Biomedical subjects

L K Curtiss

Publications and source records attributed to L K Curtiss.

At least 19 recordsLinked to original sources

PubMed1999

Studying low-density lipoprotein-monoclonal antibody complexes using dynamic laser light scattering and analytical ultracentrifugation.

Monoclonal antibody complexes have proven very useful in the study of low-density lipoproteins (LDLs). Thus, complexes composed of two different monoclonal antibodies, selected from a panel of 11 different antibodies, and LDL have been employed to map apolipoprotein B (apoB) on the surface of the LDL. In this way, apoB was found to surround the LDL as a ribbon with a bow [Chatterton, J. E., et al. (1995) J. Lipid Res. 36, 2027-2037]. Moreover, monoclonal MB19, which recognizes a polymorphic site, has been employed to quantitate the two different allelic forms of apoB found on LDL in human sera, and in this way, we assessed the effect of most of the known common polymorphisms of this protein as well as detected the depletion of the normal allele product in two forms of familial defective apoB-100 [Chatterton, J. E., et al. (1995) Biochemistry 34, 9571-9580; Pullinger, C. R., et al. (1995) J. Clin. Invest. 95, 1225-1234]. In this paper, these studies have been extended by examining by dynamic light scattering and sedimentation velocity techniques the complexes formed with only one antibody, and complexes formed using two antibodies. Our data show that the largest complex formed with a single monoclonal antibody was that of an LDL dimer; no larger, nonspecific complexes were present. With two antibodies, a variety of complexes were seen. Thus, monoclonal antibodies MB47 and 4G3, which bound about 55 degrees apart, formed a very stable dimer. Monoclonal antibodies MB47 and 2D8, which bound 136 degrees apart, formed a very stable tetramer, with four LDLs held together in probably a circular structure with four monoclonal antibodies. Finally, monoclonal antibodies 2D8 and 1D1, which bound 86 degrees apart, probably formed a less stable LDL tetramer, held together by three to four monoclonal antibodies. A rationale for these structures is discussed, as well as the biological relevance of these complexes.

Animals↗

PubMed1999

ApoA1 reduces free cholesterol accumulation in atherosclerotic lesions of ApoE-deficient mice transplanted with ApoE-expressing macrophages.

Along with apolipoprotein (apo) E, which promotes cholesterol efflux from foam cells, apoA1-containing high density lipoprotein (HDL) is thought to facilitate the transport of cholesterol from lesions. This role for apoA1 was tested in vivo by lethally irradiating apoE-deficient and apoE- plus apoA1-deficient mice and reconstituting them with bone marrow cells isolated from wild-type (WT) mice. ApoE, but not apoA1, was synthesized by the transplanted bone marrow-derived cells. Therefore, this transplantation procedure generated apoE-deficient animals with atherosclerotic lesions that contained both apoE and apoA1 (E/A1 mice) and apoE-deficient animals with lesions that contained apoE but no apoA1 (E/A1o mice). As shown previously, the transplanted WT macrophage-derived apoE dramatically lowered the plasma hypercholesterolemia in both groups. On feeding with an atherogenic diet after transplantation, plasma cholesterol levels were raised in both groups of mice, but the levels in the E/A1 mice at 20 weeks were 2- to 3-fold higher than in E/A1o mice. Immunohistochemical staining verified that apoE was abundant in lesions of both groups, whereas apoA1 was detected in the lesions of E/A1 mice only. Despite a 2- to 3-fold lower total plasma cholesterol in the E/A1o mice, the free cholesterol recovered from isolated aortas was approximately 60% higher and the mean lesion area in serial sections of the aortic valves 45% larger. Therefore, apoA1 reduces free cholesterol accumulation in vivo in atherosclerotic lesions.

Animals↗

PubMed1999

Monoclonal autoantibodies specific for oxidized phospholipids or oxidized phospholipid-protein adducts inhibit macrophage uptake of oxidized low-density lipoproteins.

We recently cloned monoclonal IgM autoantibodies which bind to epitopes of oxidized low-density lipoprotein (OxLDL) from apoE-deficient mice (EO- autoantibodies). We now demonstrate that those EO- autoantibodies that were originally selected for binding to copper-oxidized low-density lipoproteins (CuOx-LDL), also bound both to the oxidized protein and to the oxidized lipid moieties of CuOx-LDL. The same EO- autoantibodies showed specific binding to products of oxidized 1-palmitoyl-2-arachidonoyl-phosphatidylcholine (OxPAPC) and to the specific oxidized phospholipid, 1-palmitoyl-2-(5-oxovaleroyl)-phosphatidyl-choline (POVPC), whereas oxidation of fatty acids (linoleic or arachidonic acid) or cholesteryl esters (cholesteryl-oleate or cholesteryl-linoleate) did not yield any binding activity. Those EO- autoantibodies that bound to oxidized phospholipids (e.g., EO6) inhibited the binding and degradation of CuOx-LDL by mouse peritoneal macrophages up to 91%, whereas other IgM EO- autoantibodies, selected for binding to malondialdehyde (MDA)-LDL, had no influence on binding of either CuOx-LDL or MDA-LDL by macrophages. F(ab')2 fragments of EO6 were equally effective as the intact EO6 in preventing the binding of CuOx-LDL by macrophages. The molar ratios of IgM to LDL needed to maximally inhibit the binding varied from approximately 8 to 25 with different CuOx-LDL preparations. Finally, a POVPC-bovine serum albumin (BSA) adduct also inhibited CuOx-LDL uptake by macrophages. These data suggest that oxidized phospholipid epitopes, present either as lipids or as lipid-protein adducts, represent one class of ligands involved in the recognition of OxLDL by macrophages, and that apoE-deficient mice have IgM autoantibodies that can bind to these neoepitopes and inhibit OxLDL uptake.

Animals↗

PubMed1999

High-density lipoprotein enhancement of anticoagulant activities of plasma protein S and activated protein C.

Low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels are associated, respectively, with either increased risk or apparent protective effects for atherothrombosis. The ability of purified LDL and HDL to downregulate thrombin formation, a contributor to atherothrombotic processes, was assessed. Purified HDL, but not LDL, significantly enhanced inactivation of coagulation factor Va by activated protein C (APC) and protein S, and HDL stimulated protein S-dependent proteolytic inactivation of Va by APC, apparently due to cleavage at Arg306 in Va. In normal plasma, added HDL enhanced APC/protein S anticoagulant activity in modified prothrombin-time clotting assays. When the anticoagulant potency of HDL was compared with phospholipid (PL) vesicles of well-defined composition using this assay, HDL appeared qualitatively different from PL vesicles because HDL showed only good anticoagulant activity, whereas PL vesicles were rather procoagulant. When 20 normal plasmas were tested using this clotting assay, apoA-I levels correlated with anticoagulant response to APC/protein S (r = 0.47, P = 0.035), but not with activated partial thromboplastin time-based APC resistance ratios. Because HDL enhances the anticoagulant protein C pathway in vitro, we speculate that HDL may help downregulate thrombin generation in vivo and that this anticoagulant action is one of HDL's beneficial activities.

Anticoagulants↗

PubMed1999

Comparison of the effects of Apo(a) kringle IV-10 and plasminogen kringles on the interactions of lipoprotein(a) with regulatory molecules.

Lipoprotein(a) [Lp(a)] is associated with atherosclerosis and with disease processes involving thrombosis. Lp(a) contains apoprotein (a) [apo(a)], which has a sequence highly homologous to plasminogen. Hence, Lp(a) binds directly to extracellular matrix, cellular plasminogen receptors and fibrin(ogen) and competes for the binding of plasminogen to these regulatory surfaces. These interactions may contribute to the proatherothrombogenic consequences of high Lp(a) levels. These interactions are mediated by lysine binding sites (LBS). Therefore, we examined the role of apo(a) kringle IV-10 [the only apo(a) kringle demonstrated to exhibit lysine binding activity in the intact lipoprotein] in the interaction of Lp(a) with these regulatory molecules. We have compared directly apo(a) KIV-10 with plasminogen K4 to examine whether these highly structurally homologous kringle modules are also functionally homologous. Futhermore, because the plasminogen K5-protease domain (K5-PD) binds directly to fibrin, we have also examined the ability of this plasminogen fragment to inhibit the interaction of Lp(a) with these regulatory molecules and with extracellular matrix. Apo(a) KIV-10 competed effectively for the binding of 125I-Lp(a) to these surfaces but was less effective than either intact Lp(a), plasminogen K4 or plasminogen. Plasminogen KS-PD was a better competitor than apo(a) KIV-10 for 125I-Lp(a) binding to the representative extracellular matrix, Matrigel, and to plasmin-treated fibrinogen. In contrast, plasminogen K5-PD did not compete for the interaction of Lp(a) with cells, although it effectively competed for plasminogen binding. These results suggest that Lp(a) recognizes sites in all of the regulatory molecules that are also recognized by apo(a) KIV-10 and that Lp(a) recognizes sites in extracellular matrix and in plasmin-modified fibrinogen that also are recognized by plasminogen K5-PD. Thus, the interaction of Lp(a) with cells is clearly distinct from that with extracellular matrix and with plasmin-treated fibrinogen and the recognition sites within Lp(a) and plasminogen for these regulatory molecules are not identical.

Apolipoproteins A↗

PubMed1999

Elimination of macrophage-specific apolipoprotein E reduces diet-induced atherosclerosis in C57BL/6J male mice.

Apolipoprotein (apo)E is synthesized in atherosclerotic lesions by macrophages, however, its role in lesions is not known. Whereas apoE could exacerbate atherosclerosis by promoting macrophage uptake of cholesterol-rich lipoproteins or modulating protective inflammatory responses, it could also restrict lesion formation by facilitating cholesterol efflux out of lesions. The role of apoE was examined in lethally irradiated male C57BL/6J wild-type (WT) mice that were repopulated with bone marrow cells (BMT) from either identical C57BL/6J mice (WT+WT BMT) or C57BL/6J apoE-deficient mice (WT+E-/- BMT). This enabled us to compare normal mice with mice possessing macrophages that did not express apoE. The participation of macrophage-derived apoE in atherosclerosis was assessed by placing the mice on an atherogenic diet. Male WT+E-/- BMT mice had significantly reduced lesion area in the aortic valves (P < 0.01) compared with male WT+WT BMT mice ( approximately 22,000 vs. approximately 49,000 microm2/section, respectively). Further evaluation revealed that plasma cholesterol, lipoprotein cholesterol distribution, and plasma apoE were similar between the two groups, indicating that these known risk factors did not account for the differences in lesion area. However, the two groups were distinguished by the amount of apoE found in the lesions. ApoE antigen was expressed abundantly in WT+WT BMT lesions, whereas WT+E-/- BMT lesions contained little apoE. These findings indicate that the majority of apoE in lesions is synthesized locally by resident macrophages, and suggest that locally produced apoE can promote diet-induced atherosclerosis in male wild-type mice.

Animals↗

PubMed1999

Protection against atherosclerosis by estrogen is independent of plasma cholesterol levels in LDL receptor-deficient mice.

Low density lipoprotein (LDL) receptor-deficient (LDLR-/-) mice consuming a high fat diet were used to assess the effect of endogenous and exogenous estradiol (E2) on atherosclerosis. Sexually mature female mice were ovariectomized (OVX) and implanted with subcutaneous, slow-release pellets designed to release 6 microg/day of exogenous 17beta-estradiol (17beta-E2 ), 17alpha-estradiol (17alpha-E2 ), or placebo (E2- deficient). Sham-operated control female (endogenous E2 ) and male mice were studied as controls. Aortic atherosclerotic lesion area was reduced by physiologic amounts of both endogenous and exogenous E2 compared to E2-deficient female mice. Although plasma cholesterol levels were reduced by exogenous E2 despite the absence of the LDL receptor, endogenous E2 was not associated with any cholesterol changes. In contrast, only 17alpha-E2 was associated with decreased fasting triglyceride. In subgroup analyses matched for time-averaged plasma total cholesterol, aortic lesion area was reduced by the presence of estradiol (E2 ). E2 protected LDLR-/- female mice from atherosclerosis and this protection was independent of changes in plasma cholesterol levels.

Animals↗

PubMed1998

The NH2-terminal region of apolipoprotein B is sufficient for lipoprotein association with glycosaminoglycans.

An initial event in atherosclerosis is the retention of lipoproteins within the intima of the vessel wall. The co-localization of apolipoprotein (apo) B and proteoglycans within lesions has suggested that retention is due to lipoprotein interaction with these highly electronegative glycoconjugates. Both apoB100- and apoB48-containing lipoproteins, i.e. low density lipoproteins (LDLs) and chylomicron remnants, are atherogenic. This suggests that retention is due to determinants in the initial 48% of apoB. To test this, the interaction of an apoB fragment (apoB17), and apoB48- and apoB100- containing lipoproteins with heparin, subendothelial matrix, and artery wall purified proteoglycans was studied. ApoB100-containing LDL from humans and human apoB transgenic mice and apoB48-containing LDLs from apoE knockout mice were used. Despite the lack of the carboxyl-terminal 52% of apoB, the apoB48-LDL bound to heparin-affinity gel as well as did apoB100-LDL. An NH2-terminal fragment containing 17% of full-length apoB was made using a recombinant adenovirus; apoB17 bound to heparin as well as did LDL. Monoclonal antibodies against the NH2-terminal region of apoB decreased apoB100 LDL binding to heparin, whereas antibodies against the LDL receptor-binding region did not alter LDL-heparin interaction. The role of the NH2-terminal region of apoB in LDL interaction with matrix molecules was also assessed. Media containing apoB17 decreased LDL binding to subendothelial matrix by 42%. Moreover, removal of the apoB17 by immunoprecipitation abrogated the inhibitory effect of these media. Antibodies to the NH2-terminal region decreased LDL binding to matrix and dermatan sulfate proteoglycans. Purified apoB17 effectively competed for binding of LDL to artery derived decorin and to subendothelial matrix. Thus, despite the presence of multiple basic amino acids near the LDL receptor-binding domain of LDL, the NH2-terminal region of apoB is sufficient for the interaction of lipoproteins with glycoconjugates produced by endothelial and smooth muscle cells. The presence of a proteoglycan-binding site in the NH2-terminal region of apoB may explain why apoB48- and apoB100-containing lipoproteins are equally atherogenic.

Animals↗

PubMed1998

Subdomain chimeras of hepatic lipase and lipoprotein lipase. Localization of heparin and cofactor binding.

To specify and localize carboxyl-terminal domain functions of human hepatic lipase (HL) and human lipoprotein lipase (LPL), two subdomain chimeras were created in which portions of the carboxyl-terminal domain were exchanged between the two lipases. The first chimera (HL-LPLC1) was composed of residues 1-344 of human HL, residues 331-388 of human LPL, and residues 415-476 of human HL. The second chimera (HL-LPLC2) consisted of just two segments, residues 1-414 of human HL and residues 389-448 of human LPL. These chimeric constructs effectively divided the HL C-terminal domain into halves, with corresponding LPL sequences either in the first or second portion of that domain. Both chimeras were lipolytically active and hydrolyzed triolein emulsions to a similar extent compared with native HL and LPL. Heparin-Sepharose chromatography demonstrated that HL-LPLC1 and HL-LPLC2 eluted at 0.80 and 1.3 M NaCl, respectively, elution positions that corresponded to native HL and LPL. Hence, substitution of LPL sequences into the HL carboxyl-terminal domain resulted in the production of functional lipases, but with distinct heparin binding properties. In addition, HL-LPLC2 trioleinase activity was responsive to apoC-II activation, although the -fold stimulation was less than that observed with native LPL. Moreover, an apoC-II fragment (residues 44-79) was specifically cross-linked to LPL and HL-LPLC2, but not to HL or HL-LPLC1. Finally, both chimeras hydrolyzed phospholipid with a specific activity similar to that of HL, which was unaffected by the presence of apoC-II. These findings indicated that in addition to a region found within the amino-terminal domain of LPL, apoC-II also interacted with the last half of the carboxyl-terminal domain (residues 389-448) to achieve maximal lipolytic activation. In addition, the relative heparin affinity of HL and LPL was determined by the final 60 carboxyl-terminal residues of each enzyme.

Apolipoprotein C-II↗

PubMed1998

Interaction between ApoB and hepatic lipase mediates the uptake of ApoB-containing lipoproteins.

Hepatic lipase (HL) on the surface of hepatocytes and endothelial cells lining hepatic sinusoids, the adrenal glands, and the ovary hydrolyzes triglycerides and phospholipids of circulating lipoproteins. Its expression significantly enhances low density lipoprotein (LDL) uptake via the LDL receptor pathway. A specific interaction between LPL, a homologous molecule to HL, and apoB has been described (Choi, S. Y., Sivaram, P., Walker, D. E., Curtiss, L. K., Gretch, D. G., Sturley, S. L., Attie, A. D., Deckelbaum, R. J., and Goldberg, I. J. (1995) J. Biol. Chem. 270, 8081-8086). The present studies tested the hypothesis that HL enhances the uptake of lipoproteins by a specific interaction of HL with apoB. On a ligand blot, HL bound to apoB26, 48, and 100 but not to apoE or apoAI. HL binding to LDL in a plate assay with LDL-coated plates was significantly greater than to bovine serum albumin-coated plates. Neither heat denatured HL nor bacterial fusion protein of HL bound to LDL in the plate assays. 125I-LDL bound to HL-saturated heparin-agarose gel with a Kd of 52 nM, and somewhat surprisingly, this binding was not inhibited by excess LPL. In cell culture experiments HL enhanced the uptake of 125I-LDL at both 4 and 37 degreesC. The enhanced binding and uptake of LDL was significantly inhibited by monoclonal anti-apoB antibodies. In contrast to LPL, both amino- and carboxyl-terminal antibodies blocked the apoB interaction with HL to the same extent. Thus, we conclude that there is a unique interaction between HL and apoB that facilitates the uptake of apoB-containing lipoproteins by cells where HL is present.

Animals↗

PubMed1998

Deletion of amino acids Glu146-->Arg160 in human apolipoprotein A-I (ApoA-ISeattle) alters lecithin:cholesterol acyltransferase activity and recruitment of cell phospholipid.

Human apolipoprotein A-I (apoA-I) has an important role in the efflux of cholesterol from peripheral cells, the first step in reverse cholesterol transport. Deletion of amino acids Glu146-->Arg160 in apoA-I (apoA-ISeattle) removes a large section of a lipid binding helix and is associated in vivo with an atherogenic lipoprotein profile characterized by a deficiency in high-density lipoproteins (HDL). In the present study, we asked whether apoA-ISeattle had normal ability to recruit lipids from cells and to form nascent high-density lipoprotein (HDL) particles and whether the altered secondary structure affected lecithin:cholesterol acyltransferase (LCAT) activity. Wild-type apoA-I and apoA-ISeattle expressed in transfected Chinese hamster ovary cells formed nascent HDL particles with similar density distribution and protein-to-lipid ratio. Phospholipid subclass distribution of apoA-ISeattle nascent HDL demonstrated a significant increase in sphingomyelin and phosphatidylethanolamine compared to wild type. ApoA-ISeattle nascent HDL had a unique size distribution compared to wild-type nascent HDL; large (9-20 nm) particles predominated while there were virtually no small (7.5 nm) particles. LCAT reactivity was impaired by apoA-ISeattle nascent HDL where cholesterol esterification was only half that of wild-type complexes. The apoA-ISeattle conformation on nascent HDL was studied with a panel of monoclonal antibodies (Mabs) specific for apoA-I. Mabs that recognize the putative LCAT activation site, residues 95-122, had normal reactivity. As expected, the Mabs that recognized residues 141-164 were unreactive because of the 146-160 deletion; in addition, there was low reactivity with a Mab that recognizes residues 220-242. The data suggest that apoA-I residues 146-160 and/or 220-242 partake in normal LCAT activation and that cooperative interactions between helices may be important for maximal cholesterol esterification.

Animals↗

PubMed1998

A minimally lipidated form of cell-derived apolipoprotein E exhibits isoform-specific stimulation of neurite outgrowth in the absence of exogenous lipids or lipoproteins.

Within the central nervous system, apolipoprotein E (apoE) synthesis is increased in response to nerve injury, a finding that may reflect a role for apoE in neuronal remodeling. Recent studies show that apoE3 promotes and apoE4 inhibits neurite outgrowth in cultured neuronal cells. Interestingly, these isoform-specific effects are observed only when apoE is presented to cells in the presence of an exogenous lipid source such as rabbit beta-very low density lipoprotein (beta-VLDL), making it difficult to discern the biologically active form of apoE or to understand the role of the lipid source. In the present study we tested whether a cell-derived lipidated form of apoE can alter neurite outgrowth in the absence of beta-VLDL by constructing Neuro-2a cell lines expressing high levels of apoE. Our results showed that endogenous apoE3 stimulated neurite outgrowth, whereas the endogenous apoE4 isoform was neutral. Furthermore, beta-VLDL antagonized the stimulatory effects of the endogenous apoE3. Characterization of the secreted apoE3 indicated that the neurite outgrowth-stimulating activity could be recovered from culture medium with an anti-apoE immunoaffinity column and was present in a poorly lipidated particle with a density between 1.19 and 1.26 g/ml. These results indicated that the biological activity of apoE3 in stimulating neurite outgrowth was inherent in the cell-derived apoE particle and was not dependent on either (a) an interaction of apoE3 with an artificial lipid source or (b) independent actions of apoE3 and beta-VLDL.

Animals↗

PubMed1998

A leukocyte homologue of the IL-8 receptor CXCR-2 mediates the accumulation of macrophages in atherosclerotic lesions of LDL receptor-deficient mice.

Chronic macrophage-mediated inflammation is central to atherosclerosis. A role of the monocyte chemotactic and activating C-C chemokine JE/monocyte chemotactic protein-1 has been proposed. However, the human C-X-C chemokines growth-regulated oncogene (GROalpha) and IL-8, and their shared receptor, CXCR-2, also can be expressed at sites of chronic inflammation. Because we detected CXCR-2 in the intima of human atherosclerotic lesions, we examined the role of leukocyte CXCR-2 expression in affecting lesion cellularity. Atherosclerosis-susceptible LDL receptor-deficient mice were irradiated, successfully repopulated with bone marrow cells that either lacked or expressed mIL-8RH (the homologue of CXCR-2), and fed an atherogenic diet for 16 wk. In recipients of mIL-8RH+/+ marrow, mIL-8RH colocalized with densely accumulated intimal MOMA-2 positive macrophages. In contrast, lesions in recipients of mIL-8RH-/- marrow lacked mIL-8RH, had little intimal MOMA-2 staining, and were less extensive. The mIL-8RH ligand KC/GROalpha was detected in the intima of all aortic atherosclerotic lesions. Thus, the capacity of leukocytes to express mIL-8RH, and associated intralesional expression of its ligands such as KC/GROalpha, mediated the intimal accumulation of macrophages in atherosclerotic lesions of LDL receptor-deficient mice.

Animals↗

PubMed1998

An apolipoprotein E synthetic peptide targets to lipoproteins in plasma and mediates both cellular lipoprotein interactions in vitro and acute clearance of cholesterol-rich lipoproteins in vivo.

Apolipoprotein (apo) E mediates lipoprotein binding to cellular lipoprotein receptors. Previously we reported that a synthetic peptide representing a linear dimeric repeat of amino acids 141-155 binds cellular LDL receptors. To prepare an apoE peptide that bound to both cholesterol-rich lipoproteins and lipoprotein receptors, an NH2-terminal acetylated apoE dimer peptide was synthesized. This acetylated peptide preferentially associated with lipoproteins in plasma, whereas nonacylated peptides were poor lipid binders. Acetylated peptide/LDL complexes (molar ratios of 4-5:1) enhanced the interaction of LDL with cultured human fibroblasts by 7-12-fold. Participation by both receptors and cell surface heparin sulfate proteoglycans was observed. When a preformed peptide/125I-LDL complex was injected intravenously into C57BL/6J apoE-deficient mice, its rate of removal was threefold higher than that of 125I-LDL alone. The liver and the spleen were major tissue distribution sites. Intravenous administration of free acetylated peptide resulted in a 30% reduction in total plasma cholesterol within 3-30 min, which reflected a 40-50% and 20-26% reduction in very low density lipoproteins and intermediate density lipoproteins, respectively. Therefore, this peptide selectively associated with cholesterol-rich lipoproteins and mediated their acute clearance in vivo.

Animals↗

PubMed1998

Chemokines and atherosclerosis.

The recruitment of mononuclear leukocytes, and the migration, growth and activation of macrophages, lymphocytes and smooth muscle cells within lesions, are critical features of the chronic inflammatory response that typifies atherogenesis. Chemokines are members of a superfamily of small polypeptides that mediate not only migration, but also growth and activation of leukocytes and a variety of other cells. Monocyte chemoattractant and activating protein-1 was the first chemokine to be implicated in leukocyte-mediated inflammation in atherosclerosis. This review emphasizes new information on the potential atherogenic roles of monocyte chemoattractant and activating protein-1 and several other closely related chemokines of the C-C subfamily. We focus particular attention on the newly recognized atherogenic role of a subgroup of closely related chemokines of the C-X-C subfamily that includes interleukin-8 and growth regulated oncogene alpha. We also discuss new studies that reveal how CD40 ligand and certain other stimuli can promote chemokine expression in atherosclerosis.

Arteriosclerosis↗

PubMed1998

An apolipoprotein E synthetic peptide selectively modulates the transcription of the gene for rat ovarian theca and interstitial cell P450 17alpha-hydroxylase, C17-20 lyase.

Ovarian theca/interstitial cells produce androgens in response to luteinizing hormone (LH) stimulation and apolipoprotein (apo) E exerts a selective effect on the type of steroid product made by these cells. We have identified an apoE synthetic peptide containing the low density lipoprotein (LDL) receptor binding domain, acetyl-Y(LRK LRKRLLRDADDL)2C, that mimics the activity of native apoE. Depending on the concentration, the apoE synthetic peptide either enhanced or inhibited the LH-stimulated production of androstenedione with concomitant changes in the mRNA for its synthetic enzyme, P450 17alpha-hydroxylase, C17-20 lyase, without any changes in progesterone production or the mRNA for its synthetic enzyme, P450 cholesterol side-chain cleavage. The apoE synthetic peptide caused changes in the rate of transcription of the mRNA for P450 17alpha-hydroxylase, C17-20 lyase without altering its stability. Pretreatment of the theca/interstitial cells with receptor-associated protein, which blocks apoE binding to members of the LDL receptor superfamily, prevented the apoE synthetic peptide-mediated stimulation of androstenedione and mRNA for P450 17alpha-hydroxylase, C17-20 lyase, but did not attenuate the inhibitory activity of the peptide. Thus, apolipoprotein E selectively altered the type of steroid made by ovarian theca/interstitial cells by regulating the transcription of mRNA for the gene for P450 17alpha-hydroxylase, C17-20 lyase, in part through its interaction with apolipoprotein E-specific receptors of the LDL receptor superfamily.

Amino Acid Sequence↗

PubMed1998

Effect of long chain polyunsaturated fatty acids in the sn-2 position of phosphatidylcholine on the interaction with recombinant high density lipoprotein apolipoprotein A-I.

The effects of polyunsaturated fatty acids (PUFA) on the structure of recombinant high density lipoprotein (rHDL) was investigated using homogeneous particles containing phosphatidylcholine (PC), [3H]cholesterol, and apolipoprotein A-I (apoA-I). The PC component of the rHDL contained sn -1 16:0 and sn -2 18:1 (POPC), 18:2 (PLPC), 20:4 (PAPC), 20:5 n-3 (PEPC), or 22:6 n-3 (PDPC). The concentration of guanidine HCl (D1/2) required to denature one-half of the apoA-I on rHDL containing long chain PUFA was reduced (1.57-1.70 m) compared to those containing POPC (2.83 m). Intrinsic apoA-I tryptophan fluorescence emission intensity and lifetimes were decreased for rHDL containing long chain PUFA compared to POPC and PLPC rHDL. Monoclonal antibody binding studies demonstrated that apoA-I had decreased immunoreactivity with monoclonal antibodies spanning amino acid residues 115-147 in rHDL containing long chain PUFA. PC lipid fluidity, measured as diphenylhexatriene (DPH) fluorescence polarization, was increased in PUFA rHDL compared to POPC rHDL. There also was a strong correlation between the number of sn -2 double bonds in rHDL and DPH fluorescence lifetime (r 2 = 0. 89). LCAT reactivity of the homogeneous size rHDL was ordered POPC = PLPC>PAPC> PEPC>PDPC. We conclude that rHDL with long chain PUFA in the sn -2 position of PC contain apoA-I that is less stable and in a different conformation than that in POPC rHDL and have a fatty acyl region that is more fluid and hydrated. The weaker interaction of apoA-I with PC containing PUFA may lead to hypercatabolism of apoA-I in plasma explaining, in part, the decreased plasma HDL and apoA-I concentrations seen with PUFA diets.

Antibodies, Monoclonal↗

PubMed1997

Influence of macrophage-derived apolipoprotein E on plasma lipoprotein distribution of apolipoprotein A-I in apolipoprotein E-deficient mice.

High density lipoprotein (HDL) cholesterol in apolipoprotein (apo) E-deficient mice is decreased. It has been suggested that apoA-I is lost from HDL in these mice because it must substitute for apoE as a structural protein for the abnormal cholesterol-rich lipoproteins. Therefore, we examined in vivo the influence of selective apoE expression on plasma HDL cholesterol in apoE-deficient mice. Bone marrow transplantation was used to establish macrophage-specific expression of apoE. Bone marrow transplantation normalized plasma triglycerides and significantly reduced total plasma cholesterol, but it did not increase hepatic apoA-I mRNA levels or total plasma apoA-I. Although total plasma apoA-I was not increased, HDL cholesterol measured following chromatographic separation was elevated twofold. Furthermore, plasma apoA-I was recovered from this HDL in animals expressing macrophage apoE. Compared to HDL of wildtype mice, this HDL had a similar chromatographic size distribution, but it lacked apoE and was more negatively charged. These studies indicated that plasma apoA-I distribution and HDL composition are influenced by apoE and that the abnormal apoA-I lipoprotein distribution of apoE-deficient mice can be altered in vivo by macrophage-derived apoE.

Animals↗