Intestinal Epithelial PTPN2 Limits Pathobiont Colonization by Immune-Directed Antimicrobial Responses

Area of Science:

• Immunology
• Microbiology
• Gastroenterology

Background:

• Loss of protein tyrosine phosphatase non-receptor type 2 (PTPN2) activity correlates with altered gut microbiome and inflammatory bowel disease (IBD).
• Adherent-invasive E. coli (AIEC) expansion is a key factor in IBD pathogenesis.
• Mechanisms by which intestinal epithelial cells (IECs) control pathobionts are not fully understood.

Purpose of the Study:

• To investigate the role of IEC-specific PTPN2 in regulating AIEC colonization.
• To elucidate the impact of PTPN2 deficiency on gut barrier function and immune responses against AIEC.

Main Methods:

• Generated tamoxifen-inducible, IEC-specific PTPN2 knockout mice (Ptpn2^ΔIEC).
• Infected mice with non-invasive E. coli K12 or fluorescent-tagged mAIEC (mAIEC^red).
• Quantified bacterial load, assessed gene/protein expression (AMPs, cytokines), measured intestinal permeability, and analyzed tight junction proteins.

Main Results:

• Ptpn2^ΔIEC mice showed increased mAIEC^red colonization in the distal colon.
• Reduced alpha-defensin AMPs (Defa5, Defa6) and MMP7 expression in Ptpn2^ΔIEC mice post-AIEC infection.
• Increased intestinal permeability (FD4) and decreased IL-22, IL-6, IL-17A cytokine levels were observed in Ptpn2^ΔIEC mice, with IL-22 partially restoring barrier function and reducing bacterial burden.

Conclusions:

• IEC-specific PTPN2 is essential for maintaining mucosal immunity and gut homeostasis.
• PTPN2 promotes antibacterial defense through coordinated epithelial-immune responses to restrict pathobiont colonization.
• Targeting PTPN2-mediated pathways may offer therapeutic strategies for IBD.