T cell-specific HIF-2α attenuates colitis by antagonizing notch-driven Th2 differentiations.

Area of Science:

• Immunology
• Gastroenterology
• Molecular Biology

Background:

• The role of hypoxia-inducible factor-2α (HIF-2α) in ulcerative colitis (UC) pathogenesis remains controversial, with studies reporting both detrimental and beneficial effects.
• Understanding the specific function of HIF-2α within T lymphocytes is crucial for clarifying its contribution to UC development.

Purpose of the Study:

• To elucidate the precise role of T lymphocyte-specific HIF-2α in the pathogenesis of ulcerative colitis.
• To investigate the molecular mechanisms by which HIF-2α influences T cell responses and intestinal inflammation.

Main Methods:

• Immunohistochemical analysis of colonic tissues from UC patients and healthy controls.
• Generation and DSS-induced colitis assessment of T/NKT cell-specific HIF-2α conditional knockout mice (HIF-2^ΔT/NKT).
• In vitro studies using primary CD4+ T cells with lentiviral-mediated manipulation of HIF-2α expression to assess protein interactions, signaling pathways, and cellular phenotypes.

Main Results:

• Increased HIF-2α expression was observed in UC colonic tissues, inversely correlated with disease severity in lymphocytes.
• T/NKT cell-specific HIF-2α deletion exacerbated DSS colitis, impairing Th2 cell polarization and increasing IL-4 production.
• HIF-2α directly binds to Notch1 intracellular domain (NICD), inhibiting Notch signaling and Th2 cell differentiation, thereby ameliorating inflammation.

Conclusions:

• T cell-intrinsic HIF-2α plays a critical protective role in ulcerative colitis.
• HIF-2α acts by restraining Notch1-NICD signaling, which limits pathological Th2 cell differentiation and reduces intestinal inflammation.
• These findings reconcile conflicting previous reports by highlighting a context-dependent mechanism for HIF-2α function in UC.