Endostatin inhibits the proliferation and migration of B16 cells by inducing macrophage polarity to M1­type.

Malignant melanoma is a common skin tumor that easily metastasizes and has a poor prognosis. Endostatin is an endogenous vascular endothelial inhibitor that mainly suppresses tumor growth by inhibiting the proliferation of vascular endothelial cells and by reducing the formation of tumor microvessels, however the immunological function of endostatin remains unclear. Previously, we have found that an over­expression endostatin (pEndostatin) plasmid induced RAW264.7 cells' polarity to M1­type macrophage. To elucidate the effect of M1­type macrophages induced by endostatin on melanoma B16 cells, the present study transfected RAW264.7 cells with pEndostatin plasmid and co­cultured them with B16 cells. Compared with the control group, the expression of matrix metalloproteinase (MMP)­2, MMP­9 and proliferating cell nuclear antigen in B16 cells was inhibited by M1­type macrophages, but cleaved Caspase­3 and cleaved Caspase­8 were significantly upregulated and the ratio of Bax/Bcl­2 was increased. These results indicated that M1 macrophages induced by pEndostatin plasmid inhibited the proliferation and migration of B16 cells and promoted their apoptosis. These findings suggest that the inhibitory effect of endostatin on melanoma is not limited to directly inhibiting tumor microvessel formation, but it may also be related to regulating changes in macrophage polarity.

Endostatin stimulates proliferation and migration of adult rat cardiac fibroblasts through PI3K/Akt pathway.

Endostatin, a non-collagenous fragment of type XVIII collagen, has anti-angiogenic roles. Although the expression level of endostatin increases in some experimental models of cardiac diseases, its effects on cardiac remodeling have not been clarified. In this study, we investigated the effect of endostatin on proliferation, migration and collagen synthesis of cardiac fibroblasts, which are activated during the cardiac remodeling following myocardial infarction. Cardiac fibroblasts were isolated from adult male Wistar rats and treated with recombinant endostatin for 20min to 24h. Cell counting assay was used to determine a cell proliferation. Boyden chamber assay was performed to determine a cell migration. Wound-healing assay was performed for detecting a wound-induced migration. Expression of collagen type I and phosphorylation of Akt, extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) were detected by Western blotting. Endostatin (100-3000ng/ml) stimulated cell proliferation, migration and wound-induced migration but not collagen type I expression. Endostatin stimulated phosphorylation of Akt (Ser473) but not ERK, JNK and p38 MAPK. LY294002 (10µM), a PI3K/Akt pathway inhibitor, significantly inhibited the endostatin-induced proliferation and migration. N-acetyl-l-cysteine (NAC) (5mM), an antioxidant, significantly inhibited the endostatin-induced Akt phosphorylation. This study for the first time demonstrated that endostatin stimulates cell proliferation, migration and wound-induced migration of adult rat cardiac fibroblasts at least partly through the reactive oxygen species-dependent activation of Akt. Our findings suggest a novel function of endostatin except for an anti-angiogenic activity during the wound-healing process following myocardial infarction.

Macrophage elastase suppresses white adipose tissue expansion with cigarette smoking.

Macrophage elastase (MMP12) is a key mediator of cigarette smoke (CS)-induced emphysema, yet its role in other smoking related pathologies remains unclear. The weight suppressing effects of smoking are a major hindrance to cessation efforts, and MMP12 is known to suppress the vascularization on which adipose tissue growth depends by catalyzing the formation of antiangiogenic peptides endostatin and angiostatin. The goal of this study was to determine the role of MMP12 in adipose tissue growth and smoking-related suppression of weight gain. Whole body weights and white adipose depots from wild-type and Mmp12-deficient mice were collected during early postnatal development and after chronic CS exposure. Adipose tissue specimens were analyzed for angiogenic and adipocytic markers and for content of the antiangiogenic peptides endostatin and angiostatin. Cultured 3T3-L1 adipocytes were treated with adipose tissue homogenate to examine its effects on vascular endothelial growth factor (VEGF) expression and secretion. MMP12 content and activity were increased in the adipose tissue of wild-type mice at 2 weeks of age, leading to elevated endostatin production, inhibition of VEGF secretion, and decreased adipose tissue vascularity. By 8 weeks of age, adipose MMP12 levels subsided, and the protein was no longer detectable. However, chronic CS exposure led to macrophage accumulation and restored adipose MMP12 activity, thereby suppressing adipose tissue mass and vascularity. Our results reveal a novel systemic role for MMP12 in postnatal adipose tissue expansion and smoking-associated weight loss by suppressing vascularity within the white adipose tissue depots.

Treatment of medulloblastoma with oncolytic measles viruses expressing the angiogenesis inhibitors endostatin and angiostatin.

BACKGROUND: Medulloblastoma is the most common type of pediatric brain tumor. Although numerous factors influence patient survival rates, more than 30% of all cases will ultimately be refractory to conventional therapies. Current standards of care are also associated with significant morbidities, giving impetus for the development of new treatments. We have previously shown that oncolytic measles virotherapy is effective against medulloblastoma, leading to significant prolongation of survival and even cures in mouse xenograft models of localized and metastatic disease. Because medulloblastomas are known to be highly vascularized tumors, we reasoned that the addition of angiogenesis inhibitors could further enhance the efficacy of oncolytic measles virotherapy. Toward this end, we have engineered an oncolytic measles virus that express a fusion protein of endostatin and angiostatin, two endogenous and potent inhibitors of angiogenesis. METHODS: Oncolytic measles viruses encoding human and mouse variants of a secretable endostatin/angiostatin fusion protein were designed and rescued according to established protocols. These viruses, known as MV-hE:A and MV-mE:A respectively, were then evaluated for their anti-angiogenic potential and efficacy against medulloblastoma cell lines and orthotopic mouse models of localized disease. RESULTS: Medulloblastoma cells infected by MV-E:A readily secrete endostatin and angiostatin prior to lysis. The inclusion of the endostatin/angiostatin gene did not negatively impact the measles virus' cytotoxicity against medulloblastoma cells or alter its growth kinetics. Conditioned media obtained from these infected cells was capable of inhibiting multiple angiogenic factors in vitro, significantly reducing endothelial cell tube formation, viability and migration compared to conditioned media derived from cells infected by a control measles virus. Mice that were given a single intratumoral injection of MV-E:A likewise showed reduced numbers of tumor-associated blood vessels and a trend for increased survival compared to mice treated with the control virus. CONCLUSIONS: These data suggest that oncolytic measles viruses encoding anti-angiogenic proteins may have therapeutic benefit against medulloblastoma and support ongoing efforts to target angiogenesis in medulloblastoma.

Inhibition of endostatin/collagen XVIII deteriorates left ventricular remodeling and heart failure in rat myocardial infarction model.

BACKGROUND: Although therapeutic angiogenesis is a most promising strategy for the treatment of myocardial infarction (MI), it remains unknown if and how endogenous angiogenesis inhibitors, such as endostatin, regulate angiogenesis in MI. In the present study the role of endostatin in left ventricular (LV) remodeling and heart failure was tested in a rat MI model. METHODS AND RESULTS: When exposed to hypoxia, rat cardiomyocytes showed increased expression of endostatin. After MI induction in the rat MI model, endostatin expression was upregulated in cardiomyocytes, and serum endostatin levels were significantly elevated. Anti-endostatin antibody treatment resulted in significantly higher mortality of MI rats than controls. The MI rats with endostatin neutralization displayed adverse LV remodeling and severe heart failure compared with control MI rats. Although angiogenesis was increased, tissue remodeling and interstitial fibrosis were further exaggerated in post-MI hearts by endostatin neutralization. Furthermore, the expression and protease activity of matrix metalloproteinases -2 and -9, and of angiotensin-converting enzyme were markedly elevated by endostatin neutralization. CONCLUSIONS: Neutralization of endostatin worsens the symptoms and outcomes of MI in a rat model. The results imply that endogenous endostatin/collagen XVIII may suppress aberrant LV remodeling and heart failure after MI. (Circ J 2010; 74: 109 - 119).

Mesalamine restores angiogenic balance in experimental ulcerative colitis by reducing expression of endostatin and angiostatin: novel molecular mechanism for therapeutic action of mesalamine.

Mesalamine (5-aminosalicylate acid, 5-ASA) is an effective treatment for ulcerative colitis (UC). The mechanisms of its actions are not fully understood. Because angiogenesis is critical for healing UC, we examined whether 5-ASA alters the angiogenic balance between angiogenic factors [e.g., vascular endothelial growth factor (VEGF)] and antiangiogenic factors (e.g., endostatin and angiostatin) in the colon in experimental UC. Rats were treated with saline or 5-ASA (100 mg/kg) twice daily and euthanized 3 or 7 days after iodoacetamide-induced UC. Clinical signs (e.g., lethargy, diarrhea) and UC lesions were measured. Expression of VEGF, endostatin, angiostatin, tissue necrosis factor alpha (TNF-alpha), and matrix metalloproteinases (MMPs) 2 and 9 was determined by Western blots, enzyme-linked immunosorbent assay, and zymography in the distal colon. 5-ASA treatment reduced lethargy and diarrhea and significantly decreased colonic lesions (by approximately 50%) compared with saline treatment in UC (both, P < 0.05). 5-ASA did not reverse the increased levels of VEGF, but it significantly reduced expression of endostatin and angiostatin in UC compared with vehicle treatment (both, P < 0.05). Furthermore, 5-ASA treatment significantly diminished increased activity of TNF-alpha and MMP9 in UC. This is the first demonstration that 5-ASA treatment reverses an imbalance between the angiogenic factor VEGF and antiangiogenic factors endostatin and angiostatin in experimental UC. The effect of 5-ASA in UC may be caused by the down-regulation of expression of endostatin and angiostatin by modulation of MMP2 and MMP9 via inhibition of TNFalpha. The inhibition of antiangiogenic factors may represent a novel molecular mechanism of the therapeutic action of 5-ASA.

Protein kinase B inhibits endostatin-induced apoptosis in HUVECs.

Endostatin is a tumor-derived angiogenesis inhibitor, and the endogenous 20 kDa carboxyl-terminal fragment of collagen XVIII. In addition to inhibiting angiogenesis,endostatin inhibits tumor growth and the induction of apoptosis in several endothelial cell types. However, the mechanisms that regulate endostatin-induced apoptotic cell death are unclear. Here, we investigated apoptotic cell death and the underlying regulatory mechanisms elicited of endostatin in human umbilical vein endothelial cells (HUVECs). Endostatin was found to induce typical apoptotic features, such as, chromatin condensation and DNA fragmentation in these cells. Thus, as the phosphoinositide 3-OH kinase (PI3K)/protein kinase B (PKB) signaling pathway has been shown to prevent apoptosis in various cell types, we investigated whether this pathway could protect cells against endostatin induced apoptosis. It was found that the inhibition of PI3K/PKB significantly increased endostatin-induced apoptosis, and that endostatininduced cell death is physiologically linked to PKB-mediated cell survival through caspase-8.

Characterization of a monoclonal antibody that antagonizes the function of human endostatin.

Endostatin, a 20-kDa proteolytic fragment of collagen XVIII, is a potent inhibitor of angiogenesis and tumor growth. The anti-angiogenic effects of endostatin include inhibition of endothelial cell migration and proliferation, and inhibition of the activity of MMP2. Structure-function analysis of endostatin that implies this contravention function buried in separate fragments of endostatin introduces new issues into the understanding of the structure-function relationship of endostatin. We developed and characterized a novel murine MAb, 4E7, to human endostatin, which antagonizes the function of endostatin. As we show here, MAb 4E7 blocks the anti-migration/adhesion effects of endostatin in vitro and the anti-angiogenesis effect of endostatin in vivo, but the inhibition effect of endostatin on endothelial cell proliferation is not affected by MAb4E7. These results suggest that the anti-migration and anti-proliferation functions of endostatin may have distinct structural foundations.