SCAP/SREBP2/LDLr通路在LPS诱导人血管平滑肌细胞泡沫化中的作用

目的：研究炎症介质——脂多糖（LPS）是否通过扰乱固醇调节元件结合蛋白裂解激活蛋白-固醇调节元件结合蛋白2（SCAP-SREBP2）复合物介导的低密度脂蛋白受体（LDLr）负反馈调控,增加人血管平滑肌细胞对天然低密度脂蛋白胆固醇（LDL）摄取,导致泡沫细胞形成。方法：人血管平滑肌细胞在无血清培养基中培养24 h后,分为对照组（继续无血清培养）;高脂组（加入LDL负荷,终浓度为25μg/ml）;高脂加LPS组（加入LDL负荷,终浓度为25μg/ml,同时加入LPS,终浓度400 ng/ml）;高脂加LPS加肝素组（加入LDL负荷,终浓度为25μg/ml,加入LPS,终浓度400 ng/ml,加入肝素,终浓度5 mg/ml）,以上各组细胞培养24 h后收获。酶化学法检测细胞内胆固醇浓度,油红O染色法检测细胞内脂质水平,Real time PCR法检测LDLr、SREBP2表达水平,细胞免疫化学法检测SCAP蛋白表达,激光共聚焦检测SCAP在内质网与高尔基体间的转位情况。结果：细胞内胆固醇测定及油红O染色发现,LPS通过增加人血管平滑肌细胞对非修饰LDL摄取,导致人血管平滑肌细胞转变为泡沫细胞。在LPS不存在时,25μg/ml LDL减少LDLr mRNA水平（P〈0.05）。然而,LPS增加LDLr mRNA水平,逆转25μg/ml LDL对LDLr的抑制效应,不恰当的增加了血管平滑肌细胞对LDL摄取（P〈0.05）,LPS刺激也导致了SCAP蛋白表达增加和SREBP2的mRNA水平升高（P〈0.05）,同时促进了SCAP从内质网转移到高尔基体。这些结果提示LPS通过增加SCAP/SREBP2复合物从内质网到高尔基体转位,干扰了胆固醇介导的LDLr负反馈调控,使非修饰LDL在血管平滑肌细胞内堆积,导致泡沫细胞形成。结论：本研究提示,在LPS刺激条件下,SCAP/SREBP2/LDLr通路可能是血管平滑肌细胞泡沫化的另一条通路。     

Influence of large molecular polymeric pigments isolated from fermented Zijuan tea on the activity of key enzymes involved in lipid metabolism in rat

Influence of large molecular polymeric pigments (LMPP) isolated from fermented Zijuan tea on the activity and mRNA expression of key enzymes involved in lipid metabolism in rat was explored. The results show that intragastric infusion of high-dose LMPP (1.215g/kg body weight) effectively suppressed the elevation in TC and LDL-C (p<0.05), and prevented the reduction in HDL-C (p<0.05), compared with the hyperlipidemia model group. LMPP significantly enhanced the activity of HL and HSL, and increased the HSL mRNA expression in the liver tissue and adipose tissue. High-LMPP treatment significantly reduced the HMG-CoA reductase expression by 56.5% in the liver compared with hyperlipidemia model group. In contrast, LDL-R expression was increased by 120% in the presence of high-LMPP treatment. These results suggest that LMPP have the hypolipidemic effect to some extent and significantly enhance HSL mRNA expression in the liver and adipose tissue, thereby increasing HSL activity in rat.     

Serial culture of murine primary airway epithelial cells and ex vivo replication of human rhinoviruses

Human rhinoviruses (HRV) are the primary etiological agents in cold infections, and represent a serious risk to individuals with chronic respiratory disease such as asthma. In order to develop treatment options for HRV infections, murine models are a crucial component in the study of infection mechanisms due to the wide array of reagents and techniques available to study murine immunology. We present here a cell culture system for studying isolated murine epithelial cell responses to HRV. Monolayers of primary mouse airway epithelial cells were maintained in a serial culture system, and the identity and purity of the cell population was confirmed via immunostaining (positive for cytokeratin, negative for vimentin). Infection of these cells with a minor group rhinovirus (HRV-1A) was evidenced by increases in viral RNA, de novo synthesis of viral proteins, and production of infectious virus. This model will be useful in experiments to define mechanisms of viral replication and host/virus interactions within airway epithelial cells.     

Deficiency in monocyte chemoattractant protein-1 modifies lipid and glucose metabolism

We describe the effect of MCP-1 deficiency in mice rendered hyperlipemic by the concomitant ablation of the LDL receptor. The MCP-1(-/-)LDLr(-/-) mice in comparison with LDLr(-/-) mice showed a decreased lipoprotein clearance, derangements in free fatty acids delivery and less glucose tolerance when fed a regular chow, and they showed a partial resistance to alterations in glucose and lipid metabolism induced by dietary fat and cholesterol. They also were less prone to the development of diet-induced obesity. Our results suggest that the role of MCP-1 in metabolism is relevant and that, although new hidden complexities are evident, the function of MCP-1/CCL2 extends far beyond the monocyte chemoattractant effect. Therefore, the regulatory mechanisms influenced by MCP-1 should be fully ascertained to understand the metabolic consequences of inflammation and before considering MCP-1 as a therapeutic target.     

脂多糖通过LDLr诱导巨噬细胞泡沫化:炎症应激下巨噬细胞泡沫化的另一条通路

目的研究炎症介质-脂多糖(LPS)诱导的炎症应激是否通过扰乱固醇调节元件结合蛋白裂解激活蛋白-固醇调节元件结合蛋白2(SCAP-SREBP2)复合物介导的低密度脂蛋白受体(LDLr)负反馈调控,增加THP-1巨噬细胞对非修饰低密度脂蛋白胆固醇(LDL)摄取,导致泡沫细胞形成。方法诱导分化成功的THP-1巨噬细胞在无血清培养基中培养4 h后,分为对照组(继续无血清培养),高脂组(加入LDL负荷,终浓度为25 mg·L-1),高脂加炎症刺激组(加入LDL负荷,终浓度为25 mg·L-1,同时加入炎症介质LPS,终浓度200μg·L-1),单纯炎症刺激组(加入炎症介质LPS,终浓度200μg·L-1),以上各组细胞培养24 h后收获。ELISA法检测细胞培养基中TNF-α浓度,酶化学法检测细胞内胆固醇浓度,琼脂糖电泳检测LDL氧化程度,Real time PCR法检测LDLr、SREBP2和SCAP mRNA表达水平,Western blot法检测LDLr、SREBP2和SCAP蛋白表达,激光共聚焦检测SCAP在内质网与高尔基体间的转位情况。结果细胞内胆固醇测定发现,炎症介质LPS通过增加THP-1巨噬细胞对非修饰LDL摄取,导致巨噬细胞转变为泡沫细胞。在无炎症介质LPS时,25 mg·L-1LDL减少LDLr mRNA和蛋白表达(P<0.05)。然而,LPS增加LDLr mRNA和蛋白表达,逆转25 mg·L-1LDL对LDLr的抑制效应,不恰当的增加了巨噬细胞对LDL摄取(P<0.05),LPS刺激也导致了SCAP和SREBP2的mRNA和蛋白过表达(P<0.05),同时促进了SCAP从内质网转移到高尔基体。这些结果提示LPS干扰了胆固醇介导的LDLr负反馈调控,使非修饰LDL在巨噬细胞内堆积,导致泡沫细胞形成。结论本研究提示,在LPS诱导的炎症应激状态条件下,天然LDL可以通过LDLr被巨噬细胞大量摄取入细胞内,导致泡沫细胞形成,这可能是巨噬细胞泡沫化的另一条通路。     

Gene delivery to brain cells with apoprotein E derived peptide conjugated to polylysine (apoEdp-PLL)

A promising strategy to carry genetic material to brain cells either in vitro or in vivo is using the LDL receptor (LDLr) on blood–brain barrier. LDLr naturally help to low density lipoproteins (LDL_S) transporting across the BBB by endocytosis. Here we present the idea of using the LDLr-mediated pathway for transporting genetic material to brain cells. A tandem dimer Sequence of apoprotein-E (apoE) (141–150) conjugated to polylysine sequence was used as a novel DNA Delivery vector for transfecting of brain cells either in vitro or in vivo.

DNA condensation occurs with this vector because electrostatic interaction between DNA and polylysine. The vector favors to protection of DNA from enzymatic degradation and also helps to DNA carrying in blood stream to reach BBB and transport it to brain cells and eventually help DNA expression in target cells.

These results suggest a novel gene delivery vector for gene therapy of brain disease.     

Molecular characterization of two novel cases of complete complement inhibitor Factor I deficiency

Factor I (FI) is the major complement inhibitor that degrades activated complement components C3b and C4b in the presence of specific cofactors. Complete FI deficiency results in secondary complement deficiency due to uncontrolled spontaneous alternative pathway activation. In this study we describe two unrelated patients with complete FI deficiency and undetectable alternative complement pathway activity. Both patients had experienced recurrent infections and arthralgia/arthritis. In one patient, analysis of genomic DNA revealed deletion of two adenine nucleotides in exon 2 of the CFI gene (c.133-134delAA), causing a frame shift and premature STOP codon/termination in the FIMAC (FI-membrane attack complex) domain (p.K45SfsX11). The other patient carried an A>T substitution in exon 6 (c.866A>T) encoding the LDLr2 (low density lipoprotein receptor) domain (p.D289V), resulting in an aspartic acid to valine change. Both patients were homozygous for the mutations while their healthy parents were heterozygous carriers. The mutations were introduced into recombinant FI, causing lack of FI expression and secretion upon transient transfection. Mutation p.K45SfsX11 theoretically allows expression of a 55 amino acid fragment of FI that lacks the serine protease domain, preventing proteolytic activity. In contrast, aspartic acid D289 is crucial for folding of FI. This report describes the molecular and functional consequences of two novel mutations of FI, providing a unique insight into the pathogenesis of complete FI deficiency in these patients.     

Molecular characterization of Complement Factor I deficiency in two Spanish families

Complement Factor I (CFI) is a regulator of the classical and alternative pathways. CFI has enzymatic activity and is able to cleave C3b and C4b. Homozygous Factor I deficiency is associated with infectious and/or autoimmune diseases.

Here we describe the biochemical and genetic characterization in two Spanish families with complete Factor I deficiency. In Family 1, the propositus suffered from several episodes of meningitis for more than a year. Biochemical complement studies showed undetectable Factor I levels in the propositus and in her sister, while their parents and a brother had partial Factor I deficiency and were healthy. In Family 2, three out of five children were homozygous for Factor I deficiency, two of whom suffered from meningitis and the third one from several infections. The parents and the other two siblings were healthy and heterozygous for Factor I deficiency.

Molecular studies showed that the two families had different mutations at exon 5 of the Factor I gene, which codifies for module LDLr1. One mutation corresponds to a 772G>A change at the donor splice site that was originally found in a family from Northern England. The second is a new missense mutation 739T>G, that generates a Cys to Gly change.     

Omega-3 as well as caloric restriction prevent the age-related modifications of cholesterol metabolism

Intracellular concentration of cholesterol is regulated by the balance between endogenous synthesis and exogenous uptake; endogenous synthesis is subject to feedback control of hepatic 3-hydroxy-3-methyl-glutaryl-CoA reductase activity, while the exogenous supply is mainly controlled by the modulation of the low-density lipoprotein receptor. During ageing, hepatic lipid modifications occur and caloric restriction are able to prevent these changes. So, the aim of this work was to evaluate the mechanisms underlying the effect exerted both by caloric restrictions and by a diet enriched with Omega-3 fatty acids, on the cholesterol plasma levels during ageing, by studying the regulation of the protein involved in cholesterol homeostasis maintenance.Livers from diet restricted and Omega-3 supplemented diet fed 24-month-old rat were used to analyze, the protein complex of cholesterol homeostasis maintenance and those ones that are able to modulate 3-hydroxy-3-methyl-glutaryl-CoA reductase.The data obtained demonstrate that both caloric restriction and Omega-3 supplemented diets are able to prevent hypercholesterolemia, by regulating HMG-CoAR activation state by controlling ROS production and p38 phosphorylation. Moreover also the age-dependent loss of LDLr membrane exposition is prevented.