Oxidative stress in conjunction with glutathione depletion has been linked with various acute and chronic degenerative disorders, yet the molecular mechanisms have remained unclear. In contrast to the belief that oxygen radicals are detrimental to cells and tissues by unspecific oxidation of essential biomolecules, we now demonstrate that oxidative stress is sensed and transduced by glutathione peroxidase 4 (GPx4) into a-yet-unrecognized cell-death pathway. Inducible GPx4 inactivation in mice and cells revealed 12/15-lipoxygenase-derived lipid peroxidation as specific downstream event, triggering apoptosis-inducing factor (AIF)-mediated cell death. Cell death could be entirely prevented either by alpha-tocopherol (alpha-Toc), 12/15-lipoxygenase inhibitors, or siRNA-mediated AIF silencing. Accordingly, 12/15-lipoxygenase-deficient cells were highly resistant to glutathione depletion. Neuron-specific GPx4 depletion caused neurodegeneration in vivo and ex vivo, highlighting the importance of this pathway in neuronal cells. Since oxidative stress is common in the etiology of many human disorders, the identified pathway reveals promising targets for future therapies.

An imaging technique lets scientists peer through the skin of a whole mouse or rat to examine its organs after death. Ali Ertürk of the Ludwig Maximilians University of Munich in Germany and his colleagues created a technique called ultimate DISCO (uDISCO), which removes pigments and lipids from the tissues of dead animals using an organic solvent. This leaves the organs and skin intact but transparent, while preserving genetically encoded fluorescent proteins. The method revealed the nervous system of a mouse in stark detail. uDISCO also shrinks bodies by up to 65%, making it possible to image whole animals using light-sheet microscopy, which excels at imaging smaller samples. Nature Methods http://dx.

Delayed neuronal cell death occurring hours after reperfusion is a hallmark of ischemic stroke and a primary target for neuroprotective strategies. In the present study, we investigated whether apoptosis-inducing factor (AIF), a caspase-independent proapoptotic protein, is responsible for neuronal cell death after glutamate toxicity and oxygen-glucose deprivation (OGD) in vitro and after experimental stroke in vivo. AIF translocated to the nucleus in which it colocalized with DNA fragmentation and nuclear apoptotic morphology after exposure to glutamate or OGD in cultured neurons or after transient middle cerebral artery occlusion (MCAo) in mice. Small inhibitory RNAmediated downregulation of AIF reduced glutamate-and OGD-induced neuronal apoptosis by 37 and 60%, respectively ( p Ͻ 0.01). Moreover, Harlequin mutant mice, which express AIF at low levels (ϳ20% of wild-type mice), displayed smaller infarct volumes (Ϫ43%; p Ͻ 0.03) and showed dramatically reduced cell death in the ischemic penumbra after 45 min of MCAo compared with wild-type littermates. Inhibition of poly(ADP-ribose) polymerase and Bid reduced nuclear AIF translocation. These results provide the first evidence for a causal role of AIF in ischemic neuronal cell death. Therefore, caspase-independent cell death signaling may provide a promising novel target for therapeutic interventions in cerebrovascular diseases.

Impaired regulation of mitochondrial dynamics, which shifts the balance towards fission, is associated with neuronal death in age-related neurodegenerative diseases, such as Alzheimer's disease or Parkinson's disease. A role for mitochondrial dynamics in acute brain injury, however, has not been elucidated to date. Here, we investigated the role of dynamin-related protein 1 (Drp1), one of the key regulators of mitochondrial fission, in neuronal cell death induced by glutamate toxicity or oxygen-glucose deprivation (OGD) in vitro, and after ischemic brain damage in vivo. Drp1 siRNA and small molecule inhibitors of Drp1 prevented mitochondrial fission, loss of mitochondrial membrane potential (MMP), and cell death induced by glutamate or tBid overexpression in immortalized hippocampal HT-22 neuronal cells. Further, Drp1 inhibitors protected primary neurons against glutamate excitotoxicity and OGD, and reduced the infarct volume in a mouse model of transient focal ischemia. Our data indicate that Drp1 translocation and associated mitochondrial fission are key features preceding the loss of MMP and neuronal cell death. Thus, inhibition of Drp1 is proposed as an efficient strategy of neuroprotection against glutamate toxicity and OGD in vitro and ischemic brain damage in vivo. Mitochondria play crucial roles in energy metabolism, regulation of free radical formation and calcium storage, thereby determining essential metabolic functions and cell survival. 1 Further, mitochondria are highly dynamic organelles that undergo constant fission and fusion and these morphological changes are required for efficient ATP production, calcium buffering, regulation of signal transduction and apoptosis. 2 In neurons, mitochondrial fission is also essential for axonal transport of the organelles into areas of high metabolic demand, 3 whereas mitochondrial fusion supports substitution and regeneration of mitochondrial proteins, mtDNA repair and functional recovery. 2,4 Consistent with the critical roles of mitochondrial dynamics in neurons, defects in mitochondrial fission and fusion proteins are associated with a wide array of inherited or acquired neurodegenerative diseases such as Charcot-Marie-Tooth disease or Alzheimer's disease, respectively. 2 Fission and fusion defects may limit mitochondrial motility, decrease energy production, promote oxidative stress and lead to accumulating of mtDNA defects, thereby promoting neuronal dysfunction and cell death. 1 Recently, enhanced mitochondrial fragmentation was associated with induction of neuronal death triggered by oxidative stress. 5 These data imply that during neuronal cell death, the tubular mitochondrial network is fragmented into smaller and functionally impaired organelles. 5 It is, however, a matter of ongoing controversy, whether mitochondrial fragmentation is cause or consequence in programmed cell death.Current knowledge of the mechanisms regulating mitochondrial dynamics indicates that fission and fusion of mitochondria are under control of highly conserved dynamin-relate...

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