FDA-approved PDE4 inhibitors reduce the dominant toxicity of ALS-FTD-associated CHCHD10 S59L.

Mutations in coiled-coil-helix-coiled-coil-helix domain containing 10( CHCHD10 ) have been identified as a genetic cause of amyotrophic lateral sclerosis and/or frontotemporal dementia(ALS-FTD). In our previous studies using in vivo Drosophila model expressing C2C10H S81L , and human cell models expressing CHCHD10 S59L , we have identified that the PINK1/Parkin pathway is activated and causes cellular toxicity. Furthermore, we demonstrated that pseudo-substrate inhibitors for PINK1 and mitofusin2 agonists mitigated the cellular toxicity of CHCHD10 S59L . Evidences using in vitro/ in vivo genetic and chemical tools indicate that inhibiting PINK1 would be the most promising treatment for CHCHD10 S59L -induced diseases. Therefore, we have investigated cellular pathways that can modulate the PINK1/Parkin pathway and reduce CHCHD10 S59L -induced cytotoxicity. Here, we report that FDA-approved PDE4 inhibitors reduced CHCHD10 S59L -induced morphological and functional mitochondrial defects in human cells and an in vivo Drosophila model expressing C2C10H S81L . Multiple PDE4 inhibitors decreased PINK1 accumulation and downstream mitophagy induced by CHCHD10 S59L . These findings suggest that PDE4 inhibitors currently available in the market may be repositioned to treat CHCHD10 S59L -induced ALS-FTD and possibly other related diseases.

TDP-43 and PINK1 mediate CHCHD10S59L mutation-induced defects in Drosophila and in vitro.

Mutations in coiled-coil-helix-coiled-coil-helix domain containing 10 (CHCHD10) can cause amyotrophic lateral sclerosis and frontotemporal dementia (ALS-FTD). However, the underlying mechanisms are unclear. Here, we generate CHCH10S59L-mutant Drosophila melanogaster and HeLa cell lines to model CHCHD10-associated ALS-FTD. The CHCHD10S59L mutation results in cell toxicity in several tissues and mitochondrial defects. CHCHD10S59L independently affects the TDP-43 and PINK1 pathways. CHCHD10S59L expression increases TDP-43 insolubility and mitochondrial translocation. Blocking TDP-43 mitochondrial translocation with a peptide inhibitor reduced CHCHD10S59L-mediated toxicity. While genetic and pharmacological modulation of PINK1 expression and activity of its substrates rescues and mitigates the CHCHD10S59L-induced phenotypes and mitochondrial defects, respectively, in both Drosophila and HeLa cells. Our findings suggest that CHCHD10S59L-induced TDP-43 mitochondrial translocation and chronic activation of PINK1-mediated pathways result in dominant toxicity, providing a mechanistic insight into the CHCHD10 mutations associated with ALS-FTD.

Histone Lysine Demethylase JMJD2D/KDM4D and Family Members Mediate Effects of Chronic Social Defeat Stress on Mouse Hippocampal Neurogenesis and Mood Disorders.

Depression, anxiety and related mood disorders are major psychiatric illnesses worldwide, and chronic stress appears to be one of the primary underlying causes. Therapeutics to treat these debilitating disorders without a relapse are limited due to the incomplete molecular understanding of their etiopathology. In addition to the well-studied genetic component, research in the past two decades has implicated diverse epigenetic mechanisms in mediating the negative effects of chronic stressful events on neural circuits. This includes the cognitive circuitry, where the dynamic hippocampal dentate gyrus (DG) neurogenesis gets affected in depression and related affective disorders. Most of these epigenetic studies have focused on the impact of acetylation/deacetylation and methylation of several histone lysine residues on neural gene expression. However, there is a dearth of investigation into the role of demethylation of these lysine residues in chronic stress-induced changes in neurogenesis that results in altered behaviour. Here, using the chronic social defeat stress (CSDS) paradigm to induce depression and anxiety in C57BL/6 mice and ex vivo DG neural stem/progenitor cell (NSCs/NPCs) culture we show the role of the members of the JMJD2/KDM4 family of histone lysine demethylases (KDMs) in mediating stress-induced changes in DG neurogenesis and mood disorders. The study suggests a critical role of JMJD2D in DG neurogenesis. Altered enrichment of JMJD2D on the promoters of Id2 (inhibitor of differentiation 2) and Sox2 (SRY-Box Transcription Factor 2) was observed during proliferation and differentiation of NSCs/NPCs obtained from the DG. This would affect the demethylation of repressive epigenetic mark H3K9, thus activating or repressing these and possibly other genes involved in regulating proliferation and differentiation of DG NSCs/NPCs. Treatment of the NSCs/NPCs culture with Dimethyloxallyl Glycine (DMOG), an inhibitor of JMJDs, led to attenuation in their proliferation capacity. Additionally, systemic administration of DMOG in mice for 10 days induced depression-like and anxiety-like phenotype without any stress exposure.

Targeting inhibitory cerebellar circuitry to alleviate behavioral deficits in a mouse model for studying idiopathic autism.

Autism spectrum disorder (ASD) encompasses wide-ranging neuropsychiatric symptoms with unclear etiology. Although the cerebellum is a key region implicated in ASD, it remains elusive how the cerebellar circuitry is altered and whether the cerebellum can serve as a therapeutic target to rectify the phenotype of idiopathic ASD with polygenic abnormalities. Using a syndromic ASD model, e.g., Black and Tan BRachyury T+Itpr3tf/J (BTBR) mice, we revealed that increased excitability of presynaptic interneurons (INs) and decreased intrinsic excitability of postsynaptic Purkinje neurons (PNs) resulted in low PN firing rates in the cerebellum. Knowing that downregulation of Kv1.2 potassium channel in the IN nerve terminals likely augmented their excitability and GABA release, we applied a positive Kv1.2 modulator to mitigate the presynaptic over-inhibition and social impairment of BTBR mice. Selective restoration of the PN activity by a new chemogenetic approach alleviated core ASD-like behaviors of the BTBR strain. These findings highlight complex mechanisms converging onto the cerebellar dysfunction in the phenotypic model and provide effective strategies for potential therapies of ASD.

A 2-oxa-spiro[5.4]decane scaffold displays neurotrophic, neurogenic and anti-neuroinflammatory activities with high potential for development as a versatile CNS therapeutic.

Following our recent discovery of a new scaffold exhibiting significant neurotrophic and neurogenic activities, a structurally tweaked analogue, embodying a 2-oxa-spiro [5.4]decane framework, has been conceptualised and found to be more potent and versatile. It exhibits enhanced neurotrophic and neurogenic action in in vitro, ex vivo and in vivo models and also shows robust neuroprotection in mouse acute cerebral stroke model. The observed attributes are traceable to the predominant activation of the TrkB-PI3K-AKT-CREB pathway. In addition, it also exhibits remarkable anti-neuroinflammatory activity by concurrently down-regulating pro-inflammatory cytokines IL-1α and IL-6, thereby providing a unique molecule with a trinity of neuroactivities, i.e. neurotrophic, neurogenic and anti-inflammatory. The new chemical entity disclosed here has the potential to be advanced as a versatile therapeutic molecule to treat stroke, depression, and possibly other neuropsychiatric disorders associated with attenuated neurotrophic/ neurogenic activity, together with heightened neuroinflammation.

Insights into the epigenetic mechanisms involving histone lysine methylation and demethylation in ischemia induced damage and repair has therapeutic implication.

Cerebral ischemic stroke is one of the leading causes of death and disability worldwide. Therapeutic interventions to minimize ischemia-induced neural damage are limited due to poor understanding of molecular mechanisms mediating complex pathophysiology in stroke. Recently, epigenetic mechanisms mostly histone lysine (K) acetylation and deacetylation have been implicated in ischemic brain damage and have expanded the dimensions of potential therapeutic intervention to the systemic/local administration of histone deacetylase inhibitors. However, the role of other epigenetic mechanisms such as histone lysine methylation and demethylation in stroke-induced damage and subsequent recovery process is elusive. Here, we established an Internal Carotid Artery Occlusion (ICAO) model in CD1 mouse that resulted in mild to moderate level of ischemic damage to the striatum, as suggested by magnetic resonance imaging (MRI), TUNEL and histopathological staining along with an evaluation of neurological deficit score (NDS), grip strength and rotarod performance. The molecular investigations show dysregulation of a number of histone lysine methylases (KMTs) and few of histone lysine demethylases (KDMs) post-ICAO with significant global attenuation in the transcriptionally repressive epigenetic mark H3K9me2 in the striatum. Administration of Dimethyloxalylglycine (DMOG), an inhibitor of KDM4 or JMJD2 class of histone lysine demethylases, significantly ameliorated stroke-induced NDS by restoring perturbed H3K9me2 levels in the ischemia-affected striatum. Overall, these results highlight the novel role of epigenetic regulatory mechanisms controlling the epigenetic mark H3K9me2 in mediating the stroke-induced striatal damage and subsequent repair following mild to moderate cerebral ischemia.

Histone Lysine Demethylases of JMJD2 or KDM4 Family are Important Epigenetic Regulators in Reward Circuitry in the Etiopathology of Depression.

Major depressive disorder (MDD) is debilitating mental illness and is one of the leading contributors to global burden of disease, but unfortunately newer and better drugs are not forthcoming. The reason is lack of complete understanding of molecular mechanisms underlying the development of this disorder. Recent research shows dysregulation in epigenetic regulatory mechanisms, particularly the transcriptionally repressive di- and tri-methylation of histone 3 lysine 9 (H3K9me2/me3) in nucleus accumbens (NAc), a critical region of the reward pathway involved in the development of anhedonia, the hallmark of depression. However, the role of histone lysine demethylases, which can remove methylation from H3K9, in particular Jumonji domain containing demethylases 2 or Jmjd2 family, has not been studied. Using social defeat stress-induced mouse model of depression, this study uncovered that transcripts of most of the Jmjd2 members were unchanged after 5 days of defeat during the onset of depression, but were downregulated after 10 days of defeat in full-blown depression. Blocking the Jumonji domain containing demethylases by chronic administration of inhibitors dimethyloxalylglycine (DMOG) and ML324 resulted in depression-like phenotype even in absence of stress exposure, which was associated with an increase in transcriptionally repressive epigenetic marks H3K9me2/me3 in NAc, causing altered neuroplastic changes as reported in NAc in depression models. Thus, we report for the first time that Jmjd2 class demethylases are critical epigenetic regulators involved in etiopathology of depression and related disorders and activation of these demethylases can be a good strategy in the treatment of MDD and related psychiatric disorders.

Differential effect of chronic stress on mouse hippocampal memory and affective behavior: Role of major ovarian hormones.

Molecular mechanisms of depression-like pathophysiology in female rodent models are less reported compared to males, despite its higher prevalence in human females. Moreover, the stress-response in brain circuitries including reward and cognition circuitries varies with age or hormonal status of the females. So, to understand the stress-induced mood and cognitive disorders in intact females (with ovaries) and ovariectomized (OVX) females, we studied changes in mouse hippocampus, a functionally heterogeneous neural structure involved in both affective and cognitive behaviors. Here, we used a 6-day Chronic Unpredictable Stress (CUS) paradigm in mice to induce depression and related mood disorders. Interestingly, intact females and OVX females showed difference in mood disorder sub-phenotypes to CUS. Similar to an earlier report of CUS affecting the critical reward circuitry structure the nucleus accumbens differently in females with and without ovaries, cognitive behavior in intact females and OVX females also responded differentially to CUS, as evident from Morris Water Maze (MWM) test results. We report that the presence or absence of ovarian hormones, particularly the estrogen, has a significant impact in altering the hippocampus related spatial memory and affective behavior, in females. Our results also illustrate that estrogen administration improves both reward and cognitive behavior, and plays a significant role in alleviating stress-induced despair behavior and enhancing spatial reference memory following a brief 6-day stressful paradigm. Further, it also indicates that the NMDA receptor subunits, GRIN2A and GRIN2B, might mediate the effects of estrogen in the hippocampal functions, thus suggestive of a translational significance of the finding.

Lichen-derived compounds show potential for central nervous system therapeutics.

BACKGROUND: Natural products from lichens are widely investigated for their biological properties, yet their potential as central nervous system (CNS) therapeutic agents is less explored. PURPOSE: The present study investigated the neuroactive properties of selected lichen compounds (atranorin, perlatolic acid, physodic acid and usnic acid), for their neurotrophic, neurogenic and acetylcholine esterase (AChE) activities. METHODS: Neurotrophic activity (neurite outgrowth) was determined using murine neuroblastoma Neuro2A cells. A MTT assay was performed to assess the cytotoxicity of compounds at optimum neurotrophic activity. Neuro2A cells treated with neurotrophic lichen compounds were used for RT-PCR to evaluate the induction of genes that code for the neurotrophic markers BDNF and NGF. Immunoblotting was used to assess acetyl H3 and H4 levels, the epigenetic markers associated with neurotrophic and/or neurogenic activity. The neurogenic property of the compounds was determined using murine hippocampal primary cultures. AChE inhibition activity was performed using a modified Ellman's esterase method. RESULTS: Lichen compounds atranorin, perlatolic acid, physodic acid and (+)-usnic acid showed neurotrophic activity in a preliminary cell-based screening based on Neuro2A neurite outgrowth. Except for usnic acid, no cytotoxic effects were observed for the two depsides (atranorin and perlatolic acid) and the alkyl depsidone (physodic acid). Perlatolic acid appears to be promising, as it also exhibited AChE inhibition activity and potent proneurogenic activity. The neurotrophic lichen compounds (atranorin, perlatolic acid, physodic acid) modulated the gene expression of BDNF and NGF. In addition, perlatolic acid showed increased protein levels of acetyl H3 and H4 in Neuro2A cells. CONCLUSION: These lichen depsides and depsidones showed neuroactive properties in vitro (Neuro2A cells) and ex vivo (primary neural stem or progenitor cells), suggesting their potential to treat CNS disorders.

Sirtuin 1 and 7 mediate resveratrol-induced recovery from hyper-anxiety in high-fructose-fed prediabetic rats.

Hyperglycaemia in diabetes is either caused by reduced availability of insulin (type 1 diabetes, T1D) or insulin resistance to the cells (type 2 diabetes, T2D). In recent years, the prevalence of T2D has increased to an alarming proportion, encompassing 95 percent of the total diabetic burden, probably due to economy-driven changes in lifestyle. Recent epidemiological studies show comorbid depression, anxiety and related mental illness. To explore the molecular mechanisms underlying this comorbid conditions, we used Sprague-Dawley rats on high-fructose diet for 8 weeks to induce prediabetic condition. Rats with this metabolic syndrome also showed hyper-anxiety when they were subjected to anxiety-related behavioural assays. Rats were administered with resveratrol, an activator of sirtuins, and metformin, a standard antidiabetic drug, simultaneously with fructose. We observed that resveratrol was more effective in protecting from both the metabolic (prediabetic) and affective (anxiety) disorders than metformin. Molecular studies showed that recovery was associated with the upregulation of few nuclear sirtuins that act epigenetically - Sirt 1 and 7, which were significantly attenuated in the striatum of prediabetic rats. In conclusion, our study showed that hyper-anxiety associated with prediabetic condition is ameliorated by resveratrol through modulation of sirtuins, which is more or less similar to metformin.

A novel natural product inspired scaffold with robust neurotrophic, neurogenic and neuroprotective action.

In search for drugs to treat neuropsychiatric disorders wherein neurotrophic and neurogenic properties are affected, two neurotrophically active small molecules specially crafted following natural product leads based on 2-oxa-spiro[5.5]-undecane scaffold, have been thoroughly evaluated for their neurotrophic, neurogenic and neuroprotective potential in ex vivo primary culture and in vivo zebrafish and mouse models. The outcome of in vivo investigations suggest that one of these molecules is more neurotrophic than neurogenic while the other one is more neurogenic than neurotrophic and the former exhibits remarkable neuroprotection in a mouse acute ischemic stroke model. The molecular mechanisms of action of these compounds appear to be through the TrkB-MEK-ERK-CREB-BDNF pathway as pre-treatment with neurotrophin receptor TrkB inhibitor ANA-12 and MEK inhibitor PD98059 attenuates the neurotrophic action of compounds.

Epigenetic regulatory mechanisms in stress-induced behavior.

Stress response is considered to have adaptive value for organisms faced with stressful condition. Chronic stress however adversely affects the physiology and may lead to neuropsychiatric disorders. Repeated stressful events in animal models have been shown to cause long-lasting changes in neural circuitries at molecular, cellular, and physiological level, leading to disorders of mood as well as cognition. Molecular studies in recent years have implicated diverse epigenetic mechanisms, including histone modifications, DNA methylation, and noncoding RNAs, that underlie dysregulation of genes in the affected neural circuitries in chronic stress-induced pathophysiology. A review of the myriad epigenetic regulatory mechanisms associated with neural and behavioral responses in animal models of stress-induced neuropsychiatric disorders is presented here. The review also deals with clinical evidence of the epigenetic dysregulation of genes in psychiatric disorders where chronic stress appears to underlie the etiopathology.

Dysfunctional glutamatergic and γ-aminobutyric acidergic activities in prefrontal cortex of mice in social defeat model of depression.

BACKGROUND: Depression is a complex neuropsychiatric syndrome that is often very severe and life threatening. In spite of the remarkable progress in understanding the neural biology, the etiopathophysiology of depression is still elusive. In this study, we have investigated molecular mechanisms in the prefrontal cortex of mice showing depression-like phenotype induced by chronic defeat stress. METHODS: Depression-like phenotype was induced in C57BL/6 mice by subjecting them to a 10-day social defeat paradigm. The metabolic activity of excitatory (glutamatergic) and inhibitory (γ-aminobutyric acid [GABA]ergic) neurons of the prefrontal cortex was measured by (1)H-[(13)C]-nuclear magnetic resonance spectroscopy together with infusion of [1,6-(13)C2]glucose. In addition, the expression level of genes associated with glutamatergic and GABAergic pathways was monitored by quantitative polymerase chain reaction. RESULTS: Mice showing depression-like phenotype exhibit significant reduction in the levels of glutamate, glutamine, N-acetyl aspartate, and taurine in the prefrontal cortex. Most importantly, findings of reduced (13)C labeling of glutamate-C4, glutamate-C3, and GABA-C2 from [1,6-(13)C2]glucose indicate decreased glutamatergic and GABAergic neuronal metabolism and neurotransmitter cycling in the depressed mice. The reduced glutamine-C4 labeling suggests decreased neurotransmitter cycling in depression. Quantitative polymerase chain reaction analysis revealed reduced transcripts of Gad1 and Eaat2 genes, which code for enzymes involved in the synthesis of GABA and the clearance of glutamate from synapses, respectively. CONCLUSIONS: These data indicate that the activities of glutamatergic and GABAergic neurons are reduced in mice showing a depression-like phenotype, which is supported by molecular data for the expression of genes involved in glutamate and GABA pathways.