Volume 123, Issue 5, Pages 1598-1606 (November 2002) Cyclooxygenase-2–derived lipoxin A4 increases gastric resistance to aspirin-induced damage  Stefano Fiorucci, Octavio Menezes de Lima, Andrea Mencarelli, Barbara Palazzetti, Eleonora Distrutti, Webb McKnight, Michael Dicay, Li Ma, Mario Romano, Antonio Morelli, John L. Wallace  Gastroenterology  Volume 123, Issue 5, Pages 1598-1606 (November 2002) DOI: 10.1053/gast.2002.36558 Copyright © 2002 American Gastroenterological Association Terms and Conditions

Fig. 1 Rats were treated orally with aspirin (50 mg/kg) and intraperitoneally with (A) celecoxib or (B) rofecoxib. Celecoxib or rofecoxib given alone (at 30 and 10 mg/kg, respectively) did not cause damage. *P < 0.05 vs. the group receiving aspirin alone. Gastroenterology 2002 123, 1598-1606DOI: (10.1053/gast.2002.36558) Copyright © 2002 American Gastroenterological Association Terms and Conditions

Fig. 2 (A) Western blot showing COX-2 expression in the rat stomach 3 hours after treatment with vehicle (lanes 1–3) or aspirin (50 mg/kg; lanes 4–6). One hundred micrograms of protein was loaded on each lane. Lane 7 shows COX-2 expression in a tissue sample taken from the margin of an ulcer in a rat. (B) Production of 15(R)-epi-LXA4 by the stomach following treatment with vehicle, aspirin (50 mg/kg), aspirin plus celecoxib (10 mg/kg), or indomethacin (Indo; 5 mg/kg). Aspirin-triggered LXA4 production was completely inhibited by celecoxib. **P < 0.01 vs. the other groups. ΨΨP < 0.01 vs. the aspirin-treated group. Gastroenterology 2002 123, 1598-1606DOI: (10.1053/gast.2002.36558) Copyright © 2002 American Gastroenterological Association Terms and Conditions

Fig. 3 Confirmation of 15-epi-LXA4 formation by gastric tissue from rats treated with aspirin alone or aspirin plus celecoxib. Drug administration and processing of the tissue was performed as described in the Materials and Methods section. After extraction, the samples were suspended with 0.5 mL of ethanol, then concentrated to 5 μL before RP-HPLC analysis. Tracings, recorded at 300-nm absorbance, are enlargements of the chromatogram section encompassing the 15-epi-LXA4 retention time (arrow). The inset shows the online UV spectrum of the product, formed by stomachs from aspirin-treated rats, eluting beneath the peak with the same retention time as that of authentic 15-epi-LXA4. Absorbing bands are expressed in nm. Gastroenterology 2002 123, 1598-1606DOI: (10.1053/gast.2002.36558) Copyright © 2002 American Gastroenterological Association Terms and Conditions

Fig. 4 (A) LXA4 dose dependently reduced the severity of aspirin (50 mg/kg)-induced gastric damage. LXA4 was administered intraperitoneally 30 minutes before aspirin administration. *P < 0.05, **P < 0.01 vs. the vehicle-treated group. (B) Boc1, an LXA4 receptor antagonist, dose dependently increased the severity of aspirin (50 mg/kg)-induced gastric damage. Boc1 was administered intraperitoneally 30 minutes prior to aspirin administration. Rats given Boc1 alone at 10 μg/kg (IP) did not exhibit any detectable gastric damage (n = 5). *P < 0.05, **P < 0.01 vs. the vehicle-treated group. Gastroenterology 2002 123, 1598-1606DOI: (10.1053/gast.2002.36558) Copyright © 2002 American Gastroenterological Association Terms and Conditions

Fig. 5 (A) Intragastric administration of aspirin (50 mg/kg) induced a marked increase in leukocyte adherence to the vascular endothelium in mesenteric postcapillary venules. Topical pre-exposure of the venules to LXA4 (3 μmol/L) for 10 minutes (solid line) resulted in a significant inhibition of aspirin-induced leukocyte adherence (dashed line). *P < 0.05 vs. the group treated with vehicle plus aspirin. (B) Leukocyte adherence in mesenteric venules of rats 30 minutes after intragastric administration of aspirin (10 mg/kg), indomethacin (5 mg/kg), or vehicle. The venules were pre-exposed for 10 minutes to an LXA4 receptor antagonist (Boc1; 10 μmol/L) or to vehicle. *P < 0.05 vs. the corresponding vehicle-treated group. (C) Leukocyte adherence in mesenteric venules 30 minutes after intragastric administration of aspirin (10 mg/kg). The vessels were pre-exposed for 10 minutes to LXA4 (3 μmol/L), 15(R)-HETE (3 μmol/L), or vehicle. *P < 0.05, **P < 0.01 vs. basal; ΨP < 0.05 vs. the vehicle-treated group. Gastroenterology 2002 123, 1598-1606DOI: (10.1053/gast.2002.36558) Copyright © 2002 American Gastroenterological Association Terms and Conditions