Long-term treatment with peony glycosides reverses chronic unpredictable mild stress-induced depressive-like behavior via increasing expression of neurotrophins in rat brain

Synergistic effects of citicoline and silymarin nanomicelles in restraint stress-exposed mice

This study evaluated the effects of citicoline and silymarin nanomicelles (SMnm) in repeated restraint stress (RRS).

METHOD

Mice were exposed to RRS for four consecutive days, 2 hrs. daily. On day 5 of the study, SMnm (25 and 50 mg/kg, i.p.) and citicoline (25 and 75 mg/kg), and a combination of them (25 mg/kg, i.p.) were initiated. On day 18, anxiety-like behavior, behavioral despair, and exploratory behavior were evaluated. The prefrontal cortex (PFC) and the hippocampus were dissected measuring brain-derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB), and tumor necrosis factor-alpha (TNF-α) through Western Blot and ELISA, respectively.

RESULTS

In RR-exposed mice, anxiety-like behavior in the elevated plus maze (EPM) was enhanced by reductions in open arm time (OAT%) P < 0.001, and open arm entry (OAE%) P < 0.001. In the forced swimming test (FST), the immobility increased P < 0.001 while the swimming and climbing reduced P < 0.001. In the open field test (OFT), general motor activity was raised P < 0.05. Further, body weights reduced P < 0.001, and tissue BDNF and pCREB expressions decreased P < 0.001 while TNF-α increased P < 0.001. Conversely, SMnm, citicoline and their combination could reduce anxiety-like behavior P < 0.001. The combination group reduced the depressive-like behaviors P < 0.001. Moreover, body weights were restored P < 0.001. Besides, BDNF and pCREB expressions increased while TNF-α reduced, P < 0.001.

CONCLUSION

The combination synergistically improved emotion-like behaviors, alleviating the inflammation and upregulating the hippocampal BDNF-mediated CREB signaling pathway.

Acute Administration of Lactate Exerts Antidepressant-like Effect Through cAMP-dependent Protein Synthesis

Lactate acts as an important metabolic substrate and signalling molecule modulating neural activities in the brain, and recent preclinical and clinical studies have revealed its antidepressant effect after acute or chronic peripheral administration. However, the neural mechanism underlying the antidepressant effect of lactate, in particular when lactate is acutely administered remains largely unknown. In the current study, we focused on forced swimming test (FST) to elucidate the neural mechanisms through which acute intracerebroventricular (ICV) infusion of lactate exerts antidepressant-like effect. A total of 238 male Sprague Dawley rats were used as experimental subjects. Results showed lactate produced antidepressant-like effect, as indicated by reduced immobility, in a dose- and time-dependent manner. Moreover, the antidepressant-like effect of lactate was dependent of new protein synthesis but not new gene expression, lactate's metabolic effect or hydroxy-carboxylic acid receptor 1 (HCAR1) activation. Furthermore, lactate rapidly promoted dephosphorylation of eukaryotic elongation factor 2 (eEF2) and increased brain-derived neurotrophic factor (BDNF) protein synthesis in the hippocampus in a cyclic adenosine monophosphate (cAMP)-dependent manner. Finally, inhibition of cAMP production blocked the antidepressant-like effect of lactate. These findings suggest that acute administration of lactate exerts antidepressant-like effect through cAMP-dependent protein synthesis.

Quantitative proteomics reveals the therapeutic effects of RFAP against depression via pathway regulation of long-term depression and potentiation

Ethnopharmacological relevance

RFAP is a compound extraction complex of four Traditional Chinese Medicine (TCM), including the dry bark of Paeonia lactiflora Pall. (Radix Paeoniae Alba), Gardenia jasminoides J. Ellis (Fructus Gardeniae), Albizia julibrissin Durazz. (Albizia julibrissin Durazz), and Paeonia × suffruticosa Andrews (Peony bark). Not only RFAP but also the individual ingredients have been commonly used for the treatment of depression in the clinic. However, the underlying mechanism of pharmacology is difficult to interpret since its holistic and multidrug nature.

Aim of the study

This study aimed to elucidate the potential antidepressant mechanism of RFAP in the treatment of chronic unpredictable mild stress (CUMS) rats' model via the quantitative proteomics approach.

Materials and methods

We established the CUMS rats' model and evaluated the efficacy of RFAP using multiple behavior assays, including the sugar preference test, open field test, and forced swimming test. Then label-free quantitative proteomics analyses were performed to evaluate the integrated changes of proteome profiling in control, CUMS, RFAP low dose, and RFAP high dose groups. Finally, we validated the critical changed proteins in the pathways of long-term depression and potentiation via RT-PCR and Western blotting assays.

Results

We successfully established the CUMS rats' model. The behavior assays indicated that the rats demonstrated a tendency to behavioral despair after four weeks. Label-free quantitative proteomics showed that 107 proteins were significantly upregulated and 163 proteins were downregulated in the CUMS group compared to the control group. These differentially expressed proteins were involved in long-term potentiation, long-term depression, nervous system development, neuronal synaptic structural constituent of ribosome, ATP metabolic process, learning or memory, and cellular lipid metabolic process. RFAP treatment partially restored the differentially expressed protein profile. The protective effect of RFAP on behavioral assessment were consistent with the results of proteomics.

Conclusions

The results indicated that RFAP exerted a synergistic effect on CUMS by regulating long-term inhibition and potentiation-related proteins.

Mechanisms of paeoniaceae action as an antidepressant

Paeoniflorin (PF) has been widely used for the treatment of depression in mice models, some Chinese herbal compound containing PF on treating depression, such as Xiaoyao San, Chaihu-Shugan-San, Danggui Shaoyao San etc. Many experiments are also verifying whether PF in these powders can be used as an effective component in the treatment of depression. Therefore, in this review the antidepressant effect of PF and its mechanism of action are outlined with particular focus on the following aspects: increasing the levels of monoamine neurotransmitters, inhibiting the HPA axis, promoting neuroprotection, enhancing neurogenesis in the hippocampus, and elevating levels of brain-derived neurotrophic factor (BDNF). This review may be helpful for the application of PF in the treatment of depression.

Antidepressant effects of the traditional Chinese herbal formula Xiao-Yao-San and its bioactive ingredients

BACKGROUND

Depression is one of the most debilitating and severe psychiatric disorders and a serious public health concern. Currently, many treatments are indicated for depression, including traditional Chinese medicinal formulae such as Xiao-Yao-San (XYS), which has effective antidepressant effects in clinical and animal studies.

PURPOSE

To summarize current evidence of XYS in terms of the preclinical and clinical studies and to identify the multi-level, multi-approach, and multi-target potential antidepressant mechanisms of XYS and active components of XYS by a comprehensive search of the related electronic databases.

METHODS

The following electronic databases were searched from the beginning to April 2022: PubMed, MEDLINE, Web of Science, Google Scholar, and China National Knowledge Infrastructure.

RESULTS

This review summarizes the antidepressant mechanisms of XYS and its active ingredients, which are reportedly correlated with monoamine neurotransmitter regulation, synaptic plasticity, and hypothalamic-pituitary-adrenal axis, etc. CONCLUSION: XYS plays a critical role in the treatment of depression by the regulation of several factors, including the monoaminergic systems, hypothalamic-pituitary-adrenal axis, synaptic plasticity, inflammation, brain-derived neurotrophic factor levels, brain-gut axis, and other pathways. However, more clinical and animal studies should be conducted to further investigate the antidepressant function of XYS and provide more evidence and recommendations for its clinical application. Our review provides an overview of XYS and guidance for future research direction.

How Oxidative Stress Induces Depression?

Depression increasingly affects a wide range and a large number of people worldwide, both physically and psychologically, which makes it a social problem requiring prompt attention and management. Accumulating clinical and animal studies have provided us with substantial insights of disease pathogenesis, especially central monoamine deficiency, which considerably promotes antidepressant research and clinical treatment. The first-line antidepressants mainly target the monoamine system, whose drawbacks mainly include slow action and treatment resistant. The novel antidepressant esketamine, targeting on central glutamatergic system, rapidly and robustly alleviates depression (including treatment-resistant depression), whose efficiency is shadowed by potential addictive and psychotomimetic side effects. Thus, exploring novel depression pathogenesis is necessary, for seeking more safe and effective therapeutic methods. Emerging evidence has revealed vital involvement of oxidative stress (OS) in depression, which inspires us to pursue antioxidant pathway for depression prevention and treatment. Fully uncovering the underlying mechanisms of OS-induced depression is the first step towards the avenue, thus we summarize and expound possible downstream pathways of OS, including mitochondrial impairment and related ATP deficiency, neuroinflammation, central glutamate excitotoxicity, brain-derived neurotrophic factor/tyrosine receptor kinase B dysfunction and serotonin deficiency, the microbiota-gut-brain axis disturbance and hypothalamic-pituitary-adrenocortical axis dysregulation. We also elaborate on the intricate interactions between the multiple aspects, and molecular mechanisms mediating the interplay. Through reviewing the related research progress in the field, we hope to depict an integral overview of how OS induces depression, in order to provide fresh ideas and novel targets for the final goal of efficient treatment of the disease.

Antidepressive-Like Effect of Aegle marmelos Leaf Extract in Chronic Unpredictable Mild Stress-Induced Depression-Like Behaviour in Rats

Background

Depression is a psychiatric disorder leading to anhedonia and lack of interest and motivation. Depressive symptoms are triggered by stressful life events, and patients with major depression are at significantly increased risk of attempting suicide. The crucial concern in depression treatment with antidepressant medications is that few weeks are required to show the therapeutic effect along with moderate side effects. The use of herbal medications is a new strategy for the treatment of depression which is often based on medicinal plants.Aegle marmelos (L.) Corr. (family: Rutaceae) is reported to have several actions on the central nervous system producing beneficial effects in anxiety, Alzheimer's disease, Parkinson's disease, epilepsy, and convulsion. Thus, the current investigation designed to assess the antidepressant activity of the standardized hydroethanolic extract of Aegle marmelos (EAM) leaves in male rats exposed to the chronic unpredictable mild stress (CUMS) paradigm.

Methods

Rats were divided in 5 groups. The control group was not subjected to experimental CUMS paradigm, while 4 other groups were subjected to CUMS paradigm to induce depression-like behaviour from day 1 to day 28. Following the CUMS paradigm, 4 groups were divided as CUMS disease control, CUMS+EAM (150 mg/kg, p.o.), CUMS+EAM (300 mg/kg, p.o.), and CUMS+imipramine (15 mg/kg, p.o.), and treatment was given for seven consecutive days to the respective groups (day 29 to day 35). Behavioural parameters such as open field test, forced swim test, sucrose feeding test, and tail suspension test on day 1, day 28, and day 35 were measured, and biochemical parameters such as plasma corticosterone level, serotonergic system (5-HT, 5-HIAA, and 5-HT/5-HIAA), mitochondrial function, and proinflammatory mediators (TNF-α, IL-1β, and IL-6) were estimated in hippocampus (HIP) and prefrontal cortex (PFC) regions of the brain on day 35, after the behavioural observations. On the other hand, phytochemical profile of Aegle marmelos was done.

Results

On day 35, EAM (300 mg/kg) significantly reduced the immobility time during the tail suspension test from 208.66 ± 4.72 s to 108.83 ± 4.81 s and forced swim test from 200.16 ± 4.12 s to 148.5 ± 4.58 s. It also enhanced the behavioural parameters in the open field test such as ambulation from 26.5 ± 2.14 to 56.5 ± 1.80, rearing from 8.33 ± 0.71 to 19 ± 0.57, time spent in centre from 9.16 ± 0.9 to 17.16 ± 0.79 s, total distance travelled from 2.36 ± 0.12 to 4.68 ± 0.10 m, and anhedonia in the sucrose feeding test from 109.33 ± 1.08 to 135.83 ± 3.91 mL. The stimulation of the HPA axis resulting elevated corticosterone level caused by CUMS was reduced by EAM (300 mg/kg) from 80.12 ± 2.020 to 48.25 ± 2.407 μg/dL. Furthermore, EAM (300 mg/kg) increase CUMS-induced changes in serotonin (5-HT) level in HIP and PFC from 3.132 ± 0.09586 to 4.518 ± 0.1812 and 4.308 ± 0.1593 to 5.262 ± 0.1014 ng/mg protein, respectively. EAM (300 mg/kg) significantly attenuated the CUMS-induced changes in proinflammatory cytokine production and mitochondrial function in HIP and PFC. One group used to determine the acute toxicity as per OECD-23 standard protocol which resulted that 300 mg/kg EAM has no significant acute toxicity. Total phenolic content and total flavonoid content of standardized hydroalcoholic extract of AM was found 95.024 ± 2.431 and 36.820 ± 3.41, respectively, and additional identification tests showed the presence of alkaloids, tannins, saponins, cardiac glycosides, flavonoids, and terpenoids.

Conclusion

On the basis of findings, EAM can be inferred as a potential antidepressant-like effect of this plan in preclinical research.

Noise Induced Depression-Like Behavior, Neuroinflammation and Synaptic Plasticity Impairments: The Protective Effects of Luteolin

Noise is a kind of sound that causes agitation and harms human health. Studies have shown that noise can lead to neuroinflammation, damage to synaptic plasticity and altered levels of neurotransmitters that may result in depression. The present study demonstrated that luteolin exerted antidepressant-like effects by improving neuroinflammation in a mouse model of noise-induced depression. Luteolin significantly alleviated noise-induced depression-like behavior. Notably, luteolin treatment not only remarkably ameliorated noise-induced inflammation in the hippocampus and prefrontal cortex, but also increased synapsin. Furthermore, luteolin treatment significantly increased the contents of serum 5-hydroxytryptamine and norepinephrine in noise-induced mice. In sum, luteolin exerts antidepressant effects indepression-like mice caused by noise, which can serve as a potential agent for the treatment of chronic noise-induced depression.

Alteration in the Expression of Genes Involved in Cerebral Glucose Metabolism as a Process of Adaptation to Stressful Conditions

Exposure to chronic stress leads to disturbances in glucose metabolism in the brain, and changes in the functioning of neurons coexisting with the development of depression. The detailed molecular mechanism and cerebral gluconeogenesis during depression are not conclusively established. The aim of the research was to assess the expression of selected genes involved in cerebral glucose metabolism of mice in the validated animal paradigm of chronic stress. To confirm the induction of depression-like disorders, we performed three behavioral tests: sucrose preference test (SPT), forced swim test (FST), and tail suspension test (TST). In order to study the cerebral glucose metabolism of the brain, mRNA levels of the following genes were determined in the prefrontal cortex of mice: Slc2a3, Gapdh, Ldha, Ldhb, and Pkfb3. It has been shown that exogenous, chronic administration of corticosterone developed a model of depression in behavioral tests. There were statistically significant changes in the mRNA level of the Slc2a3, Ldha, Gapdh, and Ldhb genes. The obtained results suggest changes in cerebral glucose metabolism as a process of adaptation to stressful conditions, and may provide the basis for introducing new therapeutic strategies for chronic stress-related depression.

5-HT Receptors and the Development of New Antidepressants

Serotonin modulates several physiological and cognitive pathways throughout the human body that affect emotions, memory, sleep, and thermal regulation. The complex nature of the serotonergic system and interactions with other neurochemical systems indicate that the development of depression may be mediated by various pathomechanisms, the common denominator of which is undoubtedly the disturbed transmission in central 5-HT synapses. Therefore, the deliberate pharmacological modulation of serotonergic transmission in the brain seems to be one of the most appropriate strategies for the search for new antidepressants. As discussed in this review, the serotonergic system offers great potential for the development of new antidepressant therapies based on the combination of SERT inhibition with different pharmacological activity towards the 5-HT system. The aim of this article is to summarize the search for new antidepressants in recent years, focusing primarily on the possibility of benefiting from interactions with various 5-HT receptors in the pharmacotherapy of depression.

The Role of Annexin A1 and Formyl Peptide Receptor 2/3 Signaling in Chronic Corticosterone-Induced Depression-Like behaviors and Impairment in Hippocampal-Dependent Memory

BACKGROUND

The activity of the Hypothalamic-Pituitary-Adrenal (HPA) axis is commonly dysregulated in stress-related psychiatric disorders. Annexin A1 (ANXA1), an endogenous ligand of Formyl Peptide Receptor (FPR) 2/3, is a member of the family of phospholipid- and calcium-binding proteins with a well-defined role in the delayed early inhibitory feedback of Glucocorticoids (GC) in the pituitary gland and implicated in the occurrence of behavioural disorders such as anxiety.

OBJECTIVE

The present study aimed to evaluate the potential role of ANXA1 and its main receptor, as a cellular mediator of behavioural disorders, in a model of Corticosterone (CORT)-induced depression and subsequently, the possible correlation between the depressive state and impairment of hippocampal memory.

METHODS

To induce the depression model, Wild-Type (WT), ANXA1 Knockout (KO), and FPR2/3 KO mice were exposed to oral administration of CORT for 28 days dissolved in drinking water. Following this, histological, biochemical and behavioural analyses were performed.

RESULTS

FPR2/3 KO and ANXA1 KO mice showed improvement in anxiety and depression-like behaviour compared with WT mice after CORT administration. In addition, FPR2/3 KO and ANXA1 KO mice showed a reduction in histological alterations and neuronal death in hippocampal sections. Moreover, CORT+ FPR2/3 KO and ANXA1 KO, exhibited a higher expression of Brain-Derived Neurotrophic Factor (BDNF), phospho-ERK, cAMP response element-binding protein (pCREB) and a decrease in Serotonin Transporter Expression (SERT) compared to WT(CORT+) mice.

CONCLUSION

In conclusion, the absence of the ANXA1 protein, even more than the absence of its main receptor (FPR 2/3), was fundamental to the inhibitory action of GC on the HPA axis; it also maintained the hippocampal homeostasis by preventing neuronal damage associated with depression.

Genus Paeonia: A comprehensive review on traditional uses, phytochemistry, pharmacological activities, clinical application, and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Paeonia, which comprises approximately 52 shrubs or herbaceous perennials around the world, is the only genus of the Paeoniaceae and is pervasively distributed in Asia, southern Europe, and North America. Many species of the genus Paeonia have been used for centuries in ethnomedical medical systems.

AIM OF THE REVIEW

The present study aims to summarize the traditional uses, clinical applications, and toxicology of the genus Paeonia, to critically evaluate the state-of-the-art phytochemical and pharmacological studies of this genus published between 2011 and 2020, and to suggest directions for further in-depth research on Paeonia medicinal resources.

MATERIALS AND METHODS

Popular and widely used databases such as PubMed, Scopus, Science Direct, and Google Scholar were searched using the various search strings; from these searches, a number of citations related to the traditional uses, phytochemistry, biological activities, clinical application, and toxicology of the genus Paeonia were retrieved.

RESULTS

The use of 21 species, 2 subspecies, and 7 varieties of the genus Paeonia as traditional herbal remedies has been reported, and many ethnomedicinal uses, such as the treatment of hematemesis, blood stasis, dysmenorrhea, amenorrhea, epilepsy, spasms, and gastritis, have been recorded. The roots and root bark are the most frequently reported parts of the plants used in medicinal applications. In phytochemical investigations, 451 compounds have been isolated from Paeonia plants to date, which contains monoterpenoid glucosides, flavonoids, tannins, stilbenes, triterpenoids and steroids, and phenols. Studies of their pharmacological activities have revealed the antioxidant, anti-inflammatory, antitumour, antibacterial, antiviral, cardiovascular protective, and neuroprotective properties of the genus Paeonia. In particular, some bioactive extracts and compounds (total glucosides of peony (TGP), paeonol, and paeoniflorin) have been used as therapeutic drugs or tested in clinical trials. In addition to the "incompatibility" of the combined use of "shaoyao" and Veratrum nigrum L. roots in traditional Chinese medicine theory, Paeonia was considered to have no obvious toxicity based on the available toxicological tests.

CONCLUSION

A large number of phytochemical and pharmacological reports have indicated that Paeonia is an important medicinal herb resource, and some of its traditional uses including the treatment of inflammation and cardiovascular diseases and its use as a neuroprotective agent, have been partially confirmed through modern pharmacological studies. Monoterpenoid glucosides are the main active constituents. Although many compounds have been isolated from Paeonia plants, the biological activities of only a few of these compounds (paeoniflorin, paeonol, and TGP) have been extensively investigated. Some paeoniflorin structural analogues and resveratrol oligomers have been preliminarily studied. With the exception of several species (P. suffruticosa, P. ostii, P. lactiflora, and P. emodi) that are commonly used in folk medicine, many medicinal species within the genus do not receive adequate attention. Conducting phytochemical and pharmacological experiments on these species can provide new clues that may lead to the discovery of medicinal resources. It is necessary to identify the effective phytoconstituents of crude extracts of Paeonia that displayed pharmacological activities by bioactivity-guided isolation. In addition, comprehensive plant quality control, and toxicology and pharmacokinetic studies are needed in the future studies.

Protocatechuic acid attenuates chronic unpredictable mild stress induced-behavioral and biochemical alterations in mice

Amelioration of oxidative stress via promoting the endogenous antioxidant system and enhancement of monoamines in brain were the important underlying antidepressant mechanism of protocatechuic acid (PCA). The aim of the present study is to explore the potential antidepressant mechanism(s) PCA in chronic unpredictable mild stress (CUMS) mice. Mice were subjected to CUMS protocol for 4 weeks, and administered with PCA (100 and 200 mg/kg) and fluoxetine (20 mg/kg) for 24 days (from day 8th to 31st). Behavioral (sucrose preference, immobility time, exploratory behavior), and biochemical alterations such as serum corticosterone, brain derived neurotrophic factor (BDNF), inflammatory cytokines, tumor necrosis factor- α (TNF-α), interleukin-6 (IL-6), and antioxidants parameters were investigated. Experimental findings revealed that CUMS subjected mice exhibited significant impairment in behavioral alterations, such as increased immobility time, impaired preference to the sucrose solution, BDNF levels and, serum corticosterone, cytokines, malondialdehyde (MDA) formation with impaired antioxidants in the hippocampus and cerebral cortex. Administration of PCA to CUMS mice attenuated the immobility time, serum corticosterone, cytokines TNF-α, and IL-6, MDA formation and improved sucrose preference, including restoration of BDNF level. Thus, the present findings demonstrated the antidepressant potential of PCA which is largely achieved probably through maintaining BDNF level, and by modulation of the oxidative stress response, cytokines systems, and antioxidant defense system in mice.

Melatonin ameliorated CUMS-induced depression-like behavior via restoring endoplasmic reticulum stress in rat hippocampus

Melatonin is a hormone synthesized and secreted by the pineal gland with the effect of regulating sleep rhythm. Circadian and sleep disturbances may be central for understanding the pathophysiology and treatment of depression. Recently, the melatonergic system has been implicated in the pathophysiology and treatment of depression. In this study, we observed the effects of melatonin on depression-like behavior induced by chronic unpredictable mild stress (CUMS) in rats, and its molecular mechanism was explored. Adult male Sprague-Dawley rats were exposed to CUMS for 4 weeks. Melatonin or saline was injected intraperitoneally. Behavioral changes of Sprague-Dawley rats were detected by the open field test, sugar preference test, elevated O maze test and forced swimming test. In addition, the plasma corticosterone level and the expression of endoplasmic reticulum stress-related protein in the hippocampus of rats were measured. Compared with the control group, the CUMS-exposed Sprague-Dawley rats showed depression-like behavior, which was significantly improved by melatonin treatment. Moreover, CUMS induced endoplasmic reticulum stress and JNK phosphorylation in the hippocampus. Melatonin treatment could significantly reverse the endoplasmic reticulum stress and JNK phosphorylation induced by CUMS. These results suggest that melatonin improves depression-like behavior by inhibiting endoplasmic reticulum stress induced by CUMS. This study demonstrates that melatonin can improve depression-like behavior induced by CUMS, which may be related to the inhibition of endoplasmic reticulum stress and JNK phosphorylation in rat hippocampus.

Total glucosides of herbaceous peony (Paeonia lactiflora Pall.) flower attenuate adenine- and ethambutol-induced hyperuricaemia in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Herbaceous peony (Paeonia lactiflora Pall.) flower has been used widely in dietotherapy in China and other countries. It has good ethnopharmacological value in the treatment of various metabolic diseases. However, the molecular mechanisms by which it lowers serum uric acid are unknown. The development of pharmaceutical resources is very important. Here, we sought to elucidate the mode of action of herbaceous peony in terms of reducing uric acid levels.

AIM OF THE STUDY

In the present research, the effects of the total glucosides of herbaceous peony flower were investigated in a rat hyperuricaemia model. Another aim of the study was to clarify the mechanism by which herbaceous peony flower (TGPF) lowers serum uric acid levels.

MATERIALS AND METHODS

A hyperuricaemic rat model was induced via intragastric administration of 100 mg/kg adenine and 250 mg/kg ethambutol hydrochloride (EH) for 23 d. Then TongFengShu 600 mg/kg, allopurinol 42 mg/kg, or TGPF (50 mg/kg, 100 mg/kg, or 200 mg/kg) was administered 1 h after the adenine and EH treatments.

RESULTS

TGPF improved weight loss and decreased serum UA, XOD, MCP-1, TNF-α, Cr, and BUN in the rats with hyperuricaemic nephropathy. TGPF downregulated renal URAT1 and GLUT9, upregulated renal OAT1, and ameliorated histopathological changes in the thymus, spleen, and kidney.

CONCLUSION

TGPF is promising as a therapeutic agent against hyperuricaemia. It regulates the uric acid transporters and diminished serum uric acid levels, and alleviates renal pathology associated with hyperuricaemia.

Bone marrow mesenchymal stem cells-derived exosomes improve injury of hippocampal neurons in rats with depression by upregulating microRNA-26a expression

OBJECTIVE

Bone marrow mesenchymal stem cells (BMSCs)-derived exosomes have been widely applied in disease therapies. However, the role of BMSCs-derived exosomes in depression remains obscure. This study aims to explore the mechanism of BMSCs-derived exosomal microRNA-26a (miR-26a) on hippocampal neuronal injury of depressed rats.

METHODS

BMSCs and their exosomes were obtained and identified. Rat models of depression were established by corticosterone injection, then injected with BMSCs-derived exosomes. The contents of superoxide dismutase (SOD), imalondialdehyde (MDA), lactate dehydrogenase (LDH), tumor necrosis factor α (TNF-α), and interleukin-1β (IL-1β) in rats' serum, hippocampal tissues and neurons were determined. The expression of miR-26a in hippocampal tissues and neurons was detected by RT-qPCR. The injury models of rat hippocampal neurons were established to figure out the role of BMSCs-derived exosomes and miR-26a in neuron apoptosis and proliferation.

RESULTS

In hippocampal tissues of depressed rats, miR-26a was lowly expressed, and BMSCs-derived exosomes upregulated miR-26a expression. BMSCs-derived exosomes restrained apoptosis in hippocampal tissues of depressed rats. BMSCs-derived exosomes and upregulated miR-26a elevated SOD level, lessened MDA, LDH, TNF-α and IL-1β levels, boosted hippocampal neuron proliferation and suppressed apoptosis in depressed rats.

CONCLUSION

Collectively, our study reveals that miR-26a is lowly expressed in depressed rats, and BMSCs-derived exosomes improve hippocampal neuron injury of rat with depression by upregulating miR-26a.

Antidepressant-like Effect of Citrus sinensis (L.) Osbeck Essential Oil and Its Main Component Limonene on Mice

The present study investigated the antidepressant-like effects of navel orange [Citrus sinensis (L.) Osbeck] essential oil (OEO) and its main components using the chronic unpredictable mild stress (CUMS) model mice and explored its possible mechanisms. The results indicated that OEO inhalation significantly ameliorated the depression-like behaviors of CUMS mice with decreased body weight, sucrose preference, curiosity, and mobility as well as shortened immobile time and attenuated dyslipidemia. Limonene was the most abundant compound in the sniffing OEO environment and mice brain after sniffing, and it was not metabolized immediately in the brain. In addition, limonene inhalation significantly restored CUMS-induced depressive behavior, hyperactivity of hypothalamic-pituitary-adrenal axis, and the decrease of monoamine neurotransmitter levels, with downregulation of brain-derived neurotrophic factor and its receptor expression in the hippocampus. Thus, the study indicates that the improvements in neuroendocrine, neurotrophic, and monoaminergic systems are related to the antidepressant effects of limonene.

Behavioural characterisation of chronic unpredictable stress based on ethologically relevant paradigms in rats

The chronic unpredictable stress (CUS) paradigm is extensively used in preclinical research. However, CUS exhibits translational inconsistencies, some of them resulting from the use of adult rodents, despite the evidence that vulnerability for many psychiatric disorders accumulates during early life. Here, we assessed the validity of the CUS model by including ethologically-relevant paradigms in juvenile rats. Thus, socially-isolated (SI) rats were submitted to CUS and compared with SI (experiment 1) and group-housed controls (experiment 1 and 2). We found that lower body-weight gain and hyperlocomotion, instead of sucrose consumption and preference, were the best parameters to monitor the progression of CUS, which also affected gene expression and neurotransmitter contents associated with that CUS-related phenotype. The behavioural characterisation after CUS placed locomotion and exploratory activity as the best stress predictors. By employing the exploratory factor analysis, we reduced each behavioural paradigm to few latent variables which clustered into two general domains that strongly predicted the CUS condition: (1) hyper-responsivity to novelty and mild threats, and (2) anxiety/depressive-like response. Altogether, the analyses of observable and latent variables indicate that early-life stress impairs the arousal-inhibition system leading to augmented and persistent responses towards novel, rewarding, and mildly-threatening stimuli, accompanied by lower body-weight gain.

Herbal medicine for psychiatric disorders: Psychopharmacology and neuroscience-based nomenclature

Objectives: Herbs are frequently and concurrently used with prescribed drugs by patients worldwide. While clinical trials have found some herbs to be as useful as standard psychiatric drugs, most clinicians are unaware of their pharmacological mechanisms.Methods: We searched English language and other language literature with English abstracts listed in PubMed website, supplemented by additional through Google Scholar's free academic paper abstract website for publications on herbs, focussing on their clinical use in mental disorders, their neurobiology and their pharmacology.Results: A major reason for herbs remaining outside of mainstream psychiatry is that the terminology and concepts in herbal medicine are not familiar to psychiatrists in general. Many publications regarding the use of herbal medicine for psychiatric disorders are deficient in details regarding diagnosis, criteria for response and the neurobiology details compared with publications on standard psychotropic drugs. Nomenclature for herbal medicine is usually confusing and is not conducive to an easy understanding of their mode of action in psychiatric disorders.Conclusions: The recent neuroscience-based nomenclature (NbN) for psychotropics methodology would be a logical application to herbal medicine in facilitating a better understanding of the use of herbal medicine in psychiatry.

Selecting an Appropriate Animal Model of Depression

Depression has become one of the most severe psychiatric disorders and endangers the health of living beings all over the world. In order to explore the molecular mechanism that underlies depression, different kinds of animal models of depression are used in laboratory experiments. However, a credible and reasonable animal model that is capable of imitating the pathologic mechanism of depression in mankind has yet to be found, resulting in a barrier to further investigation of depression. Nevertheless, it is possible to explain the pathologic mechanism of depression to a great extent by a rational modeling method and behavioral testing. This review aims to provide a reference for researchers by comparing the advantages and disadvantages of some common animal depression models.

Exposure to jet lag aggravates depression-like behaviors and age-related phenotypes in rats subject to chronic corticosterone

Our previous finding demonstrated that chronic corticosterone (CORT) may be involved in mediating the pathophysiology of premature aging in rats. Frequent jet lag increases the risk for many diseases, including obesity and type 2 diabetes, and is associated with the aging processes. However, the effect of jet lag on CORT-induced depression and its association with aging phenotypes remain unclear. In this study, the rats were exposed to both CORT and jet lag treatment, and the differences were analyzed and compared to rats with single CORT treatment. Our results showed that jet lag treatment aggravated CORT-induced depression-like behavior evidenced by sucrose intake test, forced swimming test, and open field test. Additionally, this treatment aggravated the shortening of telomeres, which possibly resulted in decreased telomerase activity, and downregulated the expression of telomere-binding factor 2 (TRF2) and telomerase reverse transcriptase compared to that in CORT rats, as revealed by quantitative real-time-polymerase chain reaction and western blot analysis, respectively. The shortening of telomeres may have been caused by increased oxidative stress, which was associated with the inhibition of sirtuin 3. Exposure to jet lag also aggravated the degeneration of mitochondrial functions, as shown by the decreases in the mRNA expression of COX1, ND1, and Tfam. Our findings provide physiological evidence that jet lag exposure may worsen stress-induced depression and age-related abnormalities.

Protocatechuic acid attenuate depressive-like behavior in olfactory bulbectomized rat model: behavioral and neurobiochemical investigations

The main objective of the present study is to investigate potential effects of PCA in OBX induced depressive-like behavior in rat model. PCA was administered at a dose of 100 mg/kg and 200 mg/kg, by per oral in OBX and sham operated rats. Behavioral (ambulatory and rearing activity and immobility time), neurochemical [serotonin (5-HT), dopamine (DA), norepinephrine (NE) and brain derived neurotrophic factor (BDNF) expression], biochemical (MDA formation, IL-6, TNF-α and antioxidants) changes in hippocampus and cerebral cortex along with serum corticosterone were investigated. Experimental findings reveals that OBX subjected rats showed alteration in behaviors like, increase in immobility time, ambulatory and rearing behaviors significantly, reduced BDNF level, 5-HT, DA,NE and antioxidant parameters along with increased serum corticosterone, MDA formation, IL-6, and TNF-α in hippocampus and cerebral cortex compared to sham operated rats. Administration of PCA significantly attenuated behavioral and neurobiochemical alterations, thus, its antidepressant-like activity is largely mediated through modulation of neurotransmitter, endocrine and immunologic systems, mainly by improvements of BDNF, 5-HT, DA, NE, reduced MDA, IL-6, and TNF-α in hippocampus and cerebral cortex.

Silymarin and silymarin nanoparticles guard against chronic unpredictable mild stress induced depressive-like behavior in mice: involvement of neurogenesis and NLRP3 inflammasome

BACKGROUND

The neuropathology of depression is quite complex. Thus, treatment failures are frequent with current antidepressants, raising the need for more effective ones.

AIMS

This study aimed to investigate the influence of silymarin on depressive-like behavior induced by chronic unpredictable mild stress (CUMS) and explore the underlying mechanisms.

METHODS

Silymarin was formulated as nanostructured lipid carriers (a lipid-based type of nanoparticle with the advantages of physical stability, good release profile, and targeted delivery). Mice were subjected to CUMS paradigm during 14 days. During this period, mice received silymarin (200 mg/kg, p.o.) per se or in its nanoparticle form or fluoxetine (10 mg/kg, p.o.). On the 15th day behavioral and biochemical parameters were analyzed.

RESULTS

Oral administration of silymarin (200 mg/kg), particularly in its nanoparticulate form, exerted an antidepressant-like effect, comparable with fluoxetine in mice, as demonstrated in the behavioral despair tests. Silymarin also reversed prefrontal cortical and hippocampal CUMS-induced oxidative stress and neuroinflammation. Furthermore, silymarin augmented neurotransmitter levels, enhanced neurogenesis and inhibited nod-like receptor protein 3 inflammasome activation. Silymarin nanoparticles were superior to silymarin in certain parameters probably due to significantly higher brain silybinin (the major active component of silymarin) concentration by 12.46 fold in the group administered silymarin nanoparticles compared with the mice which were administered silymarin per se.

CONCLUSIONS

The antidepressant-like effect of silymarin can be attributed to its antioxidant and anti-inflammatory effects as well as increased neurogenesis in the prefrontal cortex and hippocampus, which delineates silymarin, especially in nanoparticle form, as a promising strategy for treatment of depression.

Direct and indirect evidences of BDNF and NGF as key modulators in depression: role of antidepressants treatment

PURPOSE

Depression is one of the most prevalent, recurrent and life-threatening mental illnesses. However, the precise mechanism underlying the disorder is not yet clearly understood. It is therefore, essential to identify the novel biomarkers which may help in the development of effective treatment.

METHODS

In this milieu, the profile of the brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were considered as biomarkers in the light of pathophysiology of depression and its treatment.

RESULTS

Previously, we have reported that BDNF level in the postmortem brain of suicide victims was significantly lower than those of normal controls. We also found decreased BDNF levels in the specific brain regions of the learned helplessness model of depression in rat, and was found to increase normal level following chronic fluoxetine hydrochloride treatment. NGF is another important member of neurotrophin, which is dysregulated in the pathophysiology of depression in some models of peripheral nerve damage and stress. The results shown evidences of the effect of antidepressants on modulating depression via the NGF in preclinical and clinical models of depression, but conflicted, therefore make it currently difficult to affirm the therapeutic role of antidepressants.

CONCLUSIONS

Here, we review some of the preclinical and clinical studies aimed at disclosing the role of BDNF and NGF mediated pathophysiological mechanisms of depression and the new therapeutic approaches targeting those key molecules. In addition, an important link between BDNF, NGF and depression has been discussed in the light of current existing knowledge.

Recent Advances in Drug Delivery System for Bioactive Glycosides from Traditional Chinese Medicine

Traditional Chinese Medicine (TCM) has been used in China for thousands of years for the prevention and treatment of various diseases. The materials that exert a therapeutic effect are called the active ingredients. The bioactive glycosides are important active ingredients from TCM that can make significant contributions to treating diseases. Because of the possibilities of various clinical applications, the properties and administration of these bioactive glycosides deserve further investigation. Their promising treatment effects, however, are hindered by their poor solubility, poor stability and rapid elimination. Therefore, it is necessary that we improve the therapeutic efficacy of bioactive glycosides by overcoming these problems. Meanwhile, some practical design strategies and novel drug delivery vehicles based on drug delivery systems provide favorable support in clinical practice for these active ingredients. This review summarizes diverse pharmacological activities of bioactive glycosides and focuses on recent advances in delivery system for these active constitutes; in particular, some glycol glycosides can effectively cure intractable diseases through targeted drug delivery. This review elucidates some design strategies for drug delivery system that are mainly based on two methods (avoiding physical barriers by changing dosage forms and enhancing the ability to bind to receptors or proteins after administration) and indicate the current challenges during the combination of delivery vehicles and these glycosides in hopes of promoting the process of receiving ideal therapeutic efficacy of them in future studies.

Serotonin receptors in depression and anxiety: Insights from animal studies

Serotonin regulates many physiological processes including sleep, appetite, and mood. Thus, serotonergic system is an important target in the treatment of psychiatric disorders, such as major depression and anxiety. This natural neurotransmitter interacts with 7 families of its receptors (5-HT1-7), which cause a variety of pharmacological effects. Using genetically modified animals and selective or preferential agonists and antagonist, numerous studies demonstrated the involvement of almost all serotonin receptor subtypes in antidepressant- or anxiolytic-like effects. In this review, based on animal studies, we discuss the possible involvement of serotonin receptor subtypes in depression and anxiety.

Changes in synaptic plasticity are associated with electroconvulsive shock-induced learning and memory impairment in rats with depression-like behavior

BACKGROUND

Accompanied with the effective antidepressant effect, electroconvulsive shock (ECS) can induce cognitive impairment, but the mechanism is unclear. Synaptic plasticity is the fundamental mechanism of learning and memory. This study aimed to investigate the effect of ECS on synaptic plasticity changes in rats with depression-like behavior.

METHODS

Chronic unpredictable mild stress procedure was conducted to establish a model of depression-like behavior. Rats were randomly divided into the following three groups: control group with healthy rats (group C), rats with depression-like behavior (group D), and rats with depression-like behavior undergoing ECS (group DE). Depression-like behavior and spatial learning and memory function were assessed by sucrose preference test and Morris water test, respectively. Synaptic plasticity changes in long-term potentiation (LTP), long-term depression (LTD), depotentiation, and post-tetanic potentiation (PTP) were tested by electrophysiological experiment.

RESULTS

ECS could exert antidepressant effect and also induced spatial learning and memory impairment in rats with depression-like behavior. And, data on electrophysiological experiment showed that ECS induced lower magnitude of LTP, higher magnitude of LTD, higher magnitude of depotentiation, and lower magnitude of PTP.

CONCLUSION

ECS-induced learning and memory impairment may be attributed to postsynaptic mechanism of LTP impairment, LTD and depotentiation enhancement, and presynaptic mechanism of PTP impairment.

Anesthetics alleviate learning and memory impairment induced by electroconvulsive shock by regulation of NMDA receptor-mediated metaplasticity in depressive rats

Along with its outstanding antidepressant effect, electroconvulsive shock (ECS) can induce learning and memory impairment. Propofol and ketamine have shown to be useful in alleviating the learning and memory impairment. Nevertheless, the mechanism still remains unclear. This study investigated the role of NMDA receptor (NMDAR)-mediated metaplasticity in the learning and memory impairment induced by ECS, as well as the neuroprotective effect of propofol and ketamine in depressive rats. Rats received ECS or ECS under anesthetics after chronic unpredictable mild stress procedure. Long-term potentiation (LTP) was tested by extracellular recording. LTD/LTP threshold was assessed by stimulation of different frequencies. Additionally, NMDAR-mediated field excitatory postsynaptic potential (fEPSP) and NMDAR input/output relationship were detected under hippocampal slice perfusion. Results showed that propofol or low-dose ketamine could partially alleviate ECS-induced LTP impairment, while propofol combined with low-dose ketamine almost reversed the LTP impairment. LTP under ECS was increased by stronger stimulation. ECS could up-regulated LTD/LTP threshold, while propofol or ketamine could down-regulate it. Moreover, ECS activated NMDAR, while propofol and ketamine could inhibit the activation of NMDAR. NMDAR input/output relationship decrease was induced by preconditioning (an analog of ECS in hippocampal slice), however, NMDAR input/output relationship increased by propofol or ketamine. In conclusion, ECS-induced cognitive impairment is caused by NMDAR-mediated metaplasticity via up-regulation of LTD/LTP threshold. Propofol or ketamine alleviates the cognitive impairment, possibly by down-regulating the threshold via inhibition of NMDAR activation induced by ECS.

Single Administration of HBK-15-a Triple 5-HT1A, 5-HT7, and 5-HT3 Receptor Antagonist-Reverses Depressive-Like Behaviors in Mouse Model of Depression Induced by Corticosterone

Studies suggest that the blockade of 5-HT1A, 5-HT7, and 5-HT3 receptor may increase the speed of antidepressant response. 1-[(2,6-Dimethylphenoxy)ethoxyethyl]-4-(2-methoxyphenyl)piperazine hydrochloride (HBK-14) and 1-[(2-chloro-6-methylphenoxy)ethoxyethyl]-4-(2-methoxyphenyl)piperazine hydrochloride (HBK-15), dual 5-HT1A and 5-HT7 antagonists, showed significant antidepressant- and anxiolytic-like properties in our previous tests in rodents. In this study, we aimed to investigate their antidepressant potential using mouse model of corticosterone-induced depression. We chose sucrose preference test, forced swim test, and elevated plus maze to determine anhedonic-, antidepressant-, and anxiolytic-like activities. We also evaluated the influence of the active compound on brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) levels in the hippocampus. Moreover, for both compounds, we performed biofunctional (5-HT3 receptor) and pharmacokinetic studies. We found that HBK-14 and HBK-15 were potent 5-HT3 receptor antagonists. HBK-14 (2.5 mg/kg) and HBK-15 (1.25 mg/kg) after intravenous (i.v.) and intraperitoneal (i.p.) administration permeated the blood-brain barrier with brain/plasma ratio lower than 1. The bioavailability of studied compounds after i.p. administration was 15% for HBK-14 and 54% for HBK-15. Chronic administration of HBK-15 (1.25 mg/kg) and fluoxetine (10 mg/kg) protected corticosterone-treated mice from anhedonic-, depressive-, and anxiety-like behaviors, as well as decreases in BDNF and NGF levels in the hippocampus. HBK-14 (2.5 mg/kg) counteracted anxiety-like behaviors in corticosterone-treated mice. Single administration of HBK-15 (1.25 mg/kg) and ketamine (1 mg/kg) reversed depression-like behavior and regulated decreased BDNF level in the hippocampus in corticosterone-treated mice. Our results suggest that simultaneous blockade of serotonergic 5-HT1A, 5-HT7, and 5-HT3 receptors might accelerate antidepressant response.

Therapeutic potential of silymarin in chronic unpredictable mild stress induced depressive-like behavior in mice

Silymarin, a plant-derived polyphenolic flavonoid of Silybum marianum, elicited significant antidepressant-like activity in an acute restraint stress model of depression. It improved monoamines, mainly 5-hydroxytryptamine (5-HT) levels in the cortex, dopamine (DA) and norepinephrine (NE) in the cerebellum in mice. The present study was undertaken to explore the antidepressant potential of silymarin in chronic unpredictable mild stress (CUMS) induced depressive-like behavior in mice, and to find out its probable mechanism(s) of action, mainly neurogenesis, neuroinflammation, and/or oxidative stress. The mice were subjected to CUMS for 28 days (4 weeks) and administered with silymarin (100 mg/kg and 200 mg/kg), or fluoxetine or vehicle from days 8 to 28 (3 weeks simultaneously). Animals were evaluated for behavioral changes, such as anhedonia by sucrose preference test, behavioral despair by forced swim test, and exploratory behaviors by an open field test. In addition, neurobiochemical alterations, mainly monoamines, 5-HT, NE, DA, neurotrophic factor BDNF, and cytokines, IL-6, TNF-α, oxidant-antioxidant parameters by determining the malondialdehyde formation (an index of lipid peroxidation process), superoxide dismutase (SOD) and catalase (CAT) activity in hippocampus and cerebral cortex along with serum corticosterone were investigated. Our findings reveal that mice subjected to CUMS exhibited lower sucrose preference, increase immobility time without affecting general locomotion of the animals, and reduce BDNF, 5-HT, NE, and DA level, increased serum corticosterone, IL-6 and TNF-α along with an oxidant-antioxidant imbalance in the hippocampus and cerebral cortex. Silymarin significantly reversed the CUMS-induced changes in the hippocampus and cerebral cortex in mice. Thus, the possible mechanism involved in the antidepressant-like activity of silymarin is correlated to the alleviation of monoaminergic, neurogenesis (enhancing 5-HT, NE, and BDNF levels), and attenuation of inflammatory cytokines system and oxidative stress by modulation of corticosterone response, restoration of antioxidant defense system in cerebral cortex and hippocampus.

Paeoniflorin Ameliorates Chronic Stress-Induced Depression-Like Behaviors and Neuronal Damages in Rats via Activation of the ERK-CREB Pathway

Neuronal damage is related to the onset and treatment of depressive disorders. Antidepressant-like effects have been elicited by paeoniflorin on animal models. The aim of this study is to demonstrate whether the neuroprotective effect of paeoniflorin on rats suffered from chronic unpredictable mild stress (CUMS) was regulated by the ERK-CREB signaling pathway. Results showed that paeoniflorin not only ameliorated depressive-like behavior with low locomotor activity and prolonged immobility duration in our forced swimming test but also reduced sucrose consumption. Paeoniflorin treatment decreased the degree of neuronal damage in the hippocampus of the model rats. Conversely, it markedly increased the mRNA levels of ERK1, ERK2, and CREB and the levels of ERK, p-ERK, CREB, and p-CREB protein expression in the hippocampus. Blockade of the ERK-CREB axis with the ERK-specific inhibitor U0126 repressed the neuroprotective and antidepressant-like effects of paeoniflorin on rats in the setting of chronic-mild-stress and abolished the recoveries of p-ERK mediated by paeoniflorin treatment. Thus, paeoniflorin possibly exerted a neuroprotective effect modulated by the ERK-CREB signaling pathway on CUMS-induced hippocampal damage in rats.

Neuroplasticity-related mechanisms underlying the antidepressant-like effects of traditional herbal medicines

Traditional herbal medicine can offer efficacious and safe alternative pharmacotherapies for depression. The ability of an herbal medicine to produce neuroadaptive processes, that enhance neuroplasticity and cellular resilience in response to chronic stress, may point to its antidepressant potential. We suggest that among many investigated herbal medicines, those that can enhance neuroplasticity may have stronger therapeutic potential. The current article presents a summary of traditional herbal medicines, which are thought to exert antidepressant-like effects in chronic stress models via neuroplasticity enhancement. Brain-derived neurotrophic factor (BDNF) is a biomarker for neuroplasticity-related mechanisms compromised in depression and recovered by conventional antidepressants, including synaptic plasticity, cell survival, neurogenesis and spine formation. We therefore presumed that if an herbal medicine up-regulates BDNF in the hippocampus and/or prefrontal cortex (PFC), its antidepressant-like effect is mediated, at least partially, via neuroplasticity-related mechanisms. Literature search was performed using the general terms depression, stress, neuroplasticity and herbal medicines. Screening of retrieved preclinical studies revealed 30 traditional herbal medicines: 8 single herbs, 15 bioactive constituents, and 7 herbal formulas. The antidepressant-like effects of these medicines were associated with reversal of chronic stress-induced impairment in neuroplasticity, most notably by BDNF up-regulation, activation of BDNF downstream signaling pathways and increase in neurogenesis in the hippocampus and/or PFC/frontal cortex. In light of the ability of these medicines to enhance neuroplasticity, we suggest that they may be suitable candidates for clinical investigation in depressed individuals. Once their efficacy, tolerability and safety will be substantiated, they may serve as natural alternatives to conventional antidepressants.

Microglia: An Interface between the Loss of Neuroplasticity and Depression

Depression has been widely accepted as a major psychiatric disease affecting nearly 350 million people worldwide. Research focus is now shifting from studying the extrinsic and social factors of depression to the underlying molecular causes. Microglial activity is shown to be associated with pathological conditions, such as psychological stress, pathological aging, and chronic infections. These are primary immune effector cells in the CNS and regulate the extensive dialogue between the nervous and the immune systems in response to different immunological, physiological, and psychological stressors. Studies have suggested that during stress and pathologies, microglia play a significant role in the disruption of neuroplasticity and have detrimental effects on neuroprotection causing neuroinflammation and exacerbation of depression. After a systematic search of literature databases, relevant articles on the microglial regulation of bidirectional neuroimmune pathways affecting neuroplasticity and leading to depression were reviewed. Although, several hypotheses have been proposed for the microglial role in the onset of depression, it is clear that all molecular pathways to depression are linked through microglia-associated neuroinflammation and hippocampal degeneration. Molecular factors such as an excess of glucocorticoids and changes in gene expression of neurotrophic factors, as well as neuro active substances secreted by gut microbiota have also been shown to affect microglial morphology and phenotype resulting in depression. This review aims to critically analyze the various molecular pathways associated with the microglial role in depression.

Desipramine rescues age-related phenotypes in depression-like rats induced by chronic mild stress

AIMS

Our previous finding demonstrates that major depressive disorder can mediate accelerated aging in rats. Desipramine is a typical tricyclic antidepressant, and can provide neuroprotection and counteract depression-like behaviors. However, whether desipramine can rescue age-related phenotypes in depressed individuals is not understood. In the present study, we investigated the physiological function of desipramine on rescuing the age-related phenotypes in these animals.

MAIN METHODS

The rats were induced by chronic mild stress paradigm, and the depression-like behaviors of rats were detected by sucrose intake test, open field test (OFT) and forced swimming test (FST). Then the depressed rats were treated by desipramine.

KEY FINDINGS

Desipramine administration was effective in counteracting depression-like behaviors by increasing the sucrose solution intake, reducing the immobility time in the FST, and increasing total distance travelled and numbers of grid line crossed in the OFT. Moreover, desipramine treatment was able to reduce the oxidative damage to rat liver, and to increase the expression of telomerase reverse transcriptase (TERT), leading to correspondingly restored telomerase activity.

SIGNIFICANCE

Our findings identify that one function of desipramine may partly be to rescue age-related phenotypes in depressed individuals induced by chronic stress.

Silymarin ameliorates experimentally induced depressive like behavior in rats: Involvement of hippocampal BDNF signaling, inflammatory cytokines and oxidative stress response

Silymarin is a polyphenolic flavonoid of Silybum marianum, exhibited neuroprotection and antidepressant like activity in acute restraint stressed mice. The main objective of the present study is to investigate possible antidepressant like activity of silymarin in experimentally induced depressive behavior in rats. The depressive behaviors were induced in rats by olfactory bulbectomized (OBX) technique. Wistar rats were administered with silymarin at a dose of 100mg/kg and 200mg/kg, by per oral in OBX and sham operated rats. Behavioral (ambulatory and rearing activity and immobility time), neurochemical [serotonin (5-HT), dopamine (DA), norepinephrine (NE) and brain derived neurotrophic factor (BDNF) level], biochemical (MDA formation, IL-6, TNF-α and antioxidants) changes in hippocampus and cerebral cortex along with serum corticosterone were investigated. Rats subjected to OBX elicited significant increase in immobility time, ambulatory and rearing behaviors, reduced BDNF level, 5-HT, DA, NE and antioxidant parameters along with increased serum corticosterone, MDA formation, IL-6, and TNF-α in hippocampus and cerebral cortex compared to sham operated rats. Administration of with silymarin significantly attenuated immobility time, ambulatory and rearing behaviors, serum corticosterone and improved BDNF expression, 5-HT, DA, NE and antioxidant paradigms in cerebral cortex as well as hippocampus. In addition, silymarin attenuated IL-6, and TNF-α significantly in hippocampus and cerebral cortex in OBX rats. Thus, silymarin exhibits anti-depressant-like activity in OBX rats due to alterations in several neurotransmitters, endocrine and immunologic systems, including BDNF, 5-HT, DA, NE, MDA formation, IL-6, and TNF-α in hippocampus and cerebral cortex as well as serum corticosterone.

Propofol ameliorates electroconvulsive shock-induced learning and memory impairment by regulation of synaptic metaplasticity via autophosphorylation of CaMKIIa at Thr 305 in stressed rats

Electroconvulsive therapy (ECT) is an effective treatment for depression, but it can induce learning and memory impairment. Our previous study found propofol (γ-aminobutyric acid (GABA) receptor agonist) could ameliorate electroconvulsive shock (ECS, an analog of ECT to animals)-induced cognitive impairment, however, the underlying molecular mechanisms remain unclear. This study aimed to investigate the effects of propofol on metaplasticity and autophosphorylation of CaMKIIa in stressed rats receiving ECS. Depressive-like behavior and learning and memory function were assessed by sucrose preference test and Morris water test respectively. LTP were tested by electrophysiological experiment, the expression of CaMKIIa, p-T305-CaMKII in hippocampus and CaMKIIα in hippocampal PSD fraction were evaluated by western blot. Results suggested ECS raised the baseline fEPSP and impaired the subsequent LTP, increased the expression of p-T305-CaMKII and decreased the expression of CaMKIIα in hippocampal PSD fraction, leading to cognitive dysfunction in stressed rats. Propofol could down-regulate the baseline fEPSP and reversed the impairment of LTP partly, decreased the expression of p-T305-CaMKII and increased the expression of CaMKIIα in hippocampal PSD fraction and alleviated ECS-induced learning and memory impairment. In conclusion, propofol ameliorates ECS-induced learning and memory impairment, possibly by regulation of synaptic metaplasticity via p-T305-CaMKII.

Metabolic profiling of Shu-Yu capsule in rat serum based on metabolic fingerprinting analysis using HPLC-ESI-MSn

The Chinese herbal formula, Shu-Yu capsule (SYC), has been successfully used to treat depression-like disorders in clinical settings. To rapidly identify the chemical constituents of SYC and its metabolites in rat serum, a simple and sensitive liquid chromatography-tandem mass spectrometry method was established in the present study. By comparing the retention times, MS and MSn spectra data in the literature and reference standards, a total of 73 compounds were identified from SYC. In rat serum, 62 components, including 13 prototype compounds and 49 metabolites were identified. Of these components, 14 metabolites were confirmed as novel metabolites of SYC. The results of the present study indicated that certain flavonoid glycosides and monoterpene glycosides were absorbed directly. Glucuronidation and sulfation were identified as the predominant metabolic pathways of the components in SYC. In addition, certain phase I reactions, including hydrolysis, demethylation and hydroxylation occurred in the rats. These results provide scientific evidence, which support further investigations of the pharmacology and mechanism of SYC.

Antidepressant-like effects of sodium butyrate and its possible mechanisms of action in mice exposed to chronic unpredictable mild stress

Sodium butyrate (NaB) has exhibited neuroprotective activity. This study aimed to explore that NaB exerts beneficial effects on chronic unpredictable mild stress (CUMS)-induced depression-like behaviors and its possible mechanisms. The behavioral tests including sucrose preference test (SPT), open field test (OFT), tail suspension test (TST) and forced swimming test (FST) were to evaluate the antidepressant effects of NaB. Then changes of Nissl's body in the hippocampus, brain serotonin (5-HT) concentration, brain-derived neurotrophic factor (BDNF) and tight junctions (TJs) proteins level were assessed to explore the antidepressant mechanisms. Our results showed that CUMS caused significant depression-like behaviors, neuropathological changes, and decreased brain 5-HT concentration, TJs protein levels and BDNF expression in the hippocampus. However, NaB treatment significantly ameliorated behavioral deficits of the CUMS-induced mice, increased 5-HT concentration, increased BDNF expression, and up-regulated Occludin and zonula occludens-1(ZO-1) protein levels in the hippocampus, which demonstrated that NaB could partially restore CUMS-induced blood-brain barrier (BBB) impairments. Besides, the pathologic changes were alleviated. In conclusion, these results demonstrated that NaB significantly improved depression-like behaviors in CUMS-induced mice and its antidepressant actions might be related with, at least in part, the increasing brain 5-HT concentration and BDNF expression and restoring BBB impairments.