Association study of the interleukin-1 beta (C-511T) genetic polymorphism with major depressive disorder, associated symptomatology, and antidepressant response

Candidate genes expression profile associated with antidepressants response in the GENDEP study: differentiating between baseline 'predictors' and longitudinal 'targets'

To improve the 'personalized-medicine' approach to the treatment of depression, we need to identify biomarkers that, assessed before starting treatment, predict future response to antidepressants ('predictors'), as well as biomarkers that are targeted by antidepressants and change longitudinally during the treatment ('targets'). In this study, we tested the leukocyte mRNA expression levels of genes belonging to glucocorticoid receptor (GR) function (FKBP-4, FKBP-5, and GR), inflammation (interleukin (IL)-1α, IL-1β, IL-4, IL-6, IL-7, IL-8, IL-10, macrophage inhibiting factor (MIF), and tumor necrosis factor (TNF)-α), and neuroplasticity (brain-derived neurotrophic factor (BDNF), p11 and VGF), in healthy controls (n=34) and depressed patients (n=74), before and after 8 weeks of treatment with escitalopram or nortriptyline, as part of the Genome-based Therapeutic Drugs for Depression study. Non-responders had higher baseline mRNA levels of IL-1β (+33%), MIF (+48%), and TNF-α (+39%). Antidepressants reduced the levels of IL-1β (-6%) and MIF (-24%), and increased the levels of GR (+5%) and p11 (+8%), but these changes were not associated with treatment response. In contrast, successful antidepressant response was associated with a reduction in the levels of IL-6 (-9%) and of FKBP5 (-11%), and with an increase in the levels of BDNF (+48%) and VGF (+20%)-that is, response was associated with changes in genes that did not predict, at the baseline, the response. Our findings indicate a dissociation between 'predictors' and 'targets' of antidepressant responders. Indeed, while higher levels of proinflammatory cytokines predict lack of future response to antidepressants, changes in inflammation associated with antidepressant response are not reflected by all cytokines at the same time. In contrast, modulation of the GR complex and of neuroplasticity is needed to observe a therapeutic antidepressant effect.

A dialogue between the immune system and brain, spoken in the language of serotonin

Neuropsychiatric disorders have long been linked to both immune system activation and alterations in serotonin (5-HT) signaling. In the CNS, the contributions of 5-HT modulate a broad range of targets, most notably, hypothalamic, limbic and cortical circuits linked to the control of mood and mood disorders. In the periphery, many are aware of the production and actions of 5-HT in the gut but are unaware that the molecule and its receptors are also present in the immune system where evidence suggests they contribute to the both innate and adaptive responses. In addition, there is clear evidence that the immune system communicates to the brain via both humoral and neuronal mechanisms, and that CNS 5-HT neurons are a direct or indirect target for these actions. Following a brief primer on the immune system, we describe our current understanding of the synthesis, release, and actions of 5-HT in modulating immune function, including the expression of 5-HT biosynthetic enzymes, receptors, and transporters that are typically studied with respect to the roles in the CNS. We then orient our presentation to recent findings that pro-inflammatory cytokines can modulate CNS 5-HT signaling, leading to a conceptualization that among the many roles of 5-HT in the body is an integrated physiological and behavioral response to inflammatory events and pathogens. From this perspective, altered 5-HT/immune conversations are likely to contribute to risk for neurobehavioral disorders historically linked to compromised 5-HT function or ameliorated by 5-HT targeted medications, including depression and anxiety disorders, obsessive-compulsive disorder (OCD), and autism. Our review raises the question as to whether genetic variation impacting 5-HT signaling genes may contribute to maladaptive behavior as much through perturbed immune system modulation as through altered brain mechanisms. Conversely, targeting the immune system for therapeutic development may provide an important opportunity to treat mental illness.

Associations of cytokine gene polymorphisms with post-stroke depression

OBJECTIVES

Inflammatory cytokines are implicated in the pathophysiology of both stroke and depression, and their production is influenced by the transcriptional activity of particular gene polymorphisms. We hypothesised that alleles related to higher pro-inflammatory and/or lower anti-inflammatory cytokine production would be associated with post-stroke depression (PSD).

METHODS

In 276 stroke cases, depression was diagnosed using DSM-IV, and classified into major PSD (N = 29), all (major plus minor) PSD (N = 77), and control (N = 199) groups. Genotyping for six pro-inflammatory polymorphisms (TNF-α -850C/T and -308G/A, IL-1β -511C/T and + 3953C/T, IL-6 -174G/C, and IL-8 -251T/A) and two anti-inflammatory polymorphisms (IL-4 + 33T/C and IL-10 -1082G/A) was conducted. Individual associations with PSD were estimated using logistic regression models. Total numbers of potential risk alleles were calculated for pro-inflammatory and anti-inflammatory cytokine genes and analysed against depression using χ(2)-tests.

RESULTS

The IL-4 + 33C/C genotype was associated with major PSD, and the IL-10 -1082A/A genotype was associated with all PSD. Increasing numbers of risk alleles for these two anti-inflammatory cytokine genotypes were significantly associated with both PSD categories. No significant associations were found with any pro-inflammatory cytokine allele.

CONCLUSIONS

Alleles associated with reduced anti-inflammatory cytokine function were associated with PSD, supporting the cytokine hypothesis in its etiology.

The genetics of selective serotonin reuptake inhibitors

Selective serotonin reuptake inhibitors (SSRIs) are among the most widely prescribed drugs in psychiatry. Based on the fact that SSRIs increase extracellular monoamine levels in the brain, the monoamine hypothesis of depression was introduced, postulating that depression is associated with too low serotonin, dopamine and noradrenaline levels. However, several lines of evidence indicate that this hypothesis is too simplistic and that depression and the efficacy of SSRIs are dependent on neuroplastic changes mediated by changes in gene expression. Because a coherent view on global gene expression is lacking, we aim to provide an overview of the effects of SSRI treatment on the final targets of 5-HT receptor signal transduction pathways, namely the transcriptional regulation of genes. We address gene polymorphisms in humans that affect SSRI efficacy, as well as in vitro studies employing human-derived cells. We also discuss the molecular targets affected by SSRIs in animal models, both in vivo and in vitro. We conclude that serotonin transporter gene variation in humans affects the efficacy and side-effects of SSRIs, whereas SSRIs generally do not affect serotonin transporter gene expression in animals. Instead, SSRIs alter mRNA levels of genes encoding serotonin receptors, components of non-serotonergic neurotransmitter systems, neurotrophic factors, hypothalamic hormones and inflammatory factors. So far little is known about the epigenetic and age-dependent molecular effects of SSRIs, which might give more insights in the working mechanism(s) of SSRIs.

Targeting IL-1 in depression

INTRODUCTION

Depression is associated with inflammation, Th1 and Th17 responses, oxidative and nitrosative stress (O&NS), autoimmune responses against neoantigenic determinants, and neuroprogression (i.e., neurodegeneration, impaired plasticity and reduced neurogenesis). These pathways involve increased monocytic activation and interleukin-1 (IL-1) levels.

AREAS COVERED

This review will highlight the putative role of IL-1 in depression and the potential use of IL-1 signaling blockade as a treatment of depression. Electronic databases, i.e., Scopus, PUBMED and Google Scholar were employed using keywords: depression, depressive-like, interleukin-1, and interleukin-1 receptor antagonist (IL-1RA).

EXPERT OPINION

Ample studies show that depression is accompanied by increased levels of IL-1 and IL-1RA, which attenuates the pro-inflammatory activities of IL-1. In some, but not all studies, antidepressant treatment decreased IL-1β levels. In translational models, IL-1β administration elicits depressive-like behaviors, neuroinflammation and neuroprogression, whereas treatment with IL-1RA yields antidepressant-like effects and attenuates neuroprogression. Anakinra, an IL-1RA, targets not only IL-1 signaling, but also Th1, Th17, O&NS and neuroprogressive pathways and therefore may be advanced to clinical Phase-II trials in depression due to medical conditions associated with an elevated IL-1/IL-1RA ratio.

Physical health and incident late-life depression: modification by cytokine genes

Inflammatory cytokines have been implicated in the pathophysiology of depression, potentially underlying its association with worse physical health. Cytokine production is influenced by the transcriptional activity of several polymorphisms. We hypothesized that alleles related to higher proinflammatory and/or lower anti-inflammatory cytokine production would strengthen the association between physical disorders and late-life depression. In a 2-year prospective study of a community sample of 521 older people, information on number of physical disorders, diagnosis of depression (Geriatric Mental State), and genotypes for 6 pro-inflammatory (tumor necrosis factor-α -850C/T and -308G/A, interleukin (IL)-1β -511C/T and +3953C/T, IL-6 -174G/C, IL-8 -251T/A) and 2 anti-inflammatory (IL-4 +33T/C, IL-10 -1082G/A) cytokine polymorphisms were ascertained. Total numbers of potential risk alleles were calculated for pro- and anti-inflammatory cytokine genes. Interactions between baseline physical disorders and cytokine genotypes were investigated for incident depression. The associations between physical disorders and incident depression were significant in the presence of 2 alleles related to higher proinflammatory cytokine production (tumor necrosis factor-α -850T and IL-8 -251A), and 1 allele related to lower anti-inflammatory cytokine production (IL-4 +33C). Significant gene-environment interactions, independent of all covariates, were found for total number of risk alleles on both pro- and anti-inflammatory cytokine genes in addition to the above 3 individual single nucleotide polymorphisms. The present findings support cytokine-mediated inflammatory pathways underlying at least some of the well-recognized association between worse physical health and late-life depression, and provide novel evidence of a genetic basis for this.

Taking the Perspective that a Depressive State Reflects Inflammation: Implications for the Use of Antidepressants

This paper reviews both the evidence that supports the characterization of depression as an inflammatory disorder and the different biochemical mechanisms that have been postulated for the connection between inflammation and depression. This association offers credible explanation for the short term efficacy of antidepressants, which have short term anti-inflammatory effects. Evidence for those anti-inflammatory effects is discussed. Evidence of the contrary long-term effects of antidepressants, which increase rather than decrease inflammation, is also reviewed. It is argued that this increase in inflammation would predict an increase in chronicity among depressed patients that have been treated with antidepressants drugs, which has been noted in the literature. A brief discussion of alternatives for decreasing inflammation, some of which have demonstrated efficacy in ameliorating depression, is presented.

Psychotropic effects of antimicrobials and immune modulation by psychotropics: implications for neuroimmune disorders

Antimicrobial compounds and psychotropic medications often share overlapping mechanisms of actions and pharmacological effects. The immune system appears to be an important site of interaction as several antimicrobials display neurological and, at times, direct psychotropic effects, while psychotropics have shown significant immunomodulatory properties. The isoniazid class of antibiotics for example has been shown to possess monoamine oxidase activity, while selective serotonin reuptake inhibitors have shown significant effects on leukocyte populations. As the importance of the immune system's role in CNS homeostasis and disease continues to move to the forefront of neuropsychiatric research, these shared pharmacological effects may provide an important insight, elucidating the complexities in neuroimmune pathophysiology and guiding the development of potential treatments.

[Clinical Applications of Peripheral Markers of Response in Antidepressant Treatment: Neurotrophins and Cytokines]

INTRODUCTION

Explanatory theories of depression have advanced in recent decades from the monoaminergic hypothesis to neurogenesis alterations to the neurohormonal hypothesis that includes the dysfunction of the inflammatory response. Currently there is a growing interest in the development of biomarkers that can contribute to diagnosis and proper treatment.

OBJECTIVES

To describe the role of neurotrophins such as brain-derived neurotrophic factor (BDNF) and cytokines in the pathophysiology of depressive disorder in addition to reviewing and analyzing evidence about their clinical application as biomarkers of antidepressant therapy.

METHOD

Relevant data research in several databases.

RESULTS AND CONCLUSIONS

In recent years evidence of alterations in neurogenesis mediated by the expression of BDNF in the hippocampus in the pathophysiology of depression has increased and there is ample evidence that BDNF is a marker of the diagnosis of depressive disorder and also of treatment effectiveness. There is little information about other neurotrophins. There has also been increased interest in relation to depression as an "inflammatory disease" and the link with cytokines in its pathogenesis. Evidence has been found for the usefulness of some cytokines especially IL-1 (interleukin 1), IL-6 (interleukin 6), and TNF (tumor necrosis factor) as biomarkers of antidepressant drug response in humans.

Psychoneuroimmunology meets neuropsychopharmacology: translational implications of the impact of inflammation on behavior

The potential contribution of chronic inflammation to the development of neuropsychiatric disorders such as major depression has received increasing attention. Elevated biomarkers of inflammation, including inflammatory cytokines and acute-phase proteins, have been found in depressed patients, and administration of inflammatory stimuli has been associated with the development of depressive symptoms. Data also have demonstrated that inflammatory cytokines can interact with multiple pathways known to be involved in the development of depression, including monoamine metabolism, neuroendocrine function, synaptic plasticity, and neurocircuits relevant to mood regulation. Further understanding of mechanisms by which cytokines alter behavior have revealed a host of pharmacologic targets that may be unique to the impact of inflammation on behavior and may be especially relevant to the treatment and prevention of depression in patients with evidence of increased inflammation. Such targets include the inflammatory signaling pathways cyclooxygenase, p38 mitogen-activated protein kinase, and nuclear factor-κB, as well as the metabolic enzyme, indoleamine-2,3-dioxygenase, which breaks down tryptophan into kynurenine. Other targets include the cytokines themselves in addition to chemokines, which attract inflammatory cells from the periphery to the brain. Psychosocial stress, diet, obesity, a leaky gut, and an imbalance between regulatory and pro-inflammatory T cells also contribute to inflammation and may serve as a focus for preventative strategies relevant to both the development of depression and its recurrence. Taken together, identification of mechanisms by which cytokines influence behavior may reveal a panoply of personalized treatment options that target the unique contributions of the immune system to depression.

Neuroimmune endocrine effects of antidepressants

Antidepressant pharmacotherapy is to date the most often used treatment for depression, but the exact mechanism of action underlying its therapeutic effect is still unclear. Many theories have been put forward to account for depression, as well as antidepressant activity, but none of them is exhaustive. Neuroimmune endocrine impairment is found in depressed patients; high levels of circulating corticosteroids along with hyperactivation of the immune system, high levels of proinflammatory cytokines, low levels of melatonin in plasma and urine, and disentrainment of circadian rhythms have been demonstrated. Moreover, antidepressant treatment seems to correct or at least to interfere with these alterations. In this review, we summarize the complex neuroimmune endocrine and chronobiological alterations found in patients with depression and how these systems interact with each other. We also explain how antidepressant therapy can modify these systems, along with some possible mechanisms of action shown in animal and human models.

Modulation of cortisol responses to the DEX/CRH test by polymorphisms of the interleukin-1beta gene in healthy adults

BACKGROUND

Recently, hypothalamus-pituitary-adrenal (HPA) axis function assessed with the combined dexamethasone (DEX)/corticotropin releasing hormone (CRH) test has been shown to be associated with response to antidepressant treatment. A polymorphism (rs16944) in the interleukin-1beta (IL-1β) gene has also been reported to be associated with the medication response in depression. These findings prompted us to examine the possible association between IL-1β gene polymorphisms and HPA axis function assessed with the DEX/CRH test.

METHODS

DEX/CRH test was performed in 179 healthy volunteers (45 males: mean age 40.5 ± 15.8 years; 134 females: mean age 47.1 ± 13.2 years). Five tagging single nucleotide polymorphisms (SNPs) of IL-1β gene (rs2853550, rs1143634, rs1143633, rs1143630, rs16944) were selected at an r2 threshold of 0.80 with a minor allele frequency > 0.1. Genotyping was performed by the TaqMan allelic discrimination assay. A two-way factorial analysis of variance (ANOVA) was performed with the DEX/CRH test results as the dependent variable and genotype and gender as independent variables. To account for multiple testing, P values < 0.01 were considered statistically significant for associations between the genotypes and the cortisol levels.

RESULTS

The cortisol levels after DEX administration (DST-Cortisol) showed significant associations with the genotypes of rs16944 (P = 0.00049) and rs1143633 (P = 0.0060), with no significant gender effect or genotype × gender interaction. On the other hand, cortisol levels after CRH administration (DEX/CRH-Cortisol) were affected by gender but were not significantly influenced by the genotype of the examined SNPs, with no significant genotype × gender interaction.

CONCLUSIONS

Our results suggest that genetic variations in the IL-1β gene contribute to the HPA axis alteration assessed by DST-Cortisol in healthy subjects. On the other hand, no significant associations of the IL-1β gene polymorphisms with the DEX/CRH-Cortisol were observed. Confirmation of our findings in futures studies may add new insight into the communication between the immune system and the HPA axis.

A review on the oxidative and nitrosative stress (O&NS) pathways in major depression and their possible contribution to the (neuro)degenerative processes in that illness

This paper reviews the body of evidence that major depression is accompanied by a decreased antioxidant status and by induction of oxidative and nitrosative (IO&NS) pathways. Major depression is characterized by significantly lower plasma concentrations of a number of key antioxidants, such as vitamin E, zinc and coenzyme Q10, and a lowered total antioxidant status. Lowered antioxidant enzyme activity, e.g. glutathione peroxidase (GPX), is another hallmark of depression. The abovementioned lowered antioxidant capacity may impair protection against reactive oxygen species (ROS), causing damage to fatty acids, proteins and DNA by oxidative and nitrosative stress (O&NS). Increased ROS in depression is demonstrated by increased levels of plasma peroxides and xanthine oxidase. Damage caused by O&NS is shown by increased levels of malondialdehyde (MDA), a by-product of polyunsaturated fatty acid peroxidation and arachidonic acid; and increased 8-hydroxy-2-deoxyguanosine, indicating oxidative DNA damage. There is also evidence in major depression, that O&NS may have changed inactive autoepitopes to neoantigens, which have acquired immunogenicity and serve as triggers to bypass immunological tolerance, causing (auto)immune responses. Thus, depression is accompanied by increased levels of plasma IgG antibodies against oxidized LDL; and increased IgM-mediated immune responses against membrane fatty acids, like phosphatidyl inositol (Pi); oleic, palmitic, and myristic acid; and NO modified amino-acids, e.g. NO-tyrosine, NO-tryptophan and NO-arginine; and NO-albumin. There is a significant association between depression and polymorphisms in O&NS genes, like manganese superoxide dismutase, catalase, and myeloperoxidase. Animal models of depression very consistently show lowered antioxidant defences and activated O&NS pathways in the peripheral blood and the brain. In animal models of depression, antidepressants consistently increase lowered antioxidant levels and normalize the damage caused by O&NS processes. Antioxidants, such as N-acetyl-cysteine, compounds that mimic GPX activity, and zinc exhibit antidepressive effects. This paper reviews the pathways by which lowered antioxidants and O&NS may contribute to depression, and the (neuro)degenerative processes that accompany that illness. It is concluded that aberrations in O&NS pathways are--together with the inflammatory processes--key components of depression. All in all, the results suggest that depression belongs to the spectrum of (neuro)degenerative disorders.

Interleukin-1beta promoter (-31T/C and -511C/T) polymorphisms in major recurrent depression

To elucidate a genetic predisposition to major depressive disorder, we investigated two polymorphisms (−31T/C and −511C/T) in the interleukin-1beta promoter region in patients who suffered from major recurrent depression. The aim of the current work was to compare alleles and genotype layout between patients with major recurrent depression and healthy people. We would like to indicate such combination of genotypes which corresponds with major recurrent depression. Correlations between genotypes for analyzed polymorphisms and number of episodes, number of points in Hamilton Depression Rating Scale, and age of onset were investigated as well. The study group consisted of 94 patients diagnosed with major recurrent depression. The control group included 206 healthy individuals. Both groups involved representatives of Caucasian population. Genotyping of polymorphisms was performed by using PCR-RFLP technique. A specific haplotype, composed of the C allele at −31 and the T allele at −511, has a tendency to have a statistically significant difference (p = 0.064) between patients and control group. Correspondence analysis revealed that genotype T/T at −31 and genotype C/C at −511 are associated with major recurrent depression. No association was found between genotypes for studied polymorphic sites and number of episodes, number of points in Hamilton Depression Rating Scale, and age of onset.

Pharmacogenetics of antidepressants

Up to 60% of depressed patients do not respond completely to antidepressants (ADs) and up to 30% do not respond at all. Genetic factors contribute for about 50% of the AD response. During the recent years the possible influence of a set of candidate genes as genetic predictors of AD response efficacy was investigated by us and others. They include the cytochrome P450 superfamily, the P-glycoprotein (ABCB1), the tryptophan hydroxylase, the catechol-O-methyltransferase, the monoamine oxidase A, the serotonin transporter (5-HTTLPR), the norepinephrine transporter, the dopamine transporter, variants in the 5-hydroxytryptamine receptors (5-HT1A, 5-HT2A, 5-HT3A, 5-HT3B, and 5-HT6), adrenoreceptor beta-1 and alpha-2, the dopamine receptors (D2), the G protein beta 3 subunit, the corticotropin releasing hormone receptors (CRHR1 and CRHR2), the glucocorticoid receptors, the c-AMP response-element binding, and the brain-derived neurotrophic factor. Marginal associations were reported for angiotensin I converting enzyme, circadian locomotor output cycles kaput protein, glutamatergic system, nitric oxide synthase, and interleukin 1-beta gene. In conclusion, gene variants seem to influence human behavior, liability to disorders and treatment response. Nonetheless, gene × environment interactions have been hypothesized to modulate several of these effects.

The heritability of postpartum depression

Postpartum depression (PPD) is a serious mood disorder that may carry life-long consequences for a woman and her family. Multiple risk factors for PPD have been identified, including psychosocial, situational, and biological stimuli, several of which are experienced by most, if not all, postpartum women. Given the commonality of these risk factors, it is unclear why fewer than 20% of postpartum women actually develop PPD. In this review, we suggest that different susceptibility to PPD among postpartum women may be explained by the presence or absence of genetic variants that confer increased risk. We review three categories of genes known to code for proteins associated with depression in the general population or proteins known to be affected by childbirth for their possible association with PPD, including genes related to central nervous system monoamine availability, proinflammatory cytokines, and brain neuropeptides. Only two studies are available in the literature to date specifically looking at polymorphisms in postpartum women as related to PPD; both are concerned with monoamine availability. These are discussed in further depth. Conclusions regarding the contribution of genetic polymorphisms to the development of PPD are mixed. Ultimately, the complexity of the disorder and the interrelationships among different genes thought to contribute to depression suggest that much more research is required to understand the heritability of PPD. The complexity of the disorder also suggests that epigenetic influences must be considered as well when discussing susceptibility.

Social interaction prevents the development of depressive-like behavior post nerve injury in mice: a potential role for oxytocin

OBJECTIVE

To examine the salubrious role of social interaction in modulating the development of allodynia (increased sensitivity to typically innocuous physical stimuli) and depressive-like behavior post peripheral nerve injury in mice. The determination of potential mechanisms that mediate social influences on the behavioral and physiological response to peripheral nerve injury.

METHODS

Mice were pair housed or socially isolated for 2 weeks before spared nerve injury (SNI). Animals were cannulated; socially isolated animals were centrally treated with oxytocin; and socially paired animals were centrally treated with an oxytocin receptor antagonist. Animals were subsequently monitored for the development of mechanical allodynia and depressive-like behavior, and tissue was collected for analysis of the central levels of the cytokine interleukin 1 beta (IL-1beta).

RESULTS

Depressive-like behavior was assessed via the Porsolt forced swim test, developed only among socially isolated mice with nerve injury. Socially isolated mice with nerve injury also were the only experimental group to exhibit increased frontal cortex IL-1beta gene expression on day 7 post injury. Moreover, central treatment of socially isolated mice with oxytocin, a neuropeptide associated with social bonding, attenuated the effects of SNI on depressive-like behavior and reduced frontal cortex IL-1beta protein levels in socially isolated animals. Conversely, pair-housed animals treated with a selective oxytocin receptor antagonist developed depressive-like behavior equivalent to that of socially isolated animals and displayed increased IL-1beta protein levels within the frontal cortex.

CONCLUSION

These data suggest that social interaction significantly alters the affective and neuroinflammatory responses to SNI through a mechanism that could involve oxytocin.

Stress and IL-1beta contribute to the development of depressive-like behavior following peripheral nerve injury

The physiological link between neuropathic pain and depression remains unknown despite a high comorbidity between these two disorders. A mouse model of spared nerve injury (SNI) was used to test the hypothesis that nerve injury precipitates depression through the induction of inflammation in the brain, and that prior exposure to stress exacerbates the behavioral and neuroinflammatory consequences of nerve injury. As compared with sham surgery, SNI induced mechanical allodynia, and significantly increased depressive-like behavior. Moreover, SNI animals displayed increased interleukin-1beta (IL-1beta) gene expression within the frontal cortex and concurrent increases in the expression of glial fibrillary acidic protein (GFAP) within the periaqueductal grey (PAG). Additionally, exposure to chronic restraint stress for 2 weeks before SNI exacerbated mechanical allodynia and depressive-like behavior, and resulted in an increase in IL-1beta gene expression in the frontal cortex and brain-derived neurotrophic factor (BDNF) gene expression in PAG. Treatment with metyrapone (MET), a corticosteroid synthesis inhibitor, before stress eliminated deleterious effects of chronic stress on SNI. Finally, this study showed that interference with IL-1beta signaling, through administration of IL-1 receptor antagonist (IL-1ra), ameliorated the effects of neuropathic pain on depressive-like behavior. Taken together, these data suggest that peripheral nerve injury leads to increased cytokine expression in the brain, which in turn, contributes to the development of depressive-like behavior. Furthermore, stress can facilitate the development of depressive-like behavior after nerve injury by promoting IL-1beta expression.

A psychoneuroimmunological review on cytokines involved in antidepressant treatment response

OBJECTIVES

The literature exploring the role that cytokine functioning plays in the pathogenesis and treatment of depressive illness is reviewed. The review focuses on the influence of antidepressants on cytokines, and on how treatment response might be affected by genetic variants of cytokines.

METHOD

The authors systematically reviewed the scientific literature on the subject over the last 20 years, searching PubMed, PsychInfo, and Cochrane databases.

RESULTS

Antidepressants modulate cytokine functioning, and these mechanisms appear to directly influence treatment outcome in depression. Antidepressants appear to normalize serum levels of major inflammatory cytokines, including interleukin (IL)-1beta, IL-6, tumor necrosis factor alpha (TNF-alpha), and interferon gamma (IFN-gamma). Antidepressants are postulated to modulate cytokine functioning through their effects on intracellular cyclic adenosyl monophosphate (cAMP), serotonin metabolism, the hypothalamo-pituitary-adrenocortical (HPA) axis or through a direct action on neurogenesis. Preliminary research shows that cytokine genotypes and functioning may be able to help predict antidepressant treatment response.

CONCLUSIONS

Current literature demonstrates an association between antidepressant action and cytokine functioning in major depression. Improved understanding of the specific pharmacologic and pharmacogenetic mechanisms is needed. Such knowledge may serve to enhance our understanding of depression, leading to promising new directions in the pathology, nosology, and treatment of depression.

Interleukin-1 beta -511C/T genetic polymorphism is associated with age of onset of geriatric depression

The pro-inflammatory cytokine interleukin-1 beta has been implicated in the pathogenesis of major depressive disorder and in cognitive function decline in the elderly. This study tests the hypothesis that a biallelic functional polymorphism in the promoter region of the interleukin-1 beta gene (IL1B -511C/T) affects vulnerability to geriatric depression and its manifestations, including age of onset, depression severity, and cognitive function. We genotyped the IL1B -511C/T polymorphism in 125 elderly inpatients diagnosed with major depression and 282 normal elderly controls. The depressed patients were evaluated at baseline after admission using the Hamilton Rating Scale for Depression (HAM-D) for depression severity and the Mini-Mental Status Examination (MMSE) for cognitive function; depression age of onset was evaluated by interview and medical records. We found no association between IL1B -511C/T genotypes and geriatric depression susceptibility (P = 0.213), depression severity (HAM-D scores; P = 0.766) or cognitive function (MMSE scores; P = 0.827); however, compared with depressed subjects carrying the -511C allele, depressed subjects who were -511T homozygotes showed a significantly later depression age of onset of 7 years (P = 0.021). Our findings suggest that the IL1B -511C/T polymorphism may be related to age at manifestation among individuals vulnerable to depression, but they do not affect the basic vulnerability to or severity of depression in elderly Chinese adults. Further study is warranted to confirm this finding and to assess its generalization to other ethnic groups.

The interleukin 1 beta (IL1B) gene is associated with failure to achieve remission and impaired emotion processing in major depression

BACKGROUND

Accumulating evidence suggests the involvement of inflammatory processes and cytokines in particular in the pathophysiology of major depression (MDD) and resistance to antidepressant treatment. Furthermore, amygdala and anterior cingulate cortex (ACC) responsiveness to emotional stimuli has been suggested as a predictor of treatment response. This study investigated the association between genetic variants of the interleukin 1 beta (IL1B) gene and amygdala and ACC responsiveness to emotional stimuli and response to antidepressant treatment.

METHODS

In this analysis, 256 Caucasian patients with MDD (145 women, 111 men) were genotyped for variants rs16944, rs1143643, and rs1143634 in the IL1B gene (2q14). Response to antidepressant treatment over 6 weeks was defined as remission (< or = 7 on the Hamilton Rating Scale for Depression-21-question) and response (>50% decrease on Hamilton Rating Scale for Depression-21-question). Brain activity under visual presentation of emotional faces was assessed in a subsample of 32 depressed patients by means of functional magnetic resonance imaging at 3 T.

RESULTS

Pharmacogenetic analyses show significant associations of the GG genotypes of single nucleotide polymorphisms (SNPs) rs16944 (odds ratio = 1.74; 95% confidence interval 1.2-4.3) and rs1143643 (odds ratio = 3.1; 95% confidence interval 1.3-7.8) (compared with the AA genotype) with nonremission after 6 weeks. The imaging analyses show that the number of G-alleles in both SNPs (rs16944 and rs1143643) was associated with reduced responsiveness of the amygdala and ACC to emotional stimulation.

CONCLUSIONS

The present study suggests a negative effect of the IL1B gene on pharmacological response and amygdala and ACC function involving the same genotypes of two SNPs (rs16944, rs116343), which taken together increase the risk of nonremission over 6 weeks of antidepressant treatment in MDD.

The -308 (G/A) single nucleotide polymorphism in the TNF-alpha gene and the risk of major depression in the elderly

OBJECTIVE

The immune system (IS) plays a key role in the mechanisms underlying major depression (MD) and pro-inflammatory cytokines seem to be particularly involved in the pathogenesis of the disease. There is growing evidence of a relationship between commonly studied single nucleotide polymorphisms (SNPs) in cytokine genes and an increased risk of MD.The aim of our study was to investigate the association between the -308(G/A) SNP in the tumour necrosis factor-alpha (TNF-alpha) gene and late-life MD in elderly people without dementia.

METHODS

Blood samples were obtained from 50 subjects enrolled at the Geriatric Department of the San Gerardo Hospital in Monza, Italy, after screening with the geriatric depression scale (GDS > or = 15) and mini-mental state evaluation (MMSE > or = 24). The -308 (G/A) SNP was genotyped by SSP-PCR amplification. Two hundred and forty age-matched healthy volunteers were taken as the control group.

RESULTS

Genotype and allele distributions in patients with MD were significantly different from those of the controls. In subjects affected by MD we found a higher percentage of the GG genotype (84 vs. 68,3%; p = 0.007) and thus of the G allele (92 vs. 81,9%; p = 0.05).The GG genotype was associated with a greater risk of developing the disease (OR 2.433, CI 1.09-5.43).

CONCLUSIONS

Our study suggests that the -308 (G/A) polymorphism in the TNF-alpha gene could play a role in determining susceptibility to MD. An activation of the TNF-alpha system could contribute to the development of MD in the elderly.

Interleukin 18 in the CNS

Interleukin (IL)-18 is a cytokine isolated as an important modulator of immune responses and subsequently shown to be pleiotropic. IL-18 and its receptors are expressed in the central nervous system (CNS) where they participate in neuroinflammatory/neurodegenerative processes but also influence homeostasis and behavior. Work on IL-18 null mice, the localization of the IL-18 receptor complex in neurons and the neuronal expression of decoy isoforms of the receptor subunits are beginning to reveal the complexity and the significance of the IL-18 system in the CNS. This review summarizes current knowledge on the central role of IL-18 in health and disease.

Cytokine polymorphisms in the pathophysiology of mood disorders

INTRODUCTION

An increasing amount of data suggests that dysregulation of the immune system, including the cytokine network, is associated with the etiology and pathophysiology of mood disorders. Genes encoding cytokines are highly polymorphic and single nucleotide polymorphisms, associated with increased or reduced cytokine production, have been described. The aim of this study was to define the genetic immunologic scenario associated with major depressive disorder (MDD) and bipolar disorder.

METHODS

Eighty-four Italian outpatients affected by bipolar disorder type I, bipolar disorder type II, or MDD, and 363 healthy controls were enrolled into the study. We analyzed allele and genotype distribution of -308 (G/A) tumor necrosis factor-a (TNF-a), +874 (T/A) interferon-g (IFN-g), -174 (G/C) interleukin (IL)-6, and -1082 (G/A) IL-10 promoter polymorphisms by Polymerase Chain Reaction Sequence Specific Primers technique.

RESULTS

We observed different genotype and allele distributions of TNF-a, IFN-g, and IL-10 polymorphisms in the three groups of patients analyzed. In particular, bipolar II patients were characterized by an absence of adenine (A) high producer allele of TNF-a (P<.001) and a lower percentage of TT high producer genotype of IFN-g (P<.001); bipolar I individuals showed reduced percentage of AA low producer genotype of IL-10 (P<.001). Both bipolar I and bipolar II patients not carrying guanine (G) high producer IL-6 allele showed a lower mean age at onset (P=.048).

CONCLUSION

These data support the existence of a genetic profile related to pro-inflammatory cytokines in patients affected by mood disorders. The differences observed across the three clinical phenotypes suggest the presence of different pathogenetic mechanisms involved in the susceptibility of phenotypically different mood disorders.

Epistasis between IL1A, IL1B, TNF, HTR2A, 5-HTTLPR and TPH2 variations does not impact alcohol dependence disorder features

We assessed a set of biological (HDL, LDL, SGOT, SGPT, GGT, HTc, Hb and T levels) and psychometric variables (investigated through HAM-D, HAM-A, GAS, Liebowitz Social Anxiety Scale, Mark & Mathews Scale, Leyton scale, and Pilowski scale) in a sample of 64 alcohol dependent patients, at baseline and after a detoxification treatment. Moreover, we recruited 47 non-consanguineous relatives who did not suffer alcohol related disorders and underwent the same tests. In both groups we genotyped 11 genetic variations (rs1800587; rs3087258; rs1799724; 5-HTTLPR; rs1386493; rs1386494; rs1487275; rs1843809; rs4570625; rs2129575; rs6313) located in genes whose impact on alcohol related behaviors and disorders has been hypothesized (IL1A, IL1B, TNF, 5-HTTLPR, TPH2 and HTR2A). We analyzed the epistasis of these genetic variations upon the biological and psychological dimensions in the cases and their relatives. Further on, we analyzed the effects of the combined genetic variations on the short - term detoxification treatment efficacy. Finally, being the only not yet investigated variation within this sample, we analyzed the impact of the rs6313 alone on baseline assessment and treatment efficacy. We detected the following results: the couple rs6313 + rs2129575 affected the Leyton -Trait at admission (p = 0.01) (obsessive-compulsive trait), whilst rs1800587 + 5-HTTLPR impacted the Pilowski test at admission (p = 0.01) (hypochondriac symptoms). These results did not survive Bonferroni correction (p < or = 0.004). This lack of association may depend on the incomplete gene coverage or on the small sample size which limited the power of the study. On the other hand, it may reflect a substantial absence of relevance of the genotype variants toward the alcohol related investigated dimensions. Nonetheless, the marginal significance we detected could witness an informative correlation worth investigating in larger samples.

Tagging SNP association study of the IL-1beta gene (IL1B) and childhood-onset mood disorders

Given substantial evidence for IL-1beta involvement in the etiology of depression, the IL1B gene is a strong candidate for involvement in susceptibility to depressive disorders. However, association studies investigating this, to date, have been limited to just two polymorphisms (rs1143627[-31T/C] and rs16944[-511C/T]) that constitute only a fraction of the genetic variation that is actually present across this gene in the population. Here, in a family-based association study of childhood-onset mood disorders (COMD), characterized by onset of depression before the age of 15, we have used a gene-wide approach, employing a panel of five tagging SNPs spanning the entire gene. Based on TDT analyses of both individual alleles and haplotypes, in a study sample of 646 families (with 782 affected children), none of the SNPs, including those implicated in transcriptional regulation of the gene, showed evidence for association with COMD. This is the largest and most comprehensive study of IL1B in relation to mood disorders that has been carried out, to date. The results do not support the involvement of IL1B as a major factor in genetic risk for early-onset mood disorders.

Inflammation and its discontents: the role of cytokines in the pathophysiology of major depression

Recognition that inflammation may represent a common mechanism of disease has been extended to include neuropsychiatric disorders including major depression. Patients with major depression have been found to exhibit increased peripheral blood inflammatory biomarkers, including inflammatory cytokines, which have been shown to access the brain and interact with virtually every pathophysiologic domain known to be involved in depression, including neurotransmitter metabolism, neuroendocrine function, and neural plasticity. Indeed, activation of inflammatory pathways within the brain is believed to contribute to a confluence of decreased neurotrophic support and altered glutamate release/reuptake, as well as oxidative stress, leading to excitotoxicity and loss of glial elements, consistent with neuropathologic findings that characterize depressive disorders. Further instantiating the link between inflammation and depression are data demonstrating that psychosocial stress, a well-known precipitant of mood disorders, is capable of stimulating inflammatory signaling molecules, including nuclear factor kappa B, in part, through activation of sympathetic nervous system outflow pathways. Interestingly, depressed patients with increased inflammatory biomarkers have been found to be more likely to exhibit treatment resistance, and in several studies, antidepressant therapy has been associated with decreased inflammatory responses. Finally, preliminary data from patients with inflammatory disorders, as well as medically healthy depressed patients, suggest that inhibiting proinflammatory cytokines or their signaling pathways may improve depressed mood and increase treatment response to conventional antidepressant medication. Translational implications of these findings include the unique opportunity to identify relevant patient populations, apply immune-targeted therapies, and monitor therapeutic efficacy at the level of the immune system in addition to behavior.

Treatment-resistant depression and mortality after acute coronary syndrome

Depression is a risk factor for morbidity and mortality in patients with coronary heart disease, especially following acute coronary syndrome. Evidence from recent clinical trials suggests that treatment-resistant depression may be associated with a particularly high risk of mortality or cardiac morbidity in patients following acute coronary syndrome. This article reviews this evidence and considers possible explanations for this relationship. Directions for future research are also considered, with particular emphasis on efforts to elucidate the underlying mechanisms and to develop more efficacious treatments for depression in patients with coronary heart disease.

Interleukin-1 (IL-1): a central regulator of stress responses

Ample evidence demonstrates that the pro-inflammatory cytokine interleukin-1 (IL-1), produced following exposure to immunological and psychological challenges, plays an important role in the neuroendocrine and behavioral stress responses. Specifically, production of brain IL-1 is an important link in stress-induced activation of the hypothalamus-pituitary-adrenal axis and secretion of glucocorticoids, which mediate the effects of stress on memory functioning and neural plasticity, exerting beneficial effects at low levels and detrimental effects at high levels. Furthermore, IL-1 signaling and the resultant glucocorticoid secretion mediate the development of depressive symptoms associated with exposure to acute and chronic stressors, at least partly via suppression of hippocampal neurogenesis. These findings indicate that whereas under some physiological conditions low levels of IL-1 promote the adaptive stress responses necessary for efficient coping, under severe and chronic stress conditions blockade of IL-1 signaling can be used as a preventive and therapeutic procedure for alleviating stress-associated neuropathology and psychopathology.

Polymorphisms in the interleukin-10 gene cluster are possibly involved in the increased risk for major depressive disorder

Background

Innate immune inflammatory response is suggested to have a role in the pathogenesis of major depressive disorder (MDD). Interleukin (IL)-10 family cytokines IL-10, IL-19, IL-20, and IL-24 are all implicated in the inflammatory processes and polymorphisms in respective genes have been associated with various immunopathological conditions. This study was carried out to investigate whether single-nucleotide polymorphisms (SNPs) in these genes are also associated with MDD.

Methods

Case-control association study was performed with seven SNPs from the IL10 gene cluster. 153 patients with MDD and 277 healthy control individuals were recruited.

Results

None of the selected SNPs were individually associated with MDD. The linkage disequilibrium (LD) analysis indicated the existence of two recombination sites in the IL10 gene cluster, thus confirming the formerly established LD pattern of this genomic region. This also created two haplotype blocks, both consisting of three SNPs. Additionally, the haplotype analysis detected a significantly higher frequency of block 2 (IL20 and IL24 genes) haplotype TGC in the patients group compared to healthy control individuals (P = 0.0097).

Conclusion

Our study established increased risk for MDD related to the IL20 and IL24 haplotype and suggests that cytokines may contribute to the pathogenesis of MDD. Since none of the block 2 SNPs were individually associated with MDD, it is possible that other polymorphisms linked to them contribute to the disease susceptibility. Future studies are needed to confirm the results and to find the possible functional explanation.

Meta-analyses of genetic studies on major depressive disorder

The genetic basis of major depressive disorder (MDD) has been investigated extensively, but the identification of MDD genes has been hampered by conflicting results from underpowered studies. We review all MDD case-control genetic association studies published before June 2007 and perform meta-analyses for polymorphisms that had been investigated in at least three studies. The study selection and data extraction were performed in duplicate by two independent investigators. The 183 papers that met our criteria studied 393 polymorphisms in 102 genes. Twenty-two polymorphisms (6%) were investigated in at least three studies. Seven polymorphisms had been evaluated in previous meta-analyses, 5 of these had new data available. Hence, we performed meta-analyses for 20 polymorphisms in 18 genes. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Statistically significant associations were found for the APOE varepsilon2 (OR, 0.51), GNB3 825T (OR, 1.38), MTHFR 677T (OR, 1.20), SLC6A4 44 bp Ins/Del S (OR, 1.11) alleles and the SLC6A3 40 bpVNTR 9/10 genotype (OR, 2.06). To date, there is statistically significant evidence for six MDD susceptibility genes (APOE, DRD4, GNB3, MTHFR, SLC6A3 and SLC6A4).

Brain interleukin-1 mediates chronic stress-induced depression in mice via adrenocortical activation and hippocampal neurogenesis suppression

Several lines of evidence implicate the pro-inflammatory cytokine interleukin-1 (IL-1) in the etiology and pathophysiology of major depression. To explore the role of IL-1 in chronic stress-induced depression and some of its underlying biological mechanisms, we used the chronic mild stress (CMS) model of depression. Mice subjected to CMS for 5 weeks exhibited depressive-like symptoms, including decreased sucrose preference, reduced social exploration and adrenocortical activation, concomitantly with increased IL-1 beta levels in the hippocampus. In contrast, mice with deletion of the IL-1 receptor type I (IL-1rKO) or mice with transgenic, brain-restricted overexpression of IL-1 receptor antagonist did not display CMS-induced behavioral or neuroendocrine changes. Similarly, whereas in wild-type (WT) mice CMS significantly reduced hippocampal neurogenesis, measured by incorporation of bromodeoxyuridine (BrdU) and by doublecortin immunohistochemistry, no such decrease was observed IL-1rKO mice. The blunting of the adrenocortical activation in IL-1rKO mice may play a causal role in their resistance to depression, because removal of endogenous glucocorticoids by adrenalectomy also abolished the depressive-like effects of CMS, whereas chronic administration of corticosterone for 4 weeks produced depressive symptoms and reduced neurogenesis in both WT and IL-1rKO mice. The effects of CMS on both behavioral depression and neurogenesis could be mimicked by exogenous subcutaneous administration of IL-1 beta via osmotic minipumps for 4 weeks. These findings indicate that elevation in brain IL-1 levels, which characterizes many medical conditions, is both necessary and sufficient for producing the high incidence of depression found in these conditions. Thus, procedures aimed at reducing brain IL-1 levels may have potent antidepressive actions.

Pharmacogenomics with antidepressants in the STAR*D study

Major depressive disorder is one of the most common psychiatric disorders worldwide. No single antidepressant has been shown to be more effective than any other in lifting depression, and the effectiveness of any particular antidepressant in an individual is difficult to predict; therefore, doctors must prescribe antidepressants based on educated guesses. SNPs can be used in clinical association studies to determine the contribution of genes to drug efficacy. Evidence is accumulating to suggest that the efficacy of antidepressants results from the combined effects of a number of genetic variants, such as SNPs. Although there are not enough data currently available to prove this hypothesis, an increasing number of genetic variants associated with antidepressant response are being discovered. In this article, we review the pharmacogenomics of the drug efficacy of antidepressants in major depressive disorder. First, we survey the SNPs and genes identified as genetic markers that are correlated and associated with the drug efficacy of antidepressants in the Sequenced Treatment Alternatives for Depression (STAR*D) study. Second, we investigate candidate genes that have been suggested as contributing to treatment-emergent suicidal ideation during the course of antidepressant treatment in the STAR*D study. Third, we briefly describe the pharmacokinetic genes examined in the STAR*D study, and finally, we summarize the limitations with respect to the pharmacogenomics studies in the STAR*D study. Future research with independent replication in large sample sizes is needed to confirm the role of the candidate genes identified in the STAR*D study in antidepressant treatment response.

Stress and glucocorticoid footprints in the brain-the path from depression to Alzheimer's disease

Increasingly, stress is recognized as a trigger of depressive episodes and recent evidence suggests a causal role of stress in the onset and progression of Alzheimer's disease (AD) pathology. Besides aging, sex is an important determinant of prevalence rates for both AD and mood disorders. In light of a recent meta-analysis indicating that depressed subjects have a higher likelihood of developing AD, a key message in this article will be that both depression and AD are stress-related disorders and may represent a continuum that should receive more attention in future neurobiological studies. Accordingly, this review considers some of the cellular mechanisms that may be involved in regulating this transition threshold. In addition, it highlights the importance of addressing the question of how aging and sex interplay with stress to influence mood and cognition, with a bias towards consideration of neuroplastic events in particular brain regions, as the basis of AD and depressive disorders.

[Brain-immune interactions and implications in psychiatric disorders]

OBJECTIVE

This review will focus on the role of cytokines in the central nervous system and its implications to depressive disorder. We will then discuss the main findings of cytokine measurements in patients with major depressive disorder.

METHOD

We searched Pubmed for studies published from 1999-2007, using the keywords depression and cytokine; and depressive disorder and cytokine. We have focused on pro-inflammatory cytokine measurements in patients with depression syndrome using DSM-criteria.

RESULTS

Several lines of evidence suggest that cytokines have effects on depression, such as the induction of sickness behavior; clinical conditions related to cytokines that also overlap depressive symptoms; and immunotherapy that can lead to depressive symptoms attenuated by antidepressant treatment. Finally, patients with depression exhibit increased levels of pro-inflammatory cytokines, although conflicting results have been described.

CONCLUSION

Cytokines may play a role in the pathophysiology of some cases of depression, although a causal link has not been established yet. Further longitudinal studies are needed to determine patterns of cytokine in patients with major depressive disorder, taking into account confounding factors closely associated with the activation of pro-inflammatory cytokines. In addition, simultaneous measurements of multiple biomarkers could provide critical insights into mechanisms underlying major depressive disorder and a variety of common cytokine-related diseases.

Association analysis between variants of the interleukin-1beta and the interleukin-1 receptor antagonist gene and antidepressant treatment response in major depression

This study investigated the possible association of the interleukin-1 beta (IL-1beta) C-511T promoter polymorphism and the interleukin-1 receptor antagonist (IL-1Ra) (86bp)(n) variable number of tandem repeats (VNTR) polymorphism with antidepressant response to paroxetine and mirtazapine treatment. The study group consisted of 101 patients suffering from DSM-IV major depression participating in a randomized double-blind controlled clinical trial. Patients homozygous for the IL-1beta-511T allele had a significantly faster and more pronounced response to paroxetine treatment than IL-1beta-511C allele carriers. No association was found for the IL-1beta C-511T polymorphism with mirtazapine treatment response. The IL-1Ra VNTR showed neither an association with paroxetine nor with mirtazapine treatment response. Our results provide further suggestive evidence that time course of response and antidepressant efficacy of paroxetine, but not of mirtazapine, is influenced in a clinically relevant manner by the IL-1beta C-511T gene variant. Our data do not support the hypothesis that the IL-1Ra (86bp)(n) VNTR affects antidepressant treatment response to paroxetine or mirtazapine. An independent replication of our finding is needed. If replicated, the IL-1beta C-511T promoter polymorphism could be considered useful for prospective confirmatory pharmacogenetic trials in patients with major depression.

Inflammation, Depression and Dementia: Are they Connected?

Chronic inflammation is now considered to be central to the pathogenesis not only of such medical disorders as cardiovascular disease, multiple sclerosis, diabetes and cancer but also of major depression. If chronic inflammatory changes are a common feature of depression, this could predispose depressed patients to neurodegenerative changes in later life. Indeed there is now clinical evidence that depression is a common antecedent of Alzheimer's disease and may be an early manifestation of dementia before the cognitive declines becomes apparent. This review summarises the evidence that links chronic low grade inflammation with changes in brain structure that could precipitate neurodegenerative changes associated with Alzheimer's disease and other dementias. For example, neuronal loss is a common feature of major depression and dementia. It is hypothesised that the progress from depression to dementia could result from the activation of macrophages in the blood, and microglia in the brain, that release pro-inflammatory cytokines. Such cytokines stimulate a cascade of inflammatory changes (such as an increase in prostaglandin E2, nitric oxide in addition to more pro-inflammatory cytokines) and a hypersecretion of cortisol. The latter steroid inhibits protein synthesis thereby reducing the synthesis of neurotrophic factors and preventing reairto damages neuronal networks. In addition, neurotoxic end products of the tryptophan-kynurenine pathway, such as quinolinic acid, accumulate in astrocytes and neurons in both depression and dementia. Thus increased neurodegeneration, reduced neuroprotection and neuronal repair are common pathological features of major depression and dementia. Such changes may help to explain why major depression is a frequent prelude to dementia in later life.

Common genetic factors for depression and cardiovascular disease

There is increasing knowledge regarding the considerable comorbidity between depression and cardiovascular disease, which are two of the most common disorders in developed countries. The associated vulnerability is not unidirectional, as the presence of cardiovascular disease can also influence mood states. Although this may be the result of psychological factors, common biological mechanisms, including genetic ones, are thought to be responsible for this interaction; we can thus question whether variations in genes could be predisposing factors. Regarding the multiple interactions in the mechanisms between depression and cardiovascular system disorders, eg, dysfunctions in the hypo-thalamic-pituitary-adrenocortical and sympathoadrenal axis and the response to stress, the importance of the sero-tonergic and immune systems, or the impact on the renin-angiotensin system, several candidate genes are being investigated. However, despite the interest in unraveling the potential susceptibility genes for both disorders, most available studies have so far dealt with the impact of polymorphisms in relation to either depression or cardiovascular disease. A few recent studies have now examined the effects of gene-gene or gene-environment interactions, and are investigating the impact of "depression-related" variants on cardiac response to stress. The first promising results were obtained with the serotonin transporter, and it may be hypothesized that this polymorphism interacts via the impact of the S allele on depression and via the effect of the L allele on platelet activation. However, the role played by various other candidate genes remains to be determined, especially regarding the question as to whether they are indicative of common pathophysiological mechanisms, or for identifying a subgroup of patients with somatic disorders that are more closely related to psychiatric symptoms.

Interleukin (IL)-12 receptor beta1 codon 378 G homozygote and allele, but not IL-1 (beta-511 promoter, 3953 exon 5, receptor antagonist), IL-2 114, IL-4-590 intron 3, IL-8 3'-UTR 2767, and IL-18 105, are associated with higher susceptibility to leiomyoma

OBJECTIVE

To investigate whether certain polymorphisms are correlated with leiomyoma susceptibility, i.e., interleukin (IL)-1, IL-2, IL-4, IL-8, IL-12, and IL-18, which are all immunomodulatory cytokines that play important roles in host immune responses against cancers.

SETTING

Departments of gynecology and genetics in a medical center.

PATIENT(S)

Women were divided into: [1] a leiomyoma group (n = 162) and [2] a nonleiomyoma group (n = 156).

INTERVENTION(S)

Genotyping for the IL-1beta-511 promoter, IL-1beta exon 5, IL-1Ra, IL-2 114, IL-4 -590 intron 3, IL-8 3'-UTR 2767, IL-12Rbeta1 codon 378, and IL-18 105 were evaluated by polymerase chain reaction-restriction fragment length polymorphism.

MAIN OUTCOME MEASUREMENT(S)

Genotypes and allelic frequencies in both groups were compared.

RESULT(S)

Proportions of IL-12Rbeta1 codon 378 *CC/CG/GG in the leiomyoma and nonleiomyoma groups were: [1] 7.4%/43.8%/48.8% and [2] 11.5%/54.5%/34%, respectively. Distributions of other polymorphisms in both groups were not significantly different. Proportions of IL-1beta-511 promoter *CC/CT/TT were: [1] 22.8%/50%/27.2% and [2] 21.8%/57.1%/21.1% in the leiomyoma and nonleiomyoma groups, respectively. The IL-1beta exon 5 *E1 homozygote/heterozygote/E2 homozygote were: [1] 96.3%/3.7%/0% and [2] 96.9%/3.1%/0% in the leiomyoma and nonleiomyoma groups, respectively. Alleles I/II/III/IV/V for IL-1Ra were: [1] 92.6%/7.1%/0.3%/0/0% and [2] 93.9%/5.7%/0%/0.4/0% in the leiomyoma and nonleiomyoma groups, respectively. The IL-2 114 G homozygote/heterozygote/T homozygote were: [1] 27.8%/49.4%/22.8% and [2] 20.5%/53.2%/26.3% in the leiomyoma and nonleiomyoma groups, respectively. The IL-4 -590 intron 3 *RP1 homozygote/heterozygote/RP2 homozygote were: [1] 64.8%/32.7%/2.5% and [2] 69.2%/26.9%/3.9% in the leiomyoma and nonleiomyoma groups, respectively. The IL-8 3'-UTR 2767 A homozygote/heterozygote/G homozygote were: [1] 14.2%/43.8%/42% and [2] 20.5%/41.7%/37.8% in the leiomyoma and nonleiomyoma groups, respectively. The IL-18 *AA/AC/CC were: [1] 56.8%/40.7%/2.5% and [2] 59%/39.7%/1.3% in the leiomyoma and nonleiomyoma groups, respectively.

CONCLUSION(S)

The IL-12Rbeta1 codon 378 *G homozygote and G allele are related to a higher susceptibility to leiomyoma. The IL-1beta-511 promoter, IL-1beta exon 5, and IL-1Ra, IL-2 114, IL-4 -590 intron 3, IL-8 3'-UTR 2767, and IL-18 105 gene polymorphisms are not correlated with the development of leiomyoma.

Pharmacogenomics of Antidepressant Medications

With the completion of the human genome project, surges in studies investigating the association of antidepressant responsiveness and select polymorphisms have been conducted. Studies have been completed investigating polymorphisms in the monoaminergic system, including the serotonin transporter gene, the serotonin 1A, 2A, and 6 receptor genes, the G-protein-coupled receptor genes, the tryptophan hydroxylase 1 gene, the monoamine oxidase gene, the dopamine receptor genes, and the noradrenergic genes. Other genes of potential interest for investigation include the nitric oxide gene, the angiotensin-converting enzyme gene, the interleukin-1 beta gene, the stress hormone system, and the phosphodiesterase genes. Many of the studies have provided positive results, but the studies are small and are limited to a specific ethnicity. Further research is needed in the area before an array of genes can be used to predetermine response to antidepressant medication.

Interleukin-1 alpha and beta, TNF-alpha and HTTLPR gene variants study on alcohol toxicity and detoxification outcome

Genetic factors may influence the liability to treatment outcome and medical complications in alcoholism. In the present study we investigated the IL-1A rs1800587, IL-1B rs3087258, TNF-alpha rs1799724 and the HTTLPR variants in a sample of 64 alcohol dependents and 47 relatives versus a set of clinical parameters and outcome measures. Alcohol dependents had a less favorable clinical profile compared to relatives (higher cholesterol, triglycerides, glucose, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, gamma-glutamyltransferase). After detoxification, all clinical indexes improved and hepatic enzyme levels were similar in alcohol dependents and relatives, except for the GGT that remained significantly higher in alcohol dependents. Alcoholic depressive and anxiety scores were significantly reduced after detoxification. IL-1A, IL-1B, TNF-alpha and HTTLPR variants were not associated with any baseline clinical index or change after detoxification. In our sample IL-1A, IL-1B, TNF-alpha and HTTLPR do not appear as liability factors for alcohol toxicity or detoxification outcome, however the small sample size may influence the observed results.

Common genetic vulnerability to depressive symptoms and coronary artery disease: a review and development of candidate genes related to inflammation and serotonin

OBJECTIVE

Although it is well established that depressive symptoms are associated with recurrent cardiac events among cardiac patients and novel cardiac events among participants with no known coronary artery disease (CAD), the nature of this association remains unclear. In this regard, little attention has been paid to the possibility that common genetic vulnerability contributes to both depressive symptoms and CAD. In this paper, we review the existing evidence for common genetic contributions to depression and CAD, primarily using evidence from twin and family studies, followed by a review of two major pathophysiological mechanisms thought to underlie covariation between depressive symptoms and CAD: inflammation and serotonin. We conclude with an overview of select candidate genes within these pathways.

METHODS

Literature review.

RESULTS

In twin studies, both depression and CAD appear heritable. In the only twin study to consider depression and CAD jointly, the correlation across heritabilities was 0.42, suggesting that nearly 20% of variability in depressive symptoms and CAD was attributable to common genetic factors. In addition, although it is plausible that genetic variation related to inflammation and serotonin may be associated with both depression and CAD, genetic variation related to inflammation has been primary examined in relation to CAD, whereas genetic variation in the serotonin system has been primarily examined in relation to depression.

CONCLUSIONS

It appears that the covariation of depressive symptoms and CAD may be attributable, in part, to a common genetic vulnerability. Although several pathways may be involved, genes within the inflammation and serotonin pathways may serve as good candidates for the first steps in identifying genetic variation important for depression, CAD or both.

Interleukin-6 genetic polymorphism and Chinese major depression

BACKGROUND

It has been reported that serum concentrations of interleukin-6 (IL-6), a pro-inflammatory cytokine, were significantly higher in major depressive disorder (MDD).

OBJECTIVES

The aim of the present study was to examine whether the IL-6 genetic variant confers susceptibility to MDD.

METHODS

We genotyped a functional polymorphism in the promoter region (position -634) of the IL-6 gene in a sample of 257 MDD patients and 105 normal controls.

RESULTS

No significant differences were demonstrated for the genotype or allele frequency of the IL-6 polymorphism when comparing the MDD and control groups.

CONCLUSIONS

Our findings suggested that the investigated IL-6 polymorphism does not affect MDD susceptibility. We propose that other genetic variations of IL-6, relating either to MDD or to the clinical manifestations of MDD, may need further investigation.

Cytokines sing the blues: inflammation and the pathogenesis of depression

Increasing amounts of data suggest that inflammatory responses have an important role in the pathophysiology of depression. Depressed patients have been found to have higher levels of proinflammatory cytokines, acute phase proteins, chemokines and cellular adhesion molecules. In addition, therapeutic administration of the cytokine interferon-alpha leads to depression in up to 50% of patients. Moreover, proinflammatory cytokines have been found to interact with many of the pathophysiological domains that characterize depression, including neurotransmitter metabolism, neuroendocrine function, synaptic plasticity and behavior. Stress, which can precipitate depression, can also promote inflammatory responses through effects on sympathetic and parasympathetic nervous system pathways. Finally, depression might be a behavioral byproduct of early adaptive advantages conferred by genes that promote inflammation. These findings suggest that targeting proinflammatory cytokines and their signaling pathways might represent a novel strategy to treat depression.