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Traumatic brain injury (TBI) can cause the pathological disruption of the blood-brain barrier (BBB) and associated neurological injury. Reducing the severity of such barrier disruption following TBI can decrease the degree of brain edema, suppress intracranial inflammation, and thereby protect against neurological damage. The BBB is made up of brain microvascular endothelial cells (BMVECs), neurons, pericytes, astrocytes, and extracellular matrix components. In prior analyses, we have demonstrated that miR-124-3p expression is enhanced in microglia-derived exosomes following TBI, with this miRNA being capable of promoting neural repair after such injury. Based upon these results, the present study was formulated to examine the impact of miR-124-3p on BMVEC function and to evaluatethe mechanistic basis for its activity by overexpressing miR-124-3p in these endothelial cells. We utilized a bEnd.3 cell scratch wound in vitro model to simulate TBI-associated brain microvascular endothelial cell injury. Lipofectamine3000 was used to transfect endothelial cells such that they overexpressed miR-124-3p. Fluorescence microscopy was used to observe the effects of miR-124-3p expression on these endothelial cells. TUNEL+CD31 immunofluorescence stainingwas employed to observe endothelial cell apoptosis. Tight junctions were observed via ionconductivity microscopy. Western blotting was used to detect the expression of tight junction proteins (occludin, ZO-1), autophagy-associated proteins (Beclin-1, p62, LC3-II/LC3-I), and mTOR-associated proteins (p-mTOR, PDE4B). Chloroquine was used to treat these injured endothelial cells overexpressing miR-124-3p, and endothelial cell apoptosis was assessed via TUNEL+CD31 immunofluorescence staining. We found that the upregulation of miR-124-3p was sufficient to suppress bEnd.3 cell apoptotic death following in vitro scratch injury while promoting the upregulation of the tight junction proteins ZO-1 and occludin in these cells, thereby reducing the degree of leakage across the cerebral microvascular endothelial barrier. These protective effects may be related to the ability of miR-124-3p to suppress mTOR signaling and to induce autophagic activity within BMVECs. These data support a model wherein miR-124-3p can inhibit mTOR signaling and promote autophagic induction in BMVECs, thereby protecting these cells against TBI-induced damage.

Brain injury has been reported to occur in sepsis and can lead to high mortality among septic patients. Previous studies suggest that ghrelin is protective for the brain, but whether ghrelin protects brain from sepsis remains unclear. Therefore, the aim of this study is to investigate the protective effect of ghrelin against sepsis-induced brain injury. Cecal ligation and puncture was performed in male C57BL/6J mice to establish the sepsis model. Ghrelin was administrated intraperitoneally at a dose of 80μg/kg. The blood-brain barrier (BBB) integrity, brain water content, inflammatory cytokines (TNF-α and IL-1β), oxidative stress (SOD and MDA) and neuronal apoptosis were assessed. In addition, the expression levels of Akt, phospho-Akt (Ser473) (p-Akt), Bcl-2 and Bax were detected by Western blot. Our results suggested that ghrelin attenuated brain edema, neuronal apoptosis and enhanced BBB integrity. Ghrelin decreased the production of TNF-α and IL-1β. Ghrelin increased the activity of SOD and decreased MDA production. Additionally, ghrelin increased the expression of p-Akt and Bcl-2 and decreased the Bax expression. The protective effects of ghrelin mentioned above were abolished by LY294002 (LY), a PI3K inhibitor. In conclusion, our results demonstrate that ghrelin attenuates brain injury in sepsis via PI3K/Akt signaling activation., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Our recent studies have identified increased expression of miR-21 in brain following traumatic brain injury (TBI), which alleviated brain edema that related to the blood-brain barrier (BBB) leakage. To analyze the potential effect of miR-21 on secondary BBB damage after TBI, we employed the fluid percussion injury rat model and manipulated the expression level of miR-21 in brain. We found that miR-21 level in brain microvascular endothelial cells (BMVECs) in lesioned cerebral cortex can be upregulated or downregulated by intracerebroventricular infusion of miR-21 agomir or antagomir. Upregulated miR-21 level conferred a better neurological outcome of TBI, and alleviated TBI-induced secondary BBB damage and loss of tight junction proteins. To explore the molecular mechanism underlying this protective effect, we detected the impact of miR-21 on the expression of Angiopoietin-1(Ang-1) and Tie-2, which can promote the expression of tight junction proteins and amplify BBB stabilization. We found that miR-21 exerts the protective effect on BBB by activating the Ang-1/Tie-2 axis in BMVECs. Thus, miR-21 could be a potential therapeutic target for interventions of secondary BBB damage after TBI., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The expression levels of microRNAs (miRNAs) including miR-21, have been reported to change in response to traumatic brain injury (TBI), suggesting that they may influence the pathophysiological process in brain injury. To analyze the potential effect of miR-21 on neurological function after TBI, we employed the fluid percussion injury rat model and manipulated the expression level of miR-21 in brain using intracerebroventricular infusion of miR-21 agomir or antagomir. We found that upregulation of miR-21 level in brain conferred a better neurological outcome after TBI by improving long-term neurological function, alleviating brain edema and decreasing lesion volume. To further investigate the mechanism underlying this protective effect, we evaluated the impact of miR-21 on apoptosis and angiogenesis in brain after TBI. We found that miR-21 inhibited apoptosis and promoted angiogenesis through regulating the expression of apoptosis- and angiogenesis-related molecules. In addition, the expression of PTEN, a miR-21 target gene, was inhibited and Akt signaling was activated in the procedure. Taken together, these data indicate that miR-21 could be a potential therapeutic target for interventions after TBI.

Traumatic brain injury (TBI) is a major cause of chronic disability and death in young adults worldwide. Multiple cellular, molecular and biochemical changes impact the development and outcome of TBI. Neuronal cell apoptosis, which is an important pathological change in secondary brain damage, is crucial to determine the functional recovery after TBI. miR-21, a widely-reported oncogene, which can reduce cell apoptosis in cancer, has been confirmed to be a pronounced up-regulated miRNA after TBI in animal model. Our study is designed to investigate whether miR-21 has the function of antiapoptosis in experimental TBI model in vitro and to explore the possible regulatory mechanism of miR-21 on neuronal apoptosis. The scratch cell injury was performed to mimic TBI-induced apoptosis in neurons, and miR-21 agomir/antagomir was transfected to up-/down-regulate the miR-21 level. Our data suggests that miR-21 can reduce the number of TUNEL-positive neurons. Meanwhile, miR-21 decreased the expression level of PTEN, and increased the phosphorylation of Akt significantly. In neurons transfected with miR-21 agomir, the expression of Bcl-2 was promoted while the caspase-3, caspase-9 and Bax level were down-regulated, which are crucially the downstream apoptosis-related proteins of PTEN-Akt signaling pathway. In conclusion, miR-21 can exert the function of reducing neuronal apoptosis through activating the PTEN-Akt signaling pathway. Our research provides new insights into the molecular mechanisms of neuronal apoptosis following TBI, which reminds that miR-21may be a potential therapeutic target for TBI treatment., (Copyright © 2014. Published by Elsevier B.V.)

Emerging evidence demonstrates that severe illness could induce critical illness-related corticosteroid insufficiency (CIRCI) and cause poor prognosis. The purpose of this study was to test the hypothesis that methylprednisolone (MP), a synthetic glucocorticoid, promotes post-traumatic apoptosis in both the hypothalamus and pituitary, resulting in acute CIRCI and increased mortality in the acute phase of traumatic brain injury (TBI). We tested this hypothesis by measuring acute CIRCI in rats subjected to fluid percussion injury (FPI) and treated with MP (5-30mg/kg). The corticosteroid response to TBI was evaluated using the corticosterone increase index (CII), where values less than 2.5 were considered indicative of acute CIRCI. The CII of MP treated rats was comparable to that of saline treated control rats before injury but was significantly decreased in injured rats receiving high-dose MP on post-injury day 7. Similarly, the incidence of acute CIRCI was significantly higher in the high-dose MP group on post-injury day 7. Furthermore, the CII of rats that did not survive post-injury was significantly lower compared to that of survival and was indicative of acute CIRCI. We also examined apoptosis in the paraventricular nucleus (PVN) of the hypothalamus and the adenohypophysis of the pituitary, using a TUNEL assay and transmission electron microscopy (TEM). The number of TUNEL-positive cells was significantly higher in injured rats treated with high-dose MP. No TUNEL-positive cells were detected in the adenohypophysis across experimental groups at either 7 or 14days after TBI. However, autopsies performed on rats that did not survive post-injury revealed obvious apoptotic cells in the adenohypophysis. Moreover, TEM revealed morphological changes characteristic of apoptosis in both the PVN and adenohypophysis of high-dose MP treated rats. These data suggest that MP therapy for TBI could increase neuronal apoptosis in both the hypothalamus and pituitary and consequently exacerbate acute CIRCI and mortality induced by TBI., (Copyright © 2011 Elsevier B.V. All rights reserved.)

MicroRNAs (miRNAs) are very important regulators of biological processes such as development, cellular differentiation, and tumor generation. MiRNA microarray has been found to be a high throughput global analysis tool for detecting miRNA expression profiling, and miRNA expression profiling will facilitate the study of the biological function of miRNAs. In this report, we describe the miRNA expression level in rat cerebral cortex after traumatic brain injury using microarray method. We choose several time points post brain injury: 6 h, 24 h, 48 h and 72 h, respectively, to reveal differential expression of miRNAs in rat brain cortex compared with control groups. Our research revealed that 136 miRNAs were expressing at 6 h post injury, in which 13 miRNAs were more than 2-fold up-regulated, and 14 miRNAs were more than 2-fold down-regulated; 118 miRNAs were expressing at 24 h post injury, in which 4 miRNAs were more than 2-fold up-regulated, and 23 miRNAs were more than 2-fold down-regulated; 149 miRNAs were expressing at 48 h post injury, in which 16 miRNAs were more than 2-fold up-regulated, and 11 miRNAs were more than 2-fold down-regulated; and 203 miRNAs were expressing at 72 h post injury, in which 19 miRNAs were more than 2-fold up-regulated, and 5 miRNAs were more than 2-fold down-regulated. Furthermore, we revealed global up-regulation of miR-21 expression within all the four time points post injury. Finally, we utilized qRT-PCR methods to verify the microarray results. The qRT-PCR results indicated good consistency with the results of the microarray method. Our microarray based analysis of microRNA expression in rat cerebral cortex after traumatic brain injury has shown that some microRNA such as miR-21 could be involved in the intricate process of TBI course.

The incidence of repetitive mild traumatic brain injury (rmTBI), one of the main risk factors for predicting neurodegenerative disorders, is increasing; however, its underlying mechanism remains unclear. As suggested by several studies, ferroptosis is possibly related to TBI pathophysiology, but its effect on rmTBI is rarely studied. Mesenchymal stromal cells (MSCs), the most studied experimental cells in stem cell therapy, exert many beneficial effects on diseases of the central nervous system, yet evidence regarding the role of MSCs in ferroptosis and post-rmTBI neurodegeneration is unavailable. Our study showed that rmTBI resulted in time-dependent alterations in ferroptosis-related biomarker levels, such as abnormal iron metabolism, glutathione peroxidase (GPx) inactivation, decrease in GPx4 levels, and increase in lipid peroxidation. Furthermore, MSC treatment markedly decreased the aforementioned rmTBI-mediated alterations, neuronal damage, pathological protein deposition, and improved cognitive function compared with vehicle control. Similarly, liproxstatin-1, a ferroptosis inhibitor, showed similar effects. Collectively, based on the above observations, MSCs ameliorate cognitive impairment following rmTBI, partially via suppressing ferroptosis, which could be a therapeutic target for rmTBI. [ABSTRACT FROM AUTHOR]

Mild traumatic brain injury (mTBI) has a relatively higher incidence in aging people due to walking problems. Cranial computed tomography and magnetic resonance imaging provide the standard diagnostic tool to identify intracranial complications in patients with mTBI. However, it is still necessary to further explore blood biomarkers for evaluating the deterioration risk at the early stage of mTBI to improve medical decision-making in the emergency department. The activation of the inflammatory response is one of the main pathological mechanisms leading to unfavorable outcomes of mTBI. As complete blood count (CBC) analysis is the most extensively used laboratory test in practice, we extracted clinical data of 994 patients with mTBI from two large clinical cohorts (MIMIC-IV and eICU-CRD) and selected inflammation-related indicators from CBC analysis to investigate their relationship with the deterioration after mTBI. The combinatorial indices neutrophil-to-lymphocyte ratio (NLR), red cell distribution width-to-platelet ratio (RPR), and NLR times RPR (NLTRP) were supposed to be potential risk predictors, and the data from the above cohorts were integratively analyzed using our previously reported method named MeDICS. We found that NLR, RPR, and NLTRP levels were higher among deteriorated patients than non-deteriorated patients with mTBI. Besides, high NLTRP was associated with increased deterioration risk, with the odds ratio increasing from NLTRP of 1–2 (2.69, 1.48–4.89) to > 2 (4.44, 1.51–13.08), using NLTRP of 0–1 as the reference. NLTRP had a moderately good prognostic performance with an area under the ROC curve of 0.7554 and a higher prediction value than both NLR and RPR, indicated by the integrated discrimination improvement index. The decision curve analysis also showed greater clinical benefits of NLTRP than NLR and RPR in a large range of threshold probabilities. Subgroup analysis further suggested that NLTRP is an independent risk factor for the deterioration after mTBI. In addition, in vivo experiments confirmed the association between NLTRP and neural/systemic inflammatory response after mTBI, which emphasized the importance of controlling inflammation in clinical treatment. Consequently, NLTRP is a promising biomarker for the deterioration risk of mTBI. It can be used in resource-limited settings, thus being proposed as a routinely available tool at all levels of the medical system. [ABSTRACT FROM AUTHOR]

Background: Repetitive mild traumatic brain injury (rmTBI) is closely associated with chronic traumatic encephalopathy (CTE). Neuroinflammation and neuropathological protein accumulation are key links to CTE progression. Exosomes play important roles in neuroinflammation and neuropathological protein accumulation and spread. Here, we explored the role of brain-derived exosomes (BDEs) in mice with rmTBI and how the inhibition of BDE release contributes to neuroprotection. Methods: GW4869 was used to inhibit exosome release, and behavioural tests, PET/CT and western blotting were conducted to explore the impact of this inhibition from different perspectives. We further evaluated cytokine expression by Luminex and microglial activation by immunofluorescence in mice with rmTBI after exosome release inhibition. Results: Inhibition of BDE release reversed cognitive impairment in mice with rmTBI, enhanced glucose uptake and decreased neuropathological protein expression. Inhibition of BDE release also changed cytokine production trends and enhanced microglial proliferation. Conclusion: In this study, we found that BDEs are key factor in cognitive impairment in mice with rmTBI and that microglia are the main target of BDEs. Thus, inhibition of exosome release may be a new strategy for improving CTE prognoses. [ABSTRACT FROM AUTHOR]

Objective：Traumatic brain injury (TBI) is one of the most serious public health problems in the world. Hydrogen (H2), a flammable, colorless, and odorless gas, has been observed to have preventive and therapeutic effects on brain trauma and other neurological disorders, but its exact mechanism has not been fully clarified. Methods: To further study the mechanism underlying the role of hydrogen gas in alleviating BBB damage after TBI, we performed the scratch injury model on cultured brain microvascular endothelial cells (bEnd.3), which formed the microvascular endothelial barrier – an integral part of the highly specialized BBB. Results: In the case of TBI, hydrogen was able to improve the decline of cell viability induced by TBI. More importantly, inhibition of PI3 K/Akt/GSK3β signal pathway or activation of autophagy reduced the protective effect of hydrogen on cell viability, indicating that such protective effect was regulated by PI3 K/Akt/GSK3β signal pathway and was related to the inhibition of autophagy. Conclusion: So we concluded that hydrogen improved the cell viability in a microvascular endothelial cell model of TBI partly through inhibition of autophagy, and inhibitory effect of hydrogen on autophagy was exerted by activating PI3 K/Akt/GSK3β signal pathway. These findings enriched our knowledge about the mechanism of hydrogen therapy against TBI. [ABSTRACT FROM AUTHOR]

Few studies have explored the effect of hydrogen on neuronal apoptosis or impaired nerve regeneration after traumatic brain injury, and the mechanisms involved in these processes are unclear. In this study, we explored neuroprotection of hydrogen‐rich medium through activation of the miR‐21/PI3K/AKT/GSK‐3β pathway in an in vitro model of traumatic brain injury. Such model adopted PC12 cells with manual scratching. Then, injured cells were cultured in hydrogen‐rich medium for 48 hours. Expression of miR‐21, p‐PI3K, p‐Akt, p‐GSK‐3β, Bax and Bcl‐2 was measured using RT‐qPCR, Western blot analysis and immunofluorescence staining. Rate of apoptosis was determined using TUNEL staining. Neuronal regeneration was assessed using immunofluorescence staining. The results showed that hydrogen‐rich medium improved neurite regeneration and inhibited apoptosis in the injured cells. Scratch injury was accompanied by up‐regulation of miR‐21, p‐PI3K, p‐Akt and p‐GSK‐3β. A miR‐21 antagomir inhibited the expression of these four molecules, while a PI3K blocker only affected the three proteins and not miR‐21. Both the miR‐21 antagomir and PI3K blocker reversed the protective effect of hydrogen. In conclusion, hydrogen exerted a neuroprotective effect against neuronal apoptosis and impaired nerve regeneration through activation of miR‐21/PI3K/AKT/GSK‐3β signalling in this in vitro model of traumatic brain injury. [ABSTRACT FROM AUTHOR]

In our recent study, we observed consistent increases in miR-124-3p levels in exosomes derived from cultured BV2 microglia which was treated with repetitive traumatic brain injury (rTBI) mouse model brain extracts. To clarify the mechanisms underlying increases in microglia-derived exosomal miR-124-3p and their role in regulating neuronal autophagy after TBI, we investigated the impact of exosomal miR-124-3p on neuronal autophagy in scratch-injured HT22 neurons and rTBI mice. We harvested injured brain extracts from rTBI mice at 3 to 21 days post injury (DPI) for the treatment of cultured BV2 microglia in vitro. We observed significant induction of autophagy following TBI in vitro, and that inhibition of activated neuronal autophagy could protect against trauma-induced injury. Our results indicated that co-culture of injured HT22 neurons with miR-124-3p overexpressing BV2 microglia exerted a protective effect by inhibiting neuronal autophagy in scratch-injured neurons. Further research revealed that these effects were achieved mainly via upregulation of exosomal miR-124-3p, and that Focal adhesion kinase family-interacting protein of 200 kDa (FIP200) plays a key role in trauma-induced autophagy. Injection of exosomes into the vena caudalis in in vivo experiments revealed that exosomal miR-124-3p was associated with decreases in the modified neurological severity score (mNSS) and improvements in Morris water maze (MWM) test results in rTBI mice. Altogether, our results indicate that increased miR-124-3p in microglial exosomes following TBI may inhibit neuronal autophagy and protect against nerve injury via their transfer into neurons. Thus, treatment with microglial exosomes enriched with miR-124-3p may represent a novel therapeutic strategy for the treatment of nerve injury after TBI. [ABSTRACT FROM AUTHOR]

Although, there is growing awareness in the progressive neurodegeneration of chronic traumatic encephalopathy, changes of immune reactions remain equivocal at best. Thus, in a clinically relevant rat repetitive mild traumatic brain injury (rmTBI) model, some immunologic cells (T cell subsets, microglia) in the injured brain and peripheral blood were analyzed by flow cytometry and immunofluorescence. In the injured brain, CD3 T cells showed a bimodal increase during 42 days post-injury (dpi). CD3CD4 T cells firstly increased and then decreased, while CD3CD8 T cells had reversed tendency. CD86/CD11b M1-like microglia increased at 42 dpi and CD206/CD11b M2-like microglia peaked at 7 dpi. In addition, peripheral immune suppression was implicated in the chronic phase after rmTBI. Taken together, the study provided useful information on long-term dynamic changes of some immune cells after rmTBI in rats. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) and antioxidant ingredients are a series of crucial signaling molecules in oxidative stress response. Under some pathological conditions such as traumatic brain injury, ischemia/reperfusion, and hypoxia in tumor, the relative excessive accumulation of ROS could break cellular homeostasis, resulting in oxidative stress and mitochondrial dysfunction. Meanwhile, autophagy is also induced. In this process, oxidative stress could promote the formation of autophagy. Autophagy, in turn, may contribute to reduce oxidative damages by engulfing and degradating oxidized substance. This short review summarizes these interactions between ROS and autophagy in related pathological conditions referred to as above with a focus on discussing internal regulatory mechanisms. The tight interactions between ROS and autophagy reflected in two aspects: the induction of autophagy by oxidative stress and the reduction of ROS by autophagy. The internal regulatory mechanisms of autophagy by ROS can be summarized as transcriptional and post-transcriptional regulation, which includes various molecular signal pathways such as ROS-FOXO3-LC3/BNIP3-autophagy, ROS-NRF2-P62-autophagy, ROS-HIF1-BNIP3/NIX-autophagy, and ROS-TIGAR-autophagy. Autophagy also may regulate ROS levels through several pathways such as chaperone-mediated autophagy pathway, mitophagy pathway, and P62 delivery pathway, which might provide a further theoretical basis for the pathogenesis of the related diseases and still need further research. [ABSTRACT FROM AUTHOR]

Cardiac injury is a common complication following traumatic brain injury (TBI) that can lead to poor clinical outcomes. Angiotensin II type 2 receptor (AT2R) activation exerts protective roles in the brain and heart, yet its potential impact on TBI or TBI-induced cardiac deficits remains elusive. The goal of this study was to investigate the influence of AT2R activation on recovery after TBI-induced cognitive and cardiac injury using the selective nonpeptide AT2R agonist compound 21 (C21). TBI was induced by cortical impact injury in male adult C57BL/6J mice, and the mice received C21 (0.03 mg/kg, intraperitoneally) starting from 24 h after TBI and continuing once daily. C21 facilitated cognitive function recovery until 1 month after TBI. C21 alleviated blood-brain barrier leakage and brain edema and inhibited the expression of proinflammatory cytokines in the brain after 3 consecutive days of treatment. C21 improved cerebral blood flow after 1 month, although the lesion volume was not affected. C21 also reduced the expression of proinflammatory cytokines in the heart after a 3-day consecutive treatment. Meanwhile, C21 benefited cardiac function, as identified by increased left ventricular ejection fraction 1 month after TBI. In addition, C21 alleviated TBI-induced cardiac hypertrophy and fibrosis; however, blood pressure was not affected. Our results demonstrate that AT2R activation ameliorates TBI-induced neurological and cardiac deficits. [ABSTRACT FROM AUTHOR]

Prognosis evaluation is crucial for the effective management of patients with acute traumatic brain injury (TBI). However, there is still a lack of routinely available blood indicators for mortality risk in clinical practice. To investigate whether blood red cell distribution width to platelet count ratio (RPR) correlates with hospital mortality of TBI, clinical data of 2220 patients with TBI were extracted from two large intensive care unit cohorts (MIMIC-III and eICU Database), and were integratively analyzed using our developed method named MeDICS. We found that higher RPR can be observed among non-survivors than survivors of TBI (p < 0.001). It had a moderately good prognostic performance for mortality with an area under receiver-operating characteristic curve (AUC) of 0.7367, which was greater than that of Glasgow Coma Scale (GCS; AUC = 0.6022). Besides, the nomogram consisting of RPR, GCS, and other risk factors was developed, where 10-fold cross-validation was performed to protect it against overfitting. A Harrell's C-index of 0.8523 was determined, suggesting an improved prognostic value based on RPR. The in vivo experiments further confirmed the association between RPR and neuro-outcome after TBI. It indicated that the continuous change in RPR post-injury is attributed to the development of inflammation, which emphasized the importance of controlling inflammatory response in clinical treatment. Taken together, RPR is a promising routinely available predictor of mortality for acute TBI. The nomogram generated from it can be used in resource-limited settings, thus be proposed as a prognosis evaluation aid for patients with TBI in all levels of medical system. [ABSTRACT FROM AUTHOR]

• Nerves injury can induce the upregulation of miR-21-5p in neuron. • Neuron-exosomes with high miR-21-5p expression induced microglia polarization. • Inflammation factors released by polarized microglia further aggravated nerves injury. Neuroinflammation is a characteristic pathological change of acute neurological deficit and chronic traumatic encephalopathy (CTE) after traumatic brain injury (TBI). Microglia are the key cell involved in neuroinflammation and neuronal injury. The type of microglia polarization determines the direction of neuroinflammation. MiR-21-5p elevated in neurons and microglia after TBI in our previous research. In this study, we explore the influence of miR-21-5p for neuroinflammation by regulating microglia polarization. In this study, PC12 and BV2 used to instead of neuron and microglia respectively. The co-cultured transwell system used to simulate interaction of PC12 and BV2 cells in vivo environment. We found that PC12-derived exosomes with containing miR-21-5p were phagocytosed by microglia and induced microglia polarization, meanwhile, the expression of miR-21-5p was increased in M1 microglia cells. Polarization of M1 microglia aggravated the release of neuroinflammation factors, inhibited the neurite outgrowth, increased accumulation of P-tau and promoted the apoptosis of PC12 cells, which formed a model of cyclic cumulative damage. Simultaneously, we also got similar results in vivo experiments. PC12-derived exosomes with containing miR-21-5p is the essential of this cyclic cumulative damage model. Therefore, regulating the expression of miR-21-5p or the secretion of exosomes may be an important novel strategy for the treatment of neuroinflammation after TBI. [ABSTRACT FROM AUTHOR]

Pyroptosis is a highly specific type of inflammatory programmed cell death that different from necrosis or apoptosis. It is initiated by cellular detection of acute damage via recognizing pathogen-associated molecular patterns (PAMPs) by NOD-like receptors (NLRs) or AIM2-like receptor (AIM2). NLRs and AIM2 could trigger the formation of a multi-protein complex, known as inflammasome. It also contains apoptotic speck-containing protein (ASC) and pro-Caspase-1, and could process the signals to induce a cascade of inflammatory response. Recently, growing evidence showed that inflammasome-mediated pyroptosis is involved in the pathogenesis of traumatic brain injury (TBI). However, less attention has been paid to their particular roles in regulating blood-brain barrier (BBB) damage, the central pathological change in secondary brain damage of TBI. Thus, we designed this research to explore the impact and mechanism of NLRs and AIM2 inflammasome-mediated pyroptosis in BBB after TBI. We employed the controlled cortical impact (CCI) mice model and manipulated the severity of pyroptosis in BBB using Caspase-1 inhibitor, Ac-YVAD-cmk. We found that TBI led to NLRs and AIM2 inflammasome-mediated pyroptosis in brain microvascular endothelial cells (BMVECs) from injured cerebral cortex. Ac-YVAD-cmk treatment inhibited pyroptosis in injured BMVECs by suppressing the expression of essential inflammasome subunit – Caspase-1 and pivotal downstream pro-inflammatory cytokines (IL-1β and IL-18), as well as hindering GSDMD cleavage and ASC oligomerization. In addition, inhibiting pyroptosis could alleviate TBI-induced BBB leakage, brain edema, loss of tight junction proteins, and the inflammatory response in injured BMVECs. These effects contributed to improving the neurological outcome of CCI mice. In conclusion, NLRs and AIM2 inflammasome-mediated pyroptosis could aggravate BBB damage after TBI. Targeting and controlling pyroptosis in injured BBB would be a promising therapeutic strategy for TBI in the future. [ABSTRACT FROM AUTHOR]

Highlights • We develop a novel rmTBI model that represents clinical settings of mild TBI & CTE. • The model does not induce any adverse effects as described in existing rmTBI models. • A short research period of 5 w post-injury was allowed for observing chronic changes. • Self-designed molded acrylic cast and concave metal disc are used in modeling. • Chronic neuroinflammation, neurodegeneration and cognitive dysfunction are observed. Abstract Background Athletes, military personnel and mobility-declined elderly people are prone to repetitive mild traumatic brain injury (rmTBI). The injury does not cause acute pathological changes, but leads to chronic neurodegeneration, long-term cognitive dysfunction and even chronic traumatic encephalopathy (CTE). Many existing rmTBI animal models reported uncontrollable adverse effects and long experiment period. Therefore, an improved model needs to be designed. New method Our rmTBI mouse model is a modification of the closed head injury method using electronic controlled cortical impact system. Discontinuous 4 impacts with 48-h interval were performed. A key facet of the model is the use of our designed molded acrylic cast and concave metal disc (as a helmet). They could scatter and transmit hitting power to the whole brain, thus produced a mild diffused injury. The procedure does not require scalp incision or craniotomy, which allows the impacting to be completed in 2 min. Results Our model did not induce acute macroscopic brain damage and brain edema. It could lead to sustained neuroinflammation and chronic neurodegeneration in injured brain, and resulted in cognitive dysfunction within 5 weeks post-injury. Comparison with existing methods Previously reported adverse effects including skull fractures, hemorrhage and brain tissue loss were not observed in our model. An experiment period of 5 weeks was allowed for observing chronic neurodegeneration and cognitive dysfunction. Conclusions Our model is beneficial to use for simplicity, reproducibility and time saver. It could serve as a platform for research on the pathogenesis, diagnosis and potential therapeutics for rmTBI and CTE. [ABSTRACT FROM AUTHOR]

Traumatic brain injury (TBI) is a major public health problem with long-term neurobehavioral sequela. The evidences have revealed that TBI is a risk factor for later development of neurodegenerative disease and both the single and repetitive brain injury can lead to the neurodegeneration. But whether the effects of accumulation play an important role in the neurodegenerative disease is still unknown. We utilized the Sprague Dawley (SD) rats to develop the animal models of repetitive mild TBI and single mild TBI in order to detect the neurobehavioral changes. The results of neurobehavioral test revealed that the repetitive mild TBI led to more severe behavioral injuries than the single TBI. There were more activated microglia cells and astrocytes in the repetitive mild TBI group than the single TBI group. In consistent with this, the levels of TNF-α and IL-6 were higher and the expression of IL-10 was lower in the repetitive mild TBI group compared with the single TBI group. The expression of amyloid precursor protein (APP) increased in the repetitive TBI group detected by ELISA and western blot. But the levels of total tau (Tau-5) and P-tau (ser202) seem no different between the two groups in most time point. In conclusion, repetitive mild TBI could lead to more severe neurobehavioral impairments and the effects of accumulation may be associated with the increased inflammation in the brain. [ABSTRACT FROM AUTHOR]