Redistribution of Bax Is an Early Step in an Apoptotic Pathway Leading to Germ Cell Death in Rats, Triggered by Mild Testicular Hyperthermia

• Published in: Biology of reproduction Vol. 63; no. 6; pp. 1683 - 1690
• Main Authors: Yamamoto, C M, Sinha Hikim, A P, Huynh, P N, Shapiro, B, Lue, Y, Salameh, W A, Wang, C, Swerdloff, R S
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01.12.2000
• Subjects: Animals; Apoptosis - physiology; Base Sequence; bcl-2-Associated X Protein; Biological and medical sciences; Blotting, Western; Fever - metabolism; Fever - pathology; Fundamental and applied biological sciences. Psychology; Germ Cells - metabolism; Germ Cells - pathology; Immunohistochemistry; Male; Mammalian male genital system; Mice; Molecular Sequence Data; Morphology. Physiology; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; Seminiferous Epithelium - cytology; Seminiferous Epithelium - growth & development; Testis - metabolism; Testis - pathology; Up-Regulation - genetics; Up-Regulation - physiology; Vertebrates: reproduction; Rat; Spermatogenesis; Body temperature; Rodentia; Germinal cell; Gene expression; Testicle; Male genital system; Vertebrata; Mammalia; Cell death; Animal; Localization; Induced hyperthermia; Apoptosis; Tumor suppressor gene
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod63.6.1683

Programmed cell death occurs spontaneously during spermatogenesis and can be induced in a cell- and stage-specific manner by mild testicular hyperthermia. Studies using transgenic mice suggest the involvement of Bcl-2 proteins in regulating germ cell apoptosis. To delineate further the pathways involved, we examined the temporal changes in proapoptotic Bax and antiapoptotic Bcl-2 in rat testes after transient exposure to heat (43°C for 15 min). Germ cell apoptosis, involving exclusively early (I–IV) and late (XII–XIV) stages, was activated within 6 h. Initiation of apoptosis was preceded by a redistribution of Bax from a cytoplasmic to perinuclear localization within 0.5 h of heating as assessed by immunocytochemical methods. In contrast, Bcl-2 is distributed both in the cytoplasm and nucleus in those cell types susceptible to heat-induced apoptosis. Despite the striking redistribution, Bax levels remained unchanged as determined by Western analysis; Bcl-2 levels increased significantly by 6 h after heat exposure. Reverse transcription-polymerase chain reaction analysis indicated no change in either Bax or Bcl-2 mRNA levels in response to heat, suggesting the involvement of post-transcriptional rather than transcriptional mechanisms mediating their activity. The marked subcellular redistribution of Bax prior to activation of apoptosis and the increase in Bcl-2 suggest an involvement of Bcl-2 family members in heat-induced apoptotic death of germ cells.