The Therapeutic Effect of the Ethyl Acetate Extract of Rhododendron Przewalskii Maxim. On Chronic Bronchitis by Inhibiting the Traf6/Nf-Κb Signaling Pathway

Abstract

Ethnopharmacological relevance:Rhododendron przewalskiiMaxim. has widely been used to treat respiratory and pulmonary diseases in western China. Our previous study showed that R. przewalskii extracts contained amounts of valuable flavonoids and presented promising anti-inflammatory and antioxidant activities.Aims of this studyThis study aimed to investigate the pharmacological effect and molecular mechanisms of R. przewalskii extract in vivo and in vitro.Materials and methodsA comprehensive strategy via incorporating pharmacodynamics and molecular biology technology was adopted to investigate the therapeutic mechanisms of R. przewalskii extract in cigar smoke (CS)-induced chronic bronchitis and LPS- induced RAW 264.7 cells. After screening the better extract and carrying out quantitative analysis, a CS-induced chronic bronchitis model and LPS-induced RAW 264.7 cells model were established to evaluate the effect of the extract in vivo and in vitro. Proteomics, q-PCR, Western blot, ELISA, molecular docking and other methods were used to explore its specific mechanism.Results: Rhododendron przewalskiiethyl acetate extract (RPEA) has the better anti-inflammatory activity with the abundant of the total flavonoid and total polyphenol. In vivo and in vitro test showed that RPEA presented the remarkable activity with a dose-dependant manner, it effectively suppressed the expression of TNF-α, IL-1β, and IL-6, and decreased MDA and ROS levels to recover pathological lung injury. Proteomics analysis showed that 340 proteins were regulated, and the key proteins in the TRAF6 and NF-κB pathways were screened. RPEA regulated TRAF6 expression and the phosphorylation of NF-κB and IκBα and inhibited the nuclear translocation of NF-κB in vivo and in vitro. Molecular docking confirmed the interaction between the active compounds of RPEA and TRAF6.ConclusionsRPEA markedly improved chronic bronchitis by suppressing the TRAF6/NF-κB pathway through binding with TRAF6 to decrease inflammation. This result provide the substantial evidence for its traditional uses, and indicate that R. przewalskii could be used as potential candidate for treating chronic bronchitis.

Note:
Funding declaration: This work was supported financially by the National Key Research and Development Program of China (2023YFD1801304, 2023YFD1800803), the National Natural Science Foundation of China (32373055, 32302924), the Outstanding Youth Fund of Gansu Province (23JRRA563), the Innovation Project of the Chinese Academy of Agricultural Sciences (No. CAAS-ASTIP-2015-LIHPS), and China Agriculture Research System (CARS-37).

Conflict of Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Ethical Approval: All animal tests were performed according to the guidelines of the Ethics Committee of Medical Sciences and approved by the Ethical Approval for Research Involving Animals of Lanzhou Institute of Husbandry and Pharmaceutical Sciences of CAAS(NO.2021-003).

Keywords: Chronic bronchitis, Rhododendron przewalskii ethyl acetate extract, inflammation, lung injury, TRAF6/NF-κB pathway