An Integrated Network Pharmacology and Cell Metabolomics Approach to Reveal the Role of Rhein, a Novel PPAR Agonist, Against Renal Fibrosis by Activating the PPAR-CPT1A Axis

Background: Rhein, an anthraquinone compound, displays extensive antifibrotic effects; however, its potential mechanisms are not fully understood. In this study, we explored the underlying molecular mechanism of action of rhein. Method: An integrated network pharmacology and cell metabolomics approach was developed based on network pharmacology and bioinformatics method, and then successfully applied to speculate the potential targets of rhein and construct a rhein-target-metabolic enzyme-metabolite network. Thereafter, the antifibrotic mechanism of rhein was validated in TGF-beta- and oleic acid-induced HK-2 and NRK-52E cells in vitro as well as a unilateral ischemia-reperfusion injury Sprague-Dawley rat model. Results: Based on the construction of the rhein-target-metabolic enzyme-metabolite network, we found that rhein played an antifibrotic role through the PPAR alpha CPT1A-l-palmitoyl-carnitine axis. In vitro experiments demonstrated that rhein effectively activated the expression of PPAR alpha and its downstream proteins (CPT1A and ACOX1) to alleviate lipid accumulation and fibrosis development. In vivo experiments indicated that rhein attenuated renal fibrosis mainly by activating the fatty acid oxidation pathway and improving lipid metabolism. Conclusion: Taken together, our findings reveal that rhein is a novel agonist of PPAR alpha, which contributes to its renoprotection through the regulation of the PPAR alpha-CPT1A axis. Moreover, our study provides a novel insight into an integrated network pharmacology-metabolomics strategy for uncovering the pharmacological mechanisms of drugs from the system perspective.