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BDNF signaling in hypothalamic circuitries regulates mammalian food intake. However, whether BDNF exerts metabolic effects on peripheral organs is currently unknown. Here, we show that the BDNF receptor TrkB.T1 is expressed by pancreatic β-cells where it regulates insulin release. Mice lacking TrkB.T1 show impaired glucose tolerance and insulin secretion. β-cell BDNF-TrkB.T1 signaling triggers calcium release from intracellular stores, increasing glucose-induced insulin secretion. Additionally, BDNF is secreted by skeletal muscle and muscle-specific BDNF knockout phenocopies the β-cell TrkB.T1 deletion metabolic impairments. The finding that BDNF is also secreted by differentiated human muscle cells and induces insulin secretion in human islets via TrkB.T1 identifies a new regulatory function of BDNF on metabolism that is independent of CNS activity. Our data suggest that muscle-derived BDNF may be a key factor mediating increased glucose metabolism in response to exercise, with implications for the treatment of diabetes and related metabolic diseases., Glucose metabolism is regulated by hypothalamic brain functions and factors produced by peripheral tissues. Here, the authors show that the regulator of food intake Brain-derived neurotrophic factor is also produced and secreted by muscle and stimulates pancreas insulin release.

Female cancer patients have a better prognosis but more adverse events with chemotherapy; less is known with other cancer treatments like radiation therapy. Previous literature has demonstrated sex-dependent effects on the hippocampi and behavioral tasks within post-natal mice after radiotherapy. We explored the differences in activity and sleep in adult male and female mice within our previously established mouse model of cranial-irradiation-induced hypersomnolence (C-RIH). Ten mice of each sex (B6 x B6D2 backcrossed with C57/b6NCr) were observed for general activity and sleep continuously over 10 days before and after therapeutic irradiation (whole brain, 15Gy, single fraction). Behavioral assessments aimed at measuring anxiety (Light Dark Box, Elevated Zero Maze) and depression (Sucrose Preference Test) related behaviors, and working memory (Y Maze) were then used to assess any radiation-induced changes in mood or cognition. Independent samples t-tests compared male and female cohorts before and after radiation. At baseline, females had significantly higher peak activity (p < 0.001), as well as day (p < 0.001), and night (p = 0.004) activity. Females also showed less anxiety in the Elevated Zero Maze (p < 0.001) and Light-Dark Box (p = 0.012). In the Y-Maze, females had significantly more alternations (entry into each arm without repeat) (p = 0.004). Males and females consumed the same proportion of sucrose solution in respect to water (p = 0.124). After radiation, males and females showed a significant decrease in activity, with females displaying a higher suppression of night activity both 1-3 days (t(18) = 2.162, p = 0.045) and 7-9 days (t(18) = 2.266, p = 0.037). Female mice also showed increased night hypersomnolence at 1-3 days (t(18) = 4.474, < p = 0.001) and 7-9 days (t(18) = 2.920, p = 0.01). Further analysis is underway on post-radiation sex differences in sleep and activity. Here we used a mouse model of C-RIH to assess the behavioral outcomes between the sexes and found marked effects on sleep and activity.

Chronic daytime sleepiness, or hypersomnolence, is one of the most common and disruptive side effects of cranial radiotherapy and is associated with disturbances in mood and cognition in primary brain tumor patients. Our laboratory previously found that increased minor allele presence of the PERIOD2 (PER2) polymorphism (rs934945, G-E mutation) correlated with a decreased likelihood of hypersomnolence in PBT patients. PER2, a key molecular component of the circadian clock, assists in the generation and maintenance of daily sleep/wake rhythms. We aim to understand the effects of this PER2 polymorphism on radiation sensitivity within our previously established mouse model of cranial-irradiation-induced hypersomnolence (C-RIH). Five cohorts of male/female transgenic mice were generated using CRISPR-Cas9, replacing the endogenous mouse CRY binding domain with one of two polymorphic variants within the human genome (G-E and conventional Per2h23). General activity and sleep were monitored continuously over 10 days before and after therapeutic irradiation (whole brain, 15Gy, single fraction). Independent samples t-tests compared knock-in groups and species variants. During the active phase, G-E knock-in mice showed less radiation-induced suppression of activity (-7% males; -20% females) relative to Per2h23 knock-ins (-18% males; -36% females). For rest, both male and female G-E mice (+4% males; +16.4% females) expressed less radiation induced sleep during their active phase than Per2h23 mice (+7% males; +27.7% females). However, this pattern did not rise to significance. Current experiments will expand the numbers of mice used in each group to further explore these initial patterns. Understanding the genetic markers that predict radiation sensitivity could help generate more patient specific methods to mitigate these negative behavioral outcomes. Our mouse models provide a platform to introduce polymorphisms and test their impact on treatment-related symptoms.

Recent studies have suggested that the use of cognitive enhancers as adjuncts to exposure-based therapy in individuals suffering from post-traumatic stress disorder (PTSD) may be beneficial. Brain cholinergic signaling through basal forebrain projections to the hippocampus is an established pathway mediating fear response and cognitive flexibility. Here we employed a genetic strategy to enhance cholinergic activity through increased signaling of the NGF receptor TrkA. This strategy leads to increased levels of the marker of cholinergic activation, acetylcholine synthesizing enzyme choline acetyltransferase, in forebrain cholinergic regions and their projection areas such as the hippocampus. Mice with increased cholinergic activity do not display any neurobehavioral abnormalities except a selective attenuation of fear response and lower fear expression in extinction trials. Reduction in fear response is rescued by the GABA antagonist picrotoxin in mutant mice, and, in wild-type mice, is mimicked by the GABA agonist midazolam suggesting that GABA can modulate cholinergic functions on fear circuitries. Importantly, mutant mice also show a reduction in fear processing under stress conditions in a single prolonged stress (SPS) model of PTSD-like behavior, and augmentation of cholinergic signaling by the drug donepezil in wild-type mice promotes extinction learning in a similar SPS model of PTSD-like behavior. Donepezil is already in clinical use for the treatment of dementia suggesting a new translational application of this drug for improving exposure-based psychotherapy in PTSD patients.

The pathophysiology of Amyotrophic Lateral Sclerosis (ALS), a disease caused by the gradual degeneration of motoneurons, is still largely unknown. Insufficient neurotrophic support has been cited as one of the causes of motoneuron cell death. Neurotrophic factors such as BDNF have been evaluated in ALS human clinical trials, but yielded disappointing results attributed to the poor pharmacokinetics and pharmacodynamics of BDNF. In the inherited ALS G93A SOD1 animal model, deletion of the BDNF receptor TrkB.T1 delays spinal cord motoneuron cell death and muscle weakness through an unknown cellular mechanism. Here we show that TrkB.T1 is expressed ubiquitously in the spinal cord and its deletion does not change the SOD1 mutant spinal cord inflammatory state suggesting that TrkB.T1 does not influence microglia or astrocyte activation. Although TrkB.T1 knockout in astrocytes preserves muscle strength and co-ordination at early stages of disease, its specific conditional deletion in motoneurons or astrocytes does not delay motoneuron cell death during the early stage of the disease. These data suggest that TrkB.T1 may limit the neuroprotective BDNF signaling to motoneurons via a non-cell autonomous mechanism providing new understanding into the reasons for past clinical failures and insights into the design of future clinical trials employing TrkB agonists in ALS.

Vav1 is a Rho/Rac (Ras-related C3 botulinum toxin substrate) guanine nucleotide exchange factor expressed in hematopoietic and endothelial cells that are involved in a wide range of cellular functions. It is also stabilized under hypoxic conditions when it regulates the accumulation of the transcription factor HIF (Hypoxia Inducible Factor)-1α, which activates the transcription of target genes to orchestrate a cellular response to low oxygen. One of the genes induced by HIF-1α is GLUT (Glucose Transporter)-1, which is the major glucose transporter expressed in vessels that supply energy to the brain. Here, we identify a role for Vav1 in providing glucose to the brain. We found that Vav1 deficiency downregulates HIF-1α and GLUT-1 levels in endothelial cells, including blood-brain barrier cells. This downregulation of GLUT-1, in turn, reduced glucose uptake to endothelial cells both in vitro and in vivo, and reduced glucose levels in the brain. Furthermore, endothelial cell-specific Vav1 knock-out in mice, which caused glucose uptake deficiency, also led to a learning delay in fear conditioning experiments. Our results suggest that Vav1 promotes learning by activating HIF-1α and GLUT-1 and thereby distributing glucose to the brain. We further demonstrate the importance of glucose transport by endothelial cells in brain functioning and reveal a potential new axis for targeting GLUT-1 deficiency syndromes and other related brain diseases.

Amyotrophic lateral sclerosis (ALS) causes rapidly progressive paralysis and death within 5 years from diagnosis due to degeneration of the motor circuits. However, a significant population of ALS patients also shows cognitive impairments and progressive hippocampal pathology. Likewise, the mutant SOD1(G93A) mouse model of ALS (mSOD1), in addition to loss of spinal motor neurons, displays altered spatial behavior and hippocampal abnormalities including loss of parvalbumin-positive interneurons (PVi) and enhanced long-term potentiation (LTP). However, the cellular and molecular mechanisms underlying these morpho-functional features are not well understood. Since removal of TrkB.T1, a receptor isoform of the brain-derived neurotrophic factor, can partially rescue the phenotype of the mSOD1 mice, here we tested whether removal of TrkB.T1 can normalize the number of PVi and the LTP in this model. Stereological analysis of hippocampal PVi in control, TrkB.T1−/−, mSOD1, and mSOD1 mice deficient for TrkB.T1 (mSOD1/T1−/−) showed that deletion of TrkB.T1 restored the number of PVi to physiological level in the mSOD1 hippocampus. The rescue of PVi neuron number is paralleled by a normalization of high-frequency stimulation-induced LTP in the pre-symptomatic mSOD1/T1−/− mice. Our experiments identified TrkB.T1 as a cellular player involved in the homeostasis of parvalbumin expressing interneurons and, in the context of murine ALS, show that TrkB.T1 is involved in the mechanism underlying structural and functional hippocampal degeneration. These findings have potential implications for hippocampal degeneration and cognitive impairments reported in ALS patients at early stages of the disease.

Brain-derived neurotrophic factor (BDNF) is a potent modulator of brain synaptic plasticity. Signaling defects caused by dysregulation of its Ntrk2 (TrkB) kinase (TrkB.FL) and truncated receptors (TrkB.T1) have been linked to the pathophysiology of several neurological and neurodegenerative disorders. We found that upregulation of Rbfox1, an RNA binding protein associated with intellectual disability, epilepsy and autism, increases selectively hippocampal TrkB.T1 isoform expression. Physiologically, increased Rbfox1 impairs BDNF-dependent LTP which can be rescued by genetically restoring TrkB.T1 levels. RNA-seq analysis of hippocampi with upregulation of Rbfox1 in conjunction with the specific increase of TrkB.T1 isoform expression also shows that the genes affected by Rbfox1 gain of function are surprisingly different from those influenced by Rbfox1 deletion. These findings not only identify TrkB as a major target of Rbfox1 pathophysiology but also suggest that gain or loss of function of Rbfox1 regulate different genetic landscapes.

TrkA is a tyrosine kinase receptor required for development and survival of the peripheral nervous system. In the adult, TrkA and its ligand NGF are peripheral pain mediators, particularly in inflammatory pain states. However, how TrkA regulates the function of nociceptive neurons and whether its activity levels may lead to sensory abnormalities is still unclear. Here we report the characterization of a 3 aa (KFG) domain that negatively regulates TrkA level and function in response to NGF. Deletion of this domain in mouse causes a reduction of TrkA ubiquitination leading to an increase in TrkA protein levels and activity. The number of dorsal root ganglia neurons is not affected by the mutation. However, mutant mice have enhanced thermal sensitivity and inflammatory pain. Together, these data suggest that ubiquitination is a mechanism used in nociceptive neurons to regulate TrkA level and function. Our results may enhance our understanding of how ubiquitination affects TrkA activation following noxious thermal stimulation and inflammatory pain.

Free radicals are implicated in causation of cerebral reperfusion injury and chronic cerebral hypoperfusion in rats is associated with functional and histopathological disturbances. Ocimum sanctum (OS), a plant widely used in Ayurveda, has been shown to possess anti-inflammatory, antioxidant and cognition-enhancing properties. In the present study, we investigated the effect of methanolic extract of OS leaves in cerebral reperfusion injury as well as long-term hypoperfusion. Occlusion of bilateral common carotid arteries (BCCA) for 30 min followed by 45 min reperfusion caused increase in lipid peroxidation and up-regulation of superoxide dismutase (SOD) activity accompanied by fall in tissue total sulfhydryl groups (TSH) in rat forebrains. Ascorbic acid levels were unchanged, however. OS pretreatment (200 mg/kg/day for 7 days) prevented this reperfusion-induced rise in lipid peroxidation and SOD activity. OS pretreatment also stabilized the levels of TSH during reperfusion. Long-term cerebral hypoperfusion (a model of cerebrovascular insufficiency and dementia) induced by permanent occlusion of BCCA for 15 days demonstrated altered exploratory behavior in open-field testing and memory deficits as tested by Morris' water maze. Histopathological examination of hypoperfused animals revealed reactive changes, like cellular edema, gliosis and perivascular inflammatory infiltrate. OS treatment (200 mg/kg/day for 15 days) significantly prevented these hypoperfusion-induced functional and structural disturbances. The results suggest that OS may be useful in treatment of cerebral reperfusion injury and cerebrovascular insufficiency states.

Azadirachta indica, a plant used widely in Ayurveda, has been reported to have anti-inflammatory, immunomodulatory and adaptogenic properties. The present study evaluates its hepatoprotective role. Fresh juice of tender leaves of Azadirachta indica (200 mg/kg body wt. p.o.) inhibited paracetamol (2 g/kg body wt. p.o.)-induced lipid peroxidation and prevented depletion of sulfhydryl groups in liver cells. There was an increase in serum marker enzymes of hepatic damage (aspartate transaminase, alanine transaminase and alkaline phosphatase) after paracetamol administration. Azadirachta indica pretreatment stabilized the serum levels of these enzymes. Histopathological observations of liver tissues corroborated these findings.

Brain Derived Neurotrophic Factor (BDNF) exerts strong pro-survival effects on developing and injured motoneurons. However, in clinical trials, BDNF has failed to benefit patients with amyotrophic lateral sclerosis (ALS). To date, the cause of this failure remains unclear. Motoneurons express the TrkB kinase receptor but also high levels of the truncated TrkB.T1 receptor isoform. Thus, we investigated whether the presence of this receptor may affect the response of diseased motoneurons to endogenous BDNF. We deleted TrkB.T1 in the hSOD1(G93A) ALS mouse model and evaluated the impact of this mutation on motoneuron death, muscle weakness and disease progression. We found that TrkB.T1 deletion significantly slowed the onset of motor neuron degeneration. Moreover, it delayed the development of muscle weakness by 33 days. Although the life span of the animals was not affected we observed an overall improvement in the neurological score at the late stage of the disease. To investigate the effectiveness of strategies aimed at bypassing the TrkB.T1 limit to BDNF signaling we treated SOD1 mutant mice with the adenosine A2A receptor agonist CGS21680, which can activate motoneuron TrkB receptor signaling independent of neurotrophins. We found that CGS21680 treatment slowed the onset of motor neuron degeneration and muscle weakness similarly to TrkB.T1 removal. Together, our data provide evidence that endogenous TrkB.T1 limits motoneuron responsiveness to BDNF in vivo and suggest that new strategies such as Trk receptor transactivation may be used for therapeutic intervention in ALS or other neurodegenerative disorders.

The molecular mechanisms underlying the effects of electroconvulsive shock (ECS) therapy, a fast-acting and very effective antidepressant therapy, are poorly understood. Changes related to neuroplasticity, including enhanced adult hippocampal neurogenesis and neuronal arborization, are believed to play an important role in mediating the effects of ECS. Here we show a dynamic upregulation of the scaffold protein tamalin, selectively in the hippocampus of animals subjected to ECS. Interestingly, this gene upregulation is functionally significant because tamalin deletion in mice abrogated ECS-induced neurogenesis in the adult mouse hippocampus. Furthermore, loss of tamalin blunts mossy fiber sprouting and dendritic arborization caused by ECS. These data suggest an essential role for tamalin in ECS-induced adult neuroplasticity and provide new insight into the pathways that are involved in mediating ECS effects.

Background Previous studies suggest that the responsiveness of TrkB receptor to BDNF is developmentally regulated in rats. Antidepressant drugs (AD) have been shown to increase TrkB signalling in the adult rodent brain, and recent findings implicate a BDNF-independent mechanism behind this phenomenon. When administered during early postnatal life, ADs produce long-lasting biochemical and behavioural alterations that are observed in adult animals. Methodology We have here examined the responsiveness of brain TrkB receptors to BDNF and ADs during early postnatal life of mouse, measured as autophosphorylation of TrkB (pTrkB). Principal Findings We found that ADs fail to induce TrkB signalling before postnatal day 12 (P12) after which an adult response of TrkB to ADs was observed. Interestingly, there was a temporally inverse correlation between the appearance of the responsiveness of TrkB to systemic ADs and the marked developmental reduction of BDNF-induced TrkB in brain microslices ex vivo. Basal p-TrkB status in the brain of BDNF deficient mice was significantly reduced only during early postnatal period. Enhancing cAMP (cyclic adenosine monophosphate) signalling failed to facilitate TrkB responsiveness to BDNF. Reduced responsiveness of TrkB to BDNF was not produced by the developmental increase in the expression of dominant-negative truncated TrkB.T1 because this reduction was similarly observed in the brain microslices of trkB.T1−/− mice. Moreover, postnatal AD administration produced long-lasting behavioural alterations observable in adult mice, but the responses were different when mice were treated during the time when ADs did not (P4-9) or did (P16-21) activate TrkB. Conclusions We have found that ADs induce the activation of TrkB only in mice older than 2 weeks and that responsiveness of brain microslices to BDNF is reduced during the same time period. Exposure to ADs before and after the age when ADs activate TrkB produces differential long-term behavioural responses in adult mice.

Pathological orin vitrooverexpression of the truncated TrkB (TrkB.T1) receptor inhibits signaling through the full-length TrkB (TrkB.FL) tyrosine kinase receptor. However, to date, the role of endogenous TrkB.T1 is still unknown. By studying mice lacking the truncated TrkB.T1 isoform but retaining normal spatiotemporal expression of TrkB.FL, we have analyzed TrkB.T1-specific physiological functions and its effect on endogenous TrkB kinase signalingin vivo. We found that TrkB.T1-deficient mice develop normally but show increased anxiety in association with morphological abnormalities in the length and complexity of neurites of neurons in the basolateral amygdala. However, no behavioral abnormalities were detected in hippocampal-dependent memory tasks, which correlated with lack of any obvious hippocampal morphological deficits or alterations in basal synaptic transmission and long-term potentiation.In vivoreduction of TrkB signaling by removal of one BDNF allele could be partially rescued by TrkB.T1 deletion, which was revealed by an amelioration of the enhanced aggression and weight gain associated with BDNF haploinsufficiency. Our results suggest that, at the physiological level, TrkB.T1 receptors are important regulators of TrkB.FL signalingin vivo. Moreover, TrkB.T1 selectively affects dendrite complexity of certain neuronal populations.

We assessed the effect of Azadirachta indica ( A. indica ), a plant that has been reported to possess antioxidant, anti-inflammatory and anxiolytic properties, on cerebral reperfusion injury and long term cerebral hypoperfusion. When blood flow to brain region that has undergone critical period of ischemia is re-established, additional injury is to be expected from the reperfusion. In the present study, bilateral common carotid artery (BCCA) occlusion for 30 min followed by 45 min reperfusion resulted in increase in lipid peroxidation, superoxide dismutase (SOD) activity and fall in total tissue sulfhydryl (T-SH) groups. A. indica pretreatment (500 mg/kg/day × 7 days) attenuated the reperfusion induced enhanced lipid peroxidation, SOD activity and prevented fall in T-SH groups. Moreover, A.indica per se increased brain ascorbic acid level, which was unchanged during reperfusion insult. Long-term cerebral hypoperfusion induced by permanent BCCA occlusion has been reported to cause behavioral and histopathological abnormalities. In the present study, as tested by open field paradigm and Morris' water maze, a propensity towards anxiety and disturbances of learning/memory were observed in animals subjected to hypoperfusion for 2 weeks. A. indica (500 mg/kg/day × 15 days) significantly reduced these hypoperfusion induced functional disturbances. Reactive changes in brain histology like gliosis, perivascular lymphocytic infiltration, recruitment of macrophages and cellular edema following long term hypoperfusion were also attenuated effectively by A. indica . We conclude that our study provides an experimental evidence for possible neuroprotective potentiality of A. indica.

Restoration of blood flow to an ischemic brain region is associated with generation of reactive oxygen species with consequent reperfusion injury. Chronic cerebral hypoperfusion induced by permanent occlusion of bilateral common carotid arteries in rats is associated with behavioral and histopathological alterations. Nimodipine, a dihydropyridine calcium channel antagonist, has potent vasodilatory effect on cerebral vessels and increases cerebral blood flow. We analyzed whether nimodipine reduces injury caused by transient forebrain ischemia and long-term cerebral hypoperfusion. Bilateral common carotid occlusion for 30 min followed by 45 min reperfusion resulted in a two-fold increase in lipid peroxidation and superoxide dismutase activity. Nimodipine pretreatment (4 mg/kg, i.p.) brought down these levels by 30 and 23%, respectively. Long-term cerebral hypoperfusion in rats caused a propensity towards anxiety and listlessness (open field paradigm) accompanied by deficits of learning and memory (Morris’ water maze testing). Additionally, histopathological observation in hypoperfused brains revealed reactive changes in the form of perivascular inflammation, gliosis and astrocytosis. Nimodipine treatment significantly alleviated these changes in behavioral and histopathological parameters. Our data confirm the protective role of nimodipine in ischemia reperfusion injury. Moreover, it suggests the beneficial role of nimodipine in cerebrovascular insufficiency states and dementia.