title: Transepithelial resistance can be regulated by the intestinal brush-border Na(+)/H(+) exchanger NHE3.
abstract: Initiation of intestinal Na(+)-glucose cotransport results in transient cell swelling and sustained increases in tight junction permeability. Since Na(+)/H(+) exchange has been implicated in volume regulation after physiological cell swelling, we hypothesized that Na(+)/H(+) exchange might also be required for Na(+)-glucose cotransport-dependent tight junction regulation. In Caco-2 monolayers with active Na(+)-glucose cotransport, inhibition of Na(+)/H(+) exchange with 200 microM 5-(N,N-dimethyl)- amiloride induced 36 +/- 2% increases in transepithelial resistance (TER). Evaluation using multiple Na(+)/H(+) exchange inhibitors showed that inhibition of the Na(+)/H(+) exchanger 3 (NHE3) isoform was most closely related to TER increases. TER increases due to NHE3 inhibition were related to cytoplasmic acidification because cytoplasmic alkalinization with 5 mM NH(4)Cl prevented both cytoplasmic acidification and TER increases. However, NHE3 inhibition did not affect TER when Na(+)-glucose cotransport was inhibited. Myosin II regulatory light chain (MLC) phosphorylation decreased up to 43 +/- 5% after inhibition of Na(+)/H(+) exchange, similar to previous studies that associate decreased MLC phosphorylation with increased TER after inhibition of Na(+)-glucose cotransport. However, NHE3 inhibitors did not diminish Na(+)-glucose cotransport. These data demonstrate that inhibition of NHE3 results in decreased MLC phosphorylation and increased TER and suggest that NHE3 may participate in the signaling pathway of Na(+)-glucose cotransport-dependent tight junction regulation.
authors.affiliation: Department of Pathology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. jturner@med.wayned.edu
authors.forename: J R
authors.initials: JR
authors.lastname: Turner
authors.forename: E D
authors.initials: ED
authors.lastname: Black
authors.forename: J
authors.initials: J
authors.lastname: Ward
authors.forename: C M
authors.initials: CM
authors.lastname: Tse
authors.forename: F A
authors.initials: FA
authors.lastname: Uchwat
authors.forename: H A
authors.initials: HA
authors.lastname: Alli
authors.forename: M
authors.initials: M
authors.lastname: Donowitz
authors.forename: J L
authors.initials: JL
authors.lastname: Madara
authors.forename: J M
authors.initials: JM
authors.lastname: Angle
mesh_terms: D000143:Acids / Q000378:metabolism; D000468:Alkalies / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology; D000959:Antihypertensive Agents / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D018938:Caco-2 Cells; D002927:Cimetidine / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004232:Diuretics / Q000494:pharmacology; D017097:Electric Impedance; D004594:Electrophysiology; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000378:metabolism*; D008689:Methacrylates / Q000494:pharmacology; D008871:Microvilli / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D012964:Sodium / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013450:Sulfones / Q000494:pharmacology; D019108:Tight Junctions / Q000378:metabolism*
chemical_list: C118956:3-(2-(3-guanidino-2-methyl-3-oxo-propenyl)-5-methylphenyl)-N-isopropylidene-2-methyl-acrylamide dihydrochloride; D000143:Acids; D000468:Alkalies; D000897:Anti-Ulcer Agents; D000959:Antihypertensive Agents; D004232:Diuretics; D006146:Guanidines; D008689:Methacrylates; D018994:Myosin Light Chains; C000613385:SLC9A3 protein, human; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine; D000584:Amiloride; D002927:Cimetidine; D012964:Sodium; D009219:Myosin-Light-Chain Kinase; D005947:Glucose; D003000:Clonidine