Perinuclear damage from nuclear envelope deterioration elicits stress responses that contribute to LMNA cardiomyopathy.

Mutations in the LMNA gene encoding lamins A/C cause an array of tissue-selective diseases, with the heart being the most commonly affected organ. Despite progress in understanding the perturbations emanating from LMNA mutations, an integrative understanding of the pathogenesis underlying cardiac dysfunction remains elusive. Using a novel conditional deletion model capable of translatome profiling, we observed that cardiomyocyte-specific Lmna deletion in adult mice led to rapid cardiomyopathy with pathological remodeling. Before cardiac dysfunction, Lmna-deleted cardiomyocytes displayed nuclear abnormalities, Golgi dilation/fragmentation, and CREB3-mediated stress activation. Translatome profiling identified MED25 activation, a transcriptional cofactor that regulates Golgi stress. Autophagy is disrupted in the hearts of these mice, which can be recapitulated by disrupting the Golgi. Systemic administration of modulators of autophagy or ER stress significantly delayed cardiac dysfunction and prolonged survival. These studies support a hypothesis wherein stress responses emanating from the perinuclear space contribute to the LMNA cardiomyopathy development.

Prenatal arsenite exposure alters maternal cardiac remodeling during late pregnancy.

Exposure to inorganic arsenic through drinking water is widespread and has been linked to many chronic diseases, including cardiovascular disease. Arsenic exposure has been shown to alter hypertrophic signaling in the adult heart, as well as in utero offspring development. However, the effect of arsenic on maternal cardiac remodeling during pregnancy has not been studied. As such, there is a need to understand how environmental exposure contributes to adverse pregnancy-related cardiovascular events. This study seeks to understand the impact of trivalent inorganic arsenic exposure during gestation on maternal cardiac remodeling in late pregnancy, as well as offspring outcomes. C57BL/6 J mice were exposed to 0 (control), 100 or 1000 µg/L sodium arsenite (NaAsO2) beginning at embryonic day (E) 2.5 and continuing through E17.5. Maternal heart function and size were assessed via transthoracic echocardiography, gravimetric measurement, and histology. Transcript levels of hypertrophic markers were probed via qRT-PCR and confirmed by western blot. Offspring outcomes were assessed through echocardiography and gravimetric measurement. We found that maternal heart size was smaller and transcript levels of Esr1 (estrogen receptor alpha), Pgrmc1 (progesterone receptor membrane component 1) and Pgrmc2 (progesterone receptor membrane component 2) reduced during late pregnancy with exposure to 1000 µg/L iAs vs. non-exposed pregnant controls. Both 100 and 1000 µg/L iAs also reduced transcription of Nppa (atrial natriuretic peptide). Akt protein expression was also significantly reduced after 1000 µg/L iAs exposure in the maternal heart with no change in activating phosphorylation. This significant abrogation of maternal cardiac hypertrophy suggests that arsenic exposure during pregnancy can potentially contribute to cardiovascular disease. Taken together, our findings further underscore the importance of reducing arsenic exposure during pregnancy and indicate that more research is needed to assess the impact of arsenic and other environmental exposures on the maternal heart and adverse pregnancy events.

Prenatal Arsenite Exposure Alters Maternal Cardiac Remodeling During Late Pregnancy.

Exposure to inorganic arsenic through drinking water is widespread and has been linked to many chronic diseases, including cardiovascular disease. Arsenic exposure has been shown to alter hypertrophic signaling in the adult heart, as well as in-utero offspring development. However, the effect of arsenic on maternal cardiac remodeling during pregnancy has not been studied. As such, there is a need to understand how environmental exposure contributes to adverse pregnancy-related cardiovascular events. This study seeks to understand the impact of trivalent inorganic arsenic exposure during gestation on maternal cardiac remodeling in late pregnancy, as well as offspring outcomes. C57BL/6J mice were exposed to 0 (control), 100 or 1000 µg/L sodium arsenite (NaAsO 2 ) beginning at embryonic day (E) 2.5 and continuing through E17.5. Maternal heart function and size were assessed via transthoracic echocardiography, gravimetric measurement, and histology. Transcript levels of hypertrophic markers were probed via qRT-PCR and confirmed by western blot. Offspring outcomes were assessed through echocardiography and gravimetric measurement. We found that exposure to 1000 µg/L iAs abrogated normal physiologic growth of the maternal heart during late pregnancy and reduced transcript levels of estrogen receptor alpha (ERα), progesterone receptor membrane component 1 (Pgrmc1) and progesterone receptor membrane component 2 (Pgrmc2). Both 100 and 1000 µg/L iAs also reduced transcription of protein kinase B (Akt) and atrial natriuretic peptide (ANP). Akt protein expression was also significantly reduced after 1000 µg/L iAs exposure in the maternal heart with no change in activating phosphorylation. This significant abrogation of maternal cardiac hypertrophy suggests that arsenic exposure during pregnancy can potentially contribute to cardiovascular disease. Taken together, our findings further underscore the importance of reducing arsenic exposure during pregnancy and indicate that more research is needed to assess the impact of arsenic and other environmental exposures on the maternal heart and adverse pregnancy events.

Hypereosinophilia causes progressive cardiac pathologies in mice.

Hypereosinophilic syndrome is a progressive disease with extensive eosinophilia that results in organ damage. Cardiac pathologies are the main reason for its high mortality rate. A better understanding of the mechanisms of eosinophil-mediated tissue damage would benefit therapeutic development. Here, we describe the cardiac pathologies that developed in a mouse model of hypereosinophilic syndrome. These IL-5 transgenic mice exhibited decreased left ventricular function at a young age which worsened with age. Mechanistically, we demonstrated infiltration of activated eosinophils into the heart tissue that led to an inflammatory environment. Gene expression signatures showed tissue damage as well as repair and remodeling processes. Cardiomyocytes from IL-5Tg mice exhibited significantly reduced contractility relative to wild type (WT) controls. This impairment may result from the inflammatory stress experienced by the cardiomyocytes and suggest that dysregulation of contractility and Ca2+ reuptake in cardiomyocytes contributes to cardiac dysfunction at the whole organ level in hypereosinophilic mice.

Cadmium exposure induces a sex-dependent decline in left ventricular cardiac function.

AIMS: Cadmium exposure is a worldwide problem that has been linked to the development of cardiovascular disease. This study aimed to elucidate mechanistic details of chronic cadmium exposure on the structure and function of the heart. MAIN METHODS: Male and female mice were exposed to cadmium chloride (CdCl2) via drinking water for eight weeks. Serial echocardiography and blood pressure measurements were performed. Markers of hypertrophy and fibrosis were assessed, along with molecular targets of Ca2+-handling. KEY FINDINGS: Males exhibited a significant reduction in left ventricular ejection fraction and fractional shortening with CdCl2 exposure, along with increased ventricular volume at end-systole, and decreased interventricular septal thickness at end-systole. Interestingly, no changes were detected in females. Experiments in isolated cardiomyocytes revealed that CdCl2-induced contractile dysfunction was also present at the cellular level, showing decreased Ca2+ transient and sarcomere shortening amplitude with CdCl2 exposure. Further mechanistic investigation uncovered a decrease in sarco/endoplasmic reticulum Ca2+-ATPase 2a (SERCA2a) protein expression and phosphorylated phospholamban levels in male hearts with CdCl2 exposure. SIGNIFICANCE: The findings of our novel study provide important insight into how cadmium exposure may act as a sex-specific driver of cardiovascular disease, and further underscore the importance of reducing human exposure to cadmium.

Perinuclear damage from nuclear envelope deterioration elicits stress responses that contribute to LMNA cardiomyopathy.

Mutations in the LMNA gene encoding nuclear lamins A/C cause a diverse array of tissue-selective diseases, with the heart being the most commonly affected organ. Despite progress in understanding the molecular perturbations emanating from LMNA mutations, an integrative understanding of the pathogenesis leading to cardiac dysfunction remains elusive. Using a novel cell-type specific Lmna deletion mouse model capable of translatome profiling, we found that cardiomyocyte-specific Lmna deletion in adult mice led to rapid cardiomyopathy with pathological remodeling. Prior to the onset of cardiac dysfunction, lamin A/C-depleted cardiomyocytes displayed nuclear envelope deterioration, golgi dilation/fragmentation, and CREB3-mediated golgi stress activation. Translatome profiling identified upregulation of Med25, a transcriptional co-factor that can selectively dampen UPR axes. Autophagy is disrupted in the hearts of these mice, which can be recapitulated by disrupting the golgi or inducing nuclear damage by increased matrix stiffness. Systemic administration of pharmacological modulators of autophagy or ER stress significantly improved the cardiac function. These studies support a hypothesis wherein stress responses emanating from the perinuclear space contribute to the development of LMNA cardiomyopathy. Teaser: Interplay of stress responses underlying the development of LMNA cardiomyopathy.

Pharmacological TRPC6 inhibition improves survival and muscle function in mice with Duchenne muscular dystrophy.

Gene mutations causing loss of dystrophin result in the severe muscle disease known as Duchenne muscular dystrophy (DMD). Despite efforts at genetic repair, DMD therapy remains largely palliative. Loss of dystrophin destabilizes the sarcolemmal membrane, inducing mechanosensitive cation channels to increase calcium entry and promote cell damage and, eventually, muscle dysfunction. One putative channel is transient receptor potential canonical 6 (TRPC6); we have shown that TRPC6 contributed to abnormal force and calcium stress-responses in cardiomyocytes from mice lacking dystrophin that were haplodeficient for utrophin (mdx/utrn+/- [HET] mice). Here, we show in both the HET mouse and the far more severe homozygous mdx/utrn-/- mouse that TRPC6 gene deletion or its selective pharmacologic inhibition (by BI 749327) prolonged survival 2- to 3-fold, improving skeletal and cardiac muscle and bone defects. Gene pathways reduced by BI 749327 treatment most prominently regulated fat metabolism and TGF-ß1 signaling. These results support the testing of TRPC6 inhibitors in human trials for other diseases as a novel DMD therapy.

OGR1-dependent regulation of the allergen-induced asthma phenotype.

The proton-sensing receptor, ovarian cancer G protein-coupled receptor (OGR1), has been shown to be expressed in airway smooth muscle (ASM) cells and is capable of promoting ASM contraction in response to decreased extracellular pH. OGR1 knockout (OGR1KO) mice are reported to be resistant to the asthma features induced by inhaled allergen. We recently described certain benzodiazepines as OGR1 activators capable of mediating both procontractile and prorelaxant signaling in ASM cells. Here we assess the effect of treatment with the benzodiazepines lorazepam or sulazepam on the asthma phenotype in wild-type (WT) and OGR1KO mice subjected to inhaled house dust mite (HDM; Dermatophagoides pteronyssius) challenge for 3 wk. In contrast to previously published reports, both WT and OGR1KO mice developed significant allergen-induced lung inflammation and airway hyperresponsiveness (AHR). In WT mice, treatment with sulazepam (a Gs-biased OGR1 agonist), but not lorazepam (a balanced OGR1 agonist), prevented allergen-induced AHR, although neither drug inhibited lung inflammation. The protection from development of AHR conferred by sulazepam was absent in OGR1KO mice. Treatment of WT mice with sulazepam also resulted in significant inhibition of HDM-induced collagen accumulation in the lung tissue. These findings suggest that OGR1 expression is not a requirement for development of the allergen-induced asthma phenotype, but OGR1 can be targeted by the Gs-biased OGR1 agonist sulazepam (but not the balanced agonist lorazepam) to protect from allergen-induced AHR, possibly mediated via suppression of chronic bronchoconstriction and airway remodeling in the absence of effects on airway inflammation.

Adaptation of the heart to Frataxin depletion: Evidence that integrated stress response can predominate over mTORC1 activation.

Friedreich's ataxia (FRDA) is an inherited disorder caused by depletion of frataxin (FXN), a mitochondrial protein required for iron-sulfur cluster (ISC) biogenesis. Cardiac dysfunction is the main cause of death. Yet pathogenesis, and, more generally, how the heart adapts to FXN loss, remain poorly understood, though are expected to be linked to an energy deficit. We modified a transgenic (TG) mouse model of inducible FXN depletion that permits phenotypic evaluation of the heart at different FXN levels, and focused on substrate-specific bioenergetics and stress signaling. When FXN protein in the TG heart was 17% of normal, bioenergetics and signaling were not different from control. When, 8 weeks later, FXN was ~ 97% depleted in the heart, TG heart mass and cardiomyocyte cross-sectional area were less, without evidence of fibrosis or apoptosis. mTORC1 signaling was activated, as was the integrated stress response, evidenced by greater phosphorylation of eIF2α relative to total eIF2α, and decreased protein translation. We interpret these results to suggest that, in TG hearts, an anabolic stimulus was constrained by eIF2α phosphorylation. Cardiac contractility was maintained in the 97%-FXN-depleted hearts, possibly contributed by an unexpected preservation of ß-oxidation, though pyruvate oxidation was lower. Bioenergetics alterations were matched by changes in the mitochondrial proteome, including a non-uniform decrease in abundance of ISC-containing proteins. Altogether, these findings suggest that the FXN depleted heart can suppress a major ATP demanding process such as protein translation, which, together with some preservation of ß-oxidation, could be adaptive, at least in the short term.

Psychosocial Stress Hastens Disease Progression and Sudden Death in Mice with Arrhythmogenic Cardiomyopathy.

Physiological stressors, such as exercise, can precipitate sudden cardiac death or heart failure progression in patients with arrhythmogenic cardiomyopathy (ACM). Yet, whether and to what extent a highly prevalent and more elusive environmental factor, such as psychosocial stress (PSS), can also increase ACM disease progression is unexplored. Here, we first quantified perceived stress levels in patients with ACM and found these levels correlated with the extent of arrhythmias and cardiac dysfunction. To determine whether the observed correlation is due to causation, we inflicted PSS-via the resident-intruder (RI) paradigm-upon Desmoglein-2 mutant mice, a vigorously used mammalian model of ACM. We found that ACM mice succumbed to abnormally high in-trial, PSS mortality. Conversely, no sudden deaths occurred in wildtype (WT) counterparts. Desmoglein-2 mice that survived RI challenge manifested markedly worse cardiac dysfunction and remodeling, namely apoptosis and fibrosis. Furthermore, WT and ACM mice displayed similar behavior at baseline, but Desmoglein-2 mice exhibited heightened anxiety following RI-induced PSS. This outcome correlated with the worsening of cardiac phenotypes. Our mouse model demonstrates that in ACM-like subjects, PSS is incisive enough to deteriorate cardiac structure and function per se, i.e., in the absence of any pre-existing anxious behavior. Hence, PSS may represent a previously underappreciated risk factor in ACM disease penetrance.

A knock-in mutation at cysteine 144 of TRIM72 is cardioprotective and reduces myocardial TRIM72 release.

TRIM72 is a membrane repair protein that protects against ischemia reperfusion (I/R) injury. We previously identified Cys144 (C144) on TRIM72 as a site of S-nitrosylation. To study the importance of C144, we generated a knock-in mouse with C144 mutated to a serine (TRIM72 C144S). We subjected ex vivo perfused mouse hearts to 20 min of ischemia followed by 90 min of reperfusion and observed less injury in TRIM72 C144S compared to WT hearts. Infarct size was smaller (54 vs 27% infarct size) and cardiac functional recovery (37 vs 62% RPP) was higher for the TRIM72 C144S mouse hearts. We also demonstrated that TRIM72 C144S hearts were protected against I/R injury using an in vivo LAD occlusion model. As TRIM72 has been reported to be released from muscle we tested whether C144 is involved in TRIM72 release. After I/R there was significantly less TRIM72 in the perfusate normalized to total released protein from the TRIM72 C144S compared to WT hearts, suggesting that C144 of TRIM72 regulates myocardial TRIM72 release during I/R injury. In addition to TRIM72's protective role in I/R injury, TRIM72 has also been implicated in cardiac hypertrophy and insulin resistance, and secreted TRIM72 has recently been shown to impair insulin sensitivity. However, insulin sensitivity (measured by glucose and insulin tolerance) of TRIM72 C144S mice was not impaired. Further, whole body metabolism, as measured using metabolic cages, was not different in WT vs TRIM72 C144S mice and we did not observe enhanced cardiac hypertrophy in the TRIM72 C144S mice. In agreement, protein levels of the TRIM72 ubiquitination targets insulin receptor ß, IRS1, and focal adhesion kinase were similar between WT and TRIM72 C144S hearts. Overall, these data indicate that mutation of TRIM72 C144 is protective during I/R and reduces myocardial TRIM72 release without impairing insulin sensitivity or enhancing the development of hypertrophy.

Diacylglycerol kinase ζ promotes allergic airway inflammation and airway hyperresponsiveness through distinct mechanisms.

Asthma is a chronic allergic inflammatory airway disease caused by aberrant immune responses to inhaled allergens, which leads to airway hyperresponsiveness (AHR) to contractile stimuli and airway obstruction. Blocking T helper 2 (TH2) differentiation represents a viable therapeutic strategy for allergic asthma, and strong TCR-mediated ERK activation blocks TH2 differentiation. Here, we report that targeting diacylglycerol (DAG) kinase zeta (DGKζ), a negative regulator of DAG-mediated cell signaling, protected against allergic asthma by simultaneously reducing airway inflammation and AHR though independent mechanisms. Targeted deletion of DGKζ in T cells decreased type 2 inflammation without reducing AHR. In contrast, loss of DGKζ in airway smooth muscle cells decreased AHR but not airway inflammation. T cell-specific enhancement of ERK signaling was only sufficient to limit type 2 airway inflammation, not AHR. Pharmacological inhibition of DGK diminished both airway inflammation and AHR in mice and also reduced bronchoconstriction of human airway samples in vitro. These data suggest that DGK is a previously unrecognized therapeutic target for asthma and reveal that the inflammatory and AHR components of asthma are not as interdependent as generally believed.

Regulation of ovarian cancer G protein-coupled receptor-1 expression and signaling.

Ovarian cancer G protein-coupled receptor 1 (OGR1) is a recently deorphanized G protein-coupled receptor shown to signal in response to low extracellular pH (↓pHo) or certain benzodiazepines. The pleiotropic nature of OGR1 signaling in human airway smooth muscle (HASM) cells suggests that OGR1 is a potential therapeutic target for the management of obstructive lung diseases. However, the basic pharmacological and regulatory features of OGR1 remain poorly understood. We employed model systems of heterologously expressed [human embryonic kidney 293 (HEK293) cells] or endogenous (HASM) OGR1 to assess changes in expression, subcellular localization, and signaling capabilities following acute or chronic treatment with ↓pHo or the benzodiazepines lorazepam and sulazepam. In HEK293 cells expressing OGR1, treatment with ↓pHo and/or lorazepam, but not sulazepam, caused rapid OGR1 internalization. In HASM cells, acute treatment with ↓pHo or benzodiazepines did not alter abundance of OGR1 mRNA; however, significant downregulation was observed following chronic treatment. Acute and chronic pretreatment of HASM cells with sulazepam or lorazepam resulted in receptor desensitization as demonstrated by reduced phosphorylation of vasodilator-stimulated phosphoprotein (VASP) or p42/p44 upon rechallenge. Acid (acute but not chronic) pretreatment of HASM cells induced desensitization of OGR1-mediated VASP (but not p42/p44) phosphorylation. In contrast to a recent study reporting OGR1 upregulation and sensitization in cardiac tissue subject to ischemic/acidic insult, chronic OGR1 activation in multiple model systems did not increase OGR1 expression or signaling capacity. The ability to induce OGR1 internalization and desensitization was activator dependent, reflecting the ability of different activators to induce specific receptor confirmations and engagement of specific heterotrimeric G proteins.

PD-1 Modulates Radiation-Induced Cardiac Toxicity through Cytotoxic T Lymphocytes.

INTRODUCTION: Combined immune checkpoint blockade has led to rare autoimmune complications, such as fatal myocarditis. Recent approvals of several anti-programmed death 1 (anti-PD-1) drugs for lung cancer treatment prompted ongoing clinical trials that directly combine PD-1 inhibitors with thoracic radiotherapy for locally advanced lung cancer. Overlapping toxicities from either modality have the potential to increase the risk for radiation-induced cardiotoxicity (RICT), which is well documented among patients with Hodgkin's disease and breast cancer. METHODS: To investigate cardiotoxicity without the compounding pulmonary toxicity from thoracic radiotherapy, we developed a technique to deliver cardiac irradiation (CIR) in a mouse model concurrently with PD-1 blockade to determine the presence of cardiac toxicity by using physiological testing and mortality as end points along with histological analysis. RESULTS: We observed an acute mortality of 30% within 2 weeks after CIR plus anti-PD-1 antibody compared with 0% from CIR plus immunoglobulin G (p = 0.023). Physiological testing demonstrated a reduced left ventricular ejection fraction (p < 0.01) by echocardiogram. Tissue analyses revealed increased immune cell infiltrates within cardiac tissue. Depletion of CD8-positive lymphocytes with anti-CD8 antibody reversed the acute mortality, suggesting that the toxicity is CD8-positive cell-mediated. To validate these findings using a clinically relevant fractionated radiotherapy regimen, we repeated the study by delivering five daily fractions of 6 Gy. Similar mortality, cardiac dysfunction, and histological changes were observed in mice receiving fractionated radiotherapy with concurrent anti-PD-1 therapy. CONCLUSIONS: This study provides strong preclinical evidence that radiation-induced cardiotoxicity is modulated by the PD-1 axis and that PD-1 blockade should be administered with careful radiotherapy planning with an effort of reducing cardiac dose.

Bitter Taste Receptor Agonists Mitigate Features of Allergic Asthma in Mice.

Asthma is characterized by airway inflammation, mucus secretion, remodeling and hyperresponsiveness (AHR). Recent research has established the bronchodilatory effect of bitter taste receptor (TAS2R) agonists in various models. Comprehensive pre-clinical studies aimed at establishing effectiveness of TAS2R agonists in disease models are lacking. Here we aimed to determine the effect of TAS2R agonists on features of asthma. Further, we elucidated a mechanism by which TAS2R agonists mitigate features of asthma. Asthma was induced in mice using intranasal house dust mite or aerosol ova-albumin challenge, and chloroquine or quinine were tested in both prophylactic and treatment models. Allergen challenge resulted in airway inflammation as evidenced by increased immune cells infiltration and release of cytokines and chemokines in the lungs, which were significantly attenuated in TAS2R agonists treated mice. TAS2R agonists attenuated features of airway remodeling including smooth muscle mass, extracellular matrix deposition and pro-fibrotic signaling, and also prevented mucus accumulation and development of AHR in mice. Mechanistic studies using human neutrophils demonstrated that inhibition of immune cell chemotaxis is a key mechanism by which TAS2R agonists blocked allergic airway inflammation and exerted anti-asthma effects. Our comprehensive studies establish the effectiveness of TAS2R agonists in mitigating multiple features of allergic asthma.

Tissue-Specific Mitochondrial Decoding of Cytoplasmic Ca2+ Signals Is Controlled by the Stoichiometry of MICU1/2 and MCU.

Mitochondrial Ca2+ uptake through the Ca2+ uniporter supports cell functions, including oxidative metabolism, while meeting tissue-specific calcium signaling patterns and energy needs. The molecular mechanisms underlying tissue-specific control of the uniporter are unknown. Here, we investigated a possible role for tissue-specific stoichiometry between the Ca2+-sensing regulators (MICUs) and pore unit (MCU) of the uniporter. Low MICU1:MCU protein ratio lowered the [Ca2+] threshold for Ca2+ uptake and activation of oxidative metabolism but decreased the cooperativity of uniporter activation in heart and skeletal muscle compared to liver. In MICU1-overexpressing cells, MICU1 was pulled down by MCU proportionally to MICU1 overexpression, suggesting that MICU1:MCU protein ratio directly reflected their association. Overexpressing MICU1 in the heart increased MICU1:MCU ratio, leading to liver-like mitochondrial Ca2+ uptake phenotype and cardiac contractile dysfunction. Thus, the proportion of MICU1-free and MICU1-associated MCU controls these tissue-specific uniporter phenotypes and downstream Ca2+ tuning of oxidative metabolism.

Orphan Nuclear Receptor Nur77 Inhibits Cardiac Hypertrophic Response to Beta-Adrenergic Stimulation.

The orphan nuclear receptor Nur77 plays critical roles in cardiovascular diseases, and its expression is markedly induced in the heart after beta-adrenergic receptor (ß-AR) activation. However, the functional significance of Nur77 in ß-AR signaling in the heart remains unclear. By using Northern blot, Western blot, and immunofluorescent staining assays, we showed that Nur77 expression was markedly upregulated in cardiomyocytes in response to multiple hypertrophic stimuli, including isoproterenol (ISO), phenylephrine (PE), and endothelin-1 (ET-1). In a time- and dose-dependent manner, ISO increases Nur77 expression in the nuclei of cardiomyocytes. Overexpression of Nur77 markedly inhibited ISO-induced cardiac hypertrophy by inducing nuclear translocation of Nur77 in cardiomyocytes. Furthermore, cardiac overexpression of Nur77 by intramyocardial injection of Ad-Nur77 substantially inhibited cardiac hypertrophy and ameliorated cardiac dysfunction after chronic infusion of ISO in mice. Mechanistically, we demonstrated that Nur77 functionally interacts with NFATc3 and GATA4 and inhibits their transcriptional activities, which are critical for the development of cardiac hypertrophy. These results demonstrate for the first time that Nur77 is a novel negative regulator for the ß-AR-induced cardiac hypertrophy through inhibiting the NFATc3 and GATA4 transcriptional pathways. Targeting Nur77 may represent a potentially novel therapeutic strategy for preventing cardiac hypertrophy and heart failure.

Obesity-induced adipokine imbalance impairs mouse pulmonary vascular endothelial function and primes the lung for injury.

Obesity is a risk factor for the development of acute respiratory distress syndrome (ARDS) but mechanisms mediating this association are unknown. While obesity is known to impair systemic blood vessel function, and predisposes to systemic vascular diseases, its effects on the pulmonary circulation are largely unknown. We hypothesized that the chronic low grade inflammation of obesity impairs pulmonary vascular homeostasis and primes the lung for acute injury. The lung endothelium from obese mice expressed higher levels of leukocyte adhesion markers and lower levels of cell-cell junctional proteins when compared to lean mice. We tested whether systemic factors are responsible for these alterations in the pulmonary endothelium; treatment of primary lung endothelial cells with obese serum enhanced the expression of adhesion proteins and reduced the expression of endothelial junctional proteins when compared to lean serum. Alterations in pulmonary endothelial cells observed in obese mice were associated with enhanced susceptibility to LPS-induced lung injury. Restoring serum adiponectin levels reversed the effects of obesity on the lung endothelium and attenuated susceptibility to acute injury. Our work indicates that obesity impairs pulmonary vascular homeostasis and enhances susceptibility to acute injury and provides mechanistic insight into the increased prevalence of ARDS in obese humans.

Downregulation of adenine nucleotide translocator 1 exacerbates tumor necrosis factor-α-mediated cardiac inflammatory responses.

Inflammation contributes significantly to cardiac dysfunction. Although the initial phase of inflammation is essential for repair and healing, excessive proinflammatory cytokines are detrimental to the heart. We found that adenine nucleotide translocator isoform-1 (ANT1) protein levels were significantly decreased in the inflamed heart of C57BL/6 mice following cecal ligation and puncture. To understand the molecular mechanisms involved, we performed small-interfering RNA-mediated knockdown of ANT1 and studied tumor necrosis factor-α (TNFα)-induced inflammatory responses in myocardium-derived H9c2 cells and cardiomyocytes. ANT1 knockdown significantly increased swollen mitochondria and mitochondrial reactive oxygen species, concomitant with increased TNFα-induced NF-κB reporter gene activity and interleukin-6 and TNFα expression. A mitochondrial-targeted antioxidant mito-TEMPO attenuated TNFα-induced mitochondrial reactive oxygen species, NF-κB reporter gene activity, and cytokine expression in ANT1 knockdown cells. Interestingly, TNFα or lipopolysaccharide (LPS) treatment significantly decreased ANT1 protein levels, suggesting a feed-forward regulation of proinflammatory cytokine expression activated by ANT1 downregulation. These data suggest that ANT1 downregulation contributes to cardiac inflammation post-cecal ligation and puncture. Preventing ANT1 downregulation could provide a novel molecular target to temper cardiac inflammation.