Cooperation between classical and alternative NF-κB pathways regulates proinflammatory responses in epithelial cells.
The transcription factor NF-κB has been causally linked to inflammatory lung diseases. Recent studies have unraveled the complexity of NF-κB activation by identifying two parallel activation pathways: the classical NF-κB pathway, which is controlled by IκB kinase complex-β (IKKβ) and RelA/p50, and the alternative pathway, which is controlled by IKKα and RelB/p52. The alternative pathway regulates adaptive immune responses and lymphoid development, yet its role in the regulation of innate immune responses remains largely unknown. In this study, we determined the relevance of the alternative NF-κB pathway in proinflammatory responses in lung epithelial cells. The exposure of C10 murine alveolar lung epithelial cells to diverse stimuli, or primary murine tracheal epithelial cells to LPS, resulted in the activation of both NF-κB pathways, based on the nuclear translocation of RelA, p50, RelB, and p52. Increases in the nuclear content of RelA occurred rapidly, but transiently, whereas increases in nuclear RelB content were protracted. The small interfering (si) RNA-mediated knockdown of IKKα, RelA, or RelB resulted in decreases of multiple LPS-induced proinflammatory cytokines. Surprisingly, the siRNA ablation of IKKα or RelB led to marked increases in the production of IL-6 in response to LPS. The simultaneous expression of constitutively active (CA)-IKKα and CA-IKKβ caused synergistic increases in proinflammatory mediators. Lastly, the disruption of the IKK signalsome inhibited the activation of both NF-κB pathways. These results demonstrate that the coordinated activation of both NF-κB pathways regulates the magnitude and nature of proinflammatory responses in lung epithelial cells.
Health Sciences Research Facility, Department of Pathology, College of Medicine, University of Vermont, Burlington, VT 05405, USA.
Jane E
JE
Tully
James D
JD
Nolin
Amy S
AS
Guala
Sidra M
SM
Hoffman
Elle C
EC
Roberson
Karolyn G
KG
Lahue
Jos
J
van der Velden
Vikas
V
Anathy
Timothy S
TS
Blackwell
Yvonne M W
YM
Janssen-Heininger
D000818:Animals; D000075368:Anoctamins; D002478:Cells, Cultured; D018118:Chloride Channels; D016207:Cytokines / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D006657:Histones / Q000378:metabolism; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D018836:Inflammation Mediators / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008168:Lung / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D061251:Primary Cell Culture; D034622:RNA Interference; D020545:Respiratory Mucosa / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction; D014132:Trachea / Q000473:pathology
C575623:Ano2 protein, rat; D000075368:Anoctamins; D018118:Chloride Channels; D016207:Cytokines; D006657:Histones; D020672:I-kappa B Proteins; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D016328:NF-kappa B