Activation of TLR4-NF-κB signaling in renal tubular epithelial cells facilitates renal allograft fibrosis by inhibiting peroxisome biogenesis

Interstitial fibrosis is a key factor affecting the long-term survival of renal allografts. The Toll-like receptor 4 (TLR4)-nuclear factor kappa B (NF-κB) signaling pathway is widely activated in renal allografts, inducing inflammation and playing a pivotal role in the progression of fibrosis. However, it remains unclear whether NF-κB activation promotes renal allograft fibrosis through non-inflammatory mechanisms. In this study, we identified a negative correlation between NF-κB expression and peroxisomal biogenesis factor 5 (PEX5). In both rat renal allograft models and human kidney-2 (HK-2) cells, TLR4/NF-κB signaling suppressed PEX5 expression, leading to impaired peroxisome biogenesis and dysfunction. Mechanistically, TLR4/NF-κB signaling downregulated PEX5 expression by upregulating DNA methyltransferase 1 (DNMT1), and pharmacological inhibition of NF-κB or DNMT1 restored PEX5 levels. Peroxisomal dysfunction promoted epithelial-to-mesenchymal transition (EMT) and impaired the ability of peroxisomes to clear hydrogen peroxide, thereby accelerating fibrosis progression. Notably, pharmacological inhibition of DNMT1 effectively delayed the progression of fibrosis in renal allografts. In conclusion, these findings demonstrate that the NF-κB/DNMT1/PEX5 signaling pathway suppresses peroxisome biogenesis in renal allografts, and the amelioration of allograft fibrosis by pharmacologic DNMT1 inhibition underscores the translational relevance of this pathway. Targeting this pathway may provide a potential therapeutic strategy to improve renal allograft survival.