Cardiac-specific expression of heme oxygenase-1 protects against ischemia and reperfusion injury in transgenic mice

Oxidative Stress in Cardiac Tissue of Patients Undergoing Coronary Artery Bypass Graft Surgery: The Effects of Overweight and Obesity

Background

Obesity is one of the major cardiovascular risk factors and is associated with oxidative stress and myocardial dysfunction. We hypothesized that obesity affects cardiac function and morbidity by causing alterations in enzymatic redox patterns.

Methods

Sixty-one patients undergoing coronary artery bypass grafting (CABG) were included in the study. Excessive right atrial myocardial tissue emerging from the operative connection to the extracorporeal circulation was harvested. Patients were assigned to control (n = 19, body mass index (BMI): <25 kg/m²), overweight (n = 25, 25 kg/m² < BMI < 30 kg/m²), or obese (n = 17, BMI: >30 kg/m²) groups. Oxidative enzyme systems were studied directly in the cardiac muscles of patients undergoing CABG who were grouped according to BMI. Molecular biological methods and high-performance liquid chromatography were used to detect the expression and activity of oxidative enzymes and the formation of reactive oxygen species (ROS).

Results

We found increased levels of ROS and increased expression of ROS-producing enzymes (i.e., p47phox, xanthine oxidase) and decreased antioxidant defense mechanisms (mitochondrial aldehyde dehydrogenase, heme oxygenase-1, and eNOS) in line with elevated inflammatory markers (vascular cell adhesion molecule-1) in the right atrial myocardial tissue and by trend also in serum (sVCAM-1 and CCL5/RANTES).

Conclusion

Increasing BMI in patients undergoing CABG is related to altered myocardial redox patterns, which indicates increased oxidative stress with inadequate antioxidant compensation. These changes suggest that the myocardium of obese patients suffering from coronary artery disease is more susceptible to cardiomyopathy and possible damage by ischemia and reperfusion, for example, during cardiac surgery.

A positive feedback regulation of Heme oxygenase 1 by CELF1 in cardiac myoblast cells

As an RNA binding protein, CUG-BP Elav-like family (CELF) has been shown to be critical for heart biological functions. However, no reports have revealed the function of CELF1 in hypertrophic cardiomyopathy (HCM). Hinted by RNA immunoprecipitation-sequencing (RIP-seq) data, the influence of the CELF protein on heme oxygenase-1 (HO-1) expression was tested by modulating CELF1 levels. Cardiac hypertrophy is related to oxidative stress-induced damage. Hence, the cardiovascular system may be protected against further injury by upregulating the expression of antioxidant enzymes, such as HO-1. During the past two decades, research has demonstrated the central role of HO-1 in the protection against diseases. Thus, understanding the molecular mechanisms underlying the modulation of HO-1 expression is profoundly important for developing new strategies to prevent cardiac hypertrophy. To elucidate the molecular mechanisms underlying HO-1 regulation by the CELF protein, we performed RNA immunoprecipitation (RIP), biotin pull-down analysis, luciferase reporter and mRNA stability assays. We found that the expression of HO-1 was downregulated by CELF1 through the conserved GU-rich elements (GREs) in HO-1 3'UTR transcripts. Correspondingly, CELF1 expression was regulated by controlling the release of carbon monoxide (CO) in H9C2 cells. The CELF1-HO-1-CO regulation axis constituted a novel positive feedback circuit. In addition, we detected the potential involvement of CELF1 and HO-1 in samples from HCM patients. We found that CELF1 and CELF2, but not HO-1, were highly expressed in HCM heart samples. Thus, a manipulation targeting CELF1 could be developed as a potential therapeutic option for cardiac hypertrophy.

Bach1: Function, Regulation, and Involvement in Disease

The transcription factor BTB and CNC homology 1 (Bach1) is widely expressed in most mammalian tissues and functions primarily as a transcriptional suppressor by heterodimerizing with small Maf proteins and binding to Maf recognition elements in the promoters of targeted genes. It has a key regulatory role in the production of reactive oxygen species, cell cycle, heme homeostasis, hematopoiesis, and immunity and has been shown to suppress ischemic angiogenesis and promote breast cancer metastasis. This review summarizes how Bach1 controls these and other cellular and physiological and pathological processes. Bach1 expression and function differ between different cell types. Thus, therapies designed to manipulate Bach1 expression will need to be tightly controlled and tailored for each specific disease state or cell type.

Modulation of the monocyte/macrophage system in heart failure by targeting heme oxygenase-1

Upon myocardial infarction (MI) immune system becomes activated by extensive necrosis of cardiomyocytes releasing intracellular molecules called damage-associated molecular patterns. Overactive and prolonged immune responses are likely to be responsible for heart failure development and progression in patients surviving the ischemic episode. Heme oxygenase-1 (HO-1) plays a crucial role in heme degradation and in this way releases carbon monoxide, free iron, and biliverdin. This stress-inducible enzyme is induced by various oxidative and inflammatory signals. Consequently, biological actions of HO-1 are not limited to degradation of a toxic heme released from hemoproteins, but also provide an adaptive cellular response against chronic inflammation and oxidative injury. Indeed, the immunomodulatory and anti-inflammatory properties of HO-1 were demonstrated in several experimental studies, as well as in human cases of genetic HO-1 deficiency. HO-1 was shown to suppress the production, myocardial infiltration and inflammatory properties of monocytes and macrophages what resulted in limitation of post-MI cardiac damage. This review specifically addresses the role of HO-1, heme and its degradation products in macrophage biology and post-ischemic cardiac repair. A more complete understanding of these mechanisms is essential to develop new therapeutic approaches.

A review on heme oxygenase-1 induction: is it a necessary evil

Heme oxygenase-1 (HO-1) is considered to be the main protein in diseases arising as a result of oxidative and inflammatory insults. Tremendous research has been carried out on HO-1 since years, pertaining its cytoprotective effect against oxidative injury and other cellular stresses. HO-1, by regulating intracellular levels of pro-oxidant heme, or by other benefits of its by-products such as carbon monoxide (CO) and biliverdin (BV) had become an important candidate protein to be up-regulated to combat diverse stressful events. Although the beneficial effects of HO-1 induction have been reported in a number of cells and tissues, a growing body of evidence indicates that this increased HO-1 expression may lead to the progression of several diseases such as neurodegeneration, carcinogenesis. But it is not clear, what accounts for the increased expression of HO-1 in cells and tissues. The observed friendly role of HO-1 in a wide range of stress conditions since times is now doubtful. Therefore, more studies are needed to elucidate the exact role of HO-1 in various stressful events. Being more concise, elucidating the effect of HO-1 up-regulation on critical genes involved in particular diseases such as cancer will help to a larger extent to comprehend the exact role of HO-1. This review will assist in understanding the dual role (protective and detrimental) of HO-1 and the signaling pathway involved and will help in unraveling the doubtful role of HO-1 induction.

Evans Blue Dye: A Revisit of Its Applications in Biomedicine

Evans blue (EB) dye has owned a long history as a biological dye and diagnostic agent since its first staining application by Herbert McLean Evans in 1914. Due to its high water solubility and slow excretion, as well as its tight binding to serum albumin, EB has been widely used in biomedicine, including its use in estimating blood volume and vascular permeability, detecting lymph nodes, and localizing the tumor lesions. Recently, a series of EB derivatives have been labeled with PET isotopes and can be used as theranostics with a broad potential due to their improved half-life in the blood and reduced release. Some of EB derivatives have even been used in translational applications in clinics. In addition, a novel necrosis-avid feature of EB has recently been reported in some preclinical animal studies. Given all these interesting and important advances in EB study, a comprehensive revisiting of EB has been made in its biomedical applications in the review.

Hmox1 promotes osteogenic differentiation at the expense of reduced adipogenic differentiation induced by BMP9 in C3H10T1/2 cells

Mesenchymal stem cells (MSCs) are multipotent progenitors that can differentiate into a variety of cell types under proper stimuli. Bone morphogenetic protein 9 (BMP9) is able to simultaneously induce both adipogenic and osteogenic differentiation of MSCs although the regulatory molecules involved remain to be fully identified and characterized. Heme oxygenase 1 (Hmox1) plays an essential role not only in fat metabolism, but also in bone development. In the present study, we investigated the functional role of Hmox1 in BMP9-induced osteogenic/adipogenic differentiation in MSCs line C3H10T1/2 and probed the possible mechanism involved. We found that BMP9 promoted the endogenous expression of Hmox1 in C3H10T1/2 cells. Overexpression of Hmox1 or cobalt protoporphyrin (CoPP), an inducer of Hmox1, increased BMP9-induced osteogenic differentiation in vitro. Subcutaneous stem cell implantation in nude mice further confirmed that Hmox1 potentiated BMP9-induced ectopic bone formation in vivo. In contrast, Hmox1 reduced BMP9-induced adipogenic differentiation in C3H10T1/2 cells. Although had no obvious effect on BMP9-induced Smad1/5/8 phosphorylation, Hmox1 enhanced phosphorylation of p38, and AKT, while decreased phosphorylation of ERK1/2. Furthermore, Hmox1 increased total β-catenin protein level, and promoted the nuclear translocation of β-catenin in C3H10T1/2 cells. Taken together, our study strongly suggests that Hmox1 is likely to potentiate osteogenic differentiation and yet decrease adipogenic differentiation induced by BMP9 possibly through regulation of multiple signaling pathways.

Edaravone Improves Septic Cardiac Function by Inducing an HIF-1α/HO-1 Pathway

Septic myocardial dysfunction remains prevalent and raises mortality rate in patients with sepsis. During sepsis, tissues undergo tremendous oxidative stress which contributes critically to organ dysfunction. Edaravone, a potent radical scavenger, has been proved beneficial in ischemic injuries involving hypoxia-inducible factor- (HIF-) 1, a key regulator of a prominent antioxidative protein heme oxygenase- (HO-) 1. However, its effect in septic myocardial dysfunction remains unclarified. We hypothesized that edaravone may prevent septic myocardial dysfunction by inducing the HIF-1/HO-1 pathway. Rats were subjected to cecal ligation and puncture (CLP) with or without edaravone infusion at three doses (50, 100, or 200 mg/kg, resp.) before CLP and intraperitoneal injection of the HIF-1α antagonist, ME (15 mg/kg), after CLP. After CLP, rats had cardiac dysfunction, which was associated with deformed myocardium, augmented lipid peroxidation, and increased myocardial apoptosis and inflammation, along with decreased activities of catalase, HIF-1α, and HO-1 in the myocardium. Edaravone pretreatment dose-dependently reversed the changes, of which high dose most effectively improved cardiac function and survival rate of septic rats. However, inhibition of HIF-1α by ME demolished the beneficial effects of edaravone at high dose, reducing the survival rate of the septic rats without treatments. Taken together, edaravone, by inducing the HIF-1α/HO-1 pathway, suppressed oxidative stress and protected the heart against septic myocardial injury and dysfunction.

Genetic deletion of 12/15 lipoxygenase promotes effective resolution of inflammation following myocardial infarction

12/15 lipoxygenase (LOX) directs inflammation and lipid remodeling. However, the role of 12/15LOX in post-myocardial infarction (MI) left ventricular remodeling is unclear. To determine the role of 12/15LOX, 8-12 week-old C57BL/6 J wild-type (WT; n = 93) and 12/15LOX^-/- (n = 97) mice were subjected to permanent coronary artery ligation and monitored at day (d)1 and d5 post-operatively. Post-MI d28 survival was measured in male and female mice. No-MI surgery mice were maintained as d0 naïve controls. 12/15LOX^-/- mice exhibited higher survival rates with lower cardiac rupture and improved LV function as compared with WT post-MI. Compared to WT, neutrophils and macrophages in 12/15LOX^-/- mice were polarized towards N2 and M2 phenotypes, respectively, with increased of expression mrc-1, ym-1, and arg-1 post-MI. 12/15LOX^-/- mice exhibited lower levels of pro-inflammatory 12-(S)-hydroperoxyeicosatetraenoic acid (12(S)-HETE) and higher CYP2J-derived epoxyeicosatrienoic acids (EETs) levels. CYP2J-derived 5,6-, 8,9-, 11,12-, and 14,15-EETs activated macrophage-specific hemeoxygenase (HO)-1 marked with increases in F4/80⁺/Ly6C^low and F4/80⁺/CD206^high cells at d5 post-MI in 12/15LOX^-/- mice. In contrast, inhibition of HO-1 led to total mortality in 12/15LOX^-/- mice by post-MI d5. 12/15LOX^-/- mice exhibited reduced collagen density and lower α-smooth muscle actin (SMA) expression at d5 post-MI, indicating delayed or limited fibroblast-to-myofibroblast differentiation. In conclusion, genetic deletion of 12/15LOX reduces 12(S)-HETE and activates CYP2J-derived EETs to promote effective resolution of inflammation post-MI leading to reduced cardiac rupture, improved LV function, and better survival.

Gaseous Signaling Molecules in Cardiovascular Function: From Mechanisms to Clinical Translation

Carbon monoxide (CO), hydrogen sulfide (H₂S), and nitric oxide (NO) constitute endogenous gaseous molecules produced by specific enzymes. These gases are chemically simple, but exert multiple effects and act through shared molecular targets to control both physiology and pathophysiology in the cardiovascular system (CVS). The gases act via direct and/or indirect interactions with each other in proteins such as heme-containing enzymes, the mitochondrial respiratory complex, and ion channels, among others. Studies of the major impacts of CO, H₂S, and NO on the CVS have revealed their involvement in controlling blood pressure and in reducing cardiac reperfusion injuries, although their functional roles are not limited to these conditions. In this review, the basic aspects of CO, H₂S, and NO, including their production and effects on enzymes, mitochondrial respiration and biogenesis, and ion channels are briefly addressed to provide insight into their biology with respect to the CVS. Finally, potential therapeutic applications of CO, H₂S, and NO with the CVS are addressed, based on the use of exogenous donors and different types of delivery systems.

Cardiovascular Abnormalities in Carbon Monoxide Poisoning

Acute carbon monoxide (CO) poisoning is the most common cause of poisoning and poisoning-related death in the United States. It manifests as broad spectrum of symptoms ranging from mild headache, nausea, and fatigue to dizziness, syncope, coma, seizures resulting in cardiovascular collapse, respiratory failure, and death. Cardiovascular complications of CO poisoning has been well reported and include myocardial stunning, left ventricular dysfunction, pulmonary edema, and arrhythmias. Acute myocardial ischemia has also been reported from increased thrombogenicity due to CO poisoning. Myocardial toxicity from CO exposure is associated with increased short-term and long-term mortality. Carboxyhemoglobin (COHb) levels do not correlate well with the clinical severity of CO poisoning. Supplemental oxygen remains the cornerstone of therapy for CO poisoning. Hyperbaric oxygen therapy increases CO elimination and has been used with wide variability in patients with evidence of neurological and myocardial injury from CO poisoning, but its benefit in limiting or reversing cardiac injury is unknown. We present a comprehensive review of literature on cardiovascular manifestations of CO poisoning and propose a diagnostic algorithm for managing patients with CO poisoning.

Discovery of Novel Small-Molecule Inducers of Heme Oxygenase-1 That Protect Human iPSC-Derived Cardiomyocytes from Oxidative Stress

Oxidative injury to cardiomyocytes plays a critical role in cardiac pathogenesis following myocardial infarction. Transplantation of stem cell-derived cardiomyocytes has recently progressed as a novel treatment to repair damaged cardiac tissue but its efficacy has been limited by poor survival of transplanted cells owing to oxidative stress in the post-transplantation environment. Identification of small molecules that activate cardioprotective pathways to prevent oxidative damage and increase survival of stem cells post-transplantation is therefore of great interest for improving the efficacy of stem cell therapies. This report describes a chemical biology phenotypic screening approach to identify and validate small molecules that protect human-induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) from oxidative stress. A luminescence-based high-throughput assay for cell viability was used to screen a diverse collection of 48,640 small molecules for protection of hiPSC-CMs from peroxide-induced cell death. Cardioprotective activity of "hit" compounds was confirmed using impedance-based detection of cardiomyocyte monolayer integrity and contractile function. Structure-activity relationship studies led to the identification of a potent class of compounds with 4-(pyridine-2-yl)thiazole scaffold. Examination of gene expression in hiPSC-CMs revealed that the hit compound, designated cardioprotectant 312 (CP-312), induces robust upregulation of heme oxygenase-1, a marker of the antioxidant response network that has been strongly correlated with protection of cardiomyocytes from oxidative stress. CP-312 therefore represents a novel chemical scaffold identified by phenotypic high-throughput screening using hiPSC-CMs that activates the antioxidant defense response and may lead to improved pharmacological cardioprotective therapies.

Loss of heme oxygenase-1 accelerates mesodermal gene expressions during embryoid body development from mouse embryonic stem cells

Heme oxygenase (HO)-1 is an inducible stress response protein and well known to protect cells and tissues against injury. Despite its important function in cytoprotection against physiological stress, the role of HO-1 in embryonic stem cell (ESC) differentiation remains largely unknown. We showed previously that induced pluripotent stem (iPS) cells that lack HO-1 are more sensitive to oxidant stress-induced cell death and more prone to lose pluripotent markers upon LIF withdrawal. To elucidate the role of HO-1 in ESC differentiation and to rule out the controversy of potential gene flaws in iPS cells, we derived and established mouse HO-1 knockout ESC lines from HO-1 knockout blastocysts. Using wild type D3 and HO-1 knockout ESCs in the 3-dimensional embryoid body (EB) differentiation model, we showed that at an early time point during EB development, an absence of HO-1 led to enhanced ROS level, concomitant with increased expressions of master mesodermal regulator brachyury and endodermal marker GATA6. In addition, critical smooth muscle cell (SMC) transcription factor serum response factor and its coactivator myocardin were enhanced. Furthermore, HO-1 deficiency increased Smad2 in ESCs and EBs, revealing a role of HO-1 in controlling Smad2 level. Smad2 not only mediates mesendoderm differentiation of mouse ESCs but also SMC development. Collectively, loss of HO-1 resulted in higher level of mesodermal and SMC regulators, leading to accelerated and enhanced SMC marker SM α-actin expression. Our results reveal a previously unrecognized function of HO-1 in regulating SMC gene expressions during ESC-EB development. More importantly, our findings may provide a novel strategy in enhancing ESC differentiation toward SMC lineage.

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Loss of HO-1 in ESCs promotes adipogenesis but reduces osteogenesis.

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During early EB development, loss of HO-1 results in robust induction of brachyury.

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During early EB development, lack of HO-1 leads to enhanced ROS level.

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Loss of HO-1 increases SMC transcription factor SRF and cofactor myocardin.

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HO-1 deficiency promotes mesodermal SMC differentiation during EB development.

A key role for peroxynitrite-mediated inhibition of cardiac ERG (Kv11.1) K+ channels in carbon monoxide-induced proarrhythmic early afterdepolarizations

Exposure to CO causes early afterdepolarization arrhythmias. Previous studies in rats have indicated that arrhythmias arose as a result of augmentation of the late Na+ current. The purpose of the present study was to examine the basis for CO-induced arrhythmias in guinea pig myocytes in which action potentials (APs) more closely resemble those of human myocytes. Whole-cell current- and voltage-clamp recordings were made from isolated guinea pig myocytes as well as from human embryonic kidney 293 (HEK293) cells that express wild-type or a C723S mutant form of ether-a-go-go-related gene (ERG; Kv11.1). We also monitored the formation of peroxynitrite (ONOO-) in HEK293 cells fluorimetrically. CO-applied as the CO-releasing molecule, CORM-2-prolonged the APs and induced early afterdepolarizations in guinea pig myocytes. In HEK293 cells, CO inhibited wild-type, but not C723S mutant, Kv11.1 K+ currents. Inhibition was prevented by an antioxidant, mitochondrial inhibitors, or inhibition of NO formation. CO also raised ONOO- levels, an effect that was reversed by the ONOO- scavenger, FeTPPS [5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrinato-iron(III)], which also prevented the CO inhibition of Kv11.1 currents and abolished the effects of CO on Kv11.1 tail currents and APs in guinea pig myocytes. Our data suggest that CO induces arrhythmias in guinea pig cardiac myocytes via the ONOO--mediated inhibition of Kv11.1 K+ channels.-Al-Owais, M. M., Hettiarachchi, N. T., Kirton, H. M., Hardy, M. E., Boyle, J. P., Scragg, J. L., Steele, D. S., Peers, C. A key role for peroxynitrite-mediated inhibition of cardiac ERG (Kv11.1) K+ channels in carbon monoxide-induced proarrhythmic early afterdepolarizations.

Sepsis-Induced Cardiomyopathy: Oxidative Implications in the Initiation and Resolution of the Damage

Cardiac dysfunction may complicate the course of severe sepsis and septic shock with significant implications for patient's survival. The basic pathophysiologic mechanisms leading to septic cardiomyopathy have not been fully clarified until now. Disease-specific treatment is lacking, and care is still based on supportive modalities. Septic state causes destruction of redox balance in many cell types, cardiomyocytes included. The production of reactive oxygen and nitrogen species is increased, and natural antioxidant systems fail to counterbalance the overwhelming generation of free radicals. Reactive species interfere with many basic cell functions, mainly through destruction of protein, lipid, and nucleic acid integrity, compromising enzyme function, mitochondrial structure and performance, and intracellular signaling, all leading to cardiac contractile failure. Takotsubo cardiomyopathy may result from oxidative imbalance. This review will address the multiple aspects of cardiomyocyte bioenergetic failure in sepsis and discuss potential therapeutic interventions.

Prolonged Allogeneic Islet Graft Survival by Protoporphyrins

Transplantation of islets of Langerhans in patients with type 1 diabetes allows for improved metabolic control and insulin independence. The need for chronic immunosuppression limits this procedure to selected patients with brittle diabetes. Definition of therapeutic strategies allowing permanent engraftment without the need for chronic immunosuppression could overcome such limitations. We tested the effect of the use of protoporphyrins (CoPP and FePP), powerful inducers of the cytoprotective protein hemeoxygenase 1 (HO-1), on allogeneic islet graft survival. Chemically induced diabetic C57BL/6 mice received DBA/2 islets. Treatment consisted in peritransplant administration of CoPP or saline. Islets were either cultured in the presence of FePP or vehicle before implant. Short-course administration of CoPP led to long-term islet allograft survival in a sizable proportion of recipients. Long-term graft-bearing animals rejected third-party islets while accepting a second set donor-specific graft permanently, without additional treatment. Preconditioning of islets with FePP by itself led to improved graft survival in untreated recipients, and provided additional advantage in CoPP-treated recipients, resulting in an increased proportion of long-term surviving grafts. Preconditioning of the graft with protoporphyrins prior to implant resulted in reduction of class II expression. Administration of protoporphyrins to the recipients of allogeneic islets also resulted in transient powerful immunosuppression with reduced lymphocyte proliferative responses, increased proportion of regulatory cells (CD4+CD25+), decreased mononuclear cell infiltrating the graft, paralleled by a systemic upregulation of HO-1 expression. All these mechanisms may have contributed to the induction of donor-specific hyporesponsiveness in a proportion of the protoporphyrintreated animals.

Splenic Ly6Chi monocytes contribute to adverse late post-ischemic left ventricular remodeling in heme oxygenase-1 deficient mice

Heme oxygenase-1 (Hmox1) is a stress-inducible protein crucial in heme catabolism. The end products of its enzymatic activity possess anti-oxidative, anti-apoptotic and anti-inflammatory properties. Cardioprotective effects of Hmox1 were demonstrated in experimental models of myocardial infarction (MI). Nevertheless, its importance in timely resolution of post-ischemic inflammation remains incompletely understood. The aim of this study was to determine the role of Hmox1 in the monocyte/macrophage-mediated cardiac remodeling in a mouse model of MI. Hmox1 knockout (Hmox1^-/-) and wild-type (WT, Hmox1^+/+) mice were subjected to a permanent ligation of the left anterior descending coronary artery. Significantly lower incidence of left ventricle (LV) free wall rupture was noted between 3rd and 5th day after MI in Hmox1^-/- mice resulting in their better overall survival. Then, starting from 7th until 21st day post-MI a more potent deterioration of LV function was observed in Hmox1^-/- than in the surviving Hmox1^+/+ mice. This was accompanied by higher numbers of Ly6C^hi monocytes in peripheral blood, as well as higher expression of monocyte chemoattractant protein-1 and adhesion molecules in the hearts of MI-operated Hmox1^-/- mice. Consequently, a greater post-MI monocyte-derived myocardial macrophage infiltration was noted in Hmox1-deficient individuals. Splenectomy decreased the numbers of circulating inflammatory Ly6C^hi monocytes in blood, reduced the numbers of proinflammatory cardiac macrophages and significantly improved the post-MI LV function in Hmox1^-/- mice. In conclusion, Hmox1 deficiency has divergent consequences in MI. On the one hand, it improves early post-MI survival by decreasing the occurrence of cardiac rupture. Afterwards, however, the hearts of Hmox1-deficient mice undergo adverse late LV remodeling due to overactive and prolonged post-ischemic inflammatory response. We identified spleen as an important source of these cardiovascular complications in Hmox1^-/- mice.

Ultraviolet-A1 irradiation therapy for systemic lupus erythematosus

Systemic lupus erythematosus (lupus, SLE) is a chronic autoimmune disease characterized by the production of autoantibodies, which bind to antigens and are deposited within tissues to fix complement, resulting in widespread systemic inflammation. The studies presented herein are consistent with hyperpolarized, adenosine triphosphate (ATP)-deficient mitochondria being central to the disease process. These hyperpolarized mitochondria resist the depolarization required for activation-induced apoptosis. The mitochondrial ATP deficits add to this resistance to apoptosis and also reduce the macrophage energy that is needed to clear apoptotic bodies. In both cases, necrosis, the alternative pathway of cell death, results. Intracellular constituents spill into the blood and tissues, eliciting inflammatory responses directed at their removal. What results is “autoimmunity.” Ultraviolet (UV)-A1 photons have the capacity to remediate this aberrancy. Exogenous exposure to low-dose, full-body, UV-A1 radiation generates singlet oxygen. Singlet oxygen has two major palliative actions in patients with lupus and the UV-A1 photons themselves have several more. Singlet oxygen depolarizes the hyperpolarized mitochondrion, triggering non-ATP-dependent apoptosis that deters necrosis. Next, singlet oxygen activates the gene encoding heme oxygenase (HO-1), a major governor of systemic homeostasis. HO-1 catalyzes the degradation of the oxidant heme into biliverdin (converted to bilirubin), Fe, and carbon monoxide (CO), the first three of these exerting powerful antioxidant effects, and in conjunction with a fourth, CO, protecting against injury to the coronary arteries, the central nervous system, and the lungs. The UV-A1 photons themselves directly attenuate disease in lupus by reducing B cell activity, preventing the suppression of cell-mediated immunity, slowing an epigenetic progression toward SLE, and ameliorating discoid and subacute cutaneous lupus. Finally, a combination of these mechanisms reduces levels of anticardiolipin antibodies and protects during lupus pregnancy. Capping all of this is that UV-A1 irradiation is an essentially innocuous, highly manageable, and comfortable therapeutic agency.

Heme Oxygenase-1 and Carbon Monoxide in the Heart: The Balancing Act Between Danger Signaling and Pro-Survival

Understanding the processes governing the ability of the heart to repair and regenerate after injury is crucial for developing translational medical solutions. New avenues of exploration include cardiac cell therapy and cellular reprogramming targeting cell death and regeneration. An attractive possibility is the exploitation of cytoprotective genes that exist solely for self-preservation processes and serve to promote and support cell survival. Although the antioxidant and heat-shock proteins are included in this category, one enzyme that has received a great deal of attention as a master protective sentinel is heme oxygenase-1 (HO-1), the rate-limiting step in the catabolism of heme into the bioactive signaling molecules carbon monoxide, biliverdin, and iron. The remarkable cardioprotective effects ascribed to heme oxygenase-1 are best evidenced by its ability to regulate inflammatory processes, cellular signaling, and mitochondrial function ultimately mitigating myocardial tissue injury and the progression of vascular-proliferative disease. We discuss here new insights into the role of heme oxygenase-1 and heme on cardiovascular health, and importantly, how they might be leveraged to promote heart repair after injury.

Combinatorial extracellular matrix microenvironments promote survival and phenotype of human induced pluripotent stem cell-derived endothelial cells in hypoxia

Recent developments in cell therapy using human induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) hold great promise for treating ischemic cardiovascular tissues. However, poor post-transplantation viability largely limits the potential of stem cell therapy. Although the extracellular matrix (ECM) has become increasingly recognized as an important cell survival factor, conventional approaches primarily rely on single ECMs for in vivo co-delivery with cells, even though the endothelial basement membrane is comprised of a milieu of different ECMs. To address this limitation, we developed a combinatorial ECM microarray platform to simultaneously interrogate hundreds of micro-scale multi-component chemical compositions of ECMs on iPSC-EC response. After seeding iPSC-ECs onto ECM microarrays, we performed high-throughput analysis of the effects of combinatorial ECMs on iPSC-EC survival, endothelial phenotype, and nitric oxide production under conditions of hypoxia (1% O2) and reduced nutrients (1% fetal bovine serum), as is present in ischemic injury sites. Using automated image acquisition and analysis, we identified combinatorial ECMs such as collagen IV+gelatin+heparan sulfate+laminin and collagen IV+fibronectin+gelatin+heparan sulfate+laminin that significantly improved cell survival, nitric oxide production, and CD31 phenotypic expression, in comparison to single-component ECMs. These results were further validated in conventional cell culture platforms and within three-dimensional scaffolds. Furthermore, this approach revealed complex ECM interactions and non-intuitive cell behavior that otherwise could not be easily determined using conventional cell culture platforms. Together these data suggested that iPSC-EC delivery within optimal combinatorial ECMs may improve their survival and function under the condition of hypoxia with reduced nutrients.

STATEMENT OF SIGNIFICANCE

Human endothelial cells (ECs) derived from induced pluripotent stem cells (iPSC-ECs) are promising for treating diseases associated with reduced nutrient and oxygen supply like heart failure. However, diminished iPSC-EC survival after implantation into diseased environments limits their therapeutic potential. Since native ECs interact with numerous extracellular matrix (ECM) proteins for functional maintenance, we hypothesized that combinatorial ECMs may improve cell survival and function under conditions of reduced oxygen and nutrients. We developed a high-throughput system for simultaneous screening of iPSC-ECs cultured on multi-component ECM combinations under the condition of hypoxia and reduced serum. Using automated image acquisition and analytical algorithms, we identified combinatorial ECMs that significantly improved cell survival and function, in comparison to single ECMs. Furthermore, this approach revealed complex ECM interactions and non-intuitive cell behavior that otherwise could not be easily determined.

Hemin, a heme oxygenase-1 inducer, restores the attenuated cardioprotective effect of ischemic preconditioning in isolated diabetic rat heart

BACKGROUND

Attenuated cardioprotective effect of ischemic preconditioning (IPC) by reduced nitric oxide (NO) is a hallmark during diabetes mellitus (DM). Recently, we reported that the formation of caveolin-endothelial nitric oxide synthase (eNOS) complex decreases the release of NO, which is responsible for attenuation of IPC-induced cardioprotection in DM rat heart. Heme oxygenase-1 (HO-1) facilitates release of NO by disrupting caveolin-eNOS complex. The activity of HO-1 is decreased during DM. This study was designed to investigate the role of hemin (HO-1 inducer) in attenuated cardioprotective effect of IPC in isolated diabetic rat heart.

METHODS

DM was induced in male Wistar rat by single dose of streptozotocin. Cardioprotective effect was assessed in terms of myocardial infarct size and release of lactate dehydrogenase and creatine kinase in coronary effluent. The release of NO was estimated indirectly by measuring the release of nitrite in coronary effluent. Perfusion of sodium nitrite, a precursor of NO, was used as a positive control.

RESULT

IPC-induced cardioprotection and increased release of nitrite were significantly attenuated in a diabetic rat as compared to a normal rat. Pretreatment with hemin and daidzein, a caveolin inhibitor, alone or in combination significantly restored the attenuated cardioprotection and increased the release of nitrite in diabetic rat heart. Zinc protoporphyrin, a HO-1 inhibitor, significantly abolished the observed cardioprotection and decreased the release of nitrite in hemin pretreated DM rat heart.

CONCLUSION

Thus, it is suggested that hemin restores the attenuated cardioprotective effect in diabetic rat heart by increasing the activity of HO-1 and subsequently release of NO.

Heme Oxygenases in Cardiovascular Health and Disease

Heme oxygenases are composed of two isozymes, Hmox1 and Hmox2, that catalyze the degradation of heme to carbon monoxide (CO), ferrous iron, and biliverdin, the latter of which is subsequently converted to bilirubin. While initially considered to be waste products, CO and biliverdin/bilirubin have been shown over the last 20 years to modulate key cellular processes, such as inflammation, cell proliferation, and apoptosis, as well as antioxidant defense. This shift in paradigm has led to the importance of heme oxygenases and their products in cell physiology now being well accepted. The identification of the two human cases thus far of heme oxygenase deficiency and the generation of mice deficient in Hmox1 or Hmox2 have reiterated a role for these enzymes in both normal cell function and disease pathogenesis, especially in the context of cardiovascular disease. This review covers the current knowledge on the function of both Hmox1 and Hmox2 at both a cellular and tissue level in the cardiovascular system. Initially, the roles of heme oxygenases in vascular health and the regulation of processes central to vascular diseases are outlined, followed by an evaluation of the role(s) of Hmox1 and Hmox2 in various diseases such as atherosclerosis, intimal hyperplasia, myocardial infarction, and angiogenesis. Finally, the therapeutic potential of heme oxygenases and their products are examined in a cardiovascular disease context, with a focus on how the knowledge we have gained on these enzymes may be capitalized in future clinical studies.

Pharmacology of Ischemia-Reperfusion. Translational Research Considerations

Ischemia-reperfusion (IRI) is a complex physiopathological mechanism involving a large number of metabolic processes that can eventually lead to cell apoptosis and ultimately tissue necrosis. Treatment approaches intended to reduce or palliate the effects of IRI are varied, and are aimed basically at: inhibiting cell apoptosis and the complement system in the inflammatory process deriving from IRI, modulating calcium levels, maintaining mitochondrial membrane integrity, reducing the oxidative effects of IRI and levels of inflammatory cytokines, or minimizing the action of macrophages, neutrophils, and other cell types. This study involved an extensive, up-to-date review of the bibliography on the currently most widely used active products in the treatment and prevention of IRI, and their mechanisms of action, in an aim to obtain an overview of current and potential future treatments for this pathological process. The importance of IRI is clearly reflected by the large number of studies published year after year, and by the variety of pathophysiological processes involved in this major vascular problem. A quick study of the evolution of IRI-related publications in PubMed shows that in a single month in 2014, 263 articles were published, compared to 806 articles in the entire 1990.

Heme oxygenase 1 controls early innate immune response of macrophages to Salmonella Typhimurium infection

Macrophages are central for the immune control of intracellular microbes. Heme oxygenase 1 (HO-1, hmox) is the first and rate limiting enzyme in the breakdown of heme originating from degraded senescent erythrocytes and heme-proteins, yielding equal amounts of iron, carbon monoxide and biliverdin. HO-1 is strongly up-regulated in macrophages in response to inflammatory signals, including bacterial endotoxin. In view of the essential role of iron for the growth and proliferation of intracellular bacteria along with known effects of the metal on innate immune function, we examined whether HO-1 plays a role in the control of infection with the intracellular bacterium Salmonella Typhimurium. We studied the course of infection in stably-transfected murine macrophages (RAW264.7) bearing a tetracycline-inducible plasmid producing hmox shRNA and in primary HO-1 knockout macrophages. While uptake of bacteria into macrophages was not affected, a significantly reduced survival of intracellular Salmonella was observed upon hmox knockdown or pharmacological hmox inhibition, which was independent of Nramp1 functionality. This could be traced to limitation of iron availability for intramacrophage bacteria along with enhanced stimulation of innate immune effector pathways, including the formation of reactive oxygen and nitrogen species and increased TNF-α expression. Mechanistically, these latter effects result from intracellular iron limitation with subsequent activation of NF-κB and further inos, tnfa and p47phox transcription along with reduced formation of the anti-inflammatory and radical scavenging molecules, CO and biliverdin as a consequence of HO-1 silencing. Taken together our data provide novel evidence that the infection-driven induction of HO-1 exerts detrimental effects in the early control of Salmonella infection, whereas hmox inhibition can favourably modulate anti-bacterial immune effector pathways of macrophages and promote bacterial elimination.

Heme oxygenase-1 regulates mitochondrial quality control in the heart

The cardioprotective inducible enzyme heme oxygenase-1 (HO-1) degrades prooxidant heme into equimolar quantities of carbon monoxide, biliverdin, and iron. We hypothesized that HO-1 mediates cardiac protection, at least in part, by regulating mitochondrial quality control. We treated WT and HO-1 transgenic mice with the known mitochondrial toxin, doxorubicin (DOX). Relative to WT mice, mice globally overexpressing human HO-1 were protected from DOX-induced dilated cardiomyopathy, cardiac cytoarchitectural derangement, and infiltration of CD11b+ mononuclear phagocytes. Cardiac-specific overexpression of HO-1 ameliorated DOX-mediated dilation of the sarcoplasmic reticulum as well as mitochondrial disorganization in the form of mitochondrial fragmentation and increased numbers of damaged mitochondria in autophagic vacuoles. HO-1 overexpression promotes mitochondrial biogenesis by upregulating protein expression of NRF1, PGC1α, and TFAM, which was inhibited in WT animals treated with DOX. Concomitantly, HO-1 overexpression inhibited the upregulation of the mitochondrial fission mediator Fis1 and resulted in increased expression of the fusion mediators, Mfn1 and Mfn2. It also prevented dynamic changes in the levels of key mediators of the mitophagy pathway, PINK1 and parkin. Therefore, these findings suggest that HO-1 has a novel role in protecting the heart from oxidative injury by regulating mitochondrial quality control.

Modification of Caffeic Acid with Pyrrolidine Enhances Antioxidant Ability by Activating AKT/HO-1 Pathway in Heart

Overproduction of free radicals during ischemia/reperfusion (I/R) injury leads to an interest in using antioxidant therapy. Activating an endogenous antioxidant signaling pathway is more important due to the fact that the free radical scavenging behavior in vitro does not always correlate with a cytoprotection effect in vivo. Caffeic acid (CA), an antioxidant, is a major phenolic constituent in nature. Pyrrolidinyl caffeamide (PLCA), a derivative of CA, was compared with CA for their antioxidant and cytoprotective effects. Our results indicate that CA and PLCA exert the same ability to scavenge DPPH in vitro. In response to myocardial I/R stress, PLCA was shown to attenuate lipid peroxydation and troponin release more than CA. These responses were accompanied with a prominent elevation in AKT and HO-1 expression and a preservation of mnSOD expression and catalase activity. PLCA also improved cell viability and alleviated the intracellular ROS level more than CA in cardiomyocytes exposed to H₂O₂. When inhibiting the AKT or HO-1 pathways, PLCA lost its ability to recover mnSOD expression and catalase activity to counteract with oxidative stress, suggesting AKT/HO-1 pathway activation by PLCA plays an important role. In addition, inhibition of AKT signaling further abolished HO-1 activity, while inhibition of HO-1 signaling attenuated AKT expression, indicating cross-talk between the AKT and HO-1 pathways. These protective effects may contribute to the cardiac function improvement by PLCA. These findings provide new insight into therapeutic approaches using a modified natural compound against oxidative stress from myocardial injuries.

The production of multi-transgenic pigs: update and perspectives for xenotransplantation

The domestic pig shares many genetic, anatomical and physiological similarities to humans and is thus considered to be a suitable organ donor for xenotransplantation. However, prior to clinical application of porcine xenografts, three major hurdles have to be overcome: (1) various immunological rejection responses, (2) physiological incompatibilities between the porcine organ and the human recipient and (3) the risk of transmitting zoonotic pathogens from pig to humans. With the introduction of genetically engineered pigs expressing high levels of human complement regulatory proteins or lacking expression of α-Gal epitopes, the HAR can be consistently overcome. However, none of the transgenic porcine organs available to date was fully protected against the binding of anti-non-Gal xenoreactive natural antibodies. The present view is that long-term survival of xenografts after transplantation into primates requires additional modifications of the porcine genome and a specifically tailored immunosuppression regimen compliant with current clinical standards. This requires the production and characterization of multi-transgenic pigs to control HAR, AVR and DXR. The recent emergence of new sophisticated molecular tools such as Zinc-Finger nucleases, Transcription-activator like endonucleases, and the CRISPR/Cas9 system has significantly increased efficiency and precision of the production of genetically modified pigs for xenotransplantation. Several candidate genes, incl. hTM, hHO-1, hA20, CTLA4Ig, have been explored in their ability to improve long-term survival of porcine xenografts after transplantation into non-human primates. This review provides an update on the current status in the production of multi-transgenic pigs for xenotransplantation which could bring porcine xenografts closer to clinical application.

Bone marrow transplantation modulates tissue macrophage phenotype and enhances cardiac recovery after subsequent acute myocardial infarction

BACKGROUND

Bone marrow transplantation (BMT) is commonly used in experimental studies to investigate the contribution of BM-derived circulating cells to different disease processes. During studies investigating the cardiac response to acute myocardial infarction (MI) induced by permanent coronary ligation in mice that had previously undergone BMT, we found that BMT itself affects the remodelling response.

METHODS AND RESULTS

Compared to matched naive mice, animals that had previously undergone BMT developed significantly less post-MI adverse remodelling, infarct thinning and contractile dysfunction as assessed by serial magnetic resonance imaging. Cardiac rupture in male mice was prevented. Histological analysis showed that the infarcts of mice that had undergone BMT had a significantly higher number of inflammatory cells, surviving cardiomyocytes and neovessels than control mice, as well as evidence of significant haemosiderin deposition. Flow cytometric and histological analyses demonstrated a higher number of alternatively activated (M2) macrophages in myocardium of the BMT group compared to control animals even before MI, and this increased further in the infarcts of the BMT mice after MI.

CONCLUSIONS

The process of BMT itself substantially alters tissue macrophage phenotype and the subsequent response to acute MI. An increase in alternatively activated macrophages in this setting appears to enhance cardiac recovery after MI.

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.

Plasma bilirubin values on admission and ventricular remodeling after a first anterior ST-segment elevation acute myocardial infarction

INTRODUCTION

Bilirubin may elicit cardiovascular protection and heme oxygenase-1 overexpression attenuated post-infarction ventricular remodeling in experimental animals, but the association between bilirubin levels and post-infarction remodeling is unknown.

MATERIALS AND METHODS

In 145 patients with a first anterior ST-segment elevation acute myocardial infarction (STEMI), we assessed whether plasma bilirubin on admission predicted adverse remodeling (left ventricular end-diastolic volume [LVEDV] increase ≥20% between discharge and 6 months, estimated by magnetic resonance imaging).

RESULTS

Patients' baseline characteristics and management were comparable among bilirubin tertiles. LVEDV increased at 6 months (P < 0.001) with respect to the initial exam, but the magnitude of this increase was similar across increasing bilirubin tertiles (10.8 [30.2], 10.1 [22.9], and 12.7 [24.3]%, P = 0.500). Median (25-75 percentile) bilirubin values in patients with and without adverse remodeling were 0.75 (0.60-0.93) and 0.73 (0.60-0.92) mg/dL (P = 0.693). Absence of final TIMI flow grade 3 (odds ratio 3.92, 95% CI 1.12-13.66) and a history of hypertension (2.04, 0.93-4.50), but not admission bilirubin, were independently associated with adverse remodeling. Bilirubin also did not predict the increase in ejection fraction at 6 months.

CONCLUSIONS

Admission bilirubin values are not related to LVEDV or ejection fraction progression after a first anterior STEMI and do not predict adverse ventricular remodeling. Key messages Bilirubin levels are inversely related to cardiovascular disease, and overexpression of heme oxygenase-1 (the enzyme that determines bilirubin production) has prevented post-infarction ventricular remodeling in experimental animals, but the association between bilirubin levels and the progression of ventricular volumes and function in patients with acute myocardial infarction remained unexplored. In this cohort of patients with a first acute anterior ST-segment elevation myocardial infarction receiving contemporary management, bilirubin levels on admission were not predictive of the changes in left ventricular volumes or ejection fraction at 6 months measured by serial cardiac magnetic resonance imaging. The data are contrary to a significant protective effect of bilirubin against post-infarction ventricular remodeling.

Anti-inflammatory effects of Saururus chinensis aerial parts in murine macrophages via induction of heme oxygenase-1

Saururus chinensis (Lour.) Baill. is a perennial plant distributed throughout Northeast Asia and its roots have been widely used as a traditional medicine for hepatitis, asthma, pneumonia, and gonorrhea. This study was designed to investigate the anti-inflammatory activity of an extract of S. chinensis of the aerial parts (rather than the root), and the signaling pathway responsible for this effect in lipopolysaccharide-stimulated murine macrophages. The subfraction 4 (SCF4) from the n-hexane layer of the ethanol extract of the aerial parts of S. chinensis exhibited the highest nitrite-inhibitory activity. SCF4 significantly inhibited the production of nitrite and the expression of pro-inflammatory mediators via heme oxygenase-1 upregulation. SCF4 caused significant phosphorylation of p38 MAPK and Akt, which subsequently induced the nuclear translocation of p-p65 nuclear factor-κB and Nrf2. SCF4 also suppressed the phosphorylation of signal transducers and activators of transcription 1 (p-STAT1). The heme oxygenase-1 inhibitor zinc protoporphyrin attenuated the inhibitory effect of SCF4 on lipopolysaccharide-stimulated nitrite production and expression of inflammatory mediators, tumor necrosis factor alpha, and p-STAT1. We identified sauchinone as the active compound in S. chinensis extract and SCF4. Sauchinone was shown to significantly inhibit nitrite production and inflammatory mediators expression via heme oxygenase-1 upregulation. These results suggest that S. chinensis extract, SCF4, and its active compound, sauchinone, could be used as an anti-inflammatory agent.

Heme oxygenase 1-mediated novel anti-inflammatory activities of Salvia plebeia and its active components

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia plebeia R. Br. (SP) has been widely used as a traditional folk medicine for the treatment of infectious diseases and pain. An anti-inflammatory potential of SP has remains largely unknown.

AIM OF THE STUDY

We tried to elucidate the principle mechanism and the active ingredients underlying the anti-inflammatory activities of SP.

MATERIALS AND METHODS

We investigated the protective activities of SP methanolic extract (SPME) and seven representative ingredients against inflammation. Quantitative analysis using HPLC-DAD-ESI/MS was conducted to determine the relative amounts of these seven active ingredients in SPME. Both in vitro murine macrophages and in vivo mouse models were employed to elucidate SP- and active ingredient-mediated anti-inflammatory effects.

RESULTS

SPME significantly reduced inflammatory processes both in vivo in a TPA-induced ear edema model and in vitro in lipopolysaccharide (LPS)-activated macrophages. SPME decreased the release of nitric oxide (NO) and prostaglandin E2 (PGE2) and expression of inducible nitric oxide synthase (iNOS). Seven active components (luteoloside (C1), nepitrin (C2), homoplantagenin (C3), luteolin (C4), nepetin (C5), hispidulin (C6), and eupatorin (C7)) of SPME were analyzed and their relative concentrations were determined, demonstrating that C2, C3, C5 and C6 were present in higher amounts than were C1, C4, and C7. These major compounds inhibited NO and PGE2 production, and iNOS and COX-II protein expression through heme oxygenase-1 (HO-1) induction via activation of nuclear factor erythroid 2-related factor2 (Nrf2).

CONCLUSION

Our data demonstrate that SPME possesses potent in vitro and in vivo anti-inflammatory activities. Nepetin and hispidulin, and their glycosides are the major active compounds in SPME, and their effects are mediated by Nrf2/HO-1 signaling. Taken together, we propose that SPME and its active ingredients may serve as novel therapeutic candidates for diseases associated with excessive inflammation.

Cardioprotective and nonprotective regimens of chronic hypoxia diversely affect the myocardial antioxidant systems

It has been documented that adaptation to hypoxia increases myocardial tolerance to ischemia-reperfusion (I/R) injury depending on the regimen of adaptation. Reactive oxygen species (ROS) formed during hypoxia play an important role in the induction of protective cardiac phenotype. On the other hand, the excess of ROS can contribute to tissue damage caused by I/R. Here we investigated the relationship between myocardial tolerance to I/R injury and transcription activity of major antioxidant genes, transcription factors, and oxidative stress in three different regimens of chronic hypoxia. Adult male Wistar rats were exposed to continuous normobaric hypoxia (FiO2 0.1) either continuously (CNH) or intermittently for 8 h/day (INH8) or 23 h/day (INH23) for 3 wk period. A control group was kept in room air. Myocardial infarct size was assessed in anesthetized open-chest animals subjected to 20 min coronary artery occlusion and 3 h reperfusion. Levels of mRNA transcripts and the ratio of reduced and oxidized glutathione (GSH/GSSG) were analyzed by real-time RT-PCR and by liquid chromatography, respectively. Whereas CNH as well as INH8 decreased infarct size, 1 h daily reoxygenation (INH23) abolished the cardioprotective effect and decreased GSH/GSSG ratio. The majority of mRNAs of antioxidant genes related to mitochondrial antioxidant defense (manganese superoxide dismutase, glutathione reductase, thioredoxin/thioredoxin reductase, and peroxiredoxin 2) were upregulated in both cardioprotective regimens (CNH, INH8). In contrast, INH23 increased only PRX5, which was not sufficient to induce the cardioprotective phenotype. Our results suggest that the increased mitochondrial antioxidant defense plays an important role in cardioprotection afforded by chronic hypoxia.

Heme Oxygenase-1 Gene Therapy Provides Cardioprotection Via Control of Post-Ischemic Inflammation: An Experimental Study in a Pre-Clinical Pig Model

BACKGROUND

Heme oxygenase-1 (HO-1) is an inducible stress-responsive enzyme converting heme to bilirubin, carbon monoxide, and free iron, which exerts anti-inflammatory and antiapoptotic effects. Although efficient cardioprotection after HO-1 overexpression has been reported in rodents, its role in attenuating post-ischemic inflammation is unclear.

OBJECTIVES

This study assessed the efficacy of recombinant adenoassociated virus (rAAV)-encoding human heme oxygenase-1 (hHO-1) in attenuating post-ischemic inflammation in a murine and a porcine ischemia/reperfusion model.

METHODS

Murine ischemia was induced by 45 min of left anterior descending occlusion, followed by 24 h of reperfusion and functional as well as fluorescent-activated cell sorting analysis. Porcine hearts were subjected to 60 min of ischemia and 24h of reperfusion before hemodynamic and histologic analyses were performed.

RESULTS

Human microvascular endothelial cells transfected with hHO-1 displayed an attenuated interleukin-6 and intercellular adhesion molecule 1 expression, resulting in reduced monocytic THP-1 cell recruitment in vitro. In murine left anterior descending occlusion and reperfusion, the post-ischemic influx of CD45(+) leukocytes, Ly-6G(+) neutrophils, and Ly-6C(high) monocytes was further exacerbated in HO-1-deficient hearts and reversed by rAAV.hHO-1 treatment. Conversely, in our porcine model of ischemia, the post-ischemic influx of myeloperoxidase-positive neutrophils and CD14(+) monocytes was reduced by 49% and 87% after rAAV.hHO-1 transduction, similar to hHO-1 transgenic pigs. Functionally, rAAV.hHO-1 and hHO-1 transgenic left ventricles displayed a smaller loss of ejection fraction than control animals.

CONCLUSIONS

Whereas HO-1 deficiency exacerbates post-ischemic cardiac inflammation in mice, hHO-1 gene therapy attenuates inflammation after ischemia and reperfusion in murine and porcine hearts. Regional hHO-1 gene therapy provides cardioprotection in a pre-clinical porcine ischemia/reperfusion model.

Bilirubin Levels and Thrombus Burden in Patients With ST-Segment Elevation Myocardial Infarction

We investigated whether serum bilirubin level (a marker of heme oxygenase activity) is a predictor of thrombus burden in patients with acute myocardial infarction. Patients (n = 229; male 72.9%; mean age 63 ± 13.4 years) who were admitted with ST-segment elevation myocardial infarction (STEMI) were enrolled. Patients were divided into 2 groups. Group 1 was defined as low thrombus burden and group 2 was defined as high thrombus burden. Patients with high thrombus burden had higher total bilirubin levels (14.4 [4.3-22.9] vs 7.7 [2.4-20.3] µmol/L, P ≤ .001), (0.84 [0.25-1.34] vs 0.45 [0.14-1.19] mg/dL P ≤ .001) and direct bilirubin levels (3.1 [2.1-8.4] vs 1.7 [0.5-6.5] µmol/L, P ≤ .001), (0.18 [0.03-0.49] vs 0.10 [0.03-0.38] mg/dL, P ≤ .001). At multivariate analysis, total bilirubin (odds ratio: 1.05, 95% confidence interval: 1.03-1.08, P ≤ .001) was the independent predictor of high thrombus burden. In conclusion, total bilirubin level is independently associated with high thrombus burden in patients with STEMI.

Induction of Heme Oxygenase-1 Deficiency and Associated Glutamate-Mediated Neurotoxicity Is a Highly Conserved HIV Phenotype of Chronic Macrophage Infection That Is Resistant to Antiretroviral Therapy

Expression of the cytoprotective enzyme heme oxygenase-1 (HO-1) is significantly reduced in the brain prefrontal cortex of HIV-positive individuals with HIV-associated neurocognitive disorders (HAND). Furthermore, this HO-1 deficiency correlates with brain viral load, markers of macrophage activation, and type I interferon responses. In vitro, HIV replication in monocyte-derived macrophages (MDM) selectively reduces HO-1 protein and RNA expression and induces production of neurotoxic levels of glutamate; correction of this HO-1 deficiency reduces neurotoxic glutamate production without an effect on HIV replication. We now demonstrate that macrophage HO-1 deficiency, and the associated neurotoxin production, is a conserved feature of infection with macrophage-tropic HIV-1 strains that correlates closely with the extent of replication, and this feature extends to HIV-2 infection. We further demonstrate that this HO-1 deficiency does not depend specifically upon the HIV-1 accessory genes nef, vpr, or vpu but rather on HIV replication, even when markedly limited. Finally, antiretroviral therapy (ART) applied to MDM after HIV infection is established does not prevent HO-1 loss or the associated neurotoxin production. This work defines a predictable relationship between HIV replication, HO-1 loss, and neurotoxin production in MDM that likely reflects processes in place in the HIV-infected brains of individuals receiving ART. It further suggests that correcting this HO-1 deficiency in HIV-infected MDM could provide neuroprotection above that provided by current ART or proposed antiviral therapies directed at limiting Nef, Vpr, or Vpu functions. The ability of HIV-2 to reduce HO-1 expression suggests that this is a conserved phenotype among macrophage-tropic human immunodeficiency viruses that could contribute to neuropathogenesis.

IMPORTANCE

The continued prevalence of HIV-associated neurocognitive disorders (HAND) underscores the need for adjunctive therapy that targets the neuropathological processes that persist in antiretroviral therapy (ART)-treated HIV-infected individuals. To this end, we previously identified one such possible process, a deficiency of the antioxidative and anti-inflammatory enzyme heme oxygenase-1 (HO-1) in the brains of individuals with HAND. In the present study, our findings suggest that the HO-1 deficiency associated with excess glutamate production and neurotoxicity in HIV-infected macrophages is a highly conserved phenotype of macrophage-tropic HIV strains and that this phenotype can persist in the macrophage compartment in the presence of ART. This suggests a plausible mechanism by which HIV infection of brain macrophages in ART-treated individuals could exacerbate oxidative stress and glutamate-induced neuronal injury, each of which is associated with neurocognitive dysfunction in infected individuals. Thus, therapies that rescue the HO-1 deficiency in HIV-infected individuals could provide additional neuroprotection to ART.

Kidneys From α1,3-Galactosyltransferase Knockout/Human Heme Oxygenase-1/Human A20 Transgenic Pigs Are Protected From Rejection During Ex Vivo Perfusion With Human Blood

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Multiple modifications of the porcine genome are required to prevent rejection after pig-to-primate xenotransplantation. Here, we produced pigs with a knockout of the α1,3-galactosyltransferase gene (GGTA1-KO) combined with transgenic expression of the human anti-apoptotic/anti-inflammatory molecules heme oxygenase-1 and A20, and investigated their xenoprotective properties.

Haeme oxygenase signalling pathway: implications for cardiovascular disease

Evidence now points to the haeme oxygenase (HO) pathway as a possible actor in modulating risk for cardiovascular disease (CVD). In particular, the HO pathway may represent a key endogenous modulator of oxidative, inflammatory, and cytotoxic stress while also exhibiting vasoregulatory properties. In this review, we summarize the accumulating experimental and emerging clinical data indicating how activity of the HO pathway and its products may play a role in mechanisms underlying the development of CVD. We also identify gaps in the literature to date and suggest future directions for investigation. Because HO pathway activity can be influenced not only by genetic traits and environmental stimuli but also by a variety of existing pharmacologic interventions, the pathway could serve as a prime target for reducing the overall burden of CVD. Further work is needed to determine the role of HO pathway products as possible prognostic markers of risk for clinical CVD events and the extent to which therapeutic augmentation or inhibition of HO pathway activity could serve to modify CVD risk.

Diverse mechanisms underlying the regulation of ion channels by carbon monoxide

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

How does the heart sense changes in oxygen tension: a role for ion channels?

SIGNIFICANCE

Oxygen plays a key role in cellular metabolism and function. Oxygen delivery to cells is crucial, and a lack of oxygen such as that which occurs during myocardial infarction can be lethal. Cells should, therefore, be able to respond to changes in oxygen tension.

RECENT ADVANCES

Since the first studies examining the acute cellular effect of hypoxia on activation of transmitter release from glomus or type I chemoreceptor cells, it is now known that virtually all cells are able to respond to changes in oxygen tension.

CRITICAL ISSUES

Despite advances made in characterizing hypoxic responses, the identity of the "oxygen sensor" remains debated. Recently, more evidence has evolved as to how cardiac myocytes sense acute changes in oxygen. This review will examine the available evidence in support of acute oxygen-sensing mechanisms providing a brief historical perspective and then more detailed insights into the heart and the role of cardiac ion channels in hypoxic responses.

FUTURE DIRECTIONS

A further understanding of these cellular processes should result in interventions that assist in preventing the deleterious effects of acute changes in oxygen tension such as alterations in contractile function and cardiac arrhythmia.

Obesity superimposed on aging magnifies inflammation and delays the resolving response after myocardial infarction

Polyunsaturated fatty acid (PUFA) intake has increased over the last 100 yr, contributing to the current obesogenic environment. Obesity and aging are prominent risk factors for myocardial infarction (MI). How obesity interacts with aging to alter the post-MI response, however, is unclear. We tested the hypothesis that obesity in aging mice would impair the resolution of post-MI inflammation. PUFA diet (PUFA aging group) feeding to 12-mo-old C57BL/6J mice for 5 mo showed higher fat mass compared with standard lab chow (LC)-fed young (LC young group; 3-5 mo old) or aging alone control mice (LC aging group). LC young, LC aging, and PUFA aging mice were subjected to coronary artery ligation to induce MI. Despite similar infarct areas post-MI, plasma proteomic profiling revealed higher VCAM-1 in the PUFA aging group compared with LC young and LC aging groups, leading to increased neutrophil infiltration in the PUFA aging group (P<0.05). Macrophage inflammatory protein-1γ and CD40 were also increased at day 1, and myeloperoxidase remained elevated at day 5, an observation consistent with delayed wound healing in the PUFA aging group. Lipidomic analysis showed higher levels of arachidonic acid and 12(S)-hydroxyeicosatetraenoic acid at day 1 post-MI in the PUFA aging group compared with the LC aging group (all P<0.05), thereby mediating neutrophil extravasation in the PUFA aging group. The inflammation-resolving enzymes 5-lipoxygenase, cyclooxygenase-2, and heme oxyegnase-1 were altered to delay wound healing post-MI in the PUFA aging group compared with LC young and LC aging groups. PUFA aging magnifies the post-MI inflammatory response and impairs the healing response by stimulating prolonged neutrophil trafficking and proinflammatory lipid mediators.

Heme oxygenase-1: an emerging therapeutic target to curb cardiac pathology

Activation of heme oxygenase-1 (HO-1), a heme-degrading enzyme responsive to a wide range of cellular stress, is traditionally considered to convey adaptive responses to oxidative stress, inflammation and vasoconstriction. These diversified effects are achieved through the degradation of heme to carbon monoxide (CO), biliverdin (which is rapidly converted to bilirubin by biliverdin reductase) and ferric iron. Recent findings have added antiproliferative and angiogenic effects to the list of HO-1/CO actions. HO-1 along with its reaction products bilirubin and CO are protective against ischemia-induced injury (myocardial infarction, ischemia-reperfusion (IR)-injury and post-infarct structural remodelling). Moreover, HO-1, and CO in particular, possess acute antihypertensive effects. As opposed to these curative potentials, the long-believed protective effect of HO-1 in cardiac remodelling in response to pressure overload and type 2 diabetes mellitus (DM) has been questioned by recent work. These challenges, coupled with emerging regulatory mechanisms, motivate further in-depth studies to help understand untapped layers of HO-1 regulation and action. The outcomes of these efforts may shed new light on critical mechanisms that could be used to harness the protective potential of this enzyme for the therapeutic benefit of patients suffering from such highly prevalent cardiovascular disorders.