Potentiating Hemorrhage in a Periadolescent Rat Model of Closed-Head Traumatic Brain Injury Worsens Hyperexcitability but Not Behavioral Deficits.

Post-traumatic epilepsy (PTE) and neurocognitive deficits are devastating sequelae of head injuries that are common in adolescents. Investigating desperately needed treatments is hindered by the difficulties in inducing PTE in rodents and the lack of established immature rat models of pediatric PTE. Hemorrhage is a significant risk factor for PTE, but compared to humans, rats are less prone to bleeding because of their rapid blood coagulation system. In this study, we promoted bleeding in the controlled cortical impact (CCI) closed-head injury model with a 20 min pre-impact 600 IU/kg intraperitoneal heparin injection in postnatal day 35 (P35) periadolescent rats, given the preponderance of such injuries in this age group. Temporo-parietal CCI was performed post-heparin (HTBI group) or post-saline (TBI group). Controls were subjected to sham procedures following heparin or saline administration. Continuous long-term EEG monitoring was performed for 3 months post-CCI. Sensorimotor testing, the Morris water maze, and a modified active avoidance test were conducted between P80 and P100. Glial fibrillary acidic protein (GFAP) levels and neuronal damage were also assessed. Compared to TBI rats, HTBI rats had persistently higher EEG spiking and increased hippocampal GFAP levels (p < 0.05). No sensorimotor deficits were detected in any group. Compared to controls, both HTBI and TBI groups had a long-term hippocampal neuronal loss (p < 0.05), as well as contextual and visuospatial learning deficits (p < 0.05). The hippocampal astrogliosis and EEG spiking detected in all rats subjected to our hemorrhage-promoting procedure suggest the emergence of hyperexcitable networks and pave the way to a periadolescent PTE rat model.

Methionine mediates resilience to chronic social defeat stress by epigenetic regulation of NMDA receptor subunit expression.

RATIONALE: Previous studies suggested that methionine (Met) levels are decreased in depressed patients. However, whether the decrease in this amino acid is important for phenotypic behaviors associated with depression has not been deciphered. OBJECTIVE: The response of individuals to chronic stress is variable, with some individuals developing depression and others becoming resilient to stress. In this study, our objective was to examine the effect of Met on susceptibility to stress. METHODS: Male C57BL/6J mice were subjected to daily defeat sessions by a CD1 aggressor, for 10 days. On day 11, the behavior of mice was assessed using social interaction and open-field tests. Mice received Met 4 h before each defeat session. Epigenetic targets were assessed either through real-rime RTPCR or through Western Blots. RESULTS: Met did not modulate anxiety-like behaviors, but rather promoted resilience to chronic stress, rescued social avoidance behaviors and reversed the increase in the cortical expression levels of N-methyl-D-aspartate receptor (NMDAR) subunits. Activating NMDAR activity abolished the ability of Met to promote resilience to stress and to rescue social avoidance behavior, whereas inhibiting NMDAR did not show any synergistic or additive protective effects. Indeed, Met increased the cortical levels of the histone methyltransferase SETDB1, and in turn, the levels of the repressive histone H3 lysine (K9) trimethylation (me3). CONCLUSIONS: Our data indicate that Met rescues susceptibility to stress by inactivating cortical NMDAR activity through an epigenetic mechanism involving histone methylation.

The Deep Roots of Addiction: A Comparative Perspective.

Addiction is a debilitating condition that extracts enormous social and economic tolls. Despite several decades of research, our knowledge of its etiology, preventive measures, and treatments is limited. A relatively recent research field with the potential to provide a more holistic understanding, and subsequently treatments, takes a phylogenetic view of addiction. This perspective is based on deep homologies at the genetic, proteomic, and behavioral levels, which are shared across all metazoan life; particularly those organisms faced with plant secondary metabolites as defensive compounds against insect herbivory. These addictive alkaloids, such as nicotine, cocaine, or cathinone, are commonly referred to as "human drugs of abuse" even though humans had little to no role in the co-evolutionary processes that determined their initial emergence or continued selection. This commentary discusses the overwhelming homologies of addictive alkaloid effects on neural systems across a wide range of taxa, as we aim to develop a broader comparative view of the "addicted brain." Taking nicotine as an example, homologous physiological responses to this compound identify common underlying cellular and molecular mechanisms that advocate for the adoption of a phylogenetic view of addiction.

Overview on Emotional Behavioral Testing in Rodent Models of Pediatric Epilepsy.

Psychiatric and cognitive disturbances are the most common comorbidities of epileptic disorders in children. The successful treatment of these comorbidities faces many challenges including their etiologically heterogonous nature. Translational neurobehavioral research in age-tailored and clinically relevant rodent seizure models offers a controlled setting to investigate emotional and cognitive behavioral disturbances, their causative factors, and potentially novel treatment interventions. In this review, we propose a conceptual framework that provides a nonsubjective approach to rodent emotional behavioral testing with a focus on the clinically relevant outcome of behavioral response adaptability. We also describe the battery of neurobehavioral tests that we tailored to seizure models with prominent amygdalo-hippocampal involvement, including testing panels for anxiety-like, exploratory, and hyperactive behaviors (the open-field and light-dark box tests), depressive-like behaviors (the forced swim test), and visuospatial navigation (Morris water maze). The review also discusses the modifications we introduced to active avoidance testing in order to simultaneously test auditory and hippocampal-dependent emotionally relevant learning and memory. When interpreting the significance and clinical relevance of the behavioral responses obtained from a given testing panel, it is important to avoid a holistic disease-based approach as a specific panel may not necessarily mirror a disease entity. The analysis of measurable behavioral responses has to be performed in the context of outcomes obtained from multiple related and complementary neurobehavioral testing panels. Behavioral testing is also complemented by mechanistic electrophysiological and molecular investigations.

Methods in Emotional Behavioral Testing in Immature Epilepsy Rodent Models.

Pediatric epilepsy is associated with prominent comorbid psychiatric and cognitive disturbances. Neurobehavioral testing is employed to characterize the cognitive and emotional behavioral derangements that accompany seizures in age-tailored and clinically relevant immature rodent seizure models. In addition to dissecting the causes of the etiologically multifaceted psychiatric and cognitive comorbidities of the epilepsies, neurobehavioral panels are essential in investigating potential neuroprotective strategies, especially during neurodevelopment. Here we describe a battery of behavioral testing panels that we tailored to our rodent seizure models with prominent amygdalo-hippocampal involvement. The panels include the open field and light-dark box tests for exploratory, hyperactive, and anxiety-like behaviors, the forced swim test for depressive-like behaviors, the Morris water maze for visuospatial navigation, and the modified active avoidance test for emotionally relevant learning and acquisition of adaptive behaviors. The behavioral laboratory setup and the employed methodologies are reviewed in details, with a special focus on the potential pitfalls that should be avoided.

Branched-chain amino acids mediate resilience to chronic social defeat stress by activating BDNF/TRKB signaling.

How individuals respond to chronic stress varies. Susceptible individuals ultimately develop depression; whereas resilient individuals live normally. In this study, our objective was to examine the effect of branched-chain amino acids (BCAA), commonly used by athletes, on susceptibility to stress. Male C57BL/6 mice were subjected to daily defeat sessions by a CD1 aggressor, for 10 days. On day11, the behavior of mice was assessed using the social interaction test, elevated plus maze and open field. Mice received the BCAA leucine, isoleucine or valine before each defeat session. Furthermore, we examined whether BCAA regulate brain derived neurotrophic factor (BDNF) signaling by using a brain-permeable tropomyosin receptor kinase B (TRKB) inhibitor, ANA-12. We also tested the effect of voluntary exercise and high protein diets on susceptibility to stress. Mice exposed to chronic stress displayed increased susceptibility and social avoidance. BCAA promoted resilience to chronic stress, rescued social avoidance behaviors and increased hippocampal BDNF levels and TRKB activation. Inhibition of TRKB signaling abolished the ability of BCAA to promote resilience to stress and to rescue social avoidance. Interestingly, we found that BCAA activate the exercise-regulated PGC1a/FNDC5 pathway known to induce hippocampal BDNF signaling. Although both voluntary exercise and BCAA promoted resilience to stress, combining them did not yield synergistic effects confirming that they affect similar pathways. We also discovered that high protein diets mimic the effect of BCAA by rescuing social deficits induced by chronic stress and increase Bdnf expression in the hippocampus. Our data indicate that BCAA, exercise and high protein diets rescue susceptibility to stress by activating the hippocampal BDNF/TRKB signaling.

Enhanced setup for wired continuous long-term EEG monitoring in juvenile and adult rats: application for epilepsy and other disorders.

BACKGROUND: The electroencephalogram (EEG) is a widely used laboratory technique in rodent models of epilepsy, traumatic brain injury (TBI), and other neurological diseases accompanied by seizures. Obtaining prolonged continuous EEG tracings over weeks to months is essential to adequately answer research questions related to the chronobiology of seizure emergence, and to the effect of potential novel treatment strategies. Current EEG recording methods include wired and the more recent but very costly wireless technologies. Wired continuous long-term EEG in rodents remains the mainstay approach but is often technically challenging due to the notorious frequent EEG cable disconnections from the rodent's head, and to poor signal-to-noise ratio especially when simultaneously monitoring multiple animals. Premature EEG cable disconnections and cable movement-related artifacts result from the animal's natural mobility, and subsequent tension on the EEG wires, as well as from potential vigorous and frequent seizures. These challenges are often accompanied by injuries to the scalp, and result in early terminations of costly experiments. RESULTS: Here we describe an enhanced customized swivel-balance EEG-cage system that allows tension-free rat mobility. The cage setup markedly improves the safety and longevity of current existing wired continuous long-term EEG. Prevention of EEG cable detachments is further enhanced by a special attention to surgical electrode anchoring to the skull. In addition to mechanically preventing premature disconnections, the detailed stepwise approach to the electrical shielding, wiring and grounding required for artifact-free high signal-to-noise ratio recordings is also included. The successful application of our EEG cage system in various rat models of brain insults and epilepsy is described with illustrative high quality tracings of seizures and electrographic patterns obtained during continuous and simultaneous monitoring of multiple rats early and up to 3 months post-brain insult. CONCLUSION: Our simple-to-implement key modifications to the EEG cage setup allow the safe acquisition of substantial high quality wired EEG data without resorting to the still costly wireless technologies.

Lestaurtinib (CEP-701) modulates the effects of early life hypoxic seizures on cognitive and emotional behaviors in immature rats.

Hypoxic encephalopathy of the newborn is a major cause of long-term neurological sequelae. We have previously shown that CEP-701 (lestaurtinib), a drug with an established safety profile in children, attenuates short-term hyperexcitability and tropomyosin-related kinase B (TrkB) receptor activation in a well-established rat model of early life hypoxic seizures (HS). Here, we investigated the potential long-term neuroprotective effects of a post-HS transient CEP-701 treatment. Following exposure to global hypoxia, 10 day old male Sprague-Dawley pups received CEP-701 or its vehicle and were sequentially subjected to the light-dark box test (LDT), forced swim test (FST), open field test (OFT), Morris water maze (MWM), and the modified active avoidance (MAAV) test between postnatal days 24 and 44 (P24-44). Spontaneous seizure activity was assessed by epidural cortical electroencephalography (EEG) between P50 and 100. Neuronal density and glial fibrillary acidic protein (GFAP) levels were evaluated on histological sections in the hippocampus, amygdala, and prefrontal cortex at P100. Vehicle-treated hypoxic rats exhibited significantly increased immobility in the FST compared with controls, and post-HS CEP-701 administration reversed this HS-induced depressive-like behavior (p < 0.05). In the MAAV test, CEP-701-treated hypoxic rats were slower at learning both context-cued and tone-signaled shock-avoidance behaviors (p < 0.05). All other behavioral outcomes were comparable, and no recurrent seizures, neuronal loss, or increase in GFAP levels were detected in any of the groups. We showed that early life HS predispose to long-lasting depressive-like behaviors, and that these are prevented by CEP-701, likely via TrkB modulation. Future mechanistically more specific studies will further investigate the potential role of TrkB signaling pathway modulation in achieving neuroprotection against neonatal HS, without causing neurodevelopmental adverse effects.

Lactate is an antidepressant that mediates resilience to stress by modulating the hippocampal levels and activity of histone deacetylases.

Chronic stress promotes depression in some individuals, but has no effect in others. Susceptible individuals exhibit social avoidance and anxious behavior and ultimately develop depression, whereas resilient individuals live normally. Exercise counteracts the effects of stress. Our objective was to examine whether lactate, a metabolite produced during exercise and known to reproduce specific brain exercise-related changes, promotes resilience to stress and acts as an antidepressant. To determine whether lactate promotes resilience to stress, male C57BL/6 mice experienced daily defeat by a CD-1 aggressor, for 10 days. On the 11th day, mice were subjected to behavioral tests. Mice received lactate before each defeat session. When compared with control mice, mice exposed to stress displayed increased susceptibility, social avoidance and anxiety. Lactate promoted resilience to stress and rescued social avoidance and anxiety by restoring hippocampal class I histone deacetylase (HDAC) levels and activity, specifically HDAC2/3. To determine whether lactate is an antidepressant, mice only received lactate from days 12-25 and a second set of behavioral tests was conducted on day 26. In this paradigm, we examined whether lactate functions by regulating HDACs using co-treatment with CI-994, a brain-permeable class I HDAC inhibitor. When administered after the establishment of depression, lactate behaved as antidepressant. In this paradigm, lactate regulated HDAC5 and not HDAC2/3 levels. On the contrary, HDAC2/3 inhibition was antidepressant-like. This indicates that lactate mimics exercise's effects and rescues susceptibility to stress by modulating HDAC2/3 activity and suggests that HDAC2/3 play opposite roles before and after establishment of susceptibility to stress.

Lactate Mediates the Effects of Exercise on Learning and Memory through SIRT1-Dependent Activation of Hippocampal Brain-Derived Neurotrophic Factor (BDNF).

Exercise promotes learning and memory formation. These effects depend on increases in hippocampal BDNF, a growth factor associated with cognitive improvement and the alleviation of depression symptoms. Identifying molecules that are produced during exercise and that mediate hippocampal Bdnf expression will allow us to harness the therapeutic potential of exercise. Here, we report that an endogenous molecule produced during exercise in male mice induces the Mus musculus Bdnf gene and promotes learning and memory formation. The metabolite lactate, which is released during exercise by the muscles, crosses the blood-brain barrier and induces Bdnf expression and TRKB signaling in the hippocampus. Indeed, we find that lactate-dependent increases in BDNF are associated with improved spatial learning and memory retention. The action of lactate is dependent on the activation of the Sirtuin1 deacetylase. SIRT1 increases the levels of the transcriptional coactivator PGC1a and the secreted molecule FNDC5, known to mediate Bdnf expression. These results reveal an endogenous mechanism to explain how physical exercise leads to the induction of BDNF, and identify lactate as a potential endogenous molecule that may have therapeutic value for CNS diseases in which BDNF signaling is disrupted.SIGNIFICANCE STATEMENT It is established that exercise promotes learning and memory formation and alleviates the symptoms of depression. These effects are mediated through inducing Bdnf expression and signaling in the hippocampus. Understanding how exercise induces Bdnf and identifying the molecules that mediate this induction will allow us to design therapeutic strategies that can mimic the effects of exercise on the brain, especially for patients with CNS disorders characterized by a decrease in Bdnf expression and who cannot exercise because of their conditions. We identify lactate as an endogenous metabolite that is produced during exercise, crosses the blood-brain barrier and promotes hippocampal dependent learning and memory in a BDNF-dependent manner. Our work identifies lactate as a component of the "exercise pill."

Combination of drug and stem cells neurotherapy: Potential interventions in neurotrauma and traumatic brain injury.

Traumatic brain injury (TBI) has been recognized as one of the major public health issues that leads to devastating neurological disability. As a consequence of primary and secondary injury phases, neuronal loss following brain trauma leads to pathophysiological alterations on the molecular and cellular levels that severely impact the neuropsycho-behavioral and motor outcomes. Thus, to mitigate the neuropathological sequelae post-TBI such as cerebral edema, inflammation and neural degeneration, several neurotherapeutic options have been investigated including drug intervention, stem cell use and combinational therapies. These treatments aim to ameliorate cellular degeneration, motor decline, cognitive and behavioral deficits. Recently, the use of neural stem cells (NSCs) coupled with selective drug therapy has emerged as an alternative treatment option for neural regeneration and behavioral rehabilitation post-neural injury. Given their neuroprotective abilities, NSC-based neurotherapy has been widely investigated and well-reported in numerous disease models, notably in trauma studies. In this review, we will elaborate on current updates in cell replacement therapy in the area of neurotrauma. In addition, we will discuss novel combination drug therapy treatments that have been investigated in conjunction with stem cells to overcome the limitations associated with stem cell transplantation. Understanding the regenerative capacities of stem cell and drug combination therapy will help improve functional recovery and brain repair post-TBI. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Epigenetic changes in diabetes.

The incidence of diabetes is increasing worldwide. Diabetes is quickly becoming one of the leading causes of death. Diabetes is a genetic disease; however, the environment plays critical roles in its development and progression. Epigenetic changes often translate environmental stimuli to changes in gene expression. Changes in epigenetic marks and differential regulation of epigenetic modulators have been observed in different models of diabetes and its associated complications. In this minireview, we will focus DNA methylation, Histone acetylation and methylation and their roles in the pathogenesis of diabetes.