Dissection of the role of paeoniflorin in the traditional Chinese medicinal formula Si-Ni-San against contact dermatitis in mice

AimsThe roles of specific active ingredients in Chinese medicinal formulas have not been clearly elucidated. In this study, we selectively deleted and replenished paeoniflorin from Si-Ni-San, a traditional Chinese prescription, and aimed to identify the molecular basis of how paeoniflorin exerted its effect in Si-Ni-San.Main methodsContact dermatitis was induced in mice with picryl chloride. Paeoniflorin was selectively deleted from Si-Ni-San by an immunoaffinity column. Quantitative real-time PCR, western blot, and enzyme-linked immunosorbent assay were used in this study.Key findingsBoth Si-Ni-San and paeoniflorin significantly reduced ear swelling in mice while the paeoniflorin-deleted Si-Ni-San (Si-Ni-SanPF−) showed little ameliorative effect. In lipopolysaccharide-evoked macrophages, Si-Ni-San and paeoniflorin markedly inhibited tumor necrosis factor-α production, cyclooxygenase-2 activity, as well as extracellular signal-regulated kinase 1/2 phosphorylation while Si-Ni-SanPF− exhibited no or slight inhibitory effect. Furthermore, the inhibitory effect on the production of tumor necrosis factor-α reappeared when different proportions of paeoniflorin were replenished in Si-Ni-SanPF−. In addition, the expression of macrophage migration inhibitory factor in T cells, rather than macrophages, was significantly inhibited by Si-Ni-San, but not Si-Ni-SanPF−. Our data indicate paeoniflorin is the principal component of Si-Ni-San, exerting negative regulation on the function of macrophages in contact dermatitis.SignificanceThe present study suggests that dissecting the role of specific constituents in medicinal formulas through selective deletion and replenishment may be a useful strategy in recognizing and validating an active ingredient in traditional Chinese medicine.