A high performance liquid chromatography(HPLC) method was established to analyze the components in Shengjiang Powder(SJP) such as emodin and curcumin and explore its therapeutic effect on experimental autoimmune encephalomyelitis(EAE) mice. To be specific, HPLC was performed to determine the content of compounds in SJP such as emodin and curcumin. A total of 72 female SPF C57 BL/6 mice were randomized into control group(equivalent volume of ultrapure water, ig), model group(equivalent volume of ultrapure water, ig), low-, medium-, and high-dose SJP groups(SJP, ig), and positive control group(prednisone acetate, ig), 12 each group. EAE was induced in mice except the control group. Administration began from the first day after immunization. The general conditions, symptom score, and body weight of the mice were recorded. On the 21 st day, mouse brain tissues were separrated. Then hematoxylin-eosin(HE) staining and Luxol Fast Blue(LFB) staining were used to detect the pathological changes of brain tissues. Immunohistochemistry(IHC) was employed to determine the myelin basic protein(MBP) level, and Western blot the expression of occludin and claudin-5, as well as the levels of interleukin-6(IL-6) and proteins in the Janus kinase 2(JAK2)/signal transducer and activator of transcription 3(STAT3) pathway and their phosphorylation levels. The mRNA expression of IL-6, JAK2, and STAT3 was detected by real-time quantitative polymerase chain reaction(qPCR). Finally, molecular docking of six main active components in SJP, including emodin and curcumin, with IL-6, JAK2 and STAT3 was performed, and the binding affinity was evaluated. The results showed that the established HPLC method demonstrated high precision, reproducibility, stability, and high recovery of samples. Compared with the model group, SJP reduced the clinical symptom score and alleviate the inflammatory infiltration of brain white matter and demyelination of EAE mice. At the same time, SJP increased the expression of occludin and claudin-5, down-regulated the mRNA expression of IL-6, JAK2, and STAT3, as well as the levels of IL-6/JAK/STAT3 proteins and the phosphorylation levels, with significant difference. Molecular docking suggested that the six active components in SJP had high binding energy with IL-6, JAK2, and STAT3 proteins. The established HPLC method is simple, accurate, and highly sensitive, which can simultaneously determine the content of emodin and curcumin in SJP. SJP may alleviate the clinical symptoms of EAE by inhibiting IL-6/JAK2/STAT3 signaling pathway, protecting the blood-brain barrier, and relieving the inflammatory response and demyelinization of brain tissue.
Keywords: IL-6/JAK2/STAT3 pathway; Shengjiang Powder; experimental autoimmune encephalomyelitis(EAE); high performance liquid chromatography.