Potential role of soluble angiopoietin-2 and Tie-2 in patients with inflammatory bowel disease

Ang-2 is a potential molecular marker for lymphatic metastasis and better response to bevacizumab therapy in ovarian cancer

PURPOSE

In ovarian cancer, there are two main routes of metastasis, namely intraperitoneal and retroperitoneal. Their biologic background is poorly understood. Identifying molecular markers involved might enable the development of tailored therapy regimens. Moreover, no reliable markers for response to anti-angiogenic treatment with bevacizumab are yet established. Angiopoietin-2 (Ang-2) is an angiogenic growth factor, involved in lymphatic activation and is associated with tumor progression. Here, we assessed the potential of Ang-2 as a molecular marker in metastasis and treatment of ovarian cancer.

METHODS

In our study, quantitative and qualitative protein Ang-2 expression in tumor tissue of ovarian cancer patients was analyzed by Western blot (n = 138) and immunohistochemistry (n = 58). Further, Ang-2 levels in blood samples were quantified in enzyme-linked immunosorbent assay (n = 38). Expression levels of different tumor spread patterns were evaluated, and survival analyses were made.

RESULTS

We observed that Ang-2 expression is significantly higher in tumors with retroperitoneal dissemination (pT1a-pT3b, pN1) compared to those showing intraperitoneal tumor growth (pT3c, pN0). In addition, patients with high Ang-2 expression have significantly longer overall survival compared to patients with low Ang-2 expression. Patients with high Ang-2 expression benefit significantly from therapy with bevacizumab.

CONCLUSION

All in all, Ang-2 may serve as a molecular marker for patients with tumors prone to spread to lymph nodes and for patients who might benefit from bevacizumab therapy.

Acidosis significantly alters immune checkpoint expression profiles of T cells from oesophageal adenocarcinoma patients

Tumour acidosis contributes to cancer progression by inhibiting anti-tumour immunity. However, the effect of acidosis on anti-tumour T cell phenotypes in oesophageal adenocarcinoma (OAC) is unknown. Therefore, this study investigated the effect of acidosis on anti-tumour T cell profiles and if immune checkpoint blockade (ICB) could enhance anti-tumour T cell immunity under acidosis. Acidic conditions substantially altered immune checkpoint expression profiles of OAC patient-derived T cells, upregulating TIM-3, LAG-3 and CTLA-4. Severe acidosis (pH 5.5) significantly decreased the percentage of central memory CD4⁺ T cells, an effect that was attenuated by ICB treatment. ICB increased T cell production of IFN-γ under moderate acidosis (pH 6.6) but not severe acidosis (pH 5.5) and decreased IL-10 production by T cells under severe acidic conditions only. A link between lactate and metastasis was also depicted; patients with nodal metastasis had higher serum lactate levels (p = 0.07) which also positively correlated with circulating levels of pro-angiogenic factor Tie-2. Our findings establish that acidosis-induced upregulation of immune checkpoints on T cells may potentially contribute to immune evasion and disease progression in OAC. However, acidic conditions curtailed ICB efficacy, supporting a rationale for utilizing systemic oral buffers to neutralize tumour acidity to improve ICB efficacy. Study schematic-PBMCs were isolated from OAC patients (A) and expanded ex vivo for 7 days using anti-CD3/28 +IL-2 T cell activation protocol (B) and further cultured for 48 h under increasing acidic conditions in the absence or presence of immune checkpoint blockade (nivolumab, ipilimumab or dual nivolumab + ipilimumab) (C). Immunophenotyping was then carried out to assess immune checkpoint expression profiles and anti-tumour T cell phenotypes (D). Serum lactate was assessed in OAC patients (E-F) and levels were correlated with patient demographics (G) and the levels of circulating immune/pro-angiogenic cytokines that were determined by multiplex ELISA (H). Key Findings-severe acidic conditions upregulated multiple immune checkpoints on T cells (I). Efficacy of ICB was curtailed under severe acidic conditions (J). Circulating lactate levels positively correlated with circulating levels of pro-angiogenic factor tie-2 and higher serum lactate levels were found in patients who had nodal metastasis (K).

Angiopoietin-2 Is an Early Predictor for Acute Gastrointestinal Injury and Intestinal Barrier Dysfunction in Patients with Acute Pancreatitis

BACKGROUNDS

Angiopoietin-2 (Ang-2) is a new predictor for acute pancreatitis (AP).

AIMS

To assess the predictive value of Ang-2 in determining the progress of AP and the subsequent acute gastrointestinal injury (AGI).

METHODS

This was a prospective study that enrolled 170 patients with AP and 100 healthy controls. Blood samples were collected within 24 h of the onset of AP.

RESULTS

The majority (108) of the patients were categorized as having MAP with the rest (62) classified as suffering from SAP. Considering AGI grading, there were 118 grade 1 and 12 grade 4 patients; in grades 2 and 3, there were 20 patients each. AP was accompanied by MODS and pancreatic necrosis in 46 and 24 cases, respectively. Eighty patients were admitted to the ICU, while mortality was reported among 7.1% patients. The plasma Ang-2 levels were higher among patients with AP than in controls. A similar trend prevailed, in patients with SAP compared to those with MAP. Ang-2 was significantly increased from AGI grade 1 through to grade 4, showing a desirable positive predictive accuracy. Moreover, Ang-2 also showed strong correlations with intestinal permeability as evaluated by d-lactate (DLA), diamine oxidase (DAO), and intestinal fatty acid binding proteins (I-FABPs). Tools (Ranson and APACHE II scores, CRP), which are used more conventionally, could not effectively distinguish the various grades of AGI. Furthermore, Ang-2 predicted poor prognosis and adverse outcomes, including mortality, among patients with AP.

CONCLUSIONS

This study showed Ang-2 to be an accurate early predictor for SAP, AGI, and intestinal barrier dysfunction, outperforming conventional biomarkers. Ang-2 levels also predicted the adverse outcomes and mortality due to AP.

Thalidomide Inhibits Angiogenesis via Downregulation of VEGF and Angiopoietin-2 in Crohn's Disease

Immune-mediated angiogenesis is important in the pathogenesis of inflammatory bowel disease and targeted treatment could alleviate the disease. Thalidomide is an effective drug in inflammatory bowel disease, which might be related to its multiple role in anti-inflammatory, immunoregulatory, and anti-angiogenesis. This study is to investigate the effect of thalidomide on angiogenesis in tissues from patients and in vitro cells. Angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), VEGF, and CD31 expressions in intestinal mucosa from pediatric CD patients before and after thalidomide treatment were measured by immunohistochemistry. Western blotting and polymerase chain reaction were performed to characterize the change of angiogenic factors before and after treatment in remission. Human umbilical vein endothelial cells (HUVECs) treated by thalidomide were used to examine its effect on endothelial cell proliferation and migration and capillary-like structures. Results showed that VEGF and Ang-2 levels were significantly greater in CD patients over controls. Thalidomide produced a significant reduction in protein expression of Ang-2 and VEGF, along with a decrease in mRNA expression of Ang-2. While, Ang-1 level did not show a statistically significant change. Thalidomide significantly inhibited cell proliferation in a dose-dependent manner. It also suppressed VEGF- and Ang-2-induced cell migration and capillary-like tube formation in HUVECs. Therefore, our study suggests that VEGF and Ang-2 levels are up-regulated in pediatric CD patients. It also indicated that thalidomide can be able to deactivate endothelium by the downregulation effect on angiogenic factors by targeting VEGF and Ang-2.

Mannitol and renal graft injury in patients undergoing deceased donor renal transplantation - a randomized controlled clinical trial

Background

Ischaemia/reperfusion (I/R) injury is associated with renal tissue damage during deceased donor renal transplantation. The effect of mannitol to reduce I/R injury during graft reperfusion in renal transplant recipients is based on weak evidence. We evaluated the effect of mannitol to reduce renal graft injury represented by 16 serum biomarkers, which are indicators for different important pathophysiological pathways. Our primary outcome were differences in biomarker concentrations between the mannitol and the placebo group 24 h after graft reperfusion. Additionally, we performed a linear mixed linear model to account biomarker concentrations before renal transplantation.

Methods

Thirty-four patients undergoing deceased donor renal transplantation were randomly assigned to receive either 20% mannitol or 0.9% NaCl placebo solution before, during, and after graft reperfusion. Sixteen serum biomarkers (MMP1, CHI3L1, CCL2, MMP8, HGF, GH, FGF23, Tie2, VCAM1, TNFR1, IGFBP7, IL18, NGAL, Endostatin, CystC, KIM1) were measured preoperatively and 24 h after graft reperfusion using Luminex assays and ELISA.

Results

Sixteen patients in each group were analysed. Tie2 differed 24 h after graft reperfusion between both groups (p = 0.011). Change of log2 transformed concentration levels over time differed significantly in four biomarkers (VCAM1,Endostatin, KIM1, GH; p = 0.007; p = 0.013; p = 0.004; p = 0.033; respectively) out of 16 between both groups.

Conclusion

This study showed no effect of mannitol on I/R injury in patients undergoing deceased renal transplantation. Thus, we do not support the routinely use of mannitol to attenuate I/R injury.

Trial registration

NCT02705573. Registered on 10th March 2016.

Role of angiopoietin-2 in inflammatory autoimmune diseases: A comprehensive review

Angiogenesis is defined as the growth of new capillaries sprouting from pre-existing vasculature. Pathological angiogenesis signals can lead to dysregulated development of new vessels. Inflammation is accompanied by pathological angiogenesis. During an inflammatory process, newly formed blood vessels provide oxygen and nutrients to the inflamed tissue, facilitating the transport of inflammatory cells. Therefore, angiogenesis is closely related to pathogenesis of inflammatory autoimmune diseases. As a member of the angiopoietin family, Angiopoietin-2 (Ang-2) plays an irreplaceable role in angiogenesis. This review will narrate the expression of Ang-2 and its role in inflammatory autoimmune diseases. Collecting this information may improve the acquaintance of Ang-2 and provide a theoretical foundation for clinical trials and drug development in the future.

Circulating angiopoietin-2 and its soluble receptor Tie-2 concentrations are related to inflammatory markers in the general population

BACKGROUND

The Angiopoietin/Tie (Tyrosine kinase with Ig and EGF homology domains) signaling axis has crucial influences on angiogenesis and the vasculature's reorganization. Moreover, angiopoietin-2 (Ang2) is discussed as a biomarker for diseases' severity and development. Previous studies reported increased Ang2 levels in patients with inflammatory diseases and associations of Ang2 with inflammation markers in relatively small samples. We aimed to assess the relation of Ang2 and Tie2 with inflammation markers in the general population.

METHODS AND RESULTS

Data of 6624 participants of the population-based Study of Health in Pomerania (SHIP-1) and the independent SHIP-Trend were used. Ang2, Tie2 and inflammatory biomarkers, including fibrinogen, high-sensitive C-reactive protein (hsCRP) and white blood cell count (WBC), were measured. Adjusted analysis of variance (ANOVA) and linear/logistic regression models were performed in the entire sample and in individuals free of hypertension and diabetes. ANOVA [adjusted means of the 1st vs. 4th Ang2 quartile: fibrinogen 3.0 vs. 3.2 g/l; hsCRP 1.2 vs. 1.6 mg/l; WBC 5.9 vs. 6.6 Gpt/l] and regression models adjusted for potential confounders revealed positive relations of Ang2 with all considered inflammation markers. These associations persisted after the exclusion of individuals with hypertension and diabetes. In contrast, Tie2 showed no clear association pattern with the investigated inflammatory markers even if a trend toward a positive relation with fibrinogen became apparent.

CONCLUSION

Ang2 was positively associated with fibrinogen, hsCRP and WBC in a large population-based setting. These findings partly agree with previous results, largely obtained in clinical samples. Ang2 has diverse postulated effects on inflammation processes, like increase of vascular leakage or influences on the adhesion of leukocytes to the vessel wall. The proinflammatory character of these effects is similar to these of fibrinogen which conforms to our findings of relations between the markers. However, further research is needed to elucidate possible functional mechanisms.

Friends Turned Foes: Angiogenic Growth Factors beyond Angiogenesis

Angiogenesis, the formation of new blood vessels from pre-existing ones is a biological process that ensures an adequate blood flow is maintained to provide the cells with a sufficient supply of nutrients and oxygen within the body. Numerous soluble growth factors and inhibitors, cytokines, proteases as well as extracellular matrix proteins and adhesion molecules stringently regulate the multi-factorial process of angiogenesis. The properties and interactions of key angiogenic molecules such as vascular endothelial growth factors (VEGFs), fibroblast growth factors (FGFs) and angiopoietins have been investigated in great detail with respect to their molecular impact on angiogenesis. Since the discovery of angiogenic growth factors, much research has been focused on their biological actions and their potential use as therapeutic targets for angiogenic or anti-angiogenic strategies in a context-dependent manner depending on the pathologies. It is generally accepted that these factors play an indispensable role in angiogenesis. However, it is becoming increasingly evident that this is not their only role and it is likely that the angiogenic factors have important functions in a wider range of biological and pathological processes. The additional roles played by these molecules in numerous pathologies and biological processes beyond angiogenesis are discussed in this review.

Regulation of Angiopoietin Signalling by Soluble Tie2 Ectodomain and Engineered Ligand Trap

Angiopoietin-1 (Angpt1) is a glycoprotein ligand important for maintaining the vascular system. It signals via a receptor tyrosine kinase expressed on the surface on endothelial cells, Tie2. This receptor can undergo regulated ectodomain cleavage that releases the ligand-binding domain (sTie2) into the circulation. The concentration of sTie2 is increased in a range of conditions, including peripheral arterial disease and myocardial infarction, where it has been suggested to bind and block Angpt1 resulting in vascular dysfunction. Here we use a joint mathematical modelling and experimental approach to assess the potential impact of sTie2 on the ability of Angpt1 to signal. We find that the concentrations of sTie2 relative to Angpt1 required to suppress signalling by the ligand are more than ten–fold higher than those ever seen in normal or disease conditions. In contrast to the endogenous sTie2, an engineered form of sTie2, which presents dimeric ligand binding sites, inhibits Angpt1 signalling at seventy-fold lower concentrations. While loss of Tie2 ectodomain can suppress Angpt1 signalling locally in the cells in which the receptor is lost, our study shows that the resulting increase in circulating sTie2 is unlikely to affect Angpt1 activity elsewhere in the body.

Angiopoietin-1 and Angiopoietin-2 in metabolic disorders: therapeutic strategies to restore the highs and lows of angiogenesis in diabetes

The morbidity and mortality of diabetes mellitus are mostly attributed to cardiovascular complications. Despite tremendous advancement in glycemic control, anti-diabetic medications have failed to revert vascular impairment once triggered by the metabolic disorder. The angiogenic growth factors, Angiopoietin-1 (Ang1) and Angiopoietin-2 (Ang2), are crucial regulators of vessel formation and maintenance starting with embryonic development and continuing through life. In mature vessels, angiopoietins control vascular permeability, inflammation and remodeling. A crucial role of angiopoietins is to drive vascular inflammation from the active to the quiescent state, enabling restoration of tissue homeostasis. The mechanism is of particular importance for healing and repair after damage, two conditions typically impaired in metabolic disorders. There is an emerging body of evidences suggesting that the imbalance of Ang1 and Ang2 regulation, leading to an increased Ang2/Ang1 ratio, represents a culprit of the vascular alterations of patients with type-2 diabetes mellitus. Pharmacological modulation of Ang1 or Ang2 actions may help prevent or delay the onset of diabetic vascular complications by restoring vessel function, favoring tissue repair and maintaining endothelial quiescence. In this review, we present a summary of the role of Ang1 and Ang2, their involvement in diabetic complications, and novel therapeutic strategies targeting angiopoietins to ameliorate vascular health in metabolic disorders.

Direct peritoneal resuscitation improves survival and decreases inflammation after intestinal ischemia and reperfusion injury

BACKGROUND

Direct peritoneal resuscitation (DPR) has previously been shown to alter blood flow in the small bowel mesenteric vessels in models of intestinal ischemia. However, a survival advantage or its effects on local tissue inflammation have not been previously demonstrated. We hypothesized that DPR would increase survival and decrease intestinal tissue inflammation after intestinal ischemia and reperfusion (I/R) injury.

METHODS

Eight-week-old male C57Bl6J mice were anesthetized and underwent midline laparotomy. I/R and DPR groups were exposed to superior mesenteric artery occlusion for 60 min with a nontraumatic clamp. Immediately after removal of the clamp, 1 mL of phosphate-buffered saline, 1 mL of minimal essential media, or 1 mL of minimal essential media supplemented with fetal bovine serum, penicillin and/or streptomycin, and glutamine were placed into the abdominal cavity of DPR groups. Animals were then closed in two layers and allowed to reperfuse for 6 h (cytokine analysis, n = 6 per group) or 7 d (survival analysis, n = 10 per group). After 6 h of reperfusion, animals were euthanized. Intestines were harvested and homogenized. Extracts were quantified for total protein content (Bradford assay), myeloperoxidase activity, tissue inflammatory cytokine, and growth factor production. P < 0.05 was significant.

RESULTS

I/R caused marked intestinal ischemia, significant mortality, and a significant increase in tissue cytokine and growth factor levels (P < 0.05). Seven-day survival was 30% for I/R without treatment and rose to 60% with DPR therapy using phosphate-buffered saline as the dialysate. DPR using plain MEM or MEM with supplements after ischemia increased 7-d survival to 90% (P < 0.05). DPR also significantly decreased intestinal tissue levels of myeloperoxidase, as well as intestinal tissue levels of multiple growth factors and inflammatory cytokines.

CONCLUSIONS

DPR increases survival and decreases intestinal inflammation after intestinal I/R injury. Translational applications are readily achievable and should be considered for patients with intestinal ischemic pathology.

Angiopoietin-2: a multifaceted cytokine that functions in both angiogenesis and inflammation

Angiogenesis and inflammation are two highly linked processes. In the last decade, several factors with dual function in both of these major pathways have been identified. This review focuses on angiopoietin-2 (Ang-2), an important proangiogenic factor that has more recently been implicated in mediating inflammatory processes as well. Ang-2 is upregulated in multiple inflammatory diseases and has been implicated in the direct control of inflammation-related signaling pathways. As a consequence of its multiple roles, designs for therapeutic targeting of Ang-2 should consider the dual function of this factor in regulating angiogenesis and inflammation.

Angiopoietins in inflammation and their implication in the development of inflammatory bowel disease. A review

BACKGROUND

Angiopoietins are essential angiogenic mediators. Since inflammatory bowel disease (IBD) involves inflammation, ulceration and regeneration of the intestinal mucosa, the angiopoietin system has been proposed as a factor to maintain pathological angiogenesis during the development of the IBD.

AIM

To review the potential role of angiopoietins in the inflammation driven by angiogenesis during the course of the IBD.

METHODS

Publications were identified by PubMed searches using the following key words: angiopoietin; Tie-2 receptor; angiogenesis; inflammatory bowel disease and inflammation, in various combinations.

RESULTS

Angiopoietin-1 acts as a regulator of blood vessel maturation and has anti-inflammatory properties, whereas angiopoietin-2 marks the onset of angiogenesis and is required for normal formation of lymph vessels. Both angiopoietins make use of their angiogenic regulatory effects via the angiopoietin tyrosine-kinase receptor (Tie-2). While angiogenesis has been shown to promote and sustain many events of inflammation, the involvement of the angiopoietin system in IBD has been reported in few studies. It is not clear whether the angiopoietins' role in the development of intestinal inflammation is due to an imbalance in the levels of these proteins or this system exerts its pro-angiogenic properties through a different mechanism during the close-loop relationship between angiogenesis and inflammation.

CONCLUSIONS

Angiopoietins have key functions in the angiogenic process, and their abnormal activation might depend on their surrounding inflamed environment. The determination of these angiogenic factors in serum and tissue could be useful for monitoring IBD progression.

Immunoregulatory protein profiles of necrotizing enterocolitis versus spontaneous intestinal perforation in preterm infants

Necrotizing enterocolitis (NEC) and spontaneous intestinal perforation (SIP) are the most common acute surgical emergencies associated with high morbidity and mortality in preterm infants. We aimed to compare the profiles of immunoregulatory proteins and identify novel mediators in plasma of NEC and SIP infants. We also investigated the expression of target genes in resected intestinal tissues and an enterocyte cell line. Using Cytokine Antibody Array assay, we reported the first comparative profiles of immunoregulatory proteins in plasma of NEC and SIP infants, and showed that dysregulated proteins belonged to functionally diversified categories, including pro- and anti-inflammation, angiogenesis, cell growth, wound healing, anti-apoptosis, cell adhesion and extracellular matrix reorganization. Validation by ELISA confirmed significantly higher concentrations of interleukin (IL)-6, angiopoietin (Ang)-2, soluble type II interleukin-1 receptor (sIL-1RII), and soluble urokinase-type plasminogen activator receptor (suPAR) in NEC infants compared with gestational age-matched control, and a lower level of an epidermal growth factor receptor, secreted form of receptor tyrosine-protein kinase ErbB3 (sErbB3), compared with SIP infants. mRNA expressions of IL1-RII and uPAR were up-regulated in resected bowel tissues from NEC infants, indicating that immunoregulation also occurred at the cellular level. In FHs-74 Int cells, Ang-2, IL1-RII and uPAR mRNA expressions were significantly induced by the combined treatment with lipopolysaccharide (LPS) and platelet activating factor (PAF). Our study provided plasmatic signatures of immunoregulatory proteins in NEC and SIP infants, and demonstrated involvement of multiple functional pathways. The magnitude of changes in these proteins was significantly more extensive in NEC infants, reflecting the different nature of injury and/or severity of inflammation. We speculate that dysregulation of IL-6, Ang-2, IL-1RII and uPAR occurred at both systemic and cellular levels, and probably mediated via LPS and endogeneous PAF signals. Such exaggerated immunologic responses may account for the high morbidity and mortality in NEC compared with SIP patients.

Role of growth factors in the development of lymphangiogenesis driven by inflammatory bowel disease: a review

Studies on angiogenesis and lymphangiogenesis have gained special relevance in research into factors potentially influencing the pathogenesis and course of inflammatory bowel disease (IBD). The results of the few existing studies on the distribution and density of lymphatic vessels and blood vessels in the context of IBD are controversial. Studies using the specific lymphatic marker podoplanin have revealed a significantly large number of lymphatic vessels in the colonic mucosa of patients with ulcerative colitis and Crohn's disease (compared to patients with normal mucosa), whereas other authors have found no significant differences. However, the role of vascular endothelial growth factor (VEGF) tyrosine-kinase receptor 3 (VEGFR-3) in the onset of IBD has not been analyzed. In recent years new biochemical, molecular, and immunohistochemical studies indicate that several families of growth factors, such as the VEGF family and their receptors, fibroblast growth factor-2, platelet-derived growth factor-BB, hepatocyte growth factor, the angiopoietin system, and integrins may play an important role in the onset of IBD. To date, no comparative studies have analyzed these growth factors and specific lymphatic markers. We examine how growth factors are involved in the development of pathological lymphangiogenesis in patients with IBD and determine whether they play a crucial role in disease exacerbation.

Angiogenin, angiopoietin-1, angiopoietin-2, and endostatin serum levels in inflammatory bowel disease

BACKGROUND

Angiogenesis is a complex process, involving a great number of mediators. It is implicated in the pathogenesis of numerous diseases, holding a critical role in inflammatory bowel disease (IBD). The objective of this study was to assess serum levels of angiogenin, angiopoietin-1, angiopoietin-2, and endostatin in IBD patients.

METHODS

Measurement of all angiogenesis mediators was performed with a commercially available enzyme-linked immunosorbent assay. Fifty-two patients with ulcerative colitis (UC), 59 with Crohn's disease (CD), and 55 healthy controls (HC) were included in the study. The values were analyzed with regard to disease and patients characteristics.

RESULTS

Angiogenin levels were significantly higher in IBD patients compared to HC (P < 0.001) and in UC and CD smoker patients compared to nonsmokers (P = 0.0121 and P = 0.005, respectively). Angiogenin levels were lower in UC patients receiving 5-aminosalicylate (5-ASA) alone, compared to those receiving combined therapy (P = 0.0478). Angiopoietin-1 levels were significantly lower in IBD patients compared to HC (P < 0.0001) and increased in smokers compared to nonsmoker UC patients (P = 0.0085). IBD patients demonstrated increased angiopoietin-2 levels compared to HC (P = 0.0131), while CD patients with disease restricted to the colon had significantly lower levels compared to other disease locations (P < 0.0001). Higher endostatin levels were recorded in UC patients with extensive colitis.

CONCLUSIONS

Elevated serum angiogenin and angiopoietin-2 levels and lower serum angiopoietin-1 levels were shown in IBD patients, as well as a different pattern of angiogenic factor alterations related to location, treatment, smoking habits and gender.

Corticosteroids modulate angiogenic soluble factors in ulcerative colitis patients

AIMS

The aim of this study was to compare angiogenic factors in serum levels of active ulcerative colitis (UC) patients and in healthy controls, and to analyze these angiogenic levels depending on the achievement of remission after oral corticosteroid treatment throughout treatment, and according to the Truelove-Witts activity index.

METHODS

Blood samples were collected from 13 patients receiving oral corticosteroids for treatment of UC flares at three different intervals--baseline, during, and after treatment--and from 26 healthy controls. Vascular endothelial growth factor (VEGF), placental growth factor (PlGF), VEGF receptor 1 (VEGFR1), angiopoietins (Ang) 1 and 2, and its receptor Tie2 were assayed by ELISA.

RESULTS

While VEGF and Ang2 levels in UC patients were higher than in healthy controls (P < 0.05), UC patients showed lower levels of Ang1 than healthy individuals (P < 0.05). In UC patients who achieved clinical remission after corticosteroid treatment, a statistically significant higher baseline serum level of PlGF was observed (22 ± 5 vs. 18 ± 2; P < 0.05). Angiogenic factor levels varied during treatment; however, they did not show a statistically significant correlation to the activity of the disease.

CONCLUSIONS

VEGF, Ang1, and Ang2 levels showed statistically significant differences between UC patients and healthy controls. Although determination of PlGF serum levels before corticosteroid treatment might be helpful to anticipate the response by UC patients, no angiogenic pattern that could accurately predict "a priori" this response to corticosteroid treatment was observed. Corticosteroids altered temporarily circulating levels of VEGF, angiopoietins and Tie2. No correlation was found between systemic levels of angiogenic factors and the clinical activity of UC.

Emerging roles of lymphatics in inflammatory bowel disease

The mobilization and recruitment of blood and lymphatic vasculatures are widely described in inflammatory bowel diseases (IBDs). Although angiogenesis contributes to intense gut inflammation, it remains unclear whether and when lymphangiogenesis amplifies or protects in IBD. The prolonged maintenance of lymphatic (over blood vessels) in inflammation indicates that lymphatic-blood vessel interactions may regulate IBD pathogenesis and restitution. Although lymphatic expansion helps to restore fluid balance and clear cytokines and immune cells, lymphatic failure results in accumulation of these factors and exacerbates IBD. Lymphatic obstruction and remodeling may impair lymphatic pumping, leading to repeated rounds of lymphangiogenesis. Early descriptions of Crohn's disease and ulcerative colitis describe colon lymphatic congestion, remodeling, expansion, and many other features that are recapitulated in experimental IBD and also by intestinal lymphatic obstruction, supporting lymphangitis as a cause and consequence of IBD. Growth factors, cytokines, gut flora, Toll receptors, and leukocytes all regulate inflammation and gut lymphatic remodeling in IBD. This review summarizes the importance of lymphatics and lymphangiogenesis in IBD etiology that may be useful in diagnosis and therapy of gut inflammation.

Dextran sulfate sodium leads to chronic colitis and pathological angiogenesis in Endoglin heterozygous mice

BACKGROUND

Pathological angiogenesis is an intrinsic component of chronic intestinal inflammation, which results in remodeling and expansion of the gut microvascular bed. Endoglin is essential for endothelial cell function and physiological angiogenesis. In this study we investigated its potential role in the regulation of inflammation by testing the response of Endoglin heterozygous (Eng(+/-)) mice to experimental colitis.

METHODS

C57BL/6 Eng(+/-) and littermate control mice drank water supplemented with 3% dextran sulfate sodium (DSS) for 5 days and were monitored for up to 26 days for clinical signs of colitis. Inflammation, crypt damage, and angiogenic index were scored on histological sections of distal colon. Levels of the vascular endothelial growth factor (VEGF) and angiopoietins were measured by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and/or Western blots. Vascular permeability was assessed using Evans Blue.

RESULTS

Eng(+/-) and control mice developed acute colitis, which peaked at day 9. While control mice recovered by days 19-26, Eng(+/-) mice progressed to chronic colitis and showed numerous vascular protrusions penetrating into the serosa of the inflamed distal colon. Prior to DSS induction, VEGF levels and vascular permeability were higher in the distal colon of Eng(+/-) mice, while angiopoietin 1 and 2 levels were unchanged. In the chronic phase of colitis, VEGF levels were increased in both groups of mice and remained significantly higher in the Eng(+/-) mice.

CONCLUSIONS

Higher VEGF levels and increased vascular permeability in the distal colon may predispose Eng(+/-) mice to progress to chronic and persistent bowel inflammation, associated with pathological angiogenesis.

Angiopoietin-2-driven vascular remodeling in airway inflammation

Vascular remodeling is a feature of chronic inflammation during which capillaries transform into venules that expand the region of the vasculature in which leakage and leukocyte emigration both occur. Recently, we found that angiopoietin/Tie2 receptor signaling drives the transformation of capillaries into venules at an early stage of the sustained inflammatory response in the airways of mice infected with Mycoplasma pulmonis. However, the precise contributions of both angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2) are not clear. In this study, we sought to determine the contribution of Ang2 to this vascular remodeling. Ang2 mRNA expression levels increased and phosphorylated Tie2 immunoreactivity in mucosal blood vessels decreased, indicative of diminished receptor signaling after infection. Selective inhibition of Ang2 throughout the infection by administration of either of two distinct function-blocking antibodies reduced the suppression of Tie2 phosphorylation and decreased the remodeling of mucosal capillaries into venules, the amount of leukocyte influx, and disease severity. These findings are consistent with Ang2 acting as an antagonist of Tie2 receptors and the reduction of Tie2 phosphorylation in endothelial cells rendering the vasculature more responsive to cytokines that promote both vascular remodeling and the consequences of inflammation after M. pulmonis infection. By blocking such changes, Ang2 inhibitors may prove beneficial in the treatment of sustained inflammation in which vascular remodeling, leakage, and leukocyte influx contribute to its pathophysiology.

Targeting the ANGPT-TIE2 pathway in malignancy

Angiopoietins (ANGPTs) are ligands of the endothelial cell receptor TIE2 and have crucial roles in the tumour angiogenic switch. Increased expression of ANGPT2 relative to ANGPT1 in tumours correlates with poor prognosis. The biological effects of the ANGPT-TIE system are context dependent, which brings into question what the best strategy is to target this pathway. This Review presents an encompassing picture of what we know about this important axis in tumour biology. The various options for therapeutic intervention are discussed to identify the best path forwards.

Serum angiopoietin-1 level is increased in patients with Behçet's disease

OBJECTIVE

Angiogenesis may be involved in the pathogenesis of Behçet's disease (BD). Some angiogenic factors such as vascular endothelial growth factor, monocyte chemoattractant protein-1, and endothelin-1 are significantly associated with BD. Here, we investigate whether Angiopoietin contributes to disease activity and clinical manifestations of BD.

METHODS

We recruited 59 consecutive patients with BD and sex- and age-matched 65 healthy control subjects for this study. We reviewed data regarding clinical features, erythrocyte sediment rate (ESR), and C-reactive protein (CRP) at the time of enrollment. Serum angiopoietin-1 and angiopoietin-2 were estimated by enzyme-linked immunosorbent assay. Statistical analyses were performed using the Student t test and Pearson's correlation coefficient analysis.

RESULTS

Levels of serum angiopoietin-1 are significantly increased in BD patients compared to controls (284.5+/-101.2 ng/ml of BD vs 237.1+/-76.4 ng/ml of controls, p=0.012). However, serum angiopoietin-2 levels are similar in both groups (974.2+/-679.3 pg/ml of BD vs 858.3+/-535.3 pg/ml of controls, p=0.562). Serum angiopoietin-1 expression is significantly elevated in patients with skin lesions (p=0.025) and positively correlated with disease duration (r=0.320, p=0.015). ESR levels are closely associated with serum angiopoietin-2 (r=0.306, p=0.018).

CONCLUSION

Angiopoiein-1 expression is enhanced in BD patients compared to controls. This preliminary study identifies that angiopoietin-1 may play an important role in the pathogenesis of BD.

An Autocrine Linkage Between Matrix Metalloproteinase-14 and Tie-2 Via Ectodomain Shedding Modulates Angiopoietin-1–Dependent Function in Endothelial Cells

Objective— The angiopoietin (Ang)–Tie-2 system plays a critical role during fetal and adult angiogenesis. Herein, we explored the Tie-2 shedding–related molecular mechanisms and the pathophysiological significance.

Methods and Results— By using a mouse hindlimb ischemia model, we observed dissociated expression between the full-length Tie-2 (fTie-2) protein and Tie-2 mRNA in thigh muscles 1 day after an ischemic operation, suggesting that fTie-2 expression was modified through the posttranscriptional regulation in vivo. A soluble form of Tie-2 produced in human umbilical vein endothelial cells was dramatically suppressed by treatment with siRNA–matrix metalloproteinase (MMP) 14 or tissue inhibitor of metalloproteinase 3, resulting in an increase in cellular fTie-2 and thereby enhancing Ang-1–dependent Akt phosphorylation and Akt-dependent endothelial functions, such as Ang-2 downregulation or an increase of endothelial viability. Phorbol-12-myristate-13 acetate (PMA) upregulates MMP-14 mRNA via protein kinase C–extracellular signal–regulated kinase pathways, and enhanced soluble Tie-2 production in an MMP-14–dependent manner, resulting in a reduction of cellular fTie-2. In addition, the PMA-induced soluble Tie-2 was mediated by the protein kinase C–extracellular signal–regulated kinase signaling pathways. Finally, downregulation of tissue inhibitor of metalloproteinase 3 and upregulation of MMP-14 mRNA were confirmed in ischemic thigh muscles 1 day after the operation.

Conclusion— An autocrine linkage between the endothelial protein kinase C–MMP-14 axis and Tie-2 shedding was shown to be a novel regulatory mechanism for the Ang–Tie-2 system and may play a role in modulating endothelial function during angiogenesis.

New biomarkers of Crohn's disease: serum biomarkers and development of diagnostic tools

Crohn's disease (CD) is a complex and heterogeneous inflammatory disorder that is part of inflammatory bowel diseases. Its diagnosis is performed on clinical presentation and results of radiography, endoscopy and histological findings. New noninvasive diagnostic biomarkers are needed to allow rapid and accurate CD discrimination. Blood-derived biomarkers correlating with disease activity, supported by genetic evidences and valid for all CD patients subtypes are still missing. Hence, no biomarkers and no related diagnostic tests are recommended or used alone for CD diagnosis in clinical practice. This review describes diagnosis tests based on the detection/quantification of specific acute-phase reactant proteins, enzymes and derived antibody response developed by inflammatory bowel disease patients for pathogens or symbiotic flora determinant, as well as autoantibodies. Their power as diagnostic tools is discussed, as well as new high-throughput techniques, such as microarrays and proteomics, for the discovery of new CD clinical biomarkers and for the development of specific CD diagnostic tests. Some rapidly evolving nanotechnologies, mathematical analysis and bioinformatics methods are also mentioned to highlight their importance for further accurate CD diagnosis.

Increased expression of VEGF and CD146 in patients with inflammatory bowel disease

BACKGROUND

Angiogenesis has been suggested as an integral part of inflammatory bowel disease pathology. Vascular endothelial growth factor has long been considered to play a central, specific role in angiogenesis. Endothelial junction adhesion molecules, such as CD146, have recently been suggested to play a potent role in angiogenesis. CD34 is expressed on vascular endothelium, and it has been reported to be upregulated on endothelium in IBD. We investigated the expression of tissue vascular endothelial growth factor, CD34 and CD146 in the inflamed mucosa of patients with active inflammatory bowel disease compared with no inflamed mucosa of healthy controls.

METHODS

Forty-two IBD patients [23 ulcerative colitis, 19 Crohn's disease] and ten healthy controls were included in the study. In colonoscopically obtained biopsies, CD34, CD146 and vascular endothelial growth factor expression were evaluated by immunohistochemistry.

RESULTS

Vascular endothelial growth factor was detected in the mucosa of all groups, and its expression was significantly higher in both Crohn's disease and ulcerative colitis compared with controls (p<0.05). Immunohistochemical staining for CD146 in the inflamed mucosa was significantly higher in both Crohn's disease and ulcerative colitis compared with controls (p=0.002). A trend of higher CD34 expression in Crohn's disease and ulcerative colitis compared with controls was also found, but the difference among the three groups was not statistically significant (p=0.09).

CONCLUSIONS

Inflamed mucosa of patients with active Crohn's disease and ulcerative colitis showed a markedly enhanced expression of VEGF and CD146, than normal mucosa of controls, indicating a possible role of angiogenesis in the pathogenesis of inflammatory bowel disease.

Multiple pathogenic roles of microvasculature in inflammatory bowel disease: a Jack of all trades

The etiology of Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel disease (IBD), is still largely unknown. However, it is now clear that the abnormalities underlying pathogenesis of intestinal inflammation are not restricted to those mediated by classic immune cells but also involve nonimmune cells. In particular, advances in vascular biology have outlined a central and multifaceted pathogenic role for the microcirculation in the initiation and perpetuation of IBD. The microcirculation and its endothelial lining play a crucial role in mucosal immune homeostasis through tight regulation of the nature and magnitude of leukocyte migration from the intravascular to the interstitial space. Chronically inflamed IBD microvessels display significant alterations in microvascular physiology and function compared with vessels from healthy and uninvolved IBD intestine. The investigation into human IBD has demonstrated how endothelial activation present in chronically inflamed IBD microvessels results in a functional phenotype that also includes leakiness, chemokine and cytokine expression, procoagulant activity, and angiogenesis. This review contemplates the newly uncovered contribution of intestinal microcirculation to pathogenesis and maintenance of chronic intestinal inflammation. In particular, we assess the multiple roles of the microvascular endothelium in innate immunity, leukocyte recruitment, coagulation and perfusion, and immune-driven angiogenesis in IBD.

Multiple pathogenic roles of microvasculature in inflammatory bowel disease: a Jack of all trades

The etiology of Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel disease (IBD), is still largely unknown. However, it is now clear that the abnormalities underlying pathogenesis of intestinal inflammation are not restricted to those mediated by classic immune cells but also involve nonimmune cells. In particular, advances in vascular biology have outlined a central and multifaceted pathogenic role for the microcirculation in the initiation and perpetuation of IBD. The microcirculation and its endothelial lining play a crucial role in mucosal immune homeostasis through tight regulation of the nature and magnitude of leukocyte migration from the intravascular to the interstitial space. Chronically inflamed IBD microvessels display significant alterations in microvascular physiology and function compared with vessels from healthy and uninvolved IBD intestine. The investigation into human IBD has demonstrated how endothelial activation present in chronically inflamed IBD microvessels results in a functional phenotype that also includes leakiness, chemokine and cytokine expression, procoagulant activity, and angiogenesis. This review contemplates the newly uncovered contribution of intestinal microcirculation to pathogenesis and maintenance of chronic intestinal inflammation. In particular, we assess the multiple roles of the microvascular endothelium in innate immunity, leukocyte recruitment, coagulation and perfusion, and immune-driven angiogenesis in IBD.

Analysis of soluble angiogenic factors in Crohn's disease: a preliminary study

AIMS

Soluble angiogenic factors could be altered in patients with Crohns disease (CD), since inflammation and angiogenesis may play a critical pathogenic role.

METHODS

Serum samples were collected from 30 patients with CD (50% female; median age 44 +/- 14 yrs) grouped according to their phenotypic behavior into equal subgroups: inflammatory, fibrostenotic and fistulizing; and 30 healthy controls (50% female; median age 43 +/- 14 yrs). Vascular endothelial growth factor (VEGF), placental growth factor (PlGF), angiopoietins (Ang) and receptors (VEGFR1, VEGFR2 and Tie2) in sera were assayed by ELISA.

RESULTS

Serum levels of VEGF (494 +/- 247 pg/ml), PlGF (36 +/- 11 pg/ml), VEGFR1 (1.9 +/- 0.3 ng/ml), Ang2 (6.0 +/- 2.3 ng/ml) and Tie2 (36 +/- 5 ng/ml) in CD patients were significantly higher than those found in healthy controls (335 +/- 118 pg/ml; 23 +/- 9 pg/ml; 1.0 +/- 0.3 ng/ml; 3.9 +/- 2.0 ng/ml; 22 +/- 7 ng/ml, respectively). Conversely, CD patients showed significantly lower serum levels of Ang1 than healthy controls (46 +/- 11 versus 67 +/- 23 pg/ml). In the case of VEGFR2 serum levels, no differences between groups were found. Finally, patients with fibrostenotic CD were characterized by elevated VEGF and Ang2 levels, while patients with an inflammatory phenotype by elevated Tie2 and PlGF levels.

CONCLUSIONS

An activated "pro-angiogenic" profile of angiogenesis soluble markers was observed in CD patients, in comparison with healthy controls. According to the phenotypic behavior, these patients showed differences in serum levels of angiogenic factors.

Angiogenesis in inflammatory bowel disease

Both ulcerative colitis and Crohn's disease, the two major forms of inflammatory bowel diseases, are recognized, at the moment, as perplexing and challenging clinical entities, in which several molecules and cell types are implicated. Recent molecular evidence proposes the intestinal microvascular remodelling or angiogenesis, as a phenomenon implicated in the pathogenesis of these chronic inflammatory disorders, together with other proposed theories involved in the pathogenesis of inflammatory bowel diseases, such as genetic, microbacterial and immune factors. Intestinal damage is followed by a physiological angiogenesis, but the abnormal expression of pro- and anti-angiogenic molecules and the changes of vascular cell types could reflect a pathological vascular remodelling. Thus, the inflammation may be favoured and maintained by a pathological angiogenesis. A better understanding of the angiogenic process may facilitate the design of more effective therapies for chronic intestinal inflammation.

Role of vascular endothelial growth factor and angiopoietin systems in serum of Crohn's disease patients

BACKGROUND

The purposes of this study were to determine soluble angiogenic factors in Crohn's disease (CD) patients and to compare these factors according to the pathological behavior of the disease in order to establish a possible relationship with its evolution in patients with CD.

METHODS

Blood samples were collected from 70 patients with CD, grouped according to their phenotypic behavior, and from 30 healthy controls. Vascular endothelial growth factor (VEGF), placental growth factor (PlGF), angiopoietin 1 (Ang1), angiopoietin 2 (Ang2), and their cognate receptors [VEGFR1, VEGFR2, and angiopoietin receptor tyrosine kinase (Tie2)] were assayed by ELISA.

RESULTS

Circulating levels of VEGF, PlGF, VEGFR1, Ang2, and Tie2 were significantly higher in CD patients than in healthy controls (489 +/- 271 versus 335 +/- 118 pg/mL, P < 0.001; 31 +/- 9 versus 23 +/- 9 pg/mL, P < 0.001; 1.7 +/- 0.4 versus 1.0 +/- 0.3 ng/mL, P < 0.001; 4.8 +/- 2.0 versus 3.9 +/- 2.0 ng/mL, P < 0.05; and 36 +/- 5 versus 22 +/- 7 ng/mL, P < 0.001, respectively). Conversely, CD patients showed significantly lower serum levels of Ang1 than healthy controls (40 +/- 12 versus 67 +/- 22 ng/mL; P < 0.001). No differences between the groups were found in VEGFR2 serum level. The circulating levels of the angiogenic factors did not differ significantly when the CD patients were classified according to pathological phenotype.

CONCLUSIONS

In comparison with healthy controls, CD patients were found to have an active angiogenic profile, as detected by significant alterations in levels of angiogenesis soluble markers. These patients did not differ in serum levels of angiogenic factors according to phenotypic disease behavior.

Angiopoietin-2 serum levels are elevated in patients with liver cirrhosis and hepatocellular carcinoma

OBJECTIVES

Liver cirrhosis is characterized by remodeling leading to nodules that are difficult to discern from hepatocellular carcinoma (HCC). Alpha-fetoprotein (AFP) serum levels are used for the screening for HCC, with limited success. We evaluated angiopoietin-2 as a serum marker in patients with cirrhosis and with HCC.

METHODS

In a retrospective study, we measured angiopoietin-2 serum levels in 131 patients with HCC, 180 patients with cirrhosis, and 40 healthy controls. We also determined AFP serum levels in patients with HCC and compared the test characteristics of both serum markers. The expression patterns of angiopoietin-2 were determined by in situ hybridization in healthy and cirrhotic livers as well as in HCC.

RESULTS

Angiopoietin-2 serum levels were elevated in patients with liver cirrhosis (P < 0.0001) compared with healthy controls. Levels were further elevated in patients with HCC compared with healthy controls (P < 0.0001) and cirrhotic patients (P < 0.0001). The combination with AFP measurements led to improved discrimination between HCC and cirrhosis. Angiopoietin-2 message was present in tumor cells of HCCs but was absent from hepatocytes of cirrhotic and healthy livers. In cirrhosis, message was detected within the strands of fibrous tissue.

CONCLUSIONS

Serum angiopoietin-2 levels are elevated in patients with cirrhosis, implicating a possible role of the angiopoietin-Tie-2 system for neoangiogenesis in cirrhosis. Serum levels are further elevated in patients with HCC, suggesting the potential use of angiopoietin-2 as a marker for the detection of cirrhosis and HCC.

Pathophysiological mechanisms of angiogenesis

The growth of new blood vessels may be either beneficial or harmful. The angiogenic process may be measured by a variety of techniques, although it may often be the quality rather than quantity of resulting blood vessels that determines function. Endothelial cells play a key role in the initiation of angiogenesis, and vascular endothelial growth factor (VEGF) may be viewed as a prototypical direct-acting angiogenic factor. VEGF acts through multiple cell surface receptors and signaling pathways to stimulate endothelial cell proliferation, survival, and migration. By inducing other growth factor expression, VEGF stimulates a cascade of angiogenic activity. Different tissues may utilize various angiogenic pathways that are modulated by diverse host tissue responses. Furthermore, a single tissue may progress through a sequence of angiogenic pathways, for example, as acute injury progresses to chronic inflammation. The phenotype of the resulting neovasculature is critically dependent on the context in which it is formed. Biomarkers of angiogenesis are being developed as an aid to assessing human disease. Histological assessment of vascular density and angiogenic factor expression, in vivo imaging, Doppler ultrasound, and biofluid assays each may have clinical utility. Therapeutic targeting of angiogenesis will depend both on the generation of acceptable pharmacological agents and on the identification of patients who may and do gain benefit from such treatments.

Inflammation and the mucosal microcirculation in inflammatory bowel disease: the ebb and flow

PURPOSE OF REVIEW

Inflammatory bowel disease pathogenesis involves the interplay of multiple biological factors, among which nonimmune cells, including the endothelium, represent a crucial component of disease pathogenesis.

RECENT FINDINGS

Endothelial cells play a key role in chronic inflammation through multiple and disparate activities. The mucosal microvasculature in inflammatory bowel disease is dysfunctional, overexpresses inflammatory molecules and undergoes intense angiogenesis, failing to exert its physiological antiinflammatory and anticoagulant activities.

SUMMARY

The mucosal microcirculation is abnormal in inflammatory bowel disease and represents a novel component of disease pathogenesis; targeting the various abnormalities of the inflammatory bowel disease microcirculation may lead to new forms of therapeutic intervention.

Role of angiogenesis in inflammatory bowel disease

Several studies have shown alterations in vascular anatomy and physiology in inflammatory bowel disease (IBD). These findings, together with the observed upregulation of the mediators of angiogenesis in IBD patients, suggest that angiogenesis possibly contributes to the initiation and perpetuation of IBD. There is considerable evidence of an interrelationship between the mechanisms of angiogenesis and chronic inflammation in IBD. The increased expression of endothelial junction adhesion molecules found in IBD patients indicates the presence of active angiogenesis. Evidence that angiogenesis is involved in IBD was also obtained from animal models of colitis, most notably from studies of angiogenesis inhibition. Serum levels of vascular endothelial growth factor (VEGF) correlate with disease activity in human IBD and fall with the use of steroids, thalidomide, or infliximab. Pharmacological inhibition of angiogenesis, therefore, has the potential to be a therapeutic strategy in IBD. This review outlines the evidence that the rate of angiogenesis is increased in the inflamed intestine in IBD and proposes lines for future research in this field.