Maximin Senou

Quantification of cells expressing the thyrotropin receptor in extraocular muscles in thyroid associated orbitopathy.

Background/aim: Thyroid associated orbitopathy (TAO) and Graves’ disease (GD) have an autoimmune pathogenesis, possibly related to the thyrotropin receptor (TSHR). The aim of this study was to determine whether TSHR immunoreactivity is correlated with disease severity or serum TSHR antibody (TRAB) levels. Methods: Orbital tissues from 30 patients with TAO were compared with those of 20 patients with strabismus and four with non-thyroid orbital inflammation. TSHR was detected by immunohistochemistry and TRAB were measured by radioreceptor assay. Results: No TSHR immunoreactivity was detected in the 24 control orbital tissues, whereas in all TAO biopsies elongated fibroblast-like cells, expressing TSHR, were present. These cells were located between the muscle cells, which were separated by oedema in the acute phase but fibrous tissue in the chronic phase of disease. Semi-thin sections showed numerous mast cells present in the chronic phase and in close contact with adipocytes. The number of TSHR immunostained cells was high in early disease, decreased with disease duration, and was positively correlated with TRAB levels at the onset of TAO. Conclusion: TSHR immunoreactivity was demonstrated specifically in TAO orbits which highlights the importance of TRAB early in the pathogenesis.

Local Induction of Adiponectin Reduces Lipopolysaccharide-Triggered Skeletal Muscle Damage

Adiponectin (ApN) exhibits metabolic and antiinflammatory properties. This hormone is exclusively secreted by adipocytes under normal conditions. We have shown that ApN was induced in tibialis anterior muscle of mice injected with lipopolysaccharide (LPS) and in C2C12 myotubes cultured with proinflammatory cytokines. We hypothesized that muscle ApN could be a local protective mechanism to counteract excessive inflammatory reaction and oxidative damage. To test this paradigm, we examined whether muscles of ApN-knockout (KO) mice exhibit a higher degree of oxidative stress and apoptosis than wild-type mice when challenged by ip LPS and whether these abnormalities may be corrected by local administration of ApN. Eventually we investigated the effects of ApN in vitro. When compared with wild-type mice, ApN-KO mice exhibited myocyte degenerescence, especially after LPS. Myocytes of ApN-KO mice also displayed much stronger immunolabeling for markers of oxidative stress (peroxiredoxin-3/5 and heme oxygenase-1) as well as for a lipid peroxidation product (hydroxynonenal). Expression of TNF-α, caspase-6, a marker of apoptosis, and nuclear factor-κB was enhanced as well. Eventually muscle electrotransfer of the ApN gene, which did not induce any rise of systemic ApN, corrected all these abnormalities in LPS-injected ApN-KO mice. Likewise, ApN attenuated LPS-induced production of proinflammatory cytokines and activation of nuclear factor-κB in C2C12 cells. Thus, induction of ApN into skeletal muscle in response to an inflammatory aggression appears to be a crucial mechanism to counteract in an autocrine or paracrine fashion excessive inflammatory damage, oxidative stress, and subsequent apoptosis.

Adiponectin and Skeletal Muscle: Pathophysiological Implications in Metabolic Stress

Upregulation of muscular adiponectin could act as a local protective mechanism to counteract cellular damage in obesity by weakening inflammation, oxidative stress, and apoptosis. To test this hypothesis, adiponectin-knockout (KO) and wild-type (WT) mice were fed a Western diet (WD). WT mice under WD conditions displayed 63% higher adiponectin expression in myocytes than those under standard laboratory diet (SLD) conditions (P = 0.011). WD-fed KO mice exhibited approximately threefold larger myocyte degeneration than WT mice (P = 0.003). Even under SLD conditions, myotubes of KO mice displayed already moderate immunolabeling for markers of oxidative stress (peroxiredoxin-3/5) and for a lipid peroxidation product (hydroxynonenal). Expression of tumor necrosis factor-α (TNF-α) and caspase-6, a marker of apoptosis, was also present. After WD challenge, immunoreactivity for these markers was strong in muscle of KO mice, although it was detected to a lesser extent in WT mice. Activation of NF-κB and caspase-6 doubled in myocytes of WD-fed KO mice when compared to WT mice (P < 0.001). Furthermore, muscle electrotransfer of the adiponectin gene prevented these abnormalities in WD-fed KO mice. Finally, gene abrogation of the adiponectin receptor 1 (AdipoR1) by siRNA recapitulated a pro-inflammatory state in C2C12 myotubes. Thus, upregulation of muscular adiponectin may be triggered by obesity and be crucial locally to counteract oxidative stress, inflammation, and apoptosis. These effects operate in an autocrine/paracrine manner via AdipoR1 and down-regulation of NF-κB signaling.

A Coherent Organization of Differentiation Proteins Is Required to Maintain an Appropriate Thyroid Function in the Pendred Thyroid

CONTEXT Pendred syndrome is caused by mutations in the gene coding for pendrin, an apical Cl-/I- exchanger. OBJECTIVE To analyze intrathyroidal compensatory mechanisms when pendrin is lacking, we investigated the thyroid of a patient with Pendred syndrome. The expression of proteins involved in thyroid hormone synthesis, markers of oxidative stress (OS), cell proliferation, apoptosis, and antioxidant enzymes were analyzed. RESULTS Three morphological zones were identified: nearly normal follicles with iodine-rich thyroglobulin in the colloid (zone 1.a), small follicles without iodine-rich thyroglobulin in lumina (zone 1.b), and destroyed follicles (zone 2). In zones 1.a, dual oxidase (Duox) and thyroid peroxidase (TPO) were localized at the apical pole, OS and cell apoptosis were absent, but ClC-5 expression was strongly increased. In zones 1.b, Duox and TPO were aberrantly present and increased in the cytosol and associated with high OS, apoptosis, cell proliferation, and increased expression of peroxiredoxin-5, catalase, and dehalogenase-1 but moderate ClC-5 expression. CONCLUSION In conclusion, the absence of pendrin is accompanied by increased ClC-5 expression that may transiently compensate for apical iodide efflux. In more affected follicles, Duox and TPO are relocated in the cytosol, leading to abnormal intracellular thyroid hormone synthesis, which results in cell destruction presumably because intracellular OS cannot be buffered by antioxidant defenses.

Role of caveolin-1 in thyroid phenotype, cell homeostasis, and hormone synthesis: in vivo study of caveolin-1 knockout mice.

In human thyroid, caveolin-1 is localized at the apex of thyrocytes, but its role there remains unknown. Using immunohistochemistry, (127)I imaging, transmission electron microscopy, immunogold electron microscopy, and quantification of H(2)O(2), we found that in caveolin-1 knockout mice thyroid cell homeostasis was disrupted, with evidence of oxidative stress, cell damage, and apoptosis. An even more striking phenotype was the absence of thyroglobulin and iodine in one-half of the follicular lumina and their presence in the cytosol, suggesting that the iodide organification and binding to thyroglobulin were intracellular rather than at the apical membrane/extracellular colloid interface. The latter abnormality may be secondary to the observed mislocalization of the thyroid hormone synthesis machinery (dual oxidases, thyroperoxidase) in the cytosol. Nevertheless, the overall uptake of radioiodide, its organification, and secretion as thyroid hormones were comparable to those of wild-type mice, suggesting adequate compensation by the normal TSH retrocontrol. Accordingly, the levels of free thyroxine and TSH were normal. Only the levels of free triiodothyronine showed a slight decrease in caveolin-1 knockout mice. However, when TSH levels were increased through low-iodine chow and sodium perchlorate, the induced goiter was more prominent in caveolin-1 knockout mice. We conclude that caveolin-1 plays a role in proper thyroid hormone synthesis as well as in cell number homeostasis. Our study demonstrates for the first time a physiological function of caveolin-1 in the thyroid gland. Because the expression and subcellular localization of caveolin-1 were similar between normal human and murine thyroids, our findings in caveolin-1 knockout mice may have direct relevance to the human counterpart.

Augmentation de l’expression des protéines antioxydantes dans l’ophtalmopathie thyroïdienne (TAO)

But mise en evidence du stress oxydatif et des mecanismes de protection des cellules musculaires en cas de TAO. Materiel et methodes prelevements de muscles extra oculaires de patients operes pour TAO (21 cas) ou pour strabisme essentiel (19 cas controles). Detection par immunohistochimie de la caspase 6 activee (marqueur d’apoptose), par immunohistochimie et RTQ-PCR des peroxyredoxines 5 et 3, de l’adiponectine et de PPARγ qui sont des proteines antioxydantes. Resultats l’immunohistochimie montre une augmentation de l’expression de la caspase 6 activee, des peroxyredoxines, de l’adiponectine et du PPARγ dans les cas TAO par rapport aux controles. Ces differents marqueurs sont exprimes par la cellule musculaire. L’adiponectine est aussi exprimee par les cellules endotheliales et de facon accrue en cas de TAO. La RTQ-PCR montre une augmentation significative de l’adiponectine (4,9 fois ; p = 0.0132) et du PPARγ (4,7 fois ; p = 0,0106) dans les muscles en cas TAO par rapport aux controles. Conclusion l’ophtalmopathie thyroidienne (TAO) entraine un stress pour la cellule musculaire de l’œil ce qui se traduit par une augmentation de l’expression de la caspase 6 activee. Au cours de la TAO, la cellule musculaire exprime de facon accrue les peroxyredoxines 5 et 3, l’adiponectine et le PPARγ. Ces proteines pourraient constituer un systeme de protection de la cellule contre le stress oxydatif. Toutefois l’adiponectine et le PPARγ pourraient provoquer l’adipogenese associee a la TAO.

Impact d’un ligand de PPARγ, la 15 déoxy- Δ12,14 prostaglandine J2, sur le stress oxydatif induit dans un modèle d’hyperplasie et d’involution thyroïdiennes

But durant la formation d’un goitre, la production d’H 2 O 2 est stimulee ; les thyrocytes sont donc exposes a un stress oxydatif important. Lors de l’involution du goitre par l’iode, l’H 2 O 2 est degradee en derives peroxydes toxiques pouvant induire une mort cellulaire accompagnee d’une reaction inflammatoire. La 15 deoxy- Δ 12,14 prostaglandine (15dPGJ2) limite-t-elle le stress oxydatif et l’inflammation thyroidiennes ? Materiel et methodes 7 groupes de rats Wistar : (1) controle, (2) goitre (nourriture carencee en iode + propylthiouracil), (3) goitre + iode (HID : 100 μg/rat, 3j), (4) goitre + thyroxine (T4 : 20 μg/rat, 3 j), (5) goitre + 15dPGJ2, (6) goitre + HID + 15dPGJ2, (7) goitre + T4+ 15dPGJ2. La 15dPGJ2 (3 μg/rat) est injectee pendant 4 j avant le sacrifice. Resultats PPARγ est exprime dans les thyrocytes. Le 4-hydroxynonenal, marqueur de peroxydation lipidique, peu exprime chez les rats controles, est fortement augmente dans les groupes goitre et goitre + HID. Il diminue nettement suite au traitement par 15dPGJ2. ED1, marqueur des macrophages actives, est faiblement exprime dans les groupes controle, goitre, goitre + 15dPGJ2. Le nombre de cellules positives augmente dans les groupes goitre+HID et goitre+T4. Le traitement par 15dPGJ2 reduit significativement l’expression de ED1. Conclusion La 15 deoxy-Δ 12,14 prostaglandine exerce un effet protecteur tant sur le stress oxydatif que sur la reaction inflammatoire.