In the present study, we found sustained inflammation due to NF-kappaB activation in human radiated arteries. The results are supported by previous in vitro findings suggesting that deoxyribonucleic acid injury, after radiation, activates NF-kappaB. We also suggest that HOXA9 might be involved in the regulation of NF-kappaB activation. The observed sustained inflammatory response can explain cardiovascular disease years after radiation.

In this model, the most striking finding regarding NO-producing enzymes was the expression of iNOS in polymorphonuclear cells and macrophages, cells that invade injured brain tissue. iNOS is thus implicated as a therapeutic target in contusional injuries. This pattern of NOS expression cannot be generalized to all types of brain injuries. The different compartments and cells that can produce NO are differentially regulated; therefore, compartmentalization can explain why NO is beneficial or detrimental, depending on the circumstances. A knowledge of different potential sites and sources of NO is required for any attempts to interfere with the pathophysiological properties of NO.

The inflammatory response is thought to be important for secondary damage following traumatic brain injury (TBI). The inducible nitric oxide synthase (iNOS) isoform is a mediator in inflammatory reactions and may catalyze substantial synthesis of NO in the injured brain. This study was undertaken to analyze neuronal degeneration and survival, cellular apoptosis and formation of nitrotyrosine following treatment with the iNOS-inhibitor L-N-iminoethyl-lysine (L-NIL) in a model of brain contusion. A brain contusion was produced using a weight-drop device in 30 rats. The animals received treatment with L-NIL or NaCl at 15 min and 12 h after the injury and were sacrificed at 24 h or 6 days after trauma. iNOS activity was measured at 24 h post-trauma by the conversion of L-[U- ( 14 )C]arginine to L-[U-( 14 )C]citrulline and immunohistochemistry for iNOS. Peroxynitrite formation was indirectly assessed by nitrotyrosine (NT) immunohistochemistry. Neuronal degeneration and survival were assessed by Fluoro-Jade (FJ) and NeuN stainings, and cellular death by TUNEL staining. iNOS activity but not iNOS immunoreactivity was significantly reduced in animals that received L-NIL. Neuronal degeneration (FJ) and NT immunoreactivity were significantly reduced at 24 h. Neuronal survival was unchanged at 24 h but increased at 6 days in L-NIL-treated animals. Cellular apoptosis of ED-1 and NeuN positive cells was significantly reduced following L-NIL treatment at 6 days after trauma. We demonstrated neuroprotection by selective inhibition of iNOS after trauma. L-NIL appeared to protect the injured brain by limiting peroxynitrite formation. Our findings support a putative harmful role of iNOS induction early after TBI.

iNOS expression was up-regulated in a time-dependent manner in human brain tissue obtained from patients undergoing surgical treatment for contusional trauma. Our human data largely parallel experimental findings in rats, indicating that such trauma models are relevant for experimental studies and treatment trials.

In this model, the most striking finding regarding NO-producing enzymes was the expression of iNOS in polymorphonuclear cells and macrophages, cells that invade injured brain tissue. iNOS is thus implicated as a therapeutic target in contusional injuries. This pattern of NOS expression cannot be generalized to all types of brain injuries. The different compartments and cells that can produce NO are differentially regulated; therefore, compartmentalization can explain why NO is beneficial or detrimental, depending on the circumstances. A knowledge of different potential sites and sources of NO is required for any attempts to interfere with the pathophysiological properties of NO.