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1.
The role of lipoproteins and serum in the formation and accumulation of cholesteryl esters in human monocyte-derived macrophages
(HMD macrophages) was investigated; studies were also carried out with IC21 cells (a cell line derived from mouse peritoneal
macrophages). Following preincubation of HMD macrophages with lipoprotein-depleted serum (LPDS), both native and acetylated
low density lipoprotein (LDL and AcLDL, respectively) stimulated the formation of cholesteryl esters with a resultant increase
in cellular cholesteryl ester content. Cholesteryl ester formation and accumulation was also stimulated in macrophages exposed
continuously to 25-hydroxycholesterol. However, the stimulation of cholesterol esterification by either lipoproteins or 25-hydroxycholesterol
was not inhibited by progesterone in HMD macrophages, but was in the IC21 cells. Cholesterol efflux and the hydrolysis of
cellular cholesterol ester, promoted by serum components, were studied in HMD macrophages preloaded with cholesteryl ester
by incubation with 25-hydroxy cholesterol. Replacement of the medium with one devoid of 25-hydroxycholesterol resulted within
24 hr in at least a 30% decrease in the cholesteryl ester content of the HMD macrophages; replacement with a medium high in
cholesterol acceptor content (LPDS or high density lipoprotein) and incubation for three days led to the most marked decreases
in cellular cholesterol content. Thus, hydrolysis of the cholesteryl esters by HMD macrophages was not dependent on the presence
of cholesterol acceptors in the medium, but cellular cholesterol content was. 相似文献
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4.
目的观察脂多糖(LPS)刺激对小鼠腹腔巨噬细胞高迁移率族蛋白B1(HMGB1)表达的影响。方法取正常Swiss小鼠腹腔巨噬细胞,以LPS分别刺激4、8、12、18、24和36h后,RT-PCR法检测小鼠腹腔巨噬细胞HMGB1基因mRNA的转录水平,Western blot法检测HMGB1蛋白的表达水平,观察LPS刺激与HMGB1释放的时效关系。结果LPS刺激后4~18h,细胞内HMGB1基因mRNA的转录水平无明显变化,24h开始明显增强,刺激24h和36h与对照组相比,差异有统计学意义,HMGB1蛋白在LPS刺激后18h开始表达明显增加,并一直持续至36h。结论LPS可促进小鼠腹腔巨噬细胞HMGB1的表达,并具有时间依赖性。 相似文献
5.
The effects of 5 μg/ml of 25-hydroxycholesterol; cholestane-3β, 5α,6β-triol; and cholesterol on acyl CoA cholesterol acyltransferase,
acid cholesteryl ester hydrolase and neutral cholesteryl ester hydrolase was studied in cultured rabbit aortic smooth muscle
cells. After 1 hour incubation, 25-hydroxycholesterol resulted in a fourfold stimulation of acyl CoA cholesterol acyltrans-ferase
activity. No stimulation by 25-hydroxycholesterol was noted before 15 minutes or after 5 hours of incubation. Neither cholestane-3β,5α,6β-triol
nor cholesterol influenced acyl CoA cholesterol acyltransferase activity at any time interval. No significant effects of any
of the sterols were noted on acid cholesteryl ester hydrolase or neutral cholesteryl ester hydrolase activity. The imbalance
between acyl CoA cholesterol acyl trans-ferase and hydrolase activities induced by 25-hydroxycholesterol could result in cholesteryl
ester accumulation by arterial smooth muscle cells, which may be associated with atherosclerosis. 相似文献
6.
Signaling by mTOR complex 1 (mTORC1) promotes anabolic cellular processes in response to growth factors, nutrients, and hormonal
cues. Numerous clinical trials employing the mTORC1 inhibitor rapamycin (aka sirolimus) to immuno-suppress patients following
organ transplantation have documented the development of hypertriglyceridemia and elevated serum free fatty acids (FFA). We
therefore investigated the cellular role of mTORC1 in control of triacylglycerol (TAG) metabolism using cultured murine 3T3-L1
adipocytes. We found that treatment of adipocytes with rapamycin reduced insulin-stimulated TAG storage ~50%. To determine
whether rapamycin reduces TAG storage by upregulating lipolytic rate, we treated adipocytes in the absence and presence of
rapamycin and isoproterenol, a β2-adrenergic agonist that activates the cAMP/protein kinase A (PKA) pathway to promote lipolysis.
We found that rapamycin augmented isoproterenol-induced lipolysis without altering cAMP levels. Rapamycin enhanced the isoproterenol-stimulated
phosphorylation of hormone sensitive lipase (HSL) on Ser-563 (a PKA site), but had no effect on the phosphorylation of HSL
S565 (an AMPK site). Additionally, rapamycin did not affect the isoproterenol-mediated phosphorylation of perilipin, a protein
that coats the lipid droplet to initiate lipolysis upon phosphorylation by PKA. These data demonstrate that inhibition of
mTORC1 signaling synergizes with the β-adrenergic-cAMP/PKA pathway to augment phosphorylation of HSL to promote hormone-induced
lipolysis. Moreover, they reveal a novel metabolic function for mTORC1; mTORC1 signaling suppresses lipolysis, thus augmenting
TAG storage. 相似文献
7.
Fresh fillets of Atlantic hake were stored at −18 °C for 120 days and changes in lipid composition and the formation of cholesterol
oxidation products (COP) during storage and subsequent grilling were evaluated. Fresh hake showed low COP levels (8.0 μg/g,
dry basis); however, a significant increase in COP (P < 0.02) and a concomitant decrease in the cholesterol and polyunsaturated fatty acids content during frozen storage and after
grilling were observed. The main cholesterol oxides present in the analyzed samples were: 19-Hydroxycholesterol, 24(S)-hydroxycholesterol, 22(S)-hydroxycholesterol, 25-hydroxycholesterol, 25(R)-hydroxycholesterol and 7-Ketocholesterol. The oxides which were more influenced by the thermal treatment were 24(S)-OH and 25(R)-OH; however, after 120 days of storage 7-ketocholesterol was the main product formed. Frozen storage and subsequent grilling
under domestic conditions are important factors in damage of cholesterol and unsaturated fatty acids levels, with consequent
production of cholesterol oxides, although the mechanism of the formation of these compounds by the different processes is
probably different.
An erratum to this article can be found at 相似文献
8.
Incubation of Caco-2 cells, a human intestinal cell line, with 25-hydroxycholesterol (25-HOC) markedly enhanced cellular cholesteryl
ester formation determined by incorporation of [14C]oleic acid into intracellular cholesteryl [14C]oleate. The stimulation by 25-HOC of cholesteryl ester formation was suppressed by staurosporine, a kinase inhibitor, but
not by cycloheximide or actinomycin D. The specific activity of microsomal acyl-coenzyme A:cholesterol acyltransferase (ACAT)
increased two-fold in cells treated with 10 μM 25-HOC for 5 h. ACAT activity decreased when microsomes were incubated without
sodium fluoride, a phosphatase inhibitor, but the decrease in ACAT activity in cells stimulated with 25-HOC was more pronounced.
The results suggest that protein phosphorylation may be involved in the stimulation of cholesteryl ester formation by 25-HOC
in Caco-2 cells. 相似文献
9.
Leyuan Xu Qianming Bai Daniel Rodriguez-Agudo Phillip B. Hylemon Douglas M. Heuman William M. Pandak Shunlin Ren 《Lipids》2010,45(9):821-832
Dysregulation of lipid metabolism is frequently associated with inflammatory conditions. The mechanism of this association
is still not clearly defined. Recently, we identified a nuclear oxysterol, 25-hydroxycholesterol-3-sulfate (25HC3S), as an
important regulatory molecule involved in lipid metabolism in hepatocytes. The present study shows that 25HC3S and its precursor,
25-hydroxycholesterol (25HC), diametrically regulate lipid metabolism and inflammatory response via LXR/SREBP-1 and IκBα/NFκB
signaling in hepatocytes. Addition of 25HC3S to primary rat hepatocytes decreased nuclear LXR and SREBP-1 protein levels,
down-regulated their target genes, acetyl CoA carboxylase 1 (ACC1), fatty acid synthase (FAS), and SREBP-2 target gene HMG
reductase, key enzymes involved in fatty acid and cholesterol biosynthesis. 25HC3S reduced TNFα-induced inflammatory response
by increasing cytoplasmic IκBα levels, decreasing NFκB nuclear translocation, and consequently repressing expression of NFκB-dependent
genes, IL-1β, TNFα, and TRAF1. NFκB-dependent promoter reporter gene assay showed that 25HC3S suppressed luciferase activity
in the hepatocytes. In contrast, 25HC elicited opposite effects by increasing nuclear LXR and SREBP-1 protein levels, and
by increasing ACC1 and FAS mRNA levels. 25HC also decreased cytoplasmic IκBα levels and further increased TNFα-induced NFκB
activation. The current findings suggest that 25HC and 25HC3S serve as potent regulators in cross-talk of lipid metabolism
and inflammatory response in the hepatocytes. 相似文献
10.
The absorption of cholesterol and of cholesterol oxidation products (oxidized cholesterols) was compared in lymph-cannulated
rats. We found that the lymphatic absorption of an intragastrically administered, emulsified lipid meal containing 25 mg of
cholesterol or 25 mg of oxidized cholesterols, within 24 h, was approximately 67 and 30%, respectively. The absorption rate
of individual oxidized cholesterols differed considerably and was approximately 30% for 7α-hydroxycholesterol, 42% for 7β-hydroxycholesterol,
32% for 5β-epoxycholesterol, 28% for 5α-epoxycholesterol, 15% for cholestanetriol and 12% for 7-ketocholesterol. Moreover,
cholesterol oxidation products delayed the absorption of oleic acid as triolein. Approximately 35 and 48% of cholesterol was
recovered in chylomicrons (CM) and very low density lipoprotein (VLDL), respectively. In contrast, 54 and 40% of the oxidized
cholesterols was recovered in CM and VLDL, respectively, although there was a significant difference in the distribution of
individual oxidized cholesterols. The results of the present study indicate that oxidized cholesterols are absorbed to a lesser
extent than is cholesterol, that they disturb fat absorption and that they distribute differently between lymphatic lipoproteins. 相似文献
11.
To address the role of cell membrane neutral sphingomyelinase (EC 3.1.4.12; SMase) in the regulation of cholesterol metabolism
in the liver parenchymal cell, we examined the effect of exogenous neutral SMase on the metabolism of cholesteryl esters and
the secretion of VLDL and biliary lipids in isolated rat hepatocytes. We show that treatment of hepatocytes with SMase (20
mU/mL) resulted in the intracellular buildup of cholesteryl esters, increased ACAT (EC 2.3.1.26) activity without affecting
the ACAT2 mRNA level, and increased cytosolic and microsomal cholesteryl ester hydrolase (EC 3.1.1.13) activity. This was
accompanied by increases in the secretion of biliary. bile acid, phospholipid, and cholesterol and in increased cholesterol
7α-hydroxylase (EC 1.14.13.17) activity and levels of mRNA, as well as decreased levels of apoB mRNA and a decreased secretion
of VLDL apoB (apoB-48, ∼45%; apoB-100, ∼32%) and lipids (∼55%). Moreover, the VLDL particles secreted had an abnormal size
and lipid composition; they were larger than controls, were relatively enriched in cholesteryl ester, and depleted in TG and
cholesterol. Cell-permeable ceramides did not replicate any of the reported effects. These findings demonstrate that the increased
cholesteryl ester turnover, oversecretion of biliary cholesterol and bile acids, and undersecretion of VLDL cholesterol and
particles are concerted responses of the primary hepatocytes to exogenous neutral SMase brought about by regulation at several
levels. We suggest that plasma membrane neutral SMase may have a specific, ceramide-independent effect in the regulation of
cholesterol out-put pathways in hepatocytes. 相似文献
12.
13.
Commercial cholesterol of bovine brain and spinal cord origin has been care-fully examined for its 24- and 26-hydroxycholesterol
content. By alternate adsorption chromatography and chromatography on Sephadex LH-20 26-hydroxycholesterol was isolated from
this course in 15 μg/g amounts, whereas 24-hydroxycholesterol was not observed.
Paper XI of this series: J.E. van Lier and L.L. Smith, Steroids 15:485–503 (1970). 相似文献
14.
目的研究阿昔莫司对巨噬细胞RAW264.7三磷酸腺苷结合盒转运子A1(ATP binding cassette transporterA1,ABCA1)及其上游调控因子肝脏X受体α(Liver X receptor,LXRα)的影响,探讨其促进胆固醇逆转运(Reversecholesterol transport,RCT)、抗动脉粥样硬化(Atherosclerosis,AS)的可能机制。方法体外培养RAW264.7细胞,将细胞分为空白对照组(不含阿昔莫司)和不同浓度的阿昔莫司干预组(分别含5、10、25μg/ml阿昔莫司),作用24 h后,采用RT-PCR法检测各组细胞中ABCA1和LXRα基因mRNA的转录水平;Western blot法检测各组细胞中ABCA1和LXRα蛋白的表达;闪烁计数法检测各组细胞内胆固醇的流出。结果阿昔莫司呈浓度依赖性地增加RAW264.7细胞中ABCA1和LXRα基因mRNA的转录水平和蛋白的表达水平(P<0.05或P<0.01)及细胞内胆固醇的流出率(P<0.01)。结论阿昔莫司可通过LXRα途径上调巨噬细胞ABCA1的表达,促使细胞内胆固醇流出,从而延缓AS的发生发展。 相似文献
15.
Ömer Küçük Jeanette Stoner-Picking Stanley Yachnin Leo I. Gordon R. Michael Williams Leonard J. Lis Maxwell P. Westerman 《Lipids》1994,29(9):657-660
The objective of this study was to investigate the effects of oxysterols (OS), namely 5α-hydroxy-6-ketocholestanol, 6-ketocholestanol
and 25-hydroxycholesterol, on specific cell-mediated cytotoxicity by C57BL/6 spleen cells against P815-X2 (a DBA/2 mastocytoma)
target cells. Cytolytic T lymphocytes (CTL) were generated by intraperitoneally injecting C57BL/6 mice with P815-X2 tumor
cells 10 d prior to the cytotoxicity experiments. Preincubation of CTL with 10−5 M 5α-hydroxy-6-ketocholestanol and 6-ketocholestanol for 45 min in lipoprotein-depleted medium resulted in an inhibition
of cytolytic activity (73 and 43%, respectively) as measured by 4-h51Cr release. At a concentration of 5×10−6 M, 5α-hydroxy-6-ketocholestanol inhibited CTL activity by 65%, whereas 6-ketocholestanol did not elicit any inhibition. By
contrast, 25-hydroxycholesterol did not inhibit CTL at either concentration, although it is known to be a potent inhibitor
of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, the rate-limiting enzyme in the cholesterol biosynthetic pathway. When
CTL were preincubated with OS in lipoprotein-replete medium, there was no inhibition of CTL activity at the respective concentrations.
The results suggest that the inhibition of CTL activity upon short-term incubation with OS is not due to the inhibition of
cholesterol synthesis, but may be due to the insertion of OS into the plasma membrane to replace cholesterol and alteration
of membrane physical properties. 相似文献
16.
目的探讨脂联素对巨噬细胞ATP结合盒转运子A1(ATP binding cassette transporter A1,ABCA1)及其上游调控因子肝脏X受体α(Liver X receptorα,LXRα)表达的影响及其在胆固醇逆转运(Reverse cholesterol transport,RCT)和抗动脉粥样硬化(Atherosclerosis,AS)中可能的作用机制。方法以不同浓度的脂联素(0、1、5、10μg/ml)体外培养巨噬细胞RAW264.7 24 h,RT-PCR法检测细胞中ABCA1和LXRα基因mRNA的转录水平,Western blot法检测细胞中ABCA1和LXRα蛋白的表达水平,闪烁计数法检测细胞内胆固醇的流出情况。结果脂联素能显著上调RAW264.7细胞中ABCA1和LXRα基因mRNA的转录水平及蛋白的表达水平(P<0.05),且呈浓度依赖性;脂联素能浓度依赖性地增加细胞内胆固醇的流出(P<0.05)。结论脂联素可通过LXRα途径上调巨噬细胞ABCA1基因的转录和翻译水平,促进胆固醇逆转运,延缓AS的发生、发展。 相似文献
17.
The beneficial roles of dietary fish oil in lowering serum TAG levels in animals and humans have been attributed in part to
the high content of two n−3 polyunsaturated very long-chain FA, EPA, and DHA. Recent studies show that EPA induces mitochondrial
β-oxidation in hepatocytes, which might contribute to the systemic lipid-lowering effect. Whether EPA affects FA storage or
oxidation in adipocytes is not clear. To investigate this possibility, 3T3-L1 adipocytes incubated with EPA (100 μM) for 24
h were assayed for β-oxidation, carnitine palmitoyl transferase 1 (CPT-1) activity, protein, and mRNA expression of CPT-1.
For comparison, cells treated with oleic acid, octanoic acid, and clofibrate, a synthetic ligand for peroxisome proliferator-activated
receptor α were also analyzed. Mitochondria were isolated by differential centrifugation, and the mitochondrial membrane acyl
chain composition was measured by GLC. EPA increased the oxidation of endogenous FA but did not inhibit lipogenesis. Oleic
acid and clofibrate did not affect FA oxidation or lipogenesis, whereas octanoic acid suppressed the oxidation of endogenous
FA and inhibited lipogenesis. Increased β-oxidation by EPA was associated with increased CPT-1 activity but without changes
in its mRNA and protein expression. EPA treatment increased the percentage of this FA in the mitochondrial membrane lipids.
We suggest that EPA increased the activity of CPT-1 and β-oxidation in adipocytes by altering the structure or dynamics of
the mitochondrial membranes. 相似文献
18.
Rocco DD Okuda LS Pinto RS Ferreira FD Kubo SK Nakandakare ER Quintão EC Catanozi S Passarelli M 《Lipids》2011,46(7):617-625
We analyzed the effect of a 6-week aerobic exercise training program on the in vivo macrophage reverse cholesterol transport
(RCT) in human cholesteryl ester transfer protein (CETP) transgenic (CETP-tg) mice. Male CETP-tg mice were randomly assigned
to a sedentary group or a carefully supervised exercise training group (treadmill 15 m/min, 30 min sessions, five sessions
per week). The levels of plasma lipids were determined by enzymatic methods, and the lipoprotein profile was determined by
fast protein liquid chromatography (FPLC). CETP activity was determined by measuring the transfer rate of 14C-cholesterol from HDL to apo-B containing lipoproteins, using plasma from CETP-tg mice as a source of CETP. The reverse cholesterol
transport was determined in vivo by measuring the [3H]-cholesterol recovery in plasma and feces (24 and 48 h) and in the liver (48 h) following a peritoneal injection of [3H]-cholesterol labeled J774-macrophages into both sedentary and exercise trained mice. The protein levels of liver receptors
were determined by immunoblot, and the mRNA levels for liver enzymes were measured using RT-PCR. Exercise training did not
significantly affect the levels of plasma lipids or CETP activity. The HDL fraction assessed by FPLC was higher in exercise-trained
compared to sedentary mice. In comparison to the sedentary group, a greater recovery of [3H]-cholesterol from the injected macrophages was found in the plasma, liver and feces of exercise-trained animals. The latter
occurred even with a reduction in the liver CYP7A1 mRNA level in exercised trained animals. Exercise training increased the
liver LDL receptor and ABCA-1 protein levels, although the SR-BI protein content was unchanged. The RCT benefit in CETP-tg
mice elicited by exercise training helps to elucidate the role of exercise in the prevention of atherosclerosis in humans. 相似文献
19.
20.
Sodium fusidate and its glycine conjugate, which have the same detergent properties as bile acids, significantly (p<0.05)
stimulate HMG-CoA reductase of cultured intestine below the critical micellar concentration (CMC) without affecting brush
border enzymes. Above CMC, both amphiphiles are cytotoxic. At concentrations between 1 and 5 mM, sodium fusidate decreased
cholesterol contents of cultured mucosa (p<0.05), the increase in synthesis only partially compensating for the sterol loss.
Oxygenated sterols, 7-keto- and 25-hydroxycholesterol, also depleted mucosal cholesterol at 0.5 mM, exerting their effect
differently by inhibiting HMG-CoA reductase (p<0.01). In contrast to their marked effect on total mucosal cholesterol contents,
brush border cholesterol was unaffected by both cholesterol and bile acid analogs. 相似文献