The Related Mechanisms Predicted through Network-Based Pharmacological Analysis and the Anti-Inflammatory Effects of Fraxinus rhynchophylla Hance Bark on Contact Dermatitis in Mice

Abstract

Fraxinus rhynchophylla Hance bark has been used to treat patients with inflammatory or purulent skin diseases in China, Japan, and Korea. This study was undertaken to determine the mechanism responsible for the effects of F. rhynchophylla and whether it has a therapeutic effect in mice with contact dermatitis (CD). In this study, the active compounds in F. rhynchophylla, their targets, and target gene information for inflammatory dermatosis were investigated using network-based pharmacological analysis. Docking analysis was conducted using AutoDock Vina. In addition, the therapeutic effect of an ethanolic extract of F. rhynchophylla (EEFR) on skin lesions and its inhibitory effects on histopathological abnormalities, inflammatory cytokines, and chemokines were evaluated. Finally, its inhibitory effects on the nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signalling pathways were observed in RAW 264.7 cells. In our results, seven active compounds were identified in F. rhynchophylla, and six were associated with seven genes associated with inflammatory dermatosis and exhibited a strong binding affinity (<-6 kcal/mol) to prostaglandin G/H synthase 2 (PTGS2). In a murine 1-fluoro-2,4-dinitrobenzene (DNFB) model, topical EEFR ameliorated the surface symptoms of CD and histopathological abnormalities. EEFR also reduced the levels of tumour necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-6, and monocyte chemotactic protein (MCP)-1 in inflamed tissues and inhibited PTGS2, the nuclear translocation of NF-κB (p65), and the activation of c-Jun N-terminal kinases (JNK) in RAW 264.7 cells. In conclusion, the bark of F. rhynchophylla has potential use as a therapeutic or cosmetic agent, and the mechanism responsible for its effects involves the suppression of inflammatory mediators, nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor (IκB)-α degradation, the nuclear translocation of NF-κB, and JNK phosphorylation.

Keywords: Fraxinus rhynchophylla; dermatosis; inflammation; skin; traditional medicine.

Figure 1

Seven active compounds and target genes in F. rhynchophylla.

Figure 2

Six active compounds with targets associated with inflammatory dermatosis.

Figure 3

Binding modes of six active compounds and COX-2 Macromolecule (grey cartoon) means COX-2.

Figure 4

Effects of EEFR on skin lesions, thickness, and color in CD mice. Skin lesions were observed using a digital camera. (a), Treatment-naïve (NOR); (b), CD control (CTL); (c), 60 µg/day EEFR; (d), 180 µg/day EEFR; (e), 600 µg/day EEFR; and (f), 150 μg/day DEX (A). Skin surface scores were used to assess symptom severities (B). Weights of 5 mm diameter skin samples were measured using a micro-balance (C). Erythema and melanin indices were determined using a dermo-spectrophotometer (D,E). EEFR, ethanolic extract of Fraxinus rhynchophylla bark; DEX, dexamethasone. Results are presented as means ± standard deviation (SD)s. ^## p < 0.01 and ^### p < 0.001 vs. NOR; * p < 0.05 and ** p < 0.01 vs. CTL.

Figure 5

Effects of EEFR on histopathological abnormalities in inflamed tissues. The sequence is the same as in Figure 4A. The yellow bars indicate epidermal thicknesses (original magnification ×100) (A). Histogram showing mean epidermal thicknesses (B) and numbers of infiltrating immune cells (C) in the six study groups. Abbreviations are as defined in Figure 4. Results are presented as means ± SDs. ^## p < 0.01 vs. NOR; * p < 0.05 vs. CTL.

Figure 6

Effects of EEFR on cytokines and chemokines in inflamed tissues. Levels of cytokines and chemokines were evaluated using the cytometric bead array (CBA) method. (A) TNF-α; (B) IFN-γ; (C) IL-6; (D) MCP-1. N.D. means not detectable; abbreviations are as defined in Figure 4. Results are presented as means ± SDs. ^## p < 0.01 and ^### p < 0.001 vs. NOR; * p < 0.05 vs. CTL.

Figure 7

Effects of EEFR on LPS-induced increases on the expression of pro-inflammatory cytokines and COX-2, and on the NF-κB and MAPK signalling pathways in RAW 264.7 cells. Pro-inflammatory cytokine, chemokine, and COX-2 expressions were assessed with RT-PCR (A). Levels of IκB-α in cytoplasm (B), p65 in nuclear fractions (C), and MAPK signalling molecules (D) were determined using Western blots.