Characterizing the Immune Cell Infiltration in Renal Interstitium and Therapeutic Targets of Drugs in Diabetic...

Immune cell infiltration in the renal interstitium contributes to the progression of diabetic nephropathy (DN), yet the precise mechanisms remain incompletely unclear.

Public multi-omics datasets were integrated for comprehensive bioinformatic analyses. Interactions between infiltrating immune cells and damaged tubular epithelial cells (TECs) were analyzed with the CellChat, and key regulators were identified by machine learning. DN was modeled in C57BL/6 mice by high-fat diet/streptozotocin. Human kidney 2 (HK-2) cells were exposed to high glucose plus palmitic acid (HGPA). Gene function was validated by Western blotting, real-time quantitative polymerase chain reaction, immunohistochemistry and surface plasmon resonance (SPR).

Renal interstitium from DN patients displayed markedly increased infiltration of M1 macrophages, regulatory T-cells, natural killer cells and other immune subsets, all correlating with indices of renal injury. CellChat analysis indicated that damaged TECs communicated with infiltrating immune cells primarily through chemokine networks centered on C-X-C motif chemokine ligand (CXCL), C-X3-C motif chemokine ligand (CX3CL), and C-C motif chemokine ligand 2 (CCL2). Retinoic acid-induced 2 (RAI2) was upregulated in DN kidneys and showed significant associations with immune infiltration and renal injury via these chemokine pathways. Consistently, RAI2 expression was elevated in kidneys of DN mice and in HGPA-treated HK-2 cells. SPR demonstrated direct, high-affinity binding of resveratrol to human RAI2 protein. Knockdown of RAI2 or treatment with resveratrol attenuated HGPA-induced apoptosis and suppressed CCL2, CXCL, and CX3CL expression levels.

RAI2 is a pivotal mediator of tubule injury and immune cell infiltration in DN, and resveratrol via direct binding to RAI2 and suppressed its function.