Male contraception has focused, to a great extent, on approaches that induce
azoospermia or severe
oligospermia through accelerated germ cell apoptosis. Understanding the specific steps in the germ cell apoptotic pathways that are affected by
male contraceptives will allow more specific targeting in future
contraceptive development. In this study, we have used a nonhuman primate model to characterize the key apoptotic pathway(s) in germ cell death after mild testicular
hyperthermia, hormonal deprivation, or combined interventions. Groups of 8 adult (7- to 10-year-old) cynomolgus monkeys (Macaca fascicularis) received one of the following treatments: 1) two empty
silastic implants; 2) two 5.5-cm
testosterone (T) implants; 3) daily exposure of testes to heat (43 degrees C for 30 min) for 2 consecutive days; and 4) two T implants plus testicular heat exposure for two consecutive days. Testicular biopsies were performed before and at Days 3, 8, and 28 of treatment. Treatment with T, heat, or both led to sustained activation of both
mitogen-activated protein kinase (MAPK) 1/3 and
MAPK14. Activation of MAPK1/3 and
MAPK14 were accompanied by an increase in
B-cell leukemia/
lymphoma (BCL) 2 levels in both cytosolic and mitochondrial fractions of testicular lysates (BAX levels remained unaffected) and
cytochrome c and DIABLO release from mitochondria. These treatments also resulted in inactivation of BCL2 through phosphorylation at
serine 70, thereby favoring the death pathway. We conclude that the
serine phosphorylation of BCL2 and activation of the
MAPK14-mediated mitochondria-dependent pathway are critical for male germ cell death in monkeys.