Assessing Antipsoriatic Effects of Bitter Pu’er Tea and Its Three Major Compounds, Strictinin, Theacrine and Epigallocatechin Gallate, in Imiquimod-Treated Mice

Psoriasis is a chronic inflammatory skin disease with hyperproliferation and aberrant differentiation of keratinocytes in association with the elevation of interleukin-17A (IL-17A) and IL-23 levels. In an animal model, psoriasis-like dermatitis was induced on the shaved dorsal skin of BALB/c mice by topical application of imiquimod (IMQ), a synthetic ligand of Toll-like receptor 7. Administration of bitter Pu’er tea significantly reduced psoriasis-like dermatitis in IMQ-treated mice, including a reduction in dorsal skin lesions, splenomegaly and the mRNA expression levels of IL-17A and IL-23. To examine putative antipsoriatic constituents, three major compounds in bitter Pu’er tea, strictinin, theacrine and epigallocatechin gallate (EGCG), were separately given as supplements to IMQ-treated mice. The results showed that all the three compounds attenuated the severity of psoriasis by reducing epidermal thickness. Only theacrine significantly attenuated splenomegaly. All the three compounds inhibited the expression of IL-23 mRNA in the skin as well as reduced the content of IL-17A+CD4+ T cells in the spleen, and strictinin was found to be relatively effective. It seemed that the antipsoriatic activity of bitter Pu’er tea was attributed to the additive effects of its multiple active compounds.