A2A R inhibition in alleviating spatial recognition memory impairment after TBI is associated with improvement in autophagic flux in RSC

Abstract

Spatial recognition memory impairment is an important complication after traumatic brain injury (TBI). We previously found that spatial recognition memory impairment can be alleviated in adenosine A_2A receptor knockout (A_2A R KO) mice after TBI, but the mechanism remains unclear. In the current study, we used manganese-enhanced magnetic resonance imaging and the Y-maze test to determine whether the electrical activity of neurons in the retrosplenial cortex (RSC) was reduced and spatial recognition memory was impaired in wild-type (WT) mice after moderate TBI. Furthermore, spatial recognition memory was damaged by optogenetically inhibiting the electrical activity of RSC neurons in WT mice. Additionally, the electrical activity of RSC neurons was significantly increased and spatial recognition memory impairment was reduced in A_2A R KO mice after moderate TBI. Specific inhibition of A_2A R in the ipsilateral RSC alleviated the impairment in spatial recognition memory in WT mice. In addition, A_2A R KO improved autophagic flux in the ipsilateral RSC after injury. In primary cultured neurons, activation of A_2A R reduced lysosomal-associated membrane protein 1 and cathepsin D (CTSD) levels, increased phosphorylated protein kinase A and phosphorylated extracellular signal-regulated kinase 2 levels, reduced transcription factor EB (TFEB) nuclear localization and impaired autophagic flux. These results suggest that the impairment of spatial recognition memory after TBI may be associated with impaired autophagic flux in the RSC and that A_2A R activation may reduce lysosomal biogenesis through the PKA/ERK2/TFEB pathway to impair autophagic flux.

Keywords: lysosomal biogenesis; manganese-enhanced magnetic resonance imaging; neuronal apoptosis; retrosplenial cortex; transcription factor EB.