The Role of Secretase Pathway in Long-term Brain Inflammation and Cognitive Impairment in an Animal Model of Severe Sepsis.

Abstract

Inflammatory cytokines are related to impaired learning and memory processes in the central nervous system, contributing to the cognitive dysfunction present in sepsis survivors. In sepsis, brain of survivors presented increased deposition of amyloid-beta (Aβ) peptide and this was associated with cognitive impairment. However, it is not known if the upregulation of secretase pathway is involved the deposition of Aβ peptide and consequent development of cognitive impairment in survivors. The aim of the study is to evaluate the effects of secretase inhibitors on behavioral, Aβ accumulation, and neuroinflammatory parameters in rats submitted to sepsis. Sepsis was induced by cecal ligation and perforation in Wistar rats, and the activity of alpha-, beta-, and gamma-secretases was determined in the hippocampus and prefrontal at different times. Additionally, in a different cohort of animal's epigallocatechin gallate, a beta-secretase inhibitor or a gamma-secretase inhibitor was administrated once a day for three consecutive days. Fifteen or 30 days after sepsis induction, Aβ content, TNF-α, IL-1β, and IL-6 and cognitive performance were determined. There was no increase in alpha-secretase activity. Both beta- and gamma-secretase activities increased, mainly late after sepsis. The inhibition of beta- or gamma-secretases improved cognitive performance 10 days after sepsis induction, and beta-secretase inhibition improved cognitive performance up to 30 days after sepsis induction. Furthermore, beta-secretase inhibition decreased IL-1β and Aβ brain levels. It was demonstrated that during sepsis development there was an increase in the amyloidogenic route, and the inhibition of this pathway promoted attenuation of neuroinflammation, Aβ peptide content, and improvement of cognitive impairment.