Iron chelates bind nitric oxide and decrease mortality in an experimental model of septic shock

Continuous NO Upcycling into Ammonia Promoted by SO2 in Flue Gas: Poison Can Be a Gift

Although ammonia (NH3) synthesis efficiency from the NO reduction reaction (NORR) is significantly promoted in recent years, one should note that NO is one of the major air pollutants in the flue gas. The limited NO conversion ratio is still the key challenge for the sustainable development of the NORR route, which potentially contributes more to contaminant emissions rather than its upcycling. Herein, we provide a simple but effective approach for continuous NO reduction into NH3, promoted by coexisting SO2 poison as a gift in the flue gas. It is significant to discover that SO2 plays a decisive role in elevating the capacity of NO absorption and reduction. A unique redox pair of SO2-NO is constructed, which contributes to the exceptionally high conversion ratio for both NO (97.59 ± 1.42%) and SO2 (99.24 ± 0.49%) in a continuous flow. The ultrahigh selectivity for both NO-to-NH3 upcycling (97.14 ± 0.55%) and SO2-to-SO42- purification (92.44 ± 0.71%) is achieved synchronously, demonstrating strong practicability for the value-added conversion of air contaminants. The molecular mechanism is revealed by comprehensive in situ technologies to identify the essential contribution of SO2 to NO upcycling. Besides, realistic practicality is realized by the efficient product recovery and resistance ability against various poisoning effects. The proposed strategy in this work not only achieves a milestone efficiency for NH3 synthesis from the NORR but also raises great concerns about contaminant resourcing in realistic conditions.

High-Pressure Mechanistic Insight into Bioinorganic NO Chemistry

Pressure is one of the most important parameters controlling the kinetics of chemical reactions. The ability to combine high-pressure techniques with time-resolved spectroscopy has provided a powerful tool in the study of reaction mechanisms. This review is focused on the supporting role of high-pressure kinetic and spectroscopic methods in the exploration of nitric oxide bioinorganic chemistry. Nitric oxide and other reactive nitrogen species (RNS) are important biological mediators involved in both physiological and pathological processes. Understanding molecular mechanisms of their interactions with redox-active metal/non-metal centers in biological targets, such as cofactors, prosthetic groups, and proteins, is crucial for the improved therapy of various diseases. The present review is an attempt to demonstrate how the application of high-pressure kinetic and spectroscopic methods can add additional information, thus enabling the mechanistic interpretation of various NO bioinorganic reactions.

Synthesis, spectral analysis, molecular docking and DFT studies of 3-(2, 6-dichlorophenyl)-acrylamide and its dimer through QTAIM approach

In this paper, an experimental study of (E)-3-(2,6-dichlorophenyl)-acrylamide and its associated dimer were analysed with molecular docking, DFT and QTAIM approach. To spot, describe, and measure the non-covalent interactions (NCIs) of the atoms in the molecules of the monomer and its dimer, some important topological parameters of the charge densities, ρ(r) acquired from the Bader's QTAIM tool are determined, quantitatively. The bond paths are shown to persist for a range of five types of NCIs such as weak conventional (C-H···Cl) and nonconventional (C-O···C and N-O···Cl), medium (N-H···Cl) and strong O-H···O NCIs revealed by the existence of BCPs (ranging from 1.921 - 3.259 Å). A comprehensive explanation of the spectroscopic data like vibrational, electronic, and NMR spectra is reported along with the NLO, reactivity. Hydroxamic acid exhibited an excellent nonlinear optical activity (β₀ = 14.8098 × 10⁻³⁰). To predict the various reactive sites in the molecule, molecular electrostatic potential diagrams were displayed.

COVID-19 as part of the hyperferritinemic syndromes: the role of iron depletion therapy

SARS-CoV-2 infection is characterized by a protean clinical picture that can range from asymptomatic patients to life-threatening conditions. Severe COVID-19 patients often display a severe pulmonary involvement and develop neutrophilia, lymphopenia, and strikingly elevated levels of IL-6. There is an over-exuberant cytokine release with hyperferritinemia leading to the idea that COVID-19 is part of the hyperferritinemic syndrome spectrum. Indeed, very high levels of ferritin can occur in other diseases including hemophagocytic lymphohistiocytosis, macrophage activation syndrome, adult-onset Still's disease, catastrophic antiphospholipid syndrome and septic shock. Numerous studies have demonstrated the immunomodulatory effects of ferritin and its association with mortality and sustained inflammatory process. High levels of free iron are harmful in tissues, especially through the redox damage that can lead to fibrosis. Iron chelation represents a pillar in the treatment of iron overload. In addition, it was proven to have an anti-viral and anti-fibrotic activity. Herein, we analyse the pathogenic role of ferritin and iron during SARS-CoV-2 infection and propose iron depletion therapy as a novel therapeutic approach in the COVID-19 pandemic.

COVID-19 as part of the hyperferritinemic syndromes: the role of iron depletion therapy

SARS-CoV-2 infection is characterized by a protean clinical picture that can range from asymptomatic patients to life-threatening conditions. Severe COVID-19 patients often display a severe pulmonary involvement and develop neutrophilia, lymphopenia, and strikingly elevated levels of IL-6. There is an over-exuberant cytokine release with hyperferritinemia leading to the idea that COVID-19 is part of the hyperferritinemic syndrome spectrum. Indeed, very high levels of ferritin can occur in other diseases including hemophagocytic lymphohistiocytosis, macrophage activation syndrome, adult-onset Still's disease, catastrophic antiphospholipid syndrome and septic shock. Numerous studies have demonstrated the immunomodulatory effects of ferritin and its association with mortality and sustained inflammatory process. High levels of free iron are harmful in tissues, especially through the redox damage that can lead to fibrosis. Iron chelation represents a pillar in the treatment of iron overload. In addition, it was proven to have an anti-viral and anti-fibrotic activity. Herein, we analyse the pathogenic role of ferritin and iron during SARS-CoV-2 infection and propose iron depletion therapy as a novel therapeutic approach in the COVID-19 pandemic.

Gelam honey scavenges peroxynitrite during the immune response

Monocytes and macrophages are part of the first-line defense against bacterial, fungal, and viral infections during host immune responses; they express high levels of proinflammatory cytokines and cytotoxic molecules, including nitric oxide, reactive oxygen species, and their reaction product peroxynitrite. Peroxynitrite is a short-lived oxidant and a potent inducer of cell death. Honey, in addition to its well-known sweetening properties, is a natural antioxidant that has been used since ancient times in traditional medicine. We examined the ability of Gelam honey, derived from the Gelam tree (Melaleuca spp.), to scavenge peroxynitrite during immune responses mounted in the murine macrophage cell line RAW 264.7 when stimulated with lipopolysaccharide/interferon-γ (LPS/IFN-γ) and in LPS-treated rats. Gelam honey significantly improved the viability of LPS/IFN-γ-treated RAW 264.7 cells and inhibited nitric oxide production-similar to the effects observed with an inhibitor of inducible nitric oxide synthase (1400W). Furthermore, honey, but not 1400W, inhibited peroxynitrite production from the synthetic substrate 3-morpholinosydnonimine (SIN-1) and prevented the peroxynitrite-mediated conversion of dihydrorhodamine 123 to its fluorescent oxidation product rhodamine 123. Honey inhibited peroxynitrite synthesis in LPS-treated rats. Thus, honey may attenuate inflammatory responses that lead to cell damage and death, suggesting its therapeutic uses for several inflammatory disorders.

Antioxidant strategies in neurocritical care

An increase in oxidative stress and overproduction of oxidizing reactive species plays an important role in the pathophysiology of several conditions encountered in the neurocritical care setting including: ischemic and hemorrhagic strokes, traumatic brain injury, acute respiratory distress syndrome, sepsis, and organ failure. The presence of oxidative stress in these conditions is supported by a large body of pre-clinical and clinical studies, and provides a rationale to support a potential therapeutic role for antioxidants. The purpose of this article is to briefly review the basic mechanisms and molecular biology of oxidative stress, summarize its role in critically ill neurological patients, and review available data regarding the potential role of antioxidant strategies in neurocritical care and future directions.

DTPA Fe(III) decreases cytokines and hypotension but worsens survival with Escherichia coli sepsis in rats

OBJECTIVE

Nonselective inhibition of nitric oxide (NO) with NO synthase antagonists decreases hypotension but worsens outcome clinically. We investigated whether iron (III) complex of diethylenetriaminepentaacetic acid [DTPA Fe(III)], a scavenger of NO as well as other oxidant mediators, has similar divergent effects in E. coli challenged rats.

METHODS

Animals with venous and arterial catheters and challenged with intrabronchial or intravenous E. coli were randomized to treatment with DTPA Fe(III) in doses from 3 to 800 mg/kg or placebo. Mean blood pressure (MBP) was measured in all animals and plasma NO, cytokines, and blood and lung leukocyte and bacteria counts in animals administered intrabronchial E. coli and DTPA Fe(III) 50 mg/kg or placebo. Animals received antibiotics and were observed 168 h.

RESULTS

Independent of drug regimen or infection site, compared to placebo, DTPA Fe(III) increased MBP although this was greater with high vs. lower doses. Despite increased MBP, DTPA Fe(III) worsened the hazards ratio of survival . At 6 and 24 h DTPA Fe(III) decreased NO but not significantly and decreased four cytokines (tumor necrosis factor-alpha, interleukins 1 and 10, and macrophage inflammatory protein 3alpha) and lung lavage neutrophils. From 6 to 24 h DTPA Fe(III) increased blood bacteria.

CONCLUSIONS

DTPA Fe(III) while increasing blood pressure has the potential to worsen outcome in sepsis. Further preclinical testing is required before this agent is applied clinically.

Inhibition of the Fenton reaction by nitrogen monoxide

The toxicity of iron is believed to originate from the Fenton reaction which produces the hydroxyl radical and/or oxoiron2+. The effect of nitrogen monoxide on the kinetics of the reaction of iron(II) bound to citrate, ethylenediamine-N,N'-diacetate (edda), ethylenediamine-N,N,N',N'-tetraacetate (edta), (N-hydroxyethyl)amine-N,N',N'-triacetate (hedta), and nitrilotriacetate (nta) with hydrogen peroxide was studied by stopped-flow spectrophotometry. Nitrogen monoxide inhibits the Fenton reaction to a large extent. For instance, hydrogen peroxide oxidizes iron(II) citrate with a rate constant of 5.8x10(3) M(-1) s(-1), but in the presence of nitrogen monoxide, the rate constant is 2.9x10(2) M(-1) s(-1) . Similar to hydrogen peroxide, the reaction of tert-butyl hydroperoxide with iron(II) complexes is also efficiently inhibited by nitrogen monoxide. Generally, nitrogen monoxide binds rapidly to a coordination site of iron(II) occupied by water. The rate of oxidation is influenced by the rate of dissociation of the nitrogen monoxide from iron(II).

Nitric oxide scavengers as a therapeutic approach to nitric oxide mediated disease

The essential role of nitric oxide (NO) in normal physiology and its involvement in the pathophysiology of a variety of diseases render the compound an attractive therapeutic target. NO donor drugs are used in the treatment of hypotension and angina where abnormalities in the L-arginine-nitric oxide pathway have been implicated. Overproduction of NO has been associated with a number of disease states including septic shock, inflammatory diseases, diabetes, ischaemia-reperfusion injury, adult respiratory distress syndrome, neurodegenerative diseases and allograft rejection. NO is produced by a group of enzymes, the nitric oxide synthases. Selective inhibition of the inducible isoform is one approach to the treatment of diseases where there is an overproduction of NO; an alternative approach is to scavenge or remove excess NO. A number of NO scavenger molecules have demonstrated pharmacological activity in disease models, particularly models of septic shock. These include organic molecules such as PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), haemoglobin derivatives such as the pyridoxalated haemoglobin polyoxyethylene conjugate (PHP), low molecular weight iron compounds of diethylenetriaminepentaacetic acid and diethyldithiocarbamate and ruthenium polyaminocarboxylate complexes. The data suggest a potential role for NO scavengers in the treatment of NO mediated disease.

Burkholderia spp. alter Pseudomonas aeruginosa physiology through iron sequestration

Pseudomonas aeruginosa and members of the Burkholderia cepacia complex often coexist in both the soil and the lungs of cystic fibrosis patients. To gain an understanding of how these different species affect each other's physiology when coexisting, we performed a screen to identify P. aeruginosa genes that are induced in the presence of Burkholderia: A random gene fusion library was constructed in P. aeruginosa PA14 by using a transposon containing a promoterless lacZ gene. Fusion strains were screened for their ability to be induced in the presence of Burkholderia strains in a cross-streak assay. Three fusion strains were induced specifically by Burkholderia species; all three had transposon insertions in genes known to be iron regulated. One of these fusion strains, containing a transposon insertion in gene PA4467, was used to characterize the inducing activity from Burkholderia: Biochemical and genetic evidence demonstrate that ornibactin, a siderophore produced by nearly all B. cepacia strains, can induce P. aeruginosa PA4467. Significantly, PA4467 is induced early in coculture with an ornibactin-producing but not an ornibactin-deficient B. cepacia strain, indicating that ornibactin can be produced by B. cepacia and detected by P. aeruginosa when the two species coexist.

Ação do ácido trissódio-cálcio-dietileno-triaminopentaacético (CaNa3DTPA) nas lesões de isquemia-reperfusão em membro posterior de rato

OBJETIVO: Ação do ácido trissódio-cálcio-dietileno-triaminopentaacético (CaNa3DTPA), quelante de ferro com ação ainda anti-viral, antiinflamatória e imunológica, na atenuação de lesões de reperfusão em músculos esqueléticos de ratos. MÉTODOS: 52 ratos Wistar, pesando 188±22g, foram anestesiados e submetidos a semi-amputação de membro posterior direito (MPD), poupando-se o fêmur, artéria e veia femorais. Foram então randomizados e distribuídos: G1-CTAN - controle anestesia, sem cirurgia e sem isquemia; G2-CTCIR - controle cirurgia, sem isquemia; G3-IRCT e G3-IRDTPA - com isquemia (4 hora) e reperfusão ( 2 horas). O G3-IRCT foi tratado, ao final da isquemia, com cloreto de sódio 0,9% e G3-IRDTPA com (CaNa3DTPA).Parâmetros: Circunferência do pé direito e peso do rato, dosagem sérica de CPK, dosagem de malonaldeído e microscopia óptica de músculos soleus bilateral. RESULTADOS: Aumento da circunferência nos G3-IRCT e G3-IRDTPA (significante no G3-IRCT quando comparado ao G1-CTAN); CPK elevado nos G3-IRCT e G3-IRDTPA comparados aos controles; MDA mais alto no membro contralateral do G3-IRDTPA, comparado ao MPD do G3-IRDTPA e ao G1-CTAN; maior edema intersticial em G3-IRCT, maior infiltrado inflamatório em G3-IRDTPA e recuperação dos níveis de glicogênio semelhantes em G3-IRCT e G3-IRDTPA. CONCLUSÃO: Apesar do menor edema no G3-IRDTPA comparado ao G3-IRCT, o CaNa3DTPA não alterou CPK sérico, MDA muscular e morfologia muscular dos animais.

Mechanistic information on the reversible binding of NO to selected iron(II) chelates from activation parameters

Mechanistic insight on the reversible binding of NO to Fe(II) chelate complexes as potential catalysts for the removal of NO from effluent gas streams has been obtained from the temperature and pressure parameters for the "on" and "off" reactions determined using a combination of flash photolysis and stopped-flow techniques. These parameters are correlated with those for water exchange reactions on the corresponding Fe(II) and Fe(III) chelate complexes, from which mechanistic conclusions are drawn. Small and positive Delta V(++) values are found for NO binding to and release from all the selected complexes, consistent with a dissociative interchange (I(d)) mechanism. The only exception in the series of studied complexes is the binding of NO to [Fe(II)(nta)(H(2)O)(2)](-). The negative volume of activation observed for this reaction supports the operation of an I(a) ligand substitution mechanism. The apparent mechanistic differences can be accounted for in terms of the electronic and structural features of the studied complexes. The results indicate that the aminocarboxylate chelates affect the rate and overall equilibrium constants, as well as the nature of the substitution mechanism by which NO coordinates to the selected complexes. There is, however, no simple correlation between the rate and activation parameters and the selected donor groups or overall charge on the iron(II) complexes.

Is nitric oxide overproduction the target of choice for the management of septic shock?

Sepsis is a heterogeneous class of syndromes caused by a systemic inflammatory response to infection. Septic shock, a severe form of sepsis, is associated with the development of progressive damage in multiple organs, and is a leading cause of patient mortality in intensive care units. Despite important advances in understanding its pathophysiology, therapy remains largely symptomatic and supportive. A decade ago, the overproduction of nitric oxide (NO) had been discovered as a potentially important event in this condition. As a result, great hopes arose that the pharmacological inhibition of NO synthesis could be developed into an efficient, mechanism-based therapeutic approach. Since then, an extraordinary effort by the scientific community has brought a deeper insight regarding the feasibility of this goal. Here we present in summary form the present state of knowledge of the biological chemistry and physiology of NO. We then proceed to a systematic review of experimental and clinical data, indicating an up-regulation of NO production in septic shock; information on the role of NO in septic shock, as provided by experiments in transgenic mice that lack the ability to up-regulate NO production; effects of pharmacological inhibitors of NO production in various experimental models of septic shock; and relevant clinical experience. The accrued evidence suggests that the contribution of NO to the pathophysiology of septic shock is highly heterogeneous and, therefore, difficult to target therapeutically without appropriate monitoring tools, which do not exist at present.

Site selectivity in the synthesis of O-methylated hydroxamic acids with diazomethane

In this paper we report the results obtained by treating some selected hydroxamic acids with diazomethane in ethereal media. The multitask reagent diazomethane was used either as a base to induce deprotonation of the chosen hydroxamic acids or as conjugated acid which undergoes one-pot methylation processes of the generated anions. Product distributions clearly showed that a high site selectivity is expressed by the different deprotonated species in the alkylation processes. Under the adopted conditions, the prevalent site of methylation is in all the cases the oxygen of the hydroxamic acid. While in aliphatic hydroxamic acids only O-alkylation is observed, in the aromatic substrates, the NH group competes with the OH function as the nucleophilic site, although the OH reactivity still dominates.

Cellular non-heme iron content is a determinant of nitric oxide-mediated apoptosis, necrosis, and caspase inhibition

In this report, we tested the hypothesis that cellular content of non-heme iron determined whether cytotoxic levels of nitric oxide (NO) resulted in apoptosis versus necrosis. The consequences of NO exposure on cell viability were tested in RAW264.7 cells (a cell type with low non-heme iron levels) and hepatocytes (cells with high non-heme iron content). Whereas micromolar concentrations of the NO donor S-nitroso-N-acetyl-DL-penicillamine induced apoptosis in RAW264.7 cells, millimolar concentrations were required to induce necrosis in hepatocytes. Caspase-3 activation and cytochrome c release were evident in RAW264.7 cells, but only cytochrome c release was detectable in hepatocytes following high dose S-nitroso-N-acetyl-DL-penicillamine exposure. Pretreating RAW264.7 cells with FeSO(4) increased intracellular non-heme iron to levels similar to those measured in hepatocytes and delayed NO-induced cell death, which then occurred in the absence of caspase-3 activation. Iron loading was also associated with the formation of intracellular dinitrosyl-iron complexes (DNIC) upon NO exposure. Cytosolic preparations containing DNIC as well as pure preparations of DNIC suppressed caspase activity. These data suggest that non-heme iron content is a key factor in determining the consequence of NO on cell viability by regulating the chemical fate of NO.

Hemoglobin toxicity in experimental bacterial peritonitis is due to production of reactive oxygen species

Hemoglobin (Hb) is a toxic molecule responsible for the extreme lethality associated with experimental Escherichia coli peritonitis, but the mechanism has yet to be elucidated. Hb, but not globin, showed toxic effects in a live E. coli model but not in a model using killed E. coli. Methemoglobin, hematin, and the well-known Fenton reagents iron and iron-EDTA demonstrated the same lethal effect in E. coli peritonitis as Hb, while the addition of the Fenton inhibitors desferrioxamine (DF) and diethylenetriamine pentaacetate removed most of the cytotoxic activity of iron. Administration of a combined dose of superoxide dismutase and catalase minimized the action of Hb and iron-EDTA, suggesting that both O(2)(.-) and H(2)O(2) are involved in the toxic action of Hb in this rat model. The combination of the antioxidative enzymes and DF further suppressed iron-mediated lethality. An electron spin resonance technique with the spin-trapping reagent 5, 5-dimethyl-1-pyroline-N-oxide (DMPO) showed O(2)(.-) generation in the peritoneal fluid of rats injected with E. coli alone or E. coli plus iron-DF, and (.)OH generation was detected in the peritoneal fluid of the rats injected with iron-EDTA. Hb did not show any spin adduct of oxygen radicals, suggesting that Hb produces non-spin-trapping radical ferryl ion, which decayed the spin adduct of DMPO. In the presence of Hb or iron-EDTA, O(2)(-)-generating activity and viability of phagocytes decreased, whereas lipid peroxidation of peritoneal phagocytes increased. Generation of oxygen radicals and lipid peroxidation did not differ in the live and dead bacterial models. Bacterial numbers in the peritoneal cavity and blood were markedly increased in the live bacterial model with Hb and iron-EDTA. The Fenton inhibitor iron-DF prevented the loss of phagocyte function, lipid peroxidation, and bacterial proliferation. These results led us to conclude that the lethal toxicity of Hb in bacterial peritonitis is associated with a Fenton-type reaction, the products of which decrease phagocyte viability, through the induction of lipid peroxidation, allowing bacterial proliferation and resulting in mortality.

The inducible nitric oxide synthase in vascular and cardiac tissue

Expression of the inducible form of nitric oxide synthase (iNOS) has been reported in a variety of cardiovascular diseases. The resulting high output nitric oxide (NO) formation, besides the level of iNOS expression, depends also on the expression of the metabolic pathways providing the enzyme with substrate and cofactor. NO may trigger short and long term effects which are either beneficial or deleterious, depending on the molecular targets with which it interacts. These interactions are governed by local factors (like the redox state). In the cardiovascular system, the major targets involve not only guanylyl cyclase, but also other haem proteins, protein thiols, iron-non-haem complexes, and superoxide anion (forming peroxynitrite). The latter has several intracellular targets and may be cytotoxic, despite the existence of endogenous defence mechanisms. These interactions may either trigger NO effects or represent releasable NO stores, able to buffer NO and prolong its effects in blood vessels and in the heart. Besides selectively inhibiting iNOS, a number of other therapeutic strategies are conceivable to alleviate deleterious effects of excessive NO formation, including peroxynitrite (ONOO-) scavenging and inhibition of metabolic pathways triggered by ONOO-. When available, these approaches might have the advantage to preserve beneficial effects of iNOS induction. Counteracting vascular hyper-responsiveness to endogenous vasoconstrictor agonists in septic shock, or inducing cardiac protection against ischaemia-reperfusion injury are examples of such beneficial effects of iNOS induction.

Iron attenuates nitric oxide level and iNOS expression in endotoxin-treated mice

The effect of exogenous Fe-citrate complex (Fe doses of 120 and 240 micromol/kg) on nitric oxide (NO) production in vivo has been studied in blood and liver tissue of endotoxin-treated mice. Fe-citrate complex was administered to mice subcutaneously at the same time with intravenous injection of Escherichia coli lipopolysaccharide (LPS). Iron-dependent decrease in NO2-/NO3- and nitrosyl hemoglobin levels in blood of animals was detected at 6 h after LPS administration, suggesting systemic attenuation of NO generation. NO production in the liver tissue of LPS-treated mice was decreased after Fe administration judging from the amount of mononitrosyl-iron complexes formed in the tissue by diethyldithiocarbamate. The iNOS protein determination in the liver tissue of LPS-treated mice demonstrated iron-dependent inhibition of iNOS expression. We have found previously that exogenous iron does not affect systemic NO level when it is given at 6 h after LPS injection, i.e. after iNOS expression. This is a first report demonstrating iron-dependent iNOS down-regulation in endotoxin-treated mice.

Iron potentiates nitric oxide scavenging by dithiocarbamates in tissue of septic shock mice

Vanin and co-workers (Kubrina et al., Biochim. Biophys. Acta 1176 (1993) 240-244; Mikoyan et al., Biochim. Biophys. Acta 1269 (1995) 19-24) reported that short term (30 min) iron (Fe) exposure potentiates nitric oxide (NO) production in tissues of septic shock mice, based on increased formation of NO complex by diethyldithiocarbamate (DETC). We have reexamined the effect of Fe administration in mice treated with Escherichia coli lipopolysaccharide (LPS) and have not found any changes in nitrosylhemoglobin (HbNO) or (NOs- + NO3-) levels in blood 30 min after Fe-citrate complex injection. However, Fe-citrate promotes NO complex formation by iron-dependent NO traps: DETC, pyrrolidinedithiocarbamate (PDTC) and N-methyl-D-glucamine dithiocarbamate (MGD), when given simultaneously at 6 h after LPS. Rather than potentiation of NO production, our data support that short-term iron treatment (30 min) enhances in vivo spin trapping ability of dithiocarbamate.

Cocaine-induced liver injury in mice is mediated by nitric oxide and reactive oxygen species

The modulating effects of nitric oxide (NO) and reactive oxygen species on cocaine-induced hepatotoxicity were examined by measuring plasma alanine aminotransferase activity and by carrying out histological studies. Liver injury was induced by a single injection of cocaine in adult male ICR mice. Pretreatment with aminoguanidine (an inhibitor of NO synthase), N-methyl-D-glucamine dithiocarbamate complex with iron ion (II) (Fe2+(MGD)2, a trapping reagent of NO) or deferoxamine complex with iron ion (III) (Fe3+-deferoxamine, a scavenger of NO) produced a marked inhibition of the hepatotoxicity induced by cocaine. In addition, pretreatment with allopurinol (an inhibitor of xanthine oxidase) and 1,3-dimethylthiourea (a scavenger of hydroxyl radical) also produced a potent inhibition. These findings suggest that a hydroxyl radical produced by the reaction of NO and superoxide anion (O2-) via peroxynitrite may be involved in the pathogenesis of cocaine hepatotoxicity.