Relationship of nitric oxide synthase induction to peroxynitrite-mediated oxidative damage during the first week after experimental traumatic brain injury

Abstract

We have previously shown the pathophysiological importance of the reactive nitrogen species peroxynitrite (PN) formed from the reaction of nitric oxide (•NO) and superoxide (O2 •−) radicals and its involvement in lipid peroxidation (LP) and protein nitration damage in brain tissue following traumatic brain injury (TBI). Nitric oxide is produced by at least three isoforms of the enzyme nitric oxide synthase (NOS) including: endothelial NOS (eNOS) in the CNS vasculature, neuronal NOS (nNOS), and inducible NOS (iNOS) in macrophages/microglia. In view of the requirement of ●NO synthesis for PN formation, we sought to address the time course of NOS expression (mRNA by real time quantitative PCR and protein by western blot) after TBI in comparison with the time course of PN-mediated protein nitration (3-nitrotyrosine, 3-NT) in ipsilateral cortex (CTX) and hippocampus (HIPP) between 3 hours and 1 week post-injury using a controlled cortical impact (CCI) mouse model of TBI in young adult CF-1 mice. Protein nitration showed a progressive posttraumatic increase that became significant in CTX at 24 hours and then peaked at 72 hours in both CTX and HIPP. During the increase in PN-derived 3-NT, there was no increase in either CTX or HIPP eNOS mRNA levels, whereas eNOS protein levels were significantly (p<0.05) increased at 48 and 72 hours in both brain regions. There was a significant decrease in HIPP, but not CTX nNOS mRNA; however, nNOS protein did not change except for a significant increase in CTX at 1 week. There was significantly increased CTX and HIPP iNOS mRNA levels at 24, 48, and 72 hours (p<.05) post-injury. In contrast, no change was seen in CTX or HIPP iNOS protein at any timepoint. Taken together, eNOS protein expression and iNOS mRNA appear to bear a coincident temporal relationship to the time course of PN-mediated protein nitrative damage after CCI-TBI suggesting that both constitutive and inducible NOS isoforms contribute ●NO for PN formation and 3-NT protein modification after TBI.

Microglial/Macrophage Polarization Dynamics following Traumatic Brain Injury

“…The lesion micro-environment would appear to be a critical determinant for the polarization and development of microglia/macrophage phenotypes, with signals within the lesion biochemical milieu determining functional cellular responses after TBI. Further, oxidative stress and generation of reactive oxygen and nitrogen species (ROS and RNS, respectively) represent important secondary injury responses after TBI, 15 and local redox signaling is known to regulate macrophage polarization and function. 16 We recently demonstrated persistent oxidative damage in perilesional cortex and chronic expression of ROS-producing nicotinamide adenine dinucleotide phosphate oxidase (NOX2) in reactive microglia up to 12 months after a single moderate-level controlled cortical impact (CCI) that was associated with progressive neurodegeneration and chronic neurological deficits in TBI mice.…”

Reactive nitrogen species in cellular signaling

“…Several disease states have been linked to the deregulation of nitric oxide production, indicating that aberrant production of nitric oxide and its products can have deleterious consequences for the cells. [18][19][20][21][22][23] All products formed by nitric oxide reactions are collectively denominated reactive nitrogen species, which include a number of compounds with very different chemical properties and reactivity.…”

Temporal and Spatial Dynamics of Nrf2-Antioxidant Response Elements Mediated Gene Targets in Cortex and Hippocampus after Controlled Cortical Impact Traumatic Brain Injury in Mice

“…The impact velocity was held at 3.50 meters/sec while the depth of cortical deformation was set at 1.0 mm (severe) as described previously. 40 Mortality after this severe CCI brain injury is rare ( < 5.0%).…”