Ferroptosis and iron mineralization involved in the death and survival of orange-spotted groupers challenged with Pseudomonas plecoglossicida

Pseudomonas plecoglossicida (P. plecoglossicida) is a pathogen in aquaculture that causes considerable economic loss. According to artificial infection experiments, the fish were classified into control group, moribund group, and survival group. Compared to the control group, both the moribund group and the survival group of fish had fewer red blood cells (RBCs) and lower oxygen saturation (SaO₂). Furthermore, the fish in the survival group has more RBCs and SaO₂ compared to the moribund group. The concentrations of total iron, ferrous iron, ferric iron, and mineralized iron in the fish spleen of the moribund and survival groups were lower compared to those of the control group. Additionally, the concentrations of these iron components in the fish spleen of the survival group were higher than those of the moribund group. The results demonstrated that iron mineralization is involved in the survival of fish challenged with P. plecoglossicida. Compared to the control and survival groups, the fish spleen had several distinguishing features in the moribund group, including less reduced glutathione (GSH), higher mitochondrial complex V activity, more lipid peroxidation, and reactive oxygen species, as well as reduced glutathione peroxidase 4 (gpx4) expression. Moreover, there were intact cell membranes, a normal nucleus size, no chromatin concentration, and disappearance of cristae in the mitochondria of the spleens of the moribund group. The characteristics of spleen cells in the moribund group were consistent with ferroptosis, suggesting that ferroptosis was involved in the death of fish challenged with P. plecoglossicida.