Abstract 5754: Rescue of Diabetes-Related Impairment of Angiogenesis by Gene Silencing of Thioredoxin-Interacting Protein
Objectives: Vascular complications of diabetes mellitus (DM) are associated with impaired angiogenesis, the mechanisms of which are poorly understood. The thioredoxin (TRX) system has been implicated in angiogenesis. Interestingly, thioredoxin-interacting protein (TXNIP), antagonist to TRX, is induced by glucose. We hypothesized that hyperglycemic-modulation of TXNIP/TRX plays a role in DM-impairment of angiogenesis.
Endothelial cells (ECs) were cultured in 5–25 mM glucose and siRNA used to modulate the TXNIP/TRX system. EC migration, proliferation, tubulogenesis, TRX activity, VEGF, qPCR and protein were examined.
Unilateral hindlimb ischemia was induced in a murine model of Type 1 DM. Txnip siRNA was delivered i.m. and limb perfusion assessed by laser Doppler, with ischemia, foot movement and capillary density also measured.
Results: Hyperglycemia induced a dose-dependent inhibition of key angiogenic events including EC migration, proliferation and tubulogenesis (62.1Â±2.8%, 72.9Â±7.0% and 48.3Â±4.7% at 25 mM vs. control; P < 0.05), with increased TXNIP expression (5.1Â±1.8-fold mRNA; 2.0Â±0.1-fold protein), enhanced TXNIP/TRX interaction and inhibition of TRX activity (59.8Â±4.8%; P<0.001). TXNIP siRNA reversed the inhibitory effects of hyperglycemia on migration, proliferation, tubulogenesis and TRX activity to levels of control. DM was associated with a profound impairment of blood flow recovery following hindlimb ischemia (0.284Â±0.038 vs. 0.582Â±0.021; P<0.001). However, i.m. delivery of Txnip siRNA dramatically increased limb perfusion in DM mice to levels not statistically different from control (0.443Â±0.047). Txnip siRNA also increased capillary density (2.0Â±0.4-fold), while ischemia and foot movement scores significantly improved in DM mice receiving Txnip siRNA (vs. DM control; P<0.05). In both models, hyperglycemia/DM reduced VEGF expression and interfered with VEGF action, while TXNIP siRNA rescued VEGF levels to that of control.
Conclusions: TXNIP plays a key role in angiogenesis and impaired neovascularization in DM, in part via modulation of VEGF. Our findings demonstrate that inhibition of TXNIP can abrogate the deleterious effects of hyperglycemia in angiogenesis.