Impaired mitochondrial respiration and protein nitration in the rat hippocampus after acute inhalation of combustion smoke

[Correlation of cardiovascular risk factors with brain iron deposition: A magnetic resonance imaging study]

OBJECTIVE

To study the correlation of common cardiovascular risk factors with brain iron deposition.

METHODS

Eighty-four elderly subjects without neurological diseases or brain trauma were included in the study. The cardiovascular risk factors were comprehensively assessed. MRI examination was performed to obtain high-resolution T1-weighted images and enhanced susceptibility weighted angiography (ESWAN) images, and R2* figure was obtained by post-processing the ESWAN sequence. High definition T1 images were segmented using computer segmentation technique. After registration to the ESWAN image, R2* values of each region of interest were extracted. Multiple linear regression analysis was used to analyze the relationship of R2* values in each area of interest with gender, age and vascular risk factors.

RESULTS

Smoking was associated with increased R2* values in the hippocampus, white matter and cortex (β=0.244, 0.317, 0.277, P<0.05 or P<0.01). Hypertension was correlated with the increase of R2* in the putamen (β=0.241, P=0.027). Hyperglycemia was associated with the increase of R2* in the thalamus (β=0.234, P<0.05). In the thalamus, the R2* value of males was higher than that of females (β=0.320, P<0.05). Age was correlated with the R2* values of thalamus, caudate nucleus, pallidus, white matter and cortex (β=-0.218、-0.254、0.216、-0.280 and -0.238, P<0.05 or P<0.01).

CONCLUSIONS

Common cardiovascular risk factors may lead to iron deposition in the brain, and the deposition patterns vary with the gender, age and different risk factors.

Elevated Neuroglobin Lessens Neuroinflammation and Alleviates Neurobehavioral Deficits Induced by Acute Inhalation of Combustion Smoke in the Mouse

Acute inhalation of combustion smoke produces long-term neurologic deficits in survivors. To study the mechanisms that contribute to the development of neurologic deficits and identify targets for prevention, we developed a mouse model of acute inhalation of combustion smoke, which supports longitudinal investigation of mechanisms that underlie the smoke induced inimical sequelae in the brain. Using a transgenic mouse engineered to overexpress neuroglobin, a neuroprotective oxygen-binding globin protein, we previously demonstrated that elevated neuroglobin preserves mitochondrial respiration and attenuates formation of oxidative DNA damage in the mouse brain after smoke exposure. In the current study, we show that elevated neuronal neuroglobin attenuates the persistent inflammatory changes induced by smoke exposure in the mouse brain and mitigates concordant smoke-induced long-term neurobehavioral deficits. Specifically, we found that increases in hippocampal density of GFAP and Iba-1 positive cells that are detected post-smoke in wild-type mice are absent in the neuroglobin overexpressing transgenic (Ngb-tg) mice. Similarly, the smoke induced hippocampal myelin depletion is not observed in the Ngb-tg mice. Importantly, elevated neuroglobin alleviates behavioral and memory deficits that develop after acute smoke inhalation in the wild-type mice. Taken together, our findings suggest that the protective effects exerted by neuroglobin in the brains of smoke exposed mice afford protection from long-term neurologic sequelae of acute inhalation of combustion smoke. Our transgenic mouse provides a tool for assessing the potential of elevated neuroglobin as possible strategy for management of smoke inhalation injury.

Acute inhalation of combustion smoke triggers neuroinflammation and persistent anxiety-like behavior in the mouse

CONTEXT

Acute inhalation of combustion smoke triggers neurologic sequelae in survivors. Due to the challenges posed by heterogeneity of smoke exposures in humans, mechanistic links between acute smoke inhalation and neuropathologic sequelae have not been systematically investigated.

METHODS

Here, using mouse model of acute inhalation of combustion smoke, we studied longitudinal neurobehavioral manifestations of smoke exposures and molecular/cellular changes in the mouse brain.

RESULTS

Immunohistochemical analyses at eight months post-smoke, revealed hippocampal astrogliosis and microgliosis accompanied by reduced myelination. Elevated expression of proinflammatory cytokines was also detected. Longitudinal testing in different neurobehavioral paradigms in the course of post-smoke recovery, revealed lasting anxiety-like behavior. The examined paradigms included the open field exploration/anxiety testing at two, four and six months post-smoke, which detected decreases in total distance traveled and time spent in the central arena in the smoke-exposed compared to sham-control mice, suggestive of dampened exploratory activity and increased anxiety-like behavior. In agreement with reduced open field activity, cued fear conditioning test revealed increased freezing in response to conditioned auditory stimulus in mice after acute smoke inhalation. Similarly, elevated plus maze testing demonstrated lesser presence in open arms of the maze, consistent with anxiety-like behavior, for the post-smoke exposure mice.

CONCLUSIONS

Taken together, our data demonstrate for the first time persistent neurobehavioral manifestations of acute inhalation of combustion smoke and provide new insights into long-term progression of events initiated by disrupted brain oxygenation that might contribute to lasting adverse sequelae in survivors of smoke inhalation injuries.

Neuroproteomic study of nitrated proteins in moderate traumatic brain injured rats treated with gamma glutamyl cysteine ethyl ester administration post injury: Insight into the role of glutathione elevation in nitrosative stress

PURPOSE

The aims of this study are to establish a time point to determine the most beneficial time to administer GCEE post incident to reduce oxidative damage and second, by using redox proteomics, to determine if GCEE can readily suppress 3-NT modification in TBI animals.

EXPERIMENTAL DESIGN

By using a moderate traumatic brain injury model with Wistar rats, it is hypothesized that the role of 3-nitrotyrosine (3-NT) formation as an intermediate will predict the involvement of protein nitration/nitrosation and oxidative damage in the brain.

RESULTS

In this experiment, the levels of protein carbonyls, 4-hydroxynonenal, and 3-nitrotyrosine were significantly elevated in TBI injured, saline treated rats compared with those who sustained an injury and were treated with 150 mg/kg of the glutathione mimetic, GCEE.

CONCLUSION AND CLINICAL RELEVANCE

Determining the existence of elevated 3-NT levels provides insight into the relationship between the protein nitration/nitrosation and the oxidative damage, which can determine the pathogenesis and progression of specific neurological diseases.

Cardiac-specific overexpression of catalase prevents diabetes-induced pathological changes by inhibiting NF-κB signaling activation in the heart

Catalase is an antioxidant enzyme that specifically catabolizes hydrogen peroxide (H2O2). Overexpression of catalase via a heart-specific promoter (CAT-TG) was reported to reduce diabetes-induced accumulation of reactive oxygen species (ROS) and further prevent diabetes-induced pathological abnormalities, including cardiac structural derangement and left ventricular abnormity in mice. However, the mechanism by which catalase overexpression protects heart function remains unclear. This study found that activation of a ROS-dependent NF-κB signaling pathway was downregulated in hearts of diabetic mice overexpressing catalase. In addition, catalase overexpression inhibited the significant increase in nitration levels of key enzymes involved in energy metabolism, including α-oxoglutarate dehydrogenase E1 component (α-KGD) and ATP synthase α and β subunits (ATP-α and ATP-β). To assess the effects of the NF-κB pathway activation on heart function, Bay11-7082, an inhibitor of the NF-κB signaling pathway, was injected into diabetic mice, protecting mice against the development of cardiac damage and increased nitrative modifications of key enzymes involved in energy metabolism. In conclusion, these findings demonstrated that catalase protects mouse hearts against diabetic cardiomyopathy, partially by suppressing NF-κB-dependent inflammatory responses and associated protein nitration.

Mass spectrometry analysis of nitrotyrosine-containing proteins

Oxidative stress plays important roles in a wide range of diseases such as cancer, inflammatory disease, neurodegenerative disorders, etc. Tyrosine nitration in a protein is a chemically stable oxidative modification, and a marker of oxidative injuries. Mass spectrometry (MS) is a key technique to identify nitrotyrosine-containing proteins and nitrotyrosine sites in endogenous and synthetic nitroproteins and nitropeptides. However, in vivo nitrotyrosine-containing proteins occur with extreme low-abundance to severely challenge the use of MS to identify in vivo nitroproteins and nitrotyrosine sites. A preferential enrichment of nitroproteins and/or nitropeptides is necessary before MS analysis. Current enrichment methods include immuno-affinity techniques, chemical derivation of the nitro group plus target isolations, followed with tandem mass spectrometry analysis. This article reviews the MS techniques and pertinent before-MS enrichment techniques for the identification of nitrotyrosine-containing proteins. This article reviews future trends in the field of nitroproteomics, including quantitative nitroproteomics, systems biological networks of nitroproteins, and structural biology study of tyrosine nitration to completely clarify the biological functions of tyrosine nitration.

Neuroglobin mitigates mitochondrial impairments induced by acute inhalation of combustion smoke in the mouse brain

CONTEXT

Acute inhalation of combustion smoke adversely affects brain homeostasis and energy metabolism. We previously showed that overexpressed neuroglobin (Ngb), neuron specific globin protein, attenuates the formation of smoke inhalation-induced oxidative DNA damage, in vivo, in the mouse brain, while others reported protection by Ngb in diverse models of brain injury, mainly involving oxidative stress and hypoxic/ischemic insults.

OBJECTIVE

To determine to what extent elevated Ngb ameliorates post smoke-inhalation brain bioenergetics and homeostasis in Ngb overexpressing transgenic mouse.

METHODS

Smoke inhalation induced changes in bioenergetics were measured in the wild type and Ngb transgene mouse brain. Modulations of mitochondrial respiration were analyzed using the Seahorse XF24 flux analyzer and changes in cytoplasmic energy metabolism were assessed by measuring enzymatic activities and lactate in the course of post smoke recovery.

RESULTS

Cortical mitochondria from Ngb transgene, better maintained ATP synthesis-linked oxygen consumption and unlike wild type mitochondria did not increase futile oxygen consumption feeding the proton leak, reflecting lesser smoke-induced mitochondrial compromise. Measurements revealed lesser reduction of mitochondrial ATP content and lesser compensatory increases in cytosolic energy metabolism, involving pyruvate kinase and lactate dehydrogenase activities as well as cytosolic lactate levels. Additionally, induction of c-Fos, the early response gene and key neuronal stress sensor, was attenuated in Ngb transgene compared to wild type brain after smoke.

CONCLUSION

Considered together, these differences reflect lesser perturbations produced by acute inhalation of combustion smoke in the Ngb overexpressing mouse, suggesting that Ngb mitigates mitochondrial dysfunction and neurotoxicity and raises the threshold of smoke inhalation-induced brain injury.

Exercise-induced neuroprotection of hippocampus in APP/PS1 transgenic mice via upregulation of mitochondrial 8-oxoguanine DNA glycosylase

Improving mitochondrial function has been proposed as a reasonable therapeutic strategy to reduce amyloid-β (Aβ) load and to modify the progression of Alzheimer's disease (AD). However, the relationship between mitochondrial adaptation and brain neuroprotection caused by physical exercise in AD is poorly understood. This study was undertaken to investigate the effects of long-term treadmill exercise on mitochondrial 8-oxoguanine DNA glycosylase-1 (OGG1) level, mtDNA oxidative damage, and mitochondrial function in the hippocampus of APP/PS1 transgenic mouse model of AD. In the present study, twenty weeks of treadmill training significantly improved the cognitive function and reduced the expression of Aβ-42 in APP/PS1 transgenic (Tg) mice. Training also ameliorated mitochondrial respiratory function by increasing the complexes I, and IV and ATP synthase activities, whereas it attenuated ROS generation and mtDNA oxidative damage in Tg mice. Furthermore, the impaired mitochondrial antioxidant enzymes and mitochondrial OGG1 activities seen in Tg mice were restored with training. Acetylation level of mitochondrial OGG1 and MnSOD was markedly suppressed in Tg mice after exercise training, in parallel with increased level of SIRT3. These findings suggest that exercise training could increase mtDNA repair capacity in the mouse hippocampus, which in turn would result in protection against AD-related mitochondrial dysfunction and phenotypic deterioration.

Combustion smoke-induced inflammation in the olfactory bulb of adult rats

BACKGROUND

The damaging effect of combustion smoke inhalation on the lung is widely reported but information on its effects on the olfactory bulb is lacking. This study sought to determine the effects of smoke inhalation on the olfactory bulb, whose afferent input neurons in the nasal mucosa are directly exposed to external stimuli, such as smoke.

METHODS

Adult male Sprague-Dawley rats were subjected to combustion smoke inhalation and sacrificed at different time points. Changes in olfactory bulb proteins including vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), Na+-K+-Cl- cotransporter 1 (NKCC1), glial fibrillary acidic protein (GFAP), and aquaporin-4 (AQP4) were evaluated by Western blot analysis. In addition, ELISA was conducted for cytokine and chemokine levels, and double immunofluorescence labeling was carried out for GFAP/VEGF, GFAP/AQP4, NeuN/nNOS, GFAP/NKCC1, NeuN/NKCC1, GFAP/Rhodamine isothiocyanate (RITC), and transferase dUTP nick end labeling (TUNEL). Aminoguanidine was administered to determine the effects of iNOS inhibition on the targets probed after smoke inhalation.

RESULTS

The results showed a significant increase in VEGF, iNOS, eNOS, nNOS, NKCC1, and GFAP expression in the bulb tissues, with corresponding increases in inflammatory cytokines and chemokines after smoke inhalation. Concurrent to this was a drastic increase in AQP4 expression and RITC permeability. Aminoguanidine administration decreased the expression of iNOS and RITC extravasation after smoke inhalation. This was coupled with a significant reduction in incidence of TUNEL + cells that was not altered with administration of L-NG-nitroarginine methyl ester (L-NAME).

CONCLUSIONS

These findings suggest that the upregulation of iNOS in response to smoke inhalation plays a major role in the olfactory bulb inflammatory pathophysiology, along with a concomitant increase in pro-inflammatory molecules, vascular permeability, and edema. Overall, these findings indicate that the olfactory bulb is vulnerable to smoke inhalation.

Pathophysiology of tobacco smoke exposure: recent insights from comparative and redox proteomics

First-hand and second-hand tobacco smoke are causally linked to a huge number of deaths and are responsible for a broad spectrum of pathologies such as cancer, cardiovascular, respiratory, and eye diseases as well as adverse effects on female reproductive function. Cigarette smoke is a complex mixture of thousands of different chemical species, which exert their negative effects on macromolecules and biochemical pathways, both directly and indirectly. Many compounds can act as oxidants, pro-inflammatory agents, carcinogens, or a combination of these. The redox behavior of cigarette smoke has many implications for smoke related diseases. Reactive oxygen and nitrogen species (both radicals and non-radicals), reactive carbonyl compounds, and other species may induce oxidative damage in almost all the biological macromolecules, compromising their structure and/or function. Different quantitative and redox proteomic approaches have been applied in vitro and in vivo to evaluate, respectively, changes in protein expression and specific oxidative protein modifications induced by exposure to cigarette smoke and are overviewed in this review. Many gel-based and gel-free proteomic techniques have already been used successfully to obtain clues about smoke effects on different proteins in cell cultures, animal models, and humans. The further implementation with other sensitive screening techniques could be useful to integrate the comprehension of cigarette smoke effects on human health. In particular, the redox proteomic approach may also help identify biomarkers of exposure to tobacco smoke useful for preventing these effects or potentially predictive of the onset and/or progression of smoking-induced diseases as well as potential targets for therapeutic strategies.

Metallothionein prevents cardiac pathological changes in diabetes by modulating nitration and inactivation of cardiac ATP synthase

Mitochondrial ATP production is the main energy source for the cell. Diabetes reduces the efficient generation of ATP, possibly due to the inactivation of ATP synthase. However, the exact mechanism by which diabetes induces inactivation of ATP synthase remains unknown, as well as whether such inactivation has a role in the development of pathological abnormalities of the diabetic heart. To address these issues, we used cardiac metallothionein-transgenic (MT-TG) and wild-type (WT) mice with streptozotocin-induced diabetes, since we have demonstrated previously that diabetes-induced cardiac damage and remodeling were found in WT diabetic mice, but not in MT-TG diabetic mice. Immunohistochemical and biochemical assays were used to compare pathological and biochemical changes of the heart between MT-TG and WT diabetic mice, and a proteomic assay to evaluate ATP synthase expression and tyrosine nitration, with its activity. LC/MS analysis revealed that diabetes increased tyrosine nitration of the ATP synthase α subunit at Tyr(271), Tyr(311), and Tyr(476), and the β subunit at Tyr(269) and Tyr(508), and also significantly reduced ATP synthase activity by ~32%. These changes were not observed in MT-TG diabetic mice. Furthermore, parallel experiments with induced expression of cardiac MT by zinc supplementation in diabetic mice produced similar effects. These results suggest that MT can preserve ATP synthase activity in streptozotocin-induced diabetes, probably through the inhibition of ATP synthase nitration.

Combustion smoke-induced inflammation in the cerebellum and hippocampus of adult rats

AIMS

The effect of combustion smoke inhalation on the respiratory system is widely reported but its effects on the central nervous system remain unclear. Here, we aimed to determine the effects of smoke inhalation on the cerebellum and hippocampus which are areas vulnerable to hypoxia injury.

METHODS

Adult male Sprague-Dawley rats were subjected to combustion smoke inhalation and sacrificed at 0.5, 3, 24 and 72 h after exposure. The cerebellum and hippocampus were subjected to Western analysis for VEGF, iNOS, eNOS, nNOS and AQP4 expression; ELISA analysis for cytokine and chemokine levels; and immunohistochemistry for GFAP/AQP4, RECA-1/RITC and TUNEL. Aminoguanidine (AG) was administered to determine the effects of iNOS after smoke inhalation.

RESULTS

Both the cerebellum and hippocampus showed a significant increase in VEGF, iNOS, eNOS, nNOS and AQP4 expression with corresponding increases in inflammatory cytokines and chemokines and increased AQP4 expression and RITC permeability after smoke exposure. AG was able to decrease the expression of iNOS, followed by VEGF, eNOS, nNOS, RITC and AQP4 after smoke exposure. There was also a significant increase in TUNEL+ cells in the cerebellum and hippocampus which were not significantly reduced by AG. Beam walk test revealed immediate deficits after smoke inhalation which was attenuated with AG.

CONCLUSION

The findings suggest that iNOS plays a major role in the central nervous system inflammatory pathophysiology after smoke inhalation exposure with concomitant increase in proinflammatory molecules, vascular permeability and oedema, for which the cerebellum appears to be more vulnerable to smoke exposure than the hippocampus.

Overexpressed neuroglobin raises threshold for nitric oxide-induced impairment of mitochondrial respiratory activities and stress signaling in primary cortical neurons

Surges of nitric oxide compromise mitochondrial respiration primarily by competitive inhibition of oxygen binding to cytochrome c oxidase (complex IV) and are particularly injurious in neurons, which rely on oxidative phosphorylation for all their energy needs. Here, we show that transgenic overexpression of the neuronal globin protein, neuroglobin, helps diminish protein nitration, preserve mitochondrial function and sustain ATP content of primary cortical neurons challenged by extended nitric oxide exposure. Specifically, in transgenic neurons, elevated neuroglobin curtailed nitric oxide-induced alterations in mitochondrial oxygen consumption rates, including baseline oxygen consumption, consumption coupled with ATP synthesis, proton leak and spare respiratory capacity. Concomitantly, activation of genes involved in sensing and responding to oxidative/nitrosative stress, including the early-immediate c-Fos gene and the phase II antioxidant enzyme, heme oxygenase-1, was diminished in neuroglobin-overexpressing compared to wild-type neurons. Taken together, these differences reflect a lesser insult produced by similar concentrations of nitric oxide in neuroglobin-overexpressing compared to wild-type neurons, suggesting that abundant neuroglobin buffers nitric oxide and raises the threshold of nitric oxide-mediated injury in neurons.

Reversible inactivation of dihydrolipoamide dehydrogenase by mitochondrial hydrogen peroxide

Under oxidative stress conditions, mitochondria are the major site for cellular production of reactive oxygen species (ROS) such as superoxide anion and H2O2 that can attack numerous mitochondrial proteins including dihydrolipoamide dehydrogenase (DLDH). While DLDH is known to be vulnerable to oxidative inactivation, the mechanisms have not been clearly elucidated. The present study was therefore designed to investigate the mechanisms of DLDH oxidative inactivation by mitochondrial reactive oxygen species (ROS). Mitochondria, isolated from rat brain, were incubated with mitochondrial respiratory substrates such as pyruvate/malate or succinate in the presence of electron transport chain inhibitors such as rotenone or antimycin A. This is followed by enzyme activity assay and gel-based proteomic analysis. The present study also examined whether ROS-induced DLDH oxidative inactivation could be reversed by reducing reagents such as DTT, cysteine, and glutathione. Results show that DLDH could only be inactivated by complex III- but not complex I-derived ROS; and the accompanying loss of activity due to the inactivation could be restored by cysteine and glutathione, indicating that DLDH oxidative inactivation by complex III-derived ROS was a reversible process. Further studies using catalase indicate that it was H2O2 instead of superoxide anion that was responsible for DLDH inactivation. Moreover, using sulfenic acid-specific labeling techniques in conjunction with two-dimensional Western blot analysis, we show that protein sulfenic acid formation (also known as sulfenation) was associated with the loss of DLDH enzymatic activity observed under our experimental conditions. Additionally, such oxidative modification was shown to be associated with preventing DLDH from further inactivation by the thiol-reactive reagent N-ethylmaleimide. Taken together, the present study provides insights into the mechanisms of DLDH oxidative inactivation by mitochondrial H2O2.

Mitochondrial dysfunction, oxidative stress, and major depressive disorder

There is controversy about depression being a physical illness, in part because a reproducible, sensitive, and specific biologic marker is not available. However, there is evidence that mitochondrial dysfunction and oxidative stress may be associated with abnormal brain function and mood disorders, such as depression. This paper reviews selected human and animal studies providing evidence that intracellular mitochondrial metabolic dysfunction in specific brain regions is associated with major depressive disorder. This supports the hypothesis that chronic mitochondrial dysfunction in specific tissues may be associated with depression. Evaluation of mitochondrial dysfunction in specific tissues may broaden the perspective of depression beyond theories about neurotransmitters or receptor sites, and may explain the persistent signs and symptoms of depression.

Progressive neuropsychiatric and brain abnormalities after smoke inhalation

A 46-year-old man inhaled combustible smoke of unknown chemical composition for 15-20 min in an automobile body shop. Within 1&emsp14;month, he noted headache, sadness, anergia, anhedonia, agitation, poor sleep and impairment of concentration, attention and learning skills. Three years later, mental status examination showed major depression and cognitive disorder manifested by apprehension, continuous sadness, agitation, exhaustion, difficulty with word finding, bradyphrenia, short-term and long-term memory impairment, and judgement impaired by impulsive and affect-laden reactions without reflection. Impairments were noted on neuropsychiatric tests, and positron emission tomography (PET) scan of the brain with (18)F-fluorodeoxyglucose showed globally decreased and heterogeneous metabolic activity in the entire brain. Treatment included sertraline, methylphenidate, valproic acid and topiramate. At 14 years after smoke inhalation injury, he had persistent cognitive impairment. Repeat brain PET scan showed areas of improvement and deterioration. This case shows long-term brain and psychiatric dysfunction resulting after toxic smoke inhalation, with some areas of the brain having progressive deterioration between years 3 and 14 after smoke inhalation.

Tyrosine nitration of voltage-dependent anion channels in cardiac ischemia-reperfusion: reduction by peroxynitrite scavenging

Excess superoxide (O(2)(-)) and nitric oxide (NO) forms peroxynitrite (ONOO(-)) during cardiac ischemia reperfusion (IR) injury, which in turn induces protein tyrosine nitration (tyr-N). Mitochondria are both a source of and target for ONOO(-). Our aim was to identify specific mitochondrial proteins that display enhanced tyr-N after cardiac IR injury, and to explore whether inhibiting O(2)(-)/ONOO(-) during IR decreases mitochondrial protein tyr-N and consequently improves cardiac function. We show here that IR increased tyr-N of 35 and 15kDa mitochondrial proteins using Western blot analysis with 3-nitrotyrosine antibody. Immunoprecipitation (IP) followed by LC-MS/MS identified 13 protein candidates for tyr-N. IP and Western blot identified and confirmed that the 35kDa tyr-N protein is the voltage-dependent anion channel (VDAC). Tyr-N of native cardiac VDAC with IR was verified on recombinant (r) VDAC with exogenous ONOO(-). We also found that ONOO(-) directly enhanced rVDAC channel activity, and rVDAC tyr-N induced by ONOO(-) formed oligomers. Resveratrol (RES), a scavenger of O(2)(-)/ONOO(-), reduced the tyr-N levels of both native and recombinant VDAC, while L-NAME, which inhibits NO generation, only reduced tyr-N levels of native VDAC. O(2)(-) and ONOO(-) levels were reduced in perfused hearts during IR by RES and L-NAME and this was accompanied by improved cardiac function. These results identify tyr-N of VDAC and show that reducing ONOO(-) during cardiac IR injury can attenuate tyr-N of VDAC and improve cardiac function.

Reversible inactivation of dihydrolipoamide dehydrogenase by Angeli's salt

Dihydrolipoamide dehydrogenase (DLDH) is a key component of 3 mitochondrial α-keto acid dehydrogenase complexes including pyruvate dehydrogenase complex, α-ketoglutarate dehydrogenase complex, and branched chain amino acid dehydrogenase complex. It is a pyridine-dependent disulfide oxidoreductase that is very sensitive to oxidative modifications by reactive nitrogen species (RNS) and reactive oxygen species (ROS). The objective of this study was to investigate the mechanisms of DLDH modification by RNS derived from Angeli's salt. Studies were conducted using isolated rat brain mitochondria that were incubated with varying concentrations of Angeli's salt followed by spectrophotometric enzyme assays, blue native gel analysis, and 2-dimensional gel-based proteomic approaches. Results show that DLDH could be inactivated by Angeli's salt in a concentration dependent manner and the inactivation was a targeting rather than a random process as peroxynitrite did not show any detectable inhibitory effect on the enzyme's activity under the same experimental conditions. Since Angeli's salt can readily decompose at physiological pH to yield nitroxyl anion (HNO) and nitric oxide, further studies were conducted to determine the actual RNS that was responsible for DLDH inactivation. Results indicate that it was HNO that exerted the effect of Angeli's salt on DLDH. Finally, two-dimensional Western blot analysis indicates that DLDH inactivation by Angeli's salt was accompanied by formation of protein s-nitrosothiols, suggesting that s-nitrosylation is likely the cause of loss in enzyme's activity. Taken together, the present study provides insights into mechanisms of DLDH inactivation induced by HNO derived from Angeli's salt.

Transgenic overexpression of neuroglobin attenuates formation of smoke-inhalation-induced oxidative DNA damage, in vivo, in the mouse brain

Acute inhalation of combustion smoke causes neurological deficits in survivors. Inhaled smoke includes carbon monoxide, noxious gases, and a hypoxic environment, which disrupt oxygenation and generate free radicals. To replicate a smoke-inhalation scenario, we developed an experimental model of acute exposure to smoke for the awake mouse/rat and detected induction of biomarkers of oxidative stress. These include inhibition of mitochondrial respiratory complexes and formation of oxidative DNA damage in the brain. DNA damage is likely to contribute to neuronal dysfunction and progression of brain injury. In the search for strategies to attenuate the smoke-initiated brain injury, we produced a transgenic mouse overexpressing the neuronal globin protein neuroglobin. Neuroglobin was neuroprotective in diverse models of ischemic/hypoxic/toxic brain injuries. Here, we report lesser inhibition of respiratory complex I and reduced formation of smoke-induced DNA damage in neuroglobin transgenic compared to wild-type mouse brain. DNA damage was assessed using the standard comet assay, as well as a modified comet assay done in conjunction with an enzyme that excises oxidized guanines that form readily under conditions of oxidative stress. Both comet assays revealed that overexpressed neuroglobin attenuates the formation of oxidative DNA damage, in vivo, in the brain. These findings suggest that elevated neuroglobin exerts neuroprotection, in part, by decreasing the impact of acute smoke inhalation on the integrity of neuronal DNA.

The nitrated proteome in heart mitochondria of the db/db mouse model: characterization of nitrated tyrosine residues in SCOT

A proteomic strategy combining 2DE, Western blot, and mass spectrometry was implemented to survey the status of tyrosine nitration in mouse heart mitochondria. Compared to normal mice, nitrated proteins in the heart mitochondria of the db/db mouse model were significantly augmented due to diabetic development. A total of 18 proteins were identified as the nitration targets. Of the nitrated proteins, succinyl-CoA:3-oxoacid CoA-transferase (SCOT) is a key enzyme involved in ketolysis and has yet to be explored how its catalysis is affected by nitration. We therefore initiated a systematic investigation toward the nitrated site(s) and the corresponding changes of SCOT catalysis. To monitor modification kinetics and nitrated residue(s), recombinant SCOT was incubated with peroxynitrite followed by examination of nitration development as well as catalytic activity changes. The nitration of recombinant SCOT steadily increased in response to increasing concentrations of peroxynitrite, while its catalysis was gradually attenuated. The nitrated sites of modified SCOT were further identified by LC-ESI-MS/MS. The MS/MS spectra indicated a +45 mass unit ion shift from [M + H](+) m/z at Tyr(4) and Tyr(76). Through site-directed mutagenesis, we found that mutation of tyrosine residues at Tyr(4) or Tyr(76) did not only significantly protect SCOT from peroxynitrite modification, but it also dramatically prevented loss of enzymatic activity. Taken together, these results indicate that the two tyrosine residues of SCOT are the priority sites attacked by NO, and their nitration status is a causal factor leading to inhibition of SCOT catalysis.

Differential inhibition of mitochondrial respiratory complexes by inhalation of combustion smoke and carbon monoxide, in vivo, in the rat brain

Combustion smoke contains gases and particulates, which act via hypoxia and cytotoxicity producing mechanisms to injure cells and tissues. While carbon monoxide (CO) is the major toxicant in smoke, its toxicity is exacerbated in the presence of other compounds. Here, we examined modulations of mitochondrial and cytosolic energy metabolism by inhalation of combustion smoke versus CO, in vivo, in the rat brain. Measurements revealed reduced activities of respiratory chain (RC) complexes, with greater inhibition by smoke than equivalent CO in ambient air. In the case of RC complex IV, inhibition by CO and smoke was similar--suggesting that complex IV inhibition is primarily by the action of CO. In contrast, inhibition of complexes I and III was greater by smoke. Increases in cytosolic lactate dehydrogenase and pyruvate kinase activities accompanied inhibition of RC complexes, likely reflecting compensatory increases in cytosolic energy production. Together, the data provide new insights into the mechanisms of smoke inhalation-induced perturbations of brain energetics, which impact neuronal function and contribute to the development of neuropathologies in survivors of exposures to CO and combustion smoke.