Constitutive intestinal NF-κB does not trigger destructive inflammation unless accompanied by MAPK activation.

Area of Science:

• Immunology
• Molecular Biology
• Gastroenterology

Background:

• Nuclear Factor-kappa B (NF-κB) is crucial for inflammation and immunity.
• NF-κB and Tumor Necrosis Factor (TNF) are elevated in inflammatory diseases causing tissue destruction.
• The exact role of persistent NF-κB activation in chronic inflammation and tissue damage is unclear.

Purpose of the Study:

• To investigate if constitutive NF-κB activation in intestinal epithelial cells (IECs) is sufficient to cause chronic inflammation and tissue damage.
• To understand the mechanisms underlying inflammation and tissue destruction in response to NF-κB activation.

Main Methods:

• Generated transgenic mice (IKKβ(EE)(IEC)) with constitutively active IκB kinase β (IKKβ) in IECs.
• Analyzed NF-κB activation, chemokine and TNF production, inflammatory cell infiltration, and tissue integrity in these mice.
• Challenged mice with immune and microbial stimuli to assess susceptibility to acute inflammation.

Main Results:

• IKKβ(EE)(IEC) mice showed NF-κB activation and chemokine production but limited TNF levels and no spontaneous tissue damage.
• These mice exhibited inflammatory cell infiltration in the small intestine lamina propria.
• Upon challenge, IKKβ(EE)(IEC) mice developed severe acute inflammation, enterocyte apoptosis, barrier disruption, and bacterial translocation, driven by TNF and MAPK activation.

Conclusions:

• Constitutive NF-κB activation in IECs alone does not cause chronic inflammation or tissue destruction.
• NF-κB activation primes the intestine for severe, destructive inflammation upon secondary immune or microbial challenge.
• TNF production, dependent on p38 and ERK MAPKs, is critical for the destructive inflammatory response.