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.

Nrf2 functions as a pyroptosis-related mediator in traumatic brain injury and is correlated with cytokines and disease severity: a bioinformatics analysis and retrospective clinical study.

Background: Traumatic brain injury (TBI) is a serious hazard to human health. Evidence has accumulated that pyroptosis plays an important role in brain trauma. The aim of this study is to screen potential key molecules between TBI and pyroptosis, and further explore their relationships with disease severity and cytokines. Methods: To acquire differentially expressed genes (DEGs) before and after brain injury, the GSE89866 dataset was downloaded from the Gene Expression Omnibus (GEO) database. Meanwhile, pyroptosis-related genes were obtained from the GeneCards database, and the intersected genes were identified as differentially expressed pyroptosis-related genes (DEPGs). Moreover, the hub genes were screened via four algorithms (namely Maximum Clique Centrality, Edge Percolated Component, BottleNeck and EcCentricity) in Cytoscape software. Blood levels of Nrf2 were measured by ELISA using a commercially available kit. Finally, we further investigated the correlation between Nrf2 levels and medical indicators in TBI such as clinical characteristics, inflammatory cytokines, and severity. Results: Altogether, we found 1,795 DEGs in GSE89866 and 98 pyroptosis-related genes in the GeneCards database. Subsequently, four hub genes were obtained, and NFE2L2 was adopted for further clinical study. By using Kruskal-Wallis test and Spearman correlation test, we found that the serum Nrf2 levels in severe TBI patients were negatively correlated with GCS scores. On the contrary, there was a positive correlation between serum Nrf2 levels and pupil parameters, Helsinki CT scores, IL-1 ß and IL-18. Conclusions: In summary, bioinformatic analyses showed NFE2L2 plays a significant role in the pathology of TBI. The clinical research indicated the increase in serum Nrf2 levels was closely related to the severity of trauma and cytokines. We speculate that serum Nrf2 may serve as a promising biochemical marker for the assessment of TBI in clinical practice.

Atorvastatin prevents endoplasmic reticulum stress-mediated apoptosis via the Nrf2/HO-1 signaling pathway in TBI mice.

BACKGROUND: Our present study evaluated the neuroprotection effects of atorvastatin by inhibiting TBI-induced ER stress, as well as the potential role of the Nrf2/HO-1 pathway in experimental TBI. METHODS: First, the mice were divided into four groups:sham, TBI, TBI+Vehicle and TBI+atorvastatin groups. The mice received atorvastatin (10 mg/kg/day) through intragastric gavage once a day for 3 days before TBI. In addition, Nrf2 WT and Nrf2 knockout mice were randomly divided into four groups: Nrf2+/+ TBI, Nrf2+/+ TBI+atorvastatin, Nrf2-/- TBI, and Nrf2-/- TBI+atorvastatin groups. Several neurobehavioral parameters were assessed post-TBI using mNSS, brain edema and the rotarod test, and the brain was isolated for molecular and biochemical analysis conducted through TUNEL staining and western blotting. . RESULTS: The results showed that atorvastatin treatment significantly improved neurological deficits, alleviated brain edema, and apoptosis caused by TBI. Western blotting analysis showed that atorvastatin significantly suppressed ER stress and its related apoptotic pathway after TBI, which may be associated with the further activation of the Nrf2/HO-1 pathway. However, compared with the Nrf2+/+ TBI+Vehicle group, Nrf2 deficiency further aggravated neurological deficits and promoted ER stress-mediated apoptosis induced by TBI. Interestingly, atorvastatin failed to improve neurological deficits but reversed apoptosis, and the loss of the beneficial properties of anti-ER stress in the Nrf2-/- TBI mice. . CONCLUSIONS: The results indicated that atorvastatin improves the neurologic functions and protects the brain from injury in the Nrf2+/+ TBI mice, primarily by counteracting ER stress-mediated apoptosis, which may be achieved through the activation of the Nrf2/HO-1 signaling pathway.

Nrf2 loss of function exacerbates endoplasmic reticulum stress-induced apoptosis in TBI mice.

Nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in neuroprotection and recover. Our studies have showed that endoplasmic reticulum (ER) stress-induced apoptosis aggravates secondary damage following traumatic brain injury (TBI). Whether Nrf2 involved in ER stress and ER stress-mediated apoptosis is not clearly investigated. This present study explored the effect of Nrf2 knockout on ER stress and ER stress-induced apoptosis in TBI mice. A lateral fluid percussion injury (FPI)model of TBI was built based on Nrf2 knockout (Nrf2(-/-)) mice and wild-type (Nrf2(+/+)) mice, and the expressions of marker proteins of ER stress and ER stress-induced apoptosis were checked at 24 h following TBI. We found that Nrf2(-/-) mice presented more severe neurological deficit, brain edema and neuronal cell apoptosis compared with Nrf2(+/+) mice. And, the TBI Nrf2(-/-) mice were significantly increased expression of marker proteins of ER stress and ER stress-induced apoptotic pathway including glucose regulated protein (GRP78), protein kinase RNA-like ER kinase (PERK), inositol requiring enzyme (IRE1), activating transcription factor 6 (ATF6), C/EBP homologous protein (CHOP), caspase-12 and caspase-3, compared with that in WT mice. These results suggest that Nrf2 could ameliorate TBI-induced second brain injury partly through ER stress signal pathway.