Mitochondrial mechanisms of cell death and neuroprotection in pediatric ischemic and traumatic brain injury

Tracing the path of disruption: 13C isotope applications in traumatic brain injury-induced metabolic dysfunction

Cerebral metabolic dysfunction is a critical pathological hallmark observed in the aftermath of traumatic brain injury (TBI), as extensively documented in clinical investigations and experimental models. An in-depth understanding of the bioenergetic disturbances that occur following TBI promises to reveal novel therapeutic targets, paving the way for the timely development of interventions to improve patient outcomes. The 13C isotope tracing technique represents a robust methodological advance, harnessing biochemical quantification to delineate the metabolic trajectories of isotopically labeled substrates. This nuanced approach enables real-time mapping of metabolic fluxes, providing a window into the cellular energetic state and elucidating the perturbations in key metabolic circuits. By applying this sophisticated tool, researchers can dissect the complexities of bioenergetic networks within the central nervous system, offering insights into the metabolic derangements specific to TBI pathology. Embraced by both animal studies and clinical research, 13C isotope tracing has bolstered our understanding of TBI-induced metabolic dysregulation. This review synthesizes current applications of isotope tracing and its transformative potential in evaluating and addressing the metabolic sequelae of TBI.

Pyruvate Dehydrogenase Complex in Neonatal Hypoxic-Ischemic Brain Injury

The disruption of cerebral energy metabolism in relation to brain damage has been the subject of extensive research. However, the pyruvate dehydrogenase complex (PDHC), which is primarily characterized by poor cerebral energy metabolism following brain trauma, has received relatively little study in comparison to newborn hypoxic-ischemic brain injury. Mitochondrial PDHC, a multienzyme complex that functions as a crucial hub in energy metabolism and acts as a central metabolic node to mediate pyruvate oxidation after glycolysis and fuel the Krebs cycle to meet energy demands, has been reported to be one cause of energy metabolism dysfunction according to recent studies. Here we assess the potential mechanisms of neonatal hypoxic-ischemic brain injury-related brain dysfunction mediated by PDHC and further discuss the neuroprotective effects of therapeutic medicines that target PDHC activation. We also provide a summary of recent research on medicines that target PDHC in neonates with hypoxic-ischemic brain damage. Through an understanding of the mechanisms by which it is modulated and an investigation of the neuroprotective techniques available to activate brain PDHC and improve neonatal hypoxic-ischemic impairment, our review emphasizes the significance of PDHC impairment in neonatal hypoxic-ischemic brain injury.

Melatonin alleviates oxidative stress-induced injury to nucleus pulposus-derived mesenchymal stem cells through activating PI3K/Akt pathway

BACKGROUND

The changes in the microenvironment of degenerative intervertebral discs cause oxidative stress injury and excessive apoptosis of intervertebral disc endogenous stem cells. The purpose of this study was to explore the possible mechanism of the protective effect of melatonin on oxidative stress injury in NPMSCs induced by H2O2.

METHODS

The Cell Counting Kit-8 assay was used to evaluate the cytotoxicity of hydrogen peroxide and the protective effects of melatonin. ROS content was detected by 2'7'-dichlorofluorescin diacetate (DCFH-DA). Mitochondrial membrane potential (MMP) was detected by the JC-1assay. Transferase mediated d-UTP Nick end labeling (TUNEL) and Annexin V/PI double staining were used to determine the apoptosis rate. Additionally, apoptosis-associated proteins and PI3K/Akt signaling pathway-related proteins were evaluated by immunofluorescence, immunoblotting and PCR. ECMs were evaluated by RT‒PCR and immunofluorescence. In vivo, X-ray, Magnetic resonance imaging (MRI) and Histological analyses were used to evaluate the protective effect of melatonin.

RESULTS

Melatonin had an obvious protective effect on NPMSCs treated with 0-10 μM melatonin for 24 h. In addition, melatonin also had obvious protective effects on mitochondrial dysfunction, decreased membrane potential and cell senescence induced by H2O2. More importantly, melatonin could significantly reduce the apoptosis of nucleus pulposus mesenchymal stem cells induced by H2O2 by regulating the expression of apoptosis-related proteins and decreasing the rate of apoptosis. After treatment with melatonin, the PI3K/Akt pathway was significantly activated in nucleus pulposus mesenchymal stem cells, while the protective effect was significantly weakened after PI3K-IN-1 treatment. In vivo, the results of X-ray, MRI and histological analyses showed that therapy with melatonin could partially reduce the degree of intervertebral disc degeneration.

CONCLUSION

Our research demonstrated that melatonin can effectively alleviate the excessive apoptosis and mitochondrial dysfunction of nucleus pulposus mesenchymal stem cells induced by oxidative stress via the PI3K/Akt pathway, which provides a novel idea for the therapy of intervertebral disc degeneration.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

This study indicates that melatonin can effectively alleviate the excessive apoptosis and mitochondrial dysfunction of NPMSCs through activating the PI3K/Akt pathway. Melatonin might serve as a promising candidate for the prevention and treatment of Intervertebral disc degeneration disease (IVDD) in the future.

Early assessment of injury with optical markers in a piglet model of neonatal encephalopathy

BACKGROUND

Opportunities for adjunct therapies with cooling in neonatal encephalopathy are imminent; however, robust biomarkers of early assessment are lacking. Using an optical platform of broadband near-infrared spectroscopy and diffuse correlation spectroscopy to directly measure mitochondrial metabolism (oxCCO), oxygenation (HbD), cerebral blood flow (CBF), we hypothesised optical indices early (1-h post insult) after hypoxia-ischaemia (HI) predicts insult severity and outcome.

METHODS

Nineteen newborn large white piglets underwent continuous neuromonitoring as controls or following moderate or severe HI. Optical indices were expressed as mean semblance (phase difference) and coherence (spectral similarity) between signals using wavelet analysis. Outcome markers included the lactate/N-acetyl aspartate (Lac/NAA) ratio at 6 h on proton MRS and TUNEL cell count.

RESULTS

CBF-HbD semblance (cerebrovascular dysfunction) correlated with BGT and white matter (WM) Lac/NAA (r2 = 0.46, p = 0.004, r2 = 0.45, p = 0.004, respectively), TUNEL cell count (r2 = 0.34, p = 0.02) and predicted both initial insult (r2 = 0.62, p = 0.002) and outcome group (r2 = 0.65 p = 0.003). oxCCO-HbD semblance (cerebral metabolic dysfunction) correlated with BGT and WM Lac/NAA (r2 = 0.34, p = 0.01 and r2 = 0.46, p = 0.002, respectively) and differentiated between outcome groups (r2 = 0.43, p = 0.01).

CONCLUSION

Optical markers of both cerebral metabolic and vascular dysfunction 1 h after HI predicted injury severity and subsequent outcome in a pre-clinical model.

IMPACT

This study highlights the possibility of using non-invasive optical biomarkers for early assessment of injury severity following neonatal encephalopathy, relating to the outcome. Continuous cot-side monitoring of these optical markers can be useful for disease stratification in the clinical population and for identifying infants who might benefit from future adjunct neuroprotective therapies beyond cooling.

Cellular and Mitochondrial NAD Homeostasis in Health and Disease

The mitochondrion has a unique position among other cellular organelles due to its dynamic properties and symbiotic nature, which is reflected in an active exchange of metabolites and cofactors between the rest of the intracellular compartments. The mitochondrial energy metabolism is greatly dependent on nicotinamide adenine dinucleotide (NAD) as a cofactor that is essential for both the activity of respiratory and TCA cycle enzymes. The NAD level is determined by the rate of NAD synthesis, the activity of NAD-consuming enzymes, and the exchange rate between the individual subcellular compartments. In this review, we discuss the NAD synthesis pathways, the NAD degradation enzymes, and NAD subcellular localization, as well as NAD transport mechanisms with a focus on mitochondria. Finally, the effect of the pathologic depletion of mitochondrial NAD pools on mitochondrial proteins' post-translational modifications and its role in neurodegeneration will be reviewed. Understanding the physiological constraints and mechanisms of NAD maintenance and the exchange between subcellular compartments is critical given NAD's broad effects and roles in health and disease.

Imaging of White Matter Injury Correlates with Plasma and Tissue Biomarkers in Pediatric Porcine Model of Traumatic Brain Injury

Traumatic brain injury (TBI) causes significant white matter injury, which has been characterized by various rodent and human clinical studies. The exact time course of imaging changes in a pediatric brain after TBI and its relation to biomarkers of injury and cellular function, however, is unknown. To study the changes in major white matter structures using a valid model of TBI that is comparable to a human pediatric brain in terms of size and anatomical features, we utilized a four-week-old pediatric porcine model of injury with controlled cortical impact (CCI). Using diffusion tensor imaging differential tractography, we show progressive anisotropy changes at major white matter tracts such as the corona radiata and inferior fronto-occipital fasciculus between day 1 and day 30 after injury. Moreover, correlational tractography shows a large part of bilateral corona radiata having positive correlation with the markers of cellular respiration. In contrast, bilateral corona radiata has a negative correlation with the plasma biomarkers of injury such as neurofilament light or glial fibrillary acidic protein. These are expected correlational findings given that higher integrity of white matter would be expected to correlate with lower injury biomarkers. We then studied the magnetic resonance spectroscopy findings and report decrease in a N-acetylaspartate/creatinine (NAA/Cr) ratio at the pericontusional cortex, subcortical white matter, corona radiata, thalamus, genu, and splenium of corpus callosum at 30 days indicating injury. There was also an increase in choline/creatinine ratio in these regions indicating rapid membrane turnover. Given the need for a pediatric TBI model that is comparable to human pediatric TBI, these data support the use of a pediatric pig model with CCI in future investigations of therapeutic agents. This model will allow future TBI researchers to rapidly translate our pre-clinical study findings into clinical trials for pediatric TBI.

Brain Energy Metabolism in Ischemic Stroke: Effects of Smoking and Diabetes

Proper regulation of energy metabolism in the brain is crucial for maintaining brain activity in physiological and different pathophysiological conditions. Ischemic stroke has a complex pathophysiology which includes perturbations in the brain energy metabolism processes which can contribute to worsening of brain injury and stroke outcome. Smoking and diabetes are common risk factors and comorbid conditions for ischemic stroke which have also been associated with disruptions in brain energy metabolism. Simultaneous presence of these conditions may further alter energy metabolism in the brain leading to a poor clinical prognosis after an ischemic stroke event. In this review, we discuss the possible effects of smoking and/or diabetes on brain glucose utilization and mitochondrial energy metabolism which, when present concurrently, may exacerbate energy metabolism in the ischemic brain. More research is needed to investigate brain glucose utilization and mitochondrial oxidative metabolism in ischemic stroke in the presence of smoking and/or diabetes, which would provide further insights on the pathophysiology of these comorbid conditions and facilitate the development of therapeutic interventions.

Metabolism of Exogenous [2,4-13C]β-Hydroxybutyrate following Traumatic Brain Injury in 21-22-Day-Old Rats: An Ex Vivo NMR Study

Traumatic brain injury (TBI) is leading cause of morbidity in young children. Acute dysregulation of oxidative glucose metabolism within the first hours after injury is a hallmark of TBI. The developing brain relies on ketones as well as glucose for energy. Thus, the aim of this study was to determine the metabolism of ketones early after TBI injury in the developing brain. Following the controlled cortical impact injury model of TBI, 21-22-day-old rats were infused with [2,4-¹³C]β-hydroxybutyrate during the acute (4 h) period after injury. Using ex vivo ¹³C-NMR spectroscopy, we determined that ¹³C-β-hydroxybutyrate (¹³C-BHB) metabolism was increased in both the ipsilateral and contralateral sides of the brain after TBI. Incorporation of the label was significantly higher in glutamate than glutamine, indicating that ¹³C-BHB metabolism was higher in neurons than astrocytes in both sham and injured brains. Our results show that (i) ketone metabolism was significantly higher in both the ipsilateral and contralateral sides of the injured brain after TBI; (ii) ketones were extensively metabolized by both astrocytes and neurons, albeit higher in neurons; (iii) the pyruvate recycling pathway determined by incorporation of the label from the metabolism of ¹³C-BHB into lactate was upregulated in the immature brain after TBI.

Irisin: A promising treatment for neurodegenerative diseases

The beneficial effects of exercise on human brain function have been demonstrated in previous studies. Myokines secreted by muscle have attracted increasing attention because of their bridging role between exercise and brain health. Regulated by PPARγ coactivator 1α, fibronectin type III domain-containing protein 5 releases irisin after proteolytic cleavage. Irisin, a type of myokine, is secreted during exercise, which induces white adipose tissue browning and relates to energy metabolism. Recently, irisin has been shown to exert a protective effect on the central nervous system. Irisin secretion triggers an increase in brain-derived neurotrophic factor levels in the hippocampus, contributing to the amelioration of cognition impairments. Irisin also plays an important role in the survival, differentiation, growth, and development of neurons. This review summarizes the role of irisin in neurodegenerative diseases and other neurological disorders. As a novel positive mediator of exercise in the brain, irisin may effectively prevent or decelerate the progress of neurodegenerative diseases in models and also improve cognitive functions. We place emphasis herein on the potential of irisin for prevention rather than treatment in neurodegenerative diseases. In ischemic diseases, irisin can alleviate the pathophysiological processes associated with stroke. Meanwhile, irisin has anxiolytic and antidepressant effects. The potential therapeutic effects of irisin in epilepsy and pain have been initially revealed. Due to the pleiotropic and beneficial properties of irisin, the possibility of irisin treating other neurological diseases could be gradually explored in the future.

Mitoquinol mesylate (MITOQ) attenuates diethyl nitrosamine-induced hepatocellular carcinoma through modulation of mitochondrial antioxidant defense systems

Diethyl nitrosamine (DEN) induced cirrhosis-hepatocellular carcinoma (HCC) model associates cancer progression with oxidative stress and mitochondrial dysfunction. This study investigated the effects of mitoquinol mesylate (MitoQ), a mitochondrial-targeted antioxidant on DEN-induced oxidative damage in HCC Wistar rats. Fifty male Wistar rats were randomly divided into five groups. Healthy control, DEN, and MitoQ groups were orally administered exactly 10 mg/kg of distilled water, DEN, and MitoQ, respectively for 16 weeks. Animals in the MitoQ + DEN group were pre-treated with MitoQ for a week followed by co-administration of 10 mg/kg each of MitoQ and DEN. DEN + MitoQ group received DEN for 8 weeks, then co-administration of 10 mg/kg each of DEN and MitoQ till the end of 16th week. Survival index, tumour incidence, hematological profile, liver function indices, lipid profile, mitochondrial membrane composition, mitochondrial respiratory enzymes, and antioxidant defense status in both mitochondrial and post-mitochondrial fractions plus expression of antioxidant genes were assessed. In MitoQ + DEN and DEN + MitoQ groups, 80% survival occurred while tumour incidence decreased by 60% and 40% respectively, compared to the DEN-only treated group. Similarly, MitoQ-administered groups showed a significant (p < 0.05) decrease in the activities of liver function enzymes while hemoglobin concentration, red blood cell count, and packed cell volume were significantly elevated compared to the DEN-only treated group. Administration of MitoQ to the DEN-intoxicated groups successfully enhanced the activities of mitochondrial F1F0-ATPase and succinate dehydrogenase; and up-regulated the expression and activities of SOD2, CAT, and GPx1. Macroscopic and microscopic features indicated a reversal of DEN-induced hepatocellular degeneration in the MitoQ + DEN and DEN + MitoQ groups. These data revealed that MitoQ intervention attenuated DEN-induced oxidative stress through modulation of mitochondrial antioxidant defense systems and alleviated the burden of HCC as a chemotherapeutic agent.

1,25(OH)2D3 Mitigates Oxidative Stress-Induced Damage to Nucleus Pulposus-Derived Mesenchymal Stem Cells through PI3K/Akt Pathway

Intervertebral disc degeneration (IVDD) is one of the main causes of low back pain. The local environment of the degenerated intervertebral disc (IVD) increases oxidative stress and apoptosis of endogenous nucleus pulposus-derived mesenchymal stem cells (NPMSCs) and weakens its ability of endogenous repair ability in degenerated IVDs. A suitable concentration of 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) has been certified to reduce oxidative stress and cell apoptosis. The current study investigated the protective effect and potential mechanism of 1,25(OH)₂D₃ against oxidative stress-induced damage to NPMSCs. The present results showed that 1,25(OH)₂D₃ showed a significant protective effect on NPMSCs at a concentration of 10⁻¹⁰ M for 24 h. Protective effects of 1,25(OH)₂D₃ were also exhibited against H₂O₂-induced NPMSC senescence, mitochondrial dysfunction, and reduced mitochondrial membrane potential. The Annexin V/PI apoptosis detection assay, TUNEL assay, immunofluorescence, western blot, and real-time quantitative polymerase chain reaction assay showed that pretreatment with 1,25(OH)₂D₃ could alleviate H₂O₂-induced NPMSC apoptosis, including the apoptosis rate and the expression of proapoptotic-related (Caspase-3 and Bax) and antiapoptotic-related (Bcl-2) proteins. The intracellular expression of p-Akt increased after pretreatment with 1,25(OH)₂D₃. However, these protective effects of 1,25(OH)₂D₃ were significantly decreased after the PI3K/Akt pathway was inhibited by the LY294002 treatment. In vivo, X-ray, MRI, and histological analyses showed that 1,25(OH)₂D₃ treatment relieved the degree of IVDD in Sprague–Dawley rat disc puncture models. In summary, 1,25(OH)₂D₃ efficiently attenuated oxidative stress-induced NPMSC apoptosis and mitochondrial dysfunction via PI3K/Akt pathway and is a promising candidate treatment for the repair of IVDD.

The Current Status of Neuroprotection in Congenital Heart Disease

Neurological deficits are a serious and common sequelae of congenital heart disease (CHD). While their underlying mechanisms have not been fully characterized, their manifestations are well-known and understood to persist through adulthood. Development of therapies to address or prevent these deficits are critical to attenuate future morbidity and improve quality of life. In this review, we aim to summarize the current status of neuroprotective therapy in CHD. Through an exploration of present research in the pre-operative, intra-operative, and post-operative phases of patient management, we will describe existing clinical and bench efforts as well as current endeavors underway within this research area.

A randomized and blinded trial of inhaled nitric oxide in a piglet model of pediatric cardiopulmonary resuscitation

AIM

Inhaled nitric oxide (iNO) during cardiopulmonary resuscitation (CPR) improved systemic hemodynamics and outcomes in a preclinical model of adult in-hospital cardiac arrest (IHCA) and may also have a neuroprotective role following cardiac arrest. The primary objectives of this study were to determine if iNO during CPR would improve cerebral hemodynamics and mitochondrial function in a pediatric model of lipopolysaccharide-induced shock-associated IHCA.

METHODS

After lipopolysaccharide infusion and ventricular fibrillation induction, 20 1-month-old piglets received hemodynamic-directed CPR and were randomized to blinded treatment with or without iNO (80 ppm) during and after CPR. Defibrillation attempts began at 10 min with a 20-min maximum CPR duration. Cerebral tissue from animals surviving 1-h post-arrest underwent high-resolution respirometry to evaluate the mitochondrial electron transport system and immunohistochemical analyses to assess neuropathology.

RESULTS

During CPR, the iNO group had higher mean aortic pressure (41.6 ± 2.0 vs. 36.0 ± 1.4 mmHg; p = 0.005); diastolic BP (32.4 ± 2.4 vs. 27.1 ± 1.7 mmHg; p = 0.03); cerebral perfusion pressure (25.0 ± 2.6 vs. 19.1 ± 1.8 mmHg; p = 0.02); and cerebral blood flow relative to baseline (rCBF: 243.2 ± 54.1 vs. 115.5 ± 37.2%; p = 0.02). Among the 8/10 survivors in each group, the iNO group had higher mitochondrial Complex I oxidative phosphorylation in the cerebral cortex (3.60 [3.56, 3.99] vs. 3.23 [2.44, 3.46] pmol O₂/s mg; p = 0.01) and hippocampus (4.79 [4.35, 5.18] vs. 3.17 [2.75, 4.58] pmol O₂/s mg; p = 0.02). There were no other differences in mitochondrial respiration or brain injury between groups.

CONCLUSIONS

Treatment with iNO during CPR resulted in superior systemic hemodynamics, rCBF, and cerebral mitochondrial Complex I respiration in this pediatric cardiac arrest model.

Mangiferin prevents the impairment of mitochondrial dynamics and an increase in oxidative stress caused by excessive fluoride in SH-SY5Y cells

Previous studies both invivo and in vitro have revealed that high levels of fluoride cause neurotoxicity. Mangiferin has been reported to possess antioxidant, antiapoptotic, and anti-inflammatory properties. The present study was designed to characterize the mechanisms by which mangiferin protects against NaF-induced neurotoxicity. Increased levels of proapoptotic Bax, Caspase-3, Caspase-9, and cleaved-caspase 3, as well as a decreased level of antiapoptotic Bcl-2 induced by fluoride in human neuroblastoma SH-SY5Y cells, these effects were prevented by pretreatment of mangiferin. In addition, mangiferin attenuated the enhancement of p-JNK, reductions of Nrf2 and HO-1, and increased level of the mitochondrial fission proteins Drp1 caused by fluoride. Moreover, oxidative stress, as reflected in the levels of reactive oxygen species, 8-hydroxy-2'-deoxyguanosine, and 4-hydroxynonenal, was elevated by fluoride and these effects were again ameliorated by mangiferin. In conclusion, protection by mangiferin against fluoride-induced neurotoxicity involves normalizing the impaired mitochondrial apoptotic pathway and dynamics and reducing oxidative stress via inactivation of the JNK and activation of the Nrf2/HO-1 pathways.

Traumatic Brain Injury: Oxidative Stress and Novel Anti-Oxidants Such as Mitoquinone and Edaravone

Traumatic brain injury (TBI) is a major health concern worldwide and is classified based on severity into mild, moderate, and severe. The mechanical injury in TBI leads to a metabolic and ionic imbalance, which eventually leads to excessive production of reactive oxygen species (ROS) and a state of oxidative stress. To date, no drug has been approved by the food and drug administration (FDA) for the treatment of TBI. Nevertheless, it is thought that targeting the pathology mechanisms would alleviate the consequences of TBI. For that purpose, antioxidants have been considered as treatment options in TBI and were shown to have a neuroprotective effect. In this review, we will discuss oxidative stress in TBI, the history of antioxidant utilization in the treatment of TBI, and we will focus on two novel antioxidants, mitoquinone (MitoQ) and edaravone. MitoQ can cross the blood brain barrier and cellular membranes to accumulate in the mitochondria and is thought to activate the Nrf2/ARE pathway leading to an increase in the expression of antioxidant enzymes. Edaravone is a free radical scavenger that leads to the mitigation of damage resulting from oxidative stress with a possible association to the activation of the Nrf2/ARE pathway as well.

Early Hyperoxia in The Intensive Care Unit is Significantly Associated With Unfavorable Neurological Outcomes in Patients With Mild-to-Moderate Aneurysmal Subarachnoid Hemorrhage

INTRODUCTION

Although oxygen administration is fundamental in the management of aneurysmal subarachnoid hemorrhage (SAH) patients in the acute stage, hyperoxia has harmful effects. The effects of hyperoxia on neurological outcomes in SAH patients are unclear. We aimed to examine the association of hyperoxia during the first 24 h in the intensive care unit (ICU) with unfavorable neurological outcomes in SAH patients.

METHODS

We retrospectively selected consecutive adult patients admitted to ICU for SAH between January 2009 and April 2018. We defined normoxia during the first 24 h in ICU as PaO2 of 60 mm Hg to 120 mm Hg, mild hyperoxia as PaO2 of 121 mm Hg to 200 mm Hg, moderate hyperoxia as PaO2 of 201 mm Hg to 300 mm Hg, and severe hyperoxia as PaO2 of >300 mm Hg. Univariate and multivariate analyses were performed to examine the association between hyperoxia during the first 24 h in ICU and unfavorable neurological outcomes (i.e., modified Rankin scale score of 3-6 at hospital discharge).

RESULTS

Among 196 SAH patients, 90 had unfavorable neurological outcomes. Hyperoxia was observed in 93.4% of patients. No significant association was observed between unfavorable neurological outcomes and hyperoxia in overall patients. However, we found that early hyperoxia in ICU was significantly associated with unfavorable neurological outcomes in SAH patients with Hunt and Kosnik (H&K) grades I to III (Relative risk, 1.84; 95% confidence interval, 1.10-2.94; P = 0.02).

CONCLUSIONS

Early hyperoxia was not associated with unfavorable neurological outcomes in overall SAH patients, but it was associated with unfavorable neurological outcomes in those with H&K grades I to III.

Non-secretory renin reduces oxidative stress and increases cardiomyoblast survival during glucose and oxygen deprivation

Although the renin-angiotensin system usually promotes oxidative stress and cell death, renin transcripts have been discovered, whose transcription product may be cardioprotective. These transcripts encode a non-secretory renin isoform that is localized in the cytosol and within mitochondria. Here we tested the hypotheses that cytosolic renin [ren(2-9)] expression promotes cell survival under hypoxia and glucose depletion by preserving the mitochondrial membrane potential (∆Ψ_m) and mitigating the accumulation of ROS. To simulate ischemic insults, we exposed H9c2 cells to glucose deprivation, anoxia or to combined oxygen-glucose deprivation (OGD) for 24 hours and determined renin expression. Furthermore, H9c2 cells transfected with the empty pIRES vector (pIRES cells) or ren(2-9) cDNA-containing vector [ren(2-9) cells] were analyzed for cell death, ∆Ψ_m, ATP levels, accumulation of ROS, and cytosolic Ca²⁺ content. In pIRES cells, expression of ren(1A-9) was stimulated under all three ischemia-related conditions. After OGD, the cells lost their ∆Ψ_m and exhibited enhanced ROS accumulation, increased cytosolic Ca²⁺ levels, decreased ATP levels as well as increased cell death. In contrast, ren(2-9) cells were markedly protected from these effects. Ren(2-9) appears to represent a protective response to OGD by reducing ROS generation and preserving mitochondrial functions. Therefore, it is a promising new target for the prevention of ischemia-induced myocardial damage.

Treatment With Tetrahydrobiopterin Improves White Matter Maturation in a Mouse Model for Prenatal Hypoxia in Congenital Heart Disease

Background Reduced oxygen delivery in congenital heart disease causes delayed brain maturation and white matter abnormalities in utero. No treatment currently exists. Tetrahydrobiopterin (BH4) is a cofactor for neuronal nitric oxide synthase. BH4 availability is reduced upon NOS activation, such as during hypoxic conditions, and leads to toxin production. We hypothesize that BH4 levels are depleted in the hypoxic brain and that BH4 replacement therapy mitigates the toxic effects of hypoxia on white matter. Methods and Results Transgenic mice were used to visualize oligodendrocytes. Hypoxia was introduced during a period of white matter development equivalent to the human third trimester. BH4 was administered during hypoxia. BH4 levels were depleted in the hypoxic brain by direct quantification (n=7-12). The proliferation (n=3-6), apoptosis (n=3-6), and developmental stage (n=5-8) of oligodendrocytes were determined immunohistologically. Total oligodendrocytes increased after hypoxia, consistent with hypoxia-induced proliferation seen previously; however, mature oligodendrocytes were less prevalent in hypoxia, and there was accumulation of immature oligodendrocytes. BH4 treatment improved the mature oligodendrocyte number such that it did not differ from normoxia, and accumulation of immature oligodendrocytes was not observed. These results persisted beyond the initial period of hypoxia (n=3-4). Apoptosis increased with hypoxia but decreased with BH4 treatment to normoxic levels. White matter myelin levels decreased following hypoxia by western blot. BH4 treatment normalized myelination (n=6-10). Hypoxia worsened sensory-motor coordination on balance beam tasks, and BH4 therapy normalized performance (n=5-9). Conclusions Suboptimal BH4 levels influence hypoxic white matter abnormalities. Repurposing BH4 for use during fetal brain development may limit white matter dysmaturation in congenital heart disease.

Fractionated mitochondrial magnetic separation for isolation of synaptic mitochondria from brain tissue

While mitochondria maintain essential cellular functions, such as energy production, calcium homeostasis, and regulating programmed cellular death, they also play a major role in pathophysiology of many neurological disorders. Furthermore, several neurodegenerative diseases are closely linked with synaptic damage and synaptic mitochondrial dysfunction. Unfortunately, the ability to assess mitochondrial dysfunction and the efficacy of mitochondrial-targeted therapies in experimental models of neurodegenerative disease and CNS injury is limited by current mitochondrial isolation techniques. Density gradient ultracentrifugation (UC) is currently the only technique that can separate synaptic and non-synaptic mitochondrial sub-populations, though small brain regions cannot be assayed due to low mitochondrial yield. To address this limitation, we used fractionated mitochondrial magnetic separation (FMMS), employing magnetic anti-Tom22 antibodies, to develop a novel strategy for isolation of functional synaptic and non-synaptic mitochondria from mouse cortex and hippocampus without the usage of UC. We compared the yield and functionality of mitochondria derived using FMMS to those derived by UC. FMMS produced 3x more synaptic mitochondrial protein yield compared to UC from the same amount of tissue, a mouse hippocampus. FMMS also has increased sensitivity, compared to UC separation, to measure decreased mitochondrial respiration, demonstrated in a paradigm of mild closed head injury. Taken together, FMMS enables improved brain-derived mitochondrial yield for mitochondrial assessments and better detection of mitochondrial impairment in CNS injury and neurodegenerative disease.

Translational approach towards determining the role of cerebral autoregulation in outcome after traumatic brain injury

Cerebral autoregulation is impaired after traumatic brain injury (TBI), contributing to poor outcome. In the context of the neurovascular unit, cerebral autoregulation contributes to neuronal cell integrity and clinically Glasgow Coma Scale is correlated to intactness of autoregulation after TBI. Cerebral Perfusion Pressure (CPP) is often normalized by use of vasoactive agents to increase mean arterial pressure (MAP) and thereby limit impairment of cerebral autoregulation and neurological deficits. However, current vasoactive agent choice used to elevate MAP to increase CPP after TBI is variable. Vasoactive agents, such as phenylephrine, dopamine, norepinephrine, and epinephrine, clinically have not sufficiently been compared regarding effect on CPP, autoregulation, and survival after TBI. The cerebral effects of these clinically commonly used vasoactive agents are incompletely understood. This review will describe translational studies using a more human like animal model (the pig) of TBI to identify better therapeutic strategies to improve outcome post injury. These studies also investigated the role of age and sex in outcome and mechanism(s) involved in improvement of outcome in the setting of TBI. Additionally, this review considers use of inhaled nitric oxide as a novel neuroprotective strategy in treatment of TBI.

Improving Understanding and Outcomes of Traumatic Brain Injury Using Bidirectional Translational Research

Recent clinical trials in traumatic brain injury (TBI) have failed to demonstrate therapeutic effects even when there appears to be good evidence for efficacy in one or more appropriate pre-clinical models. While existing animal models mimic the injury, difficulties in translating promising therapeutics are exacerbated by the lack of alignment of discrete measures of the underlying injury pathology between the animal models and human subjects. To address this mismatch, we have incorporated reverse translation of bedside experience to inform pre-clinical studies in a large animal (pig) model of TBI that mirror practical clinical assessments. Cerebral autoregulation is impaired after TBI, contributing to poor outcome. Cerebral perfusion pressure (CPP) is often normalized by use of vasoactive agents to increase mean arterial pressure (MAP) and thereby limit impairment of cerebral autoregulation and neurological deficits. Vasoactive agents clinically used to elevate MAP to increase CPP after TBI, such as phenylephrine (Phe), dopamine (DA), norepinephrine (NE), and epinephrine (EPI), however, have not been compared sufficiently regarding effect on CPP, autoregulation, and survival after TBI, and clinically, current vasoactive agent use is variable. The cerebral effects of these clinically commonly used vasoactive agents are not known. This review will emphasize pediatric work and will describe bidirectional translational studies using a more human-like animal model of TBI to identify better therapeutic strategies to improve outcome post-injury. These studies in addition investigated the mechanism(s) involved in improvement of outcome in the setting of TBI.

Normobaric hyperoxia in wartime pediatric trauma casualties

BACKGROUND

Mounting evidence suggests hyperoxia therapy may be harmful. We describe injury characteristics and survival outcomes for pediatric trauma casualties in Iraq and Afghanistan, stratified by partial pressure of arterial oxygen (PaO2). Secondarily, we performed subgroup analyses for severe traumatic brain injury (TBI) and massive transfusion of blood products (MT).

METHODS

We utilized Department of Defense Trauma Registry data. We included subjects <18 years. We excluded subjects without an arterial blood gas (ABG). We stratified subjects as hyperoxemia (PaO2 100-300 mmHg) and extreme hyperoxemia (PaO2 >300 mmHg).

RESULTS

January 2007-January 2016, 3439 pediatric encounters were in the database. Of those, 1323 had an ABG, with 291 (22%) demonstrating hyperoxemia and 43 (3.3%) extreme hyperoxemia. The median age was 8, most were male (76%) in Afghanistan (69%), and injured by explosive (42%). There were no significant differences in survival between subjects with no hyperoxemia, hyperoxemia, and extreme hyperoxemia (92% vs 87% vs 86%; p = 0.078). Also, there were no significant differences in survival between groups among TBI and MT subjects, and there were no increased odds of survival between groups on multivariable regression analyses.

CONCLUSIONS

Hyperoxemia was common among hospitalized, wartime pediatric trauma casualties in Iraq and Afghanistan that underwent ABG analysis. Survival to hospital discharge rates were not significantly different between subjects with hyperoxemia and subjects without hyperoxemia.

Cerebrovascular function and mitochondrial bioenergetics after ischemia-reperfusion in male rats

The underlying factors promoting increased mitochondrial proteins, mtDNA, and dilation to mitochondrial-specific agents in male rats following tMCAO are not fully elucidated. Our goal was to determine the morphological and functional effects of ischemia/reperfusion (I/R) on mitochondria using electron microscopy, Western blot, mitochondrial oxygen consumption rate (OCR), and Ca2+ sparks activity measurements in middle cerebral arteries (MCAs) from male Sprague Dawley rats (Naïve, tMCAO, Sham). We found a greatly increased OCR in ipsilateral MCAs (IPSI) compared with contralateral (CONTRA), Sham, and Naïve MCAs. Consistent with our earlier findings, the expression of Mitofusin-2 and OPA-1 was significantly decreased in IPSI arteries compared with Sham and Naïve. Mitochondrial morphology was disrupted in vascular smooth muscle, but morphology with normal and perhaps greater numbers of mitochondria were observed in IPSI compared with CONTRA MCAs. Consistently, there were significantly fewer baseline Ca2+ events in IPSI MCAs compared with CONTRA, Sham, and Naïve. Mitochondrial depolarization significantly increased Ca2+ sparks activity in the IPSI, Sham, Naïve, but not in the CONTRA group. Our data indicate that altered mitochondrial structure and function occur in MCAs exposed to I/R and that these changes impact not only OCR but Ca2+ sparks activity in both IPSI and CONTRA MCAs.

Effect of Acetyl-L-carnitine Used for Protection of Neonatal Hypoxic-Ischemic Brain Injury on Acute Kidney Changes in Male and Female Rats

Neonatal hypoxia-ischemia (HI) is a common cause of brain injury in infants. Acute kidney injury frequently occurs after birth asphyxia and is associated with adverse outcome. Treatment with acetyl-L-carnitine (ALCAR) after HI protects brain and improves outcome. Rat pups underwent carotid ligation and 75 min hypoxia on postnatal day 7 to determine effects of HI on kidney which is understudied in this model. HI + ALCAR pups were treated at 0, 4 and 24 h after HI. The organic cation/carnitine transporter 2 (OCTN2), transports ALCAR and functions to reabsorb carnitine and acylcarnitines from urine. At 24 h after injury OCTN2 levels were significantly decreased in kidney from HI pups, 0.80 ± 0.04 (mean ± SEM, p < 0.01), compared to sham controls 1.03 ± 0.04, and HI + ALCAR pups 1.11 ± 0.06. The effect of HI on the level of pyruvate dehydrogenase (PDH) was determined since kidney has high energy requirements. At 24 h after HI, kidney PDH/β-actin ratios were significantly lower in HI pups, 0.98 ± 0.05 (mean ± SEM, p < 0.05), compared to sham controls 1.16 ± 0.06, and HI + ALCAR pups 1.24 ± 0.03, p < 0.01. Treatment of pups with ALCAR after HI prevented the decrease in renal OCTN2 and PDH levels at 24 h after injury. Protection of PDH and OCTN2 after HI would improve energy metabolism in kidney, maintain tissue carnitine levels and overall carnitine homeostasis which is essential for neonatal health.

Detection of brain specific cardiolipins in plasma after experimental pediatric head injury

Cardiolipin (CL) is a mitochondria-specific phospholipid that is central to maintenance and regulation of mitochondrial bioenergetic and metabolic functions. CL molecular species display great tissue variation with brain exhibiting a distinct, highly diverse CL population. We recently showed that the appearance of unique brain-type CLs in plasma could serve as a brain-specific marker of mitochondrial/tissue injury in patients after cardiac arrest. Mitochondrial dysfunction has been increasingly implicated as a critical mechanism underlying the pathogenesis of traumatic brain injury (TBI). Therefore, we hypothesized that unique, brain-specific CL species from the injured brain are released to the peripheral circulation after TBI. To test this hypothesis, we performed a high-resolution mass spectrometry based phospholipidomics analysis of post-natal day (PND)17 rat brain and plasma after controlled cortical impact. We found a time-dependent increase in plasma CLs after TBI including the aforementioned brain-specific CL species early after injury, whereas CLs were significantly decreased in the injured brain. Compositional and quantitative correlational analysis suggested a possible release of CL into the systemic circulation following TBI. The identification of brain-type CLs in systemic circulation may indicate underlying mitochondrial dysfunction/loss after TBI. They may have potential as pharmacodynamics response biomarkers for targeted therapies.

Sex differences in pediatric traumatic brain injury

The response of the developing brain to traumatic injury is different from the response of the mature, adult brain. There are critical developmental trajectories in the young brain, whereby injury can lead to long term functional abnormalities. Emerging preclinical and clinical literature supports the presence of significant sex differences in both the response to and the recovery from pediatric traumatic brain injury (TBI). These sex differences are seen at all pediatric ages, including neonates/infants, pre-pubertal children, and adolescents. As importantly, the response to neuroprotective therapies or treatments can differ between male and females subjects. These sex differences can result from several biologic origins, and may manifest differently during the various phases of brain and body development. Recognizing and understanding these potential sex differences is crucial, and should be considered in both preclinical and clinical studies of pediatric TBI.

Pressure passivity of cerebral mitochondrial metabolism is associated with poor outcome following perinatal hypoxic ischemic brain injury

Hypoxic ischemic encephalopathy (HIE) leads to significant morbidity and mortality. Impaired autoregulation after hypoxia-ischaemia has been suggested to contribute further to injury. Thalamic lactate/N-Acetylasperate (Lac/NAA) peak area ratio of > 0.3 on proton (¹H) magnetic resonance spectroscopy (MRS) is associated with poor neurodevelopment outcome following HIE. Cytochrome-c-oxidase (CCO) plays a central role in mitochondrial oxidative metabolism and ATP synthesis. Using a novel broadband NIRS system, we investigated the impact of pressure passivity of cerebral metabolism (CCO), oxygenation (haemoglobin difference (HbD)) and cerebral blood volume (total haemoglobin (HbT)) in 23 term infants following HIE during therapeutic hypothermia (HT). Sixty-minute epochs of data from each infant were studied using wavelet analysis at a mean age of 48 h. Wavelet semblance (a measure of phase difference) was calculated to compare reactivity between mean arterial blood pressure (MABP) with oxCCO, HbD and HbT. OxCCO-MABP semblance correlated with thalamic Lac/NAA ( r = 0.48, p = 0.02). OxCCO-MABP semblance also differed between groups of infants with mild to moderate and severe injury measured using brain MRI score ( p = 0.04), thalamic Lac/NAA ( p = 0.04) and neurodevelopmental outcome at one year ( p = 0.04). Pressure passive changes in cerebral metabolism were associated with injury severity indicated by thalamic Lac/NAA, MRI scores and neurodevelopmental assessment at one year of age.

Longitudinal Metabolite Changes after Traumatic Brain Injury: A Prospective Pediatric Magnetic Resonance Spectroscopic Imaging Study

The aims of this study were to evaluate longitudinal metabolite changes in traumatic brain injury (TBI) subjects and determine whether early magnetic resonance spectroscopic imaging (MRSI) changes in discrete brain regions predict 1-year neuropsychological outcomes. Three-dimensional (3D) proton MRSI was performed in pediatric subjects with complicated mild (cMild), moderate, and severe injury, acutely (6-17 days) and 1-year post-injury along with neurological and cognitive testing. Longitudinal analysis found that in the cMild/Moderate group, all MRSI ratios from 12 regions returned to control levels at 1 year. In the severe group, only cortical gray matter regions fully recovered to control levels whereas N-acetylaspartate (NAA) ratios from the hemispheric white matter and subcortical regions remained statistically different from controls. A factor analysis reduced the data to two loading factors that significantly differentiated between TBI groups; one included acute regional NAA variables and another consisted of clinically observed variables (e.g., days in coma). Using scores calculated from the two loading factors in a logistic regression model, we found that the percent accuracy for classification of TBI groups was greatest for the dichotomized attention measure (93%), followed by Full Scale Intelligence Quotient at 91%, and the combined memory Z-score measure (90%). Using the acute basal ganglia NAA/creatine (Cr) ratio alone achieved a higher percent accuracy of 94.7% for the attention measure whereas the acute thalamic NAA/Cr ratio alone achieved a higher percent accuracy of 91.9% for the memory measure. These results support the conclusions that reduced NAA is an early indicator of tissue injury and that measurements from subcortical brain regions are more predictive of long-term cognitive outcome.

Neuroanatomical correlates of emotion-processing in children with unilateral brain lesion: A preliminary study of limbic system organization

In this study, MRI and DTI were employed to examine subcortical volume and microstructural properties (FA, MD) of the limbic network, and their relationships with affect discrimination in 13 FL (6 right FL, M = 10.17 years; 7 left FL; M = 10.09) and 13 typically-developing children (TD; M = 10.16). Subcortical volume of the amygdala, hippocampus and thalamus and FA and MD of the fornix and anterior thalamic radiation (ATR) were examined. Results revealed no group differences across emotion-perception tasks or amygdalar volume. However, contrasting neuroanatomical patterns were observed in right versus left FL youth. Right FL participants showed increased left hippocampal and thalamic volume relative to left FL participants; whereas, the latter group showed increased right thalamic volume. DTI findings also indicated right FL children show greater MD of right fornix than other groups, whereas, left FL youth showed greater MD of left fornix. Right FL youth also showed lower FA of right fornix than left FL children, whereby the latter showed greater FA of left fornix and ATR. Differential associations between DTI indices and auditory/visual emotion-perception were observed across FL groups. Findings indicate diverging brain-behavioral relationships for emotion-perception among right and left FL children.

Comparison of the detrimental features of microglia and infiltrated macrophages in traumatic brain injury: A study using a hypnotic bromovalerylurea

Microglia and blood-borne macrophages in injured or diseased brains are difficult to distinguish because they share many common characteristics. However, the identification of microglia-specific markers and the use of flow cytometry have recently made it easy to discriminate these types of cells. In this study, we analyzed the features of blood-borne macrophages, and activated and resting microglia in a rat traumatic brain injury (TBI) model. Oxidative injury was indicated in macrophages and neurons in TBI lesions by the presence of 8-hydroxy-2'-deoxyguanosine (8-OHdG). Generation of mitochondrial reactive oxygen species (ROS) was markedly observed in granulocytes and macrophages, but not in activated or resting microglia. Dihydroethidium staining supported microglia not being the major source of ROS in TBI lesions. Furthermore, macrophages expressed NADPH oxidase 2, interleukin-1β (IL-1β), and CD68 at higher levels than microglia. In contrast, microglia expressed transforming growth factor β1 (TGFβ1), interleukin-6 (IL-6), and tumor necrosis factor α at higher levels than macrophages. A hypnotic, bromovalerylurea (BU), which has anti-inflammatory effects, reduced both glycolysis and mitochondrial oxygen consumption. BU administration inhibited chemokine CCL2 expression, accumulation of monocytes/macrophages, 8-OHdG generation, mitochondrial ROS generation, and proinflammatory cytokine expression, and markedly ameliorated the outcome of the TBI model. Yet, BU did not inhibit microglial activation or expression of TGFβ1 and insulin-like growth factor 1 (IGF-1). These results indicate that macrophages are the major aggravating cell type in TBI lesions, in particular during the acute phase. Activated microglia may even play favorable roles. Reduction of cellular energy metabolism in macrophages and suppression of CCL2 expression in injured tissue may lead to amelioration of TBI.

T Cells and Regulated Cell Death: Kill or Be Killed

Cell death plays two major complementary roles in T cell biology: mediating the removal of cells that are targeted by T cells and the removal of T cells themselves. T cells serve as major actors in the adaptive immune response and function by selectively killing cells which are infected or dysfunctional. This feature is highly involved during homeostatic maintenance, and is relied upon and modulated in the context of cancer immunotherapy. The vital recognition and elimination of both autoreactive T cells and cells which are unable to recognize threats is a highly selective and regulated process. Moreover, detection of potential threats will result in the activation and expansion of T cells, which on resolution of the immune response will need to be eliminated. The culling of these T cells can be executed via a multitude of cell death pathways which are used in context-specific manners. Failure of these processes may result in an accumulation of misdirected or dysfunctional T cells, leading to complications such as autoimmunity or cancer. This review will focus on the role of cell death regulation in the maintenance of T cell homeostasis, as well as T cell-mediated elimination of infected or dysfunctional cells, and will summarize and discuss the current knowledge of the cellular mechanisms which are implicated in these processes.

Neuroprotective Effects of Cyclosporine in a Porcine Pre-Clinical Trial of Focal Traumatic Brain Injury

Mitochondrial dysfunction is thought to be a hallmark of traumatic brain injury (TBI) and plays a pivotal role in the resulting cellular injury. Cyclophilin D-mediated activation of the mitochondrial permeability transition pore has been suggested to contribute to this secondary injury cascade. Cyclosporine possesses neuroprotective properties that have been attributed to the desensitization of mitochondrial permeability transition pore activation. In vivo animal experiments have demonstrated neuroprotective effects of cyclosporine in more than 20 independent experimental studies in a multitude of different experimental models. However, the majority of these studies have been carried out in rodents. The aim of the present study was to evaluate the efficacy of a novel and cremophor/kolliphor EL-free lipid emulsion formulation of cyclosporine in a translational large animal model of TBI. A mild-to-moderate focal contusion injury was induced in piglets using a controlled cortical impact device. After initial step-wise analyses of pharmacokinetics and comparing with exposure of cyclosporine in clinical TBI trials, a 5-day dosing regimen with continuous intravenous cyclosporine infusion (20 mg/kg/day) was evaluated in a randomized and blinded placebo-controlled setting. Cyclosporine reduced the volume of parenchymal injury by 35%, as well as improved markers of neuronal injury, as measured with magnetic resonance spectroscopic imaging. Further, a consistent trend toward positive improvements in brain metabolism and mitochondrial function was observed in the pericontusional tissue. In this study, we have demonstrated efficacy using a novel cyclosporine formulation in clinically relevant and translatable outcome metrics in a large animal model of focal TBI.

Mitochondrial-targeted antioxidant MitoQ provides neuroprotection and reduces neuronal apoptosis in experimental traumatic brain injury possibly via the Nrf2-ARE pathway

Mitoquinone (MitoQ) is a powerful mitochondrial-targeted antioxidant whose neuroprotective effects have been shown in a variety of animal models of neurological diseases. However, its roles in traumatic brain injury (TBI) remain unexplored. The primary objective of this study was to investigate the neuroprotection afforded by MitoQ in a mouse model of TBI, and the involvement of the Nrf2-ARE signaling pathway in the putative neuroprotective mechanism. Mice were randomly divided into four groups: sham group, TBI group, TBI + vehicle group, and TBI + MitoQ group. MitoQ (4 mg/kg, administered intraperitoneally) or an equal volume of vehicle was given at 30 min after TBI. After 24 h, brain samples were harvested for analysis. The results demonstrated that treatment with MitoQ significantly improved neurological deficits, alleviated brain edema and inhibited cortical neuronal apoptosis. Furthermore, MitoQ administration increased the activity of antioxidant enzymes, including superoxide dismutase (SOD) and glutathione peroxidase (GPx), whereas it decreased the malondialdehyde (MDA) content. In addition, MitoQ treatment reduced Bax protein translocation to mitochondria and cytochrome c release into the cytosol. Moreover, MitoQ greatly accelerated the Nrf2 nuclear translocation and subsequently upregulated the expression of Nrf2 downstream proteins, including heme oxygenase-1 (HO-1) and quinone oxidoreductase 1 (Nqo1). In conclusion, the results in the study demonstrate that MitoQ exerts neuroprotective effects in the mouse model of TBI, possibly by activating the Nrf2-ARE pathway.

CsA attenuates compression-induced nucleus pulposus mesenchymal stem cells apoptosis via alleviating mitochondrial dysfunction and oxidative stress

AIMS

This study aims to investigate the protective effects and potential mechanisms of cyclosporine A (CsA), which efficiently inhibits mitochondrial permeability transition pore (MPTP) opening, on compression-induced apoptosis of human nucleus pulposus mesenchymal stem cells (NP-MSCs).

MATERIALS AND METHODS

Human NP-MSCs were subjected to various periods of 1.0 MPa compression. Cell viability was evaluated using cell counting kit-8 (CCK-8) assay. The cellular ultrastructure and ATP level were analyzed via transmission electron microscopy (TEM) and ATP detection kit respectively. The apoptosis ratio was determined using Annexin V/PI dual staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays. The levels of apoptosis-associated molecules (cleaved caspase-3, Bax and Bcl-2) were analyzed by western blot and qRT-PCR. Additionally, MPTP opening, mitochondrial membrane potential (MMP) and the levels of oxidative stress-related indicators (ROS), superoxide dismutase (SOD) and malondialdehyde (MDA) were monitored.

KEY FINDINGS

Annexin V/PI dual staining and detection of apoptosis-associated molecules demonstrated that compression significantly up-regulated apoptosis level of NP-MSCs in a time-dependent manner. CsA greatly down-regulated compression-mediated NP-MSC apoptosis and the cell death ratio. Compression also notably exacerbated mitochondrial dysfunction, ATP depletion and oxidative stress in NP-MSCs, all of which were rescued by CsA.

SIGNIFICANCE

Our results demonstrated that CsA efficiently inhibited compression-induced NP-MSCs apoptosis by alleviating mitochondrial dysfunction and oxidative stress. These findings provide new insights into intervertebral disc (IVD) degeneration (IVDD), and suggest CsA treatment as a potential strategy for delaying or even preventing IVDD.

Traumatic Brain Injury, Sleep Disorders, and Psychiatric Disorders: An Underrecognized Relationship

Traumatic brain injury (TBI) is commonplace among pediatric patients and has a complex, but intimate relationship with psychiatric disease and disordered sleep. Understanding the factors that influence the risk for the development of TBI in pediatrics is a critical component of beginning to address the consequences of TBI. Features that may increase risk for experiencing TBI sometimes overlap with factors that influence the development of post-concussive syndrome (PCS) and recovery course. Post-concussive syndrome includes physical, psychological, cognitive and sleep-wake dysfunction. The comorbid presence of sleep-wake dysfunction and psychiatric symptoms can lead to a more protracted recovery and deleterious outcomes. Therefore, a multidisciplinary evaluation following TBI is necessary. Treatment is generally symptom specific and mainly based on adult studies. Further research is necessary to enhance diagnostic and therapeutic approaches, as well as improve the understanding of contributing pathophysiology for the shared development of psychiatric disease and sleep-wake dysfunction following TBI.

Brain metabolism and severe pediatric traumatic brain injury

Age-dependent changes in brain metabolism may influence the response to and tolerance of secondary insults, potentially affecting outcomes. More complete characterization of brain metabolism across the clinical trajectory of severe pediatric TBI is needed to improve our ability to measure and better mitigate the impact of secondary insults. Better management of secondary insults will impact clinical care and the probability of success of future neuroprotective clinical trials. Improved bedside monitoring and imaging technologies will be required to achieve these goals. Effective and sustained integration of brain metabolism information into the pediatric critical care setting will be equally challenging and important.

Tetrahydrocurcumin reduces oxidative stress-induced apoptosis via the mitochondrial apoptotic pathway by modulating autophagy in rats after traumatic brain injury

Tetrahydrocurcumin (THC) has been identified as a multi-functional neuroprotective agent in numerous neurological disorders. Oxidative stress as a result of injury may induce neuronal apoptosis after traumatic brain injury (TBI). Treatment with THC may improve neurological function following TBI by attenuating oxidative stress and apoptosis and by enhancing autophagy. The purpose of this study was to investigate the mechanism of neuroprotection by THC against oxidative stress-induced neuronal apoptosis after TBI. We hypothesized that neuroprotection by THC may involve modulation of autophagy and the mitochondria apoptotic pathway. We used western blot analysis to evaluate the effect of THC on proteins involved in mitochondrial autophagy and apoptosis after TBI. The terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) assay and immunofluorescence staining were used to confirm the role of THC in apoptosis and autophagy, respectively. THC-induced neuroprotection was assessed by neurological severity scoring (NSS) and by measuring the brain water content. We demonstrated that treatment with THC increased expression of autophagy-associated proteins LC3-II and Beclin-1 at 24 h post-TBI. Treatment with THC also reduced expression of malondialdehyde (MDA) and increased glutathione peroxidase (GPx) activity. Further, treatment with THC attenuated apoptosis by modulating mitochondrial apoptosis and reducing oxidative stress. Treatment with 3-methyladenine (3-MA) mitigated autophagy activation and reversed the inhibitory effect of THC on the translocation of Bax to the mitochondrial membrane. Moreover, treatment with THC improved neurological function and reduced the brain water content in rats after TBI. We concluded that the neuroprotective effects of THC are mediated by enhancing autophagy activation and by attenuation of oxidative stress and apoptosis after TBI, probably by modulating the mitochondrial apoptotic pathway. We suggest that THC may be an effective therapeutic agent to treat TBI.

Erythropoietin: Endogenous Protection of Ischemic Brain

The human brain requires uninterrupted delivery of blood-borne oxygen and nutrients to sustain its function. Focal ischemia, particularly, ischemic stroke, and global ischemia imposed by cardiac arrest disrupt the brain's fuel supply. The resultant ATP depletion initiates a complex injury cascade encompassing intracellular Ca²⁺ overload, glutamate excitotoxicity, oxido-nitrosative stress, extracellular matrix degradation, and inflammation, culminating in neuronal and astroglial necrosis and apoptosis, neurocognitive deficits, and even death. Unfortunately, brain ischemia has proven refractory to pharmacological intervention. Many promising treatments afforded brain protection in animal models of focal and global ischemia, but failed to improve survival and neurocognitive recovery of stroke and cardiac arrest patients in randomized clinical trials. The culprits are the blood-brain barrier (BBB) that limits transferral of medications to the brain parenchyma, and the sheer complexity of the injury cascade, which presents a daunting array of targets unlikely to respond to monotherapies. Erythropoietin is a powerful neuroprotectant capable of interrupting multiple aspects of the brain injury cascade. Preclinical research demonstrates erythropoietin's ability to suppress glutamate excitotoxicity and intracellular Ca²⁺ overload, dampen oxidative stress and inflammation, interrupt the apoptotic cascade, and preserve BBB integrity. However, the erythropoietin dosages required to traverse the BBB and achieve therapeutically effective concentrations in the brain parenchyma impose untoward side effects. Recent discoveries that hypoxia induces erythropoietin production within the brain and that neurons, astroglia, and cerebrovascular endothelium harbor membrane erythropoietin receptors, raise the exciting prospect of harnessing endogenous erythropoietin to protect the brain from the ravages of ischemia-reperfusion.

Cerebral Blood Flow Autoregulation and Dysautoregulation

This article provides a review of cerebral autoregulation, particularly as it relates to the clinician scientist experienced in neuroscience in anesthesia and critical care. Topics covered are biological mechanisms; methods used for assessment of autoregulation; effects of anesthetics; role in control of cerebral hemodynamics in health and disease; and emerging areas, such as role of age and sex in contribution to dysautoregulation. Emphasis is placed on bidirectional translational research wherein the clinical informs the study design of basic science studies, which, in turn, informs the clinical to result in development of improved therapies for treatment of central nervous system conditions.

Molecular chaperones and hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is a disease that occurs when the brain is subjected to hypoxia, resulting in neuronal death and neurological deficits, with a poor prognosis. The mechanisms underlying hypoxic-ischemic brain injury include excitatory amino acid release, cellular proteolysis, reactive oxygen species generation, nitric oxide synthesis, and inflammation. The molecular and cellular changes in HIE include protein misfolding, aggregation, and destruction of organelles. The apoptotic pathways activated by ischemia and hypoxia include the mitochondrial pathway, the extrinsic Fas receptor pathway, and the endoplasmic reticulum stress-induced pathway. Numerous treatments for hypoxic-ischemic brain injury caused by HIE have been developed over the last half century. Hypothermia, xenon gas treatment, the use of melatonin and erythropoietin, and hypoxic-ischemic preconditioning have proven effective in HIE patients. Molecular chaperones are proteins ubiquitously present in both prokaryotes and eukaryotes. A large number of molecular chaperones are induced after brain ischemia and hypoxia, among which the heat shock proteins are the most important. Heat shock proteins not only maintain protein homeostasis; they also exert anti-apoptotic effects. Heat shock proteins maintain protein homeostasis by helping to transport proteins to their target destinations, assisting in the proper folding of newly synthesized polypeptides, regulating the degradation of misfolded proteins, inhibiting the aggregation of proteins, and by controlling the refolding of misfolded proteins. In addition, heat shock proteins exert anti-apoptotic effects by interacting with various signaling pathways to block the activation of downstream effectors in numerous apoptotic pathways, including the intrinsic pathway, the endoplasmic reticulum-stress mediated pathway and the extrinsic Fas receptor pathway. Molecular chaperones play a key role in neuroprotection in HIE. In this review, we provide an overview of the mechanisms of HIE and discuss the various treatment strategies. Given their critical role in the disease, molecular chaperones are promising therapeutic targets for HIE.

Adaptive responses of neuronal mitochondria to bioenergetic challenges: Roles in neuroplasticity and disease resistance

An important concept in neurobiology is "neurons that fire together, wire together" which means that the formation and maintenance of synapses is promoted by activation of those synapses. Very similar to the effects of the stress of exercise on muscle cells, emerging findings suggest that neurons respond to activity by activating signaling pathways (e.g., Ca²⁺, CREB, PGC-1α, NF-κB) that stimulate mitochondrial biogenesis and cellular stress resistance. These pathways are also activated by aerobic exercise and food deprivation, two bioenergetic challenges of fundamental importance in the evolution of the brains of all mammals, including humans. The metabolic 'switch' in fuel source from liver glycogen store-derived glucose to adipose cell-derived fatty acids and their ketone metabolites during fasting and sustained exercise, appears to be a pivotal trigger of both brain-intrinsic and peripheral organ-derived signals that enhance learning and memory and underlying synaptic plasticity and neurogenesis. Brain-intrinsic extracellular signals include the excitatory neurotransmitter glutamate and the neurotrophic factor BDNF, and peripheral signals may include the liver-derived ketone 3-hydroxybutyrate and the muscle cell-derived protein irisin. Emerging findings suggest that fasting, exercise and an intellectually challenging lifestyle can protect neurons against the dysfunction and degeneration that they would otherwise suffer in acute brain injuries (stroke and head trauma) and neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's disease. Among the prominent intracellular responses of neurons to these bioenergetic challenges are up-regulation of antioxidant defenses, autophagy/mitophagy and DNA repair. A better understanding of such fundamental hormesis-based adaptive neuronal response mechanisms is expected to result in the development and implementation of novel interventions to promote optimal brain function and healthy brain aging.

Regulation of Ketone Body Metabolism and the Role of PPARα

Ketogenesis and ketolysis are central metabolic processes activated during the response to fasting. Ketogenesis is regulated in multiple stages, and a nuclear receptor peroxisome proliferator activated receptor α (PPARα) is one of the key transcription factors taking part in this regulation. PPARα is an important element in the metabolic network, where it participates in signaling driven by the main nutrient sensors, such as AMP-activated protein kinase (AMPK), PPARγ coactivator 1α (PGC-1α), and mammalian (mechanistic) target of rapamycin (mTOR) and induces hormonal mediators, such as fibroblast growth factor 21 (FGF21). This work describes the regulation of ketogenesis and ketolysis in normal and malignant cells and briefly summarizes the positive effects of ketone bodies in various neuropathologic conditions.

Cyclosporin A protects against Lead neurotoxicity through inhibiting mitochondrial permeability transition pore opening in nerve cells

Mitochondria play a key role in the process of lead (Pb)-induced impairment in nervous system. To further clarify the underlying mechanism of Pb neurotoxicity, this study was designed to investigate the role of mitochondrial permeability transition (MPT) and cyclophilin D (CyPD), a component of MPT pore (MPTP), in Pb-induced mitochondrial apoptosis in nerve cells. In SH-SY5Y and PC12 cells, Cyclosporin A (CSA), a special inhibitor of CyPD, could alleviate cell death, lactate dehydrogenase (LDH) leakage and adenosine 5 triphosphate (ATP) decrease caused by PbAc. In the following experiments, we found PbAc increased the protein level of CyPD and induced MPT pore (MPTP) opening. When cells were pretreated with CSA to inhibit MPTP opening, the Pb-induced impairment of mitochondrial morphology (swelling and rupture) and the loss of mitochondria were attenuated. In addition, CSA obviously ameliorated the Pb-induced damage of mitochondrial function, such as reactive oxygen species (ROS) boost and mitochondrial membrane potential (MMP) collapse, as well as the release of cytochrome C (Cyto C) and apoptosis-inducing factor (AIF) from mitochondria. These beneficial effects could finally result in cell survival under Pb-exposure conditions. Furthermore, scavenging ROS also significantly abrogated MPTP opening and attenuated Pb neurotoxicity. Therefore, we found that MPT played an important role in Pb-induced mitochondrial damage and, ultimately, cell death. Our results provided a potential strategy for inhibiting PbAc neurotoxicity. However, due to the high Pb concentrations used in this study further investigations at Pb concentrations closer to human exposure are needed to verify the results.

Pathophysiology and Treatment of Severe Traumatic Brain Injuries in Children

Traumatic brain injuries (TBIs) in children are a major cause of morbidity and mortality worldwide. Severe TBIs account for 15,000 admissions annually and a mortality rate of 24% in children in the United States. The purpose of this article is to explore pathophysiologic events, examine monitoring techniques, and explain current treatment modalities and nursing care related to caring for children with severe TBI. The primary injury of a TBI is because of direct trauma from an external force, a penetrating object, blast waves, or a jolt to the head. Secondary injury occurs because of alterations in cerebral blood flow, and the development of cerebral edema leads to necrotic and apoptotic cellular death after TBI. Monitoring focuses on intracranial pressure, cerebral oxygenation, cerebral edema, and cerebrovascular injuries. If abnormalities are identified, treatments are available to manage the negative effects caused to the cerebral tissue. The mainstay treatments are hyperosmolar therapy; temperature control; cerebrospinal fluid drainage; barbiturate therapy; decompressive craniectomy; analgesia, sedation, and neuromuscular blockade; and antiseizure prophylaxis.

Sex-dependent mitochondrial respiratory impairment and oxidative stress in a rat model of neonatal hypoxic-ischemic encephalopathy

Increased male susceptibility to long-term cognitive deficits is well described in clinical and experimental studies of neonatal hypoxic-ischemic encephalopathy. While cell death signaling pathways are known to be sexually dimorphic, a sex-dependent pathophysiological mechanism preceding the majority of secondary cell death has yet to be described. Mitochondrial dysfunction contributes to cell death following cerebral hypoxic-ischemia (HI). Several lines of evidence suggest that there are sex differences in the mitochondrial metabolism of adult mammals. Therefore, this study tested the hypothesis that brain mitochondrial respiratory impairment and associated oxidative stress is more severe in males than females following HI. Maximal brain mitochondrial respiration during oxidative phosphorylation was two-fold more impaired in males following HI. The endogenous antioxidant glutathione was 30% higher in the brain of sham females compared to males. Females also exhibited increased glutathione peroxidase (GPx) activity following HI injury. Conversely, males displayed a reduction in mitochondrial GPx4 protein levels and mitochondrial GPx activity. Moreover, a 3-4-fold increase in oxidative protein carbonylation was observed in the cortex, perirhinal cortex, and hippocampus of injured males, but not females. These data provide the first evidence for sex-dependent mitochondrial respiratory dysfunction and oxidative damage, which may contribute to the relative male susceptibility to adverse long-term outcomes following HI. Lower basal GSH levels, lower post-hypoxic mitochondrial glutathione peroxidase (mtGPx) activity, and mitochondrial glutathione peroxidase 4 (mtGPx4) protein levels may contribute to the susceptibility of the male brain to oxidative damage and mitochondrial dysfunction following neonatal hypoxic-ischemia (HI). Treatment of male pups with acetyl-L-carnitine (ALCAR) protects against the loss of mtGPx activity, mtGPx4 protein, and increases in protein carbonylation after HI. These findings provide novel insight into the pathophysiology of sexually dimorphic outcomes following HI.

Plasticity in the Neonatal Brain following Hypoxic-Ischaemic Injury

Hypoxic-ischaemic damage to the developing brain is a leading cause of child death, with high mortality and morbidity, including cerebral palsy, epilepsy, and cognitive disabilities. The developmental stage of the brain and the severity of the insult influence the selective regional vulnerability and the subsequent clinical manifestations. The increased susceptibility to hypoxia-ischaemia (HI) of periventricular white matter in preterm infants predisposes the immature brain to motor, cognitive, and sensory deficits, with cognitive impairment associated with earlier gestational age. In term infants HI causes selective damage to sensorimotor cortex, basal ganglia, thalamus, and brain stem. Even though the immature brain is more malleable to external stimuli compared to the adult one, a hypoxic-ischaemic event to the neonate interrupts the shaping of central motor pathways and can affect normal developmental plasticity through altering neurotransmission, changes in cellular signalling, neural connectivity and function, wrong targeted innervation, and interruption of developmental apoptosis. Models of neonatal HI demonstrate three morphologically different types of cell death, that is, apoptosis, necrosis, and autophagy, which crosstalk and can exist as a continuum in the same cell. In the present review we discuss the mechanisms of HI injury to the immature brain and the way they affect plasticity.

Protective effects of formononetin against rhabdomyolysis-induced acute kidney injury by upregulating Nrf2 in vivo and in vitro

Acute kidney injury (AKI) is a well-known organ injury frequently observed after rhabdomyolysis (RM).