Carbon monoxide, reactive oxygen signaling, and oxidative stress

Nrf2-mediated HO-1 induction contributes to antioxidant capacity of a Schisandrae Fructus ethanol extract in C2C12 myoblasts

This study was designed to confirm the protective effect of Schisandrae Fructus, which are the dried fruits of Schisandra chinensis (Turcz.) Baill, against oxidative stress-induced cellular damage and to elucidate the underlying mechanisms in C2C12 myoblasts. Preincubating C2C12 cells with a Schisandrae Fructus ethanol extract (SFEE) significantly attenuated hydrogen peroxide (H₂O₂)-induced inhibition of growth and induced scavenging activity against intracellular reactive oxygen species (ROS) induced by H₂O₂. SFEE also inhibited comet tail formation and phospho-histone γH2A.X expression, suggesting that it prevents H₂O₂-induced cellular DNA damage. Furthermore, treating C2C12 cells with SFEE significantly induced heme oxygenase-1 (HO-1) and phosphorylation of nuclear factor-erythroid 2 related factor 2 (Nrf2). However, zinc protoporphyrin IX, a potent inhibitor of HO-1 activity, significantly reversed the protective effects of SFEE against H₂O₂-induced growth inhibition and ROS generation in C2C12 cells. Additional experiments revealed that the potential of the SFEE to induce HO-1 expression and protect against H₂O₂-mediated cellular damage was abrogated by transient transfection with Nrf2-specific small interfering RNA, suggesting that the SFEE protected C2C12 cells against oxidative stress-induced injury through the Nrf2/HO-1 pathway.

The Human Endogenous Protection System against Cell-Free Hemoglobin and Heme Is Overwhelmed in Preeclampsia and Provides Potential Biomarkers and Clinical Indicators

Preeclampsia (PE) complicates 3-8% of all pregnancies and manifests clinically as hypertension and proteinuria in the second half of gestation. The pathogenesis of PE is not fully understood but recent studies have described the involvement of cell-free fetal hemoglobin (HbF). Hypothesizing that PE is associated with prolonged hemolysis we have studied the response of the cell-free Hb- and heme defense network. Thus, we have investigated the levels of cell-free HbF (both free, denoted HbF, and in complex with Hp, denoted Hp-HbF) as well as the major human endogenous Hb- and heme-scavenging systems: haptoglobin (Hp), hemopexin (Hpx), α1-microglobulin (A1M) and CD163 in plasma of PE women (n = 98) and women with normal pregnancies (n = 47) at term. A significant increase of the mean plasma HbF concentration was observed in women with PE. Plasma levels of Hp and Hpx were statistically significantly reduced, whereas the level of the extravascular heme- and radical scavenger A1M was significantly increased in plasma of women with PE. The Hpx levels significantly correlated with maternal blood pressure. Furthermore, HbF and the related scavenger proteins displayed a potential to be used as clinical biomarkers for more precise diagnosis of PE and are candidates as predictors of identifying pregnancies with increased risk of obstetrical complications. The results support that PE pathophysiology is associated with increased HbF-concentrations and an activation of the physiological Hb-heme defense systems.

N-acetylcysteine inhibits the up-regulation of mitochondrial biogenesis genes in livers from rats fed ethanol chronically

BACKGROUND

Chronic ethanol (EtOH) administration to experimental animals induces hepatic oxidative stress and up-regulates mitochondrial biogenesis. The mechanisms by which chronic EtOH up-regulates mitochondrial biogenesis have not been fully explored. In this work, we hypothesized that oxidative stress is a factor that triggers mitochondrial biogenesis after chronic EtOH feeding. If our hypothesis is correct, co-administration of antioxidants should prevent up-regulation of mitochondrial biogenesis genes.

METHODS

Rats were fed an EtOH-containing diet intragastrically by total enteral nutrition for 150 days, in the absence or presence of the antioxidant N-acetylcysteine (NAC) at 1.7 g/kg/d; control rats were administered isocaloric diets where carbohydrates substituted for EtOH calories.

RESULTS

EtOH administration significantly increased hepatic oxidative stress, evidenced as decreased liver total glutathione and reduced glutathione/glutathione disulfide ratio. These effects were inhibited by co-administration of EtOH and NAC. Chronic EtOH increased the expression of mitochondrial biogenesis genes including peroxisome proliferator-activated receptor gamma-coactivator-1 alpha and mitochondrial transcription factor A, and mitochondrial DNA; co-administration of EtOH and NAC prevented these effects. Chronic EtOH administration was associated with decreased mitochondrial mass, inactivation and depletion of mitochondrial complex I and complex IV, and increased hepatic mitochondrial oxidative damage, effects that were not prevented by NAC.

CONCLUSIONS

These results suggest that oxidative stress caused by chronic EtOH triggered the up-regulation of mitochondrial biogenesis genes in rat liver, because an antioxidant such as NAC prevented both effects. Because NAC did not prevent liver mitochondrial oxidative damage, extra-mitochondrial effects of reactive oxygen species may regulate mitochondrial biogenesis. In spite of the induction of hepatic mitochondrial biogenesis genes by chronic EtOH, mitochondrial mass and function decreased probably in association with mitochondrial oxidative damage. These results also predict that the effectiveness of NAC as an antioxidant therapy for chronic alcoholism will be limited by its limited antioxidant effects in mitochondria, and its inhibitory effect on mitochondrial biogenesis.

A metal carbonyl-protein needle composite designed for intracellular CO delivery to modulate NF-κB activity

Carbon monoxide (CO) has been recognized as a messenger for signal transduction in living cells and tissues. For intracellular CO delivery, several metal carbonyl complexes have been used as CO-releasing molecules (CO-RMs). To improve the properties of CO-RMs, such as the stability and the CO release rate, ligands and carriers of the metal complexes have been exploited. Here we report the development of an efficient intracellular CO delivery system using a protein scaffold. We used a protein needle reconstructed from gene product 5 of bacteriophage T4, which has high cellular permeability and stability. When ruthenium carbonyl complexes are conjugated to the needle using a His-tag triad at the C-terminus, the resulting composite has a significantly higher cellular uptake efficiency of Ru carbonyl and a 12-fold prolonged CO release rate relative to Ru(CO)3Cl(glycinate), a widely used CO-RM. We demonstrate that CO delivered by the composite activates the transcriptional factor nuclear factor-kappaB (NF-κB), which in turn leads to significant induction of expression of its target genes, HO1, NQO1, and IL6, through generation of reactive oxygen species (ROS). The signaling pathway is distinct from that of tumor necrosis factor (TNF)-α-induced activation of NF-κB. The protein needle-based CO-RM can be exploited to elucidate the biological functions of CO and used in the development of protein-based organometallic tools for modulation of cellular signaling.

The HO-1/CO system regulates mitochondrial-capillary density relationships in human skeletal muscle

The heme oxygenase-1 (HO-1)/carbon monoxide (CO) system induces mitochondrial biogenesis, but its biological impact in human skeletal muscle is uncertain. The enzyme system generates CO, which stimulates mitochondrial proliferation in normal muscle. Here we examined whether CO breathing can be used to produce a coordinated metabolic and vascular response in human skeletal muscle. In 19 healthy subjects, we performed vastus lateralis muscle biopsies and tested one-legged maximal O2 uptake (V̇o2max) before and after breathing air or CO (200 ppm) for 1 h daily for 5 days. In response to CO, there was robust HO-1 induction along with increased mRNA levels for nuclear-encoded mitochondrial transcription factor A (Tfam), cytochrome c, cytochrome oxidase subunit IV (COX IV), and mitochondrial-encoded COX I and NADH dehydrogenase subunit 1 (NDI). CO breathing did not increase V̇o2max (1.96 ± 0.51 pre-CO, 1.87 ± 0.50 post-CO l/min; P = not significant) but did increase muscle citrate synthase, mitochondrial density (139.0 ± 34.9 pre-CO, 219.0 ± 36.2 post-CO; no. of mitochondrial profiles/field), myoglobin content and glucose transporter (GLUT4) protein level and led to GLUT4 localization to the myocyte membrane, all consistent with expansion of the tissue O2 transport system. These responses were attended by increased cluster of differentiation 31 (CD31)-positive muscle capillaries (1.78 ± 0.16 pre-CO, 2.37 ± 0.59 post-CO; capillaries/muscle fiber), implying the enrichment of microvascular O2 reserve. The findings support that induction of the HO-1/CO system by CO not only improves muscle mitochondrial density, but regulates myoglobin content, GLUT4 localization, and capillarity in accordance with current concepts of skeletal muscle plasticity.

CO-Releasing Molecules Have Nonheme Targets in Bacteria: Transcriptomic, Mathematical Modeling and Biochemical Analyses of CORM-3 [Ru(CO)3Cl(glycinate)] Actions on a Heme-Deficient Mutant of Escherichia coli

AIMS

Carbon monoxide-releasing molecules (CORMs) are being developed with the ultimate goal of safely utilizing the therapeutic potential of CO clinically, including applications in antimicrobial therapy. Hemes are generally considered the prime targets of CO and CORMs, so we tested this hypothesis using heme-deficient bacteria, applying cellular, transcriptomic, and biochemical tools.

RESULTS

CORM-3 [Ru(CO)3Cl(glycinate)] readily penetrated Escherichia coli hemA bacteria and was inhibitory to these and Lactococcus lactis, even though they lack all detectable hemes. Transcriptomic analyses, coupled with mathematical modeling of transcription factor activities, revealed that the response to CORM-3 in hemA bacteria is multifaceted but characterized by markedly elevated expression of iron acquisition and utilization mechanisms, global stress responses, and zinc management processes. Cell membranes are disturbed by CORM-3.

INNOVATION

This work has demonstrated for the first time that CORM-3 (and to a lesser extent its inactivated counterpart) has multiple cellular targets other than hemes. A full understanding of the actions of CORMs is vital to understand their toxic effects.

CONCLUSION

This work has furthered our understanding of the key targets of CORM-3 in bacteria and raises the possibility that the widely reported antimicrobial effects cannot be attributed to classical biochemical targets of CO. This is a vital step in exploiting the potential, already demonstrated, for using optimized CORMs in antimicrobial therapy.

Fast responding and selective near-IR Bodipy dye for hydrogen sulfide sensing

A Bodipy based, highly selective probe for hydrogen sulfide has been designed, synthesized and demonstrated to detect H2S in living cells. In this design, the reduction of two arylazido groups change the charge transfer characteristics of the 3,5-distyryl substituents on the Bodipy core, producing a 20 nm bathochromic spectral shift in the absorption band, and quenching of the emission by 85% compared to the original intensity, through photoinduced electron transfer.

Diverse mechanisms underlying the regulation of ion channels by carbon monoxide

Carbon monoxide (CO) is firmly established as an important, physiological signalling molecule as well as a potent toxin. Through its ability to bind metal-containing proteins, it is known to interfere with a number of intracellular signalling pathways, and such actions can account for its physiological and pathological effects. In particular, CO can modulate the intracellular production of reactive oxygen species, NO and cGMP levels, as well as regulate MAPK signalling. In this review, we consider ion channels as more recently discovered effectors of CO signalling. CO is now known to regulate a growing number of different ion channel types, and detailed studies of the underlying mechanisms of action are revealing unexpected findings. For example, there are clear areas of contention surrounding its ability to increase the activity of high conductance, Ca(2+) -sensitive K(+) channels. More recent studies have revealed the ability of CO to inhibit T-type Ca(2+) channels and have unveiled a novel signalling pathway underlying tonic regulation of this channel. It is clear that the investigation of ion channels as effectors of CO signalling is in its infancy, and much more work is required to fully understand both the physiological and the toxic actions of this gas. Only then can its emerging use as a therapeutic tool be fully and safely exploited.

Novel lead structures and activation mechanisms for CO-releasing molecules (CORMs)

Carbon monoxide (CO) is an endogenous small signalling molecule in the human body, produced by the action of haem oxygenase on haem. Since it is very difficult to apply safely as a gas, solid storage and delivery forms for CO are now explored. Most of these CO-releasing molecules (CORMs) are based on the inactivation of the CO by coordinating it to a transition metal centre in a prodrug approach. After a brief look at the potential cellular target structures of CO, an overview of the design principles and activation mechanisms for CO release from a metal coordination sphere is given. Endogenous and exogenous triggers discussed include ligand exchange reactions with medium, enzymatically-induced CO release and photoactivated liberation of CO. Furthermore, the attachment of CORMs to hard and soft nanomaterials to confer additional target specificity to such systems is critically assessed. A survey of analytical methods for the study of the stoichiometry and kinetics of CO release, as well as the tracking of CO in living systems by using fluorescent probes, concludes this review. CORMs are very valuable tools for studying CO bioactivity and might lead to new drug candidates; however, in the design of future generations of CORMs, particular attention has to be paid to their drug-likeness and the tuning of the peripheral 'drug sphere' for specific biomedical applications. Further progress in this field will thus critically depend on a close interaction between synthetic chemists and researchers exploring the physiological effects and therapeutic applications of CO.

Sargassum horneri methanol extract rescues C2C12 murine skeletal muscle cells from oxidative stress-induced cytotoxicity through Nrf2-mediated upregulation of heme oxygenase-1

BACKGROUND

Sargassum horneri, an edible marine brown alga, is typically distributed along the coastal seas of Korea and Japan. Although several studies have demonstrated the anti-oxidative activity of this alga, the regulatory mechanisms have not yet been defined. The aim of the present study was to examine the cytoprotective effects of S. horneri against oxidative stress-induced cell damage in C2C12 myoblasts.

METHODS

We demonstrated the anti-oxidative effects of a methanol extract of S. horneri (SHME) in a hydrogen peroxide (H2O2)-stimulated C2C12 myoblast model. Cytotoxicity was determined using the 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyl-tetrazolium assay and mode of cell death by cell cycle analysis. DNA damage was measured using a comet assay and expression of phospho-histone γH2A.X (p-γH2A.X). Levels of cellular oxidative stress as reactive oxygen species (ROS) accumulation were measured using 2',7'-dichlorofluorescein diacetate. The involvement of selected genes in the oxidative stress-mediated signaling pathway was explored using Western blot analysis.

RESULTS

SHME attenuated H2O2-induced growth inhibition and exhibited scavenging activity against intracellular ROS that were induced by H2O2. The SHME also inhibited comet tail formation, p-γH2A.X expression, and the number of sub-G1 hypodiploid cells, suggesting that it prevents H2O2-induced cellular DNA damage and apoptotic cell death. Furthermore, the SHME significantly enhanced the expression of heme oxygenase-1 (HO-1) associated with induction of nuclear factor-erythroid 2 related factor 2 (Nrf2) in a time- and concentration-dependent manner. Moreover, the protective effect of the SHME on H2O2-induced C2C12 cell damage was significantly abolished by zinc protoporphyrin IX, a HO-1 competitive inhibitor, in C2C12 cells.

CONCLUSIONS

These findings suggest that the SHME augments cellular antioxidant defense capacity through both intrinsic free radical scavenging activity and activation of the Nrf2/HO-1 pathway, protecting C2C12 cells from H2O2-induced oxidative cytotoxicity.

Schisandrae semen essential oil attenuates oxidative stress-induced cell damage in C2C12 murine skeletal muscle cells through Nrf2‑mediated upregulation of HO‑1

The aim of the present study was to examine the cytoprotective effects of Schisandrae semen essential oil (SSeo), purified from Schisandrae fructus, against oxidative stress-induced cell damage in C2C12 myoblasts. SSeo attenuated hydrogen peroxide (H2O2)-induced growth inhibition and exhibited scavenging activity against the intracellular reactive oxygen species (ROS) that were induced by H2O2. SSeo also inhibited comet tail formation, chromatin condensation and phosphor-histone γH2A.X expression, suggesting that it prevents H2O2-induced cellular DNA damage and apoptotic cell death. Furthermore, SSeo significantly enhanced the expression of heme oxygenase-1 (HO‑1) associated with the induction of nuclear factor erythroid-2-related factor 2 (Nrf2) in a time- and concentration‑dependent manner. In addition, the protective effect of SSeo on H2O2‑induced C2C12 cell damage was significantly inhibited by zinc protoporphyrin IX, an HO‑1 competitive inhibitor, in C2C12 cells. These findings suggest that SSeo augments the cellular antioxidant defense capacity through intrinsic free radical scavenging activity and activation of the Nrf2/HO‑1 pathway, thereby protecting the C2C12 cells from H2O2‑induced oxidative cytotoxicity. As a result, SSeo may have therapeutic potential in the development of functional foods and as the raw material for medicines to protect against oxidative stress.

Curcumin-induced heme oxygenase-1 expression prevents H2O2-induced cell death in wild type and heme oxygenase-2 knockout adipose-derived mesenchymal stem cells

Mesenchymal stem cell (MSC) administration is a promising adjuvant therapy to treat tissue injury. However, MSC survival after administration is often hampered by oxidative stress at the site of injury. Heme oxygenase (HO) generates the cytoprotective effector molecules biliverdin/bilirubin, carbon monoxide (CO) and iron/ferritin by breaking down heme. Since HO-activity mediates anti-apoptotic, anti-inflammatory, and anti-oxidative effects, we hypothesized that modulation of the HO-system affects MSC survival. Adipose-derived MSCs (ASCs) from wild type (WT) and HO-2 knockout (KO) mice were isolated and characterized with respect to ASC marker expression. In order to analyze potential modulatory effects of the HO-system on ASC survival, WT and HO-2 KO ASCs were pre-treated with HO-activity modulators, or downstream effector molecules biliverdin, bilirubin, and CO before co-exposure of ASCs to a toxic dose of H₂O₂. Surprisingly, sensitivity to H₂O₂-mediated cell death was similar in WT and HO-2 KO ASCs. However, pre-induction of HO-1 expression using curcumin increased ASC survival after H₂O₂ exposure in both WT and HO-2 KO ASCs. Simultaneous inhibition of HO-activity resulted in loss of curcumin-mediated protection. Co-treatment with glutathione precursor N-Acetylcysteine promoted ASC survival. However, co-incubation with HO-effector molecules bilirubin and biliverdin did not rescue from H₂O₂-mediated cell death, whereas co-exposure to CO-releasing molecules-2 (CORM-2) significantly increased cell survival, independently from HO-2 expression. Summarizing, our results show that curcumin protects via an HO-1 dependent mechanism against H₂O₂-mediated apoptosis, and likely through the generation of CO. HO-1 pre-induction or administration of CORMs may thus form an attractive strategy to improve MSC therapy.

The effect of hyperbaric oxygen therapy on kidneys in a rat model

Background. Hyperbaric oxygen therapy (HBOT) is used for treating various medical conditions. As far as known yet, HBOT is safe with few major side effects that are easy to avoid using a proper protocol. Renal tubular damage was observed in rats exposed to HBOT in a preliminary study conducted in our institution. Aim. We aim to assess whether HBOT causes renal damage and, if so, whether this is dose dependent. Methods. Thirty-one rats were randomly assigned to three groups. The first group received 10-days HBOT, 100% oxygen at a pressure of 2 atmospheres absolute (2 ATA) for 60 minutes/day, the second received the same treatment for 5 days and the third served as the control. Rat weight, survival, renal function tests, and renal histopathology were analyzed. Results. There were no significant changes in renal function tests in the plasma (cystatin C, urea, creatinine, and electrolytes) between the groups. No significant differences were observed in weight gain or renal histopathological evaluation between all groups. Conclusion. HBOT in this protocol does not cause renal impairment in a rat model, which reinforces the assumption that HBOT is safe in healthy rats, regarding renal function. Further research should be focused on the effect/safety of HBOT on nonhealthy kidneys.

Effects of serum bilirubin on atherosclerotic processes

This review highlights the protective roles of bilirubin against the atherosclerotic process. Bilirubin belongs to the superfamily of tetrapyrrolic compounds formed during heme catabolism. Although for decades bilirubin was considered to be a harmful waste product, recent epidemiologic studies have shown that serum bilirubin levels have consistently been inversely associated with cardiovascular disease (CVD), as well as cardiovascular risk factors such as metabolic syndrome and diabetes. These clinical studies are supported by in vitro and in vivo experimental data and have demonstrated that bilirubin not only has an ability to scavenge overproduced reactive oxygen species and inhibit vascular smooth muscle cell proliferation but, additionally, has anti-inflammatory effects. In this review, we will discuss the inverse association of serum bilirubin and CVD and cardiovascular risk factors established in various clinical studies. We also review detailed experimental studies about the effect of bilirubin on atherosclerotic processes. In vitro, animal and human studies have proved that bilirubin inhibits oxidation of cholesterol which is an important step of atherosclerosis. Bilirubin attenuates chemotactic activity of monocytes and strongly inhibits adhesion of leukocytes to venule and production of pro-inflammatory cytokines. Bilirubin has inhibited serum-driven smooth muscle cell cycle progression at the G1 phase. Lastly, we will discuss briefly the influence of bilirubin on lipoprotein composition and endothelial dysfunction.

Interaction between HY1 and H2O2 in auxin-induced lateral root formation in Arabidopsis

Haem oxygenase-1 (HO-1) and hydrogen peroxide (H2O2) are two key downstream signals of auxin, a well-known phytohormone regulating plant growth and development. However, the inter-relationship between HO-1 and H2O2 in auxin-mediated lateral root (LR) formation is poorly understood. Herein, we revealed that exogenous auxin, 1-naphthylacetic acid (NAA), could simultaneously stimulate Arabidopsis HO-1 (HY1) gene expression and H2O2 generation. Subsequently, LR formation was induced. NAA-induced HY1 expression is dependent on H2O2. This conclusion was supported by analyzing the removal of H2O2 with ascorbic acid (AsA) and dimethylthiourea (DMTU), both of which could block NAA-induced HY1 expression and LR formation. H2O2-induced LR formation was inhibited by an HO-1 inhibitor zinc protoporphyrin IX (Znpp) in wild-type and severely impaired in HY1 mutant hy1-100. Simultaneously, HY1 is required for NAA-mediated H2O2 generation, since Znpp inhibition of HY1 blocked the NAA-induced H2O2 production and LR formation. Genetic data demonstrated that hy1-100 was significantly impaired in H2O2 production and LR formation in response to NAA, compared with wild-type plants. The addition of carbon monoxide-releasing molecule-2 (CORM-2), the carbon monoxide (CO) donor, induced H2O2 production and LR formation, both of which were decreased by DMTU. Moreover, H2O2 and CORM-2 mimicked the NAA responses in the regulation of cell cycle genes expression, all of which were blocked by Znpp or DMTU, respectively, confirming that both H2O2 and CO were important in the early LR initiation. In summary, our pharmacological, genetic and molecular evidence demonstrated a close inter-relationship between HY1 and H2O2 existing in auxin-induced LR formation in Arabidopsis.

Carbon monoxide--physiology, detection and controlled release

Carbon monoxide (CO) is increasingly recognized as a cell-signalling molecule akin to nitric oxide (NO). CO has attracted particular attention as a potential therapeutic agent because of its reported anti-hypertensive, anti-inflammatory and cell-protective effects. We discuss recent progress in identifying new effector systems and elucidating the mechanisms of action of CO on, e.g., ion channels, as well as the design of novel methods to monitor CO in cellular environments. We also report on recent developments in the area of CO-releasing molecules (CORMs) and materials for controlled CO application. Novel triggers for CO release, metal carbonyls and degradation mechanisms of CORMs are highlighted. In addition, potential formulations of CORMs for targeted CO release are discussed.

Carbon monoxide signaling in human red blood cells: evidence for pentose phosphate pathway activation and protein deglutathionylation

AIMS

The biochemistry underlying the physiological, adaptive, and toxic effects of carbon monoxide (CO) is linked to its affinity for reduced transition metals. We investigated CO signaling in the vasculature, where hemoglobin (Hb), the CO most important metal-containing carrier is highly concentrated inside red blood cells (RBCs).

RESULTS

By combining NMR, MS, and spectrophotometric techniques, we found that CO treatment of whole blood increases the concentration of reduced glutathione (GSH) in RBC cytosol, which is linked to a significant Hb deglutathionylation. In addition, this process (i) does not activate glycolytic metabolism, (ii) boosts the pentose phosphate pathway (PPP), (iii) increases glutathione reductase activity, and (iv) decreases oxidized glutathione concentration. Moreover, GSH concentration was partially decreased in the presence of 2-deoxyglucose and the PPP antagonist dehydroepiandrosterone. Our MS results show for the first time that, besides Cys93, Hb glutathionylation occurs also at Cys112 of the β-chain, providing a new potential GSH source hitherto unknown.

INNOVATION

This work provides new insights on the signaling and antioxidant-boosting properties of CO in human blood, identifying Hb as a major source of GSH release and the PPP as a metabolic mechanism supporting Hb deglutathionylation.

CONCLUSIONS

CO-dependent GSH increase is a new RBC process linking a redox-inactive molecule, CO, to GSH redox signaling. This mechanism may be involved in the adaptive responses aimed to counteract stress conditions in mammalian tissues.

Chemical sensing of neurotransmitters

This review focuses on the chemosensors for neurotransmitters published for the last 12 years, covering biogenic amines (dopamine, epinephrine, norepinephrine, serotonin, histamine and acetylcholine), amino acids (glutamate, aspartate, GABA, glycine and tyrosine), and adenosine.

The Janus face of the heme oxygenase/biliverdin reductase system in Alzheimer disease: it's time for reconciliation

Alzheimer disease (AD) is the most common form of dementia among the elderly and is characterized by progressive loss of memory and cognition. These clinical features are due in part to the increase of reactive oxygen and nitrogen species that mediate neurotoxic effects. The up-regulation of the heme oxygenase-1/biliverdin reductase-A (HO-1/BVR-A) system is one of the earlier events in the adaptive response to stress. HO-1/BVR-A reduces the intracellular levels of pro-oxidant heme and generates equimolar amounts of the free radical scavengers biliverdin-IX alpha (BV)/bilirubin-IX alpha (BR) as well as the pleiotropic gaseous neuromodulator carbon monoxide (CO) and ferrous iron. Two main and opposite hypotheses for a role of the HO-1/BVR-A system in AD propose that this system mediates neurotoxic and neuroprotective effects, respectively. This apparent controversy was mainly due to the fact that for over about 20years HO-1 was the only player on which all the analyses were focused, excluding the other important and essential component of the entire system, BVR. Following studies from the Butterfield laboratory that reported alterations in BVR activity along with decreased phosphorylation and increased oxidative/nitrosative post-translational modifications in the brain of subjects with AD and amnestic mild cognitive impairment (MCI) subjects, a debate was opened on the real pathophysiological and clinical significance of BVR-A. In this paper we provide a review of the main discoveries about the HO/BVR system in AD and MCI, and propose a mechanism that reconciles these two hypotheses noted above of neurotoxic and the neuroprotective aspects of this important stress responsive system.

Carbon monoxide inhalation increases microparticles causing vascular and CNS dysfunction

We hypothesized that circulating microparticles (MPs) play a role in pro-inflammatory effects associated with carbon monoxide (CO) inhalation. Mice exposed for 1h to 100 ppm CO or more exhibit increases in circulating MPs derived from a variety of vascular cells as well as neutrophil activation. Tissue injury was quantified as 2000 kDa dextran leakage from vessels and as neutrophil sequestration in the brain and skeletal muscle; and central nervous system nerve dysfunction was documented as broadening of the neurohypophysial action potential (AP). Indices of injury occurred following exposures to 1000 ppm for 1h or to 1000 ppm for 40 min followed by 3000 ppm for 20 min. MPs were implicated in causing injuries because infusing the surfactant MP lytic agent, polyethylene glycol telomere B (PEGtB) abrogated elevations in MPs, vascular leak, neutrophil sequestration and AP prolongation. These manifestations of tissue injury also did not occur in mice lacking myeloperoxidase. Vascular leakage and AP prolongation were produced in naïve mice infused with MPs that had been obtained from CO poisoned mice, but this did not occur with MPs obtained from control mice. We conclude that CO poisoning triggers elevations of MPs that activate neutrophils which subsequently cause tissue injuries.

Carbon monoxide alleviates ethanol-induced oxidative damage and inflammatory stress through activating p38 MAPK pathway

Stress-inducible protein heme oxygenase-1(HO-1) is well-appreciative to counteract oxidative damage and inflammatory stress involving the pathogenesis of alcoholic liver diseases (ALD). The potential role and signaling pathways of HO-1 metabolite carbon monoxide (CO), however, still remained unclear. To explore the precise mechanisms, ethanol-dosed adult male Balb/c mice (5.0g/kg.bw.) or ethanol-incubated primary rat hepatocytes (100mmol/L) were pretreated by tricarbonyldichlororuthenium (II) dimmer (CORM-2, 8mg/kg for mice or 20μmol/L for hepatocytes), as well as other pharmacological reagents. Our data showed that CO released from HO-1 induction by quercetin prevented ethanol-derived oxidative injury, which was abolished by CO scavenger hemoglobin. The protection was mimicked by CORM-2 with the attenuation of GSH depletion, SOD inactivation, MDA overproduction, and the leakage of AST, ALT or LDH in serum and culture medium induced by ethanol. Moreover, CORM-2 injection or incubation stimulated p38 phosphorylation and suppressed abnormal Tnfa and IL-6, accompanying the alleviation of redox imbalance induced by ethanol and aggravated by inflammatory factors. The protective role of CORM-2 was abolished by SB203580 (p38 inhibitor) but not by PD98059 (ERK inhibitor) or SP600125 (JNK inhibitor). Thus, HO-1 released CO prevented ethanol-elicited hepatic oxidative damage and inflammatory stress through activating p38 MAPK pathway, suggesting a potential therapeutic role of gaseous signal molecule on ALD induced by naturally occurring phytochemicals.

Synthesis, spectroscopic properties, and photoinduced CO-release studies of functionalized ruthenium(II) polypyridyl complexes: versatile building blocks for development of CORM-peptide nucleic acid bioconjugates

A series of ruthenium(II) dicarbonyl complexes of formula [RuCl2(L)(CO)2] (L = bpy(CH3,CH3) = 4,4'-dimethyl-2,2'-bipyridine, bpy(CH3,CHO) = 4'-methyl-2,2'-bipyridine-4-carboxyaldehyde, bpy(CH3,COOH) = 4'-methyl-2,2'-bipyridine-4-carboxylic acid, CppH = 2-(pyridin-2-yl)pyrimidine-4-carboxylic acid, dppzcH = dipyrido[3,2-a:2',3'-c]phenazine-11-carboxylic acid), and [RuCl(L)(CO)2](+) (L = tpy(COOH) = 6-(2,2':6',2″-terpyridine-4'-yloxy)hexanoic acid) has been synthesized. In addition, a high-yield synthesis of a peptide nucleic acid (PNA) monomer containing the 2-(pyridin-2-yl)pyrimidine ligand was also developed, and this compound was used to prepare the first Ru(II) dicarbonyl complex, [RuCl2(Cpp-L-PNA)(CO)2],(Cpp-L-PNA = tert-butyl-N-[2-(N-9-fluorenylmethoxycarbonyl)aminoethyl]-N-[6-(2-(pyridin-2-yl)pyrimidine-4-carboxamido)hexanoyl]glycinate) attached to a PNA monomer backbone. Such metal-complex PNA-bioconjugates are attracting profound interest for biosensing and biomedical applications. Characterization of all complexes has been undertaken by IR and NMR spectroscopy, mass spectrometry, elemental analysis, and UV-vis spectroscopy. Investigation of the CO-release properties of the Ru(II) complexes in water/dimethyl sulfoxide (49:1) using the myoglobin assay showed that they are stable under physiological conditions in the dark for at least 60 min and most of them even for up to 15 h. In contrast, photoinduced CO release was observed upon illumination at 365 nm, the low-energy shoulder of the main absorption maximum centered around 300 nm, establishing these compounds as a new class of PhotoCORMs. While the two 2,2'-bipyridine complexes release 1 equiv of CO per mole of complex, the terpyridine, 2-(2'-pyridyl)pyrimidine, and dipyrido[3,2-a:2',3'-c]phenazine complexes are less effective CO releasers. Attachment of the 2-(2'-pyridyl)pyrimidine complex to a PNA backbone as in [RuCl2(Cpp-L-PNA)CO2] did not significantly change the spectroscopic or CO-release properties compared to the parent complex. Thus, a novel class of Ru(II)-based PhotoCORMs has been established which can be coupled to carrier delivery vectors such as PNA to facilitate cellular uptake without loss of the inherent CORM properties of the parent compound.

CuAAC click functionalization of azide-modified nanodiamond with a photoactivatable CO-releasing molecule (PhotoCORM) based on [Mn(CO)3(tpm)]+

The copper-catalyzed 1,3-dipolar azide-alkyne cycloaddition (CuAAC) was used for the first time to attach a biologically active carbon monoxide delivery agent to modified nanodiamond (ND) as a highly biocompatible carrier. The [Mn(CO)(3)(tpm)](+) photoactivatable CO-releasing molecule (PhotoCORM) on the surface retained the carbon monoxide release properties of the parent compound as shown with the myoglobin assay.

Adaptive redox response of mesenchymal stromal cells to stimulation with lipopolysaccharide inflammagen: mechanisms of remodeling of tissue barriers in sepsis

Acute bacterial inflammation is accompanied by excessive release of bacterial toxins and production of reactive oxygen and nitrogen species (ROS and RNS), which ultimately results in redox stress. These factors can induce damage to components of tissue barriers, including damage to ubiquitous mesenchymal stromal cells (MSCs), and thus can exacerbate the septic multiple organ dysfunctions. The mechanisms employed by MSCs in order to survive these stress conditions are still poorly understood and require clarification. In this report, we demonstrated that in vitro treatment of MSCs with lipopolysaccharide (LPS) induced inflammatory responses, which included, but not limited to, upregulation of iNOS and release of RNS and ROS. These events triggered in MSCs a cascade of responses driving adaptive remodeling and resistance to a "self-inflicted" oxidative stress. Thus, while MSCs displayed high levels of constitutively present adaptogens, for example, HSP70 and mitochondrial Sirt3, treatment with LPS induced a number of adaptive responses that included induction and nuclear translocation of redox response elements such as NFkB, TRX1, Ref1, Nrf2, FoxO3a, HO1, and activation of autophagy and mitochondrial remodeling. We propose that the above prosurvival pathways activated in MSCs in vitro could be a part of adaptive responses employed by stromal cells under septic conditions.

Aqueous extract of unripe Rubus coreanus fruit attenuates atherosclerosis by improving blood lipid profile and inhibiting NF-κB activation via phase II gene expression

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Rubus coreanus has been used as a traditional herbal medicine for alleviation of inflammatory and vascular diseases in Asian countries.

AIM OF THE STUDY

The anti-atherogenic effect of unripe Rubus coreanus fruit extract (URFE) and its underlying mechanism were analyzed in mice fed a high-fat diet (HFD) and in cell culture system.

MATERIALS AND METHODS

Mouse was freely given HFD alone or supplemented with URFE for 14 weeks, followed by analysis of atherosclerotic lesions and serum lipid levels. For in vitro assay, macrophages were pretreated with URFE, followed by stimulation with lipopolysaccharide (LPS). Expression levels of inflammatory genes (TNF-α, IL-1β, and iNOS) and phase II genes (heme oxygenase-1, glutamate cysteine lygase, and peroxiredoxine-1) as well as intracellular reactive oxygen species (ROS) level and NF-κB activation pathway were analyzed in cultured macrophages as well as mouse sera and aortic tissues.

RESULTS

URFE supplementation reduced HFD-induced atherosclerotic lesion formation which was correlated with decreased levels of lipids, lipid peroxides, and inflammatory mediators (TNF-α, IL-1β, and nitric oxide) in sera as well as suppression of inflammatory gene in aortic tissues. In addition, pre-treatment of macrophages with URFE also suppressed LPS-induced NF-κB activation, ROS production, and inflammatory and phase II gene expressions. Inhibition of phase II enzyme and protein activities attenuated the suppressive effects URFE on ROS production, NF-κB activation, and inflammatory gene expression.

CONCLUSION

These results suggest that URFE attenuates atherosclerosis by improving blood lipid profile and inhibiting NF-κB activation via phase II antioxidant gene expression.

Haem oxygenase modifies salinity tolerance in Arabidopsis by controlling K⁺ retention via regulation of the plasma membrane H⁺-ATPase and by altering SOS1 transcript levels in roots

Reactive oxygen species (ROS) production is a common denominator in a variety of biotic and abiotic stresses, including salinity. In recent years, haem oxygenase (HO; EC 1.14.99.3) has been described as an important component of the antioxidant defence system in both mammalian and plant systems. Moreover, a recent report on Arabidopsis demonstrated that HO overexpression resulted in an enhanced salinity tolerance in this species. However, physiological mechanisms and downstream targets responsible for the observed salinity tolerance in these HO mutants remain elusive. To address this gap, ion transport characteristics (K(+) and H(+) fluxes and membrane potentials) and gene expression profiles in the roots of Arabidopsis thaliana HO-overexpressing (35S:HY1-1/2/3/4) and loss-of-function (hy-100, ho2, ho3, and ho4) mutants were compared during salinity stress. Upon acute salt stress, HO-overexpressing mutants retained more K(+) (less efflux), and exhibited better membrane potential regulation (maintained more negative potential) and higher H(+) efflux activity in root epidermis, compared with loss-of-function mutants. Pharmacological experiments suggested that high activity of the plasma membrane H(+)-ATPase in HO overexpressor mutants provided the proton-motive force required for membrane potential maintenance and, hence, better K(+) retention. The gene expression analysis after 12h and 24h of salt stress revealed high expression levels of H(+)-ATPases (AHA1/2/3) and Na(+)/H(+) antiporter [salt overly sensitive1 (SOS1)] transcripts in the plasma membrane of HO overexpressors. It is concluded that HO modifies salinity tolerance in Arabidopsis by controlling K(+) retention via regulation of the plasma membrane H(+)-ATPase and by altering SOS1 transcript levels in roots.

Low dose of carbon monoxide intraperitoneal injection provides potent protection against GalN/LPS-induced acute liver injury in mice

Carbon monoxide (CO) is an important effector-signaling molecule involved in various pathophysiological processes. Here we investigated the protective effects of exogenous CO in a murine model of acute liver damage induced by d-galactosamine (GalN) and lipopolysaccharide (LPS). Exogenous CO gas was administered to mice via intraperitoneal injection (first at a dose of 15 ml kg(-1) and then, 6 h later, 8 ml kg(-1)), which caused a significant elevation of blood carboxyhemoglobin levels of up to 12-14% for more than 12 h. GalN/LPS were given to induce acute liver damage in mice 30 min prior to CO exposure. This showed that GalN/LPS induced severe liver injury in mice, whereas CO injection remarkably improved the survival rate of mice and led to attenuated hepatocellular damage. CO exhibited anti-oxidative capabilities by inhibiting hepatic malondialdehyde contents and restoring superoxide dismutase and glutathione, as well as by reducing inducible NOS/NO production. The anti-apoptotic and anti-inflammatory effects of CO were substantial, characterized by a notable inhibition of hepatocyte apoptosis and a reduction of pro-inflammatory cytokines in mice. Our findings thus supported the hypothesis that exogenous CO provides protective effects against acute liver damage in mice, mainly dependent on its anti-oxidative, anti-inflammatory and anti-apoptotic properties.

Peroxynitrite mediates disruption of Ca2+ homeostasis by carbon monoxide via Ca2+ ATPase degradation

AIM

Sublethal carbon monoxide poisoning causes prolonged neurological damage involving oxidative stress. Given the central role of Ca(2+) homeostasis and its vulnerability to stress, we investigated whether CO disrupts neuronal Ca(2+) homeostasis.

RESULTS

Cytosolic Ca(2+) transients evoked by muscarine in SH-SY5Y cells were prolonged by CO (applied via the donor CORM-2), and capacitative Ca(2+) entry (CCE) was dramatically enhanced. Ca(2+) store mobilization by cyclopiazonic acid was similarly augmented, as was the subsequent CCE, and that evoked by thapsigargin. Ca(2+) rises evoked by depolarization were also enhanced by CO, and Ca(2+) levels often did not recover in its presence. CO increased intracellular nitric oxide (NO) and all effects of CO were prevented by inhibiting NO formation. However, NO donors did not mimic the effects of CO. The antioxidant ascorbic acid inhibited effects of CO on Ca(2+) signaling, as did the peroxynitrite scavenger, FeTPPS, and CO increased peroxynitrite formation. Finally, CO caused significant loss of plasma membrane Ca(2+)ATPase (PMCA) protein, detected by Western blot, and this was also observed in brain tissue of rats exposed to CO in vivo.

INNOVATION

The cellular basis of CO-induced neurotoxicity is currently unknown. Our findings provide the first data to suggest signaling pathways through which CO causes neurological damage, thereby opening up potential targets for therapeutic intervention.

CONCLUSION

CO stimulates formation of NO and reactive oxygen species which, via peroxynitrite formation, inhibit Ca(2+) extrusion via PMCA, leading to disruption of Ca(2+) signaling. We propose this contributes to the neurological damage associated with CO toxicity.

Pathological conditions involving extracellular hemoglobin: molecular mechanisms, clinical significance, and novel therapeutic opportunities for α(1)-microglobulin

Hemoglobin (Hb) is the major oxygen (O(2))-carrying system of the blood but has many potentially dangerous side effects due to oxidation and reduction reactions of the heme-bound iron and O(2). Extracellular Hb, resulting from hemolysis or exogenous infusion, is shown to be an important pathogenic factor in a growing number of diseases. This review briefly outlines the oxidative/reductive toxic reactions of Hb and its metabolites. It also describes physiological protection mechanisms that have evolved against extracellular Hb, with a focus on the most recently discovered: the heme- and radical-binding protein α(1)-microglobulin (A1M). This protein is found in all vertebrates, including man, and operates by rapidly clearing cytosols and extravascular fluids of heme groups and free radicals released from Hb. Five groups of pathological conditions with high concentrations of extracellular Hb are described: hemolytic anemias and transfusion reactions, the pregnancy complication pre-eclampsia, cerebral intraventricular hemorrhage of premature infants, chronic inflammatory leg ulcers, and infusion of Hb-based O(2) carriers as blood substitutes. Finally, possible treatments of these conditions are discussed, giving a special attention to the described protective effects of A1M.

Therapeutic approach to neurodegenerative diseases by medical gases: focusing on redox signaling and related antioxidant enzymes

Oxidative stress in the central nervous system is strongly associated with neuronal cell death in the pathogenesis of several neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. In order to overcome the oxidative damage, there are some protective signaling pathways related to transcriptional upregulation of antioxidant enzymes, such as heme oxygenase-1 (HO-1) and superoxide dismutase (SOD)-1/-2. Their expression is regulated by several transcription factors and/or cofactors like nuclear factor-erythroid 2 (NF-E2) related factor 2 (Nrf2) and peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α). These antioxidant enzymes are associated with, and in some cases, prevent neuronal death in animal models of neurodegenerative diseases. They are activated by endogenous mediators and phytochemicals, and also by several gases such as carbon monoxide (CO), hydrogen sulphide (H₂S), and hydrogen (H₂). These might thereby protect the brain from severe oxidative damage and resultant neurodegenerative diseases. In this paper, we discuss how the expression levels of these antioxidant enzymes are regulated. We also introduce recent advances in the therapeutic uses of medical gases against neurodegenerative diseases.

Heme cytotoxicity and the pathogenesis of immune-mediated inflammatory diseases

Heme, iron (Fe) protoporphyrin IX, functions as a prosthetic group in a range of hemoproteins essential to support life under aerobic conditions. The Fe contained within the prosthetic heme groups of these hemoproteins can catalyze the production of reactive oxygen species. Presumably for this reason, heme must be sequestered within those hemoproteins, thereby shielding the reactivity of its Fe-heme. However, under pathologic conditions associated with oxidative stress, some hemoproteins can release their prosthetic heme groups. While this heme is not necessarily damaging per se, it becomes highly cytotoxic in the presence of a range of inflammatory mediators such as tumor necrosis factor. This can lead to tissue damage and, as such, exacerbate the pathologic outcome of several immune-mediated inflammatory conditions. Presumably, targeting “free heme” may be used as a therapeutic intervention against these diseases.

The carbon monoxide releasing molecule CORM-2 attenuates Pseudomonas aeruginosa biofilm formation

Chronic infections resulting from biofilm formation are difficult to eradicate with current antimicrobial agents and consequently new therapies are needed. This work demonstrates that the carbon monoxide-releasing molecule CORM-2, previously shown to kill planktonic bacteria, also attenuates surface-associated growth of the Gram-negative pathogen Pseudomonas aeruginosa by both preventing biofilm maturation and killing bacteria within the established biofilm. CORM-2 treatment has an additive effect when combined with tobramycin, a drug commonly used to treat P. aeruginosa lung infections. CORM-2 inhibited biofilm formation and planktonic growth of the majority of clinical P. aeruginosa isolates tested, for both mucoid and non-mucoid strains. While CORM-2 treatment increased the production of reactive oxygen species by P. aeruginosa biofilms, this increase did not correlate with bacterial death. These data demonstrate that CO-RMs possess potential novel therapeutic properties against a subset of P. aeruginosa biofilm related infections.

Mitochondria: redox metabolism and dysfunction

Mitochondria are the main intracellular location for fuel generation; however, they are not just power plants but involved in a range of other intracellular functions including regulation of redox homeostasis and cell fate. Dysfunction of mitochondria will result in oxidative stress which is one of the underlying causal factors for a variety of diseases including neurodegenerative diseases, diabetes, cardiovascular diseases, and cancer. In this paper, generation of reactive oxygen/nitrogen species (ROS/RNS) in the mitochondria, redox regulatory roles of certain mitochondrial proteins, and the impact on cell fate will be discussed. The current state of our understanding in mitochondrial dysfunction in pathological states and how we could target them for therapeutic purpose will also be briefly reviewed.

ZmHO-1, a maize haem oxygenase-1 gene, plays a role in determining lateral root development

Previous results revealed that haem oxygenase-1 (HO-1)/carbon monoxide (CO) system is involved in auxin-induced adventitious root formation. In this report, a cDNA for the gene ZmHO-1, encoding an HO-1 protein, was cloned from Zea mays seedlings. ZmHO-1 has a conserved HO signature sequence and shares highest homology with rice SE5 (OsHO-1) protein. We further discovered that N-1-naphthylacetic acid (NAA), haemin, and CO aqueous solution, led to the induction of ZmHO-1 expression as well as the thereafter promotion of lateral root development. These effects were specific for ZmHO-1 since the potent HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX) differentially blocked the above actions. The addition of haemin and CO were able to reverse the auxin depletion-triggered inhibition of lateral root formation as well as the decreased ZmHO-1 transcripts. Molecular evidence showed that the haemin- or CO-mediated the modulation of target genes responsible for lateral root formation, including ZmCDK and ZmCKI2, could be blocked by ZnPPIX. Overexpression of ZmHO-1 in transgenic Arabidopsis plants resulted in promotion of lateral root development as well as the modulation of cell cycle regulatory gene expressions. Overall, our results suggested that a maize HO-1 gene is required for the lateral root formation.

Developing drug molecules for therapy with carbon monoxide

The use of Carbon Monoxide (CO) as a therapeutic agent has already been tested in human clinical trials. Pre-clinically, CO gas administration proved beneficial in animal models of various human diseases. However, the use of gaseous CO faces serious obstacles not the least being its well-known toxicity. To fully realise the promise of CO as a therapeutic agent, it is key to find novel avenues for CO delivery to diseased tissues in need of treatment, without concomitant formation of elevated, toxic blood levels of carboxyhemoglobin (COHb). CO-releasing molecules (CO-RMs) have the potential to constitute safe treatments if CO release in vivo can be controlled in a spatial and temporal manner. It has already been demonstrated in animals that CO-RMs can release CO and mimic the therapeutic effects of gaseous CO. While demonstrating the principle of treatment with CO-RMs, these first generation compounds are not suitable for human use. This tutorial review summarises the biological and chemical behaviour of CO, the current status of CO-RM development, and derives principles for the creation of the next generation of CO-RMs for clinical applications in humans.

Carbon monoxide: a vital signalling molecule and potent toxin in the myocardium

Endogenous carbon monoxide (CO) is generated through the heme oxygenase-catalysed degradation of heme and is now established as an important, biologically active molecule capable of modulating a number of signalling pathways. Such pathways include those involving nitric oxide/guanylate cyclase, reactive oxygen species (ROS) and MAP kinases. In the heart, up-regulation of the inducible form of heme oxygenase (HO-1) following stresses such as ischemia/reperfusion provides cardioprotection, and much evidence indicates that CO accounts for many of these beneficial effects. One target of CO appears to be the L-type Ca(2+) channel; CO inhibits recombinant and native forms of this cardiac channel via mitochondria-derived ROS, which likely contributes to the protective effects of CO. In stark contrast, exposure to exogenous CO is toxic: chronic, low-level exposure can lead to myocardial injury and fibrosis, whereas acute exposure is associated with life-threatening arrhythmias. The molecular mechanisms accounting for such effects remain to be elucidated, but require future study before the potentially beneficial effects of CO therapy can be safely exploited. This article is part of a Special Issue entitled "Local Signaling in Myocytes".

The effect of melatonin on the developmental potential and implantation rate of mouse embryos

OBJECTIVE

Melatonin is a scavenger agent that has been used to promote in vitro embryo development. This study was designed to show the effects of melatonin on the quality and quantity rate of preimplantation mouse embryo development and pregnancy.

MATERIALS AND METHODS

In this experimental study, super ovulated, mated mice were killed by cervical dislocation to collect two-cell zygotes from the oviduct of pregnant 1 day NMRI mice. Zygotes were cultured to the hatching blastocyst stage and the numbers of embryos at different stages were recorded under an inverted microscope. The cleavage rates of two-cell zygotes were assayed until the blastocyst and hatching blastocyst stage in drops of T6 medium that contained either melatonin (1, 10, and 100×10(6), 10 and 100×10(9) M) or no melatonin. The cell numbers of blastocysts were determined by differential staining, implantation outcomes were studied, and development and pregnancy rate were compared by the Chi-square (development) and Fisher's exact (pregnancy rate) tests.

RESULTS

The addition of 10 and 100 nM melatonin to the embryo culture media promoted the development of the two-cell stage embryos to blastocyst and hatching blastocysts (p<0.01) and caused a significant increase in total cell number (TCN), trophoectoderm (TE), and inner cell mass (ICM) of the blastocysts (p<0.01). A difference was observed in the percentage of transferred embryos that were successfully implanted between the control and treatment groups (p<0.05).

CONCLUSION

The data indicate that 10 and 100 nM of melatonin positively impact mouse embryo cleavage rates, blastocyst TCN, and their implantation. Therefore, melatonin at low concentrations promotes an embryonic culture system in mice.

CO metabolism, sensing, and signaling

CO is a colorless and odorless gas produced by the incomplete combustion of hydrocarbons, both of natural and anthropogenic origin. Several microorganisms, including aerobic and anaerobic bacteria and anaerobic archaea, use exogenous CO as a source of carbon and energy for growth. On the other hand, eukaryotic organisms use endogenous CO, produced during heme degradation, as a neurotransmitter and as a signal molecule. CO sensors act as signal transducers by coupling a "regulatory" heme-binding domain to a "functional" signal transmitter. Although high CO concentrations inhibit generally heme-protein actions, low CO levels can influence several signaling pathways, including those regulated by soluble guanylate cyclase and/or mitogen-activated protein kinases. This review summarizes recent insights into CO metabolism, sensing, and signaling.

Cyclo(His-Pro) exerts anti-inflammatory effects by modulating NF-κB and Nrf2 signalling

Cyclo(His-Pro) is an endogenous cyclic dipeptide that exerts oxidative damage protection by selectively activating the transcription factor Nrf2 signalling pathway. Given the existence of a tight interplay of the Nrf2/NF-κB systems and that the pro-inflammatory response is governed by transcription factor NF-κB, here we sought to investigate whether and how cyclo(His-Pro) interferes with the cross-talk between the antioxidant Nrf2/heme oxygenase-1 and the pro-inflammatory NF-κB pathways. By knocking down the Nrf2 gene, we confirmed that cyclo(His-Pro) inhibits NF-κB nuclear accumulation induced by paraquat in rat pheochromocytoma PC12 cells via the Nrf2/heme oxygenase-1 pathway. The protection required functional heme oxygenase-1 activity, since zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, prevented NF-κB inhibition, and the presence of exogenous carbon monoxide and bilirubin afforded cytoprotection against paraquat-induced toxicity by preventing NF-κB activation. Cyclooxygenase-2 and matrix metalloproteinase 3, two gene products governed by NF-κB, were down-regulated by cyclo(His-Pro) and up-regulated in heme oxygenase-1 knock-down cells. We validated the general mechanism underlying the anti-inflammatory effects by treating PC12 and murine microglial BV2 cells with different pro-inflammatory agents. Finally, cyclo(His-Pro) reduced 12-otetradecanoylphorbol-13-acetate-induced oedema in mouse ear inflammation model. Results, by showing that cyclo(His-pro) suppresses the pro-inflammatory NF-κB signalling via the Nrf2-mediated heme oxygenase-1 activation, contribute to the understanding of essential cellular pathways and allow the proposal of cyclo(His-Pro) as an in vivo anti-inflammatory compound.