MiR-221-5p regulates blood-brain barrier dysfunction through the angiopoietin-1/-2/Tie-2 signaling axis after subarachnoid hemorrhage.

AIM: To explore the potential role of microRNA miR-221-5p on the angiopoietin-1 (Ang-1)/Ang-2/Tie-2 signaling axis after subarachnoid hemorrhage (SAH) in a rat model. METHODS: Aspects of the rat's behavior were measured using the Kaoutzanis scoring system to test neurological responses. This included feeding behavior, body contraction, motor, and eye-opening responses. Brain sections were studied using transmission electron microscopy and Evans blue extravasation. Levels of Ang-1, Ang-2, and Tie-2 were determined by Western blot, while miR-221-5p was quantified using stem-loop real-time quantitative PCR (RT-qPCR). RESULTS: The SAH group responded worse to the neurological response test than the sham-operated group. The intercellular space was widened in the SAH group, but not in the sham-operated group. Evans blue dye leaked significantly more into brain tissue cells of the SAH group. Stem-loop qRT-PCR showed elevated miR-221-5p levels. Additionally, Ang-1 and Tie-2 were reduced but Ang-2 expression was increased after SAH. This led to a significant reduction of the Ang-1/Ang-2 ratio in the brain tissue, which was associated with the destruction of the blood-brain barrier. CONCLUSION: The data indicate that miR-221-5p might regulate blood-brain barrier dysfunction through the Ang-1/Ang-2/Tie-2 signaling axis, suggesting that it should be further investigated as a potential novel biomarker.

A new look at angiogenesis inhibition of geniposide in experimental arthritis by blocking angiopoietin-2 exocytosis.

Angiogenesis is a key player in the pathogenesis of rheumatoid arthritis. Exocytosis from Weibel-Palade bodies is a prerequisite for angiopoietin-2 (Ang-2) to activate endothelial cells and initiate angiogenesis. Geniposide (GE) was previously reported to exert anti-angiogenic effects. The aim of this study was to shed light on whether and how GE regulates Ang-2 exocytosis. A rat model of adjuvant arthritis (AA) was established to evaluate the therapeutic effect of GE (60 and 120 mg/kg) especially in synovial angiogenesis. In addition, the Matrigel plug assay was used to detect the effect of GE (120 and 240 mg/kg) on angiogenesis in AA mice. In vitro, sphingosine-1-phosphate (S1P)-stimulated human umbilical vein endothelial cells (HUVECs) were used to investigate the effect and mechanism of GE on Ang-2 exocytosis. It was found that GE improved the symptoms of AA rats and inhibited angiogenesis in AA, which may be related to the down-regulation of S1P receptors 1, 3 (S1PR1, S1PR3), phospholipase Cß3 (PLCß3), inositol 1,4,5-trisphosphate receptor (IP3 R) and Ang-2 expression. The results of in vitro experiments showed that S1P induced rapid release of Ang-2 from HUVECs with multigranular exocytosis. Suppression of the S1P/S1PR1/3/PLCß3/Ca2+ signal axis by the S1PR1/3 inhibitor VPC23019 and the IP3 R inhibitor 2-APB blocked Ang-2 exocytosis, accompanied by diminished angiogenesis in vitro. GE dose-dependently weakened S1P/S1PR1/3/PLCß3/Ca2+ signal axis activation, Ang-2 exocytosis and angiogenesis in HUVECs (p < 0.05, p < 0.01). Overall, these findings revealed that angiogenesis inhibition of GE was partly attributed to the intervention of Ang-2 exocytosis through negatively modulating the S1P/S1PR1/3/PLCß3/Ca2+ signal axis, providing a novel strategy for rheumatoid arthritis anti-angiogenic therapy.

IGF-PLGA microspheres promote angiogenesis and accelerate skin flap repair and healing by inhibiting oxidative stress and regulating the Ang 1/Tie 2 signaling pathway.

Random flaps are widely used in the treatment of injuries, tumors, congenital malformations, and other diseases. However, postoperative skin flaps are prone to ischemic necrosis, leading to surgical failure. Insulin-like growth factor- 1(IGF-1) belongs to the IGF family and exerts its growth-promoting effects in various tissues through autocrine or paracrine mechanisms. Its application in skin flaps and other traumatic diseases is relatively limited. Poly (lactic-co-glycolic acid) (PLGA) is a degradable high-molecular-weight organic compound commonly used in biomaterials. This study prepared IGF-PLGA sustained-release microspheres to explore their impact on the survival rate of flaps both in vitro and in vivo, as well as the mechanisms involved. The research results demonstrate that IGF-PLGA has a good sustained-release effect. At the cellular level, it can promote 3T3 cell proliferation by inhibiting oxidative stress, inhibit apoptosis, and enhance the tube formation ability of human umbilical vein endothelial cells (HUVEC) . At the animal level, it accelerates flap healing by promoting vascularization through the inhibition of oxidative stress. Furthermore, this study reveals the role of IGF-PLGA in activating the Angiopoietin-1(Ang1)/Tie2 signaling pathway in promoting flap vascularization, providing a strong theoretical basis and therapeutic target for the application of IGF-1 in flaps and other traumatic diseases.

Ang1/Tie2/VE-Cadherin Signaling Regulates DPSCs in Vascular Maturation.

Adding dental pulp stem cells (DPSCs) to vascular endothelial cell-formed vessel-like structures can increase the longevity of these vessel networks. DPSCs display pericyte-like cell functions and closely assemble endothelial cells (ECs). However, the mechanisms of DPSC-derived pericyte-like cells in stabilizing the vessel networks are not fully understood. In this study, we investigated the functions of E-DPSCs, which were DPSCs isolated from the direct coculture of human umbilical vein endothelial cells (HUVECs) and DPSCs, and T-DPSCs, which were DPSCs treated by transforming growth factor beta 1 (TGF-ß1), in stabilizing blood vessels in vitro and in vivo. A 3-dimensional coculture spheroid sprouting assay was conducted to compare the functions of E-DPSCs and T-DPSCs in vitro. Dental pulp angiogenesis in the severe combined immunodeficiency (SCID) mouse model was used to explore the roles of E-DPSCs and T-DPSCs in vascularization in vivo. The results demonstrated that both E-DPSCs and T-DPSCs possess smooth muscle cell-like cell properties, exhibiting higher expression of the mural cell-specific markers and the suppression of HUVEC sprouting. E-DPSCs and T-DPSCs inhibited HUVEC sprouting by activating TEK tyrosine kinase (Tie2) signaling, upregulating vascular endothelial (VE)-cadherin, and downregulating vascular endothelial growth factor receptor 2 (VEGFR2). In vivo study revealed more perfused and total blood vessels in the HUVEC + E-DPSC group, HUVEC + T-DPSC group, angiopoietin 1 (Ang1) pretreated group, and vascular endothelial protein tyrosine phosphatase (VE-PTP) inhibitor pretreated group, compared to HUVEC + DPSC group. In conclusion, these data indicated that E-DPSCs and T-DPSCs could stabilize the newly formed blood vessels and accelerate their perfusion. The critical regulating pathways are Ang1/Tie2/VE-cadherin and VEGF/VEGFR2 signaling.

Female sex protects against renal edema, but not lung edema, in mice with partial deletion of the endothelial barrier regulator Tie2 compared to male sex.

BACKGROUND: The endothelial angiopoietin/Tie2 system is an important regulator of endothelial permeability and targeting Tie2 reduces hemorrhagic shock-induced organ edema in males. However, sexual dimorphism of the endothelium has not been taken into account. This study investigated whether there are sex-related differences in the endothelial angiopoietin/Tie2 system and edema formation. METHODS: Adult male and female heterozygous Tie2 knockout mice (Tie2+/-) and wild-type controls (Tie2+/+) were included (n = 9 per group). Renal and pulmonary injury were determined by wet/dry weight ratio and H&E staining of tissue sections. Protein levels were studied in plasma by ELISA and pulmonary and renal mRNA expression levels by RT-qPCR. RESULTS: In Tie2+/+ mice, females had higher circulating angiopoietin-2 (138%, p<0.05) compared to males. Gene expression of angiopoietin-1 (204%, p<0.01), angiopoietin-2 (542%, p<0.001) were higher in females compared to males in kidneys, but not in lungs. Gene expression of Tie2, Tie1 and VE-PTP were similar between males and females in both organs. Renal and pulmonary wet/dry weight ratio did not differ between Tie2+/+ females and males. Tie2+/+ females had lower circulating NGAL (41%, p<0.01) compared to males, whereas renal NGAL and KIM1 gene expression was unaffected. Interestingly, male Tie2+/- mice had 28% higher renal wet/dry weight ratio (p<0.05) compared to Tie2+/+ males, which was not observed in females nor in lungs. Partial deletion of Tie2 did not affect circulating angiopoietin-1 or angiopoietin-2, but soluble Tie2 was 44% and 53% lower in males and females, respectively, compared to Tie2+/+ mice of the same sex. Renal and pulmonary gene expression of angiopoietin-1, angiopoietin-2, estrogen receptors and other endothelial barrier regulators was comparable between Tie2+/- and Tie2+/+ mice in both sexes. CONCLUSION: Female sex seems to protect against renal, but not pulmonary edema in heterozygous Tie2 knock-out mice. This could not be explained by sex dimorphism in the endothelial angiopoietin/Tie2 system.

Glycation of fibronectin impairs angiopoietin-1/Tie-2 signaling through uncoupling Tie-2-α5ß1 integrin crosstalk.

The dysfunction of angiopoietin-1 (Ang-1)/Tie-2 signaling pathways has been implicated in diabetic complications. However, the underlying molecular mechanisms remain unclear. Fibronectin (FN) is thought to have an important role in regulating Ang-1/Tie-2 signaling activation. But no previous study has investigated the effects of FN glycation on Ang-1/Tie-2 signaling. In the present study, FN was glycated by methylglyoxal (MGO) to investigate whether the glycation of FN contributes to diabetes-induced Ang-1/Tie-2 signaling impairment and to understand the molecular mechanisms involved. The results demonstrated that MGO-glycated FN significantly impaired Ang-1-evoked phosphorylation of Tie-2 and Akt, Ang-1-induced endothelial cell migration and tube formation and Ang-1-mediated cell survival. The glycation of FN also inhibited the binding of α5ß1 integrin to Tie-2. Moreover, FN was remarkably modified by AGEs in aortae derived from db/db mice, indicating the glycation of FN in vivo. Ang-1-induced aortic ring vessel outgrowth and Ang-1-mediated cell survival were also both significantly inhibited in aortae from db/db mice compared to that from the wild type littermates. Moreover, FN, rather than glycated FN partly restored aortic ring angiogenesis in db/db mice, indicating that the angiogenesis defect in the db/db mice are due to FN glycation. Collectively, the results in the present study suggest that the glycation of FN impairs Ang-1/Tie-2 signaling pathway by uncoupling Tie-2-α5ß1 integrin crosstalk. This may provide a mechanism for Ang-1/Tie-2 signaling dysfunction and angiogenesis failure in diabetic ischaemic diseases.

KRAS mutation-driven angiopoietin 2 bestows anti-VEGF resistance in epithelial carcinomas.

Defining reliable surrogate markers and overcoming drug resistance are the most challenging issues for improving therapeutic outcomes of antiangiogenic drugs (AADs) in cancer patients. At the time of this writing, no biomarkers are clinically available to predict AAD therapeutic benefits and drug resistance. Here, we uncovered a unique mechanism of AAD resistance in epithelial carcinomas with KRAS mutations that targeted angiopoietin 2 (ANG2) to circumvent antivascular endothelial growth factor (anti-VEGF) responses. Mechanistically, KRAS mutations up-regulated the FOXC2 transcription factor that directly elevated ANG2 expression at the transcriptional level. ANG2 bestowed anti-VEGF resistance as an alternative pathway to augment VEGF-independent tumor angiogenesis. Most colorectal and pancreatic cancers with KRAS mutations were intrinsically resistant to monotherapies of anti-VEGF or anti-ANG2 drugs. However, combination therapy with anti-VEGF and anti-ANG2 drugs produced synergistic and potent anticancer effects in KRAS-mutated cancers. Together, these data demonstrate that KRAS mutations in tumors serve as a predictive marker for anti-VEGF resistance and are susceptible to combination therapy with anti-VEGF and anti-ANG2 drugs.

A comprehensive insight into the role of molecular pathways affected by the Angiopoietin and Tie system involved in hematological malignancies' pathogenesis.

Angiogenesis has been recognized as a critical factor in developing solid tumors and hematological malignancies. How angiogenesis affects the molecular pathways in malignancies is still a mystery. The angiopoietin family, one of the known molecular mediators for angiogenesis, encourages angiogenesis by attaching to Tie receptors on cell surfaces. Angiopoietin, Tie, and particularly the molecular pathways they mediate have all been the subject of recent studies that have established their diagnostic, prognostic, and therapeutic potential. Here, we've reviewed the function of molecular pathways impacted by the Angiogenin and Tie system in hematological malignancies.

The expression analyses of GSK3B, VEGF, ANG1, and ANG2 in human brain microvascular endothelial cells treated with the synthetic cannabinoid XLR-11.

The endocannabinoid system receptors, cannabinoid receptors type-1 (CBR-1) and -2 (CBR-2), are implicated in several behavioral and cognitive processes. Many studies have indicated a correlation between cannabinoid receptors and angiogenesis. The current study aims to reveal the possible molecular signaling involved in brain angiogenesis induced by the activation of CBR-1 and CBR-2. We investigated whether the synthetic cannabinoid XLR-11, an agonist of CBR-1 and CBR-2, influences the mRNA and protein expression of vascular endothelial growth factor (VEGF), angiopoietin-1 (ANG1) and -2 (ANG2) in human brain microvascular endothelial cells (hBMVEs). Furthermore, we determined the phosphorylation of glycogen synthase kinase 3 beta (GSK3B) expression. Treatment of hBMVEs cells with XLR-11 elevated the mRNA levels of VEGF, ANG1, and ANG2. The secretion of these proangiogenic factors was increased in the media. Furthermore, the intracellular expression of VEGF, ANG1, ANG2, and GSK3B was significantly increased. This current research provides a new possible approach by targeting the cannabinoid receptors to control and regulate brain angiogenesis for treating a variety of angiogenesis-related diseases. This could be achived by using different agonists or antagonists of the cannabinoid receptors based on the nature of the diseases.

Angiopoietin-1 promotes triple-negative breast cancer cell proliferation by upregulating carboxypeptidase A4.

Angiopoietin-1 (ANG1) is a pro-angiogenic regulator that contributes to the progression of solid tumors by stimulating the proliferation, migration and tube formation of vascular endothelial cells, as well as the renewal and stability of blood vessels. However, the functions and mechanisms of ANG1 in triple-negative breast cancer (TNBC) are unclear. The clinical sample database shows that a higher level of ANG1 in TNBC is associated with poor prognosis compared to non-TNBC. In addition, knockdown of ANG1 inhibits TNBC cell proliferation and induces cell cycle G1 phase arrest and apoptosis. Overexpression of ANG1 promotes tumor growth in nude mice. Mechanistically, ANG1 promotes TNBC by upregulating carboxypeptidase A4 (CPA4) expression. Overall, the ANG1-CPA4 axis can be a therapeutic target for TNBC.

Anti-Arthritic Effect of Edaravone Against Complete Freund Adjuvant Induced Arthritis via Osteoclast Differentiation and HIF-1α-VEGF-ANG-1 Axis.

Background: Bone dysfunction is a crucial problem that occurs during rheumatoid arthritis (RA) disease. Osteoclast plays a significant role in bone resorption and osteoclast differentiation and its enhancement of bone destruction. Edaravone remarkably exhibited free radical scavenging and anti-inflammatory effects. The objective of the current investigation is to comfort the inhibitory effect of Edaravone (ED) against complete Freund adjuvant (CFA) rat model via inhibition of angiogenesis and inflammation. Methods: Subcutaneous injection of CFA (1%) was used to induce arthritis; the rats were divided into different groups and received the oral administration of ED. Paw edema, body weight, and arthritis score were regularly estimated. Biochemical parameters were estimated, respectively. We also estimate the level of hypoxia-inducible factor-1α (HIF-1α), angiopoietin 1 (ANG-1), and vascular endothelial growth factor (VEGF). We also checked into how ED affected the differentiation of osteoclasts utilising a co-culture system with monocytes and synovial fibroblasts in arthritis rats. Results: ED treatment significantly (P<0.001) suppressed the arthritis score and paw edema and improved the body weight. ED treatment significantly (P<0.001) altered the antioxidant parameters and pro-inflammatory cytokines: inflammatory mediator nuclear kappa B factor (NF-κB), cyclooxygenase-2 (COX-2), and prostaglandin E2 (PGE2), respectively. Furthermore, ED treatment significantly (P<0.001) suppressed the level of ANG-1, HIF-1α, and VEGF, respectively. The results suggest that ED suppressed osteoclast differentiation and also decreased the level of cytokines and osteopontin (OPN), receptor activator for nuclear factor-κ B Ligand (RANKL) and macrophage colony stimulating factor (M-CSF) in the co-culture supernatant of monocytes and synovial fibroblasts. Conclusion: Edaravone could mitigate CFA via inhibiting angiogenesis and inflammatory reactions, which may be linked with the HIF-1α-VEGF-ANG-1 axis and also enhance the bone destruction of murine arthritis via suppression of osteoclast differentiation and inflammatory reaction.

Increased Angiopoietin-1 and -2 levels in human vitreous are associated with proliferative diabetic retinopathy.

BACKGROUND: Diabetic retinopathy is a frequent complication of diabetes mellitus and a leading cause of blindness in adults. The objective of this study was to elucidate the diabetic retinopathy pathophysiology in more detail by comparing protein alterations in human vitreous of different diabetic retinopathy stages. METHODS: Vitreous samples were obtained from 116 patients undergoing pars plana vitrectomy. Quantitative immunoassays were performed of angiogenic factors (VEGF-A, PIGF, Angiopoietin-1, Angiopoietin-2, Galectin-1) as well as cytokines (IL-1ß, IL-8, IFN-γ, TNF-α, CCL3) in samples from control patients (patients who don't suffer from diabetes; n = 58) as well as diabetes mellitus patients without retinopathy (n = 25), non-proliferative diabetic retinopathy (n = 12), and proliferative diabetic retinopathy patients (n = 21). In addition, correlation analysis of protein levels in vitreous samples and fasting glucose values of these patients as well as correlation analyses of protein levels and VEGF-A were performed. RESULTS: We detected up-regulated levels of VEGF-A (p = 0.001), PIGF (p<0.001), Angiopoietin-1 (p = 0.005), Angiopoietin-2 (p<0.001), IL-1ß (p = 0.012), and IL-8 (p = 0.018) in proliferative diabetic retinopathy samples. Interestingly, we found a strong positive correlation between Angiopoietin-2 and VEGF-A levels as well as a positive correlation between Angiopoietin-1 and VEGF-A. CONCLUSION: This indicated that further angiogenic factors, besides VEGF, but also pro-inflammatory cytokines are involved in disease progression and development of proliferative diabetic retinopathy. In contrast, factors other than angiogenic factors seem to play a crucial role in non-proliferative diabetic retinopathy development. A detailed breakdown of the pathophysiology contributes to future detection and treatment of the disease.

Ang-1 Inhibited Endoplasmic Reticulum Stress and Apoptosis of VECs in Rats with aSAH-induced CVS Through the Regulated PI3K/Akt Pathway.

AIMS: To explore angiopoietin-1 (Ang-1) involved in cerebral vasospasm (CVS) after aneurysmal subarachnoid hemorrhage (aSAH) through its effect on endoplasmic reticulum stress (ERS) and apoptosis of vascular endothelial cells (VECs). BACKGROUND: CVS accounts for high morbidity and mortality of aSAH. Abnormal cellular physiological processes of VECs play a critical role in aSAH-induced CVS. In addition, Ang-1 is involved in regulating vascular structure and function. OBJECTIVE: To study the role of Ang-1 played in CVS and the underlying mechanism. METHODS: Blood samples of 130 aSAH patients were collected from 2016 to 2020 at West China Hospital of Sichuan University. A two-hemorrhage rodent model was employed to structure an aSAH-induced CVS rat model. Moreover, oxyHb was used to treat VECs to construct a CVS cell model in vitro. ELISA was used to measure the level of Ang-1 and HE staining to assess the rat's basilar arteries. Subsequently, CCK-8 was used to detect cell viability ability, and flow cytometry was used to test the cell apoptosis rate. Western blotting was used to determine the expression level of ERS marker and apoptosis-related proteins. RESULTS: There was an abnormally low expression of Ang-1 in CVS patients and CVS rats; besides, oxyHb treatment decreased Ang-1 in VECs in a concentration-dependent manner. Ang-1 treatment led to the thinner basilar artery wall and lumen circumference in CVS rats; moreover, in oxyHbtreated VECs, Ang-1 treatment inhibited ERS and apoptosis. In addition, the expression of p-PI3K and p-Akt in the CVS group decreased, while the expression of p53 in the CVS group increased. The expression of p-PI3K and p-Akt in 8 CVS rats negatively correlates with the expression of Ang- 1, but the correlation between p53 and Ang-1 was positive. Furthermore, the results suggested that Ang-1 suppressed ERS and apoptosis of VECs through the regulated PI3K/Akt/p53 pathway. CONCLUSION: Elevated Ang-1 inhibited p53-mediated ERS and apoptosis of VECs through the activated PI3K/Akt pathway; Ang-1 might be an attractive treatment strategy for CVS.

Intracellular angiopoietin-1 promotes TKI-resistance via activation of JAK/STAT5 pathway in chronic myeloid leukemia.

Drug resistance from BCR-ABL tyrosine kinase inhibitors (TKIs) and other chemotherapeutics results in treatment failure and disease progression in chronic myeloid leukemia (CML). However, the mechanism is still uncertain. In this study, we investigated the role of angiopoietin-1 (ANG-1) as a potential prognostic factor for drug resistance in CML. Both intracellular and secretory ANG-1 (iANG-1 and sANG-1) were overexpressed in multidrug-resistant CML samples. The IC50 value was higher in primary CD34+ CD38- cells with more ANG-1. Silencing ANG-1significantly sensitized three TKI-resistant CML cell lines to imatinib (IM) while recombinant human ANG-1 failed to retain cell survival in vitro. This indicated the important role of iANG-1 as opposed to sANG-1 in CML drug resistance. Moreover, a similar effect was observed in xenograft mice models bearing ANG-1-silenced CML cells. Subsequently, pathway analysis and protein validation experiments showed activation of the JAK/STAT pathway and augmentation of STAT5a phosphorylation in ANG-1 restored CML cells. Upstream Src phosphorylation, which plays a crucial role in CML drug resistance, was also upregulated as a key event in iANG-1-related JAK/STAT pathway activation. In conclusion, our study elucidated a new BCR-ABL independent molecular mechanism induced by intracytoplasmic ANG-1 overexpression as a potential strategy for overcoming CML resistance.

Local and Systemic Overexpression of COMP-Ang1 Induces Ang1/Tie2-Related Thrombocytopenia and SDF-1/CXCR4-Dependent Anemia.

While supplemental angiopoietin-1 (Ang1) improves hematopoiesis, excessive Ang1 induces bone marrow (BM) impairment, hematopoietic stem cell (HSC) senescence, and erythropoietic defect. Here, we examined how excessive Ang1 disturbs hematopoiesis and explored whether hematopoietic defects were related to its level using K14-Cre;c-Ang1 and Col2.3-Cre;c-Ang1 transgenic mice that systemically and locally overexpress cartilage oligomeric matrix protein-Ang1, respectively. We also investigated the impacts of Tie2 inhibitor and AMD3100 on hematopoietic development. Transgenic mice exhibited excessive angiogenic phenotypes, but K14-Cre;c-Ang1 mice showed more severe defects in growth and life span with higher presence of Ang1 compared with Col2.3-Cre;c-Ang1 mice. Dissimilar to K14-Cre;c-Ang1 mice, Col2.3-Cre;c-Ang1 mice did not show impaired BM retention or senescence of HSCs, erythropoietic defect, or disruption of the stromal cell-derived factor 1 (SDF-1)/CXCR4 axis. However, these mice exhibited a defect in platelet production depending on the expression of Tie2 and globin transcription factor 1 (GATA-1), but not GATA-2, in megakaryocyte progenitor (MP) cells. Treatment with Tie2 inhibitor recovered GATA-1 expression in MP cells and platelet production without changes in circulating RBC in transgenic mice. Consecutive AMD3100 administration not only induced irrecoverable senescence of HSCs but also suppressed formation of RBC, but not platelets, via correlated decreases in number of erythroblasts and their GATA-1 expression in B6 mice. Our results indicate that genetic overexpression of Ang1 impairs hematopoietic development depending on its level, in which megakaryopoiesis is preferentially impaired via activation of Ang1/Tie2 signaling, whereas erythropoietic defect is orchestrated by HSC senescence, inflammation, and disruption of the SDF-1/CXCR4 axis.

Serum angiopoietin-1 concentration does not distinguish patients with ischaemic stroke from those presenting to hospital with ischaemic stroke mimics.

BACKGROUND: A previous study found that circulating angiopoietin-1 (angpt-1) concentrations were significantly lower in patients who had a recent ischaemic stroke compared to healthy controls. The primary aim of this study was to assess whether serum angpt-1 could be used as a diagnostic test of ischemic stroke in patients presenting to hospital as an emergency. Exploratory analyses investigated the association of proteins functionally related to angpt-1 (angpt-2, Tie-2, matrix metalloproteinase-9 and vascular endothelial growth factors A, C and D) with ischaemic stroke diagnosis. METHODS: Patients presenting to Townsville University Hospital for emergency assessment of stroke-like symptoms were consecutively recruited and provided a blood sample. After assessment by a consultant neurologist, patients were grouped into those who did, or did not have ischaemic stroke. The potential for serum angpt-1 to diagnose ischaemic stroke was assessed using receiver operator characteristic (ROC) curves. Cross-sectional analyses appraised inter-group differences in the serum concentration of other proteins. RESULTS: One-hundred and twenty-six patients presenting to Townsville University Hospital for emergency assessment of stroke-like symptoms were recruited (median time from symptom onset to hospital presentation: 2.6 (inter-quartile range: 1.2-4.6) hours). Serum angpt-1 had poor ability to diagnose ischaemic stroke in analyses using the whole cohort, or in sensitivity analyses (area under the ROC curve 0.51 (95% CI: 0.41-0.62) and 0.52 (95% CI: 0.39-0.64), respectively). No associations of serum angpt-1 concentration with ischaemic stroke severity, symptom duration or aetiology were observed. Serum concentrations of the other assessed proteins did not differ between patient groups. CONCLUSIONS: Serum angpt-1 concentration is unlikely to be useful for emergency diagnosis of ischaemic stroke.

The Emerging Role of Pericyte-Derived Extracellular Vesicles in Vascular and Neurological Health.

Pericytes (PCs), as a central component of the neurovascular unit, contribute to the regenerative potential of the central nervous system (CNS) and peripheral nervous system (PNS) by virtue of their role in blood flow regulation, angiogenesis, maintenance of the BBB, neurogenesis, and neuroprotection. Emerging evidence indicates that PCs also have a role in mediating cell-to-cell communication through the secretion of extracellular vesicles (EVs). Extracellular vesicles are cell-derived, micro- to nano-sized vesicles that transport cell constituents such as proteins, nucleic acids, and lipids from a parent originating cell to a recipient cell. PC-derived EVs (PC-EVs) play a crucial homeostatic role in neurovascular disease, as they promote angiogenesis, maintain the integrity of the blood-tissue barrier, and provide neuroprotection. The cargo carried by PC-EVs includes growth factors such as endothelial growth factor (VEGF), connecting tissue growth factors (CTGFs), fibroblast growth factors, angiopoietin 1, and neurotrophic growth factors such as brain-derived neurotrophic growth factor (BDNF), neuron growth factor (NGF), and glial-derived neurotrophic factor (GDNF), as well as cytokines such as interleukin (IL)-6, IL-8, IL-10, and MCP-1. The PC-EVs also carry miRNA and circular RNA linked to neurovascular health and the progression of several vascular and neuronal diseases. Therapeutic strategies employing PC-EVs have potential in the treatment of vascular and neurodegenerative diseases. This review discusses current research on the characteristic features of EVs secreted by PCs and their role in neuronal and vascular health and disease.

Cooperation of Angiopoietin-2 and Angiopoietin-4 in Schlemm's Canal Maintenance.

Purpose: Defects in the iridocorneal angle tissues, including the trabecular meshwork (TM) and Schlemm's canal (SC), impair aqueous humor flow and increase the intraocular pressure (IOP), eventually resulting in glaucoma. Activation of endothelial tyrosine kinase receptor Tie2 by angiopoietin-1 (Angpt1) has been demonstrated to be essential for SC formation, but roles of the other two Tie2 ligands, Angpt2 and Angpt4, have been controversial or not yet characterized, respectively. Methods: Angpt4 expression was investigated using genetic cell fate mapping and reporter mice. Congenital deletion of Angpt2 and Angpt4 and tamoxifen-inducible deletion of Angpt1 in mice were used to study the effects of Angpt4 deletion alone and in combination with the other angiopoietins. SC morphology was examined with immunofluorescent staining. IOP measurements, electron microscopy, and histologic evaluation were used to study glaucomatous changes. Results: Angpt4 was postnatally expressed in the TM. While Angpt4 deletion alone did not affect SC and Angpt4 deletion did not aggravate Angpt1 deletion phenotype, absence of Angpt4 combined with Angpt2 deletion had detrimental effects on SC morphology in adult mice. Consequently, Angpt2-/-;Angpt4-/- mice displayed glaucomatous changes in the eye. Mice with Angpt2 deletion alone showed only moderate SC defects, but Angpt2 was necessary for proper limbal vasculature development. Mechanistically, analysis of Tie2 phosphorylation suggested that Angpt2 and Angpt4 cooperate as agonistic Tie2 ligands in maintaining SC integrity. Conclusions: Our results indicated an additive effect of Angpt4 in SC maintenance and Tie2 activation and a spatiotemporally regulated interplay between the angiopoietins in the mouse iridocorneal angle.

Selective histamine H2 receptor agonists alleviate blood-brain barrier disruption by promoting the expression of vascular protective factors following traumatic brain injury in mice.

Histamine is a major neurotransmitter and alleviates neuronal damage after ischemic injury via H2 receptors. Herein, we investigated the effects of H2 receptor agonists on the blood-brain barrier (BBB) disruption after traumatic brain injury (TBI). Male ddY mice were used to generate the TBI model, in which a fluid percussion injury (FPI) was induced by a hydraulic impact. The BBB disruption was evaluated using Evans blue extravasation. H2 receptor agonists, amthamine and dimaprit, were administered into the lateral cerebroventricle (i.c.v.) or tail vein (i.v.) from 3 hours to 3 days after FPI. The i.c.v. or i.v. administration of amthamine and dimaprit reduced FPI-induced Evans blue extravasation and promoted mRNA expression of vascular protective factors, including angiopoietin-1 and sonic hedgehog. The co-administration of ranitidine, a H2 receptor antagonist, inhibited these effects. Expression of the H2 receptor was observed in astrocytes and brain microvascular endothelial cells (BMECs) in the injured cortex. Treatment with amthamine and dimaprit promoted mRNA expression of vascular protective factors in astrocytes and BMECs. These results suggest that H2 receptor agonists alleviate TBI-induced BBB disruption by increasing the expression of vascular protective factors in astrocytes and BMECs.

Angiogenesis, Metabolism, Endothelial and Platelet Markers in Diabetes and Cardiovascular Disease.

Introduction: Diabetes is a leading risk factor for cardiovascular disease (CVD), the pathophysiology of both being linked to metabolic, endothelial, renal, angiogenic and platelet abnormalities. We hypothesised that abnormalities in these systems are more adverse in those whose CVD is compounded by diabetes, compared to those with diabetes or CVD alone. Materials and methods: Serum or plasma from 66 patients with diabetes alone, 76 with CVD alone, and 70 with both diabetes and CVD i.e. diabetic cardiovascular disease, was probed for markers of angiogenesis [angiopoietin 1 and 2, vascular endothelial growth factor (VEGF) and endoglin], metabolic [soluble receptor for advanced glycation products (sRAGE), leptin, lipocalin-2, interleukin-8, and cystatin-C], the endothelium (von Willebrand factor, endothelial microparticles and soluble E selectin)], and the platelet (platelet microparticles and soluble P selectin) by ELISA, Luminex or flow cytometry. Results: VEGF (p = 0.04), von Willebrand factor (p = 0.001) and endothelial microparticles (p = 0.042) were all higher in diabetic cardiovascular disease than in diabetes alone and cardiovascular disease alone. Soluble E selectin was higher in diabetic cardiovascular disease than in diabetes alone (p = 0.045), whilst cystatin-C (p = 0.004) and soluble P selectin (p < 0.001) were higher in diabetes and diabetic cardiovascular disease than in cardiovascular disease alone. There were no differences in angiopoietin 1 or 2, endoglin, sRAGE, leptin, lipocalin-2, or interleukin-8. Conclusion: Angiopoietin 1 or 2, endoglin, sRAGE, leptin, lipocalin-2, interleukin-8, and cystatin-c cannot differentiate diabetes from cardiovascular disease, or both conditions combined. Our data point to a more adverse endothelial (von Willebrand factor, endothelial microparticles), and angiogenic profile (VEGF) in those with diabetic cardiovascular disease, supporting the view that this group should be targeted more aggressively.