Loss of TGFbeta, Apoptosis, and Bcl-2 in Erectile Dysfunction and Upregulation of p53 and HIF-1alpha in...

Vasculogenic erectile dysfunction (ED) is associated with collagen replacement of the cavernosal smooth muscle, mediated by an increase in transforming growth factor (TGF)-production secondary to hypoxemia. We tested the hypothesis that human ED is the result of an increase in apoptosis of the cavernosal smooth muscle cells with replacement by collagen, mediated by the TGFbeta upregulation. We also examined the tissue for proteins associated with apoptosis. Human cavernosal tissue was procured from impotent men at the time of prosthesis insertion. Normal corpous cavernosum served as a control. The TUNEL assay was used to assess apoptosis. Immunohistochemistry staining was used to detect TGFbeta and Bcl-2 expression, while Western blot analysis was used to detect expression of Bcl-2, p53, and hypoxia-inducible factor (HIF)-1a. Immunohistochemistry showed downregulation of TGFbeta protein expression in the corpus cavernosum of men with ED. Apoptotic nuclei were noted in cavernosal smooth muscle from a potent man but were not found in cavernosal tissue from men with ED. To gain insight into the possible mechanism of apoptosis in men with ED, the proto-oncogene Bcl-2, a potential inhibitor of apoptosis, was examined. Both immunohistochemistry and Western analysis revealed the presence of Bcl-2 in the cavernosal nerve of a potent man but its absence in cavernosal tissue from men with ED. Thus, loss of Bcl-2 expression correlated with the loss of apoptosis. In contrast, Western blotting demonstrated upregulation of p53 and HIF-1a expression in the cavernosal tissues from the men with ED and diabetes. Male ED follows an active process characterized by a loss of TGFb expression, apoptosis, and Bcl-2 expression. However, there is upregulation of p53 and HIF-1a in men with diabetes. These data support the possibility of hypoxia-mediated ED in diabetes via upregulation of p53 and HIF-1a but does not substantiate a role for TGFbeta in ED.