Exploring the molecular mechanism of Suoquan pill in the treatment of diabetic kidney disease based on network pharmacology, molecular docking, in vitro experiment

Background: Diabetic kidney disease (DKD) is a microvascular complication of diabetes mellitus and is the main cause of end-stage renal failure. Suoquan pills (SQP) has a variety of pharmacological activities and multiple therapeutic effects, and it is used clinically as a basic formula for the treatment of DKD. Methods: Public databases were used to identify SQP compounds and the potential targets of SQP and DKD. A drug-component-therapeutic target network was constructed. Protein-protein interaction network analysis, Gene Ontology functional analysis, and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis were used to analyse the potential molecular mechanisms of SQP based on common targets of drugs and diseases. Molecular docking simulations were conducted to confirm the binding abity of the core compounds to key targets. The efficacy and predicted molecular mechanisms of SQP were validated using cell counting kit-8 assay, flow cytometry, and western blotting with HK-2 cells as a model. Results: Network pharmacology analysis showed that 26 compounds and 207 potential targets of SQP were involved in the treatment of DKD; boldine, denudatin B, pinocembrin, kaempferoid, and quercetin were considered core compounds, and epidermal growth factor receptor (EGFR) and proto-oncogene, non-receptor tyrosine kinase (SRC) were considered key targets. Gene Ontology enrichment analysis indicated that protein phosphorylation and negative regulation of apoptotic processes are important biological processes in the treatment of DKD by SQP. Molecular docking confirmed the excellent binding abilities of boldine, denudatin B, kaempferide, and quercetin to EGFR and SRC. The results of in vitro experiments showed that treatment with an ethanolic extract of SQP significantly protected HK-2 cells from high glucose-induced cell damage. In addition, the SQP ethanol extract inhibited the phosphorylation of EGFR and SRC, suppressed the apoptosis rate, and regulated apoptosis-related proteins in HK-2 cells under high glucose stress. Conclusion: This study systematically and intuitively illustrated the possible pharmacological mechanisms of SQP against DKD through multiple components, targets, and signalling pathways, especially the inhibition of EGFR and SRC phosphorylation and apoptosis.