Role of basic fibroblast growth factor in the suppression of apoptotic caspase-3 during chronic gastric ulcer healing

Abstract

Background: In the course of ulcer healing an array of factors compel mucosal cells to proliferate, differentiate, and migrate to the site of injury. The recognition of triggering cues requires close interaction between the regulatory proteins integrating the growth factor and cytokine- mediated signals that propel cells through the cycle events, or to signal apoptosis. In this study, we analyzed the interplay between mucosal expression of the receptor-bound basic fibroblast growth factor (bFGF-R) and cyclin-dependent kinase (Cdk2), and the activity of apoptotic protease, caspase-3, and constitutive nitric oxide synthase (cNOS) during chronic gastric ulcer healing.

Methods: The experiments were conducted with gastric mucosa of rats at different stages of acetic acid-induced chronic gastric ulcer healing.

Results: The ulcer onset (2 days following injury) was characterized by a massive epithelial apoptosis associated with a 33-fold increase in caspase-3 activity and a 7.6-fold drop in cNOS, while the mucosal expression of Cdk2 fell by an 18% and that of bFGF-R by 12%. The ulcer healing was accompanied by a rapid elevation in bFGF-R and Cdk2, and a slow recovery in cNOS activity, while the caspase-3 activity and epithelial apoptosis showed a marked decline. The bFGF-R and Cdk2 reached their maximums of 2.2-2.3-fold at 4-6 day of healing, while the caspase-3 activity and the apoptotic DNA fragmentation showed a 3-fold decline by the 7th day of healing. However, the activity of cNOS remained about 50% lower than that of the controls.

Conclusions: Taken together, these results provide strong indications that the initial phase of ulcer healing involves the inhibition of apoptotic caspase activities by a signaling events initiated by bFGF-receptor activation and propagated by the regulatory kinases that propel the cell cycle progression. Our findings also point towards participation of cNOS in the suppression of proapoptotic activities in gastric mucosa.