Trehalose induced antidepressant-like effects and autophagy enhancement in mice

NSC689857, an inhibitor of Skp2, produces antidepressant-like effects in mice

We have previously reported that two inhibitors of an E3 ligase S-phase kinase-associated protein 2 (Skp2), SMIP004 and C1, have an antidepressant-like effect in non-stressed and chronically stressed mice. This prompted us to ask whether other Skp2 inhibitors could also have an antidepressant effect. Here, we used NSC689857, another Skp2 inhibitor, to investigate this hypothesis. The results showed that administration of NSC689857 (5 mg/kg) produced an antidepressant-like effect in a time-dependent manner in non-stressed male mice, which started 8 days after drug administration. Dose-dependent analysis showed that administration of 5 and 10 mg/kg, but not 1 mg/kg, of NSC689857 produced antidepressant-like effects in both non-stressed male and female mice. Administration of NSC689857 (5 mg/kg) also induced antidepressant-like effects in non-stressed male mice when administered three times within 24 h (24, 5, and 1 h before testing) but not when administered acutely (1 h before testing). In addition, NSC689857 and fluoxetine coadministration produced additive antidepressant-like effects in non-stressed male mice. These effects of NSC689857 were not associated with the changes in locomotor activity. Administration of NSC689857 (5 mg/kg) also attenuated depression-like behaviors in male mice induced by chronic social defeat stress, suggesting therapeutic potential of NSC689857 in depression. Overall, these results suggest that NSC689857 is capable of exerting antidepressant-like effects in both non-stressed and chronically stressed mice.

MKP1 may be involved in the occurrence of depression by regulating hippocampal autophagy in rats

BACKGROUND

Mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP1) is upregulated in the hippocampus of patients with depression, while pharmacological inhibition of hippocampal MKP1 can mitigate depression-like behaviors in rodents. In addition, MAPK signaling regulates autophagy, and antidepressants were recently shown to target autophagic signaling pathways. We speculated that MKP1 contributes to depression by enhancing hippocampal autophagy through dephosphorylation of the MAPK isoform ERK1/2.

METHODS

We established a rat depression model by exposure to chronic unpredictable mild stress (CUMS), and then examined depression-like behaviors in the sucrose preference test (SPT) and forced swimming test (FST) as well as expression changes in hippocampal MKP1, ERK1/2, phosphorylated ERK1/2, and autophagy-related proteins LC3II by Western blotting and immunostaining. These same measurements were repeated in rats exposed to CUMS following hippocampal infusion of a MKP1-targeted shRNA. Finally, the effects of MKP1 expression level on autophagy we examined in rat GMI-R1 microglia.

RESULTS

CUMS-exposed rats demonstrated anhedonia in the SPT and helplessness in the FST, two core depression-like behaviors. Expression levels of MKP1 and LC3II were upregulated in the hippocampus of CUMS rats, suggesting enhanced autophagy, while pERK/ERK was downregulated. Knockdown of hippocampal MKP1 mitigated depression-like behaviors, downregulated hippocampal LC3II expression, and upregulated hippocampal pERK/ERK. Similarly, MKP1 knockdown in GMI-R1 cells upregulated pERK/ERK and reduced the number of LC3II autophagosomes, while MKP1 overexpression had the opposite effects.

CONCLUSION

Enhanced hippocampal autophagy via MKP1-mediated ERK dephosphorylation may contribute to the development of depression.

Critical role of miR-21/exosomal miR-21 in autophagy pathway

Activation of autophagy, a process of cellular stress response, leads to the breakdown of proteins, organelles, and other parts of the cell in lysosomes, and can be linked to several ailments, such as cancer, neurological diseases, and rare hereditary syndromes. Thus, its regulation is very carefully monitored. Transcriptional and post-translational mechanisms domestically or in whole organisms utilized to control the autophagic activity, have been heavily researched. In modern times, microRNAs (miRNAs) are being considered to have a part in post-translational orchestration of the autophagic activity, with miR-21 as one of the best studied miRNAs, it is often more than expressed in cancer cells. This regulatory RNA is thought to play a major role in a plethora of processes and illnesses including growth, cancer, cardiovascular disease, and inflammation. Different studies have suggested that a few autophagy-oriented genes, such as PTEN, Rab11a, Atg12, SIPA1L2, and ATG5, are all targeted by miR-21, indicating its essential role in the regulation.

Immunotherapy for depression: Recent insights and future targets

Depression stands as a prominent contributor to global disability, entailing an elevated risk of suicide. Substantial evidence supports the notion that immune dysregulation may play a role in the development of depression and impede responses to antidepressant treatments. Immune dysregulation may cause depression in susceptible individuals through raising inflammatory responses. Differences in immune cell types and the release of pro-inflammatory mediators are observed in the blood and cerebrospinal fluid of patients with major depressive disorder, which is associated with neuroimmune dysfunction. Therefore, the interaction of peripheral and central immune targets in depression needs to be understood. Urgent attention is required for the development of innovative therapeutics directed at modulating immune responses for the treatment of depression. This review delineates the immune mechanisms involved in the pathogenesis of depression, assesses the therapeutic potential of immune system targeting for depression treatment, and deliberates on the merits and constraints of employing immunotherapy in the management of depression.

Autophagy markers, cognitive deficits and depressive symptoms in Parkinson's disease

Depressive symptoms are common in Parkinson's disease (PD). The relationships between autophagy and PD or depression have been documented. However, no studies explored the role of autophagy markers associated with depressive symptoms in PD. Our study aimed to investigate the relationships between autophagy markers, cognitive impairments and depressive symptoms in PD patients. A total of 163 PD patients aged 50-80 years were recruited. Plasma concentrations of autophagy markers (LC3-I, LC3-II and p62/SQSTM1) and glycolipid parameters were measured. Depressive symptoms, cognitive impairments, and motor function were assessed using the Hamilton Depression Rating Scale-17 (HAMD-17), the Montreal Cognitive Assessment (MoCA), and the Movement Disorders Society Unified Parkinson's Rating Scale Part III (MDS-UPDRS-III), respectively. There were no significant differences between depressed and non-depressed PD patients for LC3-I, LC3-II, LC3-II/LC3-I and p62/SQSTM1. After controlling confounding variables, LC3-II/LC3-I showed an independent relationship with depressive symptoms in PD patients (Beta = 10.082, t = 2.483, p = 0.014). Moreover, in depressive PD patients, p62/SQSTM1 was associated with MoCA score (Beta = - 0.002, t = - 2.380, p = 0.020); Further, p62/SQSTM1 was related to naming ability; in addition, p62/SQSTM1 was independently associated with delayed recall (Beta = - 0.001, t = - 2.452, p = 0.017). LC3-II/LC3-I was related to depressive symptoms in PD patients. In depressive PD patients, p62/SQSTM1 was associated with cognitive function, especially naming ability and delayed recall.

Does treatment with autophagy-enhancers and/or ROS-scavengers alleviate behavioral and neurochemical consequences of low-dose rotenone-induced mild mitochondrial dysfunction in mice?

Bipolar-disorder's pathophysiology and the mechanism by which medications exert their beneficial effect is yet unknown, but others' and our data implicate patients' brain mitochondrial-dysfunction and its amendment by mood-stabilizers. We recently designed a novel mouse bipolar-disorder-like model using chronic administration of a low-dose of the oxidative-phosphorylation complex I inhibitor, rotenone. Four and eight weeks rotenone treatment induced manic- and depressive-like behavior, respectively, accompanied by mood-related neurochemical changes. Here we aimed to investigate whether each of the autophagy-enhancers lithium (a mood-stabilizer), trehalose and resveratrol and/or each of the reactive oxygen species (ROS)-scavengers, resveratrol and N-acetylcystein and/or the combinations lithium+resveratrol or trehalose+N-acetylcystein, can ameliorate behavioral and neurochemical consequences of neuronal mild mitochondrial-dysfunction. We observed that lithium, trehalose and N-acetylcystein reversed rotenone-induced manic-like behavior as well as deviations in protein levels of mitochondrial complexes and the autophagy marker LC3-II. This raises the possibility that mild mitochondrial-dysfunction accompanied by impaired autophagy and a very mild increase in ROS levels are related to predisposition to manic-like behavior. On the other hand, although, as expected, most of the drugs tested eliminated the eight weeks rotenone-induced increase in protein levels of all hippocampal mitochondrial complexes, only lithium ubiquitously ameliorated the depressive-like behaviors. We cautiously deduce that aberrant autophagy and/or elevated ROS levels are not involved in predisposition to the depressive phase of bipolar-like behavior. Rather, that amending the depressive-like characteristics requires different mitochondria-related interventions. The latter might be antagonizing N-methyl-D-aspartate receptors (NMDARs), thus protecting from disruption of mitochondrial calcium homeostasis and its detrimental consequences. In conclusion, our findings suggest that by-and-large, among the autophagy-enhancers and ROS-scavengers tested, lithium is the most effective in counteracting rotenone-induced changes. Trehalose and N-acetylcystein may also be effective in attenuating manic-like behavior.

Metabolic Associated Fatty Liver Disease as a Risk Factor for the Development of Central Nervous System Disorders

MAFLD/NAFLD is the most ordinary liver disease categorized by hepatic steatosis with the increase of surplus fat in the liver and metabolic liver dysfunction, which is associated with bigger mortality and a high medical burden. An association between MAFLD/NAFLD and central nervous system disorders including psychological disorders has been demonstrated. Additionally, MAFLD/NAFLD has been correlated with various types of neurodegenerative disorders such as amyotrophic lateral sclerosis or Parkinson’s disease. Contrasted to healthy controls, patients with MAFLD/NAFLD have a greater prevalence risk of extrahepatic complications within multiple organs. Dietary interventions have emerged as effective strategies for MAFLD/NAFLD. The PI3K/AKT/mTOR signaling pathway involved in the regulation of Th17/Treg balance might promote the pathogenesis of several diseases including MAFLD/NAFLD. As extrahepatic complications may happen across various organs including CNS, cooperative care with individual experts is also necessary for managing patients with MAFLD/NAFLD.

Disaccharide Trehalose in Experimental Therapies for Neurodegenerative Disorders: Molecular Targets and Translational Potential

Induction of autophagy is a prospective approach to the treatment of neurodegeneration. In the recent decade, trehalose attracted special attention. It is an autophagy inducer with negligible adverse effects and is approved for use in humans according to FDA requirements. Trehalose has a therapeutic effect in various experimental models of diseases. This glucose disaccharide with a flexible α-1-1'-glycosidic bond has unique properties: induction of mTOR-independent autophagy (with kinase AMPK as the main target) and a chaperone-like effect on proteins imparting them natural spatial structure. Thus, it can reduce the accumulation of neurotoxic aberrant/misfolded proteins. Trehalose has an anti-inflammatory effect and inhibits detrimental oxidative stress partially owing to the enhancement of endogenous antioxidant defense represented by the Nrf2 protein. The disaccharide activates lysosome and autophagosome biogenesis pathways through the protein factors TFEB and FOXO1. Here we review various mechanisms of the neuroprotective action of trehalose and touch on the possibility of pleiotropic effects. Current knowledge about specific features of trehalose pharmacodynamics is discussed. The neuroprotective effects of trehalose in animal models of major neurodegenerative disorders such as Alzheimer's, Parkinson's, and Huntington's diseases are examined too. Attention is given to translational transition to clinical trials of this drug, especially oral and parenteral routes of administration. Besides, the possibility of enhancing the therapeutic benefit via a combination of mTOR-dependent and mTOR-independent autophagy inducers is analyzed. In general, trehalose appears to be a promising multitarget tool for the inhibition of experimental neurodegeneration and requires thorough investigation of its clinical capabilities.

Trehalose ameliorates prodromal non-motor deficits and aberrant protein accumulation in a rotenone-induced mouse model of Parkinson's disease

Trehalose has been recently revealed as an attractive candidate to prevent and modify Parkinson's disease (PD) progression by regulating autophagy; however, studies have only focused on the reduction of motor symptoms rather than the modulation of disease course from prodromal stage. This study aimed to evaluate whether trehalose has a disease-modifying effect at the prodromal stage before the onset of a motor deficit in 8-week-old male C57BL/6 mice exposed to rotenone. We found significant decrease in tyrosine hydroxylase immunoreactivity in the substantia nigra and motor dysfunction after 2 weeks rotenone treatment. Mice exposed to rotenone for a week showed an accumulation of protein aggregates in the brain and prodromal non-motor deficits, such as depression and olfactory dysfunction, prior to motor deficits. Trehalose significantly improved olfactory dysfunction and depressive-like behaviors and markedly reduced α-synuclein and p62 deposition in the brain. Trehalose further ameliorated motor impairment and loss of nigral tyrosine hydroxylase-positive cells in rotenone-treated mice. We demonstrated that prodromal non-motor signs in a rotenone-induced PD mouse model are associated with protein aggregate accumulation in the brain and that an autophagy inducer could be valuable to prevent PD progression from prodromal stage by regulating abnormal protein accumulation.

Low-Dose Aspirin Augments the Anti-Inflammatory Effects of Low-Dose Lithium in Lipopolysaccharide-Treated Rats

Mounting evidence suggests that immune-system dysfunction and inflammation play a role in the pathophysiology and treatment of mood-disorders in general and of bipolar disorder in particular. The current study examined the effects of chronic low-dose aspirin and low-dose lithium (Li) treatment on plasma and brain interleukin-6 and tumor necrosis factor-α production in lipopolysaccharide (LPS)-treated rats. Rats were fed regular or Li-containing food (0.1%) for six weeks. Low-dose aspirin (1 mg/kg) was administered alone or together with Li. On days 21 and 42 rats were injected with 1 mg/kg LPS or saline. Two h later body temperature was measured and rats were sacrificed. Blood samples, the frontal-cortex, hippocampus, and the hypothalamus were extracted. To assess the therapeutic potential of the combined treatment, rats were administered the same Li + aspirin protocol without LPS. We found that the chronic combined treatment attenuated LPS-induced hypothermia and significantly reduced plasma and brain cytokine level elevation, implicating the potential neuroinflammatory diminution purportedly present among the mentally ill. The combined treatment also significantly decreased immobility time and increased struggling time in the forced swim test, suggestive of an antidepressant-like effect. This preclinical evidence provides a potential approach for treating inflammation-related mental illness.

The different autophagy degradation pathways and neurodegeneration

The term autophagy encompasses different pathways that route cytoplasmic material to lysosomes for degradation and includes macroautophagy, chaperone-mediated autophagy, and microautophagy. Since these pathways are crucial for degradation of aggregate-prone proteins and dysfunctional organelles such as mitochondria, they help to maintain cellular homeostasis. As post-mitotic neurons cannot dilute unwanted protein and organelle accumulation by cell division, the nervous system is particularly dependent on autophagic pathways. This dependence may be a vulnerability as people age and these processes become less effective in the brain. Here, we will review how the different autophagic pathways may protect against neurodegeneration, giving examples of both polygenic and monogenic diseases. We have considered how autophagy may have roles in normal CNS functions and the relationships between these degradative pathways and different types of programmed cell death. Finally, we will provide an overview of recently described strategies for upregulating autophagic pathways for therapeutic purposes.

Autophagy as a gateway for the effects of methamphetamine: From neurotransmitter release and synaptic plasticity to psychiatric and neurodegenerative disorders

As a major eukaryotic cell clearing machinery, autophagy grants cell proteostasis, which is key for neurotransmitter release, synaptic plasticity, and neuronal survival. In line with this, besides neuropathological events, autophagy dysfunctions are bound to synaptic alterations that occur in mental disorders, and early on, in neurodegenerative diseases. This is also the case of methamphetamine (METH) abuse, which leads to psychiatric disturbances and neurotoxicity. While consistently altering the autophagy machinery, METH produces behavioral and neurotoxic effects through molecular and biochemical events that can be recapitulated by autophagy blockade. These consist of altered physiological dopamine (DA) release, abnormal stimulation of DA and glutamate receptors, as well as oxidative, excitotoxic, and neuroinflammatory events. Recent molecular insights suggest that METH early impairs the autophagy machinery, though its functional significance remains to be investigated. Here we discuss evidence suggesting that alterations of DA transmission and autophagy are intermingled within a chain of events underlying behavioral alterations and neurodegenerative phenomena produced by METH. Understanding how METH alters the autophagy machinery is expected to provide novel insights into the neurobiology of METH addiction sharing some features with psychiatric disorders and parkinsonism.

Mitochondrial and Autophagic Regulation of Adult Neurogenesis in the Healthy and Diseased Brain

Adult neurogenesis is a highly regulated process during which new neurons are generated from neural stem cells in two discrete regions of the adult brain: the subventricular zone of the lateral ventricle and the subgranular zone of the dentate gyrus in the hippocampus. Defects of adult hippocampal neurogenesis have been linked to cognitive decline and dysfunction during natural aging and in neurodegenerative diseases, as well as psychological stress-induced mood disorders. Understanding the mechanisms and pathways that regulate adult neurogenesis is crucial to improving preventative measures and therapies for these conditions. Accumulating evidence shows that mitochondria directly regulate various steps and phases of adult neurogenesis. This review summarizes recent findings on how mitochondrial metabolism, dynamics, and reactive oxygen species control several aspects of adult neural stem cell function and their differentiation to newborn neurons. It also discusses the importance of autophagy for adult neurogenesis, and how mitochondrial and autophagic dysfunction may contribute to cognitive defects and stress-induced mood disorders by compromising adult neurogenesis. Finally, I suggest possible ways to target mitochondrial function as a strategy for stem cell-based interventions and treatments for cognitive and mood disorders.

Molecular Basis of Neuronal Autophagy in Ageing: Insights from Caenorhabditis elegans

Autophagy is an evolutionarily conserved degradation process maintaining cell homeostasis. Induction of autophagy is triggered as a response to a broad range of cellular stress conditions, such as nutrient deprivation, protein aggregation, organelle damage and pathogen invasion. Macroautophagy involves the sequestration of cytoplasmic contents in a double-membrane organelle referred to as the autophagosome with subsequent degradation of its contents upon delivery to lysosomes. Autophagy plays critical roles in development, maintenance and survival of distinct cell populations including neurons. Consequently, age-dependent decline in autophagy predisposes animals for age-related diseases including neurodegeneration and compromises healthspan and longevity. In this review, we summarize recent advances in our understanding of the role of neuronal autophagy in ageing, focusing on studies in the nematode Caenorhabditis elegans.

Role of BDNF-mTORC1 Signaling Pathway in Female Depression

Depression is a common psychological and mental disorder, characterized by low mood, slow thinking and low will, and even suicidal tendencies in severe cases. It imposes a huge mental and economic burden on patients and their families, and its prevention and treatment have become an urgent public health problem. It is worth noting that there is a significant gender difference in the incidence of depression. Studies have shown that females are far more likely to suffer from depression than males, confirming a close relationship between estrogen and the onset of depression. Moreover, recent studies suggest that the brain-derived neurotrophic factor- (BDNF-) mammalian target of rapamycin complex-1 (mTORC1) signaling pathway is a crucial target pathway for improving depression and mediates the rapid antidepressant-like effects of various antidepressants. However, it is not clear whether the BDNF-mTORC1 signaling pathway mediates the regulation of female depression and how to regulate female depression. Hence, we focused on the modulation of estrogen-BDNF-mTORC1 signaling in depression and its possible mechanisms in recent years.

Identification of the antidepressive properties of C1, a specific inhibitor of Skp2, in mice

We have reported that SMIP004, an inhibitor of S-phase kinase-associated protein 2 (Skp2), displays antidepressant-like activities in stress-naïve and chronically stressed mice. Here, we investigated the antidepressant-like effect of C1, another inhibitor of Skp2, in mouse models following acute or chronic drug administration at different doses and treatment times by using the tail suspension test (TST), forced swimming test (FST), and social interaction test (SIT). The time- and dose-dependent results showed that the antidepressant-like effect of C1 occurred 8 days after the drug treatment, and C1 produced antidepressant-like activities at the dose of 5 and 10 but not 1 mg/kg in male or female mice. C1 administration (5 mg/kg) also induced antidepressant-like effects in stress-naïve mice in a three-times administration mode within 24 h (24, 5, and 1 h before the test) but not in an acute administration mode (1 h before the test). The C1 and fluoxetine co-administration produced additive effect on depression-like behaviors in stress-naïve mice. The antidepressant-like effect of C1 was not associated with the change in locomotor activity, as no increased locomotor activity was observed in different treatment modes. Furthermore, the long-term C1 treatment (5 mg/kg) was found to ameliorate the depression-like behaviors in chronic social defeat stress-exposed mice, suggesting that C1 can produce antidepressant-like actions in stress conditions. Since C1 is a specific inhibitor of Skp2, our results demonstrate that inhibition of Skp2 might be a potential strategy for the treatment of depression, and Skp2 may be potential target for the development of novel antidepressants.

Autophagy status as a gateway for stress-induced catecholamine interplay in neurodegeneration

The catecholamine-containing brainstem nuclei locus coeruleus (LC) and ventral tegmental area (VTA) are critically involved in stress responses. Alterations of catecholamine systems during chronic stress may contribute to neurodegeneration, including cognitive decline. Stress-related catecholamine alterations, while contributing to anxiety and depression, might accelerate neuronal degeneration by increasing the formation of toxic dopamine and norepinephrine by-products. These, in turn, may impair proteostasis within a variety of cortical and subcortical areas. In particular, the molecular events governing neurotransmission, neuroplasticity, and proteostasis within LC and VTA affect a variety of brain areas. Therefore, we focus on alterations of autophagy machinery in these nuclei as a relevant trigger in this chain of events. In fact, these catecholamine-containing areas are mostly prone to autophagy-dependent neurodegeneration. Thus, we propose a dynamic hypothesis according to which stress-induced autophagy alterations within the LC-VTA network foster a cascade towards early neurodegeneration within these nuclei.

The Role of Mitochondria in Mood Disorders: From Physiology to Pathophysiology and to Treatment

Mitochondria are cellular organelles involved in several biological processes, especially in energy production. Several studies have found a relationship between mitochondrial dysfunction and mood disorders, such as major depressive disorder and bipolar disorder. Impairments in energy production are found in these disorders together with higher levels of oxidative stress. Recently, many agents capable of enhancing antioxidant defenses or mitochondrial functioning have been studied for the treatment of mood disorders as adjuvant therapy to current pharmacological treatments. A better knowledge of mitochondrial physiology and pathophysiology might allow the identification of new therapeutic targets and the development and study of novel effective therapies to treat these specific mitochondrial impairments. This could be especially beneficial for treatment-resistant patients. In this article, we provide a focused narrative review of the currently available evidence supporting the involvement of mitochondrial dysfunction in mood disorders, the effects of current therapies on mitochondrial functions, and novel targeted therapies acting on mitochondrial pathways that might be useful for the treatment of mood disorders.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Autophagy in the Regulation of Tissue Differentiation and Homeostasis

Autophagy is a constitutive pathway that allows the lysosomal degradation of damaged components. This conserved process is essential for metabolic plasticity and tissue homeostasis and is crucial for mammalian post-mitotic cells. Autophagy also controls stem cell fate and defective autophagy is involved in many pathophysiological processes. In this review, we focus on established and recent breakthroughs aimed at elucidating the impact of autophagy in differentiation and homeostasis maintenance of endothelium, muscle, immune system, and brain providing a suitable framework of the emerging results and highlighting the pivotal role of autophagic response in tissue functions, stem cell dynamics and differentiation rates.

Autophagy in Neuronal Development and Plasticity

Autophagy is a highly conserved intracellular clearance pathway in which cytoplasmic contents are trafficked to the lysosome for degradation. Within neurons, it helps to remove damaged organelles and misfolded or aggregated proteins and has therefore been the subject of intense research in relation to neurodegenerative disease. However, far less is understood about the role of autophagy in other aspects of neuronal physiology. Here we review the literature on the role of autophagy in maintaining neuronal stem cells and in neuronal plasticity in adult life and we discuss how these contribute to structural and functional deficits observed in a range of human disorders.

Rapid action of mechanism investigation of Yixin Ningshen tablet in treating depression by combinatorial use of systems biology and bioinformatics tools

ETHNOPHARMACOLOGICAL RELEVANCE

Yixin Ningshen tablet is a CFDA-approved TCM formula for treating depression clinically. However, little is known about its active compounds and related potential target proteins, so far, no researches have been performed to investigate its mechanism of action for the treatment of depression.

AIM OF THE STUDY

Here we develop an original bioinformatics pipeline composed of text mining tools, database querying and systems biology combinatorial analysis, which is applied to rapidly explore the mechanism of action of Yixin Ningshen tablet in treating depression.

MATERIALS AND METHODS

Text mining and database query were applied to identify active compounds in Yixin Ningshen tablet for the treatment of depression. Then SwissTargetPrediction was used to predict their potential target proteins. PubMed was retrieved to summarize known depression related systems biology results. Ingenuity Pathway Analysis (IPA) tools and STRING were applied to construct a compound-target protein-gene protein-differential protein-differential metabolite network with the integration of compound-target interaction and systems biology results, as well as enrich the target proteins related pathways. ChEMBL and CDOCKER were used to validate the compound-target interactions.

RESULTS

62 active compounds and their 286 potential target proteins were identified in Yixin Ningshen tablet for the treatment of depression. The construction of compound-target protein-gene protein-differential protein-differential metabolite network shrinked the number of potential target proteins from 286 to 133. Pathway enrichment analysis of target proteins indicated that Neuroactive ligand-receptor interaction, Calcium signaling pathway, Serotonergic synapse, cAMP signaling pathway and Gap junction were the common primary pathways regulated by both Yixin Ningshen Tablet and anti-depressant drugs, and MAPK, Relaxin, AGE-RAGE, Estrogen, HIF-1, Jak-STAT signaling pathway, Endocrine resistance, Arachidonic acid metabolism and Regulation of actin cytoskeleton were the specifically main pathways regulated by Yixin Ningshen tablet for the treatment of depression. Further validations based on references and molecular docking results demonstrated that Yixin Ningshen tablet could primarily target MAPT, CHRM1 and DRD1, thus regulating serotonergic neurons, cholinergic transmission, norepinephrine and dopamine reuptake for the treatment of depression.

CONCLUSIONS

This study displays the power of extensive mining of public data and bioinformatical repositories to provide answers for a specific pharmacological question. It furthermore demonstrates how the usage of such a combinatorial approach is advantageous for the biologist in terms of experimentation time and costs.

A Novel Cosegregating DCTN1 Splice Site Variant in a Family with Bipolar Disorder May Hold the Key to Understanding the Etiology

A novel cosegregating splice site variant in the Dynactin-1 (DCTN1) gene was discovered by Next Generation Sequencing (NGS) in a family with a history of bipolar disorder (BD) and major depressive diagnosis (MDD). Psychiatric illness in this family follows an autosomal dominant pattern. DCTN1 codes for the largest dynactin subunit, namely p150^Glued, which plays an essential role in retrograde axonal transport and in neuronal autophagy. A GT→TT transversion in the DCTN1 gene, uncovered in the present work, is predicted to disrupt the invariant canonical splice donor site IVS22 + 1G > T and result in intron retention and a premature termination codon (PTC). Thus, this splice site variant is predicted to trigger RNA nonsense-mediated decay (NMD) and/or result in a C-terminal truncated p150^Glued protein (ct-p150^Glued), thereby negatively impacting retrograde axonal transport and neuronal autophagy. BD prophylactic medications, and most antipsychotics and antidepressants, are known to enhance neuronal autophagy. This variant is analogous to the dominant-negative GLUED Gl¹ mutation in Drosophila, which is responsible for a neurodegenerative phenotype. The newly identified variant may reflect an autosomal dominant cause of psychiatric pathology in this affected family. Factors that affect alternative splicing of the DCTN1 gene, leading to NMD and/or ct-p150^Glued, may be of fundamental importance in contributing to our understanding of the etiology of BD as well as MDD.

Sugars and Sweeteners: Structure, Properties and In Silico Modeling

Several studies report the effects of excessive use of sugars and sweeteners in the diet. These include obesity, cardiac diseases, diabetes, and even lymphomas, leukemias, cancers of the bladder and brain, chronic fatigue syndrome, Parkinson's disease, Alzheimer's disease, multiple sclerosis, autism, and systemic lupus. On the other hand, each sugar and sweetener has a distinct metabolic assimilation process, and its chemical structure plays an important role in this process. Several scientific papers present the biological effects of the sugars and sweeteners in relation to their chemical structure. One important issue dealing with the sugars is the degree of similarity in their structures, focusing mostly on optical isomerism. Finding and developing new sugars and sweeteners with desired properties is an emerging research area, in which in silico approaches play an important role.

SUMO conjugation as regulator of the glucocorticoid receptor-FKBP51 cellular response to stress

In order to adequately respond to stressful stimuli, glucocorticoids (GCs) target almost every tissue of the body. By exerting a negative feedback loop in the hypothalamic-pituitary-adrenal (HPA) axis GCs inhibit their own synthesis and restore homeostasis. GCs actions are mostly mediated by the GC receptor (GR), a member of the nuclear receptor superfamily. Alterations of the GR activity have been associatedto different diseases including mood disorders and can lead to severe complication. Therefore, understanding the molecular complexity of GR modulation is mandatory for the development of new and effective drugs for treating GR-associated disorders. FKBP51 is a GR chaperone that has gained much attention because it is a strong inhibitor of GR activity and has a crucial role in psychiatric diseases. Both GR and FKBP51 activity are regulated by SUMOylation, a posttranslational (PTM). In this review, we focus on the impact of SUMO-conjugation as a regulator of this pathway.

BDNF-TrkB pathway mediates antidepressant-like roles of H2 S in diabetic rats via promoting hippocampal autophagy

Hydrogen sulfide (H₂ S) plays antidepressant-like roles in diabetic rats. However, the underlying mechanisms remain unclear. Brain-derived neurotropic factor (BDNF), a neurotrophic factor, plays important regulatory roles in depression by its high-affinity tropomysin-related kinase B (TrkB) receptor. Autophagy also is implicated in modulation of depression. Previous work confirmed the modulatory roles of H₂ S in BDNF protein expression and autophagy. Thus, in this study, we explored whether the BDNF-TrkB pathway mediates the antidepressant-like effects of H₂ S in diabetic rats and whether this process is achieved via promoting hippocampal autophagy. We demonstrated that H₂ S upregulated the expressions of BDNF and p-TrkB proteins in the hippocampus of streptozotocin (STZ)-induced diabetic rats. K252a (an inhibitor of BDNF-TrkB pathway) reversed the antidepressant-like roles of H₂ S, as evidenced by the tail suspension, forced swimming, novelty suppressed feeding, and elevated plus-maze tests. Furthermore, K252a abolished H₂ S-promoted hippocampal autophagy in diabetic rats, as evidenced by a decrease in the number of autolysosome, downregulation of Beclin-1 (a regulator of autophagy in the early stage of the formation of autophagosomal membranes and its level is positively correlated with autophagic activity) expression, and upregulation of P62 (a substrate of autophagic degradation and its level is inversely correlated with autophagic activity) expression, in the hippocampus of rats co-treated with NaHS and STZ. Taken together, these data indicated that the BDNF-TrkB pathway mediates the antidepressant-like roles of H₂ S in diabetic rats by enhancing hippocampal autophagy.

Identification of PIKfyve kinase as a target in multiple myeloma

The cellular cytotoxicity of APY0201, a PIKfyve inhibitor, against multiple myeloma was initially identified in an unbiased in vitro chemical library screen. The activity of APY0201 was confirmed in all 25 cell lines tested and in 40% of 100 ex vivo patient-derived primary samples, with increased activity in primary samples harboring trisomies and lacking t(11;14). The broad anti-multiple myeloma activity of PIKfyve inhibitors was further demonstrated in confirmatory screens and showed the superior potency of APY0201 when compared to the PIKfyve inhibitors YM201636 and apilimod, with a mid-point half maximal effective concentration (EC₅₀) at nanomolar concentrations in, respectively, 65%, 40%, and 5% of the tested cell lines. Upregulation of genes in the lysosomal pathway and increased cellular vacuolization were observed in vitro following APY0201 treatment, although these cellular effects did not correlate well with responsiveness. We confirm that PIKfyve inhibition is associated with activation of the transcription factor EB, a master regulator of lysosomal biogenesis and autophagy. Furthermore, we established an assay measuring autophagy as a predictive marker of APY0201 sensitivity. Overall, these findings indicate promising activity of PIKfyve inhibitors secondary to disruption of autophagy in multiple myeloma and suggest a strategy to enrich for likely responders.

Activation of autophagy in the retina after optic nerve crush injury in rats

AIM

To investigate the activation of autophagy in rat retina after optic nerve crush (ONC) and evaluate its relationship with apoptosis of retinal ganglion cells (RGCs).

METHODS

The ONC model was established. Western blots were performed to investigate expression of p62, LC3 and Beclin-1. Transmission electron microscopy was performed to discover the autophagosomes in the retina after ONC. Immunohistochemistry was used to confirm the distribution of LC3. TUNEL was performed to confirm the relationship between autophagy and RGC apoptosis.

RESULTS

p62/Beclin-1 ratio was declined shortly after ONC until to day 7 after ONC and then restored to a normal level at day 21. There was an opposite change in the LC3-II/LC3I ratio in the retina compared to the p62/Beclin-1 ratio. Increased autophagosomes were found after ONC using transmission electron microscopy, and most of the LC3-stained cells were colocalized with RGCs and Müller cells. More LC3-immunoreactive cells and apoptotic RGCs were found on day 7 following ONC.

CONCLUSION

Possible activation of autophagy in RGCs after ONC; autophagy mainly occurred in RGCs and Müller cells, and the apoptosis of RGCs after ONC may be partly associated with autophagic activation.

Trehalose as glucose surrogate in proliferation and cellular mobility of adult neural progenitor cells derived from mouse hippocampus

The disaccharide trehalose (TRE) represents a natural energy supply for distinct non-mammalian species. Evidence has shown that TRE impacts on various properties including the stabilization of protein structure and cell membranes, which are important neuroprotective features against neurodegeneration. In this study, we tested the specific effect of TRE on cell proliferation and mobilization using an established experimental paradigm of adult neural progenitor cells (NPCs) derived from murine hippocampus. NPC proliferation, both measured by growth curve analysis over 25 days and by bromodeoxyuridine (BrdU) incorporation, was not altered by adding TRE instead of GLC to the culture media. Using Boyden chamber experiments, the mobility in regular glucose-containing media did not differ from glucose-free TRE-supplemented media. Our observation suggests that TRE has the capacity to replace glucose (GLC) as energy source in neural cells in our experimental paradigm.

Dual Role of Autophagy in Diseases of the Central Nervous System

Autophagy is a vital lysosomal degradation and recycling pathway in the eukaryotic cell, responsible for maintaining an intricate balance between cell survival and cell death, necessary for neuronal survival and function. This dual role played by autophagy raises the question whether this process is a protective or a destructive pathway, the contributor of neuronal cell death or a failed attempt to repair aberrant processes? Deregulated autophagy at different steps of the pathway, whether excessive or downregulated, has been proposed to be associated with neurodegenerative disorders such as Alzheimer's-, Huntington's-, and Parkinson's-disease, known for their intracellular accumulation of protein aggregates. Recent observations of impaired autophagy also appeared in psychiatric disorders such as schizophrenia and bipolar disorder suggesting an additional contribution to the pathophysiology of mental illness. Here we review the current understanding of autophagy's role in various neuropsychiatric disorders and, hitherto, the prevailing new potential autophagy-related therapeutic strategies for their treatment.

Trehalose elevates brain zinc levels following controlled cortical impact in a mouse model of traumatic brain injury

Zinc (Zn) deficiency is a clinical consequence of brain injury that can result in neuropathological outcomes that are exacerbated with age. Here, we present laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) imaging data showing modulation of brain Zn levels by the disaccharide trehalose in aged mice following a controlled cortical impact model of traumatic brain injury. In this proof-of-concept study, trehalose induced an increase in brain zinc levels, providing important preliminary data for larger studies using this simple carbohydrate as a modulator of this essential micronutrient in traumatic brain injury. Our results may have further implications for the treatment of a variety of neurodegenerative diseases and other disorders of the nervous system.

FePt/GO Nanosheets Suppress Proliferation, Enhance Radiosensitization and Induce Autophagy of Human Non-Small Cell Lung Cancer Cells

With the advancement of nanotechnology, various nanocomposites have been applied in the diagnostics and treatment of cancer. We synthetized FePt nanoparticles which were assembled on the surface of graphene oxide (GO). These novel FePt/GO nanosheets simultaneously act as a chemotherapy drug and enhance radiosensitivity. In this study, transmission electron microscope, dynamic light scattering, X-ray photoelectron spectroscope and Fourier transform infrared spectroscopy were used to characterize surface morphology and chemical composition of FePt/GO nanosheets (NSs). Their cytotoxicity in various cancer and normal cells was evaluated by cell counting kit-8 assay, and their effects on radiosensitization were determined by colony formation assay. To explore the underlying mechanisms, we measured the intracellular reactive oxygen species levels and autophagy formation. Monodansylcadaverine-staining, Western Blotting and ultrastructure analysis were utilized to assess autophagy. The results demonstrated that FePt/GO NSs not only selectively suppressed the proliferation of cancer cells, but also increased their radiosensitization. Moreover, FePt/GO NSs induced autophagy, which might result in promoted sensibilization of radiotherapy. In conclusion, with good safety and efficacy, FePt/GO NSs are safe and effective to suppress proliferation, enhance radiosensitization and induce autophagy of human non-small cell lung cancer cells. They are potential for the treatment of lung cancer.

Cytotoxic Activity of the Histone Deacetylase 3-Selective Inhibitor Pojamide on MDA-MB-231 Triple-Negative Breast Cancer Cells

We examined the effects of the ferrocene-based histone deacetylase-3 inhibitor Pojamide (N¹-(2-aminophenyl)-N⁸-ferrocenyloctanediamide) and its two derivatives N¹-(2-aminophenyl)-N⁶-ferrocenyladipamide and N¹-(2-aminophenyl)-N⁸-ferroceniumoctanediamide tetrafluoroborate on triple-negative MDA-MB-231 breast cancer cells. Viability/growth assays indicated that only the first two compounds at 70 μM concentration caused an approximate halving of cell number after 24 h of exposure, whereas the tetrafluoroborate derivative exerted no effect on cell survival nor proliferation. Flow cytometric and protein blot analyses were performed on cells exposed to both Pojamide and the ferrocenyladipamide derivative to evaluate cell cycle distribution, apoptosis/autophagy modulation, and mitochondrial metabolic state in order to assess the cellular basis of the cytotoxic effect. The data obtained show that the cytotoxic effect of the two deacetylase inhibitors may be ascribed to the onset of non-apoptotic cell death conceivably linked to a down-regulation of autophagic processes and an impairment of mitochondrial function with an increase in intracellular reactive oxygen species. Our work expands the list of autophagy-regulating drugs and also provides a further example of the role played by the inhibition of autophagy in breast cancer cell death. Moreover, the compounds studied may represent attractive and promising targets for subsequent molecular modeling for anti-neoplastic agents in malignant breast cancer.

Is There a Role of Autophagy in Depression and Antidepressant Action?

Autophagy has been recognized as evolutionary conserved intracellular pathway that ensures energy, organelle, and protein homeostasis through lysosomal degradation of damaged macromolecules and organelles. It is activated under various stress situations, e.g., food deprivation or proteotoxic conditions. Autophagy has been linked to several diseases, more recently also including stress-related diseases such as depression. A growing number of publications report on the role of autophagy in neurons, also referred to as "neuronal autophagy" on the one hand, and several studies describe effects of antidepressants-or of compounds that exert antidepressant-like actions-on autophagy on the other hand. This minireview highlights the emerging evidence for the involvement of autophagy in the pathology and treatment of depression and discusses current limitations as well as potential avenues for future research.

Effect of Trehalose Supplementation on Autophagy and Cystogenesis in a Mouse Model of Polycystic Kidney Disease

Autophagy impairment has been demonstrated in the pathogenesis of autosomal dominant polycystic kidney disease (ADPKD) and could be a new target of treatment. Trehalose is a natural, nonreducing disaccharide that has been shown to enhance autophagy. Therefore, we investigated whether trehalose treatment reduces renal cyst formation in a Pkd1-hypomorphic mouse model. Pkd1 miRNA transgenic (Pkd1 miR Tg) mice and wild-type littermates were given drinking water supplemented with 2% trehalose from postnatal day 35 to postnatal day 91. The control groups received pure water or 2% sucrose for the control of hyperosmolarity. The effect on kidney weights, cystic indices, renal function, cell proliferation, and autophagic activities was determined. We found that Pkd1 miR Tg mice had a significantly lower renal mRNA expression of autophagy-related genes, including atg5, atg12, ulk1, beclin1, and p62, compared with wild-type control mice. Furthermore, immunohistochemical analysis showed that cystic lining cells had strong positive staining for the p62 protein, indicating impaired degradation of the protein by the autophagy-lysosome pathway. However, trehalose treatment did not improve reduced autophagy activities, nor did it reduce relative kidney weights, plasma blood urea nitrogen levels, or cystatin C levels in Pkd1 miR Tg mice. Histomorphological analysis revealed no significant differences in the renal cyst index, fibrosis score, or proliferative score among trehalose-, sucrose-, and water-treated groups. Our results demonstrate that adding trehalose to drinking water does not modulate autophagy activities and renal cystogenesis in Pkd1-deficient mice, suggesting that an oral supplement of trehalose may not affect the progression of ADPKD.

SMAC Mimetics Induce Autophagy-Dependent Apoptosis of HIV-1-Infected Resting Memory CD4+ T Cells

Long-lived resting memory CD4+ T cells (TCM) are a major reservoir of latent HIV infection. We hypothesized that latent HIV-TCM cells are maintained by aberrant expression of cell survival factors, including XIAP, BIRC2/cIAP1, and beclin-1. DIABLO/SMAC mimetics are therapeutic agents that compromise cell survival by hijacking host apoptotic machinery. We found that DIABLO/SMAC mimetics (birinapant, GDC-0152, and embelin) selectively kill HIV-TCM without increasing virus production or targeting uninfected TCM. Treatment of HIV-TCM with DIABLO/SMAC mimetics promoted XIAP and BIRC2 degradation, which triggered autophagy and the formation of a cell death complex consisting of pro-apoptotic (FADD, RIPK1, RIPK3, and caspase 8) and autophagy (ATG5, ATG7, and SQSTM1) proteins. Genetic or pharmacological inhibition of autophagy induction, but not autophagy-mediated degradation, abrogated this interaction and subsequent cell death. Our findings identify a mechanism whereby DIABLO/SMAC mimetics exploit autophagy and apoptotic machinery to selectively induce killing of HIV-TCM without viral reactivation while sparing uninfected cells.

mTOR-Related Brain Dysfunctions in Neuropsychiatric Disorders

The mammalian target of rapamycin (mTOR) is an ubiquitously expressed serine-threonine kinase, which senses and integrates several intracellular and environmental cues to orchestrate major processes such as cell growth and metabolism. Altered mTOR signalling is associated with brain malformation and neurological disorders. Emerging evidence indicates that even subtle defects in the mTOR pathway may produce severe effects, which are evident as neurological and psychiatric disorders. On the other hand, administration of mTOR inhibitors may be beneficial for a variety of neuropsychiatric alterations encompassing neurodegeneration, brain tumors, brain ischemia, epilepsy, autism, mood disorders, drugs of abuse, and schizophrenia. mTOR has been widely implicated in synaptic plasticity and autophagy activation. This review addresses the role of mTOR-dependent autophagy dysfunction in a variety of neuropsychiatric disorders, to focus mainly on psychiatric syndromes including schizophrenia and drug addiction. For instance, amphetamines-induced addiction fairly overlaps with some neuropsychiatric disorders including neurodegeneration and schizophrenia. For this reason, in the present review, a special emphasis is placed on the role of mTOR on methamphetamine-induced brain alterations.

Inhibition of mTORC1 Signaling Reverts Cognitive and Affective Deficits in a Mouse Model of Parkinson's Disease

Non-motor symptoms, including cognitive deficits and affective disorders, are frequently diagnosed in Parkinson’s disease (PD) patients and are only partially alleviated by dopamine replacement therapy. Here, we used a 6-hydroxydopamine (6-OHDA) mouse model of PD to examine the effects exerted on non-motor symptoms by inhibition of the mammalian target of rapamycin complex 1 (mTORC1), which is involved in the control of protein synthesis, cell growth, and metabolism. We show that rapamycin, which acts as an allosteric inhibitor of mTORC1, counteracts the impairment of novel object recognition. A similar effect is produced by PF-4708671, an inhibitor of the downstream target of mTORC1, ribosomal protein S6 kinase (S6K). Rapamycin is also able to reduce depression-like behavior in PD mice, as indicated by decreased immobility in the forced swim test. Moreover, rapamycin exerts anxiolytic effects, thereby reducing thigmotaxis in the open field and increasing exploration of the open arm in the elevated plus maze. In contrast to rapamycin, administration of PF-4708671 to PD mice does not counteract depression- and anxiety-like behaviors. Altogether, these results identify mTORC1 as a target for the development of drugs that, in combination with standard antiparkinsonian agents, may widen the efficacy of current therapies for the cognitive and affective symptoms of PD.

Nicotine alleviates chronic stress-induced anxiety and depressive-like behavior and hippocampal neuropathology via regulating autophagy signaling

Recently, we reported that chronic nicotine significantly improved chronic stress-induced impairments of cognition and the hippocampal synaptic plasticity in mice, however, the underlying mechanism still needs to be explored. In the present study, 32 male C57BL/6 mice were divided into four groups: control (CON), stress (CUS), stress with chronic nicotine administration (CUS + Nic) and chronic nicotine administration (Nic). The anxiety-like behavior and neuropathological alteration of DG neurons were examined. Moreover, PC12 cells were examined with corticosterone in the presence or absence of nicotine. Both cell viability and apoptosis were determined. When treated simultaneously with an unpredictable chronic mild stress (CUS), nicotine (0.2 mg/kg/d) attenuated behavioral deficits and neuropathological alterations of DG neurons. Moreover, Western blotting showed that chronic nicotine also elevated the level of autophagy makers including Beclin-1 and LC3 II triggered by CUS. In addition, concomitant treatment with nicotine (10 μM) significantly attenuated the loss of PC12 cell viability (p < .01) and apoptosis compared to that of corticosterone treatment alone. Besides, chronic nicotine also enhanced the protein and RNA expression levels of autophagy makers triggered by corticosterone, such as Beclin-1, LC3 II and p62/SQSTM1. However, the above improvements were significantly blocked by autophagy inhibitor 3-MA. Importantly, the activation of the PI3K/Akt/mTOR signaling was carefully tested to illuminate the effects of chronic nicotine. Consequently, chronic nicotine played a role of neuroprotection in either CUS mice or corticosterone cells associating with the enhancement of the autophagy signaling, which was involved in activating the PI3K/Akt/mTOR signaling.

mTOR Inhibition Mitigates Molecular and Biochemical Alterations of Vigabatrin-Induced Visual Field Toxicity in Mice

BACKGROUND

Gamma-vinyl-γ-aminobutyric acid (GABA) (vigabatrin) is an antiepileptic drug and irreversible GABA transaminase inhibitor associated with visual field impairment, which limits its clinical utility. We sought to relate altered visual evoked potentials associated with vigabatrin intake to transcriptional changes in the mechanistic target of rapamycin (mTOR) pathway and GABA receptors to expose further mechanisms of vigabatrin-induced visual field loss.

METHODS

Vigabatrin was administered to mice via an osmotic pump for two weeks to increase GABA levels. Visual evoked potentials were examined, eye samples were collected, and gene expression was measured by quantitative reverse transcription-polymerase chain reaction. Similarly, human retinal pigment epithelial cells (ARPE19) were exposed to vigabatrin and treated with mTOR inhibitors for mTOR pathway analysis and to assess alterations in organelle accumulation by microscopy.

RESULTS

Dysregulated expression of transcripts in the mTOR pathway, GABA_A/B receptors, metabotropic glutamate (Glu) receptors 1/6, and GABA/glutamate transporters in the eye were found in association with visual evoked potential changes during vigabatrin administration. Rrag genes were upregulated in both mouse eye and ARPE19 cells. Immunoblot of whole eye revealed greater than three fold upregulation of a 200 kDa band when immunoblotted for ras-related guanosine triphosphate binding D. Microscopy of ARPE19 cells revealed selective reversal of vigabatrin-induced organelle accumulation by autophagy-inducing drugs, notably Torin 2. Changes in the mTOR pathway gene expression, including Rrag genes, were corrected by Torin 2 in ARPE19 cells.

CONCLUSIONS

Our studies, indicating GABA-associated augmentation of RRAG and mTOR signaling, support further preclinical evaluation of mTOR inhibitors as a therapeutic strategy to potentially mitigate vigabatrin-induced ocular toxicity.

IP3 accumulation and/or inositol depletion: two downstream lithium's effects that may mediate its behavioral and cellular changes

Lithium is the prototype mood stabilizer but its mechanism is still unresolved. Two hypotheses dominate-the consequences of lithium's inhibition of inositol monophosphatase at therapeutically relevant concentrations (the 'inositol depletion' hypothesis), and of glycogen-synthase kinase-3. To further elaborate the inositol depletion hypothesis that did not decisively determine whether inositol depletion per se, or phosphoinositols accumulation induces the beneficial effects, we utilized knockout mice of either of two inositol metabolism-related genes-IMPA1 or SMIT1, both mimic several lithium's behavioral and biochemical effects. We assessed in vivo, under non-agonist-stimulated conditions, ³H-inositol incorporation into brain phosphoinositols and phosphoinositides in wild-type, lithium-treated, IMPA1 and SMIT1 knockout mice. Lithium treatment increased frontal cortex and hippocampal phosphoinositols labeling by several fold, but decreased phosphoinositides labeling in the frontal cortex of the wild-type mice of the IMPA1 colony strain by ~50%. Inositol metabolites were differently affected by IMPA1 and SMIT1 knockout. Inositoltrisphosphate administered intracerebroventricularly affected bipolar-related behaviors and autophagy markers in a lithium-like manner. Namely, IP₃ but not IP₁ reduced the immobility time of wild-type mice in the forced swim test model of antidepressant action by 30%, an effect that was reversed by an antagonist of all three IP₃ receptors; amphetamine-induced hyperlocomotion of wild-type mice (distance traveled) was 35% reduced by IP₃ administration; IP₃ administration increased hippocampal messenger RNA levels of Beclin-1 (required for autophagy execution) and hippocampal and frontal cortex protein levels ratio of Beclin-1/p62 by about threefold (p62 is degraded by autophagy). To conclude, lithium affects the phosphatidylinositol signaling system in two ways: depleting inositol, consequently decreasing phosphoinositides; elevating inositol monophosphate levels followed by phosphoinositols accumulation. Each or both may mediate lithium-induced behavior.

Lack of effect of chronic ketamine administration on depression-like behavior and frontal cortex autophagy in female and male ICR mice

The acute antidepressant effects of ketamine provide hope for the development of a fast acting approach to treat depression but the consequences of chronic treatment with ketamine are still unclear. One theory regarding the acute effect is that ketamine acts through activation of mTOR but chronic activation of mTOR may lead to reduced autophagy and reduced autophagy could have negative consequences on neuronal plasticity and survival and on affect. To study the interaction between chronic ketamine administration, autophagy and depression the present study tested the effects of 3 weeks daily administration of 5 or 10mg/kg ketamine in both female and male ICR mice on behavior in the open field and the forced swim test and on frontal cortex levels of beclin-1 and p62, two proteins that serve as markers of autophagy. The results show that acute administration of ketamine results in an antidepressant-like effect in the FST, chronic ketamine had no effects in the behavioral tests. There was no difference in the acute or chronic groups between female and male mice. Additionally, chronic ketamine did not alter frontal cortex levels of autophagy markers. The present study suggests that in ICR mice, chronic ketamine does not have the same clear effects that are seen after acute treatment. The lack of difference between females and males and the lack of effects on autophagy after chronic treatment is discussed.