Analysis of Testosterone Effects on Sonic Hedgehog Signaling in Juvenile, Adolescent and Adult Sprague Dawley Rat Penis

Abstract

Introduction Smooth muscle apoptosis is a major contributing factor to erectile dysfunction (ED) development in prostatectomy and diabetic patients and animal models. A critical regulator of penile smooth muscle and apoptosis is Sonic hedgehog (SHH). The SHH protein is decreased in ED models and SHH treatment of cavernous nerve (CN) injured rats prevents smooth muscle apoptosis. A close association between androgen deficiency and ED has been suggested in the literature, but few studies have examined the molecular effects on penile smooth muscle and on known signaling mechanisms that regulate morphology. Aim Examine testosterone and SHH interaction in eugonadal adult, adolescent and juvenile rats by performing castration studies and treatment with supraphysiological testosterone. Methods The eugonadal adult Sprague Dawley rats were either treated with testosterone for 7 or 14 days (N=14) or were castrated for 4 or 7 days (N=12). The juvenile rats were treated with testosterone for 8 days (N=7). The adolescent rats were castrated and sacrificed at P88 (N=8). The control rats had empty vehicle (N=22) or sham surgery (N=20). Main Outcome Measures The active form of SHH protein and mRNA were quantified by semi-quantitative immunohistochemical analysis and real-time reverse transcriptase polymerase chain reaction (RT-PCR). Results Testosterone treatment did not alter SHH signaling in juvenile rats. Shh mRNA increased 3.2-fold and SHH protein increased 1.2-fold in rats castrated during puberty. In adult rats, castration decreased Shh mRNA 3.2-fold but did not alter SHH protein. Testosterone supplement in adult rats increased Shh mRNA 2.3-fold and decreased SHH protein 1.3-fold. Conclusions SHH signaling is independent of testosterone in normal juvenile rats and is sensitive to testosterone during adolescence, while testosterone supplement in the adult adversely impacts SHH signaling in a very similar manner to that observed with CN injury.

Translational Perspective on the Role of Testosterone in Sexual Function and Dysfunction

“…Castration in the adult caused an inverse response with decreased Shh mRNA but not protein. Supra-physiological testosterone in the adult increased Shh mRNA and decreased SHH protein [91], reflecting earlier findings that a narrow range of testosterone may impact penile morphology and growth factors.…”

“…Testosterone induced relaxation in human isolated corpora cavernosal strips by activation of smooth muscle adenosine triphosphate-sensitive K + channels [63]. Castration caused age dependent alterations in sonic hedgehog (SHH) protein and mRNA expression [91]. SHH protein and RNA increased when rats were castrated during puberty.…”

A Dual Role for SHH during Phallus Development in a Marsupial

“…There is still insufficient data on these interactions in the phallus, but our data suggests that in the tammar, SHH appears to be downregulated in the presence of androgens, but this appears to differ from which is observed in other species [Ogino et al, 2004;Bond et al, 2010;Miyagawa et al, 2011]. One possible explanation for the variation in the response of SHH to androgens could be explained by stage specific differences.…”

“…In juvenile rats, androgens did not affect SHH , but castration of adolescents elevated SHH levels and suggests that androgens were suppressing SHH expression at certain times. In contrast, testosterone supplement in adult rats increased Shh mRNA but decreased SHH protein [Bond et al, 2010]. The varied response in different species and stages suggests that the interaction between SHH and androgens remains unclear.…”

Peer Review #1 of "Testosterone improves erectile function through inhibition of reactive oxygen species generation in castrated rats (v0.1)"

“…Testosterone is overwhelmingly important in regulating erectile physiology through various signaling pathways (Bond et al 2010;Chua et al 2009;Zhang et al 2011b). Erectile dysfunction (ED) is a common symptom in hypogonadal men that can lead to decreased self-confidence, depression and other symptoms that seriously influence the quality of life (Yohannes et al 2010) .…”