Leukotrienes in the pathogenesis of NSAID-induced gastric and intestinal mucosal damage

Leukotriene C4/D4 induces P-selectin and sialyl Lewis(x)-dependent alterations in leukocyte kinetics in vivo

The objective of this study was to assess the effect of leukotriene C4 (LTC4) on the flux of rolling leukocytes, leukocyte rolling velocity, and leukocyte adhesion in postcapillary venules in vivo and to study the underlying molecular mechanisms involved. LTC4 (20 nmol/L) induced a rapid and significant increase in leukocyte rolling flux that was inhibitable by an anti-P-selectin antibody and soluble sialyl Lewis(x) (sLe(x)). LTC4 also induced a significant reduction in leukocyte rolling velocity, an event that was independent of P-selectin but entirely dependent on sLe(x). This LTC4-induced reduction in leukocyte rolling velocity was independent of any hemodynamic alterations. Another P-selectin effector, histamine, did not affect leukocyte rolling velocity even at > 5000 times the concentration of LTC4. Treatment with an anti-L-selectin antibody had no effect on the LTC4-induced increase in leukocyte rolling or reduction in rolling velocity. Inhibition of LTC4 bioconversion to LTD4 by pretreatment with L-serine (100 mumol/L) prevented the LTC4-induced increase in leukocyte rolling flux and the LTC4-induced reduction in leukocyte rolling velocity. A subtle, yet significant, increase in leukocyte adhesion was also observed with LTC4. Pretreatment with a platelet-activating factor receptor antagonist returned the LTC4-induced leukocyte rolling velocity to baseline levels. The addition of a very low concentration of platelet-activating factor (1 nmol/L) induced significant leukocyte adhesion in the presence of LTC4 but not histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic effects of misoprostol in combination with the NSAID, diclofenac, on gastrointestinal tract of pigs. Relation to diarrheagenic activity, leukocyte infiltration, and mucosal leukotrienes

To determine the mode of protective effects of misoprostol against the chronic gastrointestinal ulceration from the NSAID, diclofenac, studies were undertaken in domestic pigs, a model of human gastrointestinal ulceration, to determine (1) the effects of repeated daily dosing for 10 days of diclofenac 5 mg/kg/day twice a day (as Voltaren tablets) on the gastrointestinal morphology, 59fe-red blood loss, mucosal myeloperoxidase (MPO) activity (as an indicator of leukocyte infiltration), and mucosal leukotrienes (LTS); and (2) the mucosal protective effects of 10-40 micrograms/kg/day misoprostol twice a day (as Cytotec tablets) given with diclofenac 5 mg/kg/day twice a day compared with diclofenac 5 mg/kg/day alone and aspirin 150 mg/kg/twice a day (USP tablets) as a standard. These effects were compared with the dose range for potential diarrheagenic effects of misoprostol (determined by fecal analysis of NA+, K+, CL-, CA2+, H2O, and phenol red transit) given alone or with diclofenac to determine if this could be discriminated from antiulcer effects of misoprostol. Plasma and gastric mucosal concentrations of the drugs were determined to establish if misoprostol affects diclofenac absorption/elimination, and vice versa. The results showed that: (1) diclofenac produced gastric mucosal damage without any prior or concurrent bleeding from the gastrointestinal tract, although aspirin significantly increased blood loss; (2) misoprostol produced a dose-related reduction in diclofenac-induced mucosal damage of the upper gastrointestinal tract; (3) no significant increase in mucosal MPO occurred with diclofenac despite mucosal damage being evident, (4) mucosal LTS were unaffected by the drug treatments; (5) plasma, gastric and intestinal concentrations of diclofenac were not affected by misoprostol, while conversely plasma misoprostol concentrations were not influenced by the diclofenac treatment; (6) no significant effects on fecal water, electrolyte, or phenol red transit times were observed with an of the drug-treatments; and (7) mild diarrhea observed as "loose bowel motions" was only observed in most pigs receiving the misoprostol treatments during fasting on days 9-10. Thus, misoprostol protects against chronic lesions/ulcers in the upper gastrointestinal tract from diclofenac without: (1) signs of diarrhea becoming evident (the latter occurring when there is reduced food intake), (2) generalized leukocyte infiltration or effects on mucosal LTs, or (3) any reduction in bioavailability of diclofenac.