Role of interleukin-4 in down-regulation of endothelin-1 during gastric ulcer healing: Effect of sucralfate

Background: The course of events associated with healing gastric mucosal injury involves an orderly interplay between the array of signaling molecules that exert their influence on the processes leading to the restoration of the mucosal integrity. In this study, we investigated the effect of antiulcer agent, sucralfate, on the mucosal apoptotic processes during gastric ulcer healing by analyzing the expression of interleukin-4 (IL:4), endothelin-1 (ET-1), tumor necrosis factor-α (TNF-α), and the mucosal activity of caspase-3, and constitutive (cNOS) and inducible nitric oxide synthase (NOS- 2). Methods: Rats with experimentally induced chronic gastric ulcers were administered twice daily for 14 days either sucralfate at 100 mg/kg or vehicle, and at different stages of treatment their stomachs were used for macroscopic and biochemical assessments. Results: The ulcer onset was characterized by a massive epithelial apoptosis associated with a 33-fold increase in caspase-3 activity, 5.7-fold increase in TNF-α, 17.5-fold increase in NOS-2 and a 3.9-fold increase in ET-1, while the mucosal expression of cNOS activity showed a 7.6-fold drop and IL-4 expression fell by 37.2%. The healing was reflected in a rapid recovery in IL-4, and a decrease in apoptosis, caspase-3, TNF-α, ET-1 and NOS-2, and a slow recovery in cNOS activity, and the process was accelerated in the sucralfate-treated group. While in the absence of sucralfate the expression of IL-4 returned to that of the normal mucosa by the 7th day of healing and that of ET-1 and TNF- α by the 14th day, an accelerated ulcer healing with sucralfate treatment was associated with IL-4 recovery by the 4 th day and that of ET-1 and TNF-α by the 10th day when the ulcer heated, while recovery in cNOS activity required 14 days. Yet, in both groups of animals the apoptotic DNA fragmentation rate, caspase-3 and the expression of NOS-2 activity remained significantly elevated even after the ulcer healed. Conclusions: The results suggest that a decrease in the mucosal expression of the regulatory cytokine IL-4 at the ulcer onset may well be a key factor causing dysregulation of ET- 1 production, induction of TNF-α, and triggering the apoptotic events that affect the efficiency of mucosal repair process. We also show that accelerated ulcer healing by sucralfate may be the result of a rapid mucosal IL-4 generation that leads to the suppression of the mucosal apoptotic events.