Anti-inflammatory effect of a pimarane diterpenoid isolated from Nepeta adenophyta Hedge. based on network Analysis approach and experimental assessment

Wei Zhao¹Meng Li²Qing Chuan Jia²Iftikhar Ali^3*Long Chen^4*

• ¹The Second Affiliated Hospital of Heilongjiang University of Chinese Medicine, Harbin, China
• ²Shandong Academy of Chinese Medicine, Jinan, China
• ³Karakoram International University, Gilgit, Pakistan
• ⁴Qilu University of Technology, Jinan, China

Background: As an important folk medicine in Pakistan, Nepeta adenophyta Hedge has been widely used to treat abdominal pain, kidney pain, and headaches, as well as for the alleviation of dysmenorrhea. The pimarane-type diterpenoids are known for their anti-inflammatory activity, but their mechanistic pathways remain understudied. 2,4b,8,8-Tetramethyl-2-vinyl-1,2,3,4,4a,4b,5,6,7,8,8a,9-dodecahydro-phenanthrene-3,5-diol (1), a pimarane diterpenoid, was detected primarily from Nepeta adenophyta Hedge through its gas chromatography-mass spectrometry (GC-MS) fragmentation pathways. The GC-MS guided isolation yielded compound 1 (NAC, Nepeta adenophyta compound) in pure form. Methods: The gas chromatography-mass spectrometry guided isolation of compound 1 was performed by column chromatography on normal silica gel. The structure was characterized by spectroscopic techniques. Then, the potential targets, pathways and hub genes of 1 for treating inflammatory diseases were screened out through network analysis, and core targets were docked with 1 via docking software. Based on the results of network analysis, an MTT assay was performed to determine cell proliferation in the RAW264.7 cell line. Inflammatory cytokines, such as Tumor Necrosis Factor-alpha (TNF-α), Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6) and Prostaglandin E2 (PGE2) were tested by Enzyme-Linked Immunosorbent Assay (ELISA). Immunofluorescence and Western blot assays were used to verify the function of 1 in the treatment of inflammation. Results: The compound 1 was isolated from Nepeta adenophyta Hedge in its pure form. The pharmaceutical network results showed that it has a potential anti-inflammatory effect through PPAR and NF-B signalling pathways. The ELISA results showed that 1 could attenuate the content of pro-inflammatory cytokines. Additionally, the translocation of NF-ĸB p65 into the nucleus was significantly decreased in the immunofluorescence method. The western blot analysis results showed that 1 significantly inhibits the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Further, it decreased the phosphorylation of nuclear factor-Kappa B inhibitor α (IκBα), and toll-like receptor 4 (TLR4) by the NF-ĸB signalling pathway. Moreover, compound 1 reduced reactive oxygen species (ROS) level and restored overexpressed heme oxygenase-1 (HO-1) and serine/threonine kinase (AKT) to basal level. Conclusion: The present study indicates that compound 1 shows a significant anti-inflammatory effect, potentially through intervention in NF-κB and PPARγ signalling pathways.