Distinct roles for IκB kinases alpha and beta in regulating pulmonary endothelial angiogenic function during late lung development

Abstract

Pulmonary angiogenesis is essential for alveolarization, the final stage of lung development that markedly increases gas exchange surface area. We recently demonstrated that activation of the nuclear factor kappa‐B (NFκB) pathway promotes pulmonary angiogenesis during alveolarization. However, the mechanisms activating NFκB in the pulmonary endothelium, and its downstream targets are not known. In this study, we sought to delineate the specific roles for the NFκB activating kinases, IKKα and IKKβ, in promoting developmental pulmonary angiogenesis. Microarray analysis of primary pulmonary endothelial cells (PECs) after silencing IKKα or IKKβ demonstrated that the 2 kinases regulate unique panels of genes, with few shared targets. Although silencing IKKα induced mild impairments in angiogenic function, silencing IKKβ induced more severe angiogenic defects and decreased vascular cell adhesion molecule expression, an IKKβ regulated target essential for both PEC adhesion and migration. Taken together, these data show that IKKα and IKKβ regulate unique genes in PEC, resulting in differential effects on angiogenesis upon inhibition, and identify IKKβ as the predominant regulator of pulmonary angiogenesis during alveolarization. These data suggest that therapeutic strategies to specifically enhance IKKβ activity in the pulmonary endothelium may hold promise to enhance lung growth in diseases marked by altered alveolarization.

Lung development and emerging roles for type 2 immunity

“…Although important for alveolarisation, it is not a major focus of this review. In mice, important mediators include vascular endothelial growth factor (VEGF) , nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) , insulin‐like growth factors , and platelet endothelial cell adhesion molecule (PECAM‐1) . Vegfa mRNA expression peaks during alveolarisation .…”

“…NF‐κB is constitutively active in neonatal developing endothelium and is needed for survival and proliferation of endothelial cells . Inhibiting NF‐κB or its activating kinases leads to impaired angiogenesis in vitro , and loss of distal pulmonary vessels and alveolar simplification in vivo . It has been suggested that disrupted alveolarisation in PECAM‐1 null mice may be caused by impaired endothelial cell motility .…”

“…Inhibiting NF‐κB signalling worsened the LPS‐induced phenotype, suggesting an anti‐inflammatory function in the developing lung . NF‐κB signalling is also beneficial in hyperoxia‐induced lung injury , compensatory lung growth after pneumonectomy , and has roles in alveolarisation and angiogenesis . However, during the saccular stage, overexpressing NF‐κB in the airway epithelium induces inflammation and disrupts lung development , and its activation in macrophages causes aberrant lung morphogenesis upon LPS exposure .…”

Developmental Expression of Transforming Growth Factor Induced Protein Promotes NF-Kappa-B Mediated Angiogenesis During Postnatal Lung Development

“…PEC were transfected NTC, integrin aV, integrin b3, or Csf3 On-Target Plus SMART pool siRNA using Lipofectamine 2000 for 6h as previously described (21).…”

“…4D). Further, we performed studies using PEC obtained from mice containing an endothelial-specific deletion of IKKb, the primary activator of NFkB in early alveolar PEC (21). Although rTGFBI increased migration in WT PEC (P<0.01), TGFBI-induced migration was absent in PEC lacking IKKb.…”