A Botanical Mixture of <i>Boswellia serrata</i> , <i>Commiphora myrrha</i> , Propolis and <i>Scutellaria baicalensis</i> Reduces Expression of Inflammatory Chemokines in Canine Keratinocytes In Vitro

BACKGROUND: Botanical ingredients can function as adjunctive therapies for managing inflammatory skin diseases. OBJECTIVES: This study aimed to investigate the anti-inflammatory effects of a mixture of Boswellia serrata, Commiphora myrrha, propolis and Scutellaria baicalensis (YSK-AB) on canine keratinocytes in vitro. METHODS: High-performance liquid chromatography (HPLC) was used to identify major components of YSK-AB. In addition, to evaluate nitric oxide (NO) production, RAW 264.7 cells were treated with YSK-AB (25, 50, 100 and 200 µg/mL) for 24 h, subsequently stimulated with lipopolysaccharide (1 µg/mL). To analyse the cytotoxic effects of YSK-AB, canine progenitor epidermal keratinocytes (CPEKs) were incubated with YSK-AB for 48 h. To investigate the effects of YSK-AB on cytokine expression, CPEKs were incubated with YSK-AB for 24 h and then stimulated with a mixture of interferon-γ and tumour necrosis factor-α (30 ng/mL each) for 24 h. The enzyme-linked immunosorbent assay (ELISA) was performed to measure chemokine (C-C motif) ligand 2 (CCL2) and CCL5. Real-time polymerase chain reaction (PCR) was used to quantify CCL17 mRNA expression. RESULTS: HPLC analysis identified four components in YSK‑AB, including 6‑hydroxy‑2,6‑dimethylhepta‑2,4‑dienal, baicalin, galangin and AKBA. CPEKs treated with 100, 150, 200 and 250 µg/mL of YSK‑AB exhibited significantly higher viability than that of the control group. In addition, YSK‑AB treatment (50, 100 and 200 µg/mL) significantly reduced NO production in RAW 264.7 cells. Furthermore, CCL17 mRNA expression and CCL2 and CCL5 protein levels were significantly reduced in YSK‑AB‑treated CPEKs compared with the control. CONCLUSIONS: YSK-AB downregulates the expression of chemokines produced by canine keratinocytes and could be a potential novel natural product-derived therapeutic agent for alleviating inflammatory skin diseases in dogs.