No abstract

Abnormal brain iron homeostasis has been proposed as a pathological event leading to oxidative stress and neuronal injury under pathological conditions. We examined the possibility that neuronal iron overload would mediate free radical production and delayed neuronal death (DND) in hippocampal CA1 area after transient forebrain ischemia (TFI). Mitochondrial free radicals (MFR) were biphasically generated in CA1 neurons 0.5-8 and 48-60 h after TFI. Treatment with Neu2000, a potent spin trapping molecule, as well as trolox, a vitamin E analogue, blocked the biphasic MFR production and attenuated DND in the CA1, regardless of whether it was administered immediately or even 24 h after reperfusion. The late increase in MFR was accompanied by iron accumulation and blocked by the administration of deferoxamine-an iron chelator. Iron accumulation was attributable to prolonged upregulation of the transferrin receptor and to increased uptake of peripheral iron through a leaky blood-brain barrier. Infiltration of ironcontaining cells and iron accumulation were attenuated by depletion of circulating blood cells through X-ray irradiation of the whole body except the head. The present findings suggest that excessive iron transported from blood mediates slowly evolving oxidative stress and neuronal death in CA1 after TFI, and that targeting ironmediated oxidative stress holds extended therapeutic time window against an ischemic event.

Blood cells are transported into the brain and are thought to participate in neurodegenerative processes following hypoxic ischemic injury. We examined the possibility that transient forebrain ischemia (TFI) causes the blood-brain barrier (BBB) to become permeable to blood cells, possibly via dysfunction and degeneration of endothelial cells in rats. Extravasation of Evans blue and immunoglobulin G (IgG) was observed in the hippocampal CA1-2 areas within 8 h after TFI, and peaked at 48 h. This extravasation was accompanied by loss of tight junction proteins, occludin, and zonula occludens-1, and degeneration of endothelial cells in the CA1-2 areas. Iron overload and mitochondrial free radical production were evident in the microvessel endothelium of the hippocampus before endothelial cell damage occurred. Administration of deferoxamine (DFO), an iron chelator, or Neu2000, an antioxidant, blocked free radical production and endothelial cell degeneration. Our findings suggest that iron overload and iron-mediated free radical production cause loss of tight junction proteins and degeneration of endothelial cells, opening of the BBB after TFI.

J. Neurochem. (2012) 122, 952–961. Abstract While free radicals and inflammation constitute major routes of neuronal injury occurring in amyotrophic lateral sclerosis (ALS), neither antioxidants nor non‐steroidal anti‐inflammatory drugs have shown significant efficacy in human clinical trials. We examined the possibility that concurrent blockade of free radicals and prostaglandin E2 (PGE2)‐mediated inflammation might constitute a safe and effective therapeutic approach to ALS. We have developed 2‐hydroxy‐5‐[2‐(4‐trifluoromethylphenyl)‐ethylaminobenzoic acid] (AAD‐2004) as a derivative of aspirin. AAD‐2004 completely removed free radicals at 50 nM as a potent spin‐trapping molecule and inhibited microsomal PGE2 synthase‐1 (mPGES‐1) activity in response to both lipopolysaccharide‐treated BV2 cell with IC50 of 230 nM and recombinant human mPGES‐1 protein with IC50 of 249 nM in vitro. In superoxide dismutase 1G93A transgenic mouse model of ALS, AAD‐2004 blocked free radical production, PGE2 formation, and microglial activation in the spinal cords. As a consequence, AAD‐2004 reduced autophagosome formation, axonopathy, and motor neuron degeneration, improving motor function and increasing life span. In these assays, AAD‐2004 was superior to riluzole or ibuprofen. Gastric bleeding was not induced by AAD‐2004 even at a dose 400‐fold higher than that required to obtain maximal therapeutic efficacy in superoxide dismutase 1G93A. Targeting both mPGES‐1‐mediated PGE2 and free radicals may be a promising approach to reduce neurodegeneration in ALS and possibly other neurodegenerative diseases.