SIRT1 Mediates Depression-Like Behaviors in the Nucleus Accumbens

Repurposing Ketamine in the Therapy of Depression and Depression-Related Disorders: Recent Advances and Future Potential

Depression represents a prevalent and enduring mental disorder of significant concern within the clinical domain. Extensive research indicates that depression is very complex, with many interconnected pathways involved. Most research related to depression focuses on monoamines, neurotrophic factors, the hypothalamic-pituitary-adrenal axis, tryptophan metabolism, energy metabolism, mitochondrial function, the gut-brain axis, glial cell-mediated inflammation, myelination, homeostasis, and brain neural networks. However, recently, Ketamine, an ionotropic N-methyl-D-aspartate (NMDA) receptor antagonist, has been discovered to have rapid antidepressant effects in patients, leading to novel and successful treatment approaches for mood disorders. This review aims to summarize the latest findings and insights into various signaling pathways and systems observed in depression patients and animal models, providing a more comprehensive view of the neurobiology of anxious-depressive-like behavior. Specifically, it highlights the key mechanisms of ketamine as a rapid-acting antidepressant, aiming to enhance the treatment of neuropsychiatric disorders. Moreover, we discuss the potential of ketamine as a prophylactic or therapeutic intervention for stress-related psychiatric disorders.

Recent Advances in the Discovery of SIRT1/2 Inhibitors via Computational Methods: A Perspective

Sirtuins (SIRTs) are classified as class III histone deacetylases (HDACs), a family of enzymes that catalyze the removal of acetyl groups from the ε-N-acetyl lysine residues of histone proteins, thus counteracting the activity performed by histone acetyltransferares (HATs). Based on their involvement in different biological pathways, ranging from transcription to metabolism and genome stability, SIRT dysregulation was investigated in many diseases, such as cancer, neurodegenerative disorders, diabetes, and cardiovascular and autoimmune diseases. The elucidation of a consistent number of SIRT-ligand complexes helped to steer the identification of novel and more selective modulators. Due to the high diversity and quantity of the structural data thus far available, we reviewed some of the different ligands and structure-based methods that have recently been used to identify new promising SIRT1/2 modulators. The present review is structured into two sections: the first includes a comprehensive perspective of the successful computational approaches related to the discovery of SIRT1/2 inhibitors (SIRTIs); the second section deals with the most interesting SIRTIs that have recently appeared in the literature (from 2017). The data reported here are collected from different databases (SciFinder, Web of Science, Scopus, Google Scholar, and PubMed) using "SIRT", "sirtuin", and "sirtuin inhibitors" as keywords.

SIRT1 Coordinates Transcriptional Regulation of Neural Activity and Modulates Depression-Like Behaviors in the Nucleus Accumbens

BACKGROUND

Major depression and anxiety disorders are significant causes of disability and socioeconomic burden. Despite the prevalence and considerable impact of these affective disorders, their pathophysiology remains elusive. Thus, there is an urgent need to develop novel therapeutics for these conditions. We evaluated the role of SIRT1 in regulating dysfunctional processes of reward by using chronic social defeat stress to induce depression- and anxiety-like behaviors. Chronic social defeat stress induces physiological and behavioral changes that recapitulate depression-like symptomatology and alters gene expression programs in the nucleus accumbens, but cell type-specific changes in this critical structure remain largely unknown.

METHODS

We examined transcriptional profiles of D1-expressing medium spiny neurons (MSNs) lacking deacetylase activity of SIRT1 by RNA sequencing in a cell type-specific manner using the RiboTag line of mice. We analyzed differentially expressed genes using gene ontology tools including SynGO and EnrichR and further demonstrated functional changes in D1-MSN-specific SIRT1 knockout (KO) mice using electrophysiological and behavioral measurements.

RESULTS

RNA sequencing revealed altered transcriptional profiles of D1-MSNs lacking functional SIRT1 and showed specific changes in synaptic genes including glutamatergic and GABAergic (gamma-aminobutyric acidergic) receptors in D1-MSNs. These molecular changes may be associated with decreased excitatory and increased inhibitory neural activity in Sirt1 KO D1-MSNs, accompanied by morphological changes. Moreover, the D1-MSN-specific Sirt1 KO mice exhibited proresilient changes in anxiety- and depression-like behaviors.

CONCLUSIONS

SIRT1 coordinates excitatory and inhibitory synaptic genes to regulate the GABAergic output tone of D1-MSNs. These findings reveal a novel signaling pathway that has potential for the development of innovative treatments for affective disorders.

A chronic stress-induced microbiome perturbation, highly enriched in Ruminococcaceae_UCG-014, promotes colorectal cancer growth and metastasis

Purpose: Mounting evidence indicates that psychological stress adversely affects cancer progression including tumor growth and metastasis. The aim of this study was to investigate the role of chronic stress-induced microbiome perturbation in colorectal cancer (CRC) progression. Methods: Chronic restraint stress (CRS) was used to establish the chronic stress mouse model, behavioral tests were used for the CRS model evaluation. Subcutaneous xenograft model and lung metastasis model were established to investigate the growth and metastasis of CRC promoted by CRS exposure. 16S rRNA gene sequencing and liquid chromatograph-mass spectrometer (LC-MS) were applied to observe the effects of CRS exposure on the alteration of the gut microbiome and microbial metabolites. Bioinformatics analysis and correlation analyses were applied to analyse the changes in the frequency of body mass, tumor volume, inflammatory factors, neuroendocrine hormones and metabolites of the gut microbiota. Results: In this study, we identifed that CRS exposure model was appropriately constructed by achieving expected increases in disease activity index and enhanced depressive-like behaviors. CRS exposure can promote growth and metastasis of CRC. Besides, the data indicated that CRS exposure not only increased the neuro- and immune-inflammation, but also weakened the gut mucosal immunological function. The 16s rRNA gene sequencing data showed that CRS exposure increased the abundance of g_Ruminococcaceae_UCG_014. Furthermore, the LC-MS data indicated that with only 2 exceptions of carpaine and DG (15:0/20:4(5Z,8Z,11Z,14Z)/0:0), the majority of these 24 metabolites were less abundant in CRS-exposed mice. Bioinformatics analysis and correlation analyses indicated that only Ruminoscoccaceae-UCG-014 was significantly associated with inflammation (IL-6), neurotransmission (5-HT), and microbial metabolism (PS). Conclusion: CRS exposure altered diversity, composition and metabolites of the gut microbiome, with Ruminococcaceae_UCG-014 perturbation consistently correlated to inflammatory responses, suggesting a particular role of this bacterial genus in CRC growth and metastasis.

A mitochondrial nexus in major depressive disorder: Integration with the psycho-immune-neuroendocrine network

Nervous system processes, including cognition and affective state, fundamentally rely on mitochondria. Impaired mitochondrial function is evident in major depressive disorder (MDD), reflecting cumulative detrimental influences of both extrinsic and intrinsic stressors, genetic predisposition, and mutation. Glucocorticoid 'stress' pathways converge on mitochondria; oxidative and nitrosative stresses in MDD are largely mitochondrial in origin; both initiate cascades promoting mitochondrial DNA (mtDNA) damage with disruptions to mitochondrial biogenesis and tryptophan catabolism. Mitochondrial dysfunction facilitates proinflammatory dysbiosis while directly triggering immuno-inflammatory activation via released mtDNA, mitochondrial lipids and mitochondria associated membranes (MAMs), further disrupting mitochondrial function and mitochondrial quality control, promoting the accumulation of abnormal mitochondria (confirmed in autopsy studies). Established and putative mechanisms highlight a mitochondrial nexus within the psycho-immune neuroendocrine (PINE) network implicated in MDD. Whether lowering neuronal resilience and thresholds for disease, or linking mechanistic nodes within the MDD pathogenic network, impaired mitochondrial function emerges as an important risk, a functional biomarker, providing a therapeutic target in MDD. Several treatment modalities have been demonstrated to reset mitochondrial function, which could benefit those with MDD.

Mitochondria in depression: The dysfunction of mitochondrial energy metabolism and quality control systems

BACKGROUND

Depression is the most disabling neuropsychiatric disorder, causing difficulties in daily life activities and social interactions. The exact mechanisms of depression remain largely unclear. However, some studies have shown that mitochondrial dysfunction would play a crucial role in the occurrence and development of depression.

AIMS

To summarize the known knowledge about the role of mitochondrial dysfunction in the pathogenesis of depression.

METHODS

We review the recent literature， including 105 articles, to summarize the mitochondrial energy metabolism and quality control systems in the occurrence and development of depression. Some antidepressants which may exert their effects by improving mitochondrial function are also discussed.

RESULTS

Impaired brain energy metabolism and (or) damaged mitochondrial quality control systems have been reported not only in depression patients but in animal models of depression. Although the classical antidepressants have not been specially designed to target mitochondria, the evidence suggests that many antidepressants may exert their effects by improving mitochondrial function.

CONCLUSIONS

This brief review focuses on the findings that implicate mitochondrial dysfunction and the quality control systems as important etiological factors in the context of depressive disorders. It will help us to understand the various concepts of mitochondrial dysfunction in the pathogenesis of depression, and to explore novel and more targeted therapeutic approaches for depression.

The role of polyunsaturated fatty acids in the neurobiology of major depressive disorder and suicide risk

Long-chain polyunsaturated fatty acids (LC-PUFAs) are obtained from diet or derived from essential shorter-chain fatty acids, and are crucial for brain development and functioning. Fundamentally, LC-PUFAs' neurobiological effects derive from their physicochemical characteristics, including length and double bond configuration, which differentiate LC-PUFA species and give rise to functional differences between n(omega)-3 and n-6 LC-PUFAs. LC-PUFA imbalances are implicated in psychiatric disorders, including major depression and suicide risk. Dietary intake and genetic variants in enzymes involved in biosynthesis of LC-PUFAs from shorter chain fatty acids influence LC-PUFA status. Domains impacted by LC-PUFAs include 1) cell signaling, 2) inflammation, and 3) bioenergetics. 1) As major constituents of lipid bilayers, LC-PUFAs are determinants of cell membrane properties of viscosity and order, affecting lipid rafts, which play a role in regulation of membrane-bound proteins involved in cell-cell signaling, including monoaminergic receptors and transporters. 2) The n-3:n-6 LC-PUFA balance profoundly influences inflammation. Generally, metabolic products of n-6 LC-PUFAs (eicosanoids) are pro-inflammatory, while those of n-3 LC-PUFAs (docosanoids) participate in the resolution of inflammation. Additionally, n-3 LC-PUFAs suppress microglial activation and the ensuing proinflammatory cascade. 3) N-3 LC-PUFAs in the inner mitochondrial membrane affect oxidative stress, suppressing production of and scavenging reactive oxygen species (ROS), with neuroprotective benefits. Until now, this wealth of knowledge about LC-PUFA biomechanisms has not been adequately tapped to develop translational studies of LC-PUFA clinical effects in humans. Future studies integrating neurobiological mechanisms with clinical outcomes may suggest ways to identify depressed individuals most likely to respond to n-3 LC-PUFA supplementation, and mechanistic research may generate new treatment strategies.

SIRT1 in the BNST modulates chronic stress-induced anxiety of male mice via FKBP5 and corticotropin-releasing factor signaling

Although clinical reports have highlighted association of the deacetylase sirtuin 1 (SIRT1) gene with anxiety, its exact role in the pathogenesis of anxiety disorders remains unclear. The present study was designed to explore whether and how SIRT1 in the mouse bed nucleus of the stria terminalis (BNST), a key limbic hub region, regulates anxiety. In a chronic stress model to induce anxiety in male mice, we used site- and cell-type-specific in vivo and in vitro manipulations, protein analysis, electrophysiological and behavioral analysis, in vivo MiniScope calcium imaging and mass spectroscopy, to characterize possible mechanism underlying a novel anxiolytic role for SIRT1 in the BNST. Specifically, decreased SIRT1 in parallel with increased corticotropin-releasing factor (CRF) expression was found in the BNST of anxiety model mice, whereas pharmacological activation or local overexpression of SIRT1 in the BNST reversed chronic stress-induced anxiety-like behaviors, downregulated CRF upregulation, and normalized CRF neuronal hyperactivity. Mechanistically, SIRT1 enhanced glucocorticoid receptor (GR)-mediated CRF transcriptional repression through directly interacting with and deacetylating the GR co-chaperone FKBP5 to induce its dissociation from the GR, ultimately downregulating CRF. Together, this study unravels an important cellular and molecular mechanism highlighting an anxiolytic role for SIRT1 in the mouse BNST, which may open up new therapeutic avenues for treating stress-related anxiety disorders.

The role and mechanism of TGF-β1 in the antidepressant-like effects of tetrahydrocurcumin

Astrocytes and the activation of inflammatory factors are associated with depression. Tetrahydrocurcumin (THC), the principal metabolite of natural curcumin, is renowned for its anti-inflammatory properties. In this research, we explored the impact of THC on the expression of inflammatory factors, neurotrophins, and transforming growth factor β1 (TGF-β1) in the prefrontal cortex after chronic restraint stress (CRS) in mice and in lipopolysaccharide (LPS)-induced TNC1 astrocytes. Our findings indicated that THC mitigated the anxiety and depression-like behaviours observed in CRS mice. It also influenced the expression of TGF-β1, p-SMAD3/SMAD3, sirtuin 1 (SIRT1), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), inducible nitric oxide synthase (iNOS), and tumour necrosis factor α (TNF-α). Specifically, THC augmented the expressions of TGF-β1, p-SMAD3/SMAD3, SIRT1, BDNF, and GDNF, whilst diminishing the expressions of iNOS and TNF-α in LPS-induced astrocytes. However, when pre-treated with SB431542, a TGF-β1 receptor inhibitor, it nullified the aforementioned effects of THC on astrocytes. Our results propose that THC delivers its anti-depressive effects through the activation of TGF-β1, enhancement of p-SMAD3/SMAD3 and SIRT1 expression, upregulation of BDNF and GDNF, and downregulation of iNOS and TNF-α. This research furnishes new perspectives on the anti-inflammatory mechanism that underpins the antidepressant-like impact of THC.

Role of SIRT1 in sepsis-induced encephalopathy: Molecular targets for future therapies

Sepsis induces neuroinflammation, BBB disruption, cerebral hypoxia, neuronal mitochondrial dysfunction, and cell death causing sepsis-associated encephalopathy (SAE). These pathological consequences lead to short- and long-term neurobehavioural deficits. Till now there is no specific treatment that directly improves SAE and its associated behavioural impairments. In this review, we discuss the underlying mechanisms of sepsis-induced brain injury with a focus on the latest progress regarding neuroprotective effects of SIRT1 (silent mating type information regulation-2 homologue-1). SIRT1 is an NAD+ -dependent class III protein deacetylase. It is able to modulate multiple downstream signals (including NF-κB, HMGB, AMPK, PGC1α and FoxO), which are involved in the development of SAE by its deacetylation activity. There are multiple recent studies showing the neuroprotective effects of SIRT1 in neuroinflammation related diseases. The proposed neuroprotective action of SIRT1 is meant to bring a promising therapeutic strategy for managing SAE and ameliorating its related behavioural deficits.

Helichrysum stoechas (L.) Moench reduces body weight gain and modulates mood disorders via inhibition of silent information regulator 1 (SIRT1) by arzanol

The prevalence of obesity is steadily rising, making safe and more efficient anti-obesity treatments an urgent medical need. Growing evidence correlates obesity and comorbidities, including anxiety and depression, with the development of a low-grade inflammation in peripheral and central tissues. We hypothesized that attenuating neuroinflammation might reduce weight gain and improve mood. We investigated the efficacy of a methanolic extract from Helichrysum stoechas (L.) Moench (HSE), well-known for its anti-inflammatory properties, and its main constituent arzanol (AZL). HPLC-ESI-MS2 and HPLC-UV were used to characterize the extract. HSE effects on mood and feeding behavior was assessed in mice. The mechanism of action of HSE and AZL was investigated in hippocampus samples and SH-SY5Y cells by western blotting and immunofluorescence. Oral administration of HSE for 3 weeks limited weight gain with no significant decrease in food intake. HSE produced an anxiolytic-like and antidepressant-like phenotype comparable to diazepam and amitriptyline, respectively, in the absence of locomotor and cognitive impairments and induced neuroprotective effects in glutamate-exposed SH-SY5Y cells. A dose-dependent reduction of SIRT1 expression was detected in SH-SY5Y cells and in hippocampal samples from HSE-treated mice. The inhibition of the SIRT1-FoxO1 pathway was induced in the hypothalamus. Molecular docking studies proposed a mechanism of SIRT1 inhibition by AZL, confirmed by the evaluation of inhibitory effects on SIRT1 enzymatic activity. HSE limited weight gain and comorbidities through an AZL-mediated SIRT1 inhibition. These activities indicate HSE an innovative therapeutic perspective for obesity and associated mood disorders.

The Gordian knot of the immune-redox systems' interactions in psychosis

During the last decades the attempt to enlighten the pathobiological substrate of psychosis, from merely focusing on neurotransmitters, has expanded into new areas like the immune and redox systems. Indeed, the inflammatory hypothesis concerning psychosis etiopathology has exponentially grown with findings reflecting dysfunction/aberration of the immune/redox systems' effector components namely cytokines, chemokines, CRP, complement system, antibodies, pro-/anti-oxidants, oxidative stress byproducts just to name a few. Yet, we still lie far from comprehending the underlying cellular mechanisms, their causality directions, and the moderating/mediating parameters affecting these systems; let alone the inter-systemic (between immune and redox) interactions. Findings from preclinical studies on the stress field have provided evidence indicative of multifaceted interactions among the immune and redox components so tightly intertwined as a Gordian knot. Interestingly the literature concerning the interactions between these same systems in the context of psychosis appears minimal (if not absent) and ambiguous. This review attempts to draw a frame of the immune-redox systems' interactions starting from basic research on the stress field and expanding on clinical studies with cohorts with psychosis, hoping to instigate new avenues of research.

Dexmedetomidine alleviates anxiety-like behaviors in female mice with musculoskeletal pain through SIRT1/p53 axis

BACKGROUND

Musculoskeletal pain is the most common form of chronic pain. Anxiety increases pain intensity and appears to have a major impact on the prevalence and also disability of musculoskeletal pain in women. We examined the effect of dexmedetomidine (DEX) on anxiety-like behaviors associated with musculoskeletal pain and the underlying molecular mechanism in female mice.

METHODS

Musculoskeletal pain was induced by injection of acidified saline into the gastrocnemius muscle in adult female mice, and the von Frey filament test is used to measure mechanical sensitivity. DEX and EX527 (SIRT1 inhibitor) were administered after modelling. Behavioral tests were used for anxiety and motor activity tests. SIRT1, p53 and acetyl-p53 were quantified by Western blot.

RESULTS

Adult female mice with musculoskeletal pain exhibit increased fear-like behavior by reducing SIRT1 expression in the medial prefrontal cortex (mPFC). While administration of DEX was able to alleviate mechanical hypersensitivity and anxiety-like behaviors by blocking SIRT1 decline and acetyl-p53 upregulation in mPFC, EX527 inhibited acetyl-p53 rise and reversed the antinociceptive and anxiolytic effects of DEX.

CONCLUSION

DEX may alleviate anxiety-like behaviors in mice with musculoskeletal pain via the SIRT1/p53 axis. These results suggest that DEX may have a potential therapeutic role in musculoskeletal pain-induced anxiety.

Plasma exosomes lncRNA-miRNA-mRNA network construction and its diagnostic efficacy identification in first-episode schizophrenia

BACKGROUND

The exosomal lncRNA-miRNA-mRNA networks in first episode schizophrenia (FOS) have not reported yet. This study examined the lncRNA, miRNA and mRNA expression level in exosome derived from first episode schizophrenia (FOS) patients, and explored the the potential of exosomes as biomarkers for schizophrenia.

METHODS

We recruited 10 FOS patients and healthy controls (HCs) respectively, examined the lncRNA, miRNA and mRNA expression level of plasma exosome by high throughput sequencing, constructed lncRNA-miRNA-mRNA network, and performed correlation analysis, GO and KEGG pathway analysis, PPI network construction and ROC analysis.

RESULTS

There were 746 differently expressed lncRNA, 22 differently expressed miRNA, and 2637 differently expressed mRNA in plasma exosome in FOS compared with HCs. Then we constructed ceRNA network consisting of 8 down-regulated lncRNA, 7 up-regulated miRNA and 65 down-regulated mRNA, and 1 up-regulated lncRNA, 1 down-regulated miRNA and 4 up-regulated mRNA. The expression level of 1 lncRNA and 7 mRNA in exosomal network were correlated with PANSS score. GO and KEGG pathway analysis showed that 4 up-regulated mRNAs were enriched in neuropsychiatric system function. Down-regulated mRNA EZH2 and SIRT1 were identified as hub gene. Finally, we detected the ROC curve of ENSG00000251562, miR-26a-5p, EZH2, miR-22-3p, SIRT1, ENSG00000251562-miR-26a-5p-EZH2, ENSG00000251562-miR-22-3p-SIRT1, and found that the AUC of ceRNA network was higher than lncRNA, miRNA and mRNA alone.

CONCLUSION

We constructed the lncRNA-miRNA-mRNA network in exosome derived from FOS plasma, and found that lncRNA-miRNA-mRNA network has potential as biomarkers for FOS.

Involvement of brain cell phenotypes in stress-vulnerability and resilience

Stress-related disorders' prevalence is epidemically increasing in modern society, leading to a severe impact on individuals' well-being and a great economic burden on public resources. Based on this, it is critical to understand the mechanisms by which stress induces these disorders. The study of stress made great progress in the past decades, from deeper into the hypothalamic-pituitary-adrenal axis to the understanding of the involvement of a single cell subtype on stress outcomes. In fact, many studies have used state-of-the-art tools such as chemogenetic, optogenetic, genetic manipulation, electrophysiology, pharmacology, and immunohistochemistry to investigate the role of specific cell subtypes in the stress response. In this review, we aim to gather studies addressing the involvement of specific brain cell subtypes in stress-related responses, exploring possible mechanisms associated with stress vulnerability versus resilience in preclinical models. We particularly focus on the involvement of the astrocytes, microglia, medium spiny neurons, parvalbumin neurons, pyramidal neurons, serotonergic neurons, and interneurons of different brain areas in stress-induced outcomes, resilience, and vulnerability to stress. We believe that this review can shed light on how diverse molecular mechanisms, involving specific receptors, neurotrophic factors, epigenetic enzymes, and miRNAs, among others, within these brain cell subtypes, are associated with the expression of a stress-susceptible or resilient phenotype, advancing the understanding/knowledge on the specific machinery implicate in those events.

Resveratrol ameliorates maternal separation-induced anxiety- and depression-like behaviors and reduces Sirt1-NF-kB signaling-mediated neuroinflammation

Maternal separation in early life has a detrimental effect on the physiological and biochemical functions of the brains of offspring and can lead to anxiety- and depression-like behaviors later in life. Resveratrol possesses a variety of pharmacological properties, including anti-inflammatory, anxiolytic, and anti-depressive effects. In rodents, resveratrol can attenuate anxiety- and depression-like behaviors induced by chronic unpredictable mild stress, estrogen deficiency, and lipopolysaccharide. However, whether resveratrol administration during adolescence can counteract these behaviors when they result from maternal separation is unknown. In this study, male C57BL/6J mice were separated from their mothers for 4 h per day from postnatal day 2 (PND 2) to PND 21; starting on PND 61, resveratrol was administered intraperitoneally at 40 mg/(kg/day^-1) for 4 weeks. At 3 months of age, anxiety and depression-like behaviors were assessed in the male offspring using a series of tasks consisting of an open field test, an elevated plus maze test, a forced swimming test, and a tail suspension test. The hippocampal levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-alpha (TNF-α) were measured by ELISA, while those of sirtuin 1 (Sirt1) and nuclear factor kappa B (NF-κB) p65 were determined by western blotting and PCR. The results showed that maternal separation led to increased anxiety- and depression-like behaviors, enhanced the levels of pro-inflammatory cytokines, and downregulated the Sirt1/NF-κB signaling pathway in the male offspring; however, these effects could be reversed by treatment with resveratrol. Our findings suggested that resveratrol can ameliorate inflammation and anxiety- and depression-like behaviors induced by maternal separation via the activation of the Sirt1/NF-κB pathway.

Study on the Mechanism for SIRT1 during the Process of Exercise Improving Depression

The mechanism behind the onset of depression has been the focus of current research in the neuroscience field. Silent information regulator 1 (SIRT1) is a key player in regulating energy metabolism, and it can regulate depression by mediating the inflammatory response (e.g., nuclear factor-kappa B (NF-κB), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β)), gene expression in the nucleus accumben (NAc) and CA1 region of the hippocampus (e.g., nescient helix-loop-helix2 (NHLH2), monoamine oxidase (MAO-A), and 5-Hydroxyindole-3-acetic acid (5-HIAA)), and neuronal regeneration in the CA3 region of the hippocampus. Exercise is an important means to improve energy metabolism and depression, but it remains to be established how SIRT1 acts during exercise and improves depression. By induction and analysis, SIRT1 can be activated by exercise and then improve the function of the hypothalamic-pituitary-adrenal (HPA) axis by upregulating brain-derived neurotrophic factors (BDNF), inhibit the inflammatory response (suppression of the NF-κB and TNF-α/indoleamine 2,3-dioxygenase (IDO)/5-Hydroxytryptamine (5-HT) pathways), and promote neurogenesis (activation of the insulin-like growth factor1 (IGF-1) and growth-associated protein-43 (GAP-43) pathways, etc.), thereby improving depression. The present review gives a summary and an outlook based on this finding and makes an analysis, which will provide a new rationale and insight for the mechanism by which exercise improves depression.

Baicalin attenuates chronic unpredictable mild stress-induced hippocampal neuronal apoptosis through regulating SIRT1/PARP1 signaling pathway

Baicalin (BA), a flavonoid glycoside extracts from Scutellaria baicalensis Georgi, has been reported to exert antidepressant effects. Emerging evidence indicates that neuronal apoptosis plays a crucial role in the pathogenesis of depression. Poly (ADP-ribose) polymerase-1 (PARP1) is established as a key regulator of the cellular apoptosis. In the present study, we explored whether BA exerts antidepressant effects by regulating PARP1 signaling pathway and elucidated the underlying mechanisms. We found that administration of BA (30 mg/kg, 60 mg/kg) alleviated chronic unpredictable mild stress (CUMS)-induced depressive-like behaviors by increasing sucrose consumption in sucrose preference test (SPT), improving activity status in open field test (OFT) and reducing rest time in tail suspension test (TST). Hematoxylin and eosin (HE) staining and Nissl staining showed that BA ameliorated CUMS-induced neuronal damage in the hippocampus. Moreover, BA significantly upregulated anti-apoptotic protein Bcl-2, downregulated pro-apoptotic protein Bax and cleaved-caspase-3 after CUMS in hippocampal of mice. Intriguingly, western blot and immunohistochemistry (IHC) results showed that the protein level of PARP1 was significantly increased in hippocampal tissue after CUMS, which was reversed by BA treatment. In primary hippocampal neurons (PHNs), BA abrogated the neuronal apoptosis caused by PARP1 overexpression. Meanwhile, BA significantly increased the protein level of SIRT1, SIRT1 inhibitor (EX-527) treatment reversed the effect of BA on reducing the protein level of PARP1 and neuronal apoptosis in CUMS-induced mice. Overall, our results indicated that BA attenuated the CUMS-induced hippocampal neuronal apoptosis through regulating the SIRT1/PARP1 signaling pathway.

Silent information regulator 1 mediates H 2 S-inhibited chronic restraint stress-induced depressive-like behaviors by regulating hippocampal autophagy

OBJECTIVES

Our previous study has demonstrated that hydrogen sulfide (H 2 S), a novel gasotransmitter, attenuates excessive autophagy and depressive-like behaviors in chronic restraint stress (CRS)-exposed rats, but the underlying molecular mechanism remains to be elucidated. Silent information regulator 1 (SIRT1), a deacetylase at the consumption of NAD+ plays an important regulatory role in depression. Hence, this study aimed to investigate whether SIRT1 mediates the protective effect of H 2 S on CRS-induced depressive-like behaviors by regulating hippocampal autophagy.

METHODS

Adult male Sprague-Dawley (SD) rats were subjected to CRS (6 h × 28 days) to induce depression-like behavior. Rats were injected with sodium hydrosulfate (NaHS, 100 μmol/kg/d, i.p.), as a donor of H 2 S, alone or in combination with Sirtinol (a SIRT1 inhibitor; 10 nmol, i.c.v.) during CRS process. The depression-like characteristics of rats were assessed by the novelty-suppressed feeding test (NSFT), tail suspension test (TST), forced swimming test (FST) and open field test (OFT). The number of hippocampal autophagosomes was detected by transmission electron microscopy. The expressions of hippocampal autophagy-related proteins were measured by western blotting analysis.

RESULTS

Sirtinol blocked the inhibitory effect of H 2 S on depressive-like behaviors in CRS-exposed rats according to NSFT, TST, FST and OFT. In addition, sirtinol reversed the protective response of H 2 S to CRS-induced excessive autophagy, as proved by the increases in the number of autophagosomes and the expression of Beclin-1 as well as a decrease in the expression of P62 in the hippocampus.

CONCLUSION

These results indicated that SIRT1 contributes to the antidepressant-like function of H 2 S during CRS via reducing hippocampal autophagy.

The sex-dependent response to psychosocial stress and ischaemic heart disease

Stress is an important risk factor for modern chronic diseases, with distinct influences in males and females. The sex specificity of the mammalian stress response contributes to the sex-dependent development and impacts of coronary artery disease (CAD). Compared to men, women appear to have greater susceptibility to chronic forms of psychosocial stress, extending beyond an increased incidence of mood disorders to include a 2- to 4-fold higher risk of stress-dependent myocardial infarction in women, and up to 10-fold higher risk of Takotsubo syndrome-a stress-dependent coronary-myocardial disorder most prevalent in post-menopausal women. Sex differences arise at all levels of the stress response: from initial perception of stress to behavioural, cognitive, and affective responses and longer-term disease outcomes. These fundamental differences involve interactions between chromosomal and gonadal determinants, (mal)adaptive epigenetic modulation across the lifespan (particularly in early life), and the extrinsic influences of socio-cultural, economic, and environmental factors. Pre-clinical investigations of biological mechanisms support distinct early life programming and a heightened corticolimbic-noradrenaline-neuroinflammatory reactivity in females vs. males, among implicated determinants of the chronic stress response. Unravelling the intrinsic molecular, cellular and systems biological basis of these differences, and their interactions with external lifestyle/socio-cultural determinants, can guide preventative and therapeutic strategies to better target coronary heart disease in a tailored sex-specific manner.

Potential Therapeutic Effects of NAMPT-Mediated NAD Biosynthesis in Depression In Vivo

This study aimed to investigate the potential therapeutic effects of nicotinamide phosphoribosyltransferase (NAMPT)-mediated adenine dinucleotide (NAD) biosynthesis in depression models in vivo. Nampt^flox/flox mice were used to evaluate the role of NAMPT in depression. NAMPT and NAD levels in the prefrontal cortex (PFC) were measured, and depression-associated behavior, cognitive function, and social interaction were evaluated. The expression levels of BDNF, pCREB, CREB, monoamine neurotransmitters, and corticosterone (CORT) were also detected in the PFC. The contents of NAMPT and NAD decreased in the PFC in Nampt^flox/flox mice. Nampt^flox/flox mice showed depression-like behaviors, cognitive function deterioration, decreased social ability, and decreased dominance. Meanwhile, there were decreased expression levels of the pCREB/CREB ratio, but not BDNF, in the PFC. Levels of DA, 5-HT, and NE were decreased, and CORT was activated in the PFC of Nampt^flox/flox mice. Additionally, the role of NAMPT-NAD was examined in rats treated with nicotinamide riboside (NR) after being exposed to chronic unexpected mild stress (CUMS). NR reversed the decreased NAMPT expression in the PFC and HIP, and the NAD content in the PFC, but not HIP in rats with CUMS-induced depression. NR also improved depressive- and anxiolytic-like behaviors, locomotor activity, and cognitive function. BDNF expression and the pCREB/CREB ratio were significantly increased in both the PFC and HIP after NR treatment. The activation of CORT and decreased content of DA were reversed after NR treatment in the PFC. There was no difference in the 5-HT content among groups in both the PFC and HIP. Taken together, NAD synthesis induced by NAMPT could be associated with depression-like behaviors in mice, and the elevated NAD level by NR improved depression in rats.

Role of sirtuin1 in impairments of emotion-related behaviors in mice with chronic mild unpredictable stress during adolescence

Long-term exposure to physical and/or psychosocial stress during early life and/or adolescence increases the risk of psychiatric disorders such as major depressive disorder and anxiety disorders. However, the molecular mechanisms underlying early stress-induced brain dysfunction are poorly understood. In the present study, mice at 4 weeks old were subjected to chronic mild unpredictable stress (CMUS) for 4 weeks, and subsequently to assays of emotion-related behaviors. Thereafter, they were sacrificed and their brains were collected for real-time quantitative polymerase chain reaction (RT-qPCR). Mice with CMUS during adolescence showed despair behavior, anxiety-like behavior, social behavior deficits, and anhedonia in forced-swim, marble-burying, social interaction, and sucrose preference tests, respectively. Additionally, RT-qPCR revealed that the expression levels of sirtuin1 (SIRT1), a NAD⁺-dependent deacetylase that mediates stress responses, were down-regulated in the prefrontal cortex and hippocampus of mice with CMUS compared with control mice. Next, to investigate the pathophysiological role of decreased Sirt1 expression levels in stress-induced behavioral deficits, we assessed the effects of resveratrol, a pharmacological activator of SIRT1, in mice exposed to CMUS. Chronic treatment with resveratrol prevented -induced social behavior deficits and depression-like behaviors. These results suggest that CMUS during adolescence decreases Sirt1 expression in the brain, leading to deficits in emotional behavior. Accordingly, SIRT1 activators, such as resveratrol, may be preventive agents against abnormalities in emotional behavior following stress during an immature period.

The Sirtuin 2 Inhibitor AK-7 Leads to an Antidepressant-Like Effect in Mice via Upregulation of CREB1, BDNF, and NTRK2 Pathways

Depression is one of the most important and serious health problems in developing countries which affects millions of people. It is associated with the decrease of the quality of life as well as suicides and mortality. The disease may show recurrent episodes in some patients. Obviously, not all the patients with depression could be treated properly, because some individuals are drug-resistant and the options for the therapy are limited. Therefore, it is crucial to investigate new molecules and pathways that may have possible antidepressant activity. Sirtuin (SIRT), known as a class III histone deacetylase, which is regulated by nicotinamide adenine dinucleotide (NAD +), is one of these molecules. In the current study, we investigated the possible antidepressant-like effect of SIRT2 inhibitor AK-7. For this purpose, behavioral tests were performed in chronic AK-7-treated mice, and the expression levels of BDNF, NGF, NTF3, CREB, NTRK2, ERK1, ERK2, and GAP43 genes were evaluated by qRT-PCR analysis in brain tissues. Protein levels for BDNF, CREB1, and NTRK2 were determined by western blot. Our data showed that AK-7 significantly decreased immobility time and showed antidepressant-like effect. In addition, AK-7 treatment significantly increased mRNA levels of CREB and NTRK2 and protein levels of CREB1, BDNF, and NTRK2. Finally, our results suggest that SIRT2 and AK-7 may have a potential role in the cellular mechanisms of depression.

A resveratrol derivative modulates TRH and TRH ‐like peptide expression throughout the brain and peripheral tissues of male rats

Introduction

Methods

Results

Conclusion

Virtual Screening in the Identification of Sirtuins’ Activity Modulators

Sirtuins are NAD⁺-dependent deac(et)ylases with different subcellular localization. The sirtuins’ family is composed of seven members, named SIRT-1 to SIRT-7. Their substrates include histones and also an increasing number of different proteins. Sirtuins regulate a wide range of different processes, ranging from transcription to metabolism to genome stability. Thus, their dysregulation has been related to the pathogenesis of different diseases. In this review, we discussed the pharmacological approaches based on sirtuins’ modulators (both inhibitors and activators) that have been attempted in in vitro and/or in in vivo experimental settings, to highlight the therapeutic potential of targeting one/more specific sirtuin isoform(s) in cancer, neurodegenerative disorders and type 2 diabetes. Extensive research has already been performed to identify SIRT-1 and -2 modulators, while compounds targeting the other sirtuins have been less studied so far. Beside sections dedicated to each sirtuin, in the present review we also included sections dedicated to pan-sirtuins’ and to parasitic sirtuins’ modulators. A special focus is dedicated to the sirtuins’ modulators identified by the use of virtual screening.

Encore: Behavioural animal models of stress, depression and mood disorders

Animal studies over the past two decades have led to extensive advances in our understanding of pathogenesis of depressive and mood disorders. Among these, rodent behavioural models proved to be of highest informative value. Here, we present a comprehensive overview of the most popular behavioural models with respect to physiological, circuit, and molecular biological correlates. Behavioural stress paradigms and behavioural tests are assessed in terms of outcomes, strengths, weaknesses, and translational value, especially in the domain of pharmacological studies.

Putative involvement of sirtuin modulators in LPS-induced sickness behaviour in mice

NAD⁺-dependent histone deacetylases (sirtuins 1-7) have been shown to be involved in various pathophysiological conditions including their involvement in cardiovascular, cancerous, neurodegenerative, immune dysregulation and inflammatory conditions. This study investigates the inflammomodulatory potential of resveratrol (RES), a sirtuin activator and sirtinol (SIR), a sirtuin inhibitor in lipopolysaccharide (LPS)-induced model of sickness behaviour in mice. Male Swiss albino mice were divided into five groups (n = 6) consisting of saline (SAL), LPS, RES, SIR, and fluoxetine (FLU) respectively, each group except LPS was prepared by intraperitoneally (i.p.) administration of SAL (10 mL/kg), RES (50 mg/kg), SIR (2 mg/kg) and FLU (10 mg/kg). Thirty minutes after the treatments, all the groups, except SAL were administered LPS (2 mg/kg, i.p.). The behavioural assays including, open field test, forced swim test, and tail suspension tests were conducted 1 h after LPS challenge. LPS administration significantly reduced the locomotor activity along with inducing a state of high immobility and that was prevented by pretreatment with RES and SIR. Further, various proinflammatory cytokines (TNF-α, IL-6, and IL-1β), and oxidative stress markers (MDA and GSH) were found to be significantly elevated in the brain homogenates after LPS treatment. SIR pretreatment abrogated the LPS-induced neuroinflammatory and oxidative stress changes, whereas RES was only effective in reducing the oxidative stress and TNF-α levels. The results of this study speculate that the role of SIRT modulators in neuroinflammatory conditions could vary with their dose, regimen and chemical properties. Further studies with detailed molecular and pharmacokinetic profiling will be needed to explore their therapeutic potentials.

LncRNA-84277 is involved in chronic pain-related depressive behaviors through miR-128-3p/SIRT1 axis in central amygdala

Long-term chronic pain can lead to depression. However, the mechanism underlying chronic pain-related depression remains unclear. Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylase (HDAC). Our previous studies have demonstrated that SIRT1 in the central nucleus of the amygdala (CeA) is involved in the development of chronic pain-related depression. In addition, increasing studies have indicated that long non-coding RNAs (lncRNAs) play a vital role in the pathogenesis of pain or depression. However, whether lncRNAs are involved in SIRT1-mediated chronic pain-related depression remains largely unknown. In this study, we identified that a novel lncRNA-84277 in CeA was the upstream molecule to regulate SIRT1 expression. Functionally, lncRNA-84277 overexpression in CeA significantly alleviated the depression-like behaviors in spared nerve injury (SNI)-induced chronic pain rats, whereas lncRNA-84277 knockdown in CeA induced the depression-like behaviors in naïve rats. Mechanically, lncRNA-84277 acted as a competing endogenous RNA (ceRNA) to upregulate SIRT1 expression by competitively sponging miR-128-3p, and therefore improved chronic pain-related depression-like behaviors. Our findings reveal the critical role of lncRNA-84277 in CeA specifically in guarding against chronic pain-related depression via a ceRNA mechanism and provide a potential therapeutic target for chronic pain-related depression.

Enhancing Endocannabinoid Signaling via β-Catenin in the Nucleus Accumbens Attenuates PTSD- and Depression-like Behavior of Male Rats

Inhibition of fatty acid amide hydrolase (FAAH), which increases anandamide levels, has been suggested as a potential treatment for stress-related conditions. We examined whether the stress-preventing effects of the FAAH inhibitor URB597 on behavior are mediated via β-catenin in the nucleus accumbens (NAc). Male rats were exposed to the shock and reminders model of PTSD and then treated with URB597 (0.4 mg/kg; i.p.). They were tested for anxiety- (freezing, startle response), depression-like behaviors (despair, social preference, anhedonia), and memory function (T-maze, social recognition). We also tested the involvement of the CB1 receptor (CB1r), β-catenin, and metabotropic glutamate receptor subtype 5 (mGluR5) proteins. URB597 prevented the shock- and reminders-induced increase in anxiety- and depressive-like behaviors, as well as the impaired memory via the CB1r-dependent mechanism. In the NAc, viral-mediated β-catenin overexpression restored the behavior of rats exposed to stress and normalized the alterations in protein levels in the NAc and the prefrontal cortex. Importantly, when NAc β-catenin levels were downregulated by viral-mediated gene transfer, the therapeutic-like effects of URB597 were blocked. We suggest a potentially novel mechanism for the therapeutic-like effects of FAAH inhibition that is dependent on β-catenin activation in the NAc in a PTSD rat model.

Basolateral Amygdala SIRT1/PGC-1α Mitochondrial Biogenesis Pathway Mediates Morphine Withdrawal-Associated Anxiety in Mice

BACKGROUND

Anxiety is a negative emotion that contributes to craving and relapse during drug withdrawal. Sirtuins 1 (SIRT1) has been reported to be critical in both negative emotions and drug addiction. However, it remains incompletely elucidated whether SIRT1 is involved in morphine withdrawal-associated anxiety.

METHODS

We established a mouse model of anxiety-like behaviors induced by morphine withdrawal and then detected neuronal activity with immunofluorescence and mitochondrial morphology with electron microscopy, mitochondrial DNA contents with quantitative real-time PCR, and mitochondrial function with the ATP content detection kit and the Mitochondrial Complex IV Activity Kit in the basolateral amygdala (BLA). The mitochondrial molecules were detected by western blot. Then we used virus-mediated downregulation and overexpression of SIRT1 in BLA to investigate the effect of SIRT1 on anxiety and mitochondrial function. Finally, we examined the effects of pharmacological inhibition of SIRT1 on anxiety and mitochondrial function.

RESULTS

We found that BLA neuronal activity, mitochondrial function, and mtDNA content were significantly higher in morphine withdrawal mice. Furthermore, the expression levels of mitochondrial molecules increased in BLA cells. Virus-mediated downregulation of SIRT1 in BLA prevented anxiety-like behaviors in morphine withdrawal mice, whereas overexpression of SIRT1 in BLA facilitated anxiety-like behaviors in untreated mice through the SIRT1/ peroxisome proliferator activated receptor gamma coactivator 1-alpha pathway. Intra-BLA infusion of selective SIRT1 antagonist EX527 effectively ameliorated anxiety-like behaviors and mitochondrial dysfunction in mice with morphine withdrawal.

CONCLUSION

Our results implicate a causal role for SIRT1 in the regulation of anxiety through actions on mitochondrial biogenesis. Inhibitors targeting SIRT1 may have therapeutic potential for the treatment of opioid withdrawal-associated anxiety.

Elevation of N-acetyltransferase 10 in hippocampal neurons mediates depression- and anxiety-like behaviors

Major depressive disorder (MDD) is one of the most debilitating and severe mental diseases globally. Increasing evidence has shown that epigenetics is critical for understanding brain function and brain disorders, including MDD. N-acetyltransferase 10 (NAT10), acting on histones, mRNA and other substrates, has been reported to be involved in epigenetic events, including histone acetylation and mRNA modifications. NAT10 is highly expressed in the brain. However, the potential effects of NAT10 on MDD are still unknown. Here, we exploited chronic mild stress (CMS) to induce anxiety- and depression-like behaviors in mice and found that the expression of NAT10 in the mouse hippocampus was upregulated after CMS treatment. Inhibition of NAT10 by pharmacological methods produced anxiolytic- and antidepressant-like effects. Neuron-specific overexpression of NAT10 in the hippocampus resulted in anxiety- and depression-like behaviors, accompanied by higher SIRT1 protein levels, and lower dendritic spine densities. Overall, it was found that elevation of NAT10 in hippocampal neurons is involved in the occurrence of anxiety- and depression-like behaviors, suggesting that NAT10 could be a potential new target for developing anxiolytics and antidepressants.

Sirtuins and neuropeptide y downregulation in Flinders Sensitive Line rat model of depression

Since the NAD+-dependent histone deacetylases sirtuin-1 (SIRT1) and sirtuin-2 (SIRT2) are critically involved in epigenetics, endocrinology and immunology and affect the longevity in model organisms, we investigated their expression in brains of 3-month-old and 14-15 months old rat model of depression Flinders Sensitive Line (FSL) and control Flinders Resistant Line (FRL) rats. In view of the dysregulated NPY system in depression, we also studied NPY in young and old FSL to explore the temporal trajectory of depressive-like-ageing interaction. Sirt1, Sirt2 and Npy mRNA were determined using qRT-PCR in prefrontal cortex (PFC) from young and old FSL and FRL, and in hippocampi from young FSL and FRL. PFC: Sirt1 expression was decreased in FSL (p = 0.001). An interaction between age and genotype was found (p = 0.032); young FSL had lower Sirt1 with respect to both age (p = 0.026) and genotype (p = 0.001). Sirt2 was lower in FSL (p = 0.003). Npy mRNA was downregulated in FSL (p = 0.001) but did not differ between the young and old rat groups. Hippocampus: Sirt1 was reduced in young FSL compared to young FRL (p = 0.005). There was no difference in Sirt2 between FSL and FRL. Npy levels were decreased in hippocampus of young FSL compared to young FRL (p = 0.003). Effects of ageing could not be investigated due to loss of samples. To conclude, i this is the first demonstration that SIRT1 and SIRT2 are changed in brain of FSL, a rat model of depression; ii the changes are age-dependent; iii sirtuins are potential targets for treatment of age-related neurodegenerative diseases.

eNAMPT actions through nucleus accumbens NAD+/SIRT1 link increased adiposity with sociability deficits programmed by peripuberty stress

Obesity is frequently associated with impairments in the social domain, and stress at puberty can lead to long-lasting changes in visceral fat deposition and in social behaviors. However, whether stress-induced changes in adipose tissue can affect fat-to-brain signaling, thereby orchestrating behavioral changes, remains unknown. We found that peripubertally stressed male-but not female-mice exhibit concomitant increased adiposity and sociability deficits. We show that reduced levels of the adipokine nicotinamide phosphoribosyltransferase (NAMPT) in fat and its extracellular form eNAMPT in blood contribute to lifelong reductions in sociability induced by peripubertal stress. By using a series of adipose tissue and brain region-specific loss- and gain-of-function approaches, we implicate impaired nicotinamide adenine dinucleotide (NAD+)/SIRT1 pathway in the nucleus accumbens. Impairments in sociability and accumbal neuronal excitability are prevented by normalization of eNAMPT levels or treatment with nicotinamide mononucleotide (NMN), a NAD+-boosting compound. We propose NAD+ boosters to treat social deficits of early life stress origin.

The stressed synapse 2.0: pathophysiological mechanisms in stress-related neuropsychiatric disorders

Stress is a primary risk factor for several neuropsychiatric disorders. Evidence from preclinical models and clinical studies of depression have revealed an array of structural and functional maladaptive changes, whereby adverse environmental factors shape the brain. These changes, observed from the molecular and transcriptional levels through to large-scale brain networks, to the behaviours reveal a complex matrix of interrelated pathophysiological processes that differ between sexes, providing insight into the potential underpinnings of the sex bias of neuropsychiatric disorders. Although many preclinical studies use chronic stress protocols, long-term changes are also induced by acute exposure to traumatic stress, opening a path to identify determinants of resilient versus susceptible responses to both acute and chronic stress. Epigenetic regulation of gene expression has emerged as a key player underlying the persistent impact of stress on the brain. Indeed, histone modification, DNA methylation and microRNAs are closely involved in many aspects of the stress response and reveal the glutamate system as a key player. The success of ketamine has stimulated a whole line of research and development on drugs directly or indirectly targeting glutamate function. However, the challenge of translating the emerging understanding of stress pathophysiology into effective clinical treatments remains a major challenge.

Hippocampal SIRT1 improves cognitive impairment by deacetylating tau protein in diabetic models

Diabetes mellitus (DM) is associated with accelerated cognitive decline. However, the mechanism of diabetic cognitive impairment remains poorly understood. In this study, we found that the expression of Sirtuin 1 (SIRT1), a nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylase, was downregulated significantly in the hippocampus of streptozotocin (STZ)-induced diabetic cognitive impairment rats. Viral overexpression of hippocampal SIRT1 ameliorated cognitive impairment in diabetic rats, but viral knockdown of hippocampal SIRT1 mimicked the diabetic effect, eliciting the cognitive decline in normal animals. Further study showed that the decreased level of SIRT1 may result in the increase of acetylated tau protein in the hippocampus, which may mediate the development of diabetic cognitive impairment. These results suggest that SIRT1 may be a key epigenetic regulator that guards against the development of diabetic cognitive impairment by deacetylating the tau protein. SIRT1 activator may serve as a new therapeutic approach for the treatment of diabetic cognitive impairment.

Cell-Type-Specific Adaptions in Striatal Medium-Sized Spiny Neurons and Their Roles in Behavioral Responses to Drugs of Abuse

Drug addiction is defined as a compulsive pattern of drug-seeking- and taking- behavior, with recurrent episodes of abstinence and relapse, and a loss of control despite negative consequences. Addictive drugs promote reinforcement by increasing dopamine in the mesocorticolimbic system, which alters excitatory glutamate transmission within the reward circuitry, thereby hijacking reward processing. Within the reward circuitry, the striatum is a key target structure of drugs of abuse since it is at the crossroad of converging glutamate inputs from limbic, thalamic and cortical regions, encoding components of drug-associated stimuli and environment, and dopamine that mediates reward prediction error and incentive values. These signals are integrated by medium-sized spiny neurons (MSN), which receive glutamate and dopamine axons converging onto their dendritic spines. MSN primarily form two mostly distinct populations based on the expression of either DA-D1 (D1R) or DA-D2 (D2R) receptors. While a classical view is that the two MSN populations act in parallel, playing antagonistic functional roles, the picture seems much more complex. Herein, we review recent studies, based on the use of cell-type-specific manipulations, demonstrating that dopamine differentially modulates dendritic spine density and synapse formation, as well as glutamate transmission, at specific inputs projecting onto D1R-MSN and D2R-MSN to shape persistent pathological behavioral in response to drugs of abuse. We also discuss the identification of distinct molecular events underlying the detrimental interplay between dopamine and glutamate signaling in D1R-MSN and D2R-MSN and highlight the relevance of such cell-type-specific molecular studies for the development of innovative strategies with potential therapeutic value for addiction. Because drug addiction is highly prevalent in patients with other psychiatric disorders when compared to the general population, we last discuss the hypothesis that shared cellular and molecular adaptations within common circuits could explain the co-occurrence of addiction and depression. We will therefore conclude this review by examining how the nucleus accumbens (NAc) could constitute a key interface between addiction and depression.

Integrative multi-omics landscape of fluoxetine action across 27 brain regions reveals global increase in energy metabolism and region-specific chromatin remodelling

Depression and anxiety are major global health burdens. Although SSRIs targeting the serotonergic system are prescribed over 200 million times annually, they have variable therapeutic efficacy and side effects, and mechanisms of action remain incompletely understood. Here, we comprehensively characterise the molecular landscape of gene regulatory changes associated with fluoxetine, a widely-used SSRI. We performed multimodal analysis of SSRI response in 27 mammalian brain regions using 310 bulk RNA-seq and H3K27ac ChIP-seq datasets, followed by in-depth characterisation of two hippocampal regions using single-cell RNA-seq (20 datasets). Remarkably, fluoxetine induced profound region-specific shifts in gene expression and chromatin state, including in the nucleus accumbens shell, locus coeruleus and septal areas, as well as in more well-studied regions such as the raphe and hippocampal dentate gyrus. Expression changes were strongly enriched at GWAS loci for depression and antidepressant drug response, stressing the relevance to human phenotypes. We observed differential expression at dozens of signalling receptors and pathways, many of which are previously unknown. Single-cell analysis revealed stark differences in fluoxetine response between the dorsal and ventral hippocampal dentate gyri, particularly in oligodendrocytes, mossy cells and inhibitory neurons. Across diverse brain regions, integrative omics analysis consistently suggested increased energy metabolism via oxidative phosphorylation and mitochondrial changes, which we corroborated in vitro; this may thus constitute a shared mechanism of action of fluoxetine. Similarly, we observed pervasive chromatin remodelling signatures across the brain. Our study reveals unexpected regional and cell type-specific heterogeneity in SSRI action, highlights under-studied brain regions that may play a major role in antidepressant response, and provides a rich resource of candidate cell types, genes, gene regulatory elements and pathways for mechanistic analysis and identifying new therapeutic targets for depression and anxiety.

Effect of SIRT1 on white matter neural network in adolescent patients with depression

BACKGROUND

This study aimed to explore the correlation between the rs12415800 polymorphism of the silent information regulator 1 (SIRT1) gene and the white matter neural circuit in adolescent patients with depression.

METHODS

We enrolled 119 participants, comprising 59 adolescent patients with depression and 60 matched healthy controls for analysis. Patients were further subdivided based on genotype; GG, AG, and AA, with G representing the wild type gene, and A representing the A allele at rs12415800.

RESULTS

We found that: (1) lower anisotropy fraction (FA) values in the left cingulate fasciculus and left anterior thalamus radiation in the AG/AA genotype were more likely to be affected by depression. (2) The FA values of the right inferior occipital-frontal fasciculus, right corticospinal tract, right inferior longitudinal fasciculus, and right superior longitudinal fasciculus regions in the depression (AG/AA) group were lower than in the depression (GG) group. (3) FA values of the right inferior occipital-frontal fasciculus left corticospinal tract, right inferior longitudinal fasciculus, left anterior thalamus radiation, right superior longitudinal fasciculus, left inferior longitudinal fasciculus, left uncinate fasciculus, and right anterior thalamus radiation in the depression (GG) group were lower than the control (GG) group.

CONCLUSIONS

The polymorphism locus of the SIRT1 gene rs12415800 may be related to changes in the microstructure of white matter fiber tracts, and patients carrying the A allele (AG/AA) have more changes in the white matter than those with the non-A allele (GG).

Fat mass and obesity-associated protein regulates RNA methylation associated with depression-like behavior in mice

Post-transcriptional modifications of RNA, such as RNA methylation, can epigenetically regulate behavior, for instance learning and memory. However, it is unclear whether RNA methylation plays a critical role in the pathophysiology of major depression disorder (MDD). Here, we report that expression of the fat mass and obesity associated gene (FTO), an RNA demethylase, is downregulated in the hippocampus of patients with MDD and mouse models of depression. Suppressing Fto expression in the mouse hippocampus results in depression-like behaviors in adult mice, whereas overexpression of FTO expression leads to rescue of the depression-like phenotype. Epitranscriptomic profiling of N6-methyladenosine (m⁶A) RNA methylation in the hippocampus of Fto knockdown (KD), Fto knockout (cKO), and FTO-overexpressing (OE) mice allows us to identify adrenoceptor beta 2 (Adrb2) mRNA as a target of FTO. ADRB2 stimulation rescues the depression-like behaviors in mice and spine loss induced by hippocampal Fto deficiency, possibly via the modulation of hippocampal SIRT1 expression by c-MYC. Our findings suggest that FTO is a regulator of a mechanism underlying depression-like behavior in mice.

Multifaced role of protein deacetylase sirtuins in neurodegenerative disease

Sirtuins, a class III histone/protein deacetylase, is a central regulator of metabolic function and cellular stress response. This plays a pivotal role in the pathogenesis and progression of diseases such as cancer, neurodegeneration, metabolic syndromes, and cardiovascular disease. Sirtuins regulate biological and cellular processes, for instance, mitochondrial biogenesis, lipid and fatty acid oxidation, oxidative stress, gene transcriptional activity, apoptosis, inflammatory response, DNA repair mechanism, and autophagic cell degradation, which are known components for the progression of the neurodegenerative diseases (NDDs). Emerging evidence suggests that sirtuins are the useful molecular targets against NDDs like, Alzheimer's Disease (AD), Parkinson's Disease (PD), Huntington's Disease (HD), and Amyotrophic Lateral Sclerosis (ALS). However, the exact mechanism of neuroprotection mediated through sirtuins remains unsettled. The manipulation of sirtuins activity with its modulators, calorie restriction (CR), and micro RNAs (miR) is a novel therapeutic approach for the treatment of NDDs. Herein, we reviewed the current putative therapeutic role of sirtuins in regulating synaptic plasticity and cognitive functions, which are mediated through the different molecular phenomenon to prevent neurodegeneration. We also explained the implications of sirtuin modulators, and miR based therapies for the treatment of life-threatening NDDs.

Influence of psychostimulants and opioids on epigenetic modification of class III histone deacetylase (HDAC)-sirtuins in glial cells

Substance abuse affects the central nervous system (CNS) and remains a global health problem. Psychostimulants, such as cocaine and methamphetamine (METH), and opioids affect neuronal function and lead to behavioral impairments via epigenetic modification. Epigenetic changes occur via classical pathways, especially the class III histone deacetylase (HDAC)-sirtuin (SIRT) family, that act as cellular sensors to regulate energy homeostasis and coordinate cellular responses to maintain genome integrity. However, SIRT family (1-7)-associated neurodegeneration has not been elucidated in the context of energy metabolism. The present study examined the effects of psychostimulants, such as cocaine and METH, and opioids, such as morphine, on SIRT family (1-7) [class I, II, III and IV] expression and cellular translocation-mediated dysfunction in astrocytes and microglial cells. The "nootropic" drug piracetam played a preventative role against psychostimulant- and opioid-induced SIRT (1-7) expression in astrocytes. These results indicate that cocaine, METH, and morphine affected deacetylation and cellular function, and these changes were prevented by piracetam in astrocytes.

Epigenetics of Aggression

Aggression is a complex behavioral trait modulated by both genetic and environmental influences on gene expression. By controlling gene expression in a reversible yet potentially lasting manner in response to environmental stimulation, epigenetic mechanisms represent prime candidates in explaining both individual differences in aggression and the development of elevated aggressive behaviors following life adversity. In this manuscript, we review the evidence for an epigenetic basis in the development and expression of aggression in both humans and related preclinical animal models. In particular, we discuss reports linking DNA methylation, histone post-translational modifications, as well as non-coding RNA, to the regulation of a variety of genes implicated in the neurobiology of aggression including neuropeptides, the serotoninergic and dopaminergic systems, and stress response related systems. While clinical reports do reveal interesting patterns of DNA methylation underlying individual differences and experience-induced aggressive behaviors, they do, in general, face the challenge of linking peripheral observations to central nervous system regulations. Preclinical studies, on the other hand, provide detailed mechanistic insights into the epigenetic reprogramming of gene expression following life adversities. Although the functional link to aggression remains unclear in most, these studies together do highlight the involvement of epigenetic events driven by DNA methylation, histone modifications, and non-coding RNA in the neuroadaptations underlying the development and expression of aggression.

miR-9-5p is involved in the rescue of stress-dependent dendritic shortening of hippocampal pyramidal neurons induced by acute antidepressant treatment with ketamine

Converging clinical and preclinical evidence demonstrates that depressive phenotypes are associated with synaptic dysfunction and dendritic simplification in cortico-limbic glutamatergic areas. On the other hand, the rapid antidepressant effect of acute ketamine is consistently reported to occur together with the rescue of dendritic atrophy and reduction of spine number induced by chronic stress in the hippocampus and prefrontal cortex of animal models of depression. Nevertheless, the molecular mechanisms underlying these morphological alterations remain largely unknown. Here, we found that miR-9-5p levels were selectively reduced in the hippocampus of rats vulnerable to Chronic Mild Stress (CMS), while acute subanesthetic ketamine restored its levels to basal condition in just 24h; miR-9-5p expression inversely correlated with the anhedonic phenotype. A decrease of miR-9-5p was reproduced in an in vitro model of stress, based on primary hippocampal neurons incubated with the stress hormone corticosterone. In both CMS animals and primary neurons, decreased miR-9-5p levels were associated with dendritic simplification, while treatment with ketamine completely rescued the changes. In vitro modulation of miR-9-5p expression showed a direct role of miR-9-5p in regulating dendritic length and spine density in mature primary hippocampal neurons. Among the putative target genes tested, Rest and Sirt1 were validated as biological targets in primary neuronal cultures. Moreover, in line with miR-9-5p changes, REST protein expression levels were remarkably increased in both CMS vulnerable animals and corticosterone-treated neurons, while ketamine completely abolished this alteration. Finally, the shortening of dendritic length in corticosterone-treated neurons was shown to be partly rescued by miR-9-5p overexpression and dependent on REST protein expression. Overall, our data unveiled the functional role of miR-9-5p in the remodeling of dendritic arbor induced by stress/corticosterone in vulnerable animals and its rescue by acute antidepressant treatment with ketamine.

Relationship between SIRT1 gene and adolescent depressive disorder with nonsuicidal self-injury behavior: Based on gene methylation and mRNA expression

OBJECTIVE

The incidence of non-suicidal self-injury (NSSI) behavior in adolescents is increasing year by year. Patients with a history of both depression and NSSI behavior tend to be at greater risk for suicide. At present, the mechanism of adolescent depressive disorder with NSSI behavior is not clear and still in research and exploration. The expression of the Silent Information Regulator 2 Related Enzyme 1 (SIRT1) gene is closely related to the level of serotonin in molecular mechanisms, and may be closely related to the occurrence and development of depressive disorder. This study aimed to explore the relationship between the SIRT1 gene and NSSI behaviors in adolescents with depressive disorder.

METHODS

A total of 15 adolescent depressed patients with NSSI behavior and 15 healthy controls were enrolled in the study. Bisulfite Sequencing PCR (BSP) was used to test the methylation level of SIRT1 gene promoter region of the participants. The real-time fluorescent quantitative PCR was conducted to measure the mRNA expression level of SIRT1 gene.

RESULTS

Our study found that the methylation level of SIRT1 gene promoter region at cytosine-guanine dinucleotide 5 (CpG5) site in depression group was higher than that of control group. Compared with that of control group, the plasma concentration of Sirt1 protein significantly decreased in depression group.

CONCLUSION

Our study investigated the methylation level and the mRNA expression of SIRT1 gene in adolescent depressive patients with NSSI behavior. The study points towards finding an in vivo molecular marker for those adolescent patients.

The role of SIRT1 in the basolateral amygdala in depression-like behaviors in mice

Previous investigations have implicated the basolateral amygdala (BLA) epigenetic mechanisms in the pathophysiology of depression. SIRT1 is a NAD+-dependent class III histone deacetylase, widely expresses in BLA. However, epigenetic mechanisms in the BLA under the regulation of SIRT1 in the depression are largely uncharacterized. Under the chronic unpredictable chronic mild stress (CUMS) mouse model, we used adeno-associated viral vectors (AAV) that encoded SIRT1-shRNA or SIRT1 to specifically knockdown or overexpress SIRT1 in BLA neurons, respectively. CUMS procedure induced significant depression symptoms including the decreased sucrose preference, the less bodyweight gained, the decreased immobile latency and the increased immobile time both in forced swim test (FST) and tail suspension test (TST). Knockdown of SIRT1 in BLA glutamatergic neurons reversed these depression-like behaviors and restored the synaptic abnormalities. Overexpression of SIRT1 in BLA glutamatergic neurons induced depression-like behaviors in non-stressed control mice. The result of protein expressions and ultrastructural changes were consistent with the behavioral results. Our study suggested that downregulation of SIRT1 in BLA has certain beneficial effect on CUMS-induced depression-like behaviors such as anorexia, anhedonia, hopelessness and despair. In addition, the increased expression of SIRT1 may be the immediate cause of depressive-like symptoms. The abnormal expression of SIRT1 may affect the transcriptional regulation mechanism and signaling protein acetylation, affecting neuroplasticity and ultimately contribute to MDD. In the stress-susceptible mice, these two mechanisms may co-exist, but the specific mechanism needs further research.

Effect of chronic handling and social isolation on emotion and cognition in adolescent rats

Adolescence is a critical period of establishing social relations through social interactions that affect the emotional development associated with stress responses, anxiety, depression, and cognitive development. We investigated the behavioral and neurobiological changes induced by handling and social isolation in adolescent rats to determine social interaction effects. Rats were randomly divided into groups and used as a control, a handling, and a social isolation group. After 12 weeks, the handling group showed a significant increase in mobility in the open field test and in tryptophan hydroxylase expression in the dorsal raphe nucleus, as well as significantly reduced immobility times in the forced swim test, compared to the control group (p < 0.05). The social isolation group, in contrast, showed a significant increase in immobility times in the forced swim test and in glucocorticoid and SIRT1 expression in the hippocampus, as well as a significant reduction in mobility in the open field test and in escape latency times in the passive avoidance test, compared to the control group (p < 0.05). The present results show that while handling did not improve cognitive function, it reduced anxiety and lowered depression levels; social isolation, in contrast, significantly impaired the animals' stress response, anxiety and depression levels, and cognitive function. Our findings indicate that handling and social isolation have a strong effect on adolescents' emotional and cognitive development into healthy adults.