Heme oxygenase-1/carbon monoxide signaling participates in the accumulation of triterpenoids of Ganoderma lucidum.

Ganoderic triterpenoids (GTs) are the primary bioactive constituents of the Basidiomycotina fungus, Ganoderma lucidum. These compounds exhibit antitumor, anti-hyperlipidemic, and immune-modulatory pharmacological activities. This study focused on GT accumulation in mycelia of G. lucidum mediated by the heme oxygenase-1 (HO-1)/carbon monoxide (CO) signaling. Compared with the control, hemin (10 µmol/L) induced an increase of 60.1% in GT content and 57.1% in HO-1 activity. Moreover, carbon monoxide-releasing molecule-2 (CORM-2), CO donor, increased GT content by 56.0% and HO-1 activity by 18.1%. Zn protoporphyrin IX (ZnPPIX), a specific HO-1 inhibitor, significantly reduced GT content by 26.0% and HO-1 activity by 15.8%, while hemin supplementation reversed these effects. Transcriptome sequencing showed that HO-1/CO could function directly as a regulator involved in promoting GT accumulation by regulating gene expression in the mevalonate pathway, and modulating the reactive oxygen species (ROS) and Ca2+ pathways. The results of this study may help enhance large-scale GT production and support further exploration of GT metabolic networks and relevant signaling cross-talk.

Lung function in men with and without HIV.

OBJECTIVES: Initial studies suggest HIV-positive persons may be at increased risk for chronic lung diseases such as chronic obstructive pulmonary disease, but have commonly relied on single-center designs, lacked HIV-negative controls, or assessed lung function with only spirometry. We tested differences in spirometry and single-breath diffusing capacity for carbon monoxide (DLCO) in persons with and without HIV. DESIGN: Cross-sectional, observational study. METHODS: Participants were enrolled from the Multicenter AIDS Cohort Study, a longitudinal cohort study of men who have sex with men (both HIV-positive and HIV-negative) at four sites in the United States. Standardized spirometry and DLCO testing were performed in all eligible, consenting participants at routine study visits. We tested associations between HIV status and spirometry and DLCO results, using linear and logistic regression. RESULTS: Among 1067 men, median age was 57 years, prevalence of current marijuana (30%), and cigarette (24%) use was high, and another 45% were former cigarette smokers. Median forced expiratory volume in 1 s was 97% of predicted normal and DLCO was 85% of predicted normal. HIV-positive persons demonstrated no statistical difference in forced expiratory volume in 1 s compared with HIV-negative persons, but had worse DLCO (adjusted difference -2.6% of predicted; 95% confidence interval: -4.7 to -0.6%) and a higher risk of DLCO impairment (odds ratio for DLCO < 60% of predicted 2.97; 95% confidence interval: 1.36-6.47). Lower DLCO was associated with lower nadir CD4 cell counts. CONCLUSION: HIV-positive men are at increased risk of abnormal gas exchange, indicated by low DLCO, compared with men without HIV.

Heme Oxygenase-1 and Carbon Monoxide Regulate Growth and Progression in Glioblastoma Cells.

In human glioma tumours, heme oxygenase-1 (HO-1) is overexpressed when compared with normal brain tissues and during oligodendroglioma progression. However, the molecular mechanisms mediated by HO-1 to promote glioblastoma remain unknown. We therefore aimed at investigating the effect of HO-1 expression and its selective enzymatic inhibition in two different cell lines (i.e. A172 and U87-MG). HO-1 was induced by hemin treatment (10 µM), and VP13/47 (100 µM) was used as a specific non-competitive inhibitor of HO-1 activity. Cell proliferation was measured by cell index measurement (xCelligence technology) and clonogenic assay, whereas cell migration was assessed by wound healing assay. Carbon monoxide-releasing molecules (CORMs) (i.e. CORM-3 and CORM-A1) were also used in a separate set of experiments to confirm the effect of HO-1 by-product in glioblastoma progression further. Our results were further validated using GSE4412 microarray dataset analysis and comparing biopsies overexpressing HO-1 with the rest of the cases. Our results showed that hemin was able to induce both HO-1 gene and protein expression in a cell-dependent manner being A172 more responsive to pharmacological upregulation of HO-1. Hemin, but not CORMs treatment, resulted in a significant increase of cell proliferation following 24 h of treatment as measured by increased cell index and colony formation capacity and such effect was abolished by VP13/47. Interestingly, both hemin and CORMs showed a significant effect on the wound healing assay also exhibiting cell specificity. Finally, our dataset analysis showed a positive correlation of HO-1 gene expression with ITGBI and ITGBII which are membrane receptors involved in cell adhesion, embryogenesis, tissue repair, immune response and metastatic diffusion of tumour cells. In conclusion, our data suggest that HO-1 and its by-product CO exhibit a cell-specific effect on various aspects of disease progression and are associated with a complex series of molecular mechanisms driving cell proliferation, survival and metastasis.

An alternative method to measure the diffusing capacity of the lung for carbon monoxide in infants.

BACKGROUND: Lung diffusion assessed by the uptake of carbon monoxide (DLCO ) and alveolar volume (VA ) by inert gas dilution are readily assessed in cooperative older subjects; however, obtaining these measurements in infants has been much more difficult. Our laboratory has measured DLCO and VA in sleeping infants using a mass spectrometer, which continuously measures gas concentrations, and demonstrated that infants with bronchopulmonary dysplasia (BPD) have lower DLCO , but no difference in VA compared to full-term controls. The mass spectrometer is expensive and lacks portability; therefore, we evaluated whether measurement of end-expiratory alveolar gas concentrations using a gas chromatograph would provide an alternative approach. METHODS: (1) Using our previously digitized data for infants with BPD and full-term controls, DLCO and VA were calculated at end-expiration rather than between 60 and 80% of expired volume, as previously reported. (2) In a new group of infants, DLCO and VA were measured using gas concentrations obtained at end-expiration with a mass spectrometer and a gas chromatograph. RESULTS: (1) Using end-expiratory concentrations, infants with BPD (n = 49) had significantly lower DLCO , but similar VA compared to healthy controls (n = 34) (DLCO : 4.2 vs 4.6 mL/min/mmHg, P = 0.047; VA : 614 vs 608 mL, P = 0.772). (2) Among newly evaluated infants (n = 28), DLCO and VA obtained with a mass spectrometer and a gas chromatograph were highly correlated (R2 = 0.94 and 0.99, respectively), and were not significantly different for the two analyzers. CONCLUSION: Measuring DLCO and VA at end-expiration using a gas chromatograph can provide an effective assessment of gas exchange in sleeping infants.

Inhaled Carbon Monoxide: From Toxin to Therapy.

Carbon monoxide (CO) is usually recognized as a toxic gas that can be used to assess lung function in the pulmonary function laboratory. The toxicity of CO relates to its high affinity for hemoglobin and other heme molecules, producing carboxyhemoglobin (HbCO). Despite that blood HbCO levels are commonly measured in patients with CO poisoning, the clinical presentation often does not correlate with the HbCO level, and clinical improvement in the patient's condition does not correlate with HbCO clearance. In patients with CO poisoning, administration of 100% O2 is standard practice. If available, hyperbaric O2 can be used, although this is controversial. Measurement of exhaled CO might be useful to estimate HbCO, such as in smoking cessation programs, but assessment of HbCO using pulse oximetry can be misleading. Endogenous CO is generated as the result of heme oxygenase activity. It is becoming increasingly recognized that the results of heme oxygenase activity, specifically CO production, might have important physiologic functions. These include effects on vascular function, inflammation, apoptosis, cell proliferation, and signaling pathways. Given the abundance of basic science supporting a therapeutic role for CO, clinical trials are exploring this potential.

Reference values for pulmonary diffusing capacity for adult native Finns.

Measurement standards for pulmonary diffusing capacity were updated in 2005 by the ATS/ERS Task Force. However, in Finland reference values published in 1982 by Viljanen et al. have been used to date. The main aim of this study was to produce updated reference models for single-breath diffusing capacity for carbon monoxide for Finnish adults. Single-breath diffusing capacity for carbon monoxide was measured in 631 healthy non-smoking volunteers (41.5% male). Reference values for diffusing capacity (DLCO), alveolar volume (VA), diffusing capacity per unit of lung volume (DLCO/VA), and lung volumes were calculated using a linear regression model. Previously used Finnish reference values were found to produce too low predicted values, with mean predicted DLCO 111.0 and 104.4%, and DLCO/VA of 103.5 and 102.7% in males and females, respectively. With the European Coalition for Steel and Coal (ECSC) reference values there was a significant sex difference in DLCO/VA with mean predicted 105.4% in males and 92.8% in females (p < .001). New reference values for DLCO, DLCO/VA, VA, vital capacity (VC), inspiratory vital capacity (IVC), and inspiratory capacity (IC) are suggested for clinical use to replace technically outdated reference values for clinical applications.

Retinal venous blood carbon monoxide response to bright light in male pigs: A preliminary study.

The physical mechanism by which light is absorbed in the eye and has antidepressant and energizing effects in Seasonal Affective Disorder and other forms of psychiatric major depression is of scientific interest. This study was designed to explore one specific aspect of a proposed humoral phototransduction mechanism, namely that carbon monoxide (CO) levels increase in retinal venous blood in response to bright light. Eleven mature male pigs approximately six months of age were kept for 7days in darkness and fasted for 12h prior to surgery. Following mild sedation, anesthesia was induced. Silastic catheters were inserted into the dorsal nasal vein through the angular vein of the eye to reach the ophthalmic sinus, from which venous blood outflowing from the eye area was collected. The animals were exposed to 5000lx of fluorescent-generated white light. CO levels in the blood were analyzed by gas chromatography before and after 80min of light exposure. At baseline, mean CO levels in the retinal venous blood were 0.43±0.05(SE)nmol/ml. After bright light, mean CO levels increased to 0.54±0.06nmol/ml (two-tailed t-test p<0.05). This study provides preliminary mammalian evidence that acute bright light exposure raises carbon monoxide levels in ophthalmic venous blood.

Role of sensory afferent nerves, lipid peroxidation and antioxidative enzymes in the carbon monoxide-induced gastroprotection against stress ulcerogenesis.

Carbon monoxide (CO) is a physiological gaseous mediator recently implicated in the mechanism of gastric mucosal defense due to its vasodilatory and antioxidative properties. Small quantities of endogenous CO are produced during heme degradation by heme oxygenase (HO-1), however, the involvement of the capsaicin-sensitive afferent neurons releasing calcitonin gene related peptide (CGRP) and anti-oxidative factors and mechanisms in the CO-induced gastroprotection against stress ulcerogenesis has been little studied. We investigated the possible role of CO released from the CO donor, tricarbonyldichlororuthenium (II) dimer (CORM-2) in the protection against water immersion and restraint stress (WRS)-induced lesions in rats with intact sensory nerves and those with capsaicin denervation and the accompanying changes in malondialdehyde (MDA) content considered as an index of lipid peroxidation, the activity of GSH and SOD-2 and gastric mucosal expression of antioxidative enzymes glutathione peroxidase (GPx) and SOD-2. Wistar rats with intact sensory nerves or those with capsaicin administered in total dose of 125 mg/kg s.c. within 3 days (capsaicin denervation) were pretreated either with 1) vehicle (saline) or 2) CORM-2 (0.1 - 0 mg/kg i.g.) with or without exogenous CGRP (10 µg/kg i.p.) and 30 min later exposed to 3.5 h of WRS. At the termination of WRS, the number of gastric lesions was counted and gastric blood flow (GBF) was assessed by H2-gas clearance technique. The mucosal content of MDA and reduced glutathione (GSH) and the activity of SOD-2 were determined and the expression of GPx-1 and SOD-2 mRNA in the gastric mucosa was analyzed by real-time PCR. The exposure of rats to 3.5 h of WRS resulted in numerous hemorrhagic gastric lesions and significantly decreased the GBF, raised MDA content and significantly decreased the mucosal SOD and GSH contents compared with intact gastric mucosa and these changes were exacerbated in rats with capsaicin denervation. Pretreatment with CORM-2 (1 mg/kg i.g.) which in our previous studies significantly reduced the ethanol and aspirin-induced gastric damage, significantly decreased the number of WRS-induced gastric lesions while raising the GBF and significantly increasing the activity of SOD and GSH (P < 0.05). The pretreatment with CORM-2 significantly decreased MDA content as compared with vehicle-pretreated rats exposed to WRS (P < 0.05). The reduction of WRS damage and the accompanying increase in the GBF as well as the significant decrease in MDA content and the increase in GSH content and SOD activity induced by CORM-2 (1 µg/kg i.g.) were all significantly altered in rats with capsaicin denervation (P < 0.05). The concurrent treatment of CORM-2 with exogenous CGRP in rats with or without sensory nerves tended to decrease the number of WRS lesions as compared with CORM-2 alone pretreated animals and significantly increased the GBF over the values measured in gastric mucosa of CORM-2 alone pretreated rats with or without capsaicin denervation. Such combined administration of CORM-2 and CGRP in rats with capsaicin denervation significantly inhibited an increase in MDA and 4-HNE content and evoked a significant increase in the GSH concentration (P < 0.05) remaining without significant effect on the increase in SOD activity observed with CORM-2 alone. The gastric mucosal expression of SOD-2- and GPx-1 mRNA was significantly increased as compared with those in intact gastric mucosa (P < 0.05). The pretreatment with CORM-2 applied with or without CGRP failed to significantly alter the mRNA expression for SOD-2 and GPx in the gastric mucosa of rats exposed to WRS. Both, the expression of SOD-2- and GPx-1 mRNA was significantly increased in capsaicin denervated rats exposed to WRS rats (P < 0.05) and this effect was abolished by the pretreatment with CORM-2. The expression of SOD-2 tended to decrease, though insignificantly, in rats pretreated with the combination of CORM-2 and CGRP as compared with that detected in CORM-2 alone in rats with capsaicin denervation. In contrast, the mRNA expression of GPx-1 was significantly decreased in gastric mucosa of capsaicin-denervated rats treated with the combination of CORM-2 and CGRP as compared with CORM-2 alone pretreated animals. We conclude that 1) CORM-2 releasing CO exerts gastroprotective activity against stress ulcerogenesis and this effect depends upon an increase in the gastric microcirculation and the vasodilatory activity of this gaseous mediator, and 2) the sensory nerve endings releasing CGRP can contribute, at least in part, to the CO-induced gastric hyperemia, the attenuation of gastric mucosal lipid peroxidation and prevention of oxidative stress as indicated by the CORM-2-induced normalization of the antioxidative enzyme expression enhanced in gastric mucosa of capsaicin-denervated rats.

Carbon Monoxide Gas Is Not Inert, but Global, in Its Consequences for Bacterial Gene Expression, Iron Acquisition, and Antibiotic Resistance.

AIMS: Carbon monoxide is a respiratory poison and gaseous signaling molecule. Although CO-releasing molecules (CORMs) deliver CO with temporal and spatial specificity in mammals, and are proven antimicrobial agents, we do not understand the modes of CO toxicity. Our aim was to explore the impact of CO gas per se, without intervention of CORMs, on bacterial physiology and gene expression. RESULTS: We used tightly controlled chemostat conditions and integrated transcriptomic datasets with statistical modeling to reveal the global effects of CO. CO is known to inhibit bacterial respiration, and we found expression of genes encoding energy-transducing pathways to be significantly affected via the global regulators, Fnr, Arc, and PdhR. Aerobically, ArcA-the response regulator-is transiently phosphorylated and pyruvate accumulates, mimicking anaerobiosis. Genes implicated in iron acquisition, and the metabolism of sulfur amino acids and arginine, are all perturbed. The global iron-related changes, confirmed by modulation of activity of the transcription factor Fur, may underlie enhanced siderophore excretion, diminished intracellular iron pools, and the sensitivity of CO-challenged bacteria to metal chelators. Although CO gas (unlike H2S and NO) offers little protection from antibiotics, a ruthenium CORM is a potent adjuvant of antibiotic activity. INNOVATION: This is the first detailed exploration of global bacterial responses to CO, revealing unexpected targets with implications for employing CORMs therapeutically. CONCLUSION: This work reveals the complexity of bacterial responses to CO and provides a basis for understanding the impacts of CO from CORMs, heme oxygenase activity, or environmental sources. Antioxid. Redox Signal. 24, 1013-1028.

Intrauterine growth restriction predicts lower lung function at school age in children born very preterm.

OBJECTIVE: Children born preterm have lower lung function compared with term-born children. Intrauterine growth restriction (IUGR) may predispose individuals to chronic obstructive pulmonary disease. The purpose of this observational study was to investigate the role of IUGR as predictor of lung function at school age in children born very preterm. We further studied the difference in lung function between term-born and preterm-born children with distinct morbidities. DESIGN: Preterm-born children and age-matched and sex-matched term-born comparison groups (88 of each) were studied at the mean age of 11 years. Spirometry and diffusing capacity of the lung for carbon monoxide (DLCO) were recorded. All preterm-born subjects with IUGR (n=23), defined as birth weight less than -2 SD, were compared with preterm-born subjects without IUGR (n=65). RESULTS: In the preterm-born children exposed to IUGR, the forced expiratory volume in 1 s (FEV1) was 5.7 (95% CI -10.2 to -1.3) and DLCO 9.2 percentage points lower (95% CI -15.7 to -2.7) than in the preterm-born children with appropriate in utero growth (expressed as percentage of predicted values). The effect of IUGR in decreasing FEV1 and DLCO remained significant after adjustment for bronchopulmonary dysplasia (BPD). Further study indicated that after adjustment with IUGR and BPD, prematurity explained reduction in FEV1 but not in DLCO. CONCLUSIONS: In children born very preterm, IUGR is an independent risk factor for a lower lung function in school age. We propose that IUGR and BPD are the major early factors predisposing the children born very preterm to lower lung function.

[Relaxation mechanism of smooth muscle cells and its relationship with penile erection].

The contractile and diastolic function of smooth muscle cells (SMCs) is closely related to penile erection and erectile dysfunction (ED). In addition to nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), sulfur dioxide (SO2), estrogen receptor (ER), P2Y receptor, perivascular tissue (PVT), and calcium activated potassium channel (Kca) are found to be involved in the relaxation of SMCs. This review updates the mechanisms of the relaxation of SMCs and its relationship with ED.

Mitochondria and carbon monoxide: cytoprotection and control of cell metabolism - a role for Ca(2+) ?

Carbon monoxide (CO) is an endogenously produced gasotransmitter with important biological functions: anti-inflammation, anti-apoptosis, vasomodulation and cell metabolism modulation. The most recognized cellular target for CO is the mitochondria. Physiological concentrations of CO generate mitochondrial reactive oxygen species (ROS), which are signalling molecules for CO-induced pathways. Indeed, small amounts of ROS promote cytoprotection by a preconditioning effect. Furthermore, CO prevents cell death by limiting mitochondrial membrane permeabilization, which inhibits the release of pro-apoptotic factors into the cytosol; both events are ROS dependent. CO also increases the ability of mitochondria to take up Ca(2+) . Mitochondrial metabolism is modulated by CO, namely by increasing TCA cycle rate, oxidative phosphorylation and mitochondrial biogenesis, which, in turn, increases ATP production. CO's modulation of metabolism might be important for cellular response to diseases, namely cancer and ischaemic diseases. Finally, another cytoprotective role of CO involves the control of Ca(2+) channels. By limiting the activity of T-type and L-type Ca(2+) channels, CO prevents excitotoxicity-induced cell death and modulates cell proliferation. Several questions concerning Ca(2+) signalling, mitochondria and CO can be asked, for instance whether CO modulation of cell metabolism would be dependent on the mitochondrial Ca(2+) uptake capacity, since small amounts of Ca(2+) can increase mitochondrial metabolism. Whether CO controls Ca(2+) communication between mitochondria and endoplasmic reticulum is another open field of research. In summary, CO emerges as a key gasotransmitter in the control of several cellular functions of mitochondria: metabolism, cell death and Ca(2+) signalling.

Activation of locus coeruleus heme oxygenase-carbon monoxide pathway promoted an anxiolytic-like effect in rats

The heme oxygenase-carbon monoxide pathway has been shown to play an important role in many physiological processes and is capable of altering nociception modulation in the nervous system by stimulating soluble guanylate cyclase (sGC). In the central nervous system, the locus coeruleus (LC) is known to be a region that expresses the heme oxygenase enzyme (HO), which catalyzes the metabolism of heme to carbon monoxide (CO). Additionally, several lines of evidence have suggested that the LC can be involved in the modulation of emotional states such as fear and anxiety. The purpose of this investigation was to evaluate the activation of the heme oxygenase-carbon monoxide pathway in the LC in the modulation of anxiety by using the elevated plus maze test (EPM) and light-dark box test (LDB) in rats. Experiments were performed on adult male Wistar rats weighing 250-300 g (n=182). The results showed that the intra-LC microinjection of heme-lysinate (600 nmol), a substrate for the enzyme HO, increased the number of entries into the open arms and the percentage of time spent in open arms in the elevated plus maze test, indicating a decrease in anxiety. Additionally, in the LDB test, intra-LC administration of heme-lysinate promoted an increase on time spent in the light compartment of the box. The intracerebroventricular microinjection of guanylate cyclase, an sGC inhibitor followed by the intra-LC microinjection of the heme-lysinate blocked the anxiolytic-like reaction on the EPM test and LDB test. It can therefore be concluded that CO in the LC produced by the HO pathway and acting via cGMP plays an anxiolytic-like role in the LC of rats.

Heme Oxygenase-1 Influences Apoptosis via CO-mediated Inhibition of K+ Channels.

Hypoxic/ischemic episodes can trigger oxidative stress-mediated loss of central neurons via apoptosis, and low pO2 is also a feature of the tumor microenvironment, where cancer cells are particularly resistant to apoptosis. In the CNS, ischemic insult increases expression of the CO-generating enzyme heme oxygenase-1 (HO-1), which is commonly constitutively active in cancer cells. It has been proposed that apoptosis can be regulated by the trafficking and activity of K(+) channels, particularly Kv2.1. We have explored the idea that HO-1 may influence apoptosis via regulation of Kv2.1. Overexpression of Kv2.1 in HEK293 cells increased their vulnerability to oxidant-induced apoptosis. CO (applied as the donor CORM-2) protected cells against apoptosis and inhibited Kv2.1 channels. Similarly in hippocampal neurones, CO selectively inhibited Kv2.1 and protected neurones against oxidant-induced apoptosis. In medulloblastoma sections we identified constitutive expression of HO-1 and Kv2.1, and in the medulloblastoma-derived cell line DAOY, hypoxic HO-1 induction or exposure to CO protected cells against apoptosis, and also selectively inhibited Kv2.1 channels expressed in these cells. These studies are consistent with a central role for Kv2.1 in apoptosis in both central neurones and cancer cells. They also suggest that HO-1 expression can strongly influence apoptosis via CO-mediated regulation of Kv2.1 activity.

[Combined pulmonary fibrosis and emphysema syndrome]. / Sindrom plucne fibroze udruzene s emfizemom.

CPFE-combined pulmonary fibrosis and emphysema is a new term for a syndrome whose main characteristic is fibrosis in lower pulmonary lobes with simultaneous emphysema in upper pulmonary lobes. CPFE patients have well preserved pulmonary test values for unexpectedly long period, but extremely lowered carbon monoxide diffusion capacity and significant arterial hypertension. All CPFE studies indicate that CPFE occurs predominately in older male population. Smoking is considered main cause in developing CPFE. Reduced survival rate is linked with arterial hypertension extent, and mortality rate is greater than that for patients with isolated pulmonary fibrosis or emphysema. This study is focused on characteristics of twelve CPFE patients. This paper describes cases of 12 patients with the syndrome of pulmonary fibrosis associated with emphysema. All patients were male, mean age of 68 years. At the certain period of life they all were smokers, but most of them were also exposed to air pollution due to their profession. Shortness of breath on exertion was present in all patients. All patients had neat pulmonary function tests with significantly reduced diffusing capacity for carbon mon- oxide (average 39%). Pulmonary arterial hypertension (PAH) averaged 56 mmHg (range 25-75 mmHg) was present in 75% of patients. Four patients died during the period of four months, of which three patients had PAH greater than 70 mmHg. The fourth patient died of lung cancer.

Macrophages sense and kill bacteria through carbon monoxide-dependent inflammasome activation.

Microbial clearance by eukaryotes relies on complex and coordinated processes that remain poorly understood. The gasotransmitter carbon monoxide (CO) is generated by the stress-responsive enzyme heme oxygenase-1 (HO-1, encoded by Hmox1), which is highly induced in macrophages in response to bacterial infection. HO-1 deficiency results in inadequate pathogen clearance, exaggerated tissue damage, and increased mortality. Here, we determined that macrophage-generated CO promotes ATP production and release by bacteria, which then activates the Nacht, LRR, and PYD domains-containing protein 3 (NALP3) inflammasome, intensifying bacterial killing. Bacterial killing defects in HO-1-deficient murine macrophages were restored by administration of CO. Moreover, increased CO levels enhanced the bacterial clearance capacity of human macrophages and WT murine macrophages. CO-dependent bacterial clearance required the NALP3 inflammasome, as CO did not increase bacterial killing in macrophages isolated from NALP3-deficient or caspase-1-deficient mice. IL-1ß cleavage and secretion were impaired in HO-1-deficient macrophages, and CO-dependent processing of IL-1ß required the presence of bacteria-derived ATP. We found that bacteria remained viable to generate and release ATP in response to CO. The ATP then bound to macrophage nucleotide P2 receptors, resulting in activation of the NALP3/IL-1ß inflammasome to amplify bacterial phagocytosis by macrophages. Taken together, our results indicate that macrophage-derived CO permits efficient and coordinated regulation of the host innate response to invading microbes.

Carbon monoxide is not always a poison gas for human organism: Physiological and pharmacological features of CO.

Carbon monoxide (CO) is an odorless, colorless and non-irritating gas. Even a small amount of CO exposure is possibly associated with specific toxic effects. CO is also produced endogenously in the body as a byproduct of heme degradation catalyzed by heme oxygenase. More recently CO has been identified as a gasotransmitter in various biological systems. However, the biological role and the therapeutic potential of carbon monoxide is not clear. This review summarizes the negative and the positive functions of carbon monoxide in various biological systems, including cardiovascular system.

Induction of heme oxygenase-1 ameliorates vascular dysfunction in streptozotocin-induced type 2 diabetic rats.

AIMS: To explore the effects of heme oxygenase-1 (HO-1) on vascular dysfunction in high fat diet streptozotocin-induced type 2 diabetic (T2D) rats. METHODS: Rats received a high-fat diet followed by a low dose of streptozotocin (30 mg/kg) to induce T2D. T2D rats were treated with hemin (1, 5, or 25mg/kg) or carbon monoxide-releasing molecule-2 (CORM-2, 5 mg/kg) for 4 weeks. Isometric contractions of aortic rings were measured. The expression of cyclooxygenase-2 (COX-2) and activities of HO, SOD, and MDA were evaluated. RESULTS: The fasting blood glucose, blood insulin levels, and IR index in T2D rats were higher than those in the control group, which were ameliorated by HO-1 inducer hemin. The antidiabetic effect was accompanied by enhanced HO activity. The vascular relaxation response to ACh was decreased in T2D rats, while treatment with hemin could prevent such decrease in vasorelaxation. An increase in COX-2 expression was found in the aortas of T2D rats. Treatment of T2D rats with COX-2 inhibitor NS398 restored ACh-induced vasodilation. COX-2 overexpression in T2D rats was inhibited by hemin. Hemin treatment also inhibited the decline of SOD activity and the increase of MDA content in the aorta of T2D rats. CORM-2, an agent which releases the HO-1 product CO, could mimic the beneficial effect of hemin. CONCLUSION: Induction of HO-1 with hemin ameliorates the abnormality of endothelium-dependent vascular relaxation in T2D rats. A possible mechanism involves suppression of reactive oxygen species production and inhibition of COX-2 up-regulation induced by diabetes mellitus.

Heme oxygenase-1: a metabolic nike.

SIGNIFICANCE: Heme degradation, which was described more than 30 years ago, is still very actively explored with many novel discoveries on its role in various disease models every year. RECENT ADVANCES: The heme oxygenases (HO) are metabolic enzymes that utilize NADPH and oxygen to break apart the heme moiety liberating biliverdin (BV), carbon monoxide (CO), and iron. Heme that is derived from hemoproteins can be toxic to the cells and if not removed immediately, it causes cell apoptosis and local inflammation. Elimination of heme from the milieu enables generation of three products that influences numerous metabolic changes in the cell. CRITICAL ISSUES: CO has profound effects on mitochondria and cellular respiration and other hemoproteins to which it can bind and affect their function, while BV and bilirubin (BR), the substrate and product of BV, reductase, respectively, are potent antioxidants. Sequestration of iron into ferritin and its recycling in the tissues is a part of the homeodynamic processes that control oxidation-reduction in cellular metabolism. Further, heme is an important component of a number of metabolic enzymes, and, therefore, HO-1 plays an important role in the modulation of cellular bioenergetics. FUTURE DIRECTIONS: In this review, we describe the cross-talk between heme oxygenase-1 (HO-1) and its products with other metabolic pathways. HO-1, which we have labeled Nike, the goddess who personified victory, dictates triumph over pathophysiologic conditions, including diabetes, ischemia, and cancer.

Carbon monoxide (CO) and hydrogen sulfide (H(2)S) in hypoxic sensing by the carotid body.

Carotid bodies are sensory organs for monitoring arterial blood oxygen (O(2)) levels, and the ensuing reflexes maintain cardio-respiratory homeostasis during hypoxia. This article provides a brief update of the role of carbon monoxide (CO) and hydrogen sulfide (H(2)S) in hypoxic sensing by the carotid body. Glomus cells, the primary site of O(2) sensing in the carotid body express heme oxygenase-2 (HO-2), a CO catalyzing enzyme. HO-2 is a heme containing enzyme and has high affinity for O(2). Hypoxia inhibits HO-2 activity and reduces CO generation. Pharmacological and genetic approaches suggest that CO inhibits carotid body sensory activity. Stimulation of carotid body activity by hypoxia may reflect reduced formation of CO. Glomus cells also express cystathionine γ-lyase (CSE), an H(2)S generating enzyme. Exogenous application of H(2)S donors, like hypoxia, stimulate the carotid body activity and CSE knockout mice exhibit severely impaired sensory excitation by hypoxia, suggesting that CSE catalyzed H(2)S is an excitatory gas messenger. Hypoxia increases H(2)S generation in the carotid body, and this response was attenuated or absent in CSE knockout mice. HO inhibitor increased and CO donor inhibited H(2)S generation. It is proposed that carotid body response to hypoxia requires interactions between HO-2-CO and CSE-H(2)S systems.