Icariin sensitizes glucocorticoid therapy in doxorubicin-induced fibrotic nephrotic syndrome via the HIF-1α/NF-κB/HDAC2 Axis

Nephrotic syndrome (NS) can progress to tubulointerstitial fibrosis, and a subset of patients exhibits reduced responsiveness to glucocorticoids (GCs). Beyond podocyte injury, the tubulointerstitial microenvironment may critically shape GC efficacy, but the mechanisms remain incompletely defined. We established a doxorubicin (DOX)-induced rat model featuring tubular epithelial injury with epithelial-to-mesenchymal transition (EMT), interstitial fibrosis, and a blunted therapeutic response to prednisone (Pred). We tested whether icariin (ICA) enhances GC efficacy by modulating the HIF-1α/NF-κB/HDAC2 axis and Glucocorticoid Receptor (GR) signaling in DOX-induced tubular injury. Rats received ICA, Pred, ICA + Pred, tacrolimus, or the HIF-1α Inhibitor PX-478. We assessed proteinuria, serum biochemistry, renal histopathology, oxidative stress indices, renal microvascular perfusion, transcriptomics, and axis signaling. DOX induced severe proteinuria and renal dysfunction, accompanied by microvascular hypoperfusion and oxidative stress, together with tubular epithelial EMT and interstitial fibrosis. These changes were associated with impaired GR signaling (reduced GR expression and nuclear localization), HDAC2 downregulation, NF-κB activation (including increased RelA acetylation), and P-glycoprotein upregulation. Pred monotherapy conferred limited benefit, whereas ICA + Pred produced greater improvements in proteinuria, renal function, and tubulointerstitial injury, with partial normalization of tubular injury- and inflammation-enriched transcriptomic programs. ICA was associated with improved microvascular perfusion and oxidative stress indices, reduced HIF-1α and P-glycoprotein expression, restored HDAC2, enhanced GR signaling, and suppression of NF-κB-linked inflammatory activity. PX-478 recapitulated key components of this response. Collectively, these data implicate a tubulointerstitial HIF-1α/NF-κB/HDAC2 axis as a key contributor to blunted GC responsiveness in fibrotic NS and support ICA as a microenvironment-targeted adjunct to enhance GC efficacy.

Glucocorticoid resistance; HIF-1α/NF-κB/HDAC2 axis; Icariin; Nephrotic syndrome; Prednisone; Tubulointerstitial fibrosis.