Biomedical subjects

Sergio Fazio

Publications and source records attributed to Sergio Fazio.

51 records · Page 3Linked to original sources

PubMed2003

The recycling of apolipoprotein E in primary cultures of mouse hepatocytes. Evidence for a physiologic connection to high density lipoprotein metabolism.

Internalization of apoE-containing very low density protein (VLDL) by hepatocytes in vivo and in vitro leads to apoE recycling and resecretion. Because of the role of apoE in VLDL metabolism, apoE recycling may influence lipoprotein assembly or remnant uptake. However, apoE is also a HDL protein, and apoE recycling may be related to reverse cholesterol transport. To investigate apoE recycling, apoE(-/-) mouse hepatocytes were incubated (pulsed) with wild-type mouse lipoproteins, and cells and media were collected at chase periods up to 24 h. When cells were pulsed with VLDL, apoE was resecreted within 30 min. Although the mass of apoE in the media decreased with time, it could be detected up to 24 h after the pulse. Intact intracellular apoE was also detectable 24 h after the pulse. ApoE was also resecreted when cells were pulsed with HDL. When apoA-I was included in the chase media after a pulse with VLDL, apoE resecretion increased 4-fold. Furthermore, human apoE was resecreted from wild-type mouse hepatocytes after a pulse with human VLDL. Finally, apoE was resecreted from mouse peritoneal macrophages after pulsing with VLDL. We conclude that 1) HDL apoE recycles in a quantitatively comparable fashion to VLDL apoE; 2) apoE recycling can be modulated by extracellular apoA-I but is not affected by endogenous apoE; and 3) recycling occurs in macrophages as well as in hepatocytes, suggesting that the process is not cell-specific.

Animals↗

PubMed2003

Macrophage apolipoprotein A-I expression protects against atherosclerosis in ApoE-deficient mice and up-regulates ABC transporters.

The antiatherogenic effect of high-density lipoprotein (HDL) and its major protein component apolipoprotein A-I (apoA-I) has been largely attributed to their key roles in reverse cholesterol transport (RCT) and cellular cholesterol efflux. Substantial evidence shows that overexpression of human apoA-I reduces atherosclerosis in animal models. However, it is uncertain whether this protection is due to an increase in plasma HDL level or to a local effect in the artery wall. To test the hypothesis that expression of human apoA-I in macrophages can promote RCT in the artery wall, we used a retroviral construct expressing human apoA-I cDNA (MFG-HAI) to transduce ApoE(-/-) bone marrow cells and then transplanted these cells into ApoE(-/-) mice with preexisting atherosclerosis. ApoE(-/-) mice reconstituted with MFG-HAI marrow had a significant reduction (30%) in atherosclerotic lesions in the proximal aorta compared to control mice that received marrow expressing MFG parental virus. Peritoneal macrophages isolated from MFG-HAI mice showed a four- to fivefold increase in mRNA expression levels of both ATP-binding cassette (ABC) A1 and ABCG1 compared to controls. Our data demonstrate that gene transfer-mediated expression of human apoA-I in macrophages can compensate in part for apoE deficiency and delay the progression of atherosclerotic lesions by stimulating ABC-dependent cholesterol efflux and RCT.

ATP-Binding Cassette Transporters↗

PubMed2003

Macrophages, inflammation, and atherosclerosis.

The macrophage plays a diverse array of roles in atherogenesis and lipoprotein metabolism. The macrophage functions as a scavenger cell, an immune mediator cell, and as a source of chemotactic molecules and cytokines. Chemokines have been implicated in promoting migration of monocytes into the arterial intima. Monocyte chemoattractant protein-1 (MCP-1) attracts monocytes bearing the chemokine receptor CCR-2. Macrophage expression of cyclooxygenase-2, a key enzyme in inflammation, promotes atherosclerotic lesion formation in low-density lipoprotein receptor (LDLR)-deficient mice. In the arterial intima, monocytes differentiate into macrophages, which accumulate cholesterol esters to form lipid-laden foam cells. Foam cell formation can be viewed as an imbalance in cholesterol homeostasis. The uptake of atherogenic lipoproteins is mediated by scavenger receptors, including SR-A and CD36. In the macrophage, ACAT-1 is responsible for esterifying free cholesterol with fatty acids to form cholesterol esters. Surprisingly, deficiency of macrophage ACAT-1 promotes atherosclerosis in LDLR-deficient mice. A number of proteins have been implicated in the process of promoting the efflux of free cholesterol from the macrophage, including apoE, ABCA1, and SRB-1. Macrophage-derived foam cells express the adipocyte fatty acid-binding protein (FABP), aP2, a cytoplasmic FABP that plays an important role in regulating systemic insulin resistance in the setting of obesity. ApoE-deficient mice null for macrophage aP2 expression develop significantly less atherosclerosis than controls wild type for macrophage aP2 expression. These results demonstrate a significant role for macrophage aP2 in the formation of atherosclerotic lesions independent of its role in systemic glucose and lipid metabolism. Furthermore, macrophages deficient in aP2 display alterations in inflammatory cytokine production. Through its distinct actions in adipocytes and macrophages, aP2 links features of the metabolic syndrome including insulin resistance, obesity, inflammation, and atherosclerosis.

Animals↗

PubMed2003

Apolipoprotein AI as therapy for atherosclerosis: does the future of preventive cardiology include weekly injections of the HDL protein?

Conventional wisdom suggests that halting or reversing long-term atherosclerosis requires increasing the amount of circulating high-density lipoprotein (HDL) coursing through the vasculature. However, recent evidence seems to indicate that reducing the size of cholesterol-containing lipid plaques might be accomplished by methods that either do not raise or, in fact, lower the amount of circulating HDL. Carriers of apoAI(Milano), a variant of apoprotein AI (a component of HDL), have reduced levels of circulating low-density lipoprotein (LDL). Intriguingly, these individuals have reduced amounts of circulating HDL and total apoAI. Infusions of the ApoAI(Milano) variant given to patients with coronary atherosclerosis appear to lead to disease regression and reduced plaque size. However, larger studies are required to provide definitive proof of apoAI(Milano)'s benefits. What is certain is that attention should be focused on the removal of cholesterol from plaques rather than simply desiring to raise HDL concentrations in patients.

Apolipoprotein A-I↗

PubMed2002

B-lymphocyte deficiency increases atherosclerosis in LDL receptor-null mice.

OBJECTIVE: Atherosclerosis is an inflammatory disease characterized by innate and adaptive immune responses. We investigated the role of B cells and antibodies in the development of atherosclerosis in low density lipoprotein (LDL) receptor-deficient (LDLR(-/-)) mice. METHODS AND RESULTS: Using wild-type and B cell-deficient mice as bone marrow donors, we were able to generate LDLR(-/-) mice that possessed <1.0% of their normal B cell population. B cell-deficient LDLR(-/-) mice on a Western diet showed marked decreases in total serum antibody and anti-oxidized LDL antibody. B cell deficiency was associated with a 30% to 40% increase in the lesion area in the proximal and distal aortas. Real-time reverse transcription-polymerase chain reaction and enzyme-linked immunospot analyses showed a decrease in proatherogenic (interferon-gamma) and antiatherogenic (interleukin-10 and transforming growth factor-beta) cytokine mRNA and a decrease in interleukin-4- and interferon-gamma-producing cells. Additionally, we observed a decrease in splenocyte proliferation to oxidized LDL in the B cell-deficient LDLR(-/-) mice, suggesting that B lymphocytes may play a role in the presentation of lipid antigen. CONCLUSIONS: Collectively, these data demonstrate that B cells and/or antibodies are protective against atherosclerosis and that this protection may be conferred by B cell-mediated immune regulation.

Animals↗

PubMed2002

Adipocyte fatty acid-binding protein, aP2, alters late atherosclerotic lesion formation in severe hypercholesterolemia.

OBJECTIVE: The adipocyte fatty acid-binding protein, aP2, has important effects on insulin resistance, lipid metabolism, and atherosclerosis. Its expression in macrophages enhances early foam cell formation and atherosclerosis in vivo. This study was designed to determine whether aP2 deficiency has a similar effect in the setting of advanced atherosclerosis and severe hypercholesterolemia. METHODS AND RESULTS: Mice deficient in aP2 and apolipoprotein E (aP2(-/-)apoE(-/-) mice) and apolipoprotein E-deficient control mice (apoE(-/-) mice) were fed a Western diet for 14 weeks. No significant differences in fasting serum levels of cholesterol, triglycerides, or free fatty acids were found between groups for each sex. Compared with apoE(-/-) control mice, male and female aP2(-/-)apoE(-/-) mice had significant reductions in mean atherosclerotic lesion size in the proximal aorta, en face aorta, and innominate/right carotid artery. Feeding the Western diet in the apoE-deficient background did not cause a significant reduction in insulin sensitivity in vivo, as determined by steady-state serum glucose levels and insulin tolerance testing. CONCLUSIONS: These data demonstrate an important role for aP2 expression in the advanced stages of atherosclerotic lesion formation. Thus, aP2 provides an important physiological link between different features of the metabolic syndrome and is a potential target for therapy of atherosclerosis.

Animals↗

PubMed2002

Cyclooxygenase-2 promotes early atherosclerotic lesion formation in LDL receptor-deficient mice.

BACKGROUND: Atherosclerosis has features of an inflammatory disease. Because cyclooxygenase (COX)-2 is expressed in atherosclerotic lesions and promotes inflammation, we tested the hypotheses that selective COX-2 inhibition would reduce early lesion formation in LDL receptor-deficient (LDLR-/-) mice and that macrophage COX-2 expression contributes to atherogenesis in LDLR-/- mice. METHODS AND RESULTS: Treatment of male LDLR-/- mice fed the Western diet with rofecoxib or indomethacin for 6 weeks resulted in significant reductions in atherosclerosis in the proximal aorta (25% and 37%) and in the aorta en face (58% and 57%), respectively. Rofecoxib treatment did not inhibit platelet thromboxane production, a COX-1-mediated process, but it significantly reduced the urinary prostacyclin metabolite 2,3-dinor-6-keto-PGF1alpha. Fetal liver cell transplantation was used to generate LDLR-/- mice null for expression of the COX-2 gene by macrophages. After 8 weeks on the Western diet, COX-2-/- --> LDLR-/- mice developed significantly less (33% to 39%) atherosclerosis than control COX-2+/+ --> LDLR-/- mice. In both the inhibitor studies and the transplant studies, serum lipids did not differ significantly between groups. CONCLUSIONS: The present studies provide strong pharmacological and genetic evidence that COX-2 promotes early atherosclerotic lesion formation in LDLR-/- mice in vivo. These results support the potential of anti-inflammatory approaches to the prevention of atherosclerosis.

Animals↗

PubMed2002

Retroviral mediated expression of the human myeloid nuclear antigen in a null cell line upregulates Dlk1 expression.

The human myeloid nuclear differentiation antigen (MNDA) is a hematopoietic cell specific nuclear protein. MNDA and other related gene products interact with and alter the activity of a large number of proteins involved in regulating specific gene transcription. MNDA and related genes exhibit expression characteristics, which suggest functions unique to specific lineages of cells, in addition to mediating the effects of interferons. Cells of the human K562 myeloid line do not express MNDA and are relatively immature compared to lines that express MNDA (HL-60, U937, and THP1). The hypothesis that MNDA influences the expression of specific genes was tested by creating MNDA expressing K562 cells using stable retroviral mediated gene transfer followed by evaluation of transcription profiles. Two macroarrays containing a total of 2,350 cDNAs of known genes showed a specific up-regulation of Dlk1 expression in MNDA expressing K562 cell clones. Real time quantitative RT-PCR analysis confirmed an average of over 3- and 7-fold upregulation of Dlk1 in two clones of MNDA expressing K562 cells. The effects on Dlk1 were also confirmed by Northern blotting. Dlk1 is essential for normal hematopoiesis and abnormal expression is a proposed marker of myelodysplastic syndrome. Additional screening of transcription profiles after induced erythroid and megakaryoblastic differentiation showed no additional gene transcripts altered by the presence of MNDA. These results indicate that MNDA alters expression of a gene essential for normal hematopoiesis.

Animals↗

PubMed2002

Cytoplasmic fatty acid-binding proteins: emerging roles in metabolism and atherosclerosis.

Cytoplasmic fatty acid-binding proteins (FABPs) are a family of proteins, expressed in a tissue-specific manner, that bind fatty acid ligands and are involved in shuttling fatty acids to cellular compartments, modulating intracellular lipid metabolism, and regulating gene expression. Several members of the FABP family have been shown to have important roles in regulating metabolism and have links to the development of insulin resistance and the metabolic syndrome. Recent studies demonstrate a role for intestinal FABP in the control of dietary fatty acid absorption and chylomicron secretion. Heart FABP is essential for normal myocardial fatty acid oxidation and modulates fatty acid uptake in skeletal muscle. Liver FABP is directly involved in fatty acid ligand signaling to the nucleus and interacts with peroxisome proliferator-activated receptors in hepatocytes. The adipocyte FABP (aP2) has been shown to affect insulin sensitivity, lipid metabolism and lipolysis, and has recently been shown to play an important role in atherosclerosis. Interestingly, expression of aP2 by the macrophage promotes atherogenesis, thus providing a link between insulin resistance, intracellular fatty acid disposition, and foam cell formation. The FABPs are promising targets for the treatment of dyslipidemia, insulin resistance, and atherosclerosis in humans.

Animals↗

PubMed2002

Cyclooxygenase-2 and atherosclerosis.

Cyclooxygenase regulates the production of eicosanoids, which modulate physiologic processes in the vessel wall contributing to atherosclerosis and thrombosis, including platelet aggregation, control of vascular tone, and the local inflammatory response. Cyclooxygenase-1 mediates production of platelet thromboxane A(2), a potent vasoconstrictor and platelet agonist, whereas both cyclooxygenase 1 and 2 contribute to production of endothelial prostacyclin, a vasodilator that inhibits platelet activation. Concerns have been raised that cyclooxygenase-2 inhibitors may increase thrombotic cardiovascular events by disturbing the balance between platelet thromboxane A(2) and endothelial prostacyclin, but this controversial issue will only be resolved by prospective clinical trials. Because cyclooxygenase-2 is upregulated in activated monocyte/macrophages, which play a key role in the pathogenesis of atherosclerosis, we have recently tested the hypothesis that pharmacological inhibition of cyclooxygenase-2 in LDL-receptor deficient mice would reduce early atherosclerosis. After 6 weeks on a Western-type diet, male LDL-receptor deficient mice treated with either rofecoxib (a selective cyclooxygenase-2 inhibitor) or indomethacin (a non-selective cyclooxygenase inhibitor) had significant reductions in atherosclerosis when compared with control mice. Also, LDL-receptor deficient mice null for macrophage cyclooxygenase-2 were generated by fetal liver cell transplantation and developed significantly less atherosclerosis than control LDL-receptor deficient mice transplanted with fetal liver cells wildtype for cyclooxygenase-2, providing genetic evidence in support of a proatherogenic role for macrophage cyclooxygenase-2 expression. These results support the potential of antiinflammatory approaches for the prevention of atherosclerosis and identify cyclooxygenase-2 as a target for intervention.

Animals↗

PubMed2002

Absence of angiotensin II type 1 receptor in bone marrow-derived cells is detrimental in the evolution of renal fibrosis.

We examined the in vivo function of the angiotensin II type 1 receptor (Agtr1) on macrophages in renal fibrosis. Fourteen days after the induction of unilateral ureteral obstruction (UUO), wild-type mice reconstituted with marrow lacking the Agtr1 gene (Agtr1(-/-)) developed more severe interstitial fibrosis with fewer interstitial macrophages than those in mice reconstituted with Agtr1(+/+) marrow. These differences were not observed at day 5 of UUO. The expression of profibrotic genes - including TGF-beta1, alpha1(I) collagen, and alpha1(III) collagen - was substantially higher in the obstructed kidneys of mice with Agtr1(-/-) marrow than in those with Agtr1(+/+) marrow at day 14 but not at day 5 of UUO. Mice with Agtr1(-/-) marrow were characterized by reduced numbers of peripheral-blood monocytes and macrophage progenitors in bone marrow. In vivo assays revealed a significantly impaired phagocytic capability in Agtr1(-/-) macrophages. In vivo treatment of Agtr1(+/+) mice with losartan reduced phagocytic capability of Agtr1(+/+) macrophages to a level comparable to that of Agtr1(-/-) macrophages. Thus, during urinary tract obstruction, the Agtr1 on bone marrow-derived macrophages functions to preserve the renal parenchymal architecture, and this function depends in part on its modulatory effect on phagocytosis.

Animals↗

PubMed2002

Rapid quantification of murine ABC mRNAs by real time reverse transcriptase-polymerase chain reaction.

Several ATP-binding cassette (ABC) transporters are critically involved in cholesterol and phospholipid efflux, reverse cholesterol transport, and play an important role in the development of atherosclerosis. Quantification of ABC mRNA is important in studying the regulation of cellular cholesterol homeostasis and mechanisms related to the pathogenesis of atherosclerosis. We have developed a one-step real time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method for measuring mRNA levels of ABCA1, ABCG1, and ABCA2 in murine tissues using the TaqMan(TM) technology. It has significant methodological benefits when compared to classic Northern blotting or semi-quantitative RT-PCR analysis. Using this method, we found high expression levels of ABCA1 in liver and macrophages, and of ABCG1 in the brain and macrophages. The expression of ABCA1 and ABCG1 were further induced in macrophages loaded with acLDL. In contrast, ABCA2 was expressed exclusively in the brain with low expression levels in the macrophages. This method provides a rapid, highly sensitive, specific, and reproducible quantification of ABC mRNA, and can be performed with nanograms of total RNA sample, thus making it a superior method for studying the regulation of ABC transporters in cholesterol efflux and its role in the pathogenesis of atherosclerosis in murine models.

ATP-Binding Cassette Transporters↗

PubMed2002

Physiological expression of macrophage apoE in the artery wall reduces atherosclerosis in severely hyperlipidemic mice.

We have previously reported that the introduction of macrophage apoE into mice lacking both apoE and the LDL receptor (apoE(-)(/-)/LDLR(-)(/-)) through bone marrow transplantation (apoE(+)(/+)/LDLR(-)(/-)-->apoE(-)(/-)/LDLR(-)(/-)) produces progressive accumulation of apoE in plasma without affecting lipid levels. This model provides a tool to study the effects of physiologically regulated amounts of macrophage apoE on atherogenesis in hyperlipidemic animals. Ten-week-old male apoE(-)(/-)/LDLR(-)(/-) mice were transplanted with either apoE(+)(/+)/LDLR(-)(/-) (n = 11) or apoE(-)(/-)/LDLR(-)(/-) (n = 14) marrow. Although there were no differences between the two groups in lipid levels at baseline or at 5 and 9 weeks after transplantation, apoE levels in the apoE(+)(/+)LDLR(-)(/-)-->apoE(-)(/-)/LDLR(-)(/-) mice increased to 4 times the apoE levels of normal mice. This resulted in a 60% decrease in aortic atherosclerosis in the apoE(+)(/+)/LDLR(-)(/-)-->apoE(-)(/-)/LDLR(-)(/-) compared with the apoE(-)(/-)/LDLR(-)(/-)-->apoE(-)(/-)/LDLR(-)(/-) controls, (15957 +/- 1907 vs. 40115 +/- 8302 micro m(2) +/- SEM, respectively). In a separate experiment, apoE(+)(/+)/LDLR(-)(/-) mice were transplanted with either apoE(+)(/+)/LDLR(-)(/-) or apoE(-)(/-)/LDLR(-)(/-) marrow and placed on a high-fat diet for 8 weeks. In the absence of macrophage apoE, lesion area was increased by 75% in the aortic sinus and by 56% in the distal aorta. These data show that physiologic levels of macrophage apoE in the vessel wall are anti-atherogenic in conditions of severe hyperlipidemia and can affect later stages of plaque development.

Animals↗

PubMed2001

Lack of macrophage fatty-acid-binding protein aP2 protects mice deficient in apolipoprotein E against atherosclerosis.

The adipocyte fatty-acid-binding protein, aP2, has an important role in regulating systemic insulin resistance and lipid metabolism. Here we demonstrate that aP2 is also expressed in macrophages, has a significant role in their biological responses and contributes to the development of atherosclerosis. Apolipoprotein E (ApoE)-deficient mice also deficient for aP2 showed protection from atherosclerosis in the absence of significant differences in serum lipids or insulin sensitivity. aP2-deficient macrophages showed alterations in inflammatory cytokine production and a reduced ability to accumulate cholesterol esters when exposed to modified lipoproteins. Apoe-/- mice with Ap2+/+ adipocytes and Ap2-/- macrophages generated by bone-marrow transplantation showed a comparable reduction in atherosclerotic lesions to those with total aP2 deficiency, indicating an independent role for macrophage aP2 in atherogenesis. Through its distinct actions in adipocytes and macrophages, aP2 provides a link between features of the metabolic syndrome and could be a new therapeutic target for the prevention of atherosclerosis.

Adipocytes↗

PubMed2001

Debate: "How low should LDL cholesterol be lowered?" Viewpoint: "It doesn't need to be very low"

The importance of low-density lipoprotein (LDL) control in the management of patients at high risk of cardiovascular events is unquestionable. The major statin trials have shown that the benefits of LDL lowering extend throughout the range of risk and the range of serum cholesterol, and have indicated that the protective effects of the intervention are mostly related to the baseline risk. Statin therapy is, for this reason, currently seen as an anti-atherogenic approach for the majority of high risk individuals and possibly all coronary heart disease patients. This debate is not about the value of statin therapy or the importance of LDL reduction, but about the goals to be set once we decide that LDL cholesterol must be reduced. With the National Cholesterol Education Program (NCEP) guidelines representing a solid middle ground, the two viewpoints in this debate try to argue, on one hand, that the LDL goals should be substantially lower than our current standards or, on the other, that a specific on-treatment LDL value may not be the most important goal to pursue. We defend the latter position by presenting the case that the most effective LDL intervention in high risk patients is to achieve a reduction of at least 30%. This strategy complies with the NCEP guidelines, as most of the high risk patients treated with an average dose of an average statin would experience a 30-40% LDL reduction that would put on-treatment LDL levels safely below goal. Our position differs from both the guidelines and the proponents of more aggressive LDL goals in the management of the two extremes of the cholesterol distribution, where our lack of interest in a predefined on-treatment LDL concentration would make us more aggressive than guidelines on low baseline LDL patients and less aggressive than guidelines on high baseline LDL patients.

Journal Article↗