Evolutionary and comparative aspects of nitric oxide,carbon monoxide and hydrogen sulfide

The concept that non-respiratory gases, such as nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S) functioned as signaling moieties is a relatively recent development, due in part to their ephemeral existence in biological tissues. However, from an evolutionary perspective these gases dominated the prebiotic and anoxic Earth and were major contributors to the origin of life and the advent of eukaryotic animals. As Earth's oxygen levels rose, NO, CO and H₂S disappeared from the environment and cells began to utilize their now well-developed metabolic pathways to compartmentalize and regulate these three gases for signaling purposes. Ironically, many of the signaling pathways have become now intimately involved in regulating oxygen delivery and their evolution has continued well into the vertebrates. This review examines the role NO, CO and H₂S played in early life and their regulatory roles in oxygen delivery during the course of vertebrate evolution.     

Deciphering the nitric oxide to carbon monoxide lung transfer ratio: physiological implications

Using simultaneous nitric oxide and carbon monoxide lung transfer measurements ( T _LNO and T _LCO), the membrane transfer capacity ( D _m) and capillary lung volume ( V _c) as well as the dimensionless ratio T _LNO/ T _LCO can be calculated. The significance of this ratio is yet unclear. Theoretically, the T _LNO/ T _LCO ratio should be inversely related to the product of  both lung alveolar capillary membrane (μ) and blood sheet thicknesses ( K ). NO and CO transfers were measured in healthy subjects in various conditions likely to be associated with changes in K and/or μ. Experimentally, deflation of the lung from 7.4 to 4.8 l decreased the T _LNO/ T _LCO ratio from 4.9 to 4.2 ( n = 25) which was consistent mainly with a thickening of the blood sheet. Compared with continuous negative pressure breathing, continuous positive pressure breathing increased this ratio suggesting a thinning of the capillary sheet. It was also observed with 12 healthy subjects that slight haemodilution that may thicken the blood sheet decreased the T _LNO/ T _LCO ratio from 4.85 to 4.52. In conclusion, the T _LNO/ T _LCO ratio is related to the thickness of the alveolar blood barrier. This ratio provides novel information for the analysis of the diffusion properties.     

Cross talk between intracellular pathogens and cell death

Infections with bacterial pathogens often results in the initiation of programmed cell death as part of the host innate immune defense, or as a bacterial virulence strategy. Induction of host cell death is controlled by an elaborate network of innate immune and cell death signaling pathways and manifests in different morphologically and functionally distinct forms of death, such as apoptosis, necroptosis, NETosis and pyroptosis. The mechanism by which host cell death restricts bacterial replication is highly cell-type and context depended, but its physiological importance is highlighted the diversity of strategies bacterial pathogens use to avoid induction of cell death or to block cell death signaling pathways. In this review, we discuss the latest insights into how bacterial pathogens elicit and manipulate cell death signaling, how different forms of cell death kill or restrict bacteria and how cell death and innate immune pathway cross talk to guard against pathogen-induced inhibition of host cell death.     

内源性CO/NO在CCK-8逆转内毒素血症大鼠低血管反应性中的作用

目的:探讨HO-1-CO-cGMP和NOS-NO-cGMP细胞信号转导通路在八肽胆囊收缩素(CCK-8)逆转内毒素血症大鼠低血管反应性中的作用。方法:按照整体用药将大鼠分为4组:对照组、LPS组、CCK组及CCK+LPS组;用离体血管环张力测定技术,观察胸主动脉环(TARs)对苯肾上腺素(PE)累积收缩反应;分别用一氧化碳(CO)供体正铁血红素(He)、血红素氧合酶1(HO-1)抑制剂锌原卟啉(ZnPP-IX)、一氧化氮合酶(NOS)底物L-精氨酸(L-Arg)、诱生型一氧化氮合酶(iNOS)选择性抑制剂氨基胍(AG)、NOS抑制剂N^ω-硝基-L-精氨酸(L-NNA)、鸟苷酸环化酶(sGC)抑制剂亚甲兰(MB)预孵育后,测定TARs对PE的收缩反应。结果:单独应用CCK-8对血管张力无明显影响;预先注射CCK-8可明显逆转LPS所致的低血管反应性;LPS及CCK+LPS组TARs用ZnPP-IX或AG孵育,可部分逆转这种低血管反应性;经L-NNA或MB孵育,可使低血管反应恢复正常;用He或L-Arg孵育可不同程度加重低血管反应状态。结论:CCK-8本身不激活HO-1和iNOS,但可影响LPS诱导的HO-1和iNOS活性上升,减少CO/NO合成,从而使cGMP含量下降,对逆转内毒素血症大鼠低血管反应性有重要作用。     

Interactions between cytokines and nitric oxide

There is now an impressive range of evidence supporting the important role of cytokines in sleep regulation (see Krueger et al., 1995; De Simoni et al., 1995). It has also been reported that inhibition of nitric oxide (NO) synthesis suppresses sleep in rabbits (Kapás et al., 1994). This is not surprising, since NO is closely involved in neurotransmission (Garthwaite, 1991; Schuman and Madison, 1994) and cytokines are the major inducers of NO synthesis (Hibbs et al., 1990). Further, it is now clear that NO plays an important role in modulating immune responses, possibly through the differential regulation of cytokine synthesis (Taylor-Robinson et al., 1994). In this article, I will provide evidence for the interactions between cytokines and nitric oxide, and discuss their implications in the regulation of immune responses. I shall illustrate these mainly with results from my coworkers and I, from our laboratory rather than attempting an exhaustive review of the subject.     

Cross talk between synaptic receptors mediates NMDA-induced suppression of inhibition

Past research has shown that calcium influx through NMDA receptors (NMDARs) depresses GABA(A) currents. We examined upstream triggers of this suppression, including involvement of target synaptic GABA(A) receptors and the NMDARs triggering suppression. In hippocampal neurons, conditioning with 20 μM NMDA for 20 s caused 50% suppression of GABA responses. The suppression was delayed by ≈ 60 s following NMDA application and persisted for at least 5 min following conditioning. Pharmacology experiments suggested a shift in both the sensitivity to GABA and a loss of functional receptors. NMDA conditioning strongly suppressed inhibitory postsynaptic currents and speeded decay kinetics. Synaptic NMDAR conditioning was necessary to suppress GABA current in pyramidal neurons; extrasynaptic NMDAR activation did not suppress, even when matched to synaptic activation. We found no evidence that specific synaptic NMDAR subunits mediate depression of GABA responses. Although physical colocalization of glutamate and GABA(A) receptors is mostly likely in extrasynaptic regions, our evidence suggests that NMDAR-induced suppression of GABA responsiveness prominently affects precise, moment-to-moment signaling from synaptic receptors to synaptic receptors.     

Cross talk between COX-2 inhibitor and hyaluronic acid in osteoarthritic chondrocytes

Both hyaluronic acid (HA) and cyclooxygenase-2 (COX-2) inhibitors are used in clinical practice in the treatment of osteoarthritis. There have been no reports regarding cross-talk between HA and COX-2 inhibitors in articular human chondrocytes. The purpose of this study was to investigate whether HA, COX-2 inhibitors or a combination of COX-2 inhibitors and HA have different effects in human articular between lower and highly degenerated chondrocytes. Isolated lower and highly degenerated chondrocytes were divided into 5 groups: ethanol (used as a control for the solvents), HA, COX-2 inhibitors, COX-2 inhibitors plus HA, or no additive. After incubating for 48 h, mitochondrial membrane potential analysis and western blotting of p38 and p44/42 mitogen-activated protein kinase (MAPK) were performed. Glycosaminoglycan, nitric oxide (NO) production and prostaglandin E2 (PGE2) concentrations were assessed. A combination of COX-2 inhibitors and HA resulted in dendritic, proliferating chondrocytes with strong red fluorescence enriched in the mitochondrial membrane, and indicated reduction of apoptosis in chondrocytes. COX-2 inhibitors alone, and a combination of COX-2 inhibitor and HA inhibited the activation of p38 in highly degenerated chondrocytes. A combination of COX-2 inhibitors and HA decreased NO production in highly degenerated chondrocytes. COX-2 inhibitors decreased PGE2 production, however, HA alone had no effect on PGE2 production. The present study demonstrated that COX-2 inhibitors and HA interacted synergistically the MAPK pathway and inhibition of NO production in highly degenerated chondrocytes. Administration of COX-2 inhibitors plus HA could be used as a new alternative way of treating osteoarthritis.     

The interplay between nitric oxide and peroxiredoxins

Peroxiredoxins participate in the antioxidant response by reducing H(2)O(2), organic peroxides and peroxynitrite. Peroxiredoxins have a conserved NH(2)-terminal cysteine residue that is oxidized to sulfenic acid during catalysis of peroxide reduction. In eukaryotes, the sulfenic acid can be further oxidized to a sulfinic acid. Resulting inactivation of peroxiredoxins favors H(2)O(2) signaling but may eventually result in oxidative stress. Interestingly, it has recently been shown that overoxidized peroxiredoxins progressively recover activity owing to sulfiredoxin, an enzyme recently characterized in yeast and mammals. This reversible peroxide-sensitive switch represents a new type of regulation that controls reactive oxygen species-mediated cytoxicity and signaling. This report presents a brief overview of the regulation by peroxiredoxins of the messenger function of H(2)O(2) and comments on the results of recent studies that addressed the consequence of nitric oxide production on both expression and redox state of peroxiredoxins in various physiopathological processes including macrophage immunostimulation, the response of dopaminergic neurons to N-methyl-d-aspartate-stimulation and the plant hypersensitive response.     

Cross talk of nitric oxide,oxygen radicals,and superoxide dismutase regulates the energy metabolism and cell death and determines the fates of aerobic life

Although oxygen is required for the energy metabolism in aerobic organisms, it generates reactive oxygen and nitrogen species that impair a wide variety of biological molecules, including lipids, proteins, and DNA, thereby causing various diseases. Because mitochondria are the major site of free radical generation, they are highly enriched with enzymes, such as Mn-type superoxide dismutase in matrix, and antioxidants including GSH on both sides of inner membranes, thus minimizing oxidative stress in and around this organelle. We recently showed that a cross talk of nitric oxide and oxygen radicals regulates the circulation, energy metabolism, reproduction, and remodeling of cells during embryonic development, and functions as a major defense system against pathogens. The present work shows that Cu/Zn-type superoxide dismutase, which has been postulated for a long time to be a cytosolic enzyme, also localizes bound to inner membranes of mitochondria, thereby minimizing oxidative stress in and around this organelle, while mitochondrial association decreases markedly with the variant types of the enzyme found in patients with familial amyotrophic lateral sclerosis. We also report that a cross talk of nitric oxide, superoxide, and molecular oxygen cooperatively regulates the fates of pathogens and their hosts and that oxidative stress in and around mitochondria also determines cell death in the development of animals and tissue injury caused by anticancer agents by some carnitine-inhibitable mechanism.     

一氧化氮与白细胞精子症不育的关系探讨

目的　探讨一氧化氮 (NO)与白细胞精子症不育的关系。方法　参照WHO标准方法 ,进行精液常规分析。采用过氧化物酶染色法检测精液中白细胞密度。用改良的低渗肿胀法检测精子细胞膜的完整性。采用镀铜镉还原荧光法 ,检测精液中NO代谢产物硝酸盐 (NO 3 )。结果　白细胞精子症不育组白细胞的密度为 (1.4 8± 0 .90 )× 10 9/L ,NO水平为 (10 3.5± 2 .0 ) μmol/L ,显著高于正常生育组的(0 .73± 0 .2 8)× 10 9/L和 (41.6± 1.8) μmol/L (P分别为<0 .0 5和 <0 .0 0 1)。精子的活动率、精子速度试验 (SVT)及精子头、尾部膜完整率 ,均明显低于生育组 (P <0 .0 1) ,而精子的死亡率则显著高于生育组 (P <0 .0 1)。结论　NO水平与白细胞密度呈正相关 ;与精子的活动率、SVT及精子头、尾膜的完整率呈负相关。表明当精液中的白细胞增高时 ,可产生过量的NO导致精子中毒受损使精子的受精能力下降     

精子运动能力与一氧化氮关系的探讨

目的探讨一氧化氮(NO)与精子运动能力的关系.方法采用镀铜镉还原荧光法,测定人精液中NO代谢产物硝酸盐(NO3-).参照WHO方法,在超高倍显微镜下观察精子存活率、活动力等. 结果 80例男性不育者其中15例NO浓度明显低于正常对照组精子活动力a b级<50%(P<0.01),以运动轨迹异常和头摆动幅度下降为主, 精子存活力>75%无明显差异(P>0.05);65例NO浓度显著高于正常对照精子活动力a b 级<50%,存活率<75% (P<0.001).结论 NO与精子运动功能有着密切关系.高浓度时明显抑制精子活动力及存活率.低浓度时精子存活率及功能有着维护作用,这对男性不育的病因研究和治疗有非常重要的临床价值.     

Purified soluble guanylyl cyclase expressed in a baculovirus/Sf9 system: stimulation by YC-1, nitric oxide, and carbon monoxide

Soluble guanylyl cyclase (sGC) is the main receptor for nitric oxide, a messenger molecule with multiple clinical implications. Understanding the activation of sGC is an important step for establishing new therapeutic principles. We have now overexpressed sGC in a baculovirus/Sf9 system optimized for high protein yields to facilitate spectral and kinetic studies of the activation mechanisms of this enzyme. It was expressed in a batch fermenter using a defined mixture of viruses encoding the α₁ and β₁ subunits of the rat lung enzyme. The expressed enzyme was purified from the cytosolic fraction by anion exchange chromatography, hydroxyapatite chromatography, and size exclusion chromatography. By use of this new method 2.5 l culture yielded about 1 mg of apparently homogeneous sGC with a content of about one heme per heterodimer without the need of a heme reconstitution step. The enzyme did not contain stoichiometric amounts of copper. The basal activities of the purified enzyme were 153 and 1259 nmol min^–1 mg^–1 in the presence of Mg²⁺ and Mn²⁺, respectively. The nitric oxide releasing agent 2-(N,N-diethylamino)-diazenolate-2-oxide (DEA/NO) stimulated the enzyme 160-fold with Mg²⁺, whereas the NO-independent activator 3-(5’-hydroxymethyl-2’-furyl)-1- benzylindazole (YC-1) induced an increase in the activity of 101-fold at a concentration of 300 μM. The combination of DEA/NO (10 μM) and YC-1 (100 μM) elicited a dose-dependent synergistic stimulation with a maximum of a 792-fold increase over the basal activity in the presence of Mg²⁺, resulting in a specific activity of 121 μmol min^–1 mg^–1. The synergistic stimulation of DEA/NO and YC-1 was attenuated by the sGC inhibitor 1H-(1,2,4)oxadiazole(4,3-a)quinoxalin-1-one (ODQ) (10 μM) by 94%. In a different experimental setup a saturated carbon monoxide solution in the absence of ambient oxygen or NO stimulated the enzyme 15-fold in the absence and 1260-fold in the presence of YC-1 compared to an argon control. The heme spectra of the enzyme showed a shift of the Soret peak from 432 to 399 and 424 nm in the presence of DEA/NO or carbon monoxide, respectively. The heme spectra were not affected by YC-1 in the absence or in the presence of DEA/NO or of carbon monoxide, which reflects the fact that YC-1 does not interact directly with the heme group of the enzyme. In summary, this study shows that our expression/purification procedure is suitable for producing large amounts of highly pure sGC which contains one heme per heterodimer without a reconstitution step. The activator experiments show that in a synergistic stimulation with YC-1 sGC can be activated maximally both by nitric oxide and by carbon monoxide and that YC-1 does not directly act via heme. The described method should help to facilitate the investigation of the new therapeutic principle of NO-independent guanylyl cyclase activators. Received: 20 May 1998 / Accepted: 5 October 1998     

Opposite effect of oxidative stress on inducible nitric oxide synthase and haem oxygenase-1 expression in intestinal inflammation: anti-inflammatory effect of carbon monoxide

Inducible nitric oxide synthase (iNOS) is expressed in intestinal epithelial cells (IEC) of patients with active inflammatory bowel disease (IBD) and in IEC of endotoxaemic rats. The induction of iNOS in IEC is an element of the NF-kappaB-mediated survival pathway. Haem oxygenase-1 (HO-1) is an AP-1-regulated gene that is induced by oxidative stress. The enzyme produces carbon monoxide (CO), which may attenuate the inflammatory response. The aim of this study was to investigate the regulation and interaction of iNOS and HO-1 in response to inflammation and oxidative stress. Male Wistar rats were treated with the thiol-modifying agent diethylmaleate (DEM) to induce oxidative stress and rendered endotoxaemic by LPS injection. Human colonic biopsies and the human colon carcinoma cell line DLD-1 were treated with DEM and the lipid peroxidation end-product 4-hydroxynonenal to induce oxidative stress and exposed to cytokine mix (CM) to mimic inflammation. In some experiments, cells were incubated with 250-400 ppm CO prior to and during stimulation with CM. HO-1 and iNOS expression was evaluated by RT-PCR, western blotting, and immunohistology. NF-kappaB activation was evaluated by EMSA. LPS induced iNOS but not HO-1 in epithelial cells of the ileum and colon. Oxidative stress strongly induced HO-1 in epithelial and inflammatory cells. Combined oxidative stress and endotoxaemia decreased iNOS expression but strongly induced HO-1 expression. Similarly, CM induced iNOS but not HO-1 in colonic biopsies and DLD-1 cells. Oxidative stress prevented iNOS induction in an NF-kappaB-dependent manner but increased HO-1 expression in CM-exposed DLD-1 cells. CO inhibited iNOS mRNA induction in CM-stimulated DLD-1 cells. These data demonstrate opposite regulation of iNOS and HO-1 in intestinal epithelial cells in response to cytokine exposure and oxidative stress. These findings suggest that iNOS (NF-kappaB driven) and HO-1 (AP-1 driven) represent mutually exclusive survival mechanisms in intestinal epithelial cells.     

Effect of carbon monoxide on equilibrium between oxygen and hemoglobin.

Oxygen dissociation curves of partially CO-saturated human whole blood drawn freshly or preserved more than 3 wk were studied. With increasing CO-hemoglobin concentrations, oxygen affinity of the blood increased and the Hill coefficient, n, fell and gradually approached unity. The changes induced by CO-hemoglobin showed practically no difference in the presence or absence of 2,3-diphosphoglycerate. The Bohr coefficient, deltalog P50/deltapH, was determined as a function of oxygen saturation for various concentrations of CO-hemoglobin. The coefficient remained essentially unchanged in the presence of CO-hemoglobin. In the presence of less than 50% CO-hemoglobin, a good agreement was observed between the observed oxygen dissociation curves and the curves calculated according to Roughton and Darling (Am. J. Physiol. 141: 17-31, 1944). Based on these results, physiological implications of carboxyhemoglobinemia are discussed quantitatively in comparison with methemoglobinemia.     

Relation between exhaled carbon monoxide levels and clinical severity of asthma

Carbon monoxide (CO) can be detected in exhaled air and is increased in asthmatic patients not treated with corticosteroids. However, it is uncertain whether exhaled CO is related to severity of asthma. To study whether exhaled CO is related to severity of asthma in clinical courses, exhaled CO concentrations were measured on a CO monitor by vital capacity manoeuvre in 20 mild asthmatics treated with inhaled beta2-agonists alone, 20 moderate asthmatics treated with inhaled corticosteroids, and 15 stable asthmatics treated with high dose inhaled corticosteroids and oral corticosteroids once a month over 1 years. Exhaled CO concentrations were also measured in 16 unstable severe asthmatics who visited the hospital every 7 or 14 days for treatment with high dose inhaled corticosteroids and oral corticosteroids. The mean values of exhaled CO in severe asthma over 1 year were 6.7 +/- 9.5 p.p.m. (n = 31, mean +/- SD) and significantly higher than those of non-smoking control subjects (1.2 +/- 0.9 p.p.m., n = 20, P < 0.01). Exhaled CO concentrations in unstable severe asthmatics were significantly higher than those in stable severe asthmatics. However, exhaled CO concentrations in mild and moderate asthmatics did not differ significantly from those in non-smoking control subjects (P > 0.20). There was a significant relationship between the exhaled CO concentrations and forced expiratory volume in one second in all asthmatic patients. These findings suggest that exhaled CO concentrations may relate to the severity of asthma and measurements of exhaled CO concentrations may be a useful means of monitoring airway inflammation in asthma.     

Nitric oxide and carbon monoxide modulate oscillations of olfactory interneurons in a terrestrial mollusk

Spontaneous or odor-induced oscillations in local field potential are a general feature of olfactory processing centers in a large number of vertebrate and invertebrate species. The ubiquity of such oscillations in the olfactory bulb of vertebrates and analogous structures in arthropods and mollusks suggests that oscillations are fundamental to the computations performed during processing of odor stimuli. Diffusible intercellular messengers such as nitric oxide (NO) and carbon monoxide (CO) also are associated with central olfactory structures in a wide array of species. We use the procerebral (PC) lobe of the terrestrial mollusk Limax maximus to demonstrate a role for NO and CO in the oscillatory dynamics of the PC lobe: synthesizing enzymes for NO and CO are associated with the PC lobes of Limax, application of NO to the Limax PC lobe increases the local field potential oscillation frequency, whereas block of NO synthesis slows or stops the oscillation, the bursting cells of the PC lobe that drive the field potential oscillation are driven to higher burst frequency by application of NO, the nonbursting cells of the PC lobe receive trains of inhibitory postsynaptic potentials, presumably from bursting cells, due to application of NO, and application of CO to the PC lobe by photolysis of caged CO results in an increase in oscillation frequency proportional to CO dosage.     

Cross talk between human regulatory T cells and antigen-presenting cells: Lessons for clinical applications

Regulatory T cells (Tregs) have a critical role in maintaining self-tolerance and immune homeostasis. There is much interest in using Tregs as a cell therapy to re-establish tolerance in conditions such as inflammatory bowel disease and type 1 diabetes, with many ongoing clinical studies testing the safety and efficacy of this approach. Manufacturing of Tregs for therapy typically involves ex vivo expansion to obtain sufficient cell numbers for infusion and comes with the risk of altering the activity of key biological processes. However, this process also offers an opportunity to tailor Treg function to maximize in vivo activity. In this review, we focus on the roles of antigen-presenting cells (APCs) in the generation and function of Tregs in humans. In addition to stimulating the development of Tregs, APCs activate Tregs and provide signals that induce specialized functional and homing marker expression. Cross talk between Tregs and APCs is a critical, often under-appreciated, aspect of Treg biology, with APCs mediating the key properties of infectious tolerance and bystander suppression. Understanding the biology of human Treg-APC interactions will reveal new ways to optimize Treg-based therapeutic approaches.     

血红素氧合酶-1/一氧化碳和一氧化氮合酶/一氧化氮系统对球囊损伤后血管重塑的影响及其两系统的相关性研究

探讨球囊损伤后血管重塑中血红素氧合酶-1(HO-1)/一氧化碳(CO)系统与一氧化氮合酶(NOS)/一氧化氮(NO)系统的作用及相互关系。家兔随机分为对照组、假手术组、胆固醇组、精氨酸组、亚硝基组、血红素组和卟啉锌组。对照组喂普通饲料,其余六组喂含1.5%胆固醇饲料,精氨酸组和亚硝基组饮水同时予L-精氨酸或亚硝基-L-精氨酸甲酯,血红素组和卟啉锌组同时分别予氯化血红素或锌原卟啉-9腹腔内注射。2周后实验组行一侧颈总动脉球囊损伤,术后续原喂养给药8周。结果显示:与胆固醇组比较,血红素组HO活性、CO生成量显著增加,核因子κB活性显著降低,内膜面积显著减小(均P<0.01);卟啉锌组呈现相反的结果;精氨酸组cNOS活性、NO生成量显著增加,核因子κB活性显著降低,内膜面积显著减小(均P<0.01);亚硝基组cNOS活性、NO生成量显著降低,核因子κB活性显著升高(均P<0.01),内膜面积变化无显著性。本研究表明,再狭窄形成中HO-1/CO与NOS/NO两系统显示互补及代偿作用,HO-1/CO系统可能通过对NOS/NO系统的代偿和调节并抑制核因子κB活性,从而抑制血管损伤后内膜增殖及负性重塑。