Ellagic Acid Attenuates Gentamicin Nephrotoxicity by Integrated Modulation of ER Stress-Associated Apoptosis-Autophagy Crosstalk and Attenuation of Nrf2/HO-1 Signaling

Background: Gentamicin-induced nephrotoxicity limits clinical pharmacotherapy and involves multiple converging stress-response pathways. Ellagic acid (EA) has renoprotective potential, yet its role in coordinating endoplasmic reticulum (ER) stress-mediated apoptosis, autophagy, and inflammation remains unclear. We hypothesized that EA co-treatment would protect the kidney by modulating ER stress-dependent pathways and associated inflammatory and adaptive signaling. Methods: For an integrated mechanistic analysis in a rat model of gentamicin nephrotoxicity, 40 male Sprague-Dawley rats were assigned to control, gentamicin (100 mg/kg), EA (100 mg/kg), and gentamicin + EA groups for 14 days. Renal function, oxidative stress, inflammatory mediators, ER stress markers, apoptosis, autophagy, tubular injury markers, and histopathological changes were assessed. Results: Gentamicin induced renal dysfunction, tubular injury, and ER stress across all unfolded protein response (UPR) branches (IRE1α, PERK, ATF6), C/EBP homologous protein (CHOP)-associated apoptosis, dysregulated autophagy, and upregulated kidney injury molecule-1 (KIM-1). A selective inflammatory signature was observed, with increased cyclooxygenase-2 (COX-2) and interleukin-6 (IL-6), whereas tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) remained unchanged. Co-administration of ellagic acid with gentamicin significantly improved renal function markers compared to the gentamicin group. In contrast, ellagic acid alone did not show significant differences compared to the control group. Notably, gentamicin induced compensatory upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) expression, while ellagic acid co-treatment attenuated this compensatory upregulation, likely secondary to reduced oxidative stress burden. Conclusions: This study provides integrated evidence that ER stress is closely associated with gentamicin nephrotoxicity. The key novel findings include selective suppression of IL-6, modulation of the apoptosis-autophagy balance, and attenuation of Nrf2/HO-1 signaling without direct reactive oxygen species (ROS) scavenging, demonstrating a multi-target framework for EA’s renoprotective effects. These findings suggest that ellagic acid mitigates renal injury in a context-dependent manner rather than confirming a direct causal mechanism.