Modulation of Oxidative Phosphorylation with IM156 Attenuates Mitochondrial Metabolic Reprogramming and Inhibits Pulmonary Fibrosis.

Metabolic reprogramming of the myofibroblast plays a fundamental role in the pathogenesis of fibrosing interstitial lung diseases. Here, we characterized the in vitro and in vivo metabolic and antifibrotic effects of IM156, an oxidative phosphorylation (OXPHOS) modulator that acts by inhibiting protein complex 1. In vitro, IM156 inhibited transforming growth factor ß (TGFß)-dependent increases in mitochondrial oxygen consumption rate and expression of myofibroblast markers in human pulmonary fibroblasts without altering cell viability or adding to TGFß-induced increases in the extracellular acidification rate. IM156 significantly increased cellular AMP-activated protein kinase (AMPK) phosphorylation and was 60-fold more potent than metformin. In vivo, chronic oral administration of IM156 was highly distributed to major peripheral organs (i.e., lung, liver, kidney, heart) and had significant dose-related effects on the plasma metabolome consistent with OXPHOS modulation and AMPK activation. IM156 increased glycolysis, lipolysis, ß-oxidation, and amino acids and decreased free fatty acids, tricarboxylic acid cycle activity, and protein synthesis. In the murine bleomycin model of pulmonary fibrosis, daily oral administration of IM156, administered 7 days after lung injury, attenuated body/lung weight changes and reduced lung fibrosis and inflammatory cell infiltration. The plasma exposures of IM156 were comparable to well tolerated doses in human studies. In conclusion, the metabolic and antifibrotic effects of IM156 suggest that OXPHOS modulation can attenuate myofibroblast metabolic reprogramming and support testing IM156 as a therapy for idiopathic pulmonary fibrosis and other fibrotic diseases. SIGNIFICANCE STATEMENT: Fibrosing interstitial lung diseases have a poor prognosis, and current antifibrotic treatments have significant limitations. This study demonstrates that attenuation of fibrogenic metabolic remodeling, by modulation of oxidative phosphorylation with IM156, prevents myofibroblast phenotype/collagen deposition and is a potentially effective and translational antifibrotic strategy.

Cardiomyocyte Homeodomain-Interacting Protein Kinase 2 Maintains Basal Cardiac Function via Extracellular Signal-Regulated Kinase Signaling.

BACKGROUND: Cardiac kinases play a critical role in the development of heart failure, and represent potential tractable therapeutic targets. However, only a very small fraction of the cardiac kinome has been investigated. To identify novel cardiac kinases involved in heart failure, we used an integrated transcriptomics and bioinformatics analysis and identified Homeodomain-Interacting Protein Kinase 2 (HIPK2) as a novel candidate kinase. The role of HIPK2 in cardiac biology is unknown. METHODS: We used the Expression2Kinase algorithm for the screening of kinase targets. To determine the role of HIPK2 in the heart, we generated cardiomyocyte (CM)-specific HIPK2 knockout and heterozygous mice. Heart function was examined by echocardiography, and related cellular and molecular mechanisms were examined. Adeno-associated virus serotype 9 carrying cardiac-specific constitutively active MEK1 (TnT-MEK1-CA) was administrated to rescue cardiac dysfunction in CM-HIPK2 knockout mice. RESULTS: To our knowledge, this is the first study to define the role of HIPK2 in cardiac biology. Using multiple HIPK2 loss-of-function mouse models, we demonstrated that reduction of HIPK2 in CMs leads to cardiac dysfunction, suggesting a causal role in heart failure. It is important to note that cardiac dysfunction in HIPK2 knockout mice developed with advancing age, but not during development. In addition, CM-HIPK2 knockout mice and CM-HIPK2 heterozygous mice exhibited a gene dose-response relationship of CM-HIPK2 on heart function. HIPK2 expression in the heart was significantly reduced in human end-stage ischemic cardiomyopathy in comparison to nonfailing myocardium, suggesting a clinical relevance of HIPK2 in cardiac biology. In vitro studies with neonatal rat ventricular CMscorroborated the in vivo findings. Specifically, adenovirus-mediated overexpression of HIPK2 suppressed the expression of heart failure markers, NPPA and NPPB, at basal condition and abolished phenylephrine-induced pathological gene expression. An array of mechanistic studies revealed impaired extracellular signal-regulated kinase 1/2 signaling in HIPK2-deficient hearts. An in vivo rescue experiment with adeno-associated virus serotype 9 TnT-MEK1-CA nearly abolished the detrimental phenotype of knockout mice, suggesting that impaired extracellular signal-regulated kinase signaling mediated apoptosis as the key factor driving the detrimental phenotype in CM-HIPK2 knockout mice hearts. CONCLUSIONS: Taken together, these findings suggest that CM-HIPK2 is required to maintain normal cardiac function via extracellular signal-regulated kinase signaling.

CXA-10, a Nitrated Fatty Acid, Is Renoprotective in Deoxycorticosterone Acetate-Salt Nephropathy.

Underlying pathogenic mechanisms in chronic kidney disease (CKD) include chronic inflammation, oxidant stress, and matrix remodeling associated with dysregulated nuclear factor-κ B, nuclear factor-κ B, and SMAD signaling pathways, respectively. Important cytoprotective mechanisms activated by oxidative inflammatory conditions are mediated by nitrated fatty acids that covalently modify proteins to limit inflammation and oxidant stress. In the present study, we evaluated the effects of chronic treatment with CXA-10 (10-nitro-9(E)-octadec-9-enoic acid) in the uninephrectomized deoxycorticosterone acetate-high-salt mouse model of CKD. After 4 weeks of treatment, CXA-10 [2.5 millligrams per kilogram (mpk), p.o.] significantly attenuated increases in plasma cholesterol, heart weight, and kidney weight observed in the model without impacting systemic arterial blood pressure. CXA-10 also reduced albuminuria, nephrinuria, glomerular hypertrophy, and glomerulosclerosis in the model. Inflammatory MCP-1 and fibrosis (collagen, fibronectin, plasminogen activator inhibitor-1, and osteopontin) renal biomarkers were significantly reduced in the CXA-10 (2.5 mpk) group. The anti-inflammatory and antifibrotic effects, as well as glomerular protection, were not observed in the enalapril-treated group. Also, CXA-10 appears to exhibit hormesis as all protective effects observed in the low-dose group were absent in the high-dose group (12.5 mpk). Taken together, these findings demonstrate that, at the appropriate dose, the nitrated fatty acid CXA-10 exhibits anti-inflammatory and antifibrotic effects in the kidney and limits renal injury in a model of CKD.

Inhibition of Apoptosis Signal-Regulating Kinase 1 Attenuates Myocyte Hypertrophy and Fibroblast Collagen Synthesis.

BACKGROUND: Cardiac remodelling is a dynamic process whereby structural and functional changes occur within the heart in response to injury or inflammation. Recent studies have demonstrated reactive oxygen species sensitive MAPK, apoptosis signal-regulating kinase 1 (ASK1) plays a critical role in cardiac remodelling. This study aims to determine the effectiveness of small molecule ASK1 inhibitors on these processes and their therapeutic potential. METHODS: Neonatal rat cardiac fibroblasts (NCF) were pre-treated with ASK1 inhibitors, G2261818A (G226) and G2358939A (G235), for 2hours before stimulated with 100nM angiotensin II (AngII), 10µM indoxyl sulphate (IS) or 10ng/ml transforming growth factor ß1 (TGFß1) for 48hours. Neonatal rat cardiac myocytes (NCM) were pre-treated with G226 and G235 for 2hours before being stimulated with 100nM AngII for 60hours, 10µM IS, 10ng/ml interleukin 1ß (IL-1ß) or tumour necrosis factor α (TNFα) for 48hours. 3H-proline and 3H-leucine incorporation was used to assess collagen turnover and hypertrophy, respectively. Pro-fibrotic, pro-hypertrophic and THP-1 inflammatory cytokine gene expressions were determined by RT-PCR. RESULTS: Both G226 and G235 dose-dependently attenuated AngII-, IS-, IL-1ß- and TNFα-stimulated NCM hypertrophy and hypertrophic gene expression, IS-, AngII- and TGFß1-stimulated NCF collagen synthesis and AngII- and TGFß1-stimulated pro-fibrotic gene expression. Inhibition of ASK1 by G226 and G235 inhibited lipopolysaccharides-stimulated inflammatory cytokine gene expression in THP-1 cells. CONCLUSIONS: Selective ASK1 inhibition confers anti-hypertrophic and anti-fibrotic effects in cardiac cells, and anti-inflammation in monocytic cells. ASK1 inhibitors may represent novel therapeutic agents to alleviate cardiac remodelling post cardiac injury where hypertrophy, fibrosis and inflammation play critical roles.

Combined TRPC3 and TRPC6 blockade by selective small-molecule or genetic deletion inhibits pathological cardiac hypertrophy.

Chronic neurohormonal and mechanical stresses are central features of heart disease. Increasing evidence supports a role for the transient receptor potential canonical channels TRPC3 and TRPC6 in this pathophysiology. Channel expression for both is normally very low but is increased by cardiac disease, and genetic gain- or loss-of-function studies support contributions to hypertrophy and dysfunction. Selective small-molecule inhibitors remain scarce, and none target both channels, which may be useful given the high homology among them and evidence of redundant signaling. Here we tested selective TRPC3/6 antagonists (GSK2332255B and GSK2833503A; IC50, 3-21 nM against TRPC3 and TRPC6) and found dose-dependent blockade of cell hypertrophy signaling triggered by angiotensin II or endothelin-1 in HEK293T cells as well as in neonatal and adult cardiac myocytes. In vivo efficacy in mice and rats was greatly limited by rapid metabolism and high protein binding, although antifibrotic effects with pressure overload were observed. Intriguingly, although gene deletion of TRPC3 or TRPC6 alone did not protect against hypertrophy or dysfunction from pressure overload, combined deletion was protective, supporting the value of dual inhibition. Further development of this pharmaceutical class may yield a useful therapeutic agent for heart disease management.

Unrestrained p38 MAPK activation in Dusp1/4 double-null mice induces cardiomyopathy.

RATIONALE: Mitogen-activated protein kinases (MAPKs) are activated in the heart by disease-inducing and stress-inducing stimuli, where they participate in hypertrophy, remodeling, contractility, and heart failure. A family of dual-specificity phosphatases (DUSPs) directly inactivates each of the MAPK terminal effectors, potentially serving a cardioprotective role. OBJECTIVE: To determine the role of DUSP1 and DUSP4 in regulating p38 MAPK function in the heart and the effect on disease. METHODS AND RESULTS: Here, we generated mice and mouse embryonic fibroblasts lacking both Dusp1 and Dusp4 genes. Although single nulls showed no molecular effects, combined disruption of Dusp1/4 promoted unrestrained p38 MAPK activity in both mouse embryonic fibroblasts and the heart, with no change in the phosphorylation of c-Jun N-terminal kinases or extracellular signal-regulated kinases at baseline or with stress stimulation. Single disruption of either Dusp1 or Dusp4 did not result in cardiac pathology, although Dusp1/4 double-null mice exhibited cardiomyopathy and increased mortality with aging. Pharmacological inhibition of p38 MAPK with SB731445 ameliorated cardiomyopathy in Dusp1/4 double-null mice, indicating that DUSP1/4 function primarily through p38 MAPK in affecting disease. At the cellular level, unrestrained p38 MAPK activity diminished cardiac contractility and Ca2+ handling, which was acutely reversed with a p38 inhibitory compound. Poor function in Dusp1/4 double-null mice also was partially rescued by phospholamban deletion. CONCLUSIONS: Our data demonstrate that Dusp1 and Dusp4 are cardioprotective genes that play a critical role in the heart by dampening p38 MAPK signaling that would otherwise reduce contractility and induce cardiomyopathy.

TRPV4 inhibition counteracts edema and inflammation and improves pulmonary function and oxygen saturation in chemically induced acute lung injury.

The treatment of acute lung injury caused by exposure to reactive chemicals remains challenging because of the lack of mechanism-based therapeutic approaches. Recent studies have shown that transient receptor potential vanilloid 4 (TRPV4), an ion channel expressed in pulmonary tissues, is a crucial mediator of pressure-induced damage associated with ventilator-induced lung injury, heart failure, and infarction. Here, we examined the effects of two novel TRPV4 inhibitors in mice exposed to hydrochloric acid, mimicking acid exposure and acid aspiration injury, and to chlorine gas, a severe chemical threat with frequent exposures in domestic and occupational environments and in transportation accidents. Postexposure treatment with a TRPV4 inhibitor suppressed acid-induced pulmonary inflammation by diminishing neutrophils, macrophages, and associated chemokines and cytokines, while improving tissue pathology. These effects were recapitulated in TRPV4-deficient mice. TRPV4 inhibitors had similar anti-inflammatory effects in chlorine-exposed mice and inhibited vascular leakage, airway hyperreactivity, and increase in elastance, while improving blood oxygen saturation. In both models of lung injury we detected increased concentrations of N-acylamides, a class of endogenous TRP channel agonists. Taken together, we demonstrate that TRPV4 inhibitors are potent and efficacious countermeasures against severe chemical exposures, acting against exaggerated inflammatory responses, and protecting tissue barriers and cardiovascular function.

Human-induced pluripotent stem cell-derived cardiomyocytes exhibit temporal changes in phenotype.

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) have been recently derived and are used for basic research, cardiotoxicity assessment, and phenotypic screening. However, the hiPS-CM phenotype is dependent on their derivation, age, and culture conditions, and there is disagreement as to what constitutes a functional hiPS-CM. The aim of the present study is to characterize the temporal changes in hiPS-CM phenotype by examining five determinants of cardiomyocyte function: gene expression, ion channel functionality, calcium cycling, metabolic activity, and responsiveness to cardioactive compounds. Based on both gene expression and electrophysiological properties, at day 30 of differentiation, hiPS-CMs are immature cells that, with time in culture, progressively develop a more mature phenotype without signs of dedifferentiation. This phenotype is characterized by adult-like gene expression patterns, action potentials exhibiting ventricular atrial and nodal properties, coordinated calcium cycling and beating, suggesting the formation of a functional syncytium. Pharmacological responses to pathological (endothelin-1), physiological (IGF-1), and autonomic (isoproterenol) stimuli similar to those characteristic of isolated adult cardiac myocytes are present in maturing hiPS-CMs. In addition, thyroid hormone treatment of hiPS-CMs attenuated the fetal gene expression in favor of a more adult-like pattern. Overall, hiPS-CMs progressively acquire functionality when maintained in culture for a prolonged period of time. The description of this evolving phenotype helps to identify optimal use of hiPS-CMs for a range of research applications.

Novel fusion of GLP-1 with a domain antibody to serum albumin prolongs protection against myocardial ischemia/reperfusion injury in the rat.

BACKGROUND: Glucagon-like peptide-1 (GLP-1) and its mimetics reduce infarct size in the setting of acute myocardial ischemia/reperfusion (I/R) injury. However, the short serum half-life of GLP-1 and its mimetics may limit their therapeutic use in acute myocardial ischemia. Domain antibodies to serum albumin (AlbudAbs) have been developed to extend the serum half-life of short lived therapeutic proteins, peptides and small molecules. In this study, we compared the effect of a long acting GLP-1 agonist, DPP-IV resistant GLP-1 (7-36, A8G) fused to an AlbudAb (GAlbudAb), with the effect of the GLP-1 mimetic, exendin-4 (short half-life GLP-1 agonist) on infarct size following acute myocardial I/R injury. METHODS: Male Sprague-Dawley rats (8-week-old) were treated with vehicle, GAlbudAb or exendin-4. Myocardial ischemia was induced 2 h following the final dose for GAlbudAb and 30 min post the final dose for exendin-4. In a subgroup of animals, the final dose of exendin-4 was administered (1 µg/kg, SC, bid for 2 days) 6 h prior to myocardial ischemia when plasma exendin-4 was at its minimum concentration (C(min)). Myocardial infarct size, area at risk and cardiac function were determined 24 h after myocardial I/R injury. RESULTS: GAlbudAb and exendin-4 significantly reduced myocardial infarct size by 28% and 23% respectively, compared to vehicle (both p < 0.01 vs. vehicle) after I/R injury. Moreover, both GAlbudAb and exendin-4 markedly improved post-ischemic cardiac contractile function. Body weight loss and reduced food intake consistent with the activation of GLP-1 receptors was observed in all treatment groups. However, exendin-4 failed to reduce infarct size when administered 6 h prior to myocardial ischemia, suggesting continuous activation of the GLP-1 receptors is needed for cardioprotection. CONCLUSIONS: Cardioprotection provided by GAlbudAb, a long acting GLP-1 mimetic, following myocardial I/R injury was comparable in magnitude, but more sustained in duration than that produced by short-acting exendin-4. Very low plasma concentrations of exendin-4 failed to protect the heart from myocardial I/R injury, suggesting that sustained GLP-1 receptor activation plays an important role in providing cardioprotection in the setting of acute myocardial I/R injury. Long-acting GLP-1 agonists such as GAlbudAb may warrant additional evaluation as novel therapeutic agents to reduce myocardial I/R injury during acute coronary syndrome.

Soluble epoxide hydrolase inhibition does not prevent cardiac remodeling and dysfunction after aortic constriction in rats and mice.

Epoxyeicosatrienoic acids, substrates for soluble epoxide hydrolase (sEH), exhibit vasodilatory and antihypertrophic activities. Inhibitors of sEH might therefore hold promise as heart failure therapeutics. We examined the ability of sEH inhibitors GSK2188931 and GSK2256294 to modulate cardiac hypertrophy, fibrosis, and function after transverse aortic constriction (TAC) in rats and mice. GSK2188931 administration was initiated in rats 1 day before TAC, whereas GSK2256294 treatment was initiated in mice 2 weeks after TAC. Four weeks later, cardiovascular function was assessed, plasma was collected for drug and sEH biomarker concentrations, and left ventricle was isolated for messenger RNA and histological analyses. In rats, although GSK2188931 prevented TAC-mediated increases in certain genes associated with hypertrophy and fibrosis (α-skeletal actin and connective tissue growth factor), the compound failed to attenuate TAC-induced increases in left ventricle mass, posterior wall thickness, end-diastolic volume and pressure, and perivascular fibrosis. Similarly, in mice, GSK2256294 did not reverse cardiac remodeling or systolic dysfunction induced by TAC. Both compounds increased the sEH substrate/product (leukotoxin/leukotoxin diol) ratio, indicating sEH inhibition. In summary, sEH inhibition does not prevent cardiac remodeling or dysfunction after TAC. Thus, targeting sEH seems to be insufficient for reducing pressure overload hypertrophy.

The discovery of potent blockers of the canonical transient receptor channels, TRPC3 and TRPC6, based on an anilino-thiazole pharmacophore.

Lead optimization of piperidine amide HTS hits, based on an anilino-thiazole core, led to the identification of analogs which displayed low nanomolar blocking activity at the canonical transient receptor channels 3 and 6 (TRPC3 & 6) based on FLIPR (carbachol stimulated) and electrophysiology (OAG stimulated) assays. In addition, the anilino-thiazole amides displayed good selectivity over other TRP channels (TRPA1, TRPV1, and TRPV4), as well as against cardiac ion channels (CaV1.2, hERG, and NaV1.5). The high oxidation potential of the aliphatic piperidine and aniline groups, as well as the lability of the thiazole amide group contributed to the high clearance observed for this class of compounds. Conversion of an isoquinoline amide to a naphthyridine amide markedly reduced clearance for the bicyclic piperidines, and improved oral bioavailability for this compound series, however TRPC3 and TRPC6 blocking activity was reduced substantially. Although the most potent anilino-thiazole amides ultimately lacked oral exposure in rodents and were not suitable for chronic dosing, analogs such as 14-19, 22, and 23 are potentially valuable in vitro tool compounds for investigating the role of TRPC3 and TRPC6 in cardiovascular disease.

Inhibition of p38 mitogen-activated protein kinase improves nitric oxide-mediated vasodilatation and reduces inflammation in hypercholesterolemia.

BACKGROUND: Oxidized low-density lipoprotein reduces endothelial nitric oxide production (an important mediator of vasoregulation) and activates p38 mitogen-activated protein kinase (MAPK), a mediator of vascular inflammation. Animal models of vascular stress have previously predicted improvements in vascular function after p38 MAPK inhibition. We hypothesized that a selective p38α/ß MAPK inhibitor (losmapimod; GW856553) would improve compromised nitric oxide-mediated vasoregulation in patients with hypercholesterolemia. METHODS AND RESULTS: Untreated hypercholesterolemic patients (low-density lipoprotein cholesterol >4.1 mmol/L) were randomized to receive losmapimod 7.5 mg (n=27) or placebo (n=29) twice daily for 28 days. Patients with known vascular disorders (eg, diabetes mellitus, coronary heart disease) were excluded. Forearm blood flow was measured by venous occlusion plethysmography in response to serial intra-arterial infusion of acetylcholine, sodium nitroprusside, and N(G)-monomethyl-L-arginine (L-NMMA). Acetylcholine and L-NMMA responses were significantly impaired (P=0.01 and P=0.03) compared with responses in control subjects (n=12). In hypercholesterolemic patients treated with losmapimod, responses to acetylcholine were improved by 25% (95% confidence interval, 5 to 48; P=0.01), to sodium nitroprusside by 20% (95% confidence interval, 3 to 40; P=0.02), and to L-NMMA by 10% (95% confidence interval, -1 to 23; P=0.07) compared with placebo. C-reactive protein was reduced by 57% (95% confidence interval, -81 to -6%; P<0.05) in patients treated with losmapimod compared with placebo. CONCLUSIONS: Losmapimod improves nitric oxide-mediated vasodilatation in hypercholesterolemic patients, which is consistent with findings in previous translational animal models. These data support the hypothesis that attenuating the inflammatory milieu by inhibiting p38 MAPK activity improves NO activity. This suggests p38 MAPK as a novel target for patients with cardiovascular disease.

Serial MRI characterization of the functional and morphological changes in mouse lung in response to cardiac remodeling following myocardial infarction.

The temporal evolution of heart failure and associated pulmonary congestion in rodent heart failure models has not yet been characterized simultaneously and noninvasively. In this study, MRI was used to assess the serial progression of left-ventricular dysfunction and lung congestion in mice following myocardial infarction (MI). Cardiac and lung (1) H MRI was performed at baseline and every 3 days up to 13 days postsurgery in sham and MI mice. Respiratory parameters and terminal lung mechanics were assessed followed by histological analysis. MRI revealed that the MI induced significant pulmonary congestion/edema as detected by increased MRI signal intensity and was associated with increased lung volume and reduced cardiac contractility. Pulmonary function was also depressed in MI-mice, reflected by a reduced tidal volume and a low minute ventilation rate. Additionally, MI significantly increased lung resistance, markedly reduced lung compliance and total lung capacity and significantly increased lung weights by 57%. Significant correlations were observed between the MRI measured lung congestion, lung volume, ejection fraction, and lung wet-weight parameters. This study demonstrates that MRI may be of significant value in evaluating therapies aimed at primary intervention for lung congestion and secondary prevention of unfavorable cardiac remodeling.

Inhibition of p38 mitogen-activated protein kinase reduces inflammation after coronary vascular injury in humans.

OBJECTIVE: To evaluate whether a p38α/ß mitogen-activated protein kinase inhibitor, SB-681323, would limit the elevation of an inflammatory marker, high-sensitivity C-reactive protein (hsCRP), after a percutaneous coronary intervention (PCI). METHODS AND RESULTS: Coronary artery stents provide benefit by maintaining lumen patency but may incur vascular trauma and inflammation, leading to myocardial damage. A key mediator for such stress signaling is p38 mitogen-activated protein kinase. Patients with angiographically documented coronary artery disease receiving stable statin therapy and about to undergo PCI were randomly selected to receive SB-681323, 7.5 mg (n=46), or placebo (n=46) daily for 28 days, starting 3 days before PCI. On day 3, before PCI, hsCRP was decreased in the SB-681323 group relative to the placebo group (29% lower; P=0.02). After PCI, there was a statistically significant attenuation in the increase in hsCRP in the SB-681323 group relative to the placebo group (37% lower on day 5 [P=0.04]; and 40% lower on day 28 [P=0.003]). There were no adverse safety signals after 28 days of treatment with SB-681323. CONCLUSIONS: In the setting of statin therapy, SB-681323 significantly attenuated the post-PCI inflammatory response, as measured by hsCRP. This inflammatory dampening implicates p38 mitogen-activated protein kinase in the poststent response, potentially defining an avenue to limit poststent restenosis.

Pharmacological inhibition of C-C chemokine receptor 2 decreases macrophage infiltration in the aortic root of the human C-C chemokine receptor 2/apolipoprotein E-/- mouse: magnetic resonance imaging assessment.

UNLABELLED: Purpose- This study assessed the pharmacological effect of a novel selective C-C chemokine receptor (CCR) 2 antagonist (GSK1344386B) on monocyte/macrophage infiltration into atherosclerotic plaque using magnetic resonance imaging (MRI) in an atherosclerotic mouse model. METHODS AND RESULTS: Apolipoprotein E(-/-) mice expressing human CCR2 were fed a Western diet (vehicle group) or a Western diet plus10 mg/kg per day of GSK1344386B (GSK1344386B group). After the baseline MRI, mice were implanted with osmotic pumps containing angiotensin II, 1000 ng/kg per minute, to accelerate lesion formation. After five weeks of angiotensin II administration, mice received ultrasmall superparamagnetic iron oxide, an MRI contrast agent for the assessment of monocyte/macrophage infiltration to the plaque, and underwent imaging. After imaging, mice were euthanized, and the heart and aorta were harvested for ex vivo MRI and histopathological examination. After 5 weeks of dietary dosing, there were no significant differences between groups in body or liver weight or plasma cholesterol concentrations. An in vivo MRI reflected a decrease in ultrasmall superparamagnetic iron oxide contrast agent uptake in the aortic arch of the GSK1344386B group (P<0.05). An ex vivo MRI of the aortic root also reflected decreased ultrasmall superparamagnetic iron oxide uptake in the GSK1344386B group and was verified by absolute iron analysis (P<0.05). Although there was no difference in aortic root lesion area between groups, there was a 30% reduction in macrophage area observed in the GSK1344386B group (P<0.05). CONCLUSIONS: An MRI was used to noninvasively assess the decreased macrophage content in the atherosclerotic plaque after selective CCR2 inhibition.

High FGF23 Levels Failed to Predict Cardiac Hypertrophy in Animal Models of Hyperphosphatemia and Chronic Renal Failure.

Increased fibroblast growth factor 23 (FGF23) levels are an independent predictor for adverse cardiac events suggesting a role as a link that drives cardiomyopathic changes in cardiorenal syndrome. The search for the underlying mechanism driving this interaction has led to the hypothesis that FGF23 causes pathogenic changes in the heart. Increased serum FGF23 has been independently shown to cause increased cardiac morbidity, mortality, and hypertrophy by signalling through FGF receptor 4. This mechanistic concept was based on preclinical studies demonstrating inhibition of FGF23 signaling through FGF4, which led to suppression of left ventricular hypertrophy and fibrosis in a 2-week rat 5/6 nephrectomy study and a 12-week (2%) high-phosphate diet mouse model in which FGF23 levels were markedly elevated. In this report, renal dysfunction was observed in the 5/6 nephrectomy model, and FGF23 levels were significantly elevated, whereas no changes in left ventricular hypertrophy were observed at 2 or 4 weeks postnephrectomy. Mice placed on a high-phosphate diet that did not cause significant renal dysfunction resulted in significantly elevated FGF23 but no changes in left ventricular hypertrophy. The in vivo studies reported here, which were performed to recapitulate the observations of FGF23 as a driver of cardiac hypertrophy, did not lend support to the FGF23-driven cardiac remodelling hypothesis.

Apoptosis signal-regulating kinase 1 inhibition reverses deleterious indoxyl sulfate-mediated endothelial effects.

AIMS: Indoxyl sulfate (IS), a protein-bound uremic toxin, is implicated in endothelial dysfunction, which contributes to adverse cardiovascular events in chronic kidney disease. Apoptosis signal regulating kinase 1 (ASK1) is a reactive oxygen species-driven kinase involved in IS-mediated adverse effects. This study assessed the therapeutic potential of ASK1 inhibition in alleviating endothelial effects induced by IS. MAIN METHODS: IS, in the presence and absence of a selective ASK1 inhibitor (GSK2261818A), was assessed for its effect on vascular reactivity in rat aortic rings, and cultured human aortic endothelial cells where we evaluated phenotypic and mechanistic changes. KEY FINDINGS: IS directly impairs endothelium-dependent vasorelaxation and endothelial cell migration. Mechanistic studies revealed increased production of reactive oxygen species-related markers, reduction of endothelial nitric oxide synthase and increased protein expression of tissue inhibitor of matrix metalloproteinase 1 (TIMP1). IS also increases angiopoietin-2 and tumour necrosis factor α gene expression and promotes transforming growth factor ß receptor abundance. Inhibition of ASK1 ameliorated the increase in oxidative stress markers, promoted autocrine interleukin 8 pro-angiogenic signalling and decreased anti-angiogenic responses at least in part via reducing TIMP1 protein expression. SIGNIFICANCE: ASK1 inhibition attenuated vasorelaxation and endothelial cell migration impaired by IS. Therefore, ASK1 is a viable intracellular target to alleviate uremic toxin-induced impairment in the vasculature.

Chronic inhibition of hypoxia-inducible factor prolyl 4-hydroxylase improves ventricular performance, remodeling, and vascularity after myocardial infarction in the rat.

BACKGROUND: Hypoxia inducible factors (HIFs) are transcription factors that are regulated by HIF-prolyl 4-hydroxylases (PHDs) in response to changes in oxygen tension. Once activated, HIFs play an important role in angiogenesis, erythropoiesis, proliferation, cell survival, inflammation, and energy metabolism. We hypothesized that GSK360A, a novel orally active HIF-PHD inhibitor, could facilitate local and systemic HIF-1 alpha signaling and protect the failing heart after myocardial infarction (MI). METHODS AND RESULTS: GSK360A is a potent (nanomolar) inhibitor of HIF-PHDs (PHD1>PHD2 = PHD3) capable of activating the HIF-1 alpha pathway in a variety of cell types including neonatal rat ventricular myocytes and H9C2 cells. Male rats treated orally with GSK360A (30 mg x kg x d) had a sustained elevation in circulating levels of erythropoietin and hemoglobin and increased hemoxygenase-1 expression in the heart and skeletal muscle. In a rat model of established heart failure with systolic dysfunction induced by ligation of left anterior descending coronary artery, chronic treatment with GSK360A for 28 days prevented the progressive reduction in ejection fraction, ventricular dilation, and increased lung weight, which were observed in the vehicle-treated animals, for up to 3 months. In addition, the microvascular density in the periinfarct region was increased (>2-fold) in GSK360A-treated animals. Treatment was well tolerated (survival was 89% in the GSK360A group vs. 82% in the placebo group). CONCLUSIONS: Chronic post-myocardial infarction treatment with a selective HIF PHD inhibitor (GSK360A) exerts systemic and local effects by stabilizing HIF-1 alpha signaling and improves long-term ventricular function, remodeling, and vascularity in a model of established ventricular dysfunction. These results suggest that HIF-PHD inhibitors may be suitable for the treatment of post-MI remodeling and heart failure.

Inhibition of apoptosis signal-regulating kinase 1 ameliorates left ventricular dysfunction by reducing hypertrophy and fibrosis in a rat model of cardiorenal syndrome.

BACKGROUND: Cardiorenal syndrome (CRS) is a major health burden worldwide in need of novel therapies, as current treatments remain suboptimal. The present study assessed the therapeutic potential of apoptosis signal-regulating kinase 1 (ASK1) inhibition in a rat model of CRS. METHODS: Adult male Sprague-Dawley rats underwent surgery for myocardial infarction (MI) (week 0) followed by 5/6 subtotal nephrectomy (STNx) at week 4 to induce to induce a combined model of heart and kidney dysfunction. At week 6, MI + STNx animals were randomized to receive either 0.5% carboxymethyl cellulose (Vehicle, n = 15, Sham = 10) or G226 (15 mg/kg daily, n = 11). Cardiac and renal function was assessed by echocardiography and glomerular filtration rate (GFR) respectively, prior to treatment at week 6 and endpoint (week 14). Haemodynamic measurements were determined at endpoint prior to tissue analysis. RESULTS: G226 treatment attenuated the absolute change in left ventricular (LV) fractional shortening and posterior wall thickness compared to Vehicle. G226 also attenuated the reduction in preload recruitable stroke work. Increased myocyte cross sectional area, cardiac interstitial fibrosis, immunoreactivity of cardiac collagen-I and III and cardiac TIMP-2 activation, were significantly reduced following G226 treatment. Although we did not observe improvement in GFR, G226 significantly reduced renal interstitial fibrosis, diminished renal collagen-I and -IV, kidney injury molecule-1 immunoreactivity as well as macrophage infiltration and SMAD2 phosphorylation. CONCLUSION: Inhibition of ASK1 ameliorated LV dysfunction and diminished cardiac hypertrophy and cardiorenal fibrosis in a rat model of CRS. This suggests that ASK1 is a critical pathway with therapeutic potential in the CRS setting.