Poloxamer188Suppresses Apoptosis And Activating Autophagy On Mice Traumatic Brain Injury Model

Objective:It has been reported that the loss in cell membrane integrity is a major contributor to the development of neuronal damage subsequent to traumatic brain injury (TBI). Our previous study has showed that TBI causes increasing of neural cell apoptosis and autophagy, and resealing of disrupted plasma membranes is a criticality therapeutic strategy for TBI. But the mechanism of rescue the subsequent damaged neuron in TBI after cell membrane integrity recovery remains elusive. Here, we utilized a copolymer membrane sealant, Poloxamer188(P188), to investigate whether the apoptosis and autophagy involve in the mechanism of rescuing cell death in our mice TBI model.Methods:Mice TBI model was established by weight drop device in adult mice based on procedures previously reported. P188was administered with tail intravenous injection after TBI. Mice were pretreated with intraperitoneal injection of propidium iodide (PI)1h before sacrificed. PI-labeling was used to identify injured cells, and the amount of PI positive cells was counted. Furthermore, the cumulative loss of brain tissue was determined to explore whether PI-positive cells could represent TBI-induced cell lost. Finally, motor test and Morris water maze were performed for detecting whether TBI-induced cell loss would result in behavior deficits. We examined the levels of apoptosis associate proteins, and the protein levels of LC-3, beclin-1,P-Akt, hVps34were also detected.Results:(1) PI-positive cells were found in all groups that surffered TBI. The number of PI-positive cells peaked in the24h time-point group, and P188treatment significantly decreased the number of PI-positive cells.(2) Compared with saline vehicle groups, P188treatment markedly reduced lesion volume and behavioral deficits which induced by TBI.(3) An elevated activated caspase-3, bax and P53protein levels were detected after TBI, but the elevation were suppressed by P188treatment. However, Bcl-2protein levels were up-regulated by P188. To further explore the mechanism of P188reduces apoptosis, cyt-c, caspase-8, caspase-9protein levels were also assessed by Western-bloting after TBI. The TBI induced up-regulation of cyt-c, caspase-8, and caspase-9protein levels were also reversed by P188.(4) Microtubule-associated protein light chain3(LC3â…¡) was up-regulated after TBI in P188treatment groups when compared with saline vehicle groups. To further investigate the mechanism of P188increases autophagy, P62, hVps34and Beclin-1protein levels were assessed. Compared with saline vehicle groups, P62level was significantly decreased vs. Vps34and Beclin-1remarkably increased in P188treatment groups.Conclusion:(1) P188remarkably attenuated TBI-induced neural cell death, lesion volume, and motor and cognitive dysfunction.(2) P188reduced TBI induced apoptosis through both extrinsic and intrinsic pathway.(3) Autophagy is activated by P188treatment after TBI. P188promoted autophagy activation may rescue the subsequent damaged cells from death following TBI.