Hypoxia-inducible factor-1 α deletion in myeloid lineage attenuates hypoxia-induced pulmonary hypertension

Hypoxemia is seen in patients with pulmonary hypertension and hypoxic pulmonary vasoconstriction worsens their clinical condition. However, vasoconstriction is not the only aspect through which hypoxia induces the progression to pulmonary hypertension. Hypoxia‐inducible factor‐1α (HIF‐1α) is a transcription factor responding to hypoxic conditions by regulating hundreds of genes involved in angiogenesis, erythropoiesis, inflammation, and proliferation. We sought to determine the contribution of HIF‐1α in myeloid lineage cells to the pulmonary vascular response to chronic exposure to hypoxia. We generated myeloid‐specific HIF‐1α knockout (MyeHIF1KO) mice by using Cre‐lox P system, and exposed them to hypoxic conditions for 3 weeks to induce pulmonary hypertension. Macrophages from MyeHIF1KO and control mice were used for western blotting, RT‐qPCR, chemotaxis assay, and ATP assay. MyeHIF1KO mice exposed to hypoxia for 3 weeks exhibited a significant reduction in the right ventricular systolic pressure accompanied by a decrease in the ratio of the right ventricular weight to left ventricular weight, muscularization of the small pulmonary arteries, and infiltration of macrophages into the lung and right ventricle compared with control mice. HIF‐1α‐deficient peritoneal macrophages showed less migration toward monocyte chemoattractant protein‐1 and a decrease in intracellular ATP levels. These results indicate that HIF‐1α in macrophages contributes to the progression of pulmonary vascular remodeling and pulmonary hypertension induced by chronic exposure to hypoxic conditions. The inhibition of myeloid‐specific HIF‐1α may be a novel therapeutic strategy for the treatment of pulmonary hypertension.

P6342Subcutaneous delivery of NPA7, first-in-class novel bispecific designer peptide: enhances cardiorenal function and suppresses renin and aldosterone in vivo and in vitro

Introduction

The rapid increase of patients of heart failure (HF) is a major health burden worldwide. Most importantly is the need to develop innovative new drugs for treatment of HF, such as sacubitril/valsartan which in part functions by enhancing the natriuretic peptides (NPs). We engineered NPA7 as a novel 30 amino acid bispecific designer peptide which activates the particulate guanylyl cyclase A receptor (pGC-A)/cGMP and for which the NPs both ANP and BNP are ligands and the Mas-receptor (MasR)/cAMP pathways for Angiotensin 1–7 (Ang1–7) is the endogenous ligand. We previously reported that acute intravenous (IV) administration of NPA7 shows cardiorenal protective and renin-aldosterone suppressing actions that go beyond the native peptides, BNP or Ang 1–7, which may have therapeutic potential for HF.

Purpose

To support the clinical development of NPA7 as a potential therapy in HF which promotes NP and MasR pathways, we investigated the actions and stability of subcutaneous (SQ) administration of NPA7 in normal canines. We also defined NPA7's peptide stability and metabolites in canine plasma.

Methods

Plasma and urinary cGMP, cardiorenal and renin-aldosterone responses to SQ injection (10μg/kg) were determined over 4 hours in normal canines (n=5) in vivo. Ex vivo, we established stability of NPA7 and key metabolites in canine serum using liquid chromatography-mass spectrometry (LC-MS). Data are expressed as mean ± SEM. * P<0.05 vs. BL.

Results

In vivo, SQ NPA7 resulted in a sustained increase at 2 hours in plasma (BL: 10±3; 120 min: 30±6* pmol/ml) and urinary (BL: 1033±198; 120 min: 5792±857* pmol/min) cGMP, GFR (BL: 29±6; 120 min: 70±12* ml/min) and sodium excretion (BL: 18±10; 120 min: 144±33* ueq/min). We observed a gradual reduction in BP at 60 min (BL: 109±4; 60 min: 99±7* mmHg) with a sustained decrease in PCWP at 4 hours (BL: 5±0.9; 240 min: 3.1±0.6* mmHg). SQ NPA7 also suppressed plasma renin and aldosterone up to 3 hours after SQ injection. LC-MS revealed that NPA7 was highly stable with both the pGC-A and MasR activating moieties intact ex vivo in canine serum with a disappearance time of 2 hours. We also identified 2 major NPA7 metabolites NPA71–27 and NPA71–28.

Conclusions

SQ NPA7 possesses cGMP activating, cardiac unloading, diuretic, natriuretic, and renin-aldosterone suppressing actions in normal canines. NPA7 is also highly stable in serum. These studies support SQ administration as an effective delivery strategy for NPA7, a first-in-class innovative bispecific dual pGC-A/MasR activator now in preclinical development for HF.

Suppression of Abdominal Aortic Aneurysm Formation in Mice by Teneligliptin, a Dipeptidyl Peptidase-4 Inhibitor

Aim: Dipeptidyl peptidase-4 (DPP-4) inhibitors lower blood glucose levels through inhibition of incretin degradation, which stimulates insulin secretion. Recent studies reported that DPP-4 inhibitors suppressed atherogenesis in apolipoprotein E-knockout (ApoEKO) mice. In this study, we investigated whether teneligliptin, a DPP-4 inhibitor, affects the development of abdominal aortic aneurysms (AAA) in ApoEKO mice.

Methods: ApoEKO mice were fed a high-fat diet (HFD) and infused with angiotensin (Ang) II by osmotic mini pumps for 4 weeks to induce AAA with (DPP-4i group) or without (control group) teneligliptin administered orally from 1 week before HFD and Ang II infusion to the end of the experiment. Confluent rat vascular smooth muscle cells (VSMCs) were serum-starved for 48 hours, then incubated with or without teneligliptin for another 24 hours and stimulated with Ang II.

Results: Treatment with teneligliptin significantly reduced the AAA formation rate (30.7% vs. 71.4% vs. control, P < 0.05), aortic dilatation (1.32 ± 0.09 mm vs. 1.76 ± 0.18 mm in the control, P < 0.05) and severity score (0.75 ± 0.28 vs. 1.91 ± 0.4 in the control, P < 0.05). Elastin degradation grade was also attenuated in DPP-4i group (2.83 ± 0.17 vs. 3.45 ± 0.16 in the control, P < 0.05). The number of macrophages infiltrating into the abdominal aorta was decreased in the DPP-4i group (51.8 ± 29.8/section vs. 219.5 ± 78.5/section in the control, P < 0.05). Teneligliptin attenuated Ang II-induced phosphorylation of extracellular signal-regulated kinase (ERK) and Akt, and mRNA expression of monocyte chemoattractant protein-1 in VSMCs.

Conclusion: Treatment with teneligliptin suppressed AAA formation in ApoEKO mice with HFD and Ang II infusion. Suppression of macrophage infiltration by teneligliptin may be involved in the inhibition of AAA formation.

A case of coronary subclavian vertebral steal syndrome successfully treated with stenting to the stenosis of left subclavian artery

Coronary subclavian vertebral steal syndrome (CSVSS) is a rare but important complication of coronary artery bypass graft surgery (CABG) when an internal mammary artery (IMA) is used. This syndrome is defined as a retrograde flow from coronary artery via the IMA and the vertebral artery to the subclavian artery due to a proximal subclavian artery stenosis. We describe a case of a 64-year-old female who underwent CABG, complaining of dyspnea and chest pain by exercise of left arm, and dizziness when she turned her face to the left. Her blood pressure was 113/69 mmHg in the left arm and 137/84 mmHg in the right arm. Coronary angiography revealed retrograde flow from the left anterior descending (LAD) artery to the left IMA. Aortography showed that the ostium of the left subclavian artery had a severe stenosis and that the left vertebral artery was visualized retrogradely. Thereby, the diagnosis of CSVSS was made. The stenosis of the left subclavian artery was successfully treated with a percutaneous transluminal angioplasty and stent implantation, resulting in the restoration of antegrade flow from the left IMA to the LAD artery and from the left subclavian artery to the left vertebral artery. She was discharged with no chest pain and dizziness. <Learning objective: CSVSS is a rare but important complication of CABG. When patients who underwent CABG using IMA grafts complain of chest pain, arm claudication, or dizziness, physicians should suspect CSVSS. Proper physical examinations such as a difference in right and left blood pressure levels and a bruit of the subclavian area are needed.>.

Thyroid Hormone and Vascular Remodeling

Both hyperthyroidism and hypothyroidism affect the cardiovascular system. Hypothyroidism is known to be associated with enhanced atherosclerosis and ischemic heart diseases. The accelerated atherosclerosis in the hypothyroid state has been traditionally ascribed to atherogenic lipid profile, diastolic hypertension, and impaired endothelial function. However, recent studies indicate that thyroid hormone has direct anti-atherosclerotic effects, such as production of nitric oxide and suppression of smooth muscle cell proliferation. These data suggest that thyroid hormone inhibits atherogenesis through direct effects on the vasculature as well as modification of risk factors for atherosclerosis. This review summarizes the basic and clinical studies on the role of thyroid hormone in vascular remodeling. The possible application of thyroid hormone mimetics to the therapy of hypercholesterolemia and atherosclerosis is also discussed.

A case of Kounis syndrome associated with transcatheter arterial chemoembolization for hepatocellular carcinoma

Kounis syndrome, which is known as allergic angina and allergic myocardial infarction today, was described as the coexistence of acute coronary syndrome with allergic reactions in 1991 by Kounis and Zavras. We report a case of a 79-year-old man with hypertension, hepatocellular carcinoma (HCC), and no allergic history. He had received transcatheter arterial chemoembolization (TACE) for treatment of HCC five times without allergic reactions. At the sixth time of TACE, he presented an anaphylactic reaction such as systemic erythema and severe arterial hypotension. Simultaneously, he complained of anterior chest pain and electrocardiogram showed significant ST segment elevation in inferior leads, indicating inferior myocardial infarction. Emergency coronary angiography, however, did not demonstrate any organic stenoses or occluded lesions of the coronary arteries. We made the diagnosis of Kounis syndrome associated with TACE. Although Kounis syndrome is a rare condition, physicians should be aware of possible co-occurrence of anaphylactic reactions and acute coronary syndrome. <Learning objective: Kounis syndrome refers to acute coronary syndrome associated with allergic or anaphylactic reactions. Physicians have to be aware and keep Kounis syndrome in mind whenever they encounter patients with an anaphylactic reaction. And immediate diagnosis and prompt treatment are needed.>.

Novel roles of hypoxia response system in glucose metabolism and obesity

Oxygen is essential for ATP production in mitochondria through oxidative phosphorylation. Metazoans are equipped with the hypoxia response system that includes hypoxia-inducible factor (HIF), prolyl hydroxylase domain protein (PHD), and von Hippel-Lindau ubiquitin ligase system to combat or adapt hypoxic conditions. PHD is an oxygen-sensing enzyme that is responsible for HIF-α hydroxylation and subsequent proteasomal degradation at normoxic conditions. In hypoxic conditions, PHD activity is inhibited and transcriptional activity of HIF is increased, resulting in the induction of a broad range of genes that are involved in glucose metabolism, angiogenesis, and erythropoiesis. A worldwide epidemic of obesity, a critical risk factor for diabetes and cardiovascular diseases, has led to intense studies on adipose tissue biology, which revealed that adipose tissue functions as an endocrine organ that affects the whole body. Recent studies also suggest that inflammation and hypoxia of adipose tissue that occur as adipose tissue mass expands play an important role in the development of insulin resistance, in which PHD/HIF pathway is critically involved. The PHD/HIF pathway may be an attractive and potential target for the treatment of obesity and associated diseases.

Abstract 98: Myeloid-Specific Deletion of Prolyl Hydroxylase Domain Protein 2 Attenuates Hypertensive Cardiovascular Remodeling

Background: Hypertension induces cardiovascular hypertrophy and fibrosis. Infiltration of inflammatory cells including macrophages is critically involved in this process. We recently reported that inhibition of prolyl hydroxylase domain protein 2 (PHD2), which hydroxylates proline residue of hypoxia-inducible factor α (HIFα) and thereby induces HIFα degradation, suppressed inflammatory responses in macrophage. We examined whether myeloid-specific PHD2 deletion affects hypertension-induced cardiovascular remodeling.

Methods and Results: Myeloid-specific PHD2-deficient mice (MyPHD2KO) were generated by crossing PHD2-floxed mice with LysM-Cre transgenic mice. HIF-1α and 2α proteins were accumulated and mRNA expression of TNFα, IL-6 and IL-1β, M1 macrophage markers, and TGF-β and connective tissue growth factor (CTGF) expression were significantly decreased in peritoneal macrophages from MyPHD2KO mice compared with those from control mice. PHD2-deficient macrophage showed attenuated migration toward MCP-1. Eight to 10 week-old mice were given L-NAME (30mg/kg), an eNOS inhibitor, dissolved in 0.9% NaCl in the drinking water for 14days. Angiotensin II (AngII, 0.8 mg/kg/day) was infused subcutaneously via an osmotic mini-pump for the last 7 days of the experiment. L-NAME/AngII comparably increased systolic blood pressure in control and MyPHD2KO mice. Cardiac interstitial fibrosis (3.4±0.4 vs. 2.3±0.4%, p<0.05), macrophage infiltration and cardiac hypertrophy induced by L-NAEM/AngII were ameliorated in MyPHD2KO mice. Echocardiography revealed that treatment with L-NAME/AngII induced left ventricular hypertrophy and reduction of ejection fraction in control mice, which were not observed in MyPHD2KO mice. L-NAME/AngII-induced expression of TGF-β, CTGF, and Collagen I was decreased in the heart of MyPHD2KO mice.

Conclusions: Myeloid specific PHD2 deletion attenuates cardiac hypertrophy and fibrosis induced by L-NAME/AngII, which may be mediated by decreased inflammation- and fibrosis-associated gene expression in macrophage. PHD2 in myeloid lineage plays a critical role in hypertensive cardiovascular remodeling.

Deletion of phd2 in myeloid lineage attenuates hypertensive cardiovascular remodeling

BACKGROUND

Hypertension induces cardiovascular hypertrophy and fibrosis. Infiltrated macrophages are critically involved in this process. We recently reported that inhibition of prolyl hydroxylase domain protein 2 (PHD2), which hydroxylates the proline residues of hypoxia-inducible factor-α (HIF-α) and thereby induces HIF-α degradation, suppressed inflammatory responses in macrophages. We examined whether myeloid-specific Phd2 deletion affects hypertension-induced cardiovascular remodeling.

METHODS AND RESULTS

Myeloid-specific PHD2-deficient mice (MyPHD2KO) were generated by crossing Phd2-floxed mice with LysM-Cre transgenic mice, resulting in the accumulation of HIF-1α and HIF-2α in macrophage. Eight- to ten-week-old mice were given N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, and Angiotensin II (Ang II) infusion. L-NAME/Ang II comparably increased systolic blood pressure in control and MyPHD2KO mice. However, MyPHD2KO mice showed less aortic medial and adventitial thickening, and macrophage infiltration. Cardiac interstitial fibrosis and myocyte hypertrophy were also significantly ameliorated in MyPHD2KO mice. Transforming growth factor-β and collagen expression were decreased in the aorta and heart from MyPHD2KO mice. Echocardiographic analysis showed that left ventricular hypertrophy and reduced ejection fraction induced by L-NAME/Ang II treatment in control mice were not observed in MyPHD2KO mice. Administration of digoxin that inhibits HIF-α synthesis to L-NAME/Ang II-treated MyPHD2KO mice reversed these beneficial features.

CONCLUSIONS

Phd2 deletion in myeloid lineage attenuates hypertensive cardiovascular hypertrophy and fibrosis, which may be mediated by decreased inflammation- and fibrosis-associated gene expression in macrophages. PHD2 in myeloid lineage plays a critical role in hypertensive cardiovascular remodeling.

Chitinase inhibition promotes atherosclerosis in hyperlipidemic mice

Chitinase 1 (CHIT1) is secreted by activated macrophages. Chitinase activity is raised in atherosclerotic patient sera and is present in atherosclerotic plaque. However, the role of CHIT1 in atherosclerosis is unknown. Preliminary studies of atherosclerosis in cynomolgous monkeys revealed CHIT1 to be closely correlated with areas of macrophage infiltration. Thus, we investigated the effects of a chitinase inhibitor, allosamidin, on macrophage function in vitro and on atherosclerotic development in vivo. In RAW264.7 cells, allosamidin elevated monocyte chemoattractant protein 1 and tumor necrosis factor alpha expression, and increased activator protein 1 and nuclear factor-κB transcriptional activity. Although inducible nitric oxide synthase, IL-6, and IL-1β expression were increased, Arg1 expression was decreased by chitinase inhibition, suggesting that suppression of CHIT1 activity polarizes macrophages into a M1 phenotype. Allosamidin decreased scavenger receptor AI, CD36, ABCA1, and ABCG1 expression which led to suppression of cholesterol uptake and apolipoprotein AI-mediated cholesterol efflux in macrophages. These effects were confirmed with CHIT1 siRNA transfection and CHIT1 plasmid transfection experiments in primary macrophages. Apolipoprotein E-deficient hyperlipidemic mice treated for 6 weeks with constant administration of allosamidin and fed an atherogenic diet showed aggravated atherosclerotic lesion formation. These data suggest that CHIT1 exerts protective effects against atherosclerosis by suppressing inflammatory responses and polarizing macrophages toward an M2 phenotype, and promoting lipid uptake and cholesterol efflux in macrophages.

Pivotal role of Rho-associated kinase 2 in generating the intrinsic circadian rhythm of vascular contractility

BACKGROUND

The circadian variation in the incidence of cardiovascular events may be attributable to the circadian changes in vascular contractility. The circadian rhythm of vascular contractility is determined by the interplay between the central and peripheral clocks. However, the molecular mechanism of the vascular intrinsic clock that generates the circadian rhythm of vascular contractility still remains largely unknown.

METHODS AND RESULTS

The agonist-induced phosphorylation of myosin light chain in cultured smooth muscle cells synchronized by dexamethasone pulse treatment exhibited an apparent circadian oscillation, with a 25.4-hour cycle length. The pharmacological inhibition and knockdown of Rho-associated kinase 2 (ROCK2) abolished the circadian rhythm of myosin light chain phosphorylation. The expression and activity of ROCK2 exhibited a circadian rhythm in phase with that of myosin light chain phosphorylation. A clock gene, RORα, activated the promoter of the ROCK2 gene, whereas its knockdown abolished the rhythmic expression of ROCK2. In the mouse aorta, ROCK2 expression exhibited the circadian oscillation, with a peak at Zeitgeber time 0/24 and a nadir at Zeitgeber time 12. The myofilament Ca(2+) sensitization induced by GTPγS and U46619, a thromboxane A2 analog, at Zeitgeber time 0/24 was greater than that seen at Zeitgeber time 12. The circadian rhythm of ROCK2 expression and myofilament Ca(2+) sensitivity was abolished in staggerer mutant mice, which lack a functional RORα.

CONCLUSIONS

ROCK2 plays a pivotal role in generating the intrinsic circadian rhythm of vascular contractility by receiving a cue from RORα. The ROCK2-mediated intrinsic rhythm of vascular contractility may underlie the diurnal variation of the incidence of cardiovascular diseases.

Abstract 396: Inhibition of Prolyl Hydroxylase Domain-containing Protein Downregulates Vascular Angiotensin II Type 1 Receptor

Background: Prolyl hydroxylase domain-containing protein (PHD) mediates hydroxylation of hypoxia-inducible factor (HIF)-1α and thereby induces proteasomal degradation of HIF-1α. Inhibition of PHD by hypoxia or hypoxia mimetics such as cobalt chloride (CoCl2) stabilizes HIF-1 and increases the expression of target genes such as vascular endothelial growth factor (VEGF). Although hypoxia activates the systemic renin angiotensin system (RAS), the role of PHD in regulating RAS remains unknown. We examined the effect of PHD inhibition on the expression of angiotensin (Ang) II type 1 receptor (AT1R) and its signaling.

Methods and Results: Hypoxia (1% O2), CoCl2 (100-300 μmol/L), and dimethyloxalylglycine (0.25-1.0 mmol/L), all known to inhibit PHD, reduced AT1R expression by 37.7±7.6, 39.6±8.4-69.7±9.9, and 13.4±6.1-25.2±7.0%, respectively (p<0.01) in cultured vascular smooth muscle cell. The same stimuli increased the expression of nuclear HIF-1α and VEGF (p<0.05), suggesting that PHD activity is inhibited. Knockdown of PHD2, a major isoform of PHDs, by RNA interference also reduced AT1R expression by 55.3±6.0% (p<0.01). CoCl2 decreased AT1R mRNA through transcriptional and posttranscriptional mechanisms (p<0.01 and <0.05, respectively). CoCl2 and PHD2 knockdown diminished Ang II-induced ERK phosphorylation (P<0.01). Over-expression of the constitutively active HIF-1α did not impact the AT1R gene promoter activity. Oral administration of CoCl2 (14 mg/kg/day) to C57BL/6J mice receiving Ang II infusion (490 ng/kg/min) for 4 weeks significantly reduced the expression of AT1R in the aorta by 60.9±11.3% (p<0.05) and attenuated coronary perivascular fibrosis by 85% (p<0.01) without affecting blood pressure. However, CoCl2 did not affect Ang II-induced renal interstitial fibrosis.

Conclusion: PHD inhibition downregulates AT1R expression independently of HIF-1α, reduces the cellular response to Ang II, and attenuates profibrotic effect of Ang II on the coronary arteries. PHD inhibition may be beneficial for the treatment of cardiovascular diseases, in which activation of RAS plays a critical role.

Beraprost sodium, a stable prostacyclin analogue, improves insulin resistance in high-fat diet-induced obese mice

Obesity induces hypertrophy of adipocyte resulting in production of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein 1 (MCP1 (CCL2)). These cytokines play an important role in the development of insulin resistance. Beraprost sodium (BPS), a prostaglandin I2 analogue, is reported to attenuate inflammation. In this study, we examined the effect of BPS on glucose metabolism in mice fed a high-fat diet (HFD). Four-week-old C57/B6 male mice were fed a HFD for 12 weeks (HFD group) and the treatment group received oral BPS (300 μg/kg per day) for the same period. Then, glucose metabolism, histological changes, and gene expression of white adipose tissue (WAT) were examined. Body weight was increased, and glucose intolerance and insulin resistance were developed in the HFD group. Treatment with BPS improved glucose tolerance and insulin action without body weight change. Histological analysis of WAT showed an increase in the size of adipocyte and macrophage infiltration in the HFD group, which was attenuated by BPS treatment. BPS reduced HFD-induced expression of MCP1 and TNF-α in WAT. BPS also attenuated hepatic steatosis induced by the HFD. These results suggest that BPS improved glucose intolerance possibly through suppression of inflammatory cytokines in WAT. BPS may be beneficial for the treatment of obesity-associated glucose intolerance.

Inhibition of prolyl hydroxylase domain-containing protein downregulates vascular angiotensin II type 1 receptor

Inhibition of prolyl hydroxylase domain-containing protein (PHD) by hypoxia stabilizes hypoxia-inducible factor 1 and increases the expression of target genes, such as vascular endothelial growth factor. Although the systemic renin-angiotensin system is activated by hypoxia, the role of PHD in the regulation of the renin-angiotensin system remains unknown. We examined the effect of PHD inhibition on the expression of angiotensin II type 1 receptor (AT(1)R). Hypoxia, cobalt chloride, and dimethyloxalylglycine, all known to inhibit PHD, reduced AT(1)R expression in vascular smooth muscle cells. Knockdown of PHD2, a major isoform of PHDs, by RNA interference also reduced AT(1)R expression. Cobalt chloride diminished angiotensin II-induced extracellular signal-regulated kinase phosphorylation. Cobalt chloride decreased AT(1)R mRNA through transcriptional and posttranscriptional mechanisms. Oral administration of cobalt chloride (14 mg/kg per day) to C57BL/6J mice receiving angiotensin II infusion (490 ng/kg per minute) for 4 weeks significantly attenuated perivascular fibrosis of the coronary arteries without affecting blood pressure level. These data suggest that PHD inhibition may be beneficial for the treatment of cardiovascular diseases by inhibiting renin-angiotensin system via AT(1)R downregulation.

Inhibition of MDM2 attenuates neointimal hyperplasia via suppression of vascular proliferation and inflammation

AIMS

Tumour protein p53 plays an important role in the vascular remodelling process as well as in oncogenesis. p53 is negatively regulated by murine double minute 2 (MDM2). A recently developed MDM2 inhibitor, nutlin-3, is a non-genotoxic activator of the p53 pathway. So far, the effect of MDM2 inhibition on vascular remodelling has not been elucidated. We therefore investigated the effect of nutlin-3 on neointima formation.

METHODS AND RESULTS

Nutlin-3 up-regulated p53 and its downstream target p21 in vascular smooth muscle cells (VSMCs). DNA synthesis assay and flow cytometric analysis revealed that nutlin-3 inhibited platelet-derived growth factor (PDGF)-induced VSMC proliferation by cell cycle arrest. This inhibitory effect was abrogated in p53-siRNA-transfected VSMCs. Furthermore, nutlin-3 inhibited PDGF-stimulated VSMC migration. Treatment with nutlin-3 attenuated neointimal hyperplasia at 28 days after vascular injury in mice, associated with up-regulation of p53 and p21. BrdU incorporation was decreased at 14 days after injury in nutlin-3-treated mice. TUNEL assay showed that nutlin-3 did not exaggerate apoptosis of the injured vessels. Infiltration of macrophages and T-lymphocytes and mRNA expression of chemokine (C-C motif) ligand-5, interleukin-6, and intercellular adhesion molecule-1 were decreased in the injured vessels of nutlin-3-treated mice. Nutlin-3 suppressed NF-κB activation in VSMCs, but not in p53-siRNA-transfected VSMCs.

CONCLUSIONS

The MDM2 antagonist nutlin-3 inhibits VSMC proliferation, migration, and NF-κB activation, and also attenuates neointimal hyperplasia after vascular injury in mice, which is associated with suppression of vascular cell proliferation and an inflammatory response. Targeting MDM2 might be a potential therapeutic strategy for the treatment of vascular proliferative diseases.

CREB-mediated IL-6 expression is required for 15(S)-hydroxyeicosatetraenoic acid-induced vascular smooth muscle cell migration

OBJECTIVE

Migration of vascular smooth muscle cells (VSMCs) from media to intima is a key event in the pathophysiology of atherosclerosis and restenosis. The lipoxygenase products of polyunsaturated fatty acids (PUFA) were shown to play a role in these diseases. cAMP response element binding protein (CREB) has been implicated in the regulation of VSMC growth and motility in response to thrombin and angiotensin II. The aim of the present study was to test the role of CREB in an oxidized lipid molecule, 15(S)-HETE-induced VSMC migration and neointima formation.

METHODS AND RESULTS

15(S)-HETE stimulated VSMC migration in CREB-dependent manner, as measured by the modified Boyden chamber method. Blockade of MEK1, JNK1, or p38MAPK inhibited 15(S)-HETE-induced CREB phosphorylation and VSMC migration. 15(S)-HETE induced expression and secretion of interleukin-6 (IL-6), as analyzed by RT-PCR and ELISA, respectively. Neutralizing anti-IL-6 antibodies blocked 15(S)-HETE-induced VSMC migration. Dominant-negative mutant-mediated blockade of ERK1/2, JNK1, p38MAPK, or CREB suppressed 15(S)-HETE-induced IL-6 expression in VSMCs. Serial 5' deletions and site-directed mutagenesis of IL-6 promoter along with chromatin immunoprecipitation using anti-CREB antibodies showed that cAMP response element is essential for 15(S)-HETE-induced IL-6 expression. Dominant-negative CREB also suppressed balloon injury-induced IL-6 expression, SMC migration from media to intimal region, and neointima formation. Adenovirus-mediated transduction of 15-lipoxygenase 2 (15-LOX2) caused increased production of 15-HETE in VSMCs and enhanced IL-6 expression, SMC migration from media to intimal region, and neointima formation in response to arterial injury.

CONCLUSIONS

The above results suggest a role for 15-LOX2-15-HETE in the regulation of VSMC migration and neointima formation involving CREB-mediated IL-6 expression.

Inhibition of Tumor Necrosis Factor-α–Induced Interleukin-6 Expression by Telmisartan Through Cross-Talk of Peroxisome Proliferator-Activated Receptor-γ With Nuclear Factor κB and CCAAT/Enhancer-Binding Protein-β

Telmisartan, an angiotensin II type 1 receptor antagonist, was reported to be a partial agonist of peroxisome proliferator-activated receptor-γ. Although peroxisome proliferator-activated receptor-γ activators have been shown to have an anti-inflammatory effect, such as inhibition of cytokine production, it has not been determined whether telmisartan has such effects. We examined whether telmisartan inhibits expression of interleukin-6 (IL-6), a proinflammatory cytokine, in vascular smooth muscle cells. Telmisartan, but not valsartan, attenuated IL-6 mRNA expression induced by tumor necrosis factor-α (TNF-α). Telmisartan decreased TNF-α–induced IL-6 mRNA and protein expression in a dose-dependent manner. Because suppression of IL-6 mRNA expression was prevented by pretreatment with GW9662, a specific peroxisome proliferator-activated receptor-γ antagonist, peroxisome proliferator-activated receptor-γ may be involved in the process. Telmisartan suppressed IL-6 gene promoter activity induced by TNF-α. Deletion analysis suggested that the DNA segment between −150 bp and −27 bp of the IL-6 gene promoter that contains nuclear factor κB and CCAAT/enhancer-binding protein-β sites was responsible for telmisartan suppression. Telmisartan attenuated TNF-α–induced nuclear factor κB– and CCAAT/enhancer-binding protein-β–dependent gene transcription and DNA binding. Telmisartan also attenuated serum IL-6 level in TNF-α–infused mice and IL-6 production from rat aorta stimulated with TNF-α ex vivo. These data suggest that telmisartan may attenuate inflammatory process induced by TNF-α in addition to the blockade of angiotensin II type 1 receptor. Because both TNF-α and angiotensin II play important roles in atherogenesis through enhancement of vascular inflammation, telmisartan may be beneficial for treatment of not only hypertension but also vascular inflammatory change.

Resveratrol attenuates angiotensin II-induced interleukin-6 expression and perivascular fibrosis

Recent studies have shown that resveratrol (3,5,4'-trihydroxystilbene), a polyphenolic compound found in grapes and red wine, has various beneficial effects on cardiovascular diseases and prolongs the life span of mice fed a high-fat diet. We hypothesized that resveratrol may attenuate vascular inflammatory response induced by angiotensin (Ang) II. We examined the effect of resveratrol on Ang II-induced interleukin (IL)-6 expression in vascular smooth muscle cells (VSMCs). Resveratrol significantly attenuated Ang II-induced IL-6 mRNA expression and IL-6 protein in the supernatant of VSMC in a dose-dependent manner. Resveratrol suppressed the IL-6 gene promoter activity. Resveratrol inhibited the Ang II-induced cAMP-response element-binding protein and nuclear factor-kappa B activity, which are critical for Ang II-induced IL-6 gene activation. An increase in the serum concentration of IL-6 induced by Ang II infusion was attenuated by an oral administration of resveratrol. Resveratrol also inhibited Ang II-induced hypertension and perivascular fibrosis of the heart. Although hydralazine reduced blood pressure level equal to resveratrol, it did not reduce the Ang II-induced IL-6 production and perivascular fibrosis. These data suggest that the inhibition of Ang II-induced vascular inflammation and high blood pressure by resveratrol may contribute, at least in part, to the anti-atherogenic effects of resveratrol.

Liver X receptor activator downregulates angiotensin II type 1 receptor expression through dephosphorylation of Sp1

Atherosclerosis is considered to be a combined disorder of lipid metabolism and chronic inflammation. Recent studies have reported that liver X receptors (LXRs) are involved in lipid metabolism and inflammation and that LXR agonists inhibit atherogenesis. In contrast, angiotensin II is well known to accelerate atherogenesis through activation of the angiotensin II type 1 receptor (AT1R). To better understand the mechanism of LXR on the prevention of atherogenesis, we examined whether activation of LXR affects AT1R expression in vascular smooth muscle cells. T0901317, a synthetic LXR ligand, decreased AT1R mRNA and protein expression with a peak reduction at 6 hours and 12 hours of incubation, respectively. A well-established ligand of LXR, 22-(R)-hydroxycholesterol, also suppressed AT1R expression. The downregulation of AT1R by T0901317 required de novo protein synthesis. AT1R gene promoter activity measured by luciferase assay revealed that the DNA segment between -61 bp and +25 bp was sufficient for downregulation. Luciferase construct with a mutation in Sp1 binding site located in this segment lost its response to T0901317. T0901317 decreased Sp1 serine phosphorylation. Although preincubation of vascular smooth muscle cells with T0901317 for 30 minutes had no effect on angiotensin II-induced extracellular signal-regulated kinase phosphorylation, phosphorylation of extracellular signal-regulated kinase by angiotensin II was markedly suppressed after 6 hours of preincubation. These results indicate that the suppression of AT1R may be one of the important mechanisms by which LXR ligands exert antiatherogenic effects.

SIRT1, a longevity gene, downregulates angiotensin II type 1 receptor expression in vascular smooth muscle cells

OBJECTIVE

Resveratrol (3,5,4'-trihydroxystilbene), a polyphenol found in red wine, is known to activate sirtuin1 (SIRT1), a longevity gene. Previous studies have demonstrated that resveratrol extends the life span of diverse species through activation of SIRT1. It was also reported that inhibition of angiotensin II function by angiotensin II type I receptor (AT1R) antagonist prolonged rat life span. We, therefore, hypothesized that resveratrol may inhibit the renin-angiontein system and examined whether resveratrol affects AT1R expression in vascular smooth muscle cells (VSMCs).

METHODS AND RESULTS

Northern and Western blot analysis revealed that resveratrol significantly decreased the expression of AT1R at mRNA and protein levels in a dose- and time-dependent manner. Overexpression of SIRT1 reduced AT1R expression whereas nicotinamide, an inhibitor of SIRT1, increased AT1R expression and reversed the resveratrol-induced AT1R downregulation. AT1R gene promoter activity was decreased by resveratrol, but resveratrol did not affect the AT1R mRNA stability. Deletion analysis showed that the most proximal region of AT1R gene promoter containing Sp1 site is responsible for downregulation. Administration of resveratrol suppressed AT1R expression in the mouse aorta and blunted angiotensin II-induced hypertension.

CONCLUSIONS

Resveratrol suppressed AT1R expression through SIRT1 activation both in vivo and in vitro. The inhibition of the renin-angiotensin system may contribute, at least in part, to the resveratrol-induced longevity and antiatherogenic effect of resveratrol.

Involvement of Mst1 in tumor necrosis factor-alpha-induced apoptosis of endothelial cells

Mammalian sterile 20-kinase 1 (Mst1), a member of the sterile-20 family protein kinase, plays an important role in the induction of apoptosis. However, little is know about the physiological activator of Mst1 and the role of Mst1 in endothelial cells (ECs). We examined whether Mst1 is involved in the tumor necrosis factor (TNF)-alpha-induced apoptosis of ECs. Western blot analysis revealed that TNF-alpha induced activation of caspase 3 and Mst1 in a time- and dose-dependent manner. TNF-alpha-induced Mst1 activation is almost completely prevented by pretreatment with Z-DEVD-FMK, a caspase 3 inhibitor. Nuclear staining with Hoechst 33258 and fluorescence-activated cell sorting of propidium iodide-stained cells showed that TNF-alpha induced apoptosis of EC. Diphenyleneiodonium, an inhibitor of NADPH oxidase, and N-acetylcysteine, a potent antioxidant, also inhibited TNF-alpha-induced activation of Mst1 and caspase 3, as well as apoptosis. Knockdown of Mst1 expression by short interfering RNA attenuated TNF-alpha-induced apoptosis but not cleavage of caspase 3. These results suggest that Mst1 plays an important role in the induction of TNF-alpha-induced apoptosis of EC. However, positive feedback mechanism between Mst1 and caspase 3, which was shown in the previous studies, was not observed. Inhibition of Mst1 function may be beneficial for maintaining the endothelial integrity and inhibition of atherogenesis.

Inducible cAMP early repressor inhibits growth of vascular smooth muscle cell

OBJECTIVE

The role of inducible cAMP early repressor (ICER), a transcriptional repressor, in the vascular remodeling process has not been determined. We examined whether ICER affects growth of vascular smooth muscle cells (VSMCs).

METHODS AND RESULTS

Semi-quantitative RT-PCR and Western blot analysis showed that expression of ICER was increased in beraprost (a prostaglandin I2 analogue)-stimulated VSMCs in a time- and dose-dependent manner. The induction of ICER was inhibited by pretreatment with H89, a protein kinase A (PKA) inhibitor, suggesting that PKA mediates the induction of ICER expression. Beraprost suppressed platelet-derived growth factor-induced thymidine incorporation in VSMCs, which was reversed by transfection of short interfering RNA for ICER, not by scramble RNA. Overexpression of ICER by an adenovirus vector attenuated neointimal formation (intima/media ratio) by 50% compared with overexpression of LacZ. The number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling-positive cells was increased and the number of Ki-67-positive cells was decreased in ICER-transduced artery.

CONCLUSION

These results suggest that ICER induces apoptosis and inhibits proliferation of VSMCs, and plays a critical role in beraprost-mediated suppression of VSMC proliferation. ICER may be an important endogenous inhibitor of vascular proliferation.

Telmisartan downregulates angiotensin II type 1 receptor through activation of peroxisome proliferator-activated receptor γ

OBJECTIVE

Telmisartan, an angiotensin II type 1 receptor (AT1R) antagonist, was found to have a unique property: it is a partial agonist of peroxisome proliferator-activated receptor gamma (PPARgamma). Since previous studies have demonstrated that PPARgamma activators suppressed AT1R expression, we examined whether telmisartan affects AT1R expression in vascular smooth muscle cells.

METHODS

Vascular smooth muscle cells were derived from the thoracic aorta of Wistar-Kyoto rat. Northern and Western blotting analysis were used to examine AT1R mRNA and protein expression, respectively. The DEAE-dextran method was used for transfection, and the promoter activity of AT1R was examined by luciferase assay.

RESULTS

Telmisartan decreased the expression of AT1R at the mRNA and protein levels in a dose- and time-dependent manner. Decreased AT1R promoter activity with unchanged mRNA stability suggested that telmisartan suppressed AT1R gene expression at the transcriptional level. However, the expression of AT1R was not suppressed by other AT1R antagonists such as candesartan or olmesartan. Since the suppression of AT1R expression was prevented by pretreatment with GW9662, a PPARgamma antagonist, PPARgamma should have participated in the process. The deletion and mutation analysis of the AT1R gene promoter indicated that a GC box located in the proximal promoter region is responsible for the telmisartan-induced downregulation.

CONCLUSION

Our data provides a novel insight into an effect of telmisartan: telmisartan inhibits AT1R gene expression through PPARgamma activation. The dual inhibition of angiotensin II function by telmisartan - AT1R blockade and downregulation - would contribute to more complete inhibition of the renin-angiotensin system.

Thyroid hormone inhibits vascular remodeling through suppression of cAMP response element binding protein activity

OBJECTIVE

Although accumulating evidences suggest that impaired thyroid function is a risk for ischemic heart disease, the molecular mechanism of anti-atherosclerotic effects of thyroid hormone is poorly defined. We examined whether thyroid hormone affects signaling pathway of angiotensin II (Ang II), which is critically involved in a broad aspect of cardiovascular disease process.

METHODS AND RESULTS

3,3',5-triiodo-L-thyronine (T3) did not show a significant effect on Ang II-induced activation of extracellular signal-regulated protein kinase or p38 mitogen-activated protein kinase in vascular smooth muscle cells (VSMCs), whereas T3 inhibited Ang II-induced activation of cAMP response element (CRE) binding protein (CREB), a nuclear transcription factor involved in the vascular remodeling process. Coimmunoprecipitaion assay revealed the protein-protein interaction between thyroid hormone receptor and CREB. T3 reduced an expression level of interleukin (IL)-6 mRNA, CRE-dependent promoter activity, and protein synthesis induced by Ang II. Administration of T3 (100 microg/100 g for 14 days) to rats attenuated neointimal formation after balloon injury of carotid artery with reduced CREB activation and BrdU incorporation.

CONCLUSIONS

These results suggested that T3 inhibits CREB/CRE signaling pathway and suppresses cytokine expression and VSMCs proliferation, which may account for, at least in part, an anti-atherosclerotic effect of thyroid hormone.

CAMP-response element-binding protein mediates tumor necrosis factor-alpha-induced vascular cell adhesion molecule-1 expression in endothelial cells

Hypertension causes endothelial dysfunction, which plays an important role in atherogenesis. The vascular cell adhesion molecule-1 (VCAM-1) contributes to atherosclerotic lesion formation by recruiting leukocytes from blood into tissues. Tumor necrosis factor-alpha (TNFalpha) induces endothelial dysfunction and VCAM-1 expression in endothelial cells (ECs). We examined whether the cAMP-response element binding protein (CREB), a transcription factor that mediates cytokine expression and vascular remodeling, is involved in TNFalpha-induced VCAM-1 expression. TNFalpha induced phosphorylation of CREB with a peak at 15 min of stimulation in a dose-dependent manner in bovine aortic ECs. Pharmacological inhibition of p38 mitogen-activated protein kinase (p38-MAPK) inhibited TNFalpha-induced CREB phosphorylation. Adenovirus-mediated overexpression of a dominant-negative form of CREB suppressed TNFalpha-induced VCAM-1 and c-fos expression. Although activating protein 1 DNA binding activity was attenuated by overexpression of dominant negative CREB, nuclear factor-kappaB activity was not affected. Our results suggest that the p38-MAPK/CREB pathway plays a critical role in TNFalpha-induced VCAM-1 expression in vascular endothelial cells. The p38MAPK/CREB pathway may be a novel therapeutic target for the treatment of atherosclerosis.

Role of cAMP response element binding protein in cardiovascular remodeling: good, bad, or both?

The cAMP response element binding protein (CREB) is a ubiquitously expressed nuclear transcription factor that is activated by various extracellular stimuli. CREB is known to regulate the expression of genes important to cell proliferation, differentiation, adaptation, and survival in many cell types. Loss of CREB function by transgenic overexpression of dominant negative CREB or targeted deletion of the CREB gene revealed that CREB is involved in the differentiation of T lymphocytes, production of growth hormone, and the long-term potentiation of neuronal memory. The role of CREB in cardiovascular system is incompletely characterized and several controversies remain. A growing body of recent evidence, however, has suggested that CREB plays an important role in the cardiovascular remodeling process, including inflammation, cell migration, and apoptosis. Thus, CREB may be a possible target for the treatment of cardiovascular diseases such as atherosclerosis, restenosis, and reperfusion injury.

cAMP-response element-binding protein mediates prostaglandin F2alpha-induced hypertrophy of vascular smooth muscle cells

Prostaglandin F(2alpha) (PGF(2alpha)) is a vasoactive factor that causes constriction and hypertrophy of vascular smooth muscle cells (VSMCs). However, the mechanism of PGF(2alpha)-induced hypertrophy is largely unknown. Cyclic AMP-response element (CRE)-binding protein (CREB), the best characterized stimulus-induced transcription factor, activates transcription of target genes with CRE and promotes cell growth. We examined the role of CREB in PGF(2alpha)-induced hypertrophy of VSMCs. PGF(2alpha) induced phosphorylation of CREB at serine 133, which is a critical marker of activation, after 5-10min of stimulation in a dose-dependent manner. Pharmacological inhibition of extracellular signal-regulated protein kinase and p38 mitogen-activated protein kinase (p38-MAPK) suppressed PGF(2alpha)-induced CREB phosphorylation. Inhibition of epidermal growth factor receptor (EGFR) and mitogen- and stress-activated protein kinase-1 also suppressed PGF(2alpha)-induced CREB phosphorylation. Overexpression of dominant-negative form of CREB (AdCREB M1), of which serine 133 was replaced with alanine, inhibited PGF(2alpha)-induced c-fos mRNA expression as well as hypertrophy of VSMCs [hypertrophy index (microg/10(4)cell); control 8.13, PGF(2alpha) 9.85, AdCREB M1 7.91, and AdCREB M1+PGF(2alpha) 8.43]. These results suggest that PGF(2alpha) activated CRE-dependent gene transcription through EGFR transactivation, and the CREB pathway plays a critical role in PGF(2alpha)-induced hypertrophy of VSMCs.

Endogenous NO Blockade Enhances Tissue Factor Expression via Increased Ca2+Influx Through MCP-1 in Endothelial Cells by Monocyte Adhesion

OBJECTIVE

Ca2+ plays an important role in tissue factor (TF) gene expression. We investigated the role of endogenous nitric oxide (NO) in the induction of TF expression in endothelial cells (ECs) by monocyte adhesion and the mechanisms of NO action.

METHODS AND RESULTS

Inhibition of endogenous NO by Nomega-nitro-L-arginine methyl ester (L-NAME) enhanced TF promoter activity and protein expression induced in human coronary ECs by monocyte adhesion, as well as EC surface TF activity. L-NAME also induced monocyte chemoattractant protein-1 (MCP-1) expression, which was blocked by an NO donor, NOC18. Exogenous MCP-1 enhanced TF expression induced by monocyte adhesion, whereas adenovirus-mediated expression of the mutant MCP-1, 7ND, abolished the L-NAME enhancement of TF expression induced by monocyte adhesion. Monocyte attachment to L-NAME-treated ECs increased Ca2+ influx, which was prevented by NOC18, anti-MCP-1 antibody or 7ND. These results indicate that the binding of increased MCP-1 induced by endogenous NO blockade to CCR2 mediated the enhancement of Ca2+ influx only when monocytes adhered to ECs, which upregulated TF expression in ECs triggered by monocyte adhesion.

CONCLUSIONS

MCP-1/CCR2 may play a role in Ca2+ influx-dependent TF regulation in the monocyte-EC interaction in the impairment of NO synthesis.

Critical Role of Mst1 in Vascular Remodeling After Injury

Objective— Apoptosis of vascular smooth muscle cells (VSMCs) is observed in chronic vascular lesions such as atherosclerotic plaques and is believed to contribute to the vascular remodeling process. Mst1 is a ubiquitously expressed serine/threonine kinase known to be activated in response to a wide variety of nonphysiological apoptotic stimuli. However, little is known of the physiological function of Mst1, and its role in VSMCs has never been examined.

Methods and Results— Treatment of VSMCs with staurosporine induced apoptosis and cleavage of Mst1, which is a marker of its activation, as well as activation of caspase 3. Adenovirus-mediated overexpression of wild-type Mst1 (AdMst1) in VSMCs increased apoptotic cells with activation of caspase 3. Mst1 was induced and activated in the balloon-injured rat carotid artery. Infection with AdMst1 in balloon-injured rat carotid artery suppressed neointimal formation compared with infection with AdLacZ. Infection with AdMst1 significantly increased the apoptotic cell number in the neointima compared with infection with AdLacZ without affecting BrdU incorporation.

Conclusion— Our results suggest that Mst1 plays an important role in the induction of apoptosis of VSMCs, mediating the vascular remodeling process, and may be a potential therapeutic target for vascular proliferative diseases.