Inhibition of imiquimod-induced psoriasis-like dermatitis in mice by herbal extracts from some Indian medicinal plants

Abstract

Psoriasis is a chronic autoimmune human skin disorder that is characterized by excessive proliferation of keratinocytes, scaly plaques, severe inflammation and erythema. The pathophysiology of psoriasis involves interplay between epidermal keratinocytes, T lymphocytes, leukocytes and vascular endothelium. Increased leukocyte recruitment and elevated levels of cytokines, growth factors and genetic factors like interleukin (IL)-1β, IL-6, IL-17, IL-22, IL-23, tumour necrosis factor (TNF)-α, interferon (IFN)-γ, transforming growth factor (TGF)-β, toll-like receptor (TLR)-2, signal transducer and activator of transcription (STAT-3), 15-lipoxygenase (LOX)-2, coiled-coil alpha-helical rod protein 1 (CCHCR1), steroidogenic acute regulatory protein (StAR) and vitamin D receptor (VDR) are the most critical factors governing the exacerbation of psoriasis. In the present study, an attempt was made to elucidate the preventive role of herbal extracts of four dermo-protective Ayurvedic plants, Tinospora cordifolia (TC), Curcuma longa (CL), Celastrus paniculatus (CP) and Aloe vera (AV), against psoriasis-like dermatitis. Parkes (P) strain mice were initially induced with psoriasis-like dermatitis using topical application of imiquimod (IMQ, 5 %), followed by subsequent treatment with the herbal extracts to examine their curative effect on the psoriasis-like dermatitis-induced mice. The extracts were orally/topically administered to mice according to their ED/LD50 doses. Phenotypical observations, histological examinations, and semi-quantitative reverse transcription PCR (RT-PCR) analyses of the skin and blood samples of the control, IMQ-treated and herbal extract-treated psoriasis-like dermatitis-induced mice lead to the conclusion that the combination extract from all the plants was instrumental in downregulating the overexpressed cytokines, which was followed by the CL extract. Moreover, lesser yet positive response was evident from CP and TC extracts. The results suggest that these plants can prove to have tremendous preventive potential against the disease and can open the way to new therapeutic strategies for psoriasis treatment.

Keywords: Ayurvedic plants; Cytokines; Histopathology; Interleukins; Psoriasis-like dermatitis; Semi-quantitative RT-PCR.