Identification of aquaporin-5 and lipid rafts in human resting saliva and their release into cevimeline-stimulated saliva.
BACKGROUND
It is unknown whether AQP5 and lipid rafts are released into human unstimulated (resting) saliva and saliva in response to secretagogues.


METHODS
In order to quantitate the salivary concentration of AQP5, we produced a polyclonal antibody for human AQP5 and developed an enzyme-like immunosorbent assay (ELISA).


RESULTS
AQP5 and lipid rafts were identified in human resting saliva. The amount of AQP5 in resting saliva showed a diurnal variation with high levels during waking hours, and an age-related decrease in AQP5 was coincident with the volume of resting saliva. Cevimeline, a muscarinic acetylcholine receptor (mAChR) agonist, induced the release of AQP5 with lipid rafts, amylase, mucin, and lysozyme. Changes in saliva AQP5 levels after cevimeline administration occurred simultaneously with changes in saliva flow rates. Confocal microscopy revealed that AQP5 was located in the apical plasma membrane and showed a diffuse pattern in parotid glands under resting conditions. Following cevimeline administration, AQP5 was predominantly associated with the APM and was localized in the lumen.


CONCLUSIONS
AQP5 and lipid rafts were released with salivary proteins from human salivary glands by the stimulation of M3 mAChRs, and that changes in saliva AQP5 levels can be used as an indicator of salivary flow rate and also as a useful index of M3 mAChR agonist's action on human salivary glands.
Pan
Yan
Y
Department of Pharmacology, The University of Tokushima Graduate School of Dentistry, 3-18-15, Kuramoto-cho, Tokushima, 770-8504, Japan.
Iwata
Fusako
F
Wang
Di
D
Muraguchi
Masahiro
M
Ooga
Keiko
K
Ohmoto
Yasukazu
Y
Takai
Masaaki
M
Cho
Gota
G
Kang
Jinsen
J
Shono
Masayuki
M
Li
Xue-jun
XJ
Okamura
Ko
K
Mori
Toyoki
T
Ishikawa
Yasuko
Y
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000681:Amylases / Q000378:metabolism; D000818:Animals; D051402:Aquaporin 5 / Q000378:metabolism*; D002940:Circadian Rhythm; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D008297:Male; D021962:Membrane Microdomains / Q000502:physiology*; D018613:Microscopy, Confocal; D008875:Middle Aged; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D011812:Quinuclidines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D043587:Receptor, Muscarinic M3 / Q000819:agonists*; D012463:Saliva / Q000187:drug effects / Q000378:metabolism*; D012469:Salivary Glands / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D012890:Sleep; D013876:Thiophenes / Q000494:pharmacology*; D014851:Wakefulness; D055815:Young Adult
C496036:AQP5 protein, human; D051402:Aquaporin 5; D011812:Quinuclidines; D043587:Receptor, Muscarinic M3; D013876:Thiophenes; D000681:Amylases; C059240:cevimeline