A well characterized pathological process occurring early after SCI is the formation of reactive oxygen (ROS) and reactive nitrogen species (RNS; Azbill et al. 1997, Xiong et al. 2007). This is sequel to increased intracellular calcium levels, mitochondrial dysfunction, arachidonic acid breakdown and activation of
inducible nitric oxide synthase (iNOS; Hall and Springer 2004, McTigue 2008). ROS and RNS cause lipid peroxidation as well as oxidative and nitrative
damage to proteins and nucleic acids (Xu et al. 2005).
Apart from cell membrane lysis; leading to neuronal
loss, free radicals invoke other types of damage particularly
on the cytoskeleton and organelles. In lipid
peroxidation, free radicals absorb an electron from a
lipid molecule, which in turn becomes less stable, thus
launching a chain reaction that ultimately leads to lysis
of the membrane and death by necrosis. In addition,
oxidative damage exacerbates mitochondrial dysfunction
(Sullivan et al. 2007) and contributes to intracellular
calcium overload which activates proteases resulting
in breakdown of cytoskeletal proteins (Xiong et al.
2007). Thus, the collective damage induced by ROS
and RNS is widespread and may be central in the etiology
of cellular death (necrotic and apoptotic) and functional
loss after SCI.