IL‐1β inhibits cGMP signaling enzyme expression in perinatal fibroblasts via NF‐κB signaling

Abstract

Lung injury causes important morbidity and mortality in newborns by disrupting pulmonary vascular function and alveolar development. Recent evidence suggests that IL‐1β signaling plays a primary role in the pathogenesis of newborn lung disease. But the mechanisms are incompletely understood. Previously we showed that nitric oxide (NO) and cGMP signaling regulate pulmonary blood flow and development in newborns. Furthermore, we determined that disruption of cGMP signaling during newborn lung injury accentuates pulmonary disease. Accordingly, here we determined whether IL‐1β inhibits cGMP signaling in the newborn lung.We used a human fetal lung fibroblast cell line (IMR‐90 cells) and primary mouse pup lung fibroblasts to test whether IL‐1β down‐regulates the expression of soluble guanylate cyclase α1 subunit (sGCα1). This is because fibroblasts have an important role in regulating newborn lung function and alveolar development and sGCα1 is a prime initiator of cGMP signaling upon NO stimulation. We determined that physiologic levels of recombinant IL‐1β rapidly decreased sGCα1 mRNA expression in the IMR‐90 cells and protein levels in the primary lung fibroblasts. This inhibition of sGCα1 expression appeared to be at a transcriptional level. This is because IL‐1β treatment did not further decrease sGCα1 mRNA levels in the fetal lung fibroblasts treated with actinomycin D. TGFβ‐activated kinase 1 (TAK1) was determined to mediate IL‐1β’s regulation of sGCα1 expression; TAK1 knock‐down protected sGCα1 mRNA expression in IL‐1β‐treated IMR‐90 cells. Moreover, heterologous expression of TAK1 in these cells revealed that this kinase is sufficient to decrease sGCα1 mRNA levels. Nuclear factor‐kappaB (NF‐κB) signaling played a critical role in the IL‐1β‐TAK1‐sGCα1 regulatory pathway; NF‐κB signaling inhibition by an IKK2 inhibitor PHA‐408 was determined to protect sGCα1 mRNA and protein expression in IL‐1β‐treated perinatal lung fibroblasts. Lastly, using tissue samples and soluble proteins obtained from transgenic mice in which active IL‐1β was conditionally expressed in lung epithelial cells, we established that IL‐1β expression is sufficient to stimulate TAK1 activation and decrease sGCα1 protein expression in the newborn lung. Together these results indicate that IL‐1β has a direct role in decreasing cGMP signaling in the newborn lung. We speculate that targeting IL‐1β and NF‐κB signaling might protect cGMP signaling in injured newborn lungs.Support or Funding InformationNIH HL096779 and HL147863 and the Swedish Government’s Grants for Medical Research supported this work.