At high concentrations, free radicals and radical-derived, nonradical reactive species are hazardous for living organisms and damage all major cellular constituents. At moderate concentrations, how...

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Free Radicals in the Physiological Control of Cell Function

The heterotrimeric G protein Gs couples hormone receptors (as well as other receptors) to the effector enzyme adenylyl cyclase and is therefore required for hormone-stimulated intracellular cAMP generation Receptors activate Gs by promoting exchange of GTP for GDP on the Gs α-subunit (Gsα) while an intrinsic GTPase activity of Gsα that hydrolyzes bound GTP to GDP leads to deactivation Mutations of specific Gsα residues (Arg201 or Gln227) that are critical for the GTPase reaction lead to constitutive activation of Gs-coupled signaling pathways, and such somatic mutations are found in endocrine tumors, fibrous dysplasia of bone, and the McCune-Albright syndrome Conversely, heterozygous loss-of-function mutations may lead to Albright hereditary osteodystrophy (AHO), a disease characterized by short stature, obesity, brachydactyly, sc ossifications, and mental deficits Similar mutations are also associated with progressive osseous heteroplasia Interestingly, paternal transmission of GNAS1 mutations leads

Endocrine Manifestations of Stimulatory G Protein α-Subunit Mutations and the Role of Genomic Imprinting

Regulatory role for a novel human thioredoxin peroxidase in NF-κB activation

To clarify the mechanisms that regulate neuroendocrine differentiation of fetal lung epithelia, we have studied the expression of the mammalian homologs of achaete-scute complex (Mash1) (Ascl1 - Mouse Genome Informatics); hairy and enhancer of split1 (Hes1); and the expression of Notch/Notch-ligand system in the fetal and adult mouse lungs, and in the lungs of Mash1- or Hes1-deficient mice. Immunohistochemical studies revealed that Mash1-positive cells seemed to belong to pulmonary neuroendocrine cells (PNEC) and their precursors. In mice deficient for Mash1, no PNEC were detected. Hes1-positive cells belong to non-neuroendocrine cells. In the mice deficient in Hes1, in which Mash1 mRNA was upregulated, PNEC appeared precociously, and the number of PNEC was markedly increased. NeuroD (Neurod1 - Mouse Genome Informatics) expression in the lung was detected in the adult, and was enhanced in the fetal lungs of Hes1-null mice. Expression of Notch1, Notch2, Notch3 and Notch4 mRNAs in the mouse lung increased with age, and Notch1 mRNA was expressed in a Hes1-dependent manner. Notch1, Notch2 and Notch3 were immunohistochemically detected in non-neuroendocrine cells. Moreover, analyses of the lungs from the gene-targeted mice suggested that expression of Delta-like 1 (Dll1 - Mouse Genome Informatics) mRNA depends on Mash1. Thus, the neuroendocrine differentiation depends on basic helix-loop-helix factors, and Notch/Notch-ligand pathways may be involved in determining the cell differentiation fate in fetal airway epithelium.

Basic helix-loop-helix transcription factors regulate the neuroendocrine differentiation of fetal mouse pulmonary epithelium.

The degenerative process of Alzheimer's disease is linked to a shift in the balance between amyloid-beta (Abeta) production, clearance, and degradation. Neprilysin has recently been implicated as a major extracellular Abeta degrading enzyme in the brain. However, there has been no direct demonstration that neprilysin antagonizes the deposition of amyloid-beta in vivo. To address this issue, a lentiviral vector expressing human neprilysin (Lenti-Nep) was tested in transgenic mouse models of amyloidosis. We show that unilateral intracerebral injection of Lenti-Nep reduced amyloid-beta deposits by half relative to the untreated side. Furthermore, Lenti-Nep ameliorated neurodegenerative alterations in the frontal cortex and hippocampus of these transgenic mice. These data further support a role for neprilysin in regulating cerebral amyloid deposition and suggest that gene transfer approaches might have potential for the development of alternative therapies for Alzheimer's disease.

https://www.jneurosci.org/content/jneuro/23/6/1992.full.pdf

Neprilysin Gene Transfer Reduces Human Amyloid Pathology in Transgenic Mice

Thyroid C cells are neural crest-derived neuroendocrine cells that can acquire features similar to serotonergic neurons. Based on developmental and phenotypic markers, we have previously proposed that C cells and serotonergic enteric neurons arise from a common sympathoadrenal progenitor. In this report, we genetically examined this relationship using mice lacking the mammalian achaete-scute homologue 1 (MASH-1) transcription factor, since MASH-1 has recently been shown to be required for differentiation of serotonergic enteric neurons. We found that MASH-1 knockout mice have a greatly reduced number of C cells based on the lack of calcitonin and serotonin immunoreactivity. In contrast, calcitonin and serotonin were still expressed in cultured mature C cells that no longer express MASH-1, demonstrating that MASH-1 is not directly required for the expression of these two markers. Hence, MASH-1 is required to establish the C-cell phenotype and supports the model that C cells lie in the neuronal differentiation pathway of the sympathoadrenal neural crest. © 1998 John Wiley & Sons, Inc. J Neurobiol 34: 126–134, 1998

Requirement of the MASH-1 transcription factor for neuroendocrine differentiation of thyroid C cells.

Binding of Upstream Stimulatory Factor and a Cell-specific Activator to the Calcitonin/Calcitonin Gene-related Peptide Enhancer

Neural expression of a novel alternatively spliced and polyadenylated Gs alpha transcript.

We have analyzed the effect of extracellular stimuli on the differentiation state of the CA77 thyroid C-cell line as a model to understand the control of neural crest cell differentiation. In contrast to the endocrine C-cell phenotype, we found that CA77 cells have a neuronal phenotype characterized by laminin-induced neurites, neuronal antigens, and calcitonin gene-related peptide (CGRP) mRNA expression. Treatment with dexamethasone and retinoic acid reversibly repressed some of these neuronal characteristics to induce features more characteristic of the parental C-cells. In the case of dexamethasone treatment, there was a partial retraction and thinning of neurites, an increased number of secretory vesicles in the cell bodies, and about a 10-fold decrease in DNA synthesis. Treatment with retinoic acid alone or in combination with dexamethasone caused decreased cell adhesion and an even more extensive retraction of the neurites. Dexamethasone also biased the steady state levels of the alternatively spliced transcripts from the calcitonin/CGRP gene to favor calcitonin relative to CGRP mRNA. While retinoic acid treatment decreased both calcitonin and CGRP mRNA levels, the combination of dexamethasone and retinoic acid still yielded the increase in calcitonin relative to CGRP mRNA. These results suggest that glucocorticoids and retinoic acid may contribute to a late and reversible differentiation of thyroid C-cells by partly repressing neuronal properties.

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Neuronal properties of a thyroid C-cell line: partial repression by dexamethasone and retinoic acid.

We have investigated whether rat thyroid C-cells can acquire a phenotype similar to serotonergic neurons. C-cells are neural crest derived endocrine cells with some intrinsic neuronal and serotonergic properties. A relatively simple isolation scheme yielded cultures of about 50% initial purity, as measured by fluorescence activated cell sorting. These enriched C-cells could extend neurites up to 550 microns on a laminin-containing substratum in the presence of NGF. The cultured C-cells expressed neurofilaments and this expression was enhanced by NGF treatment. The C-cells also expressed two markers of the sympathoadrenal neural crest lineage, the mammalian achaete scute homolog-1 (MASH-1) transcription factor, and the B2 cell surface antigen. Interestingly, MASH-1 was not detectable after the C-cells were placed in culture, which is consistent with neuronal differentiation, since MASH-1 is only expressed in neuronal progenitors prior to differentiation. We then demonstrated that C-cells possess the fundamental features of serotonergic neurons: synthesis and secretion, uptake, and feedback control. The enriched C-cells, as well as the CA77 C-cell line, showed 5-HT immunostaining, expression of tryptophan hydroxylase mRNA, 5-HT1B autoreceptor mRNA, and 5-HT transporter mRNA and activity. NGF greatly induced 5-HT transporter activity as determined by sensitivity to sertraline, a selective 5-HT reuptake inhibitor. Based on these results, we propose that thyroid C-cells are derived from a vagal sympathoadrenal progenitor, similar to serotonergic enteric neurons, and can undergo neuronal transdifferentiation. Hence, these cells should provide suitable and convenient models for molecular and cellular studies on serotonergic neurons.

https://www.jneurosci.org/content/jneuro/15/9/6167.full.pdf

Thomas M. Lanigan

Papers

Requirement of the MASH-1 transcription factor for neuroendocrine differentiation of thyroid C cells.

Binding of Upstream Stimulatory Factor and a Cell-specific Activator to the Calcitonin/Calcitonin Gene-related Peptide Enhancer

Neural expression of a novel alternatively spliced and polyadenylated Gs alpha transcript.

Neuronal properties of a thyroid C-cell line: partial repression by dexamethasone and retinoic acid.

Induction of a serotonergic and neuronal phenotype in thyroid C-cells