Amelioration of 5-Fluorouracil–Induced Hepatorenal Toxicity by Epigallocatechin Gallate–Functionalized Selenium Nanoparticles: A Multi-Targeted Protective Approach

5-Fluorouracil (5-FU) is a cornerstone chemotherapeutic agent that is extensively utilized in the management of malignancies; however, its clinical utility is constrained by its narrow therapeutic index and dose-limiting toxicities. The study aimed to study the hepato-nephroprotective effects of epigallocatechin gallate (EGCG) and EGCG mediated selenium nanoparticles and their effect in mitigating the toxicity induced by 5-FU. EGCG-functionalized selenium nanoparticles (EGCG-SeNPs) were produced by mixing sodium selenite, with EGCG acting as both the reducing and stabilizing agent. Nanoparticles were characterized using UV-vis spectroscopy, FT-IR, dynamic light scattering, zeta potential analysis, and transmission electron microscopy. 35 adult rats were randomly assigned to control, 5-FU, 5-FU + Na2SeO3, 5-FU + EGCG, and 5-FU + EGCG-SeNPs groups. Hepatorenal toxicity was induced by intraperitoneal 5-FU administration during the final five days of the experiment. Serum biochemical markers, tissue oxidative stress, antioxidant enzyme, inflammatory cytokine levels, and apoptosis-related gene expression were evaluated. Immunohistochemical analysis of Nrf2 and Keap1 and histopathological examination of tissues were performed. 5-FU induced severe hepatorenal toxicity, evidenced by marked elevations in liver and kidney function biomarkers, excessive oxidative stress, inflammatory cytokine overproduction, NF-κB activation, and apoptotic signaling. Treatment with EGCG-SeNPs markedly ameliorated 5-FU-induced hepatic and renal dysfunction, restoring liver enzyme and kidney biomarker levels to near-normal levels more effectively than EGCG or sodium selenite alone. EGCG-SeNPs significantly suppressed lipid peroxidation, NGAL, and inflammatory mediators while robustly enhancing antioxidant defenses and activating the Nrf2/HO-1 pathway with concomitant Keap-1 downregulation, strongly inhibited NF-κB signaling, normalized cytokine balance, reduced poly (ADP-ribose) (PAR) activation, and attenuated apoptosis. EGCG–SeNPs confer superior protection against 5-FU–induced hepatorenal toxicity compared to EGCG or inorganic selenium alone. The potent protective effects of EGCG–SeNPs are mediated through coordinated antioxidant, anti-inflammatory, and anti-apoptotic mechanisms, primarily via activation of the Nrf2/HO-1 axis and suppression of NF-κB signaling.