-regulated in lung lysates and media of remodeled arterioles. Recombinant IL-6 stimulated the proliferation and regulated endothelial cells in increasing ET-1 and decreasing ET receptor B.

SIGNIFICANCE

These data describe a murine model, which displays the most important features of human severe PAH. We assume that inflammation, particularly IL-6 regulating ET signaling, plays a crucial role in forming plexogenic lesions. This model is thus reliable and might be used for a better understanding of severe PAH progression and treatment.

Differential gene expression in relation to the clinical characteristics of human brain arteriovenous malformations

Arteriovenous malformations (AVMs) of the central nervous system are considered as congenital disorders. They are composed of abnormally developed dilated arteries and veins and are characterized microscopically by the absence of a capillary network. We previously reported DNA fragmentation and increased expression of apoptosis-related factors in AVM lesions. In this article, we used microarray analysis to examine differential gene expression in relation to clinical manifestations in 11 AVM samples from Japanese patients. We categorized the genes with altered expression into four groups: death-related, neuron-related, inflammation-related, and other. The death-related differentially expressed genes were MMP9, LIF, SOD2, BCL2A1, MMP12, and HSPA6. The neuron-related genes were NPY, S100A9, NeuroD2, S100Abeta, CAMK2A, SYNPR, CHRM2, and CAMKV. The inflammation-related genes were PTX3, IL8, IL6, CXCL10, GBP1, CHRM3, CXCL1, IL1R2, CCL18, and CCL13. In addition, we compared gene expression in those with or without clinical characteristics including deep drainer, embolization, and high-flow nidus. We identified a small number of genes. Using these microarray data we are able to generate and test new hypotheses to explore AVM pathophysiology. Microarray analysis is a useful technique to study clinical specimens from patients with brain vascular malformations.

The role of perivascular adipose tissue in vascular smooth muscle cell growth

Adipose tissue is the largest endocrine organ, producing various adipokines and many other substances. Almost all blood vessels are surrounded by perivascular adipose tissue (PVAT), which has not received research attention until recently. This review will discuss the paracrine actions of PVAT on the growth of underlying vascular smooth muscle cells (VSMCs). PVAT can release growth factors and inhibitors. Visfatin is the first identified growth factor derived from PVAT. Decreased adiponectin and increased tumour necrosis factor-α in PVAT play a pathological role for neointimal hyperplasia after endovascular injury. PVAT-derived angiotensin II, angiotensin 1-7, reactive oxygen species, complement component 3, NO and H(2) S have a paracrine action on VSMC contraction, endothelial or fibroblast function; however, their paracrine actions on VSMC growth remain to be directly verified. Factors such as monocyte chemoattractant protein-1, interleukin-6, interleukin-8, leptin, resistin, plasminogen activator inhibitor type-1, adrenomedullin, free fatty acids, glucocorticoids and sex hormones can be released from adipose tissue and can regulate VSMC growth. Most of them have been verified for their secretion by PVAT; however, their paracrine functions are unknown. Obesity, vascular injury, aging and infection may affect PVAT, causing adipocyte abnormality and inflammatory cell infiltration, inducing imbalance of PVAT-derived growth factors and inhibitors, leading to VSMC growth and finally resulting in development of proliferative vascular disease, including atherosclerosis, restenosis and hypertension. In the future, using cell-specific gene interventions and local treatments may provide definitive evidence for identification of key factor(s) involved in PVAT dysfunction-induced vascular disease and thus may help to develop new therapies.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Circulating endotoxin and interleukin-6 levels are associated with Doppler-evaluated pulmonary vascular resistance in cirrhotic patients

PURPOSE

Endotoxin and interleukin-6 levels (IL-6) have been involved in the development of pulmonary hypertension (PH) in non-cirrhotic experimental models and subjects. High circulating levels of both substances have been detected in cirrhosis. The association between circulating endotoxin and IL-6 levels and echocardiographically evaluated pulmonary vascular resistance (PVR) in cirrhotic patients are investigated.

METHODS

Thirty-seven cirrhotic patients were studied: 25 with PVR <120 dynes s cm(-5) (group 1) and 12 with PVR >120 dynes s cm(-5) (group 2). Plasma endotoxin and serum IL-6 levels were measured. The PVR and cardiac output (CO) by Doppler ultrasound, mean arterial pressure (MAP), and systemic vascular resistance (SVR) as the ratio MAP/CO were evaluated.

RESULTS

Child-Pugh scores, MAP, CO, and SVR were similar in both groups. Endotoxin levels were correlated significantly with IL-6 levels (r = 0.342; P = 0.03). Endotoxin and IL-6 levels were significantly higher in group 2 compared to group 1 (2.26 [0.39-8.4] vs. 0.85 [0.37-7.6] EU/mL; P = 0.04 and 37.4 [7.85-106.5] vs. 8.36 [3.15-53.7] pg/mL; P < 0.001, respectively). The PVR was correlated significantly with endotoxin levels in group 2 (r = 0.587; P = 0.04) and with IL-6 levels in group 1 (r = 0.529; P = 0.01) and group 2 (r = 0.760; P = 0.004), respectively.

CONCLUSIONS

Our results suggest that endotoxin and IL-6 may contribute to cirrhosis-associated PH. In this regard, modulation of these substances could improve pulmonary pressures in cirrhotic patients.

Effect of tocopherol supplementation during last trimester of pregnancy on mRNA abundances of interleukins and angiogenesis in ovine placenta and uterus

BACKGROUND

Interleukins (IL) play an important role in angiogenesis. Tocopherol possesses immunomodulating effect in addition to antioxidant property. The objective of this study was to determine whether gamma tocopherol's (gT) angiogenic activity in placental network is enhanced via promoting interleukins.

METHODS

Pregnant ewes (N=18) were supplemented, orally, with 500 mg of alpha tocopherol (aT; N=6) or 1,000 mg of gT (N=7) or placebo (CON; N=5) once daily from 107 to 137 days post breeding. Uterine and placental tissue samples were obtained at the end of supplementation to evaluate relative mRNA expressions of IL-1b, IL-6, IL-8, Tumor Necrosis Factor (TNF) alpha, Vascular Endothelial Growth Factor (VEGF), kinase insert domain receptor (KDR; VGFR2; a type III receptor tyrosine kinase), and soluble fms-like tyrosine kniase-1 (sFlt1 or sVEGFR1) in uterus, caruncle and cotyledon.

RESULTS

Oral supplementation of gT increased IL-6, IL-8, KDR and VEGF mRNA abundances whereas sFlt1 mRNA abundance was suppressed in uterus, caruncle and cotyledon, compared to aT and placebo treated ewes (P<0.05). The TNF alpha and IL-1b mRNA abundances were suppressed in uterus, caruncle and cotyledon but TNF alpha is higher in gT group compared to aT group (P<0.05), whereas IL-1b was similar between treatment groups (P>0.1).

CONCLUSIONS

Gamma tocopherol supplementation increased IL-6, IL-8, and KDR mRNA abundances and suppressed sFlt1 and TNFalpha mRNA abundances thereby increased VEGF mRNA expression and angiogenesis in placental vascular network during late gestation. It is plausible that the angiogenic effect of gamma tocopherol in placental vascular network is exerted via an alternate path by enhancing IL-6 and IL-8.

Human umbilical cord blood plasma can replace fetal bovine serum for in vitro expansion of functional human endothelial colony-forming cells

BACKGROUND AIMS

A hierarchy of endothelial colony-forming cells (ECFC) with different levels of proliferative potential has been identified in human circulating blood and blood vessels. ECFC has recently become an attractive target for new vascular regenerative therapies; however, in vitro expansion of ECFC typically depends on the presence of fetal bovine serum (FBS) or fetal calf serum (FCS) in the culture medium, which is not appropriate for its therapeutic application.

METHODS

To identify optimal conditions for in vitro expansion of ECFC, the effects of human endothelial serum-free medium (SFM) supplemented with six pro-angiogenic cytokines and human umbilical cord blood plasma (HCP) were investigated. The in vitro morphology, proliferation, surface antigen expression and in vivo vessel-forming ability were utilized for examining the effects of medium on ECFC.

RESULTS

This novel formulation of endothelial cell culture medium allows us, for the first time, to isolate and expand human ECFC efficiently in vitro with a low concentration of HCP (1.5%) and without bovine serum additives. In this serum-reduced medium (SRM), human ECFC colony yields remained quantitatively similar to those cultured in a high concentration (10%) of bovine serum-supplemented medium. SRM-cultured ECFC displayed a robust clonal proliferative ability in vitro and human vessel-forming capacity in vivo.

CONCLUSIONS

The present study provides a novel method for the expansion of human ECFC in vitro and will help to advance approaches for using the cells in human therapeutic trials.

HCMV-encoded chemokine receptor US28 mediates proliferative signaling through the IL-6-STAT3 axis

US28 is a viral G protein (heterotrimeric guanosine triphosphate-binding protein)-coupled receptor encoded by the human cytomegalovirus (HCMV). In addition to binding and internalizing chemokines, US28 constitutively activates signaling pathways linked to cell proliferation. Here, we show increased concentrations of vascular endothelial growth factor and interleukin-6 (IL-6) in supernatants of US28-expressing NIH 3T3 cells. Increased IL-6 was associated with increased activation of the signal transducer and activator of transcription 3 (STAT3) through upstream activation of the Janus-activated kinase JAK1. We used conditioned growth medium, IL-6-neutralizing antibodies, an inhibitor of the IL-6 receptor, and short hairpin RNA targeting IL-6 to show that US28 activates the IL-6-JAK1-STAT3 signaling axis through activation of the transcription factor nuclear factor kappaB and the consequent production of IL-6. Treatment of cells with a specific inhibitor of STAT3 inhibited US28-dependent [(3)H]thymidine incorporation and foci formation, suggesting a key role for STAT3 in the US28-mediated proliferative phenotype. US28 also elicited STAT3 activation and IL-6 secretion in HCMV-infected cells. Analyses of tumor specimens from glioblastoma patients demonstrated colocalization of US28 and phosphorylated STAT3 in the vascular niche of these tumors. Moreover, increased phospho-STAT3 abundance correlated with poor patient outcome. We propose that US28 induces proliferation in HCMV-infected tumors by establishing a positive feedback loop through activation of the IL-6-STAT3 signaling axis.

Interleukin-6 as a potential therapeutic target for pulmonary arterial hypertension

Interleukin-6 (IL-6) is a pleiotropic cytokine with a wide range of biologic activities in immune regulation, hematopoiesis, inflammation, and oncogenesis. Recent accumulating evidence indicates a pathologic role for IL-6 in promoting proliferation of both smooth muscle and endothelial cells in the pulmonary arterioles, resulting in development of pulmonary arterial hypertension (PAH). Here, we describe a patient with mixed connective tissue disease and severe, refractory PAH. Her functional activity and hemodynamic parameters dramatically responded to tocilizumab, a humanized monoclonal antibody to human IL-6 receptor, which was aimed at treating multicentric Castleman's disease. It appears that IL-6 blockade may hold promise as an adjunct drug in treatment of PAH in idiopathic form as well as in association with connective tissue disease.

IL-17 stimulates migration of carotid artery vascular smooth muscle cells in an MMP-9 dependent manner via p38 MAPK and ERK1/2-dependent NF-kappaB and AP-1 activation

Inappropriate vascular remodeling is thought to be the main cause of restenosis following angioplasty. Migration of vascular smooth muscle cells (VSMC) into lumina, which is promoted by degradation of the extracellular matrix by matrix metalloproteinases (MMPs) plays a causal role in pathological vascular remodeling. The aim of the present research is to explore the effects of a novel cytokine, IL-17, on migration of VSMC and MMP-9 secretion. Carotid artery VSMC was isolated from Sprague-Dawley rats. Expression of MMP-9 and cell migration induced by IL-17 and its related signal pathway were detected. The results showed that IL-17-induced migration of VSMC in an MMP-9-dependent manner. IL-17-induced MMP-9 expression was via p38 MAPK and ERK1/2 dependent NF-kappaB and AP-1 activation. The present results demonstrated that IL-17 may play a role in vascular remodeling and targeting IL-17 or its specific downstream mediators is a potentially novel therapeutic pathway for attenuating the post-angioplastic restenosis.

Vascular endothelial growth factor regulates germ cell survival during establishment of spermatogenesis in the bovine testis

Vascular endothelial growth factor-A (VEGFA) is a hypoxia-inducible peptide essential for angiogenesis and targets nonvascular cells in a variety of tissues and cell types. The objective of the current study was to determine the function of VEGF during testis development in bulls. We used an explant tissue culture and treatment approach to test the hypothesis that VEGFA-164 could regulate the biological activity of bovine germ cells. We demonstrate that VEGFA, KDR, and FLT1 proteins are expressed in germ and somatic cells in the bovine testis. Treatment of bovine testis tissue with VEGFA in vitro resulted in significantly more germ cells following 5 days of culture when compared with controls. Quantitative real-time RT-PCR analysis determined that VEGF treatment stimulated an intracellular response that prevents germ cell death in bovine testis tissue explants, as indicated by increased expression of BCL2 relative to BAX and decreased expression of BNIP3 at 3, 6, and 24 h during culture. Blocking VEGF activity in vitro using antisera against KDR and VEGF significantly reduced the number of germ cells in VEGF-treated testis tissue to control levels at 120 h. Testis grafting provided in vivo evidence that bovine testis tissue treated with VEGFA for 5 days in culture contained significantly more differentiating germ cells compared with controls. These findings support the conclusion that VEGF supports germ cell survival and sperm production in bulls.

Thrombosis and hemorrhage in the acute period following Gamma Knife surgery for arteriovenous malformation

Bleeding of an arteriovenous malformation (AVM) following stereotactic radiosurgery (SRS) is a known risk during the latency interval, but hemorrhage in the 30-day period following radiosurgery rarely has been reported in the literature. The authors present the case of a 57-year-old man who underwent Gamma Knife surgery for a large AVM, and they provide radiographic documentation of a thrombus in the primary draining vein immediately preceding an AVM hemorrhage within 9 days after radiosurgery. They postulate that the pathophysiology of an AVM hemorrhage in the acute period following SRS is related to an association among tissue irradiation, acute inflammatory response, and vessel thrombosis.

The authors also review the literature on risk factors for hemorrhage due to untreated and radiosurgically treated AVMs. Recent evidence on the role of inflammation in the pathogenesis of AVMs and the pathophysiology of AVM rupture is presented. Inflammatory markers have been demonstrated in brain AVM tissue, and the association between inflammation and AVM hemorrhage has been established. There is an acute inflammatory response following tissue irradiation, resulting in structural and functional vascular changes that can lead to vessel thrombosis. Early hemorrhage following radiosurgical treatment of AVMs may be related to the acute inflammatory response and associated vascular changes that occur in irradiated tissue. In the first stage of a planned 2-stage Gamma Knife treatment for a large AVM in the featured case, the superior posteromedial portion of the primary draining vein was included in the treatment field. The authors present the planning images and subsequent CT scans demonstrating a new venous thrombus in the primary draining vein. An acute inflammatory response following radiosurgery with resultant acute venous thrombus formation and venous obstruction is proposed as one mechanism of an AVM hemorrhage in this patient. Radiographic evidence of the time course of thrombosis and hemorrhage supports the hypothesis that acute venous obstruction is a cause of intracranial hemorrhage.

Resveratrol attenuates angiotensin II-induced interleukin-6 expression and perivascular fibrosis

Recent studies have shown that resveratrol (3,5,4'-trihydroxystilbene), a polyphenolic compound found in grapes and red wine, has various beneficial effects on cardiovascular diseases and prolongs the life span of mice fed a high-fat diet. We hypothesized that resveratrol may attenuate vascular inflammatory response induced by angiotensin (Ang) II. We examined the effect of resveratrol on Ang II-induced interleukin (IL)-6 expression in vascular smooth muscle cells (VSMCs). Resveratrol significantly attenuated Ang II-induced IL-6 mRNA expression and IL-6 protein in the supernatant of VSMC in a dose-dependent manner. Resveratrol suppressed the IL-6 gene promoter activity. Resveratrol inhibited the Ang II-induced cAMP-response element-binding protein and nuclear factor-kappa B activity, which are critical for Ang II-induced IL-6 gene activation. An increase in the serum concentration of IL-6 induced by Ang II infusion was attenuated by an oral administration of resveratrol. Resveratrol also inhibited Ang II-induced hypertension and perivascular fibrosis of the heart. Although hydralazine reduced blood pressure level equal to resveratrol, it did not reduce the Ang II-induced IL-6 production and perivascular fibrosis. These data suggest that the inhibition of Ang II-induced vascular inflammation and high blood pressure by resveratrol may contribute, at least in part, to the anti-atherogenic effects of resveratrol.

Airway epithelium stimulates smooth muscle proliferation

Communication between the airway epithelium and stroma is evident during embryogenesis, and both epithelial shedding and increased smooth muscle proliferation are features of airway remodeling. Hence, we hypothesized that after injury the airway epithelium could modulate airway smooth muscle proliferation. Fully differentiated primary normal human bronchial epithelial (NHBE) cells at an air-liquid interface were co-cultured with serum-deprived normal primary human airway smooth muscle cells (HASM) using commercially available Transwells. In some co-cultures, the NHBE were repeatedly (x4) scrape-injured. An in vivo model of tracheal injury consisted of gently denuding the tracheal epithelium (x3) of a rabbit over 5 days and then examining the trachea by histology 3 days after the last injury. Our results show that HASM cell number increases 2.5-fold in the presence of NHBE, and 4.3-fold in the presence of injured NHBE compared with HASM alone after 8 days of in vitro co-culture. In addition, IL-6, IL-8, monocyte chemotactic protein (MCP)-1 and, more markedly, matrix metalloproteinase (MMP)-9 concentration increased in co-culture correlating with enhanced HASM growth. Inhibiting MMP-9 release significantly attenuated the NHBE-dependent HASM proliferation in co-culture. In vivo, the injured rabbit trachea demonstrated proliferation in the smooth muscle (trachealis) region and significant MMP-9 staining, which was absent in the uninjured control. The airway epithelium modulates smooth muscle cell proliferation via a mechanism that involves secretion of soluble mediators including potential smooth muscle mitogens such as IL-6, IL-8, and MCP-1, but also through a novel MMP-9-dependent mechanism.

Interleukin-6 overexpression induces pulmonary hypertension

Inflammatory cytokine interleukin (IL)-6 is elevated in the serum and lungs of patients with pulmonary artery hypertension (PAH). Several animal models of PAH cite the potential role of inflammatory mediators. We investigated role of IL-6 in the pathogenesis of pulmonary vascular disease. Indices of pulmonary vascular remodeling were measured in lung-specific IL-6-overexpressing transgenic mice (Tg(+)) and compared to wild-type (Tg(-)) controls in both normoxic and chronic hypoxic conditions. The Tg(+) mice exhibited elevated right ventricular systolic pressures and right ventricular hypertrophy with corresponding pulmonary vasculopathic changes, all of which were exacerbated by chronic hypoxia. IL-6 overexpression increased muscularization of the proximal arterial tree, and hypoxia enhanced this effect. It also reproduced the muscularization and proliferative arteriopathy seen in the distal arteriolar vessels of PAH patients. The latter was characterized by the formation of occlusive neointimal angioproliferative lesions that worsened with hypoxia and were composed of endothelial cells and T-lymphocytes. IL-6-induced arteriopathic changes were accompanied by activation of proangiogenic factor, vascular endothelial growth factor, the proproliferative kinase extracellular signal-regulated kinase, proproliferative transcription factors c-MYC and MAX, and the antiapoptotic proteins survivin and Bcl-2 and downregulation of the growth inhibitor transforming growth factor-beta and proapoptotic kinases JNK and p38. These findings suggest that IL-6 promotes the development and progression of pulmonary vascular remodeling and PAH through proproliferative antiapoptotic mechanisms.

Vascular cells contribute to atherosclerosis by cytokine- and innate-immunity-related inflammatory mechanisms

Cardiovascular diseases are the human diseases with the highest death rate and atherosclerosis is one of the major underlying causes of cardiovascular diseases. Inflammatory and innate immune mechanisms, employing monocytes, innate receptors, innate cytokines, or chemokines are suggested to be involved in atherogenesis. Among the inflammatory pathways the cytokines are central players. Plasma levels of cytokines and related proteins, such as CRP, have been investigated in cardiovascular patients, tissue mRNA expression was analyzed and correlations to vascular diseases established. Consistent with these findings the generation of cytokine-deficient animals has provided direct evidence for a role of cytokines in atherosclerosis. In vitro cell culture experiments further support the suggestion that cytokines and other innate mechanisms contribute to atherogenesis. Among the initiation pathways of atherogenesis are innate mechanisms, such as toll-like-receptors (TLRs), including the endotoxin receptor TLR4. On the other hand, innate cytokines, such as IL-1 or TNF, or even autoimmune triggers may activate the cells. Cytokines potently activate multiple functions relevant to maintain or spoil homeostasis within the vessel wall. Vascular cells, not least smooth muscle cells, can actively contribute to the inflammatory cytokine-dependent network in the blood vessel wall by: (i) production of cytokines; (ii) response to these potent cell activators; and (iii) cytokine-mediated interaction with invading cells, such as monocytes, T-cells, or mast cells. Activation of these pathways results in accumulation of cells and increased LDL- and ECM-deposition which may serve as an 'immunovascular memory' resulting in an ever-growing response to subsequent invasions. Thus, vascular cells may potently contribute to the inflammatory pathways involved in development and acceleration of atherosclerosis.

Interleukin-6 stimulates circulating blood-derived endothelial progenitor cell angiogenesis in vitro

Circulating blood endothelial progenitor cells (EPCs) contribute to postnatal vasculogenesis, providing a novel therapeutic target for vascular diseases. However, the molecular mechanism of EPC-induced vasculogenesis is unknown. Interleukin-6 plays multiple functions in angiogenesis and vascular remodeling. Our previous study demonstrated that the polymorphism (174G>C) in IL-6 gene promoter was associated with brain vascular disease. In this study, we investigated if IL-6 receptor is expressed in human EPCs derived from circulating mononuclear cells, and if interleukin-6 (IL-6) stimulates EPC angiogenesis in vitro. First, we isolated and cultured mononuclear cells from adult human circulating blood. We obtained EPC clones that were further cultured and expended for the angiogenesis study. We found that the EPCs possessed human mature endothelial cell phenotypes; however, they proliferated much faster than mature endothelial cells (P<0.05). We then found that IL-6 receptor (gp-80) was expressed in the EPCs, and that administration of IL-6 could activate receptor gp80/gp130 signaling pathways including downstream extracellular signal-regulated kinase 1/2 and STAT3 phosphorylation in EPCs. Furthermore, IL-6 stimulated EPC proliferation, migration, and matrigel tube formation in a dose-dependent manner (P<0.05); anti-IL-6 antibodies or IL-6 receptor could abolish these effects (P<0.05). These results suggest that IL-6 plays a crucial role in the biologic behavior of blood-derived EPCs, which may help clarify the mechanism of IL-6 inflammatory-related diseases.

Environmental enrichment counteracts Alzheimer's neurovascular dysfunction in TgCRND8 mice

We and others have recently demonstrated that cognitive and physical stimulation in form of environmental enrichment reduces cerebral beta-amyloid (Abeta) deposition in transgenic mouse models of Alzheimer's disease. This effect was independent from amyloid precursor protein (APP) expression or processing and rather a consequence of enhanced clearance of Abeta. However, the detailed mechanisms remain unclear. In the present study, we show that environmental enrichment in TgCRND8 mice (carrying human APP(Swedish+Indiana)) affect the neurovascular unit by increased angiogenesis and differential regulation of Abeta receptor/transporter molecules, namely up-regulation of LRP1, ApoE and A2M as well as down-regulation of RAGE so that brain to blood Abeta clearance is facilitated. These results suggest a hitherto unknown effect of environmental enrichment counteracting the vascular dysfunction in Alzheimer diseased brain.

Pulmonary arterial hypertension: a disease of tethers, SNAREs and SNAPs?

Histological and electron microscopic studies over the past four decades have highlighted "plump," "enlarged" endothelial, smooth muscle, and fibroblastic cellular elements with increased endoplasmic reticulum, Golgi stacks, and vacuolation in pulmonary arterial lesions in human and in experimental (hypoxia and monocrotaline) pulmonary arterial hypertension. However, the contribution of disrupted intracellular membrane trafficking in the pathobiology of this disease has received insufficient attention. Recent studies suggest a pathogenetic role of the disruption of intracellular trafficking of vasorelevant proteins and cell-surface receptors in the development of this disease. The purpose of this essay is to highlight the molecular regulation of vesicular trafficking by membrane tethers, SNAREs and SNAPs, and to suggest how their dysfunction, directly and/or indirectly, might contribute to development of pulmonary arterial hypertension in experimental models and in humans, including that due to mutations in bone morphogenetic receptor type 2.