Abstract 1171: High Glucose Reduces Cathepsin L Activity and Impairs Invasion of Endothelial Progenitor Cells
Endothelial progenitor cells (EPC) significantly contribute to neovascularization and endothelial regeneration. Risk factors for coronary artery disease, particularly diabetes, impair number and function of EPC. As we have recently shown, expression and activity of the matrix degrading cysteine protease cathepsin L in EPC is required for tissue invasion and improvement of neovascularization. Therefore, we investigated the effect of high glucose on EPC invasion and cathepsin L activity. Incubation of EPC with high levels of glucose (15–50 mM) dose-dependently decreased cathepsin L activity (glucose 25 mM: 49.6 ± 7% compared to mannitol treatment; p < 0.05, n = 7), whereas MMP-2 and MMP-9 activity were only reduced to 78 ± 6% and 77 ± 5%, respectively, compared to mannitol (p < 0.05). Protein expression of cathepsin L was also significantly diminished with high glucose (36 ± 8% of control, p < 0.05), whereas the reduction of cathepsin L mRNA was less pronounced (25 mM: 84 ± 7% of control, n = 8, p < 0.05), suggesting that a posttranscriptional mechanism is responsible for cathepsin L down-regulation. As a functional consequence, high glucose (25 mM) decreased EPC invasion capacity in a modified Boyden chamber (38 ± 5% of control, n = 4, p < 0.05) and the gelatinolytic activity of EPC as measured by modified zymography (57 ± 14% of control, n = 6, p < 0.05). Importantly, even under normoglycaemic ex vivo culture conditions, EPC of patients with diabetes type IIb (HbA1c: 7.8 ± 0.3% Hb, n = 14) exhibited a significantly impaired cathepsin L activity (60 ± 9% of controls, p < 0.01) as compared to healthy controls (n = 13) and a significantly attenuated cathepsin L protein expression (64.3 ± 3% of controls, p < 0.05, n = 4 each). Taken together, high glucose significantly reduces the protein expression and activity of cathepsin L, which is involved in matrix degradation and required for tissue invasion of EPC into the ischemic tissue, and, thereby, may influence the functional capacity of EPC to improve neovascularization in diabetics.