IL-6 mobilizes bone marrow-derived cells to the vascular wall, resulting in neointima formation via inflammatory effects

Circulating Interleukin-6 and CD16 positive monocytes increase following angioplasty of an arteriovenous fistula

Arteriovenous fistulas are the ideal form of vascular access that allows provision of haemodialysis. Stenotic lesions caused by neointimal hyperplasia commonly occur resulting in patients requiring a fistuloplasty. This is effective but there is a high recurrence rate. We sought to investigate the effects of a fistuloplasty on monocyte populations. Blood samples were taken from patients before and after their fistuloplasty procedure. Samples were analysed using flow cytometry, ELISA and Luminex assays. Univariate cox regression was carried out to investigate associations with post fistuloplasty patency. At 1-2 days post fistuloplasty, the proportion of classical (CD14++CD16-) monocytes decreased (p < 0.001), whilst intermediate (CD14++CD16+) and non-classical (CD14+CD16+) monocytes increased (both p < 0.01) in a cohort of 20 patients. A time course study carried out in 5 patients showed that this was due to an increase in absolute numbers of non-classical and intermediate monocytes. Higher levels of non-classical monocytes pre-fistuloplasty were associated with an increased risk for patency loss (p < 0.05). We measured 41 soluble factors in plasma samples taken before a fistuloplasty in 54 patients, with paired post-fistuloplasty samples (1-2 days) available in 30 patients. After correcting for false discovery, the only factor with a significant change in level was IL-6 (P = 0.0003, q = 0.0124). In a further time-course study in 6 patients, peak level of IL-6 occurred 2-3 h post fistuloplasty. This study demonstrates that there is a systemic inflammatory response to the fistuloplasty procedure and that monocyte subsets and IL-6 may be important in the pathophysiology of restenosis.

Preventive Effect and Mechanism of Crossostephium chinense Extract on Balloon Angioplasty-Induced Neointimal Hyperplasia

Balloon angioplasty-induced neointimal hyperplasia remains a clinical problem that must be resolved. The bioactivities of the Crossostephium chinense extract (CCE) have demonstrated potential in preventing the progression of restenosis. The present study evaluated whether CCE can suppress balloon angioplasty-induced neointima formation and elucidated its possible pharmacological mechanisms. A rat model of carotid arterial balloon angioplasty was established to evaluate the inhibitory effect of CCEs on neointimal hyperplasia. Two cell lines, A10 vascular smooth muscle cells (VSMCs) and RAW264.7 macrophages, were used to investigate the potential regulatory activities and pharmacological mechanisms of CCEs in cell proliferation and migration and in inflammation. Our in vitro results indicated that CCE3, the ethanolic extract of C. chinense, exerted the strongest growth inhibitory and antimigratory effects on VSMCs. CCE3 blocked the activation of focal adhesion kinase, platelet-derived growth factor receptor-β (PDGFRB), and its downstream molecules (AKT and mTOR) and reduced the expression of matrix metalloproteinase-2. In addition, our findings revealed that CCE3 significantly increased the expression of miRNA-132, an inhibitory regulator of inflammation and restenosis, and suppressed the expression of inflammation-related molecules (inducible nitric oxide synthase, cyclooxygenase-2, interleukin- (IL-) 1β, and IL-6). Our in vivo study results indicated that balloon injury-induced neointimal hyperplasia was inhibited by CCE3. CCE3 could reduce neointima formation in balloon-injured arteries, and this effect may be partially attributed to the CCE3-induced suppression of PDGFRB-mediated downstream pathways and inflammation-related molecules.

The novel exchange protein activated by cyclic AMP 1 (EPAC1) agonist, I942, regulates inflammatory gene expression in human umbilical vascular endothelial cells (HUVECs)

Exchange protein activated by cyclic AMP (EPAC1) suppresses multiple inflammatory actions in vascular endothelial cells (VECs), partly due to its ability to induce expression of the suppressor of cytokine signalling 3 (SOCS3) gene, the protein product of which inhibits interleukin 6 (IL6) signalling through the JAK/STAT3 pathway. Here, for the first time, we use the non-cyclic nucleotide EPAC1 agonist, I942, to determine its actions on cellular EPAC1 activity and cyclic AMP-regulated gene expression in VECs. We demonstrate that I942 promotes EPAC1 and Rap1 activation in HEK293T cells and induces SOCS3 expression and suppresses IL6-stimulated JAK/STAT3 signalling in HUVECs. SOCS3 induction by I942 in HUVECs was blocked by the EPAC1 antagonist, ESI-09, and EPAC1 siRNA, but not by the broad-spectrum protein kinase A (PKA) inhibitor, H89, indicating that I942 regulates SOCS3 gene expression through EPAC1. RNA sequencing was carried out to further identify I942-regulated genes in HUVECs. This identified 425 I942-regulated genes that were also regulated by the EPAC1-selective cyclic AMP analogue, 007, and the cyclic AMP-elevating agents, forskolin and rolipram (F/R). The majority of genes identified were suppressed by I942, 007 and F/R treatment and many were involved in the control of key vascular functions, including the gene for the cell adhesion molecule, VCAM1. I942 and 007 also inhibited IL6-induced expression of VCAM1 at the protein level and blocked VCAM1-dependent monocyte adhesion to HUVECs. Overall, I942 represents the first non-cyclic nucleotide EPAC1 agonist in cells with the ability to suppress IL6 signalling and inflammatory gene expression in VECs.

•

The novel EPAC1 ligand I942 activates cellular EPAC1 and Rap1 GTPase.

•

I942 induces SOCS3 gene expression in vascular endothelial cells (VECs).

•

I942 suppresses JAK/STAT3 signalling from the IL6 receptor in VECs.

•

I942 regulates 425 novel gene targets in VECs.

•

I942 suppresses VCAM1 expression and monocyte adhesion in VECs.

Sonic hedgehog-dependent activation of adventitial fibroblasts promotes neointima formation

Aims

Adventitial cells have been suggested to contribute to neointima formation, but the functional relevance and the responsible signalling pathways are largely unknown. Sonic hedgehog (Shh) is a regulator of vasculogenesis and promotes angiogenesis in the adult.

Methods and results

Here we show that proliferation of vascular smooth muscle cells (SMC) after wire-induced injury in C57BL/6 mice is preceded by proliferation of adventitial fibroblasts. Simultaneously, the expression of Shh and its downstream signalling protein smoothened (SMO) were robustly increased within injured arteries. In vitro, combined stimulation with Shh and platelet-derived growth factor (PDGF)-BB strongly induced proliferation and migration of human adventitial fibroblasts. The supernatant of these activated fibroblasts contained high levels of interleukin-6 and -8 and strongly induced proliferation and migration of SMC. Inhibition of SMO selectively prevented fibroblast proliferation, cytokine release, and paracrine SMC activation. Mechanistically, we found that PDGF-BB activates protein kinase A in fibroblasts and thereby induces trafficking of SMO to the plasma membrane, where it can be activated by Shh. In vivo, SMO-inhibition significantly prevented the proliferation of adventitial fibroblasts and neointima formation following wire-induced injury.

Conclusions

The initial activation of adventitial fibroblasts is essential for the subsequent proliferation of SMC and neointima formation. We identified SMO-dependent Shh signalling as a specific process for the activation of adventitial fibroblasts.

Cellular and Oxidative Mechanisms Associated with Interleukin-6 Signaling in the Vasculature. Int J Mol Sci. 2017;18. [PMID: 29186034 PMCID: PMC5751166 DOI: 10.3390/ijms18122563]

Reactive oxygen species, particularly superoxide, promote endothelial dysfunction and alterations in vascular structure. It is increasingly recognized that inflammatory cytokines, such as interleukin-6 (IL-6), contribute to endothelial dysfunction and vascular hypertrophy and fibrosis. IL-6 is increased in a number of cardiovascular diseases, including hypertension. IL-6 is also associated with a higher incidence of future cardiovascular events and all-cause mortality. Both immune and vascular cells produce IL-6 in response to a number of stimuli, such as angiotensin II. The vasculature is responsive to IL-6 produced from vascular and non-vascular sources via classical IL-6 signaling involving a membrane-bound IL-6 receptor (IL-6R) and membrane-bound gp130 via Jak/STAT as well as SHP2-dependent signaling pathways. IL-6 signaling is unique because it can also occur via a soluble IL-6 receptor (sIL-6R) which allows for IL-6 signaling in tissues that do not normally express IL-6R through a process referred to as IL-6 trans-signaling. IL-6 signaling mediates a vast array of effects in the vascular wall, including endothelial activation, vascular permeability, immune cell recruitment, endothelial dysfunction, as well as vascular hypertrophy and fibrosis. Many of the effects of IL-6 on vascular function and structure are representative of loss or reductions in nitric oxide (NO) bioavailability. IL-6 has direct effects on endothelial nitric oxide synthase activity and expression as well as increasing vascular superoxide, which rapidly inactivates NO thereby limiting NO bioavailability. The goal of this review is to highlight both the cellular and oxidative mechanisms associated with IL-6-signaling in the vascular wall in general, in hypertension, and in response to angiotensin II.

The epigenetic factor PCAF regulates vascular inflammation and is essential for intimal hyperplasia development

Objective

Genetic P300/CBP-associated factor (PCAF) variation affects restenosis-risk in patients. PCAF has lysine acetyltransferase activity and promotes nuclear factor kappa-beta (NFκB)-mediated inflammation, which drives post-interventional intimal hyperplasia development. We studied the contributing role of PCAF in post-interventional intimal hyperplasia.

Methods and results

PCAF contribution to inflammation and intimal hyperplasia was assessed in leukocytes, macrophages and vascular smooth muscle cells (vSMCs) in vitro and in a mouse model for intimal hyperplasia, in which a cuff is placed around the femoral artery. PCAF deficiency downregulate CCL2, IL-6 and TNF-alpha expression, as demonstrated on cultured vSMCs, leukocytes and macrophages. PCAF KO mice showed a 71.8% reduction of vSMC-rich intimal hyperplasia, a 73.4% reduction of intima/media ratio and a 63.7% reduction of luminal stenosis after femoral artery cuff placement compared to wild type (WT) mice. The association of PCAF and vascular inflammation was further investigated using the potent natural PCAF inhibitor garcinol. Garcinol treatment reduced CCL2 and TNF-alpha expression, as demonstrated on cultured vSMCs and leukocytes.

To assess the effect of garcinol treatment on vascular inflammation we used hypercholesterolemic ApoE*3-Leiden mice. After cuff placement, garcinol treatment resulted in reduced arterial leukocyte and macrophage adherence and infiltration after three days compared to untreated animals.

Conclusions

These results identify a vital role for the lysine acetyltransferase PCAF in the regulation of local inflammation after arterial injury and likely the subsequent vSMC proliferation, responsible for intimal hyperplasia.

Preoperative factors predicting saphenous vein graft occlusion in coronary artery bypass grafting: a multivariate analysis

Saphenous vein segments are frequently used as aortocoronary bypass grafts, particularly in patients over 65 years of age. In the majority of patients, venous grafts maintain their patency for 5–6 years; however, some become occluded within 12 months after surgery. There are some defined predictive biological factors used to assess saphenous vein graft long-term patency rates, but little is known about molecular parameters for estimating the risk of early vein occlusion. The pathogenesis of this process involves the proliferation of stem cells, as well as progenitor cells, in the graft wall. Histologically, this is reflected by CD34 and CD133 expression in endothelial and smooth muscle cells. Thus, the aim of present work was to perform a multivariate analysis of stem cell and progenitor cell markers in saphenous vein graft walls before transplantation to arterial circulation and correlate these results with early graft occlusion. A total of 718 patients, who underwent coronary artery bypass grafting using a saphenous vein graft, were enrolled in this prospective study. CD34, CD133 and von Willebrand factor expression was evaluated via immunohistochemistry. A multivariate analysis revealed that strong CD133 expression in smooth muscle cells can be considered a risk factor for early graft failure. Our findings suggest that CD133 expression in smooth muscle cells of the tunica media in saphenous vein grafts obtained from coronary artery bypass graft patients before graft transplantation to coronary circulation might predict the possibility of early graft occlusion.

Differential effects of IL-6 blockade tocilizumab and TNF inhibitors on angiogenesis in synovial tissues from patients with rheumatoid arthritis

OBJECTIVE

To compare the influences of tocilizumab (TCZ) and TNF inhibitors (TNFi) on the angiogenesis in synovial tissues of rheumatoid arthritis (RA).

METHODS

Synovial tissues were obtained during joint operations from 13 RA patients treated with TCZ for at least 4 months with or without previous use of TNFi, from 13 RA patients with TNFi alone and from 10 RA patients with only conventional synthetic DMARDs (csDMARDs). Synovial tissues were evaluated by hematoxylin and eosin stain as well as by immunohistological staining with anti-CD31 in which the microvessel densities (MVD) were quantitated. Synovial histopathology was scored for various components.

RESULTS

The most remarkable change in the synovium with TCZ was reduced angiogenesis as well as degeneration of lining layers irrespective of the previous use of TNFi. Thus, MVD in patients treated with TCZ with or without previous TNFi were significantly decreased compared with those in patients with TNFi alone or with csDMARDs. Moreover, MVD was significantly correlated with lining layer proliferation, but not with synovial stromal proliferation or inflammatory changes.

CONCLUSIONS

These results demonstrated that inhibition of angiogenesis is a unique action of TCZ. Moreover, the data also suggest that lining layers proliferation might be closely associated with angiogenesis.

Cytosolic Hsp60 orchestrates the survival and inflammatory responses of vascular smooth muscle cells in injured aortic vessels

AIMS

Pro-inflammatory response of vascular smooth muscle cells (VSMCs) is triggered by endothelial damage and a causative step for thrombosis and neointimal thickening in the injured arterial vessels. Therefore, we investigate a role of cytosolic Hsp60 as a novel pro-inflammatory mediator in VSMCs.

METHODS AND RESULTS

Hsp60 was detected in the cytosol of VSMCs. The selective depletion of cytosolic Hsp60 in VSMCs reduced the IκB kinase activation, repressed the induction of nuclear factor (NF)-κB-dependent survival genes (MnSOD and Bfl-1/A1), and enhanced apoptotic death in response to TNF-α. Moreover, a quantitative RNA sequencing revealed that the expression of 75 genes among the 774 TNF-α-inducible genes was significantly reduced by the depletion of cytosolic Hsp60. In particular, the expression of pro-inflammatory cytokines/chemokines, such as CCL2, CCL20, and IL-6, was regulated by the cytosolic Hsp60 in VSMCs. Finally, the depletion of cytosolic Hsp60 markedly inhibited the neointimal thickening in the balloon-injured arterial vessels by inducing apoptotic cell death and inhibiting chemokine production.

CONCLUSIONS

This study provides the first evidence that cytosolic Hsp60 could be a therapeutic target for preventing VSMC hyperplasia and inflammatory response in the injured vessels.

The future of EPAC-targeted therapies: agonism versus antagonism

•

Although tractable to drug development, targeting of cAMP signalling has side effects.

•

Selectively targeting EPAC1 and EPAC2 cAMP sensor enzymes may limit some of these off-target effects.

•

EPAC agonists could be used to treat vascular inflammation (EPAC1) or type 2 diabetes (EPAC2).

•

EPAC1 and EPAC2 antagonists could be used to treat heart disease.

Pharmaceutical manipulation of cAMP levels exerts beneficial effects through the regulation of the exchange protein activated by cAMP (EPAC) and protein kinase A (PKA) signalling routes. Recent attention has turned to the specific regulation of EPAC isoforms (EPAC1 and EPAC2) as a more targeted approach to cAMP-based therapies. For example, EPAC2-selective agonists could promote insulin secretion from pancreatic β cells, whereas EPAC1-selective agonists may be useful in the treatment of vascular inflammation. By contrast, EPAC1 and EPAC2 antagonists could both be useful in the treatment of heart failure. Here we discuss whether the best way forward is to design EPAC-selective agonists or antagonists and the current strategies being used to develop isoform-selective, small-molecule regulators of EPAC1 and EPAC2 activity.

Intracranial atherosclerosis: correlation between in-vivo 3T high resolution MRI and pathology

BACKGROUND

High-resolution MRI (HRMRI) is a promising tool for studying intracranial atherosclerotic disease (ICAD) in-vivo, but its use to understand the pathophysiology of ICAD has been limited by a lack of correlation between MRI signal characteristics and pathology in intracranial arteries.

DESCRIPTION OF CASE

A patient with symptomatic left cavernous carotid stenosis underwent 3T HRMRI and died 4 days later. In-vivo HRMRI and postmortem histopathology images were compared. MRI signal characteristics consistent with atherosclerotic plaque composed of lipid and loose matrix, fibrous tissue, and calcium were correlated with pathology findings. Intraplaque hemorrhage was not present on HRMRI or pathology.

CONCLUSIONS

This report demonstrates correlation between atherosclerotic plaque components visualized on 3T HRMRI images obtained in-vivo and pathological specimens of a symptomatic ICAD plaque, providing an important step in developing HRMRI as an in-vivo research tool to understand ICAD pathology.