Thyrotropin Alters T Cell Development in the Thymus in Subclinical Hypothyroidism Mouse Model

Clinical presentation and prognosis of COVID-19 in older adults with hypothyroidism: data from the GeroCovid observational study

BACKGROUND

The prevalence of hypothyroidism among older patients hospitalized for COVID-19 and its association with mortality is unclear. This study aims to investigate the prevalence of hypothyroidism in older COVID-19 inpatients and verify if this comorbidity is associated with a specific pattern of onset symptoms and a worse prognosis.

METHODS

COVID-19 inpatients aged ≥ 60 years, participating in the GeroCovid acute wards cohort, were included. The history of hypothyroidism was derived from medical records and the use of thyroid hormones. Sociodemographic data, comorbidities, symptoms/signs at the disease onset and inflammatory markers at ward admission were compared between people with vs without history of hypothyroidism. The association between hypothyroidism and in-hospital mortality was tested through Cox regression.

RESULTS

Of the 1245 patients included, 8.5% had a history of hypothyroidism. These patients were more likely to present arterial hypertension and obesity compared with those without an history of hypothyroidism. Concerning COVID-19 clinical presentation, patients with hypothyroidism had less frequently low oxygen saturation and anorexia but reported muscle pain and loss of smell more commonly than those without hypothyroidism. Among the inflammatory markers, patients with hypothyroidism had higher lymphocytes values. At Cox regression, hypothyroidism was associated with reduced in-hospital mortality only in the univariable model (HR = 0.66, 95% CI 0.45-0.96, p = 0.03); conversely, no significant result were observed after adjusting for potential confounders (HR = 0.69, 95% CI 0.47-1.03, p = 0.07).

CONCLUSIONS

Hypothyroidism does not seem to substantially influence the prognosis of COVID-19 in older people, although it may be associated with peculiar clinical and biochemical features at the disease onset.

Thyroid Disrupting Chemicals in Mixture Perturb Thymocyte Differentiation in Xenopus laevis Tadpoles

Endocrine disrupting chemicals (EDCs) can perturb the hypothalamic-pituitary-thyroid axis affecting human and wildlife health. Thyroid hormones (TH) are crucial regulators of metabolism, growth, and differentiation. The perinatal stage is most reliant on TH, thus vulnerable to TH disrupting chemicals. Dysregulation of TH signaling during perinatal development can weaken T cell function in maturity, raising the question of whether TH disrupting chemicals can perturb thymocyte development. Using Xenopus laevis tadpoles as model, we determined TH disrupting effects and thymocyte alterations following exposure to a mixture of common waterborne TH disrupting chemicals at concentrations similar to those found in contaminated water. This mixture included naphthalene, ethylene glycol, ethoxylated nonylphenol, and octylphenol, which have documented TH disrupting activity. Besides hypertrophy-like pathology in the thyroid gland and delayed metamorphosis, exposure to the mixture antagonized TH receptor-induced transcription of the Krüppel-like factor 9 transcription factor and significantly raised thyroid-stimulating hormone gene expression in the brain, two genes that modulate thymocyte differentiation. Importantly, exposure to this mixture reduced the number of Xenopus immature cortical thymocyte-specific-antigen (CTX+) and mature CD8+ thymocytes, whereas co-exposure with exogenous TH (T3) abolished the effect. When each chemical of the mixture was individually tested, only ethylene glycol induced significant antagonist effects on brain, thymic gene expression, and CD8+ thymocytes. These results suggest that EDCs in mixture are more potent than each chemical alone to perturb thymocyte development through TH-dependent pathway, and provide a starting point to research TH influence on thymocyte development.

Alterations in thymocyte populations under conditions of endotoxin tolerance

Background:

Endotoxin tolerance (ET) is a protective phenomenon in which pre-treatment with a tolerance dose of lipopolysaccharide (LPS) leads to dramatically elevated survival. Accumulating evidence has shown that peripheral T cells contribute to the induction of ET. However, what happens to T cell development in the thymus under ET conditions remains unclear. The purpose of this study was to analyze the alterations in thymocyte populations (double-positive [DP] and single-positive [SP] cells) under ET conditions.

Methods:

Mice were intraperitoneally injected with LPS at a concentration of 5 mg/kg to establish an LPS tolerance model and were divided into two groups: a group examined 72 h after LPS injection (72-h group) and a group examined 8 days after LPS injection (8-day group). Injection of phosphate-buffered saline was used as a control (control group). Changes in thymus weight, cell counts, and morphology were detected in the three groups. Moreover, surface molecules such as CD4, CD8, CD44, CD69, and CD62L were analyzed using flow cytometry. Furthermore, proliferation, apoptosis, cytokine production, and extracellular signal-regulated kinase (ERK) pathway signaling were analyzed in thymocyte populations. The polymorphism and length of the T-cell receptor (TCR) β chain complementarity-determining region 3 (CDR3) were analyzed using capillary electrophoresis DNA laser scanning analysis (ABI 3730).

Results:

Thymus weight and cell counts were decreased in the early stage but recovered by the late stage in a murine model of LPS-induced ET. Moreover, the proportions of DP cells (control: 72.130 ± 4.074, 72-h: 10.600 ± 3.517, 8-day: 84.770 ± 2.228), CD4⁺ SP cells (control: 15.770 ± 4.419, 72-h: 44.670 ± 3.089, 8-day: 6.367 ± 0.513), and CD8⁺ SP cells (control: 7.000 ± 1.916, 72-h: 34.030 ± 3.850, 8-day: 5.133 ± 0.647) were obviously different at different stages of ET. The polymorphism and length of TCR β chain CDR3 also changed obviously, indicating the occurrence of TCR rearrangement and thymocyte diversification. Further analysis showed that the expression of surface molecules, including CD44, CD69, and CD62L, on thymocyte populations (DP and SP cells) were changed to different degrees. Finally, the proliferation, apoptosis, cytokine production, and ERK pathway signaling of thymocyte populations were changed significantly.

Conclusion:

These data reveal that alterations in thymocyte populations might contribute to the establishment of ET.

Lymphocyte to monocyte ratio may predict increased carotid intima-media thickness in patients with subclinical hypothyroidism

BACKGROUND

Inflammation has an important role in the pathogenesis of atherosclerosis. Lymphocyte-to-monocyte ratio (LMR) is accepted as an indicator of inflammation.

OBJECTIVE

Our aim was to scrutinize the relationship between LMR and subclinical atherosclerosis (SubAth) measured by carotid intima-media thickness (CIMT) in subclinical hypothyroidism (SubHT).

METHODS

Newly identified 190 SubHT patients were prospectively included into the study. Blood samples were taken for measuring laboratory parameters. Then, CIMT was computed. Patients were seperated into 2 groups by their CIMT value (Group-1: ≤0.9 and Group-2: >0.9 mm), and then stratified into tertiles pursuant to LMR and thyroid-stimulating hormone (TSH) levels, respectively.

RESULTS

59 patients had an increased CIMT value (Group-2), and 131 patients had a normal CIMT value (Group-1). Group-2 had a lower LMR and a greater high-sensitivity C-reactive protein (hsCRP), CIMT and TSH than Group-1 (for all, p < 0.05). Patients in the lowest tertile of LMR had a higher hsCRP, TSH and CIMT than those in the highest tertile (for all, p < 0.05). LMR was negatively associated with hsCRP, CIMT and TSH (for all, p < 0.05). LMR and TSH were independent predictors of increased CIMT.

CONCLUSIONS

Pre-ultrasonographic LMR, which is a simple and inexpensive inflammatory marker, may give additional predictive information to determine SubAth in SubHT.

Long non-coding RNA NEAT1 regulates endothelial functions in subclinical hypothyroidism through miR-126/TRAF7 pathway

Subclinical hypothyroidism (SCH) is associated with increased risks of endothelial dysfunction and atherosclerosis, but the mechanisms remain unclear. In our previous study, microRNA-126-3p was downregulated in SCH, but the role and regulatory mechanism of miR-126 in SCH has not been investigated. A SCH mouse model was established by feeding mice methimazole. Both primary endothelial cells (ECs) and HUVECs were cultured. The expression levels of key molecules were detected via quantitative RT-PCR, western blotting, and immunofluorescence. Wire myography was used to analyze the changes in vascular tones. A dual-luciferase assay was used to investigate the relationship between lncRNAs, microRNAs and target genes. In detail, it was shown that the expression levels of miR-126-3p were significantly decreased in both the SCH vasculature and HUVECs. MiR-126 supplementation suppressed HUVEC apoptosis and improved vascular function. Moreover, miR-126 could bind to the 3'-untranslated region of TRAF7, thus, regulating the C-FLIP pathway and endothelial apoptosis. Furthermore, lncRNA NEAT1 was upregulated upon TSH treatment and could function as a ceRNA and bind to miR-126, thus, modulating its expression level and vascular function. Finally, the NEAT1/miR-126/TRAF7 axis functions in response to TSH and regulates endothelial functions in SCH in vitro and in vivo. In conclusion, dysregulation of the NEAT1/miR-126/TRAF7 axis is responsible for impaired endothelial functions in SCH. Targeting this axis might become a promising treatment strategy or improving endothelial functions in SCH.

Hypothyroidism impairs the host immune response during the acute phase of Chagas disease

Diseases associated with thyroid hypofunction have been the subject of studies in infectious models, since several authors have demonstrated a pivotal role of iodinated hormones (thyroxine and triiodothyronine) in the modulation of immune effector responses. Using a model of hypothyroidism induced by anti-thyroid drug, we investigated the influence of hypothyroidism in the course of acute Trypanosoma cruzi infection. For this, male Hannover Wistar rats were challenged with methimazole for 21 days (0.02% in drinking water), and water for control counterparts. After confirmation of the hypothyroidism, rats were intraperitoneally challenged with 1x10⁵ blood trypomastigotes of the Y strain of T. cruzi. Our findings suggest that hypothyroidism impairs animal weight gain, but does not affect the health of essential organs. Interestingly, infected hypothyroid animals had a significant increase in thymic cell death, with consequent drop in lymphocyte frequency in whole blood (evaluated on the 11th day of infection). Analyzing the percentage of immune cells in the spleen, we found a strong influence of hypothyroidism as a negative regulator of B cells, and antigenic ability of macrophages (RT1b expression) in the course of the experimental chagasic infection. Enhanced serum IL-17A concentration was induced by T. cruzi infection, but hypothyroidism impaired the production of this mediator as seen in infected hypothyroid animals. Taken together, our work suggests for the first time that hypothyroidism may adversely interfere with the modulation of effective immunity in the early phase of Chagas' disease.

Novel Splicing of Immune System Thyroid Stimulating Hormone β-Subunit-Genetic Regulation and Biological Importance

Thyroid stimulating hormone (TSH), a glycoprotein hormone produced by the anterior pituitary, controls the production of thyroxine (T₄) and triiodothyronine (T₃) in the thyroid. TSH is also known to be produced by the cells of the immune system; however, the physiological importance of that to the organism is unclear. We identified an alternatively-spliced form of TSHβ that is present in both humans and mice. The TSHβ splice variant (TSHβv), although produced at low levels by the pituitary, is the primary form made by hematopoietic cells in the bone marrow, and by peripheral leukocytes. Recent studies have linked TSHβv functionally to a number of health-related conditions, including enhanced host responses to infection and protection against osteoporosis. However, TSHβv also has been associated with autoimmune thyroiditis in humans. Yet to be identified is the process by which the TSHβv isoform is produced. Here, a set of genetic steps is laid out through which human TSHβv is generated using splicing events that result in a novel transcript in which exon 2 is deleted, exon 3 is retained, and the 3' end of intron 2 codes for a signal peptide of the TSHβv polypeptide.

Association of increased eomesodermin, BCL6, and granzyme B expression with major clinical manifestations of Hashimoto's thyroiditis - an observational study

PURPOSE

Studies of cytotoxic T cells and their respective lineage master regulators have been limited in Hashimoto's thyroiditis (HT). It is unclear whether their transcriptomes are changed in HT patients and how these changes are associated with the thyroid damage, major clinical manifestations, and disease progression.

METHODS

We explored the gene expression patterns of selected transcription factors [eomesodermin (EOMES), BACH2, BCL6, TCF1] and cytolytic molecules [granzyme B (GZMB)] in peripheral blood (PB) T cells of 10 healthy controls and 30 HT patients of various subtypes (hypothyroid, untreated HT; L-thyroxine (T4)-treated HT, and spontaneously euthyroid HT) using real-time quantitative PCR.

RESULTS

EOMES (Mann-Whitney P = 0.044), GZMB (P = 0.028), and BCL6 mRNA (P = 0.001) were overrepresented in PB T cells from HT and showed levels varying by age, thyroid volume and disease severity. BCL6 transcripts were predominantly enriched in severely affected, hypothyroid cases, both on and off LT4. Increased EOMES RNA expression was associated with advancing age, lower thyroid volumes and higher peak adjusted TSH levels over the course of the disease. The body mass-adjusted, steady-state maintenance dose of LT4 increased with GZMB and BCL6 levels in PB T cells of hypothyroid cases, mostly postmenopausal women having long-standing, non-goitrous and atrophic disease form.

CONCLUSIONS

Our exploratory results suggest a role for GZMB, EOMES, and BCL6 in the context of HT, thyroid injury, and aggressive/advanced disease forms. Functions enriched within differentially expressed transcripts could be an important new target in understanding the pathogenesis of HT.