Background: STAT1 and STAT3, members of the cytoplasmic family of signal transducers and activators of transcription factors (STAT), have been associated with numerous inflammatory pathologies, including inflammatory bowel disease, hepatitis, and acute lung injury. But little is known about their role in the pancreas. Peptide YY (PYY), an inhibitory gastrointestinal hormone, ameliorates pancreatitis in vivo and in vitro. In addition, we have shown that PYY attenuates transcription factors, such as nuclear transcription factor (NF)-kappaB and Smad3/4, which mediate inflammation. We hypothesized that tumor necrosis factor (TNF)-alpha would induce STAT1 and STAT3, and PYY would attenuate their transcription factor binding.
Study design: Rat pancreatic acinar cells were treated with recombinant TNF-alpha (200 ng/mL); PYY (3-36; 500 pM) was added 30 minutes post-TNF-alpha treatment. Cells were harvested at 2 hours, and nuclear protein and conditioned media were extracted. Levels of amylase secretion and cytokine production were measured using commercially available kits. STAT transcription factor binding was determined by protein/DNA array analysis and densitometry; results were verified again by electrophoretic mobility shift assay (EMSA) and ELISA-based assay.
Results: Amylase production was considerably increased (p < 0.05) as early as 5 minutes after addition of exogenous TNF-alpha and remained elevated for 24 hours. PYY decreased amylase production to control levels. A notable increase (p < 0.05) in the production of cytokines interleukin (IL)-1beta, IL-4, IL-6, IL-10, and TNF-alpha was observed with TNF-alpha treatment; production was reduced with PYY. TNF-alpha substantially upregulated STAT1 and STAT3 (two-fold or greater); PYY downregulated their binding activity to control levels. Results from both the electrophoretic mobility shift assay- and the ELISA-based assays verified STAT1 and STAT3 responses to TNF-alpha and PYY.
Conclusions: In pancreatic acinar cells, TNF-alpha activated STAT1 and STAT3, known mediators of inflammatory cytokines. Interestingly, PYY attenuated their protein/DNA binding, which may have an impact on development of the disease. Additional investigation of STAT proteins and PYY could provide new therapeutic strategies for pancreatitis.