Inducible nitric oxide synthase is involved in the modulation of depressive behaviors induced by unpredictable chronic mild stress

Amino acid metabolites profiling in unpredictable chronic mild stress-induced depressive rats and the protective effects of Gastrodia elata Blume and gastrodin

ETHNOPHARMACOLOGICAL RELEVANCE

Major depressive disorder (MDD) is a prevalent condition that affects approximately 350 million people worldwide. Several studies have identified changes in amino acids in the blood of MDD patients, suggesting their potential as biomarkers to better understand their role in depression. Gastrodia elata Blume (GEB) and its active compound gastrodin (GAS) are recognized for their antidepressant properties. However, their effects on amino acid profiles and their potential role in alleviating depression remain poorly understood. Understanding how GEB and GAS influence amino acid metabolism may offer novel insights into their mechanisms in alleviating depression, potentially leading to more targeted therapeutic strategies.

AIM OF THE STUDY

This study aimed to investigate the potential role of supplementing GEB and its active compound GAS to reverse altered amino acid profiles in depressed rats.

MATERIALS AND METHODS

To achieve this, six-week-old SD rats were induced depressive-like behaviors by the UCMS rat model for 5 weeks. Groups receiving GEB or GAS were administered orally via gavage daily within the UCMS model. Serum samples were collected and analyzed using a targeted metabolomics approach employing LC-MS for amino acid profiling.

RESULTS

A total of 38 amino acid metabolites were identified, 17 of which were significantly altered following UCMS. UCMS rats exhibited perturbed arginine biosynthesis, arginine and proline metabolism pathways. Changes in key amino acids in these metabolic pathways were reversed following supplementation with GEB and GAS, which also alleviated depressive symptoms.

CONCLUSIONS

In conclusion, UCMS-induced depression in rats causes changes in some amino acid metabolites similar to those found in human depression, validating its relevance as a model for studying depression. Additionally, the research suggests that GEB and GAS may exert antidepressant effects by regulating amino acid metabolism.

Deciphering the genetic underpinnings of neuroticism: A Mendelian randomization study of druggable gene targets

BACKGROUND

Neuroticism, known for its association with a greater risk of psychiatric conditions such as depression and anxiety, is a critical focus of research.

METHODS

Cis-expression quantitative trait loci (eQTLs) from 31,684 whole blood samples provided by the eQTLGen Consortium, alongside data from a large neuroticism cohort, were analyzed to identify genes causally linked to neuroticism. To further explore the influence of gene expression changes on neuroticism, colocalization analysis was conducted. Identified drug targets were assessed for potential side effects using a phenome-wide association study (PheWAS). Additionally, we utilized multiple databases to explore the interactions between drugs and genes for drug prediction and assess the current medications for drug repurposing.

RESULTS

The analysis involved a total of 4473 druggable genes, with two-sample Mendelian randomization (MR) identifying 186 genes that are causally linked to neuroticism. Colocalization analysis highlighted 11 genes (TLR4, MMRN1, EP300, BRAF, ORM1, ACVR1B, LRRC17, NOS2, ADAMTS6, GPX1, and VCL) with a posterior probability of colocalization (PPH4) >0.8. PheWAS revealed that drugs targeting BRAF, LRRC17, ADAMTS6, and GPX1 were also associated with other traits. Notably, six of these genes (TLR4, MMRN1, BRAF, ACVR1B, NOS2, and GPX1) are already being explored for drug development in psychiatric and other diseases.

CONCLUSION

This study pinpointed six genes as promising therapeutic targets for neuroticism. The repurposing and development of drugs targeting these genes hold potential for managing neuroticism and associated psychiatric disorders.

Knocking out Selenium Binding Protein 1 Induces Depressive-Like Behavior in Mice

Selenium binding protein 1 (SELENBP1) is involved in neurologic disorders, such as multiple sclerosis, spinal cord injury, Parkinson's disease, epilepsy, and schizophrenia. However, the role of SELENBP1 in the neurogenesis of depression, which is a neurologic disorder, and the underlying mechanisms of oxidative stress and inflammation in depression remain unknown. In this study, we evaluated the changes in the expression levels of SELENBP1 in the hippocampus of a mouse model of depression and in the serum of human patients with depression using the Gene Expression Omnibus database. These changes were validated using blood samples from human patients with depression and mouse models with chronic unpredictable mild stress (CUMS)-induced depressive-like behavior. We also investigated the effects of SELENBP1 knockout (KO) on inflammation, oxidative stress, and hippocampal neurogenesis in mice with CUMS-induced depression. Our results revealed that SELENBP1 levels was decreased in the blood of human patients with depression and in the hippocampus of mice with CUMS-induced depression. SELENBP1 KO increased CUMS-induced depressive behavior in mice and caused dysregulation of inflammatory cytokines and oxidative stress. This led to a decrease in the numbers of doublecortin- and Ki67-positive cells, which might aggravate CUMS-induced depressive symptoms. These findings suggest that SELENBP1 might be involved in the regulation of neurogenesis in mice with depression and could be served as a potential target for diagnosing and treating depression.

Stress-induced mucin 13 reductions drive intestinal microbiome shifts and despair behaviors

Depression is a prevalent psychological condition with limited treatment options. While its etiology is multifactorial, both chronic stress and changes in microbiome composition are associated with disease pathology. Stress is known to induce microbiome dysbiosis, defined here as a change in microbial composition associated with a pathological condition. This state of dysbiosis is known to feedback on depressive symptoms. While studies have demonstrated that targeted restoration of the microbiome can alleviate depressive-like symptoms in mice, translating these findings to human patients has proven challenging due to the complexity of the human microbiome. As such, there is an urgent need to identify factors upstream of microbial dysbiosis. Here we investigate the role of mucin 13 as an upstream mediator of microbiome composition changes in the context of stress. Using a model of chronic stress, we show that the glycocalyx protein, mucin 13, is selectively reduced after psychological stress exposure. We further demonstrate that the reduction of Muc13 is mediated by the Hnf4 transcription factor family. Finally, we determine that deleting Muc13 is sufficient to drive microbiome shifts and despair behaviors. These findings shed light on the mechanisms behind stress-induced microbial changes and reveal a novel regulator of mucin 13 expression.

The Pathophysiological Underpinnings of Gamma-Band Alterations in Psychiatric Disorders

Investigating the biophysiological substrates of psychiatric illnesses is of great interest to our understanding of disorders' etiology, the identification of reliable biomarkers, and potential new therapeutic avenues. Schizophrenia represents a consolidated model of γ alterations arising from the aberrant activity of parvalbumin-positive GABAergic interneurons, whose dysfunction is associated with perineuronal net impairment and neuroinflammation. This model of pathogenesis is supported by molecular, cellular, and functional evidence. Proof for alterations of γ oscillations and their underlying mechanisms has also been reported in bipolar disorder and represents an emerging topic for major depressive disorder. Although evidence from animal models needs to be further elucidated in humans, the pathophysiology of γ-band alteration represents a common denominator for different neuropsychiatric disorders. The purpose of this narrative review is to outline a framework of converging results in psychiatric conditions characterized by γ abnormality, from neurochemical dysfunction to alterations in brain rhythms.

Immunoregulatory role of the gut microbiota in inflammatory depression

Inflammatory depression is a treatment-resistant subtype of depression. A causal role of the gut microbiota as a source of low-grade inflammation remains unclear. Here, as part of an observational trial, we first analyze the gut microbiota composition in the stool, inflammatory factors and short-chain fatty acids (SCFAs) in plasma, and inflammatory and permeability markers in the intestinal mucosa of patients with inflammatory depression (ChiCTR1900025175). Gut microbiota of patients with inflammatory depression exhibits higher Bacteroides and lower Clostridium, with an increase in SCFA-producing species with abnormal butanoate metabolism. We then perform fecal microbiota transplantation (FMT) and probiotic supplementation in animal experiments to determine the causal role of the gut microbiota in inflammatory depression. After FMT, the gut microbiota of the inflammatory depression group shows increased peripheral and central inflammatory factors and intestinal mucosal permeability in recipient mice with depressive and anxiety-like behaviors. Clostridium butyricum administration normalizes the gut microbiota, decreases inflammatory factors, and displays antidepressant-like effects in a mouse model of inflammatory depression. These findings suggest that inflammatory processes derived from the gut microbiota can be involved in neuroinflammation of inflammatory depression.

Bavachin ameliorates neuroinflammation and depressive-like behaviors in streptozotocin-induced diabetic mice through the inhibition of PKCδ

Depression and diabetes are closely linked; however, the pathogenesis of depression associated with diabetes is unclear, and there are no clinically effective antidepressant drugs for diabetic patients with depression. Bavachin is an important active ingredient in Fructus Psoraleae. In this study, we evaluated the anti-neuroinflammatory and antidepressant effects associated with diabetes and the molecular mechanisms of bavachin in a streptozotocin-induced diabetes mouse model. We found that bavachin clearly decreased streptozotocin (STZ)-induced depressive-like behaviors in mice. It was further found that bavachin significantly inhibited microglia activation and the phosphorylation level of PKCδ and inhibited the activation of the NF-κB pathway in vivo and in vitro. Knockdown of PKCδ with siRNA-PKCδ partially reversed the inhibitory effect of bavachin on the NF-κB pathway and the level of pro-inflammatory factors. We further found that PKCδ directly bound to bavachin based on molecular docking and pull-down assays. We also found that bavachin improved neuroinflammation-induced neuronal survival and functional impairment and that this effect may be related to activation of the ERK and Akt pathways mediated by the BDNF pathway. Taken together, these data suggested that bavachin, by targeting inhibition PKCδ to inhibit the NF-κB pathway, further reduced the inflammatory response and oxidative stress and subsequently improved diabetic neuronal survival and function and finally ameliorated diabetes-induced depressive-like behaviors in mice. For the first time, we found that bavachin is a potential agent for the treatment of diabetes-associated neuroinflammation and depression and that PKCδ is a potential target for the treatment of diabetes-associated neuroinflammation, including depression.

The antidepressant-like effect of doxycycline is associated with decreased nitric oxide metabolite levels in the prefrontal cortex

Doxycycline is an antibiotic that has shown neuroprotective, anti-inflammatory, and antidepressant-like effects. Low doses of doxycycline revert the behavioral and neuroinflammatory responses induced by lipopolysaccharide treatment in a mice model of depression. However, the molecular mechanisms involved in the antidepressant action of doxycycline are not yet understood. Doxycycline inhibits the synthesis of nitric oxide (NO), which increases after stress exposure. Inducible NO synthase (iNOS) inhibition also causes antidepressant-like effects in animal models sensitive to antidepressant-like effects such as the forced swimming test (FST). However, no direct study has yet investigated if the antidepressant-like effects of doxycycline could involve changes in NO-mediated neurotransmission. Therefore, this study aimed at investigating: i) the behavioral effects induced by doxycycline alone or in association with ineffective doses of a NO donor (sodium nitroprusside, SNP) or an iNOS inhibitor (1400 W) in mice subjected to the FST; and ii) doxycycline effects in NO metabolite levels in the prefrontal cortex and hippocampus these animals. Male mice (8 weeks) received i.p. injection of saline or doxycycline (10, 30, and 50 mg/kg), alone or combined with SNP (0.1, 0.5, and 1 mg/kg) or 1400 W (1, 3, and 10 µg/kg), and 30 min later were submitted to the FST. Animals were sacrificed immediately after, and NO metabolites nitrate/nitrite (NOx) were measured in the prefrontal cortex and hippocampus. Doxycycline (50 mg/kg) reduced both the immobility time in the FST and NOx levels in the prefrontal cortex of mice compared to the saline group. The antidepressant-like effect of doxycycline in the FST was prevented by SNP (1 mg/kg) pretreatment. Additionally, sub-effective doses of doxycycline (30 mg/kg) associated with 1400 W (1 µg/kg) induced an antidepressant-like effect in the FST. Altogether, our data suggest that the reducing NO levels in the prefrontal cortex through inhibition of iNOS could be related to acute doxycycline treatment resulting in rapid antidepressant-like effects in mice.

Clotrimazole ameliorates chronic mild stress-induced depressive-like behavior in rats; crosstalk between the HPA, NLRP3 inflammasome, and Wnt/β-catenin pathways

Depression is a major emotional disorder that has a detrimental effect on quality of life. The chronic mild stress (CMS)-depression model was adopted in rats to evaluate the neurotherapeutic effect of Clotrimazole (CLO) and investigate the possible mechanisms of its antidepressant action via its impact on the hypothalamic pituitary adrenal (HPA) axis and the stress hormone, cortisol. It was found that azole antifungals affect steroidogenesis and the HPA axis. Behavioral, histopathological, inflammatory, and apoptotic pathways were assessed. Serum cortisol, inflammasome biomarkers, hippocampal NLRP3, caspase-1, and IL-18, and the canonical Wnt/β-catenin neurogenesis biomarkers, Wnt3a, and non-phosphorylated β-catenin levels were also determined. Different stressors were applied for 28 days to produce depressive-like symptoms, and CLO was administered at a daily dose of 30 mg/kg body weight. Subsequently, behavioral and biochemical tests were carried out to assess the depressive-like phenotype in rats. Stressed rats showed increased immobility time in the forced swimming test (FST), decreased grooming time in the splash test (ST), increased serum cortisol levels, increased inflammasome biomarkers, and decreased neurogenesis. However, administration of CLO produced significant antidepressant-like effects in rats, which were accompanied by a significant decrease in immobility time in FST, an increase in grooming time in ST, a decrease in serum cortisol level, a decrease in inflammasome biomarkers, and an increase in neurogenesis biomarkers. The antidepressant mechanism of CLO involves the HPA axis and the anti-inflammatory effect, followed by neurogenesis pathway activation. Therefore, CLO may have the potential to be a novel antidepressant candidate.

Ninjinyoeito Prevents Onset of Depression-Like Behavior and Reduces Hippocampal iNOS Expression in Senescence-Accelerated Mouse Prone 8 Mice

Late-life depression is a globally prevalent disorder. Ninjinyoeito (NYT), a traditional Japanese herbal medicine, attenuates depressive symptoms in older patients. However, the mechanisms underlying the antidepressive effect of NYT are unknown. In this study, we investigated the mechanism of the action of NYT using senescence-accelerated mouse prone 8 (SAMP8) mice, which exhibit accelerated aging. SAMP8 mice were treated with NYT starting at 12 weeks of age. Twelve-week-old SAMP8 mice did not show prolonged immobility time in the tail suspension test compared with age-matched SAMR1 mice (normal aging control). At 34 weeks of age, vehicle-treated SAMP8 mice displayed prolonged immobility time compared with SAMR1 mice. NYT-treated SAMP8 mice showed a shorter immobility time than that of vehicle-treated SAMP8 mice. Notably, NYT decreased hippocampal inducible nitric oxide synthase (iNOS) expression in SAMP8 mice. There was no difference in iNOS expression between SAMR1 and vehicle-treated SAMP8 mice. Subchronic (5 days) administration of an iNOS inhibitor, 1400 W, shortened the immobility time in SAMP8 mice. These results suggest that NYT prevents an increase in immobility time of SAMP8 mice by decreasing iNOS levels in the hippocampus. Therefore, the antidepressive effect of NYT in older patients might be mediated, at least in part, by the downregulation of iNOS in the brain. Our data suggest that NYT is useful to prevent the onset of depression with aging.

Glutamine Supplementation Preserves Glutamatergic Neuronal Activity in the Infralimbic Cortex, Which Delays the Onset of Mild Cognitive Impairment in 3×Tg-AD Female Mice

It was recently found that glutamine (Gln) supplementation activates glutamatergic neurotransmission and prevents chronic-stress-induced mild cognitive impairment (MCI). In this study, we evaluated the effects of Gln on glutamatergic activity in the medial prefrontal cortex and the onset of cognitive impairment in a triple-transgenic Alzheimer's disease mouse model (3×Tg-AD). Female 3×Tg-AD mice were fed a normal diet (3×Tg) or a Gln-supplemented diet (3×Tg+Gln) from 2 to 6 months of age. Glutamatergic neuronal activity was analyzed at 6 months, and cognitive function was examined at 2, 4, and 6 months. 3×Tg mice exhibited a decrease in glutamatergic neurotransmission in the infralimbic cortex, but 3×Tg+Gln mice did not. The 3×Tg group showed MCI at 6 months of age, but the 3×Tg+Gln group did not. The expressions of amyloid peptide, inducible nitric oxide synthase, and IBA-1 were not elevated in the infralimbic cortex in the 3×Tg+Gln group. Therefore, a Gln-supplemented diet could delay the onset of MCI even in a mouse model predisposed to cognitive impairment and dementia through genetic modification.

Microglial NLRP3 inflammasome activation mediates diabetes-induced depression-like behavior via triggering neuroinflammation

BACKGROUND

Abundant evidence suggests that the prevalence and risk of depression in people with diabetes is high. However, the pathogenesis of diabetes-related depression remains unclear. Since neuroinflammation is associated with the pathophysiology of diabetic complications and depression, this study aims to elucidate the neuroimmune mechanism of diabetes-related depression.

METHODS

Male C57BL/6 mice were injected with streptozotocin to establish a diabetes model. After screening, diabetic mice were treated with the NLRP3 inhibitor MCC950. Then, metabolic indicators and depression-like behaviors were evaluated in these mice, as well as their central and peripheral inflammation. To explore the mechanism of high glucose-induced microglial NLRP3 inflammasome activation, we performed in vitro studies focusing on its canonical upstream signal I (TLR4/MyD88/NF-κB) and signal II (ROS/PKR/P₂X₇R/TXNIP).

RESULTS

Diabetic mice exhibited depression-like behaviors and activation of NLRP3 inflammasome in hippocampus. In vitro high-glucose (50 mM) environment primed microglial NLRP3 inflammasome by promoting NF-κB phosphorylation in a TLR4/MyD88-independent manner. Subsequently, high glucose activated the NLRP3 inflammasome via enhancing intracellular ROS accumulation, upregulating P₂X₇R, as well as promoting PKR phosphorylation and TXNIP expression, thereby facilitating the production and secretion of IL-1β. Inhibition of NLRP3 with MCC950 significantly restored hyperglycemia-induced depression-like behavior and reversed the increase in IL-1β levels in the hippocampus and serum.

CONCLUSION

The activation of NLRP3 inflammasome, probably mainly in hippocampal microglia, mediates the development of depression-like behaviors in STZ-induced diabetic mice. Targeting the microglial inflammasome is a feasible strategy for the treatment of diabetes-related depression.

MAD2B Blunts Chronic Unpredictable Stress and Corticosterone Stimulation-Induced Depression-Like Behaviors in Mice

BACKGROUND

Depression is a prevalent and recurrent psychiatric disorder. Aberrant neural structure and activity play fundamental roles in the occurrence of depression. Mitotic arrest deficient protein (MAD2B) is highly expressed in neurons and may be implicated in synaptic plasticity in the central nervous system. However, the effect of MAD2B in depression, as well as the related molecular mechanism, is uncertain.

METHODS

Here, we employed mouse models of depression induced by chronic unpredictable stress exposure or corticosterone (CORT) stimulation. Depression-like behaviors in mice were evaluated by sucrose preference, forced swimming, and tail suspension tests. Hippocampal MAD2B overexpression was mediated by adeno-associated virus 8 containing enhanced green fluorescent protein. In vitro primary neuronal cells were obtained from the hippocampus of rat embryos and were treated with CORT, and MAD2B overexpression was performed using lentivirus. MAD2B and glutamate metabotropic receptor 4 (GRM4) levels were evaluated by western blots and quantitative PCR. Primary neuronal miR-29b-3p expression was detected by quantitative PCR.

RESULTS

MAD2B expression was reduced in the hippocampus in mice exhibiting depressive-like behaviors. However, hippocampal MAD2B overexpression protected mice from developing either chronic unpredictable stress- or CORT-induced depression-like behaviors, an effect associated with reduced expression of GRM4, a presynaptic receptor involved in depression. Moreover, MAD2B overexpression in primary neuronal cells also decreased GRM4 expression while enhancing the level of miR-29b-3p; this phenomenon was also observed under CORT stimulation.

CONCLUSIONS

Our results suggest an important role of neuronal MAD2B in the pathogenesis of depression via the miR-29b-3p/GRM4 signaling pathway. MAD2B could be a potential therapeutic target for depressive disorders.

Combined effects of nitric oxide synthase 3 genetic variant and childhood emotional abuse on earlier onset of suicidal behaviours

Marked heterogeneity in suicide attempters has been observed, with earlier onset being linked to stronger heritability, more childhood maltreatment. Nitric oxide signalling system might be implicated in this relationship through its role in the stress response/adaptation. This study examined how NOS genetic variants and childhood maltreatment were associated with age at first suicide attempt (SA). Adult patients with SA history (N = 414) filled in the Childhood Trauma Questionnaire, and six functionally relevant NOS2 and NOS3 polymorphisms were genotyped. Analyses included χ², Mann-Whitney U tests, Kendall's regression, multivariate linear and Cox survival regressions, and a moderation analysis. The NOS3 promotor 27-bp variable number tandem repeat (VNTR) bb homozygous state and childhood emotional abuse were independently associated with earlier age at first SA, which was robust after controlling for confounders [regression coefficient - 3.975, 95% CI -6.980 - (-0.970), p = 0.010, and - 1.088, 95% CI -2.172 - (-0.004), p = 0.049]. No interaction was observed. In the Cox proportional hazards model for age at first SA, the hazard ratio for patients with childhood emotional abuse and NOS3 27-bp VNTR bb was 0.533 (95% CI 0.394-0.720, p < 0.001) compared to patients without. Intermediate scores were observed with either only the risk genotype or only childhood emotional abuse. A graded relationship was also observed for repeated SA, family history of SA, and severe SA history. These results are preliminary due to a low statistical power and call for replication and further characterization of the role of nitric oxide system in the susceptibility to early-onset SB.

Antidepressant effects of cherry leaf decoction on a chronic unpredictable mild stress rat model based on the Glu/GABA-Gln metabolic loop

Cherry leaves (Prunus pseudocerasus Lindl. [Rosaceae]), a traditional Chinese herbal medicine, can regulate the factors closely related to depression including inflammatory cytokines, oxidative stress and blood glucose level. However, the antidepressant effects of cherry leaves and underlying neuromodulatory mechanisms remain relatively have not been elucidated explicitly. The present study investigated the antidepressant effects of cherry leaf decoction (CLD). The underlying neuromodulatory mechanism was explored by examining the glutamate (Glu)/γ-aminobutyric acid (GABA)-glutamine (Gln) metabolic loop. The chronic unpredictable mild stress (CUMS) rodent model was used in this study. The main flavonoids components of CLD were identified using high-performance liquid chromatography (HPLC). The antidepressant effects of CLD were assessed throughout behavioural tests including the bodyweight, sucrose preference test (SPT), forced swimming test (FPT) and tail suspension test (TST). Moreover, The baseline levels of serum adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were quantified. The expression of proteins integrally involved in the Glu/GABA-Gln metabolic loop were observed and quantified by Western blotting, reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. This study found that CLD ameliorated depressive-like behaviours induced by CUMS. The increase of serum ACTH and CORT baseline levels induced by CUMS was also reversed after CLD intervention. Furthermore, CUMS reduced the expression of GAD65, GAD67, GLT-1, GS and GABA_A and increased NMDAR1 levels in the rat hippocampus, which was normalized by CLD treatment. The findings demonstrated that CLD could ameliorate the depression-like behaviours induced by CUMS, potentially through the inhibition of hypothalamic-pituitary-adrenal (HPA) axis hyperactivity and the regulation of Glu/GABA-Gln metabolic loop.

The Relationship between Stress, Inflammation, and Depression

A narrative review about the relationship between stress, inflammation, and depression is made as follows: Chronic stress leads to various stress-related diseases such as depression. Although most human diseases are related to stress exposure, the common pathways between stress and pathophysiological processes of different disorders are still debatable. Chronic inflammation is a crucial component of chronic diseases, including depression. Both experimental and clinical studies have demonstrated that an increase in the levels of pro-inflammatory cytokines and stress hormones, such as glucocorticoids, substantially contributes to the behavioral alterations associated with depression. Evidence suggests that inflammation plays a key role in the pathology of stress-related diseases; however, this link has not yet been completely explored. In this study, we aimed to determine the role of inflammation in stress-induced diseases and whether a common pathway for depression exists. Recent studies support pharmacological and non-pharmacological treatment approaches significantly associated with ameliorating depression-related inflammation. In addition, major depression can be associated with an activated immune system, whereas antidepressants can exert immunomodulatory effects. Moreover, non-pharmacological treatments for major depression (i.e., exercise) may be mediated by anti-inflammatory actions. This narrative review highlights the mechanisms underlying inflammation and provides new insights into the prevention and treatment of stress-related diseases, particularly depression.

DFO treatment protects against depression-like behaviors and cognitive impairment in CUMS mice

Depression has several negative effects on emotion as well as learning and memory abilities. Previous studies showed that depression could exacerbate inflammation, which in turn further aggravated depression. Deferoxamine (DFO) is a chelating agent binding iron and aluminium, and is clinically applied to treat acute ion poisoning and hemochromatosis. Researches showed that it could reduce inflammation via increasing the expression of hypoxia-inducible factor-1alpha (HIF-1α). Here, we established a chronic unpredictable mild stress (CUMS) model to investigate whether DFO exerted a neuroprotective function in depression. The results demonstrated that CUMS (4 weeks) effectively induced depression-like behaviors in mice based on sucrose preference test (SPT), forced swim test (FST), tail suspension test (TST), open field test (OFT), and elevated plus-maze test (EPT). It also brought cognitive deficits based on Morris water maze (MWM) test and the impairment of synaptic plasticity based on in vivo electrophysiological recordings. Additionally, CUMS exposure significantly decreased the expression of hippocampal synapse related proteins and the spine density of neurons in the DG region, accompanied by increasing the expression of hippocampal inflammatory cytokines, and promoted the activation of microglia in the hippocampus. The expression of HIF-1α was down-regulated as expected. However, DFO distinctly reversed the CUMS-induced impairments. The mechanism is associated with the DFO inhibition of inflammation by upregulating HIF-1 expression, thereby alleviating a series of pathology changes. Together, these findings suggest that DFO likely plays a protective role in cognitive impairments and synaptic plasticity deficits resulting from depression.

Defects of parvalbumin-positive interneurons in the ventral dentate gyrus region are implicated depression-like behavior in mice

Depression is an increasingly common but extremely serve mood disorder that remains poorly understood and inadequately treated. Fast-spiking parvalbumin-positive interneurons (PVIs), a subpopulation of GABAergic interneurons (GABA, g-aminobutyric acid), exhibit a widespread distribution throughout the hippocampus, and has been reported to play an important role in a variety of mental disorders. However, the relationship between depression and hippocampal PVIs remains unclear. Here in this present study, a series of experiments were conducted to clarify the potential relationship. Here, chronic unpredicted mild stress (CUMS) and Lipopolysaccharide (LPS) injection were introduced to induce depression-like behavior in mice, and led to a clear decline in PVIs numbers in the ventral hippocampal (vHPC), particularly in the ventral dentate gyrus (vDG) subfield. After a selectively removal of the PVIs in PV-ires-Cre::Ai14 mice, we confirmed that ablation of PVIs from the vDG induced depression-like behavior. Furthermore, we found that the removal of vDG-PVIs induced depression likely to be accounted for upregulation of neuroinflammation. These findings facilitate us better understand the role of hippocampal PVIs in depression.

Genetic Ablation of the Inducible Form of Nitric Oxide in Male Mice Disrupts Immature Neuron Survival in the Adult Dentate Gyrus

Inducible nitric oxide synthase (iNOS) is an enzyme upregulated in the brain during neuroimmune stimuli which is associated with an oxidative and pro-inflammatory environment in several brain regions, including the hippocampal formation and the prefrontal cortex. The dentate gyrus of the hippocampal formation is the site of a process known as adult hippocampal neurogenesis (AHN). Although many endogenous and extrinsic factors can modulate AHN, the exact participation of specific proinflammatory mediators such as iNOS in these processes remains to be fully elucidated. Here, we investigated how the total genetic ablation of iNOS impacts the hippocampal neurogenic niche and microglial phenotype and if these changes are correlated to the behavioral alterations observed in iNOS knockout (K.O.) mice submitted or not to the chronic unpredictable stress model (CUS - 21 days protocol). Contrary to our initial hypothesis, at control conditions, iNOS K.O. mice displayed no abnormalities on microglial activation in the dentate gyrus. However, they did exhibit impaired newborn cells and immature neuron survival, which was not affected by CUS. The reduction of AHN in iNOS K.O. mice was accompanied by an increased positive coping response in the tail suspension test and facilitation of anxiety-like behaviors in the novelty suppressed feeding. Next, we investigated whether a pro-neurogenic stimulus would rescue the neurogenic capacity of iNOS K.O. mice by administering in control and CUS groups the antidepressant escitalopram (ESC). The chronic treatment with ESC could not rescue the neurogenic capacity or the behavioral changes observed in iNOS K.O. mice. Besides, in the ventromedial prefrontal (vmPFC) cortex there was no change in the expression or the chronic activation of PV neurons (evaluated by double labeling PV with FOSB) in the prelimbic (PrL) or infralimbic subregions. FOSB expression, however, increased in the PrL of iNOS K.O. mice. Our results suggest that iNOS seems essential for the survival of newborn cells and immature neurons in the hippocampus and seem to partially explain the anxiogenic-like behavior observed in iNOS K.O. mice. On the other hand, the iNOS ablation appears to result in increased activity of the PrL which could explain the antidepressant-like behaviors of iNOS K.O mice.

The Role of Fgf9 in the Antidepressant Effects of Exercise and Fluoxetine in Chronic Unpredictable Mild Stress Mice

OBJECTIVE

The neurotrophic hypothesis of depression posits that stress and depression decrease neurotrophic factor expression in brain, whereas antidepressants and exercise can contribute to the blockade of stress effects and produce antidepressant effects. Fibroblast growth factor 9 (FGF9), a member of the fibroblast growth factor (FGF) family, has been reported to be dysregulated in depression. The present study aimed to determine whether and how Fgf9 mediates the antidepressant effects of fluoxetine and exercise in chronic unpredictable mild stress (CUMS) mice.

METHODS

Male C57BL/6 mice were exposed to CUMS for 7 weeks. From the fourth week, CUMS-exposed mice were subjected to fluoxetine treatment or swimming exercise for 4 weeks. Forced swim test, tail suspension test, and hole-board test were used to assess behaviors of mice. Real-time polymerase chain reaction was used to examine hippocampal messenger RNA levels of Fgf9, Fgf2, FgfR1, FgfR2, and FgfR3. Western blotting was used to examine the protein levels of Fgf9, protein kinase B (Akt), and phosphorylation of Akt at Ser473 in mouse hippocampus.

RESULTS

Our results demonstrated that CUMS induced depression-like behaviors, which were reversed by fluoxetine treatment and swimming exercise. Moreover, we found that CUMS resulted in a dysregulation of Fgf9, Fgf2, and FgfR2 expression, whereas fluoxetine and swimming restored the FGF expression in CUMS-exposed mice. An analysis of the proteins suggests that the antidepressant effects of fluoxetine and exercise in CUMS-exposed mice were associated with ameliorated Fgf9/Akt signaling.

CONCLUSIONS

Our findings have demonstrated that swimming exercise mimics the antidepressant effects of fluoxetine by regulating Fgf9 in CUMS-exposed mice, which may offer new mechanism-based therapeutic targets for depression.

Allium hookeri Extracts Improve Scopolamine-Induced Cognitive Impairment via Activation of the Cholinergic System and Anti-Neuroinflammation in Mice

Allium hookeri (AH) is a medicinal food that has been used in Southeast Asia for various physiological activities. The objective of this study was to investigate the activation of the cholinergic system and the anti-neuroinflammation effects of AH on scopolamine-induced memory impairment in mice. Scopolamine (1 mg/kg body weight, i.p.) impaired the performance of the mice on the Y-maze test, passive avoidance test, and water maze test. However, the number of error actions was reduced in the AH groups supplemented with leaf and root extracts from AH. AH treatment improved working memory and avoidance times against electronic shock, increased step-through latency, and reduced the time to reach the escape zone in the water maze test. AH significantly improved the cholinergic system by decreasing acetylcholinesterase activity, and increasing acetylcholine concentration. The serum inflammatory cytokines (IL-1β, IL-6, and IFN-γ) increased by scopolamine treatment were regulated by the administration of AH extracts. Overexpression of NF-κB signaling and cytokines in liver tissue due to scopolamine were controlled by administration of AH extracts. AH also significantly decreased Aβ and caspase-3 expression but increased NeuN and ChAT. The results suggest that AH extracts improve cognitive effects, and the root extracts are more effective in relieving the scopolamine-induced memory impairment. They have neuroprotective effects and reduce the development of neuroinflammation.

Long-term inflammatory pain does not impact exploratory behavior and stress coping strategies in mice

ABSTRACT

Pain puts patients at risk for developing psychiatric conditions such as anxiety and depression. Preclinical mouse models of pain-induced affective behavior vary widely in methodology and results, impairing progress towards improved therapeutics. To systematically investigate the effect of long-term inflammatory pain on exploratory behavior and stress coping strategy, we assessed male C57BL/6J mice in the forced swim test (FST), elevated zero maze, and open field test at 4 and 6 weeks postinjection of Complete Freund's Adjuvant, while controlling for testing order and combination. Inflammatory pain did not induce a passive stress coping strategy in the FST and did not reduce exploratory behavior in the elevated zero maze or the open field test. Using systematic correlational analysis and composite behavioral scores, we found no consistent association among measures for mice with or without inflammatory pain. A meta-analysis of similar studies indicated a modest, significant effect of Complete Freund's Adjuvant on exploratory behavior, but not immobility in the FST, and high heterogeneity among effect sizes in all 3 paradigms. Given the urgency for understanding the mechanisms of pain comorbidities and identifying novel therapies, these findings support the reallocation of our limited resources away from such unreliable assays and toward motivated and naturalistic behaviors. Future studies in pain and psychiatric translational research may benefit by considering outcomes beyond binary categorization, quantifying the associations between multiple measured behaviors, and agnostically identifying subtle yet meaningful patterns in behaviors.

The Anti-Neuroinflammatory Effect of Fuzi and Ganjiang Extraction on LPS-Induced BV2 Microglia and Its Intervention Function on Depression-Like Behavior of Cancer-Related Fatigue Model Mice

The Chinese herb couple Fuzi and Ganjiang (FG) has been a classic combination of traditional Chinese medicine that is commonly used clinically in China for nearly 2000 years. Traditional Chinese medicine suggests that FG can treat various ailments, including heart failure, fatigue, gastrointestinal upset, and depression. Neuroinflammation is one of the main pathogenesis of many neurodegenerative diseases in which microglia cells play a critical role in the occurrence and development of neuroinflammation. FG has been clinically proven to have an efficient therapeutic effect on depression and other neurological disorders, but its mechanism remains unknown. Cancer-related fatigue (CRF) is a serious threat to the quality of life of cancer patients and is characterized by both physical and psychological fatigue. Recent studies have found that neuroinflammation is a key inducement leading to the occurrence and development of CRF. Traditional Chinese medicine theory believes that extreme fatigue and depressive symptoms of CRF are related to Yang deficiency, and the application of Yang tonic drugs such as Fuzi and Ganjiang can relieve CRF symptoms, but the underlying mechanisms remain unknown. In order to define whether FG can inhibit CRF depression-like behavior by suppressing neuroinflammation, we conducted a series of experimental studies in vitro and in vivo. According to the UPLC-Q-TOF/MS^E results, we speculated that there were 49 compounds in the FG extraction, among which 30 compounds were derived from Fuzi and 19 compounds were derived from Ganjiang. Our research data showed that FG can effectively reduce the production of pro-inflammatory mediators IL-6, TNF-α, ROS, NO, and PGE₂ and suppress the expression of iNOS and COX2, which were related to the inhibition of NF-κB/activation of Nrf2/HO-1 signaling pathways. In addition, our research results revealed that FG can improve the depression-like behavior performance of CRF model mice in the tail suspension test, open field test, elevated plus maze test, and forced swimming test, which were associated with the inhibition of the expression of inflammatory mediators iNOS and COX2 in the prefrontal cortex and hippocampus of CRF model mice. Those research results suggested that FG has a satisfactory effect on depression-like behavior of CRF, which was related to the inhibition of neuroinflammation.

Interaction of air cold plasma with Saccharomyces cerevisiae in the multi-scale microenvironment for improved ethanol yield

In this study, the long-acting mechanism of reactive species was investigated for enhanced ethanol production of Saccharomyces cerevisiae. The results indicated that short-lifetime active species from gas phase plasma dissolved into various liquid microenvironments with different media (water, buffer, medium, and cells), forming different types and amounts of reactive species in multi-scale microenvironments, such as extracellular reactive nitrogen species, endocellular reactive oxygen and nitrogen species. The sustained elevation of cytoplasm calcium concentration with treatment time depended on the activated calcium channels of Cch1p/Mid1p in cell membrane and Yvc1p in vacuole membrane by these species. Accordingly, the Ca²⁺ increase promoted the H⁺-ATPase expression. Consequently, 75.6% ATP hydrolysis induced about 5 fold NADH increase compared with the control. Ultimately, the bioethanol yield increased by 34.2% compared to the control. These results promote the development of atmospheric cold plasma as a promising bio-process enhancement technology for improved target product yields of microbes in fermentation industry.

Biological Evaluation of Aegle marmelos Fruit Extract and Isolated Aegeline in Alleviating PainDepression Dyad: In Silico Analysis of Aegeline on MAO-A and iNOS

Pain and depression have been assessed to co-occur in up to 80% of patients, and this comorbidity is more debilitating and pricier for the patients as compared to either of these disorders alone. Aegle marmelos is a well-known medicinal plant with a broad spectrum of pharmacological activities. Aegeline is a relatively unexplored molecule present in Aegle marmelos. Therefore, the current investigation aims to explore the potential of Aegle marmelos fruit extract (AMFE) and isolated aegeline against the reserpine-induced pain-depression dyad. In the current investigation, aegeline was isolated from AMFE, followed by spectroscopic characterization, i.e., using NMR and mass analyses. AMFE (200 mg kg^-1 p.o) and aegeline (10 mg kg^-1 p.o.) were administered to reserpinized (0.5 mg kg^-1 s.c.) mice, and clorgyline (3 mg kg^-1 i.p.) was taken as the standard drug. AMFE and aegeline significantly alleviated the reserpine-induced reduction in a pain threshold and an increase in immobility as observed in behavioral tests of pain and depression, respectively. In silico molecular docking studies of aegeline showed a good binding interaction at the active sites of MAO-A and iNOS. The in vivo analysis showed that AMFE and aegeline treatment significantly decreased the monoamine oxidase-A (MAO-A) activity, serum interleukin-6 (IL-6) level, and lipid peroxidation, along with an increase in the reduced glutathione level in comparison to the reserpine-treated group. Immunofluorescence studies also showed that AMFE and aegeline abrogated the reserpine-induced increase in iNOS expression. Conclusively, the results delineate that AMFE and aegeline might exert a protective effect via downregulating the MAO-A hyperactivity, IL-6 level, oxidative and nitrosative stress.

SAHA attenuates rotenone-induced toxicity in primary microglia and HT-22 cells

Rotenone is an industrial and environmental toxicant that has been strongly associated with neurodegeneration. It is clear that rotenone induces inflammatory and oxidative stress; however, information on the role of histone acetylation in neurotoxicity is limited. Epigenetic alterations, neuroinflammation, and oxidative stress play a role in the progression of neurodegeneration and can be caused by exposure to environmental chemicals, such as rotenone. Histone modifications, such as methylation and acetylation, play an important role in mediating epigenetic changes. Therefore, we here investigated the effects of histone acetylation on rotenone-induced inflammation and oxidative stress in both primary mouse microglia and hippocampal HT-22 cells using the pan-histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA). Our results showed that SAHA suppressed the inflammatory response by decreasing nuclear factor kappa B and inducible nitric oxide synthase expression. Additionally, SAHA inhibited the rotenone-induced elevation of interleukin 6 and tumor necrosis factor α levels in both cell lines. Furthermore, SAHA improved the rotenone-induced antioxidant status by mitigating the decrease in cellular glutathione levels. Additionally, SAHA prevented the rotenone-induced increase in the HDAC activity in microglial and hippocampal HT-22 cells. Together, our results showed that SAHA reduced rotenone-induced inflammatory and oxidative stress, suggesting a role for histone deacetylation in environmental-related neurotoxicity.

Nitric oxide mediates the antidepressant-like effect of modafinil in mouse forced swimming and tail suspension tests

OBJECTIVES

Previous studies have suggested antidepressant properties for modafinil; however, the underlying mechanisms mediating the antidepressant effect of modafinil have not been well recognized in clinical and animal studies. Nitric oxide (NO) is involved in the pathophysiology of depression. We attempted to investigate the possible role of NO in the antidepressant-like effect of modafinil in mouse forced swimming test (FST) and tail suspension test (TST).

METHODS

The antidepressant-like effect of modafinil (25, 50 and 75 mg/kg), alone and in combination with l-arginine, l-arg, (100 mg/kg) and N^G-l-arginine methyl ester, l-NAME (5 mg/kg), was evaluated using FST and TST. Following behavioral tests, the hippocampi were dissected out to measure nitrite levels.

RESULTS

Findings suggested that administration of modafinil at doses of 50 and 75 mg/kg significantly reduced immobility time in the FST and TST. Furthermore, administration of l-arg and l-NAME increased and decreased, respectively, the immobility time in the FST and TST. We showed that co-administration of a sub-effective dose of modafinil (25 mg/kg) plus l-NAME potentiated the antidepressant-like effect of the sub-effective dose of modafinil. In addition, co-treatment of an effective dose of modafinil (75 mg/kg) with l-arg attenuated the antidepressant-like effect of the effective dose of modafinil. We showed that the antidepressant-like effect of modafinil is associated with decreased nitrite levels in the hippocampus.

CONCLUSIONS

Our findings for the first time support that the modulation of NO, partially at least, is involved in the antidepressant-like effect of modafinil in mouse FST and TST.

Jiao-Tai-Wan Ameliorates Depressive-Like Behavior through the A1R Pathway in Ovariectomized Mice after Unpredictable Chronic Stress

Objective

This study was aimed at observing the effect Jiao-Tai-Wan in menopausal depression.

Methods

In this paper, we used ovariectomized mice subjected to chronic unpredictable stress as a menopausal depression model. After the chronic stress, mice were administrated with JTW (3.3 and 6.6mg/kg) and imipramine (10 mg/kg) for 14 days. On the 14th day, mice were subjected to the behavior test like the forced swim test, tail suspension test, and locomotor activity or were sacrificed to assess the protein changes in different brain regions.

Results

The administration of JTW at doses of 3.3 and 6.6mg/kg (p.o.) significantly shortened the duration of immobility in forced swim and tail suspension tests. There was no obvious difference in locomotor activity among all the groups. The western blot analysis data indicated that treatment with JTW (3.3 and 6.6 mg/kg, p.o.) prominently increased the A₁R protein and the downstream protein ERK1/2 levels in the prefrontal cortex and hippocampus. However, the administration of JTW did not influence c-Fos protein in either the prefrontal cortex or hippocampus.

Conclusion

Our findings suggest that JTW plays a vital role in ameliorating menopausal depression symptoms in the A₁R-ERK1/2 pathway in the prefrontal cortex and hippocampus.

Minocycline prevents the depressive-like behavior through inhibiting the release of HMGB1 from microglia and neurons

BACKGROUND

Our previous study reports the causal role of high mobility group box 1 (HMGB1) in the development of depression; and we find glycyrrhizic acid (GZA) can be a potential treatment for major depressive disorder (MDD) considering its inhibition of HMGB1 activity. This study aims to further explore the exact cell types that release HMGB1 in the hippocampus.

METHODS

We detected the effects of microglia conditioned medium on primary astrocytes and neurons. The effects of minocycline on depressive-like behaviors were tested in BABLB/c mice after four weeks of chronic unpredictable mild stress (CUMS) exposure. Furthermore, the immunofluorescence (IF) assays, hematoxylin-eosin (HE) and TUNEL staining were used to observe hippocampal slices to evaluate the release of HMGB1. The cytoplasmic translocations of HMGB1 protein were assayed by western-blot.

RESULTS

Exposure to CUMS caused an active release of HMGB1 from microglia and neurons in the hippocampus. After minocycline administration for inhibiting the activation of microglia, both microglia and neurons reduced the release of HMGB1 and the protein level of central and peripheral HMGB1 recovered accordingly. Along with blocking the release of HMGB1, behavioral and cognitive deficits induced by CUMS were improved significantly by minocycline. In addition, the supernatant of primary microglia stimulated the secretion of HMGB1 in primary neurons, not in astrocytes, at 24 h after 4 h-LPS treatment.

CONCLUSION

All the evidence supported our hypotheses that microglia and neurons are the main cell sources of HMGB1 release under CUMS condition, and that the release of HMGB1 by microglia may play an important role in the development of depressive-like behavior.

Chronic stress and endothelial dysfunction: mechanisms, experimental challenges, and the way ahead

Although chronic stress is an important risk factor for cardiovascular diseases (CVD) onset, the underlying mechanisms driving such pathophysiological complications remain relatively unknown. Here, dysregulation of innate stress response systems and the effects of downstream mediators are strongly implicated, with the vascular endothelium emerging as a primary target of excessive glucocorticoid and catecholamine action. Therefore, this review article explores the development of stress-related endothelial dysfunction by focusing on the following: 1) assessing the phenomenon of stress and complexities surrounding this notion, 2) discussing mechanistic links between chronic stress and endothelial dysfunction, and 3) evaluating the utility of various preclinical models currently employed to study mechanisms underlying the onset of stress-mediated complications such as endothelial dysfunction. The data reveal that preclinical models play an important role in our efforts to gain an increased understanding of mechanisms underlying stress-mediated endothelial dysfunction. It is our understanding that this provides a good foundation going forward, and we propose that further efforts should be made to 1) more clearly define the concept of stress and 2) standardize protocols of animal models with specific guidelines to better indicate the mental complications that are simulated.

Chronic Restraint Stress Induces Gastric Mucosal Inflammation with Enhanced Oxidative Stress in a Murine Model

Background

Although the underlying mechanisms of chronic stress are still unknown, this condition has been related to the pathophysiology of gastric mucosal inflammation, whose development is accelerated by oxidative stress. The present study investigates how chronic stress influences gastric mucosal oxidative stress and inflammation.

Methods

Eight-week-old C57BL/6J male mice were subjected to two-week intermittent restraint stress. The expressions of CD11b (a specific for monocyte/macrophage), monocyte/macrophage cell surface markers (CD68 and F4/80), NADPH oxidase-4 (Nox-4) and 8-hydroxy-2’-deoxyguanosine (8-OHdG, a sensitive biomarker of oxidative stress) were determined using immunohistochemistry, RT-PCR, and enzyme-linked immunosorbent assay, respectively. The expressions of antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, were examined by RT-PCR and Western blotting. The expressions of proinflammatory cytokines, including monocyte chemoattractant protein-1 (MCP-1), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α), were determined using immunohistochemistry and RT-PCR, respectively.

Results

Chronic stress increased the lymphocytic infiltration and inflammation within the gastric mucosa of mice. Stress remarkably increased the expression levels of CD11b and mRNA expression levels of CD68 and F4/80 in the mucosa of the stomach of stressed mice. Stress remarkably increased both mRNA and plasma concentrations of Nox-4 and 8-OHdG; and markedly reduced gastric mRNA and protein expression levels of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase. The expressions of proinflammatory cytokines (MCP-1, IL-1β, and TNF-α) were predominantly observed in the gastric mucosal layers of the stressed mice. Furthermore, stress remarkably elevated the gastric mucosal mRNA expression levels of MCP-1, IL-1β, and TNF-α.

Conclusion

Two weeks of restraint stress induced gastric inflammation in the murine model with enhanced oxidative stress and reduced anti-oxidative system.

Effects of venlafaxine on the expression level and methylation status of genes involved in oxidative stress in rats exposed to a chronic mild stress

Recent human and animal studies indicate that oxidative and nitrosative stress may play a role in the aetiology and pathogenesis of depression. This study investigates the effect of chronic administration of the serotonin‐norepinephrine reuptake inhibitor, venlafaxine, on the expression and methylation status of SOD1, SOD2, GPx1, GPx4, CAT, NOS1 and NOS2 in the brain and blood of rats exposed to a chronic mild stress (CMS) model of depression. Separate groups of animals were exposed to CMS for 2 or 7 weeks; the second group received saline or venlafaxine (10 mg/kg/d, IP) for 5 weeks. After completion of both stress conditions and drug administration, the mRNA and protein expression of selected genes and the methylation status of their promoters were measured in peripheral mononuclear blood cells (PBMCs) and in brain structures (hippocampus, amygdala, hypothalamus, midbrain, cortex, basal ganglia) with the use of TaqMan Gene Expression Assay, Western blot and methylation‐sensitive high‐resolution melting techniques. CMS caused a decrease in sucrose consumption, and this effect was normalized by fluoxetine. In PBMCs, SOD1, SOD2 and NOS2 mRNA expression changed only after venlafaxine administration. In brain, CAT, Gpx1, Gpx4 and NOS1 gene expression changed following CMS or venlafaxine exposure, most prominently in the hippocampus, midbrain and basal ganglia. CMS increased the methylation of the Gpx1 promoter in PBMCs, the second Gpx4 promoter in midbrain and basal ganglia, and SOD1 and SOD2 in hippocampus. The CMS animals treated with venlafaxine displayed a significantly higher CAT level in midbrain and cerebral cortex. CMS caused an elevation of Gpx4 in the hippocampus, which was lowered in cerebral cortex by venlafaxine. The results indicate that CMS and venlafaxine administration affect the methylation of promoters of genes involved in oxidative and nitrosative stress. They also indicate that peripheral and central tissue differ in their response to stress or antidepressant treatments. It is possible that that apart from DNA methylation, a crucial role of expression level of genes may be played by other forms of epigenetic regulation, such as histone modification or microRNA interference.

These findings provide strong evidence for thesis that analysis of the level of mRNA and protein expression as well as the status of promoter methylation can help in understanding the pathomechanisms of mental diseases, including depression, and the mechanisms of action of drugs effective in their therapy.

Glutamine Supplementation Prevents Chronic Stress-Induced Mild Cognitive Impairment

We recently reported that glutamine (Gln) supplementation protected glutamatergic neurotransmission from the harmful effects of chronic stress. Altered glutamatergic neurotransmission is one of the main causes of cognitive disorders. However, the cognitive enhancer function of Gln has not been clearly demonstrated thus far. Here, we evaluated whether and how Gln supplementation actually affects chronic stress-induced cognitive impairment. Using a chronic immobilization stress (CIS) mouse model, we confirmed that chronic stress induced mild cognitive impairment (MCI) and neuronal damage in the hippocampus. In contrast, Gln-supplemented mice did not show evidence of MCI. To investigate possible underlying mechanisms, we confirmed that CIS increased plasma corticosterone levels as well as brain and plasma levels of reactive oxygen/nitrogen species. CIS also increased levels of inducible nitric oxide synthase and NADPH oxidase subunits (p47^phox and p67^phox) in both the prefrontal cortex and CA1 region of the hippocampus. CIS decreased the number of synaptic puncta in the prefrontal cortex and hippocampus, but these effects were inhibited by Gln supplementation. Taken together, the present results suggest that Gln is an effective agent against chronic stress-induced MCI.

DRIMC: an improved drug repositioning approach using Bayesian inductive matrix completion

Motivation

One of the most important problems in drug discovery research is to precisely predict a new indication for an existing drug, i.e. drug repositioning. Recent recommendation system-based methods have tackled this problem using matrix completion models. The models identify latent factors contributing to known drug-disease associations, and then infer novel drug-disease associations by the correlations between latent factors. However, these models have not fully considered the various drug data sources and the sparsity of the drug-disease association matrix. In addition, using the global structure of the drug-disease association data may introduce noise, and consequently limit the prediction power.

Results

In this work, we propose a novel drug repositioning approach by using Bayesian inductive matrix completion (DRIMC). First, we embed four drug data sources into a drug similarity matrix and two disease data sources in a disease similarity matrix. Then, for each drug or disease, its feature is described by similarity values between it and its nearest neighbors, and these features for drugs and diseases are mapped onto a shared latent space. We model the association probability for each drug-disease pair by inductive matrix completion, where the properties of drugs and diseases are represented by projections of drugs and diseases, respectively. As the known drug-disease associations have been manually verified, they are more trustworthy and important than the unknown pairs. We assign higher confidence levels to known association pairs compared with unknown pairs. We perform comprehensive experiments on three benchmark datasets, and DRIMC improves prediction accuracy compared with six stat-of-the-art approaches.

Availability and implementation

Source code and datasets are available at https://github.com/linwang1982/DRIMC.

Supplementary information

Supplementary data are available at Bioinformatics online.

Inducible nitric oxide synthase: Regulation, structure, and inhibition

A considerable number of human diseases have an inflammatory component, and a key mediator of immune activation and inflammation is inducible nitric oxide synthase (iNOS), which produces nitric oxide (NO) from l-arginine. Overexpressed or dysregulated iNOS has been implicated in numerous pathologies including sepsis, cancer, neurodegeneration, and various types of pain. Extensive knowledge has been accumulated about the roles iNOS plays in different tissues and organs. Additionally, X-ray crystal and cryogenic electron microscopy structures have shed new insights on the structure and regulation of this enzyme. Many potent iNOS inhibitors with high selectivity over related NOS isoforms, neuronal NOS, and endothelial NOS, have been discovered, and these drugs have shown promise in animal models of endotoxemia, inflammatory and neuropathic pain, arthritis, and other disorders. A major issue in iNOS inhibitor development is that promising results in animal studies have not translated to humans; there are no iNOS inhibitors approved for human use. In addition to assay limitations, both the dual modalities of iNOS and NO in disease states (ie, protective vs harmful effects) and the different roles and localizations of NOS isoforms create challenges for therapeutic intervention. This review summarizes the structure, function, and regulation of iNOS, with focus on the development of iNOS inhibitors (historical and recent). A better understanding of iNOS' complex functions is necessary before specific drug candidates can be identified for classical indications such as sepsis, heart failure, and pain; however, newer promising indications for iNOS inhibition, such as depression, neurodegenerative disorders, and epilepsy, have been discovered.

Repeated Nitrous Oxide Exposure Exerts Antidepressant-Like Effects Through Neuronal Nitric Oxide Synthase Activation in the Medial Prefrontal Cortex

Clinical studies have demonstrated that exposure to the inhalational general anesthetic nitrous oxide (N₂O) produces antidepressant effects in depressed patients. However, the mechanisms underlying the antidepressant effects of N₂O remain largely unknown. Neuronal nitric oxide synthase (nNOS)-mediated nitric oxide (NO) synthesis is essential for brain function and underlies the molecular mechanisms of many neuromodulators. We hypothesized that activation of the nNOS/NO pathway in the medial prefrontal cortex (mPFC) might mediate the antidepressant effects of N₂O. In this study, we revealed that repeated N₂O exposure produced antidepressant-like responses in mice. Our mechanistic exploration showed that repeated N₂O exposure increased burst firing activity and that the expression levels of BDNF with nNOS activation were dependent in the mPFC. In particular, the antidepressant-like effects of N₂O were also antagonized by local nNOS inhibition in the mPFC. In summary, our results indicated that N₂O exposure enhances BDNF expression levels and burst firing rates in an nNOS activation dependent manner, which might underlie the pharmacological mechanism of the antidepressant-like effects of N₂O exposure. The present study appears to provide further mechanistic evidence supporting the antidepressant effects of N₂O.

Effect of ketamine combined with DHA on lipopolysaccharide-induced depression-like behavior in rats

Depression has become a common mental illness, and studies have shown that neuroinflammation is associated with depression. Ketamine is a rapid antidepressant. In order to obtain better antidepressant effects, it is necessary to explore the efficacy of combination therapy with ketamine and other antidepressants. DHA is an unsaturated fatty acid with excellent application prospects due to its safety and antidepressant effects. This study was designed to investigate the effect of ketamine combined with DHA on lipopolysaccharide-induced depression-like behavior. In behavioral experiments, lipopolysaccharide prolongs the immobility time of the forced swimming and tail suspension tests in rats and reduces the sucrose preference. The combination of ketamine and DHA can reverse these changes and work better than the single application. Nissl staining showed that ketamine combined with DHA can reverse the nerve damage caused by lipopolysaccharide. Cell morphology observation the combination of ketamine and DHA group was more complete than that of LPS group. The combination of ketamine and DHA significantly decreased the levels of IL-1, IL-6 and TNF-ɑin hippocampus and PC12 cells and increased the content of BDNF. Immunofluorescence results showed that ketamine combined with DHA can effectively inhibit PP65 nuclear translocation. Western blot results showed that ketamine combined with DHA can effectively inhibit the expression of NF-KB in hippocampus and PC12 cells, and increase the expression of P-CREB and BDNF. In summary, the combination of ketamine with DHA may be a more effective treatment for depression caused by inflammation and is mediated by inhibition of the inflammatory pathway.

Legumain acts on neuroinflammatory to affect CUS-induced cognitive impairment

Cognitive impairment has been widely recognized as a central feature of depression. Legumain, a lysosomal cysteine protease, plays an important role in cancer, atherosclerosis, inflammation and other pathological conditions. Meanwhile, it has been reported that the activation of legumain aggravates the cognitive impairment in neurodegenerative diseases. In this study, we explored the role of legumain in cognitive impairment of stressed mice. Legumain knockout (legumain KO) and wildtype (WT) mice were divided into four groups: control group, chronic mild unpredictable stressed (CUS) group, legumain KO group and legumain KO + CUS group. Our results demonstrated that CUS (4 weeks) induced cognitive impairment in mice effectively based on Morris water maze (MWM) test and novel object recognition (NOR) test and decreased the synaptic plasticity. Additionally, CUS exposure significantly decreased the expression of hippocampal synapse related proteins and the cell density in the DG region, accompanied by increasing the expression of hippocampal inflammatory cytokines and promoting the activation of microglia in the hippocampus. Legumain KO distinctly restored the CUS-induced negative effects on the indicators mentioned above. In conclusion, our results suggested that legumain may be an effective therapeutic target for cognitive impairment as was seen within the CUS model and legumain KO reduced the level of neuroinflammation, thereby improving the hippocampal synaptic plasticity and cognitive impairment of stressed mice.

Nitric oxide: Antidepressant mechanisms and inflammation

Millions of individuals worldwide suffers from mood disorders, especially major depressive disorder (MDD), which has a high rate of disease burden in society. Although targeting the biogenic amines including serotonin, and norepinephrine have provided invaluable links with the pharmacological treatment of MDD over the last four decades, a growing body of evidence suggest that other biologic systems could contribute to the pathophysiology and treatment of MDD. In this chapter, we highlight the potential role of nitric oxide (NO) signaling in the pathophysiology and thereby treatment of MDD. This has been investigated over the last four decades by showing that (i) levels of NO are altered in patients with major depression; (ii) modulators of NO signaling exert antidepressant effects in patients with MDD or in the animal studies; (iii) NO signaling could be targeted by a variety of antidepressants in animal models of depression; and (iv) NO signaling can potentially modulate the inflammatory pathways that underlie the pathophysiology of MDD. These findings, which hypothesize an NO involvement in MDD, can provide a new insight into novel therapeutic approaches for patients with MDD in the future.

Chronic stress augments esophageal inflammation, and alters the expression of transient receptor potential vanilloid 1 and protease‑activated receptor 2 in a murine model

Stress is a pivotal factor for inflammation, reactive oxygen species (ROS) production and formation of visceral hypersensitivity (VH) in the process of gastroesophageal reflux disease (GERD). In the present study, the effects of stress on esophageal inflammation, oxidative stress and VH were investigated in a chronic restraint stress mouse model. C57BL/6J male mice were subjected to 2 weeks of intermittent restraint stress, and histopathological analysis revealed that stress induced esophageal inflammation and fibrosis, while no distinct changes were detected in non‑stressed control mice. In addition, increased NADPH oxidase 4 expression was observed in the plasma and esophagus of stressed mice, indicating accumulation of ROS. The expression levels of antioxidants, including Mn‑superoxide dismutase (MnSOD), Cu/Zn‑SOD, catalase and glutathione peroxidase, were also analyzed using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). In addition, transient receptor potential vanilloid 1 (TRPV‑1) and protease‑activated receptor 2 (PAR‑2), which are crucial receptors for VH, were measured by immunohistochemistry and RT‑qPCR. The results demonstrated that stress markedly reduced antioxidant expression, while it significantly upregulated TRPV‑1 and PAR‑2 expression levels in the mouse esophagus. Finally, 2 weeks of restraint stress significantly increased the esophageal and plasma levels of inflammatory cytokines, including interleukin (IL)‑6, IL‑8, interferon‑γ and tumor necrosis factor‑α. Taken together, the present study results indicated that stress‑induced esophageal inflammation and ROS generation involves VH.

Subchronic stress effects on vascular reactivity in C57BL/6 strain mice

BACKGROUND AND AIMS

There is a close relationship between psychosocial stress and the development of cardiovascular diseases. It has been reported that there are different alterations in endothelial function in this relationship. However, results obtained in different experimental stress models are controversial. Herein, we studied the effects of subchronic stress induced by movement restraint on several cardiovascular responses and plasma corticosterone concentration in male adult mice.

METHODS

Experiments were performed in adult male mice of C57BL/6 strain. Animals were allocated into three groups: Control group A, without manipulation; Control group B, with manipulation (quantitation of blood pressure); and Experimental group, with quantitation of blood pressure and exposure to movement restraint. In vivo, heart rate and blood pressure were registered. In vitro, in aortic rings, vascular reactivity was analyzed. Additionally, plasma corticosterone concentration was quantified.

RESULTS

In vivo, subchronic stress did not produce changes on heart rate either on blood pressure. In vitro, aortic rings with and without endothelium from control group B and experimental group showed: 1) a significant decrease in the maximal tension developed in response to phenylephrine; 2) this decrease was reverted by L-NAME. However, aortic rings from all groups, developed the same tension in response to high K⁺ solution. In aortic rings from animals of the experimental group, an increase in the maximal relaxation induced by carbachol was observed. This relaxation was prevented and/or reversed by L-NAME. Plasma corticosterone concentration was higher in the experimental group than that in the control group A.

CONCLUSIONS

Exposition to subchronic movement restraint did not produce alterations in neurovegetative responses in this strain mice. But according to vasomotor responses observed, the results suggest that this subchronic stress model induces an increase in the synthesis/release of nitric oxide, both from endothelial cells and vascular smooth muscle. In accordance with the aforementioned results, we propose that C57BL/6 mice strain is sensitive to subchronic movement restraint stress model.

Cytokine gene expression profiles in goldfish (Carassius auratus) during Gyrodactylus kobayashii infection

Monogeneans of the genus Gyrodactylus are well-known pathogens causing huge mortalities in wild and cultured fish. Cytokine expression is one of most important host defense mechanisms against parasite infections. In this study, the expression pattern of the key pro-inflammatory (IL-1β, IL-8, IFN-γ, TNF-α, IL-12 and iNOS) and anti-inflammatory cytokine genes (IL-10, TGFβ and IL-4) of Gyrodactylus kobayashii infected goldfish (Carassius auratus) were determined by real-time quantitative PCR analysis. Our results showed that G. kobayashii infection caused increased expression of the pro-inflammatory cytokines including IFN-γ, TNF-α and iNOS in all detected tissues throughout the infection period. Among these genes, iNOS has the highest transcript level accompanied with increased nitric oxide (NO) concentration in the serum of all infected goldfish. The mRNA level of IL-1β in the liver, spleen and head kidney was significantly up-regulated during the early stage of infection (days 2-8). While high expression level of IL-8 and IL-12 was observed during the elimination phase of infection (days 10-14). As for anti-inflammatory cytokines, the expression profiles of IL-10 were distinct from those of TGF-β and IL-4. Specifically, the mRNA level of IL-10 did not increase in the spleen and head kidney during the early stage of infection, while increased expression of TGF-β and IL-4 were likewise seen. Besides, all infected fish had significantly higher complement C3 but lower IgM levels than the non-infected fish. The results provide insights into the interaction between gyrodactylids and the fish host, and indicate that systemic cytokine responses are critical for controlling parasite infection in fish.

The Unpredictable Chronic Mild Stress Protocol for Inducing Anhedonia in Mice

Depression is a highly prevalent and debilitating condition, only partially addressed by current pharmacotherapies. The lack of response to treatment by many patients prompts the need to develop new therapeutic alternatives and to better understand the etiology of the disorder. Pre-clinical models with translational merits are rudimentary for this task. Here we present a protocol for the unpredictable chronic mild stress (UCMS) method in mice. In this protocol, adolescent mice are chronically exposed to interchanging unpredictable mild stressors. Resembling the pathogenesis of depression in humans, stress exposure during the sensitive period of mice adolescence instigates a depressive-like phenotype evident in adulthood. UCMS can be used for screenings of antidepressants on the variety of depressive-like behaviors and neuromolecular indices. Among the more prominent tests to assess depressive-like behavior in rodents is the sucrose preference test (SPT), which reflects anhedonia (core symptom of depression). The SPT will also be presented in this protocol. The ability of UCMS to induce anhedonia, instigate long-term behavioral deficits and enable reversal of these deficits via chronic (but not acute) treatment with antidepressants strengthens the protocol's validity compared to other animal protocols for inducing depressive-like behaviors.