Effects of Serum Potassium on Mortality in Patients With ST-Elevation Myocardial Infarction.

INTRODUCTION: Disturbances in potassium levels can induce ventricular arrhythmias and heighten mortality in patients with ST-elevation myocardial infarction (STEMI). This study evaluates the influence of sK levels on seven-day mortality and incidence of ventricular arrhythmias in STEMI patients to further improve clinical guidelines and outcomes. METHODS: This retrospective, propensity-matched study analyzed approximately 250,000 acute STEMI patients from 55 major academic medical centers/healthcare organizations (HCOs) in the US Collaborative Network of the TriNetX database. The sK levels recorded on the day of STEMI diagnosis were categorized into four cohorts: sK ≤ 3.4 (hypokalemia), 3.5 ≤ sK ≤ 4.5 (normal-control), 4.6 ≤ sK ≤ 5.0 (high-normal), and sK ≥ 5.1 (hyperkalemia). Patient cohorts were propensity-matched using linear and logistic regression for demographics. Outcomes of seven-day mortality, ventricular tachycardia (VT), and ventricular fibrillation (VF) were compared between these cohorts and the control group. RESULTS: The analysis showed hypokalemia was linked to significantly higher seven-day mortality (7.2% vs. 4.3%; RR 1.69; p<0.001), and increased rates of VT and VF. Similarly, hyperkalemia was associated with elevated mortality (12.7% vs. 4.6%; RR 2.76; p<0.001), VT, and VF rates. High-normal sK levels showed increased mortality (7.4% vs. 4.7%; RR 1.58; p<0.001), but unchanged VT or VF rates compared to the normal sK group. CONCLUSION: This comprehensive study highlights the correlation of sK levels with death in STEMI patients, revealing a nearly doubled risk of mortality with hypokalemia and almost triples with hyperkalemia. More notably, the mortality for STEMIs is higher for high-normal vs normal sK values. Additionally, hypokalemia and hyperkalemia were found to significantly elevate VT and VF risks.

Cryopreserved human precision-cut lung slices provide an immune competent pulmonary test system for "on-demand" use and long-term cultures.

Human precision-cut lung slices (hPCLS), considered a highly relevant ex vivo model of the lung, offer native architecture and cells of the lung tissue including respiratory parenchyma, small airways, and immune competent cells. However, the irregular availability of donor lungs has limited the accessibility of this system. As described here, thousands of hPCLS can be created from 1 lung, cryopreserved, and used "on demand" by applying slicing and cryopreservation methodology improvements. Fresh and cryopreserved (∼7 and ∼34 weeks; F&C) hPCLS from 1 donor lung were cultured for up to 29 days and evaluated for biomass, viability, tissue integrity, and inflammatory markers in response to lipopolysaccharide (LPS; 5 µg/ml) and Triton X-100 (TX100; 0.1%) challenge (24 h) at days 1, 8, 15, 22, and 29 following culture initiation. The F&C hPCLS retained biomass, viability, and tissue integrity throughout the 29 days and demonstrated immune responsiveness with up to ∼30-fold LPS-induced cytokine increases. Histologically, more than 70% of normal cytomorphological features were preserved in all groups through day 29. Similar retention of tissue viability and immune responsiveness post cryopreservation (4-6 weeks) and culture (up to 14 days) was observed in hPCLS from additional 3 donor lungs. Banking cryopreserved hPCLS from various donors (and disease states) provides a critical element in researching human-derived pulmonary tissue. The retention of viability and functional responsiveness (≥4 weeks) allows evaluation of long-term, complex endpoints reflecting key events in Adverse Outcome Pathways and positions hPCLS as a valuable human-relevant model for use in regulatory applications.

Exposure to combustion derived particulate matter exacerbates influenza infection in neonatal mice by inhibiting IL22 production.

BACKGROUND: Particulate matter (PM) containing environmentally persistent free radicals (EPFRs) are formed during various combustion processes, including the thermal remediation of hazardous wastes. Exposure to PM adversely affects respiratory health in infants and is associated with increased morbidity and mortality due to acute lower respiratory tract infections. We previously reported that early-life exposure to PM damages the lung epithelium and suppresses immune responses to influenza virus (Flu) infection, thereby enhancing Flu severity. Interleukin 22 (IL22) is important in resolving lung injury following Flu infection. In the current study, we determined the effects of PM exposure on pulmonary IL22 responses using our neonatal mouse model of Flu infection. RESULTS: Exposure to PM resulted in an immediate (0.5-1-day post-exposure; dpe) increase in IL22 expression in the lungs of C57BL/6 neonatal mice; however, this IL22 expression was not maintained and failed to increase with either continued exposure to PM or subsequent Flu infection of PM-exposed mice. This contrasts with increased IL22 expression in age-matched mice exposed to vehicle and Flu infected. Activation of the aryl hydrocarbon receptor (AhR), which mediates the induction and release of IL22 from immune cells, was also transiently increased with PM exposure. The microbiome plays a major role in maintaining epithelial integrity and immune responses by producing various metabolites that act as ligands for AhR. Exposure to PM induced lung microbiota dysbiosis and altered the levels of indole, a microbial metabolite. Treatment with recombinant IL22 or indole-3-carboxaldehyde (I3A) prevented PM associated lung injury. In addition, I3A treatment also protected against increased mortality in Flu-infected mice exposed to PMs. CONCLUSIONS: Together, these data suggest that exposure to PMs results in failure to sustain IL22 levels and an inability to induce IL22 upon Flu infection. Insufficient levels of IL22 may be responsible for aberrant epithelial repair and immune responses, leading to increased Flu severity in areas of high PM.

The α7 nicotinic acetylcholine receptor agonist GTS-21 improves bacterial clearance in mice by restoring hyperoxia-compromised macrophage function.

BACKGROUND: Mechanical ventilation, in combination with supraphysiological concentrations of oxygen (i.e., hyperoxia), is routinely used to treat patients with respiratory distress, such as COVID-19. However, prolonged exposure to hyperoxia compromises the clearance of invading pathogens by impairing macrophage phagocytosis. Previously, we have shown that the exposure of mice to hyperoxia induces the release of the nuclear protein high mobility group box-1 (HMGB1) into the pulmonary airways. Furthermore, extracellular HMGB1 impairs macrophage phagocytosis and increases the mortality of mice infected with Pseudomonas aeruginosa (PA). The aim of this study was to determine whether GTS-21 (3-(2,4-dimethoxybenzylidene) anabaseine), an α7 nicotinic acetylcholine receptor (α7nAChR) agonist, could (1) inhibit hyperoxia-induced HMGB1 release into the airways; (2) enhance macrophage phagocytosis and (3) increase bacterial clearance from the lungs in a mouse model of ventilator-associated pneumonia. METHOD: GTS-21 (0.04, 0.4, and 4 mg/kg) or saline were administered by intraperitoneal injection to mice that were exposed to hyperoxia (≥ 99% O2) and subsequently challenged with PA. RESULTS: The systemic administration of 4 mg/kg i.p. of GTS-21 significantly increased bacterial clearance, decreased acute lung injury and decreased accumulation of airway HMGB1 compared to the saline control. To determine the mechanism of action of GTS-21, RAW 264.7 cells, a macrophage-like cell line, were incubated with different concentrations of GTS-21 in the presence of 95% O2. The phagocytic activity of macrophages was significantly increased by GTS-21 in a dose-dependent manner. In addition, GTS-21 significantly inhibited the cytoplasmic translocation and release of HMGB1 from RAW 264.7 cells and attenuated hyperoxia-induced NF-κB activation in macrophages and mouse lungs exposed to hyperoxia and infected with PA. CONCLUSIONS: Our results indicate that GTS-21 is efficacious in improving bacterial clearance and reducing acute lung injury via enhancing macrophage function by inhibiting the release of nuclear HMGB1. Therefore, the α7nAChR represents a possible pharmacological target to improve the clinical outcome of patients on ventilators by augmenting host defense against bacterial infections.

Expression of Concern to: The α7 nicotine acetylcholine receptor agonist GTS-21 improves bacterial clearance in mice by restoring hyperoxia-compromised macrophage function.

The Editors-in-Chief would like to alert readers that this article (Sitapara et al. 2014) is part of an investigation being conducted by the journal following the conclusions of an institutional enquiry at the University of Liverpool with respect to the quantitative mass spectrometry-generated results regarding acetylated and redox-modified HMGB1.

Radical containing combustion derived particulate matter enhance pulmonary Th17 inflammation via the aryl hydrocarbon receptor.

BACKGROUND: Pollutant particles containing environmentally persistent free radicals (EPFRs) are formed during many combustion processes (e.g. thermal remediation of hazardous wastes, diesel/gasoline combustion, wood smoke, cigarette smoke, etc.). Our previous studies demonstrated that acute exposure to EPFRs results in dendritic cell maturation and Th17-biased pulmonary immune responses. Further, in a mouse model of asthma, these responses were enhanced suggesting exposure to EPFRs as a risk factor for the development and/or exacerbation of asthma. The aryl hydrocarbon receptor (AHR) has been shown to play a role in the differentiation of Th17 cells. In the current study, we determined whether exposure to EPFRs results in Th17 polarization in an AHR dependent manner. RESULTS: Exposure to EPFRs resulted in Th17 and IL17A dependent pulmonary immune responses including airway neutrophilia. EPFR exposure caused a significant increase in pulmonary Th17 cytokines such as IL6, IL17A, IL22, IL1ß, KC, MCP-1, IL31 and IL33. To understand the role of AHR activation in EPFR-induced Th17 inflammation, A549 epithelial cells and mouse bone marrow-derived dendritic cells (BMDCs) were exposed to EPFRs and expression of Cyp1a1 and Cyp1b1, markers for AHR activation, was measured. A significant increase in Cyp1a1 and Cyp1b1 gene expression was observed in pulmonary epithelial cells and BMDCs in an oxidative stress and AHR dependent manner. Further, in vivo exposure of mice to EPFRs resulted in oxidative stress and increased Cyp1a1 and Cyp1b1 pulmonary gene expression. To further confirm the role of AHR activation in pulmonary Th17 immune responses, mice were exposed to EPFRs in the presence or absence of AHR antagonist. EPFR exposure resulted in a significant increase in pulmonary Th17 cells and neutrophilic inflammation, whereas a significant decrease in the percentage of Th17 cells and neutrophilic inflammation was observed in mice treated with AHR antagonist. CONCLUSION: Exposure to EPFRs results in AHR activation and induction of Cyp1a1 and in vitro this is dependent on oxidative stress. Further, our in vivo studies demonstrated a role for AHR in EPFR-induced pulmonary Th17 responses including neutrophilic inflammation.

A Neonatal Murine Model of MRSA Pneumonia.

Pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of morbidity and mortality in infants particularly following lower respiratory tract viral infections such as Respiratory Syncytial Virus (RSV). However, the mechanisms by which co-infection of infants by MRSA and RSV cause increased lung pathology are unknown. Because the infant immune system is qualitatively and quantitatively different from adults we developed a model of infant MRSA pneumonia which will allow us to investigate the effects of RSV co-infection on disease severity. We infected neonatal and adult mice with increasing doses of MRSA and demonstrate that neonatal mice have delayed kinetics in clearing the bacteria in comparison to adult mice. There were differences in recruitment of immune cells into the lung following infection. Adult mice exhibited an increase in neutrophil recruitment that coincided with reduced bacterial titers followed by an increase in macrophages. Neonatal mice, however, exhibited an early increase in neutrophils that did not persist despite continued presence of the bacteria. Unlike the adult mice, neonatal mice failed to exhibit an increase in macrophages. Neonates exhibited a decrease in phagocytosis of MRSA suggesting that the decrease in clearance was partially due to deficient phagocytosis of the bacteria. Both neonates and adults responded with an increase in pro-inflammatory cytokines following infection. However, in contrast to the adult mice, neonates did not express constitutive levels of the anti-microbial peptide Reg3γ in the lung. Infection of neonates did not stimulate expression of the co-stimulatory molecule CD86 by dendritic cells and neonates exhibited a diminished T cell response compared to adult mice. Overall, we have developed a neonatal model of MRSA pneumonia that displays a similar delay in bacterial clearance as is observed in the neonatal intensive care unit and will be useful for performing co-infection studies.

Ascorbic Acid Attenuates Hyperoxia-Compromised Host Defense against Pulmonary Bacterial Infection.

Supraphysiological concentrations of oxygen (hyperoxia) can compromise host defense and increase susceptibility to bacterial infections, causing ventilator-associated pneumonia. The phagocytic activity of macrophages is impaired by hyperoxia-induced increases in the levels of reactive oxygen species (ROS) and extracellular high-mobility group box protein B1 (HMGB1). Ascorbic acid (AA), an essential nutrient and antioxidant, has been shown to be beneficial in various animal models of ROS-mediated diseases. The aim of this study was to determine whether AA could attenuate hyperoxia-compromised host defense and improve macrophage functions against bacterial infections. C57BL/6 male mice were exposed to hyperoxia (≥98% O2, 48 h), followed by intratracheal inoculation with Pseudomonas aeruginosa, and simultaneous intraperitoneal administration of AA. AA (50 mg/kg) significantly improved bacterial clearance in the lungs and airways, and significantly reduced HMGB1 accumulation in the airways. The incubation of RAW 264.7 cells (a macrophage-like cell line) with AA (0-1,000 µM) before hyperoxic exposure (95% O2) stabilized the phagocytic activity of macrophages in a concentration-dependent manner. The AA-enhanced macrophage function was associated with significantly decreased production of intracellular ROS and accumulation of extracellular HMGB1. These data suggest that AA supplementation can prevent or attenuate the development of ventilator-associated pneumonia in patients receiving oxygen support.

The α7 nicotinic acetylcholine receptor agonist GTS-21 improves bacterial clearance in mice by restoring hyperoxia-compromised macrophage function.

Mechanical ventilation with supraphysiological concentrations of oxygen (hyperoxia) is routinely used to treat patients with respiratory distress. However, prolonged exposure to hyperoxia compromises the ability of the macrophage to phagocytose and clear bacteria. Previously, we showed that the exposure of mice to hyperoxia elicits the release of the nuclear protein high mobility group box-1 (HMGB1) into the airways. Extracellular HMGB1 impairs macrophage phagocytosis and increases the mortality of mice infected with Pseudomonas aeruginosa (PA). The aim of this study was to determine whether GTS-21 [3-(2,4 dimethoxybenzylidene)-anabaseine dihydrochloride], an α7 nicotinic acetylcholine receptor (α7nAChR) agonist, could inhibit hyperoxia-induced HMGB1 release into the airways, enhance macrophage function and improve bacterial clearance from the lungs in a mouse model of ventilator-associated pneumonia. GTS-21 (0.04, 0.4 and 4 mg/kg) or saline was systemically administered via intraperitoneal injection to mice that were exposed to hyperoxia (≥99% O2) and subsequently challenged with PA. We found that systemic administration of 4 mg/kg GTS-21 significantly increased bacterial clearance, decreased acute lung injury and decreased accumulation of airway HMGB1. To investigate the cellular mechanism of these observations, RAW 264.7 cells, a macrophagelike cell line, were incubated with different concentrations of GTS-21 in the presence of 95% O2. The phagocytic activity of macrophages was significantly increased by GTS-21 in a dose-dependent manner. In addition, hyperoxia-induced hyperacetylation of HMGB1 was significantly reduced in macrophages incubated with GTS-21. Furthermore, GTS-21 significantly inhibited the cytoplasmic translocation and release of HMGB1 from these macrophages. Our results indicate that GTS-21 is effective in improving bacterial clearance and reducing acute lung injury by enhancing macrophage function via inhibiting the release of nuclear HMGB1. Therefore, the α7nAChR represents a possible pharmacological target to improve the clinical outcome of patients on ventilators by augmenting host defense against bacterial infections.

High Mobility Group Box-1 mediates hyperoxia-induced impairment of Pseudomonas aeruginosa clearance and inflammatory lung injury in mice.

Mechanical ventilation with supraphysiological concentrations of oxygen (hyperoxia) is routinely used to treat patients with respiratory distress. However, a significant number of patients on ventilators exhibit enhanced susceptibility to infections and develop ventilator-associated pneumonia (VAP). Pseudomonas aeruginosa (PA) is one of the most common species of bacteria found in these patients. Previously, we demonstrated that prolonged exposure to hyperoxia can compromise the ability of alveolar macrophages (AMs), an essential part of the innate immunity, to phagocytose PA. This study sought to investigate the potential molecular mechanisms underlying hyperoxia-compromised innate immunity against bacterial infection in a murine model of PA pneumonia. Here, we show that exposure to hyperoxia (≥ 99% O2) led to a significant elevation in concentrations of airway high mobility group box-1 (HMGB1) and increased mortality in C57BL/6 mice infected with PA. Treatment of these mice with a neutralizing anti-HMGB1 monoclonal antibody (mAb) resulted in a reduction in bacterial counts, injury, and numbers of neutrophils in the lungs, and an increase in leukocyte phagocytic activity compared with mice receiving control mAb. This improved phagocytic function was associated with reduced concentrations of airway HMGB1. The correlation between phagocytic activity and concentrations of extracellular HMGB1 was also observed in cultured macrophages. These results indicate a pathogenic role for HMGB1 in hyperoxia-induced impairment with regard to a host's ability to clear bacteria and inflammatory lung injury. Thus, HMGB1 may provide a novel molecular target for improving hyperoxia-compromised innate immunity in patients with VAP.