María del Mar Montesinos

Control of dendritic cell maturation and function by triiodothyronine

Accumulating evidence indicates a functional crosstalk between immune and endocrine mechanisms in the modulation of innate and adaptive immunity. However, the impact of thyroid hormones (THs) in the initiation of adaptive immune responses has not yet been examined. Here we investigated the presence of thyroid hormone receptors (TRs) and the impact of THs in the physiology of mouse dendritic cells (DCs), specialized antigen‐presenting cells with the unique capacity to fully activate naive T cells and orchestrate adaptive immunity. Both immature and lipopolysaccharide‐matured bone marrow‐derived DCs expressed TRs at mRNA and protein levels, showing a preferential cytoplasmic localization. Remarkably, physiological levels of triiodothyronine (T3) stimulated the expression of DC maturation markers (major histocompatability complex II, CD80, CD86, and CD40), markedly in‐creased the secretion of interleukin‐12, and stimulated the ability of DCs to induce naive T cell proliferation and IFN‐γ production in allogeneic T cell cultures. Analysis of the mechanisms involved in these effects revealed the ability of T3 to influence the cytoplasmic‐nuclear shuttling of nuclear factor‐κB on primed DCs. Our study provides the first evidence for the presence of TRs on bone marrow‐derived DCs and the ability of THs to regulate DC maturation and function. These results have profound implications in immunopathology, including cancer and autoimmune manifestations of the thyroid gland at the crossroads of the immune and endocrine systems. Mascanfroni, I., Montesinos, M., Susperreguy, S., Cervi, L., Ilarregui, J. M., Ramseyer, V. D., Masini‐Repiso, A. M., Targovnik, H. M., Rabinovich, G. A., Pellizas, C. G. Control of dendritic cell maturation and function by triiodothyronine. FASEB J. 22, 1032–1042 (2008)

Nuclear Factor (NF)-κB-dependent Thyroid Hormone Receptor β1 Expression Controls Dendritic Cell Function via Akt Signaling

Despite considerable progress in our understanding of the interplay between immune and endocrine systems, the role of thyroid hormones and their receptors in the control of adaptive immunity is still uncertain. Here, we investigated the role of thyroid hormone receptor (TR) β1 signaling in modulating dendritic cell (DC) physiology and the intracellular mechanisms underlying these immunoregulatory effects. Exposure of DCs to triiodothyronine (T3) resulted in a rapid and sustained increase in Akt phosphorylation independently of phosphatidylinositol 3-kinase activation, which was essential for supporting T3-induced DC maturation and interleukin (IL)-12 production. This effect was dependent on intact TRβ1 signaling as small interfering RNA-mediated silencing of TRβ1 expression prevented T3-induced DC maturation and IL-12 secretion as well as Akt activation and IκB-ϵ degradation. In turn, T3 up-regulated TRβ1 expression through mechanisms involving NF-κB, suggesting an autocrine regulatory loop to control hormone-dependent TRβ1 signaling. These findings were confirmed by chromatin immunoprecipitation analysis, which disclosed a new functional NF-κB consensus site in the promoter region of the TRB1 gene. Thus, a T3-induced NF-κB-dependent mechanism controls TRβ1 expression, which in turn signals DCs to promote maturation and function via an Akt-dependent but PI3K-independent pathway. These results underscore a novel unrecognized target that regulates DC maturation and function with critical implications in immunopathology at the cross-roads of the immune-endocrine circuits.

Dexamethasone counteracts the immunostimulatory effects of triiodothyronine (T3) on dendritic cells

Glucocorticoids (GCs) are widely used as anti-inflammatory and immunosuppressive agents. Several studies have indicated the important role of dendritic cells (DCs), highly specialized antigen-presenting and immunomodulatory cells, in GC-mediated suppression of adaptive immune responses. Recently, we demonstrated that triiodothyronine (T3) has potent immunostimulatory effects on bone marrow-derived mouse DCs through a mechanism involving T3 binding to cytosolic thyroid hormone receptor (TR) β1, rapid and sustained Akt activation and IL-12 production. Here we explored the impact of GCs on T3-mediated DC maturation and function and the intracellular events underlying these effects. Dexamethasone (Dex), a synthetic GC, potently inhibited T3-induced stimulation of DCs by preventing the augmented expression of maturation markers and the enhanced IL-12 secretion through mechanisms involving the GC receptor. These effects were accompanied by increased IL-10 levels following exposure of T3-conditioned DCs to Dex. Accordingly, Dex inhibited the immunostimulatory capacity of T3-matured DCs on naive T-cell proliferation and IFN-γ production while increased IL-10 synthesis by allogeneic T cell cultures. A mechanistic analysis revealed the ability of Dex to dampen T3 responses through modulation of Akt phosphorylation and cytoplasmic-nuclear shuttling of nuclear factor-κB (NF-κB). In addition, Dex decreased TRβ1 expression in both immature and T3-maturated DCs through mechanisms involving the GC receptor. Thus GCs, which are increased during the resolution of inflammatory responses, counteract the immunostimulatory effects of T3 on DCs and their ability to polarize adaptive immune responses toward a T helper (Th)-1-type through mechanisms involving, at least in part, NF-κB- and TRβ1-dependent pathways. Our data provide an alternative mechanism for the anti-inflammatory effects of GCs with critical implications in immunopathology at the cross-roads of the immune-endocrine circuits.

Thyroid hormone receptor α1–β1 expression in epididymal epithelium from euthyroid and hypothyroid rats

The objectives of the present work were to assess whether epithelial cells from the different segments of epididymis express TRα1–β1 isoforms, to depict its subcellular immunolocalization and to evaluate changes in their expression in rats experimentally submitted to a hypothyroid state by injection of 131I. In euthyroid and hypothyroid groups, TR protein was expressed in epididymal epithelial cells, mainly in the cytoplasmic compartment while only a few one showed a staining in the nucleus as well. A similar TR immunostaining pattern was detected in the different segments of the epididymis. In hypothyroid rats, the number of TR-immunoreactive epithelial cells as well as the intensity of the cytoplasmic staining significantly increased in all sections analyzed. In consonance to the immunocytochemical analysis, the expression of TRα1–β1 isoforms, assessed by Western blot revealed significantly higher levels of TR in cytosol compared to the nuclear fractions. Furthermore, TR expression of both α1 and β1 isoforms and their mRNA levels were increased by the hypothyroid state. The immuno-electron-microscopy showed specific reaction for TR in principal cells associated with eucromatin, cytosolic matrix and mitochondria. The differences in expression levels assessed in control and thyroidectomized rats ascertain a specific function of TH on this organ.

Antitumor Responses Stimulated by Dendritic Cells Are Improved by Triiodothyronine Binding to the Thyroid Hormone Receptor β

Bidirectional cross-talk between the neuroendocrine and immune systems orchestrates immune responses in both physiologic and pathologic settings. In this study, we provide in vivo evidence of a critical role for the thyroid hormone triiodothyronine (T3) in controlling the maturation and antitumor functions of dendritic cells (DC). We used a thyroid hormone receptor (TR) β mutant mouse (TRβPV) to establish the relevance of the T3-TRβ system in vivo. In this model, TRβ signaling endowed DCs with the ability to stimulate antigen-specific cytotoxic T-cell responses during tumor development. T3 binding to TRβ increased DC viability and augmented DC migration to lymph nodes. Moreover, T3 stimulated the ability of DCs to cross-present antigens and to stimulate cytotoxic T-cell responses. In a B16-OVA mouse model of melanoma, vaccination with T3-stimulated DCs inhibited tumor growth and prolonged host survival, in part by promoting the generation of IFNγ-producing CD8(+) T cells. Overall, our results establish an adjuvant effect of T3-TRβ signaling in DCs, suggesting an immediately translatable method to empower DC vaccination approaches for cancer immunotherapy.

S-Nitrosylation of NF-κB p65 Inhibits TSH-Induced Na+/I− Symporter Expression

Nitric oxide (NO) is a ubiquitous signaling molecule involved in a wide variety of cellular physiological processes. In thyroid cells, NO-synthase III-endogenously produced NO reduces TSH-stimulated thyroid-specific gene expression, suggesting a potential autocrine role of NO in modulating thyroid function. Further studies indicate that NO induces thyroid dedifferentiation, because NO donors repress TSH-stimulated iodide (I(-)) uptake. Here, we investigated the molecular mechanism underlying the NO-inhibited Na(+)/I(-) symporter (NIS)-mediated I(-) uptake in thyroid cells. We showed that NO donors reduce I(-) uptake in a concentration-dependent manner, which correlates with decreased NIS protein expression. NO-reduced I(-) uptake results from transcriptional repression of NIS gene rather than posttranslational modifications reducing functional NIS expression at the plasma membrane. We observed that NO donors repress TSH-induced NIS gene expression by reducing the transcriptional activity of the nuclear factor-κB subunit p65. NO-promoted p65 S-nitrosylation reduces p65-mediated transactivation of the NIS promoter in response to TSH stimulation. Overall, our data are consistent with the notion that NO plays a role as an inhibitory signal to counterbalance TSH-stimulated nuclear factor-κB activation, thus modulating thyroid hormone biosynthesis.

The thyroid hormone triiodothyronine reinvigorates dendritic cells and potentiates anti-tumor immunity

ABSTRACT Dendritic cell (DC) cancer vaccines have shown limited clinical benefit. Thus, the identification of signals and molecular pathways that potentiate the immunogenicity of DCs has become a major challenge in cancer research. Our studies demonstrate that triiodothyronine endows DCs with enhanced ability to stimulate cytotoxic T-cell responses with implications in DC-based immunotherapy.

Nitric oxide-repressed Forkhead factor FoxE1 expression is involved in the inhibition of TSH-induced thyroid peroxidase levels

Thyroid peroxidase (TPO) is essential for thyroid hormone synthesis mediating the covalent incorporation of iodine into tyrosine residues of thyroglobulin process known as organification. Thyroid-stimulating hormone (TSH) via cAMP signaling is the main hormonal regulator of TPO gene expression. In thyroid cells, TSH-stimulated nitric oxide (NO) production inhibits TSH-induced thyroid-specific gene expression, suggesting a potential autocrine role of NO in modulating thyroid function. Indeed, NO donors downregulate TSH-induced iodide accumulation and organification in thyroid cells. Here, using FRTL-5 thyroid cells as model, we obtained insights into the molecular mechanism underlying the inhibitory effects of NO on iodide organification. We demonstrated that NO donors inhibited TSH-stimulated TPO expression by inducing a cyclic guanosine monophosphate-dependent protein kinase-mediated transcriptional repression of the TPO gene. Moreover, we characterized the FoxE1 binding site Z as mediator of the NO-inhibited TPO expression. Mechanistically, we demonstrated that NO decreases TSH-induced FoxE1 expression, thus repressing the transcripcional activation of TPO gene. Taken together, we provide novel evidence reinforcing the inhibitory role of NO on thyroid cell function, an observation of potential pathophysiological relevance associated with human thyroid pathologies that come along with changes in the NO production.

Growth hormone treatment in children with idiopathic short stature: correlation of growth response with peripheral thyroid hormone action

Objective  Idiopathic short stature (ISS) describes short children with normal GH secretion. Although GH treatment increases their heights, growth response to the therapy differs among patients. Thyroid hormones (TH) are essential for longitudinal growth acting mainly through TH receptors (TR) α and β. We have previously reported that GH treatment reduced peripheral TH action in Turner Syndrome by TR down‐regulation. The aims of the study were to assess the effect of GH treatment to ISS on peripheral TH action and the correlation between thyroid status and growth response to the therapy.

Growth hormone (GH) treatment reduces peripheral thyroid hormone action in girls with Turner syndrome

Objective  Turner syndrome (TS) is an indication for GH therapy in spite of the modest growth response. Somatic growth depends not only on GH insulin‐like growth factor I (IGF‐I) axis but also on thyroid hormone (TH) status. We have previously reported that supraphysiological IGF‐I levels diminished TH actions in rat tissues by reducing the nuclear TH receptor (TR). GH treatment to TS patients induces high IGF‐I levels and therefore a reduction of TH action in tissues may be expected. We aimed at evaluating the effect of GH therapy in TS girls on peripheral TH action.