D-4F induces heme oxygenase-1 and extracellular superoxide dismutase, decreases endothelial cell sloughing, and improves vascular reactivity in rat model of diabetes

Background - Apolipoprotein A1 mimetic peptide, synthesized from D-amino acid (D-4F), enhances the ability of HDL to protect LDL against oxidation in atherosclerotic animals. Methods and Results - We investigated the mechanisms by which D-4F provides antioxidant effects in a diabetic model. Sprague-Dawley rats developed diabetes with administration of streptozotocin (STZ). We examined the effects of daily D-4F (100 mu g/100 g of body weight, intraperitoneal injection) on superoxide (O-2(-)), extracellular superoxide dismutase (EC-SOD), vascular heme oxygenase (HO-1 and HO-2) levels, and circulating endothelial cells in diabetic rats. In response to D-4F, both the quantity and activity of HO-1 were increased. O-2(-) levels were elevated in diabetic rats (74.8 +/- 8 x 10(3) cpm/10 mg protein) compared with controls (38.1 +/- 8 x 10(3) cpm/10 mg protein; P < 0.01). D-4F decreased O-2(-) levels to 13.23 +/- 1 x 10(3) ( P < 0.05 compared with untreated diabetics). The average number of circulating endothelial cells was higher in diabetics (50 +/- 6 cells/ mL) than in controls (5 +/- 1 cells/mL) and was significantly decreased in diabetics treated with D-4F (20 +/- 3 cells/ mL; P < 0.005). D-4F also decreased endothelial cell fragmentation in diabetic rats. The impaired relaxation typical of blood vessels in diabetic rats was prevented by administration of D-4F (85.0 +/- 2.0% relaxation). Western blot analysis showed decreased EC-SOD in the diabetic rats, whereas D-4F restored the EC-SOD level. Conclusions - We conclude that an increase in circulating endothelial cell sloughing, superoxide anion, and vasoconstriction in diabetic rats can be prevented by administration of D-4F, which is associated with an increase in 2 antioxidant proteins, HO-1 and EC-SOD.