Nitric oxide, derived from inducible nitric oxide synthase, decreases hypoxia inducible factor-1alpha in macrophages during aspirin-induced mesenteric inflammation.
OBJECTIVE
Nitric oxide (NO) modulates expression of hypoxia inducible factor-1 (HIF-1), a transcription factor regulating function of myeloid cells. Here, we have assessed the role played by NO, formed by inducible NOS (iNOS), in the inflammation induced by aspirin in the gut, by modulating HIF-1 activity.


METHODS
The role of iNOS-derived NO on leucocyte-endothelial interactions induced by aspirin was evaluated by intravital microscopy in mesenteric venules of rats pretreated with selective iNOS inhibitors, 1400W or l-N6-(1-iminoethyl)-lysine. NO was localized by fluorescence microscopy, using DAF-FM. iNOS, HIF-1alpha and CD36 were localized by immunohistochemistry.


RESULTS
Leucocyte-endothelial interactions increased at 6 h and returned to normal levels 24 h after aspirin administration. Numbers of migrated leucocytes were similar between 6 and 24 h after aspirin. iNOS expression and iNOS-derived NO synthesis were observed in leucocytes of the mesentery of aspirin-treated rats. Blockade of iNOS activity in aspirin-treated rats: (i) did not modify leucocyte infiltration at 6 h, but reduced the number of polymorphonuclear leucocyte and increased that of macrophages at 24 h; (ii) increased HIF-1alpha immunostaining in macrophages of the mesentery; and (iii) prevented the decrease in CD36 immunostaining induced by aspirin in these cells.


CONCLUSIONS
NO, associated with acute gut inflammation induced by aspirin, diminished HIF-1alpha stabilization in macrophages. Early inhibition of iNOS-derived NO synthesis, by increasing the activity of HIF-1 in these cells, may accelerate the clearance of leucocytes.
Díez
I
I
Departamento de Farmacología and CIBERehd, Universidad de Valencia, Spain.
Calatayud
S
S
Hernández
C
C
Quintana
E
E
O'Connor
J E
JE
Esplugues
J V
JV
Barrachina
M D
MD
D000818:Animals; D001241:Aspirin / Q000633:toxicity*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D007150:Immunohistochemistry; D007249:Inflammation / Q000139:chemically induced*; D008297:Male; D008643:Mesentery / Q000187:drug effects* / Q000473:pathology; D008856:Microscopy, Fluorescence; D009569:Nitric Oxide / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D004791:Enzyme Inhibitors; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D001241:Aspirin