Genetic ablation of the transcription repressor Bach1 leads to myocardial protection against ischemia/reperfusion in mice

Renal denervation improves mitochondrial oxidative stress and cardiac hypertrophy through inactivating SP1/BACH1-PACS2 signaling

BACKGROUND

Renal denervation (RDN) has been proved to relieve cardiac hypertrophy; however, its detailed mechanisms remain obscure. This study investigated the detailed protective mechanisms of RDN against cardiac hypertrophy during hypertensive heart failure (HF).

METHODS

Male 5-month-old spontaneously hypertension (SHR) rats were used in a HF rat model, and male Wistar-Kyoto (WKY) rats of the same age were used as the baseline control. Myocardial hypertrophy and fibrosis were evaluated by hematoxylin-eosin (HE) staining and Masson staining. The expression of target molecule was analyzed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), Western blot, immunohistochemical and immunofluorescence, respectively. Cardiomyocyte hypertrophy was induced by norepinephrine (NE) in H9c2 cells in vitro and evaluated by brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP), β-myosin heavy chain (β-MHC), and α-myosin heavy chain (α-MHC) levels. Oxidative stress was determined by malondialdehyde (MDA) level, superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) enzyme activities. Mitochondrial function was measured by mitochondrial membrane potential, adenosine triphosphate (ATP) production, mitochondrial DNA (mtDNA) number, and mitochondrial complex I-IV activities. Molecular mechanism was assessed by dual luciferase reporter and chromatin immunoprecipitation (ChIP) assays.

RESULTS

RDN decreased sympathetic nerve activity, attenuated myocardial hypertrophy and fibrosis, and improved cardiac function in the rat model of HF. In addition, RDN ameliorated mitochondrial oxidative stress in myocardial tissues as evidenced by reducing MDA and mitochondrial reactive oxygen species (ROS) levels, and enhancing SOD and GSH-Px activities. Moreover, phosphofurin acid cluster sorting protein 2 (PACS-2) and broad-complex, tramtrak and bric à brac (BTB) domain and cap'n'collar (CNC) homolog 1 (BACH1) were down-regulated by RDN. In NE-stimulated H9c2 cells, PACS-2 and BACH1 levels were markedly elevated, and knockdown of them could suppress NE-induced oxidative stress, cardiomyocyte hypertrophy, fibrosis, as well as mitochondrial dysfunction. Transforming growth factor beta1(TGFβ1)/SMADs signaling pathway was inactivated by RDN in the HF rats, which sequentially inhibited specificity protein 1 (SP1)-mediated transcription of PACS2 and BACH1.

CONCLUSION

Collectively, these data demonstrated that RDN improved cardiac hypertrophy and sympathetic nerve activity of HF rats via repressing BACH1 and PACS-2-mediated mitochondrial oxidative stress by inactivating TGF-β1/SMADs/SP1 pathway, which shed lights on the cardioprotective mechanism of RDN in HF.

Disruption of BACH1 Protects AC16 Cardiomyocytes Against Hypoxia/Reoxygenation-Evoked Injury by Diminishing CDKN3 Transcription

Reperfusion after myocardial infarction (MI) can lead to myocardial ischemia/reperfusion (I/R) damage. The transcription factor (TF) broad-complex, tramtrack, and bric-a-brac (BTB) and cap'n'collar (CNC) homology 1 (BACH1) is implicated in the injury. However, the downstream mechanisms of BACH1 in affecting myocardial hypoxia/reoxygenation (H/R) damage are still fully understood. AC16 cells were stimulated with H/R conditions to model cardiomyocytes under H/R. mRNA analysis was performed by quantitative real-time PCR. Protein levels were gauged by immunoblot analysis. The effect of BACH1/cyclin-dependent kinase inhibitor 3 (CDKN3) on H/R-evoked injury was assessed by measuring cell viability via Cell Counting Kit-8 (CCK-8), apoptosis (flow cytometry and caspase 3 activity), ferroptosis via Fe2+, glutathione (GSH), reactive oxygen species (ROS) and malondialdehyde (MDA) markers and inflammation cytokines interleukin-1beta (IL-1β) and tumor necrosis factor alpha (TNF-α). The BACH1/CDKN3 relationship was examined by chromatin immunoprecipitation (ChIP) experiment and luciferase assay. BACH1 was increased in MI serum and H/R-stimulated AC16 cardiomyocytes. Functionally, disruption of BACH1 mitigated H/R-evoked in vitro apoptosis, ferroptosis and inflammation of AC16 cardiomyocytes. Mechanistically, BACH1 activated CDKN3 transcription and enhanced CDKN3 protein expression in AC16 cardiomyocytes. Our rescue experiments validated that BACH1 disruption attenuated H/R-evoked AC16 cardiomyocyte apoptosis, ferroptosis and inflammation by downregulating CDKN3. Additionally, BACH1 disruption could activate the adenosine monophosphate-activated protein kinase (AMPK) signaling by downregulating CDKN3 in H/R-stimulated AC16 cardiomyocytes. Our study demonstrates that BACH1 activates CDKN3 transcription to induce H/R-evoked damage of AC16 cardiomyocytes partially via AMPK signaling.

Cardiac-specific BACH1 ablation attenuates pathological cardiac hypertrophy by inhibiting the Ang II type 1 receptor expression and the Ca2+/CaMKII pathway

AIMS

BACH1 is up-regulated in hypertrophic hearts, but its function in cardiac hypertrophy remains largely unknown. This research investigates the function and mechanisms of BACH1 in the regulation of cardiac hypertrophy.

METHODS AND RESULTS

Male cardiac-specific BACH1 knockout mice or cardiac-specific BACH1 transgenic (BACH1-Tg) mice and their respective wild-type littermates developed cardiac hypertrophy induced by angiotensin II (Ang II) or transverse aortic constriction (TAC). Cardiac-specific BACH1 knockout in mice protected the hearts against Ang II- and TAC-induced cardiac hypertrophy and fibrosis, and preserved cardiac function. Conversely, cardiac-specific BACH1 overexpression markedly exaggerated cardiac hypertrophy and fibrosis and reduced cardiac function in mice with Ang II- and TAC-induced hypertrophy. Mechanistically, BACH1 silencing attenuated Ang II- and norepinephrine-stimulated calcium/calmodulin-dependent protein kinase II (CaMKII) signalling, the expression of hypertrophic genes, and hypertrophic growth of cardiomyocytes. Ang II stimulation promoted the nuclear localization of BACH1, facilitated the recruitment of BACH1 to the Ang II type 1 receptor (AT1R) gene promoter, and then increased the expression of AT1R. Inhibition of BACH1 attenuated Ang II-stimulated AT1R expression, cytosolic Ca2+ levels, and CaMKII activation in cardiomyocytes, whereas overexpression of BACH1 led to the opposite effects. The increased expression of hypertrophic genes induced by BACH1 overexpression upon Ang II stimulation was suppressed by CaMKII inhibitor KN93. The AT1R antagonist, losartan, significantly attenuated BACH1-mediated CaMKII activation and cardiomyocyte hypertrophy under Ang II stimulation in vitro. Similarly, Ang II-induced myocardial pathological hypertrophy, cardiac fibrosis, and dysfunction in BACH1-Tg mice were blunted by treatment with losartan.

CONCLUSION

This study elucidates a novel important role of BACH1 in pathological cardiac hypertrophy by regulating the AT1R expression and the Ca2+/CaMKII pathway, and highlights potential therapeutic target in pathological cardiac hypertrophy.

LPS preconditioning of MSC-CM improves protection against hypoxia/reoxygenation-induced damage in H9c2 cells partly via HMGB1/Bach1 signalling

Mesenchymal stem cell-derived conditioned medium (MSC-CM) improves cardiac function after myocardial infarction; however, this cardioprotective effect is moderate and transient. Lipopolysaccharide (LPS) pretreatment partially improves MSC-CM-mediated cardioprotective effects owing to the presence of paracrine factors. However, the mechanism underlying these improved effects remains unknown. To study the effect of LPS-pretreated MSC-CM on hypoxia/reoxygenation (H/R)-induced injury, MSCs were treated with or without LPS (400 ng/mL) for 48 h, and the supernatant was collected (MSC-CM). Subsequently, H9c2 cells were co-cultured with Nor-CM (CM derived from LPS-untreated MSCs) and LPS-CM (CM derived from LPS-pretreated MSCs) for 24 h and subjected to H/R. MSC-CM inhibited the progression of H/R-induced injury in H9c2 cells, and this protective effect was enhanced via LPS pretreatment as evidenced by the improved apoptosis assessment index (i.e. caspase-3 and B-cell lymphoma-2 [Bcl-2] expression) and decreased levels of lactic dehydrogenase (LDH) and cardiac troponin (cTn). In addition, the results of haematoxylin-eosin staining (H&E), transmission electron microscopy (TEM) and TdT-mediated dUTP nick-end labelling (TUNEL) validated that MSC-CM inhibited H/R-induced injury in H9c2 cardiomyocytes. LPS pretreatment downregulated the expression of high mobility group box-1 (HMGB1) and BTB and CNC homology-1 (Bach1) proteins in MSCs but upregulated the expression of vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF) and insulin-like growth factor (IGF). HMGB1 knockdown (MSC/siHMGB1-CM) significantly decreased the expression of Bach1 and increased the expression of VEGF, HGF and IGF. Bach1 knockdown (MSC/siBach1-CM) did not alter the production of HMGB1 but increased the expression of VEGF and IGF. LPS pretreatment did not alter the expression of the paracrine factors VEGF and HGF in the MSC/siHMGB1 group but increased their expression in the MSC/siBach1 group. The myocyte anti-apoptotic effects of MSCs/siBach1-CM were similar to those of untreated MSCs, which were not enhanced by LPS. LPS-pretreated MSC-CM protects H9c2 cells against H/R-induced injury partly through the HMGB1/Bach1 signalling pathway.

Protections of transcription factor BACH2 and natural product myricetin against pathological cardiac hypertrophy and dysfunction

Pathological hypertrophic myocardium under consistent adverse stimuli eventually can cause heart failure. This study aims to explore the role of BACH2, a member of the basic region leucine zipper transcription factor family, in cardiac hypertrophy and failure. Transverse aortic constriction surgery was operated to induce cardiac hypertrophy and failure in mice. BACH2 was overexpressed in mice through tail vein injection of AAV9-Bach2. Mice with systemic or cardiac-specific knockdown of Bach2 were adopted. Neonatal rat ventricular myocytes (NRVMs) were isolated and infected with lentivirus to overexpress Bach2 or transfected with siRNA to knock down Bach2. Our data showed that overexpression of BACH2 ameliorated TAC-induced cardiac hypertrophy and failure in mice and decreased isoproterenol (ISO)-triggered myocyte hypertrophy in NRVMs. Systemic or cardiac-specific knockdown of Bach2 worsened the cardiac hypertrophy and failure phenotype in mice. Further assays showed that BACH2 bound to the promotor region of Akap6 at the -600 to -587 site and repressed its expression, which functioned as a crucial scaffold for cardiac hypertrophy and failure signaling pathways. Small molecular natural product library screening suggested that myricetin could up-regulate expression of Bach2 and simultaneously suppress the transcriptional levels of hypertrophic marker genes Bnp and Myh7. Further studies showed that myricetin exerted a BACH2-dependent protective effect against cardiac hypertrophy in vivo and in vitro. Taken together, our findings demonstrated that BACH2 plays a crucial role in the regulation of cardiac hypertrophy and failure and can be a potential therapeutic target in the future.

Construction and validation of molecular subtypes of coronary artery disease based on ferroptosis-related genes

Background

This study aims to construct a reliable diagnostic model for coronary artery disease (CAD) patients and explore its potential mechanism by consensus molecular subtypes of ferroptosis-related genes.

Methods

GSE12288 and GSE20680 were downloaded from Gene Expression Omnibus database. CAD patients were divided into different molecular subtypes according to the expression level of ferroptosis-related genes. Then, the distribution of differentially expressed genes, functional annotations and immune infiltration cells between the two subtypes were compared. Finally, a prognostic model of ferroptosis-related genes in CAD was constructed and verified.

Results

Two different molecular subtypes of CAD were obtained according to the expression level of ferroptosis-related genes. Then, a total of 1944 differentially expressed genes (DEGs) were found, among which, 236 genes were up-regulated and 1708 genes were down-regulated. In addition, 43 DEGs were ferroptosis-related genes. Functional enrichment analysis showed that these DEGs between two subtypes of CAD were mainly enriched in immune-related pathways and processes, such as T cell receptor, mTOR, NOD-like receptor and Toll-like receptor signaling pathways. We also found that 21 immune cells were significantly changed between two subtypes of CAD. The LASSO method was performed to identify and construct the 16 ferroptosis-related genes-based diagnostic signature. Diagnostic efficiency of diagnostic signature measured by AUC in the training set and validation cohort was 0.971 and 0.899, respectively.

Conclusions

This study contributes to a more comprehensive understanding of the mechanism of ferroptosis-related genes in CAD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02719-1.

Cardiac protection induced by urocortin-2 enables the regulation of apoptosis and fibrosis after ischemia and reperfusion involving miR-29a modulation

Urocortin-2 (Ucn-2) has demonstrated cardioprotective actions against myocardial ischemia-reperfusion (I/R) injuries. Herein, we explored the protective role of Ucn-2 through microRNAs (miRNAs) post-transcriptional regulation of apoptotic and pro-fibrotic genes. We determined that the intravenous administration of Ucn-2 before heart reperfusion in a Wistar rat model of I/R recovered cardiac contractility and decreased fibrosis, lactate dehydrogenase release, and apoptosis. The infusion of Ucn-2 also inhibited the upregulation of 6 miRNAs in revascularized heart. The in silico analysis indicated that miR-29a and miR-451_1∗ are predicted to target many apoptotic and fibrotic genes. Accordingly, the transfection of neonatal rat ventricular myocytes with mimics overexpressing miR-29a, but not miR-451_1∗, prevented I/R-induced expression of pro- and anti-apoptotic genes such as Apaf-1, Hmox-1, and Cycs, as well as pro-fibrotic genes Col-I and Col-III. We also confirmed that Hmox-1, target of miR-29a, is highly expressed at the mRNA and protein levels in adult rat heart under I/R, whereas, Ucn-2 abolished I/R-induced mRNA and protein upregulation of HMOX-1. Interestingly, a significant upregulation of Hmox-1 was observed in the ventricle of ischemic patients with heart failure, correlating negatively with the left ventricle ejection fraction. Altogether, these data indicate that Ucn-2, through miR-29a regulation, provides long-lasting cardioprotection, involving the post-transcriptional regulation of apoptotic and fibrotic genes.

Associations of Transcription Factor 21 Gene Polymorphisms with the Growth and Body Composition Traits in Broilers

Simple Summary

The functional SNPs discovered in this work will give helpful information on the crucial molecular markers that may be employed in breeding efforts to improve the heart development of broiler chickens.

Abstract

This study aims to identify molecular marker loci that could be applied in broiler breeding programs. In this study, we used public databases to locate the Transcription factor 21 (TCF21) gene that affected the economically important traits in broilers. Ten single nucleotide polymorphisms were detected in the TCF21 gene by monoclonal sequencing. The polymorphisms of these 10 SNPs in the TCF21 gene were significantly associated (p < 0.05) with multiple growth and body composition traits. Furthermore, the TT genotype of g.-911T>G was identified to significantly increase the heart weight trait without affecting the negative traits, such as abdominal fat and reproduction by multiple methods. Thus, it was speculated that the g.-911T>G identified in the TCF21 gene might be used in marker-assisted selection in the broiler breeding program.

Genetic BACH1 deficiency alters mitochondrial function and increases NLRP3 inflammasome activation in mouse macrophages

BTB-and-CNC homologue 1 (BACH1), a heme-regulated transcription factor, mediates innate immune responses via its functional role in macrophages. BACH1 has recently been shown to modulate mitochondrial metabolism in cancer cells. In the current study, we utilized a proteomics approach and demonstrate that genetic deletion of BACH1 in mouse macrophages is associated with decreased levels of various mitochondrial proteins, particularly mitochondrial complex I. Bioenergetic studies revealed alterations of mitochondrial energy metabolism in BACH1−/− macrophages with a shift towards increased glycolysis and decreased oxidative phosphorylation. Moreover, these cells exhibited enhanced mitochondrial membrane potential and generation of mitochondrial reactive oxygen species (mtROS) along with lower levels of mitophagy. Notably, a higher inducibility of NLRP3 inflammasome activation in response to ATP and nigericin following challenge with lipopolysaccharide (LPS) was observed in BACH1-deficient macrophages compared to wild-type cells. Mechanistically, pharmacological inhibition of mtROS markedly attenuated inflammasome activation. In addition, it is shown that inducible nitric oxide synthase and cyclooxygenase-2, both of which are markedly induced by LPS in macrophages, are directly implicated in BACH1-dependent regulation of NLRP3 inflammasome activation. Taken together, the current findings indicate that BACH1 is critical for immunomodulation of macrophages and may serve as a target for therapeutic approaches in inflammatory disorders.

Heme Oxygenase 1 in Vertebrates: Friend and Foe

HO-1 is the inducible form of the enzyme heme-oxygenase. HO-1 catalyzes heme breakdown, reducing the levels of this important oxidant molecule and generating antioxidant, anti-inflammatory, and anti-apoptotic byproducts. Thus, HO-1 has been described as an important stress response mechanism during both physiologic and pathological processes. Interestingly, some findings are demonstrating that uncontrolled levels of HO-1 byproducts can be associated with cell death and tissue destruction as well. Furthermore, HO-1 can be located in the nucleus, influencing gene transcription, cellular proliferation, and DNA repair. Here, we will discuss several studies that approach HO-1 effects as a protective or detrimental mechanism in different pathological conditions. In this sense, as the major organs of vertebrates will deal specifically with distinct types of stresses, we discuss the HO-1 role in each of them, exposing the contradictions associated with HO-1 expression after different insults and circumstances.

MicroRNA-532-5p upregulation protects neurological deficits after ischemic stroke through inhibition of BTB and CNC homology 1

OBJECTIVE

MicroRNA (miR)-532-5p has been reported to protect against ischemic stroke (IS), while the underlying mechanism of miR-532-5p targeting BTB and CNC homology 1 (BACH1) in IS remains unknown. Thus, we aim to detect the role of miR-532-5p in IS via targeting BACH1.

METHODS

Blood samples were collected from IS patients and healthy controls. Rat middle cerebral artery occlusion (MCAO) models were established and intracerebrally injected with altered miR-532-5p or BACH1 plasmid vectors to reveal their roles in neurological function, brain tissue pathology and inflammation in MCAO. Expression of miR-532-5p and BACH1 in patients' blood samples and rat brain tissues was assessed, and the targeting relationship between miR-532-5p and BACH1 was confirmed.

RESULTS

MiR-532-5p was downregulated and BACH1 was upregulated in IS. BACH1 was targeted by miR-532-5p. Restored miR-532-5p or inhibited BACH1 improved neurological function and inhibited inflammation and apoptosis in MCAO rats. On the contrary, miR-532-5p reduction or BACH1 overexpression had totally opposite effects on MCAO rats. The protective role of miR-532-5p for MCAO rats was reversed by upregulated BACH1.

CONCLUSION

MiR-532-5p upregulation protects against neurological deficits after IS through inhibition of BACH1.

MicroRNA-30c-5p protects against myocardial ischemia/reperfusion injury via regulation of Bach1/Nrf2

MicroRNAs (miRNAs) are critical regulatory factors in myocardial ischemia/reperfusion (I/R) injury. The miRNA miR-30c-5p has been reported as a key mediator in several myocardial abnormalities. However, the precise roles and mechanisms of miR-30c-5p in myocardial I/R injury remain not well-studied. This project aimed to explore the potential function of this miRNA in mediating myocardial I/R injury. Significant induction of miR-30c-5p was observed in myocardial tissue of rats with myocardial I/R injury in vivo and cardiomyocytes with hypoxia/re‑oxygenation (H/R) injury in vitro. Functional studies elucidated that forced expression of miR-30c-5p in rats effectively reduced infarct area, cardiac apoptosis, oxidative stress and inflammation induced by myocardial I/R injury. Moreover, in vitro cardiomyocytes with forced expression of miR-30c-5p were also protected from H/R-induced apoptosis, oxidative stress and inflammation. Importantly, BTB domain and CNC homology 1 (Bach1) was identified as a new target of miR-30c-5p. miR-30c-5p was shown to promote the activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) via the inhibition of Bach1. The re-expression of Bach1 reversed miR-30c-5p-mediated-cardioprotective effects against myocardial I/R injury in vivo or H/R injury in vitro. Overall, our results demonstrate that forced expression of miR-30c-5p exhibited beneficial effects against myocardial I/R injury through enhancement of Nrf2 activation via inhibition of Bach1. This work reveals a novel molecular mechanism for myocardial I/R injury at the miRNA level and suggests a therapeutic value of miR-30c-5p in treatment of myocardial I/R injury.

Circular RNA Microarray Analyses in Hepatic Ischemia-Reperfusion Injury With Ischemic Preconditioning Prevention

Ischemic preconditioning (IPC) represents an effective intervention to relieve hepatic ischemia-reperfusion injury (IRI). Systematic detection of circRNA expression revealing the protection effect of IPC still remains to be elucidated. Here, we applied a microarray to detect circRNA and mRNA expression in ischemic liver with and without IPC (n = 3 in each group). Compared with the sham group, there were 39 circRNAs and 432 mRNAs increased and 38 circRNAs and 254 mRNAs decreased (fold change ≥1.5, P < 0.05) in the group of hepatic IRI. As the result of IPC intervention, 43 circRNAs and 64 mRNAs were increased, and 7 circRNAs and 31 mRNAs were decreased in the IPC group when compared with IRI. We then identified circRNA_017753 as the most possible target that may closely relate to IPC protective signaling and predicted Jade1 as the target related to circRNA_017753. Three possible circRNA-miRNA-mRNA axes were constructed that may play a vital role in protective mechanisms in IPC. The study for the first time systematically detects the dysregulated circRNAs and mRNAs in response to hepatic IRI and IPC intervention. Our profile and bioinformatic analysis provide numerous novel clues to understanding the pathophysiologic mechanism of IPC protection against hepatic IRI.

Bach1 plays an important role in angiogenesis through regulation of oxidative stress

Bach1 is a known transcriptional repressor of the heme oxygenase-1 (HO-1) gene. The purpose of this study was to determine whether angiogenesis is accelerated by genetic ablation of Bach1 in a mouse ischemic hindlimb model. Hindlimb ischemia was surgically induced in wild-type (WT) mice, Bach1-deficient (Bach1-/-) mice, apolipoprotein E-deficient (ApoE-/-) mice, and Bach1/ApoE double-knockout (Bach1-/-/ApoE-/-) mice. Blood flow recovery after hindlimb ischemia showed significant improvement in Bach1-/- mice compared with that in WT mice. Bach1-/-/ApoE-/- mice showed significantly improved blood flow recovery compared with that in ApoE-/- mice to the level of that in WT mice. Migration of endothelial cells in ApoE-/- mice was significantly decreased compared with that in WT mice. Migration of endothelial cells significantly increased in Bach1-/-/ApoE-/- mice compared with that in ApoE-/- mice to the level of that in WT mice. The expression levels of HO-1, peroxisome proliferator-activated receptor γ co-activator-1α, angiopoietin 1, and fibroblast growth factor 2 in endothelial cells isolated from Bach1-/-/ApoE-/- mice were significantly higher than those in ApoE-/- mice. Oxidative stress assessed by anti-acrolein antibody staining in ischemic tissues and urinary 8-isoPGF2α excretion were significantly increased in ApoE-/- mice compared with those in WT and Bach1-/- mice. Oxidative stress was reduced in Bach1-/-/ApoE-/- mice compared with that in ApoE-/- mice. These findings suggest that genetic ablation of Bach1 plays an important role in ischemia-induced angiogenesis under the condition of increased oxidative stress. Bach1 could be a potential therapeutic target to reduce oxidative stress and potentially improve angiogenesis for patients with peripheral arterial disease.

Cell therapy for the treatment of heart disease: Renovation work on the broken heart is still in progress

Cardiovascular disease (CVD) continues to be the number one killer in the aging population. Heart failure (HF) is also an important cause of morbidity and mortality in patients with congenital heart disease (CHD). Novel therapeutic approaches that could restore stable heart function are much needed in both paediatric and adult patients. Regenerative medicine holds promises to provide definitive solutions for correction of congenital and acquired cardiac defects. In this review article, we recap some important aspects of cardiovascular cell therapy. First, we report quantifiable data regarding the scientific advancements in the field and how this has been translated into tangible outcomes according clinical studies and related meta-analyses. We then comment on emerging trends and technologies, such as the use of second-generation cell products, including pericyte-like vascular progenitors, and reprogramming of cells by different approaches including modulation of oxidative stress. The more affordable and feasible strategy of repurposing clinically available drugs to awaken the intrinsic healing potential of the heart will be discussed in the light of current social, financial, and ethical context. Cell therapy remains a work in progress field. Uncertainty in the ability of the experts and policy makers to solve urgent medical problems is growing in a world that is significantly influenced by them. This is particularly true in the field of regenerative medicine, due to great public expectations, polarization of leadership and funding, and insufficient translational vision. Cardiovascular regenerative medicine should be contextualized in a holistic program with defined priorities to allow a complete realization. Reshaping the notion of medical expertise is fundamental to fill the current gap in translation.

Prognostic Value of Total Bilirubin in Patients With ST-Segment Elevation Acute Myocardial Infarction Undergoing Primary Coronary Intervention

Background: Bilirubin, a natural product of heme catabolism, has antioxidant and anti-inflammatory activities and is inversely associated with stable coronary artery disease. However, the relationship between the bilirubin levels and long-term outcomes in patients with ST-segment elevation myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention (PPCI) remains unknown. This study aimed to establish a score model based on bilirubin for predicting major adverse cardiovascular events (MACEs) and stratify patients to the level of care. Methods and Results: Data of 4,151 consecutive patients with STEMI who underwent PPCI were evaluated, and 3,708 cases were analyzed. The total bilirubin (TBil) levels were measured during admission, and the study population was divided into two groups. The high TBil group (n = 143) comprised patients who had a TBil level of ≥22 μmmol/L, and the low TBil group (n = 3,565) comprised patients who had a TBil level of <22 μmmol/L. The median follow-up period was 754 days (2.066 years). The MACE was significantly lower in the high TBil group than in the low TBil group (3.5% vs. 11.0%, p = 0.001). In the multivariate Cox regression analysis, a significant association was noted between the TBil levels and adjusted risk of MACE (hazard ratio, 0.279; 95% confidence interval, 0.088-0.877; p = 0.029). A prediction score model composed of TBil, age, hypertension history, and other eight variables was developed, with scores ranging from 0 to 500. The scores categorized patients into low-, medium-, and high-risk categories. The cumulative survival rate was significantly higher in the low-risk group than in the medium- and high-risk groups for MACE, all-cause death, cardiac death, recurrent myocardial infarction, and ischemic stroke (p < 0.001, p < 0.001, p < 0.001, p = 0.030, and p = 0.001, respectively). The area under the curve of the TBil score was 0.768; this was significantly greater in the pairwise comparison with the Global Registry of Acute Coronary Events score (p = 0.0012). Conclusion: The new prediction score model based on TBil could be used in clinical practice to support risk stratification as recommended in the clinical guidelines.

Cannabinoids in Metabolic Syndrome and Cardiac Fibrosis

PURPOSE OF REVIEW

This article provides a concise overview of how cannabinoids and the endocannabinoid system (ECS) have significant implications for the prevention and treatment of metabolic syndrome (MetS) and for the treatment of cardiovascular disorders, including cardiac fibrosis.

RECENT FINDINGS

Over the past few years, the ECS has emerged as a pivotal component of the homeostatic mechanisms for the regulation of many bodily functions, including inflammation, digestion, and energy metabolism. Therefore, the pharmacological modulation of the ECS by cannabinoids represents a novel strategy for the management of many diseases. Specifically, increasing evidence from preclinical research studies has opened new avenues for the development of cannabinoid-based therapies for the management and potential treatment of MetS and cardiovascular diseases. Current information indicates that modulation of the ECS can help maintain overall health and well-being due to its homeostatic function. From a therapeutic perspective, cannabinoids and the ECS have also been shown to play a key role in modulating pathophysiological states such as inflammatory, neurodegenerative, gastrointestinal, metabolic, and cardiovascular diseases, as well as cancer and pain. Thus, targeting and modulating the ECS with cannabinoids or cannabinoid derivatives may represent a major disease-modifying medical advancement to achieve successful treatment for MetS and certain cardiovascular diseases.

Bach1 promotes muscle regeneration through repressing Smad-mediated inhibition of myoblast differentiation

It has been reported that Bach1-deficient mice show reduced tissue injuries in diverse disease models due to increased expression of heme oxygenase-1 (HO-1)that possesses an antioxidant function. In contrast, we found that Bach1 deficiency in mice exacerbated skeletal muscle injury induced by cardiotoxin. Inhibition of Bach1 expression in C2C12 myoblast cells using RNA interference resulted in reduced proliferation, myotube formation, and myogenin expression compared with control cells. While the expression of HO-1 was increased by Bach1 silencing in C2C12 cells, the reduced myotube formation was not rescued by HO-1 inhibition. Up-regulations of Smad2, Smad3 and FoxO1, known inhibitors of muscle cell differentiation, were observed in Bach1-deficient mice and Bach1-silenced C2C12 cells. Therefore, Bach1 may promote regeneration of muscle by increasing proliferation and differentiation of myoblasts.

Ferroptosis is controlled by the coordinated transcriptional regulation of glutathione and labile iron metabolism by the transcription factor BACH1

Ferroptosis is an iron-dependent programmed cell death event, whose regulation and physiological significance remain to be elucidated. Analyzing transcriptional responses of mouse embryonic fibroblasts exposed to the ferroptosis inducer erastin, here we found that a set of genes related to oxidative stress protection is induced upon ferroptosis. We considered that up-regulation of these genes attenuates ferroptosis induction and found that the transcription factor BTB domain and CNC homolog 1 (BACH1), a regulator in heme and iron metabolism, promotes ferroptosis by repressing the transcription of a subset of the erastin-induced protective genes. We noted that these genes are involved in the synthesis of GSH or metabolism of intracellular labile iron and include glutamate-cysteine ligase modifier subunit (Gclm), solute carrier family 7 member 11 (Slc7a11), ferritin heavy chain 1 (Fth1), ferritin light chain 1 (Ftl1), and solute carrier family 40 member 1 (Slc40a1). Ferroptosis has also been previously shown to induce cardiomyopathy, and here we observed that Bach1-/- mice are more resistant to myocardial infarction than WT mice and that the severity of ischemic injury is decreased by the iron-chelator deferasirox, which suppressed ferroptosis. Our findings suggest that BACH1 represses genes that combat labile iron-induced oxidative stress, and ferroptosis is stimulated at the transcriptional level by BACH1 upon disruption of the balance between the transcriptional induction of protective genes and accumulation of iron-mediated damage. We propose that BACH1 controls the threshold of ferroptosis induction and may represent a therapeutic target for alleviating ferroptosis-related diseases, including myocardial infarction.

BACH1 mediates the antioxidant properties of aged garlic extract

In clinical studies, aged garlic extract (AGE) has been shown to improve endothelial dysfunction. The activation of nuclear factor erythroid 2 like 2 (Nrf2)-dependent gene expression is a proposed mechanism for maintaining vascular homeostasis. S-1-propenylcysteine (S1PC) and S-allylcysteine (SAC) are two predominant sulfur-containing amino acids present in AGE. However, it remains unclear as to whether the two sulfur amino acids activate Nrf2 in cells. Nitric oxide (NO) is an important signaling molecule and one of the activators of the Nrf2 pathway. In a previous study, we examined the effects of the two sulfur amino acids on NO signaling for modulating the Nrf2-dependent antioxidant response. Neither S1PC nor SAC were found to affect the expression of Nrf2-regulated genes, such as heme oxygenase-1 (HMOX1) in human umbilical vein endothelial cells. However, S1PC was found to augment HMOX1 expression, induced by NO donors, such as NOR3. NOR3 was found to induce the nuclear accumulation of NRF2 protein and concomitantly enhance the degradation of BTB domain and CNC homolog 1 (BACH1), a transcriptional repressor that competes with NRF2. Notably, on our previous study, S1PC enhanced the NOR3-induced downregulation of BACH1, but did not further enhance the NOR3-induced accumulation of NRF2. The findings of that study indicated that the S1PC-induced degradation of BACH1 may provide a basis for the antioxidant effects of AGE. Thus, in this review, we aimed to provide a current overview of the antioxidant effects of AGE and sulfur-containing amino acids.

Core-Shell Polymer-Based Nanoparticles Deliver miR-155-5p to Endothelial Cells

Heart failure occurs in over 30% of the worldwide population and most commonly originates from cardiovascular diseases such as myocardial infarction. microRNAs (miRNAs) target and silence specific mRNAs, thereby regulating gene expression. Because the endogenous miR-155-5p has been ascribed to vasculoprotection, loading it onto positively charged, core-shell poly(isobutylcyanoacrylate) (PIBCA)-polysaccharide nanoparticles (NPs) was attempted. NPs showed a decrease (p < 0.0001) in surface electrical charge (ζ potential), with negligible changes in size or shape when loaded with the anionic miR-155-5p. Presence of miR-155-5p in loaded NPs was further quantified. Cytocompatibility up to 100 μg/mL of NPs for 2 days with human coronary artery endothelial cells (hCAECs) was documented. NPs were able to enter hCAECs and were localized in the endoplasmic reticulum (ER). Expression of miR-155-5p was increased within the cells by 75-fold after 4 hours of incubation (p < 0.05) and was still noticeable at day 2. Differences between loaded NP-cultured cells and free miRNA, at days 1 (p < 0.05) and 2 (p < 0.001) suggest the ability of prolonged load release in physiological conditions. Expression of miR-155-5p downstream target BACH1 was decreased in the cells by 4-fold after 1 day of incubation (p < 0.05). This study is a first proof of concept that miR-155-5p can be loaded onto NPs and remain intact and biologically active in endothelial cells (ECs). These nanosystems could potentially increase an endogenous cytoprotective response and decrease damage within infarcted hearts.

MicroRNA-98-5p ameliorates oxygen-glucose deprivation/reoxygenation (OGD/R)-induced neuronal injury by inhibiting Bach1 and promoting Nrf2/ARE signaling

MicroRNA-98-5p (miR-98-5p) is a stress-related microRNA (miRNA) that plays an important role in regulating cell survival, apoptosis, and oxidative stress in multiple cell types and diseases. However, little is known about the role of miR-98-5p in cerebral ischemia/reperfusion injury. In this study, we investigated the role and mechanism of miR-98-5p in regulating neuronal injury induced by oxygen-glucose deprivation/reoxygenation (OGD/R), an in vitro model of cerebral ischemia/reperfusion injury. We found that miR-98 expression was significantly altered in neurons in response to OGD/R treatment. Functional experiments showed that overexpression of miR-98-5p inhibited OGD/R-induced apoptosis and reactive oxygen species (ROS) production in neurons, whereas inhibition of miR-98-5p showed the opposite effect. Interestingly, bioinformatics analysis predicted that BTB and CNC homology 1 (Bach1) was a potential target gene of miR-98-5p, that was verified by dual-luciferase reporter assay. Moreover, overexpression of miR-98-5p inhibited Bach1 expression while suppression of miR-98-5p promoted Bach1 expression in neurons. Notably, miR-98-5p was shown to regulate the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and the activity of the antioxidant response element (ARE). However, overexpression of Bach1 or silencing of Nrf2 significantly abolished the miR-98-5p-mediated neuroprotective effect. Overall, these results demonstrate that miR-98-5p ameliorates OGD/R-induced neuronal injury in vitro through targeting to promote activation of Nrf2/ARE signaling. Our study suggests that miR-98-5p may play a potential role in cerebral ischemia/reperfusion injury and represents a potential therapeutic target for neuroprotection.

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.

BACH transcription factors in innate and adaptive immunity

BTB and CNC homology (BACH) proteins are transcriptional repressors of the basic region leucine zipper (bZIP) transcription factor family. Recent studies indicate widespread roles of BACH proteins in controlling the development and function of the innate and adaptive immune systems, including the differentiation of effector and memory cells of the B and T cell lineages, CD4+ regulatory T cells and macrophages. Here, we emphasize similarities at a molecular level in the cell-type-specific activities of BACH factors, proposing that competitive interactions of BACH proteins with transcriptional activators of the bZIP family form a common mechanistic theme underlying their diverse actions. The findings contribute to a general understanding of how transcriptional repressors shape lineage commitment and cell-type-specific functions through repression of alternative lineage programmes.

Genetic ablation of Bach1 gene enhances recovery from hyperoxic lung injury in newborn mice via transient upregulation of inflammatory genes

BACKGROUND

BTB and CNC homology 1 (Bach1) is a transcriptional repressor of heme oxygenase (HO)-1. The effects of Bach1 disruption on hyperoxic lung injury in newborn mice have not been determined. We aimed to investigate the role of Bach1 in the newborns exposed to hyperoxia.

METHODS

Bach1^-/- and WT newborn mice were exposed to 21% or 95% oxygen for 4 d and were then allowed to recover in room air. Lung histology was assessed and lung Bach1, HO-1, interleukin (IL)-6, and monocyte chemoattractant protein (MCP)-1 mRNA levels were evaluated using RT-PCR. Lung inflammatory cytokine levels were determined using cytometric bead arrays.

RESULTS

After 10 d recovery from neonatal hyperoxia, Bach1^-/- mice showed improved lung alveolarization compared with WT. HO-1, IL-6, and MCP-1 mRNA levels and IL-6 and MCP-1 protein levels were significantly increased in the Bach1^-/- lungs exposed to neonatal hyperoxia. Although an increase in apoptosis was observed in the Bach1^-/- and WT lungs after neonatal hyperoxia, there were no differences in apoptosis between these groups.

CONCLUSION

Bach1^-/- newborn mice were well-recovered from hyperoxia-induced lung injury. This effect is likely achieved by the antioxidant/anti-inflammatory activity of HO-1 or by the transient overexpression of proinflammatory cytokines.

Heme oxygenase-1 protects spinal cord neurons from hydrogen peroxide-induced apoptosis via suppression of Cdc42/MLK3/MKK7/JNK3 signaling

The mechanisms by which oxidative stress induces spinal cord neuron death has not been completely understood. Investigation on the molecular signal pathways involved in oxidative stress-mediated neuronal death is important for development of new therapeutics for oxidative stress-associated spinal cord disorders. In current study we examined the role of heme oxygenase-1 (HO-1) in the modulation of MLK3/MKK7/JNK3 signaling, which is a pro-apoptotic pathway, after treating primary spinal cord neurons with H2O2. We found that MLK3/MKK7/JNK3 signaling was substantially activated by H2O2 in a time-dependent manner, demonstrated by increase of activating phosphorylation of MLK3, MKK7 and JNK3. H2O2 also induced expression of HO-1. Transduction of neurons with HO-1-expressing adeno-associated virus before H2O2 treatment introduced expression of exogenous HO-1 in neurons. Exogenous HO-1 reduced phosphorylation of MLK3, MKK7 and JNK3. Consistent with its inhibitory effect on MLK3/MKK7/JNK3 signaling, exogenous HO-1 decreased H2O2-induced neuronal apoptosis and necrosis. Furthermore, we found that exogenous HO-1 inhibited expression of Cdc42, which is crucial for MLK3 activation. In addition, HO-1-induced down-regulation of MLK3/MKK7/JNK3 signaling might be related to up-regulation of microRNA-137 (mir-137). A mir-137 inhibitor alleviated the inhibitory effect of HO-1 on JNK3 activation. This inhibitor also increased neuronal death even when exogenous HO-1 was expressed. Therefore, our study suggests a novel mechanism by which HO-1 exerted its neuroprotective efficacy on oxidative stress.

Heme Oxygenase-1 Inhibits Neuronal Apoptosis in Spinal Cord Injury through Down-Regulation of Cdc42-MLK3-MKK7-JNK3 Axis

The mechanism by which spinal cord injury (SCI) induces neuronal death has not been thoroughly understood. Investigation on the molecular signal pathways involved in SCI-mediated neuronal apoptosis is important for development of new therapeutics for SCI. In the current study, we explore the role of heme oxygenase-1 (HO-1) in the modulation of mixed lineage kinase 3/mitogen-activated protein kinase kinase/cJUN N-terminal kinase 3 (MLK3/MKK7/JNK3) signaling, which is a pro-apoptotic pathway, after SCI. We found that MLK3/MKK7/JNK3 signaling was activated by SCI in a time-dependent manner, demonstrated by increase in activating phosphorylation of MLK3, MKK7, and JNK3. SCI also induced HO-1 expression. Administration of HO-1-expressing adeno-associated virus before SCI introduced expression of exogenous HO-1 in injured spinal cords. Exogenous HO-1 reduced phosphorylation of MLK3, MKK7, and JNK3. Consistent with its inhibitory effect on MLK3/MKK7/JNK3 signaling, exogenous HO-1 decreased SCI-induced neuronal apoptosis and improved neurological score. Further, we found that exogenous HO-1 inhibited expression of cell division cycle 42 (Cdc42), which is crucial for MLK3 activation. In vitro experiments indicated that Cdc42 was essential for neuronal apoptosis, while transduction of neurons with HO-1-expressing adeno-associated virus significantly reduced neuronal apoptosis to enhance neuronal survival. Therefore, our study disclosed a novel mechanism by which HO-1 exerted its neuroprotective efficacy. Our discovery might be valuable for developing a new therapeutic approach for SCI.

Heme oxygenase-1 promotes neuron survival through down-regulation of neuronal NLRP1 expression after spinal cord injury

Background

Understanding the mechanisms underlying neuronal death in spinal cord injury (SCI) and developing novel therapeutic approaches for SCI-induced damage are critical for functional recovery. Here we investigated the role of heme oxygenase-1 (HO-1) in neuroprotection after SCI.

Methods

Adeno-associated virus expressing HO-1 was prepared and injected into rat spinal cords before SCI model was performed. HO-1 expression, inflammasome activation, and the presence of inflammatory cytokines were determined by quantitative polymerase chain reaction, immunohistological staining, immunoblot, and immunoprecipitation. Neuronal apoptosis was assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling. The hindlimb locomotor function was evaluated for extent of neurologic damage. In an in vitro model, hydrogen peroxide was used to induce similar inflammasome activation in cultured primary spinal cord neurons, followed by evaluation of above parameters with or without transduction of HO-1-expressing adeno-associated virus.

Results

Endogenous HO-1 expression was found in spinal cord neurons after SCI in vivo, in association with the expression of Nod-like receptor protein 1 (NLRP1) and the formation of NLRP1 inflammasomes. Administration of HO-1-expressing adeno-associated virus effectively decreased expression of NLRP1, therefore alleviating NLRP1 inflammasome-induced neuronal death and improving functional recovery. In the in vitro model, exogenous HO-1 expression protected neurons from hydrogen peroxide-induced neuronal death by inhibiting NLRP1 expression. In addition, HO-1 inhibited expression of activating transcription factor 4 (ATF4), which is a transcription factor regulating NLRP1 expression.

Conclusions

HO-1 protects spinal cord neurons after SCI through inhibiting NLRP1 inflammasome formation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0521-y) contains supplementary material, which is available to authorized users.

Bach1 Induces Endothelial Cell Apoptosis and Cell-Cycle Arrest through ROS Generation

The transcription factor BTB and CNC homology 1 (Bach1) regulates genes involved in the oxidative stress response and cell-cycle progression. We have recently shown that Bach1 impairs cell proliferation and promotes apoptosis in cultured endothelial cells (ECs), but the underlying mechanisms are largely uncharacterized. Here we demonstrate that Bach1 upregulation impaired the blood flow recovery from hindlimb ischemia and this effect was accompanied both by increases in reactive oxygen species (ROS) and cleaved caspase 3 levels and by declines in the expression of cyclin D1 in the injured tissues. We found that Bach1 overexpression induced mitochondrial ROS production and caspase 3-dependent apoptosis and its depletion attenuated H₂O₂-induced apoptosis in cultured human microvascular endothelial cells (HMVECs). Bach1-induced apoptosis was largely abolished when the cells were cultured with N-acetyl-l-cysteine (NAC), a ROS scavenger. Exogenous expression of Bach1 inhibited the cell proliferation and the expression of cyclin D1, induced an S-phase arrest, and increased the expression of cyclin E2, which were partially blocked by NAC. Taken together, our results suggest that Bach1 suppresses cell proliferation and induces cell-cycle arrest and apoptosis by increasing mitochondrial ROS production, suggesting that Bach1 may be a promising treatment target for the treatment of vascular diseases.

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.

Bach1 Represses Wnt/β-Catenin Signaling and Angiogenesis

RATIONALE

Wnt/β-catenin signaling has an important role in the angiogenic activity of endothelial cells (ECs). Bach1 is a transcription factor and is expressed in ECs, but whether Bach1 regulates angiogenesis is unknown.

OBJECTIVE

This study evaluated the role of Bach1 in angiogenesis and Wnt/β-catenin signaling.

METHODS AND RESULTS

Hind-limb ischemia was surgically induced in Bach1(-/-) mice and their wild-type littermates and in C57BL/6J mice treated with adenoviruses coding for Bach1 or GFP. Lack of Bach1 expression was associated with significant increases in perfusion and vascular density and in the expression of proangiogenic cytokines in the ischemic hindlimb of mice, with enhancement of the angiogenic activity of ECs (eg, tube formation, migration, and proliferation). Bach1 overexpression impaired angiogenesis in mice with hind-limb ischemia and inhibited Wnt3a-stimulated angiogenic response and the expression of Wnt/β-catenin target genes, such as interleukin-8 and vascular endothelial growth factor, in human umbilical vein ECs. Interleukin-8 and vascular endothelial growth factor were responsible for the antiangiogenic response of Bach1. Immunoprecipitation and GST pull-down assessments indicated that Bach1 binds directly to TCF4 and reduces the interaction of β-catenin with TCF4. Bach1 overexpression reduces the interaction between p300/CBP and β-catenin, as well as β-catenin acetylation, and chromatin immunoprecipitation experiments confirmed that Bach1 occupies the TCF4-binding site of the interleukin-8 promoter and recruits histone deacetylase 1 to the interleukin-8 promoter in human umbilical vein ECs.

CONCLUSIONS

Bach1 suppresses angiogenesis after ischemic injury and impairs Wnt/β-catenin signaling by disrupting the interaction between β-catenin and TCF4 and by recruiting histone deacetylase 1 to the promoter of TCF4-targeted genes.

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.

Protective role of hemeoxygenase-1 in gastrointestinal diseases

Disorders and diseases of the gastrointestinal system encompass a wide array of pathogenic mechanisms as a result of genetic, infectious, neoplastic, and inflammatory conditions. Inflammatory diseases in general are rising in incidence and are emerging clinical problems in gastroenterology and hepatology. Hemeoxygenase-1 (HO-1) is a stress-inducible enzyme that has been shown to confer protection in various organ-system models. Its downstream effectors, carbon monoxide and biliverdin have also been shown to offer these beneficial effects. Many studies suggest that induction of HO-1 expression in gastrointestinal tissues and cells plays a critical role in cytoprotection and resolving inflammation as well as tissue injury. In this review, we examine the protective role of HO-1 and its downstream effectors in modulating inflammatory diseases of the upper (esophagus and stomach) and lower (small and large intestine) gastrointestinal tract, the liver, and the pancreas. Cytoprotective, anti-inflammatory, anti-proliferative, antioxidant, and anti-apoptotic activities of HO-1 make it a promising if not ideal therapeutic target for inflammatory diseases of the gastrointestinal system.

Wearing red for signaling: the heme-bach axis in heme metabolism, oxidative stress response and iron immunology

The connection between gene regulation and metabolism is an old issue that warrants revisiting in order to understand both normal as well as pathogenic processes in higher eukaryotes. Metabolites affect the gene expression by either binding to transcription factors or serving as donors for post-translational modification, such as that involving acetylation and methylation. The focus of this review is heme, a prosthetic group of proteins that includes hemoglobin and cytochromes. Heme has been shown to bind to several transcription factors, including Bach1 and Bach2, in higher eukaryotes. Heme inhibits the transcriptional repressor activity of Bach1, resulting in the derepression of its target genes, such as globin in erythroid cells and heme oxygenase-1 in diverse cell types. Since Bach2 is important for class switch recombination and somatic hypermutation of immunoglobulin genes as well as regulatory and effector T cell differentiation and the macrophage function, the heme-Bach2 axis may regulate the immune response as a signaling cascade. We discuss future issues regarding the topic of the iron/heme-gene regulation network based on current understanding of the heme-Bach axis, including the concept of "iron immunology" as the synthesis of the iron metabolism and the immune response.

Induction of heme oxygenase I (HMOX1) by HPP-4382: a novel modulator of Bach1 activity

Oxidative stress is generated by reactive oxygen species (ROS) produced in response to metabolic activity and environmental factors. Increased oxidative stress is associated with the pathophysiology of a broad spectrum of inflammatory diseases. Cellular response to excess ROS involves the induction of antioxidant response element (ARE) genes under control of the transcriptional activator Nrf2 and the transcriptional repressor Bach1. The development of synthetic small molecules that activate the protective anti-oxidant response network is of major therapeutic interest. Traditional small molecules targeting ARE-regulated gene activation (e.g., bardoxolone, dimethyl fumarate) function by alkylating numerous proteins including Keap1, the controlling protein of Nrf2. An alternative is to target the repressor Bach1. Bach1 has an endogenous ligand, heme, that inhibits Bach1 binding to ARE, thus allowing Nrf2-mediated gene expression including that of heme-oxygenase-1 (HMOX1), a well described target of Bach1 repression. In this report, normal human lung fibroblasts were used to screen a collection of synthetic small molecules for their ability to induce HMOX1. A class of HMOX1-inducing compounds, represented by HPP-4382, was discovered. These compounds are not reactive electrophiles, are not suppressed by N-acetyl cysteine, and do not perturb either ROS or cellular glutathione. Using RNAi, we further demonstrate that HPP-4382 induces HMOX1 in an Nrf2-dependent manner. Chromatin immunoprecipitation verified that HPP-4382 treatment of NHLF cells reciprocally coordinated a decrease in binding of Bach1 and an increase of Nrf2 binding to the HMOX1 E2 enhancer. Finally we show that HPP-4382 can inhibit Bach1 activity in a reporter assay that measures transcription driven by the human HMOX1 E2 enhancer. Our results suggest that HPP-4382 is a novel activator of the antioxidant response through the modulation of Bach1 binding to the ARE binding site of target genes.

A novel predictor of infarct-related artery patency before percutaneous intervention and in-hospital outcomes for ST-segment elevation myocardial infarction patients: serum bilirubin level

Introduction

Previous studies have reported a relationship between serum bilirubin levels and coronary artery disease (CAD). However, data are rare up to now regarding the relation of bilirubin levels with infarct-related artery (IRA) patency in the setting of ST-segment elevation myocardial infarction (STEMI). Moreover, previous studies reported that increased bilirubin was related to impaired post-intervention coronary flow. To our knowledge, the association between serum total bilirubin (TB) levels and pre-primary percutaneous coronary intervention (PCI) with patency of IRA flow in STEMI patients has not been investigated.

Aim

To evaluate the association of TB with pre-primary PCI, coronary flow and in-hospital major adverse cardiac events (MACE) in patients with STEMI.

Material and methods

A total of 360 consecutive patients with STEMI (mean age = 61.4 ±13.7 years) admitted within 12 h from the time of symptom onset were enrolled. Patients were divided into 2 groups based on the serum TB levels. We defined normal flow as pre-PCI TIMI 3 flow, while impaired flow was defined as pre-PCI TIMI ≤ 2 flow.

Results

Pre-PCI impaired flow was higher in the TB group than pre-PCI normal flow (p < 0.001). In-hospital mortality and MACE were significantly higher in the high TB group (p = 0.002, p < 0.001 respectively). In the receiver operating characteristic curve analysis, TB > 0.825 mg/dl predicted impaired IRA flow before p-PCI with a sensitivity of 79% and specificity of 71%.

Conclusions

The TB is an inexpensive and readily available marker for STEMI patients undergoing PCI. It can be used for risk stratification in this patient population.

Bach1 deficiency and accompanying overexpression of heme oxygenase-1 do not influence aging or tumorigenesis in mice

Oxidative stress contributes to both aging and tumorigenesis. The transcription factor Bach1, a regulator of oxidative stress response, augments oxidative stress by repressing the expression of heme oxygenase-1 (HO-1) gene (Hmox1) and suppresses oxidative stress-induced cellular senescence by restricting the p53 transcriptional activity. Here we investigated the lifelong effects of Bach1 deficiency on mice. Bach1-deficient mice showed longevity similar to wild-type mice. Although HO-1 was upregulated in the cells of Bach1-deficient animals, the levels of ROS in Bach1-deficient HSCs were comparable to those in wild-type cells. Bach1^−/−; p53^−/− mice succumbed to spontaneous cancers as frequently as p53-deficient mice. Bach1 deficiency significantly altered transcriptome in the liver of the young mice, which surprisingly became similar to that of wild-type mice during the course of aging. The transcriptome adaptation to Bach1 deficiency may reflect how oxidative stress response is tuned upon genetic and environmental perturbations. We concluded that Bach1 deficiency and accompanying overexpression of HO-1 did not influence aging or p53 deficiency-driven tumorigenesis. Our results suggest that it is useful to target Bach1 for acute injury responses without inducing any apparent deteriorative effect.

Bach1 deficiency protects pancreatic β-cells from oxidative stress injury

BTB and CNC homology 1 (Bach1) is a transcriptional repressor of antioxidative enzymes, such as heme oxygenase-1 (HO-1). Oxidative stress is reportedly involved in insulin secretion impairment and obesity-associated insulin resistance. However, the role of Bach1 in the development of diabetes is unclear. HO-1 expression in the liver, white adipose tissue, and pancreatic islets was markedly upregulated in Bach1-deficient mice. Unexpectedly, glucose and insulin tolerance tests showed no differences in obese wild-type (WT) and obese Bach1-deficient mice after high-fat diet loading for 6 wk, suggesting minimal roles of Bach1 in the development of insulin resistance. In contrast, Bach1 deficiency significantly suppressed alloxan-induced pancreatic insulin content reduction and the resultant glucose elevation. Furthermore, TUNEL-positive cells in pancreatic islets of Bach1-deficient mice were markedly decreased, by 60%, compared with those in WT mice. HO-1 expression in islets was significantly upregulated in alloxan-injected Bach1-deficient mice, whereas expression of other antioxidative enzymes, e.g., catalase, superoxide dismutase, and glutathione peroxidase, was not changed by either alloxan administration or Bach1 deficiency. Our results suggest that Bach1 deficiency protects pancreatic β-cells from oxidative stress-induced apoptosis and that the enhancement of HO-1 expression plays an important role in this protection.

BTB and CNC homolog 1 (Bach1) deficiency ameliorates TNBS colitis in mice: role of M2 macrophages and heme oxygenase-1

BACKGROUND

BTB and CNC homolog 1 (Bach1) is a transcriptional repressor of heme oxygenase-1 (HO-1), which plays an important role in the protection of cells and tissues against acute and chronic inflammation. However, the role of Bach1 in the gastrointestinal mucosal defense system remains little understood. HO-1 supports the suppression of experimental colitis and localizes mainly in macrophages in colonic mucosa. This study was undertaken to elucidate the Bach1/HO-1 system's effects on the pathogenesis of experimental colitis.

METHODS

This study used C57BL/6 (wild-type) and homozygous Bach1-deficient C57BL/6 mice in which colonic damage was induced by the administration of an enema of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Subsequently, they were evaluated macroscopically, histologically, and biochemically. Peritoneal macrophages from the respective mice were isolated and analyzed. Then, wild-type mice were injected with peritoneal macrophages from the respective mice. Acute colitis was induced similarly.

RESULTS

TNBS-induced colitis was inhibited in Bach1-deficient mice. TNBS administration increased the expression of HO-1 messenger RNA and protein in colonic mucosa in Bach1-deficient mice. The expression of HO-1 mainly localized in F4/80-immunopositive and CD11b-immunopositive macrophages. Isolated peritoneal macrophages from Bach1-deficient mice highly expressed HO-1 and also manifested M2 macrophage markers, such as Arginase-1, Fizz-1, Ym1, and MRC1. Furthermore, TNBS-induced colitis was inhibited by the transfer of Bach1-deficient macrophages into wild-type mice.

CONCLUSIONS

Deficiency of Bach1 ameliorated TNBS-induced colitis. Bach1-deficient macrophages played a key role in protection against colitis. Targeting of this mechanism is applicable to cell therapy for human inflammatory bowel disease.

Does Serum Bilirubin level on admission predict TIMI flow grade and in-hospital MACE in patients with STEMI undergoing primary PCI

We evaluated the association of total bilirubin with post-percutaneous coronary intervention (PCI) coronary blood flow and in-hospital major adverse cardiac events (MACEs) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary PCI. A total of 536 consecutive patients with STEMI (male 79%, mean age = 59.9 ± 12.6 years) admitted within 6 hours from symptom onset were enrolled. Patients were divided into 2 groups based on the thrombolysis in myocardial infarction (MI) flow grade. In-stent thrombosis, nonfatal MI, and in-hospital mortality were significantly higher in no-reflow group (P = .007, P = .002, and P < .001, respectively). On multivariate regression, the total bilirubin levels remained independent predictors of no-reflow (odds ratio [OR] 1.586, 95% confidence interval [CI] 1.02-2.47; P = .042) and in-hospital MACE (OR 1.399, 95% CI 1.053-1.857; P = .020). Serum bilirubin levels were independently associated with no-reflow and in-hospital MACE in patients with STEMI undergoing primary PCI.

Prognostic value of total bilirubin in patients with ST-segment elevation acute myocardial infarction undergoing primary coronary intervention

Previous studies have shown that the serum total bilirubin (TB) concentration was inversely related with stable coronary artery disease, diabetes mellitus, hypertension, and metabolic syndromes. The relation between TB levels and in-hospital and long-term outcomes in patients with ST-segment elevation myocardial infarction (STEMI) who undergo primary percutaneous coronary intervention (PCI) is not known. Data from 1,624 consecutive patients with STEMI who underwent primary PCI were evaluated. TB was measured after primary PCI, and the study population was divided into tertiles. The high TB group (n = 450) was defined as a value in the upper third tertile (>0.9 mg/dl) and the low TB group (n = 1,174) as any value in the lower 2 tertiles (≤0.9 mg/dl). The in-hospital mortality rate was significantly greater in the high TB group than in the low TB group (4% vs 1.5%, p = 0.003). In the multivariate analyses, a significant association was noted between high TB levels and the adjusted risk of in-hospital cardiovascular mortality (odds ratio 3.24, 95% confidence interval 1.27 to 8.27, p = 0.014). In the receiver operating characteristic curve analysis, TB >0.90 mg/dl was identified as an effective cutpoint in patients with STEMI for in-hospital cardiovascular mortality (area under the curve 0.66, 95% confidence interval 0.55 to 0.76, p = 0.001). The mean follow-up period was 26.2 months. No differences were seen in the long-term mortality rates between the 2 groups. In conclusion, high TB is independently associated with in-hospital adverse outcomes in patients with STEMI who undergo primary PCI. However, no association was found with long-term mortality.