Antidepressant drugs diversely affect autophagy pathways in astrocytes and neurons--dissociation from cholesterol homeostasis

Phosphatidic acid is involved in regulation of autophagy in neurons in vitro and in vivo

Major depressive disorder (MDD) is a common and severe psychiatric disease, which does not only lead to variety of neuropsychiatric symptoms, but unfortunately in a relatively large proportion of cases also to suicide. The pathogenesis of MDD still requires definition. We have previously shown that ceramide is increased in the blood plasma of patients with MDD. In mouse models of MDD, which are induced by treatment with corticosterone or application of chronic unpredictable stress, increased blood plasma ceramide also increased and caused an inhibition of phospholipase D in endothelial cells of the hippocampus and reduced phosphatidic acid levels in the hippocampus. Here, we demonstrated that corticosterone treatment of PC12 cells resulted in reduced cellular autophagy, which is corrected by treatment with phosphatidic acid. In vivo, treatment of mice with corticosterone or chronic unpredictable stress also reduced autophagy in hippocampus neurons. Autophagy was normalized upon i.v. injection of phosphatidic acid in these mouse models of MDD. In an attempt to identify targets of phosphatidic acid in neurons, we demonstrated that corticosterone reduced levels of the ganglioside GM1 in PC-12 cells and the hippocampus of mice, which were normalized by treatment of cells or i.v. injection of mice with phosphatidic acid. GM1 application also normalized autophagy in cultured neurons. Phosphatidic acid and GM1 corrected stress-induced alterations in behavior, i.e., mainly anxiety and anhedonia, in experimental MDD in mice. Our data suggest that phosphatidic acid may regulate via GM1 autophagy in neurons.

The Antidepressant Drug Amitriptyline Affects Human SH-SY5Y Neuroblastoma Cell Proliferation and Modulates Autophagy

Amitriptyline is a tricyclic antidepressant commonly used for depressive disorders and is prescribed off-label for several neurological conditions like neuropathic pain, migraines and anxiety. Besides their action on the reuptake of monoaminergic neurotransmitters, tricyclic antidepressants interact with several additional targets that may contribute to either therapeutic or adverse effects. Here, we investigated the effects of amitriptyline on proliferation and autophagy (i.e., an evolutionarily conserved catabolic pathway responsible for the degradation and recycling of cytoplasmic material) in human SH-SY5Y neuroblastoma cell cultures. The dose and time-dependent upregulation of the autophagy marker LC3II and the autophagy receptor p62, with the accumulation of LAMP1 positive compartments, were observed in SH-SY5Y cells exposed to the amitriptyline. These effects were accompanied by reduced cell viability and decreased clonogenic capacity, without a significant induction of apoptosis. Decrease viability and clonogenic activity were still observed in autophagy deficient Atg5-/- MEF and following pre-treatment of SH-SY5Y culture with the autophagy inhibitor chloroquine, suggesting that they were independent from autophagy modulation. Our findings demonstrate that amitriptyline acts on pathways crucial for cell and tissue homeostasis (i.e., autophagy and proliferation) and pose the basis for further studies on the potential therapeutic application of amitriptyline, as well as the consequences of its use for long-term treatments.

Acid sphingomyelinase inhibition induces cerebral angiogenesis post-ischemia/reperfusion in an oxidative stress-dependent way and promotes endothelial survival by regulating mitochondrial metabolism

Acid sphingomyelinase (ASM) inhibitors are widely used for the treatment of post-stroke depression. They promote neurological recovery in animal stroke models via neurorestorative effects. In a previous study, we found that antidepressants including amitriptyline, fluoxetine, and desipramine increase cerebral angiogenesis post-ischemia/reperfusion (I/R) in an ASM-dependent way. To elucidate the underlying mechanisms, we investigated the effects of the functional ASM inhibitor amitriptyline in two models of I/R injury, that is, in human cerebral microvascular endothelial hCMEC/D3 cells exposed to oxygen-glucose deprivation and in mice exposed to middle cerebral artery occlusion (MCAO). In addition to our earlier studies, we now show that amitriptyline increased mitochondrial reactive oxygen species (ROS) formation in hCMEC/D3 cells and increased ROS formation in the vascular compartment of MCAO mice. ROS formation was instrumental for amitriptyline's angiogenic effects. ROS formation did not result in excessive endothelial injury. Instead, amitriptyline induced a profound metabolic reprogramming of endothelial cells that comprised reduced endothelial proliferation, reduced mitochondrial energy metabolism, reduced endoplasmic reticulum stress, increased autophagy/mitophagy, stimulation of antioxidant responses and inhibition of apoptotic cell death. Specifically, the antioxidant heme oxygenase-1, which was upregulated by amitriptyline, mediated amitriptyline's angiogenic effects. Thus, heme oxygenase-1 knockdown severely compromised angiogenesis and abolished amitriptyline's angiogenic responses. Our data demonstrate that ASM inhibition reregulates a complex network of metabolic and mitochondrial responses post-I/R that contribute to cerebral angiogenesis without compromising endothelial survival.

Empagliflozin-activated AMPK elicits neuroprotective properties in reserpine-induced depression via regulating dynamics of hippocampal autophagy/inflammation and PKCζ-mediated neurogenesis

RATIONALE

Major depression has been an area of extensive research during the last decades, for it represents a leading cause of disability and suicide. The stark rise of depression rates influenced by life stressors, economic threats, pandemic era, and resistance to classical treatments, has made the disorder rather challenging. Adult hippocampal neurogenesis and plasticity are particularly sensitive to the dynamic interplay between autophagy and inflammation. In fact, the intricate balance between the two processes contributes to neuronal homeostasis and survival.

OBJECTIVES

Having demonstrated promising potentials in AMPK activation, a major metabolic sensor and autophagy regulator, empagliflozin (Empa) was investigated for possible antidepressant properties in the reserpine rat model of depression.

RESULTS

While the reserpine protocol elicited behavioral, biochemical, and histopathological changes relevant to depression, Empa outstandingly hindered these pathological perturbations. Importantly, hippocampal autophagic response markedly declined with reserpine which disrupted the AMPK/mTOR/Beclin1/LC3B machinery and, conversely, neuro-inflammation prevailed under the influence of the NLRP3 inflammasome together with oxidative/nitrative stress. Consequently, AMPK-mediated neurotrophins secretion obviously deteriorated through PKCζ/NF-κB/BDNF/CREB signal restriction. Empa restored hippocampal monoamines and autophagy/inflammation balance, driven by AMPK activation. By promoting the atypical PKCζ phosphorylation (Thr403) which subsequently phosphorylates NF-κB at Ser311, AMPK successfully reinforced BDNF/CREB signal and hippocampal neuroplasticity. The latter finding was supported by hippocampal CA3 toluidine blue staining to reveal intact neurons.

CONCLUSION

The current study highlights an interesting role for Empa as a regulator of autophagic and inflammatory responses in the pathology of depression. The study also pinpoints an unusual contribution for NF-κB in neurotrophins secretion via AMPK/PKCζ/NF-κB/BDNF/CREB signal transduction. Accordingly, Empa can have special benefits in diabetic patients with depressive symptoms.

LIMITATIONS

The influence of p-NF-κB (Ser311) on NLRP3 inflammasome assembly and activation has not been investigated, which can represent an interesting point for further research.

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.

Kaempferol-3-O-sophoroside (PCS-1) contributes to modulation of depressive-like behaviour in C57BL/6J mice by activating AMPK

BACKGROUND AND PURPOSE

Kaempferol-3-O-sophoroside (PCS-1) is the main component in Crocus sativus (Saffron), a herb with mood-enhancing properties. AMP-activated protein kinase (AMPK) is a potential therapeutic target for depression. This study explores the antidepressive-like properties of PCS-1 and its AMPK activation to confirm AMPK as a target for antidepression.

EXPERIMENTAL APPROACH

Corticosterone (CORT)-induced PC12 cell injury served as an in vitro model to evaluate the neuroprotective effect of PCS-1. Neuro-2a cells and primary neurons were utilized to evaluate the synaptogenesis role of PCS-1. CORT-induced mouse depression model and chronic unpredictable mild stress (CUMS) model were used to assess the antidepressive-like properties of PCS-1 through behavioural tests, magnetic resonance imaging, and biochemical index measurements. Western blot and immunofluorescence assays were used to study the mechanisms of PCS-1. Cellular thermal shift assay was used to confirm the binding target.

KEY RESULTS

PCS-1 (12.5-50 μM) ameliorated CORT-induced PC12 cell damage, oxidative stress and inflammation. PCS-1 alone promoted an increase in synapses in Neuro-2a cells and primary neurons. Oral administration of PCS-1 (10 and 20 mg·kg-1 ) ameliorated weight loss, dyskinesia, and hippocampal volume reduction induced by CORT and CUMS. PCS-1 bound to AMPK to improve the expression of brain-derived neurotrophic factor (BDNF) and induce autophagy.

CONCLUSION AND IMPLICATIONS

PCS-1 binds to AMPK to promote BDNF production and autophagy enhancement, ultimately achieving antidepressant effects. This study provides support for the clinical application of saffron petals and provides further evidence for AMPK as a potential target for antidepression.

Targeting mitophagy for depression amelioration: a novel therapeutic strategy

Major depressive disorder is a global psychiatric condition characterized by persistent low mood and anhedonia, which seriously jeopardizes the physical and mental well-being of affected individuals. While various hypotheses have been proposed to explicate the etiology of depression, the precise pathogenesis and effective treatment of this disorder remain elusive. Mitochondria, as the primary organelles responsible for cellular energy production, possess the ability to meet the essential energy demands of the brain. Research indicated that the accumulation of damaged mitochondria is associated with the onset of depression. Mitophagy, a type of cellular autophagy, specifically targets and removes excess or damaged mitochondria. Emerging evidence demonstrated that mitophagy dysfunction was involved in the progression of depression, and several pharmacological interventions that stimulating mitophagy exerted excellent antidepressant actions. We provided an overview of updated advancements on the regulatory mechanism of mitophagy and the mitophagy abnormality in depressed patients and animals, as well as in cell models of depression. Meanwhile, various therapeutic strategies to restore mitophagy for depression alleviation were also discussed in this review.

Role of Tyrosine Nitrosylation in Stress-Induced Major Depressive Disorder: Mechanisms and Implications

Major depressive disorder (MDD) has a lifetime prevalence of approximately 10% and is one of the most common diseases worldwide. Although many pathogenetic mechanisms of MDD have been proposed, molecular details and a unifying hypothesis of the pathogenesis of MDD remain to be defined. Here, we investigated whether tyrosine nitrosylation, which is caused by reaction of the C-atom 3 of the tyrosine phenol ring with peroxynitrate (ONOO-), plays a role in experimental MDD, because tyrosine nitrosylation may affect many cell functions altered in MDD. To this end, we induced stress through glucocorticoid application or chronic environmental unpredictable stress and determined tyrosine nitrosylation in the hippocampus through immuno-staining and ELISA. The role of catalases and peroxidases for tyrosine nitrosylation was measured using enzyme assays. We show that glucocorticoid- and chronic unpredictable environmental stress induced tyrosine nitrosylation in the hippocampus. Long-term treatment of stressed mice with the classical antidepressants amitriptyline or fluoxetine prevented tyrosine nitrosylation. Tyrosine nitrosylation was also prevented through i.v. application of anti-ceramide antibodies or recombinant ceramidase to neutralize or degrade, respectively, blood plasma ceramide that has been recently shown to induce experimental MDD. Finally, the application of phosphatidic acid, previously shown to be reduced in the hippocampus upon stress, also reverted stress-induced tyrosine nitrosylation. The inhibition of tyrosine nitrosylation by interfering with the formation of NO radicals at least partly restored normal behavior in stressed mice. These data suggest that tyrosine nitrosylation might contribute to the pathogenesis of MDD and targeting this process might contribute to the treatment of MDD.

Longitudinal effects of ketamine on cell proliferation and death in the CNS of zebrafish

Zebrafish is known for its widespread neurogenesis and regenerative capacity, as well as several biological advantages, which turned it into a relevant animal model in several areas of research, namely in toxicological studies. Ketamine is a well-known anesthetic used both in human as well as veterinary medicine, due to its safety, short duration and unique mode of action. However, ketamine administration is associated with neurotoxic effects and neuronal death, which renders its use on pediatric medicine problematic. Thus, the evaluation of ketamine effects administration at early stages of neurogenesis is of pivotal importance. The 1-4 somites stage of zebrafish embryo development corresponds to the beginning of segmentation and formation of neural tube. In this species, as well as in other vertebrates, longitudinal studies are scarce, and the evaluation of ketamine long-term effects in adults is poorly understood. This study aimed to assess the effects of ketamine administration at the 1-4 somites stage, both in subanesthetic and anesthetic concentrations, in brain cellular proliferation, pluripotency and death mechanisms in place during early and adult neurogenesis. For that purpose, embryos at the 1-4 somites stage (10,5hours post fertilization - hpf) were distributed into study groups and exposed for 20minutes to ketamine concentrations at 0.2/0.8mg/mL. Animals were grown until defined check points, namely 50 hpf, 144 hpf and 7 months adults. The assessment of the expression and distribution patterns of proliferating cell nuclear antigen (PCNA), of sex-determining region Y-box 2 (Sox 2), apoptosis-inducing factor (AIF) and microtubule-associated protein 1 light chain 3 (LC3) was performed by Western-blot and immunohistochemistry. The results evidenced the main alterations in 144 hpf larvae, namely in autophagy and in cellular proliferation at the highest concentration of ketamine (0.8mg/mL). Nonetheless, in adults no significant alterations were seen, pointing to a return to a homeostatic stage. This study allowed clarifying some of the aspects pertaining the longitudinal effects of ketamine administration regarding the CNS capacity to proliferate and activate the appropriate cell death and repair mechanisms leading to homeostasis in zebrafish. Moreover, the results indicate that ketamine administration at 1-4 somites stage in the subanesthetic and anesthetic concentrations despite some transitory detrimental effects at 144 hpf, is long-term safe for CNS, which are newly and promising results in this research field.

Canagliflozin attenuates chronic unpredictable mild stress induced neuroinflammation via modulating AMPK/mTOR autophagic signaling

Although vast progress has been made to understand the pathogenesis of depression, existing antidepressant remedies, with several adverse effects, are not fully adequate. Interestingly, new emerging theories implicating an altered HPA-axis, tryptophan metabolism, neuroinflammation and altered gut integrity were proposed to further identify novel therapeutic targets. Along these lines, canagliflozin (CAN), a novel antidiabetic medication with anti-inflammatory and neuroprotective activity may present an effective treatment for depression; nevertheless, no studies have explored its effect on depressive disorder yet. To this end, this study aimed to investigate the possible antidepressant activity of CAN in CUMS and the mechanisms underlying its action on the gut-brain inflammation axis as well as the alteration in the TRY/KYN pathway in addition to its role in modulating the autophagic signaling cascade. Interestingly, CAN successfully attenuated the CUMS-induced elevations in despair and anhedonic behaviors as well as the elevated serum CORT. Furthermore, it enhanced gut integrity via hampering the CUMS-induced colonic inflammation and amending colonic tight junction proteins. The enhanced gut integrity was further corroborated by a notable anti-inflammatory and neuroprotective activity manifested via the observed mitigation of immune cell activation in addition to IDO hippocampal protein content and promotion of the autophagy cascade. Our findings postulate the possible anti-inflammatory and neuroprotective effects of CAN and the implication of TRY/KYN and AMPK/mTOR signaling pathways in the CUMS-induced MDD. Hence, this study shed light to the promising role of CAN in the augmentation of the current antidepressant treatments.

Identification of Autophagy as a Functional Target Suitable for the Pharmacological Treatment of Mitochondrial Membrane Protein-Associated Neurodegeneration (MPAN) In Vitro

Mitochondrial membrane protein-associated neurodegeneration (MPAN) is a relentlessly progressive neurodegenerative disorder caused by mutations in the C19orf12 gene. C19orf12 has been implicated in playing a role in lipid metabolism, mitochondrial function, and autophagy, however, the precise functions remain unknown. To identify new robust cellular targets for small compound treatments, we evaluated reported mitochondrial function alterations, cellular signaling, and autophagy in a large cohort of MPAN patients and control fibroblasts. We found no consistent alteration of mitochondrial functions or cellular signaling messengers in MPAN fibroblasts. In contrast, we found that autophagy initiation is consistently impaired in MPAN fibroblasts and show that C19orf12 expression correlates with the amount of LC3 puncta, an autophagy marker. Finally, we screened 14 different autophagy modulators to test which can restore this autophagy defect. Amongst these compounds, carbamazepine, ABT-737, LY294002, oridonin, and paroxetine could restore LC3 puncta in the MPAN fibroblasts, identifying them as novel potential therapeutic compounds to treat MPAN. In summary, our study confirms a role for C19orf12 in autophagy, proposes LC3 puncta as a functionally robust and consistent readout for testing compounds, and pinpoints potential therapeutic compounds for MPAN.

Ginseng total saponins and Fuzi total alkaloids exert antidepressant-like effects in ovariectomized mice through BDNF-mTORC1, autophagy and peripheral metabolic pathways

BACKGROUND

Shenfu decoction (SFD) is a classic Chinese medicine prescription that has a strong cardiotonic effect. The combination of ginseng (the dried root of Panax ginseng C. A. Meyer) and Fuzi (processed product of sub-root of Aconitum carmichaeli Debx), the main constituents of SFD, has been reported to improve the pharmacological effect of each other. Moreover, research has shown that the main active components of SFD, ginseng total saponins (GTS) and Fuzi total alkaloids (FTA), have antidepressant activity. However, the effects of these ingredients on depressive-like behavior induced by ovariectomy, a model of menopausal depression, have not been studied.

PURPOSE

Our research aims to elucidate the antidepressant-like effects of GTS and FTA compatibility (GF) in ovariectomized mice and the potential mechanisms.

METHODS

To elucidate the antidepressant-like effects of GF in mice in ovariectomy condition, behavioral tests were performed after 7 days of intragastric administration of different doses of GF. Underlying molecular mechanisms of CREB-BDNF, BDNF-mTORC1 and autophagy signaling were detected by western blotting, serum metabolites were examined by UPLC-QE plus-MS and dendritic spine density was determined by Golgi-Cox staining.

RESULTS

GF remarkably decreased the immobility time in the forced swim test. GF also increased levels of pCREB/CREB, BDNF, Akt, mTORC1 and p62 in the prefrontal cortex and hippocampus, as well as decreased LC3-II/LC3-I in the prefrontal cortex and hippocampus of ovariectomized mice. Furthermore, 15 serum differential metabolites (9 of which are lipids and lipid molecules) were identified by metabonomics. Next, the antidepressant-like effects of GF was blocked by rapamycin, an inhibitor of mTORC1. The antidepressant actions of GF on levels of pCREB, mTORC1, LC3-Ⅱ/LC3-Ⅰ and p62 in the prefrontal cortex and the levels of BDNF, Akt, mTORC1 and p62 in the hippocampus were inhibited by rapamycin, and the dendritic spines density was also regulated.

CONCLUSION

GF has antidepressant effects in ovariectomized mice, and like other antidepressants, these effects involve activation of BDNF-mTORC1, autophagy regulation and consequent effects on hippocampal synaptic plasticity. Moreover, metabolomic results suggest that GF also has effects on peripheral lipid profiles that may provide potential biomarkers for these antidepressant-like effects. These results indicate that GF is worthy of further exploration as a promising pharmaceutical treatment for depression. This study provides a new direction for the development of new indications for traditional Chinese medicine compounds.

Ketamine May Exert Rapid Antidepressant Effects Through Modulation of Neuroplasticity, Autophagy, and Ferroptosis in the Habenular Nucleus

Major depressive disorder is a burdensome condition with few treatment options, and traditional antidepressants are characterized by slow onset. Sub-anesthetic ketamine has rapid-onset effects for the treatment of major depressive disorder (MDD), the mechanisms of which remain elusive. In this study, we explored whether neuroplasticity, autophagy, and ferroptosis in the habenular nucleus are involved in the rapid antidepressant process of ketamine. The results showed that Chronic Restraint Stress (CRS) treated rats exhibited decreased neuroplasticity, inhibition of autophagy, and enhanced ferroptosis. Depression-like symptoms were significantly improved after ketamine treatment in CRS rats, with changes in physiological parameters. Ketamine-treated CRS rats showed a significant improvement in habenular nuclear neuroplasticity. Electron microscopy observed that ketamine triggered autophagy, with increased levels of autophagy-related proteins. Ferroptosis was inhibited by ketamine by electron microscopy, with increased FTH1 and GPX4 levels and decreased Tfr1 levels. In conclusion, our findings demonstrate that ketamine may exert rapid antidepressant effects by improving neuroplasticity, activating autophagy, and inhibiting ferroptosis in the nuclear complex.

Ketamine induces rapid antidepressant effects via the autophagy-NLRP3 inflammasome pathway

BACKGROUND

Sub-anesthetic ketamine has rapid-onset effects for the treatment of major depressive disorder (MDD). However, the mechanism underlying ketamine's antidepressant properties remains unclear. Recent studies have reported an interrelationship between autophagy and the inflammasome, both of which are involved in the pathophysiology of MDD. In this study, we assess whether ketamine exerts its antidepressant effects via an association with the autophagy-NLRP3 inflammasome pathway.

METHODS

We established a depressive-like rat model by treating Wistar Kyoto rats with chronic restraint stress (CRS) for 28 days. Microglial cells from newborn Sprague-Dawley rats were used for in vitro experiments.

RESULTS

We found sub-anesthetic ketamine treatment reversed depressive-like behavior in CRS rats. Ketamine triggered autophagy in the microglia of prefrontal cortex (PFC) and (hippocampus) HPC, with increased levels of LC3B, decreased levels of p62 protein, and elevated autophagosomes both in vivo and in vitro. Moreover, NLRP3 inflammasome activation was also inhibited by ketamine, with reduced expression of NLRP3-ASC-CASP1 assembly and decreased IL-1β levels in cerebrospinal fluid (CSF) as well as in the serum. Increased BDNF levels and synaptophysin levels were detected in the ketamine-treated group. The rapid anti-depressive effects, elevation of autophagy, reduction in NLRP3, and neuroplasticity-related factors induced by ketamine could be significantly blocked by the autophagy inhibitor Baf A1 (0.1 mg/kg).

CONCLUSIONS

Our findings demonstrate that sub-anesthetic doses of ketamine exert their antidepressant-like effects by inhibiting inflammation and initiating neuroprotection via autophagy activation. These data might help expand future investigations on the antidepressant properties of ketamine.

The Emerging Role of Astrocytic Autophagy in Central Nervous System Disorders

Astrocytes act as "housekeeping cells" for maintaining cerebral homeostasis and play an important role in many disorders. Recent studies further highlight the contribution of autophagy to astrocytic functions, including astrogenesis, the astrocytic removal of neurotoxins or stressors, and astrocytic polarization. More importantly, genetic and pharmacological approaches have provided evidence that outlines the contributions of astrocytic autophagy to several brain disorders, including neurodegeneration, cerebral ischemia, and depression. In this study, we summarize the emerging role of autophagy in regulating astrocytic functions and discuss the contributions of astrocytic autophagy to different CNS disorders.

The Multifaceted Roles of Autophagy in Infectious, Obstructive, and Malignant Airway Diseases

Autophagy is a highly conserved dynamic process by which cells deliver their contents to lysosomes for degradation, thus ensuring cell homeostasis. In response to environmental stress, the induction of autophagy is crucial for cell survival. The dysregulation of this degradative process has been implicated in a wide range of pathologies, including lung diseases, representing a relevant potential target with significant clinical outcomes. During lung disease progression and infections, autophagy may exert both protective and harmful effects on cells. In this review, we will explore the implications of autophagy and its selective forms in several lung infections, such as SARS-CoV-2, Respiratory Syncytial Virus (RSV) and Mycobacterium tuberculosis (Mtb) infections, and different lung diseases such as Cystic Fibrosis (CF), Chronic Obstructive Pulmonary Disease (COPD), and Malignant Mesothelioma (MM).

Research progress on classical traditional chinese medicine formula xiaoyaosan in the treatment of depression

Depression is an emotional disorder that is problematic in psychiatry owing to its unclear etiology and unknown pathogenesis. Traditional Chinese medicine formulations such as Xiaoyaosan have been widely used throughout history to treat depression. In this review, we have focused on recent evidences elucidating the links between Xiaoyaosan and the treatment of depression. Data from animal and clinical studies, focusing on the pharmacological mechanisms, clinical applications, and effective materials that form the basis for the treatment of depression are presented and discussed. We found that the antidepressant effects of Xiaoyaosan are related to the effects of monoamine neurotransmitters, regulation of the hypothalamic-pituitary-adrenal axis, neuroplasticity, synaptic plasticity, inflammatory response, neuroprotection, brain-gut axis, regulation of intestinal microbiota, oxidative stress, and autophagy for reducing neuronal apoptosis. This review highlights the current evidence supporting the use of Xiaoyaosan as an antidepressant and provides an overview of the potential mechanisms involved.

Tricyclic antidepressants target FKBP51 SUMOylation to restore glucocorticoid receptor activity

FKBP51 is an important inhibitor of the glucocorticoid receptor (GR) signaling. High FKBP51 levels are associated to stress-related disorders, which are linked to GR resistance. SUMO conjugation to FKBP51 is necessary for FKBP51's inhibitory action on GR. The GR/FKBP51 pathway is target of antidepressant action. Thus we investigated if these drugs could inhibit FKBP51 SUMOylation and therefore restore GR activity. Screening cells using Ni²⁺ affinity and in vitro SUMOylation assays revealed that tricyclic antidepressants- particularly clomipramine- inhibited FKBP51 SUMOylation. Our data show that clomipramine binds to FKBP51 inhibiting its interaction with PIAS4 and therefore hindering its SUMOylation. The inhibition of FKBP51 SUMOylation decreased its binding to Hsp90 and GR facilitating FKBP52 recruitment, and enhancing GR activity. Reduction of PIAS4 expression in rat primary astrocytes impaired FKBP51 interaction with GR, while clomipramine could no longer exert its inhibitory action. This mechanism was verified in vivo in mice treated with clomipramine. These results describe the action of antidepressants as repressors of FKBP51 SUMOylation as a molecular switch for restoring GR sensitivity, thereby providing new potential routes of antidepressant intervention.

Deficient Autophagy in Microglia Aggravates Repeated Social Defeat Stress-Induced Social Avoidance

Major depressive disorder (MDD) is associated with repeated exposure to environmental stress. Autophagy is activated under various stress conditions that are associated with several diseases in the brain. This study was aimed at elucidating the autophagy signaling changes in the prefrontal cortex (PFC) under repeated social defeat (RSD) to investigate the involvement of microglial autophagy in RSD-induced behavioral changes. We found that RSD stress, an animal model of MDD, significantly induced initial autophagic signals followed by increased transcription of autophagy-related genes (Atg6, Atg7, and Atg12) in the PFC. Similarly, significantly increased transcripts of ATGs (Atg6, Atg7, Atg12, and Atg5) were confirmed in the postmortem PFC of patients with MDD. The protein levels of the prefrontal cortical LC3B were significantly increased, whereas p62 was significantly decreased in the resilient but not in susceptible mice and patients with MDD. This indicates that enhanced autophagic flux may alleviate stress-induced depression. Furthermore, we identified that FKBP5, an early-stage autophagy regulator, was significantly increased in the PFC of resilient mice at the transcript and protein levels. In addition, the resilient mice exhibited enhanced autophagic flux in the prefrontal cortical microglia, and the autophagic deficiency in microglia aggravated RSD-induced social avoidance, indicating that microglial autophagy involves stress-induced behavioral changes.

3,4-Methylenedioxy methamphetamine, synthetic cathinones and psychedelics: From recreational to novel psychotherapeutic drugs

The utility of classical drugs used to treat psychiatric disorders (e.g., antidepressants, anxiolytics) is often limited by issues of lack of efficacy, delayed onset of action or side effects. Psychoactive substances have a long history of being used as tools to alter consciousness and as a gateway to approach the unknown and the divinities. These substances were initially obtained from plants and animals and more recently by chemical synthesis, and its consumption evolved toward a more recreational use, leading to drug abuse-related disorders, trafficking, and subsequent banning by the authorities. However, these substances, by modulation of certain neurochemical pathways, have been proven to have a beneficial effect on some psychiatric disorders. This evidence obtained under medically controlled conditions and often associated with psychotherapy, makes these substances an alternative to conventional medicines, to which in many cases the patient does not respond properly. Such disorders include post-traumatic stress disease and treatment-resistant depression, for which classical drugs such as MDMA, ketamine, psilocybin and LSD, among others, have already been clinically tested, reporting successful outcomes. The irruption of new psychoactive substances (NPS), especially during the last decade and despite their recreational and illicit uses, has enlarged the library of substances with potential utility on these disorders. In fact, many of them were synthetized with therapeutic purposes and were withdrawn for concrete reasons (e.g., adverse effects, improper pharmacological profile). In this review we focus on the basis, existing evidence and possible use of synthetic cathinones and psychedelics (specially tryptamines) for the treatment of mental illnesses and the properties that should be found in NPS to obtain new therapeutic compounds.

Fluoxetine Potentiates Phagocytosis and Autophagy in Microglia

Fluoxetine is a classic antidepressant drug, and its immunomodulatory effects have recently been reported in many disease models. In addition, it has strong antineuroinflammatory effects in stroke and neurodegenerative animal models. However, the effect of fluoxetine on microglia phagocytosis and its molecular mechanisms have not yet been studied. In this study, we investigated whether fluoxetine has a regulatory effect on microglial function. Microglia cell lines and primary mouse microglia were treated with fluoxetine, and the production of inflammatory cytokines and neurotrophic factors and the phagocytosis of amyloid β were measured. Fluoxetine significantly attenuated the production of lipopolysaccharide-induced proinflammatory cytokines and oxidative stress in microglia. Fluoxetine also significantly potentiated microglia phagocytosis and autophagy. In addition, autophagy flux inhibitors attenuated fluoxetine-induced phagocytosis. In conclusion, fluoxetine induces autophagy and potentiates phagocytosis in microglia, which can be a novel molecular mechanism of the neuroinflammatory and neuroprotective effects of fluoxetine.

New Molecular Targets for Antidepressant Drugs

Major depressive disorder (MDD) is a common and severe mental disorder that is usually recurrent and has a high risk of suicide. This disorder manifests not only with psychological symptoms but also multiple changes throughout the body, including increased risks of obesity, diabetes, and cardiovascular disease. Peripheral markers of oxidative stress and inflammation are elevated. MDD is therefore best described as a multisystem whole-body disease. Pharmacological treatment with antidepressants usually requires several weeks before the desired effects manifest. Previous theories of depression, such as the monoamine or neurogenesis hypotheses, do not explain these characteristics well. In recent years, new mechanisms of action have been discovered for long-standing antidepressants that also shed new light on depression, including the sphingolipid system and the receptor for brain-derived neurotrophic factor (BDNF).

Combined morphological and proteome profiling reveals target-independent impairment of cholesterol homeostasis

Unbiased profiling approaches are powerful tools for small-molecule target or mode-of-action deconvolution as they generate a holistic view of the bioactivity space. This is particularly important for non-protein targets that are difficult to identify with commonly applied target identification methods. Thereby, unbiased profiling can enable identification of novel bioactivity even for annotated compounds. We report the identification of a large bioactivity cluster comprised of numerous well-characterized drugs with different primary targets using a combination of the morphological Cell Painting Assay and proteome profiling. Cluster members alter cholesterol homeostasis and localization due to their physicochemical properties that lead to protonation and accumulation in lysosomes, an increase in lysosomal pH, and a disturbed cholesterol homeostasis. The identified cluster enables identification of modulators of cholesterol homeostasis and links regulation of genes or proteins involved in cholesterol synthesis or trafficking to physicochemical properties rather than to nominal targets.

The interaction between autophagy and neuroinflammation in major depressive disorder: From pathophysiology to therapeutic implications

The past decade has revealed neuroinflammation as an important mechanism of major depressive disorder (MDD). Nod-like receptors family pyrin domain containing 3 (NLRP3) inflammasome is the key regulator interleukin-1β (IL-1β) maturation, whose activation has been reported in MDD patients and various animal models. Function as a dominant driver of neuroinflammation, NLRP3 bridges the gap between immune activation with stress exposure, and further leads to subsequent occurrence of neuropsychiatric disorders such as MDD. Of note, autophagy is a tightly regulated cellular degradation pathway that removes damaged organelles and intracellular pathogens, and maintains cellular homeostasis from varying insults. Serving as a critical cellular monitoring system, normal functioned autophagy signaling prevents excessive NLRP3 inflammasome activation and subsequent release of IL-1 family cytokines. This review will describe the current understanding of how autophagy regulates NLRP3 inflammasome activity and discuss the implications of this regulation on the pathogenesis of MDD. The extensive crosstalk between autophagy pathway and NLRP3 inflammasome is further discussed, as it is critical for developing new therapeutic strategies for MDD aimed at modulating the neuroinflammatory responses.

Differential and paradoxical roles of new-generation antidepressants in primary astrocytic inflammation

Background

Selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) are commonly used new-generation drugs for depression. Depressive symptoms are thought to be closely related to neuroinflammation. In this study, we used up-to-date protocols of culture and stimulation and aimed to understand how astrocytes respond to the antidepressants.

Methods

Primary astrocytes were isolated and cultured using neurobasal-based serum-free medium. The cells were treated with a cytokine mixture comprising complement component 1q, tumor necrosis factor α, and interleukin 1α with or without pretreatments of antidepressants. Cell viability, phenotypes, inflammatory responses, and the underlying mechanisms were analyzed.

Results

All the SSRIs, including paroxetine, fluoxetine, sertraline, citalopram, and fluvoxamine, show a visible cytotoxicity within the range of applied doses, and a paradoxical effect on astrocytic inflammatory responses as manifested by the promotion of inducible nitric oxide synthase (iNOS) and/or nitric oxide (NO) and the inhibition of interleukin 6 (IL-6) and/or interleukin 1β (IL-1β). The SNRI venlafaxine was the least toxic to astrocytes and inhibited the production of IL-6 and IL-1β but with no impact on iNOS and NO. All the drugs had no regulation on the polarization of astrocytic A1 and A2 types. Mechanisms associated with the antidepressants in astrocytic inflammation route via inhibition of JNK1 activation and STAT3 basal activity.

Conclusions

The study demonstrated that the antidepressants possess differential cytotoxicity to astrocytes and function differently, also paradoxically for the SSRIs, to astrocytic inflammation. Our results provide novel pieces into understanding the differential efficacy and tolerability of the antidepressants in treating patients in the context of astrocytes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02097-z.

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.

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.

Amitriptyline interferes with autophagy-mediated clearance of protein aggregates via inhibiting autophagosome maturation in neuronal cells

Amitriptyline is a tricyclic antidepressant commonly prescribed for major depressive disorders, as well as depressive symptoms associated with various neurological disorders. A possible correlation between the use of tricyclic antidepressants and the occurrence of Parkinson's disease has been reported, but its underlying mechanism remains unknown. The accumulation of misfolded protein aggregates has been suggested to cause cellular toxicity and has been implicated in the common pathogenesis of neurodegenerative diseases. Here, we examined the effect of amitriptyline on protein clearance and its relevant mechanisms in neuronal cells. Amitriptyline exacerbated the accumulation of abnormal aggregates in both in vitro neuronal cells and in vivo mice brain by interfering with the (1) formation of aggresome-like aggregates and (2) autophagy-mediated clearance of aggregates. Amitriptyline upregulated LC3B-II, but LC3B-II levels did not increase further in the presence of NH₄Cl, which suggests that amitriptyline inhibited autophagic flux rather than autophagy induction. Amitriptyline interfered with the fusion of autophagosome and lysosome through the activation of PI3K/Akt/mTOR pathway and Beclin 1 acetylation, and regulated lysosome positioning by increasing the interaction between proteins Arl8, SKIP, and kinesin. To the best of our knowledge, we are the first to demonstrate that amitriptyline interferes with autophagic flux by regulating the autophagosome maturation during autophagy in neuronal cells. The present study could provide neurobiological clue for the possible correlation between the amitriptyline use and the risk of developing neurodegenerative diseases.

Cross-disease analysis of depression, ataxia and dystonia highlights a role for synaptic plasticity and the cerebellum in the pathophysiology of these comorbid diseases

BACKGROUND

There is growing evidence that the neuropsychiatric and neurological disorders depression, ataxia and dystonia share common biological pathways. We therefore aimed to increase our understanding of their shared pathophysiology by investigating their shared biological pathways and molecular networks.

METHODS

We constructed gene sets for depression, ataxia, and dystonia using the Human Phenotype Ontology database and genome-wide association studies, and identified shared genes between the three diseases. We then assessed shared genes in terms of functional enrichment, pathway analysis, molecular connectivity, expression profiles and brain-tissue-specific gene co-expression networks.

RESULTS

The 33 genes shared by depression, ataxia and dystonia are enriched in shared biological pathways and connected through molecular complexes in protein-protein interaction networks. Biological processes common/shared to all three diseases were identified across different brain tissues, highlighting roles for synaptic transmission, synaptic plasticity and nervous system development. The average expression of shared genes was significantly higher in the cerebellum compared to other brain regions, suggesting these genes have distinct cerebellar functions. Several shared genes also showed high expression in the cerebellum during prenatal stages, pointing to a functional role during development.

CONCLUSIONS

The shared pathophysiology of depression, ataxia and dystonia seems to converge onto the cerebellum that maybe particularly vulnerable to changes in synaptic transmission, regulation of synaptic plasticity and nervous system development. Consequently, in addition to regulating motor coordination and motor function, the cerebellum may likely play a role in mood processing.

Spermidine, an autophagy inducer, as a therapeutic strategy in neurological disorders

Spermidine is a naturally occurring endogenous polyamine synthesized from diamine putrescine. It is a well-known autophagy inducer that maintains cellular and neuronal homeostasis. Healthy brain development and function are dependent on brain polyamine concentration. Polyamines interact with the opioid system, glutamatergic signaling and neuroinflammation in the neuronal and glial compartments. Among the polyamines, spermidine is found highest in the human brain. Age-linked fluctuations in the spermidine levels may possibly contribute to the impairments in neural network and neurogenesis. Exogenously administered spermidine helps in the treatment of brain diseases. Further, current studies highlight the ability of spermidine to promote longevity by inducing autophagy. Still, the causal neuroprotective mechanism of spermidine in neuronal dysfunction remains unidentified. This review aims to summarize various neuroprotective effects of spermidine related to anti-aging/ anti-inflammatory properties and the prevention of neurotoxicity that helps in achieving beneficial effects in age-related neurological disorder. We also expose the signaling cascades modulated by spermidine which might result in therapeutic action. The present review highlights clinical studies along with in-vivo and in-vitro preclinical studies to provide a new dimension for the therapeutic potential of spermidine in neurological disorders.

Stress and signaling pathways regulating autophagy: From behavioral models to psychiatric disorders

Autophagy is a process of degradation and recycling of cytoplasmatic components by the lysosomes. In the central nervous system (CNS), autophagy is involved in cell surveillance, neuroinflammation, and neuroplasticity. Neuropsychiatric conditions are associated with functional disturbances at molecular and cellular levels, causing significant impairments in cell homeostasis. Additionally, emerging evidence supports that dysfunctions in autophagy contribute to the pathophysiology of neurological diseases. However, the studies on autophagy in psychiatric disorders are highly heterogeneous and have several limitations, mainly to assess causality and determine the autophagy flux in animals and human samples. Besides, the role of this mechanism in non-neuronal cells in the CNS is only recently being explored. Thus, this review summarizes and discusses the changes in the autophagy pathway in animal models of psychiatric disorders and the limitations underlying the significant findings. Moreover, we compared these findings with clinical studies. Understanding the involvement of autophagy in psychiatric conditions, and the limitation of our current models may contribute to the development of more effective research approaches and possibly pharmacological therapies.

Antidepressant-Like Effects of Coumaroylspermidine Extract From Safflower Injection Residues

In this study, a total coumaroylspermidine extract (CSE), which included four coumaroylspermidine compounds, was prepared from safflower injection (a traditional Chinese medicine) residues for the first time. The total content of the four coumaroylspermidine compounds was determined to be 64.86 ± 0.41% using high-performance liquid chromatography. We then evaluated the anti-depressant effect of CSE by using a chronic unpredictable mild stress (CUMS) model in rats. Results of sucrose preference tests, open field tests, and forced swimming tests suggest that CSE exhibits a significant anti-depressant effect. In studies to explore the mechanism, CSE was found to inhibit the increases in levels of corticosterone and decreases in levels of 5-hydroxytryptamine, dopamine, and noradrenaline induced by CUMS. Metabolic profiling showed that 10 endogenous metabolites and four metabolic pathways were altered after CSE treatment. Thus, this study not only found a spermidine extract with antidepressant effect from safflower injection residue for the first time but also provided a way for the efficient utilize of safflower injection residue.

The beclin 1 interactome: Modification and roles in the pathology of autophagy-related disorders

Beclin 1 a yeast Atg6/VPS30 orthologue has a significant role in autophagy process (Macroautophagy) and protein sorting. The function of beclin 1 depends on the interaction with several autophagy-related genes (Atgs) and other proteins during the autophagy process. The role mediated by beclin 1 is controlled by various conditions and factors. Beclin 1 is regulated at the gene and protein levels by different factors. These regulations could subsequently alter the beclin 1 induced autophagy process. Therefore, it is important to study the components of beclin 1 interactome and factors affecting its expression. Expression of this gene is differentially regulated under different conditions in different cells or tissues. So, the regulation part is important to study as beclin 1 is one of the candidate genes involved in diseases related to autophagy dysfunction. This review focuses on the functions of beclin 1, its interacting partners, regulations at gene and protein level, and the role of beclin 1 interactome in relation to various diseases along with the recent developments in the field.

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.

Patchouli alcohol protects against chronic unpredictable mild stress-induced depressant-like behavior through inhibiting excessive autophagy via activation of mTOR signaling pathway

Patchouli alcohol (PA), a tricyclic sesquiterpene, is the major chemical component of patchouli oil. This study investigated the antidepressant-like effect and mechanism of PA in chronic unpredictable mild stress (CUMS). Our results showed that PA markedly attenuated CUMS-induced depressant-like behaviors, including an effective increase of sucrose preference and spontaneous exploratory capacity, as well as reduction of immobility time. In addition, PA markedly attenuated CUMS-induced mTOR, p70S6K, and 4E-BP-1 phosphorylation reduction in the hippocampus. Furthermore, PA reversed CUMS-induced increases in LC3-II and p62 levels and CUMS-induced decrease in PSD-95 and SYN-I levels. These results indicated that the antidepressant-like effect of PA was correlated with the activation of the mTOR signaling pathway. Moreover, behavioral experimental results showed that the antidepressant-like effect of PA was blocked by rapamycin (autophagy inducer and mTOR inhibitor) and chloroquine (autophagic flux inhibitor). These results suggest that PA exerted antidepressant-like effect in CUMS rats through inhibiting autophagy, repairing synapse, and restoring autophagic flux in the hippocampus by activating the mTOR signaling pathway. The results render PA a promising antidepressant agent worthy of further development into a pharmaceutical drug for the treatment of depression.

SKP2 attenuates autophagy through Beclin1-ubiquitination and its inhibition reduces MERS-Coronavirus infection

Autophagy is an essential cellular process affecting virus infections and other diseases and Beclin1 (BECN1) is one of its key regulators. Here, we identified S-phase kinase-associated protein 2 (SKP2) as E3 ligase that executes lysine-48-linked poly-ubiquitination of BECN1, thus promoting its proteasomal degradation. SKP2 activity is regulated by phosphorylation in a hetero-complex involving FKBP51, PHLPP, AKT1, and BECN1. Genetic or pharmacological inhibition of SKP2 decreases BECN1 ubiquitination, decreases BECN1 degradation and enhances autophagic flux. Middle East respiratory syndrome coronavirus (MERS-CoV) multiplication results in reduced BECN1 levels and blocks the fusion of autophagosomes and lysosomes. Inhibitors of SKP2 not only enhance autophagy but also reduce the replication of MERS-CoV up to 28,000-fold. The SKP2-BECN1 link constitutes a promising target for host-directed antiviral drugs and possibly other autophagy-sensitive conditions.

Here, Gassen et al. show that S-phase kinase-associated protein 2 (SKP2) is responsible for lysine-48-linked poly-ubiquitination of beclin 1, resulting in its proteasomal degradation, and that inhibition of SKP2 enhances autophagy and reduces replication of MERS coronavirus.

Astrocytes autophagy in aging and neurodegenerative disorders

Astrocytes can serve multiple functions in maintaining cellular homeostasis of the central nervous system (CNS), and normal functions for autophagy in astrocytes is considered to have very vital roles in the pathogenesis of aging and neurodegenerative diseases. Autophagy is a major intracellular lysosomal (or its yeast analog, vacuolar) clearance pathways involved in the degradation and recycling of long-lived proteins, oxidatively damaged proteins and dysfunctional organelles by lysosomes. Current evidence has shown that autophagy might influence inflammation, oxidative stress, aging and function of astrocytes. Although the interrelation between autophagy and inflammation, oxidative stress, aging or neurological disorders have been addressed in detail, the influence of astrocytes mediated-autophagy in aging and neurodegenerative disorders has yet to be fully reviewed. In this review, we will summarize the most up-to-date findings and highlight the role of autophagy in astrocytes and link autophagy of astrocytes to aging and neurodegenerative diseases. Due to the prominent roles of astrocytic autophagy in age-related neurodegenerative diseases, we believe that we can provide new suggestions for the treatment of these disorders.

Is Autophagy Involved in the Diverse Effects of Antidepressants?

Autophagy has received increased attention as a conserved process governing cellular energy and protein homeostasis that is thus relevant in a range of physiological and pathophysiological conditions. Recently, autophagy has also been linked to depression, mainly through its involvement in the action of antidepressants. Some antidepressant drugs and psychotropic medication have been reported to exert beneficial effects in other diseases, for example, in cancer and neurodegenerative diseases. This review collates the evidence for the hypothesis that autophagy contributes to the effects of antidepressants beyond depression treatment.

Baseline Serum Levels of Beclin-1, but Not Inflammatory Factors, May Predict Antidepressant Treatment Response in Chinese Han Patients With MDD: A Preliminary Study

Currently, the choice of medical treatment for major depressive disorder (MDD) is primarily based on a trial-and-error process. Thus, identification of individual factors capable of predicting treatment response is of great clinical relevance. Recent work points towards beclin-1 and inflammatory factors as potential biomarkers of antidepressant treatment response. The primary aim of the study was to investigate whether pre-treatment serum levels of beclin-1 and inflammatory factors could predict antidepressant treatment response in Chinese Han patients with MDD. Forty patients with MDD were treated with either a selective serotonin reuptake inhibitor (SSRI) (paroxetine in 20 cases) or a serotonin-norepinephrine reuptake inhibitor (SNRI) (duloxetine in 13 cases and venlafaxine in 7 cases). Depression scores and serum levels of beclin-1 were measured at the baseline and after 8 weeks of antidepressant treatment. Serum C-reactive protein (CRP), interleukin (IL)-1B, and IL-6 levels were determined using enzyme-linked immunosorbent assay kits at the baseline. Twenty-seven patients were identified as treatment responders, whereas 13 were identified as non-responders after 8 weeks of antidepressant treatment. Baseline serum beclin-1 levels were significantly higher in non-responders than in responders (p = 0.001), whereas no differences were found in baseline serum CRP, IL-1B, or IL-6 levels between responders and non-responders. There were no significant correlations between baseline levels of beclin-1 and baseline IL-1β, IL-6, and CRP levels-neither in the total sample nor in responder and non-responder groups. Moreover, logistic regression models and a random forest model showed that baseline serum beclin-1, but not inflammatory factors, was an independent and the most important predictor for antidepressant treatment response. Furthermore, serum beclin-1 levels were significantly increased in responders (p = 0.027) but not in non-responders after 8 weeks of treatment (p = 0.221). Baseline serum beclin-1 levels may be a predictive biomarker of antidepressant response in patients with MDD. Moreover, beclin-1 may be involved in the therapeutic effect of antidepressant drugs.

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.

Bafilomycin A1 alleviates depression‑like symptoms in chronic unpredictable mild stress rats

Major depression is a multifactorial disease. Emerging evidence has suggested that autophagy is involved in the pathological process of depressive disorders. Bafilomycin A1 (Baf A1), is an inhibitor of vacuolar H+‑ATPase that is frequently used at high concentrations to block late‑phase autophagy. However, whether Baf A1 has antidepressant effects remains to be elucidated. The current study aimed to evaluate the antidepressant effects of Baf A1 in rats with chronic unpredictable mild stress (CUMS) and its potential mechanism. The CUMS animal model was established. The sucrose preference test, open‑field test (OFT) and forced swim test (FST) were applied to evaluate the depressive behavior. Synaptic plasticity‑associated proteins synaptophysin and postsynaptic density protein 95 were measured by western blotting and immunofluorescence. Apoptosis‑ and autophagy‑associated proteins in addition to pro‑inflammatory cytokines, including interleukin‑1β and tumor necrosis factor‑α, were detected by western blotting, reverse transcription‑quantitative polymerase chain reaction or ELISA. A 4‑week treatment period with Baf A1 markedly ameliorated CUMS‑induced behavioral abnormalities, including increasing sucrose intake, improving locomotor activity in the OFT, and decreasing immobility time in the FST. In addition, treatment with Baf A1 restored the dysregulation of synaptic plasticity and inhibited neuroinflammation in rats exposed to CUMS. Furthermore, Baf A1 decreased the levels of apoptosis‑ and autophagy‑associated proteins induced by CUMS. The present study demonstrated that Bafilomycin A1 resulted in antidepressant effects in rats, which may be mediated by the reversal of apoptosis, autophagy and neuroinflammation in the hippocampus.

Beyond autophagy: a novel role for autism-linked Wdfy3 in brain mitophagy

WD repeat and FYVE domain-containing 3 (WDFY3; also known as Autophagy-Linked FYVE or Alfy) is an identified intellectual disability, developmental delay and autism risk gene. This gene encodes for a scaffolding protein that is expressed in both the developing and adult central nervous system and required for autophagy and aggrephagy with yet unexplored roles in mitophagy. Given that mitochondrial trafficking, dynamics and remodeling have key roles in synaptic plasticity, we tested the role of Wdfy3 on brain bioenergetics by using Wdfy3^+/lacZ mice, the only known Wdfy3 mutant animal model with overt neurodevelopmental anomalies that survive to adulthood. We found that Wdfy3 is required for sustaining brain bioenergetics and morphology via mitophagy. Decreased mitochondrial quality control by conventional mitophagy was partly compensated for by the increased formation of mitochondria-derived vesicles (MDV) targeted to lysosomal degradation (micromitophagy). These observations, extended through proteomic analysis of mitochondria-enriched cortical fractions, showed significant enrichment for pathways associated with mitophagy, mitochondrial transport and axon guidance via semaphorin, Robo, L1cam and Eph-ephrin signaling. Collectively, our findings support a critical role for Wdfy3 in mitochondrial homeostasis with implications for neuron differentiation, neurodevelopment and age-dependent neurodegeneration.

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.

Antidepressants act by inducing autophagy controlled by sphingomyelin-ceramide

Major depressive disorder (MDD) is a common and severe disease characterized by mood changes, somatic alterations, and often suicide. MDD is treated with antidepressants, but the molecular mechanism of their action is unknown. We found that widely used antidepressants such as amitriptyline and fluoxetine induce autophagy in hippocampal neurons via the slow accumulation of sphingomyelin in lysosomes and Golgi membranes and of ceramide in the endoplasmic reticulum (ER). ER ceramide stimulates phosphatase 2A and thereby the autophagy proteins Ulk, Beclin, Vps34/Phosphatidylinositol 3-kinase, p62, and Lc3B. Although treatment with amitriptyline or fluoxetine requires at least 12 days to achieve sphingomyelin accumulation and the subsequent biochemical and cellular changes, direct inhibition of sphingomyelin synthases with tricyclodecan-9-yl-xanthogenate (D609) results in rapid (within 3 days) accumulation of ceramide in the ER, activation of autophagy, and reversal of biochemical and behavioral signs of stress-induced MDD. Inhibition of Beclin blocks the antidepressive effects of amitriptyline and D609 and induces cellular and behavioral changes typical of MDD. These findings identify sphingolipid-controlled autophagy as an important target for antidepressive treatment methods and provide a rationale for the development of novel antidepressants that act within a few days.