Intestinal epithelial PTPN2 limits pathobiont colonization by immune-directed antimicrobial responses

Area of Science:

• Gastroenterology
• Immunology
• Microbiology

Background:

• Loss of protein tyrosine phosphatase non-receptor type 2 (PTPN2) activity is linked to inflammatory bowel disease (IBD) and altered gut microbiota.
• Adherent-invasive E. coli (AIEC) expansion is associated with IBD pathogenesis, but mechanisms of host restriction are unclear.

Purpose of the Study:

• To investigate the role of intestinal epithelial cell (IEC)-specific PTPN2 in regulating AIEC colonization and host defense.
• To understand how PTPN2 influences the intestinal barrier and immune responses against bacterial pathobionts.

Main Methods:

• Utilized tamoxifen-inducible IEC-specific Ptpn2 knockout mice (Ptpn2∆IEC) and control littermates.
• Infected mice with noninvasive E. coli K12 or fluorescent-tagged mAIEC (mAIECred) and quantified bacterial load.
• Assessed mRNA/protein expression, cytokine levels (IL-22, IL-6, IL-17A), and intestinal barrier function using fluorescent dextran probes.

Main Results:

• Ptpn2∆IEC mice showed increased mAIECred colonization in the distal colon compared to controls.
• Reduced expression of alpha-defensin antimicrobial peptides (AMPs) and MMP7 was observed in Ptpn2∆IEC mice post-mAIECred infection.
• Increased intestinal permeability (FD4) and decreased IL-22, IL-6, and IL-17A cytokine levels were noted in Ptpn2∆IEC mice after mAIECred infection.
• Recombinant IL-22 administration reversed permeability defects and reduced bacterial burden.

Conclusions:

• Intestinal epithelial PTPN2 is essential for mucosal immunity and gut homeostasis.
• PTPN2 promotes antibacterial defense through coordinated epithelial-immune responses, restricting pathobiont colonization.
• Targeting PTPN2-mediated pathways may offer therapeutic strategies for IBD and related conditions.