G Protein-Coupled Estrogen Receptor (GPER) and ERs Are Modulated in the Testis–Epididymal Complex in the Normal and Cryptorchid Dog

TL;DR

This study examines how estrogen receptors and related proteins are affected in the reproductive system of dogs with cryptorchidism, a condition where testes fail to descend.

Contribution

The study reveals altered expression of GPER and ERs in the testis–epididymal complex of cryptorchid dogs, suggesting a potential role in the condition.

Findings

GPER and ER-alpha are upregulated in the reproductive tract of cryptorchid dogs.

ER-beta is downregulated in the same condition.

SOD1 and Nrf2 expression is modulated, possibly linked to estrogen receptor changes.

Abstract

The testicular function as well as the maintenance and control of spermatogenesis are regulated by a delicate balance between androgens and estrogens. Cryptorchidism, largely diffused in canine species, is a congenital abnormality of the genitourinary tract, due to the failure to descend by one or both testes into the scrotal sac. In consideration of the possible role of estrogenic molecules affecting testicular descent, the aim of this study was to determine the distribution and expression (proteins and relative mRNAs levels) of two nuclear estrogen receptors (ERs), ER-alpha and ER-beta and a trans-membrane G protein-coupled estrogen receptor (GPER), in the testis–epididymal complex of the dog. In addition, in these tissues the expression level of two proteins as SOD1 and Nrf2 normally associated with oxidative stress was investigated to evaluate possible relation with ERs. Collectively, the results obtained by using Immunohistochemistry, Western blot and qRT-PCR showed changes in the distribution and expression of the GPER and ERs between the normal and cryptorchid dog. In detail, an upregulation of GPER and ER-alpha and a downregulation of ER-beta in the canine cryptorchid reproductive tract was observed in association with a modulation of SOD1 and Nrf2 expression.

There is growing evidence by the literature that the unbalance between androgens and estrogens is a relevant condition associated with a common canine reproductive disorder known as cryptorchidism. The role of estrogens in regulating testicular cell function and reproductive events is supposedly due to the wide expression of two nuclear estrogen receptors (ERs), ER-alpha and ER-beta and a trans-membrane G protein-coupled estrogen receptor (GPER) in the testis. In this study, immunohistochemistry, Western blotting and qRT-PCR were used to assess the distribution and expression of GPER in the testis–epididymal complex in the normal and cryptorchid dog. ER-alpha and ER-beta were also evaluated to better characterize the relative abundances of all three receptors. In addition, in these tissues, the expression level of two proteins as SOD1 and Nrf2 normally associated with oxidative stress was investigated to evaluate a possible relationship with ERs. Our data revealed changes in the distribution and expression of the GPER between the normal and cryptorchid dog. In particular, dogs affected by cryptorchidism showed an upregulation of GPER at level of the examined reproductive tract. Also considering the obtained result of a modulation of SOD1 and Nrf2 expression, we could hypothesize the involvement of GPER in the cryptorchid condition. Further studies are, however, necessary to characterize the role of GPER and its specific signaling mechanisms.

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