Calcium-sensing receptor stimulates secretion of an interferon-γ-induced monokine (CXCL10) and monocyte chemoattractant protein-3 in immortalized GnRH neurons

Authors

  • Sanghamitra Bandyopadhyay,

    1. Neurochemistry Laboratory, Department of Psychiatry and Genetics and Aging Research Unit, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts
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  • Kyeong-Hoon Jeong,

    1. Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine and Membrane Biology Program, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts
    2. Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, Boston, Massachusetts
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  • Jacob Tfelt Hansen,

    1. Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine and Membrane Biology Program, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts
    2. Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, Boston, Massachusetts
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  • Peter M. Vassilev,

    1. Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine and Membrane Biology Program, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts
    2. Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, Boston, Massachusetts
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  • Edward M. Brown,

    1. Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine and Membrane Biology Program, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts
    2. Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, Boston, Massachusetts
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  • Naibedya Chattopadhyay

    Corresponding author
    1. Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine and Membrane Biology Program, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts
    2. Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, Boston, Massachusetts
    • Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, and Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115
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Abstract

Biology of GnRH neurons is critically dependent on extracellular Ca2+ (Ca2+o). We evaluated differences in gene expression patterns with low and high Ca2+o in an immortalized GnRH neuron line, GT1-7 cells. Mouse global oligonucleotide microarray was used to evaluate transcriptional differences among the genes regulated by elevated Ca2+o. Our result identified two interferon-γ (IFNγ)-inducible chemokines, CXCL9 and CXCL10, and a beta chemokine, monocyte chemoattractant protein-3 (MCP-3/CCL7), being up-regulated in GT1-7 cells treated with high Ca2+o (3.0 mM) compared with low Ca2+o (0.5 mM). Up-regulation of these mRNAs by elevated Ca2+o was confirmed by quantitative PCR. Elevated Ca2+o stimulated secretion of CXCL10 and MCP-3 but not CXCL9 in GT1-7 cells, and this effect was mediated by an extracellular calcium-sensing receptor (CaR) as the dominant negative CaR attenuated secretion of CXCL10 and MCP-3. CXCL10 and MCP-3 were localized in mouse GnRH neurons in the preoptic hypothalamus. Suppression of K+ channels (BK channels) with 25 nM charybdotoxin inhibited high-Ca2+o-stimulated CXCL10 release. Accordingly, CaR activation by a specific CaR agonist, NPS-467, resulted in the activation of a Ca2+-activated K+ channel in these cells. CaR-mediated MCP-3 secretion involves the PI3 kinase pathway in GT1-7 cells. MCP-3 stimulated chemotaxis of astrocytes treated with transforming growth factor-β (TGFβ). With TGFβ-treated astrocytes, we next observed that conditioned medium from GT1-7 cells treated with high Ca2+ promoted chemotaxis of astrocytes, and this effect was attenuated by a neutralizing antibody to MCP-3. These results implicate CaR as an important regulator of GnRH neuron function in vivo by stimulating secretion of heretofore unsuspected cytokines, i.e., CXCL10 and MCP-3. © 2007 Wiley-Liss, Inc.

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