Modulation of Cl-/OH- exchange activity in Caco-2 cells by nitric oxide.
The present studies were undertaken to determine the direct effects of nitric oxide (NO) released from an exogenous donor, S-nitroso-N-acetyl pencillamine (SNAP) on Cl-/OH- exchange activity in human Caco-2 cells. Our results demonstrate that NO inhibits Cl-/OH- exchange activity in Caco-2 cells via cGMP-dependent protein kinases G (PKG) and C (PKC) signal-transduction pathways. Our data in support of this conclusion can be outlined as follows: 1) incubation of Caco-2 cells with SNAP (500 microM) for 30 min resulted in approximately 50% inhibition of DIDS-sensitive 36Cl uptake; 2) soluble guanylate cyclase inhibitors Ly-83583 and (1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one significantly blocked the inhibition of Cl-/OH- exchange activity by SNAP; 3) addition of 8-bromo-cGMP (8-BrcGMP) mimicked the effects of SNAP; 4) specific PKG inhibitor KT-5823 significantly inhibited the decrease in Cl-/OH- exchange activity in response to either SNAP or 8-BrcGMP; 5) Cl-/OH-exchange activity in Caco-2 cells in response to SNAP was not altered in the presence of protein kinase A (PKA) inhibitor (Rp-cAMPS), demonstrating that the PKA pathway was not involved; 6) the effect of NO on Cl-/OH- exchange activity was mediated by PKC, because each of the two PKC inhibitors chelerythrine chloride and calphostin C blocked the SNAP-mediated inhibition of Cl-/OH- exchange activity; 7) SO/OH- exchange in Caco-2 cells was unaffected by SNAP. Our results suggest that NO-induced inhibition of Cl-/OH- exchange may play an important role in the pathophysiology of diarrhea associated with inflammatory bowel diseases.
Saksena
Seema
S
Section of Digestive and Liver Diseases, Department of Medicine, University of Illinois at Chicago and Chicago Veteran's Affairs System: West Side Division, Chicago, Illinois 60612, USA.
Gill
Ravinder K
RK
Syed
Irfan A
IA
Tyagi
Sangeeta
S
Alrefai
Waddah A
WA
Ramaswamy
K
K
Dudeja
Pradeep K
PK
D017920:Antiporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018938:Caco-2 Cells; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D006152:Cyclic GMP / Q000502:physiology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
D017920:Antiporters; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D013873:Thionucleotides; C093920:chloride-base exchanger; C016957:adenosine-3',5'-cyclic phosphorothioate; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP