Background: Cognitive dysfunction as a common comorbidity of epilepsy often manifests as learning and memory impairments in patients with temporal lobe epilepsy (TLE). The pathogenetic molecular mechanisms underlying epilepsy-associated cognitive dysfunction are incompletely understood. We investigated the role of cAMP response element binding protein (CREB) and its downstream signaling pathways in the pathogenesis of cognitive impairment in mice with TLE.
Methods: Plasmid vectors of CREB-specific short-hairpin RNAs and CREB cDNA were prepared and transfected into primary neurons. Neuronal apoptosis and mitochondrial oxidative stress were assessed by flow cytometry. For in vivo studies, TLE in mice was induced by pilocarpine injection, and TLE-associated memory decline was evaluated using the Morris water maze after treatment with the CREB inhibitor 666-15, with or without the mitochondria-specific antioxidant MitoQ. CREB and its downstream mediators were examined by Western blotting analysis and quantitative reverse transcription polymerase chain reaction.
Results: CREB knockdown induced mitochondrial reactive oxygen species production and apoptosis in primary neurons whereas CREB overexpression brought the opposite effects. The TLE mice exhibited elevated oxidative stress and neuronal apoptosis with decreased expression of CREB and its downstream mediators including PKA, CaMKIV, arc, and c-fos. CREB inhibition exacerbated TLE-associated oxidative neuronal apoptosis and memory decline. MitoQ treatment restored the expression of CREB and its downstream mediators, and prevented TLE-associated oxidative neuronal damage and memory deficits aggravated by CREB inhibition.
Conclusion: CREB plays a significant role in TLE-associated oxidative neuronal damage and memory impairment. This novel finding provides the evidence of the relationship between CREB and mitochondrial oxidative stress and cognitive dysfunction in epilepsy. Mitochondria-specific antioxidants such as MitoQ may alleviate TLE-associated cognitive dysfunction through activation of CREB and its downstream signaling pathways.
Keywords: Apoptosis; Cognitive impairment; Epilepsy; Oxidative stress; cAMP response element binding protein.
© 2020 S. Karger AG, Basel.