Aruni Bhatnagar

Particulate Matter Air Pollution and Cardiovascular Disease An Update to the Scientific Statement From the American Heart Association

In 2004, the first American Heart Association scientific statement on “Air Pollution and Cardiovascular Disease” concluded that exposure to particulate matter (PM) air pollution contributes to cardiovascular morbidity and mortality. In the interim, numerous studies have expanded our understanding of this association and further elucidated the physiological and molecular mechanisms involved. The main objective of this updated American Heart Association scientific statement is to provide a comprehensive review of the new evidence linking PM exposure with cardiovascular disease, with a specific focus on highlighting the clinical implications for researchers and healthcare providers. The writing group also sought to provide expert consensus opinions on many aspects of the current state of science and updated suggestions for areas of future research. On the basis of the findings of this review, several new conclusions were reached, including the following: Exposure to PM <2.5 &mgr;m in diameter (PM2.5) over a few hours to weeks can trigger cardiovascular disease–related mortality and nonfatal events; longer-term exposure (eg, a few years) increases the risk for cardiovascular mortality to an even greater extent than exposures over a few days and reduces life expectancy within more highly exposed segments of the population by several months to a few years; reductions in PM levels are associated with decreases in cardiovascular mortality within a time frame as short as a few years; and many credible pathological mechanisms have been elucidated that lend biological plausibility to these findings. It is the opinion of the writing group that the overall evidence is consistent with a causal relationship between PM2.5 exposure and cardiovascular morbidity and mortality. This body of evidence has grown and been strengthened substantially since the first American Heart Association scientific statement was published. Finally, PM2.5 exposure is deemed a modifiable factor that contributes to cardiovascular morbidity and mortality.

The Aldo-Keto Reductase Superfamily and its Role in Drug Metabolism and Detoxification

The aldo-keto reductase (AKR) superfamily comprises enzymes that catalyze redox transformations involved in biosynthesis, intermediary metabolism, and detoxification. Substrates of AKRs include glucose, steroids, glycosylation end-products, lipid peroxidation products, and environmental pollutants. These proteins adopt a (β /α )8 barrel structural motif interrupted by a number of extraneous loops and helixes that vary between proteins and bring structural identity to individual families. The human AKR family differs from the rodent families. Due to their broad substrate specificity, AKRs play an important role in the phase II detoxification of a large number of pharmaceuticals, drugs, and xenobiotics.

Metabolism of the Lipid Peroxidation Product, 4-Hydroxy-trans-2-nonenal, in Isolated Perfused Rat Heart*

The metabolism of 4-hydroxy-trans-2-nonenal (HNE), an α,β-unsaturated aldehyde generated during lipid peroxidation, was studied in isolated perfused rat hearts. High performance liquid chromatography separation of radioactive metabolites recovered from [3H]HNE-treated hearts revealed four major peaks. Based on the retention times of synthesized standards, peak I, which accounted for 20% radioactivity administered to the heart, was identified to be due to glutathione conjugates of HNE. Peaks II and III, containing 2 and 37% radioactivity, were assigned to 1,4-dihydroxy-2-nonene (DHN) and 4-hydroxy-2-nonenoic acid, respectively. Peak IV was due to unmetabolized HNE. The electrospray ionization mass spectrum of peak I revealed two prominent metabolites with m/z values corresponding to [M + H]+ of HNE and DHN conjugates with glutathione. The presence of 4-hydroxy-2-nonenoic acid in peak III was substantiated using gas chromatography-chemical ionization mass spectroscopy. When exposed to sorbinil, an inhibitor of aldose reductase, no GS-DHN was recovered in the coronary effluent, and treatment with cyanamide, an inhibitor of aldehyde dehydrogenase, attenuated 4-hydroxy-2-nonenoic acid formation. These results show that the major metabolic transformations of HNE in rat heart involve conjugation with glutathione and oxidation to 4-hydroxy-2-nonenoic acid. Further metabolism of the GS-HNE conjugate involves aldose reductase-mediated reduction, a reaction catalyzed in vitro by homogenous cardiac aldose reductase.

Cardioprotection by N-Acetylglucosamine Linkage to Cellular Proteins

Background— The modification of proteins with O-linked &bgr;-N-acetylglucosamine (O-GlcNAc) represents a key posttranslational modification that modulates cellular function. Previous data suggest that O-GlcNAc may act as an intracellular metabolic or stress sensor, linking glucose metabolism to cellular function. Considering this, we hypothesized that augmentation of O-GlcNAc levels represents an endogenously recruitable mechanism of cardioprotection. Methods and Results— In mouse hearts subjected to in vivo ischemic preconditioning, O-GlcNAc levels were significantly elevated. Pharmacological augmentation of O-GlcNAc levels in vivo was sufficient to reduce myocardial infarct size. We investigated the influence of O-GlcNAc levels on cardiac injury at the cellular level. Lethal oxidant stress of cardiac myocytes produced a time-dependent loss of cellular O-GlcNAc levels. This pathological response was largely reversible by pharmacological augmentation of O-GlcNAc levels and was associated with improved cardiac myocyte survival. The diminution of O-GlcNAc levels occurred synchronously with the loss of mitochondrial membrane potential in isolated cardiac myocytes. Pharmacological enhancement of O-GlcNAc levels attenuated the loss of mitochondrial membrane potential. Proteomic analysis identified voltage-dependent anion channel as a potential target of O-GlcNAc modification. Mitochondria isolated from adult mouse hearts with elevated O-GlcNAc levels had more O-GlcNAc–modified voltage-dependent anion channel and were more resistant to calcium-induced swelling than cardiac mitochondria from vehicle mice. Conclusions— O-GlcNAc signaling represents a unique endogenously recruitable mechanism of cardioprotection that may involve direct modification of mitochondrial proteins critical for survival such as voltage-dependent anion channel.

Electronic Cigarettes A Policy Statement From the American Heart Association

For decades, advocacy for tobacco control has been a priority of the American Heart Association (AHA). In partnership with major public health organizations, the association has made major strides in tobacco use prevention and cessation by prioritizing evidence-based strategies such as increasing excise taxes; passing comprehensive smoke-free air laws; facilitating US Food and Drug Administration (FDA) authority to regulate tobacco, including comprehensive tobacco cessation treatment within healthcare plans; and supporting adequate funding of comprehensive tobacco control programs in different states. These tobacco control efforts have cut in half the youth smoking rate from 1997 to 2007 and have saved >8 million lives in the past 50 years.1 However, the work is far from done and has stalled, especially for people living below the poverty line, those with mental illnesses,2 and those with low educational attainment.3 Unless current trends reverse, ≈5.6 million children alive today in the United States will die prematurely of smoking-related diseases.1 Even now, cigarette smoking kills nearly half a million Americans each year, and an additional 16 million individuals suffer from smoking-related illness, which costs the United States

Cardioprotective and Antiapoptotic Effects of Heme Oxygenase-1 in the Failing Heart

289 billion dollars annually in direct medical care and other economic costs.1 This statement reviews the latest science concerning one of the newest classes of products to enter the tobacco product landscape—electronic cigarettes (e-cigarettes), also called electronic nicotine delivery systems (ENDS)—and provides an overview on design, operations, constituents, toxicology, safety, user profiles, public health, youth access, impact as a cessation aid, and secondhand exposure. On the basis of the current evidence, we provide policy recommendations in key areas of tobacco control such as clean indoor air laws, taxation, regulation, preventing youth access, marketing and advertising to youth, counseling for cessation, surveillance, and defining e-cigarettes in state laws. The statement concludes by outlining a future …

Nitric oxide (NO) induces nitration of protein kinase Cepsilon (PKCepsilon), facilitating PKCepsilon translocation via enhanced PKCepsilon-RACK2 interactions : a novel mechanism of no-triggered activation of PKCepsilon

Background— Heme oxygenase-1 (HO-1) is an inducible stress-response protein that imparts antioxidant and antiapoptotic effects. However, its pathophysiological role in cardiac remodeling and chronic heart failure (HF) is unknown. We hypothesized that induction of HO-1 in HF alleviates pathological remodeling. Methods and Results— Adult male nontransgenic and myocyte-restricted HO-1 transgenic mice underwent either sham operation or coronary ligation to induce HF. Four weeks after ligation, nontransgenic HF mice exhibited postinfarction left ventricular (LV) remodeling and dysfunction, hypertrophy, fibrosis, oxidative stress, apoptosis, and reduced capillary density, associated with a 2-fold increase in HO-1 expression in noninfarcted myocardium. Compared with nontransgenic mice, HO-1 transgenic HF mice exhibited significantly (P<0.05) improved postinfarction survival (94% versus 57%) and less LV dilatation (end-diastolic volume, 46±8 versus 85±32 &mgr;L), mechanical dysfunction (ejection fraction, 65±9% versus 49±16%), hypertrophy (LV/tibia length 4.4±0.4 versus 5.2±0.6 mg/mm), interstitial fibrosis (11.2±3.1% versus 18.5±3.5%), and oxidative stress (3-fold reduction in tissue malondialdehyde). Moreover, myocyte-specific HO-1 overexpression in HF promoted tissue neovascularization and ameliorated myocardial p53 expression (2-fold reduction) and apoptosis. In isolated mitochondria, mitochondrial permeability transition was inhibited by HO-1 in a carbon monoxide (CO)–dependent manner and was recapitulated by the CO donor tricarbonylchloro(glycinato)ruthenium(II) (CORM-3). HO-1–derived CO also prevented H2O2-induced cardiomyocyte apoptosis and cell death. Finally, in vivo treatment with CORM-3 alleviated postinfarction LV remodeling, p53 expression, and apoptosis. Conclusions— HO-1 induction in the failing heart is an important cardioprotective adaptation that opposes pathological LV remodeling, and this effect is mediated, at least in part, by CO-dependent inhibition of mitochondrial permeability transition and apoptosis. Augmentation of HO-1 or its product, CO, may represent a novel therapeutic strategy for ameliorating HF.

Induction of Rat Aortic Smooth Muscle Cell Growth by the Lipid Peroxidation Product 4-Hydroxy-2-Nonenal

Activation of protein kinase C (PKC) ε by nitric oxide (NO) has been implicated in the development of cardioprotection. However, the cellular mechanisms underlying the activation of PKCε by NO remain largely unknown. Nitration of protein tyrosine residues has been shown to alter functions of a variety of proteins, and NO-derived peroxynitrite is known as a strong nitrating agent. In this investigation, we demonstrate that NO donors promote translocation and activation of PKCε in an NO- and peroxynitrite-dependent fashion. NO induces peroxynitrite-mediated tyrosine nitration of PKCε in rabbit cardiomyocytes in vitro, and nitrotyrosine residues were also detected on PKCε in vivo in the rabbit myocardium preconditioned with NO donors. Furthermore, coimmunoprecipitation of PKCε and its receptor for activatedC kinase, RACK2, illustrated a peroxynitrite-dependent increase in PKCε-RACK2 interactions in NO donor-treated cardiomyocytes. Moreover, using an enzyme-linked immunosorbent assay-based protein-protein interaction assay, PKCε proteins treated with the peroxynitrite donor SIN-1 exhibited enhanced binding to RACK2 in an acellular environment. Our data demonstrate that post-translational modification of PKCε by NO donors, namely nitration of PKCε, facilitates its interaction with RACK2 and promotes translocation and activation of PKCε. These findings offer a plausible novel mechanism by which NO activates the PKC signaling pathway.

Unsaturated lipid peroxidation-derived aldehydes activate autophagy in vascular smooth-muscle cells

BACKGROUND Atherosclerotic lesion formation is a complex process, in part mediated by inflammatory and oxidative mechanisms including lipid peroxidation. To further characterize the potential role of lipid peroxidation products in atherogenesis, we studied the effects of 4-hydroxy-2-nonenal (HNE) on rat aortic smooth muscle cell growth. METHODS AND RESULTS HNE, at concentrations of 1.0 and 2.5 micromol/L, significantly stimulated rat aortic smooth muscle cell growth as determined by cell counts, [3H]-thymidine uptake, and incorporation of bromo-deoxyuridine. To characterize the mechanism of HNE-induced mitogenesis, its effect on activation of intracellular growth signaling pathways was examined. Treatment with HNE resulted in activation of extracellular signal-regulated protein kinases ERK1 and ERK2, induction of c-fos and c-jun protein expression, and an increase in transcription factor AP-1 DNA binding activity. In addition, HNE induced expression of platelet-derived growth factor-AA (PDGF-AA) protein, and an anti-PDGF-AA antibody specifically inhibited HNE-mediated DNA synthesis, suggesting that growth factor induction may play a role in HNE-induced vascular smooth muscle cell growth. The role of redox-sensitive mechanisms in this process was further supported by the observation that HNE-induced DNA synthesis and AP-1 activation were inhibited by the antioxidants N-acetylcysteine and pyrrolidine dithiocarbamate. CONCLUSIONS These data demonstrate that HNE, one of several important lipid peroxidation products, induces rat aortic smooth muscle cell growth through redox-sensitive mechanisms and growth factor expression. These observations are consistent with a role for lipid peroxidation products in vascular smooth muscle cell growth in atherogenesis.

Mitogenic responses of vascular smooth muscle cells to lipid peroxidation-derived aldehyde 4-hydroxy-trans-2-nonenal (HNE): Role of aldose reductase-catalyzed reduction of the HNE-glutathione conjugates in regulating cell growth

Proteins modified by aldehydes generated from oxidized lipids accumulate in cells during oxidative stress and are commonly detected in diseased or aged tissue. The mechanisms by which cells remove aldehyde-adducted proteins, however, remain unclear. Here, we report that products of lipid peroxidation such as 4-HNE (4-hydroxynonenal) and acrolein activate autophagy in rat aortic smooth-muscle cells in culture. Exposure to 4-HNE led to the modification of several proteins, as detected by anti-protein-4-HNE antibodies or protein-bound radioactivity in [3H]4-HNE-treated cells. The 4-HNE-modified proteins were gradually removed from cells. The removal of 4-HNE-modified proteins was not affected by the oxidized protein hydrolase inhibitor, acetyl leucine chloromethyl ketone, or lactacystin, although it was significantly decreased by PSI (proteasome inhibitor I), the lysosome/proteasome inhibitor MG-132 (carbobenzoxy-L-leucyl-L-leucyl-leucinal), insulin or the autophagy inhibitor 3-MA (3-methyladenine). Pre-incubation of cells with rapamycin accelerated the removal of 4-HNE-modified proteins. Treatment with 4-HNE, nonenal and acrolein, but not nonanal or POVPC (1-palmitoyl-2-oxovaleroyl phosphatidyl choline), caused a robust increase in LC3-II (microtubule-associated protein 1 light chain 3-II) formation, which was increased also by rapamycin, but prevented by insulin. Electron micrographs of 4-HNE-treated cells showed extensive vacuolization, pinocytic body formation, crescent-shaped phagophores, and multilamellar vesicles. Treatment with 3-MA and MG-132, but not proteasome-specific inhibitors, induced cell death in 4-HNE-treated cells. Collectively, these results show that lipid peroxidation-derived aldehydes stimulate autophagy, which removes aldehyde-modified proteins, and that inhibition of autophagy precipitates cell death in aldehyde-treated cells. Autophagy may be an important mechanism for the survival of arterial smooth-muscle cells under conditions associated with excessive lipid peroxidation.