Nature Brain disorders across the lifespan

Brain and other nervous-system disorders impose a disproportionate burden on those in low- and middle-income countries. For over a decade, the Fogarty International Center and its NIH partners have supported research and capacity-building to provide context-sensitive solutions to this public health challenge. This supplement outlines the overarching and intersecting research priorities for addressing causes, prevention, treatment and rehabilitation, as well as opportunities to strengthen scientific capacity that can promote global nervous system health."

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The role of microbes and autoimmunity in the pathogenesis of neuropsychiatric illness.

To illustrate how microbes might participate in the pathogenesis of neuropsychiatric illness by triggering the production of autoantibodies that bind to brain targets.

RECENT FINDINGS:

Some studies link exposure to infectious agents to development of brain disorders; others have identified autoantibodies in individuals with these conditions without finding evidence of pathogens. Neither line of work demonstrates consistent associations between a specific neuropsychiatric disease and a particular environmental trigger or immune marker. Growing evidence suggests that the microbiome conditions host immunity to microbes and xenobiotics, and regulates autoimmune responses that can affect the central nervous system (CNS). The presence of CNS receptors for cytokines and other immune molecules underscores the importance of brain-immune crosstalk in maintaining normal function. An increased prevalence of familial autoimmunity, exposure to pathogens prenatally and postnatally, and findings of antibrain antibodies is common in disorders as diverse as schizophrenia, obsessive-compulsive disorder and autism, and suggests that differences in exposure timing and genetic vulnerability toward autoimmunity are important determinants of neuropsychiatric outcomes.

SUMMARY:

Microbes, both pathogenic and commensal, can induce autoantibodies that bind to brain and affect behavior in susceptible hosts. Interventions that correct the microbial balance or diminish autoantibody binding may be effective in diverse neuropsychiatric conditions mediated by autoimmunity.

The microbiome-gut-brain axis during early life regulates the hippocampal serotonergic system in a sex-dependent manner.

Bacterial colonisation of the intestine has a major role in the post-natal development and maturation of the immune and endocrine systems. These processes are key factors underpinning central nervous system (CNS) signalling. Regulation of the microbiome-gut-brain axis is essential for maintaining homeostasis, including that of the CNS. However, there is a paucity of data pertaining to the influence of microbiome on the serotonergic system. Germ-free (GF) animals represent an effective preclinical tool to investigate such phenomena. Here we show that male GF animals have a significant elevation in the hippocampal concentration of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid, its main metabolite, compared with conventionally colonised control animals. Moreover, this alteration is sex specific in contrast with the immunological and neuroendocrine effects which are evident in both sexes. Concentrations of tryptophan, the precursor of serotonin, are increased in the plasma of male GF animals, suggesting a humoral route through which the microbiota can influence CNS serotonergic neurotransmission. Interestingly, colonisation of the GF animals post weaning is insufficient to reverse the CNS neurochemical consequences in adulthood of an absent microbiota in early life despite the peripheral availability of tryptophan being restored to baseline values. In addition, reduced anxiety in GF animals is also normalised following restoration of the intestinal microbiota. These results demonstrate that CNS neurotransmission can be profoundly disturbed by the absence of a normal gut microbiota and that this aberrant neurochemical, but not behavioural, profile is resistant to restoration of a normal gut flora in later life

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• Animals' microbial communities linked to their behavior (sciencedaily.com)

Toxoplasma on the Brain: Understanding Host-Pathogen Interactions in Chronic CNS Infection

Toxoplasma gondii is a prevalent obligate intracellular parasite which chronically infects more than a third of the world's population. Key to parasite prevalence is its ability to form chronic and nonimmunogenic bradyzoite cysts, which typically form in the brain and muscle cells of infected mammals, including humans. While acute clinical infection typically involves neurological and/or ocular damage, chronic infection has been more recently linked to behavioral changes. Establishment and maintenance of chronic infection involves a balance between the host immunity and parasite evasion of the immune response. Here, we outline the known cellular interplay between Toxoplasma gondii and cells of the central nervous system and review the reported effects of Toxoplasma gondii on behavior and neurological disease. Finally, we review new technologies which will allow us to more fully understand host-pathogen interactions.

The T.Gondii host/pathogen interactome 

Crosstalk between metabolic and neuropsychiatric disorders - F1000 Biology Reports - F1000

Evidence supporting the concurrence of metabolic disturbances (e.g. insulin resistance, diabetes and obesity) and neuropsychiatric disorders has been demonstrated in both human and animal studies, suggesting the possibility that they have shared pathophysiological mechanisms. During the past decade, our understanding for the role of insulin in both normal and abnormal central nervous system (CNS) processes has become increasingly refined. Evidence indicates that insulin is a pleiotropic peptide, critical to neurotrophism, neuroplasticity, and neuromodulation. Moreover, the role of insulin underscores its importance in the development of several neuropsychiatric disorders, including, but not limited to, mechanisms involved in the pathogenesis and progression towards diabetes, obesity, and neurodegenerative disorders, such as Alzheimer's disease. This review focuses on the insulin-mediated effects on normal and abnormal brain function and discusses why targeting insulin-related pathways in the brain may emerge as a new approach for refining treatment of neurological and psychiatric disorders.