Evren Caglayan

Ischemic Preconditioning for Prevention of Contrast Medium–Induced Nephropathy Randomized Pilot RenPro Trial (Renal Protection Trial)

Background— Contrast medium–induced acute kidney injury is associated with substantial morbidity and mortality. The underlying mechanism has been attributed in part to ischemic kidney injury. The aim of this randomized, double-blind, sham-controlled trial was to assess the impact of remote ischemic preconditioning on contrast medium–induced acute kidney injury.nnMethods and Results— Patients with impaired renal function (serum creatinine >1.4 mg/dL or estimated glomerular filtration rate <60 mL · min−1 · 1.73 m−2) undergoing elective coronary angiography were randomized in a 1:1 ratio to standard care with (n=50) or without ischemic preconditioning (n=50; intermittent arm ischemia through 4 cycles of 5-minute inflation and 5-minute deflation of a blood pressure cuff). Overall, both study groups were at high risk of developing contrast medium–induced acute kidney injury according to the Mehran risk score. The primary end point was the incidence of contrast medium–induced kidney injury, defined as an increase in serum creatinine ≥25% or ≥0.5 mg/dL above baseline at 48 hours after contrast medium exposure. Contrast medium–induced acute kidney injury occurred in 26 patients (26%), 20 (40%) in the control group and 6 (12%) in the remote ischemic preconditioning group (odds ratio, 0.21; 95% confidence interval, 0.07–0.57; P =0.002). No major adverse events were related to remote ischemic preconditioning.nnConclusions— Remote ischemic preconditioning before contrast medium use prevents contrast medium–induced acute kidney injury in high-risk patients. Our findings merit a larger trial to establish the effect of remote ischemic preconditioning on clinical outcomes.nnClinical Trial Registration— URL: [http://www.germanctr.de][1]. Unique identifier: U1111-1118-8098.nn# Clinical Perspective {#article-title-44}nn [1]: http://www.germanctr.de.Background— Contrast medium–induced acute kidney injury is associated with substantial morbidity and mortality. The underlying mechanism has been attributed in part to ischemic kidney injury. The aim of this randomized, double-blind, sham-controlled trial was to assess the impact of remote ischemic preconditioning on contrast medium–induced acute kidney injury. Methods and Results— Patients with impaired renal function (serum creatinine >1.4 mg/dL or estimated glomerular filtration rate <60 mL · min−1 · 1.73 m−2) undergoing elective coronary angiography were randomized in a 1:1 ratio to standard care with (n=50) or without ischemic preconditioning (n=50; intermittent arm ischemia through 4 cycles of 5-minute inflation and 5-minute deflation of a blood pressure cuff). Overall, both study groups were at high risk of developing contrast medium–induced acute kidney injury according to the Mehran risk score. The primary end point was the incidence of contrast medium–induced kidney injury, defined as an increase in serum creatinine ≥25% or ≥0.5 mg/dL above baseline at 48 hours after contrast medium exposure. Contrast medium–induced acute kidney injury occurred in 26 patients (26%), 20 (40%) in the control group and 6 (12%) in the remote ischemic preconditioning group (odds ratio, 0.21; 95% confidence interval, 0.07–0.57; P=0.002). No major adverse events were related to remote ischemic preconditioning. Conclusions— Remote ischemic preconditioning before contrast medium use prevents contrast medium–induced acute kidney injury in high-risk patients. Our findings merit a larger trial to establish the effect of remote ischemic preconditioning on clinical outcomes. Clinical Trial Registration— URL: http://www.germanctr.de. Unique identifier: U1111-1118-8098.

Remote Ischemic Preconditioning and Renoprotection: From Myth to a Novel Therapeutic Option?

There is currently no effective prophylactic regimen available to prevent contrast-induced AKI (CI-AKI), a frequent and life-threatening complication after cardiac catheterization. Therefore, novel treatment strategies are required to decrease CI-AKI incidence and to improve clinical outcomes in these patients. Remote ischemic preconditioning (rIPC), defined as transient brief episodes of ischemia at a remote site before a subsequent prolonged ischemia/reperfusion injury of the target organ, is an adaptational response that protects against ischemic and reperfusion insult. Indeed, several studies demonstrated the tissue-protective effects of rIPC in various target organs, including the kidneys. In this regard, rIPC may offer a novel noninvasive and virtually cost-free treatment strategy for decreasing CI-AKI incidence. This review evaluates the current experimental and clinical evidence for rIPC as a potential renoprotective strategy, and discusses the underlying mechanisms and key areas for future research.

Profilin-1 Is Expressed in Human Atherosclerotic Plaques and Induces Atherogenic Effects on Vascular Smooth Muscle Cells

Background Profilin-1 is an ubiquitous actin binding protein. Under pathological conditions such as diabetes, profilin-1 levels are increased in the vascular endothelium. We recently demonstrated that profilin-1 overexpression triggers indicators of endothelial dysfunction downstream of LDL signaling, and that attenuated expression of profilin-1 confers protection from atherosclerosis in vivo. Methodology Here we monitored profilin-1 expression in human atherosclerotic plaques by immunofluorescent staining. The effects of recombinant profilin-1 on atherogenic signaling pathways and cellular responses such as DNA synthesis (BrdU-incorporation) and chemotaxis (modified Boyden-chamber) were evaluated in cultured rat aortic and human coronary vascular smooth muscle cells (VSMCs). Furthermore, the correlation between profilin-1 serum levels and the degree of atherosclerosis was assessed in humans. Principal Findings In coronary arteries from patients with coronary heart disease, we found markedly enhanced profilin expression in atherosclerotic plaques compared to the normal vessel wall. Stimulation of rat aortic and human coronary VSMCs with recombinant profilin-1 (10−6 M) in vitro led to activation of intracellular signaling cascades such as phosphorylation of Erk1/2, p70S6 kinase and PI3K/Akt within 10 minutes. Furthermore, profilin-1 concentration-dependently induced DNA-synthesis and migration of both rat and human VSMCs, respectively. Inhibition of PI3K (Wortmannin, LY294002) or Src-family kinases (SU6656, PP2), but not PLCγ (U73122), completely abolished profilin-induced cell cycle progression, whereas PI3K inhibition partially reduced the chemotactic response. Finally, we found that profilin-1 serum levels were significantly elevated in patients with severe atherosclerosis in humans (p<0.001 vs. no atherosclerosis or control group). Conclusions Profilin-1 expression is significantly enhanced in human atherosclerotic plaques compared to the normal vessel wall, and the serum levels of profilin-1 correlate with the degree of atherosclerosis in humans. The atherogenic effects exerted by profilin-1 on VSMCs suggest an auto-/paracrine role within the plaque. These data indicate that profilin-1 might critically contribute to atherogenesis and may represent a novel therapeutic target.

Disruption of Platelet-Derived Growth Factor–Dependent Phosphatidylinositol 3-Kinase and Phospholipase Cγ 1 Activity Abolishes Vascular Smooth Muscle Cell Proliferation and Migration and Attenuates Neointima Formation In Vivo

OBJECTIVESnWe tested the hypothesis whether selective blunting of platelet-derived growth factor (PDGF)-dependent vascular smooth muscle cell (VSMC) proliferation and migration is sufficient to prevent neointima formation after vascular injury.nnnBACKGROUNDnTo prevent neointima formation and stent thrombosis after coronary interventions, it is essential to inhibit VSMC proliferation and migration without harming endothelial cell function. The role of PDGF-a potent mitogen and chemoattractant for VSMC that does not affect endothelial cells-for neointima formation remains controversial.nnnMETHODSnTo decipher the signaling pathways that control PDGF beta receptor (βPDGFR)-driven VSMC proliferation and migration, we characterized 2 panels of chimeric CSF1R/βPDGFR mutants in which the binding sites for βPDGFR-associated signaling molecules (Src, phosphatidylinositol 3-kinase [PI3K], GTPase activating protein of ras, SHP-2, phospholipase Cγ 1 [PLCγ]) were individually mutated. Based on in vitro results, the importance of PDGF-initiated signals for neointima formation was investigated in genetically modified mice.nnnRESULTSnOur results indicate that the chemotactic response to PDGF requires the activation of Src, PI3K, and PLCγ, whereas PDGF-dependent cell cycle progression is exclusively mediated by PI3K and PLCγ. These 2 signaling molecules contribute to signal relay of the βPDGFR by differentially regulating cyclin D1 and p27(kip1). Blunting of βPDGFR-induced PI3K and PLCγ signaling by a combination mutant (F3) completely abolished the mitogenic and chemotactic response to PDGF. Disruption of PDGF-dependent PI3K and PLCγ signaling in mice expressing the F3 receptor led to a profound reduction of neointima formation after balloon injury.nnnCONCLUSIONSnSignaling by the activated βPDGFR, particularly through PI3K and PLCγ, is crucial for neointima formation after vascular injury. Disruption of these specific signaling pathways is sufficient to attenuate pathogenic processes such as vascular remodeling in vivo.

Transforming Growth Factor β1 Oppositely Regulates the Hypertrophic and Contractile Response to β-Adrenergic Stimulation in the Heart

Background Neuroendocrine activation and local mediators such as transforming growth factor-β1 (TGF-β1) contribute to the pathobiology of cardiac hypertrophy and failure, but the underlying mechanisms are incompletely understood. We aimed to characterize the functional network involving TGF-β1, the renin-angiotensin system, and the β-adrenergic system in the heart. Methods Transgenic mice overexpressing TGF-β1 (TGF-β1-Tg) were treated with a β-blocker, an AT1-receptor antagonist, or a TGF-β-antagonist (sTGFβR-Fc), were morphologically characterized. Contractile function was assessed by dobutamine stress echocardiography in vivo and isolated myocytes in vitro. Functional alterations were related to regulators of cardiac energy metabolism. Results Compared to wild-type controls, TGF-β1-Tg mice displayed an increased heart-to-body-weight ratio involving both fibrosis and myocyte hypertrophy. TGF-β1 overexpression increased the hypertrophic responsiveness to β-adrenergic stimulation. In contrast, the inotropic response to β-adrenergic stimulation was diminished in TGF-β1-Tg mice, albeit unchanged basal contractility. Treatment with sTGF-βR-Fc completely prevented the cardiac phenotype in transgenic mice. Chronic β-blocker treatment also prevented hypertrophy and ANF induction by isoprenaline, and restored the inotropic response to β-adrenergic stimulation without affecting TGF-β1 levels, whereas AT1-receptor blockade had no effect. The impaired contractile reserve in TGF-β1-Tg mice was accompanied by an upregulation of mitochondrial uncoupling proteins (UCPs) which was reversed by β-adrenoceptor blockade. UCP-inhibition restored the contractile response to β-adrenoceptor stimulation in vitro and in vivo. Finally, cardiac TGF-β1 and UCP expression were elevated in heart failure in humans, and UCP – but not TGF-β1 – was downregulated by β-blocker treatment. Conclusions Our data support the concept that TGF-β1 acts downstream of angiotensin II in cardiomyocytes, and furthermore, highlight the critical role of the β-adrenergic system in TGF-β1-induced cardiac phenotype. Our data indicate for the first time, that TGF-β1 directly influences mitochondrial energy metabolism by regulating UCP3 expression. β-blockers may act beneficially by normalizing regulatory mechanisms of cellular hypertrophy and energy metabolism.

Natriuretic peptides in therapy for decompensated heart failure.

Congestive heart failure (CHF) is the most frequent cause of hospitalization for patients >65xa0years of age and continues to be a major public health burden among the ageing population. Unlike therapy for chronic CHF, there has been only modest progress in medical treatment for acutely decompensated CHF over the past several decades. Moreover, current treatment—consisting generally of diuretic, inotropic, and vasodilatory agents–is associated with many limitations in clinical practice. Natriuretic peptides provide a promising mechanism of action in the pathophysiologic background for CHF treatment based on their vasodilatory and diuretic properties and effective inhibition of the renin–angiotensin–aldosterone system, which is activated early in the course of CHF. Nesiritide (Natrecor® or Noratak®) is a recombinant natriuretic peptide that has the same 32 amino-acid sequence as human B-type natriuretic peptide. Nesiritide has been shown to improve dyspnea and hemodynamic parameters in patients with decompensated heart failure. Ularitide is a synthetic form of urodilatin, a natriuretic peptide hormone secreted by the kidney. Recent clinical studies suggest that ularitide may play a role in managing decompensated heart failure. This review provides an update on natriuretic peptides and their therapeutic potential in advanced CHF.

Controlling cardiomyocyte length: the role of renin and PPAR-γ

AIMSnRenin and peroxisome proliferator-activated receptor (PPAR-γ) interact directly with cardiomyocytes and influence protein synthesis. We investigated their effects and interaction on the size of cardiomyocytes.nnnMETHODS AND RESULTSnEffects of renin and PPAR-γ activation were studied in cultured adult rat ventricular cardiomyocytes, transgenic mice with a cardiomyocyte-restricted knockout of PPAR-γ, and transgenic rats overexpressing renin, TGR(mRen2)27. The length and width of cardiomyocytes were analysed 24 h after administration of factors. Renin caused an unexpected effect on the length of cardiomyocytes that was inhibited by mannose-6-phosphate and monensin, but not by administration of glucose-6-phosphate. Endothelin-1 used as a classical pro-hypertrophic agonist increased cell width but not cell length. Renin caused an activation of p38 and p42/44 mitogen-activated protein (MAP) kinases. The latter activation was impaired by mannose-6-phosphate. Inhibition of p42/44 but not of p38 MAP kinase activation attenuated the effect of renin on cell length. In contrast, activation of PPAR-γ reduced cell length. Feeding wild-type mice with pioglitazone, a PPAR-γ agonist, reduced cell length. Cardiomyocytes isolated from PPAR-γ knockout mice were longer, and their length was not affected by pioglitazone. Cardiomyocytes isolated from TGR(mRen2)27 rats were longer than those of non-transgenic littermates. Cell length was reduced by feeding these mice with pioglitazone. Pioglitazone affected cell length independent of blood pressure.nnnCONCLUSIONnThe length of cardiomyocytes is controlled by the activation of cardiac-specific mannose-6-phosphate/insulin-like growth factor II receptors and activation of PPAR-γ. This type of cell size modification differs from that of any other known pro-hypertrophic agonists.

Impact of Rescue-Thrombolysis during Cardiopulmonary Resuscitation in Patients with Pulmonary Embolism

Background Cardiac arrest in patients with pulmonary embolism (PE) is associated with high morbidity and mortality. Thrombolysis is expected to improve the outcome in these patients. However studies evaluating rescue-thrombolysis in patients with PE are missing, mainly due to the difficulties of clinical diagnosis of PE. We aimed to determine the success influencing factors of thrombolysis during resuscitation in patients with PE. Methodology/Principal Findings We analyzed retrospectively the outcome of 104 consecutive patients with confirmed (nu200a=u200a63) or highly suspected (nu200a=u200a41) PE and monitored cardiac arrest. In all patients rtPA was administrated for thrombolysis during cardiopulmonary resuscitation. In 40 of the 104 patients (38.5%) a return of spontaneous circulation (ROSC) could be achieved successfully. Patients with ROSC received thrombolysis significantly earlier after CPR onset compared to patients without ROSC (13.6±1.2 min versus 24.6±0.8 min; p<0.001). 19 patients (47.5%) out of the 40 patients with initially successful resuscitation survived to hospital discharge. In patients with hospital discharge thrombolysis therapy was begun with a significantly shorter delay after cardiac arrest compared to all other patients (11.0±1.3 vs. 22.5±0.9 min; p<0.001). Conclusion Rescue-thrombolysis should be considered and started in patients with PE and cardiac arrest, as soon as possible after cardiac arrest onset.

Randomized Control of Sympathetic Drive With Continuous Intravenous Esmolol in Patients With Acute ST-Segment Elevation Myocardial Infarction: The BEtA-Blocker Therapy in Acute Myocardial Infarction (BEAT-AMI) Trial

OBJECTIVESnThis study sought to evaluate the role of esmolol-induced tight sympathetic control in patients with ST-segment elevation myocardial infarction (STEMI).nnnBACKGROUNDnElevated sympathetic drive has a detrimental effect on patients with acute STEMI. The effect of beta-blocker-induced heart rate mediated sympathetic control on myocardial damage is unknown.nnnMETHODSnThe authors conducted a prospective, randomized, single-blind trial involving patients with STEMI and successful percutaneous intervention (Killip class I and II). Patients were randomly allocated to heart rate control with intravenous esmolol for 24 h or placebo. The primary outcome was the maximum change in troponin T release as a prognostic surrogate marker for myocardial damage. A total of 101 patients were enrolled in the study.nnnRESULTSnThere was a significant difference between patients allocated to placebo and those who received sympathetic control with esmolol in terms of maximum change in troponin T release: the median serum troponin T concentration increased from 0.2 ng/ml (interquartile range [IQR] 0.1 to 0.7 ng/ml) to 1.3 ng/ml (IQR: 0.6 to 4.7 ng/ml) in the esmolol group and from 0.3 ng/ml (IQR: 0.1 to 1.2 ng/ml) to 3.2 ng/ml (IQR: 1.5 to 5.3 ng/ml) in the placebo group (p = 0.010). The levels of peak creatine kinase (CK), CK subunit MB (CK-MB), and n-terminal brain natriuretic peptide (NT-proBNP) were lower in the esmolol group compared with placebo (CK 619 U/l [IQR: 250-1,701 U/l] vs. 1,308 U/l [IQR: 610 to 2,324 U/l]; pxa0= 0.013; CKMB: 73.5 U/l [IQR: 30 to 192 U/l]xa0vs. 158.5 U/l [IQR: 74 to 281 U/l]; pxa0= 0.005; NT-proBNP: 1,048 pg/ml (IQR: 623 to 2,062 pg/ml] vs. 1,497 pg/ml [IQR: 739 to 3,318 pg/ml]; pxa0= 0.059). Cardiogenic shock occurred in three patients in the placebo group and in none in the esmolol group.nnnCONCLUSIONSnEsmolol treatment statistically significantly decreased troponin T, CK, CK-MB and NT-proBNP release as surrogate markers for myocardial injury in patients with STEMI. (Heart Rate Control After Acute Myocardial Infarction; DRKS00000766).

PI3-kinase/Akt-dependent antiapoptotic signaling by the PDGF α receptor is negatively regulated by Src family kinases

Regulation of growth factor dependent cell survival is crucial for development and disease progression. Here, we report a novel function of Src kinases as a negative regulator of platelet‐derived growth factor (PDGF) dependent cell survival. We characterized a series of PDGF α receptor (PDGFRA) mutants, which lack the binding sites for Src, phosphatidylinositol 3′‐kinase (PI3K), SHP‐2 or phospholipase C‐γ. We found that PDGFRA‐dependent cell survival was mainly mediated through activation of PI3K, and was negatively regulated by Src. Characterization of the downstream signaling events revealed that PI3K activates the protein kinase Akt, which in turn phosphorylates and thus inactivates proapoptotic Forkhead transcription factors. Src phosphorylates the ubiquitin‐ligase c‐Cbl, which is required for degradation of the activated receptor. Consequently, overexpression of c‐Cbl prevented PDGFRA‐mediated cell survival, whereas it did not affect this response, when Src was unable to associate with the receptor. This novel function of Src in antiapoptotic signaling introduces Src kinases as an interesting therapeutic target in apoptosis related diseases.