HtrA2 is up-regulated in the rat testis after experimental cryptorchidism.
OBJECTIVE
The aim of the present study was to elucidate the role of high temperature requirement A2 (HtrA2) in germ cell loss in the heat-stressed testis.


METHODS
We examined the expression of HtrA2, caspase-9 activity and proteolytic activity of HtrA2 in the rat testis, and their in vivo responses to experimental cryptorchid treatment.


RESULTS
Northern analysis revealed the expression of HtrA2 mRNA peaked at days 1 and 7 after cryptorchid treatment. While expression of HtrA2 mRNA was seen in the spermatogonium, spermatocytes and some spermatids in normal adult rat testis, experimental cryptorchidism treatment resulted in a marked increase in its signal intensity in spermatocytes and some spermatids, and the layers of spermatogonium and early primary spermatocytes became negative at days 1 and 7 after the treatment. However, the spermatogonium, Sertoli cells and interstitial cells appeared to have strong intensities at days 14, 28 and 56 after the treatment. Western analysis revealed the expression of HtrA2 protein peaked at day 2 coinciding with the increase of positive spermatogonium, the appearance of protein-positive interstitial cells, and day 28 coinciding with the reappearance of protein-positive interstitial cells. Caspase-9 activity peaked at day 2 and HtrA2 proteolytic activity peaked at day 28. Consequently, the first peak of HtrA2 mRNA expression was followed by the peak of caspase-9 activity and the second peak was followed by the peak of proteolytic activity; however, the second peak of mRNA expression had considerable chronological difference from that of the protein.


CONCLUSIONS
These findings suggest the probabilities that the heat stress results in germ cell death by a caspase-independent manner with the elevation of HtrA2 proteolytic activity, as well as a caspase-dependent manner with the elevation of caspase-9 activity.
Department of Urology, Saitama Medical Center, Saitama Medical School, Kawagoe, Saitama, Japan. hayashi@saitama-med.ac.jp
Tetsuo
T
Hayashi
Soichiro
S
Yoshida
Atsushi
A
Yoshinaga
Rena
R
Ohno
Nobuyuki
N
Ishii
Takumi
T
Yamada
D000818:Animals; D017209:Apoptosis; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D003456:Cryptorchidism / Q000378:metabolism*; D000074923:High-Temperature Requirement A Serine Peptidase 2; D008297:Male; D024101:Mitochondrial Proteins; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012697:Serine Endopeptidases / Q000096:biosynthesis* / Q000235:genetics; D013737:Testis / Q000378:metabolism*; D015854:Up-Regulation
D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D012697:Serine Endopeptidases; D000074923:High-Temperature Requirement A Serine Peptidase 2; C506435:Casp9 protein, rat; D053453:Caspase 9; D020169:Caspases