Increased serum laminin and angiogenin concentrations in patients with peripheral arterial occlusive disease

Angiogenin Levels and Carotid Intima-Media Thickness in Patients with Type 1 Diabetes and Metabolic Syndrome

It is well documented that in patients with type 1 diabetes (DM1), decreased levels of angiogenin are associated with the development of overt nephropathy. However, little is known about angiogenin levels and subclinical macrovascular organ damage in patients with DM1 and concomitant metabolic syndrome (MS). Therefore, we analyzed the relationship between angiogenin levels and carotid intima-media thickness (cIMT) in DM1 patients with and without MS. We found that angiogenin concentration was significantly lower in DM1 patients compared to controls, while the cIMT measurements were comparable. Exclusion of patients with MS, patients with hypertension, undergoing treatment, or cigarette smokers did not change these findings. Of note, when comparing the subgroups of DM1 patients with and without MS, there was no significant difference between angiogenin levels. However, we did note a significant difference in these levels after the exclusion of smokers. The comparison of cIMT in these subgroups showed a significant difference between the study subgroups. This difference was no longer observed when the age of the patients was taken into account. In summary, it can be concluded that metabolic syndrome in patients with type 1 diabetes does not appear to impact angiogenin levels or cIMT.

Angiogenin-A Proposed Biomarker for Cardiovascular Disease-Is Not Associated With Long-Term Survival in Patients With Peripheral Artery Disease

We evaluated angiogenin as a prospective biomarker in peripheral artery disease (PAD) patients with and without claudication symptoms. A pilot study suggested an elevation of angiogenin in critical limb ischemia. However, in PAD patients, the predictive value of angiogenin has not yet been evaluated. For this purpose, 342 patients with PAD (age: 69 ± 10 years, 34.5% women) were followed-up for 7 years in a cross-sectional study. Angiogenin was measured by enzyme-linked immunosorbent assay. All-cause and cardiovascular mortality were analyzed by Cox regression. Angiogenin levels were higher in men (P = .001) and were associated with patient waist-to-hip ratio (P < .001), fasting triglycerides (P = .011), and inversely with estimated glomerular filtration rate (P = .009). However, angiogenin showed no association with age, characteristics of diabetes, markers of lipid metabolism, or C-reactive protein. Angiogenin did not correlate with markers of angiogenesis such as vascular endothelial growth factor, angiopoietin-2, or tie-2. Furthermore, angiogenin was not associated with PAD Fontaine stages or with patient ankle-brachial index in addition to all-cause mortality (hazard ratio [HR] = 1.09 [95% CI: 0.89-1.34]) or cardiovascular morality (HR = 1.05 [0.82-1.35]). These results suggest that angiogenin does not provide further information regarding outcome prediction in patients with PAD.

GSTM1 Modulates Expression of Endothelial Adhesion Molecules in Uremic Milieu

Deletion polymorphism of glutathione S-transferase M1 (GSTM1), a phase II detoxification and antioxidant enzyme, increases susceptibility to end-stage renal disease (ESRD) as well as the development of cardiovascular diseases (CVD) among ESRD patients and leads to their shorter cardiovascular survival. The mechanisms by which GSTM1 downregulation contributes to oxidative stress and inflammation in endothelial cells in uremic conditions have not been investigated so far. Therefore, the aim of the present study was to elucidate the effects of GSTM1 knockdown on oxidative stress and expression of a panel of inflammatory markers in human umbilical vein endothelial cells (HUVECs) exposed to uremic serum. Additionally, we aimed to discern whether GSTM1-null genotype is associated with serum levels of adhesion molecules in ESRD patients. HUVECs treated with uremic serum exhibited impaired redox balance characterized by enhanced lipid peroxidation and decreased antioxidant enzyme activities, independently of the GSTM1 knockdown. In response to uremic injury, HUVECs exhibited alteration in the expression of a series of inflammatory cytokines including retinol-binding protein 4 (RBP4), regulated on activation, normal T cell expressed and secreted (RANTES), C-reactive protein (CRP), angiogenin, dickkopf-1 (Dkk-1), and platelet factor 4 (PF4). GSTM1 knockdown in HUVECs showed upregulation of monocyte chemoattractant protein-1 (MCP-1), a cytokine involved in the regulation of monocyte migration and adhesion. These cells also have shown upregulated intracellular and vascular cell adhesion molecules (ICAM-1 and VCAM-1). In accordance with these findings, the levels of serum ICAM-1 and VCAM-1 (sICAM-1 and sVCAM-1) were increased in ESRD patients lacking GSTM1, in comparison with patients with the GSTM1-active genotype. Based on these results, it may be concluded that incubation of endothelial cells in uremic serum induces redox imbalance accompanied with altered expression of a series of cytokines involved in arteriosclerosis and atherosclerosis. The association of GSTM1 downregulation with the altered expression of adhesion molecules might be at least partly responsible for the increased susceptibility of ESRD patients to CVD.

Changes in FGF-23, Neutrophil/Platelet Activation Markers, and Angiogenin in Advanced Chronic Kidney Disease and Their Effect on Arterial Stiffness

AIMS

The aims of this study were to measure changes in fibroblast growth factor 23 (FGF-23), neutrophil (elastase, lactoferrin)/platelet activation marker (mean platelet volume-to-platelet count ratio [MPR]), and angiogenin according to the stage of chronic kidney disease (CKD), and to evaluate the association of FGF-23, elastase, lactoferrin, MPR, and angiogenin with arterial stiffness using brachial-ankle pulse wave velocity (ba-PWV) in CKD patients.

METHODS

According to the estimated glomerular filtration rate (eGFR) calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, the patients were allocated to five groups: (1) normal controls (eGFR ≥90 mL/min/1.73 m2 without pathologic, urine [proteinuria], blood [electrolyte], and imaging abnormalities; n = 22); (2) CKD stage 2 (eGFR 60-89 mL/min/1.73 m2; n = 17); (3) CKD stage 3 (eGFR 30-59 mL/min/1.73 m2; n = 22); (4) CKD stage 4 (eGFR 15-30 mL/min/1.73 m2; n = 17); and (5) CKD stage 5-hemodialysis (HD) (n = 30). All the patients were free of clinically apparent cardiovascular disease. Serum FGF-23, elastase, lactoferrin, and angiogenin concentrations and the MPR were measured to study the association of the above parameters with the clinical (age, sex, presence of diabetes mellitus, and blood pressure), biochemical (calcium, phosphorus, uric acid, intact parathyroid hormone [PTH], low-density lipoprotein cholesterol, and high-sensitivity C-reactive protein), and ba-PWV values of the CKD patients.

RESULTS

(1) The mean ba-PWV values were 1,497.2 ± 206.4 cm/s in the controls, 1,649.0 ± 247.9 cm/s in the CKD stage 2 group (p < 0.05 vs. controls), 1,655.8 ± 260.3 cm/s in the CKD stage 3 group (p < 0.05 vs. controls), 1,823.0 ± 402.4 cm/s in the CKD stage 4 group (p < 0.05 vs. controls and CKD stages 2 and 3), and 1,905.2 ± 374.1 cm/s in the CKD stage 5-HD group (p < 0.05 vs. controls and CKD stage 2). (2) The mean log10(FGF-23) concentration values were 0.77 ± 0.27, 0.97 ± 0.48, 1.10 ± 0.35 (p < 0.05 vs. controls and CKD stage 2), 1.35 ± 0.48 (p < 0.05 vs. controls and CKD stages 2 and 3), and 2.12 ± 0.82 (p < 0.05 vs. controls and CKD stages 2-4); the mean angiogenin levels were 230.6 ± 70.5 pg/mL, 283.0 ± 53.5 pg/mL (p < 0.05 vs. controls), 347.3 ± 76.9 pg/mL (p < 0.05 vs. controls and CKD stage 2), 445.9 ± 90.6 pg/mL (p < 0.05 vs. controls and CKD stages 2 and 3), and 370.9 ± 142.4 pg/mL (p < 0.05 vs. controls and CKD stages 2 and 3). (3) In the stage 3-4 CKD/HD patients, the mean elastase-to-neutrophil and lactoferrin-to-neutrophil ratios were significantly lower than in the controls and the stage 2 CKD patients. (4) Our multivariate linear regression analyses showed that age, pulse pressure, mean arterial pressure, PTH, and FGF-23 were independently associated with ba-PWV values.

CONCLUSIONS

Circulating FGF-23 and angiogenin concentrations gradually increased as CKD advanced, whereas neutrophil activation markers were significantly lower in the stage 3-4 CKD/HD patients than in the controls and stage 2 CKD patients. FGF-23 was weakly associated with ba-PWV values in patients with CKD/HD and no previous cardiovascular disease.

Three decades of research on angiogenin: a review and perspective

As a member of the vertebrate-specific secreted ribonucleases, angiogenin (ANG) was first isolated and identified solely by its ability to induce new blood vessel formation, and now, it has been recognized to play important roles in various physiological and pathological processes through regulating cell proliferation, survival, migration, invasion, and/or differentiation. ANG exhibits very weak ribonucleolytic activity that is critical for its biological functions, and exerts its functions through activating different signaling transduction pathways in different target cells. A series of recent studies have indicated that ANG contributes to cellular nucleic acid metabolism. Here, we comprehensively review the results of studies regarding the structure, mechanism, and function of ANG over the past three decades. Moreover, current problems and future research directions of ANG are discussed. The understanding of the function and mechanism of ANG in a wide context will help to better delineate its roles in diseases, especially in cancer and neurodegenerative diseases.

Niaspan attenuates the adverse effects of bone marrow stromal cell treatment of stroke in type one diabetic rats

AIMS

Our previous studies have found that bone-marrow-stromal cells (BMSC) therapy improves functional recovery after stroke in non-diabetic rats while increases brain hemorrhage and induces arteriosclerosis-like changes in type-one-diabetic (T1DM) rats. Niaspan treatment of stroke increases vascular stabilization, decreases brain hemorrhage and blood-brain-barrier (BBB) leakage in T1DM rats. We therefore tested the hypothesis that combination therapy of BMSC with Niaspan attenuates the side effects of BMSC monotherapy in T1DM rats.

METHODS

T1DM-rats induced by streptozotocin were subjected to 2 hours of middle-cerebral-artery occlusion (MCAo) and treated with: 1) PBS; 2) BMSC (5×10(6)); 3) Niaspan (40 mg/kg) daily for 14 days; 4) BMSC (5×10(6)) +Niaspan (40 mg/kg, daily for 14 days) combination starting at 24 hours after MCAo. All rats were monitored for 14 days.

RESULTS

Combination BMSC+Niaspan treatment of T1DM-MCAo rats did not increase brain hemorrhage, and significantly decreased BBB leakage and vascular arteriosclerosis-like changes as well as decreased Angiogenin, matrix metalloproteinase 9 (MMP9) and ED1 expression in ischemic brain and internal-carotid-artery compared to non-treatment control and BMSC monotherapy animals.

CONCLUSIONS

Combination therapy using BMSC with Niaspan decreases BBB leakage and cerebral arteriosclerosis-like changes. These beneficial effects may be attributed to the decreased expression of Angiogenin, MMP9 and ED1.

The relationship between serum levels of angiogenin, bFGF, VEGF, and ocular involvement in patients with Behçet's disease

OBJECTIVES

The aim of this study was to investigate the possible role of angiogenin, vascular endothelial growth factor, (VEGF) and basic fibroblast growth factor (bFGF) in the pathogenesis of BD.

DESIGN AND METHODS

Sixty-five patients with BD and 21 healthy control subjects were included in the study, and serum angiogenin, bFGF, and VEGF concentrations were measured by using in-vitro enzyme immunoassay (ELISA) kits according to the manufacturer's instructions.

RESULTS

The median serum angiogenin level was significantly higher in patients with BD (391.8; range:151.6-594.8 pg/ml) than controls (298.8; range:241.9-449.6 pg/ml) (p = 0.001). The levels were similar in both ocular and non-ocular BD patients (p = 0.537). The mean serum bFGF level was higher in patients with BD (38.8 ± 12.3 pg/ml) than controls (33.2 ± 11.3 pg/ml); the median serum VEGF level was also higher in BD patients (239.7; range:53-991.3 pg/ml) than controls (189.4; range:53.6-357.9 pg/ml). But these differences were not statistically significant. Serum bFGF and VEGF levels were also not different statistically in ocular and non-ocular Behçet's patients. There was no statistically significant relationship between serum angiogenin, bFGF, and VEGF levels and the presence of active eye disease or anatomic location of uveitis. While there was a correlation of borderline significance in angiogenin levels between the patients with anterior uveitis and panuveitis (p = 0.053), we did not obtain any correlation between serum angiogenin, bFGF, and VEGF levels and the duration of BD.

CONCLUSIONS

This study suggests that angiogenin may be associated with pathophysiology of BD, and highlights the need of further investigation of the role of angiogenin, bFGF, and VEGF serum levels in BD susceptibility and its clinical manifestations.

Ethnic/racial differences in circulating markers of angiogenesis and their association with cardiovascular risk factors and cardiovascular disease

OBJECTIVE

To determine (a) whether ethnic/racial differences exist in circulating markers of angiogenesis (Angiopoietin-1 (Ang-1), Angiopoietin-2 (Ang-2), soluble Tie-2 receptor (sTie-2) and Angiogenin) between South Asian (SA; from India, Pakistan and Bangladesh); Black African-Caribbean and White (W) ethnic groups, and (b) associations between these markers in stable cardiovascular disease (CVD) and its risk factors.

PATIENTS AND METHODS

We recruited 243 subjects (82 SA, 84 Black and 77 W) with symptomatic and clinically confirmed CVD (n=108), risk factor controls (with ≥ 1 cardiovascular risk factor, e.g. smoking, diabetes mellitus, dyslipidaemia, hypertension) and with ankle brachial pressure index >1) (n=64) and healthy controls free of CVD and risk factors (n=56). Angiogenic markers were measured by enzyme linked immunoassay.

RESULTS

In healthy controls, angiogenin was higher in SA and Black subjects, compared to Whites (p<0.05). sTie-2 correlated inversely with angiogenin (p=0.001), was higher in women (p=0.029) and was lower in smokers (p=0.007). Overall, age (p=0.001) was the only independent factor associated with angiopoietin-1. Angiogenin (p=0.01) and SBP (p=0.014) were both independently higher in the Black group compared to the White group.

CONCLUSIONS

Ethnic, racial, and demographic differences are evident in certain circulating markers of angiogenesis. With the exception of an effect of smoking on sTie-2, these differences are not influenced by the presence of other risk factors, nor the presence of stable cardiovascular disease.

Adverse effects of bone marrow stromal cell treatment of stroke in diabetic rats

BACKGROUND AND PURPOSE

Cell therapy with bone marrow stromal cells (BMSCs) improves functional recovery after stroke in nondiabetic rats. However, its effect on diabetics with stroke is unknown. This study investigated the effect of BMSCs on stroke outcome in Type 1 diabetic (T1DM) rats.

METHODS

T1DM was induced in adult male Wistar rats by injecting streptozotocin. Nondiabetic and T1DM rats were subjected to 2 hours of middle cerebral artery occlusion (MCAO), treated with or without BMSCs (3×10(6)) at 24 hours after MCAO, and monitored for 14 days.

RESULTS

Functional benefit was not detected in T1DM-MCAO treated with BMSC rats compared with corresponding T1DM-MCAO controls. BMSC treatment in T1DM-MCAO rats had increased mortality, blood-brain barrier leakage, brain hemorrhage, and angiogenesis. Internal carotid artery neointimal formation and cerebral arteriole narrowing/occlusion were also observed in T1DM-MCAO+BMSCs rats compared with T1DM-MCAO controls (P<0.05), but not in nondiabetic stroke rats. We further studied the underlying mechanisms responsible for BMSC-induced blood-brain barrier leakage and accelerated vascular damage in T1DM-MCAO rats. We found that the expression of angiogenin (an angiogenic factor) and ED1 (a marker for macrophages) was significantly increased in the T1DM-MCAO+BMSC rats in the ischemic brain and internal carotid artery compared with nontreated T1DM-MCAO rats, but not in nondiabetic stroke rats.

CONCLUSIONS

BMSC therapy in T1DM-MCAO rats does not improve functional outcome. On the contrary, it increases blood-brain barrier leakage and cerebral artery neointimal formation, and arteriosclerosis, which possibly is due to increased expression of angiogenin. Thus, BMSC treatment starting 24 hours after MCAO may not be beneficial for diabetic subjects with stroke.

High serum angiogenin at diagnosis predicts for failure on long-term treatment response and for poor overall survival in non-Hodgkin lymphoma

BACKGROUND

Angiogenin is a potent inducer of angiogenesis. We prospectively evaluated the prognostic significance of serum angiogenin from 204 consecutive non-Hodgkin lymphoma (NHL) patients diagnosed and treated in a single institution.

METHODS

Serum angiogenin, VEGF, and bFGF concentrations at diagnosis were determined using a quantitative sandwich enzyme immunoassay technique. Kaplan-Meier survival curves were compared by the log-rank test. Multivariate survival analyses were performed using the parametric model of Weibull and the non-parametric proportional hazards model of Cox.

RESULTS

Patients with a high serum angiogenin at diagnosis (>median; 401 ng/ml) had significantly lower 5-year survival rate than those with a low (≤ median) angiogenin (42% versus 63%, respectively; P = 0.0073). Serum angiogenin provided additional information to the International Prognostic Index (IPI) identifying a subgroup (serum angiogenin >median and IPI>1) with very poor prognosis (5-year survival 19%, P < 0.0001). In receiver operating characteristic (ROC) analyses the accuracy of the IPI to correctly classify patients with favourable or poor survival was improved from fair to good by complementing the IPI with serum angiogenin concentration. With patients who initially achieved complete response (CR) after chemotherapy, a high angiogenin at diagnosis (>median; relative risk (RR) 2.38; P = 0.0077) and an advanced tumour stage (III-IV; RR 2.41; P = 0.0087) were the only independent predictors for patients with unfavourable outcome although first responding well to therapy.

CONCLUSIONS

We conclude that elevated serum angiogenin surfaced as an independent predictor for failure in long-term treatment response and for poor overall survival in a series of 204 NHL patients, and might thus also complement the IPI in identifying the patients with particularly aggressive and/or treatment resistant disease.

The systemic angiogenic response during bone healing

INTRODUCTION

Angiogenesis is known to be a critical and closely regulated step during bone formation and fracture healing driven by a complex interaction of various cytokines. Delays in bone healing or even nonunion might therefore be associated with altered concentrations of specific angiogenic factors. These alterations might in turn be reflected by changes in serum concentrations.

METHOD

To determine physiological time courses of angiogenic cytokines during fracture healing as well as possible changes associated with failed consolidation, we prospectively collected serum samples from patients who had sustained surgical treatment for a long bone fracture. Fifteen patients without fracture healing 4 months after surgery (nonunion group) were matched to a collective of 15 patients with successful healing (union group). Serum concentrations of angiogenin (ANG), angiopoietin 2 (Ang-2), basic fibroblast growth factor (bFGF), platelet derived growth factor AB (PDGF-AB), pleiotrophin (PTN) and vascular endothelial growth factor (VEGF) were measured using enzyme linked immunosorbent assays over a period of 24 weeks.

RESULTS

Compared to reference values of healthy uninjured controls serum concentrations of VEGF, bFGF and PDGF were increased in both groups. Peak concentrations of these cytokines were reached during early fracture healing. Serum concentrations of bFGF and PDGF-AB were significantly higher in the union group at 2 and 4 weeks after the injury when compared to the nonunion group. Serum concentrations of ANG and Ang-2 declined steadily from the first measurement in normal healing fractures, while no significant changes over time could be detected for serum concentrations of these factures in nonunion patients. PTN serum levels increased asymptotically over the entire investigation in timely fracture healing while no such increase could be detected during delayed healing.

CONCLUSION

We conclude that fracture healing in human subjects is accompanied by distinct changes in systemic levels of specific angiogenic factors. Significant alterations of these physiologic changes in patients developing a fracture nonunion over time could be detected as early as 2 (bFGF) and 4 weeks (PDGF-AB) after initial trauma surgery.

Plasma indices of angiogenesis in rheumatoid disease: relationship to cardiovascular risk factors and cardiac function

INTRODUCTION

Rheumatoid Disease (RD) is associated with increased rates of cardiovascular disease (CVD). Angiogenesis is central to RD, and well-recognized in CVD. We hypothesised that plasma levels of two indices associated with angiogenesis, vascular endothelial growth factor (VEGF) and angiogenin, would be higher among RD patients compared to healthy controls (HC), would relate to CVD risk factors, calculated 10-year coronary heart disease (CHD) and stroke risk scores.

METHODS

144 clinic patients with established RD and 63 HC were recruited in a cross-sectional study. RD patients were grouped according to the presence (RD-CVD, n=73 or absence (non-CVD RD; n=71) of CVD risk factors. Angiogenin and VEGF levels were quantified by ELISA.

RESULTS

There were no significant differences for VEGF or angiogenin, between RD-CVD, non-CVD RD and HC groups (p=NS). Calculated risks for both CHD (p=0.017) and stroke (p=0.016) were higher when RD-CVD was compared to non-CVD RD and HC. Upon multivariate analysis, methotrexate use (p=0.006) and prior mycocardial infarction (MI) (p=0.034) were associated with higher angiogenin levels; body mass index (BMI) (p=0.034) and presence of RD (p=0.029) itself predicted lower levels. For RD patients, serum creatinine (p<0.001) and CRP levels, VEGF levels, and NSAID/COX2 inhibitor use (all p<0.05) were independently associated with CHD risk; plasma VEGF and serum creatinine levels were independently associated with stroke risk (p<0.05).

CONCLUSIONS

Although levels of angiogenin were not significantly different between HC and RD patients, RD may have some influence on their variation. Methotrexate use and prior MI predicted higher angiogenin levels, whilst levels of VEGF were negatively associated with 10-year CHD and stroke risk.

Mechanisms of action of angiogenin

Angiogenin induces angiogenesis by activating vessel endothelial and smooth muscle cells and triggering a number of biological processes, including cell migration, invasion, proliferation, and formation of tubular structures. It has been reported that angiogenin plays its functions mainly through four pathways: (1) exerting its ribonucleolytic activity; (2) binding to membrane actin and then inducing basement membrane degradation; (3) binding to a putative 170-kDa protein and subsequently transducing signal into cytoplasm; and (4) translocating into the nucleus of target cells directly and then enhancing ribosomal RNA transcription. Angiogenin can also translocate into the nucleus of cancer cells and induces the corresponding cell proliferation. Furthermore, angiogenin has neuroprotective activities in the central nervous system and the loss of its function may be related to amyotrophic lateral sclerosis. This review intends to conclude the mechanisms underlying these actions of angiogenin and give a perspective on future research.

Elevated angiogenin levels in chronic heart failure

BACKGROUND

Abnormal indices of angiogenesis have been reported in chronic heart failure (CHF). We tested the hypothesis that circulating angiogenin (a potent inducer of neovascularization in vivo) is higher in CHF patients compared with controls and associated with indices of CHF severity: brain natriuretic peptide (BNP), Simpson's left ventricular ejection fraction (EF), and New York Heart Association (NYHA) class.

METHODS

Using a cross-sectional approach, we measured serum angiogenin and BNP levels in 109 consecutive patients with CHF (85 males; mean age 60 (standard deviation (SD) 10 yrs) and 112 asymptomatic controls with normal cardiac function and related levels to echocardiographic parameters.

RESULTS

Angiogenin was significantly higher in CHF patients compared to controls (P < 0.001). On univariate analysis, angiogenin was positively associated with age, plasma glucose, insulin, and BNP (all P < 0.001); and negatively correlated with diastolic blood pressure (P = 0.04) and EF (P = 0.002). Angiogenin levels increased in an ordinal fashion with NYHA class, exaggerated by the presence of diabetes mellitus (pseudo R2 = 0.15, P < 0.001). In multivariate analysis, angiogenin levels were only associated with deteriorating NYHA classification (beta = 0.14 (95% confidence interval (CI) 0.09-0.19), P < 0.001). Angiogenin was also a modest discriminator for the presence of CHF (area under the curve 0.72; 95% CI 0.62-0.82), P < 0.001).

CONCLUSION

Angiogenin is related to worsening heart failure severity (NYHA classification), with the highest levels in NYHA class III. Further research is warranted to determine the validity of angiogenin in a diagnostic and prognostic capacity in CHF.

Angiogenin: a review of the pathophysiology and potential clinical applications

Angiogenin is a member of the ribonuclease (RNase) superfamily: enzymes of innate substrate specificity, but divergent functional capacities. Angiogenin is a normal constituent of the circulation and contained in a vasculature that rarely undergoes proliferation, but in some physiological and pathological conditions its levels increase in blood, promoting neovascularization. Hence, angiogenesis is a common pathophysiological attribute of angiogenin. In malignant disease, the most studied pathological state in regard to angionenin, abnormally high levels are seen, which may be of prognostic significance. Angiogenin has also been studied in other non-malignant pathological states. The aim of this review article is to provide an overview of the biochemistry and physiology of angiogenin, specifically in relation to the human pathological states where angiogenin has been implicated and finally, its potential clinical applications.

Elevated expression of angiogenin in prostate cancer and its precursors

PURPOSE

Angiogenin is a polypeptide involved in the formation and establishment of new blood vessels necessary for growth and metastasis of numerous malignant neoplasms, including prostatic adenocarcinoma. Antiangiogenin therapy inhibits the establishment, growth, and metastasis of prostatic adenocarcinoma in animal studies. In this study, we have investigated the expression of angiogenin in prostatic adenocarcinoma, high-grade prostatic intraepithelial neoplasia, and adjacent benign prostatic epithelium in a large cohort of prostatectomy specimens.

METHODS

We have studied the expression of angiogenin by immunohistochemistry in prostatic adenocarcinoma, high-grade prostatic intraepithelial neoplasia, and adjacent benign prostatic tissue in 107 human total prostatectomy specimens.

RESULTS

The percentage of cells staining positively for angiogenin in benign prostatic glandular epithelium (mean = 17%) was significantly less than for high-grade prostatic intraepithelial neoplasia (mean = 58%, P < 0.001) and prostatic adenocarcinoma (mean = 60%, P < 0.001). Compared with adjacent benign prostatic epithelium, the staining intensity was significantly greater in high-grade prostatic intraepithelial neoplasia (P < 0.001) and prostatic adenocarcinoma (P < 0.001). Furthermore, staining intensity has significantly stronger in prostatic adenocarcinoma versus high-grade prostatic intraepithelial neoplasia (P = 0.0023). However, there was no correlation of angiogenin expression with various clinical and pathologic variables examined, including age at surgery, Gleason scores, pathologic stage, tumor extent, angiolymphatic invasion, extraprostatic extension, seminal vesical invasion, lymph node metastasis, surgical margin status, presence of prostatic intraepithelial neoplasia, and perineural invasion.

CONCLUSION

Angiogenin expression in prostatic tissue increases as prostatic epithelial cells evolve from a benign to an invasive phenotype. The increasing expression of prostatic adenocarcinoma in the progression from benign prostate to high-grade prostatic intraepithelial neoplasia and ultimately to prostatic adenocarcinoma are consistent with previous studies showing the influential role that angiogenin plays in the growth, invasion, and metastasis of prostatic adenocarcinoma and many other malignant tumors.

Systemic regulation of angiogenesis and matrix degradation in bone regeneration--distraction osteogenesis compared to rigid fracture healing

Aim of this study was the investigation of systemic biochemical regulation mechanisms of bone regeneration by angiogenic and matrix-degrading enzymes during distraction osteogenesis compared to rigid osteotomy bone healing. Serum samples of 10 otherwise healthy patients with callus distraction for lower limb-lengthening and 10 osteotomy patients undergoing elective axis correction have been collected prospectively in a standardized time schedule before and up to 6 months after the procedure. At the end of the individual investigation period, concentrations of metalloproteinases (MMP-9, -13), tissue inhibitors of metalloproteinases (TIMP-1, TIMP-2) and the angiogenic factors angiogenin and VEGF have been detected by use of commercially available enzyme immunoassays. Results have been compared to our preliminary study on proMMP-1-3. In distraction osteogenesis, significantly elevated serum concentrations compared to baseline could be detected postoperatively for proMMP-1, MMP-9, TIMP-1, angiogenin and VEGF but not for proMMP-2, proMMP-3 or TIMP-2. In patients with rigid osteotomy healing, MMP-9, TIMP-1, TIMP-2, angiogenin and VEGF were significantly increased respectively. Comparison of both patient collectives revealed significantly higher increases of serum proMMP-1, VEGF and TIMP-1 in distraction patients during the lengthening period and significantly higher serum concentrations of TIMP-2 in late fracture healing period in osteotomy patients. Serum levels of MMP-13 were below the lowest standards, and therefore quantitative analysis was not possible. Bone regeneration in distraction osteogenesis and rigid osteotomy healing is accompanied by systemic increase of matrix-degrading and angiogenic factors in a certain time course and quantity. This might reflect biochemical regulation of local bone healing in the circulation. ProMMP-1, VEGF and TIMP-1 seem to be key regulatory factors during distraction osteogenesis.

The effects of growth hormone status on circulating levels of vascular growth factors

BACKGROUND

Vascular growth factors are important not only in angiogenesis but also for the maintenance of normal endothelial integrity and function. Elevated levels of vascular endothelial growth factor (VEGF), angiopoietin-2, hepatocyte growth factor (HGF), endostatin and angiogenin have been associated with endothelial dysfunction and atherosclerosis. Both acromegaly and growth hormone deficiency (GHD) are associated with endothelial dysfunction and changes in blood vessel morphology.

AIM

To investigate the effect of GH status on the circulating levels of angiogenic factors.

DESIGN

We measured the levels of six endothelial growth modulators, four angiogenic growth factors and two inhibitors of angiogenesis in 35 untreated acromegalics, 36 untreated GH-deficient subjects and 101 normal control subjects. Fifteen GH-deficient subjects were also studied before and 1 year after treatment with GH.

RESULTS

Mean angiogenin concentrations were increased in acromegaly and decreased in GH-deficient subjects compared to control subjects. Endostatin levels showed a similar pattern although the elevated levels in acromegalic subjects did not achieve statistical significance. Angiogenin and endostatin levels both correlated significantly with IGF-I levels (R = 0.61, P < 0.001 and R = 0.22, P < 0.01, respectively). The relationship between angiogenin and IGF-I levels remained significant even after correction for gender, age, body mass index (BMI) and insulin resistance. There were no significant differences in the levels of HGF, VEGF, VEGF-C or angiopoietin-2 between the three groups. VEGF-D levels were elevated in both acromegalic and GH-deficient male subjects. A similar pattern was apparent in female subjects. After GH treatment, a significant reduction in VEGF-D levels and a significant rise in endostatin levels were observed in GH-deficient subjects. A nonsignificant increase in angiogenin levels was also observed.

CONCLUSION

These data indicate that significant perturbations in the levels of vascular growth modulators are present in both acromegaly and GHD. While changes in endostatin and angiogenin levels appear to correlate with IGF-I levels, VEGF-D levels show similar perturbations in both acromegaly and GHD. Further studies are required to determine the relationship of the perturbations to endothelial dysfunction in these conditions.

Serum angiogenin in inflammatory bowel disease

Angiogenesis-promoting cytokines have been suggested to play an important role in inflammatory bowel disease (IBD) since they promote inflammation by increasing vascular permeability and mediate tissue repair by activating fibroblasts. The aim of the present study was to evaluate the serum levels of angiogenin, a potent angiogenic factor, in patients with ulcerative colitis (UC) and Crohn's disease (CD). Angiogenin serum levels were measured in 154 IBD patients (78 UC and 76 CD), in 18 cases with other causes of intestinal inflammation, and in 84 matched healthy controls using a commercially available enzyme-linked immunosorbent assay. Angiogenin levels were assessed in terms of disease activity, type, localization, and treatment. Mean (+/-SD) serum angiogenin levels were 526.5+/-224.1 ng/ml in UC patients, 508.8+/-228.5 ng/ml in CD patients, 394.6+/-137.6 ng/ml in healthy controls, and 448.1+/-167.8 ng/ml in patients with non-IBD intestinal inflammation. A statistically significant difference among the mean levels of angiogenin in the four groups was found (P = 0.0003). IBD patients with early disease had a significantly lower mean serum angiogenin compared with patients with late disease (P = 0.03). No significant association between angiogenin levels and disease activity, localization, disease type, or treatment was found. Serum angiogenin is elevated in patients with IBD. The increased serum angiogenin suggests that angiogenin may mediate angiogenesis and vascular permeability in the mucosa of patients with IBD.

Serum laminin and collagen IV in inflammatory bowel disease

BACKGROUND

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AIMS

Laminin and collagen IV have been proposed as extracellular matrix serum markers. Because fibrosis is a major complication of inflammatory bowel disease, serum concentrations of laminin and collagen IV were measured in patients with ulcerative colitis (UC) and Crohn's disease (CD) and compared with inflammatory and healthy controls.

METHODS

Laminin and collagen IV serum concentrations were measured in 170 patients with inflammatory bowel disease (86 UC and 84 CD), in 23 patients with other causes of intestinal inflammation, and in 80 matched healthy controls using commercially available enzyme linked immunosorbent assays. Laminin and collagen IV concentrations were correlated with disease activity, type, localisation, and treatment.

RESULTS

Mean (SD) serum laminin concentrations were 281.0 (110.1) ng/ml in patients with UC, 275.6 (106.7) ng/ml in patients with CD, 192.0 (17.8) ng/ml in healthy controls, and 198.5 (32.5) ng/ml in inflammatory controls. Mean (SD) serum collagen IV concentrations were 72.8 (22.9) ng/ml in patients with UC, 71.0 (18.2) in patients with CD, 79.8 (12.2) ng/ml in healthy controls, and 88.9 (24.6) ng/ml in inflammatory controls. There was a significant difference among the four groups (p < 0.0001) for both markers. There was a strong correlation between serum laminin, but not collagen IV, and disease activity in both diseases. No significant association was found between these markers and disease localisation or disease type.

CONCLUSIONS

Serum concentrations of laminin are increased, whereas serum concentrations of collagen IV are decreased, in patients with inflammatory bowel disease. They may be useful surrogate markers for sustained inflammation and tissue remodelling.

Over-expression and secretion of angiogenin in intrauterine growth retardation placenta

Human angiogenin is a potent inducer of neovascularization. There is a strong evidence to suggest that it might be involved in morphological and angiogenic changes in the placenta, that are necessary for a successful fetal outcome during pregnancy. However, its precise role in the pathogenesis of abnormal pregnancies is yet unknown. Intrauterine growth retardation (IUGR), an abnormal pregnancy is not a specific disease entity per se, but rather a manifestation of many possible fetal and maternal disorders. In this study, we demonstrated, for the first time, that placental explants in vitro secrete significantly elevated levels of angiogenin in placental tissues from patients with IUGR. We also observed enhanced mRNA expression in placenta from these patients. In addition, using the immunohistochemical methods, we observed identical staining of angiogenin to villous syncytiotrophobalst and fetal endothelial cells in both IUGR and normal placenta. Functionally active placental explants were used to detect immunoreactive angiogenin in conditioned media of all the samples from IUGR placenta and normal term group. The mean levels of angiogenin secreted by IUGR placenta were 1.4-, 1.6-, and 1.3-fold higher (P < 0.01) than normal term samples at 24, 48, and 72 hr of culture, respectively. Expression profiles of angiogenin from term and IUGR cases are in agreement with its mRNA levels and immunoblot analysis. In conclusion, the significant elevated levels of angiogenin in IUGR placenta may provide a molecular mechanism for the abnormal placental development.

Expression and localization of angiogenin in placenta: enhanced levels at term over first trimester villi

Human angiogenin, a 14-kDa non-glycosylated polypeptide with both angiogenic and ribonucleolytic activities, is implicated in angiogenesis, a complex process of proliferation and formation of new capillary blood vessels from existing blood vessels. Placental growth requires extensive angiogenesis, which develops its vascular structure in both fetal chorionic villi and maternal deciduas. In this study, we investigated the expression profiles of angiogenin in placental villi from early and late gestation at both mRNA and protein levels using explant cultures in vitro followed by RT-PCR, immunoblot, and immunohistochemical analyses. From functionally active placental explants, angiogenin was detected in conditioned media of all the samples from first trimester and term group. The mean levels of angiogenin produced by term villi were found to be 2.6-, 2.1-, and 2.2-fold higher (P < 0.01) than first trimester villi at 24, 48, and 72 hr of culture, respectively. Expression profiles of angiogenin from term and first trimester villi seem to agree with its mRNA levels and immunoblot analysis; the expression in term villi was twice that in first trimester villi. The presence of angiogenin in placental villi and upregulation of its production towards term indicate that angiogenin production by the placenta is specific to the developmental stage. In conclusion, the observed changes in the localization and mRNA expression of angiogenin during placental development raise the possibility that it is involved in morphological and angiogenic changes in this endocrine organ vital to the successful fetal outcome during pregnancy.

Blood levels of angiogenin and vascular endothelial growth factor are elevated in myelodysplastic syndromes and in acute myeloid leukemia

Angiogenesis is of prognostic importance not only in solid tumors but also in malignant blood diseases. We measured levels of vascular endothelial growth factor (VEGF), angiogenin (ANG), and basic fibroblast growth factor (bFGF) in peripheral blood samples from 65 patients with myelodysplastic syndrome (MDS), from 25 patients with de novo acute myeloid leukemia (AML), and from 50 healthy donors. In matched samples, VEGF levels in serum were substantially higher than VEGF levels in plasma (380.7 +/- 56 pg/ml vs. 45.3 +/- 4.5 pg/ml, mean +/- SEM, p < 0.001), whereas serum and plasma levels of ANG were comparable and significantly correlated (r = 0.8; p < 0.01). Compared to normal controls (1.3 +/- 0.09 pg), serum levels of VEGF corrected for the peripheral blood platelet count (VEGF/10(6) platelets, VEGF(PLT)) were elevated in patients with refractory anemia (RA; 3.1 +/- 0.8 pg, p < 0.01), and reached maximal values in patients with advanced stage MDS (RAEB, RAEB-t) (3.5 +/- 0.6 pg, p < 0.001), de novo AML (3.6 +/- 1.1 pg, p < 0.05), and chronic myelomonocytic leukemia (CMML; 3.7 +/- 0.9 pg; p < 0.001). Levels of soluble ANG were elevated in RA (351 +/- 25.7 ng/ml, p < 0.001), in RAEB/RAEB-t (402 +/- 17.9 ng/ml; p < 0.001), in CMML (413.8 +/- 29.5 ng/ml; p < 0.001), and in patients with AML (305.1 +/- 17.1 ng/ml; p < 0.01, controls 255.4 +/- 8.1 ng/ml). Serum bFGF was neither elevated in MDS nor in AML patients. These results suggest that VEGF(PLT) is a marker of disease progression in MDS. Moreover, we show for the first time that elevated blood levels of ANG can be found in patients with myeloid malignancies, suggesting a role of ANG in the pathogenesis of these diseases.

Homocysteine and laminin are not prognostic markers in patients with septic inflammatory response syndrome

The aim of this study was to measure plasma homocysteine and laminin concentrations in patients with nonbacteremic systemic inflammatory response syndrome (SIRS) and to compare them with those of a healthy control group. Concerning laminin, significant increased concentrations could be observed in the SIRS group compared to the control group, but for homocysteine, no significance could be observed. In summary, homocysteine and laminin levels are not useful in the prediction of a patient's outcome.

Vitamin C deficiency in guinea pigs differentially affects the expression of type IV collagen, laminin, and elastin in blood vessels

Vitamin C deficiency causes morphologic changes in the endothelial and smooth muscle compartments of guinea pig blood vessels. Endothelial cells synthesize the basement membrane components, type IV collagen and laminin, and smooth muscle cells synthesize elastin in blood vessels. Therefore, we examined the possibility that vitamin C deficiency affects the expression of these proteins. Decreased expression of types I and II collagens in other tissues of vitamin C-deficient guinea pigs is associated with weight loss and the consequent induction of insulin-like growth factor binding proteins; thus we also used food deprivation to induce weight loss. Female guinea pigs received a vitamin C-free diet, supplemented orally with ascorbate. Vitamin C-deficient guinea pigs received the same diet but no ascorbate, and the food-deprived group received no food, but were supplemented with vitamin C. Concentrations of mRNAs for basement membrane components and elastin in blood vessels were measured by Northern blotting; overall basement membrane metabolism was assessed by measuring immunoreactive laminin and type IV 7S collagen in serum. Laminin mRNA in blood vessels and serum laminin concentrations were unaffected by vitamin C deficiency. Concentrations of type IV collagen and elastin mRNAs in blood vessels were not significantly affected in moderately scorbutic guinea pigs (0-7% weight loss), but with increased weight loss, type IV collagen mRNA was 57% (P < 0.05) and elastin mRNA was 3% (P < 0. 01) of normal values. In food-deprived guinea pigs, type IV collagen mRNA was 51% (P < 0.05) and elastin mRNA was 35% (P < 0.05) of normal. Serum type IV 7S collagen concentrations were 25% of normal in scorbutic guinea pigs with extensive weight loss. The lower expression of type IV collagen and elastin mRNAs in blood vessels may contribute to defects observed in blood vessels during scurvy.

Detection, quantitation, and localization of bovine angiogenin by immunological assays

Bovine angiogenin (bAng) is a potent blood vessel inducing protein found in bovine serum and milk. Antisera have been raised against bAng. Western blot analysis for bAng indicated that the polyclonal antibody recognized bAng specifically, and no cross-reactivity with bovine RNase A, a protein homologous to bAng, was observed. The sandwich enzyme-linked immunosorbent assay for bAng was sensitive to 10 pg of bAng, and this assay was able to quantitate bAng in bovine serum (100-180 ng/mL) and milk (4-8 micrograms/mL). Strong positive immunohistochemical reactions were detected in alveolar cells, the secretion of alveolar cells and excretory ducts in sections of cow mammary gland, epithelial cells of visceral peritoneum and bile-duct in sections of cow liver, and epithelial cells and mucous glands in sections of cow gallbladder. These results suggest that epithelial cells and secretory cells are major sites of angiogenin synthesis.