Relevance of caspase activity during apoptosis in pubertal rat spermatogenesis.
Caspases are a family of cysteine-proteases, activated upon several different stimuli, which execute apoptosis in many cell death models. Previous work of our group has shown rats have the highest rate of apoptosis during the first wave of spermatogenesis (between 20 and 25 days after birth), as evaluated by TUNEL and caspase activity. However, the hierarchical order of caspase activation and the relevance of each caspase during germ cell apoptosis are not clear. Thus, the goal of this work is to take a pharmacological approach to dissect the apoptosis pathway of caspase activation. Results showed that intratesticular injection of a caspase-8 inhibitor (z-IETD-fmk), or a pan-caspase inhibitor (z-VAD- fmk), significantly decreased the cleavage of p115 and PARP, two endogenous substrates of caspases, in 22-day-old rats. Additionally, these inhibitors promoted a significant reduction in the number of apoptotic germ cells. On the other hand, intratesticular injection of two different inhibitors of the intrinsic pathway (z-LEHD-fmk and minocycline) did not have any effect upon caspase substrates cleavage (p115 and PARP) or the number of apoptotic germ cells. Therefore, we conclude that the extrinsic pathway of apoptosis plays an important role in physiological germ cell apoptosis during the first round of spermatogenesis in the rat.
Codelia
Veronica A
VA
Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile and Millennium Nucleus for Developmental Biology, Santiago, Chile.
Cisternas
Pablo
P
Moreno
Ricardo D
RD
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053181:Caspase 8 / Q000378:metabolism*; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000096:biosynthesis; D006801:Humans; D008297:Male; D051381:Rats; D064067:Rho Guanine Nucleotide Exchange Factors; D012741:Sexual Maturation / Q000187:drug effects / Q000502:physiology*; D013091:Spermatogenesis / Q000187:drug effects / Q000502:physiology*; D013094:Spermatozoa / Q000201:enzymology*
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D064067:Rho Guanine Nucleotide Exchange Factors; C505528:Casp8 protein, rat; D053181:Caspase 8