Impaired autophagic flux is associated with the severity of trauma and the role of A2AR in brain cells after traumatic brain injury

Abstract

Recent studies have shown that after traumatic brain injury (TBI), the number of autophagosomes is markedly increased in brain cells surrounding the wound; however, whether autophagy is enhanced or suppressed by TBI remains controversial. In our study, we used a controlled cortical impact system to establish models of mild, moderate and severe TBI. In the mild TBI model, the levels of autophagy-related protein 6 (Beclin1) and autophagy-related protein 12 (ATG12)-autophagy-related protein 5 (ATG5) conjugates were increased, indicating the enhanced initiation of autophagy. Furthermore, the level of the autophagic substrate sequestosome 1 (SQSTM1) was decreased in the ipsilateral cortex. This result, together with the results observed in tandem mRFP-GFP-LC3 adeno-associated virus (AAV)-infected mice, indicates that autophagosome clearance was also increased after mild TBI. Conversely, following moderate and severe TBI, there was no change in the initiation of autophagy, and autophagosome accumulation was observed. Next, we used chloroquine (CQ) to artificially impair autophagic flux in the injured cortex of the mild TBI model and found that the severity of trauma was obviously exacerbated. In addition, autophagic flux and trauma severity were significantly improved in adenosine A2A receptor (A2AR) knockout (KO) mice subjected to moderate TBI. Thus, A2AR may be involved in regulating the impairment of autophagic flux in response to brain injury. Our findings suggest that whether autophagy is increased after TBI is associated with whether autophagic flux is impaired, and the impairment of autophagic flux exacerbates the severity of trauma. Furthermore, A2AR may be a target for alleviating the impairment in autophagic flux after TBI.