UTP induces osteopontin expression through a coordinate action of NFkappaB, activator protein-1, and upstream stimulatory factor in arterial smooth muscle cells

Analysis of the TID-I and TID-L Splice Variants' Expression Profile under In Vitro Differentiation of Human Mesenchymal Bone Marrow Cells into Osteoblasts

Bone formation is a complex process regulated by a variety of pathways that are not yet fully understood. One of the proteins involved in multiple osteogenic pathways is TID (DNAJA3). The aim of this work was to study the association of TID with osteogenesis. Therefore, the expression profiles of the TID splice variants (TID-L, TID-I) and their protein products were analyzed during the proliferation and differentiation of bone marrow mesenchymal stromal cells (B-MSCs) into osteoblasts. As the reference, the hFOB1.19 cell line was used. The phenotype of B-MSCs was confirmed by the presence of CD73, CD90, and CD105 surface antigens on ~97% of cells. The osteoblast phenotype was confirmed by increased alkaline phosphatase activity, calcium deposition, and expression of ALPL and SPP1. The effect of silencing the TID gene on the expression of ALPL and SPP1 was also investigated. The TID proteins and the expression of TID splice variants were detected. After differentiation, the expression of TID-L and TID-I increased 5-fold and 3.7-fold, respectively, while their silencing resulted in increased expression of SPP1. Three days after transfection, the expression of SPP1 increased 7.6-fold and 5.6-fold in B-MSCs and differentiating cells, respectively. Our preliminary study demonstrated that the expression of TID-L and TID-I changes under differentiation of B-MSCs into osteoblasts and may influence the expression of SPP1. However, for better understanding the functional association of these results with the relevant osteogenic pathways, further studies are needed.

RAB6A functions as a critical modulator of the stem-like subsets in cholangiocarcinoma

RAB6A is a member of RAB GTPase family and plays an important role in the targeted transport of neurotrophic receptors and inflammatory cytokines. RAB6A-mediated secretory pathway is involved in many physiological and pathological processes. Defects in RAB6A-mediated secretory pathway may lead to the development of many diseases, including cancer. However, its role in cholangiocarcinoma (CCA) has not yet been revealed. We explored the regulatory role of RAB6A in the stem-like subsets of CCA. We showed that RAB6A knockdown (KD) impedes cancer stem cells (CSCs) properties and epithelial-mesenchymal transition in vitro and that suppression of RAB6A inhibits tumor growth in vivo. We screened target cargos of RAB6A in CCA cells and identified a extracellular matrix component as the target cargo. RAB6A binds directly to OPN, and RAB6A KD suppressed OPN secretion and inhibited the interaction between OPN and αV integrin receptor. Moreover, RAB6A KD inhibited the AKT signaling pathway, which is a downstream effector of the integrin receptor signaling. In addition, shRNA targeting OPN blocked endogenous expression of OPN and consequently weakened CSCs properties in RAB6A-formed spheres. Similarly, inhibitor of AKT signaling, MK2206 also impedes oncogenic function of RAB6A in the stem-like subsets of CCA cells. In conclusion, our findings showed that RAB6A sustains CSCs phenotype maintenance by modulating the secretion of OPN and consequentially activating the downstream AKT signaling pathway. Targeting the RAB6A/OPN axis may be an effective strategy for CCA therapy.

BET inhibitor suppresses melanoma progression via the noncanonical NF-κB/SPP1 pathway

Background: Bromodomain and extra-terminal domain (BET) inhibitors have shown profound efficacy against hematologic malignancies and solid tumors in preclinical studies. However, the underlying molecular mechanism in melanoma is not well understood. Here we identified secreted phosphoprotein 1 (SPP1) as a melanoma driver and a crucial target of BET inhibitors in melanoma. Methods: Bioinformatics analysis and meta-analysis were used to evaluate the SPP1 expression in normal tissues, primary melanoma, and metastatic melanoma. Real-time PCR (RT-PCR) and Western blotting were employed to quantify SPP1 expression in melanoma cells and tissues. Cell proliferation, wound healing, and Transwell assays were carried out to evaluate the effects of SPP1 and BET inhibitors in melanoma cells in vitro. A xenograft mouse model was used to investigate the effect of SPP1 and BET inhibitors on melanoma in vivo. Chromatin immunoprecipitation (ChIP) assay was performed to evaluate the regulatory mechanism of BET inhibitors on SPP1. Results: SPP1 was identified as a melanoma driver by bioinformatics analysis, and meta-analysis determined it to be a diagnostic and prognostic biomarker for melanoma. SPP1 overexpression was associated with poor melanoma prognosis, and silencing SPP1 suppressed melanoma cell proliferation, migration, and invasion. Through a pilot drug screen, we identified BET inhibitors as ideal therapeutic agents that suppressed SPP1 expression. Also, SPP1 overexpression could partially reverse the suppressive effect of BET inhibitors on melanoma. We further demonstrated that bromodomain-containing 4 (BRD4) regulated SPP1 expression. Notably, BRD4 did not bind directly to the SPP1 promoter but regulated SPP1 expression through NFKB2. Silencing of NFKB2 resembled the phenotype of BET inhibitors treatment and SPP1 silencing in melanoma. Conclusion: Our findings highlight SPP1 as an essential target of BET inhibitors and provide a novel mechanism by which BET inhibitors suppress melanoma progression via the noncanonical NF-κB/SPP1 pathway.

Suppression of metastasis through inhibition of chitinase 3-like 1 expression by miR-125a-3p-mediated up-regulation of USF1

Rationale: Chitinase 3-like 1 (Chi3L1) protein is up-regulated in various diseases including solid cancers. According to Genome-Wide Association Study (GWAS)/Online Mendelian Inheritance in Man (OMIM)/Differentially Expressed Gene (DEG) analyses, Chi3L1 is associated with 38 cancers, and more highly associated with cancer compared to other oncogenes such as EGFR, TNFα, etc. However, the mechanisms and pathways by which Chi3L1 is associated with cancer are not clear. In current study, we investigated the role of Chi3L1 in lung metastasis. Methods: We performed the differentially expressed gene analysis to explore the genes which are associated with Chi3L1 using the web-based platform from Biomart. We investigated the metastases in lung tissues of C57BL/6 mice injected with B16F10 melanoma following treatment with Ad-shChi3L1. We also investigated the expression of USF1 and Chi3L1 in Chi3L1 KD mice lung tissues by Western blotting and IHC. We also analyzed lung cancer cells metastases induced by Chi3L1 using migration and cell proliferation assay in human lung cancer cell lines. The involvement of miR-125a-3p in Chi3L1 regulation was determined by miRNA qPCR and luciferase reporter assay. Results: We showed that melanoma metastasis in lung tissues was significantly reduced in Chi3L1 knock-down mice, accompanied by down-regulation of MMP-9, MMP-13, VEGF, and PCNA in Chi3L1 knock-down mice lung tissue, as well as in human lung cancer cell lines. We also found that USF1 was conversely expressed against Chi3L1. USF1 was increased by knock-down of Chi3L1 in mice lung tissues, as well as in human lung cancer cell lines. In addition, knock-down of USF1 increased Chi3L1 levels in addition to augmenting metastasis cell migration and proliferation in mice model, as well as in human cancer cell lines. Moreover, in human lung tumor tissues, the expression of Chi3L1 was increased but USF1 was decreased in a stage-dependent manner. Finally, Chi3L1 expression was strongly regulated by the indirect translational suppressing activity of USF1 through induction of miR-125a-3p, a target of Chi3L1. Conclusion: Metastases in mice lung tissues and human lung cancer cell lines were decreased by KD of Chi3L1. USF1 bound to the Chi3L1 promoter, however, Chi3L1 expression was decreased by USF1, despite USF1 enhancing the transcriptional activity of Chi3L1. We found that USF1 induced miR-125a-3p levels which suppressed Chi3L1 expression. Ultimately, our results suggest that lung metastasis is suppressed by knock-down of Chi3L1 through miR-125a-3p-mediated up-regulation of USF1.

α-Iso-Cubebene Inhibits PDGF-Induced Vascular Smooth Muscle Cell Proliferation by Suppressing Osteopontin Expression

α-Iso-cubebene (ICB) is a dibenzocyclooctadiene lignin contained in Schisandra chinensis (SC), a well-known medicinal herb that ameliorates cardiovascular symptoms. Thus, we examined the effect of ICB on vascular smooth muscle cell (VSMC) proliferation, a key feature of diverse vascular diseases. When VSMCs primary cultured from rat thoracic aorta were stimulated with PDGF (1-10 ng/ml), cell proliferation and osteopontin (OPN) expression were concomitantly up-regulated, but these effects were attenuated when cells were treated with MPIIIB10, a neutralizing monoclonal antibody for OPN. In aortic tissues exposed to PDGF, sprouting VSMC numbers increased, which was attenuated in tissues from OPN-deficient mice. Furthermore, VSMC proliferation and OPN expression induced by PDGF were attenuated dose-dependently by ICB (10 or 30 μg/ml). Reporter assays conducted using OPN promoter-luciferase constructs showed that the promoter region 538-234 bp of the transcription start site was responsible for transcriptional activity enhancement by PDGF, which was significantly inhibited by ICB. Putative binding sites for AP-1 and C/EBPβ in the indicated promoter region were suggested by TF Search, and increased binding of AP-1 and C/EBPβ in PDGF-treated VSMCs was demonstrated using a ChIP assay. The increased bindings of AP-1 and C/EBPβ into OPN promoter were attenuated by ICB. Moreover, the PDGF-induced expression of OPN was markedly attenuated in VSMCs transfected with siRNA for AP-1 and C/EBPβ. These results indicate that ICB inhibit VSMC proliferation by inhibiting the AP-1 and C/EBPβ signaling pathways and thus downregulating OPN expression.

Inflammation and vascular smooth muscle cell dedifferentiation following carotid artery ligation

Following vascular injury medial smooth muscle cells dedifferentiate and migrate through the internal elastic lamina where they form a neointima. The goal of the current study was to identify changes in gene expression that occur before the development of neointima and are associated with the early response to injury. Vascular injury was induced in C57BL/6 mice and in Myh11-creER(T2) mTmG reporter mice by complete ligation of the left carotid artery. Reporter mice were used to visualize cellular changes in the injured vessels. Total RNA was isolated from control carotid arteries or from carotid arteries 3 days following ligation of C57BL/6 mice and analyzed by Affymetrix microarray and quantitative RT-PCR. This analysis revealed decreased expression of mRNAs encoding smooth muscle-specific contractile proteins that was accompanied by a marked increase in a host of mRNAs encoding inflammatory cytokines following injury. There was also marked decrease in molecules associated with BMP, Wnt, and Hedgehog signaling and an increase in those associated with B cell, T cell, and macrophage signaling. Expression of a number of noncoding RNAs were also altered following injury with microRNAs 143/145 being dramatically downregulated and microRNAs 1949 and 142 upregulated. Several long noncoding RNAs showed altered expression that mirrored the expression of their nearest coding genes. These data demonstrate that following carotid artery ligation an inflammatory cascade is initiated that is associated with the downregulation of coding and noncoding RNAs that are normally required to maintain smooth muscle cells in a differentiated state.

Histone deacetylase inhibitor apicidin increases expression of the α-secretase ADAM10 through transcription factor USF1-mediated mechanisms

ADAM10 (a disintegrin and metalloproteinase domain-containing protein 10) is the α-secretase that is involved in APP (β-amyloid precursor protein) processing. Enhancement of the nonamyloidogenic APP pathway by ADAM10 provides therapeutic potential for Alzheimer's disease (AD). By using high-throughput screening that targeted ADAM10, we determined that apicidin-an inhibitor of HDACs (histone deacetylases)-significantly increased mRNA and protein levels of ADAM10 in SH-SY5Y cells. A luciferase assay revealed that the nucleotides -444 to -300 in the ADAM10 promoter were sufficient to mediate this effect. In addition, knockdown of USF1 (upstream transcription factor 1) and HDAC2/3 prevented apicidin regulation of ADAM10. Moreover, USF1 acetylation was increased by apicidin, which enhanced the association of USF1 with HDAC2/3 and with the ADAM10 promoter. We further found that apicidin did not affect the phosphorylation of ERK or USF1; however, ERK inhibitor U0126 blocked the effect of apicidin on ADAM10. Finally, apicidin increased the level of α-site C-terminal fragment from APP and reduced the production of β-amyloid peptide 1-42. Collectively, our study provides evidence that ADAM10 expression can be regulated by HDAC2/3 inhibitor apicidin via USF1-dependent mechanisms in which ERK signaling plays an important role. Thus, HDAC regulation of ADAM10 might shed new light on the understanding of AD pathology.-Hu, X.-T., Zhu, B.-L., Zhao, L.-G., Wang, J.-W., Liu, L., Lai, Y.-J., He, L., Deng, X.-J., Chen, G.-J. Histone deacetylase inhibitor apicidin increases expression of the α-secretase ADAM10 through transcription factor USF1-mediated mechanisms.

Purinergic transmission in blood vessels

There are nineteen different receptor proteins for adenosine, adenine and uridine nucleotides, and nucleotide sugars, belonging to three families of G protein-coupled adenosine and P2Y receptors, and ionotropic P2X receptors. The majority are functionally expressed in blood vessels, as purinergic receptors in perivascular nerves, smooth muscle and endothelial cells, and roles in regulation of vascular contractility, immune function and growth have been identified. The endogenous ligands for purine receptors, ATP, ADP, UTP, UDP and adenosine, can be released from different cell types within the vasculature, as well as from circulating blood cells, including erythrocytes and platelets. Many purine receptors can be activated by two or more of the endogenous ligands. Further complexity arises because of interconversion between ligands, notably adenosine formation from the metabolism of ATP, leading to complex integrated responses through activation of different subtypes of purine receptors. The enzymes responsible for this conversion, ectonucleotidases, are present on the surface of smooth muscle and endothelial cells, and may be coreleased with neurotransmitters from nerves. What selectivity there is for the actions of purines/pyrimidines comes from differential expression of their receptors within the vasculature. P2X1 receptors mediate the vasocontractile actions of ATP released as a neurotransmitter with noradrenaline (NA) from sympathetic perivascular nerves, and are located on the vascular smooth muscle adjacent to the nerve varicosities, the sites of neurotransmitter release. The relative contribution of ATP and NA as functional cotransmitters varies with species, type and size of blood vessel, neuronal firing pattern, the tone/pressure of the blood vessel, and in ageing and disease. ATP is also a neurotransmitter in non-adrenergic non-cholinergic perivascular nerves and mediates vasorelaxation via smooth muscle P2Y-like receptors. ATP and adenosine can act as neuromodulators, with the most robust evidence being for prejunctional inhibition of neurotransmission via A1 adenosine receptors, but also prejunctional excitation and inhibition of neurotransmission via P2X and P2Y receptors, respectively. P2Y2, P2Y4 and P2Y6 receptors expressed on the vascular smooth muscle are coupled to vasocontraction, and may have a role in pathophysiological conditions, when purines are released from damaged cells, or when there is damage to the protective barrier that is the endothelium. Adenosine is released during hypoxia to increase blood flow via vasodilator A2A and A2B receptors expressed on the endothelium and smooth muscle. ATP is released from endothelial cells during hypoxia and shear stress and can act at P2Y and P2X4 receptors expressed on the endothelium to increase local blood flow. Activation of endothelial purine receptors leads to the release of nitric oxide, hyperpolarising factors and prostacyclin, which inhibits platelet aggregation and thus ensures patent blood flow. Vascular purine receptors also regulate endothelial and smooth muscle growth, and inflammation, and thus are involved in the underlying processes of a number of cardiovascular diseases.

Purinergic signaling and blood vessels in health and disease

Purinergic signaling plays important roles in control of vascular tone and remodeling. There is dual control of vascular tone by ATP released as a cotransmitter with noradrenaline from perivascular sympathetic nerves to cause vasoconstriction via P2X1 receptors, whereas ATP released from endothelial cells in response to changes in blood flow (producing shear stress) or hypoxia acts on P2X and P2Y receptors on endothelial cells to produce nitric oxide and endothelium-derived hyperpolarizing factor, which dilates vessels. ATP is also released from sensory-motor nerves during antidromic reflex activity to produce relaxation of some blood vessels. In this review, we stress the differences in neural and endothelial factors in purinergic control of different blood vessels. The long-term (trophic) actions of purine and pyrimidine nucleosides and nucleotides in promoting migration and proliferation of both vascular smooth muscle and endothelial cells via P1 and P2Y receptors during angiogenesis and vessel remodeling during restenosis after angioplasty are described. The pathophysiology of blood vessels and therapeutic potential of purinergic agents in diseases, including hypertension, atherosclerosis, ischemia, thrombosis and stroke, diabetes, and migraine, is discussed.

Emerging avenues linking inflammation and cancer

The role of inflammation in carcinogenesis has been extensively investigated and well documented. Many biochemical processes that are altered during chronic inflammation have been implicated in tumorigenesis. These include shifting cellular redox balance toward oxidative stress; induction of genomic instability; increased DNA damage; stimulation of cell proliferation, metastasis, and angiogenesis; deregulation of cellular epigenetic control of gene expression; and inappropriate epithelial-to-mesenchymal transition. A wide array of proinflammatory cytokines, prostaglandins, nitric oxide, and matricellular proteins are closely involved in premalignant and malignant conversion of cells in a background of chronic inflammation. Inappropriate transcription of genes encoding inflammatory mediators, survival factors, and angiogenic and metastatic proteins is the key molecular event in linking inflammation and cancer. Aberrant cell signaling pathways comprising various kinases and their downstream transcription factors have been identified as the major contributors in abnormal gene expression associated with inflammation-driven carcinogenesis. The posttranscriptional regulation of gene expression by microRNAs also provides the molecular basis for linking inflammation to cancer. This review highlights the multifaceted role of inflammation in carcinogenesis in the context of altered cellular redox signaling.

Chromatin remodeling underlies the senescence-associated secretory phenotype of tumor stromal fibroblasts that supports cancer progression

Age is a major risk factor for the development of cancer. Senescent fibroblasts, which accumulate with age, secrete protumorigenic factors collectively referred to as the senescence-associated secretory phenotype (SASP). Here, we examined the molecular mechanisms that control SASP activation, focusing on the known SASP factor osteopontin (OPN). We found that expression of the canonical SASP members interleukin (IL)-6 and IL-8, but not OPN, were dependent upon a persistent DNA damage response (DDR) as evidenced by ATM and NF-κB activation. Treatment with several histone deacetylase (HDAC) inhibitors robustly activated SASP in the absence of DNA breaks, suggesting that DDR-dependent SASP activation occurs in response to chromatin remodeling rather than physical breaks in DNA. In the setting of HDAC inhibition, IL-6 and IL-8 expression remained dependent upon ATM and NF-κB, while OPN expression remained independent of these factors. Further analysis revealed that HDAC1 inhibition was sufficient to induce OPN expression, which is interesting given that loss of HDAC1 expression correlates with increased OPN expression within the stromal compartment of invasive breast cancers. Importantly, fibroblasts treated with HDAC inhibitors promoted tumor growth in vivo. Our findings therefore indicate that HDAC modulation plays an important role in stromal cell activation, with important implications for the use of HDAC inhibitors in the treatment of cancer.

Osteoprotegerin, but not osteopontin, as a potential predictor of vascular calcification in normotensive subjects

We conducted a cross-sectional observation study that included 500 asymptomatic subjects to investigate the relationship between bone metabolism and coronary artery calcification (CAC) in hypertensive conditions. Osteoprotegerin (OPG) and osteopontin (OPN) levels and their associations with hypertension were analyzed to predict CAC in 316 subjects. Multislice computed tomography was used to quantify CAC. Multivariate analysis of variance was used to test the non-interactive effects of hypertension, CAC severity and biomarker levels, and the logistic regression model was applied to predict the risk of CAC. OPG and OPN concentrations were significantly higher in the hypertensive than the normotensive subjects, at 3.0 (2.3-4.0) pmol l(-1) and 51 (21-136) ng ml(-1) vs. 2.4 (2.0-3.0) pmol l(-1) and 41 (13-63) ng ml(-1), respectively. The OPG level, but not OPN level, increased with age (r = 0.29; P = 0.0001). Zero or minimal CAC (<10 Agatston units (AU)) was observed in 63% of the subjects, mild (11-100 AU) in 17%, moderate (101-400 AU) in 12% and severe (401-1000 AU)-to-extensive (>1000 AU) in 8%. In hypertensive subjects, only glomerular filtration rate (GFR) (β = -0.67) and gender (β = 0.52) were significant predictors for CAC (R = 0.68). In normotensive patients, GFR (β = -0.81), gender (β = 0.48) and log-transformed OPG levels (β = 0.15) were significant predictors for CAC. OPG levels were associated with an increased risk of CAC in normotensive subjects only (odds ratio: 3.37; 95% confidence interval (1.63-6.57); P = 0.0002). OPG predicted a premature state of vascular calcification in asymptomatic normotensive individuals, and renal function significantly contributed to this process in both hypertensive and normotensive subjects.

Uridine adenosine tetraphosphate (Up4A) is a strong inductor of smooth muscle cell migration via activation of the P2Y2 receptor and cross-communication to the PDGF receptor

The recently discovered dinucleotide uridine adenosine tetraphosphate (Up(4)A) was found in human plasma and characterized as endothelium-derived vasoconstrictive factor (EDCF). A further study revealed a positive correlation between Up(4)A and vascular smooth muscle cell (VSMC) proliferation. Due to the dominant role of migration in the formation of atherosclerotic lesions our aim was to investigate the migration stimulating potential of Up(4)A. Indeed, we found a strong chemoattractant effect of Up(4)A on VSMC by using a modified Boyden chamber. This migration dramatically depends on osteopontin secretion (OPN) revealed by the reduction of the migration signal down to 23% during simultaneous incubation with an OPN-blocking antibody. Due to inhibitory patterns using specific and unspecific purinoreceptor inhibitors, Up(4)A mediates it's migratory signal mainly via the P2Y(2). The signaling behind the receptor was investigated with luminex technique and revealed an activation of the extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathway. By use of the specific PDGF receptor (PDGFR) inhibitor AG1296 and siRNA technique against PDGFR-β we found a strongly reduced migration signal after Up(4)A stimulation in the PDGFR-β knockdown cells compared to control cells. In this study, we present substantiate data that Up(4)A exhibits migration stimulating potential probably involving the signaling cascade of MEK1 and ERK1/2 as well as the matrix protein OPN. We further suggest that the initiation of the migration process occurs predominant through direct activation of the P2Y(2) by Up(4)A and via transactivation of the PDGFR.

Expression and function of osteopontin in vascular adventitial fibroblasts and pathological vascular remodeling

Osteopontin is known to play important roles in various diseases including vascular disorders. However, little is known about its expression and function in vascular adventitial fibroblasts. Adventitial fibroblasts have been shown to play a key role in pathological vascular remodeling associating with various vascular disorders. In this study, we measured activation of Osteopontin and its biological functions in cultured adventitial fibroblasts and injured rat carotid injury arteries induced by balloon angioplasty. Our results showed that angiotensin II and aldosterone increased Osteopontin expression in adventitial fibroblasts in a time- and concentration-dependent manner. MAPKs and AP-1 pathways were involved in Osteopontin upregulation. In addition, Adventitial fibroblast migration stimulated by Angiotensin II and aldosterone required OPN expression. Perivascular delivery of antisense oligonucleotide for Osteopontin suppressed neointimal formation post-injury. We concluded that upregulation of Osteopontin expression in adventitial fibroblasts might be important in the pathogenesis of vascular remodeling after arterial injury.

Aldosterone-induced osteopontin gene transcription in vascular smooth muscle cells involves glucocorticoid response element

Osteopontin (OPN) is known to be one of the cytokines that is involved in the vascular inflammation caused by aldosterone (Aldo). Previous reports have shown that Aldo increases OPN transcripts, and the mechanisms for this remain to be clarified. In this study, we investigated how Aldo increases OPN transcripts in the vascular smooth muscle cells of rats. Aldosterone increased OPN transcripts time-dependently as well as dose-dependently. This increase was diminished by eplerenone, a mineralocorticoid receptor (MR) antagonist. Luciferase promoter assays showed that the OPN promoter deleted to the -1599 site retained the same promoting ability as the full-length OPN promoter when stimulated by 10(-7) M Aldo, but the promoter deleted to the -1300 site lost the promoting ability. A glucocorticoid response element (GRE) is located in that deleted region. Luciferase assays of a mutated promoter without the GRE lost the luciferase upregulation, although mutated promoters with the deletion of other consensus sites maintained the promoter activity. The binding of the Aldo-MR complex to the GRE fragment was confirmed by an electrophoretic-mobility shift assay. This is the first report showing that Aldo regulates the transcriptional levels of OPN and inflammatory responses in the vasculature through a specific GRE site in the OPN promoter region.

In vitro and in vivo osteogenic activity of licochalcone A

We investigated the in vitro and in vivo osteogenic activity of licochalcone A. At low concentrations, licochalcone A stimulated the differentiation of mouse pre-osteoblastic MC3T3-E1 subclone 4 (MC4) cells and enhanced the bone morphogenetic protein (BMP)-2-induced stimulation of mouse bi-potential mesenchymal precursor C2C12 cells to commit to the osteoblast differentiation pathway. This osteogenic activity of licochalcone A was accompanied by the activation of extracellular-signal regulated kinase (ERK). The involvement of ERK was confirmed in a pharmacologic inhibition study. Additionally, noggin (a BMP antagonist) inhibited the osteogenic activity of licochalcone A in C2C12 cells. Licochalcone A also enhanced the BMP-2-stimulated expression of various BMP mRNAs. This suggested that the osteogenic action of licochalcone A in C2C12 cells could be dependent on BMP signaling and/or expression. We then tested the in vivo osteogenic activity of licochalcone A in two independent animal models. Licochalcone A accelerated the rate of skeletal development in zebrafish and enhanced woven bone formation over the periosteum of mouse calvarial bones. In summary, licochalcone A induced osteoblast differentiation with ERK activation in both MC4 and C2C12 cells and it exhibited in vivo osteogenic activity in zebrafish skeletal development and mouse calvarial bone formation. The dual action of licochalcone A in stimulating bone formation and inhibiting bone resorption, as described in a previous study, might be beneficial in treating bone-related disorders.

Effect of simvastatin on collagen I deposition in non-infarcted myocardium: role of NF-κB and osteopontin

The novel biological effect of statins in alleviating myocardium fibrosis following infarction has been increasingly recognized, yet the underlying mechanisms are not fully understood. The purpose of this study was to characterize the effect of simvastatin on myocardial fibrosis and collagen I deposition in the non-infarcted region after myocardial infarction (MI) and to identify the role of NF-κB and osteopontin in simvastatin-mediated inhibition of post-MI collagen over-expression. A rat model of MI was generated by ligating the left anterior descending coronary artery. The rats surviving the MI operation were randomly divided into the following 3 groups: myocardial infarction (MI, vehicle), simvastatin (Sim, 30 mg·kg-1·day-1), and pyrrolidine dithiocarbamate (PDTC, an inhibitor of NF-κB, 100 mg·kg-1·day-1). Four weeks after MI, cardiac function, mRNAs, and protein expression in non-infarcted myocardium were analyzed. Myocardial fibrosis and collagen I over-expression were observed following MI, accompanied by an increase of NF-κB and osteopontin. Simvastatin improved post-MI left ventricular dysfunction and ameliorated post-MI associated changes to several cardiac parameters, including the left ventricular end diastolic pressure (LVEDP), the maximal rate of pressure development (+dP/dtmax), and the maximal rate of pressure decline (-dP/dtmax). Concurrently, simvastatin significantly suppressed the over-expression of NF-κB, osteopontin, and collagen I in the non-infarcted region following MI. Inhibition of NF-κB by PDTC also reduced osteopontin over-expression and excessive collagen I production and improved the above functional myocardial parameters. These results show that post-MI myocardial fibrosis and collagen I over-expression in the non-infarcted region is associated with activation of NF-κB and osteopontin up-regulation. The anti-fibrotic effect of simvastatin following MI is associated with the attenuation of the expression of osteopontin and NF-κB. The inhibition of NF-κB activation could be the process upstream of osteopontin suppression in the simvastatin-mediated effect.

Osteopontin expression correlates with nuclear factor-κB activation and apoptosis downregulation in clear cell renal cell carcinoma

Osteopontin (OPN) is a phosphoglycoprotein implicated in tumorigenesis and tumor cell metastasis. Apoptosis inhibition is one of the mechanisms that contribute to development and progression of cancer, and might be initiated by OPN interaction with tumor cells. The aim of this study was to analyze the relation between OPN and nuclear factor-kappa B (NF-κB) expression in clear cell renal cell carcinoma (CCRCC), as well as their relation to apoptotic activity of tumor cells. Expression of OPN protein and p65 NF-κB subunit was analyzed immunohistochemically in 87 CCRCC samples, and compared mutually and with apoptotic index. Expression of OPN mRNA was analyzed using quantitative real-time PCR and compared with OPN and NF-κB protein expression in 22 CCRCC samples. Statistical analysis showed an association of p65 NF-κB with OPN mRNA (p=0.015) and protein (p<0.001). Also, we found an inverse relationship of OPN with NF-κB protein expression and apoptotic activity of tumor cells (p=0.006 and p=0.022, respectively). Our results indicate that p65 NF-κB signaling pathway may be involved in OPN-mediated CCRCC progression, partly by protecting tumor cells from apoptosis. Therefore, both molecules can constitute potential targets for therapeutic intervention in CCRCC.

Nuclear factor of activated T cells regulates osteopontin expression in arterial smooth muscle in response to diabetes-induced hyperglycemia

OBJECTIVE

Hyperglycemia is a recognized risk factor for cardiovascular disease in diabetes. Recently, we reported that high glucose activates the Ca(2+)/calcineurin-dependent transcription factor nuclear factor of activated T cells (NFAT) in arteries ex vivo. Here, we sought to determine whether hyperglycemia activates NFAT in vivo and whether this leads to vascular complications.

METHODS AND RESULTS

An intraperitoneal glucose-tolerance test in mice increased NFATc3 nuclear accumulation in vascular smooth muscle. Streptozotocin-induced diabetes resulted in increased NFATc3 transcriptional activity in arteries of NFAT-luciferase transgenic mice. Two NFAT-responsive sequences in the osteopontin (OPN) promoter were identified. This proinflammatory cytokine has been shown to exacerbate atherosclerosis and restenosis. Activation of NFAT resulted in increased OPN mRNA and protein in native arteries. Glucose-induced OPN expression was prevented by the ectonucleotidase apyrase, suggesting a mechanism involving the release of extracellular nucleotides. The calcineurin inhibitor cyclosporin A or the novel NFAT blocker A-285222 prevented glucose-induced OPN expression. Furthermore, diabetes resulted in higher OPN expression, which was significantly decreased by in vivo treatment with A-285222 for 4 weeks or prevented in arteries from NFATc3(-/-) mice.

CONCLUSIONS

These results identify a glucose-sensitive transcription pathway in vivo, revealing a novel molecular mechanism that may underlie vascular complications of diabetes.

Osteopontin, CD44, and NFkappaB expression in gastric adenocarcinoma

PURPOSE

Osteopontin (OPN) binds to CD44 and nuclear factor-kappaB (NFkappaB) and OPN mediates tumorigenesis, invasion and metastasis, but the interrelationships between OPN, CD44 and NFkappaB are not fully understood, and especially in gastric carcinogenesis. We examined the expressions of OPN, CD44, and NFkappaB in untreated gastric adenocarcinomas.

MATERIALS AND METHODS

The materials from 211 cases of gastric adenocarcinoma were immunostained for OPN, CD44 and NFkappaB by using a tissue microarray. The OPN mRNA expression was measured in 10 cases by performing real-time RT-PCR.

RESULTS

The expression of OPN, CD44 and NFkappaB was noted in 61.7%, 11.4% and 26.6% of the adenocarcinoma tissues, respectively. No significant correlation was detected among the expressions of these proteins. The OPN protein expression was negatively correlated with angioinvasion (p<0.05) and patient survival (p<0.05), whereas the CD44 and NFkappaB protein expressions were not correlated with any of the clinicopathological factors we examined. The depth of invasion, lymph node status and perineural invasions were prognostic factors based on the Cox analysis. The OPN mRNA expression showed no significant difference between the adenocarcinoma and the paired normal mucosa on real-time RT-PCR.

CONCLUSION

OPN may have a currently undetermined role in gastric carcinogenesis, and CD44 and NFkappaB may have minor roles in gastric adenocarcinoma.

Baicalein stimulates osteoblast differentiation via coordinating activation of MAP kinases and transcription factors

The identification of anabolic agents that directly stimulate bone formation has recently attracted greater interest. Here, baicalein was identified as a natural compound that stimulates the differentiation of mouse osteoblastic MC3T3-E1 subclone 4 cells. Baicalein induced the activation of NF-kappaB in the initiation stage of osteoblast differentiation, and it activated the MAP kinase/NF-kappaB signaling pathway and induced the expression of osteoblast differentiation markers in the early stage. In the late stage, baicalein stimulated the calcium deposition with the activation of MAP kinases and AP-1 family members such as Fra-1 and Fra-2. Another transcription factor, NFATc1, was slightly induced by baicalein in the late stage. Thus, baicalein could stimulate the osteoblast differentiation via the activation of complexly coordinated signaling pathways that include MAP kinases and transcription factors such as NF-kappaB, AP-1, and NFATc1.

NF-kappaB activation in renal tubular epithelial cells by oxalate stimulation

OBJECTIVES

The transcription factor nuclear factor-kappaB (NF-kappaB) is involved in inflammatory and immune responses through the induction of various cytokines and growth factors. Recently, the coordinated action of NF-kappaB and activator protein-1 was reported in osteopontin (OPN) expression. In the present study, we demonstrated that oxalate induces OPN expression by activating NF-kappaB in renal tubular cells. Furthermore, we investigated the inhibitory effect of N-acetyl-L-cysteine (NAC) on NF-kappaB activation in the human renal tubular cell line.

METHODS

All of the experiments were carried out using human kidney-2 cells, which are human proximal tubular epithelial cells immortalized by transduction with the human papillomavirus 16E6/E7 gene. The time-dependent extraction of total protein was performed after the uptake of 0.5 mM oxalate by the cells. The NF-kappaB activation and OPN expression were examined by western blotting and immunocytochemistry.

RESULTS

As a result of oxalate stimulation, the amount of p65 subunit in the nucleus increased significantly (P < 0.05), and NAC significantly inhibited the translocation of p65 into the nucleus (P < 0.05).

CONCLUSION

These observations indicate that NAC can be used as a drug to prevent stone formation.

Retinoic acid utilizes CREB and USF1 in a transcriptional feed-forward loop in order to stimulate MKP1 expression in human immunodeficiency virus-infected podocytes

Nef-induced podocyte proliferation and dedifferentiation via mitogen-activated protein kinase 1,2 (MAPK1,2) activation plays a role in human immunodeficiency virus (HIV) nephropathy pathogenesis. All-trans retinoic acid (atRA) reverses the HIV-induced podocyte phenotype by activating cyclic AMP (cAMP)/protein kinase A (PKA) and inhibiting MAPK1,2. Here we show that atRA, through cAMP and PKA, triggers a feed-forward loop involving CREB and USF1 to induce biphasic stimulation of MKP1. atRA stimulated CREB and USF1 binding to the MKP1 gene promoter, as shown by gel shifting and chromatin immunoprecipitation assays. CREB directly mediated the early phase of atRA-induced MKP1 stimulation; whereas the later phase was mediated by CREB indirectly through induction of USF1. These findings were confirmed by a reporter gene assay using the MKP1 promoter with mutation of CRE or Ebox binding sites. Consistent with these findings, the biological effects of atRA on podocytes were inhibited by silencing either MKP1, CREB, or USF1 with small interfering RNA. atRA also induced CREB phosphorylation and MKP1 expression and reduced MAPK1,2 phosphorylation in kidneys of HIV type 1-infected transgenic mice. We conclude that atRA induces sustained activation of MKP1 to suppress Nef-induced activation of the Src-MAPK1,2 pathway, thus returning the podocyte to a more differentiated state. The mechanism involves a feed-forward loop where activation of one transcription factor (TF) (CREB) leads to induction of a second TF (USF1).

Synergistic induction of osteopontin by aldosterone and inflammatory cytokines in mesangial cells

Hypertensive nephrosclerosis is characterized by activation of the renin-angiotensin-aldosterone system in combination with an inflammatory response characterized by an infiltration of T-cells and mononuclear cells, which release proinflammatory cytokines like IL-1beta/TNFalpha. In various models of experimental hypertensive disease the chemokine osteopontin (OPN) enhances further leukocyte infiltration. Therefore, we investigated the induction of OPN expression in renal mesangial cells (MCs) by aldosterone and the inflammatory cytokines IL-1beta/TNFalpha. Incubation with aldosterone resulted in a time- and concentration-dependent increase in OPN mRNA and protein. OPN mRNA expression followed a biphasic time course with an early increase between 4 and 8 h and the second phase starting at 14 h. The early phase was independent of protein synthesis, indicating a direct effect of aldosterone. Aldosterone-mediated induction of OPN was prevented by spironolactone, indicative of a receptor-mediated aldosterone effect. The mineralocorticoid receptor (MR) was identified in MCs by RT-PCR and immunoprecipitation, and shown to interact with a putative aldosterone-response element of the OPN promoter. The proinflammatory cytokines IL-1beta and TNFalpha only marginally affected OPN expression in MCs. However, coincubation of aldosterone and the cytokines synergistically increased OPN mRNA and protein levels. Since the synergistic effect on OPN mRNA was inhibited by diphenyleneiodonium, we assume an involvement of reactive oxygen species (ROS). We conclude that the chemokine OPN is a target gene of aldosterone in renal MCs, which is activated via the MR, and that proinflammatory cytokines enhance aldosterone-dependent OPN expression. In vivo, this may result in further leukocyte infiltration aggravating hypertensive nephrosclerosis.

Association analysis of allelic variants of USF1 in coronary atherosclerosis

OBJECTIVE

USF1 regulates the transcription of more than 40 cardiovascular related genes and is well established as a gene associated with familial combined hyperlipidemia, a condition increasing the risk for coronary heart disease. No detailed data, however, exists on the impact of this gene to the critical outcome at the tissue level: different types of atherosclerotic lesions.

METHODS AND RESULTS

We analyzed the USF1 in 2 autopsy series of altogether 700 middle-aged men (the Helsinki Sudden Death Study) with quantitative morphometric measurements of coronary atherosclerosis. SNP rs2516839, tagging common USF1 haplotypes, associated with the presence of several types of atherosclerotic lesions, particularly with the proportion of advanced atherosclerotic plaques (P=0.02) and area of calcified lesions (P<0.001) of the coronary arteries. Importantly, carriers of risk alleles of rs2516839 also showed a 2-fold risk for sudden cardiac death (genotype TT versus CC; OR 2.10, 95% CI 1.17 to 3.75, P=0.04). The risk effect of rs2516839 was present also in aorta samples of the men.

CONCLUSIONS

Our findings in this unique study sample suggest that USF1 contributes to atherosclerosis, the pathological arterial wall phenotype resulting in coronary heart disease and in its most dramatic consequence-sudden cardiac death.

Osteopontin in Rat Renal Fibroblasts

Osteopontin (OPN), a proinflammatory cytokine, plays an important role in renal fibrosis. We reported that plasma OPN levels were higher in patients with primary aldosteronism than with essential hypertension. However, the regulatory mechanism of OPN by aldosterone remains unclear. Here, we report the transcriptional regulation of OPN expression by aldosterone and the functional effects of aldosterone-mediated OPN transcription in renal fibroblasts. Aldosterone induced OPN expression in a dose-dependent manner with significant responses at 10 nmol/L (1.6±0.2-fold of controls, P <0.05, n=5) and elicited maximal effects at 10 μmol/L (3.5±0.4-fold of controls, P <0.01, n=5). Aldosterone increased OPN expression in a time-dependent manner with a maximal effect after 48 hours (2.7±0.3-fold of controls, P <0.01, n=5). This effect was abolished by the mineralocorticoid receptor (MR) antagonist spironolactone. Luciferase promoter deletion assays identified a novel cis regulatory element (−2153 to −1758) in the OPN promoter that is responsive to aldosterone. This element contains an activator protein-1 (AP-1) and nuclear factor kappa B (NFκB) site. Electrophoretic mobility shift assays, supershift assays, and chromatin immunoprecipitation assays identified both AP-1 and NFκB as the DNA binding proteins induced by aldosterone with spironolactone inhibiting aldosterone-induced AP-1 or NFκB activity. OPN-siRNA inhibited completely the induction of cell proliferation, type I, III, and IV collagen synthesis by aldosterone. These results indicate that aldosterone induced MR-mediated OPN expression through AP-1 and NFκB activation and suggest that aldosterone plays an important role in renal fibrosis through the induction of OPN.

First functional polymorphism in CFTR promoter that results in decreased transcriptional activity and Sp1/USF binding

Growing evidences show that functionally relevant polymorphisms in various promoters alter both transcriptional activity and affinities of existing protein-DNA interactions, and thus influence disease progression in humans. We previously reported the -94G>T CFTR promoter variant in a female CF patient in whom any known disease-causing mutation has been detected. To investigate whether the -94G>T could be a regulatory variant, we have proceeded to in silico analyses and functional studies including EMSA and reporter gene assays. Our data indicate that the promoter variant decreases basal CFTR transcriptional activity in different epithelial cells and alters binding affinities of both Sp1 and USF nuclear proteins to the CFTR promoter. The present report provides evidence for the first functional polymorphism that negatively affects the CFTR transcriptional activity and demonstrates a cooperative role of Sp1 and USF transcription factors in transactivation of the CFTR gene promoter.

The role of ERK signaling in protein hydrogel remodeling by vascular smooth muscle cells

Collagen type I and fibrin hydrogels have been used for cell-based therapies and tissue engineering. These matrices can be broken down and remodeled by cells, but the effects that these proteins have on cell function are not completely understood. We examined activation of the extracellular signal-regulated kinase (ERK) signaling pathway by vascular smooth muscle cells (VSMC) in response to 2D and 3D matrices of type I collagen, fibrin, or a 1:1 composite mixture of these proteins. After 3 days of culture, ERK phosphorylation, osteopontin secretion, and MMP-2 activation were all markedly increased in 3D matrices, compared with 2D substrates. A strong positive correlation existed between these protein markers of the synthetic phenotype and phosphorylated ERK levels, and this relationship persisted across matrix geometries and compositions. Cell proliferation in 3D matrices was inversely correlated to ERK activation, while on 2D substrates a modest positive correlation was observed. Pharmacologic inhibition of ERK signaling confirmed that this pathway was involved in the observed phenotype shifts. This study suggests that contextual activation of the ERK pathway results in different effects on cell phenotype, depending on the geometry and composition of the ECM. These findings add to our understanding of cell function and remodeling in protein-based hydrogel biomaterials.

CREB mediates UTP-directed arterial smooth muscle cell migration and expression of the chemotactic protein osteopontin via its interaction with activator protein-1 sites

The transcription factor cAMP responsive element-binding protein (CREB) has been found to be involved in arterial smooth muscle cell (SMC) migration. We previously demonstrated that osteopontin (OPN) expression is a key step for UTP-mediated migration of arterial SMCs and that activator protein (AP)-1, nuclear factor kappaB, and upstream stimulatory transcription factors are involved in this OPN expression. The present study aims to determine the role of CREB in UTP-induced migration and OPN expression in cultured SMCs. We found that CREB is activated by UTP via extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase pathways but not by protein kinase A. Both overexpression of a dominant negative CREB and CREB small interfering RNA treatment suppressed UTP-induced OPN expression and SMC migration. Gel-shift and chromatin immunoprecipitation assays revealed that CREB binds 2 AP-1 sites (-1870 and -76) and a cAMP responsive element-like site (-1403) on the OPN promoter. Mutations of these sites showed that only the 2 AP-1 sites were required for UTP-induced OPN expression. Moreover, gel-supershift and sequential chromatin immunoprecipitation assays suggested that CREB was associated with c-Fos on the AP-1 sites of the OPN promoter. These results demonstrate that CREB participates in the induction of UTP-activated OPN expression via its binding to 2 AP-1 sites and is thus involved in UTP-mediated SMC migration.

P2 receptors in atherosclerosis and postangioplasty restenosis

Atherosclerosis is an immunoinflammatory process that involves complex interactions between the vessel wall and blood components and is thought to be initiated by endothelial dysfunction [Ross (Nature 362:801–09, 1993); Fuster et al. (N Engl J Med 326:242–50, 1992); Davies and Woolf (Br Heart J 69:S3–S11, 1993)]. Extracellular nucleotides that are released from a variety of arterial and blood cells [Di Virgilio and Solini (Br J Pharmacol 135:831–42, 2002)] can bind to P2 receptors and modulate proliferation and migration of smooth muscle cells (SMC), which are known to be involved in intimal hyperplasia that accompanies atherosclerosis and postangioplasty restenosis [Lafont et al. (Circ Res 76:996–002, 1995)]. In addition, P2 receptors mediate many other functions including platelet aggregation, leukocyte adherence, and arterial vasomotricity. A direct pathological role of P2 receptors is reinforced by recent evidence showing that upregulation and activation of P2Y₂ receptors in rabbit arteries mediates intimal hyperplasia [Seye et al. (Circulation 106:2720–726, 2002)]. In addition, upregulation of functional P2Y receptors also has been demonstrated in the basilar artery of the rat double-hemorrhage model [Carpenter et al. (Stroke 32:516–22, 2001)] and in coronary artery of diabetic dyslipidemic pigs [Hill et al. (J Vasc Res 38:432–43, 2001)]. It has been proposed that upregulation of P2Y receptors may be a potential diagnostic indicator for the early stages of atherosclerosis [Elmaleh et al. (Proc Natl Acad Sci U S A 95:691–95, 1998)]. Therefore, particular effort must be made to understand the consequences of nucleotide release from cells in the cardiovascular system and the subsequent effects of P2 nucleotide receptor activation in blood vessels, which may reveal novel therapeutic strategies for atherosclerosis and restenosis after angioplasty.

Breast cancer metastasis suppressor 1 (BRMS1) inhibits osteopontin transcription by abrogating NF-kappaB activation

Background

Osteopontin (OPN), a secreted phosphoglycoprotein, has been strongly associated with tumor progression and aggressive cancers. MDA-MB-435 cells secrete very high levels of OPN. However metastasis-suppressed MDA-MB-435 cells, which were transfected with breast cancer metastasis suppressor 1 (BRMS1), expressed significantly less OPN. BRMS1 is a member of mSin3-HDAC transcription co-repressor complex and has been shown to suppress the metastasis of breast cancer and melanoma cells in animal models. Hence we hypothesized that BRMS1 regulates OPN expression.

Results

The search for a BRMS1-regulated site on the OPN promoter, using luciferase reporter assays of the promoter deletions, identified a novel NF-κB site (OPN/NF-κB). Electrophoretic mobility shift assays and chromatin immunoprecipitations (ChIP) confirmed this site to be an NF-κB-binding site. We also show a role of HDAC3 in suppression of OPN via OPN/NF-κB.

Conclusion

Our results show that BRMS1 regulates OPN transcription by abrogating NF-κB activation. Thus, we identify OPN, a tumor-metastasis activator, as a crucial downstream target of BRMS1. Suppression of OPN may be one of the possible underlying mechanisms of BRMS1-dependent suppression of tumor metastasis.

Amiodarone Induces Angiotensinogen Gene Expression in Lung Alveolar Epithelial Cells through Activation Protein-1

Previous work from this laboratory has shown that amiodarone induces alveolar epithelial cell apoptosis that was abrogated by antagonists of angiotensin II. In this study, amiodarone up-regulated angiotensinogen mRNA and protein in primary cultures of rat type II pneumocytes and in the human A549 cell line. The mechanism of amiodarone-induced angiotensinogen expression was studied in A549 cells with a human angiotensinogen promoter-luciferase reporter (angiotensinogen/luciferase). Amiodarone (3 microg/ml) induced both angiotensinogen/luciferase and endogenous angiotensinogen mRNA; the latter was completely blocked by actinomycin-D. Amiodarone did not affect the half-life of endogenous angiotensinogen mRNA. Deletion analyses of angiotensinogen/luciferase identified at least two amiodarone-responsive domains in the angiotensinogen promoter between -350 to -260 bp and -203 to -46 bp. DNA/Protein array and electrophoretic mobility shift assays showed that amiodarone increases DNA binding of both activation protein-1 and STAT-5 transcription factors. Site-directed mutagenesis of three IL-6-responsive signal transducer activator of transcription (STAT) binding sites within the amiodarone-response domains had no effect on amiodarone-induced angiotensinogen/luciferase expression. In contrast, amiodarone-induced angiotensinogen/luciferase expression was abrogated by a dominant-negative fos construct and was stimulated over five times by c-fos and c-jun expressed together but not separately. Mutagenesis of the activation protein-1 binding site at -15 to -12 bp completely eliminated the response to amiodarone. These data show that activation protein-1 family transcription factors mediate amiodarone-induced angiotensinogen expression in human alveolar epithelial cells and identify an activation protein-1 site, located between the TATA (DNA sequence) box and the transcription initiation site, that is required for the response.

P2 receptors in atherosclerosis and postangioplasty restenosis

Atherosclerosis is an immunoinflammatory process that involves complex interactions between the vessel wall and blood components and is thought to be initiated by endothelial dysfunction [1-3]. Extracellular nucleotides that are released from a variety of arterial and blood cells [4] can bind to P2 receptors and modulate proliferation and migration of smooth muscle cells (SMC), which is known to be involved in intimal hyperplasia that accompanies atherosclerosis and postangioplasty restenosis [5]. In addition, P2 receptors mediate many other functions, including platelet aggregation, leukocyte adherence, and arterial vasomotoricity. A direct pathological role of P2 receptors is reinforced by recent evidence showing that up-regulation and activation of P2Y(2) receptors in rabbit arteries mediates intimal hyperplasia [6]. In addition, up-regulation of functional P2Y receptors also has been demonstrated in the basilar artery of the rat double-hemorrhage model [7] and in coronary arteries of diabetic dyslipidemic pigs [8]. It has been proposed that up-regulation of P2Y receptors may be a potential diagnostic indicator for the early stages of atherosclerosis [9]. Therefore, particular effort must be made to understand the consequences of nucleotide release from cells in the cardiovascular system and the subsequent effects of P2 nucleotide receptor activation in blood vessels, which may reveal novel therapeutic strategies for atherosclerosis and restenosis after angioplasty.