S-Adenosylmethionine Decarboxylase Activity Is Decreased in the Rat Cortex After Traumatic Brain Injury

Abstract: S -Adenosyl- l -methionine decarboxylase (SAMdc) and l -ornithine decarboxylase (ODC) are major enzymes regulating polyamine synthesis. Following ischemia, putrescine content increases as a result of post-traumatic activation of ODC and inhibition of SAMdc. These alterations are thought to mediate edema and cell death. The purpose of this study was to quantify SAMdc activity and edema in the brain following controlled cortical impact injury. Anesthetized adult male rats underwent a right parietal craniectomy and were subjected to cortical impact injury. Tissues were obtained from three bilateral regions: parietal cortex, motor area (CPm); parietal cortex, somatosensory area (CPs); and the pyriform cortex (CPF). SAMdc activity was determined in the postmitochondrial fraction from homogenates of fresh, unfrozen tissues by measuring the decarboxylation of S -adenosyl- l -[ carboxyl -¹⁴C]methionine. Basal SAMdc activity was determined in unoperated rats, and regional differences were noted: Activity was lower in the CPF than in the CPm and CPs. SAMdc activity decreased to the greatest extent in the ipsilateral CPm (impact site) from 1 to 72 h following traumatic brain injury. Significant edema was found in the ipsilateral CPm 1, 8, 16, 24, and 48 h after injury. Decreased SAMdc activity impairs the conversion of putrescine to polyamines and may contribute to delayed pathological changes in the brain after traumatic injury.     

Delayed Phospholipid Degradation in Rat Brain After Traumatic Brain Injury

Abstract: Lipid second messengers such as arachidonic acid and its metabolites and diacylglycerols (DAGs) are affected in brain injury. Therefore, changes in the pool size and the fatty acid composition of free fatty acids (FFAs) and DAGs were analyzed in different rat brain areas 4 and 35 days after traumatic injury. Cortical impact injury of low-grade severity was applied in the right frontal somatosensory cortex. Four days after injury, FFAs and DAGs were increased by three- and twofold, respectively, in the injured cortex and to a lesser extent in the contralateral cortex compared with sham-operated animals. Docosahexaenoic acid followed by stearic acid, and arachidonic acid, displayed the greatest changes in both FFAs and DAGs. By day 35, free stearic, oleic, and arachidonic acids remained elevated in the damaged cortex (1.5-fold each). DAGs showed the greatest change, reaching values 2.7-fold higher than sham in all frontal and occipital cortical areas, including brainstem. Oleoyl- and arachidonoyl-DAGs (four- and threefold increase, respectively) followed by docosahexaenoyl-DAGs (twofold) contributed to the DAG accumulation. These results reveal that traumatic brain injury triggers a sustained and time-dependent activation of phospholipase-mediated signaling pathways leading to membrane phospholipid degradation and targeting, early on, docosahexaenoyl phospholipid-enriched excitable membranes.     

NLRP3 Inflammasome Is Involved in Q-VD-OPH Induced Necroptosis Following Cerebral Ischemia-Reperfusion Injury

Necroptosis is a manner of caspase-independent cell death,which accounts for delayed ischemic cerebral injury, and can be used as a novel tool to expand the treatment time window in ischemic cerebral injury. Q-VD-OPH, a novel pan caspase inhibitor, has been identified as an inducer of necroptosis. In this study, we determined the optimal dose of Q-VD-OPH, which induces necroptosis in rats by the middle cerebral artery occlusion, followed by reperfusion. Furthermore, we report that the NLRP3 inflammasome is involved in necroptosis, with levels of NLRP3 inflammasome proteins as well as inflammatory cytokines, such as IL-1β, being elevated. We also demonstrated that NLRP3 was not only expressed in microglia and vascular endothelial cell, but also in neurons when necroptosis is induced with Q-VD-OPH. Inhibition of NLRP3 by glyburide strongly suppressed the expression of NLRP3 inflammasome proteins and IL-1β, and markedly reduced brain tissue damage. Our findings provide evidence that pretreatment with Q-VD-OPH suppresses apoptosis and induces necroptosis in the cerebral ischemia-reperfusion model. We also identified that the NLRP3 inflammasome plays an important role in neuronal necroptosis, and that NLRP3 inflammasome deficiency reduces brain tissue damage after cerebral ischemia-reperfusion injury in rats.     

神经干细胞移植对脑损伤大鼠整合素表达的影响

目的探讨神经干细胞（NSCs）移植对大鼠创伤性脑损伤（TBI）整合素（integrin）表达的影响。方法从E14大鼠胚胎分离NSCs,进行原代培养及传代培养;对NSCs进行诱导分化;采用免疫细胞化学技术对NSCs和其分化为神经元的表型进行鉴定。采用改良的Feeney法制备创伤性脑损伤模型。利用脑立体定位仪和微量注射泵进行NSCs脑内移植。采用免疫组织化学技术、免疫印迹技术和RT—PCR技术检测在移植后不同时间脑组织损伤区整合素的表达。结果在培养基中,NSCs呈球团状悬浮生长,Nestin表达阳性。用含10％胎牛血清的培养基对NSCs进行体外诱导分化后第2d,多数细胞伸出突起,以后突起逐渐延长,分支增加。分化后第5d,部分细胞呈βⅢ-微管蛋白阳性。整合素阳性产物主要表达于细胞膜,呈棕黄色。在对照组及移植组均可见阳性细胞表达。在不同时间点,NSCs移植组移植点及其周围脑组织中整合素的mRNA表达均显著高于对照组（P〈O．01）。整合素的蛋白表达结果和tuRNA表达结果相一致。结论移植NSCs至TBI大鼠损伤脑组织,在移植点周围脑组织中整合素的表达显著增加。     

Propofol Administration Modulates AQP-4 Expression and Brain Edema After Traumatic Brain Injury

The increased intracranial pressure caused by brain edema following traumatic brain injury (TBI) always leads to poor patient prognosis. Aquaporin-4 (AQP-4) plays an important role in edema formation and resolution, which may provide a novel therapeutic target for edema treatment. In this present study, we found that propofol treatment, within a short time, after TBI significantly reduced brain edema in a controlled cortical injury rat model and suppressed in vivo expression of AQP-4. The ameliorating effect of propofol was associated with attenuated expression of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). In addition, the regulatory effect of propofol on AQP-4 expression was investigated in cultured astrocytes. Results showed that propofol could block the stimulatory effect of IL-1β and TNF-α on AQP-4 expression in cultured astrocytes. We also found that both NFκB and p38/MAPK pathways were involved in IL-1β and TNF-α-induced AQP-4 expression and that propofol functions as a dual inhibitor of NFκB and p38/MAPK pathways. In conclusion, treatment with propofol, within a short time, after TBI attenuates cerebral edema and reduces the expression of AQP-4. Propofol modulates acute AQP-4 expression by attenuating IL-1β and TNF-α expression and inhibiting IL-1β and TNF-α induced AQP-4 expression.     

Triglyceride is a Good Biomarker of Increased Injury Severity on a High Fat Diet Rat After Traumatic Brain Injury

Neurochemical Research - Injury severity is correlated with poor prognosis after traumatic brain injury (TBI). It is not known whether triglycerides (TGs) or total cholesterol (TC) is good...     

Cyclooxygenase Products of Arachidonic Acid Metabolism in Cat Cerebral Cortex After Experimental Concussive Brain Injury

Previous studies have suggested that following experimental fluid percussion brain injury, increased prostaglandin (PG) synthesis, with its concomitant production of oxygen free radicals, causes functional and morphological abnormalities of the cerebral arterioles. The purpose of this study was to chemically determine if PGs are altered following this injury. To facilitate interpretation of neurochemical measurements the cats were ventilated, blood pressure was measured, and a cranial window, for microscopic observation of pial arteriolar diameter was inserted. PG levels were determined in quick-frozen cortical tissue removed from control and 3 groups of injured cats at 1.5, 8,0, and 60 min after injury. Analysis of PGE2, PGF2 alpha, and 6-keto-PGF1 alpha was performed by HPLC and GC/MS. The control levels of PGE2, PGF2 alpha, and 6-keto-PGF1 alpha were 216 +/- 44, 210 +/- 48, and 48 +/- 12 ng/g wet weight, respectively. Following injury, produced by a 22 ms increase in intracranial pressure, the pial arterioles dilated irreversibly and a transient hypertensive response occurred, thereby producing hyperemia. During the maximum hyperemic response, the total PGs were 75% of control. At 8 min after injury, when blood pressure returned to control level, the PGs were 158% of control and PGs fell to 111% of control at 60 min. These experiments supported our previous studies implicating increased PG synthesis in te genesis of the physiologic and morphologic sequelae of experimental concussive brain injury.     

Voluntary Alcohol Intake following Blast Exposure in a Rat Model of Mild Traumatic Brain Injury

Alcoholism is a frequent comorbidity following mild traumatic brain injury (mTBI), even in patients without a previous history of alcohol dependence. Despite this correlational relationship, the extent to which the neurological effects of mTBI contribute to the development of alcoholism is unknown. In this study, we used a rodent blast exposure model to investigate the relationship between mTBI and voluntary alcohol drinking in alcohol naïve rats. We have previously demonstrated in Sprague Dawley rats that blast exposure leads to microstructural abnormalities in the medial prefrontal cortex (mPFC) and other brain regions that progress from four to thirty days. The mPFC is a brain region implicated in alcoholism and drug addiction, although the impact of mTBI on drug reward and addiction using controlled models remains largely unexplored. Alcohol naïve Sprague Dawley rats were subjected to a blast model of mTBI (or sham conditions) and then tested in several common measures of voluntary alcohol intake. In a seven-week intermittent two-bottle choice alcohol drinking test, sham and blast exposed rats had comparable levels of alcohol intake. In a short access test session at the conclusion of the two-bottle test, blast rats fell into a bimodal distribution, and among high intake rats, blast treated animals had significantly elevated intake compared to shams. We found no effect of blast when rats were tested for an alcohol deprivation effect or compulsive drinking in a quinine adulteration test. Throughout the experiment, alcohol drinking was modest in both groups, consistent with other studies using Sprague Dawley rats. In conclusion, blast exposure had a minimal impact on overall alcohol intake in Sprague Dawley rats, although intake was increased in a subpopulation of blast animals in a short access session following intermittent access exposure.     

Modulation of Antioxidant Enzyme Expression by PTU-Induced Hypothyroidism in Cerebral Cortex of Postnatal Rat Brain

This study aimed to elucidate the effect of 6-n-propylthiouracil (PTU)-induced hypothyroidism on oxidative stress parameters and expression of antioxidant enzymes in cerebral cortex of rat brain during postnatal development. A significant decrease in levels of lipid peroxidation and H₂O₂ were seen in 7 and 30 days old PTU-treated rats with respect to their controls. Significantly decreased activities of superoxide dismutase (SOD) and catalase (CAT) along with the translated products of SOD1 and SOD2 were observed in 7, 15 and 30 days old PTU-treated rats as compared to their respective controls. However, increase in translated product of CAT was seen in all age groups of PTU-treated rats. Glutathione peroxidase activity was decreased in 7 days and increased in 15 days old PTU-treated rats with respect to their control groups. Histological sections clearly show a decline in neuronal migration with neurons packed together in the hypothyroid group as compared to the control.     

Traumatic Brain Injury Induces an Up-Regulation of Hs1-Associated Protein X-1 (Hax-1) in Rat Brain Cortex

HS1-associated protein X-1 (Hax-1) is an intracellular protein with anti-apoptotic properties that, in addition to suppressing cell death by inhibiting the activation of initiator caspase-9 and death caspase-3, is involved in an increasing number of signaling cascades. However, its expression and function in the central nervous system lesion are still unclear. In this study, we performed a traumatic brain injury (TBI) model in adult rats and investigated the dynamic changes of Hax-1 expression in the brain cortex. Western blot and immunohistochemistry analysis revealed that Hax-1 was present in normal brain. It gradually increased, reached a peak at day 3 after TBI, and then declined during the following days. Double immunofluorescence staining showed that Hax-1 immunoreactivity (IR) was found in neurons, but not astrocytes and microglia. Moreover, the 3rd day post injury was the apoptotic peak implied by the alteration of caspase-3, Bcl-2 and TUNEL. All these results suggested that Hax-1 may be involved in the pathophysiology of TBI and further research is needed to have a good understanding of its function and mechanism.     

Decreased Resting Functional Connectivity after Traumatic Brain Injury in the Rat

Traumatic brain injury (TBI) contributes to about 10% of acquired epilepsy. Even though the mechanisms of post-traumatic epileptogenesis are poorly known, a disruption of neuronal networks predisposing to altered neuronal synchrony remains a viable candidate mechanism. We tested a hypothesis that resting state BOLD-fMRI functional connectivity can reveal network abnormalities in brain regions that are connected to the lesioned cortex, and that these changes associate with functional impairment, particularly epileptogenesis. TBI was induced using lateral fluid-percussion injury in seven adult male Sprague-Dawley rats followed by functional imaging at 9.4T 4 months later. As controls we used six sham-operated animals that underwent all surgical operations but were not injured. Electroencephalogram (EEG)-functional magnetic resonance imaging (fMRI) was performed to measure resting functional connectivity. A week after functional imaging, rats were implanted with bipolar skull electrodes. After recovery, rats underwent pentyleneterazol (PTZ) seizure-susceptibility test under EEG. For image analysis, four pairs of regions of interests were analyzed in each hemisphere: ipsilateral and contralateral frontal and parietal cortex, hippocampus, and thalamus. High-pass and low-pass filters were applied to functional imaging data. Group statistics comparing injured and sham-operated rats and correlations over time between each region were calculated. In the end, rats were perfused for histology. None of the rats had epileptiform discharges during functional imaging. PTZ-test, however revealed increased seizure susceptibility in injured rats as compared to controls. Group statistics revealed decreased connectivity between the ipsilateral and contralateral parietal cortex and between the parietal cortex and hippocampus on the side of injury as compared to sham-operated animals. Injured animals also had abnormal negative connectivity between the ipsilateral and contralateral parietal cortex and other regions. Our data provide the first evidence on abnormal functional connectivity after experimental TBI assessed with resting state BOLD-fMRI.     

Upregulation of 3-MST Relates to Neuronal Autophagy After Traumatic Brain Injury in Mice

3-mercaptopyruvate sulfurtransferase (3-MST) was a novel hydrogen sulfide (H₂S)-synthesizing enzyme that may be involved in cyanide degradation and in thiosulfate biosynthesis. Over recent years, considerable attention has been focused on the biochemistry and molecular biology of H₂S-synthesizing enzyme. In contrast, there have been few concerted attempts to investigate the changes in the expression of the H₂S-synthesizing enzymes with disease states. To investigate the changes of 3-MST after traumatic brain injury (TBI) and its possible role, mice TBI model was established by controlled cortical impact system, and the expression and cellular localization of 3-MST after TBI was investigated in the present study. Western blot analysis revealed that 3-MST was present in normal mice brain cortex. It gradually increased, reached a peak on the first day after TBI, and then reached a valley on the third day. Importantly, 3-MST was colocalized with neuron. In addition, Western blot detection showed that the first day post injury was also the autophagic peak indicated by the elevated expression of LC3. Importantly, immunohistochemistry analysis revealed that injury-induced expression of 3-MST was partly colabeled by LC3. However, there was no colocalization of 3-MST with propidium iodide (cell death marker) and LC3 positive cells were partly colocalized with propidium iodide. These data suggested that 3-MST was mainly located in living neurons and may be implicated in the autophagy of neuron and involved in the pathophysiology of brain after TBI.     

Niche Cells Crosstalk In Neuroinflammation After Traumatic Brain Injury

Traumatic brain injury (TBI) is recognized as the disease with high morbidity and disability around world in spite of the work ongoing in neural protection. Due to heterogeneity among the patients, it''s still hard to acquire satisfying achievements in clinic. Neuroinflammation, which exists since primary injury occurs, with elusive duality, appear to be of significance from recovery of injury to neurogenesis. In recent years, studied have revealed that communication in neurogenic niche is more than “cell to cell” communication, and study on NSCs represent it as central role in the progress of neural regeneration. Hence, the neuroinflammation-affecting crosstalk after TBI, and clarifying definitive role of NSCs in the course of regeneration is a promising subject for researchers, for its great potential in overcoming the frustrating status quo in clinic, promoting welfare of TBI patient.     

Alterations in Regional Brain Catecholamine Concentrations After Experimental Brain Injury in the Rat

Abstract: Although activation of brain catecholaminergic systems has been implicated in the cerebrovascular and metabolic changes during subarachnoid hemorrhage, cerebral ischemia, cortical ablation, and cortical freeze lesions, little is known of the response of regional brain catecholamine systems to traumatic brain injury. The present study was designed to characterize the temporal changes in concentrations of norepinephrine (NE), dopamine (DA), and epinephrine (E) in discrete brain regions following experimental fluid-percussion traumatic brain injury in rats. Anesthetized rats were subjected to fluid-percussion brain injury of moderate severity (2.2–2.3 atm) and killed at 1 h, 6 h, 24 h, 1 week, and 2 weeks postinjury (n = 6 per timepoint). Control animals (surgery and anesthesia without injury) were killed at identical timepoints (n = 6 per timepoint). Tissue concentrations of NE, DA, and E were evaluated using HPLC. Following brain injury, an acute decrease was observed in DA concentrations in the injured cortex ( p < 0.05) at 1 h postinjury, which persisted up to 2 weeks postinjury. Striatal concentrations of DA were significantly increased ( p < 0.05) only at 6 h postinjury. Hypothalamic concentrations of DA and NE increased significantly beginning at 1 h postinjury ( p < 0.05 and p < 0.05, respectively) and persisted up to 24 h for DA ( p < 0.05) and 1 week ( p < 0.05) for NE. These data suggest that acute alterations occur in regional concentrations of brain catecholamines following brain trauma, which may persist for prolonged periods postinjury.     

Sigma-1 Receptor Modulates Neuroinflammation After Traumatic Brain Injury

Traumatic brain injury (TBI) remains a significant clinical problem and contributes to one-third of all injury-related deaths. Activated microglia-mediated inflammatory response is a distinct characteristic underlying pathophysiology of TBI. Here, we evaluated the effect and possible mechanisms of the selective Sigma-1 receptor agonist 2-(4-morpholinethyl)-1-phenylcyclohexanecarboxylate (PRE-084) in mice TBI model. A single intraperitoneal injection 10 μg/g PRE-084, given 15 min after TBI significantly reduced lesion volume, lessened brain edema, attenuated modified neurological severity score, increased the latency time in wire hang test, and accelerated body weight recovery. Moreover, immunohistochemical analysis with Iba1 staining showed that PRE-084 lessened microglia activation. Meanwhile, PRE-084 reduced nitrosative and oxidative stress to proteins. Thus, Sigma-1 receptors play a major role in inflammatory response after TBI and may serve as useful target for TBI treatment in the future.