SDF-1-induced adhesion of monocytes to vascular endothelium is modulated by azelnidipine via protein kinase C inhibition

Azelnidipine Inhibits the Differentiation and Activation of THP-1 Macrophages through the L-Type Calcium Channel

Aim: Recently, calcium channel blockers (CCBs) have been reported to reduce atherosclerosis with anti-inflammatory or antiatherosclerotic effects in vivo. It is well established that monocytes and macrophages play important roles in promoting atherosclerosis. However, the effects of CCBs on macrophage activation remain unclear. The aim of this study was to evaluate the effects of azelnidipine, a dihydropyridine L-type CCB, on the activation of macrophages and to clarify the mechanisms of the effects of CCBs on atherosclerosis.

Methods: THP-1 monocytes, a human leukemic cell line, were stimulated with 50 ng/mL of phorbol-12-myristate-13-acetate (PMA) 1 h after pretreatment with 10 µM azelnidipine or dimethyl sulfoxide (DMSO), and harvested.

Results: Azelnidipine blocked the expression of intercellular adhesion molecule-1 quantified by FACS analysis. The expression levels of Apo E and MMP9, which are markers of macrophage differentiation, were inhibited by azelnidipine as evaluated by quantitative RT-PCR. The level of LOX-1 mRNA, a scavenger receptor, was also reduced significantly by pretreatment with 10 µM azelnidipine. Azelnidipine also lowered the uptake of acetylated LDL. The expression of the L-type calcium channel Cav1.2 was 10-fold higher after 24 h of PMA stimulation. A knockdown of the CACNA1C gene, which encodes Cav1.2 protein in humans, with siRNA blocked the effect of reducing adhesion by azelnidipine, indicating that the effects of azelnidipine on macrophage differentiation were expressed through the CACNA1C gene.

Conclusion: Our results suggest that azelnidipine has potent antiatherosclerotic properties by inhibition of macrophage activation through Cav1.2.

Trimethylamine N-oxide in atherogenesis: impairing endothelial self-repair capacity and enhancing monocyte adhesion

Several studies have reported a strong association between high plasma level of trimethylamine N-oxide (TMAO) and atherosclerosis development. However, the exact mechanism underlying this correlation is unknown. In the present study, we try to explore the impact of TMAO on endothelial dysfunction. After TMAO treatment, human umbilical vein endothelial cells (HUVECs) showed significant impairment in cellular proliferation and HUVECs-extracellular matrix (ECM) adhesion compared with control. Likewise, TMAO markedly suppressed HUVECs migration in transwell migration assay and wound healing assay. In addition, we found TMAO up-regulated vascular cell adhesion molecule-1 (VCAM-1) expression, promoted monocyte adherence, activated protein kinase C (PKC) and p-NF-κB. Interestingly, TMAO-stimulated VCAM-1 expression and monocyte adherence were diminished by PKC inhibitor. These results demonstrate that TMAO promotes early pathological process of atherosclerosis by accelerating endothelial dysfunction, including decreasing endothelial self-repair and increasing monocyte adhesion. Furthermore, TMAO-induced monocyte adhesion is partly attributable to activation of PKC/NF-κB/VCAM-1.

Single cell sorting identifies progenitor cell population from full thickness bovine articular cartilage

OBJECTIVE

To date, no approved clinical intervention successfully prevents the progressive degradation of injured articular cartilage that leads to osteoarthritis (OA). Stem/progenitor cell populations within tissues of diarthrodial joint have shown their therapeutic potential in treating OA. However, this potential has not been fully realized due in part to the heterogeneity of these subpopulations. Characterization of clonal populations derived from a single cell may help identify more homogenous stem/progenitor populations within articular cartilage. Moreover, chondrogenic potential of clonal populations from different zones could be further examined to elucidate their differential roles in maintaining articular cartilage homeostasis.

METHOD

We combined Fluorescence-activated cell sorting (FACS) and clonogenicity screening to identify stem/progenitor cells cloned from single cells. High-efficiency colony-forming cells (HCCs) were isolated, and evaluated for stem/progenitor cell characteristics. HCCs were also isolated from different zones of articular cartilage. Their function was compared by lineage-specific gene expression, and differentiation potential.

RESULTS

A difference in colony-forming efficiency was observed in terms of colony sizes. HCCs were highly clonogenic and multipotent, and overexpressed stem/progenitor cell markers. Also, proliferation and migration associated genes were over-expressed in HCCs. HCCs showed zonal differences with deep HCCs more chondrogenic and osteogenic than superficial HCCs.

CONCLUSION

Our approach is a simple yet practical way to identify homogeneous stem/progenitor cell populations with clonal origin. The discovery of progenitor cells demonstrates the intrinsic self-repairing potential of articular cartilage. Differences in differentiation potential may represent the distinct roles of superficial and deep zone stem/progenitor cells in the maintenance of articular cartilage homeostasis.

Stromal cell-derived factor-1 promoted angiogenesis and inflammatory cell infiltration in aneurysm walls

OBJECT

A small percentage of cerebral aneurysms rupture, but when they do, the effects are devastating. Current management of unruptured aneurysms consists of surgery, endovascular treatment, or watchful waiting. If the biology of how aneurysms grow and rupture were better known, a novel drug could be developed to prevent unruptured aneurysms from rupturing. Ruptured cerebral aneurysms are characterized by inflammation-mediated wall remodeling. The authors studied the role of stromal cell-derived factor-1 (SDF-1) in inflammation-mediated wall remodeling in cerebral aneurysms.

METHODS

Human aneurysms, murine carotid artery aneurysms, and murine intracranial aneurysms were studied using immunohistochemistry. Flow cytometry analysis was performed on blood from mice developing carotid or intracranial aneurysms. The effect of SDF-1 on endothelial cells and macrophages was studied by chemotaxis cell migration assay and capillary tube formation assay. Anti-SDF-1 blocking antibody was given to mice and compared with control (vehicle)-administered mice for its effects on the walls of carotid aneurysms and the development of intracranial aneurysms.

RESULTS

Human aneurysms, murine carotid aneurysms, and murine intracranial aneurysms all expressed SDF-1, and mice with developing carotid or intracranial aneurysms had increased progenitor cells expressing CXCR4, the receptor for SDF-1 (p < 0.01 and p < 0.001, respectively). Human aneurysms and murine carotid aneurysms had endothelial cells, macrophages, and capillaries in the walls of the aneurysms, and the presence of capillaries in the walls of human aneurysms was associated with the presence of macrophages (p = 0.01). Stromal cell-derived factor-1 promoted endothelial cell and macrophage migration (p < 0.01 for each), and promoted capillary tube formation (p < 0.001). When mice were given anti-SDF-1 blocking antibody, there was a significant reduction in endothelial cells (p < 0.05), capillaries (p < 0.05), and cell proliferation (p < 0.05) in the aneurysm wall. Mice given anti-SDF-1 blocking antibody developed significantly fewer intracranial aneurysms (33% vs 89% in mice given control immunoglobulin G, respectively; p < 0.05).

CONCLUSIONS

These data suggest SDF-1 is associated with angiogenesis and inflammatory cell migration and proliferation in the walls of aneurysms, and may have a role in the development of intracranial aneurysms.

From blood islands to blood vessels: morphologic observations and expression of key molecules during hyaloid vascular system development

PURPOSE

The mode of development of the human hyaloid vascular system (HVS) remains unclear. Early studies suggested that these blood vessels formed by vasculogenesis, while the current concept seems to favor angiogenesis as the mode of development. We examined embryonic and fetal human HVS using a variety of techniques to gain new insights into formation of this vasculature.

METHODS

Embryonic and fetal human eyes from 5.5 to 12 weeks gestation (WG) were prepared for immunohistochemical analysis or for light and electron microscopy. Immunolabeling of sections with a panel of antibodies directed at growth factors, transcription factors, and hematopoietic stem cell markers was employed.

RESULTS

Light microscopic examination revealed free blood islands (BI) in the embryonic vitreous cavity (5.5-7 WG). Giemsa stain revealed that BI were aggregates of mesenchymal cells and primitive nucleated erythroblasts. Free cells were also observed. Immunolabeling demonstrated that BI were composed of mesenchymal cells that expressed hemangioblast markers (CD31, CD34, C-kit, CXCR4, Runx1, and VEGFR2), erythroblasts that expressed embryonic hemoglobin (Hb-ε), and cells that expressed both. Few cells were proliferating as determined by lack of Ki67 antigen. As development progressed (12 WG), blood vessels became more mature structurally with pericyte investment and basement membrane formation. Concomitantly, Hb-ε and CXCR4 expression was down-regulated and von Willebrand factor expression was increased with the formation of Weibel-Palade bodies.

CONCLUSIONS

Our results support the view that the human HVS, like the choriocapillaris, develops by hemo-vasculogenesis, the process by which vasculogenesis, erythropoiesis, and hematopoiesis occur simultaneously from common precursors, hemangioblasts.

Protein kinase C mediates platelet secretion and thrombus formation through protein kinase D2

Platelets are highly specialized blood cells critically involved in hemostasis and thrombosis. Members of the protein kinase C (PKC) family have established roles in regulating platelet function and thrombosis, but the molecular mechanisms are not clearly understood. In particular, the conventional PKC isoform, PKCα, is a major regulator of platelet granule secretion, but the molecular pathway from PKCα to secretion is not defined. Protein kinase D (PKD) is a family of 3 kinases activated by PKC, which may represent a step in the PKC signaling pathway to secretion. In the present study, we show that PKD2 is the sole PKD member regulated downstream of PKC in platelets, and that the conventional, but not novel, PKC isoforms provide the upstream signal. Platelets from a gene knock-in mouse in which 2 key phosphorylation sites in PKD2 have been mutated (Ser707Ala/Ser711Ala) show a significant reduction in agonist-induced dense granule secretion, but not in α-granule secretion. This deficiency in dense granule release was responsible for a reduced platelet aggregation and a marked reduction in thrombus formation. Our results show that in the molecular pathway to secretion, PKD2 is a key component of the PKC-mediated pathway to platelet activation and thrombus formation through its selective regulation of dense granule secretion.

Azelnidipine and amlodipine anti-coronary atherosclerosis trial in hypertensive patients undergoing coronary intervention by serial volumetric intravascular ultrasound analysis in Juntendo University (ALPS-J)

BACKGROUND

A previous study reported that amlodipine retarded coronary plaque progression in patients with coronary artery disease. The goal of this multicenter study was to determine which calcium-channel blockers (CCBs) other than amlodipine attenuated the progression of plaque volume (PV) accessed by intravascular ultrasound (IVUS).

METHODS AND RESULTS

ALPS-J was a prospective, randomized open-label study conducted at 5 centers. Patients who had hypertension and were scheduled for coronary intervention were enrolled. Subjects were randomly assigned to receive 16 mg/day of azelnidipine or 5mg/day of amlodipine administered for 48 weeks. The primary endpoint was the percent change in coronary PV measured by IVUS. Between 2007 and 2009, 199 patients were enrolled; 115 had evaluable IVUS images at both baseline and after 48 weeks of treatment. Blood pressure significantly reduced to 128/68 mmHg at follow-up. The lipid profiles in the 2 groups were comparable (low-density lipoprotein cholesterol: 97 mg/dl). The %change in PV showed a significant regression of 4.67 and 4.85% in the azelnidipine and amlodipine groups, respectively. The upper limit of the 95% confidence interval of the mean difference in %change PV between the 2 groups (0.18%, 95% confidence interval 4.62 to 4.98%) did not exceed the pre-defined non-inferiority margin of 6.525%.

CONCLUSIONS

ALPS-J demonstrated that azelnidipine was not inferior to amlodipine for primary efficacy. In addition to standard medical therapy, dihydropyridine CCBs will retard PV progression in hypertensive patients.

CXCR4 antagonist AMD3100 attenuates colonic damage in mice with experimental colitis

AIM: To investigate the effects of the chemokine stromal cell-derived factor-1 (CXCL12) receptor (CXCR4) antagonist AMD3100 on colonic inflammation and epithelial barrier in dextran sulfate sodium (DSS)-induced colitis in mice.

METHODS: Experimental colitis was induced by administration of 5% DSS for 7 d, and assays performed on intestinal segments from the ileocecal valve to the anus. Colonic morphology was examined by hematoxylin and eosin staining. Colonic cytokines were determined by enzyme-linked immunosorbent assay. Myeloperoxidase (MPO) activity (indicator of inflammatory infiltration) was observed spectrophotometrically. Gut permeability was assessed by mucosal-to-serosal clearance of fluorescein isothiocyanate-conjugated dextran 4000 (FD4) in everted gut sacs. The apoptosis of colonic epithelium was assessed by Hoechst-33342 staining. To further elucidate the role of CXCR4 in colonic inflammation, we also investigated the effect of AMD3100 on migration and cytokine production of isolated peripheral blood mononuclear cells (PBMCs).

RESULTS: DSS-induced colitis was characterized by morphologic changes, as well as increased colonic cytokines, inflammatory infiltration, epithelial apoptosis, and intestinal permeability in mice. In AMD3100-treated mice, epithelial destruction, inflammatory infiltration, and submucosal edema were markedly reduced; colonic tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interferon-γ (IFN-γ) levels, as well as MPO activity were significantly decreased. Increased intestinal permeability in DSS-treated mice was significantly reduced by AMD3100. The number of apoptotic cells in colitis mice was markedly increased after DSS administration, and decreased when treated with the CXCR4 antagonist AMD3100. In pre-activated PBMCs, CXCL12 stimulation significantly increased the migration of PBMCs, and was inhibited by AMD3100. Moderately increased TNF-α, IL-6, and IFN-γ from CXCL12-treated PBMCs were also reduced by AMD3100.

CONCLUSION: The CXCR4 antagonist AMD3100 exerts therapeutic effects on experimental colitis by inhibiting colonic inflammation and enhancing epithelial barrier integrity.

Casein-derived tripeptide, Val-Pro-Pro (VPP), modulates monocyte adhesion to vascular endothelium

AIM

A food-derived bioactive tripeptide, Val-Pro-Pro (VPP), has been shown to possess angiotensin I-converting enzyme (ACE) inhibitory activity and foods containing such peptides exhibit an anti-hypertensive effect in clinical settings.

METHODS

The present study focused on the effect of VPP on monocyte adhesion to endothelium under flow conditions using phorbol 12-myristate 13-acetate (PMA)-stimulated monocytic THP-1 cells.

RESULTS

Pre-incubation of THP-1 cells with VPP (1 mM, 24 hours) significantly decreased the PMA-induced adhesion of THP-1 cells (p<0.05) to human umbilical vein endothelial cells (HUVECs). PMA-induced up-regulation of beta1 and beta2 integrin activation in THP-1 cells was downregulated by VPP, which significantly suppressed only the PMA-induced phosphorylation of JNK (p<0.05) in THP-1 cells. In addition, preincubation of THP-1 with SP600125, a specific inhibitor of JNK, resulted in significant reduction of the PMA-induced adhesion of THP-1. Interestingly, another tripeptide with comparable ACE inhibitory activity, Leu-Gly-Pro (LGP), failed to reduce the PMA-induced adhesion of THP-1, suggesting a distinct anti-inflammatory effect of VPP on THP-1 adhesion.

CONCLUSION

These observations suggest that VPP moderates monocyte adhesion to inflamed endothelia via attenuation of the JNK pathway in monocytes, which might contribute to the primary prevention of atherosclerosis.

Protein kinase Calpha: disease regulator and therapeutic target

Protein kinase Cα (PKCα) is a member of the AGC (which includes PKD, PKG and PKC) family of serine/threonine protein kinases that is widely expressed in mammalian tissues. It is closely related in structure, function and regulation to other members of the protein kinase C family, but has specific functions within the tissues in which it is expressed. There is substantial recent evidence, from gene knockout studies in particular, that PKCα activity regulates cardiac contractility, atherogenesis, cancer and arterial thrombosis. Selective targeting of PKCα therefore has potential therapeutic value in a wide variety of disease states, although will be technically complicated by the ubiquitous expression and multiple functions of the molecule.

Azelnidipine and amlodipine anti-coronary atherosclerosis trial in hypertensive patients undergoing coronary intervention by serial volumetric intravascular ultrasound analysis in Juntendo university (ALPS-J)

PURPOSE

Many trials have shown that calcium channel blockers (CCBs) can reduce the cardiovascular (CV) events in patients with coronary artery disease (CAD). The mechanisms of this effect could be associated with plaque regression due to the anti-atherosclerotic properties of CCBs. The goal of this study is to determine the effects of CCB on volumetric quantitative changes of coronary plaques accessed by intravascular ultrasound (IVUS). To confirm this hypothesis, a multicenter randomized trial of CCBs treatment with azelnidipine or amlodipine will be conducted in hypertensive CAD patients undergoing elective percutaneous coronary intervention (PCI).

METHODS AND RESULTS

Patients who have hypertension and are scheduled for PCI will be enrolled. Subjects will be randomized to azelnidipine or amlodipine and observed for 48 weeks. The primary endpoint will be the percent change of coronary plaque volume. The secondary endpoint will include inflammatory markers, antioxidant activity, and incidence of composite cardiovascular events.

CONCLUSIONS

In this study, we will investigate the improvement of coronary plaque with IVUS by treatment with two dihydropyridine CCBs in hypertensive patients undergoing elective PCI. This result will lead to the discovery of more effective drug therapy for inhibition of coronary events.

Polymorphisms of fractalkine receptor CX3CR1 gene in patients with symptomatic and asymptomatic carotid artery stenosis

AIM

The chemokine fractalikine is expressed in vascular endothelium, exerting a pro-atherogenic effect. Two single-nucleotide polymorphisms of the CX3CR1 gene (T280M and V249I) affect frac-talkine receptor expression and function. We aimed to assess the prevalence of CX3CR1 polymor-phisms and the association with ischemic cerebrovascular attacks in a cohort of carotid atheromatous disease patients and age-matched controls.

METHODS

Using PCR-RFLP, we analyzed allelotypes for T280M and V249I in 150 patients with and 151 controls without carotid atherosclerosis assessed using carotid duplex ultrasound; the subjects were patients admitted for any reason to a tertiary hospital. Genotype data were compared with modifiable risk factors for cerebrovascular disease and the reason for admission, using ischemic stroke as an endpoint. Stroke types associated with carotid atherosclerosis were analysed separately.

RESULTS

The M280 allelic frequency was lower among carotid atherosclerosis patients than controls (0.15 versus 0.23, adjusted OR 0.47, 95% CI 0.30-0.74). Absence of M280 allele was an indepen-dent factor associated with carotid atherosclerosis (OR 3.70, 95% CI 1.92-7.14), stronger than hypertension, dyslipidemia, diabetes and cigarette smoking. The I249 allele was also under-repre-sented in carotid atherosclerosis; this was not statistically significant. T280M and V249I genotypes were not associated with admission due to ischemic stroke of the large vessel subtype (TOAST classi-fication, 73 episodes), whereas carotid atherosclerosis, previous ischemic event, age, hypertension, diabetes, hyperlipidemia and cigarette smoking were all independently associated.

CONCLUSIONS

The M280 fractalkine receptor gene allele is associated with a lower risk of carotid ath-eromatous disease, independent from the modifiable cerebrovascular risk factors.

Angiotensin-Converting Enzyme Inhibitor Attenuates Monocyte Adhesion to Vascular Endothelium through Modulation of Intracellular Zinc

To elucidate an anti-inflammatory role of angiotensin-converting enzyme inhibitors (ACEIs) in cardiovascular disease, we studied the effect of ACEIs in monocyte adhesion to endothelial cells and underlying molecular mechanisms. Treatment of human monocytic THP-1 cells with monocyte chemoattractant protein-1 (MCP-1; 100 ng/ml; 10 min) significantly increased their adhesion to human umbilical vein endothelial cells (HUVECs) under flow condition (P < 0.001). Preincubation of THP-1 cells with imidaprilat (50 nM; 4 h), an active metabolite of imidapril, reduced MCP-1-triggered THP-1 cell adhesion (P < 0.01). Similar effects were obtained with experiments using human peripheral monocytes (P < 0.05). MCP-1 activated protein kinase C (PKC)alpha in THP-1 cells, resulting in the up-regulation of alpha4 and beta2 integrin. Imidaprilat attenuated MCP-1-induced PKC activation and integrin up-regulation in THP-1 cells. Imidaprilat also inhibited THP-1 cell adhesion induced by phorbol 12-myristate 13-acetate (PMA), a potent PKC activator. In attempt to elucidate the mechanisms for the modulation of PKC activity by imidaprilat, we found that MCP-1 or PMA increased labile zinc in THP-1 cells, which was canceled by imidaprilat. Indeed, zinc/pyrithione activated PKC and increased THP-1 cell adhesion. Zinc chelator as well as PKC inhibitor inhibited these processes, suggesting the role for labile zinc in PKC activation and THP-1 cell adhesion. Imidaprilat attenuated zinc/pyrithione-induced PKC activation and THP-1 cell adhesion. These data suggest that ACEI reduces MCP-1 or PMA-triggered monocyte adhesion to activated HUVECs by modulating labile zinc in monocytes. Our findings may point out a novel anti-inflammatory mechanism of ACEIs in atherogenesis.