Rutaecarpine ameliorates imiquimod-induced psoriasis-like dermatitis in mice associated with alterations in the gut microbiota

Abstract

Psoriasis is accepted as a chronic, inflammatory, immune-mediated skin disease triggered by complex environmental and genetic factors. For a long time, disease recurrence, drug rejection, and high treatment costs have remained enormous challenges and burdens to patients and clinicians. Natural products with effective immunomodulatory and anti-inflammatory activities from medicinal plants have the potential to combat psoriasis and complications. Herein, an imiquimod (IMQ)-induced psoriasis-like dermatitis model is established in mice. The model mice are treated with 1% rutaecarpine (RUT) (external use) or the oral administration of RUT at different concentrations. Furthermore, high-throughput 16S rRNA gene sequencing is applied to analyze the changes in the diversity and composition of the gut microbiota. Based on the observation of mouse dorsal skin changes, RUT can protect against inflammation to improve psoriasis-like skin damage in mice. Additionally, RUT could suppress the expression levels of proinflammatory cytokines (IL-23, IL-17A, IL-22, IL-6, and IFN-α) within skin tissue samples. Concerning gut microbiota, we find obvious variations within the composition of gut microflora between IMQ-induced psoriasis mice and RUT-treated psoriasis mice. RUT effectively mediates the recovery of gut microbiota in mice induced by IMQ application. Psoriasis is linked to the production of several inflammatory cytokines and gut microbiome alterations. This research shows that RUT might restore gut microbiota homeostasis, reduce inflammatory cytokine production, and ameliorate psoriasis symptoms. In conclusion, the gut microbiota might be a therapeutic target or biomarker for psoriasis that aids in clinical diagnosis and therapy.

Keywords: gut microbiota; inflammatory factor; psoriasis; rutaecarpine (RUT).

Figure 1

Rutaecarpine (RUT) ameliorated imiquimod (IMQ)-induced psoriasis-like skin damage in mice (A) Schematic diagram of model establishment and RUT administration. (B) Mice were grouped into control, IMQ, IMQ+Matrix excipient, IMQ+1% RUT, IMQ+oral phosphate-buffered saline (PBS) and 20/40/80 mg/kg/d RUT groups; the appearance of the dorsal skin was examined. (C) The psoriasis area and severity index (PASI) score evaluations. (D) Hematoxylin and eosin (H&E) staining for pathological changes (50×, 100×). Data are presented as the mean±standard deviation (SD) of three independent experiments. Scale bar: 100 or 200 μm. n=6, *P<0.05, **P<0.01 compared to the control group; #P<0.05, ##P<0.01 compared to the IMQ+matrix excipient group; &&P<0.01 compared to the IMQ+PBS excipient group.

Figure 2

RUT downregulated inflammatory cytokines in IMQ-induced psoriasis-like mice (A) Immunohistochemistry (IHC) assays (left) and corresponding quantitative analysis (right) were performed to measure the levels of IL-23 and IL-17A in skin tissues from different groups (200×). Scale bar: 50 μm. (B) qRT-PCR was used to analyze the mRNA expressions of inflammatory cytokines (IL-23, IL-17A, IL-22, IL-6, and IFN-α) in skin tissues. (C) Western blot analysis was used to detect the protein levels of inflammatory cytokines (IL-23, IL-17A, IL-22, IL-6, and IFN-α). Data are presented as the mean±SD of three independent experiments. n=6, *P<0.05, **P<0.01 compared to the control group; #P<0.05, ## P<0.01 compared to the IMQ+Matrix excipient group; & P<0.05, &&P<0.01 compared to the IMQ+PBS excipient group.

Figure 3

RUT affected the diversity of the gut microbiota in psoriasis-like dermatitis mice (A) The rank abundance curve was used to evaluate sequencing depth. (B,C) The α-diversity and β-diversity analysis of gut microbiota was performed. (D) Venn diagram showing changes in the number of gut microbiota. (E) The relative abundance of gut microbiota at the phylum level. n=6.

Figure 4

RUT affected the composition and abundance of the gut microbiota (A) Heatmap analysis showing the relative abundance of the top 20 genera-phylum gut microbiota in different samples/groups. (B) Relative abundance of gut microbiota at the genus level. n=6.

Figure 5

RUT altered the structure of the gut microbiota (A) Principal component analysis (PCA) was used to analyze the diversity of gut microbiota. (B) Nonmetric multidimensional scaling (NMDS) was used to analyze the differences between groups. (C) The abundance of gut microbiota changes is shown at the species level. n=6.