title: D-Aspartate Induces Proliferative Pathways in Spermatogonial GC-1 Cells.
abstract: D-aspartate (D-Asp) is an endogenous amino acid present in vertebrate tissues, with particularly high levels in the testis. In vivo studies indicate that D-Asp indirectly stimulates spermatogenesis through the hypothalamic-pituitary-gonadal axis. Moreover, in vitro studies have demonstrated that D-Asp up-regulates testosterone production in Leydig cells by enhancing expression of the steroidogenic acute regulatory protein. In this study, a cell line derived from immortalized type-B mouse spermatogonia retaining markers of mitotic germ cells (GC-1) was employed to explore more direct involvement of D-Asp in spermatogenesis. Activity and protein expression of markers of cell proliferation were determined at intervals during incubation in D-Asp-containing medium. D-Asp induced phosphorylation of ERK and Akt proteins, stimulated expression of PCNA and Aurora B, and enhanced mRNA synthesis and protein expression of P450 aromatase and protein expression of Estrogen Receptor β (ERβ). These results are the first demonstration of a direct effect of D-Asp on spermatogonial mitotic activity. Considering that spermatogonia express the NR1 subunit of the N-Methyl-D-Aspartic Acid receptor (NMDAR), we suggest that their response to D-Asp depends on NMDAR-mediated activation of the ERK and Akt pathways and is further enhanced by activation of the P450 aromatase/ERβ pathway.
authors.affiliation: Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Seconda Università di Napoli, Caserta, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Santillo
authors.affiliation: Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Seconda Università di Napoli, Caserta, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Falvo
authors.affiliation: Dipartimento di Psicologia, Seconda Università di Napoli, Caserta, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Chieffi
authors.affiliation: Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Seconda Università di Napoli, Caserta, Italy.
authors.forename: Maria Maddalena
authors.initials: MM
authors.lastname: Di Fiore
authors.affiliation: Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Seconda Università di Napoli, Caserta, Italy.
authors.forename: Rosalba
authors.initials: R
authors.lastname: Senese
authors.affiliation: Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Seconda Università di Napoli, Caserta, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Chieffi Baccari
mesh_terms: D000818:Animals; D001141:Aromatase / Q000235:genetics / Q000378:metabolism; D064107:Aurora Kinase B / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D026603:D-Aspartic Acid / Q000378:metabolism* / Q000494:pharmacology*; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D008954:Models, Biological; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013091:Spermatogenesis / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D013093:Spermatogonia / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism
chemical_list: D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger; D026603:D-Aspartic Acid; D001141:Aromatase; C576924:Aurkb protein, mouse; D064107:Aurora Kinase B; D051057:Proto-Oncogene Proteins c-akt