Increased stress-induced inflammatory responses in male patients with major depression and increased early life stress

Molecular epidemiology, cancer-related symptoms, and cytokines pathway

The Human Genome Project and HapMap have led to a better appreciation of the importance of common genetic variation in determining cancer risk, created potential for predicting response to therapy, and made possible the development of targeted prevention and therapeutic interventions. Advances in molecular epidemiology can be used to explore the role of genetic variation in modulating the risk for severe and persistent symptoms, such as pain, depression, and fatigue, in patients with cancer. The same genes that are implicated in cancer risk might also be involved in the modulation of therapeutic outcomes. For example, polymorphisms in several cytokine genes are potential markers for genetic susceptibility both for cancer risk and for cancer-related symptoms. These genetic polymorphisms are stable markers and easily and reliably assayed to explore the extent to which genetic variation might prove useful in identifying patients with cancer at high-risk of symptom development. Likewise, they could identify subgroups who might benefit most from symptom intervention, and contribute to developing personalized and more effective therapies for persistent symptoms.

The link between childhood trauma and depression: insights from HPA axis studies in humans

Childhood trauma is a potent risk factor for developing depression in adulthood, particularly in response to additional stress. We here summarize results from a series of clinical studies suggesting that childhood trauma in humans is associated with sensitization of the neuroendocrine stress response, glucocorticoid resistance, increased central corticotropin-releasing factor (CRF) activity, immune activation, and reduced hippocampal volume, closely paralleling several of the neuroendocrine features of depression. Neuroendocrine changes secondary to early-life stress likely reflect risk to develop depression in response to stress, potentially due to failure of a connected neural circuitry implicated in emotional, neuroendocrine and autonomic control to compensate in response to challenge. However, not all of depression is related to childhood trauma and our results suggest the existence of biologically distinguishable subtypes of depression as a function of childhood trauma that are also responsive to differential treatment. Other risk factors, such as female gender and genetic dispositions, interfere with components of the stress response and further increase vulnerability for depression. Similar associations apply to a spectrum of other psychiatric and medical disorders that frequently coincide with depression and are aggravated by stress. Taken together, this line of evidence demonstrates that psychoneuroendocrine research may ultimately promote optimized clinical care and help prevent the adverse outcomes of childhood trauma.

Acute deviations from long-term trait depressive symptoms predict systemic inflammatory activity

OBJECTIVE

Depressive symptoms increase morbidity and mortality from coronary heart disease and systemic inflammation has been proposed as the underlying mechanism. While higher levels of inflammatory mediators have been found in dysphoric individuals, it is not known whether long-term or short-term mood changes are responsible for this phenomenon.

METHODS

A sample of 65 young women provided weekly web-based self-ratings of depressive mood over a period of 20 weeks using the CES-D, and systemic inflammation was assessed by measuring plasma interleukin-6 (IL-6) and C-reactive protein (CRP) before and after the observation period. CES-D ratings were used to develop state and trait indicators of depressed mood and evaluate their relationship with inflammatory mediators.

RESULTS

Hierarchical linear regressions controlling for baseline inflammation, age, and BMI revealed that trait levels of depressive symptoms were not associated with IL-6 (beta=0.09; n.s.) and CRP (beta=0.01; n.s.) concentrations after the observation period. In contrast, state levels of depressive symptoms were associated with changes in IL-6, but not CRP, particularly when they were indexed as the disparity between a person's trait level of symptoms and her CES-D score just prior to IL-6 assessment (beta=0.35; p=0.03).

CONCLUSION

These results lead us to conclude that in young women, state, rather than trait depressed mood stimulates peripheral inflammation as measured by IL-6. This pattern suggests that in this age group, fast-reacting inflammatory mediators such as IL-6 probably respond to short-term changes, for example, in stress hormones or stress hormone sensitivity, rather than long-term dysregulations of allostatic mechanisms.

Biology of post-traumatic stress disorder in childhood and adolescence

Diverse patterns of cortisol secretion with consistently high circulating catecholamines have been reported in post-traumatic stress disorder (PTSD), an anxiety state that develops after exposure to traumatic life events. Indeed, peripheral cortisol levels have been reported to be low or normal in the majority of adult chronic PTSD studies, whereas, in most paediatric studies, high cortisol values have been documented. Longitudinal studies on PTSD biology, including the transition from childhood to adulthood, may shed light on these discrepancies. In children, elevated evening salivary cortisol in the aftermath of the trauma was predictive of PTSD development 6 months later, whereas plasma interleukin-6 correlated positively with evening cortisol and was equally predictive of later PTSD. Longitudinal assessment of PTSD children 1 and 6 months later revealed progressive normalisation of cortisol levels, whereas noradrenaline concentrations became gradually higher. We hypothesise that, in adults with chronic PTSD, low cortisol levels, together with high catecholamines, may reflect a late event in the natural history of the disorder, months or years after the trauma. The progressive divergence of cortisol and noradrenaline concentrations over time may be responsible for PTSD maintenance in children and explain the differences between the child and adult PTSD endophenotypes. In adults studied immediately after the trauma, and by contrast to children, low cortisol levels are predictive of later PTSD development. Our hypothesis that low cortisol levels may reflect a previous trauma, earlier in development, is supported by the well established observation that prior trauma is a risk factor for a new PTSD diagnosis. The developmental stage of an individual in relation to previous exposure to trauma and PTSD vulnerability are crucial variables that may determine clinical and biological PTSD phenotypes and explain the discrepancies between adults and children in reported cortisol levels.

Inflammatory cytokine alterations in schizophrenia: a systematic quantitative review

BACKGROUND

Cytokines play an important role in infection and inflammation and are crucial mediators of the cross-talk between the brain and the immune system. Schizophrenia would be associated with an imbalance in inflammatory cytokines, leading to a decrease in Th1 and an increase in Th2 cytokine secretion. However, data published so far have been inconsistent. The primary objective of the present meta-analysis was to verify whether the cytokine imbalance hypothesis of schizophrenia is substantiated by evidence.

METHODS

Cross-sectional studies were included if they assessed in vivo plasma or serum cytokine concentrations and/or in vitro secretion of cytokines by peripheral blood leukocytes from schizophrenia patients and healthy volunteers.

RESULTS

Data from 62 studies involving a total sample size of 2298 schizophrenia patients and 1858 healthy volunteers remained for analysis. Ten cytokines were assessed, including the prototypic Th1 and Th2 cytokines gamma interferon (IFN-gamma) and interleukin 4 (IL-4) as well as IL-2, soluble IL-2 receptor (sIL-2R), IL-1beta, IL-1 receptor antagonist (IL-1RA), tumor necrosis factor-alpha (TNF-alpha), IL-6, soluble IL-6 receptor (sIL-6R), and IL-10. The results show that an increase occurs in in vivo IL-1RA, sIL-2R, and IL-6 and a decrease occurs in in vitro IL-2 in schizophrenia. No significant effect sizes were obtained for the other cytokines.

CONCLUSIONS

These findings provide the first evidence of establishment of an inflammatory syndrome in schizophrenia, which refutes the current hypothesis of a Th2 slant. Caveats are presented to data interpretation, including the role of stress and the effect of weight gain that develops in schizophrenia.

The hygiene hypothesis and psychiatric disorders

The hygiene hypothesis proposes that several chronic inflammatory disorders (allergies, autoimmunity, inflammatory bowel disease) are increasing in prevalence in developed countries because a changing microbial environment has perturbed immunoregulatory circuits which normally terminate inflammatory responses. Some stress-related psychiatric disorders, particularly depression and anxiety, are associated with markers of ongoing inflammation, even without any accompanying inflammatory disorder. Moreover, pro-inflammatory cytokines can induce depression, which is commonly seen in patients treated with interleukin-2 or interferon-alpha. Therefore, some psychiatric disorders in developed countries might be attributable to failure of immunoregulatory circuits to terminate ongoing inflammatory responses. This is discussed in relation to the effects of the immune system on a specific group of brain serotonergic neurons involved in the pathophysiology of mood disorders.

Depressive disorders and immunity: 20 years of progress and discovery

Since the inception of Brain, Behavior and Immunity twenty years ago, many exciting developments have occurred regarding the relationship between depression and the immune system. These developments have increasingly put the field of psychoneuroimmunology into a clinical context with important translational implications. Initial studies focused on the impact of depression on relatively narrowly defined immunologic endpoints, which ultimately found their relevance in studies examining the effect of depression on immunologically-based diseases including infectious illnesses, autoimmune disorders, and cancer as well as more recently cardiovascular disease. Mechanistic studies have also greatly contributed to an understanding of those facets of depression, which might mediate these effects. More recently, the reciprocal influences of the immune system on the brain and behavior including depression have taken center stage. Increasing data now indicate that activated inflammatory processes can influence multiple aspects of CNS function including neurotransmitter metabolism, neuroendocrine function, and information processing leading to behavioral changes in humans that bespeak depression. These latter developments have intrigued scientists investigating the pathophysiology of depression and warrant consideration as some of the most exciting new developments in psychiatry in the past 20 years. What the future holds is a world of promise as multiple translational targets derived from the cytokine model of depression work their way into the clinical arena as drug targets for further development. Moreover, the work has served to instantiate brain-immune interactions as an essential component in psychiatric and medical co-morbidities and their impact on health and illness.

The relationship between cytokines and pain/depression: A review and current status

Cytokines are small protein molecules secreted in response to immune stimuli. Recent research has outlined important roles for proinflammatory cytokines in the cascade of normal physiologic responses to environmental stresses, encompassing so-called sickness behavior that is thought to be an adaptive response to infection and other illnesses. Cytokines are involved in signaling that activates central nervous system glial cells. This activation is part of a poorly understood interaction between immune challenge or injury and host that can lead to the development or facilitation of persistent mood symptoms or pathologic pain. This article reviews evidence that may enhance our understanding of how pathologic symptoms, such as mood disorders and neuropathic pain, may emerge from proinflammatory cytokine activation. Possible conceptualizations of these illnesses and potential treatment implications are explored.

Cytokine-effects on glucocorticoid receptor function: relevance to glucocorticoid resistance and the pathophysiology and treatment of major depression

Glucocorticoids play an essential role in the response to environmental stressors, serving initially to mobilize bodily responses to challenge and ultimately serving to restrain neuroendocrine and immune reactions. A number of diseases including autoimmune, infectious and inflammatory disorders as well as certain neuropsychiatric disorders such as major depression have been associated with decreased responsiveness to glucocorticoids (glucocorticoid resistance), which is believed to be related in part to impaired functioning of the glucocorticoid receptor (GR). Glucocorticoid resistance, in turn, may contribute to excessive inflammation as well as hyperactivity of corticotropin releasing hormone and sympathetic nervous system pathways, which are known to contribute to a variety of diseases as well as behavioral alterations. Recent data indicate that glucocorticoid resistance may be a result of impaired GR function secondary to chronic exposure to inflammatory cytokines as may occur during chronic medical illness or chronic stress. Indeed, inflammatory cytokines and their signaling pathways including mitogen-activated protein kinases, nuclear factor-kappaB, signal transducers and activators of transcription, and cyclooxygenase have been found to inhibit GR function. Mechanisms include disruption of GR translocation and/or GR-DNA binding through protein-protein interactions of inflammatory mediators with the GR itself or relevant steroid receptor cofactors as well as alterations in GR phosphorylation status. Interestingly, cAMP signal transduction pathways can enhance GR function and inhibit cytokine signaling. Certain antidepressants have similar effects. Thus, further understanding the effects of cytokines on GR signaling and the mechanisms involved may reveal novel therapeutic targets for reversal of glucocorticoid resistance and restoration of glucocorticoid-mediated inhibition of relevant bodily/immune responses during stress and immune challenge.