Supplementary Material for: CXCL6 Orchestrates Macrophage-Driven Inflammation in Diabetic Kidney Disease and Represents a Druggable Target

Diabetic kidney disease (DKD), a leading cause of end-stage renal disease (ESRD), is characterized by progressive tubular interstitial injury preceding glomerular damage. Renal exposure to high glucose, oxidative stress, and advanced glycation end products promotes tubulointerstitial fibrosis by activating tubular cells and inducing inflammatory infiltration. Using weighted gene correlation network analysis (WGCNA) and differential gene expression analysis across three datasets, we identified CXCL6, a C-X-C motif chemokine, as a pivotal regulator in DKD pathogenesis. Single-cell RNA sequencing (scRNA-seq) revealed that CXCL6 is predominantly expressed in tubular epithelial cells, with elevated urinary CXCL6 levels correlating positively with serum creatinine and albumin-to-creatinine ratio and negatively with estimated glomerular filtration rate. Functional experiments demonstrated that high glucose exposure upregulates CXCL6 in HK-2 cells, facilitating macrophage recruitment and polarization into pro-inflammatory phenotypes, thereby amplifying inflammatory cytokine release. Salvianolic acid B (Sal-B), identified through virtual screening and molecular docking, effectively reduced CXCL6 secretion, inhibited macrophage migration, and suppressed inflammatory cytokine production. These findings establish CXCL6 as a key mediator of tubulointerstitial inflammation and fibrosis in DKD and highlight Sal-B as a potential therapeutic agent targeting CXCL6-driven pathways.