Targeting Oxidative Stress and Inflammation in Pembrolizumab-Induced Renal Injury: A Comparative Evaluation of the Protective Effects of Flunarizine and Carvacrol in Rats

Background: Pembrolizumab, a programmed cell death protein 1 (PD-1) inhibitor, is widely employed in oncological practice; however, its propensity to induce nephrotoxicity through immune-mediated oxidative and inflammatory mechanisms remains an insufficiently characterized clinical concern. The present study comparatively investigated the renoprotective effects of flunarizine, a voltage-dependent calcium channel antagonist, and carvacrol, a monoterpene, against pembrolizumab-induced renal injury in rats. Methods: Twenty-four male Wistar albino rats were assigned to four groups (n = 6): healthy control (HG), pembrolizumab alone (PZB), flunarizine+pembrolizumab (FLPZ), and carvacrol+pembrolizumab (CCPZ). Pembrolizumab was administered intraperitoneally at 5 mg/kg; flunarizine orally at 5 mg/kg and carvacrol intraperitoneally at 50 mg/kg, once daily for seven consecutive days. Renal oxidative status was assessed by measuring malondialdehyde (MDA) and total glutathione (tGSH) levels. Histopathological evaluation was performed using hematoxylin and eosin staining. Two double immunofluorescence panels were employed to assess 3,3′-dityrosine/Hepatitis A virus cellular receptor 1 (HAVCR1) and cyclooxygenase-1 (COX-1)/cyclooxygenase-2 (COX-2) expression, respectively. Results: Pembrolizumab caused pronounced oxidative stress and inflammatory responses in renal tissue, leading to a significant increase in renal MDA levels and a marked decrease in tGSH levels. These biochemical alterations were accompanied by severe tubular degeneration and increased expression of 3,3′-dityrosine, which is associated with oxidative damage, as well as HAVCR1, a marker of cellular injury, and COX-1 and COX-2, which reflect inflammatory activity. These findings indicate that pembrolizumab disrupts the renal redox balance and activates both oxidative and inflammatory pathways in kidney tissue. Flunarizine and carvacrol significantly reduced these pathological changes. Both agents attenuated oxidative stress markers and supported antioxidant defenses, thereby alleviating tissue damage. However, flunarizine demonstrated a more pronounced renoprotective effect across all evaluated parameters, restoring MDA and tGSH levels closer to physiological values and reducing tubular injury to a minimal level. Carvacrol showed a more limited but still statistically significant protective effect. Conclusions: Both agents confer significant renoprotection against pembrolizumab-induced oxidative injury; however, flunarizine exhibits a more robust protective profile, likely attributable to its capacity to attenuate calcium-mediated mitochondrial dysfunction and preserve cellular bioenergetic homeostasis.