Figure 1.

Multifunctional roles of galectins in mucosal intestinal inflammation. A coordinated network of galectin family members, which exerts either anti-inflammatory or proinflammatory responses, conditions epithelial barrier maintenance and immune gut homeostasis. Galectin-1 (Gal-1) promotes the secretion of growth factors and anti-inflammatory cytokines by epithelial cells (ECs), induces apoptosis of activated Th1 and Th17 cells, inhibits secretion of proinflammatory cytokines by dendritic cells (DCs) and T lymphocytes, and favors an anti-inflammatory (M2) macrophage phenotype. Similar to Gal-1, Gal-2 displays several anti-inflammatory properties, but also promotes wound healing and tissue regeneration in ECs. In animal models of colitis, Gal-3 shows mostly proinflammatory functions, inhibiting the polarization of macrophages toward an M2 phenotype, whereas Gal-4 exhibits both anti- and proinflammatory properties within the intestinal inflamed mucosa, depending on the experimental setting analyzed. By blocking production of proinflammatory cytokines, Gal-4 prevented inflammation and favored epithelial regeneration. However, through binding to memory T-cells, Gal-4 led to T-cell activation and perpetuated intestinal inflammation.