LXRα Promotes Abdominal Aortic Aneurysm Formation Through UHRF1 Epigenetic Modification of miR-26b-3p

BACKGROUND

Abdominal aortic aneurysm (AAA) is a severe aortic disease without effective pharmacological approaches. The nuclear hormone receptor LXRα (liver X receptor α), encoded by the NR1H3 gene, serves as a critical transcriptional mediator linked to several vascular pathologies, but its role in AAA remains elusive.

METHODS

Through integrated analyses of human and murine AAA gene expression microarray data sets, we identified NR1H3 as a candidate gene regulating AAA formation. To investigate the role of LXRα in AAA formation, we used global Nr1h3-knockout and vascular smooth muscle cell-specific Nr1h3-knockout mice in 2 AAA mouse models induced with angiotensin II (1000 ng·kg·min; 28 days) or calcium chloride (CaCl2; 0.5 mol/L; 42 days).

RESULTS

Upregulated LXRα was observed in the aortas of patients with AAA and in angiotensin II- or CaCl2-treated mice. Global or vascular smooth muscle cell-specific Nr1h3 knockout inhibited AAA formation in 2 mouse models. Loss of LXRα function prevented extracellular matrix degeneration, inflammation, and vascular smooth muscle cell phenotypic switching. Uhrf1, an epigenetic master regulator, was identified as a direct target gene of LXRα by integrated analysis of transcriptome sequencing and chromatin immunoprecipitation sequencing. Susceptibility to AAA development was consistently enhanced by UHRF1 (ubiquitin-like containing PHD and RING finger domains 1) in both angiotensin II- and CaCl2-induced mouse models. We then determined the CpG methylation status and promoter accessibility of UHRF1-mediated genes using CUT&Tag (cleavage under targets and tagmentation), RRBS (reduced representation bisulfite sequencing), and ATAC-seq (assay for transposase-accessible chromatin with sequencing) in vascular smooth muscle cells, which revealed that the recruitment of UHRF1 to the promoter of miR-26b led to DNA hypermethylation accompanied by relatively closed chromatin states, and caused downregulation of miR-26b expression in AAA. Regarding clinical significance, we found that underexpression of miR-26b-3p correlated with high risk in patients with AAA. Maintaining miR-26b-3p expression prevented AAA progression and alleviated the overall pathological process.

CONCLUSIONS

Our study reveals a pivotal role of the LXRα/UHRF1/miR-26b-3p axis in AAA and provides potential biomarkers and therapeutic targets for AAA.

The JNK signaling pathway against titanium-particle-induced osteoclastogenesis and bone resorption in vivo

OBJECTIVE

The c-Jun N-terminal kinases (JNK) signaling pathway may be involved in the regulation of osteoclast development. The purpose of this investigation was to investigate whether SB600125, a JNK inhibitor, could attenuate titanium-particle-induced inflammatory osteolysis in vivo.

MATERIALS AND METHODS

A total of 45 mice were randomly divided into a Sham group, a Titanium group, and a Titanium + JNK inhibitor group, 15 mice per group. After establishing an air pouch bone graft model, we injected phosphate-buffered saline (PBS), titanium particles, or titanium particles + JNK inhibitor into the air pouch of the three groups. The pouch membranes containing bone implants were taken for morphological and molecular analysis 14 days after the mice were sacrificed.

RESULTS

General morphological structure observation results, Hematoxylin and Eosin (H&E)-Stained Sections, anti-tartaric acid phosphatase (TRAP) staining, and the transmission electron microscope showed that SB600125, by inhibiting the expression of JNK, attenuated titanium particle-induced inflammatory osteolysis (p<0.05). Immunohistochemical appearance results and reverse transcription-polymerase chain reaction (RT-PCR) results showed SB600125 reduced expression of IL-6, and TNF-α in osteolytic sites stimulated with wear debris (p<0.05). The Western blot results showed the expression of the p-JNK protein in the titanium particle + SB600125 group was significantly reduced compared to the titanium particle stimulation group (p<0.05).

CONCLUSIONS

Interfering with the JNK signaling pathway may be beneficial in reducing osteolysis, providing a therapeutic target for preventing and treating aseptic loosening caused by debris-induced inflammatory osteolysis.

Plasma metabolic fingerprints for large-scale screening and personalized risk stratification of metabolic syndrome

Direct diagnosis and accurate assessment of metabolic syndrome (MetS) allow for prompt clinical interventions. However, traditional diagnostic strategies overlook the complex heterogeneity of MetS. Here, we perform metabolomic analysis in 13,554 participants from the natural cohort and identify 26 hub plasma metabolic fingerprints (PMFs) associated with MetS and its early identification (pre-MetS). By leveraging machine-learning algorithms, we develop robust diagnostic models for pre-MetS and MetS with convincing performance through independent validation. We utilize these PMFs to assess the relative contributions of the four major MetS risk factors in the general population, ranked as follows: hyperglycemia, hypertension, dyslipidemia, and obesity. Furthermore, we devise a personalized three-dimensional plasma metabolic risk (PMR) stratification, revealing three distinct risk patterns. In summary, our study offers effective screening tools for identifying pre-MetS and MetS patients in the general community, while defining the heterogeneous risk stratification of metabolic phenotypes in real-world settings.

BMP6 knockdown enhances cardiac fibrosis in a mouse myocardial infarction model by upregulating AP-1/CEMIP expression

BACKGROUND

The cardiac repair process following a myocardial infarction is a key factor in patient prognosis. In this repair process, cardiac fibrosis takes a critically important role. Among those featured genes for fibrosis, transforming growth factor beta (TGF-β) is known to be involved in the fibrosis in various organs. And bone morphogenetic protein (BMP)6 belongs to the TGF-β superfamily. Although BMPs are known to play exclusive roles in cardiac repair processes, the character of BMP6 in cardiac remodelling remains unclear.

PURPOSE

This study aimed to investigate how BMP6 functioned in cardiac fibrosis following myocardial infarction (MI).

RESULTS

In this paper, we demonstrated that BMP6 expression was upregulated after myocardial infarction in wild-type (WT) mice. Furthermore, BMP6^-/- mice showed a more significant decline in cardiac function and lower survival curves after MI. An enlarged infarct area, increased fibrosis and more pronounced inflammatory infiltration were observed in BMP6^-/- mice compared to WT mice. The expression of collagen I, collagen III and α-SMA was increased in BMP6^-/- mice. In vitro, through gain-of-function and loss-of-function experiments, it was demonstrated that BMP6 decreases collagen secretion in fibroblasts. Mechanistically, knocking down BMP6 promoted AP-1 phosphorylation, which in turn promotes CEMIP expression, led to an acceleration in the progression of cardiac fibrosis. Finally, it was found that rhBMP6 would alleviate ventricular remodelling abnormalities after myocardial infarction.

CONCLUSION

Therefore, BMP6 may be a novel molecular target for improving myocardial fibrosis and cardiac function after myocardial infarction.

A low-cost edge AI-chip-based system for real-time algae species classification and HAB prediction

Harmful Algal Blooms (HAB) are damaging to ecosystem functions and pose challenges to environmental and fisheries management. The key to HAB management and understanding the complex algal growth dynamics is the development of robust systems for real-time monitoring of algae populations and species. Previous algae classification studies mainly rely on the combination of an in-situ imaging flow cytometer and an off-site lab-based algae classification model such as Random Forest (RF) for the analysis of high-throughput images. An on-site AI algae monitoring system on top of an edge AI chip embedded with the proposed Algal Morphology Deep Neural Network (AMDNN) model is developed to achieve real-time algae species classification and HAB prediction. Based on a detailed examination of real-world algae images, dataset augmentation is first performed: consisting of orientation, flipping, blurring, and Resizing with Aspect ratio Preserved (RAP). The dataset augmentation is shown to significantly improve classification performance which is superior to that of the competitive RF model. And the attention heatmaps show that for relatively regular-shaped algal species (e.g., Vicicitus), the model weights the color and texture information heavily; while the shape-related features are more important for complex-shaped algae (e.g., Chaetoceros). The AMDNN is tested on a dataset of 11,250 algae images containing the 25 most common HAB classes in Hong Kong subtropical waters with 99.87% test accuracy. Based on the fast and accurate algae classification, the AI-chip-based on-site system is applied to a one-month dataset in February 2020; the predicted trends of total cell counts and targeted HAB species counts are in good agreement with observations. The proposed edge AI algae monitoring system provides a platform for the development of practical HAB early warning systems that can effectively support environmental risk and fisheries management.

Characterizing the cellular and molecular variabilities of peripheral immune cells in healthy recipients of BBIBP-CorV inactivated SARS-CoV-2 vaccine by single-cell RNA sequencing

Over 3 billion doses of inactivated vaccines for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been administered globally. However, our understanding of the immune cell functional transcription and T cell receptor (TCR)/B cell receptor (BCR) repertoire dynamics following inactivated SARS-CoV-2 vaccination remains poorly understood. Here, we performed single-cell RNA and TCR/BCR sequencing on peripheral blood mononuclear cells at four time points after immunization with the inactivated SARS-CoV-2 vaccine BBIBP-CorV. Our analysis revealed an enrichment of monocytes, central memory CD4⁺ T cells, type 2 helper T cells and memory B cells following vaccination. Single-cell TCR-seq and RNA-seq comminating analysis identified a clonal expansion of CD4⁺ T cells (but not CD8⁺ T cells) following a booster vaccination that corresponded to a decrease in the TCR diversity of central memory CD4⁺ T cells and type 2 helper T cells. Importantly, these TCR repertoire changes and CD4⁺ T cell differentiation were correlated with the biased VJ gene usage of BCR and the antibody-producing function of B cells post-vaccination. Finally, we compared the functional transcription and repertoire dynamics in immune cells elicited by vaccination and SARS-CoV-2 infection to explore the immune responses under different stimuli. Our data provide novel molecular and cellular evidence for the CD4⁺ T cell-dependent antibody response induced by inactivated vaccine BBIBP-CorV. This information is urgently needed to develop new prevention and control strategies for SARS-CoV-2 infection. (ClinicalTrials.gov Identifier: NCT04871932).Trial registration: ClinicalTrials.gov identifier: NCT04871932..

Hydrogen sulfide alleviates mitochondrial damage and ferroptosis by regulating OPA3-NFS1 axis in doxorubicin-induced cardiotoxicity

Ferroptosis is a major cause of cardiotoxicity induced by doxorubicin (DOX). Previous studies have shown that hydrogen sulfide (H₂S) inhibits ferroptosis in cardiomyocytes and myoblasts, but the underlying mechanism has not been fully elucidated. In this study, we investigated the role of H₂S in protecting against DOX-induced cardiotoxicity both in vivo and in vitro, and elucidated the potential mechanisms involved. We found that DOX downregulated the expression of glutathione peroxidase 4 (GPX4) and NFS1, and upregulated the expression of acyl-coenzyme A synthetase long-chain family member 4 (ACSL4) expression level, resulting in increased lipid peroxidation and ferroptosis. Additionally, DOX inhibited MFN2 expression and increased DRP1 and FIS1 expression, leading to abnormal mitochondrial structure and function. In contrast, exogenous H₂S inhibited DOX-induced ferroptosis by restoring GPX4 and NFS1 expression, and reducing lipid peroxidation in H9C2 cells. This effect was similar to that of the ferroptosis antagonist ferrostatin-1 (Fer-1) in protecting against DOX-induced cardiotoxicity. We further demonstrated that the protective effect of H₂S was mediated by the key mitochondrial membrane protein optic atrophy 3 (OPA3), which was downregulated by DOX and restored by exogenous H₂S. Overexpression of OPA3 alleviated DOX-induced mitochondrial dysfunction and ferroptosis both in vivo and in vitro. Mechanistically, NFS1 has an inhibitory effect on ferroptosis, and NFS1 deficiency increases the susceptibility of cardiomyocytes to ferroptosis. OPA3 is involved in the regulation of ferroptosis by interacting with NFS1. Post-translationally, DOX promoted OPA3 ubiquitination, while exogenous H₂S antagonized OPA3 ubiquitination by promoting OPA3 s-sulfhydration. In summary, our findings suggested that H₂S protects against DOX-induced cardiotoxicity by inhibiting ferroptosis via targeting the OPA3-NFS1 axis. This provides a potential therapeutic strategy for the treatment of DOX-induced cardiotoxicity.

Mechanical injury accentuates lipid deposition in ApoE-/- mice and advance aortic valve stenosis: A novel modified aortic valve stenosis model

Background

Current mouse models still have limitations in studying aortic valve stenosis (AVS). A suitable animal model bearing a close resemblance to the pathophysiological processes of humans needs to be developed. Here, we combined two risk factors to create a mouse model that mimics the pathological features of human AVS.

Methods and results

We combined WI and hyperlipidemia in ApoE^-/- mice to explore the synergistic effect on the stenosis of the aortic valve. Transthoracic echocardiography revealed progressively increased peak velocity with age in ApoE^-/- mice to velocities above C57 mice when fed a high-fat diet after wire injury. Moreover, ApoE^-/- mice demonstrated lower cusp separation and lower aortic valve area after 8 weeks vs. C57 mice. Gross morphology and MRI showed advanced thickening, sclerosis aortic valve, narrowing of the orifice area, and micro-CT showed obvious calcification in the aortic valves in the hyperlipidemia group after wire injury. Histopathology studies showed thickening and fibrosis of aortic valve leaflets in the hyperlipidemia group after wire injury. Notably, lipid deposition was observed in ApoE^-/- mice 8 weeks after wire injury, accompanied by overexpressed apoB and apoA proteins. After wire injury, the hyperlipidemia group exhibited augmented inflammation, ROS production, and apoptosis in the leaflets. Moreover, the combination group exhibited advanced fibro-calcific aortic valves after wire injury.

Conclusion

Overall, we present the synergistic effect of wire injury and hyperlipidemia on lipoproteins deposition in the development of AVS in ApoE^-/- mice, this model bear close resemblance to human AVS pathology.

Circadian nuclear receptor Rev-erbalpha is expressed by platelets and potentiates platelet activation and thrombus formation

Background

Adverse cardiovascular events have day/night patterns with peaks in the morning, potentially related to endogenous circadian clock control of platelet activation. Circadian nuclear receptor Rev-erbα is an essential and negative component of the circadian clock.

Purpose

We aim to investigate the expression profile and biological function of Rev-erbα in platelets.

Methods and results

Here we report the presence and functions of circadian nuclear receptor Rev-erbα in human and mouse platelets. Both human and mouse platelet Rev-erbα showed a circadian rhythm that positively correlated with platelet aggregation. Global Rev-erbα knockout and platelet-specific Rev-erbα knockout mice exhibited defective in hemostasis as assessed by prolonged tail-bleeding times. Rev-erbα deletion also reduced ferric chloride-induced carotid arterial occlusive thrombosis, prevented collagen/epinephrine-induced pulmonary thromboembolism, and protected against microvascular microthrombi obstruction and infarct expansion in an acute myocardial infarction model. In vitro thrombus formation assessed by CD41-labeled platelet fluorescence intensity was significantly reduced in Rev-erbα knockout mouse blood. Platelets from Rev-erbα knockout mice exhibited impaired agonist-induced aggregation responses, integrin αIIbβ3 activation and α-granule release. Consistently, pharmacological inhibition of Rev-erbα by specific antagonists decreased platelet activation markers in both mouse and human platelets. Mechanistically, mass spectrometry and co-immunoprecipitation analyses revealed that Rev-erbα potentiated platelet activation via oligophrenin-1-mediated RhoA/ERM (ezrin/radixin/moesin) pathway.

Conclusion

We provide the first evidence that circadian protein Rev-erbα is functionally expressed in platelets and potentiates platelet activation and thrombus formation. Rev-erbα may serve as a novel therapeutic target for managing thrombosis-based cardiovascular disease.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): This work was supported by grants from the National Science Fund for Distinguished Young Scholars (81625002), the National Natural Science Foundation of China (81930007).

The transcription factor zinc fingers and homeoboxes 2 alleviates NASH by transcriptional activation of phosphatase and tensin homolog

BACKGROUND AND AIMS

NASH, which is a common clinical condition predisposing to advanced liver diseases, has become a worldwide epidemic. A large and growing unmet therapeutic need for this condition reflects incomplete understanding of its pathogenesis. In the current study, we identified a transcription factor, zinc fingers and homeoboxes 2 (ZHX2), in hepatocytes as a protective factor against steatohepatitis.

APPROACH AND RESULTS

We found that hepatic ZHX2 was significantly suppressed in NASH models and steatotic hepatic cells. Hepatocyte-specific ablation of ZHX2 exacerbated NASH-related phenotypes in mice, including lipid accumulation, enhanced inflammation, and hepatic fibrosis. Conversely, hepatocyte-specific overexpression of ZHX2 significantly alleviated the progression of NASH in an experimental setting. Integrated analysis of transcriptomic profiling and chromatin immunoprecipitation sequencing data demonstrated that the phosphatase and tensin homolog (PTEN) was a target gene of ZHX2 in hepatocyte. ZHX2 bound to the promoter of PTEN gene and subsequently promoted the transcription of PTEN, which mediated the beneficial role of ZHX2 against NASH.

CONCLUSIONS

The current findings demonstrate a protective role of ZHX2 against NASH progression by transcriptionally activating PTEN. These findings shed light on the therapeutic potential of targeting ZHX2 for treating NASH and related metabolic disorders.

OUP accepted manuscript

Aims

Adverse cardiovascular events have day/night patterns with peaks in the morning, potentially related to endogenous circadian clock control of platelet activation. Circadian nuclear receptor Rev-erbα is an essential and negative component of the circadian clock. To date, the expression profile and biological function of Rev-erbα in platelets have never been reported.

Methods and results

Here, we report the presence and functions of circadian nuclear receptor Rev-erbα in human and mouse platelets. Both human and mouse platelet Rev-erbα showed a circadian rhythm that positively correlated with platelet aggregation. Global Rev-erbα knockout and platelet-specific Rev-erbα knockout mice exhibited defective in haemostasis as assessed by prolonged tail-bleeding times. Rev-erbα deletion also reduced ferric chloride-induced carotid arterial occlusive thrombosis, prevented collagen/epinephrine-induced pulmonary thromboembolism, and protected against microvascular microthrombi obstruction and infarct expansion in an acute myocardial infarction model. In vitro thrombus formation assessed by CD41-labelled platelet fluorescence intensity was significantly reduced in Rev-erbα knockout mouse blood. Platelets from Rev-erbα knockout mice exhibited impaired agonist-induced aggregation responses, integrin αIIbβ3 activation, and α-granule release. Consistently, pharmacological inhibition of Rev-erbα by specific antagonists decreased platelet activation markers in both mouse and human platelets. Mechanistically, mass spectrometry and co-immunoprecipitation analyses revealed that Rev-erbα potentiated platelet activation via oligophrenin-1-mediated RhoA/ERM (ezrin/radixin/moesin) pathway.

Conclusion

We provided the first evidence that circadian protein Rev-erbα is functionally expressed in platelets and potentiates platelet activation and thrombus formation. Rev-erbα may serve as a novel therapeutic target for managing thrombosis-based cardiovascular disease.

Key question

Adverse cardiovascular events have day/night patterns with peaks in the morning, potentially related to endogenous circadian clock control of platelet activation. Whether circadian nuclear receptor Rev-erba is present in platelets and regulates platelet function remains unknown.

Key finding

We provide the first evidence that Rev-erba is functionally expressed in platelets and acts as a positive regulator of platelet activation/thrombus formation through the oligophrenin-1-mediated RhoA/ERM signalling pathway.

Take home message

Our observations highlight the importance of circadian clock machinery in platelet physiology and support the notion that Rev-erba may serve as a novel therapeutic target for managing thrombosis-based cardiovascular diseases.

Characteristics of US military personnel with atrial fibrillation and associated deployment and retention rates

INTRODUCTION

Atrial fibrillation (AF) is an arrhythmia impacting military occupational performances. Despite being a recognised disqualifying condition, there is no literature describing US military service members with AF. This study aims to describe members with AF diagnoses, the distribution of treatment strategies and associated deployment and retention rates.

METHODS

Active duty service members identified with AF from 2004 to 2019 were investigated. Cardiovascular profiles, AF management strategies and military dispositions were assessed by electronic medical record review.

RESULTS

386 service members (mean age 35.0±9.4 years; 94% paroxysmal AF) with AF diagnoses were identified. 91 (24%) had hypertension followed by 75 (19%) with sleep apnoea. Mean CHA₂DS₂-VASc scores were low (0.39±0.65). Rhythm treatments were used in 173 (45%) followed by rate control strategies in 155 (40%). 161 (42%) underwent pulmonary vein isolation (PVI). In subgroup analysis of 365 personnel, 147 (40%) deployed and 248 (68%) remained active duty after AF diagnosis. Deployment and retention rates did not differ between those who received no medical therapy, rate control or rhythm strategies (p=0.9039 and p=0.6192, respectively). PVI did not significantly impact deployment or retention rates (p=0.3903 and p=0.0929, respectively).

CONCLUSION

Service members with AF are young with few AF risk factors. Rate and rhythm medical therapies were used evenly. Over two-thirds met retention standards and 40% deployed after diagnosis. There were no differences in deployment or retention between groups who receive rate therapy, rhythm medical therapy or PVI. Prospective evaluation of the efficacy of specific AF therapies on AF burden and symptomatology in service members is needed.

Loss of dynamic regulation of G protein-coupled receptor kinase 2 by nitric oxide leads to cardiovascular dysfunction with aging

Nitric oxide (NO) and S-nitrosothiol (SNO) are considered cardio- and vasoprotective substances. We now understand that one mechanism in which NO/SNOs provide cardiovascular protection is through their direct inhibition of cardiac G protein-coupled receptor (GPCR) kinase 2 (GRK2) activity via S-nitrosylation of GRK2 at cysteine 340 (C340). This maintains GPCR homeostasis, including β-adrenergic receptors, through curbing receptor GRK2-mediated desensitization. Previously, we have developed a knockin mouse (GRK2-C340S) where endogenous GRK2 is resistant to dynamic S-nitrosylation, which led to increased GRK2 desensitizing activity. This unchecked regulation of cardiac GRK2 activity resulted in significantly more myocardial damage after ischemic injury that was resistant to NO-mediated cardioprotection. Although young adult GRK2-C340S mice show no overt phenotype, we now report that as these mice age, they develop significant cardiovascular dysfunction due to the loss of SNO-mediated GRK2 regulation. This pathological phenotype is apparent as early as 12 mo of age and includes reduced cardiac function, increased cardiac perivascular fibrosis, and maladaptive cardiac hypertrophy, which are common maladies found in patients with cardiovascular disease (CVD). There are also vascular reactivity and aortic abnormalities present in these mice. Therefore, our data demonstrate that a chronic and global increase in GRK2 activity is sufficient to cause cardiovascular remodeling and dysfunction, likely due to GRK2’s desensitizing effects in several tissues. Because GRK2 levels have been reported to be elevated in elderly CVD patients, GRK2-C340 mice can give insight into the aged-molecular landscape leading to CVD.

NEW & NOTEWORTHY Research on G protein-coupled receptor kinase 2 (GRK2) in the setting of cardiovascular aging is largely unknown despite its strong established functions in cardiovascular physiology and pathophysiology. This study uses a mouse model of chronic GRK2 overactivity to further investigate the consequences of long-term GRK2 on cardiac function and structure. We report for the first time that chronic GRK2 overactivity was able to cause cardiac dysfunction and remodeling independent of surgical intervention, highlighting the importance of GRK activity in aged-related heart disease.

The small molecule macrophage migration inhibitory factor antagonist MIF098, inhibits pulmonary hypertension associated with murine SLE

Pulmonary arterial hypertension (PAH) is a severe complication of systemic lupus erythematosus (SLE), with unclear etiopathogenesis. We evaluated the role of macrophage migration inhibitory factor (MIF), which has been implicated in idiopathic pulmonary hypertension (PH), in SLE-associated PAH. Circulating MIF was measured in SLE patients, SLE-PAH patients, and healthy donors. In situ pulmonary artery MIF protein expression was determined in spontaneous SLE mice (MRL/lpr) and hypoxia-induced C57BL/6J mice. Daily MIF098 was administered to C57BL/6J mice, and these mice were maintained in a hypoxic chamber for 4 weeks. The right ventricular systolic pressure (RVSP) and pathological characteristics of the pulmonary artery (PA), such as hyperproliferation, muscularization, and fibrosis were then measured in each group of mice. Data were also obtained in vitro using pulmonary smooth muscle cells (PASMC) challenged with platelet-derived growth factor (PDGF)-BB or 1% O₂ hypoxia. As a result, circulating MIF was elevated in SLE-PAH patients compared with SLE patients or healthy donors. Higher RVSP SLE mice produced more MIF protein than lower RVSP SLE mice in the pulmonary artery. MIF098 decreased RVSP and inhibited distal pulmonary artery hyperproliferation, muscularization, and collagen deposition in hypoxia challenged mice. In addition, MIF098 inhibited PASMC proliferation and migration by regulating mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2 (MAPK/ERK1/2) signal- and cell-cycle-related proteins. MIF098 also reduced collagen synthesis by inhibiting the TGFβ1/Smad2/Smad3 pathway in cell-based experiments. In conclusion, MIF may serve as a biomarker and a therapeutic target of SLE-associated PAH. Pharmacologic MIF antagonism may be an effective means to ameliorate SLE-PAH.

Melatonin stabilizes rupture-prone vulnerable plaques via regulating macrophage polarization in a nuclear circadian receptor RORα-dependent manner

Rupture of vulnerable plaques is the main trigger of acute cardio-cerebral vascular events, but mechanisms responsible for transforming a stable atherosclerotic into a vulnerable plaque remain largely unknown. Melatonin, an indoleamine hormone secreted by the pineal gland, plays pleiotropic roles in the cardiovascular system; however, the effect of melatonin on vulnerable plaque rupture and its underlying mechanisms remains unknown. Here, we generated a rupture-prone vulnerable carotid plaque model induced by endogenous renovascular hypertension combined with low shear stress in hypercholesterolemic ApoE^-/- mice. Melatonin (10 mg/kg/d by oral administration for 9 weeks) significantly prevented vulnerable plaque rupture, with lower incidence of intraplaque hemorrhage (42.9% vs. 9.5%, P = 0.014) and of spontaneous plaque rupture with intraluminal thrombus formation (38.1% vs. 9.5%, P = 0.029). Mechanistic studies indicated that melatonin ameliorated intraplaque inflammation by suppressing the differentiation of intraplaque macrophages toward the proinflammatory M1 phenotype, and circadian nuclear receptor retinoid acid receptor-related orphan receptor-α (RORα) mediated melatonin-exerted vasoprotection against vulnerable plaque instability and intraplaque macrophage polarization. Further analysis in human monocyte-derived macrophages confirmed the role of melatonin in regulating macrophage polarization by regulating the AMPKα-STATs pathway in a RORα-dependent manner. In summary, our data provided the first evidence that melatonin-RORα axis acts as a novel endogenous protective signaling pathway in the vasculature, regulates intraplaque inflammation, and stabilizes rupture-prone vulnerable plaques.

Melatonin differentially regulates pathological and physiological cardiac hypertrophy: Crucial role of circadian nuclear receptor RORα signaling

Exercise-induced physiological hypertrophy provides protection against cardiovascular disease, whereas disease-induced pathological hypertrophy leads to heart failure. Emerging evidence suggests pleiotropic roles of melatonin in cardiac disease; however, the effects of melatonin on physiological vs pathological cardiac hypertrophy remain unknown. Using swimming-induced physiological hypertrophy and pressure overload-induced pathological hypertrophy models, we found that melatonin treatment significantly improved pathological hypertrophic responses accompanied by alleviated oxidative stress in myocardium but did not affect physiological cardiac hypertrophy and oxidative stress levels. As an important mediator of melatonin, the retinoid-related orphan nuclear receptor-α (RORα) was significantly decreased in human and murine pathological hypertrophic cardiomyocytes, but not in swimming-induced physiological hypertrophic murine hearts. In vivo and in vitro loss-of-function experiments indicated that RORα deficiency significantly aggravated pathological cardiac hypertrophy, and notably weakened the anti-hypertrophic effects of melatonin. Mechanistically, RORα mediated the cardioprotection of melatonin in pathological hypertrophy mainly by transactivation of manganese-dependent superoxide dismutase (MnSOD) via binding to the RORα response element located in the promoter region of the MnSOD gene. Furthermore, MnSOD overexpression reversed the pro-hypertrophic effects of RORα deficiency, while MnSOD silencing abolished the anti-hypertrophic effects of RORα overexpression in pathological cardiac hypertrophy. Collectively, our findings provide the first evidence that melatonin exerts an anti-hypertrophic effect on pathological but not physiological cardiac hypertrophy via alleviating oxidative stress through transactivation of the antioxidant enzyme MnSOD in a RORα-dependent manner.

Trabecular microstructure is influenced by race and sex in Black and White young adults

Lower fracture rates in Black men and women compared to their White counterparts are incompletely understood. High-resolution imaging specific to trabecular bone may provide insight. Black participants have enhanced trabecular morphology. These differences may contribute to the lower fracture risk in Black versus White individuals.

INTRODUCTION

Lower fracture rates in Black men and women compared to their White counterparts may be explained by favorable bone microstructure in Black individuals. Individual trabecular segmentation (ITS) analysis, which characterizes the alignment and plate- and rod-like nature of trabecular bone using high-resolution peripheral quantitative computed tomography (HR-pQCT), may provide insight into trabecular differences by race/ethnic origin.

PURPOSE

We determined differences in trabecular bone microarchitecture, connectivity, and alignment according to race/ethnic origin and sex in young adults.

METHODS

We analyzed HR-pQCT scans of 184 adult (24.2 ± 3.4 years) women (n = 51 Black, n = 50 White) and men (n = 34 Black, n = 49 White). We used ANCOVA to compare bone outcomes, and adjusted for age, height, and weight.

RESULTS

Overall, the effect of race on bone outcomes did not differ by sex, and the effect of sex on bone outcomes did not differ by race. After adjusting for covariates, Black participants and men of both races had greater trabecular plate volume fraction, plate thickness, plate number density, plate surface area, and greater axial alignment of trabeculae, leading to higher trabecular bone stiffness compared to White participants and women, respectively (p < 0.05 for all).

CONCLUSION

These findings demonstrate that more favorable bone microarchitecture in Black individuals compared to White individuals and in men compared to women is not unique to the cortical bone compartment. Enhanced plate-like morphology and greater trabecular axial alignment, established in young adulthood, may contribute to the improved bone strength and lower fracture risk in Black versus White individuals and in men compared to women.

Restricting mitochondrial GRK2 post-ischemia confers cardioprotection by reducing myocyte death and maintaining glucose oxidation

Increased abundance of GRK2 [G protein-coupled receptor (GPCR) kinase 2] is associated with poor cardiac function in heart failure patients. In animal models, GRK2 contributes to the pathogenesis of heart failure after ischemia-reperfusion (IR) injury. In addition to its role in down-regulating activated GPCRs, GRK2 also localizes to mitochondria both basally and post-IR injury, where it regulates cellular metabolism. We previously showed that phosphorylation of GRK2 at Ser⁶⁷⁰ is essential for the translocation of GRK2 to the mitochondria of cardiomyocytes post-IR injury in vitro and that this localization promotes cell death. Here, we showed that mice with a S670A knock-in mutation in endogenous GRK2 showed reduced cardiomyocyte death and better cardiac function post-IR injury. Cultured GRK2-S670A knock-in cardiomyocytes subjected to IR in vitro showed enhanced glucose-mediated mitochondrial respiratory function that was partially due to maintenance of pyruvate dehydrogenase activity and improved glucose oxidation. Thus, we propose that mitochondrial GRK2 plays a detrimental role in cardiac glucose oxidation post-injury.

Ubiquitin-Specific Protease 4 Is an Endogenous Negative Regulator of Metabolic Dysfunctions in Nonalcoholic Fatty Liver Disease in Mice

Nonalcoholic fatty liver disease (NAFLD), characterized by hepatic steatosis (HS), insulin resistance (IR), and inflammation, poses a high risk of cardiometabolic disorders. Ubiquitin specific protease 4 (USP4), a deubiquitinating enzyme, is pivotally involved in regulating multiple inflammatory pathways; however, the role of USP4 in NAFLD is unknown. Here, we report that USP4 expression was dramatically down-regulated in livers from NAFLD patients and different NAFLD mouse models induced by high-fat diet (HFD) or genetic deficiency (ob/ob) as well as in palmitate-treated hepatocytes. Hepatocyte-specific USP4 depletion exacerbated HS, IR, and inflammatory response in HFD-induced NAFLD mice. Conversely, hepatic USP4 overexpression notably alleviated the pathological alterations in two different NAFLD models. Mechanistically, hepatocyte USP4 directly bound to and deubiquitinated transforming growth factor-β activated kinase 1 (TAK1), leading to a suppression of the activation of downstream nuclear factor kappa B (NF-κB) and c-Jun N-terminal kinase (JNK) cascades, which, in turn, reversed the disruption of insulin receptor substrate/protein kinase B/glycogen synthase kinase 3 beta (IRS-AKT-GSK3β) signaling. In addition, USP4-TAK1 interaction and subsequent TAK1 deubiquitination were required for amelioration of metabolic dysfunctions. Conclusion: Collectively, the present study provides evidence that USP4 functions as a pivotal suppressor in NAFLD and related metabolic disorders. (Hepatology 2018; 00:000-000).

Effects of farnesoid-X-receptor SUMOylation mutation on myocardial ischemia/reperfusion injury in mice

Myocardial ischemia/reperfusion (MI/R) injury induces excessive cellular apoptosis and contributes significantly to final infarct size. We previously demonstrated that a nuclear receptor, Farnesoid X receptor (FXR), plays a crucial role in mediating myocardial apoptosis. The FXR functions are regulated by post translational modifications (PTM). However, whether the proapoptotic effect of FXR in MI/R injury is regulated by PTM remains unclear. Here, we aimed to study the effect of SUMOylation, a PTM involved in the pathogenesis of MI/R injury per se, on the proapoptotic effect of FXR in MI/R injury. We observed that FXR could be SUMOylated in heart tissues, and FXR SUMOylation levels were downregulated in ischemia reperfused myocardium. By overexpression of SUMOylation-defective FXR mutant, it was demonstrated that decreased SUMOylation augmented the detrimental effect of FXR, via activation of mitochondrial apoptosis pathway and autophagy dysfunction in MI/R injury. Further mechanistic studies suggested that decreased SUMOylation levels increased the transcription activity of FXR, and the subsequently upregulated FXR target gene SHP mediated the proapoptotic effects of FXR. Taken together, we provided the first evidence that the cardiac effects of FXR could be regulated by SUMOylation, and that manipulating FXR SUMOylation levels may hold therapeutic promise for constraining MI/R injury.

MiR-125a-5p ameliorates monocrotaline-induced pulmonary arterial hypertension by targeting the TGF-β1 and IL-6/STAT3 signaling pathways

Pulmonary vascular remodeling due to excessive proliferation and resistance to apoptosis of pulmonary artery smooth muscle cells (PASMCs) is the hallmark feature of pulmonary arterial hypertension (PAH). Recent evidence suggests that miR-125a-5p plays a role in a rat model of monocrotaline-induced PAH (MCT-PAH); however, the underlying mechanism is currently unknown. Here, we examined the expression profile of miR-125a-5p in MCT-PAH rats and investigated the putative therapeutic effect of miR-125a-5p using the miR-125a-5p agomir. In addition, the miR-125a-5p agomir or antagomir was transfected into rat PASMCs, and proliferation and apoptosis were measured. Activity of the miR-125a-5p target STAT3 was measured using a luciferase reporter assay, and the expression of downstream molecules was measured using RT–qPCR and/or western blot analysis. Importantly, inducing miR-125a-5p expression in vivo slowed the progression of MCT-PAH by reducing systolic pulmonary arterial pressure, the Fulton index, and pulmonary vascular remodeling. Moreover, overexpressing miR-125a-5p inhibited the proliferation and promoted the apoptosis of PASMCs. In addition, stimulating PASMCs with TGF-β1 or IL-6 upregulated miR-125a-5p expression, whereas overexpressing miR-125a-5p reduced TGF-β1 and IL-6 production, as well as the expression of their downstream targets STAT3 and Smad2/3; in contrast, downregulating miR-125a-5p increased TGF-β1 and IL-6 production. Finally, a dual-luciferase reporter assay revealed that miR-125a-5p targets the 3′-UTR of STAT3, suppressing the downstream molecules PCNA, Bcl-2, and Survivin. Taken together, these findings suggest that miR-125a-5p ameliorates MCT-PAH in rats, has a negative feedback regulation with TGF-β1 and IL-6, and regulates the proliferation and apoptosis of PASMCs by directly targeting STAT3.

A study in rats suggests that the small RNA molecule miR-125a-5p is a promising therapeutic target for treating pulmonary arterial hypertension (PAH). This type of high blood pressure is due to the narrowing of arteries that carry blood from the heart to the lungs and at present has no cure. Jieyan Shen at Shanghai Jiao Tong University, China, and colleagues found that PAH lowers the levels of miR-125a-5p in rat pulmonary arteries and that administration of miR-125a-5p as an early preventative treatment reduced disease progression. miR-125a-5p slowed the proliferation of pulmonary artery smooth muscle cells and triggered cell death by directly interacting with a gene expression regulator and reducing the production of certain pro-inflammatory signaling molecules. Targeting miR-125a-5p’s mechanism of action could represent a new treatment approach for this chronic, life-changing disease.

Abstract P6-12-17: Identifying risk factors and effect modifiers of trastuzumab-induced cardiotoxicity among multi-ethnic women with early-stage HER2-positive breast cancer

Introduction: Trastuzumab-based adjuvant therapy is the current standard of care for early-stage HER2-positive breast cancer. However, trastuzumab has also been associated with an increased risk of cardiotoxicity, especially when given following an anthracycline. Trastuzumab-induced cardiotoxicity (TIC) can present as asymptomatic left ventricular ejection fraction (LVEF) decline or symptomatic heart failure. Our objective was to identify predictors of TIC among multi-ethnic patients with early-stage HER2-positive breast cancer. Unlike prior observational studies, our study included a high representation of racial/ethnic minorities, who are at increased risk of cardiovascular disease (CVD) compared to non-Hispanic whites.

Methods: We conducted a retrospective cohort study in patients with stage I-III HER2-positive breast cancer, diagnosed from 2007 to 2015 at Columbia University Medical Center (CUMC) in New York, NY, who had received adjuvant trastuzumab therapy. Participants had at least two serial echocardiograms or MUGA scans to assess TIC, which was defined as at least a 10% decrease in LVEF from baseline or LVEF &lt;50%. LVEF recovery was defined as at least a 10% increase in LVEF or LVEF &gt;50%. We conducted descriptive statistics and univariate and multivariable logistic regression to estimate the associations between socio-demographic factors, breast tumor and treatment characteristics, and CVD risk factors (including smoking status, body mass index [BMI], hypertension, diabetes, hyperlipidemia, coronary artery disease) and TIC. Interactions between race/ethnicity and CVD risk factors were assessed using a logistic regression model.

Results: In our study population (N=279), the mean age was 52.7 years (standard deviation, 12.1) with 36.6% non-Hispanic white, 18.3% non-Hispanic black, 34.8% Hispanic, and 10.4% Asian patients. There were no differences by race/ethnicity in tumor and treatment characteristics (over half had prior anthracyclines), but racial/ethnic minorities had higher BMI and were more likely to have hypertension compared to non-Hispanic whites. About a third of patients developed TIC and 14.7% had an LVEF decline to &lt;50%, of which 15 (16.1%) experienced LVEF recovery. In multivariable analysis, prior anthracycline use and hypertension were significantly associated with increased odds of developing TIC (odds ratio [OR]: 2.25, 95% confidence interval [CI]: 1.25, 4.06; OR: 2.13, 95% CI: 1.15, 3.93, respectively). There was a significant interaction (p=0.027) between race/ethnicity and hypertension on odds of developing TIC with hypertensive non-Hispanic white patients experiencing 6.05 (95% CI: 2.19, 16.75) times the odds of developing TIC compared to non-hypertensive non-Hispanic whites.

Discussion: We observed a higher incidence of TIC and lower incidence of LVEF recovery compared to previous clinical trials. Given patient selection for clinical trials, our results may be more representative of clinical practice settings. We found a particularly high risk among non-Hispanic white patients with hypertension. Patients with hypertension may require closer blood pressure monitoring and treatment with anti-hypertensives in order to reduce risk of developing cardiotoxicity.

Citation Format: Yuan A, Topkara V, Hershman DL, Kalinsky K, Accordino MK, Trivedi MS, Yu A, Genkinger JM, Crew KD. Identifying risk factors and effect modifiers of trastuzumab-induced cardiotoxicity among multi-ethnic women with early-stage HER2-positive breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-12-17.

The desumoylating enzyme sentrin-specific protease 3 contributes to myocardial ischemia reperfusion injury

Sentrin-specific protease 3 (SENP3), a member of the desumoylating enzyme family, is known as a redox sensor and could regulate multiple cellular signaling pathways. However, its implication in myocardial ischemia reperfusion (MIR) injury is unclear. Here, we observed that SENP3 was expressed and upregulated in the mouse heart depending on reactive oxygen species (ROS) production in response to MIR injury. By utilizing siRNA-mediated cardiac specific gene silencing, SENP3 knockdown was demonstrated to significantly reduce MIR-induced infarct size and improve cardiac function. Mechanistic studies indicated that SENP3 silencing ameliorated myocardial apoptosis mainly via suppression of endoplasmic reticulum (ER) stress and mitochondrial-mediated apoptosis pathways. By contrast, adenovirus-mediated cardiac SENP3 overexpression significantly exaggerated MIR injury. Further molecular analysis revealed that SENP3 promoted mitochondrial translocation of dynamin-related protein 1 (Drp1) in reperfused myocardium. In addition, mitochondrial division inhibitor-1 (Mdivi-1), a pharmacological inhibitor of Drp1, significantly attenuated the exaggerated mitochondrial abnormality and cardiac injury by SENP3 overexpression after MIR injury. Taken together, we provide the first direct evidence that SENP3 upregulation pivotally contributes to MIR injury in a Drp1-dependent manner, and suggest that SENP3 suppression may hold therapeutic promise for constraining MIR injury.

G protein-coupled receptor kinase 2 promotes cardiac hypertrophy

The increase in protein activity and upregulation of G-protein coupled receptor kinase 2 (GRK2) is a hallmark of cardiac stress and heart failure. Inhibition of GRK2 improved cardiac function and survival and diminished cardiac remodeling in various animal heart failure models. The aim of the present study was to investigate the effects of GRK2 on cardiac hypertrophy and dissect potential molecular mechanisms. In mice we observed increased GRK2 mRNA and protein levels following transverse aortic constriction (TAC). Conditional GRK2 knockout mice showed attenuated hypertrophic response with preserved ventricular geometry 6 weeks after TAC operation compared to wild-type animals. In isolated neonatal rat ventricular cardiac myocytes stimulation with angiotensin II and phenylephrine enhanced GRK2 expression leading to enhanced signaling via protein kinase B (PKB or Akt), consecutively inhibiting glycogen synthase kinase 3 beta (GSK3β), such promoting nuclear accumulation and activation of nuclear factor of activated T-cells (NFAT). Cardiac myocyte hypertrophy induced by in vitro GRK2 overexpression increased the cytosolic interaction of GRK2 and phosphoinositide 3-kinase γ (PI3Kγ). Moreover, inhibition of PI3Kγ as well as GRK2 knock down prevented Akt activation resulting in halted NFAT activity and reduced cardiac myocyte hypertrophy. Our data show that enhanced GRK2 expression triggers cardiac hypertrophy by GRK2-PI3Kγ mediated Akt phosphorylation and subsequent inactivation of GSK3β, resulting in enhanced NFAT activity.

Deficiency of liver-X-receptor-α reduces glucose uptake and worsens post-myocardial infarction remodeling

Liver X receptor α (LXRα) is an endogenous protective receptor against ischemic heart diseases. However, whether LXRα regulated glucose metabolism in ischemic heart diseases has not been investigated. In this study we investigated the involvement of LXRα on glucose metabolism in cardiac remodeling after myocardial infarction (MI). MI was induced in mice by permanent ligation of the left anterior descending coronary artery (LCA). Genetic LXRα deletion significantly worsened cardiac remodeling and impaired cardiac function at 4 weeks after MI. Cardiac 18F-fluorodeoxyglucose (FDG) uptake by positron emission tomography (PET) demonstrated that the FDG standardized uptake value (SUV) was significantly lower in LXRα^-/- mice as compared to WT mice. Mechanistically, GLUT1/4 and AMPK phosphorylation were significantly downregulated while CD36 expression was markedly upregulated in LXRα^-/- mice. This study demonstrated that deficiency of LXRα decreased glucose uptake after MI, resulting in a metabolic shift that suppressed glucose metabolism, which was in association with adverse cardiac remodeling.

Cardiac Fibroblast GRK2 Deletion Enhances Contractility and Remodeling Following Ischemia/Reperfusion Injury

RATIONALE

G protein-coupled receptor kinase 2 (GRK2) is an important molecule upregulated after myocardial injury and during heart failure. Myocyte-specific GRK2 loss before and after myocardial ischemic injury improves cardiac function and remodeling. The cardiac fibroblast plays an important role in the repair and remodeling events after cardiac ischemia; the importance of GRK2 in these events has not been investigated.

OBJECTIVE

The aim of this study is to elucidate the in vivo implications of deleting GRK2 in the cardiac fibroblast after ischemia/reperfusion injury.

METHODS AND RESULTS

We demonstrate, using Tamoxifen inducible, fibroblast-specific GRK2 knockout mice, that GRK2 loss confers a protective advantage over control mice after myocardial ischemia/reperfusion injury. Fibroblast GRK2 knockout mice presented with decreased infarct size and preserved cardiac function 24 hours post ischemia/reperfusion as demonstrated by increased ejection fraction (59.1±1.8% versus 48.7±1.2% in controls; P<0.01). GRK2 fibroblast knockout mice also had decreased fibrosis and fibrotic gene expression. Importantly, these protective effects correlated with decreased infiltration of neutrophils to the ischemia site and decreased levels of tumor necrosis factor-α expression and secretion in GRK2 fibroblast knockout mice.

CONCLUSIONS

These novel data showing the benefits of inhibiting GRK2 in the cardiac fibroblast adds to previously published data showing the advantage of GRK2 ablation and reinforces the therapeutic potential of GRK2 inhibition in the heart after myocardial ischemia.

Novel Protective Role for Ubiquitin-Specific Protease 18 in Pathological Cardiac Remodeling

Ubiquitin-specific protease 18 (USP18), a USP family member, is involved in antiviral activity and cancer inhibition. Although USP18 is expressed in heart, the role of USP18 in the heart and in cardiac diseases remains unknown. Here, we show that USP18 expression is elevated in both human dilated hearts and hypertrophic murine models. Cardiomyocyte-specific overexpression of USP18 in mice significantly blunted cardiac remodeling as evidenced by mitigated myocardial hypertrophy, fibrosis, ventricular dilation, and preserved ejection function, whereas USP18-deficient mice displayed exacerbated cardiac remodeling under the same pathological stimuli. Similar results were observed for in vitro angiotensin II-induced neonatal rat cardiomyocyte hypertrophy. The antihypertrophic effects of USP18 under hypertrophic stimuli were associated with the blockage of the transforming growth factor-β-activated kinase 1-p38/c-Jun N-terminal kinase 1/2 signaling cascade. Blocking transforming growth factor-β-activated kinase 1-p38/c-Jun N-terminal kinase 1/2 signaling with a pharmacological inhibitor (5Z-7-oxozeaenol) greatly reversed the detrimental effects observed in USP18-knockout mice subjected to aortic banding. Our data indicate that USP18 inhibits cardiac hypertrophy and postpones cardiac dysfunction during the remodeling process, which is dependent on its modulation of the transforming growth factor-β-activated kinase 1-p38/c-Jun N-terminal kinase 1/2 signaling axis. Thus, USP18 is a potent therapeutic target for heart failure treatment.

Abstract 301: Initial Increase of Klf5 and Ppara Expression After Myocardial Ischemia/Reperfusion in Mice Appears to be Critical for Survival

Krüppel-like factors (KLF) have important roles in metabolism. We previously found that KLF5 is a positive transcriptional regulator of peroxisome proliferator-activated receptor α ( Ppara) , a central regulator of cardiac fatty acid oxidation (FAO). Mice with cardiomyocyte-specific Klf5 ablation ( α MHC-Klf5 -/- ) had reduced cardiac Ppara expression and FAO. At age 6-12 months these mice develop distinct cardiac dysfunction. The role of PPARα activation in I/R injury is unclear as both beneficial and detrimental effects have been reported. We aimed to study if Ppara expression changes during I/R are driven by KLF5 and explore its protective or detrimental role. Wild type mice were subjected to in vivo I/R or sham surgery. I/R resulted in an initial increase in Ppara , and its target gene pyruvate dehydrogenase kinase 4 ( Pdk4) mRNA after 2h reperfusion, followed by decreased expression after 24h reperfusion. The Ppara expression is associated with parallel changes in cardiac Klf5 mRNA expression. Concurrent, there was a decrease of cardiac FAO-related genes carnitine palmitoyl-transferase 1β ( Cpt1b), very long chain acyl-CoA dehydrogenase (Vlcad), and acyl-CoA oxidase ( Aox) in mice with I/R. To define the cell type causing the temporal changes in Klf5 and Ppara after I/R we isolated primary cardiomyocytes and fibroblasts. Our data suggest a similar effect in primary isolated cardiomyocytes only. Klf5 mRNA expression is increased after 2 hour hypoxia and normalized after 4 hour re-oxygenation in cardiomyocytes, whereas there are no changes after hypoxia/normoxia in fibroblasts. To assess the importance of cardiomyocyte KLF5 in I/R we used α MHC-Klf5 -/- mice. Interestingly, despite reduced FAO, 7 month old αMHC-Klf5 -/- mice subjected to I/R had a marked increase in mortality; 4 of 7 αMHC-Klf5 -/- mice died within the first 24h of reperfusion while no mortality was observed in age-matched wild type mice that underwent I/R. In conclusion, I/R is associated with an increase in Klf5 and Ppara in the first hours of reperfusion followed by a decrease in Klf5 and Ppara , likely accounted for by cardiomyocytes. Increased mortality for α MHC-Klf5 -/- mice with I/R injury suggests that the initial increase may be an adaptive response that is critical for survival.

Abstract 449: GRK2-S670A Mice Reveal Cardioprotection Post Ischemia-reperfusion

β-adrenergic receptors (βARs) are critical regulators of cardiac contractility whose function are drastically impaired during heart failure (HF). Activated βARs are regulated via phosphorylation by G-protein coupled receptor kinase-2 (GRK2) and subsequent interaction with β-arrestin. Numerous studies have shown that GRK2 is elevated in human HF and animal models demonstrate that it contributes to HF pathogenesis after ischemic injury (IR). Further, our lab has uncovered non-canonical actions of GRK2 that are involved in HF development. One such novel action of GRK2 is within mitochondria where we have shown increased GRK2 localization after oxidative stress. Our lab has shown that in the heart, phosphorylation of GRK2 via Map kinase at residue Ser670 promotes binding to Hsp90 and further enhances translocation of GRK2 to the mitochondria after oxidative stress such as ischemia. To determine the ultimate role of this pathway in the post-ischemic heart we have generated novel GRK2-S670A mice where all endogenous GRK2 cannot be phosphorylated at this residue. Baseline characterization of these mice along with their controls, show a minimal phenotype, however we have found significant differences post-IR. Compared to control mice (NLC), GRK2-S670A have significantly less infarction size 24 hrs after IR and echocardiography and hemodynamics revealed significantly improved cardiac function in GRK2-S670A mice post-IR. GRK2-S670A mice showed improved ejection fraction (52.83%+/- 2.826 S670A vs 42.38%+/- 1.603 NLC) and smaller infarcted areas (9.942%+/- 1.763 S670A vs 20.78%+/- 3.579 NLC) when compared to NLC mice. Further, we found that mitochondrial GRK2 protein levels were lower in the GRK2-S670A mice at the area at risk (0.1428+/-0.02485 S670A vs 0.2327+/- 0.023 NLC). Overall, our data suggest that phosphorylation at Ser670 of GRK2 might act as a “biological switch” in cardiomyocytes, where un-phosphorylated GRK2 is readily available in the cytoplasm to desensitize receptors such as βARs, but upon phosphorylation, GRK2 translocates to the mitochondria leading to detrimental effects including cell death. This mechanism suggests a novel way to develop pharmacological interventions to aid in the treatment of HF.

Loss of Adult Cardiac Myocyte GSK-3 Leads to Mitotic Catastrophe Resulting in Fatal Dilated Cardiomyopathy

RATIONALE

Cardiac myocyte-specific deletion of either glycogen synthase kinase (GSK)-3α and GSK-3β leads to cardiac protection after myocardial infarction, suggesting that deletion of both isoforms may provide synergistic protection. This is an important consideration because of the fact that all GSK-3-targeted drugs, including the drugs already in clinical trial target both isoforms of GSK-3, and none are isoform specific.

OBJECTIVE

To identify the consequences of combined deletion of cardiac myocyte GSK-3α and GSK-3β in heart function.

METHODS AND RESULTS

We generated tamoxifen-inducible cardiac myocyte-specific mice lacking both GSK-3 isoforms (double knockout). We unexpectedly found that cardiac myocyte GSK-3 is essential for cardiac homeostasis and overall survival. Serial echocardiographic analysis reveals that within 2 weeks of tamoxifen treatment, double-knockout hearts leads to excessive dilatative remodeling and ventricular dysfunction. Further experimentation with isolated adult cardiac myocytes and fibroblasts from double-knockout implicated cardiac myocytes intrinsic factors responsible for observed phenotype. Mechanistically, loss of GSK-3 in adult cardiac myocytes resulted in induction of mitotic catastrophe, a previously unreported event in cardiac myocytes. Double-knockout cardiac myocytes showed cell cycle progression resulting in increased DNA content and multinucleation. However, increased cell cycle activity was rivaled by marked activation of DNA damage, cell cycle checkpoint activation, and mitotic catastrophe-induced apoptotic cell death. Importantly, mitotic catastrophe was also confirmed in isolated adult cardiac myocytes.

CONCLUSIONS

Together, our findings suggest that cardiac myocyte GSK-3 is required to maintain normal cardiac homeostasis, and its loss is incompatible with life because of cell cycle dysregulation that ultimately results in a severe fatal dilated cardiomyopathy.

Oral chronic GVHD outcomes and resource utilization: a subanalysis from the chronic GVHD consortium

OBJECTIVES

This study evaluated the extent to which oral chronic graft-versus-host disease (cGVHD) consensus assessments are predictive of management across institutions with and without oral medicine (OM) centers, and whether ancillary care guidelines are followed within clinical practice.

METHODS

Longitudinal oral cGVHD data were abstracted from the cGVHD Consortium, and additional mouth-specific management data were analyzed across five transplant centers.

RESULTS

Seventy-nine patients with 656 visits were observed for a median of 7.1 months with one visit per follow-up month. Ancillary therapies for oral cGVHD were prescribed for 67% of patients for a median of 0.46 months (per follow-up month) at OM centers and 0.78 months at non-OM centers. Patients treated with ancillary therapy were more likely to have an National Institutes of Health (NIH) mouth score of ≥1 (P < 0.001, odds ratio: 5.1) and mouth pain (P = 0.01, odds ratio: 2.6). The odds ratios of receiving ancillary therapy from OM experts were higher than transplant physicians (53%; P = 0.03).

CONCLUSIONS

Oral cGVHD consensus assessments corresponding with ancillary therapy use were mouth pain and NIH mouth score, with higher odds ratios of receiving therapy from OM experts. Ancillary care guidelines for oral cGVHD are reflected in academic clinical practice with respect to utilization of recommended prescriptions.

Abstract 408: Myocardial Knockdown of Mir-375 Attenuates Post-mi Inflammatory Response and Left Ventricular Dysfunction via Pdk-1-akt Signaling Axis

MicroRNAs are known to be dysregulated in the ischemic heart disease and have emerged as potential therapeutic targets for treatment of myocardial infarction (MI). Recently MicroRNA-375 has been shown to be up-regulated in humans with MI. In this study, we assessed whether inhibition of the miR-375 using an i.v.-delivered locked nucleic acid (LNA)-modified anti-miR (LNA-antimiR-375) can provide therapeutic benefit in mice with pre-existing pathological cardiac remodeling and dysfunction due to myocardial infarction (MI).After the induction of acute myocardial infarction, mice were treated with either control or LNA based miR-375 inhibitor, and inflammatory response, cardiomyocyte apoptosis and LV functional and structural remodeling changes were evaluated. Anti-miR-375 therapy significantly suppressed infiltration of inflammatory cells, expression of proinflammatory cytokines in the myocardium and cardiomyocyte apoptosis. These changes were associated with miR-375 mediated activation of 3-phosphoinositide-dependent protein kinase 1 (PDK-1) and downstream AKT phosphorylation on Thr-308. LNA anti-miR-375 therapy significantly improved LV functions, reduced infarct size, and attenuated infarct wall thinning. Moreover, LNA based miR-375 therapy significantly increased capillary density in the infarcted myocardium. Further, our in vitro studies demonstrated that miR-375 negatively regulates the expression of PDK-1 by directly targeting the 3’UTR of the PDK-1 transcript. Taken together, our studies demonstrate that anti miR-375 therapy suppresses inflammatory response, cardiomyocyte death and contributes to improved LV function and enhanced angiogenesis via activation of PDK-1/AKT signaling.

Abstract 47: Loss of the Cardio Protection Inferred by S-nitrosylation of GRK2 At Cysteine 340 Leads to Decreased Cardiac Performance and a Hypertensive Phenotype With Aging

In the next 35 years, the global population of individuals above 60 years of age will double to approximately 2 billion. In the aged population, cardiovascular diseases are known to occur at a higher prevalence ultimately leading to increased mortality. G protein-coupled receptors (GPCRs) have been identified as vital regulators of cardiac function. GPCR kinases (GRKs) are important in cardiac GPCR regulation through desensitization of these receptors. GRK2 is highly expressed in the heart, and has been widely characterized due to its upregulation in heart failure. Studies from our lab have shown that elevated GRK2 levels in ischemia-reperfusion (I/R) injury result in a pro-death phenotype. Interestingly, cardio-protection can be inferred via S-nitrosylation of GRK2 at cysteine 340. Further, we have generated a knock-in GRK2 340S mouse, in which cysteine 340 was mutated to block dynamic GRK2 S-nitrosylation. GRK2 340S mice are more susceptible to I/R injury. Given that GRK2 340S mice are more susceptible to oxidative stress, and there is a nitroso-redox imbalance in senescence, it is possible that these mice are more likely to exhibit decreased cardiac performance as they age. Therefore, we hypothesize that with age GRK2 340S knockin mice will develop an overall worsened cardiac phenotype compared to control wild-type (WT) mice. To test this hypothesis, 340S and WT mice were aged for a year, and cardiac function was evaluated via echocardiography. Aged 340S mice exhibited significantly decreased ejection fraction and fraction shortening relative to aged WT controls. Prior to tissue harvesting, in-vivo hemodynamics was conducted via Millar catheterization. At baseline, aged 340S mice exhibited increased systolic blood pressure compared to aged WT mice. At the conclusion of this protocol, mice were sacrificed and heart weight (HW), body weight (BW), and tibia length (TL) measured to evaluate cardiac hypertrophy. Aged 340S mice exhibited significantly increased HW/BW and HW/TL ratios, indicative of cardiac hypertrophy, relative to aged WT controls. Taken together, these data suggest that with age, loss of the cardio protection inferred by S-nitrosylation of GRK2 at leads to decreased cardiac performance, and an overall worsened cardiac phenotype.

Abstract 113: Klf5 and Ppara Expression is Increased at the Early Stage and Reduced at the Late Stage of Myocardial Ischemia/Reperfusion in Mice

Inhibition of cardiac fatty acid oxidation (FAO) is considered beneficial after ischemia reperfusion (I/R). Krüppel-like factors (KLF) have an important role in metabolism. In a model of cardiac energetic deficiency (LPS-treated mice), in silico promoter analysis and whole genome array analysis indicated cardiac KLF5 as important regulator of Ppara . Gene expression analysis in human ventricular myocytes (AC16) treated with Ad-Klf5 followed by ChIP analysis confirmed that KLF5 is a positive transcriptional regulator of Ppara . Mice with cardiomyocyte-specific Klf5 ablation (αMHC-Klf5 -/- ) that we made had reduced cardiac Ppara expression and other FAO-related genes. The role of PPARα activation in I/R injury is unclear as both beneficial and detrimental effects have been reported. We aimed to gain insight in the effects of KLF5 and PPARα on acute I/R injury.

To mimic I/R in vitro , AC16 cells were subjected to hypoxia (9.5 h) followed by short (1h) or prolonged (14h) normoxia. Ppara expression was initially (1h) increased (p<0.05) and then (14 h) decreased (p<0.05). Klf5 expression pattern showed a trend of similar changes . Infarction was performed by 30 min of left coronary artery occlusion followed by 2 or 24 hours of reperfusion in wild type mice. I/R resulted in a trend for an initial increase in Klf5 (2-fold, p=0.05), Ppara (3-fold, p=0.08), and Pdk4 (8-fold, p<0.01) mRNA at 2h post-surgery. Klf5 (2-fold; p<0.01) and Ppara (9-fold; p<0.05) expression were decreased 24h post-surgery. Consistent with Ppara changes, there was a 2-fold decrease of Cpt1 (p<0.01) and Vlcad (p<0.01) and a trend for decreased Aox (2-fold), Lcad (2-fold), and Pdk4 (6-fold) compared to sham. Echocardiography indicated normal cardiac function after 24h post-surgery. Despite reduced FAO, αMHC-Klf5 -/- mice subjected to I/R had a marked increase in mortality; 40% (4 of 10) of αMHC-Klf5 -/- mice died within the first 24h of reperfusion while no mortality was observed in wild type mice that underwent I/R.

In conclusion, I/R is associated with an increase in Klf5 and Ppara in the first hours of reperfusion followed by a decrease in Klf5 and Ppara . Increased mortality for αMHC-Klf5 -/- mice with I/R injury suggests that the initial increase may be an adaptive response that is critical for survival.

Abstract 92: The Mitochondrial Calcium Uniporter is Necessary for Metabolic Matching of Contractile Demand During Acute Sympathetic Stress

Contractility is mediated by a variable flux in intracellular calcium (Ca 2+ ), which is proposed to be integrated into mitochondria to regulate cardiac energetics. Moreover, m Ca 2+ -overload is known to activate the mitochondrial permeability transition pore (MPTP) and induce cell death. Recent studies have reported that the Mcu gene encodes the channel-forming portion of the mitochondrial calcium uniporter (MCU) and is required for m Ca 2+ uptake. To examine the role of m Ca 2+ in the heart, we generated a conditional, cardiac-specific knockout model and deleted Mcu in adult mice ( Mcu-cKO ). Loss of Mcu protected against myocardial ischemia-reperfusion (IR) injury by preventing the activation of the MPTP. In addition while we found no baseline phenotype, Mcu -cKO mice lacked contractile responsiveness to beta-adrenergic receptor stimulation as assessed by invasive hemodynamics (Fig 1) and in parallel were unable to activate mitochondrial dehydrogenases and increase cardiac NADH levels. Further experimental analyses in isolated adult cardiomyocytes confirmed a lack of energetic responsiveness to acute sympathetic stress (isoproterenol failure to mediate an increase in NADH, Fig 2), supporting the hypothesis that the physiological function of the MCU in the heart is to modulate Ca 2+ -dependent metabolism during the ‘fight or flight’ response.

The Mitochondrial Calcium Uniporter Matches Energetic Supply with Cardiac Workload during Stress and Modulates Permeability Transition

Cardiac contractility is mediated by a variable flux in intracellular calcium (Ca(2+)), thought to be integrated into mitochondria via the mitochondrial calcium uniporter (MCU) channel to match energetic demand. Here, we examine a conditional, cardiomyocyte-specific, mutant mouse lacking Mcu, the pore-forming subunit of the MCU channel, in adulthood. Mcu(-/-) mice display no overt baseline phenotype and are protected against mCa(2+) overload in an in vivo myocardial ischemia-reperfusion injury model by preventing the activation of the mitochondrial permeability transition pore, decreasing infarct size, and preserving cardiac function. In addition, we find that Mcu(-/-) mice lack contractile responsiveness to acute β-adrenergic receptor stimulation and in parallel are unable to activate mitochondrial dehydrogenases and display reduced bioenergetic reserve capacity. These results support the hypothesis that MCU may be dispensable for homeostatic cardiac function but required to modulate Ca(2+)-dependent metabolism during acute stress.

Vaginal deployment and tenofovir delivery by microbicide gels

Gels are one of the soft material platforms being evaluated to deliver topically acting anti-HIV drugs (microbicides) to the vaginal environment. For each drug, its loaded concentration, gel properties and applied volume, and frequency of dosing can be designed to optimize PK and, thence, PD. These factors also impact user sensory perceptions and acceptability. Deterministic compartmental modeling of vaginal deployment and drug delivery achieved by test gels can help delineate how multiple parameters characterizing drug, vehicle, vaginal environment, and dosing govern details of PK and PD and also gel leakage from the canal. Such microbicide delivery is a transport process combining convection, e.g., from gel spreading along the vaginal canal, with drug diffusion in multiple compartments, including gel, mucosal epithelium, and stroma. The present work builds upon prior models of gel coating flows and drug diffusion (without convection) in the vaginal environment. It combines and extends these initial approaches in several key ways, including: (1) linking convective drug transport due to gel spreading with drug diffusion and (2) accounting for natural variations in dimensions of the canal and the site of gel placement therein. Results are obtained for a leading microbicide drug, tenofovir, delivered by three prototype microbicide gels, with a range of rheological properties. The model includes phosphorylation of tenofovir to tenofovir diphosphate (which manifests reverse transcriptase activity in host cells), the stromal concentration distributions of which are related to reference prophylactic values against HIV. This yields a computed summary measure related to gel protection ("percent protected"). Analyses illustrate tradeoffs amongst gel properties, drug loading, volume and site of placement, and vaginal dimensions, in the time and space history of gel distribution and tenofovir transport to sites of its anti-HIV action and concentrations and potential prophylactic actions of tenofovir diphosphate therein.

Vitamin D receptor activation protects against myocardial reperfusion injury through inhibition of apoptosis and modulation of autophagy

AIMS

To determine the roles of vitamin D receptor (VDR) in ischemia/reperfusion-induced myocardial injury and to investigate the underlying mechanisms involved.

RESULTS

The endogenous VDR expression was detected in the mouse heart, and myocardial ischemia/reperfusion (MI/R) upregulated VDR expression. Activation of VDR by natural and synthetic agonists reduced myocardial infarct size and improved cardiac function. Mechanistically, VDR activation inhibited endoplasmic reticulum (ER) stress (determined by the reduction of CCAAT/enhancer-binding protein homologous protein expression and caspase-12 activation), attenuated mitochondrial impairment (determined by the decrease of mitochondrial cytochrome c release and caspase-9 activation), and reduced cardiomyocyte apoptosis. Furthermore, VDR activation significantly inhibited MI/R-induced autophagy dysfunction (determined by the inhibition of Beclin 1 over-activation, the reduction of autophagosomes, the LC3-II/LC3-I ratio, p62 protein abundance, and the restoration of autophagy flux). Moreover, VDR activation inhibited MI/R-induced oxidative stress through a metallothionein-dependent mechanism. The cardioprotective effects of VDR agonists mentioned earlier were impaired in the setting of cardiac-specific VDR silencing. In contrast, adenovirus-mediated cardiac VDR overexpression decreased myocardial infarct size and improved cardiac function through attenuating oxidative stress, and inhibiting apoptosis and autophagy dysfunction.

INNOVATION AND CONCLUSION

Our data demonstrate that VDR is a novel endogenous self-defensive and cardioprotective receptor against MI/R injury, via mechanisms (at least in part) reducing oxidative stress, and inhibiting apoptosis and autophagy dysfunction-mediated cell death.

High-throughput screening identifies small molecules that enhance the pharmacological effects of oligonucleotides

The therapeutic use of antisense and siRNA oligonucleotides has been constrained by the limited ability of these membrane-impermeable molecules to reach their intracellular sites of action. We sought to address this problem using small organic molecules to enhance the effects of oligonucleotides by modulating their intracellular trafficking and release from endosomes. A high-throughput screen of multiple small molecule libraries yielded several hits that markedly potentiated the actions of splice switching oligonucleotides in cell culture. These compounds also enhanced the effects of antisense and siRNA oligonucleotides. The hit compounds preferentially caused release of fluorescent oligonucleotides from late endosomes rather than other intracellular compartments. Studies in a transgenic mouse model indicated that these compounds could enhance the in vivo effects of a splice-switching oligonucleotide without causing significant toxicity. These observations suggest that selected small molecule enhancers may eventually be of value in oligonucleotide-based therapeutics.

Liver X receptor agonist treatment attenuates cardiac dysfunction in type 2 diabetic db/db mice

BACKGROUND

Liver X receptor (LXR) plays a critical regulatory role in metabolism and inflammation, and has been demonstrated to be involved in cardiovascular physiology/pathology. In the present study, we investigated the effect of GW3965, a potent LXR agonist, on diabetic cardiomyopathy (DCM) in type 2 diabetic db/db mice.

METHODS AND RESULTS

Non-diabetic db/+ mice and diabetic db/db mice received either vehicle or LXR agonist GW3965 for 12 weeks. Systemic insulin resistance was evaluated by glucose tolerance test and homeostasis model assessment for insulin resistance. Endpoint cardiac function was assessed by echocardiography and catheterization. Ventricular tissue was collected for histology and gene/protein expression analysis. Untreated db/db diabetic mice exhibited diastolic dysfunction with adverse structural remodeling (including myocardial fibrosis and increased apoptosis). Treatment with GW3965 remarkably attenuated myocardial dysfunction and structural remodeling in diabetic db/db mice. Mechanistically, GW3965 restored Akt phosphorylation and inhibited MAP kinases phosphorylation, and reduced oxidative/nitrative stress and inflammation response in the diabetic myocardium.

CONCLUSIONS

Our data demonstrate that GW3965 exerts a cardioprotective effect against DCM by (at least in part) attenuating insulin resistance, modulating Akt and MAP kinases pathways, and reducing oxidative/nitrative stress and inflammatory response. These findings strongly suggest that LXR agonist may have therapeutic potential in treating DCM.

Activation of liver-X-receptor α but not liver-X-receptor β protects against myocardial ischemia/reperfusion injury

BACKGROUND

Liver-X-receptors, LXRα (NR1H3) and LXRβ (NR1H2), encode 2 different but highly homologous isoforms of transcription factors belonging to the nuclear receptor superfamily. Whether LXRα and LXRβ subtypes have discrete roles in the regulation of cardiac physiology/pathology is unknown. We determine the role of each LXR subtype in myocardial ischemia/reperfusion (MI/R) injury.

METHODS AND RESULTS

Mice (wild type; those genetically depleted of LXRα, LXRβ, or both; and those overexpressing LXRα or LXRβ by in vivo intramyocardial adenoviral vector) were subjected to MI/R injury. Both LXRα and LXRβ were detected in wild-type mouse heart. LXRα, but not LXRβ, was significantly upregulated after MI/R. Dual activation of LXRα and LXRβ by natural and synthetic agonists reduced myocardial infarction and improved contractile function after MI/R. Mechanistically, LXR activation inhibited MI/R-induced oxidative stress and nitrative stress, attenuated endoplasmic reticulum stress and mitochondrial dysfunction, and reduced cardiomyocyte apoptosis in ischemic/reperfused myocardium. The aforementioned cardioprotective effects of LXR agonists were impaired in the setting of cardiac-specific gene silencing of LXRα, but not LXRβ subtype. Moreover, LXRα/β double-knockout and LXRα-knockout mice, but not LXRβ-knockout mice, increased MI/R injury, exacerbated MI/R-induced oxidative/nitrative stress, and aggravated endoplasmic reticulum stress and mitochondrial dysfunction. Furthermore, cardiac LXRα, not LXRβ, overexpression via adenoviral transfection suppressed MI/R injury.

CONCLUSIONS

Our study provides the first direct evidence that the LXRα, but not LXRβ, subtype is a novel endogenous cardiac protective receptor against MI/R injury. Drug development strategies specifically targeting LXRα may be beneficial in treating ischemic heart disease.

Abstract 80: Cardiac Fibroblast GRK2 Deletion Enhances Contractility and Remodeling following Ischemia/Reperfusion Injury

Decades of research have identified G Protein Coupled Receptor Kinase 2 (GRK2) as an important molecule that is upregulated in the cardiomyocyte after myocardial injury and during heart failure development. Research from our lab has convincingly demonstrated that myocyte-specific loss of GRK2 both before and after myocardial ischemic injury improves cardiac function and remodeling. Recent studies have reported that GRK2 is also upregulated in the cardiac fibroblast in the failing heart, suggesting a potential role for this molecule in the most abundant cell type in the heart. However, the in vivo implications of GRK2 expression in the fibroblast following cardiac stress remain a mystery. Tamoxifen inducible, fibroblast-specific GRK2 knockout mice (Col1α2CreER/GRK2flox) were treated with tamoxifen along with their control murine counterparts (GRK2flox alone) for 10 days to induce deletion of GRK2 in fibroblasts. Two weeks later mice were subjected to ischemia/reperfusion (I/R) injury via coronary artery occlusion for 30 minutes followed by periods of reperfusion. Fibroblast GRK2 knockout mice presented with preserved cardiac function 24 hours post-I/R compared to control mice as demonstrated by increased ejection fraction (58.1±1.8% vs. 48.7±1.2%, respectively, N=11-14, p=0.0005). GRK2 knockout mice also presented with decreased fibrosis in the infarcted area 72 hours following I/R injury as shown by Masson’s Trichrome staining. In line with decreased fibrosis, these mice also expressed decreased amounts of TGFβ1 and Collagen I. Additionally, α-smooth muscle actin expression is significantly diminished, indicating reduced fibroblast to myofibroblast transformation. These data suggest that GRK2 plays a key role up-stream in fibroblast activation and function in the ischemic heart and indicate that, like in the cardiomyocyte, inhibition of GRK2 in the cardiac fibroblast is a potential therapeutic target to limit cardiac dysfunction and remodeling after ischemic injury.