Down-regulation of p21-activated kinase 1 by progestin and its increased expression in the eutopic endometrium of women with endometriosis.
BACKGROUND
P21-activated kinase 1 (Pak1) integrates various signaling pathways that are vital to cell survival and function. This study was performed to evaluate whether sex steroids may regulate the expression of Pak1 in endometrial cells as well as whether its expression is increased in the eutopic endometrium of women with endometriosis.


METHODS
Following in vitro estradiol (E(2)) and/or medroxyprogesterone acetate (MPA) treatment of Ishikawa cells and endometrial stromal cells (ESCs), Pak1 protein was analyzed utilizing western blot analysis and immunocytochemistry. Immunohistochemistry was performed to evaluate Pak1 immunoreactivity semiquantitatively in women with endometriosis and in controls. To assess the role of Pak1 on endometrial cell viability, crystal violet assay was performed following transfection of Ishikawa cells with Pak1 small interfering RNA (siRNA).


RESULTS
In vitro treatment with E(2) plus MPA or MPA alone led to a significant decrease of Pak1 protein in Ishikawa cells and ESCs (both P < 0.05 versus control). Immunohistochemistry also revealed that Pak1 protein is significantly decreased during the secretory phase in both epithelial and stromal cells in the control subjects (P < 0.001 and P < 0.01, respectively). The immunoreactivity of Pak1 in glandular cells was significantly increased in the eutopic endometrium of women with endometriosis compared with the controls during the secretory phase (P < 0.01). Crystal violet assay has shown that transfection of Ishikawa cells with Pak1 siRNA led to a significant decrease of cellular viability (P < 0.05).


CONCLUSIONS
These findings suggest that Pak1 is down-regulated by progesterone during the secretory phase in normal endometrium and increased Pak1 activity during the secretory phase might lead to establishment of endometriosis.
Kim
Sung Hoon
SH
Department of Obstetrics and Gynecology, University of Ulsan College of Medicine, Asan Medical Center, 388-1, Pungnap-2dong, Songpa-gu, Seoul 138-736, South Korea. kimsung@amc.seoul.kr
Lee
Hoi Woul
HW
Kim
Young Hoon
YH
Koo
Yun Hee
YH
Chae
Hee Dong
HD
Kim
Chung Hoon
CH
Lee
Pil Ryang
PR
Kang
Byung Moon
BM
D000328:Adult; D002460:Cell Line; D015536:Down-Regulation / Q000187:drug effects*; D004715:Endometriosis / Q000378:metabolism*; D004717:Endometrium / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology*; D008597:Menstrual Cycle / Q000378:metabolism; D011372:Progestins / Q000494:pharmacology*; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D054462:p21-Activated Kinases / Q000235:genetics* / Q000378:metabolism
D011372:Progestins; D034741:RNA, Small Interfering; D004958:Estradiol; D017258:Medroxyprogesterone Acetate; C515903:PAK1 protein, human; D054462:p21-Activated Kinases