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MCH Neurons Regulate Permeability of the Median Eminence Barrier.

ABSTRACT: Melanin-concentrating hormone (MCH)-expressing neurons are key regulators of energy and glucose homeostasis. Here, we demonstrate that they provide dense projections to the median eminence (ME) in close proximity to tanycytes and fenestrated vessels. Chemogenetic activation of MCH neurons as well as optogenetic stimulation of their projections in the ME enhance permeability of the ME by increasing fenestrated vascular loops and enhance leptin action in the arcuate nucleus of the hypothalamus (ARC). Unbiased phosphoRiboTrap-based assessment of cell activation upon chemogenetic MCH neuron activation reveals MCH-neuron-dependent regulation of endothelial cells. MCH neurons express the vascular endothelial growth factor A (VEGFA), and blocking VEGF-R signaling attenuates the leptin-sensitizing effect of MCH neuron activation. Our experiments reveal that MCH neurons directly regulate permeability of the ME barrier, linking the activity of energy state and sleep regulatory neurons to the regulation of hormone accessibility to the ARC.

SUBMITTER: Jiang H

PROVIDER: S-EPMC7383232 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Hypothalamic gonadotropin-releasing hormone (GnRH) neurons are required for fertility in all mammalian species studied to date. In rodents, GnRH neuron cell bodies reside in the rostral hypothalamus, and most extend a single long neuronal process in the caudal direction to terminate at the median eminence (ME), the site of hormone secretion. The molecular cues that GnRH neurites use to grow and navigate to the ME during development, however, remain poorly described. Reverse transcription-PCR (RT-PCR) identified mRNAs encoding Netrin-1, and its receptor, DCC, in the fetal preoptic area (POA) and mediobasal hypothalamus (MBH), respectively, from gestational day 12.5 (GD12.5), a time when the first GnRH neurites extend toward the MBH. Moreover, a subpopulation of GnRH neurons from GD14.5 through GD18.5 express the Netrin-1 receptor, DCC, suggesting a role for Netrin-1/DCC signaling in GnRH neurite growth and/or guidance. In support of this notion, when GD15.5 POA explants, containing GnRH neurons actively extending neurites, were grown in three-dimensional collagen gels and challenged with exogenous Netrin-1 (100 ng/ml or 400 ng/ml) GnRH neurite growth was stimulated. In addition, Netrin-1 provided from a fixed source was able to stimulate outgrowth, although it did not appear to chemoattract GnRH neurites. Finally, the effects of Netrin-1 on the outgrowth of GnRH neurites could be inhibited by blocking either L-type voltage-gated calcium channels (VGCCs) with nifedipine (10 µM), or ryanodine receptors with ryanodine (10 µM). This is consistent with the role of Ca2+ from extra- and intracellular sources in Netrin-1/DCC-dependent growth cone motility in other neurons. These results indicate that Netrin-1 directly stimulates the growth of a subpopulation of GnRH neurites that express DCC, provide further understanding of the mechanisms by which GnRH nerve terminals arrive at their site of hormone secretion, and identify an additional neuronal population whose neurites utilize Netrin-1/DCC signaling for their development.

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MCH Neurons Regulate Permeability of the Median Eminence Barrier.

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