IL-1 promotes α-epithelial Sodium Channel (α-ENaC) expression in murine lung epithelial cells: involvement of NF-κB.

Intra-amniotic exposure to proinflammatory cytokines such as interleukin-1 (IL-1) correlates with a decreased incidence of respiratory distress syndrome (RDS) in infants following premature birth. At birth, inadequate absorption of fluid from the fetal lung contributes to the onset RDS. Lung fluid clearance is coupled to Na+ transport via epithelial sodium channels (ENaC). In this study, we assessed the effects of IL-1 on the expression of ENaC, particularly the α-subunit which is critical for fetal lung fluid clearance at birth. Cultured mouse lung epithelial (MLE-12) cells were treated with either IL-1α or IL-1ß to determine their effects on α-ENaC expression. Changes in IL-1-induced α-ENaC levels in the presence of IL-1 receptor antagonist (IL-1ra), cycloheximide, NF-κB inhibitor, and MAP kinase inhibitors were investigated. IL-1α and IL-1ß independently induced a significant increase of α-ENaC mRNA and protein after 24 h compared to untreated cells. IL-1-dependent increases in α-ENaC protein were mitigated by IL-1ra and cycloheximide. IL-1 exposure induced NF-κB binding activity. Attenuation of IL-1-induced NF-κB activation by its inhibitor SN50 decreased α-ENaC protein abundance. Inhibition of ERK 1,2 MAPK significantly decreased both IL-1α and ß-induced α-ENaC protein expression whereas inhibition of p38 MAPK only blocked IL-1ß-induced α-ENaC protein levels. In contrast, IL-1-induced α-ENaC protein levels were unaffected by a c-Jun N-terminal kinase (JNK) inhibitor. Our results suggest that in MLE-12 cells, IL-1-induced elevation of α-ENaC is mediated via NF-κB activation and in part involves stimulation of the ERK 1,2 and p38 MAPK signaling pathways.

Protein kinase A and mitogen-activated protein kinase pathways mediate cAMP induction of alpha-epithelial Na+ channels (alpha-ENaC).

A major mechanism for Na+ transport across epithelia occurs through epithelial Na+ channels (ENaC). ENaC is a multimeric channel consisting of three subunits (alpha, beta, and gamma). The alpha-subunit is critical for ENaC function. In specific culture conditions, the rat submandibular gland epithelial cell line (SMG-C6) demonstrates minimal Na+ transport properties and exposure to dibutyryl cAMP (DbcAMP) for up to 48 h caused an elevation of alpha-ENaC mRNA and protein expression and amiloride-sensitive short-circuit current (I(SC)). Here we examined the early signaling pathways evoked by DbcAMP which contribute to the eventual increase in Na+ transport is present. Treatment with either of the protein kinase A (PKA) inhibitors KT5720 or H-89 followed by exposure to 1 mM DbcAMP for 24 h markedly attenuated DbcAMP-induced alpha-ENaC protein formation and I(SC). Exposure of SMG-C6 cells to 1 mM DbcAMP induced a rapid, transient phosphorylation of the cAMP response element binding protein (CREB). This response was attenuated in the presence of either KT5720 or H-89. Dominant-negative CREB decreased DbcAMP-induced alpha-ENaC expression. Suppression of the extracellular signal-regulated protein kinase (ERK 1,2) with PD98059 or the p38 mitogen-activated protein kinase (MAPK) pathway with SB203580 reduced DbcAMP-induced alpha-ENaC protein levels in SMG-C6 cells. DbcAMP-induced phosphorylation of CREB was markedly attenuated by PD98059 or SB203580. DbcAMP-induced activation of the either the p38 or the ERK 1,2 MAPK pathways was abolished by either of the PKA inhibitors, H-89 or KT5720. Cross talk between these signaling pathways induced by DbcAMP via the activation of CREB appears to contribute to increased levels of alpha-ENaC observed after 24 h of treatment in SMG-C6 epithelial cells.

What Do Pediatric Residents Gain From an Experience in Juvenile Justice? A Qualitative Analysis of Community-Based Learning.

BACKGROUND: Training in advocacy and community pediatrics often involves the use of community site visits. However, data on the specific knowledge, skills, and attitudes gained from these experiences are limited. In this study we used qualitative analysis of written narratives to explore the response of residents to a juvenile justice experience. METHODS: Pediatric residents participated in a week-long experience in the juvenile probation department and completed a written narrative. Narratives were analyzed using grounded theory to explore the effects of this experience on residents' views of youth in the juvenile justice system. RESULTS: Analysis of 29 narratives revealed 13 themes relating to 5 core concepts: social determinants of behavior, role of professionals and institutions, achieving future potential, resolving discrepancies, and distancing. A conceptual model was developed to explore the interactions of these concepts in the resident view of youth in the juvenile justice system. Of the themes only 3 (23%) were related to content explicitly covered in the assigned reading materials. CONCLUSIONS: Several important concepts emerged as elements of this experience, many of which were not covered in the explicit curriculum. Variability in attitudinal response to the experience raised important questions about the influence of the ideological framework of the learner and the hidden curriculum on the learning that occurs in community settings. We propose a theoretical model that delineates the factors that influence learning in community settings to guide educators in planning these types of experiences.

Effects of a patient's name and image on medical knowledge acquisition.

PURPOSE: To assess whether there are differences in medical students' (MS) knowledge acquisition after being provided a virtual patient (VP) case summary with a patient's name and facial picture included compared to no patient's name or image. METHOD: 76 MS from four clerkship blocks participated. Blocks one and three (Treatment group) were provided case materials containing the patient's name and facial picture while blocks two and four (Control group) were provided similar materials without the patient's name or image. Knowledge acquisition was evaluated with a multiple-choice-question examination (CQA_K). RESULTS: Treatment group CQA_K scores were 64.6% (block one, n = 18) and 76.0% (block three, n = 22). Control group scores were 71.7%, (block two, n = 17) and 68.4% (block four, n = 19). ANOVA F-test among the four block mean scores was not significant; F (3, 72) = 1.68, p = 0.18, η2=0.07. Only 22.2% and 27.3% of the MS from blocks one and three respectively correctly recalled the patient's name while 16.7% and 40.9% recalled the correct final diagnosis of the patient. CONCLUSIONS: These results suggest that including a patient's name and facial picture on reading materials may not improve MS knowledge acquisition. Corroborating studies should be performed before applying these results to the design of instructional materials.

Postnatal glucocorticoids induce alpha-ENaC formation and regulate glucocorticoid receptors in the preterm rabbit lung.

At birth, lung fluid clearance is coupled to Na+ transport through epithelial Na+ channels (ENaC) in the distal lung epithelium. We evaluated the effect of postnatal glucocorticoids (GC) on lung alpha-ENaC expression in preterm 29-day gestational age (GA) fetal rabbits. Postnatal treatment of 29-day GA fetuses with 0.5 mg/kg of dexamethasone (Dex) iv resulted in a 2- and 22-fold increase in lung alpha-ENaC mRNA expression compared with saline-treated fetuses after 8 and 16 h, respectively. Lung alpha-ENaC protein levels in Dex-treated fetuses were also elevated compared with saline-treated counterparts. The extravascular lung water (EVLW)/dry lung tissue weight ratios of 29-day GA fetuses treated with either saline or Dex decreased over 24 h compared with that observed at birth; however, at 24 h, the EVLW/dry lung tissue weight ratios of saline- and Dex-treated fetuses were similar. Dex-induced alpha-ENaC mRNA and protein levels were attenuated by glucocorticoid receptor (GCR) antagonist RU-486 in fetal distal lung epithelial cells isolated from 29-day GA fetuses, indicating that GC-dependent augmentation of lung alpha-ENaC requires the presence of functional GCR. Lung GCR mRNA expression and protein levels were elevated in 29-day GA fetuses compared with fetuses at earlier GA. Exposure of 29-day GA fetuses to Dex for 16 h caused a 2.1-fold increase in lung GCR mRNA expression, but GCR protein levels were decreased in Dex-treated fetuses after 24 h. We conclude that postnatal treatment of preterm 29-day GA fetal rabbits with GC results in an elevation of lung alpha-ENaC accompanied by an autoregulation of pulmonary GCR.