Resolution of endothelial activation and down-regulation of Tie2 receptor in psoriatic skin after infliximab therapy

Abstract

Psoriasis is a common dermatosis characterized by erythematous skin plaques and associated arthritis. Microvessels of the papillary dermis in psoriatic lesions are elongated, tortuous, and dilated, which contributes significantly to the proinflammatory response. Angiopoietin (Ang) 1 and 2 and their receptor, Tie2, are a family of growth factors recognized in inflammatory lesions to be critical for new blood vessel growth and maintenance, with recent studies suggesting tumor necrosis factor (TNF)-alpha-induced angiogenesis is in part mediated by the Tie2 receptor. The aim of this study was to evaluate the effect of anti-TNF-alpha therapy on angiogenic growth factor expression and on the cellular infiltrate in psoriatic lesional skin. Sixteen patients with moderate to severe psoriasis and associated psoriatic arthritis (n = 13) received infliximab infusions (3-5 mg/kg) at baseline and at 2 and 6 weeks. Clinical assessments and skin biopsies were undertaken at baseline, and at 2 and 12 weeks. Ang 1, Ang 2, Tie2, and TNF-alpha messenger RNA expression were quantified by real-time polymerase chain reaction. Protein expression of vascular endothelial growth factor, Ang 2, Tie2, TNF-alpha, and the inflammatory infiltrate was determined using immunohistology. We conducted clinical assessments including Psoriasis Area and Severity Index, percentage body surface area, Arthritis Disease Activity Score, and Health Assessment Questionnaire. At baseline expression of Ang 1/2, vascular endothelial growth factor, Tie2, and TNF-alpha messenger RNA and protein were greater in preinvolved skin compared with uninvolved skin (P < .05). Infliximab produced a significant reduction in protein expression of Ang 2, vascular endothelial growth factor, and Tie2 (P < .001) along with a decrease in messenger RNA expression of Ang 1 (P < .045) and Tie2 (P < .021). This was paralleled by a significant reduction in the inflammatory infiltrate scores (P < .001) and platelet-endothelial cell adhesion molecule (CD31) expression (P = .001), suggesting deactivation of endothelial cell. There was a 93% mean reduction in Psoriasis Area and Severity Index (P = .001), and a significant reduction in Disease Activity Score 28 (P = .012) and mean Health Assessment Questionnaire scores by week 12. This study involves a small number of patients. These results suggest infliximab is both effective and well tolerated in severe psoriasis, resulting in deactivation of endothelium and down-regulation of growth factor and cytokine expression, leading to a decrease in the cellular infiltrate and clinical improvement in psoriasis. Furthermore, the effect of infliximab on growth factor expression, in particular Tie2, supports previous in vitro work suggesting TNF-alpha may be a major regulator of the Ang/Tie2 pathway.