Dynamic expression of caspases protein levels and activity, but not mRNA, in the primate corpus luteum during the menstrual cycle

PELUFFO, MC; YOUNG, KA; STOUFFER, RL

Cincinnati, Ohio

Congreso; 36th SSR Annual Meeting; 2003

SSR (Society for the Study of Reproduction)

Caspases (CASP) play a central role in the execution of programmed cell death, or apoptosis. We hypothesized that CASP-dependant apoptosis occurs during the tissue remodeling that is associated with the formation and regression of the primate corpus luteum (CL). Therefore, studies were designed to determine if mRNA and/or protein expression plus activity levels of CASP 2, 3, 8, and 9 vary in the primate CL of the natural menstrual cycle. CL (n_3-4/stage) from rhesus monkeys were collected during the early (ECL, d3 post LH surge), mid (MCL, d7), mid-late (MLCL, d10), late (LCL, d14), and very-late (VLCL, d18; menses) luteal phase. Total RNA was extracted for sq RT-PCR (CASP 2, 3, 8) and real time PCR (CASP 2) analysis; protein was isolated for ELISA (CASP 3) and fluorometric caspase activity (CASP 2, 3, 8, 9) assessments. Portions of the CL were fixed in formalin and used for immunohistochemistry (CASP 2) analyses. PCR analysis revealed no significant changes in mRNA levels for CASP 2, 3, and 8 throughout the stages of the CL lifespan (p_0.05). Although CASP mRNA expression did not change, immunolabeling for CASP 2 protein (proapoptotic isoform) in granulosa-luteal cells increased in LCL and VLCL as compared to earlier stages. Also, CASP 3 protein levels (active form) were 2-to 58-fold higher in MLCL as compared to other stages (p_ 0.05). Assessment of enzyme activity for CASP 2 revealed a 5-fold increase between ECL and MLCL (p_0.05). CASP 3 enzyme activity also increased 2- to 6-fold in MLCL as compared to all other groups (p_ 0.05). Similarly, enzyme activity for CASP 8 and 9 increased in the MLCL 10- and 5-fold, respectively, as compared to ECL (p_0.05). In all CL stages, enzyme activity for CASP 3 was 45-68% higher than CASP 2 activity, and 90-96% higher than CASP 8 or 9 activity. These results suggest that the regulation of CASP in the primate CL is not at the transcriptional level, but rather at the level of translation or enzyme activation. Caspase activity peaked around the onset of CL regression (MLCL), and declined as luteal regression progressed (L to VLCL). Since caspase activation results in programmed cell death, apoptosis may be involved in the initial stage of luteolysis in the primate CL during the menstrual cycle. Supported by: HD20869, HD18185, RR00163, HD42896 (KAY), and NICHD Fogarty D43TW00668 (MCP).