Direct pharmacological targeting of RAC1 by chlorogenic acid: A novel therapeutic approach for mesangial proliferative glomerulonephritis.

Mesangial proliferative glomerulonephritis (MsPGN) is a common cause of end-stage renal disease, characterized by mesangial cell proliferation within glomeruli. Mesangial cell activation triggered by inflammation is a key factor in the development of MsPGN. However, effective therapeutic strategies targeting this process are still limited. Here, we uncovered, for the first time, the direct effects of chlorogenic acid (CGA), a naturally occurring small-molecule compound with anti-inflammatory and antiproliferative properties, on mesangial cells in an anti-Thy1 nephritis animal model. A multi-dimensional pharmacological platform integrating laser microdissection-coupled glomerular proteomics affinity deconvolution, surface plasmon resonance, molecular dynamics, and enzyme assays identified Ras-related C3 botulinum toxin substrate 1 (RAC1) as the direct target of CGA. Mechanistically, CGA competitively binds to the LYS15, PRO33, and THR34 amino acid residues-located within residues 57-65 of the GTP/GDP-binding domain of RAC1, inhibiting its activation and subsequently reducing AKT phosphorylation while suppressing Thrombospondin-1 secretion from mesangial cells-a key ligand for macrophage CD36 receptors. This interaction deactivates macrophages and lowers the levels of inflammatory cytokines, including TNFα, IL1β, and IL6. Significantly, as a novel natural RAC1 inhibitor, CGA disrupts mesangial-macrophage crosstalk by dual suppression of regional immunity and cellular proliferation, thus conferring renal protection in MsPGN models. Our findings highlight CGA as a promising pharmacotherapy, offering a mechanism-driven, natural product-based strategy to mitigate MsPGN progression.