Cell Mol Life Sci Research Articles

Single-Molecule Study of Actin Filament Severing by Gelsolin using Total Internal Reflection Fluorescence Microscopy

Gelsolin-family proteins are regulators of actin polymerization dynamics.[1] To understand the mechanism of actin filament (F-actin) severing by gelsolin at the single-molecule level an in vitro total internal reflection fluorescence (TIRF) microscopy[2] assay has been developed. Preliminary TIRF data confirm that gelsolin sever F-actin.[3] These real-time microscopic observations are in concert with the structural and biochemical studies that have established activation of gelsolin by calcium ions. [3],[4],[5] To further ascertain a) if gelsolin preferentially binds to F-actin rather than sequestering actin monomers (G-actin), b) if it preferentially binds and severs ADP-F-actin or ATP-F-actin, and c) if gelsolin or cofilin, a member of actin depolymerizing factor (ADF), sever gelsolin-capped F-actin better than native filaments, dual color TIRFM assays are undertaken. Results will be discussed in the context of structural and biochemical data on gelsolin-family of proteins.[1] P. Silacci et al, Cell Mol Life Sci 2004, 61: 2614-2623[2] J.R. Kuhn, T. D. Pollard, Biophys. J 2005. 88:1387-1402[3] S. Nag et al, Proc. Natl. Acad. Sci. 2009, 106 :1371313718[4] R.C. Robinson et al, Science 1999. 286: 1939-1942[5] K. Narayan et al, Febs Lett. 2003. 552:82-85

Nestin in Human Skin: Exclusive Expression in Intramesenchymal Skin Compartments and Regulation by Leptin

Cutaneous nestin+ cells are of substantial interest in regenerative medicine. However, the location of nestin+ cells in situ remains controversial. We therefore sought to determine their location in female human scalp skin, using stringently controlled immunohistochemical techniques, Western blot analysis, and in situ hybridization and complementing those techniques with relative and quantitative reverse transcriptase-PCR of enzymatically digested or laser-capture microdissected human hair follicle (HF) compartments. We show here that the immunoreactivity (IR) patterns obtained with anti-nestin antibodies are highly dependent on the tissue-fixation and immunohistochemical methods used. NESTIN mRNA could not be detected within HF-associated epithelial cells in situ or in RNA extracts of the microdissected HF epithelium. Instead, NESTIN transcripts were found only in intramesenchymal skin compartments. Individual cells showing both, specific nestin IR and NESTIN mRNA were detectable in the connective-tissue sheaths of human HFs, sebaceous and sweat glands. Moreover, stimulation of organ-cultured human scalp skin with the adipokine leptin increased the number of nestin+ cells in these intramesenchymal skin locations, whereas no specific nestin IR could be induced by leptin within the HF epithelium, including the bulge. Therefore, nestin expression at the gene and protein levels in human scalp skin is restricted to the periappendage mesenchyme and can be stimulated by leptin.

The arrythmogenic potential of post-myocardial infarction cytokine treatment

a front page story in The New York Times ([22][1]) at the end of March 2001 reported that “the basis of a possible revolution in treating heart attack patients has been laid by three reports of using stem cells from bone marrow to repair heart tissue in animals.” Those three reports ([11][2], [

Tangier Disease in Severely Progressive Coronary and Peripheral Artery Disease

A 37-year-old man was first referred to our lipid clinic in December 2007 for plasma lipid alteration. He presented with large, orange tonsils (Figure 1) and hepatosplenomegaly. There was no evidence of corneal opacities nor of other ocular abnormalities, and there were no nervous system abnormalities as assessed by sensitive and motor electromyography. Figure 1. Orange large tonsils. Hematologic abnormalities included thrombocytopenia and erythrocytes with altered morphology (stomatocytes; Figure 2) and function (decreased osmotic resistance). Serum levels of total cholesterol, triglycerides, and high-density lipoprotein (HDL) cholesterol were 58, 184, and 4 mg/dL, respectively; plasma apolipoprotein A-I concentrations were very low (3.9 mg/dL); and apolipoprotein A-II plasma levels were 1.7 mg/dL. Figure 2. Peripheral blood erythrocytes with numerous stomatocytes. The patient’s father (58 years of age) had serum levels of total cholesterol, HDL cholesterol, and apolipoprotein A-I of 127, 25, and 99.5 mg/dL, respectively. Moreover, he had a …

Alpha-synuclein overexpression and aggregation exacerbates impairment of mitochondrial functions by augmenting oxidative stress in human neuroblastoma cells

Overexpression of alpha-synuclein and oxidative stress has been implicated in the neuronal cell death in Parkinson's disease. Alpha-synuclein associates with mitochondria and excessive accumulation of alpha-synuclein causes impairment of mitochondrial functions. However, the mechanism of mitochondrial impairment caused by alpha-synuclein is not fully understood. We recently reported that alpha-synuclein associates with mitochondria and that overexpression of alpha-synuclein causes nitration of mitochondrial proteins and release of cytochrome c from the mitochondria [Parihar M.S., Parihar A., Fujita M., Hashimoto M., Ghafourifar P. Mitochondrial association of alpha-synuclein causes oxidative stress. Cell Mol Life Sci. 2008a;65:1272–1284]. The present study shows that overexpression of alpha-synuclein A53T or A30P mutants or wild-type in human neuroblastoma cells augmented aggregation of alpha-synuclein. Immunoblotting and immuno-gold electron transmission microscopy show localization of alpha-synuclein aggregates within the mitochondria of overexpressing cells. Overexpressing cells show increased mitochondrial reactive oxygen species, increased protein tyrosine nitration, decreased mitochondrial transmembrane potential, and hampered cellular respiration. These findings suggest an important role for mitochondria in cellular responses to alpha-synuclein.

Mass Spectral Identification of Vc1.1 and Differential Distribution of Conopeptides in the Venom Duct of Conus victoriae. Effect of Post-Translational Modifications and Disulfide Isomerisation on Bioactivity

Molluscs of the genus Conus (cone shells) are carnivorous, feeding on marine worms, small fish and other marine molluscs. They capture their prey by injecting venom containing hundreds of neurally active peptide components. These peptides are classed as conotoxins and consist of small disulfide-bonded peptides exhibiting a high degree of post-translational modifications (PTMs). The functional roles of these modifications remain largely unknown. Two of the most frequently observed modifications are γ-carboxylation of glutamate and hydroxylation of proline (Buczek et al. Cell Mol Life Sci 62:3067, 2005). Vc1.1 is an α-conotoxin from Conus victoriae (Sandall et al. Biochemistry 42(22):6904–6911, 2003) and the only form of this peptide which has been detected in the venom is the γ-glutamate and hydroxyproline (Vc1.1.P6O:E14Gla) version of the molecule (Jakubowski et al. Toxicon 47(6):688–699, 2006). In order to investigate the role of PTMs, we did mass spectral profiling of the venom duct of C. victoriae looking at changes in mass and the number of peptides detected. We synthesised a number of predicted Vc1.1-PTM peptides together with the three possible disulfide isoforms of Vc1.1 and assessed the possible functional role of the PTM conopeptides by measuring the in vitro activity at the cognate neuronal nicotinic acetylcholine receptors (nAChRs). In addition we looked for their presence Vc1.1 venom by mass spectrometry and by this approach we were able to detect unmodified Vc1.1 in C. victoriae venom for the first time.

On the role of protein structural dynamics in the catalytic activity and thermostability of serine protease subtilisin Carlsberg

The effect of structural dynamics on enzyme activity and thermostability has thus far only been investigated in detail for the serine protease alpha-chymotrypsin (for a recent review see Solá et al., Cell Mol Life Sci 2007, 64(16): 2133-2152). Herein, we extend this type of study to a structurally unrelated serine protease, specifically, subtilisin Carlsberg. The protease was incrementally glycosylated with chemically activated lactose to obtain various subtilisin glycoconjugates which were biophysically characterized. Near UV-CD spectroscopy revealed that the tertiary structure was unaffected by the glycosylation procedure. H/D exchange FT-IR spectroscopy was performed to assess the changes in structural dynamics of the enzyme. It was found that increasing the level of glycosylation caused a linearly dependent reduction in structural dynamics. This led to an increase in thermostability and a decrease in the catalytic turnover rate for both, the enzyme acylation and deacylation steps. These results highlight the possibility that a structural dynamics-activity relationship might be a phenomenon generally found in serine proteases.

Neprilysin gene expression requires binding of the amyloid precursor protein intracellular domain to its promoter: implications for Alzheimer disease

Amyloid beta-peptide (Abeta) accumulation leads to neurodegeneration and Alzheimer disease; however, amyloid metabolism is a dynamic process and enzymic mechanisms exist for Abeta removal. Considerable controversy surrounds whether the intracellular domain of the amyloid precursor protein (AICD) regulates expression of the Abeta-degrading metalloprotease, neprilysin (NEP). By comparing two neuroblastoma cell lines differing substantially in NEP expression, we show by chromatin immunoprecipitation (ChIP) that AICD is bound directly to the NEP promoter in high NEP-expresser (NB7) cells but not in low-expresser (SH-SY5Y) cells. The methylation status of the NEP promoter does not regulate expression in these cells, whereas the histone deacetylase inhibitors trichostatin A and valproate partly restore NEP expression and activity in SH-SY5Y cells. ChIP analysis also reveals AICD binding to the NEP promoter in rat primary neurons but not in HUVEC cells. Chromatin remodelling of crucial Alzheimer disease-related genes by valproate could provide a new therapeutic strategy.

Production of the Soluble Form of KIT, s-KIT, Abolishes Stem Cell Factor-Induced Melanogenesis in Human Melanocytes

The signaling of stem cell factor (SCF) and its receptor KIT (membrane-bound KIT; m-KIT) plays an important role in melanocyte development, survival, proliferation, and melanogenesis. It has been demonstrated in other systems that a soluble form of m-KIT released from the cell surface (s-KIT) regulates SCF signaling, although there have been no reports pertaining to the existence and the biological role of s-KIT in melanocytes. In this study, we therefore examined the involvement of s-KIT in melanogenesis. Western blotting analysis revealed that treatment with phorbol 12-myristate-13-acetate (PMA) or 4-aminophenylmercuric acetate (APMA) induced s-KIT production in cultured human melanocytes. Inhibitors of tumor necrosis factor-alpha-converting enzyme (TACE) and metalloproteinases (MMPs) muted this release of s-KIT into the media. Human recombinant s-KIT added to melanocytes inhibited SCF-induced phosphorylation of m-KIT, resulting in suppression of SCF-induced melanogenesis. Additionally, APMA-induced s-KIT production abolished SCF-induced melanogenesis as effectively as a KIT-neutralizing antibody. Concomitantly, APMA and TACE inhibitors significantly decreased and increased melanin synthesis, respectively, in an in vitro skin model. Taken together, these findings provided an insight into the elaborate mechanism of SCF/m-KIT signaling in human melanocytes and suggested that production of s-KIT contributes to the regulation of human skin pigmentation. Journal of Investigative Dermatology (2008) 128, 1763-1772; doi:10.1038/jid.2008.9; published online 31 January 2008.

Letter by Pignier and Le Grand Regarding Article “Acute Administration of Fish Oil Inhibits Triggered Activity in Isolated Myocytes From Rabbits and Patients With Heart Failure”

HomeCirculationVol. 118, No. 3Letter by Pignier and Le Grand Regarding Article “Acute Administration of Fish Oil Inhibits Triggered Activity in Isolated Myocytes From Rabbits and Patients With Heart Failure” Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBLetter by Pignier and Le Grand Regarding Article “Acute Administration of Fish Oil Inhibits Triggered Activity in Isolated Myocytes From Rabbits and Patients With Heart Failure” Christophe Pignier, PhD and Bruno Le Grand, PhD Christophe PignierChristophe Pignier Pierre Fabre Research Center, Cardiovascular Diseases II Division, Castres, France Search for more papers by this author and Bruno Le GrandBruno Le Grand Pierre Fabre Research Center, Cardiovascular Diseases II Division, Castres, France Search for more papers by this author Originally published15 Jul 2008https://doi.org/10.1161/CIRCULATIONAHA.108.778373Circulation. 2008;118:e69To the Editor:We read with a great interest the article by den Ruijter et al,1 which showed that acute application of ω3-polyunsaturated fatty acids (DHA and EPA) reduced action potential duration and decreased diastolic and systolic intracellular calcium in myocytes from pathological hearts explanted from rabbits and humans. Consequently, ω3-polyunsaturated fatty acids abolished triggered activity and reduced the number of delayed afterdepolarizations and calcium levels after transients.The purpose of our letter is to point out that a major mechanism is missing from those proposed by the authors: inhibition by ω3-polyunsaturated fatty acids of the persistent sodium current. In contrast to the well-known rapid sodium channels that activate and inactivate very quickly, a different mode of gating has been reported. Channels that fail to inactivate completely produce a late or persistent sodium current that is responsible for a long-lasting influx of Na+, which is converted in Ca2+ overload through the activation of the reverse mode of the Na+–Ca2+ exchanger. Persistent sodium current (INa) amplitude is increased in patients with an history of cardiac ischemia2 and in some patients with mutations in the SCN5A gene. Therefore, enhancement of persistent INa is observed and is associated with cellular damages and left ventricular dysfunction in a variety of pathological states, including heart failure.3,4 It has now become apparent that persistent INa plays an important role in the genesis of ischemia-induced ventricular damages and also in arrhythmias observed in failing hearts and that persistent INa represents an attractive target to focus on to provide protection from Na+-induced Ca2+ overload. We previously reported5 that DHA and EPA, in a same range of concentration used in the study by den Ruijter et al,1 concentration-dependently reduced the persistent INa artificially induced with veratridine, as well as the one involved in LQT3 syndrome.We do not claim that inhibition of persistent INa by ω3-polyunsaturated fatty acids is the unique mechanism to prevent triggered activity in myocytes, but we strongly believe that this effect constitutes a key mechanism for the reduction of the abnormalities of calcium homeostasis in failing heart.DisclosuresNone. References 1 den Ruijter HM, Berecki G, Verkerk AO, Bakker D, Baartscheer A, Schumacher CA, Belterman CNW, de Jonge N, Fiolet JWT, Brower IA, Coronel R. Acute administration of fish oil inhibits triggered activity in isolated myocytes from rabbits and patients with heart failure. Circulation. 2008; 117: 536–544.LinkGoogle Scholar2 Saint DA. The role of the persistent Na+ current during cardiac ischemia and hypoxia. J Cardiovasc Electrophysiol. 2006; 17: S96–S103.CrossrefMedlineGoogle Scholar3 Undrovinas AI, Maltsev VA, Sabbath HN. Repolarization abnormalities in cardiomyocytes of dogs with chronic heart failure: role of sustained inward current. Cell Mol Life Sci. 1999; 55: 494–505.CrossrefMedlineGoogle Scholar4 Valdivia CR, Chu WW, Pu J, Foell JD, Haworth RA, Wolff MR, Kamp TJ, Makielski JC. Increased late sodium current in myocytes from a canine heart failure model and from failing human heart. J Mol Cell Cardiol. 2005; 38: 475–483.CrossrefMedlineGoogle Scholar5 Pignier C, Revenaz C, Rauly-Lestienne I, Cussac D, Delhon A, Gardette J, Le Grand B. Direct protective effects of poly-unsaturated fatty acids, DHA and EPA, against activation of cardiac late sodium current: a mechanism for ischemia selectivity. Basic Res Cardiol. 2007; 102: 553–564.CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetails July 15, 2008Vol 118, Issue 3 Advertisement Article InformationMetrics https://doi.org/10.1161/CIRCULATIONAHA.108.778373PMID: 18625900 Originally publishedJuly 15, 2008 PDF download Advertisement SubjectsArrhythmias

Teed Off

See related article, pages 1340–1349 In this issue of Circulation Research , Bakker et al1 report that the T-box transcription factor Tbx3 is required for development of the mouse atrioventricular conduction system. This study adds to the increasingly complex roles for T-box genes in the regulation of cell lineage maturation and proliferation in the developing heart. Previous studies from this same group have implicated Tbx3 in control of mouse sinoatrial node development and pacemaker activity.2 A closely related factor Tbx2 also contributes to atrioventricular (AV) canal specification by repressing genes expressed in the chamber myocardium.3,4 Mutations in human TBX5 cause Holt–Oram syndrome, which includes conduction system disease, and mice with heterozygous mutations in Tbx5 develop progressive AV block and other conduction anomalies.5–7 Additional T-box factors including Tbx1, Tbx20, and Tbx18 are expressed in distinct compartments of the heart and have critical functions in cardiac cell lineage maturation, proliferation, and morphogenesis.8 It is becoming increasingly apparent that multiple T-box transcription factors are important regulators of conduction system differentiation and patterning while also contributing to many other aspects of heart cell lineage development and morphogenesis. Bakker et al1 report that Tbx3 is required for maturation of the atrioventricular conduction system based on loss of function studies in mice. Mice lacking Tbx3 do not survive past embryonic day (E)14.5 and exhibit abnormal gene expression in conduction system progenitor cells, as well as severe structural malformations, including double outlet right ventricle and ventricular septal defects. Particular attention was paid to the crest of the interventricular septum, where the AV bundle components of the central conduction system will develop. In normal mice, the myocytes in the crest of the interventricular septum diversify from the rest of the septum myocardium with increased expression of Tbx3 , Tbx5 , …

Nuclear Receptors

Nuclear Receptors

Netrin-1: a potential universal biomarker for acute kidney injury

acute kidney injury (AKI) is commonly associated with high mortality and morbidity rates, which strongly depend on the time of the diagnosis to allow therapeutic interventions. Recent studies clearly indicate that routine assessments of kidney function based on serum creatinine and blood urea

Cyclic GMP/Protein Kinase G Phosphorylation of Smad3 Blocks Transforming Growth Factor-β–Induced Nuclear Smad Translocation

See related article, pages 185–192 In response to hemodynamic overload, the heart undergoes a complex adaptive remodeling process that involves cardiac myocyte hypertrophy, transformation of fibroblast into myofibroblast, high-level expression of extracellular matrix (ECM) proteins, interstitial fibrosis, and cell death.1 Differentiation of cardiac fibroblasts into myofibroblasts is critical to the production and deposition of collagens and plays a decisive role in myocardial fibrosis and morphological alterations during the progression of adaptive myocardial hypertrophy to decompensation and heart failure.1,2 Among the plethora of identified fibrogenic factors, transforming growth factor (TGF)-β3 plays a fundamental role in hypertrophic and fibrotic remodeling of the heart, where it regulates cardiomyocyte growth, fibroblast activation, and ECM deposition.4,5 The expression of ventricular TGF-β mRNA and protein is increased in numerous models of pathological cardiac hypertrophy and in cardiac cells in response to putative hypertrophic stimuli.6,7 In vitro, TGF-β activates myofibroblast transformation and increases ECM production.7 Blockade of TGF-β signaling is predicted to blunt fibrosis.5 Recent studies from Chen et al8 convincingly demonstrated that disruption of TGF-β signaling by inducible dominant-negative mutation of the TGF-β receptor type II (TβRII) gene significantly reduced the pressure overload–induced myofibroblast transformation and interstitial fibrosis in mouse heart. Thus, there is considerable interest in understanding how signaling by TGF-β receptors is transduced and how the inevitable damage produced could be mitigated. Of the 3 isoforms of TGF-β expressed in mammals,9,10 TGF-β1 is expressed in the adult heart, where it is secreted by cardiomyocytes and myofibroblasts and retained in significant amounts in ECM as a latent cytokine. Recent advances have led to clear description of downstream of TGF-β signal transduction pathways initiated by binding of TGF-β to membrane-bound heteromeric receptor kinases (TβRI and TβRII) that transduce intracellular signals via both Smad and non-Smad pathways …

Ultrasensitive gene regulation by positive feedback loops in nucleosome modification

Eukaryotic transcription involves the synergistic interaction of many different proteins. However, the question remains how eukaryotic promoters achieve ultrasensitive or threshold responses to changes in the concentration or activity of a single transcription factor (TF). We show theoretically that by recruiting a histone-modifying enzyme, a TF binding non-cooperatively to a single site can change the balance between opposing positive feedback loops in histone modification to produce a large change in gene expression in response to a small change in concentration of the TF. This mechanism can also generate bistable promoter responses, allowing a gene to be on in some cells and off in others, despite the cells being in identical conditions. In addition, the system provides a simple means by which the activities of many TFs could be integrated at a promoter.

Dictyostelium Extracellular Vesicles Containing Hoechst 33342 Transfer the Dye into the Nuclei of Living Cells: A Fluorescence Study

Cells of the eukaryotic unicellular microorganism Dictyostelium discoideum are constitutively resistant to vital staining of their nuclei by the DNA-specific dye Hoechst 33342. By studying the mechanisms of this resistance, we evidenced that these cells expel vesicles containing the dye for detoxification (Tatischeff et al., Cell Mol Life Sci, 54: 476-87, 1998). The question to be addressed in the present work is the potential use of these extracellular vesicles as a biological drug delivery tool, using Hoechst 33342 as a model of a DNA-targeting drug. After cell growth with or without the dye, vesicles were prepared from the cell-free growth medium by differential centrifugation, giving rise to two types of vesicles. Negative staining electron microscopy showed their large heterogeneity in size. Using fluorescence techniques, data were obtained on the dye loading and its environment inside the vesicles. By UV video-microscopy, it was demonstrated that the dye-containing vesicles were able to deliver it into the nuclei of naive Dictyostelium cells, thus overcoming their constitutive resistance to the free dye. A vesicle-mediated dye-transfer into the nuclei of living human leukaemia multidrug resistant K562r cells was also observed.

High quality binding modes in docking ligands to proteins

Multiple near-optimal conformations of protein-ligand complexes provide a better chance for accurate representation of biomolecular interactions, compared with a single structure. We present ISE-dock--a docking program which is based on the iterative stochastic elimination (ISE) algorithm. ISE eliminates values that consistently lead to the worst results, thus optimizing the search for docking poses. It constructs large sets of such poses with no additional computational cost compared with single poses. ISE-dock is validated using 81 protein-ligand complexes from the PDB and its performance was compared with those of Glide, GOLD, and AutoDock. ISE-dock has a better chance than the other three to find more than 60% top single poses under RMSD = 2.0 A and more than 80% under RMSD = 3.0 A from experimental. ISE alone produced at least one 3.0 A or better solutions among the top 20 poses in the entire test set. In 98% of the examined molecules, ISE produced solutions that are closer than 2.0 A from experimental. Paired t-tests (PTT) were used throughout to assess the significance of comparisons between the performances of the different programs. ISE-dock provides more than 100-fold docking solutions in a similar time frame as LGA in AutoDock. We demonstrate the usefulness of the large near optimal populations of ligand poses by showing a correlation between the docking results and experiments that support multiple binding modes in p38 MAP kinase (Pargellis et al., Nat Struct Biol 2002;9:268-272] and in Human Transthyretin (Hamilton, Benson, Cell Mol Life Sci 2001;58:1491-1521).

Cloning and Characterization of Two Human VIP1-like Inositol Hexakisphosphate and Diphosphoinositol Pentakisphosphate Kinases

Eukaryotes possess numerous inositol phosphate (IP) and diphosphoinositol phosphate (PP-IPs or inositol pyrophosphates) species that act as chemical codes important for intracellular signaling pathways. Production of IP and PP-IP molecules occurs through several classes of evolutionarily conserved inositol phosphate kinases. Here we report the characterization of a human inositol hexakisphosphate (IP6) and diphosphoinositol pentakisphosphate (PP-IP5 or IP7) kinase with similarity to the yeast enzyme Vip1, a recently identified IP6/IP7 kinase (Mulugu, S., Bai, W., Fridy, P. C., Bastidas, R. J., Otto, J. C., Dollins, D. E., Haystead, T. A., Ribeiro, A. A., and York, J. D. (2007) Science 316, 106-109). Recombinant human VIP1 exhibits in vitro IP6 and IP7 kinase activities and restores IP7 synthesis when expressed in mutant yeast. Expression of human VIP1 in HEK293T cells engineered to produce high levels of IP7 results in dramatic increases in bisdiphosphoinositol tetrakisphosphate (PP2-IP4 or IP8). Northern blot analysis indicates that human VIP1 is expressed in a variety of tissues and is enriched in skeletal muscle, heart, and brain. The subcellular distribution of tagged human VIP1 is indicative of a cytoplasmic non-membrane localization pattern. We also characterized human and mouse VIP2, an additional gene product with nearly 90% similarity to VIP1 in the kinase domain, and observed both IP6 and IP7 kinase activities. Our data demonstrate that human VIP1 and VIP2 function as IP6 and IP7 kinases that act along with the IP6K/Kcs1-class of kinases to convert IP6 to IP8 in mammalian cells, a process that has been found to occur in response to various stimuli and signaling events.

Old Drug, New Tricks

See related article, pages 156–165 Ironically, even though there are currently only a few drugs to specifically treat low high-density lipoprotein (HDL), numerous drugs have been observed to inadvertently alter HDL levels.1 This has been particularly noted for some antihypertensive drugs. Because they are used long-term, any positive or negative effect of antihypertensive drugs on lipids and lipoproteins can significantly impact on their effectiveness in preventing cardiovascular disease. Recently, advances in our understanding of HDL metabolism have helped us to unravel the mechanism of action of these and other drugs that unexpectedly alter HDL levels. This work has largely been led by the laboratory of Shinji Yokoyama and colleagues, who have previously identified the mechanism of action of three drugs on HDL metabolism. Probucol, which has been used to treat patients at risk for cardiovascular disease, is an antioxidant and lowers LDL, but it also lowers HDL. Probucol is now known to decrease HDL by inhibiting the activity of the ABCA1 transporter,2 a key protein involved in reverse cholesterol transport pathway and in HDL biogenesis.3 Verapamil, a calcium channel blocker, which can be used as antihypertensive and antiarrhythmic agent, and fenofibrate, a lipid-lowering drug, both raise HDL by increasing the gene expression of the ABCA1 transporter.4,5 In this issue of Circulation Research ,6 Iwamoto et al describe the mechanism of action of a fourth agent that unexpectedly alters HDL, namely the antihypertensive agent doxazosin. The results of this study raise the possibility of a new strategy for developing drugs to increase HDL. Doxazosin (Cardura) is a quinazoline based compound that is sold by Pfizer and is a long lasting selective inhibitor of the α-1a subtype of adrenergic receptors. It blocks the binding of norepinephrine to adrenergic receptors in the autonomic nervous system, which leads …

Myocardial 15-Epi-lipoxin A 4 Generation Provides a New Mechanism for the Immunomodulatory Effects of Statins and Thiazolidinediones

“In matters of observation, chance favors only the prepared mind.” This famous maxim of Louis Pasteur, spoken in 1854 during his inaugural lecture as Professor and Dean at the University of Lille, can be applied today to the fortuitous observation that hydroxymethylglutaryl–coenzyme A (HMG-CoA) reductase inhibitors, in addition to their designed lipid-lowering effects, display a fascinating array of antiinflammatory properties. Post hoc analyses of the West of Scotland Coronary Prevention Study (WOSCOPS) population, and more recently the Cholesterol and Recurrent Events (CARE), Myocardial Ischemia Reduction With Aggressive Cholesterol Lowering (MIRACL), Long-term Intervention With Pravastatin in Ischemic Disease (LIPID), and Heart Protection Study (HPS) trials, have all found benefits conferred by statins that are independent of low-density lipoprotein cholesterol–lowering alone.1 Only through careful analyses of early clinical trials of statins administered for lowering cholesterol and cardiovascular events did scientists uncover additional benefit for these agents in cardiac protection beyond their ability to reduce cholesterol synthesis. Inflammation and immune responses are now appreciated to play pivotal roles in the pathobiology of atherosclerosis,2 and recent clinical and basic investigations have uncovered important immunomodulatory roles for statins.3 Of interest, the peroxisome proliferator-activated receptor family of transcription factors is activated by and cooperates with statins in their antiinflammatory actions. In this issue of Circulation , Birnbaum and colleagues4 present evidence for increased myocardial production of 15-epi-lipoxin (LX)A4 by atorvastatin and the peroxisome proliferator-activated receptor-γ ligand pioglitazone. The generation of 15-epi-LXA4 would provide a novel mechanism for immune regulation by statins because this arachidonic acid–derived chalone displays potent antiinflammatory and proresolving properties,5 including many that have also been observed with statins (Table). View this table: Shared Antiinflammatory Actions of Statins and 15-Epi-lipoxin A4 Article p 929 Cell activation initiates the rapid generation of eicosanoids …