Michael Avella - Academia.edu (original) (raw)

Papers by Michael Avella

Research paper thumbnail of Incorporation of lycopene into chylomicron remnant-like particles enhances their induction of lipid accumulation in macrophages

Biochemical and Biophysical Research Communications, Dec 26, 2003

Lipid accumulation in macrophages exposed to chylomicron remnant-like particles containing the di... more Lipid accumulation in macrophages exposed to chylomicron remnant-like particles containing the dietary antioxidant lycopene was investigated. After incubation with THP-1 macrophages (48 h), chylomicron remnant-like particles containing lycopene (lycCRLPs) as compared to those without (CRLPs) caused significantly more lipid accumulation in the cells, and this was due to increases in both the triacylglycerol (+100%) and cholesterol (+62%) content. In addition, expression of mRNA for diacylglycerol acyltransferase (DGAT), a key enzyme in triacylglycerol synthesis, was significantly decreased by lycCRLPs, but not CRLPs. These findings suggest that lycopene from the diet may promote, rather than retard, lipid accumulation in macrophages during its transport in the blood in chylomicron remnants.

Research paper thumbnail of Oxidation of chylomicron remnant-like particles inhibits their uptake by THP-1 macrophages by apolipoprotein E-dependent processes

Biochimica and Biophysica Acta Molecular and Cell Biology of Lipids, Jul 31, 2007

The influence of the oxidative state of chylomicron remnants (CMR) on the mechanisms of their upt... more The influence of the oxidative state of chylomicron remnants (CMR) on the mechanisms of their uptake and induction of lipid accumulation by macrophages derived from the human monocyte cell line, THP-1, during foam cell formation was investigated using chylomicron-remnant-like particles (CRLPs) at 3 different levels of oxidation. The oxidative state of CRLPs was varied by exposure to CuSO 4 (oxCRLPs) or incorporation of the antioxidant, probucol (pCRLPs) into the particles. oxCRLPs caused significantly less accumulation of triacylglycerol in the macrophages than CRLPs, and their rate of uptake was lower, while pCRLPs caused more lipid accumulation and were taken up faster. Uptake of all 3 types of particles was inhibited to a similar extent when entry via the low density lipoprotein (LDL) receptor related protein (80-90%), LDL receptor (− 30-40%), CD36 (− 40%) and phagocytosis (− 35-40%) was blocked using lactoferrin, excess LDL, anti-CD36 and cytochalasin D, respectively, but blocking scavenger receptors-A or -B1 using poly inosinic acid or excess HDL had no effect. These findings show that oxidation of CRLPs lowers their rate of uptake and induction of lipid accumulation in macrophages. However, oxidation does not change the main pathways of internalisation of CRLPs into THP-1 macrophages, which occur mainly via the LRP with some contribution from the LDLr, while CD36 and phagocytosis have only a minor role, regardless of the oxidative state of the particles. Thus, the effects of CMR oxidation on foam cell formation contrast sharply with those of LDL oxidation and this may be important in the role of dietary oxidized lipids and antioxidants in modulating atherosclerosis.

Research paper thumbnail of Neutral cholesteryl ester hydrolase activity in rat peritoneal macrophages: regulation by cyclic AMP

Biochemical Society transactions, 1995

Research paper thumbnail of Chylomicron remnants derived from fish oil are bound and internalised more rapidly by isolated hepatocytes than those derived from olive or palm oil

Biochemical Society transactions, 1998

Research paper thumbnail of The differential hepatic uptake of chylomicron remnants of different fatty acid composition is not mediated by hepatic lipase

British Journal of Nutrition, 2001

The hypothesis that hepatic lipase mediates the differential hepatic uptake of chylomicron remnan... more The hypothesis that hepatic lipase mediates the differential hepatic uptake of chylomicron remnants of different fatty acid composition, demonstrated in previous work from our laboratory, was tested by investigating the effect of antibodies to the enzyme on the uptake of remnants enriched with saturated or n-3 polyunsaturated fatty acids by the perfused rat liver. After perfusion of rat livers with polyclonal antibodies to rat hepatic lipase raised in rabbits or with rabbit non-immune serum for 15 min, [3H]oleate-labelled chylomicron remnants, derived from chylomicrons of rats given a bolus of either palm (rich in saturated fatty acids) oil or fish (rich in n-3 polyunsaturated fatty acids) oil, were added. The disappearance of radioactivity from the perfusate during 120 min and its recovery in the liver at the end of the experiments were then measured. Although the rabbit anti-rat hepatic lipase antiserum was shown to inhibit hepatic lipase activity by up to 90%, and to bind extensively to hepatic sinusoidal surfaces when added to the perfusate, radioactivity from remnants of chylomicrons from rats given a bolus of fish oil as compared with palm oil disappeared from the perfusate and appeared in the liver more rapidly in the presence both the antiserum and the non-immune serum, and the differences between the uptake of the two types of remnants were similar. We conclude, therefore, that differential interaction with hepatic lipase is not responsible for the differences in the rate of removal of chylomicron remnants of different fatty acid composition from the blood.

Research paper thumbnail of 4.P.238 Influence of the type of dietary fat on the biliary excretion of cholesterol from chylomicron remnants in the perfused liver

Research paper thumbnail of Dietary fats induce human monocyte activation in vitro

Biochemical Society Transactions, 2007

In early atherosclerosis the frequency of activated monocytes in the peripheral circulation is am... more In early atherosclerosis the frequency of activated monocytes in the peripheral circulation is amplified, and migration of monocytes into the walls of the aorta and large arteries is increased, due partly to de novo expression or activation of monocyte adhesion molecules. Although there is increasing evidence that CMRs (chylomicron remnants) are strongly atherogenic, the outcomes of interactions between blood monocytes and circulating CMRs are not known. Here, we have studied the effects of CRLPs (CMR-like particles) on THP-1 human monocyte oxidative burst. The particles induced a significant increase in reactive oxygen species within 1 h, which persisted for 24 h. We suggest that monocyte-CMR interactions may be important in early atherosclerosis when many activated monocytes are found in susceptible areas of the artery wall.

Research paper thumbnail of PO1-8 Effects of Fatty Acids Delivered in Chylomicron Remnants on the Hepatic Expression of Genes Regulating Synthesis and Secretion of VLDL

Research paper thumbnail of Differential effects of low-density lipoprotein and chylomicron remnants on lipid accumulation in human macrophages

Experimental Biology and Medicine, Jun 1, 2004

The effects of low-density lipoprotein (LDL) and chylomicron remnants on lipid accumulation in hu... more The effects of low-density lipoprotein (LDL) and chylomicron remnants on lipid accumulation in human monocyte-derived macrophages (HMDMs) and in macrophages derived from the human monocyte cell line THP-1 were compared. The HMDMs or THP-1 macrophages were incubated with LDL, oxidized LDL (oxLDL), chylomicron remnant-like particles (CMR-LPs), or oxidized CMR-LPs (oxCMR-LPs), and the amount and type of lipid accumulated were determined. As expected, the lipid content of both cell types was increased markedly by oxLDL but not LDL, and this was due to a rise in cholesterol, cholesteryl ester (CE), and triacylglycerol (TG) levels. In contrast, both CMR-LPs and oxCMR-LPs caused a considerable increase in cellular lipid in HMDMs and THP-1 macrophages, but in this case there was a greater rise in the TG than in the cholesterol or CE content. Lipid accumulation in response to oxLDL, CMR-LPs, and oxCMR-LPs was prevented by the ACAT inhibitor CI976 in HMDMs but not in THP-1 macrophages, where TG levels remained markedly elevated. The rate of incorporation of [ 3 H]oleate into CE and TG in THP-1 macrophages was increased by oxLDL, CMR-LPs, and oxCMR-LPs, but incorporation into TG was increased to a greater extent with CMR-LPs and oxCMR-LPs compared with oxLDL. These results demonstrate that both CMR-LPs and oxCMR-LPs cause lipid accumulation in human macrophages comparable to that seen with oxLDL and that oxidation of the remnant particles does not enhance this effect. They also demonstrate that a greater proportion of the lipid accumulated in response to CMR-LPs compared with oxLDL is TG rather than cholesterol or CE and that this is associated with a higher rate of TG synthesis. This study, therefore, provides further evidence to suggest that chylomicron remnants have a role in foam cell formation that is distinct from that of oxLDL.

Research paper thumbnail of Chylomicron remnants and lipid accumulation in J774 macrophages: influence of cellular oxidation state

Atherosclerosis Supplements, 2001

... Issue Date: 2001. Publisher: Elsevier Science. Citation: Botham KM, Napolitano M, Rivabene R,... more ... Issue Date: 2001. Publisher: Elsevier Science. Citation: Botham KM, Napolitano M, Rivabene R, Avella M, Bravo E. Chylomicron remnants and lipid accumulation in J774 macrophages: influence of cellular oxidation state. Atherosclerosis supplements 2001;2(2): ...

Research paper thumbnail of The effects of dietary n-3 polyunsaturated fatty acids delivered in chylomicron remnants on the transcription of genes regulating synthesis and secretion of very-low-density lipoprotein by the liver: modulation by cellular oxidative state

Experimental biology and medicine (Maywood, N.J.), 2003

The influence of chylomicron remnants enriched in n-3 or n-6 polyunsaturated fatty acids (PUFA) (... more The influence of chylomicron remnants enriched in n-3 or n-6 polyunsaturated fatty acids (PUFA) (derived from fish or corn oil, respectively) on the expression of mRNA for four genes involved in the regulation of the synthesis, assembly, and secretion of very-low-density lipoprotein (VLDL) in the liver was investigated in normal rat hepatocytes and after manipulation of the cellular oxidative state by incubation with N-acetyl cysteine (NAC) or CuSO(4). The four genes investigated were those encoding apolipoprotein B (apoB), the microsomal triacylglycerol transfer protein (MTP), and the enzymes acyl coenzyme A:diacylglycerol acyltransferase (DGAT) and acyl coenzyme A:cholesterol acyltransferase 2 (ACAT2), which play a role in the regulation of triacylglycerol and cholesteryl ester synthesis, respectively. mRNA levels for apoB, MTP, and DGAT were unaffected by either fish or corn oil chylomicron remnants, but the amount of ACAT2 mRNA was significantly reduced after incubation of the h...

Research paper thumbnail of The effect of cyclic AMP analogues on cholesteryl ester synthesis and hydrolysis in cultured rat peritoneal macrophages

Biochemical Society transactions, 1997

Research paper thumbnail of Influence of dietary fats on human monocyte activation in vitro

Atherosclerosis Supplements, 2008

Abstracts / Atherosclerosis Supplements 9 (2008) 83-102 99 associated with differences in postpra... more Abstracts / Atherosclerosis Supplements 9 (2008) 83-102 99 associated with differences in postprandial lipemia relates to the small sample size of postprandial studies. More recently, we have carried out postprandial study [Genetics of Lipid Lowering Drugs and Diet Network (GOLDN)] including over 1000 subjects that in addition to receiving a standardized initial fat load, they were subjected to a second one after receiving several weeks of fenofibrate treatment. Moreover, we used NMR to measure lipoprotein subclasses in the fasting and postprandial phases. Using this experimental design, we are currently examining a large number of candidate genes to characterize which ones act as significant modulators of lipemic response and other cardiovascular risk factors (i.e., inflammation biomarkers). Preliminary data for some of these candidate genes (i.e., perilipin) will be presented.

Research paper thumbnail of PO1-8 Effects of Fatty Acids Delivered in Chylomicron Remnants on the Hepatic Expression of Genes Regulating Synthesis and Secretion of VLDL

Atherosclerosis Supplements, 2007

Research paper thumbnail of Postprandial phase time influences the uptake of TAG from postprandial TAG-rich lipoproteins by THP-1 macrophages

British Journal of Nutrition, 2014

Postprandial TAG-rich lipoproteins (TRL) can be taken up by macrophages, leading to the formation... more Postprandial TAG-rich lipoproteins (TRL) can be taken up by macrophages, leading to the formation of foam cells, probably via receptor-mediated pathways. The present study was conducted to investigate whether the postprandial time point at which TRL are collected modulates this process. A meal containing refined olive oil was given to nine healthy young men and TRL were isolated from their serum at 2, 4 and 6 h postprandially. The lipid class and apoB compositions of TRL were determined by HPLC and SDS-PAGE, respectively. The accumulation of lipids in macrophages was determined after the incubation of THP-1 macrophages with TRL. The gene expression of candidate receptors was measured by real-time PCR. The highest concentrations of TAG, apoB48 and apoB100 in TRL were observed at 2 h after the consumption of the test meal. However, excessive intracellular TAG accumulation in THP-1 macrophages was observed in response to incubation with TRL isolated at 4 h, when their particle size (estimated as the TAG:apoB ratio) was intermediate. The abundance of mRNA transcripts in macrophages in response to incubation with TRL was down-regulated for LDL receptor (LDLR), slightly up-regulated for VLDL receptor and remained unaltered for LDLR-related protein, but no effect of the postprandial time point was observed. In contrast, the mRNA expression of scavenger receptors SRB1, SRA2 and CD36 was higher when cells were incubated with TRL isolated at 4 h after the consumption of the test meal. In conclusion, TRL led to excessive intracellular TAG accumulation in THP-1 macrophages, which was greater when cells were incubated with intermediate-sized postprandial TRL isolated at 4 h and was associated with a significant increase in the mRNA expression of scavenger receptors.

Research paper thumbnail of Th-P15:104 Triglyceride-rich lipoproteins derived from pomace olive oil have differential effects on the expression of MRNA for macrophage receptors

Atherosclerosis Supplements, 2006

Objective: Rerearcherr believe that incubation of macrophager (mac) only with modified LDL can re... more Objective: Rerearcherr believe that incubation of macrophager (mac) only with modified LDL can rerult in cholerterol accumulation rufficient to form foam cellr. We have invertigated whether mac can become foam cellr with unmodified native LDL.

Research paper thumbnail of Comparison of the effects of low density lipoprotein and chylomicron remnants on foam cell formation in the human monocytic cell line THP1

Atherosclerosis Supplements, 2001

Research paper thumbnail of Fatty acid composition of chylomicron remnant-like particles influences their uptake and induction of lipid accumulation in macrophages

FEBS Journal, 2006

... Clara De Pascale 1 ,; Michael Avella 1 ,; Javier S. Perona 2 ,; Valentina Ruiz-Gutierrez 2 ,;... more ... Clara De Pascale 1 ,; Michael Avella 1 ,; Javier S. Perona 2 ,; Valentina Ruiz-Gutierrez 2 ,; Caroline PD Wheeler-Jones 1 ,; Kathleen M. Botham 1. ... Lipid peroxidation products after incubation of the four types of CRLP with CuSO 4 (10 µm) for 6 h were significantly lower with olive ...

Research paper thumbnail of Protection of chylomicron remnants from oxidation by incorporation of probucol into the particles enhances their uptake by human macrophages and increases lipid accumulation in the cells

European Journal of Biochemistry, 2004

The effects of protection of chylomicron remnants from oxidation on their uptake and induction of... more The effects of protection of chylomicron remnants from oxidation on their uptake and induction of lipid accumulation in macrophages were investigated using chylomicron remnant-like particles (CRLPs) containing the lipophilic antioxidant drug, probucol, and macrophages derived from the human monocyte cell line, THP-1. The total lipid content of THP-1 macrophages was markedly higher (·2.2) after 48 h of incubation of THP-1 macrophages with CRLPs containing probucol (pCRLPs) when compared to CRLPs without probucol, and this was because of increases in triacylglycerol (·2.3) and cholesterol (·1.8) levels, while cholesteryl ester concentrations were not significantly changed. Determination of the uptake of CRLPs and pCRLPs by the cells using particles labelled with the fluorescent probe 1,1¢dioctadecyl-3,3,3¢3¢-tetramethylindo-carbocyanine perchlorate showed that pCRLPs are taken up at a faster rate than CRLPs. The synthesis of triacylglycerol, as measured by the incorporation of [ 3 H]oleate and [ 3 H]glycerol, was also increased in macrophages incubated with pCRLPs as compared to CRLPs without probucol, but phospholipid and cholesteryl ester formation from [ 3 H]oleate was unaffected. In addition, no differences between the effects of CRLPs and pCRLPs on the expression of mRNA for a range of genes believed to be involved in lipoprotein uptake, intracellular lipid metabolism and the efflux of cholesterol from macrophages was detected. These results suggest that antioxidants carried in chylomicron remnants enhance lipid accumulation in macrophages by increasing the rate of uptake of the particles and raising the intracellular synthesis of triacylglycerol, but not cholesteryl ester, and that these effects are brought about by changes at the post-transcriptional level. Antioxidants carried in chylomicron remnants therefore may promote the development of atherosclerosis, and this is likely to be particularly important in conditions where clearance of remnants from the circulation is delayed.

Research paper thumbnail of Comparison of short- and long-term effects of different dietary fats on the hepatic uptake and metabolism of chylomicron remnants in rats

British Journal of Nutrition, 1998

The uptake and metabolism of [14C]oleate-labelled chylomicron remnants derived from olive oil, ma... more The uptake and metabolism of [14C]oleate-labelled chylomicron remnants derived from olive oil, maize oil, palm oil, fish oil or butter fat was investigated using perfused livers from rats fed on the corresponding fat-supplemented diet (providing 40% of the dietary energy) or a low-fat diet for 21 d. The percentage of added [14C]oleate-labelled remnant removed from the perfusate was similar for livers from rats fed on the fat-supplemented diets irrespective of the type of fat fed, whereas livers from rats fed on the low-fat diet removed more labelled fish oil and butter fat remnants than olive, maize or palm oil remnants. Following hepatic uptake in the fat-supplemented groups, the oxidation of [14C]oleate-labelled remnant lipid from maize oil, fish oil, and butter fat remnants was greater than that of the lipids from olive and palm oil remnants, although only the oxidation of lipids from maize and palm oil remnants was increased by prior fat-supplementation of the diet. In addition, the livers from rats fed on the fish-oil-supplemented diet incorporated more [14C]oleate-labelled remnant lipid into phospholipid compared with the livers from rats fed on the other fat-supplemented diets or the low-fat diets. These investigations show that both prior fat feeding and the composition of the fat fed, as well as the fatty acid composition of the chylomicron remnant particles themselves, influence the uptake and metabolism of chylomicron remnants by the liver.

Research paper thumbnail of Incorporation of lycopene into chylomicron remnant-like particles enhances their induction of lipid accumulation in macrophages

Biochemical and Biophysical Research Communications, Dec 26, 2003

Lipid accumulation in macrophages exposed to chylomicron remnant-like particles containing the di... more Lipid accumulation in macrophages exposed to chylomicron remnant-like particles containing the dietary antioxidant lycopene was investigated. After incubation with THP-1 macrophages (48 h), chylomicron remnant-like particles containing lycopene (lycCRLPs) as compared to those without (CRLPs) caused significantly more lipid accumulation in the cells, and this was due to increases in both the triacylglycerol (+100%) and cholesterol (+62%) content. In addition, expression of mRNA for diacylglycerol acyltransferase (DGAT), a key enzyme in triacylglycerol synthesis, was significantly decreased by lycCRLPs, but not CRLPs. These findings suggest that lycopene from the diet may promote, rather than retard, lipid accumulation in macrophages during its transport in the blood in chylomicron remnants.

Research paper thumbnail of Oxidation of chylomicron remnant-like particles inhibits their uptake by THP-1 macrophages by apolipoprotein E-dependent processes

Biochimica and Biophysica Acta Molecular and Cell Biology of Lipids, Jul 31, 2007

The influence of the oxidative state of chylomicron remnants (CMR) on the mechanisms of their upt... more The influence of the oxidative state of chylomicron remnants (CMR) on the mechanisms of their uptake and induction of lipid accumulation by macrophages derived from the human monocyte cell line, THP-1, during foam cell formation was investigated using chylomicron-remnant-like particles (CRLPs) at 3 different levels of oxidation. The oxidative state of CRLPs was varied by exposure to CuSO 4 (oxCRLPs) or incorporation of the antioxidant, probucol (pCRLPs) into the particles. oxCRLPs caused significantly less accumulation of triacylglycerol in the macrophages than CRLPs, and their rate of uptake was lower, while pCRLPs caused more lipid accumulation and were taken up faster. Uptake of all 3 types of particles was inhibited to a similar extent when entry via the low density lipoprotein (LDL) receptor related protein (80-90%), LDL receptor (− 30-40%), CD36 (− 40%) and phagocytosis (− 35-40%) was blocked using lactoferrin, excess LDL, anti-CD36 and cytochalasin D, respectively, but blocking scavenger receptors-A or -B1 using poly inosinic acid or excess HDL had no effect. These findings show that oxidation of CRLPs lowers their rate of uptake and induction of lipid accumulation in macrophages. However, oxidation does not change the main pathways of internalisation of CRLPs into THP-1 macrophages, which occur mainly via the LRP with some contribution from the LDLr, while CD36 and phagocytosis have only a minor role, regardless of the oxidative state of the particles. Thus, the effects of CMR oxidation on foam cell formation contrast sharply with those of LDL oxidation and this may be important in the role of dietary oxidized lipids and antioxidants in modulating atherosclerosis.

Research paper thumbnail of Neutral cholesteryl ester hydrolase activity in rat peritoneal macrophages: regulation by cyclic AMP

Biochemical Society transactions, 1995

Research paper thumbnail of Chylomicron remnants derived from fish oil are bound and internalised more rapidly by isolated hepatocytes than those derived from olive or palm oil

Biochemical Society transactions, 1998

Research paper thumbnail of The differential hepatic uptake of chylomicron remnants of different fatty acid composition is not mediated by hepatic lipase

British Journal of Nutrition, 2001

The hypothesis that hepatic lipase mediates the differential hepatic uptake of chylomicron remnan... more The hypothesis that hepatic lipase mediates the differential hepatic uptake of chylomicron remnants of different fatty acid composition, demonstrated in previous work from our laboratory, was tested by investigating the effect of antibodies to the enzyme on the uptake of remnants enriched with saturated or n-3 polyunsaturated fatty acids by the perfused rat liver. After perfusion of rat livers with polyclonal antibodies to rat hepatic lipase raised in rabbits or with rabbit non-immune serum for 15 min, [3H]oleate-labelled chylomicron remnants, derived from chylomicrons of rats given a bolus of either palm (rich in saturated fatty acids) oil or fish (rich in n-3 polyunsaturated fatty acids) oil, were added. The disappearance of radioactivity from the perfusate during 120 min and its recovery in the liver at the end of the experiments were then measured. Although the rabbit anti-rat hepatic lipase antiserum was shown to inhibit hepatic lipase activity by up to 90%, and to bind extensively to hepatic sinusoidal surfaces when added to the perfusate, radioactivity from remnants of chylomicrons from rats given a bolus of fish oil as compared with palm oil disappeared from the perfusate and appeared in the liver more rapidly in the presence both the antiserum and the non-immune serum, and the differences between the uptake of the two types of remnants were similar. We conclude, therefore, that differential interaction with hepatic lipase is not responsible for the differences in the rate of removal of chylomicron remnants of different fatty acid composition from the blood.

Research paper thumbnail of 4.P.238 Influence of the type of dietary fat on the biliary excretion of cholesterol from chylomicron remnants in the perfused liver

Research paper thumbnail of Dietary fats induce human monocyte activation in vitro

Biochemical Society Transactions, 2007

In early atherosclerosis the frequency of activated monocytes in the peripheral circulation is am... more In early atherosclerosis the frequency of activated monocytes in the peripheral circulation is amplified, and migration of monocytes into the walls of the aorta and large arteries is increased, due partly to de novo expression or activation of monocyte adhesion molecules. Although there is increasing evidence that CMRs (chylomicron remnants) are strongly atherogenic, the outcomes of interactions between blood monocytes and circulating CMRs are not known. Here, we have studied the effects of CRLPs (CMR-like particles) on THP-1 human monocyte oxidative burst. The particles induced a significant increase in reactive oxygen species within 1 h, which persisted for 24 h. We suggest that monocyte-CMR interactions may be important in early atherosclerosis when many activated monocytes are found in susceptible areas of the artery wall.

Research paper thumbnail of PO1-8 Effects of Fatty Acids Delivered in Chylomicron Remnants on the Hepatic Expression of Genes Regulating Synthesis and Secretion of VLDL

Research paper thumbnail of Differential effects of low-density lipoprotein and chylomicron remnants on lipid accumulation in human macrophages

Experimental Biology and Medicine, Jun 1, 2004

The effects of low-density lipoprotein (LDL) and chylomicron remnants on lipid accumulation in hu... more The effects of low-density lipoprotein (LDL) and chylomicron remnants on lipid accumulation in human monocyte-derived macrophages (HMDMs) and in macrophages derived from the human monocyte cell line THP-1 were compared. The HMDMs or THP-1 macrophages were incubated with LDL, oxidized LDL (oxLDL), chylomicron remnant-like particles (CMR-LPs), or oxidized CMR-LPs (oxCMR-LPs), and the amount and type of lipid accumulated were determined. As expected, the lipid content of both cell types was increased markedly by oxLDL but not LDL, and this was due to a rise in cholesterol, cholesteryl ester (CE), and triacylglycerol (TG) levels. In contrast, both CMR-LPs and oxCMR-LPs caused a considerable increase in cellular lipid in HMDMs and THP-1 macrophages, but in this case there was a greater rise in the TG than in the cholesterol or CE content. Lipid accumulation in response to oxLDL, CMR-LPs, and oxCMR-LPs was prevented by the ACAT inhibitor CI976 in HMDMs but not in THP-1 macrophages, where TG levels remained markedly elevated. The rate of incorporation of [ 3 H]oleate into CE and TG in THP-1 macrophages was increased by oxLDL, CMR-LPs, and oxCMR-LPs, but incorporation into TG was increased to a greater extent with CMR-LPs and oxCMR-LPs compared with oxLDL. These results demonstrate that both CMR-LPs and oxCMR-LPs cause lipid accumulation in human macrophages comparable to that seen with oxLDL and that oxidation of the remnant particles does not enhance this effect. They also demonstrate that a greater proportion of the lipid accumulated in response to CMR-LPs compared with oxLDL is TG rather than cholesterol or CE and that this is associated with a higher rate of TG synthesis. This study, therefore, provides further evidence to suggest that chylomicron remnants have a role in foam cell formation that is distinct from that of oxLDL.

Research paper thumbnail of Chylomicron remnants and lipid accumulation in J774 macrophages: influence of cellular oxidation state

Atherosclerosis Supplements, 2001

... Issue Date: 2001. Publisher: Elsevier Science. Citation: Botham KM, Napolitano M, Rivabene R,... more ... Issue Date: 2001. Publisher: Elsevier Science. Citation: Botham KM, Napolitano M, Rivabene R, Avella M, Bravo E. Chylomicron remnants and lipid accumulation in J774 macrophages: influence of cellular oxidation state. Atherosclerosis supplements 2001;2(2): ...

Research paper thumbnail of The effects of dietary n-3 polyunsaturated fatty acids delivered in chylomicron remnants on the transcription of genes regulating synthesis and secretion of very-low-density lipoprotein by the liver: modulation by cellular oxidative state

Experimental biology and medicine (Maywood, N.J.), 2003

The influence of chylomicron remnants enriched in n-3 or n-6 polyunsaturated fatty acids (PUFA) (... more The influence of chylomicron remnants enriched in n-3 or n-6 polyunsaturated fatty acids (PUFA) (derived from fish or corn oil, respectively) on the expression of mRNA for four genes involved in the regulation of the synthesis, assembly, and secretion of very-low-density lipoprotein (VLDL) in the liver was investigated in normal rat hepatocytes and after manipulation of the cellular oxidative state by incubation with N-acetyl cysteine (NAC) or CuSO(4). The four genes investigated were those encoding apolipoprotein B (apoB), the microsomal triacylglycerol transfer protein (MTP), and the enzymes acyl coenzyme A:diacylglycerol acyltransferase (DGAT) and acyl coenzyme A:cholesterol acyltransferase 2 (ACAT2), which play a role in the regulation of triacylglycerol and cholesteryl ester synthesis, respectively. mRNA levels for apoB, MTP, and DGAT were unaffected by either fish or corn oil chylomicron remnants, but the amount of ACAT2 mRNA was significantly reduced after incubation of the h...

Research paper thumbnail of The effect of cyclic AMP analogues on cholesteryl ester synthesis and hydrolysis in cultured rat peritoneal macrophages

Biochemical Society transactions, 1997

Research paper thumbnail of Influence of dietary fats on human monocyte activation in vitro

Atherosclerosis Supplements, 2008

Abstracts / Atherosclerosis Supplements 9 (2008) 83-102 99 associated with differences in postpra... more Abstracts / Atherosclerosis Supplements 9 (2008) 83-102 99 associated with differences in postprandial lipemia relates to the small sample size of postprandial studies. More recently, we have carried out postprandial study [Genetics of Lipid Lowering Drugs and Diet Network (GOLDN)] including over 1000 subjects that in addition to receiving a standardized initial fat load, they were subjected to a second one after receiving several weeks of fenofibrate treatment. Moreover, we used NMR to measure lipoprotein subclasses in the fasting and postprandial phases. Using this experimental design, we are currently examining a large number of candidate genes to characterize which ones act as significant modulators of lipemic response and other cardiovascular risk factors (i.e., inflammation biomarkers). Preliminary data for some of these candidate genes (i.e., perilipin) will be presented.

Research paper thumbnail of PO1-8 Effects of Fatty Acids Delivered in Chylomicron Remnants on the Hepatic Expression of Genes Regulating Synthesis and Secretion of VLDL

Atherosclerosis Supplements, 2007

Research paper thumbnail of Postprandial phase time influences the uptake of TAG from postprandial TAG-rich lipoproteins by THP-1 macrophages

British Journal of Nutrition, 2014

Postprandial TAG-rich lipoproteins (TRL) can be taken up by macrophages, leading to the formation... more Postprandial TAG-rich lipoproteins (TRL) can be taken up by macrophages, leading to the formation of foam cells, probably via receptor-mediated pathways. The present study was conducted to investigate whether the postprandial time point at which TRL are collected modulates this process. A meal containing refined olive oil was given to nine healthy young men and TRL were isolated from their serum at 2, 4 and 6 h postprandially. The lipid class and apoB compositions of TRL were determined by HPLC and SDS-PAGE, respectively. The accumulation of lipids in macrophages was determined after the incubation of THP-1 macrophages with TRL. The gene expression of candidate receptors was measured by real-time PCR. The highest concentrations of TAG, apoB48 and apoB100 in TRL were observed at 2 h after the consumption of the test meal. However, excessive intracellular TAG accumulation in THP-1 macrophages was observed in response to incubation with TRL isolated at 4 h, when their particle size (estimated as the TAG:apoB ratio) was intermediate. The abundance of mRNA transcripts in macrophages in response to incubation with TRL was down-regulated for LDL receptor (LDLR), slightly up-regulated for VLDL receptor and remained unaltered for LDLR-related protein, but no effect of the postprandial time point was observed. In contrast, the mRNA expression of scavenger receptors SRB1, SRA2 and CD36 was higher when cells were incubated with TRL isolated at 4 h after the consumption of the test meal. In conclusion, TRL led to excessive intracellular TAG accumulation in THP-1 macrophages, which was greater when cells were incubated with intermediate-sized postprandial TRL isolated at 4 h and was associated with a significant increase in the mRNA expression of scavenger receptors.

Research paper thumbnail of Th-P15:104 Triglyceride-rich lipoproteins derived from pomace olive oil have differential effects on the expression of MRNA for macrophage receptors

Atherosclerosis Supplements, 2006

Objective: Rerearcherr believe that incubation of macrophager (mac) only with modified LDL can re... more Objective: Rerearcherr believe that incubation of macrophager (mac) only with modified LDL can rerult in cholerterol accumulation rufficient to form foam cellr. We have invertigated whether mac can become foam cellr with unmodified native LDL.

Research paper thumbnail of Comparison of the effects of low density lipoprotein and chylomicron remnants on foam cell formation in the human monocytic cell line THP1

Atherosclerosis Supplements, 2001

Research paper thumbnail of Fatty acid composition of chylomicron remnant-like particles influences their uptake and induction of lipid accumulation in macrophages

FEBS Journal, 2006

... Clara De Pascale 1 ,; Michael Avella 1 ,; Javier S. Perona 2 ,; Valentina Ruiz-Gutierrez 2 ,;... more ... Clara De Pascale 1 ,; Michael Avella 1 ,; Javier S. Perona 2 ,; Valentina Ruiz-Gutierrez 2 ,; Caroline PD Wheeler-Jones 1 ,; Kathleen M. Botham 1. ... Lipid peroxidation products after incubation of the four types of CRLP with CuSO 4 (10 µm) for 6 h were significantly lower with olive ...

Research paper thumbnail of Protection of chylomicron remnants from oxidation by incorporation of probucol into the particles enhances their uptake by human macrophages and increases lipid accumulation in the cells

European Journal of Biochemistry, 2004

The effects of protection of chylomicron remnants from oxidation on their uptake and induction of... more The effects of protection of chylomicron remnants from oxidation on their uptake and induction of lipid accumulation in macrophages were investigated using chylomicron remnant-like particles (CRLPs) containing the lipophilic antioxidant drug, probucol, and macrophages derived from the human monocyte cell line, THP-1. The total lipid content of THP-1 macrophages was markedly higher (·2.2) after 48 h of incubation of THP-1 macrophages with CRLPs containing probucol (pCRLPs) when compared to CRLPs without probucol, and this was because of increases in triacylglycerol (·2.3) and cholesterol (·1.8) levels, while cholesteryl ester concentrations were not significantly changed. Determination of the uptake of CRLPs and pCRLPs by the cells using particles labelled with the fluorescent probe 1,1¢dioctadecyl-3,3,3¢3¢-tetramethylindo-carbocyanine perchlorate showed that pCRLPs are taken up at a faster rate than CRLPs. The synthesis of triacylglycerol, as measured by the incorporation of [ 3 H]oleate and [ 3 H]glycerol, was also increased in macrophages incubated with pCRLPs as compared to CRLPs without probucol, but phospholipid and cholesteryl ester formation from [ 3 H]oleate was unaffected. In addition, no differences between the effects of CRLPs and pCRLPs on the expression of mRNA for a range of genes believed to be involved in lipoprotein uptake, intracellular lipid metabolism and the efflux of cholesterol from macrophages was detected. These results suggest that antioxidants carried in chylomicron remnants enhance lipid accumulation in macrophages by increasing the rate of uptake of the particles and raising the intracellular synthesis of triacylglycerol, but not cholesteryl ester, and that these effects are brought about by changes at the post-transcriptional level. Antioxidants carried in chylomicron remnants therefore may promote the development of atherosclerosis, and this is likely to be particularly important in conditions where clearance of remnants from the circulation is delayed.

Research paper thumbnail of Comparison of short- and long-term effects of different dietary fats on the hepatic uptake and metabolism of chylomicron remnants in rats

British Journal of Nutrition, 1998

The uptake and metabolism of [14C]oleate-labelled chylomicron remnants derived from olive oil, ma... more The uptake and metabolism of [14C]oleate-labelled chylomicron remnants derived from olive oil, maize oil, palm oil, fish oil or butter fat was investigated using perfused livers from rats fed on the corresponding fat-supplemented diet (providing 40% of the dietary energy) or a low-fat diet for 21 d. The percentage of added [14C]oleate-labelled remnant removed from the perfusate was similar for livers from rats fed on the fat-supplemented diets irrespective of the type of fat fed, whereas livers from rats fed on the low-fat diet removed more labelled fish oil and butter fat remnants than olive, maize or palm oil remnants. Following hepatic uptake in the fat-supplemented groups, the oxidation of [14C]oleate-labelled remnant lipid from maize oil, fish oil, and butter fat remnants was greater than that of the lipids from olive and palm oil remnants, although only the oxidation of lipids from maize and palm oil remnants was increased by prior fat-supplementation of the diet. In addition, the livers from rats fed on the fish-oil-supplemented diet incorporated more [14C]oleate-labelled remnant lipid into phospholipid compared with the livers from rats fed on the other fat-supplemented diets or the low-fat diets. These investigations show that both prior fat feeding and the composition of the fat fed, as well as the fatty acid composition of the chylomicron remnant particles themselves, influence the uptake and metabolism of chylomicron remnants by the liver.