engleski

Diversity of cell death pathways involved in spinal cord injury induced by metabolic perturbations mimicking ischemia and magnesium ions.

A prerequisite to the development of mechanism- based neuroprotective strategies for acute spinal cord injury (SCI) is a detailed understanding of the early pathophysiological changes to prevent later disability and paralysis. The immediate damage spreads from the initial injury site through excitotoxicity and metabolic dysfunction (ischemia, free radicals and neuroinflammation) to spared tissue (secondary damage). The aim of this research is the identification of molecular and cellular mechanisms underlying this process. Using an in vitro neonatal rat spinal cord model, an experimental protocol (pathological medium, PM) has been developed in our lab to mimic the profound metabolic perturbation (hypoxia, aglycemia, oxidative stress, acidosis, toxic free radicals) occurring in vivo after ischemic SCI, a condition worsened by extracellular Mg2+ (1 mM). In the present study, we sought to identify the cells predominantly affected by PM and Mg2+ coapplication, and the involvement of different molecular death pathways with a focus on the spinal lumbar region which contains the locomotor networks of the hindlimbs. One h PM+Mg2+ application induced early (3h later) pyknosis chiefly in the spinal white matter (via caspase 3-dependent apoptosis), and, much less, in the grey matter. Furthermore, overactivation of poly (ADP- ribose) polymerase 1 (PARP1) was detected in spinal cord lysates, suggesting cell death via the process of parthanatos. In accordance with this finding, translocation of mitochondrial apoptosis- inducing factor (AIF), namely the intracellular effector of parthanatos, was observed in the cell nuclear fraction where it induces chromatin condensation and large-scale DNA fragmentation. In particular, motoneurons showed, immediately after PM+Mg2+ washout, AIF immunopositivity that reached a peak 24h later, and lacked the canonical markers of apoptosis. Our results show that standard extracellular Mg2+ amplified the consequences of dysmetabolic SCI that comprised not only white matter apoptosis, but also progressive motoneuronal degeneration via PARP1-dependent cell death pathways.

cell death; spinal cord injury; metabolic perturbations

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