Effect of Intracavernous Administration of Angiopoietin-4 on Erectile Function in the Streptozotocin-Induced Diabetic Mouse

Abstract

IntroductionErectile dysfunction (ED) is a highly prevalent complication of diabetes, and the severity of endothelial dysfunction is one of the most important factors in reduced responsiveness to oral phosphodiesterase type 5 inhibitors.

AimTo study the effects of human angiopoietin-4 (Ang-4) protein on erectile function in diabetic mice.

MethodsDiabetes was induced by intraperitoneal injection of streptozotocin into 8-week-old C57BL/6J male mice. At 8 weeks after the induction of diabetes, the animals were divided into four groups: control nondiabetic mice and diabetic mice receiving two successive intracavernous injections of phosphate buffered saline (days -3 and 0), a single intracavernous injection of Ang-4 protein (day 0), or two successive intracavernous injections of Ang-4 protein (days -3 and 0).

Main Outcome MeasuresOne week after treatment, we measured erectile function by electrical stimulation of the cavernous nerve. The penis was harvested and stained with hydroethidine or antibodies to Ang-4, platelet/endothelial cell adhesion molecule-1, and phosphorylated endothelial nitric oxide synthase (eNOS). We also determined the differential expression of Ang-4 in cavernous tissue in the control and diabetic mice. The effect of Ang-4 protein on the phosphorylation of Tie-2, Akt, and eNOS was determined in human umbilical vein endothelial cells (HUVECs) by Western blot.

ResultsThe cavernous expression of Ang-4 was downregulated in diabetic mice; Ang-4 was mainly expressed in endothelial cells. Local delivery of Ang-4 protein significantly increased cavernous endothelial content, induced eNOS phosphorylation, and decreased the generation of superoxide anion and apoptosis in diabetic mice. Ang-4 protein strongly increased the phosphorylation of Tie-2, Akt, and eNOS in HUVECs. Repeated intracavernous injections of Ang-4 induced significant restoration of erectile function in diabetic mice (87% of control values), whereas a single intracavernous injection of Ang-4 protein elicited modest improvement.

ConclusionsCavernous endothelial regeneration by use of Ang-4 protein may have potential for the treatment of vascular disease-induced ED, such as diabetic ED. Kwon M-H, Ryu J-K, Kim WJ, Jin H-R, Song K-M, Kwon K-D, Batbold D, Yin GN, Koh GY, and Suh J-K. Effect of intracavernous administration of angiopoietin-4 on erectile function in the streptozotocin-induced diabetic mouse. J Sex Med 2013;10:2912-2927.