Pathophysiology of Depression: Stingless Bee Honey Promising as an Antidepressant

Depression is a debilitating psychiatric disorder impacting an individual’s quality of life. It is the most prevalent mental illness across all age categories, incurring huge socio-economic impacts. Most depression treatments currently focus on the elevation of neurotransmitters according to the monoamine hypothesis. Conventional treatments include tricyclic antidepressants (TCAs), norepinephrine–dopamine reuptake inhibitors (NDRIs), monoamine oxidase inhibitors (MAOIs), and serotonin reuptake inhibitors (SSRIs). Despite numerous pharmacological strategies utilising conventional drugs, the discovery of alternative medicines from natural products is a must for safer and beneficial brain supplement. About 30% of patients have been reported to show resistance to drug treatments coupled with functional impairment, poor quality of life, and suicidal ideation with a high relapse rate. Hence, there is an urgency for novel discoveries of safer and highly effective depression treatments. Stingless bee honey (SBH) has been proven to contain a high level of antioxidants compared to other types of honey. This is a comprehensive review of the potential use of SBH as a new candidate for antidepressants from the perspective of the monoamine, inflammatory and neurotrophin hypotheses.

Is serotonin uptake by peripheral tissues sensitive to hypoxia exposure?

In the Gulf toadfish (Opsanus beta), the serotonin (5-HT) transporter (SERT) is highly expressed in the heart, and the heart and gill both demonstrate the capacity for SERT-mediated uptake of 5-HT from the circulation. Because 5-HT is a potent vasoconstrictor in fish, we hypothesized that hypoxia exposure may increase 5-HT uptake by these tissues-and increase excretion of 5-HT-to prevent branchial vasoconstriction that would hamper gas exchange. Spot sampling of blood, bile, and urine revealed that fish exposed to chronic hypoxia (1.83 ± 0.12 mg·L^-1 O₂ for 24-26 h) had 41% lower plasma 5-HT in the ventral aorta (immediately following the heart) than in the hepatic vein (immediately before the heart), suggesting enhanced cardiac 5-HT uptake during hypoxia. 5-HT concentrations in the bile were greater than those in the urine, but there were no effects of acute (1.31 ± 0.06 mg·L^-1 O₂ for 25 min) or chronic hypoxia on 5-HT levels in these fluids. In 5-HT radiotracer experiments, the presence of tracer in the bile decreased upon hypoxia exposure, but, surprisingly, neither acute nor chronic hypoxia-induced changes in [³H]5-HT uptake in the heart, gill, or other tissues. Given the likely impact of the hypoxia exposure on metabolic rate, future studies should examine the effects of a milder hypoxia exposure on 5-HT uptake into these tissues and the role of 5-HT degradation.

Low-Frequency Oscillations of In Vivo Ambient Extracellular Brain Serotonin

Serotonin is an important neurotransmitter that plays a major role in many aspects of neuroscience. Fast-scan cyclic voltammetry measures fast in vivo serotonin dynamics using carbon fiber microelectrodes. More recently, fast-scan controlled-adsorption voltammetry (FSCAV) has been developed to measure slower, minute-to-minute changes in ambient extracellular serotonin. We have previously demonstrated that FSCAV measurements of basal serotonin levels give critical information regarding brain physiology and disease. In this work, we revealed the presence of low-periodicity fluctuations in serotonin levels in mouse hippocampi, measured in vivo with FSCAV. Using correlation analyses, we found robust evidence of oscillations in the basal serotonin levels, which had a period of 10 min and were not present in vitro. Under control conditions, the oscillations did not differ between male and female mice, nor do they differ between mice that underwent a chronic stress paradigm and those in the control group. After the acute administration of a selective serotonin reuptake inhibitor, we observed a shift in the frequency of the oscillations, leading us to hypothesize that the newly observed fluctuations were transporter regulated. Finally, we optimized the experimental parameters of the FSCAV to measure at a higher temporal resolution and found more pronounced shifts in the oscillation frequency, along with a decreased oscillation amplitude. We postulate that this work may serve as a potential bridge for studying serotonin/endocrine interactions that occur on the same time scale.

Mesembryanthemum tortuosum L. alkaloids modify anxiety-like behaviour in a zebrafish model

ETHNOPHARMACOLOGICAL RELEVANCE

Mesembryanthemum tortuosum L. (previously known as Sceletium tortuosum (L.) N.E. Br.) is indigenous to South Africa and traditionally used to alleviate anxiety, stress and depression. Mesembrine and its alkaloid analogues such as mesembrenone, mesembrenol and mesembranol have been identified as the key compounds responsible for the reported effects on the central nervous system.

AIM OF THE STUDY

To investigate M. tortuosum alkaloids for possible anxiolytic-like effects in the 5-dpf in vivo zebrafish model by assessing thigmotaxis and locomotor activity.

MATERIALS AND METHODS

Locomotor activity and reverse-thigmotaxis, recognised anxiety-related behaviours in 5-days post fertilization zebrafish larvae, were analysed under simulated stressful conditions of alternating light-dark challenges. Cheminformatics screening and molecular docking were also performed to rationalize the inhibitory activity of the alkaloids on the serotonin reuptake transporter, the accepted primary mechanism of action of selective serotonin reuptake inhibitors. Mesembrine has been reported to have inhibitory effects on serotonin reuptake, with consequential anti-depressant and anxiolytic effects.

RESULTS

All four alkaloids assessed decreased the anxiety-related behaviour of zebrafish larvae exposed to the light-dark challenge. Significant increases in the percentage of time spent in the central arena during the dark phase were also observed when larvae were exposed to the pure alkaloids (mesembrenone, mesembrenol, mesembrine and mesembrenol) compared to the control. However, mesembrenone and mesembranol demonstrated a greater anxiolytic-like effect than the other alkaloids. In addition to favourable pharmacokinetic and physicochemical properties revealed via in silico predictions, high-affinity interactions characterized the binding of the alkaloids with the serotonin transporter.

CONCLUSIONS

M. tortuosum alkaloids demonstrated an anxiolytic-like effect in zebrafish larvae providing evidence for its traditional and modern day use as an anxiolytic.

Beneficial effects of irisin in experimental paroxetine-induced hyperprolactinemia

OBJECTIVE

It is known that selective serotonin reuptake inhibitors (SSRIs), represent an important and effective treatment of depression and other psychological disorders, these medications can increase prolactin levels mainly through activation of the serotonergic pathway. In this study, we aimed to determine the beneficial effects of irisin on paroxetine, a SSRI, induced hyperprolectinemia and in some other reproductive hormonal changes associated with hyperprolactinemia.

METHODS

Thirty two male Spraque-Dawley rats were used and divided into four groups including sham-operated control (vehicle), irisin (100 ng/kg/day for 28 days with mini-osmotic pumps), paroxetine (treated with 20 mg/kg paroxetine by oral gavage), irisin and paroxetine+irisin groups (n = 8). Serum prolactin (PRL), kisspeptin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone and 5-alpha reductase levels were determined with enzyme-linked immunosorbent analysis (ELISA).

RESULTS

In animals treated with paroxetine, PRL level increased and testosterone level decreased significantly (p < 0.05). Serum LH level was significantly increased in the group, but no significant changes were observed in the FSH, kisspeptin and 5-alpha reductase levels. Serum prolactin levels was significantly decreased in the group treated with irisin. While no significant difference was observed in kisspeptin, FSH and 5-alpha reductase levels, an increase in serum LH and testosterone levels with irisin administration (p < 0.05).

CONCLUSION

In conclusion, chronic irisin exposure may reverse paroxetine-induced hyperprolactinemia. These results indicate that irisin may have the potential to be used as a therapeutic agent by primarily affecting paroxetine-induced increased prolactin and decreased testosterone levels.

Multiple Pre-Treatment miRNAs Levels in Untreated Major Depressive Disorder Patients Predict Early Response to Antidepressants and Interact with Key Pathways

Major depressive disorder (MDD) is a life-impairing disorder, and early successful treatment is important for a favorable prognosis. However, early response to antidepressants differs widely among individuals, and is difficult to predict pre-treatment. As miRNAs have been reported to play important roles in depression, identification of miRNAs associated with antidepressant treatment responses and their interacting genes and pathways will be beneficial in understanding the predictors and molecular mechanisms of depression treatment. This randomized control trial examined miRNAs correlated with the early therapeutic effect of selective serotonin reuptake inhibitors (SSRIs; paroxetine or sertraline) and mirtazapine monotherapy. Before medication, we comprehensively analyzed the miRNA expression of 92 depressed participants and identified genes and pathways interacting with miRNAs. A total of 228 miRNAs were significantly correlated with depressive symptoms improvements after 2 weeks of SSRIs treatment, with miR-483.5p showing the most robust correlation. These miRNAs are involved in 21 pathways, including TGF-β, glutamatergic synapse, long-term depression, and the mitogen-activated protein kinase (MAPK) signaling pathways. Using these miRNAs enabled us to predict SSRI response at week 2 with a 57% difference. This study shows that pre-treatment levels of miRNAs could be used to predict early responses to antidepressant administration, a knowledge of genes, and an identification of genes and pathways associated with the antidepressant response.

Potential Role of the Antidepressants Fluoxetine and Fluvoxamine in the Treatment of COVID-19

Mapping non-canonical cellular pathways affected by approved medications can accelerate drug repurposing efforts, which are crucial in situations with a global impact such as the COVID-19 pandemic. Fluoxetine and fluvoxamine are well-established and widely-used antidepressive agents that act as serotonin reuptake inhibitors (SSRI-s). Interestingly, these drugs have been reported earlier to act as lysosomotropic agents, inhibitors of acid sphingomyelinase in the lysosomes, and as ligands of sigma-1 receptors, mechanisms that might be used to fight severe outcomes of COVID-19. In certain cases, these drugs were administered for selected COVID-19 patients because of their antidepressive effects, while in other cases, clinical studies were performed to assess the effect of these drugs on treating COVID-19 patients. Clinical studies produced promising data that encourage the further investigation of fluoxetine and fluvoxamine regarding their use in COVID-19. In this review, we summarize experimental data and the results of the performed clinical studies. We also provide an overview of previous knowledge on the tissue distribution of these drugs and by integrating this information with the published experimental results, we highlight the real opportunity of using these drugs in our fight against COVID-19.

Comparison of pre-operative platelet functions by thromboelastogram in patients selective serotonin reuptake inhibitors user and non-user

BACKGROUND

The use of antidepressant drugs, in particular selective serotonin reuptake inhibitors (SSRIs), has increased in recent years. Using SSRIs can cause changes in serotonin metabolism. Serotonin provides platelet aggregation and plays a role in the regulation of vascular tone and coagulation processes. The aim of this study was to evaluate the effects of SSRI use on coagulation functions with thromboelastogram (TEG) in patients undergoing surgical operation and to compare with non-user cases.

METHODS

The study was designed for 60 patients whose physical status was classified according to the American Society of Anes-thesiology (ASA) classification as ASA I-II were included in the study. During routine pre-operative blood tests, 2 ml complete blood sample used and TEG performed. The cases were divided into two groups as SSRI user and non-user and analyzed.

RESULTS

R value was higher in SSRI user patients than in non-user patients. The MA value was significantly lower in SSRI user. There was no statistically significant difference in other parameters. In the evaluation based on duration of SSRI use, there was no statistically significant difference between those whose duration of use was more than 1 year and <1 year.

CONCLUSION

When the coagulation process was evaluated by TEG method, it was seen that the onset of clotting was prolonged and thrombus formation was slowed down in SSRI users. The results did not reveal that SSRI alone was the cause of bleeding, but it was concluded that slowing the process might be important, especially for surgical operations.

Fluoxetine regulates the neuronal differentiation of neural stem cells transplanted into rat brains after stroke by increasing the 5HT level

Fluoxetine, a 5-HT uptake inhibitor, has been adopted for the treatment of post-stroke depression in recent years. It has been confirmed to induce neuronal regeneration in vivo, but its effect on inducing stem cell differentiation after transplantation has not yet been verified. To evaluate its regulatory effect on stem cell differentiation, fluoxetine was used in this study to treat rats with cerebral ischemia after neural stem cell (NSC) transplantation. The results showed that the proportion of NSCs differentiating into neurons significantly increased after fluoxetine treatment. In NSC adherent culture, the addition of 5-HT but not of fluoxetine significantly increased the neuronal differentiation ratio of NSCs. Moreover, the addition of 5-HT2A or 5-HT3A antagonists inhibited this effect. In addition, Western blotting revealed that the increase in 5-HT inhibited ERK2 phosphorylation and upregulated neurogenin1 expression. In conclusion, fluoxetine increased the 5-HT level and promoted neuronal differentiation, thereby upregulating neurogenin1 expression and downregulating ERK2 phosphorylation.

Hippocampal Over-Expression of Cyclooxygenase-2 (COX-2) Is Associated with Susceptibility to Stress-Induced Anhedonia in Mice

The phenomenon of individual variability in susceptibility/resilience to stress and depression, in which the hippocampus plays a pivotal role, is attracting increasing attention. We investigated the potential role of hippocampal cyclooxygenase-2 (COX-2), which regulates plasticity, neuroimmune function, and stress responses that are all linked to this risk dichotomy. We used a four-week-long chronic mild stress (CMS) paradigm, in which mice could be stratified according to their susceptibility/resilience to anhedonia, a key feature of depression, to investigate hippocampal expression of COX-2, a marker of microglial activation Iba-1, and the proliferation marker Ki67. Rat exposure, social defeat, restraints, and tail suspension were used as stressors. We compared the effects of treatment with either the selective COX-2 inhibitor celecoxib (30 mg/kg/day) or citalopram (15 mg/kg/day). For the celecoxib and vehicle-treated mice, the Porsolt test was used. Anhedonic (susceptible) but not non-anhedonic (resilient) animals exhibited elevated COX-2 mRNA levels, increased numbers of COX-2 and Iba-1-positive cells in the dentate gyrus and the CA1 area, and decreased numbers of Ki67-positive cells in the subgranular zone of the hippocampus. Drug treatment decreased the percentage of anhedonic mice, normalized swimming activity, reduced behavioral despair, and improved conditioned fear memory. Hippocampal over-expression of COX-2 is associated with susceptibility to stress-induced anhedonia, and its pharmacological inhibition with celecoxib has antidepressant effects that are similar in size to those of citalopram.

Pharmacological Management of Apathy in Dementia

Apathy is a highly prevalent symptom of dementia. Despite its association with faster cognitive and functional decline, decreased quality of life and increased mortality, no therapies are currently approved to treat apathy. The objective of this review was to summarize the drugs that have been studied for apathy treatment in patients with dementia (specifically Alzheimer's disease [AD], Huntington's disease [HD] and Parkinson's disease [PD] dementia; dementia with Lewy bodies [DLB]; vascular dementia [VaD]; and frontotemporal dementia [FTD]) based on their putative mechanisms of action. A search for relevant studies was performed using ClinicalTrials.gov and PubMed. Eligible studies were randomized controlled trials that were available in English and included at least one drug intervention and an apathy measure scale. A total of 52 studies that included patients with AD (n = 33 studies), PD (n = 5), HD (n = 1), DLB (n = 1), FTD (n = 3), VaD (n = 1), VaD and AD (n = 4), VaD and mixed dementia (n = 1), and AD, VaD and mixed dementia (n = 3) were eligible for inclusion. These studies showed that methylphenidate, olanzapine, cholinesterase inhibitors, choline alphoscerate, citalopram, memantine, and mibampator are the only beneficial drugs in AD-related apathy. For PD-related apathy, only methylphenidate, rotigotine and rivastigmine showed benefits. Regarding FTD- and DLB-related apathy, initial studies with agomelatine and rivastigmine showed benefits, respectively. As for HD- and only-VaD-related apathy, no drugs demonstrated benefits. With regards to mixed populations, memantine, galantamine and gingko biloba showed effects on apathy in the AD plus VaD populations and nimodipine in the VaD plus mixed dementia populations. Of the drugs with positive results, some are already prescribed to patients with dementia to target other symptoms, some have characteristics-such as medical contraindications (e.g., cardiovascular) and adverse effects (e.g., gastrointestinal disturbances)-that limit their clinical use and some require further study. Future studies should investigate apathy as a primary outcome, making use of appropriate sample sizes and study durations to ensure durability of results. There should also be a consensus on using scales with high test/retest and interrater reliabilities to limit the inconsistencies between clinical trials. In conclusion, there are currently no US FDA-approved drugs that target apathy in dementia, so there is an ongoing need for the development of such drugs.

Modulation of microglial activation by antidepressants

BACKGROUND

Recent studies have suggested that microglial activation plays a key role in the pathogenesis of depression. In fact, neuroinflammation is associated with a phenotypic change of microglia, consisting of morphological differences, increased release of cytokines and oxidative stress products, which may contribute to the development and maintenance of depression. Antidepressants, including selective serotonin re-uptake inhibitors and serotonin-norepinephrine reuptake inhibitors, have been shown to act on the immune and oxidative stress mechanisms commonly found to be disrupted in depression. Thus, the inhibition of microglial activation may be one of the mechanisms through which they exert an antidepressant action.

AIM

This is the first review summarising in vitro and ex vivo studies investigating the effects of different classes of antidepressants on microglia activation, by examining cellular changes and/or via measuring the production of immune and/or oxidative stress signalling molecules, in microglia models of neuroinflammation with either lipopolysaccharide (LPS) or cytokines. A total of 23 studies were identified, 18 using LPS stimulation and 5 using cytokines stimulation.

RESULTS

Overall, the studies show that antidepressants, such as selective serotonin re-uptake inhibitors, serotonin-norepinephrine reuptake inhibitors, monoamine oxidase inhibitors and tricyclic antidepressants prevented microglial activation, including reduced microglial reactivity and decreased immune and oxidative stress products, in both models. However, specific antidepressants, such as bupropion and agomelatine did not prevent interferon-gamma (IFN-γ)-induced microglial activation; and for other antidepressants, including phenelzine, venlafaxine and sertraline, the results of different studies were inconsistent.

CONCLUSIONS

Overall, results summarised in this review support the hypothesis that the action of at least certain classes of antidepressants may involve regulation of microglial activation, especially when in presence of increased levels of inflammation.

Low plasma serotonin linked to higher nigral iron in Parkinson's disease

A growing body of evidence suggests nigral iron accumulation plays an important role in the pathophysiology of Parkinson's disease (PD), contributing to dopaminergic neuron loss in the substantia nigra pars compacta (SNc). Converging evidence suggests this accumulation might be related to, or increased by, serotonergic dysfunction, a common, often early feature of the disease. We investigated whether lower plasma serotonin in PD is associated with higher nigral iron. We obtained plasma samples from 97 PD patients and 89 controls and MRI scans from a sub-cohort (62 PD, 70 controls). We measured serotonin concentrations using ultra-high performance liquid chromatography and regional iron content using MRI-based quantitative susceptibility mapping. PD patients had lower plasma serotonin (p < 0.0001) and higher nigral iron content (SNc: p < 0.001) overall. Exclusively in PD, lower plasma serotonin was correlated with higher nigral iron (SNc: r(58) =  - 0.501, p < 0.001). This correlation was significant even in patients newly diagnosed (< 1 year) and stronger in the SNc than any other region examined. This study reveals an early, linear association between low serotonin and higher nigral iron in PD patients, which is absent in controls. This is consistent with a serotonin-iron relationship in the disease process, warranting further studies to determine its cause and directionality.

Double-blind, randomized, placebo-controlled pilot study of the phosphodiesterase-3 inhibitor cilostazol as an adjunctive to antidepressants in patients with major depressive disorder

AIMS

Cilostazol (CLS) has shown antidepressant effect in cardiovascular patients, post-stroke depression, and animal models through its neurotrophic and antiinflammatory activities. Consequently, we aimed to investigate its safety and efficacy in patients with MDD by conducting double-blind, randomized, placebo-controlled pilot study.

METHODS

80 participants with MDD (DSM-IV criteria) and Hamilton Depression Rating Scale (HDRS) score >20 were treated with CLS 50 mg or placebo twice daily plus escitalopram (ESC) 20 mg once daily for six weeks. Patients were evaluated by HDRS scores (weeks 0, 2, 4, and 6). Serum levels of CREB1, BDNF, 5-HT, TNF-α, NF- κB, and FAM19A5 were assessed pre- and post-treatment.

RESULTS

Co-administration of CLS had markedly decreased HDRS score at all-time points compared to the placebo group (p < 0.001). Early improvement, response, and remission rates after 6 weeks were significantly higher in the CLS group (90%, 90%, 80%, respectively) than in the placebo group (25%, 65%, 50% respectively) (p < 0.001). Moreover, the CLS group was superior to the placebo group in modulation of the measured neurotrophic and inflammatory biomarkers.

CONCLUSION

CLS is safe and effective short-term adjunctive therapy in patients with MDD with no other comorbid conditions. Trial registration ID:NCT04069819.

Tryptophan Hydroxylase 2 Deficiency Modifies the Effects of Fluoxetine and Pargyline on the Behavior, 5-HT- and BDNF-Systems in the Brain of Zebrafish (Danio rerio)

The mechanisms of resistance to antidepressant drugs is a key and still unresolved problem of psychopharmacology. Serotonin (5-HT) and brain-derived neurotrophic factor (BDNF) play a key role in the therapeutic effect of many antidepressants. Tryptophan hydroxylase 2 (TPH2) is the rate-limiting enzyme in 5-HT synthesis in the brain. We used zebrafish (Danio rerio) as a promising model organism in order to elucidate the effect of TPH2 deficiency caused by p-chlorophenylalanine (pCPA) on the alterations in behavior and expression of 5-HT-related (Tph2, Slc6a4b, Mao, Htr1aa, Htr2aa) and BDNF-related (Creb, Bdnf, Ntrk2a, Ngfra) genes in the brain after prolonged treatment with two antidepressants, inhibitors of 5-HT reuptake (fluoxetine) and oxidation (pargyline). In one experiment, zebrafish were treated for 72 h with 0.2 mg/L fluoxetine, 2 mg/L pCPA, or the drugs combination. In another experiment, zebrafish were treated for 72 h with 0.5 mg/L pargyline, 2 mg/L pCPA, or the drugs combination. Behavior was studied in the novel tank diving test, mRNA levels were assayed by qPCR, 5-HT and its metabolite concentrations were measured by HPLC. The effects of interaction between pCPA and the drugs on zebrafish behavior were observed: pCPA attenuated “surface dwelling” induced by the drugs. Fluoxetine decreased mRNA levels of Tph2 and Htr2aa genes, while pargyline decreased mRNA levels of Slc6a4b and Htr1aa genes. Pargyline reduced Creb, Bdnf and Ntrk2a genes mRNA concentration only in the zebrafish treated with pCPA. The results show that the disruption of the TPH2 function can cause a refractory to antidepressant treatment.

Simultaneous serotonin and dopamine monitoring across timescales by rapid pulse voltammetry with partial least squares regression

Many voltammetry methods have been developed to monitor brain extracellular dopamine levels. Fewer approaches have been successful in detecting serotonin in vivo. No voltammetric techniques are currently available to monitor both neurotransmitters simultaneously across timescales, even though they play integrated roles in modulating behavior. We provide proof-of-concept for rapid pulse voltammetry coupled with partial least squares regression (RPV-PLSR), an approach adapted from multi-electrode systems (i.e., electronic tongues) used to identify multiple components in complex environments. We exploited small differences in analyte redox profiles to select pulse steps for RPV waveforms. Using an intentionally designed pulse strategy combined with custom instrumentation and analysis software, we monitored basal and stimulated levels of dopamine and serotonin. In addition to faradaic currents, capacitive currents were important factors in analyte identification arguing against background subtraction. Compared to fast-scan cyclic voltammetry-principal components regression (FSCV-PCR), RPV-PLSR better differentiated and quantified basal and stimulated dopamine and serotonin associated with striatal recording electrode position, optical stimulation frequency, and serotonin reuptake inhibition. The RPV-PLSR approach can be generalized to other electrochemically active neurotransmitters and provides a feedback pipeline for future optimization of multi-analyte, fit-for-purpose waveforms and machine learning approaches to data analysis.

Mortality Risk Among Patients With COVID-19 Prescribed Selective Serotonin Reuptake Inhibitor Antidepressants

IMPORTANCE

Antidepressant use may be associated with reduced levels of several proinflammatory cytokines suggested to be involved with the development of severe COVID-19. An association between the use of selective serotonin reuptake inhibitors (SSRIs)-specifically fluoxetine hydrochloride and fluvoxamine maleate-with decreased mortality among patients with COVID-19 has been reported in recent studies; however, these studies had limited power due to their small size.

OBJECTIVE

To investigate the association of SSRIs with outcomes in patients with COVID-19 by analyzing electronic health records (EHRs).

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used propensity score matching by demographic characteristics, comorbidities, and medication indication to compare SSRI-treated patients with matched control patients not treated with SSRIs within a large EHR database representing a diverse population of 83 584 patients diagnosed with COVID-19 from January to September 2020 and with a duration of follow-up of as long as 8 months in 87 health care centers across the US.

EXPOSURES

Selective serotonin reuptake inhibitors and specifically (1) fluoxetine, (2) fluoxetine or fluvoxamine, and (3) other SSRIs (ie, not fluoxetine or fluvoxamine).

MAIN OUTCOMES AND MEASURES

Death.

RESULTS

A total of 3401 adult patients with COVID-19 prescribed SSRIs (2033 women [59.8%]; mean [SD] age, 63.8 [18.1] years) were identified, with 470 receiving fluoxetine only (280 women [59.6%]; mean [SD] age, 58.5 [18.1] years), 481 receiving fluoxetine or fluvoxamine (285 women [59.3%]; mean [SD] age, 58.7 [18.0] years), and 2898 receiving other SSRIs (1733 women [59.8%]; mean [SD] age, 64.7 [18.0] years) within a defined time frame. When compared with matched untreated control patients, relative risk (RR) of mortality was reduced among patients prescribed any SSRI (497 of 3401 [14.6%] vs 1130 of 6802 [16.6%]; RR, 0.92 [95% CI, 0.85-0.99]; adjusted P = .03); fluoxetine (46 of 470 [9.8%] vs 937 of 7050 [13.3%]; RR, 0.72 [95% CI, 0.54-0.97]; adjusted P = .03); and fluoxetine or fluvoxamine (48 of 481 [10.0%] vs 956 of 7215 [13.3%]; RR, 0.74 [95% CI, 0.55-0.99]; adjusted P = .04). The association between receiving any SSRI that is not fluoxetine or fluvoxamine and risk of death was not statistically significant (447 of 2898 [15.4%] vs 1474 of 8694 [17.0%]; RR, 0.92 [95% CI, 0.84-1.00]; adjusted P = .06).

CONCLUSIONS AND RELEVANCE

These results support evidence that SSRIs may be associated with reduced severity of COVID-19 reflected in the reduced RR of mortality. Further research and randomized clinical trials are needed to elucidate the effect of SSRIs generally, or more specifically of fluoxetine and fluvoxamine, on the severity of COVID-19 outcomes.

Sustained escitalopram administration affects glucose metabolism in the rat brain

Escitalopram is a selective serotonin reuptake inhibitor (SSRIs) antidepressant, drug that is currently used as first-line agents for the treatment of depression and it is also used in the treatment of other psychiatric disorders. The main goal of this study was to identify which brain areas are affected by escitalopram administration. This study was carried out on male Wistar rats that received escitalopram daily over 14 days and that were studied by 2-deoxy-2[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG)-PET on the last day of treatment. Computed tomography (CT) images were acquired immediately before each PET scan and the main effects of drug administration were elucidated by Statistical Parametric Mapping. The results obtained indicated that repeated exposure to escitalopram increased metabolic activity in the retrosplenial and posterior cingulate cortices, while it decreased such activity in the ventral hippocampus, cerebellum, brainstem and midbrain regions, including the raphe nuclei and ventral tegmental area. Therefore, repeated exposure to escitalopram alters the activity of several brain areas closely related to the serotonergic system, and previously identified as key regions in the antidepressant effect induced by SSRIs. Furthermore, some of the changes found, such as the dampened metabolism in the ventral tegmental area, are similar to changes that have been described after treating with other fast-acting antidepressant approaches.

Acute Neurofunctional Effects of Escitalopram in Pediatric Anxiety: A Double-Blind, Placebo-Controlled Trial

OBJECTIVE

Amygdala-ventrolateral prefrontal cortex (VLPFC) circuitry is disrupted in pediatric anxiety disorders, yet how selective serotonin reuptake inhibitors (SSRIs) affect this circuitry is unknown. We examined the impact of the SSRI escitalopram on functional connectivity (FC) within this circuit, and whether early FC changes predicted treatment response in adolescents with generalized anxiety disorder (GAD).

METHOD

Resting-state functional magnetic resonance (MR) images were acquired before and after 2 weeks of treatment in 41 adolescents with GAD (12-17 years of age) who received double-blind escitalopram or placebo for 8 weeks. Change in amygdala-based whole-brain FC and anxiety severity were analyzed.

RESULTS

Controlling for age, sex, and pretreatment anxiety, escitalopram increased amygdala-VLPFC connectivity compared to placebo (F = 17.79, p = .002 FWE-corrected). This early FC change predicted 76.7% of the variability in improvement trajectory in patients who received escitalopram (p < .001) but not placebo (p = .169); the predictive power of early amygdala-VLPFC FC change significantly differed between placebo and escitalopram (p = .013). Furthermore, this FC change predicted improvement better than baseline FC or clinical/demographic characteristics. Exploratory analyses of amygdala subfields' FC revealed connectivity of left basolateral amygdala (BLA) -VLPFC (F = 19.64, p < .001 FWE-corrected) and superficial amygdala-posterior cingulate cortex (F = 22.92, p = .001 FWE-corrected) were also increased by escitalopram, but only BLA-VLPFC FC predicted improvement in anxiety over 8 weeks of treatment.

CONCLUSION

In adolescents with GAD, escitalopram increased amygdala-prefrontal connectivity within the first 2 weeks of treatment, and the magnitude of this change predicted subsequent clinical improvement. Early normalization of amygdala-VLPFC circuitry might represent a useful tool for identifying future treatment responders as well as a promising biomarker for drug development.

CLINICAL TRIAL REGISTRATION INFORMATION

Neurofunctional Predictors of Escitalopram Treatment Response in Adolescents With Anxiety; https://www.clinicaltrials.gov/; NCT02818751.

Kir4.1 Dysfunction in the Pathophysiology of Depression: A Systematic Review

A serotonergic dysfunction has been largely postulated as the main cause of depression, mainly due to its effective response to drugs that increase the serotonergic tone, still currently the first therapeutic line in this mood disorder. However, other dysfunctional pathomechanisms are likely involved in the disorder, and this may in part explain why some individuals with depression are resistant to serotonergic therapies. Among these, emerging evidence suggests a role for the astrocytic inward rectifier potassium channel 4.1 (Kir4.1) as an important modulator of neuronal excitability and glutamate metabolism. To discuss the relationship between Kir4.1 dysfunction and depression, a systematic review was performed according to the PRISMA statement. Searches were conducted across PubMed, Scopus, and Web of Science by two independent reviewers. Twelve studies met the inclusion criteria, analyzing Kir4.1 relationships with depression, through in vitro, in vivo, and post-mortem investigations. Increasing, yet not conclusive, evidence suggests a potential pathogenic role for Kir4.1 upregulation in depression. However, the actual contribution in the diverse subtypes of the disorder and in the comorbid conditions, for example, the epilepsy-depression comorbidity, remain elusive. Further studies are needed to better define the clinical phenotype associated with Kir4.1 dysfunction in humans and the molecular mechanisms by which it contributes to depression and implications for future treatments.

Assessment of antidepressant-like effects of dextromethorphan on differential reinforcement of low-rate 72-s performance in rats

The effectiveness of ketamine for treatment-resistant depression along with several other clinical advantages, such as rapid onset and reduced adverse effects associated with serotonin transporter inhibition, has garnered interest in other similar acting psychedelics as novel antidepressant drugs. The antitussive dextromethorphan exhibits glutamate N-methyl-d-aspartate receptor antagonism, sigma-1 receptor agonism, and serotonin reuptake inhibition, which has exhibited antidepressant effects in limited human studies and animal models. The present study sought to further examine dextromethorphan using a differential reinforcement of low-rate 72-s schedule, which can be used to screen antidepressant drugs, in male and female rats. The tricyclic antidepressant drug imipramine and the psychostimulant d-amphetamine also were examined. Sex differences were not shown for baseline performance or for the drugs tested. Further, performance did not differ between the estrus and diestrus stages. Dextromethorphan alone and with quinidine produced an antidepressant-like effect by reducing the number of responses emitted, increasing the number of reinforcers earned, and shifting inter-response times to the right, although significant response suppression occurred at these doses. An antidepressant-like effect was shown with imipramine, but d-amphetamine increased the number of responses emitted and did not affect the number of reinforcers earned. The present findings provide additional support for antidepressant effects produced by dextromethorphan.

The selective serotonin reuptake inhibitors enhance the cytotoxicity of sorafenib in hepatocellular carcinoma cells

Sertraline and fluoxetine are the two most commonly used selective serotonin reuptake inhibitors (SSRIs) in the treatment of depression. Accumulating evidence has revealed that SSRIs can reduce the risk of hepatocellular carcinoma (HCC), but their therapeutic effects in HCC have not yet been elucidated. Previous studies have reported that sertraline and fluoxetine can suppress the growth of gastric carcinoma, melanoma and nonsmall cell lung cancers by inhibiting the mammalian target rapamycin (mTOR) activity. In this study, we found that sertraline and fluoxetine blocked the protein kinase B (AKT)/mTOR pathway and suppressed the growth of HCC cells in vitro, in xenografts and in diethylnitrosamine/carbon tetrachloride (DEN/CCL4)-induced primary liver mouse model. Sertraline and fluoxetine can synergize with sorafenib, the first approved standard therapy for advanced HCC, to inhibit the viability of HCC cells in vitro and in vivo. In addition, the combination of sorafenib and SSRIs synergistically inhibited the effects of the AKT/mTOR pathway. These results reveal novel therapeutic effects of a combination of SSRIs and sorafenib in HCC.

Pre-treatment allostatic load and metabolic dysregulation predict SSRI response in major depressive disorder: a preliminary report

BACKGROUND

Major depressive disorder (MDD) is associated with increased allostatic load (AL; a measure of physiological costs of repeated/chronic stress-responding) and metabolic dysregulation (MetD; a measure of metabolic health and precursor to many medical illnesses). Though AL and MetD are associated with poor somatic health outcomes, little is known regarding their relationship with antidepressant-treatment outcomes.

METHODS

We determined pre-treatment AL and MetD in 67 healthy controls and 34 unmedicated, medically healthy MDD subjects. Following this, MDD subjects completed 8-weeks of open-label selective serotonin reuptake inhibitor (SSRI) antidepressant treatment and were categorized as 'Responders' (⩾50% improvement in depression severity ratings) or 'Non-responders' (<50% improvement). Logistic and linear regressions were performed to determine if pre-treatment AL or MetD scores predicted SSRI-response. Secondary analyses examined cross-sectional differences between MDD and control groups.

RESULTS

Pre-treatment AL and MetD scores significantly predicted continuous antidepressant response (i.e. absolute decreases in depression severity ratings) (p = 0.012 and 0.014, respectively), as well as post-treatment status as a Responder or Non-responder (p = 0.022 and 0.040, respectively), such that higher pre-treatment AL and MetD were associated with poorer SSRI-treatment outcomes. Pre-treatment AL and MetD of Responders were similar to Controls, while those of Non-responders were significantly higher than both Responders (p = 0.025 and 0.033, respectively) and Controls (p = 0.039 and 0.001, respectively).

CONCLUSIONS

These preliminary findings suggest that indices of metabolic and hypothalamic-pituitary-adrenal-axis dysregulation are associated with poorer SSRI-treatment response. To our knowledge, this is the first study to demonstrate that these markers of medical disease risk also predict poorer antidepressant outcomes.

Amplification by tramadol of PGD2-induced osteoprotegerin synthesis in osteoblasts: Involvement of μ-opioid receptor and 5-HT transporter

Tramadol, a weak μ-opioid receptor (MOR) agonist with inhibitory effects on the reuptake of serotonin (5-hydroxytryptamine; 5-HT) and norepinephrine, is an effective analgesic to chronic pains. Osteoprotegerin produced by osteoblasts is essential for bone remodeling to suppress osteoclastic bone resorption. We previously reported that prostaglandin D₂ (PGD₂) induces osteoprotegerin synthesis whereby p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) are involved in osteoblast-like MC3T3-E1 cells. Herein, we investigated the mechanism underlying the effect of tramadol on the PGD₂-induced osteoprotegerin synthesis in these cells. Tramadol enhanced the PGD₂-induced release and mRNA expression of osteoprotegerin. Naloxone, a MOR antagonist, reduced the amplification by tramadol of the PGD₂-stimulated osteoprotegerin release. Not the selective norepinephrine reuptake inhibitor reboxetine but the selective serotonin reuptake inhibitors fluvoxamine and sertraline upregulated the PGD₂-induced osteoprotegerin release, which was further amplified by morphine. Tramadol enhanced PGD₂-stimulated phosphorylation of p38 MAP kinase and SAPK/JNK, but not p44/p42 MAP kinase. Both SB203580 and SP600125 suppressed the tramadol effect to enhance the PGD₂-stimulated osteoprotegerin release. Tramadol enhanced the PGE₂-induced osteoprotegerin release as well as PGD₂. These results suggest that tramadol amplifies the PGD₂-induced osteoprotegerin synthesis at the upstream of p38 MAP kinase and SAPK/JNK in the involvement of both MOR and 5-HT transporter in osteoblasts.