title: Caspase-3 and caspase-activated deoxyribonuclease are associated with testicular germ cell apoptosis resulting from reduced intratesticular testosterone.
abstract: The purpose of the present study was to examine the possible involvement of caspase-3 and caspase-activated deoxyribonuclease in rat testicular germ cell apoptosis resulting from reduced intratesticular testosterone concentration. Adult Sprague Dawley rats received LH-suppressive testosterone- and estradiol-filled SILASTIC capsules of 2.5 and 0.1 cm, respectively, a regimen known to rapidly reduce testosterone production by the testes and to produce azoospermia within 8 wk. Germ cell internucleosomal DNA cleavage increased compared with control levels by 1 wk postimplantation and increased further through 4 wk. In situ terminal deoxynucleotidyltransferase-mediated deoxy-UTP nick end labeling revealed that spermatocytes represented the predominant apoptotic cell type. Modest immunoreactivity for active caspase-3 was localized to the cytoplasm or perinuclear region of the germ cells of control testes. After testosterone and estradiol administration, however, intense staining for caspase-3 was localized to the nuclei of spermatocytes. Western blotting revealed significantly increased caspase-3 cleavage (activation) in nuclei isolated from germ cells after rats were administered testosterone and estradiol. Cleavage of the caspase-3 substrate protein, poly(ADP-ribose) polymerase, was seen after testosterone and estradiol treatment. Additionally, the caspase-activated deoxyribonuclease protein content was significantly increased in germ cells after rats were administered testosterone and estradiol, and caspase-activated deoxyribonuclease immunoreactivity was localized to the nuclei of apoptotic spermatocytes. Taken together, these results indicate that germ cell apoptosis resulting from a reduced intratesticular testosterone concentration is caspase-3 activation dependent and suggest that the translocation of active caspase-3 and caspase-activated deoxyribonuclease to the nucleus may be involved in the induction of germ cell apoptosis.
authors.affiliation: Division of Reproductive Biology, Department of Biochemistry and Molecular Biology, The Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205, USA. jmkim@jhsph.edu
authors.forename: J M
authors.initials: JM
authors.lastname: Kim
authors.forename: S R
authors.initials: SR
authors.lastname: Ghosh
authors.forename: A C
authors.initials: AC
authors.lastname: Weil
authors.forename: B R
authors.initials: BR
authors.lastname: Zirkin
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D008297:Male; D009929:Organ Size / Q000502:physiology; D011065:Poly(ADP-ribose) Polymerases / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D013094:Spermatozoa / Q000502:physiology*; D013737:Testis / Q000033:anatomy & histology / Q000502:physiology; D013739:Testosterone / Q000037:antagonists & inhibitors*
chemical_list: D013739:Testosterone; D011065:Poly(ADP-ribose) Polymerases; D003851:Deoxyribonucleases; C109663:caspase-activated deoxyribonuclease; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases