Role of peroxynitrite in secondary oxidative damage after spinal cord injury

Abstract

Peroxynitrite (PON, ONOO ) ), formed by nitric oxide synthasegenerated nitric oxide radical ( AE NO) and superoxide radical (O 2 AE) ), is a crucial player in post-traumatic oxidative damage. In the present study, we determined the spatial and temporal characteristics of PON-derived oxidative damage after a moderate contusion injury in rats. Our results showed that 3-nitrotyrosine (3-NT), a specific marker for PON, rapidly accumulated at early time points (1 and 3 h) and a significant increase compared with sham rats was sustained to 1 week after injury. Additionally, there was a coincident and maintained increase in the levels of protein oxidation-related protein carbonyl and lipid peroxidation-derived 4-hydroxynonenal (4-HNE). The peak increases of 3-NT and 4-HNE were observed at 24 h post-injury. In our immunohistochemical results, the co-localization of 3-NT and 4-HNE results indicates that PON is involved in lipid peroxidative as well as protein nitrative damage. One of the consequences of oxidative damage is an exacerbation of intracellular calcium overload, which activates the cysteine protease calpain leading to the degradation of several cellular targets including cytoskeletal protein (a-spectrin). Western blot analysis of a-spectrin breakdown products showed that the 145-kDa fragments of aspectrin, which are specifically generated by calpain, were significantly increased as soon as 1 h following injury although the peak increase did not occur until 72 h post-injury. The later activation of calpain is most likely linked to PON-mediated secondary oxidative impairment of calcium homeostasis. Scavengers of PON, or its derived free radical species, may provide an improved antioxidant neuroprotective approach for the treatment of post-traumatic oxidative damage in the injured spinal cord.

Temporal and Spatial Dynamics of Peroxynitrite-Induced Oxidative Damage After Spinal Cord Contusion Injury

“…The current results, as well as those of earlier studies (Bao et al, 2003; Genovese et al, 2007; Liu et al, 2005; Scott et al, 1999; Scott et al, 2003; Scott et al, 2005; Xiong et al, 2007; Xiong and Hall, 2009), suggest that the administration of antioxidants that target PN or PN-derived radicals within the first hours after SCI should provide effective neuroprotection. In agreement with this idea, compounds that can either scavenge peroxynitrite such as uric acid (Scott et al, 2005) or FeTSPP (Genovese et al, 2007), or its derived free radicals such as tempol (Hillard et al, 2004; Xiong and Hall, 2009) have been reported to attenuate post-SCI spinal tissue damage.…”

“…Prior studies in other laboratories (Liu et al, 2000; Scott et al, 1999) and our own (Xiong et al, 2007) have demonstrated 3-NT immunostaining in the injured spinal cord. Furthermore, recent work in our laboratory has provided convincing evidence for an important role of PN in the oxidative damage that occurs in the injured spinal cord and its relationship to other secondary injury events including intracellular calcium overload, mitochondrial dysfunction, and calpain-mediated cytoskeletal protein degradation (Xiong et al, 2007).…”

“…Previous studies have shown that there is an increase in 3-NT levels in spinal cord tissue during the first hours and days after acute contusion SCI (Bao et al, 2003; Liu et al, 2000; Scott et al, 1999; Scott et al, 2003; Xiong et al, 2007). Additional work has demonstrated that the infusion of PN at levels that mimic the estimated concentration produced in the contused spinal cord produces nitrative immunostaining and neuronal damage similar to that produced by contusion injury (Liu et al, 2005).…”

“…Additional work has demonstrated that the infusion of PN at levels that mimic the estimated concentration produced in the contused spinal cord produces nitrative immunostaining and neuronal damage similar to that produced by contusion injury (Liu et al, 2005). The increase in 3-NT is paralleled by increases in LP products (Xiong et al, 2007) and the activation of the DNA repair enzyme poly-ADP ribose polymerase (Scott et al, 1999; Scott et al, 2004); both of these pathochemical events are known to be capable of being produced by PN (Beckman et al, 1990; Beckman, 1991; Beckman, 2002; Pacher et al, 2007; Radi et al, 1991). A recent report from our laboratory has shown that the coincident increase in the levels of 3-NT and the LP product 4-HNE during the first hour after injury persists at least until 7 days post-injury (Xiong et al, 2007).…”

“…The increase in 3-NT is paralleled by increases in LP products (Xiong et al, 2007) and the activation of the DNA repair enzyme poly-ADP ribose polymerase (Scott et al, 1999; Scott et al, 2004); both of these pathochemical events are known to be capable of being produced by PN (Beckman et al, 1990; Beckman, 1991; Beckman, 2002; Pacher et al, 2007; Radi et al, 1991). A recent report from our laboratory has shown that the coincident increase in the levels of 3-NT and the LP product 4-HNE during the first hour after injury persists at least until 7 days post-injury (Xiong et al, 2007). However, none of these prior reports has fully documented the spatial and temporal characteristics of PN-mediated oxidative damage in the injured cord related to protein nitration (3-NT) and LP (4-HNE).…”