Investigating galectin-3 in vasculopathy associated with inflammatory arthritis

Cardiovascular comorbidities are the primary cause of death in patients with rheumatoid arthritis. Galectin-3, a pro-inflammatory binding protein, regulates a broad range of biological processes such as cell adhesion, chemoattraction and cell activation and is involved in pathological processes, including inflammation, organ fibrosis, cancer and autoimmunity. Galectin-3 is expressed in immune cells, including T cells, yet the mechanisms by which galectin-3 links systemic T cell dysregulation in arthritis associated vasculopathy are largely unknown. The studies presented in this Thesis test the ability of a small-molecule inhibitor of galectin3, GB1107, to prevent vascular pathology in inflammatory arthritis. Initial studies used the collagen induced arthritis (CIA) mouse model to investigate galectin-3 inhibition on vascular inflammation. Immunohistochemistry was used to track leukocyte accumulation in the thoracic perivascular adipose tissue (PVAT) and myography to measure constriction responses in the thoracic aorta as a marker of vascular dysfunction. Consistent with cardiovascular associations in rheumatoid arthritis, immunohistochemistry of thoracic aortas showed a significant increase in galectin-3-positive cells and CD3 T cell staining in the vascular tissue of mice with CIA. Treatment with GB1107 caused a reduction in T cells within thoracic PVAT. However, treatment with GB1107 did not improve vascular constriction defects at this chronic stage of CIA. To determine if galectin-3 may be mediating its effects via immune cells, galectin-3 expression was characterised in CD4 T cell differentiation assays. A unique and significant increase in galectin-3 expression and secretion was observed in Th17-polarising conditions. Notably, Th17 cell differentiation was inhibited by GB1107 in a concentration dependent manner. Additionally, the use of GB1107 and galectin-3-/-ells (Lgals3-/-) identified a role of galectin-3 in Th17 proliferation, establishing galectin-3 as a potential therapeutic target in diseases where Th17 cells are involved and are pathogenic. Later studies used the antigen induced arthritis (AIA) model of inflammatory arthritis which features a Th17 driven synovitis. Galectin-3 expression was upregulated in CD4 T cells during AIA and treatment with GB1107 led to a reduction in CD4 cells in the inflamed synovium. Furthermore, treatment with GB1107 led to the full restoration of vascular constriction responses, suggesting that inhibition of galectin-3 could be beneficial in the application of arthritis associated vasculopathy. Galectin-3 promotes Th17 cell differentiation and proliferation and regulates vascular T cell accumulation in CIA. Inhibiting galectin-3 using GB1107 fully restores vascular constriction responses in AIA and has potential to limit Th17-mediated pathology in chronic inflammatory diseases