Biology subjects

Sugawa, T.

Publications and source records attributed to Sugawa, T..

2 recordsLinked to original sources

bioRxiv2023

Transcriptomic Landscape of Hyperthyroidism in Mice Overexpressing Thyroid Stimulating Hormone

Hyperthyroidism is a condition with excessive thyroid hormone secretion. Activation of thyroid stimulating hormone receptor (TSHR) fundamentally leads to hyperthyroidism. The details of TSHR signaling remain to be elucidated. We conducted transcriptome analyses for hyperthyroid mice that we generated by overexpressing TSH. TSH overexpression via hydrodynamic gene delivery with pLIVE-TSHB and pLIVE-CGA vectors consistently caused hyperthyroidism and goiters for at least 4 weeks in C57BL/6J mice. RNA sequencing analysis of their thyroid glands revealed that thiamazole slightly changed the thyroid transcriptome, which reinforces a conventional theory that thiamazole decreases thyroid hormone secretion via inhibition of thyroid peroxidase activity. Meanwhile, TSH overexpression drastically changed the thyroid transcriptome. In particular, enrichment analyses identified the cell cycle, phosphatidylinositol-3 kinase/Akt pathway, and Ras-related protein 1 pathway as possibly associated with goiter development. Regarding the role of TSHR signaling in hyperthyroidism, it is noteworthy that Slc26a4 was exclusively upregulated among genes crucial to thyroid hormone secretion at both 1 and 4 weeks after hydrodynamic gene delivery. To verify the relationship between this upregulation and hyperthyroidism, we overexpressed TSH in Slc26a4 knockout mice. TSH overexpression caused hyperthyroidism in Slc26a4 knockout mice, equivalent to that in control mice. To summarize, we analyzed hyperthyroid mice generated by TSH overexpression. We did not observe significant changes in known genes and pathways involved in thyroid hormone secretion. Thus, our datasets might include candidate genes that have not yet been identified as regulators of thyroid function. Our transcriptome datasets regarding hyperthyroidism can contribute to future research on TSHR signaling.

physiology↗

bioRxiv2022

TRIAC disrupts cerebral thyroid hormone action via a negative feedback loop and heterogenous distribution among organs

3,3,5-triiodothyroacetic acid (TRIAC) is a metabolite of endogenous thyroid hormones (THs) that can bind to and activate TH receptors. As TRIAC was previously detected in sewage effluent, we aimed to investigate exogenous TRIACs potential for endocrine disruption. We administered either TRIAC or 3,3,5-triiodo-L-thyronine (LT3) to both euthyroid mice and 6-propyl-2-thiouracil-induced hypothyroid mice. In hypothyroid mice, TRIAC alleviated growth retardation, suppressed the hypothalamus-pituitary-thyroid (HPT) axis, and upregulated TH-responsive genes in the pituitary gland, liver, and heart. We observed that, unlike LT3, TRIAC does not upregulate the expression of TH-responsive genes in the cerebrum. Measurement of organ-specific TRIAC levels suggested that TRIAC was not efficiently trafficked into the cerebrum. Furthermore, by analyzing euthyroid mice, we found that cerebral TRIAC levels did not increase despite TRIAC administration at higher concentrations, whereas serum and cerebral TH levels were substantially decreased. Hence, TH-responsive genes in the cerebrum appear to be downregulated by TRIAC. In summary, TRIAC administration decreases circulating TH levels by suppressing the HPT axis, while the consequent attenuation of TH actions was compensated by TRIAC in peripheral tissues but not in the cerebrum due to the relative impermeability of the blood-brain barrier towards TRIAC. We verified that exogenous TRIAC disrupts TH actions in the cerebrum. This disruption is apparently due to the additive effects of circulating endogenous THs being depleted via a negative feedback loop involving the HPT axis and heterogenous distribution of TRIAC among different organs. Our findings indicate that environmental TRIAC poses a potential neurodevelopmental risk.

ecology↗