RESUMO
The adrenal cortex undergoes multiple structural and functional rearrangements to satisfy the systemic needs for steroids during fetal life, postnatal development, and adulthood. A fully functional adrenal cortex relies on the proper subdivision in regions or 'zones' with distinct but interconnected functions, which evolve from the early embryonic stages to adulthood, and rely on a fine-tuned gene network. In particular, the steroidogenic activity of the fetal adrenal is instrumental in maintaining normal fetal development and growth. Here, we review and discuss the most recent advances in our understanding of embryonic and fetal adrenal development, including the known causes for adrenal dys-/agenesis, and the steroidogenic pathways that link the fetal adrenal with the hormone system of the mother through the fetal-placental unit. Finally, we discuss what we think are the major open questions in the field, including, among others, the impact of osteocalcin, thyroid hormone, and other hormone systems on adrenal development and function, and the reliability of rodents as models of adrenal pathophysiology.
Assuntos
Córtex Suprarrenal , Placenta , Gravidez , Feminino , Humanos , Reprodutibilidade dos Testes , Córtex Suprarrenal/fisiologia , CorticosteroidesRESUMO
Classical congenital adrenal hyperplasia (CAH) caused by pathogenic variants in the steroid 21-hydroxylase gene (CYP21A2) is a severe life-threatening condition. We present a detailed investigation of the molecular and functional characteristics of a novel pathogenic variant in this gene. The patient, 46 XX newborn, was diagnosed with classical salt wasting CAH in the neonatal period after initially presenting with ambiguous genitalia. Multiplex ligation-dependent probe analysis demonstrated a full deletion of the paternal CYP21A2 gene, and Sanger sequencing revealed a novel de novo CYP21A2 variant c.694-696del (E232del) in the other allele. This variant resulted in the deletion of a non-conserved single amino acid, and its functional relevance was initially undetermined. We used both in silico and in vitro methods to determine the mechanistic significance of this mutation. Computational analysis relied on the solved structure of the protein (Protein-data-bank ID 4Y8W), structure prediction of the mutated protein, evolutionary analysis, and manual inspection. We predicted impaired stability and functionality of the protein due to a rotatory disposition of amino acids in positions downstream of the deletion. In vitro biochemical evaluation of enzymatic activity supported these predictions, demonstrating reduced protein levels to 22% compared to the wild-type form and decreased hydroxylase activity to 1-4%. This case demonstrates the potential of combining in-silico analysis based on evolutionary information and structure prediction with biochemical studies. This approach can be used to investigate other genetic variants to understand their potential effects.
Assuntos
Simulação por Computador , Mutação/genética , Esteroide 21-Hidroxilase/química , Esteroide 21-Hidroxilase/genética , Pré-Escolar , Evolução Molecular , Feminino , Humanos , Lactente , Recém-NascidoRESUMO
The analysis of vertebrate limb bud development provides insight of general relevance into the signaling networks that underlie the controlled proliferative expansion of large populations of mesenchymal progenitors, cell fate determination and initiation of differentiation. In particular, extensive genetic analysis of mouse and experimental manipulation of chicken limb bud development has revealed the self-regulatory feedback signaling systems that interlink the main morphoregulatory signaling pathways including BMPs and their antagonists. It this review, we showcase the key role of BMPs and their antagonists during limb bud development. This review provides an understanding of the key morphoregulatory interactions that underlie the highly dynamic changes in BMP activity and signal transduction as limb bud development progresses from initiation and setting-up the signaling centers to determination and formation of the chondrogenic primordia for the limb skeletal elements.
Assuntos
Proteínas Morfogenéticas Ósseas/metabolismo , Botões de Extremidades/embriologia , Botões de Extremidades/crescimento & desenvolvimento , Transdução de Sinais/fisiologia , Animais , Proteínas Morfogenéticas Ósseas/genética , Regulação da Expressão Gênica no Desenvolvimento , Camundongos , Modelos Genéticos , Organogênese/genética , Organogênese/fisiologia , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Transdução de Sinais/genética , VertebradosRESUMO
SMAD4 is an essential mediator of canonical TGFß/BMP signal transduction and we inactivated Smad4 in mouse limb buds from early stages onward to study its functions in the mesenchyme. While this Smad4 inactivation did not alter the early Sox9 distribution, prefiguring the chondrogenic primordia of the stylopod and zeugopod, it disrupted formation of all Sox9-positive digit ray primordia. Specific inactivation of Smad4 during handplate development pointed to its differential requirement for posterior and anterior digit ray primordia. At the cellular level, Smad4 deficiency blocked the aggregation of Sox9-positive progenitors, thereby preventing chondrogenic differentiation as revealed by absence of collagen type II. The progressive loss of SOX9 due to disrupting digit ray primordia and chondrogenesis was paralleled by alterations in genes marking other lineages. This pointed to a general loss of tissue organization and diversion of mutant cells toward non-specific connective tissue. Conditional inactivation of Bmp2 and Bmp4 indicated that the loss of digit ray primordia and increase in connective tissue were predominantly a consequence of disrupting SMAD4-mediated BMP signal transduction. In summary, our analysis reveals that SMAD4 is required to initiate: (1) formation of the Sox9-positive digit ray primordia; and (2) aggregation and chondrogenic differentiation of all limb skeletal elements.
Assuntos
Botões de Extremidades/embriologia , Fatores de Transcrição SOX9/metabolismo , Proteína Smad4/genética , Proteína Smad4/metabolismo , Animais , Proteína Morfogenética Óssea 2/metabolismo , Proteína Morfogenética Óssea 4/metabolismo , Diferenciação Celular/genética , Células Cultivadas , Condrogênese/genética , Colágeno Tipo II/deficiência , Tecido Conjuntivo/metabolismo , Extremidades/embriologia , Fatores de Crescimento de Fibroblastos/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Proteínas Hedgehog/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Botões de Extremidades/citologia , Botões de Extremidades/metabolismo , Camundongos , Transdução de Sinais/genética , Células-TroncoRESUMO
Cholesterol is the precursor of all steroids, but how cholesterol flux is controlled in steroidogenic tissues is poorly understood. The cholesterol exporter ABCG1 is an essential component of the reverse cholesterol pathway and its global inactivation results in neutral lipid redistribution to tissue macrophages. The function of ABCG1 in steroidogenic tissues, however, has not been explored. To model this, we inactivated Abcg1 in the mouse adrenal cortex, which led to an adrenal-specific increase in transcripts involved in cholesterol uptake and de novo synthesis. Abcg1 inactivation did not affect adrenal cholesterol content, zonation, or serum lipid profile. Instead, we observed a moderate increase in corticosterone production that was not recapitulated by the inactivation of the functionally similar cholesterol exporter Abca1. Altogether, our data imply that Abcg1 controls cholesterol uptake and biosynthesis and regulates glucocorticoid production in the adrenal cortex, introducing the possibility that ABCG1 variants may account for physiological or subclinical variation in stress response.
Assuntos
Membro 1 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Córtex Suprarrenal , Colesterol , Animais , Camundongos , Córtex Suprarrenal/metabolismo , Transporte Biológico , Colesterol/metabolismo , Corticosterona , Glucocorticoides , Membro 1 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismoRESUMO
Genetic defects affecting steroid biosynthesis cause cortisol deficiency and differences of sex development; among these defects are recessive mutations in the steroidogenic enzymes CYP11A1 and CYP11B, whose function is supported by reducing equivalents donated by ferredoxin reductase (FDXR) and ferredoxin. So far, mutations in the mitochondrial flavoprotein FDXR have been associated with a progressive neuropathic mitochondriopathy named FDXR-related mitochondriopathy (FRM), but cortisol insufficiency has not been documented. However, patients with FRM often experience worsening or demise following stress associated with infections. We investigated 2 female patients with FRM carrying the potentially novel homozygous FDXR mutation p.G437R with ambiguous genitalia at birth and sudden death in the first year of life; they presented with cortisol deficiency and androgen excess compatible with 11-hydroxylase deficiency. In addition, steroidogenic FDXR-variant cell lines reprogrammed from 3 patients with FRM fibroblasts displayed deficient mineralocorticoid and glucocorticoid production. Finally, Fdxr-mutant mice allelic to the severe p.R386W human variant showed reduced progesterone and corticosterone production. Therefore, our comprehensive studies show that human FDXR variants may cause compensated but possibly life-threatening adrenocortical insufficiency in stress by affecting adrenal glucocorticoid and mineralocorticoid synthesis through direct enzyme inhibition, most likely in combination with disturbed mitochondrial redox balance.
Assuntos
Insuficiência Adrenal , Ferredoxina-NADP Redutase , Humanos , Feminino , Insuficiência Adrenal/genética , Insuficiência Adrenal/metabolismo , Animais , Camundongos , Ferredoxina-NADP Redutase/genética , Ferredoxina-NADP Redutase/metabolismo , Mutação , Hidrocortisona/metabolismo , Lactente , Doenças Mitocondriais/genética , Doenças Mitocondriais/metabolismo , Masculino , Fibroblastos/metabolismo , Transtornos do Desenvolvimento Sexual/genética , Transtornos do Desenvolvimento Sexual/metabolismo , Transtornos do Desenvolvimento Sexual/patologiaRESUMO
Aldosterone synthase (CYP11B2) represents a promising drug target because its genetic dysregulation is causally associated with cardiovascular disease, its autonomous activity leads to primary aldosteronism, and its deficiency leads to salt wasting syndromes. The serendipitous discovery that the dextro-rotatory stereoisomer of the racemic aromatase (CYP19A1) inhibitor CGS16949A mediates potent CYP11B2 inhibition led to the purification and clinical development of dexfadrostat phosphate. To characterize the pharmacophore of dexfadrostat phosphate, structure-based enzyme coordination with CYP11B2, CYP11B1 and CYP19A1 was combined with steroid turnover upon in vitro and clinical treatment. Dexfadrostat, but not its 5S-enantiomer (5S-fadrozole), precisely coordinates with the catalytic heme moiety in the space of the CYP11B2 substrate binding pocket forming a tight and stable complex. Conversely, neither rigid nor flexible docking led to a plausible coordination geometry for dexfadrostat in steroid 11ß-hydroxylase (CYP11B1 - orthologue to CYP11B2) or in CYP19A1. The inhibitory preference of dexfadrostat was confirmed in vitro using an adrenal cortex-derived cell line. Dexfadrostat phosphate treatment of healthy subjects in the context of a clinical phase 1 study led to a dose-dependent decrease in urinary aldosterone secretion, accompanied by an increase in urinary corticosterone and deoxycorticosterone metabolites. Increased urinary corticosterone metabolites are indicative of CYP11B2 (18-oxidase) inhibition with clinical features reminiscent of patients with inborn corticosterone methyloxidase type II deficiency. An off-target effect on CYP19A1 was not observed as indicated by no clinical changes in testosterone and estradiol levels. Therefore, dexfadrostat exhibits the ideal structural features for binding and catalytic inhibition of CYP11B2 but not CYP11B1. Clinically, treatment with dexfadrostat phosphate leads to suppression of aldosterone levels by inhibiting predominantly one or both final CYP11B2-mediated reactions.
Assuntos
Citocromo P-450 CYP11B2 , Esteroide 11-beta-Hidroxilase , Humanos , Esteroide 11-beta-Hidroxilase/genética , Citocromo P-450 CYP11B2/metabolismo , Corticosterona , Aldosterona/metabolismo , Fosfatos , Fadrozol/farmacologiaRESUMO
Adrenarche is an early event in sexual maturation in prepubertal children and corresponds to the postnatal development of the adrenocortical zona reticularis (zR). However, the molecular mechanisms that govern the onset and maturation of zR remain unknown. Using tissue laser microdissection combined with transcript quantification and immunodetection, we showed that the human zR receives low levels of cholesterol in comparison with other adrenal layers. To model this metabolic condition, we challenged adrenal cells in vitro using cholesterol deprivation. This resulted in reprogramming the steroidogenic pathway toward inactivation of 3-beta-hydroxysteroid dehydrogenase type 2 (HSD3B2), increased CYB5A expression, and increased biosynthesis of dehydroepiandrosterone (DHEA), 3 key features of zR maturation during adrenarche. Finally, we found that cholesterol deprivation leads to decreased transcriptional activity of POU3F2, which normally stimulates the expression of HSD3B2 by directly binding to its promoter. These findings demonstrate that cholesterol deprivation can account, at least in part, for the acquisition of a zR-like androgenic program in humans.
Assuntos
Glândulas Suprarrenais , Adrenarca , Glândulas Suprarrenais/metabolismo , Adrenarca/fisiologia , Androgênios/metabolismo , Criança , Desidroepiandrosterona/metabolismo , Humanos , Zona Reticular/metabolismoRESUMO
The adult human adrenal cortex produces steroid hormones that are crucial for life, supporting immune response, glucose homeostasis, salt balance and sexual maturation. It consists of three histologically distinct and functionally specialized zones. The fetal adrenal forms from mesodermal material and produces predominantly adrenal C19 steroids from its fetal zone, which involutes after birth. Transition to the adult cortex occurs immediately after birth for the formation of the zona glomerulosa and fasciculata for aldosterone and cortisol production and continues through infancy until the zona reticularis for adrenal androgen production is formed with adrenarche. The development of this indispensable organ is complex and not fully understood. This article gives an overview of recent knowledge gained of adrenal biology from two perspectives: one, from basic science studying adrenal development, zonation and homeostasis; and two, from adrenal disorders identified in persons manifesting with various isolated or syndromic forms of primary adrenal insufficiency.
Assuntos
Insuficiência Adrenal/metabolismo , Zona Glomerulosa/crescimento & desenvolvimento , Zona Reticular/crescimento & desenvolvimento , Insuficiência Adrenal/patologia , Aldosterona/metabolismo , Androgênios/metabolismo , Animais , Humanos , Hidrocortisona/metabolismo , Zona Glomerulosa/patologia , Zona Reticular/patologiaRESUMO
BACKGROUND: Macrophages play a key role in iron homeostasis. In peripheral tissues, they are known to polarize into classically activated (or M1) macrophages and alternatively activated (or M2) macrophages. Little is known on whether the polarization program influences the ability of macrophages to store or recycle iron and the molecular machinery involved in the processes. DESIGN AND METHODS: Inflammatory/M1 and alternatively activated/M2 macrophages were propagated in vitro from mouse bone-marrow precursors and polarized in the presence of recombinant interferon-γ or interleukin-4. We characterized and compared their ability to handle radioactive iron, the characteristics of the intracellular iron pools and the expression of molecules involved in internalization, storage and export of the metal. Moreover we verified the influence of iron on the relative ability of polarized macrophages to activate antigen-specific T cells. RESULTS: M1 macrophages have low iron regulatory protein 1 and 2 binding activity, express high levels of ferritin H, low levels of transferrin receptor 1 and internalize--albeit with low efficiency -iron only when its extracellular concentration is high. In contrast, M2 macrophages have high iron regulatory protein binding activity, express low levels of ferritin H and high levels of transferrin receptor 1. M2 macrophages have a larger intracellular labile iron pool, effectively take up and spontaneously release iron at low concentrations and have limited storage ability. Iron export correlates with the expression of ferroportin, which is higher in M2 macrophages. M1 and M2 cells activate antigen-specific, MHC class II-restricted T cells. In the absence of the metal, only M1 macrophages are effective. CONCLUSIONS: Cytokines that drive macrophage polarization ultimately control iron handling, leading to the differentiation of macrophages into a subset which has a relatively sealed intracellular iron content (M1) or into a subset endowed with the ability to recycle the metal (M2).
Assuntos
Regulação da Expressão Gênica/fisiologia , Ferro/metabolismo , Ativação de Macrófagos/fisiologia , Macrófagos/metabolismo , Animais , Apoferritinas/biossíntese , Apoferritinas/imunologia , Proteínas de Transporte de Cátions/biossíntese , Proteínas de Transporte de Cátions/imunologia , Regulação da Expressão Gênica/efeitos dos fármacos , Inflamação/imunologia , Inflamação/metabolismo , Interferon gama/imunologia , Interferon gama/metabolismo , Interferon gama/farmacologia , Interleucina-4/imunologia , Interleucina-4/metabolismo , Interleucina-4/farmacologia , Ferro/imunologia , Proteína 1 Reguladora do Ferro/biossíntese , Proteína 1 Reguladora do Ferro/imunologia , Proteína 2 Reguladora do Ferro/biossíntese , Proteína 2 Reguladora do Ferro/imunologia , Ativação Linfocitária/efeitos dos fármacos , Ativação Linfocitária/fisiologia , Ativação de Macrófagos/efeitos dos fármacos , Macrófagos/citologia , Macrófagos/imunologia , Camundongos , Receptores da Transferrina/biossíntese , Receptores da Transferrina/imunologia , Linfócitos T/citologia , Linfócitos T/imunologia , Linfócitos T/metabolismoRESUMO
Adrenocortical carcinoma (ACC) is a rare and aggressive malignancy with limited therapeutic options. The lack of mouse models that recapitulate the genetics of ACC has hampered progress in the field. We analyzed The Cancer Genome Atlas (TCGA) dataset for ACC and found that patients harboring alterations in both p53/Rb and Wnt/ß-catenin signaling pathways show a worse prognosis compared with patients that harbored alterations in only one. To model this, we utilized the Cyp11b2(AS)Cre mouse line to generate mice with adrenocortical-specific Wnt/ß-catenin activation, Trp53 deletion, or the combination of both. Mice with targeted Wnt/ß-catenin activation or Trp53 deletion showed no changes associated with tumor formation. In contrast, alterations in both pathways led to ACC with pulmonary metastases. Similar to ACCs in humans, these tumors produced increased levels of corticosterone and aldosterone and showed a high proliferation index. Gene expression analysis revealed that mouse tumors exhibited downregulation of Star and Cyp11b1 and upregulation of Ezh2, similar to ACC patients with a poor prognosis. Altogether, these data show that altering both Wnt/ß-catenin and p53/Rb signaling is sufficient to drive ACC in mouse. This autochthonous model of ACC represents a new tool to investigate the biology of ACC and to identify new treatment strategies.
Assuntos
Neoplasias do Córtex Suprarrenal/genética , Modelos Animais de Doenças , Proteína Supressora de Tumor p53/genética , Via de Sinalização Wnt/genética , beta Catenina/genética , Neoplasias do Córtex Suprarrenal/patologia , Carcinoma Adrenocortical/genética , Carcinoma Adrenocortical/patologia , Animais , Proliferação de Células/genética , Perfilação da Expressão Gênica/métodos , Regulação Neoplásica da Expressão Gênica , Humanos , Estimativa de Kaplan-Meier , Camundongos Knockout , Camundongos Transgênicos , PrognósticoRESUMO
Rosettes are widely used in epithelial morphogenesis during embryonic development and organogenesis. However, their role in postnatal development and adult tissue maintenance remains largely unknown. Here, we show zona glomerulosa cells in the adult adrenal cortex organize into rosettes through adherens junction-mediated constriction, and that rosette formation underlies the maturation of adrenal glomerular structure postnatally. Using genetic mouse models, we show loss of ß-catenin results in disrupted adherens junctions, reduced rosette number, and dysmorphic glomeruli, whereas ß-catenin stabilization leads to increased adherens junction abundance, more rosettes, and glomerular expansion. Furthermore, we uncover numerous known regulators of epithelial morphogenesis enriched in ß-catenin-stabilized adrenals. Among these genes, we show Fgfr2 is required for adrenal rosette formation by regulating adherens junction abundance and aggregation. Together, our data provide an example of rosette-mediated postnatal tissue morphogenesis and a framework for studying the role of rosettes in adult zona glomerulosa tissue maintenance and function.
Assuntos
Junções Aderentes/metabolismo , Morfogênese , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/metabolismo , Zona Glomerulosa/crescimento & desenvolvimento , beta Catenina/metabolismo , Junções Aderentes/genética , Junções Aderentes/ultraestrutura , Neoplasias das Glândulas Suprarrenais/cirurgia , Animais , Animais Recém-Nascidos , Feminino , Humanos , Masculino , Camundongos , Camundongos Knockout , Microscopia Eletrônica de Transmissão , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/genética , Zona Glomerulosa/citologia , Zona Glomerulosa/metabolismo , Zona Glomerulosa/ultraestrutura , beta Catenina/genéticaRESUMO
Activating mutations in the canonical Wnt/ß-catenin pathway are key drivers of hyperplasia, the gateway for tumor development. In a wide range of tissues, this occurs primarily through enhanced effects on cellular proliferation. Whether additional mechanisms contribute to ß-catenin-driven hyperplasia remains unknown. The adrenal cortex is an ideal system in which to explore this question, as it undergoes hyperplasia following somatic ß-catenin gain-of-function (ßcat-GOF) mutations. Targeting ßcat-GOF to zona Glomerulosa (zG) cells leads to a progressive hyperplastic expansion in the absence of increased proliferation. Instead, we find that hyperplasia results from a functional block in the ability of zG cells to transdifferentiate into zona Fasciculata (zF) cells. Mechanistically, zG cells demonstrate an upregulation of Pde2a, an inhibitor of zF-specific cAMP/PKA signaling. Hyperplasia is further exacerbated by trophic factor stimulation leading to organomegaly. Together, these data indicate that ß-catenin drives adrenal hyperplasia through both proliferation-dependent and -independent mechanisms.
Assuntos
Hiperplasia Suprarrenal Congênita/metabolismo , Hiperplasia Suprarrenal Congênita/patologia , beta Catenina/metabolismo , Hiperplasia Suprarrenal Congênita/genética , Animais , Transdiferenciação Celular/fisiologia , Feminino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , beta Catenina/genéticaRESUMO
The circadian glucocorticoid (GC) rhythm is dependent on a molecular clock in the suprachiasmatic nucleus (SCN) and an adrenal clock that is synchronized by the SCN. To determine whether the adrenal clock modulates GC responses to stress, experiments used female and male Cyp11A1Cre/+::Bmal1Fl/Fl knockout [side-chain cleavage (SCC)-KO] mice, in which the core clock gene, Bmal1, is deleted in all steroidogenic tissues, including the adrenal cortex. Following restraint stress, female and male SCC-KO mice demonstrate augmented plasma corticosterone but not plasma ACTH. In contrast, following submaximal scruff stress, plasma corticosterone was elevated only in female SCC-KO mice. Adrenal sensitivity to ACTH was measured in vitro using acutely dispersed adrenocortical cells. Maximal corticosterone responses to ACTH were elevated in cells from female KO mice without affecting the EC50 response. Neither the maximum nor the EC50 response to ACTH was affected in male cells, indicating that female SCC-KO mice show a stronger adrenal phenotype. Parallel experiments were conducted using female Cyp11B2 (Aldosterone Synthase)Cre/+::Bmal1Fl/Fl mice and adrenal cortex-specific Bmal1-null (Ad-KO) mice. Plasma corticosterone was increased in Ad-KO mice following restraint or scruff stress, and in vitro responses to ACTH were elevated in adrenal cells from Ad-KO mice, replicating data from female SCC-KO mice. Gene analysis showed increased expression of adrenal genes in female SCC-KO mice involved in cell cycle control, cell adhesion-extracellular matrix interaction, and ligand receptor activity that could promote steroid production. These observations underscore a role for adrenal Bmal1 as an attenuator of steroid secretion that is most prominent in female mice.
Assuntos
Fatores de Transcrição ARNTL/metabolismo , Córtex Suprarrenal/metabolismo , Corticosterona/sangue , Glucocorticoides/metabolismo , Fatores de Transcrição ARNTL/genética , Hormônio Adrenocorticotrópico , Animais , Enzima de Clivagem da Cadeia Lateral do Colesterol/genética , Enzima de Clivagem da Cadeia Lateral do Colesterol/metabolismo , Feminino , Genótipo , Masculino , Camundongos , Camundongos Knockout , Proteínas Circadianas Period/genética , Proteínas Circadianas Period/metabolismo , Fatores Sexuais , Estresse FisiológicoRESUMO
The glucocorticoid (GC) rhythm is entrained to light-dark (LD) cycles via a molecular clock in the suprachiasmatic nucleus (SCN) and is maintained by an adrenal clock synchronized by SCN-dependent signals. Targeted deletion of the core clock gene Bmal1 can disrupt adrenal clock function. The requirement of the adrenal clock to stabilize the circadian GC rhythm during exposure to aberrant LD cycles was determined using novel aldosterone synthase (AS)Cre/+::Bmal1Fl/Fl mice in which Bmal1 deletion occurred during postnatal adrenal transdifferentiation. To examine whether adrenal Bmal1 deletion results in loss of the adrenal clock, mice were crossed with mPER2::Luciferase (mPER2Luc/+) mice. Adrenals from ASCre/+::Bmal1+/+::PER2Luc/+ [control (CTRL)] mice show mPER2Luc rhythms ex vivo, whereas slices from ASCre/+::Bmal1Fl/Fl::PER2Luc/+ [knockout (KO)] mice show dampened rhythms. To monitor corticosterone rhythmicity, mice were implanted with subcutaneous microdialysis probes and sampled at 60-minute intervals for up to 3 days under 12:12-hour [τ (T) 24] LD or 3.5:3.5-hour (T7) LD cycles. Corticosterone rhythms were entrained to T24 LD in CTRL and KO mice. Under T7 LD, circadian corticosterone rhythms persisted in most CTRL mice but not KO mice. Hyperadrenocorticism also was observed in KO mice under T7 LD, reflected by increased corticosterone peak amplitude, total daily corticosterone, and responses to ACTH. Analysis of dysregulated adrenal genes in KO mice exposed to aberrant light identified candidates involved in cholesterol metabolism and trafficking, including steroidogenic acute regulatory protein, which could increase steroidogenesis. Our results show that the adrenal clock functions to buffer steroidogenic responses to aberrant light and stabilize circadian GC rhythmicity.
Assuntos
Fatores de Transcrição ARNTL/genética , Glândulas Suprarrenais/fisiologia , Ritmo Circadiano/fisiologia , Citocromo P-450 CYP11B2/genética , Glucocorticoides/metabolismo , Luz/efeitos adversos , Proteínas Circadianas Period/genética , Glândulas Suprarrenais/crescimento & desenvolvimento , Hormônio Adrenocorticotrópico/sangue , Animais , Animais Recém-Nascidos , Transdiferenciação Celular/genética , Ritmo Circadiano/genética , Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/genética , Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/metabolismo , Corticosterona/sangue , Citocromo P-450 CYP11B2/metabolismo , Feminino , Masculino , Camundongos , Camundongos Knockout , Proteínas Circadianas Period/metabolismo , Fotoperíodo , Núcleo Supraquiasmático/metabolismoRESUMO
The adult adrenal cortex is organized into concentric zones, each specialized to produce distinct steroid hormones. Cellular composition of the cortex is highly dynamic and subject to diverse signaling controls. Cortical homeostasis and regeneration rely on centripetal migration of steroidogenic cells from the outer to the inner cortex, which is accompanied by direct conversion of zona glomerulosa (zG) into zona fasciculata (zF) cells. Given the important impact of tissue structure and growth on steroidogenic function, it is essential to understand the mechanisms governing adrenal zonation and homeostasis. Towards this end, we review the distinctions between each zone by highlighting their morphological and ultra-structural features, discuss key signaling pathways influencing zonal identity, and evaluate current evidence for long-term self-renewing stem cells in the adult cortex. Finally, we review data supporting zG-to-zF transdifferentiation/direct conversion as a major mechanism of adult cortical renewal.