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Published on: February 16, 2015
Key apoptotic pathways for heat-induced programmed germ cell death in the testis
Amiya P Sinha Hikim1, Yanhe Lue, Cindy M Yamamoto
1Division of Endocrinology, Department of Medicine, Harbor-University of California-Los Angeles Medical Center, Box 446, 1000 West Carson Street, Torrance, CA 90509, USA. hikim@gcrc.rei.edu
Endocrinology
|June 18, 2003
Summary
Mild heat exposure triggers germ cell apoptosis in rat testes by activating the mitochondria and endoplasmic reticulum pathways. This process involves specific protein changes and caspase activation, independent of Fas signaling.
Area of Science:
- Reproductive Biology
- Cell Biology
- Molecular Biology
Background:
- Heat stress is a known factor affecting male reproductive function.
- Germ cell apoptosis (programmed cell death) is crucial for spermatogenesis regulation.
- The precise molecular mechanisms of heat-induced germ cell apoptosis are not fully understood.
Purpose of the Study:
- To elucidate the molecular pathways involved in heat-induced germ cell apoptosis in rat testes.
- To investigate the role of specific proteins and signaling pathways in this process.
Main Methods:
- Exposure of rat testes to mild heat (43°C for 15 min).
- Analysis of protein localization (Bax, cytochrome c) using Western blotting and cell fractionation.
- Assessment of caspase activation (caspase 9, 3, 6, 7) and poly(ADP) ribose polymerase cleavage.
- Studies using FasL-defective gld mice to evaluate the role of Fas signaling.
Main Results:
- Heat exposure rapidly induced stage- and cell-specific germ cell apoptosis.
- Bax redistribution from cytoplasm to paranuclear localization preceded apoptosis initiation.
- Cytosolic translocation of cytochrome c and activation of caspases 9, 3, 6, and 7 were observed.
- Bax accumulation in the endoplasmic reticulum was detected early in apoptosis.
- Heat-induced germ cell apoptosis was not blocked in FasL-defective mice, suggesting Fas independence.
Conclusions:
- Mitochondrial and endoplasmic reticulum-dependent pathways are critical for heat-induced germ cell apoptosis in the testis.
- The Fas signaling pathway is dispensable for this type of apoptosis.
- Understanding these pathways provides insight into male infertility causes and potential therapeutic targets.
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