Evaluation of recombinant endostatin in the treatment of atherosclerotic plaques and neovascularization in rabbits

Endostatin in Renal and Cardiovascular Diseases

Endostatin, a protein derived from the cleavage of collagen XVIII by the action of proteases, is an endogenous inhibitor known for its ability to inhibit proliferation and migration of endothelial cells, angiogenesis, and tumor growth. Angiogenesis is defined as the formation of new blood vessels from pre-existing vasculature, which is crucial in many physiological processes, such as embryogenesis, tissue regeneration, and neoplasia.

SUMMARY

Increasing evidence shows that dysregulation of angiogenesis is crucial for the pathogenesis of renal and cardiovascular diseases. Endostatin plays a pivotal role in the regulation of angiogenesis. Recent studies have provided evidence that circulating endostatin increases significantly in patients with kidney and heart failure and may also contribute to disease progression.

KEY MESSAGE

In the current review, we summarize the latest findings on preclinical and clinical studies analyzing the impact of endostatin on renal and cardiovascular diseases.

Altered Vascular Extracellular Matrix in the Pathogenesis of Atherosclerosis

Cardiovascular disease continues to grow as a massive global health burden, with coronary artery disease being one of its most lethal varieties. The pathogenesis of atherosclerosis induces changes in the blood vessel and its extracellular matrix (ECM) in each vascular layer. The alteration of the ECM homeostasis has significant modulatory effects on the inflammatory response, the proliferation and migration of vascular smooth muscle cells, neointimal formation, and vascular fibrosis seen in atherosclerosis. In this literature review, the role of the ECM, the multitude of components, and alterations to these components in the pathogenesis of atherosclerosis are discussed with a focus on versatile cellular phenotypes in the structure of blood vessel. An understanding of the various effects of ECM alterations opens up a plethora of therapeutic options that would mitigate the substantial health toll of atherosclerosis on the global population.

Effect of endostatin on Wnt pathway of stem-like cells in bladder cancer in tumor microenvironment

Wnt/β-catenin signaling pathway modulates miscellaneous biological events in cells including gene expression, cell growth, apoptosis, metabolism and transition. The aim of this study was to investigate the effect of endostatin on Wnt signaling pathway of stem-like cells in bladder cancer in tumor microenvironment. The qRT-PCR assay and western blot were conducted to evaluate related factors expressions of Wnt signaling pathway in both bladder cancer 5637 cells and stem cells. Loss of function assays were carried out to detect the influence of endostatin on the proliferation, migration, cell proliferation and apoptosis of bladder cancer cells. We demonstrated that endostatin triggered the degradation of β-catenin, a key mediator of Wnt signaling. The activation of the endostatin blocked β-catenin function and inhibited cell growth and migration of bladder cancer. In order to verify that the Wnt/β-catenin signaling pathway was inhibited by endostain in 5637 bladder cancer cells and stem cells, the Wnt/β-catenin signaling pathway-associated molecules, including DKK1, LRP5, TCF4, β-catenin, cyclin D1, and c-Myc, were evaluated in 5637 bladder cancer cells and stem cells. The western blotting results showed that expressions of these molecules were remarkably increased in the 5637 bladder cancer cells and stem cells compared to the control group. In summary, our study demonstrated that endostatin inhibited angiogenesis. The downregulation of the Wnt/β-catenin pathway may be engaged in the suppression of angiogenesis by endostatin in bladder cancer cells and cancer stem cells.

Ultrasound Microbubble Delivery Targeting Intraplaque Neovascularization Inhibits Atherosclerotic Plaque in an APOE-deficient Mouse Model

BACKGROUND/AIM

Intraplaque neovascularization is often associated with plaque formation, development and instability, and clinical symptoms in atherosclerosis. The aim of the present study was to investigate a new strategy for treating athrosclerosis by ultrasound-targeted microbubble delivery (UTMD) targeting intraplaque neovascularization in an APOE-deficient mouse model of atherosclerosis.

MATERIALS AND METHODS

A mouse model of atherosclerosis was induced by feeding Apoe^-/- mice a hypercholesterolemic diet and was verified with hematoxylin and eosin staining and intercellular adhesion molecule 1 (ICAM-1) expression. Targeted microbubbles (MB) were prepared by conjugating microbubbles with biotinylated antibody to ICAM1 (MBi) or with both biotinylated anti-ICAM1 and the angiogenesis inhibitor Endostar (MBie). The targeted microbubbles were analyzed with epifluorescence microscopy and flow cytometry. The animals with induced atherosclerotic plaques received MBi or MBie followed by UTMD treatment. Endostar treatment alone was given to other animals for comparison. Morphological assessment of atherosclerotic plaques was performed after treatment. The expression of angiogenesis marker CD31 was detected by immunohistochemical analysis.

RESULTS

Atherosclerotic plaques developed in the entire aorta with significant intraplaque ICAM-1 expression in the APOE-deficient mice following a 30-week hypercholesterolemic diet. Microbubbles were successfully conjugated with anti-ICAM-1 and Endostar, with a conjugation rate of 98.3% and 63.5%, respectively. UTMD with MBie significantly reduced the area of atherosclerotic plaque as compared to the model control (p<0.05). Treatment with Endostar and UTMD with MBie significantly reduced CD31 expression compared with the model control group (p<0.01). Greater significant inhibitory effect on CD31 expression was found in the group treated with UTMD and MBie compared to the Endostar- and UTMD with MBi groups (p<0.01).

CONCLUSION

UTMD targeting intraplaque neovascularization was found to inhibit atherosclerotic plaque in a mouse model of atherosclerosis, suggesting the potential of microbubble-mediated ultrasound technology in aiding drug delivery for atherosclerosis treatment.

The effects of pigment epithelium-derived factor on atherosclerosis: putative mechanisms of the process

Cardiovascular disease (CVD) is a leading cause of death worldwide. Atherosclerosis is believed to be the major cause of CVD, characterized by atherosclerotic lesion formation and plaque disruption. Although remarkable advances in understanding the mechanisms of atherosclerosis have been made, the application of these theories is still limited in the prevention and treatment of atherosclerosis. Therefore, novel and effective strategies to treat high-risk patients with atherosclerosis require further development. Pigment epithelium-derived factor (PEDF), a glycoprotein with anti-inflammatory, anti-oxidant, anti-angiogenic, anti-thrombotic and anti-tumorigenic properties, is of considerable interest in the prevention of atherosclerosis. Accumulating research has suggested that PEDF exerts beneficial effects on atherosclerotic lesions and CVD patients. Our group, along with colleagues, has demonstrated that PEDF may be associated with acute coronary syndrome (ACS), and that the polymorphisms of rs8075977 of PEDF are correlated with coronary artery disease (CAD). Moreover, we have explored the anti-atherosclerosis mechanisms of PEDF, showing that oxidized-low density lipoprotein (ox-LDL) reduced PEDF concentrations through the upregulation of reactive oxygen species (ROS), and that D-4F can protect endothelial cells against ox-LDL-induced injury by preventing the downregulation of PEDF. Additionally, PEDF might alleviate endothelial injury by inhibiting the Wnt/β-catenin pathway. These data suggest that PEDF may be a novel therapeutic target for the treatment of atherosclerosis. In this review, we will summarize the role of PEDF in the development of atherosclerosis, focusing on endothelial dysfunction, inflammation, oxidative stress, angiogenesis and cell proliferation. We will also discuss its promising therapeutic implications for atherosclerosis.

Endostatin: a promising biomarker in the cardiovascular continuum?

The current review article aims to provide an up-to-date summary of previous studies in humans that have reported the association between circulating endostatin levels and different cardiovascular phenotypes. We also aim to provide suggestions for future directions of future research evaluating endostatin as a clinically relevant cardiovascular biomarker. With a few exceptions, higher circulating levels of endostatin seem to reflect vascular and myocardial damage, and a worsened prognosis for cardiovascular events or mortality in individuals with hypertension, diabetes, kidney disease, cardiovascular disease, as well as in the general population. Circulating endostatin seems to be a promising biomarker for cardiovascular pathology, but there is not enough evidence to date to support the use of endostatin measurements in clinical practice.

The Relation between Serum Endostatin Level and Carotid Atherosclerosis in Healthy Residents of Japan: Results from the Kyushu and Okinawa Population Study (KOPS)

AIM

To examine the association between the serum endostatin levels and subclinical atherosclerosis independent of traditional risk factors in a healthy Japanese population.

METHODS

Among 1,057 residents who attended free public physical examinations between 2010 and 2011, we evaluated the data of 648 healthy residents for whom the serum endostatin level and common carotid intima-media thickness (IMT) were successfully measured.

RESULTS

The median endostatin level was 63.7 ng/mL (interquartile ranges: 49.7-93.2 ng/mL), and the mean carotid IMT was 0.68±0.12 mm. Residents with above median endostatin had significantly higher carotid IMT than did those with below median endostatin (0.71±0.14 vs. 0.65±0.09 mm, P＜0.001). Multiple linear regression analysis demonstrated that increased serum endostatin is significantly associated with carotid IMT (above vs. below median endostatin level; beta=0.11, P=0.03), independent of the known covariates of age, sex, body mass index, drinking and smoking status, systolic blood pressure, diastolic blood pressure, hemoglobin A1c, low density lipoprotein cholesterol, estimated glomerular filtration rate, and log-transformed high sensitive C-reactive protein.

CONCLUSIONS

A higher serum endostatin level reflected subclinical atherosclerosis in this Japanese population.

Angiotensin II-accelerated vulnerability of carotid plaque in a cholesterol-fed rabbit model-assessed with magnetic resonance imaging comparing to histopathology

This study sought to reveal the effect of angiotensin II (Ang II)-induced atherosclerotic vulnerability in rabbits and to determine whether in vivo magnetic resonance imaging (MRI) can determine the effect of Ang II on atherosclerotic development over time. In total, 24 elderly male New Zealand white rabbits underwent an intravascular balloon injury in the left common carotid artery (LCCA) and were subsequently fed a high cholesterol diet for 12 weeks. At 8 weeks, rabbits were randomly assigned to receive either Ang II (1.4 mg/kg/d, Ang II group) or vehicle (phosphate-buffered saline, control) via a subcutaneous osmotic minipump for 4 weeks. The rabbits were imaged three times: at baseline and at 8 and 12 weeks. After the 12-week MRI scanning, rabbits were euthanized to obtain pathological and histological data. Atherosclerotic plaques were identified in the 21 rabbits that survived the 12-week trial. Typical feature of vulnerable plaques (VP), intraplaque hemorrhage, were observed in 6 of 10 animals (60.0%) in the Ang II group. The Cohen K value of MR imaging between the AHA classifications was 0.82 (0.73–0.91; P < 0.001). MRI revealed that the change in carotid morphology were significantly different between the Ang II and control group plaques. Our results support an important role for Ang II in plaque vulnerability by promoting intraplaque neovascularization and hemorrhage as well as inflammation. The vulnerable features induced by Ang II in rabbit carotid plaques could be accurately monitored with MRI in vivo and confirmed with histomorphology.

Octanoylated ghrelin attenuates angiogenesis induced by oxLDL in human coronary artery endothelial cells via the GHSR1a-mediated NF-κB pathway

OBJECTIVE

Low concentrations of oxidized low-density lipoprotein (oxLDL) promote the in vitro angiogenesis of endothelial cells and play an important role in plaque angiogenesis, which may cause plaque vulnerability and enhance the risk of intravascular thrombosis. The aim of this research was to investigate the effects of octanoylated ghrelin on oxLDL-induced angiogenesis and the underlying molecular mechanisms involved in this process.

MATERIALS/METHODS

Human coronary artery endothelial cells (HCAECs) were incubated with 5 μg/ml oxLDL and treated with various concentrations of octanoylated ghrelin (10(-9)-10(-6)M) with or without inhibitors for 24h. Cell proliferation, migration, and in vitro angiogenesis were analyzed by bromodeoxyuridine (BrdU) staining and BrdU enzyme-linked immunosorbent assay (ELISA), transwell assay, and tube formation on Matrigel, respectively. NF-κB (nuclear factor κB) expression was determined by Western-blot analysis.

RESULTS

Treatment with oxLDL at 5 μg/ml enhanced the proliferation, migration and tube formation of HCAECs. In contrast, pretreatment with octanoylated ghrelin significantly attenuated in vitro angiogenesis in oxLDL-induced HCAECs. In addition, Western blot analysis indicated that NF-κB expression was increased after oxLDL treatment, and that this effect was significantly reversed by pretreatment with octanoylated ghrelin. However, the NF-κB inhibitor PDTC or the GHSR1a inhibitor [D-Lys3]-GHRP-6 abolished the effects of octanoylated ghrelin on the inhibition of angiogenesis and NF-κB p65 expression induced by oxLDL.

CONCLUSIONS

These findings suggest that octanoylated ghrelin attenuates angiogenesis induced by oxLDL in HCAECs via the inhibition of GHSR1a-mediated NF-κB pathway. Furthermore, octanoylated ghrelin may promote the stability of vulnerable plaques by inhibiting plaque angiogenesis.

The therapeuatic effect of Endostar on soft carotid plaque neovascularization in patients with non-small cell lung cancer

The purpose of this study was to investigate the effect of the angiogenesis inhibitor Endostar on carotid plaque neovascularization in patients with non-small cell lung cancer (NSCLC) using contrast-enhanced ultrasound (CEUS). Ninety-one patients who had NSCLC with soft carotid plaques were selected for treatment either with the NP regimen (vinorelbine + cisplatin) (43 patients) or with the ENP regimen (Endostar + NP) (48 patients). Plaque thickness and neovascularization of the plaque were assessed before and at 1 month after treatment using CEUS. Enhanced intensity (EI) of CEUS was used for quantification of plaque neovascularization. There was no significant changes in any group in thickness of plaque between recruitment and 1 month after treatment (P > 0.05 for all). There was no significant change in the EI of plaque in the controls or NP groups at 1 month after treatment (P > 0.05), while EI in the ENP group was significantly reduced at 1 month after treatment (P < 0.01) and significantly lower than that in the controls or NP group at 1 month after treatment (P < 0.001 both). This study indicates that carotid soft plaque neovascularization in patients with NSCLC can be reduced by anti-angiogenesis treatment.

Endostar, a modified recombinant human endostatin, suppresses angiogenesis through inhibition of Wnt/β-catenin signaling pathway

Endostar, a novel modified recombinant human endostatin, is now widely studied for the treatment of diseases that are characterized or caused by pathological angiogenesis. However, its molecular mechanism remains unclear. In this study, we investigated the effects of Endostar on the Wnt/β-catenin signaling pathway, which has emerged as an important aspect of angiogenesis. We showed that Endostar significantly inhibited the proliferation, migration, invasion, and capillary-like tube formation of human umbilical vascular endothelial cells in a dose-dependent manner. Using a luciferase reporter assay, we also demonstrated that Endostar suppressed β-catenin-dependent T cell factor transcriptional activity in increasing doses. Moreover, we found that Endostar treatment also restricted the stabilized mutant β-catenin-mediated increase in transcriptional activity, suggesting that Endostar exerts its inhibitory influence on Wnt/β-catenin signaling by targeting β-catenin or its downstream molecules. Western blot and immunofluorescence results revealed that Endostar significantly decreased nuclear and total β-catenin levels. Finally, we discovered that Endostar down-regulated cyclin D1 and VEGF, two proteins that are known as the downstream targets of Wnt/β-catenin signaling and that also play important roles in angiogenesis. Our findings suggested that Endostar inhibits angiogenesis and that the downregulation of the Wnt/β-catenin signaling pathway may be involved in the inhibition of angiogenesis by Endostar. These results support the use of Endostar in further clinical applications.

Serum endostatin concentrations are higher in men with symptoms of intermittent claudication

Objectives. A cleavage fragment of collagen XVIII, endostatin, is released into the circulation and has been demonstrated to have antiangiogenic effects in animal models. We hypothesized that circulating endostatin would be increased in patients with symptoms of lower limb peripheral artery disease. Design. Cross-sectional study. Participants. Community dwelling older men. Measurements. Intermittent claudication was defined using the Edinburgh Claudication Questionnaire (ECQ). Serum endostatin was measured by a commercial ELISA. The association of serum endostatin with intermittent claudication was examined using logistic regression adjusting for age, diabetes, hypertension, dyslipidemia, coronary heart disease, and stroke. Results. Serum endostatin was measured in 1114 men who completed the ECQ. 106 men had intermittent claudication, 291 had atypical pain, and 717 had no lower limb pain. Mean (±standard deviation) serum endostatin concentrations (ng/mL) were 145.22 ± 106.93 for men with intermittent claudication, 129.11 ± 79.80 for men with atypical pain, and 116.34 ± 66.57 for men with no lower limb pain; P < 0.001. A 70 ng/mL increase in endostatin was associated with a 1.17-fold rise in the adjusted odds of having intermittent claudication (OR 1.17, 95% confidence interval 1.00–1.37, and P = 0.050). Conclusions. Serum endostatin is raised in older men who have symptoms of intermittent claudication. The role of endostatin in the genesis and outcome of peripheral artery disease requires further investigation.

Exercise increases serum endostatin levels in female and male patients with diabetes and controls

Background

Type 2 diabetes mellitus (T2DM) is often associated with atherosclerotic changes in coronary vessels, most notably plaques. The angiostatic parameter endostatin is able to inhibit angiogenesis in tissue as well as in plaques and therefore plays an important role in physiological and pathological neovascularisation. The aim of the present study was to investigate sex-specific differences and the influence of exercise on circulating endostatin levels in patients suffering from diabetes, and control subjects.

Methods

In total, 42 T2DM-patients and 45 control subjects were investigated. They underwent a graded physical stress test (ergometry). Serum endostatin levels were measured in venous blood at rest and directly after reaching maximum workload.

Results

Females showed significantly higher endostatin levels at baseline measurements compared to men, independently of their underlying disease. In both female and male T2DM-patients endostatin levels were significantly lower compared to controls. Both groups and sexes showed a significant increase of endostatin after physical stress, whereas the extent of endostatin-increase was between 10.59-15.05%.

Conclusion

Middle-aged healthy female individuals as well as female T2DM-patients showed higher circulating serum endostatin levels compared to males, suggesting a hormonal influence on baseline circulating endostatin amounts. Exercise-induced increase in endostatin is also observable in patients suffering from T2DM. Concerning vascularisation, lower endostatin levels in T2DM might be advantageous. Concerning plaque stability, lower levels might be prejudicial.

Trial registration

Clinical Trial Registration-URL: http://clinicaltrials.gov/ct2/results?term=NCT01165515