Indoleamine 2,3-dioxygenase is upregulated in the brain of rats with acute pancreatitis

Background: Acute pancreatitis (AP) has an effect on both inflammatory/autoimmune processes and psychological states, but the pathophysiological causes of pancreatic encephalopathy in the brain are unclear. We hypothesized that the peripheral immune/inflammatory response during AP can affect indolamine 2,3-dioxygenase (IDO) expression and serotonin content in the brain.

Methods: About 210 male Sprague Dawley rats were randomly divided into five groups: control (0 h) and 6 h, 24 h, 48 h and 72 h experimental groups. Acute pancreatitis was induced by an injection of a sodium taurocholate solution via a cannulated bile-pancreatic duct. We measured the plasma TNF-α and IL-6 levels; serotonin, 5-HIAA and the protein concentration levels of IDO and monoamine oxidase A (MAO-A) were evaluated in the striatum, hippocampus and left prefrontal cortex.

Results: The IL-6 and the TNF-α levels increased in the 24 h, 48 h and 72 h groups. The IDO concentrations of both the 72 h group in the hippocampus and 48 h, 72 h groups in the prefrontal cortex increased; in the corpus striatum, the IDO concentrations fluctuated without statistical significance. The MAO-A protein concentration of the 6 h and 24 h groups decreased in the striatum, hippocampus and prefrontal cortex. There were no statistically significant differences found in the serotonin and 5-HIAA concentrations.

Conclusions: During the process of AP, cytokines, such as IL-6 and TNF-α, may play a role in activation of neuronal pathways utilizing the metabolic enzyme IDO, which may play an important role in determining the mental symptomatology accompanying AP.