A water-soluble iron-porphyrin complex capable of rescuing CO-poisoned red blood cells.

We describe herein a small-molecule platform that exhibits key properties needed by an antidote for CO poisoning. The design features an iron-porphyrin complex with bulky substituents above and below the macrocyclic plane to provide a hydrophobic pocket for CO binding and to prevent the formation of inactive oxo-bridged dimers. Peripheral charged groups impart water solubility. We demonstrate that the Fe(II) complex of a porphyrin with 2,6-diphenyl-4-sulfophenyl meso substituents can bind CO, stoichiometrically sequester CO from carboxyhemoglobin, and rescue CO-poisoned red blood cells.

Breathing Micelles for Combinatorial Treatment of Rheumatoid Arthritis.

Breathing process involves inhalation and exhalation of different gases in animals. The gas exchange of the breathing process plays a critical role in maintaining the physiological functions of living organisms. Although artificial breathing materials exhibiting volume expansion and contraction upon alternate exposure to different gases have been well explored, those being able to realize the gas exchange remain elusive. Herein, we report breathing micelles (BM) capable of inhaling nitric oxide (NO) and exhaling carbon monoxide (CO), both of which are endogenous gaseous signaling molecules. We demonstrate that BM can simultaneously scavenge overproduced NO and attenuate proinflammatory cytokines in lipopolysaccharide (LPS)-challenged macrophage cells. In vivo studies revealed that BM outperformed conventional nonsteroidal anti-inflammatory drugs such as dexamethasone (Dexa) in treatment of rheumatoid arthritis (RA) in adjuvant-induced arthritis (AIA) rats, likely due to the combinatorial effect of NO depletion, CO-mediated deactivation of inducible NO synthase (iNOS) and activation of heme oxygenase-1 (HO-1). This work provides new insights into artificial BM for potential biomedical applications.

Magnesium sulfate ameliorates carbon monoxide­induced cerebral injury in male rats.

Carbon monoxide (CO) has been shown to induce several cardiovascular abnormalities, as well as necrosis, apoptosis and oxidative stress in the brain. Magnesium sulfate (MS) has been shown to have beneficial activities against hypoxia in the brain. In the present study, the possible protective effects of MS against CO­induced cerebral ischemia were investigated. For this purpose, 25 male Wistar rats were exposed to 3,000 ppm CO for 1 h. The animals were divided into 5 groups (n=5 in each group) as follows: The negative control group (not exposed to CO), the positive control group (CO exposed and treated with normal saline), and 3 groups of CO­exposed rats treated with MS (75, 150 and 300 mg/kg/day) administered intraperitoneally for 5 consecutive days. On the 5th day, the animals were sacrificed and the brains were harvested for the evaluation of necrosis, apoptosis and oxidative stress. Histopathological evaluation revealed that MS reduced the number and intensity of necrotic insults. The Bax/Bcl2 ratio and malondialdehyde (MDA) levels were significantly decreased in a dose­dependent manner in the MS­treated rats compared to the positive control group, while a significant dose­dependent increase in Akt expression, a pro­survival protein, was observed. In addition, MS administration reduced pro­apoptotic indice levels, ameliorated histological insults, favorably modulated oxidative status and increased Akt expression levels, indicating a possible neuroprotective effect in the case of CO poisoning. On the whole, the findings of this study indicate that MS may prove to be useful in protecting against CO­induced cerebral injury.

[Protective effects of endogenous carbon monoxide against myocardial ischemia-reperfusion injury in rats].

The present study is aimed to explore the effects of endogenous carbon monoxide on the ischemia-reperfusion in rats. Wistar rats were intraperitoneally injected with protoporphyrin cobalt chloride (CoPP, an endogenous carbon monoxide agonist, 5 mg/kg), zinc protoporphyrin (ZnPP, an endogenous carbon monoxide inhibitor, 5 mg/kg) or saline. Twenty-four hours after injection, the myocardial ischemia-reperfusion model was made by Langendorff isolated cardiac perfusion system, and cardiac function parameters were collected. Myocardial cGMP content was measured by ELISA, and the endogenous carbon monoxide in plasma and myocardial enzymes in perfusate at 10 min after reperfusion were measured by colorimetry. The results showed that before ischemia the cardiac functions of CoPP, ZnPP and control groups were stable, and there were no significant differences. After reperfusion, cardiac functions had significant differences among the three groups (P < 0.05). Compared with pre-ischemia, the cardiac function decreased and obvious cardiac arrest was shown in control and ZnPP groups, while the cardiac function in CoPP group did not change significantly, maintaining a relatively stable level. At the same time, three groups' carbon monoxide level, myocardial enzymology and the cardiac function recovery time after reperfusion also had significant differences (P < 0.05). Compared with those in control group, recovery after reperfusion was faster, activities of creatine kinase and lactic dehydrogenase were significantly decreased, plasma CO and myocardial cGMP contents were significantly increased in CoPP group, while these changes were completely opposite in ZnPP group. It is concluded that endogenous carbon monoxide can maintain cardiac function, shorten the time of cardiac function recovery, and play a protective role in cardiac ischemia-reperfusion.

Gaseous Mediators in Gastrointestinal Mucosal Defense and Injury.

Of the numerous gaseous substances that can act as signaling molecules, the best characterized are nitric oxide, carbon monoxide and hydrogen sulfide. Contributions of each of these low molecular weight substances, alone or in combination, to maintenance of gastrointestinal mucosal integrity have been established. There is considerable overlap in the actions of these gases in modulating mucosal defense and responses to injury, and in some instances they act in a cooperative manner. Each also play important roles in regulating inflammatory and repair processes throughout the gastrointestinal tract. In recent years, significant progress has been made in the development of novel anti-inflammatory and cytoprotective drugs that exploit the beneficial activities of one or more of these gaseous mediators.

Therapeutic Potential of Heme Oxygenase-1/carbon Monoxide System Against Ischemia-Reperfusion Injury.

BACKGROUND: Ischemia-reperfusion (I/R) injury causes the dysfunctions of different major organs, leading to morbidity and mortality on the global scale. Among a battery of therapeutic targets, the heme oxygenase- 1 (HO-1)/carbon monoxide (CO) system has been evaluated for the development of new therapies against I/R injury. The enzyme HO-1 catalyzes the degradation of heme into three biologically active end products, namely biliverdin/bilirubin, CO and ferrous ion. Interestingly, CO is one of a few bioactive gaseous molecules with the capability of regulating inflammation, cell survival and growth. In fact, several CO-releasing compounds have been developed for directly reprogramming the intracellular apoptotic, inflammatory and proliferative signaling networks. In parallel, chemical and genetic approaches have also been evaluated for up-regulating HO-1 expression as an endogenous mechanism to ameliorate I/R injury and heal wounds. METHODS: In this review, we discussed the recent studies on the therapeutic potential of HO-1/CO system in the treatment of I/R injury in the heart, brain, liver, kidney, lung, intestine and retina. We focused on the activities and underlying mechanisms of various therapeutic strategies to regulate HO-1/CO system against I/R injury. RESULTS: A large number of studies have demonstrated that HO-1/CO system exhibits potent anti-oxidative, antiapoptotic, anti-inflammatory and cytoprotective activities against I/R injury. The regulation of HO-1/CO expression has been achieved either by genetic overexpression of HO-1 cDNA or pharmacological induction with drugs including curcumin and resveratrol. CONCLUSION: The HO-1/CO system is a potential target for treating I/R injury. Further studies should be directed to in vivo efficacy and clinical application of HO-1/CO system in the therapy of I/R injury.

Gasotransmitters in cancer: from pathophysiology to experimental therapy.

The three endogenous gaseous transmitters - nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) - regulate a number of key biological functions. Emerging data have revealed several new mechanisms for each of these three gasotransmitters in tumour biology. It is now appreciated that they show bimodal pharmacological character in cancer, in that not only the inhibition of their biosynthesis but also elevation of their concentration beyond a certain threshold can exert anticancer effects. This Review discusses the role of each gasotransmitter in cancer and the effects of pharmacological agents - some of which are in early-stage clinical studies - that modulate the levels of each gasotransmitter. A clearer understanding of the pharmacological character of these three gases and the mechanisms underlying their biological effects is expected to guide further clinical translation.

Carbon monoxide modulates electrical activity of murine myocardium via cGMP-dependent mechanisms.

Carbon monoxide (CO) is critical in cell signaling, and inhalation of gaseous CO can impact cardiovascular physiology. We have investigated electrophysiological effects of CO and their potential cGMP-dependent mechanism in isolated preparations of murine myocardium. The standard microelectrode technique was used to record myocardial action potentials (APs). Exogenous CO (0.96 × 10(-4)-4.8 × 10(-4) M) decreased AP duration in atrial and ventricular tissue and accelerated pacemaking activity in sinoatrial node. Inhibitors of heme oxygenases (zinc and tin protoporphyrin IX), which are responsible for endogenous CO production, induced the opposite effects. Inhibitor of soluble guanylate cyclase (sGC), ODQ (10(-5) M) halved CO-induced AP shortening, while sGC activator azosidnone (10(-5) M-3 × 10(-4) M) and cGMP analog BrcGMP (3 × 10(-4) M) induced the same effects as CO. To see if CO effects are attributed to differential regulation of phosphodiesterase 2 (PDE2) and 3 (PDE3), we used inhibitors of these enzymes. Milrinone (2 × 10(-6) M), selective inhibitor of cGMP-downregulated PDE3, blocked CO-induced rhythm acceleration. EHNA(2 × 10(-6) M), which inhibits cGMP-upregulated PDE2, attenuated CO-induced AP shortening, but failed to induce any positive chronotropic effect. Our findings indicate that PDE2 activity prevails in working myocardium, while PDE3 is more active in sinoatrial node. The results suggest that cardiac effects of CO are at least partly attributed to activation of sGC and subsequent elevation of cGMP intracellular content. In sinoatrial node, this leads to PDE3 inhibition, increased cAMP content, and positive chronotropy, while it also causes PDE2 stimulation in working myocardium, thereby enhancing cAMP degradation and producing AP shortening. Thus, CO induces significant alterations of cardiac electrical activity via cGMP-dependent mechanism and should be considered as a novel regulator of cardiac electrophysiology.

A unified electrocatalytic description of the action of inhibitors of nickel carbon monoxide dehydrogenase.

Several small molecules and ions, notably carbon monoxide, cyanide, cyanate, and hydrogen sulfide, are potent inhibitors of Ni-containing carbon monoxide dehydrogenases (Ni-CODH) that catalyze very rapid, efficient redox interconversions of CO(2) and CO. Protein film electrochemistry, which probes the dependence of steady-state catalytic rate over a wide potential range, reveals how these inhibitors target particular oxidation levels of Ni-CODH relating to intermediates (C(ox), C(red1), and C(red2)) that have been established for the active site. The following properties are thus established: (1) CO suppresses CO(2) reduction (CO is a product inhibitor), but its binding affinity decreases as the potential becomes more negative. (2) Cyanide totally inhibits CO oxidation, but its effect on CO(2) reduction is limited to a narrow potential region (between -0.5 and -0.6 V), below which CO(2) reduction activity is restored. (3) Cyanate is a strong inhibitor of CO(2) reduction but inhibits CO oxidation only within a narrow potential range just above the CO(2)/CO thermodynamic potential--EPR spectra confirm that cyanate binds selectively to C(red2). (4) Hydrogen sulfide (H(2)S/HS(-)) inhibits CO oxidation but not CO(2) reduction--the complex on/off characteristics are consistent with it binding at the same oxidation level as C(ox) and forming a modified version of this inactive state rather than reacting directly with C(red1). The results provide a new perspective on the properties of different catalytic intermediates of Ni-CODH--uniting and clarifying many previous investigations.

Inhibition of endogenous CO by ZnPP protects against stress-induced gastric lesion in adult male albino rats.

Carbon monoxide (CO) has been found to be produced in every living cell in a biochemical reaction catalyzed by heme-oxygenase (HO) enzyme which degrades heme into biliverdin, CO, and iron. Endogenous CO is not a waste product, but acts as a chemical messenger mediating and modulating many intracellular biochemical reactions that regulate physiological functions. This study was designed to investigate the effect of inhibition of endogenous CO production by zinc protoporphyrin (ZnPP), an HO inhibitor, on the gastric secretion and ulceration induced by cold-restraint stress (CRS) in adult male albino rats. Rats were pylorically ligated and divided randomly into the following groups (six rats each): control, ZnPP treated (50 µmol/kg/day, s.c. for 10 days), CRS, and stressed ZnPP treated groups. Blood samples were collected from the retro-orbital sinus of anesthetized rats for determination of CO concentration. We found that ZnPP pretreatment significantly decreased HO-1 level, CO level, and volume of gastric juice as compared to the control non-stressed rats. In the present study, ZnPP pretreatment proved to be protective against development of ulcerative lesions in CRS model as evidenced by reduction of the ulcer index, and this could be mediated through reduction of free and total acidity of gastric secretion and decreased lipid peroxidation but with significantly decreased gastric protective nitric oxide and prostaglandin E(2) levels. In conclusion and according to our results, the protective effect of ZnPP on CRS-induced gastric ulcers despite of inhibition of endogenous CO could be attributed to the presence of zinc which is known to have a protective anti-ulcer effect.

Targeting gaseous molecules to protect against cerebral ischaemic injury: mechanisms and prospects.

1. Ischaemic brain injury is a leading cause of death and disability in many countries. However, the pathological mechanisms underlying ischaemic brain injury, including oxidative stress, calcium overload, excitotoxicity and neuronal apoptosis, are perplexing and this makes it difficult to find effective novel drugs for the treatment of the condition. 2. Recently, gaseous molecules such as nitric oxide (NO), carbon monoxide (CO), hydrogen sulphide (H(2)S) and hydrogen (H(2)) have attracted considerable interest because of their physiological and pathophysiological roles in various body systems. Emerging evidence indicates that gaseous molecules are involved in the pathological processes of ischaemic brain damage. 3. In the present review, we summarize evidence regarding the involvement of gaseous molecules in ischaemic brain injury and discuss the therapeutic potential of targeting gaseous molecules. 4. Collectively, the available data suggest that the application of these biological gas molecules and their pharmacological regulators may be a potential therapeutic approach for the treatment of ischaemic brain injury.

Vasoactivity of the gasotransmitters hydrogen sulfide and carbon monoxide in the chicken ductus arteriosus.

Besides nitric oxide (NO) and carbon monoxide (CO), hydrogen sulfide (H(2)S) is a third gaseous messenger that may play a role in controlling vascular tone and has been proposed to serve as an O(2) sensor. However, whether H(2)S is vasoactive in the ductus arteriosus (DA) has not yet been studied. We investigated, using wire myography, the mechanical responses induced by Na(2)S (1 µM-1 mM), which forms H(2)S and HS(-) in solution, and by authentic CO (0.1 µM-0.1 mM) in DA rings from 19-day chicken embryos. Na(2)S elicited a 100% relaxation (pD(2) 4.02) of 21% O(2)-contracted and a 50.3% relaxation of 62.5 mM KCl-contracted DA rings. Na(2)S-induced relaxation was not affected by presence of the NO synthase inhibitor l-NAME, the soluble guanylate cyclase (sGC) inhibitor ODQ, or the K(+) channel inhibitors tetraethylammonium (TEA; nonselective), 4-aminopyridine (4-AP, K(V)), glibenclamide (K(ATP)), iberiotoxin (BK(Ca)), TRAM-34 (IK(Ca)), and apamin (SK(Ca)). CO also relaxed O(2)-contracted (60.8% relaxation) and KCl-contracted (18.6% relaxation) DA rings. CO-induced relaxation was impaired by ODQ, TEA, and 4-AP (but not by L-NAME, glibenclamide, iberiotoxin, TRAM-34 or apamin), suggesting the involvement of sGC and K(V) channel stimulation. The presence of inhibitors of H(2)S or CO synthesis as well as the H(2)S precursor L-cysteine or the CO precursor hemin did not significantly affect the response of the DA to changes in O(2) tension. Endothelium-dependent and -independent relaxations were also unaffected. In conclusion, our results indicate that the gasotransmitters H(2)S and CO are vasoactive in the chicken DA but they do not suggest an important role for endogenous H(2)S or CO in the control of chicken ductal reactivity.

The role of heme oxygenase-1 in the proliferation and odontoblastic differentiation of human dental pulp cells.

INTRODUCTION: It was recently reported that heme oxygenase-1 (HO-1) activity is related to stem cell differentiation; however, the involvement of HO-1 in pulp cell growth and differentiation has not been well explored. The purpose of this study was to investigate the role of HO-1 in the growth and differentiation of human dental pulp cells (HDPCs). METHODS: We evaluated cell growth by MTT assay, mineralization by alizarin red staining, and differentiation marker mRNA expression by reverse transcriptase polymerase chain reaction. RESULTS: HO-1 induction by cobaltic protoporphyrin IX (CoPP) in HDPCs increased cell growth and mineralization and up-regulated the messenger RNA expression of such odontoblastic markers as alkaline phosphatase, osteopontin, bone sialoprotein, dentin matrix protein-1, and dentin sialophosphoprotein. Carbon monoxide scavenger, iron chelator, HO-1 inhibitor, and HO-1 small interfering RNA (siRNA) attenuated HDPC growth and differentiation. CONCLUSIONS: CoPP treatment results in dental pulp cell proliferation and odontoblast differentiation that appears partly mediated by HO-1. Our results suggest that odontoblastic differentiation and growth are positively regulated by HO-1 induction and negatively regulated by HO-1 inhibition. Thus, pharmacologic HO-1 induction might represent a potent therapeutic approach for pulp capping and the regeneration of HDPCs.

[ZnPP IX and L-NAME reduce the cGMP content in the penile tissue of rats].

OBJECTIVE: To investigate the effects of CO release inhibitor zinc protoporphyria IX (ZnPP IX) and NO release inhibitor L-NAME on the content of cGMP in the penile tissue of rats. METHODS: Thirty Wistar rats were randomly divided into a normal control, a ZnPP IX, and an L-NAME group, given saline (1 ml/kg/d), ZnPP IX (45 micromol/kg/d) and L-NAME (50 mg/kg/d), respectively, for 7 days. Then all the rats were killed, homogenate made from their penile tissues and detected for the contents of NOS, NO, CO and cGMP. RESULTS: The contents of CO, NOS, NO and cGMP were all reduced in both the ZnPP IX and L-NAME groups as compared with the control group (P < 0.05). CONCLUSION: ZnPP IX and L-NAME can reduce the concentrations of CO and NO in the penile tissues of rats, and consequently the content of cGMP.

Melatonin administration acutely decreases the diffusing capacity of carbon monoxide in human lungs.

BACKGROUND: Most physiological measurements of the pulmonary diffusing capacity use carbon monoxide (CO) as a tracer gas. Similar to CO, melatonin binds the hemoglobin in the blood. OBJECTIVE: The present study was designed to assess the effect of exogenous melatonin administration on pulmonary functions including diffusing capacity for carbon monoxide (DL(CO)) in healthy subjects. METHODS: The study was performed in a randomized, double-blind, placebo-controlled manner. DL(CO) was measured in 22 healthy male volunteers (age 18-25 years) who were randomized to melatonin (n = 11) and placebo administration (n = 11). At baseline, DL(CO), alveolar volume (V(A)) and other spirometric parameters such as forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), peak expiratory flow (PEF) and maximal voluntary ventilation (MVV) were measured. DL(CO) was then corrected for the hemoglobin concentration. Measurements were repeated in a double-blind fashion 60 min after the administration of melatonin (1 mg) or placebo. RESULTS: DL(CO) was significantly decreased (39.31 +/- 4.75 vs. 34.82 +/- 6.18 ml/min/mm Hg) 60 min after the melatonin administration (p = 0.01), while FEV(1), FVC, FEV(1)/FVC, PEF and MVV values did not demonstrate significant differences. Placebo administration did not result in significant alteration in any of these parameters. CONCLUSIONS: In healthy subjects, oral administration of melatonin acutely influences the DL(CO) without affecting other pulmonary function test results. We conclude that melatonin may have a reducing effect on the DL(CO) in the lungs.

Inhibition of endogenous carbon monoxide production induces transient retention losses in the day-old chick when trained using a single trial passive avoidance learning task.

Carbon monoxide (CO) is most often thought of as an exogenous toxin rather than as a possible endogenous nootrope. However, a limited number of studies have suggested that CO is necessary in memory processing for at least some tasks. While nitric oxide (NO) and CO are known activators of guanylyl cyclase (GC), only the effect of NO on GC has been extensively investigated as a mechanism underlying memory processing. The aim of the present study was to determine if inhibition of CO production would have an effect on memory processing. Using chicks trained on a single trial passive avoidance task, inhibition of CO production using zinc (II) deuteroporphyrin IX 2,4-bis ethylene glycol (ZnBG; 5 microM) resulted in two transient retention losses occurring at around 40 and 130 min post-training. The timing of these transient retention losses was similar to those observed following inhibition of GC, using the same species and task in a previous study. This supports the notion that CO is necessary in memory processing for this task and may act through a GC-dependent mechanism. As ZnBG also directly inhibits GC or nitric oxide synthase (NOS) at high concentrations, a second experiment was carried-out to confirm the specificity of ZnBG for heme oxygenase (HO) at the concentration used. The action of ZnBG was challenged with the HO agonist hemin (100 microM) and the transient deficits were abolished. This confirmed that the action of ZnBG on memory was through a CO-related mechanism rather than directly on GC or NOS. In this way the specificity of ZnBG (5 microM) for HO could be confirmed. The results support a role for endogenous CO in memory processing, possibly through activation of GC. In addition, the transient retention losses observed following administration of ZnBG suggest that CO may be necessary for memory retrieval and not formation as previously thought.

Role of heme oxygenase/carbon monoxide pathway on the vascular response to noradrenaline in portal hypertensive rats.

1. Portal hypertension (PH), a major syndrome in cirrhosis, producing hyperdynamic splanchnic circulation and hyperaemia. In order to elucidate the contribution of heme oxygenase to the vascular hyporeactivity, we assessed the activity of heme oxygenase-1 (HO-1), measured the in vivo pressure response to noradrenaline (NA) and investigated the effects of blocking the carbon monoxide (CO) and nitric oxide (NO) pathways in a prehepatic model of PH in rats. 2. Portal hypertension was induced by partial portal vein ligation (PPVL). Noradrenaline was injected intravenously. Liver, spleen and mesentery homogenates were prepared for measurement of HO-1 activity and expression. Four groups of rats were used: (i) a sham group; (ii) a PPVL group; (iii) a sham group pretreated with Zn-protoporphyrin IX (ZnPPIX); and (iv) a PPVL group pretreated with ZnPPIX. Each group was studied before and after treatment with the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). 3. For basal pressures and the pressure response to NA, inhibition of CO and NO pathways by ZnPPIX and L-NAME, respectively, produced an increase in mean arterial pressure (MAP) in sham-operated and in PH rats. Similarly, when both inhibitors were used together in either sham or PPVL rats, a greater increase in MAP was observed. 4. These results, together with the increased HO-1 activity and expression only in the PH group, have led us to suggest that the heme oxygenase/CO pathway is involved in the vascular response to NA in PH rats.

Investigation of the role of the N-terminal proline, the distal heme ligand in the CO sensor CooA.

A unique feature of CooA, a heme-containing transcription factor, is that the N-terminal proline is the distal heme ligand in the ferrous state, and this ligand is displaced upon CO binding. To investigate the importance of Pro(2) in CO-dependent DNA binding, several CooA variants that alter N-terminal ligation were characterized. Electronic absorption, electron paramagnetic resonance, and magnetic circular dichroism spectra of these variants provide the most definitive evidence that Pro(2) is the distal ligand in Fe(III) CooA. Furthermore, the functional and spectroscopic properties of these proteins depended on whether a weak ligand occupied the distal heme coordination site: for CooA variants in which distal coordination is disrupted, the DNA-binding affinities and Fe(II)-CO spectral properties showed an unexpected dependence on the order of CO addition and heme reduction. If N-terminal variant samples were incubated with CO before the heme was reduced, the proteins displayed DNA-binding affinities and Fe(II)-CO spectral characteristics similar to those of wild-type (WT) CooA. However, if the same samples were incubated with CO after the heme was reduced, the extent of functional and spectral similarity to WT CooA negatively correlated with the amount of high-spin heme present in the ferric state. From these data, it was inferred that the absence of a distal heme ligand in the ferric state prevents WT-like CO binding to the ferrous state, and it was hypothesized that correct CO binding is inhibited by the collapse of the distal heme pocket upon reduction. Together with the observation that L116H CooA, a variant in which His(116) replaces Pro(2) as the distal heme ligand, binds CO more slowly than WT CooA, these data indicate that the presence of a weak distal heme ligand, not specifically ligation by the N-terminal proline, is crucial for proper function. The role of Pro(2) in CooA is apparently to direct CO to bind on the distal side of heme and to help maintain the integrity of the distal heme pocket during the redox-mediated ligand switch.

[Autotrophic synthesis of polyalkanoates by Alcaligenes eutrophus in presence of carbon monoxide]. / Avtotropnyi sintez polioksialkanoatov bakteriiami Alcaligenes eutrophus v prisutstvii monookisi ugleroda.

The CO-resistant strain B5786 of the hydrogen-oxidizing bacterium Alcaligenes eutrophus was found to be able to synthesize polyhydroxyalkanoates (PHAs) under the conditions of growth limitation by nitrogen deficiency (the factor that promotes PHA synthesis) and growth inhibition by carbon monoxide. The gas mixtures that contained from 5 to 20 vol% CO did not inhibit the key enzymes of PHA synthesis--beta-ketothiolase, acetoacetyl-CoA reductase, hydroxybutyrate dehydrogenase, and PHA synthase. In the presence of CO, cells accumulated up to 70-75 wt% PHA (with respect to the dry biomass) without any noticeable increase in the consumption of the gas substrate. Chromatographic-mass spectrometric analysis showed that the PHA synthesized by A. eutrophus is a copolymer containing more than 99 mol% beta-hydroxybutyrate and trace amounts of beta-hydroxyvalerate. The PHA synthesized under the conditions described did not differ from that synthesized by A. eutrophus cells from electrolytic hydrogen.

Inhibition of the central heme oxygenase-carbon monoxide pathway increases 2-deoxy-D-glucose-induced hypothermia in rats.

The present study was designed to test the hypothesis that carbon monoxide (CO) plays a role in 2-deoxy-D-glucose (2-DG)-induced hypothermia. The body temperature (T(b)) of awake, unrestrained rats was measured before and after systemic administration of 2-DG (50 mg/kg) and intracerebroventricular administration of zinc deuteroporphyrin 2,4-bis glycol (ZnDPBG, a heme-oxygenase inhibitor, 200 nmol/4 microl). We observed a significant reduction in body temperature after 2-DG injection. ZnDPBG alone caused no significant change in body temperature. When the two treatments were combined, 2-DG-induced hypothermia was significantly increased. The data indicate that heme oxygenase-carbon monoxide pathway plays a key role in 2-DG-induced hypothermia, inhibiting 2-DG-induced hypothermia.