Activation of TNFR1 ectodomain shedding by mitochondrial Ca2+ determines the severity of inflammation in mouse lung microvessels

Soluble tumour necrosis factor receptor 1 predicts hospitalization in children and young adults with dengue virus infection in the Philippines

BACKGROUND

Dengue fever is a common cause of acute febrile illness in the tropics and requires hospitalization for intravenous (IV) fluid therapy in a minority of patients. Predicting which patients will progress to severe disease is challenging. Soluble tumour necrosis factor receptor 1 (sTNFR1) is associated with severe dengue and may have prognostic value.

METHODS

Prospective cohort study of outpatients in the Philippines with dengue fever, confirmed by NS1 antigenemia or IgM seropositivity. sTNFR1 was measured at presentation and patients were followed for 14-21 days for hospitalization (primary outcome), duration of stay, IV fluid resuscitation, hemoconcentration, and thrombocytopenia (secondary outcomes).

RESULTS

244 patients (median age 9 years, 40 % female, 26 % uncomplicated dengue, 73 % dengue with warning signs, 0.82 % severe dengue) were included. The median sTNFR1 plasma concentration was 3000pg/mL (IQR 2400-3700) at clinic presentation, decreasing to 1800 (IQR 1600-2100) after recovery. 181 patients (74 %) required hospitalization. Plasma sTNFR1 concentration > 2800 pg/mL, measured at clinic presentation, was associated with subsequent hospitalization (relative risk 1.5, 95 %CI 1.2-1.7, p < 0.0001). Elevated sTNFR1 was also associated with longer duration of stay, IV fluid requirement, hemoconcentration, and thrombocytopenia. sTNFR1 was also associated with a marker of systemic inflammation (procalcitonin), and circulating markers of endothelial activation (Ang2, sTie-2, sVCAM-1, and endoglin).

CONCLUSION

Elevated sTNFR1 is predictive of subsequent hospitalization among outpatients with DENV infection. It shows promise as a marker that could guide triage to reduce the large healthcare burden of dengue in resource-constrained settings.

Macrophage-specific lipid nanoparticle therapy blocks the lung's mechanosensitive immunity due to macrophage-epithelial interactions

The lung's mechanosensitive immune response, which occurs when pulmonary alveoli are overstretched, is a major impediment to ventilation therapy for hypoxemic respiratory failure. The cause is not known. We tested the hypothesis that alveolar stretch causes stretch of alveolar macrophages (AMs), leading to the immune response. In lungs viewed by optical imaging, sessile AMs expressed gap junctional protein connexin-43 (Cx43), and they communicated with the alveolar epithelium through gap junctions. Alveolar hyperinflation increased Ca2+ in the AMs but did not stretch the AMs. The Ca2+ response, and concomitant TNFα secretion by AMs were blocked in mice with AM-specific deletion of Cx43. The AM responses, as also lung injury due to mechanical ventilation at high tidal volume, were inhibited by AM-specific delivery of lipid nanoparticles containing Xestospongin C, which blocked the induced Ca2+ increases. We conclude, Cx43- and Ca2+-dependent AM-epithelial interactions determine the lung's mechanosensitive immunity, providing a basis for therapy for ventilator-induced lung injury.

Studying the Pulmonary Endothelium in Health and Disease: An Official American Thoracic Society Workshop Report

Lung endothelium resides at the interface between the circulation and the underlying tissue, where it senses biochemical and mechanical properties of both the blood as it flows through the vascular circuit and the vessel wall. The endothelium performs the bidirectional signaling between the blood and tissue compartments that is necessary to maintain homeostasis while physically separating both, facilitating a tightly regulated exchange of water, solutes, cells, and signals. Disruption in endothelial function contributes to vascular disease, which can manifest in discrete vascular locations along the artery-to-capillary-to-vein axis. Although our understanding of mechanisms that contribute to endothelial cell injury and repair in acute and chronic vascular disease have advanced, pathophysiological mechanisms that underlie site-specific vascular disease remain incompletely understood. In an effort to improve the translatability of mechanistic studies of the endothelium, the American Thoracic Society convened a workshop to optimize rigor, reproducibility, and translation of discovery to advance our understanding of endothelial cell function in health and disease.

A spotlight on the aged pulmonary artery

The ever-increasing life expectancy of the global population introduces a critical perspective on the impact of aging as an immutable cardiovascular risk factor, particularly manifesting in the alterations observed in the pulmonary artery (PA). Mechanisms contributing to aging-induced changes in PA include endothelial dysfunction, chronic inflammation, and structural changes in the arterial wall over time. These alterations extend beyond mere elasticity, exerting profound effects on pulmonary hemodynamics. The propensity of PAs to develop atherosclerotic plaques underscores an intriguing facet of vascular aging, although the available literature is currently insufficient to comprehensively assess their true incidence. While recognizing the inherent risk of periprocedural complications, right heart catheterization (RHC) stands out as the gold standard for precise hemodynamic evaluation. Echocardiography, a widely employed method, proves valuable for screening pulmonary hypertension (PH), yet falls short of diagnostic capability. Technological advancements usher in a new era with non-invasive modalities such as cardiac magnetic resonance (CMR) imaging emerging as promising tools. These innovations demonstrate their prowess in providing accurate assessments of PA stiffness and hemodynamics, offering a glimpse into the future landscape of diagnostic methodologies. As we navigate the intersection of aging and pulmonary vascular health, this review aims to address mechanisms and techniques for assessing PA aging, highlighting the need for comprehensive assessments to guide clinical decision making in an increasingly aging population.

The rs11684747 and rs55790676 SNPs of ADAM17 influence tuberculosis susceptibility and plasma levels of TNF, TNFR1, and TNFR2

Introduction

The proteolytic activity of A Disintegrin and Metalloproteinase 17 (ADAM17) regulates the release of tumor necrosis factor (TNF) and TNF receptors (TNFRs) from cell surfaces. These molecules play important roles in tuberculosis (TB) shaping innate immune reactions and granuloma formation.

Methods

Here, we investigated whether single nucleotide polymorphisms (SNPs) of ADAM17 influence TNF and TNFRs levels in 224 patients with active TB (ATB) and 118 healthy close contacts. Also, we looked for significant associations between SNPs of ADAM17 and ATB status. TNF, TNFR1, and TNFR2 levels were measured in plasma samples by ELISA. Four SNPs of ADAM17 (rs12692386, rs1524668, rs11684747, and rs55790676) were analyzed in DNA isolated from peripheral blood leucocytes. The association between ATB status, genotype, and cytokines was analyzed by multiple regression models.

Results

Our results showed a higher frequency of rs11684747 and rs55790676 in close contacts than ATB patients. Coincidentally, heterozygous to these SNPs of ADAM17 showed higher plasma levels of TNF compared to homozygous to their respective ancestral alleles. Strikingly, the levels of TNF and TNFRs distinguished participant groups, with ATB patients displaying lower TNF and higher TNFR1/TNFR2 levels compared to their close contacts.

Conclusion

These findings suggest a role for SNPs of ADAM17 in genetic susceptibility to ATB.

Endothelial cell dynamics in sepsis-induced acute lung injury and acute respiratory distress syndrome: pathogenesis and therapeutic implications

Sepsis, a prevalent critical condition in clinics, continues to be the leading cause of death from infections and a global healthcare issue. Among the organs susceptible to the harmful effects of sepsis, the lungs are notably the most frequently affected. Consequently, patients with sepsis are predisposed to developing acute lung injury (ALI), and in severe cases, acute respiratory distress syndrome (ARDS). Nevertheless, the precise mechanisms associated with the onset of ALI/ARDS remain elusive. In recent years, there has been a growing emphasis on the role of endothelial cells (ECs), a cell type integral to lung barrier function, and their interactions with various stromal cells in sepsis-induced ALI/ARDS. In this comprehensive review, we summarize the involvement of endothelial cells and their intricate interplay with immune cells and stromal cells, including pulmonary epithelial cells and fibroblasts, in the pathogenesis of sepsis-induced ALI/ARDS, with particular emphasis placed on discussing the several pivotal pathways implicated in this process. Furthermore, we discuss the potential therapeutic interventions for modulating the functions of endothelial cells, their interactions with immune cells and stromal cells, and relevant pathways associated with ALI/ARDS to present a potential therapeutic strategy for managing sepsis and sepsis-induced ALI/ARDS.

Mitochondria of lung venular capillaries mediate lung-liver cross talk in pneumonia

Failure of the lung's endothelial barrier underlies lung injury, which causes the high mortality acute respiratory distress syndrome (ARDS). Multiple organ failure predisposes to the mortality, but mechanisms are poorly understood. Here, we show that mitochondrial uncoupling protein 2 (UCP2), a component of the mitochondrial inner membrane, plays a role in the barrier failure. Subsequent lung-liver cross talk mediated by neutrophil activation causes liver congestion. We intranasally instilled lipopolysaccharide (LPS). Then, we viewed the lung endothelium by real-time confocal imaging of the isolated, blood-perfused mouse lung. LPS caused alveolar-capillary transfer of reactive oxygen species and mitochondrial depolarization in lung venular capillaries. The mitochondrial depolarization was inhibited by transfection of alveolar Catalase and vascular knockdown of UCP2. LPS instillation caused lung injury as indicated by increases in bronchoalveolar lavage (BAL) protein content and extravascular lung water. LPS or Pseudomonas aeruginosa instillation also caused liver congestion, quantified by liver hemoglobin and plasma aspartate aminotransferase (AST) increases. Genetic inhibition of vascular UCP2 prevented both lung injury and liver congestion. Antibody-mediated neutrophil depletion blocked the liver responses, but not lung injury. Knockdown of lung vascular UCP2 mitigated P. aeruginosa-induced mortality. Together, these data suggest a mechanism in which bacterial pneumonia induces oxidative signaling to lung venular capillaries, known sites of inflammatory signaling in the lung microvasculature, depolarizing venular mitochondria. Successive activation of neutrophils induces liver congestion. We conclude that oxidant-induced UCP2 expression in lung venular capillaries causes a mechanistic sequence leading to liver congestion and mortality. Lung vascular UCP2 may present a therapeutic target in ARDS.NEW & NOTEWORTHY We report that mitochondrial injury in lung venular capillaries underlies barrier failure in pneumonia, and venular capillary uncoupling protein 2 (UCP2) causes neutrophil-mediated liver congestion. Using in situ imaging, we found that epithelial-endothelial transfer of H2O2 activates UCP2, depolarizing mitochondria in venular capillaries. The conceptual advance from our findings is that mitochondrial depolarization in lung capillaries mediates liver cross talk through circulating neutrophils. Pharmacologic blockade of UCP2 could be a therapeutic strategy for lung injury.

Overview of the Mechanisms of Oxidative Stress: Impact in Inflammation of the Airway Diseases

Inflammation of the human lung is mediated in response to different stimuli (e.g., physical, radioactive, infective, pro-allergenic or toxic) such as cigarette smoke and environmental pollutants. They often promote an increase in inflammatory activities in the airways that manifest themselves as chronic diseases (e.g., allergic airway diseases, asthma, chronic bronchitis/chronic obstructive pulmonary disease (COPD) or even lung cancer). Increased levels of oxidative stress (OS) reduce the antioxidant defenses, affect the autophagy/mitophagy processes, and the regulatory mechanisms of cell survival, promoting inflammation in the lung. In fact, OS potentiate the inflammatory activities in the lung, favoring the progression of chronic airway diseases. OS increases the production of reactive oxygen species (ROS), including superoxide anions (O₂^-), hydroxyl radicals (OH) and hydrogen peroxide (H₂O₂), by the transformation of oxygen through enzymatic and non-enzymatic reactions. In this manner, OS reduces endogenous antioxidant defenses in both nucleated and non-nucleated cells. The production of ROS in the lung can derive from both exogenous insults (cigarette smoke or environmental pollution) and endogenous sources such as cell injury and/or activated inflammatory and structural cells. In this review, we describe the most relevant knowledge concerning the functional interrelation between the mechanisms of OS and inflammation in airway diseases.

Salvianolic acid A regulates pyroptosis of endothelial cells via directly targeting PKM2 and ameliorates diabetic atherosclerosis

Rescuing endothelial cells from pyroptotic cell death emerges as a potential therapeutic strategy to combat diabetic atherosclerosis. Salvianolic acid A (SAA) is a major water-soluble phenolic acid in the Salvia miltiorrhiza Bunge, which has been used in traditional Chinese medicine (TCM) and health food products for a long time. This study investigated whether SAA-regulated pyruvate kinase M2 (PKM2) functions to protect endothelial cells. In streptozotocin (STZ)-induced diabetic ApoE-/- mice subjected to a Western diet, SAA attenuated atherosclerotic plaque formation and inhibited pathological changes in the aorta. In addition, SAA significantly prevented NLRP3 inflammasome activation and pyroptosis of endothelial cells in the diabetic atherosclerotic aortic sinus or those exposed to high glucose. Mechanistically, PKM2 was verified to be the main target of SAA. We further revealed that SAA directly interacts with PKM2 at its activator pocket, inhibits phosphorylation of Y105, and hinders the nuclear translocation of PKM2. Also, SAA consistently decreased high glucose-induced overproduction of lactate and partially lactate-dependent phosphorylation of PKR (a regulator of the NLRP3 inflammasome). Further assay on Phenylalanine (PKM2 activity inhibitor) proved that SAA exhibits the function in high glucose-induced pyroptosis of endothelial cells dependently on PKM2 regulation. Furthermore, an assay on c16 (inhibitor of PKR activity) with co-phenylalanine demonstrated that the regulation of the phosphorylated PKR partially drives PKM2-dependent SAA modulation of cell pyroptosis. Therefore, this article reports on the novel function of SAA in the pyroptosis of endothelial cells and diabetic atherosclerosis, which provides important insights into immunometabolism reprogramming that is important for diabetic cardiovascular disease complications therapy.

Targeting the mitochondria in chronic respiratory diseases

Mitochondria are one of the basic essential components for eukaryotic life survival. It is also the source of respiratory ATP. Recently published studies have demonstrated that mitochondria may have more roles to play aside from energy production. There is an increasing body of evidence which suggest that mitochondrial activities involved in normal and pathological states contribute to significant impact to the lung airway morphology and epithelial function in respiratory diseases such as asthma, COPD, and lung cancer. This review summarizes the pathophysiological pathways involved in asthma, COPD, lung cancer and highlights potential treatment strategies that target the malfunctioning mitochondria in such ailments. Mitochondria are responsive to environmental stimuli such as infection, tobacco smoke, and inflammation, which are essential in the pathogenesis of respiratory diseases. They may affect mitochondrial shape, protein production and ultimately cause dysfunction. The impairment of mitochondrial function has downstream impact on the cytosolic components, calcium control, response towards oxidative stress, regulation of genes and proteins and metabolic activities. Several novel compounds and alternative medicines that target mitochondria in asthma and chronic lung diseases have been discussed here. Moreover, mitochondrial enzymes or proteins that may serve as excellent therapeutic targets in COPD are also covered. The role of mitochondria in respiratory diseases is gaining much attention and mitochondria-based treatment strategies and personalized medicine targeting the mitochondria may materialize in the near future. Nevertheless, more in-depth studies are urgently needed to validate the advantages and efficacy of drugs that affect mitochondria in pathological states.

The mitochondrial calcium uniporter of pulmonary type 2 cells determines severity of acute lung injury

Acute Lung Injury (ALI) due to inhaled pathogens causes high mortality. Underlying mechanisms are inadequately understood. Here, by optical imaging of live mouse lungs we show that a key mechanism is the viability of cytosolic Ca²⁺ buffering by the mitochondrial Ca²⁺ uniporter (MCU) in the lung’s surfactant-secreting, alveolar type 2 cells (AT2). The buffering increased mitochondrial Ca²⁺ and induced surfactant secretion in wild-type mice, but not in mice with AT2-specific MCU knockout. In the knockout mice, ALI due to intranasal LPS instillation caused severe pulmonary edema and mortality, which were mitigated by surfactant replenishment prior to LPS instillation, indicating surfactant’s protective effect against alveolar edema. In wild-type mice, intranasal LPS, or Pseudomonas aeruginosa decreased AT2 MCU. Loss of MCU abrogated buffering. The resulting mortality was reduced by spontaneous recovery of MCU expression, or by MCU replenishment. Enhancement of AT2 mitochondrial buffering, hence endogenous surfactant secretion, through MCU replenishment might be a therapy against ALI.

Acute lung injury caused by inhalation of pathogens leads to mortality, but the mechanisms are unclear. Here, the authors show in mice that that loss of the mitochondrial calcium uniporter (MCU) of alveolar type 2 cells (AT2) impaired mitochondrial Ca²⁺ buffering and surfactant secretion, and increased mortality, in response to LPS instillation, suggesting the MCU as a potential therapeutic target in ALI.

Size-based effects of anthropogenic ultrafine particles on activation of human lung macrophages

The anthropogenic particulate matter (PM), suspended air dust that can be inhaled by humans and deposited in the lungs, is one of the main pollutants in the industrialized cities atmosphere. Recent studies have shown that PM has adverse effects on respiratory diseases. These effects are mainly due to the ultrafine particles (PM0.1, PM < 100 nm), which, thanks to their PM size, are efficiently deposited in nasal, tracheobronchial, and alveolar regions. Pulmonary macrophages are a heterogeneous cell population distributed in different lung compartments, whose role in inflammatory response to injury is of particular relevance. In this study, we investigated the effect of PM0.1 on Human Lung Macrophages (HLMs) activation evaluated as proinflammatory cytokines and chemokine release, Reactive Oxygen Species (ROS) production and intracellular Ca²⁺concentration ([Ca²⁺]_i). Furthermore, PM0.1, after removal of organic fraction, was fractionated in nanoparticles both smaller (NP20) and bigger (NP100) than 20 nm by a properlydeveloped analytical protocol, allowed isolating their individual contribution. Interestingly, while PM0.1 and NP20 induced stimulatory effects on HLM cytokines release, NP100 had not effect. In particular, PM0.1 induced IL-6, IL-1β, TNF-α, but not CXCL8, release from HLMs. Moreover, PM0.1, NP20 and NP100 did not induce β-glucuronidase release, a preformed mediator contained in HLMs. The long time necessary for cytokines release (18 h) suggested that PM0.1 and NP20 could induce ex-novo production of the tested mediators. Accordingly, after 6 h of incubation, PM0.1 and NP20 induced mRNA expression of IL-6, TNF-α and IL-1β. Moreover, NP20 induced ROS production and [Ca²⁺]_i increase in a time-dependent manner, without producing cytotoxicity. Collectively, the present data highlight the main proinflammatory role of NP20 among PM fractions. This is particularly of concern because this fraction is not currently covered by legal limits as it is not easily measured at the exhausts by the available technical methodologies, suggesting that it is mandatory to search for new monitoring techniques and strategies for limiting NP20 formation.

Recent trends in the application of nanoparticles in cancer therapy: The involvement of oxidative stress

In the biomedical area, the interdisciplinary field of nanotechnology has the potential to bring numerous unique applications, including better tactics for cancer detection, diagnosis, and therapy. Nanoparticles (NPs) have been the topic of many research and material applications throughout the last decade. Unlike small-molecule medications, NPs are defined by distinct physicochemical characteristics, such as a large surface-to-volume ratio, which allows them to permeate live cells with relative ease. The versatility of NPs as both therapeutics and diagnostics makes them ideal for a broad spectrum of illnesses, from infectious diseases to cancer. A significant amount of data has been participated in the current scientific publications, emphasizing the concept that NPs often produce reactive oxygen species (ROS) to a larger degree than micro-sized particles. It is important to note that oxidative stress governs a wide range of cell signaling cascades, many of which are responsible for cancer cell cytotoxicity. Here, we aimed to provide insight into the signaling pathways triggered by oxidative stress in cancer cells in response to several types of nanomaterials, such as metallic and polymeric NPs and quantum dots. We discuss recent advances in developing integrated anticancer medicines based on NPs targeted to destroy malignant cells by increasing their ROS setpoint.

Mitochondria Lead the Way: Mitochondrial Dynamics and Function in Cellular Movements in Development and Disease

The dynamics, distribution and activity of subcellular organelles are integral to regulating cell shape changes during various physiological processes such as epithelial cell formation, cell migration and morphogenesis. Mitochondria are famously known as the powerhouse of the cell and play an important role in buffering calcium, releasing reactive oxygen species and key metabolites for various activities in a eukaryotic cell. Mitochondrial dynamics and morphology changes regulate these functions and their regulation is, in turn, crucial for various morphogenetic processes. In this review, we evaluate recent literature which highlights the role of mitochondrial morphology and activity during cell shape changes in epithelial cell formation, cell division, cell migration and tissue morphogenesis during organism development and in disease. In general, we find that mitochondrial shape is regulated for their distribution or translocation to the sites of active cell shape dynamics or morphogenesis. Often, key metabolites released locally and molecules buffered by mitochondria play crucial roles in regulating signaling pathways that motivate changes in cell shape, mitochondrial shape and mitochondrial activity. We conclude that mechanistic analysis of interactions between mitochondrial morphology, activity, signaling pathways and cell shape changes across the various cell and animal-based model systems holds the key to deciphering the common principles for this interaction.

Tumor necrosis factor receptor-1 is selectively sequestered into Schwann cell extracellular vesicles where it functions as a TNFα decoy

Schwann cells (SCs) are known to produce extracellular vesicles (EV) that participate in cell-cell communication by transferring cargo to target cells, including mRNAs, microRNAs, and biologically active proteins. Herein, we report a novel mechanism whereby SC EVs may regulate PNS physiology, especially in injury, by controlling the activity of TNFα. SCs actively sequester tumor necrosis factor receptor-1 (TNFR1) into EVs at high density, accounting for about 2% of the total protein in SC EVs (~1000 copies TNFR1/EV). Although TNFR2 was robustly expressed by SCs in culture, TNFR2 was excluded from SC EVs. SC EV TNFR1 bound TNFα, decreasing the concentration of free TNFα available to bind to cells and thus served as a TNFα decoy. SC EV TNFR1 significantly inhibited TNFα-induced p38 MAPK phosphorylation in cultured SCs. When TNFR1 was proteolytically removed from SC EVs using tumor necrosis factor-α converting enzyme (TACE) or neutralized with antibody, the ability of TNFα to activate p38 MAPK in the presence of these EVs was restored. As further evidence of its decoy activity, SC EV TNFR1 modified TNFα activities in vitro including: (1) regulation of expression of other cytokines; (2) effects on SC morphology; and (3) effects on SC viability. SC EVs also modified the effects of TNFα on sciatic nerve morphology and neuropathic pain-related behavior in vivo. By sequestering TNFR1 in EVs, SCs may buffer against the potentially toxic effects of TNFα. SC EVs provide a novel mechanism for the spatial and temporal regulation of neuro-inflammation.

Immune control of Mycobacterium tuberculosis is dependent on both soluble TNFRp55 and soluble TNFRp75

Tuberculosis presents a global health challenge, and tumour necrosis factor (TNF) signalling is required for host immunity against Mycobacterium tuberculosis (Mtb). TNF receptor shedding, however, compromises effective immunity by reducing bioactive TNF through the formation of inactive complexes. In this study, we first compared the effect of total soluble TNF receptors using a transgenic p55^ΔNS /p75^-/- murine strain on host protection during a low-dose aerosol Mtb H37Rv challenge. We report that the presence of membrane-bound TNFRp55 alone in the absence of TNFRp75 results in superior control of a primary Mtb infection where p55^ΔNS /p75^-/- hyperactive dendritic cells displayed an increased capacity to induce a hyperactive Mtb-specific CD4⁺ T-cell response. p55^ΔNS /p75^-/- dendritic cells expressed a higher frequency of MHCII and increased MFIs for both CD86 and MHCII, while CD4⁺ T cells had higher expression of CD44 and IFN-γ. Next, the relative contributions of soluble TNFRp55 and soluble TNFRp75 to host protection against either primary Mtb infection or during reactivation of latent tuberculosis were delineated by comparing the experimental outcomes of control C57BL/6 mice to transgenic p55^ΔNS /p75^-/- , p55^ΔNS and p75^-/- mouse strains. We found that soluble TNFRp55 is redundant for immune regulation during the chronic stages of a primary Mtb infection. However, TNFRp55 together with soluble TNFRp75 has a crucial role in immune regulation of reactivation of latent tuberculosis.

Oxidative Stress in Cancer Cell Metabolism

Reactive oxygen species (ROS) are important in regulating normal cellular processes whereas deregulated ROS leads to the development of a diseased state in humans including cancers. Several studies have been found to be marked with increased ROS production which activates pro-tumorigenic signaling, enhances cell survival and proliferation and drives DNA damage and genetic instability. However, higher ROS levels have been found to promote anti-tumorigenic signaling by initiating oxidative stress-induced tumor cell death. Tumor cells develop a mechanism where they adjust to the high ROS by expressing elevated levels of antioxidant proteins to detoxify them while maintaining pro-tumorigenic signaling and resistance to apoptosis. Therefore, ROS manipulation can be a potential target for cancer therapies as cancer cells present an altered redox balance in comparison to their normal counterparts. In this review, we aim to provide an overview of the generation and sources of ROS within tumor cells, ROS-associated signaling pathways, their regulation by antioxidant defense systems, as well as the effect of elevated ROS production in tumor progression. It will provide an insight into how pro- and anti-tumorigenic ROS signaling pathways could be manipulated during the treatment of cancer.

Actin fence therapy with exogenous V12Rac1 protects against acute lung injury

High mortality in acute lung injury (ALI) results from sustained proinflammatory signaling by alveolar receptors, such as TNF-α receptor type 1 (TNFR1). Factors that determine the sustained signaling are not known. Unexpectedly, optical imaging of live alveoli revealed a major TNF-α–induced surge of alveolar TNFR1 due to a Ca²⁺-dependent mechanism that decreased the cortical actin fence. Mouse mortality due to inhaled LPS was associated with cofilin activation, actin loss, and the TNFR1 surge. The constitutively active form of the GTPase, Rac1 (V12Rac1), given intranasally (i.n.) as a noncovalent construct with a cell-permeable peptide, enhanced alveolar filamentous actin (F-actin) and blocked the TNFR1 surge. V12Rac1 also protected against ALI-induced mortality resulting from i.n. instillation of LPS or of Pseudomonas aeruginosa. We propose a potentially new therapeutic paradigm in which actin enhancement by exogenous Rac1 strengthens the alveolar actin fence, protecting against proinflammatory receptor hyperexpression, and therefore blocking ALI.

Extracellular Vesicles for the Treatment of Radiation-Induced Normal Tissue Toxicity in the Lung

Human stem cell-derived extracellular vesicles (EV) provide many advantages over cell-based therapies for the treatment of functionally compromised tissue beds and organ sites. Here we sought to determine whether human embryonic stem cell (hESC)-derived EV could resolve in part, the adverse late normal tissue complications associated with exposure of the lung to ionizing radiation. The hESC-derived EV were systemically administered to the mice via the retro-orbital sinus to explore the potential therapeutic benefits following exposure to high thoracic doses of radiation (14 Gy). Data demonstrated that hESC-derived EV treatment significantly improved overall survival of the irradiated cohorts (P < 0.001). Increased survival was also associated with significant reductions in lung fibrosis as quantified by CBCT imaging (P < 0.01, 2 weeks post-irradiation). Qualitative histological analyses revealed reduced indications of radiation induced pulmonary injury in animals treated with EV. EV were then subjected to a rigorous proteomic analysis to ascertain the potential bioactive cargo that may prove beneficial in ameliorating radiation-induced normal tissue toxicities in the lung. Proteomics validated several consensus exosome markers (e.g., CD68) and identified major classes of proteins involved in nuclear pore complexes, epigenetics, cell cycle, growth and proliferation, DNA repair, antioxidant function, and cellular metabolism (TCA cycle and oxidative phosphorylation, OXYPHOS). Interestingly, EV were also found to contain mitochondrial components (mtDNA, OXYPHOS protein subunits), which may contribute to the metabolic reprograming and recovery of radiation-injured pulmonary tissue. To evaluate the safety of EV treatments in the context of the radiotherapeutic management of tumors, mice harboring TC1 tumor xenografts were subjected to the same EV treatments shown to forestall lung fibrosis. Data indicated that over the course of one month, no change in the growth of flank tumors between treated and control cohorts was observed. In conclusion, present findings demonstrate that systemic delivery of hESC-derived EV could ameliorate radiation-induced normal tissue complications in the lung, through a variety of potential mechanisms based on EV cargo analysis.

The Mitochondrial Calcium Uniporter of Pulmonary Type 2 Cells Determines Severity of ARDS

Acute lung immunity to inhaled pathogens elicits defensive pneumonitis that may convert to the Acute Respiratory Distress Syndrome (ARDS), causing high mortality. Mechanisms underlying the conversion are not understood, but are of intense interest because of the ARDS-induced mortality in the ongoing Covid-19 pandemic. Here, by optical imaging of live lungs we show that key to the lethality is the functional status of mitochondrial Ca2+ buffering across the mitochondrial Ca2+ uniporter (MCU) in the alveolar type 2 cells (AT2), which protect alveolar stability. In mice subjected to ARDS by airway exposure to lipopolysaccharide (LPS), or to Pseudomonas aeruginosa, there was marked loss of MCU expression in AT2. The ability of mice to survive ARDS depended on the extent to which the MCU expression recovered, indicating that the viability of Ca2+ buffering by AT2 mitochondria critically determines ARDS severity. Mitochondrial transfer to enhance AT2 MCU expression might protect against ARDS.

Stem Cells, Cell Therapies, and Bioengineering in Lung Biology and Disease 2019

A workshop entitled "Stem Cells, Cell Therapies and Bioengineering in Lung Biology and Diseases" was hosted by the University of Vermont Larner College of Medicine in collaboration with the National Heart, Lung and Blood Institute, the Alpha-1 Foundation, the Cystic Fibrosis Foundation, the International Society for Cell and Gene Therapy and the Pulmonary Fibrosis Foundation. The event was held from July 15 to 18, 2019 at the University of Vermont, Burlington, Vermont. The objectives of the conference were to review and discuss the current status of the following active areas of research: 1) technological advancements in the analysis and visualisation of lung stem and progenitor cells; 2) evaluation of lung stem and progenitor cells in the context of their interactions with the niche; 3) progress toward the application and delivery of stem and progenitor cells for the treatment of lung diseases such as cystic fibrosis; 4) progress in induced pluripotent stem cell models and application for disease modelling; and 5) the emerging roles of cell therapy and extracellular vesicles in immunomodulation of the lung. This selection of topics represents some of the most dynamic research areas in which incredible progress continues to be made. The workshop also included active discussion on the regulation and commercialisation of regenerative medicine products and concluded with an open discussion to set priorities and recommendations for future research directions in basic and translation lung biology.

Behҫet's Disease, and the Role of TNF-α and TNF-α Blockers

In this both narrative and systematic review, we explore the role of TNF-α in the immunopathogenesis of Behçet's disease (BD) and the effect of treatment with TNF-α blockers. BD is an auto-inflammatory disease, characterized by recurrent painful oral ulcerations. The pathogenesis of BD is not yet elucidated; it is assumed that TNF-α may play a key role. In the narrative review, we report an increased production of TNF-α, which may be stimulated via TLR-signaling, or triggered by increased levels of IL-1β and IFN-γ. The abundance of TNF-α is found in both serum and in sites of inflammation. This increased presence of TNF-α stimulates T-cell development toward pro-inflammatory subsets, such as Th17 and Th22 cells. Treatment directed against the surplus of TNF-α is investigated in the systematic review, performed according to the PRISMA guideline. We searched the Pubmed and Cochrane database, including comparative studies only. After including 11 studies, we report a beneficial effect of treatment with TNF-α blockers on the various manifestations of BD. In conclusion, the pivotal role of TNF-α in the immunopathogenesis of BD is reflected in both the evidence of their pro-inflammatory effects in BD and in the evidence of the positive effect of treatment on the course of disease in BD.

The Role of Metabolic Remodeling in Macrophage Polarization and Its Effect on Skeletal Muscle Regeneration

Significance: Macrophages are crucial for tissue homeostasis. Based on their activation, they might display classical/M1 or alternative/M2 phenotypes. M1 macrophages produce pro-inflammatory cytokines, reactive oxygen species (ROS), and nitric oxide (NO). M2 macrophages upregulate arginase-1 and reduce NO and ROS levels; they also release anti-inflammatory cytokines, growth factors, and polyamines, thus promoting angiogenesis and tissue healing. Moreover, M1 and M2 display key metabolic differences; M1 polarization is characterized by an enhancement in glycolysis and in the pentose phosphate pathway (PPP) along with a decreased oxidative phosphorylation (OxPhos), whereas M2 are characterized by an efficient OxPhos and reduced PPP. Recent Advances: The glutamine-related metabolism has been discovered as crucial for M2 polarization. Vice versa, flux discontinuities in the Krebs cycle are considered additional M1 features; they lead to increased levels of immunoresponsive gene 1 and itaconic acid, to isocitrate dehydrogenase 1-downregulation and to succinate, citrate, and isocitrate over-expression. Critical Issues: A macrophage classification problem, particularly in vivo, originating from a gap in the knowledge of the several intermediate polarization statuses between the M1 and M2 extremes, characterizes this field. Moreover, the detailed features of metabolic reprogramming crucial for macrophage polarization are largely unknown; in particular, the role of β-oxidation is highly controversial. Future Directions: Manipulating the metabolism to redirect macrophage polarization might be useful in various pathologies, including an efficient skeletal muscle regeneration. Unraveling the complexity pertaining to metabolic signatures that are specific for the different macrophage subsets is crucial for identifying new compounds that are able to trigger macrophage polarization and that might be used for therapeutical purposes.

Endothelial mitochondria determine rapid barrier failure in chemical lung injury

Acid aspiration, which can result from several etiologies, including postoperative complications, leads to direct contact of concentrated hydrochloric acid (HCl) with the alveolar epithelium. As a result, rapid endothelial activation induces alveolar inflammation, leading to life-threatening pulmonary edema. Because mechanisms underlying the rapid endothelial activation are not understood, here we determined responses in real time through optical imaging of alveoli of live mouse lungs. By alveolar micropuncture, we microinfused concentrated HCl in the alveolar lumen. As expected, acid contact with the epithelium caused rapid, but transient, apical injury. However, there was no concomitant membrane injury to the endothelium. Nevertheless, H2O2-mediated epithelial-endothelial paracrine signaling induced endothelial barrier failure, as detected by microvascular dextran leakage and lung water quantification. Remarkably, endothelial mitochondria regulated the barrier failure by activating uncoupling protein 2 (UCP2), thereby inducing transient mitochondrial depolarization that led to cofilin-induced actin depolymerization. Knockdown, or endothelium-targeted deletion of UCP2 expression, blocked these responses, including pulmonary edema. To our knowledge, these findings are the first to mechanistically implicate endothelial mitochondria in acid-induced barrier deterioration and pulmonary edema. We suggest endothelial UCP2 may be a therapeutic target for acid-induced acute lung injury.

Pathological effects of ionizing radiation: endothelial activation and dysfunction

The endothelium, a tissue that forms a single layer of cells lining various organs and cavities of the body, especially the heart and blood as well as lymphatic vessels, plays a complex role in vascular biology. It contributes to key aspects of vascular homeostasis and is also involved in pathophysiological processes, such as thrombosis, inflammation, and hypertension. Epidemiological data show that high doses of ionizing radiation lead to cardiovascular disease over time. The aim of this review is to summarize the current knowledge on endothelial cell activation and dysfunction after ionizing radiation exposure as a central feature preceding the development of cardiovascular diseases.

Application of a novel in vivo imaging approach to measure pulmonary vascular responses in mice

Noninvasive imaging of the murine pulmonary vasculature is challenging due to the small size of the animal, limits of resolution of the imaging technology, terminal nature of the procedure, or the need for intravenous contrast. We report the application of laboratory-based high-speed, high-resolution x-ray imaging, and image analysis to detect quantitative changes in the pulmonary vascular tree over time in the same animal without the need for intravenous contrast. Using this approach, we detected an increased number of vessels in the pulmonary vascular tree of animals after 30 min of recovery from a brief exposure to inspired gas with 10% oxygen plus 5% carbon dioxide (mean ± standard deviation: 2193 ± 382 at baseline vs. 6177 ± 1171 at 30 min of recovery; P < 0.0001). In a separate set of animals, we showed that the total pulmonary blood volume increased (P = 0.0412) while median vascular diameter decreased from 0.20 mm (IQR: 0.15-0.28 mm) to 0.18 mm (IQR: 0.14-0.26 mm; P = 0.0436) over the respiratory cycle from end-expiration to end-inspiration. These findings suggest that the noninvasive, nonintravenous contrast imaging approach reported here can detect dynamic responses of the murine pulmonary vasculature and may be a useful tool in studying these responses in models of disease.

iRhom2 loss alleviates renal injury in long-term PM2.5-exposed mice by suppression of inflammation and oxidative stress

Particulate matter (PM2.5) is a risk factor for organ injury and disease progression, such as lung, brain and liver. However, its effects on renal injury and the underlying molecular mechanism have not been understood. The inactive rhomboid protein 2 (iRhom2), also known as rhomboid family member 2 (Rhbdf2), is a necessary modulator for shedding of tumor necrosis factor-α (TNF-α) in immune cells, and has been explored in the pathogenesis of chronic renal diseases. In the present study, we found that compared to the wild type (iRhom2^+/+) mice, iRhom2 knockout (iRhom2^-/-) protected PM_2.5-exposed mice from developing severe renal injury, accompanied with improved renal pathological changes and functions. iRhom2^-/- mice exhibited reduced inflammatory response, as evidenced by the reduction of interleukin 1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α) and IL-18 in kidney samples, which might be, at least partly, through inactivating TNF-α converting enzyme/TNF-α receptors (TACE/TNFRs) and inhibitor of α/nuclear factor κ B (IκBα/NF-κB) signaling pathways. In addition, oxidative stress was also restrained by iRhom2^-/- in kidney of PM_2.5-exposed mice by enhancing heme oxygenase/nuclear factor erythroid 2-related factor 2 (HO-1/Nrf-2) expressions, and reducing phosphorylated c-Jun N-terminal kinase (JNK). In vitro, blockage of HO-1 or Nrf-2 rescued the inflammatory response and oxidative stress that were reduced by iRhom2 knockdown in PM_2.5-incubated RAW264.7 cells. Similar results were observed in JNK activator-treated cells. Taken together, our findings indicated that iRhom2 played an essential role in regulating PM_2.5-induced chronic renal damage, thus revealing a potential target for preventing chronic kidney diseases development.

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Suppression of iRhom2 negatively regulates inflammatory response in mouse macrophages RAW264.7 cells.

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iRhom2 deficiency alleviates PM2.5-induced renal injury by reducing inflammatory infiltration.

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iRhom2 inhibition reduces oxidative stress and JNK activation in PM2.5-induced renal injury in vitro and in vivo.

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PM2.5-induced renal injury via iRhom2-regulated oxidative stress and inflammation.

Bacterial-Host Interactions: Physiology and Pathophysiology of Respiratory Infection

It has long been thought that respiratory infections are the direct result of acquisition of pathogenic viruses or bacteria, followed by their overgrowth, dissemination, and in some instances tissue invasion. In the last decades, it has become apparent that in contrast to this classical view, the majority of microorganisms associated with respiratory infections and inflammation are actually common members of the respiratory ecosystem and only in rare circumstances do they cause disease. This suggests that a complex interplay between host, environment, and properties of colonizing microorganisms together determines disease development and its severity. To understand the pathophysiological processes that underlie respiratory infectious diseases, it is therefore necessary to understand the host-bacterial interactions occurring at mucosal surfaces, along with the microbes inhabiting them, during symbiosis. Current knowledge regarding host-bacterial interactions during asymptomatic colonization will be discussed, including a plausible role for the human microbiome in maintaining a healthy state. With this as a starting point, we will discuss possible disruptive factors contributing to dysbiosis, which is likely to be a key trigger for pathobionts in the development and pathophysiology of respiratory diseases. Finally, from this renewed perspective, we will reflect on current and potential new approaches for treatment in the future.

Pulmonary vascular endothelium: the orchestra conductor in respiratory diseases

The European Respiratory Society (ERS) Research Seminar entitled “Pulmonary vascular endothelium: orchestra conductor in respiratory diseases - highlights from basic research to therapy” brought together international experts in dysfunctional pulmonary endothelium, from basic science to translational medicine, to discuss several important aspects in acute and chronic lung diseases. This review will briefly sum up the different topics of discussion from this meeting which was held in Paris, France on October 27–28, 2016. It is important to consider that this paper does not address all aspects of endothelial dysfunction but focuses on specific themes such as: 1) the complex role of the pulmonary endothelium in orchestrating the host response in both health and disease (acute lung injury, chronic obstructive pulmonary disease, high-altitude pulmonary oedema and pulmonary hypertension); and 2) the potential value of dysfunctional pulmonary endothelium as a target for innovative therapies.

Neutralization of MMP-2 and TNFR1 Regulates the Severity of S. aureus-Induced Septic Arthritis by Differential Alteration of Local and Systemic Proinflammatory Cytokines in Mice

Despite advancement in the field of antibiotics septic arthritis remains a serious concern till date. Staphylococcus aureus is the most common bacterium that causes septic arthritis. Severity of this disease is directly correlated with chronic inflammation induced by proinflammatory cytokines like TNF-α, interleukin (IL)-1β, IL-6, and induction of matrix metalloproteinases (MMPs) including MMP-2. The objective of our study was to evaluate the role of MMP-2 and tumor necrosis factor receptor 1 (TNFR1) in the pathogenesis of S. aureus infection-induced septic arthritis. Mice were infected with live S. aureus (5 × 10⁶ cells/ml) followed by administration of MMP-2 inhibitor and TNFR1 antibody. Arthritis index showed highest reduction in severity of arthritis in mice treated with both MMP-2 inhibitor and TNFR1 antibody after infection. Combined neutralization of MMP-2 and TNFR1 led to marked diminution in bacterial count in the combined group. Lowest levels of pro inflammatory cytokines like TNF-α, IL-1β, IL-6, and IFN-γ were observed in both serum and synovial tissues indicating maximum protection in S. aureus arthritis during combination treatment. Increment in the level of IL-10 in the combination group could be positively correlated with the recovery of arthritis. Similarly, expressions of COX-2 and iNOS, markers of acute inflammation were also significantly reduced in the combination group due to resolution of inflammation. Levels of O2^.- and NO also showed a significant fall in case of the group treated with MMP-2 inhibitor and TNFR1 antibody both. Neutralization of both MMP-2 and TNFR1 caused rapid decline in recruitment of neutrophil and macrophages in the synovial tissues as evident from reduced MPO and MCP-1 levels, respectively, compared to other groups. Overall, it can be suggested that administration of MMP-2 inhibitor and TNFR1 antibody in combination is protective against the severity of inflammation and cartilage destruction associated with S. aureus infection-induced septic arthritis by altering the levels of cytokines.

Elevated Markers of Death Receptor-Activated Apoptosis are Associated with Increased Risk for Development of Diabetes and Cardiovascular Disease

Background

An increased rate of cell death by apoptosis has been implicated in both diabetes and atherosclerosis. Apoptosis can be induced through activation of the death receptors TNF receptor 1 (TNFR-1), TRAIL receptor 2 (TRAILR-2) and Fas. Soluble forms of these receptors are found in plasma. The objective of this study was to determine if soluble death receptors are markers of receptor-activated apoptosis and predict risk for development of diabetes and cardiovascular events.

Methods

Fas ligand was used to induce apoptosis in peripheral blood mononuclear cells and INS-1 pancreatic β-cells and release of TNFR-1, TRAILR-2 and Fas measured by ELISA. Proximity Extension Assay was used to analyze plasma levels of TNFR-1, TRAILR-2 and Fas in baseline samples of 4742 subjects in the Malmö Diet and Cancer Study and related to development of diabetes and cardiovascular events during 19.2 years of follow-up.

Results

Activation of apoptosis by Fas ligand was associated with release of soluble Fas, TNFR-1 and TRAILR-2 in both cell types. Circulating levels of all three receptors were higher in subjects with diabetes and correlated with markers of impaired glucose metabolism in non-diabetic subjects. Among the latter, those in the highest tertile of soluble Fas, TNFR-1 and TRAILR-2 had increased risk for development of diabetes and cardiovascular events. These associations became weaker when adjusting for cardiovascular risk factors in Cox regression models, but remained significant for TRAILR-2 with incident diabetes, cardiovascular mortality, myocardial infarction and ischemic stroke, and for TNFR-1 with myocardial infarction.

Conclusion

The present study demonstrates an association between several cardiovascular risk factors and elevated levels of circulating markers of apoptotic cell death. It also shows that subjects with high levels of these biomarkers have increased risk of diabetes and CVD. This implies that soluble death receptors are markers of β-cell and vascular injury and potentially could be used as surrogate markers of therapeutic efficiency in risk factor interventions.

•Receptor-activated apoptosis is associated with release of soluble death receptors that act as biomarkers of apoptosis •Several cardiovascular risk factors including markers of impaired glucose metabolism associate with elevated plasma levels of death receptors •Subjects with high plasma levels of death receptors have an increased risk of diabetes and cardiovascular disease

Atherosclerosis has been proposed to develop in response to chronic arterial injury caused by cardiovascular risk factors. The present study provides clinical evidence for this hypothesis by demonstrating an association between several cardiovascular risk factors and elevated levels of circulating markers of apoptotic cell death and that subjects with high levels of these biomarkers have increased risk of cardiovascular mortality, MI and stroke. These observations point to the possibility that the plasma level of soluble death receptors can be used as surrogate markers of arterial injury and atherosclerotic disease activity in cardiovascular interventions. Finally, our findings imply that soluble death receptors also may serve as biomarkers of the damage caused by metabolic stress to β-cells and risk for development of type 2 diabetes.

Oxidative stress and reactive oxygen species in endothelial dysfunction associated with cardiovascular and metabolic diseases

Reactive oxygen species (ROS) are reactive intermediates of molecular oxygen that act as important second messengers within the cells; however, an imbalance between generation of reactive ROS and antioxidant defense systems represents the primary cause of endothelial dysfunction, leading to vascular damage in both metabolic and atherosclerotic diseases. Endothelial activation is the first alteration observed, and is characterized by an abnormal pro-inflammatory and pro-thrombotic phenotype of the endothelial cells lining the lumen of blood vessels. This ultimately leads to reduced nitric oxide (NO) bioavailability, impairment of the vascular tone and other endothelial phenotypic changes collectively termed endothelial dysfunction(s). This review will focus on the main mechanisms involved in the onset of endothelial dysfunction, with particular focus on inflammation and aberrant ROS production and on their relationship with classical and non-classical cardiovascular risk factors, such as hypertension, metabolic disorders, and aging. Furthermore, new mediators of vascular damage, such as microRNAs, will be discussed. Understanding mechanisms underlying the development of endothelial dysfunction is an important base of knowledge to prevent vascular damage in metabolic and cardiovascular diseases.

Mitochondria-meditated pathways of organ failure upon inflammation

Liver failure induced by systemic inflammatory response (SIRS) is often associated with mitochondrial dysfunction but the mechanism linking SIRS and mitochondria-mediated liver failure is still a matter of discussion. Current hypotheses suggest that causative events could be a drop in ATP synthesis, opening of mitochondrial permeability transition pore, specific changes in mitochondrial morphology, impaired Ca²⁺ uptake, generation of mitochondrial reactive oxygen species (mtROS), turnover of mitochondria and imbalance in electron supply to the respiratory chain. The aim of this review is to critically analyze existing hypotheses, in order to highlight the most promising research lines helping to prevent liver failure induced by SIRS. Evaluation of the literature shows that there is no consistent support that impaired Ca⁺⁺ metabolism, electron transport chain function and ultrastructure of mitochondria substantially contribute to liver failure. Moreover, our analysis suggests that the drop in ATP levels has protective rather than a deleterious character. Recent data suggest that the most critical mitochondrial event occurring upon SIRS is the release of mtROS in cytoplasm, which can activate two specific intracellular signaling cascades. The first is the mtROS-mediated activation of NADPH-oxidase in liver macrophages and endothelial cells; the second is the acceleration of the expression of inflammatory genes in hepatocytes. The signaling action of mtROS is strictly controlled in mitochondria at three points, (i) at the site of ROS generation at complex I, (ii) the site of mtROS release in cytoplasm via permeability transition pore, and (iii) interaction with specific kinases in cytoplasm. The systems controlling mtROS-signaling include pro- and anti-inflammatory mediators, nitric oxide, Ca²⁺ and NADPH-oxidase. Analysis of the literature suggests that further research should be focused on the impact of mtROS on organ failure induced by inflammation and simultaneously providing a new theoretical basis for a targeted therapy of overwhelmed inflammatory response.

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Relationship between mitochondrial dysfunction and high lethality upon sepsis.

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Criteria to define critical for lethality mitochondrial dysfunction.

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ATP, calcium, mitochondrial ultrastructure and apoptosis, upon inflammation.

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Regulation of inflammatory processes by mitochondrial ROS.

Mitochondrial Dysfunction in Airway Disease

There is increasing appreciation that mitochondria serve cellular functions beyond oxygen sensing and energy production. Accordingly, it has become important to explore noncanonical roles of mitochondria in normal and pathophysiological processes that influence airway structure and function in the context of diseases such as asthma and COPD. Mitochondria can sense upstream processes such as inflammation, infection, tobacco smoke, and environmental insults important in these diseases and in turn can respond to such stimuli through altered mitochondrial protein expression, structure, and resultant dysfunction. Conversely, mitochondrial dysfunction has downstream influences on cytosolic and mitochondrial calcium regulation, airway contractility, gene and protein housekeeping, responses to oxidative stress, proliferation, apoptosis, fibrosis, and certainly metabolism, which are all key aspects of airway disease pathophysiology. Indeed, mitochondrial dysfunction is thought to play a role even in normal processes such as aging and senescence and in conditions such as obesity, which impact airway diseases. Thus, understanding how mitochondrial structure and function play central roles in airway disease may be critical for the development of novel therapeutic avenues targeting dysfunctional mitochondria. In this case, it is likely that mitochondria of airway epithelium, smooth muscle, and fibroblasts play differential roles, consistent with their contributions to disease biology, underlining the challenge of targeting a ubiquitous cellular element of existential importance. This translational review summarizes the current state of understanding of mitochondrial processes that play a role in airway disease pathophysiology and identifying areas of unmet research need and opportunities for novel therapeutic strategies.

Roles of extracellular nucleotides and P2 receptors in ectodomain shedding

Ectodomain shedding of integral membrane receptors results in the release of soluble molecules and modification of the transmembrane portions to mediate or modulate extracellular and intracellular signalling. Ectodomain shedding is stimulated by a variety of mechanisms, including the activation of P2 receptors by extracellular nucleotides. This review describes in detail the roles of extracellular nucleotides and P2 receptors in the shedding of various cell surface molecules, including amyloid precursor protein, CD23, CD62L, and members of the epidermal growth factor, immunoglobulin and tumour necrosis factor families. This review discusses the mechanisms involved in P2 receptor-mediated shedding, demonstrating central roles for the P2 receptors, P2X7 and P2Y2, and the sheddases, ADAM10 and ADAM17, in this process in a number of cell types.

Mitochondria dysfunction: A novel therapeutic target in pathological lung remodeling or bystander?

The renascence in mitochondrial research has fueled breakthroughs in our understanding of mitochondrial biology identifying major roles in biological processes ranging from cellular oxygen sensing and regulation of intracellular calcium levels through to initiation of apoptosis or a shift in cell phenotype. Chronic respiratory diseases are no exception to the resurgent interest in mitochondrial biology. Microscopic observations of lungs from patients with chronic respiratory diseases such as pulmonary arterial hypertension, asthma and COPD show accumulation of dysmorphic mitochondria and provide the first evidence of mitochondrial dysfunction in diseased lungs. Recent mechanistic insights have established links between mitochondrial dysfunction or aberrant biogenesis and the pathogenesis of chronic respiratory diseases through playing a causative role in structural remodeling of the lung. The aim here is to discuss the case for a mitochondrial basis of lung remodeling in patients with chronic respiratory diseases. The present article will focus on the question of whether currently available data supports mitochondrial mechanisms as a viable point of therapeutic intervention in respiratory diseases and suggestions for future avenues of research in this rapidly evolving field.

Macrophage-epithelial interactions in pulmonary alveoli

Alveolar macrophages have been investigated for years by approaches involving macrophage extraction from the lung by bronchoalveolar lavage, or by cell removal from lung tissue. Since extracted macrophages are studied outside their natural milieu, there is little understanding of the extent to which alveolar macrophages interact with the epithelium, or with one another to generate the lung's innate immune response to pathogen challenge. Here, we review new evidence of macrophage-epithelial interactions in the lung, and we address the emerging understanding that the alveolar epithelium plays an important role in orchestrating the macrophage-driven immune response.

Dissecting Redox Biology Using Fluorescent Protein Sensors

SIGNIFICANCE

Fluorescent protein sensors have revitalized the field of redox biology by revolutionizing the study of redox processes in living cells and organisms.

RECENT ADVANCES

Within one decade, a set of fundamental new insights has been gained, driven by the rapid technical development of in vivo redox sensing. Redox-sensitive yellow and green fluorescent protein variants (rxYFP and roGFPs) have been the central players.

CRITICAL ISSUES

Although widely used as an established standard tool, important questions remain surrounding their meaningful use in vivo. We review the growing range of thiol redox sensor variants and their application in different cells, tissues, and organisms. We highlight five key findings where in vivo sensing has been instrumental in changing our understanding of redox biology, critically assess the interpretation of in vivo redox data, and discuss technical and biological limitations of current redox sensors and sensing approaches.

FUTURE DIRECTIONS

We explore how novel sensor variants may further add to the current momentum toward a novel mechanistic and integrated understanding of redox biology in vivo. Antioxid. Redox Signal. 24, 680-712.

The Reactive Oxygen Species in Macrophage Polarization: Reflecting Its Dual Role in Progression and Treatment of Human Diseases

High heterogeneity of macrophage is associated with its functions in polarization to different functional phenotypes depending on environmental cues. Macrophages remain in balanced state in healthy subject and thus macrophage polarization may be crucial in determining the tissue fate. The two distinct populations, classically M1 and alternatively M2 activated, representing the opposing ends of the full activation spectrum, have been extensively studied for their associations with several disease progressions. Accumulating evidences have postulated that the redox signalling has implication in macrophage polarization and the key roles of M1 and M2 macrophages in tissue environment have provided the clue for the reasons of ROS abundance in certain phenotype. M1 macrophages majorly clearing the pathogens and ROS may be crucial for the regulation of M1 phenotype, whereas M2 macrophages resolve inflammation which favours oxidative metabolism. Therefore how ROS play its role in maintaining the homeostatic functions of macrophage and in particular macrophage polarization will be reviewed here. We also review the biology of macrophage polarization and the disturbance of M1/M2 balance in human diseases. The potential therapeutic opportunities targeting ROS will also be discussed, hoping to provide insights for development of target-specific delivery system or immunomodulatory antioxidant for the treatment of ROS-related diseases.

FXYD5 Protein Has a Pro-inflammatory Role in Epithelial Cells

The FXYD proteins are a family of small membrane proteins that share an invariant four amino acid signature motif F-X-Y-D and act as tissue-specific regulatory subunits of the Na,K-ATPase. FXYD5 (also termed dysadherin or RIC) is a structurally and functionally unique member of the FXYD family. As other FXYD proteins, FXYD5 specifically interacts with the Na,K-ATPase and alters its kinetics by increasing Vmax However, unlike other family members FXYD5 appears to have additional functions, which cannot be readily explained by modulation of transport kinetics. Knockdown of FXYD5 in MDA-MB-231 breast cancer cells largely decreases expression and secretion of the chemokine CCL2 (MCP-1). A related effect has also been observed in renal cell carcinoma cells. The current study aims to further characterize the relationship between the expression of FXYD5 and CCL2 secretion. We demonstrate that transfection of M1 epithelial cell line with FXYD5 largely increases lipopolysaccharide (LPS) stimulated CCL2 mRNA and secretion of the translated protein. We have completed a detailed analysis of the molecular events leading to the above response. Our key findings indicate that FXYD5 generates a late response by increasing the surface expression of the TNFα receptor, without affecting its total protein level, or mRNA transcription. LPS administration to mice demonstrates induced secretion of CCL2 and TNFα in FXYD5-expressing lung peripheral tissue, which suggests a possible role for FXYD5 in normal epithelia during inflammation.

Mesenchymal stem cell-conditioned media suppresses inflammation-associated overproliferation of pulmonary artery smooth muscle cells in a rat model of pulmonary hypertension

Inflammation-associated overproliferation of pulmonary artery smooth muscle cells (PASMCs) is considered to be involved in the pathogenesis of pulmonary hypertension (PH). The administration of mesenchymal stem cell-conditioned media (MSC-CM) has displayed benefits in the treatment of PH, however, the exact mechanism has yet to be elucidated. The present study aimed to determine whether MSC-CM is able to suppress overproliferation of PASMCs in PH via immunoregulation. By the administration of MSC-CM to monocrotaline (MCT)-induced PH rats, and the development of an in vitro co-culture system comprised of PASMCs and activated T cells, the therapeutic effects of MSC-CM on PH, and the changes in the expression of correlated factors, including TNF-α, calcineurin (CaN) and nuclear factor of activated T cells (NFAT), were assessed. Immunohistochemical staining results indicated that MSC-CM was able to significantly suppress the production of TNF-α in MCT-induced PH and co-culture systems; and reverse transcription-quantitative polymerase chain reaction results showed significant downregulation of the expression of CaN and NFATc2 in PASMCs (P<0.01). Furthermore, MSC-CM was able to significantly suppress CaN activity and NFATc2 activation (P<0.01), thus inhibiting the overproliferation of PASMCs. Finally, MSC-CM improved abnormalities in hemodynamics and pulmonary histology in MCT-induced PH. In conclusion, the findings of the current study suggest that administration of MSC-CM has the potential to suppress inflammation-associated overproliferation of PASMCs due to its immunosuppressive effects in PH and, thus, may serve as a beneficial therapeutic strategy.

An in vitro model for the assessment of stem cell fate following implantation within the infarct microenvironment identifies ISL-1 expression as the strongest predictor of c-Kit(+) cardiac progenitor cells' therapeutic potential

Cell therapy has the potential to drastically improve clinical outcomes for the 1.45 million patients suffering from a myocardial infarction (MI) each year in the U.S. However, the limitations associated with this treatment - including poor engraftment, significant cell death and poor differentiation potential - have prevented its widespread application clinically. To optimize functional improvements provided by transplanted cells, there is a need to develop methods that increase cellular retention and viability, while supporting differentiation and promoting paracrine signaling. Current in vivo models are expensive, difficult to access and manipulate and are time consuming. We have developed an in vitro model of MI which allows for a straightforward, consistent and relatively accurate prediction of cell fate following injection in vivo. The model demonstrated how the infarct environment impairs cellular engraftment and differentiation, but identified an implantation strategy which enhanced cell fate in vitro. Multivariate linear regression identified variables within the model that regulated vascular differentiation potential including oxygen tension, stiffness and cytokine presence, while cardiac differentiation was more accurately predicted by Isl-1 expression in the original cell isolate than any other variable present within the model system. The model highlighted how the cells' sensitivity to the infarct variables varied from line to line, which emphasizes the importance of the model system for the prediction of cell fate on a patient specific basis. Further development of this model system could help predict the clinical efficacy of cardiac progenitor cell therapy at the patient level as well as identify the optimal strategy for cell delivery.

Mesenchymal stem cells suppress CaN/NFAT expression in the pulmonary arteries of rats with pulmonary hypertension

Inflammation and hyperproliferation of pulmonary artery smooth muscle cells (PASMCs) is considered the primary pathological feature of pulmonary hypertension (PH). The present study determined that mesenchymal stem cells (MSCs) suppress the expression of calcineurin (CaN) and nuclear factor of activated T-cells (NFAT) in the pulmonary arteries of rats, and this may exert a therapeutic effect on PH. The potential therapeutic effects of MSCs on PH were assessed via the transplantation of human umbilical cord-derived MSCs, which were cultured in serum-free medium, into a monocrotaline (MCT)-induced PH rat model. Subsequently, the expression levels of tumor necrosis factor (TNF)-α in lung tissue and plasma, and of CaN and NFATc2 in pulmonary arteries were assessed. In the rat model of MCT-induced PH, investigated in the present study, TNF-α expression levels were detected in the lung tissue, and the levels of TNF-α in the plasma were increased. Furthermore, in addition to hemodynamic changes and the evident medial hypertrophy of the pulmonary muscular arterioles, CaN and NFATc2 expression levels were significantly upregulated in the pulmonary arteries. In the present study, the transplantation of MSCs, cultured in serum-free medium, decreased the levels of TNF-α in the lung tissue and plasma of rats, and downregulated CaN and NFATc2 expression in the pulmonary arteries. Furthermore, hemodynamic abnormalities and medial hypertrophy of the pulmonary muscular arterioles were notably improved. Therefore, the results of the present study may suggest that the administration of MSCs in PH may suppress the production of TNF-α, and downregulate the expression of CaN and NFATc2 in pulmonary arteries, which may provide an effective treatment for PH by suppressing the pathological proliferation of PASMCs.

Monocyte Tumor Necrosis Factor-α-Converting Enzyme Catalytic Activity and Substrate Shedding in Sepsis and Noninfectious Systemic Inflammation

Objectives:

To determine the effect of severe sepsis on monocyte tumor necrosis factor-α–converting enzyme baseline and inducible activity profiles.

Design:

Observational clinical study.

Setting:

Mixed surgical/medical teaching hospital ICU.

Patients:

Sixteen patients with severe sepsis, 15 healthy volunteers, and eight critically ill patients with noninfectious systemic inflammatory response syndrome.

Interventions:

None.

Measurements and Main Results:

Monocyte expression of human leukocyte antigen-D-related peptide, sol-tumor necrosis factor production, tumor necrosis factor-α–converting enzyme expression and catalytic activity, tumor necrosis factor receptor 1 and 2 expression, and shedding at 48-hour intervals from day 0 to day 4, as well as p38-mitogen activated protein kinase expression. Compared with healthy volunteers, both sepsis and systemic inflammatory response syndrome patients’ monocytes expressed reduced levels of human leukocyte antigen-D-related peptide and released less sol-tumor necrosis factor on in vitro lipopolysaccharide stimulation, consistent with the term monocyte deactivation. However, patients with sepsis had substantially elevated levels of basal tumor necrosis factor-α–converting enzyme activity that were refractory to lipopolysaccharide stimulation and this was accompanied by similar changes in p38-mitogen activated protein kinase signaling. In patients with systemic inflammatory response syndrome, monocyte basal tumor necrosis factor-α–converting enzyme, and its induction by lipopolysaccharide, appeared similar to healthy controls. Changes in basal tumor necrosis factor-α–converting enzyme activity at day 0 for sepsis patients correlated with Acute Physiology and Chronic Health Evaluation II score and the attenuated tumor necrosis factor-α–converting enzyme response to lipopolysaccharide was associated with increased mortality. Similar changes in monocyte tumor necrosis factor-α–converting enzyme activity could be induced in healthy volunteer monocytes using an in vitro two-hit inflammation model. Patients with sepsis also displayed reduced shedding of monocyte tumor necrosis factor receptors upon stimulation with lipopolysaccharide.

Conclusions:

Monocyte tumor necrosis factor-α–converting enzyme catalytic activity appeared altered by sepsis and may result in reduced shedding of tumor necrosis factor receptors. Changes seemed specific to sepsis and correlated with illness severity. A better understanding of how tumor necrosis factor-α–converting enzyme function is altered during sepsis will enhance our understanding of sepsis pathophysiology, which will help in the assessment of patient inflammatory status and ultimately may provide new strategies to treat sepsis.

The potential regulatory role of vitamin D in the bioenergetics of inflammation

PURPOSE OF REVIEW

The extraskeletal health benefits of vitamin D still need scientific endorsement. Obesity and related chronic diseases are pathogenically linked by inflammation, which carries a considerable energetic cost. Recent techniques for the determination of the bioenergetic demand of inflammation, offer an avenue to cement the regulatory role of vitamin D in this process.

RECENT FINDINGS

Nuclear vitamin D receptors may be translocated into mitochondria of certain cell types, opening up a pathway for direct action on cellular bioenergetics. Classical M1 (inflammatory)/M2(anti-inflammatory) phenotypes can vary with the clinical context. M2 macrophages do not always depend on oxidative metabolism/fatty acid oxidation. Newer methodologies offer real-time bioenergetic measurements that can be used as an index of metabolic health.

SUMMARY

Vitamin D may prove to be a therapeutic agent for inflammation of chronic disease and understanding its role in cellular bioenergetics may offer a diagnostic/prognostic indicator of its action.