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

Cristiana Iosef,Katherine R Concepcion,Andrew Oman,Lihua Ying,Westin K Chan,Cristina M Alvira,Shailaja P Rao,Min Liu

doi:10.1111/jcmm.13741

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.

Highlights

Pulmonary vasculature growth by angiogenesis is essential for alveolarization, the final stage of lung development that occurs after term birth, and markedly increases the gas exchange surface area of the lung.[1]
Analyses of the genes differentially regulated by the IKKs revealed multiple factors important in cell cycle checkpoints and proliferation which were altered by silencing IKKa, including cyclin D1 (CCND1),[14] the transcription factor E2F315 and Akt3.16 In contrast, fewer genes relevant to proliferation appeared dysregulated by IKKb silencing but included up-regulation of Flt[1], a molecule able to antagonize VEGFmediated angiogenic function.[17]
We previously identified the NFjB as an essential regulator of pulmonary angiogenesis during postnatal lung growth and alveolarization.[8,13]

Summary

| INTRODUCTION

Pulmonary vasculature growth by angiogenesis is essential for alveolarization, the final stage of lung development that occurs after term birth, and markedly increases the gas exchange surface area of the lung.[1]. IKKa is increased in the vasculature of lung adenocarcinomas, and over-expression of IKKa, but not IKKb, in HUVECs promotes in vitro angiogenesis.[10] In contrast, homozygous deletion of IKKb in endothelial cells disrupts placental vascularization and impairs EC survival and migration.[11] Taken together, these data suggested that IKKa and IKKb may direct independent functions in the vasculature, with each kinase serving as the predominant regulator of angiogenesis depending on the tissue type and/or stage of development. These data suggest that IKKa and IKKb regulate distinct but complementary patterns of genes important for angiogenic function in the pulmonary circulation and identify IKKb as the predominant regulator of angiogenesis in the pulmonary endothelium during postnatal lung development

| METHODS

| RESULTS

Findings

| DISCUSSION