Serotonin of mast cell origin contributes to hippocampal function

Psychology Department, Columbia University, 406 Schermerhorn Hall, 1190 Amsterdam Ave., New York, NY 10027, USA.
European Journal of Neuroscience (Impact Factor: 3.18). 05/2012; 36(3):2347-59. DOI: 10.1111/j.1460-9568.2012.08138.x
Source: PubMed


In the central nervous system, serotonin, an important neurotransmitter and trophic factor, is synthesized by both mast cells and neurons. Mast cells, like other immune cells, are born in the bone marrow and migrate to many tissues. We show that they are resident in the mouse brain throughout development and adulthood. Measurements based on capillary electrophoresis with native fluorescence detection indicate that a significant contribution of serotonin to the hippocampal milieu is associated with mast cell activation. Compared with their littermates, mast cell-deficient C57BL/6 Kit(W-sh/W-sh) mice have profound deficits in hippocampus-dependent spatial learning and memory and in hippocampal neurogenesis. These deficits are associated with a reduction in cell proliferation and in immature neurons in the dentate gyrus, but not in the subventricular zone - a neurogenic niche lacking mast cells. Chronic treatment with fluoxetine, a selective serotonin reuptake inhibitor, reverses the deficit in hippocampal neurogenesis in mast cell-deficient mice. In summary, the present study demonstrates that mast cells are a source of serotonin, that mast cell-deficient C57BL/6 Kit(W-sh/W-sh) mice have disrupted hippocampus-dependent behavior and neurogenesis, and that elevating serotonin in these mice, by treatment with fluoxetine, reverses these deficits. We conclude that mast cells contribute to behavioral and physiological functions of the hippocampus and note that they play a physiological role in neuroimmune interactions, even in the absence of inflammatory responses.

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    • "N-cadherin or synaptic cell adhesion molecule (SynCAM) (Suzuki et al. 2004; Furuno et al. 2005). Mast cell-derived serotonin contributes to neurogenesis and to the behavioral and physiological function of the hippocampus (Nautiyal et al. 2012). Mast cell proteases, such as tryptase, signal nerves through PARs; PAR2 activation has been implicated in increased intestinal permeability and visceral hypersensitivity in rodents (Déry et al. 1998; Vergnolle et al. 2001; Coelho et al. 2002; Cenac et al. 2003). "
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    ABSTRACT: Since first described by Paul Ehrlich in 1878, mast cells have been mostly viewed as effectors of allergy. It has been only in the past two decades that mast cells have gained recognition for their involvement in other physiological and pathological processes. Mast cells have a widespread distribution and are found predominantly at the interface between the host and the external environment. Mast cell maturation, phenotype and function are a direct consequence of the local microenvironment and have a marked influence on their ability to specifically recognize and respond to various stimuli through the release of an array of biologically active mediators. These features enable mast cells to act as both first responders in harmful situations as well as to respond to changes in their environment by communicating with a variety of other cells implicated in physiological and immunological responses. Therefore, the critical role of mast cells in both innate and adaptive immunity, including immune tolerance, has gained increased prominence. Conversely, mast cell dysfunction has pointed to these cells as the main offenders in several chronic allergic/inflammatory disorders, cancer and autoimmune diseases. This review summarizes the current knowledge of mast cell function in both normal and pathological conditions with regards to their regulation, phenotype and role.
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    • "KMO inactivation prevents IL-1β inhibition of neurogenesis, suggesting a powerful role for IDO and the TRYCAT pathway in driving inflammation induced decreased neurogenesis. TDO and IDO activation decreases mast cell serotonin production, also important to dentate gyrus neurogenesis, as well as learning and mood [148]. Such data emphasizes the importance of the TRYCATs in mediating depression/somatization associations with degenerative and regenerative processes in PD. "
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    ABSTRACT: The integration of disparate data types provides a more complete picture of complex biological systems. Here we combine small-volume metabolomic and transcriptomic platforms to determine subtle chemical changes and to link metabolites and genes to biochemical pathways. Capillary electrophoresis-mass spectrometry (CE-MS) and whole-genome gene expression arrays, aided by integrative pathway analysis, were utilized to survey metabolomic/transcriptomic hippocampal neurochemistry. We measured changes in individual hippocampi from the mast cell mutant mouse strain, C57BL/6 KitW-sh/W-sh. These mice have a naturally occurring mutation in the white spotting locus that causes reduced c-Kit receptor expression and an inability of mast cells to differentiate from their hematopoietic progenitors. Compared with their littermates, the mast cell-deficient mice have profound deficits in spatial learning, memory, and neurogenesis. A total of 18 distinct metabolites were identified in the hippocampus that discriminated between the C57BL/6 KitW-sh/W-sh and control mice. The combined analysis of metabolite and gene expression changes revealed a number of altered pathways. Importantly, results from both platforms indicated that multiple pathways are impacted, including amino acid metabolism, increasing the confidence in each approach. Because the CE-MS and expression profiling are both amenable to small-volume analysis, this integrated analysis is applicable to a range of volume-limited biological systems.
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