Seasonal changes in NRF2 antioxidant pathway regulates winter depression-like behavior

Celastrol alleviates diabetic vascular injury via Keap1/Nrf2-mediated anti-inflammation

Introduction: Celastrol (Cel) is a widely used main component of Chinese herbal medicine with strong anti-inflammatory, antiviral and antitumor activities. In the present study, we aimed to elucidate the cellular molecular protective mechanism of Cel against diabetes-induced inflammation and endothelial dysfunction. Methods: Type 2 diabetes (T2DM) was induced by db/db mice, and osmotic pumps containing Cel (100 μg/kg/day) were implanted intraperitoneally and were calibrated to release the drug for 28 days. In addition, human umbilical vein endothelial cells (HUVECs) were cultured in normal or high glucose and palmitic acid-containing (HG + PA) media in the presence or absence of Cel for 48 h. Results: Cel significantly ameliorated the hyperglycemia-induced abnormalities in nuclear factor (erythroid-derived 2)-like protein 2 (Nrf2) pathway activity and alleviated HG + PA-induced oxidative damage. However, the protective effect of Cel was almost completely abolished in HUVECs transfected with short hairpin (sh)RNA targeting Nrf2, but not by nonsense shRNA. Furthermore, HG + PA reduced the phosphorylation of AMP-activated protein kinase (AMPK), the autophagic degradation of p62/Kelch-like ECH-associated protein 1 (Keap1), and the nuclear localization of Nrf2. However, these catabolic pathways were inhibited by Cel treatment in HUVECs. In addition, compound C (AMPK inhibitors) and AAV9-sh-Nrf2 reduced Cel-induced Nrf2 activation and angiogenesis in db/db mice. Discussion: Taking these findings together, the endothelial protective effect of Cel in the presence of HG + PA may be at least in part attributed to its effects to reduce reactive oxygen species (ROS) and inflammation through p62/Keap1-mediated Nrf2 activation.

NADPH-oxidases as potential pharmacological targets for thrombosis and depression comorbidity

There is a complex interrelationship between the nervous system and the cardiovascular system. Comorbidities of cardiovascular diseases (CVD) with mental disorders, and vice versa, are prevalent. Adults with mental disorders such as anxiety and depression have a higher risk of developing CVD, and people with CVD have an increased risk of being diagnosed with mental disorders. Oxidative stress is one of the many pathways associated with the pathophysiology of brain and cardiovascular disease. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) is one of the major generators of reactive oxygen species (ROS) in mammalian cells, as it is the enzyme that specifically produces superoxide. This review summarizes recent findings on the consequences of NOX activation in thrombosis and depression. It also discusses the therapeutic effects and pharmacological strategies of NOX inhibitors in CVD and brain disorders. A better comprehension of these processes could facilitate the development of new therapeutic approaches for the prevention and treatment of the comorbidity of thrombosis and depression.

A transcriptional program underlying the circannual rhythms of gonadal development in medaka

To cope with seasonal environmental changes, organisms have evolved approximately 1-y endogenous circannual clocks. These circannual clocks regulate various physiological properties and behaviors such as reproduction, hibernation, migration, and molting, thus providing organisms with adaptive advantages. Although several hypotheses have been proposed, the genes that regulate circannual rhythms and the underlying mechanisms controlling long-term circannual clocks remain unknown in any organism. Here, we show a transcriptional program underlying the circannual clock in medaka fish (Oryzias latipes). We monitored the seasonal reproductive rhythms of medaka kept under natural outdoor conditions for 2 y. Linear regression analysis suggested that seasonal changes in reproductive activity were predominantly determined by an endogenous program. Medaka hypothalamic and pituitary transcriptomes were obtained monthly over 2 y and daily on all equinoxes and solstices. Analysis identified 3,341 seasonally oscillating genes and 1,381 daily oscillating genes. We then examined the existence of circannual rhythms in medaka via maintaining them under constant photoperiodic conditions. Medaka exhibited approximately 6-mo free-running circannual rhythms under constant conditions, and monthly transcriptomes under constant conditions identified 518 circannual genes. Gene ontology analysis of circannual genes highlighted the enrichment of genes related to cell proliferation and differentiation. Altogether, our findings support the "histogenesis hypothesis" that postulates the involvement of tissue remodeling in circannual time-keeping.

Orphan nuclear receptor nr4a1 regulates winter depression-like behavior in medaka

About 10% of the population suffers from depression in winter at high latitude. Although it has become a serious public health issue, its underlying mechanism remains unknown and new treatments and therapies are required. As an adaptive strategy, many animals also exhibit depression-like behavior in winter. Previously, it has been reported that celastrol, a traditional Chinese medicine, can rescue winter depression-like behavior in medaka, an excellent model of winter depression. Nuclear receptor subfamily 4 group A member 1 (nr4a1, also known as nur77) is a known target of celastrol, and the signaling pathway of nr4a1 was suggested to be inactive in medaka brain during winter, implying the association of nr4a1 and winter depression-like behavior. However, the direct evidence for its involvement in winter depression-like behavior remains unclear. The present study found that nr4a1 was suppressed in the medaka brain under winter conditions. Cytosporone B, nr4a1 chemical activator, reversed winter depression-like behavior under winter conditions. Additionally, nr4a1 mutant fish generated by CRISPR/Cas9 system showed decreased sociability under summer conditions. Therefore, our results demonstrate that the seasonal regulation of nr4a1 regulates winter depression-like behavior and offers potential therapeutic target.

Self-immolative nanocapsules precisely regulate depressive neuronal microenvironment for synergistic antidepression therapy

BACKGROUND

Pharmacotherapy constitutes the first-line treatment for depression. However, its clinical use is hindered by several limitations, such as time lag, side effects, and narrow therapeutic windows. Nanotechnology can be employed to shorten the onset time by ensuring permeation across the blood brain barrier (BBB) to precisely deliver more therapeutic agents; unfortunately, formidable challenges owing to the intrinsic shortcomings of commercial drugs remain.

RESULTS

Based on the extraordinary capability of monoamines to regulate the neuronal environment, we engineer a network nanocapsule for delivering serotonin (5-hydroxytryptamine, 5-HT) and catalase (CAT) to the brain parenchyma for synergistic antidepression therapy. The nanoantidepressants are fabricated by the formation of 5-HT polymerization and simultaneous payload CAT, following by surface modifications using human serum albumin and rabies virus glycoprotein. The virus-inspired nanocapsules benefit from the surface-modifying strategies and exhibit pronounced BBB penetration. Once nanocapsules reach the brain parenchyma, the mildly acidic conditions trigger the release of 5-HT from the sacrificial nanocapsule. Releasing 5-HT further positively regulate moods, relieving depressive symptoms. Meanwhile, cargo CAT alleviates neuroinflammation and enhances therapeutic efficacy of 5-HT.

CONCLUSION

Altogether, the results offer detailed information encouraging the rational designing of nanoantidepressants and highlighting the potential of nanotechnology in mental health disorder therapies.

Variation in responses to photoperiods and temperatures in Japanese medaka from different latitudes

Seasonal changes are more robust and dynamic at higher latitudes than at lower latitudes, and animals sense seasonal changes in the environment and alter their physiology and behavior to better adapt to harsh winter conditions. However, the genetic basis for sensing seasonal changes, including the photoperiod and temperature, remains unclear. Medaka (Oryzias latipes species complex), widely distributed from subtropical to cool-temperate regions throughout the Japanese archipelago, provides an excellent model to tackle this subject. In this study, we examined the critical photoperiods and critical temperatures required for seasonal gonadal development in female medaka from local populations at various latitudes. Intraspecific differences in critical photoperiods and temperatures were detected, demonstrating that these differences were genetically controlled. Most medaka populations could perceive the difference between photoperiods for at least 1 h. Populations in the Northern Japanese group required 14 h of light in a 24 h photoperiod to develop their ovaries, whereas ovaries from the Southern Japanese group developed under 13 h of light. Additionally, Miyazaki and Ginoza populations from lower latitudes were able to spawn under short-day conditions of 11 and 10 h of light, respectively. Investigation of the critical temperature demonstrated that the Higashidori population, the population from the northernmost region of medaka habitats, had a critical temperature of over 18 °C, which was the highest critical temperature among the populations examined. The Miyazaki and the Ginoza populations, in contrast, were found to have critical temperatures under 14 °C. When we conducted a transplant experiment in a high-latitudinal environment using medaka populations with different seasonal responses, the population from higher latitudes, which had a longer critical photoperiod and a higher critical temperature, showed a slower reproductive onset but quickly reached a peak of ovarian size. The current findings show that low latitudinal populations are less responsive to photoperiodic and temperature changes, implying that variations in this responsiveness can alter seasonal timing of reproduction and change fitness to natural environments with varying harshnesses of seasonal changes. Local medaka populations will contribute to elucidating the genetic basis of seasonal time perception and adaptation to environmental changes.

The Nrf2 Pathway in Depressive Disorders: A Systematic Review of Animal and Human Studies

There is increasing interest in the involvement of antioxidative systems in protecting from depression. Among these, Nrf2 occupies a central place. We aimed to review the role of Nrf2 in depression. For this reason, we conducted a PubMed search using as search strategy (psychiatr*[ti] OR schizo*[ti] OR psychot*[ti] OR psychos*[ti] OR depress*[ti] OR MDD[ti] OR BD[ti] OR bipolar[ti] OR Anxiety[ti] OR antidepress*[ti] OR panic[ti] OR obsess*[ti] OR compulsio*[ti] OR “mood disord*”[ti] OR phobi*[ti] OR agoraphob*[ti] OR anorex*[ti] OR anorect*[ti] OR bulimi*[ti] OR “eating disorder*”[ti] OR neurodevelopm*[ti] OR retardation[ti] OR autism[ti] OR autistic[ti] OR ASM[ti] OR adhd[ti] OR “attention-deficit”[ti]) AND nrf2, which on the 9th of March produced 208 results of which 89 were eligible for our purposes. Eligible articles were studies reporting data of Nrf2 manipulations or content by any treatment in human patients or animals with any animal model of depression. Most studies were on mice only (N = 58), 20 on rats only, and three on both rats and mice. There were two studies on cell lines (in vitro) and one each on nematodes and fish. Only four studies were conducted in humans, one of which was post mortem. Most studies were conducted on male animals; however, human studies were carried out on both men and women. The results indicate that Nrf2 is lower in depression and that antidepressant methods (drugs or other methods) increase it. Antioxidant systems and plasticity-promoting molecules, such as those in the Nrf2–HO-1, BDNF–TrkB, and cyclic AMP–CREB pathways, could protect from depression, while glycogen synthase kinase-3β and nuclear factor κB oppose these actions, thus increasing depressive-like behaviours. Since Nrf2 is also endowed with tumorigenic and atherogenic potential, the balance between benefits and harms must be taken into account in designing novel drugs aiming at increasing the intracellular content of Nrf2.

Celastrol targeting Nedd4 reduces Nrf2-mediated oxidative stress in astrocytes after ischemic stroke

Stroke is the second leading cause of death worldwide, and oxidative stress plays a crucial role. Celastrol exhibits strong antioxidant properties in several diseases; however, whether it can affect oxidation in cerebral ischemic-reperfusion injury (CIRI) remains unclear. This study aimed to determine whether celastrol could reduce oxidative damage during CIRI and to elucidate the underlying mechanisms. Here, we found that celastrol attenuated oxidative injury in CIRI by upregulating nuclear factor E2-related factor 2 (Nrf2). Using alkynyl-tagged celastrol and liquid chromatography-tandem mass spectrometry, we showed that celastrol directly bound to neuronally expressed developmentally downregulated 4 (Nedd4) and then released Nrf2 from Nedd4 in astrocytes. Nedd4 promoted the degradation of Nrf2 through K48-linked ubiquitination and thus contributed to astrocytic reactive oxygen species production in CIRI, which was significantly blocked by celastrol. Furthermore, by inhibiting oxidative stress and astrocyte activation, celastrol effectively rescued neurons from axon damage and apoptosis. Our study uncovered Nedd4 as a direct target of celastrol, and that celastrol exerts an antioxidative effect on astrocytes by inhibiting the interaction between Nedd4 and Nrf2 and reducing Nrf2 degradation in CIRI.

Celastrol: The new dawn in the treatment of vascular remodeling diseases

Evidence is mounting that abnormal vascular remodeling leads to many cardiovascular diseases (CVDs). This suggests that vascular remodeling can be a crucial target for the prevention and treatment of CVDs. Recently, celastrol, an active ingredient of the broadly used Chinese herb Tripterygium wilfordii Hook F, has attracted extensive interest for its proven potential to improve vascular remodeling. Substantial evidence has shown that celastrol improves vascular remodeling by ameliorating inflammation, hyperproliferation, and migration of vascular smooth muscle cells, vascular calcification, endothelial dysfunction, extracellular matrix remodeling, and angiogenesis. Moreover, numerous reports have proven the positive effects of celastrol and its therapeutic promise in treating vascular remodeling diseases such as hypertension, atherosclerosis, and pulmonary artery hypertension. The present review summarizes and discusses the molecular mechanism of celastrol regulating vascular remodeling and provides preclinical proof for future clinical applications of celastrol.

Developmental impacts of Nrf2 activation by dimethyl fumarate (DMF) in the developing zebrafish (Danio rerio) embryo

Dimethyl fumarate (DMF) is pharmaceutical activator of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates of many cellular antioxidant response pathways, and has been used to treat inflammatory diseases such as multiple sclerosis. However, DMF has been shown to produce adverse effects on offspring in animal studies and as such is not recommended for use during pregnancy. The goal of this work is to better understand how these adverse effects are initiated and the role of DMF-induced Nrf2 activation during three critical windows of development in embryonic zebrafish (Danio rerio): pharyngula, hatching, and protruding-mouth stages. To evaluate Nrf2 activation, wildtype zebrafish, and mutant zebrafish (nrf2afh318/fh318) embryos with a loss of function mutation in Nrf2a, the co-ortholog to human Nrf2, were treated for 6 h with DMF (0-20 μM) beginning at the pharyngula, hatching, or protruding-mouth stage and assessed for survival and morphology. Nrf2a mutant fish had an increase in survival, however, morphology studies demonstrated Nrf2a mutant fish had more severe deformities occurring with exposures during the hatching stage. To verify Nrf2 cellular localization and downstream impacts on protein-S-glutathionylation in situ, a concentration below the LOAEL was chosen (7 μM) for immunohistochemistry and S-glutathionylation. Embryos were imaged via epifluorescence microscopy studies, the Nrf2a protein in the body tissue was decreased with DMF only when exposed at the hatching stage, while total protein S-glutathionylation was modulated by Nrf2a activity and DMF during the pharyngula and protruding-mouth stage. The pancreatic islet and liver were further analyzed via confocal microscopy. Pancreatic islets and liver also had tissue specific differences with Nrf2a protein expression and protein S-glutathionylation. This work demonstrates how critical windows of exposure and Nrf2a activity may influence toxicity of DMF and highlights tissue-specific changes in Nrf2a protein levels and S-glutathionylation in pancreatic islet and liver during embryonic development.

The treatment of depression - searching for new ideas

Depression is a severe mental health problem that affects people regardless of social status or education, is associated with changes in mood and behavior, and can result in a suicide attempt. Therapy of depressive disorders is based mainly on drugs discovered in the 1960s and early 1970s. Selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) are frontline pharmacological strategies for the medical treatment of depression. In addition, approved by FDA in 2019, esketamine [as nasal spray; N-methyl-D-aspartate (NMDA) receptors antagonist with additional effects on α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, L-type voltage-dependent calcium channel (L-VDCC), opioid receptors, and monoaminergic receptors] is an essential compound in suicide and drug-resistant depression. However, the treatment of depression is burdened with severe side effects, and in many cases, it is ineffective. An equally important issue is the choice of antidepressant therapy in people with comorbid somatic diseases, for example, due to possible interactions with the patient's other drugs. Therefore, there is a great need for new antidepressants with different mechanisms of action and the need to refine the search for new substances. The purpose of this review was to discuss new research directions and new trends that dominate laboratories worldwide. We have reviewed the literature to present new points on the pharmacological target of substances with antidepressant activity. In addition, we propose a new perspective on depressive therapies.

Celastrol and thymoquinone alleviate aluminum chloride-induced neurotoxicity: Behavioral psychomotor performance, neurotransmitter level, oxidative-inflammatory markers, and BDNF expression in rat brain

Exposure to aluminum chloride (AlCl₃) induces progressive multiregional neurodegeneration in animal models by promoting oxidative stress and neuroinflammation. The current study was designed to assess the potential efficacy of the natural antioxidants celastrol and thymoquinone (TQ) for alleviating AlCl₃-induced psychomotor abnormalities and oxidative-inflammatory burden in male albino rats. Four treatment groups were compared: (i) a vehicle control group, (ii) a AlCL₃ group receiving daily intraperitoneal (i.p.) injection of AlCl₃ (10 mg/kg) for 6 weeks, (iii) a AlCl₃ plus TQ (10 mg/kg, i.p.) cotreatment group, and (iv) a AlCl₃ plus celastrol (1 mg/kg, i.p.) cotreatment group. Open-field, rotarod, and forced swimming tests were conducted to assess locomotor activity, motor coordination, anxiety-like behavior, and depressive-like behavior. Acetylcholine (ACh), dopamine, and serotonin levels were measured in brain homogenates. Malondialdehyde (MDA), total antioxidant capacity (TAC), and catalase activity were measured as oxidative stress markers, while tumor necrosis factor-α (TNF-α) and interlukin-6 (IL-6) expression levels were measured as inflammatory markers. Brain derived neurotrophic factor (BDNF) mRNA was measured as an index for the endogenous neuroprotective response. Daily AlCl₃ injection reduced free ambulation, impaired motor coordination, promoted anxiety- and depression-like behaviors, reduced whole-brain ACh, dopamine, and serotonin concentrations, increased MDA accumulation, reduced TAC, elevated TNF-α and IL-6, and suppressed BDNF mRNA expression. All of these effects were significantly reversed by TQ or celastrol cotreatment. Thus, TQ and celastrol may be promising treatments for AlCl₃-induced neurotoxicity as well as neurodegenerative diseases involving oxidative stress and neuroinflammation.

Photoperiodic Changes in Both Hypothalamus Neurotransmitters and Circulating Gonadal Steroids Metabolomic Profiles in Relation to Seasonal Reproduction in Male Quail

Both hypothalamic neurotransmitters and serum steroid hormones are impacted by photoperiod and have effects on physiology and seasonal reproductive. However, the relationship between circulating gonadal steroids and hypothalamic neurotransmitters underlying different photoperiod is still unclear. To further understand the crosstalk of neurotransmitters and steroids in seasonal reproduction, metabolic changes of 27 neurotransmitters concentrated in hypothalamus tissues and 42 steroids hormones in serum were assessed during two artificial photoperiodic programs. The results showed that photoperiod induce testicular atrophy and recrudescence. In L-to-S groups, significantly decreased levels of testosterone concentration were found in serum (P < 0.001) and increased 11-Dehydrocorticosterone (P < 0.05); Testosterone were almost undetectable at SD_14d. In addition, the hypothalamus exhibited significantly increased arginine and 4-aminobutyric acid (GABA) concentration and decreased serotonin and epinephrine content (P < 0.01 or P < 0.05). Accordingly, serum testosterone and androstenedione became detectable at LD_3d in the S-to-L group and were markedly increase at LD_7d. Furthermore, Serum androstenedione showed a significant increase with long light expose (P < 0.01). Additionally, the hypothalamus exhibited both significantly increased L.Tryptophan and phenylalanine concentration, as well as decreased L-glutamine and L-glutamine.acid content (P < 0.01 or P < 0.05). Serotonin metabolism showed significant differences between L-to-S group and S-to-L group. Furthermore, in the correlation analysis, serum testosterone had a positive correlation with 5-Hydroxyindole-3-acetic acid (5-HIAA), while Androstenedione was significantly negative with L.Tryptophan in L-to-S (P < 0.05). However, in S-to-L group, serum testosterone showed strong negative correlation with both serotonin and 5-HIAA (P < 0.05), but positive correlation with L.Tryptophan (P < 0.01), while Androstenedione was significantly negative correlation with both serotonin (P < 0.05) and L-Glutamine (P < 0.01). Photoperiod also had significant effects on the mRNA expression. We found significant differences in gene expression patterns of both serotonin signaling and steroid biosynthesis, while MAOB, NR5A1, and 3β-HSD showed an opposite tendency between two groups. Taken together, our results revealed that circulating gonadal steroids and hypothalamic neurotransmitters were significantly impact quail’s seasonal reproduction. Circulating gonadal steroids have different effects on neurotransmitter at different photoperiodism, which may coordinately influence the seasonal reproduction of quails.

Adenylate kinase 1 overexpression increases locomotor activity in medaka fish

Maintenance of the energy balance is indispensable for cell survival and function. Adenylate kinase (Ak) is a ubiquitous enzyme highly conserved among many organisms. Ak plays an essential role in energy regulation by maintaining adenine nucleotide homeostasis in cells. However, its role at the whole organism level, especially in animal behavior, remains unclear. Here, we established a model using medaka fish (Oryzias latipes) to examine the function of Ak in environmental adaptation. Medaka overexpressing the major Ak isoform Ak1 exhibited increased locomotor activity compared to that of the wild type. Interestingly, this increase was temperature dependent. Our findings suggest that cellular energy balance can modulate locomotor activity.

Strain-Specific Liver Metabolite Profiles in Medaka

The relationship between genetic variation and phenotypic traits is often poorly understood since specific genotypes do not always easily translate into associated phenotypes, especially for complex disorders. The genetic background has been shown to affect metabolic pathways and thus contribute to variations in the metabolome. Here, we tested the suitability of NMR metabolomics for comparative analysis of fish lines as a first step towards phenotype-genotype association studies. The Japanese rice fish, medaka (Oryzias latipes), is a widely used genetic vertebrate model with several isogenic inbred laboratory strains. We used liver extracts of medaka iCab and HO5 strains as a paradigm to test the feasibility of distinguishing the metabolome of two different inbred strains. Fifteen metabolites could be detected in uni- and multivariate analyses that showed strain-specific levels. Differences could be assigned to specific metabolic pathways. Our results show that NMR spectroscopy is a suitable method to detect variance of the metabolome caused by subtle genetic differences. Thus, it has the potential to address genotype–phenotype associations in medaka, providing an additional level of phenotypic analysis.

Characterization of tmt-opsin2 in Medaka Fish Provides Insight Into the Interplay of Light and Temperature for Behavioral Regulation

One of the big challenges in the study of animal behavior is to combine molecular-level questions of functional genetics with meaningful combinations of environmental stimuli. Light and temperature are important external cues, influencing the behaviors of organisms. Thus, understanding the combined effect of light and temperature changes on wild-type vs. genetically modified animals is a first step to understand the role of individual genes in the ability of animals to cope with changing environments. Many behavioral traits can be extrapolated from behavioral tests performed from automated motion tracking combined with machine learning. Acquired datasets, typically complex and large, can be challenging for subsequent quantitative analyses. In this study, we investigate medaka behavior of tmt-opsin2 mutants vs. corresponding wild-types under different light and temperature conditions using automated tracking combined with a convolutional neuronal network and a Hidden Markov model-based approach. The temperatures in this study can occur in summer vs. late spring/early autumn in the natural habitat of medaka fish. Under summer-like temperature, tmt-opsin2 mutants did not exhibit changes in overall locomotion, consistent with previous observations. However, detailed analyses of fish position revealed that the tmt-opsin2 mutants spent more time in central locations of the dish, possibly because of decreased anxiety. Furthermore, a clear difference in location and overall movement was obvious between the mutant and wild-types under colder conditions. These data indicate a role of tmt-opsin2 in behavioral adjustment, at least in part possibly depending on the season.

Nrf2 Alleviates Cognitive Dysfunction and Brain Inflammatory Injury via Mediating Wfs1 in Rats with Depression-Like Behaviors

Depression is a major threat to global mental health and demands targeted therapeutic regimens. The current study set out to evaluate the regulatory mechanism of nuclear factor erythroid-2 related factor 2 (Nrf2) in depression-induced cognitive dysfunction and inflammatory injury. First, depressive rat models were established via chronic unpredicted mild stress (CUMS) treatment. Cognitive function of rats was assessed by a series of behavioral tests. Rats were further stereotactically injected with Nrf2 overexpression vector, with expression patterns of Nrf2, miR-17-5p, and wolfram syndrome 1 (Wfs1) detected using qRT-PCR and Western blot assay. In addition, pathological changes of murine hippocampus were analyzed using hematoxylin-eosin staining. In vitro cell models were additionally established using lipopolysaccharide. Cell viability was detected via the CCK-8 method. Moreover, levels of TNF-α, IL-1β, and IL-10 were detected via ELISA. Furthermore, the binding relationships between Nrf2 and the miR-17-5p promoter, miR-17-5p, and Wfs1 were verified. It was found that Nrf2 was weakly expressed in CUMS-treated rats, whereas Nrf2 upregulation alleviated cognitive dysfunction and brain inflammatory injury. Meanwhile, Nrf2 inhibited miR-17-5p expression via binding to the miR-17-5p promoter. miR-17-5p was also found to limit Wfs1 transcription. miR-17-5p overexpression or Wfs1 downregulation partly reversed the role of Nrf2 in reliving inflammatory injury of murine hippocampal neurons. Overall, our findings indicated that Nrf2 inhibited miR-17-5p expression and promoted Wfs1 transcription, thereby alleviating cognitive dysfunction and inflammatory injury in rats with depression-like behaviors.

The Therapeutic Potential of Celastrol in Central Nervous System Disorders: Highlights from In Vitro and In Vivo Approaches

Celastrol, the most abundant compound derived from the root of Tripterygium wilfordii, largely used in traditional Chinese medicine, has shown preclinical and clinical efficacy for a broad range of disorders, acting via numerous mechanisms, including the induction of the expression of several neuroprotective factors, the inhibition of cellular apoptosis, and the decrease of reactive oxygen species (ROS). Given the crucial implication of these pathways in the pathogenesis of Central Nervous System disorders, both in vitro and in vivo studies have focused their attention on the possible use of this compound in these diseases. However, although most of the available studies have reported significant neuroprotective effects of celastrol in cellular and animal models of these pathological conditions, some of these data could not be replicated. This review aims to discuss current in vitro and in vivo lines of evidence on the therapeutic potential of celastrol in neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases, amyotrophic lateral sclerosis, Huntington’s disease, multiple sclerosis, and cadmium-induced neurodegeneration, as well as in psychiatric disorders, such as psychosis and depression. In vitro and in vivo studies focused on celastrol effects in cerebral ischemia, ischemic stroke, traumatic brain injury, and epilepsy are also described.

The regulation of animal behavior by cellular stress responses

Cellular stress responses exist to detect the effects of stress on cells, and to activate protective mechanisms that promote resilience. As well as acting at the cellular level, stress response pathways can also regulate whole organism responses to stress. One way in which animals facilitate their survival in stressful environments is through behavioral adaptation; this review considers the evidence that activation of cellular stress responses plays an important role in mediating the changes to behavior that promote organismal survival upon stress.

Activation of BDNF by transcription factor Nrf2 contributes to antidepressant-like actions in rodents

The transcription factor erythroid 2-related factor 2 (Nrf2) and brain-derived neurotrophic factor (BDNF) play a key role in depression. However, the molecular mechanisms underlying the crosstalk between Nrf2 and BDNF in depression remain unclear. We examined whether Nrf2 regulates the transcription of Bdnf by binding to its exon I promoter. Furthermore, the role of Nrf2 and BDNF in the brain regions from mice with depression-like phenotypes was examined. Nrf2 regulated the transcription of Bdnf by binding to its exon I promoter. Activation of Nrf2 by sulforaphane (SFN) showed fast-acting antidepressant-like effects in mice by activating BDNF as well as by inhibiting the expression of its transcriptional repressors (HDAC2, mSin3A, and MeCP2) and revising abnormal synaptic transmission. In contrast, SFN did not affect the protein expression of BDNF and its transcriptional repressor proteins in the medial prefrontal cortex (mPFC) and hippocampus, nor did it reduce depression-like behaviors and abnormal synaptic transmission in Nrf2 knockout mice. In the mouse model of chronic social defeat stress (CSDS), protein levels of Nrf2 and BDNF in the mPFC and hippocampus were lower than those of control and CSDS-resilient mice. In contrast, the protein levels of BDNF transcriptional repressors in the CSDS-susceptible mice were higher than those of control and CSDS-resilient mice. These data suggest that Nrf2 activation increases the expression of Bdnf and decreases the expression of its transcriptional repressors, which result in fast-acting antidepressant-like actions. Furthermore, abnormalities in crosstalk between Nrf2 and BDNF may contribute to the resilience versus susceptibility of mice against CSDS.

Creation of a gene expression portrait of depression and its application for identifying potential treatments

Depression is a complex mental health disorder and the goal here was to identify a consistent underlying portrait of expression that ranks all genes from most to least dysregulated and indicates direction of change relative to controls. Using large-scale neural gene expression depression datasets, a combined portrait (for men and women) was created along with one for men and one for women only. The depressed brain was characterized by a "hypo" state, that included downregulation of activity-related genes, including EGR1, FOS, and ARC, and indications of a lower brain temperature and sleep-like state. MAP kinase and BDNF pathways were enriched with overlapping genes. Expression patterns suggested decreased signaling for GABA and for neuropeptides, CRH, SST, and CCK. GWAS depression genes were among depression portrait genes and common genes of interest included SPRY2 and PSEN2. The portraits were used with the drug repurposing approach of signature matching to identify treatments that could reverse depression gene expression patterns. Exercise was identified as the top treatment for depression for the combined and male portraits. Other non-traditional treatments that scored well were: curcumin, creatine, and albiflorin. Fluoxetine scored best among typical antidepressants. The creation of the portraits of depression provides new insights into the complex landscape of depression and a novel platform for evaluating and identifying potential new treatments.

Photoperiodic regulation of dopamine signaling regulates seasonal changes in retinal photosensitivity in mice

At high latitudes, approximately 10% of people suffer from depression during the winter season, a phenomenon known as seasonal affective disorder (SAD). Shortened photoperiod and/or light intensity during winter season are risk factors for SAD, and bright light therapy is an effective treatment. Interestingly, reduced retinal photosensitivity along with the mood is observed in SAD patients in winter. However, the molecular basis underlying seasonal changes in retinal photosensitivity remains unclear, and pharmacological intervention is required. Here we show photoperiodic regulation of dopamine signaling and improvement of short day–attenuated photosensitivity by its pharmacological intervention in mice. Electroretinograms revealed dynamic seasonal changes in retinal photosensitivity. Transcriptome analysis identified short day-mediated suppression of the Th gene, which encodes tyrosine hydroxylase, a rate-limiting enzyme for dopamine biosynthesis. Furthermore, pharmacological intervention in dopamine signaling through activation of the cAMP signaling pathway rescued short day–attenuated photosensitivity, whereas dopamine receptor antagonists decreased photosensitivity under long-day conditions. Our results reveal molecular basis of seasonal changes in retinal photosensitivity in mammals. In addition, our findings provide important insights into the pathogenesis of SAD and offer potential therapeutic interventions.

Modulation of cellular circadian clocks by triterpenoids

Many living organisms on earth have clock systems in their body. It has increasingly become clear that a disturbance in the internal clocks has negative effects on our body. Terpenes are organic compounds found in various plants that are reported to have several pharmacological actions. In this study, we focused on commercially available 27 triterpenoids and evaluated their influence on the circadian rhythm of human U2OS cells and mouse NIH3T3 cells. The expression level of Per2, one of the core clock genes, was measured using luminescent reporters over the time period of a few days. We found that 8 triterpenoids reset the phase of the circadian clocks. Representative compounds were corosolic acid, cucurbitacin B, and celastrol; similar effects were also confirmed with some structural analogues of cucurbitacin B and celastrol. These compounds shifted the phase bilaterally depending on the stimulus timing and also acted as synchronizers in desynchronized cells. The effective concentrations of cucurbitacin B and celastrol were less than 0.5 μM. In addition, cucurbitacin B and celastrol were also found to be effective in tissue explants in mice. Furthermore, celastrol dose-dependently shortened the period length of NIH3T3 cells. Some of these compounds are found in edible and medicinal plants and may help regulate our circadian clocks in everyday life.

Light and Hormones in Seasonal Regulation of Reproduction and Mood

Organisms that inhabit the temperate zone exhibit various seasonal adaptive behaviors, including reproduction, hibernation, molting, and migration. Day length, known as photoperiod, is the most noise-free and widely used environmental cue that enables animals to anticipate the oncoming seasons and adapt their physiologies accordingly. Although less clear, some human traits also exhibit seasonality, such as birthrate, mood, cognitive brain responses, and various diseases. However, the molecular basis for human seasonality is poorly understood. Herein, we first review the underlying mechanisms of seasonal adaptive strategies of animals, including seasonal reproduction and stress responses during the breeding season. We then briefly summarize our recent discovery of signaling pathways involved in the winter depression-like phenotype in medaka fish. We believe that exploring the regulation of seasonal traits in animal models will provide insight into human seasonality and aid in the understanding of human diseases such as seasonal affective disorder (SAD).