Effect of fish scale ointment on diabetic foot ulcer by inducing ferroptosis via the nuclear factor E2-related factor 2 pathway.

BACKGROUND: Excessive oxidative stress plays a key role in the development of diabetic complications, including impaired ulcer healing. Previous studies have shown that fish scale ointment can promote wound healing. AIM: To preliminarily investigate the effect of fish scale ointment on wound healing in a diabetic foot ulcer (DFU) rat model by examining its regulation of the nuclear factor E2-related factor 2 (Nrf2) pathway and induction of ferroptosis. METHODS: Fish scale ointment (collagen product) was prepared from 500 g of silver carp scales. A diabetic rat model was induced by high-fat and high-sugar feeding combined with intraperitoneal streptozotocin injections. For the DFU rat model, ulcer wounds were created by removing dorsal foot hair and cutting the skin to the fascia. The diabetic rats were randomized into five groups: Model, fish scale collagen (FSC), control + liproxstatin-1 (Lip-1), model + Lip-1, and FSC + Lip-1. In each group, treatments were administered once daily by topical application and intraperitoneal injection for 14 days. Wound healing was evaluated on days 7 and 14 after treatment. Hematoxylin and eosin staining was used to assess wound injury and capillary formation. Basic fibroblast growth factor (bFGF) and CD31 levels in wound tissue were measured by immunohistochemistry. Additionally, malondialdehyde (MDA), glutathione (GSH), ferroptosis-associated genes, and iron ion concentrations were quantified using assay kits. Protein levels of Nrf2, heme oxygenase-1 (HO-1), and glutathione peroxidase 4 (GPX4) were determined using Western blotting. RESULTS: Compared with the control group, the model group showed slower wound healing, reduced angiogenesis, decreased bFGF and CD31 levels, increased iron ion concentration and MDA levels, reduced GSH levels, and decreased Nrf2, HO-1, and GPX4 protein expression (all P < 0.05). The FSC, model + Lip-1, and FSC + Lip-1 groups showed increased wound healing and angiogenesis, elevated bFGF and CD31 expression, lowered iron ion concentration and MDA levels, increased GSH levels, and enhanced Nrf2, HO-1, and GPX4 protein levels compared with the model group (P < 0.05). Improvements were more pronounced in the FSC + Lip-1 group compared with the FSC group (P < 0.05). CONCLUSION: Fish scale ointment promotes angiogenesis and wound healing in DFU rat models by inhibiting ferroptosis, possibly through the activation of the Nrf2 pathway.