Altered expression of genes involved in inflammation and apoptosis in frontal cortex in major depression

Up-regulation of metallothionein gene expression in parkinsonian astrocytes

The role of glial cells in Parkinson's disease (PD) is unclear. We have previously reported a striking up-regulation of DnaJB6 heat shock protein in PD substantia nigra astrocytes. Whole genome transcriptome analysis also indicated increased expression of metallothionein genes in substantia nigra and cortex of sporadic PD cases. Metallothioneins are metal-binding proteins in the CNS that are released by astrocytes and associated with neuroprotection. Metallothionein expression was investigated in 18 PD cases and 15 non-PD controls using quantitative real-time polymerase chain reaction (qRT-PCR), in situ hybridisation (ISH) and immunocytochemistry (ICC). We observed a strong increase in the expression of metallothioneins MT1E, MT1F, MT1G, MT1H, MT1M, MT1X and MT2A in both PD nigra and frontal cortex. Expression of LRP2 (megalin), the neuronal metallothionein receptor was also significantly increased. qRT-PCR confirmed metallothionein up-regulation. Astrocytes were found to be the main source of metallothioneins 1 and 2 based on ISH results, and this finding was confirmed by ICC. Our findings demonstrate metallothionein expression by reactive astrocytes in PD nigra and support a neuroprotective role for these cells. The traditional view that nigral astrocytes are non-reactive in PD is clearly incorrect. However, it is possible that astrocytes are themselves affected by the disease process which may explain their comparatively modest and previously overlooked response.

Serum levels of interleukin-6 and interleukin-10 in relation to depression scores in patients with cardiovascular risk factors

It is currently unknown whether elevated cytokine levels in depression are confined to any specific subgroup of depressive patients. In this study, medical out-patients presenting with cardiovascular risk factors (N = 356) were assessed for both cognitive-affective and physical symptoms of depression using the Hospital Anxiety and Depression Scale (HADS) and the Maastricht questionnaire (MQ), respectively. In study participants assigned to the highest (≥21) and lowest (≤5) quartile for the MQ score, serum levels of cytokines were measured. We found highly significant associations between cognitive-affective symptoms of depression and elevated serum levels of interleukin-6 (IL-6; ρ = .231; p = .002) and interleukin-10 (IL-10; ρ = .370; p < .001), respectively. In multiple regression models elevated IL-10 serum concentration was independently related to cognitive-affective symptoms of depression (ρ = .165; p = .002). When all cytokines were included in one model, elevated IL-10 serum concentrations remained a significant predictor for depressive mood (ρ = .157; p = .009). In patients with cardiovascular risk factors and extreme scores for vital exhaustion, elevated serum IL-6 and even more IL-10 concentrations are linked to the presence of depressive mood. Future studies will have to test whether the so far unreported association of IL-10 with depressive mood represents a causal pathway involved in the pathogenesis or in the prognostic effect of depressive mood in cardiac patients.

The GABAergic deficit hypothesis of major depressive disorder

Increasing evidence points to an association between major depressive disorders (MDDs) and diverse types of GABAergic deficits. In this review, we summarize clinical and preclinical evidence supporting a central and causal role of GABAergic deficits in the etiology of depressive disorders. Studies of depressed patients indicate that MDDs are accompanied by reduced brain concentration of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) and by alterations in the subunit composition of the principal receptors (GABA(A) receptors) mediating GABAergic inhibition. In addition, there is abundant evidence that suggests that GABA has a prominent role in the brain control of stress, the most important vulnerability factor in mood disorders. Furthermore, preclinical evidence suggests that currently used antidepressant drugs (ADs) designed to alter monoaminergic transmission and nonpharmacological therapies may ultimately act to counteract GABAergic deficits. In particular, GABAergic transmission has an important role in the control of hippocampal neurogenesis and neural maturation, which are now established as cellular substrates of most if not all antidepressant therapies. Finally, comparatively modest deficits in GABAergic transmission in GABA(A) receptor-deficient mice are sufficient to cause behavioral, cognitive, neuroanatomical and neuroendocrine phenotypes, as well as AD response characteristics expected of an animal model of MDD. The GABAergic hypothesis of MDD suggests that alterations in GABAergic transmission represent fundamentally important aspects of the etiological sequelae of MDDs that are reversed by monoaminergic AD action.

Sertoli cell therapy: a novel possible treatment strategy for treatment-resistant major depressive disorder

By the year 2020, depression will be the 2nd most common health problem in the world. Current medications to treat depression are effective in less than 50% of patients. There is the need for novel treatments for depression to address the high rates of resistance to current treatment and the chronic residual symptoms in many patients treated for depression. The heterogeneity of major depressive disorder suggests that multiple neurocircuits and neurochemicals are involved in its pathogenesis thus, finding an alternative to neurotransmitter agonist- or antagonist-based treatments offers an important new approach. Cellular therapy is an emerging treatment strategy for multiple diseases, including depression. Based upon their in vivo function as "nurse cells" within the testis and the documented viability, efficacy, and safety of Sertoli cells transplanted into multiple tissues, including brain, the potential for these cells to provide a neuroprotective, anti-inflammatory, and trophic environment for neurons should be considered. It is proposed that the combination of self-protective, immunoregulatory and trophic properties of Sertoli cells may confer a unique potential for depression treatment and avoid many of the risks and challenges associated with stem cell therapies. At the very least, studies of the effects of Sertoli cell transplantation will add substantially to our understanding of the cellular and molecular processes that underlie depression.

Recent advances in psychoneuroimmunology: Inflammation in psychiatric disorders

Psychiatric disorders are common and complex and their precise biological underpinnings remain elusive. Multiple epidemiological, molecular, genetic and gene expression studies suggest that immune system dysfunction may contribute to the risk for developing psychiatric disorders including schizophrenia, bipolar disorder, and major depressive disorder. However, the precise mechanisms by which inflammation-related events confer such risk are unclear. In this review, we examine the peripheral and central evidence for inflammation in psychiatric disorders and the potential molecular mechanisms implicated including inhibition of neurogenesis, apoptosis, the HPA-axis, the role of brain-derived neurotrophic factor and the interplay between the glutamatergic, dopaminergic and serotonergic neurotransmitter systems.

N-3 (omega-3) Fatty acids in postpartum depression: implications for prevention and treatment

A growing body of clinical and epidemiological evidence suggests that low dietary intake and/or tissue levels of n-3 (omega-3) polyunsaturated fatty acids (PUFAs) are associated with postpartum depression. Low tissue levels of n-3 PUFAs, particularly docosahexaenoic acid (DHA), are reported in patients with either postpartum or nonpuerperal depression. Moreover, the physiological demands of pregnancy and lactation put childbearing women at particular risk of experiencing a loss of DHA from tissues including the brain, especially in individuals with inadequate dietary n-3 PUFA intake or suboptimal metabolic capabilities. Animal studies indicate that decreased brain DHA in postpartum females leads to several depression-associated neurobiological changes including decreased hippocampal brain-derived neurotrophic factor and augmented hypothalamic-pituitary-adrenal responses to stress. Taken together, these findings support a role for decreased brain n-3 PUFAs in the multifactorial etiology of depression, particularly postpartum depression. These findings, and their implications for research and clinical practice, are discussed.

Behavior and pro-inflammatory cytokine variations among submissive and dominant mice engaged in aggressive encounters: moderation by corticosterone reactivity

Psychosocial stressors contribute to the pathophysiology of affective disorders and variations of cytokine functioning have been implicated in this process. The present investigation demonstrated, in mice, the impact of stressful aggressive encounters on activity levels, plasma corticosterone and cytokine concentrations, and on cytokine mRNA expression within the prefrontal cortex (PFC) and hippocampus. As glucocorticoids have been tied to cytokine variations, mice were subdivided into low or high corticosterone responders, defined in terms of circulating hormone levels 75 min post-confrontation. Interestingly, stressor-induced effects among low and high responders varied as a function of whether mice were submissive or dominant during the aggressive bout. Agonistic encounters elicited subsequent hyperactivity, particularly among low corticosterone responders and among dominant mice. Plasma levels of corticosterone and interleukin (IL)-6 concomitantly increased after aggressive encounters and varied with dominance status and with the low versus high corticosterone response. Among the low responders corticosterone and IL-6 increases were modest and only apparent among submissive mice, whereas among high responders these elevations were more pronounced and comparable in submissive and dominant mice. Aggressive episodes also increased IL-1β and IL-6 mRNA brain expression. The IL-1β rise was greater in the PFC and hippocampus of submissive mice that were low responders. Among high responders IL-1β and IL-6 increased in both groups, although in the PFC this effect was specific to dominant mice. The data are discussed in terms of their relevance to the impact of aggressive encounters on affective behaviors, and to the role that cytokines might play in this regard.