Oxidative stress is associated with region-specific neuronal death during thiamine deficiency

Thiamine deficiency (TD) is a model of chronic impairment of oxidative metabolism and selective neuronal loss. TD leads to region-specific neuronal death and elevation of inducible nitric oxide synthase (iNOS) in macrophages/microglia in mouse brain. Identification of the initial site of neuronal death in the submedial thalamic nucleus allowed us to test the role of iNOS and oxidative stress in TD-induced neuronal death. The pattern of neuronal loss, which begins after 9 days of TD, overlapped with induction of the oxidative stress marker heme oxygenase-1 (HO-1) in microglia. Neuronal death and microglial HO-1 induction spread to engulf the whole thalamus after 11 days of TD. As in past studies, reactive iron and ferritin accumulated in microglia beginning on day 10. The lipid peroxidation product, 4-hydroxynonenal (HNE) accumulated in the remaining thalamic neurons only after 11 days of TD. These responses were not likely mediated by iNOS because HO-1 induction and HNE accumulation were comparable in iNOS knockout mice and wild-type controls. These results show that region and cell specific oxidative stress is associated with selective neurodegeneration during TD. Thus, TD is a useful model to help elucidate neuron-microglial interaction in neurodegenerative diseases associated with oxidative stress.