Generation of peroxynitrite in localised, moderate temperature burns

Increased poly(ADP-ribosyl)ation in skeletal muscle tissue of pediatric patients with severe burn injury: prevention by propranolol treatment

Activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) has been shown to promote cellular energetic collapse and cellular necrosis in various forms of critical illness. Most of the evidence implicating the PARP pathway in disease processes is derived from preclinical studies. With respect to PARP and burns, studies in rodent and large animal models of burn injury have demonstrated the activation of PARP in various tissues and the beneficial effect of its pharmacological inhibition. The aims of the current study were to measure the activation of PARP in human skeletal muscle biopsies at various stages of severe pediatric burn injury and to identify the cell types where this activation may occur. Another aim of the study was to test the effect of propranolol (an effective treatment of patients with burns) on the activation of PARP in skeletal muscle biopsies. Poly(ADP-ribose) polymerase activation was measured by Western blotting for its product, poly(ADP-ribose) (PAR). The localization of PARP activation was determined by PAR immunohistochemistry. The results showed that PARP becomes activated in the skeletal muscle tissue after burns, with the peak of the activation occurring in the middle stage of the disease (13-18 days after burns). Even at the late stage of the disease (69-369 days after burn), an elevated degree of PARP activation persisted in some of the patients. Immunohistochemical studies localized the staining of PAR primarily to vascular endothelial cells and occasionally to resident mononuclear cells. There was a marked suppression of PARP activation in the skeletal muscle biopsies of patients who received propranolol treatment. We conclude that human burn injury is associated with the activation of PARP. We hypothesize that this response may contribute to the inflammatory responses and cell dysfunction in burns. Some of the clinical benefit of propranolol in burns may be related to its inhibitory effect on PARP activation.

Molecular biological effects of selective neuronal nitric oxide synthase inhibition in ovine lung injury

Neuronal nitric oxide synthase is critically involved in the pathogenesis of acute lung injury resulting from combined burn and smoke inhalation injury. We hypothesized that 7-nitroindazole, a selective neuronal nitric oxide synthase inhibitor, blocks central molecular mechanisms involved in the pathophysiology of this double-hit insult. Twenty-five adult ewes were surgically prepared and randomly allocated to 1) an uninjured, untreated sham group (n = 7), 2) an injured control group with no treatment (n = 7), 3) an injury group treated with 7-nitroindazole from 1-h postinjury to the remainder of the 24-h study period (n = 7), or 4) a sham-operated group subjected only to 7-nitroindazole to judge the effects in health. The combination injury was associated with twofold increased activity of neuronal nitric oxide synthase and oxidative/nitrosative stress, as indicated by significant increases in plasma nitrate/nitrite concentrations, 3-nitrotyrosine (an indicator of peroxynitrite formation), and malondialdehyde lung tissue content. The presence of systemic inflammation was evidenced by twofold, sixfold, and threefold increases in poly(ADP-ribose) polymerase, IL-8, and myeloperoxidase lung tissue concentrations, respectively (each P < 0.05 vs. sham). These molecular changes were linked to tissue damage, airway obstruction, and pulmonary shunting with deteriorated gas exchange. 7-Nitroindazole blocked, or at least attenuated, all these pathological changes. Our findings suggest 1) that nitric oxide formation derived from increased neuronal nitric oxide synthase activity represents a pivotal reactive agent in the patho-physiology of combined burn and smoke inhalation injury and 2) that selective neuronal nitric oxide synthase inhibition represents a goal-directed approach to attenuate the degree of injury.

Effect of melatonin on burn-induced gastric mucosal injury in rats

We studied the effect of melatonin treatment on gastric mucosal damage induced by experimental burns and its possible relation to changes in gastric lipid peroxidation status. Melatonin was intraperitoneally applied immediately after third-degree burns over 30% of total body skin surface area of rats. Malondialdehyde (MDA), uric acid (UA) and sulphydril (SH) levels were determined in gastric mucosa and blood plasma and used as biomarkers of the oxidative stress. The results showed that the skin burn caused oxidative stress evidenced by accumulation of MDA and UA as well as the depletion of SHs in gastric mucosa. Plasma MDA concentrations were elevated, while plasma SH concentrations were decreased after burns. Melatonin (10 mg per kg body weight) protected gastric mucosa from oxidative damage by suppressing lipid peroxidation and activating the antioxidant defence. It may be hypothesised that melatonin restores the redox balance in the gastric mucosa and protects it from burn-induced oxidative injury. Melatonin has no significant influence on the concentrations of plasma MDA and antioxidants after burn; therefore, it should largely be considered as a limiting factor for tissue-damage.

Nano titanium dioxide photocatalytic protein tyrosine nitration: a potential hazard of TiO2 on skin

Protein tyrosine nitration is a prevalent post-translational modification which occurs as a result of oxidative and nitrative stress, it may be directly involved in the onset and/or progression of diseases. Considering the existence of nano titanium dioxide (TiO(2)) in environment and sunscreen products along with the high content of nitrite in sweat, the UV-exposed skin may be a significant target for the photosensitized damage. In this paper, tyrosine nitration of bovine serum albumin (BSA) was initiated in the UV-irradiated reaction mixture containing 0.2-3.0mg/ml of three commercially nano TiO(2) products and 0.25-1.0mM NO2-. It was found that anatase TiO(2) and Degussa P25 TiO(2) showed prominent photocatalytic activity on promoting the formation of protein tyrosine nitration, and the optimum condition for the reaction was around physiological pH. Meanwhile, the photocatalytic effect of rutile on protein tyrosine nitration was subtle. The potential physiological significance of nano TiO(2)-photocatalytic protein nitration was also demonstrated in mouse skin homogenate. Although the relationship between photocatalytic protein tyrosine nitration and chronic cutaneous diseases needs further study, the toxicity of nano TiO(2) to the skin disease should be paid more attention in the production and utilization process.

Protective effects of green tea polyphenols in the 6-OHDA rat model of Parkinson's disease through inhibition of ROS-NO pathway

BACKGROUND

Nitric oxide (NO) and related pathways are thought to play an important role in the pathogenesis of Parkinson's disease (PD). Our in vitro experiments suggested that green tea polyphenols (GTP) might protect dopamine neurons through inhibition of NO and reactive oxygen species (ROS).

METHODS

Immunohistochemistry, terminal deoxynucleotidyl transferase-mediated dUTP Nick End Labeling assay, electron spin resonance spin trapping, enzyme linked immunosorbent assay, and molecular biological methods were used to investigate the effects of GTP in an unilateral 6-hydroxydopamine (6-OHDA)-treated rat model of PD.

RESULTS

GTP treatment dose-dependently protected dopaminergic neurons by preventing from midbrain and striatal 6-OHDA-induced increase in 1) both ROS and NO levels, 2) lipid peroxidation, 3) nitrite/nitrate content, 4) inducible nitric oxide synthase, and 5) protein-bound 3-nitro-tyrosine. Moreover, GTP treatment dose-dependently preserved the free radical scavenging capability of both the midbrain and the striatum.

CONCLUSIONS

These results support the in vivo protection of GTP against 6-OHDA and suggest that GTP treatment might represent a neuroprotective treatment of PD.

Protective effect of green tea polyphenols on the SH-SY5Y cells against 6-OHDA induced apoptosis through ROS-NO pathway

Green tea polyphenols (GTP) are thought to help prevent oxidative stress-related diseases, such as cancer, cardiovascular disease, neurodegenerative disease, and aging. We here investigate the protective mechanisms of GTP on SH-SY5Y cells against apoptosis induced by the pro-parkinsonian neurotoxin 6-hydroxydopamine (6-OHDA). GTP rescued the changes in condensed nuclear and apoptotic bodies, attenuated 6-OHDA-induced early apoptosis, prevented the decrease in mitochondrial membrane potential, and suppressed accumulation of reactive oxygen species (ROS) and of intracellular free Ca(2+). GTP also counteracted the 6-OHDA-induced nitric oxide increase and overexpression of nNOS and iNOS, and decreased the level of protein-bound 3-nitrotyrosine (3-NT). In addition, GTP inhibited the autooxidation of 6-OHDA and scavenged oxygen free radicals in a dose- and time-dependent manner. Our results show that the protective effects of GTP on SH-SY5Y cells are mediated, at least in part, by controlling the ROS-NO pathway.

Skin nitric oxide and its metabolites are increased in nonburned skin after thermal injuries

Local and systemic inflammation can lead to progression of burn wounds, converting second- to third-degree wounds or extending the burn to adjacent areas. Previous studies have suggested that the skin is an important site of production of nitric oxide (NO), synthesized by inducible nitric oxide synthase (iNOS) activation after injury. NO increases in burned wounds, but its formation in noninjured skin has not been investigated. We hypothesized that after severe burns, NO and cytotoxic peroxynitrite would increase in noninjured skin. We also tested the hypothesis that BBS-2, a specific inhibitor of iNOS, would impair NO formation after burn. Thirteen female sheep were randomized into burn injury and smoke inhalation (n = 5, group 1), burn and smoke treated with BBS-2 (n = 3, group 2), and sham (saline treatment, no injury) (n = 5, group 3). All the animals, including the sham-injury group, were mechanically ventilated for 48 h. Samples of nonburned skin and plasma were collected from each animal, and levels of NO and its metabolites were evaluated using a NO chemiluminescent detector. Nitrotyrosine and iNOS expression were determined in the skin by Immunoperoxidase staining, and scoring of masked slides (epidermis, hair follicles, vessels, glands, and stroma) was performed. Skin NO and metabolites significantly increased in the burn and smoke injury group, and this was inhibited by BBS-2. Nitrotyrosine expression also increased significantly in the skin of burned animals. BBS-2 prevented the increase of NOx but not the increase of nitrotyrosine expression in skin. Plasma levels of NO increased in burned animals when compared with sham, but this increase was not significant. The increase of NO and its metabolites after burn in noninjured skin is followed by a significant increase in peroxynitrite, a potent cytotoxic mediator.

Effects of a thermal injury on brain and blood nitric oxide (NO) content in the rat

In the present study, the effects of a thermal injury on the nitric oxide (NO)-ergic system was investigated in freely moving rats. Using a voltammetric method allowing direct and in situ NO measurements, a significant decrease in cortical NO concentration was observed during the 24h following burning procedure. Since in the burning procedure halothane was employed, it was verified that this anaesthetic did not induce significant effect on cortical NO level. Experiments conducted in ex vivo conditions showed that blood NO and nitrites (NO(2)(-)) + nitrates (NO(3)(-)) concentrations increased strongly after burn injury while hypothalamic inducible NO-synthase (NOS(2)) mRNA level decreased significantly. A thermal injury was thus accompanied by a rapid impairment of the NO-ergic pathways, which might partly have been responsible for numerous changes occurring after burn injury.

Role of intracellular calcium mobilization and cell-density-dependent signaling in oxidative-stress-induced cytotoxicity in HaCaT keratinocytes

Peroxynitrite is a nitric-oxide-derived cytotoxic mediator produced in a broad range of inflammatory conditions, ranging from sunburn erythema to contact hypersensitivity. Our previous work has shown that in HaCaT cells the cytotoxic activity of peroxynitrite involves both apoptotic and necrotic routes with poly(ADP-ribose) polymerase activation serving as a mol-ecular switch diverting the default apoptotic pathway toward necrosis. Nonetheless, keratinocytes are regarded as highly resistant toward environmental noxa including oxidative stress. We set out to investigate the possible role of two parameters, intracellular calcium mobilization and high cell density, in protecting HaCaT cells from peroxynitrite/oxidative-stress-induced cytotoxicity. First we characterized the effect of peroxynitrite on the calcium homeostasis of HaCaT cells and demonstrated that both authentic peroxynitrite and the peroxynitrite generating compound 3-morpholino-sydnonimine triggered an elevation in intracellular calcium levels. Moreover, we established that treatment of cells with the cell-permeable calcium chelator BAPTA-AM provided significant cytoprotection against peroxynitrite- and hydrogen-peroxide-induced cytotoxicity. Furthermore, when cells reached confluence they were highly resistant to the toxic effects of peroxynitrite, hydrogen peroxide, and superoxide. The resistance to oxidative stress provided by calcium chelation and high cell density involved inhibiting the activation of both poly(ADP-ribose) polymerase and caspases. Our data may provide an explanation for the resistance to oxidative stress of superficial, highly differentiated keratinocytes and indicate that basal proliferative keratinocytes are sensitive in vivo targets of oxidative stress injury.

Dissociation between gene expression and protein contents of tissue superoxide dismutase in a rat model of lethal burns

The aim of this study was to examine the changes in the tissue Cu/Zn- and the Mn-SOD contents and gene expression following mild and severe burns in a rodent burn model. Thirty-eight male Wistar rats, weighing 208-278g, were divided into a sham burn group and two burn groups, with one receiving burns to 35% of the body surface and the other to 60%. Twenty animals of the burn groups were monitored daily for 7 days after injuries to examine survival. Six animals in the sham, 35 or 60% burn group were sacrificed at 3h postburn, and the blood, lungs and kidneys were collected for a biological analysis. The Cu/Zn- and Mn-SOD contents of the tissue and plasma specimens were measured using ELISA. The mRNA expressions of Cu/Zn- and Mn-SOD were determined by a Northern blot analysis. The survival rate of the 60% burn group for 7 days was 30%, whereas the survival rate of the 35% burn group was 100%. The mRNA expressions of Mn-SODs in the lung and the kidney were significantly higher in the 60% burn group than in 35% burn or sham burn group, as was the mRNA expression of lung Cu/Zn-SOD. Nevertheless, the tissue SOD contents in the 60% burn group (mortality 70%) did not exceed those in the 35% group. Based on these findings, tissue SOD synthesis is thus suggested to be inhibited in lethal burns in spite of a strong mRNA expression of SOD.

Nitric oxide-peroxynitrite-poly(ADP-ribose) polymerase pathway in the skin

In the last decade it has become well established that in the skin, nitric oxide (NO), a diffusable gas, mediates various physiologic functions ranging from the regulation of cutaneous blood flow to melanogenesis. If produced in excess, NO combines with superoxide anion to form peroxynitrite (ONOO-), a cytotoxic oxidant that has been made responsible for tissue injury during shock, inflammation and ischemia-reperfusion. The opposite effects of NO and ONOO- on various cellular processes may explain the 'double-edged sword' nature of NO depending on whether or not cellular conditions favour peroxynitrite formation. Peroxynitrite has been shown to activate the nuclear nick sensor enzyme, poly(ADP-ribose) polymerase (PARP). Overactivation of PARP depletes the cellular stores of NAD+, the substrate of PARP, and the ensuing 'cellular energetic catastrophy' results in necrotic cell death. Whereas the role of NO in numerous skin diseases including wound healing, burn injury, psoriasis, irritant and allergic contact dermatitis, ultraviolet (UV) light-induced sunburn erythema and the control of skin infections has been extensively documented, the intracutaneous role of peroxynitrite and PARP has not been fully explored. We have recently demonstrated peroxynitrite production, DNA breakage and PARP activation in a murine model of contact hypersensitivity, and propose that the peroxynitrite-PARP route represents a common pathway in the pathomechanism of inflammatory skin diseases. Here we briefly review the role of NO in skin pathology and focus on the possible roles played by peroxynitrite and PARP in various skin diseases.

Peroxynitrite production, DNA breakage, and poly(ADP-ribose) polymerase activation in a mouse model of oxazolone-induced contact hypersensitivity

Peroxynitrite-induced poly(ADP-ribose) polymerase activation has been implicated in the pathogenesis of various inflammatory conditions. Here we have investigated whether peroxynitrite and poly(ADP-ribose) polymerase may play a role in the pathophysiology of the elicitation phase of contact hypersensitivity. We have detected nitrotyrosine, DNA breakage, and poly(ADP-ribose) polymerase activation in the epidermis of mice in an oxazolone-induced contact hypersensitivity model. As tyrosine nitration is mostly mediated by peroxynitrite, a nitric-oxide-derived cytotoxic oxidant capable of causing DNA breakage, we have applied peroxynitrite directly on mouse skin and showed poly(ADP-ribose) polymerase activation in keratinocytes and in some scattered dermal cells. We have also investigated the cellular effects of peroxynitrite in HaCaT cells, a human keratinocyte cell line. We found that peroxynitrite inhibited cell proliferation and at higher concentrations also caused cytotoxicity. Peroxynitrite activates poly(ADP-ribose) polymerase in HaCaT cells and poly(ADP-ribose) polymerase activation contributes to peroxynitrite-induced cytotoxicity, as indicated by the cytoprotective effect of the poly(ADP-ribose) polymerase inhibitor 3-aminobenzamide. The cytoprotective effect of 3-aminobenzamide cannot be attributed to inhibition of apoptosis, as apoptotic parameters (caspase activation and DNA fragmentation) were not reduced in the presence of 3-aminobenzamide in peroxynitrite-treated cells. Moreover, poly(ADP-ribose) polymerase inhibition by 3-aminobenzamide dose-dependently reduced interferon-induced intercellular adhesion molecule 1 expression as well as interleukin-1beta-induced interleukin-8 expression. Our results indicate that peroxynitrite and poly(ADP-ribose) polymerase regulate keratinocyte function and death in contact hypersensitivity.

Tyrosine nitration: localisation, quantification, consequences for protein function and signal transduction

The nitration of free tyrosine or protein tyrosine residues generates 3-nitrotyrosine the detection of which has been utilised as a footprint for the in vivo formation of peroxynitrite and other reactive nitrogen species. The detection of 3-nitrotyrosine by analytical and immunological techniques has established that tyrosine nitration occurs under physiological conditions and levels increase in most disease states. This review provides an updated, comprehensive and detailed summary of the tissue, cellular and specific protein localisation of 3-nitrotyrosine and its quantification. The potential consequences of nitration to protein function and the pathogenesis of disease are also examined together with the possible effects of protein nitration on signal transduction pathways and on the metabolism of proteins.