Mesocortical BDNF signaling mediates antidepressive-like effects of lithium

Brain region-specific roles of brain-derived neurotrophic factor in social stress-induced depressive-like behavior

Brain-derived neurotrophic factor is a key factor in stress adaptation and avoidance of a social stress behavioral response. Recent studies have shown that brain-derived neurotrophic factor expression in stressed mice is brain region-specific, particularly involving the corticolimbic system, including the ventral tegmental area, nucleus accumbens, prefrontal cortex, amygdala, and hippocampus. Determining how brain-derived neurotrophic factor participates in stress processing in different brain regions will deepen our understanding of social stress psychopathology. In this review, we discuss the expression and regulation of brain-derived neurotrophic factor in stress-sensitive brain regions closely related to the pathophysiology of depression. We focused on associated molecular pathways and neural circuits, with special attention to the brain-derived neurotrophic factor-tropomyosin receptor kinase B signaling pathway and the ventral tegmental area-nucleus accumbens dopamine circuit. We determined that stress-induced alterations in brain-derived neurotrophic factor levels are likely related to the nature, severity, and duration of stress, especially in the above-mentioned brain regions of the corticolimbic system. Therefore, BDNF might be a biological indicator regulating stress-related processes in various brain regions.

α4 nicotinic receptors on GABAergic neurons mediate a cholinergic analgesic circuit in the substantia nigra pars reticulata

Nicotinic acetylcholine receptors (nAChRs) regulate pain pathways with various outcomes depending on receptor subtypes, neuron types, and locations. But it remains unknown whether α4β2 nAChRs abundantly expressed in the substantia nigra pars reticulata (SNr) have potential to mitigate hyperalgesia in pain states. We observed that injection of nAChR antagonists into the SNr reduced pain thresholds in naïve mice, whereas injection of nAChR agonists into the SNr relieved hyperalgesia in mice, subjected to capsaicin injection into the lower hind leg, spinal nerve injury, chronic constriction injury, or chronic nicotine exposure. The analgesic effects of nAChR agonists were mimicked by optogenetic stimulation of cholinergic inputs from the pedunculopontine nucleus (PPN) to the SNr, but attenuated upon downregulation of α4 nAChRs on SNr GABAergic neurons and injection of dihydro-β-erythroidine into the SNr. Chronic nicotine-induced hyperalgesia depended on α4 nAChRs in SNr GABAergic neurons and was associated with the reduction of ACh release in the SNr. Either activation of α4 nAChRs in the SNr or optogenetic stimulation of the PPN-SNr cholinergic projection mitigated chronic nicotine-induced hyperalgesia. Interestingly, mechanical stimulation-induced ACh release was significantly attenuated in mice subjected to either capsaicin injection into the lower hind leg or SNI. These results suggest that α4 nAChRs on GABAergic neurons mediate a cholinergic analgesic circuit in the SNr, and these receptors may be effective therapeutic targets to relieve hyperalgesia in acute and chronic pain, and chronic nicotine exposure.

Multiple integrated social stress induces depressive-like behavioral and neural adaptations in female C57BL/6J mice

Despite women representing most of those affected by major depression, preclinical studies have focused almost exclusively on male subjects, partially due to a lack of ideal animal paradigms. As the persistent need regarding the sex balance of neuroscience research and female-specific pathology of mental disorders surges, the establishment of natural etiology-based and systematically validated animal paradigms for depression with female subjects becomes an urgent scientific problem. This study aims to establish, characterize, and validate a "Multiple Integrated Social Stress (MISS)" model of depression in female C57BL/6J mice by manipulating and integrating daily social stressors that females are experiencing. Female C57BL/6J mice randomly experienced social competition failure in tube test, modified vicarious social defeat stress, unescapable overcrowding stress followed by social isolation on each day, for ten consecutive days. Compared with their controls, female MISS mice exhibited a relatively decreased preference for social interaction and sucrose, along with increased immobility in the tail suspension test, which could last for at least one month. These MISS mice also exhibited increased levels of blood serum corticosterone, interleukin-6 L and 1β. In the pharmacological experiment, MISS-induced dysfunctions in social interaction, sucrose preference, and tail suspension tests were amended by systematically administrating a single dose of sub-anesthetic ketamine, a rapid-onset antidepressant. Compared with controls, MISS females exhibited decreased c-Fos activation in their anterior cingulate cortex, prefrontal cortex, nucleus accumbens and some other depression-related brain regions. Furthermore, 24 h after the last exposure to the paradigm, MISS mice demonstrated a decreased center zone time in the open field test and decreased open arm time in the elevated plus-maze test, indicating anxiety-like behavioral phenotypes. Interestingly, MISS mice developed an excessive nesting ability, suggesting a likely behavioral phenotype of obsessive-compulsive disorder. These data showed that the MISS paradigm was sufficient to generate pathological profiles in female mice to mimic core symptoms, serum biochemistry and neural adaptations of depression in clinical patients. The present study offers a multiple integrated natural etiology-based animal model tool for studying female stress susceptibility.

Myelin-associated oligodendrocytic basic protein-dependent myelin repair confers the long-lasting antidepressant effect of ketamine

Ketamine exhibits rapid and sustained antidepressant effects. As decreased myelination has been linked to depression pathology, changes in myelination may be a pivotal mechanism underlying ketamine's long-lasting antidepressant effects. Although ketamine has a long-lasting facilitating effect on myelination, the precise roles of myelination in ketamine's sustained antidepressant effects remain unknown. In this study, we employed spatial transcriptomics (ST) to examine ketamine's lasting effects in the medial prefrontal cortex (mPFC) and hippocampus of mice subjected to chronic social defeat stress and identified several differentially expressed myelin-related genes. Ketamine's ability to restore impaired myelination in the brain by promoting the differentiation of oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes was demonstrated. Moreover, we showed that inhibiting the expression of myelin-associated oligodendrocytic basic protein (Mobp) blocked ketamine's long-lasting antidepressant effects. We also illustrated that α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) signaling mediated ketamine's facilitation on myelination. In addition, we found that the (R)-stereoisomer of ketamine showed stronger effects on myelination than (S)-ketamine, which may explain its longer-lasting antidepressant effects. These findings reveal novel mechanisms underlying the sustained antidepressant effects of ketamine and the differences in antidepressant effects between (R)-ketamine and (S)-ketamine, providing new insights into the role of myelination in antidepressant mechanisms.

Impaired Ventrolateral Periaqueductal Gray-Ventral Tegmental area Pathway Contributes to Chronic Pain-Induced Depression-Like Behavior in Mice

Chronic pain conditions within clinical populations are correlated with a high incidence of depression, and researchers have reported their high rate of comorbidity. Clinically, chronic pain worsens the prevalence of depression, and depression increases the risk of chronic pain. Individuals suffering from chronic pain and depression respond poorly to available medications, and the mechanisms underlying the comorbidity of chronic pain and depression remain unknown. We used spinal nerve ligation (SNL) in a mouse model to induce comorbid pain and depression. We combined behavioral tests, electrophysiological recordings, pharmacological manipulation, and chemogenetic approaches to investigate the neurocircuitry mechanisms of comorbid pain and depression. SNL elicited tactile hypersensitivity and depression-like behavior, accompanied by increased and decreased glutamatergic transmission in dorsal horn neurons and midbrain ventrolateral periaqueductal gray (vlPAG) neurons, respectively. Intrathecal injection of lidocaine, a sodium channel blocker, and gabapentin ameliorated SNL-induced tactile hypersensitivity and neuroplastic changes in the dorsal horn but not depression-like behavior and neuroplastic alterations in the vlPAG. Pharmacological lesion of vlPAG glutamatergic neurons induced tactile hypersensitivity and depression-like behavior. Chemogenetic activation of the vlPAG-rostral ventromedial medulla (RVM) pathway ameliorated SNL-induced tactile hypersensitivity but not SNL-elicited depression-like behavior. However, chemogenetic activation of the vlPAG-ventral tegmental area (VTA) pathway alleviated SNL-produced depression-like behavior but not SNL-induced tactile hypersensitivity. Our study demonstrated that the underlying mechanisms of comorbidity in which the vlPAG acts as a gating hub for transferring pain to depression. Tactile hypersensitivity could be attributed to dysfunction of the vlPAG-RVM pathway, while impairment of the vlPAG-VTA pathway contributed to depression-like behavior.

Low-dose lithium mono- and adjunctive therapies improve MK-801-induced cognitive impairment and schizophrenia-like behavior in mice - Evidence from altered prefrontal lobe Ca2+ activity

BACKGROUND

Few studies have evaluated lithium either as monotherapy or in combination with anti-psychotic agents to improve cognition in murine models of schizophrenia.

METHODS

Visualization of Ca²⁺ activity in the prefrontal cortex was used to characterize brain neural activity. Novel object recognition (NOR), Morris water maze (MWM), and fear conditioning (FCT) tests were used to characterize cognitive performance; while pre-pulse inhibition (PPI), elevated plus maze (EPM) and the open field test (OFT) were used to characterize schizophrenia-like behavior.

RESULTS

A 28-day course of low-dose lithium (human equivalent dose of 250 mg/day) combined with moderate-dose quetiapine (human equivalent dose of 600 mg/day) improved Ca²⁺ ratio by 70.10 %, PPI by 69.28 %, NOR by 70.09 %, MWM by 71.28 %, FCT by 68.56 %, EPM by 70.95 % and OFT by 75.23 % compared to the results of positive controls. Unexpectedly, moderate-dose lithium (human equivalent dose of 500 mg/day) used either as monotherapy or as an adjunct with quetiapine worsened Ca²⁺ activity, PPI, MWM, FCT, EPM, and OPT.

LIMITATIONS

Our study cannot explain the contrasting positive and negative effects of low-dose and moderate-dose lithium, respectively, when used either as monotherapies or as adjuncts. Further studies, especially Western blotting, may reveal molecular mechanisms of action.

CONCLUSIONS

Low-dose lithium (human equivalent dose of 250 mg/day) combined with moderate-dose quetiapine (human equivalent dose of 600 mg/day) provided the best improvements. Furthermore, benefits persisted for 14 days post-treatment. Our data provide directions for further research of therapeutic alternatives to mitigate schizophrenia-related cognopathy.

Appropriate Macronutrients or Mineral Elements Are Beneficial to Improve Depression and Reduce the Risk of Depression

Depression is a common mental disorder that seriously affects the quality of life and leads to an increasing global suicide rate. Macro, micro, and trace elements are the main components that maintain normal physiological functions of the brain. Depression is manifested in abnormal brain functions, which are considered to be tightly related to the imbalance of elements. Elements associated with depression include glucose, fatty acids, amino acids, and mineral elements such as lithium, zinc, magnesium, copper, iron, and selenium. To explore the relationship between these elements and depression, the main literature in the last decade was mainly searched and summarized on PubMed, Google Scholar, Scopus, Web of Science, and other electronic databases with the keywords "depression, sugar, fat, protein, lithium, zinc, magnesium, copper, iron, and selenium". These elements aggravate or alleviate depression by regulating a series of physiological processes, including the transmission of neural signals, inflammation, oxidative stress, neurogenesis, and synaptic plasticity, which thus affect the expression or activity of physiological components such as neurotransmitters, neurotrophic factors, receptors, cytokines, and ion-binding proteins in the body. For example, excessive fat intake can lead to depression, with possible mechanisms including inflammation, increased oxidative stress, reduced synaptic plasticity, and decreased expression of 5-Hydroxytryptamine (5-HT), Brain Derived Neurotrophic Factor (BDNF), Postsynaptic density protein 95(PSD-95), etc. Supplementing mineral elements, such as selenium, zinc, magnesium, or lithium as a psychotropic medication is mostly used as an auxiliary method to improve depression with other antidepressants. In general, appropriate nutritional elements are essential to treat depression and prevent the risk of depression.

Lithium engages autophagy for neuroprotection and neuroplasticity: translational evidence for therapy

Here an overview is provided on therapeutic/neuroprotective effects of Lithium (Li⁺) in neurodegenerative and psychiatric disorders focusing on the conspicuous action of Li⁺ through autophagy. The effects on the autophagy machinery remain the key molecular mechanisms to explain the protective effects of Li⁺ for neurodegenerative diseases, offering potential therapeutic strategies for the treatment of neuropsychiatric disorders and emphasizes a crossroad linking autophagy, neurodegenerative disorders, and mood stabilization. Sensitization by psychostimulants points to several mechanisms involved in psychopathology, most also crucial in neurodegenerative disorders. Evidence shows the involvement of autophagy and metabotropic Glutamate receptors-5 (mGluR5) in neurodegeneration due to methamphetamine neurotoxicity as well as in neuroprotection, both in vitro and in vivo models. More recently, Li⁺ was shown to modulate autophagy through its action on mGluR5, thus pointing to an additional way of autophagy engagement by Li⁺ and to a substantial role of mGluR5 in neuroprotection related to neural e neuropsychiatry diseases. We propose Li⁺ engagement of autophagy through the canonical mechanisms of autophagy machinery and through the intermediary of mGluR5.

Mood and behavior regulation: interaction of lithium and dopaminergic system

Lithium is one of the most effect mood-stabilizing drugs prescribed especially for bipolar disorder. Lithium has wide range effects on different molecular factors and neural transmission including dopaminergic signaling. On the other hand, mesolimbic and mesocortical dopaminergic signaling is significantly involved in the pathophysiology of neuropsychiatric disorders. This review article aims to study lithium therapeutic mechanisms, dopaminergic signaling, and the interaction of lithium and dopamine. We concluded that acute and chronic lithium treatments often reduce dopamine synthesis and level in the brain. However, some studies have reported conflicting results following lithium treatment, especially chronic treatment. The dosage, duration, and type of lithium administration, and the brain region selected for measuring dopamine level were not significant differences in different chronic treatments used in previous studies. It was suggested that lithium has various mechanisms affecting dopaminergic signaling and mood, and that many molecular factors can be involved, including brain-derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB), β-catenin, protein kinase B (Akt), and glycogen synthase kinase-3 beta (GSK-3β). Thus, molecular effects of lithium can be the most important mechanisms of lithium that also alter neural transmissions including dopaminergic signaling in mesolimbic and mesocortical pathways.

VTA-NAc glutaminergic projection involves in the regulation of pain and pain-related anxiety

Background

Besides the established role of dopamine neurons and projections in nociceptive stimuli, the involvement of ventral tegmental area (VTA) glutamatergic projections to nucleus accumbens (NAc) in pain remains unknown. In the present study, we aimed to examine the role of VTA glutamatergic projections to NAc in painful stimuli and its related behavioral changes.

Methods

Unilateral chronic constrictive injury (CCI) of sciatic nerve or intraplantar hind paw injections (i.pl.) of complete Freund's adjuvant (CFA) were used to develop pathological pain models in wild-type and VGluT2-Cre mice. The involvement of VTA glutamatergic neurons with projections to NAc in CCI-induced pain model was noted by c-Fos labeling and firing rate recordings. Pain response and pain-related behavior changes to the artificial manipulation of the VTA glutamatergic projections to NAc were observed by Hargreaves tests, von Frey tests, open field tests, elevated maze tests, and sucrose preference tests.

Results

Glutamatergic neurons in VTA had efferent inputs to shell area of the NAc. The CCI pain model significantly increased neuronal activity and firing rate in VTA glutamate neurons with projections to NAc. The photoinhibition of these glutamatergic projections relieved CCI-induced neuropathic pain and CFA-induced acute and chronic inflammatory pain. Moreover, pathological neuropathic pain-induced anxiety and less sucrose preference were also relieved by inhibiting the VTA glutamatergic projections to NAc.

Conclusion

Together, glutamatergic inputs from VTA to NAc contribute to chronic neuropathic and inflammatory pain and pain-related anxiety and depressive behaviors, providing a mechanism for developing novel therapeutic methods.

Lithium therapy subdues neuroinflammation to maintain pyramidal cells arborization and rescues neurobehavioural impairments in ovariectomized rats

Oestrogen deprivation as a consequence of menopause alters the brain neuronal circuit and results in the development of neurobehavioural symptoms later. Hormone replacement therapy to some extent helps to overcome these abnormalities but is associated with various adverse events. Lithium therapy is being used to manage multiple neuropsychiatric disorders and is reported to maintain structural synaptic plasticity, suppress neuroinflammation, and promote adult neurogenesis. The present study examined the effect of lithium treatment on the neurobehavioural impairments in ovariectomized rat model mimicking clinical postmenopausal condition. A protective effect of lithium treatment was observed on the reconsolidation of spatial and recognition memory along with depression-like behaviour in ovariectomized rats. The Golgi-Cox staining revealed increased dendritic length and spine density in the pyramidal neurons of the CA1 region of the hippocampus, layer V of the somatosensory cortex, and layer II/III of the prefrontal cortex in the treated group. A significant reduction in pro-inflammatory markers, Il2, II6, and Il1b, was observed in the hippocampus, somatosensory cortex, and prefrontal cortex following lithium treatment. mRNA expression studies of Gfap and Pparg, along with histopathological analysis, suggested reactive astrogliosis to be a major contributor of neuroinflammation in ovariectomized rats that was normalized following lithium treatment. Further, the treatment inhibited Gsk-3β activity and maintained the normal level of β-catenin, CREB, and BDNF. The results revealed a defensive role of lithium against ovariectomy-induced neurobehavioural impairments, thus suggesting it to be a potential therapeutic agent for managing postmenopausal neurological symptoms.

Functional Contribution of the Medial Prefrontal Circuitry in Major Depressive Disorder and Stress-Induced Depressive-Like Behaviors

Despite decades of research on the neurobiology of major depressive disorder (MDD), the mechanisms underlying its expression remain unknown. The medial prefrontal cortex (mPFC), a hub region involved in emotional processing and stress response elaboration, is highly impacted in MDD patients and animal models of chronic stress. Recent advances showed alterations in the morphology and activity of mPFC neurons along with profound changes in their transcriptional programs. Studies at the circuitry level highlighted the relevance of deciphering the contributions of the distinct prefrontal circuits in the elaboration of adapted and maladapted behavioral responses in the context of chronic stress. Interestingly, MDD presents a sexual dimorphism, a feature recognized in the molecular field but understudied on the circuit level. This review examines the recent literature and summarizes the contribution of the mPFC circuitry in the expression of MDD in males and females along with the morphological and functional alterations that change the activity of these neuronal circuits in human MDD and animal models of depressive-like behaviors.

Plasma exosomes from depression ameliorate inflammation-induced depressive-like behaviors via sigma-1 receptor delivery

A growing body of studies indicated that exosomes are one of vital players in pathological process of neuropsychiatric diseases, but their role in major depressive disorder (MDD) remains poorly understood. Here we purified plasma exosomes from depression including lipopolysaccharide (LPS)-challenged depression, chronic restraint stress (CRS)-induced depression, MDD subjects, and from control mice or volunteers. The therapeutic effect of these exogenous exosomes was assessed utilizing behavioral tests and biochemical approaches in the LPS-caused depression or microglial BV2 cells. The expression of exosomal sigma-1 receptor (Sig-1R) was evaluated by western blotting. The role of Sig-1R in the biological function of exosomes was determined using Sig-1R knockout mice and HEK 293 cells. Our results revealed that injection of exosomes from depression models or patients rather than normal controls significantly ameliorated depressive-like behaviors, deficiency of BDNF expression and neuro-inflammation in LPS-challenged mice. In addition, co-culture with exosomes from depression models or patients instead of from controls prevented LPS-induced inflammation responses in microglial BV2 cells. Moreover, Sig-1R was demonstrated for the first time to significantly be enriched in exosomes from depression models or patients compared with that from normal controls. However, Sig-1R null exosomes no longer emerged antidepressant-like action in LPS-challenged mice. Thus, we demonstrated that plasma exosomes from depression exerted antidepressant-like effects in a Sig-1R dependent manner in the LPS-induced depression. This work improves our understanding of the exosomes in depression, suggesting a novel exosomes-based approach for MDD treatment.

lncRNA MIR155HG Alleviates Depression-Like Behaviors in Mice by Regulating the miR-155/BDNF Axis

Depression is one of most common psychiatric disorders, and the detailed molecular mechanism remains to be fully elucidated. Brain-derived neurotrophic factor (BDNF) is a critical neurotrophic factor that is decreased and closely involved in the development of depression. Noncoding RNAs are central regulators of cellular activities that modulate target genes. However, the roles of long noncoding RNA (lncRNA) MIR155HG and miRNA-155 (miR-155) in the pathophysiology of depression are unclear. In the present study, we aimed to explore the effects of lncRNA MIR155HG and miR-155 on the development of depression and uncover the underlying molecular mechanism. Real-time quantitative polymerase chain reaction was used to examine the expression of MIR155HG and miR-155. Western blotting was applied to measure the expression of BDNF. A luciferase reporter assay was utilized to determine the regulatory relationship between MIR155HG and miR-155. Our current work found that lncRNA MIR155HG and BDNF levels decreased while miR-155 levels increased in the hippocampal region of CUMS (chronic unpredictable mild stress) mice, a well-accepted mouse model of depression. Moreover, MIR155HG rescued while miR-155 exacerbated the depression-like behaviors of CUMS mice. Through bioinformatics analysis and luciferase reporter assays, we found that MIR155HG directly bound to and negatively modulated the expression of miR-155. Moreover, increased miR-155 was found to repress the expression of BDNF, a critical neurotrophic factor that has been reported to alleviate the depression-like behaviors of CUMS mice. Our present study revealed that lncRNA MIR155HG protected CUMS mice by regulating the miR-155/BDNF axis. Our study aimed to understand the pathophysiology of depression and provided potential therapeutic targets to diagnose and treat depression.