Role of p44/p42 MAP kinase in the age-dependent increase in vascular smooth muscle cell proliferation and neointimal formation

Correlation Between Calcification Characteristics of Carotid Atherosclerotic Plaque and Plaque Vulnerability

Purpose

To investigate the relationship between calcification characteristics of carotid atherosclerotic plaque and lipid rich necrotic core (LRNC) and intraplaque hemorrhage (IPH).

Methods

Patients with severe carotid stenosis undergoing carotid endarterectomy (CEA) were selected. Ultrasound and CT angiography (CTA) were performed to evaluate the calcification characteristics of the plaque before the surgery.

Results

A total of 142 patients were included and 142 pathological specimens of postoperative plaque were obtained accordingly. There were 78 plaques (54.9%) with LRNC and 41 (28.9%) with IPH. The plaque with LRNC had higher calcification rate (93.6%) compared with the plaque with IPH (87.8%). LRNC was often found in multiple calcification (P = 0.003) and mixed type calcification (P = 0.001). Multiple calcification was more likely to combine with IPH (P = 0.008), while simple basal calcification was not likely to combine IPH (P = 0.002). Smaller granular calcification was more likely to be associated with IPH (P < 0.05). In multivariate regression analysis of IPH and calcification characteristics, simple basal calcification was still a protective factor for IPH (OR, 0.25; 95% CI, 0.09–0.66; P = 0.005), while multiple calcification was closely related to the occurrence of IPH (OR, 3.58; 95% CI, 1.49–8.61; P = 0.004).

Conclusion

Calcification characteristics of carotid atherosclerotic plaques are closely related to the vulnerability of plaques, especially multiple calcification and mixed type calcification.

MHY2013 Modulates Age-related Inflammation and Insulin Resistance by Suppressing the Akt/FOXO1/IL-1β Axis and MAPK-mediated NF-κB Signaling in Aged Rat Liver

Chronic inflammation is a major risk factor underlying aging and age-associated diseases. It impairs normal lipid accumulation, adipose tissue function, and mitochondrial function, which eventually lead to insulin resistance. Peroxisome proliferator-activated receptors (PPARs) critically regulate gluconeogenesis, lipid metabolism, and the lipid absorption and breakdown process, and PPAR activity decreases in the liver during aging. In the present study, we investigated the ability of 2-(4-(5,6-methylenedioxybenzo[d]thiazol-2-yl)-2-methylphenoxy)-2-methylpropanoic acid (MHY2013), synthesized PPARα/PPARβ/PPARγ pan agonist, to suppress the inflammatory response and attenuate insulin resistance in aged rat liver. Six- and 20-month-old rats were divided into 4 groups: young and old rats fed ad libitum; and old rats fed ad libitum supplemented with MHY2013 (1 mg and 5 mg/kg/d for 4 wk). We found that MHY2013 supplementation efficiently downregulated the activity of nuclear factor-κB through JNK/ERK/p38 mitogen-activated protein kinase signaling in the liver of aged rats. In addition, MHY2013 treatment increased hepatic insulin signaling, and the downstream signaling activity of FOXO1, which is negatively regulated by Akt. Downregulation of Akt increases expression of FOXO1, which acts as a transcription factor and increases transcription of interleukin-1β, leading to hepatic inflammation. The major finding of this study is that MHY2013 acts as a therapeutic agent against age-related inflammation associated with insulin resistance by activating PPARα, PPARβ, and PPARγ. Thus, the study provides evidence for the anti-inflammatory properties of MHY2013, and the role it plays in the regulation of age-related alterations in signal transduction pathways.

Notoginsenoside R1 inhibits vascular smooth muscle cell proliferation, migration and neointimal hyperplasia through PI3K/Akt signaling

Restenosis caused by neointimal hyperplasia significantly decreases long-term efficacy of percutaneous transluminal angioplasty (PTA), stenting, and by-pass surgery for managing coronary and peripheral arterial diseases. A major cause of pathological neointima formation is abnormal vascular smooth muscle cell (VSMC) proliferation and migration. Notoginsenoside R1 (NGR1) is a novel saponin that is derived from Panax notoginseng and has reported cardioprotective, neuroprotective and anti-inflammatory effects. However, its role in modulating VSMC neointima formation remains unexplored. Herein, we report that NGR1 inhibits serum-induced VSMC proliferation and migration by regulating VSMC actin cytoskeleton dynamics. Using a mouse femoral artery endothelium denudation model, we further demonstrate that systemic administration of NGR1 had a potent therapeutic effect in mice, significantly reducing neointimal hyperplasia following acute vessel injury. Mechanistically, we show that NGR1’s mode of action is through inhibiting the activation of phosphatidylinositol 3-kinase (PI3K)/Akt signaling. Taken together, this study identified NGR1 as a potential therapeutic agent for combating restenosis after PTA in cardiovascular diseases.

Loss of Spry1 attenuates vascular smooth muscle proliferation by impairing mitogen-mediated changes in cell cycle regulatory circuits

Signals from growth factors or mechanical stimuli converge to promote vascular smooth muscle cell (VSMC) migration and proliferation, key events in the pathogenesis of intimal hyperplasia upon vascular injury. Spry1, a regulator of receptor tyrosine kinases (RTK), plays a role in maintaining the contractile phenotype of VSMC. The aim of the current study was to determine the role of Spry1 in VSMC proliferation in vitro and injury induced neointimal hyperplasia in vivo. VSMC proliferation and neointima formation were evaluated in cultured human aortic SMC (hAoSMC) and ligation-induced injury of mouse carotid arteries from Spry1 gene targeted mice, and their corresponding wild type littermates. Human Spry1 or non-targeting control lentiviral shRNAs were used to knock down Spry1 in hAoSMC. Time course cell cycle analysis showed a reduced fraction of S-phase cells at 12 and 24 h after growth medium stimulation in Spry1 shRNA transduced hAoSMC. Consistent with reduced S-phase entry, the induction of cyclinD1 and the levels of pRbS807/S811, pH3Ser10, and pCdc2 were also reduced, while the cell cycle inhibitor p27Kip1 was maintained in Spry1 knockdown hAoSMC. In vivo, loss of Spry1 attenuated carotid artery ligation-induced neointima formation in mice, and this effect was accompanied by a decrease in cell proliferation similar to the in vitro results. Our findings demonstrate that loss of Spry1 attenuates mitogen-induced VSMC proliferation, and thus injury-induced neointimal hyperplasia likely via insufficient activation of Akt signaling causing decreased cyclinD1 and increased p27Kip1 and a subsequent decrease in Rb and cdc2 phosphorylation.

In search for geroprotectors: in silico screening and in vitro validation of signalome-level mimetics of young healthy state

Populations in developed nations throughout the world are rapidly aging, and the search for geroprotectors, or anti-aging interventions, has never been more important. Yet while hundreds of geroprotectors have extended lifespan in animal models, none have yet been approved for widespread use in humans. GeroScope is a computational tool that can aid prediction of novel geroprotectors from existing human gene expression data. GeroScope maps expression differences between samples from young and old subjects to aging-related signaling pathways, then profiles pathway activation strength (PAS) for each condition. Known substances are then screened and ranked for those most likely to target differential pathways and mimic the young signalome. Here we used GeroScope and shortlisted ten substances, all of which have lifespan-extending effects in animal models, and tested 6 of them for geroprotective effects in senescent human fibroblast cultures. PD-98059, a highly selective MEK1 inhibitor, showed both life-prolonging and rejuvenating effects. Natural compounds like N-acetyl-L-cysteine, Myricetin and Epigallocatechin gallate also improved several senescence-associated properties and were further investigated with pathway analysis. This work not only highlights several potential geroprotectors for further study, but also serves as a proof-of-concept for GeroScope, Oncofinder and other PAS-based methods in streamlining drug prediction, repurposing and personalized medicine.

Effects of age and exercise training on coronary microvascular smooth muscle phenotype and function

Coronary microvascular function and blood flow responses during acute exercise are impaired in the aged heart but can be restored by exercise training. Coronary microvascular resistance is directly dependent on vascular smooth muscle function in coronary resistance arterioles; therefore, we hypothesized that age impairs contractile function and alters the phenotype of vascular smooth muscle in coronary arterioles. We further hypothesized that exercise training restores contractile function and reverses age-induced phenotypic alterations of arteriolar smooth muscle. Young and old Fischer 344 rats underwent 10 wk of treadmill exercise training or remained sedentary. At the end of training or cage confinement, contractile responses, vascular smooth muscle proliferation, and expression of contractile proteins were assessed in isolated coronary arterioles. Both receptor- and non-receptor-mediated contractile function were impaired in coronary arterioles from aged rats. Vascular smooth muscle shifted from a differentiated, contractile phenotype to a secretory phenotype with associated proliferation of smooth muscle in the arteriolar wall. Expression of smooth muscle myosin heavy chain 1 (SM1) was decreased in arterioles from aged rats, whereas expression of phospho-histone H3 and of the synthetic protein ribosomal protein S6 (rpS6) were increased. Exercise training improved contractile responses, reduced smooth muscle proliferation and expression of rpS6, and increased expression of SM1 in arterioles from old rats. Thus age-induced contractile dysfunction of coronary arterioles and emergence of a secretory smooth muscle phenotype may contribute to impaired coronary blood flow responses, but arteriolar contractile responsiveness and a younger smooth muscle phenotype can be restored with late-life exercise training. NEW & NOTEWORTHY Aging impairs contractile function of coronary arterioles and induces a shift of the vascular smooth muscle toward a proliferative, noncontractile phenotype. Late-life exercise training reverses contractile dysfunction of coronary arterioles and restores a young phenotype to the vascular smooth muscle.

Age-related Impairment of Vascular Structure and Functions

Among age-related diseases, cardiovascular and cerebrovascular diseases are major causes of death. Vascular dysfunction is a key characteristic of these diseases wherein age is an independent and essential risk factor. The present work will review morphological alterations of aging vessels in-depth, which includes the discussion of age-related microvessel loss and changes to vasculature involving the capillary basement membrane, intima, media, and adventitia as well as the accompanying vascular dysfunctions arising from these alterations.

A Novel Protective Function of 5-Methoxytryptophan in Vascular Injury

5-Methoxytryptophan (5-MTP), a 5-methoxyindole metabolite of tryptophan metabolism, was recently shown to suppress inflammatory mediator-induced cancer cell proliferation and migration. However, the role of 5-MTP in vascular disease is unknown. In this study, we investigated whether 5-MTP protects against vascular remodeling following arterial injury. Measurements of serum 5-MTP levels in healthy subjects and patients with coronary artery disease (CAD) showed that serum 5-MTP concentrations were inversely correlated with CAD. To test the role of 5-MTP in occlusive vascular disease, we subjected mice to a carotid artery ligation model of neointima formation and treated mice with vehicle or 5-MTP. Compared with vehicle-treated mice, 5-MTP significantly reduced intimal thickening by 40% 4 weeks after ligation. BrdU incorporation assays revealed that 5-MTP significantly reduced VSMC proliferation both in vivo and in vitro. Furthermore, 5-MTP reduced endothelial loss and detachment, ICAM-1 and VCAM-1 expressions, and inflammatory cell infiltration in the ligated arterial wall, suggesting attenuation of endothelial dysfunction. Signaling pathway analysis indicated that 5-MTP mediated its effects predominantly via suppressing p38 MAPK signaling in endothelial and VSMCs. Our data demonstrate a novel vascular protective function of 5-MTP against arterial injury-induced intimal hyperplasia. 5-MTP might be a therapeutic target for preventing and/or treating vascular remodeling.

Efficacy of female rat models in translational cardiovascular aging research

Cardiovascular disease is the leading cause of death in women in the United States. Aging is a primary risk factor for the development of cardiovascular disease as well as cardiovascular-related morbidity and mortality. Aging is a universal process that all humans undergo; however, research in aging is limited by cost and time constraints. Therefore, most research in aging has been done in primates and rodents; however it is unknown how well the effects of aging in rat models translate into humans. To compound the complication of aging gender has also been indicated as a risk factor for various cardiovascular diseases. This review addresses the systemic pathophysiology of the cardiovascular system associated with aging and gender for aging research with regard to the applicability of rat derived data for translational application to human aging.

Proinflammation of aging central arteries: a mini-review

Arterial aging is a cornerstone of organismal aging. The central arterial wall structurally and functionally remodels under chronic proinflammatory stress over a lifetime. The low-grade proinflammation that accompanies advancing age causes arterial wall thickening and stiffening. These structural and functional alterations are consequences of adverse molecular and cellular events, e.g. an increase in local angiotensin II signaling that induces an inflammatory phenotypic shift of endothelial and smooth muscle cells. Thus, interventions to restrict proinflammatory signaling are a rational approach to delay or prevent age-associated adverse arterial remodeling.

Valsartan ameliorates ageing-induced aorta degeneration via angiotensin II type 1 receptor-mediated ERK activity

Angiotensin II (Ang II) plays important roles in ageing-related disorders through its type 1 receptor (AT1 R). However, the role and underlying mechanisms of AT1R in ageing-related vascular degeneration are not well understood. In this study, 40 ageing rats were randomly divided into two groups: ageing group which received no treatment (ageing control), and valsartan group which took valsartan (selective AT1R blocker) daily for 6 months. 20 young rats were used as adult control. The aorta structure were analysed by histological staining and electron microscopy. Bcl-2/Bax expression in aorta was analysed by immunohistochemical staining, RT-PCR and Western blotting. The expressions of AT1 R, AT2 R and mitogen-activated protein kinases (MAPKs) were detected. Significant structural degeneration of aorta in the ageing rats was observed, and the degeneration was remarkably ameliorated by long-term administration of valsartan. With ageing, the expression of AT1R was elevated, the ratio of Bcl-2/Bax was decreased and meanwhile, an important subgroup of MAPKs, extracellular signal-regulated kinase (ERK) activity was elevated. However, these changes in ageing rats could be reversed to some extent by valsartan. In vitro experiments observed consistent results as in vivo study. Furthermore, ERK inhibitor could also acquire partial effects as valsartan without affecting AT1R expression. The results indicated that AT1R involved in the ageing-related degeneration of aorta and AT1R-mediated ERK activity was an important mechanism underlying the process.

Central arterial aging and the epidemic of systolic hypertension and atherosclerosis

The structure and function of central arteries change throughout the lifetime of humans and animals. Since atherosclerosis and hypertension are prevalent in epidemic proportion among older persons, it is reasonable to hypothesize that specific mechanisms that underlie the arterial substrate that has been altered by an "aging process" are intimately linked to arterial diseases. Indeed, recent studies reveal a profile of arterial cell and matrix properties that emerges with advancing age within the grossly normal appearing aortic wall of both animals and humans. This profile is proinflammatory, and is manifested by intimal infiltration of fetal cells, increased production of angiotensin II (Ang II)-signaling pathway molecules, eg, matrix metalloproteases (MMPs), and monocyte chemoattractant protein (MCP-1), transforming growth factor B1 (TGF-beta1), enhanced activation of MMPs, TGF-beta, and NADPH oxidase, and reduced nitric oxide (NO) bioavailability. This profile is similar to that induced at younger ages in experimental animal models of hypertension or atherosclerosis. In humans, this proinflammatory state, which occurs in the absence of lipid deposition, appears to be attributable to aging, per se. Other well known human risk factors, eg, altered lipid metabolism, smoking, and lack of exercise, interact with this arterial substrate that is altered by aging and render the aging human artery fertile soil for facilitation of the initiation and progression of arterial diseases. Therapies to reduce or retard this age-associated proinflammatory state within the grossly appearing arterial wall central arteries, in addition to slowing arterial aging, per se, may have a substantial impact on the quintessential age-associated arterial diseases of our society.

Hispolon attenuates balloon-injured neointimal formation and modulates vascular smooth muscle cell migration via AKT and ERK phosphorylation

The pathological mechanism of restenosis is attributed primarily to excessive proliferation and migration of vascular smooth muscle cells (VSMC). The preventive effects of hispolon (1) on balloon injury-induced neointimal formation were investigated, and 1 showed potent activity in inhibiting fetal bovine serum-induced VSMC outgrowth. Hispolon (1) significantly inhibited VSMC migration, as shown by trans-well assays. Compound 1 decreased the expression and secretion of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9). The expression of the endogenous inhibitors of these proteins, namely, tissue inhibitors of MMP (TIMP-1 and TIMP-2), increased. The inhibition by noncytotoxic doses of 1 of VSMC migration was through its negative regulatory effects on FAK phosphorylation, ERK1/2 phosphorylation, and PI3K/AKT. These results demonstrate that 1 can inhibit the migration of VSMC by reduced expression of MMP-9 through the suppression of the FAK signaling pathway and of the activity of PI3K/AKT. The data obtained suggest that 1 might block balloon injury-induced neointimal hyperplasia via the inhibition of VSMC proliferation and migration, without inducing apoptosis.

Comparison of 12-lipoxygenase expression in vascular smooth muscle cells from old normotensive Wistar-Kyoto rats with spontaneously hypertensive rats

Vascular aging and essential hypertension cause similar structural and molecular modifications in the vasculature. The 12-lipoxygenase (LO) pathway of arachidonic acid metabolism is linked to cell growth and the pathology of hypertension. Thus, elevated expression of 12-LO has been observed in vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR). In the present study, we investigated the differences in 12-LO expression and activity between VSMCs from old normotensive Wistar-Kyoto rats (old WKY, 90-week old) and SHR (13-week old). The protein and mRNA expression of basal or angiotensin II (Ang II)-induced 12-LO in old WKY VSMCs were higher than those in SHR VSMCs. The degradation rate of 12-LO mRNA in old WKY VSMCs was slower than that in SHR VSMCs. However, basal or Ang II-induced 12-LO mRNAs in both old WKY and SHR VSMCs decayed more rapidly than that in young WKY (13-week old) VSMCs. Higher expression of 12-LO in old WKY VSMCs than in SHR VSMCs was correlated with the expression level of Ang II subtype 1 receptor (AT(1)R). The reduced levels of nitric oxide (NO) in old WKY and SHR VSMCs compared with young WKY VSMCs were similar, and there was no significant difference in NO production between old WKY and SHR VSMCs transfected with 12-LO siRNA. In addition, in contrast to the proliferation of SHR VSMCs, the proliferation of old WKY VSMCs was not dependent on 12-LO activation. These results suggest that the potential role of 12-LO in normotensive aging vasculature may be different from that in SHR vasculature.

MAPK phosphorylation of connexin 43 promotes binding of cyclin E and smooth muscle cell proliferation

RATIONALE

Dedifferentiation of vascular smooth muscle cells (VSMC) leading to a proliferative cell phenotype significantly contributes to the development of atherosclerosis. Mitogen-activated protein kinase (MAPK) phosphorylation of proteins including connexin 43 (Cx43) has been associated with VSMC proliferation in atherosclerosis.

OBJECTIVE

To investigate whether MAPK phosphorylation of Cx43 is directly involved in VSMC proliferation.

METHODS AND RESULTS

We show in vivo that MAPK-phosphorylated Cx43 forms complexes with the cell cycle control proteins cyclin E and cyclin-dependent kinase 2 (CDK2) in carotids of apolipoprotein-E receptor null (ApoE(-/-)) mice and in C57Bl/6 mice treated with platelet-derived growth factor-BB (PDGF). We tested the involvement of Cx43 MAPK phosphorylation in vitro using constructs for full-length Cx43 (Cx43) or the Cx43 C-terminus (Cx43(CT)) and produced null phosphorylation Ser>Ala (Cx43(MK4A)/Cx43(CTMK4A)) and phospho-mimetic Ser>Asp (Cx43(MK4D)/Cx43(CTMK4D)) mutations. Coimmunoprecipitation studies in primary VSMC isolated from Cx43 wild-type (Cx43(+/+)) and Cx43 null (Cx43(-/-)) mice and analytic size exclusion studies of purified proteins identify that interactions between cyclin E and Cx43 requires Cx43 MAPK phosphorylation. We further demonstrate that Cx43 MAPK phosphorylation is required for PDGF-mediated VSMC proliferation. Finally, using a novel knock-in mouse containing Cx43-MK4A mutation, we show in vivo that interactions between Cx43 and cyclin E are lost and VSMC proliferation does not occur after treatment of carotids with PDGF and that neointima formation is significantly reduced in carotids after injury.

CONCLUSIONS

We identify MAPK-phosphorylated Cx43 as a novel interacting partner of cyclin E in VSMC and show that this interaction is critical for VSMC proliferation. This novel interaction may be important in the development of atherosclerotic lesions.

Central Arterial Aging and Angiotensin II Signaling

Arterial remodeling over time is a cornerstone of normal systemic aging. The age-associated arterial structural and functional changes in the intima, the media, and the adventitia are closely linked to angiotensin II (Ang II) signaling. A growing line of evidence indicates that essential elements of Ang II signaling, which encompasses milk fat globule epidermal growth factor-8, calpain-1, transforming growth factor-β1, matrix metalloproteinase-2/9, monocyte chemoattractant protein-1, nicotinamide adenine dinucleotide phosphate-oxidase, and reactive oxygen species, are upregulated within the central arterial wall in rats, nonhuman primates, and humans during aging. In vitro studies show that the elevation of Ang II signaling induces the accumulation of collagen and advanced glycated end-products, the degradation of elastin, and the increased cell cycle disorder, invasion, and hypertrophy of endothelial and vascular smooth muscle cells. Further, in vivo studies demonstrate that increased Ang II signaling accelerates arterial aging. Conversely, attenuating Ang II signaling via an inhibition of angiotensin conversing enzyme or a blockade of AT1 activation retards age-associated arterial remodeling. This review attempts to integrate complex facts of Ang II signaling within the aged central arterial wall and may shed light on new therapeutic targets for arterial aging.

Shear stress modulation of smooth muscle cell marker genes in 2-D and 3-D depends on mechanotransduction by heparan sulfate proteoglycans and ERK1/2

Background

During vascular injury, vascular smooth muscle cells (SMCs) and fibroblasts/myofibroblasts (FBs/MFBs) are exposed to altered luminal blood flow or transmural interstitial flow. We investigate the effects of these two types of fluid flows on the phenotypes of SMCs and MFBs and the underlying mechanotransduction mechanisms.

Methodology/Principal Findings

Exposure to 8 dyn/cm² laminar flow shear stress (2-dimensional, 2-D) for 15 h significantly reduced expression of α-smooth muscle actin (α-SMA), smooth muscle protein 22 (SM22), SM myosin heavy chain (SM-MHC), smoothelin, and calponin. Cells suspended in collagen gels were exposed to interstitial flow (1 cmH₂O, ∼0.05 dyn/cm², 3-D), and after 6 h of exposure, expression of SM-MHC, smoothelin, and calponin were significantly reduced, while expression of α-SMA and SM22 were markedly enhanced. PD98059 (an ERK1/2 inhibitor) and heparinase III (an enzyme to cleave heparan sulfate) significantly blocked the effects of laminar flow on gene expression, and also reversed the effects of interstitial flow on SM-MHC, smoothelin, and calponin, but enhanced interstitial flow-induced expression of α-SMA and SM22. SMCs and MFBs have similar responses to fluid flow. Silencing ERK1/2 completely blocked the effects of both laminar flow and interstitial flow on SMC marker gene expression. Western blotting showed that both types of flows induced ERK1/2 activation that was inhibited by disruption of heparan sulfate proteoglycans (HSPGs).

Conclusions/Significance

The results suggest that HSPG-mediated ERK1/2 activation is an important mechanotransduction pathway modulating SMC marker gene expression when SMCs and MFBs are exposed to flow. Fluid flow may be involved in vascular remodeling and lesion formation by affecting phenotypes of vascular wall cells. This study has implications in understanding the flow-related mechanobiology in vascular lesion formation, tumor cell invasion, and stem cell differentiation.

Arterial aging: a journey into subclinical arterial disease

PURPOSE OF REVIEW

Age-associated arterial alterations in cells, matrix, and biomolecules are the foundation for the initiation and progression of cardiovascular diseases in older persons. This review focuses on the latest advances on the intertwining of aging and disease within the arterial wall at the cell and molecular levels.

RECENT FINDINGS

Endothelial dysfunction, vascular smooth muscle cell (VSMC) proliferation/invasion/secretion, matrix fragmentation, collagenization and glycation are characteristics of an age-associated arterial phenotype that creates a microenvironment enriched with reactive oxygen species (ROS) for the pathogenesis of arterial disease. This niche creates an age-associated arterial secretory phenotype (AAASP), which is orchestrated by the concerted effects of numerous age-modified angiotensin II signaling molecules. Most of these biomolecular, cell, and matrix modifications that constitute the AAASP can be elicited by experimental hypertension or atherosclerosis at a younger age. The arterial AAASP also shares features of a senescence-associated secretory phenotype (SASP) identified in other mesenchymocytes, that is, fibroblasts.

SUMMARY

A subclinical AAASP evolves during aging. Targeting this subclinical AAASP may reduce the incidence and progression of the quintessential age-associated arterial diseases, that is, hypertension and atherosclerosis.

Age-related changes in redox signaling and VSMC function

Epidemiological studies have shown that advancing age is associated with an increased prevalence of cardiovascular disease (CVD). Vascular smooth muscle cells (VSMC) comprise the major arterial cell population, and changes in VSMC behavior, function, and redox status with age contribute to alterations in vascular remodeling and cell signaling. Over two decades of work on aged animal models provide support for age-related changes in VSMC and/or arterial tissues. Enhanced production of reactive oxygen species (ROS) and insufficient removal by scavenging systems are hallmarks of vascular aging. VSMC proliferation and migration are core processes in vascular remodeling and influenced by growth factors and signaling networks. The intrinsic link between gene regulation and aging often relates directly to transcription factors and their regulatory actions. Modulation of growth factor signaling leads to up- or downregulation of transcription factors that control expression of genes associated with VSMC proliferation, inflammation, and ROS production. Four major signaling pathways related to the transcription factors, AP-1, NF-kappaB, FoxO, and Nrf2, will be reviewed. Knowledge of age-related changes in signaling pathways in VSMC that lead to alterations in cell behavior and function consistent with disease progression may help in efforts to attenuate age-related CVD, such as atherosclerosis.

Interstitial flow induces MMP-1 expression and vascular SMC migration in collagen I gels via an ERK1/2-dependent and c-Jun-mediated mechanism

The migration of vascular smooth muscle cells (SMCs) and fibroblasts into the intima after vascular injury is a central process in vascular lesion formation. The elevation of transmural interstitial flow is also observed after damage to the vascular endothelium. We have previously shown that interstitial flow upregulates matrix metalloproteinase-1 (MMP-1) expression, which in turn promotes SMC and fibroblast migration in collagen I gels. In this study, we investigated further the mechanism of flow-induced MMP-1 expression. An ERK1/2 inhibitor PD-98059 completely abolished interstitial flow-induced SMC migration and MMP-1 expression. Interstitial flow promoted ERK1/2 phosphorylation, whereas PD-98059 abolished flow-induced activation. Silencing ERK1/2 completely abolished MMP-1 expression and SMC migration. In addition, interstitial flow increased the expression of activator protein-1 transcription factors (c-Jun and c-Fos), whereas PD-98059 attenuated flow-induced expression. Knocking down c-jun completely abolished flow-induced MMP-1 expression, whereas silencing c-fos did not affect MMP-1 expression. Taken together, our data indicate that interstitial flow induces MMP-1 expression and SMC migration in collagen I gels via an ERK1/2-dependent and c-Jun-mediated mechanism and suggest that interstitial flow, ERK1/2 MAPK, c-Jun, and MMP-1 may play important roles in SMC migration and neointima formation after vascular injury.

Randomized controlled trial of aspirin and clopidogrel versus aspirin and placebo on markers of smooth muscle proliferation before and after peripheral angioplasty

OBJECTIVE

In peripheral arterial disease (PAD) patients, a limiting factor in the success of percutaneous transluminal angioplasty (PTA) is the development of restenosis secondary to vascular smooth muscle cell (SMC) proliferation. Following endothelial damage and platelet activation, there is release of factors and adhesion molecules which affect SMC proliferation. The aim of this study was to determine the effect of combination antiplatelet therapy (clopidogrel and aspirin compared with aspirin and placebo) on the ability of plasma from PAD patients undergoing PTA to stimulate SMCs in vitro. We further aimed to investigate the effect of combination treatment on the levels of circulating adhesion molecules and factors, which are known to mediate SMC proliferation in experimental models.

METHODS

Fifty patients were randomized to receive blinded clopidogrel or placebo, for thirty days, in addition to their daily 75 mg aspirin. To measure proliferative capacity, diluted plasma was incubated for 15 minutes with 24 hour-growth-arrested rat vascular smooth muscle cells, and extracellular regulated kinase (ERK)1/2 activation was analyzed by Western blotting at baseline, one hour pre-PTA, one hour, 24 hours and 30 days post-PTA. Plasma platelet-derived growth factor (PDGF), sE-selectin, intracellular adhesion molecule-1 (sICAM-1), and von Willebrand factor (vWF) were measured by ELISA, at the same five timepoints. Platelet activation was measured by flow cytometry of ADP-stimulated platelet fibrinogen binding at baseline and one hour post-PTA.

RESULTS

ADP-stimulated platelet fibrinogen binding was significantly inhibited by clopidogrel before and after PTA. ERK 1/2 activation was significantly increased post-PTA in both the aspirin/clopidogrel and aspirin/placebo groups (P < .001). There was a statistically significant decrease in PDGF (P = .004), and increase in vWF (P = .026), following loading with clopidogrel. sICAM-1 levels significantly decreased (P = .016) in the aspirin/placebo group following PTA. There were no other significant changes and also there was no statistically significant difference between the two treatment groups for each of ERK 1/2, sICAM-1, sE-selectin, or vWF.

CONCLUSIONS

This is the first study to show in-vitro ERK 1/2 activation (a surrogate marker of SMC proliferation) increases post-PTA. Combination antiplatelet therapy had no significant effect on this, although it did reduce PDGF. Further work is required to evaluate potential therapeutic treatments, which may reduce peripheral PTA-induced smooth muscle cell activation.

CLINICAL RELEVANCE

High rates of restenosis remain the major limitation of peripheral arterial angioplasty and stenting.The restenotic lesion occurs secondary to platelet activation, released circulating factors, and subsequent smooth musclecell proliferation and migration into the intima. Methods to limit the restenotic lesion are poorly understood. This paperinvestigates the effect of PTA on smooth muscle cell activation and the release of factors in plasma which mediate SMCproliferation. It also examines the effect of combination antiplatelet therapy as a potential therapeutic strategy.

Angiotensin II induces endothelial cell senescence via the activation of mitogen-activated protein kinases

Vascular endothelial cells have a finite cell lifespan and eventually enter an irreversible growth arrest, cellular senescence. The functional changes associated with cellular senescence are thought to contribute to human aging and age-related cardiovascular disorders, for example, atherosclerosis. Angiotensin II (Ang II), a principal effector of the renin-angiotensin system (RAS), an important signaling molecule involved in atherogenic stimuli, is known to promote aging and cellular senescence. In the present study, induction of Ang II promoted a growth arrest with phenotypic characteristics of cell senescence, such as enlarged cell shapes, increased senescence-associated beta-galactosidase (SA-beta-gal) positive staining cells, and depressed cell proliferation. Ang II drastically decreased the expression level of Bcl-2, in part via the activation of extracellular signal-regulated kinase (ERK). Our results suggest that Ang II can induce HUVEC senescence; one of its molecular mechanisms is a probability that the mitogen-activated protein kinase (MAPK) signal pathway is involved in the process of pathological and physiological senescence of endothelial cells as well as vascular aging.

Ageing-exaggerated proliferation of vascular smooth muscle cells is related to attenuation of Jagged1 expression in endothelial cells

AIMS

Ageing has been shown to enhance neointima formation due to abnormal growth of vascular smooth muscular cells (VSMC), which is regulated by endothelial functions. The mechanism of how endothelium affects the growth of VSMC in the process remains unclear. We here examined the role of Jagged1, a regulator of cell growth.

METHODS AND RESULTS

Male Sprague-Dawley rats at 3 (young) and 22 (old) months of age were subjected to a balloon catheter injury in the thoracic aorta. After 4 weeks, the neointima formation in the injured artery of old rats was more than that of young rats. Compared with the young rats, the increase in Jagged1 expression in the endothelium of old rats after the injury was delayed, weakened, and shortened, suggesting an impaired response of Jagged1 to the injury. In contrast, the increase in the expression of proliferating cell nuclear antigen in the neointima was more significant and maintained longer in old rats than in the young ones. Moreover, the expression of Jagged1 in the cultured arterial endothelial cells (EC) of old animals was less than those of the young ones, which promoted the Platelet-derived growth factor (PDGF)-induced growth and migration of the co-cultured VSMC. Furthermore, suppression of Jagged1 expression by a small interfering RNA in the EC of young rats reduced alpha-smooth muscle actin and calponin expression and also intensified the PDGF-increased growth and migration of the co-cultured VSMC.

CONCLUSION

Ageing enhanced VSMC proliferation, at least in part, through impairing Jagged1 expression in the EC after vascular injury.

Chondroitin sulfate inhibits the nuclear translocation of nuclear factor-kappaB in interleukin-1beta-stimulated chondrocytes

Chondroitin sulfate is referred as a symptomatic slow-acting drug for osteoarthritis because it improves articular function, and reduces joint swelling and effusion. In addition, chondroitin sulfate prevents joint space narrowing of the knee. We hypothesized that the anti-inflammatory effect of chondroitin sulfate is associated to a decrease in the activation of mitogen-activated protein kinases (MAPK) and of the transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). Cultured rabbit chondrocytes were stimulated with interleukin-1beta (IL-1beta) in presence of chondroitin sulfate. Nuclear translocation of NF-kappaB and AP-1, and nitrite concentrations (as an index for nitric oxide) was assessed 48 hr later. The effect of chondroitin sulfate on IL-1beta activation of extracellular signal-regulated kinase 1/2 (Erk1/2) and p38MAPK was documented by immunoblot. The effect of chondroitin sulfate on sodium nitroprusside-induced apoptosis was evaluated with the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling assay. Chondroitin sulfate reduced IL-1beta-induced NF-kappaB nuclear translocation, but not AP-1 translocation, it decreased IL-1beta-induced phosphorylation of Erk1/2 and abrogated p38MAPK phosphorylation, but did not prevent IL-1beta-induced increase in nitrite. Finally, chondroitin sulfate decreased nitroprusside-induced apoptosis of the chondrocytes. These results suggest that some of the biological activities of chondroitin sulfate may be associated to the reduction in Erk1/2 and p38MAPK phosphorylation and nuclear transactivation of NF-kappaB.

Suppression of age-related inflammatory NF-κB activation by cinnamaldehyde

Redox sensitive, pro-inflammatory nuclear transcription factor NF-kappaB plays a key role in both inflammation and aging processes. In a redox state disrupted by oxidative stress, pro-inflammatory genes are upregulated by the activation of NF-kappaB through diverse kinases. Thus, the search and characterization of new substances that modulate NF-kappaB are of recent research interest. Cinnamaldehyde (CNA) is the major component of cinnamon bark oil, which has been widely used as a flavoring agent in foodstuffs such as beverages and ice cream. In the present study, CNA was examined for its molecular modulation of inflammatory NF-kappaB activation via the redox-related NIK/IKK and MAPK pathways through the reduction of oxidative stress. Results show that age-related NF-kappaB activation upregulated NF-kappaB targeting genes, inflammatory iNOS, and COX-2, all of which were inhibited effectively by CNA. Our study further shows that CNA inhibited the activation of NF-kappaB via three signal transduction pathways, NIK/IKK, ERK, and p38 MAPK. Our results indicate that CNA's antioxidative effect and the restoration of redox balance were responsible for its anti-inflammatory action. Thus, the significance of the current study is the new information revealing the anti-inflammatory properties of CNA and the role it plays in the regulation of age-related alterations in signal transduction pathways.

Sex-specific regulation of gene expression in the aging monkey aorta

Although increased vascular stiffness is more prominent in aging males than females, and males are more prone to vascular disease with aging, no study has investigated the genes potentially responsible for sex differences in vascular aging. We tested the hypothesis that the transcriptional adaptation to aging differs in males and females using a monkey model, which is not only physiologically and phylogenetically closer to humans than the more commonly studied rodent models but also is not afflicted with the most common forms of vascular disease that accompany the aging process in humans, e.g., atherosclerosis, hypertension, and diabetes. The transcriptional profile of the aorta was compared by high-density microarrays between young and old males or females ( n = 6/group). About 600 genes were expressed differentially when comparing old versus young animals. Surprisingly, <5% of these genes were shared between males and females. Radical differences between sexes were especially apparent for genes regulating the extracellular matrix, which relates to stiffness. Aging males were also more prone than females to genes switching smooth muscle cells from the “contractile” to “secretory” phenotype. Other sex differences involved genes participating in DNA repair, stress response, and cell signaling. Therefore, major differences of gene regulation exist between males and females in vascular aging, which may underlie the physiological differences characterizing aging arteries in males and females. Furthermore, the analyses in young monkeys demonstrated differences in genes regulating vascular structure, implying that the sex differences in vascular stiffness that develop with aging are programmed at an early age.

Ginsenoside Rg1 inhibits tumor necrosis factor-alpha (TNF-alpha)-induced human arterial smooth muscle cells (HASMCs) proliferation

In China, the ginseng root began to be used in medicine over 2000 years ago. Ginsenosides are the most important component isolated from ginseng. The aim of this study was to determine the effects of ginsenoside Rg1 on the proliferation and molecular mechanism in cultured human arterial vascular smooth muscle cell (HASMC) induced by tumor necrosis factor-alpha (TNF-alpha). It was shown that ginsenoside Rg1 significantly inhibited TNF-alpha-induced HASMC proliferation in a dose-dependent manner. Treatment with ginsenoside Rg1, which blocked the cell cycle in the G1-phase, induced a downregulation of cyclin D1 and an upregulation in the expression of p53, p21(WAF/CIP1), and p27(KIP1). MEK inhibitors PD98059, U0126, and phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin, but not p38-inhibitor SB203580 or JNK-inhibitor SP600125 significantly aggravated ginsenoside Rg1-inhibited HASMC proliferation. Ginsenoside Rg1 markedly inactivated the extracellular signal-regulated kinases (ERK1/2) and protein kinase B (PKB), indicating that the inhibition of ginsenoside Rg1 on HASMC proliferation was associated with ERK and PI3K/PKB pathways. The inactivation of ERK and PI3K/PKB pathways and modulation of cell-cycle proteins by ginsenoside Rg1 may be of importance in inhibition of HASMCs proliferation.

Load-induced focal adhesion mechanotransduction is altered with aging in the Fischer 344/NNiaHSd x Brown Norway/BiNia rat aorta

The focal adhesion kinase (FAK) pathway has emerged as a critical component for mediating numerous cellular responses including control of cell growth, differentiation, and adaptation. Here we compared the expression, basal activation, and the ability of increased intraluminal pressure to activate FAK and focal adhesion-associated proteins in the aorta of adult (6 months old) and very aged (36 months old) Fischer 344/NNiaHSd x Brown Norway/BiNia (F344/NXBN) rats. Immunoblot analysis showed increases in the aortic content of FAK (15%), FAK related non-kinase (p41-FRNK) (28%), Src (92%), RhoA (41%), and paxillin (23%) in the very aged aortae. Increased age significantly changed the basal phosphorylation status of FAK and paxillin. Application of aortic intraluminal pressure (200 mm Hg) amplified the phosphorylation of FAK (Tyr 925), Src (Tyr 416), and paxillin (Tyr 188) in adult animals while aortic loading in the very aged animals failed to induce FAK (Tyr 925) phosphorylation. Aging did not alter the load-induced regulation of RhoA; however, FRNK (p41) translocation between cytosolic and membrane compartments was increased. These results confirm previous observations that FAK and focal adhesion-associated proteins are mechanically regulated and expand these studies to suggest that FAK mechanotransduction is altered with aging.

Isoelectric focusing technology quantifies protein signaling in 25 cells

A previously undescribed isoelectric focusing technology allows cell signaling to be quantitatively assessed in <25 cells. High-resolution capillary isoelectric focusing allows isoforms and individual phosphorylation forms to be resolved, often to baseline, in a 400-nl capillary. Key to the method is photochemical capture of the resolved protein forms. Once immobilized, the proteins can be probed with specific antibodies flowed through the capillary. Antibodies bound to their targets are detected by chemiluminescence. Because chemiluminescent substrates are flowed through the capillary during detection, localized substrate depletion is overcome, giving excellent linearity of response across several orders of magnitude. By analyzing pan-specific antibody signals from individual resolved forms of a protein, each of these can be quantified, without the problems associated with using multiple antibodies with different binding avidities to detect individual protein forms.

Betaine suppresses proinflammatory signaling during aging: the involvement of nuclear factor-kappaB via nuclear factor-inducing kinase/IkappaB kinase and mitogen-activated protein kinases

Betaine is an important human nutrient obtained from various foods. In the present study, we assessed the anti-inflammatory effect of betaine on nuclear factor-kappaB (NF-kappaB) during aging. Sprague-Dawley (SD) rats, ages 7 and 21 months, were used in this study. The older rats were fed betaine. To elucidate the effect of betaine on oxidative stress-induced NF-kappaB and its signaling pathway at molecular levels, YPEN-1 cells were used. Results showed that betaine suppressed NF-kappaB and its related gene expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), vascular cell adhesion molecule-1 (VCAM-1), and intracellular cell adhesion molecule-1 (ICAM-1) in aged kidney. Furthermore, betaine attenuated oxidative stress-induced NF-kappaB via nuclear factor-inducing kinase/IkappaB kinase (NIK/IKK) and mitogen-activated protein kinases (MAPKs) in the YPEN-1 cells. On the basis of these results, we concluded that betaine suppressed the age-related NF-kappaB activities associated with upregulated NIK/IKK and MAPKs that were induced by oxidative stress. Thus, betaine might be useful as a preventive agent against the activation of NF-kappaB induced during inflammation and aging.

Aging alters vascular mechanotransduction: pressure-induced regulation of p70S6k in the rat aorta

Physical forces are important regulators of vascular structure and function though it is unknown how aging may affect the ability of the vasculature to respond to mechanical stimuli. We investigated the pressure-induced activation of ribosomal S6-kinase (p70S6k) and its pathway-related proteins (Akt, GSK-3beta, SHP-2, PTEN) in aortae from young adult (6 month), aged (30 month), and very aged (36 month) Fischer 344 x Brown Norway F1 hybrid rats. With aging, the aortic tissue content of Akt. SHP-2, and PTEN was significantly increased while total p70S6k and GSK-3beta were unchanged. By comparison, the basal phosphorylation of p70S6k at Thr 389 and Thr 421/Ser 424 was increased ( approximately 40%) and unchanged, respectively, while Akt decreased (approximately 37%), GSK-3beta was unchanged, SHP-2 increased (approximately 73.5%), and PTEN increased (approximately 120%) in the aortae of very aged rats. Acute pressurization of aortae resulted in similar increases in phosphorylation of Akt among the different age groups. By comparison, pressure-induced phosphorylation of p70S6k at Thr 389, GSK-3beta and SHP-2 decreased; whereas, PTEN dephosphorylation was increased in 36-month versus 6-month aortae. The results indicate marked alterations in the p70S6k signaling pathway with aging. The implications of these findings on age-associated vessel remodeling are discussed.

Increasing donor age adversely impacts beneficial effects of bone marrow but not smooth muscle myocardial cell therapy

We evaluated the impact of donor age on the efficacy of myocardial cellular therapy for ischemic cardiomyopathy. Characteristics of smooth muscle cells (SMC), bone marrow stromal cells (MSCs), and skeletal muscle cells (SKMCs) from young, adult, and old rats were compared in vitro. Three weeks after coronary ligation, 3.5 million SMCs (n = 11) or MSCs (n = 9) from old syngenic rats or culture medium (n = 6) were injected into the ischemic region. Five weeks after implantation, cardiac function was assessed by echocardiography and the Langendorff apparatus. In the in vitro study, the numbers and proliferation of MSCs from fresh bone marrow and SKMCs from fresh tissue but not SMCs were markedly diminished in old animals (P < 0.05 both groups). SKMCs from old animals did not reach confluence. After treatment with 5-azacytidine (azacitidine), the myogenic potential of old MSCs was decreased compared with young MSCs. In the in vivo study, both SMC and MSC transplantation induced significant angiogenesis compared with media injections (P < 0.05 both groups). Transplantation of SMCs but not MSCs prevented scar thinning (P = 0.03) and improved ejection fraction and fractional shortening (P < 0.05). Load-independent indices of cardiac function in a Langendorff preparation confirmed improved function in the aged SMC group (P = 0.01) but not in the MSC group compared with the control group. In conclusion, donor age adversely impacts the efficacy of cellular therapy for myocardial regeneration and is cell-type dependent. SMCs from old donors retain their ability to improve cardiac function after implantation into ischemic myocardium.

Endothelial stress induces the release of vitamin D-binding protein, a novel growth factor

Endothelial cells (EC) under stress release paracrine mediators that facilitate accumulation of vascular smooth muscle cells (VSCM) at sites of vascular injury. We found that medium conditioned by serum-starved EC increase proliferation and migration of VSCM in vitro. Fractionation of the conditioned medium followed by mass spectral analysis identified one bioactive component as vitamin D-binding protein (DBP). DBP induced both proliferation and migration of VSMC in vitro in association with increased phosphorylation of ERK 1/2. PD 98059, a biochemical inhibitor of ERK 1/2, abrogated these proliferative and migratory responses in VSMC. DBP is an important carrier for the vitamin-D sterols, 25-hydroxyvitamin-D, and 1alpha,25-dihydroxyvitamin-D. Both sterols inhibited the activity of DBP on VSMC, suggesting that vitamin D binding sites are important for initiating the activities of DBP on VSMC. Release of DBP at sites of endothelial injury represents a novel pathway favoring accumulation of VSMC at sites of vascular injury.

Taurine suppresses platelet-derived growth factor (PDGF) BB-induced PDGF-β receptor phosphorylation by protein tyrosine phosphatase-mediated dephosphorylation in vascular smooth muscle cells

In atherosclerosis, abnormal vascular smooth muscle cell (VSMC) proliferation plays an important role to form fibroproliferative lesions and platelet-derived growth factor (PDGF)-BB is one of the most potent chemoattractants and proliferative factors for VSMCs. Taurine, sulfur-containing beta-amino acid, has been considered to prevent the development of atherosclerosis, although the molecular mechanism remains obscure. Previously, we demonstrated that taurine significantly suppressed PDGF-BB-induced cell proliferation, DNA synthesis, immediate-early gene expressions and extracellular signal-regulated kinase (ERK) 1/2 phosphorylation in VSMCs. The present study was aimed at elucidating the precise molecular mechanism of taurine in PDGF-BB signaling pathway. We showed that taurine significantly suppressed PDGF-BB-induced phosphorylation of PDGF-beta receptor and activation of its downstream signaling molecules such as Ras, MAPK/ERK kinase (MEK)1/2 and Akt. Because taurine did not attenuate phorbol 12-myristate 13-acetate (PMA)-induced PDGF-beta receptor-independent ERK1/2 phosphorylation, we further investigated the suppressive mechanism of taurine in PDGF-beta receptor level. Although taurine did not directly affect PDGF receptor autophosphorylation in vitro, taurine promoted PDGF-beta receptor dephosphorylation and restored PDGF-BB-induced suppression of protein tyrosine phosphatase (PTPase) activity. Taken together, we propose that taurine could prevent or delay the progression of atherosclerosis by PTPase-mediated suppression of PDGF-beta receptor phosphorylation, and by decreasing the activation of its downstream signaling molecules in VSMCs.

Cross-talk between dyslipidemia and renin-angiotensin system and the role of LOX-1 and MAPK in atherogenesis studies with the combined use of rosuvastatin and candesartan

There is increasing evidence of cross-talk between dyslipidemia and renin-angiotensin system (RAS) in atherogenesis. Both dyslipidemia and RAS activation enhance the expression of a newly described receptor for oxidized-low density lipoprotein (ox-LDL), lectin-like ox-LDL receptor-1 (LOX-1). We postulated that the blockade of dyslipidemia with rosuvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor and RAS with candesartan, an angiotensin II type 1 receptor blocker, would have a synergistic inhibitory effect on LOX-1 expression and atherogenesis. Apo-E knockout mice were fed a high-cholesterol diet (1% cholesterol, HC-diet) alone, or HC-diet with rosuvastatin (1mg/(kgd)), candesartan (1mg/(kgd)) or with both. Twelve weeks later the extent of atherosclerosis was determined by Sudan IV staining. Apo-E knockout mice on HC-diet had extensive atherosclerosis. Both rosuvastatin and candesartan decreased the extent of atherosclerosis (by 23 and 26%, respectively), despite the HC-diet; however, the combination of rosuvastatin and candesartan reduced atherosclerosis further (by 67%). Rosuvastatin decreased plasma levels of total cholesterol by over 50%, whereas candesartan had no effect. LOX-1 protein expression was found to be markedly up-regulated in HC-diet-fed apo-E knockout mice. While rosuvastatin and candesartan each had a small inhibitory effect on the expression of LOX-1 in the atherosclerotic tissues, the combination totally blocked the up-regulation of LOX-1. P38 mitogen-activated protein kinase (MAPK) expression and phosphorylation were increased in apo-E knockout mice, attenuated by rosuvastatin or candesartan alone, and completely blocked by the combination of the two agents. P44/42 MAPK expression and phosphorylation were not affected by the HC-diet, rosuvastatin, candesartan, or their combination. This study demonstrates the potent effect of rosuvastatin and candesartan on atherogenesis, as well as on the expression of LOX-1 and on the activation of p38 MAPK, but not p44/42 MAPK.

Effects of aging on pressure-induced MAPK activation in the rat aorta

With increasing age, the cardiovascular system experiences substantial alterations in cellular morphology and function. Whilst the factors regulating these changes are unknown, the mitogen-activated protein kinase (MAPK) pathways have emerged as critical components for mediating numerous cellular responses including control of cell growth, differentiation and adaptation. Here we compare the expression, basal activation and the ability of increased pressure to activate the MAPK pathways in adult (6-month-old), aged (30-month-old) and very aged (36-month-old) Fischer 344xBrown Norway F1 hybrid rats. Histochemical analysis demonstrated an age-related increase in tunica media thickness of approximately 11 and 21% in aortae from aged and very aged animals, respectively. Western blot analysis of the MAPK family extracellular signal-regulated kinase (ERK 1/2), p38, and c-Jun NH2 -terminal kinase (JNK) MAPKs showed differential expression and activation among these proteins with age. Expression of ERK 1/2, p38, and JNK were unchanged, slightly increased (10+/-17.5%) or significantly increased (72.3+/-27%), respectively, in very aged aortae. In contrast, basal activation levels of these proteins were reduced (-26.2+/-7.4%), markedly increased (97.0+/-16.8%), and slightly increased (14.4+/-4.5%), respectively, in very aged compared with 6-month rat aortae. An acute increase of aortic intraluminal pressure (200 mmHg) indicated that ERK 1/2 regulation differed from p38 or JNK. Pressure loading-induced phosphorylation of ERK1/2 was unchanged or increased with aging while p38 and JNK phosphorylation was attenuated (P<0.01). These observations confirm previous conclusions that MAPK proteins are regulated mechanically and expand these studies to suggest that MAPK expression and the control of activation are changed with aging.

Age-related changes in plaque composition

OBJECTIVE

The extent of atherosclerotic plaque burden and the incidence of atherosclerosis-related cardiovascular events accelerate with increasing age. The composition of the plaque is associated with plaque thrombosis and acute coronary occlusion. Surprisingly, however, the relation between advancing age and atherosclerotic plaque composition is still unclear. In the present study, we investigated the association between plaque characteristics and advancing age in a population of patients with haemodynamically significant carotid artery stenosis.

METHODS

Patients (N=383), ages 39-89 years, underwent carotid endarterectomy (CEA). Morphometric analysis was performed on the dissected atherosclerotic plaques to study the prevalence of fibrous and atheromatous plaques. Picro sirius red, haematoxylin eosin, alfa actin and CD68 stainings were performed to investigate the extent of collagen, calcification, smooth muscle cells and macrophages in carotid plaques, respectively. The presence of metalloproteinases-2 and -9 was assessed by ELISA.

RESULTS

With aging, a decrease in fibrous plaques and an increase in atheromatous plaques were observed. This was accompanied by an age-associated decrease in smooth muscle cell content in carotid plaques. Macrophage content slightly increased with age. In addition, total matrix metalloprotease (MMP)-2 was negatively and MMP-9 positively related with age. Differences in plaque phenotype were most prominent for the youngest age quartile compared with older age quartiles.

CONCLUSIONS

With increasing age, the morphology of atherosclerotic plaques from patients with carotid artery stenosis changes. Plaques become more atheromatous and contain less smooth muscle cells with increasing age. Local inflammation and MMP-9 levels slightly increased with age in plaques obtained from patients suffering from haemodynamically significant advanced atherosclerotic lesions.

Regulation of vascular smooth muscle cell proliferation: role of NF-kappaB revisited

The transcription factor NF-kappaB regulates cell cycle progression and proliferation in a number of cell types. An important unresolved issue is the potential role of NF-kappaB in the proliferation of vascular smooth muscle cells (VSMCs) as a basis for the development of vascular disease. To investigate the contribution of NF-kappaB to mitogen-induced proliferation of VSMCs, a knock-in mouse model expressing the NF-kappaB superrepressor IkappaBalphaDeltaN (c(IkappaBalphaDeltaN)) was used. Comparing wild-type and IkappaBalphaDeltaN-expressing VSMCs, we found that proliferation rates did not differ after mitogenic stimulation by platelet-derived growth-factor-BB (PDGF-BB) or serum. In line with this, NF-kappaB activation was not observed in VSMCs derived from transgenic mice expressing an NF-kappaB-dependent lacZ reporter (c((Igk)3conalacZ)). We further show, that classical mitogenic signaling pathways (namely mitogen-activated protein kinase [MAPK] and the phosphatidyl-inositol-3-OH-kinase [PI3K] pathways) control VSMC proliferation, but independently of NF-kappaB activation. In contrast to VSMCs, mouse embryonic fibroblasts (MEFs) derived from IkappaBalphaDeltaN-expressing mice showed significantly impaired proliferation rates after mitogenic stimulation. This was reflected by strongly impaired cyclin D1 expression in serum-stimulated MEFs derived from (c(IkappaBalphaDeltaN)) mice. These results implicate that essential pathogenetic functions of NF-kappaB in the development of atherosclerosis involve apoptotic and inflammatory signaling of VSMCs rather than proliferation. They further provide genetic evidence for a cell-type restricted requirement of NF-kappaB in the control of cellular proliferation.

Age affects ERK1/2 and NRF2 signaling in the regulation of GCLC expression

We previously reported that activator protein-1 (AP-1) DNA binding activity was increased in vascular smooth muscle cells (VSMC) from old rats when exposed to high glucose or tumor necrosis factor (TNF-alpha) (Li et al., 2003. J Cell Physiol 197:418-425). We have now examined the relationship between the age-dependent activation of the ERK1/2-AP-1 pathway and modulation of constitutive gene expression of the catalytic subunit of glutamate-cysteine ligase (GCLC) in response to high glucose and TNF-alpha. GCLC mRNA levels were higher in VSMC from old rats compared to young, a pattern consistent with its protein levels. To determine whether age-related activation of ERK1/2-AP-1 signaling is responsible for the up-regulation of GCLC, the MEK inhibitors, PD98059 and U0126, were used to block ERK1/2 in VSMC from old rats. An increase in GCLC with inhibitors was observed, diminishing the likelihood of ERK1/2-AP-1 activation as the up-regulating signal for GCLC. However, the transcription factor Nrf2 was higher in nuclei and accompanied by increased Nrf2-ARE binding in VSMC from old rats. Furthermore, MEK inhibitors increased nuclear Nrf2 and Nrf2/ARE binding. These data suggest opposing effects of Nrf2 and ERK1/2 signaling in the modulation of GCLC expression in old animals.

EGF-induced proliferation of adult human pancreatic duct cells is mediated by the MEK/ERK cascade

Human postnatal pancreatic duct cells are a potential source of new beta cells. Factors regulating proliferation of human pancreatic duct cells in vitro are unknown. In several other cell types, this process is influenced by ligands of the ErbB receptor family. The expression and functionality of the ErbB family members and their possible role in duct cell proliferation were determined. In cultured adult human pancreatic duct cells the different members of the ErbB family (ErbB1-4) were present at transcript and protein level. Stimulation of the duct cells with epidermal growth factor (EGF) and betacellulin results in Tyr-phosphorylation of ErbB1 and ErbB2, followed by activation of Shc, MEK1/2 and ERK1/2. Duct cells with activated ErbB signaling changed morphology and motility. EGF induced proliferation of a fraction of the duct cells and treatment with PD98059 prevented Ki67 expression in EGF-supplemented cells. When transduced with recombinant adenovirus expressing constitutively activated MEK1, duct cells proliferate and spread even in the absence of EGF. Importantly, the adult human duct cells retain their capacity to recapitulate ngn3-induced embryonic (neuro)endocrine differentiation after proliferation. Therefore, the present data support a possible role for human adult pancreatic duct cells, following expansion and transdifferentiation, as a source of insulin by transplantation to type I diabetes patients.

Inhibition of Vascular Smooth Muscle Cell Proliferation and Neointimal Formation in Injured Arteries by a Novel, Oral Mitogen-Activated Protein Kinase/Extracellular Signal–Regulated Kinase Inhibitor

BACKGROUND

Mitogen-activated protein kinases (MAPKs) are rapidly induced after arterial injury in different animal models. However, their precise role in vascular smooth muscle cell (VSMC) proliferation and neointimal formation in vivo remains to be determined.

METHODS AND RESULTS

We investigated the properties of a novel, selective inhibitor of the upstream kinase, MAPK/extracellular signal-regulated kinase, that is orally active (PD0185625). In vitro, PD0185625 was shown to abrogate p44/p42 MAPK activation in VSMCs after serum stimulation. This was associated with a dose-dependent inhibition of VSMC proliferation. In vivo, PD0185625 was administered orally to rats (200 mg x kg(-1) x d(-1)) beginning 2 days before balloon injury of the left carotid artery and for 2 weeks thereafter. Treatment with PD0185625 led to nearly complete inhibition of p44/p42 MAPK activation after balloon injury. This resulted in a significant decrease in VSMC proliferation (BrdU incorporation) at day 7 after injury. Moreover, neointimal formation was significantly reduced in PD0185625-treated animals at 14 and 28 days after arterial injury. We found that PD0185625 did not increase the rate of apoptotic cell death but prevented cell cycle progression and induced a G1 block.

CONCLUSIONS

PD0185625 reduced neointimal formation after arterial injury. The mechanism involved inhibition of VSMC proliferation via a G1 block of the cell cycle. Orally active selective MAPK inhibitors could represent a novel therapeutic approach for vascular diseases.

Proliferation of Neointimal Smooth Muscle Cells after Arterial Injury

The growth factor signaling mechanisms responsible for neointimal smooth muscle cell (SMC) proliferation and accumulation, a characteristic feature of many vascular pathologies that can lead to restenosis after angioplasty, remain to be identified. Here, we examined the contribution of fibroblast growth factor receptors (FGFRs) 2 and 3 as well as novel fibroblast growth factors (FGFs) to such proliferation. Balloon catheter injury to the rat carotid artery stimulated the expression of two distinctly spliced FGFR-2 isoforms, differing only by the presence or absence of the acidic box, and two distinctly spliced FGFR-3 isoforms containing the acidic box and differing only by the presence of either the IIIb or IIIc exon. Post-injury arterial administration of recombinant adenoviruses expressing dominant negative mutant forms of these FGFRs were used to assess the roles of the endogenous FGFR isoforms in neointimal SMC proliferation. Dominant negative FGFR-2 containing the acidic box inhibited such proliferation by 40%, whereas the dominant negative FGFR-3 forms had little effect. Expression of FGF-9, known to be capable of binding to all four neointimal FGFR-2/-3 isoforms, was abundant within the neointima. FGF-9 markedly stimulated both the proliferation of neointimal SMCs and the activation of extracellular signal-related kinases 1/2, effects which were abrogated by the administration of antisense FGF-9 oligonucleotides to injured arteries and the expression of the dominant negative FGFR-2 adenovirus in cultured neointimal SMCs. These studies demonstrate that, although multiple FGFRs are induced in neointimal SMCs following arterial injury, specific interactions between distinctly spliced FGFR-2 isoforms and FGF-9 contribute to the proliferation of these SMCs.

Angioplasty-induced superoxide anions and neointimal hyperplasia in the rabbit carotid artery: suppression by the isoflavone trans-tetrahydrodaidzein

Reactive oxygen species (ROS) may contribute to the development of stenosis in balloon catheter injured arteries. As isoflavones exhibit effects on ROS and cell proliferation In vitro that appear useful in preventing such stenosis, we examined the effects of the isoflavone trans-tetrahydrodaidzein (trans-THD) on development of neointimal lesions in relation to elevations in ROS in balloon catheter injured arteries. Carotid arteries of rabbits treated with either vehicle or trans-THD were injured with an inflated balloon catheter and cell proliferation, collagen content, ROS and vessel structure determined over the ensuing 28 days. Seven days after injury neointimal smooth muscle cell proliferation was reduced by 50% (p < 0.05) whilst medial cell proliferation was largely unaffected (p > 0.10). At this time ROS levels in vehicle-treated rabbits were elevated 3-fold compared to uninjured arteries (p < 0.05). Treatment with trans-THD reduced ROS levels to those seen in uninjured arteries (p > 0.05). The antiproliferative effects of trans-THD on intimal cell proliferation persisted 14 days after the injury, and twenty eight days after injury the size of the lumen in trans-THD-treated animals was 27% greater (p < 0.05) and the intima area: vessel area reduced by 40% (p < 0.05). The small effects of trans-THD on collagen accumulation was not statistically significant, indicating that effects on neointimal cell proliferation was the major mechanism by which this isoflavone attenuated development of the neointima. Intimal smooth muscle cells and ROS represent potentially important targets for the antiproliferative actions of trans-THD in injured arteries. Strategies using such isoflavones may be useful for preventing restenosis after vascular manipulations in humans.

Rat aortic MCP-1 and its receptor CCR2 increase with age and alter vascular smooth muscle cell function

OBJECTIVE

With age, rat arterial walls thicken and vascular smooth muscle cells (VSMCs) exhibit enhanced migration and proliferation. Monocyte chemotactic protein-1 (MCP-1) affects these VSMC properties in vitro. Because arterial angiotensin II, which induces MCP-1 expression, increases with age, we hypothesized that aortic MCP-1 and its receptor CCR2 are also upregulated and affect VSMC properties.

METHODS AND RESULTS

Both MCP-1 and CCR2 mRNAs and proteins increased in old (30-month) versus young (8-month) F344xBN rat aortas in vivo. Cellular MCP-1 and CCR2 staining colocalized with that of alpha-smooth muscle actin in the thickened aortas of old rats and were expressed by early-passage VSMCs isolated from old aortas, which, relative to young VSMCs, exhibited increased invasion, and the age difference was abolished by vCCI, an inhibitor of CCR2 signaling. MCP-1 treatment of young VSMCs induced migration and increased their ability to invade a synthetic basement membrane. The MCP-1-dependent VSMC invasiveness was blocked by vCCI. After MCP-1 treatment, migration and invasion capacities of VSMCs from young aortas no longer differed from those of VSMCs isolated from older rats.

CONCLUSIONS

Arterial wall and VSMC MCP-1/CCR2 increase with aging. MCP-1 enhances VSMC migration and invasion, and thus, MCP-1/CCR2 signaling may play a role in age-associated arterial remodeling.