Mechanisms of Mechanical Force Induced Pulmonary Vascular Endothelial Hyperpermeability

Obesity-associated reduction of miR-150-5p in extracellular vesicles promotes ventilator-induced lung injury by modulating the lysosomal degradation of VE-cadherin

Obese patient has a high risk of ventilator-induced lung injury (VILI) but its underlying mechanisms remain elusive. This study was designed to explore the role of circulating plasma extracellular vesicles (EVs) on the progression of VILI in the context of obesity. After high tidal volume mechanical ventilation, mice treated with plasma EVs from obese patients developed more severe lung damage than mice treated with plasma EVs from normal controls. miRNA sequencing of plasma EVs from obese patients revealed a significant downregulation of miR-150-5p compared to the others. miR-150-5p was found to target on XBP1s which subsequently regulated RAB7 as verified through dual-luciferase assays. This pathway promoted lysosomal degradation of vascular endothelial (VE)-cadherin, leading to an increased endothelial permeability. Obese mice showed an enhanced XBP1s/RAB7 expression, reduced VE-cadherin levels, and aggravated endothelial barrier damage and all of which intensified VILI. Administration of miR-150-5p agomir in obese mice mitigated VILI. Thus, this study highlights the low levels of miR-150-5p in EVs from obese patients modulated VILI severity via the XBP1s/RAB7 axis and the lysosomal degradation of VE-cadherin.

Paeoniflorin protects the vascular endothelial barrier in mice with sepsis by activating RXRα signaling

OBJECTIVE

Sepsis is a life-threatening condition characterized by organ dysfunction resulting from the body's aberrant response to infection. A primary indicator of early sepsis is vascular leakage due to endothelial injury. The immunomodulatory effects of paeoniflorin are well established. However, its effect on vascular endothelial injury in sepsis remains to be verified.

METHODS

The sepsis model was established by cecal ligation and puncture (CLP), along with simultaneous administration of paeoniflorin. The therapeutic effectiveness of paeoniflorin was evaluated by assessing the survival rate, the bacterial load in blood and the histopathological lung tissue injury. The pulmonary vascular endothelial barrier integrity was assessed using immunofluorescence, western blot, Evans blue dye, and qPCR. Human umbilical vein endothelial cells (HUVECs) were used for in vitro validation and exploration of the underlying mechanisms.

RESULTS

The CLP mice exhibited significant damage to pulmonary tissue and breakdown of endothelial barrier. Administration of paeoniflorin markedly improved survival rates, mitigated lung injury, and preserved the integrity of the pulmonary vascular endothelial barrier in CLP mice which was confirmed by in vitro experiments. Pharmacological mechanism studies showed that the protective effects of paeoniflorin on the vascular endothelium was achieved through activation of RXRα signaling, which could be reversed by RXRα knockdown.

CONCLUSION

Our experiments demonstrates the protective effect of paeoniflorin on the vascular endothelial barrier through activation of the RXRα, thereby offering potential therapeutic options for sepsis treatment. We also identified RXRα as a novel transcription factor for VE-cadherin, providing a potential new intervention target for vascular endothelial barrier damage in sepsis.

Effect of aging on pulmonary cellular responses during mechanical ventilation

Acute respiratory distress syndrome (ARDS) results in substantial morbidity and mortality, especially in elderly people. Mechanical ventilation, a common supportive treatment for ARDS, is necessary for maintaining gas exchange but can also propagate injury. We hypothesized that aging leads to alterations in surfactant function, inflammatory signaling, and microvascular permeability within the lung during mechanical ventilation. Young and aged male mice were mechanically ventilated, and surfactant function, inflammation, and vascular permeability were assessed. Additionally, single-cell RNA-Seq was used to delineate cell-specific transcriptional changes. The results showed that, in aged mice, surfactant dysfunction and vascular permeability were significantly augmented, while inflammation was less pronounced. Differential gene expression and pathway analyses revealed that alveolar macrophages in aged mice showed a blunted inflammatory response, while aged endothelial cells exhibited altered cell-cell junction formation. In vitro functional analysis revealed that aged endothelial cells had an impaired ability to form a barrier. These results highlight the complex interplay between aging and mechanical ventilation, including an age-related predisposition to endothelial barrier dysfunction, due to altered cell-cell junction formation, and decreased inflammation, potentially due to immune exhaustion. It is concluded that age-related vascular changes may underlie the increased susceptibility to injury during mechanical ventilation in elderly patients.

Mechanisms of mechanical stimulation in the development of respiratory system diseases

During respiration, mechanical stress can initiate biological responses that impact the respiratory system. Mechanical stress plays a crucial role in the development of the respiratory system. However, pathological mechanical stress can impact the onset and progression of respiratory diseases by influencing the extracellular matrix and cell transduction processes. In this article, we explore the mechanisms by which mechanical forces communicate with and influence cells. We outline the basic knowledge of respiratory mechanics, elucidating the important role of mechanical stimulation in influencing respiratory system development and differentiation from a microscopic perspective. We also explore the potential mechanisms of mechanical transduction in the pathogenesis and development of respiratory diseases such as asthma, lung injury, pulmonary fibrosis, and lung cancer. Finally, we look forward to new research directions in cellular mechanotransduction, aiming to provide fresh insights for future therapeutic research on respiratory diseases.

Notch transcriptional target tmtc1 maintains vascular homeostasis

Proper lung function requires the maintenance of a tight endothelial barrier while simultaneously permitting the exchange of macromolecules and fluids to underlying tissue. Disruption of this barrier results in an increased vascular permeability in the lungs, leading to acute lung injury. In this study, we set out to determine whether transcriptional targets of Notch signaling function to preserve vascular integrity. We tested the in vivo requirement for Notch transcriptional signaling in maintaining the pulmonary endothelial barrier by using two complementary endothelial-specific Notch loss-of-function murine transgenic models. Notch signaling was blocked using endothelial-specific activation of an inhibitor of Notch transcriptional activation, Dominant Negative Mastermindlike (DNMAML; CDH5CreERT2), or endothelial-specific loss of Notch1 (Notch1f/f; CDH5CreERT2). Both Notch mutants increased vascular permeability with pan-Notch inhibition by DNMAML showing a more severe phenotype in the lungs and in purified endothelial cells. RNA sequencing of primary lung endothelial cells (ECs) identified novel Notch targets, one of which was transmembrane O-mannosyltransferase targeting cadherins 1 (tmtc1). We show that tmtc1 interacts with vascular endothelial cadherin (VE-cadherin) and regulates VE-cadherin egress from the endoplasmic reticulum through direct interaction. Our findings demonstrate that Notch signaling maintains endothelial adherens junctions and vascular homeostasis by a transcriptional mechanism that drives expression of critical factors important for processing and transport of VE-cadherin.

PGC-1α/LDHA signaling facilitates glycolysis initiation to regulate mechanically induced bone remodeling under inflammatory microenvironment

The mechanosensitivity of inflammation can alter cellular mechanotransduction. However, the underlying mechanism remains unclear. This study aims to investigate the metabolic mechanism of inflammation under mechanical force to guide tissue remodeling better. Herein, we found that inflammation hindered bone remodeling under mechanical force, accompanied by a simultaneous enhancement of oxidative phosphorylation (OXPHOS) and glycolysis. The control of metabolism direction through GNE-140 and Visomitin revealed that enhanced glycolysis might act as a compensatory mechanism to resist OXPHOS-induced osteoclastogenesis by promoting osteogenesis. The inhibited osteogenesis induced by inflammatory mechanical stimuli was concomitant with a reduced expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). PGC-1α knockdown impeded osteogenesis under mechanical force and facilitated osteoclastogenesis by enhancing OXPHOS. Conversely, PGC-1α overexpression attenuated the impairment of bone remodeling by inflammatory mechanical signals through promoting glycolysis. This process benefited from the PGC-1α regulation on the transcriptional and translational activity of lactate dehydrogenase A (LDHA) and the tight control of the extracellular acidic environment. Additionally, the increased binding between PGC-1α and LDHA proteins might contribute to the glycolysis promotion within the inflammatory mechanical environment. Notably, LDHA suppression effectively eliminated the bone repair effect mediated by PGC-1α overexpression within inflammatory mechanical environments. In conclusion, this study demonstrated a novel molecular mechanism illustrating how inflammation orchestrated glucose metabolism through glycolysis and OXPHOS to affect mechanically induced bone remodeling.

The link between neutrophils, NETs, and NLRP3 inflammasomes: The dual effect of CD177 and its therapeutic potential in acute respiratory distress syndrome/acute lung injury

Neutrophils are important inflammatory effector cells that protect against foreign invasion but also cause self-harm. Numerous neutrophils infiltrate the lungs in acute respiratory distress syndrome/acute lung injury (ARDS/ALI) patients. However, the exact impact of neutrophil infiltration on ARDS's onset and progression remains unclear. To investigate this, we analyzed two ARDS-related datasets from the Gene Expression Omnibus public database and discovered an association between CD177, a neutrophil-specific surface protein, and ARDS progression. We used quantitative flow cytometry to assess CD177+ neutrophils in the peripheral blood of clinical ARDS patients vs healthy controls, finding a significant increase in CD177+ neutrophils percentage among total neutrophils in ARDS patients. This finding was further confirmed in ALI mouse models. Subsequent animal experiments showed that anti-CD177 effectively reduces pulmonary edema, neutrophil infiltration, and inflammatory cytokine release, along with a decrease in reactive oxygen species (ROS) and myeloperoxidase (MPO) levels. We also established an in vitro co-culture system to mimic neutrophil and lung epithelial cell interactions. In the anti-CD177 group, we observed decreased expression of NLRP3, caspase 1, peptidyl arginine deiminase (PAD4), MPO, and ROS, along with a reduction in certain inflammatory cytokines. These results indicate a crucial role for the CD177 gene in ARDS's development and progression. Inhibiting CD177 may help mitigate excessive activation of NLRP3 inflammasomes, ROS, and neutrophil extracellular traps (NETs), thus alleviating ARDS.

Talin mechanotransduction in disease

Talin protein (Talin 1/2) is a mechanosensitive cytoskeleton protein. The unique structure of the Talin plays a vital role in transmitting mechanical forces. Talin proteins connect the extracellular matrix to the cytoskeleton by linking to integrins and actin, thereby mediating the conversion of mechanical signals into biochemical signals and influencing disease progression as potential diagnostic indicators, therapeutic targets, and prognostic indicators of various diseases. Most studies in recent years have confirmed that mechanical forces also have a crucial role in the development of disease, and Talin has been found to play a role in several diseases. Still, more studies need to be done on how Talin is involved in mechanical signaling in disease. This review focuses on the mechanical signaling of Talin in disease, aiming to summarize the mechanisms by which Talin plays a role in disease and to provide references for further studies.

Interaction between mitochondrial homeostasis and barrier function in lipopolysaccharide-induced endothelial cell injury

This study aimed to investigate the effects of mitochondrial homeostasis on lipopolysaccharide (LPS)-induced endothelial cell barrier function and the mechanisms that underlie these effects. Cells were treated with LPS or oligomycin (mitochondrial adenosine triphosphate synthase inhibitor) and the mitochondrial morphology, mitochondrial reactive oxygen species (mtROS), and mitochondrial membrane potential (ΔΨm) were evaluated. Moreover, the shedding of glycocalyx-heparan sulphate (HS), the levels of HS-specific degrading enzyme heparanase (HPA), and the expression of occludin and zonula occludens (ZO-1) of Tight Junctions (TJ)s, which are mediated by myosin light chain phosphorylation (p-MLC), were assessed. Examining the changes in mitochondrial homeostasis showed that adding heparinase III, which is an exogenous HPA, can destroy the integrity of glycocalyx. LPS simultaneously increased mitochondrial swelling, mtROS, and ΔΨm. Without oligomycin effects, HS, HPA levels, and p-MLC were found to be elevated, and the destruction of occludin and ZO-1 increased. Heparinase III not only damaged the glycocalyx by increasing HS shedding but also increased mitochondrial swelling and mtROS and decreased ΔΨm. Mitochondrial homeostasis is involved in LPS-induced endothelial cell barrier dysfunction by aggravating HPA and p-MLC levels. In turn, the integrated glycocalyx protects mitochondrial homeostasis.

Deficiency of S100A8/A9 attenuates pulmonary microvascular leakage in septic mice

BACKGROUND

We have reported a positive correlation between S100 calcium-binding protein (S100) A8/S100A9 and sepsis-induced lung damage before. However, limited knowledge exists concerning the biological role of S100A8/A9 in pulmonary vascular endothelial barrier dysfunction, as well as the diagnostic value of S100A8/A9 in sepsis.

METHODS

Sepsis was induced in C57BL/6J mice and S100A9-knockout (KO) mice through the cecal ligation and puncture (CLP). Pulmonary vascular leakage was determined by measuring extravasated Evans blue (EB). Reverse transcription polymerase chain reaction and the histological score were used to evaluate inflammation and lung injury, respectively. Recombinant S100A8/A9 (rhS100A8/A9) was used to identify the effects of S100A8/A9 on endothelial barrier dysfunction in human umbilical vein endothelial cells (HUVECs). Additionally, the diagnostic value of S100A8/A9 in sepsis was assessed using receiver operating characteristic.

RESULTS

S100A8/A9 expression was up-regulated in the lungs of CLP-operated mice. S100A9 KO significantly reversed CLP-induced hypothermia and hypotension, resulting in an improved survival rate. S100A9 KO also decreased the inflammatory response, EB leakage, and histological scores in the lungs of CLP-operated mice. Occludin and VE-cadherin expressions were decreased in the lungs of CLP-operated mice; However, S100A9 KO attenuated this decrease. Moreover, CLP-induced signal transducer and activator of transcription 3 (STAT3) and p38/extracellular signal-regulated kinase (ERK) signalling activation and apoptosis were mitigated by S100A9 KO in lungs. In addition, rhS100A8/A9 administration significantly decreased occludin and VE-cadherin expressions, increased the phosphorylated (p)-ERK/ERK, p-p38/p38, and B-cell leukaemia/lymphoma 2 protein (Bcl-2)-associated X protein/Bcl-2 ratios in HUVECs.

CONCLUSION

The present study demonstrated S100A8/A9 aggravated sepsis-induced pulmonary inflammation, vascular permeability, and lung injury. This was achieved, at least partially, by activating the P38/STAT3/ERK signalling pathways. Moreover, S100A8/A9 showed the potential as a biomarker for sepsis diagnosis.

Irbesartan eases lipopolysaccharide-induced lung injury In Vitro and In Vivo

Acute lung injury (ALI) is classified as a devastating pulmonary disorder contributing to significant incidence and fatality rate. Irbesartan (IRB) is an angiotensin II receptor blocker that has been proposed to protect against oleic acid-induced ALI. To this end, the current study is concentrated on ascertaining the role of IRB in ALI and figuring out the probable action mechanism. First, cell counting kit-8 (CCK-8) appraised the viability of human pulmonary microvascular endothelial cells (HPMVECs) exposed to ascending concentrations of IRB. HPMVEC injury model and a mouse model of ALI induced by lipopolysaccharide (LPS) were pretreated by IRB. In vitro, cell viability was estimated by CCK-8 assay, and lactate dehydrogenase (LDH) release was tested by LDH assay kit. Enzyme-linked immunosorbent assay (ELISA) and Western blotting estimated the expression levels of inflammatory factors. Fluorescein isothiocyanate-dextran was used to assess HPMVEC permeability. Western blotting examined the expression of adherent and tight junction proteins. In vivo, hematoxylin and eosin staining evaluated lung tissue damage and lung wet/dry (W/D) weight was measured. ELISA analyzed the levels of inflammatory factors in the serum and bronchoalveolar lavage fluid (BALF), and Western blotting examined the expression of inflammatory factors. The total cell, neutrophil, and macrophage numbers in BALF were determined using a cell counter. Lung capillary permeability was assayed by Evans blue albumin and total protein concentration in BALF was measured using bicinchoninic acid method. Immunofluorescence assay and Western blotting examined the expression of adherent and tight junction proteins in lung tissues. It was observed that IRB dose-dependently enhanced the viability while reduced LDH release, inflammatory response as well as permeability in LPS-challenged HPMVECs in vitro. In addition, LPS-stimulated lung tissue damage, pulmonary edema, inflammatory response as well as lung capillary permeability in vivo were all reversed following IRB treatment. Collectively, IRB treatment might elicit protective behaviors against LPS-triggered ALI.

Crystal ribcage: a platform for probing real-time lung function at cellular resolution

Understanding the dynamic pathogenesis and treatment response in pulmonary diseases requires probing the lung at cellular resolution in real time. Despite advances in intravital imaging, optical imaging of the lung during active respiration and circulation has remained challenging. Here, we introduce the crystal ribcage: a transparent ribcage that allows multiscale optical imaging of the functioning lung from whole-organ to single-cell level. It enables the modulation of lung biophysics and immunity through intravascular, intrapulmonary, intraparenchymal and optogenetic interventions, and it preserves the three-dimensional architecture, air-liquid interface, cellular diversity and respiratory-circulatory functions of the lung. Utilizing these capabilities on murine models of pulmonary pathologies we probed remodeling of respiratory-circulatory functions at the single-alveolus and capillary levels during disease progression. The crystal ribcage and its broad applications presented here will facilitate further studies of nearly any pulmonary disease as well as lead to the identification of new targets for treatment strategies.

Delivery systems of therapeutic nucleic acids for the treatment of acute lung injury/acute respiratory distress syndrome

Acute lung injury (ALI)/ acute respiratory distress syndrome (ARDS) is a devastating inflammatory lung disease with a high mortality rate. ALI/ARDS is induced by various causes, including sepsis, infections, thoracic trauma, and inhalation of toxic reagents. Corona virus infection disease-19 (COVID-19) is also a major cause of ALI/ARDS. ALI/ARDS is characterized by inflammatory injury and increased vascular permeability, resulting in lung edema and hypoxemia. Currently available treatments for ALI/ARDS are limited, but do include mechanical ventilation for gas exchange and treatments supportive of reduction of severe symptoms. Anti-inflammatory drugs such as corticosteroids have been suggested, but their clinical effects are controversial with possible side-effects. Therefore, novel treatment modalities have been developed for ALI/ARDS, including therapeutic nucleic acids. Two classes of therapeutic nucleic acids are in use. The first constitutes knock-in genes for encoding therapeutic proteins such as heme oxygenase-1 (HO-1) and adiponectin (APN) at the site of disease. The other is oligonucleotides such as small interfering RNAs and antisense oligonucleotides for knock-down expression of target genes. Carriers have been developed for efficient delivery for therapeutic nucleic acids into the lungs based on the characteristics of the nucleic acids, administration routes, and targeting cells. In this review, ALI/ARDS gene therapy is discussed mainly in terms of delivery systems. The pathophysiology of ALI/ARDS, therapeutic genes, and their delivery strategies are presented for development of ALI/ARDS gene therapy. The current progress suggests that selected and appropriate delivery systems of therapeutic nucleic acids into the lungs may be useful for the treatment of ALI/ARDS.

Protective effects of areca nut polyphenols on hypoxic damage of rat pulmonary microvascular endothelial cells

OBJECTIVE

To investigate the protective effects of areca nut polyphenols on hypoxic damage of rat pulmonary microvascular endothelial cells (PMVECs).

METHODS

Malondialdehyde and superoxide dismutase (SOD) were used to determine the optimal modeling of lung hypoxic injury cells. CCK-8 method was used to detect cell viability for determining the effective dose of areca nut polyphenols. Rat PMVECs were divided into control group, hypoxia model group and areca nut polyphenols group. BCA method was used to detect the protein concentration of each group, and the oxidative stress level in PMVECs was measured. Western blotting was used to detect the expression of inflammatory and apoptosis-related proteins. Immunofluorescence staining was used to detect the expression of occludin and zonula occludens (ZO) 1. Transwell chamber was used to detect transendothelial electrical resistance, and rhodamine fluorescent dye was used to detect PMVECs barrier permeability.

RESULTS

The hypobaric hypoxia-induced cell injury model was established by culturing PMVECs for 48 h at 1% oxygen concentration. The 20 μg/mL areca nut polyphenols significantly reversed the survival rate and the oxidative stress of PMVECs in hypoxia model group (all P<0.05). Areca nut polyphenols had significant inhibitory effect on the up-regulation of inflammation-related proteins, including nuclear factor-κB (NF-κB) and nuclear factor-E2-related factor (Nrf) 2 in hypoxia model group (all P<0.05). And areca nut polyphenols could reduce hypoxia-induced PMVECs apoptosis by down-regulating the expressions of apoptosis-related proteins, including cysteine aspartic acid specific protease (caspase) 3, Bcl-2 associated X protein (Bax) in PMVECs (all P<0.05). In addition, areca nut polyphenols effectively improves the transendothelial electrical resistance and barrier permeability of PMVECs through elevating the expression of occludin and ZO-1 (all P<0.05).

CONCLUSION

Areca nut polyphenols can inhibit the hypoxic damage of PMVECs by reducing oxidative stress and apoptosis down-regulating the expression of inflammatory proteins and reducing membrane permeability.

Connexin and Pannexin Large-Pore Channels in Microcirculation and Neurovascular Coupling Function

Microcirculation homeostasis depends on several channels permeable to ions and/or small molecules that facilitate the regulation of the vasomotor tone, hyperpermeability, the blood–brain barrier, and the neurovascular coupling function. Connexin (Cxs) and Pannexin (Panxs) large-pore channel proteins are implicated in several aspects of vascular physiology. The permeation of ions (i.e., Ca²⁺) and key metabolites (ATP, prostaglandins, D-serine, etc.) through Cxs (i.e., gap junction channels or hemichannels) and Panxs proteins plays a vital role in intercellular communication and maintaining vascular homeostasis. Therefore, dysregulation or genetic pathologies associated with these channels promote deleterious tissue consequences. This review provides an overview of current knowledge concerning the physiological role of these large-pore molecule channels in microcirculation (arterioles, capillaries, venules) and in the neurovascular coupling function.