Reduced expression of apolipoprotein E receptor type 2 in peripheral blood lymphocytes from patients with major depressive disorder

The protein corona and its effects on nanoparticle-based drug delivery systems

In most cases, once nanoparticles (NPs) enter the blood, their surface is covered by biological molecules, especially proteins, forming a so-called protein corona (PC). As a result, what the cells of the body "see" is not the NPs as formulated by the chemists, but the PC. In this way, the PC can influence the effects of the NPs and even mask the desired effects of the NP components. While this can argue for trying to inhibit protein-nanomaterial interactions, encapsulating NPs in an endogenous PC may increase their clinical usefulness. In this review, we briefly introduce the concept of the PC, its formation and its effects on the behavior of NPs. We also discuss how to reduce the formation of PCs or exploit them to enhance NP functions. Studying the interactions between proteins and NPs will provide insights into their clinical activity in health and disease. STATEMENT OF SIGNIFICANCE: The formation of protein corona (PC) will affect the operation of nanoparticles (NPs) in vivo. Since there are many proteins in the blood, it is impossible to completely overcome the formation of PC. Therefore, the use of PCs to deliver drug is the best choice. De-opsonins adsorbed on NPs can reduce macrophage phagocytosis and cytotoxicity of NPs, and prolong their circulation in blood. Albumin, apolipoprotein and transferrin are typical de-opsonins. In present review, we mainly discuss how to optimize the delivery of nanoparticles through the formation of albumin corona, transferrin corona and apolipoprotein corona in vivo or in vitro.

The Bidirectional Relationship of Depression and Inflammation: Double Trouble

Depression represents the number one cause of disability worldwide and is often fatal. Inflammatory processes have been implicated in the pathophysiology of depression. It is now well established that dysregulation of both the innate and adaptive immune systems occur in depressed patients and hinder favorable prognosis, including antidepressant responses. In this review, we describe how the immune system regulates mood and the potential causes of the dysregulated inflammatory responses in depressed patients. However, the proportion of never-treated major depressive disorder (MDD) patients who exhibit inflammation remains to be clarified, as the heterogeneity in inflammation findings may stem in part from examining MDD patients with varied interventions. Inflammation is likely a critical disease modifier, promoting susceptibility to depression. Controlling inflammation might provide an overall therapeutic benefit, regardless of whether it is secondary to early life trauma, a more acute stress response, microbiome alterations, a genetic diathesis, or a combination of these and other factors.

Using Next-Generation Sequencing Transcriptomics To Determine Markers of Post-traumatic Symptoms: Preliminary Findings from a Post-deployment Cohort of Soldiers

Post-traumatic stress disorder is a concerning psychobehavioral disorder thought to emerge from the complex interaction between genetic and environmental factors. For soldiers exposed to combat, the risk of developing this disorder is twofold and diagnosis is often late, when much sequela has set in. To be able to identify and diagnose in advance those at “risk” of developing post-traumatic stress disorder, would greatly taper the gap between late sequelae and treatment. Therefore, this study sought to determine whether the transcriptome can be used to track the development of post-traumatic stress disorder in this unique and susceptible cohort of individuals. Gene expression levels in peripheral blood samples from 85 Canadian infantry soldiers (n = 58 participants negative for symptoms of post-traumatic stress disorder and n = 27 participants with symptoms of post-traumatic stress disorder) following return from deployment to Afghanistan were determined using RNA sequencing technology. Count-based gene expression quantification, normalization and differential analysis (with thorough correction for confounders) revealed genes associated to PTSD; LRP8 and GOLM1. These preliminary results provide a proof-of-principle for the diagnostic utility of blood-based gene expression profiles for tracking symptoms of post-traumatic stress disorder in soldiers returning from tour. It is also the first to report transcriptome-wide expression profiles alongside a post-traumatic symptom checklist.

Effects of soft electrophiles on selenium physiology

This review examines the effects of neurotoxic electrophiles on selenium (Se) metabolism. Selenium-dependent enzymes depend on the unique and elite functions of selenocysteine (Sec), the 21st proteinogenic amino acid, to perform their biochemical roles. Humans possess 25 selenoprotein genes, ~ half of which are enzymes (selenoenzymes) required for preventing, controlling, or reversing oxidative damage, while others participate in regulating calcium metabolism, thyroid hormone status, protein folding, cytoskeletal structure, Sec synthesis and Se transport. While selenoproteins are expressed in tissue dependent distributions and levels in all cells of all vertebrates, they are particularly important in brain development, health, and functions. As the most potent intracellular nucleophile, Sec is subject to binding by mercury (Hg) and other electron poor soft neurotoxic electrophiles. Epidemiological and environmental studies of the effects of exposures to methyl-Hg (CH₃Hg⁺), elemental Hg (Hg°), and/or other metallic/organic neurotoxic soft electrophiles need to consider the concomitant effects of all members of this class of toxicants in relation to the Se status of their study populations. The contributions of individual electrophiles' discrete and cooperative rates of Se sequestration need to be evaluated in relation to tissue Se reserves of the exposed populations to identify sensitive subgroups which may be at accentuated risk due to poor Se status. Additional study is required to examine possibilities of inherited, acquired, or degenerative neurological disorders of Se homeostasis that may influence vulnerability to soft electrophile exposures. Investigations of soft electrophile toxicity will be enhanced by considering the concomitant effects of combined exposures on tissue Se-availability in relation to pathological consequences during fetal development or in relation to etiologies of neurological disorders and neurodegenerative diseases. Since selenoenzymes are molecular "targets" of soft electrophiles, concomitant evaluation of aggregate exposures to these toxicants in relation to dietary Se intakes will assist regulatory agencies in their goals of improving and protecting public health.

Low Very low-Density Lipoprotein Cholesterol but High Very low-Density Lipoprotein Receptor mRNA Expression in Peripheral White Blood Cells: An Atherogenic Phenotype for Atherosclerosis in a Community-Based Population

Very low-density lipoprotein cholesterol (VLDL-C), via binding very low-density lipoprotein receptor (VLDLR), can induce the development of atherosclerosis. Besides monocytes, VLDLR expression is detected in various peripheral white blood cells (WBCs), yet its underlying role remains unclear. We thereby aimed to test the hypothesis that VLDLR in all types of peripheral WBCs may be involved in the association between VLDL-C and atherosclerosis. VLDLR mRNA expression in peripheral WBC and plasma VLDL-C levels were measured in 747 participants from a community-based study. Plaque prevalence and total plaque area (TPA) were used to evaluate the burden of carotid atherosclerosis. VLDL-C was positively associated with atherosclerosis risk, whereas this association was modified by VLDLR mRNA level. In participants with the lowest VLDL-C but the highest VLDLR mRNA expression, the risk for plaque prevalence unexpectedly was the highest. This association was also observed for TPA. Moreover, this association remained unchanged after adjusting for WBC or monocytes. Our findings described an atherogenic phenotype characterized by low VLDL-C but high VLDLR mRNA expression in peripheral WBCs, which suggested that VLDLR in all types of peripheral WBCs may be involved in lipid deposition, and VLDL-C and VLDLR may co-determine the development of atherosclerosis.

An Act of Balance Between Adaptive and Maladaptive Immunity in Depression: a Role for T Lymphocytes

Historically the monoaminergic neurotransmitter system, in particular the serotonergic system, was seen as being responsible for the pathophysiology of major depressive disorder (MDD). With the advent of psychoneuroimmunology an important role of the immune system in the interface between the central nervous systems (CNS) and peripheral organ systems has emerged. In addition to the well-characterised neurobiological activities of cytokines, T cell function in the context of depression has been neglected so far. In this review we will investigate the biological roles of T cells in depression. Originally it was thought that the adaptive immune arm including T lymphocytes was excluded from the CNS. It is now clear that peripheral naïve T cells not only carry out continuous surveillance within the brain but also maintain neural plasticity. Furthermore animal studies demonstrate that regulatory T lymphocytes can provide protection against maladaptive behavioural responses associated with depression. Psychogenic stress as a major inducer of depression can lead to transient trafficking of T lymphocytes into the brain stimulating the secretion of certain neurotrophic factors and cytokines. The separate and combined mechanism of CD4 and CD8 T cell activation is likely to determine the response pattern of CNS specific neurokines and neurotrophins. Under chronic stress-induced neuroinflammatory conditions associated with depression, T cell responses may become maladaptive and can be involved in neurodegeneration. Additionally, intracellular adhesion and MHC molecule expression as well as glucocorticoid receptor expression within the brain may play a role in determining T lymphocyte functionality in depression. Taken together, T lymphocyte mechanisms, which confer susceptibility or resilience to MDD, are not yet fully understood. Further insight into the cellular and molecular mechanisms which balance the adaptive and maladaptive roles of T lymphocytes may provide a better understanding of both the neuro- degenerative and -regenerative repair functions as present within the neuroimmune network during depression. Furthermore T cells may be important players in restoration of normal behaviour and immune cell homeostasis in depression.

Gene expression: biomarker of antidepressant therapy?

While antidepressant therapy is an essential treatment of major depression, a substantial group of treated patients do not respond to therapy, or suffer from severe side effects. Moreover, the time of onset of the clinical improvement is often delayed. Antidepressants as currently available usually enhance serotonergic, noradrenergic and dopaminergic neurotransmission and may contribute to the inadequate remission rates for major depression. Therefore biomarkers enabling the identification of subgroups of patients and also finding unprecedented targets would provide the basis for personalized medication and thus improve treatment efficacy and reduce side effects. Several pharmacogenetic studies on antidepressant treatment response using single nucleotide polymorphism (SNPs) mapping have been performed but provided only modest findings. Therefore the analysis of gene expression to integrate genomic activity and environmental effects promises a new approach to cope with the complexity of factors influencing antidepressant treatment. Here gene expression studies focusing on candidate genes and genome-wide approaches using RNA derived from peripheral blood cells are reviewed. The most promising findings exist for hypothalamic-pituitary-adrenal (HPA) axis, inflammation and neuroplasticity related genes. However, straightforward translation into tailored treatment is still unlikely. Contradictory results limit the clinical use of the findings. Future studies are necessary, which could include functional analysis and consider gene-environment interactions.

Depression pathogenesis and treatment: what can we learn from blood mRNA expression?

Alterations in several biological systems, including the neuroendocrine and immune systems, have been consistently demonstrated in patients with major depressive disorder. These alterations have been predominantly studied using easily accessible systems such as blood and saliva. In recent years there has been an increasing body of evidence supporting the use of peripheral blood gene expression to investigate the pathogenesis of depression, and to identify relevant biomarkers. In this paper we review the current literature on gene expression alterations in depression, focusing in particular on three important and interlinked biological domains: inflammation, glucocorticoid receptor functionality and neuroplasticity. We also briefly review the few existing transcriptomics studies. Our review summarizes data showing that patients with major depressive disorder exhibit an altered pattern of expression in several genes belonging to these three biological domains when compared with healthy controls. In particular, we show evidence for a pattern of 'state-related' gene expression changes that are normalized either by remission or by antidepressant treatment. Taken together, these findings highlight the use of peripheral blood gene expression as a clinically relevant biomarker approach.

Serotonin transporter clustering in blood lymphocytes as a putative biomarker of therapeutic efficacy in major depressive disorder

BACKGROUND

Serotonin transporter (SERT) binding is decreased in lymphocytes of depression patients and this decrease is partially reversed by antidepressant medication. However, recent evidence has shown that clustering of SERT on cell membranes is very important for receptor functionality. Alteration in SERT clustering on peripheral lymphocytes does not affect symptoms severity. At the most it is associated or predicts responsivity to treatment.

METHODS

We collected blood samples from 38 untreated and newly diagnosed depression patients at the time of diagnosis and after 8weeks of pharmacological treatment and of 38 control subjects. We used the Hamilton Scale to quantify the level of depression in patients both before and after pharmacological treatment. We then used immunocytochemistry to assess SERT protein clusters in lymphocyte blood samples.

RESULTS

We found an increase in SERT cluster size, but not the number of SERT clusters, in naïve depression patients compared to control subjects. Based on the distribution of SERT cluster size we differentiated the naïve depression patients into two groups (D-I and D-II). Naïve D-I and D-II patients initially showed similar Hamilton scores. However, after pharmacological treatment the D-II patients showed a greater decrease in Hamilton scores than did the D-I patients, and they had an increase in the number of SERT clusters.

LIMITATIONS

The data should be replicated in a larger cohort of patients and with a proper clinical trial.

CONCLUSIONS

We propose that SERT clustering in blood lymphocytes may be a putative biomarker for antidepressant efficacy in major depressive disorder.