Dimethyl sulfoxide (dmso)

All animal care and the experiments were approved and conducted at the National Chung Hsing University (IACUC No.:111-056) according to the guidelines for the care and use of laboratory animals. Eight- to ten-week-old female BALB/c mice were housed in a regular setting with unrestricted access to food and water. Imiquimod (IMQ, Ensign Laboratories Pty Ltd., Mulgrave, Australia) was routinely used to produce psoriasis in the mouse model [20 (link)]. The dorsal skin of the mice was shaved, and 5% IMQ cream was applied topically at a dosage of 62.5 mg per 5 cm² for six consecutive days. IRh at levels of 50 and 100 mg/kg (ChemFaces, Wuhan, China) dissolved in DMSO and glyceryl trioctanoate (10:90 v/v) was administered intragastrically one day before IMQ therapy started and again daily until the sixth day of the IMQ application (IRh 50 and 100 mg/kg/day, in IMQ-IRh-50 and IMQ-IRh-100 groups, respectively). In addition to IRh, 10% DMSO (JTBaker, Phillipsburg, NJ, USA) and 90% glyceryl trioctanoate (Sigma-Aldrich, St. Louis, MO, USA) were administered intragastrically to the mice in the IMQ + vehicle (IMQ-V) group. Mice in the naïve group were simply shaved without pharmacological treatment.

Dulbecco’s Modified Eagle Medium (DMEM) and fetal bovine serum were purchased from Gibco (Grand Island, NY, USA). RPMI 1640 medium came from Cytiva (Marlborough, MA, USA), and penicillin/streptomycin antibiotics came from Invitrogen (Carlsbad, CA, USA). EZ-Cytox reagent was obtained from DoGenBio (Seoul, South Korea). Griess reagent, dimethyl sulfoxide (DMSO), protocatechuic acid, and lipopolysaccharide (LPS) were purchased from Sigma-Aldrich (St. Louis, MO, USA). The ELISA kits for PGE₂, TNF-α, IL-6, IL-8, and IL-1β were purchased from R&D Systems, Inc. (Minneapolis, MN, USA). Isookanin was obtained from ChemFaces Biochemical Co. Ltd. (Wuhan, Hubei, China), and dissolved in DMSO. The luciferase assay system and lipofectamine™ 3000 reagent were purchased from Promega Co. (Madison, TN, USA) and Invitrogen (Waltham, MA, USA), respectively. Mitogen-activated protein kinases (MAPKs) antibodies (p-ERK1/2, ERK1/2, p-p38, p38, p-SAPK/JNK, SAPK/JNK) were purchased from Cell Signaling Technology, Inc. (Danvers, MA, USA), while secondary antibodies were purchased from Santa Cruz Biotechnology, Inc. (Dallas, TX, USA).