Effect of IL-1β on pancreatic acinar cells mitochondrial TPP carrier-mediated uptake: Inhibition mediated via the intracellular NF-κB signaling pathway.

We investigated the effect(s) of pro-inflammatory cytokines on carrier-mediated thiamin pyrophosphate (TPP) uptake by pancreatic acinar cells (PACs) mitochondria using mouse-derived PAC 266-6 cells and human primary PACs as models. First, we assessed the level of expression of the mitochondrial TPP transporter (MTPPT) mRNA in pancreatic tissue of patients with chronic pancreatitis and found the level to be significantly lower than that in normal control subjects. We then examined the effects of exposing PACs to IL-1β, IL-6, and TNF-α on mitochondrial TPP uptake and observed significant inhibition by all these pro-inflammatory cytokines. Focusing on IL-1β (since it showed a more severe effect), we found this pro-inflammatory cytokine to also cause a significant inhibition in MTPPT protein and mRNA expression, as well as in activity of the promoter. Effect on the latter, appeared to be mediated via a decrease in the binding affinity of NF-Y (a nuclear factor that drives promoter activity) as well as via epigenetic mechanism/histone-modification were significant reduction in levels of enrichment of the activator markers H3K4-trimethylation and H3K9-acetylation, and an increase in level of enrichment of the repressor marker H3K27-trimethylation were observed. Finally, evidence was obtained suggesting a role for the intracellular NF-κB signaling pathway in mediating the effects of IL-1β on PAC mitochondrial TPP uptake process. These results show that exposure of PACs to IL-1β causes inhibition in mitochondrial TPP uptake, and that this effect is exerted at the level of transcription and is mediated via the NF-κB signaling pathway.