The effects of therapeutic sulfide on myocardial apoptosis in response to ischemia-reperfusion injury

Hydrogen sulfide (H2S) releasing agents: chemistry and biological applications

Hydrogen sulfide (H2S) is a newly recognized signaling molecule with very potent cytoprotective actions. The fields of H2S physiology and pharmacology have been rapidly growing in recent years, but a number of fundamental issues must be addressed to advance our understanding of the biology and clinical potential of H2S in the future. Hydrogen sulfide releasing agents (also known as H2S donors) have been widely used in these fields. These compounds are not only useful research tools, but also potential therapeutic agents. It is therefore important to study the chemistry and pharmacology of exogenous H2S and to be aware of the limitations associated with the choice of donors used to generate H2S in vitro and in vivo. In this review we summarized the developments and limitations of currently available donors including H2S gas, sulfide salts, garlic-derived sulfur compounds, Lawesson's reagent/analogs, 1,2-dithiole-3-thiones, thiol-activated donors, photo-caged donors, and thioamino acids. Some biological applications of these donors were also discussed.

Role of Hydrogen Sulfide in Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury is one of the major causes of high morbidity, disability, and mortality in the world. I/R injury remains a complicated and unresolved situation in clinical practice, especially in the field of solid organ transplantation. Hydrogen sulfide (H₂S) is the third gaseous signaling molecule and plays a broad range of physiological and pathophysiological roles in mammals. H₂S could protect against I/R injury in many organs and tissues, such as heart, liver, kidney, brain, intestine, stomach, hind-limb, lung, and retina. The goal of this review is to highlight recent findings regarding the role of H₂S in I/R injury. In this review, we present the production and metabolism of H₂S and further discuss the effect and mechanism of H₂S in I/R injury.

Mesoporous silica nanoparticles for glutathione-triggered long-range and stable release of hydrogen sulfide

Mesoporous silica nanoparticles (MSNs) that can stably load therapeutic drugs and release them in response to a specific trigger are of great interest in disease diagnosis and treatment. However, the controlled-release of gaseous drug molecules such as hydrogen sulfide (H₂S) from a long-range and stable MSN-based system still presents a great challenge. Herein, a MSN-based glutathione (GSH)-triggered controlled-release H₂S system has been fabricated with high entrapment efficiency (99.0 ± 0.3%) and loading content (44.2 ± 0.1%) of diallyl trisulfide (DATS). After the addition of GSH (2 mM), DATS-MSN (100 μg mL^-1) steadily releases moderate amounts of H₂S (peaking at the 4th hour, ∼60 μM) in phosphate buffer solution (PBS). The release of H₂S in plasma is similar to a physiological process (peaking at the 4th hour) and the DATS-MSN remains in the plasma of a rat's system over 9 hours without significantly affecting the blood pressure, heart rate and cardiac function. Moderate quantities of nanoparticles can be taken up by cardiomyocytes in vitro, while in vivo study shows that nanoparticles mainly accumulate in the liver and spleen, affecting the H₂S level in these organs. Furthermore, DATS-MSN shows excellent biocompatibility, as well as superior cytoprotection and an isolated heart protection effect of H₂S under ischemic/reperfusion injury. This study provides a new insight into controlled-release applications of MSN-based H₂S releasing systems both in vitro and in vivo.

The Cardioprotective Effects of Hydrogen Sulfide in Heart Diseases: From Molecular Mechanisms to Therapeutic Potential

Hydrogen sulfide (H₂S) is now recognized as a third gaseous mediator along with nitric oxide (NO) and carbon monoxide (CO), though it was originally considered as a malodorous and toxic gas. H₂S is produced endogenously from cysteine by three enzymes in mammalian tissues. An increasing body of evidence suggests the involvement of H₂S in different physiological and pathological processes. Recent studies have shown that H₂S has the potential to protect the heart against myocardial infarction, arrhythmia, hypertrophy, fibrosis, ischemia-reperfusion injury, and heart failure. Some mechanisms, such as antioxidative action, preservation of mitochondrial function, reduction of apoptosis, anti-inflammatory responses, angiogenic actions, regulation of ion channel, and interaction with NO, could be responsible for the cardioprotective effect of H₂S. Although several mechanisms have been identified, there is a need for further research to identify the specific molecular mechanism of cardioprotection in different cardiac diseases. Therefore, insight into the molecular mechanisms underlying H₂S action in the heart may promote the understanding of pathophysiology of cardiac diseases and lead to new therapeutic targets based on modulation of H₂S production.

Role of hydrogen sulfide in brain synaptic remodeling

Synapses are the functional connection between neurons which are necessary for the transfer of electric activity or chemical activity from one cell to another. Synapses are formed by the pre- and postsynaptic membrane which communicates between pre- and postneurons while a neurochemical modulator is operated in this process. H2S has been known as a toxic gas with rotten eggs smell. However, increasing number of researches show that it regulate a variety of physiological and pathological processes in mammals. Hence, H2S is a physiologically important molecule and has been referred to as the third gaseous molecule alongside carbon monoxide and nitric oxide. The previous era has made an exponential development in the physiological and pathological significance of H2S. Specifically, in the central nervous system, H2S facilitates long-term potentiation and regulates intracellular calcium concentration in brain cells. We as well as others have also shown that H2S has antioxidant, antiapoptotic, and anti-inflammatory properties against various neurodegenerative disorders such as stroke, Alzheimer's disease, and vascular dementia. In this chapter, we highlight the current knowledge of H2S and its neuroprotective effects with a special emphasis on synaptic remodeling.

Regulation of mitochondrial bioenergetic function by hydrogen sulfide. Part II. Pathophysiological and therapeutic aspects

Emerging work demonstrates the dual regulation of mitochondrial function by hydrogen sulfide (H2 S), including, at lower concentrations, a stimulatory effect as an electron donor, and, at higher concentrations, an inhibitory effect on cytochrome C oxidase. In the current article, we overview the pathophysiological and therapeutic aspects of these processes. During cellular hypoxia/acidosis, the inhibitory effect of H2 S on complex IV is enhanced, which may shift the balance of H2 S from protective to deleterious. Several pathophysiological conditions are associated with an overproduction of H2 S (e.g. sepsis), while in other disease states H2 S levels and H2 S bioavailability are reduced and its therapeutic replacement is warranted (e.g. diabetic vascular complications). Moreover, recent studies demonstrate that colorectal cancer cells up-regulate the H2 S-producing enzyme cystathionine β-synthase (CBS), and utilize its product, H2 S, as a metabolic fuel and tumour-cell survival factor; pharmacological CBS inhibition or genetic CBS silencing suppresses cancer cell bioenergetics and suppresses cell proliferation and cell chemotaxis. In the last chapter of the current article, we overview the field of H2 S-induced therapeutic 'suspended animation', a concept in which a temporary pharmacological reduction in cell metabolism is achieved, producing a decreased oxygen demand for the experimental therapy of critical illness and/or organ transplantation.

H2S during circulatory shock: some unresolved questions

Numerous papers have been published on the role of H2S during circulatory shock. Consequently, knowledge about vascular sulfide concentrations may assume major importance, in particular in the context of "acute on chronic disease", i.e., during circulatory shock in animals with pre-existing chronic disease. This review addresses the questions (i) of the "real" sulfide levels during circulatory shock, and (ii) to which extent injury and pre-existing co-morbidity may affect the expression of H2S producing enzymes under these conditions. In the literature there is a huge range on sulfide blood levels during circulatory shock, in part as a result of the different analytical methods used, but also due to the variable of the models and species studied. Clearly, some of the very high levels reported should be questioned in the context of the well-known H2S toxicity. As long as "real" sulfide levels during circulatory shock are unknown and/or undetectable "on line" due to the lack of appropriate techniques, it appears to be premature to correlate the measured blood levels of hydrogen sulfide with the severity of shock or the H2S therapy-related biological outcomes. The available data on the tissue expression of the H2S-releasing enzymes during circulatory shock suggest that a "constitutive" CSE expression may play a crucial role of for the maintenance of organ function, at least in the kidney. The data also indicate that increased CBS and CSE expression, in particular in the lung and the liver, represents an adaptive response to stress states.

A role for H2S in the microcirculation of newborns: the major metabolite of H2S (thiosulphate) is increased in preterm infants

Excessive vasodilatation during the perinatal period is associated with cardiorespiratory instability in preterm neonates. Little evidence of the mechanisms controlling microvascular tone during circulatory transition exists. We hypothesised that hydrogen sulphide (H₂S), an important regulator of microvascular reactivity and central cardiac function in adults and animal models, may contribute to the vasodilatation observed in preterm newborns. Term and preterm neonates (24–43 weeks gestational age) were studied. Peripheral microvascular blood flow was assessed by laser Doppler. Thiosulphate, a urinary metabolite of H₂S, was determined by high performance liquid chromatography as a measure of 24 hr total body H₂S turnover for the first 3 days of postnatal life. H₂S turnover was greatest in very preterm infants and decreased with increasing gestational age (p = 0.0001). H₂S turnover was stable across the first 72 hrs of life in older neonates. In very preterm neonates, H₂S turnover increased significantly from day 1 to 3 (p = 0.0001); and males had higher H₂S turnover than females (p = 0.04). A significant relationship between microvascular blood flow and H₂S turnover was observed on day 2 of postnatal life (p = 0.0004). H₂S may play a role in maintaining microvascular tone in the perinatal period. Neonates at the greatest risk of microvascular dysfunction characterised by inappropriate peripheral vasodilatation - very preterm male neonates - are also the neonates with highest levels of total body H₂S turnover suggesting that overproduction of this gasotransmitter may contribute to microvascular dysfunction in preterms. Potentially, H₂S is a target to selectively control microvascular tone in the circulation of newborns.

Discoveries of hydrogen sulfide as a novel cardiovascular therapeutic

Hydrogen sulfide (H2S) is an endogenously produced gaseous signaling molecule that elicits a number of cytoprotective effects in mammalian species. H2S was originally considered toxic at elevated levels, but 15 years ago the labile molecule was discovered in mammalian tissue and termed a gasotransmitter, thus opening the door for research aimed towards understanding its physiologic nature. Since then, novel findings have depicted the beneficial aspects of H2S therapy, such as vasodilation, antioxidant upregulation, inflammation inhibition, and activation of anti-apoptotic pathways. These cytoprotective alterations effectively treat multiple forms of cardiac injury at the preclinical level of research. The field has progressed towards instituting novel H2S donors that prove more effective at activating the subsequent cardioprotective enhancements over longer time periods. As more findings explore the efficacy of H2S, research focused on detection of sulfhydrated targets is on the rise. Understanding the molecular mechanisms that stem from H2S treatment may lead the field towards powerful therapeutics in the clinical setting. This review will discuss the cytoprotective and cardioprotective effects of H2S therapy, provide analysis on the molecular alterations that lead to these enhancements, and explore recently developed therapeutics that may bring this gasotransmitter into the clinic in the near future.

Hydrogen sulfide reduces regional myocardial ischemia injury through protection of mitochondrial function

Hydrogen sulfide (H2S) is a signaling gasotransmitter, involved in various physiological and pathological processes. H2S-donating drugs have been tested to conjugate the beneficial effects of H2S with other pharmaceutical properties. It has been shown that the endogenous cystathionine-γ-lyase (CSE)/H2S pathway participates in myocardial ischemia injury in isolated hearts in rats. The present study aimed to investigate the cytoprotective action of H2S against acute myocardial ischemia injury in rats. Isolated rat hearts were perfused and subjected to ischemic conditions for 4 h. The hearts were assigned to five groups: Sham, model, infarct plus low-dose (5 µmol/l) NaHS, infarct plus middle-dose (10 µmol/l) NaHS and infarct plus high-dose (20 µmol/l) NaHS. The administration of NaHS enhanced the activity of CSE, increased the content of H2S and reduced infarct volumes following myocardial ischemia injury. Furthermore, the administration of NaHS attenuated the injury to organelles (including the mitochondria, nucleus and myofilaments) by reducing lactate dehydrogenase activity, decreasing the level of mitochondrial malondialdehyde and increasing the activities of superoxide dismutase and glutathione peroxidase in the ischemic myocardial mitochondria. These protective effects of H2S against myocardial ischemia injury appeared to be mediated by its antioxidant activities and the preservation of mitochondrial function.

Therapeutic applications of PARP inhibitors: anticancer therapy and beyond

The aim of this article is to describe the current and potential clinical translation of pharmacological inhibitors of poly(ADP-ribose) polymerase (PARP) for the therapy of various diseases. The first section of the present review summarizes the available preclinical and clinical data with PARP inhibitors in various forms of cancer. In this context, the role of PARP in single-strand DNA break repair is relevant, leading to replication-associated lesions that cannot be repaired if homologous recombination repair (HRR) is defective, and the synthetic lethality of PARP inhibitors in HRR-defective cancer. HRR defects are classically associated with BRCA1 and 2 mutations associated with familial breast and ovarian cancer, but there may be many other causes of HRR defects. Thus, PARP inhibitors may be the drugs of choice for BRCA mutant breast and ovarian cancers, and extend beyond these tumors if appropriate biomarkers can be developed to identify HRR defects. Multiple lines of preclinical data demonstrate that PARP inhibition increases cytotoxicity and tumor growth delay in combination with temozolomide, topoisomerase inhibitors and ionizing radiation. Both single agent and combination clinical trials are underway. The final part of the first section of the present review summarizes the current status of the various PARP inhibitors that are in various stages of clinical development. The second section of the present review summarizes the role of PARP in selected non-oncologic indications. In a number of severe, acute diseases (such as stroke, neurotrauma, circulatory shock and acute myocardial infarction) the clinical translatability of PARP inhibition is supported by multiple lines of preclinical data, as well as observational data demonstrating PARP activation in human tissue samples. In these disease indications, PARP overactivation due to oxidative and nitrative stress drives cell necrosis and pro-inflammatory gene expression, which contributes to disease pathology. Accordingly, multiple lines of preclinical data indicate the efficacy of PARP inhibitors to preserve viable tissue and to down-regulate inflammatory responses. As the clinical trials with PARP inhibitors in various forms of cancer progress, it is hoped that a second line of clinical investigations, aimed at testing of PARP inhibitors for various non-oncologic indications, will be initiated, as well.

Protective effects of hydrogen sulfide against chronic alcohol intake-induced left ventricular remodeling in rats

PURPOSE

To investigate the protective effects of hydrogen sulfide (H(2)S) against chronic alcohol intake-induced left ventricular remodeling and explore the potential mechanisms involved.

METHODS

Rats were randomly divided into 4 groups: alcohol group, NaHS group, alcohol + NaHS group, and control group. The echocardiographic and morphometric studies were performed to assess left ventricular remodeling. Oxidative stress was evaluated by detecting MDA, GSH-Px, Tot-SOD, CuZn-SOD and Mn-SOD in the supernatant. Cardiomyocyte apoptotic rate was determined by flow cytometry with Annexin V/PI staining. Western blotting was conducted to detect the expression of Bcl-2 family of apoptosis regulator proteins.

RESULTS

The echocardiographic and morphometric data indicated that H(2)S has protective effects against chronic alcohol intake-induced left ventricular remodeling. Our findings showed a significant increase in MDA level and decreases in GSH-Px, Tot-SOD, CuZn-SOD and Mn-SOD activities in the alcohol group compared to the control group, while in the alcohol + NaHS group, a significant decrease in MDA level and increases in GSH-Px, Tot-SOD, CuZn-SOD and Mn-SOD activities were found compared to the alcohol group. The apoptotic rate in the alcohol group was significantly higher than in the control group, whereas apoptotic rate in the alcohol + NaHS group was significantly lower than in the alcohol group. In addition, Bcl-2 and Bcl-xL expression was upregulated and Bax expression was downregulated in the alcohol + NaHS group compared to the alcohol group.

CONCLUSIONS

Our study demonstrates that H(2)S protects against chronic alcohol intake-induced left ventricular remodeling via attenuating oxidative stress and apoptosis.

Gaseous therapeutics in acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) remain major causes of morbidity and mortality in critical care medicine despite advances in therapeutic modalities. ALI can be associated with sepsis, trauma, pharmaceutical or xenobiotic exposures, high oxygen therapy (hyperoxia), and mechanical ventilation. Of the small gas molecules (NO, CO, H₂S) that arise in human beings from endogenous enzymatic activities, the physiological significance of NO is well established, whereas that of CO or H₂S remains controversial. Recent studies have explored the potential efficacy of inhalation therapies using these small gas molecules in animal models of ALI. NO has vasoregulatory and redox-active properties and can function as a selective pulmonary vasodilator. Inhaled NO (iNO) has shown promise as a therapy in animal models of ALI including endotoxin challenge, ischemia/reperfusion (I/R) injury, and lung transplantation. CO, another diatomic gas, can exert cellular tissue protection through antiapoptotic, anti-inflammatory, and antiproliferative effects. CO has shown therapeutic potential in animal models of endotoxin challenge, oxidative lung injury, I/R injury, pulmonary fibrosis, ventilator-induced lung injury, and lung transplantation. H₂S, a third potential therapeutic gas, can induce hypometabolic states in mice and can confer both pro- and anti-inflammatory effects in rodent models of ALI and sepsis. Clinical studies have shown variable results for the efficacy of iNO in lung transplantation and failure for this therapy to improve mortality in ARDS patients. No clinical studies have been conducted with H₂S. The clinical efficacy of CO remains unclear and awaits further controlled clinical studies in transplantation and sepsis.

Hydrogen sulfide preconditioning protects rat liver against ischemia/reperfusion injury by activating Akt-GSK-3β signaling and inhibiting mitochondrial permeability transition

Hydrogen sulfide (H2S) is the third most common endogenously produced gaseous signaling molecule, but its impact on hepatic ischemia/reperfusion (I/R) injury, especially on mitochondrial function, remains unclear. In this study, rats were randomized into Sham, I/R, ischemia preconditioning (IPC) or sodium hydrosulfide (NaHS, an H2S donor) preconditioning groups. To establish a model of segmental (70%) warm hepatic ischemia, the hepatic artery, left portal vein and median liver lobes were occluded for 60 min and then unclamped to allow reperfusion. Preconditioning with 12.5, 25 or 50 μmol/kg NaHS prior to the I/R insult significantly increased serum H2S levels, and, similar to IPC, NaHS preconditioning decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the plasma and prevented hepatocytes from undergoing I/R-induced necrosis. Moreover, a sub-toxic dose of NaHS (25 μmol/kg) did not disrupt the systemic hemodynamics but dramatically inhibited mitochondrial permeability transition pore (MPTP) opening and thus prevented mitochondrial-related cell death and apoptosis. Mechanistic studies revealed that NaHS preconditioning markedly increased the expression of phosphorylated protein kinase B (p-Akt), phosphorylated glycogen synthase kinase-3 beta (p-GSK-3β) and B-cell lymphoma-2 (Bcl-2) and decreased the release of mitochondrial cytochrome c and cleaved caspase-3/9 levels. Therefore, NaHS administration prior to hepatic I/R ameliorates mitochondrial and hepatocellular damage through the inhibition of MPTP opening and the activation of Akt-GSK-3β signaling. Furthermore, this study provides experimental evidence for the clinical use of H2S to reduce liver damage after perioperative I/R injury.

Serial measurement of hFABP and high-sensitivity troponin I post-PCI in STEMI: how fast and accurate can myocardial infarct size and no-reflow be predicted?

The objective of this study was to compare heart-specific fatty acid binding protein (hFABP) and high-sensitivity troponin I (hsTnI) via serial measurements to identify early time points to accurately quantify infarct size and no-reflow in a preclinical swine model of ST-elevated myocardial infarction (STEMI). Myocardial necrosis, usually confirmed by hsTnI or TnT, takes several hours of ischemia before plasma levels rise in the absence of reperfusion. We evaluated the fast marker hFABP compared with hsTnI to estimate infarct size and no-reflow upon reperfused (2 h occlusion) and nonreperfused (8 h occlusion) STEMI in swine. In STEMI (n = 4) and STEMI + reperfusion (n = 8) induced in swine, serial blood samples were taken for hFABP and hsTnI and compared with triphenyl tetrazolium chloride and thioflavin-S staining for infarct size and no-reflow at the time of euthanasia. hFABP increased faster than hsTnI upon occlusion (82 ± 29 vs. 180 ± 73 min, P < 0.05) and increased immediately upon reperfusion while hsTnI release was delayed 16 ± 3 min (P < 0.05). Peak hFABP and hsTnI reperfusion values were reached at 30 ± 5 and 139 ± 21 min, respectively (P < 0.05). Infarct size (containing 84 ± 0.6% no-reflow) correlated well with area under the curve for hFABP (r(2) = 0.92) but less for hsTnI (r(2) = 0.53). At 50 and 60 min reperfusion, hFABP correlated best with infarct size (r(2) = 0.94 and 0.93) and no-reflow (r(2) = 0.96 and 0.94) and showed high sensitivity for myocardial necrosis (2.3 ± 0.6 and 0.4 ± 0.6 g). hFABP rises faster and correlates better with infarct size and no-reflow than hsTnI in STEMI + reperfusion when measured early after reperfusion. The highest sensitivity detecting myocardial necrosis, 0.4 ± 0.6 g at 60 min postreperfusion, provides an accurate and early measurement of infarct size and no-reflow.

Hydrogen sulfide chemical biology: pathophysiological roles and detection

Hydrogen sulfide (H2S) is the most recent endogenous gasotransmitter that has been reported to serve many physiological and pathological functions in different tissues. Studies over the past decade have revealed that H2S can be synthesized through numerous pathways and its bioavailability regulated through its conversion into different biochemical forms. H2S exerts its biological effects in various manners including redox regulation of protein and small molecular weight thiols, polysulfides, thiosulfate/sulfite, iron-sulfur cluster proteins, and anti-oxidant properties that affect multiple cellular and molecular responses. However, precise measurement of H2S bioavailability and its associated biochemical and pathophysiological roles remains less well understood. In this review, we discuss recent understanding of H2S chemical biology, its relationship to tissue pathophysiological responses and possible therapeutic uses.

Hydrogen sulfide preconditions the db/db diabetic mouse heart against ischemia-reperfusion injury by activating Nrf2 signaling in an Erk-dependent manner

Hydrogen sulfide (H2S) therapy protects nondiabetic animals in various models of myocardial injury, including acute myocardial infarction and heart failure. Here, we sought to examine whether H2S therapy provides cardioprotection in the setting of type 2 diabetes. H2S therapy in the form of sodium sulfide (Na2S) beginning 24 h or 7 days before myocardial ischemia significantly decreased myocardial injury in db/db diabetic mice (12 wk of age). In an effort to evaluate the signaling mechanism responsible for the observed cardioprotection, we focused on the role of nuclear factor E2-related factor (Nrf2) signaling. Our results indicate that diabetes does not alter the ability of H2S to increase the nuclear localization of Nrf2, but does impair aspects of Nrf2 signaling. Specifically, the expression of NADPH quinine oxidoreductase 1 was increased after the acute treatment, whereas the expression of heme-oxygenase-1 (HO-1) was only increased after 7 days of treatment. This discrepancy was found to be the result of an increased nuclear expression of Bach1, a known repressor of HO-1 transcription, which blocked the binding of Nrf2 to the HO-1 promoter. Further analysis revealed that 7 days of Na2S treatment overcame this impairment by removing Bach1 from the nucleus in an Erk1/2-dependent manner. Our findings demonstrate for the first time that exogenous administration of Na2S attenuates myocardial ischemia-reperfusion injury in db/db mice, suggesting the potential therapeutic effects of H2S in treating a heart attack in the setting of type 2 diabetes.

Effects of red wine and vodka on collateral-dependent perfusion and cardiovascular function in hypercholesterolemic swine

BACKGROUND

Moderate consumption of alcohol, particularly red wine, has been shown to decrease cardiac risk. We used a hypercholesterolemic swine model of chronic ischemia to examine the effects of 2 alcoholic beverages on the heart.

METHODS AND RESULTS

Yorkshire swine fed a high-cholesterol diet underwent left circumflex ameroid constrictor placement to induce chronic ischemia at 8 weeks of age. One group (HCC, n=9) continued on the diet alone, the second (HCW, n=8) was supplemented with red wine (pinot noir, 12.5% alcohol, 375 mL daily), and the third (HCV, n=9) was supplemented with vodka (40% alcohol, 112 mL daily). After 7 weeks, cardiac function was measured, and ischemic myocardium was harvested for analysis of perfusion, myocardial fibrosis, vessel function, protein expression, oxidative stress, and capillary density. Platelet function was measured by aggregometry. Perfusion to the ischemic territory as measured by microsphere injection was significantly increased in both HCW and HCV compared with HCC at rest, but in only the HCW group under ventricular pacing. Microvessel relaxation response to adenosine 5'-diphosphate was improved in the HCW group alone as was regional contractility in the ischemic territory, although myocardial fibrosis was decreased in both HCW and HCV. Expression of proangiogenic proteins phospho-endothelial nitric oxide synthase and vascular endothelial growth factor was increased in both HCW and HCV, whereas phospho-mammalian target of rapamycin was increased only in the HCV group. Expression of Sirt-1 and downstream antioxidant phospho-FoxO1 was increased only in the HCW group. Protein oxidative stress was decreased in the HCW group alone, whereas capillary density was increased only in the HCV group. There was no significant difference in platelet function between groups.

CONCLUSION

Moderate consumption of red wine and vodka may reduce cardiovascular risk by improving collateral-dependent perfusion through different mechanisms. Red wine may offer increased cardioprotection related to its antioxidant properties.

Effects of autologous bone marrow mononuclear cells implantation on cholangiocytes apoptosis in model of intrahepatic ischemic type biliary lesion in rabbits

AIM

To investigate the effects of autologous bone marrow mononuclear cells (BM-MNCs) implantation on regulation of cholangiocyte apoptosis in a model of intrahepatic ischemic type biliary lesion (ITBL) in rabbits.

MATERIALS AND METHODS

Thirty Japanese white rabbits were divided randomly into 3 groups (10 per group) including controls (group A), ITBL model (group B), and BM-MNCs implantation groups (group C). All rabbits underwent the same surgical procedure to prepare the liver for graft removal during transplantation. Subsequently, no additional vascular intervention was performed in group A. In group B, the hepatic artery and common bile duct were clamped with microvascular clips for 2 hours, where after the clips were removed to recover the blood supply. Group C received, BM-MNCs (10(8) cells per rabbit) injected through the hepatic artery after removing the clips. The animals were killed 4 weeks after operation. The survival rate, histopathologic examination, cholangiocyte apoptosis with terminal uridine nick-end labeling (TUNEL) staining and expressions of Bcl-2 and Bax proteins were examined using immunohistochemical staining.

RESULTS

Group A animals showed a survival of 100%; the rates in groups B and C were both 90%. Histopathologic examination revealed normal intrahepatic cholangiocytes in group A, obviously damaged ones in group B, and alleviated damage in group C. TUNEL staining indicated apoptosis of cholangiocytes in group B was more serious than that in group A or group C. Immunohistochemical staining demonstrated significantly decreased Bcl-2 expression in group B compared with that in group A; Bcl-2 expression in group C returned to the level of group A. Simultaneously, the Bax expression presented adverse results; the ratios of Bcl-2/Bax were ranked as group A > group C > group B.

CONCLUSION

Implantation of autologous BM-MNCs significantly reduced apoptosis of intrahepatic cholangiocytes and prevented or abated intrahepatic ITBL.

Neuropeptide Y improves myocardial perfusion and function in a swine model of hypercholesterolemia and chronic myocardial ischemia

Pharmacologically induced angiogenesis could be a promising option in clinical situations with diffuse inoperable coronary artery disease e.g. metabolic syndrome and diabetes mellitus. The failure of focused cytokine, stem cell and gene therapies to achieve both perfusion and functional improvement in clinical trials suggests a more centralized control mechanism. Neuropeptide-Y (NPY) is one such natural neurotransmitter that is known to exert a multifaceted role during neo-angiogenesis and can possibly act as the central control. To date, the ability to harness the 'master switch' nature of NPY in a specific experimental model of metabolic syndrome and chronic myocardial ischemia has not been conclusively demonstrated. We hypothesized that infiltration of NPY into an area of chronic ischemia in a metabolic syndrome swine model would induce angiogenesis and improve myocardial perfusion and function. An osmotic pump was inserted three weeks after surgical induction of focal myocardial ischemia. We delivered either NPY or placebo for five weeks, after which the myocardial tissue was harvested for analysis. Assessments of myocardial perfusion and function were performed at each stage of the experiment. Local infiltration of NPY significantly improved collateral vessel formation, blood flow and myocardial function. We believe activation of NPY receptors may be a potential target therapy for patients with diffuse coronary artery disease.

Hydrogen sulfide and inflammation: the good, the bad, the ugly and the promising

Hydrogen sulfide is rapidly gaining ground as a physiological mediator of inflammation, but there is no clear consensus as to its precise role in inflammatory signaling. This article discusses the disparate anti-inflammatory ('the good') and proinflammatory ('the bad') effects of endogenous and pharmacological H(2)S in disparate animal model and cell culture systems. We also discuss 'the ugly', such as problems of using wholly specific inhibitors of enzymatic H(2)S synthesis, and the use of pharmacological donor compounds, which release H(2)S too quickly to be physiologically representative of endogenous H(2)S synthesis. Furthermore, recently developed slow-release H(2)S donors, which offer a more physiological approach to understanding the complex role of H(2)S in acute and chronic inflammation ('the promising') are discussed.

Hydrogen sulfide in cell survival: a double-edged sword

Hydrogen sulfide (H(2)S) has been found to play an important role as a signal molecule in regulating cell survival. It appears paradoxical that, on one side, H(2)S acts as a physiological intercellular messenger to stimulate cell growth, and on the other side, it may display cytotoxic activity. This article summarizes the current body of evidence demonstrating the cytoprotective versus cytotoxic effects of H(2)S in mammalian cells and describes the janus-faced properties of this important gasotransmitter. This article will also provide a brief description of the current signaling mechanisms that have been demonstrated to be responsible for these different actions. The pharmacologic regulation of H(2)S production and the potential clinical significance of H(2)S are highlighted.

Hydrogen sulfide in the mammalian cardiovascular system

For more than a century, hydrogen sulfide (H(2)S) has been regarded as a toxic gas. This review surveys the growing recognition of the role of H(2)S as an endogenous signaling molecule in mammals, with emphasis on its physiological and pathological pathways in the cardiovascular system. In biological fluids, H(2)S gas is a weak acid that exists as about 15% H(2)S, 85% HS(-), and a trace of S(2-). Here, we use "H(2)S" to refer to this mixture. H(2)S has been found to influence heart contractile functions and may serve as a cardioprotectant for treating ischemic heart diseases and heart failure. Alterations of the endogenous H(2)S level have been found in animal models with various pathological conditions such as myocardial ischemia, spontaneous hypertension, and hypoxic pulmonary hypertension. In the vascular system, H(2)S exerts biphasic regulation of a vascular tone with varying effects based on its concentration and in the presence of nitric oxide. Over the past decade, several H(2)S-releasing compounds (NaHS, Na(2)S, GYY4137, etc.) have been utilized to test the effect of exogenous H(2)S under different physiological and pathological situations in vivo and in vitro. H(2)S has been found to promote angiogenesis and to protect against atherosclerosis and hypertension, while excess H(2)S may promote inflammation in septic or hemorrhagic shock. H(2)S-releasing compounds and inhibitors of H(2)S synthesis hold promise in alleviating specific disease conditions. This comprehensive review covers in detail the effects of H(2)S on the cardiovascular system, especially in disease situations, and also the various underlying mechanisms.

Inhaled hydrogen sulfide improves graft function in an experimental model of lung transplantation

OBJECTIVES

Ischemia/reperfusion injury (IRI) is a common complication of lung transplantation (LTx). Hydrogen sulfide (H(2)S) is a novel agent previously shown to slow metabolism and scavenge reactive oxygen species, potentially mitigating IRI. We hypothesized that pretreatment with inhaled H(2)S would improve graft function in an ex vivo model of LTx.

METHODS

Rabbits (n = 10) were ventilated for 2 h prior to heart-lung bloc procurement. The treatment group (n = 5) inhaled room air (21% O(2)) supplemented with 150 ppm H(2)S while the control group (n = 5) inhaled room air alone. Both groups were gradually cooled to 34°C. All heart-lung blocs were then recovered and cold-stored in low-potassium dextran solution for 18 h. Following storage, the blocs were reperfused with donor rabbit blood in an ex vivo apparatus. Serial clinical parameters were assessed and serial tissue biochemistry was examined.

RESULTS

Prior to heart-lung bloc procurement, rabbits pretreated with H(2)S exhibited similar oxygenation (P = 0.1), ventilation (P = 0.7), and heart rate (P = 0.5); however, treated rabbits exhibited consistently higher mean arterial blood pressures (P = 0.01). During reperfusion, lungs pretreated with H(2)S had better oxygenation (P < 0.01) and ventilation (P = 0.02), as well as lower pulmonary artery pressures (P < 0.01). Reactive oxygen species levels were lower in treated lungs during reperfusion (P = 0.01). Additionally, prior to reperfusion, treated lungs demonstrated more preserved mitochondrial cytochrome c oxidase activity (P = 0.01).

CONCLUSIONS

To our knowledge, this study represents the first reported therapeutic use of inhaled H(2)S in an experimental model of LTx. After prolonged ischemia, lungs pretreated with inhaled H(2)S exhibited improved graft function during reperfusion. Donor pretreatment with inhaled H(2)S represents a potentially novel adjunct to conventional preservation techniques and merits further exploration.

Medical gases: a novel strategy for attenuating ischemia-reperfusion injury in organ transplantation?

Ischemia reperfusion injury (IRI) is an inevitable clinical consequence in organ transplantation. It can lead to early graft nonfunction and contribute to acute and chronic graft rejection. Advanced molecular biology has revealed the highly complex nature of this phenomenon and few definitive therapies exist. This paper reviews factors involved in the pathophysiology of IRI and potential ways to attenuate it. In recent years, inhaled nitric oxide, carbon monoxide, and hydrogen sulfide have been increasingly explored as plausible novel medical gases that can attenuate IRI via multiple mechanisms, including microvascular vasorelaxation, reduced inflammation, and mitochondrial modulation. Here, we review recent advances in research utilizing inhaled nitric oxide, carbon monoxide, and hydrogen sulfide in animal and human studies of IRI and postulate on its future applications specific to solid organ transplantation.

Total plasma sulfide as a marker of shock severity in nonsurgical adult patients

Previous animal and human studies have suggested that total plasma sulfide plays a role in the pathophysiology of shock. This study's aim was to determine the value of total plasma sulfide as a marker of shock severity in nonsurgical adult patients admitted to the ICU. Forty-one patients, with various types of shock (septic, cardiogenic, obstructive, and hypovolemic), were included in the study, with an average total plasma sulfide concentration of 23.2 ± 26.3 µM. Survivors (of shock) had lower total plasma sulfide concentrations than nonsurvivors (13.0 ± 26.3 vs. 31.9 ± 31.5 µM; P = 0.02). Total plasma sulfide correlated with dose of administered norepinephrine (R linear = 0.829; P = 0.001) and with Acute Physiology and Chronic Health Evaluation II (APACHE II) score (R cubic = 0.767; P = 0.001). Area under the receiver operating characteristic for total plasma sulfide as a predictor of ICU mortality was 0.739 (confidence interval, 0.587-0.892; P = 0.009). Even after correcting for APACHE II score and lactate values, total plasma sulfide correlated with mortality (odds ratio, 1.058; 95% confidence interval, 1.001-1.118; P = 0.045). The study provides evidence that, in nonsurgical adult ICU patients admitted because of any type of shock, total plasma sulfide correlates with administered norepinephrine dose at admission, severity of disease (APACHE II score ≥30 points), and survival outcome.

A hypothesis on biological protection from space radiation through the use of new therapeutic gases as medical counter measures

Radiation exposure to astronauts could be a significant obstacle for long duration manned space exploration because of current uncertainties regarding the extent of biological effects. Furthermore, concepts for protective shielding also pose a technically challenging issue due to the nature of cosmic radiation and current mass and power constraints with modern exploration technology. The concern regarding exposure to cosmic radiation is biological damage that is associated with increased oxidative stress. It is therefore important and would be enabling to mitigate and/or prevent oxidative stress prior to the development of clinical symptoms and disease. This paper hypothesizes a "systems biology" approach in which a combination of chemical and biological mitigation techniques are used conjunctively. It proposes using new, therapeutic, medical gases as chemical radioprotectors for radical scavenging and as biological signaling molecules for management of the body's response to exposure. From reviewing radiochemistry of water, biological effects of CO, H₂, NO, and H₂S gas, and mechanisms of radiation biology, it can be concluded that this approach may have therapeutic potential for radiation exposure. Furthermore, it also appears to have similar potential for curtailing the pathogenesis of other diseases in which oxidative stress has been implicated including cardiovascular disease, cancer, chronic inflammatory disease, hypertension, ischemia/reperfusion (IR) injury, acute respiratory distress syndrome, Parkinson's and Alzheimer's disease, cataracts, and aging. We envision applying these therapies through inhalation of gas mixtures or ingestion of water with dissolved gases.

Hydrogen sulfide decreases reactive oxygen in a model of lung transplantation

BACKGROUND

Ischemia-reperfusion injury is a common complication after lung transplantation. Ischemia-reperfusion injury is thought to be mediated by reactive oxygen species (ROS). Hydrogen sulfide (H(2)S) is a novel agent that has been previously shown to scavenge ROS and slow metabolism. We evaluated the effect of infused H(2)S on the presence of ROS after reperfusion in an ex vivo model of lung transplantation.

METHODS

Heart-Lung blocks were recovered from New Zealand white rabbits (n = 12) and cold stored in Perfadex solution for 18 h. After storage, the heart-lung blocks were reperfused ex vivo with donor rabbit blood. In the treatment group (n = 7), a bolus of sodium H(2)S was added at the beginning of reperfusion (100 μg/kg) and continuously infused throughout the 2-h experiment (1 mg/kg/h). The vehicle group (n = 5) received an equivalent volume of saline. Serial airway and pulmonary artery pressures and arterial and venous blood gases were measured.

RESULTS

Oxygenation and pulmonary artery pressures were similar between the 2 groups. However, treatment with H(2)S resulted in a dramatic reduction in the presence of ROS after 2 h of reperfusion (4,851 ± 2,139 versus 235 ± 462 related fluorescence units/mg protein; P = 0.003). A trend was seen toward increased levels of cyclic guanosine monophosphate in the H(2)S-treated group (3.08 ± 1.69 versus 1.73 ± 1.41 fmol/mg tissue; P = .23).

CONCLUSIONS

After prolonged ischemia, infusion of H(2)S during reperfusion was associated with a significant decrease in the presence of ROS, a suspected mediator of ischemia-reperfusion injury. To our knowledge, the present study represents the first reported therapeutic use of H(2)S in an experimental model of lung transplantation.

Hydrogen sulfide: a gasotransmitter of clinical relevance

Though the existence of hydrogen sulfide (H2S) in biological tissues has been known for over 300 years, it is the most recently appreciated of the gasotransmitters as a physiologic messenger molecule. The enzymes cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS) had long been speculated to generate H2S, and inhibitors of these enzymes had been employed to characterize influences of H2S in various organs. Definitive evidence that H2S is a physiologic regulator came with the development of mice with targeted deletion of CSE and CBS. Best characterized is the role of H2S, formed by CSE, as an endothelial derived relaxing factor that normally regulates blood pressure by acting through ATP-sensitive potassium channels. H2S participates in various phases of the inflammatory process, predominantly exerting anti-inflammatory actions. Currently, the most advanced efforts to develop therapeutic agents involve the combination of H2S donors with non-steroidal anti-inflammatory drugs (NSAIDs). The H2S releasing moiety provides cytoprotection to gastric mucosa normally adversely affected by NSAIDs while the combination of H2S and inhibition of prostaglandin synthesis may afford synergistic anti-inflammatory influences.

Hydrogen sulfide mitigates cardiac remodeling during myocardial infarction via improvement of angiogenesis

Exogenous hydrogen sulfide (H2S) leads to down-regulation of inflammatory responses and provides myocardial protection during acute ischemia/reperfusion injury; however its role during chronic heart failure (CHF) due to myocardial infarction (MI) is yet to be unveiled. We previously reported that H2S inhibits antiangiogenic factors such, as endostatin and angiostatin, but a little is known about its effect on parstatin (a fragment of proteinase-activated receptor-1, PAR-1). We hypothesize that H2S inhibits parstatin formation and promotes VEGF activation, thus promoting angiogenesis and significantly limiting the extent of MI injury. To verify this hypothesis MI was created in 12 week-old male mice by ligation of left anterior descending artery (LAD). Sham surgery was performed except LAD ligation. After the surgery mice were treated with sodium hydrogen sulfide (30 μmol/l NaHS, a donor for H2S, in drinking water) for 4 weeks. The LV tissue was analyzed for VEGF, flk-1 and flt-1, endostatin, angiostatin and parstatin. The expression of VEGF, flk-1 and flt-1 were significantly increased in treated mice while the level of endostatin, angiostatin and parstatin were decreased compared to in untreated mice. The echocardiography in mice treated with H2S showed the improvement of heart function compared to in untreated mice. The X-ray and Doppler blood flow measurements showed enhancement of cardiac-angiogenesis in mice treated with H2S. This observed cytoprotection was associated with an inhibition of anti-angiogenic proteins and stimulation of angiogenic factors. We established that administration of H2S at the time of MI ameliorated infarct size and preserved LV function during development of MI in mice. These results suggest that H2S is cytoprotective and angioprotective during evolution of MI.

Sodium sulfide prevents water diffusion abnormality in the brain and improves long term outcome after cardiac arrest in mice

AIM OF THE STUDY

Sudden cardiac arrest (CA) is one of the leading causes of death worldwide. Previously we demonstrated that administration of sodium sulfide (Na(2)S), a hydrogen sulfide (H(2)S) donor, markedly improved the neurological outcome and survival rate at 24 h after CA and cardiopulmonary resuscitation (CPR) in mice. In this study, we sought to elucidate the mechanism responsible for the neuroprotective effects of Na(2)S and its impact on the long-term survival after CA/CPR in mice.

METHODS

Adult male mice were subjected to potassium-induced CA for 7.5 min at 37°C whereupon CPR was performed with chest compression and mechanical ventilation. Mice received Na(2)S (0.55 mgkg(-1) i.v.) or vehicle 1 min before CPR.

RESULTS

Mice that were subjected to CA/CPR and received vehicle exhibited a poor 10-day survival rate (4/12) and depressed neurological function. Cardiac arrest and CPR induced abnormal water diffusion in the vulnerable regions of the brain, as demonstrated by hyperintense diffusion-weighted imaging (DWI) 24 h after CA/CPR. Extent of hyperintense DWI was associated with matrix metalloproteinase 9 (MMP-9) activation, worse neurological outcomes, and poor survival rate at 10 days after CA/CPR. Administration of Na(2)S prevented the development of abnormal water diffusion and MMP-9 activation and markedly improved neurological function and long-term survival (9/12, P<0.05 vs. Vehicle) after CA/CPR.

CONCLUSION

These results suggest that administration of Na(2)S 1 min before CPR improves neurological function and survival rate at 10 days after CA/CPR by preventing water diffusion abnormality in the brain potentially via inhibiting MMP-9 activation early after resuscitation.

The liver as a central regulator of hydrogen sulfide

The liver is likely exposed to high levels of hydrogen sulfide (H2S) from endogenous hepatic synthesis and exogenous sources from the gastrointestinal tract. Little is known about the consequence of H2S exposure on the liver or hepatic regulation of H2S levels. We hypothesized that the liver has a high capacity to metabolize H2S and that H2S oxidation is decreased during sepsis, a condition in which hepatic O2 is limited and H2S synthesis is increased. Using a nonrecirculating isolated and perfused liver system, we demonstrated rapid hepatic H2S metabolism up to an infusion concentration of 200' μM H2S. Hydrogen sulfide metabolism was associated with an increase in O2 consumption from a baseline 96.7 ± 7.6 μmol O2/min/kg to 109 ± 7.4 μmol O2/min/kg at an infusion concentration of 150 μM H2S (P < 0.001). Removal of O2 from the perfusate decreased H2S clearance from a maximal 97% to only 23%. Livers isolated from rats subjected to cecal ligation and puncture (CLP) did not differ significantly from control livers in their capacity to metabolize H2S, suggesting that H2S oxidation remains a priority during sepsis. To test whether H2S induces O2 consumption in vivo, intravital microscopy was utilized to monitor the oxygen content in the hepatic microenvironment. Infusion of H2S increased the NADH/NAD+ ratio (645 gray-scale-unit increase, P = 0.035) and decreased hepatic O2 availability visualized with Ru(Phen)3(2+) (439 gray-scale-unit increase, P = 0.040). We conclude that the liver has a high hepatic capacity for H2S metabolism. Moreover, H2S oxidation consumes available oxygen and may exacerbate the tissue hypoxia associated with sepsis.

Hydrogen sulfide protects H9c2 cells against doxorubicin-induced cardiotoxicity through inhibition of endoplasmic reticulum stress

The roles of hydrogen sulfide (H(2)S) and endoplasmic reticulum (ER) stress in doxorubicin (DOX)-induced cardiotoxicity are still unclear. This study aimed to dissect the hypothesis that H(2)S could protect H9c2 cells against DOX-induced cardiotoxicity by inhibiting ER stress. Our results showed that exposure of H9c2 cells to DOX significantly inhibited the expression and activity of cystathionine-γ-lyase (CSE), a synthetase of H(2)S, accompanied by the decreased cell viability and the increased reactive oxygen species (ROS) accumulation. In addition, exposure of cells to H(2)O(2) (an exogenous ROS) mimicked the inhibitory effect of DOX on the expression and activity of CSE. Pretreatment with N-acetyl-L: -cysteine (NAC) (a ROS scavenger) attenuated intracellular ROS accumulation, cytotoxicity, and the inhibition of expression and activity of CSE induced by DOX. Notably, the ER stress-related proteins, including glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) were obviously upregulated in DOX-treated H9c2 cells. Pretreatment with sodium hydrosulfide (NaHS, a H(2)S donor) before DOX exposure markedly suppressed DOX-induced overexpressions of GRP78 and CHOP, cytotoxicity and oxidative stress. In conclusion, we have demonstrated that ROS-mediated inhibition of CSE is involved in DOX-induced cytotoxicity in H9c2 cells, and that exogenous H(2)S can confer protection against DOX-induced cardiotoxicity partly through inhibition of ER stress.

Hydrogen sulfide-releasing aspirin modulates xenobiotic metabolizing enzymes in vitro and in vivo

The balance between phase-I carcinogen-activating and phase-II detoxifying xenobiotic metabolizing enzymes is critical to determining an individual's risk for cancer. We evaluated the effect of Hydrogen sulfide-releasing aspirin (HS-ASA) on xenobiotic metabolizing enzymes in HT-29 human colon and Hepa 1c1c7 mouse liver adenocarcinoma cells and in Wistar rats. HS-ASA inhibited the growth of HT-29 and Hepa 1c1c7 cells, with an IC(50) of 3.2 ± 0.3 μM and 4.2 ± 0.4 μM, respectively. The IC(50) for ASA in both cell lines was greater than 5000 μM at 24h. In these cell lines, HS-ASA caused a dose-dependent increase in activity and expression of the phase-II enzymes glutathione S-transferase (GST) and NAD(P)H:quinoneoxireductase (NQO1). It also caused an increase in UDP-glucuronosyltransferase (UGT) expression. The levels of CYP 1A1 a phase-I enzyme was increased by HS-ASA in both cell lines. Pretreatment of cells with NaF, an esterase inhibitor, abrogated the HS-ASA-mediated increases in NQO1 enzyme activity. HS-ASA increased the protein levels of the transcription factor Nrf2, which is a regulator of the phase-II enzymes. In vivo, HS-ASA at 100mg/kg/day had no effect on rat's weights; it induced a 3.4-fold and 1.4-fold increase in hepatic GST and NQO1 enzyme activities, respectively. GST and NQO1 protein levels were also increased. In contrast to that in cultured cells, CYP 1A1 protein levels were not altered in vivo. Therefore, HS-ASA induces phase-II enzymes, at least in part, through the action of H(2)S and by modulating Nrf2; these effects may be part of its mechanism of action against carcinogenesis.

Inhibition of ROS-activated ERK1/2 pathway contributes to the protection of H2S against chemical hypoxia-induced injury in H9c2 cells

Hydrogen sulfide (H(2)S) has been shown to exert cardioprotective effects. However, the roles of extracellular signal-regulated protein kinases 1/2 (ERK1/2) in H(2)S-induced cardioprotection have not been completely elucidated. In this study, cobalt chloride (CoCl(2)), a chemical hypoxia mimetic agent, was applied to treat H9c2 cells to establish a chemical hypoxia-induced cardiomyocyte injury model. The results showed that pretreatment with NaHS (a donor of H(2)S) before exposure to CoCl(2) attenuated the decreased cell viability, the increased apoptosis rate, the loss of mitochondrial membrane potential (ΔΨm), and the intracellular accumulation of reactive oxygen species (ROS) in H9c2 cells. Exposure of H9c2 cells to CoCl(2) or hydrogen peroxide (H(2)O(2)) upregulated expression of phosphorylated (p) ERK1/2, which was reduced by pretreatment with NaHS or N-acetyl-L-cysteine, a ROS scavenger. More importantly, U0126, a selective inhibitor of ERK1/2, mimicked the above cytoprotection of H(2)S against CoCl(2)-induced injury in H9c2 cells. In conclusion, these results indicate that H(2)S protects H9c2 cells against chemical hypoxia-induced injury partially by inhibiting ROS-mediated activation of ERK1/2.

Tribulosin suppresses apoptosis via PKC epsilon and ERK1/2 signaling pathway during hypoxia/reoxygenation in neonatal rat ventricular cardiac myocytes

Tribulosin (tigogenin 3-O-β-D-xylopyranosyl(1-2)-[β-D-xylopyranosyl (1-3)]-β-D-glucopyranosyl (1-4)-[a-L-rhamnopyranosyl(1-2)]-β-D-galactopyranoside), a component of gross saponins of Tribulus terrestris, has been shown to produce cytoprotective effects in heart. Yet, the precise mechanisms are not fully understood. We examined the mechanisms of tribulosin on myocardial protection. Ventricular myocytes were isolated from the heart of neonatal rats and were exposed to 3 h of hypoxia followed by 2 h reoxygenation. Apoptosis was induced by hypoxia/reoxygenation (H/R), and the expression of protein kinase C epsilon (PKCϵ) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) in cultured neonatal rat cardiac myocytes was detected. The results indicated that treatment with tribulosin in the culture medium protected cardiac myocytes against apoptosis induced by H/R. PKCϵ and ERK1/2 expression increased after pretreated with tribulosin. In the presence of PKCϵ inhibitor co-treated with tribulosin, the expression of ERK1/2 was decreased in H/R cardiac myocytes. While preconditioned with PD98059, ERK1/2 inhibitor, no effects on the expression of PKCϵ were detected. Tribulosin has protective effects on cardiac myocytes against apoptosis induced by H/R injury via PKCϵ and ERK1/2 signaling pathway.

High-fat diet alters prostanoid balance and perfusion in ischemic myocardium of naproxen-treated swine

BACKGROUND

The effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on the cardiovascular system remains controversial, especially in patients with cardiovascular comorbidities. We used a swine model of chronic myocardial ischemia to investigate whether hypercholesterolemia alters the cardiovascular effects of the nonselective NSAID naproxen.

METHODS

Yorkshire swine were fed normal chow (NAP; n = 7) or a high-fat diet (HF-NAP; n = 8). Chronic myocardial ischemia was created in all animals by left circumflex ameroid constrictor placement. All swine were started on oral naproxen (440 mg/day) at the time of ameroid placement. After 7 weeks, myocardial perfusion and microvessel reactivity in the ischemic territory were assessed. Tissue levels of prostanoid metabolites 11-dehydrothromboxane B2 (11-d-TXB₂) and 6-keto-prostaglandin F1-α (6-k-PGF(1α)) were measured. Tissue was analyzed for capillary density and protein expression.

RESULTS

Myocardial perfusion was significantly decreased in the HF-NAP group both at rest and during ventricular pacing. Microvessel relaxation responses to sodium nitroprusside and adenosine 5'-diphosphate were similar between groups. Tissue 11-d-TXB₂ levels were similar between groups, but tissue 6-k-PGF(1α) was significantly decreased in the HF-NAP group (P = .001). Expression of thromboxane synthase was significantly higher in the HF-NAP group (P = .02), while prostacyclin synthase expression was significantly decreased in the HF-NAP group (P = .04). Capillary density was higher in the HF-NAP group (P = .005). Proangiogenic vascular endothelial growth factor (VEGF; P = .0002) and Akt (P = .01) were downregulated in the HF-NAP group.

CONCLUSION

A high-fat diet impairs tissue perfusion in ischemic myocardium of naproxen-treated swine by shifting the prostanoid balance to favor production of thromboxane over prostacyclin. Dietary modification may improve myocardial blood flow and alter the safety profile in chronically ischemic cardiac patients taking naproxen.

Effects of cyclooxygenase inhibition on cardiovascular function in a hypercholesterolemic swine model of chronic ischemia

The cardiovascular effects of cyclooxygenase (COX) inhibition remain controversial, especially in the setting of cardiovascular comorbidities. We examined the effects of nonselective and selective COX inhibition on cardiovascular function in a hypercholesterolemic swine model of chronic ischemia. Twenty-four intact male Yorkshire swine underwent left circumflex ameroid constrictor placement and were subsequently given either no drug (HCC; n = 8), a nonselective COX inhibitor (440 mg/day naproxen; HCNS; n = 8), or a selective COX-2 inhibitor (200 mg/day celecoxib; HCCX; n = 8). After 7 wk, myocardial functional was measured and myocardium from the nonischemic ventricle and ischemic area-at-risk (AAR) were analyzed. Regional function as measured by segmental shortening was improved in the AAR of HCCX compared with HCC. There was no significant difference in perfusion to the nonischemic ventricle between groups, but myocardial perfusion in the AAR was significantly improved in the HCCX group compared with controls at rest and during pacing. Endothelium-dependent microvessel relaxation was diminished by ischemia in HCC animals, but both naproxen and celecoxib improved vessel relaxation in the AAR compared with controls, and also decreased the vasoconstrictive response to serotonin. Thromboxane levels in the AAR were decreased in both HCNS and HCCX compared with HCC, whereas prostacyclin levels were decreased only in HCNS, corresponding to a decrease in prostacyclin synthase expression. Chronic ischemia increased apoptosis in Troponin T negative cells and intramyocardial fibrosis, both of which were reduced by celecoxib administration in the AAR. Capillary density was decreased in both the HCNS and HCCX groups. Protein oxidative stress was decreased in both HCNS and HCCX, whereas lipid oxidative stress was decreased only in the HCCX group. Thus nonselective and especially selective COX inhibition may have beneficial myocardial effects in the setting of hypercholesterolemia and chronic ischemia. Whether these effects modulate cardiovascular risk in patients taking these drugs remains to be seen, but evidence to date suggests that they do not.