Integrated strategy of LC-MS and network pharmacology for predicting active constituents and pharmacological mechanisms of Ranunculus japonicus Thunb. for treating rheumatoid arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Ranunculus japonicus Thunb. (short for R. japonicus) is a topically applied herb with the activities of removing jaundice, nebula and edema, preventing malaria, stopping asthma, promoting diuresis and relieving pain. It was firstly recorded in Zhouhou Beiji Fang and has been used for the treatment of malaria, ulcers, carbuncle, jaundice, migraine, stomachache, toothache and arthritis for over 1800 years.

AIM OF THE STUDY

This study aimed to uncover the potentially effective components of R. japonicus and the pharmacological mechanisms against rheumatoid arthritis (RA) by combing LC-MS and network pharmacology.

MATERIALS AND METHODS

Firstly, the chemical constituents of R. japonicus were qualitatively identified by UPLC-ESI-LTQ-Orbitrap MS. Then we performed target prediction by PharmMapper, protein-protein interaction (PPI) analysis via String, GO and KEGG pathway enrichment analysis by DAVID and constructed the compound-target-pathway network using Cytoscape. Thirdly, crucial compounds in the network were quantitatively analyzed to achieve quality control of R. japonicus. Finally, the pharmacological activities of R. japonicus and two potentially bioactive ingredients were validated in RA-FLSs (Rheumatoid Arthritis Fibroblast-like Synoviocytes) in vitro.

RESULTS

Overall fifty-four ingredients of R. japonicus were identified and forty-five components were firstly discovered in R. japonicus. Among them, twenty-seven validated compounds were predicted to act on twenty-five RA-related targets and they might exhibit therapeutic effects against RA via positive regulation of cell migration, etc. Nine potentially bioactive components of R. japonicus which played important roles in the compound-target-pathway network were simultaneously quantified by an optimized UPLC-ESI-Triple Quad method. In vitro, compared to control group, R. japonicus extract, berberine and yangonin significantly inhibited the migration capacity of RA-FLSs after 24 h treatment.

CONCLUSION

This study clarified that R. japonicus and the bioactive ingredients berberine and yangonin might exert therapeutic actions for RA via suppressing the aggressive phenotypes of RA-FLSs through combined LC-MS technology and network pharmacology tools for the first time. The present research provided deeper understanding into the chemical profiling, pharmacological activities and quality control of R. japonicus and offered reference for further scientific research and clinical use of R. japonicus in treating RA.

First Report of Leaf Spot Disease on Walnut Caused by Colletotrichum fioriniae in China

In May 2014, a severe leaf spot disease was observed on walnut tree (Juglans regia L.) in Hechi, Guangxi, China. Leaf spots were circular to semicircular in shape, water-soaked, later becoming grayish white in the center with a dark brown margin and bordered by a tan halo. Necrotic lesions were approximately 3 to 4 mm in diameter. Diseased leaves were collected from 10 trees in each of five commercial orchards. The diseased leaves were cut into 5 × 5 mm slices, dipped in 75% ethanol for 30 s, washed three times in sterilized water, sterilized with 0.1% (w/v) HgCl₂ for 3 min, and then rinsed five times with sterile distilled water. These slices were placed on potato dextrose agar (PDA), followed by incubating at 28°C for about 3 to 4 days. Fungal isolates were obtained from these diseased tissues, transferred onto PDA plates, and incubated at 28°C. These isolates produced gray aerial mycelium and then became pinkish gray with age. Moreover, the reverse of the colony was pink. The growth rate was 8.21 to 8.41 mm per day (average = 8.29 ± 0.11, n = 3) at 28°C. The colonies produced pale orange conidial masses and were fusiform with acute ends, hyaline, sometimes guttulate, 4.02 to 5.25 × 13.71 to 15.72 μm (average = 4.56 ± 0.31 × 14.87 ± 1.14 μm, n = 25). The morphological characteristics and measurements of this fungal isolate matched the previous descriptions of Colletotrichum fioriniae (Marcelino & Gouli) R.G. Shivas & Y.P. Tan (2). Meanwhile, these characterizations were further confirmed by analysis of the partial sequence of five genes: the internal transcribed spacer (ITS) of the ribosomal DNA, beta-tubulin (β-tub) gene, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene, chitin synthase 3(CHS-1) gene, and actin (ACT) gene, with universal primers ITS4/ITS5, T1/βt2b, GDF1/GDR1, CHS1-79F/CHS1-354R, and ACT-512F/ACT-783R, respectively (1). BLAST of these DNA sequences using the nucleotide database of GenBank showed a high identify (ITS, 99%; β-tub, 99%; GAPDH, 99%; CHS-1, 99%; and ACT, 100%) with the previously deposited sequences of C. fioriniae (ITS, KF278459.1, NR111747.1; β-tub, AB744079.1, AB690809.1; GAPDH, KF944355.1, KF944354.1; CHS-1, JQ948987.1, JQ949005.1; and ACT, JQ949625.1, JQ949626.1). Koch's postulates were fulfilled by inoculating six healthy 1-year-old walnut trees in July 2014 with maximum and minimum temperatures of 33 and 26°C. The 6-mm mycelial plug, which was cut from the margin of a 5-day-old colony of the fungus on PDA, was placed onto each pin-wounded leaf, ensuring good contact between the mycelium and the wound. Non-colonized PDA plugs were placed onto pin-wounds as negative controls. Following inoculation, both inoculated and control plants were covered with plastic bags. Leaf spots, similar to those on naturally infected plants, were observed on the leaves inoculated with C. fioriniae within 5 days. No symptoms were observed on the negative control leaves. Finally, C. fioriniae was re-isolated from symptomatic leaves; in contrast, no fungus was isolated from the control, which confirmed Koch's postulates. To our knowledge, this is the first report of leaf disease on walnut caused by C. fioriniae. References: (1) L. Cai et al. Fungal Divers. 39:183, 2009. (2) R. G. Shivas and Y. P. Tan. Fungal Divers. 39:111, 2009.