In vitro bisphenol A impairs testicular energy metabolism and spermatogenesis through nuclear estrogen receptors activation in zebrafish

Abstract

This study investigated the effects of bisphenol A (BPA) and the involvement of nuclear estrogen receptors (ESR) on testicular energy metabolism and spermatogenesis in zebrafish. Testes were incubated with DMSO, 10 pM or 10 μM BPA for 6 or 72 h, with some samples pre-incubated with the ESRα/β antagonist ICI 182,780. Gene and protein expressions were analyzed using real-time PCR and Western blot, respectively. Additionally, immunohistochemistry assessed protein expression, and testicular cell surface proportions were analyzed with Ilastik software. Results showed that 10 pM BPA (6 h) increased the expression of lactate dehydrogenase (ldhba), alanine aminotransferase (gpt2), pyruvate carboxylase, estrogen receptor β1 (esr2b), and P-element induced wimpy testis-like. After 72 h, outer dense fiber protein 3b expression decreased through ESRα/β, and BPA reduced spermatid and spermatozoa proportions, also mediated by ESRα/β activation. Moreover, 10 pM BPA decreased pyruvate kinase M1/2a (pkma) expression, whereas 10 μM BPA reduced gpt2 and estrogen-related receptor levels, as well as increased monocarboxylate transporter 4 (mct4), estrogen receptor β2 (esr2b) and synaptonemal complex protein 3 (scp3) expressions. Furthermore, the reduced relative expression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase and ldhba, as well as increased expression of glycogen phosphorylase by 10 μM BPA were dependent on ESRα/β. Additionally, BPA affected cell numbers expressing LDH and PKM via ESRα/β and increased the immunocontent of PKMA, PCNA, and ERK 1/2 phosphorylation. These results indicate that exposure of male fish to environmental concentrations of BPA impairs testicular energy metabolism and spermatogenesis in zebrafish through ESRα/β activation.