BRCA2 protein deficiency exaggerates doxorubicin-induced cardiomyocyte apoptosis and cardiac failure.

The tumor suppressor breast cancer susceptibility gene 2 (BRCA2) plays an important role in the repair of DNA damage, and loss of BRCA2 predisposes carriers to breast and ovarian cancers. Doxorubicin (DOX) remains the cornerstone of chemotherapy in such individuals. However, it is often associated with cardiac failure, which once manifests carries a poor prognosis. Because BRCA2 regulates genome-wide stability and facilitates DNA damage repair, we hypothesized that loss of BRCA2 may increase susceptibility to DOX-induced cardiac failure. To this aim, we generated cardiomyocyte-specific BRCA2 knock-out (CM-BRCA2(-/-)) mice using the Cre-loxP technology and evaluated their basal and post-DOX treatment phenotypes. Although CM-BRCA2(-/-) mice exhibited no basal cardiac phenotype, DOX treatment resulted in markedly greater cardiac dysfunction and mortality in CM-BRCA2(-/-) mice compared with control mice. Apoptosis in left ventricular (LV) sections from CM-BRCA2(-/-) mice compared with that in corresponding sections from wild-type (WT) littermate controls was also significantly enhanced after DOX treatment. Microscopic examination of LV sections from DOX-treated CM-BRCA2(-/-) mice revealed a greater number of DNA double-stranded breaks and the absence of RAD51 focus formation, an essential marker of double-stranded break repair. The levels of p53 and the p53-related proapoptotic proteins p53-up-regulated modulator of apoptosis (PUMA) and Bax were significantly increased in samples from CM-BRCA2(-/-) mice. This corresponded with increased Bax to Bcl-2 ratios and elevated cytochrome c release in the LV sections of DOX-treated CM-BRCA2(-/-) mice. Taken together, these data suggest a critical and previously unrecognized role of BRCA2 as a gatekeeper of DOX-induced cardiomyocyte apoptosis and susceptibility to overt cardiac failure. Pharmacogenomic studies evaluating cardiac function in BRCA2 mutation carriers treated with doxorubicin are encouraged.

Adiponectin primes human monocytes into alternative anti-inflammatory M2 macrophages.

Altered macrophage kinetics is a pivotal mechanism of visceral obesity-induced inflammation and cardiometabolic risk. Because monocytes can differentiate into either proatherogenic M1 macrophages or anti-inflammatory M2 macrophages, approaches that limit M1 while promoting M2 differentiation represent a unique therapeutic strategy. We hypothesized that adiponectin may prime human monocytes toward the M2 phenotype. Adiponectin promoted the alternative activation of human monocytes into anti-inflammatory M2 macrophages as opposed to the classically activated M1 phenotype. Adiponectin-treated cells displayed increased M2 markers, including the mannose receptor (MR) and alternative macrophage activation-associated CC chemokine-1. Incubation of M1 macrophages with adiponectin-treated M2-derived culture supernatant resulted in a pronounced inhibition of tumor necrosis factor-alpha and monocyte chemotactic protein-1 secretion. Activation of human monocytes into M2 macrophages by adiponectin was mediated, in addition to AMP-activated protein kinase and peroxisome proliferator-activated receptor (PPAR)-gamma, via PPAR-alpha. Furthermore, macrophages isolated from adiponectin knockout mice demonstrated diminished levels of M2 markers such as MR, which were restored with adiponectin treatment. We report a novel immunoregulatory mechanism through which adiponectin primes human monocyte differentiation into anti-inflammatory M2 macrophages. Conditions associated with low adiponectin levels, such as visceral obesity and insulin resistance, may promote atherosclerosis, in part through aberrant macrophage kinetics.

Effects of ezetimibe add-on to statin therapy on adipokine production in patients with metabolic syndrome and stable vascular disease.

The aim of this study was to determine whether the addition of ezetimibe to ongoing statin therapy in patients with atherosclerosis and metabolic syndrome would favorably affect levels of inflammatory markers and adipokines. Individuals with the metabolic syndrome exhibit higher levels of inflammatory biomarkers and adipokines, which have been implicated in the pathobiology of cardiovascular risk. The impact of the addition of ezetimibe to statin therapy on these proinflammatory mediators is unclear. Fifty patients with metabolic syndrome and concomitant vascular disease receiving stable statin monotherapy, with low-density lipoprotein cholesterol (LDL-C) levels >77.4 mg/dL (>2.0 mM), were treated with ezetimibe 10 mg per day for 12 weeks. The primary study end point was the % change in adiponectin levels from baseline to 12 weeks. Secondary study end points included % changes in the levels of other circulating inflammatory markers, adipokines, and plasma lipids. The addition of ezetimibe to statin therapy resulted in a significant reduction in total cholesterol and LDL-C and the ratio of total cholesterol to high-density lipoprotein cholesterol. However, ezetimibe add-on treatment had no effect on the primary outcome of plasma adiponectin or on any of the secondary outcomes, including leptin, hsCRP, tumor necrosis factor-α, or interleukin-6 concentrations. These observations remained unchanged after adjusting for body mass index and for background statin used. The addition of ezetimibe to stable statin therapy in patients with vascular disease and metabolic syndrome, who were not at guideline recommended LDL-C levels, did not alter adipokine levels after 12 weeks. Short-term add-on with ezetimibe may not be associated with additional inflammatory benefits beyond improvements in cholesterol homeostasis.

The incretin system and cardiometabolic disease.

Rates of type 2 diabetes, obesity and their associated detrimental cardiovascular effects are rapidly increasing. Despite the availability of several treatment options for type 2 diabetes and the use of intensive regimens combining several antidiabetic drugs, less than one-half of all patients reach a target glycosylated hemoglobin level of less than 7%. Disease progression due to ongoing deterioration of pancreatic islet cell health and beta-cell function is likely responsible. Therefore, there is a need to identify new pharmacological compounds that may not only treat hyperglycemia, but may also correct impaired glucose homeostasis and preserve endogenous beta-cell function. Identification and characterization of the incretin system and its effect on glucose homeostasis have resulted in the development of new antidiabetic agents that target these concerns. The current review examines the incretin effect and the pharmacological agents that have been developed based on the understanding of this physiological system. The influence of incretins on the cardiovascular system beyond the proatherogenic effect of type 2 diabetes will also be discussed.

Visfatin activates eNOS via Akt and MAP kinases and improves endothelial cell function and angiogenesis in vitro and in vivo: translational implications for atherosclerosis.

Improving endothelial nitric oxide synthase (eNOS) bioactivity and endothelial function is important to limit native, vein graft, and transplant atherosclerosis. Visfatin, a NAD biosynthetic enzyme, regulates the activity of the cellular survival factor, Sirt1. We hypothesized that visfatin may improve eNOS expression, endothelial function, and postnatal angiogenesis. In human umbilical vein (HUVEC) and coronary artery endothelial cells, we evaluated the effects of recombinant human visfatin on eNOS protein and transcript expression and mRNA stability, in the presence and absence of visfatin RNA silencing. We also assessed visfatin-induced protein kinase B (Akt) activation and its association with src-tyrosine kinases, phosphorylation of Ser(1177) within eNOS in the presence and absence of phosphatidylinositol 3-kinase (PI 3-kinase) inhibition with LY-294002, and evaluated the contributory role of extracellular signal-regulated kinase 1/2. Finally, we determined the impact of visfatin on HUVEC migration, proliferation, inflammation-induced permeability, and in vivo angiogenesis. Visfatin (100 ng/ml) upregulated and stabilized eNOS mRNA and increased the production of nitric oxide and cGMP. Visfatin-treated HUVEC demonstrated greater proliferation, migration, and capillary-like tube formation but less tumor necrosis factor-alpha-induced permeability; these effects were decreased in visfatin gene-silenced cells. Visfatin increased total Akt and Ser(473)-phospho-Akt expression with concomitant rises in eNOS phosphorylation at Ser(1177); these effects were blocked by LY-2940002. Studies with PP2 showed that the nonreceptor tyrosine kinase, src, is an upstream stimulator of the PI 3-kinase-Akt pathway. Visfatin also activated mitogen-activated protein (MAP) kinase through PI 3-kinase, and mitogen/extracellular signal-regulated kinase inhibition attenuated visfatin-elicited Akt and eNOS phosphorylation. Visfatin-filled Matrigel implants showed an elevated number of infiltrating vessels, and visfatin treatment produced significant recovery of limb perfusion following hindlimb ischemia. These results indicate a novel effect of visfatin to stimulate eNOS expression and function in endothelial cells, via a common upstream, src-mediated signaling cascade, which leads to activation of Akt and MAP kinases. Visfatin represents a translational target to limit endothelial dysfunction, native, vein graft and transplant atherosclerosis, and improve postnatal angiogenesis.

A population-based study of the drug interaction between proton pump inhibitors and clopidogrel.

BACKGROUND: Most proton pump inhibitors inhibit the bioactivation of clopidogrel to its active metabolite. The clinical significance of this drug interaction is unknown. METHODS: We conducted a population-based nested case-control study among patients aged 66 years or older who commenced clopidogrel between Apr. 1, 2002, and Dec. 31, 2007, following hospital discharge after treatment of acute myocardial infarction. The cases in our study were those readmitted with acute myocardial infarction within 90 days after discharge. We performed a secondary analysis considering events within 1 year. Event-free controls (at a ratio of 3:1) were matched to cases on age, percutaneous coronary intervention and a validated risk score. We categorized exposure to proton pump inhibitors before the index date as current (within 30 days), previous (31-90 days) or remote (91-180 days). RESULTS: Among 13 636 patients prescribed clopidogrel following acute myocardial infarction, we identified 734 cases readmitted with myocardial infarction and 2057 controls. After extensive multivariable adjustment, current use of proton pump inhibitors was associated with an increased risk of reinfarction (adjusted odds ratio [OR] 1.27, 95% confidence interval [CI] 1.03-1.57). We found no association with more distant exposure to proton pump inhibitors or in multiple sensitivity analyses. In a stratified analysis, pantoprazole, which does not inhibit cytochrome P450 2C19, had no association with readmission for myocardial infarction (adjusted OR 1.02, 95% CI 0.70-1.47). INTERPRETATION: Among patients receiving clopidogrel following acute myocardial infarction, concomitant therapy with proton pump inhibitors other than pantoprazole was associated with a loss of the beneficial effects of clopidogrel and an increased risk of reinfarction.

Plasmodium falciparum malaria occurring 8 years after leaving an endemic area.

A 29-year-old patient who was born in Angola developed Plasmodium falciparum malaria 8 years after leaving Africa. She had not returned to a malaria-endemic area, and there were no apparent risks of local or nosocomial acquisition of malaria in Canada. She recovered after treatment with oral quinine sulfate and doxycycline.

Adiponectin deficiency promotes endothelial activation and profoundly exacerbates sepsis-related mortality.

Sepsis is a multifactorial, and often fatal, disorder typically characterized by widespread inflammation and immune activation with resultant endothelial activation. In the present study, we postulated that the adipokine adiponectin serves as a critical modulator of survival and endothelial activation in sepsis. To this aim, we evaluated both loss-of-function (adiponectin gene-deficient mice) and subsequent gain-of-function (recombinant adiponectin reconstitution) strategies in two well-established inflammatory models, cecal ligation perforation (CLP) and thioglyocollate-induced peritonitis. Adipoq(-/-) mice, subjected to CLP, exhibited a profound ( approximately 8-fold) reduction in survival compared with their wild-type Adipoq(+/+) littermates after 48 h. Furthermore, compared with wild-type controls, thioglycollate challenge resulted in a markedly greater influx of peritoneal neutrophils in Adipoq(-/-) mice accompanied by an excess production of key chemoattractant cytokines (IL-12p70, TNFalpha, MCP-1, and IL-6) and upregulation of aortic endothelial adhesion molecule VCAM-1 and ICAM-1 expressions. Importantly, all of these effects were blunted by recombinant total adiponectin administration given 3 days prior to thioglycollate challenge. The protective effects of adiponectin were ascribed largely to higher-order adiponectin oligomers, since administration of recombinant C39A trimeric adiponectin did not attenuate endothelial adhesion molecule expression in thioglycollate-challenged Adipoq(-/-) mice. These data suggest a critical role of adiponectin as a modulator of survival and endothelial inflammation in experimental sepsis and a potential mechanistic link between adiposity and increased sepsis.

Impaired endothelial function in C-reactive protein overexpressing mice.

Increasing evidence suggests that the inflammatory biomarker, C-reactive protein (CRP), may play a causal role in the development and progression of atherothrombosis. Since endothelial dysfunction is an early and integral component of atherosclerosis, we hypothesized that endothelial homeostasis would be impaired in CRP-overexpressing CRP transgenic (CRPtg) mice. Male CRPtg and wild-type mice were injected thrice over 2 weeks with vehicle or turpentine to induce the inflammation-sensitive CRP transgene. Serum human CRP levels in turpentine-treated CRPtg mice was 276.28 +/- 95.7 microg/ml. Human CRP was undetectable in the sera of wild-type mice and present at only low levels (1.41 +/- 0.2 microg/ml) in vehicle-treated CRPtg mice (n=6-8 mice/group). Aortic segments from turpentine-induced CRP-overexpressing CRPtg mice demonstrated impaired endothelium-dependent responses to acetylcholine vs. those from vehicle-treated CRPtg controls (57.1 +/- 9.5% vs. 85.0 +/- 5.0%, P<0.05, n=6). Nitric oxide release as well as phosphorylated eNOS protein expression from isolated aortic segments of CRPtg mice overexpressing CRP were markedly reduced compared to that from vehicle-treated controls. Masson's trichrome staining revealed increased perivascular fibrosis in CRP-overexpressing CRPtg mice. CRP overexpression was also associated with augmented aortic endothelial staining for VCAM-1 and MCP-1 and enhanced macrophage infiltration. Mice overexpressing the human CRP gene exhibit endothelial dysfunction, possibly via reduced NO bioavailability, with resultant changes in vascular structure. These data further support a role for CRP in mediating endothelial dysfunction.

The endocannabinoid system and cardiometabolic risk.

Worldwide, the rates of obesity are rapidly rising. Abdominal obesity in particular is associated with increased cardiovascular risk factors, namely increased triglycerides, low high-density lipoprotein (HDL) cholesterol, elevated blood pressure and increased plasma glucose. The cluster of these obesity-related metabolic disorders identifies individuals with the cardiometabolic syndrome, who are at particular risk for cardiovascular disease and type 2 diabetes. The accumulation of intra-abdominal fat and the subsequent development of visceral obesity rely on the body's mechanisms to store energy and to stimulate appetite. The endocannabinoid system has been implicated in the regulation of energy balance and has emerged as a critical target for the modulation of visceral obesity and insulin resistance. Its overactivity appears to be associated with the development of obesity. The current review examines the role of the endocannabinoid system in cardiometabolic disease and its basis as a target for modulating cardiovascular risk.

Adiponectin and cardiovascular disease: state of the art?

The cardiometabolic syndrome, associated with increased cardiovascular disease risk in the industrialized world, is estimated to affect one in four adults. Although the mechanisms linking obesity and cardiovascular disease remain unclear, research continues to unravel the molecular pathways behind this pandemic. Adipose tissue has emerged as a metabolically active participant in mediating vascular complications, serving as an active endocrine and paracrine organ secreting adipokines, which participate in diverse metabolic processes. Among these adipokines is adiponectin, which seems to possess antiatherogenic and anti-inflammatory effects and may be protective against cardiovascular disease development. The current review describes the pathophysiology of adiponectin in atherosclerotic disease.

C-reactive protein alters antioxidant defenses and promotes apoptosis in endothelial progenitor cells.

OBJECTIVE: C-reactive protein (CRP) has been suggested to participate in the development of atherosclerosis, in part, by promoting endothelial dysfunction and impairing endothelial progenitor cell (EPC) survival and differentiation. In the present study, we evaluated the effects of CRP on antioxidative enzymes, reactive oxygen species production, telomerase activity, and apoptosis in human circulating EPCs. METHODS AND RESULTS: EPCs, isolated from peripheral venous blood, were cultured in the absence or presence of native pentameric azide and lipopolysaccharide (LPS)-free CRP (0, 5, 15, and 20 microg/mL), N-acetylcysteine (NAC), hydrogen peroxide (H2O2) or monoclonal anti-CRP antibodies. Fluorescence-activated cell sorter (FACS) analysis was used for the measurement of intracellular H2O2 and superoxide (O2(-)) by loading cells with 2',7'-dichlorodihydrofluorescein diacetate (H2DCF-DA). Apoptosis was evaluated with Annexin V immunostaining and cytosolic cytochrome c expression. Western blot analysis was used for the determination of manganese superoxide dismutase (MnSOD) and glutathione peroxidase expression, and polymerase chain reaction enzyme-linked immunosorbent assay was used to assess telomerase activity. Incubation of EPCs with CRP caused a concentration dependent increase in reactive oxygen species (ROS) production and apoptosis, with an effect quantitatively similar to H2O2. This effect was attenuated during coincubation with NAC or anti-CRP antibodies. Furthermore, CRP altered EPC antioxidative enzyme levels, demonstrating a reduced expression of glutathione peroxidase and a significant increase in MnSOD expression. Transfection of EPCs with MnSOD-RNAi resulted in a reduction in CRP-induced ROS production, apoptosis, and telomerase inactivation. CONCLUSIONS: CRP, at concentrations known to predict cardiovascular events, may serve to impair EPC antioxidant defenses, and promote EPC sensitivity toward oxidant-mediated apoptosis and telomerase inactivation. These data further support a direct role of CRP in the development and/or progression of atherothrombosis.

Stem cell factor deficiency is vasculoprotective: unraveling a new therapeutic potential of imatinib mesylate.

Evidence suggests that bone marrow (BM) cells may give rise to a significant proportion of smooth muscle cells (SMCs) that contribute to intimal hyperplasia after vascular injury; however, the molecular pathways involved and the timeline of these events remain poorly characterized. We hypothesized that the stem cell factor (SCF)/c-Kit tyrosine kinase signaling pathway is critical to neointimal formation by BM-derived progenitors. Wire-induced femoral artery injury in mice reconstituted with wild-type BM cells expressing yellow fluorescent protein was performed, which revealed that 66+/-12% of the SMCs (alpha-smooth muscle actin-positive [alphaSMA(+)] cells) in the neointima were from BM. To characterize the role of the SCF/c-Kit pathway, we used c-Kit deficient W/W(v) and SCF-deficient Steel-Dickie mice. Strikingly, vascular injury in these mice resulted in almost a complete inhibition of neointimal formation, whereas wild-type BM reconstitution of c-Kit mutant mice led to neointimal formation in a similar fashion as wild-type animals, as did chronic administration of SCF in matrix metalloproteinase-9-deficient mice, a model of soluble SCF deficiency. Pharmacological antagonism of the SCF/c-Kit pathway with imatinib mesylate (Gleevec) or ACK2 (c-Kit antibody) also resulted in a marked reduction in intimal hyperplasia. Vascular injury resulted in the local upregulation of SCF expression. c-Kit(+) progenitor cells (PCs) homed to the injured vascular wall and differentiated into alphaSMA(+) cells. Vascular injury also caused an increase in circulating SCF levels which promoted CD34(+) PC mobilization, a response that was blunted in mutant and imatinib mesylate-treated mice. In vitro, SCF promoted adhesion of BM PCs to fibronectin. Additionally, anti-SCF antibodies inhibited adhesion of BM PCs to activated SMCs and diminished SMC differentiation. These data indicate that SCF/c-Kit signaling plays a pivotal role in the development of neointima by BM-derived PCs and that the inhibition of this pathway may serve as a novel therapeutic target to limit aberrant vascular remodeling.

C-Reactive protein upregulates receptor for advanced glycation end products expression in human endothelial cells.

The receptor for advanced glycation end products (RAGE) may play an important role in inflammatory processes and endothelial activation, likely to accelerate the processes of coronary atherosclerotic development, especially in diabetic patients. The factors that regulate arterial expression of RAGE are not completely clear. C-reactive protein (CRP) is identified as a key proinflammatory cytokine in patients with atherosclerosis. Therefore, we tested the hypothesis that RAGE expression in endothelial cells can be upregulated by CRP. Human saphenous vein endothelial cells were incubated with human recombinant CRP, free of sodium azide and endotoxin. RAGE protein expression was measured by flow-cytometric analysis and Western blotting. CRP caused a significant increase in RAGE protein expression at a dose as low as 5 mug/mL, with expression peaking at 24 to 48 hours after CRP incubation. The effects of modified monomeric CRP on RAGE protein expression were comparable with that of native pentameric CRP. At the mRNA level, CRP not only increased RAGE gene expression but also attenuated the degradation of RAGE mRNA. Furthermore, RNA interference of RAGE gene expression significantly decreased the level of macrophage chemoattractant protein 1, a key downstream mediator of CRP activity. Therefore, CRP at concentrations known to predict future vascular events upregulates RAGE expression in human endothelial cells at both the protein and mRNA level. Silencing of the RAGE gene prevents CRP-induced macrophage chemoattractant protein 1 activation. These data reinforce the mechanistic links among inflammation, endothelial dysfunction, and atherothrombosis.