Cyp11b1 Null Mouse, a Model of Congenital Adrenal Hyperplasia
Centre for Cardiovascular Science, University of Edinburgh, Edinburgh EH16 4TJ, Scotland, United Kingdom. Journal of Biological Chemistry
(Impact Factor: 4.57).
12/2008; 284(6):3925-34. DOI: 10.1074/jbc.M805081200
Patients with congenital adrenal hyperplasia arising from mutations of 11beta-hydroxylase, the final enzyme in the glucocorticoid biosynthetic pathway, exhibit glucocorticoid deficiency, adrenal hyperplasia driven by unsuppressed hypothalamo-pituitary-adrenal activity, and excess mineralocorticoid activity caused by the accumulation of deoxycorticosterone. A mouse model, in which exons 3-7 of Cyp11b1 (the gene encoding 11beta-hydroxylase) were replaced with cDNA encoding enhanced cyan fluorescent protein, was generated to investigate the underlying disease mechanisms. Enhanced cyan fluorescent protein was expressed appropriately in the zona fasciculata of the adrenal gland, and targeted knock-out was confirmed by urinary steroid profiles and, immunocytochemically, by the absence of 11beta-hydroxylase. The null mice exhibited glucocorticoid deficiency, mineralocorticoid excess, adrenal hyperplasia, mild hypertension, and hypokalemia. They also displayed glucose intolerance. Because rodents do not synthesize adrenal androgens, changes in reproductive function such as genital virilization of females were not anticipated. However, adult homozygote females were infertile, their ovaries showing an absence of corpora lutea and a central proliferation of disorganized steroidogenic tissue. Null females responded normally to superovulation, suggesting that raised systemic progesterone levels also contribute to infertility problems. The model reveals previously unrecognized phenotypic subtleties of congenital adrenal hyperplasia.
Available from: Nicole Gallo-Payet
- "Thus , all of the mechanisms likely modulating cAMP levels also likely modulate p44 / p42 mapk activation and function . This is per - haps why the absence of mutations in MC2R ( review in Clark and Weber , 1998 ) or the absence of the key markers of zona glomeru - losa ( Lee et al . , 2005 ) or zona fasciculata ( Mullins et al . , 2009 ) affect not only steroidogenesis , but also the structural organization of the gland ."
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ABSTRACT: Adrenocorticotropin hormone (ACTH) exerts trophic effects on adrenocortical cells. We studied the phosphorylation of mitogen-activated proteins kinases (MAPKs) in human embryonic kidney cells stably expressing the ACTH receptor, MC2R, and its accessory protein MRAPβ and in primary cultures of human adrenal fasciculata cells. ACTH induced a maximal increase in p44/p42(mapk) and of p38 MAPK phosphorylation after 5min. Neither the overexpression of wild-type arrestin2, arrestin3 or their respective dominant negative forms affected p44/p42(mapk) phosphorylation. However, preincubation with the recycling inhibitors brefeldin A and monensin attenuated both cAMP accumulation and p44/p42(mapk) phosphorylation proportionally. Cyclic AMP-related PKA inhibitors (H89, KI(6-22)) and Rp-cAMPS decreased p44/p42(mapk) phosphorylation but not ACTH-mediated cAMP production. The selective Epac1/2 activator, 8-pCPT-2'-O-MecAMP, did not modify the effect of ACTH. Thus, cAMP/PKA, but not cAMP/Epac1/2 pathways, or arrestin-coupled internalization of MC2R is involved in ACTH-induced p44/p42(mapk) phosphorylation by human MC2R. Together, ACTH binding to MC2R stimulates PKA-dependent p44/p42(mapk) phosphorylation.
Molecular and Cellular Endocrinology 12/2010; 336(1-2):31-40. DOI:10.1016/j.mce.2010.12.030 · 4.41 Impact Factor
- "Mice were killed by CO2 inhalation after restraint stress, maximizing plasma corticosterone levels. Heparinized blood was collected by cardiac puncture, and plasma was stored for measurement of electrolytes, osmolality (freezing point depression), and hormones (32). "
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ABSTRACT: We investigated the effects on urinary steroid and electrolyte excretion and renal gene expression of chronic infusions of ACTH in the mouse. ACTH caused a sustained increase in corticosteroid excretion; aldosterone excretion was only transiently elevated. There was an increase in the excretion of deoxycorticosterone, a weak mineralocorticoid, to levels of physiological significance. Nevertheless, we observed neither antinatriuresis nor kaliuresis in ACTH-treated mice, and plasma renin activity was not suppressed. We identified no changes in expression of mineralocorticoid target genes. Water turnover was increased in chronic ACTH-treated mice, as were hematocrit and hypertonicity: volume contraction is consistent with high levels of glucocorticoid. ACTH-treated mice exhibited other signs of glucocorticoid excess, such as enhanced weight gain and involution of the thymus. We identified novel ACTH-induced changes in 1) genes involved in vitamin D (Cyp27b1, Cyp24a1, Gc) and calcium (Sgk, Calb1, Trpv5) metabolism associated with calciuria and phosphaturia; 2) genes that would be predicted to desensitize the kidney to glucocorticoid action (Nr3c1, Hsd11b1, Fkbp5); and 3) genes encoding transporters of enzyme systems associated with xenobiotic metabolism and oxidative stress. Although there is evidence that ACTH-induced hypertension is a function of physiological cross talk between glucocorticoids and mineralocorticoids, the present study suggests that the major changes in electrolyte and fluid homeostasis and renal function are attributable to glucocorticoids. The calcium and organic anion metabolism pathways that are affected by ACTH may explain some of the known adverse effects associated with glucocorticoid excess.
Physiological Genomics 11/2009; 40(3):158-66. DOI:10.1152/physiolgenomics.00088.2009 · 2.37 Impact Factor
Available from: Emad Al-Dujaili
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ABSTRACT: Clinical studies have established aldosterone as a critical physiological and pathophysiological factor in salt and water homeostasis, blood pressure control and in heart failure. Genetic and physiological studies of mice are used to model these processes. A sensitive and specific assay for aldosterone is therefore needed to monitor adrenocortical activity in murine studies of renal function and cardiovascular diseases.
Antibodies against aldosterone were raised in sheep as previously described. HRP-Donkey-anti-sheep IgG enzyme tracer was produced in our laboratory using the Lightning-Link HRP technique. Aldosterone ELISA protocol was validated and optimised to achieve the best sensitivity. The assay was validated by analysing the urine of mice collected under various experimental conditions designed to stimulate or suppress aldosterone in the presence of other potentially interfering steroid hormones.
Cross-reactivity with the steroids most likely to interfere was minimal: corticosterone=0.0028%, cortisol=0.0006%, DOC=0.0048% except for 5alpha-dihydro-aldosterone=1.65%. Minimum detection limit of this ELISA was 5.2 pmole/L (1.5 pg/mL). The validity of urinary aldosterone ELISA was confirmed by the excellent correlation between results obtained before and after solvent extraction and HPLC separation step (Y=1.092X+0.03, R(2)=0.995, n=54). Accuracy studies, parallelism and imprecision data were determined and all found to be satisfactory. Using this assay, mean urinary aldosterone levels were (i) approximately 60-fold higher in females than males mice; (ii) increased 6-fold by dietary sodium restriction; (iii) increased 10-fold by ACTH infusion and (iv) reduced by >60% in Cyp11b1 null mice.
We describe an ELISA for urinary aldosterone that is suitable for repeated non-invasive measurements in mice. Female aldosterone levels are higher than males. Unlike humans, most aldosterone in mouse urine is not conjugated. Increased levels were noted in response to dietary sodium restriction and ACTH treatment. The sensitivity of the assay is sufficient to detect suppressed levels in mouse models of congenital adrenal hyperplasia.
Steroids 12/2008; 74(4-5):456-62. DOI:10.1016/j.steroids.2008.12.012 · 2.64 Impact Factor
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