Effect of basic fibroblast growth factor on autophagy of nerve cells in rats after traumatic brain injury

Abstract

Objective To investigate the effect of basic fibroblast growth factor (bFGF) on autophagy of nerve cells in rats after traumatic brain injury (TBI). Methods A total of 120 healthy adult male SD rats were randomly divided into sham group, TBI+ vehicle group, and TBI+ bFGF group by random number table method, with 40 rats in each group. PinPoint™ Precision Cortical Impactor was used to simulate the pathological damage after TBI. In the sham group, the dura was exposed without impact. In the TBI+ bFGF group, 250 μg/kg of human recombinant bFGF was given in the nasal cavity 1 hour before the modeling, while in the sham group and TBI+ Vehicle group, the same amount of saline was given in the nasal cavity 1 hour before the modeling. The necrotic cells were observed by propidium iodide(PI)staining 6 hours after injury. The effect of bFGF on the nerve function after TBI in rats was evaluated with modified neurological severity score (mNSS) 24 hours after injury. The water content of brain tissue was measured by dry and wet method 48 hours after injury. The ratio of Beclin-1, P62 protein and microtubule-associated protein 1 light 3 (LC3)-II/I protein was detected by western blot. The volume of brain injury was calculated by integral method of brain tissue section. The positive neuron specific nuclear protein (NeuN) cells were observed by immunofluorescence staining. The apoptotic cells were observed by TUNEL. Results Compared with the sham group [(4.0±1.2)%], the percentage of necrotic cells in TBI+ vehicle group [(54.3±10.1)%] and TBI+ bFGF group [(34.5±10.5)%] increased significantly (P<0.05), but the percentage of necrotic cells in TBI+ bFGF group increased less than that in TBI+ vehicle group (P<0.05). Compared with the sham group [(0.3±0.5)points], the mNSS in the TBI+ vehicle group [(5.8±0.8)points] and TBI+ bFGF group [(4.7±1.1)points] were significantly increased (P<0.05), but the mNSS of TBI+ bFGF group was lower than that of TBI+ vehicle group (P<0.05). Compared with the sham group [(76.7±0.7)%], the water content of brain tissue of TBI+ vehicle group [(79.2±0.5)%] and TBI+ bFGF group [(78.4±1.0)%]were significantly increased (P<0.05), but the water content of TBI+ bFGF group was significantly lower than that of TBI+ vehicle group (P<0.05). Compared with the sham group, protein expression of Beclin-1 and LC3-II/I in TBI+ vehicle group and TBI+ bFGF group were significantly improved (P<0.05), P62 protein expression was significantly decreased (P<0.05), the volume of brain tissue injury was significantly increased (P<0.05), the number of positive NeuN cells increased significantly (P<0.05), and the number of apoptotic cells and apoptotic cells were significantly increased (P<0.05). Compared with the TBI+ Vehicle group, the up-regulation of Beclin-1 protein and LC3-II/I protein ratio was obviously inhibited in the TBI+ bFGF group (P<0.05), the down-regulation of P62 protien was significantly suppressed, the volume of brain tissue injury was significantly decreased, and the number of positive NeuN cells and apoptotic cells was significantly reduced (P<0.05). Conclusion The bFGF can significantly inhibit excessive autophagy in rats after TBI, reduce brain edema, reduce cell apoptosis and necrosis, and improve neural function. Key words: Fibroblast growth factor 2; Autophagy; Brain injuries; Brain edema; Apoptosis