Actions of Thyroid Hormone Analogues on Chemokines

Pediatric endocrinopathies related to COVID-19: an update

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the seventh coronavirus to be linked to human disease. The SARS-CoV-2 virus may have several pathophysiologic interactions with endocrine systems, resulting in disruptions in glucose metabolism, hypothalamus and pituitary function, adrenal function, and mineral metabolism. An increasing amount of evidence demonstrates both the influence of underlying endocrine abnormalities on the outcome of COVID-19 and the effect of the SARS-CoV-2 virus on endocrine systems. However, a systematic examination of the link to pediatric endocrine diseases has been missing.

DATA SOURCES

The purpose of this review is to discuss the impact of SARS-CoV-2 infection on endocrine systems and to summarize the available knowledge on COVID-19 consequences in children with underlying endocrine abnormalities. For this purpose, a literature search was conducted in EMBASE, and data that were discussed about the effects of COVID-19 on endocrine systems were used in the current study.

RESULTS

Treatment suggestions were provided for endocrinopathies associated with SARS-CoV-2 infection.

CONCLUSIONS

With the global outbreak of COVID-19, it is critical for pediatric endocrinologists to understand how SARS-CoV-2 interacts with the endocrine system and the therapeutic concerns for children with underlying problems who develop COVID-19. While children and adults share certain risk factors for SARS-CoV-2 infection sequelae, it is becoming obvious that pediatric responses are different and that adult study results cannot be generalized. While pediatric research gives some insight, it also shows the need for more study in this area.

Cardiovascular and Neuronal Consequences of Thyroid Hormones Alterations in the Ischemic Stroke

Ischemic stroke is one of the leading global causes of neurological morbidity and decease. Its etiology depends on multiple events such as cardiac embolism, brain capillaries occlusion and atherosclerosis, which ultimately culminate in blood flow interruption, incurring hypoxia and nutrient deprivation. Thyroid hormones (THs) are pleiotropic modulators of several metabolic pathways, and critically influence different aspects of tissues development. The brain is a key TH target tissue and both hypo- and hyperthyroidism, during embryonic and adult life, are associated with deranged neuronal formation and cognitive functions. Accordingly, increasing pieces of evidence are drawing attention on the consistent relationship between the THs status and the acute cerebral and cardiac diseases. However, the concrete contribution of THs systemic or local alteration to the pathology outcome still needs to be fully addressed. In this review, we aim to summarize the multiple influences that THs exert on the brain and heart patho-physiology, to deepen the reasons for the harmful effects of hypo- and hyperthyroidism on these organs and to provide insights on the intricate relationship between the THs variations and the pathological alterations that take place after the ischemic injury.

Risk Predictors of 3-Month and 1-Year Outcomes in Heart Failure Patients with Prior Ischemic Stroke

Background: Despite available therapy, mortality, and readmission rates within 60–90 days of discharge for patients hospitalized with heart failure (HF) are higher compared to the 1-year rates. This study sought to identify the risk factors of the combined endpoint of all-cause readmission or death among HF patients. Methods: Patients with a diagnosis of HF aged 65 or older were included in this prospective observational cohort study. The outcomes were estimated within 3-months and 1 year of discharge. Risk modeling was performed using a multivariable Cox regression analysis of HF patients older than 65 who had experienced ischemic stroke. Results: A total of 951 HF patients enrolled, of whom 340 (35.8%) had suffered a prior ischemic stroke. Significant predictors of increased 3-month all-cause readmission or death included DBP (p = 0.045); serum albumin (p = 0.025), TSH (p = 0.017); and discharge without ACE-inhibitor/ARB/ARNI (p = 0.025), β-blockers (p = 0.029), and antiplatelet drugs (p = 0.005). Heart rate (p = 0.040), laboratory parameters—including serum albumin (p = 0.003), CRP p = 0.028), and FT4 (p = 0.018)—and discharge without β-blockers (p = 0.003), were significant predictors of increased 1-year all-cause readmission and death. Conclusions: Without β-blockers, lower serum albumin and abnormal thyroid function increase the risks of readmission and death in elderly HF patients who have had an ischemic stroke by 3 months and 1 year after discharge. The other factors, such as being without ACEI/ARB and a high heart rate, only increase risks before 3 months or 1 year, not both.

Targeted Modulation of Interferon Response-Related Genes with IFN-Alpha/Lambda Inhibition

Interferon (IFN) signaling resulting from external or internal inflammatory processes initiates the rapid release of cytokines and chemokines to target viral or bacterial invasion, as well as cancer and other diseases. Prolonged exposure to IFNs, or the overexpression of other cytokines, leads to immune exhaustion, enhancing inflammation and leading to the persistence of infection and promotion of disease. Hence, to control and stabilize an excessive immune response, approaches for the management of inflammation are required. The potential use of peptides as anti-inflammatory agents has been previously demonstrated. Our team discovered, and previously published, a 9-amino-acid cyclic peptide named ALOS4 which exhibits anti-cancer properties in vivo and in vitro. We suggested that the anti-cancer effect of ALOS4 arises from interaction with the immune system, possibly through the modulation of inflammatory processes. Here, we show that treatment with ALOS4 decreases basal cytokine levels in mice with chronic inflammation and prolongs the lifespan of mice with acute systemic inflammation induced by irradiation. We also show that pretreatment with ALOS4 reduces the expression of IFN alpha, IFN lambda, and selected interferon-response genes triggered by polyinosinic-polycytidylic acid (Poly I:C), a synthetic analog of viral double-stranded RNA, while upregulating the expression of other genes with antiviral activity. Hence, we conclude that ALOS4 does not prevent IFN signaling, but rather supports the antiviral response by upregulating the expression of interferon-response genes in an interferon-independent manner.

Possible Contributions of Nongenomic Actions of Thyroid Hormones to the Vasculopathic Complex of COVID-19 Infection

BACKGROUND

Integrin αvβ3 is a cell membrane structural protein whose extracellular domain contains a receptor for L-thyroxine (T4). The integrin is expressed in rapidly dividing cells and its internalization is prompted by T4. The protein binds viruses and we have raised the possibility elsewhere that action of free T4 (FT4)-when he latter is increased in the nonthyroidal illness syndrome (NTIS) known to complicate COVID-19 infecction-may enhance cellular uptke of SARS-CoV-2 and its receptor.

OBJECTIVE

Because T4 also acts nongenomically via the integrin to promote platelet aggregation and angiogenesis, we suggest here that T4 may contribute to the coagulopathy and endothelial abnormalities that can develop in COVID-19 infections, particularly when the lung is primary affected.

DISCUSSION AND CONCLUSIONS

Elevated FT4 has been described in the NTIS of COVID-19 patients and may be associated with increased illness severity, but the finding of FT4 elevation is inconsistent in the NTIS literature. Circulating 3,5',3'-triiodo-L-thyronine (reverse T3, rT3) are frequently elevated in NTIS. Thought to be biologically inactive, rT3in fact stimulates cancer cell proliferation via avb3 and also may increase actin polymerization. We propose here that rT3 in the NTIS complicating systemic COVIF-19 infection may support coagulation and disordered blood vessel formation via actin polymerization.

Thyroid Function During and After COVID-19 Infection: A Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can lead to multiorgan dysfunction through pulmonary and systemic inflammation. Infection also affects the thyroid gland directly via cytopathological effects of the virus or indirectly through cytokines, complement systems and coagulation mechanisms. The thyroid gland regulates innate and adaptive immune systems by genomic and nongenomic pathways. During or after SARS-CoV-2 infection, Graves' disease and subacute thyroiditis might be triggered, resulting in hyperthyroidism; alternatively, the effect of the virus on the hypophyseal.hypothalamic axis might cause central hypothyroidism. Severe cases of coronavirus disease 2019 (COVID-19) can present with hypoxia, which requires the use of dexamethasone. This can depress basal serum concentrations of 3,5,3'-triiodothyronine. Thyroid function should be monitored when using dexamethasone in patients with COVID-19. This article briefly reviews the direct and indirect effects of SARS-CoV-2 on the thyroid gland and function.

In Vivo Clearance of Apoptotic Debris From Tumor Xenografts Exposed to Chemically Modified Tetrac: Is There a Role for Thyroid Hormone Analogues in Efferocytosis?

Apoptosis is induced in cancer cells and tumor xenografts by the thyroid hormone analogue tetraiodothyroacetic acid (tetrac) or chemically modified forms of tetrac. The effect is initiated at a hormone receptor on the extracellular domain of plasma membrane integrin αvβ3. The tumor response to tetrac includes 80% reduction in size of glioblastoma xenograft in two weeks of treatment, with absence of residual apoptotic cancer cell debris; this is consistent with efferocytosis. The molecular basis for efferocytosis linked to tetrac is incompletely understood, but several factors are proposed to play roles. Tetrac-based anticancer agents are pro-apoptotic by multiple intrinsic and extrinsic pathways and differential effects on specific gene expression, e.g., downregulation of the X-linked inhibitor of apoptosis (XIAP) gene and upregulation of pro-apoptotic chemokine gene, CXCL10. Tetrac also enhances transcription of chemokine CXCR4, which is relevant to macrophage function. Tetrac may locally control the conformation of phagocyte plasma membrane integrin αvβ3; this is a cell surface recognition system for apoptotic debris that contains phagocytosis signals. How tetrac may facilitate the catabolism of the engulfed apoptotic cell debris requires additional investigation.

Extranuclear effects of thyroid hormones and analogs during development: An old mechanism with emerging roles

Thyroid hormones, T₃ (triiodothyronine) and T₄ (thyroxine), induce a variety of long-term effects on important physiological functions, ranging from development and growth to metabolism regulation, by interacting with specific nuclear or cytosolic receptors. Extranuclear or nongenomic effects of thyroid hormones are mediated by plasma membrane or cytoplasmic receptors, mainly by αvβ3 integrin, and are independent of protein synthesis. A wide variety of nongenomic effects have now been recognized to be elicited through the binding of thyroid hormones to this receptor, which is mainly involved in angiogenesis, as well as in cell cancer proliferation. Several signal transduction pathways are modulated by thyroid hormone binding to αvβ3 integrin: protein kinase C, protein kinase A, Src, or mitogen-activated kinases. Thyroid hormone-activated nongenomic effects are also involved in the regulation of Na⁺-dependent transport systems, such as glucose uptake, Na⁺/K⁺-ATPase, Na⁺/H⁺ exchanger, and amino acid transport System A. Of note, the modulation of these transport systems is cell-type and developmental stage-dependent. In particular, dysregulation of Na⁺/K⁺-ATPase activity is involved in several pathological situations, from viral infection to cancer. Therefore, this transport system represents a promising pharmacological tool in these pathologies.

Transcriptome-wide association study identifies multiple genes and pathways associated with thyroid function

Thyroid dysfunction is a common endocrine disease measured by thyroid-stimulating hormone (TSH) level. Although more than 70 genetic loci associated with TSH have been reported through genome-wide association studies (GWASs), the variants can only explain a small fraction of the thyroid function heritability. To identify novel candidate genes for thyroid function, we conducted the first large-scale transcriptome-wide association study (TWAS) for thyroid function using GWAS-summary data for TSH levels in up to 119 715 individuals combined with pre-computed gene expression weights of six panels from four tissue types. The candidate genes identified by TWAS were further validated by TWAS replication and gene expression profiles. We identified 74 conditionally independent genes significantly associated with thyroid function, such as PDE8B (P = 1.67 × 10-282), PDE10A (P = 7.61 × 10-119), NR3C2 (P = 1.50 × 10-92), and CAPZB (P = 3.13 × 10-79). After TWAS replication using UKBB datasets, 26 genes were replicated for significant associations with thyroid-relevant diseases/traits. Among them, 16 gene were causal for their associations to thyroid-relevant diseases/traits and further validated in differential expression analyses, including two novel genes (MFSD6 and RBM47) that did not implicate in previous GWASs. Enrichment analyses detected several pathways associated with thyroid function, such as the cAMP signaling pathway (P = 7.27 × 10-4), hemostasis (P = 3.74 × 10-4), and platelet activation, signaling, and aggregation (P = 9.98 × 10-4). Our study identified multiple candidate genes and pathways associated with thyroid function, providing novel clues for revealing the genetic mechanisms of thyroid function and disease.

Expression of functional thyroid-stimulating hormone receptor in microglia

OBJECTIVE

The purpose of the present study was to clarify the expression of thyroid-stimulating hormone receptor (TSHR) in microglial cells, and to explore its function.

MATERIALS AND METHODS

Expression of TSHR in microglia was determined by Western blot, immunocytofluorescence and double immunohistofluorescence. Cyclic adenosine 3',5'-monophosphate (cAMP) production was measured after thyrotropin receptor stimulating antibody (TSAb) treatment.

RESULTS

Results showed that TSHR protein was expressed and mainly located in the mouse microglia membrane. Moreover, TSAb stimulated cAMP production in mouse microglia (p<0.05).

CONCLUSIONS

This study demonstrated the presence of TSHR in microglial cells. Brain TSHR was able to respond specifically to TSAb stimulation, suggesting that TSHR expression is functional. As microglia are innate immune cells that maintain environmental stability in the central nervous system and play a key role in many neuroimmune diseases, expression of functional TSHR in microglia has important pathophysiological implications.

Impact of COVID-19 on the thyroid gland: an update

Coronavirus disease 2019 (COVID-19) is the pandemic of the new millennium. COVID-19 can cause both pulmonary and systemic inflammation, potentially determining multi-organ dysfunction. Data on the relationship between COVID-19 and thyroid have been emerging, and rapidly increasing since March 2020. The thyroid gland and the virus infection with its associated inflammatory-immune responses are known to be engaged in complex interplay. SARS-CoV-2 uses ACE2 combined with the transmembrane protease serine 2 (TMPRSS2) as the key molecular complex to infect the host cells. Interestingly, ACE2 and TMPRSS2 expression levels are high in the thyroid gland and more than in the lungs. Our literature search provided greater evidence that the thyroid gland and the entire hypothalamic-pituitary-thyroid (HPT) axis could be relevant targets of damage by SARS-CoV-2. Specifically, COVID-19-related thyroid disorders include thyrotoxicosis, hypothyroidism, as well as nonthyroidal illness syndrome. Moreover, we noticed that treatment plans for thyroid cancer are considerably changing in the direction of more teleconsultations and less diagnostic and therapeutical procedures. The current review includes findings that could be changed soon by new results on the topic, considering the rapidity of worldwide research on COVID-19.

Infection and Immunometabolism in the Central Nervous System: A Possible Mechanistic Link Between Metabolic Imbalance and Dementia

Metabolic syndromes are frequently associated with dementia, suggesting that the dysregulation of energy metabolism can increase the risk of neurodegeneration and cognitive impairment. In addition, growing evidence suggests the link between infections and brain disorders, including Alzheimer's disease. The immune system and energy metabolism are in an intricate relationship. Infection triggers immune responses, which are accompanied by imbalance in cellular and organismal energy metabolism, while metabolic disorders can lead to immune dysregulation and higher infection susceptibility. In the brain, the activities of brain-resident immune cells, including microglia, are associated with their metabolic signatures, which may be affected by central nervous system (CNS) infection. Conversely, metabolic dysregulation can compromise innate immunity in the brain, leading to enhanced CNS infection susceptibility. Thus, infection and metabolic imbalance can be intertwined to each other in the etiology of brain disorders, including dementia. Insulin and leptin play pivotal roles in the regulation of immunometabolism in the CNS and periphery, and dysfunction of these signaling pathways are associated with cognitive impairment. Meanwhile, infectious complications are often comorbid with diabetes and obesity, which are characterized by insulin resistance and leptin signaling deficiency. Examples include human immunodeficiency virus (HIV) infection and periodontal disease caused by an oral pathogen Porphyromonas gingivalis. This review explores potential interactions between infectious agents and insulin and leptin signaling pathways, and discuss possible mechanisms underlying the relationship between infection, metabolic dysregulation, and brain disorders, particularly focusing on the roles of insulin and leptin.

Nano-Strategies Targeting the Integrin αvβ3 Network for Cancer Therapy

Integrin αvβ3, a cell surface receptor, participates in signaling transduction pathways in cancer cell proliferation and metastasis. Several ligands bind to integrin αvβ3 to regulate proliferation and metastasis in cancer cells. Crosstalk between the integrin and other signal transduction pathways also plays an important role in modulating cancer proliferation. Carcinoembryonic antigen cell adhesion molecule 6 (CEACAM6) activates the downstream integrin FAK to stimulate biological activities including cancer proliferation and metastasis. Blockage of signals related to integrin αvβ3 was shown to be a promising target for cancer therapies. 3,3′,5,5′-tetraiodothyroacetic acid (tetrac) completely binds to the integrin with the thyroid hormone to suppress cancer proliferation. The (E)-stilbene analog, resveratrol, also binds to integrin αvβ3 to inhibit cancer growth. Recently, nanotechnologies have been used in the biomedical field for detection and therapeutic purposes. In the current review, we show and evaluate the potentiation of the nanomaterial carrier RGD peptide, derivatives of PLGA-tetrac (NDAT), and nanoresveratrol targeting integrin αvβ3 in cancer therapies.

Anti-Cancer Activities of Thyrointegrin αvβ3 Antagonist Mono- and Bis-Triazole Tetraiodothyroacetic Acid Conjugated via Polyethylene Glycols in Glioblastoma

Integrin αvβ3 receptors are overexpressed in different tumors and their associated neovascularization and hence, represent a potential cancer target. We previously synthesized a high affinity thyrointegrin αvβ3, P4000-bi-TAT (tetrac derivative), with potent anticancer properties. However, the long polydisperse PEG conjugate showed large scaleup and analytical/bioanalytical issues. Hence, in the present study, we synthesized a mono versus bi-triazole tetrac with discrete monodisperse PEG, which provided improvement in scaleup and bioanalysis. In the present study, we compared binding affinity and anticancer activates with a smaller PEG size (P1600-bi-TAT, Compound 2) and the removal of one TAT molecule (P1600-m-TAT, Compound 3) versus P4000-bi-TAT, Compound 1. The results of the selectivity and affinity of TATs showed greater affinity to integrin αvβ3. The xenograft weights and tumor cell viabilities were decreased by >90% at all doses compared to the control (ON Treatment, *** p < 0.001) in cells treated with Compounds 1, 2, and 3 in U87-Luc-treated mice. The in vivo luminescent signals of U87-luc cells reflect the proliferation and distribution of tumor cells in the animals and the maximum intensity corresponding to the maximum tumor cells that the animals could tolerate. We found that the three thyrointegrin αvβ3 antagonists exhibited optimal therapeutic efficacy against U87 or primary glioblastoma cells. Biological studies showed that decreasing the PEG linker size (1600 vs. 4000) or having mono-TAT or bi-TAT had no significant impact on their αvβ3 binding affinity, anti-angiogenesis, or overall anti-cancer efficacy.

Coronaviruses and Integrin αvβ3: Does Thyroid Hormone Modify the Relationship?

BACKGROUND

Uptake of coronaviruses by target cells involves binding of the virus by cell ectoenzymes. For the etiologic agent of COVID-19 (SARS-CoV-2), a receptor has been identified as angiotensin-converting enzyme-2 (ACE2). Recently it has been suggested that plasma membrane integrins may be involved in the internalization and replication of clinically important coronaviruses. For example, integrin αvβ3 is involved in the cell uptake of a model porcine enteric α-coronavirus that causes human epidemics. ACE2 modulates the intracellular signaling generated by integrins.

OBJECTIVE

We propose that the cellular internalization of αvβ3 applies to uptake of coronaviruses bound to the integrin, and we evaluate the possibility that clinical host T4 may contribute to target cell uptake of coronavirus and to the consequence of cell uptake of the virus.

DISCUSSION AND CONCLUSIONS

The viral binding domain of the integrin is near the Arg-Gly-Asp (RGD) peptide-binding site and RGD molecules can affect virus binding. In this same locale on integrin αvβ3 is the receptor for thyroid hormone analogues, particularly, L-thyroxine (T4). By binding to the integrin, T4 has been shown to modulate the affinity of the integrin for other proteins, to control internalization of αvβ3 and to regulate the expression of a panel of cytokine genes, some of which are components of the 'cytokine storm' of viral infections. If T4 does influence coronavirus uptake by target cells, other thyroid hormone analogues, such as deaminated T4 and deaminated 3,5,3'-triiodo-L-thyronine (T3), are candidate agents to block the virus-relevant actions of T4 at integrin αvβ3 and possibly restrict virus uptake.

Nongenomic Actions of Thyroid Hormone: The Integrin Component

The extracellular domain of plasma membrane integrin αvβ3 contains a cell surface receptor for thyroid hormone analogues. The receptor is largely expressed and activated in tumor cells and rapidly dividing endothelial cells. The principal ligand for this receptor is l-thyroxine (T₄), usually regarded only as a prohormone for 3,5,3'-triiodo-l-thyronine (T₃), the hormone analogue that expresses thyroid hormone in the cell nucleus via nuclear receptors that are unrelated structurally to integrin αvβ3. At the integrin receptor for thyroid hormone, T₄ regulates cancer and endothelial cell division, tumor cell defense pathways (such as anti-apoptosis), and angiogenesis and supports metastasis, radioresistance, and chemoresistance. The molecular mechanisms involve signal transduction via mitogen-activated protein kinase and phosphatidylinositol 3-kinase, differential expression of multiple genes related to the listed cell processes, and regulation of activities of other cell surface proteins, such as vascular growth factor receptors. Tetraiodothyroacetic acid (tetrac) is derived from T₄ and competes with binding of T₄ to the integrin. In the absence of T₄, tetrac and chemically modified tetrac also have anticancer effects that culminate in altered gene transcription. Tumor xenografts are arrested by unmodified and chemically modified tetrac. The receptor requires further characterization in terms of contributions to nonmalignant cells, such as platelets and phagocytes. The integrin αvβ3 receptor for thyroid hormone offers a large panel of cellular actions that are relevant to cancer biology and that may be regulated by tetrac derivatives.

Facilitation of microglial motility by thyroid hormones requires the presence of neurons in cell culture: A distinctive feature of the brainstem versus the cortex

Microglia are critical for the refinement of neural networks that takes place during the perinatal period. Their phenotype and actions are guided by the signals produced by neighbouring cells and hormones present in their surrounding milieu. Cell populations and the signals they produce differ between regions. The fact that thyroid hormones (THs) promote the growth and morphological differentiation of microglia within the cortex contributes to the TH's powerful actions on the developing brain. The brainstem is especially active during early life owing to its role in generation of the rhythmic respiratory motor command. Despite evidences indicating that THs are necessary to proper development of the neural networks regulating this vital homeostatic function, their actions on microglia originating from the brainstem remain unknown. Using primary cultured microglia from newborn mice (C57BL/6J), we first report that regulation of microglial motility by THs is different between cortex and brainstem. Microglial motility (μm traveled over 3 h) was monitored with or without triiodothyronine (T3, 1μM). Exposure to T3 did not stimulate microglial motility from brainstem, but significantly stimulated (316 %) when they were co-cultured with neurons. Motility of cortex microglia was stimulated to the similar extent either with or without neurons. These data suggest that the microglial function in different regions of the brain is determined by the surrounding environment.

Platelet ATP, Thyroid Hormone Receptor on Integrin αvβ3 and Cancer Metastasis

Activated platelets may contribute to the metastatic behavior of tumor cells when the cancer cells and platelets interact. The interaction requires cell and platelet surface integrin. Thyroid hormone as L-thyroxine (T4) is the principal ligand for a hormone receptor on integrin αvβ3 on tumor cells and platelets. T4 activates the integrin, promoting platelet aggregation and degranulation (local ATP release) and stimulating tumor cell proliferation. By a variety of molecular mechanisms reviewed here, extracellular ATP promotes tumor cell invasiveness and metastasis and supports a role for T4 as a pro-metastatic factor.

The Role of Thyroid Hormones in Hepatocyte Proliferation and Liver Cancer

Thyroid hormones T3 and T4 (thyroxine) control a wide variety of effects related to development, differentiation, growth and metabolism, through their interaction with nuclear receptors. But thyroid hormones also produce non-genomic effects that typically start at the plasma membrane and are mediated mainly by integrin αvβ3, although other receptors such as TRα and TRβ are also able to elicit non-genomic responses. In the liver, the effects of thyroid hormones appear to be particularly important. The liver is able to regenerate, but it is subject to pathologies that may lead to cancer, such as fibrosis, cirrhosis, and non-alcoholic fatty liver disease. In addition, cancer cells undergo a reprogramming of their metabolism, resulting in drastic changes such as aerobic glycolysis instead of oxidative phosphorylation. As a consequence, the pyruvate kinase isoform M2, the rate-limiting enzyme of glycolysis, is dysregulated, and this is considered an important factor in tumorigenesis. Redox equilibrium is also important, in fact cancer cells give rise to the production of more reactive oxygen species (ROS) than normal cells. This increase may favor the survival and propagation of cancer cells. We evaluate the possible mechanisms involving the plasma membrane receptor integrin αvβ3 that may lead to cancer progression. Studying diseases that affect the liver and their experimental models may help to unravel the cellular pathways mediated by integrin αvβ3 that can lead to liver cancer. Inhibitors of integrin αvβ3 might represent a future therapeutic tool against liver cancer. We also include information on the possible role of exosomes in liver cancer, as well as on recent strategies such as organoids and spheroids, which may provide a new tool for research, drug discovery, and personalized medicine.

New Interfaces of Thyroid Hormone Actions With Blood Coagulation and Thrombosis

Substantial clinical evidence indicates hyperthyroidism enhances coagulation and increases the risk of thrombosis. In vitro and clinical evidence implicate multiple mechanisms for this risk. Genomic actions of thyroid hormone as 3,5,3′-triiodo-L-thyronine (T₃) via a nuclear thyroid hormone receptor have been implicated, but recent evidence shows that nongenomic mechanisms initiated at the receptor for L-thyroxine (T₄) on platelet integrin αvβ3 are prothrombotic. The T₄-initiated mechanisms involve platelet activation and, in addition, cellular production of cytokines and chemokines such as CX3CL1 with procoagulatory activities. These procoagulant actions of T₄ are particulary of note because within cells T4 is not seen to be functional, but to be only a prohormone for T₃. Finally, it is also possible that thyroid hormone stimulates platelet-endothelial cell interaction involved in local thrombus generation. In this brief review, we survey mechanisms by which thyroid hormone is involved in coagulation and platelet functions. It is suggested that the threshold should be lowered for considering the possibility that clinically significant clotting may complicate hyperthyroidism. The value of routine measurement of partial thromboplastin time or circulating D-dimer in patients with hyperthyroid or in patients treated with thyrotropin-suppressing dosage of T₄ requires clinical testing.

A Role for Iodide and Thyroglobulin in Modulating the Function of Human Immune Cells

Iodine is an essential element required for the function of all organ systems. Although the importance of iodine in thyroid hormone synthesis and reproduction is well known, its direct effects on the immune system are elusive. Human leukocytes expressed mRNA of iodide transporters (NIS and PENDRIN) and thyroid-related proteins [thyroglobulin (TG) and thyroid peroxidase (TPO)]. The mRNA levels of PENDRIN and TPO were increased whereas TG transcripts were decreased post leukocyte activation. Flow cytometric analysis revealed that both PENDRIN and NIS were expressed on the surface of leukocyte subsets with the highest expression occurring on monocytes and granulocytes. Treatment of leukocytes with sodium iodide (NaI) resulted in significant changes in immunity-related transcriptome with an emphasis on increased chemokine expression as probed with targeted RNASeq. Similarly, treatment of leukocytes with NaI or Lugol’s iodine induced increased protein production of both pro- and anti-inflammatory cytokines. These alterations were not attributed to iodide-induced de novo thyroid hormone synthesis. However, upon incubation with thyroid-derived TG, primary human leukocytes but not Jurkat T cells released thyroxine and triiodothyronine indicating that immune cells could potentially influence thyroid hormone balance. Overall, our studies reveal the novel network between human immune cells and thyroid-related molecules and highlight the importance of iodine in regulating the function of human immune cells.

Ischemic Stroke and Impact of Thyroid Profile at Presentation: A Systematic Review and Meta-analysis of Observational Studies

BACKGROUND

Stroke is the fifth leading cause of mortality in the United States and a leading cause of disability. A complex relationship between thyroid hormone levels and severity of, and outcome after, stroke has been described.

AIM

Our objective is to identify the association between baseline thyroid function profile and outcome after acute ischemic stroke.

METHODS

Studies looking at the association between thyroid function and functional stroke outcomes were identified from available electronic databases from inception to December 16, 2016. Study-specific risk ratios were extracted and combined with a random effects model meta-analysis.

RESULTS

In the analysis of 12 studies with 5218 patients, we found that subclinical hypothyroidism was associated with better modified Rankin scale scores at 1 and 3 months (odds ratio [OR] 2.58, 95% confidence interval [CI] 1.13-5.91, P = .03 and OR 2.28, 95% CI 1.13-3.91, P = .003, respectively) compared with the euthyroid cases. Likewise, patients with higher initial thyrotropin-releasing hormone (TSH) and fT3 or T3 levels had favorable outcomes at discharge (mean differences of TSH .12 [95% CI .03-.22, P = .009] and of fT3 .36 (CI .20-.53, P < .0001]) and at 3 months (mean differences of TSH .25 [95% CI .03-.47, P = .03] and of T3 8.60 [CI 4.58-12.61, P < .0001]).

CONCLUSIONS

Elevated initial TSH (clinical or subclinical hypothyroidism) may correspond to better functional outcomes, whereas low initial T3/fT3 might correlate with worse outcomes in acute ischemic stroke among clinically euthyroid patients. This complex relation merits further well-designed investigations. Whether correcting thyroid profile with hormone supplementation or antagonism may lead to improved outcomes will require large, prospective, interventional studies.

Molecular Basis of Nongenomic Actions of Thyroid Hormone

Nongenomic actions of thyroid hormone are initiated by the hormone at receptors in the plasma membrane, in cytoplasm, or in mitochondria and do not require the interaction of nuclear thyroid hormone receptors (TRs) with their primary ligand, 3,5,3'-triiodo-l-thyronine (T₃). Receptors involved in nongenomic actions may or may not have structural homologies with TRs. Certain nongenomic actions that originate at the plasma membrane may modify the state and function of intranuclear TRs. Reviewed here are nongenomic effects of the hormone-T₃ or, in some cases, l-thyroxine (T₄)-that are initiated at (a) truncated TRα isoforms, e.g., p30 TRα1, (b) cytoplasmic proteins, or (c) plasma membrane integrin αvβ3. p30 TRα1 is not transcriptionally competent, binds T₃ at the cell surface, and consequently expresses a number of important functions in bone cells. Nongenomic hormonal control of mitochondrial respiration involves a TRα isoform, and another truncated TRα isoform nongenomically regulates the state of cellular actin. Cytoplasmic hormone-binding proteins involved in nongenomic actions of thyroid hormone include ketimine reductase, pyruvate kinase, and TRβ that shuttle among intracellular compartments. Functions of the receptor for T₄ on integrin αvβ3 include stimulation of proliferation of cancer and endothelial cells (angiogenesis) and regulation of transcription of cancer cell survival pathway genes. T₄ serves as a prohormone for T₃ in genomic actions of thyroid hormone, but T₄ is a hormone at αvβ3 and more important to cancer cell function than is T₃. Thus, characterization of nongenomic actions of the hormone has served to broaden our understanding of the cellular roles of T₃ and T₄.