Mechanistic Study of Indigo naturalis in Treating Psoriasis---Short-Term Manipulation of Inflammation or Long-Term Induction of Immunoregulation

Psoriasis is a chronic inflammatory dermatosis induced by altered interactions between the immune system and skin and characterized by hyperplasia of the epidermis (acanthosis), infiltration of leukocytes into both the dermis and epidermis, and dilation and growth of blood vessels. Our previous studies have shown that topical application of indigo naturalis significantly improves psoriatic symptoms and demonstrated that the anti-psoriatic effects of indigo naturalis are mediated by promoting differentiation and inhibiting proliferation of epidermal keratinocytes. However, the potential effect of indigo naturalis on the immune system is unknown. Currently, growing evidence demonstrates that activated T cells are the primary modulators in the pathogenesis of psoriasis and psoriasis is believed to be a mixed Th1/Th17 disease with strong IL-17and interferon-γ (IFN-γ) signatures. The identification of elevated levels of IFN-γ, tumor necrosis factor (TNF-α), IL-12, IL-17 and IL 22 in cutaneous lesions and in the serum of psoriatic patients supports the theory that these Th1/Th17-related cytokines directly or indirectly act on keratinocytes leading to their activation and hyperproliferation. We suppose the therapeutic effect of indigo naturalis in psoriasis may involve inhibiting the activation of Th1 and Th17 cells that produce pro-inflammatory cytokines, thereby regulating the hyperplasia of epidermis induced by Th1/Th17 related cytokines. To test this hypothesis, this third-year proposal is designed to determine whether the efficacy of indigo naturalis in treating psoriasis is in part due to inhibiting pro-inflammatory cytokines produced by Th1/Th17 cells, using peripheral blood and lesional psoriasis samples from patients undergoing treatment with indigo naturalis ointment. We will compare the expressions of IL-17 and IFN-γ or other Th1/Th17 related cytokines from 20 patients with psoriasis before treatment, and while being treating with indigo naturalis ointment at week 8 and week 16. Intracellular cytokines will be quantified by flow cytometry and plasma cytokines will be measured by enzyme-linked immunosorbent assay (ELISA). The expressions of PCNA, involucrin, CD3, CD4, IFN-γ, IL-17, and IL-22 in psoriatic lesional skin at pre- and post-treatment will be analyzed by immunofluorescence. Furthermore, we will also investigate the effect of recombinant cytokines and cultured medium collected from peripheral blood mononuclear cells of patients pre- and post-treatment with indigo naturalis on cultured epidermal keratinocytes, and explore the effect of indigo naturalis on IFN-γ, IL-17 and IL-22 produced by activated mononuclear cells of patients with psoriasis. We expect indigo naturalis may regulate the expression of T1/Th17 related pro-inflammatory cytokines in peripheral blood and skin lesions in patients with psoriasis. These results should not only improve our understanding of the pharmacologic mechanism of indigo naturalis in psoriatic treatment but also suggest applications in the treatment of other autoimmune dermatoses, such as atopic dermatitis, in the future.

Project ID:PC10108-0821
External Project ID:NSC101-2320-B182A-009-MY3