RAD51 Plays a Crucial Role in Halting Cell Death Program Induced by Ionizing Radiation in Bovine Oocytes

• Published in: Biology of reproduction Vol. 86; no. 3; p. 76
• Main Authors: KUJJO, LoroL, RONNINGEN, Reg, SMITH, George W, KURUMIZAKA, Hitoshi, YOKOYAMA, Shigeyuki, CIBELLI, Jose B, PEREZ, Gloria I, ROSS, Pablo, PEREIRA, Ricardo J. G, RODRIGUEZ, Ramon, BEYHAN, Zeki, GOISSIS, Marcelo D, BAUMANN, Thomas, KAGAWA, Wataru, CAMSARI, Cagri
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01.03.2012
• Subjects: Animals; Annexin A5 - metabolism; Apoptosis - radiation effects; Biological and medical sciences; Caspase 3 - metabolism; Cattle; Cells, Cultured; Cytochromes c - metabolism; DNA Damage - radiation effects; Female; Fundamental and applied biological sciences. Psychology; Mice; Models, Animal; Oocytes - cytology; Oocytes - metabolism; Oocytes - radiation effects; Rad51 Recombinase - physiology; Radiation, Ionizing; Vertebrates: reproduction; female germ cells; oocytes; solar/cosmic radiation; Rodentia; Ox; Germinal cell; Vertebrata; Reproduction; Mammalia; RAD51; Mouse; Cell death; Animal; Female; bovine; Artiodactyla; Ungulata; Oocyte; ionizing radiation; Apoptosis
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod.111.092064

Reproductive health of humans and animals exposed to daily irradiants from solar/cosmic particles remains largely understudied. We evaluated the sensitivities of bovine and mouse oocytes to bombardment by krypton-78 (1 Gy) or ultraviolet B (UV-B; 100 microjoules). Mouse oocytes responded to irradiation by undergoing massive activation of caspases, rapid loss of energy without cytochrome-c release, and subsequent necrotic death. In contrast, bovine oocytes became positive for annexin-V, exhibited cytochrome-c release, and displayed mild activation of caspases and downstream DNAses but with the absence of a complete cell death program; therefore, cytoplasmic fragmentation was never observed. However, massive cytoplasmic fragmentation and increased DNA damage were induced experimentally by both inhibiting RAD51 and increasing caspase 3 activity before irradiation. Microinjection of recombinant human RAD51 prior to irradiation markedly decreased both cytoplasmic fragmentation and DNA damage in both bovine and mouse oocytes. RAD51 response to damaged DNA occurred faster in bovine oocytes than in mouse oocytes. Therefore, we conclude that upon exposure to irradiation, bovine oocytes create a physiologically indeterminate state of partial cell death, attributed to rapid induction of DNA repair and low activation of caspases. The persistence of these damaged cells may represent an adaptive mechanism with potential implications for livestock productivity and long-term health risks associated with human activity in space.