THE PANCREATITIS-ASSOCIATED PROTEIN IS INDUCED BY FREE-RADICALS IN AR4-2J CELLS AND CONFERS CELL RESISTANCE TO APOPTOSIS

Background & Aims: Free radicals are involved in the pathogenesis of a cute pancreatitis, during which pancreatitis-associated protein (PAP)- I is overexpressed. We explored whether PAP-I expression could be indu ced by oxidative stress and whether it could affect apoptosis. Methods : AR4-2J cells were exposed to H2O2 or menadione, and PAP-I messenger RNA (mRNA) expression was analyzed by Northern blotting. Results: Maxi mal expression was observed with 0.1 mmol/L H2O2 or with 0.05 mmol/L m enadione. Induction was detectable after 12 hours, reached a climax at 18 hours, and then decreased. Pretreatment of the cells with pyrrolid ine dithiocarbamate completely abolished PAP-I mRNA induction, suggest ing involvement of NF kappa B in the signaling pathway. These findings were confirmed in transient transfection assays using a plasmid conta ining the PAP-I promoter linked to the chloramphenicol acetyltransfera se reporter gene. Then the relationship between PAP-I induction and pr otection against cell damage during oxidative stress was considered. C onstitutive PAP-I expression in AR4-2J cells after transfection with P AP-I complementary DNA conferred significant resistance to apoptosis i nduced by low doses of H2O2 but not to necrosis induced by high doses of H2O2. Conclusions: These results suggest that during oxidative stre ss, PAP-I might be part of a mechanism of pancreatic cell protection a gainst apoptosis.