Endothelial-specific Loss of IFT88 Promotes Endothelial-to-Mesenchymal Transition and Exacerbates Bleomycin-induced Pulmonary Fibrosis

SIRT2 inhibition attenuates myofibroblast transition through autophagy-mediated ciliogenesis in renal epithelial cells

Myofibroblast transition plays a crucial role in both fibrotic diseases and wound healing. Although SIRT2 regulates fibrosis, its mechanisms of action remain poorly understood. This study aimed to investigate the effects of SIRT2 inhibition on myofibroblast transition in human renal cells under quiescent conditions. HK-2 kidney proximal tubular epithelial cells were starved of serum, resulting in the formation of primary cilia. Transforming growth factor-β (TGF-β) stimulation reduced both the number of ciliated cells and ciliary length. The ciliary defects resulted from a failure in autophagy termination, leading to the accumulation of OFD1, a negative regulator of ciliogenesis, at centriolar satellites. This phenomenon was correlated with the upregulation of fibrosis-related proteins. To elucidate the role of SIRT2 in the autophagy-ciliogenesis-fibrosis axis, cells were treated with AGK2, a specific inhibitor of SIRT2. AGK2 treatment promoted the formation of both autophagosomes and autolysosomes and facilitated OFD1 degradation at the centriolar satellites, resulting in the lengthening of primary cilia. Restoration of primary cilia by AGK2 was associated with the suppression of myofibroblast transition. In conclusion, SIRT2 inhibition attenuates TGF-β-induced fibrosis by promoting autophagy-mediated ciliogenesis. This study highlights SIRT2 as a potential therapeutic target for fibrotic diseases.

Targeting endothelial cells: A novel strategy for pulmonary fibrosis treatment

Endothelial cells (ECs) are a monolayer of flat cells lining the inner surfaces of blood and lymphatic vessels. They play a key role in many physiological and pathological processes. Specifically, they maintain vascular permeability and structural stability and participate in immune responses, inflammation, coagulation, and other vital functions. ECs play a decisive role in various age-related diseases; however, their involvement in pulmonary fibrosis (PF) remains poorly understood. PF refers to a group of chronic interstitial lung diseases characterised by progressive scarring of the pulmonary parenchyma, primarily caused by aberrant tissue repair mechanisms. These changes lead to irreversible loss of lung function. Although the exact pathophysiological mechanism underlying PF has not yet been elucidated, recent studies have indicated that ECs may play a pivotal role in PF. This review outlines the involvement of pulmonary vascular ECs in PF, focusing on the regulation of vascular remodelling and endothelial barrier integrity and on the maintenance of angiogenesis through EC-specific markers, such as vascular endothelial growth factor. This review also explores processes such as endothelial-to-mesenchymal transition, immune cell interactions, anti-EC antibody reactions, metabolic dysregulation, and cellular senescence. By elucidating recent advancements in understanding the role of ECs in PF and examining drugs targeting ECs for the treatment of PF, this study provides novel insights into the pathological mechanisms of PF and the development of endothelium-based therapeutic agents.

Ciliopathy interacts with neonatal anesthesia to cause non-apoptotic caspase-mediated motor deficits

Increasing evidence suggests that anesthesia may induce developmental neurotoxicity, yet the influence of genetic predispositions associated with congenital anomalies on this toxicity remains largely unknown. Children with congenital heart disease often exhibit mutations in cilia-related genes and ciliary dysfunction, requiring sedation for their catheter or surgical interventions during the neonatal period. Here we demonstrate that briefly exposing ciliopathic neonatal mice to ketamine causes motor skill impairments, which are associated with a baseline deficit in neocortical layer V neuron apical spine density and their altered dynamics during motor learning.. These neuromorphological changes were linked to augmented non-apoptotic neuronal caspase activation. Neonatal caspase suppression rescued the spine density and motor deficits, confirming the requirement for sublethal caspase signaling in appropriate spine formation and motor learning. Our findings suggest that ciliopathy interacts with ketamine to induce motor impairments, which is reversible through caspase inhibition. Furthermore, they underscore the potential for ketamine- induced sublethal caspase responses in shaping neurodevelopmental outcomes.

The potential therapeutic effect of human umbilical cord mesenchymal stem cell-derived exosomes in bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of preterm infants, with its incidence rising due to improved survival rates of these infants. BPD results from a combination of prenatal and postnatal factors, such as mechanical ventilation, oxygen toxicity, and infections, all of which significantly impact the prognosis and growth of affected infants. Current treatment options for BPD are largely supportive and do not address the underlying pathology. Exosomes are cell-derived bilayer-enclosed membrane structures enclosing proteins, lipids, RNAs, growth factors, cytokines and metabolites. They have become recognized as crucial regulators of intercellular communication in various physiological and pathological processes. Previous studies have revealed the therapeutic potential of human umbilical cord mesenchymal stem cells-derived exosomes (HUCMSCs-Exos) in promoting tissue repair and regeneration. Therefore, HUCMSCs-Exos maybe a promising and effective therapeutic modality for BPD. In this review, we firstly provide a comprehensive overview of BPD, including its etiology and the mechanisms of lung injury. Then we detail the isolation, characterization, and contents of HUCMSCs-Exos, and discuss their potential mechanisms of HUCMSCs-Exos in BPD treatment. Additionally, we summarize current clinical trials and discuss the challenges in translating these findings from bench to bedside. This review aims to lay the groundwork for future clinical applications of HUCMSCs-Exos in treating BPD.

Disruption of blood-brain barrier and endothelial-to-mesenchymal transition are attenuated by Astragalus polysaccharides mediated through upregulation of ETS1 expression in experimental autoimmune encephalomyelitis

Blood-brain barrier (BBB) breakdown, an early hallmark of multiple sclerosis (MS), remains crucial for MS progression. Our previous works have confirmed that Astragalus polysaccharides (APS) can significantly ameliorate demyelination and disease progression in experimental autoimmune encephalomyelitis (EAE) mice. However, it remains unclear whether APS protects BBB and the potential mechanism. In this study, we found that APS effectively reduced BBB leakage in EAE mice, which was accompanied by a decreased level of endothelial-to-mesenchymal transition (EndoMT) in the central nervous system (CNS). We further induced EndoMT in the mouse brain endothelial cells (bEnd.3) by interleukin-1β (IL-1β) in vitro. The results showed that APS treatment could inhibit IL-1β-induced EndoMT and endothelial cell dysfunction. In addition, the transcription factor ETS1 is a central regulator of EndoMT related to the compromise of BBB. We tested the regulation of APS on ETS1 and identified the expression of ETS1 was upregulated in both EAE mice and bEnd.3 cells by APS. ETS1 knockdown facilitated EndoMT and endothelial cell dysfunction, which completely abolished the regulatory effect of APS. Collectively, APS treatment could protect BBB integrity by inhibiting EndoMT, which might be associated with upregulating ETS1 expression. Our findings indicated that APS has potential value in the prevention of MS.

Endothelial-to-Mesenchymal Transition in Cardiovascular Pathophysiology

Under different pathophysiological conditions, endothelial cells lose endothelial phenotype and gain mesenchymal cell-like phenotype via a process known as endothelial-to-mesenchymal transition (EndMT). At the molecular level, endothelial cells lose the expression of endothelial cell-specific markers such as CD31/platelet-endothelial cell adhesion molecule, von Willebrand factor, and vascular-endothelial cadherin and gain the expression of mesenchymal cell markers such as α-smooth muscle actin, N-cadherin, vimentin, fibroblast specific protein-1, and collagens. EndMT is induced by numerous different pathways triggered and modulated by multiple different and often redundant mechanisms in a context-dependent manner depending on the pathophysiological status of the cell. EndMT plays an essential role in embryonic development, particularly in atrioventricular valve development; however, EndMT is also implicated in the pathogenesis of several genetically determined and acquired diseases, including malignant, cardiovascular, inflammatory, and fibrotic disorders. Among cardiovascular diseases, aberrant EndMT is reported in atherosclerosis, pulmonary hypertension, valvular disease, fibroelastosis, and cardiac fibrosis. Accordingly, understanding the mechanisms behind the cause and/or effect of EndMT to eventually target EndMT appears to be a promising strategy for treating aberrant EndMT-associated diseases. However, this approach is limited by a lack of precise functional and molecular pathways, causes and/or effects, and a lack of robust animal models and human data about EndMT in different diseases. Here, we review different mechanisms in EndMT and the role of EndMT in various cardiovascular diseases.

Primary cilia suppress the fibrotic activity of atrial fibroblasts from patients with atrial fibrillation in vitro

Atrial fibrosis serves as an arrhythmogenic substrate in atrial fibrillation (AF) and contributes to AF persistence. Treating atrial fibrosis is challenging because atrial fibroblast activity is multifactorial. We hypothesized that the primary cilium regulates the profibrotic response of AF atrial fibroblasts, and explored therapeutic potentials of targeting primary cilia to treat fibrosis in AF. We included 25 patients without AF (non-AF) and 26 persistent AF patients (AF). Immunohistochemistry using a subset of the patients (non-AF: n = 10, AF: n = 10) showed less ciliated fibroblasts in AF versus non-AF. Acetylated α-tubulin protein levels were decreased in AF, while the gene expressions of AURKA and NEDD9 were highly increased in AF patients' left atrium. Loss of primary cilia in human atrial fibroblasts through IFT88 knockdown enhanced expression of ECM genes, including FN1 and COL1A1. Remarkably, restoration or elongation of primary cilia by an AURKA selective inhibitor or lithium chloride, respectively, prevented the increased expression of ECM genes induced by different profibrotic cytokines in atrial fibroblasts of AF patients. Our data reveal a novel mechanism underlying fibrotic substrate formation via primary cilia loss in AF atrial fibroblasts and suggest a therapeutic potential for abrogating atrial fibrosis by restoring primary cilia.

Protein Disulfide Isomerase 4 Is an Essential Regulator of Endothelial Function and Survival

Endothelial autophagy plays an important role in the regulation of endothelial function. The inhibition of endothelial autophagy is associated with the reduced expression of protein disulfide isomerase 4 (PDIA-4); however, its role in endothelial cells is not known. Here, we report that endothelial cell-specific loss of PDIA-4 leads to impaired autophagic flux accompanied by loss of endothelial function and apoptosis. Endothelial cell-specific loss of PDIA-4 also induced marked changes in endothelial cell architecture, accompanied by the loss of endothelial markers and the gain of mesenchymal markers consistent with endothelial-to-mesenchymal transition (EndMT). The loss of PDIA-4 activated TGFβ-signaling, and inhibition of TGFβ-signaling suppressed EndMT in PDIA-4-silenced endothelial cells in vitro. Our findings help elucidate the role of PDIA-4 in endothelial autophagy and endothelial function and provide a potential target to modulate endothelial function and/or limit autophagy and EndMT in (patho-)physiological conditions.

Airway ciliated cells in adult lung homeostasis and COPD

Cilia are organelles emanating from the cell surface, consisting of an axoneme of microtubules that extends from a basal body derived from the centrioles. They are either isolated and nonmotile (primary cilia), or grouped and motile (motile cilia). Cilia are at the centre of fundamental sensory processes and are involved in a wide range of human disorders. Pulmonary cilia include motile cilia lining the epithelial cells of the conductive airways to orchestrate mucociliary clearance, and primary cilia found on nondifferentiated epithelial and mesenchymal cells acting as sensors and cell cycle keepers. Whereas cilia are essential along the airways, their regulatory molecular mechanisms remain poorly understood, resulting in a lack of therapeutic strategies targeting their structure or functions. This review summarises the current knowledge on cilia in the context of lung homeostasis and COPD to provide a comprehensive overview of the (patho)biology of cilia in respiratory medicine with a particular emphasis on COPD.

Exosomal miR-218 derived from mesenchymal stem cells inhibits endothelial-to-mesenchymal transition by epigenetically modulating of BMP2 in pulmonary fibrosis

Endothelial-to-mesenchymal transition (EndMT), the process by which endothelial cells lose their characteristics and acquire mesenchymal phenotypes, participates in the pathogenic mechanism of idiopathic pulmonary fibrosis. Recently, exosomes derived from human umbilical cord mesenchymal stem cells (hucMSC-Exos) has been introduced as a promising treatment in organ fibrosis. This study aimed to explore the effects as well as the molecular mechanism for hucMSC-Exo in pulmonary fibrosis. The intravenous administration of hucMSC-Exos alleviated bleomycin-induced pulmonary fibrosis in vivo. Moreover, hucMSC-Exos elevated miR-218 expression and restored endothelial properties weakened by TGF-β in endothelial cells. Knockdown of miR-218 partially abrogated the inhibition effect of hucMSC-Exos on EndMT. Our mechanistic study further demonstrated that MeCP2 was the direct target of miR-218. Overexpressing MeCP2 aggravated EndMT and caused increased CpG islands methylation at BMP2 promoter, which lead to BMP2 post-transcriptional gene silence. Transfection of miR-218 mimic increased BMP2 expression as well, which was downregulated by overexpression of MeCP2. Taken together, these findings indicate exosomal miR-218 derived from hucMSCs may possess anti-fibrotic properties and inhibit EndMT through MeCP2/BMP2 pathway, providing a new avenue of preventive application in pulmonary fibrosis.

Intestinal overgrowth of Candida albicans exacerbates bleomycin-induced pulmonary fibrosis in mice with dysbiosis

Increasing evidence indicates an interaction between the intestinal microbiota and diseases in distal organs. However, the relationship between pulmonary fibrosis and the intestinal microbiota, especially intestinal fungal microbiota, is poorly understood. Thus, this study aimed to determine the effects of changes in the intestinal fungal microbiota on the pathogenesis of pulmonary fibrosis. Mice with intestinal overgrowth of Candida albicans, which was established by oral administration of antibiotics plus C. albicans, showed accelerated bleomycin-induced pulmonary fibrosis relative to the control mice (i.e. without C. albicans treatment). In addition, the mice with intestinal overgrowth of C. albicans showed enhanced Th17-type immunity, and treatment with IL-17A-neutralizing antibody alleviated pulmonary fibrosis in these mice but not in the control mice. This result indicates that IL-17A is involved in the pathogenesis of C. albicans-exacerbated pulmonary fibrosis. Even before bleomycin treatment, the expression of Rorc, the master regulator of Th17, was already upregulated in the pulmonary lymphocytes of the mice with intestinal overgrowth of C. albicans. Subsequent administration of bleomycin triggered these Th17-skewed lymphocytes to produce IL-17A, which enhanced endothelial-mesenchymal transition. These results suggest that intestinal overgrowth of C. albicans exacerbates pulmonary fibrosis via IL-17A-mediated endothelial-mesenchymal transition. Thus, it might be a potential therapeutic target in pulmonary fibrosis. This study may serve as a basis for using intestinal fungal microbiota as novel therapeutic targets in pulmonary fibrosis. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

CAPILLARY LEAK AND EDEMA AFTER RESUSCITATION: THE POTENTIAL CONTRIBUTION OF REDUCED ENDOTHELIAL SHEAR STRESS CAUSED BY HEMODILUTION

ABSTRACT

Normal shear stress is essential for the normal structure and functions of the microcirculation. Hemorrhagic shock leads to reduced shear stress due to reduced tissue perfusion. Although essential for the urgent restoration of cardiac output and systemic blood pressure, large volume resuscitation with currently available solutions causes hemodilution, further reducing endothelial shear stress. In this narrative review, we consider how the use of currently available resuscitation solutions results in persistent reduction in endothelial shear stress, despite successfully increasing cardiac output and systemic blood pressure. We consider how this reduced shear stress causes (1) a failure to restore normal vasomotor function and normal tissue perfusion thus leading to persistent tissue hypoxia and (2) increased microvascular endothelial permeability resulting in edema formation and impaired organ function. We discuss the need for clinical research into resuscitation strategies and solutions that aim to quickly restore endothelial shear stress in the microcirculation to normal.

S1PR1 attenuates pulmonary fibrosis by inhibiting EndMT and improving endothelial barrier function

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal disease of unknown etiology. Its pathological manifestations include excessive proliferation and activation of fibroblasts and deposition of extracellular matrix. Endothelial cell-mesenchymal transformation (EndMT), a novel mechanism that generates fibroblast during IPF, is responsible for fibroblast-like phenotypic changes and activation of fibroblasts into hypersecretory cells. However, the exact mechanism behind EndMT-derived fibroblasts and activation is uncertain. Here, we investigated the role of sphingosine 1-phosphate receptor 1 (S1PR1) in EndMT-driven pulmonary fibrosis.

METHODS

We treated C57BL/6 mice with bleomycin (BLM) in vivo and pulmonary microvascular endothelial cells with TGF-β1 in vitro. Western blot,flow cytometry, and immunofluorescence were used to detect the expression of S1PR1 in endothelial cells. To evaluate the effect of S1PR1 on EndMT and endothelial barrier and its role in lung fibrosis and related signaling pathways, S1PR1 agonist and antagonist were used in vitro and in vivo.

RESULTS

Endothelial S1PR1 protein expression was downregulated in both in vitro and in vivo models of pulmonary fibrosis induced by TGF-β1 and BLM, respectively. Downregulation of S1PR1 resulted in EndMT, indicated by decreased expression of endothelial markers CD31 and VE-cadherin, increased expression of mesenchymal markers α-SMA and nuclear transcription factor Snail, and disruption of the endothelial barrier. Further mechanistic studies found that stimulation of S1PR1 inhibited TGF-β1-mediated activation of the Smad2/3 and RhoA/ROCK1 pathways. Moreover, stimulation of S1PR1 attenuated Smad2/3 and RhoA/ROCK1 pathway-mediated damage to endothelial barrier function.

CONCLUSIONS

Endothelial S1PR1 provides protection against pulmonary fibrosis by inhibiting EndMT and attenuating endothelial barrier damage. Accordingly, S1PR1 may be a potential therapeutic target in progressive IPF.

Vascular mechanotransduction

This review aims to survey the current state of mechanotransduction in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), including their sensing of mechanical stimuli and transduction of mechanical signals that result in the acute functional modulation and longer-term transcriptomic and epigenetic regulation of blood vessels. The mechanosensors discussed include ion channels, plasma membrane-associated structures and receptors, and junction proteins. The mechanosignaling pathways presented include the cytoskeleton, integrins, extracellular matrix, and intracellular signaling molecules. These are followed by discussions on mechanical regulation of transcriptome and epigenetics, relevance of mechanotransduction to health and disease, and interactions between VSMCs and ECs. Throughout this review, we offer suggestions for specific topics that require further understanding. In the closing section on conclusions and perspectives, we summarize what is known and point out the need to treat the vasculature as a system, including not only VSMCs and ECs but also the extracellular matrix and other types of cells such as resident macrophages and pericytes, so that we can fully understand the physiology and pathophysiology of the blood vessel as a whole, thus enhancing the comprehension, diagnosis, treatment, and prevention of vascular diseases.

Endothelial cell-derived MMP19 promotes pulmonary fibrosis by inducing E(nd)MT and monocyte infiltration

BACKGROUND

Matrix metalloproteinases (MMPs) play important roles in remodeling the extracellular matrix and in the pathogenesis of idiopathic pulmonary fibrosis (IPF). MMP19, which is an MMP, was significantly upregulated in hyperplastic alveolar epithelial cells in IPF lung tissues and promoted epithelial-mesenchymal transition (EMT). Recent studies have demonstrated that endothelial-to-mesenchymal transition (E(nd)MT) contributes to pulmonary fibrosis. However, the role of MMP19 in pulmonary vascular injury and repair and E(nd)MT remains unclear.

METHODS

To determine the role of MMP19 in E(nd)MT and pulmonary fibrosis. MMP19 expressions were determined in the lung endothelial cells of IPF patients and bleomycin (BLM)-induced mice. The roles of MMP19 in E(nd)MT and endothelial barrier permeability were studied in the MMP19 cDNA-transfected primary human pulmonary microvascular endothelial cells (HPMECs) and MMP19 adenoassociated virus (MMP19-AAV)-infected mice. The regulatory mechanism of MMP19 in pulmonary fibrosis was elucidated by blocking its interacting proteins SDF1 and ET1 with AMD3100 and Bosentan, respectively.

RESULTS

In this study, we found that MMP19 expression was significantly increased in the lung endothelial cells of IPF patients and BLM-induced mice compared to the control groups. MMP19 promoted E(nd)MT and the migration and permeability of HPMECs in vitro, stimulated monocyte infiltration into the alveolus, and aggravated BLM-induced pulmonary fibrosis in vivo. SDF1 and Endothelin-1 (ET1) were physically associated with MMP19 in HPMECs and colocalized with MMP19 in endothelial cells in IPF patient lung tissues. AMD3100 and bosentan alleviated the fibrosis induced by MMP19 in the BLM mouse model.

CONCLUSION

MMP19 promoted E(nd)MT by interacting with ET1 and stimulated monocyte infiltration into lung tissues via the SDF1/CXCR4 axis, thus aggravating BLM-induced pulmonary fibrosis. Vascular integrity regulated by MMP19 could be a promising therapeutic target for suppressing pulmonary fibrosis. Video abstract.

MicroRNA miR-378-3p is a novel regulator of endothelial autophagy and function

Autophagy is a highly conserved cellular process in which cytoplasmic materials are internalized into an autophagosome that later fuses with a lysosome for their degradation and recycling. MicroRNAs (miRNAs) are integral regulators in various cellular processes including autophagy and endothelial function. Accordingly, we hypothesize that miRNA, miR-378-3p, is an essential regulator of endothelial autophagy and endothelial function. MiR-378-3p expression was measured following inhibition and activation of autophagy in endothelial cells. A gain- or loss-of function approach was employed to either overexpress or inhibit the expression of miR-378-3p, respectively, in cultured endothelial cells, and markers of autophagy and indices of endothelial function, such as proliferation, migration and tube forming potential were measured. Inhibition and activation of autophagy up- and down-regulated the expression of miR-378-3p, respectively. Furthermore, miR-378a-3p overexpression was associated with impaired autophagy indicated by a reduced LC3-II/LC3-I ratio, and endothelial function indicated by increased proliferation associated with reduced p21 expression, reduced angiogenic potential and increased migration, which were associated with reduced expression of endothelial nitric oxide synthase (eNOS), an essential regulator of endothelial function. Accordingly, miR-378a-3p inhibition was associated with reduced cell proliferation, migration and increased eNOS in endothelial cells. Apoptosis was not affected in cells transfected with antagomir. Using in silico approach, Protein Disulfide Isomerase Family A Member 4 (PDIA-4) was identified and confirmed as a target of miR-378-3p. PDIA-4 expression was significantly reduced or enhanced in miR-378-3p-overexpressing or -silenced endothelial cells, respectively. Our findings show an inverse relationship between miR-378-3p and endothelial autophagy and function, providing a novel insight about the epigenetic regulation of these processes.

[Inducible co-stimulatory molecules participate in mesenteric vascular endothelial-mesenchymal transition and sclerosis of mesenteric vessels in spontaneously hypertensive rats]

OBJECTIVE

To investigate the correlation of inducible co-stimulatory molecules (ICOS) with mesenteric vascular endothelial- mesenchymal transition (EndMT) and sclerosis in spontaneously hypertensive rats (SHR).

METHODS

Twenty 4-week-old WKY rats and 20 SHRs of the same strain were both randomly divided into 4 groups for observation at 4, 6, 10 and 30 weeks of age. ICOS expression frequency in rat spleen CD4+T cells was analyzed using flow cytometry, and the expressions of ICOS, VE-cad, α-SMA and Col3 mRNA in rat mesentery were detected by RT-PCR. The distributions of ICOS, IL-17A and TGF-β in rat mesentery were detected by immunohistochemistry. The levels of IL-17A and TGF-β in rat plasma were measured using ELISA. The morphological changes of rat mesenteric vessels were observed with Masson staining. Spearman or Pearson correlation analyses were used to evaluate the correlation between ICOS expression and the expressions of the markers of vascular EndMT and sclerosis.

RESULTS

Compared with the control WKY rats, the SHRs began to show significantly increased systolic blood pressure and ICOS expression frequency on CD4+T cells at 6 weeks of age (P < 0.05). In the SHRs, the mRNA and protein expressions of ICOS, α-SMA, Col3, IL-17A and TGF-β in the mesentery were significantly higher than those in control group (P < 0.05), while the mRNA and protein expressions of VE-cad started to reduce significantly at 10 weeks of age (P < 0.05). The plasma levels of IL-17A and TGF-β were significantly increased in SHRs since 6 weeks of age (P < 0.05) with progressive worsening of mesenteric vascular sclerosis (P < 0.05). ICOS mRNA and protein expression levels in the mesenteric tissues of SHRs began to show positive correlations with α-SMA and Col3 expression levels and the severity of vascular sclerosis at 6 weeks of age (P < 0.05) and a negative correlation with VE-cad expression level at 10 weeks (P < 0.05).

CONCLUSION

ICOS play an important pathogenic role in EndMT and sclerosis of mesenteric vessels in essential hypertension by mediating related immune responses.

Lactate promotes endothelial-to-mesenchymal transition via Snail1 lactylation after myocardial infarction

High levels of lactate are positively associated with the prognosis and mortality in patients with heart attack. Endothelial-to-mesenchymal transition (EndoMT) plays an important role in cardiac fibrosis. Here, we report that lactate exerts a previously unknown function that increases cardiac fibrosis and exacerbates cardiac dysfunction by promoting EndoMT following myocardial infarction (MI). Treatment of endothelial cells with lactate disrupts endothelial cell function and induces mesenchymal-like function following hypoxia by activating the TGF-β/Smad2 pathway. Mechanistically, lactate induces an association between CBP/p300 and Snail1, leading to lactylation of Snail1, a TGF-β transcription factor, through lactate transporter monocarboxylate transporter (MCT)-dependent signaling. Inhibiting Snail1 diminishes lactate-induced EndoMT and TGF-β/Smad2 activation after hypoxia/MI. The MCT inhibitor CHC mitigates lactate-induced EndoMT and Snail1 lactylation. Silence of MCT1 compromises lactate-promoted cardiac dysfunction and EndoMT after MI. We conclude that lactate acts as an important molecule that up-regulates cardiac EndoMT after MI via induction of Snail1 lactylation.

Loss of fatty acid binding protein 3 ameliorates lipopolysaccharide-induced inflammation and endothelial dysfunction

Circulating fatty acid-binding protein 3 (FABP3) is an effective biomarker of myocardial injury and peripheral artery disease (PAD). The endothelium, which forms the inner most layer of every blood vessel, is exposed to higher levels of FABP3 in PAD or following myocardial injury, but the pathophysiological role of endothelial FABP3, the effect of FABP3 exposure on endothelial cells, and related mechanisms are unknown. Here, we aimed to evaluate the pathophysiological role of endothelial FABP3 and related mechanisms in vitro. Our molecular and functional in vitro analyses show that (1) FABP3 is basally expressed in endothelial cells; (2) inflammatory stress in the form of lipopolysaccharide (LPS) upregulated endothelial FABP3 expression; (3) loss of endogenous FABP3 protected endothelial cells against LPS-induced endothelial dysfunction; however, exogenous FABP3 exposure exacerbated LPS-induced inflammation; (4) loss of endogenous FABP3 protected against LPS-induced endothelial dysfunction by promoting cell survival and anti-inflammatory and pro-angiogenic signaling pathways. Together, these findings suggest that gain-of endothelial FABP3 exacerbates, whereas loss-of endothelial FABP3 inhibits LPS-induced endothelial dysfunction by promoting cell survival and anti-inflammatory and pro-angiogenic signaling. We propose that an increased circulating FABP3 in myocardial injury or PAD patients may be detrimental to endothelial function, and therefore, therapies aimed at inhibiting FABP3 may improve endothelial function in diseased states.

Endothelial cell-specific loss of eNOS differentially affects endothelial function

The endothelium maintains and regulates vascular homeostasis mainly by balancing interplay between vasorelaxation and vasoconstriction via regulating Nitric Oxide (NO) availability. Endothelial nitric oxide synthase (eNOS) is one of three NOS isoforms that catalyses the synthesis of NO to regulate endothelial function. However, eNOS’s role in the regulation of endothelial function, such as cell proliferation and migration remain unclear. To gain a better understanding, we genetically knocked down eNOS in cultured endothelial cells using sieNOS and evaluated cell proliferation, migration and also tube forming potential in vitro. To our surprise, loss of eNOS significantly induced endothelial cell proliferation, which was associated with significant downregulation of both cell cycle inhibitor p21 and cell proliferation antigen Ki-67. Knockdown of eNOS induced cell migration but inhibited formation of tube-like structures in vitro. Mechanistically, loss of eNOS was associated with activation of MAPK/ERK and inhibition of PI3-K/AKT signaling pathway. On the contrary, pharmacologic inhibition of eNOS by inhibitors L-NAME or L-NMMA, inhibited cell proliferation. Genetic and pharmacologic inhibition of eNOS, both promoted endothelial cell migration but inhibited tube-forming potential. Our findings confirm that eNOS regulate endothelial function by inversely controlling endothelial cell proliferation and migration, and by directly regulating its tube-forming potential. Differential results obtained following pharmacologic versus genetic inhibition of eNOS indicates a more complex mechanism behind eNOS regulation and activity in endothelial cells, warranting further investigation.

TGF-β-induced CCR8 promoted macrophage transdifferentiation into myofibroblast-like cells

Background: Idiopathic pulmonary fibrosis (IPF) is an interstitial disease of unknown origin, characterized by tissue fibrosis, for which currently there is no effective treatment. Macrophages, the main immune cells in lung tissue, are involved in the whole process of pulmonary fibrosis. In recent years, intercellular transformation has led to wide spread concern among pulmonary fibrosis researchers. Macrophages with flexible heterogeneity and plasticity participate in different physiological processes in the body. Cell chemokine receptor 8 (CCR8) is expressed in a variety of cells and plays a significant chemotactic role in the induction of cell activation and migration. It can also promote the differentiation of macrophages under certain environmental conditions. The current study is intended to explore the role of CCR8 in macrophage to myofibroblast transdifferentiation (MMT) in IPF. Methods: We conducted experiments using CCR8-specific small interfering RNA (siRNA), an autophagy inhibitor (3-methyladenine, 3-MA), and an agonist (rapamycin) to explore the underlying mechanisms of macrophage transdifferentiation into myofibroblast cells in transforming growth factor-beta (TGF-β)-induced pulmonary fibrosis. Results: TGF-β treatment increased the CCR8 protein level in a time- and dose-dependent manner in mouse alveolar macrophages, as well as macrophage transdifferentiation-related markers, including vimentin, collagen 1, and a-SMA, and cell migration. In addition, the levels of autophagy were enhanced in macrophages treated with TGF-β. We found that 3-MA, an autophagy inhibitor, decreased the expression levels of macrophage transdifferentiation-related markers and attenuated cell migration. Furthermore, the inhibition of CCR8 via CCR8-specific siRNA reduced the levels of autophagy and macrophage transdifferentiation-related markers, and inhibited the cell migration. Enhancing autophagy with rapamycin attenuated the inhibition effect of CCR8-specific siRNA on macrophage migration and the increase in myofibroblast marker proteins. Conclusions: Our findings showed that the macrophages exposed to TGF-β had the potential to transdifferentiate into myofibroblasts and CCR8 was involved in the process. The effect of CCR8 on TGF-β-induced macrophage transdifferentiation occurs mainly through autophagy. Targeting CCR8 may be a novel therapeutic strategy for the treatment of IPF.

Primary Cilia and Their Role in Acquired Heart Disease

Primary cilia are non-motile plasma membrane extrusions that display a variety of receptors and mechanosensors. Loss of function results in ciliopathies, which have been strongly linked with congenital heart disease, as well as abnormal development and function of most organ systems. Adults with congenital heart disease have high rates of acquired heart failure, and usually die from a cardiac cause. Here we explore primary cilia’s role in acquired heart disease. Intraflagellar Transport 88 knockout results in reduced primary cilia, and knockout from cardiac endothelium produces myxomatous degeneration similar to mitral valve prolapse seen in adult humans. Induced primary cilia inactivation by other mechanisms also produces excess myocardial hypertrophy and altered scar architecture after ischemic injury, as well as hypertension due to a lack of vascular endothelial nitric oxide synthase activation and the resultant left ventricular dysfunction. Finally, primary cilia have cell-to-cell transmission capacity which, when blocked, leads to progressive left ventricular hypertrophy and heart failure, though this mechanism has not been fully established. Further research is still needed to understand primary cilia’s role in adult cardiac pathology, especially heart failure.

Mechanobiology of Microvascular Function and Structure in Health and Disease: Focus on the Coronary Circulation

The coronary microvasculature plays a key role in regulating the tight coupling between myocardial perfusion and myocardial oxygen demand across a wide range of cardiac activity. Short-term regulation of coronary blood flow in response to metabolic stimuli is achieved via adjustment of vascular diameter in different segments of the microvasculature in conjunction with mechanical forces eliciting myogenic and flow-mediated vasodilation. In contrast, chronic adjustments in flow regulation also involve microvascular structural modifications, termed remodeling. Vascular remodeling encompasses changes in microvascular diameter and/or density being largely modulated by mechanical forces acting on the endothelium and vascular smooth muscle cells. Whereas in recent years, substantial knowledge has been gathered regarding the molecular mechanisms controlling microvascular tone and how these are altered in various diseases, the structural adaptations in response to pathologic situations are less well understood. In this article, we review the factors involved in coronary microvascular functional and structural alterations in obstructive and non-obstructive coronary artery disease and the molecular mechanisms involved therein with a focus on mechanobiology. Cardiovascular risk factors including metabolic dysregulation, hypercholesterolemia, hypertension and aging have been shown to induce microvascular (endothelial) dysfunction and vascular remodeling. Additionally, alterations in biomechanical forces produced by a coronary artery stenosis are associated with microvascular functional and structural alterations. Future studies should be directed at further unraveling the mechanisms underlying the coronary microvascular functional and structural alterations in disease; a deeper understanding of these mechanisms is critical for the identification of potential new targets for the treatment of ischemic heart disease.

The dynamic organelle primary cilia: emerging roles in organ fibrosis

PURPOSE OF REVIEW

Primary cilia, the antenna-like organelles on most mammalian cells, host key components of multiple morphogen signal transduction pathways. Mutations in genes responsible for primary cilia assembly and function generally result in pathological conditions known as ciliopathies, which underlie several diseases, including various forms of fibrosis. Primary cilia modulate cellular responses to extracellular cues, including TGF-β and morphogens, such as Hedgehog. Aberrant morphogen signaling is recognized as essential for the transition of mesenchymal progenitor cells to myofibroblasts, the key step in fibrosis. This article aims to provide a critical overview of recent developments and insights in primary cilia biology relevant to fibrosis.

RECENT FINDINGS

Several studies have highlighted the association of altered primary cilia with various forms of fibrosis. In a rather complex manner, the presence of primary cilia seems to be required for initiation of myofibroblast transition, whereas its loss promotes myofibroblast transition at a later stage. Recent evidence also suggested that noncanonical functions of ciliary transport proteins may influence, such cellular transitions independently of primary cilia. The possibility of opposing signaling regulations being topologically separated between primary cilia and plasma membrane could also be critical for fibrosis.

SUMMARY

Recent progress in the field suggests that primary cilia are critical mediators of the pathogenesis of fibrosis. Understanding the potential role of primary cilia in fibrosis and the underlying mechanisms may pave the way for entirely new approaches for fibrosis prevention and treatment of SSc.

[Role of interleukin-6 in human umbilical vein endothelial cell to mesenchymal cell transformation]

Objective: To observe the effect of interleukin-6 (IL-6) on the phenotype and function of human umbilical vein endothelial cells (HUVECs) and explore the role of IL-6 in the process of endothelial-to-mesenchymal transition (EndMT). Methods: The experimental research method was used. Fresh umbilical cord discarded after normal maternal delivery was collected. On the second day of the primary cell isolation and cultivation, the cell morphology was observed under inverted phase contrast microscope. HUVECs of the 4th passage were identified by immunofluorescence method, and 2 batches of HUVECs ofthe 3rd to 5th passages were used for the subsequent experiments. The first batch of cells were divided into 6 groups according to the random number table (the same below): blank control group, 5 ng/mL IL-6 group, 10 ng/mL IL-6 group, 25 ng/mL IL-6 group, 50 ng/mL IL-6 group, and 100 ng/mL IL-6 group. The second batch of cells were divided into 4 groups: blank control group, 10 ng/mL IL-6 group, 25 ng/mL IL-6 group,and 50 ng/mL IL-6 group; the cells in blank control group was cultured with complete culture medium only, while the cells in the other groups were added with IL-6 of the corresponding final mass concentrations.Cells from the 1st batch were cultured for 72 hours after grouping, the morphology of HUVECS in the 6 groups was observed under inverted phase contrast microscope. At 72 h after grouping culture, the positive expressions of coagulation factor Ⅷ and α vascular smooth muscle actin (α-SMA) in HUVECs in the 6 groups were detected by immunofluorescence method, and the ratio of the number of double positive cells to the number of coagulation factor Ⅷ positive cells (the ratio of double positive cells for short) was calculated, with 6 samples per group; mRNA expression levels of vascular endothelial cadherin and α-SMA of HUVECs in 6 groups were detected by reverse transcription-polymerase chain reaction, with 3 samples per group.Cells from the 2nd batch were cultured 72 hours after grouping, the protein expression levels of vascular endothelial cadherin, α-SMA, and type Ⅰ collagen in the 4 groups were detected by Western blotting, with 3 samples per group. Data were statistically analyzed with one-way analysis of variance and Bonferroni correction. Results: On the 2nd day after isolation and cultivation, the primary cells were in short spindle shape or polygon, cells of the 4th passage were identified as HUVECs by immunofluorescence method. At 72 hours of culture after grouping, the cells from the 1st batch in the 6 groups changed to long spindle shape morphologically along with the increase of IL-6 concentration, the intercellular connections decreased or disappeared with the gap between cells becoming larger. At 72 h after grouping culture, compared with that inblank control group, the ratio of double positive cells in 25 ng/mL IL-6 group, 50 ng/mL IL-6 group, and 100 ng/mL IL-6 group were significantly increased (P<0.01); compared with that in 5 ng/mL IL-6 group, the ratio of double positive cells in 25 ng/mL IL-6 group, 50 ng/mL IL-6 group, and 100 ng/mL IL-6 group were significantly increased (P<0.01); compared with that in 10 ng/mL IL-6 group, the ratio of double positive cells in 50 ng/mL IL-6 group and 100 ng/mL IL-6 group were significantly increased (P<0.01); the ratio of double positive cells in 100 ng/mL IL-6 group was significantly increased compared with those in 25 ng/mL IL-6 group and 50 ng/mL IL-6 group (P<0.01). At 72 h after grouping culture, compared with that in blank control group, the mRNA expression levels of vascular endothelial cadherin of cells in 25 ng/mL IL-6 group, 50 ng/mL IL-6 group, and 100 ng/mL IL-6 group were significantly decreased (P<0.01 or P<0.05); compared with that in 5 ng/mL IL-6 group, the mRNA expression levels of vascular endothelial cadherin of cells in 50 ng/mL IL-6 group and 100 ng/mL IL-6 group were significantly decreased (P<0.01); compared with that in 10 ng/mL IL-6 group, the mRNA expression levels of vascular endothelial cadherin of cells in 50 ng/mL IL-6 group and 100 ng/mL IL-6 group were significantly decreased (P<0.01); compared with that in 25 ng/mL IL-6 group, the mRNA expression levels of vascular endothelial cadherin of cells in 50 ng/mL IL-6 group and 100 ng/mL IL-6 group were significantly decreased (P<0.01). At 72 h after grouping culture, compared with that in blank control group, the mRNA expression levels of α-SMA of cells in 5 ng/mL IL-6 group, 10 ng/mL IL-6 group, 25 ng/mL IL-6 group, 50 ng/mL IL-6, group, and 100 ng/mL IL-6 group were significantly increased (P<0.05 or P<0.01). Cells from the 2nd batch were cultured for 72 hours after grouping. Compared with 1.391±0.026 in blank control group, the protein expressions of vascular endothelial cadherin of cells in 10 ng/mL IL-6 group (1.185±0.063), in 25 ng/mL IL-6 group (0.717±0.078), and in 50 ng/mL IL-6 group (0.239±0.064) were significantly decreased (P<0.05); compared with that in 10 ng/mL IL-6 group, the protein expressions of vascular endothelial cadherin of cells in 25 ng/mL IL-6 group and 50 ng/mL IL-6 group were significantly decreased (P<0.01); compared with that in 25 ng/mL IL-6 group, the protein expression of vascular endothelial cadherin of cells in 50 ng/mL IL-6 group was significantly decreased (P<0.01). At 72 h after grouping culture, compared with that in blank control group, the protein expression levels of α-SMA of cells in 10 ng/mL IL-6 group, 25 ng/mL IL-6 group, and 50 ng/mL IL-6 group were significantly increased (P<0.01); compared with that in 10 ng/mL IL-6 group, the protein expression levels of α-SMA of cells in 25 ng/mL IL-6 group and 50 ng/mL IL-6 group were significantly increased (P<0.01). At 72 h after grouping culture, compared with that in blank control group, the protein expressions of type Ⅰ collagen of cells in 25 ng/mL IL-6 group and 50 ng/mL IL-6 group were significantly increased (P<0.05). Conclusions: After IL-6 treatment, the phenotype and function of HUVECS showed the characteristics of mesenchymal cells in a concentration-dependent manner. The inflammatory factor can promote the process of EndMT, and become one of the important factors regulating the mechanism of tissue fibrosis.

Pravastatin-induced changes in expression of long non-coding and coding RNAs in endothelial cells

OBJECTIVE

Atherosclerosis is the main cause of the cardiovascular disease (CVD). Elevated blood cholesterol and inflammation of the endothelium are two major mechanisms contributing to the establishment of atherosclerotic plaques. Statins, such as pravastatin, are blood-cholesterol lowering drugs commonly prescribed for patients with or at risk for CVDs. In addition to lowering blood cholesterols, statins have recently been shown to improve endothelial function in both hyper- and normocholesterolemic patients with atherosclerosis. To understand the molecular mechanisms underlying the endothelial function improvement by statins, we assessed the RNA profile of pravastatin-treated endothelial cells, particularly their mRNAs and long non-coding RNAs (lncRNAs).

METHODS

Human umbilical vein endothelial cells (HUVECs) treated with pravastatin (10 µM) for 24 hr were profiled for lncRNAs and mRNAs using the Arraystar Human lncRNA Expression Microarray V3.0.

RESULTS

Of the 30,584 different lncRNAs screened, 95 were significantly upregulated, while 86 were downregulated in HUVECs responding to pravastatin. LINC00281 and BC045663 were the most upregulated (~8-fold) and downregulated (~3.5-fold) lncRNAs, respectively. Of the 26,106 different mRNAs screened in the pravastatin-treated HUVEC samples, 190 were significantly upregulated, while 90 were downregulated. Assigning the differentially expressed genes by bioinformatics into functional groups revealed their molecular signaling involvement in the following physiological processes: osteoclast differentiation, Rap1 signaling pathway, hematopoiesis, immunity, and neurotrophin signaling pathway.

CONCLUSIONS

This is the first lncRNA and mRNA expression profiling of pravastatin-mediated changes in human endothelial cells. Our results reveal potential novel targets and mechanisms for pravastatin-mediated vascular protection in atherosclerosis.

BReast CAncer susceptibility gene 2 deficiency exacerbates oxidized LDL-induced DNA damage and endothelial apoptosis

Mutations in the tumor suppressor gene BRCA2 (BReast CAncer susceptibility gene 2) predispose carriers to breast, ovarian, and other cancers. In response to DNA damage, BRCA2 participates in homology-directed DNA damage repair to maintain genome stability. Genome-wide association studies have identified an association between BRCA2 single nucleotide polymorphisms and plasma-lipid levels and lipid deregulation in humans. To date, DNA damage, apoptosis, and lipid deregulation are recognized as central pathways for endothelial dysfunction and atherosclerosis; however, the role of BRCA2 in endothelial dysfunction remains to be elucidated. To determine the role of BRCA2 in endothelial dysfunction, BRCA2 was silenced in human umbilical vein endothelial cells (ECs) and assessed for markers of DNA damage, apoptosis, and endothelial function following oxidized low-density lipoprotein (oxLDL) treatment. OxLDL was found to induce significant reactive oxygen species (ROS) production in BRCA2-silenced ECs. This increase in ROS production was associated with exacerbated DNA damage evidenced by increased expression and activation of DNA double-stranded break (DSB) marker γH2AX and reduced RAD51-foci formation-an essential regulator of DSB repair. Increased DSBs were associated with enhanced expression and activation of pro-apoptotic p53 and significant apoptosis in oxLDL-treated BRCA2-silenced ECs. Loss of BRCA2 in ECs was further associated with oxLDL-induced impaired tube-forming potential and eNOS expression. Collectively, the data reveals, for the first time, a novel role of BRCA2 as a regulator of EC survival and function in the setting of oxLDL treatment in vitro. Additionally, the data provide important clues regarding the potential susceptibility of BRCA2 mutation carriers to endothelial dysfunction, atherosclerosis, and other cardiovascular diseases.

Blocking protein phosphatase 2A with a peptide protects mice against bleomycin-induced pulmonary fibrosis

Emerging data indicate that endothelial-mesenchymal transition (EndMT) is involved in the pathogenesis of idiopathic pulmonary fibrosis (IPF). A previous study noted that blocking the activity of protein phosphatase 2 A (PP2A) could attenuate EndMT. However, the treatment effects of PP2A inhibitors in pulmonary fibrosis remain not investigated. In the present study, we used a PP2A inhibitor, a newly designed peptide named TAT-Y127WT, to determine the role of PP2A in pulmonary fibrosis. Herein, we showed that TAT-Y127WT protected mice against BLM-induced pulmonary fibrosis by attenuating lung injury and fibrosis. Furthermore, a mechanistic study indicated that TAT-Y127WT could alleviate EndMT in the lungs following BLM induction. Overall, our data showed that PP2A might participate in pulmonary fibrogenesis by promoting EndMT, and TAT-Y127WT could be a potential candidate for new anti-fibrotic therapies for IPF patients.