Higher Levels of Pro-inflammatory Cytokines Are Associated With Higher Levels of Glutamate in the Anterior Cingulate Cortex in Depressed Adolescents

Association of new onset seizure and COVID-19 vaccines and long-term follow-up: A systematic review and meta-analysis

OBJECTIVE

Seizures have been reported as an adverse event of the COVID-19 vaccine. However, there is no solid evidence of increased seizure occurrence compared to the general population. This study was undertaken to investigate seizure occurrence among COVID-19 vaccine recipients compared to unvaccinated controls.

METHODS

A systematic search was made of PubMed, Web of Science, Scopus, and Cochrane Library up to April 9, 2024. Studies reporting seizure occurrence following COVID-19 vaccination were included. This study is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses framework and was conducted using random- and common-effect models. The risk of bias in the studies was evaluated by the Newcastle-Ottawa Scale. The outcome of interest was new onset seizure incidence proportion compared among (1) COVID-19 vaccine recipients, (2) unvaccinated cohorts, and (3) various types of COVID-19 vaccines.

RESULTS

Forty studies were included, of which seven entered the meta-analysis. Results of the pooled analysis of the new onset seizure incidence (21- or 28-day period after vaccination) in 13 016 024 vaccine recipients and 13 013 262 unvaccinated individuals by pooling the cohort studies did not show any statistically significant difference between the two groups (odds ratio [OR] = .48, 95% confidence interval [CI] = .19-1.20, p = .12, I2 = 95%, τ2 = .7145). Pooling four studies accounting for 19 769 004 mRNA versus 47 494 631 viral vector vaccine doses demonstrated no significant difference in terms of new onset seizure incidence between the groups (OR = 1.18, 95% CI = .78-1.78, p = .44, I2 = 0%, τ2 = .004).

SIGNIFICANCE

This systematic review and meta-analysis shows no statistically significant difference in the risk of new onset seizure incidence between COVID-19 vaccinated individuals and unvaccinated individuals.

Association of New-Onset Seizures With SARS-CoV-2 Vaccines: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Importance

Seizures have been reported as an adverse effect of the SARS-CoV-2 vaccine. However, no study has answered the question of whether there is any association between seizures in the general population and COVID-19 vaccination.

Objective

To evaluate the seizure incidence among SARS-CoV-2 vaccine recipients compared with those who received a placebo.

Data Sources

A systematic search of MEDLINE (via PubMed), Web of Science, Scopus, Cochrane Library, Google Scholar, review publications, editorials, letters to editors, and conference papers, along with the references of the included studies from December 2019 to July 7, 2023.

Study Selection

Randomized clinical trials (RCTs) reporting seizure incidence with SARS-CoV-2 vaccination were included.

Data Extraction and Synthesis

This study is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses framework and used the Mantel-Haenszel method with random- and common-effect models. The risk of bias of the studies was assessed using the Cochrane assessment tool for RCTs.

Main Outcomes and Measures

The outcome of interest was new-onset seizure incidence proportion compared among (1) SARS-CoV-2 vaccine recipients and (2) placebo recipients.

Results

Six RCTs were included in the study. Results of the pooled analysis comparing the incidence of new-onset seizure between the 63 521 vaccine and 54 919 placebo recipients in the 28-day follow-up after vaccine/placebo injection showed no statistically significant difference between the 2 groups (9 events [0.014%] in vaccine and 1 event [0.002%] in placebo recipients; odds ratio [OR], 2.70; 95% CI, 0.76-9.57; P = .12; I2 = 0%, τ2 = 0, Cochran Q P = .74). Likewise, in the entire blinded-phase period after injection, with a median of more than 43 days, no significant difference was identified between the vaccine and placebo groups regarding incident new-onset seizure (13/43 724 events [0.03%] in vaccine and 5/40 612 [0.012%] in placebo recipients; OR, 2.31; 95% CI, 0.86-6.23, P = .10, I2 = 0%, τ2 = 0, Cochran Q P = .95).

Conclusions and Relevance

According to this systematic review and meta-analysis, there was no statistically significant difference in the risk of new-onset seizure incidence between vaccinated individuals and placebo recipients.

The Interplay of Peer Victimization and Parasympathetic Nervous System Activity on Acute Inflammatory Stress Responses in Adolescence

This study examined the extent to which adolescent peer victimization predicted acute inflammatory responses to stress, and whether both resting parasympathetic nervous system (PNS) activity and PNS stress reactivity moderated this association. 83 adolescents (Mage = 14.89, SDage = 0.52, 48% female) reported their history of peer victimization and were exposed to a standardized social stress task before and after which dried blood spot samples were collected to assay inflammatory markers. Inflammatory responses to the stress task were assessed with a latent inflammatory change factor using the cytokines interleukin-6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor-α (TNF-α). PNS functioning, indexed by high-frequency heart rate variability, was measured at rest and during the stressor. Contrary to hypotheses, analyses revealed no direct relation between peer victimization and acute inflammatory responses, and resting PNS activity did not moderate this association. However, peer victimization predicted stronger inflammatory responses among adolescents with weaker PNS reactivity to the stress task (b = 0.63, p = .02). This association was not observed among adolescents with stronger PNS reactivity, for whom a negative but non-significant trend was found. Weaker PNS reactivity may thus indicate victimized adolescents' vulnerability for acute inflammatory responses, whereas stronger PNS reactivity may indicate adolescents' resilience to a social stressor.

The Relationship between Neurobiological Function and Inflammation in Depressed Children and Adolescents: A Scoping Review

INTRODUCTION

Neurobiological dysfunction is associated with depression in children and adolescents. While research in adult depression suggests that inflammation may underlie the association between depression and brain alterations, it is unclear if altered levels of inflammatory markers provoke neurobiological dysfunction in early-onset depression. The aim of this scoping review was to provide an overview of existing literature investigating the potential interaction between neurobiological function and inflammation in depressed children and adolescents.

METHODS

Systematic searches were conducted in six databases. Primary research studies that included measures of both neurobiological functioning and inflammation among children (≤18 years) with a diagnosis of depression were included.

RESULTS

Four studies (240 participants; mean age 16.0 ± 0.6 years, 62% female) meeting inclusion criteria were identified. Studies primarily examined the inflammatory markers interleukin 6, tumor necrosis factor alpha, C-reactive protein, and interleukin 1 beta. Exploratory whole brain imaging and analysis as well as region of interest approaches focused on the anterior cingulate cortex, basal ganglia, and white matter tracts were conducted. Most studies found correlations between neurobiological function and inflammatory markers; however, depressive symptoms were not observed to moderate these effects.

CONCLUSIONS

A small number of highly heterogeneous studies indicate that depression may not modulate the association between altered inflammation and neurobiological dysfunction in children and adolescents. Replication in larger samples using consistent methodological approaches (focus on specific inflammatory markers, examine certain brain areas) is needed to advance the knowledge of potential neuro-immune interactions early in the course of depression.

Longitudinal trajectories of anterior cingulate glutamate and subclinical psychotic experiences in early adolescence: the impact of bullying victimization

Previous studies reported decreased glutamate levels in the anterior cingulate cortex (ACC) in non-treatment-resistant schizophrenia and first-episode psychosis. However, ACC glutamatergic changes in subjects at high-risk for psychosis, and the effects of commonly experienced environmental emotional/social stressors on glutamatergic function in adolescents remain unclear. In this study, adolescents recruited from the general population underwent proton magnetic resonance spectroscopy (MRS) of the pregenual ACC using a 3-Tesla scanner. We explored longitudinal data on the association of combined glutamate-glutamine (Glx) levels, measured by MRS, with subclinical psychotic experiences. Moreover, we investigated associations of bullying victimization, a risk factor for subclinical psychotic experiences, and help-seeking intentions, a coping strategy against stressors including bullying victimization, with Glx levels. Finally, path analyses were conducted to explore multivariate associations. For a contrast analysis, gamma-aminobutyric acid plus macromolecule (GABA+) levels were also analyzed. Negative associations were found between Glx levels and subclinical psychotic experiences at both Times 1 (n = 219, mean age 11.5 y) and 2 (n = 211, mean age 13.6 y), as well as for over-time changes (n = 157, mean interval 2.0 y). Moreover, effects of bullying victimization and bullying victimization × help-seeking intention interaction effects on Glx levels were found (n = 156). Specifically, bullying victimization decreased Glx levels, whereas help-seeking intention increased Glx levels only in bullied adolescents. Finally, associations among bullying victimization, help-seeking intention, Glx levels, and subclinical psychotic experiences were revealed. GABA+ analysis revealed no significant results. This is the first adolescent study to reveal longitudinal trajectories of the association between glutamatergic function and subclinical psychotic experiences and to elucidate the effect of commonly experienced environmental emotional/social stressors on glutamatergic function. Our findings may deepen the understanding of how environmental emotional/social stressors induce impaired glutamatergic neurotransmission that could be the underpinning of liability for psychotic experiences in early adolescence.

Neighborhood disadvantage and parenting predict longitudinal clustering of uncinate fasciculus microstructural integrity and clinical symptomatology in adolescents

Parenting behaviors and neighborhood environment influence the development of adolescents' brains and behaviors. Simultaneous trajectories of brain and behavior, however, are understudied, especially in these environmental contexts. In this four-wave study spanning 9-18 years of age (N=224 at baseline, N=138 at final assessment) we used longitudinal k-means clustering to identify clusters of participants with distinct trajectories of uncinate fasciculus (UF) fractional anisotropy (FA) and anxiety symptoms; we examined behavioral outcomes and identified environmental factors that predicted cluster membership. We identified three clusters of participants: 1) high UF FA and low symptoms ("low-risk"); 2) low UF FA and high symptoms ("high-risk"); and 3) low UF FA and low symptoms ("resilient"). Adolescents in disadvantaged neighborhoods were more likely to be in the resilient than high-risk cluster if they also experienced maternal warmth. Thus, neighborhood disadvantage may confer neural risk for psychopathology that can be buffered by maternal warmth, highlighting the importance of considering multiple environmental influences in understanding emotional and neural development in youth.

Protocol for teen inflammation glutamate emotion research (TIGER): Toward predictors of treatment response and clinical course in depressed adolescents

Adolescent-onset depression is a prevalent and debilitating condition commonly associated with treatment refractory depression and non-response to first-line antidepressants. There are, however, no objective tests to determine who may or may not respond to antidepressants. As depressed adolescents are especially vulnerable to the lifelong consequences of ineffectively-treated depression, it is critical to identify neurobiological predictors of treatment non-response in this population. Here, we describe the scientific rationale and protocol for the Teen Inflammation Glutamate Emotion Research (TIGER) study, a prospective 18-month investigation of 160 depressed adolescents who will be assessed before and after treatment with selective serotonin reuptake inhibitors. TIGER will be using ultra-high field imaging to test the effects of acute stress and antidepressant treatment on inflammatory and glutamatergic processes hypothesized to underlie depression maintenance. Results from this work will motivate future studies testing alternative therapeutics for depressed adolescents at risk for treatment resistant depression. ClinicalTrials.gov Identifier: NCT05329441.

The relationship between self-perceived fatigue, muscle endurance, and circulating markers of inflammation in participants of the Copenhagen aging and Midlife Biobank (CAMB)

BACKGROUND

Fatigue, low muscle endurance, muscle weakness and low-grade inflammation are strongly related to frailty at higher age. When signs of self-perceived fatigue and low muscle endurance are interrelated with low-grade inflammation at midlife, they might be used as early markers for frailty. This study investigated whether the interrelationships among self-perceived fatigue, muscle endurance and inflammation can be observed at midlife.

METHODS

A total of 965 participants of the Copenhagen Aging and Midlife Biobank (aged 52 ± 4 years, 536 males, 426 females) were assessed for self-perceived fatigue (20-item multidimensional fatigue inventory), muscle endurance (grip work), circulating markers of inflammation (hsCRP, IL-6, IL-10, TNF-alpha and IFN-γ), daily physical activity (PAS-2), body composition (%body fat assessed by bio-impedance) and self-reported health status. Participants were categorised (correcting for age and gender) according to high fatigue and/or low muscle endurance, differences in inflammatory profile between fatigue categories were assessed by ANCOVA (corrected for PAS-2, %body fat and presence of inflammatory conditions).

RESULTS

Overall, muscle endurance, fatigue and inflammatory markers were significantly interrelated. Higher levels of hsCRP (p < 0.001), IL-6 (p < 0.001), IL-10 (p = 0.035) and TNF-alpha (p = 0.028) were observed in participants presenting both low muscle endurance and high fatigue. IFN-γ was highest in those with high fatigue but normal muscle endurance (p = 0.015).

CONCLUSIONS

Middle-aged participants with higher fatigue in combination with low muscle endurance show higher levels of inflammation, independently from physical activity, body fat and inflammatory pathology. The underlying mechanisms should be identified and future studies should also investigate whether these individuals show early signs of reduced physiological reserve capacity, which in later life come to full expression by means of frailty.

Preparation and processing of dried blood spots for microRNA sequencing

Dried blood spots (DBS) are biological samples commonly collected from newborns and in geographic areas distanced from laboratory settings for the purposes of disease testing and identification. MicroRNAs (miRNAs)-small non-coding RNAs that regulate gene activity at the post-transcriptional level-are emerging as critical markers and mediators of disease, including cancer, infectious diseases, and mental disorders. This protocol describes optimized procedural steps for utilizing DBS as a reliable source of biological material for obtaining peripheral miRNA expression profiles. We outline key practices, such as the method of DBS rehydration that maximizes RNA extraction yield, and the use of degenerate oligonucleotide adapters to mitigate ligase-dependent biases that are associated with small RNA sequencing. The standardization of miRNA readout from DBS offers numerous benefits: cost-effectiveness in sample collection and processing, enhanced reliability and consistency of miRNA profiling, and minimal invasiveness that facilitates repeated testing and retention of participants. The use of DBS-based miRNA sequencing is a promising method to investigate disease mechanisms and to advance personalized medicine.

Epigenetic regulation in major depression and other stress-related disorders: molecular mechanisms, clinical relevance and therapeutic potential

Major depressive disorder (MDD) is a chronic, generally episodic and debilitating disease that affects an estimated 300 million people worldwide, but its pathogenesis is poorly understood. The heritability estimate of MDD is 30-40%, suggesting that genetics alone do not account for most of the risk of major depression. Another factor known to associate with MDD involves environmental stressors such as childhood adversity and recent life stress. Recent studies have emerged to show that the biological impact of environmental factors in MDD and other stress-related disorders is mediated by a variety of epigenetic modifications. These epigenetic modification alterations contribute to abnormal neuroendocrine responses, neuroplasticity impairment, neurotransmission and neuroglia dysfunction, which are involved in the pathophysiology of MDD. Furthermore, epigenetic marks have been associated with the diagnosis and treatment of MDD. The evaluation of epigenetic modifications holds promise for further understanding of the heterogeneous etiology and complex phenotypes of MDD, and may identify new therapeutic targets. Here, we review preclinical and clinical epigenetic findings, including DNA methylation, histone modification, noncoding RNA, RNA modification, and chromatin remodeling factor in MDD. In addition, we elaborate on the contribution of these epigenetic mechanisms to the pathological trait variability in depression and discuss how such mechanisms can be exploited for therapeutic purposes.

The association between peripheral inflammation, brain glutamate and antipsychotic response in Schizophrenia: Data from the STRATA collaboration

Glutamate and increased inflammation have been separately implicated in the pathophysiology of schizophrenia and the extent of clinical response to antipsychotic treatment. Despite the mechanistic links between pro-inflammatory and glutamatergic pathways, the relationships between peripheral inflammatory markers and brain glutamate in schizophrenia have not yet been investigated. In this study, we tested the hypothesis that peripheral levels of pro-inflammatory cytokines would be positively associated with brain glutamate levels in schizophrenia. Secondary analyses determined whether this relationship differed according to antipsychotic treatment response. The sample consisted of 79 patients with schizophrenia, of whom 40 were rated as antipsychotic responders and 39 as antipsychotic non-responders. Brain glutamate levels were assessed in the anterior cingulate cortex (ACC) and caudate using proton magnetic resonance spectroscopy (1H-MRS) and blood samples were collected for cytokine assay on the same study visit (IL-6, IL-8, IL-10, TNF- α and IFN-γ). Across the whole patient sample, there was a positive relationship between interferon-gamma (IFN-γ) and caudate glutamate levels (r = 0.31, p = 0.02). In the antipsychotic non-responsive group only, there was a positive relationship between interleukin-8 (IL-8) and caudate glutamate (r = 0.46, p = 0.01). These findings provide evidence to link specific peripheral inflammatory markers and caudate glutamate in schizophrenia and may suggest that this relationship is most marked in patients who show a poor response to antipsychotic treatment.

Protective effect of Nr4a2 (Nurr1) against LPS-induced depressive-like behaviors via regulating activity of microglia and CamkII neurons in anterior cingulate cortex

Neuroinflammation is tightly associated with onset of depression. The nuclear receptor related 1 protein (Nurr1, also called Nr4a2), its roles in dopaminergic neurons is well understood, which can alleviate inflammation. Nevertheless, potential effects of Nr4a2 on neuroinflammation associated with depression still remains unclear. Chronic lipopolysaccharides (LPS) stress induced depressive-behaviors were confirmed via behavioral tests. Differentially expressed genes were detected by using RNA-sequencing. The anterior cingulate cortex (ACC) tissues were collected for biochemical experiments. The Golgi-Cox staining and virus labeling were used to evaluate the dendritic spines. We applied fluoxetine (FLX) and amodiaquine dihydrochloride (AQ, a highly selective agonist of Nr4a2) in mice. Overexpression experiments were performed by injecting with AAV-Nr4a2-EGFP into ACC. Chemogenetic activation of CamkII neurons via injecting the hM3Dq virus. Mice treated with LPS displayed depressive- and anxiety-like behaviors. The reduction of Nr4a2 and FosB induced by LPS were rescued by pretreatment with FLX or AQ. More importantly, LPS-induced behavior deficits in mice were also alleviated via fluoxetine treatment and pharmacological activation the expression of Nr4a2. Meanwhile, enhancing the level of Nr4a2 could improve dendritic spines loss of neuron and morphological changes in microglia. Overexpression of Nr4a2 in ACC reversed the depressive- and anxiety-like behaviors caused by LPS administration. Activation of CamkII neurons in ACC could robustly increase the expression of Nr4a2 and improve LPS-induced behavior deficits. Our findings demonstrate that the Nr4a2 may regulate depressive-like behaviors via alleviating the impairment of morphology and function on microglia and CamkII neurons induced by chronic neuroinflammation.

Early life stress, systemic inflammation, and neural correlates of implicit emotion regulation in adolescents

Exposure to early life stress (ELS) increases the risk for developing psychopathology; however, the mechanisms underlying this association are not clear. In this study we examined systemic inflammation as a pathway that may link exposure to stress to altered neural correlates of implicit emotion regulation in adolescents with varying levels of exposure to ELS (n = 83; 52 females, 31 males; 15.63 ± 1.10 years). We measured ventrolateral prefrontal cortex (vlPFC) activation and functional connectivity (FC) between the bilateral amygdala and the vlPFC as adolescents completed an affect labeling task in the scanner and assessed concentrations of C-reactive protein (CRP) using a dried blood spot protocol. We found that CRP levels were negatively associated with vlPFC activation during implicit regulation of negatively-valenced stimuli, and that cumulative severity of ELS exposure moderated this neuroimmune association. Severity of ELS also significantly moderated the association between CRP levels and FC between the bilateral amygdala and l-vlPFC during implicit emotion regulation: in adolescents who had been exposed to more severe ELS, higher CRP was associated with more negative frontoamygdala FC during implicit regulation of negatively-valenced stimuli. Thus, ELS may disrupt the normative association between the immune system and the neural processes that underlie socioemotional functioning potentially increasing adolescents' risk for maladaptive outcomes.

Glutamate Neurotoxicity and Destruction of the Blood–Brain Barrier: Key Pathways for the Development of Neuropsychiatric Consequences of TBI and Their Potential Treatment Strategies

Traumatic brain injury (TBI) is associated with significant cognitive and psychiatric conditions. Neuropsychiatric symptoms can persist for years following brain injury, causing major disruptions in patients’ lives. In this review, we examine the role of glutamate as an aftereffect of TBI that contributes to the development of neuropsychiatric conditions. We hypothesize that TBI causes long-term blood–brain barrier (BBB) dysfunction lasting many years and even decades. We propose that dysfunction in the BBB is the central factor that modulates increased glutamate after TBI and ultimately leads to neurodegenerative processes and subsequent manifestation of neuropsychiatric conditions. Here, we have identified factors that determine the upper and lower levels of glutamate concentration in the brain after TBI. Furthermore, we consider treatments of disruptions to BBB integrity, including repairing the BBB and controlling excess glutamate, as potential therapeutic modalities for the treatment of acute and chronic neuropsychiatric conditions and symptoms. By specifically focusing on the BBB, we hypothesize that restoring BBB integrity will alleviate neurotoxicity and related neurological sequelae.

Baihe Dihuang (Lilium Henryi Baker and Rehmannia Glutinosa) decoction attenuates somatostatin interneurons deficits in prefrontal cortex of depression via miRNA-144-3p mediated GABA synthesis and release

ETHNOPHARMACOLOGICAL RELEVANCE

Baihe Dihuang Decoction is a well-known traditional Chinese medicine prescription (Also known as Lilium Henryi Baker and Rehmannia Glutinosa Decoction, LBRD) composed of Lilium Henryi Baker bulb and raw juice from Rehmannia Glutinosa (Gaertn) DC with the curative efficacy of nourishing yin and clearing heat based on the Chinese herbal medicine theory. It has been used as routine medication in treating depression combined with conventional western medicine in China for years.

AIM OF THE STUDY

LBRD can attenuates GABAergic deficits in the medial prefrontal cortex (mPFC) of depression. This study aimed to investigate the mechanism of antidepressive properties of LBRD in the prefrontal GABAergic interneuron subtypes, including parvalbumin (PV), somatostatin (SST), vasoactive intestinal peptide (VIP)-positive neuron.

MATERIALS AND METHODS

In this project, chronic unpredicted mild stress paradigm was adopted to construct depression model. After treated with LBRD standard decoction and behaviors test, the level of GABA associated miRNA/mRNA and GABAergic subtype-specific markers were detected by qRT-PCR and Western blot. The lncRNAs/miRNAs/GABA regulatory axis was verified by luciferase reporter assay, RNA immunoprecipitation, RNA pull-down assay, and theses changes were measured in LBRD administration with the use of immunofluorescence staining and RNA-fluorescence in situ hybridization.

RESULTS

In the current study, we found that LBRD exhibited high efficacy based on the results of behavioral tests. Meanwhile, LBRD also improved the reduced GABA levels in depression by increasing the expression of lncRNA Neat1 and Malat1, as well as decreasing miRNA-144-3p and miRNA-15b-5p. Moreover, the level of Sst mRNA and protein that were harvested from the mPFC tissues of depression group was significantly lower than those in the control mice. While, these changes can be reverted by LBRD standard decoction administration. Whereas, neither chronic stress nor treatment can change the level of PV and VIP mRNAs and protein expression. In the SST-positive neuron of mPFC tissues, treatment with LBRD standard decoction resulted in the elevation of Gad-67, VGAT, GAT-3 and a reduction of miRNA-144-3p expression.

CONCLUSIONS

These findings suggested that LBRD antidepressant activities may be related to ameliorating the SST-positive neuron deficits via regulating the miRNA-144-3p mediated GABA synthesis and release.

Endoplasmic Reticulum Stress and Its Role in Homeostasis and Immunity of Central and Peripheral Neurons

Neuronal cells are specialists for rapid transfer and translation of information. Their electrical properties relay on a precise regulation of ion levels while their communication via neurotransmitters and neuropeptides depends on a high protein and lipid turnover. The endoplasmic Reticulum (ER) is fundamental to provide these necessary requirements for optimal neuronal function. Accumulation of misfolded proteins in the ER lumen, reactive oxygen species and exogenous stimulants like infections, chemical irritants and mechanical harm can induce ER stress, often followed by an ER stress response to reinstate cellular homeostasis. Imbedded between glial-, endothelial-, stromal-, and immune cells neurons are constantly in communication and influenced by their local environment. In this review, we discuss concepts of tissue homeostasis and innate immunity in the central and peripheral nervous system with a focus on its influence on ER stress, the unfolded protein response, and implications for health and disease.

Inflammatory cytokines and callosal white matter microstructure in adolescents

Adolescent depression is characterized by heightened inflammation and altered connectivity of fronto-cingulate-limbic tracts, including the genu of the corpus callosum (CCG) and the uncinate fasciculus (UF). No studies, however, have yet examined the association between inflammation, measured by peripheral levels of cytokines, and white matter connectivity of fronto-cingulate-limbic tracts in adolescents. Here, 56 depressed adolescents (32 females, 3 non-binary; 16.23 ± 1.28 years) and 19 controls (10 females; 15.72 ± 1.17 years) completed a diffusion-weighted MRI scan at 3 Tesla. We conducted deterministic tractography to segment bilateral corpus callosum (genu and splenium) and UF and computed mean fractional anisotropy (FA) in each tract. A subset of participants (43 depressed and 17 healthy controls) also provided dried blood spot samples from which we assayed interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-ɑ) using a Luminex multiplex array. Depressed participants did not differ from controls in FA of the corpus callosum or UF (all FDR-corrected ps > 0.056) but exhibited higher levels of inflammation than did controls (IL-6: β = 0.91, FDR-corrected p = 0.006; TNF-α: β = 0.76, FDR-corrected p = 0.006). Although diagnostic group did not moderate the associations between inflammatory cytokines and FA in the CCG and UF, across both groups, greater peripheral inflammation was associated with lower FA in the CCG (IL-6: β = -0.38; FDR-corrected p = 0.044; TNF-ɑ: β = -0.41, FDR-corrected p = 0.044). This study is the first to examine associations between peripheral inflammation and white matter microstructure of fronto-cingulate-limbic tracts in depressed and nondepressed adolescents. Future mechanistic studies are needed to confirm our findings; nevertheless, our results suggest that heightened inflammation is an important component of neurophenotypes that are relevant to adolescent depression.

Preventive strategies for adolescent depression: What are we missing? A focus on biomarkers

Adolescent depression is an important global issue with several unmet needs that still must be addressed and, to date, there are only few effective preventive strategies to reduce the burden of this disorder worldwide. In this mini-review, the evidence and potential ways to improve an early detection will be discussed as well as prompt interventions by focusing on a better understanding of the risks underlying the developing of adolescent depression from both a sociodemographic and a biological perspective.

The neuroimmune response during stress: A physiological perspective

Stress is an essential adaptive response that enables the organism to cope with challenges and restore homeostasis. Different stressors require distinctive corrective responses in which immune cells play a critical role. Hence, effects of stress on immunity may vary accordingly. Indeed, epidemiologically, stress can induce either inflammation or immune suppression in an organism. However, in the absence of a conceptual framework, these effects appear chaotic, leading to confusion. Here, we examine how stressor diversity is imbedded in the neuroimmune axis. Stressors differ in the brain patterns they induce, diversifying the neuronal and endocrine mediators dispatched to the periphery and generating a wide range of potential immune effects. Uncovering this complexity and diversity of the immune response to different stressors will allow us to understand the involvement of stress in pathological conditions, identify ways to modulate it, and even harness the therapeutic potential embedded in an adaptive response to stress.