Role of lysophosphatidylcholine in brush-border intestinal alkaline phosphatase release and restoration.
Intestinal alkaline phosphatase (IAP) is a brush-border membrane ectoenzyme (BBM-IAP) that is released into the lumen (L-IAP) after a high-fat diet. We examined the effects of oil feeding and the addition of mixed-lipid micelles on the formation of L-IAP in oil-fed rat intestine, Caco-2 cell monolayers, and mouse intestinal loops. We localized IAP in the duodenum of rats fed corn oil using fluorescence microscopy with enzyme-labeled fluorescence-97 as substrate. Four hours after oil feeding, L-IAP increased approximately 10-fold accompanied by the loss of BBM-IAP, consistent with BBM-IAP release. Rat IAP isozyme mRNAs progressively increased 4-6 h after oil feeding, followed by the increase of IAP activity in the subapical location at 6 h, consistent with the restoration of IAP protein. Postprandial lipid-micelle components, sodium taurocholate with or without oleic acid, mono-oleylglycerol, cholesterol, or lysophosphatidylcholine (lysoPC) were applied singly or as mixed-lipid micelles to the apical surface of polarized Caco-2 cell monolayers. LysoPC increased L-IAP >10-fold over basal release. LysoPC released IAP into the apical medium more than other intestinal brush-border enzymes, 5'-nucleotidase, sucrase, aminopeptidase N, and lactase, without comparable lactate dehydrogenase release or cell injury. LysoPC increased human IAP mRNA levels by 1.5-fold in Caco-2 cells. Luminally applied lysoPC also increased release of IAP preferentially in mouse intestinal loops. These data show that lysoPC accelerates the formation of L-IAP from BBM-IAP, followed by enhanced IAP synthesis, suggesting the role that lysoPC might play in the turnover of brush-border proteins.
Nakano
Takanari
T
Department of Biochemistry, Biomedical Research Center, Saitama Medical University, Saitama, Japan. nk.takanari@gmail.com
Inoue
Ikuo
I
Alpers
David H
DH
Akiba
Yasutada
Y
Katayama
Shigehiro
S
Shinozaki
Rina
R
Kaunitz
Jonathan D
JD
Ohshima
Susumu
S
Akita
Masumi
M
Takahashi
Seiichiro
S
Koyama
Iwao
I
Matsushita
Makoto
M
Komoda
Tsugikazu
T
D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism; D018938:Caco-2 Cells; D003314:Corn Oil / Q000008:administration & dosage*; D004386:Duodenum / Q000201:enzymology; D004847:Epithelial Cells / Q000201:enzymology; D058851:GPI-Linked Proteins; D006801:Humans; D007422:Intestines / Q000201:enzymology*; D007527:Isoenzymes; D008244:Lysophosphatidylcholines / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008823:Micelles; D008871:Microvilli / Q000201:enzymology; D019518:Postprandial Period; D021381:Protein Transport; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D000951:Antigens, Neoplasm; D058851:GPI-Linked Proteins; D007527:Isoenzymes; D008244:Lysophosphatidylcholines; D008823:Micelles; D012333:RNA, Messenger; D003314:Corn Oil; C063088:ALPI protein, human; D000469:Alkaline Phosphatase