Anti-psoriasis effect of water-processed rosin in mice

Ethnopharmacological relevance Rosin, an exudate of conifer trees such as Pinus masscnlana (Pinaceae), has been used to treat psoriasis for nearly two thousand years in China despite its so far undefined pharmacology. Unfortunately, the rosin intoxication is noted from time to time, but the water-boiled rosin (WBR) has been documented to be safer. This study was performed to evaluate the in vivo anti-psoriasis efficacy of WBR. Materials and methods The main phytochemicals in WBR were quantified by high performance liquid chromatography (HPLC). WBR was evaluated in the imiquimod-induced psoriasis-like inflammation mouse model for its anti-psoriasis effect at 130, 260, and 390 mg/kg, which were set according to the dose used for patients. Through a combination of q-PCR, flow cytometry, and histopathological and immunohistochemical (IHC) analysis, the in vivo efficacy was assessed in terms of the psoriasis area severity index (PASI), epidermal keratinocyte proliferation, Th1 and Th17 cell numbers in spleen, and mRNA expressions of inflammatory cytokines. Result Oral administration of WBR ameliorates the psoriasis-like dermatitis in the imiquimod-generated mouse model. In particular, WBR given at 260 or 390 mg/kg significantly restores the normal keratinization of dorsal lesion if compared with the untreated psoriatic mice. Such an effect was addressed to correlate to the Th1/Th17 cell reduction in spleen and the suppressed expression of IL-17A, IL-17F, IL-22, IL-23, TNF-α, K17, and proliferating cell nuclear antigen (PCNA) after the WBR administration. Conclusion WBR is effective in the imiquimod-induced psoriasis-like inflammation mouse model with the efficacy arising from its proliferation inhibition of Th1/Th17 cells and epidermal keratinocytes via the down-regulation of the relevant inflammatory cytokines such as IL-23, IL-17A, and IL-17F. Collectively, WBR harvested and processed in the traditional manner is an efficacious psoriasis-treating agent.