Expression of aquaporin 8 and its up-regulation by cyclic adenosine monophosphate in human WISH cells.
OBJECTIVE
Water absorption across the fetal chorioamniotic membranes is a critical regulatory pathway for amniotic fluid volume homeostasis. Aquaporins are cell membrane proteins that significantly enhance membrane permeability to water by acting as water channels. We recently demonstrated that aquaporin 8 is expressed in human amnion, chorion, and placenta. Thus, aquaporin 8 expression represents a molecular mechanism of amniotic water absorption through intramembranous pathways. The current study sought to determine whether aquaporin 8 is expressed in human amnion-derived cell culture and to explore its regulation by second messenger cyclic adenosine monophosphate.


METHODS
Human amnion-derived WISH cells were cultured. Total RNA was isolated and reverse transcriptase-polymerase chain reaction was used to determine aquaporin 8 gene expression. To determine the effect of cyclic adenosine monophosphate on aquaporin 8 expression, WISH cells were cultured in the presence of either monobutyryl cyclic adenosine monophosphate or the cyclic adenosine monophosphate-elevating agent forskolin. Multiplex semiquantitative reverse transcriptase-polymerase chain reaction was carried out to quantify aquaporin 8 messenger RNA levels.


RESULTS
Reverse transcriptase-polymerase chain reaction detected aquaporin 8 expression in WISH cells. After forskolin treatment for 2 hours, aquaporin 8 messenger RNA expression in WISH cells increased 4-fold (P <.001). Stimulation of aquaporin 8 gene expression by colforsin was observed throughout the study period of 20 hours. Incubation of WISH cells with monobutyryl cyclic adenosine monophosphate resulted in a 2-fold increase in aquaporin 8 messenger RNA level (P <.001). However, stimulation of aquaporin 8 gene expression by monobutyryl cyclic adenosine monophosphate attenuated to baseline level after 20 hours of monobutyryl cyclic adenosine monophosphate treatment.


CONCLUSIONS
The current study demonstrates the expression of aquaporin 8 water channel in human amnion-derived WISH cells and aquaporin 8 expression up-regulation by second messenger cyclic adenosine monophosphate. Aquaporin 8 messenger RNA demonstrates a relatively short biologic half-life in vitro, which renders its rapid responsiveness to regulation
Wang
Shengbiao
S
Department of Obstetrics and Gynecology, Harbor-UCLA Research and Education Institute, School of Medicine, University of California, Los Angeles 90502, USA. sheng@gcrc.rei.edu
Chen
Jiexiong
J
Au
Katherine T
KT
Ross
Michael G
MG
D000650:Amnion / Q000166:cytology; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D003994:Bucladesine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D004847:Epithelial Cells; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007473:Ion Channels; D012333:RNA, Messenger / Q000378:metabolism; D015854:Up-Regulation
D020346:Aquaporins; D007473:Ion Channels; D012333:RNA, Messenger; C108330:aquaporin 8; C002373:monobutyryl cyclic AMP; D005576:Colforsin; D003994:Bucladesine; D000242:Cyclic AMP