Role of the p21 cyclin-dependent kinase inhibitor in limiting intimal cell proliferation in response to arterial injury

Role of PCK2 in the proliferation of vascular smooth muscle cells in neointimal hyperplasia

Vascular smooth muscle cell (VSMC) proliferation is a hallmark of neointimal hyperplasia (NIH) in atherosclerosis and restenosis post-balloon angioplasty and stent insertion. Although numerous cytotoxic and cytostatic therapeutics have been developed to reduce NIH, it is improbable that a multifactorial disease can be successfully treated by focusing on a preconceived hypothesis. We, therefore, aimed to identify key molecules involved in NIH via a hypothesis-free approach. We analyzed four datasets (GSE28829, GSE43292, GSE100927, and GSE120521), evaluated differentially expressed genes (DEGs) in wire-injured femoral arteries of mice, and determined their association with VSMC proliferation in vitro. Moreover, we performed RNA sequencing on platelet-derived growth factor (PDGF)-stimulated human VSMCs (hVSMCs) post-phosphoenolpyruvate carboxykinase 2 (PCK2) knockdown and investigated pathways associated with PCK2. Finally, we assessed NIH formation in Pck2 knockout (KO) mice by wire injury and identified PCK2 expression in human femoral artery atheroma. Among six DEGs, only PCK2 and RGS1 showed identical expression patterns between wire-injured femoral arteries of mice and gene expression datasets. PDGF-induced VSMC proliferation was attenuated when hVSMCs were transfected with PCK2 siRNA. RNA sequencing of PCK2 siRNA-treated hVSMCs revealed the involvement of the Akt-FoxO-PCK2 pathway in VSMC proliferation via Akt2, Akt3, FoxO1, and FoxO3. Additionally, NIH was attenuated in the wire-injured femoral artery of Pck2-KO mice and PCK2 was expressed in human femoral atheroma. PCK2 regulates VSMC proliferation in response to vascular injury via the Akt-FoxO-PCK2 pathway. Targeting PCK2, a downstream signaling mediator of VSMC proliferation, may be a novel therapeutic approach to modulate VSMC proliferation in atherosclerosis.

Identification of Potential Ferroptosis-Related Biomarkers and Immune Infiltration in Human Coronary Artery Atherosclerosis

Objective

Ferroptosis is a specific subtype of programmed cell death, which plays an essential role in the immune-associated disease, atherosclerosis (AS). The purpose of this study was to identify potential ferroptosis-related gene biomarkers and its association with immune infiltration characteristics in atherosclerosis with bioinformatics methods.

Methods

Differentially expressed genes (DEGs) between AS and control groups were screened from GSE40231, analyzed for functional enrichment and then intersected with ferroptosis-related genes. Then, a random forest model was constructed based on these differentially expressed ferroptosis-related genes (DE-FRGs) and validated with dataset GSE132651. The performance of the models was evaluated with the area under receiver operating characteristic curves (AUC). Finally, we analyzed the correlation between DE-FRGs above and the characteristics of immune infiltration via CIBERSORT method.

Results

Six DE-FRGs (IL6, ANGPTL7, CDKN1A, AKR1C3, NOX4 and VLDLR) were detected based on dataset of GSE40231. Furthermore, a random forest model was constructed based on them with a compelling diagnostic performance of AUC = 0.8974 in the validation dataset GSE132651. In addition, the proportion of follicular helper T (Tfh) cells was significantly higher in AS group (P < 0.001). And we found significant correlation relationship between Tfh and expression level of ANGPTL7 (R = 0.35, P < 0.01), CDKN1A (R = 0.4, P < 0.0001), AKR1C3 (R = 0.64, P < 0.0001), NOX4 (R = 0.32, P < 0.01) and VLDLR (R = −0.43, P < 0.0001).

Conclusion

This study identified 6 DE-FRGs and validated a predicted model for the early prediction of AS, which also proved the close relationship between ferroptosis and immunity in the pathogenesis of AS.

Endothelial sprouting, proliferation, or senescence: tipping the balance from physiology to pathology

Therapeutic modulation of vascular cell proliferation and migration is essential for the effective inhibition of angiogenesis in cancer or its induction in cardiovascular disease. The general view is that an increase in vascular growth factor levels or mitogenic stimulation is beneficial for angiogenesis, since it leads to an increase in both endothelial proliferation and sprouting. However, several recent studies showed that an increase in mitogenic stimuli can also lead to the arrest of angiogenesis. This is due to the existence of intrinsic signaling feedback loops and cell cycle checkpoints that work in synchrony to maintain a balance between endothelial proliferation and sprouting. This balance is tightly and effectively regulated during tissue growth and is often deregulated or impaired in disease. Most therapeutic strategies used so far to promote vascular growth simply increase mitogenic stimuli, without taking into account its deleterious effects on this balance and on vascular cells. Here, we review the main findings on the mechanisms controlling physiological vascular sprouting, proliferation, and senescence and how those mechanisms are often deregulated in acquired or congenital cardiovascular disease leading to a diverse range of pathologies. We also discuss alternative approaches to increase the effectiveness of pro-angiogenic therapies in cardiovascular regenerative medicine.

Nicotinamide mononucleotide (NMN) supplementation promotes anti-aging miRNA expression profile in the aorta of aged mice, predicting epigenetic rejuvenation and anti-atherogenic effects

Understanding molecular mechanisms involved in vascular aging is essential to develop novel interventional strategies for treatment and prevention of age-related vascular pathologies. Recent studies provide critical evidence that vascular aging is characterized by NAD+ depletion. Importantly, in aged mice, restoration of cellular NAD+ levels by treatment with the NAD+ booster nicotinamide mononucleotide (NMN) exerts significant vasoprotective effects, improving endothelium-dependent vasodilation, attenuating oxidative stress, and rescuing age-related changes in gene expression. Strong experimental evidence shows that dysregulation of microRNAs (miRNAs) has a role in vascular aging. The present study was designed to test the hypothesis that age-related NAD+ depletion is causally linked to dysregulation of vascular miRNA expression. A corollary hypothesis is that functional vascular rejuvenation in NMN-treated aged mice is also associated with restoration of a youthful vascular miRNA expression profile. To test these hypotheses, aged (24-month-old) mice were treated with NMN for 2 weeks and miRNA signatures in the aortas were compared to those in aortas obtained from untreated young and aged control mice. We found that protective effects of NMN treatment on vascular function are associated with anti-aging changes in the miRNA expression profile in the aged mouse aorta. The predicted regulatory effects of NMN-induced differentially expressed miRNAs in aged vessels include anti-atherogenic effects and epigenetic rejuvenation. Future studies will uncover the mechanistic role of miRNA gene expression regulatory networks in the anti-aging effects of NAD+ booster treatments and determine the links between miRNAs regulated by NMN and sirtuin activators and miRNAs known to act in the conserved pathways of aging and major aging-related vascular diseases.

Hypoxia Promotes Vascular Smooth Muscle Cell Proliferation through microRNA-Mediated Suppression of Cyclin-Dependent Kinase Inhibitors

Regulation of vascular smooth muscle cell (VSMC) proliferation is essential to maintain vascular homeostasis. Hypoxia induces abnormal proliferation of VSMCs and causes vascular proliferative disorders, such as pulmonary hypertension and atherosclerosis. As several cyclin/cyclin-dependent kinase (CDK) complexes and CDK inhibitors (CKIs) control cell proliferation, in this study, we investigated CKIs involved in the hypoxia-induced proliferation process of human primary pulmonary artery smooth muscle cells to understand the underlying molecular mechanism. We demonstrated that p15, p16, and p21 are downregulated in pulmonary artery smooth muscle cells when exposed to hypoxia. In addition, we identified novel hypoxia-induced microRNAs (hypoxamiRs) including miR-497, miR-1268a, and miR-665 that are upregulated under hypoxia and post-transcriptionally regulate p15, p16, and p21 genes, respectively, by directly targeting their 3'UTRs. These miRNAs promoted the proliferation of VSMCs, and their inhibition decreased VSMC proliferation even in hypoxic conditions. Overall, this study revealed that miRNA-mediated regulatory mechanism of CKIs is essential for hypoxia-induced proliferation of VSMCs. These findings provide insights for a better understanding of the pathogenesis of vascular proliferative disorders.

MicroRNA-296: a promising target in the pathogenesis of atherosclerosis?

Atherosclerosis has been recognized as an inflammatory disease involving the vascular wall. MicroRNAs are a group of small noncoding RNAs to regulate gene expression at the transcriptional level through mRNA degradation or translation repression. Recent studies suggest that miR-296 may play crucial roles in the regulation of angiogenesis, inflammatory response, cholesterol metabolism, hypertension, cellular proliferation and apoptosis. In this review, we primarily discussed the molecular targets of miR-296 involved in the development of atherosclerosis, which may provide a basis for future investigation and a better understanding of the biological functions of miR-296 in atherosclerosis.

Enhanced Rb/E2F and TSC/mTOR Pathways Induce Synergistic Inhibition in PDGF-Induced Proliferation in Vascular Smooth Muscle Cells

Platelet-derived growth factor (PDGF) plays an essential role in proliferation of vascular smooth muscle cells (VSMCs). The Rb/E2F and TSC/mTOR pathways contribute to the proliferation of VSMCs, but its exact roles in PDGF-induced proliferation are unclear. In this study, we demonstrated the roles of Rb/E2F and TSC/mTOR pathways in PDGF-induced proliferation in VSMCs. We found that PDGF stimulates the activity of E2F and mTOR pathways, and knockdown of either Rb or TSC2 increases PDGF-induced proliferation in VSMCs. More interestingly, we revealed that enhancing both E2F and mTOR activity leads to synergistic inhibition of PDGF-induced proliferation in VSMCs. We further identified that the synergistic inhibition effect is caused by the induced oxidative stress. Summarily, these data suggest the important regulations of Rb/E2F and TSC/mTOR pathways in PDGF-induced proliferation in VSMCs, and also present a promising way to limit deregulated proliferation by PDGF induction in VSMCs.

Preclinical Restenosis Models: Challenges and Successes

Coronary artery disease remains a major problem for Western societies. The advent of percutaneous interventions, including stents has brought clinical care to a new level of efficacy, yet problems remain. Restenosis following stenting in human coronary arteries appears at last to be yielding to therapeutic strategies, especially drug eluting stents. Because therapeutic percutaneous coronary intervention is widely dominated by the intracoronary stent, restenosis therapies must include the stented coronary artery. Animal models and in particular the porcine coronary model seem to represent the human coronary artery reaction to stenting. It mimics several clinical conditions including thrombosis and neointimal formation. A key question in the era of intravascular technologies is how well this and other models can predict clinical events. This paper discusses the models and their application.

Herbal composition of Cinnamomum cassia, Pinus densiflora, Curcuma longa and Glycyrrhiza glabra prevents atherosclerosis by upregulating p27 (Kip1) expression

Background

Kiom-18 is a novel composition of Cinnamomum cassia, Pinus densiflora, Curcuma longa and Glycyrrhiza glabra. Curcuma longa and Glycyrrhiza glabra, which are traditional medicines in Asia, have been reported to demonstrate preventive effects against atherosclerosis; however, they have not yet been developed into functional atherosclerosis treatments. We therefore studied the anti-atherosclerotic effects and possible molecular mechanisms of Kiom-18 using vascular smooth muscle cells (VSMCs).

Methods

To assess the anti-proliferative effect of Kiom-18 in vitro, we performed thymidine incorporation, cell cycle progression, immunoblotting and immunofluorescence assays in VSMCs stimulated by platelet derived-growth factor (PDGF)-BB. In addition, we used LDLr knockout mice to identify the effects of Kiom-18 as a preliminary result in an atherosclerosis animal model.

Results

Kiom-18 inhibited platelet-derived growth factor (PDGF)-BB-stimulated-VSMC proliferation and DNA synthesis. Additionally, Kiom-18 arrested the cell cycle transition of G₀/G₁ stimulated by PDGF-BB and its cell cycle-related proteins. Correspondingly, the level of p27^kip1 expression was upregulated in the presence of the Kiom-18 extract. Moreover, in an atherosclerosis animal model of LDLr knockout mice, Kiom-18 extract showed a preventive effect for the formation of atherosclerotic plaque and suppressed body weight, fat weight, food treatment efficiency, neutrophil count, and triglyceride level.

Conclusions

These results indicate that Kiom-18 exerts anti-atherosclerotic effects by inhibiting VSMC proliferation via G₀/G₁ arrest, which upregulates p27^Kip1 expression.

p21WAF1 Is Required for Interleukin-16-Induced Migration and Invasion of Vascular Smooth Muscle Cells via the p38MAPK/Sp-1/MMP-9 Pathway

Interleukin-16 (IL-16) is a lymphocyte chemoattractant factor well known for its role in immune responses, but its role in vascular disease is unknown. Here, we explored the novel physiological function of IL-16 in vascular smooth muscle cells (VSMCs). The expression of IL-16 and its receptor CD4 was observed in VSMCs. Treatment with IL-16 enhanced the migration and invasion by VSMCs without altering the proliferative potential. IL-16 induced MMP-9 expression via the binding activity of transcription factors NF-κB, AP-1, and Sp-1 motifs in VSMCs. Among the relevant signaling pathways examined, only p38MAPK phosphorylation was significantly stimulated in IL-16-treated VSMCs. Treatment with p38MAPK inhibitor SB203580 prevented the IL-16-induced migration and invasion of VSMCs. SB203580 treatment inhibited the MMP-9 expression and activation of Sp-1 binding in IL-16-treated VSMCs, and siRNA knockdown of CD4 expression blocked the induction of migration, invasion, p38MAPK phosphorylation, MMP-9 expression, and Sp-1 binding activation stimulated by IL-16. The IL-16 induced cell-cycle-inhibitor p21WAF1 expression in VSMCs, but had no effect on the expression levels of other cell-cycle negative regulators. Finally, blockage of p21WAF1 function with specific siRNA abolished the IL-16-induced elevation of migration, invasion, p38MAPK phosphorylation, MMP-9 expression, and Sp-1 binding activation in VSMCs. Taken together, p21WAF1 was required for the induction of p38MAPK-mediated MMP-9 expression via activation of the Sp-1 binding motif, which led to migration and invasion of VSMCs interacting with IL-16/CD4. These results could provide that IL-16 is a new target in the treatment of vascular diseases such as atherosclerosis and re-stenosis.

p27(Kip1) and p21(Cip1)-independent proliferative inhibition of vascular smooth muscle cells cultured in type-I collagen matrix honeycombs

The proliferation of vascular smooth muscle cells (SMCs) contributes to atherosclerotic plaque formation and restenosis. Cyclin-dependent kinase inhibitors, such as p27(Kip1) and p21(Cip1), are known to play significant roles in the control of the aberrant proliferation of SMCs. Primary cultured SMCs stop proliferating immediately when cultured in three-dimensional matrices of type-I collagen "honeycombs" structures. To clarify whether p27(Kip1) and p21(Cip1) are involved in the proliferative inhibition of SMCs cultured in honeycombs, the characteristics of SMCs derived from the aorta of both wild-type mice (p27[+/+] SMCs) and p27(Kip1) knockout mice (p27[-/-] SMCs) were investigated. Although the growth of p27(-/-) SMCs cultured on plates was faster than that of p27(+/+) SMCs, the number of both p27(+/+) and p27(-/-) SMCs did not change when they were cultured in honeycombs. p21(Cip1) expression was decreased but maintained in p27(-/-) SMCs cultured on plates and in honeycombs. Knockdown of p21(Cip1) in p27(-/-) SMCs promoted proliferation on plates. On the contrary, p21(Cip1) knockdown had no effect on the proliferation of p27(-/-) SMCs cultured in honeycombs. In conclusion, p27(Kip1) and p21(Cip1) are insufficient for the proliferative inhibition of SMCs cultured in honeycombs.

Alpha1beta1 and integrin-linked kinase interact and modulate angiotensin II effects in vascular smooth muscle cells

The effects of angiotensin II (Ang II) on vascular smooth muscle cells (VSMC) are modulated by reactive oxygen species (ROS) and also involve integrin engagement. However, the potential link between alpha1beta1 integrin signaling with NOX system and their combined contribution to Ang II effects on VSMC have not been investigated. We aimed to elucidate the moslecular mechanisms underlying the activation of these two pathways in Ang II effects on VSMC. Ang II-induced VSMC migration (2-fold increase) and proliferation (2.5-fold increase) is modulated by alpha1beta1 integrin, being inhibited by obtustatin, a specific alpha1beta1 integrin blocker. Ang II also stimulates ROS production in VSMC (140%) that is NOX1 dependent, being completely inhibited in NOX1 silenced cells. The ROS production develops in two peaks, and the second peak is maintained by NOX2 activation. Apocynin and obtustatin inhibit the NOX2-associated second peak, but not the first peak of ROS production, which is related to NOX1 activation. Corroborating the involvement of alpha1beta1 integrin, the pretreatment of VSMC with obtustatin impaired Ang II-induced FAK phosphorylation, AKT activation, p21 degradation and the increase of ILK expression. Silencing of ILK blocked cell migration, AKT phosphorylation and the second peak of ROS, but partially inhibits (70%) VSMC proliferation induced by Ang II. The data demonstrate a novel role for NOX2 in Ang II effects on VSMC, and suggest alpha1beta1 integrin and ILK as target molecules to the development of more effective therapeutic interventions in cardiovascular diseases.

Cinnamon and its Components Suppress Vascular Smooth Muscle Cell Proliferation by Up-Regulating Cyclin-Dependent Kinase Inhibitors

Cinnamomum cassia bark has been used in traditional herbal medicine to treat a variety of cardiovascular diseases. However, the antiproliferative effect of cinnamon extract on vascular smooth muscle cells (VSMCs) and the corresponding restenosis has not been explored. Hence, after examining the effect of cinnamon extract on VSMC proliferation, we investigated the possible involvement of signal transduction pathways associated with early signal and cell cycle analysis, including regulatory proteins. Besides, to identify the active components, we investigated the components of cinnamon extract on VSMC proliferation. Cinnamon extract inhibited platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation and suppressed the PDGF-stimulated early signal transduction. In addition, cinnamon extract arrested the cell cycle and inhibited positive regulatory proteins. Correspondingly, the protein levels of p21 and p27 not only were increased in the presence of cinnamon extract, also the expression of proliferating cell nuclear antigen (PCNA) was inhibited by cinnamon extract. Besides, among the components of cinnamon extract, cinnamic acid (CA), eugenol (EG) and cinnamyl alcohol significantly inhibited the VSMC proliferation. Overall, the present study demonstrates that cinnamon extract inhibited the PDGF-BB-induced proliferation of VSMCs through a G0/G1 arrest, which down-regulated the expression of cell cycle positive regulatory proteins by up-regulating p21 and p27 expression.

Incidence and Expression of Circulating Cell Free p53-Related Genes in Acute Myocardial Infarction Patients

AIM

The circulating RNA levels are predictive markers in several diseases. We determined the levels of circulating p53-related genes in patients with acute ST-segment elevation myocardial infarction (STEMI), indicating major heart muscle damage.

METHODS

Plasma RNA was extracted from the patients (n=45) upon their arrival to the hospital (STEMI 0h) and at four hours post-catheterization (STEMI 4h) as well as from controls (n=34).

RESULTS

Of 18 circulating p53-related genes, nine genes were detectable. A significantly lower incidence of circulating p21 (p ＜ 0.0001), Notch1 (p=0.042) and BTG2 (p ＜ 0.0001) was observed in the STEMI 0h samples in comparison to the STEMI 4h and control samples. Lower expression levels (2.1-fold) of circulating BNIP3L (p=0.011), p21 (3.4-fold, p=0.005) and BTG2 (6.3-fold, p=0.0001) were observed in the STEMI 0h samples in comparison to the STEMI 4h samples, with a 7.4-fold lower BTG2 expression (p ＜ 0.001) and 2.6-fold lower p21 expression (p=0.034) compared to the control samples. Moreover, the BNIP3L expression (borderline significance, p=0.0655) predicted the level of peak troponin, a marker of myocardial infarction. In addition, the BNIP3L levels on admission (p=0.0025), at post-catheterization (p=0.020) and the change between the groups (p=0.0079) were inversely associated with troponin. The BNIP3L (p=0.0139) and p21 levels (p=0.0447) were also associated with a longer time to catheterization.

CONCLUSIONS

Our results suggest that circulating downstream targets of p53 are inhibited during severe AMI and subsequently re-expressed after catheterization, uncovering possible novel death-or-survival decisions regarding the fate of p53 in the heart and the potential use of its target genes as prognostic biomarkers for oxygenation normalization.

The COP9 signalosome and vascular function: intriguing possibilities?

Disorders of vascular function contribute importantly to cardiovascular disease which represents a substantial cause of morbidity and mortality worldwide. An emerging paradigm in the study of cardiovascular diseases is that protein ubiquitination and turnover represent key pathological mechanisms. Our understanding of these processes in the vasculature is growing but remains incomplete. Since protein ubiquitination and turnover can represent a terminal event in the life of a given protein, entry into these pathways must be highly regulated. However, at present understanding of these regulatory mechanisms, particularly in the vasculature, is fragmentary. The COP9 (constitutive photomorphogenic mutant 9) signalosome (CSN) is a heteromeric protein complex implicated in the control of protein degradation. The CSN participates critically in the control of Cullin Ring Ligases (CRLs), at least in part via the detachment of a small protein, Nedd8 (deneddylation). CRLs are one of the largest groups of ubiquitin ligases, which represent the most selective control point for protein ubiquitination. Thus, the CSN by virtue of its ability to control the CRLs ubiquitin ligase activity is ideally positioned to effect selective modulation of protein turnover. This review surveys currently available data regarding the potential role of the CSN in control of vascular function. Data potentially linking the CSN to control of regulatory proteins involved in vascular smooth muscle proliferation and to vascular smooth muscle contraction are presented with the intent of providing potentially intriguing possibilities for future investigation.

The microRNA miR-34c inhibits vascular smooth muscle cell proliferation and neointimal hyperplasia by targeting stem cell factor

The fine balance between proliferation and differentiation of vascular smooth muscle cells (VSMCs) is indispensable for the maintenance of healthy blood vessels, whereas an increase in proliferation participates in pathologic cardiovascular events such as atherosclerosis and restenosis. Here we report that microRNA-34c (miR-34c) targets stem cell factor (SCF) to inhibit VSMC proliferation and neointimal hyperplasia. In an animal model, miR-34c was significantly increased in the rat carotid artery after catheter injury. Transient transfection of miR-34c to either VSMCs or A10 cells inhibited cell survival by inducing apoptosis, which was accompanied by an increase in expression of p21, p27, and Bax. Transfection of miR-34c also attenuated VSMC migration. Bioinformatics showed that SCF is a target candidate of miR-34c. miR-34c down-regulated luciferase activity driven by a vector containing the 3'-untranslated region of SCF in a sequence-specific manner. Forced expression of SCF in A10 cells induced proliferation and migration, whereas knocking-down of SCF reduced cell survival and migration. miR-34c antagomir-induced VSMC proliferation was blocked by SCF siRNA. Delivery of miR-34c to rat carotid artery attenuated the expression of SCF and blocked neointimal hyperplasia. These results suggest that miR-34c is a new modulator of VSMC proliferation and that it inhibits neointima formation by regulating SCF.

Role of Krüppel-like factor 4 and its binding proteins in vascular disease

Krüppel-like factor 4(KLF4) is a zinc-finger transcription factor that plays a key role in cellular differentiation and proliferation during normal development and in various diseases, such as cancer. The results of recent studies have revealed that KLF4 is expressed in multiple vascular cell types, including phenotypically modulated smooth muscle cells(SMCs), endothelial cells and monocytes/macrophages and contributes to the progression of vascular diseases by activating or repressing the transcription of multiple genes via its associations with a variety of partner proteins. For example, KLF4 decreases the expression of markers of SMC differentiation by interacting with serum response factor, ELK1 and histone deacetylases. KLF4 also suppresses SMC proliferation by associating with p53. In addition, KLF4 enhances arterial medial calcification in concert with RUNX2. Furthermore, endothelial KLF4 represses arterial inflammation by binding to nuclear factor-κB. This article summarizes the role of KLF4 in vascular disease with a particular focus on in vivo studies and reviews recent progress in our understanding of the regulatory mechanisms involved in KLF4- mediated gene transcription.

The microRNA miR-132 targets Lrrfip1 to block vascular smooth muscle cell proliferation and neointimal hyperplasia

OBJECTIVE

The proliferation and remodeling of vascular smooth muscle cells (VSMCs) is an important pathological event in atherosclerosis and restenosis. Here we report that microRNA-132 (miR-132) blocks vascular smooth muscle cells (VSMC) proliferation by inhibiting the expression of LRRFIP1 [leucine-rich repeat (in Flightless 1) interacting protein-1].

METHODS AND RESULTS

MicroRNA microarray revealed that miR-132 was upregulated in the rat carotid artery after catheter injury, which was further confirmed by quantitative real-time RT-PCR. Transfection of a miR-132 mimic significantly inhibited the proliferation of VSMCs, whereas transfection of a miR-132 antagomir increased it. miR-132 mimic inhibited VSMC migration and induced apoptosis. miR-132 mimic increased the protein amounts of both p27 and smooth muscle (SM) α-actin, whereas it decreased SM α-actin and Bcl2. Bioinformatics showed that LRRFIP1 is a target candidate of miR-132. miR-132 down-regulated luciferase activity driven by a vector containing the 3'-untranslated region of Lrrfip1 in a sequence-specific manner. LRRFIP1 induced VSMC proliferation and increased phosphorylation of ERK. Immunohistochemical analysis revealed that Lrrfip1 was clearly expressed along with the basal laminar area of smooth muscle, and its expression pattern was disrupted 7 days after arterial injury. LRRFIP1 mRNA was decreased 14 days after injury. Delivery of miR-132 to rat carotid artery reduced LRRFIP1 expression and attenuated neointimal proliferation in carotid artery injury models.

CONCLUSIONS

Our results suggest that miR-132 is a novel regulator of VSMC proliferation that represses neointimal formation by inhibiting LRRFIP1 expression.

Bilirubin inhibits neointima formation and vascular smooth muscle cell proliferation and migration

Bilirubin is a heme metabolite generated by the concerted action of the enzymes heme oxygenase and biliverdin reductase. Although long considered a toxic byproduct of heme catabolism, recent preclinical, and clinical studies indicate the bilirubin exerts beneficial effects in the circulation. In the present study, we determined whether local administration of bilirubin attenuates neointima formation following injury of rat carotid arteries. In addition, the ability of bilirubin to regulate the proliferation and migration of human arterial smooth muscle cells (SMCs) was investigated. Local perivascular administration of bilirubin immediately following balloon injury of rat carotid arteries significantly attenuated neointima formation. Bilirubin-mediated inhibition of neointimal thickening was associated with a significant decrease in ERK activity and cyclin D1 and A protein expression, and an increase in p21 and p53 protein expression in injured blood vessels. Treatment of human aortic SMCs with bilirubin inhibited proliferation and migration in a concentration-dependent manner without affecting cell viability. In addition, bilirubin resulted in a concentration-dependent increase in the percentage of cells in the G₀/G₁ phase of the cell cycle and this was paralleled by a decrease in the fraction of cells in the S and G₂M phases of the cell cycle. Finally, bilirubin had no effect on mitochondrial function and ATP content of vascular SMCs. In conclusion, these studies demonstrate that bilirubin inhibits neointima formation after arterial injury and this is associated with alterations in the expression of cell cycle regulatory proteins. Furthermore, bilirubin blocks proliferation and migration of human arterial SMCs and arrests SMCs in the G₀/G₁ phase of the cell cycle. Bilirubin represents an attractive therapeutic agent in treating occlusive vascular disease.

Increased gene dosage of the Ink4/Arf locus does not attenuate atherosclerosis development in hypercholesterolaemic mice

RATIONALE

Human genome-wide association studies have identified genetic variants in the chromosome 9p21 region that confer increased risk of coronary artery disease and other age-related diseases. These variants are located in a block of high linkage disequilibrium with the neighboring Ink4/Arf tumor-suppressor locus (also named CDKN2A/CDKN2B). Since previous studies suggest an atheroprotective role of the Ink4/Arf locus, here we assessed whether gain-of-function of the encoded genes can be exploited therapeutically to reduce atherosclerosis.

METHODS

Generation and characterization of apolipoprotein E-null mice carrying an additional transgenic copy of the entire Ink4/Arf locus (apoE-/-Super-Ink4/Arf) that reproduces the normal expression and regulation of the endogenous locus.

RESULTS

Although liver and aorta of apoE-/-Super-Ink4/Arf mice only showed a trend towards increased Ink4/Arf transcript levels compared to apoE-/- controls, cultured macrophages with increased Ink4/Arf gene dosage exhibited augmented apoptosis induced by irradiation with ultraviolet light, indicating that low level of transgene overexpression can lead to augmented Ink4/Arf function. However, increased Ink4/Arf gene dosage did not affect atherosclerosis development in different vascular regions of both male and female apoE-/- mice fed either normal or high-fat diet. Increased gene dosage of Ink4/Arf similarly had no effect on atheroma cell composition or collagen content, an index of plaque stability.

CONCLUSION

In contrast with previous studies demonstrating cancer resistance in Super-Ink4/Arf mice carrying an additional transgenic copy of the entire Ink4/Arf locus, our results cast doubt on the potential of Ink4/Arf activation as a strategy for the treatment of atherosclerotic disease.

The scaffolding protein EBP50 promotes vascular smooth muscle cell proliferation and neointima formation by regulating Skp2 and p21(cip1)

OBJECTIVE

The Ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50) is a scaffolding protein known to regulate ion homeostasis in the kidney and intestine. Previous work showed that EBP50 expression increases after balloon injury in rat carotids. This study was designed to determine the role of EBP50 on vascular smooth muscle cells (VSMC) proliferation and the development of neointimal hyperplasia.

METHODS AND RESULTS

Wire injury was performed in wild type (WT) and EBP50 knockout (KO) mice. Two weeks after injury, neointima formation was 80% lower in KO than in WT mice. Proliferation of KO VSMC was significantly lower than WT cells and overexpression of EBP50 increased VSMC proliferation. Akt activity and expression of S-phase kinase protein2 decreased in KO cells resulting in the stabilization of the cyclin-dependent kinase inhibitor, p21(cip1). Consequently, KO cells were arrested in G(0)/G(1) phase. Consistent with these observations, p21(cip1) was detected in injured femoral arteries of KO but not WT mice. No differences in apoptosis between WT and KO were observed.

CONCLUSIONS

EBP50 is critical for neointima formation and induces VSMC proliferation by decreasing S-phase kinase protein2 stability, thereby accelerating the degradation of the cell cycle inhibitor p21(cip1).

Inhibitory effect of n-butylidenephthalide on neointimal hyperplasia in balloon injured rat carotid artery

This investigation was designed to determine the inhibitory effects and mechanisms of n-butylidenephthalide (BP) from Angelica sinensis on smooth muscle cell (SMC) proliferation in vitro and in balloon injured rat carotid artery. Treatment of cultured rat aorta SMC-derived A7r5 cells with 25-100 μg/mL BP significantly inhibited the proliferation and arrested the cell cycle in G(0)/G(1) phase. BP induced the expression and migration of Nur77 from the nucleus to the cytoplasm. Among signal pathways, JNK and p38 MAPK were phosphorylated after BP treatment. In vivo, the neointimal area of common carotid artery 2 weeks after balloon injury reduced significantly in Sprague-Dawley rats treated with 150-300 mg/kg BP compared with the control. The proliferative activity indicated by immunohistochemical detection of Ki-67 positive cells in the neointima was significantly decreased in the 60-300 mg/kg BP treatment groups. The apoptotic activity indicated by cleaved caspase-3 positive cells and Nur77 positive cells in the neointima was significantly increased in rats treated with 60-300 mg/kg BP. This study demonstrated BP inhibited neointimal hyperplasia in balloon injured rat carotid artery due to its dual effects of proliferative inhibition and apoptotic induction on SMCs. Up-regulation of Nur77 gene may partly explain the antihyperplasia activity of BP on the neointima.

Epigenetic regulation of vascular smooth muscle cell proliferation and neointima formation by histone deacetylase inhibition

OBJECTIVE

Proliferation of smooth muscle cells (SMC) in response to vascular injury is central to neointimal vascular remodeling. There is accumulating evidence that histone acetylation constitutes a major epigenetic modification for the transcriptional control of proliferative gene expression; however, the physiological role of histone acetylation for proliferative vascular disease remains elusive.

METHODS AND RESULTS

In the present study, we investigated the role of histone deacetylase (HDAC) inhibition in SMC proliferation and neointimal remodeling. We demonstrate that mitogens induce transcription of HDAC 1, 2, and 3 in SMC. Short interfering RNA-mediated knockdown of either HDAC 1, 2, or 3 and pharmacological inhibition of HDAC prevented mitogen-induced SMC proliferation. The mechanisms underlying this reduction of SMC proliferation by HDAC inhibition involve a growth arrest in the G(1) phase of the cell cycle that is due to an inhibition of retinoblastoma protein phosphorylation. HDAC inhibition resulted in a transcriptional and posttranscriptional regulation of the cyclin-dependent kinase inhibitors p21(Cip1) and p27(Kip). Furthermore, HDAC inhibition repressed mitogen-induced cyclin D1 mRNA expression and cyclin D1 promoter activity. As a result of this differential cell cycle-regulatory gene expression by HDAC inhibition, the retinoblastoma protein retains a transcriptional repression of its downstream target genes required for S phase entry. Finally, we provide evidence that these observations are applicable in vivo by demonstrating that HDAC inhibition decreased neointima formation and expression of cyclin D1 in a murine model of vascular injury.

CONCLUSIONS

These findings identify HDAC as a critical component of a transcriptional cascade regulating SMC proliferation and suggest that HDAC might play a pivotal role in the development of proliferative vascular diseases, including atherosclerosis and in-stent restenosis.

Inhibition of intimal hyperplasia after stenting by over-expression of p15: a member of the INK4 family of cyclin-dependent kinase inhibitors

We evaluated the role of p15(Ink4), a member of the INK4 family of CDK inhibitors on vascular smooth muscle cells (VSMCs) proliferation, cell cycle progression and intimal hyperplasia after stenting. Aortic VSMCs transduced with either adenovirus encoding for p15(Ink4) or β-galactosidase were assessed for DNA synthesis, cell cycle progression, and pRb phosphorylation. Rabbit carotid arteries were stented and treated with peri-adventitial delivery of saline or adenovirus encoding for p15(Ink4) or β-galactosidase. p15(Ink4) transgene and protein expression were evaluated at 24 h and 72 h, respectively. In-stent cell proliferation was evaluated by BrdU at day 7. Histomorphometric analysis of in-stent intimal hyperplasia was performed at 10 weeks. Human p15(Ink4) DNA was detected in transduced VSMCs at 24h. p15(Ink4) over-expression reduced VSMCs DNA synthesis by 60%. Cell cycle progression was inhibited, with a 30% increase in G1 population accompanied by inhibition of pRb phosphorylation. Human p15(Ink4) transgene was identified in transduced stented arteries but not in control arteries. p15(Ink4) immunostaining was increased and cell proliferation significantly reduced by 50% in p15(Ink4) transduced arteries. Intimal cross-sectional area (CSA) of p15(Ink4)-treated group was significantly lower than the β-gal treated and non-transduced groups (p=0.008). There were no differences in the intimal or medial inflammatory response between groups. p15(Ink4) over-expression blocks cell cycle progression leading to inhibition of VSMCs proliferation. Peri-adventitial delivery of p15(Ink4) significantly inhibits in-stent intimal hyperplasia.

Identification of an up-regulated anti-apoptotic network in the internal thoracic artery

BACKGROUND

The radial artery (RA) is known as an atherosclerosis-prone vessel in contrast to the atherosclerosis-resistant internal thoracic artery (ITA). The purpose of the present study was to compare the gene expression profile of these arteries from the same patient in order to identify genes involved in atherogenesis or intimal hyperplasia.

METHODS

Paired specimens of RA and ITA (n=6) were analyzed by histomorphometry and whole genome microarray. The microarray data underwent pathway analysis to identify biological networks. Laser microdissection (LMD) was used to identify the cellular expression of candidate genes in the intimal or medial layer of the ITA and RA.

RESULTS

Histomorphometric analyses revealed a significantly higher degree of intimal hyperplasia in the RA compared to the ITA. 552 genes were differentially expressed in the ITA and RA. qRT-PCR confirmed a significant up-regulation of six anti-apoptotic genes. p21 (11.8-fold, p=0.011), CCL2 (5.4-fold, p=0.034), SOCS3 (7.2-fold, p=0.002), IER3 (4.1-fold, p=0.048), MCL-1 (2.6-fold, p=0.025) and IL-6 (17.8-fold, p=0.046) were up-regulated in the ITA. LMD confirmed that cells of the intimal layer of the ITA consistently expressed higher levels of all six candidate genes than those of the RA.

CONCLUSIONS

Microarray analysis and qRT-PCR identified significantly up-regulated genes in the ITA involved in an anti-apoptotic network. LMD revealed a higher expression of all anti-apoptotic genes in the intimal area of the ITA. These genes may play an important role in protecting the intima of the ITA from developing hyperplasia and atherosclerosis.

Stat3-dependent acute Rantes production in vascular smooth muscle cells modulates inflammation following arterial injury in mice

Inflammation is a key component of arterial injury, with VSMC proliferation and neointimal formation serving as the final outcomes of this process. However, the acute events transpiring immediately after arterial injury that establish the blueprint for this inflammatory program are largely unknown. We therefore studied these events in mice and found that immediately following arterial injury, medial VSMCs upregulated Rantes in an acute manner dependent on Stat3 and NF-kappaB (p65 subunit). This led to early T cell and macrophage recruitment, processes also under the regulation of the cyclin-dependent kinase inhibitor p21Cip1. Unique to VSMCs, Rantes production was initiated by Tnf-alpha, but not by Il-6/gp130. This Rantes production was dependent on the binding of a p65/Stat3 complex to NF-kappaB-binding sites within the Rantes promoter, with shRNA knockdown of either Stat3 or p65 markedly attenuating Rantes production. In vivo, acute NF-kappaB and Stat3 activation in medial VSMCs was identified, with acute Rantes production after injury substantially reduced in Tnfa-/- mice compared with controls. Finally, we generated mice with SMC-specific conditional Stat3 deficiency and confirmed the Stat3 dependence of acute Rantes production by VSMCs. Together, these observations unify inflammatory events after vascular injury, demonstrating that VSMCs orchestrate the arterial inflammatory response program via acute Rantes production and subsequent inflammatory cell recruitment.

Obovatol from Magnolia obovata inhibits vascular smooth muscle cell proliferation and intimal hyperplasia by inducing p21Cip1

AIMS

Obovatol is isolated from Magnolia obovata leaves and this active component has various pharmacological properties such as anti-oxidant, anti-platelet, anti-fungal and anti-inflammatory activities. In the present study, we investigated the inhibitory effects of obovatol on in vitro vascular smooth muscle cell (VSMC) proliferation and in vivo neointimal formation in a rat carotid artery injury model.

METHODS AND RESULTS

Obovatol (1-5 microM) exerted concentration-dependent inhibition on platelet-derived growth factor (PDGF)-BB-induced rat VSMC proliferation, without exhibiting any cellular toxicity or apoptosis, as determined by cell count, [3H]thymidine incorporation and Annexin-V-binding analyses. Treatment with obovatol blocked the cell cycle in G1 phase by down-regulating the expression of cyclins and CDKs, and selectively up-regulating the expression of p21Cip1, a well-known CDK inhibitor. Effects of perivascular delivery of obovatol were assessed 14 days after injury. The angiographic mean luminal diameters of the obovatol-treated groups (100 microg and 1 mg: 0.78+/-0.06 and 0.77+/-0.07AU, respectively) were significantly larger than that of the control group (0.58+/-0.07AU). The obovatol-treated groups (100 microg and 1mg: 0.14+/-0.04 and 0.09+/-0.03 mm2, respectively) showed significant reduction in neointimal formation versus the control group (0.17+/-0.02 mm2). Immunohistochemical staining demonstrated strong expression of p21Cip1 in the neointima of the obovatol-treated groups.

CONCLUSIONS

These data suggest that obovatol inhibits VSMC proliferation by perturbing cell cycle progression, possibly due to activation of p21Cip1 pathway. These results also show that obovatol may have potential as an anti-proliferative agent for the treatment of restenosis and atherosclerosis.

Aging increases p16INK4a expression in vascular smooth-muscle cells

Alteration of VSMC (vascular smooth-muscle cell) physiology is associated with the development of atherosclerosis and restenosis. We hypothesize that aging up-regulates the expression of p16INK4a in VSMCs, which may increase the susceptibility of blood vessels to vascular occlusive diseases. Aortic VSMCs were obtained from young and aged mice. Cells from aged mice grew more slowly than those from their younger counterparts. Progression of cell cycle in response to serum stimulation was significantly inhibited in those cells with aging, as determined by FACS after propidium iodide staining. A significant up-regulation of p16INK4a (2.5-fold, P=0.0012) was found in VSMC from aged animals using gene arrays. The up-regulation of this gene was further confirmed by quantitative RT–PCR (reverse transcription–PCR) and Western-blot experiments. Immunostaining for p16INK4a confirmed that aortas from aged mice contained more p16INK4a+ SMA (smooth-muscle cell actin)+ cells than aortas from young animals (26.79±2.45 versus 7.06±1.44, P=0.00027, n=4). In conclusion, we have shown that aging up-regulates the expression of p16INK4a in VSMC in both cultures and arteries. The increase in p16INK4a in the vasculature with aging may modify VSMC's response to post-injury stress and therefore accelerate the development of age-related cardiovascular diseases.

Regulation of cell cycle entry by PTEN in smooth muscle cell proliferation of human coronary artery bypass conduits

Proliferation of smooth muscle cells (SMCs) is the key event in the pathogenesis of intimal hyperplasia (IH) leading to coronary artery bypass graft (CABG) occlusion. The saphenous vein (SV) conduits are often affected by IH, while the internal mammary artery (IMA) conduits remain remarkably patent. SMC proliferation is mediated by the cell cycle, under the control of cyclin-dependent kinases (cdks), cdk-inhibitors and the retinoblastoma protein (Rb). Early passage of the SMCs through the cell cycle involves crossing the non-reversible G(1) checkpoint, the restriction (R) point. In this study, we investigated the effect of mitogenic insulin-like growth factor (IGF)-1 stimulation on the R-point and its relationship with the phosphorylation of Rb protein and the cdk inhibitors p21 and p27 in SV and IMA SMCs. We observed no change in the R-point following IGF-1 activation in either SV or IMA SMCs. However, Rb-phosphorylation occurred much earlier and was quantitatively greater in SV SMCs than IMA. Overexpression of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in SV SMCs followed by IGF-1 activation significantly decreased the expression of cyclin E and pRb and induced p27 expression in SV SMCs, while, pRb levels were markedly decreased and p27 levels were significantly increased in IMA SMCs. Silencing the PTEN gene by siRNA transfection of IMA SMCs significantly induced the expression of pRb and inhibited p27 expression, while, the expression levels of cyclin E, pRb, p21 and p27 were unaffected by the silencing of PTEN in SV SMCs. These results demonstrate that the PTEN plays a critical role in regulating cell cycle entry. Therefore, overexpression of PTEN possibly by means of gene therapy could be a viable option in regulating the cell cycle in SV SMCs in the treatment of vein graft disease.

Enhanced susceptibility of cyclin kinase inhibitor p21 knockout mice to high fat diet induced atherosclerosis

Cyclin kinase inhibitor p21 is one of the most potent inhibitors of aortic smooth muscle cell proliferation, a key mediator of atherosclerosis. This study tests if p2l deficiency will result in severe atherosclerosis in a mouse model. p21-/- and strain matched wild type mice were fed with high fat diet for 21 weeks. Analysis for biochemical parameters (cholesterol, triglycerides) in serum and mRNA expression of CD36, HO-1, TGF-beta, IFN-gamma, TNF-alpha, PPAR-gamma and NADPH oxidase components (p22phox, NOX-1 and Rac-1) was performed in aortic tissues by Real Time PCR. p21-/- mice gained significantly (p < 0.01) more weight than wild type mice, triglycerides (p < 0.05) and cholesterol levels (p < 0.01) were more pronounced in the sera of p21-/- compared to wild type mice fed with high fat diet. High fat diet resulted in significantly decreased TGF-beta (p < 0.02), HO-l (p < 0.02) and increased CD36 (p < 0.03) mRNA expression in aortic tissues of p21-/- mice compared to animal fed with regular diet. IFN-gamma mRNA expression (235 +/- 11 folds) increased significantly in high fat diet fed p21-/- mice and a multifold modulation of PPAR-gamma(136 +/- 7), p22phox, NOX-1 and Rac-1 (15-35-folds) mRNA in aortic tissues from p21-/- mice compared to the wild type mice. Severity of atherosclerotic lesions was significantly higher in p21-/- compared to wild type mice. The results demonstrate that the deficiency of p21 leads to altered expression of pro-atherogenic genes, and severe atherosclerosis in mice fed with high fat diet. This opens the possibility of p21 protein as a therapeutic tool to control progression of atherosclerosis.

Hemin inhibits hypertensive rat vascular smooth muscle cell proliferation through regulation of cyclin D and p21

We tested the hypothesis that HO-1 (heme oxygenase-1) activity varied between vascular smooth muscle cells (VSMC) in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. HO-1 levels were measured under baseline and hemin-stimulated conditions and cell proliferation was monitored. Basal HO-1 levels in untreated cells were lower in SHR compared to WKY rats. Treatment with hemin increased HO-1 mRNA and protein levels in the cells obtained from WKY rats compared to that of SHR rats. However, hemin-treatment showed a greater inhibitory effect on VSMC proliferation in SHR rats than in WKY rats. Tin protoporphyrin IX (SnPPIX) showed a greater reversal of the anti-proliferative effect of hemin on cells from SHR rats than WKY. Similarly, VSMC proliferation from SHR was significantly inhibited in VSMC transfected with the HO-1 gene. These inhibitory effects were associated with cell cycle arrest in the G1 phase. The level of cyclin D, and cyclin dependent kinase inhibitor p21 was higher in SHR cells progressing through the G1 phase. Treatment of the cells with hemin down-regulated the expression of cyclin D and up-regulated that of p21. These results indicate that hemin, an HO-1 inducer, may play a more critical role in VSMC proliferation in SHR than WKY.

Copper chelator ATN-224 inhibits endothelial function by multiple mechanisms

Copper is required for the proliferation of endothelial cells and copper-lowering therapy reduces tumour growth in animal models. It has been reported that ATN-224, a novel copper chelator, potently inhibits the activity of the copper-dependent enzyme superoxide dismutase 1 (SOD1) in endothelial cells. We performed microarray analysis of gene expression in endothelial cells exposed to ATN-224 which revealed upregulation of stress response genes including heme-oxygenase 1 (HO-1) and differential regulation of several genes previously implicated in angiogenesis including CXCR4, ANGP2, PGES2, RHAMM, ITB4 and AQP1 (p<0.01). These changes were confirmed on qPCR. Treatment of HUVEC with ATN-224 caused increased superoxide levels, phospho-ERK signalling, nuclear NRF1 expression, HO-1 expression and induction of the anti-apoptotic proteins P21, BCL2 and BCLXL. There was also nuclear translocation of SOD1. SOD1 RNA interference replicated the effects of ATN-224 on endothelial cell function but did not cause upregulation of HO-1 or PGES2, suggesting additional mechanisms of action of ATN-224. Downregulation of AQP1, which has been shown to have a role in angiogenesis, was seen with both ATN-224 and SOD1 siRNA. AQP1 expression could be rescued after ATN-224 by added copper. RNA interference to AQP1 inhibited endothelial proliferation and migration, confirming the role of AQP1 in endothelial cell function. Therefore regulation of AQP1 may represent an important action of copper chelation therapy.

Arginase promotes neointima formation in rat injured carotid arteries

OBJECTIVE

Arginase stimulates the proliferation of cultured vascular smooth muscle cells (VSMCs); however, the influence of arginase on VSMC growth in vivo is not known. This study investigated the impact of arginase on cell cycle progression and neointima formation after experimental arterial injury.

METHODS AND RESULTS

Balloon injury of rat carotid arteries resulted in a sustained increase in arginase activity in the vessel wall and the induction of arginase I protein in both the media and neointima of injured vessels. Furthermore, local perivascular application of the potent and selective arginase inhibitors S-(2-boronoethyl)-L-cysteine (BEC) or N(G)-hydroxy-nor-L-arginine (L-OHNA) immediately after injury markedly attenuated medial and neointimal DNA synthesis and neointima formation. Substantial arginase I protein and arginase activity was also detected in rat cultured aortic VSMCs. Moreover, treatment of VSMCs with BEC or L-OHNA, or knockdown of arginase I protein, arrested cells in the G(0)/G(1) phase of the cell cycle and induced the expression of the cyclin-dependent protein kinase inhibitor, p21.

CONCLUSIONS

This study demonstrates that arginase is essential for VSMCs to enter the cell cycle and that arginase I contributes to the remodeling response after arterial injury. Arginase I represents a potentially new therapeutic target for the treatment of vasculoproliferative disorders.

Inhibitory effect of Ginkgo biloba extract on hyperhomocysteinemia-induced intimal thickening in rabbit abdominal aorta after balloon injury

Ginkgo biloba extract (GBE) has been widely used to treat cardiovascular and cerebrovascular disorders. Hyperhomocysteinemia (Hhcy) is associated with the risk of atherosclerosis and restenosis after angioplasty. The objective of this study was to investigate whether GBE could attenuate the Hhcy-induced intimal thickening after balloon injury in rabbit abdominal aorta. It was observed in this study that GBE could decrease the neointima area (NA) and the ratio of the neointima area to the media area (NA/MA), down-regulate the mRNA expression of matrix metalloproteinase-9 (MMP-9) and up-regulate the protein expression of p21 (WAF1/CIP1) (p21). It suggests that GBE can reverse the Hhcy-induced neointima formation in rabbits following balloon injury, and the suppressive effect of GBE on the migration and proliferation of vascular smooth muscle cells (VSMCs) may contribute to its actions.

NFATc1 targets cyclin A in the regulation of vascular smooth muscle cell multiplication during restenosis

Platelet-derived growth factor BB (PDGF-BB) induced cyclin A expression and CDK2 activity in vascular smooth muscle cells (VSMC). Inhibition of nuclear factors of activated T cell (NFAT) activation by cyclosporin A (CsA) and VIVIT suppressed PDGF-BB-induced cyclin A expression and CDK2 activity, resulting in blockade of VSMC in the G(1) phase. In addition, CsA- and VIVIT-mediated inhibition of NFATs and small interfering RNA-targeted down-regulation of cyclin A levels suppressed PDGF-BB-induced VSMC DNA synthesis. PDGF-BB also induced cyclin A mRNA levels in VSMC in an NFAT-dependent manner. Cloning and bioinformatic analysis of rat cyclin A promoter revealed the presence of NFAT-binding elements, and PDGF-BB induced the binding of NFATs to these regulatory sequences in a CsA- and VIVIT-sensitive manner. Chromatin immunoprecipitation analysis showed that NFATc1 binds to the cyclin A promoter in response to PDGF-BB in a VIVIT-sensitive manner. Furthermore, PDGF-BB induced cyclin A promoter-luciferase reporter gene activity in VSMC, and it was inhibited by both CsA and VIVIT. Balloon injury induced cyclin A expression and CDK2 activity in rat carotid arteries, and these responses were also blocked by VIVIT. In addition, VIVIT attenuated balloon injury-induced SMC proliferation, resulting in reduced restenosis. Down-regulation of NFATc1 by its small interfering RNA inhibited PDGF-BB-induced cyclin A expression and DNA synthesis both in rat and human VSMC. Together, these findings demonstrate that the cyclin A-CDK2 complex may be a potential effector of NFATs, specifically NFATc1, in mediating SMC multiplication leading to neointima formation. Therefore, NFATs may be used as target molecules for the development of therapeutic agents against vascular diseases such as restenosis.

p21Cip1 modulates arterial wound repair through the stromal cell-derived factor-1/CXCR4 axis in mice

Cyclin-dependent kinase inhibitors, including p21Cip1, are implicated in cell turnover and are active players in cardiovascular wound repair. Here, we show that p21Cip1 orchestrates the complex interactions between local vascular and circulating immune cells during vascular wound repair. In response to femoral artery mechanical injury, mice with homozygous deletion of p21Cip1 displayed accelerated proliferation of VSMCs and increased immune cell infiltration. BM transplantation experiments indicated that local p21Cip1 plays a pivotal role in restraining excessive proliferation during vascular wound repair. Increased local vascular stromal cell-derived factor-1 (SDF-1) levels were observed after femoral artery injury in p21+/+ and p21-/- mice, although this was significantly greater in p21-/- animals. In addition, disruption of SDF-1/CXCR4 signaling inhibited the proliferative response during vascular remodeling in both p21+/+ and p21-/- mice. We provide evidence that the JAK/STAT signaling pathway is an important regulator of vascular SDF-1 levels and that p21Cip1 inhibits STAT3 binding to the STAT-binding site within the murine SDF-1 promoter. Collectively, these results suggest that p21Cip1 activity is essential for the regulation of cell proliferation and inflammation after arterial injury in local vascular cells and that the SDF-1/CXCR4 signaling system is a key mediator of vascular proliferation in response to injury.

Regulation of alloimmune Th1 responses by the cyclin-dependent kinase inhibitor p21 following transplantation

BACKGROUND

The cyclin-dependent kinase (cdk) inhibitor p21 inhibits cellular proliferation of many cell types, including T cells. Autoimmune models, however, have yielded conflicting results regarding the role of cdk inhibitors and T-cell function. The role of p21 in T-cell function after transplantation has not been investigated directly. We hypothesized that p21 plays an important role in alloantigen-driven responses in vitro in mixed lymphocyte cultures (MLC) and in vivo using the heterotopic murine cardiac allograft model.

METHODS

Wild type (WT) and p21-deficient (p21-/-) mice were used as recipients, and the effects of p21 overexpression were assessed by transplanting p21 adenoviral-transfected cardiac allografts. Enzyme-linked immunospot (ELISPOT) and 3H-thymidine incorporation were used to evaluate for T-cell priming and proliferation in vitro, whereas graft histology was evaluated for rejection.

RESULTS

When stimulated with alloantigens in vitro, splenocytes from p21-/- mice mounted enhanced proliferative responses and decreased Th2 responses relative to their WT counterparts. No differences in Th1 responses were noted when p21-/- cells were stimulated with alloantigens in vitro; however, after cardiac transplantation, Th1 responses were enhanced in p21-/- recipients relative to WT mice. This enhanced in vivo Th1 response was associated with exacerbated graft rejection in p21-/- recipients. Interestingly, p21 transfection of WT allografts inhibited graft rejection and Th1 priming.

CONCLUSIONS

p21 controls the intensity of the immune response posttransplantation, with overexpression inhibiting allograft rejection. Our data demonstrate that p21 controls T-cell priming and suggest that p21 and other cdk inhibitors may serve as potential targets for therapeutic manipulation of alloimmune responses.

Nitric oxide regulates steroid synthesis by bovine antral granulosa cells in a chemically defined medium

Nitric oxide (NO) in bovine ovary has been characterized as one of the controllers of granulosa cells' (GC) steroidogenesis and apoptosis. One of the pathways used by NO to have these effects is cGMP. The objectives of the present study were to verify the effect of sodium nitroprusside (SNP), a NO donor, on steroidogenesis, cell viability (mitochondrial activity) and GC cell cycle distribution and if this effect occurs by the NO-cGMP signaling pathway with the addition of SNP with or without 1H-[1,2,3] oxadiaziolo[4,3a]quinoxaline-1-one (ODQ), a selective soluble guanylate cyclase inhibitor. The antral GC from 3 to 5mm diameter cattle follicles was cultured without treatment (control), with ODQ (10(-4)M) and 10(-5), 10(-3) and 10(-1)M SNP with or without ODQ for 24h. Nitrate/nitrite (NO(3)(-)/N0(2)(-)) concentrations were evaluated by Griess method, progesterone (P(4)) and 17beta-estradiol (E(2)) concentrations by chemiluminescence, viability and cell cycle stage by MTT method (3-[4,5-dimethylthiazol-2yl]-2,3 dipheniltetrazolium bromide) and flow cytometry, respectively. Nitrate/nitrite concentration in culture medium increased (P<0.05) in a dose-dependent manner according to SNP concentration added to the culture medium. The GC cultured without treatment, with ODQ and with 10(-5)M SNP in the presence or absence of ODQ developed into cell aggregates and did not vary in cell viability (P>0.05), while GC cultured with 10(-3) and 10(-1)M SNP with or without ODQ presented disorganized GC aggregates or did not develop into cell aggregates and also had substantially decreased cell viability (mitochondrial activity inhibition) and steroids synthesis (P<0.05), and effects were not reversed with us of ODQ. Most GC cultured without treatment (control) or with ODQ, 10(-5) and 10(-3)M SNP with or without ODQ were in the G0/G1 (80-75%) stage and in a lesser proportion (20-25%) in the S+G2/M stage of the cell cycle, while the 10(-1)M SNP treatment resulted in GC in G1 phase arrest. The treatment with 10(-5)M SNP increased (P<0.05) E(2) synthesis and inhibited (P<0.05) progesterone synthesis. The addition of ODQ reversed (P<0.05) the stimulatory effect of 10(-5)M SNP treatment on E(2), but not on P(4) synthesis (P>0.05). These results demonstrated that E(2) synthesis by antral GC from small follicles is modulated by lesser NO concentrations via the cGMP pathway, but not P(4) while steroids inhibition cGMP pathway independent, mitochondrial damage and the interference on cell cycle progression caused by greater NO concentration can lead to cell death.