Activation of autophagy after blast-induced traumatic brain injury in mice

Alterations of retinal autophagy after a blast simulated microgravity in rats

Emerging research has confirmed the crucial role of autophagy, an endogenous repair mechanism, in various blast injuries. However, its role in explosive ocular injury (EOI) under microgravity (MG) and normal gravity (NG) environments remains poorly understood. Therefore, this study aimed to investigate the changes in retinal lesions and retinal autophagy over time following EOI under both NG and MG environments. This study employed the hind-limb unloading model in Sprague-Dawley (SD) rats to simulate MG conditions and used self-made device with compressed gas to induce EOI. SD rats were randomly divided into six groups as follows: normal gravity control group (NG + non-EOI group), normal gravity model group at 1 day post-EOI injury (NG + EOI 1dpi group, n = 20), normal gravity model group at 7 days post-EOI injury (NG + EOI 7dpi group, n = 20), microgravity control group (MG + non-EOI group), microgravity model group at 1 day post-EOI injury (MG + EOI 1dpi group, n = 20), and microgravity model group at 7 days post-EOI injury (MG + EOI 7dpi group, n = 20). Evaluations of ocular health (gross pathology and histology), and retinal autophagy (histology and WB) were conducted before EOI, as well as at 1 and 7 days following EOI. Compared to the NG + non-EOI group, the NG + EOI group rats exhibited significant increases in autophagy-related proteins and genes in the retina, including Beclin1, LC3Ⅱ/LC3Ⅰ, ATF4, GRP78, CHOP, ATG5, and ATG7, along with a decrease in p62, indicating an elevation in retinal autophagy and ER-phagy levels. Retinal lesions, disintegration, and autophagosomes in the ganglion cell layer (GCL) and photoreceptor inner/outer segment layers (PISL/POSL) diminished over time in the NG + EOI group rats. Meanwhile, the MG + EOI group rats exhibited more severe retinal lesions and disintegration, along with an increased number of autophagosomes in the GCL and PISL/POSL, with these symptoms worsening over time compared to the MG + non-EOI group. Compared to the MG + non-EOI group, the MG + EOI group rats exhibited significant decreases in autophagy-related proteins and genes in the retina, including Beclin1, LC3Ⅱ/LC3Ⅰ, ATF4, GRP78, CHOP, ATG5, and ATG7, along with an increase in p62, suggesting a reduction in retinal autophagy levels. Taken together, retinal autophagy and ER-phagy may serve as a self-protective mechanism following EOI under NG conditions. However, under MG conditions, EOI may disrupt this protective mechanism, potentially causing irreversible retinal damage and increasing the risk of blindness in astronauts.

[Expression and significance of hypoxia-inducible factor 1α and Bcl-2/adenovirus E1B19kDa-interacting protein 3 in children with traumatic brain injury]

OBJECTIVES

To dynamically observe the changes in hypoxia-inducible factor 1α (HIF-1α) and Bcl-2/adenovirus E1B19kDa-interacting protein 3 (BNIP3) in children with traumatic brain injury (TBI) and evaluate their clinical value in predicting the severity and prognosis of pediatric TBI.

METHODS

A prospective study included 47 children with moderate to severe TBI from January 2021 to July 2023, categorized into moderate (scores 9-12) and severe (scores 3-8) subgroups based on the Glasgow Coma Scale. A control group consisted of 30 children diagnosed and treated for inguinal hernia during the same period, with no underlying diseases. The levels of HIF-1α, BNIP3, autophagy-related protein Beclin-1, and S100B were compared among groups. The predictive value of HIF-1α, BNIP3, Beclin-1, and S100B for the severity and prognosis of TBI was assessed using receiver operating characteristic (ROC) curves.

RESULTS

Serum levels of HIF-1α, BNIP3, Beclin-1, and S100B in the TBI group were higher than those in the control group (P<0.05). Among the TBI patients, the severe subgroup had higher levels of HIF-1α, BNIP3, Beclin-1, and S100B than the moderate subgroup (P<0.05). Correlation analysis showed that the serum levels of HIF-1α, BNIP3, Beclin-1, and S100B were negatively correlated with the Glasgow Coma Scale scores (P<0.05). After 7 days of treatment, serum levels of HIF-1α, BNIP3, Beclin-1, and S100B in both non-surgical and surgical TBI patients decreased compared to before treatment (P<0.05). ROC curve analysis indicated that the areas under the curve for predicting severe TBI based on serum levels of HIF-1α, BNIP3, Beclin-1, and S100B were 0.782, 0.835, 0.872, and 0.880, respectively (P<0.05), and for predicting poor prognosis of TBI were 0.749, 0.775, 0.814, and 0.751, respectively (P<0.05).

CONCLUSIONS

Serum levels of HIF-1α, BNIP3, and Beclin-1 are significantly elevated in children with TBI, and their measurement can aid in the clinical assessment of the severity and prognosis of pediatric TBI.

Impaired autophagic flux in the human brain after traumatic brain injury

Emerging evidence indicates that dysfunctional autophagic flux significantly contributes to the pathology of experimental traumatic brain injury (TBI). The current study aims to clarify its role post-TBI using brain tissues from TBI patients. Histological examinations, including hematoxylin and eosin, Nissl staining, and brain water content analysis, were employed to monitor brain damage progression. Electron microscopy was used to visualize autophagic vesicles. Western blotting and immunohistochemistry were performed to analyze the levels of important autophagic flux-related proteins such as Beclin1, autophagy-related protein 5, lipidated microtubule-associated protein light-chain 3 (LC3-II), autophagic substrate sequestosome 1 (SQSTM1/p62), and cathepsin D (CTSD), a lysosomal enzyme. Immunofluorescence assays evaluated LC3 colocalization with NeuN, P62, or CTSD, and correlation analysis linked autophagy-related protein levels with brain water content and Nissl bodies. Early-stage TBI results showed increased autophagic vesicles and LC3-positive neurons, suggesting autophagosome accumulation due to enhanced initiation and reduced clearance. As TBI progressed, LC3-II and P62 levels increased, while CTSD levels decreased. This indicates autophagosome overload from impaired degradation rather than increased initiation. The study reveals a potential association between worsening brain damage and impaired autophagic flux post-TBI, positioning improved autophagic flux as a viable therapeutic target for TBI.