Brain, behavior, and immunity
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Brain Behav. Immun. · Aug 2014
ReviewImmune system: a possible nexus between cannabinoids and psychosis.
Endocannabinoid system is involved in the regulation of the brain-immune axis. Cannabis consumption is related with the development, course, and severity of psychosis. The epidemiological evidence for increased occurrence of immunological alterations in patients with psychosis has not been sufficiently addressed. The aim of this review is to establish whether there is any scientific evidence of the influence of cannabinoids on aspects of immunity that affect susceptibility to psychotic disorder induction. ⋯ The actions of cannabinoids through the immune system are quite regular and predictable in the peripheral but remain fuzzy in the central nervous system. Despite this uncertainty, it may be hypothesized that exposure to exocannabinoids, in particular during adolescence might prompt immunological dysfunctions that potentially cause a latent vulnerability to psychosis. Further investigations are warranted to clarify the relationship between the immunological effects of cannabis and psychosis.
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Mammals live in a co-evolutionary association with the plethora of microorganisms that reside at a variety of tissue microenvironments. The microbiome represents the collective genomes of these co-existing microorganisms, which is shaped by host factors such as genetics and nutrients but in turn is able to influence host biology in health and disease. Niche-specific microbiome, prominently the gut microbiome, has the capacity to effect both local and distal sites within the host. ⋯ The microbiome poises the peripheral immune homeostasis and predisposes host susceptibility to CNS autoimmune diseases such as multiple sclerosis. Neural, endocrine and metabolic mechanisms are also critical mediators of the microbiome-CNS signaling, which are more involved in neuro-psychiatric disorders such as autism, depression, anxiety, stress. Research on the role of microbiome in CNS disorders deepens our academic knowledge about host-microbiome commensalism in central regulation and in practicality, holds conceivable promise for developing novel prognostic and therapeutic avenues for CNS disorders.
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Brain Behav. Immun. · Feb 2014
ReviewAfferent and efferent immunological pathways of the brain. Anatomy, function and failure.
Immunological privilege appears to be a product of unique lymphatic drainage systems for the brain and receptor-mediated entry of inflammatory cells through the blood-brain barrier. Most organs of the body have well-defined lymphatic vessels that carry extracellular fluid, antigen presenting cells, lymphocytes, neoplastic cells and even bacteria to regional lymph nodes. The brain has no such conventional lymphatics, but has perivascular pathways that drain interstitial fluid (ISF) from brain parenchyma and cerebrospinal fluid (CSF) from the subarachnoid space to cervical lymph nodes. ⋯ This pathway does allow the traffic of lymphocytes and antigen presenting cells from CSF to cervical lymph nodes. Efferent pathways by which lymphocytes enter the brain are regulated by selected integrins on lymphocytes and selective receptors on vascular endothelial cells. Here we review: (1) the structure and function of afferent lymphatic drainage of ISF and CSF, (2) mechanisms involved in the efferent pathways by which lymphocytes enter the brain and (3) the failure of lymphatic drainage of the brain parenchyma with age and the role of such failure in the pathogenesis of Alzheimer's disease.
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Brain Behav. Immun. · Mar 2013
ReviewSurgery and stress promote cancer metastasis: new outlooks on perioperative mediating mechanisms and immune involvement.
Surgery for the removal of a primary tumor presents an opportunity to eradicate cancer or arrest its progression, but is also believed to promote the outbreak of pre-existing micrometastases and the initiation of new metastases. These deleterious effects of surgery are mediated through various mechanisms, including psychological and physiological neuroendocrine and paracrine stress responses elicited by surgery. In this review we (i) describe the many risk factors that arise during the perioperative period, acting synergistically to make this short timeframe critical for determining long-term cancer recurrence, (ii) present newly identified potent immunocyte populations that can destroy autologous tumor cells that were traditionally considered immune-resistant, thus invigorating the notion of immune-surveillance against cancer metastasis, (iii) describe in vivo evidence in cancer patients that support a role for anti-cancer immunity, (iv) indicate neuroendocrine and paracrine mediating mechanisms of stress- and surgery-induced promotion of cancer progression, focusing on the prominent role of catecholamines and prostaglandins through their impact on anti-cancer immunity, and through direct effects on the malignant tissue and its surrounding, (v) discuss the impact of different anesthetic approaches and other intra-operative procedures on immunity and cancer progression, and (vi) suggest prophylactic measures against the immunosuppressive and cancer promoting effects of surgery.
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Brain Behav. Immun. · Feb 2013
ReviewAt the extreme end of the psychoneuroimmunological spectrum: delirium as a maladaptive sickness behaviour response.
Delirium is a common and severe neuropsychiatric syndrome characterised by acute deterioration and fluctuations in mental status. It is precipitated mainly by acute illness, trauma, surgery, or drugs. Delirium affects around one in eight hospital inpatients and is associated with multiple adverse consequences, including new institutionalisation, worsening of existing dementia, and death. ⋯ We discuss inflammatory and stress-related triggers of delirium in the context of new animal models that allow us to dissect some aspects of the mechanisms underpinning these episodes. We discuss some differences between the sickness behaviour syndrome model and delirium in the context of the complexity in the latter due to other factors such as prior pathology, psychological stress and drug effects. We conclude that, with appropriate caveats, the study of sickness behaviour in the vulnerable brain offers a promising route to uncover the mechanisms of this common and serious unmet medical need.