Maternal 3,3'-Diiodothyronine Sulfate Formation from Guinea Pig Placenta Perfused with 3,3',5-Triodothyronine
UMass Chan AffiliationsDepartment of Medicine, Division of Endocrinology and Metabolism
Document TypeJournal Article
sulfation of thyroid hormone
Endocrinology, Diabetes, and Metabolism
Hormones, Hormone Substitutes, and Hormone Antagonists
Reproductive and Urinary Physiology
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AbstractOBJECTIVE: Serum 3, 3',5-triiodothyronine (T3) remains low in near-term fetus to prevent the growing fetus from undue exposure to its active catabolic effect in mammals. The present study was undertaken to gain insight in the role of placenta in T3 metabolism, fetal to maternal transfer of T3, and its metabolites by in situ placenta perfusion with outer-ring labeled [(125)I]-T3 in pregnant guinea pig, a species showing increased sulfated 3, 3'-diiodothyronine (T2S) levels in maternal serum in late pregnancy (term = 65 days), similarly to humans in pregnancy. MATERIALS AND METHODS: One-pass placenta perfusions performed on pregnant guinea pigs were studied between 58 - 65 days of gestation. In two separate experiments, the umbilical artery of the guinea pig placenta was perfused in situ at 37 degrees C with outer-ring labeled [(125)I]-T3. Maternal sera and umbilical effluents were obtained for analysis at the end of a 60-minute perfusion, when the steady-state levels of radioactivity were reached in the placenta effluent after 30-minute. RESULTS: Sulfated [(125)I]-T2S was readily detected in the maternal serum as the major metabolite of T3 following the perfusion of placenta with [(125)I]-T3, suggesting that placental inner-ring deiodinase and sulfotransferase may play an important role in fetal T3 homeostasis and in the fetal to maternal transfer of sulfated iodothyronine metabolites. CONCLUSIONS: The expression of type 3 deiodinase (D3) and thyroid hormone sulfotransferase activity in placenta may play an important role to protect developing organs against undue exposure to active thyroid hormone in late gestation in the fetus. The combined activities of D3 and sulfotransferase promoted a placental transfer of T2S into maternal circulation. The maternal circulation of T2S is fetal T3 in origin and its role as a fetal thyroid function biomarker deserves further evaluations and studies.
Wu SY, Emerson CH, Tjioe E, Chen DB. Maternal 3,3'-Diiodothyronine Sulfate Formation from Guinea Pig Placenta Perfused with 3,3',5-Triodothyronine. Endocrinol Disord. 2021 Sep;5(7):01-6. doi: 10.31579/2640-1045/101. Epub 2021 Oct 25. PMID: 35098142; PMCID: PMC8797160. Link to article on publisher's site
Permanent Link to this Itemhttp://hdl.handle.net/20.500.14038/42692
RightsCopyright: © 2021 Sing-yung Wu, This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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CIS/SOCS Proteins in Growth Hormone Action: A DissertationDu, Ling (2000-10-01)CIS/SOCS (cytokine-inducible SH2 protein/suppressor of cytokine signaling) are a family of proteins that are thought to act as negative regulators of signaling by erythropoetin, interleukin-6 and other cytokines whose receptors are related to the growth hormone receptor (GHR), and like growth hormone (GH), signal through the JAK/STAT pathway. We examined the possibility that CIS/SOCS proteins may also be involved in GH signaling, in particular, in termination of the transient insulin-like effects of GH. mRNAs for CIS, SOCS3, and to a lesser extent SOCS1 were detectable by Northern blot analysis of rat adipocyte total RNA, and the expression of CIS and SOCS3 was markedly increased 30 min after incubation with 500 ng/ml hGH. Both CIS and SOCS3 were detected in adipocyte extracts by immunoprecipitation and immunoblotting with their corresponding antisera. GH stimulated the tyrosine phosphorylation of a 120 kDa protein (p120) that was co-precipitated from adipocyte extracts along with αCIS and detected in Western blots with phospho-tyrosine antibodies. However, no tyrosine phosphorylated proteins in these cell extracts were immunoprecipitated with antibodies to CIS3/SOCS3. p120 was later identified as the GHR based on the observations that two GHR antibodies recognized p120 in scale-up experiments and that p120 and the GHR share several characteristics, including their molecular weights, tyrosine phosphorylation upon GH stimulation, interaction with CIS, similar extent of glycosylation as judged by electrophoretic mobility shift after Endo F digestion, comparable mobility shifts upon thrombin digestion, and N-terminal histidine-tagging. The findings, however, do not rule out the possibility that there might be other tyrosine phosphorylated 120 kDa protein(s) that interact with CIS and contribute to the p120 signal, as well as the GHR. Further studies of the association of CIS with the GHR revealed that CIS might selectively interact with multiply tyrosine phosphorylated forms of the GHR, and these tyrosines are likely located near the carboxyl end of the GHR. Overexpression of CIS partially inhibited GH-induced STAT5 phosphorylation in CHO cells. Studies in freshly isolated and GH-deprived (sensitive) adipocytes revealed that the abundance of CIS does not correlate with the termination of the insulin-like effects of GH or the emergence of refractoriness. Neither the association of CIS with the GHR nor the tyrosine phosphorylation status of the GHR, JAK2 and STAT5 appear responsible for refractoriness in adipocytes. These data imply that some negative regulators other than CIS might contribute to the termination of GH-induced insulin-like effects in adipocytes.
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The Epigenetic Silencing of PMP24 During the Progression of Prostate Cancer from an Androgen-Dependent to Androgen-Independent State in the LNCAP Cell Model: a DissertationWu, Mengchu (2005-01-20)One important objective of prostate cancer (PCa) research is to understand the molecular basis underlying the progression of these cancers from an androgen dependent to an androgen independent state. Hypermethylation of the promoter CpG islands is associated with the transcriptional silencing of specific gene sets in each tumor type and subtype. Transcriptional silencing of antitumor genes via CpG island hypermethylation could be a mechanism mediating PCa progression from an androgen-dependent to an androgen-independent state. Hypermethylation associated gene silencing has been reported for a great number of genes in PCa with the exception of the genes that undergo methylation associated silencing specifically during cancer development to androgen independence. The first aim of this thesis is to identify novel glenes which undergo DNA hypermethylation associated gene silencing during the cancer progression. The androgen-dependent (AD, as defined as the inability of celill to proliferate in the absence of androgen) PCa cell line LNCaP gives rise to the androgen-independent (AI) subline LNCaPcs generated by maintaining LNCaP in medium with charcoal-stripped (CS) serum for over 30 passages. This LNCaP cell model was used to identify differentially methylated sequences between the two genomes using the Methylation-Sensitive Restriction Fingerprinting (MSRF) technique. One sequence identified is located in a 5' CpG island, which encompasses part of the promoter, exon 1, and part of intron 1, of the Peroxisomal Membrane Protein 24 KD (PMP24) gene. PMP24 is silenced in concert with the hypermethylation of its CpG island in AI LNCaPcsand PC-3 cell lines. The silencing is reactivated by the treatment with a DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5AZAdC). PMP24 is specifically silenced in PCa cancer cell lines and shows potential antitumor properties. These results demonstrate the utility of MSRF in the identification of novel, differentially methylated DNA sequences in the genome and suggest that hypermethylation-mediated silencing of PMP24 is an epigenetic event involved in PCa progression to androgen independence. The next study investigated the molecular mechanism for DNA methylation associated gene silencing of PMP24 in AI LNCaPcs and PC-3 cell lines. We demonstrated that PMP24 transcription is repressed by the disruption of transcription factor binding to a critical cis-element by hypermethylation of its promoter CpG island. We found a CpG containing activator protein 2 (AP-2) cis-element in the intron 1 of PMP24 whose first CpG dinucleotidle is essential for the sequence-specific protein binding and the promoter activity of the gene. We presented first in cellulo evidence that the methylation of AP-2 cis-element alone but not the whole CpG island, using a newly developed methylated oligonucleotides treatment, is sufficient for the downregulation of PMP24. Our study is the first to report that the silencing mechanism for PMP24 in AI LNCaPcs and PC-3 is mediated by the complete methylation of a single GpG site of AP-2 cis-element in the intron 1 part of the CpG island, which interferes with transcription factor binding. Most interestingly, the promoter CpG island of PMP24 is hypermethylated in AD LNCaP cells with the incomplete methylation specifically at the AP-2 cis-element. The silencing of PMP24 in AD LNCaP cells was reactivated not by the 5AZAdC treatment but by the treatment with Trichostatin A (TSA), a histone deacetylase inhibitor. An alternative silencing mechanism for PMP24 other than the interference with transcription factor binding by methylation is therefore likely involved at this androgen-dependent stage. During the androgen ablation process, this mechanism is either evolved by the spread of methylation in the promoter CpG island or selected against, leading to the methylation-dominant silencing mechanism in the AI cells as seen in LNCaPcsand PC-3 cells. Taken together, this thesis emphasized the important role of DNA methylation in the progression of PCa into androgen independence. Particular respect should be paid to the specific CpG dinucleotides in cis-elements critical for the promoter activity, whose complete methylation could dominate the silencing mechanism which is independent of androgen. 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