Aryl Hydrocarbon Receptor Activation in Pulmonary Alveolar Epithelial Cells Limits Inflammation and Preserves Lung Epithelial Cell Integrity.

The aryl hydrocarbon receptor (AHR) is a receptor/transcription factor widely expressed in the lung. The physiological roles of AHR expressed in the alveolar epithelium remain unclear. In this study, we tested the hypothesis that alveolar epithelial AHR activity plays an important role in modulating inflammatory responses and maintaining alveolar integrity during lung injury and repair. AHR is expressed in alveolar epithelial cells (AECs) and is active. AHR activation with the endogenous AHR ligand, FICZ (5,11-dihydroindolo[3,2-b] carbazole-6-carboxaldehyde), significantly suppressed inflammatory cytokine expression in response to inflammatory stimuli in primary murine AECs and in the MLE-15 epithelial cell line. In an LPS model of acute lung injury in mice, coadministration of FICZ with LPS suppressed protein leak, reduced neutrophil accumulation in BAL fluid, and suppressed inflammatory cytokine expression in lung tissue and BAL fluid. Relevant to healing following inflammatory injury, AHR activation suppressed TGF-ß-induced expression of genes associated with epithelial-mesenchymal transition. Knockdown of AHR in primary AECs with shRNA or in CRISPR-Cas-9-induced MLE-15 cells resulted in upregulation of α-smooth muscle actin (αSma), Col1a1, and Fn1 and reduced expression of epithelial genes Col4a1 and Sdc1. MLE-15 clones lacking AHR demonstrated accelerated wound closure in a scratch model. AHR activation with FICZ enhanced barrier function (transepithelial electrical resistance) in primary murine AECs and limited decline of transepithelial electrical resistance following inflammatory injury. AHR activation in AECs preserves alveolar integrity by modulating inflammatory cytokine expression while enhancing barrier function and limiting stress-induced expression of mesenchymal genes.

Prescription of potentially inappropriate medications after an intensive care unit stay for acute respiratory failure.

BACKGROUND: Among survivors of critical illness, prescription of potentially inappropriate medications (PIM) at hospital discharge is thought to be an important, modifiable patient safety concern. To date, there are little empirical data evaluating this issue. RESEARCH QUESTION: The objective of this study was to determine the frequency of PIM prescribed to survivors of acute respiratory failure (ARF) at hospital discharge and explore their association with readmissions or death within 90 days of hospital discharge. STUDY DESIGN AND METHODS: Prospective multicenter cohort study of ARF survivors admitted to ICUs and discharged home. Prospective of new PIMs with a high-adverse-effect profile ("high impact") at discharge was the primary exposure. Potential inappropriateness was determined by a structured consensus process using Screening Tool of Older Persons' Prescriptions-Screening Tool to Alert to Right Treatment, Beers' criteria, and clinical context of prescriptions by a multidisciplinary team. Covariate balancing propensity score was used for the primary analysis. RESULTS: Of the 195 Addressing Post Intensive Care Syndrome-01 (APICS-01) patients, 169 (87%) had ≥1 new medications prescribed at discharge, with 154 (91.1%) prescribed with one or more high-impact (HI) medications. Patients were prescribed a median of 5 [3-7] medications, of which 3 [1-4] were HI. Twenty percent of HI medications were potentially inappropriate. Medications with significant central nervous system side-effects were most prescribed potentially inappropriately. Forty-six (30%) patients experienced readmission or death within 90 days of hospital discharge. After adjusting for prespecified covariates, the association between prescription of potentially inappropriate HI medications and the composite primary outcome did not meet the prespecified threshold for statistical significance (risk ratio: 0.54; 0.26-1.13; p = 0.095) or with the constituent endpoints: readmission (risk ratio: 0.57, 0.27-1.11) or death (0.7, 0.05-9.32). CONCLUSION: At hospital discharge, most ARF survivors are prescribed medications with a high-adverse-effect profile and approximately one-fifth are potentially inappropriate. Although prescription of such medications was not associated with 90-day readmissions and mortality, these results highlight an area for additional investigation.

Association Between Unmet Nonmedication Needs After Hospital Discharge and Readmission or Death Among Acute Respiratory Failure Survivors: A Multicenter Prospective Cohort Study.

OBJECTIVES: To characterize early unmet nonmedication discharge needs (UDNs), classified as durable medical equipment (DME), home health services (HHS), and follow-up medical appointments (FUAs) and explore their association with 90-day readmission and mortality among survivors of acute respiratory failure (ARF) who were discharged home. DESIGN: Prospective multicenter cohort study. SETTING: Six academic medical centers across United States. PARTICIPANTS: Adult survivors of ARF who required an ICU stay and were discharged home from hospital. INTERVENTIONS: None. Exposure of interest was the proportion of UDN for the following categories: DME, HHS, and FUA ascertained within 7-28 days after hospital discharge. MEASUREMENTS AND MAIN RESULTS: Two hundred eligible patients were recruited between January 2019 and August 2020. One-hundred ninety-five patients were included in the analytic cohort: 118 were prescribed DME, 134 were prescribed HHS, and 189 needed at least one FUA according to discharge plans. 98.4% (192/195) had at least one identified nonmedication need at hospital discharge. Median (interquartile range) proportion of unmet needs across three categories were 0 (0-15%) for DME, 0 (0-50%) for HHS, and 0 (0-25%) for FUA, and overall was 0 (0-20%). Fifty-six patients (29%) had 90-day death or readmission. After adjusting for prespecified covariates, having greater than the median level of unmet needs was not associated with an increased risk of readmission or death within 90 days of discharge (risk ratio, 0.89; 0.51-1.57; p = 0.690). Age, hospital length of stay, Acute Physiology and Chronic Health Evaluation II severity of illness score, and Multidimensional Scale Perceived Social Support score were associated with UDN. CONCLUSIONS: UDN were common among survivors of ARF but not significantly associated a composite outcome of 90-day readmission or death. Our results highlight the substantial magnitude of UDN and identifies areas especially vulnerable to lapses in healthcare coordination.

Association between unmet medication needs after hospital discharge and readmission or death among acute respiratory failure survivors: the addressing post-intensive care syndrome (APICS-01) multicenter prospective cohort study.

INTRODUCTION: Survivors of acute respiratory failure (ARF) commonly experience long-lasting physical, cognitive, and/or mental health impairments. Unmet medication needs occurring immediately after hospital discharge may have an important effect on subsequent recovery. METHODS AND ANALYSIS: In this multicenter prospective cohort study, we enrolled ARF survivors who were discharged directly home from their acute care hospitalization. The primary exposure was unmet medication needs. The primary outcome was hospital readmission or death within 3 months after discharge. We performed a propensity score analysis, using inverse probability weighting for the primary exposure, to evaluate the exposure-outcome association, with an a priori sample size of 200 ARF survivors. RESULTS: We enrolled 200 ARF survivors, of whom 107 (53%) were female and 77 (39%) were people of color. Median (IQR) age was 55 (43-66) years, APACHE II score 20 (15-26) points, and hospital length of stay 14 (9-21) days. Of the 200 participants, 195 (98%) were in the analytic cohort. One hundred fourteen (57%) patients had at least one unmet medication need; the proportion of medication needs that were unmet was 6% (0-15%). Fifty-six (29%) patients were readmitted or died by 3 months; 10 (5%) died within 3 months. Unmet needs were not associated (risk ratio 1.25; 95% CI 0.75-2.1) with hospital readmission or death, although a higher proportion of unmet needs may have been associated with increased hospital readmission (risk ratio 1.7; 95% CI 0.96-3.1) and decreased mortality (risk ratio 0.13; 95% CI 0.02-0.99). DISCUSSION: Unmet medication needs are common among survivors of acute respiratory failure shortly after discharge home. The association of unmet medication needs with 3-month readmission and mortality is complex and requires additional investigation to inform clinical trials of interventions to reduce unmet medication needs. Study registration number: NCT03738774 . The study was prospectively registered before enrollment of the first patient.

Key role of microRNA in the regulation of granulocyte macrophage colony-stimulating factor expression in murine alveolar epithelial cells during oxidative stress.

GM-CSF is an endogenous pulmonary cytokine produced by normal alveolar epithelial cells (AEC) that is a key defender of the alveolar space. AEC GM-CSF expression is suppressed by oxidative stress through alternations in mRNA turnover, an effect that is reversed by treatment with recombinant GM-CSF. We hypothesized that specific microRNA (miRNA) would play a key role in AEC GM-CSF regulation. A genome-wide miRNA microarray identified 19 candidate miRNA altered in primary AEC during oxidative stress with reversal by treatment with GM-CSF. Three of these miRNA (miR 133a, miR 133a*, and miR 133b) are also predicted to bind the GM-CSF 3'-untranslated region (UTR). PCR for the mature miRNA confirmed induction during oxidative stress that was reversed by treatment with GM-CSF. Experiments using a GM-CSF 3'-UTR reporter construct demonstrated that miR133a and miR133b effects on GM-CSF expression are through interactions with the GM-CSF 3'-UTR. Using lentiviral transduction of specific mimics and inhibitors in primary murine AEC, we determined that miR133a and miR133b suppress GM-CSF expression and that their inhibition both reverses oxidant-induced suppression of GM-CSF expression and increases basal expression of GM-CSF in cells in normoxia. In contrast, these miRNAs are not active in regulation of GM-CSF expression in murine EL4 T cells. Thus, members of the miR133 family play key roles in regulation of GM-CSF expression through effects on mRNA turnover in AEC during oxidative stress. Increased understanding of GM-CSF gene regulation may provide novel miRNA-based interventions to augment pulmonary innate immune defense in lung injury.

Unintended Consequences of Code Status in the Intensive Care Unit: What Happens After a Do-Not-Resuscitate Order Is Placed? A Retrospective Cohort Study.

Background: Some clinicians suspect that patients with do-not-resuscitate (DNR) orders receive less aggressive care. Extrapolation from code status to goals of care could cause significant harm. This study asked the question: Do DNR orders in the intensive care unit (ICU) lead to a decrease in invasive interventions? Methods: This was a retrospective cohort study of ICU patients from three teaching hospitals. All ICU patients were assessed for inclusion. Exclusion criteria were medical futility and death, comfort care, or ICU discharge <48 hours after DNR initiation. Five hundred thirty-six patients met inclusion criteria. One hundred forty-five were included in the final analysis. Primary outcomes were occurrence of invasive interventions after DNR initiation-surgical operation, central line, ventilation, dialysis, or other procedure. Secondary outcomes were antibiotic administration, blood transfusion, mortality, and discharge location. Results: Patients with DNR orders underwent fewer surgical operations (14.5% vs. 31.1%, p = 0.002), but more central lines (42.1% vs. 23.0%, p = 0.009), ventilator use (49.0% vs. 18.9%, p < 0.001), and dialysis (20.0% vs. 4.1%, p = 0.002), compared with patients without DNR orders. Transfusions and antibiotic use decreased similarly over admission for both groups (transfusions: ß = 1.25; p = 0.59; and antibiotics: ß = 1.44; p = 0.27). Mortality and hospice discharges were higher for DNR patients (p < 0.001.). Conclusions: DNR status did not decrease the number of nonoperative interventions patients received as compared with full code counterparts. Although differences in populations existed, patients with DNR orders were likely to receive a similar number of invasive interventions. This finding suggests that providers do not wholesale limit these options for patients with code status limitations.

Health Expectations and Quality of Life After Acute Respiratory Failure: A Multicenter Prospective Cohort Study.

BACKGROUND: Patients often have high expectations for recovery after critical illness, but the impact of these expectations on subsequent quality of life (QoL) after serious illnesses has not been evaluated empirically. RESEARCH QUESTION: Among adult survivors of acute respiratory failure (ARF), are met vs unmet expectations for health associated with self-reported QoL 6 months after discharge? STUDY DESIGN AND METHODS: This was a prospective longitudinal cohort study enrolling consecutive adult patients with ARF managed in ICUs at five academic medical centers. At hospital discharge, we evaluated participants' expected health 6 months in the future via a visual analog scale (VAS; range, 0-100), with higher scores representing better expected health. At 6-month follow-up, perceived health was assessed using the EQ-5D VAS, and QoL was assessed using the World Health Organization Quality of Life Brief Version (WHOQOL-BREF) instrument. Participants' health expectations were categorized as having been met when perceived health at 6 months was no more than eight points lower than their expectation at study enrollment. The primary analysis compared WHOQOL-BREF domain scores (range, 0-100) at 6 months after discharge in patients with met vs unmet health expectations using the nonparametric Mann-Whitney U test. Secondary analysis modeled WHOQOL-BREF domain scores using multivariate regression, and sensitivity analyses assessed QoL using EQ-5D-5L index values. RESULTS: In the primary analysis, QoL was significantly better among participants with met vs unmet health expectations across all domains of the WHOQOL-BREF: physical health (estimated difference in scores: median, 19 [interquartile range (IQR), 12-15]; P < .001), psychological health (median, 12 [IQR, 6-18]; P < .001), social relationships (median, 6 [IQR, 0-13]; P = .02), and environmental health (median, 12 [IQR, 6-13]; P < .001). In multivariate regression, the difference between expected and perceived health remained associated significantly with the physical health domain score. INTERPRETATION: Fulfillment of health expectations is associated with better QoL after ARF, suggesting a mechanism underpinning successful ICU recovery programs that incorporate normalization and expectation management.

Fulfillment of Patient Expectations after Acute Respiratory Failure: A Multicenter Prospective Cohort Study.

Rationale: Discussion of patient expectations for recovery is a component of intensive care unit (ICU) follow-up clinics. However, few studies have formally evaluated recovery-related expectations of ICU survivors. Objectives: To estimate the prevalence of unmet expectations for recovery 6 months after hospital discharge among adult survivors of acute respiratory failure (ARF). Methods: This was a prospective, longitudinal, cohort study of survivors of ARF discharged to home from five U.S. medical centers. Expectations for functional recovery were assessed by asking which activities and instrumental activities of daily living (I/ADLs) survivors expected to perform independently at 6 months. Survivors' expectations for overall health status were assessed using a visual analogue scale ranging from 0 to 100. At 6-month follow-up, participants reported which I/ADLs they could perform independently and rated their overall health status using a 100-point visual analogue scale. We defined a participant's functional expectations as being met if they reported independently performing I/ADLs as expected at hospital discharge. Health expectations were considered to be met when self-rated health status at 6 months was no more than 8 points lower than expected at enrollment. Results: Among 180 enrollees, 169 (94%) were alive, and 160 of these (95%) participated in 6-month follow-up. Functional expectations were met for 71% of participating survivors, and overall health expectations were met for 50%. Expectations for functional independence were high, ranging from 87% (housekeeping) to 99% (using a telephone). General health expectations were variable (median, 85; interquartile range [IQR], 75-95). At 6-month follow-up, self-rated, overall health ranged from 2 to 100 (median, 80; IQR, 60-85). In exploratory analyses, participants with met versus unmet expectations differed most in formal education (functional expectations standardized difference = 0.88; health expectations standardized difference = 0.41). Conclusions: Expectations of survivors of ARF about independent functioning were high and generally met, but half had unmet general health expectations 6 months after discharge. It is difficult to predict whose health expectations will be unmet, but possessing less formal education may be a risk factor. Clinical trial registered with www.clinicaltrials.gov (NCT03797313).

Effect of alveolar epithelial cell plasticity on the regulation of GM-CSF expression.

Local pulmonary expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) is critically important for defense of the pulmonary alveolar space. It is required for surfactant homeostasis and pulmonary innate immune responses and is protective against lung injury and aberrant repair. Alveolar epithelial cells (AEC) are a major source of GM-CSF; however, the control of homeostatic expression of GM-CSF is incompletely characterized. Increasing evidence suggests considerable plasticity of expression of AEC phenotypic characteristics. We tested the hypothesis that this plasticity extends to regulation of expression of GM-CSF using 1) MLE-12 cells (a commonly used murine cell line expressing some features of normal type II AEC, 2) primary murine AEC incubated under standard conditions [resulting in rapid spreading and loss of surfactant protein C (SP-C) expression with induction of the putative type I cell marker (T1α)], or 3) primary murine AEC on a hyaluronic acid/collagen matrix in defined medium, resulting in preservation of SP-C expression. AEC in standard cultures constitutively express abundant GM-CSF, with further induction in response to IL-1ß but little response to TNF-α. In contrast, primary cells cultured to preserve SP-C expression and MLE-12 cells both express little GM-CSF constitutively, with significant induction in response to TNF-α and limited response to IL-1ß. We conclude that constitutive and cytokine-induced expression of GM-CSF by AEC varies in concert with other cellular phenotypic characteristics. These changes may have important implications both for the maintenance of normal pulmonary homeostasis and for the process of repair following lung injury.

GM-CSF provides autocrine protection for murine alveolar epithelial cells from oxidant-induced mitochondrial injury.

Exposure of mice to hyperoxia induces alveolar epithelial cell (AEC) injury, acute lung injury and death. Overexpression of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the lung protects against these effects, although the mechanisms are not yet clear. Hyperoxia induces cellular injury via effects on mitochondrial integrity, associated with induction of proapoptotic members of the Bcl-2 family. We hypothesized that GM-CSF protects AEC through effects on mitochondrial integrity. MLE-12 cells (a murine type II cell line) and primary murine type II AEC were subjected to oxidative stress by exposure to 80% oxygen and by exposure to H(2)O(2). Exposure to H(2)O(2) induced cytochrome c release and decreased mitochondrial reductase activity in MLE-12 cells. Incubation with GM-CSF significantly attenuated these effects. Protection induced by GM-CSF was associated with Akt activation. GM-CSF treatment also resulted in increased expression of the antiapoptotic Bcl-2 family member, Mcl-1. Primary murine AEC were significantly more tolerant of oxidative stress than MLE-12 cells. In contrast to MLE-12 cells, primary AEC expressed significant GM-CSF at baseline and demonstrated constitutive activation of Akt and increased baseline expression of Mcl-1. Treatment with exogenous GM-CSF further increased Akt activation and Mcl-1 expression in primary AEC. Conversely, suppression of AEC GM-CSF expression by use of GM-CSF-specific small interfering RNA resulted in decreased tolerance of oxidative stress, Furthermore, silencing of Mcl-1 prevented GM-CSF-induced protection. We conclude that GM-CSF protects alveolar epithelial cells against oxidative stress-induced mitochondrial injury via the Akt pathway and its downstream components, including Mcl-1. Epithelial cell-derived GM-CSF may contribute to intrinsic defense mechanisms limiting lung injury.

Mechanisms of suppression of alveolar epithelial cell GM-CSF expression in the setting of hyperoxic stress.

Pulmonary expression of granulocyte/macrophage colony-stimulating factor (GM-CSF) is critically important for normal functional maturation of alveolar macrophages. We found previously that lung GM-CSF is dramatically suppressed in mice exposed to hyperoxia. Alveolar epithelial cells (AEC) are a major source of GM-CSF in the peripheral lung, and in vivo hyperoxia resulted in greatly reduced expression of GM-CSF protein by AEC ex vivo. We now explore the mechanisms responsible for this effect, using primary cultures of murine AEC exposed to hyperoxia in vitro. Exposure of AEC to 80% oxygen/5% CO(2) for 48 h did not induce overt toxicity, but resulted in significantly decreased GM-CSF protein and mRNA expression compared with cells in normoxia. Similar effects were seen when AEC were stressed with serum deprivation, an alternative inducer of oxidative stress. The effects in AEC were opposite those in a murine lung epithelial cell line (MLE-12 cells), in which hyperoxia induced GM-CSF expression. Both hyperoxia and serum deprivation resulted in increased intracellular reactive oxygen species (ROS) in AEC. Hyperoxia and serum deprivation induced significantly accelerated turnover of GM-CSF mRNA. Treatment of AEC with catalase during oxidative stress preserved GM-CSF protein and mRNA and was associated with stabilization of GM-CSF mRNA. We conclude that hyperoxia-induced suppression of AEC GM-CSF expression is a function of ROS-induced destabilization of GM-CSF mRNA. We speculate that AEC oxidative stress results in significantly impaired pulmonary innate immune defense due to effects on local GM-CSF expression in the lung.

Evaluating the association between unmet healthcare needs and subsequent clinical outcomes: protocol for the Addressing Post-Intensive Care Syndrome-01 (APICS-01) multicentre cohort study.

INTRODUCTION: As short-term mortality declines for critically ill patients, a growing number of survivors face long-term physical, cognitive and/or mental health impairments. After hospital discharge, many critical illness survivors require an in-depth plan to address their healthcare needs. Early after hospital discharge, numerous survivors experience inadequate care or a mismatch between their healthcare needs and what is provided. Many patients are readmitted to the hospital, have substantial healthcare resource use and experience long-lasting morbidity. The objective of this study is to investigate the gap in healthcare needs occurring immediately after hospital discharge and its association with hospital readmissions or death for survivors of acute respiratory failure (ARF). METHODS AND ANALYSIS: In this multicentre prospective cohort study, we will enrol 200 survivors of ARF in the intensive care unit (ICU) who are discharged directly home from their acute care hospital stay. Unmet healthcare needs, the primary exposure of interest, will be evaluated as soon as possible within 1 to 4 weeks after hospital discharge, via a standardised telephone assessment. The primary outcome, death or hospital readmission, will be measured at 3 months after discharge. Secondary outcomes (eg, quality of life, cognitive impairment, depression, anxiety and post-traumatic stress disorder) will be measured as part of 3-month and 6-month telephone-based follow-up assessments. Descriptive statistics will be reported for the exposure and outcome variables along with a propensity score analysis, using inverse probability weighting for the primary exposure, to evaluate the relationship between the primary exposure and outcome. ETHICS AND DISSEMINATION: The study received ethics approval from Vanderbilt University Medical Center Institutional Review Board (IRB) and the University of Utah IRB (for the Veterans Affairs site). These results will inform both clinical practice and future interventional trials in the field. We plan to disseminate the results in peer-reviewed journals, and via national and international conferences. TRIAL REGISTRATION DETAILS: ClinicalTrials.gov (NCT03738774). Registered before enrollment of the first patient.

A 73-Year-Old Man With Progressive Whole Body Subcutaneous Gas After Pleural Catheter Removal.

CASE PRESENTATION: A 73-year-old man presented to the ED of an outside hospital with asymptomatic chest wall swelling 10 h after discharge from our hospital. Four days earlier, he had presented to our hospital with increased dyspnea, cough, and sputum production. His history was notable for severe COPD with bullous emphysema. Chest imaging demonstrated bilateral opacities and a collection of gas and liquid in the major fissure of the left lung. A catheter was placed into the collection of gas and liquid under imaging guidance. After 4 days, the catheter was removed without event and the patient was discharged from the hospital with an extended course of antibiotics. Imaging performed in the ED revealed gas in the tissues of the chest wall and no evidence of a pneumothorax. He was transported back to our hospital by helicopter.

Approaches to Addressing Post-Intensive Care Syndrome among Intensive Care Unit Survivors. A Narrative Review.

Critical illness can be lethal and devastating to survivors. Improvements in acute care have increased the number of intensive care unit (ICU) survivors. These survivors confront a range of new or worsened health states that collectively are commonly denominated post-intensive care syndrome (PICS). These problems include physical, cognitive, psychological, and existential aspects, among others. Burgeoning interest in improving long-term outcomes for ICU survivors has driven an array of potential interventions to improve outcomes associated with PICS. To date, the most promising interventions appear to relate to very early physical rehabilitation. Late interventions within aftercare and recovery clinics have yielded mixed results, although experience in heart failure programs suggests the possibility that very early case management interventions may help improve intermediate-term outcomes, including mortality and hospital readmission. Predictive models have tended to underperform, complicating study design and clinical referral. The complexity of the health states associated with PICS suggests that careful and rigorous evaluation of multidisciplinary, multimodality interventions-tied to the specific conditions of interest-will be required to address these important problems.

Contrasting effects of hyperoxia on GM-CSF gene transcription in alveolar epithelial cells and T cells.

Granulocyte/macrophage colony-stimulating factor (GM-CSF) is critically important for normal pulmonary innate immunity and for functional maturation of alveolar macrophages. Alveolar epithelial cells (AEC) are a major source of GM-CSF in the lung and express this growth factor constitutively, whereas most other cells, including T cells, express GM-CSF following inflammatory stimulation. AEC expression of GM-CSF is suppressed by oxidative stress, at least in part through induction of microRNA leading to increased mRNA turnover. In this report, we compare and contrast the effect of hyperoxia on transcriptional aspects of gene regulation of GM-CSF in lung epithelia and T cells of human and mouse origin. Similar to primary murine AEC, human H820 cells that express multiple characteristics of normal alveolar epithelial cells express GM-CSF constitutively, with decreased expression and increased mRNA turnover following exposure to hyperoxia. In contrast, hyperoxia induces augmented GM-CSF expression in human and murine activated T cells, in association with enhanced GM-CSF mRNA stability. Alveolar epithelial cells demonstrate constitutive transcription, with the proximal promoter in an open configuration in normoxia, without change in hyperoxia. Conversely, in both human and murine T cells, hyperoxia increased GM-CSF gene transcription. The proximal promoter was in a closed configuration in unstimulated T cells but became accessible upon activation and still more accessible in activated T cells exposed to hyperoxia. These fundamental differences in molecular regulation of GM-CSF expression highlight the distinctive niche of alveolar epithelial cell expression of GM-CSF and offer insights into the biology of GM-CSF in the setting of acute lung injury.