BDNF/TrkB Pathway Mediates the Antidepressant-Like Role of H2S in CUMS-Exposed Rats by Inhibition of Hippocampal ER Stress

Exploring the association between BDNF related signaling pathways and depression: A literature review

Depression is a debilitating mental disease that inflicts significant harm upon individuals and society, yet effective treatment options remain elusive. At present, the pathogenesis of multiple depression is not fully clear, but its occurrence can be related to biological or environmental pathways, among which Brain-derived neurotrophic factor (BDNF) can unequivocally act on two downstream receptors, tyrosine kinase receptor (TrkB) and the p75 neurotrophin receptor (p75NTR), then affect the related signal pathways, affecting the occurrence and development of depression. Accumulating studies have revealed that BDNF-related pathways are critical in the pathophysiology of depression, and their interaction can further influence the efficacy of depression treatment. In this review, we mainly summarized the signaling pathways associated with BDNF and classified them according to different receptors and related molecules, providing promising insights and future directions in the treatment of depression.

Vilazodone Alleviates Neurogenesis-Induced Anxiety in the Chronic Unpredictable Mild Stress Female Rat Model: Role of Wnt/β-Catenin Signaling

Defective β-catenin signaling is accompanied with compensatory neurogenesis process that may pave to anxiety. β-Catenin has a distinct role in alleviating anxiety in adolescence; however, it undergoes degradation by the degradation complex Axin and APC. Vilazodone (VZ) is a fast, effective antidepressant with SSRI activity and 5-HT1A partial agonism that amends somatic and/or psychic symptoms of anxiety. Yet, there is no data about anxiolytic effect of VZ on anxiety-related neurogenesis provoked by stress-reduced β-catenin signaling. Furthermore, females have specific susceptibility toward psychopathology. The aim of the present study is to uncover the molecular mechanism of VZ relative to Wnt/β-catenin signaling in female rats. Stress-induced anxiety was conducted by subjecting the rats to different stressful stimuli for 21 days. On the 15th day, stressed rats were treated with VZ(10 mg/kg, p.o.) alone or concomitant with the Wnt inhibitor: XAV939 (0.1 mg/kg, i.p.). Anxious rats showed low β-catenin level turned over by Axin-1 with unanticipated reduction of APC pursued with elevated protein levels of neurogenesis-stimulating proteins: c-Myc and pThr183-Erk likewise gene expressions of miR-17-5p and miR-18. Two weeks of VZ treatment showed anxiolytic effect figured by alleviation of hippocampal histological examination. VZ protected β-catenin signal via reduction in Axin-1 and elevation of APC conjugated with modulation of β-catenin downstream targets. The cytoplasmic β-catenin turnover by Axin-1 was restored by XAV939. Herein, VZ showed anti-anxiety effect, which may be in part through regaining the balance of the reduced β-catenin and its subsequent exaggerated response of p-Erk, c-Myc, Dicer-1, miR-17-5p, and miR-18.

Sodium Hydrosulfide Reverts Chronic Stress-Induced Cardiovascular Alterations by Reducing Oxidative Stress

ABSTRACT

Chronic stress induces a group of unrecognized cardiovascular impairments, including elevated hemodynamic variables and vascular dysfunction. Moreover, hydrogen sulfide (H 2 S), a gasotransmitter that regulates the cardiovascular system decreases under chronic stress. Thus, this study assessed the impact of sodium hydrosulfide (NaHS) (H 2 S donor) on chronic restraint stress (CRS)-induced cardiovascular changes. For that purpose, male Wistar rats were restrained for 2 hours a day in a transparent acrylic tube over 8 weeks. Then, body weight, relative adrenal gland weight, serum corticosterone, H 2 S-synthesizing enzymes, endothelial nitric oxide synthetize expression, reactive oxygen species levels, lipid peroxidation, and reduced glutathione-to-oxidized glutathione (GSH 2 :GSSG) ratio were determined in the thoracic aorta. The hemodynamic variables were measured in vivo by the plethysmograph method. The vascular function was evaluated in vitro as vasorelaxant responses induced by carbachol or sodium nitroprusside, and norepinephrine (NE)-mediated vasocontractile responses in the thoracic aorta. CRS increased (1) relative adrenal gland weight; (2) hemodynamic variables; (3) vasoconstrictor responses induced by NE, (4) reactive oxygen species levels, and (5) lipid peroxidation in the thoracic aorta. In addition, CRS decreased (1) body weight; (2) vasorelaxant responses induced by carbachol; (3) GSH content, and (4) GSH 2 :GSSG ratio. Notably, NaHS administration (5.6 mg/kg) restored hemodynamic variables and lipid peroxidation and attenuated the vasoconstrictor responses induced by NE in the thoracic aorta. In addition, NaHS treatment increased relative adrenal gland weight and the GSH 2 :GSSG ratio. Taken together, our results demonstrate that NaHS alleviates CRS-induced hypertension by reducing oxidative stress and restoring vascular function in the thoracic aorta.

Potential Crosstalk between the PACAP/VIP Neuropeptide System and Endoplasmic Reticulum Stress-Relevance to Multiple Sclerosis Pathophysiology

Multiple sclerosis (MS) is an immune-mediated disorder characterized by focal demyelination and chronic inflammation of the central nervous system (CNS). Although the exact etiology is unclear, mounting evidence indicates that endoplasmic reticulum (ER) stress represents a key event in disease pathogenesis. Pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP) are two structurally related neuropeptides that are abundant in the CNS and are known to exert neuroprotective and immune modulatory roles. Activation of this endogenous neuropeptide system may interfere with ER stress processes to promote glial cell survival and myelin self-repair. However, the potential crosstalk between the PACAP/VIP system and ER stress remains elusive. In this review, we aim to discuss how these peptides ameliorate ER stress in the CNS, with a focus on MS pathology. Our goal is to emphasize the importance of this potential interaction to aid in the identification of novel therapeutic targets for the treatment of MS and other demyelinating disorders.

Hydrogen Sulfide Prevents LPS-Induced Depression-like Behavior through the Suppression of NLRP3 Inflammasome and Pyroptosis and the Improvement of Mitochondrial Function in the Hippocampus of Mice

Hydrogen sulfide (H2S) has been implicated to have antidepressive effects. We sought to investigate the prevention effects of H2S donor NaHS on depression-like behavior induced by lipopolysaccharide (LPS) in mice and its potential mechanisms. Sucrose preference, force swimming, open field, and elevate zero maze were used to evaluate depression-like behavior. NF-κB and NLRP3 inflammasome activation and mitochondrial function in the hippocampus were determined. It was found that depression-like behavior induced by LPS was prevented by NaHS pretreatment. LPS caused NF-κB and NLRP3 inflammasome activation in the hippocampus as evidenced by increased phosphorylated-p65 levels and increased NLRP3, ASC, caspase-1, and mature IL-1β levels in the hippocampus, which were also blocked by NaHS. LPS increased GSDMD-N levels and TUNEL-positive cells in the hippocampus, which was prevented by NaHS. Abnormal mitochondrial morphology in the hippocampus was found in LPS-treated mice. Mitochondrial membrane potential and ATP production were reduced, and ROS production was increased in the hippocampus of LPS-treated mice. NaHS pretreatment improved impaired mitochondrial morphology and increased membrane potential and ATP production and reduced ROS production in the hippocampus of LPS-treated mice. Our data indicate that H2S prevents LPS-induced depression-like behaviors by inhibiting NLRP3 inflammasome activation and pyroptosis and improving mitochondrial function in the hippocampus.

Dysregulated cystathionine-β-synthase/hydrogen sulfide signaling promotes chronic stress-induced colonic hypermotility in rats

BACKGROUND

Hydrogen sulfide (H₂ S), an important endogenous gasotransmitter, is involved in the modulation of gastrointestinal motility, but whether it mediates the intestinal dysmotility in irritable bowel syndrome (IBS) is not known. This study explored the significance of cystathionine-β-synthase (CBS)/H₂ S signaling in stress-induced colonic dysmotility.

METHODS

A rat model of IBS was established using chronic water avoidance stress (WAS). Colonic pathological alterations were detected histologically. Intestinal motility was determined by intestinal transit time (ITT) and fecal water content (FWC). Visceral sensitivity was assessed using the visceromotor response (VMR) to colorectal distension (CRD). Real-time PCR, Western blotting, and immunostaining were performed to identify the expression of CBS in the colon. The contractions of distal colon were studied in an organ bath system and H₂ S content was measured by ELISA. The effects of SAM, a selective CBS activator, on colonic dysmotility were examined. MEK1 was tested as a potential upstream effector of CBS/H₂ S loss.

KEY RESULTS

After 10 days of WAS, the ITT was decreased and FWC was increased, and the VMR magnitude in response to CRD was enhanced. The colonic CBS expression and H₂ S levels were significantly declined in WAS-exposed rats, and the density of CBS-positive enteric neurons in the myenteric plexus in WAS-treated rats was lower than that in controls. SAM treatment relieved WAS-induced colonic hypermotility via increased H₂ S production. AZD6244, a selective inhibitor of MEK1, partially reversed CBS downregulation and colonic hypermotility in WAS-treated rats.

CONCLUSIONS & INFERENCES

Decreased CBS/H₂ S signaling through increased MEK1 signaling might be important in the pathogenesis of chronic stress-induced colonic hypermotility. SAM could be administered for disorders associated with intestinal hypermotility.

18β-Glycyrrhetinic Acid Ameliorates Neuroinflammation Linked Depressive Behavior Instigated by Chronic Unpredictable Mild Stress via Triggering BDNF/TrkB Signaling Pathway in Rats

Evidence shows that inflammatory responses may encompass the onset of severe depressive illness. Traditionally used licorice contains 18β-glycyrrhetinic acid (18βGA), which has been demonstrated to reduce inflammation and oxidative stress. This study investigates the antidepressant effects of 18βGA and the underlying mechanism in rats exposed to chronic unpredictable mild stress (CUMS). Wistar rats were exposed to CUMS for 36 consecutive days to establish depression. 18βGA (10, 20, and 50 mg/kg) or fluoxetine was given once daily (from day 30 to day 36). Thereafter, behavior parameters (sucrose preference test, forced-swimming test, open-field test, body weight), pro-inflammatory cytokines, neurotransmitters, adrenocorticotropic hormone (ACTH), corticosterone (CORT), and liver biomarkers were studied. Immunohistochemistry and western blot analyses were conducted to investigate the protein's expression. 18βGA (20 and 50 mg/kg) treatment increased sucrose intake, locomotion in the open-field test, decreased immobility time in the forced swim test, and improved body weight in CUMS-exposed rats. The therapy of 18βGA dramatically declined cytokines, ACTH and CORT and improved 5HT and norepinephrine in CUMS rats. Furthermore, BDNF and TrkB proteins were down-regulated in CUMS group, which was increased to varying degrees by 18βGA at doses of 20 and 50 mg/kg. Therefore, 18βGA ameliorates depressive-like behavior persuaded by chronic unpredictable mild stress, decreases neuroinflammation, liver biomarkers, stress hormones, and improves body weight, brain neurotransmitter concentration via activating on BDNF/TrkB signaling pathway in both PFC and hippocampus in rats.

Hydrogen Sulfide Biomedical Research in China-20 Years of Hindsight

Hydrogen sulfide (H2S) is an important gasotransmitter that is produced by mammalian cells and performs profound physiological and pathophysiological functions. Biomedical research on H2S metabolism and function in China began 20 years ago, which pioneered the examination of the correlation of abnormal H2S metabolism and cardiovascular diseases. Over the last two decades, research teams in China have made numerous breakthrough discoveries on the effects of H2S metabolism on hypertension, atherosclerosis, pulmonary hypertension, shock, angiogenesis, chronic obstructive pulmonary disease, pain, iron homeostasis, and testicle function, to name a few. These research developments, carried by numerous research teams all over China, build nationwide research network and advance both laboratory study and clinical applications. An integrated and collaborative research strategy would further promote and sustain H2S biomedical research in China and in the world.

7,8-Dihydroxyflavone alleviates Endoplasmic Reticulum Stress in cafeteria diet-induced metabolic syndrome

AIMS

Prolonged Endoplasmic Reticulum Stress (ERS) is involved in the pathogenesis of metabolic syndrome, including type-2 diabetes mellitus, cardiovascular diseases, atherosclerosis, obesity, and fatty liver disease. There have been significant efforts to discover molecules to treat ERS and/or to ameliorate associate symptoms. In this study, we investigated the effect of 7,8-Dihydroxyflavone (7,8-DHF) on ERS in liver and pancreas tissues in a cafeteria (CAF) diet induced metabolic syndrome model.

MAIN METHODS

Male C57BL/6 mice were fed CAF diet for 16 weeks and 7,8-DHF was administered intraperitoneally (5 mg/kg/day) for last four weeks. 78-kDa glucose-regulated protein (GRP78) and C/EBP homologous protein (CHOP) in liver and pancreas tissues, insulin and interleukin-1β (IL-1β) in serum were analyzed by ELISA method and serum biochemistry parameters were analyzed with autoanalyzer. GRP78 and CHOP gene expression levels were determined by qRT-PCR. In addition, histopathological analyzes were performed on liver and pancreas tissues.

KEY FINDINGS

Findings revealed that CAF diet caused metabolic abnormalities, insulin resistance and inflammation in serum and triggered ERS in pancreas and liver tissues. 7,8-DHF treatment significantly reduced metabolic abnormalities by reducing serum biochemical parameters, HOMO-IR and IL-1β levels. qRT-PCR and ELISA results indicated that 7,8-DHF treatment down-regulated GRP78 and CHOP expression and protein levels in the liver and GRP78 expression in pancreas. Efficiency of 7,8-DHF in these tissues was also demonstrated by histopathological tests.

SIGNIFICANCE

In conclusion, CAF diet-induced metabolic syndrome model, 7,8-DHF suppressed ERS and ERS-induced metabolic disorders in both liver and pancreas. Therefore, 7,8-DHF may potentially be a novel therapeutic compound to ameliorate ERS and related metabolic symptoms.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Sodium hydrosulfide reverses β2-microglobulin-induced depressive-like behaviors of male Sprague-Dawley rats: Involving improvement of synaptic plasticity and enhancement of Warburg effect in hippocampus

BACKGROUND

Our previous works demonstrated that β2-microglobulin (β2m), a systemic pro-aging factor, induce depressive-like behaviors. Hydrogen sulfide (H₂S) is identified as a potential target for treatment of depression. The aim of the present work is to explore whether H₂S antagonizes β2m-induced depressive-like behaviors and the underlying mechanisms.

METHODS

The depressive-like behaviors were detected using the novelty suppressed feeding test (NSFT), tail suspension test (TST), forced swimming test (FST) and open field test (OFT). The expressions of Warburg-related proteins, including hexokinase II (HK II), pyruvate kinase M2 (PKM2), Lactate dehydrogenase A (LDHA), pyruvate dehydrogenase (PDH) and pyruvate dehydrogenase kinase 1(PDK1), and synaptic plasticity-related proteins, including postsynaptic density protein 95 (PSD95) and synaptophysin1 (SYN1), were determined by western blotting.

RESULT

we found that NaHS (the donor of H₂S) attenuated the depressive-like behaviors in the β2m-exposed rats, as judged by NSFT, TST, FST, and OFT. We also demonstrated that NaHS enhanced the synaptic plasticity, as evidenced by the upregulations of PSD95 and SYN1 expressions in the hippocampus of β2m-exposed rats. Furthermore, NaHS improved the Warburg effect in the hippocampus of β2m-exposed rats, as evidenced by the upregulations of HK II, PKM2, LDHA and PDK1 expressions, and the downregulation of PDH expression.

CONCLUSION

H₂S prevents β2m-induced depressive-like behaviors, which is involved in improvement of hippocampal synaptic plasticity as a result of enhancement of hippocampal Warburg effect.

Effect and mechanism of BDNF/TrkB signaling on vestibular compensation

Brain-derived neurotrophic factor (BDNF) regulates neuronal plasticity by targeting the tyrosine kinase B receptor (TrkB) receptor, but limited researches concentrate on the role of BDNF/TrkB signaling in vestibular compensation. In this study, rats with unilateral vestibular dysfunction were established by unilateral labyrinthectomy (UL) and infusion with siBDNF or 7, 8-Dihydroxyflavone (7,8-DHF, a TrkB receptor agonist). The behavioral scores of rats with vestibular deficits were determined and the rotarod test was performed after UL. BDNF and TrkB levels after UL were determined by western blot and quantitative reverse transcription PCR (qRT-PCR). 5-bromo-2'-deoxyuridine (BrdU)-positive cells (newly generated cells) and GAD67-positive cells (GABAergic neurons) were identified by immunohistochemistry. Glial fibrillary acidic protein (GFAP) (astrocyte marker)-positive cells were identified and GABA type A receptor (GABAAR) expression was detected by immunofluorescence. We found that after UL, BDNF and TrkB levels were up-regulated with a maximum value at 4 h, and then progressively down-regulated during 4 h ~ 7 d. Blocking BDNF/TrkB signaling inhibited the recovery from vestibular deficits, decreased the numbers of newly generated cells and astrocytes in medial vestibular nucleus (MVN), inferior vestibular nerve (IVN), superior vestibular nerve (SVN) and lateral vestibular nucleus (LVN), and disrupted the balances of GABAergic neurons and GABAAR expressions in the left (lesioned) side and right (intact) side of MVN, whereas activation of BDNF/TrkB signaling caused opposite results. The current study indicated that BDNF/TrkB signaling avails vestibular compensation, depending on the number of newly generated cells and astrocytes, the rebalance of GABAergic neurons, and GABAAR expression in bilateral MVN.

Hydrogen sulphide attenuates neuronal apoptosis of substantia nigra by re-establishing autophagic flux via promoting leptin signalling in a 6-hydroxydopamine rat model of Parkinson's disease

Previous studies reveal that hydrogen sulphide (H₂ S) exerts neuroprotection against neurotoxin-induced Parkinson's disease (PD), but the underlying mechanism remains elusive. The present study was aimed to investigate whether H₂ S inhibits neuronal apoptosis of substantia nigra with the involvement of autophagy via promoting leptin signalling in 6-hydroxydopamine (6-OHDA)-induced PD rats. In this study, neuronal apoptosis was analysed by TUNEL staining, the activity of caspase-3 was measured by Caspase-3 fluorometric assay kit, the expressions of Bax, Bcl-2, Beclin-1, LC3II, P62 and leptin were determined by Western blot analysis, and the numbers of autophagosomes and autolysosomes were assessed by transmission electron microscopy. Results showed that NaHS, a donor of exogenous H₂ S, mitigates 6-OHDA-induced the increases in the numbers of TUNEL-positive cells, the activity of caspase-3 and the expression of Bax, and attenuates 6-OHDA-induced a decrease in the expression of Bcl-2 in substantia nigra of rats. In addition, 6-OHDA enhanced the expressions of Beclin-1, LC3-II and P62, increased the number of autophagosomes, and decreased the number of autolysosomes in the substantia nigra, which were also blocked by administration of NaHS. Furthermore, NaHS reversed 6-OHDA-induced the down-regulation of leptin expression in the substantia nigra, and treatment with leptin-OBR, a blocking antibody of leptin receptor, attenuated the inhibition of NaHS on neuronal apoptosis and the improvement of NaHS on the blocked autophagic flux in substantia nigra of 6-OHDA-treated rats. Taken together, these results demonstrated that H₂ S attenuates neuronal apoptosis of substantia nigra depending on restoring impaired autophagic flux through up-regulating leptin signalling in PD.

Hydrogen sulfide attenuates induction and prevents progress of the 6-hydroxydopamine-induced Parkinsonism in rat through activation of ATP-sensitive potassium channels and suppression of ER stress

PURPOSE

Studies argue in favor of hydrogen sulfide (H₂S) as the next potent therapeutic agent for neurodegenerative diseases. In present study, we investigated the effect of long term treatment with NaHS (as donor of H₂S) on induction and progress of the 6-hydroxydopamine (6-OHDA) -induced Parkinsonism in rat.

METHODS

The 6-OHDA was injected into medial forebrain bundle of right hemisphere by stereotaxic surgery. Behavioral tests and treatments were carried out to eight weeks after the toxin. Immunohistochemistry and western blotting were carried out to evaluate the survival of tyrosine hydroxylase (TH) -positive neurons in substantia nigra (SN) and also expression of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP), the markers of endoplasmic reticulum (ER) stress, in striatum and SN.

RESULTS

Eight weeks assessment of the behavioral symptoms showed that NaHS especially at dose of 100 μmol/kg attenuates remarkably induction of the Parkinsonism and prevents its progress. NaHS also increased the survival of TH- positive neurons and suppressed 6-OHDA- induced overexpression of GRP78 and CHOP. Blockade of ATP-sensitive potassium (K-ATP) channels with glibenclamide (Glib) prevented markedly the effect of NaHS on both the induction phase and survival of TH- positive neurons. But Glib did not affect the preventing effect of NaHS on the progress phase and its suppressing effect on the overexpression of ER stress markers.

CONCLUSION

H₂S attenuates induction of the 6-OHDA- induced Parkinsonism and also increases the survival of dopaminergic neurons through activation of K-ATP channels. H₂S also prevents progress of the Parkinsonism probably through suppression of ER stress.

The Role of the Signaling Pathways Involved in the Effects of Hydrogen Sulfide on Endoplasmic Reticulum Stress

Endoplasmic reticulum (ER) is a kind of organelle with multiple functions including protein synthesis, modification and folding, calcium storage, and lipid synthesis. Under stress conditions, ER homeostasis is disrupted, which is defined as ER stress (ERS). The accumulation of unfolded proteins in the ER triggers a stable signaling network named unfolded protein response (UPR). Hydrogen sulfide is an important signal molecule regulating various physiological and pathological processes. Recent studies have shown that H₂S plays an important role in many diseases by affecting ERS, but its mechanism, especially the signaling pathways, is not fully understood. Therefore, in this review, we summarize the recent studies about the signaling pathways involved in the effects of H₂S on ERS in diseases to provide theoretical reference for the related in-depth researches.

Astrocyte Intracellular Ca2+and TrkB Signaling in the Hippocampus Could Be Involved in the Beneficial Behavioral Effects of Antidepressant Treatment

Although monoaminergic-based antidepressant drugs are largely used to treat major depressive disorder (MDD), their mechanisms are still incompletely understood. Intracellular Ca²⁺ (iCa²⁺) and Calmodulin 1(CaM-1) homeostasis have been proposed to participate in the therapeutic effects of these compounds. We investigated whether intra-hippocampal inhibition of CaM-1 would modulate the behavioral responses to chronic treatment with imipramine (IMI) or 7-nitroindazole (7-NI), a selective inhibitor of the neuronal nitric oxide synthase 1 (NOS1) enzyme that shows antidepressant-like effects. We also investigated the interactions of IMI and CaM-1 on transient astrocyte iCa²⁺ evoked by glutamate stimuli. Intra-hippocampal microinjection of the lentiviral delivered (LV) short hairpin iRNA-driven against the CaM-1 mRNA (LV-shRNA-CaM-1) or the CaM-1 inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalene sulphonamide (W-7) blocked the antidepressant-like effect of chronic treatment with IMI or 7-NI. The shRNA also inhibited the mRNA expression of the tropomyosin receptor kinase B (TrkB) in the microinjection region. The iCa²⁺ in ex vivo hippocampus slices stained with fluorescent Ca²⁺indicator Oregon Green 488 BAPTA-1 revealed that IMI increased the intensity and duration of iCa²⁺ oscillation and reduced the number of events evoked by glutamate stimuli, evaluated by using CCD imaging and the % ΔF/Fo parameters. The pre-treatment with W-7 fully antagonized this effect. The present results indicate that the behavioral benefits of chronic antidepressant treatment might be associated with astrocyte intracellular Ca²⁺dynamics and TrkB mRNA expression in the hippocampus.

Hippocampal miRNA-144 Modulates Depressive-Like Behaviors in Rats by Targeting PTP1B

BACKGROUND

Depression is the common mental disorder in the world. However, the pathophysiology mechanism underlying depression remains elusive. It has been reported that aberrant expression of miR-144 is closely related to depression. This study was to investigate whether and how miR-144 involves in depressive-like behaviors in a chronic unpredictable mild stress (CUMS) animal model.

METHODS

A rat model of CUMS was established, and qRT-PCR was performed to detect the expression of miR-144 in the hippocampus of a depressed rat. The lentiviral vector carried miR-144 (LV-miR-144) was injected into the hippocampus of the CUMS rat to investigate the effects of miR-144 on the behaviors and PTP1B/TrkB/BDNF signal transduction in the hippocampus of the rat. The interaction between miR-144 and PTP1B was investigated by biological analyses and dual-luciferase reporter assay.

RESULTS

The results showed that CUMS rats had typical depressive behaviors, and the expression of miR-144 in the hippocampus of CUMS rats was significantly lower than that of the control group. In addition, PTP1B protein expression was significantly up-regulated, while the expression of pTrkB and BDNF protein was significantly down-regulated in the hippocampus of CUMS rats. Moreover, PTP1B was a direct target of miR-144, and miR-144 could activate the downstream TrkB/BDNF signaling pathway by inhibiting the expression of PTP1B in primary hippocampus neurons.

CONCLUSION

MiR-144 played an anti-depressive role in hippocampus dysfunction by inhibiting PTP1B and activating the TrkB/BDNF signaling pathway in the hippocampus of CUMS rats.

Sulfur dioxide derivatives produce antidepressant- and anxiolytic-like effects in mice

Sulfur dioxide (SO₂) can be endogenously generated from sulfur-containing amino acids in animals and humans. Increasing evidence shows that endogenous SO₂ may act as a gaseous molecule to participate in many physiological and pathological processes. However, the role of SO₂ and its derivatives in the central nervous system remains poorly understood. The present study explored the protective effects of exogenous SO₂ derivatives (Na₂SO₃:NaHSO₃, 3:1 M/M) on cellular injury in vitro by using the cell proliferation assay (MTS), cell counting kit 8 assay (CCK-8), and cyto-flow assay in the corticosterone (CORT)-induced PC12 cell injury model. We also examined the antidepressant and anxiolytic effects of SO₂ derivatives on the chronic mild stress (CMS)-induced depression mouse model by using the open field test, novelty suppressed feeding test, forced swimming test, tail suspension test, and sucrose preference test. In the MTS and CCK-8 assays, we found that preexposure of SO₂ derivatives significantly blocked CORT-induced decrease of cellular survival without causing any negative effects. Results from the cyto-flow assay indicated that treatment with SO₂ derivatives could reverse CORT-induced early and late apoptosis of PC12 cells. Systemic treatment with SO₂ derivatives produced markedly antidepressant- and anxiolytic-like activities in mice under normal condition and rapidly reversed CMS-induced depressive- and anxiety-like behaviors. In conclusion, these findings indicate that exogenous SO₂ derivatives show protective properties against the detrimental effects of stress and exert antidepressant- and anxiolytic-like actions. The present study suggests that exogenous SO₂ derivatives are potential therapeutic agents for the treatment of depression, anxiety, and other stress-related diseases.

Differential serum exosome microRNA profile in a stress-induced depression rat model

BACKGROUND

Increasing evidence has shown the important role of exosomes in the maintenance of brain function and pathogenesis of brain disease, but little is known about their association with depression. The aim of this project was to explore the miRNA profile of exosomes in the serum of rats with depression induced by chronic unpredictable mild stress (CUMS).

METHODS

A rat model of depression was replicated via CUMS. Behavioral performance was observed, and serum exosomes were isolated and identified. The protein expression levels of brain-derived neurotrophic factor (BDNF), TrkB, and synaptotagmin 1 in the hippocampus, prefrontal cortex (PFC), and serum exosomes were measured. GO and KEGG enrichment analysis of differential genes was carried out using the R package clusterProfiler.

RESULTS

The CUMS rats showed depression-like behaviors, together with decreased expression levels of BDNF, TrkB, and synaptotagmin 1 in the hippocampus, PFC, and serum exosomes. GO and KEGG enrichment analysis indicated that the differential expression of miRNAs might play an important role in the pathogenesis of stress-induced depression through the MAPK pathway, Wnt pathway, and mTOR pathway.

LIMITATIONS

The protein expression levels of BDNF, TrkB, and synaptotagmin 1 were measured only in the hippocampus and PFC. The function of the differentially expressed miRNAs was not verified in the animal model, which should be investigated in detail in future studies.

CONCLUSIONS

The miRNA profile was altered in rats with stress-induced depression, which might be considered a potential biomarker for the early diagnosis of depression.

Prenatal ethanol exposure increases susceptibility to depression- and anxiety-like behavior in adult female offspring and its underlying mechanism

Epidemiological investigations have found that maternal alcohol intake increases the risk of mental illness in offspring. Our study investigated changes of depression- and anxiety-like behaviors in adult offspring caused by prenatal ethanol exposure (PEE) and explored the potential mechanism. After Wistar rats were intragastrically administered ethanol at a dose of 4 g/kg·d on the 9-20 t h days of pregnancy, the offspring were given 21 days of chronic unpredictable mild stress (CUMS) starting from the 9th week after birth. Before CUMS, the behavioral results showed that the PEE offspring appeared excited and anxious. After CUMS, the PEE offspring rats were more sensitive to the same intensity of stimulation, and then the behavioral disorders aggravated. In adult offspring from the PEE group, the intercellular space was enlarged in the hippocampus, and there was a loss of pyramidal cells. The expression of brain-derived neurotrophic factor (BDNF) decreased; the mRNA expression of the glucocorticoid receptor and synaptic plasticity-related genes decreased; the apoptosis-related genes expressed disrupted. In order to determine whether hippocampal injury and dysfunction resulted from ethanol directly or indirectly, we performed in vitro study. The outcome was accompanied by disrupted gene expression related to neurogenesis and synaptic plasticity. PEE increases the susceptibility of adult female offspring to depression- and anxiety-like behaviors, and its mechanism may be related to the toxic effects of ethanol, both directly and indirectly. The latter inhibits the hippocampal BDNF pathway, leading to the disruption of hippocampal neurogenesis, apoptosis and decreased synaptic plasticity.

Anxiolytic and antioxidant effects of Euterpe oleracea Mart. (açaí) seed extract in adult rat offspring submitted to periodic maternal separation

Many studies suggest a protective role of phenolic compounds in mood disorders. We aimed to assess the effect of Euterpe oleracea (açaí) seed extract (ASE) on anxiety induced by periodic maternal separation (PMS) in adult male rats. Animals were divided into 6 groups: control, ASE, fluoxetine (FLU), PMS, PMS+ASE, and PMS+FLU. For PMS, pups were separated daily from the dam for 3 h between postnatal day (PN) 2 and PN21. ASE (200 mg·kg^-1·day^-1) and FLU (10 mg·kg^-1·day^-1) were administered by gavage for 34 days after stress induction, starting at PN76. At PN106 and PN108, the rats were submitted to open field (OF) and forced swim tests, respectively. At PN110, the rats were sacrificed by decapitation. ASE increased time spent in the center area in the OF test, glucocorticoid receptors in the hypothalamus, tropomyosin receptor kinase B (TRKB) levels in the hippocampus, and nitrite levels and antioxidant activity in the brain stem (PMS+ASE group compared with PMS group). ASE also reduced plasma corticotropin-releasing hormone levels, adrenal norepinephrine levels, and oxidative damage in the brain stem in adult male offspring submitted to PMS. In conclusion, ASE treatment has an anti-anxiety effect in rats submitted to PMS by reducing hypothalamic-pituitary-adrenal axis reactivity and increasing the nitric oxide (NO)-brain-derived neurotrophic factor (BDNF)-TRKB pathway and antioxidant defense in the central nervous system. Novelty ASE has anti-anxiety and antioxidant effects in early-life stress. ASE reduces hypothalamic-pituitary-adrenal axis reactivity. The anxiolytic effect of ASE may involve activation of the NO-BDNF-TRKB pathway in the central nervous system.

HS-GC-IMS-Based metabonomics study of Baihe Jizihuang Tang in a rat model of chronic unpredictable mild stress

The aim of this study was to investigate the differences in volatile organic compounds (VOCs) obtained from the feces of a Baihe Jizihuang Tang (BHT)-treated rat depression model. Rats were subjected to chronic unpredictable mild stress (CUMS), and the differences in VOCs were analyzed by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), NIST software, principal component analysis, and orthogonal partial least squares discriminant analysis. Eleven biomarkers were identified on the basis of VOC migration time, and their relative peak intensities were analyzed. A metabonomic model was established using multivariate statistical analysis. The study demonstrated the metabonomics of CUMS rats and the intervention effect of BHT and also highlighted the potential therapeutic effects of the traditional Chinese medicine (TCM) Jingfang for the clinical treatment of complex diseases, which was in line with the holistic and systemic approaches of TCM. This study augments the use of metabonomics based on HS-GC-IMS in research studies. Using this method, there is no need to pre-process samples by extraction or derivatization, and the VOC component of the sample can be detected directly and rapidly. In conclusion, this study establishes a simple, convenient, and fast technique, which can help identify clinical biomarkers for rapid medical diagnosis.

Stress-induced blood brain barrier disruption: Molecular mechanisms and signaling pathways

Stress is a nonspecific response to a threat or noxious stimuli with resultant damaging consequences. Stress is believed to be an underlying process that can trigger central nervous system disorders such as depression, anxiety, and post-traumatic stress disorder. Though the pathophysiological basis is not completely understood, data have consistently shown a pivotal role of inflammatory mediators and hypothalamo-pituitary-adrenal (HPA) axis activation in stress induced disorders. Indeed emerging experimental evidences indicate a concurrent activation of inflammatory signaling pathways and not only the HPA axis, but also, peripheral and central renin-angiotensin system (RAS). Furthermore, recent experimental data indicate that the HPA and RAS are coupled to the signaling of a range of central neuro-transmitter, -mediator and -peptide molecules that are also regulated, at least in part, by inflammatory signaling cascades and vice versa. More recently, experimental evidences suggest a critical role of stress in disruption of the blood brain barrier (BBB), a neurovascular unit that regulates the movement of substances and blood-borne immune cells into the brain parenchyma, and prevents peripheral injury to the brain substance. However, the mechanisms underlying stress-induced BBB disruption are not exactly known. In this review, we summarize studies conducted on the effects of stress on the BBB and integrate recent data that suggest possible molecular mechanisms and signaling pathways underlying stress-induced BBB disruption. Key molecular targets and pharmacological candidates for treatment of stress and related illnesses are also summarized.

Optimization of food deprivation and sucrose preference test in SD rat model undergoing chronic unpredictable mild stress

BACKGROUND

The chronic unpredictable mild stress (CUMS) model has long been considered the best model for exploring the pathophysiological mechanisms underlying depression. However, there are no widely recognised standards for strategies for modeling and for behavioral testing. The present study aimed to optimize the protocols for food deprivation and the sucrose preference test (SPT) for the CUMS model.

METHODS

We first evaluated the effects of different long periods of food deprivation on the body weight of Sprague Dawley (SD) rats by testing food deprivation for 24 hours (8:00-8:00+), food deprivation for 12 hours during the daytime (8:00-20:00) and food deprivation for 12 hours at night (20:00-8:00+). Next, we established a SD rat CUMS model with 15 different stimulations, and used body weight measurement, SPT, forced swim test (FST), open field test (OFT) and Morris water maze (MWM) test to verify the success of the modeling. In the SPT, consumption of sucrose and pure water within 1 and 12 hours was measured.

RESULTS

Twelve hours of food deprivation during the daytime (8:00-20:00) had no effect on body weight, while 12 hours of food deprivation at night (20:00-8:00+) and 24 hours of food deprivation (8:00-8:00+) significantly reduced the mean body weight of the SD rats. When SPT was used to verify the successful establishment of the CUMS rat model, sucrose consumption measured within 12 hours was less variable than that measured within 1 hour.

CONCLUSIONS

Twelve hours of food deprivation in the daytime (8:00-20:00) may be considered a mild stimulus for the establishment of a CUMS rat model. Measuring sucrose consumption over 12 hours is recommended for SPT.

Effect of N-palmitoylethanolamine-oxazoline on comorbid neuropsychiatric disturbance associated with inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic disorder characterized by inflammation of the gastrointestinal (GI) tract, and it is associated with different neurological disorders. Recent evidence has demonstrated that the gut-brain-axis has a central function in the perpetuation of IBS, and for this reason, it can be considered a possible therapeutic target. N-Palmitoylethanolamine-oxazoline (PEA-OXA) possesses anti-inflammatory and potent neuroprotective effects. Although recent studies have explained the neuroprotective properties of PEA-OXA, nothing is known about its effects on the gut-brain axis during colitis. The aim of this study is to explore the mechanism and the effect of PEA-OXA on the gut-brain axis in rats subjected to experimental colitis induced by oral administration of dextran sulfate sodium (DSS). Daily oral administration of PEA-OXA (10 mg/kg daily o.s.) was able to decrease the body weight loss, macroscopic damage, colon length, histological alteration, and inflammation after DSS induction. Additionally, PEA-OXA administration enhanced neurotrophic growth factor release and decreased the astroglial and microglial activation induced by DSS. Moreover, PEA-OXA restored intestinal permeability and tight junctions (TJs) as well as reduced apoptosis in the colon and brain. In our work, we demonstrated, for the first time, the action of PEA-OXA on the gut-brain axis in a model of DSS-induced colitis and its implication on the "secondary" effects associated with colonic disturbance.

Hydrogen Sulfide Plays an Important Protective Role through Influencing Endoplasmic Reticulum Stress in Diseases

The endoplasmic reticulum is an important organelle responsible for protein synthesis, modification, folding, assembly and transport of new peptide chains. When the endoplasmic reticulum protein folding ability is impaired, the unfolded or misfolded proteins accumulate to lead to endoplasmic reticulum stress. Hydrogen sulfide is an important signaling molecule that regulates many physiological and pathological processes. Recent studies indicate that H₂S plays an important protective role in many diseases through influencing endoplasmic reticulum stress, but its mechanism is not fully understood. This article reviewed the progress about the effect of H₂S on endoplasmic reticulum stress and its mechanisms involved in diseases in recent years to provide theoretical basis for in-depth study.

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

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

Natural alkaloids from lotus plumule ameliorate lipopolysaccharide-induced depression-like behavior: integrating network pharmacology and molecular mechanism evaluation

Depression is a mental disorder that brings severe burdens to patients and their families. Neuroinflammation and neurotrophins are involved in depression. Lotus plumule is a nutritional food with medicinal values. In the present study, we tried to clarify the anti-depressive effect and molecular mechanism of lotus plumule. Network pharmacological analysis, behavior tests, qRT-PCR and western blotting were used. We found 7 potential active components and 91 targets from the TCMSP database. KEGG analysis suggested that lotus plumule significantly affected nitrogen metabolism, calcium signaling, and inflammatory mediator regulation signaling pathways. Consistent with those effects, total alkaloids of lotus plumule (TLA) and active alkaloids differently suppressed the nitric oxide (NO) production and pro-inflammatory mediators. TLA and higenamine significantly ameliorated LPS-induced depression-like behavior, increased BDNF levels, suppressed microglia activation, and inhibited the expression of ER stress-related proteins. Meanwhile, TLA and higenamine activated microglia autophagy by increasing the beclin-1 and LC3B-II expression. Additionally, in the presence of autophagy inhibitor 3-MA, TLA and higenamine did not reduce the LPS-induced NO production or pro-inflammatory mediators. Collectively, TLA and higenamine attenuated LPS-induced depression-like behavior by regulating BDNF-mediated ER stress and autophagy. Therefore, drinking tea of lotus plumule may provide a potential strategy for preventing depression.

Antidepressant-like Effects Induced by Chronic Blockade of the Purinergic 2X7 Receptor through Inhibition of Non-like Receptor Protein 1 Inflammasome in Chronic Unpredictable Mild Stress Model of Depression in Rats

Objective

Purinergic 2X7 receptor (P2X7R) activation is known to be involved in pathogenesis of depression. Our aims were to investigate P2X7R-activated inflammasome pathways in parallel with induction of depression and to test the antidepressant-like effects of the selective P2X7R antagonist Brilliant Blue G (BBG) in a rat model of chronic unpredictable mild stress (CUMS).

Methods

Male Wistar albino rats were divided into control, CUMS, CUMS+BBG25 (25 mg/kg/day) and CUMS+BBG50 (50 mg/kg/day) groups (n=10 for each group). Various stressors were applied to rats for 6 weeks to establish the CUMS model and daily BBG treatment was started at the end of 3rd week. Sucrose preference test and forced swim test (FST) were performed to assess antidepressant-like effects. Brain samples were obtained for real-time polymerase chain reaction and immunohistochemistry analysis.

Results

In FST, duration of immobility was reduced in the CUMS+BBG50 group. Also, BBG treatment significantly enhanced sucrose preference. While NLRP3 gene expression levels were unchanged in rats exposed to the CUMS protocol, expression levels of other inflammasome pathway factors NLRP1, caspase-1, ASC, NF-κB, IL-1β, IL-6 and P2X7R were increased. BBG treatment reduced expression levels of these factors. Likewise, Iba-1 and GFAP immunoreactivities were enhanced by the CUMS protocol and this action was reversed by BBG treatment.

Conclusion

Chronic administration of BBG in CUMS model results in antidepressant-like activity in a dose dependent manner. Molecular and histological results show that these effects might be at least partially related to the suppression of inflammasome-related neuroinflammatory responses and suggest involvement of NLRP1 in depression.

Neuroprotective Effects of dl-3-n-Butylphthalide against Doxorubicin-Induced Neuroinflammation, Oxidative Stress, Endoplasmic Reticulum Stress, and Behavioral Changes

Doxorubicin (DOX) is a broad-spectrum antitumor drug while its use is limited due to its neurobiological side effects associated with depression. We investigated the neuroprotective efficacy of dl-3-n-butylphthalide (dl-NBP) against DOX-induced anxiety- and depression-like behaviors in rats. dl-NBP was given (30 mg/kg) daily by gavage over three weeks starting seven days before DOX administration. Elevated plus maze (EPM) test, forced swimming test (FST), and sucrose preference test (SPT) were performed to assess anxiety- and depression-like behaviors. Our study showed that the supplementation of dl-NBP significantly mitigated the behavioral changes induced by DOX. To further explore the mechanism of neuroprotection induced by dl-NBP, several biomarkers including oxidative stress markers, endoplasmic reticulum (ER) stress markers, and neuroinflammatory cytokines in the hippocampus were quantified. The results showed that dl-NBP treatment alleviated DOX-induced neural apoptosis. Meanwhile, DOX-induced oxidative stress and ER stress in the hippocampus were significantly ameliorated in dl-NBP pretreatment group. Our study found that dl-NBP alleviated the upregulation of malondialdehyde (MDA), nitric oxide (NO), CHOP, glucose-regulated protein 78 kD (GRP-78), and caspase-12 and increased the levels of reduced glutathione (GSH) and activities of catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GPx) in the hippocampus of rats exposed to DOX. Additionally, the gene expression of interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-alpha (TNF-α) and protein levels of inducible nitric oxide synthase (iNOS) were significantly increased in DOX-treated group, whereas DOX-induced neuroinflammation was significantly attenuated in dl-NBP supplementation group. In conclusion, dl-NBP could alleviate DOX-induced anxiety- and depression-like behaviors via attenuating oxidative stress, ER stress, inflammatory reaction, and neural apoptosis, providing a basis as a therapeutic potential against DOX-induced neurotoxicity.