Death receptor response in rodent testis after mono-(2-ethylhexyl) phthalate exposure.
Apoptosis of testicular germ cells is critical for the maintenance of functional spermatogenesis. Previously, we have demonstrated that the Fas (Apo-1, CD95) receptor participates in the regulation of germ cell apoptosis, particularly after toxicant-induced Sertoli cell injury. In this study, we show that germ cells from B6.SMNC3H-Fas(gld,gld) (gld) mice that express a dysfunctional form of FasL still undergo significant apoptosis, albeit at a lower incidence than seen in B6 mice, following mono-(2-ethylhexyl) phthalate (MEHP)-induced Sertoli cell injury. In addition, we show the presence of Fas, TRAIL-R1 (Death Receptor-4, DR4), and TRAIL-R2 (DR5) in the testis of C57BL/6 (B6) and gld mice (4 weeks old), and Sprague-Dawley rats (5 weeks old) and their responsiveness after MEHP treatment. More importantly, Western blot analysis of cellular fractions showed an increase in death receptor localization on the membrane fractions taken from Sprague-Dawley rats. Immunohistochemical analysis indicated localization of Fas and DR5 primarily to the spermatocyte subpopulation of germ cells. Examination of downstream receptor-mediated signals (i.e., cleavage of procaspase-8 and NFkappaB activation) revealed an early increase in NFkappaB-DNA binding and an increase in procaspase-8 processing in mutant gld mice. In summary, germ cell-associated death receptors, as well as downstream signaling elements, appear to be responsive to MEHP-induced Sertoli cell injury. Whether this is directly responsible for the increases in germ cell apoptosis after MEHP exposure is yet to be determined. The observed robust and early increase in Fas in wild-type testis and diminished rates of germ cell apoptosis in mutant testis (gld and lpr(cg)) reiterates the importance of the Fas signaling pathway.
Giammona
C John
CJ
College of Pharmacy, Division of Pharmacology and Toxicology, The University of Texas at Austin, Austin, Texas 78712-1074, USA.
Sawhney
Pragati
P
Chandrasekaran
Yamini
Y
Richburg
John H
JH
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004051:Diethylhexyl Phthalate / Q000031:analogs & derivatives* / Q000633:toxicity*; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D016328:NF-kappa B / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis* / Q000378:metabolism; D013090:Spermatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013737:Testis / Q000187:drug effects* / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
D016328:NF-kappa B; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; C105190:TNFRSF10A protein, human; C505639:TNFRSF10B protein, human; C505640:Tnfrsf10b protein, mouse; C505644:Tnfrsf10b protein, rat; D019014:fas Receptor; D004247:DNA; D004051:Diethylhexyl Phthalate; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505526:Casp8 protein, mouse; C505528:Casp8 protein, rat; C506434:Casp9 protein, mouse; C506435:Casp9 protein, rat; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; C016599:mono-(2-ethylhexyl)phthalate