Promoting MPhi transepithelial migration by stimulating the epithelial cell P2Y(2) receptor

Area of Science:

• Gastroenterology
• Immunology
• Cell Biology

Background:

• Neutrophil recruitment is known in inflammatory bowel diseases, but macrophage (MPhi) recruitment to the intestinal epithelium is less understood.
• Extracellular adenosine and uridine 5'-triphosphate (ATP and UTP) act as leukocyte chemoattractants.
• Intestinal epithelial cells (IECs) play a role in immune cell trafficking.

Purpose of the Study:

• To investigate the effects of extracellular nucleotides (ATP and UTP) on macrophage and neutrophil migration and adhesion across intestinal epithelial cells.
• To elucidate the molecular mechanisms, including P2Y2 receptor and ICAM-1 involvement, in nucleotide-mediated immune cell recruitment.
• To explore the potential role of macrophages as anchors for neutrophil adhesion in the context of intestinal inflammation.

Main Methods:

• Utilized Caco-2 cell monolayers to model intestinal epithelium and assess transepithelial migration of neutrophil-like (PLB-985) and macrophage-like (U-937) cells.
• Stimulated IECs with ATP and UTP and measured immune cell adhesion.
• Administered nucleotides to mice with induced intestinal inflammation and analyzed CD68+ macrophage infiltration in the colonic epithelium.
• Investigated the role of P2Y2 receptor and ICAM-1 in mediating macrophage adhesion using specific inhibitors or genetic approaches (implied).

Main Results:

• ATP and UTP significantly promoted the transepithelial migration of both neutrophil-like and macrophage-like cells across Caco-2 monolayers.
• Macrophage-like cells adhered to nucleotide-stimulated IEC monolayers.
• In vivo studies showed CD68+ macrophage infiltration in the colonic epithelium of inflamed mice.
• Nucleotide stimulation of IECs activated the P2Y2 receptor, increasing ICAM-1 expression and mediating macrophage adhesion.
• Nucleotide-stimulated IECs did not increase neutrophil adhesion directly, but adherent macrophages facilitated neutrophil adhesion.

Conclusions:

• Extracellular nucleotides (ATP and UTP) play a crucial role in promoting macrophage migration and adhesion to the intestinal epithelium.
• The P2Y2 receptor and ICAM-1 are key mediators of nucleotide-induced macrophage adhesion to IECs.
• Macrophages may act as critical anchors for neutrophil recruitment in the inflamed intestine, contributing to inflammatory bowel diseases.
• These findings identify potential therapeutic targets for inflammatory bowel diseases and other gastrointestinal disorders.