Derivation, validation, and transcriptomic assessment of pediatric septic shock phenotypes identified through latent profile analyses: Results from a prospective multi-center observational cohort

Background

Sepsis poses a grave threat, especially among children, but treatments are limited due to clinical and biological heterogeneity among patients. Thus, there is an urgent need for precise subclassification of patients to guide therapeutic interventions.

Methods

We used clinical, laboratory, and biomarker data from a prospective multi-center pediatric septic shock cohort to derive phenotypes using latent profile analyses. Thereafter, we trained a support vector machine model to assign phenotypes in a hold-out validation set. We tested interactions between phenotypes and common sepsis therapies on clinical outcomes and conducted transcriptomic analyses to better understand the phenotype-specific biology. Finally, we compared whether newly identified phenotypes overlapped with established gene-expression endotypes and tested the utility of an integrated subclassification scheme.

Findings

Among 1,071 patients included, we identified two phenotypes which we named 'inflamed' (19.5%) and an 'uninflamed' phenotype (80.5%). The 'inflamed' phenotype had an over 4-fold risk of 28-day mortality relative to those 'uninflamed'. Transcriptomic analysis revealed overexpression of genes implicated in the innate immune response and suggested an overabundance of developing neutrophils, pro-T/NK cells, and NK cells among those 'inflamed'. There was no significant overlap between endotypes and phenotypes. However, an integrated subclassification scheme demonstrated varying survival probabilities when comparing endophenotypes.

Interpretation

Our research underscores the reproducibility of latent profile analyses to identify clinical and biologically informative pediatric septic shock phenotypes with high prognostic relevance. Pending validation, an integrated subclassification scheme, reflective of the different facets of the host response, holds promise to inform targeted intervention among those critically ill.

A Targeted Analysis of Serial Cytokine Measures and Nonpulmonary Organ System Failure in Children With Acute Respiratory Failure: Individual Measures and Trajectories Over Time

OBJECTIVES

There is a need for research exploring the temporal trends of nonpulmonary organ dysfunction (NPOD) and biomarkers in order to identify unique predictive or prognostic phenotypes. We examined the associations between the number and trajectories of NPODs and plasma biomarkers of early and late inflammatory cascade activation, specifically plasma interleukin-1 receptor antagonist (IL-1ra) and interleukin-8 (IL-8), respectively, in the setting of acute respiratory failure (ARF).

DESIGN

Secondary analysis of the Randomized Evaluation for Sedation Titration for Respiratory Failure clinical trial and Biomarkers in Acute Lung Injury (BALI) ancillary study.

SETTING

Multicenter.

PATIENTS

Intubated pediatric patients with ARF.

INTERVENTIONS

NPODs were evaluated against plasma IL-1ra and IL-8 levels on individual days (1 to 4 d after intubation) and longitudinally across days.

MEASUREMENTS AND MAIN RESULTS

Within the BALI cohort, 432 patients had at least one value for IL-1ra or IL-8 within days 0 through 5. 36.6% had a primary diagnosis of pneumonia, 18.5% had a primary diagnosis of sepsis and 8.1% died. Multivariable logistic regression models showed that increasing levels of both plasma IL-1ra and IL-8 were statistically significantly associated with increasing numbers of NPODs (IL-1ra: days 1-3; IL-8: days 1-4), independent of sepsis diagnosis, severity of oxygenation defect, age, and race/ethnicity. Longitudinal trajectory analysis identified four distinct NPOD trajectories and seven distinct plasma IL-1ra and IL-8 trajectories. Multivariable ordinal logistic regression revealed that specific IL-1ra and IL-8 trajectory groups were associated with greater NPOD trajectory group ( p = 0.004 and p < 0.0001, respectively), independent of severity of oxygenation defect, age, sepsis diagnosis, and race/ethnicity.

CONCLUSIONS

Both the inflammatory biomarkers and number of NPODs exhibit distinct trajectories over time with strong associations with one another. These biomarkers and their trajectory patterns may be useful in evaluating the severity of multiple organ dysfunction syndrome in critically ill children and identifying those phenotypes with time-sensitive, treatable traits.

NFKB2 haploinsufficiency identified via screening for IFN-α2 autoantibodies in children and adolescents hospitalized with SARS-CoV-2-related complications

BACKGROUND

Autoantibodies against type I IFNs occur in approximately 10% of adults with life-threatening coronavirus disease 2019 (COVID-19). The frequency of anti-IFN autoantibodies in children with severe sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is unknown.

OBJECTIVE

We quantified anti-type I IFN autoantibodies in a multicenter cohort of children with severe COVID-19, multisystem inflammatory syndrome in children (MIS-C), and mild SARS-CoV-2 infections.

METHODS

Circulating anti-IFN-α2 antibodies were measured by a radioligand binding assay. Whole-exome sequencing, RNA sequencing, and functional studies of peripheral blood mononuclear cells were used to study any patients with levels of anti-IFN-α2 autoantibodies exceeding the assay's positive control.

RESULTS

Among 168 patients with severe COVID-19, 199 with MIS-C, and 45 with mild SARS-CoV-2 infections, only 1 had high levels of anti-IFN-α2 antibodies. Anti-IFN-α2 autoantibodies were not detected in patients treated with intravenous immunoglobulin before sample collection. Whole-exome sequencing identified a missense variant in the ankyrin domain of NFKB2, encoding the p100 subunit of nuclear factor kappa-light-chain enhancer of activated B cells, aka NF-κB, essential for noncanonical NF-κB signaling. The patient's peripheral blood mononuclear cells exhibited impaired cleavage of p100 characteristic of NFKB2 haploinsufficiency, an inborn error of immunity with a high prevalence of autoimmunity.

CONCLUSIONS

High levels of anti-IFN-α2 autoantibodies in children and adolescents with MIS-C, severe COVID-19, and mild SARS-CoV-2 infections are rare but can occur in patients with inborn errors of immunity.

Understanding clinical and biological heterogeneity to advance precision medicine in paediatric acute respiratory distress syndrome

Paediatric acute respiratory distress syndrome (PARDS) is a heterogeneous clinical syndrome that is associated with high rates of mortality and long-term morbidity. Factors that distinguish PARDS from adult acute respiratory distress syndrome (ARDS) include changes in developmental stage and lung maturation with age, precipitating factors, and comorbidities. No specific treatment is available for PARDS and management is largely supportive, but methods to identify patients who would benefit from specific ventilation strategies or ancillary treatments, such as prone positioning, are needed. Understanding of the clinical and biological heterogeneity of PARDS, and of differences in clinical features and clinical course, pathobiology, response to treatment, and outcomes between PARDS and adult ARDS, will be key to the development of novel preventive and therapeutic strategies and a precision medicine approach to care. Studies in which clinical, biomarker, and transcriptomic data, as well as informatics, are used to unpack the biological and phenotypic heterogeneity of PARDS, and implementation of methods to better identify patients with PARDS, including methods to rapidly identify subphenotypes and endotypes at the point of care, will drive progress on the path to precision medicine.

Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2)

OBJECTIVES

We sought to update our 2015 work in the Second Pediatric Acute Lung Injury Consensus Conference (PALICC-2) guidelines for the diagnosis and management of pediatric acute respiratory distress syndrome (PARDS), considering new evidence and topic areas that were not previously addressed.

DESIGN

International consensus conference series involving 52 multidisciplinary international content experts in PARDS and four methodology experts from 15 countries, using consensus conference methodology, and implementation science.

SETTING

Not applicable.

PATIENTS

Patients with or at risk for PARDS.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Eleven subgroups conducted systematic or scoping reviews addressing 11 topic areas: 1) definition, incidence, and epidemiology; 2) pathobiology, severity, and risk stratification; 3) ventilatory support; 4) pulmonary-specific ancillary treatment; 5) nonpulmonary treatment; 6) monitoring; 7) noninvasive respiratory support; 8) extracorporeal support; 9) morbidity and long-term outcomes; 10) clinical informatics and data science; and 11) resource-limited settings. The search included MEDLINE, EMBASE, and CINAHL Complete (EBSCOhost) and was updated in March 2022. Grading of Recommendations, Assessment, Development, and Evaluation methodology was used to summarize evidence and develop the recommendations, which were discussed and voted on by all PALICC-2 experts. There were 146 recommendations and statements, including: 34 recommendations for clinical practice; 112 consensus-based statements with 18 on PARDS definition, 55 on good practice, seven on policy, and 32 on research. All recommendations and statements had agreement greater than 80%.

CONCLUSIONS

PALICC-2 recommendations and consensus-based statements should facilitate the implementation and adherence to the best clinical practice in patients with PARDS. These results will also inform the development of future programs of research that are crucially needed to provide stronger evidence to guide the pediatric critical care teams managing these patients.

Clinical Outcomes of Acute Respiratory Failure Associated With Noninvasive and Invasive Ventilation in a Pediatric ICU

BACKGROUND

It remains unknown if pediatric patients failing initial noninvasive ventilation (NIV) experience worse clinical outcomes than those successfully treated with NIV or those primarily intubated.

METHODS

This was a single-center, retrospective review of patients admitted with acute respiratory failure to the University of Michigan pediatric intensive care or cardiothoracic ICUs and receiving NIV or invasive mechanical ventilation as first-line therapy.

RESULTS

One hundred seventy subjects met inclusion criteria and were enrolled: 65 NIV success, 55 NIV failure, and 50 invasive mechanical ventilation alone. Of those failing NIV, median time to intubation was 1.8 (interquartile range [IQR] < 1-7) h. On multivariable regression, ICU-free days were significantly different between groups (NIV success: 22.9 ± 6.9 d; NIV failure: 13.0 ± 6.6 d; invasive ventilation: 12.5 ± 6.9 d; P < .001 across all groups). Multivariable regression revealed no difference in ventilator-free days between NIV failure and invasive ventilation groups (15.4 ± 10.1 d vs 15.9 ± 9.7 d, P = .71). Of 64 subjects (37.6%) meeting Pediatric Acute Lung Injury Consensus Conference pediatric ARDS criteria, only 14% were successfully treated with NIV. Ventilator-free days were similar between the NIV failure and invasive ventilation groups (11.6 vs 13.2 d, P = .47). On multivariable analysis, ICU-free days were significantly different across pediatric ARDS groups (P < .001): NIV success: 20.8 + 31.7 d; NIV failure: 8.3 + 23.8 d; invasive alone: 8.9 + 23.9 d, yet no significant difference in ventilator-free days between those with NIV failure versus invasive alone (11.6 vs 13.2 d, P = .47).

CONCLUSIONS

We demonstrated that critically ill pediatric subjects unsuccessfully trialed on NIV did not experience increased ICU length of stay or fewer ventilator-free days when compared to those on invasive mechanical ventilation alone, including in the pediatric ARDS subgroup. Our findings are predicated on a median time to intubation of < 2 h in the NIV failure group and the provision of adequate monitoring while on NIV.

Analysis of inflammatory cytokines in the chest tube drainage of post-operative superior cavopulmonary connection patients

INTRODUCTION

Prolonged pleural effusions are common post Fontan operation and are associated with morbidity. Fontan pleural effusions have elevated proinflammatory cytokines. Little is known about the chest tube drainage after a superior cavopulmonary connection. We examined the chest tube drainage and the inflammatory profiles in post-operative superior cavopulmonary connection patients.

METHODS

This prospective cohort study enrolled 25 patients undergoing superior cavopulmonary connection and 10 age-similar controls. Data are also compared to 25 previously published Fontan patients and their 15 age-similar controls. Chest tube samples were analysed with a 17-cytokine BioPlex Assay. Descriptive statistics and univariate comparisons were made between groups.

RESULTS

Duration of chest tube drainage was significantly shorter in superior cavopulmonary connection patients (median 4 days, [interquartile range 3-5 days]) versus Fontan patients (10 days, [7-11 days], p < 0.0001). Cytokine concentrations were higher on post-operative day 1 in superior cavopulmonary connection patients versus Fontan patients (all p ≤ 0.01), however levels were comparable to age-similar controls. While proinflammatory IL 8, MIP-1β, and TNF-α concentrations increased in chest tube drainage of Fontan patients from post-operative day 1 to last chest tube day (all p < 0.0001), there was no change in these biomarkers in superior cavopulmonary connection patients, their controls, or Fontan controls.

CONCLUSIONS

Our study demonstrates that after superior cavopulmonary connection, proinflammatory cytokines in the chest tube drainage remain similar to biventricular controls of both age groups, unlike the significant rise over time observed in Fontan patients. Inflammation within the chest tube drainage is likely not innate to single ventricle patients.

Identification of phenotypes in paediatric patients with acute respiratory distress syndrome: a latent class analysis

BACKGROUND

Previous latent class analysis of adults with acute respiratory distress syndrome (ARDS) identified two phenotypes, distinguished by the degree of inflammation. We aimed to identify phenotypes in children with ARDS in whom developmental differences might be important, using a latent class analysis approach similar to that used in adults.

METHODS

This study was a secondary analysis of data aggregated from the Randomized Evaluation of Sedation Titration for Respiratory Failure (RESTORE) clinical trial and the Genetic Variation and Biomarkers in Children with Acute Lung Injury (BALI) ancillary study. We used latent class analysis, which included demographic, clinical, and plasma biomarker variables, to identify paediatric ARDS (PARDS) phenotypes within a cohort of children included in the RESTORE and BALI studies. The association of phenotypes with clinically relevant outcomes and the performance of paediatric data in adult ARDS classification algorithms were also assessed.

FINDINGS

304 children with PARDS were included in this secondary analysis. Using latent class analysis, a two-class model was a better fit for the cohort than a one-class model (p<0·001). Latent class analysis identified two classes: class 1 (181 [60%] of 304 patients with PARDS) and class 2 (123 [40%] of 304 patients with PARDS), referred to as phenotype 1 and 2 hereafter. Phenotype 2 was characterised by higher concentrations of inflammatory biomarkers, a higher incidence of vasopressor use, and more frequent diagnosis of sepsis, consistent with the adult hyperinflammatory phenotype. All levels of severity of PARDS were observed across both phenotypes. Children with the hyperinflammatory phenotype (phenotype 2) had worse clinical outcomes than those with the hypoinflammatory phenotype (phenotype 1), with a longer duration of mechanical ventilation (median 10·0 days [IQR 6·3-21·0] for phenotype 2 vs 6·6 days [4·1-10·8] for phenotype 1, p<0·0001), and higher incidence of mortality (17 [13·8%] of 123 patients vs four [2·2%] of 181 patients, p=0·0001). When using adult phenotype classification algorithms in children, the soluble tumour necrosis factor receptor-1 (sTNFr1), vasopressor use, and interleukin (IL)-6 variables gave an area under the curve (AUC) of 0·956, and the sTNFr1, vasopressor use, and IL-8 variables gave an AUC of 0·954, compared with the gold standard of latent class analysis.

INTERPRETATION

Latent class analysis identified two phenotypes in children with ARDS with characteristics similar to those in adults, including worse outcomes among patients with the hyperinflammatory phenotype. PARDS phenotypes should be considered in design and analysis of future clinical trials in children.

FUNDING

US National Institutes of Health.

Differences in the Genomic Profiles of Immunoparalyzed and Nonimmunoparalyzed Children With Sepsis: A Pilot Study

OBJECTIVES

Sepsis-induced immunoparalysis represents a pathologic downregulation of leukocyte function shown to be associated with adverse outcomes, although its mechanisms remain poorly understood. Our goal was to compare genome-wide gene expression profiles of immunoparalyzed and nonimmunoparalyzed children with sepsis to identify genes and pathways associated with immunoparalysis.

DESIGN

Prospective observational study.

PATIENTS

Twenty-six children with lower respiratory tract infection meeting criteria for sepsis, severe sepsis, or septic shock admitted to the PICU.

SETTING

Two tertiary care PICUs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Innate immune function was assayed ex vivo by measuring release of tumor necrosis factor-α from whole blood after incubation with lipopolysaccharide for 4 hours. Immunoparalysis was defined as a tumor necrosis factor-α production capacity less than 200 pg/mL. Ten of the 26 children were immunoparalyzed. There were 17 significant differentially expressed genes when comparing genome-wide gene expression profiles of immunoparalyzed and nonimmunoparalyzed children (false discovery rate < 0.05). Nine genes showed increased expression in immunoparalyzed children (+1.5- to +8.8-fold change). Several of these dampen the immune system. Eight showed decreased expression in immunoparalyzed children (-1.7- to -3.9-fold change), several of which are involved in early regulation and activation of immune function. Functional annotation clustering using differentially expressed genes with p value of less than 0.05 showed three clusters related to immunity with significant enrichment scores (2.2-4.5); the most significant gene ontology terms in these clusters were antigen processing and presentation and negative regulation of interleukin-6 production. Network analysis identified potential protein interactions that may be involved in the development of immunoparalysis in children.

CONCLUSIONS

In this exploratory analysis, immunoparalyzed children with sepsis showed increased expression of genes that dampen the immune system and decreased expression of genes involved in regulation and activation of the immune system. Analysis also implicated other proteins as potentially having as yet unidentified roles in the development of immunoparalysis.

Patterns of Delirium in a Pediatric Intensive Care Unit and Associations With Noise Pollution

OBJECTIVE

Delirium is a common problem in the Pediatric Intensive Care Unit (PICU) and is associated with increased length of stay, cost and mortality. This study evaluated the relationship between noise pollution and delirium risk. Design: This is a Quality Improvement (QI) initiative at an academic PICU. Sound levels were monitored and patients were screened for delirium using the Cornell Assessment of Pediatric Delirium (CAPD). Setting PICU Patients: All PICU patients Interventions: None Measurements and Main Results: Over the 83-week study period (2015-2017), the median [IQR] CAPD score was 8 [3 to 14]. Nursing compliance with the CAPD was 72.2%. The proportion of patients screening positive for delirium (CAPD ≥ 9) was 45.9%. A total of 329 711 hly decibel (dB) measurements were collected and reported. Occupied rooms were louder than unoccupied rooms (51.8 [51.6-51.9] dB vs. 49.8 [49.7-49.9] dB, respectively, p < 0.001). Days (10 AM to 4 PM) were louder than nights (11 PM to 5 AM) (52.8 [52.7-53.0] dB vs. 50.7 [49.9-51.5] dB, respectively p < 0.001) in occupied rooms. Winter (Nov-Feb) months were louder than summer (May-Aug) months (52.0 [51.8-52.3] dB vs. 51.5 [51.3-51.7] dB, respectively, p < 0.002) in occupied rooms. Median weekly nighttime noise levels and CAPD scores demonstrated a correlation coefficient of 0.6 (p < 0.001). Median weekly risk of mortality (ROM) and CAPD scores demonstrated a correlation coefficient of 0.15 (p < 0.01). Conclusions: Significant noise pollution exists in the PICU with a moderate correlation between nighttime noise levels and CAPD scores. This could potentially implicate noise pollution as a risk factor for the development of delirium.

Thrombomodulin is associated with increased mortality and organ failure in mechanically ventilated children with acute respiratory failure: biomarker analysis from a multicenter randomized controlled trial

BACKGROUND

Acute respiratory failure (ARF) can progress to acute respiratory distress syndrome and death. Biomarkers may allow for risk stratification and prognostic enrichment in ARF. Thrombomodulin (TM) is a transmembrane antithrombotic mediator expressed in endothelial cells. It is cleaved into its soluble form (sTM) during inflammation and vascular injury. Levels of sTM correlate with inflammation and end organ dysfunction.

METHODS

This was a prospective observational study of 432 patients aged 2 weeks-17 years requiring invasive mechanical ventilation. It was ancillary to the multicenter clinical trial, Randomized Evaluation of Sedation Titration for Respiratory Failure (RESTORE). After consent, patients had up to 3 plasma samples collected at 24-h intervals within 5 days after intubation. sTM was assayed by ELISA. The Hazard ratio (HR) for 90-day mortality was determined by Cox regression. Mixed effect models (MEM) were used to test for association with extrapulmonary multiorgan failure (MOF) and oxygenation index (OI). Age, race, sex and PRISM-III scores were used as confounding variables for multivariable analyses.

RESULTS

sTM values ranged from 16.6 to 670.9 ng/ml within 5 days after intubation. Higher sTM was associated with increased 90-day mortality (n = 432, adjusted HR = 1.003, p = 0.02) and worse OI in the first 5 days after intubation (n = 252, Estimate = 0.02, p < 0.01). Both initial and slope of sTM were associated with increased extrapulmonary MOF in unadjusted and adjusted analyses (Intercept, Estimate = 0.003, p < 0.0001; and slope, Estimate = 0.01, p = 0.0009, n = 386).

CONCLUSIONS

Plasma sTM is associated with mortality, severity of hypoxic respiratory failure and worsening extrapulmonary MOF in children with ARF. This suggests a role of vascular injury in the pathogenesis of ARF and provides potential applicability towards targeted therapies.

TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT00814099 . In healthy lung endothelium, thrombomodulin (TM) recruits thrombin to activate Protein-C (PC/APC), that inhibits plasminogen activator-1 (PAI-1) and thrombosis. In inflamed and damaged endothelium, TM is cleaved into its soluble form (sTM), precluding its usual regulation of thrombosis. In this study, we measured plasma sTM levels in pediatric patients with respiratory failure and found that sTM correlated with mortality and other clinical markers of poor outcomes.

Association of patient weight status with plasma surfactant protein D, a biomarker of alveolar epithelial injury, in children with acute respiratory failure

AIMS AND OBJECTIVES

Alveolar epithelial injury is a key determinant of acute respiratory failure (ARF) severity. Plasma surfactant protein D (SP-D), a biomarker of alveolar epithelial injury, is lower in obese adults with ARF compared to their lean peers. We aimed to determine if children with ARF have similar variance in plasma SP-D associated with their weight status on admission.

METHODS

Plasma SP-D was measured on days 0, 1, or 2 in children (1-18 years) with ARF enrolled in the genetic variation and biomarkers in children with acute lung injury and RESTORE studies. Weight classification (underweight, normal, overweight, and obese) was based on body mass index or weight-for-height z-scores. Associations between weight group and SP-D on each day were tested.

RESULTS

Inclusion criteria were met in 212 subjects, 24% were obese. There were no differences among weight groups in SP-D levels on days 0 and 1. However, on day 2, there was a statistically significant linear trend for lower SP-D levels as weight increased in both the univariate analysis (P = .02) and when adjusting for age, ethnicity, and diagnosis of pediatric acute respiratory distress syndrome (P = .05).

CONCLUSIONS

Obesity was associated with lower plasma SP-D levels on day 2 of ARF. This finding may be explained by altered ARF pathogenesis in obese individuals or a reduced incidence of ventilator-induced lung injury.

The common K333Q polymorphism in long-chain acyl-CoA dehydrogenase (LCAD) reduces enzyme stability and function

The fatty acid oxidation enzyme long-chain acyl-CoA dehydrogenase (LCAD) is expressed at high levels in human alveolar type II (ATII) cells in the lung. A common polymorphism causing an amino acid substitution (K333Q) was previously linked to a loss of LCAD antigen in the lung tissue in sudden infant death syndrome. However, the effects of the polymorphism on LCAD function has not been tested. The present work evaluated recombinant LCAD K333Q. Compared to wild-type LCAD protein, LCAD K333Q exhibited significantly reduced enzymatic activity. Molecular modeling suggested that K333 is within interacting distance of the essential FAD cofactor, and the K333Q protein showed a propensity to lose FAD. Exogenous FAD only partially rescued the activity of LCAD K333Q. LCAD K333Q protein was less stable than wild-type when incubated at physiological temperatures, likely explaining the observation of dramatically reduced LCAD antigen in primary ATII cells isolated from individuals homozygous for K333Q. Despite the effect of K333Q on activity, stability, and antigen levels, the frequency of the polymorphism was not increased among infants and children with lung disease.

Early Use of Adjunctive Therapies for Pediatric Acute Respiratory Distress Syndrome: A PARDIE Study

Rationale: Few data exist to guide early adjunctive therapy use in pediatric acute respiratory distress syndrome (PARDS).Objectives: To describe contemporary use of adjunctive therapies for early PARDS as a framework for future investigations.Methods: This was a preplanned substudy of a prospective, international, cross-sectional observational study of children with PARDS from 100 centers over 10 study weeks.Measurements and Main Results: We investigated six adjunctive therapies for PARDS: continuous neuromuscular blockade, corticosteroids, inhaled nitric oxide (iNO), prone positioning, high-frequency oscillatory ventilation (HFOV), and extracorporeal membrane oxygenation. Almost half (45%) of children with PARDS received at least one therapy. Variability was noted in the median starting oxygenation index of each therapy; corticosteroids started at the lowest oxygenation index (13.0; interquartile range, 7.6-22.0) and HFOV at the highest (25.7; interquartile range, 16.7-37.3). Continuous neuromuscular blockade was the most common, used in 31%, followed by iNO (13%), corticosteroids (10%), prone positioning (10%), HFOV (9%), and extracorporeal membrane oxygenation (3%). Steroids, iNO, and HFOV were associated with comorbidities. Prone positioning and HFOV were more common in middle-income countries and less frequently used in North America. The use of multiple ancillary therapies increased over the first 3 days of PARDS, but there was not an easily identifiable pattern of combination or order of use.Conclusions: The contemporary description of prevalence, combinations of therapies, and oxygenation threshold for which the therapies are applied is important for design of future studies. Region of the world, income, and comorbidities influence adjunctive therapy use and are important variables to include in PARDS investigations.

Impact of Bilateral Infiltrates on Inflammatory Biomarker Levels and Clinical Outcomes of Children With Oxygenation Defect

OBJECTIVES

The 2015 definition for pediatric acute respiratory distress syndrome did not require the presence of bilateral infiltrates. We tested the hypothesis that pediatric patients meeting oxygenation criteria for pediatric acute respiratory distress syndrome but without bilateral infiltrates would have different inflammatory biomarker levels and clinical outcomes than those with bilateral infiltrates.

DESIGN

Secondary analysis of a prospective cohort study.

SETTING

Twenty-two PICUs.

PATIENTS

Four-hundred forty-six patients age 2 weeks to 17 years intubated for respiratory failure with oxygenation index greater than or equal to 4 or oxygenation saturation index greater than or equal to 5 on the day of intubation or the day after.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients with bilateral infiltrates, either on the day of intubation or within the following 2 days, were compared with children who never developed bilateral infiltrates. Two analyses were performed to test 1) whether bilateral infiltrates are associated with elevated interleukin-1 receptor antagonist or interleukin-8 and 2) whether bilateral infiltrates are associated with worse clinical outcomes. Patients with bilateral infiltrates more often had a primary diagnosis of pneumonia (41% vs 28%; p = 0.02) and less often asthma (8% vs 23%; p < 0.01). After controlling for age, gender, and primary diagnosis, interleukin-1 receptor antagonist was higher on study days 1 and 2 in patients with bilateral infiltrates. There was no difference in interleukin-8 levels. After adjusting for age, gender, Pediatric Risk of Mortality score, and severity of oxygenation defect, presence of bilateral infiltrates was associated with longer duration of mechanical ventilation in survivors (hazard ratio, 0.64; 95% CI, 0.49-0.82; p < 0.01); this association was independent of primary diagnosis. Overall mortality was 9%; mortality was higher in those without bilateral infiltrates (14% vs 8%; p = 0.04).

CONCLUSIONS

Children meeting pediatric acute respiratory distress syndrome oxygenation criteria with bilateral infiltrates on chest radiograph experience a more intense early inflammatory response. Bilateral infiltrates are associated with longer time on the ventilator independent of oxygenation defect severity.

Surfactant Protein D Is Associated With Severe Pediatric ARDS, Prolonged Ventilation, and Death in Children With Acute Respiratory Failure

BACKGROUND

Elevated surfactant protein D (SP-D) is a relatively specific indicator of lung injury and is associated with both acute and chronic lung disease in adults and respiratory distress syndrome in premature infants. The relationship between plasma SP-D and lung injury in children with acute respiratory failure is unclear.

RESEARCH QUESTION

Is plasma SP-D associated with lung injury or outcome in children with acute respiratory failure?

STUDY DESIGN AND METHODS

This was a prospective cohort study in children 2 weeks to 17 years of age with acute respiratory failure who participated in the BALI multi-center study. Analyses were done using SP-D levels in plasma from the first sample taken on either the day of intubation or one of the following 2 days. SP-D level was measured by enzyme-linked immunosorbent assay.

RESULTS

Plasma samples from 350 patients were used in the analysis; 233 had pediatric ARDS (PARDS). SP-D levels varied across primary diagnoses (P < .001). Elevated SP-D levels were associated with severe PARDS after adjusting for age, pediatric risk of mortality III (PRISM-III), and primary diagnosis (OR = 1.02; CI = 1.01-1.04; P = .011). Multivariable analyses also indicated that elevated SP-D levels were associated with death (OR = 1.02; CI = 1.01-1.04; P = .004), duration of mechanical ventilation (P = .012), PICU length of stay (P = .019), and highest oxygenation index (P = .040). SP-D levels also correlated with age (r_s = 0.16, P = .002).

INTERPRETATION

Elevated plasma SP-D levels are associated with severe PARDS and poor outcomes in children with acute respiratory failure. Future studies will determine whether SP-D can be used to predict the degree of lung injury or response to treatment and whether SP-D is useful in identifying PARDS endotypes.

A prospective investigation of interleukin-8 levels in pediatric acute respiratory failure and acute respiratory distress syndrome

Background

The association of plasma interleukin-8 (IL-8), or IL-8 genetic variants, with pediatric acute respiratory distress syndrome (PARDS) in children with acute respiratory failure at risk for PARDS has not been examined. The purpose of this study was to examine the association of early and sequential measurement of plasma IL-8 and/or its genetic variants with development of PARDS and other clinical outcomes in mechanically ventilated children with acute respiratory failure.

Methods

This was a prospective cohort study of children 2 weeks to 17 years of age with acute airways and/or parenchymal lung disease done in 22 pediatric intensive care units participating in the multi-center clinical trial, Randomized Evaluation of Sedation Titration for Respiratory Failure (RESTORE). Plasma IL-8 levels were measured within 24 h of consent and 24 and 48 h later. DNA was purified from whole blood, and IL-8 single nucleotide polymorphisms, rs4073, rs2227306, and rs2227307, were genotyped.

Results

Five hundred forty-nine patients were enrolled; 480 had blood sampling. Plasma IL-8 levels ranged widely from 4 to 7373 pg/mL. Highest IL-8 levels were observed on the day of intubation with subsequent tapering. Levels of IL-8 varied significantly across primary diagnoses with the highest levels occurring in patients with sepsis and the lowest levels in those with asthma. Plasma IL-8 was strongly correlated with oxygenation defect and severity of illness. IL-8 was consistently higher in PARDS patients compared to those without PARDS; levels were 4–12 fold higher in non-survivors compared to survivors. On multivariable analysis, IL-8 was independently associated with death, duration of mechanical ventilation, and PICU length of stay on all days measured, but was not associated with PARDS development. There was no association between the IL-8 single nucleotide polymorphisms, rs4073, rs2227306, and rs2227307, and PARDS development or plasma IL-8 level.

Conclusions

When measured sequentially, plasma IL-8 was robustly associated with multiple, relevant clinical outcomes including mortality, but was not associated with PARDS development. The wide range of plasma IL-8 levels exhibited in this cohort suggests that further study into the heterogeneity of this patient population and its impact on individual responses to PARDS treatment is warranted.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2342-8) contains supplementary material, which is available to authorized users.

Loss of myeloid-specific protein phosphatase 2A enhances lung injury and fibrosis and results in IL-10-dependent sensitization of epithelial cell apoptosis

Protein phosphatase 2A (PP2A), a ubiquitously expressed Ser/Thr phosphatase is an important regulator of cytokine signaling and cell function. We previously showed that myeloid-specific deletion of PP2A (LysM^crePP2A^-/-) increased mortality in a murine peritoneal sepsis model. In the current study, we assessed the role of myeloid PP2A in regulation of lung injury induced by lipopolysaccharide (LPS) or bleomycin delivered intratracheally. LysM^crePP2A^-/- mice experienced increased lung injury in response to both LPS and bleomycin. LysM^crePP2A^-/- mice developed more exuberant fibrosis in response to bleomycin, elevated cytokine responses, and chronic myeloid inflammation. Bone marrow-derived macrophages (BMDMs) from LysM^crePP2A^-/- mice showed exaggerated inflammatory cytokine release under conditions of both M1 and M2 activation. Notably, secretion of IL-10 was elevated under all stimulation conditions, including activation of BMDMs by multiple Toll-like receptor ligands. Supernatants collected from LPS-stimulated LysM^crePP2A^-/- BMDMs induced epithelial cell apoptosis in vitro but this effect was mitigated when IL-10 was also depleted from the BMDMs by crossing LysM^crePP2A^-/- mice with systemic IL-10^-/- mice (LysM^crePP2A^-/- × IL-10^-/-) or when IL-10 was neutralized. Despite these findings, IL-10 did not directly induce epithelial cell apoptosis but sensitized epithelial cells to other mediators from the BMDMs. Taken together our results demonstrate that myeloid PP2A regulates production of multiple cytokines but that its effect is most pronounced on IL-10 production. Furthermore, IL-10 sensitizes epithelial cells to apoptosis in response to myeloid-derived mediators, which likely contributes to the pathogenesis of lung injury and fibrosis in this model.

Identification of molecular signatures of cystic fibrosis disease status with plasma-based functional genomics

Although cystic fibrosis (CF) is attributed to dysfunction of a single gene, the relationships between the abnormal gene product and the development of inflammation and progression of lung disease are not fully understood, which limits our ability to predict an individual patient's clinical course and treatment response. To better understand CF progression, we characterized the molecular signatures of CF disease status with plasma-based functional genomics. Peripheral blood mononuclear cells (PBMCs) from healthy donors were cultured with plasma samples from CF patients ( n = 103) and unrelated, healthy controls ( n = 31). Gene expression levels were measured with an Affymetrix microarray (GeneChip Human Genome U133 Plus 2.0). Peripheral blood samples from a subset of the CF patients ( n = 40) were immunophenotyped by flow cytometry, and the data were compared with historical data for age-matched healthy controls ( n = 351). Plasma samples from another subset of CF patients ( n = 56) and healthy controls ( n = 16) were analyzed by multiplex enzyme-linked immunosorbent assay (ELISA) for numerous cytokines and chemokines. Principal component analysis and hierarchical clustering of induced transcriptional data revealed disease-specific plasma-induced PBMC profiles. Among 1,094 differentially expressed probe sets, 51 genes were associated with pancreatic sufficient status, and 224 genes were associated with infection with Pseudomonas aeruginosa. The flow cytometry and ELISA data confirmed that various immune modulators are relevant contributors to the CF molecular signature. This study provides strong evidence for distinct molecular signatures among CF patients. An understanding of these molecular signatures may lead to unique molecular markers that will enable more personalized prognoses, individualized treatment plans, and rapid monitoring of treatment response.

Mechanisms of red blood cell transfusion-related immunomodulation

Red blood cell (RBC) transfusion is common in critically ill, postsurgical, and posttrauma patients in whom both systemic inflammation and immune suppression are associated with adverse outcomes. RBC products contain a multitude of immunomodulatory mediators that interact with and alter immune cell function. These interactions can lead to both proinflammatory and immunosuppressive effects. Defining clinical outcomes related to immunomodulatory effects of RBCs in transfused patients remains a challenge, likely due to complex interactions between individual blood product characteristics and patient-specific risk factors. Unpacking these complexities requires an in-depth understanding of the mechanisms of immunomodulatory effects of RBC products. In this review, we outline and classify potential mediators of RBC transfusion-related immunomodulation and provide suggestions for future research directions.

Quality Improvement Initiative to Reduce Pediatric Intensive Care Unit Noise Pollution With the Use of a Pediatric Delirium Bundle

OBJECTIVES:

Noise pollution in pediatric intensive care units (PICU) contributes to poor sleep and may increase risk of developing delirium. The Environmental Protection Agency (EPA) recommends <45 decibels (dB) in hospital environments. The objectives are to assess the degree of PICU noise pollution, to develop a delirium bundle targeted at reducing noise, and to assess the effect of the bundle on nocturnal noise pollution.

METHODS:

This is a QI initiative at an academic PICU. Thirty-five sound sensors were installed in patient bed spaces, hallways, and common areas. The pediatric delirium bundle was implemented in 8 pilot patients (40 patient ICU days) while 108 non-pilot patients received usual care over a 28-day period.

RESULTS:

A total of 20,609 hourly dB readings were collected. Hourly minimum, average, and maximum dB of all occupied bed spaces demonstrated medians [interquartile range] of 48.0 [39.0-53.0], 52.8 [48.1-56.2] and 67.0 [63.5-70.5] dB, respectively. Bed spaces were louder during the day (10AM to 4PM) than at night (11PM to 5AM) (53.5 [49.0-56.8] vs. 51.3 [46.0-55.3] dB, P < 0.01). Pilot patient rooms were significantly quieter than non-pilot patient rooms at night (n=210, 45.3 [39.7-55.9]) vs. n=1841, 51.2 [46.9-54.8] dB, P < 0.01). The pilot rooms compliant with the bundle had the lowest hourly nighttime average dB (44.1 [38.5-55.5]).

CONCLUSIONS:

Substantial noise pollution exists in our PICU, and utilizing the pediatric delirium bundle led to a significant noise reduction that can be perceived as half the loudness with hourly nighttime average dB meeting the EPA standards when compliant with the bundle.

Myeloid-Specific Gene Deletion of Protein Phosphatase 2A Magnifies MyD88- and TRIF-Dependent Inflammation following Endotoxin Challenge

Protein phosphatase 2A (PP2A) is a member of the intracellular serine/threonine phosphatases. Innate immune cell activation triggered by pathogen-associated molecular patterns is mediated by various protein kinases, and PP2A plays a counter-regulatory role by deactivating these kinases. In this study, we generated a conditional knockout of the α isoform of the catalytic subunit of PP2A (PP2ACα). After crossing with myeloid-specific cre-expressing mice, effective gene knockout was achieved in various myeloid cells. The myeloid-specific knockout mice (lyM-PP2A^fl/fl) showed higher mortality in response to endotoxin challenge and bacterial infection. Upon LPS challenge, serum levels of TNF-α, KC, IL-6, and IL-10 were significantly increased in lyM-PP2A^fl/fl mice, and increased phosphorylation was observed in MAPK pathways (p38, ERK, JNK) and the NF-κB pathway (IKKα/β, NF-κB p65) in bone marrow-derived macrophages (BMDMs) from knockout mice. Heightened NF-κB activation was not associated with degradation of IκBα; instead, enhanced phosphorylation of the NF-κB p65 subunit and p38 phosphorylation-mediated TNF-α mRNA stabilization appear to contribute to the increased TNF-α expression. In addition, increased IL-10 expression appears to be due to PP2ACα-knockout-induced IKKα/β hyperactivation. Microarray experiments indicated that the Toll/IL-1R domain-containing adaptor inducing IFN-β/ TNFR-associated factor 3 pathway was highly upregulated in LPS-treated PP2ACα-knockout BMDMs, and knockout BMDMs had elevated IFN-α/β production compared with control BMDMs. Serum IFN-β levels from PP2ACα-knockout mice treated with LPS were also greater than those in controls. Thus, we demonstrate that PP2A plays an important role in regulating inflammation and survival in the setting of septic insult by targeting MyD88- and Toll/IL-1R domain-containing adaptor inducing IFN-β-dependent pathways.

Association of polymorphisms in genes of factors involved in regulation of splicing of cystic fibrosis transmembrane conductance regulator mRNA with acute respiratory distress syndrome in children with pneumonia

BACKGROUND

Previous work has demonstrated a strong association between lung injury in African American children with pneumonia and a polymorphic (TG)mTn region in cystic fibrosis transmembrane conductance (CFTR) involved in the generation of a nonfunctional CFTR protein lacking exon 9. A number of splicing factors that regulate the inclusion/exclusion of exon 9 have been identified. The objective of this study was to determine whether genetic variants in these splicing factors were associated with acute respiratory distress syndrome (ARDS) in children with pneumonia.

METHODS

This is a prospective cohort genetic association study of lung injury in African American and non-Hispanic Caucasian children with community-acquired pneumonia evaluated in the emergency department or admitted to the hospital. Linkage-disequilibrium-tag single nucleotide polymorphisms (LD-tag SNPs) in genes of the following splicing factors (followed by gene name) involved in exon 9 skipping PTB1 (PTBP1), SRp40 (SFRS1), SR2/ASF (SFRS5), TDP-43 (TARDBP), TIA-1 (TIA1), and U2AF(65) (U2AF2) were genotyped. SNPs in the gene of the splicing factor CELF2 (CELF2) were selected by conservation score. Multivariable analysis was used to examine association between genotypes and ARDS.

RESULTS

The African American cohort (n = 474) had 29 children with ARDS and the non-Hispanic Caucasian cohort (n = 304) had 32 children with ARDS. In the African American group multivariable analysis indicated that three variants in CELF2, rs7068124 (p = 0.004), rs3814634 (p = 0.032) and rs10905928 (p = 0.044), and two in TIA1, rs2592178 (p = 0.005) and rs13402990 (p = 0.018) were independently associated with ARDS. In the non-Hispanic Caucasian group, a single variant in CELF2, rs2277212 (p = 0.014), was associated with increased risk of developing ARDS.

CONCLUSIONS

The data indicate that SNPs in CELF2 may be associated with the risk of developing ARDS in both African American and non-Hispanic Caucasian children with pneumonia and suggest that the potential role of the splicing factor CELF2 in ARDS should be explored further.

Refining the continuum of CFTR-associated disorders in the era of newborn screening

Clinical heterogeneity in cystic fibrosis (CF) often causes diagnostic uncertainty in infants without symptoms and in older patients with milder phenotypes. We performed a cross-sectional evaluation of a comprehensive set of clinical and laboratory descriptors in a physician-defined cohort (N = 376; Children's Hospital of Wisconsin and the American Family Children's Hospital CF centers in Milwaukee and Madison, WI, USA) to determine the robustness of categorizing CF (N = 300), cystic fibrosis transmembrane conductance regulator (CFTR)-related disorder (N = 19), and CFTR-related (CRMS) metabolic syndrome (N = 57) according to current consensus guidelines. Outcome measures included patient demographics, clinical measures, sweat chloride levels, CFTR genotype, age at diagnosis, airway microbiology, pancreatic function, infection, and nutritional status. The CF cohort had a significantly higher median sweat chloride level (105 mmol/l) than CFTR-related disorder patients (43 mmol/l) and CFTR-related metabolic syndrome patients (35 mmol/l; p ≤ 0.001). Patient groups significantly differed in pancreatic sufficiency, immunoreactive trypsinogen levels, sweat chloride values, genotype, and positive Pseudomonas aeruginosa cultures (p ≤ 0.001). An automated classification algorithm using recursive partitioning demonstrated concordance between physician diagnoses and consensus guidelines. Our analysis suggests that integrating clinical information with sweat chloride levels, CFTR genotype, and pancreatic sufficiency provides a context for continued longitudinal monitoring of patients for personalized and effective treatment.

Lack of association of the caspase-12 long allele with community-acquired pneumonia in people of African descent

Community-acquired pneumonia (CAP) is a common cause of sepsis. Active full-length caspase-12 (CASP12L), confined to the people of African descent, has been associated with increased susceptibility to and mortality from severe sepsis. The objective of this study was to determine whether CASP12L was a marker for susceptibility and/or severity of CAP. We examined three CAP cohorts and two control populations: 241 adult Memphis African American CAP patients, 443 pediatric African American CAP patients, 90 adult South African CAP patients, 120 Memphis healthy adult African American controls and 405 adult Chicago African American controls. Clinical outcomes including mortality, acute respiratory distress syndrome (ARDS), septic shock or severe sepsis, need for mechanical ventilation, and S. pneumoniae bacteremia. Neither in the three individual CAP cohorts nor in the combined CAP cohorts, was mortality in CASP12L carriers significantly different from that in non-CASP12L carriers. No statistically significant association between genotype and any measures of CAP severity was found in any cohort. We conclude that the functional CASP12L allele is not a marker for susceptibility and/or severity of CAP.

Transcriptional signatures as a disease-specific and predictive inflammatory biomarker for type 1 diabetes

The complex milieu of inflammatory mediators associated with many diseases is often too dilute to directly measure in the periphery, necessitating development of more sensitive measurements suitable for mechanistic studies, earlier diagnosis, guiding therapeutic decisions and monitoring interventions. We previously demonstrated that plasma samples from recent-onset type 1 diabetes (RO T1D) patients induce a proinflammatory transcriptional signature in freshly drawn peripheral blood mononuclear cells (PBMCs) relative to that of unrelated healthy controls (HC). Here, using cryopreserved PBMC, we analyzed larger RO T1D and HC cohorts, examined T1D progression in pre-onset samples, and compared the RO T1D signature to those associated with three disorders characterized by airway infection and inflammation. The RO T1D signature, consisting of interleukin-1 cytokine family members, chemokines involved in immunocyte chemotaxis, immune receptors and signaling molecules, was detected during early pre-diabetes and found to resolve post-onset. The signatures associated with cystic fibrosis patients chronically infected with Pseudomonas aeruginosa, patients with confirmed bacterial pneumonia, and subjects with H1N1 influenza all reflected immunological activation, yet each were distinct from one another and negatively correlated with that of T1D. This study highlights the remarkable capacity of cells to serve as biosensors capable of sensitively and comprehensively differentiating immunological states.

MAPK and JAK-STAT signaling pathways are involved in the oxidative stress-induced decrease in expression of surfactant protein genes

Oxidative stress is generated by reactive oxygen species (ROS) including hydrogen peroxide (H(2)O(2)), hydroxyl radical (•OH ) and superoxide anion (O(2--)), which are produced as by-products of cellular metabolism. An imbalance in cellular redox status is a potent pathogenic factor that contributes to various chronic inflammatory diseases. In this study, we demonstrate that H(2)O(2 )decreases surfactant protein A, B and ABCA3 mRNA level, and increases SP-D mRNA level in human pulmonary lung epithelial cells. The decreased mRNA level of SP-A and SP-B were significant with a maximum inhibition of 79 and 87%, respectively by 150 µM H(2)O(2 )after 24 hrs of incubation. In addition, ABCA3 mRNA level was decreased with a maximum inhibition of 55% by 150 µM H(2)O(2 )after 12 hrs of incubation. In contrast, 150 µM H(2)O(2 )caused the SP-D mRNA level to increase to 200% of control after 8 hrs of incubation. The H(2)O(2)-induced gene repression or activation of SP-A, SP-B, SP-D and ABCA3 was blocked by pretreatment with the antioxidants N-acetyl-L-cysteine (NAC) and catalase. Furthermore, the inhibition of SP-A and SP-B was associated with reduced thyroid transcription factor -1 (TTF-1) DNA binding activity, and this reduced TTF-1 binding activity may be due to decreased TTF-1 protein expression level. The analyses of signal transduction pathways that may play a role in the regulation of gene expression by H(2)O(2 )using several specific inhibitors showed that U0126, an inhibitor of ERK1/2 upstream kinase MEK1/2, blocked both H(2)O(2)-induced inhibition of SP-A and SP-B gene expression, whereas SB203580, an inhibitor of p38 MAPK, partially blocked H(2)O(2)-mediated inhibition of SP-A gene expression but not SP-B expression. In contrast, AG-490, a specific inhibitor of JAK-STAT pathway, blocked H(2)O(2)-mediated inhibition of SP-B gene expression but not SP-A expression. Immunoblot analyses using specific phosphor-antibodies demonstrated that ERK1/2, p38 MAPK and STAT3 are phosphorylated by oxidative stress suggesting that H(2)O(2)-induced inhibition of SP-A and SP-B gene expression is associated with MAPK and JAKSTAT signaling pathway. These data, therefore, suggest that H(2)O(2 )affects SP-A and SP-B gene regulation by reducing TTF-1 DNA binding activity via MAPKs or STAT signaling pathways.

Alpha-adrenergic receptor gene polymorphisms and cardiovascular reactivity to stress in Black adolescents and young adults

Cardiovascular reactivity to stress and α-adrenergic receptor (α-AR) function may contribute to the development of hypertension. As Black Americans have an increased risk of hypertension, we evaluated associations between α(1A) -AR (Arg492Cys), α(2A) -AR (-1291C/G), and α(2B) -AR (Ins/Del301-303) gene variants and cardiovascular reactivity in 500 normotensive Black youth. Heart rate, preejection period, total peripheral resistance, and blood pressure were measured during cold and psychological stress. The Arg492Cys polymorphism in the α(1A) -AR gene was associated with heart rate reactivity to stress, but the association depended on sex. The -1291C/G promoter polymorphism in the α(2A) -AR gene was associated with vascular reactivity to stress; vasoconstriction increased as a linear function of the number of copies of the variant G allele. Thus, specific associations emerged between genetic variations in α-Ars and cardiovascular reactivity in young Blacks.

Role of angiotensin-converting enzyme gene polymorphism in persistent pulmonary hypertension of the newborn

AIM

To evaluate the association of angiotensin-converting enzyme (ACE) gene polymorphism with risk/severity of persistent pulmonary hypertension of the newborn (PPHN) among at risk infants.

METHODS

Infants ≥ 34 weeks with respiratory distress at birth were recruited. PPHN was diagnosed clinically and by cardiac echocardiogram. Control group consisted of infants with respiratory distress who did not develop PPHN. ACE genotyping (DD, II, DI genotypes) and serum ACE levels were determined.

RESULTS

A total of 120 infants were included (PPHN = 44; control = 76). Frequency of ACE DD genotype was not different between the two groups of infants (25% versus 33%). Among PPHN infants, severity of illness did not differ between genotypes. Mean (SD) serum ACE levels [15 (9) versus 24 (13) versus 29 (14) U/L] were positively associated with the number of D alleles and inversely associated with infants' gestational age (GA) and level of cardiovascular support.

CONCLUSION

Angiotensin-converting enzyme gene polymorphism did not impact the risk or severity of PPHN among infants ≥ 34 weeks GA.

Beta-adrenergic receptor gene polymorphisms and cardiovascular reactivity to stress in Black adolescents and young adults

Cardiovascular reactivity to stress and beta-adrenergic receptor (beta-AR) function may contribute to the development of hypertension. As Black Americans have an increased risk of hypertension, we evaluated associations between beta(1)-AR (Arg389Gly) and beta(2)-AR (Arg16Gly, Gln27Glu) gene variants and cardiovascular reactivity in 500 Black youth. Heart rate, preejection period, total peripheral resistance, and blood pressure reactivity were measured during cold and psychological stress. The Arg389Gly polymorphism in the beta(1)-AR was associated with preejection period reactivity in males but not in females. The Arg16Gly polymorphism in the beta(2)-AR was associated with diastolic blood pressure reactivity only during video game stress. An association between the Gln27Glu polymorphism in the beta(2)-AR and vascular reactivity depended on sex. Thus, specific patterns of associations emerged between genetic variations in beta-ARs and cardiovascular reactivity in young Blacks.

Surfactant protein A2 polymorphisms and disease severity in a respiratory syncytial virus-infected population

OBJECTIVE

To examine whether genetic variations within the surfactant protein A2 (SP-A2) gene are associated with respiratory syncytial virus (RSV) disease severity in infected children.

STUDY DESIGN

Naturally infected children aged < or =24 months were prospectively enrolled in 3 RSV seasons. SP-A2 genotyping was performed. Independent clinical predictors of disease severity were analyzed. The association of SP-A2 genetic diversity and disease severity was tested by using multivariate logistic regression models and 4 levels of disease gradation as outcome measures.

RESULTS

Homozygosity of the 1A(0) allele was protective against hospitalization (odds ratio [OR] = 0.15, P = .0010). This remained significant in African American patients (OR = 0.24, P = .042) and Caucasian patients (OR = 0.05, P = .021) after adjustment for other co-variates. Hospitalized children with the 1A(2) allele demonstrated significant protection from severe disease with univariate analyses, but only a trend for protection with multivariate analyses. Patients homozygous or heterozygous for an asparagine at amino acid position 9 were twice or more likely to need intensive care unit admission (OR = 2.15, P = .022), require intubation (OR = 3.04, P = .005), and have a hospitalization lasting > or =4 days (OR = 1.89, P = .02) compared with children homozygous for a threonine at this position.

CONCLUSIONS

SP-A2 polymorphisms are associated with the severity of RSV infection in infants.

Identification and characterization of a novel ABCA3 mutation

Mutations in the gene coding for ATP-binding cassette protein A3 (ABCA3) are recognized as a genetic cause of lung disease of varying severity. Characterization of a number of mutant ABCA3 proteins has demonstrated that the mutations generally affect intracellular localization or the ability of the protein to hydrolyze ATP. A novel heterozygous mutation that results in the substitution of cysteine for arginine at amino acid 295 in ABCA3 was identified in a premature infant with chronic respiratory insufficiency and abnormal lamellar bodies. Sequencing of DNA performed in study participants demonstrated that this was a mutation and not a common variant. Plasmid vectors containing ABCA3 with the identified novel mutation tagged with green fluorescent protein on the carboxy terminus were generated. The effect of the mutation on protein function was characterized by examining the glycosylation state of the mutant protein in transiently transfected HEK293 cells and by examining ATP hydrolysis activity of the mutant protein with a vanadate-induced nucleotide trapping assay in stably transfected HEK293 cells. The ABCA3 protein containing the R295C mutation undergoes normal glycosylation and intracellular localization but has dramatically reduced ATP hydrolysis activity (12% of wild type). The identification of one copy of this novel mutation in a premature infant with chronic respiratory insufficiency suggests that ABCA3 haploinsufficiency together with lung prematurity may result in more severe, or more prolonged, respiratory failure.

Beta2-adrenergic receptor polymorphisms in African American children with status asthmaticus

BACKGROUND

The beta2-adrenergic receptor plays a central role in the bronchodilator response to beta2-agonists in patients with asthma. Genetic polymorphisms within the gene coding for this receptor influence responsiveness of the receptor. A number of these polymorphisms differ in frequency in the African American and white populations.

OBJECTIVE

To determine the frequency of specific beta2-adrenergic receptor polymorphisms in African American children with status asthmaticus and to examine whether a specific genotype is associated with the clinical response to therapy.

DESIGN

Cohort of African American children diagnosed with status asthmaticus.

SETTING

Tertiary care children's hospital.

PATIENTS

A total of 31 African American children with status asthmaticus.

INTERVENTION

Blood samples were obtained from children at admission. Genotypes were determined by polymerase chain reaction amplification and restriction enzyme digestion.

MAIN OUTCOME MEASURES

The requirement for admission to the pediatric intensive care unit, need for mechanical ventilation, institution of various therapies, and length of stay.

RESULTS

The genotypes of the polymorphic sites at amino acid positions 16 and 27 in the beta2-adrenergic receptor were determined. There were no significant differences between the various genotypes in the percentage of children requiring pediatric intensive care unit admission, mechanical ventilation, terbutaline treatment, or length of stay. However, in children heterozygous for Glu at position 27 of the beta2-adrenergic receptor, the percentage of patients requiring aminophylline treatment, in addition to beta2-agonist therapy, was significantly higher than that seen in patients homozygous for Gln at that position (5/10 [50%] vs. 1/21 [5%], respectively; p = .002).

CONCLUSIONS

African American children with status asthmaticus who have the Gln/Glu genotype at amino acid position 27 of the beta2-adrenergic receptor may benefit from aminophylline treatment in addition to beta2-agonist therapy.

Caspases-2, -3, and -7 are involved in thapsigargin-induced apoptosis of SH-SY5Y neuroblastoma cells

Caspase-2 has been reported to play a role in the cell death observed under a number of different conditions; however, it is unclear whether caspase-2 plays a role in cell death triggered by endoplasmic reticulum (ER) stress. The purpose of this study was to determine whether caspase-2 is involved in SH-SY5Y neuroblastoma cell death caused by thapsigargin-induced ER stress. Thapsigargin treatment (1 microM, 16 hr) stimulated the proteolytic processing of caspases-2, -3, and -7, suggesting that these caspases are activated by ER stress. The role of these caspases in thapsigargin-induced cell death was examined by using cell-permeable caspase inhibitors. In the absence of pretreatment with caspase inhibitors, thapsigargin (0.1 microM, 20 hr) reduced the number of viable cells to 53.9% +/- 3.3% of starting-time control. Pretreatment for 90 min with either the pan-caspase inhibitor Z-VAD-FMK or the caspase-2-selective inhibitor Z-VDVAD-FMK inhibited thapsigargin-stimulated cell death, resulting in the number of viable cells being 115.6% +/- 5.3% (P < 0.001) and 69.3% +/- 2.9% (P < 0.01), respectively, of starting-time control. Neither the caspase-3- and -7-selective inhibitor Z-DEVD-FMK nor the caspase-9-selective inhibitor Z-LEHD-FMK significantly affected thapsigargin-stimulated cell death. An anticaspase-12-reactive protein was also identified in SH-SY5Y cells, but thapsigargin had no effect on proteolysis of this protein. These data demonstrate that caspases-2, -3, and -7 are involved in ER stress-mediated death of SH-SY5Y cells.

Genetic polymorphisms in sepsis

CONTEXT

Wide variability exists in the susceptibility to and outcome from sepsis even within similar intensive care unit populations. Some of this variability in the host may be due to genetic variation in genes coding for components of the innate immune response.

OBJECTIVE

To review the evidence for a genetic influence on the susceptibility to and outcome from sepsis.

DESIGN

Literature review.

PATIENTS

Variety of adult and pediatric patients with various critical illnesses and infections.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Susceptibility to clinical symptoms of sepsis and outcome as measured by severity of disease and mortality.

RESULTS

Polymorphisms in genes coding for proteins involved in the recognition of bacterial pathogens (Toll-like receptor 4, CD14, Fc(gamma)RIIa, and mannose-binding lectin) and the response to bacterial pathogens (tumor necrosis factor-alpha, interleukin (IL)-1alpha, IL-1beta, IL-1 receptor agonist, IL-6, IL-10, heat shock proteins, angiotensin I converting enzyme, plasminogen activator inhibitor-1) can influence the amount or function of the protein produced in response to bacterial stimuli. Evidence is discussed suggesting that some of these genetic polymorphisms influence the susceptibility to and outcome from sepsis.

CONCLUSION

Host genetic variability in the regulatory and coding regions of genes for components of the innate immune system may influence the susceptibility to and/or outcome from sepsis. The disparate results observed in many studies of polymorphisms in sepsis emphasize the need for future studies to be larger, to include the analysis of multiple polymorphisms, and to be better designed with respect to control populations to identify the degree of influence that genetic variability has on sepsis.

Association between surfactant protein B + 1580 polymorphism and the risk of respiratory failure in adults with community-acquired pneumonia

OBJECTIVE

Pulmonary surfactant protein (SP)-B plays a vital role in the formation and function of surfactant in the lung. A genetic polymorphism (SP-B + 1580) is postulated to result in diminished activity of SP-B. The objective was to determine whether the SP-B + 1580 CC genotype is associated with an increased risk of respiratory failure and ARDS in adults with community-acquired pneumonia.

DESIGN

Prospective cohort of adults diagnosed with community-acquired pneumonia.

SETTING

Hospital system.

PATIENTS

We enrolled 402 adults > or = 18 yrs of age with community-acquired pneumonia; 158 were white, 243 were African American, and one was Asian.

INTERVENTIONS

Genotypic analysis was performed on DNA isolated from whole blood using polymerase chain reaction amplification and DdeI restriction enzyme digestion.

MEASUREMENTS AND MAIN RESULTS

We recorded the requirement for mechanical ventilation, the presence of acute respiratory distress syndrome (ARDS) or septic shock, and mortality. Sixty-three patients required mechanical ventilation, 12 patients developed ARDS, and 35 patients developed septic shock. Genotypic frequencies at the SP-B + 1580 site were T/T 183 of 402 (0.45), T/C 160 of 402 (0.40), and C/C 59 of 402 (0.15). Of the 59 patients who were C/C at the SP-B + 1580 site, 21 (0.356) required mechanical ventilation, compared with 26 of 160 patients (0.163) who were T/C and 16 of 183 (0.087) patients who were T/T (p < .001). ARDS developed in five of 59 (0.085) patients with the C/C genotype, compared with six of 160 (.038) patients with T/C and one of 183 patients with T/T (0.005, p < .009). Septic shock occurred in 12 of 59 (0.203) patients with the C/C genotype, compared with 13 of 160 (0.081) patients with T/C and ten of 183 (0.055) patients with T/T (p < .001). Mortality rate was not different between the three genotypes.

CONCLUSION

Carriage of the C allele at the SP-B + 1580 site is associated with ARDS, septic shock, and the need for mechanical ventilation in adults with community-acquired pneumonia.

Atypical SCH23390 binding sites are present on bovine adrenal medullary membranes

D1-selective dopamine receptor agonists inhibit secretagogue-stimulated catecholamine secretion from bovine adrenal chromaffin cells. The purpose of the studies reported here was to use the radiolabeled D1-selective dopamine receptor antagonist, SCH23390, to characterize putative D1-like dopamine receptors responsible for this effect. Characterization of SCH23390 binding sites demonstrated an unusual pharmacological profile inconsistent with classical D1-like receptors. [125I]SCH23390 bound to adrenal medullary membranes was competed for by nonradioactive iodo-SCH23390 (Kd = 490 +/- 50 nM), but not by (+)butaclamol. Other classical D1 antagonists had little, if any, effect. Competition with dopamine receptor agonists demonstrated a relative rank order of potency profile characteristic of D1-like dopamine receptors, however, K(i)s were higher than those found in other tissues. The K(i)s for competition of [125I]SCH23390 binding by Cl-APB and SKF38393 (16 and 118 microM, respectively) are nearly identical to the IC(50)s previously observed for inhibition of secretion (9 and 100 microM, respectively). Combined these data suggest that adrenal medullary membranes contain a novel SCH23390 binding site involved in the inhibition of secretion by D1-selective agonists.

Differential inhibition of secretagogue-stimulated sodium uptake in adrenal chromaffin cells by activation of D4 and D5 dopamine receptors

Recent studies have demonstrated that D1-selective and D2-selective dopamine receptor agonists inhibit catecholamine secretion and Ca2+ uptake into bovine adrenal chromaffin cells by receptor subtypes that we have identified by PCR as D5, a member of the D1-like dopamine receptor subfamily, and D4, a member of the D2-like dopamine receptor subfamily. The purpose of this study was to determine whether activation of D5 or D4 receptors inhibits influx of Na+, which could explain inhibition of secretion and Ca2+ uptake by dopamine agonists. D1-selective agonists preferentially inhibited both dimethylphenylpiperazinium- (DMPP) and veratridine-stimulated 22Na+ influx into chromaffin cells. The D1-selective agonists chloro-APB hydrobromide (CI-APB; 100 microM) and SKF-38393 (< 00 microM) inhibited DMPP-stimulated Na+ uptake by 87.5 +/- 2.3 and 59.7 +/- 4.5%, respectively, whereas the D2-selective agonist bromocriptine (100 microM) inhibited Na+ uptake by only 22.9 +/- 5.0%. Veratridine-stimulated Na+ uptake was inhibited 95.1 +/- 3.2 and 25.7 +/- 4.7% by 100 microM CI-APB or bromocriptine, respectively. The effect of CI-APB was concentration dependent. A similar IC50 (approximately 18 microM) for inhibition of both DMPP- and veratridine-stimulated Na+ uptake was obtained. The addition of 8-bromo-cyclic AMP (1 mM) had no effect on either DMPP- or veratridine-stimulated Na+ uptake. These observations suggest that D1-selective agonists are inhibiting secretagogue-stimulated Na+ uptake in a cyclic AMP-independent manner.

Dopaminergic inhibition of catecholamine secretion from chromaffin cells: evidence that inhibition is mediated by D4 and D5 dopamine receptors

Previous studies have suggested that activation of D2-like dopamine receptors inhibits catecholamine secretion from adrenal chromaffin cells. The purpose of this study was to determine whether the activation of D1-like receptors on chromaffin cells affects either catecholamine release from the cells or the inhibition of secretion by D2-like dopamine receptors. Both D1- and D2-selective agonists inhibited secretion elicited by dimethylphenylpiperazinium (DMPP), veratridine, and high K+ levels. The D1-selective agonists 6-chloro-7,8-dihydroxy-3-allyl-1-phenyl-2,3,4,5- tetrahydro-1H-3-benzazepine (CI-APB) and SKF-38393 inhibited DMPP-stimulated catecholamine secretion in a concentration-dependent manner; 50% inhibition was obtained with approximately 10 microM CI-APB and approximately 100 microM SKF-38393. Of the D2-selective agonists, bromocriptine was a more potent inhibitor of DMPP-stimulated catecholamine release than was quinpirole. The inhibition of secretion caused by CI-APB or SKF-38393 was additive with the inhibition caused by bromocriptine. Pertussis toxin treatment (50 ng/ml, 18 h) attenuated the inhibitory effect of D2-selective, but not D1-selective, dopamine agonists. In addition, forskolin-stimulated adenylyl cyclase activity was inhibited by D2-selective, but not D1-selective, agonists. Neither D1- nor D2-selective agonists stimulated adenylyl cyclase activity in the cells, although cyclase activity was stimulated by forskolin, carbachol, and vasoactive intestinal peptide. DMPP-stimulated Ca2+ uptake was inhibited by both D1- and D2-selective dopamine agonists. PCR analysis was used to determine which of the dopamine receptor subtypes within the D1-like and D2-like subfamilies was responsible for the observed inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Down-regulation of protein kinase C activity preferentially attenuates high K(+)-stimulated tyrosine hydroxylase activity in adrenal chromaffin cells cultured with insulin-like growth factor-I

The purpose of this study was to determine whether the loss of protein kinase C (PKC) from adrenal chromaffin cells affected the enhancement of high K(+)- and forskolin-stimulated tyrosine hydroxylase (tyrosine 3-monooxygenase, EC 1.14.16.2) activity observed in cells treated with insulin-like growth factor-I (IGF-I). Forskolin-stimulated tyrosine hydroxylase activation was not affected by down-regulation of PKC. High K(+)-stimulated tyrosine hydroxylase activity decreased substantially after treating the cells for approximately 18 h with active, but not inactive, phorbol ester (300 nM). After down-regulation of PKC, high K(+)-stimulated tyrosine hydroxylase activity in cells cultured with IGF-I decreased by 61 +/- 5% (n = 14) compared to 36 +/- 8% (n = 14) in cells cultured without IGF-I. These data suggest that PKC is required for the enhancement of high K(+)-stimulated tyrosine hydroxylase activity observed with IGF-I treatment.

Insulin-like growth factor-I-enhanced secretion is abolished in protein kinase C-deficient chromaffin cells

Previous studies have demonstrated that bovine chromaffin cells cultured in medium with 10 nM insulin-like growth factor-I (IGF-I) secrete about twofold more catecholamine when exposed to secretory stimuli than do cells cultured without IGF-I. The purpose of this study was to determine whether protein kinase C (PKC) is involved in the effect of IGF-I on secretion from these cells. PKC was down-regulated in the cells by 16-18 h of treatment with beta-phorbol didecanoate (beta-PDD; 100 nM). Such treatment had no effect on high-K(+)-stimulated secretion from cells cultured without IGF-I; however, secretion from cells cultured with IGF-I was reduced to a level comparable to that in cells cultured without the peptide. The inactive isomer, alpha-PDD (100 nM), had no effect on secretion from untreated or IGF-I-treated chromaffin cells. The effect of beta-PDD was time and concentration dependent, with 100 nM beta-PDD producing a maximal effect in 8-10 h. In situ PKC activity measured in permeabilized cells treated with PMA (300 nM) was decreased by approximately 40% by 10 h and was reduced to almost basal levels by 18 h. Immunoblotting experiments demonstrated that both alpha- and epsilon-PKC were lost from the cells with time courses similar to that seen in the in situ PKC assay. Overnight treatment with the PKC inhibitor H7 (100 microM) prevented the enhanced secretion normally seen in IGF-I-treated cells, whereas HA1004 had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin-like growth factor-I enhances tyrosine hydroxylase activation in bovine chromaffin cells

Previous studies have shown that insulin-like growth factor-I (IGF-I) enhances secretagogue-stimulated Ca2+ uptake and catecholamine release in bovine chromaffin cells. This report describes the effect of IGF-I on the activity of tyrosine hydroxylase (tyrosine 3-monooxygenase, EC 1.14.16.2), the major regulatory enzyme in the pathway of catecholamine biosynthesis. Tyrosine hydroxylase activity was assayed by measuring 3,4-dihydroxyphenylalanine (Dopa) accumulation in the presence of brocresine, an inhibitor of Dopa decarboxylase. Chromaffin cells cultured in serum-free medium produced approximately 40% less Dopa when stimulated by 55 mM K+ than did cells that had been cultured in the presence of serum. Incubation of cells for 3 days in serum-free medium containing 10 nM IGF-I restored high K(+)-stimulated Dopa accumulation to a level comparable to that seen in cells cultured continuously in serum-containing medium. In eight experiments, IGF-I increased high K(+)-stimulated Dopa accumulation (expressed as picomoles per minute per milligram of protein) by 96 +/- 13%. IGF-I increased the protein content of chromaffin cells by approximately 30%; consequently, its effect on tyrosine hydroxylase activity was even greater when Dopa synthesis was expressed as picomoles per minute per 10(7) cells. IGF-I also enhanced the rate of Dopa accumulation in cells stimulated by dimethylphenylpiperazinium, 8-bromo-cyclic AMP, phorbol 12,13-dibutyrate, or Ba2+. The effect of IGF-I on high K(+)-stimulated tyrosine hydroxylase activity was measurable when enzyme activity was assayed in vitro, suggesting that this effect was due to a stable modification of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Two types of Ca2+ currents are found in bovine chromaffin cells: facilitation is due to the recruitment of one type

1. Whole-cell Ca2+ currents in cultured bovine chromaffin cells were studied using patch-clamp electrophysiology. With Ba2+ or Ca2+ as the current carriers, two separate components of whole-cell current could be distinguished by biophysical and pharmacological criteria. These components of Ca2+ current were different from T- or N-type Ca2+ channels previously described, as they were not inactivated at a holding potential of -60 mV. 2. Depolarization of the cells past -20 mV in 10 mM-Ba2+ activated a single component of Ca2+ current, called the 'standard' current. This current showed no detectable voltage-dependent inactivation, but did show marked current-dependent inactivation as steady-state inactivation (H-infinity) plots obtained in the presence of Ba2+ were quite different from those obtained from Ca2+. 3. In most chromaffin cells large pre-depolarizations or repetitive depolarizations in the physiological range activated a second component of Ca2+ current called 'facilitation'. Facilitation was observed with either Ca2+ or Ba2+ as the charge carrier. Recruiting facilitation increased whole-cell currents by an average of 60%. 4. Pre-pulses to +120 mV lasting 200 ms completely activated facilitation. Pre-pulses longer than 800 ms started to inactivate facilitation, while pre-pulses longer than 2500 ms completely inactivated this component of Ca2+ current. Because only outward currents were recorded at +120 mV, it is likely that facilitation inactivated in a voltage-dependent manner. 5. When the extracellular Ba2+ concentration was increased in the range from 2 to 90 mM activation of both facilitation and standard Ca2+ currents shifted in the depolarizing direction. In 2 mM-Ba2+ facilitation activated at potentials 10 mV more negative than the standard component, while in 90 mM-Ba2+, facilitation activated at a potential about 10 mV more depolarized than the standard component. Thus, the voltage sensor for the facilitation Ca2+ current appeared to sense more surface charge than did the standard Ca2+ current. 6. Tail currents measured at -20 and -30 mV in the absence of facilitation (without pre-pulses) showed one time constant for current deactivation. Tail currents measured with both facilitation and standard currents activated showed a significantly slower deactivation rate than that seen with the standard current alone. 7. The dihydropyridine antagonist nisoldipine (1 microM) completely suppressed the facilitation Ca2+ current even when cells were held at negative holding potentials (-80 mV). In contrast, the standard current was unaffected by 1 microM-nisoldipine, even at depolarized holding potentials (-20 mV).(ABSTRACT TRUNCATED AT 400 WORDS)

Studies on the effect of insulin-like growth factor-I on catecholamine secretion from chromaffin cells

Chromaffin cells cultured in serum-free medium secreted a smaller percentage of their catecholamine stores in response to stimulation by high K+ (55 mM) than did cells cultured in serum-containing medium. Addition of insulin-like growth factor-I (IGF-I) to serum-free medium restored high K(+)-stimulated catecholamine secretion to the levels seen in serum-treated cultures. In contrast, addition of IGF-I to serum-containing medium had little effect on catecholamine secretion. These results suggest that serum contains IGF-I or another factor that maintains the secretory responsiveness of chromaffin cells. IGF-I not only enhanced high K(+)-stimulated catecholamine secretion, but also augmented secretion elicited by the nicotinic agonist dimethyl-phenylpiperazinium, the dihydropyridine agonist Bay K 8644, and Ba2+. IGF-I did not affect the dependence of catecholamine secretion on extracellular Ca2+ concentration nor did it affect the time course of secretion. Experiments using 45Ca2+ demonstrated that IGF-I treatment enhanced Ca2+ uptake into the cells. When cells were permeabilized by treatment with digitonin, Ca2(+)-dependent catecholamine secretion was slightly, but consistently, greater from IGF-I-treated cells than from untreated cells. Our results suggest that IGF-I may enhance catecholamine secretion partly by increasing Ca2+ entry into the cells and partly by affecting a step distal to Ca2+ entry.

Characterization of insulin-like growth factor-I receptors in PC12 pheochromocytoma cells and bovine adrenal medulla

Competitive binding studies indicated that PC12 cells have receptors for insulin-like growth factor-I (IGF-I). There are approximately 11,000 +/- 1,500 IGF-I receptors/cell; these receptors have an apparent KD for IGF-I of 7.2 +/- 0.6 nM. Covalent cross-linking of 125I-IGF-I to PC12 cells labeled a 125,000-130,000-Mr protein, presumably the alpha-subunit of the IGF-I receptor. Although PC12 cells also have insulin receptors, the 125I-IGF-I appeared to be cross-linked to IGF-I receptors, because 100 nM IGF-I competed for labeling but 100 nM insulin did not. Bovine chromaffin cells also have IGF-I receptors. The protein tyrosyl kinase activity of IGF-I receptors from bovine adrenal medulla and PC12 cells was examined after purification of the receptors by wheat germ agglutinin-Sepharose chromatography. IGF-I (10 nM) stimulated autophosphorylation of the beta-subunits of the IGF-I receptors from both preparations; the beta-subunits from both sources had Mr values of approximately 97,000. IGF-I also stimulated phosphorylation of the synthetic substrate poly(Glu:Tyr)4:1 by both receptor preparations. IGF-I (IC50 of approximately 0.2 nM) was much more potent than insulin at stimulating phosphorylation of poly(Glu:Tyr) by the bovine adrenal medulla preparation. A maximal concentration of IGF-I (10 nM) increased phosphorylation approximately threefold. IGF-I was slightly more effective than insulin at stimulating the phosphorylation of poly(Glu:Tyr) by the PC12 cell receptor preparation, but neither ligand produced a maximal effect at concentrations up to 100 nM. This result probably reflects the presence of comparable numbers of IGF-I and insulin receptors on PC12 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Bovine chromaffin cells have insulin-like growth factor-I (IGF-I) receptors: IGF-I enhances catecholamine secretion

The binding of 125I-insulin-like growth factor-I (125I-IGF-I) to bovine chromaffin cells was measured. Chromaffin cell cultures contained 111,000 +/- 40,000 IGF-I binding sites/cell. These sites bound IGF-I with a KD of 1.1 +/- 0.3 nM and had a much lower affinity for insulin. Cross-linking studies showed that 125I-IGF-I bound to a protein that had an Mr of approximately 125,000, similar to the Mr of the alpha subunit of the IGF-I receptor in other tissues. Cells cultured with IGF-I (10 nM) for 4 days exhibited an almost twofold increase in high K+-evoked catecholamine secretion. Insulin was much less potent than IGF-I in enhancing catecholamine secretion. These data indicate that binding of IGF-I to its receptors on chromaffin cells can modulate the function of these cells.

Insulin and insulin-like growth factors stimulate deoxyribonucleic acid synthesis in PC12 pheochromocytoma cells

The effects of insulin and insulin-like growth factors (IGFs) on the replication of PC12 pheochromocytoma cells were investigated. Incubation of PC12 cells for 2-3 days in low (0.3%) serum medium decreased [3H]thymidine incorporation into PC12 cell DNA to approximately 30% of that in control (15% serum) medium. Incubation of the cells in low serum medium also slowed the growth of the cultures and increased the percentage of cells in the G0/G1 phase of the cell cycle. Addition of insulin to cells in low serum medium increased [3H]thymidine incorporation into the cells, increased the number of cells in PC12 cultures, and decreased the percentage of cells in the G0/G1 phase of the cell cycle. IGF-I and IGF-II also increased [3H]thymidine incorporation into PC12 cells incubated in low serum medium. IGF-I (EC50, approximately 0.3 nM) was a more potent stimulus of [3H]thymidine incorporation than was insulin (EC50, approximately 3.5 nM). These data suggest that insulin and IGFs are growth factors for PC12 cells, and that the growth-promoting effects of these agents may be mediated by a type I IGF receptor on PC12 cells.

Purification and preliminary characterization of a macromolecular inhibitor of glucocorticoid receptor binding to DNA

Rat liver cytosol contains a heat-labile macromolecule that inhibits the binding of the transformed glucocorticoid-receptor complex to nuclei or DNA-cellulose (Milgrom, E., and Atger, M. (1975) J. Steroid Biochem. 6, 487-492; Simons, S. S., Jr., Martinez, H. M., Garcea, R. L., Baxter, J. D., and Tomkins, G. M. (1976) J. Biol. Chem. 251, 334-343. We have developed a quantitative assay for the inhibitor and have purified it 600-700-fold by ammonium sulfate precipitation, ethanol precipitation, and phosphocellulose and Sephacryl S-300 chromatography. The inhibitory activity copurifies with a Mr = 37,000 protein doublet. Under low salt conditions, both the inhibitory activity and the 37-kDa protein doublet behave as high Mr aggregates that subsequently dissociate in the presence of salt. The inhibitor is positively charged at physiological pH, and it is not affected by digestion with several serine proteases or RNase. The inhibitor does not affect the transformation process, and it does not cause the release of steroid-receptor complexes that have been prebound to DNA-cellulose. The inhibitor preparation does not cleave receptors in L-cell cytosol that are covalently labeled with the site-specific affinity steroid [3H]dexamethasone 21-mesylate. If the steroid-receptor complex is first separated from the great majority of cytosol protein by transforming it and binding it to DNA-cellulose, addition of the inhibitor preparation results in receptor cleavage. Under these conditions, cleavage can be blocked with 1-chloro-3-tosylamido-7-amino-L-2-heptanone and antipain, but protease inhibitors do not affect the inhibition of DNA binding that occurs in whole cytosol. The inhibitor acts through an interaction with the receptor, not with DNA. We suggest that the inhibitor may prove to be a useful tool for studying the interaction of the steroid-receptor complex with DNA or nuclei and speculate that it may be important in determining normal events of the receptor cycle as they occur in the intact cell.