Role of NRF2 in immune modulator expression in developing lung

Area of Science:

• Cell Biology
• Developmental Biology
• Immunology

Background:

• Alveolar type II cells protect the lung epithelium post-birth from pathogens and high oxygen.
• Surfactant protein A (SP-A) is an immune modulator developmentally upregulated with surfactant phospholipid synthesis.
• The transcription factor NRF2 plays a role in cellular defense mechanisms.

Purpose of the Study:

• To investigate the role of NRF2 and co-regulated factors in the differentiation of human fetal lung epithelial cells.
• To examine the expression of immune modulators during lung epithelial cell differentiation.
• To elucidate the developmental regulation of NRF2 and associated pathways in mouse fetal lung.

Main Methods:

• Culture of human fetal lung (HFL) epithelial cells with cAMP stimulation.
• NRF2 knockdown experiments.
• Analysis of gene expression (SP-A, TDO2, AhR, NQO1, C/EBPβ, PPARγ) and protein localization in HFL cells.
• In vivo studies in mouse fetal lung (MFL) at different developmental stages (14.5-18.5 dpc).
• Western blot analysis for phosphorylated proteins and histone modifiers.

Main Results:

• cAMP-mediated differentiation of HFL cells induced NRF2, C/EBPβ, PPARγ, SP-A, TDO2, AhR, and NQO1.
• Hypoxia inhibited cAMP induction of NRF2 and SP-A.
• NRF2 knockdown reduced the induction of C/EBPβ, PPARγ, and immune modulators.
• Endogenous NRF2 binding to SP-A and immune modulator gene promoters increased during differentiation.
• Developmental increase in Nrf2, SP-A, Tdo2, Ahr, Nqo1, and decreased Keap1 in MFL.
• NRF2 induction in MFL correlated with NF-κB p65 nuclear localization, decreased p38 MAPK phosphorylation, increased DUSP1, induced CBP, and decreased HDAC4.

Conclusions:

• Type II cells protect the alveolar epithelium through NRF2 and immune modulator expression, preventing inflammation and oxidative stress.
• Lung cancer cells may exploit this developmental pathway for immune tolerance and survival.