Testosterone regulates RhoA/Rho-kinase signaling in two distinct animal models of chemical diabetes.
BACKGROUND
The contractile RhoA/Rho-kinase (ROCK) signaling pathway is upregulated in penile tissue in animal models of experimental diabetes and has been proposed to contribute to diabetes-related erectile dysfunction (ED).


OBJECTIVE
To investigate the effect of testosterone (T) on the RhoA/ROCK signaling in diabetes.


METHODS
We used two distinct animal models of chemical diabetes (alloxan-induced in the rabbit and streptozotocin-induced in the rat) with or not T supplementation.


METHODS
The effect of diabetes and T supplementation on RhoA/ROCK signaling was evaluated as responsiveness to the selective ROCK inhibitor Y-27632 either by "in vitro" contractility study (diabetic rabbit) or "in vivo" as erectile response elicited by intracavernous injections (diabetic rats). RhoA/ROCK gene and protein expression were also analyzed.


RESULTS
In both models, hypogonadism was observed, characterized by reduced T plasma level and androgen-dependent accessory glands atrophy. Diabetic animals showed a significant increase in responsiveness to increasing concentrations of Y-27632. T substitution (30 mg/kg, weekly) completely prevented hypogonadism and diabetes-induced penile hypersensitivity to Y-27632. To test whether this effect was due to a T-dependent regulation of RhoA/ROCK gene expression, we measured RhoA/ROCK mRNA. Both isoforms of ROCK (ROCK1/ROCK2) were analyzed by real-time reverse transcriptase polymerase chain reaction (RT-PCR) in rat penile samples. We found that ROCK1 mRNA was significantly increased (P < 0.05) in penile tissues from diabetic animals and maintained at the control values by T, as also confirmed by semiquantitative RT-PCR in rabbit. Conversely, RhoA and ROCK2 mRNA expression was not influenced either by diabetic condition or by T administration. Accordingly, ROCK1 protein expression, as evaluated by Western blot and immunohistochemistry analysis, was increased in penile samples from diabetic animals and normalized by T.


CONCLUSIONS
Our data further support the hypothesis that the overexpression of RhoA/ROCK signaling contributes to diabetes-related ED. Moreover, treating hypogonadism in course of diabetes may maintain erectile function also by normalizing RhoA/ROCK pathway upregulation.
Vignozzi
Linda
L
Andrology Unit, Florence, Italy.
Morelli
Annamaria
A
Andrology Unit, Florence, Italy.
Filippi
Sandra
S
Interdep. Laboratory of Functional and Cellular Pharmacology of Reproduction, Departments of Pharmacology and Clinical Physiopathology, University of Florence, Florence, Italy.
Ambrosini
Stefano
S
Department of Anatomy, Histology and Forensic Medicine, University of Florence, Florence, Italy.
Mancina
Rosa
R
Andrology Unit, Florence, Italy.
Luconi
Michaela
M
Endocrinology Unit, Department of Clinical Physiopathology, Center for Research, Transfer and High Education DENOTHE, University of Florence, Florence, Italy.
Mungai
Sara
S
Andrology Unit, Florence, Italy.
Vannelli
Gabriella Barbara
GB
Department of Anatomy, Histology and Forensic Medicine, University of Florence, Florence, Italy.
Zhang
Xin-Hua
XH
Andrology Unit, Florence, Italy.
Forti
Gianni
G
Endocrinology Unit, Department of Clinical Physiopathology, Center for Research, Transfer and High Education DENOTHE, University of Florence, Florence, Italy.
Maggi
Mario
M
Andrology Unit, Florence, Italy. Electronic address: m.maggi@DFC.UNIFI.IT.
D000496:Alloxan; D000577:Amides / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000150:complications / Q000378:metabolism*; D004195:Disease Models, Animal; D007172:Erectile Dysfunction / Q000201:enzymology* / Q000209:etiology / Q000517:prevention & control*; D007006:Hypogonadism / Q000209:etiology; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D010413:Penis / Q000187:drug effects / Q000201:enzymology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013311:Streptozocin; D013739:Testosterone / Q000378:metabolism* / Q000494:pharmacology*; D015854:Up-Regulation; D054460:rho-Associated Kinases
D000577:Amides; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; C108830:Y 27632; D013739:Testosterone; D013311:Streptozocin; D000496:Alloxan; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases