Mary G. Sorci-Thomas - US grants

The incidence of premature coronary atherosclerosis in the human population. Highly correlated to decreased concentrations of high density lipoprotein or its major apolipoprotein A-I, this condition is referred to as hypoalphalipoproteinemia. The goal of the studies proposed in this application are to elucidate the molecular mechanisms which are responsible for regulating the production of high density lipoproteins at the level of apo-A-I gene expression. In order to clearly define differences based on apo A-I gene expression and to relate these differences to variation in apo A- I production, a recently described model system will be used. It is well established that the African green monkey develops a less severe hypercholesterolemia and atherosclerosis than the cynomolgus monkey when fed levels of cholesterol and fat resembling the North American diet. An important feature of this difference is that African green monkeys have a substantially higher (3 fold) level of plasma HDL and apo A-I concentration than cynomolgus monkeys, factors which may contribute to their greater ability to resist the development of atherosclerosis. Furthermore, apo A-I mRNA abundance in both the liver and small intestine have been found to correlate with the level of hepatic apo A-I production and apo A- I plasma concentration for both the African green and cynomolgus monkey. The studies proposed in this application, therefore, will seek to determine if this species-specific difference in the levels of tissue apo A-I mRNA reflect differences in the regulation and expression of the primate apo A-I gene. To do this, the apo A-I gene will be isolated and sequenced from both African green and cynomolgus monkeys. The degree of sequence homology between the two species will be compared, as well as to the human apo A-I gene sequence. Relative rates of apo A-I transcription will be measured and, the apo A-I mRNA steady state abundance measurements will be correlated to the rates of apo A-I gene transcription for liver and small intestine in both species. 5'flanking sequences of the apo A-I gene for both the African green and cynomolgus monkey will be analyzed by deletion mapping analysis to identify regulatory elements which responsible for species-specific expression of the primate apo A-I gene. The entire apo A-I gene cluster will be investigated in both primate species to determine whether apo A-I, apo C-III and apo A-VI exists as a multi-gene family. The knowledge gained by the completion of these studies will be used to develop strategies for the treatment of hypoalphalipoproteinemia and coronary heart disease.

The incidence of premature coronary atherosclerosis in the human population is highly correlated to decreased concentrations of high density lipoprotein (HDL) and its major apoprotein, apo A-I found in the blood. Transgenic and knockout animal studies have shown conclusively that the "protective effect" of circulating HDL is primarily a function of its unique ability to accept and organize cholesterol. It is also a function of its ability to activate the enzyme lecithin: cholesterol acyltransferase (LCAT) for cholesterol acyltransferase (LCAT) for cholesterol to cholesterol ester conversion in the plasma compartment. The directional movement of cholesterol from the artery wall and peripheral tissues towards its only site of catabolism, the live, involves a number of well studied steps. Apo-AI appears to be to be plays a key role in each of these steps. Apo A-I is the primary acceptor for effluxed cholesterol from peripheral cells. Together with phospholipid, apo A-I and cholesterol form nascent discoidal HDL which is the preferred substrate for the plasma LCAT. This enzyme is responsible for converting newly effluxed cholesterol to cholesterol ester. Accumulation of the hydrophobic cholesterol ester as a lipid droplet in the core of spherical HDL and its ultimate delivery of cholesterol ester to the live completes the "reverse cholesterol transport" pathway. In this research proposal. we will investigate the molecular basis for the "activation of the enzyme LCAT by apo A-I. This important enzymatic pathway is known to be defective in humans who carry certain mutations within the apo A-I coding sequence. However, it is not known "how" the apo A-I protein on the surface of a nascent discoidal HDL particle co-activate this catalytic process. Therefore, to elucidate the molecular mechanism of this process we will construct a series of specific amino acid mutants using PCR mutagenesis, then produce these proteins in milligram quantities using our baculoviral Sf-9 cell system. The mutant apo A-I proteins will be extensively studied using both biochemical and biophysical techniques to determine which key structural features are responsible for properly orienting the nascent HDL phospholipid acyl chain for LCAT catalysis.

The incidence of premature coronary atherosclerosis in the human population is highly correlated to decreased concentrations of plasma high density lipoproteins (HDL) and its major apoprotein, apolipoprotein A-I (apo A-I). Transgenic and knockout mouse studies have shown that circulating HDL apo A-I primarily plays a "protective function" in response to high levels of atherogenic lipoproteins through its ability to accept, organize and transport cholesterol out of the artery to the liver for uptake and excretion into bile. This "reverse cholesterol transport pathway" is highly dependent upon apo A-I's ester conversion in the plasma. Blockage or reduction in apo A-I's ability to carry out this function can lead to reduced reverse cholesterol transport and inefficient removal of peripheral tissue cholesterol. Data from the applicants' laboratory show that structural alterations in the conformation of plasma apo A-I can have a more profound effect on HDL apo A-I formation and maturation than merely the absence of native apo A-I alone. Their studies show that LCAT activation and thus, plasma cholesterol esterification is inhibited by the presence of a mutant form of apo A-I in plasma. The mutant apo A-I does this by inhibiting plasma cholesterol esterification even in plasma containing native or wild type apo A-I. Thus, they propose to investigate the molecular and cellular basis for the severe disruption in HDL metabolism resulting from the hepatic expression of the mutant human apo A-I, termed 6 apo A-I. This mutant of apo A-I lacks repeat 6, a single proline punctuated 22-mer and has been shown to have a similar plasma lipoprotein phenotype to a known human apo A-I mutation, called apo A-I. In a newly created transgenic mouse model, designated Tg6 apo A-I the applicants propose to conduct dietary-cholesterol feeding studies to determine if mutant apo A-I protects against atherosclerosis in mice with hypercholesterolemia. They also plan to elucidate the molecular and cellular basis for 6 apo A-I's disruption of HDL apo A-I metabolism.

The primary focus of this research project is to investigate the mechanisms through which apolipoprotein A-I (apo A-I) acts on high density lipoproteins (HDL) to activate lecithin:cholesterol acyltransferase (LCAT) thereby promoting the maturation of HDL particles and the removal of excess cholesterol from peripheral tissues of the body. The overall hypothesis we are testing is that negatively and positively charged residues within repeat 6 are responsible for LCAT activation either through direct apo A-I to LCAT interactions or through the formation a intra-molecular salt bridge(s) which stabilize a conformation of apo A-I that interacts with LCAT. To test this hypothesis, we will carry out three specific aims. The first aim will be to determine the lipid-bound conformation of apo A-I on discs and spheres using fluorescence resonance energy transfer (FRET) and chemical crosslinking combined with electrospray mass spectroscopy. This information will help to establish a "conformational map" of lipid-bound apo A-I before binding to LCAT and aid in determining if the conformation of lipid-bound apo A-I is altered once LCAT binds to its substrate. Our second aim will be to map contact sites between apo A-I and LCAT using a photoactivatible crosslinker attached to cysteine residues placed at specific sites within repeat 6. These studies will allow us to definitively show that apo A-I and LCAT interact during activation. These studies will also tell us specifically which apo A-I side-chain residue(s) potentially interact with LCAT. Thirdly, we will determine the in vitro and in vivo significance of the 4 negative and 6 positively charged residues within repeat 6. These studies will be carried out using apo A-I mutagenesis and in vitro LCAT assays. We will also develop and study transgenic animals expressing mutant forms of apo A-I. In summary, these studies will allow us to elucidate the mechanism responsible for activation of LCAT by apo A-I and the metabolic importance of apo A-I charged repeat 6 residues on HDL metabolism and the development of atherosclerosis. It is our hope that this information may eventually lead to new therapies for the prevention and treatment of atherosclerosis and CHD.

DESCRIPTION (provided by applicant): This proposal is focused on elucidating the role of high density lipoprotein apolipoprotein A-l in reverse cholesterol transport as it relates to the prevention of inflammation and progression of atherosclerosis. We have produced and characterized a new double knockout animal model, the LDL receptor -/- and apoA-I -/- mouse in order to study and elucidate mechanisms by which HDL apoA-1 stimulates the removal of peripheral tissue cholesterol, modulates inflammation, and prevents the progression of atherosclerosis. Previous studies in hypercholesterolemic mice indicate that HDL apoA-I plays two important roles. The first, involves the removal of cholesterol from peripheral tissues preventing accumulation within the artery wall. Secondly, apoA-l serves to modulate the expression of adhesion molecules on endothelial cells lining the artery and modulates the induction of oxidative stress and inflammation. Preliminary studies from our group have shown that LDL receptor -/-, apoA-I -/- mice fed a Western diet containing 0.1% cholesterol and 10% fat show an approximate approximately 12-fold greater accumulation of cholesterol in peripheral tissues when compared to LDL receptor -/- only mice. Therefore, in this proposal we plan to test our main hypothesis that in the absence of plasma HDL apoA-I reverse cholesterol transport to the liver is severely limited, allowing for dramatic accumulation of foam cell derived cholesterol ester in peripheral tissues, the onset of inflammation, and the development of atherosclerosis. To test this hypothesis, we plan to measure cholesterol flux in vivo including; absorption, hepatic cholesterol synthesis and secretion, extrahepatic cholesterol synthesis, acquisition and cholesterol turnover in chow and diet-fed LDL receptor -/-, apoA-I -/- mice and compare to LDL receptor -/- and apoA-I -/- only mice. We also plan to test the hypothesis that inhibition of reverse cholesterol transport and the onset of inflammation in LDL receptor -/-, apoA-I-/- mice is reversible by restoring plasma HDL apoA-I concentration to LDL receptor -/-, apoA-l -/- mice using helper-dependent adenoviral technology. We believe that these studies will lead to important new information regarding the role of apoA-l in the initial stages of atherosclerosis development and define the link between hypercholesterolemia and inflammation and their respective roles in the pathogenesis of atherosclerosis.

DESCRIPTION (provided by applicant): This application is for partial support of the 2006 Gordon Research Conference on Lipoprotein Metabolism to be held at Mt. Holyoke, College in South Hadley, MA on July 2-7, 2006. This conference will focus on important new developments in lipid and lipoprotein metabolism, particularly in those areas that impact on human metabolic disease and the development of atherosclerotic vascular disease. Basic molecular and cell biological studies and in vivo studies in humans and animal models will be presented. Topics will include the role of lipids in development, apoprotein structure and function, high density lipoprotein inflammation and oxidation in atherosclerosis, human genetics of lipoprotein metabolism, mechanism of hyperlipidemia-induced atherosclerosis, molecular physiology of lipid metabolism, regulation of lipid synthesis and transport by nuclear receptors, ABC transporters, and lipid uptake and storage. Nine sessions are planned: 1. Emerging Role of Lipids in Development 2. Apoprotein Structure and Function 3. HDL, Inflammation and Oxidation in Atherosclerosis 4. Genetic Determinants of Lipoprotein Transport 5. Mechanisms of Hyperlipidemia-induced Atherosclerosis 6. Molecular physiology of lipid metabolism 7. Regulation of Lipoprotein Metabolism by Nuclear Hormone Receptors 8. ABC Transporters 9. Lipid Uptake and Storage This conference will be a major vehicle for the presentation and integration of the latest developments in lipoprotein and lipid metabolism. Emphasis will be placed on in-depth presentations and thorough discussions of new, largely unpublished studies. Important aims of the Gordon Research Conference on Lipoprotein Metabolism are to include the diversity of qualified professionals and to foster interactions among young investigators, post-doctoral fellows, graduate students, and senior investigators.

Atherosclerosis is a chronic inflammatory disease that is promoted by the consumption of dietary fat and cholesterol. The extent to which atherosclerosis progresses to cause coronary occlusion and/or death is mediated by the presence of plasma apoA-l, the main protein constituent of high density lipoproteins (HDL). The role of HDL apoA-l in whole body cholesterol homeostasis has been extensively investigated and its role is to direct cholesterol from the periphery to the liver for excretion. Despite intensive investigations, major questions remain regarding the mechanism by which apoA-l regulates cellular cholesterol levels and how the apoprotien's unique structural features facilitate cholesterol transport. To more completely understand the structural basis for apoA-l's role in cholesterol transport, we will carry out three specific aims that will clarify the structural reorganization necessary for the formation of nascent HDL via ABCA1. In Aim 1 we propose to address the role of apoA-l in cholesterol homeostasis by determining the conformation of apoA-l on four different sized subclasses of ABCA1 generated nascent HDL. Also as part of Aim 1, we will examine the 'unfolding'steps'through which lipid-free apoA-l acquires lipid from ABCA1. To do this we will construct a series of 'tethered'disulfide apoA-l mutants that will prevent key intermediate unfolding steps through which the 4-helix bundle must transition as it organizes and binds phospholipid and cholesterol. In the Aim 2, we will investigate the mechanistic basis for the dominant negative repression of wild-type apoA-l HDL, as observed in humans who carry this mutation, by investigating the lipidation of the helix 6 mutant, L159R apoA-l by ABCA1. Our preliminary studies suggest that this single amino acid substitution mutant, L159R apoA-l, competes with wild-type apoA-l for phospholipid and cholesterol, resulting in a reduction in the overall lipidation of wild-type apoA-l by ABCA1 in a model cell culture system. In Aim 3, we plan to determine whether the dominant negative phenotype associated with the L159R apoA-l mutant is pro- or antiatherogenic in hyperlipidemic mice. Using transgenic mice that express wild-type or L159R apoA-l, we will determine the extent to which the mutant apoA-l protects against the development of atherosclerosis, as well as investigating the in vivo basis for the low concentration of L159R apoA-l in plasma as it relates to the dominant negative phenotype.

DESCRIPTION (provided by applicant): Accelerated atherosclerosis displays a complex pathogenesis including alterations in lipids, inflammatory state involving the immune system. HDL apoA-I protects against these changes mainly through its ability to organize and recruit cholesterol and oxygenated forms of cholesterol and phospholipids from immune cells protecting them from dysregulation and apoptosis. In the current proposal, we will investigate the molecular mechanisms responsible for immune cell cholesterol deposition, accelerated atherosclerosis and the development of an autoimmune phenotype in response to an atherogenic diet in LDL receptor, apoA-Idouble knockout (DKO) mice. In previous studies, when DKO and LDLr-/- (SKO) mice were fed an atherogenic diet, DKO mice developed enlarged peripheral lymph nodes (LNs) and spleens compared to SKO mice. DKO LN were enriched in cholesterol ester (CE) and contained expanded populations of CE enriched T, B, dendritic cells and macrophages. Plasma antibodies to dsDNA and oxidized LDL were also increased in DKO suggesting an autoimmune phenotype. Both LN enlargement and LN CE accumulation were "prevented" when diet-fed DKO mice were treated with apoA-I at the time the diet was initiated. Regardless of the level of dietary cholesterol, DKO mice consistently showed lower plasma cholesterol than SKO mice, yet greater aortic cholesterol deposition and inflammation. Therefore, the goal of this proposal is to use the DKO mouse to investigate the mechanisms by which apoA-I 1) modulates CE and oxysterol accumulation and activation in lymphocytes, 2) alters the proliferation and/or apoptosis of CE loaded lymphocytes, 3) affects the contribution of T cells and DC to plaque infiltration in both progression and regression of atherosclerosis in diet-fed DKO mice. PUBLIC HEALTH RELEVANCE: Atherosclerosis is a chronic inflammatory disease that is initiated by cellular cholesterol dysregulation at the vessel wall. Our proposed studies will investigate the mechanisms explaining the role of apoA-I in regulating lymphocyte cholesterol homeostasis, autoimmunity and atherosclerosis. These studies will likely provide new targets for therapeutic interventions to control the inflammatory processes that exacerbate atherosclerosis.

DESCRIPTION (provided by applicant): The oxidation status of HDL plays an important role in determining how this lipoprotein prevents or promotes atherosclerosis. Since patients with normal levels of HDL experience atherogenic events (ie., stroke, myocardial infarction), HDL function itself may be a stronger indicator of cardiovascular disease than the actual levels of HDL cholesterol. Bioassays of HDL function are complex, time-consuming, technician- and technique-dependent and difficult to reproduce between labs. Thus, highly efficient assays of HDL function are desperately needed. In this application, we hypothesize that the biophysics of HDL interactions with biomolecules the mediate HDL-dependent cholesterol metabolism represent a novel source of physiological information that can be used to assess the functional state of HDL. Using biolayer interferometry (BLI), a new label-free technique for measuring biomolecular interactions, we will develop a series of novel assays of HDL function to determine if and the extent to which oxidation impacts on the ability of HDL to interact with 1) anti- and pro-inflammatory enzymes (paraoxonase [PON1], platelet activating factor acetylhydrolase [PAF-AH], myeloperoxidase [MPO] and xanthine oxidase [XO]) to prevent LDL oxidation; 2) or ATP binding cassette (ABC) transporter 1 (ABCA1)/ABCG1, lecithin cholesteryl acyl transferase (LCAT), cholesteryl ester transfer protein (CETP) and scavenger receptor class B1 (SR-B1) to mediate HDL-cholesterol release, esterification, transfer and uptake, respectively. The mechanisms by which HDL is anti-inflammatory or participates in reverse cholesterol transport is directly dependent on the ability of HDL to bind these biomolecules. As such, any oxidation-induced changes in HDL binding affinity for these biomolecules should provide a sensitive index of HDL functionality. In Aim 1, we propose to measure the extent to which oxidized lipids and proteins in reconstituted HDL (r-HDL) impair HDL function using established in vitro bioassays of cholesterol release, esterification, transfer and uptake. In Aim 2, we will ue BLI assays to determine how oxidized lipids and proteins in r-HDL alter binding rates and affinity for the proteins and enzymes that mediate HDL's ability to inhibit LDL oxidation or promote specific steps in the reverse cholesterol transport pathway. In Aim 3, we propose to verify and validate that BLI assays by 1) correlating BLI assays with bioassays of HDL function in established murine models of vascular disease and 2) by using BLI assays to predict which patients have clinically-diagnosed atherosclerosis in case-controlled, blinded human studies. Successful completion of these studies will lay the foundation for the development of a new clinical assay for determining HDL functionality. Validation of these new assays will allow us to identify which patients have dysfunctional HDL in a time frame and for a cost that is compatible with clinical reference laboratories. Development of these novel assays will make it possible, for the first time, to perform large clinical studies to fully test the idea that dysfunctional HDL is better indicator of atherosclerotic risk.

DESCRIPTION (provided by applicant): T regulatory lymphocytes (Treg) maintain immune tolerance by suppressing both innate and adaptive immune cells. Tregs are atheroprotective, yet Treg phenotypes and function are disturbed during atherosclerosis progression. High-density lipoproteins (HDL) are atheroprotective, in large part due to their function in reverse cholesterol transport. However, HDL also performs cholesterol-independent functions, including the transport of sphingosine-1-phosphate (S1P), an important lipid mediator of immunity. Apolipoprotein M, found on HDL, binds S1P to aid in delivery of S1P to cells in the vasculature, including cells involved in adaptive immunity. Based upon our work and that of others, S1P most likely acts to impart differential effects on cytokine production by dendritic cells and lymphocyte depending on the microenvironment. We hypothesize that a novel function of HDL in adaptive immunity is related to the ability of HDL to stabilize Treg homeostasis and suppressive activity in vivo during atherogenesis. We will test our hypotheses in 2 specific aims. Specific Aim 1 will test the hypothesis that HDL regulates Treg homeostasis in atherosclerosis through S1P action. Specific Aim 2 will identify mechanisms for how HDL-S1P impacts both cell-autonomous dendritic cell and Treg actions to preserve Treg function in atherosclerosis.

? DESCRIPTION (provided by applicant): The overall goal of this grant proposal entitled Biogenesis of HDL Through Cholesterol Efflux and ApoA-I Structural Reorganization is to define a novel role for Procollagen C Proteinase Enhancer 2 (PCPE2) in the formation and function of HDL as it relates to the progression of atherosclerosis. By 2025, worldwide death due to atherosclerosis and associated complications is projected to surpass that of every major disease, including cancer, infection and trauma. The total cost of atherosclerosis-related diseases in the U.S. alone is estimated to be $286 billion annually. After statins, there is no break-through strategy in the pipeline to combat this deadly global disease. Our laboratory has studied the role of HDL apoA-I in atherosclerosis for the last 25 years and have shown, as others have, that apoA-I is an important modulator of atherosclerosis. Despite this clarity, all attempts to reduce atherosclerosis in humans by pharmacologically raising HDL levels have failed. Many believe this is a result of increasing plasma HDL concentrations without increasing or raising its functionality. Therefore, we expect to show that PCPE2 enhances HDL functionality at both the level of cholesterol efflux, as well as, its role in HDL turnover and catabolism. To do this we have crafted three specific aims. Specific Aim 1: To investigate molecular transitions of specific apoA-I helical domains responsible for promoting the biogenesis of nascent HDL (nHDL). Specific Aim 2: Delineate the role of the accessory protein, PCPE2 in nHDL assembly by examining interactions between these two proteins and to determine how this interaction affects the opening of lipid-free apoA-I. Specific Aim 3. Examine the role PCPE2 plays in mediating HDL metabolism and in the development of atherosclerosis in a newly created LDLr- /-, PCPE2-/- mouse model. At the end of the project, we expect that PCPE2 will be found to be a novel molecule mechanistically involved in increasing HDL functionality in humans providing a new strategy for combating atherosclerosis.

PROJECT SUMMARY The receptor-ligand complex of scavenger receptor class B type I (SR-BI) and high density lipoprotein (HDL) is responsible for removal of cholesteryl ester (CE) from the body. This process is crucial to the prevention of hypercholesterolemia and atherosclerosis. Recently, a study in mice reported that knocking out (KO) procollagen endopeptidase enhancer 2 (PCPE2), an extracellular matrix protein, resulted in a paradoxical finding of increased plasma HDL associated with a greater extent of atherosclerosis. Additional investigation demonstrated that in spite of increased SR-BI levels in livers of PCPE2 KO mice, both plasma cholesterol clearance and sterol excretion were reduced. Based on these novel findings, we suggest that PCPE2 either directly interacts with HDL particles or with SR-BI, or a combination of the two, to stabilize HDL interaction(s) with the receptor and/or provide a scaffold to hold SR-BI in place within the membrane. In this multi-PI application Dr. Sorci-Thomas and Dr. Sahoo propose to carry out collaborative studies to test the hypothesis that PCPE2 functionalizes SR-BI receptors on the cell surface to facilitate bidirectional cholesterol transport. In Aim 1 we investigate how SR-BI works in synergy with PCPE2 to maintain cellular cholesterol homeostasis. A newly-generated CRISPR/Cas9 PCPE2-deleted 3T3 cell line and a new tissue-specific PCPE2 knockout mouse model will be used to elucidate the physiological relevance of the partnership between SR-BI and PCPE2, and define how they work together to promote receptor translocation and bidirectional cholesterol transport. Preliminary data already support a unique physiological role for this partnership in mouse adipose tissue, in isolated mouse adipocytes and in differentiated 3T3 cells, suggesting that these two proteins play a significant role in lipid storage. Aim 2 will explore the mechanism defining how SR-BI partners with PCPE2 to enhance CE uptake from HDL. Specifically, we will determine if PCPE2 facilitates SR-BI oligomerization on the plasma membrane, a process that is postulated to enable HDL-CE delivery into cells, perhaps by orchestrating interactions between HDL and SR-BI. This will be tested in both freshly isolated adipocytes as well as in our PCPE2-deleted 3T3 cell line recently created using CRISPR/Cas9 methods. In Aim 2, utilizing a combination of mutagenesis, and innovative biochemical and mass spectrometry strategies, we will identify specific regions of interaction between PCPE2 and SR-BI or PCPE2 and HDL. Together, these innovative studies will exploit the complementary expertise of the Sorci-Thomas and Sahoo labs to identify novel mechanisms that regulate SR- BI's function in bidirectional cholesterol transport. The findings from these studies will help identify new therapeutic strategies for preventing hypercholesterolemia and its associated pathologies such as atherosclerosis.

The Councils on Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB) and Peripheral Vascular Disease (PVD) of the American Heart Association (AHA) hold an annual Spring Meeting, the most recent of which, Vascular Discovery: From Genes to Medicine, was planned to be held in Chicago, but ultimately was switched into the AHA's very first fully virtual meeting in May 2020. The conference was a resounding success with 964 registrants representing 31 different countries. Five hundred and forty-three abstracts were submitted for our virtual conference, a slight 3% decrease compared to the previous year when the meeting was held face-to-face in Boston. These encouraging statistics provide tangible evidence of the broad interest and commitment of the scientific community in the topic areas of ATVB, PVD and vascular medicine, and the overwhelming enthusiasm for the format and atmosphere of this meeting. Basic scientists, translational researchers and clinicians, seasoned investigators and early career scientists enjoy coming to this AHA Spring meeting. The next Vascular Discovery conference will be held May 20-22, 2021 at the New Orleans Marriott, LA. As with previous applications, this proposal specifically requests support for our Young Investigator Travel Awards. Knowing that early stage investigators are the future of our scientific progress, a major emphasis of our annual conference is to encourage the active involvement of the younger cohort of investigators in the ATVB and PVD Councils of the AHA and recognize their achievements. These awards are an integral part of our strategy to recruit, retain and actively engage young investigators in the fields of arteriosclerosis, thrombosis, vascular biology and vascular medicine research that are of major importance to the NIH-NHLBI and the health of the U.S. population.