A new perspective on depression and neuroinflammation: Non-coding RNA

Microglial cannabinoid receptor 2 and epigenetic regulation: Implications for the treatment of depression

Depression, often stress-induced, is closely related to neuroinflammation, in which microglia, the brain's immune cells, are the leading players. Microglia shift between a quiescent and an active state, promoting both pro- and anti-inflammatory responses. Cannabinoid type 2 (CB2) receptor encoded by the CNR2 gene is a key player to modulate inflammatory activity. CB2 receptor is highly controlled at the epigenetic level, especially in response to stressful stimuli, positioning it between stress, neuroinflammation, and depression. The following review addresses how epigenetic regulation of CNR2 expression affects depression and the dissection, further, of molecular pathways driving neuroinflammation-related depressive states. The present study emphasizes the therapeutic potential of CB2 receptor agonists that selectively interact with activated microglia and opens a new avenue for the treatment of depression associated with neuroinflammation. The review, therefore, provides a framework of underlying mechanisms for developing novel therapeutic strategies that focus on relieving symptoms by modulating the neuroinflammatory response. Finally, this review underlines the possibilities of therapeutic interventions taking into account CB2 receptors in combating depression.

Immunity in neuromodulation: probing neural and immune pathways in brain disorders

Immunity finely regulates brain function. It is directly involved in the pathological processes of neurodegenerative diseases such as Parkinson's and Alzheimer's disease, post-stroke conditions, multiple sclerosis, traumatic brain injury, and psychiatric disorders (mood disorders, major depressive disorder (MDD), anxiety disorders, psychosis disorders and schizophrenia, and neurodevelopmental disorders (NDD)). Neuromodulation is currently a leading therapeutic strategy for the treatment of these disorders, but little is yet known about its immune impact on neuronal function and its precise beneficial or harmful consequences. We review relevant clinical and preclinical studies and identify several specific immune modifications. These data not only provide insights into how neuromodulation acts to optimize immune-brain interactions, but also pave the way for a better understanding of these interactions in pathological processes.

Effects of the LINC00641/miR-323a-3p/EIF4G2 axis on behaviors and brain monoamine neurotransmitters in chronic unpredictable mild stress mice

OBJECTIVE

This paper aimed to probe the role of the LINC00641/miR-323a-3p/EIF4G2 axis in regulating behavioral and brain monoamine neurotransmitter levels in a mouse model of depression induced by chronic unpredictable mild stress (CUMS).

METHODS

A CUMS-induced depression model was established in mice. A series of behavioral tests, comprising the sucrose preference, tail suspension, as well as forced swimming tests, were conducted. Levels of LINC00641, miR-323a-3p, and EIF4G2 in hippocampal tissues were measured. Biochemical indices, including 5-HT, NE, and DA, were analyzed. Hippocampal neuron structure and apoptosis were evaluated. The targeting relationship among LINC00641, miR-323a-3p, and EIF4G2 was validated experimentally.

RESULTS

CUMS mice exhibited reduced sucrose preference, prolonged immobilization time in behavioral tests, decreased 5-HT, NE, and DA levels, and increased hippocampal neuron apoptosis. Overexpression of LINC00641 or knockdown of miR-323a-3p significantly alleviated depression-like behaviors and restored monoamine neurotransmitter levels. LINC00641 regulated EIF4G2 expression by targeting miR-323a-3p, while miR-323a-3p and EIF4G2 also modulated depression through LINC00641.

CONCLUSION

Upregulation of LINC00641 improves depression-like behaviors and enhances monoamine neurotransmission in CUMS mice via the miR-323a-3p/EIF4G2 axis, underscoring its potent as a therapeutic target for depression.

Effect of the MIAT/microRNA 130a-3p/Pdgfra axis on retinal microglia activation in mice with chronic retinal hypoperfusion injury

This paper aimed to address the function of the MIAT/miR-130a-3p/Pdgfra axis in retinal microglia activation in chronic retinal hypoperfusion injury (CRHI) mice. CRHI mouse models were constructed through bilateral common carotid artery occlusion (BCCAO). MIAT, Pdgfra, and miR-130a-3p expression levels in retinal tissues and cells were assessed. The expression of genes linked to the Nlrp3 inflammatory vesicle pathway (Gsdmd, Asc, Tlr4, Casp1, and Casp8) was assessed. Serum contents of inflammatory cytokines IL-18 and IL-1β were determined. Iba-1/Casp1/Csdmd expression was tested. Moreover, the interplay between miR-130a-3p and MIAT, as well as associations between Pdgfra and miR-130a-3p were verified. MIAT and Pdgfra expression was enhanced and miR-130a-3p diminished in BCCAO mouse models. MIAT downregulation reduced IL-18 and IL-1β contents and repressed microglia activation in BCCAO mice, and histopathological results also displayed raised mouse retinal thickness and diminished apoptosis. Both inhibiting miR-130a-3p and overexpressing Pdgfra can reverse the delayed effects of MIAT interference on CRHI. MIAT regulates miR-130a-3p to stimulate the expression of Pdgfra, thereby further promoting retinal microglia activation in CRHI mice. This provides potential targets for the development of innovative treatment approaches for retinal disorders.

Circular RNAs in neurological conditions - computational identification, functional validation, and potential clinical applications

Non-coding RNAs (ncRNAs) have gained significant attention in recent years due to advancements in biotechnology, particularly high-throughput total RNA sequencing. These developments have led to new understandings of non-coding biology, revealing that approximately 80% of non-coding regions in the genome possesses biochemical functionality. Among ncRNAs, circular RNAs (circRNAs), first identified in 1976, have emerged as a prominent research field. CircRNAs are abundant in most human cell types, evolutionary conserved, highly stable, and formed by back-splicing events which generate covalently closed ends. Notably, circRNAs exhibit high expression levels in neural tissue and perform diverse biochemical functions, including acting as molecular sponges for microRNAs, interacting with RNA-binding proteins to regulate their availability and activity, modulating transcription and splicing, and even translating into functional peptides in some cases. Recent advancements in computational and experimental methods have enhanced our ability to identify and validate circRNAs, providing valuable insights into their biological roles. This review focuses on recent developments in circRNA research as they related to neuropsychiatric and neurodegenerative conditions. We also explore their potential applications in clinical diagnostics, therapeutics, and future research directions. CircRNAs remain a relatively underexplored area of non-coding biology, particularly in the context of neurological disorders. However, emerging evidence supports their role as critical players in the etiology and molecular mechanisms of conditions such as schizophrenia, bipolar disorder, major depressive disorder, Alzheimer's disease, and Parkinson's disease. These findings suggest that circRNAs may provide a novel framework contributing to the molecular dysfunctions underpinning these complex neurological conditions.

Epigenetic Modifications and Neuroplasticity in the Pathogenesis of Depression: A Focus on Early Life Stress

Major depressive disorder (MDD) is a debilitating mental illness, and it is considered to be one of the leading causes of disability globally. The etiology of MDD is multifactorial, involving an interplay between biological, psychological, and social factors. Early life represents a critical period for development. Exposure to adverse childhood experiences is a major contributor to the global burden of disease and disability, doubling the risk of developing MDD later in life. Evidence suggests that stressful events experienced during that timeframe play a major role in the emergence of MDD, leading to epigenetic modifications, which might, in turn, influence brain structure, function, and behavior. Neuroplasticity seems to be a primary pathogenetic mechanism of MDD, and, similarly to epigenetic mechanisms, it is particularly sensitive to stress in the early postnatal period. In this review, we will collect and discuss recent studies supporting the role of epigenetics and neuroplasticity in the pathogenesis of MDD, with a focus on early life stress (ELS). We believe that understanding the epigenetic mechanisms by which ELS affects neuroplasticity offers potential pathways for identifying novel therapeutic targets for MDD, ultimately aiming to improve treatment outcomes for this debilitating disorder.

Carvacrol alleviates CUMS-induced depressive-like behaviors and cognitive impairment by reducing oxidative stress and neuroinflammation in mice

The present study aimed to evaluate the protective potential of carvacrol against depressive-like behavior and cognitive impairment prompted by chronic unpredictable mild stress (CUMS) in mice. The animals were divided into six groups: Control (non-stressed), CARV (carvacrol at 50 mg/kg, p.o.), FLU (fluoxetine at 10 mg/kg, p.o.), CUMS (stressed), CUMS + CARV and CUMS + FLU, and the groups with CUMS were subjected to different stressors for 28 days. After treatment, mice underwent behavioral testing (open field, forced swimming, sucrose preference, social interaction, novel object recognition and Y-maze) and brain areas were removed for oxidative stress (MDA, nitrite/nitrate and GSH levels) and cytokine (IL-1β and TNF-α) content assays. The results revealed that CARV administration reversed depressive-like behavior and significantly ameliorated the cognitive deficit induced by CUMS, as well as was able to attenuate oxidative stress (decreased MDA and nitrite/nitrate levels and increased GSH levels). In addition, a significant reduction in hippocampal IL-1β and TNF-α levels was observed, demonstrating a potential anti-neuroinflammatory activity. Taken together, the antioxidant and anti-inflammatory activities observed in this study indicate that CARV is a promising drug for antidepressant treatment.

Aging, sex, metabolic and life experience factors: Contributions to neuro-inflammaging in Alzheimer's disease research

Alzheimer's disease (AD) is prevalent around the world, yet our understanding of the disease is still very limited. Recent work suggests that the cornerstone of AD may include the inflammation that accompanies it. Failure of a normal pro-inflammatory immune response to resolve may lead to persistent central inflammation that contributes to unsuccessful clearance of amyloid-beta plaques as they form, neuronal death, and ultimately cognitive decline. Individual metabolic, and dietary (lipid) profiles can differentially regulate this inflammatory process with aging, obesity, poor diet, early life stress and other inflammatory factors contributing to a greater risk of developing AD. Here, we integrate evidence for the interface between these factors, and how they contribute to a pro-inflammatory brain milieu. In particular, we discuss the importance of appropriate polyunsaturated fatty acids (PUFA) in the diet for the metabolism of specialised pro-resolving mediators (SPMs); raising the possibility for dietary strategies to improve AD outlook.

Deciphering the therapeutic potential of SheXiangXinTongNing: Interplay between gut microbiota and brain metabolomics in a CUMS mice model, with a focus on tryptophan metabolism

Depression, a prevalent and multifaceted mental disorder, has emerged as a significant public health concern due to its escalating prevalence and heightened risk of severe suicidality. Given its profound impact, the imperative for preventing and intervening in depression is paramount. Substantial evidence underscores intricate connections between depression and cardiovascular health. SheXiangXinTongNing (XTN), a recognized traditional Chinese medicine for treating Coronary Heart Disease (CHD), prompted our exploration into its antidepressant effects and underlying mechanisms. In this investigation, we assessed XTN's antidepressant potential using the chronic unpredictable mild stress (CUMS) mice model and behavioral tests. Employing network pharmacology, we delved into the intricate mechanisms at play. We characterized the microbial composition and function in CUMS mice, both with and without XTN treatment, utilizing 16S rRNA sequencing and metabolomics analysis. The joint analysis of these results via Cytoscape identified pivotal metabolic pathways. In the realm of network pharmacology, XTN administration exhibited antidepressant effects by modulating pathways such as IL-17, neuroactive ligand-receptor interaction, PI3K-Akt, cAMP, calcium, and dopamine synapse signaling pathways. Our findings revealed that XTN significantly mitigated depression-like symptoms and cognitive deficits in CUMS mice by inhibiting neuroinflammation and pyroptosis. Furthermore, 16S rRNA sequencing unveiled that XTN increased the alpha-diversity and beta-diversity of the gut microbiome in CUMS mice. Metabolomics analysis identified brain metabolites crucial for distinguishing between the CUMS and CUMS+XTN groups, with a focus on pathways like Tryptophan metabolism and Linoleic acid metabolism. Notably, specific bacterial families, including Alloprevotella, Helicobacter, Allobaculum, and Clostridia, exhibited robust co-occurring relationships with brain tryptophan metabolomics, hinting at the potential mediating role of gut microbiome alterations and metabolites in the efficacy of XTN treatment. In conclusion, our study unveils modifications in microbial compositions and metabolic functions may be pivotal in understanding the response to XTN treatment, offering novel insights into the mechanisms underpinning the efficacy of antidepressants.

Areca Thirteen Pill Improves Depression in Rat by Modulation of the Chemokine/Chemokine Receptor Axis

Depressive disorder is a severe and complex mental illness. There are a few anti-depressive medications that can reduce depressive symptoms, but with adverse or side effects. GaoYou-13 (GY-13), commonly known as Areca Thirteen Pill, is a traditional medicine for depression treatment with significant clinical impact. However, the molecular mechanism of GY-13 has not been fully elucidated. This study aimed to explore and explain the action and mechanism of GY-13 in treatment for depression. SD male rats were stimulated differently daily for 42 days to construct a depression rat model and divided into six groups: the control, CUMS model, GY-13L, GY-13 M, GY-13H, and FLUO. The body weight of was measured on day 7, 14, 21, 28, 35, and 42 or different days, and the behavioral tests (Open-field test, Sucrose preference test, Morris water maze) were made alongside. After the rats were decapitated, the rat brains were stained with Nissl or H&E dyes. The serums of TNF-α and IL-1β were tested. The protein of p-IKKα, p-IкBα, and p-NFкBp65 was traced. Then nano-LC-MS/MS analysis was made to detect the mechanism of GY-13. The active ingredients, drug targets, and key pathways of GY-13 in treating depression were analyzed through network pharmacology and molecular docking. With immunohistochemistry, quantitative RT-PCR, and western-blot techniques, the therapeutic mechanism of GY-13 was traced and analyzed. This study revealed that GY-13 significantly enhances autonomous and exploratory behavior, sucrose consumption, learning and memory ability, and hippocampal neuronal degeneration, which inhibits inflammation. In addition, omics analysis showed several proteins were altered in the hippocampus of rats following CUMS and GY-13 treatment. Bioinformatics analysis and network pharmacology revealed the antidepressant effects of GY-13 are related to the chemokine/chemokine receptor axis. Immunohistochemistry, western blotting and RT-PCR assay further support the findings of omics analysis. We highlighted the importance of the chemokine/chemokine receptor axis in the treatment of depression, as well as showed GY-13 can be used as a novel targeted therapy for depression treatment.

Marine natural products: potential agents for depression treatment

Depression is a common psychiatric disorder. Due to the disadvantages of current clinical drugs, including poor efficacy and unnecessary side effects, research has shifted to novel natural products with minimal or no adverse effects as therapeutic alternatives. The ocean is a vast ecological home, with a wide variety of organisms that can produce a large number of natural products with unique structures, some of which have neuroprotective effects and are a valuable source for the development of new drugs for depression. In this review, we analyzed preclinical and clinical studies of natural products derived from marine organisms with antidepressant potential, including the effects on the pathophysiology of depression, and the underlying mechanisms of these effects. It is expected to provide a reference for the development of new antidepressant drugs.

circSKA3 promotes colorectal cancer metastases through miR-1238 and methylation

Colorectal cancer (CRC) is becoming one of the most common cancers overworld, which causes a high rate of death in patients. circRNAs are non-coding RNAs(ncRNAs), which have been reported to be involved in the development of many cancers, including CRC. However, the exact mechanism that how circRNAs function through in CRC remains unclear. In this study, we firstly used GEO database and bioinformatic methods to identify the significant changed circRNAs, with circSKA3 being the most significantly upregulated circRNAs in CRC tissues. PCR results further confirmed higher expression of circSKA3 in CRC patients. CCK-8, scratch, and transwell assays indicated that circSKA3 could promote the proliferation, migration, and invasion of CRC cell lines for cell detection. Dual-luciferase assays were carried out to detect the downstream targets of circSKA3, and a binding site between circSKA3 and miR-1238 was identified and miR-1238 could also combine with YTHDF2. Overexpression of YTHDF2 rescued the decreased cell proliferation, migration, and invasion caused by miR-1238 overexpression. RIP assay further indicated that YTHDF2 could decrease the methylation of STAT5A. In summary, our study found that circSKA3 was upregulated in CRC tissues comparing with normal tissues. circSKA3 could increase the expression ofYTHDF2 through sponging miR-1238 to decrease the methylation of STAT5A, which could provide a novel target for CRC treatment.

Targeting autophagy to counteract neuroinflammation: A novel antidepressant strategy

Depression is a common disease that affects physical and mental health and imposes a considerable burden on afflicted individuals and their families worldwide. Depression is associated with a high rate of disability and suicide. It causes a severe decline in productivity and quality of life. Unfortunately, the pathophysiological mechanisms underlying depression have not been fully elucidated, and the risk of its treatment is still presented. Studies have shown that the expression of autophagic markers in the brain and peripheral inflammatory mediators are dysregulated in depression. Autophagy-related genes regulate the level of autophagy and change the inflammatory response in depression. Depression is related to several aspects of immunity. The regulation of the immune system and inflammation by autophagy may lead to the development or deterioration of mental disorders. This review highlights the role of autophagy and neuroinflammation in the pathophysiology of depression, sumaries the autophagy-targeting small moleculars, and discusses a novel therapeutic strategy based on anti-inflammatory mechanisms that target autophagy to treat the disease.

Profiling Small RNA From Brain Extracellular Vesicles in Individuals With Depression

BACKGROUND

Major depressive disorder (MDD) is a leading cause of disability with significant mortality risk. Despite progress in our understanding of the etiology of MDD, the underlying molecular changes in the brain remain poorly understood. Extracellular vesicles (EVs) are lipid-bound particles that can reflect the molecular signatures of the tissue of origin. We aimed to optimize a streamlined EV isolation protocol from postmortem brain tissue and determine whether EV RNA cargo, particularly microRNAs (miRNAs), have an MDD-specific profile.

METHODS

EVs were isolated from postmortem human brain tissue. Quality was assessed using western blots, transmission electron microscopy, and microfluidic resistive pulse sensing. EV RNA was extracted and sequenced on Illumina platforms. Functional follow-up was performed in silico.

RESULTS

Quality assessment showed an enrichment of EV markers, as well as a size distribution of 30 to 200 nm in diameter, and no contamination with cellular debris. Small RNA profiling indicated the presence of several RNA biotypes, with miRNAs and transfer RNAs being the most prominent. Exploring miRNA levels between groups revealed decreased expression of miR-92a-3p and miR-129-5p, which was validated by qPCR and was specific to EVs and not seen in bulk tissue. Finally, in silico functional analyses indicate potential roles for these 2 miRNAs in neurotransmission and synaptic plasticity.

CONCLUSION

We provide a streamlined isolation protocol that yields EVs of high quality that are suitable for molecular follow-up. Our findings warrant future investigations into brain EV miRNA dysregulation in MDD.

CircDYM attenuates microglial apoptosis via CEBPB/ZC3H4 axis in LPS-induced mouse model of depression

Major depressive disorder (MDD) is a highly prevalent condition and one of the most common psychiatric disorders worldwide. Circular RNA (circRNA) has been increasingly implicated in MDD. However, a comprehensive understanding of circRNA and microglial apoptosis in depression is incomplete. Here, we show that circDYM inhibits microglial apoptosis induced by LPS via CEBPB/ZC3H4 axis. CircDYM prevents the translocation of CEBPB from cytoplasm to the nucleus by binding with CEBPB. Moreover, LPS-induced CEBPB nuclear entry downregulates the expression of ZC3H4, in which promotes autophagy and apoptosis in microglia. Taken together, our findings provide new insights into the relationship between circDYM and microglial apoptosis and shed new light on the function of this novel mechanism in depression-associated complex changes in the brain.

Association between prenatal period exposure to ambient air pollutants and development of postpartum depression: a systematic review and meta-analysis

There is body of evidence supporting a role for maternal exposure to ambient air pollutants and postpartum depression (PPD). We attempted to review the literature systematically to assess the association between exposure to both ambient air particulate matters within pregnancy and PPD. The effect estimates extracting across each study were standardized to a 10 μg/m3 change. The random-effects model was applied to pool odds ratios. According to the three included cohort articles, exposure to PM10 within second trimester (OR = 1.26, 95% CI = 1.15-1.37) was significantly associated with higher odds of PPD. However, there was no significant association between having exposure to other ambient air pollutants and PPD. This meta-analysis showed that air pollutants could be associated with an increased risk of PPD.

Promising new pharmacological targets for depression: The search for efficacy

Pharmacological treatment of major depressive disorder (MDD) still relies on the use of serotonergic drugs, despite their limited efficacy. A few mechanistically new drugs have been developed in recent years, but many fail in clinical trials. Several hypotheses have been proposed to explain MDD pathophysiology, indicating that physiological processes such as neuroplasticity, circadian rhythms, and metabolism are potential targets. Here, we review the current state of pharmacological treatments for MDD, as well as the preclinical and clinical evidence for an antidepressant effect of molecules that target non-serotonergic systems. We offer some insights into the challenges facing the development of new antidepressant drugs, and the prospect of finding more effectiveness for each target discussed.

Astroglial Connexin 43-Mediated Gap Junctions and Hemichannels: Potential Antidepressant Mechanisms and the Link to Neuroinflammation

Major depression disorder (MDD) is a neuropsychiatric disorder associated with a high suicide rate and a higher disability rate than any other disease. Evidence suggests that the pathological mechanism of MDD is related to astrocyte dysfunction. Depression is mainly associated with the expression of connexin 43 (Cx43) and the function of Cx43-mediated gap junctions and hemichannels in astrocytes. Moreover, neuroinflammation has been a hotspot in research on the pathology of depression, and Cx43-mediated functions are thought to be involved in neuroinflammation-related depression. However, the specific mechanism of Cx43-mediated functions in neuroinflammation-related depression pathology remains unclear. Therefore, this review summarizes and discusses Cx43 expression, the role of gap junction intercellular communication, and its relationship with neuroinflammation in depression. This review also focuses on the effects of antidepressant drugs (e.g., monoamine antidepressants, psychotropic drugs, and N-methyl-D-aspartate receptor antagonists) on Cx43-mediated function and provides evidence for Cx43 as a novel target for the treatment of MDD. The pathogenesis of MDD is related to astrocyte dysfunction, with reduced Cx43 expression, GJ dysfunction, decreased GJIC and reduced BDNF expression in the depressed brain. The effect of Cx43 on neuroinflammation-related depression involving inflammatory cytokines, glutamate excitotoxicity, and HPA axis dysregulation. Antidepressant drugs targeting Cx43 can effectively relieve depressive symptoms.

Neuroprotective Effects of Phenolic Antioxidant Tert-butylhydroquinone (tBHQ) in Brain Diseases

Human life and health are gravely threatened by brain diseases. The onset and progression of the illnesses are influenced by a variety of factors, including pathogenic causes, environmental factors, mental issues, etc. According to scientific studies, neuroinflammation and oxidative stress play a significant role in the development and incidence of brain diseases by producing pro-inflammatory cytokines and oxidative tissue damage to induce inflammation and apoptosis. Neuroinflammation, oxidative stress, and oxidative stress-related changes are inseparable factors in the etiology of several brain diseases. Numerous neurodegenerative diseases have undergone substantial research into the therapeutic alternatives that target oxidative stress, the function of oxidative stress, and the possible therapeutic use of antioxidants. Formerly, tBHQ is a synthetic phenolic antioxidant, which has been widely used as a food additive. According to recent researches, tBHQ can suppress the processes that lead to neuroinflammation and oxidative stress, which offers a fresh approach to treating brain diseases. In order to achieve the goal of decreasing inflammation and apoptosis, tBHQ is a specialized nuclear factor erythroid 2-related factor (Nrf2) activator that decreases oxidative stress and enhances antioxidant status by upregulating the Nrf2 gene and reducing nuclear factor kappa-B (NF-κB) activity. This article reviews the effects of tBHQ on neuroinflammation and oxidative stress in recent years and looks into how tBHQ inhibits neuroinflammation and oxidative stress through human, animal, and cell experiments to play a neuroprotective role in Alzheimer's disease (AD), stroke, depression, and Parkinson's disease (PD). It is anticipated that this article will be useful as a reference for upcoming research and the creation of drugs to treat brain diseases.

Oxidative Stress in Depression: The Link with the Stress Response, Neuroinflammation, Serotonin, Neurogenesis and Synaptic Plasticity

Depression is a prevalent, complex, and highly debilitating disease. The full comprehension of this disease is still a global challenge. Indeed, relapse, recurrency, and therapeutic resistance are serious challenges in the fight against depression. Nevertheless, abnormal functioning of the stress response, inflammatory processes, neurotransmission, neurogenesis, and synaptic plasticity are known to underlie the pathophysiology of this mental disorder. The role of oxidative stress in disease and, particularly, in depression is widely recognized, being important for both its onset and development. Indeed, excessive generation of reactive oxygen species and lack of efficient antioxidant response trigger processes such as inflammation, neurodegeneration, and neuronal death. Keeping in mind the importance of a detailed study about cellular and molecular mechanisms that are present in depression, this review focuses on the link between oxidative stress and the stress response, neuroinflammation, serotonergic pathways, neurogenesis, and synaptic plasticity's imbalances present in depression. The study of these mechanisms is important to lead to a new era of treatment and knowledge about this highly complex disease.

Dissecting early life stress-induced adolescent depression through epigenomic approach

Early life stress (ELS), such as abuse and neglect during childhood, can lead to psychiatric disorders in later life. Previous studies have suggested that ELS can cause profound changes in gene expression through epigenetic mechanisms, which can lead to psychiatric disorders in adulthood; however, studies on epigenetic modifications associated with ELS and psychiatric disorders in adolescents are limited. Moreover, how these epigenetic modifications can lead to psychiatric disorders in adolescents is not fully understood. Commonly, DNA methylation, histone modification, and the regulation of noncoding RNAs have been attributed to the reprogramming of epigenetic profiling associated with ELS. Although only a few studies have attempted to examine epigenetic modifications in adolescents with ELS, existing evidence suggests that there are commonalities and differences in epigenetic profiling between adolescents and adults. In addition, epigenetic modifications are sex-dependent and are influenced by the type of ELS. In this review, we have critically evaluated the current evidence on epigenetic modifications in adolescents with ELS, particularly DNA methylation and the expression of microRNAs in both preclinical models and humans. We have also clarified the impact of ELS on psychiatric disorders in adolescents to predict the development of neuropsychiatric disorders and to prevent and recover these disorders through personalized medicine.

Is depression the missing link between inflammatory mediators and cancer?

Patients with cancer are at greater risk of developing depression in comparison to the general population and this is associated with serious adverse effects, such as poorer quality of life, worse prognosis and higher mortality. Although the relationship between depression and cancer is now well established, a common underlying pathophysiological mechanism between the two conditions is yet to be elucidated. Existing theories of depression, based on monoamine neurotransmitter system dysfunction, are insufficient as explanations of the disorder. Recent advances have implicated neuroinflammatory mechanisms in the etiology of depression and it has been demonstrated that inflammation at a peripheral level may be mirrored centrally in astrocytes and microglia serving to promote chronic levels of inflammation in the brain. Three major routes to depression in cancer in which proinflammatory mediators are implicated, seem likely. Activation of the kynurenine pathway involving cytokines, increases tryptophan catabolism, resulting in diminished levels of serotonin which is widely acknowledged as being the hallmark of depression. It also results in neurotoxic effects on brain regions thought to be involved in the evolution of major depression. Proinflammatory mediators also play a crucial role in impairing regulatory glucocorticoid mediated feedback of the hypothalamic-pituitary-adrenal axis, which is activated by stress and considered to be involved in both depression and cancer. The third route is via the glutamatergic pathway, whereby glutamate excitotoxicity may lead to depression associated with cancer. A better understanding of the mechanisms underlying these dysregulated and other newly emerging pathways may provide a rationale for therapeutic targeting, serving to improve the care of cancer patients.

Inflammatory pathophysiological mechanisms implicated in postpartum depression

Postpartum Depression (PPD) is a serious psychiatric disorder of women within the first year after delivery. It grievously damages women's physical and mental health. Inflammatory reaction theory is well-established in depression, and also has been reported associated with PPD. This review summarized the inflammatory pathophysiological mechanisms implicated in PPD, including decreased T cell activation, increased proinflammatory cytokines secretion, active kynurenine pathway, and initiated NLRP3 inflammasome. Clinical and preclinical research are both gathered. Potential therapeutical alternatives targeting the inflammatory mechanisms of PPD were introduced. In addition, this review briefly discussed the differences of inflammatory mechanisms between PPD and depression. The research of inflammation in PPD is limited and seems just embarking, which indicates the direction we can further study. As a variety of risky factors contribute to PPD collectively, therapy for women with PPD should be comprehensive, and clinical heterogeneity should be taken into consideration. As PPD has a predictability, early clinical screening and interventions are also needed. This review aims to help readers better understand the inflammatory pathological mechanisms in PPD, so as to identify biomarkers and potential therapeutic targets in the future.

Tryptophan Metabolism in Depression: A Narrative Review with a Focus on Serotonin and Kynurenine Pathways

Depression is a common and serious disorder, characterized by symptoms like anhedonia, lack of energy, sad mood, low appetite, and sleep disturbances. This disease is very complex and not totally elucidated, in which diverse molecular and biological mechanisms are involved, such as neuroinflammation. There is a high need for the development of new therapies and gaining new insights into this disease is urgent. One important player in depression is the amino acid tryptophan. This amino acid can be metabolized in two important pathways in the context of depression: the serotonin and kynurenine pathways. These metabolic pathways of tryptophan are crucial in several processes that are linked with depression. Indeed, the maintenance of the balance of serotonin and kynurenine pathways is critical for the human physiological homeostasis. Thus, this narrative review aims to explore tryptophan metabolism (particularly in the serotonin and kynurenine pathways) in depression, starting with a global overview about these topics and ending with the focus on these pathways in neuroinflammation, stress, microbiota, and brain-derived neurotrophic factor regulation in this disease. Taken together, this information aims to clarify the metabolism of tryptophan in depression, particularly the serotonin and kynurenine pathways.

Next RNA Therapeutics: The Mine of Non-Coding

The growing knowledge on several classes of non-coding RNAs (ncRNAs) and their different functional roles has aroused great interest in the scientific community. Beyond the Central Dogma of Biology, it is clearly known that not all RNAs code for protein products, and they exert a broader repertoire of biological functions. As described in this review, ncRNAs participate in gene expression regulation both at transcriptional and post-transcriptional levels and represent critical elements driving and controlling pathophysiological processes in multicellular organisms. For this reason, in recent years, a great boost was given to ncRNA-based strategies with potential therapeutic abilities, and nowadays, the use of RNA molecules is experimentally validated and actually exploited in clinics to counteract several diseases. In this review, we summarize the principal classes of therapeutic ncRNA molecules that are potentially implied in disease onset and progression, which are already used in clinics or under clinical trials, highlighting the advantages and the need for a targeted therapeutic strategy design. Furthermore, we discuss the benefits and the limits of RNA therapeutics and the ongoing development of delivery strategies to limit the off-target effects and to increase the translational application.