Granulocyte macrophage colony-stimulating factor ameliorates DSS-induced experimental colitis

Area of Science:

• Immunology
• Gastroenterology
• Inflammation Research

Background:

• Sargramostim (granulocyte macrophage colony-stimulating factor, GM-CSF) is a hematopoietic growth factor that stimulates innate intestinal immunity.
• Clinical trials indicate sargramostim induces response and remission in Crohn's disease patients.
• The mechanism of action for GM-CSF in inflammatory bowel disease requires further elucidation, particularly its role in dendritic cells (DCs).

Purpose of the Study:

• To investigate the therapeutic mechanism of GM-CSF in an acute colitis model.
• To determine the role of dendritic cells, specifically plasmacytoid DCs (pDCs), in GM-CSF's anti-colitis effects.
• To explore the involvement of type 1 interferons (IFNs) in GM-CSF's therapeutic action.

Main Methods:

• Acute colitis was induced in Balb/c mice using dextran sulfate sodium (DSS).
• Mice were treated with GM-CSF or phosphate-buffered saline (PBS).
• The role of pDCs was assessed using a specific monoclonal antibody (mAb 440c), and gene/protein expression was analyzed via microarray, RT-PCR, and Bio-plex.

Main Results:

• GM-CSF significantly ameliorated DSS-induced colitis, improving clinical and histological outcomes.
• GM-CSF treatment reduced expression of pro-inflammatory genes (TNF-alpha, IL1-beta) and increased pDC populations and type 1 IFN production.
• Blocking pDCs with mAb 440c abrogated GM-CSF's therapeutic effect, while IFN-beta administration mimicked it, indicating a pDC- and type 1 IFN-dependent mechanism.

Conclusions:

• GM-CSF demonstrates efficacy in treating DSS-induced colitis.
• The therapeutic mechanism of GM-CSF in colitis is dependent on the 440c+ plasmacytoid dendritic cell population.
• GM-CSF's action involves the induction of type 1 interferons and modulation of dendritic cell function.