Tissue-specific regulation of glucocorticoid receptor mRNA by dexamethasone

The effect of glucocorticoids on tissue-specific regulation of glucocorticoid receptor mRNA was studied in intact and adrenalectomized rats. Glucocorticoid receptor mRNA was examined by Northern blot hybridization and quantitated by slot blot hybridization using a glucocorticoid cRNA probe. Glucocorticoid receptor mRNA was greatest in the lung with the relative levels in other tissues as follows: spleen, 70%; brain, 55%; liver, 50%; kidney, 43%; heart, 35%; adrenal, 13%; and testis only 8%. A tissue-specific difference in glucocorticoid receptor mRNA accumulation was found after adrenalectomy. There was little change in glucocorticoid receptor mRNA levels in liver and lung, but the brain and kidney demonstrated a 40 and 80% increase in mRNA, respectively. In contrast, dexamethasone treatment resulted in a consistent decrease of 40-60% in the accumulation of glucocorticoid receptor mRNA in all tissues studied. These results provide in vivo evidence for the autoregulation of the glucocorticoid receptor by its homologous ligand and demonstrate the existence of tissue-specific regulation of the glucocorticoid receptor mRNA levels in states of glucocorticoid excess and depletion.     

Tissue-specific and hormonal regulation of angiotensinogen minigenes in transgenic mice.

Angiotensinogen is the precursor of the potent vasoactive peptide angiotensin II, and is therefore an important determinant of blood pressure and electrolyte homeostasis. In order to map the tissue-specific and inducible enhancer elements governing angiotensinogen gene expression in transgenic mice, we constructed minigenes containing either 0.75 kb or 4 kb or 5' flanking DNA from the BALB/c angiotensinogen gene. Sequences necessary and sufficient to mediate induction by glucocorticoids, oestrogen and bacterial endotoxin were contained on the minigene bearing 0.75 kb of DNA upstream of the capsite. This construct was also able to confer tissue specificity in the majority of organs producing angiotensinogen. In the testis and salivary gland, differences between the donor (BALB/c) and recipient (Swiss) strains were responsible for the apparently aberrant expression of the minigene constructs. The genetic lesion responsible for these expression polymorphisms has been characterized using recombinant inbred mice. An EcoRI restriction fragment length polymorphism which co-segregates with the angiotensinogen expression phenotypes into many inbred mouse strains is also described.     

Tissue-specific transcriptional regulation and metabolite accumulation in tomato (Solanum lycopersicum L.)

Protoplasma - Tomato is an excellent model for studying fruit development, ripening, and other secondary metabolic pathways such as carotenoid biosynthetic pathway, flavonoid pathway, and many...     

Developmental regulation of hepatic ceruloplasmin mRNA and serum activity by exogenous thyroxine and dexamethasone.

Ceruloplasmin (Cp) is a copper-dependent oxidase with roles that include the regulation of iron metabolism, participation in the acute-phase response to inflammation, and antioxidant systems. Although developmental increases in hepatic Cp gene expression and serum activity have been described, the molecular mechanisms that are responsible for this regulation are not fully understood. The studies described here explored the possible role of glucocorticoids and thyroxine (T4) in the early neonatal development of Cp by the administration of these hormones on postnatal Day 1 (24 hr after birth), and the measurement of both hepatic Cp mRNA and serum activity through postnatal Day 10. Administration of the synthetic glucocorticoid hormone, dexamethasone (2 micrograms/g body wt), resulted in an increase in Cp mRNA on Days 3-7 that was accompanied by an increase in serum Cp activity that reached statistical significance at Day 10. Exogenous T4 (2 micrograms/g body wt) significantly increased Cp mRNA 24 hr after administration. Serum Cp activity was also significantly elevated by the early neonatal administration of T4. Furthermore, gestational hypothyroidism resulted in a significant decrease in Cp activity after postnatal Day 3. These data suggest a role for thyroid hormone and possibly glucocorticoids in the normal developmental regulation of Cp.     

Tissue-specific regulation of inflammation.

Proteins of the complement system are important effectors and modulators of inflammation. The complement cascade is triggered by microbes, tissue debris, and specific antibodies. Serum complement proteins are derived primarily from liver, but extrahepatic complement synthesis is important in homeostasis and in local host defenses. Tissue-specific regulation of expression of complement genes is governed by mechanisms similar to those that regulate other "acute phase reactants." That is, tissue injury or infection elicit changes in expression of these acute phase proteins, which, although variable in kinetics, magnitude, and direction, are a consequence of an elaborate system of cell-to-cell communication. This communication is mediated via a complex network of cytokines, including the interferons, interleukins, several growth factors, and sex hormones. The cell biological and molecular biological details of these mechanisms are now under active investigation. An understanding in molecular terms of the balance between proinflammatory and counterregulatory forces on complement gene expression should provide new insight into the functions of complement and the design of novel therapies for disorders of inflammation.     

Tissue-specific regulation of the concentration of calbindin D28K mRNA in the developing chicken

A BamHI-HindIII restriction fragment containing the 5'-terminal portion of the gene encoding chicken Calbindin D28K was sequenced and used as a probe in Northern-blot hybridizations to RNA extracted from the brain and intestine of chickens at various stages of development. In both tissues Calbindin D28K mRNA consists of a family of three species, which differ by size. In the intestine Calbindin D28K mRNAs appear at hatching and reach a peak at day 7. In the brain the same RNA species are easily detected at least 7 days before hatching, show a moderate increase at hatching and remain essentially constant during the first 10 days of adult life. The concentration of Calbindin D28K mRNAs in the intestine is strictly dependent on Vitamin D, while it is not in the cerebellum.     

Tissue-specific accumulation of carotenoids in carrot roots

Raman spectroscopy can be used for sensitive detection of carotenoids in living tissue and Raman mapping provides further information about their spatial distribution in the measured plant sample. In this work, the relative content and distribution of the main carrot (Daucus carota L.) root carotenoids, α-, β-carotene, lutein and lycopene were assessed using near-infrared Fourier transform Raman spectroscopy. The pigments were measured simultaneously in situ in root sections without any preliminary sample preparation. The Raman spectra obtained from carrots of different origin and root colour had intensive bands of carotenoids that could be assigned to β-carotene (1,520 cm⁻¹), lycopene (1,510 cm⁻¹) and α-carotene/lutein (1,527 cm⁻¹). The Raman mapping technique revealed detailed information regarding the relative content and distribution of these carotenoids. The level of β-carotene was heterogeneous across root sections of orange, yellow, red and purple roots, and in the secondary phloem increased gradually from periderm towards the core, but declined fast in cells close to the vascular cambium. α-carotene/lutein were deposited in younger cells with a higher rate than β-carotene while lycopene in red carrots accumulated throughout the whole secondary phloem at the same level. The results indicate developmental regulation of carotenoid genes in carrot root and that Raman spectroscopy can supply essential information on carotenogenesis useful for molecular investigations on gene expression and regulation.     

Tissue-specific regulation of two functional malic enzyme mRNAs by triiodothyronine

Rat liver malic enzyme (ME) synthesis is known to be regulated by 3,5,3'-triiodo-L-thyronine (T3). Hybridization of 32P-labeled ME cDNA with RNA extracted from normal and T3-induced livers (15 or 50 micrograms/100 g body weight for 10 days) showed an increase in the ME mRNA concentration by approximately 11-fold in T3-treated rats. ME activity and ME mass were stimulated to the same degree as ME mRNA. Northern blot analysis of either total or poly(A+) RNA revealed two distinct ME mRNAs (21 and 27 S) which were equally induced by T3 treatment. Both mRNAs were shown by in vitro translation assay to program the synthesis of the same immunoprecipitable protein corresponding to full-sized ME. From all the above, we concluded that both messages code for active enzyme. ME activity and ME mRNA were also detected in nonhepatic tissues for which different responses to T3 induction were observed without direct correlation with their respective content of T3 nuclear receptor. Increases in ME activity and level of hybridizable ME mRNA were seen 48 h after a single administration of T3 (200 micrograms/100 g body weight) in liver, kidney, and heart (10.3- and 15.5-, 1.7- and 2.6-, and 1.72- and 3.4-fold above basal values, respectively). Lower levels of induction could already be detected after 24 h, liver being the most stimulated tissue. ME was not affected in brain, lung, testis, and spleen. Northern blot analysis showed that both ME mRNAs are present in all tissues tested, although in different relative proportions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tissue-specific regulation of protein synthesis by insulin and free fatty acids

The purpose of the study described herein was to investigate how the mammalian target of rapamycin (mTOR)-signaling pathway and eukaryotic initiation factor 2B (eIF2B) activity, both having key roles in the translational control of protein synthesis in skeletal muscle, are regulated in cardiac muscle of rats in response to two different models of altered free fatty acid (FFA) and insulin availability. Protein synthetic rates were reduced in both gastrocnemius and heart of 3-day diabetic rats. The reduction was associated with diminished mTOR-mediated signaling and eIF2B activity in the gastrocnemius but only with diminished mTOR signaling in the heart. In response to the combination of acute hypoinsulinemia and hypolipidemia induced by administration of niacin, protein synthetic rates were also diminished in both gastrocnemius and heart. The niacin-induced changes were associated with diminished mTOR signaling and eIF2B activity in the heart but only with decreased mTOR signaling in the gastrocnemius. In the heart, mTOR signaling and eIF2B activity correlated with cellular energy status and/or redox potential. Thus FFAs may contribute to the translational control of protein synthesis in the heart but not in the gastrocnemius. In contrast, insulin, but not FFAs, is required for the maintenance of protein synthesis in the gastrocnemius.     

Tissue-specific regulation of zinc metabolism and metallothionein genes by interleukin 1

Interleukin 1 (IL 1) production is stimulated by infection, cellular injury, and inflammation. This cytokine directs a wide spectrum of host responses. Human interleukin 1 alpha (IL 1 alpha) was used to examine the time course of effects on zinc metabolism as part of the acute phase response. IL 1 produced a transient depression in the serum zinc concentration and increased serum ceruloplasmin. Metallothionein levels were increased in liver 14-fold after IL 1. Increased expression of metallothionein-1 and -2 genes following IL 1 were observed in liver, bone marrow, and thymus. Pulse-labeling experiments with i.v.-administered 65Zn showed that IL 1 drastically altered zinc distribution kinetics among tissues. More 65Zn was taken up (and/or retained) by the liver, bone marrow, and thymus 6 h after IL 1, whereas correspondingly less 65Zn was found in bone, skin, and intestine. Uptake by other tissues was not affected by IL 1. Chromatography of cytosol from tissues with increased 65Zn uptake suggests the IL 1-induced redistribution may be driven by enhanced metallothionein synthesis. Collectively, the results show that IL 1 regulates zinc metabolism and may direct its preferential, tissue-specific distribution via elevated metallothionein-1 and -2 gene expression.