TRPV4 Regulates the Macrophage Metabolic Response to Limit Sepsis-induced Lung Injury.

Sepsis is a systemic inflammatory response that requires effective macrophage metabolic functions to resolve ongoing inflammation. Previous work showed that the mechanosensitive cation channel, transient receptor potential vanilloid 4 (TRPV4), mediates macrophage phagocytosis and cytokine production in response to lung infection. Here, we show that TRPV4 regulates glycolysis in a stiffness-dependent manner by augmenting macrophage glucose uptake by GLUT1. In addition, TRPV4 is required for LPS-induced phagolysosome maturation in a GLUT1-dependent manner. In a cecal slurry mouse model of sepsis, TRPV4 regulates sepsis-induced glycolysis as measured by BAL fluid (BALF) lactate and sepsis-induced lung injury as measured by BALF total protein and lung compliance. TRPV4 is necessary for bacterial clearance in the peritoneum to limit sepsis-induced lung injury. It is interesting that BALF lactate is increased in patients with sepsis compared with healthy control participants, supporting the relevance of lung cell glycolysis to human sepsis. These data show that macrophage TRPV4 is required for glucose uptake through GLUT1 for effective phagolysosome maturation to limit sepsis-induced lung injury. Our work presents TRPV4 as a potential target to protect the lung from injury in sepsis.

Vasopressin Response and Clinical Trajectory in Septic Shock Patients.

BACKGROUND: In septic shock, vasopressors aim to improve tissue perfusion and prevent persistent organ dysfunction, a characteristic of chronic critical illness (CCI). Adjunctive vasopressin is often used to decrease catecholamine dosage, but the association of vasopressin response with subsequent patient outcomes is unclear. We hypothesized vasopressin response is associated with favorable clinical trajectory. METHODS: We included patients with septic shock receiving vasopressin as a catecholamine adjunct in this retrospective cohort study. We defined vasopressin response as a lowering of the catecholamine dose required to maintain mean arterial pressure ≥65 mm Hg, 6 h after vasopressin initiation. Clinical trajectories were adjudicated as early death (ED; death before day 14), CCI (ICU stay ≥14 days with persistent organ dysfunction), or rapid recovery (RR; not meeting ED or CCI criteria). Trajectories were placed on an ordinal scale with ED the worst outcome, CCI next, and RR the best outcome. The association of vasopressin response with clinical trajectory was assessed with multivariable ordinal logistic regression. RESULTS: In total 938 patients were included; 426 (45.4%) were vasopressin responders. The most frequent trajectory was ED (49.8%), 29.7% developed CCI, and 20.5% had rapid recovery. In survivors to ICU day 14 (those without ED), 59.2% had CCI and 40.8% experienced RR. Compared with vasopressin non-responders, vasopressin responders less frequently experienced ED (42.5% vs. 55.9%) and more frequently experienced RR (24.6% vs. 17.0%; P < 0.01). After controlling for confounders, vasopressin response was independently associated with higher odds of developing a better clinical trajectory (OR 1.63; 95% CI 1.26-2.10). Medical patients most frequently developed ED and survivors more commonly developed CCI than RR; surgical patients developed the three trajectories with similar frequency (P < 0.01). CONCLUSIONS: Vasopressin responsive status was associated with improved clinical trajectory in septic shock patients. Early vasopressin response is a potential novel prognostic marker for short-term clinical trajectory.

Hemodynamic Response to Vasopressin Dosage of 0.03 Units/Min vs. 0.04 Units/Min in Patients With Septic Shock.

BACKGROUND: Arginine vasopressin (AVP) is suggested as an adjunct to norepinephrine in patients with septic shock. Guidelines recommend an AVP dosage up to 0.03 units/min, but 0.04 units/min is commonly used in practice based on initial studies. This study was designed to compare the incidence of hemodynamic response between initial fixed-dosage AVP 0.03 units/min and AVP 0.04 units/min. METHODS: This retrospective, multi-hospital health system, cohort study included adult patients with septic shock receiving AVP as an adjunct to catecholamine vasopressors. Patients were excluded if they received an initial dosage other than 0.03 units/min or 0.04 units/min, or AVP was titrated within the first 6 hours of therapy. The primary outcome was hemodynamic response, defined as a mean arterial pressure ≥65 mm Hg and a decrease in catecholamine dosage at 6 hours after AVP initiation. Inverse probability of treatment weighting (IPTW) based on the propensity score for initial AVP dosage receipt was utilized to estimate adjusted exposure effects. RESULTS: Of the 1536 patients included in the observed data, there was a nearly even split between initial AVP dosage of 0.03 units/min (n = 842 [54.8%]) and 0.04 units/min (n = 694 [45.2%]). Observed patients receiving AVP 0.03 units/min were more frequently treated at the main campus academic medical center (96.3% vs. 52.2%, p < 0.01) and in a medical intensive care unit (87.4% vs. 39.8%, p < 0.01). The IPTW analysis included 1379 patients with achievement of baseline covariate balance. There was no evidence for a difference between groups in the incidence of hemodynamic response (0.03 units/min 50.0% vs. 0.04 units/min 53.1%, adjusted relative risk 1.06 [95% CI 0.94, 1.20]). CONCLUSIONS: Initial AVP dosing varied by hospital and unit type. Although commonly used, an initial AVP dosage of 0.04 units/min was not associated with a higher incidence of early hemodynamic response to AVP in patients with septic shock.

Pathophysiology and Management of Neurogenic Pulmonary Edema in Patients with Acute Severe Brain Injury.

Acute brain injury (ABI) consists of any acquired insult to the brain and is a significant cause of morbidity and mortality worldwide. Approximately 20% to 30% of patients with ABI develop a lung injury called neurogenic pulmonary edema (NPE), and its development often results in poor outcomes. This article provides a narrative review of the evidence regarding proposed mechanisms of injury, diagnosis, and treatment of NPE in the critical care setting. PubMed and Ovid databases were searched for observational or prospective studies relevant to the diagnosis and treatment of NPE. Overall, studies showed that although the specific mechanisms responsible for NPE remain uncertain, putative mechanisms include vaso- and venoconstriction, catecholamine release with resultant pulmonary vasoconstriction called the "blast injury theory," increased vagal tone, and increased capillary permeability. Diagnosis involves identifying signs of pulmonary edema in patients who experienced a neurologic insult. Management strategies aim to address both brain and lung injury, and treatment modalities appear to work best when balanced toward maintaining a normal physiologic state. In summary, NPE is an often underdiagnosed but important sequela of ABI, which may result in additional long-term morbidity. It is therefore an important entity for providers to recognize and tailor their clinical approach toward.

Ethanol Exposure Attenuates Immune Response in Sepsis via Sirtuin 2 Expression.

BACKGROUND: Sepsis and septic shock kill over 270,000 patients per year in the United States. Sepsis transitions from a hyper-inflammatory to a hypo-inflammatory phase. Alcohol dependence is a risk factor for mortality from sepsis. Ethanol (EtOH) exposure impairs pathogen clearance through mechanisms that are not fully understood. Sirtuin 2 (SIRT2) interferes with pathogen clearance in immune cells but its role in the effects of EtOH on sepsis is unknown. We studied the effect of EtOH exposure on hyper- and hypo-inflammation and the role of SIRT2 in mice. METHODS: We exposed C57Bl/6 (WT) mice to EtOH via drinking water and used intraperitoneal cecal slurry (CS)-induced sepsis to study: (i) 7-day survival, (ii) leukocyte adhesion (LA) in the mesenteric microcirculation during hyper- and hypo-inflammation, (iii) peritoneal cavity bacterial clearance, and (iv) SIRT2 expression in peritoneal macrophages. Using EtOH-exposed and lipopolysaccharide (LPS)-stimulated RAW 264.7 (RAW) cell macrophages for 4 hours or 24 hours, we studied: (i) tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), and SIRT2 expression, and (ii) the effect of the SIRT2 inhibitor AK-7 on inflammatory response at 24 hours. Lastly, we studied the effect of EtOH on sepsis in whole body Sirt2 knockout (SIRT2KO) mice during hyper- and hypo-inflammation, bacterial clearance, and 7-day survival. RESULTS: WT EtOH-sepsis mice showed: (i) Decreased survival, (ii) Muted LA in the microcirculation, (iii) Lower plasma TNF-α and IL-6 expression, (iv) Decreased bacterial clearance, and (v) Increased SIRT2 expression in peritoneal macrophages versus vehicle-sepsis. EtOH-exposed LPS-stimulated RAW cells showed: (i) Muted TNF-α, IL-6, and increased IL-10 expression at 4 hours, (ii) endotoxin tolerance at 24 hours, and (iii) reversal of endotoxin tolerance with the SIRT2 inhibitor AK-7. EtOH-exposed SIRT2KO-sepsis mice showed greater 7-day survival, LA, and bacterial clearance than WT EtOH-sepsis mice. CONCLUSION: EtOH exposure decreases survival and reduces the inflammatory response to sepsis via increased SIRT2 expression. SIRT2 is a potential therapeutic target in EtOH with sepsis.

Predictors of Ventricular Dysrhythmias in Neurology Intensive Care Unit Patients with Prolonged QTc.

INTRODUCTION: Acute neurological injury and several medications commonly administered in the Neuro ICU pose a risk of fatal cardiac dysrhythmias. The objective of this study is to identify the predictors of ventricular dysrhythmias in the Neuro ICU patients with prolonged QTc, thereby helping the clinicians make important treatment decisions. METHODS: We performed a retrospective review of all consecutive adults admitted to the Neuro ICU from January 2015 to September 2015 with a QTc interval ≥ 450 ms on electrocardiogram. RESULTS: A total of 170 patients with a mean age of 66 years (SD ± 16) were included in the final analysis. Eighty-seven patients (51%) were women. Median duration of hospitalization was 9 days (IQR 4-16). Most common primary diagnosis was ischemic stroke (38%) followed by cerebral hemorrhage (19%) and subarachnoid hemorrhage (8%). Mean QTc was 487 ms (SD ± 35, range 450-659 ms). There were 27 episodes (16%) of monomorphic non-sustained ventricular tachycardia and one episode of Torsades (1%). Three cardiac arrests (2%) were recorded, none resulting from ventricular dysrhythmias. In multivariate analysis, prolonged QTc ≥ 492 ms (p = 0.0008), supratentorial acute ischemic stroke (p = 0.005), prolonged hospitalization (p = 0.03), and premature ventricular complexes on ECG (p = 0.047) were all independently associated with increased risk of ventricular dysrhythmias. CONCLUSIONS: In this group of patients with prolonged QTc in the Neuro ICU, we observed several episodes of non-sustained ventricular tachycardia and identified important risk factors associated with their occurrence. This knowledge is essential to inform clinical decisions.

GAPDH Binding to TNF-α mRNA Contributes to Posttranscriptional Repression in Monocytes: A Novel Mechanism of Communication between Inflammation and Metabolism.

Expression of the inflammatory cytokine TNF is tightly controlled. During endotoxin tolerance, transcription of TNF mRNA is repressed, although not entirely eliminated. Production of TNF cytokine, however, is further controlled by posttranscriptional regulation. In this study, we detail a mechanism of posttranscriptional repression of TNF mRNA by GAPDH binding to the TNF 3' untranslated region. Using RNA immunoprecipitation, we demonstrate that GAPDH-TNF mRNA binding increases when THP-1 monocytes are in a low glycolysis state, and that this binding can be reversed by knocking down GAPDH expression or by increasing glycolysis. We show that reducing glycolysis decreases TNF mRNA association with polysomes. We demonstrate that GAPDH-TNF mRNA binding results in posttranscriptional repression of TNF and that the TNF mRNA 3' untranslated region is sufficient for repression. Finally, after exploring this model in THP-1 cells, we demonstrate this mechanism affects TNF expression in primary human monocytes and macrophages. We conclude that GAPDH-TNF mRNA binding regulates expression of TNF based on cellular metabolic state. We think this mechanism has potentially significant implications for treatment of various immunometabolic conditions, including immune paralysis during septic shock.

Safety of Phenylephrine Infusion Through Peripheral Intravenous Catheter in the Neurological Intensive Care Unit.

OBJECTIVE: The traditional approach for infusing vasopressors is to insert central venous catheters, which is associated with several complications. Phenylephrine is a commonly used vasopressor in the neurologic intensive care unit (neuro ICU), and due to its modest potency, the risk of local tissue injury from extravasation may be overestimated. The purpose of this study was to evaluate the safety of phenylephrine infusion through peripheral intravenous catheter (PIV) in the neuro ICU. PATIENTS AND METHODS: Retrospective review of all consecutive adults admitted to the neuro ICU receiving phenylephrine infusion via PIV at a tertiary academic medical center from September 2012 to November 2015. RESULTS: Two hundred seventy-seven patients with a mean age of 65 years (standard deviation [SD]: ±15) were included in the final analysis. The most common indications for phenylephrine use were hemodynamic augmentation (40%) and postoperative hypotension (32%). The most common location of PIV-infusing phenylephrine was proximal upper extremity (50%). The most common PIV gauge was 20 (41%). The mean maximum dose of phenylephrine was 79 µg/min (SD: ±53, range: 5-200) or 1.04 µg/kg/min (SD: ±0.74, range: 0.07-3.49) and was continued for a mean duration of 19 hours (SD: ±18, range: 1-129). Nine (3%) total episodes of PIV infiltration were noted, none requiring intervention for significant tissue injury or limb ischemia. CONCLUSION: Infusion of phenylephrine through PIV is safe when used in moderate doses for a short time and can be considered in lieu of placing a central line solely for this purpose.

Sirtuins and Immuno-Metabolism of Sepsis.

Sepsis and septic shock are the leading causes of death in non-coronary intensive care units worldwide. During sepsis-associated immune dysfunction, the early/hyper-inflammatory phase transitions to a late/hypo-inflammatory phase as sepsis progresses. The majority of sepsis-related deaths occur during the hypo-inflammatory phase. There are no phase-specific therapies currently available for clinical use in sepsis. Metabolic rewiring directs the transition from hyper-inflammatory to hypo-inflammatory immune responses to protect homeostasis during sepsis inflammation, but the mechanisms underlying this immuno-metabolic network are unclear. Here, we review the roles of NAD+ sensing Sirtuin (SIRT) family members in controlling immunometabolic rewiring during the acute systemic inflammatory response associated with sepsis. We discuss individual contributions among family members SIRT 1, 2, 3, 4 and 6 in regulating the metabolic switch between carbohydrate-fueled hyper-inflammation to lipid-fueled hypo-inflammation. We further highlight the role of SIRT1 and SIRT2 as potential "druggable" targets for promoting immunometabolic homeostasis and increasing sepsis survival.

Sequential actions of SIRT1-RELB-SIRT3 coordinate nuclear-mitochondrial communication during immunometabolic adaptation to acute inflammation and sepsis.

We reported that NAD(+)-dependent SIRT1, RELB, and SIRT6 nuclear proteins in monocytes regulate a switch from the glycolysis-dependent acute inflammatory response to fatty acid oxidation-dependent sepsis adaptation. We also found that disrupting SIRT1 activity during adaptation restores immunometabolic homeostasis and rescues septic mice from death. Here, we show that nuclear SIRT1 guides RELB to differentially induce SIRT3 expression and also increases mitochondrial biogenesis, which alters bioenergetics during sepsis adaptation. We constructed this concept using TLR4-stimulated THP1 human promonocytes, a model that mimics the initiation and adaptation stages of sepsis. Following increased expression, mitochondrial SIRT3 deacetylase activates the rate-limiting tricarboxylic acid cycle (TCA) isocitrate dehydrogenase 2 and superoxide dismutase 2, concomitant with increases in citrate synthase activity. Mitochondrial oxygen consumption rate increases early and decreases during adaptation, parallel with modifications to membrane depolarization, ATP generation, and production of mitochondrial superoxide and whole cell hydrogen peroxide. Evidence of SIRT1-RELB induction of mitochondrial biogenesis included increases in mitochondrial mass, mitochondrial-to-nuclear DNA ratios, and both nuclear and mitochondrial encoded proteins. We confirmed the SIRT-RELB-SIRT3 adaptation link to mitochondrial bioenergetics in both TLR4-stimulated normal and sepsis-adapted human blood monocytes and mouse splenocytes. We also found that SIRT1 inhibition ex vivo reversed the sepsis-induced changes in bioenergetics.

Forecasting disease trajectories in critical illness: comparison of probabilistic dynamic systems to static models to predict patient status in the intensive care unit.

OBJECTIVE: Conventional prediction models fail to integrate the constantly evolving nature of critical illness. Alternative modelling approaches to study dynamic changes in critical illness progression are needed. We compare static risk prediction models to dynamic probabilistic models in early critical illness. DESIGN: We developed models to simulate disease trajectories of critically ill COVID-19 patients across different disease states. Eighty per cent of cases were randomly assigned to a training and 20% of the cases were used as a validation cohort. Conventional risk prediction models were developed to analyse different disease states for critically ill patients for the first 7 days of intensive care unit (ICU) stay. Daily disease state transitions were modelled using a series of multivariable, multinomial logistic regression models. A probabilistic dynamic systems modelling approach was used to predict disease trajectory over the first 7 days of an ICU admission. Forecast accuracy was assessed and simulated patient clinical trajectories were developed through our algorithm. SETTING AND PARTICIPANTS: We retrospectively studied patients admitted to a Cleveland Clinic Healthcare System in Ohio, for the treatment of COVID-19 from March 2020 to December 2022. RESULTS: 5241 patients were included in the analysis. For ICU days 2-7, the static (conventional) modelling approach, the accuracy of the models steadily decreased as a function of time, with area under the curve (AUC) for each health state below 0.8. But the dynamic forecasting approach improved its ability to predict as a function of time. AUC for the dynamic forecasting approach were all above 0.90 for ICU days 4-7 for all states. CONCLUSION: We demonstrated that modelling critical care outcomes as a dynamic system improved the forecasting accuracy of the disease state. Our model accurately identified different disease conditions and trajectories, with a <10% misclassification rate over the first week of critical illness.

NAD+-dependent sirtuin 1 and 6 proteins coordinate a switch from glucose to fatty acid oxidation during the acute inflammatory response.

The early initiation phase of acute inflammation is anabolic and primarily requires glycolysis with reduced mitochondrial glucose oxidation for energy, whereas the later adaptation phase is catabolic and primarily requires fatty acid oxidation for energy. We reported previously that switching from the early to the late acute inflammatory response following TLR4 stimulation depends on NAD(+) activation of deacetylase sirtuin 1 (SirT1). Here, we tested whether NAD(+) sensing by sirtuins couples metabolic polarity with the acute inflammatory response. We found in TLR4-stimulated THP-1 promonocytes that SirT1 and SirT 6 support a switch from increased glycolysis to increased fatty acid oxidation as early inflammation converts to late inflammation. Glycolysis enhancement required hypoxia-inducing factor-1α to up-regulate glucose transporter Glut1, phospho-fructose kinase, and pyruvate dehydrogenase kinase 1, which interrupted pyruvate dehydrogenase and reduced mitochondrial glucose oxidation. The shift to late acute inflammation and elevated fatty acid oxidation required peroxisome proliferator-activated receptor γ coactivators PGC-1α and ß to increase external membrane CD36 and fatty acid mitochondrial transporter carnitine palmitoyl transferase 1. Metabolic coupling between early and late responses also required NAD(+) production from nicotinamide phosphoryltransferase (Nampt) and activation of SirT6 to reduce glycolysis and SirT1 to increase fatty oxidation. We confirmed similar shifts in metabolic polarity during the late immunosuppressed stage of human sepsis blood leukocytes and murine sepsis splenocytes. We conclude that NAD(+)-dependent bioenergy shifts link metabolism with the early and late stages of acute inflammation.

Effect of Ethanol-exposure on Innate Immune Response in Sepsis.

Alcohol use disorder, reported by one in eight critically ill patients, is a risk factor for death in sepsis patients. Sepsis, the leading cause of death kills over 270,000 patients in the United States alone and remains without targeted therapy. Immune response in sepsis transitions from an early hyper-inflammation to persistent inflammation and immunosuppression and multiple organ dysfunction during late sepsis. Innate immunity is the first line of defense against pathogen invasion. Ethanol exposure is known to impair innate and adaptive immune response and bacterial clearance in sepsis patients. Specifically, ethanol-exposure is known to modulate every aspect of innate immune response with and without sepsis. Multiple molecular mechanisms are implicated in causing dysregulated immune response in ethanol-exposure with sepsis, but targeted treatments have remained elusive. In this manuscript, we outline the effects of ethanol-exposure on various innate immune cell types in general and during sepsis.

Echocardiographic profiles and hemodynamic response after vasopressin initiation in septic shock: A cross-sectional study.

PURPOSE: Vasopressin, used as a catecholamine adjunct, is a vasoconstrictor that may be detrimental in some hemodynamic profiles, particularly left ventricular (LV) systolic dysfunction. This study tested the hypothesis that echocardiographic parameters differ between patients with a hemodynamic response after vasopressin initiation and those without a response. METHODS: This retrospective, single-center, cross-sectional study included adults with septic shock receiving catecholamines and vasopressin with an echocardiogram performed after shock onset but before vasopressin initiation. Patients were grouped by hemodynamic response, defined as decreased catecholamine dosage with mean arterial pressure ≥ 65 mmHg six hours after vasopressin initiation, with echocardiographic parameters compared. LV systolic dysfunction was defined as LV ejection fraction (LVEF) <45%. RESULTS: Of 129 included patients, 72 (56%) were hemodynamic responders. Hemodynamic responders, versus non-responders, had higher LVEF (61% [55%,68%] vs. 55% [40%,65%]; p = 0.02) and less-frequent LV systolic dysfunction (absolute difference  -16%; 95% CI -30%,-2%). Higher LVEF was associated with higher odds of hemodynamic response (for each LVEF 10%, response OR 1.32; 95% CI 1.04-1.68). Patients with LV systolic dysfunction, versus without LV systolic dysfunction, had higher mortality risk (HR(t) = e[0.81-0.1*t]; at t = 0, HR 2.24; 95% CI 1.08-4.64). CONCLUSIONS: Pre-drug echocardiographic profiles differed in hemodynamic responders after vasopressin initiation versus non-responders.

Adjunctive Vasopressors in Patients with Septic Shock: Protocol for a Systematic Review and Meta-Analysis.

Background: Over one-third of patients with septic shock have adjunctive vasopressors added to first-line vasopressors. However, no randomized trial has detected improved mortality with adjunctive vasopressors. Published systematic reviews and meta-analysis have sought to inform the use of adjunctive vasopressors, yet each published review has limitations that hinder its interpretation. This review aims to overcome the limitations of previous reviews by systematically synthesizing the direct evidence for adjunctive vasopressor therapy use in adult patients with septic shock. Methods: We will conduct a systematic review and meta-analysis of randomized controlled trials evaluating adjunctive vasopressors (vasopressin analogues, angiotensin II, hydroxocobalamin, methylene blue, and catecholamine analogues) in adult patients with septic shock. Relevant studies will be identified through comprehensive searches of MEDLINE, Embase, CENTRAL, and reference lists of previous systematic reviews. Only randomized trials comparing adjunctive vasopressors (>75% of subjects on vasopressors at enrollment) to standard care vasopressors in adults with septic shock (>75% of subjects having septic shock) will be included. Titles and abstracts will be screened, full-text articles assessed for eligibility, and data extracted from included studies. Outcomes of interest include short-term mortality, intermediate-term mortality, kidney replacement therapy, digital/peripheral ischemia, and venous thromboembolism. Pairwise meta-analysis using a random-effects model will be utilized to estimate the risk ratio for the outcomes. Risk of bias will be adjudicated with the Cochrane Risk of Bias 2 tool, and GRADE will be used to rate the certainty of the body of evidence. Discussion: Although adjunctive vasopressors are commonly used in patients with septic shock their effect on patient-important outcomes is unclear. This study is planned to use rigorous systematic review methodology, including strict adhere to established guidelines, in order to overcome limitations of previously-published reviews and inform clinical practice and treatment guidelines for the use of adjunctive vasopressors in adults with septic shock. Systematic review registration: PROSPERO CRD4202327984.

Nonbronchoscopic Bronchoalveolar Lavage Improves Respiratory Culture Accuracy in Critically Ill Patients.

OBJECTIVES: Diagnosis of pneumonia is challenging in critically ill, intubated patients due to limited diagnostic modalities. Endotracheal aspirate (EA) cultures are standard of care in many ICUs; however, frequent EA contamination leads to unnecessary antibiotic use. Nonbronchoscopic bronchoalveolar lavage (NBBL) obtains sterile, alveolar cultures, avoiding contamination. However, paired NBBL and EA sampling in the setting of a lack of gold standard for airway culture is a novel approach to improve culture accuracy and limit antibiotic use in the critically ill patients. DESIGN: We designed a pilot study to test respiratory culture accuracy between EA and NBBL. Adult, intubated patients with suspected pneumonia received concurrent EA and NBBL cultures by registered respiratory therapists. Respiratory culture microbiology, cell counts, and antibiotic prescribing practices were examined. SETTING: We performed a prospective pilot study at the Cleveland Clinic Main Campus Medical ICU in Cleveland, Ohio for 22 months from May 2021 through March 2023. PATIENTS OR SUBJECTS: Three hundred forty mechanically ventilated patients with suspected pneumonia were screened. Two hundred fifty-seven patients were excluded for severe hypoxia (Fio2 ≥ 80% or positive end-expiratory pressure ≥ 12 cm H2O), coagulopathy, platelets less than 50,000, hemodynamic instability as determined by the treating team, and COVID-19 infection to prevent aerosolization of the virus. INTERVENTIONS: All 83 eligible patients were enrolled and underwent concurrent EA and NBBL. MEASUREMENTS AND MAIN RESULTS: More EA cultures (42.17%) were positive than concurrent NBBL cultures (26.51%, p = 0.049), indicating EA contamination. The odds of EA contamination increased by eight-fold 24 hours after intubation. EA was also more likely to be contaminated with oral flora when compared with NBBL cultures. There was a trend toward decreased antibiotic use in patients with positive EA cultures if paired with a negative NBBL culture. Alveolar immune cell populations were recovered from NBBL samples, indicating successful alveolar sampling. There were no major complications from NBBL. CONCLUSIONS: NBBL is more accurate than EA for respiratory cultures in critically ill, intubated patients. NBBL provides a safe and effective technique to sample the alveolar space for both clinical and research purposes.

Altered anti-viral immune responses in monocytes in overweight heavy drinkers.

Alcohol abuse causes increased susceptibility to respiratory syndromes like bacterial pneumonia and viral infections like SARS-CoV-2. Heavy drinkers (HD) are at higher risk of severe COVID-19 if they are also overweight, yet the molecular mechanisms are unexplored. Single-cell RNA-sequencing (scRNA-seq) was performed on peripheral blood mononuclear cells from lean or overweight HD and healthy controls (HC) after challenge with a dsRNA homopolymer (PolyI:C) to mimic a viral infection and/or with lipopolysaccharide (LPS). All monocyte populations responded to both PolyI:C and LPS with pro-inflammatory gene expression. However, the expression of interferon-stimulated genes, essential for inhibiting viral pathogenesis, was greatly reduced in overweight patients. Interestingly, the number of upregulated genes in response to the PolyI:C challenge was far greater in monocytes from HD compared to HC, including much stronger pro-inflammatory cytokine and interferon-γ signaling responses. These results suggest that increased body weight reduced anti-viral responses while heavy drinking increased pro-inflammatory cytokines.

Dysregulated cellular redox status during hyperammonemia causes mitochondrial dysfunction and senescence by inhibiting sirtuin-mediated deacetylation.

Perturbed metabolism of ammonia, an endogenous cytotoxin, causes mitochondrial dysfunction, reduced NAD+ /NADH (redox) ratio, and postmitotic senescence. Sirtuins are NAD+ -dependent deacetylases that delay senescence. In multiomics analyses, NAD metabolism and sirtuin pathways are enriched during hyperammonemia. Consistently, NAD+ -dependent Sirtuin3 (Sirt3) expression and deacetylase activity were decreased, and protein acetylation was increased in human and murine skeletal muscle/myotubes. Global acetylomics and subcellular fractions from myotubes showed hyperammonemia-induced hyperacetylation of cellular signaling and mitochondrial proteins. We dissected the mechanisms and consequences of hyperammonemia-induced NAD metabolism by complementary genetic and chemical approaches. Hyperammonemia inhibited electron transport chain components, specifically complex I that oxidizes NADH to NAD+ , that resulted in lower redox ratio. Ammonia also caused mitochondrial oxidative dysfunction, lower mitochondrial NAD+ -sensor Sirt3, protein hyperacetylation, and postmitotic senescence. Mitochondrial-targeted Lactobacillus brevis NADH oxidase (MitoLbNOX), but not NAD+ precursor nicotinamide riboside, reversed ammonia-induced oxidative dysfunction, electron transport chain supercomplex disassembly, lower ATP and NAD+ content, protein hyperacetylation, Sirt3 dysfunction and postmitotic senescence in myotubes. Even though Sirt3 overexpression reversed ammonia-induced hyperacetylation, lower redox status or mitochondrial oxidative dysfunction were not reversed. These data show that acetylation is a consequence of, but is not the mechanism of, lower redox status or oxidative dysfunction during hyperammonemia. Targeting NADH oxidation is a potential approach to reverse and potentially prevent ammonia-induced postmitotic senescence in skeletal muscle. Since dysregulated ammonia metabolism occurs with aging, and NAD+ biosynthesis is reduced in sarcopenia, our studies provide a biochemical basis for cellular senescence and have relevance in multiple tissues.

Alcohol and Immunology: Mechanisms of multi-organ damage. Summary of the 2022 alcohol and Immunology research interest group (AIRIG) meeting.

On October 26th, 2022 the annual Alcohol and Immunology Research Interest Group (AIRIG) meeting was held as a satellite symposium at the annual meeting of the Society for Leukocyte Biology in Hawaii. The 2022 meeting focused broadly on the immunological consequences of acute, chronic, and prenatal alcohol exposure and how these contribute to damage in multiple organs and tissues. These included alcohol-induced neuroinflammation, impaired lung immunity, intestinal dysfunction, and decreased anti-microbial and anti-viral responses. In addition, research presented covered multiple pathways behind alcohol-induced cellular dysfunction, including mitochondrial metabolism, cellular bioenergetics, gene regulation, and epigenetics. Finally, the work presented highlighted potential biomarkers and novel avenues of treatment for alcohol-induced organ damage.

NAD+-dependent SIRT1 deacetylase participates in epigenetic reprogramming during endotoxin tolerance.

Gene-selective epigenetic reprogramming and shifts in cellular bioenergetics develop when Toll-like receptors (TLR) recognize and respond to systemic life-threatening infections. Using a human monocyte cell model of endotoxin tolerance and human leukocytes from acute systemic inflammation with sepsis, we report that energy sensor sirtuin 1 (SIRT1) coordinates the epigenetic and bioenergy shifts. After TLR4 signaling, SIRT1 rapidly accumulated at the promoters of TNF-α and IL-1ß, but not IκBα; SIRT1 promoter binding was dependent on its co-factor, NAD(+). During this initial process, SIRT1 deacetylated RelA/p65 lysine 310 and nucleosomal histone H4 lysine 16 to promote termination of NFκB-dependent transcription. SIRT1 then remained promoter bound and recruited de novo induced RelB, which directed assembly of the mature transcription repressor complex that generates endotoxin tolerance. SIRT1 also promoted de novo expression of RelB. During sustained endotoxin tolerance, nicotinamide phosphoribosyltransferase (Nampt), the rate-limiting enzyme for endogenous production of NAD(+), and SIRT1 expression increased. The elevation of SIRT1 required protein stabilization and enhanced translation. To support the coordination of bioenergetics in human sepsis, we observed elevated NAD(+) levels concomitant with SIRT1 and RelB accumulation at the TNF-α promoter of endotoxin tolerant sepsis blood leukocytes. We conclude that TLR4 stimulation and human sepsis activate pathways that couple NAD(+) and its sensor SIRT1 with epigenetic reprogramming.