COMP-Ang1 Potentiates EPC Treatment of Ischemic Brain Injury by Enhancing Angiogenesis Through Activating AKT-mTOR Pathway and Promoting Vascular Migration Through Activating Tie2-FAK Pathway

mTOR (Mammalian Target of Rapamycin): Hitting the Bull's Eye for Enhancing Neurogenesis After Cerebral Ischemia?

Ischemic stroke remains a leading cause of morbidity and disability around the world. The sequelae of serious neurological damage are irreversible due to body's own limited repair capacity. However, endogenous neurogenesis induced by cerebral ischemia plays a critical role in the repair and regeneration of impaired neural cells after ischemic brain injury. mTOR (mammalian target of rapamycin) kinase has been suggested to regulate neural stem cells ability to self-renew and differentiate into proliferative daughter cells, thus leading to improved cell growth, proliferation, and survival. In this review, we summarized the current evidence to support that mTOR signaling pathways may enhance neurogenesis, angiogenesis, and synaptic plasticity following cerebral ischemia, which could highlight the potential of mTOR to be a viable therapeutic target for the treatment of ischemic brain injury.

COMP-Ang1: Therapeutic potential of an engineered Angiopoietin-1 variant

The Angiopoietin-1/2 system is an opportune target for therapeutic intervention in a wide range of vascular pathologies, particularly through its association with endothelium. The complex multi-domain structure of native human Angiopoietin-1 has hindered its widespread applicability as a therapeutic agent, prompting the search for alternative approaches to mimicking the Ang1:Tie2 signalling axis; a system with highly complex patterns of regulation involving multiple structurally similar molecules. An engineered variant, Cartilage Oligomeric Matrix Protein - Angiopoietin-1 (COMP-Ang1), has been demonstrated to overcome the limitations of the native molecule and activate the Tie2 pathway with several fold greater potency than Ang1, both in vitro and in vivo. The therapeutic efficacy of COMP-Ang1, at both the vascular and systemic levels, is evident from multiple studies. Beneficial impacts on skeletal muscle regeneration, wound healing and angiogenesis have been reported alongside renoprotective, anti-hypertensive and anti-inflammatory effects. COMP-Ang1 has also demonstrated synergy with other compounds to heighten bone repair, has been leveraged for potential use as a co-therapeutic for enhanced targeted cancer treatment, and has received considerable attention as an anti-leakage agent for microvascular diseases like diabetic retinopathy. This review examines the vascular Angiopoietin:Tie2 signalling mechanism, evaluates the potential therapeutic merits of engineered COMP-Ang1 in both vascular and systemic contexts, and addresses the inherent translational challenges in moving this potential therapeutic from bench-to-bedside.

COMP-Ang1 Stabilizes Hyperglycemic Disruption of Blood-Retinal Barrier Phenotype in Human Retinal Microvascular Endothelial Cells

Purpose

Current treatments for diabetic retinopathy (DR) have considerable limitations, underpinning the need for new therapeutic options. In this article, the ability of an engineered angiopoietin-1 variant (COMP-Ang1) to ameliorate the injurious effects of hyperglycemia on barrier integrity in a human retinal microvascular endothelial cell (HRMvEC) model is comprehensively investigated.

Methods

Confluent HRMvECs were treated (0–72 hours) with d-glucose (5 or 30 mM) in the absence and presence of COMP-Ang1 (10–200 ng/mL). l-glucose (30 mM) was used as osmotic control. Posttreatment, intact cell monolayers were monitored for permeability to FITC-dextran 40 kDa. Cells were also harvested for analysis of interendothelial junction targets by RT-qPCR and Western blotting. The impact of receptor tyrosine kinase Tie2 gene silencing on COMP-Ang1 efficacy was also evaluated.

Results

Treatment with 30 mM d-glucose (but not l-glucose) demonstrated a time-dependent elevation in the mean rate of FITC-dextran diffusion across intact HRMvEC monolayers, in parallel with significant reductions in mRNA/protein levels of occludin, claudin-5, ZO-1, and VE-Cadherin. These effects were all attenuated by COMP-Ang1 in a concentration-dependent fashion, with 200 ng/mL recovering barrier function by ∼88%, and recovering reduced interendothelial junction protein levels by more than 50%. Finally, Tie2 knockdown by small interfering RNA silencing blocked the ability of COMP-Ang1 to mitigate against hyperglycemia-induced permeabilization of HRMvECs and depletion of junctional expression levels.

Conclusions

In summary, this article presents a reproducible in vitro cell study that quantifies the concentration-dependent efficacy of COMP-Ang1 to mitigate the injurious effects of hyperglycemic challenge on HRMvEC barrier properties via Tie2-mediated signaling.

Pivotal micro factors associated with endothelial cells

Objective:

Recent studies have shown the important influence of various micro factors on the general biological activity and function of endothelial cells (ECs). Vascular endothelial growth factor (VEGF) and angiogenin (ANG) are classic micro factors that promote proliferation, differentiation, and migration of ECs. The underlying pathophysiological mechanisms and related pathways of these micro factors remain the focus of current research.

Data sources:

An extensive search was undertaken in the PubMed database by using keywords including “micro factors” and “endothelial cell.” This search covered relevant research articles published between January 1, 2007 and December 31, 2018.

Study selection:

Original articles, reviews, and other articles were searched and reviewed for content on micro factors of ECs.

Results:

VEGF and ANG have critical functions in the occurrence, development, and status of the physiological pathology of ECs. Other EC-associated micro factors include interleukin 10, tumor protein P53, nuclear factor kappa B subunit, interleukin 6, and tumor necrosis factor. The results of Gene Ontology analysis revealed that variations were mainly enriched in positive regulation of transcription by the RNA polymerase II promoter, cellular response to lipopolysaccharides, negative regulation of apoptotic processes, external side of the plasma membrane, cytoplasm, extracellular regions, cytokine activity, growth factor activity, and identical protein binding. The results of the Kyoto Encyclopedia of Genes and Genomes analysis revealed that micro factors were predominantly enriched in inflammatory diseases.

Conclusions:

In summary, the main mediators, factors, or genes associated with ECs include VEGF and ANG. The effect of micro factors on ECs is complex and multifaceted. This review summarizes the correlation between ECs and several micro factors.

Sitagliptin protects diabetic rats with acute myocardial infarction through induction of angiogenesis: role of IGF-1 and VEGF

Angiogenesis is regulated in a tissue-specific manner in all patients, especially those with diabetes. In this study, we describe a novel molecular pathway of angiogenesis regulation in diabetic rats with myocardial infarction (MI) and examine the cardioprotective effects of different doses of sitagliptin. Male rats were divided into 5 groups: normal vehicle group, diabetic group, diabetic + MI, diabetic + MI + 5 mg/kg sitagliptin, and diabetic + MI + 10 mg/kg sitagliptin. Isoproterenol in diabetic rats resulted in significant (p < 0.05) disturbance to the electrocardiogram, cardiac histopathological manifestations, and an increase in inflammatory markers compared with the vehicle and diabetic groups. Treatment with sitagliptin improved the electrocardiogram and histopathological sections, upregulated vascular endothelial growth factor (VEGF) and transmembrane phosphoglycoprotein protein (CD34) in cardiac tissues, and increased serum insulin-like growth factor 1 (IGF-1) and decreased cardiac tissue homogenate for interleukin 6 (IL-6) and cyclooxygenase 2 (COX-2). A relationship was found between serum IGF-1 and cardiac VEGF and CD34 accompanied by an improvement in cardiac function of diabetic rats with MI. Therefore, the observed effects of sitagliptin occurred at least partly through an improvement in angiogenesis and the mitigation of inflammation. Consequently, these data suggest that sitagliptin may contribute, in a dose-dependent manner, to protection against acute MI in diabetic individuals.

CPNE3 promotes migration and invasion in non-small cell lung cancer by interacting with RACK1 via FAK signaling activation

Approximately 90% of patients diagnosed with non-small cell lung cancer (NSCLC) die due to distant metastases. However, the complicated molecular and cellular mechanisms involved in lung cancer metastasis remain poorly understood. Copine III (CPNE3), a member of a Ca²⁺-dependent phospholipid-binding protein family, was identified as a novel metastasis-associated protein in NSCLC in our previous study, however, its function in metastasis remains unclear. Here, we found that CPNE3 was expressed at high levels in NSCLC tissues and advanced TNM stages and was significantly associated with poor prognosis. In addition, CPNE3 interacted with phosphorylated erb-b2 receptor tyrosine kinase 2 (pErbB2) and receptor of activated protein C kinase 1 (RACK1) and activated the focal adhesion (FA) signaling pathway in NSCLC cells. Moreover, knockdown of RACK1 inhibited cell motility in the CPNE3-overexpressed NSCLC cells. These findings offer mechanistic insights into the oncogenic roles of CPNE3 and the pivotal effects of CPNE3 as a biomarker and therapeutic target for NSCLC metastasis.

Integrin α5β1-Ang1/Tie2 receptor cross-talk regulates brain endothelial cell responses following cerebral ischemia

We have previously demonstrated that in response to cerebral ischemia (CI), the growth factor angiopoietin-1 (Ang1) and α5β1 integrin are both induced in cerebral vessels, which likely provide positive signals driving the endogenous angiogenic response and vascular protection after CI. However, the precise relationship between endothelial Ang1 and α5β1 integrin after CI remains poorly understood. Here, we investigated the effects of the interaction between the Ang1/Tie2 system and α5β1 integrin on brain endothelial cells (BECs) under cerebral ischemic conditions in vivo and in vitro. Immunofluorescence analysis demonstrated that integrin α5β1 co-localized with Tie2/phosphorylated Tie2 on cerebral vessels in the penumbra. The in vitro study showed that oxygen-glucose deprivation/restoration (OGD/R) induced the expression of the Ang1 receptor Tie2 on BECs in a manner similar to that for integrin α5 and Ang1 in response to OGD/R, accompanied by increased activation of Tie2 and its downstream effectors focal adhesion kinase (FAK) and Akt. Knockdown of α5 integrin markedly suppressed OGD/R-induced Tie2 receptor activation in BECs, while in contrast, priming BECs with Ang1 promoted the expression of α5 integrin as well as the Tie2 downstream transcription factor Ets-1 in OGD-treated BECs. In line with this, Ets-1 knockdown significantly attenuated Ang1-mediated upregulation of α5 integrin. Functionally, Ang1 induced cell migration and tube formation of BECs after OGD, but this effect was inhibited by diminishment of the levels of α5 integrin in BECs. Taken together, our data indicate that the Ang1/Tie2 system cross-talks with integrin α5β1 in BECs after CI, which may contribute to the endogenous angiogenic vascular protective response following CI.

ANGPTL3 possibly promotes cardiac angiogenesis through improving proangiogenic ability of endothelial progenitor cells after myocardial infarction

Angiopoietin Like protein 3 (ANGPTL3) is at present considered as a central molecular target for therapy designed to reduce atherogenic lipids and atherosclerosis. However, concerns about the safety of inactivation of ANGPTL3 in patients with coronary artery disease (CAD) especially myocardial infarction (MI) have been raised. ANGPTL3 is reported to possess proangiogenic property. Angiogenesis is critical to the recovery of MI. Endothelial progenitor cells (EPCs) have multiple differentiation potential and play an important role in the angiogenesis post-MI. Promoting the function of EPCs could facilitate the angiogenesis and recovery of MI. Previous studies have shown that ANGPTL3 can promote angiogenesis in corneal of rats and promote angiogenesis of endothelial cells by binding to integrin ανβ3 receptors and promoting phosphorylation of protein kinase B (AKT). Our institution found that activated AKT can up-regulate the expression of microRNA-126 (miR-126), which can promote the proangiogenic ability of EPCs. The integrin ανβ3 receptors and AKT also express in EPCs and are closely related to proangiogenic function. Therefore, we hypothesized that ANGPTL3 could improve function of EPCs by binding to integrin ανβ3 receptors and up-regulating miR-126 expression via activating AKT, thus promoting the formation of new blood vessels, attenuating myocardial ischemia and improving heart function.

Stem cells and heart disease - Brake or accelerator?

After two decades of intensive research and attempts of clinical translation, stem cell based therapies for cardiac diseases are not getting closer to clinical success. This review tries to unravel the obstacles and focuses on underlying mechanisms as the target for regenerative therapies. At present, the principal outcome in clinical therapy does not reflect experimental evidence. It seems that the scientific obstacle is a lack of integration of knowledge from tissue repair and disease mechanisms. Recent insights from clinical trials delineate mechanisms of stem cell dysfunction and gene defects in repair mechanisms as cause of atherosclerosis and heart disease. These findings require a redirection of current practice of stem cell therapy and a reset using more detailed analysis of stem cell function interfering with disease mechanisms. To accelerate scientific development the authors suggest intensifying unified computational data analysis and shared data knowledge by using open-access data platforms.

WISP-1 positively regulates angiogenesis by controlling VEGF-A expression in human osteosarcoma

In recent years, much research has focused on the role of angiogenesis in osteosarcoma, which occurs predominantly in adolescents and young adults. The vascular endothelial growth factor-A (VEGF-A) pathway is the key regulator of angiogenesis and in osteosarcoma. VEGF-A expression has been recognized as a prognostic marker in angiogenesis. Aberrant WNT1-inducible signaling pathway protein-1 (WISP-1) expression is associated with various cancers. However, the function of WISP-1 in osteosarcoma angiogenesis is poorly understood. We demonstrate a positive correlation between WISP-1 and VEGF-A expression in human osteosarcoma. Moreover, we show that WISP-1 promotes VEGF-A expression in human osteosarcoma cells, subsequently inducing human endothelial progenitor cell (EPC) migration and tube formation. The focal adhesion kinase (FAK), Jun amino-terminal kinase (JNK), and hypoxia-inducible factor (HIF)-1α signaling pathways were activated after WISP-1 stimulation, while FAK, JNK, and HIF-1α inhibitors or small interfering RNA (siRNA) abolished WISP-1-induced VEGF-A expression and angiogenesis. In vitro and in vivo studies revealed down-regulation of microRNA-381 (miR-381) in WISP-1-induced VEGF-A expression and angiogenesis. Our findings reveal that WISP-1 enhances VEGF-A expression and angiogenesis through the FAK/JNK/HIF-1α signaling pathways, as well as via down-regulation of miR-381 expression. WISP-1 may be a promising target in osteosarcoma angiogenesis.

Novel nervous and multi-system regenerative therapeutic strategies for diabetes mellitus with mTOR

Throughout the globe, diabetes mellitus (DM) is increasing in incidence with limited therapies presently available to prevent or resolve the significant complications of this disorder. DM impacts multiple organs and affects all components of the central and peripheral nervous systems that can range from dementia to diabetic neuropathy. The mechanistic target of rapamycin (mTOR) is a promising agent for the development of novel regenerative strategies for the treatment of DM. mTOR and its related signaling pathways impact multiple metabolic parameters that include cellular metabolic homeostasis, insulin resistance, insulin secretion, stem cell proliferation and differentiation, pancreatic β-cell function, and programmed cell death with apoptosis and autophagy. mTOR is central element for the protein complexes mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2) and is a critical component for a number of signaling pathways that involve phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), AMP activated protein kinase (AMPK), silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), Wnt1 inducible signaling pathway protein 1 (WISP1), and growth factors. As a result, mTOR represents an exciting target to offer new clinical avenues for the treatment of DM and the complications of this disease. Future studies directed to elucidate the delicate balance mTOR holds over cellular metabolism and the impact of its broad signaling pathways should foster the translation of these targets into effective clinical regimens for DM.

Regeneration in the nervous system with erythropoietin

Globally, greater than 30 million individuals are afflicted with disorders of the nervous system accompanied by tens of thousands of new cases annually with limited, if any, treatment options. Erythropoietin (EPO) offers an exciting and novel therapeutic strategy to address both acute and chronic neurodegenerative disorders. EPO governs a number of critical protective and regenerative mechanisms that can impact apoptotic and autophagic programmed cell death pathways through protein kinase B (Akt), sirtuins, mammalian forkhead transcription factors, and wingless signaling. Translation of the cytoprotective pathways of EPO into clinically effective treatments for some neurodegenerative disorders has been promising, but additional work is necessary. In particular, development of new treatments with erythropoiesis-stimulating agents such as EPO brings several important challenges that involve detrimental vascular outcomes and tumorigenesis. Future work that can effectively and safely harness the complexity of the signaling pathways of EPO will be vital for the fruitful treatment of disorders of the nervous system.

Intravitreal AAV2.COMP-Ang1 Prevents Neurovascular Degeneration in a Murine Model of Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of blindness in the working-age population in the U.S. The vision-threatening processes of neuroglial and vascular dysfunction in DR occur in concert, driven by hyperglycemia and propelled by a pathway of inflammation, ischemia, vasodegeneration, and breakdown of the blood retinal barrier. Currently, no therapies exist for normalizing the vasculature in DR. Here, we show that a single intravitreal dose of adeno-associated virus serotype 2 encoding a more stable, soluble, and potent form of angiopoietin 1 (AAV2.COMP-Ang1) can ameliorate the structural and functional hallmarks of DR in Ins2Akita mice, with sustained effects observed through six months. In early DR, AAV2.COMP-Ang1 restored leukocyte-endothelial interaction, retinal oxygenation, vascular density, vascular marker expression, vessel permeability, retinal thickness, inner retinal cellularity, and retinal neurophysiological response to levels comparable with nondiabetic controls. In late DR, AAV2.COMP-Ang1 enhanced the therapeutic benefit of intravitreally delivered endothelial colony-forming cells by promoting their integration into the vasculature and thereby stemming further visual decline. AAV2.COMP-Ang1 single-dose gene therapy can prevent neurovascular pathology, support vascular regeneration, and stabilize vision in DR.

Phosphorylation of JNK Increases in the Cortex of Rat Subjected to Diabetic Cerebral Ischemia

Previous studies have demonstrated that the c-Jun N-terminal kinase (JNK) pathway plays an important role in inducing neuronal apoptosis following cerebral ischemic injury. JNK signaling pathway in activated during cerebral ischemic injury. It participates in ischemia-induced neuronal apoptosis. However, whether JNK signaling is involved in the process of neuronal apoptosis of diabetes-induced cerebral ischemia is largely unknown. This study was undertaken to evaluate the influence of cerebral ischemia-reperfusion injury on phosphorylation of JNK in diabetic rats. Twenty-four adult streptozotocin induced diabetic and 24 adult non-diabetic rats were randomly subjected to 15 min of forebrain ischemia followed by reperfusion for 0, 1, 3, and 6 h. Sixteen sham-operated diabetic and non-diabetic rats were used as controls. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL). Protein expression of phospho-JNK was examined by immunohistochemistry and Western blot. The numbers of TUNEL-positive cells and phospho-JNK protein expression in the cerebral cortices after 1, 3 and 6 h reperfusion was significantly higher in diabetic rats compared to non-diabetic animals subjected to ischemia and reperfusion (p < 0.05). Western blot analysis showed significantly higher phospho-JNK protein expression in the cerebral cortices of the diabetic rats after 1 and 3 h reperfusion than that was presented in non-diabetic animals subjected to ischemia and reperfusion (p < 0.05). These findings suggest that increased phosphorylation of JNK may be associated with diabetes-enhanced ischemic brain damage.

Stem cell guidance through the mechanistic target of rapamycin

Stem cells offer great promise for the treatment of multiple disorders throughout the body. Critical to this premise is the ability to govern stem cell pluripotency, proliferation, and differentiation. The mechanistic target of rapamycin (mTOR), 289-kDa serine/threonine protein kinase, that is a vital component of mTOR Complex 1 and mTOR Complex 2 represents a critical pathway for the oversight of stem cell maintenance. mTOR can control the programmed cell death pathways of autophagy and apoptosis that can yield variable outcomes in stem cell survival and be reliant upon proliferative pathways that include Wnt signaling, Wnt1 inducible signaling pathway protein 1 (WISP1), silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), and trophic factors. mTOR also is a necessary component for the early development and establishment of stem cells as well as having a significant impact in the regulation of the maturation of specific cell phenotypes. Yet, as a proliferative agent, mTOR can not only foster cancer stem cell development and tumorigenesis, but also mediate cell senescence under certain conditions to limit invasive cancer growth. mTOR offers an exciting target for the oversight of stem cell therapies but requires careful consideration of the diverse clinical outcomes that can be fueled by mTOR signaling pathways.