Hyperpermeability of intestinal epithelial monolayers is induced by NO: effect of low extracellular pH.
Nitric oxide (NO.) increases the permeability of Caco-2BBe enterocytic monolayers. Many of the toxic effects of NO. are thought to be mediated by the peroxynitrite anion (ONOO-), which, under mildly acidic conditions, can rearrange to yield an intermediate with reactivity similar to toxic OH.. Accordingly, we assessed the permeability of Caco-2BBe cells grown on permeable supports for 24 h in media titrated to normal or acidic extracellular pH (pHo) with or without the NO. donors 3-morpholinosydnonimine (SIN-1) or sodium nitroprusside (SNP). Incubation with 2 mM SIN-1 at pHo 6.8 or 0.6 mM SNP at pHo 6.5 increased permeability (apical-to-basolateral flux of fluorescein sulfonic acid), whereas at pHo 7.4 permeability was unaffected by these concentrations of NO. donors. Accumulation of NO2/NO3 in medium (index of NO. release) was not increased by incubation of cells with SIN-1 or SNP under mildly acidic conditions. Under acidic but not control conditions, incubation with SIN-1 caused disruption of perijunctional actin filaments as assessed by fluorescence microscopy. At pHo 6.8 and 6.5 (but not 7.4), SIN-1 significantly decreased intracellular levels of both ATP and glutathione. Incubation with 5 mM deferoxamine or 500 uM ascorbic acid (ONOO- scavengers) abrogated SIN-1-induced hyperpermeability. We conclude that mild acidosis augments NO.-induced intestinal epithelial permeability, possibly by promoting oxidant-mediated cytoskeletal damage and/or ATP depletion.
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Department of Surgery, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA.
Menconi
M J
MJ
Smith
M
M
Aguirre
D E
DE
Fink
M P
MP
D000255:Adenosine Triphosphate / Q000378:metabolism; D001205:Ascorbic Acid / Q000494:pharmacology; D018938:Caco-2 Cells; D002463:Cell Membrane Permeability / Q000187:drug effects; D003676:Deferoxamine / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009569:Nitric Oxide / Q000494:pharmacology*
D009569:Nitric Oxide; D006859:Hydrogen; D000255:Adenosine Triphosphate; D005978:Glutathione; D003676:Deferoxamine; D001205:Ascorbic Acid