Inhibition of Mitochondrial Fission by Drp-1 Blockade by Short-Term Leptin and Mdivi-1 Treatment Improves White Adipose Tissue Abnormalities in Obesity and Diabetes

BACKGROUND

Obesity and type 2 diabetes are chronic diseases characterized by insulin resistance, mitochondrial dysfunction and morphological abnormalities.

OBJECTIVE

We have investigated if dysregulation of mitochondrial dynamics and biogenesis is involved in an animal model of obesity and diabetes.

METHODS

The effect of short-term leptin and mdivi-1 -a selective inhibitor of Drp-1 fission-protein- treatment on mitochondrial dynamics and biogenesis was evaluated in epididymal white adipose tissue (WAT) from male ob/ob mice.

RESULTS

An increase in Drp-1 protein levels and a decrease in Mfn2 and OPA-1 protein expression were observed with enhanced and sustained mitochondrial fragmentation in ob/ob mice compared to wt C57BL/6 animals (p<0.05). The content of mitochondrial DNA and PGC-1α mRNA expression -both parameters of mitochondrial biogenesis- were reduced in ob/ob mice (p<0.05). Treatment with leptin and mdivi-1 significantly increased mitochondrial biogenesis, improved fusion-to-fission balance and attenuated mitochondrial dysfunction, thus inducing white-to-beige adipocyte transdifferentiation. Measurements of glucose and lipid oxidation in adipocytes revealed that both leptin and mdivi-1 increase substrates oxidation while in vivo determination of blood glucose concentration showed decreased levels by 50% in ob/ob mice, almost to the wt level.

CONCLUSIONS

Pharmacological targeting of Drp-1 fission protein may be a potential novel therapeutic tool for obesity and type 2 diabetes.

Progesterone protective effects in neurodegeneration and neuroinflammation

Progesterone is a neuroprotective, promyelinating and anti-inflammatory factor for the nervous system. Here, we review the effects of progesterone in models of motoneurone degeneration and neuroinflammation. In neurodegeneration of the Wobbler mouse, a subset of spinal cord motoneurones showed increased activity of nitric oxide synthase (NOS), increased intramitochondrial NOS, decreased activity of respiratory chain complexes, and decreased activity and protein expression of Mn-superoxide dismutase type 2 (MnSOD2). Clinically, Wobblers suffered several degrees of motor impairment. Progesterone treatment restored the expression of neuronal markers, decreased the activity of NOS and enhanced complex I respiratory activity and MnSOD2. Long-term treatment with progesterone increased muscle strength, biceps weight and survival. Collectively, these data suggest that progesterone prevented neurodegeneration. To study the effects of progesterone in neuroinflammation, we employed mice with experimental autoimmune encephalomyelitis (EAE). EAE mice spinal cord showed increased mRNA levels of the inflammatory mediators tumour necrosis factor (TNF)α and its receptor TNFR1, the microglial marker CD11b, inducible NOS and the toll-like receptor 4. Progesterone pretreatment of EAE mice blocked the proinflammatory mediators, decreased Iba1+ microglial cells and attenuated clinical signs of EAE. Therefore, reactive glial cells became targets of progesterone anti-inflammatory effects. These results represent a starting point for testing the usefulness of neuroactive steroids in neurological disorders.

Modulation of liver mitochondrial NOS is implicated in thyroid-dependent regulation of O(2) uptake

Changes in O(2) uptake at different thyroid status have been explained on the basis of the modulation of mitochondrial enzymes and membrane biophysical properties. Regarding the nitric oxide (NO) effects, we tested whether liver mitochondrial nitric oxide synthase (mtNOS) participates in the modulation of O(2) uptake in thyroid disorders. Wistar rats were inoculated with 400 microCi (131)I (hypothyroid group), 20 microg thyroxine (T(4))/100 g body wt administered daily for 2 wk (hyperthyroid group) or vehicle (control). Basal metabolic rate, mitochondrial function, and mtNOS activity were analyzed. Systemic and liver mitochondrial O(2) uptake and cytochrome oxidase activity were lower in hypothyroid rats with respect to controls; mitochondrial parameters were further decreased by L-arginine (-42 and -34%, P < 0.05), consistent with 5- to 10-fold increases in matrix NO concentration. Accordingly, mtNOS expression (75%) and activity (260%) were selectively increased in hypothyroidism and reverted by hormone replacement without changes in other nitric oxide isoforms. Moreover, mtNOS activity correlated with serum 3,5,3'-triiodothyronine (T(3)) and O(2) uptake. Increased mtNOS activity was also observed in skeletal muscle mitochondria from hypothyroid rats. Therefore, we suggest that modulation of mtNOS is a substantial part of thyroid effects on mitochondrial O(2) uptake.

Peroxynitrite-mediated mitochondrial dysfunction

Peroxynitrite anion (ONOO(-)) is a potent biological oxidant produced by the near diffusion-limited reaction of superoxide and nitric oxide. Peroxynitrite has been implicated in diverse forms of free radical-induced tissue injury. Experimental evidence showed that exogenous and endogenous peroxynitrite causes alterations of the structure and function of mitochondrial proteins, leading to mitochondrial dysfunction and cellular or organ injury. These data are discussed along with its physiopathological implications.

Overexpression of neutrophil neuronal nitric oxide synthase in Parkinson's disease

Much evidence supports a role of nitric oxide (.NO) and peroxynitrite (ONOO(-)) in experimental and idiopathic Parkinson's disease (PD); moreover, an overexpression of neuronal nitric oxide synthase (nNOS) was recently reported in the basal ganglia of PD patients. In accord, we previously found a 50% increased.NO production rate during the respiratory burst of circulating neutrophils (PMN) from PD patients. As PMN express the nNOS isoform, the objective of the present study was to ascertain whether this increased.NO production is representative of nNOS gene upregulation. PMN were isolated from blood samples obtained from seven PD patients and seven age- and sex-matched healthy donors; nNOS mRNA was amplified by reverse transcriptase-polymerase chain reaction and the products were hybridized with a probe for nNOS. Nitrotyrosine-containing proteins and nNOS were detected by Western blot and NO production rate was measured spectrophotometrically by the conversion of oxymyoglobin to metmyoglobin. The results showed that both.NO production and protein tyrosine nitration were significantly increased in PMN isolated from PD patients (PD 0.09 +/- 0.01 vs 0.06 +/- 0.008 nmol min(-1) 10(6) cells(-1); P < 0.05). In addition, five of the seven PD patients showed about 10-fold nNOS mRNA overexpression; while two of the seven PD patients showed an expression level similar to that of the controls; detection of nNOS protein was more evident in the former group. In summary, it is likely that overexpression of nNOS and formation of ONOO(-) in PMN cells from PD patients emphasizes a potential causal role of.NO in the physiopathology of the illness.

Reactions of peroxynitrite in the mitochondrial matrix

Superoxide radical (O2-) and nitric oxide (NO) produced at the mitochondrial inner membrane react to form peroxynitrite (ONOO-) in the mitochondrial matrix. Intramitochondrial ONOO- effectively reacts with a few biomolecules according to reaction constants and intramitochondrial concentrations. The second-order reaction constants (in M(-1) s(-1)) of ONOO- with NADH (233 +/- 27), ubiquinol-0 (485 +/- 54) and GSH (183 +/- 12) were determined fluorometrically by a simple competition assay of product formation. The oxidation of the components of the mitochondrial matrix by ONOO- was also followed in the presence of CO2, to assess the reactivity of the nitrosoperoxocarboxylate adduct (ONOOCO2-) towards the same reductants. The ratio of product formation was about similar both in the presence of 2.5 mM CO2 and in air-equilibrated conditions. Liver submitochondrial particles supplemented with 0.25-2 microM ONOO- showed a O2- production that indicated ubisemiquinone formation and autooxidation. The nitration of mitochondrial proteins produced after addition of 200 microM ONOO- was observed by Western blot analysis. Protein nitration was prevented by the addition of 50-200 microM ubiquinol-0 or GSH. An intramitochondrial steady state concentration of about 2 nM ONOO- was calculated, taking into account the rate constants and concentrations of ONOO- coreactants.

Regulation of mitochondrial respiration by oxygen and nitric oxide

Although the regulation of mitochondrial respiration and energy production in mammalian tissues has been exhaustively studied and extensively reviewed, a clear understanding of the regulation of cellular respiration has not yet been achieved. In particular, the role of tissue pO2 as a factor regulating cellular respiration remains controversial. The concept of a complex and multisite regulation of cellular respiration and energy production signaled by cellular and intercellular messengers has evolved in the last few years and is still being researched. A recent concept that regulation of cellular respiration is regulated by ADP, O2 and NO preserves the notion that energy demands drive respiration but places the kinetic control of both respiration and energy supply in the availability of ADP to F1-ATPase and of O2 and NO to cytochrome oxidase. In addition, recent research indicates that NO participates in redox reactions in the mitochondrial matrix that regulate the intramitochondrial steady state concentration of NO itself and other reactive species such as superoxide radical (O2-) and peroxynitrite (ONOO-). In this way, NO acquires an essential role as a mitochondrial regulatory metabolite. No exhibits a rich biochemistry and a high reactivity and plays an important role as intercellular messenger in diverse physiological processes, such as regulation of blood flow, neurotransmission, platelet aggregation and immune cytotoxic response.

Oxidation of ubiquinol by peroxynitrite: implications for protection of mitochondria against nitrosative damage

A major pathway of nitric oxide utilization in mitochondria is its conversion to peroxynitrite, a species involved in biomolecule damage via oxidation, hydroxylation and nitration reactions. In the present study the potential role of mitochondrial ubiquinol in protecting against peroxynitrite-mediated damage is examined and the requirements of the mitochondrial redox status that support this function of ubiquinol are established. (1) Absorption and EPR spectroscopy studies revealed that the reactions involved in the ubiquinol/peroxynitrite interaction were first-order in peroxynitrite and zero-order in ubiquinol, in agreement with the rate-limiting formation of a reactive intermediate formed during the isomerization of peroxynitrite to nitrate. Ubiquinol oxidation occurred in one-electron transfer steps as indicated by the formation of ubisemiquinone. (2) Peroxynitrite promoted, in a concentration-dependent manner, the formation of superoxide anion by mitochondrial membranes. (3) Ubiquinol protected against peroxynitrite-mediated nitration of tyrosine residues in albumin and mitochondrial membranes, as suggested by experimental models, entailing either addition of ubiquinol or expansion of the mitochondrial ubiquinol pool caused by selective inhibitors of complexes III and IV. (4) Increase in membrane-bound ubiquinol partially prevented the loss of mitochondrial respiratory function induced by peroxynitrite. These findings are analysed in terms of the redox transitions of ubiquinone linked to both nitrogen-centred radical scavenging and oxygen-centred radical production. It may be concluded that the reaction of mitochondrial ubiquinol with peroxynitrite is part of a complex regulatory mechanism with implications for mitochondrial function and integrity.

The regulation of mitochondrial oxygen uptake by redox reactions involving nitric oxide and ubiquinol

The reversible inhibitory effects of nitric oxide (.NO) on mitochondrial cytochrome oxidase and O(2) uptake are dependent on intramitochondrial.NO utilization. This study was aimed at establishing the mitochondrial pathways for.NO utilization that regulate O-(2) generation via reductive and oxidative reactions involving ubiquinol oxidation and peroxynitrite (ONOO(-)) formation. For this purpose, experimental models consisting of intact mitochondria, ubiquinone-depleted/reconstituted submitochondrial particles, and ONOO(-)-supplemented mitochondrial membranes were used. The results obtained from these experimental approaches strongly suggest the occurrence of independent pathways for.NO utilization in mitochondria, which effectively compete with the binding of.NO to cytochrome oxidase, thereby releasing this inhibition and restoring O(2) uptake. The pathways for.NO utilization are discussed in terms of the steady-state levels of.NO and O-(2) and estimated as a function of O(2) tension. These calculations indicate that mitochondrial.NO decays primarily by pathways involving ONOO(-) formation and ubiquinol oxidation and, secondarily, by reversible binding to cytochrome oxidase.

Endogenous peroxynitrite mediates mitochondrial dysfunction in rat diaphragm during endotoxemia

It has been shown that nitric oxide (NO), synthesized by the inducible NO synthase (iNOS) expressed in the diaphragm during endotoxemia, participates in the development of muscular contractile failure. The aim of the present study was to investigate whether this deleterious action of NO was related to its effects on cellular oxidative pathways. Rats were inoculated with E. coli lipopolysaccharide (LPS) or sterile saline solution (controls) and studied at 3 and 6 h after inoculation. iNOS protein and activity could be detected in the rat diaphragm as early as 3 h after LPS, with a sustained steady-state concentration of 0.5 microM NO in the muscle associated with increased detection of hydrogen peroxide (H(2)O(2)). In vitro, the same NO concentration produced a marked increase in H(2)O(2) production by isolated control diaphragm mitochondria, thus reflecting a higher intramitochondrial concentration of nondiffusible superoxide anion (O(2)(-.)). In a similar way, whole diaphragmatic muscle and diaphragm mitochondria from endotoxemic rats showed a progressive increase in H(2)O(2) production associated with uncoupling and decreased phosphorylating capacity. Simultaneous with the maximal impairment in respiration (6 h after LPS), nitration of mitochondrial proteins (a peroxynitrite footprint) was detected and diaphragmatic force was reduced. Functional mitochondrial abnormalities, nitration of mitochondrial proteins, and the decrease in force were significantly attenuated by administration of the NOS inhibitor L-NMMA. These results show that increased and sustained NO levels lead to a consecutive formation of O(2)(-.) that reacts with NO to form peroxynitrite, which in turn impairs mitochondrial function, which probably contributes to the impairment of muscle contractility. during endotoxemia.

Circulating plasma factors in Parkinson's disease enhance nitric oxide release of normal human neutrophils

Nitric oxide (*NO)-mediated toxicity has been involved in neurodegenerative diseases, including Parkinson's disease (PD). We have recently reported an increase of about 50% in *NO production rate in PMA-activated polymorphonuclear leukocytes (PMN) from either newly diagnosed or chronically treated PD patients. As humoral factors in sera from PD patients could inhibit cell dopaminergic activity, the aim of this study was to determine whether a plasma circulating factor from PD patients could modify *NO metabolism in PMN from healthy control subjects. To this purpose, we determined simultaneously the maximal production rate of *NO and hydrogen peroxide (H2O2) of PMA-activated PMN isolated from healthy control subjects in the presence of aliquots of plasma of PD patients. The results showed that, after 30 min incubation, plasma from newly diagnosed (n=4) or from L-Dopa chronically treated (n=7) PD patients enhanced *NO release in neutrophils isolated from healthy controls by about 50% and 47% respectively, with respect to non-parkinsonian control plasma (n = 10); in the same condition, H2O2 production did not differ among the groups. These data suggest that an overproduction of *NO related to plasma circulating factors, already detected at initial stages of the disease, participates in the pathophysiology of Parkinson's disease.

The reaction of nitric oxide with ubiquinol: kinetic properties and biological significance

The reaction of nitric oxide (*NO) with ubiquinol-0 and ubiquinol-2, short-chain analogs of coenzyme Q, was examined in anaerobic and aerobic conditions in terms of formation of intermediates and stable molecular products. The chemical reactivity of ubiquinol-0 and ubiquinol-2 towards *NO differed only quantitatively, the reactions of ubiquinol-2 being slightly faster than those of ubiquinol-0. The ubiquinol/*NO reaction entailed oxidation of ubiquinol to ubiquinone and reduction of *NO to NO-, the latter identified by its reaction with metmyoglobin to form nitroxylmyoglobin and indirectly by measurement of nitrous oxide (N2O) by gas chromatography. Both the rate of ubiquinone accumulation and *NO consumption were linearly dependent on ubiquinol and *NO concentrations. The stoichiometry of *NO consumed per either ubiquinone formed or ubiquinol oxidized was 1.86 A 0.34. The reaction of *NO with ubiquinols proceeded with intermediate formation of ubisemiquinones that were detected by direct EPR. The second order rate constants of the reactions of ubiquinol-0 and ubiquinol-2 with *NO were 0.49 and 1.6 x 10(4) M(-1)s(-1), respectively. Studies in aerobic conditions revealed that the reaction of *NO with ubiquinols was associated with O2 consumption. The formation of oxyradicals - identified by spin trapping EPR- during ubiquinol autoxidation was inhibited by *NO, thus indicating that the O2 consumption triggered by *NO could not be directly accounted for in terms of oxyradical formation or H2O2 accumulation. It is suggested that oxyradical formation is inhibited by the rapid removal of superoxide anion by *NO to yield peroxynitrite, which subsequently may be involved in the propagation of ubiquinol oxidation. The biological significance of the reaction of ubiquinols with *NO is discussed in terms of the cellular O2 gradients, the steady-state levels of ubiquinols and *NO, and the distribution of ubiquinone (largely in its reduced form) in biological membranes with emphasis on the inner mitochondrial membrane.

Effect of nitric oxide donors on oxygen-dependent cytotoxic responses mediated by neutrophils

We analyzed the effect of nitric oxide (NO) on oxygen-dependent cytotoxic responses mediated by neutrophils against unopsonized erythrocytes using three NO donors: S-nitrosoglutathione (GSNO), S-nitroso-N-acetylpenicillamine (SNAP), and sodium nitroprusside (SNP). Neutrophils were treated with these compounds for 1-2 min at 37 degrees C and cytotoxicity was then triggered in the presence of NO donors by precipitating immune complexes, aggregated IgG, the chemotactic peptide FMLP, or opsonized zymosan. GSNO induced, in all cases, a marked increase in cytotoxic responses, while SNAP moderately increased cytotoxicity triggered by immune complexes, aggregated IgG, or Z, opsonized zymosen, without modifying those responses induced by FMLP. By contrast, SNP dramatically suppressed cytotoxicity triggered by all of the stimuli assessed. The enhancing effects mediated by GSNO and SNAP did not depend on the stimulation of guanylyl cyclase and were prevented by the NO scavengers hemoglobin and PTIO (2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide). The inhibitory activity of SNP, on the other hand, was not prevented by NO scavengers, suggesting that it cannot be ascribed to the release of NO. In another set of experiments, neutrophils were pretreated with GSNO or SNAP for different times. Then cells were washed to remove NO donors from the culture medium, and cytotoxicity was triggered by different stimuli. It was found that neutrophils must be pretreated with NO donors for at least 4 h to increase cytotoxic responses, and pretreatment for longer periods (i.e., 8 or 18 h) further increased cytotoxicity. Not only cytotoxic responses, but also the production of O2- and H2O2, and the release of myeloperoxidase were increased under these conditions.

Effect of Nitric Oxide Donors on Oxygen-Dependent Cytotoxic Responses Mediated by Neutrophils

We analyzed the effect of nitric oxide (NO) on oxygen-dependent cytotoxic responses mediated by neutrophils against unopsonized erythrocytes using three NO donors: S-nitrosoglutathione (GSNO), S-nitroso-N-acetylpenicillamine (SNAP), and sodium nitroprusside (SNP). Neutrophils were treated with these compounds for 1–2 min at 37°C and cytotoxicity was then triggered in the presence of NO donors by precipitating immune complexes, aggregated IgG, the chemotactic peptide FMLP, or opsonized zymosan. GSNO induced, in all cases, a marked increase in cytotoxic responses, while SNAP moderately increased cytotoxicity triggered by immune complexes, aggregated IgG, or Z, opsonized zymosen, without modifying those responses induced by FMLP. By contrast, SNP dramatically suppressed cytotoxicity triggered by all of the stimuli assessed. The enhancing effects mediated by GSNO and SNAP did not depend on the stimulation of guanylyl cyclase and were prevented by the NO scavengers hemoglobin and PTIO (2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide). The inhibitory activity of SNP, on the other hand, was not prevented by NO scavengers, suggesting that it cannot be ascribed to the release of NO. In another set of experiments, neutrophils were pretreated with GSNO or SNAP for different times. Then cells were washed to remove NO donors from the culture medium, and cytotoxicity was triggered by different stimuli. It was found that neutrophils must be pretreated with NO donors for at least 4 h to increase cytotoxic responses, and pretreatment for longer periods (i.e., 8 or 18 h) further increased cytotoxicity. Not only cytotoxic responses, but also the production of O2− and H2O2, and the release of myeloperoxidase were increased under these conditions.

[Shock: concepts for a definition]

The shock syndrome has been classically considered as a consequence of both decreased tissue perfusion and O2 supply; however, in some types of shock like septic or traumatic ones, regional blood flows may be increased. A decade ago, mitochondrial alterations consistent with uncoupling of oxidative phosphorylation were reported in either endotoxemic or hemorrhagic experimental shock or in humans. Recently, the discovery of nitric oxide (NO) and its increase in the shock state, has opened new perspectives in the understanding of this problem. Nitric oxide produces vasodilatation and, at the same time, increases the mitochondrial production of O2 active species like superoxide anion. Both radicals react to form a strong oxidant that is able to nitrate the phenolic rings of proteins: peroxynitrite. This effect leads to the impairment of the activities of different mitochondrial enzymes like succinate dehydrogenase and ATPase and the mitochondrial function and finally, to decreased energy levels and to multiorgan failure. The increase in NO release is due to the effects of circulating peptides and of increased adhesion of neutrophils to the endothelium and to the positive effects of inflammatory mediators like TNF-alpha and cytokines on inducible NOS (iNOS) expression in endothelium and tissues. It is suggested that the shock state is the consequence of an imbalance between NO and O2 and their metabolites.

Nitric oxide regulates oxygen uptake and hydrogen peroxide release by the isolated beating rat heart

Isolated rat heart perfused with 1.5-7.5 microM NO solutions or bradykinin, which activates endothelial NO synthase, showed a dose-dependent decrease in myocardial O2 uptake from 3.2 +/- 0.3 to 1.6 +/- 0.1 (7.5 microM NO, n = 18, P < 0.05) and to 1.2 +/- 0.1 microM O2.min-1.g tissue-1 (10 microM bradykinin, n = 10, P < 0.05). Perfused NO concentrations correlated with an induced release of hydrogen peroxide (H2O2) in the effluent (r = 0.99, P < 0.01). NO markedly decreased the O2 uptake of isolated rat heart mitochondria (50% inhibition at 0.4 microM NO, r = 0.99, P < 0.001). Cytochrome spectra in NO-treated submitochondrial particles showed a double inhibition of electron transfer at cytochrome oxidase and between cytochrome b and cytochrome c, which accounts for the effects in O2 uptake and H2O2 release. Most NO was bound to myoglobin; this fact is consistent with NO steady-state concentrations of 0.1-0.3 microM, which affect mitochondria. In the intact heart, finely adjusted NO concentrations regulate mitochondrial O2 uptake and superoxide anion production (reflected by H2O2), which in turn contributes to the physiological clearance of NO through peroxynitrite formation.

Effects of respiratory burst inhibitors on nitric oxide production by human neutrophils

Human neutrophils (PMN) activated by N-formylmethionyl-leucyl-phenylalanine (fMLP) simultaneously release nitric oxide (.NO), superoxide anion (O2.-) and its dismutation product, hydrogen peroxide (H2O2). To assess whether .NO production shares common steps with the activation of the NADPH oxidase, PMN were treated with inhibitors and antagonists of intracellular signaling pathways and subsequently stimulated either with fMLP or with a phorbol ester (PMA). The G-protein inhibitor, pertussis toxin (1-10 micrograms/ml) decreased H2O2 yield without significantly changing .NO production in fMLP-stimulated neutrophils; no effects were observed in PMA-activated cells. The inhibition of tyrosine kinases by genistein (1-25 micrograms/ml) completely abolished H2O2 release by fMLP-activated neutrophils; conversely, .NO production increased about 1.5- and 3-fold with fMLP and PMA, respectively. Accordingly, orthovanadate, an inhibitor of phosphotyrosine phosphatase, markedly decreased .NO production and increased O2.- release. On the other hand, inhibition of protein kinase C with staurosporine and the use of burst antagonists like adenosine, cholera toxin or dibutyryl-cAMP diminished both H2O2 and .NO production. The results suggest that the activation of the tyrosine kinase pathway in stimulated human neutrophils controls positively O2.- and H2O2 generation and simultaneously maintains .NO production in low levels. In contrast, activation of protein kinase C is a positive modulator for O2.- and .NO production.

Neutrophil function, nitric oxide, and blood oxidative stress in Parkinson's disease

We studied nitrogen radical nitric oxide (.NO) release and reactive oxygen species (ROS) production by isolated neutrophils after phorbol myristate acetate (PMA) stimulation in 12 newly diagnosed and nine treated Parkinson's disease (PD) patients and 10 age-matched healthy controls. Neutrophils of both groups of PD patients had an elevated PMA-activated release of .NO [61 and 57%, respectively, higher than that of controls (p < 0.05)]. In contrast, H2O2 release was only significantly increased by 56% in chronically treated patients. In agreement, the maximum rate of luminol-dependent chemiluminescence, which partly represents O2- H2O2- .NO interactions, was increased only in the treated group. When other blood markers of oxidative stress were compared, only erythrocyte catalase activity was decreased in both PD patient series by 33 and 39%, respectively (p < 0.05), whereas plasma antioxidant capacity and erythrocyte superoxide dismutase activity levels were decreased only in treated PD patients. This study suggests that neutrophils express a primary alteration of .NO release in PD patients, whereas H2O2 and oxidative-stress parameters are more probably related to the evolution of PD or to effects of treatment with L-dopa.

Nitric oxide inhibits electron transfer and increases superoxide radical production in rat heart mitochondria and submitochondrial particles

Nitric oxide (.NO) released by S-nitrosoglutathione (GSNO) inhibited enzymatic activities of rat heart mitochondrial membranes. Cytochrome oxidase activity was inhibited to one-half at an effective .NO concentration of 0.1 microM, while succinate- and NADH-cytochrome-c reductase activities were half-maximally inhibited at 0.3 microM .NO. Submitochondrial particles treated with .NO (either from GSNO or from a pure solution) showed increased O(-)(2) and H202 production when supplemented with succinate alone, at rates that were comparable to those of control particles with added succinate and antimycin. Rat heart mitochondria treated with .NO also showed increased H2O2 production. Cytochrome spectra and decreased enzymatic activities in the presence of .NO are consistent with a multiple inhibition of mitochondrial electron transfer at cytochrome oxidase and at the ubiquinone-cytochrome b region of the respiratory chain, the latter leading to the increased O2- production. Electrochemical detection showed that the buildup of a .NO concentration from GSNO was interrupted by submitochondrial particles supplemented with succinate and antimycin and was restored by addition of superoxide dismutase. The inhibitory effect of .NO on cytochrome oxidase was also prevented under the same conditions. Apparently, mitochondrial O2- reacts with .NO to form peroxynitrate and, by removing .NO, reactivates the previously inhibited cytochrome oxidase. It is suggested that, at physiological concentrations of .NO, inhibition of electron transfer, .NO-induced O2- production, and ONOO- formation participate in the regulatory control of mitochondrial oxygen uptake.

Oxidative stress in rodent closed duodenal loop pancreatitis

CONCLUSION

Production of excited oxygen species is earlier in the liver than in the pancreas and could contribute to damage in a reflux model. Treatment with SOD could attenuate 59% light emission in pancreas, but did not modify serum enzyme levels or pancreatic edema, resulting as an insufficient isolated therapy. Unexpectedly, it was found an increased plasma antioxidant capacity that was related to total bilirubin levels, and declined at late stages probably denoting other circulating antioxidant consumption.

BACKGROUND

Oxidative stress has been shown to play a role in different models of acute pancreatitis, although it has not been studied in the severe necrohemorrhagic model produced by closed duodenal loop pancreatitis.

METHODS

We studied Sprague Dawley female rats in two groups: a closed duodenal loop pancreatitis group and a control, sham-operated group. In order to evidence the oxygen excited species production, in situ spontaneous chemiluminescence from living and naturally perfused pancreas and liver was measured at 0, 0.5, 1.5, 3, 6, 12, and 24 h after the duodenal ligature. Blood pancreatic amylase and aminotransferases levels were determined as expression of tissue damage in pancreas and liver. At the same time, plasma antioxidant capacity was measured by the peroxyl radical trapping capability of plasma samples compared to that of Trolox (synthetic analog of vitamin E), and results are expressed as Trolox equivalence. Bovine superoxide dismutase (SOD) was administered to attenuate oxygen free radicals activity at the beginning of the peroxidation chain and also as a therapeutic tool.

RESULTS

The experimental procedure induced a severe pancreatitis, as evidenced by pancreatic enzymes that rose markedly in the early hours of disease and remained heightened throughout the experiment. The results show early light emission from the liver at 3 h and peak levels at 12 h, whereas in the pancreas, luminescence increased at 6 h and doubled later at 12 h, both returning to control levels at 24 h.

Nitric oxide synthase inhibitors decrease human polymorphonuclear leukocyte luminol-dependent chemiluminescence

Nitric oxide synthase (NOS) inhibitors have been reported to modulate luminol-dependent chemiluminescence (CL) in rat macrophages, whereas the potent oxidant peroxynitrite (ONOO-) was shown to react with luminol to yield CL in a cell-free system. We evaluated the role of the L-arginine/NOS pathway in luminol CL by phorbol ester-activated human polymorphonuclear (PMN) leukocytes using the NOS inhibitors NG-monomethyl-L-arginine (L-NMMA) and N-iminoethyl-L-ornithine (L-NIO). Nitric oxide (.NO) release was determined by oxidation of oxymyoglobin. In addition, the effect of NOS inhibitors on superoxide anion O2.-) production was measured. Luminol CL was notably diminished by L-NMMA in a dose-dependent manner. Superoxide dismutase (SOD) also decreased luminol CL and L-NMMA potentiated light emission decrease produced by SOD. Nitric oxide and O2.- production was significantly decreased by L-NMMA; moreover, luminol-dependent CL but not O2.- production was attenuated by L-NIO. These data suggest that products of catalytic activity of both .NO synthase and NADPH oxidase are required to elicit maximal luminol CL in this system. These studies demonstrate that the NOS synthase pathway is involved in luminol CL by human PMN, and they suggest that ONOO- would be an unrecognized mediator in this phenomenon.

Isoproterenol-dependent decrease in oxygen uptake and respiratory enzyme activities in rat myocardial tissue and mitochondria

OBJECTIVE

Myocardial damage induced by isoproterenol is believed to be secondary to increased oxygen demands on the heart. Our objective was to test an additional primary action of isoproterenol on tissue and mitochondrial oxidative metabolism and to compare these effects with the effects of other adrenergic agents in the presence of adrenergic inhibitors.

DESIGN

Prospective, dose-response study.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Fifty Sprague-Dawley female rats (200 to 350 g), slightly anesthetized with ether and divided into several groups.

INTERVENTIONS

In 26 rats, the heart was removed, cut into fine slices (0.5-mm thickness), and placed in an ice-cold buffer. In 22 animals, the hearts were perfused in the Langendorff manner and chopped and processed for mitochondrial studies.

MEASUREMENTS AND MAIN RESULTS

We determined the following: a) the direct "in vitro" effects of isoproterenol and related catecholamines on normal oxygen uptake using myocardial slices; b) rat heart oxygen consumption and mitochondrial oxygen uptake from isolated organs, perfused with isoproterenol; c) measurements of enzyme activities in submitochondrial particles from the same perfused hearts; and d) the direct effects of isoproterenol on normal mitochondria isolated from normal nonperfused hearts. The oxygen uptake was determined polarographically with a Clark-type electrode and enzymatic activities were assayed by spectrophotometric reduction of cytochrome c at 550 nm with different mitochondrial substrates. Isoproterenol (0.01 to 100 nM) decreased the oxygen uptake by the heart slices in a dose-dependent manner. In comparison, epinephrine or norepinephrine per se did not change the parameter. However, with the addition of alpha-adrenergic receptor inhibitors, oxygen uptake decreased to values similar to those values obtained with isoproterenol. Also, mitochondria isolated from hearts perfused with isoproterenol had decreased state 3 respiratory rates (by 50%) and decreased respiratory control ratios (by 30%), without changes in adenosine 5'-diphosphate/oxygen ratios. The respiratory chain enzyme activities were also lowered.

CONCLUSIONS

The data suggest that while isoproterenol increases "in vivo" oxygen uptake by the working rat heart, isoproterenol can simultaneously decrease maximal adenosine 5'-diphosphate-induced mitochondrial oxygen uptake and in vitro myocardial tissue oxygen uptake, probably by modifying the mitochondrial respiratory enzymes. This action could be counteracted by alpha-adrenergic agonist effects.

Liver oxygen uptake dependence and mitochondrial function in septic rats

Defective oxygen consumption and a pathological dependence of oxygen uptake on O2 supply have been considered important events in sepsis. To relate these features with tissue and mitochondrial metabolism, we studied oxygen uptake in whole isolated and perfused rat liver at two O2 supply levels, in the same liver slices, and in isolated liver mitochondria. Experimental sepsis in rats was induced by cecal ligation and double-gauge puncture. The results showed that liver and tissue slices from septic animals had a 60% greater O2 uptake than that of controls and that, during sepsis, liver O2 uptake was markedly dependent on O2 supply. Concomitantly, mitochondrial O2 uptake was nearly 30% greater with malate-glutamate as substrate, but not with succinate; lowering O2 concentration in the medium did not alter the enhanced function. In submitochondrial, only NADH-dehydrogenase activity was 100% higher in septic samples. At least, in some tissues, O2 dependence is a function of O2 availability, sensitized by increased mitochondrial O2 uptake related to changes in respiratory enzymes.

Decreased production of nitric oxide by human neutrophils during septic multiple organ dysfunction syndrome. Comparison with endotoxin and cytokine effects on normal cells

The objective of this study was to determine nitric oxide (NO) and superoxide anion release (O-2) by neutrophils (PMNs) in the septic multiple organ dysfunction syndrome (MODS) and to compare them with the response of normal cells to lipopolysaccharide (LPS) and cytokines. NO production was measured by the release of nitrites in the medium, its maximal production rate by a modified oxyhemoglobin assay and O-2 by standard methods. Normal cells were incubated with LPS, gamma interferon (IFN-gamma), or tumor necrosis factor (TNF-alpha) alone or in combination. Results showed that PMN release of both NO and O-2 was reduced in septic samples; in contrast, an association of LPS, IFN-gamma, and TNF-alpha promoted maximal NO release by normal cells (40-50%). We conclude that while interaction of normal PMNs with cytokines increases NO and O-2 release, progression of sepsis to a multiple organ dysfunction impairs these responses in both functions.

Oxidative stress in muscle and liver of rats with septic syndrome

Sepsis, as infection associated to systemic manifestations, was produced in rats by cecal ligation and double perforation. Sham-operated rats were used as controls. The spontaneous chemiluminescence of rat adductor muscle and liver were measured at 6, 12, 24, and 30 h after the surgical procedure. Muscle chemiluminescence showed a maximal increase of about twofold (control emission 10 +/- 1 cps/cm2) after 6-12 h of sepsis, while liver chemiluminescence increased by about 80% (control emission: 11 +/- 1 cps/cm2) after 24 h of sepsis. The activities of muscle antioxidant enzymes were found maximally diminished after 12 h of sepsis: 46% decrease for Mn-superoxide dismutase, 83% decrease for catalase, and 55% decrease for glutathione peroxidase. In liver, only catalase activity showed a 52% decrease after 24 h of sepsis. State 3 oxygen uptake of muscle mitochondria with either malate-glutamate or succinate as substrates was 40% decreased after 12 h of sepsis in both cases. State 4 oxygen uptake of muscle mitochondria was not affected. The rate of H2O2 production of muscle mitochondria after 12 h of sepsis with either malate-glutamate or succinate as substrates was increased about 2.5 times but was not affected when assayed in the presence of as rotenone and antimycin. The oxygen uptake of liver mitochondria isolated from septic rats did not show differences as compared with those of control rats after 6 to 24 h of sepsis. Oxidative stress appears to occur in skeletal muscle early at the onset of the septic syndrome, with inhibition of active mitochondrial respiration and inactivation of antioxidant enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of nitric oxide and hydrogen peroxide production and formation of peroxynitrite during the respiratory burst of human neutrophils

Nitric oxide (.NO) release, oxygen uptake and hydrogen peroxide (H2O2) production elicited by increasing phorbol 12-myristate 13-acetate (PMA) concentrations were measured in human neutrophils. Half-maximal activities were sequentially elicited at about 0.0001-0.001 micrograms PMA/ml (.NO) and 0.001-0.01 micrograms PMA/ml (H2O2). At saturated PMA concentrations, .NO production, oxygen uptake and H2O2 release were 0.56 +/- 0.04, 3.32 +/- 0.52 and 1.19 +/- 0.17 nmol.min-1.10(6) cells-1. .NO production accounts for about 30% of the total oxygen uptake. Luminol-dependent chemiluminescence, reported to detect NO reactions in other inflammatory cells, was also half-maximally activated at about 0.001-0.01 micrograms PMA/ml. Preincubation with NG-monomethyl-L-arginine (L-NMMA) decreased O2 uptake and .NO release but increased H2O2 production, while superoxide dismutase (SOD) increased .NO detection by 30%. Chemiluminescence was also reduced by preincubation with L-NMMA and/or SOD. The results indicate that .NO release is part of the integrated response of stimulated human neutrophils and that, in these cells, kinetics of .NO and O2.- release favour the formation of other oxidants like peroxynitrite.

Oxidative stress in skeletal muscle during sepsis in rats

Skeletal muscle is a target organ during sepsis; nevertheless, there is no evidence of a possible free radical overproduction with tissue damage in this situation. We studied Sprague Dawley female rats in two groups: a septic group with cecal ligation and double cecal perforation and a control group that was sham operated. Hind limb adductor muscles spontaneous chemiluminescence was measured at 2, 4, 6, 12, 24, and 30 hr after the surgical procedure as the expression of oxygen excited species generation. Muscle samples were also taken and activity of the principal antioxidant enzymes--superoxide dismutase (SOD), catalase, and glutathione peroxidase--as well as myeloperoxidase, an index of neutrophil infiltration was determined. CPK seric assays at 12 and 24 hr were used to reflect muscle injury and revealed high levels. Previously administered bovine superoxide dismutase was employed to prevent or attenuate oxidative stress. The results showed that light emission by rat skeletal muscle doubled from 4 to 12 hr of sepsis and could be attenuated with SOD pretreatment. Observed changes may be attributed to the production of oxygen free radicals that do not depend on local neutrophil infiltration. The detoxifying antioxidant enzyme activities in skeletal muscle were diminished (Mn SOD 46% at 6 hr, catalase 83% at 12 hr glutathione peroxidase 55% at 12 hr), which would also facilitate muscle septic damage.