Carbon monoxide increases inducible NOS expression that mediates CO-induced myocardial damage during ischemia-reperfusion

Practical Recommendations for the Evaluation and Management of Cardiac Injury Due to Carbon Monoxide Poisoning

Carbon monoxide (CO) is a relatively frequent cause of poisoning evaluated in emergency departments. The risk of neurologic injuries, such as cognitive, psychological, vestibular, and motor deficits, is 25% to 50%. However, the risk of cardiac injuries should also be considered. Among patients with CO poisoning, the mortality in patients with myocardial injury is approximately 3 times greater than that in patients without myocardial injury. In large-scale studies, up to 69.2% of patients with acute CO poisoning exhibiting elevated troponin I levels and no underlying cardiovascular illnesses had late gadolinium enhancement on cardiac magnetic resonance, suggesting covert CO-induced myocardial fibrosis. Myocardial damage can be evaluated using electrocardiography, echocardiography, computed tomography, and cardiac magnetic resonance. This paper offers recommendations for cardiac evaluations based on our collective experience of managing >2,000 cases of acute CO poisoning with supporting information taken from peer-reviewed published reports on CO poisoning.

Clinical and Echocardiographic Predictors for the Presence of Late Gadolinium Enhancement on Cardiac Magnetic Resonance Imaging in Patients with Carbon Monoxide Poisoning

Late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMRI) reflects the burden of myocardial damage in carbon monoxide (CO) poisoning. This study aimed to identify the clinical and echocardiographic parameters that can predict myocardial LGE on CMRI in CO poisoning. This prospective observational study included patients who presented with acute CO poisoning and elevated troponin I and underwent echocardiography and CMRI to identify myocardial damage at a tertiary university hospital between August 2017 and May 2019 and August 2020 and July 2022. Based on the CMRI findings, participants were categorized into LGE and non-LGE groups. The median age of the 155 patients was 51.0 years, and 98 (63.2%) were males. Median times from emergency department arrival to either CMRI or echocardiography were 3.0 days each. The LGE group included 99 (63.9%) patients with LGE positivity on CMRIs. Time from rescue to hyperbaric oxygen therapy >4 h (odds ratio (OR): 3.31, 95% confidence interval (CI): 1.28-8.56, p = 0.01); serum lactate levels >2 mmol/L (OR: 2.62, 95% CI: 1.20-5.73, p = 0.02); and left ventricular global longitudinal strain >-16% (OR: 2.95, 95% CI: 1.35-6.47, p = 0.007) were significant predictors of LGE positivity. The area under the curve of these predictors was 0.711. Our prediction model, which combines the clinical parameters with left ventricular global longitudinal strain, may be helpful in the early detection of LGE positivity.

CD38 Deficiency Alleviates Diabetic Cardiomyopathy by Coordinately Inhibiting Pyroptosis and Apoptosis

Diabetic cardiomyopathy is one of the diabetes mellitus-induced cardiovascular complications that can result in heart failure in severe cases, which is characterized by cardiomyocyte apoptosis, local inflammation, oxidative stress, and myocardial fibrosis. CD38, a main hydrolase of NAD+ in mammals, plays an important role in various cardiovascular diseases, according to our previous studies. However, the role of CD38 in diabetes-induced cardiomyopathy is still unknown. Here, we report that global deletion of the CD38 gene significantly prevented diabetic cardiomyopathy induced by high-fat diet plus streptozotocin (STZ) injection in CD38 knockout (CD38-KO) mice. We observed that CD38 expression was up-regulated, whereas the expression of Sirt3 was down-regulated in the hearts of diabetic mice. CD38 deficiency significantly promoted glucose metabolism and improved cardiac functions, exemplified by increased left ventricular ejection fraction and fractional shortening. In addition, we observed that CD38 deficiency markedly decreased diabetes or high glucose and palmitic acid (HG + PA)-induced pyroptosis and apoptosis in CD38 knockout hearts or cardiomyocytes, respectively. Furthermore, we found that the expression levels of Sirt3, mainly located in mitochondria, and its target gene FOXO3a were increased in CD38-deficient hearts and cardiomyocytes with CD38 knockdown under diabetic induction conditions. In conclusion, we demonstrated that CD38 deficiency protected mice from diabetes-induced diabetic cardiomyopathy by reducing pyroptosis and apoptosis via activating NAD+/Sirt3/FOXO3a signaling pathways.

Air Pollution and Cardiac Diseases: A Review of Experimental Studies

Air pollution is associated with around 6.5 million premature deaths annually, which are directly related to cardiovascular diseases, and the most dangerous atmospheric pollutants to health are as follows: NO2, SO2, CO, and PM. The mechanisms underlying the observed effects have not yet been clearly defined. This work aims to conduct a narrative review of experimental studies to provide a more comprehensive and multiperspective assessment of how the effect of atmospheric pollutants on cardiac activity can result in the development of cardiac diseases. For this purpose, a review was carried out in databases of experimental studies, excluding clinical trials, and epidemiological and simulation studies. After analyzing the available information, the existence of pathophysiological effects of the different pollutants on cardiac activity from exposure during both short-term and long-term is evident. This narrative review based on experimental studies is a basis for the development of recommendations for public health.

Impact of air pollution on cardiovascular aging

The world population is aging rapidly, and by some estimates, the number of people older than 60 will double in the next 30 years. With the increase in life expectancy, adverse effects of environmental exposures start playing a more prominent role in human health. Air pollution is now widely considered the most detrimental of all environmental risk factors, with some studies estimating that almost 20% of all deaths globally could be attributed to poor air quality. Cardiovascular diseases are the leading cause of death worldwide and will continue to account for the most significant percentage of non-communicable disease burden. Cardiovascular aging with defined pathomechanisms is a major trigger of cardiovascular disease in old age. Effects of environmental risk factors on cardiovascular aging should be considered in order to increase the health span and reduce the burden of cardiovascular disease in older populations. In this review, we explore the effects of air pollution on cardiovascular aging, from the molecular mechanisms to cardiovascular manifestations of aging and, finally, the age-related cardiovascular outcomes. We also explore the distinction between the effects of air pollution on healthy aging and disease progression. Future efforts should focus on extending the health span rather than the lifespan.

Fabrication of CO-releasing surface to enhance the blood compatibility and endothelialization of TiO2 nanotubes on titanium surface

Although the construction of nanotube arrays with the micro-nano structures on the titanium surfaces has demonstrated a great promise in the field of blood-contacting materials and devices, the limited surface hemocompatibility and delayed endothelial healing should be further improved. Carbon monoxide (CO) gas signaling molecule within the physiological concentrations has excellent anticoagulation and the ability to promote endothelial growth, exhibiting the great potential for the blood-contact biomaterials, especially the cardiovascular devices. In this study, the regular titanium dioxide nanotube arrays were firstly prepared in situ on the titanium surface by anodic oxidation, followed by the immobilization of the complex of sodium alginate/carboxymethyl chitosan (SA/CS) on the self-assembled modified nanotube surface, the CO-releasing molecule (CORM-401) was finally grafted onto the surface to create a CO-releasing bioactive surface to enhance the biocompatibility. The results of scanning electron microscopy (SEM), X-ray energy dispersion spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) revealed that the CO-releasing molecules were successfully immobilized on the surface. The modified nanotube arrays not only exhibited excellent hydrophilicity but also could slowly release CO gas molecules, and the amount of CO release increased when cysteine was added. Furthermore, the nanotube array can promote albumin adsorption while inhibit fibrinogen adsorption to some extent, demonstrating its selective albumin adsorption; although this effect was somewhat reduced by the introduction of CORM-401, it can be significantly enhanced by the catalytic release of CO. The results of hemocompatibility and endothelial cell growth behaviors showed that, as compared with the CORM-401 modified sample, although the SA/CS-modified sample had better biocompatibility, in the case of cysteine-catalyzed CO release, the released CO could not only reduce the platelet adhesion and activation as well as hemolysis rate, but also promote endothelial cell adhesion and proliferation as well as vascular endothelial growth factor (VEGF) and nitric oxide (NO) expression. As a result, the research of the present study demonstrated that the releasing CO from TiO₂ nanotubes can simultaneously enhance the surface hemocompatibility and endothelialization, which could open a new route to enhance the biocompatibility of the blood-contacting materials and devices, such as the artificial heart valve and cardiovascular stents.

The different facets of heme-oxygenase 1 in innate and adaptive immunity

Heme oxygenase (HO) enzymes are responsible for the main oxidative step in heme degradation, generating equimolar amounts of free iron, biliverdin and carbon monoxide. HO-1 is induced as a crucial stress response protein, playing protective roles in physiologic and pathological conditions, due to its antioxidant, anti-apoptotic and anti-inflammatory effects. The mechanisms behind HO-1-mediated protection are being explored by different studies, affecting cell fate through multiple ways, such as reduction in intracellular levels of heme and ROS, transcriptional regulation, and through its byproducts generation. In this review we focus on the interplay between HO-1 and immune-related signaling pathways, which culminate in the activation of transcription factors important in immune responses and inflammation. We also discuss the dual interaction of HO-1 and inflammatory mediators that govern resolution and tissue damage. We highlight the dichotomy of HO-1 in innate and adaptive immune cells development and activation in different disease contexts. Finally, we address different known anti-inflammatory pharmaceuticals that are now being described to modulate HO-1, and the possible contribution of HO-1 in their anti-inflammatory effects.

Anti-apoptotic Effect of MiR-223-3p Suppressing PIK3C2A in Cardiomyocytes from Myocardial Infarction Rat Through Regulating PI3K/Akt Signaling Pathway

We aimed to explore the regulatory mechanism of the axis of miR-223-3p-PIK3C2A-PI3K/Akt on cardiomyocyte apoptosis in rats with myocardial infarction. Thirty 8-week-old healthy male SD rats were used for establishing the sham group and the model group, with HE staining, TUNEL staining, and TTC staining performed. After the identification of the targeting relationship between PIK3C2A and miR-223-3p, experimental rats were randomly divided into seven groups by plasmid transfection, including the Blank group, negative control (NC) group, miR-223-3p mimic group, miR-223-3p inhibitor group, siRNA-PIK3C2A group, oe-PIK3C2A group, and miR-223-3p inhibitor + oe-PIK3C2A group. Four weeks after transfection, the expression levels of miR-223-3p and PIK3C2A in tissues as well as PI3K, Akt, Bax, and bcl-2 mRNA in cells were detected by qRT-PCR and western blot, in combination with the detection of apoptosis rate by flow cytometry. Compared with the sham group, the model group showed typical myocardial injury and abnormal staining, higher apoptotic index, and larger myocardial infarction area (all P < 0.05). PIK3C2A was the target gene of miR-223-3p. The expression level of miR-223-3p in model group was significantly lower than that in sham group, while the mRNA and protein expression levels of PIK3C2A increased significantly (all P < 0.05). In cell tests, the expression level of miR-223-3p increased significantly in miR-223-3p mimic group (P < 0.05), which, however, showed no significant change in siRNA-PIK3C2A group (P > 0.05). MiR-223-3p inhibitor group and siRNA-PIK3C2A group had obviously increased PI3K, Akt, mTOR and Bcl-2 mRNA, and protein expression, while decreased mRNA and protein expression of PIK3C2A and Bax (all P < 0.05); miR-223-3p mimic groups had the opposite trends (all P < 0.05). siRNA-PIK3C2A + miR-223-3p mimic showed no obvious change relative to the control groups (all P > 0.05). Low expression of miR-223-3p may downregulate PIK3C2A expression, resulting in the inhibition of myocardial cell apoptosis in rats with myocardial infarction via the activation of PI3K/Akt signaling pathway.

Endogenous Cardiotonics: Search And Problems

Medicinal preparations currently used for the treatment of patients with chronic cardiac failure involve those that reduce the heart load (vasodilators, diuretics, beta-blockers, and angiotensin-converting enzyme (ACE) inhibitors). Cardiotonic drugs with the cAMP-dependent mechanism are unsuitable for long-term administration due to the intensification of metabolic processes and an increase in the oxygen demand of the myocardium and all tissues of the body. For many years, digoxin has remained the only preparation enhancing the efficiency of myocardial performance. The detection of digoxin and ouabain in intact animals has initiated a search for other compounds with cardiotonic activity. The review summarizes current data on the effect exerted on the heart performance by endogenous compounds, from simple, such as NO and CO, to steroids, fatty acids, polypeptides, and proteins. Controversial questions and problems with the introduction of scientific achievements into clinical practice are discussed. The results obtained by the authors and their colleagues after many years of studies on the cardiotropic properties of serum lipoproteins are also reported. The experimentally established cardiotonic activity of apoprotein A-1, which is accompanied by a decrease in the relative consumption of oxygen, maybe of great interest.

Increased Risk of Congestive Heart Failure Following Carbon Monoxide Poisoning

BACKGROUND

Carbon monoxide poisoning (COP) is an important public health issue around the world. It may increase the risk of myocardial injury, but the association between COP and congestive heart failure (CHF) remains unclear. We conducted a study incorporating data from epidemiological and animal studies to clarify this issue.

METHODS

Using the National Health Insurance Database of Taiwan, we identified patients with COP diagnosed between 1999 and 2012 and compared them with patients without COP (non-COP cohort) matched by age and the index date at a 1:3 ratio. The comparison for the risk of CHF between the COP and non-COP cohorts was made using Cox proportional hazards regression. We also established a rat model to evaluate cardiac function using echocardiography and studied the pathological changes following COP.

RESULTS

The 20 942 patients in the COP cohort had a higher risk for CHF than the 62 826 members in the non-COP cohort after adjusting for sex and underlying comorbidities (adjusted hazard ratio, 2.01 [95% CI, 1.74-2.32]). The increased risk of CHF persisted even after 2 years of follow-up (adjusted hazard ratio, 1.85 [95% CI, 1.55-2.21]). In the animal model, COP led to a decreased left ventricular ejection fraction on echocardiography and damage to cardiac cells with remarkable fibrotic changes.

CONCLUSIONS

Our epidemiological data showed an increased risk of CHF was associated with COP, which was supported by the animal study. We suggest close follow-up of cardiac function for patients with COP to facilitate early intervention and further studies to identify other long-term effects that have not been reported in the literature.

Regulation of Endothelial and Vascular Functions by Carbon Monoxide via Crosstalk With Nitric Oxide

Carbon monoxide (CO), generated by heme oxygenase (HO), has been considered a signaling molecule in both the cardiovascular and central nervous systems. The biological function of the HO/CO axis is mostly related to other gaseous molecules, including nitric oxide (NO), which is synthesized by nitric oxide synthase (NOS). Healthy blood vessels are essential for the maintenance of tissue homeostasis and whole-body metabolism; however, decreased or impaired vascular function is a high-risk factor of cardiovascular and neuronal diseases. Accumulating evidence supports that the interplay between CO and NO plays a crucial role in vascular homeostasis and regeneration by improving endothelial function. Moreover, endothelial cells communicate with neighboring cells, such as, smooth muscle cells, immune cells, pericytes, and astrocytes in the periphery and neuronal vascular systems. Endogenous CO could mediate the cell-cell communication and improve the physiological functions of the cardiovascular and neurovascular systems via crosstalk with NO. Thus, a forward, positive feedback circuit between HO/CO and NOS/NO pathways can maintain cardiovascular and neurovascular homeostasis and prevent various human diseases. We discussed the crucial role of CO-NO crosstalk in the cardiovascular and neurovascular systems.

Cardiovascular effects of air pollution: current evidence from animal and human studies

Air pollution is a global health concern. Particulate matter (PM)_2.5, a component of ambient air pollution, has been identified by the World Health Organization as one of the pollutants that poses the greatest threat to public health. Cardiovascular health effects have been extensively documented, and these effects are still being researched to provide an overview of recent literature regarding air pollution-associated cardiovascular morbidity and mortality in humans. Additionally, potential mechanisms through which air pollutants affect the cardiovascular system are discussed based on human and additional animal studies. We used the strategy of a narrative review to summarize the scientific literature of studies that were published in the past 7 yr. Searches were carried out on PubMed and Web of Science using predefined search queries. We obtained an initial set of 800 publications that were filtered to 78 publications that were relevant to include in this review. Analysis of the literature showed significant associations between air pollution, especially PM_2.5, and the risk of elevated blood pressure (BP), acute coronary syndrome, myocardial infarction (MI), cardiac arrhythmia, and heart failure (HF). Prominent mechanisms that underlie the adverse effects of air pollution include oxidative stress, systemic inflammation, endothelial dysfunction, autonomic imbalance, and thrombogenicity. The current review underscores the relevance of air pollution as a global health concern that affects cardiovascular health. More rigorous standards are needed to reduce the cardiovascular disease burden imposed by air pollution. Continued research on the health impact of air pollution is needed to provide further insight.

Effect of Smoking on Outcomes of Primary PCI in Patients With STEMI

BACKGROUND

Smoking is a well-established risk factor for ST-segment elevation myocardial infarction (STEMI); however, once STEMI occurs, smoking has been associated with favorable short-term outcomes, an observation termed the "smoker's paradox." It has been postulated that smoking might exert protective effects that could reduce infarct size, a strong independent predictor of worse outcomes after STEMI.

OBJECTIVES

The purpose of this study was to determine the relationship among smoking, infarct size, microvascular obstruction (MVO), and adverse outcomes after STEMI.

METHODS

Individual patient-data were pooled from 10 randomized trials of patients with STEMI undergoing primary percutaneous coronary intervention. Infarct size was assessed at median 4 days by either cardiac magnetic resonance imaging or technetium-99m sestamibi single-photon emission computed tomography. Multivariable analysis was used to assess the relationship between smoking, infarct size, and the 1-year rates of death or heart failure (HF) hospitalization and reinfarction.

RESULTS

Among 2,564 patients with STEMI, 1,093 (42.6%) were recent smokers. Smokers were 10 years younger and had fewer comorbidities. Infarct size was similar in smokers and nonsmokers (adjusted difference: 0.0%; 95% confidence interval [CI]: -3.3% to 3.3%; p = 0.99). Nor was the extent of MVO different between smokers and nonsmokers. Smokers had lower crude 1-year rates of all-cause death (1.0% vs. 2.9%; p < 0.001) and death or HF hospitalization (3.3% vs. 5.1%; p = 0.009) with similar rates of reinfarction. After adjustment for age and other risk factors, smokers had a similar 1-year risk of death (adjusted hazard ratio [adjHR]: 0.92; 95% CI: 0.46 to 1.84) and higher risks of death or HF hospitalization (adjHR: 1.49; 95% CI: 1.09 to 2.02) as well as reinfarction (adjHR: 1.97; 95% CI: 1.17 to 3.33).

CONCLUSIONS

In the present large-scale individual patient-data pooled analysis, recent smoking was unrelated to infarct size or MVO, but was associated with a worse prognosis after primary PCI in STEMI. The smoker's paradox may be explained by the younger age and fewer cardiovascular risk factors in smokers compared with nonsmokers.

Gasotransmitter signaling in energy homeostasis and metabolic disorders

Gasotransmitters are small molecules of gases, including nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO). These three gasotransmitters can be endogenously produced and regulate a wide range of pathophysiological processes by interacting with specific targets upon diffusion in the biological media. By redox and epigenetic regulation of various physiological functions, NO, H₂S, and CO are critical for the maintenance of intracellular energy homeostasis. Accumulated evidence has shown that these three gasotransmitters control ATP generation, mitochondrial biogenesis, glucose metabolism, insulin sensitivity, lipid metabolism, and thermogenesis, etc. Abnormal generation and metabolism of NO, H₂S, and/or CO are involved in various abnormal metabolic diseases, including obesity, diabetes, and dyslipidemia. In this review, we summarized the roles of NO, H₂S, and CO in the regulation of energy homeostasis as well as their involvements in the metabolism of dysfunction-related diseases. Understanding the interaction among these gasotransmitters and their specific molecular targets are very important for therapeutic applications.

High-Sensitivity Troponin I and Creatinine Kinase-Myocardial Band in Screening for Myocardial Injury in Patients with Carbon Monoxide Poisoning

Myocardial dysfunction due to acute carbon monoxide (CO) poisoning is common and associated with poor outcomes. The role of cardiac markers, including creatine kinase-myocardial band (CK-MB), high-sensitivity troponin I (hsTnI), and brain natriuretic peptide (BNP), in identifying patients with CO-induced cardiomyopathy were evaluated. This single-center, retrospective cohort study included 905 consecutive adult patients in the CO poisoning registry from February 2009 to December 2019. Cardiomyopathy was defined as any abnormality on transthoracic echocardiography (TTE), including left ventricular systolic and diastolic dysfunction, right ventricular dysfunction, and wall motion abnormalities. The areas under receiver operating curves (AUCs) for biomarkers were compared. Of the 850 included patients, 101 (11.9%) had CO-induced cardiomyopathy. Initial and peak hsTnI and CK-MB concentrations, and initial BNP concentrations were significantly higher in patients with than without cardiomyopathy (all P-values < 0.01), but the AUCs were higher for hsTnI (0.894) and CK-MB (0.864) than for BNP (0.796). Initial TnI > 0.01 ng/mL and CK-MB > 1.5 ng/mL each had 95% sensitivity and 97% negative predictive value for CO-induced cardiomyopathy. Higher hsTnI or CK-MB levels on admission can identify patients at high-risk of CO-induced cardiomyopathy and can be a screening tool for CO poisoning.

Variant angina induced by carbon monoxide poisoning: A CARE compliant case report

RATIONALE

Carbon monoxide (CO) poisoning can cause severe damage to the nervous system, and can also cause serious damage to organs, such as the heart, kidneys, and lungs. CO damage to myocardial cells has been previously reported. This can lead to serious complications, such as myocardial infarction.

PATIENT CONCERNS

A 47-year-old female patient complained of sudden chest pain for 30 minutes. Before admission, the patient had non-radiating burning chest pain after inhalation of soot.

DIAGNOSIS

An electrocardiogram showed that myocardial ischemia was progressively aggravated, manifested by progressive ST-segment elevation, and accompanied by T wave inversion and other changes. No obvious coronary stenosis was observed in a coronary angiographic examination. Therefore, the patient was considered to have developed variant angina resulting from CO poisoning-induced coronary artery spasm.

INTERVENTIONS

The patient was treated with drugs for improving blood circulation and preventing thrombosis, and underwent hyperbaric oxygen therapy.

OUTCOMES

Clinical symptoms relieved after the treatment.

LESSONS

Findings from this case suggest that CO can cause coronary artery spasm and it is one of the predisposing factors of variant angina. For these patients, hyperbaric oxygen therapy can improve blood circulation and prevent formation of thrombus and encephalopathy.

Role of oxidative stress in cardiovascular disease outcomes following exposure to ambient air pollution

Exposure to ambient air pollution is associated with adverse cardiovascular outcomes. These are manifested through several, likely overlapping, pathways including at the functional level, endothelial dysfunction, atherosclerosis, pro-coagulation and alterations in autonomic nervous system balance and blood pressure. At numerous points within each of these pathways, there is potential for cellular oxidative imbalances to occur. The current review examines epidemiological, occupational and controlled exposure studies and research employing healthy and diseased animal models, isolated organs and cell cultures in assessing the importance of the pro-oxidant potential of air pollution in the development of cardiovascular disease outcomes. The collective body of data provides evidence that oxidative stress (OS) is not only central to eliciting specific cardiac endpoints, but is also implicated in modulating the risk of succumbing to cardiovascular disease, sensitivity to ischemia/reperfusion injury and the onset and progression of metabolic disease following ambient pollution exposure. To add to this large research effort conducted to date, further work is required to provide greater insight into areas such as (a) whether an oxidative imbalance triggers and/or worsens the effect and/or is representative of the consequence of disease progression, (b) OS pathways and cardiac outcomes caused by individual pollutants within air pollution mixtures, or as a consequence of inter-pollutant interactions and (c) potential protection provided by nutritional supplements and/or pharmacological agents with antioxidant properties, in susceptible populations residing in polluted urban cities.

The Role of Peroxisome Proliferator-Activated Receptor γ in Mediating Cardioprotection Against Ischemia/Reperfusion Injury

Myocardial infarction (MI) is a serious cardiovascular disease resulting in high rates of morbidity and mortality. Although advances have been made in restoring myocardial perfusion in ischemic areas, decreases in cardiomyocyte death and infarct size are still limited, attributing to myocardial ischemia/reperfusion (I/R) injury. It is necessary to develop therapies to restrict myocardial I/R injury and protect cardiomyocytes against further damage after MI. Many studies have suggested that peroxisome proliferator-activated receptor γ (PPARγ), a ligand-inducible nuclear receptor that predominantly regulates glucose and lipid metabolism, is a promising therapeutic target for ameliorating myocardial I/R injury. Thus, this review focuses on the role of PPARγ in cardioprotection during myocardial I/R. The cardioprotective effects of PPARγ, including attenuating oxidative stress, inhibiting inflammatory responses, improving glucose and lipid metabolism, and antagonizing apoptosis, are described. Additionally, the underlying mechanisms of cardioprotective effects of PPARγ, such as regulating the expression of target genes, influencing other transcription factors, and modulating kinase signaling pathways, are further discussed.

Carbon Monoxide Poisoning: Pathogenesis, Management, and Future Directions of Therapy

Carbon monoxide (CO) poisoning affects 50,000 people a year in the United States. The clinical presentation runs a spectrum, ranging from headache and dizziness to coma and death, with a mortality rate ranging from 1 to 3%. A significant number of patients who survive CO poisoning suffer from long-term neurological and affective sequelae. The neurologic deficits do not necessarily correlate with blood CO levels but likely result from the pleiotropic effects of CO on cellular mitochondrial respiration, cellular energy utilization, inflammation, and free radical generation, especially in the brain and heart. Long-term neurocognitive deficits occur in 15-40% of patients, whereas approximately one-third of moderate to severely poisoned patients exhibit cardiac dysfunction, including arrhythmia, left ventricular systolic dysfunction, and myocardial infarction. Imaging studies reveal cerebral white matter hyperintensities, with delayed posthypoxic leukoencephalopathy or diffuse brain atrophy. Management of these patients requires the identification of accompanying drug ingestions, especially in the setting of intentional poisoning, fire-related toxic gas exposures, and inhalational injuries. Conventional therapy is limited to normobaric and hyperbaric oxygen, with no available antidotal therapy. Although hyperbaric oxygen significantly reduces the permanent neurological and affective effects of CO poisoning, a portion of survivors still have substantial morbidity. There has been some early success in therapies targeting the downstream inflammatory and oxidative effects of CO poisoning. New methods to directly target the toxic effect of CO, such as CO scavenging agents, are currently under development.

The role of hydrogen sulfide in homocysteine-induced cardiodynamic effects and oxidative stress markers in the isolated rat heart

This study aimed to assess the role of H2S in homocysteine-induced cardiodynamic effects in the isolated rat heart. The hearts were retrogradely perfused according to the Langendorff technique. The maximum and minimum rates of pressure in the left ventricle (dp/dt max, dp/dt min), systolic and diastolic left ventricular pressures (SLVP, DLVP), heart rate (HR), and coronary flow (CF) were measured. A spectrophotometrical method was used to measure the following oxidative stress markers: index of lipid peroxidation (thiobarbituric acid reactive substances, TBARS), nitrite level (NO2−), superoxide anion radicals (O2•−), and hydrogen peroxide (H2O2) concentrations. The administration of 10 µmol/l DL-homocysteine (DL-Hcy) alone decreased dp/dt max, SLVP, and CF but did not change any oxidative stress parameters. The administration of 10 µmol/l DL-propargylglycine (DL-PAG) decreased all cardiodynamic parameters and increased the concentration of O2•−. The co-administration of DL-Hcy and DL-PAG induced a significant decrease in all estimated cardiodynamic parameters and decreased the concentration of NO2− and O2•− but increased the levels of TBARS and H2O2. Homocysteine shows a lower pro-oxidative effect in the presence of hydrogen sulfide (H2S), which indicates a potential anti-oxidative capacity of H2S.

Possible role of antioxidants and nitric oxide inhibitors against carbon monoxide poisoning: Having a clear conscience because of their potential benefits

Carbon monoxide poisoning is one of the important emergency situations manifested by primarily acute and chronic anoxic central nervous system (CNS) injuries and other organ damages. Current descriptions and therapeutic approaches have been focused on the anoxic pathophysiology. However, this point of view incompletely explains some of the outcomes and needs to be investigated extensively. Considering this, we propose that reactive oxygen species (ROS) including especially nitric oxide (NO) are likely to be a key concept to understand the emergency related to CO poisoning and to discover new therapeutic modalities in CO toxicity. If we consider the hypothesis that ROS is involved greatly in acute and chronic toxic effects of CO on CNS and some other vital organs such as heart, it follows that the antioxidant and anti-NO therapies might give the clinicians more opportunities to prevent deep CNS injury. In support of this, we review the subject in essence and summarize clinical and experimental studies that support a key role of ROS in the explanation of pathophysiology of CO toxicity as well as new treatment modalities after CO poisoning.

Targeting heme oxygenase-1 and carbon monoxide for therapeutic modulation of inflammation

The heme oxygenase-1 (HO-1) enzyme system remains an attractive therapeutic target for the treatment of inflammatory conditions. HO-1, a cellular stress protein, serves a vital metabolic function as the rate-limiting step in the degradation of heme to generate carbon monoxide (CO), iron, and biliverdin-IXα (BV), the latter which is converted to bilirubin-IXα (BR). HO-1 may function as a pleiotropic regulator of inflammatory signaling programs through the generation of its biologically active end products, namely CO, BV and BR. CO, when applied exogenously, can affect apoptotic, proliferative, and inflammatory cellular programs. Specifically, CO can modulate the production of proinflammatory or anti-inflammatory cytokines and mediators. HO-1 and CO may also have immunomodulatory effects with respect to regulating the functions of antigen-presenting cells, dendritic cells, and regulatory T cells. Therapeutic strategies to modulate HO-1 in disease include the application of natural-inducing compounds and gene therapy approaches for the targeted genetic overexpression or knockdown of HO-1. Several compounds have been used therapeutically to inhibit HO activity, including competitive inhibitors of the metalloporphyrin series or noncompetitive isoform-selective derivatives of imidazole-dioxolanes. The end products of HO activity, CO, BV and BR may be used therapeutically as pharmacologic treatments. CO may be applied by inhalation or through the use of CO-releasing molecules. This review will discuss HO-1 as a therapeutic target in diseases involving inflammation, including lung and vascular injury, sepsis, ischemia-reperfusion injury, and transplant rejection.

Endothelial function does not improve with high-intensity continuous exercise training in SHR: implications of eNOS uncoupling

Exercise training is a well-recognized way to improve vascular endothelial function by increasing nitric oxide (NO) bioavailability. However, in hypertensive subjects, unlike low- and moderate-intensity exercise training, the beneficial effects of continuous high-intensity exercise on endothelial function are not clear, and the underlying mechanisms remain unknown. The aim of this study was to investigate the impact of high-intensity exercise on vascular function, especially on the NO pathway, in spontaneous hypertensive rats (SHR). These effects were studied on WKY, sedentary SHR and SHR that exercised at moderate (SHR-MOD) and high intensity (SHR-HI) on a treadmill (1 h per day; 5 days per week for 6 weeks at 55% and 80% of their maximal aerobic velocity, respectively). Endothelial function and specific NO contributions to acetylcholine-mediated relaxation were evaluated by measuring the aortic ring isometric forces. Endothelial nitric oxide synthase (eNOS) expression and phosphorylation (ser1177) were evaluated by western blotting. The total aortic and eNOS-dependent reactive oxygen species (ROS) production was assessed using electron paramagnetic resonance in aortic tissue. Although the aortas of SHR-HI had increased eNOS levels without alteration of eNOS phosphorylation, high-intensity exercise had no beneficial effect on endothelium-dependent vasorelaxation, unlike moderate exercise. This result was associated with increased eNOS-dependent ROS production in the aortas of SHR-HI. Notably, the use of the recoupling agent BH4 or a thiol-reducing agent blunted eNOS-dependent ROS production in the aortas of SHR-HI. In conclusion, the lack of a positive effect of high-intensity exercise on endothelial function in SHR was mainly explained by redox-dependent eNOS uncoupling, resulting in a switch from NO to O2(-) generation.