Pancreatitis-associated protein I (PAP I), an acute phase protein induced by cytokines. Identification of two functional interleukin-6 response elements in the rat PAP I promoter region.

Expression of the pancreatitis-associated protein I (PAP I), an exocrine pancreatic protein, increases rapidly and strongly in acinar cells during the acute phase of pancreatitis. This is reminiscent of the response to stress of acute phase proteins. We have previously demonstrated that serum factors from rats with acute pancreatitis, but not from healthy rats, could induce endogenous PAP I gene expression in the acinar cell line AR-42J (Dusetti, N., Mallo, G., Dagorn, J.-C., Iovanna, J. L. (1994) Biochem. Biophys. Res. Commun. 204, 238-243). In the present work, we have evaluated the influence of several mediators of inflammation on rat PAP I gene transcription in these cells. Tumor necrosis factor alpha induced an increase in PAP I mRNA expression, and interferon gamma caused an even greater increase in PAP I mRNA level. These stimulations were antagonized by dexamethasone. Interleukin (IL)-1, IL-6, or dexamethasone alone were ineffective. Combinations of IL-1 with IL-6 or dexamethasone were also ineffective. IL-6 and dexamethasone together induced a marked stimulation of PAP I gene transcription, and this effect was slightly attenuated by IL-1. To analyze the cis-regulatory elements responsible for the induction of transcription, we fused a 1.2-kilobase segment of the rat PAP I promoter to the chloramphenicol acetyltransferase (CAT) gene as reporter. The resultant chimeric DNA was transfected into AR-42J cells. Addition of IL-6 or dexamethasone was ineffective, whereas their mixture increased the CAT activity 12 times. Progressive deletions of the PAP I promoter were then fused to the CAT gene, and the constructs were transfected to AR-42J cells. A 12-fold increase in CAT activity was seen upon IL-6/dexamethasone treatment with constructs containing more than 274 base pairs upstream from the cap site. In that region, two sequences are similar to the canonical IL-6 response element. Site-directed mutagenesis of these regions strongly decreased induction, showing that they were functional. PAP I should therefore be classified among acute phase proteins of class 2, whose expression is increased by IL-6 acting in combination with glucocorticoids.