Abstract
Ischemia-reperfusion (IR) of the testis results in germ-cell-specific apoptosis (GCA) and a reduction in daily sperm production. This has been correlated with and is dependent upon neutrophil recruitment to the testis. In a rat model of testicular IR, this has also been correlated with an increase in reactive oxygen species (ROS). We have investigated ROS in the mouse testis after IR and determined whether the observed GCA is mediated via a mitochondrial caspase-9-dependent pathway involving the upstream mediators caspase 2 and BAX. Mice were subjected to a 2-h period of testicular ischemia followed by reperfusion. An accumulation of 8-isoprostane, a marker of oxidative stress, occurred 4 h after reperfusion. Activation of a mitochondrial dependent pathway to GCA after testicular IR was determined based on the observations that both BAX and caspase 2 translocated to the mitochondria, and that an increase occurred in cytoplasmic cytochrome c. Moreover, microinfusion of a specific caspase 9 inhibitor significantly reduced active caspase 3 after testicular IR and the number of apoptotic germ cells. These results suggest that oxidative stress products accumulate in the testis following IR and demonstrate that the observed GCA is stimulated through a mitochondrial caspase-9-dependent pathway. The identification of the germ-cell apoptotic pathway induced after testicular IR, including the key players in the pathway subsequent to ROS (BAX, caspase 9, and caspase 2), aids our understanding of IR injury in the testis and provides a wider background for the development of therapeutic interventions to rescue testis function.
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Acknowledgements
The authors wish to acknowledge the services of the Cell Science Core of the Center for Research in Reproduction at the University of Virginia (NICHD Specialized Cooperative Centers Program in Reproductive Research: U54 HD28934).
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The work was supported by grants P50 DK45179 and DK53072.
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Lysiak, J.J., Zheng, S., Woodson, R. et al. Caspase-9-dependent pathway to murine germ cell apoptosis: mediation by oxidative stress, BAX, and caspase 2. Cell Tissue Res 328, 411–419 (2007). https://doi.org/10.1007/s00441-006-0341-y
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DOI: https://doi.org/10.1007/s00441-006-0341-y