Effect of 6-Hydroxydopamine on Iron Metabolism in MO3.13 Oligodendrocytes

Iron accumulation in the substantia nigra is a hallmark of Parkinson's disease (PD), but its cellular drivers remain unclear. Oligodendrocytes, the most iron-rich cells in the brain, have been implicated in PD pathology. Our previous studies showed that 6-hydroxydopamine (6-OHDA) promotes iron accumulation in neurons and astrocytes by increasing iron influx and decreasing efflux. However, its effects on oligodendrocyte iron metabolism remain unknown. In this study, we examined how 6-OHDA affects iron homeostasis and inflammatory gene expression in MO3.13 oligodendrocytes. Using MTT, calcein-AM fluorescence assays, RT-PCR, and Western blotting, we compared undifferentiated and differentiated cells. In undifferentiated oligodendrocytes, 6-OHDA increased transferrin receptor 1 (TfR1) and iron regulatory protein 1 (IRP1) while reducing ferroportin 1 (FPN1), resulting in enhanced iron uptake and reduced export. In contrast, differentiated cells showed decreased TfR1 and IRP1 and increased FPN1, promoting iron efflux. 6-OHDA also induced stage-specific inflammatory responses. In undifferentiated cells, IL-1β and TNF-α mRNA levels rose in a dose-dependent manner, whereas differentiated cells selectively upregulated IL-1β. These results suggest that undifferentiated oligodendrocytes undergo iron-related inflammation that may promote differentiation, while differentiated cells respond with a more restricted cytokine profile. This study is the first to demonstrate that 6-OHDA promotes iron accumulation in undifferentiated oligodendrocytes by disrupting the IRP1-mediated balance between TfR1 and FPN1. Moreover, 6-OHDA induces distinct inflammatory responses depending on the stage of oligodendrocyte differentiation. These findings highlight the dual role of oligodendrocytes as both iron reservoirs and modulators of the neuroinflammatory microenvironment, providing new insights into the cellular mechanisms underlying nigral iron accumulation in PD, and suggesting that oligodendrocytes play a critical regulatory role in PD pathogenesis.