scholarly journals 20-Hydroxyvitamin D2is a noncalcemic analog of vitamin D with potent antiproliferative and prodifferentiation activities in normal and malignant cells

2011 ◽  
Vol 300 (3) ◽  
pp. C526-C541 ◽  
Author(s):  
Andrzej T. Slominski ◽  
Tae-Kang Kim ◽  
Zorica Janjetovic ◽  
Robert C. Tuckey ◽  
Radoslaw Bieniek ◽  
...  
Keyword(s):  
Vitamin D ◽  
Catalytic Efficiency ◽  
Human Keratinocytes ◽  
Melanoma Cells ◽  
Time Dependent ◽  
Epidermal Keratinocytes ◽  
Dependent Manner ◽  
Cell Type ◽  
Comparable Rate

20-hydroxyvitamin D2[20(OH)D2] inhibits DNA synthesis in epidermal keratinocytes, melanocytes, and melanoma cells in a dose- and time-dependent manner. This inhibition is dependent on cell type, with keratinocytes and melanoma cells being more sensitive than normal melanocytes. The antiproliferative activity of 20(OH)D2is similar to that of 1,25(OH)2D3and of newly synthesized 1,20(OH)2D2but significantly higher than that of 25(OH)D3. 20(OH)D2also displays tumorostatic effects. In keratinocytes 20(OH)D2inhibits expression of cyclins and stimulates involucrin expression. It also stimulates CYP24 expression, however, to a significantly lower degree than that by 1,25(OH)2D3or 25(OH)D3. 20(OH)D2is a poor substrate for CYP27B1 with overall catalytic efficiency being 24- and 41-fold lower than for 25(OH)D3with the mouse and human enzymes, respectively. No conversion of 20(OH)D2to 1,20(OH)2D2was detected in intact HaCaT keratinocytes. 20(OH)D2also demonstrates anti-leukemic activity but with lower potency than 1,25(OH)2D3. The phenotypic effects of 20(OH)D2are mediated through interaction with the vitamin D receptor (VDR) as documented by attenuation of cell proliferation after silencing of VDR, by enhancement of the inhibitory effect through stable overexpression of VDR and by the demonstration that 20(OH)D2induces time-dependent translocation of VDR from the cytoplasm to the nucleus at a comparable rate to that for 1,25(OH)2D3. In vivo tests show that while 1,25(OH)2D3at doses as low as 0.8 μg/kg induces calcium deposits in the kidney and heart, 20(OH)D2is devoid of such activity even at doses as high as 4 μg/kg. Silencing of CY27B1 in human keratinocytes showed that 20(OH)D2does not require its transformation to 1,20(OH)2D2for its biological activity. Thus 20(OH)D2shows cell-type dependent antiproliferative and prodifferentiation activities through activation of VDR, while having no detectable toxic calcemic activity, and is a poor substrate for CYP27B1.

The Natural Flavonoid Naringenin Inhibits the Cell Growth of WilmsTumorinChildren by Suppressing TLR4/NF-κB Signaling

2020 ◽  
Vol 20 ◽  
Author(s):  
Hongtao Li ◽  
Peng Chen ◽  
Lei Chen ◽  
Xinning Wang
Keyword(s):  
Cell Growth ◽  
Western Blot ◽  
Wilms Tumor ◽  
Critical Role ◽  
Time Dependent ◽  
Luciferase Assay ◽  
Dependent Manner ◽  
Tlr4 Expression ◽  
Protein Levels

Background: Nuclear factor kappa B (NF-κB) is usually activated in Wilms tumor (WT) cells and plays a critical role in WT development. Objective: The study purpose was to screen a NF-κB inhibitor from natural product library and explore its effects on WT development. Methods: Luciferase assay was employed to assess the effects of natural chemical son NF-κB activity. CCK-8 assay was conducted to assess cell growth in response to naringenin. WT xenograft model was established to analyze the effect of naringenin in vivo. Quantitative real-time PCR and Western blot were performed to examine the mRNA and protein levels of relative genes, respectively. Results: Naringenin displayed significant inhibitory effect on NF-κB activation in SK-NEP-1 cells. In SK-NEP-1 and G-401 cells, naringenin inhibited p65 phosphorylation. Moreover, naringenin suppressed TNF-α-induced p65 phosphorylation in WT cells. Naringenin inhibited TLR4 expression at both mRNA and protein levels in WT cells. CCK-8 staining showed that naringenin inhibited cell growth of the two above WT cells in dose-and time-dependent manner, whereas Toll-like receptor 4 (TLR4) over expression partially reversed the above phenomena. Besides, naringenin suppressed WT tumor growth in dose-and time-dependent manner in vivo. Western blot found that naringenin inhibited TLR4 expression and p65 phosphorylation in WT xenograft tumors. Conclusion: Naringenin inhibits WT development viasuppressing TLR4/NF-κB signaling

In vivo acute testicular testosterone response to injection of luteinizing hormone in the rat fetus

1993 ◽  
Vol 128 (3) ◽  
pp. 268-273 ◽  
Author(s):  
René Habert
Keyword(s):  
Plasma Concentration ◽  
Luteinizing Hormone ◽  
Leydig Cells ◽  
Time Dependent ◽  
Fetal Life ◽  
Dependent Manner ◽  
Adult Rats ◽  
Rat Fetus ◽  
Age Related

The acute in vivo testosterone response to LH stimulation and its change during late fetal life were determined in the rat. In 18.5-day-old fetuses, testicular testosterone content was increased in a dose-and time-dependent manner after fetal subcutaneous LH injection. The maximum response was small: the testicular content and plasma concentration were increased by 200% and 2 50% over basal values respectively, while they were increased 1100% and 1200% in adult rats. Similarly, comparable low responses were obtained after subcutaneously injecting the fetuses with human chorionic gonadotropin (hCG) and after injecting LH into the vitelline vein. Between days 18.5 and 21.5 of fetal life, the testosterone levels in the testis and plasma of uninjected or PBS-injected fetuses decreased and were comparable in both groups. In maximally LH-stimulated fetuses, the testicular content did not change with age, and plasma concentration was lower on day 21.5 than on day 18.5. Since the number of Leydig cells increases 1.5 to 2-fold between days 18.5 and 21.5, these results show an age-related decrease in basal and maximally LH-stimulated in vivo testosterone secretions per Leydig cell during late fetal life.

scholarly journals Metformin Inhibited Growth, Invasion and Metastasis of Esophageal Squamous Cell Carcinoma in Vitro and in Vivo

2018 ◽  
Vol 51 (3) ◽  
pp. 1276-1286 ◽  
Author(s):  
Feng Liang ◽  
Yu-Gang Wang ◽  
Changcheng Wang
Keyword(s):  
Squamous Cell Carcinoma ◽  
Plasma Glucose Level ◽  
Caspase 3 ◽  
Time Dependent ◽  
Dependent Manner ◽  
Metformin Treatment ◽  
Invasion And Migration ◽  
And Migration

Background/Aims: This study aimed at investigating the effects of metformin on the growth and metastasis of esophageal squamous cell carcinoma (ESCC) in vitro and in vivo. Methods: Two human ESCC cell lines EC9706 and Eca109 were selected and challenged with metformin in this study. Western blot assay was performed to detect th level of Bcl-2, Bax and Caspase-3. Scratch wound assay, transwell assay and Millicell invasion assay were used to assay the invasion and migration of EC9706 and Eca109 cells. Nude mice tumor models were used to assay the growth and lung metastasis of ESCC cells after metformin treatment. The plasma glucose level was also assayed. Results: We found that metformin significantly inhibited proliferation and induced apoptosis of both ESCC cell lines in a dose- and time-dependent manner, and the expression of Bcl-2 was down-regulated and Bax and Caspase-3 were up-regulated. Metformin significantly inhibited the invasion and migration of EC9706 and Eca109 cells (p < 0.05). mRNA and protein levels of MMP-2 and MMP-9 decreased significantly upon treatment with metformin of 10mM for 12, 24 and 48h in a time-dependent manner (p < 0.05). In line with in vitro results, in vivo experiments demonstrated that metformin inhibited tumorigenicity, inhibited lung metastasis and down-regulated the expression of MMP-2 and MMP-9. Moreover, we showed that metformin treatment did not cause significant alteration in liver and renal functions and plasma glucose level. Conclusion: Our study for the first time demonstrated the anti-invasive and anti-metastatic effects of metformin on human ESCC cells both in vitro and in vivo, which might be associated with the down-regulation of MMP-2 and MMP-9. As a whole, our results indicate the potential of metformin to be developed as a chemotherapeutic agent for patients with ESCC and might stimulate future studies on this area.

scholarly journals Genetic engineering for in vivo optical interrogation of neuronal responses to cell type-specific silencing

2021 ◽  
Author(s):  
Firat Terzi ◽  
Johannes Knabbe ◽  
Sidney B. Cambridge
Keyword(s):  
High Resolution ◽  
Genetic Engineering ◽  
Transgene Expression ◽  
Neuronal Morphology ◽  
Dependent Manner ◽  
Cell Type ◽  
Fluorescent Marker ◽  
Genetic Perturbations ◽  
Cell Type Specific

SummaryGenetic engineering of quintuple transgenic brain tissue was used to establish a low background, Cre-dependent version of the inducible Tet-On system for fast, cell type-specific transgene expression in vivo. Co-expression of a constitutive, Cre-dependent fluorescent marker selectively allowed single cell analyses before and after inducible, tet-dependent transgene expression. Here, we used this method for acute, high-resolution manipulation of neuronal activity in the living brain. Single induction of the potassium channel Kir2.1 produced cell type-specific silencing within hours that lasted for at least three days. Longitudinal in vivo imaging of spontaneous calcium transients and neuronal morphology demonstrated that prolonged silencing did not alter spine densities or synaptic input strength. Furthermore, selective induction of Kir2.1 in parvalbumin interneurons increased the activity of surrounding neurons in a distance-dependent manner. This high-resolution, inducible interference and interval imaging of individual cells (high I5, ‘HighFive’) method thus allows visualizing temporally precise, genetic perturbations of defined cells.

scholarly journals Envoplakin, a novel precursor of the cornified envelope that has homology to desmoplakin.

1996 ◽  
Vol 134 (3) ◽  
pp. 715-729 ◽  
Author(s):  
C Ruhrberg ◽  
M A Hajibagheri ◽  
M Simon ◽  
T P Dooley ◽  
F M Watt
Keyword(s):  
Plasma Membrane ◽  
Terminal Differentiation ◽  
Human Keratinocytes ◽  
Single Copy ◽  
Epidermal Keratinocytes ◽  
Single Copy Gene ◽  
Cornified Envelope ◽  
Keratin Filaments ◽  
Copy Gene

The cornified envelope is a layer of transglutaminase cross-linked protein that is deposited under the plasma membrane of keratinocytes in the outermost layers of the epidermis. We present the sequence of one of the cornified envelope precursors, a protein with an apparent molecular mass of 210 kD. The 210-kD protein is translated from a 6.5-kb mRNA that is transcribed from a single copy gene. The mRNA was upregulated during suspension-induced terminal differentiation of cultured human keratinocytes. Like other envelope precursors, the 210-kD protein became insoluble in SDS and beta-mercaptoethanol on activation of transglutaminases in cultured keratinocytes. The protein was expressed in keratinizing and nonkeratinizing stratified squamous epithelia, but not in simple epithelia or nonepithelial cells. Immunofluorescence staining showed that in epidermal keratinocytes, both in vivo and in culture, the protein was upregulated during terminal differentiation and partially colocalized with desmosomal proteins. Immunogold EM confirmed the colocalization of the 210-kD protein and desmoplakin at desmosomes and on keratin filaments throughout the differentiated layers of the epidermis. Sequence analysis showed that the 210-kD protein is homologous to the keratin-binding proteins desmoplakin, bullous pemphigoid antigen 1, and plectin. These data suggest that the 210-kD protein may link the cornified envelope to desmosomes and keratin filaments. We propose that the 210-kD protein be named "envoplakin."

CRM1/XPO1 Represents a Promising Therapeutic Target for Treatment of Chronic Lymphocytic Leukemia

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 232-232
Author(s):  
Rosa Lapalombella ◽  
Caroline Berglund ◽  
Emilia Mahoney ◽  
Katie Williams ◽  
Shruti Jha ◽  
...  
Keyword(s):  
Small Molecule ◽  
Cytotoxic Effect ◽  
Stromal Cell ◽  
Time Dependent ◽  
Dependent Manner ◽  
Spontaneous Apoptosis ◽  
Stromal Cell Line ◽  
Equity Ownership

Abstract Abstract 232 Exportin 1 (CRM1, XPO1) is a nuclear exporter that promotes the transit of tumor suppressor proteins (TSPs) including p53, I-κB, and FOXO3A out of the nucleus, thereby preventing their activity and contributing to disrupted apoptosis and enhanced proliferation. Recently, whole-genome sequencing in patients with CLL allowed the identification of recurrent mutations in a highly conserved region of CRM1 that can potentially affects its gene function, suggesting a direct role for CRM1 in the pathogenesis of CLL (Puente XS, et al: Nature 75:101, 2011). However the role of CRM1 and the consequences of its mutation in the development of CLL have yet to be explored. CRM1 has been shown to be up-regulated in hematologic and various solid tumors, making it a highly attractive molecular target impacting multiple pro apoptotic pathways. KPT-SINEs are new, potent and irreversible small molecule selective inhibitors of nuclear export developed by Karyopharm that specifically and irreversibly bind to CRM1 and block the function of this protein. CLL is characterized by disrupted apoptosis caused both by co-dependent stromal elements and aberrant activation of several survival-promoting signaling/transcriptional pathways including PI3K/Akt, NF-kB, and p53. Because of the distinct subtypes of CLL and multiple signaling pathways dysregulated, a therapeutic agent targeting a single biological pathway is unlikely to be effective. Thus, pursuit of CRM1 inhibition as a novel strategy aimed to restore multiple death pathways is crucial and has broad implications for many types of patients. Our preliminary work demonstrated CRM1 is over-expressed in CLL cells compared to normal B cells at a protein (3 fold, p<0.005) and mRNA level (2.6 fold p=0.014). Inhibition of CRM1 by KPT-185 induced apoptosis in primary patient CLL cells in a dose and time dependent manner (EC50<500nM) while limited cytotoxicity against normal PBMC and isolated B, NK and T cells was observed (EC50 values >20 μM). Additionally, KPT-185 treatment of NK cells had no effect on their function as measured by ability of NK cells to mediate antibody dependent (ADCC) as wekk as direct cytotoxicity. The effect of KPT-185 on T function is currently under evaluation. Nuclear accumulation of FOXO3, p53 and IkB was also observed in primary CLL cells in a time dependent manner as shown by western blot and confocal microscopy. The evaluation of activated target genes is currently ongoing. Given the importance of microenvironmental stimuli on survival of CLL cells and response to therapy, we evaluated the ability of KPT-185 to induce cytotoxicity of CLL cells in the presence or absence of soluble factors such as CPG, CD40L, BAFF, TNF-α, IL-6, or IL-4, which are known to reduce the spontaneous apoptosis associated with CLL cells. KPT-185 treatment abrogated the protection induced by each of these factors suggesting that KPT-SINEs can disrupt signaling from the microenvironment that lead to in vivo CLL cell survival and potentially drug resistance. Interestingly the cytotoxic effect elicited by KPT-185 was enhanced in CPG activated cells (p=0.02). We also tested the ability of KPT-185 to kill CLL cells under coculture conditions with Hs5 stromal cell line. Coculture of CLL cells alone for 48 hours on the Hs5 stromal cell line resulted in a marked reduction of spontaneous apoptosis suggesting a strong protective effect elicited (P<0.001) by the stromal cells. Interestingly the cytotoxic effect mediated by KPT-185 was enhanced under coculture conditions (p=0.013). KPT-185 was also proven to be effective on murine TCL1+ cells (EC50<500nM) in vitro. The in vivo efficacy of this compound and other structurally related analogs is currently being assessed in an ongoing study in theTCL1 mouse model of CLL. In conclusion CRM1 represents a novel target that has not been adequately explored in CLL. KPT-SINEs are a class of promising therapeutic agents with proven selective in vitro activity in CLL cells providing the rationale for developing small molecule, drug-like CRM1 inhibitors for the treatment of this disease. Disclosures: Sandanayaka: Karyopharm Therapeutics: Employment. Shechter:Karyopharm Therapeutics: Employment. McCauley:Karyopharm Therapeutics: Employment. Shacham:Karyopharm: Equity Ownership. Kauffman:Karyopharm: Equity Ownership.

scholarly journals Cell type-specific control of protein synthesis and proliferation by FGF-dependent signaling to the translation repressor 4E-BP

2016 ◽  
Vol 113 (27) ◽  
pp. 7545-7550 ◽  
Author(s):  
Rachel Ruoff ◽  
Olga Katsara ◽  
Victoria Kolupaeva
Keyword(s):  
Protein Synthesis ◽  
Translational Control ◽  
Bone Development ◽  
Binding Protein ◽  
Initiation Factor ◽  
Start Codon ◽  
Dependent Manner ◽  
Fgf Signaling ◽  
Cell Type

Regulation of protein synthesis plays a vital role in posttranscriptional modulation of gene expression. Translational control most commonly targets the initiation of protein synthesis: loading 40S ribosome complexes onto mRNA and AUG start codon recognition. This step is initiated by eukaryotic initiation factor 4E (eIF4E) (the m7GTP cap-binding protein), whose binding to eIF4G (a scaffolding subunit) and eIF4A (an ATP-dependent RNA helicase) leads to assembly of active eIF4F complex. The ability of eIF4E to recognize the cap is prevented by its binding to eIF4E binding protein (4E-BP), which thereby inhibits cap-dependent translation by sequestering eIF4E. The 4E-BP activity is, in turn, inhibited by mTORC1 [mTOR (the mechanistic target of rapamycin) complex 1] mediated phosphorylation. Here, we define a previously unidentified mechanism of mTOR-independent 4E-BP1 regulation that is used by chondrocytes upon FGF signaling. Chondrocytes are responsible for the formation of the skeleton long bones. Unlike the majority of cell types where FGF signaling triggers proliferation, chondrocytes respond to FGF with inhibition. We establish that FGF specifically suppresses protein synthesis in chondrocytes, but not in any other cells of mesenchymal origin. Furthermore, 4E-BP1 repressor activity is necessary not only for suppression of protein synthesis, but also for FGF-induced cell-cycle arrest. Importantly, FGF-induced changes in the 4E-BP1 activity observed in cell culture are likewise detected in vivo and reflect the action of FGF signaling on downstream targets during bone development. Thus, our findings demonstrate that FGF signaling differentially impacts protein synthesis through either stimulation or repression, in a cell-type–dependent manner, with 4E-BP1 being a key player.

Hormone-Conditional Activation of Bcr-Abl Kinase Highlights Stat5 Anti-Apoptotic Pathway Prior to Promoting Cell Growth.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3380-3380
Author(s):  
Ratanakanit Harnprasopwat ◽  
Naoyuki Takahashi ◽  
Seiichiro Kobayashi ◽  
Kazuaki Yokoyama ◽  
Kiyoko Izawa ◽  
...  
Keyword(s):  
Kinase Activity ◽  
Time Dependent ◽  
Viable Cell Number ◽  
Dependent Manner ◽  
Comparable Rate ◽  
Gm Csf ◽  
Abl Kinase ◽  
C Terminus ◽  
Custom Made ◽  
Dose Dependent

Abstract Abstract 3380 Bcr-Abl protein elicits a diverse array of downstream signals and is responsible for development of Philadelphia chromosome (Ph)-positive leukemias. In this fusion protein, disruption or deletion of a N-terminal coiled-coil (CC) region of Bcr results in substantially decreased tyrosine kinase activity and defective cellular transformation, indicating the essential role of Abl oligomerization in its constitutive kinase activity. Fusion of the estrogen receptor (ER) ligand binding domain (LBD) to the C-terminus of Abl generates a ligand-activated tarnsforming version, while additional sequences in Bcr may also be required for oncogenic competence since Bcr-Abl mutants containing just the extreme CC region cannot transform fibroblasts. To revisit the mechanism of Bcr-Abl-induced leukemogenesis and especially to dissect early signaling events upon Bcr-Abl activation, we applied this fusion technology to construct p190DccER, a p190Bcr-Abl mutant including ER-LBD at the C-terminus but not CC region at the N-terminus. GM-CSF-dependent human TF-1 cells were virally transduced with p190DccER as well as wild-type p190 (WT), p190Dcc and vector control, respectively, and a series of transformants were subjected to biological assays as well as biochemical analysis During a few days after switch from GM-CSF to 4-HT, viable cell number of p190DccER-transformed TF-1 cells was not increased but maintained, and thereafter proliferated at the comparable rate to GM-CSF-supported cells. Their growth was dose-dependent on 4-HT unless not more than 1.0mM. The effect of 4-HT on TF-1/p190DccER cells was easily canceled by imatinib in a dose-dependent manner. The profile of phosphotyrosine containing proteins quite resembled between 4-HT-treated TF-1/p190DccER cells and TF-1/p190WT cells. Unexpectedly, stable detection of autophosphorylated p190DccER required as long as several hours or beyond a day after 4-HT stimulation and so did phospho-CrkL. This can be explained by the observation that ligand-free p190DccER was highly unstable, and upon 4-HT binding, its stability increased in a time-dependent manner. Such a stabilizing mechanism might be adapted to substrate proteins including CrkL, which are directly bound to and phosphorylated by Bcr-Abl. On the contrary, 4-HT-induced tyrosine phosphorylation of Stat5 could be observed within 10min, suggesting its dominant role in the initial anti-apoptotic phase triggered by p190DccER. Next, we investigated gene expression profiling of TF-1/p190DccER cells using custom-made oligonucleotide DNA microarray and found a small number of genes differentially expressed before and after 4-HT treatment. Quantitative real-time polymerase chain reaction (QR-PCR) analysis confirmed that seven genes (BCL-XL, HIF-1A, HSPA1A, WT1, PRAME, BAG3 and GATA2) were significantly upregulated by 4-HT in a time-dependent manner. To identify Stat5 target genes among these candidates, we created a doxycycline (DOX)-inducible lentiviral expression system for constitutively active Stat5 mutant (mStat5A1*6). Then, selective activation of Stat5 in TF-1 cells resulted in suppression of apoptosis after GM-CSF withdrawal, and significantly upregulated five of seven candidate genes (BCL-XL, HIF-1A, HSPA1A, WT1, PRAME). These results suggest that the Bcr-Abl/Stat5 pathway is likely to integrate multiple effector molecules to prevent apoptosis, and that they are potential molecular targets in Ph-positive leukemias. The present experimental system helps us to perform functional dissection of signal transducers activated by Bcr-Abl kinase. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Platelet-Released Growth Factors Induce Differentiation of Primary Keratinocytes

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Andreas Bayer ◽  
Mersedeh Tohidnezhad ◽  
Justus Lammel ◽  
Sebastian Lippross ◽  
Peter Behrendt ◽  
...  
Keyword(s):  
Gene Expression ◽  
Growth Factors ◽  
Terminal Differentiation ◽  
Human Keratinocytes ◽  
Keratinocyte Differentiation ◽  
Dependent Manner ◽  
Primary Human Keratinocytes ◽  
Transglutaminase 1 ◽  
Keratin 1

Autologous thrombocyte concentrate lysates, for example, platelet-released growth factors, (PRGFs) or their clinically related formulations (e.g., Vivostat PRF®) came recently into the physicians’ focus as they revealed promising effects in regenerative and reparative medicine such as the support of healing of chronic wounds. To elucidate the underlying mechanisms, we analyzed the influence of PRGF and Vivostat PRF on human keratinocyte differentiation in vitro and on epidermal differentiation status of skin wounds in vivo. Therefore, we investigated the expression of early (keratin 1 and keratin 10) and late (transglutaminase-1 and involucrin) differentiation markers. PRGF treatment of primary human keratinocytes decreased keratin 1 and keratin 10 gene expression but induced involucrin and transglutaminase-1 gene expression in an epidermal growth factor receptor- (EGFR-) dependent manner. In concordance with these results, microscopic analyses revealed that PRGF-treated human keratinocytes displayed morphological features typical of keratinocytes undergoing terminal differentiation. In vivo treatment of artificial human wounds with Vivostat PRF revealed a significant induction of involucrin and transglutaminase-1 gene expression. Together, our results indicate that PRGF and Vivostat PRF induce terminal differentiation of primary human keratinocytes. This potential mechanism may contribute to the observed beneficial effects in the treatment of hard-to-heal wounds with autologous thrombocyte concentrate lysates in vivo.

3,3′,5′-Triiodothyronine inhibits ontogenetic development of iodothyronine-5′-deiodinase in the liver of the neonatal mouse

1988 ◽  
Vol 119 (2) ◽  
pp. 181-188 ◽  
Author(s):  
Doo Chol Han ◽  
Kanji Sato ◽  
Yuko Fujii ◽  
Minoru Ozawa ◽  
Hidehito Imamura ◽  
...  
Keyword(s):  
Single Injection ◽  
Inhibitory Effect ◽  
Antagonistic Effect ◽  
Time Dependent ◽  
Dependent Manner ◽  
Neonatal Mice ◽  
Dose Dependent Decrease ◽  
Dose Dependent

Abstract. To elucidate the effect of rT3 on iodothyronine-5′-deiodinating activity (I-5′-DA) in the liver of neonatal mice, rT3 was injected sc on the 5–8th day after birth and I-5′-DA in the liver was determined. A single injection of rT3 (0.01–1 μg/g) inhibited the ontogenetically developing I-5′-DA in a dose- and time-dependent manner. The inhibitory effect was reversible and specific for I-5′-DA. Lineweaver-Burk analysis revealed that the time- and dose-dependent decrease in the enzyme activity was due to a decrease in Vmax with no alteration in Km values (5 × 10−8 mol/l). The maximal inhibitory effect was observed at a dose of 1 μg rT3/g, whereas the inhibitory effect was diminished at greater doses (4–10 μg/g), probably owing to a contamination with T4 of the rT3 preparation administered. Furthermore, consistent with our previous in vitro findings, rT3 inhibited the I-5′-DA induced by T3 in the liver of neonatal mice. These findings suggest that rT3 inhibited I-5′-DA in the liver of neonatal mice by decreasing the amount of enzyme available to the substrate and that rT3 also elicited an antagonistic effect against T3 in the induction of I-5′-DA in vivo.

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