Hypoxia-induced mitogenic factor (HIMF/FIZZ1/RELMalpha) increases lung inflammation and activates pulmonary...

Area of Science:

• Pulmonary Medicine
• Immunology
• Molecular Biology

Background:

• Hypoxia-induced mitogenic factor (HIMF) is a secreted protein involved in vascular remodeling and fibrosis.
• Previous studies suggested Th2 cytokine (IL-4, IL-13) regulation of HIMF via STAT6 in pulmonary fibrosis.
• The role of IL-4 in HIMF-induced pulmonary hypertension and vascular remodeling remained unclear.

Purpose of the Study:

• To investigate the role of IL-4 signaling in hypoxia-induced pulmonary hypertension and HIMF expression.
• To elucidate the mechanisms by which HIMF influences lung inflammation and vascular remodeling.

Main Methods:

• Utilized hypoxia-induced pulmonary hypertension models in wild-type (WT), IL-4 knockout (KO), and STAT6 KO mice.
• Assessed HIMF expression, vascular remodeling markers (hypertrophy, collagen deposition), and inflammatory cell infiltration.
• Conducted in vitro studies using pulmonary microvascular endothelial cells to examine HIMF and IL-4 interactions.

Main Results:

• Lung HIMF expression increased similarly in WT, IL-4 KO, and STAT6 KO mice under hypoxia, indicating Th2 independence.
• HIMF-induced proliferation, hypertrophy, and extracellular matrix deposition were significantly reduced in IL-4 KO mice.
• HIMF-induced angiogenic factors (VEGF, MCP-1) and macrophage infiltration were suppressed in IL-4 KO mice.
• HIMF treatment increased IL-4 levels in WT mice, and in vitro, HIMF stimulated endothelial cells via the IL-4/IL-4Rα system.

Conclusions:

• IL-4 signaling is not required for hypoxia-induced HIMF expression but plays a critical role in mediating HIMF's effects on lung vascular remodeling and inflammation.
• HIMF promotes lung inflammation and vascular remodeling through an IL-4-dependent pathway, involving endothelial cell activation and chemokine production.