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CD1a expression in psoriatic skin following treatment with propylthiouracil, an antithyroid thioureylene
© Elias et al; licensee BioMed Central Ltd. 2003
Received: 01 April 2003
Accepted: 03 July 2003
Published: 03 July 2003
The antithyroid thioureylenes, propylthiouracil (PTU) and methimazole (MMI), are effective in the treatment of patients with plaque psoriasis. The mechanism of action of the drugs in psoriasis is unknown. Since the drugs reduce circulating IL-12 levels in patients with Graves' hyperthyroidism, the effect of propylthiouracil on CD1a expression in psoriatic lesions was examined in biopsy samples of patients with plaque psoriasis. CD1a is a marker of differentiated skin antigen presenting cells (APC, Langerhans cells). Langerhans cells and skin monocyte/macrophages are the source of IL-12, a key cytokine involved in the events that lead to formation of the psoriatic plaque.
Biopsy specimens were obtained from six patients with plaque psoriasis who were treated with 300 mg propylthiouracil (PTU) daily for three months. Clinical response to PTU as assessed by PASI scores, histological changes after treatment, and CD1a expression in lesional skin before and after treatment were studied.
Despite significant improvement in clinical and histological parameters the expression of CD1a staining cells in the epidermis did not decline with propylthiouracil treatment.
It appears that the beneficial effect of propylthiouracil in psoriasis is mediated by mechanisms other than by depletion of skin antigen-presenting cells.
Psoriasis is a common skin disorder affecting 1 to 3 percent of the world's population.[1, 2] Treatment of the disease results in costs that range between 0.7 to more than 4 billion dollars annually in the US alone . One of the most cost-effective forms of potential treatment for the disease is the use of antithyroid thioureylenes such a propylthiouracil. We previously reported the effectiveness of thioureylene treatment in patients with plaque psoriasis [4–7], a finding since confirmed by others . The mechanism of action of antithyroid thioureylenes in psoriasis remains unclear. The drugs have been studied with relation to their effect in Graves' hyperthyroidism which, like psoriasis, is an autoimmune disorder [9–12] Antithyroid thioureylenes, of which propylthiouracil, methimazole and carbimazole are used in clinical practice, have known immunomodulatory properties [13, 14] and, in the case of psoriasis, also have antiproliferative effects as demonstrated by their ability to produce a decline in markers of cellular proliferation such as proliferative cell nuclear antigen (PCNA).
Skin antigen-presenting cells (Langerhans cells) appear to play an important role in the initiating events that lead to the cytokine cascade that results in keratinocyte proliferation and development of psoriatic lesions [16–18]. Effective therapeutic approaches to psoriasis treatment, such as psoralen UV-A therapy (PUVA), which result in depletion of APCs in the skin [19, 20], and UV-B , lead to one of the most sustained improvement in psoriasis. IL-12, a product of Langerhans cells and skin monocytes plays a pivotal role in T-cell activation that leads to formation of the psoriatic plaque . IL-12 levels are also significantly raised in patients with Graves' hyperthyroidism and are reduced following treatment with propylthiouracil .
CD1a is expressed in differentiated antigen-presenting cells and monocytes and is used as a marker for the presence of these cells in the skin[24–26]. The CD1 molecules are the products of five CD1 genes located on chromosome 1. The genes are closely related to the mixed histocompatibilty complex (MHC) genes indicating origin from a common precursor . CD1 molecules, however, have limited sequence homology to MHC class I and II molecules, and unlike the MHC molecules are also capable of binding non-protein antigens [28, 29].
The present study was performed to examine the effect of propylthiouracil treatment of patients with plaque psoriasis on CD1a expression in their psoriatic lesions in order to determine whether this form of therapy resulted in depletion of APCs from affected skin, that could account for the therapeutic benefit of PTU in this disorder.
Clinical evaluation was performed by the same dermatologist (VSN) at the time of patient entry into the study and monthly intervals until completion of the study. Scoring was based on the PASI scoring system .
Biopsy samples were taken from patients at the start and after 3 months of PTU treatment from the same psoriatic lesion. Skin samples were obtained using a 5 mm punch biopsy under aseptic conditions with local anesthesia. The biopsies were frozen and stored at -70°C until processed. Indirect immunoperoxidase staining was used to identify CD1a.
Biopsy specimens were viewed by a dermatopathologist (RJB). Histological scoring was made with a 5-point scoring system graded from 0 to 4 (0 = normal, 1 = slight, 2 - moderate, 3 = severe, 4 = very severe) based on criteria noted below after examination of four consecutive high-power fields. Histological scoring took into account hypogranulosis, parakeratosis and the inflammatory infiltrate in the epidermis and superficial dermis. The total score reported was the sum of the individual parameters. Epidermal hyperplasia was measured with an oculomicrometer from top of the epidermis to the base of the ridges.
Thyroid function tests were performed in all volunteers prior to entry into the study and again at monthly intervals until study completion at twelve weeks. The tests consisted of measurement of serum free T4 (FT4) and thyroid-stimulating hormone (TSH). Complete blood counts (CBC) were also obtained at the same time intervals.
Tissue samples from biopsy specimens stored at -70°C were taken and embedded in paraffin. 4 μm sections were coated onto slides and allowed to dry overnight at 55°C. An RBC block (2.5 ml, 30% H2O2 in 100 ml methanol) was applied for 40 min after which the slides were washed in tap water until clean. Following a series of washing with PBS, the slides were washed with blocking serum (5% horse serum) for 20 min after which antibody for CD1a (1:100 dilution) was applied for 30 minutes. The slides were washed with PBS for 5 min after which anti-mouse antibody (1:200 dilution) was applied and the slides washed again in PBS for 5 minutes. Tertiary antibody (ABC kit) was added for 30 min and the slides were then washed for with PBS. DAB was applied in the dark (10 min), the slides were washed in distilled water (5 min), counterstained with hematoxylin, washed with tap water, dehydrated and mounted.
Results were expressed as the absolute number of positive staining dendritic cells counted over a 1 mm length of the epidermis. Only cells with clearly defined nuclei present in the suprabasal layers of the epidermis were counted.
The results are expressed as mean ± SD. Statistical analysis was performed using the t-test for paired observations. Level of significance was p < 0.05.
Clinical Response and PASI Scores
All patients showed some improvement in their psoriasis with near-complete resolution in 4 patients. PASI scores declined from 21.40 ± 6.81 at baseline to 7.85 ± 4.35 at completion of the study (p < 0.004). Clinical improvement became apparent about three weeks after therapy.
Histological scores also declined significantly from 7.17 ± 2.78 at baseline to 3.00 ± 2.61 at the end of 12 weeks PTU treatment (p < 002). Epidermal thickness decreased from 0.52 ± 0.17 mm to 0.26 ± 1.11 mm (p < 0.007).
Serum TSH, FT4 and CBC
CBC remained normal (7.85 ± 0.53 vs. 8.05 ± 1.31 cells/μL, p = ns) during the entire study with no patient demonstrating any leucopenia. Serum TSH concentrations remained within the euthyroid range with no patient exhibiting clinical signs or offering complaints suggestive of hypothyroidism. Serum free thyroxine (FT4) showed no significant change. Serum TSH slowed a slight rise in some patients with the group as a whole showing no significant elevation of TSH (1.72 ± 0.98 μU/ml vs. 2.73 ± 1.43 μU/ml, p = ns). The rise did not exceed the normal range, and all patients remained clinically euthyroid.
Expression of CD1a in Psoriatic Plaques
The efficacy of antithyroid thioureylenes as agents in the treatment of plaque psoriasis is well established [4, 5, 7, 8] The mechanism of action of these agents in psoriasis remains unclear. The drugs can potentially act by reducing the cytokine signals that lead to keratinocyte proliferation or by reducing keratinocyte proliferation. A key element in the generation of the cytokine signals responsible for formation of a psoriatic plaque is the skin antigen-presenting cell or Langerhans cell. Therapeutic modalities deplete such cells, that often lead to improvement in psoriasis. The best example of such an approach is treatment with UV-A and psoralens, as well as UV-B, which result in depletion of APCs and produce one of the most long-lasting remissions of the disease which might last in some instances for as long as 6 months [31, 32] A key antigenic marker of skin APCs is CD1a. Langerhans cell precursors arise from CD34 positive monocytes/macrophages in the marrow [33, 34]. They circulate in the blood before localizing in the skin, primarily in dermal connective tissue. In the dermis, the Langerhans precursors are strongly HLA-DR (Ia) positive, and are relatively non-phagocytic, "indeterminate cells." CD1a expression is not pronounced in the precursors and is not significantly expressed until the cells become differentiated.[35–38] Differentiated cells localize to the midepidermis, demonstrate characteristic Birbeck granules, and exhibit dendritic appendages. These differentiated cells, although usually stable, sometime exhibit proliferative activity and increase in many cutaneous immune response states [23, 39, 40]. The inability of PTU to reduce CD1a expression in biopsy samples of patients with psoriasis suggests that the mechanism of action of this drug is psoriasis is not due to any effect on skin antigen-presenting cells or production of IL-12, a motive cytokine that is responsible for initiation and maintenance of the cytokine stimulatory cascade that leads to formation of the psoriatic plaque . In support of this argument is the fact that circulating IL-12 did not show any significant change with PTU treatment (submitted). Additional studies are being performed which address whether PTU treatment of patients with plaque psoriasis leads to reduced in situ IL-12 expression, alters production of the IL-35 or IL-40 components of the IL-70 heterodimer, as well as exerts an effect by enhancing apoptosis in the proliferated keratinocytes that make up the psoriatic plaque which would result in clinical improvement.
The authors gratefully acknowledge the valuable assistance of Eduardo Delgardo (nurse co-coordinator) and Manxu Zhao (histopathology technician).
Partial support for this study was provided by a research gift from the Stiefel Company, Coral Gables, Florida, USA
- Linden KG, Weinstein GD: current perspectives with an emphasis on treatment. Am J Med 1999, 107: 595–605. 10.1016/S0002-9343(99)00284-3View ArticlePubMedGoogle Scholar
- Greaves MW, Weinstein GD: Treatment of psoriasis. N Engl J Med 1995, 332: 581–8. 10.1056/NEJM199503023320907View ArticlePubMedGoogle Scholar
- Javitz HS, Ward MM, Farber E, Nail L, Vallow SG: The direct cost of care for psoriasis and psoriatic arthritis in the United States. J Am Acad Dermatol 2002, 46: 850–60. 10.1067/mjd.2002.119669View ArticlePubMedGoogle Scholar
- Elias AN, Barr RJ: Low-dose oral propylthiouracil in the treatment of plaque psoriasis. Int J Dermatol 1995, 34: 519–20.View ArticlePubMedGoogle Scholar
- Elias AN, Goodman MM, Rohan MK: Effect of propylthiouracil and methimazole on serum levels of interleukin-2 receptors in patients with psoriasis. Int J Dermatol 1993, 32: 537–40.View ArticlePubMedGoogle Scholar
- Elias AN, Goodman MM, Liem WH, Barr RJ: Propylthiouracil in psoriasis: results of an open trial. J Am Acad Dermatol 1993, 29: 78–81.View ArticlePubMedGoogle Scholar
- Elias AN, Goodman MM, Rohan MK, Alpern K, Barr RJ: Methimazole (2-mercapto 1-methyl imidazole) in psoriasis – results of an open trial. Dermatology 1993, 187: 26–9.View ArticlePubMedGoogle Scholar
- Kose K, Utas S, Yazici C, Akdas A, Kelestimur F: Effect of propylthiouracil on adenosine deaminase activity and thyroid function in patients with psoriasis. Br J Dermatol 2001, 144: 1121–6. 10.1046/j.1365-2133.2001.04221.xView ArticlePubMedGoogle Scholar
- Aust G, Sittig D, Steinert M, Lamesch P, Lohmann T: Graves' disease is associated with an altered CXCR3 and CCR5 expression in thyroid-derived compared to peripheral blood lymphocytes. Clin Exp Immunol 2002, 127: 479–85. 10.1046/j.1365-2249.2002.01778.xView ArticlePubMedPubMed CentralGoogle Scholar
- Gupta MK: Thyrotropin receptor antibodies: advances and importance of detection techniques in thyroid diseases. Clin Biochem 1992, 25: 193–9.View ArticlePubMedGoogle Scholar
- Kohn LD, Shimojo N, Kohno Y, Suzuki K: An animal model of Graves' disease: understanding the cause of autoimmune hyperthyroidism. Rev Endocr Metab Disord 2000, 1: 59–67. 10.1023/A:1010064403940View ArticlePubMedGoogle Scholar
- Kohn LD, Kosugi S, Ban T, Saji M, Ikuyama S, Giuliani C, Hidaka A, Shimura H, Akamizu T, Tahara K, et al.: Molecular basis for the autoreactivity against thyroid stimulating hormone receptor. Int Rev Immunol 1992, 9: 135–65.View ArticlePubMedGoogle Scholar
- Ohtani N, Zebedee Z, Huot TJ, Stinson JA, Sugimoto M, Ohashi Y, Sharrocks AD, Peters G, Hara E: Opposing effects of Ets and Id proteins on p16INK4a expression during cellular senescence. Nature 2001, 409: 1067–70. 10.1038/35059131View ArticlePubMedGoogle Scholar
- Wilson R, McKillop JH, Chopra M, Thomson JA: The effect of antithyroid drugs on B and T cell activity in vitro. Clin Endocrinol (Oxf) 1988,28(4):389–97.View ArticleGoogle Scholar
- Elias AN, Barr RJ, Rohan MK, Dangaran K: Effect of orally administered antithyroid thioureylenes on PCNA and P53 expression in psoriatic lesions. Int J Dermatol 1995, 34: 280–3.View ArticlePubMedGoogle Scholar
- Nickoloff BJ: The immunologic and genetic basis of psoriasis. Arch Dermatol 1999, 135: 1104–10. 10.1001/archderm.135.9.1104PubMedGoogle Scholar
- Hong K, Chu A, Ludviksson BR, Berg EL, Ehrhardt RO: IL-12, independently of IFN-gamma, plays a crucial role in the pathogenesis of a murine psoriasis-like skin disorder. J Immunol 1999, 162: 7480–91.PubMedGoogle Scholar
- Cheng J, Tu Y, Li J, Huang C, Liu Z, Liu D: A study on the expression of interleukin (IL)-10 and IL-12 P35, P40 mRNA in the psoriatic lesions. J Tongji Med Univ 2001, 21: 86–8.View ArticlePubMedGoogle Scholar
- Friedmann PS: Disappearance of epidermal Langerhans cells during PUVA therapy. Br J Dermatol 1981, 105: 219–21.View ArticlePubMedGoogle Scholar
- Czernielewski J, Juhlin L, Shroot S, Brun P: Langerhans' cells in patients with psoriasis: effect of treatment with PUVA, PUVA bath, etretinate and anthralin. Acta Derm Venereol 1985, 65: 97–101.PubMedGoogle Scholar
- Dawe RS, Wainwright NJ, Cameron H, Ferguson J: Narrow-band (TL-01) ultraviolet B phototherapy for chronic plaque psoriasis: three times or five times weekly treatment? Br J Dermatol 1998, 138: 833–9. 10.1046/j.1365-2133.1998.02221.xView ArticlePubMedGoogle Scholar
- de Rie MA: Interleukin 12 and psoriasis. Dermatology 1999, 199: 101. 10.1159/000018213View ArticlePubMedGoogle Scholar
- Tamura M, Matsuura B, Miyauchi S, Onji M: Dendritic cells produce interleukin-12 in hyperthyroid mice. Eur J Endocrinol 1999, 141: 625–9.View ArticlePubMedGoogle Scholar
- Athanasas-Platsis S, Savage NW, Winning TA, Walsh LJ: Induction of the CD1a Langerhans cell marker on human monocytes. Arch Oral Biol 1995, 40: 157–60. 10.1016/0003-9969(94)00152-2View ArticlePubMedGoogle Scholar
- Jones JL, Berth-Jones J, Fletcher A, Hutchinson PE: Assessment of epidermal dendritic cell markers and T-lymphocytes in psoriasis. J Pathol 1994, 174: 77–82.View ArticlePubMedGoogle Scholar
- Dobmeyer JM, Dobmeyer TS, Schopf RE: Importance of HLA-DR+ and CD1a+ epidermal cells for cytokine production in psoriasis. Adv Exp Med Biol 1995, 378: 539–41.View ArticlePubMedGoogle Scholar
- Albertson DG, Fishpool R, Sherrington P, Nacheva E, Milstein C: Sensitive and high resolution in situ hybridization to human chromosomes using biotin labelled probes: assignment of the human thymocyte CD1 antigen genes to chromosome 1. EMBO J 1988, 7: 2801–5.PubMedPubMed CentralGoogle Scholar
- Calabi F, Milstein C: A novel family of human major histocompatibility complex-related genes not mapping to chromosome 6. Nature 1986, 323: 540–3.View ArticlePubMedGoogle Scholar
- Beckman EM, Melian A, Behar SM, Sieling PA, Chatterjee D, Furlong ST, Matsumoto R, Rosat JP, Modlin RL, Porcelli SA: CD1c restricts responses of mycobacteria-specific T cells. Evidence for antigen presentation by a second member of the human CD1 family. J Immunol 1996, 157: 2795–803.PubMedGoogle Scholar
- Fredriksson T, Pettersson U: Severe psoriasis – oral therapy with a new retinoid. Dermatologica 1978, 157: 238–44.View ArticlePubMedGoogle Scholar
- Asawanonda P, Anderson RR, Chang Y, Taylor CR: 308-nm excimer laser for the treatment of psoriasis: a dose-response study. Arch Dermatol 2000, 136: 619–24.View ArticlePubMedGoogle Scholar
- Larko O: Phototherapy of psoriasis – clinical aspects and risk evaluation. Acta Derm Venereol Suppl (Stockh) 1982, 103: 1–42.Google Scholar
- Ebner S, Ratzinger G, Krosbacher B, Schmuth M, Weiss A, Reider D, Kroczek RA, Herold M, Heufler C, Fritsch P, Romani N: Production of IL-12 by human monocyte-derived dendritic cells is optimal when the stimulus is given at the onset of maturation, and is further enhanced by IL-4. J Immunol 2001, 166: 633–41.View ArticlePubMedGoogle Scholar
- Caux C, Dezutter-Dambuyant C, Schmitt D, Banchereau J: GM-CSF and TNF-alpha cooperate in the generation of dendritic Langerhans cells. Nature 1992, 360: 258–61. 10.1038/360258a0View ArticlePubMedGoogle Scholar
- Breathnach AS: Aspects of epidermal ultrastructure. J Invest Dermatol 1975, 65: 2–15.View ArticlePubMedGoogle Scholar
- Plath T, Detjen K, Welzel M, von Marschall Z, Murphy D, Schirner M, Wiedenmann B, Rosewicz S: A novel function for the tumor suppressor p16(INK4a): induction of anoikis via upregulation of the alpha(5)beta(1) fibronectin receptor. J Cell Biol 2000, 150: 1467–78. 10.1083/jcb.150.6.1467View ArticlePubMedPubMed CentralGoogle Scholar
- Nestle FO, Nickoloff BJ: Dermal dendritic cells are important members of the skin immune system. Adv Exp Med Biol 1995, 378: 111–6.View ArticlePubMedGoogle Scholar
- Lenz A, Heine M, Schuler G, Romani N: Human and murine dermis contain dendritic cells. Isolation by means of a novel method and phenotypical and functional characterization. J Clin Invest 1993, 92: 2587–96.View ArticlePubMedPubMed CentralGoogle Scholar
- Czernielewski J, Vaigot P, Prunieras M: Epidermal Langerhans cells – a cycling cell population. J Invest Dermatol 1985, 84: 424–6.View ArticlePubMedGoogle Scholar
- Kanitakis J, Hoyo E, Perrin C, Schmitt D: Electron-microscopic observation of a human epidermal Langerhans cell in mitosis. J Dermatol 1993, 20: 35–9.View ArticlePubMedGoogle Scholar
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-5945/3/3/prepub
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