Leptin modulates the expression of secreted and membrane-associated mucins in colonic epithelial cells by targeting PKC, PI3K, and MAPK pathways.
Mucins play an essential role in the protection and repair of gastrointestinal mucosa. We recently showed that luminal leptin strongly stimulated mucin secretion in vivo in rat colon. In the present study, we challenged the hypothesis that leptin may act directly on goblet cells to induce mucin expression in rat and human intestinal mucin-producing cells (DHE and HT29-MTX). The endoluminal effect of leptin was also studied in vivo in rat perfused colon model. The presence of leptin receptors was demonstrated in the two cell lines by Western blot and RT-PCR. In rat DHE cells, leptin (0.01-10 nmol/l, 60 min) dose dependently increased the secretion of mucins (210 +/- 3% of controls) and the expression of Muc2, Muc3, and Muc4 (twofold basal level) but not of Muc1 and Muc5AC. Luminal perfusion of leptin (60 min, 0.1-100 nmol/l) in rat colon also increased the mRNA level of Muc2, Muc3, and Muc4 but not of Muc1. In human HT29-MTX cells, leptin (0.01-10 nmol/l, 60 min) dose dependently enhanced MUC2, MUC5AC, and MUC4 mRNA levels. These effects were prevented by pretreatment of cells with the leptin mutein L39A/D40A/F41A, which acts as a receptor antagonist. Finally, pathway inhibition experiments suggest that leptin increased mucin expression by activating PKC-, phosphatidyl inositol 3-kinase-, and MAPK-dependent pathways but not the JAK/STAT pathway. In conclusion, leptin may contribute significantly to membrane-associated and secreted mucin production via a direct stimulation of colonic epithelial cells and the activation of leptin receptors. These data are consistent with a role for leptin in regulation of the intestinal barrier function.
El Homsi
Mahmoud
M
INSERM UMR865, Faculté de Médecine R. Laennec, 7 rue Guillaume Paradin, 69008 Lyon, France.
Ducroc
Robert
R
Claustre
Jean
J
Jourdan
Gérard
G
Gertler
Arieh
A
Estienne
Monique
M
Bado
André
A
Scoazec
Jean-Yves
JY
Plaisancié
Pascale
P
D000818:Animals; D002460:Cell Line; D003106:Colon / Q000166:cytology*; D004847:Epithelial Cells / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D020738:Leptin / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D055271:Mucin 5AC; D055262:Mucin-2; D055263:Mucin-3; D055264:Mucin-4; D009077:Mucins / Q000096:biosynthesis* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D011493:Protein Kinase C / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000502:physiology; D054411:Receptors, Leptin
D020738:Leptin; D055271:Mucin 5AC; D055262:Mucin-2; D055263:Mucin-3; D055264:Mucin-4; D009077:Mucins; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; C515448:LEPR protein, human; C524625:MUC2 protein, human; C524658:MUC4 protein, human; C524678:MUC5AC protein, human; C524628:Muc2 protein, rat; C524651:Muc3 protein, rat; C524660:Muc4 protein, rat; C524680:Muc5ac protein, rat