The role of peroxiredoxin 6 in biosynthesis of FAHFAs.

Peroxiredoxin 6 (Prdx6) is a multifunctional enzyme, a unique member of the peroxiredoxin family, with an important role in antioxidant defense. Moreover, it has also been linked with the biosynthesis of anti-inflammatory and anti-diabetic lipids called fatty acid esters of hydroxy fatty acids (FAHFAs) and many diseases, including cancer, inflammation, and metabolic disorders. Here, we performed metabolomic and lipidomic profiling of subcutaneous adipose tissue from mouse models with genetically modified Prdx6. Deletion of Prdx6 resulted in reduced levels of FAHFAs containing 13-hydroxylinoleic acid (13-HLA). Mutation of Prdx6 C47S impaired the glutathione peroxidase activity and reduced FAHFA levels, while D140A mutation, responsible for phospholipase A2 activity, showed only minor effects. Targeted analysis of oxidized phospholipids and triacylglycerols in adipocytes highlighted a correlation between FAHFA and hydroxy fatty acid production by Prdx6 or glutathione peroxidase 4. FAHFA regioisomer abundance was negatively affected by the Prdx6 deletion, and this effect was more pronounced in longer and more unsaturated FAHFAs. The predicted protein model of Prdx6 suggested that the monomer-dimer transition mechanism might be involved in the repair of longer-chain peroxidized phospholipids bound over two monomers and that the role of Prdx6 in FAHFA synthesis might be restricted to branching positions further from carbon 9. In conclusion, our work linked the peroxidase activity of Prdx6 with the levels of FAHFAs in adipose tissue.

Atherogenic Indices as a Predictor of Aortic Calcification in Prostate Cancer Patients Assessed Using 18F-Sodium Fluoride PET/CT.

A major pathophysiological cause of cardiovascular disease is vascular plaque calcification. Fluorine 18−Sodium Fluoride (18F-NaF) PET/CT can be used as a sensitive imaging modality for detection of vascular calcification. The aim of this study was to find a non-invasive, cost-efficient, and readily available metric for predicting vascular calcification severity. This retrospective study was performed on 36 participants who underwent 18F-NaF fused PET/CT scans. The mean standard uptake values (SUVs) were calculated from manually sectioned axial sections over the aortic arch and thoracic aorta. Correlation analyses were performed between SUVs and calculated atherogenic indices (AIs). Castelli's Risk Index I (r = 0.63, p < 0.0001), Castelli's Risk Index II (r = 0.64, p < 0.0001), Atherogenic Coefficient (r = 0.63, p < 0.0001), Atherogenic Index of Plasma (r = 0.51, p = 0.00152), and standalone high-density lipoprotein (HDL) cholesterol (r = −0.53, p = 0.000786) were associated with aortic calcification. AIs show strong association with aortic arch and thoracic aorta calcifications. AIs are better predictors of vascular calcification compared to standalone lipid metrics, with the exception of HDL cholesterol. Clinical application of AIs provides a holistic metric beneficial for enhancing screening and treatment protocols.

Synthetic Secoisolariciresinol Diglucoside (LGM2605) Prevents Asbestos-Induced Inflammation and Genotoxic Cell Damage in Human Mesothelial Cells.

Although alveolar macrophages play a critical role in malignant transformation of mesothelial cells following asbestos exposure, inflammatory and oxidative processes continue to occur in the mesothelial cells lining the pleura that may contribute to the carcinogenic process. Malignant transformation of mesothelial cells following asbestos exposure occurs over several decades; however, amelioration of DNA damage, inflammation, and cell injury may impede the carcinogenic process. We have shown in an in vitro model of asbestos-induced macrophage activation that synthetic secoisolariciresinol diglucoside (LGM2605), given preventively, reduced inflammatory cascades and oxidative/nitrosative cell damage. Therefore, it was hypothesized that LGM2605 could also be effective in reducing asbestos-induced activation and the damage of pleural mesothelial cells. LGM2605 treatment (50 µM) of huma n pleural mesothelial cells was initiated 4 h prior to exposure to asbestos (crocidolite, 20 µg/cm2). Supernatant and cells were evaluated at 0, 2, 4, and 8 h post asbestos exposure for reactive oxygen species (ROS) generation, DNA damage (oxidized guanine), inflammasome activation (caspase-1 activity) and associated pro-inflammatory cytokine release (IL-1ß, IL-18, IL-6, TNFα, and HMGB1), and markers of oxidative stress (malondialdehyde (MDA) and 8-iso-prostaglandin F2a (8-iso-PGF2α). Asbestos induced a time-dependent ROS increase that was significantly (p < 0.0001) reduced (29.4%) by LGM2605 treatment. LGM2605 pretreatment also reduced levels of asbestos-induced DNA damage by 73.6% ± 1.0%. Although levels of inflammasome-activated cytokines, IL-1ß and IL-18, reached 29.2 pg/mL ± 0.7 pg/mL and 43.9 pg/mL ± 0.8 pg/mL, respectively, LGM2605 treatment significantly (p < 0.0001) reduced cytokine levels comparable to baseline (non-asbestos exposed) values (3.8 pg/mL ± 0.2 pg/mL and 5.4 pg/mL ± 0.2 pg/mL, respectively). Furthermore, levels of IL-6 and TNFα in asbestos-exposed mesothelial cells were high (289.1 pg/mL ± 2.9 pg/mL and 511.3 pg/mL ± 10.2 pg/mL, respectively), while remaining undetectable with LGM2605 pretreatment. HMGB1 (a key inflammatory mediator and initiator of malignant transformation) release was reduced 75.3% ± 0.4% by LGM2605. Levels of MDA and 8-iso-PGF2α, markers of oxidative cell injury, were significantly (p < 0.001) reduced by 80.5% ± 0.1% and 76.6% ± 0.3%, respectively. LGM2605, given preventively, reduced ROS generation, DNA damage, and inflammasome-activated cytokine release and key inflammatory mediators implicated in asbestos-induced malignant transformation of normal mesothelial cells.

Donor extracellular vesicle trafficking via the pleural space represents a novel pathway for allorecognition after lung transplantation.

Restoration of lymphatic drainage across the bronchial anastomosis after lung transplantation requires several weeks. As donor antigen and antigen presenting cell trafficking via lymphatics into graft-draining lymph nodes is an important component of the alloresponse, alternative pathways must exist that account for rapid rejection after pulmonary transplantation. Here, we describe a novel allorecognition pathway mediated through donor extracellular vesicle (EV) trafficking to mediastinal lymph nodes via the pleural space. Pleural fluid collected early after lung transplantation in rats and humans contains donor-specific EVs. In a fully MHC mismatched rat model of lung transplantation, we demonstrate EVs carrying donor antigen preferentially accumulate in mediastinal lymph nodes and colocalize with MHC II expressing cells within 4 h of engraftment. Injection of allogeneic EVs into pleural space of syngeneic lung transplant recipients confirmed their selective trafficking to mediastinal lymph nodes and resulted in activation of T cells in mediastinal, but not peripheral lymph nodes. Thus, we have uncovered an alternative pathway of donor antigen trafficking where pulmonary EVs released into the pleural space traffic to locoregional lymph nodes via pleural lymphatics. This pathway obviates the need for restoration of lymphatics across the bronchial anastomosis for trafficking of donor antigen to draining lymph nodes.

Pulmonary vascular inflammation with fatal coronavirus disease 2019 (COVID-19): possible role for the NLRP3 inflammasome.

BACKGROUND: Pulmonary hyperinflammation is a key event with SARS-CoV-2 infection. Acute respiratory distress syndrome (ARDS) that often accompanies COVID-19 appears to have worse outcomes than ARDS from other causes. To date, numerous lung histological studies in cases of COVID-19 have shown extensive inflammation and injury, but the extent to which these are a COVID-19 specific, or are an ARDS and/or mechanical ventilation (MV) related phenomenon is not clear. Furthermore, while lung hyperinflammation with ARDS (COVID-19 or from other causes) has been well studied, there is scarce documentation of vascular inflammation in COVID-19 lungs. METHODS: Lung sections from 8 COVID-19 affected and 11 non-COVID-19 subjects, of which 8 were acute respiratory disease syndrome (ARDS) affected (non-COVID-19 ARDS) and 3 were from subjects with non-respiratory diseases (non-COVID-19 non-ARDS) were H&E stained to ascertain histopathological features. Inflammation along the vessel wall was also monitored by expression of NLRP3 and caspase 1. RESULTS: In lungs from COVID-19 affected subjects, vascular changes in the form of microthrombi in small vessels, arterial thrombosis, and organization were extensive as compared to lungs from non-COVID-19 (i.e., non-COVID-19 ARDS and non-COVID-19 non-ARDS) affected subjects. The expression of NLRP3 pathway components was higher in lungs from COVID-19 ARDS subjects as compared to non-COVID-19 non-ARDS cases. No differences were observed between COVID-19 ARDS and non-COVID-19 ARDS lungs. CONCLUSION: Vascular changes as well as NLRP3 inflammasome pathway activation were not different between COVID-19 and non-COVID-19 ARDS suggesting that these responses are not a COVID-19 specific phenomenon and are possibly more related to respiratory distress and associated strategies (such as MV) for treatment.

Circulating Donor Lung-specific Exosome Profiles Enable Noninvasive Monitoring of Acute Rejection in a Rodent Orthotopic Lung Transplantation Model.

BACKGROUND: There is a critical need for development of biomarkers to noninvasively monitor for lung transplant rejection. We investigated the potential of circulating donor lung-specific exosome profiles for time-sensitive diagnosis of acute rejection in a rat orthotopic lung transplant model. METHODS: Left lungs from Wistar transgenic rats expressing human CD63-GFP, an exosome marker, were transplanted into fully MHC-mismatched Lewis recipients or syngeneic controls. Recipient blood was collected between 4 h and 10 d after transplantation, and plasma was processed for exosome isolation by size exclusion column chromatography and ultracentrifugation. Circulating donor exosomes were profiled using antihuman CD63 antibody quantum dot on the nanoparticle detector and via GFP trigger on the nanoparticle flow cytometer. RESULTS: In syngeneic controls, steady-state levels of circulating donor exosomes were detected at all posttransplant time points. Allogeneic grafts lost perfusion by day 8, consistent with acute rejection. Levels of circulating donor exosomes peaked on day 1, decreased significantly by day 2, and then reached baseline levels by day 3. Notably, decrease in peripheral donor exosome levels occurred before grafts had histological evidence of acute rejection. CONCLUSIONS: Circulating donor lung-specific exosome profiles enable an early detection of acute rejection before histologic manifestation of injury to the pulmonary allograft. As acute rejection episodes are a major risk factor for the development of chronic lung allograft dysfunction, this biomarker may provide a novel noninvasive diagnostic platform that can translate into earlier therapeutic intervention for lung transplant patients.

Inhibition of Peroxiredoxin 6 PLA2 Activity Decreases Oxidative Stress and the Severity of Acute Lung Injury in the Mouse Cecal Ligation and Puncture Model.

The use of agents to inhibit the production of reactive oxygen species (ROS) has been proposed for the treatment of Acute Lung Injury (ALI). However, this approach also inhibits the bactericidal activity of polymorphonuclear leucocytes (PMN) and other cells, raising the possibility of aggravating lung injury in ALI associated with bacterial infection. We used the cecal ligation and puncture (CLP) model of ALI associated with sepsis to investigate the effect of inhibiting NADPH oxidase 2 (NOX2)-derived ROS production, the main source of ROS in lungs. A phospholipase A2 inhibitor called peroxiredoxin 6 inhibitory peptide-2 (PIP-2) was used to inhibit NOX2 activation; the peptide prevents liberation of Rac, a necessary NOX2 co-factor. At 18 h after intravenous treatment with 2 µg PIP-2 /gram body weight (wt), the number of colony-forming bacteria in lungs and peritoneal fluid of mice with CLP was approximately doubled as compared to untreated mice. Treatment with 10 µg PIP-2/g body wt resulted in 100% mortality within 18 h. Antibiotic treatment abolished both the increase in lung bacteria with low dose PIP-2 and the increased mortality with high dose PIP-2. Treatment with PIP-2 plus antibiotics resulted in significantly improved lung histology, decreased PMN infiltration, decreased lung fluid accumulation, and decreased oxidative lung injury compared to antibiotics alone. We conclude that the administration of PIP-2 provides partial protection against lung injury in a model of ALI due to bacterial infection, while concurrent antibiotic treatment abolishes the deleterious effects of PIP-2 on lung bacterial clearance. These results suggest that addition of PIP-2 to the antibiotic regimen is beneficial for treatment of ALI associated with bacterial infection.

Utility of FDG PET/CT in assessing bowel inflammation.

PURPOSE: To develop a methodology for the quantification of gastrointestinal (GI) inflammation as indicated by 2-deoxy-2-(18F)fluoro-D-glucose (FDG) uptake on positron-emissions tomography/computed tomography (PET/CT) imaging. This is intended to investigate the feasibility of using standard uptake value (SUV) levels to assess levels of GI inflammation in humans. METHODS: 131 participants were injected with a weight-controlled dose of FDG 180 minutes prior to PET/CT scanning. Operator-guided software was used to segment the GI tract and perform (SUV) calculations. Regions of interest (ROIs) were created using CT images and stacked to create three dimensional volumes of interest (VOIs). These VOIs defined 6 sections of the GI tract: esophagus, stomach, descending colon, ascending and transverse colon, bowel below the ilium and small bowel above the ilium. RESULTS: This study found a significant correlation between age and average FDG uptake (avg-SUV) of the GI tract (P=.0003) with the esophagus showing the highest significance. Correlations were found between avg-SUV of the sigmoid segment and the group average (P<.0001), and between the descending colon VOI and the group (P<.0001). Intra-operator reproducibility over 3 trials showed a coefficient of variation (CV) of .63%. Inter-operator CV over 5 randomly selected patients was 5.6% over the entire GI tract. CONCLUSION: This study shows that FDG-PET/CT imaging is a promising technique for quantifying bowel inflammation, despite the fact that age related inflammation may not be of clinical utility. The fact that we were able to detect these subtle changes indicates this as an avenue for potential future investigation.

Vascular Inflammation in Lungs of Patients with Fatal Coronavirus Disease 2019 (COVID-19): Possible Role for the NLRP3 Inflammasome.

Background: Hyperinflammation is a key event that occurs with SARS-CoV-2 infection. In the lung, hyperinflammation leads to structural damage to tissue. To date, numerous lung histological studies have shown extensive alveolar damage, but there is scarce documentation of vascular inflammation in postmortem lung tissue. Methods: Lung sections from 8 COVID-19 affected and 11 non-COVID-19 subjects [of which 8 were acute respiratory disease syndrome (ARDS) affected and 3 were from subjects with non-respiratory diseases] were stained for H & E to ascertain histopathological features including presence of thrombi/microthrombi. Inflammation along the vessel wall was also monitored by quantification of the expression of moieties of the NLRP3 inflammasome pathway (NLRP3 and caspase-1). Results: In lungs from "fatal COVID-19", vascular changes in the form of microthrombi in small vessels, arterial thrombosis, and organization were extensive as compared to lungs from "non-COVID-19 non respiratory disease" affected subjects. The NLRP3 pathway components were significantly higher in lungs from COVID-19 subjects as compared to non-COVID-19 fatal cases without respiratory disease. No significant differences were observed between COVID-19 lungs and non-COVID-19 ARDS lungs. Conclusion: We posit that inflammasome formation along the vessel wall is a characteristic of lung inflammation that accompanies COVID-19. Thus, the NLRP3 inflammasome pathway seems to be probable candidate that drives amplification of inflammation post SARS-CoV-2 infection.

Copper Oxide Nanoparticle-Induced Acute Inflammatory Response and Injury in Murine Lung Is Ameliorated by Synthetic Secoisolariciresinol Diglucoside (LGM2605).

Metal-oxide nanoparticles (MO-NPs), such as the highly bioreactive copper-based nanoparticles (CuO-NPs), are widely used in manufacturing of hundreds of commercial products. Epidemiological studies correlated levels of nanoparticles in ambient air with a significant increase in lung disease. CuO-NPs, specifically, were among the most potent in a set of metal-oxides and carbons studied in parallel regarding DNA damage and cytotoxicity. Despite advances in nanotoxicology research and the characterization of their toxicity, the exact mechanism(s) of toxicity are yet to be defined. We identified chlorination toxicity as a damaging consequence of inflammation and myeloperoxidase (MPO) activation, resulting in macromolecular damage and cell damage/death. We hypothesized that the inhalation of CuO-NPs elicits an inflammatory response resulting in chlorination damage in cells and lung tissues. We further tested the protective action of LGM2605, a synthetic small molecule with known scavenging properties for reactive oxygen species (ROS), but most importantly, for active chlorine species (ACS) and an inhibitor of MPO. CuO-NPs (15 µg/bolus) were instilled intranasally in mice and the kinetics of the inflammatory response in lungs was evaluated 1, 3, and 7 days later. Evaluation of the protective action of LGM2605 was performed at 24 h post-challenge, which was selected as the peak acute inflammatory response to CuO-NP. LGM2605 was given daily via gavage to mice starting 2 days prior to the time of the insult (100 mg/kg). CuO-NPs induced a significant inflammatory influx, inflammasome-relevant cytokine release, and chlorination damage in mouse lungs, which was mitigated by the action of LGM2605. Preventive action of LGM2605 ameliorated the adverse effects of CuO-NP in lung.

A Peptide Inhibitor of Peroxiredoxin 6 Phospholipase A2 Activity Significantly Protects against Lung Injury in a Mouse Model of Ventilator Induced Lung Injury (VILI).

Ventilator induced lung injury (VILI) is a lung injury syndrome associated with mechanical ventilation, most frequently for treatment of Acute Lung Injury (ALI), and generally secondary to the use of greater than physiologic tidal volumes. To reproduce this syndrome experimentally, C57Bl/6 mice were intubated and ventilated with low (4 mL/Kg body weight) or high (12 mL/Kg) tidal volume for 6 h. Lung parameters with low volume ventilation were unchanged from non-ventilated (control) mice. High tidal volume ventilation resulted in marked lung injury with increased neutrophils in the bronchoalveolar lavage fluid (BALf) indicating lung inflammation, increase in both protein in BALf and lung dry/wet weight indicating lung edema, increased lung thiobarbituric acid reactive substances (TBARS) and 8-isoprostanes indicating lung lipid peroxidation, and increased lung protein carbonyls indicating protein oxidation. Either intratracheal or intravenous pretreatment of mice with a 9 amino acid peptide called peroxiredoxin 6 inhibitor peptide-2 (PIP-2) significantly reduced all parameters of lung injury by ~50-80%. PIP-2 inhibits NADPH oxidase type 2 (NOX2) activation. We propose that PIP-2 does not affect the mechanically induced lung damage component of VILI but does significantly reduce the secondary inflammatory component.

Diminishing Efficacy of Prone Positioning With Late Application in Evolving Lung Injury.

OBJECTIVES: It is not known how lung injury progression during mechanical ventilation modifies pulmonary responses to prone positioning. We compared the effects of prone positioning on regional lung aeration in late versus early stages of lung injury. DESIGN: Prospective, longitudinal imaging study. SETTING: Research imaging facility at The University of Pennsylvania (Philadelphia, PA) and Medical and Surgical ICUs at Massachusetts General Hospital (Boston, MA). SUBJECTS: Anesthetized swine and patients with acute respiratory distress syndrome (acute respiratory distress syndrome). INTERVENTIONS: Lung injury was induced by bronchial hydrochloric acid (3.5 mL/kg) in 10 ventilated Yorkshire pigs and worsened by supine nonprotective ventilation for 24 hours. Whole-lung CT was performed 2 hours after hydrochloric acid (Day 1) in both prone and supine positions and repeated at 24 hours (Day 2). Prone and supine images were registered (superimposed) in pairs to measure the effects of positioning on the aeration of each tissue unit. Two patients with early acute respiratory distress syndrome were compared with two patients with late acute respiratory distress syndrome, using electrical impedance tomography to measure the effects of body position on regional lung mechanics. MEASUREMENTS AND MAIN RESULTS: Gas exchange and respiratory mechanics worsened over 24 hours, indicating lung injury progression. On Day 1, prone positioning reinflated 18.9% ± 5.2% of lung mass in the posterior lung regions. On Day 2, position-associated dorsal reinflation was reduced to 7.3% ± 1.5% (p < 0.05 vs Day 1). Prone positioning decreased aeration in the anterior lungs on both days. Although prone positioning improved posterior lung compliance in the early acute respiratory distress syndrome patients, it had no effect in late acute respiratory distress syndrome subjects. CONCLUSIONS: The effects of prone positioning on lung aeration may depend on the stage of lung injury and duration of prior ventilation; this may limit the clinical efficacy of this treatment if applied late.

Vascular Inflammation in Lungs of Patients with Fatal Coronavirus Disease 2019 (COVID-19) Infection: Possible role for the NLRP3 inflammasome.

Hyperinflammation is a key event that occurs with SARS-CoV-2 infection. In the lung, hyperinflammation leads to structural damage to tissue. To date, numerous lung histological studies have shown extensive alveolar damage, but there is scarce documentation of vascular inflammation in postmortem lung tissue. Here we document histopathological features and monitor the NLRP3 inflammasome in fatal cases of disease caused by SARS Cov2 (COVID-19). We posit that inflammasome formation along the vessel wall is a characteristic of lung inflammation that accompanies COVID-19 and that it is a probable candidate that drives amplification of inflammation post infection.

Severe Impairment of Microcirculatory Perfused Vessel Density Is Associated With Postoperative Lactate and Acute Organ Injury After Cardiac Surgery.

OBJECTIVE: Resuscitation after cardiac surgery needs to address multiple pathophysiological processes that are associated with significant morbidity and mortality. Functional microcirculatory derangements despite normal systemic hemodynamics have been previously described but must be tied to clinical outcomes. The authors hypothesized that microcirculatory dysfunction after cardiac surgery would include impaired capillary blood flow and impaired diffusive capacity and that subjects with the lowest quartile of perfused vessel density would have an increased postoperative lactate level and acute organ injury scores. DESIGN: Prospective, observational study. SETTING: A single, tertiary university cardiovascular surgical intensive care unit. PARTICIPANTS: 25 adults undergoing elective cardiac surgery requiring cardiopulmonary bypass. INTERVENTION: Sublingual microcirculation was imaged using incident dark field microscopy before and 2 to 4 hours after surgery in the intensive care unit. MEASUREMENTS AND MAIN RESULTS: Compared with baseline measurements, postoperative vessel-by-vessel microvascular flow index (2.9 [2.8-2.9] v 2.5 [2.4-2.7], p < 0.0001) and perfused vessel density were significantly impaired (20.7 [19.3-22.9] v 16.3 [12.8-17.9], p < 0.0001). The lowest quartile of perfused vessel density (<12.8 mm/mm2) was associated with a significantly increased postoperative lactate level (6.0 ± 2.9 v 1.8 ± 1.2, p < 0.05), peak lactate level (7.6 ± 2.8 v 2.8 ± 1.5, p = 0.03), and sequential organ failure assessment (SOFA) score at 24 and 48 hours. CONCLUSION: In patients undergoing cardiac surgery, there was a significant decrease in postoperative microcirculatory convective blood flow and diffusive capacity during early postoperative resuscitation. Severely impaired perfused vessel density, represented by the lowest quartile of distribution, is significantly related to hyperlactatemia and early organ injury.

Acute e-cig inhalation impacts vascular health: a study in smoking naïve subjects.

This study was designed to investigate the acute effects of nonnicotinized e-cigarette (e-cig) aerosol inhalation in nonsmokers both in terms of blood-based markers of inflammation and oxidative stress and evaluate their association with hemodynamic-metabolic MRI parameters quantifying peripheral vascular reactivity, cerebrovascular reactivity, and aortic stiffness. Thirty-one healthy nonsmokers were subjected to two blood draws and two identical MRI protocols, each one before and after a standardized e-cig vaping session. After vaping, the serum levels of C-reactive protein, soluble intercellular adhesion molecule, and the danger signal machinery high-mobility group box 1 (HMGB1) and its downstream effector and the NLR family pyrin domain containing 3 (NLRP3) inflammasome (as monitored by its adaptor protein ASC) increased significantly relative to the respective baseline (prevaping) values. Moreover, nitric oxide metabolites and reactive oxygen species production decreased and increased, respectively. These observations were paralleled by impaired peripheral vascular reactivity (with reduced flow-mediated dilation and attenuated hyperemic response after a cuff-occlusion test) and metabolic alterations expressed by decreased venous oxygen saturation, postvaping. The current results suggest propagation of inflammation signaling via activation of the danger signaling axis (HMGB1-NLRP3). The findings indicate that a single episode of vaping has adverse impacts on vascular inflammation and function.NEW & NOTWORTHY Endothelial cell signaling and blood biomarkers were found to correlate with functional vascular changes in a single episode e-cigarettes inhalation in healthy adults. This is indicative of the potential of e-cigarettes (even when inhaled acutely) to lead of vascular dysfunction.

Metabolic Imaging and Biological Assessment: Platforms to Evaluate Acute Lung Injury and Inflammation.

Pulmonary inflammation is a hallmark of several pulmonary disorders including acute lung injury and acute respiratory distress syndrome. Moreover, it has been shown that patients with hyperinflammatory phenotype have a significantly higher mortality rate. Despite this, current therapeutic approaches focus on managing the injury rather than subsiding the inflammatory burden of the lung. This is because of the lack of appropriate non-invasive biomarkers that can be used clinically to assess pulmonary inflammation. In this review, we discuss two metabolic imaging tools that can be used to non-invasively assess lung inflammation. The first method, Positron Emission Tomography (PET), is widely used in clinical oncology and quantifies flux in metabolic pathways by measuring uptake of a radiolabeled molecule into the cells. The second method, hyperpolarized 13C MRI, is an emerging tool that interrogates the branching points of the metabolic pathways to quantify the fate of metabolites. We discuss the differences and similarities between these techniques and discuss their clinical applications.

Pulmonary pyruvate metabolism as an index of inflammation and injury in a rat model of acute respiratory distress syndrome.

Increased pulmonary lactate production is correlated with severity of lung injury and outcome in acute respiratory distress syndrome (ARDS) patients. This study was conducted to investigate the relative contributions of inflammation and hypoxia to the lung's metabolic shift to glycolysis in an experimental animal model of ARDS using hyperpolarized (HP) 13 C MRI. Fifty-three intubated and mechanically ventilated male rats were imaged using HP 13 C MRI before, and 1, 2.5 and 4 hours after saline (sham) or hydrochloric acid (HCl; 0.5 ml/kg) instillation in the trachea, followed by protective and nonprotective mechanical ventilation (HCl-PEEP and HCl-ZEEP) or the start of moderate or severe hypoxia (Hyp90 and Hyp75 groups). Pulmonary and cardiac HP lactate-to-pyruvate ratios were compared among groups for different time points. Postmortem histology and immunofluorescence were used to assess lung injury severity and quantify the expression of innate inflammatory markers and local tissue hypoxia. HP pulmonary lactate-to-pyruvate ratio progressively increased in rats with lung injury and moderate hypoxia (HCl-ZEEP), with no significant change in pulmonary lactate-to-pyruvate ratio in noninjured but moderately hypoxic rats (Hyp90). Pulmonary lactate-to-pyruvate ratio was elevated in otherwise healthy lung tissue only in severe systemic hypoxia (Hyp75 group). ex vivo histological and immunopathological assessment further confirmed the link between elevated glycolysis and the recruitment into and presence of activated neutrophils in injured lungs. HP lactate-to-pyruvate ratio is elevated in injured lungs predominantly as a result of increased glycolysis in activated inflammatory cells, but can also increase due to severe inflammation-induced hypoxia.

New Insights From MRI and Cell Biology Into the Acute Vascular-Metabolic Implications of Electronic Cigarette Vaping.

The popularity of electronic cigarettes (e-cigs) has grown at a startling rate since their introduction to the United States market in 2007, with sales expected to outpace tobacco products within a decade. Spurring this trend has been the notion that e-cigs are a safer alternative to tobacco-based cigarettes. However, the long-term health impacts of e-cigs are not yet known. Quantitative magnetic resonance imaging (MRI) approaches, developed in the authors' laboratory, provide conclusive evidence of acute deleterious effects of e-cig aerosol inhalation in the absence of nicotine in tobacco-naïve subjects. Among the pathophysiologic effects observed are transient impairment of endothelial function, vascular reactivity, and oxygen metabolism. The culprits of this response are currently not fully understood but are likely due to an immune reaction caused by the aerosol containing thermal breakdown products of the e-liquid, including radicals and organic aldehydes, with particle concentrations similar to those emitted by conventional cigarettes. The acute effects observed following a single vaping episode persist for 1-3 h before subsiding to baseline and are paralleled by build-up of biological markers. Sparse data exist on long-term effects of vaping, and it is likely that repeated regular exposure to e-cig aerosol during vaping will lead to chronic conditions since there would be no return to baseline conditions as in the case of an isolated vaping episode. This brief review aims to highlight the potential of pairing MRI, with its extraordinary sensitivity to structure, physiology and metabolism at the holistic level, with biologic investigations targeting serum and cellular markers of inflammation and oxidative stress. Such a multi-modal framework should allow interpretation of the impact of e-cigarette vaping on vascular health at the organ level in the context of the underlying biological alterations. Applications of this approach to the study of other lifestyle-initiated pathologies including hypertension, hypercholesterolemia, and metabolic syndrome are indicated.

Correction: Fisher, Aron B., et al. A Peptide Inhibitor of NADPH Oxidase (NOX2) Activation Markedly Decreases Mouse Lung Injury and Mortality Following Administration of Lipopolysaccharide (LPS). Int. J. Mol. Sci. 2019, 20, 2395.

The authors wish to make the following corrections to our previously published paper [1] [...].