Interactions of multiple gas-transducing systems: hallmarks and uncertainties of CO, NO, and H2S gas biology

The Role of Bioactive Small Molecules in COPD Pathogenesis

Chronic obstructive pulmonary disease (COPD) is recognized as a predominant contributor to mortality worldwide, which causes significant burdens to both society and individuals. Given the limited treatment options for COPD, there lies a critical realization: the imperative for expeditious development of novel therapeutic modalities that can effectively alleviate disease progression and enhance the quality of life experienced by COPD patients. Within the intricate field of COPD pathogenesis, an assortment of biologically active small molecules, encompassing small protein molecules and their derivatives, assumes crucial roles through diverse mechanisms. These mechanisms relate to the regulation of redox balance, the inhibition of the release of inflammatory mediators, and the modulation of cellular functions. Therefore, the present article aims to explore and elucidate the distinct roles played by different categories of biologically active small molecules in contributing to the pathogenesis of COPD.

Endogenous sulfur dioxide deficiency as a driver of cardiomyocyte senescence through abolishing sulphenylation of STAT3 at cysteine 259

OBJECTIVE

Cardiomyocyte senescence is an important contributor to cardiovascular diseases and can be induced by stressors including DNA damage, oxidative stress, mitochondrial dysfunction, epigenetic regulation, etc. However, the underlying mechanisms for the development of cardiomyocyte senescence remain largely unknown. Sulfur dioxide (SO2) is produced endogenously by aspartate aminotransferase 2 (AAT2) catalysis and plays an important regulatory role in the development of cardiovascular diseases. The present study aimed to explore the effect of endogenous SO2 on cardiomyocyte senescence and the underlying molecular mechanisms.

APPROACH AND RESULTS

We interestingly found a substantial reduction in the expression of AAT2 in the heart of aged mice in comparison to young mice. AAT2-knockdowned cardiomyocytes exhibited reduced SO2 content, elevated expression levels of Tp53, p21Cip/Waf, and p16INk4a, enhanced SA-β-Gal activity, and elevated level of γ-H2AX foci. Notably, supplementation with a SO2 donor ameliorated the spontaneous senescence phenotype and DNA damage caused by AAT2 deficiency in cardiomyocytes. Mechanistically, AAT2 deficiency suppressed the sulphenylation of signal transducer and activator of transcription 3 (STAT3) facilitated its nuclear translocation and DNA-binding capacity. Conversely, a mutation in the cysteine (Cys) 259 residue of STAT3 blocked SO2-induced STAT3 sulphenylation and subsequently prevented the inhibitory effect of SO2 on STAT3-DNA-binding capacity, DNA damage, and cardiomyocyte senescence. Additionally, cardiomyocyte (cm)-specific AAT2 knockout (AAT2cmKO) mice exhibited a deterioration in cardiac function, cardiomegaly, and cardiac aging, whereas supplementation with SO2 donors mitigated the cardiac aging and remodeling phenotypes in AAT2cmKO mice.

CONCLUSION

Downregulation of the endogenous SO2/AAT2 pathway is a crucial pathogenic mechanism underlying cardiomyocyte senescence. Endogenous SO2 modifies STAT3 by sulphenylating Cys259, leading to the inhibition of DNA damage and the protection against cardiomyocyte senescence.

Electrochemical Detection of Gasotransmitters: Status and Roadmap

Gasotransmitters, including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), are a class of gaseous, endogenous signaling molecules that interact with one another in the regulation of critical cardiovascular, immune, and neurological processes. The development of analytical sensing mechanisms for gasotransmitters, especially multianalyte mechanisms, holds vast importance and constitutes a growing area of study. This review provides an overview of electrochemical sensing mechanisms with an emphasis on opportunities in multianalyte sensing. Electrochemical methods demonstrate good sensitivity, adequate selectivity, and the most well-developed potential for the multianalyte detection of gasotransmitters. Future research will likely address challenges with sensor stability and biocompatibility (i.e., sensor lifetime and cytotoxicity), sensor miniaturization, and multianalyte detection in biological settings.

The effects of CORM3 or NaHS on the oxidative stress caused by chronic kidney disease in rats: potential interaction between CO and H2S signaling pathway

Neurotoxicity is implicated as a severe complication of chronic kidney disease (CKD). Accumulation of urea and other toxic compounds leads to oxidative stress, inflammation and destruction of the blood-brain barrier. Carbon monoxide (CO) and hydrogen sulfide (H2S) have been shown to have anti-inflammatory, anti-apoptotic, and anti-proliferative properties. The aims of the present study were evaluated the protective effects of CO-releasing molecule (CORM3) and H2S donor (NaHS) on oxidative stress and neuronal death induced by CKD in the hippocampus and prefrontal cortex by considering interaction between CO and H2S on CBS expression. CORM3 or NaHS significantly compensated deficits in the antioxidant defense mechanisms, suppressed lipid peroxidation and reduced neuronal death in hippocampus and prefrontal cortex and improvement the markers of renal injury that induced by CKD. In addition, CORM3 or NaHS significantly improved CBS expression which were reduced by CKD. However, improving effects of CORM3 on antioxidant defense mechanisms, lipid peroxidation, neuronal death, renal injury and CBS expression were prevented by amino-oxy acetic acid (AOAA) (CBS inhibitor) and reciprocally improving effects of NaHS on all above indices were prevented by zinc protoporphyrin IX (Znpp) (HO-1 inhibitor). In conclusion, this study demonstrated that formation of CO and H2S were interdependently improved CKD-induced oxidative stress and neuronal death, which is may be through increased expression of CBS.

Hydrogen Sulfide Ligation in Hemoglobin I of Lucina pectinata─A QM/MM and Local Mode Study

In this study, we investigated the interaction between the H2S ligand and the heme pocket of hemoglobin I (HbI) of Lucina pectinata for the wild-type protein; three known mutations where distal glutamine is replaced by hydrophobic valine (Gln64Val) and hydrophilic histidine in both protonation forms (Gln64Hisϵ and Gln64Hisδ); five known mutations of the so-called phenyl cage, replacing the hydrophobic phenylalanines Phe29 and Phe43 with tyrosine (Tyr), valine (Val), or leucine (Leu); and two additional mutations, Phe68Tyr and Phe68Val, in order to complement previous studies with new insights about the binding mechanism at the molecular level. A particular focus was on the intrinsic strengths of the chemical bonds involved, utilizing local vibrational force constants based on combined quantum mechanical-molecular mechanical calculations. Wild-type protein and mutations clustered into two distinct groups: Group 1 protein systems with a proton acceptor in the distal protein pocket, close to one of the H2S bonds, and Group 2 protein systems without a hydrogen acceptor close by in the active site of the protein. According to our results, the interactions between H2S and HbI of Lucina pectinata involve two important elements, namely, binding of H2S to Fe of the heme group, followed by the proton transfer from the HS bond to the distal residue. The distal residue is additionally stabilized by a second proton transfer from the distal residue to COO- of the propionate group in heme. We could identify the FeS bond as a key player and discovered that the strength of this bond depends on two mutual factors, namely, the strength of the HS bond involved in the proton transfer and the electrostatic field of the protein pocket qualifying the FeS bond as a sensitive probe for monitoring changes in H2S ligation upon protein mutations. We hope our study will inspire and guide future experimental studies, targeting new promising mutations such as Phe68Tyr, Phe68Val, or Phe43Tyr/Phe68Val.

The chemistry of hydropersulfides (RSSH) as related to possible physiological functions

Hydropersulfides (RSSH) are oxidized thiol (RSH) derivatives that have been shown to be biologically prevalent with likely important functions (along with other polysulfur compounds). The functional utility of RSSH can be gleaned from their unique chemical properties. That is, RSSH possess chemical reactivity not present in other biologically relevant sulfur species that should allow them to be used in specific ways in biology as effector/signaling molecules. For example, compared to RSH, RSSH are considered to be superior nucleophiles, reductants and metal ligands. Moreover, unlike RSH, RSSH can be either reductants/nucleophiles or oxidants/electrophiles depending on the protonated state. It has also become clear that studies related to the chemical biology and physiology of hydrogen suflide (H₂S) must also consider the effects of RSSH (and related polysulfur species) as they are biochemically linked. Herein is a discussion of the relevant chemistry of RSSH that can serve as a basis for understanding how RSSH can be used by cells to, for example, combat stresses and used in signaling. Also, discussed are some current experimental studies regarding the biological activity of RSSH that can be explained by their chemical properties.

Reactive Sulfur Species Omics Analysis in the Brain Tissue of the 5xFAD Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder whereby oxidative stress augmentation results in mitochondrial dysfunction and cell death by apoptosis. Emerging evidence indicates that reactive sulfur species (RSS), such as glutathione hydropersulfide (GSSH), is endogenously produced, functions as potent antioxidants, and regulate redox signaling through the formation of protein polysulfides. However, the relationship between RSS and AD pathogenesis is not fully understood. In this study, we analyzed endogenous RSS production in the brain tissue of a familial AD model (5xFAD) mouse using multiple RSS-omics approaches. Memory impairment, increased amyloid plaques, and neuroinflammation have been confirmed in 5xFAD mice. Quantitative RSS omics analysis revealed that the total polysulfide content was significantly decreased in the brains of 5xFAD mice, whereas there was no significant difference in the levels of glutathione, GSSH, or hydrogen sulfide between wild-type and 5xFAD mice. In contrast, a significant decline in the protein polysulfide status was observed in the brains of 5xFAD mice, suggesting that RSS production and subsequent redox signaling might be altered during the onset and progression of AD. Our findings have important implications for understanding the significance of RSS in the development of preventive and therapeutic strategies for AD.

Perinatal Garlic Oil Supplementation Averts Rat Offspring Hypertension Programmed by Maternal Chronic Kidney Disease

Garlic (Allium sativum) is a functional food, having hydrogen sulfide (H₂S)-releasing capacity, which exhibits considerable effects on hypertension and gut microbiota. H₂S is strongly associated with hypertension and chronic kidney disease (CKD). Maternal CKD leads to hypertension in adult rat progeny, which was linked to disruption of the gut microbiota. This study validated the benefits of perinatal garlic oil supplementation against offspring hypertension induced by maternal CKD via modulation of H₂S signaling, nitric oxide (NO), and the gut microbiota. Before pregnancy, female rats received a 0.5% adenine diet for 3 weeks to develop an animal model to mimic human CKD. Garlic oil (100 mg/kg/day) or vehicle was administered to pregnant rats by oral gavage during gestation and lactation. Perinatal garlic oil supplementation protected against maternal CKD-induced hypertension in offspring at 12 weeks of age. The beneficial effects of garlic oil are associated with enhanced H₂S signaling, increased NO bioavailability, and shifts in gut microbiota. Perinatal garlic oil supplementation reduces abundance of genera Variovorax, Nocardia, Sphingomonas, and Rhodococcus. Our findings provide insight into the role of early H₂S-targeted intervention as a preventive strategy in hypertension for further translational research.

Small-Molecule Fluorescent Probes for Detecting Several Abnormally Expressed Substances in Tumors

Malignant tumors have always been the biggest problem facing human survival, and a huge number of people die from cancer every year. Therefore, the identification and detection of malignant tumors have far-reaching significance for human survival and development. Some substances are abnormally expressed in tumors, such as cyclooxygenase-2 (COX-2), nitroreductase (NTR), pH, biothiols (GSH, Cys, Hcy), hydrogen sulfide (H₂S), hydrogen sulfide (H₂O₂), hypochlorous acid (HOCl) and NADH. Consequently, it is of great value to diagnose and treat malignant tumors due to the identification and detection of these substances. Compared with traditional tumor detection methods, fluorescence imaging technology has the advantages of an inexpensive cost, fast detection and high sensitivity. Herein, we mainly introduce the research progress of fluorescent probes for identifying and detecting abnormally expressed substances in several tumors.

Hydrogen Sulfide-to-Thiosulfate Ratio Associated with Blood Pressure Abnormalities in Pediatric CKD

Identifying children with chronic kidney disease (CKD) at high risk of cardiovascular disease (CVD) and ensuring they receive appropriate treatment can prevent CVD events and mortality later in life. Hydrogen sulfide (H2S) is a gaseous signaling molecule participating in CVD and CKD. Thiosulfate is not only an oxidation product of H2S but is also a H2S donor. We examined whether H2S, thiosulfate, and their combined ratio have differential associations with CVD risk markers in 56 children and adolescents aged 6–18 years with CKD stages G1–G4. Up to two-thirds of CKD children showed higher BP load on 24 h ambulatory blood pressure monitoring (ABPM), even in the early stage. CKD children with ABPM abnormalities had a higher H2S-to-thiosulfate ratio, while H2S-related parameters were not affected by the severity of CKD. The H2S-to-thiosulfate ratio was positively correlated with 24 h systolic BP (SBP), nighttime SBP, and carotid artery intima-media thickness (cIMT). After adjusting for confounders, H2S was negatively associated with LV mass, thiosulfate was positively associated with 24-DBP, and the H2S-to-thiosulfate ratio was positively correlated with nighttime SBP and cIMT. Our data demonstrate differential associations in circulating H2S, thiosulfate, and their combined ratio with CVD risk in childhood CKD. Further studies are required to determine whether targeting the H2S signaling pathway can develop novel therapeutic strategies against CVD in this high-risk population.

Carbon monoxide signaling and soluble guanylyl cyclase: Facts, myths, and intriguing possibilities

The endogenous signaling roles of carbon monoxide (CO) have been firmly established at the pathway level. For CO's molecular mechanism(s) of actions, hemoproteins are generally considered as possible targets. Importantly, soluble guanylyl cyclase (sGC) is among the most widely referenced molecular targets. However, the affinity of CO for sGC (K_d: 240 μM) is much lower than for other highly abundant hemoproteins in the body, such as myoglobin (K_d: 29 nM) and hemoglobin (K_d: 0.7 nM-4.5 μM), which serve as CO reservoirs. Further, most of the mechanistic studies involving sGC activation by CO were based on in-vitro or ex-vivo studies using CO concentrations not readily attenable in vivo and in the absence of hemoglobin as a competitor in binding. As such, whether such in-vitro/ex-vivo results can be directly extrapolated to in-vivo studies is not clear because of the need for CO to be transferred from a high-affinity binder (e.g., hemoglobin) to a low-affinity target if sGC is to be activated in vivo. In this review, we discuss literature findings of sGC activation by CO and the experimental conditions; examine the myths in the disconnect between the low affinity of sGC for CO and the reported activation of sGC by CO; and finally present several possibilities that may lead to additional studies to improve our understanding of this direct CO-sGC axis, which is yet to be convincingly established as playing generally critical roles in CO signaling in vivo.

The Interaction of NO and H2S in Boar Spermatozoa under Oxidative Stress

Various recent studies dedicated to the role of nitric oxide (NO) and hydrogen sulfide (H2S) in somatic cells provide evidence for an interaction of the two gasotransmitters. In the case of male gametes, only the action of a single donor of each gasotransmitter has been investigated up until today. It has been demonstrated that, at low concentrations, both gasotransmitters alone exert a positive effect on sperm quality parameters. Moreover, the activity of gaseous cellular messengers may be affected by the presence of oxidative stress, an underlying condition of several male reproductive disorders. In this study, we explored the effect of the combination of two donors SNP and NaHS (NO and H2S donors, respectively) on boar spermatozoa under oxidative stress. We applied NaHS, SNP, and their combination (DD) at 100 nM concentration in boar spermatozoa samples treated with Fe2+/ascorbate system. After 90 min of incubation at 38 °C, we have observed that progressive motility (PMot) and plasma membrane integrity (PMI) were improved (p < 0.05) in DD treatment compared to the Ctr sample under oxidative stress (CtrOX). Moreover, the PMot of DD treatment was higher (p < 0.05) than that of NaHS. Similar to NaHS, SNP treatment did not overcome the PMot and PMI of CtrOX. In conclusion, for the first time, we provide evidence that the combination of SNP and NaHS surmounts the effect of single-donor application in terms of PMot and PMI in porcine spermatozoa under oxidative stress.

Sulfide Oxidation Evidences the Immediate Cellular Response to a Decrease in the Mitochondrial ATP/O2 Ratio

The present article will not attempt to deal with sulfide per se as a signaling molecule but will aim to examine the consequences of sulfide oxidation by mitochondrial sulfide quinone reductase in mammalian cells. This oxidation appears first as a priority to avoid self-poisoning by endogenous sulfide and second to occur with the lowest ATP/O₂ ratio when compared to other mitochondrial substrates. This is explained by the injection of electrons in the respiratory chain after complex I (as for succinate) and by a sulfur oxidation step implying a dioxygenase that consumes oxygen but does not contribute to mitochondrial bioenergetics. Both contribute to increase cellular oxygen consumption if sulfide is provided below its toxic level (low µM). Accordingly, if oxygen supply or respiratory chain activity becomes a limiting factor, small variations in sulfide release impact the cellular ATP/ADP ratio, a major metabolic sensor.

The Biological/Physiological Utility of Hydropersulfides (RSSH) and Related Species: What Is Old Is New Again

Significance: Hydrogen sulfide (H₂S) is reported to be an important mediator involved in numerous physiological processes. H₂S and hydropersulfides (RSSH) species are intimately linked biochemically. Therefore, interest in the mechanisms of the biological activity of H₂S has led to investigations of the chemical biology of RSSH since they are likely to coexist in a biological system. Currently it is hypothesized that RSSH may be responsible for a least part of the observed H₂S-mediated biology/physiology. Recent Advances: It has been recently touted that thiols (RSH) and RSSH have some important differences in terms of their chemical biology and that the generation of RSSH from RSH is purposeful to exploit these chemical differences as a response to a physiological or biological stress. This transformation may represent an unappreciated/unrecognized biological mechanism for dealing with cellular stresses. Critical Issues: Although recent studies indicate a diverse and potentially important chemical biology associated with RSSH species, these ideas have their foundations in early studies (some over 60 years old). It is vital to recognize the nature of this early work to fully appreciate the current ideas regarding RSSH biology. Importantly, these early studies were performed before the realization of purposeful H₂S biosynthesis (before 1996). Future Directions: Taking clues from the past studies of RSSH chemistry and biology, progress in delineating the chemical biology of RSSH will continue. Determination of the possible relevance of RSSH chemical biology to signaling and cellular physiology will be a primary focus of many future studies. Antioxid. Redox Signal. 36, 244-255.

Hydrogen Sulfide: An Emerging Precision Strategy for Gas Therapy

Advances in nanotechnology have enabled the rapid development of stimuli-responsive therapeutic nanomaterials for precision gas therapy. Hydrogen sulfide (H₂ S) is a significant gaseous signaling molecule with intrinsic biochemical properties, which exerts its various physiological effects under both normal and pathological conditions. Various nanomaterials with H₂ S-responsive properties, as new-generation therapeutic agents, are explored to guide therapeutic behaviors in biological milieu. The cross disciplinary of H₂ S is an emerging scientific hotspot that studies the chemical properties, biological mechanisms, and therapeutic effects of H₂ S. This review summarizes the state-of-art research on H₂ S-related nanomedicines. In particular, recent advances in H₂ S therapeutics for cancer, such as H₂ S-mediated gas therapy and H₂ S-related synergistic therapies (combined with chemotherapy, photodynamic therapy, photothermal therapy, and chemodynamic therapy) are highlighted. Versatile imaging techniques for real-time monitoring H₂ S during biological diagnosis are reviewed. Finally, the biosafety issues, current challenges, and potential possibilities in the evolution of H₂ S-based therapy that facilitate clinical translation to patients are discussed.

Hydropersulfides (RSSH) and Nitric Oxide (NO) Signaling: Possible Effects on S-Nitrosothiols (RS-NO)

S-Nitrosothiol (RS-NO) formation in proteins and peptides have been implicated as factors in the etiology of many diseases and as possible regulators of thiol protein function. They have also been proposed as possible storage forms of nitric oxide (NO). However, despite their proposed functions/roles, there appears to be little consensus regarding the physiological mechanisms of RS-NO formation and degradation. Hydropersulfides (RSSH) have recently been discovered as endogenously generated species with unique reactivity. One important reaction of RSSH is with RS-NO, which leads to the degradation of RS-NO as well as the release of NO. Thus, it can be speculated that RSSH can be a factor in the regulation of steady-state RS-NO levels, and therefore may be important in RS-NO (patho)physiology. Moreover, RSSH-mediated NO release from RS-NO may be a possible mechanism allowing RS-NO to serve as a storage form of NO.

Potentials of CCL21 and CBS as Therapeutic Approaches for Breast Cancer

OBJECTIVE

The present research set out to ascertain the roles of CC chemokine ligand 21 (CCL21) and cystathionine beta-synthase (CBS) in breast cancer (BC) cell biological behaviors and the relationship of CCL21 and CBS expression with the clinicopathological features of patients with BC.

METHODS

Immunohistochemistry of CCL21 or CBS was performed in 18 intraductal cancer tissues, 124 invasive BC tissues, 50 paraneoplastic tissues, 50 lobular hyperplasia tissues, and 30 normal breast tissues. For cell experiments, two human BC cell lines (MDA-MB-231 and MCF-7) and a human breast epithelial cell line (MCF-10A) were utilized to detect the expression of CCL21 and CBS. After loss- and gain-of-function assays for CCL21 or CBS, the expression of CBS and CCL21 was measured by quantitative real-time polymerase chain reaction and western blot. Additionally, BC cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and 5-ethynyl-2'-deoxyuridine staining, and BC cell migration was determined by scratch test and Transwell assay.

RESULTS

In the clinical data, the positive rate of CCL21 or CBS was significantly higher in invasive BC tissues than in intraductal BC tissues, lobular hyperplasia tissues, paraneoplastic tissues, and normal breast tissues (p < 0.05 or p < 0.01). CBS or CCL21 expression shared close association with the clinicopathological characteristics and the poor prognosis of BC patients. In cell experiments, overexpression of CCL21 or CBS enhanced the proliferative and migratory abilities of BC cells.

CONCLUSION

CCL21 and CBS promoted BC cell migration and proliferation. CCL21 or CBS expression was strongly related to the poor prognosis of BC patients.

The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity

Nitric oxide (NO) is an important signaling molecule that is involved in a wide range of physiological and pathological events in biology. Metal coordination chemistry, especially with iron, is at the heart of many biological transformations involving NO. A series of heme proteins, nitric oxide synthases (NOS), soluble guanylate cyclase (sGC), and nitrophorins, are responsible for the biosynthesis, sensing, and transport of NO. Alternatively, NO can be generated from nitrite by heme- and copper-containing nitrite reductases (NIRs). The NO-bearing small molecules such as nitrosothiols and dinitrosyl iron complexes (DNICs) can serve as an alternative vehicle for NO storage and transport. Once NO is formed, the rich reaction chemistry of NO leads to a wide variety of biological activities including reduction of NO by heme or non-heme iron-containing NO reductases and protein post-translational modifications by DNICs. Much of our understanding of the reactivity of metal sites in biology with NO and the mechanisms of these transformations has come from the elucidation of the geometric and electronic structures and chemical reactivity of synthetic model systems, in synergy with biochemical and biophysical studies on the relevant proteins themselves. This review focuses on recent advancements from studies on proteins and model complexes that not only have improved our understanding of the biological roles of NO but also have provided foundations for biomedical research and for bio-inspired catalyst design in energy science.

Carbon Monoxide in Renal Physiology, Pathogenesis and Treatment of Renal Disease

Carbon monoxide (CO) is one of the endogenous gaseous messengers or gasotransmitters, and is a paramount mediator in physiological and disease conditions. In this review, we focus on the functions of CO in normal and pathological renal physiology. We discuss endogenous renal CO production and signaling in the normal kidney, the characteristic of CO-releasing molecules (CORMs) modalities, and outline its regulatory functions in renal physiology. This article summarizes the mechanisms as well as the effect of CO in the evolving field of renal diseases. We predict numerous innovative CO applications forevolvingcutting-edge scholarly work in the future.

Ultrafast photochemistry of a molybdenum carbonyl-nitrosyl complex with a triazacyclononane coligand

Transition metal complexes capable of releasing small molecules such as carbon monoxide and nitric oxide upon photoactivation are versatile tools in various fields of chemistry and biology. In this work, we report on the ultrafast photochemistry of [Mo(CO)₂(NO)(iPr₃tacn)]PF₆ (iPr₃tacn = 1,4,7-triisopropyl-1,4,7-triazacyclononane), which was characterized under continuous illumination and with femtosecond UV-pump/UV-probe and UV-pump/MIR-probe spectroscopy, as well as with stationary calculations. The experimental and theoretical results demonstrate that while the photodissociation of one of the two CO ligands upon UV excitation can be inferred both on an ultrafast timescale as well as under exposure times of several minutes, no evidence of NO release is observed under the same conditions. The binding mode of the diatomic ligands is impacted by the electronic excitation, and transient intermediates are observed on a timescale of tens of picoseconds before CO is released from the coordination sphere. Furthermore, based on calculated potential energy scans, we suggest that photolysis of NO could be possible after a subsequent excitation of an electronically excited state with a second laser pulse, or by accessing low-lying excited states that otherwise cannot be directly excited by light.

Disposable Nitric Oxide Generator Based on a Structurally Deformed Nitrite-Type Layered Double Hydroxide

The inhalation of nitric oxide (NO), which acts as a selective vasodilator of pulmonary blood vessels, is an established medical treatment. However, its wide adoption has been limited by the lack of a convenient delivery technique of this unstable gas. Here we report that a solid mixture of Fe^IISO₄·7H₂O and a layered double hydroxide (LDH) containing nitrite (NO₂^-) in the interlayer spaces (NLDH) stably generates NO at a therapeutic level (∼40 ppm over 12 h from freshly mixed solids; ∼80 ppm for 5-10 h from premixed solids) under air flow (0.25 L min^-1) if the NLDH has been prepared by using a reconstruction method. Mg/Al-type LDH was calcined at 550 °C to remove interlayer CO₃^2- and then treated with NaNO₂ in water to reconstruct the NLDH. This one-pot, organic solvent-free process can be performed at large scales and is suitable for mass production. Humid air promotes anion exchange between NO₂^- and SO₄^2- in the solid mixture, resulting in persistent interactions of NO₂^- and Fe²⁺, generating NO. In contrast to the previously reported NLDH prepared using an anion-exchange method, the reconstructed NLDH exhibits stable and persistent generation of NO because of partial deformation of the layered structures (e.g., particle aggregation, reduced crystallinity, and enhanced basicity). Degradation of the solid mixture is suppressed under dry conditions, so that a portable cartridge column that is readily available as an NO source for emergency situations can be prepared. This work demonstrates that the interlayer nanospace of LDH serves as a reaction mediator for excellent controllability of solid-state reactions. This inexpensive and disposable NO generator will facilitate NO inhalation therapy in developing countries and nonhospital locations.

Amperometric Sensing of Carbon Monoxide: Improved Sensitivity and Selectivity via Nanostructure-Controlled Electrodeposition of Gold

A series of gold (Au) nanostructures, having different morphologies, were fabricated for amperometric selective detection of carbon monoxide (CO), a biologically important signaling molecule. Au layers were electrodeposited from a precursor solution of 7 mM HAuCl4 with a constant deposition charge (0.04 C) at various deposition potentials. The obtained Au nanostructures became rougher and spikier as the deposition potential lowered from 0.45 V to 0.05 V (vs. Ag/AgCl). As prepared Au layers showed different hydrophobicity: The sharper morphology, the greater hydrophobicity. The Au deposit formed at 0.05 V had the sharpest shape and the greatest surface hydrophobicity. The sensitivity of an Au deposit for amperometric CO sensing was enhanced as the Au surface exhibits higher hydrophobicity. In fact, CO selectivity over common electroactive biological interferents (L-ascorbic acid, 4-acetamidophenol, 4-aminobutyric acid and nitrite) was improved eminently once the Au deposit became more hydrophobic. The most hydrophobic Au was also confirmed to sense CO exclusively without responding to nitric oxide, another similar gas signaling molecule, in contrast to a hydrophobic platinum (Pt) counterpart. This study presents a feasible strategy to enhance the sensitivity and selectivity for amperometric CO sensing via the fine control of Au electrode nanostructures.

Electrochemical Modulation of Carbon Monoxide-Mediated Cell Signaling

Despite the critical role played by carbon monoxide (CO) in physiological and pathological signaling events, current approaches to deliver this messenger molecule are often accompanied by off-target effects and offer limited control over release kinetics. To address these challenges, we develop an electrochemical approach that affords on-demand release of CO through reduction of carbon dioxide (CO2 ) dissolved in the extracellular space. Electrocatalytic generation of CO by cobalt phthalocyanine molecular catalysts modulates signaling pathways mediated by a CO receptor soluble guanylyl cyclase. Furthermore, by tuning the applied voltage during electrocatalysis, we explore the effect of the CO release kinetics on CO-dependent neuronal signaling. Finally, we integrate components of our electrochemical platform into microscale fibers to produce CO in a spatially-restricted manner and to activate signaling cascades in the targeted cells. By offering on-demand local synthesis of CO, our approach may facilitate the studies of physiological processes affected by this gaseous molecular messenger.

Gasotransmitters for the Therapeutic Prevention of Hypertension and Kidney Disease

Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S), three major gasotransmitters, are involved in pleiotropic biofunctions. Research on their roles in hypertension and kidney disease has greatly expanded recently. The developing kidney can be programmed by various adverse in utero conditions by so-called renal programming, giving rise to hypertension and kidney disease in adulthood. Accordingly, early gasotransmitter-based interventions may have therapeutic potential to revoke programming processes, subsequently preventing hypertension and kidney disease of developmental origins. In this review, we describe the current knowledge of NO, CO, and H₂S implicated in pregnancy, including in physiological and pathophysiological processes, highlighting their key roles in hypertension and kidney disease. We summarize current evidence of gasotransmitter-based interventions for prevention of hypertension and kidney disease in animal models. Continued study is required to assess the interplay among the gasotransmitters NO, CO, and H₂S and renal programming, as well as a greater focus on further clinical translation.

Circulating levels of hydrogen sulphide negatively correlate to nitrite levels in gestational hypertensive and preeclamptic pregnant women

Endothelial dysfunction is a hallmark of preeclampsia and the role of nitric oxide (NO) has been extensively studied in this pregnancy complication. In recent years, hydrogen sulphide (H₂ S) has arisen as a new gasotransmitter with an impact on endothelial function. However, the involvement of H₂ S in the pathophysiology of preeclampsia is not fully understood, and only a few studies with limited sample size have investigated circulating levels of H₂ S in preeclamptic patients. Moreover, H₂ S levels have not been previously evaluated in gestational hypertension. Furthermore, the relationship between H₂ S and NO in these hypertensive disorders of pregnancy has yet to be determined. We measured H₂ S levels in plasma of 120 healthy pregnant women, 88 gestational hypertensive and 62 preeclamptic women. We also measured plasma nitrite in a subset of patients and carried out correlation analysis between plasma H₂ S and nitrite in these three groups. We found that plasma H₂ S was elevated in preeclampsia and further increased in gestational hypertension compared to healthy pregnancy. Plasma nitrite was reduced in gestational hypertension and preeclampsia, and these levels were negatively correlated with H₂ S in both gestational hypertension and preeclampsia, but not in healthy pregnancy. Our results indicate that increases in H₂ S may represent a mechanism triggered as an attempt to compensate reduced NO in gestational hypertension and preeclampsia. Future studies are warranted to investigate the mechanisms underlying H₂ S/NO interaction on mediating endothelial dysfunction in these hypertensive disorders of pregnancy.

Polysulfide inhibits hypoxia-elicited hypoxia-inducible factor activation in a mitochondria-dependent manner

In cellular signaling, the diverse physiological actions of biological gases, including O₂, CO, NO, and H₂S, have attracted much interest. Hypoxia-inducible factors (HIFs), including HIF-1 and HIF-2, are transcription factors that respond to reduced intracellular O₂ availability. Polysulfides are substances containing varying numbers of sulfur atoms (H₂S_n) that are generated endogenously from H₂S by 3-mercaptopyruvate sulfurtransferase in the presence of O₂, and regulate ion channels, specific tumor suppressors, and protein kinases. However, the effect of polysulfides on HIF activation in hypoxic mammalian cells is largely unknown. Here, we have investigated the effect of polysulfide on cells in vitro. In established cell lines, polysulfide donors reversibly reduced cellular O₂ consumption and inhibited hypoxia-induced HIF-1α protein accumulation and the expression of genes downstream of HIFs; however, these effects were not observed in anoxia. In Von Hippel-Lindau tumor suppressor (VHL)- and mitochondria-deficient cells, polysulfides did not affect HIF-1α protein synthesis but destabilized it in a VHL- and mitochondria-dependent manner. For the first time, we show that polysulfides modulate intracellular O₂ homeostasis and regulate HIF activation and subsequent hypoxia-induced gene expression in a VHL- and mitochondria-dependent manner.

Cardiac function dependence on carbon monoxide

Nitric oxide, studied to evaluate its role in cardiovascular physiology, has cardioprotective and therapeutic effects in cellular signaling, mitochondrial function, and in regulating inflammatory processes. Heme oxygenase (major role in catabolism of heme into biliverdin, carbon monoxide (CO), and iron) has similar effects as well. CO has been suggested as the molecule that is responsible for many of the above mentioned cytoprotective and therapeutic pathways as CO is a signaling molecule in the control of physiological functions. This is counterintuitive as toxic effects are related to its binding to hemoglobin. However, CO is normally produced in the body. Experimental evidence indicates that this toxic gas, CO, exerts cytoprotective properties related to cellular stress including the heart and is being assessed for its cytoprotective and cytotherapeutic properties. While survival of adult cardiomyocytes depends on oxidative phosphorylation (survival and resulting cardiac function is impaired by mitochondrial damage), mitochondrial biogenesis is modified by the heme oxygenase-1/CO system and can result in promotion of mitochondrial biogenesis by associating mitochondrial redox status to the redox-active transcription factors. It has been suggested that the heme oxygenase-1/CO system is important in differentiation of embryonic stem cells and maturation of cardiomyocytes which is thought to mitigate progression of degenerative cardiovascular diseases. Effects on other cardiac cells are being studied. Acute exposure to air pollution (and, therefore, CO) is associated with cardiovascular mortality, myocardial infarction, and heart failure, but changes in the endogenous heme oxygenase-1 system (and, thereby, CO) positively affect cardiovascular health. We will review the effect of CO on heart health and function in this article.

Novel Hydrogen Sulfide (H2S)-Releasing BW-HS-101 and Its Non-H2S Releasing Derivative in Modulation of Microscopic and Molecular Parameters of Gastric Mucosal Barrier

Hydrogen sulfide (H2S) is an endogenously produced molecule with anti-inflammatory and cytoprotective properties. We aimed to investigate for the first time if a novel, esterase-sensitive H2S-prodrug, BW-HS-101 with the ability to release H2S in a controllable manner, prevents gastric mucosa against acetylsalicylic acid-induced gastropathy on microscopic and molecular levels. Wistar rats were pretreated intragastrically with vehicle, BW-HS-101 (0.5-50 μmol/kg) or its analogue without the ability to release H2S, BW-iHS-101 prior to ASA administration (125 mg/kg, intragastrically). BW-HS-101 was administered alone or in combination with nitroarginine (L-NNA, 20 mg/kg, intraperitoneally) or zinc protoporphyrin IX (10 mg/kg, intraperitoneally). Gastroprotective effects of BW-HS-101 were additionally evaluated against necrotic damage induced by intragastrical administration of 75% ethanol. Gastric mucosal damage was assessed microscopically, and gastric blood flow was determined by laser flowmetry. Gastric mucosal DNA oxidation and PGE2 concentration were assessed by ELISA. Serum and/or gastric protein concentrations of IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, IL-13, VEGF, GM-CSF, IFN-γ, TNF-α, and EGF were determined by a microbeads/fluorescent-based multiplex assay. Changes in gastric mucosal iNOS, HMOX-1, SOCS3, IL1-R1, IL1-R2, TNF-R2, COX-1, and COX-2 mRNA were assessed by real-time PCR. BW-HS-101 or BW-iHS-101 applied at a dose of 50 μmol/kg protected gastric mucosa against ASA-induced gastric damage and prevented a decrease in the gastric blood flow level. H2S prodrug decreased DNA oxidation, systemic and gastric mucosal inflammation with accompanied upregulation of SOCS3, and EGF and HMOX-1 expression. Pharmacological inhibition of nitric oxide (NO) synthase but not carbon monoxide (CO)/heme oxygenase (HMOX) activity by L-NNA or ZnPP, respectively, reversed the gastroprotective effect of BW-HS-101. BW-HS-101 also protected against ethanol-induced gastric injury formation. We conclude that BW-HS-101, due to its ability to release H2S in a controllable manner, prevents gastric mucosa against drugs-induced gastropathy, inflammation and DNA oxidation, and upregulate gastric microcirculation. Gastroprotective effects of this H2S prodrug involves endogenous NO but not CO activity and could be mediated by cytoprotective and anti-inflammatory SOCS3 and EGF pathways.

Hydrogen Sulfide and Carbon Monoxide Tolerance in Bacteria

Hydrogen sulfide and carbon monoxide share the ability to be beneficial or harmful molecules depending on the concentrations to which organisms are exposed. Interestingly, humans and some bacteria produce small amounts of these compounds. Since several publications have summarized the recent knowledge of its effects in humans, here we have chosen to focus on the role of H₂S and CO on microbial physiology. We briefly review the current knowledge on how bacteria produce and use H₂S and CO. We address their potential antimicrobial properties when used at higher concentrations, and describe how microbial systems detect and survive toxic levels of H₂S and CO. Finally, we highlight their antimicrobial properties against human pathogens when endogenously produced by the host and when released by external chemical donors.

New possible silver lining for pancreatic cancer therapy: Hydrogen sulfide and its donors

As one of the most lethal diseases, pancreatic cancer shows a dismal overall prognosis and high resistance to most treatment modalities. Furthermore, pancreatic cancer escapes early detection during the curable period because early symptoms rarely emerge and specific markers for this disease have not been found. Although combinations of new drugs, multimodal therapies, and adjuvants prolong survival, most patients still relapse after surgery and eventually die. Consequently, the search for more effective treatments for pancreatic cancer is highly relevant and justified. As a newly re-discovered mediator of gasotransmission, hydrogen sulfide (H₂S) undertakes essential functions, encompassing various signaling complexes that occupy key processes in human biology. Accumulating evidence indicates that H₂S exhibits bimodal modulation of cancer development. Thus, endogenous or low levels of exogenous H₂S are thought to promote cancer, whereas high doses of exogenous H₂S suppress tumor proliferation. Similarly, inhibition of endogenous H₂S production also suppresses tumor proliferation. Accordingly, H₂S biosynthesis inhibitors and H₂S supplementation (H₂S donors) are two distinct strategies for the treatment of cancer. Unfortunately, modulation of endogenous H₂S on pancreatic cancer has not been studied so far. However, H₂S donors and their derivatives have been extensively studied as potential therapeutic agents for pancreatic cancer therapy by inhibiting cell proliferation, inducing apoptosis, arresting cell cycle, and suppressing invasion and migration through exploiting multiple signaling pathways. As far as we know, there is no review of the effects of H₂S donors on pancreatic cancer. Based on these concerns, the therapeutic effects of some H₂S donors and NO–H₂S dual donors on pancreatic cancer were summarized in this paper. Exogenous H₂S donors may be promising compounds for pancreatic cancer treatment.

Palladium Probe Consisting of Naphthalimide and Ethylenediamine for Selective Turn-On Sensing of CO and Cell Imaging

An assay to detect carbon monoxide (CO), one of the gaseous signaling molecules, has been prepared using a new palladium complex probe. The ethylenediamine group linked to the naphthalimide fluorophore coordinates to Pd(II) which intramolecularly quenches the emission. Upon treatment with CO, the absorbance of the turn-on fluorescent sensor changes due to the formation of a complex between Pd(II) and CO at room temperature in a phosphate buffer. As the concentration of CO increases, the probe peak emission intensity at 527 nm gradually increases. Other analyte controls, such as K⁺, Mg²⁺, Al³⁺, Zn²⁺, Cr³⁺, Hg²⁺, Fe³⁺, alanine, glycine, leucine, lysine, serine, threonine, tyrosine, F^-, Cl^-, Br^-, NO, NO₂^-, NO₃^-, HCO₃^-, CH₃COO^-, H₂O₂, ^•OH, and ^tBuOO^•, exhibit no significant effect on emission intensity. The response time of the probe to CO was quite fast because of the relatively weak coordination of Pd(II) to the pendent ethylenediamine group. The Pd probe is capable of detecting CO in aqueous buffer as well as in living cells with high selectivity and stability, providing a potential real-time indicator for studying CO-involved reactions in biological systems.

Direct Targets and Subsequent Pathways for Molecular Hydrogen to Exert Multiple Functions: Focusing on Interventions in Radical Reactions

Molecular hydrogen (H₂) was long regarded as non-functional in mammalian cells. We overturned the concept by demonstrating that H₂ exhibits antioxidant effects and protects cells against oxidative stress. Subsequently, it has been revealed that H₂ has multiple functions in addition to antioxidant effects, including antiinflammatory, anti-allergic functions, and as cell death and autophagy regulation. Additionally, H₂ stimulates energy metabolism. As H₂ does not readily react with most biomolecules without a catalyst, it is essential to identify the primary targets with which H₂ reacts or interacts directly. As a first event, H₂ may react directly with strong oxidants, such as hydroxyl radicals (•OH) in vivo. This review addresses the key issues related to this in vivo reaction. •OH may have a physiological role because it triggers a free radical chain reaction and may be involved in the regulation of Ca2+- or mitochondrial ATP-dependent K+-channeling. In the subsequent pathway, H₂ suppressed a free radical chain reaction, leading to decreases in lipid peroxide and its end products. Derived from the peroxides, 4-hydroxy-2-nonenal functions as a mediator that up-regulates multiple functional PGC-1α. As the other direct target in vitro and in vivo, H₂ intervenes in the free radical chain reaction to modify oxidized phospholipids, which may act as an antagonist of Ca2+-channels. The resulting suppression of Ca2+-signaling inactivates multiple functional NFAT and CREB transcription factors, which may explain H₂ multi-functionality. This review also addresses the involvement of NFAT in the beneficial role of H₂ in COVID-19, Alzheimer's disease and advanced cancer. We discuss some unsolved issues of H₂ action on lipopolysaccharide signaling, MAPK and NF-κB pathways and the Nrf2 paradox. Finally, as a novel idea for the direct targeting of H2, this review introduces the possibility that H₂ causes structural changes in proteins via hydrate water changes.

Inhaled Gases as Therapies for Post-Cardiac Arrest Syndrome: A Narrative Review of Recent Developments

Despite recent advances in the management of post-cardiac arrest syndrome (PCAS), the survival rate, without neurologic sequelae after resuscitation, remains very low. Whole-body ischemia, followed by reperfusion after cardiac arrest (CA), contributes to PCAS, for which established pharmaceutical interventions are still lacking. It has been shown that a number of different processes can ultimately lead to neuronal injury and cell death in the pathology of PCAS, including vasoconstriction, protein modification, impaired mitochondrial respiration, cell death signaling, inflammation, and excessive oxidative stress. Recently, the pathophysiological effects of inhaled gases including nitric oxide (NO), molecular hydrogen (H₂), and xenon (Xe) have attracted much attention. Herein, we summarize recent literature on the application of NO, H₂, and Xe for treating PCAS. Recent basic and clinical research has shown that these gases have cytoprotective effects against PCAS. Nevertheless, there are likely differences in the mechanisms by which these gases modulate reperfusion injury after CA. Further preclinical and clinical studies examining the combinations of standard post-CA care and inhaled gas treatment to prevent ischemia-reperfusion injury are warranted to improve outcomes in patients who are being failed by our current therapies.

Clinical Significance of CBS and CCL21 in Gallbladder Adenocarcinomas and Squamous Cell/Adenosquamous Carcinomas

Gallbladder cancer (GBC) is a rare disease with high mortality. However, no biomarkers for the carcinogenesis, progression, prognosis, and early diagnosis are clinically available. This study investigated the expressions of cystathionine-β-synthase (CBS) and C-C chemokine receptor 7 (CCR7) protein and their clinical and pathologic significances in gallbladder squamous cell/adenosquamous carcinomas (SC/ASC) and adenocarcinomas (AC). CBS and chemokine ligand 21 (CCL21) expression was measured using immunohistochemistry in 69 SC/ASCs and 146 ACs. A significantly high percentage of patients with an age above 45 years, lymph node metastasis, and invasion was observed in the SCs/ASCs compared with ACs (P<0.05). Both AC and SC/ASC patients with positive CBS and CCL21 expression exhibited a high tumor-lymph node-metastasis stage, lymph node metastasis, and invasion compared with patients with negative CBS and CCL21 expression (P<0.05 or P<0.01). SC/ASC patients with positive CBS expression was prone to have a larger tumor size than those with negative expression (P<0.05). Positive CBS and CCL21 expression correlated with poor differentiation and larger tumor size in AC patients. Positive CBS and CCL21 are closely associated with a decreased overall survival in SC/ASC and AC patients (P<0.05 or P<0.01) and were independent factors for a poor-prognosis. Both CBS and CCL21 showed a good overall diagnostic performance for SC/ASC (AUC=0.742 and AUC=0.764, respectively) and AC (AUC=0.734 and AUC=0.718, respectively). In conclusion, positive CBS and CCL21 expression are closely associated with the clinical severity and poor prognosis in GBC, and can be a marker for the diagnosis of AC and SC/ASC type of GBC.

Generation of Rat Monoclonal Antibody to Detect Hydrogen Sulfide and Polysulfides in Biological Samples

Hydrogen sulfide (H₂S) is endogenously produced by enzymes and via reactive persulfide/polysulfide degradation; it participates in a variety of biological processes under physiological and pathological conditions. H₂S levels in biological fluids, such as plasma and serum, are correlated with the severity of various diseases. Therefore, development of a simple and selective H₂S measurement method would be advantageous. This study aimed to generate antibodies specifically recognizing H₂S derivatives and develop a colorimetric immunoassay for measuring H₂S in biological samples. We used N-ethylmaleimide (NEM) as an H₂S detection agent that forms a stable bis-S-adduct (NEM-S-NEM). We also prepared bis-S-heteroadduct with 3-maleimidopropionic acid, which, in conjugation with bovine serum albumin, was to immunize Japanese white rabbits and Wistar rats to enable generation of polyclonal and monoclonal antibodies, respectively. The generated antibodies were evaluated by competitive enzyme-linked immunosorbent assay. We could obtain two stable hybridoma cell lines producing monoclonal antibodies specific for NEM-S-NEM. By immunoassay with the monoclonal antibody, the H₂S level in mouse plasma was determined as 0.2 μM, which was identical to the level detected by mass spectrometry. Taken together, these monoclonal antibodies can be a useful tool for a simple and highly selective immunoassay to detect H₂S in biological samples.

A simple method for the preparation and injection of gas mixtures into a gas chromatograph using a two-component device

Environmental sciences are expanding and are based on standardized and certified calibrations when measurements are required. When a gaseous composition is quantified, commercial standards are used. Here, we report on a two-component device for the preparation and injection of gas mixtures at the appropriate levels of pressure and volume. The two-component calibrator/injector can be used simultaneously or separately depending on the experimental objective but their combination is extremely effective for injecting gas mixtures at low concentrations. The quantity of gas introduced into a gas chromatograph with the injector can be adapted to the sensitivity of the detector or to avoid column overload. The calibrator provides for a large range of gas-mixture concentrations, from ppm to % mol/mol with an error of preparation of around 1% and an accuracy of less than 3%. This device prepares a variety of gas mixtures (hydrogen, methane and dioxide of carbon) which are compared with certified mixtures by means of gas chromatographic measurements. The results show good agreement between prepared and certified mixtures with a maximum difference of 2% which remains within the relative error of commercial standard. In addition, the preparation of dissolved methane at different concentrations in seawater is presented as a direct application of the calibrator.

Coronary and cerebral metabolism-blood flow coupling and pulmonary alveolar ventilation-blood flow coupling may be disabled during acute carbon monoxide poisoning

Current evidence indicates that the toxicity of carbon monoxide (CO) poisoning results from increases in reactive oxygen species (ROS) generation plus tissue hypoxia resulting from decreases in capillary Po₂ evoked by effects of increases in blood [carboxyhemoglobin] on the oxyhemoglobin dissociation curve. There has not been consideration of how increases in Pco could influence metabolism-blood flow coupling, a physiological mechanism that regulates the uniformity of tissue Po₂, and alveolar ventilation-blood flow coupling, a mechanism that increases the efficiency of pulmonary O₂ uptake. Using published data, I consider hypotheses that these coupling mechanisms, triggered by O₂ and CO sensors located in arterial and arteriolar vessels in the coronary and cerebral circulations and in lung intralobar arteries, are disrupted during acute CO poisoning. These hypotheses are supported by calculations that show that the Pco in these vessels can reach levels during CO poisoning that would exert effects on signal transduction molecules involved in these coupling mechanisms.NEW & NOTEWORTHY This article introduces and supports a postulate that the tissue hypoxia component of carbon monoxide poisoning results in part from impairment of physiological adaptation mechanisms whereby tissues can match regional blood flow to O₂ uptake, and the lung can match regional blood flow to alveolar ventilation.

Increased expression of cystathionine beta-synthase and chemokine ligand 21 is closely associated with poor prognosis in extrahepatic cholangiocarcinoma

The expression of Cystathionine beta-synthase (CBS) and Chemokine ligand 21 (CCL21) is associated with the tumorigenesis and progression of a variety of tumors, but whether alterations in their expression levels correlates with the carcinogenesis and progression of EHCC is still unknown. This study investigated the clinicopathological significance of CBS and CCL21 expression in EHCC.We investigated the correlations between the expression of CBS and CCL21 and clinicopathological characteristics in EHCC using EnVision immunohistochemistry.The expression of CBS and CCL21 was significantly higher in EHCC tumors than in nontumor tissues (P < .05 and P < .01). EHCC patients with CBS and CCL21 expression combined with lymph node metastasis, tumor cell invasion, and TNM III/IV stage had more severe conditions than those with no lymph node metastasis, distant invasion and TNM I/II stage (P < .01). Kaplan-Meier survival analysis showed that the overall survival rates for EHCC patients with negative CBS or CCL21 reaction were significantly higher than those for patients with positive CBS or CCL21 reaction((P < .01). CBS or CCL21 expression was revealed as an independent poor prognostic factor for EHCC patients by Cox multivariate analysis.The present study indicates that CBS and CCL21 expression is closely associated with the pathogenesis of clinical, pathological and biological behaviors and poor prognosis in EHCC.

Heme is required for carbon monoxide activation of mitochondrial BKCa channel

Carbon monoxide (CO) is an endogenously synthesized gaseous mediator and is involved in the regulation of numerous physiological processes. Mitochondria, in which hemoproteins are abundant, are among the targets for CO action. Large-conductance calcium-activated (mitoBK_Ca) channels in the inner mitochondrial membrane share multiple biophysical similarities with the BK_Ca channels of the plasma membrane and could be a potential target for CO. To test this hypothesis, the activity of the mitoBK_Ca channels in human astrocytoma U-87 MG cell mitochondria was assessed with the patch-clamp technique. The effects of CO-releasing molecules (CORMs), such as CORM-2, CORM-401, and CORM-A1, were compared to the application of a CO-saturated solution to the mitoBK_Ca channels in membrane patches. The applied CORMs showed pleiotropic effects including channel inhibition, while the CO-containing solution did not significantly modulate channel activity. Interestingly, CO applied to the mitoBK_Ca channels, which were inhibited by exogenously added heme, stimulated the channel. To summarize, our findings indicate a requirement of heme binding to the mitoBK_Ca channel for channel modulation by CO and suggest that CORMs might have complex unspecific effects on mitoBK_Ca channels.

Physiological response and transcription profiling analysis reveal the role of glutathione in H2S-induced chilling stress tolerance of cucumber seedlings

Recent reports have uncovered the multifunctional role of H₂S in the physiological response of plants to biotic and abiotic stresses. Here, we studied whether NaHS (an H₂S donor) pretreatment could provoke the tolerance of cucumber (Cucumis sativus L.) seedlings subsequently exposed to chilling stress and whether glutathione was involved in this process. Results showed that cucumber seedlings sprayed with NaHS exhibited remarkably increased chilling tolerance, as evidenced by the observed plant tolerant phenotype, as well as the lower levels of electrolyte leakage (EL), malondialdehyde (MDA) content, hydrogen peroxide (H₂O₂) content and RBOH mRNA abundance, compared with the control plants. In addition, NaHS treatment increased the endogenous content of the reduced glutathione (GSH) and the ratio of reduced/oxidized glutathione (GSH/GSSG), meanwhile, the higher net photosynthetic rate (Anet), the light-saturated CO₂ assimilation rate (Asat), the photochemical efficiency (Fv/Fm) and the maximum photochemical efficiency of PSII in darkness (ФPSII) as well as the mRNA levels and activities of the key photosynthetic enzymes (Rubisco, TK, SBPase and FBA) were observed in NaHS-treated seedlings under chilling stress, whereas this effect of NaHS was weakened by buthionine sulfoximine (BSO, an inhibitor of glutathione) or 6-Aminonicotinamide (6-AN, a specific pentose inhibitor and thus inhibits the NADPH production), which preliminarily proved the interaction between H₂S and GSH. Moreover, transcription profiling analysis revealed that the GSH-associated genes (GST Tau, MAAI, APX, GR, GS and MDHAR) were significantly up-regulated in NaHS-treated cucumber seedlings, compared to the H₂O-treated seedlings under chilling stress. Thus, novel results highlight the importance of glutathione as a downstream signal of H₂S-induced plant tolerance to chilling stress.

Controlled release of H2S and NO gases through CO2-stimulated anion exchange

Difficulties related to handling gases are a common bottleneck for applications. Although solid materials that release gas molecules under external stimuli exist, they require an external energy or a device for reliable operation. Herein, we report a CO₂ stimulus for controlled release of p.p.m.-level functional gases from solid materials. A CO₂-preferential anion-exchange property of layered double hydroxides and redox reactions in gas molecules are combined to release various gases (including H₂S and NO) under ambient air from HS⁻ and NO₂⁻-incorporated layered double hydroxides, respectively. The profiles of gas release are mainly governed by the difference of pK_a between H₂CO₃ and resulting acids (formed through protonation of interlayer anions), and are not so susceptible to the variation of relative humidity in air. Moreover, structural modulation of solid materials enables fine control of the gas release profiles. The use of safe, ubiquitous, and nearly constant (~400 p.p.m. in atmosphere) CO₂ stimulus offers broad applications for functional gases.

Solid materials releasing gas molecules under external stimuli usually require external energy for reliable operation. Here the authors synthesize layered double hydroxides for the autonomous release of H₂S and NO gases in response to CO₂-stimulus.

Modulation of oxidative–nitrosative stress and inflammatory response by rapamycin in target and distant organs in rats exposed to hindlimb ischemia–reperfusion: the role of mammalian target of rapamycin

Mammalian target of rapamycin (mTOR) has been recognized with potential immunomodulatory properties playing an important role in various physiopathological processes including ischemia–reperfusion (I/R) injury. I/R injury stimulate reactive oxygen and nitrogen species by activating nicotinamide adenine dinucleotide phosphate oxidase and inducible nitric oxide synthase, respectively. Controversial results have been obtained in different I/R models following localized I/R; however, the precise role of the mTOR signaling pathway remains undefined. The objective of the current study was to evaluate the role of the mTOR in oxidative–nitrosative stress and inflammation in hindlimb I/R-induced injury in target and remote organ injuries. In rats subjected to I/R, an increased expression of ribosomal protein S6 (rpS6), inhibitor κB (IκB)-α, nuclear factor-κB (NF-κB) p65, inducible nitric oxide synthase, cyclooxygenase 2, gp91phox, and levels of tumor necrosis factor α, nitrite, nitrotyrosine, malondialdehyde and the activities of myeloperoxidase and catalase in the tissues and (or) sera were detected. Treatment with rapamycin, a selective inhibitor of mTOR, reversed all the I/R-induced changes as manifested by its anti-inflammatory and antioxidant effects in kidney and gastrocnemius muscle of rats. Collectively, these findings suggest that rapamycin protects against I/R-induced oxidative–nitrosative stress and inflammation leading to organ injuries via suppression of mTOR/IκB-α/NF-κB signaling pathway.

Hydrogen Sulfide: Emerging Role in Bladder, Kidney, and Prostate Malignancies

Hydrogen sulfide (H₂S) is the latest member of the gasotransmitter family and known to play essential roles in cancer pathophysiology. H₂S is produced endogenously and can be administered exogenously. Recent studies showed that H₂S in cancers has both pro- and antitumor roles. Understanding the difference in the expression and localization of tissue-specific H₂S-producing enzymes in healthy and cancer tissues allows us to develop tools for cancer diagnosis and treatment. Urological malignancies are some of the most common cancers in both men and women, and their early detection is vital since advanced cancers are recurrent, metastatic, and often resistant to treatment. This review summarizes the roles of H₂S in cancer and looks at current studies investigating H₂S activity and expression of H₂S-producing enzymes in urinary cancers. We specifically focused on urothelial carcinoma, renal cell carcinoma, and prostate cancer, as they form the majority of newly diagnosed urinary cancers. Recent studies show that besides the physiological activity of H₂S in cancer cells, there are patterns between the development and prognosis of urinary cancers and the expression of H₂S-producing enzymes and indirectly the H₂S levels. Though controversial and not completely understood, studying the expression of H₂S-producing enzymes in cancer tissue may represent an avenue for novel diagnostic and therapeutic strategies for addressing urological malignancies.

Systemic Administration of Carbon Monoxide-Releasing Molecule-3 Protects the Skeletal Muscle in Porcine Model of Compartment Syndrome

OBJECTIVES

Acute limb compartment syndrome, a complication of musculoskeletal trauma, results in muscle necrosis and cell death. Carbon monoxide, liberated from the carbon monoxide-releasing molecule-3, has been shown protective in a rat model of compartment syndrome. The purpose of this study was to test the effect of carbon monoxide-releasing molecule-3 in a preclinical large animal model of compartment syndrome, with the ultimate goal of developing a pharmacologic adjunct treatment for compartment syndrome.

DESIGN

Animal research study.

SETTING

Basic research laboratory in a hospital setting.

SUBJECTS

Male Yorkshire-Landrace pigs (50-60 kg).

INTERVENTIONS

Pigs underwent 6 hours of intracompartmental pressure elevation by infusing fluid into the anterior compartment of the right hind limb. Carbon monoxide-releasing molecule-3 was administered systemically (2 mg/kg, IV) at fasciotomy, followed by 3-hour reperfusion.

MEASUREMENTS AND MAIN RESULTS

Muscle perfusion, inflammation, injury, and apoptosis were assessed in the skeletal muscle. Systemic leukocyte activation was assessed during compartment syndrome and reperfusion. Elevation of hind limb intracompartmental pressure resulted in significant microvascular perfusion deficits (44% ± 1% continuously perfused capillaries in compartment syndrome vs 76% ± 4% in sham; p < 0.001), increased tissue injury (ethidium bromide/bisbenzimide of 0.31 ± 0.07 in compartment syndrome vs 0.17 ± 0.03 in sham; p < 0.05), apoptosis (fluorescence in vivo/bisbenzimide of 0.26 ± 0.06 in compartment syndrome vs 0.13 ± 0.03 in sham; p < 0.05), and systemic leukocyte activation (14.7 relative luminescence units/10 polymorphonuclear leukocytes in compartment syndrome vs 1.0 ± 0.1 in baseline; p < 0.001). Systemic application of carbon monoxide-releasing molecule-3 at fasciotomy increased the number of continuously perfused capillaries (68% ± 3%; p < 0.001), diminished tissue injury (ethidium bromide/bisbenzimide of 0.13 ± 0.04; p < 0.05), apoptosis (fluorescence in vivo/bisbenzimide of 0.12 ± 0.03; p < 0.05), and blocked systemic leukocyte activation (3.9 ± 0.3 relative luminescence unit/10 polymorphonuclear leukocytes; p < 0.001).

CONCLUSIONS

Administration of carbon monoxide-releasing molecule-3 at fasciotomy offered protection against compartment syndrome-induced microvascular perfusion deficit, tissue injury, and systemic leukocyte activation. The data suggest the potential therapeutic application of carbon monoxide-releasing molecule-3 to patients at risk of developing compartment syndrome.

Exhaled carbon monoxide levels correlate with incidence of oral mucosal lesions independent of smoking status

Carbon monoxide (CO) is an important component of tobacco smoke, but also environmental toxicity. This study analyzed possible correlation between exhaled CO level and oral health indicators in two geographically distributed populations during health-promoting public events organized for local communities in cities with high and low environmental pollution in Poland (907 patients). Self-reported, instructor-led, oral health questionnaire was developed to monitor current and previous mucosal lesion incidence. Exhaled CO correlated with subjects smoking status and environmental CO exposure: highest in smoking inhabitants of Krakow (12 ppm), with lower levels in smokers from Kozienice (6.5 ppm) and non-smokers from Krakow (6 ppm), and lowest for Kozienice non-smokers (2 ppm) (p < 0.001). After propensity score matching and adjustment for smoking status, demography and comorbidities odds ratio for mucosal lesion incidence was 1.46 (1.31-1.63), p < 0.001) per 1 ppm increase of exhaled CO level. This result might implicate a possible role of environmental pollution factors in oral health pathology.

Air pollution may affect the assessment of smoking habits by exhaled carbon monoxide measurements

BACKGROUND

While European air quality policies reduce ambient carbon monoxide (CO) concentrations in general, there are still areas affected by high environmental CO exposure from transportation, industry and burning low-quality fossil fuels. We investigated, how these CO amounts might influence exhaled CO measurements used to monitor the smoking status of healthy subjects.

METHODS

A cross-sectional study of healthy adults living in areas of high air pollution (N = 742) and low air pollution (N = 197) in Poland. They completed a survey regarding their smoking habits and underwent necessary body measurements including exhaled CO concentration levels.

RESULTS

Ambient CO levels were much higher in highly pollutes cities. Also exhaled CO levels in subjects from high pollution areas were significantly higher, independent of subject smoking status (8.25 ppm vs. 3.26 ppm). Smokers exhaled more CO than non-smokers. Although the duration of smoking did not affect the CO levels, they were proportional to the number of cigarettes smoked during the day, especially for higher amounts of cigarettes and in unpolluted areas. It was possible to differentiate active from passive smokers in all areas, but the difference for passive smokers vs. non-smokers was significant only in low pollution city inhabitants.

CONCLUSIONS

Exhaled CO levels were confirmed to be a good indicator of smoking status and smoking pattern in healthy subjects. However, high environmental CO levels both increase baseline exhaled CO concentrations in non-smokers affecting their discrimination from passive smokers, and obscure categorizing cigarette consumption in heavy smokers. These findings add important evidence on both understanding of exhaled CO monitoring results and a significance of environmental CO exposure in areas with high pollution.