[Skip to Content]
Access to paid content on this site is currently suspended due to excessive activity being detected from your IP address 54.163.129.96. Please contact the publisher to request reinstatement.
[Skip to Content Landing]
Download PDF
Figure 1.
Oral administration of troglitazone improved chronic psoriasis in patient 1. A and D, Before therapy. B and E, After 5 weeks of taking troglitazone, 400 mg/d. C and F, After 4 additional months of taking troglitazone, 600 mg/d.

Oral administration of troglitazone improved chronic psoriasis in patient 1. A and D, Before therapy. B and E, After 5 weeks of taking troglitazone, 400 mg/d. C and F, After 4 additional months of taking troglitazone, 600 mg/d.

Figure 2.
Oral administration of troglitazone improved chronic psoriasis in patient 2. A and C, Elbows before therapy. B and D, Elbows after taking troglitazone, 200 mg/d for 2 weeks and 400 mg/d for 6 additional weeks.

Oral administration of troglitazone improved chronic psoriasis in patient 2. A and C, Elbows before therapy. B and D, Elbows after taking troglitazone, 200 mg/d for 2 weeks and 400 mg/d for 6 additional weeks.

Figure 3.
Ligands for peroxisome proliferator-activated receptor-γ inhibit the proliferation of normal and psoriatic human keratinocytes but not human dermal fibroblasts. For each concentration, 6 replicates were performed; the mean±SE of the percentage of the mean control value is shown. A, Dose-response inhibition of proliferation by troglitazone treatment in normal and psoriatic keratinocytes maintained in serum-free media. B, Dose-response inhibition of growth by troglitazone treatment in normal keratinocytes maintained in supplemented media. C, Dose-response inhibition of growth by 15-deoxy-Δ-12,14-prostaglandin J2 in normal keratinocytes maintained in supplemented media. D, Absence of dose-response inhibition of growth by troglitazone treatment in normal human dermal fibroblasts maintained in serum-free media. For A-C, P<.001; for D, P=.97 by analysis of variance.

Ligands for peroxisome proliferator-activated receptor-γ inhibit the proliferation of normal and psoriatic human keratinocytes but not human dermal fibroblasts. For each concentration, 6 replicates were performed; the mean±SE of the percentage of the mean control value is shown. A, Dose-response inhibition of proliferation by troglitazone treatment in normal and psoriatic keratinocytes maintained in serum-free media. B, Dose-response inhibition of growth by troglitazone treatment in normal keratinocytes maintained in supplemented media. C, Dose-response inhibition of growth by 15-deoxy-Δ-12,14-prostaglandin J2 in normal keratinocytes maintained in supplemented media. D, Absence of dose-response inhibition of growth by troglitazone treatment in normal human dermal fibroblasts maintained in serum-free media. For A-C, P<.001; for D, P=.97 by analysis of variance.

Figure 4.
Oral administration of troglitazone ameliorates the abnormal histological phenotype of human psoriatic skin transplanted onto severe combined immunodeficient (SCID) mice (hematoxylin-eosin, original magnification ×40). A, Human psoriatic lesional skin transplanted onto an untreated SCID mouse for 6 weeks. B, Human psoriatic lesional skin transplanted onto a SCID mouse that was treated with troglitazone, 200 µg orally for 6 weeks.

Oral administration of troglitazone ameliorates the abnormal histological phenotype of human psoriatic skin transplanted onto severe combined immunodeficient (SCID) mice (hematoxylin-eosin, original magnification ×40). A, Human psoriatic lesional skin transplanted onto an untreated SCID mouse for 6 weeks. B, Human psoriatic lesional skin transplanted onto a SCID mouse that was treated with troglitazone, 200 µg orally for 6 weeks.

1.
Sander  HMMorris  LFPhillips  CMHarrison  PEMenter  A The annual cost of psoriasis. J Am Acad Dermatol. 1993;28422- 425Article
2.
McKay  IALeigh  IM Altered keratinocyte growth and differentiation in psoriasis. Clin Dermatol. 1995;13105- 114Article
3.
Barker  JN The pathophysiology of psoriasis. Lancet. 1991;338227- 230Article
4.
Greaves  MWWeinstein  GD Treatment of psoriasis. N Engl J Med. 1995;332581- 588Article
5.
McKay  IAWinyard  PLeigh  IMBustin  SA Nuclear transcription factors: potential targets for new modes of intervention in skin disease. Br J Dermatol. 1994;131591- 597Article
6.
Henry  RR Thiazolidinediones. Endocrinol Metab Clin North Am. 1997;26553- 573Article
7.
Spiegelman  BM PPAR-γ: adipogenic regulator and thiazolidinedione receptor. Diabetes. 1998;47507- 514Article
8.
Mueller  ESarraf  PTontonoz  P  et al.  Terminal differentiation of human breast cancer through PPAR γ. Mol Cell. 1998;1465- 470Article
9.
Kubota  TKoshizuka  KWilliamson  EA  et al.  Ligand for peroxisome proliferator-activated receptor γ (troglitazone) has potent antitumor effect against human prostate cancer both in vitro and in vivo. Cancer Res. 1998;583344- 3352
10.
Sarraf  PMueller  EJones  D  et al.  Differentiation and reversal of malignant changes in colon cancer through PPAR γ. Nat Med. 1998;41046- 1052Article
11.
Morikang  EBenson  SCKurtz  TWPershadsingh  HA Effects of thiazolidinediones on growth and differentiation of human aorta and coronary myocytes. Am J Hypertens. 1997;10440- 446
12.
Law  REMeehan  WPXi  XP  et al.  Troglitazone inhibits vascular smooth muscle cell growth and intimal hyperplasia. J Clin Invest. 1996;981897- 1905Article
13.
Dubey  RKZhang  HYReddy  SRBoegehold  MAKotchen  TA Pioglitazone attenuates hypertension and inhibits growth of renal arteriolar smooth muscle in rats. Am J Physiol. 1993;265R726- R732
14.
Varani  JNickoloff  BMRMitra  RDixit  VVoorhees  JJ All-trans retinoic acid stimulates growth of adult human keratinocytes cultured in growth factor deficient medium, inhibits production of thrombospondin and fibronectin and reduces adhesion. J Invest Dermatol. 1989;93449- 454Article
15.
Varani  JFligiel  SESchuger  L  et al.  Effects of all-trans retinoic acid and Ca++ on human skin in organ culture. Am J Pathol. 1993;142189- 198
16.
Varani  JKang  SStoll  SElder  JT Human psoriatic skin in organ culture: comparison with normal skin exposed to exogenous growth factors and effects on an antibody to the EGF receptor. Pathobiology. 1998;66253- 259Article
17.
Varani  JPerone  PGriffiths  CEInman  DRFligiel  SEVoorhees  JJ All-trans retinoic acid (RA) stimulates events in organ-cultured human skin that underlie repair: adult skin from sun-protected and sun-exposed sites responds in an identical manner to RA while neonatal foreskin responds differently. J Clin Invest. 1994;941747- 1756Article
18.
Varani  J Preservation of human skin structure and function in organ culture. Histol Histopathol. 1998;13775- 783
19.
Nickoloff  BJKunkel  SLBurdick  MStrieter  RM Severe combined immunodeficiency mouse and human psoriatic skin chimeras: validation of a new animal model. Am J Pathol. 1995;146580- 588
20.
Pershadsingh  HASproul  JABenjamin  EFinnegan  JANMAmin  NM Treatment of psoriasis with troglitazone therapy [letter]. Arch Dermatol. 1998;1341304- 1305Article
21.
Spencer  CMMarkham  A Troglitazone. Drugs. 1997;5489- 101Article
22.
Forman  BMTontonoz  PChen  JBrun  RPSpiegelman  BMEvans  RM 15-Deoxy-Δ 12, 14-prostaglandin J2 is a ligand for the adipocyte determination factor PPAR γ. Cell. 1995;83803- 812Article
23.
Kliewer  SALenhard  JMWillson  TMPatel  IMorris  DCLehmann  JM A prostaglandin J2 metabolite binds peroxisome proliferator-activated receptor γ and promotes adipocyte differentiation. Cell. 1995;83813- 819Article
24.
Stern  RS Psoriasis. Lancet. 1997;350349- 353Article
25.
Elbrecht  AChen  YLCullinan  CA  et al.  Molecular cloning, expression and characterization of human peroxisome proliferator activated receptors γ1 and γ2. Biochem Biophys Res Comm. 1996;224431- 437Article
26.
Mukherjee  RJow  LCroston  GEPaterniti Jr  JR Identification characterization, and tissue distribution of human peroxisome proliferator-activated receptor (PPAR) isoforms PPARγ2 versus PPARγ1 and activation with retinoid X receptor agonists and antagonists. J Biol Chem. 1997;2728071- 8076Article
27.
Rivier  MSafonova  IGriffiths  CEMAilhaud  GMicher  S Differential expression of peroxisome proliferator activated receptor subtypes during the differentiation of human keratinocytes. J Invest Dermatol. 1998;1111116- 1121Article
28.
Henseler  TChristophers  E Disease concomitance in psoriasis. J Am Acad Dermatol. 1995;32982- 986Article
29.
Ibrahimi  ATeboul  LGaillard  D  et al.  Evidence for a common mechanism of action for fatty acids and thiazolidinedione antidiabetic agents on gene expression in preadipose cells. Mol Pharmacol. 1994;461070- 1076
30.
Garner  WLOyatsu  YZuccaro  CRodriquez  JLSmith  DJMarcelo  CL The effect of essential fatty acid supplementation on keratinocyte replication. Prostaglandins Leukot Essent Fatty Acids. 1995;52349- 355Article
31.
Grimminger  FMayser  P Lipid mediators, free fatty acids and psoriasis. Prostaglandins Leukot Essent Fatty Acids. 1995;521- 15Article
32.
Zhang  FSowers  JRRam  JLStandley  PRPeuler  JD Effects of pioglitazone on calcium channels in vascular smooth muscle. Hypertension. 1994;24170- 175Article
33.
Van Ruissen  FVan de Kerkhof  PCSchalkwijk  J Signal transduction pathways in epidermal proliferation and cutaneous inflammation. Clin Dermatol. 1995;13161- 190Article
34.
Altiok  SXu  MSpiegelman  BM PPAR γ induces cell cycle withdrawal: inhibition of E2F/DP DNA-binding activity via down-regulation of PP2A. Genes Dev. 1997;111987- 1998Article
35.
Chinetti  GGriglio  SAntonucci  M  et al.  Activation of proliferator-activated receptors α and γ induces apoptosis in human monocyte-derived macrophages. J Biol Chem. 1998;27325573- 25580Article
36.
Elstner  EMuller  CKoshizuka  K  et al.  Ligands for peroxisome proliferator-activated receptor γ and retinoic acid receptor inhibit growth and induce apoptosis of human breast cancer cells in vitro and in BNX mice. Proc Natl Acad Sci U S A. 1998;958806- 8811Article
37.
Komine  MFreedberg  IMBlumenberg  M Regulation of epidermal expression of keratin K17 in inflammatory skin diseases. J Invest Dermatol. 1996;107569- 575Article
38.
Tomic-Canic  MKomine  MFreedberg  IMBlumenberg  M Epidermal signal transduction and transcription factor activation in activated keratinocytes. J Dermatol Sci. 1998;17167- 181Article
39.
Boehncke  WHWortmann  SKaufmann  RMielke  VSterry  W A subset of macrophages located along the basement membrane ("lining cells") is a characteristic histopathological feature of psoriasis. Am J Dermatopathol. 1995;17139- 144Article
40.
van den Oord  JJde Wolf-Peeters  C Epithelium-lining macrophages in psoriasis. Br J Dermatol. 1994;130589- 594Article
41.
Mizutani  HOhmoto  YMizutani  TMurata  MShimizu  M Role of increased production of monocytes TNF-α, IL-1β and IL-6 in psoriasis: relation to focal infection, disease activity and responses to treatments. J Dermatol Sci. 1997;14145- 153Article
42.
Ricote  MLi  ACWillson  TMKelly  CJGlass  CK The peroxisome proliferator-activated receptor-γ is a negative regulator of macrophage activation. Nature. 1998;39179- 82Article
43.
Jiang  CYTing  ATSeed  B PPAR-γ agonists inhibit production of monocyte inflammatory cytokines. Nature. 1998;39182- 86Article
44.
Schoonjans  KMartin  GStaels  BAuwerx  J Peroxisome proliferator-activated receptors, orphans with ligands and functions. Curr Opin Lipidol. 1997;8159- 166Article
45.
Mangelsdorf  DJThummel  CBeato  M  et al.  The nuclear receptor superfamily: the second decade. Cell. 1995;83835- 839Article
46.
Reichrath  JMunssinger  TKerber  A  et al.  In situ detection of retinoid-X receptor expression in normal and psoriatic human skin. Br J Dermatol. 1995;133168- 175Article
47.
Mukherjee  RDavies  PJCrombie  DL  et al.  Sensitization of diabetic and obese mice to insulin by retinoid X receptor agonists. Nature. 1997;386407- 410Article
48.
Ellis  CNKang  SVinik  AIGrekin  RCCunningham  WJVoorhees  JJ Glucose and insulin responses are improved in patients with psoriasis during therapy with etretinate. Arch Dermatol. 1987;123471- 475Article
49.
Yang  XYWang  LHChen  T  et al.  Activation of human T lymphocytes is inhibited by peroxisome proliferator-activated receptor γ (PPARγ) agonists: PPARγ co-association with transcription factor NAFT. J Biol Chem. 2000;2754541- 4544Article
50.
Clark  RBBishop-Bailey  DEstrada-Hernandez  THla  TPuddington  LPadula  SJ The nuclear receptor PPARγ and immunoregulation: PPARγ mediates inhibition of helper T cell responses. J Immunol. 2000;1641364- 1371Article
Study
May 2000

Troglitazone Improves Psoriasis and Normalizes Models of Proliferative Skin DiseaseLigands for Peroxisome Proliferator-Activated Receptor-γ Inhibit Keratinocyte Proliferation

Author Affiliations

From the Departments of Dermatology (Drs Ellis and Fisher) and Pathology (Drs Varani, Zeigler, and Chi), University of Michigan Medical School, Ann Arbor; the Department of Family Medicine, University of California, Irvine, and Kern Medical Center, Bakersfield, Calif (Dr Pershadsingh); the Department of Biological Sciences, California State University, Hayward (Dr Benson); and the Department of Laboratory Medicine, University of California, San Francisco (Dr Kurtz). Drs Ellis and Benson have served as ad hoc consultants for Bethesda Pharmaceuticals, Mill Valley, Calif. Drs Pershadsingh and Kurtz own stock in and are principals in Bethesda Pharmaceuticals.

Arch Dermatol. 2000;136(5):609-616. doi:10.1001/archderm.136.5.609
Abstract

Background  Psoriasis is often treated with agents that activate nuclear hormone receptors for glucocorticoids, retinoids, and vitamin D. The peroxisome proliferator-activated receptor-γ (PPARγ) is a related nuclear hormone receptor that can be activated by its ligands, including the thiazolidinediones.

Objective  To assess whether treatment with troglitazone, a currently available thiazolidinedione used to treat diabetes mellitus, has an effect on psoriasis in normoglycemic patients and whether ligands for PPARγ have an effect on models of psoriasis.

Design  Open-label administration of troglitazone in patients with psoriasis and evaluation of drug actions in cellular, organ, and transplant models of psoriasis.

Setting  University and community hospital outpatient departments and university laboratories.

Patients  Patients with chronic, stable plaque psoriasis and control subjects. Five patients with psoriasis received troglitazone (none withdrew); 10 different untreated patients and 10 controls provided tissue samples.

Interventions  Oral troglitazone therapy at various dosages in patients with psoriasis; also, use of troglitazone, ciglitazone, and 15-deoxy-Δ-12,14-prostaglandin J2 in psoriasis models.

Main Outcome Measures  Investigator-determined clinical results in patients and cell counts and histological evidence in models.

Results  All patients' psoriasis improved substantially during troglitazone therapy. Peroxisome proliferator-activated receptor-γ was expressed in human keratinocytes; ligands for PPARγ inhibited the proliferation of normal and psoriatic human keratinocytes in culture. Troglitazone treatment normalized the histological features of psoriatic skin in organ culture and reduced the epidermal hyperplasia of psoriasis in the severe combined immunodeficient mouse and human skin transplant model of psoriasis (P<.05 compared with untreated controls).

Conclusions  Peroxisome proliferator-activated receptor-γ might be a useful intracellular target for the treatment of psoriasis; further study is needed to assess the clinical value of ligands for PPARγ, including troglitazone.

PSORIASIS IS a common and often debilitating skin disorder that affects 1% to 2% of the US population.1 Disordered differentiation and hyperproliferation of keratinocytes with inflammation are the hallmarks of psoriasis; however, the pathophysiological features of this disorder are complex and its etiology is unknown.2,3 A variety of therapies are available for psoriasis.4 Nevertheless, because of problems with adverse effects and variability in clinical response, there is a desire for new treatments.

Nuclear hormone receptors have proved to be useful targets in the development of antipsoriatic drugs.5 Although ligands for such receptors (including glucocorticoid, retinoid, and vitamin D receptors) are commonly used as antipsoriatic agents, each of these treatments has limitations, and new therapeutic options in psoriasis are needed.4

The thiazolidinediones are a novel class of insulin-sensitizing agents used for the treatment of type 2 diabetes mellitus.6,7 Thiazolidinediones act as ligands for the peroxisome proliferator-activated receptor-γ (PPARγ), a member of the nuclear hormone receptor superfamily that includes the retinoic acid receptor and the vitamin D receptor. Ligand activation of PPARγ by thiazolidinediones can inhibit proliferation and promote differentiation in a variety of malignant and nonmalignant tissues,813 although the effects on skin are unknown.

In view of the antiproliferative effects of ligands for PPARγ, we gave troglitazone, a thiazolidinedione marketed in the United States, orally to patients with psoriasis. With this description of 2 normoglycemic patients, we now have treated 5 patients with troglitazone in an open fashion. We also report our investigations into the effects of ligands for PPARγ in experimental cellular and animal models of psoriasis.

PATIENTS, MATERIALS, AND METHODS
PATIENTS

Five patients with moderate to severe psoriasis provided informed consent for the new use of troglitazone for the treatment of psoriasis. Ten different untreated patients with psoriasis and 10 control subjects provided skin samples after giving informed consent. The University of Michigan Health System institutional review board approved the procedures. We used skin from any individual in only one of the studies described herein.

ANALYSIS OF PPARγ mRNA AND PROTEIN

Human epidermal keratinocytes (Clonetics Inc, San Diego, Calif) were grown in monolayer cultures.14 Peroxisome proliferator-activated receptor-γ messenger RNA (mRNA) was detected in human keratinocytes by reverse transcriptase–polymerase chain reaction (RT-PCR) analysis; PPARγ protein was detected by immunoblotting and immunocytochemical studies. For RT-PCR analysis, RNA was prepared from quiescent human keratinocytes and reverse transcribed to generate complementary DNA, which was amplified by PCR to detect message for PPARγ1 and PPARγ2. The primers used for PCR amplification of PPARγ1 were 5-′CTC GAG GAC ACC GGA GAG-3′ (upstream) and 5′-GTC ATT TCT GCG GCC ACG-3′ (downstream). These primers specifically amplify a 50–base pair fragment of the 5′ untranslated region of PPARγ1 (Genbank accession number X90563). The primers used to amplify PPARγ2 were 5′-GGT GAA ACT CTG GGA GAT TCT-3′ (upstream) and 5′-TGT AAT CTG CAA CCA CTG GAT-3′ (downstream).These primers amplify a 277–base pair fragment from the N-terminal region of PPARγ2 (Genbank accession number U63415). The PCR products were analyzed by 2.5% agarose gel electrophoresis.

Immunoblotting was performed after sodium dodecyl sulfate–polyacrylamide gel electrophoresis separation of keratinocyte protein extracts using a rabbit anti-PPARγ antibody and an enhanced chemiluminescence detection system (Amersham Corp, Arlington Heights, Ill). Immunofluorescence cytochemical analysis was performed on methanol-fixed and permeabilized keratinocytes using rabbit anti-PPARγ antibody and fluorescein isothiocyanate–labeled goat antirabbit IgG.

CELL CULTURE AND PROLIFERATION ASSAYS

Studies were performed with keratinocytes (obtained from Clonetics Inc or prepared from biopsy samples of skin of 8 controls and lesional skin of 5 patients with psoriasis) maintained in either keratinocyte basal medium (KBM) or keratinocyte growth medium (HyClone Laboratories, Logan, Utah). Each is a low Ca++ (0.15 mmol/L) modification of MCDB-153 medium; KBM contains no serum or exogenous growth factors, and keratinocyte growth medium is supplemented with several growth factors, including human recombinant epidermal growth factor (0.1 ng/mL), insulin (2.5 µg/mL), and pituitary extract (2% vol/vol). For proliferation assays, cells were plated in 24-well dishes at 2 × 104 cells per well. Twenty-four hours after attachment, troglitazone (Parke-Davis Pharmaceuticals, Ann Arbor, Mich), ciglitazone (Upjohn Co, Kalamazoo, Mich), 15-deoxy-Δ-12,14-prostaglandin J2 (Cayman Chemical Co, Ann Arbor), or dimethyl sulfoxide vehicle was added at indicated concentrations. Control and treated keratinocytes were incubated for 3 to 8 days and then counted. Cell numbers were determined in 6 replicates of each experimental condition using the MTS assay 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-H-tetrazolium as described in the CellTiter 96 Aqueous Non-Radioactive Cell Proliferation Assay (Promega Corp, Madison, Wis) or the neutral red dye assay. The effect of thiazolidinediones on the growth of human dermal fibroblasts in KBM supplemented with calcium, 1.4 mmol/L, was assessed using fibroblasts prepared from biopsy specimens of skin of 5 controls.

STUDIES IN ORGAN CULTURED HUMAN SKIN

Under serum-free conditions, normal and psoriatic human skin can be maintained in organ culture for days and abnormal histological features of psoriasis persist.1518 Pieces of skin from 2 controls and from psoriasis lesions from 2 patients were placed into wells of a 96-well dish containing 250 µL of culture medium. The culture medium consisted of KBM supplemented with calcium chloride to a final Ca++ concentration of 1.4 mmol/L. The tissue pieces were incubated at 37°C in 5% carbon dioxide and 95% air for 8 days with fresh culture medium as previously described.15,16,18 Various concentrations of troglitazone or dimethyl sulfoxide vehicle alone were added at days 2, 4, and 6. At the end of the incubation period, tissue pieces were fixed in 10% buffered formalin and embedded in paraffin. Sectioned tissues were stained with hematoxylin-eosin and evaluated by light microscopy.

STUDIES IN THE SEVERE COMBINED IMMUNODEFICIENT MOUSE AND HUMAN SKIN TRANSPLANT MODEL OF PSORIASIS

Human psoriasis skin engrafted onto severe combined immunodeficient (SCID) mice maintains its histological characteristics.19 Lesional psoriasis skin from 3 patients was obtained and divided into portions. One portion from each patient was reserved; the remaining tissue was divided and transplanted onto CB17 SCID mice as previously described.19 Each SCID mouse received 2 pieces of psoriatic skin from one of the human patients. The transplanted tissue was allowed to heal for 4 weeks, after which 11 animals (with 21 pieces of psoriasis; 1 piece did not survive) were fed once daily for 6 weeks with 200 µg of troglitazone dissolved in 300 µL of sugar-free gelatin dessert; 3 animals (with 6 pieces of psoriasis) fed plain gelatin dessert served as controls. At the end of treatment, the human skin pieces were removed, fixed in 10% buffered formalin, embedded in paraffin, sectioned, and stained with hematoxylin-eosin. Under light microscopy, we traced the epidermal boundaries and determined the area of the epidermis (in square micrometers) across 3 nonoverlapping regions (NIH Image software, version 1.61; National Institutes of Health, Bethesda, Md). The average of the 3 measurements is an index of epidermal hyperplasia of the psoriatic epidermis for each piece of skin.

STATISTICAL ANALYSIS

We compared counts of keratinocytes in culture at all concentrations for each experimental condition with counts of keratinocytes maintained under similar conditions (but without experimental agents added) by analysis of variance; we calculated the average of the epidermal hyperplasia indices for each patient for each "treatment" assignment in SCID mice (nontransplanted skin, transplanted skin on untreated mice, and transplanted skin on treated mice) and compared the means across treatment assignments by repeated-measures analysis of variance with the Tukey studentized range for pairwise comparisons (SigmaStat; SSPS Inc, Chicago, Ill). Differences were considered statistically significant at P<.05; data are given as mean±SE.

RESULTS
PATIENT REPORTS
Patient 1

A 37-year-old nondiabetic man who had chronic, generalized plaque psoriasis since age 14 years presented with 80% of his body surface involved with psoriasis (Figure 1). He began taking oral troglitazone (400 mg once daily for 5 weeks and 600 mg daily thereafter) without any other form of psoriasis therapy. After 5 weeks of troglitazone therapy, the patient showed a marked improvement in all lesions, and by 12 weeks his psoriasis was in nearly complete remission, with involvement of less than 5% of his body surface. This response has now been sustained for longer than 5 months with therapy (Figure 1). There were no adverse effects.

Patient 2

A 42-year-old nondiabetic man had chronic lesions of psoriasis over 30% of his body surface. Five months before presentation he was unresponsive to topical and systemic treatment with glucocorticoids. Oral administration of troglitazone, 200 mg/d for 2 weeks followed by 400 mg/d for 10 weeks, resulted in remission of psoriasis (Figure 2). Troglitazone use was continued for 12 additional weeks at 200 mg/d. Eight weeks after stopping therapy his psoriasis was still in remission. There were no adverse effects.

Patients 3-5

Patients with psoriasis and concomitant diabetes mellitus had improvement of both conditions under therapy with troglitazone, 400 to 600 mg/d; these patients have been described previously.20

PPARγ IS EXPRESSED IN HUMAN KERATINOCYTES

Immunofluorescence analysis of human keratinocytes treated with anti-PPARγ antibody revealed an intense signal in the nucleus and perinuclear region consistent with the expression of an intracellular receptor. Reverse transcriptase–polymerase chain reaction analysis demonstrated the presence of mRNA for both PPARγ1 and PPARγ2 isoforms in human keratinocytes; Western blot analysis of protein extracts using an antibody that reacts with both PPARγ isoforms revealed a distinct band corresponding to a protein of the expected size for PPARγ of 62 kd.

LIGANDS FOR PPARγ INHIBIT GROWTH OF NORMAL AND PSORIATIC HUMAN KERATINOCYTES BUT NOT DERMAL FIBROBLASTS

Use of the PPARγ ligand troglitazone inhibited in a dose-dependent manner the growth of normal and psoriatic keratinocytes maintained in serum-free media (P<.001 for each) (Figure 3, A). In normal keratinocytes maintained in supplemented growth media, higher concentrations of troglitazone were required for the antiproliferative effects (P<.001) (Figure 3, B). In all cases, inhibition of keratinocyte proliferation was observed with concentrations of troglitazone that can be attained in plasma during administration of standard oral doses of the drug for the treatment of type 2 diabetes mellitus.21 Use of ciglitazone, another thiazolidinedione, also inhibited proliferation of normal and psoriatic keratinocytes in a dose-dependent and saturable fashion (data not shown). In supplemented media, addition of the prostaglandin metabolite 15-deoxy-Δ-12,14-prostaglandin J2, a natural ligand for PPARγ,22,23 inhibited proliferation of cultured keratinocytes in a dose-dependent fashion (P<.001) (Figure 3, C). Thus, the inhibition of proliferation in keratinocytes likely represents a general effect of ligands for PPARγ and is not unique to thiazolidinediones. However, troglitazone treatment did not affect the growth of human dermal fibroblasts in serum-free media at any of the concentrations tested (P=.97) (Figure 3, D).

TROGLITAZONE AMELIORATES THE HISTOLOGICAL PHENOTYPE OF PSORIASIS WHEN IN ORGAN CULTURE OR TRANSPLANTED ONTO SCID MICE

After incubation for 8 days, the histological appearance of cultured normal skin resembled that of freshly biopsied skin, and lesional psoriatic skin in culture continued to express typical abnormal histological features (as seen in previous studies16,18). The abnormal phenotype of the psoriatic skin was qualitatively nearly normal in all organ cultures treated with 2.2 µmol of troglitazone; psoriasis tissue treated with 1.1 µmol of troglitazone showed similar changes, whereas tissue treated with 0.2 µmol of troglitazone did not.

The typical histological appearance of psoriasis was maintained in lesional psoriatic skin from 3 patients transplanted onto untreated control SCID mice (as validated previously19). In lesional psoriatic skin transplanted onto SCID mice treated with troglitazone orally, overall skin thickness was reduced, a more normal pattern of epidermal differentiation occurred, the granular layer (which is decreased or lacking in the untreated psoriatic skin) was present in much of the epidermis, and the inflammatory response was reduced (Figure 4). The index of epidermal hyperplasia was 70±6 × 104 µm2 for psoriatic skin not transplanted onto SCID mice, 74±2 × 104 µm2 for psoriatic skin transplanted onto untreated SCID mice (P>.05 compared with nontransplanted skin), and 49±2 × 104 µm2 for psoriatic skin transplanted onto troglitazone-treated SCID mice (P<.05 compared with nontransplanted and transplanted skin on untreated mice).

COMMENT

Ligands for nuclear hormone receptors expressed in skin (eg, retinoic acid, vitamin D, and glucocorticoid receptors) have proved to be of considerable value in the treatment of dermatologic diseases, including psoriasis.4,24 In the present studies, we found that thiazolidinedione ligands for the nuclear hormone receptor PPARγ might offer a new therapeutic approach to the management of psoriasis.

Peroxisome proliferator-activated receptor-γ was originally believed to be expressed in just a few tissues, including fat. However, recent studies25,26 in humans have demonstrated the presence of PPARγ in a variety of tissues. In a recent study,27 PPARγ was detected in keratinocytes by gel mobility shift and RT-PCR assays, and herein we demonstrate that human keratinocytes express mRNA and protein for the nuclear hormone receptor PPARγ.

In the present studies, we found that structurally different ligands for PPARγ inhibit human keratinocyte proliferation, a characteristic feature of psoriasis. We also found that troglitazone, a PPARγ ligand used to treat type 2 diabetes mellitus, ameliorates the abnormal histological phenotype of human psoriatic skin in culture and in an animal model in vivo.

In addition, we demonstrated that oral administration of troglitazone improved psoriasis in a few patients. Although troglitazone treatment has been associated with rare cases of hepatic failure, newer PPARγ ligands, such as pioglitazone hydrochloride and rosiglitazone, have not been reported to induce this adverse effect and may be better agents to try as psoriasis therapies.

The occurrence of psoriasis in patients with diabetes mellitus is not uncommon, and these conditions may coexist more often than predicted from the prevalence rates of either disorder alone.28 Three patients with type 2 diabetes mellitus and psoriasis had clinically significant improvement in their psoriatic lesions when we treated them with troglitazone.20

We have now observed antipsoriatic effects of troglitazone in 2 normoglycemic patients with moderate to severe chronic psoriasis. It would be unusual for stable, chronic plaque psoriasis to undergo such complete and sustained remissions as we observed in these patients either spontaneously or because of a placebo effect, suggesting that a troglitazone treatment–induced effect occurred.

The observation that several different ligands for PPARγ inhibit proliferation of keratinocytes, together with the important role of keratinocyte hyperproliferation in the pathogenesis of psoriasis, suggests that the antipsoriatic effects of troglitazone might be mediated at least in part by the antiproliferative effects of PPARγ activation. Certain fatty acids, such as linoleic acid, are weak activators of PPARγ and have also been shown to decrease the replication rate of cultured keratinocytes.29,30 Moreover, in some patients with psoriasis, dietary supplements of some fatty acids have been associated with lesion improvement.31

Thiazolidinediones may exert a host of other actions such as blockade of calcium channels and mitogen-activated protein kinase signaling pathways that could also affect cell proliferation and the pathogenesis of psoriasis independent of effects on PPARγ activation.12,32,33 However, others have provided compelling evidence that, at least in some cell lines, antiproliferative or apoptotic effects of thiazolidinediones are indeed mediated via PPARγ.3436 The inhibition of proliferation of keratinocytes is unlikely to represent simply a toxic effect of the drugs because the growth inhibitory effects are reversible on removal of the drugs from the culture medium (data not shown). In a variety of other normal cell lines studied under conditions similar to those used in keratinocytes, we and others1113,34 showed that the antiproliferative effects of these agents are reversible and are without obvious cytotoxic effects or effects on lactic dehydrogenase release, exclusion of trypan blue, or viability assays of mitochondrial function.

The mechanisms by which thiazolidinediones affect the cell cycle or programmed cell death may vary among different cell types. We did not find an effect of troglitazone on fibroblasts. This suggests that troglitazone's therapeutic benefit in psoriasis is not the result of interference with any putative dermal effect on the epidermis. We do not know whether the antiproliferative effects of PPARγ ligands in keratinocytes are mediated through the same intracellular pathways involved in the growth effects of these agents in breast, prostate, colon, vascular smooth muscle, and fat cells.

The pathophysiological features of psoriasis are complex, and the antipsoriatic effects of thiazolidinediones may involve more than just their effects on cell cycle control and proliferation of keratinocytes. Disordered cellular immunity involving inflammatory cytokines (eg, tumor necrosis factor α, interleukin [IL] 1, and IL-6) and proinflammatory transcription factors (eg, nuclear factor-κB, signal transducer and activator of transcription [STAT], and activator protein-1) have been implicated in the pathogenesis of psoriatic epidermal inflammation.3,33,37,38 Macrophages may interact with basal keratinocytes in the pathogenesis of psoriasis, and keratinocytes and monocytes may elaborate inflammatory cytokines, including IL-1, IL-2, IL-6, and tumor necrosis factor α.3941

Studies42,43 demonstrating anti-inflammatory effects of PPARγ ligands raise the possibility that the antipsoriatic effects of thiazolidinediones might also be mediated through inhibition of skin inflammation. Peroxisome proliferator-activated receptor-γ is markedly up-regulated in activated macrophages, and ligands for PPARγ can inhibit the activities of nuclear factor-κB, STAT, and activator protein-1, and down-regulate inflammatory cytokines such as tumor necrosis factor α.42,43

In our SCID mouse model, the inflammatory infiltrate in transplanted psoriatic skin was reduced during oral troglitazone therapy. Nevertheless, this may not have been a primary mechanism of the salutary effect of troglitazone on the skin transplant; our studies were not designed to determine whether ligands for PPARγ affect the immunologic determinants of psoriasis. Future studies of the anti-inflammatory effects of thiazolidinediones are warranted.

For ligands of PPARγ to affect the transcription of specific proteins and generate a biologic effect, PPARγ must associate with (ie, form a heterodimer with) another nuclear hormone receptor, the retinoid X receptor (RXR),44,45 which is also expressed in human keratinocytes.46 Peroxisome proliferator-activated receptor-γ–RXR heterodimers, together with one or both of their ligands (such as a thiazolidinedione for PPARγ or 9-cis retinoic acid for RXR), activate peroxisome proliferator response elements in DNA, leading to a change in protein transcription.

The cooperative interaction of PPARγ and RXR at the molecular level suggests that ligands for each might share several therapeutic effects. Indeed, retinoids have efficacy in dermatologic disorders, certain forms of cancer, and type 2 diabetes mellitus.47,48 In a similar fashion, thiazolidinediones, originally developed for the treatment of type 2 diabetes mellitus, are now being investigated for treatment of various skin disorders and selected malignancies. Our findings of antipsoriatic effects of PPARγ ligands in cell and animal models and patients suggest that ligands for PPARγ may be of clinical value in the treatment of psoriasis.

Since the manuscript was accepted for publication, others49,50 have reported that ligands of PPARγ inhibit T-cell activation and the production of IL-2. These findings support an immunomodulatory mechanism of action for ligands of PPARγ in the treatment of psoriasis.

In March 2000, the manufacturer of troglitazone voluntarily discontinued its sale in the United States because of reports of liver toxicity.

Back to top
Article Information

Accepted for publication September 30, 1999.

This work was supported by grant R41 AR44767 from the National Institutes of Health, Bethesda, Md, and by Bethesda Pharmaceuticals.

We thank Navin M. Amin, MD, for assistance and Ted A. Hamilton, MS(Biostat), for statistical support.

Reprints: Charles N. Ellis, MD, Department of Dermatology, University of Michigan Medical School, 1910 A. Alfred Taubman Center, 1500 E Medical Center Dr, Ann Arbor, MI 48109-0314.

References
1.
Sander  HMMorris  LFPhillips  CMHarrison  PEMenter  A The annual cost of psoriasis. J Am Acad Dermatol. 1993;28422- 425Article
2.
McKay  IALeigh  IM Altered keratinocyte growth and differentiation in psoriasis. Clin Dermatol. 1995;13105- 114Article
3.
Barker  JN The pathophysiology of psoriasis. Lancet. 1991;338227- 230Article
4.
Greaves  MWWeinstein  GD Treatment of psoriasis. N Engl J Med. 1995;332581- 588Article
5.
McKay  IAWinyard  PLeigh  IMBustin  SA Nuclear transcription factors: potential targets for new modes of intervention in skin disease. Br J Dermatol. 1994;131591- 597Article
6.
Henry  RR Thiazolidinediones. Endocrinol Metab Clin North Am. 1997;26553- 573Article
7.
Spiegelman  BM PPAR-γ: adipogenic regulator and thiazolidinedione receptor. Diabetes. 1998;47507- 514Article
8.
Mueller  ESarraf  PTontonoz  P  et al.  Terminal differentiation of human breast cancer through PPAR γ. Mol Cell. 1998;1465- 470Article
9.
Kubota  TKoshizuka  KWilliamson  EA  et al.  Ligand for peroxisome proliferator-activated receptor γ (troglitazone) has potent antitumor effect against human prostate cancer both in vitro and in vivo. Cancer Res. 1998;583344- 3352
10.
Sarraf  PMueller  EJones  D  et al.  Differentiation and reversal of malignant changes in colon cancer through PPAR γ. Nat Med. 1998;41046- 1052Article
11.
Morikang  EBenson  SCKurtz  TWPershadsingh  HA Effects of thiazolidinediones on growth and differentiation of human aorta and coronary myocytes. Am J Hypertens. 1997;10440- 446
12.
Law  REMeehan  WPXi  XP  et al.  Troglitazone inhibits vascular smooth muscle cell growth and intimal hyperplasia. J Clin Invest. 1996;981897- 1905Article
13.
Dubey  RKZhang  HYReddy  SRBoegehold  MAKotchen  TA Pioglitazone attenuates hypertension and inhibits growth of renal arteriolar smooth muscle in rats. Am J Physiol. 1993;265R726- R732
14.
Varani  JNickoloff  BMRMitra  RDixit  VVoorhees  JJ All-trans retinoic acid stimulates growth of adult human keratinocytes cultured in growth factor deficient medium, inhibits production of thrombospondin and fibronectin and reduces adhesion. J Invest Dermatol. 1989;93449- 454Article
15.
Varani  JFligiel  SESchuger  L  et al.  Effects of all-trans retinoic acid and Ca++ on human skin in organ culture. Am J Pathol. 1993;142189- 198
16.
Varani  JKang  SStoll  SElder  JT Human psoriatic skin in organ culture: comparison with normal skin exposed to exogenous growth factors and effects on an antibody to the EGF receptor. Pathobiology. 1998;66253- 259Article
17.
Varani  JPerone  PGriffiths  CEInman  DRFligiel  SEVoorhees  JJ All-trans retinoic acid (RA) stimulates events in organ-cultured human skin that underlie repair: adult skin from sun-protected and sun-exposed sites responds in an identical manner to RA while neonatal foreskin responds differently. J Clin Invest. 1994;941747- 1756Article
18.
Varani  J Preservation of human skin structure and function in organ culture. Histol Histopathol. 1998;13775- 783
19.
Nickoloff  BJKunkel  SLBurdick  MStrieter  RM Severe combined immunodeficiency mouse and human psoriatic skin chimeras: validation of a new animal model. Am J Pathol. 1995;146580- 588
20.
Pershadsingh  HASproul  JABenjamin  EFinnegan  JANMAmin  NM Treatment of psoriasis with troglitazone therapy [letter]. Arch Dermatol. 1998;1341304- 1305Article
21.
Spencer  CMMarkham  A Troglitazone. Drugs. 1997;5489- 101Article
22.
Forman  BMTontonoz  PChen  JBrun  RPSpiegelman  BMEvans  RM 15-Deoxy-Δ 12, 14-prostaglandin J2 is a ligand for the adipocyte determination factor PPAR γ. Cell. 1995;83803- 812Article
23.
Kliewer  SALenhard  JMWillson  TMPatel  IMorris  DCLehmann  JM A prostaglandin J2 metabolite binds peroxisome proliferator-activated receptor γ and promotes adipocyte differentiation. Cell. 1995;83813- 819Article
24.
Stern  RS Psoriasis. Lancet. 1997;350349- 353Article
25.
Elbrecht  AChen  YLCullinan  CA  et al.  Molecular cloning, expression and characterization of human peroxisome proliferator activated receptors γ1 and γ2. Biochem Biophys Res Comm. 1996;224431- 437Article
26.
Mukherjee  RJow  LCroston  GEPaterniti Jr  JR Identification characterization, and tissue distribution of human peroxisome proliferator-activated receptor (PPAR) isoforms PPARγ2 versus PPARγ1 and activation with retinoid X receptor agonists and antagonists. J Biol Chem. 1997;2728071- 8076Article
27.
Rivier  MSafonova  IGriffiths  CEMAilhaud  GMicher  S Differential expression of peroxisome proliferator activated receptor subtypes during the differentiation of human keratinocytes. J Invest Dermatol. 1998;1111116- 1121Article
28.
Henseler  TChristophers  E Disease concomitance in psoriasis. J Am Acad Dermatol. 1995;32982- 986Article
29.
Ibrahimi  ATeboul  LGaillard  D  et al.  Evidence for a common mechanism of action for fatty acids and thiazolidinedione antidiabetic agents on gene expression in preadipose cells. Mol Pharmacol. 1994;461070- 1076
30.
Garner  WLOyatsu  YZuccaro  CRodriquez  JLSmith  DJMarcelo  CL The effect of essential fatty acid supplementation on keratinocyte replication. Prostaglandins Leukot Essent Fatty Acids. 1995;52349- 355Article
31.
Grimminger  FMayser  P Lipid mediators, free fatty acids and psoriasis. Prostaglandins Leukot Essent Fatty Acids. 1995;521- 15Article
32.
Zhang  FSowers  JRRam  JLStandley  PRPeuler  JD Effects of pioglitazone on calcium channels in vascular smooth muscle. Hypertension. 1994;24170- 175Article
33.
Van Ruissen  FVan de Kerkhof  PCSchalkwijk  J Signal transduction pathways in epidermal proliferation and cutaneous inflammation. Clin Dermatol. 1995;13161- 190Article
34.
Altiok  SXu  MSpiegelman  BM PPAR γ induces cell cycle withdrawal: inhibition of E2F/DP DNA-binding activity via down-regulation of PP2A. Genes Dev. 1997;111987- 1998Article
35.
Chinetti  GGriglio  SAntonucci  M  et al.  Activation of proliferator-activated receptors α and γ induces apoptosis in human monocyte-derived macrophages. J Biol Chem. 1998;27325573- 25580Article
36.
Elstner  EMuller  CKoshizuka  K  et al.  Ligands for peroxisome proliferator-activated receptor γ and retinoic acid receptor inhibit growth and induce apoptosis of human breast cancer cells in vitro and in BNX mice. Proc Natl Acad Sci U S A. 1998;958806- 8811Article
37.
Komine  MFreedberg  IMBlumenberg  M Regulation of epidermal expression of keratin K17 in inflammatory skin diseases. J Invest Dermatol. 1996;107569- 575Article
38.
Tomic-Canic  MKomine  MFreedberg  IMBlumenberg  M Epidermal signal transduction and transcription factor activation in activated keratinocytes. J Dermatol Sci. 1998;17167- 181Article
39.
Boehncke  WHWortmann  SKaufmann  RMielke  VSterry  W A subset of macrophages located along the basement membrane ("lining cells") is a characteristic histopathological feature of psoriasis. Am J Dermatopathol. 1995;17139- 144Article
40.
van den Oord  JJde Wolf-Peeters  C Epithelium-lining macrophages in psoriasis. Br J Dermatol. 1994;130589- 594Article
41.
Mizutani  HOhmoto  YMizutani  TMurata  MShimizu  M Role of increased production of monocytes TNF-α, IL-1β and IL-6 in psoriasis: relation to focal infection, disease activity and responses to treatments. J Dermatol Sci. 1997;14145- 153Article
42.
Ricote  MLi  ACWillson  TMKelly  CJGlass  CK The peroxisome proliferator-activated receptor-γ is a negative regulator of macrophage activation. Nature. 1998;39179- 82Article
43.
Jiang  CYTing  ATSeed  B PPAR-γ agonists inhibit production of monocyte inflammatory cytokines. Nature. 1998;39182- 86Article
44.
Schoonjans  KMartin  GStaels  BAuwerx  J Peroxisome proliferator-activated receptors, orphans with ligands and functions. Curr Opin Lipidol. 1997;8159- 166Article
45.
Mangelsdorf  DJThummel  CBeato  M  et al.  The nuclear receptor superfamily: the second decade. Cell. 1995;83835- 839Article
46.
Reichrath  JMunssinger  TKerber  A  et al.  In situ detection of retinoid-X receptor expression in normal and psoriatic human skin. Br J Dermatol. 1995;133168- 175Article
47.
Mukherjee  RDavies  PJCrombie  DL  et al.  Sensitization of diabetic and obese mice to insulin by retinoid X receptor agonists. Nature. 1997;386407- 410Article
48.
Ellis  CNKang  SVinik  AIGrekin  RCCunningham  WJVoorhees  JJ Glucose and insulin responses are improved in patients with psoriasis during therapy with etretinate. Arch Dermatol. 1987;123471- 475Article
49.
Yang  XYWang  LHChen  T  et al.  Activation of human T lymphocytes is inhibited by peroxisome proliferator-activated receptor γ (PPARγ) agonists: PPARγ co-association with transcription factor NAFT. J Biol Chem. 2000;2754541- 4544Article
50.
Clark  RBBishop-Bailey  DEstrada-Hernandez  THla  TPuddington  LPadula  SJ The nuclear receptor PPARγ and immunoregulation: PPARγ mediates inhibition of helper T cell responses. J Immunol. 2000;1641364- 1371Article
×