Countering iron-driven pathology in the CNS with novel neuroprotective analogs

Multiple sclerosis is a chronic inflammatory disease of the central nervous system that leads to progressive neurodegeneration. Among its many pathological features, the accumulation of iron within the brain has gained increasing attention. Despite extensive imaging evidence of iron deposition around and within lesions, especially in deep grey matter, the consequences and the cellular responses to excess iron in the central nervous system remain poorly understood. In this thesis, I investigated how cells of the central nervous system respond to oxidative stress and iron overload. I first characterized the antioxidant enzyme response across several animal models of multiple sclerosis. My results showed that microglia and macrophages consistently upregulated antioxidant enzymes, whereas astrocytes and oligodendrocytes did not exhibit a comparable response. To directly examine the impact of iron in the central nervous system, I developed a new animal model in which ferrous iron, the reactive form of iron, was injected into the white matter of the mouse spinal cord. Unexpectedly, the resulting injury was confined to the adjacent grey matter, which enabled detailed investigation of iron-induced neurodegeneration. I found that neurons exhibited oxidative stress but failed to upregulate protective antioxidant enzymes, while microglia increased several antioxidant enzymes but not glutathione peroxidase 4, the key enzyme responsible for neutralizing lipid peroxidation. These findings suggested that endogenous antioxidant defenses may be insufficient to counter iron toxicity. Therefore, I tested the efficacy of classic ferroptosis inhibitors such as ferrostatin-1 and liproxstatin-1 in protecting neurons against iron. My results showed that, although these drugs were protective in culture, they were not suitable for animal use because of their poor solubility in saline. To overcome this limitation, we designed and synthesized two new analogs with improved solubility, including PZ16044, which demonstrated comparable efficacy to ferrostatin-1 in cell culture. Additionally, treatment with PZ16044 reduced neuronal loss and prevented motor deficits in the iron-injection model. Overall, this thesis provides new insight into the antioxidant responses of the cells in the central nervous system, establishes a model for studying iron-induced neurodegeneration, and introduces a promising therapeutic analog capable of mitigating iron-driven neuronal injury.