Indole-3-Carbinol Selectively Prevents Chronic Stress-Induced Depression-but not Anxiety-Like Behaviors via Suppressing Pro-Inflammatory Cytokine Production and Oxido-Nitrosative Stress in the Brain

Indole-3-Carbinol and Its Derivatives as Neuroprotective Modulators

Brain-derived neurotrophic factor (BDNF) and its downstream tropomyosin receptor kinase B (TrkB) signaling pathway play pivotal roles in the resilience and action of antidepressant drugs, making them prominent targets in psychiatric research. Oxidative stress (OS) contributes to various neurological disorders, including neurodegenerative diseases, stroke, and mental illnesses, and exacerbates the aging process. The nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant responsive element (ARE) serves as the primary cellular defense mechanism against OS-induced brain damage. Thus, Nrf2 activation may confer endogenous neuroprotection against OS-related cellular damage; notably, the TrkB/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway, stimulated by BDNF-dependent TrkB signaling, activates Nrf2 and promotes its nuclear translocation. However, insufficient neurotrophin support often leads to the downregulation of the TrkB signaling pathway in brain diseases. Thus, targeting TrkB activation and the Nrf2-ARE system is a promising therapeutic strategy for treating neurodegenerative diseases. Phytochemicals, including indole-3-carbinol (I3C) and its metabolite, diindolylmethane (DIM), exhibit neuroprotective effects through BDNF's mimetic activity; Akt phosphorylation is induced, and the antioxidant defense mechanism is activated by blocking the Nrf2-kelch-like ECH-associated protein 1 (Keap1) complex. This review emphasizes the therapeutic potential of I3C and its derivatives for concurrently activating neuronal defense mechanisms in the treatment of neurodegenerative diseases.

The relationship between serum resolvin D1, NLRP3, cytokine levels, and adolescents with first-episode medication-naïve major depressive disorder

BACKGROUND

Inflammation has become a critical pathological mechanism of Major Depressive Disorder (MDD). NLRP3 is a critical inflammatory pathway to maintain the immune balance. Recently, preclinical evidence showed that Resolvin D1 might potentially offer a new option for antidepressant treatment due to its protective effects through the inhibition of neuroinflammation. However, whether they have clinical value in the diagnosis and treatment evaluation of adolescent depression was unclear.

METHODS

Forty-eight untreated first-episode adolescent patients with moderate to severe major depressive disorder, as well as 30 healthy adolescents (HCs, age and gender-matched), were enrolled for this study. Their ages ranged from 13 to 18 (15.75 ± 1.36) years. The patients were treated with fluoxetine for 6-8 weeks. HDRS-17 was used to evaluate the severity of depressive symptoms. Venous blood samples were collected at baseline for the two groups and at the time-point of post-antidepressant treatment for the patients. Serum concentrations of RvD1, NLRP3, IL-1β, IL-18, and IL-4 were measured by enzyme-linked immunosorbent assays (ELISA) pre- and post-fluoxetine treatment.

RESULTS

Serum levels of RvD1 and anti-inflammatory cytokine IL-4 were significantly elevated in adolescents with MDD compared to healthy adolescents, but no significant difference in NLRP3, IL-1β, and IL-18 between the two groups. Meanwhile, RvD1 (positively) and IL-4 (negatively) were correlated with the severity of symptoms (HDRS-17 scores) after adjusting age, gender, and BMI. Interestingly, fluoxetine treatment significantly reduced the serum levels of RvD1, NLRP3, IL-1β, and IL-18 in MDD adolescents but increased the levels of IL-4 relative to baseline. Furthermore, we observed that serum levels of RvD1 might be an excellent distinguishing indicator for depression and healthy adolescents.

CONCLUSIONS

Our study is the first to compare RvD1 and NLRP3 between adolescent MDD and HCs. Our findings of reactive increase of RvD1 in adolescent MDD comprised a novel and critical contribution. Our results showed the presence of inflammation resolution unbalanced in adolescents with MDD and indicated that RvD1 might be an ideal biomarker for diagnosing and treating adolescent MDD.

Unmoving and uninflamed: Characterizing neuroinflammatory dysfunction in the Wistar-Kyoto rat model of depression

Reductionistic research on depressive disorders has been hampered by the limitations of animal models. Recently, it has been hypothesized that neuroinflammation is a key player in depressive disorders. The Wistar-Kyoto (WKY) rat is an often-used animal model of depression, but no information so far exists on its neuroinflammatory profile. As such, we compared male young adult WKY rats to Wistar (WS) controls, with regard to both behavioral performance and brain levels of key neuroinflammatory markers. We first assessed anxiety- and depression-like behaviors in a battery consisting of the Elevated Plus Maze (EPM), the Novelty Suppressed Feeding (NSFT), Open Field (OFT), Social Interaction (SIT), Forced Swim (FST), Sucrose Preference (SPT), and Splash tests (ST). We found that WKY rats displayed increased NSFT feeding latency, decreased OFT center zone permanence, decreased EPM open arm permanence, decreased SIT interaction time, and increased immobility in the FST. However, WKY rats also evidenced marked hypolocomotion, which is likely to confound performance in such tests. Interestingly, WKY rats performed similarly, or even above, to WS levels in the SPT and ST, in which altered locomotion is not a significant confound. In a separate cohort, we assessed prefrontal cortex (PFC), hippocampus and amygdala levels of markers of astrocytic (GFAP, S100A10) and microglial (Iba1, CD86, Ym1) activation status, as well as of three key proinflammatory cytokines (IL-1β, IL-6, TNF-α). There were no significant differences between strains in any of these markers, in any of the regions assessed. Overall, results highlight that behavioral data obtained with WKY rats as a model of depression must be carefully interpreted, considering the marked locomotor activity deficits displayed. Furthermore, our data suggest that, despite WKY rats replicating many depression-associated neurobiological alterations, as shown by others, this is not the case for neuroinflammation-related alterations, thus representing a novel limitation of this model.

Dietary glucosinolates derived isothiocyanates: chemical properties, metabolism and their potential in prevention of Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia affecting millions of people worldwide. It is a progressive, irreversible, and incurable neurodegenerative disorder that disrupts the synaptic communication between millions of neurons, resulting in neuronal death and functional loss due to the abnormal accumulation of two naturally occurring proteins, amyloid β (Aβ) and tau. According to the 2018 World Alzheimer's Report, there is no single case of an Alzheimer's survivor; even 1 in 3 people die from Alzheimer's disease, and it is a growing epidemic across the globe fruits and vegetables rich in glucosinolates (GLCs), the precursors of isothiocyanates (ITCs), have long been known for their pharmacological properties and recently attracted increased interest for the possible prevention and treatment of neurodegenerative diseases. Epidemiological evidence from systematic research findings and clinical trials suggests that nutritional and functional dietary isothiocyanates interfere with the molecular cascades of Alzheimer's disease pathogenesis and prevent neurons from functional loss. The aim of this review is to explore the role of glucosinolates derived isothiocyanates in various molecular mechanisms involved in the progression of Alzheimer's disease and their potential in the prevention and treatment of Alzheimer's disease. It also covers the chemical diversity of isothiocyanates and their detailed mechanisms of action as reported by various in vitro and in vivo studies. Further clinical studies are necessary to evaluate their pharmacokinetic parameters and effectiveness in humans.

Pharmacological evaluation of the anxiolytic-like effects of an aqueous extract of the Raphanus sativus L. sprouts in mice

Raphanus sativus L. (Brassicaceae), commonly known as radish, is consumed worldwide as a vegetable. However, its benefits on mental health are unknown. The aim of this study was to evaluate its anxiolytic-like effects and safety using different experimental models. An aqueous extract of R. sativus sprouts (AERSS) was pharmacologically evaluated by intraperitoneal route (i.p.) at 10, 30, and 100 mg/kg and orally (p.o.) at 500 mg/kg on behavior by using open-field and plus-maze tests. In addition, its acute toxicity (LD₅₀) was determined by the Lorke's method. Diazepam (1 mg/kg, i.p.) and buspirone (4 mg/kg, i.p.) were the reference drugs. A significant and anxiolytic-like dosage of AERSS (30 mg/kg, i.p.) resembling the effects of reference drugs was chosen to explore the involvement of GABA_A/BDZs site (flumazenil, 5 mg/kg, i.p.) and serotonin 5-HT_1A receptors (WAY100635, 1 mg/kg, i.p.) as a possible mechanism of action. A 500 mg/kg, p.o. dosage of AERSS produced an anxiolytic-like response equivalent to 100 mg/kg, i.p. No acute toxicity was observed since a LD₅₀ > 2000 mg/kg, i.p. The phytochemical analysis allowed the identification and quantification of major presence of sulforaphene (2500 µM), sulforaphane (15 µM), iberin (0.75 µM), and indol-3-carbinol (0.75 µM), as major constituents. Both the GABA_A/BDZs site and serotonin 5-HT_1A receptors were involved in the anxiolytic-like activity of AERSS, depending on the pharmacological parameter or the experimental assay tested. Our results demonstrate that the anxiolytic activity of R. sativus sprouts involves GABA_A/BDZs site and serotonin 5-HT_1A receptors supporting its health benefits in the treatment of anxiety beyond the satisfaction of basic nutritional needs.

Cardamom oil ameliorates behavioral and neuropathological disorders in a rat model of depression induced by reserpine

ETHNOPHARMACOLOGICAL RELEVANCE

Depression is a public health problem. Despite the availability of treatment options, its prevalence is increasing. A high rate of treatment failure is often reported, along with considerable side effects associated with synthetic antidepressants. Therefore, developing effective and safe antidepressants from traditional herbs or natural products as an alternative strategy is warranted to avoid side effects and increase drug efficacy. In traditional medicine, cardamom has traditionally been used to treat conditions like asthma, tooth and gum infections, cataracts, nausea, diarrhea, and even depression and anxiety as well as some problems with the heart, kidneys, and digestive system.

AIM OF THE STUDY

The current study aimed to evaluate the antidepressant activity of cardamom oil in a rat model of depression induced by reserpine and compare it with the activity of the antidepressant drug fluoxetine.

MATERIALS AND METHODS

Depression-like symptoms were induced in male rats by daily i. p. injection of reserpine (0.2 mg/kg/d for 15 d followed by 0.1 mg/kg/d for 21 d to maintain the depressive state), and the rats were treated with cardamom oil (oral dose = 200 mg/kg/d) for 21 d along with the maintenance dose of reserpine. We performed behavioral tests (forced swimming test and open-field test) and evaluated biochemical markers of depression.

RESULTS

Our findings revealed that cardamom oil attenuated depression-like symptoms in reserpine-injected rats by improving the behavioral changes measured by the forced swimming test and the locomotor activities measured by the open-field test. In reserpine-injected rats, cardamom oil exerted antidepressant-like effects by modulating lower levels of brain monoamine neurotransmitters (serotonin, norepinephrine, and dopamine), GSH, and higher oxido-nitrosative stress parameters (malondialdehyde and nitric oxide). Moreover, cardamom oil alleviated depression-like behaviors by lowering monoamine oxidase activity and raising the activities of Na⁺/K⁺-ATPase and acetylcholinesterase and levels of a brain-derived neurotrophic factor in the cortex and hippocampus.

CONCLUSION

We recommend the use of cardamom oil as a safe and reliable treatment or an adjuvant for preventing depression-like symptoms in patients suffering from depression.

Involvement of the gut-brain axis in vascular depression via tryptophan metabolism: A benefit of short chain fatty acids

Cerebral hemodynamic dysfunction and hypoperfusion have been found to underlie vascular depression, but whether the gut-brain axis is involved remains unknown. In this study, a rat model of bilateral common carotid artery occlusion (BCCAO) was adopted to mimic chronic cerebral hypoperfusion. A reduced sucrose preference ratio, increased immobility time in the tail suspension test and forced swim test, and compromised gut homeostasis were found. A promoted conversion of tryptophan (Trp) into kynurenine (Kyn) instead of 5-hydroxytryptamine (5-HT) was observed in the hippocampus and gut of BCCAO rats. Meanwhile, 16S ribosomal RNA gene sequencing suggested a compromised profile of the gut SCFA-producing microbiome, with a decreased serum level of SCFAs revealed by targeted metabolomics analysis. With SCFA supplementation, BCCAO rats exhibited ameliorated depressive-like behaviors and improved gut dysbiosis, compared with the salt-matched BCCAO group. Enzyme-linked immunosorbent assays and quantitative RT-PCR suggested that SCFA supplementation suppressed the conversion of Trp to Kyn and rescued the reduction in 5-HT levels in the hippocampus and gut. In addition to inhibiting the upregulation of inflammatory cytokines, SCFA supplementation ameliorated the activated oxidative stress and reduced the number of microglia and the expression of its proinflammatory markers in the hippocampus post BCCAO. In conclusion, our data suggested the participation of the gut-brain axis in vascular depression, shedding light on the neuroprotective potential of treatment with gut-derived SCFAs.