Neurotrophic Properties of Silexan, an Essential Oil from the Flowers of Lavender-Preclinical Evidence for Antidepressant-Like Properties

The need for guidance in antidepressant drug development: Revisiting the role of the forced swim test and tail suspension test

Depressive disorders are one of the most common mental disorders globally and progress in treating these disorders has been hampered, in part, by a lack of suitable nonclinical efficacy tests. Two common tests used in nonclinical efficacy studies of antidepressants-the forced swim test (FST) and tail suspension test (TST)-have come under criticism in recent years for their inconsistency and lack of validity, yet they continue to be used in the pharmaceutical industry. In this review, we provide a rationale for why international pharmaceutical regulatory and guidance agencies should begin issuing direction on methods for non-clinical efficacy testing that traditionally use the FST and TST, particularly considering that some regulators, such as those in the U.S. and E.U., allow the authorization of clinical trials to proceed without requiring tests in animals. The area of antidepressant drug discovery represents an important opportunity for reducing the attrition of psychiatric drugs, harmonizing regulatory requirements, and reducing animal use. Specific recommendations for the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) have been provided.

Lavender oil preparation Silexan is effective in mild-to-moderate major depression: a randomized, placebo- and reference-controlled trial

Anxiety and depressive disorders have overlapping symptoms and share common neurobiological pathways. Antidepressant drugs have been demonstrated to be efficacious in anxiety as well. Vice versa, it may also be promising to investigate the efficacy of anxiolytic drugs such as silexan in major depressive disorder (MDD). Patients with a mild or moderate, single or recurrent episode of MDD and a total score of 19-34 points on the Montgomery Åsberg Depression Rating Scale (MADRS) were randomized to receive 1 × 80 mg/d silexan, 1 × 50 mg/d sertraline, or placebo double-blind, double-dummy for 56 days. The primary outcome measure was the MADRS total score change between baseline and treatment end. Treatment groups were compared using a treatment policy estimand. 498 subjects (silexan 170, sertraline 171, placebo 157) were treated and analyzed. After 8 weeks, silexan and sertraline were superior to placebo for MADRS total score reduction, with absolute differences to placebo of 2.17 (95% confidence interval: 0.58; 3.76) points and 2.59 (1.02; 4.17) points, respectively (p < 0.01). Moreover, silexan was superior to placebo for alleviation of functional impairment according to the Sheehan Disability Scale with a difference of 2.40 (1.04; 3.76) points (p < 0.001). Both treatments were well tolerated; eructation was the most frequent adverse effect of silexan. The study confirms the antidepressant efficacy of silexan in mild or moderate MDD, including significant improvements in the subjects' functional capacity. The results for sertraline confirm the assay sensitivity of the trial. Both drugs were well tolerated.Trial registrationEudraCT2020-000688-22 first entered on 12/08/2020.

Effect of a New Substance with Pyridoindole Structure on Adult Neurogenesis, Shape of Neurons, and Behavioral Outcomes in a Chronic Mild Stress Model in Rats

Despite an accumulating number of studies, treatments for depression are currently insufficient. Therefore, the search for new substances with antidepressant potential is very important. In this study, we hypothesized that treatment with a newly synthesized pyridoindole derivative compound SMe1EC2M3 would result in protective and antidepressant-like effects on behavioral outcomes and reverse the impaired adult hippocampal neurogenesis caused by chronic mild stress (CMS). We found that chronic administration of 5 mg/kg and 25 mg/kg SMe1EC2M3 to adult Sprague Dawley rats ameliorated the consequences of CMS on immobility and swimming time in a forced swim test. A slight sedative effect of the highest dose of SMe1EC2M3 in the nonstress group was observed in the open field. SMe1EC2M3 in the highest dose ameliorated CMS-induced decreases in the sucrose preference test. Administration of SMe1EC2M3 significantly increased SOX2-positive cells in the hippocampal dentate gyrus (DG) in CMS compared to control animals. A significant reduction in glial fibrillary acid protein (GFAP)-positive cells in the DG of CMS compared to control animals was observed. Administration of both 5 and 25 mg/kg SMe1EC2M3 significantly increased signal of GFAP-positive cells in the DG of CMS animals. No such effects of SMe1EC2M3 were observed in the cornu ammonis hippocampal area. Additionally, we found that incubation of primary hippocampal neurons in the presence of 1.50 µM SMe1EC2M3 significantly stimulated the length of neurites. Overall, we found that the negative effects of CMS on depression-like behavior are partially reduced by the administration of SMe1EC2M3 and are associated with changes in hippocampal neurogenesis and neuronal differentiation. SMe1EC2M3 represents a potential drug candidate with positive neuroplastic effects and neurogenesis-associated effects in therapeutic approaches to depression.

Psychiatric manifestations of post-COVID-19 syndrome: the potential benefit of Silexan

Objective: Psychiatric symptoms are common and bothersome in individuals with post-COVID-19 syndrome. Because they are often mixed and subthreshold, established treatment regimens cannot be applied. There is an urgent need to identify therapeutics for affected patients. Silexan, a proprietary essential oil from Lavandula angustifolia, has demonstrated efficacy against anxiety, comorbid symptoms, and subthreshold and mixed syndromes. The aim of the current narrative review is to examine the therapeutic potential of Silexan for psychiatric manifestations in patients with post-COVID-19 syndrome.Methods: We reviewed clinical evidence regarding the efficacy of Silexan and first clinical experience in patients with psychiatric symptoms attributable to the post-COVID-19 syndrome. Furthermore, we discussed potential modes of action based on nonclinical data.Results: Silexan has demonstrated therapeutic efficacy for the treatment of generalised anxiety disorder; subsyndromal anxiety disorders; comorbid depressive, somatic, and sleep disturbance symptoms; and mixed anxiety and depression. Emerging clinical experience also suggests the effectiveness and tolerability of Silexan for patients with post-COVID-19 syndrome. This can be explained by the fact that the therapeutic profile of Silexan overlaps with the spectrum of psychiatric symptoms in such patients.Conclusion: Preliminary findings indicate a promising potential of Silexan for the treatment of psychiatric manifestations in patients with post-COVID-19 syndrome.Key pointsAnxiety and mixed neuropsychiatric manifestations are commonly observed in patients with post-COVID-19 syndrome.Silexan has anxiolytic properties and can alleviate comorbid depressive, somatic, and sleep impairment symptoms.Silexan exhibits several biological mechanisms, such as neurotrophic and anti-inflammatory properties, which have the potential to positively impact post-COVID-19 disease.Silexan has a favourable safety profile and high acceptance among patients.Emerging data suggest that Silexan can alleviate neuropsychiatric symptoms in patients with post-COVID-19 syndrome.Silexan should be considered as a therapeutic in patients with psychiatric manifestations of post-COVID-19 syndrome.

Saffron essential oil ameliorates CUMS-induced depression-like behavior in mice via the MAPK-CREB1-BDNF signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Saffron, the dried stigma of Crocus sativus L., has a long history of use in the treatment of depression in traditional Chinese medicine and Islamic medicine. The unique aroma of saffron, primarily derived from its volatile oil, has been widely used by folk to mitigate anxiety and depression via sniffing because the aroma of saffron has a pleasant and invigorating effect.

AIM OF THE STUDY

This study aimed to investigate the antidepressant effect and the underlying mechanism of saffron essential oil (SEO) in mice exposed to chronic unpredictable mild stress (CUMS).

MATERIALS AND METHODS

In this study, compounds of SEO were identified using gas chromatography-mass spectrometry analysis, while network pharmacology was used to predict potential active compounds, antidepressant targets, and related signaling pathways of SEO. The CUMS depression model was further used to explore the therapeutic effect and possible mechanism of SEO. During the modeling period, mice were regularly administered fluoxetine (3.6 mg/kg, i.g.) or diluted SEO (2%, 4%, and 6% SEO, inhalation). The antidepressant and neuroprotective effects of SEO were evaluated by behavior tests (the open field test, the sucrose preference test, the tail suspension test, and the forced swimming test), hematoxylin-eosin staining, and Nissl staining. The enzyme-linked immunosorbent assay kits were used to measure dopamine (DA), 5-serotonin (5-HT), brain-derived neurotrophic factor (BDNF), and γ-aminobutyric acid (GABA) levels in serum. The relative abundance of Raf1, MEK1, P-ERK1/2/ERK1/2, P-CREB1/CREB1, BDNF, and P-Trk B/Trk B in the hippocampus was determined using western blot (WB).

RESULTS

According to the network pharmacology analysis, seven active SEO compounds mediated 113 targets related to depression treatment, most of which were enriched in the 5-HT synapse, calcium signaling pathway, and cAMP signaling pathway. In vivo experiments indicated that fluoxetine and SEO improved depression-like behaviors in depressed mice. The levels of 5-HT, DA, BDNF, and GABA in serum increased significantly. Histopathological examinations revealed that fluoxetine and SEO ameliorated neuronal damage in the hippocampus. WB analysis showed that the relative expressions of Raf1, MEK1, P-ERK1/2/ERK1/2, P-CREB1/CREB1, BDNF, and P-Trk B/Trk B were significantly higher in the fluoxetine and SEO groups than in the CUMS group.

CONCLUSION

Overall, these findings suggest that SEO significantly alleviates the depressive symptoms in CUMS exposed mice and partially restores hippocampal neuronal damage. Meanwhile, the best efficacy was observed in 4% SEO. Furthermore, the antidepressant mechanism of SEO is primarily dependent on the regulation of the MAPK-CREB1-BDNF signaling pathway.

Beneficial effects of Silexan on co-occurring depressive symptoms in patients with subthreshold anxiety and anxiety disorders: randomized, placebo-controlled trials revisited

Silexan is a proprietary active substance produced from Lavandula angustifolia, with proven anxiolytic efficacy in subthreshold and generalized anxiety disorder as well as in mixed anxiety and depressive disorder with beneficial impact on anxiety-related sleep disturbances. The pharmacological profile and clinical observations suggest that Silexan may also have an antidepressant effect. To investigate the effect of Silexan on co-occurring depressive symptoms, we present a meta-analysis of the five placebo-controlled clinical trials hitherto performed with Silexan in subthreshold anxiety (n = 3) and anxiety disorders (n = 2). Patients of all trials received Silexan 1 × 80 mg/day or placebo for 10 weeks according to random assignment. Assessment of the antidepressant effect was based on item 'depressed mood' from the Hamilton Anxiety Rating Scale (HAMA) administered in all trials and on the total scores of the Montgomery Åsberg Depression Rating Scale (MADRS) or the Hamilton Depression Rating Scale (HAMD) used in three trials. After 10-week treatment, patients receiving Silexan showed significantly more pronounced score reduction for HAMA item 'depressed mood' than those in the placebo group (p = 0.01). Significant superiority of Silexan over placebo could also be shown for mean MADRS or HAMD total score reduction (three studies; p < 0.01). Silexan-treated patients with more severe depressive symptoms at baseline showed more pronounced improvements than those with milder symptoms. Our meta-analysis clearly shows that Silexan has a beneficial effect on co-occurring depressive symptoms in patients with subthreshold anxiety and anxiety disorders and may, hence, lead to important therapeutic implications for depressive disorders.

Morinda officinalis oligosaccharides mitigate chronic mild stress-induced inflammation and depression-like behaviour by deactivating the MyD88/PI3K pathway via E2F2

Morinda officinalis oligosaccharides (MOs) are natural herbal extracts that have been shown to exert antidepressant effects. However, the mechanism of this effect remains unclear. Here, we explored the mechanism by which MOs improved experimental depression. Using a chronic mild stress (CMS) murine model, we examined whether MOs could protect against depressive-like behaviour. Lipopolysaccharide (LPS)- and ATP-treated BV2 cells were used to examine the potential mechanism by which MOs mediate the inflammatory response. We found that MOs prevented the CMS-induced reduction in the sucrose preference ratio in the sucrose preference test (SPT) and shortened the immobility durations in both the tail suspension test (TST) and forced swim test (FST). We also noticed that MOs suppressed inflammatory effects by deactivating the MyD88/PI3K pathway via E2F2 in CMS mice or LPS- and ATP-stimulated BV2 cells. Furthermore, overexpression of E2F2 blunted the beneficial effects of MOs in vitro. Collectively, these data showed that MOs exerted antidepressant effects in CMS mice by targeting E2F2-mediated MyD88/PI3K signalling pathway.

Novel Pharmacological Approaches to the Treatment of Depression

Major depressive disorder is one of the most prevalent mental health disorders. Monoamine-based antidepressants were the first drugs developed to treat major depressive disorder. More recently, ketamine and other analogues were introduced as fast-acting antidepressants. Unfortunately, currently available therapeutics are inadequate; lack of efficacy, adverse effects, and risks leave patients with limited treatment options. Efforts are now focused on understanding the etiology of depression and identifying novel targets for pharmacological treatment. In this review, we discuss promising novel pharmacological targets for the treatment of major depressive disorder. Targeting receptors including N-methyl-D-aspartate receptors, peroxisome proliferator-activated receptors, G-protein-coupled receptor 39, metabotropic glutamate receptors, galanin and opioid receptors has potential antidepressant effects. Compounds targeting biological processes: inflammation, the hypothalamic-pituitary-adrenal axis, the cholesterol biosynthesis pathway, and gut microbiota have also shown therapeutic potential. Additionally, natural products including plants, herbs, and fatty acids improved depressive symptoms and behaviors. In this review, a brief history of clinically available antidepressants will be provided, with a primary focus on novel pharmaceutical approaches with promising antidepressant effects in preclinical and clinical studies.

Effects of Lavender on Anxiety, Depression, and Physiological Parameters: Systematic Review and Meta-Analysis

PURPOSE

The recent evidence suggested substantial anxiolytic efficacy of lavender. The aim of this study was to examine the efficacy of lavender for anxiety, depression, and physiological parameters and to elucidate the differential effects of lavender on anxiety and depression by study characteristics.

METHODS

A systematic review and meta-analysis was performed following the PRISMA guidelines. We searched PubMed, Embase, Cochrane Library, Web of Science, and Cumulative Index of Nursing and Allied Health Literature databases for randomized controlled trials investigating the efficacy of lavender on anxiety, depression, or physiological parameters in humans. We assessed the risk of bias within studies with the revised Cochrane risk of bias tool for randomized trials. We used random effect model to estimate the average effect and computed bias-corrected standardized mean difference as effect size metric, Hedges' ĝ for all outcomes.

RESULTS

Lavender was superior to placebo or no treatment in reducing anxiety (Hedges' ĝ = -0.72, 95% confidence interval [CI] -0.90 to -0.55, p value <.001), depression (Hedges' ĝ = -0.43, 95% CI, -0.59 to -0.27, p value <.001), and systolic blood pressure (Hedges' ĝ = -0.23, 95% CI, -0.41to -0.05, p value = .01). The moderator analysis by meta-regression indicated that route of administration accounted 6.5% (p value = .187) for the heterogeneity in anxiolytic effects, sessions of treatment accounted 13.2% (p value = .055), and participants' health state accounted 8.9% (p value = .131) for the variance in anxiolytic effects.

CONCLUSION

Lavender aromatherapy showed substantial effect in reducing anxiety and depression, and sessions of administration increased the anxiolytic effects. The effects on physiological parameters showed small with inconsistent significances and randomized controlled trials on the effect of lavender on depression were scarce. Future trials on depression and physiological parameters are recommended, and increasing the sessions of administration is recommended.

Nutraceuticals in mental diseases - Bridging the gap between traditional use and modern pharmacology

In evidence-based pharmacotherapy, the complexity of etiopathogenesis and pathophysiology of mental diseases has attracted comparably little consideration so far. The choice of currently available pharmacotherapies is predominantly guided by specific clinical phenotypes and is limited by low response rates and clinically relevant side effects. Nutraceuticals typically represent multicomponent compounds and may offer high therapeutic potential, by simultaneously addressing multiple aspects in mental disease pathogenesis with rather little side effects. Here, recent pharmacological research on natural products is assessed with focus on a multitarget therapeutic concept, based on shared molecular mechanisms, and in particular, on how far nutraceuticals might address such multitargets. Overcoming deficits regarding clearly defined compositions, concentration-dependent and causative structure-activity-response relationships, evaluation of bioavailability, metabolic fate, and long-term safety are crucial for translating potential plant-based drug candidates into proof-of-concept clinical studies.