Protective Role of Thiamine Pyrophosphate Against Erlotinib-Induced Oxidative and Inflammatory Damage in Rat Optic Nerve

Background: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) such as erlotinib are widely used in non-small-cell lung cancer treatment, and accumulating evidence indicates they can markedly increase ocular toxicity. Nonetheless, whether erlotinib causes optic nerve injury has not been investigated before and remains a subject worth investigating. This study aimed to examine the impact of erlotinib on oxidative stress, inflammation, and histopathological changes in rat optic nerve tissue and evaluate the potential neuroprotective role of thiamine pyrophosphate (TPP). Methods: Twenty-four male Wistar rats were randomly assigned to four groups: healthy control, TPP alone, erlotinib alone, and erlotinib + TPP. Erlotinib (10 mg/kg, orally, on alternate days) and TPP (20 mg/kg, intraperitoneally, daily) were administered for two consecutive weeks. Optic nerve samples were analyzed for malondialdehyde (MDA), total glutathione (tGSH), superoxide dismutase (SOD), catalase (CAT), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α), followed by histopathological examination. Results: Erlotinib treatment significantly increased MDA, IL-1β, and TNF-α levels while reducing tGSH, SOD, and CAT activity, demonstrating oxidative stress and an inflammatory response. Co-administration of TPP ameliorated these changes by lowering reactive oxygen species, restoring antioxidant capacity, and attenuating inflammation. Histopathological alterations, including astrocyte degeneration, edema, and vascular congestion, were evident after erlotinib exposure but were significantly alleviated when TPP was administered concurrently. Conclusions: Erlotinib induces oxidative and inflammatory optic nerve injury, while TPP co-treatment offers significant neuroprotection. These findings support TPP as a potential adjunct to reduce EGFR-TKI-related ocular toxicity and highlight importance of redox modulation in limiting treatment-associated side effects.