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Previous work showed a role of BNIP3 in myocardial remodeling and progression to HFrEF. We utilized a multiomics approach to unravel BNIP3-related molecular mechanisms in the pathogenesis of HFrEF. BNIP3 knockdown in HFrEF improved glycolysis, pyruvate metabolism, branched-chain amino acid catabolism, and oxidative phosphorylation, and restored endoplasmic reticulum (ER)-mitochondrial (mt) calcium and ion homeostasis. These effects of BNIP3 on cardiac metabolism were related to its interaction and downregulation, and/or phosphorylation, of specific mt-proteins involved in the aforementioned metabolic pathways, including the MICOS and SLC25A families of carrier proteins. BNIP3 affected ER-mt-calcium and ion homeostasis via its interaction-induced VDAC1 dimerization and modulation of VDAC1 phosphorylation at Ser104 and Ser241, and the downregulation of LETM1. At the ER level, BNIP3 interacted with the enzyme SERCA2a and the PKA signaling complex, leading to the downregulation of SERCA2a and PKA-mediated Ser16 phospholamban phosphorylation. Additionally, BNIP3 attenuated AMPK and PRKCE activity by modulating AMPK phosphorylation at Ser485/491 and Ser377 residues, and PRKCE phosphorylation at Thr521 and Thr710 residues. BNIP3 also interacted with sarcomeric, cytoskeletal, and cellular transcription and translation proteins, and affected their expression and/or phosphorylation. In conclusion, BNIP3 modulates multiple pathobiological processes and constitutes an attractive therapeutic target in HFrEF.

In response to an injury, such as myocardial infarction, prolonged hypertension or a cardiotoxic agent, the heart initially adapts through the activation of signal transduction pathways, to counteract, in the short-term, for the cardiac myocyte loss and or the increase in wall stress. However, prolonged activation of these pathways becomes detrimental leading to the initiation and propagation of cardiac remodeling leading to changes in left ventricular geometry and increases in left ventricular volumes; a phenotype seen in patients with systolic heart failure (HF). Here, we describe the creation of a rat model of pressure overload induced moderate remodeling and early systolic dysfunction (MOD) by ascending aortic banding (AAB) via a vascular clip with an internal area of 2 mm 2 . The surgery is performed in 200 g Sprague-Dawley rats. The MOD HF phenotype develops at 8-12 weeks after AAB and is characterized noninvasively by means of echocardiography. Previous work suggests the activation of signal transduction pathways and altered gene expression and post-translational modification of proteins in the MOD HF phenotype that mimic those seen in human systolic HF; therefore, making the MOD HF phenotype a suitable model for translational research to identify and test potential therapeutic anti-remodeling targets in HF. The advantages of the MOD HF phenotype compared to the overt systolic HF phenotype is that it allows for the identification of molecular targets involved in the early remodeling process and the early application of therapeutic interventions. The limitation of the MOD HF phenotype is that it may not mimic the spectrum of diseases leading to systolic HF in human. Moreover, it is a challenging phenotype to create, as the AAB surgery is associated with high mortality and failure rates with only 20% of operated rats developing the desired HF phenotype.

Patients with advanced congestive heart failure (CHF) or chronic kidney disease often have increased angiotensin II (Ang II) levels and cachexia. We previously demonstrated that Ang II, via its type 1 receptor, causes muscle protein breakdown and apoptosis and inhibits satellite cell (SC) proliferation and muscle regeneration, likely contributing to cachexia in CHF and chronic kidney disease. In contrast, Ang II, via its type 2 receptor (AT2R) expression, is robustly induced during SC differentiation, and it potentiates muscle regeneration. To understand the mechanisms regulating AT2R expression and its potential role in muscle regeneration in chronic diseases, we used a mouse model of CHF and found that muscle regeneration was markedly reduced and that this was accompanied by blunted increase of AT2R expression. We performed AT2R promoter reporter analysis during satellite cell differentiation and found that the 70 bp upstream of the AT2R transcription start site contain a core promoter region, and regions upstream of 70 bp to 3 kbp are dispensable for AT2R induction. Instead, AT2R intron 2 acts as a transcriptional enhancer during SC differentiation. Further deletion/mutation analysis revealed that multiple transcription factor binding sites in the +286/+690 region within intron 2 coordinately regulate AT2R transcription. Importantly, +286/+690 enhancer activity was suppressed in CHF mouse skeletal muscle, suggesting that AT2R expression is suppressed in CHF via inhibition of AT2R intronic enhancer activity, leading to lowered muscle regeneration. Thus targeting intron 2 enhancer element could lead to the development of a novel intervention to increase AT2R expression in SCs and potentiate skeletal muscle regenerative capacity in chronic diseases., (© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.)

Importance: Patients with chronic kidney disease (CKD) are at an increased risk of cardiovascular disease (CVD) compared with the general population. Prior studies have produced contradictory results on the association of dietary sodium intake with risk of CVD, and this relationship has not been investigated in patients with CKD., Objective: To evaluate the association between urinary sodium excretion and clinical CVD events among patients with CKD., Design, Setting, and Participants: A prospective cohort study of patients with CKD from 7 locations in the United States enrolled in the Chronic Renal Insufficiency Cohort Study and followed up from May 2003 to March 2013., Exposures: The cumulative mean of urinary sodium excretion from three 24-hour urinary measurements and calibrated to sex-specific mean 24-hour urinary creatinine excretion., Main Outcomes and Measures: A composite of CVD events defined as congestive heart failure, stroke, or myocardial infarction. Events were reported every 6 months and confirmed by medical record adjudication., Results: Among 3757 participants (mean age, 58 years; 45% women), 804 composite CVD events (575 heart failure, 305 myocardial infarction, and 148 stroke) occurred during a median 6.8 years of follow-up. From lowest (<2894 mg/24 hours) to highest (≥4548 mg/24 hours) quartile of calibrated sodium excretion, 174, 159, 198, and 273 composite CVD events occurred, and the cumulative incidence was 18.4%, 16.5%, 20.6%, and 29.8% at median follow-up. In addition, the cumulative incidence of CVD events in the highest quartile of calibrated sodium excretion compared with the lowest was 23.2% vs 13.3% for heart failure, 10.9% vs 7.8% for myocardial infarction, and 6.4% vs 2.7% for stroke at median follow-up. Hazard ratios of the highest quartile compared with the lowest quartile were 1.36 (95% CI, 1.09-1.70; P = .007) for composite CVD events, 1.34 (95% CI, 1.03-1.74; P = .03) for heart failure, and 1.81 (95% CI, 1.08-3.02; P = .02) for stroke after multivariable adjustment. Restricted cubic spline analyses of the association between sodium excretion and composite CVD provided no evidence of a nonlinear association (P = .11) and indicated a significant linear association (P < .001)., Conclusions and Relevance: Among patients with CKD, higher urinary sodium excretion was associated with increased risk of CVD., Competing Interests: Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Steigerwalt reported having received support from Medtronic as a principal investigator for 2 trials and travel expenses from ATCOR. Dr Townsend reported having received support from Medtronic, Janssen, Relypsa, and UpToDate. No other disclosures were reported.

Background: Chronic kidney disease is a risk factor for heart failure (HF). Patients with chronic kidney disease without diagnosed HF have an increased burden of symptoms characteristic of HF. It is not known whether these symptoms are associated with occurrence of new onset HF., Methods and Results: We studied the association of a modified Kansas City Cardiomyopathy Questionnaire with newly identified cases of hospitalized HF among 3093 participants enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study who did not report HF at baseline. The annually updated Kansas City Cardiomyopathy Questionnaire score was categorized into quartiles (Q1-4) with the lower scores representing the worse symptoms. Multivariable-adjusted repeated measure logistic regression models were adjusted for demographic characteristics, clinical risk factors for HF, N-terminal probrain natriuretic peptide level and left ventricular hypertrophy, left ventricular systolic and diastolic dysfunction. Over a mean (±SD) follow-up period of 4.3±1.6 years, there were 211 new cases of HF hospitalizations. The risk of HF hospitalization increased with increasing symptom quartiles; 2.62, 1.85, 1.14, and 0.74 events per 100 person-years, respectively. The median number of annual Kansas City Cardiomyopathy Questionnaire assessments per participant was 5 (interquartile range, 3-6). The annually updated Kansas City Cardiomyopathy Questionnaire score was independently associated with higher risk of incident HF hospitalization in multivariable-adjusted models (odds ratio, 3.30 [1.66-6.52]; P=0.001 for Q1 compared with Q4)., Conclusions: Symptoms characteristic of HF are common in patients with chronic kidney disease and are associated with higher short-term risk for new hospitalization for HF, independent of level of kidney function, and other known HF risk factors., (© 2015 American Heart Association, Inc.)

Background: Heart failure (HF), a debilitating disease in a growing number of adults, exerts structural and neurohormonal changes in both cardiac and skeletal muscles. However, these alterations and their affected molecular pathways remain uncharacterized. Disease progression is known to transform skeletal muscle fiber composition by unknown mechanisms. In addition, perturbation of specific hormonal pathways, including those involving skeletal muscle insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-binding protein-5 (IGFB-5) appears to occur, likely affecting muscle metabolism and regeneration. We hypothesized that changes in IGF-1 and IGFB-5 mRNA levels correlate with the transformation of single-skeletal muscle fiber myosin heavy chain isoforms early in disease progression, making these molecules valuable markers of skeletal muscle changes in heart failure., Materials and Methods: To investigate these molecules during "early" events in HF patients, we obtained skeletal muscle biopsies from New York Heart Association (NYHA) Class II HF patients and controls for molecular analyses of single fibers, and we also quantified isometric strength and muscle size., Results: There were more (P < 0.05) single muscle fibers coexpressing two or more myosin heavy chains in the HF patients (30% ± 7%) compared to the control subjects (13% ± 2%). IGF-1 and IGFBP-5 expression was fivefold and 15-fold lower in patients with in HF compared to control subjects (P < 0.05), respectively. Strikingly, there was a correlation in IGF-1 expression and muscle cross-sectional area (P < 0.05) resulting in a decrease in whole-muscle quality (P < 0.05) in the HF patients, despite no significant decrease in isometric strength or whole-muscle size., Conclusion: These data indicate that molecular alterations in myosin heavy chain isoforms, IGF-1, and IGFB-5 levels precede the gross morphological and functional deficits that have previously been associated with HF, and may be used as a predictor of functional outcome in patients.

Background: Epidemiological studies typically diagnose heart failure (HF) at the time of hospitalization, and have not evaluated the prevalence of HF symptoms in CKD patients without a prior HF diagnosis., Methods and Results: We modified the Kansas City Cardiomyopathy Questionnaire (KCCQ) to detect and quantify symptoms characteristic of HF (dyspnea, edema, and fatigue) among 2883 chronic kidney disease (CKD) patients without diagnosed heart failure in the Chronic Renal Insufficiency Cohort (CRIC). The KCCQ is a 23-item instrument that quantifies the impact of dyspnea, fatigue, and edema on physical, social, and emotional functions (scored 0 to 100). The median KCCQ score was 92, and 25% had KCCQ scores <75. Compared with cystatin C‑based estimated glomerular filtration rate >50 mL·min·1.73 m(2) (reference), estimated glomerular filtration rate 40 to 50, 30 to 40, and <30 were independently associated with lower KCCQ scores (<75); adjusted odds ratios and (95% CI): 1.38 (1.06-1.78), 1.39 (1.09-1.82), and 2.15 (1.54-3.00), respectively. Lower hemoglobin (Hb) levels also had independent associations with KCCQ <75: Hb >14 g/dL (reference), Hb 13 to 14 g/dL (1.03; 0.76-1.40), Hb 12 to 13 g/dL (1.41; 1.04-1.91), Hb 11 to 12 g/dL (1.56; 1.12-2.16); and Hb <1 g/dL (1.65; 1.15-2.37)., Conclusion: CKD patients without diagnosed HF have a substantial burden of symptoms characteristic of HF, particularly among those with lower estimated glomerular filtration rate and hemoglobin levels., (Published by Elsevier Inc.)

Purpose of Review: Congestive heart failure is increasing in prevalence and represents a major public health problem. The syndrome of advanced heart failure often includes muscle wasting, commonly termed cardiac cachexia, which is a predictor of poor outcome. Mechanisms of cardiac cachexia are poorly understood, but there is recent evidence that increased angiotensin II, interacting with the insulin-like growth factor-1 system, plays an important role., Recent Findings: In animals, angiotensin II produces weight loss through a pressor-independent mechanism, accompanied by decreased levels of circulating and skeletal muscle insulin-like growth factor-1 and increased mRNA levels of the ubiquitin ligases atrogin-1 and Muscle RING finger-1 in skeletal muscle. Reduced insulin-like growth factor-1 action in muscle leads to increased proteolysis, through the ubiquitin-proteasome pathway, and increased apoptosis. These changes are blocked by muscle-specific expression of insulin-like growth factor-1, likely to be via the Akt/mTOR/p70S6K signaling pathway., Summary: The link between insulin-like growth factor-1, the ubiquitin-proteasome pathway, and angiotensin II effects has widespread clinical implications for the understanding of mechanisms of catabolic conditions. Therapeutic interventions targeting cross-talk mechanisms between angiotensin II and insulin-like growth factor-1 effects could provide new approaches for the treatment of muscle wasting.

Metabolic remodeling plays an important role in the pathophysiology of heart failure (HF). We sought to characterize metabolic remodeling and implicated signaling pathways in two rat models of early systolic dysfunction (MOD), and overt systolic HF (SHF). Tandem mass tag-labeled shotgun proteomics, phospho-(p)-proteomics, and non-targeted metabolomics analyses were performed in left ventricular myocardium tissue from Sham, MOD, and SHF using liquid chromatography–mass spectrometry, n = 3 biological samples per group. Mitochondrial proteins were predominantly down-regulated in MOD (125) and SHF (328) vs. Sham. Of these, 82% (103/125) and 66% (218/328) were involved in metabolism and respiration. Oxidative phosphorylation, mitochondrial fatty acid β-oxidation, Krebs cycle, branched-chain amino acids, and amino acid (glutamine and tryptophan) degradation were highly enriched metabolic pathways that decreased in SHF > MOD. Glycogen and glucose degradation increased predominantly in MOD, whereas glycolysis and pyruvate metabolism decreased predominantly in SHF. PKA signaling at the endoplasmic reticulum–mt interface was attenuated in MOD, whereas overall PKA and AMPK cellular signaling were attenuated in SHF vs. Sham. In conclusion, metabolic remodeling plays an important role in myocardial remodeling. PKA and AMPK signaling crosstalk governs metabolic remodeling in progression to SHF. [ABSTRACT FROM AUTHOR]

The mitochondria are mostly abundant in the heart, a beating organ of high- energy demands. Their function extends beyond being a power plant of the cell including redox balance, ion homeostasis and metabolism. They are dynamic organelles that are tethered to neighboring structures, especially the endoplasmic reticulum. Together, they constitute a functional unit implicated in complex physiological and pathophysiological processes. Their topology in the cell, the cardiac myocyte in particular, places them at the hub of signaling and calcium homeostasis, making them master regulators of cell survival or cell death. Perturbations in mitochondrial function play a central role in the pathophysiology of myocardial remodeling and progression of heart failure. In this minireview, we summarize important pathophysiological mechanisms, pertaining to mitochondrial morphology, dynamics and function, which take place in compensated hypertrophy and in progression to overt systolic heart failure. Published work in the last few years has expanded our understanding of these important mechanisms; a key prerequisite to identifying therapeutic strategies targeting mitochondrial dysfunction in heart failure. [ABSTRACT FROM AUTHOR]

Introduction: Patients with advanced congestive heart failure (CHF) or chronic kidney disease (CKD) often have increased angiotensin II (Ang II) levels and cachexia. We previously demonstrated that Ang II type 2 receptor (AT2R) potentiates skeletal muscle stem (satellite) cell (SC) differentiation and muscle regenerative capacity. However, mechanisms whereby AT2R regulates SC differentiation, and its potential involvement in cachexia development remain unknown. Methods: AT2R siRNA was transfected to primary cultured SCs and the changes in AT2R downstream signaling pathways were analyzed by phosphoprotein array, on which 1318 unique antibodies against various phosphoproteins are spotted. The identified signaling pathway was pharmacologically and genetically manipulated both in vitro and in vivo, and the skeletal muscle regenerative capacity was analyzed by qRT-PCR, western blotting and immunohistochemistry. Results: We found that 20 phosphoproteins were upregulated (>1.4 fold change) and 28 were downregulated (<0.7 fold change) after AT2R knockdown. Among these proteins, we found an increase in p-Akt (Ser473) and p-GSK-3β (Ser9) during SC differentiation both in vitro (SC culture) and in vivo (injury-induced skeletal muscle regeneration), suggesting an activation of β-catenin pathway. Consistently, β-catenin TCF/LEF reporter (TOPFlash) assay showed an increase in β-catenin activity both in vitro and in vivo. siRNA-mediated AT2R knockdown in cultured SCs significantly decreased p-Akt (Ser473) and p-GSK-3β(Ser9) phosphorylation and TOPFlash activity, and importantly, inhibited SC differentiation. Treatment of AT2R knocked-down SCs with GSK-3βinhibitor BIO or Wnt3A restored β-catenin activity, resulting in the restoration of SC differentiation. These data indicate that AT2R positively regulates SC differentiation via Akt/GSK-3β/β-catenin pathway. Importantly, we found that skeletal muscle regeneration was reduced (decreased regenerating myofiber size and myogenin/desmin expression) in a mouse myocardial infarction model of CHF, concomitant with marked reduction in AT2R expression and decreased β-catenin activity. In these mice, hindlimb injection of BIO restored β-catenin activity and muscle regenerative capacity. Conclusions: These data indicate that AT2R/Akt/GSK-3β/β-catenin pathway plays a critical role in regulating SC differentiation and muscle regeneration, and could be a novel therapeutic target in wasting disorders such as CHF and CKD. [ABSTRACT FROM AUTHOR]

Introduction: Patients with advanced congestive heart failure (CHF) or chronic kidney disease (CKD) often have increased angiotensin II (Ang II) levels and cachexia. We previously demonstrated that Ang II infusion in rodents causes skeletal muscle wasting, likely contributing to cachexia in CHF and CKD. We also demonstrated that Ang II type 1 receptor (AT1R) activation in skeletal muscle stem (satellite) cells (SCs) inhibits SC proliferation and muscle regenerative capacity. We hypothesize that Ang II-mediated SC inhibition contributes to the development of muscle wasting in high Ang II condition. Methods: We generated tamoxifen-inducible, SC-specific AT1R knockout mice (SC-AT1R-/-; generated by crossing SC-specific Pax7CreERand AT1R floxed mice). By breeding SC-AT1R-/-and control mice with Cre-reporter mouse line, SCs and their progenies were labeled with EYFP. These mice were infused with Ang II (1.5 μg/kg/min) and muscle regeneration and wasting were analyzed by qRT-PCR, western blotting and immunohistochemistry. Results: Ang II reduced skeletal muscle regeneration in vivo, indicated by the reduced number of regenerating myofibers in hindlimb muscles after cardiotoxin injury (71.9% decrease vs. control, p<0.001), and by the reduction of SC proliferation/differentiation markers MyoD and myogenin (56.5% and 62.5% decrease, respectively, by qRT-PCR, p<0.001). In contrast, hindlimb muscles of SC-AT1R-/-mice were protected against Ang II-mediated reduction in skeletal muscle regenerative capacity; the number of regenerating myofibers and expression of MyoD and myogenin were restored. Ang II inhibited primary cultured SC proliferation via AT1R signaling in vitro, and SC proliferative capacity was restored in AT1R null SCs. Importantly, we found that there was a significant recovery from Ang II-induced muscle wasting in SC-AT1R-/-mice. SC lineage tracing (EYFP labeling) and gene expression analyses revealed that AT1R-deficient SCs had significantly higher regenerative capacity in high Ang II condition, leading to increased number of newly formed/repaired myofibers (12.4±2.7% of total myofibers in SC-AT1R-/-and ND in control, p<0.001), resulting in the restoration of muscle mass and cross sectional area in SC-AT1R-/-mice. Conclusions: These data indicate that inhibition of AT1R signaling in SCs could have a therapeutic potential to treat muscle wasting in chronic diseases with high Ang II, such as CHF and CKD. [ABSTRACT FROM AUTHOR]

Introduction: Skeletal muscle atrophy occurs via two main systems, namely, autophagy and ubiquitin-proteasome system (UPS). Although we have previously shown that angiotensin II (Ang II) induces skeletal muscle atrophy via UPS activation, little is known about Ang II-mediated autophagy in skeletal muscle. Therefore, we aimed to investigate whether Ang II modulates autophagy in skeletal muscle in mice. Methods: FVB mice (10 -12 weeks-old) were infused with Ang II (1.0 μg/kg/day) for 7 days; pair-fed (PF) group was infused with saline and served as control. Tibialis anterior (TA) muscle was used for western blot, RT-qPCR, mitochondrial respiration assay, as well as enzymatic activity, and extensor digitorum longus muscle was used for Transmission Electronic Microscopy (TEM). Results: Ang II infusion reduced mouse body weight (12%, p=0.0001) and caused muscle loss (p&lt0.05). Ang II inhibited phosphorylation of UKL1 at Ser317 (p-ULK1), leading to suppressed p-beclin1 (Ser14) and p-ATG14 (Ser29), critical proteins to initiate autophagosome formation. Ang II also blunted the LC3B-II conversion and increased p62/SQTSM1 protein expression (hallmark of autophagosome cargo accumulation), whereas lysosomal enzymatic activities (cathepsins B and L) were not altered. These data indicate that Ang II impairs the initial step of autophagosome formation. TEM analysis revealed that Ang II caused an accumulation of mitochondria with abnormal cristae and swollen morphology, likely due to reduced autophagosomes. These changes were associated with increased PINK1 protein expression, decreased PGC-1α gene and protein expressions. Importantly, Ang II markedly reduced the oxygen consumption rate in isolated mitochondria. These data strongly indicate that Ang II impairs mitochondrial function and its clearance, which may potentially induce muscle wasting. Conclusions: Here we show that Ang II inhibits critical molecules involved in the initiation of autophagy, which leads to suppression autophagosome formation (e.g. reduced LC3B-II conversion). This likely promotes an accumulation of damaged mitochondria and ubiquitinated proteins. Our data strongly suggest that autophagy is critical to induce skeletal muscle deregulation in Ang II-infused mice and raises the possibility of a new therapeutic target in wasting disorders such as heart failure. [ABSTRACT FROM AUTHOR]

Abstract: Cachexia is a serious complication of many chronic diseases, such as congestive heart failure (CHF) and chronic kidney disease (CKD). Many factors are involved in the development of cachexia, and there is increasing evidence that angiotensin II (Ang II), the main effector molecule of the renin–angiotensin system (RAS), plays an important role in this process. Patients with advanced CHF or CKD often have increased Ang II levels and cachexia, and angiotensin-converting enzyme (ACE) inhibitor treatment improves weight loss. In rodent models, an increase in systemic Ang II leads to weight loss through increased protein breakdown, reduced protein synthesis in skeletal muscle and decreased appetite. Ang II activates the ubiquitin–proteasome system via generation of reactive oxygen species and via inhibition of the insulin-like growth factor-1 signaling pathway. Furthermore, Ang II inhibits 5′ AMP-activated protein kinase (AMPK) activity and disrupts normal energy balance. Ang II also increases cytokines and circulating hormones such as tumor necrosis factor-α, interleukin-6, serum amyloid-A, glucocorticoids and myostatin, which regulate muscle protein synthesis and degradation. Ang II acts on hypothalamic neurons to regulate orexigenic/anorexigenic neuropeptides, such as neuropeptide-Y, orexin and corticotropin-releasing hormone, leading to reduced appetite. Also, Ang II may regulate skeletal muscle regenerative processes. Several clinical studies have indicated that blockade of Ang II signaling via ACE inhibitors or Ang II type 1 receptor blockers prevents weight loss and improves muscle strength. Thus the RAS is a promising target for the treatment of muscle atrophy in patients with CHF and CKD. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting. [Copyright &y& Elsevier]

Abstract: Both the sympathetic nervous system and the proinflammatory cytokine interleukin-18 (IL-18) play key roles in the pathophysiology of the hypertrophied failing heart. IL-18 binding protein (IL-18BP), a natural inhibitor of IL-18, counters its biological effects. β-AR stimulation induces IL-18 expression, but whether it also regulates IL-18BP is not known. Here we demonstrate that the β-AR agonist isoproterenol (ISO) increases steady state IL-18BP mRNA and protein levels in adult mouse cardiomyocytes in a β2-AR-dependent manner. We cloned mouse Il18bp 5′cis-regulatory region, and identified putative CREB and C/EBPβ transcription factor-binding sites. Forced expression of mutant CREB or C/EBPβ knockdown markedly attenuated ISO-induced Il18bp transcription and deletion or mutation of CREB and C/EBP motifs in the Il18bp promoter reduced ISO-induced promoter-reporter gene activity. ISO induced CREB and C/EBPβ activation in cardiomyocytes via PI3K/Akt and ERK1/2. Importantly, ISO-induced hypertrophy in vitro was dependent on IL-18 induction as it was blunted by IL-18 neutralizing antibodies and forced expression of IL-18BP. Moreover, ISO-induced hypertrophy was markedly attenuated in IL-18 null and IL-18BP transgenic mice. These data support the novel concept that β-AR activation, in addition to inducing cardiomyocyte hypertrophy via IL-18, concomitantly induces a countering effect by stimulating IL-18BP expression, and that ISO-induced cardiomyocyte hypertrophy may result from a net effect of IL-18 and IL-18BP induction. [Copyright &y& Elsevier]

Abstract: The transmembrane glycoprotein extracellular matrix metalloproteinase inducer (EMMPRIN), and the pleiotropic proinflammatory cytokine interleukin (IL)-18, play critical roles in myocardial remodeling, by inducing matrix degrading metalloproteinases (MMPs). Previously we showed that IL-18 induces EMMPRIN expression in cardiomyocytes via MyD88/IRAK4/TRAF6/JNK-dependent Sp1 activation. Here in reciprocal studies we demonstrate that EMMPRIN is a potent inducer of IL-18 transcription, protein expression and protein secretion in primary mouse cardiomyocytes. We show for the first time that EMMPRIN stimulates the activation of NF-κB, AP-1, CREB, and ATF-2 in cardiomyocytes, and induces IL-18 expression via Rac1-dependent PI3K/Akt/IKK/NF-κB and MKK7/JNK/AP-1 signaling. Moreover, EMMPRIN induces robust time-dependent induction of various MMP mRNAs. EMMPRIN also induces the mRNA of TIMPs 1 and 3, but in a delayed fashion. These results suggest that IL-18-induced EMMPRIN expression may favor net MMP expression and ECM destruction, and thus identify both as potential therapeutic targets in countering adverse myocardial remodeling. [Copyright &y& Elsevier]