The effects of poloxamer 188 on the autophagy induced by traumatic brain injury.

Poloxamer 188 (P188) has been reported to reseal plasma membranes and attenuate TBI-induced neuronal death by suppressing apoptosis. Recent studies also confirm increased autophagy after traumatic brain injury (TBI). The present study aimed to investigate the effects of plasmalemmal resealing by P188 on neuronal autophagy in TBI. Scratch test was performed in rat cell line PC-12 in vitro, followed by immunofluorescence analysis of LC3 24h after PC-12 cell stretch-injury in vitro. CD1 mice were randomized into saline and P188-treatment groups (both undergoing intravenous injection of 4mg/ml, 100μl via the caudal vein 30min after TBI) as well as sham group. To analyze the effect of P188 on autophagy, the LC3 protein levels were assessed by western blotting 1h, 6h, 12h, 24h, and 48h after TBI. The autophagy-associated protein levels of Beclin-1, Bcl-2, and p62 were likewise determined. In vitro, the scratch test showed that the wound healing rate was significantly improved at 12h and 24h in P188 groups, and LC3 immunofluorescence analysis indicated that P188 induced extensive formation of LC3 puncta in PC-12 cells. In vivo, western blotting analyses revealed elevations of the LC3-II/LC3-I and Beclin-1/bcl-2 ratios as well as downregulation of p62 in the saline group, in contrast with the more significant increases of LC3-II/LC3-I and Beclin-1/bcl-2 ratios and the further downregulation of p62 in P188-treated group. These results revealed that plasma membranes were resealed after TBI, in which P188 aggravated autophagy in vivo.