title: Mechanisms of lysophosphatidic acid (LPA) mediated stimulation of intestinal apical Cl-/OH- exchange.
abstract: Lysophosphatidic acid (LPA), a potent bioactive phospholipid, is a natural component of food products like soy and egg yolk. LPA modulates a number of epithelial functions and has been shown to inhibit cholera toxin-induced diarrhea. Antidiarrheal effects of LPA are known to be mediated by inhibiting chloride secretion. However, the effects of LPA on chloride absorption in the mammalian intestine are not known. The present studies examined the effects of LPA on apical Cl(-)/OH(-) exchangers known to be involved in chloride absorption in intestinal epithelial cells. Caco-2 cells were treated with LPA, and Cl(-)/OH(-) exchange activity was measured as DIDS-sensitive (36)Cl(-) uptake. Cell surface biotinylation studies were performed to evaluate the effect of LPA on cell surface levels of apical Cl(-)/OH(-) exchangers, downregulated in adenoma (DRA) (SLC26A3), and putative anion transporter-1 (SLC26A6). Treatment of Caco-2 cells with LPA (100 muM) significantly stimulated Cl(-)/OH(-) exchange activity. Specific agonist for LPA2 receptor mimicked the effects of LPA. LPA-mediated stimulation of Cl(-)/OH(-) exchange activity was dependent on activation of phosphatidylinositol 3-kinase/Akt signaling pathway. Consistent with the functional activity, LPA treatment resulted in increased levels of DRA on the apical membrane. Our results demonstrate that LPA stimulates apical Cl(-)/OH(-) exchange activity and surface levels of DRA in intestinal epithelial cells. This increase in Cl(-)/OH(-) exchange may contribute to the antidiarrheal effects of LPA.
authors.affiliation: Section of Digestive Diseases and Nutrition, Department of Physiology, University of Illinois at Chicago, Chicago, IL 60612, USA.
authors.forename: Amika
authors.initials: A
authors.lastname: Singla
authors.forename: Alka
authors.initials: A
authors.lastname: Dwivedi
authors.forename: Seema
authors.initials: S
authors.lastname: Saksena
authors.forename: Ravinder K
authors.initials: RK
authors.lastname: Gill
authors.forename: Waddah A
authors.initials: WA
authors.lastname: Alrefai
authors.forename: Krishnamurthy
authors.initials: K
authors.lastname: Ramaswamy
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Dudeja
mesh_terms: D017920:Antiporters / Q000378:metabolism*; D001639:Bicarbonates / Q000378:metabolism*; D018938:Caco-2 Cells; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism*; D003967:Diarrhea / Q000188:drug therapy / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D008246:Lysophospholipids / Q000378:metabolism / Q000494:pharmacology*; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008871:Microvilli / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D049368:Receptors, Lysophosphatidic Acid / Q000819:agonists / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000076988:Sulfate Transporters
chemical_list: D017920:Antiporters; D001639:Bicarbonates; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D008246:Lysophospholipids; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D049368:Receptors, Lysophosphatidic Acid; C081011:SLC26A3 protein, human; C439529:SLC26A6 protein, human; D000076988:Sulfate Transporters; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; C032881:lysophosphatidic acid