Angiostatin inhibits coronary angiogenesis during impaired production of nitric oxide

Elevated fluid shear stress enhances postocclusive collateral artery growth and gene expression in the pig hind limb

OBJECTIVE

The role of fluid shear stress (FSS) in collateral vessel growth remains disputed and prospective in vivo experiments to test its morphogenic power are rare. Therefore, we studied the influence of FSS on arteriogenesis in a new model with extremely high levels of collateral flow and FSS in pig and rabbit hind limbs.

METHODS AND RESULTS

A side-to-side anastomosis was created between the distal stump of one of the bilaterally occluded femoral arteries with the accompanying vein. This clamps the collateral reentry pressure at venous levels and increases collateral flow, which is directed to a large part into the venous system. This decreases circumferential wall stress and markedly increases FSS. One week after anastomosis, angiographic number and size of collaterals were significantly increased. Maximal collateral flow exceeded by 2.3-fold that obtained in the ligature-only hind limb. Capillary density increased in lower leg muscles. Immunohistochemistry revealed augmented proliferative activity of endothelial and smooth muscle cells. Intercellular adhesion molecule-1 and vascular cell adhesion molecule (VCAM)-1 were upregulated, and monocyte invasion was markedly increased. In 2-dimensional gels, actin-regulating cofilin1 and cofilin2, destrin, and transgelin2 showed the highest degree of differential regulation.

CONCLUSIONS

High levels of FSS cause a strong arteriogenic response, reinstate cellular proliferation, stimulate cytoskeletal rearrangement, and normalize maximal conductance. FSS is the initiating molding force in arteriogenesis. The role of fluid shear stress on the development of a collateral circulation was studied by abruptly increasing collateral blood flow by a distal femoral artery-to-vein anastomosis. This increased number and size of collateral vessels to a hitherto unknown degree. Fluid shear stress is the primary and strongest arteriogenic stimulus.

Chronic Hyperglycemia Attenuates Coronary Collateral Development and Impairs Proliferative Properties of Myocardial Interstitial Fluid by Production of Angiostatin

Background— Development of coronary collateral vessels is impaired in patients with diabetes mellitus. We tested the hypothesis that hyperglycemia alone attenuates collateral development and abolishes proliferative properties of myocardial interstitial fluid (MIF) by enhancing expression of matrix metalloproteinases (MMP) and angiostatin.

Methods and Results— Chronically instrumented dogs were randomly assigned to receive an infusion of normal saline (control; n=9) or 70% dextrose in water to increase blood glucose to 350 to 400 mg/dL for 8 h/d (hyperglycemia; n=7) in the presence or absence (sham; n=9) of brief (2 minutes), repetitive coronary artery occlusions (1/h; 8/d for 21 days). Collateral perfusion increased to 41±11% and 49±6% of normal zone flow in control dogs on days 14 and 21 ( P <0.05) but remained unchanged over 21 days in hyperglycemic and sham dogs (12±3% and 13±3%, respectively). A progressive reduction of the postocclusive peak reactive hyperemic response was also observed in control dogs (16±1 to 10±1 Hz · 10 2 on days 1 and 21, respectively) but not in hyperglycemic (17±2 to 20±2) or sham (17±2 to 16±1) dogs. Endothelial cell tube formation was produced by MIF obtained from control dogs but not hyperglycemic or sham dogs. Coincubation of MIF from hyperglycemic dogs with an angiostatin antibody restored endothelial cell tube formation. MMP-9 activity and expression of angiostatin were increased in dogs receiving exogenous glucose compared with controls

Conclusions— Chronic hyperglycemia abolishes development of coronary collateral vessels by increasing MMP-9 activity and angiostatin expression in dogs.

Angiostatin and matrix metalloprotease expression following ischemic acute renal failure

Ischemic injury to the kidney results in blood vessel loss and predisposition to chronic renal disease. Angiostatin is a proteolytic cleavage product of plasminogen that inhibits angiogenesis, promotes apoptosis of endothelial cells, and disrupts capillary integrity. A combination of lysine-Sepharose enrichment followed by Western blotting was used to study the expression of angiostatin in response to the induction of ischemic renal injury. No angiostatin products were readily detectable in kidneys of sham-operated control rats. In contrast, both 38- and 50-kDa forms of angiostatin were dramatically enhanced in the first 3 days following 45-min ischemia-reperfusion injury. Renal angiostatin levels declined but remained detectable at late time points postrecovery (8–35 days postischemia). Angiostatin-like immunoreactivity was also elevated in the plasma and in urine for up to 35 days following injury. Lysine-Sepharose extracts of either kidney or urine inhibited vascular endothelial cell growth factor-induced proliferation of human aortic endothelial cells in vitro; an effect that was blocked by coincubation with an angiostatin antibody. RT-PCR verified that mRNA of the parent protein plasminogen was produced in the liver, but it was not present in either sham-operated or postischemic kidney. Matrix metalloproteinase (MMP)-2 and MMP-9, which may mediate angiostatin generation, were enhanced in postischemic kidney tissue and were localized to the renal tubules, interstitial cells, and the tubulo-interstitial space. These data indicate the possible local synthesis of angiostatin following acute renal failure (ARF) and suggest a possible role for MMPs in this activity. Renal angiostatin generation following ARF may modulate renal capillary density postischemia and thereby influence chronic renal function.

Collateralization and the response to obstruction of epicardial coronary arteries

Occlusive coronary disease is an important cause of global morbidity and mortality. While mechanical revascularization is effective, some individuals are not amenable to such interventions, and have a poorer prognosis. However, collateral circulation can protect and preserve myocardium around the time of coronary occlusion, contribute to better residual myocardial contractility, and lessen symptoms. We describe the anatomy and physiology of coronary collateralization, its component parts (angiogenesis and arteriogenesis), the current methods for definition of the collateral response and how this might be manipulated. The manipulation of this process is a realistic possibility for future adjuvant treatment of coronary artery disease.

Nitric oxide inhibits matrix metalloproteinase-2 expression via the induction of activating transcription factor 3 in endothelial cells

Nitric oxide (NO) has been shown to inhibit migration of cells in which various matrix metalloproteinases (MMPs) are involved. The underlying molecular mechanisms of this inhibition remain elusive. Endothelial cells (ECs) constitutively produce MMP-2. The effect of NO on MMP-2 expression was examined. A dose-dependent inhibition of MMP-2 mRNA level was demonstrated in ECs treated with NO. ECs infected with adenovirus carrying endothelial NO synthase (Ade-NOS) reduced MMP-2 expression. The inhibitory effect of NO on MMP-2 expression was a transcriptional event because NO reduced MMP-2 promoter activity. NO treatment of ECs consequently suppressed MMP-2 secretion revealed by zymographic assay. Functional analysis of MMP-2 promoter (1716 base pairs) indicated that the p53-binding site (-1659 to -1629) was crucial for MMP-2 promoter activity. Activating transcription factor 3 (ATF3) has been reported to act as a transcriptional repressor for p53. ECs treated with NO induced ATF3 expression. Consistently, Ade-NOS-infected ECs showed an increase of ATF3 level. Moreover, ECs either over-expressed ATF3 or, when treated with an ATF3 activator (MG-132; carbobenzoxy-l-leucyl-l-leucyl-l-leucinal), resulted in a repression of MMP-2 promoter activity. Because of MMP-2 suppression by NO, ECs treated with NO inhibited endothelial migration, a phenomenon similar to that of ECs treated with MMP-2 antibody or MG-132. These results indicate that NO-attenuating endothelial migration is mediated at least in part by its reduction of MMP-2 expression via the up-regulation of ATF3. This study provides a molecular basis that supports the notion that NO acts as a negative regulator in endothelial migration.

Reduced pericardial levels of endostatin correlate with collateral development in patients with ischemic heart disease

OBJECTIVES

We investigated whether pericardial levels of a pro-angiogenic factor (vascular endothelial growth factor, VEGF) or an anti-angiogenic factor (endostatin) related to the presence of coronary collateral circulation in patients with significant coronary artery disease (CAD).

BACKGROUND

Coronary collateralization favorably alters the prognosis of patients with occlusive CAD. The specific factors that mediate and maintain collateral formation in coronary vessel occlusion are yet to be identified.

METHODS

Coronary angiograms from 39 patients undergoing coronary artery bypass surgery were evaluated for the absence of collaterals (n = 20) or the presence of Rentrop classification grade 3 collaterals (n = 19). Pericardial fluid samples were obtained at the time of surgery and were assayed for the VEGF and endostatin by enzyme-linked immunosorbent assay comparing the two groups of patients.

RESULTS

Vascular endothelial growth factor levels were not significantly different between the groups (28.86 +/- 4.67 pg/ml vs. 24.39 +/- 3.08 pg/ml, p = 0.43). However, pericardial fluid endostatin levels were nearly 40% lower in patients with grade 3 collateralization compared with those lacking angiographic evidence of collaterals (15.17 +/- 1.87 ng/ml vs. 24.25 +/- 2.08 ng/ml, p < 0.0025).

CONCLUSIONS

Pericardial fluid levels of endostatin, but not VEGF, are associated with the presence or absence of collaterals in patients with CAD. These data suggest that the angiogenesis inhibitor endostatin levels may locally modulate coronary collateral formation.

Tetranectin Binds to the Kringle 1-4 Form of Angiostatin and Modifies Its Functional Activity

Tetranectin is a plasminogen kringle 4 domain-binding protein present in plasma and various tissue locations. Decreased plasma tetranectin or increased tetranectin in stroma of cancers correlates with cancer progression and adverse prognosis. A possible mechanism through which tetranectin could influence cancer progression is by altering activities of plasminogen or the plasminogen fragment, angiostatin. Tetranectin was found to bind to the kringle 1-4 form of angiostatin (AST $;{\text{K1-4}}$ ). In addition, tetranectin inhibited binding of plasminogen or AST $;{\text{K1-4}}$ to extracellular matrix (ECM) deposited by endothelial cells. Finally, tetranectin partially counteracted the ability of AST $;{\text{K1-4}}$ to inhibit proliferation of endothelial cells. This latter effect of tetranectin was specific for AST $;{\text{K1-4}}$ since it did not counteract the antiproliferative activities of the kringle 1-3 form of angiostatin (AST $;{\text{K1-3}}$ ) or endostatin. These findings suggest that tetranectin may modulate angiogenesis through interactions with AST.

Molecule action mechanisms of NM-3 on human gastric cancer SGC-7901 cells in vivo or in vitro

AIM: To study the molecule action mechanisms of NM-3 on the growth of human gastric cancer SGC-7901 cells in vivo or in vitro.

METHODS: SGC-7901 from human non-differentiated gastric cancer cell line was cultured with NM-3 at 100 mg/mL for 24 h. We observed its inhibitory rate and the density of micro-vascular growth in grafted mice with human gastric cancer SGC-7901. The apoptosis of human gastric cancer SGC-7901 was revealed in NM-3 treatment group by using terminal deoxynucleotidyl transferase-mediated deoxy-uridine triphosphate-fluorescene nick end labeling (TUNEL) method and flow cytometry analysis.

RESULTS: The growth of SGC-7901 cells was markedly inhibited compared with control growp, which was smaller than that in normal saline control group (4.17 g ± 0.22 g vs 9.45 g ± 1.38 g, P < 0.01). The level of apoptosis of human gastric cell line SGC-7901 was obviously increased in NM-3 treatment group at 1 mg.L^-1 for 24 h. NM-3 inducing apoptotic index in NM-3 plus carboplatin group was 3.5 times that of carboplatin control group (TUNEL: 27.98% ± 6.12% vs 12.94% ± 2.12%, FACScan: 26.86% ± 5.69% vs 11.86% ± 1.09%, P < 0.01). Western blot analysis showed that the apoptotic index of human gastric cancer was elevated for 12, 24 and 36 h with an evident time-effect relationship in groups at 100 mg.L^-1. NM-3 enhanced the inhibitive effects and sensitivity of chemotherapy for human gastric cancer in nude mice. These results suggested that NM-3 played a key inhibitive role in the growth of grafted human gastric cancer in nude mice.

CONCLUSION: NM-3 can inhibit the growth of human gastric cancer cell line SGC-7901, and enhance the sensitivity of carboplatin on SGC-7901 and induced its apoptosis.

Reactive oxygen species are critical mediators of coronary collateral development in a canine model

Recent evidence suggests that reactive oxygen species (ROS) promote proliferation and migration of vascular smooth muscle (VSMC) and endothelial cells (EC). We tested the hypothesis that ROS serve as crucial messengers during coronary collateral development. Dogs were subjected to brief (2 min), repetitive coronary artery occlusions (1/h, 8/day, 21 day duration) in the absence (occlusion, n = 8) or presence of N-acetylcysteine (NAC) (occlusion + NAC, n = 8). A sham group (n = 8) was instrumented identically but received no occlusions. In separate experiments, ROS generation after a single 2-min coronary artery occlusion was assessed with dihydroethidium fluorescence. Coronary collateral blood flow (expressed as a percentage of normal zone flow) was significantly increased (71 +/- 7%) in occlusion dogs after 21 days but remained unchanged (13 +/- 3%) in sham dogs. Treatment with NAC attenuated increases in collateral blood flow (28 +/- 8%). Brief coronary artery occlusion and reperfusion caused ROS production (256 +/- 33% of baseline values), which was abolished with NAC (104 +/- 12%). Myocardial interstitial fluid produced tube formation and proliferation of VSMC and EC in occlusion but not in NAC-treated or sham dogs. The results indicate that ROS are critical for the development of the coronary collateral circulation.

Nitric oxide in vascular biology

Nitric oxide is a highly versatile heterodiatomic molecule that effects a variety of actions in the vasculture. Originally identified as a principal determination of vascular tone, nitric oxide has since been recognized to exert anti thrombotic, antiproliferative, and anti-inflammatory effects in the vasculture. At higher concentrations and in the setting of other oxidants, nitric oxide can promote vascular pathology. In this review, we summarize the molecular mechanisms of nitric oxides actions in vascular biology and pathology.

Decreased hepatic nitric oxide production contributes to the development of rat sinusoidal obstruction syndrome

This study examined the role of decreased nitric oxide (NO) in the microcirculatory obstruction of hepatic sinusoidal obstruction syndrome (SOS). SOS was induced in rats with monocrotaline. Monocrotaline caused hepatic vein NO to decrease by 30% at 24 hours and by 70% at 72 hours; this decrease persisted throughout late SOS. N(G)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase, exacerbated monocrotaline toxicity, whereas V-PYRRO/NO, a liver-selective NO donor prodrug, restored NO levels, preserved sinusoidal endothelial cell (SEC) integrity and sinusoidal perfusion as assessed by in vivo microscopy and electron microscopy, and prevented clinical and histologic evidence of SOS. NO production in vitro by SEC and Kupffer cells, the 2 major liver cell sources of NO, decreases largely in parallel with loss of cell viability after exposure to monocrotaline. Increased matrix metalloproteinase (MMP) activity increases early on in SOS and this increase in activity has been implicated in initiating SOS. Infusion of V-PYRRO-NO prevented the monocrotaline-induced increase in MMP-9. In conclusion, decreased hepatic NO production contributes to the development of SOS. Infusion of an NO donor preserves SEC integrity and prevents development of SOS. These findings show that a decrease in NO contributes to SOS by allowing up-regulation of MMP activity, loss of sinusoidal integrity, and subsequent disruption of sinusoidal perfusion.

Inhaled nitric oxide inhibits the release of matrix metalloproteinase-2, but not platelet activation, during extracorporeal membrane oxygenation in adult rabbits

BACKGROUND/PURPOSE

In neonates receiving extracorporeal membrane oxygenation (ECMO), platelet activation and dysfunction occur with the release of matrix metalloproteinase (MMP)-2, which stimulates platelet aggregation. Because inhaled nitric oxide (NO) reduces pulmonary hypertension and inhibits platelet aggregation, the authors examined the effects of inhaled NO on platelet activation induced by ECMO.

METHODS

Ten adult white New Zealand rabbits were instrumented for ECMO and assigned randomly to receive either inhaled NO at 40 ppm or 30% oxygen for 1 hour before ECMO and continued for 4 hours after starting ECMO. Platelet counts, collagen-induced platelet aggregation ex vivo, plasma MMP-2, and MMP-9 activities were measured.

RESULTS

(1) ECMO caused thrombocytopenia, decreased platelet aggregation, and increased plasma MMP-2 and MMP-9 activities in controls. (2) Inhaled NO inhibited platelet aggregation before ECMO but did not affect the ECMO-induced thrombocytopenia and platelet activation. (3) Inhaled NO significantly abolished the ECMO-induced increase in plasma MMP-2 but not MMP-9 activities.

CONCLUSIONS

Although inhaled NO did not inhibit the platelet activation during ECMO in adult rabbits, it attenuated the increase in plasma MMP-2 activity that may be important for neonates treated with ECMO.

Angiostatin: a negative regulator of endothelial-dependent vasodilation

BACKGROUND

Angiostatin is known to inhibit certain aspects of endothelial function, eg, angiogenesis. Here we investigated the effects of angiostatin on another aspect of endothelial function, vasodilation, and examined mechanisms of inhibition--namely, association of heat-shock protein 90 (hsp90) with endothelial nitric oxide synthase (eNOS) and endothelial generation of nitric oxide (*NO) and superoxide anion (O2-). This avenue of investigation was based on recent reports suggesting that hsp90 modulates NOS production of *NO and O2-.

METHODS AND RESULTS

Effects of angiostatin on vasodilation were determined in arterioles with the use of videomicroscopy in response to endothelium- and *NO-dependent vasodilators, acetylcholine (ACh) and vascular endothelial growth factor (VEGF), and an endothelium-independent agonist, papaverine. Association of hsp90 with eNOS was determined in rat aortas and bovine aortic endothelial cells (BAECs). Effects of angiostatin on *NO and O2- generation by BAECs were determined by ozone chemiluminescence and superoxide dismutase (SOD)--inhibitable ferricytochrome c reduction, respectively. Angiostatin impaired vasodilation mediated by ACh and VEGF but not papaverine. Pretreating arterioles with polyethylene glycolated--SOD (PEG-SOD) improved vasodilation to ACh and VEGF. Angiostatin decreased the association of hsp90 with eNOS in aortas and BAEC cultures and increased O2- generation in stimulated BAECs by an Lgamma-nitroargininemethylester (L-NAME)--inhibitable mechanism.

CONCLUSIONS

These data indicate angiostatin alters endothelial function by allowing eNOS to generate O2- on activation. Such changes in enzyme function begin to explain, in part, why angiostatin is antiangiogenic and impairs endothelium-dependent vasodilation.

Nitric oxide and cardiovascular protection

Nitric oxide (NO) plays a critical role in ischemic heart disease and ischemia-reperfusion. There is an increasing body of evidence to support the role of NO in myocardial and vascular protection in disease. The finding that NO might act as a trigger of late ischemic preconditioning (IPC) might lead to the development of novel anti-ischemic therapy. The role of NO signaling in the cardioprotective effects of ACE inhibitors and angiotensin II type 1 receptor(AT(1)) receptor antagonists is an active area of study.

An automated coronary artery occlusion device for stimulating collateral development in vivo

INTRODUCTION

Repetitive, brief coronary artery occlusions produce collateral development in experimental animals. This model causes coronary collateralization in a highly reproducible fashion, but the process is very labor intensive. We report the design and use of a fully automated hydraulic coronary occlusion device capable of producing repetitive coronary occlusions and enhancement of coronary collateral development in dogs.

METHODS

The device consists of analog electronics that allow adjustment of occlusion number, frequency, pressure and duration, and mechanical components responsible for the coronary occlusion. The motor and piston of the device are coupled to a chronically implanted hydraulic vascular occluder placed around the left anterior descending coronary artery (LAD) of dogs instrumented for measurement of systemic and coronary hemodynamics. One group of dogs (n = 6) underwent brief (2 min) LAD occlusions once per hour, eight times per day, 5 days/week for 3 weeks to stimulate collateral development (measured using radioactive microspheres). Another group of dogs (n = 6) that did not receive repetitive occlusions served as controls.

RESULTS

The device reproducibly produced repetitive LAD occlusions for the duration, frequency, and time interval initially programmed. A time-dependent increase in transmural collateral blood flow was observed in dogs undergoing repetitive occlusions using the device. Collateral blood flow was unchanged in dogs that did not undergo occlusions.

DISCUSSION

The automated occluder device reliably produces repetitive coronary occlusions and may facilitate further study of coronary collateral development in response to chronic myocardial ischemia.

An intramyocardial catheter for repeated in vivo sampling of interstitial fluid

INTRODUCTION

Coronary collateral development is an important adaptive response to chronic myocardial ischemia. Characterization of mitogenic factors responsible for collateral formation has been an elusive goal because these substances are difficult to sample from the myocardial interstitium at multiple times. We report the implantation of an exchange catheter capable of in vivo sampling of myocardial interstitial fluid in chronically instrumented dogs.

METHODS

The catheter consisted of multiple perforations within a 2-cm segment of Micro-Renathane tubing that was implanted into the left ventricular myocardium between the left anterior descending (LAD) and left circumflex coronary artery (LCCA) perfusion territories and secured to the epicardium with a Silastic disk. Dogs (n=5) underwent brief (2 min) LAD occlusions once per hour, 8 times/day, 7 days/week for 2 weeks to stimulate coronary collateral growth. Another group of dogs (n=6) without repetitive coronary occlusions served as controls. Myocardial interstitial fluid was collected daily, and mitogenic activity was evaluated by the proliferative responses of growth-arrested, cultured vascular smooth muscle and endothelial cells.

RESULTS

All dogs tolerated catheter implantation without complication. Each catheter functioned well throughout the duration of the experiment. Myocardial interstitial fluid obtained using the exchange catheter in this model of repetitive coronary occlusion produced marked proliferation of vascular smooth muscle and endothelial cells in vitro.

DISCUSSION

The exchange catheter enables chronic in vivo sampling of myocardial interstitial fluid and may facilitate identification of mitogens involved in coronary collateral development.