Apelin Receptor Can Act as a Specific Marker and Promising Therapeutic Target for Infantile Hemangioma

Apelin/APJ: Another Player in the Cancer Biology Network

The apelinergic system exerts multiple biological activities in human pathologies, including cancer. Overactivation of apelin/APJ, which has been detected in many malignant tumors, and the strong correlation with progression-free and overall survival, suggested the role of an oncogene for the apelin gene. Emerging evidence sheds new light on the effects of apelin on cellular functions and homeostasis in cancer cells and supports a direct role for this pathway on different hallmarks of cancer: "sustaining proliferative signaling", "resisting cell death", "activating invasion and metastasis", "inducing/accessing vasculature", "reprogramming cellular metabolism", "avoiding immune destruction" and "tumor-promoting inflammation", and "enabling replicative immortality". This article reviews the currently available literature on the intracellular processes regulated by apelin/APJ, focusing on those pathways correlated with tumor development and progression. Furthermore, the association between the activity of the apelinergic axis and the resistance of cancer cells to oncologic treatments (chemotherapy, immunotherapy, radiation) suggests apelin/APJ as a possible target to potentiate traditional therapies, as well as to develop diagnostic and prognostic applications. This issue will be also covered in the review.

Advances in the therapeutic potentials of ligands of the apelin receptor APJ

Angiotensin II protein J receptor, APJ, is a type A G protein coupled receptor. Endogenous apelin and elabela peptides stimulate APJ via distinct signalling profiles. A complex signalling map of elabela-stimulated APJ was published in 2022. Dimerization or oligomerization of APJ with itself or other receptor(s) can affect APJ signalling. Apelin has been shown to tolerate mutations and/or modifications at multiple sites without abolishing activity. This offers a great opportunity to design and engineer variants with desired signalling profiles and enhanced resistance to breakdown by peptidases. Several biased agonists with enhanced therapeutic potential have been generated. APJ agonists have therapeutic potential in multiple diseases including cardiovascular, renal, pulmonary and metabolic diseases, and viral infections. APJ antagonists may have therapeutic potential in cancer and retinopathy, and in related diseases in which unwanted angiogenesis is to be halted. A growing understanding of APJ signalling pathways and the robust therapeutic potential of associated ligands for many serious diseases will stimulate the clinical development of APJ ligands.

Immunohistochemical and ultrastructural identification of telocytes in the infantile hemangioma

Telocytes (TCs) are a distinctive cell entity of the stromal microenvironment of multiple tumors; to date, their existence in infantile hemangioma (IH) remains almost unexplored. This study was therefore undertaken to characterize the immunophenotype, location, morphology, and ultrastructure of telocytes in the IH by means of immunohistochemistry, immunofluorescence confocal microscopy, and transmission electron microscopy. Telocytes were initially identified by CD34, PDGFR-α, Vimentin, and AQP-1 immunostaining. Analyzing the spatial relationship among telocytes, stem cells, endothelial cells, pericytes in the IH with AQP-1/CD31, AQP-1/Glut-1, AQP-1/α-SMA, AQP-1/CD146 and AQP-1/CD133 double immunofluorescence. TCs were immunonegative for CD31, Glut-1, CD146, α-SMA, CD133, and C-kit in the IH. The ultrastructural examination confirmed the presence of TCs, namely stromal cells with characteristic cytoplasmic processes (i.e. telopodes) forming labyrinthine networks around microvessels and releasing extracellular vesicles. Our study provides evidence that telocytes are present and PDGFR-α and AQP-1 are specific antigenic markers in the IH.

Identifying Potential Diagnostic and Therapeutic Targets for Infantile Hemangioma Using WGCNA and Machine Learning Algorithms

Infantile hemangioma (IH) is the most common benign vascular tumor during infancy and childhood and is characterized by abnormal vascular development. It is the most common vascular tumor and its related mechanisms and treatments remain a problem. IH-related biomarkers have been identified using transcriptome analysis and can be used to predict clinical outcomes. This study aimed to identify the key target genes for IH treatment and explore their possible roles in the IH pathophysiology. Gene records were acquired from the Gene Expression Omnibus database. Utilizing integrated weighted gene co-expression network examination, gene clusters were determined. Single-sample gene set enrichment analysis was performed to gauge immune infiltration. Essential genes were identified via Random Forest and Least Absolute Selection and Shrinkage Operator analyses. Ultimately, a set of five pivotal genes associated with the ailment was identified (NETO2, IDO1, KDR, MEG3, and TMSB15A). A nomogram for predicting IH diagnosis was constructed based on hub genes. The calibration curve showed valid agreement between the prediction and conclusion that the key genes in the model were clinically significant. Neuropilin and Tolloid-like 2 (NETO2) are closely associated with tumor development. The role value of NETO2 expression levels increased in hemangioma-derived endothelial cells (HemECs). After silencing NETO2, the growth and migration of cancer cells were significantly restrained. This study revealed the critical role of NETO2 in IH development, suggesting that targeting NETO2 may be effective in improving the therapeutic outcome of IH.

Serum apelin as a potential biomarker for infantile hemangiomas

BACKGROUND

Infantile hemangiomas (IHs) are common benign vascular tumors in infants. Apelin, an endogenous cytokine, is implicated in the angiogenesis of neoplastic diseases. We aimed to explore the association between apelin and IHs, providing a foundation for clinical applications.

METHODS

We identified differential expression of apelin in proliferative IHs compared to healthy controls (HCs) through bioinformatics analysis of publicly available databases and verified by Immunofluorescence. Enzyme-linked immunosorbent assay was used to quantify the serum levels of apelin and vascular endothelial growth factor (VEGF) in a cohort of 116 cases of proliferative IHs, 65 cases of capillary malformations (CMs), and 70 HCs.

RESULTS

Apelin and APJ (APLNR, apelin receptor) were identified as the significantly upregulated differentially expressed genes (DEGs) in proliferative IHs. Immunofluorescence staining indicated high expression of apelin in proliferative IHs, while minimal expression in non-IH lesions. Apelin in IHs was reduced following 6 months of propranolol treatment. Serum apelin levels were significantly higher in the IH group compared to both the CM and HC groups. Moreover, apelin exhibited excellent discriminatory ability in distinguishing IHs from HCs, with an area under the curve (AUC) exceeding 0.90. A positive correlation was observed between the levels of apelin and the size of superficial IHs. The expression profiles of VEGF and apelin in IHs were found to be consistent.

CONCLUSIONS

Apelin shows promise as a potential biomarker for IHs. The association between apelin and IH size, as well as its responsiveness to propranolol treatment, indicates its possible utility as a valuable indicator for the therapeutic evaluation of IHs.

Ginseng-derived nanoparticles alleviate inflammatory bowel disease via the TLR4/MAPK and p62/Nrf2/Keap1 pathways

Inflammatory bowel disease (IBD) is closely linked to the homeostasis of the intestinal environment, and exosomes can be used to treat IBD due to their high biocompatibility and ability to be effectively absorbed by the intestinal tract. However, Ginseng-derived nanoparticles (GDNPs) have not been studied in this context and their mechanism of action remains unclear. Here, we investigated GDNPs ability to mediate intercellular communication in a complex inflammatory microenvironment in order to treat IBD. We found that GDNPs scavenge reactive oxygen species from immune cells and intestinal epithelial cells, inhibit the expression of pro-inflammatory factors, promote the proliferation and differentiation of intestinal stem cells, as well as enhancing the diversity of the intestinal flora. GDNPs significantly stabilise the intestinal barrier thereby promoting tissue repair. Overall, we proved that GDNPs can ameliorate inflammation and oxidative stress in vivo and in vitro, acting on the TLR4/MAPK and p62/Keap1/Nrf2 pathways, and exerting an anti-inflammatory and antioxidant effect. GDNPs mitigated IBD in mice by reducing inflammatory factors and improving the intestinal environment. This study offers new evidence of the potential therapeutic effects of GDNPs in the context of IBD, providing the conceptual ground for an alternative therapeutic strategy.

Combinative effects of β-elemene and propranolol on the proliferation, migration, and angiogenesis of hemangioma

Hemangioma (HA) is one of the most common benign vascular tumors among children. Propranolol is used as the first-line treatment for hemangioma and is a non-selective blocker of the β-adrenergic receptor. β-elemene is a compound extracted from Rhizoma zedoariae and has been approved for the treatment of tumors in clinical practice. However, the combinatorial effects of β-elemene and propranolol in the treatment of HA remains unclear. This study explored the combinative effects and mechanisms of β-elemene and propranolol using hemangioma-derived endothelial cells (HemECs). Cytotoxic assays showed that the combinatorial treatment of β-elemene and propranolol did not increase the cytotoxic effects of HemECs. Furthermore, functional analysis showed that the combinatorial treatment with β-elemene and propranolol significantly inhibited the proliferation, migration, and tube formation of the HemECs compared to the single treatment regimens. Mechanistic analysis showed that combinative treatment with β-elemene and propranolol synergistically down-regulated the hypoxia-inducible factor-1 alpha/vascular endothelial growth factor-A (HIF-1-α/VEGFA) signaling pathway. Additionally, in a xenograft tumor model, angiogenesis in the combinatorial treatment group was significantly lower than in the control, propranolol, and β-elemene treatment alone groups. Our results suggest that β-elemene combined with propranolol can significantly inhibit the proliferation, migration, and tube formation of HemECs via synergistically down-regulating the HIF-1-α/VEGFA signaling pathway without increasing any cytotoxic side effects.

Rbpj Deficiency Disrupts Vascular Remodeling via Abnormal Apelin and Cdc42 (Cell Division Cycle 42) Activity in Brain Arteriovenous Malformation

BACKGROUND

Brain arteriovenous malformations (bAVM) are characterized by enlarged blood vessels, which direct blood through arteriovenous shunts, bypassing the artery-capillary-vein network and disrupting blood flow. Clinically, bAVM treatments are invasive and not routinely applicable. There is critical need to understand mechanisms of bAVM pathologies and develop pharmacological therapies.

METHODS

We used an in vivo mouse model of Rbpj-mediated bAVM, which develops pathologies in the early postnatal period and an siRNA in vitro system to knockdown RBPJ in human brain microvascular endothelial cells (ECs). To understand molecular events regulated by endothelial Rbpj, we conducted RNA-Seq and chromatin immunoprecipitation-Seq analyses from isolated brain ECs.

RESULTS

Rbpj-deficient (mutant) brain ECs acquired abnormally rounded shape (with no change to cell area), altered basement membrane dynamics, and increased endothelial cell density along arteriovenous shunts, compared to controls, suggesting impaired remodeling of neonatal brain vasculature. Consistent with impaired endothelial cell dynamics, we found increased Cdc42 (cell division cycle 42) activity in isolated mutant ECs, suggesting that Rbpj regulates small GTPase (guanosine triphosphate hydrolase)-mediated cellular functions in brain ECs. siRNA-treated, RBPJ-deficient human brain ECs displayed increased Cdc42 activity, disrupted cell polarity and focal adhesion properties, and impaired migration in vitro. RNA-Seq analysis from isolated brain ECs identified differentially expressed genes in mutants, including Apelin, which encodes a ligand for G protein-coupled receptor signaling known to influence small GTPase activity. Chromatin immunoprecipitation-Seq analysis revealed chromatin loci occupied by Rbpj in brain ECs that corresponded to G-protein and Apelin signaling molecules. In vivo administration of a competitive peptide antagonist against the Apelin receptor (Aplnr/Apj) attenuated Cdc42 activity and restored endothelial cell morphology and arteriovenous connection diameter in Rbpj-mutant brain vessels.

CONCLUSIONS

Our data suggest that endothelial Rbpj promotes rearrangement of brain ECs during cerebrovascular remodeling, through Apelin/Apj-mediated small GTPase activity, and prevents bAVM. By inhibiting Apelin/Apj signaling in vivo, we demonstrated pharmacological prevention of Rbpj-mediated bAVM.