Protective Role of Adenosine Triphosphate Against Tamoxifen-Induced Retinal Toxicity in a Rat Model

Background and Objectives: Tamoxifen, a cornerstone selective estrogen receptor modulator in breast cancer therapy, is increasingly recognized to be associated with retinal toxicity characterized by mitochondrial dysfunction, oxidative stress, lipid peroxidation, and oxidative DNA injury. By targeting mitochondrial bioenergetic dysfunction and redox disequilibrium, adenosine triphosphate (ATP) emerges as a biologically plausible candidate for retinal cytoprotection. This study aimed to evaluate the protective effect of ATP against tamoxifen-induced retinal toxicity in a rat model. Materials and Methods: Twenty-four male albino Wistar rats were randomly assigned to four groups: healthy control (HG), ATP-alone (ATPG, 4 mg/kg, intraperitoneally), tamoxifen-alone (TAMG, 5 mg/kg, orally), and tamoxifen plus ATP-treated (ATAG; ATP, 4 mg/kg, intraperitoneally; tamoxifen, 5 mg/kg, orally). Treatments were administered once daily for 30 days. Oxidative stress markers (malondialdehyde, total glutathione), antioxidant enzyme activities (superoxide dismutase, catalase), and oxidative DNA damage (8-hydroxy-2'-deoxyguanosine) were assessed in ocular tissues. Retinal histopathological evaluation included hematoxylin-eosin staining with semiquantitative assessment of edema, vascular congestion, polymorphonuclear leukocyte infiltration, and cytoplasmic vacuolization, together with quantitative measurements of retinal layer thicknesses and ganglion cell layer (GCL) cell counts. Results: Tamoxifen administration induced marked oxidative stress, antioxidant depletion, and increased oxidative DNA damage in ocular tissues, accompanied by significant thickening of retinal layers, reduced GCL cell counts, and pronounced disruption of retinal architecture. By comparison, ATP co-administration significantly suppressed lipid peroxidation and restored antioxidant defenses, thereby reducing oxidative DNA damage and preserving retinal structural integrity, as reflected by partial normalization of retinal layer thicknesses, preservation of GCL cell counts, and the presence of only mild residual edema. Conclusions: These findings indicate that ATP attenuates tamoxifen-induced retinal toxicity by supporting mitochondrial energy balance and redox homeostasis. Accordingly, ATP administration may represent a promising protective approach for reducing retinal injury associated with long-term tamoxifen therapy.