Troglitazone improves psoriasis and normalizes models of proliferative skin disease -: Ligands for peroxisome proliferator-activated receptor-γ inhibit keratinocyte proliferation

Background: Psoriasis is often treated with agents that activate nuclear hormone receptors for glucocorticoids, retinoids, and vitamin D. The peroxisome proliferator-activated receptor-gamma (PPAR gamma) 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 PPAR gamma 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-Delta-12,14-prostaglandin J(2) 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-gamma was expressed in human keratinocytes; ligands for PPAR gamma 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-gamma might be a useful intracellular target for the treatment of psoriasis; further study is needed to assess the clinical value of ligands for PPAR gamma, including troglitazone.