Expression of STAT3 and SOCS3 in pancreatic acinar cells

Background. The signal transducer and activator of transcription (STAT) and suppressor of cytokine signaling 3 (SOCS3) pathways are involved in organ inflammation. In the pancreas, however, the STAT3 and SOCS3 response to inflammatory stimuli is unknown. Therefore, we hypothesized that mRNA expression for these signaling proteins would be induced in response to pro-inflammatory mediators TNF alpha and LPS. Because activation of STAT3 and SOCS3 is also linked to cytokine stimulation, we tested TNF alpha and LPS, either alone or in combination with IL-1 beta or IL-6 in an in vitro model using rat pancreatic acinar cells. Methods. Rat pancreatic acinar cells (AR42J) were treated with combinations of LPS (10 mu g/ml) or TNF alpha (10, 100, or 200 ng/ml) in the presence or absence of IL-1 beta or IL-6 for 15, 30, 45, 60, 180, or 360 min. At each time point, total RNA was purified and analyzed via RT-PCR for STAT3 and SOCS3 mRNA expression. Results. LPS and TNFa activated STAT3 and SOCS3 in pancreatic acinar cells. STAT3 mRNA expression was significantly (P < 0.01) increased above controls without further stimulation by IL-6 or IL1-beta. Significant increases in SOCS3 expression were observed with LPS + IL-6 at 30,45,60,180, min (P < 0.05). SOCS3 mRNA expression with LPS + IL-1 beta treatment was maximal by 1 h (P < 0.05). Enhanced STAT3 expression was evident by 3 h with TNF alpha alone (P < 0.01). The addition of cytokines kept STAT3 mRNA levels high. At 200 ng/ml TNF alpha, SOCS3 mRNA levels were increased, but significantly reduced in the presence of IL-1 beta or IL-6 (P < 0.05). Conclusions. We have shown that LPS and TNFa are potent mediators of STAT3 and SOCS3 expression in the pancreas and that the cytokines IL-6 and IL-1 beta are indirectly involved in the signaling pathway. Alteration of the STAT pathway should be explored as a therapeutic target for treatment of pancreatic inflammation. (c) 2005 Elsevier Inc. All rights reserved.