mTORC1 is a mechanosensor that regulates surfactant function and lung compliance during ventilator-induced lung injury.

The acute respiratory distress syndrome (ARDS) is a highly lethal condition that impairs lung function and causes respiratory failure. Mechanical ventilation (MV) maintains gas exchange in patients with ARDS but exposes lung cells to physical forces that exacerbate injury. Our data demonstrate that mTOR complex 1 (mTORC1) is a mechanosensor in lung epithelial cells and that activation of this pathway during MV impairs lung function. We found that mTORC1 is activated in lung epithelial cells following volutrauma and atelectrauma in mice and humanized in vitro models of the lung microenvironment. mTORC1 is also activated in lung tissue of mechanically ventilated patients with ARDS. Deletion of Tsc2, a negative regulator of mTORC1, in epithelial cells impairs lung compliance during MV. Conversely, treatment with rapamycin at the time MV is initiated improves lung compliance without altering lung inflammation or barrier permeability. mTORC1 inhibition mitigates physiologic lung injury by preventing surfactant dysfunction during MV. Our data demonstrate that, in contrast to canonical mTORC1 activation under favorable growth conditions, activation of mTORC1 during MV exacerbates lung injury and inhibition of this pathway may be a novel therapeutic target to mitigate ventilator-induced lung injury during ARDS.

Acute Intraoperative Hypoxemia During Right Pneumonectomy-The Heart and Lung Interaction: A Case Report.

A 75-year-old woman with a history of right-upper lobectomy for adenocarcinoma presented for a right completion pneumonectomy due to 2 new fluorodeoxyglucose-avid densities on the remaining lung. After uneventful anesthetic induction and surgical resection with modest blood loss, the patient developed refractory hypoxemia on emergence without significant hemodynamic changes. Despite delivery of fraction of inspired oxygen (Fio2) = 1.0, confirmed position of the double-lumen tube, and exclusion of common causes of hypoxemia, hypoxemia persisted. An emergent transesophageal echocardiogram revealed a significant intracardiac shunt due to a patent foramen ovale. Specific cardiorespiratory management to achieve a positive left-right heart pressure gradient resulted in prompt normoxemia and successful extubation.

Post-sepsis immunosuppression depends on NKT cell regulation of mTOR/IFN-γ in NK cells.

As treatment of the early, inflammatory phase of sepsis improves, post-sepsis immunosuppression and secondary infection have increased in importance. How early inflammation drives immunosuppression remains unclear. Although IFN-γ typically helps microbial clearance, we found that increased plasma IFN-γ in early clinical sepsis was associated with the later development of secondary Candida infection. Consistent with this observation, we found that exogenous IFN-γ suppressed macrophage phagocytosis of zymosan in vivo, and antibody blockade of IFN-γ after endotoxemia improved survival of secondary candidemia. Transcriptomic analysis of innate lymphocytes during endotoxemia suggested that NKT cells drove IFN-γ production by NK cells via mTORC1. Activation of invariant NKT (iNKT) cells with glycolipid antigen drove immunosuppression. Deletion of iNKT cells in Cd1d-/- mice or inhibition of mTOR by rapamycin reduced immunosuppression and susceptibility to secondary Candida infection. Thus, although rapamycin is typically an immunosuppressive medication, in the context of sepsis, rapamycin has the opposite effect. These results implicated an NKT cell/mTOR/IFN-γ axis in immunosuppression following endotoxemia or sepsis. In summary, in vivo iNKT cells activated mTORC1 in NK cells to produce IFN-γ, which worsened macrophage phagocytosis, clearance of secondary Candida infection, and mortality.

Whole blood RNA sequencing reveals a unique transcriptomic profile in patients with ARDS following hematopoietic stem cell transplantation.

BACKGROUND: The acute respiratory distress syndrome (ARDS) is characterized by the acute onset of hypoxemia and bilateral lung infiltrates in response to an inciting event, and is associated with high morbidity and mortality. Patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) are at increased risk for ARDS. We hypothesized that HSCT patients with ARDS would have a unique transcriptomic profile identifiable in peripheral blood compared to those that did not undergo HSCT. METHODS: We isolated RNA from banked peripheral blood samples from a biorepository of critically ill ICU patients. RNA-Seq was performed on 11 patients with ARDS (5 that had undergone HSCT and 6 that had not) and 12 patients with sepsis without ARDS (5 that that had undergone HCST and 7 that had not). RESULTS: We identified 687 differentially expressed genes between ARDS and ARDS-HSCT (adjusted p-value < 0.01), including IFI44L, OAS3, LY6E, and SPATS2L that had increased expression in ARDS vs. ARDS-HSCT; these genes were not differentially expressed in sepsis vs sepsis-HSCT. Gene ontology enrichment analysis revealed that many differentially expressed genes were related to response to type I interferon. CONCLUSIONS: Our findings reveal significant differences in whole blood transcriptomic profiles of patients with non-HSCT ARDS compared to ARDS-HSCT patients and point toward different immune responses underlying ARDS and ARDS-HSCT that contribute to lung injury.

A phase I trial of low-dose inhaled carbon monoxide in sepsis-induced ARDS.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is a prevalent disease with significant mortality for which no effective pharmacologic therapy exists. Low-dose inhaled carbon monoxide (iCO) confers cytoprotection in preclinical models of sepsis and ARDS. METHODS: We conducted a phase I dose escalation trial to assess feasibility and safety of low-dose iCO administration in patients with sepsis-induced ARDS. Twelve participants were randomized to iCO or placebo air 2:1 in two cohorts. Four subjects each were administered iCO (100 ppm in cohort 1 or 200 ppm in cohort 2) or placebo for 90 minutes for up to 5 consecutive days. Primary outcomes included the incidence of carboxyhemoglobin (COHb) level ≥10%, prespecified administration-associated adverse events (AEs), and severe adverse events (SAEs). Secondary endpoints included the accuracy of the Coburn-Forster-Kane (CFK) equation to predict COHb levels, biomarker levels, and clinical outcomes. RESULTS: No participants exceeded a COHb level of 10%, and there were no administration-associated AEs or study-related SAEs. CO-treated participants had a significant increase in COHb (3.48% ± 0.7% [cohort 1]; 4.9% ± 0.28% [cohort 2]) compared with placebo-treated subjects (1.97% ± 0.39%). The CFK equation was highly accurate at predicting COHb levels, particularly in cohort 2 (R2 = 0.9205; P < 0.0001). Circulating mitochondrial DNA levels were reduced in iCO-treated participants compared with placebo-treated subjects. CONCLUSION: Precise administration of low-dose iCO is feasible, well-tolerated, and appears to be safe in patients with sepsis-induced ARDS. Excellent agreement between predicted and observed COHb should ensure that COHb levels remain in the target range during future efficacy trials. TRIAL REGISTRATION: ClinicalTrials.gov NCT02425579. FUNDING: NIH grants P01HL108801, KL2TR002385, K08HL130557, and K08GM102695.

Metabolome alterations in severe critical illness and vitamin D status.

BACKGROUND: Metabolic homeostasis is substantially disrupted in critical illness. Given the pleiotropic effects of vitamin D, we hypothesized that metabolic profiles differ between critically ill patients relative to their vitamin D status. METHODS: We performed a metabolomics study on biorepository samples collected from a single academic medical center on 65 adults with systemic inflammatory response syndrome or sepsis treated in a 20-bed medical ICU between 2008 and 2010. To identify key metabolites and metabolic pathways related to vitamin D status in critical illness, we first generated metabolomic data using gas and liquid chromatography mass spectroscopy. We followed this by partial least squares-discriminant analysis to identify individual metabolites that were significant. We then interrogated the entire metabolomics profile using metabolite set enrichment analysis to identify groups of metabolites and pathways that were differentiates of vitamin D status. Finally we performed logistic regression to construct a network model of chemical-protein target interactions important in vitamin D status. RESULTS: Metabolomic profiles significantly differed in critically ill patients with 25(OH)D ≤ 15 ng/ml relative to those with levels >15 ng/ml. In particular, increased 1,5-anhydroglucitol, tryptophan betaine, and 3-hydroxyoctanoate as well as decreased 2-arachidonoyl-glycerophosphocholine and N-6-trimethyllysine were strong predictors of 25(OH)D >15 ng/ml. The combination of these five metabolites led to an area under the curve for discrimination for 25(OH)D > 15 ng/ml of 0.82 (95% CI 0.71-0.93). The metabolite pathways related to glutathione metabolism and glutamate metabolism are significantly enriched with regard to vitamin D status. CONCLUSION: Vitamin D status is associated with differential metabolic profiles during critical illness. Glutathione and glutamate pathway metabolism, which play principal roles in redox regulation and immunomodulation, respectively, were significantly altered with vitamin D status.

Zinc deficiency primes the lung for ventilator-induced injury.

Mechanical ventilation is necessary to support patients with acute lung injury, but also exacerbates injury through mechanical stress-activated signaling pathways. We show that stretch applied to cultured human cells, and to mouse lungs in vivo, induces robust expression of metallothionein, a potent antioxidant and cytoprotective molecule critical for cellular zinc homeostasis. Furthermore, genetic deficiency of murine metallothionein genes exacerbated lung injury caused by high tidal volume mechanical ventilation, identifying an adaptive role for these genes in limiting lung injury. Stretch induction of metallothionein required zinc and the zinc-binding transcription factor MTF1. We further show that mouse dietary zinc deficiency potentiates ventilator-induced lung injury, and that plasma zinc levels are significantly reduced in human patients who go on to develop acute respiratory distress syndrome (ARDS) compared with healthy and non-ARDS intensive care unit (ICU) controls, as well as with other ICU patients without ARDS. Taken together, our findings identify a potentially novel adaptive response of the lung to stretch and a critical role for zinc in defining the lung's tolerance for mechanical ventilation. These results demonstrate that failure of stretch-adaptive responses play an important role in exacerbating mechanical ventilator-induced lung injury, and identify zinc and metallothionein as targets for lung-protective interventions in patients requiring mechanical ventilation.

Human Sepsis Eicosanoid and Proresolving Lipid Mediator Temporal Profiles: Correlations With Survival and Clinical Outcomes.

OBJECTIVE: To identify and measure recently described chemical mediators, termed specialized pro-resolving mediators that actively regulate the resolution of acute-inflammation, and correlate measurements with clinical outcomes. DESIGN: Herein, deidentified plasma was collected from sepsis patients (n = 22 subjects) within 48 hours of admission to the ICU and on days 3 and 7 thereafter and subjected to lipid mediator profiling. SETTING: Brigham and Women's Hospital Medical Intensive Care Unit. SUBJECTS: Patients in the medical ICU with sepsis. MEASUREMENTS AND MAIN RESULTS: In all patients, we identified more than 30 bioactive mediators and pathway markers in peripheral blood using established criteria for arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid metabolomes. These included inflammation initiating mediators leukotriene B4 and prostaglandin E2 and pro-resolving mediators resolvin D1, resolvin D2, and protectin D1. In sepsis nonsurvivors, we found significantly higher inflammation-initiating mediators including prostaglandin F2α and leukotriene B4 and pro-resolving mediators, including resolvin E1, resolvin D5, and 17R-protectin D1 than was observed in surviving sepsis subjects. This signature was present at ICU admission and persisted for 7 days. Further analysis revealed increased respiratory failure in nonsurvivors. Higher inflammation-initiating mediators (including prostaglandin F2α) and select proresolving pathways were associated with the development of acute respiratory distress syndrome, whereas other traditional clinical indices were not predictive of acute respiratory distress syndrome development. CONCLUSIONS: These results provide peripheral blood lipid mediator profiles in sepsis that correlate with survival and acute respiratory distress syndrome development, thus suggesting plausible novel biomarkers and biologic targets for critical illness.

Time-Limited Trials of Intensive Care for Critically Ill Patients With Cancer: How Long Is Long Enough?

IMPORTANCE: Time-limited trials of intensive care are commonly used in patients perceived to have a poor prognosis. The optimal duration of such trials is unknown. Factors such as a cancer diagnosis are associated with clinician pessimism and may affect the decision to limit care independent of a patient's severity of illness. OBJECTIVE: To identify the optimal duration of intensive care for short-term mortality in critically ill patients with cancer. DESIGN, SETTING, AND PARTICIPANTS: Decision analysis using a state-transition microsimulation model was performed to simulate the hospital course of patients with poor-prognosis primary tumors, metastatic disease, or hematologic malignant neoplasms admitted to medical and surgical intensive care units. Transition probabilities were derived from 920 participants stratified by sequential organ failure assessment (SOFA) scores to identify severity of illness. The model was validated in 3 independent cohorts with 349, 158, and 117 participants from quaternary care academic hospitals. Monte Carlo microsimulation was performed, followed by probabilistic sensitivity analysis. Outcomes were assessed in the overall cohort and in solid tumors alone. INTERVENTIONS: Time-unlimited vs time-limited trials of intensive care. MAIN OUTCOMES AND MEASURES: 30-day all-cause mortality and mean survival duration. RESULTS: The SOFA scores at ICU admission were significantly associated with mortality. A 3-, 8-, or 15-day trial of intensive care resulted in decreased mean 30-day survival vs aggressive care in all but the sickest patients (SOFA score, 5-9: 48.4% [95% CI, 48.0%-48.8%], 60.6% [95% CI, 60.2%-61.1%], and 66.8% [95% CI, 66.4%-67.2%], respectively, vs 74.6% [95% CI, 74.3%-75.0%] with time-unlimited aggressive care; SOFA score, 10-14: 36.2% [95% CI, 35.8%-36.6%], 44.1% [95% CI, 43.6%-44.5%], and 46.1% [95% CI, 45.6%-46.5%], respectively, vs 48.4% [95% CI, 48.0%-48.8%] with aggressive care; SOFA score, ≥ 15: 5.8% [95% CI, 5.6%-6.0%], 8.1% [95% CI, 7.9%-8.3%], and 8.3% [95% CI, 8.1%-8.6%], respectively, vs 8.8% [95% CI, 8.5%-9.0%] with aggressive care). However, the clinical magnitude of these differences was variable. Trial durations of 8 days in the sickest patients offered mean survival duration that was no more than 1 day different from time-unlimited care, whereas trial durations of 10 to 12 days were required in healthier patients. For the subset of patients with solid tumors, trial durations of 1 to 4 days offered mean survival that was not statistically significantly different from time-unlimited care. CONCLUSIONS AND RELEVANCE: Trials of ICU care lasting 1 to 4 days may be sufficient in patients with poor-prognosis solid tumors, whereas patients with hematologic malignant neoplasms or less severe illness seem to benefit from longer trials of intensive care.