TNF-alpha represses transcription of human Bone Morphogenetic Protein-4 in lung epithelial cells.

Bone Morphogenetic Proteins are key signaling molecules in vertebrate development. Little is known about Bmp gene regulation in any organ. In Drosophila, the Bmp gene, dpp is regulated by Dorsal, the invertebrate homologue of Rel-NF-kB. In this study we examined whether TNF-alpha, which activates NF-kB, can regulate Bmp4 gene expression. TNF-alpha reduced Bmp4 mRNA in lung adenocarcinoma A549 cells and repressed transcriptional activity of the human Bmp4 promoter in a dose-dependent manner. Similar repression was observed when the Bmp4 promoter was co-transfected with a p65 (RelA) expression vector in the absence of TNF-alpha treatment, suggesting that RelA mediates the effect of TNF-alpha. In support of this finding, the repressor effect of TNF-alpha on Bmp4 was abrogated by a co-transfected dominant negative mutant of IkB (S32A/S36A). The human Bmp4 promoter contains 3 putative consensus binding sites for NF-kB. Surprisingly, only one of the latter binding sites was capable of binding NF-kB. Repressor effect of NF-kB was not dependent on any of the three binding sites, but localized to a 122 bp fragment which bound both RelA and SP1. SP1 stimulated transcription, whereas increasing doses of RelA opposed this effect. In vivo, TNF-alpha inhibited branching morphogenesis and LacZ gene expression in Bmp4-lacz transgenic lungs. These data support a model in which TNF-alpha-induced RelA interacts with SP1 to bring about transcriptional repression of Bmp4 gene. These findings provide a mechanistic paradigm for interactions between mediators of inflammation and morphogenesis with relevant implications for normal lung development and pathogenesis of disease.

Risk of need for extracorporeal membrane oxygenation support in neonates with congenital diaphragmatic hernia treated with inhaled nitric oxide.

BACKGROUND: Congenital diaphragmatic hernia (CDH) is often associated with severe pulmonary hypoplasia resulting in hypoxemic respiratory failure unresponsive to advanced medical management including the use of inhaled nitric oxide (iNO). For these patients, extracorporeal membrane oxygenation (ECMO) serves as the last potentially effective treatment choice. Since the efficacy of iNO in this patient population is not known and since most neonatal intensive care units using iNO for the treatment of these critically ill neonates do not provide ECMO, the ability to more accurately predict which patient is at risk for failing medical management with iNO and requires a timely transfer to an ECMO center can be life saving. Therefore, in this study, we sought to determine the risk factors for the need for ECMO in a cohort of 27 neonates with isolated left CDH and hypoxemic respiratory failure treated with iNO. STUDY DESIGN: In this retrospective study, 27 patients with left CDH were identified during a 2-year period. During the study period, strict clinical guidelines had been used to standardize iNO therapy, to provide adequate lung inflation and cardiovascular support, and to recognize treatment failures and the need for ECMO. Logistic regression analysis was used to study the relationship between the need for ECMO and a set of suspected risk factors. RESULTS: When subjected to logistic regression analysis, only the presence of a pneumothorax remained significantly associated with the need for ECMO (OR=22; 95% CI=2.18 to 222), while none of the other variables examined such as mean airway pressure, FiO2, PaO2, or PaCO2 were predictors for the need of ECMO after 6 hours of treatment with iNO. CONCLUSION: These data indicate that a prompt transfer to an ECMO center should be initiated for hypoxemic patients with CDH receiving medical management with iNO if they develop an air leak syndrome.