Intercellular adhesion molecule-1 (ICAM-1) in Graves' disease: contrast between in vivo and in vitro results

Antibody-Based Tracers for PET/SPECT Imaging of Chronic Inflammatory Diseases

Chronic inflammatory diseases are often progressive, resulting not only in physical damage to patients but also social and economic burdens, making early diagnosis of them critical. Nuclear medicine techniques can enhance the detection of inflammation by providing functional as well as anatomical information when combined with other modalities such as magnetic resonance imaging, computed tomography or ultrasonography. Although small molecules and peptides were mainly used for the treatment and imaging of chronic inflammatory diseases in the past, antibodies and their fragments have also been emerging for chronic inflammatory diseases as they show high specificity to their targets and can have various biological half-lives depending on how they are engineered. In addition, imaging with antibodies or their fragments can visualize the in vivo biodistribution of the probes or help monitor therapeutic responses, thereby providing physicians with a greater understanding of drug behavior in vivo and another means of monitoring their patients. In this review, we introduce various targets and radiolabeled antibody-based probes for the molecular imaging of chronic inflammatory diseases in preclinical and clinical studies. Targets can be classified into three different categories: 1) cell-adhesion molecules, 2) surface markers on immune cells, and 3) cytokines or enzymes. The limitations and future directions of using radiolabeled antibodies for imaging inflammatory diseases are also discussed.

Functional interleukin-17 receptor A are present in the thyroid gland in intractable Graves disease

Th17 lymphocytes and its main cytokine, IL-17, play an important role in autoimmune thyroid diseases, such as intractable Graves disease (GD). IL-17 signals are transmitted through its receptor, IL-17RA. The intrathyroid expression of IL-17RA in intractable GD is not understood. In this study, ELISA was used to measure serum IL-17 levels in patients with untreated GD, intractable GD or GD in remission and healthy controls. Real-time PCR, flow cytometry and immunofluorescence staining evaluated IL-17RA mRNA and protein expression in thyrocytes. IL-6, chemokine ligand 10 (CXCL10) and intercellular adhesion molecule (ICAM)-1 expression was measured in IL-17-stimulated thyrocyte cultures to evaluate the functional status of IL-17RA. Our data indicates that serum IL-17 levels are significantly increased in intractable GD and affected thyrocytes show functional IL-17R expression. These changes facilitate the IL-17-mediated upregulation of IL-6, CXCL10, and ICAM-1. The IL-17/IL-17R interaction could be a potential target for therapeutic interventions in intractable GD.

Serum levels of adhesion molecules ICAM-1 and VCAM-1 and tissue inhibitor of metalloproteinases, TIMP-1, are elevated in patients with autoimmune thyroid disorders: relevance to vascular inflammation

Serum levels of ICAM-1 (Inter Cellular Adhesion Molecule-1), VCAM-1 (Vascular cell Adhesion Molecule-1-I), TIMP-1 (tissue inhibitor of metalloproteinases 1) and MMP-9 (Metalloproteinase 9) are well established markers of inflammation. The physiopathological link between inflammation, atherosclerosis and autoimmunity is well demonstrated. However, serum levels of these biomarkers in patients with autoimmune-mediated dysthyroidism, including their evolution after improvement of the thyroid disorder have not been assessed. So, we evaluated the circulating levels of these markers in autoimmune and in non-autoimmune-mediated dysthyroid patients, and their evolution after treatment of thyroid disease. We conducted a prospective study to evaluate these markers before and after treatment in hyperthyroid patients (n = 33; 28 patients with autoimmune disease), hypothyroid patients (n = 38; 33 patients with autoimmune disease) and euthyroid subjects (n = 33). At baseline, serum levels of ICAM-1, VCAM-1 and TIMP-1 were significantly elevated in patients with hyperthyroidism as compared to euthyroid and hypothyroid patients (respectively p = 0.0005 and p < 0.0001). In multivariate analysis, the differences remained significant for VCAM-1 and TIMP-1. Median levels of ICAM-1, VCAM-1 and TIMP-1 were significantly higher in patients with autoimmune-mediated dysthyroidism compared to euthyroid patients (respectively p < 0.0001 and p = 0.002). In hyperthyroid patients, ICAM-1, VCAM-1 and TIMP-1 concentrations fell significantly after they had become euthyroid (respectively p = 0.0006; p < 0.0001 and p = 0.0009), although VCAM-1 values remained higher than those observed in the control group (p = 0.005). We found that autoimmune-mediated dysthyroidism were associated with increased peripheral blood concentrations of VCAM-1, ICAM-1 and TIMP-1. Whether these biological abnormalities translate into increase intima remodelling and atherosclerosis remains to be studied.

Influence of iodide excess and interferon-gamma on human primary thyroid cell proliferation, thyroglobulin secretion, and intracellular adhesion molecule-1 and human leukocyte antigen-DR expression

BACKGROUND

The effect of iodide on thyroid cell proliferation and function in vivo or in cultured thyroid cells has been previously reported and is still controversial. The aim of this study was to clarify these conflicting results by examining if prolonged high iodide exposition with or without interferon (IFN)-gamma has an effect on human primary thyroid cell proliferation, thyroglobulin (Tg) production, and intercellular adhesion molecule-1 (ICAM-1) and human leukocyte antigen (HLA)-DR expression.

METHODS

Primary human thyroid cells were used. Cells were cultured in Coon's modified Ham's F-12 medium supplemented with 5% fetal calf serum in monolayer conditions to induce proliferation and were aggregated for molecular expression and Tg production analysis. HLA-DR and ICAM-1 expression were measured by flow cytometry and Tg by immunometric assay.

RESULTS

Potassium iodide (KI) was more potent in arresting primary human thyroid cell proliferation as compared to sodium iodide and the effect was mediated by its action at G0/G1 and G2/M phases of the cell cycle. There were no signs of apoptosis or necrosis. An excess of KI alone did not change the expression of HLA-DR and Tg production, but gradually increased ICAM-1. Low-dose IFN-gamma and excess KI in combination transiently inhibited HLA-DR expression, while ICAM-1 was expressed at a higher level than with IFN-gamma alone. Tg production was moderately increased with low-dose IFN-gamma. However, a combination of high-dose KI with low-dose IFN-gamma significantly decreased Tg secretion, compared with IFN-gamma alone.

CONCLUSIONS

Augmented ICAM-1 in the presence of iodide excess and low-dose IFN-gamma could induce secretion of proinflammatory cytokines and lymphocytic infiltration in the thyroid gland. Decreased Tg production in the presence of KI excess and IFN-gamma could explain the development of hypothyroidism after adding iodide in a diet of subjects that already have lymphocytic infiltration and/or mild inflammation in the thyroid gland.

Different intrathyroid expression of intercellular adhesion molecule-1 (ICAM-1) in Hashimoto's thyroiditis and Graves' disease: analysis at mRNA level and association with B7.1 costimulatory molecule

Cultured thyroid epithelial cells can be induced to express intercellular adhesion molecule-1 (ICAM-1, or CD54). However, constitutive follicular expression of ICAM-1 has been reported only in thyroid autoimmunity. We evaluated the expression of ICAM-1 mRNA and protein on thyroid tissue from different autoimmune thyroid diseases, and its relationship with other immunologically relevant surface markers, namely costimulatory molecules of B7 family. Thyroid tissue sections were obtained by surgically removed thyroid glands from 6 patients with Hashimoto's thyroiditis (HT), 6 with Graves' disease (GD) and 3 with multinodular nontoxic goiter. We used in situ hybridization to localize ICAM-1 mRNA, and immunohistochemical analysis by alkaline phosphatase anti-alkaline phosphatase (APAAP) method. We showed a clear hybridization pattern, localized in follicular cells, in sections of glands with HT. The hybridization pattern was far less pronounced in GD: no staining was apparent on follicular cells. These results were strictly consistent with those obtained by means of immunohistochemistry. Moreover, double-staining experiments demonstrated colocalization of ICAM-1 and B7.1 molecules in HT, whereas no B7.1 expression was observed in Graves' or in non-autoimmune thyroid diseases. These data agree with the hypothesis of distinct immunoregulatory phenomena and effector mechanisms in the 2 main autoimmune thyroid diseases.

Thyrotropin modulates interferon-gamma-mediated intercellular adhesion molecule-1 gene expression by inhibiting Janus kinase-1 and signal transducer and activator of transcription-1 activation in thyroid cells

TSH is known as an important hormone that plays the major role not only in the maintenance of normal physiology but also in the regulation of immunomodulatory gene expression in thyrocytes. The adhesion molecule intercellular adhesion molecule-1 (ICAM-1) was identified as one of the proteins that are abnormally expressed in the thyroid gland during autoimmune thyroid diseases. In this study we found that TSH inhibits interferon-gamma (IFNgamma)-mediated expression of the ICAM-1 gene, and we investigated the involved mechanisms in rat FRTL-5 thyroid cells. After exposure to IFNgamma, ICAM-1 expression is positively regulated at the level of transcription. This effect occurs via the IFNgamma-activated site (GAS) element in the ICAM-1 promoter as a consequence of the activation of STAT1 (signal transducer and activator of transcription-1), but not of STAT3. On the other hand, after exposure to TSH plus IFNgamma, ICAM-1 transcription is negatively modulated. We found that this inhibitory effect of TSH also occurs via the GAS element. Electrophoretic mobility shift assays confirmed that the IFNgamma-induced DNA-binding activities of STAT1 were reduced by TSH. Furthermore, our results showed that the inhibitory effect of TSH on IFNgamma signaling is caused by inhibition of tyrosine phosphorylation on STAT1, Janus kinase-1 (Jak1), and IFNgamma receptor a, but not Jak2. In conclusion, we have identified a novel mechanism in which TSH modulates the IFNgamma-mediated Jak/STAT signaling pathway through the inhibition of Jak1 and STAT1.

Thyrocyte proliferation by cellular adhesion to infiltrating lymphocytes through the intercellular adhesion molecule-1/lymphocyte function-associated antigen-1 pathway in Graves' disease

Graves' disease (GD) is an autoimmune thyroid disease characterized by infiltration of lymphocytes into the thyroid, and intrathyroid lymphocytes are known to play an important role in the pathogenesis of GD. However, it remains to be understood how lymphocytes adhere to thyrocytes and regulate the thyrocyte function through cellular adhesion. We studied the mechanisms of T cell adhesion to thyrocytes using intrathyroid mononuclear cells (ITMC) and thyrocytes purified from the thyroids of patients with GD. The following novel features of cellular adhesion of ITMC to thyrocytes in the regulation of the thyrocyte function in GD were observed: 1) GD-ITMC expressed lymphocyte function-associated antigen (LFA)-1, which became an active adhesive configuration much higher than peripheral blood mononuclear cells (PBMC) from normal volunteers and GD patients; 2) GD-thyrocytes expressed a high quantity of intercellular adhesion molecule (ICAM)-1; 3) GD-ITMC adhered to GD-thyrocytes, whereas normal PBMC required activation stimuli by phorbol myriacetate, a pharmacological integrin-trigger, to adhere to GD- thyrocytes; 4) monoclonal antibody-blocking studies showed that the adhesion of the activated PBMC and ITMC to thyrocytes was mainly mediated by the LFA-1/ICAM-1 pathway; 5) the adhesion of GD-thyrocytes to the activated-PBMC or ITMC induced the proliferation of the thyrocytes, which was blocked by the addition of ICAM-1 and/or LFA-1 monoclonal antibodies; and 6) in GD thyrocytes of early cultures, ICAM-1 expression on GD-thyrocytes and its adhesion to LFA-1 on phorbol myriacetate-activated PBMC or ITMC were not modulated by the addition of interleukin-1beta or interferon-gamma, and proliferation of thyrocytes by the cellular adhesion via the ICAM-1/LFA-1 pathway was independent of the proliferative response of these cytokines. Taken together, these results suggest that lymphocytes infiltrating GD thyroid induce proliferation of GD-thyrocyte by the cellular adhesion to thyrocytes via ICAM-1/LFA-1, which may lead to the development of a goiter.

Hormone-dependent regulation of intercellular adhesion molecule-1 gene expression: cloning and analysis of 5'-regulatory region of rat intercellular adhesion molecule-1 gene in FRTL-5 rat thyroid cells

Intercellular adhesion molecule-1 (ICAM-1) has been suggested to play an important role in the perpetuation of autoimmune thyroid disease. To clarify the regulation of ICAM-1 gene in thyroid cells, we investigated ICAM-1 expression in the FRTL-5 thyroid cell model and defined several elements in the 5'-regulatory region that are important for transcriptional regulation of the rat ICAM-1 gene. Cells maintained in medium with 5% serum but without hydrocortisone, insulin, and thyrotropin (TSH) express the highest levels of ICAM-1 RNA. TSH/forskolin downregulate ICAM-1 RNA levels independent of the presence or absence of hydrocortisone or insulin. Moreover, TSH/forskolin decrease ICAM-1 RNA levels that are maximally induced by two cytokines: 100 ng/mL tumor necrosis factor-alpha (TNF-alpha) or 100 U/ml interferon-gamma (IFN-gamma). The effect of TSH/forskolin, as well as TNF-alpha and IFN-gamma, on ICAM-1 RNA levels is transcriptional. Thus, we cloned a 1.8-kb fragment of the 5'-flanking region of the rat ICAM-1 gene, upstream of the translational start site, and showed that TNF-alpha or IFN-gamma caused a 3.5- and greater than 12-fold increase respectively, in its promoter activity, when linked to a luciferase reporter gene and stably transfected into FRTL-5 cells. TSH or forskolin, in contrast, halved the activity of the full length chimera within 24 hours and significantly suppressed the TNF-alpha and IFN-gamma-induced increase (>50%; p < 0.02). Using 5'-deletion mutants, we located the element important for the TNF-alpha effect between -431 and -175 bp; we additionally show that deletion of a NF-kappaB core element within this region, TTGGAAATTC (-240 to -230 bp), causes the loss of TNF-alpha inducibility. The effect of IFN-gamma could be localized between -175 bp and -97 bp from the start of translation. This region contains 2 regulatory elements known to be involved in IFN-gamma action in other eukaryotic cells, an IFN-gamma activated site (GAS), -138 to -128 bp, and Spl site, -112 to -108 bp. Deletion of the 10 bp GAS sequence resulted in the complete loss of IFN-gamma induction of pCAM-175 promoter activity. TSH and forskolin action was also mapped between -175 bp and -97 bp from the start of translation. The mutant construct, pCAM-175delGAS mutl, which has no GAS sequence, exhibited no TSH-mediated suppression of promoter activity. We thus show that TSH/cAMP can downregulate ICAM-1 gene expression and inhibit the activity of cytokines (TNF-alpha and IFN-gamma) to increase ICAM-1 gene expression in FRTL-5 thyroid cells. We also localized elements on the 5'-flanking region of ICAM-1 important for these actions. We propose that this TSH/cyclic adenosine monophosphate (cAMP) action is a component of the mechanism to preserve self-tolerance of the thyroid during hormone-induced growth and function of the gland, and it may attenuate cytokine action during inflammatory reactions.

Adhesion molecules in autoimmune disease

Leukocyte activation, circulation, and localization to inflammatory sites are dependent on adherence to molecules on other cells or to extracellular matrix ligands. Adhesion molecule expression and interactions are probably involved in initiation and propagation of autoimmune diseases. Adhesion molecules pertinent to the development of autoimmunity are the subject of this review. Material in this review was generated by a manual and a computerized search of medical literature pertaining to adhesion molecules and specific autoimmune diseases. Topics covered include adhesion molecule classification, regulation of adhesion, and characterization of adhesion receptors in specific autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus, Sjögren's syndrome, autoimmune thyroid disease, multiple sclerosis, and diabetes mellitus. Adhesion molecules are classified into selectin, integrin, and immunoglobulin supergene family groups. Increased adhesion molecule expression and avidity changes occurring with cellular activation are the principal methods regulating leukocyte adhesion. Tumor necrosis factor-alpha (TNF alpha), interferon-gamma (IFN-gamma), and interleukin-1 (IL-1) stimulate adhesion receptor expression on lymphoid and nonlymphoid tissues. Although differences between specific autoimmune diseases exist, key interactions facilitating the development of autoimmune inflammation appear to include L-selectin/P-selectin/E-selectin, lymphocyte function-associated antigen-1 (LFA-1)/intercellular adhesion molecule-1 (ICAM-1), very late antigen-4 (VLA-4)/vascular cell adhesion molecule-1 (VCAM-1), and alpha 4B7/MadCAM or VCAM-1 adhesion. Administration of anti-adhesion molecule antibodies in experimental animal models of autoimmunity and in a preliminary trial with RA patients has been successful in preventing or reducing autoimmune disease severity. A vast array of adhesive interactions occurs between immunocompetent cells, endothelium, extracellular matrix, and target tissues during the evolution of an autoimmune disease. Further characterization of leukocyte migration patterns and adherence should clarify pathogenic processes in specific autoimmune diseases and identify potential therapeutic targets for their treatment.

Enhanced expression of MHC class I molecules on cultured human thyroid follicular cells infected with reovirus through induction of type 1 interferons

Certain viruses are known to modulate the cellular expression of MHC molecules. We have investigated whether reovirus types 1 or 3 can alter the normal MHC molecule expression on cultured human thyroid follicular cells (TFC). Primary TFC cultures were established from eight human thyroid donors and MHC class I and II expression was assessed by indirect immunofluorescence microscopy. Both types of reovirus enhanced MHC class I expression on TFC from all thyroid donors. Class II MHC protein was strongly induced by type 1 reovirus on TFC from one donor, while weak induction of expression, by either reo-1 or reo-3 virus, was noted on the TFC of five other donors. Studies on the mechanism(s) of MHC class I hyperexpression showed that mouse MoAb against the type 3 reovirus haemagglutinin (anti-HA3) reduced the ability of the virus to induce hyperexpression of class I MHC molecules on TFC. However, supernatant harvested from type 3 reovirus-infected TFC cultures maintained its ability to enhance class I expression after incubation with anti-HA3. Moreover, adding rabbit anti-sera to interferon-alpha (IFN-alpha) or IFN-beta inhibited the increased class I MHC expression on TFC by both types of reovirus. These data suggest that reoviruses (types 1 and 3) can enhance MHC class I on cultured TFC. The mechanism of MHC class I enhancement is most probably through the release of IFN-alpha and IFN-beta.

Cellular immunity in autoimmune thyroid disease

Autoimmune thyroid disease occurs in a genetically susceptible patient after triggering events including bacterial and viral infections, environmental insults, drugs or hormones. These triggering events may break the tolerance to self-antigen, leading to emergence of autoreactive T cells. One or more T cell clones that recognize the self-antigen is(are) assumed to be involved in initiating autoimmune processes. Following this, T cell clones expand and migrate from the peripheral blood into the thyroid gland. Migration of mononuclear cells is controlled by inflammatory cytokines and adhesion molecules. Intrathyroidal T cells may interact with dendritic-like cells, thyrocytes expressed with HLA-DR antigens, B cells and extracellular matrix, resulting in the proliferation of T cells, production of cytokines and autoantibodies. These interactions are also regulated by inflammatory cytokines and adhesion molecules. When the initial immune response is completed, a secondary immune response ensues, that may be of considerable complexity involving reaction of infiltrating T cells to a variety of tissue-specific and tissue-non-specific antigens. These immune responses may contribute to the recurring immunologic activity and maintenance of autoantibody overproduction.

Characterization of neural cell adhesion molecule (NCAM) expression in thyroid follicular cells: induction by cytokines and over-expression in autoimmune glands

NCAM (CD56) is a cell surface glycoprotein of the immunoglobulin superfamily expressed on neuroendocrine and natural killer (NK) cells which has considerable molecular heterogeneity due to differential splicing and post-translational modifications. NCAM has been detected in the thyroid follicular cells (thyrocytes) immunohistologically. We report here the molecular form, the modulation by cytokines and the levels of expression in thyroid pathology. By using a panel of MoAbs to NCAM on Western blots from thyrocyte extract we have determined that these cells express the 140- and 180-kD forms of NCAM. Exposure of primary cultures of thyrocytes to interferon-gamma (IFN-gamma), and even more, to the combination of IFN-gamma plus tumour necrosis factor-alpha (TNF-alpha) induced a clear increase in the expression of NCAM as assessed by FACS analysis. NCAM expression in thyrocytes was assessed by immunofluorescence in 59 surgical specimens of thyroid glands, and was found increased in 11/17 (64%) of Graves', in 5/25 (20%) of multinodular goitre (MNG) and in occasional adenoma glands. No correlation was found with the expression of HLA class I, class II or the degree of lymphocytic infiltration scored in adjacent sections, but it was often seen in areas infiltrated by macrophages. In conclusion, NCAM is an adhesion molecule whose expression is clearly increased in thyrocytes in autoimmune glands, probably as a consequence of exposure to cytokines locally released. Since one of the forms of NCAM expressed by thyrocytes has the capability to generate intracellular signal it may play a role in normal thyroid function. In addition, NCAM may facilitate the recognition of thyrocytes by lymphocytes, particularly by NK CD56+ lymphocytes.

Perforin expression by thyroid-infiltrating T cells in autoimmune thyroid disease

Infiltration of the thyroid gland by lymphocytes is a hall-mark of autoimmune thyroid disease; it is particularly evident in Hashimoto's thyroiditis but is also seen in most patients with Graves' disease. Infiltrating cells are comprised primarily of T lymphocytes, of which only a minority appears to be activated. Their precise pathogenic role is largely unknown. Since perforin has been a marker for functionally activated cytotoxic T cells in situ we elected to assess the presence of perforin-containing cells in thyroid-infiltrating lymphocytes and establish their phenotype. Cells were isolated from seven subtotal thyroidectomy specimens, five from patients with Graves' disease and two with Hashimoto's thyroiditis. The novel findings were as follows: CD4+ perforin-containing T cells occurred only in Hashimoto's glands, suggesting a class II-restricted component of cytotoxicity; in Graves' disease, and to a lesser extent in Hashimoto's, perforin-expressing cells were primarily T cell receptor alpha beta- CD4-CD8- (double negative); double negative perforin-containing cells in peripheral blood of normal individuals were largely gamma delta + T cells. In Hashimoto's samples, the predominant population of T cells expressing perforin was CD8+. By comparison, in studies of the synovial fluid of knee joints from patients with rheumatoid arthritis only a minor population of the perforin-containing cells was double-negative. The data suggest significant differences in cytotoxic autoimmune mechanisms between the two autoimmune thyroid diseases. Functional characterization of double-negative T cells is necessary to define their role in autoimmunity.

The potential immunological role of the thyroid cell in autoimmune thyroid disease

Over the last decade it has become evident that thyroid follicular cells express a number of immunologically active molecules in autoimmune thyroid disease that may endow them with the capacity to interact with cells of the classical immune system. Expression of major histocompatibility complex class II molecules is induced by gamma-interferon, but there is no evidence yet that thyroid follicular cells can concurrently express the costimulatory signals necessary for class II expression to result in T cell stimulation: in this situation, class II expression may have a protective role, inducing T cell anergy. Thyroid follicular cells also express a variety of cell surface proteins (in particular CD59) that may protect the cells from complement attack. On the other hand, the expression of adhesion molecules and cytokines by thyrocytes would seem to be harmful, as these are likely to exacerbate autoimmune injury. Further study of the immunological role of thyroid follicular cells will shed new light on the pathogenesis of Graves' disease and autoimmune hypothyroidism, and may lead to novel therapeutic approaches to these disorders.