Therapeutic potential of cell-permeable PEP-1-Srxn1 in mitigating oxidative and ischemic damage in the hippocampus

In the present study, we validated the neuroprotective effects of sulfiredoxin 1 (Srxn1) against oxidative damage in HT22 cells and ischemic damage in gerbil hippocampus. To efficiently deliver Srxn1 protein into cells or the hippocampus, a PEP-1-Srxn1 fusion protein was synthesized, and efficient delivery was visualized in HT22 mouse hippocampal neuronal cells. PEP-1-Srxn1 was delivered to HT22 cells in a concentration- and incubation time-dependent manner and showed significantly higher levels at 36 h after incubation for 1 h. Morphologically, the delivered protein was localized in the cytoplasm of HT22 cells. In addition, PEP-1-Srxn1 treatment significantly ameliorated formation of reactive oxygen species, DNA fragmentation, and cell death in HT22 cells induced by treatment with 100 μM H₂O₂. In gerbils, PEP-1-Srxn1 treatment significantly alleviated transient ischemia-induced forebrain hyperactivity 1 d after ischemia and memory deficits 4 d after ischemia. Neuroprotective effects were confirmed by morphological analysis of the hippocampal CA1 region 4 or 10 d after ischemia. Treatment with PEP-1-Srxn1 significantly ameliorated the formation of reactive oxygen species and lipid peroxidation in the hippocampus during the early stages (3-12 h) of ischemia. In addition, treatment with PEP-1-Srxn1 alleviated the ischemia-induced reduction of glutathione levels in the hippocampus. PEP-1-Srxn1 also decreased ischemia-induced microglial activation and pro-inflammatory cytokine release in the hippocampus. These results suggest that PEP-1-Srxn1 is a potential therapeutic agent for reducing neuronal damage induced by oxidative or ischemic damage.