A novel strategy to activate cytoprotective genes in the injured brain

Abstract: The transcription factor nuclear factor E2-related factor 2 (Nrf2) regulates the expression of multiple cytoprotective genes that have been shown to offer protection in response to a number of insults. The present study describes a novel strategy to increase expression of Nrf2-responsive genes in brain injured mice. Under normal conditions, the adapter protein Kelch-like ECH-associated protein 1 (Keap1) binds to Nrf2 and promotes its proteosomal degradation in the cytoplasm. The amino acid sequence DEETGE, located at amino acid 77–82 of Nrf2, is critical for Nrf2–Keap1 interaction, and synthetic peptides containing this sequence can be used to disrupt the complex in vitro. We observed that intracerebroventricular (i.c.v.) infusion of a peptide containing the DEETGE sequence along with the cell transduction domain of the HIV-TAT protein (TAT–DEETGE) into brain-injured mice did not increase the mRNA levels for Nrf2-driven genes. However, when a calpain cleavage sequence was introduced between the TAT sequence and the DEETGE sequence, the new peptide (TAT–CAL–DEETGE) increased the mRNA levels of these genes. Increased gene expression was not observed when the TAT–CAL–DEETGE peptide was injected into uninjured animals. Furthermore, injection of TAT–CAL–DEETGE peptides before or after brain injury reduced blood–brain barrier compromise, a prominent secondary pathology that negatively influences outcome. The present strategy to increase Nrf2-responsive gene expression can be adapted to treat other insults or diseases based on their underlying mechanism(s) of cellular damage. [Copyright &y& Elsevier]