Protective effects of a novel 5-HT3 receptor antagonist, N-n-butyl-3-methoxy quinoxaline-2-carboxamide (6o) against chronic unpredictable mild stress-induced behavioral changes and biochemical alterations

Targeting inflammation: a potential approach for the treatment of depression

Major depressive disorder (MDD) or Depression is one of the serious neuropsychiatric disorders affecting over 280 million people worldwide. It is 4th important cause of disability, poor quality of life, and economic burden. Women are more affected with the depression as compared to men and severe depression can lead to suicide. Most of the antidepressants predominantly work through the modulation on the availability of monoaminergic neurotransmitter (NTs) levels in the synapse. Current antidepressants have limited efficacy and tolerability. Moreover, treatment resistant depression (TRD) is one of the main causes for failure of standard marketed antidepressants. Recently, inflammation has also emerged as a crucial factor in pathological progression of depression. Proinflammatory cytokine levels are increased in depressive patients. Antidepressant treatment may attenuate depression via modulation of pathways of inflammation, transformation in structure of brain, and synaptic plasticity. Hence, targeting inflammation may be emerged as an effective approach for the treatment of depression. The present review article will focus on the preclinical and clinical studies that targets inflammation. In addition, it also concentrates on the therapeutic approaches' that targets depression via influence on the inflammatory signaling pathways. Graphical abstract demonstrate the role of various factors in the progression and neuroinflammation, oxidative stress. It also exhibits the association of neuroinflammation, oxidative stress with depression.

Antidepressant functions of Jie Yu Chu Fan capsule in promoting hippocampal nerve cell neurogenesis in a mouse model of chronic unpredictable mild stress

Background

Depression is a major public health challenge that imposes a great societal burden. Depression has been attributed to the decreased level of neurotransmitters and brain-derived neurotrophic factor (BDNF) levels. Chinese herbal medicine Jie Yu Chu Fan (JYCF) capsule has been shown to be effective in the management of depression. However, the mechanism has yet to be determined. This study aimed to explore the activity of JYCF against depression by establishing a mouse model of chronic unpredictable mild stress (CUMS) with fluoxetine as the positive control drug.

Methods

The open field test, sucrose preference test, forced swim test, and tail suspension test were carried out to observe the behavioral changes of animals. The levels of norepinephrine (NE), dopamine (DA), and 5-hydroxytryptamine, as well as their respective metabolic products 5-hydroxyindoleacetic acid, homovanillic acid (HVA), and 3,4-dihydroxyphenylacetic acid in the mouse hippocampi were quantified by high-performance liquid chromatography (HPLC). Cell proliferation and apoptosis, and early and mature nerve cells in the hippocampi were observed by immunofluorescence. Reverse transcription polymerase chain reaction was used to identify BDNF expression in the hippocampi.

Results

After 5 weeks of unpredictable stimulation, a CUMS mouse model was successfully obtained, as indicated by sharply decreased sucrose preference and locomotor activity, as well as an increased immobility time in the forced swim test. Our results demonstrated that treatment with JYCF (1 and 5 g/kg) and fluoxetine (20 mg/kg) dramatically reversed the behavioral abnormalities in CUMS mice. At 1 g/kg, JYCF significantly increased NE, DA, and HVA levels in the hippocampi of CUMS mice. JYCF up-regulated the mRNA expression of BDNF and promoted cell proliferation in hippocampi of CUMS mice.

Conclusions

Our study demonstrated that JYCF exhibits antidepressant activity comparable to that of fluoxetine in CUMS mice. Moreover, the antidepressant-like activity of JYCF was shown to be mediated by enhancing hippocampal nerve cell neurogenesis through increasing the levels of monoamine neurotransmitters and BDNF expression.

Response of Htr3a knockout mice to antidepressant treatment and chronic stress

BACKGROUND AND PURPOSE

It has recently been suggested that 5-HT₃ receptor blockade enhances the efficacy of selective 5-HT (serotonin) reuptake inhibitor (SSRI) antidepressants and may reverse stress-induced deficits in rodents.

EXPERIMENTAL APPROACH

To further explore this hypothesis, we used mice lacking the 5-HT₃ receptor (Htr3a KO) and their wild-type (WT) controls to assess their response in behavioural paradigms relevant to anxiety and depression. Mice were studied under basal, antidepressant treatments and chronic social defeat stress (CSDS) conditions.

KEY RESULTS

In basal conditions, Htr3a KO mice displayed anxiolytic- and antidepressant-like behaviours in the elevated plus maze, the social interaction and the forced swim tests (FST), but behaved as WT mice in response to acute citalopram in the FST. However, the effects of fluoxetine were blunted in Htr3a KO mice in these same tests. In an in vitro electrophysiological paradigm, a low-dose citalopram treatment triggered 5-HT_1A receptor desensitization only in the dorsal raphe nucleus of Htr3a KO, although a high dose desensitized 5-HT_1A autoreceptor function equally in Htr3a KO and WT mice, suggesting that citalopram may become effective at lower doses when 5-HT₃ receptors are inactivated. In addition, Htr3a deletion blocked CSDS-induced modification in the cortical expression of two genes involved in oxidative stress, CaMKIIa and SOD1.

CONCLUSIONS AND IMPLICATIONS

Taken together, these data show that Htr3a deletion promotes SSRI efficacy and prevents the occurrence of stress-induced deleterious effects, suggesting that the 5-HT₃ receptor may represent an interesting target for the treatment of stress-related disorders.

5HT3 receptors: Target for new antidepressant drugs

5HT3 receptors (5HT3Rs) have long been identified as a potential target for antidepressants. Several studies have reported that antagonism of 5HT3Rs produces antidepressant-like effects. However, the exact role of 5HT3Rs and the mode of antidepressant action of 5HT3R antagonists still remain a mystery. Here, we provide a comprehensive overview of 5HT3Rs: (a) regional and subcellular distribution of 5HT3Rs in discrete brain regions, (b) preclinical and clinical evidence supporting the antidepressant effect of 5HT3R antagonists, and (c) neurochemical, biological and neurocellular signaling pathways associated with the antidepressant action of 5HT3R antagonists. 5HT3Rs located on the serotonergic and other neurotransmitter interneuronal projections control their release and affect mood and emotional behavior; however, new evidence suggests that apart from modulating the neurotransmitter functions, 5HT3R antagonists have protective effects in the pathogenic events including hypothalamic-pituitary-adrenal-axis hyperactivity, brain oxidative stress and impaired neuronal plasticity, pointing to hereby unknown and novel mechanisms of their antidepressant action. Nonetheless, further investigations are warranted to establish the exact role of 5HT3Rs in depression and antidepressant action of 5HT3R antagonists.

The role of serotonergic, adrenergic and dopaminergic receptors in antidepressant-like effect

Depression is a serious global illness, becoming more and more common in developed countries. Because of specific symptoms it is considered as a leading cause of disability all over the world with a high death factor due to suicides. There are many antidepressants used in the therapy, but still more than 30% of patients do not respond to the treatment. The heterogeneous nature of the illness and its complex, unclear aetiology may be responsible for these difficulties. Next to the main monoaminergic hypothesis of depression there are also many other approaches connected with the pathophysiology of the disease, including hypothalamic-pituitary-adrenal axis dysregulation, dopaminergic, cholinergic, glutamatergic or GABA-ergic neurotransmission. Nevertheless, it can be unambiguously stated that serotonergic, noradrenergic and dopaminergic systems are precisely connected with pathogenesis of depression, and should be therefore considered as valuable targets in patients' treatment. Bearing that in mind, this review presents the role of serotonergic, adrenergic and dopaminergic receptors in antidepressant-like effect.

The Functional Study of a Chinese Herbal Compounded Antidepressant Medicine--Jie Yu Chu Fan Capsule on Chronic Unpredictable Mild Stress Mouse Model

Jie Yu Chu Fan capsule (JYCF) is a new compounded Chinese herbal medicine for the treatment of depression. The present study was designed to explore the antidepressant effects and the possible mechanisms of JYCF by using chronic unpredictable mild stress (CUMS) mouse model and comparing results to that of fluoxetine. Behavioral tests including an open field test, sucrose preference test and forced swim test were performed to evaluate the antidepressant effects of JYCF. The concentrations of monoamine neurotransmitters and metabolic products including norepinephrine (NE), 5-hydroxytryptamine (5-HT), dopamine (DA), 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the cerebral cortex and hippocampus of mice were determined by means of high performance liquid chromatography with electrochemical detection (HPLC-EC). The results show that a successful mouse CUMS model was established through 5 weeks of continuous unpredictable stimulation, as indicated by the significant decrease in sucrose preference and locomotor activity and increase in immobility time in the forced swim test. Chronic treatment of JYCF (1.25, 2.5 and 5 g/kg) and fluoxetine (20mg/kg) significantly reversed the CUMS-induced behavioral abnormalities. JYCF (1.25, 2.5 and 5 g/kg) significantly increased NE in CUMS mouse prefrontal cortex (P < 0.01, P < 0.01, P < 0.05 respectively) and 5-HT in hippocampus (P < 0.05). In summary, our findings suggest that JYCF exerts comparable antidepressant-like effects to that of fluoxetine in CUMS mice. Besides, the antidepressant-like effect of JYCF is mediated by the increase of monoaminergic transmitters including 5-HT and NE.