Monocyte chemotactic protein 1 amplifies serotonin-induced vascular smooth muscle cell proliferation

Adipocyte calcium sensing receptor is not involved in visceral adipose tissue inflammation or atherosclerosis development in hyperlipidemic Apoe-/- mice

The calcium sensing receptor (CaSR) is a G-protein coupled receptor that especially plays an important role in the sensing of extracellular calcium to maintain its homeostasis. Several in-vitro studies demonstrated that CaSR plays a role in adipose tissue metabolism and inflammation, resulting in systemic inflammation and contributing to atherosclerosis development. The aim of this study was to investigate whether adipocyte CaSR plays a role in adipose tissue inflammation in-vivo and atherosclerosis development. By using a newly established conditional mature adipocyte specific CaSR deficient mouse on a hyperlipidemic and atherosclerosis prone Apoe^−/− background it could be shown that CaSR deficiency in adipocytes does neither contribute to initiation nor to progression of atherosclerotic plaques as judged by the unchanged lesion size or composition. Additionally, CaSR deficiency did not influence gonadal visceral adipose tissue (vAT) inflammation in-vivo, although a small decrease in gonadal visceral adipose cholesterol content could be observed. In conclusion, adipocyte CaSR seems not to be involved in vAT inflammation in-vivo and does not influence atherosclerosis development in hyperlipidemic Apoe^−/− mice.

A novel quinone derived from 5-hydroxyindoleacetic acid reacts with protein: Possible participation of oxidation of serotonin and its metabolite in the development of atherosclerosis

The modification of 5-hydroxyindoleacetic acid (5HIAA) by myeloperoxidase with a xanthine oxidase system was investigated by chromatographic analyses. Two major products were identified as a dimer and quinone (indoleacetate dione) of 5HIAA. The formation of a quinone moiety was also confirmed by chemical trapping with o-phenylenediamine. In the presence of N-acetyl-cysteine (NAC), a quinone-NAC adduct was formed. When glyceraldehyde 3-phosphate dehydrogenase was exposed to the myeloperoxidase system with 5HIAA, quinone adducts were formed on the protein molecule. A monoclonal antibody was prepared using a quinone-modified protein as an immunogen to immunochemically detect the quinone on a protein. The established antibody recognized the quinone-NAC adduct, quinone-modified poly-L-lysine, and quinone-modified low-density lipoprotein. Quinone-modified proteins in human atherosclerotic lesions were immunohistochemically observed using the established antibody to the quinone and also a monoclonal antibody to tryptamine dione-modified protein, suggesting an occurrence of in vivo oxidation of serotonin and 5HIAA, accompanied by covalent adduction to biomolecules.

Dysregulated apoptosis of the venous wall in chronic venous disease and portal hypertension

Introduction

The etiology of varicose veins remains elusive. We hypothesized that abnormal cell cycle events in the vein wall may contribute to changes in the structural integrity, thus predisposing to the development of varicosities. The present study was designed to determine whether or not the same molecular apoptotic pathway exists between great saphenous and splenic veins.

Methods

Thirty-six samples of diseased splenic veins and varicose great saphenous veins were collected. Twenty-five samples of control splenic and great saphenous veins were also collected. The apoptotic cell proteins expression was immunohistochemically stained with antibodies (anti-Bax and anti-Bcl-xl). Apoptosis was evaluated by the terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) assay and immunofluorescence staining. The morphology of apoptotic cells was observed with an electron microscope.

Results

The apoptotic ratio in walls (intima and media) of diseased splenic vein and varicose great saphenous vein groups were significantly lower than the corresponding regions in the splenic vein and great saphenous vein groups ( p < 0.01), respectively. A significant difference was not noted in the ratio change of apoptotic cells between the diseased splenic vein and varicose great saphenous vein groups ( p > 0.05). The high positive expression of Bcl-xl proteins was detected in the diseased splenic vein and varicose great saphenous vein groups, respectively. While the high positive expression of Bax proteins was also observed in the splenic vein and great saphenous vein groups, respectively. Electron microscopic observations confirmed that endothelial and smooth muscle cells in diseased splenic vein, varicose great saphenous vein, splenic vein, and great saphenous vein walls exhibited apoptotic morphologic features, such as fuzzy mitochondrial cristae, medullary changes, and margination of the nuclear chromatin.

Conclusions

Our results showed the same dysregulation of apoptosis via the intrinsic pathway in diseased splenic veins and varicose great saphenous veins. This observational study suggests that apoptotic down-regulation in the veins wall is a cause of diseased splenic veins and varicose great saphenous veins, but does not exclude the possibility that other mechanisms are involved.

Long-acting progestin-only contraceptives impair endometrial vasculature by inhibiting uterine vascular smooth muscle cell survival

Molecular mechanisms responsible for abnormal endometrial vasculature in women receiving long-acting progestin-only contraceptives (LAPCs) are unknown. We hypothesize that LAPCs impair vascular smooth muscle cell (VSMC) and pericyte proliferation and migration producing thin-walled hyperdilated fragile microvessels prone to bleeding. Proliferating cell nuclear antigen (PCNA) and α-smooth muscle actin (αSMA) double-immunostaining assessed VSMC differentiation and proliferation in endometria from women before and after DepoProvera (Depo) treatment and from oophorectomized guinea pigs (OVX-GPs) treated with vehicle, estradiol (E2), medroxyprogesterone acetate (MPA), or E2+MPA. Whole-genome profiling, proliferation, and migration assays were performed on cultured VSMCs treated with MPA or etonogestrel (ETO). Endometrial vessels of Depo-administered women displayed reduced αSMA immunoreactivity and fewer PCNA (+) nuclei among αSMA (+) cells (P < 0.008). Microarray analysis of VSMCs identified several MPA- and ETO-altered transcripts regulated by STAT1 signaling (P < 2.22 × 10(-6)), including chemokine (C-C motif) ligand 2 (CCL2). Both MPA and ETO reduce VSMC proliferation and migration (P < 0.001). Recombinant CCL2 reversed this progestin-mediated inhibition, whereas a STAT1 inhibitor abolished the CCL2 effect. Similarly, the endometria of MPA treated OVX-GPs displayed decreased αSMA staining and fewer PCNA (+) nuclei in VSMC (P < 0.005). In conclusion, LAPCs promote abnormal endometrial vessel formation by inhibiting VSMC proliferation and migration.

Panaxquin quefolium diolsaponins dose-dependently inhibits the proliferation of vascular smooth muscle cells by downregulating proto-oncogene expression

Objectives:

Panax quinquefolium saponins (PQS) potentially prevent atherosclerosis in vivo. The proliferation of vascular smooth muscle cells (VSMCs) plays an important role in coronary heart disease and restenosis after percutaneous coronary intervention. Here, we investigated the potential effect of Panax quinquefolium diolsaponins (PQDS), a subtype of PQS, on angiotensin II (AngII)-induced VSMC proliferation.

Materials and Methods:

Isolated rat VSMCs were identified by immunocytochemical analysis. Cell proliferation was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The cell cycle and proliferation index were analyzed using flow cytometry. The messenger ribonucleic acid (mRNA) expression of proto-oncogenes was evaluated using reverse transcription polymerase chain reaction.

Results:

Over 98% of cultured VSMCs were immunopositive for anti-α-smooth muscle actin. AngII promoted cell proliferation, whereas PQDS significantly suppressed VSMC growth in a dose-dependent manner. Moreover, PQDS suppressed AngII-induced proliferation of VSMCs by arresting the Gap 0/Gap 1 phase. Down-regulated mRNA expressions of proto-oncogenes occurred after PQDS application.

Conclusions:

Our study demonstrates that PQDS may reduce AngII-stimulated VSMC proliferation by suppressing the expression of proto-oncogenes. These results may provide insights for the development of novel traditional Chinese medicines to prevent atherosclerosis.

Monocyte chemoattractant protein-1/CCR2 axis promotes vein graft neointimal hyperplasia through its signaling in graft-extrinsic cell populations

OBJECTIVE

To evaluate direct versus indirect monocyte chemoattractant protein (MCP)-1/CCR2 signaling and to identify the cellular producers and effectors for MCP-1 during neointimal hyperplasia (NIH) development in vein grafts.

METHODS AND RESULTS

Genomic analysis revealed an overrepresentation of 13 inflammatory pathways in wild-type vein grafts compared with CCR2 knockout vein grafts. Further investigation with various vein graft-host combinations of MCP-1- and CCR2-deficient mice was used to modify the genotype of cells both inside (graft-intrinsic group) and outside (graft-extrinsic group) the vein wall. CCR2 deficiency inhibited NIH only when present in cells extrinsic to the graft wall, and MCP-1 deficiency required its effectiveness in cells both intrinsic and extrinsic to the graft wall to suppress NIH. Deletion of either MCP-1 or CCR2 was equally effective in inhibiting NIH. CCR2 deficiency in the predominant neointimal cell population had no impact on NIH. Direct MCP-1 stimulation of primary neointimal smooth muscle cells had minimal influence on cell proliferation and matrix turnover, confirming an indirect mechanism of action.

CONCLUSIONS

MCP-1/CCR2 axis accelerates NIH via its signaling in graft-extrinsic cells, particularly circulating inflammatory cells, with cells both intrinsic and extrinsic to the graft wall being critical MCP-1 producers. These findings underscore the importance of systemic treatment for anti-MCP-1/CCR2 therapies.

Monocyte chemoattractant protein-1 is associated with silent cerebral infarction in patients on haemodialysis

BACKGROUND

In patients with chronic renal failure undergoing haemodialysis (HD), silent cerebral infarctions (SCI) are associated with high mortality. Levels of monocyte chemoattractant protein-1 (MCP-1) increase with renal dysfunction and may be a novel predictor for cerebrovascular events. We tested the hypothesis that increased MCP-1 concentration correlate with the occurrence of SCI in HD patients.

METHODS

Using cranial magnetic resonance imaging (MRI) findings, 52 Japanese patients undergoing HD were divided into two groups: with SCI (61 ± 7 years, mean ± SD, n= 28) and without SCI (60 ± 6 years, n= 24). The gender, metabolic profiles and MCP-1 concentration were compared between the two groups.

RESULTS

The level of MCP-1 was higher in the with-SCI group than in the without-SCI group (P < 0.0001). The proportion of smokers was higher in the with-SCI group (P < 0.05) than in the without-SCI group. Plasma level of high-density lipoprotein cholesterol was lower, while uric acid level was higher, in the with-SCI group (P < 0.05 and P < 0.05 respectively) compared to the without-SCI group. Multiple logistic regression analysis identified MCP-1 level as being significantly associated with the presence of SCI (odds ratio 1.48, 95% confidence interval = 1.10-5.75, P < 0.0001).

CONCLUSIONS

This study indicates that patients with chronic renal failure who are maintained on HD exhibit an increased prevalence of SCI, and that MCP-1 is significantly associated with the presence of SCI in HD patients.

High plasma 5-hydroxyindole-3-acetic acid concentrations in subjects with metabolic syndrome

OBJECTIVE

Serotonin mediates vasoconstriction and induces the activation of platelets, which may promote atherosclerosis. The aim of this study was to investigate whether plasma 5-hydroxyindole-3-acetic acid (5-HIAA; a derivative end product of serotonin) concentrations are high in subjects with metabolic syndrome (MetS) and to investigate the relationship between plasma 5-HIAA concentrations and clinical and biochemical metabolic parameters.

RESEARCH DESIGN AND METHODS

Plasma 5-HIAA concentrations were measured in 311 subjects (152 men and 159 women) recruited from the Oike Clinic, which provides regular health check-ups for employees. We evaluated the relationship between plasma 5-HIAA concentrations and clinical and biochemical metabolic parameters, including waist circumference, serum lipid concentrations, fasting plasma glucose, or blood pressure.

RESULTS

Plasma 5-HIAA concentrations were higher in subjects with MetS than in those without, in both men (6.5 ± 4.4 vs. 4.9 ± 1.3 ng/mL, P < 0.005) and women (7.9 ± 6.5 vs. 5.2 ± 1.6 ng/mL, P < 0.005). In men, fasting plasma glucose (r = 0.197, P = 0.0146) was positively correlated, whereas HDL cholesterol (r = -0.217, P = 0.0071) was negatively correlated, with logarithmic (log) (plasma 5-HIAA concentrations). In women, triglycerides (r = 0.252, P = 0.0013) and fasting plasma glucose (r = 0.344, P < 0.0001) were positively correlated, whereas HDL cholesterol (r = -0.328, P < 0.0001) was negatively correlated, with log (5-HIAA concentrations). Furthermore, log (plasma 5-HIAA concentrations) were higher in subjects with more components of MetS.

CONCLUSIONS

Plasma 5-HIAA concentrations are high in subjects with MetS, suggesting the potential importance of serotonin in the development of cardiovascular disease in MetS.

Associations of NF-kappaB and bax with apoptosis in varicose veins of women of different age groups

The study aimed at detecting apoptotic endothelial cells (ECs) and smooth muscle cells (SMCs) together with determining expression of NF-kappaB (p105/p50) and Bax in varicose vein walls. Women (n = 35) undergoing the excision of varicose veins were divided into 3 groups: younger than 35 years (I), 36–50 years (II), and older than 50 years (III). Apoptosis was determined by the TUNEL method, NF-kappaB and Bax expression by immunohistochemistry. The percentage of apoptotic ECs and SMCs in the layers of varicose vein wall increased in groups II and III. NF-kappaB expression had the lowest level in Group II with particularly low level in the media. Contrariwise, Bax expression levels in Group II were increased. The study revealed that in varicose veins ECs and SMCs apoptosis increased with advancing age. If increase in apoptosis during earlier stages of varicosities is probably regulated by intrinsic pathway, then in older patients other signaling pathways may be involved.

Monocyte chemotactic protein-1 promotes inflammatory vascular repair of murine carotid aneurysms via a macrophage inflammatory protein-1α and macrophage inflammatory protein-2-dependent pathway

BACKGROUND

Up to 5% of the population may have a brain aneurysm. If the brain aneurysm ruptures, there is >50% mortality, and more than one third of survivors are dependent. Brain aneurysms detected before rupture can be treated to prevent rupture, or ruptured aneurysms can be treated to prevent rerupture. Endovascular coiling of brain aneurysms is the treatment of choice for some aneurysms; however, up to one quarter of aneurysms may recur. The coiled aneurysms that do not recur are characterized by inflammatory intra-aneurysmal tissue healing; therefore, we studied the biology of this process, specifically the role of monocyte chemotactic protein-1 (MCP-1), a cytokine known for tissue healing.

METHODS AND RESULTS

We created coils with a 50:50 poly-dl-lactic glycolic acid (PLGA) coating that released MCP-1 at 3 different doses (100 μg/mL, 1 mg/mL, and 10 mg/mL) and performed a dose-response study for effect on intra-aneurysmal tissue healing in a murine carotid aneurysm model. We then demonstrated that MCP-1 (100 μg/mL)-releasing coils promote significantly greater aneurysm tissue in-growth than bare platinum or PLGA-only coils. We show that MCP-1 recruits the migration of fibroblasts, macrophages, smooth muscle cells, and endothelial cells in vitro in cell migration assays and in vivo in murine carotid aneurysms. Using gfp(+) bone marrow-transplant chimeric mice, we demonstrate that the MCP-1-recruited fibroblasts and macrophages are derived from the bone marrow. We demonstrate that this MCP-1-mediated vascular inflammatory repair occurs via a macrophage inflammatory protein (MIP)-1α- and MIP-2-dependent pathway. MCP-1 released from coiled murine aneurysms causes significant upregulation of MIP-1α and MIP-2 expression by cytokine array assay. Blocking MIP-1α and MIP-2 with antagonist antibody causes a significant decrease in MCP-1-mediated intra-aneurysmal tissue healing.

CONCLUSION

Our findings suggest that MCP-1 has a critical role in promoting inflammatory intra-aneurysmal tissue healing in an MIP-1α- and MIP-2-dependent pathway.

Circulating cytokine concentrations in dogs with different degrees of myxomatous mitral valve disease

Cytokines have been associated with the progression of congestive heart failure (CHF) in humans and may be implicated in the pathophysiology of myxomatous mitral valve disease (MMVD) in dogs. The aim of this study was to determine the serum concentrations of cytokines in dogs with MMVD. The study included 16 Cairn terriers with no or minimal mitral regurgitation (MR), 41 Cavalier King Charles Spaniels (CKCS) with different degrees of MR and 11 dogs of different breeds with CHF due to MMVD. Granulocyte-macrophage colony-stimulating factor, interferon-γ, interleukin (IL)-2, IL-6, IL-7, IL-8, IL-10, IL-15, IL-18, keratinocyte-derived chemokine, interferon-γ-induced protein and monocyte chemoattractant protein-1 (MCP-1) were measured using a canine-specific multiplex immunoassay. CHF dogs had significantly higher MCP-1 concentrations than dogs with no or minimal MR. Among the CKCS, IL-2 and IL-7 decreased with increasing left atrial size and IL-7 also decreased with increasing MR. IL-8 decreased with increasing left ventricular end-systolic internal dimensions. MCP-1 was increased in CHF dogs compared to healthy control dogs and IL-2, IL-7 and IL-8 decreased with increasing indices of disease severity. The results suggest a role for these cytokines in canine MMVD and CHF.

Therapeutic potential for protein kinase C inhibitor in vascular restenosis

Vascular restenosis, an overreaction of biological response to injury, is initialized by thrombosis and inflammation. This response is characterized by increased smooth muscle cell migration and proliferation. Available pharmacological treatments include anticoagulants, antiplatelet agents, immunosuppressants, and antiproliferation agents. Protein kinase C (PKC), a large family of serine/threonine kinases, has been shown to participate in various pathological stages of restenosis. Consequently, PKC inhibitors are expected to exert a wide range of pharmacological activities therapeutically beneficial for restenosis. In this review, the roles of PKC isozymes in platelets, leukocytes, endothelial cells, and smooth muscle cells are discussed, with emphasis given to smooth muscle cells. We will describe cellular and animal studies assessing prevention of restenosis with PKC inhibitors, particularly targeting -α, -β, -δ, and -ζ isozymes. The delivery strategy, efficacy, and safety of such PKC regulators will also be discussed.

SDF-1alpha/CXCL12 enhances GABA and glutamate synaptic activity at serotonin neurons in the rat dorsal raphe nucleus

The serotonin (5-hydroxytryptamine; 5-HT) system has a well-characterized role in depression. Recent reports describe comorbidities of mood-immune disorders, suggesting an immunological component may contribute to the pathogenesis of depression as well. Chemokines, immune proteins which mediate leukocyte trafficking, and their receptors are widely distributed in the brain, mediate neuronal patterning, and modulate various neuropathologies. The purpose of this study was to investigate the neuroanatomical relationship and functional impact of the chemokine stromal cell-derived factor-1alpha/CXCL12 and its receptor, CXCR4, on the serotonin dorsal raphe nucleus (DRN) system in the rat using anatomical and electrophysiological techniques. Immunohistochemical analysis indicates that over 70% of 5-HT neurons colocalize with CXCL12 and CXCR4. At a subcellular level, CXCL12 localizes throughout the cytoplasm whereas CXCR4 concentrates to the outer membrane and processes of 5-HT neurons. CXCL12 and CXCR4 also colocalize on individual DRN cells. Furthermore, electrophysiological studies demonstrate CXCL12 depolarization of 5-HT neurons indirectly via glutamate synaptic inputs. CXCL12 also enhances the frequency of spontaneous inhibitory and excitatory postsynaptic currents (sIPSC and sEPSC). CXCL12 concentration-dependently increases evoked IPSC amplitude and decreases evoked IPSC paired-pulse ratio selectively in 5-HT neurons, effects blocked by the CXCR4 antagonist AMD3100. These data indicate presynaptic enhancement of GABA and glutamate release at 5-HT DRN neurons by CXCL12. Immunohistochemical analysis further shows CXCR4 localization to DRN GABA neurons, providing an anatomical basis for CXCL12 effects on GABA release. Thus, CXCL12 indirectly modulates 5-HT neurotransmission via GABA and glutamate synaptic afferents. Future therapies targeting CXCL12 and other chemokines may treat serotonin related mood disorders, particularly depression experienced by immune-compromised individuals.

Fractalkine/CX3CL1 enhances GABA synaptic activity at serotonin neurons in the rat dorsal raphe nucleus

Serotonin (5-hydroxytryptamine; 5-HT) has an important role in mood regulation, and its dysfunction in the central nervous system (CNS) is associated with depression. Reports of mood and immune disorder co-morbidities indicate that immune-5-HT interactions may mediate depression present in immune compromised disease states including HIV/AIDS, multiple sclerosis, and Parkinson's disease. Chemokines, immune proteins that induce chemotaxis and cellular adhesion, and their G-protein coupled receptors distribute throughout the CNS, regulate neuronal patterning, and mediate neuropathology. The purpose of this study is to investigate the neuroanatomical and neurophysiological relationship between the chemokine fractalkine/CX3CL1 and its receptor CX3CR1 with 5-HT neurons in the rat midbrain raphe nuclei (RN). Immunohistochemistry was used to examine the colocalization of CX3CL1 or CX3CR1 with 5-HT in the RN, and whole-cell patch-clamp recordings in rat brain slices were used to determine the functional impact of CX3CL1 on 5-HT dorsal raphe nucleus (DRN) neurons. Greater than 70% of 5-HT neurons colocalize with CX3CL1 and CX3CR1 in the RN. CX3CL1 localizes as discrete puncta throughout the cytoplasm, whereas CX3CR1 concentrates to the perinuclear region of 5-HT neurons and exhibits microglial expression. CX3CL1 and CX3CR1 also colocalize with one another on individual RN cells. Electrophysiology studies indicate a CX3CL1-mediated enhancement of spontaneous inhibitory postsynaptic current (sIPSC) amplitude and dose-dependent increase of evoked IPSC (eIPSC) amplitude without affecting eIPSC paired-pulse ratio, a finding observed selectively in 5-HT neurons. CX3CL1's effect on eIPSC amplitude is blocked by pretreatment with an anti-CX3CL1 neutralizing antibody. Thus, CX3CL1 enhances postsynaptic GABA receptor number or sensitivity on 5-HT DRN neurons under conditions of both spontaneous and synaptically-evoked GABA release. CX3CL1 may indirectly inhibit 5-HT neurotransmission by increasing the sensitivity of 5-HT DRN neurons to GABA inputs. Therapies targeting CX3CL1 may treat serotonin related mood disorders, including depression experienced by patients with compromised immune systems.

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.

St. John's Wort protein, p27SJ, regulates the MCP-1 promoter

St. John's Wort is commonly known for its antiviral, antidepressant, and cytotoxic properties, but traditionally St. John's Wort has also been used to treat inflammation. In this study, we sought to characterize the mechanisms used by St. John's Wort to treat inflammation by examining the effect of the recently isolated protein from St. John's Wort, p27SJ on the expression of MCP-1. By employing an adenovirus expression vector, we demonstrate that a low concentration of p27SJ upregulates the MCP-1 promoter through the transcription factor C/EBPbeta. In addition, we found that C/EBPbeta-homologous protein (CHOP) or siRNA-C/EBPbeta significantly reduced the ability of p27SJ to activate MCP-1 gene expression. Results from protein-protein interaction studies illustrate the existence of a physical interaction between p27SJ and C/EBPbeta in microglial cells. The use of chromatin immunoprecipitation assay (ChIP) led to the identification of a new cis-element that is responsive to C/EBPbeta within the MCP-1 promoter. Association of C/EBPbeta with MCP-1 DNA was not affected by the presence of p27SJ. The biological activity of MCP-1 produced by cultures of adenovirus-p27SJ transduced cells was increased relative to controls as measured by the transmigration of human Jurkat cells. Thus, we conclude that at high concentration, p27SJ is a potential agent that may be developed as a modulator of MCP-1 leading to the inhibition of the cytokine-mediated inflammatory responses.

Role of Endothelium-derived CC Chemokine Ligand 2 in Idiopathic Pulmonary Arterial Hypertension

RATIONALE

Inflammatory cytokines may affect pulmonary vascular remodeling in idiopathic pulmonary arterial hypertension (IPAH). CC chemokine ligand 2 (CCL2) is synthesized by vascular cells and can stimulate monocyte/macrophage migration and smooth muscle cell (SMC) proliferation.

OBJECTIVES

To investigate the role of CCL2 in IPAH.

METHODS

CCL2 levels in plasma, monocytes, lungs, and medium from pulmonary endothelial cell (P-EC) or pulmonary artery SMC (PA-SMC) cultures were measured by ELISA and Western blot analysis. CCL2 receptor CCR2 mRNA levels in monocytes, P-ECs, and PA-SMCs were measured by real-time polymerase chain reaction. Effect of CCL2 on PA-SMC proliferation and migration was assessed using [3H]thymidine incorporation and a modified Boyden's chamber. The effect of endothelial cell-derived CCL2 on monocyte migration was measured using a modified Boyden's chamber.

MEASUREMENTS AND MAIN RESULTS

Compared with control subjects, we found the following in patients with IPAH: elevated CCL2 protein levels in plasma and lung tissue, whereas monocyte CCL2 levels were similar between patients and control subjects, and elevated CCL2 release by P-ECs or PA-SMCs. P-ECs released twice as much CCL2 than did PA-SMCs. Monocyte migration was markedly increased in the presence of P-ECs, and the increase was larger with P-ECs from patients with IPAH. CCL2-blocking antibodies reduced P-ECs' chemotactic activity by 60%. Compared with controls, PA-SMCs from patients exhibited stronger migratory and proliferative responses to CCL2, in keeping with the finding that CCR2 was markedly increased in PA-SMCs from patients.

CONCLUSIONS

These results suggest that CCL2 overproduction may be a feature of the abnormal P-EC phenotype in IPAH, contributing to the inflammatory process and to pulmonary vascular remodeling.

Obesity-associated mouse adipose stem cell secretion of monocyte chemotactic protein-1

Studies showed that monocyte chemotactic protein-1 (MCP-1) concentrations are increased in obesity. In our current study, we demonstrate that plasma MCP-1 level in leptin-deficient ob/ob mice is significantly higher than in lean mice. Furthermore, we determined that basal adipose tissue MCP-1 mRNA levels are significantly higher in ob/ob mice compared with lean mice. To determine the mechanisms underlying obesity-associated increases in plasma and adipose tissue MCP-1 levels, we determined adipose tissue cell type sources of MCP-1 production. Our data show that adipose tissue stem cells (CD34(+)), macrophages (F4/80(+)), and stromal vascular fraction (SVF) cells express significantly higher levels of MCP-1 compared with adipocytes under both basal and lipopolysaccharide (LPS)-stimulated conditions. Furthermore, basal and LPS-induced MCP-1 secretion levels were the same for both adipose F4/80(+) and CD34(+) cells, whereas adipose CD34(+) cells have twofold higher cell numbers (30% of total SVF cells) compared with F4/80(+) macrophages (15%). Our data also show that CD34(+) cells from visceral adipose tissue depots secrete significantly higher levels of MCP-1 ex vivo when compared with CD34(+) cells from subcutaneous adipose tissue depots. Taken together, our data suggest that adipose CD34(+) stem cells may play an important role in obesity-associated increases in plasma MCP-1 levels.

Impact of increased plasma serotonin levels and carotid atherosclerosis on vascular dementia

Serotonin (5-HT), a potent vasoconstrictor in the large cerebral arteries, is considered to play a key role in atherothrombosis and to be implicated in ischemic cerebrovascular events followed by delayed neuronal death. The present study aims at evaluating the relationship between plasma levels of 5-HT and vascular dementia (VaD) caused by stroke or atherosclerotic small vessel disease. Carotid artery intima-media thickness (IMT), plaques, plasma 5-HT levels and atherosclerotic parameters were determined in 20 patients with VaD and 40 age-matched controls. Age, gender, body mass index, systolic and diastolic blood pressure, fasting plasma glucose levels and serum levels of insulin, triglycerides, high-density lipoprotein cholesterol, leptin, adiponectin and interleukin-6 and plasma levels of plasminogen activator inhibitor-1 were not significantly different between the two groups. Serum levels of insulin-like growth factor-1 (IGF-1) were significantly lower in VaD patients than in controls. Plasma 5-HT levels, serum levels of hepatocyte growth factor (HGF), low-density lipoprotein (LDL) cholesterol and high-sensitive C-reactive protein (hs-CRP), max IMT and plaque frequency were significantly greater in VaD patients than in controls. There was a significant positive correlation of max IMT with 5-HT or HGF levels. Multiple logistic regression analysis revealed that increased plasma levels of 5-HT and carotid plaque prevalence had significantly independent association with VaD as compared with serum levels of IGF-1, HGF, LDL cholesterol and hs-CRP. These results suggest that increased plasma levels of 5-HT and carotid atherosclerotic plaques may be involved in the pathogenesis and progression of VaD.

Vascular Remodeling in Transplant Vasculopathy

As therapeutic strategies to prevent acute rejection progressively improve, transplant vasculopathy (TV) constitutes the single most important limitation for long-term functioning of solid organ allografts. In TV, allograft arteries characteristically develop severe, diffuse intimal hyperplastic lesions that eventually compromise luminal flow and cause ischemic graft failure. Traditional immunosuppressive strategies that check acute allograft rejection do not prevent TV; indeed 50% of transplant recipients will have significant disease within five years of organ transplantation, and 90% will have significant TV a decade after their surgery. TV can involve the entire length of the transplanted arterial bed, including penetrating intraorgan arterioles. Indeed, the luminal narrowing of such penetrating vessels may be the most functionally significant because arterioles represent the major contributors to tissue vascular resistance. Because of the diffuseness of TV involvement in the allograft vascular bed, the only currently definitive therapy requires re-transplantation. Nevertheless, as we better understand the pathogenesis and critical mediators of these lesions, pharmacological advances can be anticipated. Other articles in this thematic review series focus on the specifics of the inciting injury, the cytokines and chemokines that drive TV development, and the nature of the recruited cells in TV lesions, as well as the pathogenic similarities between TV and other vascular lesions such as atherosclerosis. This review focuses on the mechanisms of vascular wall remodeling in TV, including the intimal accumulation of smooth muscle-like cells and associated extracellular matrix, medial smooth muscle cell degeneration, and adventitial fibrosis. A brief overview highlights the aneurysmal changes that can accrue when vessel wall inflammation has a cytokine profile distinct from the typical proinflammatory interferon-gamma-dominated milieu.

Pioglitazone Prevents Acute and Chronic Cardiac Allograft Rejection

Background— Peroxisome proliferator–activated receptor-γ plays an important role in regulating inflammation. Although cardiac transplantation is an established therapy for patients with end-stage heart disease, allograft rejection is a major concern for long-term survival. We investigated the role of pioglitazone in acute and chronic rejection in a murine cardiac transplantation model.

Methods and Results— We performed heterotopic murine cardiac transplantation in total allomismatch or major histocompatibility complex class II–mismatched combinations. Recipient mice were given standard chow or chow containing pioglitazone (3 mg · kg −1 · d −1 ) beginning 1 day before cardiac transplantation. In acute rejection, animals given pioglitazone showed significantly longer cardiac allograft survival than control mice (mean survival time, 34.6±7.8 versus 8.4±0.4 days; P <0.003). Treatment with pioglitazone significantly suppressed graft expression of interferon-γ and monocyte chemoattractant protein-1. In chronic rejection, neointimal hyperplasia was significantly lower in allografts from mice treated with pioglitazone (luminal occlusion, 25.1±8.8%) than in those from control mice (65.8±7.3%, P <0.001). Pioglitazone-treated allografts showed significantly reduced expression of interferon-γ, interleukin-10, and monocyte chemoattractant protein-1. We performed mixed lymphocyte reactions and in vitro proliferation assays of smooth muscle cells. Addition of pioglitazone to mixed lymphocyte reactions inhibited proliferation of T cells. Smooth muscle cells showed significant proliferation when cocultured with activated splenocytes. This proliferation was significantly inhibited by the addition of pioglitazone (1 μmol/L).

Conclusions— Pioglitazone prolongs allograft survival and attenuates neointimal hyperplasia through the suppression of proliferation of smooth muscle cells. Pioglitazone may be a novel means to prevent acute and chronic allograft rejection.

Research progress of vasculopathy in portal hypertension

Portal hypertension, one of the vascular diseases, not only has lesions in liver, but also changes in vascular structures and functions of extrahepatic portal system, systemic system and pulmonary circulation. The pathological changes of vasculopathy in portal hypertension include remodeling of arterialized visceral veins, intimal injury of visceral veins and destruction of contractile structure in visceral arterial wall. The mechanisms of vasculopathy in portal hypertension may be attributed to the changes of hemodynamics in portal system, immune response, gene modulation, vasoactive substances, and intrahepatic blood flow resistance. Portal hypertension can cause visceral hyperdynamic circulation, and the development and progression of visceral vasculopathy, while visceral vasculopathy can promote the development and progression of portal hypertension and visceral hyperdynamic circulation in turn. The aforementioned three factors interact in the pathogenesis of hepatic cirrhosis-induced portal hypertension and are involved in hemorrhage due to varicose vein rupture.

Production of chemokines by perivascular adipose tissue: a role in the pathogenesis of atherosclerosis?

OBJECTIVE

Obesity is associated with an increased risk for cardiovascular disease. Although it is known that white adipose tissue (WAT) produces numerous proinflammatory and proatherogenic cytokines and chemokines, it is unclear whether adipose-derived chemotactic signals affect the chronic inflammation in atherosclerosis.

METHODS AND RESULTS

Histological examination showed that perivascular WAT (pWAT) is in close proximity to vascular walls, particularly at sites that have a tendency to develop atherosclerosis. In rodents, the amount of pWAT is markedly increased by a high-fat diet. At a functional level, supernatant from subcutaneous and pWAT strongly induced the chemotaxis of peripheral blood leukocytes. The migration of granulocytes and monocytes was mostly mediated by interleukin-8 and monocyte chemoattractant protein-1, respectively, whereas both chemokines contributed to the migration of activated T cells. Moreover, pWAT produces these chemokines, as shown by immunohistochemistry and by explant culture. The accumulation of macrophages and T cells at the interface between pWAT and the adventitia of human atherosclerotic aortas may reflect this prochemotactic activity of pWAT.

CONCLUSIONS

Human pWAT has chemotactic properties through the secretion of different chemokines, and we propose that pWAT might contribute to the progression of obesity-associated atherosclerosis.

Reactive oxygen species and ERK 1/2 mediate monocyte chemotactic protein-1-stimulated smooth muscle cell migration

Monocyte chemotactic protein-1 (MCP-1), a potent chemoattractant for monocytes, is thought to play a major role in atherosclerosis, but whether its atherogenic effects involve the direct modulation of vascular smooth muscle cell (SMC) functions remains unclear. This study examined the effects of MCP-1 on the migration of cultured A7r5 SMCs and the signaling pathways involved. Addition of recombinant MCP-1 stimulated SMC migration in modified Boyden chambers coated with type I collagen in a concentration-dependent manner, with 10(-9) M being maximally effective. Using untreated A7r5 cells, two MCP-1 receptors, CCR2 and CCR4, were detected and MCP-1 secretion was significantly increased by stimulation with platelet-derived growth factor. MCP-1-stimulated A7r5 migration was completely blocked by the NAD(P)H oxidase inhibitor, diphenylene iodonium (DPI), and dose-dependently inhibited by polyethylene glycol-conjugated superoxide dismutase (PEG-SOD), suggesting a role for reactive oxygen species (ROS) in this process. During MCP-1 stimulation, ROS production increased rapidly, then gradually decayed over 60 min, and this effect was markedly decreased by pretreatment with DPI or PEG-SOD. Interestingly, U0126 and PD98059, which inhibit activation of extracellular signal-regulated kinases 1/2 (ERK 1/2), significantly inhibited MCP-1-activated ROS generation. Furthermore, transfection of an active mutant of MEK1 (ERK 1/2 kinase) markedly increased superoxide production in rat aortic smooth muscle cells, as detected by dihydroethydium staining, suggesting that ERK 1/2 activation stimulates ROS generation. ERK 1/2 activation was increased for at least 30 min in cells incubated with MCP-1, and this effect was abolished by U0126 or DPI pretreatment. These results demonstrate that MCP-1 is a chemoattractant for SMCs and that MCP-1-stimulated migration requires both ROS production and ERK 1/2 activation in a positive activation loop, which may contribute to the atherogenic effects of MCP-1.

Serotonin acts as an up-regulator of acyl-coenzyme A:cholesterol acyltransferase-1 in human monocyte-macrophages

Acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) converts intracellular free cholesterol into cholesterol ester for storage in lipid droplets and plays an important role in the formation of macrophage-derived foam cells in atherosclerotic lesions. Serotonin (5-HT), a potent vasoconstrictor that is released from activated platelets, increases uptake of oxidized low-density lipoprotein (LDL) by macrophages, leading to foam cell formation, and contributes to the development of atherosclerotic plaque. However, it is not yet known whether 5-HT affects ACAT-1 expression in human monocyte-macrophages as the molecular mechanism of enhanced foam cell formation by 5-HT remains unclear. We examined the effects of 5-HT on ACAT-1 expression during differentiation of cultured human monocytes into macrophages. Expression of ACAT-1 protein but not 5-HT2A receptor increased in a time-dependent manner. 5-HT increased ACAT activity in a concentration-dependent manner after 7 days in primary monocyte culture. Immunoblotting analysis showed that 5-HT at 10 microM increased ACAT-1 protein expression level by two-fold, and this effect was abolished completely by a 5-HT2A receptor antagonist (sarpogrelate), its major metabolite (M-1), a G protein inactivator (GDP-beta-S), a protein kinase C (PKC) inhibitor (rottlerin), a Src family inhibitor (PP2), or a mitogen-activated protein kinase (MAPK) kinase inhibitor (PD98059). Northern blotting analysis indicated that among the four ACAT-1 mRNA transcripts (2.8-, 3.6-, 4.3-, and 7.0-kb), the levels of the 2.8- and 3.6-kb transcripts were selectively up-regulated by approximately 1.7-fold by 5-HT (10 microM). The results of the present study suggested that 5-HT may play a crucial role in macrophage-derived foam cell formation by up-regulating ACAT-1 expression via the 5-HT2A receptor/G protein/c-Src/PKC/MAPK pathway, contributing to the progression of atherosclerotic plaque.

Sarpogrelate: cardiovascular and renal clinical potential

Sarpogrelate is a selective 5-hydroxytryptamine receptor subtype 2A (5-HT2A) antagonist. It is metabolised to racemic M-1 and both enantiomers of M-1 are also antagonists of 5-HT2A receptors. Sarpogrelate inhibits responses to 5-HT mediated by 5-HT2A receptors such as platelet aggregation, vasoconstriction and vascular smooth muscle proliferation. There is no information available on the pharmacokinetics of sarpogrelate. Sarpogrelate is efficacious in animal models of thrombosis, coronary artery spasm, atherosclerosis, restenosis, peripheral vascular disease, pulmonary hypertension, ischaemic heart disease, myocardial infarction, diabetes and kidney disease. Small clinical trials indicate that sarpogrelate may be beneficial in the treatment of coronary artery disease, angina, restenosis, heart valve prostheses surgery, diabetes mellitus, Raynaud's phenomenon, systemic sclerosis and Buerger's disease. Larger, randomised, double-blind, placebo-controlled clinical trials of sarpogrelate in intermittent claudication, coronary artery disease, restenosis and diabetes should be considered.

Significance of the level of monocyte chemoattractant protein-1 in human atherosclerosis

BACKGROUND

Monocyte chemoattractant protein-1 (MCP-1), a potent chemoattractant for monocytes, plays an important role in the earliest events of atherogenesis. However, direct evidence of the effects of MCP-1 on atherosclerosis in chronic hemodialysis (HD) patients has not been reported.

METHODS AND RESULTS

The serum MCP-1 concentrations and the intimal - medial thickness (IMT) in the carotid arteries were measured in 42 non-diabetic chronic HD patients and 20 age-matched controls. The expression of MCP-1 was examined immunohistochemically in radial arterial tissues obtained from the HD patients. IMT and the serum concentration of MCP-1 in the HD patients were both significantly greater than in controls. Multiple regression analysis revealed that the serum concentration of MCP-1 was an independent factor influencing IMT. Tissue immunostaining showed that MCP-1 is expressed in both endothelial and smooth muscle cells and that its level of expression correlates with the serum concentration of MCP-1.

CONCLUSIONS

An increase in MCP-1 may be an important factor in the progression of atherosclerosis in non-diabetic HD patients.

Chemokines in the Pathogenesis of Vascular Disease

Our increasing appreciation of the importance of inflammation in vascular disease has focused attention on the molecules that direct the migration of leukocytes from the blood stream to the vessel wall. In this review, we summarize roles of the chemokines, a family of small secreted proteins that selectively recruit monocytes, neutrophils, and lymphocytes to sites of vascular injury, inflammation, and developing atherosclerosis. Chemokines induce chemotaxis through the activation of G-protein-coupled receptors, and the receptors that a given leukocyte expresses determines the chemokines to which it will respond. Monocyte chemoattractant protein 1 (MCP-1), acting through its receptor CCR2, appears to play an early and important role in the recruitment of monocytes to atherosclerotic lesions and in the formation of intimal hyperplasia after arterial injury. Acute thrombosis is an often fatal complication of atherosclerotic plaque rupture, and recent evidence suggests that MCP-1 contributes to thrombin generation and thrombus formation by generating tissue factor. Because of their critical roles in monocyte recruitment in vascular and nonvascular diseases, MCP-1 and CCR2 have become important therapeutic targets, and efforts are underway to develop potent and specific antagonists of these and related chemokines.

Inhibition of intimal hyperplasia in transgenic mice conditionally expressing the chemokine-binding protein M3

Chemokines have been implicated in the pathogenesis of a wide variety of diseases. This report describes the generation of transgenic mice that conditionally express M3, a herpesvirus protein that binds and inhibits chemokines. In response to doxycycline, M3 expression was induced in a variety of tissues and M3 was detectable in the blood by Western blotting. No gross or histological abnormalities were seen in mice expressing M3. To determine whether M3 expression could modify a significant pathophysiological response, we examined its effect on the development of intimal hyperplasia in response to femoral arterial injury. Intimal hyperplasia is thought to play a critical role in the development of restenosis after percutaneous transluminal coronary angioplasty and in the progression of atherosclerosis. Induction of M3 expression resulted in a 67% reduction in intimal area and a 68% reduction in intimal/medial ratio after femoral artery injury. These data support a role for chemokines in regulating intimal hyperplasia and suggest that M3 may be effective in attenuating this process. This transgenic mouse model should be a valuable tool for investigating the role of chemokines in a variety of pathological states.

MCP-1-dependent signaling in CCR2(-/-) aortic smooth muscle cells

Monocyte chemoattractant protein-1 (MCP-1, CCL2) is a mediator of inflammation that has been implicated in the pathogenesis of a wide variety of human diseases. CCR2, a heterotrimeric G-coupled receptor, is the only known receptor that functions at physiologic concentrations of MCP-1. Despite the importance of CCR2 in mediating MCP-1 responses, several recent studies have suggested that there may be another functional MCP-1 receptor. Using arterial smooth muscle cells (SMC) from CCR2(-/-) mice, we demonstrate that MCP-1 induces tissue-factor activity at physiologic concentrations. The induction of tissue factor by MCP-1 is blocked by pertussis toxin and 1,2-bis(O-aminophenyl-ethane-ethan)-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, suggesting that signal transduction through the alternative receptor is G(alphai)-coupled and dependent on mobilization of intracellular Ca(2+). MCP-1 induces a time- and concentration-dependent phosphorylation of the mitogen-activated protein kinases p42/44. The induction of tissue factor activity by MCP-1 is blocked by PD98059, an inhibitor of p42/44 activation, but not by SB203580, a selective p38 inhibitor. These data establish that SMC possess an alternative MCP-1 receptor that signals at concentrations of MCP-1 that are similar to those that activate CCR2. This alternative receptor may be important in mediating some of the effects of MCP-1 in atherosclerotic arteries and in other inflammatory processes.

ERK Is Regulated by Sodium-Proton Exchanger in Rat Aortic Vascular Smooth Muscle Cells

The purposes of this study were to test 1) the relationship between two widely studied mitogenic effector pathways, and 2) the hypothesis that sodium-proton exchanger type 1 (NHE-1) is a regulator of extracellular signal-regulated protein kinase (ERK) activation in rat aortic smooth muscle (RASM) cells. Angiotensin II (Ang II) and 5-hydroxytryptamine (5-HT) stimulated both ERK and NHE-1 activities, with activation of NHE-1 preceding that of ERK. The concentration-response curves for 5-HT and Ang II were superimposable for both processes. Inhibition of NHE-1 with pharmacological agents or by isotonic replacement of sodium in the perfusate with choline or tetramethylammonium greatly attenuated ERK activation by 5-HT or Ang II. Similar maneuvers significantly attenuated 5-HT- or Ang II-mediated activation of MEK and Ras but not transphosphorylation of the epidermal growth factor (EGF) receptor. EGF receptor blockade attenuated ERK activation, but not NHE-1 activation by 5-HT and Ang II, suggesting that the EGF receptor and NHE-1 work in parallel to stimulate ERK activity in RASM cells, converging distal to the EGF receptor but at or above the level of Ras in the Ras-MEK-ERK pathway. Receptor-independent activation of NHE-1 by acute acid loading of RASM cells resulted in the rapid phosphorylation of ERK, which could be blocked by pharmacological inhibitors of NHE-1 or by isotonic replacement of sodium, closely linking the proton transport function of NHE-1 to ERK activation. These studies identify NHE as a new regulator of ERK activity in RASM cells.

Endogenous VEGF-A is responsible for mitogenic effects of MCP-1 on vascular smooth muscle cells

Vessel wall remodeling is a complex phenomenon in which the loss of differentiation of vascular smooth muscle cells (VSMCs) occurs. We investigated the role of rat macrophage chemoattractant protein (MCP)-1 on rat VSMC proliferation and migration to identify the mechanism(s) involved in this kind of activity. Exposure to very low concentrations (1-100 pg/ml) of rat MCP-1 induced a significant proliferation of cultured rat VSMCs assessed as cell duplication by the counting of total cells after exposure to test substances. MCP-1 stimulated VSMC proliferation and migration in a two-dimensional lateral sheet migration of adherent cells in culture. Endogenous vascular endothelial growth factor-A (VEGF-A) was responsible for the mitogenic activity of MCP-1, because neutralizing anti-VEGF-A antibody inhibited cell proliferation in response to MCP-1. On the contrary, neutralizing anti-fibroblast growth factor-2 and anti-platelet-derived growth factor-bb antibodies did not affect VSMC proliferation induced by MCP-1. RT-PCR and Western blot analyses showed an increased expression of either mRNA or VEGF-A protein after MCP-1 activation (10-100 pg/ml), whereas no fms-like tyrosine kinase (Flt)-1 receptor upregulation was observed. Because we have previously demonstrated that hypoxia (3% O2) can enhance VSMC proliferation induced by VEGF-A through Flt-1 receptor upregulation, the effects of hypoxia on the response of VSMCs to MCP-1 were investigated. Severe hypoxia (3% O2) potentiated the growth-promoting effect of MCP-1, which was able to significantly induce cell proliferation even at a concentration as low as 0.1 pg/ml. These findings demonstrate that low concentrations of rat MCP-1 can directly promote rat VSMC proliferation and migration through the autocrine production of VEGF-A.

Mitogen-induced activation of Na+/H+ exchange in vascular smooth muscle cells involves janus kinase 2 and Ca2+/calmodulin

The sodium/proton exchanger type 1 (NHE-1) plays an important role in the proliferation of vascular smooth muscle cells (VSMC). We have examined the regulation of NHE-1 by two potent mitogens, serotonin (5-HT, 5-hydroxytryptamine) and angiotensin II (Ang II), in cultured VSMC derived from rat aorta. 5-HT and Ang II rapidly activated NHE-1 via their G protein-coupled receptors (5-HT(2A) and AT(1)) as assessed by proton microphysiometry of quiescent cells and by measurements of intracellular pH on a FLIPR (fluorometric imaging plate reader). Activation of NHE-1 was blocked by inhibitors of phospholipase C, CaM, and Jak2 but not by pertussis toxin or inhibitors of protein kinase C. Immunoprecipitation/immunoblot studies showed that 5-HT and Ang II induce phosphorylation of Jak2 and induce the formation of signal transduction complexes that included Jak2, CaM, and NHE-1. The cell-permeable Ca(2+) chelator BAPTA-AM blocked activation of Jak2, complex formation between Jak2 and CaM, and tyrosine phosphorylation of CaM, demonstrating that elevated intracellular Ca(2+) is essential for those events. Thus, mitogen-induced activation of NHE-1 in VSMC is dependent upon elevated intracellular Ca(2+) and is mediated by the Jak2-dependent tyrosine phosphorylation of CaM and subsequent increased binding of CaM to NHE-1, similar to the pathway previously described for the bradykinin B(2) receptor in inner medullary collecting duct cells of the kidney [Mukhin, Y. V., et al. (2001) J. Biol. Chem. 276, 17339-17346]. We propose that this pathway represents a fundamental mechanism for the rapid regulation of NHE-1 by G(q/11) protein-coupled receptors in multiple cell types.

Monocyte chemotactic protein-1 directly induces human vascular smooth muscle proliferation

Although monocyte chemotactic protein-1 (MCP-1) is best known for its ability to recruit mononuclear cells, few studies have examined the effects of this chemokine on other events in the vascular response to injury. The purpose of the present study was to determine the influence of MCP-1 on human vascular smooth muscle (VSMC) proliferation. MCP-1 induced concentration-dependent VSMC proliferation as measured by bromodeoxyuridine (BrdU) uptake. Direct cell counting demonstrated a twofold increase in VSMC after stimulation with MCP-1. This mitogenic effect was similar to that observed with the prototypical atherogenic cytokine platelet-derived growth factor. Immunohistochemistry and Western blot analysis revealed that MCP-1 increased both proliferating nuclear cell antigen and cyclin A expression. Whereas MCP-1 did not promote nuclear factor-kappaB activation, MCP-1-induced VSMC proliferation appeared to be dependent on phosphotidylinositol 3-kinase activation. In conclusion, MCP-1 directly induces VSMC growth, which is associated with activation of cell cycle proteins and intracellular proliferative signals. Within the inflammatory paradigm of vascular remodeling, these data suggest that MCP-1 is more than simply a chemokine but also a potent mitogen for VSMC proliferation.

Synergistic effect of urotensin II with serotonin on vascular smooth muscle cell proliferation

BACKGROUND

Urotensin II (U-II), the most potent vasoconstrictor, and serotonin (5-HT) are known to play an important role in pulmonary hypertension. However, little is known about the effect of U-II and its interaction with 5-HT on vascular smooth muscle cell (VSMC) proliferation.

OBJECTIVE

We assessed the interaction between U-II and 5-HT in inducing VSMC proliferation.

METHODS

Growth-arrested rabbit VSMCs were incubated in serum-free medium with different concentrations of U-II and 5-HT. VSMC proliferation was examined by the increase in [3H]thymidine incorporation into DNA and cell number.

RESULTS

U-II or 5-HT induced [3H]thymidine incorporation in a dose-dependent manner with a maximal effect at a concentration of 50 nmol/l (161%) or 50 micromol/l (205%), respectively. When added together, low concentrations of U-II (50 nmol/l) and 5-HT (1 micromol/l) interacted synergistically in inducing [3H]thymidine incorporation (382%). These effects on [3H]thymidine incorporation were paralleled by an increase in cell number. The G-protein inactivator GDP-beta-S (100 micromol/l), protein kinase C (PKC) inhibitor Ro31-8220 (0.1 micromol/l), Src family tyrosine kinase inhibitor PP2 (1 micromol/l), and mitogen-activated protein kinase (MAPK) kinase inhibitor PD098059 (10 micromol/l) inhibited the mitogenic effects of U-II and 5-HT and also their interaction in inducing [3H]thymidine incorporation.

CONCLUSION

Our results suggest that U-II and 5-HT may induce the synergistic interaction in inducing VSMC proliferation via a G-protein-coupled receptor/PKC/Src tyrosine kinase/MAPK pathway, thus contributing to the relatively rapid development of atherosclerosis in hypertensive vascular disease.