The Impact of Pulmonary Disorders on Neurological Health (Lung-Brain Axis).

The brain and lungs, vital organs in the body, play essential roles in maintaining overall well-being and survival. These organs interact through complex and sophisticated bi-directional pathways known as the 'lung-brain axis', facilitated by their close proximity and neural connections. Numerous studies have underscored the mediation of the lung-brain axis by inflammatory responses and hypoxia-induced damage, which are pivotal to the progression of both pulmonary and neurological diseases. This review aims to delve into how pulmonary diseases, including acute/chronic airway diseases and pulmonary conditions, can instigate neurological disorders such as stroke, Alzheimer's disease, and Parkinson's disease. Additionally, we highlight the emerging research on the lung microbiome which, drawing parallels between the gut and lungs in terms of microbiome contents, may play a significant role in modulating brain health. Ultimately, this review paves the way for exciting avenues of future research and therapeutics in addressing respiratory and neurological diseases.

Parenchymal cues define Vegfa-driven venous angiogenesis by activating a sprouting competent venous endothelial subtype.

Formation of organo-typical vascular networks requires cross-talk between differentiating parenchymal cells and developing blood vessels. Here we identify a Vegfa driven venous sprouting process involving parenchymal to vein cross-talk regulating venous endothelial Vegfa signaling strength and subsequent formation of a specialized angiogenic cell, prefabricated with an intact lumen and pericyte coverage, termed L-Tip cell. L-Tip cell selection in the venous domain requires genetic interaction between vascular Aplnra and Kdrl in a subset of venous endothelial cells and exposure to parenchymal derived Vegfa and Apelin. Parenchymal Esm1 controls the spatial positioning of venous sprouting by fine-tuning local Vegfa availability. These findings may provide a conceptual framework for understanding how Vegfa generates organo-typical vascular networks based on the selection of competent endothelial cells, induced via spatio-temporal control of endothelial Kdrl signaling strength involving multiple parenchymal derived cues generated in a tissue dependent metabolic context.

The contribution of the nervous system in the cancer progression.

Cancer progression is driven by genetic mutations, environmental factors, and intricate interactions within the tumor microenvironment (TME). The TME comprises of diverse cell types, such as cancer cells, immune cells, stromal cells, and neuronal cells. These cells mutually influence each other through various factors, including cytokines, vascular perfusion, and matrix stiffness. In the initial or developmental stage of cancer, neurotrophic factors such as nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor are associated with poor prognosis of various cancers by communicating with cancer cells, immune cells, and peripheral nerves within the TME. Over the past decade, research has been conducted to prevent cancer growth by controlling the activation of neurotrophic factors within tumors, exhibiting a novel attemt in cancer treatment with promising results. More recently, research focusing on controlling cancer growth through regulation of the autonomic nervous system, including the sympathetic and parasympathetic nervous systems, has gained significant attention. Sympathetic signaling predominantly promotes tumor progression, while the role of parasympathetic signaling varies among different cancer types. Neurotransmitters released from these signalings can directly or indirectly affect tumor cells or immune cells within the TME. Additionally, sensory nerve significantly promotes cancer progression. In the advanced stage of cancer, cancer-associated cachexia occurs, characterized by tissue wasting and reduced quality of life. This process involves the pathways via brainstem growth and differentiation factor 15-glial cell line-derived neurotrophic factor receptor alpha-like signaling and hypothalamic proopiomelanocortin neurons. Our review highlights the critical role of neurotrophic factors as well as central nervous system on the progression of cancer, offering promising avenues for targeted therapeutic strategies. [BMB Reports 2024; 57(4): 167-175].

Single-cell transcriptomics reveals functionally specialized vascular endothelium in brain.

The blood-brain barrier (BBB) limits the entry of leukocytes and potentially harmful substances from the circulation into the central nervous system (CNS). While BBB defects are a hallmark of many neurological disorders, the cellular heterogeneity at the neurovascular interface, and the mechanisms governing neuroinflammation are not fully understood.Through single-cell RNA sequencing of non-neuronal cell populations of the murine cerebral cortex during development, adulthood, ageing, and neuroinflammation, we identify reactive endothelial venules, a compartment of specialized postcapillary endothelial cells that are characterized by consistent expression of cell adhesion molecules, preferential leukocyte transmigration, association with perivascular macrophage populations, and endothelial activation initiating CNS immune responses. Our results provide novel insights into the heterogeneity of the cerebral vasculature and a useful resource for the molecular alterations associated with neuroinflammation and ageing.

Donor cell memory confers a metastable state of directly converted cells.

Generation of induced oligodendrocyte progenitor cells (iOPCs) from somatic fibroblasts is a strategy for cell-based therapy of myelin diseases. However, iOPC generation is inefficient, and the resulting iOPCs exhibit limited expansion and differentiation competence. Here we overcome these limitations by transducing an optimized transcription factor combination into a permissive donor phenotype, the pericyte. Pericyte-derived iOPCs (PC-iOPCs) are stably expandable and functionally myelinogenic with high differentiation competence. Unexpectedly, however, we found that PC-iOPCs are metastable so that they can produce myelination-competent oligodendrocytes or revert to their original identity in a context-dependent fashion. Phenotypic reversion of PC-iOPCs is tightly linked to memory of their original transcriptome and epigenome. Phenotypic reversion can be disconnected from this donor cell memory effect, and in vivo myelination can eventually be achieved by transplantation of O4+ pre-oligodendrocytes. Our data show that donor cell source and memory can contribute to the fate and stability of directly converted cells.

Integrin-linked kinase controls retinal angiogenesis and is linked to Wnt signaling and exudative vitreoretinopathy.

Familial exudative vitreoretinopathy (FEVR) is a human disease characterized by defective retinal angiogenesis and associated complications that can result in vision loss. Defective Wnt/ß-catenin signaling is an established cause of FEVR, whereas other molecular alterations contributing to the disease remain insufficiently understood. Here, we show that integrin-linked kinase (ILK), a mediator of cell-matrix interactions, is indispensable for retinal angiogenesis. Inactivation of the murine Ilk gene in postnatal endothelial cells results in sprouting defects, reduced endothelial proliferation and disruption of the blood-retina barrier, resembling phenotypes seen in established mouse models of FEVR. Retinal vascularization defects are phenocopied by inducible inactivation of the gene for α-parvin (Parva), an interactor of ILK. Screening genomic DNA samples from exudative vitreoretinopathy patients identifies three distinct mutations in human ILK, which compromise the function of the gene product in vitro. Together, our data suggest that defective cell-matrix interactions are linked to Wnt signaling and FEVR.

Dll4 and Notch signalling couples sprouting angiogenesis and artery formation.

Endothelial sprouting and proliferation are tightly coordinated processes mediating the formation of new blood vessels during physiological and pathological angiogenesis. Endothelial tip cells lead sprouts and are thought to suppress tip-like behaviour in adjacent stalk endothelial cells by activating Notch. Here, we show with genetic experiments in postnatal mice that the level of active Notch signalling is more important than the direct Dll4-mediated cell-cell communication between endothelial cells. We identify endothelial expression of VEGF-A and of the chemokine receptor CXCR4 as key processes controlling Notch-dependent vessel growth. Surprisingly, genetic experiments targeting endothelial tip cells in vivo reveal that they retain their function without Dll4 and are also not replaced by adjacent, Dll4-positive cells. Instead, activation of Notch directs tip-derived endothelial cells into developing arteries and thereby establishes that Dll4-Notch signalling couples sprouting angiogenesis and artery formation.

Yes-associated protein regulates endothelial cell contact-mediated expression of angiopoietin-2.

Angiogenesis is regulated by the dynamic interaction between endothelial cells (ECs). Hippo-Yes-associated protein (YAP) signalling has emerged as a key pathway that controls organ size and tissue growth by mediating cell contact inhibition. However, the role of YAP in EC has not been defined yet. Here, we show expression of YAP in the developing front of mouse retinal vessels. YAP subcellular localization, phosphorylation and activity are regulated by VE-cadherin-mediated-EC contacts. This VE-cadherin-dependent YAP phosphorylation requires phosphoinositide 3-kinase-Akt activation. We further identify angiopoietin-2 (ANG-2) as a potential transcriptional target of YAP in regulating angiogenic activity of EC in vitro and in vivo. Overexpression of YAP-active form in EC enhances angiogenic sprouting, and this effect is blocked by ANG-2 depletion or soluble Tie-2 treatment. These findings implicate YAP as a critical regulator in angiogenesis and provide new insights into the mechanism coordinating junctional stability and angiogenic activation of ECs.

Distinct roles of DKK1 and DKK2 in tumor angiogenesis.

Tumor angiogenesis is essential for tumor invasive growth and metastasis, and generates abnormal vascular structures unlike developmental neovessel formation. To reduce tumor vascular abnormalities such as leakage and perivascular cell coverage deficiency that limit cancer therapy effectiveness, novel therapeutic approaches focus on vessel normalization. We have previously shown that Dickkopf-1 (DKK1), a Wnt antagonist, inhibits and its homolog DKK2 enhances, angiogenesis in normal tissues. In the present study, we investigated the effects of DKK1 and DKK2 on tumor growth and angiogenesis. Treatment of B16F10 melanoma-bearing mice with adenovirus expressing DKK1 significantly reduced tumor growth but DKK2 increased growth compared with controls. Similar pattern of tumor growth was observed in endothelial-specific DKK1 and DKK2 transgenic mice. Interestingly, tumor vascular density and perfusion were significantly decreased by DKK1 but increased by DKK2. Moreover, coverage of blood vessels by pericytes was reduced by DKK1, while DKK2 increased it. We further observed that DKK1 diminished retinal vessel density and increased avascular area in an in vivo murine model of oxygen-induced retinopathy, whereas DKK2 showed opposite results. These findings demonstrate that DKK1 and DKK2 have differential roles in normalization and functionality of tumor blood vessels, in addition to angiogenesis.

The Wnt pathway and the roles for its antagonists, DKKS, in angiogenesis.

The Wnt signaling pathway is involved in a wide range of developmental and physiological processes, such as cell fate specification, tissue morphogenesis, and homeostasis. Thus, its dysregulation has been found in multiple diseases, including some cardiovascular disorders. The loss or gain of function of Wnt pathway components results in abnormal vascular development and angiogenesis. Further study has revealed that Wnt signaling in endothelial cells appears to contribute to vascular morphogenesis and endothelial cell specification. Owing to the significance of Wnt signaling in angiogenesis, Wnt antagonists have been considered potential treatments for neovascular disorders. In line with this, members of the Dkk protein family (Dkks), well-known Wnt antagonists, have been recently found to regulate angiogenesis. This review summarizes our present knowledge of the roles of Wnt signaling and Wnt antagonists, particularly Dkks, in angiogenic regulation and explores the therapeutic potential of Wnt antagonists.

Misexpression of Dickkopf-1 in endothelial cells, but not in chondrocytes or hypertrophic chondrocytes, causes defects in endochondral ossification.

Developing cartilage serves as a template for long-bone development during endochondral ossification. Although the coupling of cartilage and bone development with angiogenesis is an important regulatory step for endochondral ossification, the molecular mechanisms are poorly understood. One possible mechanism involves the action of Dickkopf (DKK), which is a family of soluble canonical Wnt antagonists with four members (DKK1-4). We initially observed opposite expression patterns of Dkk1 and Dkk2 during angiogenesis and chondrocyte differentiation: downregulation of Dkk1 and upregulation of Dkk2. We examined the in vivo role of Dkk1 and Dkk2 in linking cartilage/bone development and angiogenesis by generating transgenic (TG) mice that specifically express Dkk1 or Dkk2 in chondrocytes, hypertrophic chondrocytes, or endothelial cells. Despite specific expression pattern during cartilage development, chondrocyte- and hypertrophic chondrocyte-specific Dkk1 and Dkk2 TG mice showed normal developmental phenotypes. However, Dkk1 misexpression in endothelial cells resulted in defects of endochondral ossification and reduced skeletal size. The defects are caused by the inhibition of angiogenesis in developing bone and subsequent inhibition of apoptosis of hypertrophic chondrocytes and cartilage resorption.

Receptor activator of nuclear factor-κB ligand is a novel inducer of myocardial inflammation.

AIMS: Although increased levels of myocardial receptor activator of nuclear factor (NF)-κB ligand (RANKL) have been reported in heart failure, the role of this pathway in mediating activation of inflammatory pathways during myocardial remodelling is less well understood. This study sought to determine the role of myocardial RANKL in regulating cytokine expression. METHODS AND RESULTS: A marked increase in RANKL expression occurred as early as 6h following transverse aortic constriction (TAC) in mouse hearts and persisted at 3 and 17 days. An increase in tumour necrosis factor-α (TNF-α), interleukin (IL)-1α, and IL-1ß was observed in the hypertrophied hearts only at 3 or 17 days after TAC. Treatment with losartan significantly attenuated TAC-induced cardiac hypertrophy, in parallel with decreased expression of RANKL, TNF-α, IL-1α, and IL-1ß. Furthermore, injection of a RANKL-neutralizing monoclonal antibody attenuated RANKL-induced cytokine expression. RANKL stimulated expression of TNF-α, IL-1α, and IL-1ß in neonatal rat cardiomyocytes via activation of NF-κB. RANKL-induced NF-κB activation and expression of these cytokines were both attenuated when RANK, receptor for RANKL, or TRAF2 or TRAF6, adaptors for RANK, was silenced by siRNA. Furthermore, inhibitors of phospholipase C (PLC), protein kinase C (PKC), and inhibitor of κB kinase also significantly inhibited RANKL-induced cellular activities, but inhibitors of phosphatidylinositol 3-kinase, extracellular signal-regulated kinase, or p38 mitogen-activated protein kinase were without effect. CONCLUSION: Our data demonstrate for the first time that the pressure-overloaded myocardium generates RANKL, which induces TNF-α, IL-1α, and IL-1ß production via a RANK-TRAF2/TRAF6-PLC-PKC-NF-κB-mediated autocrine mechanism.

The WNT antagonist Dickkopf2 promotes angiogenesis in rodent and human endothelial cells.

Neovessel formation is a complex process governed by the orchestrated action of multiple factors that regulate EC specification and dynamics within a growing vascular tree. These factors have been widely exploited to develop therapies for angiogenesis-related diseases such as diabetic retinopathy and tumor growth and metastasis. WNT signaling has been implicated in the regulation and development of the vascular system, but the detailed mechanism of this process remains unclear. Here, we report that Dickkopf1 (DKK1) and Dickkopf2 (DKK2), originally known as WNT antagonists, play opposite functional roles in regulating angiogenesis. DKK2 induced during EC morphogenesis promoted angiogenesis in cultured human endothelial cells and in in vivo assays using mice. Its structural homolog, DKK1, suppressed angiogenesis and was repressed upon induction of morphogenesis. Importantly, local injection of DKK2 protein significantly improved tissue repair, with enhanced neovascularization in animal models of both hind limb ischemia and myocardial infarction. We further showed that DKK2 stimulated filopodial dynamics and angiogenic sprouting of ECs via a signaling cascade involving LRP6-mediated APC/Asef2/Cdc42 activation. Thus, our findings demonstrate the distinct functions of DKK1 and DKK2 in controlling angiogenesis and suggest that DKK2 may be a viable therapeutic target in the treatment of ischemic vascular diseases.

The cell adhesion molecule L1 promotes gallbladder carcinoma progression in vitro and in vivo.

Recent studies have demonstrated that the cell adhesion molecule, L1, is expressed in several malignant tumor types and its expression correlates with tumor progression and metastasis. However, the role of L1 in gallbladder carcinoma (GBC) remains unclear. Here, we demonstrate that L1 is expressed in GBC cells and plays an important role in the growth, motility, invasiveness, and adhesiveness of GBC cells. Specific depletion or overexpression of L1 in the GBC cell lines JCRB1033 and SNU-308, respectively, was achieved by lentivirus-mediated transduction and expression of an L1 mRNA-specific short hairpin RNA or full-length human L1. Stable depletion of L1 led to a significant decrease in GBC cell proliferation, migration and invasion, as well as decreased intracellular signaling through AKT and FAK. Overexpression of L1 in GBC cells enhanced these cellular activities. In a GBC xenograft nude mouse model, suppression of L1 markedly reduced tumor growth and increased the survival of tumor-bearing mice whereas L1 overexpression stimulated tumorigenicity. Taken together, these results suggest that L1 plays a crucial role in GBC progression and may be a novel therapeutic target in GBC treatment.

Clec14a is specifically expressed in endothelial cells and mediates cell to cell adhesion.

Clec14a is a member of the thrombomodulin (TM) family, but its function has not yet been determined. Here, we report that Clec14a is a plasma membrane protein of endothelial cells (ECs) expressed specifically in the vasculature of mice. Deletion mutant analysis revealed that Clec14a mediates cell-cell adhesion through its C-type lectin-like domain. Knockdown of Clec14a in ECs suppressed cell migratory activity and filopodial protrusion, and delayed formation of tube-like structures. These findings demonstrate that Clec14a is a novel EC-specific protein that appears to play a role in cell-cell adhesion and angiogenesis.

Interleukin-33 induces angiogenesis and vascular permeability through ST2/TRAF6-mediated endothelial nitric oxide production.

Interleukin-33 (IL-33), a member of the IL-1 cytokine family, is emerging as a new regulator of immune responses and inflammatory vascular diseases. Although IL-33 and its cognate receptor ST2 appear to be expressed in vascular cells, the precise role of IL-33 in the vasculature has not been determined. In this study, we report a novel role of IL-33 as a potent endothelial activator, promoting both angiogenesis and vascular permeability. IL-33 increased proliferation, migration, and morphologic differentiation of human endothelial cells, consistently with increased angiogenesis in vivo. IL-33 also increased endothelial permeability with reduced vascular endothelial-cadherin-facilitated cell-cell junctions in vitro and induced vascular leakage in mouse skin. These effects of IL-33 were blocked by knockdown of ST2. Ligation of IL-33 with ST2 rapidly increased endothelial nitric oxide (NO) production through TRAF6-mediated activation of phosphoinoside-3-kinase, Akt, and endothelial NO synthase. Moreover, pharmacologic or genetic blockage of endothelial NO generation resulted in the inhibition of angiogenesis and vascular hyperpermeability induced by IL-33. These data demonstrate that IL-33 promotes angiogenesis and vascular leakage by stimulating endothelial NO production via the ST2/TRAF6-Akt-eNOS signaling pathway. These findings open new perspectives for the role of IL-33 in the pathogenesis of angiogenesis-dependent and inflammatory vascular diseases.