Metabolic Mechanisms of Hexavalent Chromium-Induced Splenic Immune Injury via Oxidative Stress and Ferroptosis Pathways in New Zealand Rabbits

Background: Hexavalent chromium (Cr(VI)) is a widespread environmental toxic heavy metal with strong oxidative properties; however, its immunotoxicity and metabolic mechanisms in rabbit spleen remain largely unclear. Methods: In this study, New Zealand rabbits were exposed to 0, 12.5, 25, and 50 mg/L Cr(VI) (as potassium dichromate, K2Cr2O7) via drinking water for four weeks to investigate splenic damage and the underlying molecular pathways. Spleen pathological injury was evaluated by hematoxylin and eosin (H&E) staining, and the distribution of T cells, B cells, and macrophages was assessed by immunohistochemistry. Antioxidant enzyme activities and antioxidant substance levels were determined using ELISA, and the relative mRNA expression of immune factor genes, antioxidant-related genes, and ferroptosis-related genes was quantified by quantitative real-time PCR (qRT-PCR). In addition, the distribution of iron in splenic tissue was detected by enhanced Prussian blue staining. Results: Our results demonstrate that high-dose Cr(VI) significantly inhibited body weight gain, induced lymphocyte atrophy, vacuolization, and widening of intercellular spaces in the splenic white pulp. Furthermore, Cr(VI) reduced T and B lymphocyte populations, promoted macrophage infiltration and inflammatory cytokine gene expression in a concentration-dependent manner, impaired total antioxidant capacity, and led to a decrease in glutathione (GSH) levels in the spleen. Additionally, Cr(VI) exposure increased iron accumulation, activated the ACSL4–NOX lipid peroxidation cascade, and downregulated GPX4 expression, ultimately triggering ferroptosis. Conclusions: These findings reveal that Cr(VI) causes splenic immune injury by disrupting oxidative homeostasis and inducing ferroptosis, providing novel insights for evaluating immunotoxicity and identifying metabolic targets under Cr(VI) pollution.