- Email: [email protected]
The Skin as a Site of Initiation of Systemic Autoimmune Disease: New Opportunities for Treatment
COMMENTARY
design including internal normal skin controls. Developments in other specialties are also showing us the way for broader use, for instance in the study of tumors (Dabrosin, 2005). Writing a Commentary such as this can make the author feel challenged — “So much to do (refer to) and so little time (column space).” Read the article by Morgan et al.(2006); follow the trail provided by the subjects and authors referred to there and in this commentary. It will lead you to around 500 articles involving microdialysis and skin, around 3,000 articles on human microdialysis in a wide range of organs and applications, and a total microdialysis bibliography approaching 10,000 articles. Think broadly about the opportunities offered by cutaneous microdialysis for application in your own special area of research. You will very likely find it worth the sweat! CONFLICT OF INTEREST
B (1997) Increased interstitial histamine concentration in the psoriatic plaque. J Invest Dermatol 109:632–5 Morgan C, Friedman P, Church M, Clough G (2006) Cutaneous microdialysis as a novel means of continuously stimulating eccrine sweat glands in vivo. J Invest Dermatol 126:1220–5
Petersen L, Nielsen H, Skov P (1995) Codeine induced histamine release in intact human skin monitored by skin microdialysis technique: comparison of intradermal injections with an atraumatic intraprobe delivery system. Clin Exp Allergy 25:1045–52
Muller M (2000) Microdialysis in clinical drug delivery studies. Adv Drug Deliv Rev 45:255–69
Simonsen L, Jorgensen A, Benfeldt E, Groth L (2004) Differentiated in vivo skin penetration of salicylic compounds in hairless rats measured by cutaneous microdialysis. Eur J Pharm Sci 21:379–88
Nilsson G (1977) On the measurement of evaporative water loss. Medical dissertation no. 48, Linköping University, Linköping, Sweden. ISBN 91-7372-131-x
Sjögren F, Svensson C, Anderson C (2002) Technical prerequisites for in vivo microdialysis determination of IL-6 in human dermis. Br J Dermatol 146:375–82
See related article on page 1307
The Skin as a Site of Initiation of Systemic Autoimmune Disease: New Opportunities for Treatment Jan P. Dutz1,2
TThe author states no conflict of interest.
REFERENCES Anderson C, Andersson T, Molander M (1991) Ethanol absorption across human skin measured by in-vivo microdialysis technique. Acta Derm Venereol 71:389–93
Dendritic cells are the coordinators of the adaptive immune response. Chronic activation of skin dendritic cells by keratinocyte expression of CD40 ligand (CD40L; CD154) leads to autoimmunity. In this issue, systemic administration of tacrolimus is shown by Loser et al. to effectively treat autoimmunity in a murine model involving transgenic keratinocyte expression of CD40L.
Andersson T, Wårdell K, Anderson C (1995) Human in vivo cutaneous microdialysis: estimation of histamine release in cold urticaria. Acta Derm Venereol 75:343–7
Journal of Investigative Dermatology (2006) 126, 1209–1212. doi:10.1038/sj.jid.5700238
Arner P, Bolinder J, Eliasson A, Lundin A, Ungerstedt U (1988) Microdialysis of adipose tissue and blood for in vivo lipolysis studies. Am J Physiol 255:E737–42
Chronic skin dendritic-cell activation and autoimmunity
Ault J, Lunte C, Meltzer N, Riley C (1992) Microdialysis sampling for the investigation of dermal drug transport. Pharm Res 9:1256– 61 Benfeldt E, Serup J, Menné T (1999) Effect of barrier perturbation on cutaneous salicylic acid penetration in human skin: in vivo pharmacokinetics using microdialysis and non-invasive quantification of barrier function. Br J Dermatol 140:739–48 Dabrosin C (2005) An in vivo technique for studies of growth factors in breast cancer. Front Biosci 10:1329–35 Ikoma A, Fartasch M, Heyer G, Miyachi Y, Handwerker H, Schmelz M (2004) Painful stimuli evoke itch in patients with chronic pruritus: central sensit ization for itch. Neurology 62:212–7 Jansson PA, Fowelin J, Smith U, Lonnroth P (1988) Characterisation by microdialysis of intracellular glucose level in subcutaneous tissue in humans. Am J Physiol 255:E218–20 Krogstad A, Lönnroth P, Larsson G, Wallin
Over the past 20 years, dendritic cells have become recognized as the prime orchestrators of the adaptive immune response (Banchereau and Steinman, 1998). These cells most efficiently activate or prime T cells (Inaba et al., 1990). More recently, their dual role as inhibitory regulators of the immune response has been appreciated (Hawiger et al., 2001). For example, Langerhans cells, long thought to be proinflammatory sentinels, have been shown to be dispensable for the cutaneous (Allan et al., 2003) or mucosal (Zhao et al., 2003)
priming of cytotoxic T cells to herpes simplex virus and to have a potentially suppressive role in contact hypersensitivity responses (Kaplan et al., 2005). With this dual role, dendritic cells are probably key players in the march to autoimmunity. Proinflammatory stimulation of dendritic cells with activation signals such as Toll-like receptors (Iwasaki and Medzhitov, 2004) or CD40 ligation (Ridge et al., 1998) results in the maturation of dendritic cells and subsequent efficient T-cell activation. Chronic dendritic-cell stimulation may result in an autoimmune phenotype. For example,
1
Departments of Dermatology and Medicine and Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada; and 2Division of Rheumatology, Department of Medicine and Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada Correspondence: Dr. Jan P. Dutz, Department of Medicine and Child & Family Research Institute, University of British Columbia, 301-835 W. 10th Avenue, Vancouver, British Columbia, Canada V5Z 4E8. E-mail: [email protected]
www.jidonline.org 1209
COMMENTARY
overexpression of CD40 ligand (CD40L; CD154) in the basal layer of the skin results in local emigration of dendritic cells (Langerhans cells), accumulation of dendritic cells in the draining lymph nodes with ensuing local lymphadenopathy, and a CD8+ T cell-mediated autoimmune disease. This experimental murine disease model is characterized by cellular autoimmune responses in the skin and formation of autoantibodies against nuclear antigens, including antiDNA antibodies (Mehling et al., 2001). Likewise, overexpression of CD154 in
|
Dendritic cells are probably key players in the march to autoimmunity.
pancreatic islets leads to islet inflammation (insulitis) and eventual diabetes (Haase et al., 2004) that are both T and B cell dependent. These models show that chronic dendritic-cell activation can lead to local as well as systemic autoimmunity. In the model developed by Mehling et al. (2001), cutaneous disease could be transferred from transgenic to nontransgenic animals by CD8+ T-cell transfer, indicating that autoreactive CD8+ T cells were sufficient to mediate skin disease and the lupus-like phenotype. How well do these models reflect spontaneous human autoimmune disease? Recently, it has been demonstrated that proportions of effector-type, perforin-expressing CD8+ T cells increase in active systemic lupus erythematosus and correlate with disease activity (Blanco et al., 2005). Further, scarring lesions of discoid lupus erythematosus are characterized by high numbers of skin-homing cytotoxic CD8+ T lymphocytes (Wenzel et al., 2005). These observations endorse a potential pathogenic role for CD8+ T cells in lupus autoimmunity and suggest that the model of Mehling et al. may in part mirror human lupus autoimmunity. Interestingly, increased skin CD40L expression (Ohta and Hamada, 2004), decreased numbers of potentially tolerogenic epidermal Langerhans cells (Gordon et al., 2005), and increased
numbers of inflammatory dermal and epidermal dendritic cells (Lowes et al., 2005) have been noted in lesional psoriasis, another disorder in which activated CD8+ T cells (Austin et al., 1998) have been implicated. This suggests that the model of Mehling et al. may also mirror other forms of skin autoimmunity. Collectively, the data suggest that dendritic cells are at the nexus of autoimmunity initiation and inhibition and that pharmacological control of the dendritic cells may have significant and yet unexplored benefits in the therapy and prevention of autoimmunity. Calcineurin inhibitors and systemic autoimmunity
Calcineurin inhibitors have been in clinical use in dermatology for over 20 years. Cyclosporine is a cyclic polypeptide that has been used in renal organ transplantation and for multiple dermatoses with excellent clinical responses in psoriasis, pyoderma gangrenosum, Behçet’s disease, and lichen planus (Ho et al., 1990). The mechanism of action of cyclosporine is now known to be related to the reduction of the calcineurin activity of T cells, resulting in decreased cytokine gene transcription (reviewed by Cardenas et al., 1995), and decreased cytotoxic degranulation (Ambach et al., 2001; Dutz et al., 1993). Tacrolimus (FK506) is a macrolide antibiotic that has a mechanism of action similar to that of cyclosporine, albeit with 10–100 times greater molecular potency and a smaller molecular weight. This has resulted in an effective topical formulation (Evans, 2005). Tacrolimus has been used as an alternative calcineurin inhibitor for organ transplantation since the 1990s (Taylor et al., 2005). Side effects of cyclosporine and tacrolimus include renal nephrotoxicity and neurotoxicity (reviewed by Taylor et al., 2005). Systemic cyclosporine use in transplantation is associated with more nephrotoxicity, whereas tacrolimus use is associated with more neurotoxicity and drug-induced diabetes (Webster et al., 2005). A limited number of studies have examined the use of oral tacrolimus for the treatment of systemic autoimmune disease. Tacrolimus has been used investigationally in rheumatoid arthritis
1210 Journal of Investigative Dermatology (2006), Volume 126
(Furst et al., 2002), polymyositis with interstitial lung disease (Oddis et al., 1999), scleroderma (Morton and Powell, 2000), and systemic lupus erythematosus (Duddridge and Powell, 1997; Politt et al., 2004) with variable effect. In this issue, Loser et al. (2006) demonstrate that systemic tacrolimus controls murine keratinocyte-expressed CD40L-induced skin and systemic autoimmunity. They convincingly demonstrate that this drug is able to reverse and prevent autoreactive CD8+ T-cell activation. Thus, CD8+ T cells from untreated but not from treated animals were able to transfer skin disease. Tacrolimus treatment also led to decreased lymphadenopathy and decreased autoantibody formation and glomerular deposition. Recent evidence suggests that calcineurin inhibitors inhibit the antigenpresenting function of dendritic cells (Lee et al., 2005) independently of T-cell effects. Unfortunately, the relative importance of this mode of action of the calcineurin inhibitors was not commented upon by Loser et al. (2006). Further, it remains unclear whether the salutary effect on autoantibody production was due to a direct action of B cells or to indirect effects on cytotoxic T cells, CD4+ T cells, or dendritic cells. Despite these minor shortcomings, the authors have ably used a novel and relevant model of skin-initiated autoimmunity to study the pharmacobiology of a currently available and effective immunomodulator. Lessons for clinical practice
What lessons can we glean? To the clinician-scientist, this work points out the importance of refining our understanding of current immunotherapies for autoimmune disease. The remarkable success noted in this murine model contrasts with the variable results noted in clinical systemic autoimmune disease (Mayer and Kushwaha, 2003). This may be a result of the higher doses used in this animal model (up to ~4 mg per kg per day on average) as compared with the doses commonly used in human clinical trials for the treatment of autoimmune disease (0.06–0.1 mg per kg per day) or in transplantation (0.2– 0.3 mg per kg per day). Interestingly, after kidney transplantation, calcineurin
COMMENTARY
inhibitors have been shown to prevent recurrence of systemic lupus erythematosus (Dong et al., 2005). Should the skin dendritic cell be found to be a major in vivo locus of action for systemic calcineurin inhibitors, this would point to the importance of targeting the skin-resident dendritic cells directly with potentially less toxic topical therapy. The active form of vitamin D, 1αdihydroxyvitamin D3, for example, is known to alter or inhibit maturation of dendritic cells and promote a tolerogenic phenotype (Berer et al., 2000). Patients with systemic lupus erythematosus are advised to avoid sunlight and often have vitamin D deficiency (Huisman et al., 2001). Yet the use of topical vitamin D analogues such as calcipotriol as adjuncts in the management of skin lupus remains largely unexplored. The efficacy of systemic calcineurin inhibitors in controlling pathogenic CD8+ T-cell activation as described here should also remind us of the possible short-term systemic use of these agents in severe dermatologic conditions in which CD8+ T-cell cytotoxic assault has been implicated. Such conditions include systemic drug hypersensitivity reactions (Zuliani et al., 2005), toxic epidermal necrolysis (Chave et al., 2005), and possibly “hyperacute” toxic epidermal necrolysis-like cutaneous lupus erythematosus (Ting et al., 2004). CONFLICT OF INTEREST The author states no conflict of interest.
REFERENCES
Blanco P, Pitard V, Viallard JF, Taupin JL, Pellegrin JL, Moreau JF (2005) Increase in activated CD8+ T lymphocytes expressing perforin and granzyme B correlates with disease activity in patients with systemic lupus erythematosus. Arthritis Rheum 52:201–11 Cardenas ME, Zhu D, Heitman J (1995) Molecular mechanisms of immunosuppression by cyclosporine, FK506, and rapamycin. Curr Opin Nephrol Hypertens 4:472–7 Chave TA, Mortimer NJ, Sladden MJ, Hall AP, Hutchinson PE (2005) Toxic epidermal necrolysis: current evidence, practical management and future directions. Br J Dermatol 153:241–53 Dong G, Panaro F, Bogetti D, Sammartino C, Rondelli D, Sankary H et al. (2005) Standard chronic immunosuppression after kidney transplantation for systemic lupus erythematosus eliminates recurrence of disease. Clin Transplant 19:56–60 Duddridge M, Powell RJ (1997) Treatment of severe and difficult cases of systemic lupus erythematosus with tacrolimus. A report of three cases. Ann Rheum Dis 56:690–2 Dutz JP, Fruman DA, Burakoff SJ, Bierer BE (1993) A role for calcineurin in degranulation of murine cytotoxic T lymphocytes. J Immunol 150:2591–8 Evans AV (2005) The expanding role of topical tacrolimus in dermatology. Clin Exp Dermatol 30:111–5 Furst DE, Saag K, Fleischmann MR, Sherrer Y, Block JA, Schnitzer T et al. (2002) Efficacy of tacrolimus in rheumatoid arthritis patients who have been treated unsuccessfully with methotrexate: a six-month, double-blind, randomized, dose-ranging study. Arthritis Rheum 46:2020–8 Gordon KB, Bonish BK, Patel T, Leonardi CL, Nickoloff BJ (2005) The tumour necrosis factoralpha inhibitor adalimumab rapidly reverses the decrease in epidermal Langerhans cell density in psoriatic plaques. Br J Dermatol 153:945–53
Allan RS, Smith CM, Belz GT, van Lint AL, Wakim LM, Heath WR et al. (2003) Epidermal viral immunity induced by CD8alpha+ dendritic cells but not by Langerhans cells. Science 301:1925–8
Haase C, Skak K, Michelsen BK, Markholst H (2004) Local activation of dendritic cells leads to insulitis and development of insulindependent diabetes in transgenic mice expressing CD154 on the pancreatic beta-cells. Diabetes 53:2588–95
Ambach A, Bonnekoh B, Gollnick H (2001) Perforin granule release from cytotoxic lymphocytes ex vivo is inhibited by ciclosporin but not by methotrexate. Skin Pharmacol Appl Skin Physiol 14:249–60
Hawiger D, Inaba K, Dorsett Y, Guo M, Mahnke K, Rivera M et al. (2001) Dendritic cells induce peripheral T cell unresponsiveness under steady state conditions in vivo. J Exp Med 194:769–79
Austin LM, Coven TR, Bhardwaj N, Steinman R, Krueger JG (1998) Intraepidermal lymphocytes in psoriatic lesions are activated GMP-17(TIA1)+CD8+CD3+ CTLs as determined by phenotypic analysis. J Cutan Pathol 25:79–88 Banchereau J, Steinman RM (1998) Dendritic cells and the control of immunity. Nature 392:245– 52 Berer A, Stockl J, Majdic O, Wagner T, Kollars M, Lechner K et al. (2000) 1,25-Dihydroxyvitamin D(3) inhibits dendritic cell differentiation and maturation in vitro. Exp Hematol 28:575–83
Ho VC, Lui H, McLean DI (1990) Cyclosporine in nonpsoriatic dermatoses. J Am Acad Dermatol 23:1248–57; discussion 1257–9 Huisman AM, White KP, Algra A, Harth M, Vieth R, Jacobs JW et al. (2001) Vitamin D levels in women with systemic lupus erythematosus and fibromyalgia. J Rheumatol 28:2535–9 Inaba K, Metlay JP, Crowley MT, Steinman RM (1990) Dendritic cells pulsed with protein antigens in vitro can prime antigen-specific, MHC-restricted T cells in situ. J Exp Med 172:631–40 Iwasaki A, Medzhitov R (2004) Toll-like receptor
control of the adaptive immune responses. Nat Immunol 5:987–95 Kaplan DH, Jenison MC, Saeland S, Shlomchik WD, Shlomchik MJ (2005) Epidermal langerhans cell-deficient mice develop enhanced contact hypersensitivity. Immunity 23:611–20 Lee YR, Yang IH, Lee YH, Im SA, Song S, Li H et al. (2005) Cyclosporin A and tacrolimus, but not rapamycin, inhibit MHC-restricted antigen presentation pathways in dendritic cells. Blood 105:3951–5 Loser K, Balkow S, Higuchi T, Apelt J, Kuhn A, Luger TA et al. (2006) FK506 controls CD40Linduced systemic autoimmunity in mice. J Invest Dermatol 126:1307–15 Lowes MA, Chamian F, Abello MV, FuentesDuculan J, Lin SL, Nussbaum R et al. (2005) Increase in TNF-α and inducible nitric oxide synthase-expressing dendritic cells in psoriasis and reduction with efalizumab (anti-CD11a). Proc Natl Acad Sci USA 102:19057–62 Mayer DF, Kushwaha SS (2003) Transplant immunosuppressant agents and their role in autoimmune rheumatic diseases. Curr Opin Rheumatol 15:219–25 Mehling A, Loser K, Varga G, Metze D, Luger TA, Schwarz T et al. (2001) Overexpression of CD40 ligand in murine epidermis results in chronic skin inflammation and systemic autoimmunity. J Exp Med 194:615–28 Morton SJ, Powell RJ (2000) Cyclosporin and tacrolimus: their use in a routine clinical setting for scleroderma. Rheumatology (Oxford) 39:865–9 Oddis CV, Sciurba FC, Elmagd KA, Starzl TE (1999) Tacrolimus in refractory polymyositis with interstitial lung disease. Lancet 353:1762–3 Ohta Y, Hamada Y (2004) In situ expression of CD40 and CD40 ligand in psoriasis. Dermatology 209:21–8 Politt D, Heintz B, Floege J, Mertens PR (2004) Tacrolimus- (FK 506) based immunosuppression in severe systemic lupus erythematosus. Clin Nephrol 62:49–53 Ridge JP, Di Rosa F, Matzinger P (1998) A conditioned dendritic cell can be a temporal bridge between a CD4+ T-helper and a T-killer cell. Nature 393:474–8 Taylor AL, Watson CJ, Bradley JA (2005) Immunosuppressive agents in solid organ transplantation: mechanisms of action and therapeutic efficacy. Crit Rev Oncol Hematol 56:23–46 Ting W, Stone MS, Racila D, Scofield RH, Sontheimer RD (2004) Toxic epidermal necrolysis-like acute cutaneous lupus erythematosus and the spectrum of the acute syndrome of apoptotic pan-epidermolysis (ASAP): a case report, concept review and proposal for new classification of lupus erythematosus vesiculobullous skin lesions. Lupus 13:941–50 Webster A, Woodroffe RC, Taylor RS, Chapman JR, Craig JC (2005) Tacrolimus versus cyclosporin as primary immunosuppression for kidney transplant recipients. Cochrane Database Syst
www.jidonline.org 1211
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Rev 4: CD003961, doi:10.1002/14651858. CD003961.pub2 Wenzel J, Uerlich M, Worrenkamper E, Freutel S, Bieber T, Tuting T (2005) Scarring skin lesions of discoid lupus erythematosus are characterized by high numbers of skin-homing cytotoxic lymphocytes associated with strong expression of the type I interferon-induced protein MxA. Br J Dermatol 153:1011–5
Zhao X, Deak E, Soderberg K, Linehan M, Spezzano D, Zhu J et al. (2003) Vaginal submucosal dendritic cells, but not Langerhans cells, induce protective Th1 responses to herpes simplex virus-2. J Exp Med 197:153–62 Zuliani E, Zwahlen H, Gilliet F, Marone C (2005) Vancomycin-induced hypersensitivity reaction with acute renal failure: resolution following cyclosporine treatment. Clin Nephrol 64:155–8
See related article on page 1366
"Bak (and Bax) to the Future" — of Primary Melanoma Prognosis? Martin Leverkus1 and Harald Gollnick1 Bcl-2 proteins either block or activate the “intrinsic” mitochondrial apoptosis pathway. Loss of expression of proapoptotic Bcl-2 proteins, namely Bax and Bak, in primary melanomas is associated with a worse long-term prognosis. Consequently, inactivation of mitochondrial signaling pathways of apoptosis may not only be a prerequisite for melanoma progression but may also hamper therapeutic efforts with chemotherapeutic drugs. Journal of Investigative Dermatology (2006) 126, 1212–1214. doi:10.1038/sj.jid.5700239
Despite major efforts to improve diagnosis and stage-specific therapy, the incidence of melanoma and its mortality rates have increased continuously over the past two decades. Unfortunately, the prognosis of melanoma patients with progressive disease is poor, in particular for patients with thick lesions or regional lymph node metastasis. For these patients, there is no general agreement among dermato-oncologists about evidence-based treatment modalities (Queirolo et al., 2005). Extensive studies during the past years have clarified that alterations within physiological signaling cascades of melanoma cells may be of utmost importance for the understanding of drug resistance mechanisms and consequently for clinical outcome following treatment (Soengas and Lowe, 2003). One major challenge is the definition of wider arrays of prognostic parameters for melanoma after surgical excision of the primary tumor, which may subsequently
justify prognosis-adapted treatment regimens for the patient. This strategy in turn may rely on information gained from the primary melanoma about signaling pathways activated or silenced during melanomagenesis (for review see Chudnovsky et al., 2005). One decisive factor for successful tumor therapy is the initiation of the cell-intrinsic apoptotic program that is largely dependent on activation of the central executioners of apoptosis, the caspases (Lavrik et al., 2005). Their activity is critical not only for successful tumor-cell death but also for the mounting of a tumor-specific immune response (Casares et al., 2005). Thus the understanding of apoptosis signaling in melanoma may ultimately result in better treatment strategies for this deadly tumor. Apoptosis is tightly regulated in a cell-specific manner by multiple signaling pathways that interact in successive and interconnected amplification loops,
1
Laboratory for Experimental Dermatology, Department of Dermatology and Venereology, Otto-vonGuericke-University Magdeburg, Magdeburg, Germany Correspondence: Dr. Martin Leverkus, Laboratory for Experimental Dermatology, Department of Dermatology and Venereology, Otto-von-Guericke-University Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany. E-mail: [email protected]
1212 Journal of Investigative Dermatology (2006), Volume 126
finally resulting in cell demise. In this issue, Fecker et al. (2006) have tackled the task of identifying novel prognostic markers in primary melanomas by expression analysis of several pro- and antiapoptotic proteins in vivo. The authors first carefully explored the specificity of their immunohistochemical analysis by demonstrating positive as well as negative staining of different tumor samples. Upon subdivision of the samples according to the presence or absence of clinical progression of these tumors over a follow-up period of 10 years, these tumors were investigated for the prognostic relevance of protein expression. What type of signals may lead to apoptosis in melanoma? In general, apoptotic signaling is broadly divided into “intrinsic” and “extrinsic” pathways: the extrinsic pathway is triggered from the outside of the cell by transmembrane proteins called death receptors (Locksley et al., 2001). These trigger apoptosis by ligand binding via recruitment of the initiator caspases caspase-8 and/or caspase-10, ultimately resulting in activation of effector caspases (for example, caspase-3; Figure 1). However, this pathway is tightly regulated by intracellular initiator caspase inhibitors such as cFLIP, and this inhibition seems to be operative in melanoma (Bullani et al., 2001). Fecker et al. (2006) investigated the protein expression of the death receptors DR4 (tumor necrosis factor-related apoptosis-inducing ligandreceptor 1 (TRAIL-R1)) and DR5 (TRAILR2) and important cell cycle regulators such as p21 and retinoblastoma protein, the tumor suppressor p53, and its inhibitor MDM2. These studies, although performed only in a limited number of superficial spreading melanomas (SSMs), did not show a significant correlation to the prognosis of primary melanoma. TRAIL-R1 and TRAIL-R2 were expressed in over 90% of primary SSMs, demonstrating that these two death receptors do not predict clinical outcome. However, because the death ligand TRAIL or agonistic antibodies to TRAIL-R1 or TRAILR2 are currently undergoing extensive preclinical tests for tumor therapy (Kelley and Ashkenazi, 2004), these results of Fecker et al. (2006), if confirmed in larger series of tumors as well as melanoma metastasis in vivo, might open a therapeutic window for these agents for
design including internal normal skin controls. Developments in other specialties are also showing us the way for broader use, for instance in the study of tumors (Dabrosin, 2005). Writing a Commentary such as this can make the author feel challenged — “So much to do (refer to) and so little time (column space).” Read the article by Morgan et al.(2006); follow the trail provided by the subjects and authors referred to there and in this commentary. It will lead you to around 500 articles involving microdialysis and skin, around 3,000 articles on human microdialysis in a wide range of organs and applications, and a total microdialysis bibliography approaching 10,000 articles. Think broadly about the opportunities offered by cutaneous microdialysis for application in your own special area of research. You will very likely find it worth the sweat! CONFLICT OF INTEREST
B (1997) Increased interstitial histamine concentration in the psoriatic plaque. J Invest Dermatol 109:632–5 Morgan C, Friedman P, Church M, Clough G (2006) Cutaneous microdialysis as a novel means of continuously stimulating eccrine sweat glands in vivo. J Invest Dermatol 126:1220–5
Petersen L, Nielsen H, Skov P (1995) Codeine induced histamine release in intact human skin monitored by skin microdialysis technique: comparison of intradermal injections with an atraumatic intraprobe delivery system. Clin Exp Allergy 25:1045–52
Muller M (2000) Microdialysis in clinical drug delivery studies. Adv Drug Deliv Rev 45:255–69
Simonsen L, Jorgensen A, Benfeldt E, Groth L (2004) Differentiated in vivo skin penetration of salicylic compounds in hairless rats measured by cutaneous microdialysis. Eur J Pharm Sci 21:379–88
Nilsson G (1977) On the measurement of evaporative water loss. Medical dissertation no. 48, Linköping University, Linköping, Sweden. ISBN 91-7372-131-x
Sjögren F, Svensson C, Anderson C (2002) Technical prerequisites for in vivo microdialysis determination of IL-6 in human dermis. Br J Dermatol 146:375–82
See related article on page 1307
The Skin as a Site of Initiation of Systemic Autoimmune Disease: New Opportunities for Treatment Jan P. Dutz1,2
TThe author states no conflict of interest.
REFERENCES Anderson C, Andersson T, Molander M (1991) Ethanol absorption across human skin measured by in-vivo microdialysis technique. Acta Derm Venereol 71:389–93
Dendritic cells are the coordinators of the adaptive immune response. Chronic activation of skin dendritic cells by keratinocyte expression of CD40 ligand (CD40L; CD154) leads to autoimmunity. In this issue, systemic administration of tacrolimus is shown by Loser et al. to effectively treat autoimmunity in a murine model involving transgenic keratinocyte expression of CD40L.
Andersson T, Wårdell K, Anderson C (1995) Human in vivo cutaneous microdialysis: estimation of histamine release in cold urticaria. Acta Derm Venereol 75:343–7
Journal of Investigative Dermatology (2006) 126, 1209–1212. doi:10.1038/sj.jid.5700238
Arner P, Bolinder J, Eliasson A, Lundin A, Ungerstedt U (1988) Microdialysis of adipose tissue and blood for in vivo lipolysis studies. Am J Physiol 255:E737–42
Chronic skin dendritic-cell activation and autoimmunity
Ault J, Lunte C, Meltzer N, Riley C (1992) Microdialysis sampling for the investigation of dermal drug transport. Pharm Res 9:1256– 61 Benfeldt E, Serup J, Menné T (1999) Effect of barrier perturbation on cutaneous salicylic acid penetration in human skin: in vivo pharmacokinetics using microdialysis and non-invasive quantification of barrier function. Br J Dermatol 140:739–48 Dabrosin C (2005) An in vivo technique for studies of growth factors in breast cancer. Front Biosci 10:1329–35 Ikoma A, Fartasch M, Heyer G, Miyachi Y, Handwerker H, Schmelz M (2004) Painful stimuli evoke itch in patients with chronic pruritus: central sensit ization for itch. Neurology 62:212–7 Jansson PA, Fowelin J, Smith U, Lonnroth P (1988) Characterisation by microdialysis of intracellular glucose level in subcutaneous tissue in humans. Am J Physiol 255:E218–20 Krogstad A, Lönnroth P, Larsson G, Wallin
Over the past 20 years, dendritic cells have become recognized as the prime orchestrators of the adaptive immune response (Banchereau and Steinman, 1998). These cells most efficiently activate or prime T cells (Inaba et al., 1990). More recently, their dual role as inhibitory regulators of the immune response has been appreciated (Hawiger et al., 2001). For example, Langerhans cells, long thought to be proinflammatory sentinels, have been shown to be dispensable for the cutaneous (Allan et al., 2003) or mucosal (Zhao et al., 2003)
priming of cytotoxic T cells to herpes simplex virus and to have a potentially suppressive role in contact hypersensitivity responses (Kaplan et al., 2005). With this dual role, dendritic cells are probably key players in the march to autoimmunity. Proinflammatory stimulation of dendritic cells with activation signals such as Toll-like receptors (Iwasaki and Medzhitov, 2004) or CD40 ligation (Ridge et al., 1998) results in the maturation of dendritic cells and subsequent efficient T-cell activation. Chronic dendritic-cell stimulation may result in an autoimmune phenotype. For example,
1
Departments of Dermatology and Medicine and Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada; and 2Division of Rheumatology, Department of Medicine and Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada Correspondence: Dr. Jan P. Dutz, Department of Medicine and Child & Family Research Institute, University of British Columbia, 301-835 W. 10th Avenue, Vancouver, British Columbia, Canada V5Z 4E8. E-mail: [email protected]
www.jidonline.org 1209
COMMENTARY
overexpression of CD40 ligand (CD40L; CD154) in the basal layer of the skin results in local emigration of dendritic cells (Langerhans cells), accumulation of dendritic cells in the draining lymph nodes with ensuing local lymphadenopathy, and a CD8+ T cell-mediated autoimmune disease. This experimental murine disease model is characterized by cellular autoimmune responses in the skin and formation of autoantibodies against nuclear antigens, including antiDNA antibodies (Mehling et al., 2001). Likewise, overexpression of CD154 in
|
Dendritic cells are probably key players in the march to autoimmunity.
pancreatic islets leads to islet inflammation (insulitis) and eventual diabetes (Haase et al., 2004) that are both T and B cell dependent. These models show that chronic dendritic-cell activation can lead to local as well as systemic autoimmunity. In the model developed by Mehling et al. (2001), cutaneous disease could be transferred from transgenic to nontransgenic animals by CD8+ T-cell transfer, indicating that autoreactive CD8+ T cells were sufficient to mediate skin disease and the lupus-like phenotype. How well do these models reflect spontaneous human autoimmune disease? Recently, it has been demonstrated that proportions of effector-type, perforin-expressing CD8+ T cells increase in active systemic lupus erythematosus and correlate with disease activity (Blanco et al., 2005). Further, scarring lesions of discoid lupus erythematosus are characterized by high numbers of skin-homing cytotoxic CD8+ T lymphocytes (Wenzel et al., 2005). These observations endorse a potential pathogenic role for CD8+ T cells in lupus autoimmunity and suggest that the model of Mehling et al. may in part mirror human lupus autoimmunity. Interestingly, increased skin CD40L expression (Ohta and Hamada, 2004), decreased numbers of potentially tolerogenic epidermal Langerhans cells (Gordon et al., 2005), and increased
numbers of inflammatory dermal and epidermal dendritic cells (Lowes et al., 2005) have been noted in lesional psoriasis, another disorder in which activated CD8+ T cells (Austin et al., 1998) have been implicated. This suggests that the model of Mehling et al. may also mirror other forms of skin autoimmunity. Collectively, the data suggest that dendritic cells are at the nexus of autoimmunity initiation and inhibition and that pharmacological control of the dendritic cells may have significant and yet unexplored benefits in the therapy and prevention of autoimmunity. Calcineurin inhibitors and systemic autoimmunity
Calcineurin inhibitors have been in clinical use in dermatology for over 20 years. Cyclosporine is a cyclic polypeptide that has been used in renal organ transplantation and for multiple dermatoses with excellent clinical responses in psoriasis, pyoderma gangrenosum, Behçet’s disease, and lichen planus (Ho et al., 1990). The mechanism of action of cyclosporine is now known to be related to the reduction of the calcineurin activity of T cells, resulting in decreased cytokine gene transcription (reviewed by Cardenas et al., 1995), and decreased cytotoxic degranulation (Ambach et al., 2001; Dutz et al., 1993). Tacrolimus (FK506) is a macrolide antibiotic that has a mechanism of action similar to that of cyclosporine, albeit with 10–100 times greater molecular potency and a smaller molecular weight. This has resulted in an effective topical formulation (Evans, 2005). Tacrolimus has been used as an alternative calcineurin inhibitor for organ transplantation since the 1990s (Taylor et al., 2005). Side effects of cyclosporine and tacrolimus include renal nephrotoxicity and neurotoxicity (reviewed by Taylor et al., 2005). Systemic cyclosporine use in transplantation is associated with more nephrotoxicity, whereas tacrolimus use is associated with more neurotoxicity and drug-induced diabetes (Webster et al., 2005). A limited number of studies have examined the use of oral tacrolimus for the treatment of systemic autoimmune disease. Tacrolimus has been used investigationally in rheumatoid arthritis
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(Furst et al., 2002), polymyositis with interstitial lung disease (Oddis et al., 1999), scleroderma (Morton and Powell, 2000), and systemic lupus erythematosus (Duddridge and Powell, 1997; Politt et al., 2004) with variable effect. In this issue, Loser et al. (2006) demonstrate that systemic tacrolimus controls murine keratinocyte-expressed CD40L-induced skin and systemic autoimmunity. They convincingly demonstrate that this drug is able to reverse and prevent autoreactive CD8+ T-cell activation. Thus, CD8+ T cells from untreated but not from treated animals were able to transfer skin disease. Tacrolimus treatment also led to decreased lymphadenopathy and decreased autoantibody formation and glomerular deposition. Recent evidence suggests that calcineurin inhibitors inhibit the antigenpresenting function of dendritic cells (Lee et al., 2005) independently of T-cell effects. Unfortunately, the relative importance of this mode of action of the calcineurin inhibitors was not commented upon by Loser et al. (2006). Further, it remains unclear whether the salutary effect on autoantibody production was due to a direct action of B cells or to indirect effects on cytotoxic T cells, CD4+ T cells, or dendritic cells. Despite these minor shortcomings, the authors have ably used a novel and relevant model of skin-initiated autoimmunity to study the pharmacobiology of a currently available and effective immunomodulator. Lessons for clinical practice
What lessons can we glean? To the clinician-scientist, this work points out the importance of refining our understanding of current immunotherapies for autoimmune disease. The remarkable success noted in this murine model contrasts with the variable results noted in clinical systemic autoimmune disease (Mayer and Kushwaha, 2003). This may be a result of the higher doses used in this animal model (up to ~4 mg per kg per day on average) as compared with the doses commonly used in human clinical trials for the treatment of autoimmune disease (0.06–0.1 mg per kg per day) or in transplantation (0.2– 0.3 mg per kg per day). Interestingly, after kidney transplantation, calcineurin
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inhibitors have been shown to prevent recurrence of systemic lupus erythematosus (Dong et al., 2005). Should the skin dendritic cell be found to be a major in vivo locus of action for systemic calcineurin inhibitors, this would point to the importance of targeting the skin-resident dendritic cells directly with potentially less toxic topical therapy. The active form of vitamin D, 1αdihydroxyvitamin D3, for example, is known to alter or inhibit maturation of dendritic cells and promote a tolerogenic phenotype (Berer et al., 2000). Patients with systemic lupus erythematosus are advised to avoid sunlight and often have vitamin D deficiency (Huisman et al., 2001). Yet the use of topical vitamin D analogues such as calcipotriol as adjuncts in the management of skin lupus remains largely unexplored. The efficacy of systemic calcineurin inhibitors in controlling pathogenic CD8+ T-cell activation as described here should also remind us of the possible short-term systemic use of these agents in severe dermatologic conditions in which CD8+ T-cell cytotoxic assault has been implicated. Such conditions include systemic drug hypersensitivity reactions (Zuliani et al., 2005), toxic epidermal necrolysis (Chave et al., 2005), and possibly “hyperacute” toxic epidermal necrolysis-like cutaneous lupus erythematosus (Ting et al., 2004). CONFLICT OF INTEREST The author states no conflict of interest.
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See related article on page 1366
"Bak (and Bax) to the Future" — of Primary Melanoma Prognosis? Martin Leverkus1 and Harald Gollnick1 Bcl-2 proteins either block or activate the “intrinsic” mitochondrial apoptosis pathway. Loss of expression of proapoptotic Bcl-2 proteins, namely Bax and Bak, in primary melanomas is associated with a worse long-term prognosis. Consequently, inactivation of mitochondrial signaling pathways of apoptosis may not only be a prerequisite for melanoma progression but may also hamper therapeutic efforts with chemotherapeutic drugs. Journal of Investigative Dermatology (2006) 126, 1212–1214. doi:10.1038/sj.jid.5700239
Despite major efforts to improve diagnosis and stage-specific therapy, the incidence of melanoma and its mortality rates have increased continuously over the past two decades. Unfortunately, the prognosis of melanoma patients with progressive disease is poor, in particular for patients with thick lesions or regional lymph node metastasis. For these patients, there is no general agreement among dermato-oncologists about evidence-based treatment modalities (Queirolo et al., 2005). Extensive studies during the past years have clarified that alterations within physiological signaling cascades of melanoma cells may be of utmost importance for the understanding of drug resistance mechanisms and consequently for clinical outcome following treatment (Soengas and Lowe, 2003). One major challenge is the definition of wider arrays of prognostic parameters for melanoma after surgical excision of the primary tumor, which may subsequently
justify prognosis-adapted treatment regimens for the patient. This strategy in turn may rely on information gained from the primary melanoma about signaling pathways activated or silenced during melanomagenesis (for review see Chudnovsky et al., 2005). One decisive factor for successful tumor therapy is the initiation of the cell-intrinsic apoptotic program that is largely dependent on activation of the central executioners of apoptosis, the caspases (Lavrik et al., 2005). Their activity is critical not only for successful tumor-cell death but also for the mounting of a tumor-specific immune response (Casares et al., 2005). Thus the understanding of apoptosis signaling in melanoma may ultimately result in better treatment strategies for this deadly tumor. Apoptosis is tightly regulated in a cell-specific manner by multiple signaling pathways that interact in successive and interconnected amplification loops,
1
Laboratory for Experimental Dermatology, Department of Dermatology and Venereology, Otto-vonGuericke-University Magdeburg, Magdeburg, Germany Correspondence: Dr. Martin Leverkus, Laboratory for Experimental Dermatology, Department of Dermatology and Venereology, Otto-von-Guericke-University Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany. E-mail: [email protected]
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finally resulting in cell demise. In this issue, Fecker et al. (2006) have tackled the task of identifying novel prognostic markers in primary melanomas by expression analysis of several pro- and antiapoptotic proteins in vivo. The authors first carefully explored the specificity of their immunohistochemical analysis by demonstrating positive as well as negative staining of different tumor samples. Upon subdivision of the samples according to the presence or absence of clinical progression of these tumors over a follow-up period of 10 years, these tumors were investigated for the prognostic relevance of protein expression. What type of signals may lead to apoptosis in melanoma? In general, apoptotic signaling is broadly divided into “intrinsic” and “extrinsic” pathways: the extrinsic pathway is triggered from the outside of the cell by transmembrane proteins called death receptors (Locksley et al., 2001). These trigger apoptosis by ligand binding via recruitment of the initiator caspases caspase-8 and/or caspase-10, ultimately resulting in activation of effector caspases (for example, caspase-3; Figure 1). However, this pathway is tightly regulated by intracellular initiator caspase inhibitors such as cFLIP, and this inhibition seems to be operative in melanoma (Bullani et al., 2001). Fecker et al. (2006) investigated the protein expression of the death receptors DR4 (tumor necrosis factor-related apoptosis-inducing ligandreceptor 1 (TRAIL-R1)) and DR5 (TRAILR2) and important cell cycle regulators such as p21 and retinoblastoma protein, the tumor suppressor p53, and its inhibitor MDM2. These studies, although performed only in a limited number of superficial spreading melanomas (SSMs), did not show a significant correlation to the prognosis of primary melanoma. TRAIL-R1 and TRAIL-R2 were expressed in over 90% of primary SSMs, demonstrating that these two death receptors do not predict clinical outcome. However, because the death ligand TRAIL or agonistic antibodies to TRAIL-R1 or TRAILR2 are currently undergoing extensive preclinical tests for tumor therapy (Kelley and Ashkenazi, 2004), these results of Fecker et al. (2006), if confirmed in larger series of tumors as well as melanoma metastasis in vivo, might open a therapeutic window for these agents for