Abstract 16836: Pioglitazone Reduces Angiogenesis by Altering Mitochondrial Function and Reducing Hypoxia Inducible Factor-1 Activation
Introduction: Thiazolidinediones (TZDs) used in type II diabetes are linked with adverse cardiovascular events by an unknown mechanism, including lower extremity revascularization. TZDs can affect mitochondria, which are oxygen sensors and therefore could regulate the angiogenic transcription factor hypoxia inducible factor 1 (HIF1) via mitochondrial derived α-ketoglutarate (αKG) and reactive oxygen species (mROS). We hypothesized that pioglitazone (PIO), a TZD, may impair angiogenesis through a mitochondrial-HIF1 dependent mechanism.
Methods/Results: Human skeletal myocytes (hSMC) cultured at pO2 120 vs. 40 mmHg were treated with PIO (20 μ g/ml) for 24h. Compared to vehicle, PIO depolarized mitochondria, increased mROS and αKG in hypoxic hSMCs. PIO decreased HIF1 activity (nuclear translocation and decreased VEGF, a HIF1 regulated gene). In vitro, using a matrigel assay, PIO directly inhibited human microvascular endothelial cell (hMVEC) angiogenesis (tubule formation). To assess the paracrine effects and exclude the direct PIO effects on hMVEC, we used a Boyden chamber matrigel bioassay where hSMCs and hMVEC were separated by a cell impermeable membrane. Pre-treatment of hypoxic hSMCs with PIO had less angiogenesis than with vehicle. In vivo, neovascularization was assessed in diabetic (JCR:LP; n=20) and non-diabetic (SD; n= 22) rats. Hindlimb ischemia was induced, and the rats were treated with a clinically relevant PIO dose (10mg/kg/day) or placebo for 14 days. Ischemic hindlimb (gastrocnemius) perfusion was decreased in PIO treated animals (contrast enhanced ultrasound and Tc99m sestamibi micro CT-SPECT), which correlated with decreased angiogenesis (von Willebrand factor and lectin) in both diabetic and non-diabetic models.
Conclusions: PIO alters mitochondrial function in hSMC, reducing HIF1 activation and inhibiting both paracrine/autocrine angiogenesis. PIO also impaired angiogenesis in diabetic and non-diabetic rats. Impairment of angiogenesis is undesirable in human diabetics with concomitant atherosclerotic vascular disease, and may be a mechanism for adverse effects of TZDs.
- © 2011 by American Heart Association, Inc.