Organ-specific model of simulated ischemia/reperfusion and hyperglycemia based on engineered heart tissue

Here we aimed to establish an in vitro engineered heart tissue (EHT) co-morbidity mimicking model of ischemia-reperfusion injury and diabetes. EHTs were generated from primary neonatal rat cardiomyocytes. Hyperglycemic conditions or hyperosmolar controls were applied for one day to model acute hyperglycemia and for seven days to model chronic hyperglycemia. 120 min' simulated ischemia (SI) was followed by 120 min' reperfusion (R) and 1-day follow-up reperfusion (FR). Normoxic controls (N) were not subjected to SI/R. Half of the EHTs was paced, the other half was left unpaced. To assess cell injury, lactate-dehydrogenase (LDH) concentration was measured. Beating force and activity (frequency) were monitored as cardiomyocyte functional parameters. LDH-release indicated relevant cell injury after SI/N in each experimental condition, with much higher effects in the chronically hyperglycemic/hyperosmolar groups. SI stopped beating of EHTs in each condition, which returned during reperfusion, with weaker recovery in chronic conditions than in acute conditions. Acutely treated EHTs showed small LDH-release and ∼80% recovery of force during reperfusion and follow-up, while chronically treated EHTs showed a marked LDH-release, only ∼30% recovery with reperfusion and complete loss of beating activity during 24 h follow-up reperfusion. We conclude that EHTs respond differently to SI/R injury in acute and chronic hyperglycemia/hyperosmolarity, and that our EHT model is a novel in vitro combination of diabetes and ischemia-reperfusion.

Evaluation of the interplay between NASH and HFpEF in varied murine age groups

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union's Horizon 2020 Research and Innovation Programme, grant agreement no. 739593

New National Excellence Program of the Ministry of Human Capacities (ÚNKP-21-3-II)

Introduction

Heart failure with preserved ejection fraction (HFpEF) is characterized by diastolic dysfunction, left ventricular hypertrophy, left atrial enlargement and increased serum levels of NT-pro-BNP. HFpEF accounts for 50% of heart failure cases, and typically develops in patients with metabolic comorbidities. Non-alcoholic fatty liver disease and subsequent steatohepatitis (NAFLD, NASH) is the most common chronic liver disease developing due to obesity. Although clinical/epidemiological data exists in humans showing that NASH may lead to cardiac dysfunction per se, experimental data in this regard is lacking.

Purpose

We aimed to evaluate whether NASH is an independent factor of cardiac dysfunction and to investigate the age-dependent effects of NASH on cardiac function.

Methods

Middle aged (10 months old) and aged (24 months old) C57Bl/6J mice were fed either control diet or Choline Deficient (CDAA) diet over a period of eight weeks. Young (2 months old) mice were used as a control. Before termination, echocardiography was performed. Upon termination, organs were isolated for further analysis.

Results

CDAA diet lead to the development of NASH in both age groups, without inducing weight gain, allowing us to investigate the direct effects of NASH on cardiac function. Left ventricular end-diastolic volume (EDV) was increased in aged animals, compared to young and middle aged animals, suggesting increased ventricular pressure. Aged animals were characterized by increased posterior wall thickness (PWT) during diastole and by increased LV mass, indicating left ventricular hypertrophy. Assessment of ejection fraction showed an age-dependent decline. Pulse wave and tissue Doppler measurements showed no difference in E/e’ ratio between the groups. However, strain analysis showed that diastolic dysfunction developed only in aged mice due to NASH.

Conclusion

We conclude that there were no observed changes in cardiac diastolic function due to NASH when using standard echocardiographic evaluation; however, the more sensitive method of strain analysis with 2D speckle tracking was able to show evidence of diastolic dysfunction due to NASH in aging animals.

Rictor is a central target of the molecular network of cardiac ProtectomiRs

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Office of Hungary (NKFIA; NVKP-16-1-2016-0017 National Heart Program and OTKA-FK 134751); MTA-SE System Pharmacology Research Group, Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary

We have previously identified several cardiac microRNAs that are involved in cardioprotection and termed them as ProtectomiRs. mRNA targets of these ProtectomiRs may reveal new drug targets for cardioprotection.

Here we aimed to identify key molecular targets of ProtectomiRs and confirm their association with cardioprotection in a translational pig model of acute myocardial infarction.

Network theoretical approach was utilized to identify 882 potential target genes of 18 previously described protectomiRs. Rictor gene was the most central and it was ranked first in the protectomiR-target mRNA molecular network with the highest node degree of 5. Therefore, expression of Rictor and its targeting microRNAs were further validated in heart samples obtained from a translational pig model of acute myocardial infarction and cardioprotection induced by pre- or postconditioning. Three out of five Rictor-targeting pig homologue of rat ProtectomiRs showed significant upregulation in postconditioned but not in preconditioned pig hearts. Rictor was downregulated at the mRNA and protein level in ischemic postconditioning but not in ischemic preconditioning.

This is the first demonstration that Rictor is the central molecular target of ProtectomiRs and that decreased Rictor expression may regulate ischemic postconditioning-, but not preconditioning-induced acute cardioprotection. We conclude that Rictor is a potential novel drug target for acute cardioprotection.

Investigation of cardiotoxicity by dipeptidyl-peptidase-4 inhibitors in a human cardiomyocyte cell line as well as in samples from chronic heart failure patients

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Horizon 2020 research and innovation programme, Ministry for Innovation and Technology

Background

Dipeptidyl-peptidase-4 (DPP4) inhibitors are relatively new therapeutic tools for type 2 diabetes. The SAVOR-TIMI-53 clinical trial has revealed an increased heart failure (HF)-associated hospitalization rate in saxagliptin treated patients. Although this critical side effect could limit the therapeutic use considerably, the mechanism by which DPP4 inhibitors damage the heart is still unclear.

Aims

We aimed to set up a relevant cellular platform to investigate mechanistically DPP4 inhibition, and the role of its potentially important neuropeptide substrates (e.g. Substance P and Neuropeptide Y). Moreover, we aim to determine the expression of DDP4 and its neuropeptide substrates in human and cellular samples.

Methods

Western blot, ELISA, and radioimmunoassay experiments were performed to investigate the expression of DPP4 and its neuropeptide substrates in human hearts and in AC16 cells. Viability measurements with calcein staining and scratch assay experiments were used to test the potentially toxic effect of DPP4 inhibitors. The localization of DPP4 mRNA was determined with RNA Scope in situ hybridization.

Results

Expression of DPP4 and NPY proteins decreased in interventricular septum samples of patients with HF compared to healthy controls. In human hearts DPP4 mRNA is detectable in cardiomyocytes, while other cell types (endothelial cells, fibroblasts, and macrophages) show negligible expression. AC16 human cardiomyocyte cell line expresses DPP4 enzyme.  Treatment with various DPP4 inhibitors administered alone or in combination with neuropeptides don’t affect cellular survival; although, in scratch assay experiments treatments with neuropeptides decreased cell migration speed in the isolated neonatal rat cardiomyocyte-fibroblast co-culture. The migration speed reducing effect of NPY was revered by the administration of saxagliptin at the highest concentration of NPY.

Conclusions

Decreased activity of DPP4 may play a role in the pathomechanism of end-stage congestive heart failure. The DPP4 enzyme could be important as a compensating mechanism against the elevated sympathetic activity in HF and for the altered neuropeptide tone. Inhibition of DPP4 could decrease this adaptive mechanism thereby exacerbating myocardial damage.

Immune checkpoint inhibition with PD-1 inhibitor induces cardiac dysfunction without overt myocarditis in C57BL/6J mice

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union’s Horizon 2020 Research and Innovation Programme under grant agreement no. 739593

“Semmelweis 250+ Kiválósági PhD Ösztöndíj” (EFOP-3.6.3-VEKOP-16-2017-00009)

Gedeon Richter Talentum Foundation’s scholarship

Background

Immune checkpoint inhibitors have revolutionized the treatment of several form of malignancies (including metastatic melanoma) by enhancing the cytotoxic effects of T cells against cancer cells. Cancer cells evade immune surveillence by increasing the expression of T cell inhibitory molecules, also known as immune checkpoints, such  as programmed cell death-1 (PD-1). Pharmacological inhibition of these molecules by immune checkpoint inhibitors (ICI) will enhance the antitumor activity of T cells. However, enhanced T cell activity may cause immune related adverse effects, including cardiotoxicity.

Aims

We aimed to investigate the effect of PD-1 inhibition on cardiac function and the underlying mechanisms in mice.

Methods

8-10 weeks old C57BL6/J mice were treated with isotype control or anti-PD-1 antibody for 2 or 4 weeks. Cardiac function and morphology was assessed by echocardiography and histology, while the transcriptomic changes were analyzed via RNA sequencing. Nitrosative stress in the heart was assessed by immunohistochemistry and qRT-PCR. Inflammatory gene expression alterations were determined by qRT-PCR in the heart and thymus.

Results

Small animal echocardiography revealed cardiac dysfunction even after 2 weeks of anti-PD-1 treatment, with distinct transcriptomic changes. Nitrosative stress was found to be elevated in the myocardium due to anti-PD-1 treatment, however, histological and qRT-PCR analysis did not reveal T cell infiltration into the myocardium and only mild inflammation was seen in the heart. In contrast, inflammatory gene expression was significantly enhanced in the thymus of anti-PD-1-treated animals, where interleukin-17 showed the most prominent increase.

Conclusions

These findings characterize cardiac dysfunction as a form of ICI-induced cardiotoxicity, which may be mediated by increased thymic inflammatory activation and cytokine production.

Transcriptomic analysis and comparative characterization of rat H9C2, human AC16 and murine HL-1 cardiac cell lines

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union's Horizon 2020 research and innovation programme

National Research, Development and Innovation Fund of Hungary

Background

Cardiac cell lines and primary cell cultures are widely used to model various cardiovascular diseases in vitro. Despite the increasing number of publications using these models, limitations of these cell lines are still undetermined.

Purpose

The aim of our study was to compare the most commonly used cardiac cell lines to primary cultures and to mature cardiac tissues by transcriptomic analysis and morphological characterization.

Methods

H9C2 (rat), AC16 (human) and HL-1 (mouse) cardiac cell lines were differentiated towards a phenotype more resembling cardiomyocytes, by methods most widely used in the literature, and cells were harvested at stages of proliferation and differentiation. Whole left ventricular tissue, neonatal primary cardiac myocytes isolated from mice and rats, or human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) were applied as references. Transcriptome analysis and immunocytochemical detection of cardiac structural proteins were performed on all cell models.

Results

RNA expression of cardiac markers (e.g. Tnnt2, Ryr2, Tnni3) was markedly lower in cell lines compared to primary cells or hiPSC-CM and adult tissue controls. Differentiation procedures induced a significant increase in cardiac- and decrease in embryonic markers in AC16 and H9C2 lines; however, the overall expression pattern of investigated genes in all cell lines showed significant differences in comparison to corresponding myocardium or primary cultures. Immunocytochemistry confirmed low expressions of structural protein alpha-actinin and troponin I in cell lines.

Conclusion

Expression patterns of cardiomyocyte markers and mRNA profile indicates low-to-moderate similarity of cell lines to primary cells/cardiac tissues regardless the differentiation protocol used. These limitations should be taken into account while choosing cells as in vitro platforms to model cardiomyocytes and cardiovascular diseases.

Detection of cannabinoid receptor type 2 in native cells and zebrafish with a highly potent, cell-permeable fluorescent probe

Despite its essential role in the (patho)physiology of several diseases, CB₂R tissue expression profiles and signaling mechanisms are not yet fully understood. We report the development of a highly potent, fluorescent CB₂R agonist probe employing structure-based reverse design. It commences with a highly potent, preclinically validated ligand, which is conjugated to a silicon-rhodamine fluorophore, enabling cell permeability. The probe is the first to preserve interspecies affinity and selectivity for both mouse and human CB₂R. Extensive cross-validation (FACS, TR-FRET and confocal microscopy) set the stage for CB₂R detection in endogenously expressing living cells along with zebrafish larvae. Together, these findings will benefit clinical translatability of CB₂R based drugs.

Detection and visualization of the cannabinoid receptor type 2 by a cell-permeable high affinity fluorescent probe platform enables tracing receptor trafficking in live cells and in zebrafish.

Interplay of Oxidative Stress and Necrosis-like Cell Death in Cardiac Ischemia/Reperfusion Injury: A Focus on Necroptosis

Extensive research work has been carried out to define the exact significance and contribution of regulated necrosis-like cell death program, such as necroptosis to cardiac ischemic injury. This cell damaging process plays a critical role in the pathomechanisms of myocardial infarction (MI) and post-infarction heart failure (HF). Accordingly, it has been documented that the modulation of key molecules of the canonical signaling pathway of necroptosis, involving receptor-interacting protein kinases (RIP1 and RIP3) as well as mixed lineage kinase domain-like pseudokinase (MLKL), elicit cardioprotective effects. This is evidenced by the reduction of the MI-induced infarct size, alleviation of myocardial dysfunction, and adverse cardiac remodeling. In addition to this molecular signaling of necroptosis, the non-canonical pathway, involving Ca2+/calmodulin-dependent protein kinase II (CaMKII)-mediated regulation of mitochondrial permeability transition pore (mPTP) opening, and phosphoglycerate mutase 5 (PGAM5)–dynamin-related protein 1 (Drp-1)-induced mitochondrial fission, has recently been linked to ischemic heart injury. Since MI and HF are characterized by an imbalance between reactive oxygen species production and degradation as well as the occurrence of necroptosis in the heart, it is likely that oxidative stress (OS) may be involved in the mechanisms of this cell death program for inducing cardiac damage. In this review, therefore, several observations from different studies are presented to support this paradigm linking cardiac OS, the canonical and non-canonical pathways of necroptosis, and ischemia-induced injury. It is concluded that a multiple therapeutic approach targeting some specific changes in OS and necroptosis may be beneficial in improving the treatment of ischemic heart disease.

Evidence of a Myenteric Plexus Barrier and Its Macrophage-Dependent Degradation During Murine Colitis: Implications in Enteric Neuroinflammation

BACKGROUND & AIMS

Neuroinflammation in the gut is associated with many gastrointestinal (GI) diseases, including inflammatory bowel disease. In the brain, neuroinflammatory conditions are associated with blood-brain barrier (BBB) disruption and subsequent neuronal injury. We sought to determine whether the enteric nervous system is similarly protected by a physical barrier and whether that barrier is disrupted in colitis.

METHODS

Confocal and electron microscopy were used to characterize myenteric plexus structure, and FITC-dextran assays were used to assess for presence of a barrier. Colitis was induced with dextran sulfate sodium, with co-administration of liposome-encapsulated clodronate to deplete macrophages.

RESULTS

We identified a blood-myenteric barrier (BMB) consisting of extracellular matrix proteins (agrin and collagen-4) and glial end-feet, reminiscent of the BBB, surrounded by a collagen-rich periganglionic space. The BMB is impermeable to the passive movement of 4 kDa FITC-dextran particles. A population of macrophages is present within enteric ganglia (intraganglionic macrophages [IGMs]) and exhibits a distinct morphology from muscularis macrophages, with extensive cytoplasmic vacuolization and mitochondrial swelling but without signs of apoptosis. IGMs can penetrate the BMB in physiological conditions and establish direct contact with neurons and glia. Dextran sulfate sodium-induced colitis leads to BMB disruption, loss of its barrier integrity, and increased numbers of IGMs in a macrophage-dependent process.

CONCLUSIONS

In intestinal inflammation, macrophage-mediated degradation of the BMB disrupts its physiological barrier function, eliminates the separation of the intra- and extra-ganglionic compartments, and allows inflammatory stimuli to access the myenteric plexus. This suggests a potential mechanism for the onset of neuroinflammation in colitis and other GI pathologies with acquired enteric neuronal dysfunction.

Development of High-Specificity Fluorescent Probes to Enable Cannabinoid Type 2 Receptor Studies in Living Cells

Pharmacological modulation of cannabinoid type 2 receptor (CB₂R) holds promise for the treatment of numerous conditions, including inflammatory diseases, autoimmune disorders, pain, and cancer. Despite the significance of this receptor, researchers lack reliable tools to address questions concerning the expression and complex mechanism of CB₂R signaling, especially in cell-type and tissue-dependent contexts. Herein, we report for the first time a versatile ligand platform for the modular design of a collection of highly specific CB₂R fluorescent probes, used successfully across applications, species, and cell types. These include flow cytometry of endogenously expressing cells, real-time confocal microscopy of mouse splenocytes and human macrophages, as well as FRET-based kinetic and equilibrium binding assays. High CB₂R specificity was demonstrated by competition experiments in living cells expressing CB₂R at native levels. The probes were effectively applied to FACS analysis of microglial cells derived from a mouse model relevant to Alzheimer's disease.

Cannabinoid-2 receptor activation ameliorates hepatorenal syndrome

STUDY RATIONALE

Hepatorenal syndrome (HRS) is a life-threatening complication of end-stage liver disease characterized by the rapid decline of kidney function. Herein, we explored the therapeutic potential of targeting the cannabinoid-2 receptor (CB₂-R) utilizing a commonly used mouse model of liver fibrosis and hepatorenal syndrome (HRS), induced by bile duct ligation (BDL).

METHODS

Gene expression analysis, histological evaluation, determination of serum levels of renal injury-biomarkers were used to characterize the BDL-induced organ injury; laser speckle analysis to measure microcirculation in the kidneys.

KEY RESULTS

We found that liver injury triggered marked inflammation and oxidative stress in the kidneys of BDL-operated mice. We detected pronounced histopathological alterations with tubular injury paralleled with increased inflammation, oxidative/nitrative stress and fibrotic remodeling both in hepatic and renal tissues as well as endothelial activation and markedly impaired renal microcirculation. This was accompanied by increased CB₂-R expression in both the liver and the kidney tissues of diseased animals. A selective CB₂-R agonist, HU-910, markedly decreased numerous markers of inflammation, oxidative stress and fibrosis both in the liver and in the kidneys. HU-910 also attenuated markers of kidney injury and improved the impaired renal microcirculation in BDL-operated mice.

CONCLUSIONS

Our results suggest that oxidative stress, inflammation and microvascular dysfunction are key events in the pathogenesis of BDL-associated renal failure. Furthermore, we demonstrate that targeting the CB₂-R by selective agonists may represent a promising new avenue to treat HRS by attenuating tissue and vascular inflammation, oxidative stress, fibrosis and consequent microcirculatory dysfunction in the kidneys.

Discovery of a NAPE-PLD inhibitor that modulates emotional behavior in mice

N-acylethanolamines (NAEs), which include the endocannabinoid anandamide, represent an important family of signaling lipids in the brain. The lack of chemical probes that modulate NAE biosynthesis in living systems hamper the understanding of the biological role of these lipids. Using a high-throughput screen, chemical proteomics and targeted lipidomics, we report here the discovery and characterization of LEI-401 as a CNS-active N-acylphosphatidylethanolamine phospholipase D (NAPE-PLD) inhibitor. LEI-401 reduced NAE levels in neuroblastoma cells and in the brain of freely moving mice, but not in NAPE-PLD KO cells and mice, respectively. LEI-401 activated the hypothalamus-pituitary-adrenal axis and impaired fear extinction, thereby emulating the effect of a cannabinoid CB₁ receptor antagonist, which could be reversed by a fatty acid amide hydrolase inhibitor. Our findings highlight the distinctive role of NAPE-PLD in NAE biosynthesis in the brain and suggest the presence of an endogenous NAE tone controlling emotional behavior.

Interplay of Liver-Heart Inflammatory Axis and Cannabinoid 2 Receptor Signaling in an Experimental Model of Hepatic Cardiomyopathy

BACKGROUND AND AIMS

Hepatic cardiomyopathy, a special type of heart failure, develops in up to 50% of patients with cirrhosis and is a major determinant of survival. However, there is no reliable model of hepatic cardiomyopathy in mice. We aimed to characterize the detailed hemodynamics of mice with bile duct ligation (BDL)-induced liver fibrosis, by monitoring echocardiography and intracardiac pressure-volume relationships and myocardial structural alterations. Treatment of mice with a selective cannabinoid-2 receptor (CB₂ -R) agonist, known to attenuate inflammation and fibrosis, was used to explore the impact of liver inflammation and fibrosis on cardiac function.

APPROACH AND RESULTS

BDL induced massive inflammation (increased leukocyte infiltration, inflammatory cytokines, and chemokines), oxidative stress, microvascular dysfunction, and fibrosis in the liver. These pathological changes were accompanied by impaired diastolic, systolic, and macrovascular functions; cardiac inflammation (increased macrophage inflammatory protein 1, interleukin-1, P-selectin, cluster of differentiation 45-positive cells); and oxidative stress (increased malondialdehyde, 3-nitrotyrosine, and nicotinamide adenine dinucleotide phosphate oxidases). CB₂ -R up-regulation was observed in both livers and hearts of mice exposed to BDL. CB₂ -R activation markedly improved hepatic inflammation, impaired microcirculation, and fibrosis. CB₂ -R activation also decreased serum tumor necrosis factor-alpha levels and improved cardiac dysfunction, myocardial inflammation, and oxidative stress, underlining the importance of inflammatory mediators in the pathology of hepatic cardiomyopathy.

CONCLUSIONS

We propose BDL-induced cardiomyopathy in mice as a model for hepatic/cirrhotic cardiomyopathy. This cardiomyopathy, similar to cirrhotic cardiomyopathy in humans, is characterized by systemic hypotension and impaired macrovascular and microvascular function accompanied by both systolic and diastolic dysfunction. Our results indicate that the liver-heart inflammatory axis has a pivotal pathophysiological role in the development of hepatic cardiomyopathy. Thus, controlling liver and/or myocardial inflammation (e.g., with selective CB₂ -R agonists) may delay or prevent the development of cardiomyopathy in severe liver disease.

Activity-based protein profiling of the human failing ischemic heart reveals alterations in hydrolase activities involving the endocannabinoid system

AIM

Acute myocardial infarction and subsequent post-infarction heart failure are among the leading causes of mortality worldwide. The endocannabinoid system has emerged as an important modulator of cardiovascular disease, however the role of endocannabinoid metabolic enzymes in heart failure is still elusive. Herein, we investigated the endocannabinoids and their metabolic enzymes in ischemic end-stage failing human hearts and non-failing controls.

METHODS AND RESULTS

Quantitative real-time PCR, targeted lipidomics, and activity-based protein profiling (ABPP) enabled assessment of the endocannabinoids and their metabolic enzymes in ischemic end-stage failing human hearts and non-failing controls. Based on lipidomic analysis, two subgroups were identified within the ischemic heart failure group; the first similar to control hearts and the second with decreased levels of the endocannabinoid 2-arachidonoyl-glycerol (2-AG) and drastically increased levels of the endocannabinoid anandamide (AEA), other N-acylethanolamines (NAEs) and free fatty acids. The altered lipid profile was accompanied by strong reductions in the activity of 13 hydrolases, including the 2-AG hydrolytic enzyme monoacylglycerol lipase (MGLL).

CONCLUSIONS

Our findings suggest the presence of different biological states within the ischemic heart failure group, based on alterations in the lipid and hydrolase activity profiles. In addition, this study demonstrates that ABPP is a valuable tool to rapidly analyze enzyme activity in clinical samples with potential for novel drug and biomarker discovery.

Disruption of Renal Arginine Metabolism Promotes Kidney Injury in Hepatorenal Syndrome in Mice

Tubular dysfunction is an important feature of renal injury in hepatorenal syndrome (HRS) in patients with end-stage liver disease. The pathogenesis of kidney injury in HRS is elusive, and there are no clinically relevant rodent models of HRS. We investigated the renal consequences of bile duct ligation (BDL)-induced hepatic and renal injury in mice in vivo by using biochemical assays, real-time polymerase chain reaction (PCR), Western blot, mass spectrometry, histology, and electron microscopy. BDL resulted in time-dependent hepatic injury and hyperammonemia which were paralleled by tubular dilation and tubulointerstitial nephritis with marked upregulation of lipocalin-2, kidney injury molecule 1 (KIM-1) and osteopontin. Renal injury was associated with dramatically impaired microvascular flow and decreased endothelial nitric oxide synthase (eNOS) activity. Gene expression analyses signified proximal tubular epithelial injury, tissue hypoxia, inflammation, and activation of the fibrotic gene program. Marked changes in renal arginine metabolism (upregulation of arginase-2 and downregulation of argininosuccinate synthase 1), resulted in decreased circulating arginine levels. Arginase-2 knockout mice were partially protected from BDL-induced renal injury and had less impairment in microvascular function. In human-cultured proximal tubular epithelial cells hyperammonemia per se induced upregulation of arginase-2 and markers of tubular cell injury.

CONCLUSION

We propose that hyperammonemia may contribute to impaired renal arginine metabolism, leading to decreased eNOS activity, impaired microcirculation, tubular cell death, tubulointerstitial nephritis and fibrosis. Genetic deletion of arginase-2 partially restores microcirculation and thereby alleviates tubular injury. We also demonstrate that BDL in mice is an excellent, clinically relevant model to study the renal consequences of HRS. (Hepatology 2018; 00:000-000).

Neuroprotection in Oxidative Stress-Related Neurodegenerative Diseases: Role of Endocannabinoid System Modulation

SIGNIFICANCE

Redox imbalance may lead to overproduction of reactive oxygen and nitrogen species (ROS/RNS) and subsequent oxidative tissue damage, which is a critical event in the course of neurodegenerative diseases. It is still not fully elucidated, however, whether oxidative stress is the primary trigger or a consequence in the process of neurodegeneration. Recent Advances: Increasing evidence suggests that oxidative stress is involved in the propagation of neuronal injury and consequent inflammatory response, which in concert promote development of pathological alterations characteristic of most common neurodegenerative diseases.

CRITICAL ISSUES

Accumulating recent evidence also suggests that there is an important interplay between the lipid endocannabinoid system [ECS; comprising the main cannabinoid 1 and 2 receptors (CB1 and CB2), endocannabinoids, and their synthetic and metabolizing enzymes] and various key inflammatory and redox-dependent processes.

FUTURE DIRECTIONS

Targeting the ECS to modulate redox state-dependent cell death and to decrease consequent or preceding inflammatory response holds therapeutic potential in a multitude of oxidative stress-related acute or chronic neurodegenerative disorders from stroke and traumatic brain injury to Alzheimer's and Parkinson's diseases and multiple sclerosis, just to name a few, which will be discussed in this overview. Antioxid. Redox Signal. 29, 75-108.

Neutrophil-Hepatic Stellate Cell Interactions Promote Fibrosis in Experimental Steatohepatitis

BACKGROUND & AIMS

Hepatic infiltration of neutrophils is a hallmark of steatohepatitis; however, the role of neutrophils in the progression of steatohepatitis remains unknown.

METHODS

A clinically relevant mouse model of steatohepatitis induced by high-fat diet (HFD) plus binge ethanol feeding was used. Liver fibrosis was examined. In vitro cell culture was used to analyze the interaction of hepatic stellate cells (HSCs) and neutrophils.

RESULTS

HFD plus one binge ethanol (HFD+1B) feeding induced significant hepatic neutrophil infiltration, liver injury, and fibrosis. HFD plus multiple binges of ethanol (HFD+mB) caused more pronounced liver fibrosis. Microarray analyses showed that the most highly activated signaling pathway in this HFD+1B model was related to liver fibrosis and HSC activation. Blockade of chemokine (C-X-C motif) ligand 1 or intercellular adhesion molecule-1 expression reduced hepatic neutrophil infiltration and ameliorated liver injury and fibrosis. Disruption of the p47phox gene (also called neutrophil cytosolic factor 1), a critical component of reactive oxygen species producing nicotinamide adenine dinucleotide phosphate-oxidase in neutrophils, diminished HFD+1B-induced liver injury and fibrosis. Co-culture of HSCs with neutrophils, but not with neutrophil apoptotic bodies, induced HSC activation and prolonged neutrophil survival. Mechanistic studies showed that activated HSCs produce granulocyte-macrophage colony-stimulating factor and interleukin-15 to prolong the survival of neutrophils, which may serve as a positive forward loop to promote liver damage and fibrosis.

CONCLUSIONS

The current data from a mouse model of HFD plus binge ethanol feeding suggest that obesity and binge drinking synergize to promote liver fibrosis, which is partially mediated via the interaction of neutrophils and HSCs. Microarray data in this article have been uploaded to NCBI's Gene Expression Omnibus (GEO accession number: GSE98153).

Selective Photoaffinity Probe That Enables Assessment of Cannabinoid CB2 Receptor Expression and Ligand Engagement in Human Cells

Chemical tools and methods that report on G protein-coupled receptor (GPCR) expression levels and receptor occupancy by small molecules are highly desirable. We report the development of LEI121 as a photoreactive probe to study the type 2 cannabinoid receptor (CB₂R), a promising GPCR to treat tissue injury and inflammatory diseases. LEI121 is the first CB₂R-selective bifunctional probe that covalently captures CB₂R upon photoactivation. An incorporated alkyne serves as ligation handle for the introduction of reporter groups. LEI121 enables target engagement studies and visualization of endogenously expressed CB₂R in HL-60 as well as primary human immune cells using flow cytometry. Our findings show that strategically functionalized probes allow monitoring of endogenous GPCR expression and engagement in human cells using tandem photoclick chemistry and hold promise as biomarkers in translational drug discovery.

Feasibility Evaluation of Myocardial Cannabinoid Type 1 Receptor Imaging in Obesity: A Translational Approach

OBJECTIVES

The aim of this study was to evaluate the feasibility of targeted imaging of myocardial cannabinoid type 1 receptor (CB1-R) and its potential up-regulation in obese mice with translation to humans using [11C]-OMAR and positron emission tomography (PET)/computed tomography (CT).

BACKGROUND

Activation of myocardial CB1-R by endocannabinoids has been implicated in cardiac dysfunction in diabetic mice. Obesity may lead to an up-regulation of myocardial CB1-R, potentially providing a mechanistic link between obesity and the initiation and/or progression of cardiomyopathy.

METHODS

Binding specificity of [11C]-OMAR to CB1-R was investigated by blocking studies with rimonabant in mice. The heart was harvested from each mouse, and its radioactivity was determined by γ-counter. Furthermore, [11C]-OMAR dynamic micro-PET/CT was carried out in obese and normal-weight mice. Ex vivo validation was performed by droplet digital polymerase chain reaction (absolute quantification) and RNAscope Technology (an in situ ribonucleic acid analysis platform). Subsequently, myocardial CB1-R expression was probed noninvasively with intravenous injection of CB1-R ligand [11C]-OMAR and PET/CT in humans with advanced obesity and normal-weight human control subjects, respectively.

RESULTS

Rimonabant significantly blocked OMAR uptake in the heart muscle compared with vehicle, signifying specific binding of OMAR to the CB1-R in the myocardium. The myocardial OMAR retention quantified by micro-PET/CT in mice was significantly higher in obese compared with normal-weight mice. Absolute quantification of CB1-R gene expression with droplet digital polymerase chain reaction and in situ hybridization confirmed CB1-R up-regulation in all major myocardial cell types (e.g., cardiomyocytes, endothelium, vascular smooth muscle cells, and fibroblasts) of obese mice. Obese mice also had elevated myocardial levels of endocannabinoids anandamide and 2-arachidonoylglycerol compared with lean mice. Translation to humans revealed higher myocardial OMAR retention in advanced obesity compared with normal-weight subjects.

CONCLUSIONS

Noninvasive imaging of cardiac CB1-R expression in obesity is feasible applying [11C]-OMAR and PET/CT. These results may provide a rationale for further clinical testing of CB1-R-targeted molecular imaging in cardiometabolic diseases.

Posttranslational modifications of calcium/calmodulin-dependent protein kinase IIδ and its downstream signaling in human failing hearts

BACKGROUND

In human failing hearts (HF) of different origin (coronary artery disease-CAD, dilated-DCM, restrictive and hypertrophic cardiomyopathy-OTHER), we investigated the active forms of Ca²⁺/calmodulin-dependent protein kinase IIδ (p-Thr²⁸⁷-CaMKIIδ, oxMet^281/282-CaMKIIδ) and their role in phenotypes of the disease.

METHODS AND RESULTS

Although basic diagnostic and clinical markers indicating the attenuated cardiac contractility and remodeling were comparable in HF groups, CaMKIIδ-mediated axis was different. P-Thr²⁸⁷-CaMKIIδ was unaltered in CAD group, whereas it was upregulated in non-ischemic cardiomyopathic groups. No correlation between the upregulated p-Thr²⁸⁷-CaMKIIδ and QT interval prolongation was detected. Unlike in DCM, oxMet^281/282-CaMKIIδ did not differ among HF groups. Independently of CaMKIIδ phosphorylation/oxidation, activation of its downstreams-phospholamban and cardiac myosin binding protein-C was significantly downregulated supporting both diminished cardiac lusitropy and inotropy in all hearts. Content of sarcoplasmic reticulum Ca²⁺-ATPase 2a in all HF was unchanged. Protein phosphatase1β was upregulated in CAD and DCM only, while 2A did not differ among groups.

CONCLUSION

This is the first demonstration that the posttranslational activation of CaMKIIδ differs in HF depending on etiology. Lower levels of downstream molecular targets of CaMKIIδ do not correlate with either activation of CaMKIIδ or the expression of major protein phosphatases in the HF. Thus, it is unlikely that these mechanisms exclusively underlie failing of the heart.

β-Caryophyllene protects against alcoholic steatohepatitis by attenuating inflammation and metabolic dysregulation in mice

BACKGROUND AND AIMS

β-Caryophyllene (BCP) is a plant-derived FDA approved food additive with anti-inflammatory properties. Some of its beneficial effects in vivo are reported to involve activation of cannabinoid CB₂ receptors that are predominantly expressed in immune cells. Here, we evaluated the translational potential of BCP using a well-established model of chronic and binge alcohol-induced liver injury.

METHODS

In this study, we investigated the effects of BCP on liver injury induced by chronic plus binge alcohol feeding in mice in vivo by using biochemical assays, real-time PCR and histology analyses. Serum and hepatic BCP levels were also determined by GC/MS.

RESULTS

Chronic treatment with BCP alleviated the chronic and binge alcohol-induced liver injury and inflammation by attenuating the pro-inflammatory phenotypic `M1` switch of Kupffer cells and by decreasing the expression of vascular adhesion molecules intercellular adhesion molecule 1, E-Selectin and P-Selectin, as well as the neutrophil infiltration. It also beneficially influenced hepatic metabolic dysregulation (steatosis, protein hyperacetylation and PPAR-α signalling). These protective effects of BCP against alcohol-induced liver injury were attenuated in CB₂ receptor knockout mice, indicating that the beneficial effects of this natural product in liver injury involve activation of these receptors. Following acute or chronic administration, BCP was detectable both in the serum and liver tissue homogenates but not in the brain.

CONCLUSIONS

Given the safety of BCP in humans, this food additive has a high translational potential in treating or preventing hepatic injury associated with oxidative stress, inflammation and steatosis.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Alcohol Misuse and Kidney Injury: Epidemiological Evidence and Potential Mechanisms

Chronic alcohol consumption is a well-known risk factor for tissue injury. The link between alcohol use disorder (AUD) and kidney injury is intriguing but controversial, and the molecular mechanisms by which alcohol may damage the kidneys are poorly understood. Epidemiological studies attempting to link AUD and kidney disease are, to date, inconclusive, and there is little experimental evidence directly linking alcohol consumption to kidney injury. However, studies conducted primarily in other organs and tissues suggest several possible mechanisms by which alcohol may promote kidney dysfunction. One possible mechanism is oxidative stress resulting from increased production of reactive oxygen species, which leads to an excessive amount of free radicals, which in turn trigger tissue injury and increase inflammation. In addition, AUD's effect on other major organs (liver, heart, intestines, and skeletal muscle) appears to promote unfavorable pathological processes that are harmful to the kidneys. Notably, these mechanisms have not yet been validated experimentally in the kidney. Additional research is needed to clarify if alcohol does indeed promote kidney injury and the mechanisms by which alcohol-induced kidney injury may occur.

Trastuzumab cardiotoxicity: from clinical trials to experimental studies

Epidermal growth factor receptor-2 (HER-2) is overexpressed in 20 to 25% of human breast cancers, which is associated with aggressive tumour growth and poor prognosis. Trastuzumab (Herceptin®) is a humanized monoclonal antibody directed against HER-2, the first highly selective form of therapy targeting HER-2 overexpressing tumours. Although initial trials indicated high efficacy and a favourable safety profile of the drug, the first large, randomized trial prompted a retrospective analysis of cardiac dysfunction in earlier trials utilizing trastuzumab. There has been ongoing debate on the cardiac safety of trastuzumab ever since, initiating numerous clinical and preclinical investigations to better understand the background of trastuzumab cardiotoxicity and evaluate its effects on patient morbidity. Here, we have given a comprehensive overview of our current knowledge on the cardiotoxicity of trastuzumab, primarily focusing on data from clinical trials and highlighting the main molecular mechanisms proposed.

LINKED ARTICLES

This article is part of a themed section on New Insights into Cardiotoxicity Caused by Chemotherapeutic Agents. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.21/issuetoc.

Chronic plus binge ethanol feeding induces myocardial oxidative stress, mitochondrial and cardiovascular dysfunction, and steatosis

Alcoholic cardiomyopathy in humans develops in response to chronic excessive alcohol consumption; however, good models of alcohol-induced cardiomyopathy in mice are lacking. Herein we describe mouse models of alcoholic cardiomyopathies induced by chronic and binge ethanol (EtOH) feeding and characterize detailed hemodynamic alterations, mitochondrial function, and redox signaling in these models. Mice were fed a liquid diet containing 5% EtOH for 10, 20, and 40 days (d) combined with single or multiple EtOH binges (5 g/kg body wt). Isocalorically pair-fed mice served as controls. Left ventricular (LV) function and morphology were assessed by invasive pressure-volume conductance approach and by echocardiography. Mitochondrial complex (I, II, IV) activities, 3-nitrotyrosine (3-NT) levels, gene expression of markers of oxidative stress (gp91phox, p47phox), mitochondrial biogenesis (PGC1α, peroxisome proliferator-activated receptor α), and fibrosis were examined. Cardiac steatosis and fibrosis were investigated by histological/immunohistochemical methods. Chronic and binge EtOH feeding (already in 10 days EtOH plus single binge group) was characterized by contractile dysfunction (decreased slope of end-systolic pressure-volume relationship and preload recruitable stroke work), impaired relaxation (decreased time constant of LV pressure decay and maximal slope of systolic pressure decrement), and vascular dysfunction (impaired arterial elastance and lower total peripheral resistance). This was accompanied by enhanced myocardial oxidative/nitrative stress (3-NT; gp91phox; p47phox; angiotensin II receptor, type 1a) and deterioration of mitochondrial complex I, II, IV activities and mitochondrial biogenesis, excessive cardiac steatosis, and higher mortality. Collectively, chronic plus binge EtOH feeding in mice leads to alcohol-induced cardiomyopathies (National Institute on Alcohol Abuse and Alcoholism models) characterized by increased myocardial oxidative/nitrative stress, impaired mitochondrial function and biogenesis, and enhanced cardiac steatosis.

Cannabidiol Limits T Cell-Mediated Chronic Autoimmune Myocarditis: Implications to Autoimmune Disorders and Organ Transplantation

Myocarditis is a major cause of heart failure and sudden cardiac death in young adults and adolescents. Many cases of myocarditis are associated with autoimmune processes in which cardiac myosin is a major autoantigen. Conventional immunosuppressive therapies often provide unsatisfactory results and are associated with adverse toxicities during the treatment of autoimmune myocarditis. Cannabidiol (CBD) is a nonpsychoactive constituent of marijuana that exerts antiinflammatory effects independent of classical cannabinoid receptors. Recently, 80 clinical trials have investigated the effects of CBD in various diseases from inflammatory bowel disease to graft versus host disease. CBD-based formulations are used for the management of multiple sclerosis in numerous countries, and CBD also received U.S. Food and Drug Administration approval for the treatment of refractory childhood epilepsy and glioblastoma multiforme. Herein, using a well-established mouse model of experimental autoimmune myocarditis (EAM) induced by immunization with cardiac myosin emmulsified in adjuvant resulting in T cell-mediated inflammation, cardiomyocyte cell death, fibrosis and myocardial dysfunction, we studied the potential beneficial effects of CBD. EAM was characterized by marked myocardial T-cell infiltration, profound inflammatory response and fibrosis (measured by quantitative real-time polymerase chain reaction, histology and immunohistochemistry analyses) accompanied by marked attenuation of both systolic and diastolic cardiac functions measured with a pressure-volume conductance catheter technique. Chronic treatment with CBD largely attenuated the CD3⁺ and CD4⁺ T cell-mediated inflammatory response and injury, myocardial fibrosis and cardiac dysfunction in mice. In conclusion, CBD may represent a promising novel treatment for managing autoimmune myocarditis and possibly other autoimmune disorders and organ transplantation.

Cardiac NO signalling in the metabolic syndrome

It is well documented that metabolic syndrome (i.e. a group of risk factors, such as abdominal obesity, elevated blood pressure, elevated fasting plasma glucose, high serum triglycerides and low cholesterol level in high-density lipoprotein), which raises the risk for heart disease and diabetes, is associated with increased reactive oxygen and nitrogen species (ROS/RNS) generation. ROS/RNS can modulate cardiac NO signalling and trigger various adaptive changes in NOS and antioxidant enzyme expressions/activities. While initially these changes may represent protective mechanisms in metabolic syndrome, later with more prolonged oxidative, nitrosative and nitrative stress, these are often exhausted, eventually favouring myocardial RNS generation and decreased NO bioavailability. The increased oxidative and nitrative stress also impairs the NO-soluble guanylate cyclase (sGC) signalling pathway, limiting the ability of NO to exert its fundamental signalling roles in the heart. Enhanced ROS/RNS generation in the presence of risk factors also facilitates activation of redox-dependent transcriptional factors such as NF-κB, promoting myocardial expression of various pro-inflammatory mediators, and eventually the development of cardiac dysfunction and remodelling. While the dysregulation of NO signalling may interfere with the therapeutic efficacy of conventional drugs used in the management of metabolic syndrome, the modulation of NO signalling may also be responsible for the therapeutic benefits of already proven or recently developed treatment approaches, such as ACE inhibitors, certain β-blockers, and sGC activators. Better understanding of the above-mentioned pathological processes may ultimately lead to more successful therapeutic approaches to overcome metabolic syndrome and its pathological consequences in cardiac NO signalling.

Functional Genomics of Cardioprotection by Ischemic Conditioning and the Influence of Comorbid Conditions: Implications in Target Identification

Ischemic heart disease including myocardial infarction develops on the basis of several risk-factors and comorbidities such as obesity, diabetes, hypertension, and hypercholesterolemia. Ischemic heart disease is the leading cause of mortality worldwide, therefore, identification of novel drug targets for cardioprotection is of great importance. Ischemic preconditioning, postconditioning, and remote conditioning trigger endogenous cardioprotective mechanisms that render the heart more resistant to lethal ischemic-reperfusion injury. However, major cardiovascular co-morbidities such as hyperlipidemia, diabetes, and their co-medications interfere with these cardioprotective mechanisms thereby limiting the efficacy of cardioprotective ischemic conditioning maneuvers. Ischemia reperfusion injury and cardioprotection by conditioning have been shown to affect global myocardial gene expression profile at the transcript level. Further understanding and the comprehensive analysis of the cardioprotective gene expression fingerprint in normal, protected, and in comorbid conditions may lead to identification of novel molecular targets for cardioprotection.

Cytoprotection by the NO-donor SNAP against ischemia/reoxygenation injury in mouse embryonic stem cell-derived cardiomyocytes

Embryonic stem cell (ESC)-derived cardiomyocytes are a promising cell source for the screening for potential cytoprotective molecules against ischemia/reperfusion injury, however, little is known on their behavior in hypoxia/reoxygenation conditions. Here we tested the cytoprotective effect of the NO-donor SNAP and its downstream cellular pathway. Mouse ESC-derived cardiomyocytes were subjected to 150-min simulated ischemia (SI) followed by 120-min reoxygenation or corresponding non-ischemic conditions. The following treatments were applied during SI or normoxia: the NO-donor S-Nitroso-N-acetyl-D,L-penicillamine (SNAP), the protein kinase G (PKG) inhibitor, the KATP channel blocker glibenclamide, the particulate guanylate cyclase activator brain type natriuretic peptide (BNP), and a non-specific NO synthase inhibitor (N-Nitro-L-arginine, L-NNA) alone or in different combinations. Viability of cells was assayed by propidium iodide staining. SNAP attenuated SI-induced cell death in a concentration-dependent manner, and this protection was attenuated by inhibition of either PKG or KATP channels. However, SI-induced cell death was not affected by BNP or by L-NNA. We conclude that SNAP protects mESC-derived cardiomyocytes against SI/R injury and that soluble guanylate-cyclase, PKG, and KATP channels play a role in the downstream pathway of SNAP-induced cytoprotection. The present mESC-derived cardiomyocyte based screening platform is a useful tool for discovery of cytoprotective molecules.