Systemic vitamin D3 attenuated oxidative injuries in the locus coeruleus of rat brain

Iron-induced oxidative injuries in locus coeruleus (LC), a major source of noradrenergic projections in the central nervous system (CNS), were investigated in chloral-hydrate anesthetized rats. Local infusion of iron dose-dependently elevated lipid peroxidation of iron-infused LC seven days after infusion. At the same time, norepinephrine content in the hippocampus ipsilateral to the iron-infused LC was decreased in a concentration-dependent manner. Our immunostaining study demonstrated reduced tyrosine hydroxylase-positive neurons in the iron-infused LC, indicating a reduction of neuron number by iron infusion. The involvement of apoptosis in iron-induced oxidative injuries was studied. An abrupt increase in cytosolic cytochrome c content was demonstrated in the infused LC 48 hours after iron infusion. TUNEL-positive cells, an indication of apoptosis, were detected in the iron-infused LC. In an attempt to prevent iron-induced neurotoxicity, vitamin D3, an active metabolite of vitamin D, was systemically administered. Iron-induced increases in cytosolic cytochrome c and TUNEL-positive cells were reduced by this treatment. Furthermore, systemic administration of vitamin D3 attenuated iron-induced oxidative injuries in the infused LC. Our data suggest that local infusion of iron in LC induced oxidative stress and resulted in programmed cell death in the LC-hippocampal noradrenergic system. Furthermore, vitamin D3 may be neuroprotective and therapeutic in attenuating iron-induced neurotoxicity in CNS.