STRUCTURALLY INTACT PAP AND REG PROTEINS ARE CRITICAL FOR THEIR IMMUNOLOGIC, BUT NOT MITOGENIC, EFFECTS

Abstract

Background: Pancreatitis associated proteins (PAPI, II) and RegI are members of the same family, are induced and are protective in acute pancreatitis (AP). We propose that this protection may be via macrophage (mθ) activation. Methods: NR8383 mθ cells (5 × 105) were cultured with recombinant PAPI, PAPII; RegI (0.06-1 mg/mL). TNFα production and expression were assessed by ELISA and PCR, respectively, and mitogenesis by MTS assay. Significance was set at p < 0.05 (Student's t-test), compared to vehicle controls. Results: Cells cultured with recombinant RegI and PAPII isolated and renatured in our lab induced expression of TNFα, when compared to controls (p < 0.05). Commercially produced PAPI, II had no effect, but, when were denatured and renatured, activity was restored. Potencies were RegI>PAPI >PAPII. A synthetic peptide C-terminus had no biological activity which is critical in structural intact protein. PAPII induced activated mθ's (mθ's activated by TNFα) in an additive manner (p < 0.05); RegI and PAPI did not. RegI and PAPI proteins were mitogenic to mθ's, regardless of source, PAPII was not. Conclusions: PAPs and Reg1 proteins induce mθ's; an intact protein 3D structure is critical for this effect. While other labs have shown that PAPI inhibits activated mθ's, we show no such inhibition by PAPI, but an additive effect by PAPII. The TNFα and mitogenic effects are separate, suggesting different receptors. PAP and Reg proteins are protective during AP by macrophage induction of TNFα, and possibly by inducing cell growth.