The mechanisms involved in cholecystokinin-8-induced atrophy in the pancreas are not known and in this study the roles of nitric oxide (NO) and NF-κB were studied in rats. CCK-8 was injected for 4 days, in a mode known to cause atrophy, and the NO formation was either decreased by Nω-nitro-L-arginine (L-NNA) or increased by S-nitroso-N-acetylpencillamine (SNAP). Activation of NF-κB was quantified by ELISA detection, apoptosis with caspase-3 and histone associated DNA-fragmentation and mitotic activity in the acinar, centroacinar and ductal cells was visualized by incorporation of [3H]-thymidine. Pancreatic histology, weight, protein- and DNA contents were studied.
Intermittent CCK injections reduced pancreatic weight, protein and DNA contents and increased apoptosis, acinar cell proliferation and NF-κB activation. It also caused vacuolisation of the acinar cells. Inhibition of endogenous NO formation by L-NNA further increased apoptosis and NF-κB activation but blocked the increased proliferation and vacuolisation of acinar cells. The DNA content was not further reduced. SNAP given together with CCK-8 increased both apoptosis and proliferation of acinar cells and strongly reduced the DNA content in the pancreas. Further, it caused vacuolisation in the acinar cells and these findings together indicate cell death by other pathways besides apoptosis. Histological examination showed no inflammation in any group.
During CCK-8 induced pancreatic atrophy endogenous NO suppresses apoptosis and stimulates regeneration of acinar cells but increases cell death by non-apoptotic pathways. Exogenous NO enhances the acinar cell turnover by increases of both proliferation and apoptotic and non-apoptotic cell deaths. NF-κB activation, in this situation, seems not to inhibit apoptosis or promote cell proliferation.