Cardiotoxicity of the cancer therapeutic agent imatinib mesylate.

Imatinib mesylate (Gleevec) is a small-molecule inhibitor of the fusion protein Bcr-Abl, the causal agent in chronic myelogenous leukemia. Here we report ten individuals who developed severe congestive heart failure while on imatinib and we show that imatinib-treated mice develop left ventricular contractile dysfunction. Transmission electron micrographs from humans and mice treated with imatinib show mitochondrial abnormalities and accumulation of membrane whorls in both vacuoles and the sarco- (endo-) plasmic reticulum, findings suggestive of a toxic myopathy. With imatinib treatment, cardiomyocytes in culture show activation of the endoplasmic reticulum (ER) stress response, collapse of the mitochondrial membrane potential, release of cytochrome c into the cytosol, reduction in cellular ATP content and cell death. Retroviral gene transfer of an imatinib-resistant mutant of c-Abl, alleviation of ER stress or inhibition of Jun amino-terminal kinases, which are activated as a consequence of ER stress, largely rescues cardiomyocytes from imatinib-induced death. Thus, cardiotoxicity is an unanticipated side effect of inhibition of c-Abl by imatinib.

Rapid and Accurate Diagnosis of Dermatophyte Infections Using the DendrisCHIP® Technology.

Dermatophytosis is a superficial fungal infection with an ever-increasing number of patients. Culture-based mycology remains the most commonly used diagnosis, but it takes around four weeks to identify the causative agent. Therefore, routine clinical laboratories need rapid, high throughput, and accurate species-specific analytical methods for diagnosis and therapeutic management. Based on these requirements, we investigated the feasibility of DendrisCHIP® technology as an innovative molecular diagnostic method for the identification of a subset of 13 pathogens potentially responsible for dermatophytosis infections in clinical samples. This technology is based on DNA microarray, which potentially enables the detection and discrimination of several germs in a single sample. A major originality of DendrisCHIP® technology is the use of a decision algorithm for probability presence or absence of pathogens based on machine learning methods. In this study, the diagnosis of dermatophyte infection was carried out on more than 284 isolates by conventional microbial culture and DendrisCHIP®DP, which correspond to the DendrisCHIP® carrying oligoprobes of the targeted pathogens implicated in dermatophytosis. While convergence ranging from 75 to 86% depending on the sampling procedure was obtained with both methods, the DendrisCHIP®DP proved to identify more isolates with pathogens that escaped the culture method. These results were confirmed at 86% by a third method, which was either a specific RT-PCR or genome sequencing. In addition, diagnostic results with DendrisCHIP®DP can be obtained within a day. This faster and more accurate identification of fungal pathogens with DendrisCHIP®DP enables the clinician to quickly and successfully implement appropriate antifungal treatment to prevent the spread and elimination of dermatophyte infection. Taken together, these results demonstrate that this technology is a very promising method for routine diagnosis of dermatophytosis.

Level of G protein-coupled receptor kinase-2 determines myocardial ischemia/reperfusion injury via pro- and anti-apoptotic mechanisms.

RATIONALE: Activation of prosurvival kinases and subsequent nitric oxide (NO) production by certain G protein-coupled receptors (GPCRs) protects myocardium in ischemia/reperfusion injury (I/R) models. GPCR signaling pathways are regulated by GPCR kinases (GRKs), and GRK2 has been shown to be a critical molecule in normal and pathological cardiac function. OBJECTIVE: A loss of cardiac GRK2 activity is known to arrest progression of heart failure (HF), at least in part by normalization of cardiac ß-adrenergic receptor (ßAR) signaling. Chronic HF studies have been performed with GRK2 knockout mice, as well as expression of the ßARKct, a peptide inhibitor of GRK2 activity. This study was conducted to examine the role of GRK2 and its activity during acute myocardial ischemic injury using an I/R model. METHODS AND RESULTS: We demonstrate, using cardiac-specific GRK2 and ßARKct-expressing transgenic mice, a deleterious effect of GRK2 on in vivo myocardial I/R injury with ßARKct imparting cardioprotection. Post-I/R infarct size was greater in GRK2-overexpressing mice (45.0±2.8% versus 31.3±2.3% in controls) and significantly smaller in ßARKct mice (16.8±1.3%, P<0.05). Importantly, in vivo apoptosis was found to be consistent with these reciprocal effects on post-I/R myocardial injury when levels of GRK2 activity were altered. Moreover, these results were reflected by higher Akt activation and induction of NO production via ßARKct, and these antiapoptotic/survival effects could be recapitulated in vitro. Interestingly, selective antagonism of ß(2)ARs abolished ßARKct-mediated cardioprotection, suggesting that enhanced GRK2 activity on this GPCR is deleterious to cardiac myocyte survival. CONCLUSION: The novel effect of reducing acute ischemic myocardial injury via increased Akt activity and NO production adds significantly to the therapeutic potential of GRK2 inhibition with the ßARKct not only in chronic HF but also potentially in acute ischemic injury conditions.

The DendrisCHIP® Technology as a New, Rapid and Reliable Molecular Method for the Diagnosis of Osteoarticular Infections.

Osteoarticular infections are major disabling diseases that can occur after orthopedic implant surgery in patients. The management of these infections is very complex and painful, requiring surgical intervention in combination with long-term antibiotic treatment. Therefore, early and accurate diagnosis of the causal pathogens is essential before formulating chemotherapeutic regimens. Although culture-based microbiology remains the most common diagnosis of osteoarticular infections, its regular failure to identify the causative pathogen as well as its long-term modus operandi motivates the development of rapid, accurate, and sufficiently comprehensive bacterial species-specific diagnostics that must be easy to use by routine clinical laboratories. Based on these criteria, we reported on the feasibility of our DendrisCHIP® technology using DendrisCHIP®OA as an innovative molecular diagnostic method to diagnose pathogen bacteria implicated in osteoarticular infections. This technology is based on the principle of microarrays in which the hybridization signals between oligoprobes and complementary labeled DNA fragments from isolates queries a database of hybridization signatures corresponding to a list of pre-established bacteria implicated in osteoarticular infections by a decision algorithm based on machine learning methods. In this way, this technology combines the advantages of a PCR-based method and next-generation sequencing (NGS) while reducing the limitations and constraints of the two latter technologies. On the one hand, DendrisCHIP®OA is more comprehensive than multiplex PCR tests as it is able to detect many more germs on a single sample. On the other hand, this method is not affected by the large number of nonclinically relevant bacteria or false positives that characterize NGS, as our DendrisCHIP®OA has been designed to date to target only a subset of 20 bacteria potentially responsible for osteoarticular infections. DendrisCHIP®OA has been compared with microbial culture on more than 300 isolates and a 40% discrepancy between the two methods was found, which could be due in part but not solely to the absence or poor identification of germs detected by microbial culture. We also demonstrated the reliability of our technology in correctly identifying bacteria in isolates by showing a convergence (i.e., same bacteria identified) with NGS superior to 55% while this convergence was only 32% between NGS and microbial culture data. Finally, we showed that our technology can provide a diagnostic result in less than one day (technically, 5 h), which is comparatively faster and less labor intensive than microbial cultures and NGS.

Inhibition of angiotensin II Gq signaling augments beta-adrenergic receptor mediated effects in a renal artery stenosis model of high blood pressure.

Chronic ventricular pressure overload states, such as hypertension, and elevated levels of neurohormones (norepinephrine, angiotensin II, endothelin-1) initiate cardiac hypertrophy and dysfunction and share the property of being able to bind to Gq-coupled 7-transmembrane receptors. The goal of the current study was to determine the role of endogenous cardiac myocyte Gq signaling and its role in cardiac hypertrophy and dysfunction during high blood pressure (BP). We induced renal artery stenosis for 8 weeks in control mice and mice expressing a peptide inhibitor of Gq signaling (GqI) using a 2 kidney, 1 clip renal artery stenosis model. 8 weeks following chronic high BP, control mice had cardiac hypertrophy and depressed function. Inhibition of cardiomyocyte Gq signaling did not reverse cardiac hypertrophy but attenuated increases in a profile of cardiac profibrotic genes and genes associated with remodeling. Inhibition of Gq signaling also attenuated the loss of cardiac function. We determined that Gq signaling downstream of angiotensin II receptor stimulation negatively impacted beta-adrenergic receptor (AR) responses and inhibition of Gq signaling was sufficient to restore betaAR-mediated responses. Therefore, in this study we found that Gq signaling negatively impacts cardiac function during high BP. Specifically, we found that inhibition of AT1-Gq signaling augmented betaAR mediated effects in a renal artery stenosis model of hypertension. These observations may underlie additional, beneficial effects of angiotensinogen converting enzyme (ACE) inhibitors and angiotensin receptor antagonists observed during times of hemodynamic stress.

GPCR signalling in hypertension: role of GRKs.

Hypertension is a prevalent condition in the developed world and disease severity is directly correlated with additional cardiovascular complications. It is estimated that 30% of the adult population in the United States has hypertension, which is classified as a systolic blood pressure > or =140 mmHg and/or a diastolic blood pressure > or =90 mmHg. A prolonged increase in afterload ultimately leads to congestive heart failure in the majority of cases. Currently, medication designed to treat hypertension is inadequate, thus new therapies need to be explored. Blood pressure is tightly regulated by blood vessel radius, which is established by hormones and/or peptides binding to GPCRs (G-protein-coupled receptors). Catecholamines and peptide hormones, such as AngII (angiotensin II), are elevated in hypertension and, therefore, signalling by these GPCRs is increased. Their signalling is tightly controlled by a class of proteins, the GRKs (GPCR kinases). Elevated levels of either GRK2 or GRK5 in both the lymphocytes and VSM (vascular smooth muscle) are associated with human hypertension and animal models of the disease. The focus of the present review is on the role GRKs, and their regulation of GPCRs, play in high blood pressure.

Enhanced sterol response element-binding protein in postintervention restenotic blood vessels plays an important role in vascular smooth muscle proliferation.

Postintervention restenosis (PIRS) after balloon angioplasty or stent implantation is a limitation for these interventional procedures even with the advent of new drug-eluting stents. Sterol regulatory element-binding proteins (SREBP) are transcription factors governing cellular lipid biosynthesis and thus critical in the regulation of the lipid-rich cell membranes. PIRS following injury results partially from newly proliferating cells expressing vascular smooth muscle cell (VSMC) markers. Platelet-derived growth factor (PDGF), lysophosphatidic acid (LPA) and alpha(1)-adrenergic receptor stimulation are well recognized diverse mitogens for VSMC activation in PIRS. We examined whether PDGF, LPA and alpha(1)-adrenergic receptor stimulation with phenylephrine (PE) regulate SREBP expression and subsequently, VSMC proliferation. Our results show that PDGF, LPA and PE upregulate SREBP-1 in a time- and dose-dependent manner. PDGF, LPA and PE-mediated proliferation is dependent on SREBP since inhibition of SREBP expression using targeted knockdown of the SREBP precursor SREBP activating protein (SCAP) by siRNA led to an attenuation of SREBP expression and decreased PDGF, LPA and PE induced proliferation. In two different in vivo PIRS models we found that SREBP-1 was enhanced in the injured blood vessel wall, especially within the neointima and co-localized with alpha-smooth muscle actin positive cells. Thus, SREBP is enhanced in the vessel wall following PIRS and is important in the regulation of pro-hyperplasia molecular signaling. SREBP inhibition may be a powerful tool to limit PIRS.

Fibroblast apoptosis precedes cardiomyocyte mass reduction during left ventricular remodeling in hypertensive rats treated with amlodipine.

BACKGROUND: A transient induction of apoptosis accompanies the normalization of left ventricular mass index in spontaneously hypertensive rats (SHR) treated with dihydropyridine calcium-channel blockers. However, the cell type undergoing apoptosis in this model and the temporal correlation with onset cardiac remodeling remain undefined. METHODS AND RESULTS: SHR were treated either with vehicle or amlodipine (20 mg/kg per day) for 4, 7, 10, 14 or 28 days. Amlodipine stably reduced systolic blood pressure by day 2 (-26 +/- 2%) and stably reduced the left ventricular concentration of atrial natriuretic peptide (ANP) mRNA by approximately 50% as early as day 4, suggesting the early reduction of cardiomyocyte stress. Left ventricular mass index was significantly reduced by day 7 (-4.6 +/- 1.5%), in coordination with reduced DNA content (-23 +/- 2%) and non-cardiomyocyte number (-17 +/- 4%). However, the cardiomyocyte cross-sectional area was reduced only starting from day 14. Caspase-3 cleavage was significantly increased at day 7 only. Ultimately, amlodipine for 28 days induced a slight increase in capillary density without affecting total cardiomyocyte number, while reducing the total number of non-cardiomyocytes down to levels seen in untreated normotensive Wistar-Kyoto rats. Bax to Bcl-2 protein ratios were increased from day 7 to day 28. In situ double labeling by the terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) method (apoptosis) combined with rhodamine-labeled lectin binding (endothelial cell marker) revealed a significant increase (> 3-fold) in TUNEL-positive, lectin-negative non-cardiomyocytes in the interstitium between days 7 and 14. CONCLUSIONS: Left ventricular remodeling induced by amlodipine in SHR involves selective deletion of excess fibroblasts via apoptosis prior to cardiomyocyte mass reduction, but after attenuation of ANP gene expression.

Negative regulation of VEGF signaling in human coronary artery endothelial cells by G protein-coupled receptor kinase 5.

G protein-coupled receptor kinase 5 (GRK5) is present in endothelial cells (ECs) and has the potential to regulate EC function through seven transmembrane-spanning receptor (7TMR) signaling. Recently, it has been appreciated that GRKs can affect receptor tyrosine kinases (RTKs). VEGF, an RTK, is one of the most potent mediators for EC function and angiogenesis; therefore, we determined the role GRK5 plays in VEGF signaling in human coronary artery ECs (HCAECs). GRK5 levels were increased by VEGF treatment in HCAECs. Adenoviral overexpression of GRK5 inhibited migration and proliferation of HCAECs in response to VEGF. GRK5 overexpression in HCAECs significantly suppressed both acute and late activation of Akt and extracellular signal-related kinase (ERKs) as well as the phosphorylation of GSK-3beta, an endogenous substrate of Akt. Coimmunoprecipitations revealed that GRK5 is physically associated with Akt. This study shows for the first time that GRK5 negatively regulates VEGF signaling in HCAECs and suggests that targeted intervention of GRK5 in ECs might be a novel therapeutic strategy to prevent and treat disorders involving altered EC function.

G protein-coupled receptor kinase 2 expression and activity are associated with blood pressure in black Americans.

Hypertension occurs with higher prevalence and morbidity in black Americans compared with other groups. Alterations in the signal transduction pathways of 7-transmembrane spanning receptors are found in hypertensive patients. G protein-coupled receptor kinases (GRKs) play an important role in regulating this receptor signaling. The 2 most abundantly expressed GRKs in the cardiovascular system are GRK2 and GRK5, and each has unique substrates. Understanding changes in expression may give us insight into activated receptors in the pathophysiological progression of hypertension. In heart failure and white hypertensives, increased GRK2 expression arises because of neurohormonal stimulation of particular receptors. GRK2 subsequently desensitizes specific receptors, including beta-adrenergic receptors. In blood pressure control, beta-adrenergic receptor desensitization could lead to increased blood pressure. GRK2 and GRK5 mRNA were evaluated in lymphocytes of black Americans via quantitative real-time PCR. GRK2 mRNA expression directly correlated with systolic blood pressure and norepinephrine levels. GRK2 was elevated >30% among those with systolic blood pressure > or =130 mm Hg. No significant correlation between GRK5 mRNA expression and blood pressure or catecholamines was observed. Diabetic status, age, sex, and body mass index were also compared with GRK2 expression using univariate and multivariate analyses. GRK2 protein expression was elevated 2-fold in subjects with higher blood pressure, and GRK activity was increased >40%. Our data suggest that GRK2, but not GRK5, is correlated with increasing blood pressure in black Americans. Understanding the receptors stimulated by increased neurohormonal activation may give insight into the pathophysiology of hypertension in this at-risk population.

Inhibition of vascular smooth muscle G protein-coupled receptor kinase 2 enhances alpha1D-adrenergic receptor constriction.

G protein-coupled receptor kinase 2 (GRK2) is a serine/theorinine kinase that phosphorylates and desensitizes agonist-bound G protein-coupled receptors. GRK2 is increased in expression and activity in lymphocytes and vascular smooth muscle (VSM) in human hypertension and animal models of the disease. Inhibition of GRK2 using the carboxyl-terminal portion of the protein (GRK2ct) has been an effective tool to restore compromised beta-adrenergic receptor (AR) function in heart failure and improve outcome. A well-characterized dysfunction in hypertension is attenuation of betaAR-mediated vasodilation. Therefore, we tested the role of inhibition of GRK2 using GRK2ct or VSM-selective GRK2 gene ablation in a renal artery stenosis model of elevated blood pressure (BP) [the two-kidney, one-clip (2K1C) model]. Use of the 2K1C model resulted in a 30% increase in conscious BP, a threefold increase in plasma norepinephrine levels, and a 50% increase in VSM GRK2 mRNA levels. BP remained increased despite VSM-specific GRK2 inhibition by either GRK2 knockout (GRK2KO) or peptide inhibition (GRK2ct). Although betaAR-mediated dilation in vivo and in situ was enhanced, alpha(1)AR-mediated vasoconstriction was also increased. Further pharmacological experiments using alpha(1)AR antagonists revealed that GRK2 inhibition of expression (GRK2KO) or activity (GRK2ct) enhanced alpha(1D)AR vasoconstriction. This is the first study to suggest that VSM alpha(1D)ARs are a GRK2 substrate in vivo.

Simultaneous administration of insulin-like growth factor-1 and darbepoetin alfa protects the rat myocardium against myocardial infarction and enhances angiogenesis.

Recent studies have shown that insulin growth factor-1 (IGF-1) and either erythropoietin (EPO) or the long-acting EPO analog Darbepoetin alfa (DA) protect the heart against ischemia/reperfusion (I/R) and myocardial infarction (MI). The present study examined the cardioprotective effect of simultaneous treatments with IGF-1 and DA in these models of cardiac injury. Rats were subjected to I/R or MI and were treated with IGF-1, DA, and a combination of IGF-1 and DA, or vehicle treatment. IGF-1 and DA treatments imparted similar protective effect by reducing infarct size. Moreover, these treatments led to improvement of cardiac function after I/R or MI compared to vehicle. In the reperfused heart, apoptosis was reduced with either or both IGF-1 and DA treatments as measured by reduced TUNEL staining and caspase-3 activity. In addition, after MI, treatment with IGF-1 or DA significantly induced angiogenesis. This angiogenic effect was enhanced significantly when IGF-1 and DA were given simultaneously compared to vehicle or either agents alone. These data indicate simultaneous pharmacological treatments with IGF-1 and DA protect the heart against I/R and MI injuries. This protection results in reduced infarct size and improved cardiac function. Moreover, this treatment reduces apoptosis and enhances angiogenesis in the ischemic heart.

Vascular smooth muscle G(q) signaling is involved in high blood pressure in both induced renal and genetic vascular smooth muscle-derived models of hypertension.

More than 30% of the US population has high blood pressure (BP), and less than a third of people treated for hypertension have it controlled. In addition, the etiology of most high BP is not known. Having a better understanding of the mechanisms underlying hypertension could potentially increase the effectiveness of treatment. Because G(q) signaling mediates vasoconstriction and vascular function can cause BP abnormalities, we were interested in determining the role of vascular smooth muscle (VSM) G(q) signaling in two divergent models of hypertension: a renovascular model of hypertension through renal artery stenosis and a genetic model of hypertension using mice with VSM-derived high BP. Inhibition of VSM G(q) signaling attenuated BP increases induced by renal artery stenosis to a similar extent as losartan, an ANG II receptor blocker and current antihypertensive therapy. Inhibition of G(q) signaling also attenuated high BP in our genetic VSM-derived hypertensive model. In contrast, BP remained elevated 25% following treatment with losartan, and prazosin, an alpha(1)-adrenergic receptor antagonist, only decreased BP by 35%. Inhibition of G(q) signaling attenuated VSM reactivity to ANG II and resulted in a 2.4-fold rightward shift in EC(50). We also determined that inhibition of G(q) signaling was able to reverse VSM hypertrophy in the genetic VSM-derived hypertensive model. These results suggest that G(q) signaling is an important signaling pathway in two divergent models of hypertension and, perhaps, optimization of antihypertensive therapy could occur with the identification of particular G(q)-coupled receptors involved.

Post-ischemic cardioprotection by A2A adenosine receptors: dependent of phosphatidylinositol 3-kinase pathway.

Activation of myocardial A2A adenosine receptors during reperfusion has been shown to be cardioprotective. The intracellular mechanisms underlying this protection remain unknown. To understand the beneficial effects of activated A2A adenosine receptors in such a state, we investigated whether the enzymes phosphatidylinositol 3-kinase (PI3K) and caspase-3 can account for this post-ischemic cardioprotective effect in an anesthetized rabbit model of myocardial infarction (30 minutes ischemia; 5 hours reperfusion). Administration of the A2A agonist CGS21680 (0.2 microg/kg/min) 5 minutes before reperfusion began (Early) reduced infarct size expressed as a percentage of the area at risk (25.7 +/- 5.3% versus 46.5 +/- 5.3% for the control group; * P < 0.05). Treatment with the A2A agonist 5 minutes after the onset of reperfusion (Late) had no effect on infarct size (38.2 +/- 6.2%). In the presence of a selective inhibitor of PI3K (LY294002), the beneficial effects of CGS21680 on infarct size was no longer observed (43.9 +/- 7.9%). After 5 hours of reperfusion, higher PI3K activity in the ischemic region was observed in the Early group compared with the other experimental groups. Caspase-3 activity was not observed in these different groups. In another set of experiments, PI3K activity was significantly higher during the first 15 minutes of reperfusion in the Early group as compared with the Control group. Caspase-3 activity increased rapidly during the first 15 minutes of reperfusion in the Control group and remained stable in the Early group. These results indicated that post-ischemic cardioprotection afforded by A2A adenosine receptor activation is PI3K-dependent and modulate rapidly other signaling pathways such as caspase-3.