ω-3多不饱和脂肪酸抗肿瘤新途径——抑制具核梭杆菌黏附宿主细胞

【背景】大量文献报道ω-3多不饱和脂肪酸尤其是二十二碳六烯酸(Docosahexaenoic Acid,DHA)与二十碳五烯酸(Eicosapentaenoic Acid,EPA)具有抗肿瘤作用,但是其抗肿瘤机制还不够完善。【目的】探究ω-3多不饱和脂肪酸、具核梭杆菌以及结直肠癌三者之间的关联。【方法】在检测二十二碳六烯酸、二十碳五烯酸、α-亚麻酸(α-Linolenic Acid,ALA)等ω-3多不饱和脂肪酸对人结直肠腺癌细胞Caco-2、正常结肠上皮细胞NCM460生长影响的基础上,检测DHA等3种多不饱和脂肪酸对具核梭杆菌黏附人体细胞以及Fap2、FadA、RadD等具核梭杆菌毒力关键基因表达的影响。【结果】30μg/mL的DHA、EPA、ALA对Caco-2生长抑制分别为9.09%、4.95%、7.52%,而对NCM460生长抑制达31.15%、25.48%、29.11%,而且相关抑制作用仅具有浓度依赖性而无时间依赖性。经30μg/mL的DHA、EPA、ALA预处理的具核梭杆菌黏附Caco-2细胞的能力分别下降81.04%(P=0)、93.63%(P=0)和68.63%(P=0);而共培养时加入DHA、EPA、ALA对具核梭杆菌黏附Caco-2细胞的能力没有显著影响。同时,30μg/mLDHA处理导致F.nucleatum的Fap2基因显著下降10.22%(P=0.027);30μg/mL EPA处理导致FadA、Fap2基因分别显著下降23.49%(P=0)、15.09%(P=0.003);30μg/mL ALA处理导致FadA基因显著下降26.75%(P=0.012)。【结论】综合上述实验结果以及DHA、EPA、ALA仅能短时间抑制具核梭杆菌生长等文献报道,我们认为,DHA、EPA等ω-3多不饱和脂肪酸并非简单地直接杀伤或抑制肿瘤细胞和F.nucleatum;抑制FadA、Fap2等黏附相关基因表达,降低F.nucleatum黏附宿主细胞能力是其抗肿瘤作用的关键组成部分。ω-3多不饱和脂肪酸等活性物质对F.nucleatum等在结直肠肿瘤发生、发展中发挥重要作用的肠道细菌的影响与机制应深入开展研究。     

“自我剪切”2A肽介导的Δ-12和ω-3脂肪酸脱氢酶以及过氧化氢酶在转基因小鼠肌肉表达研究

哺乳动物因为缺乏Δ-12和ω-3脂肪酸脱氢酶,不能自身合成必需的多不饱和脂肪酸．目前,通过转基因技术在哺乳动物体内表达ω-3脂肪酸脱氢酶,能将长链的n-6多不饱和脂肪酸转化成n-3多不饱和脂肪酸,造成体内长链的n-6多不饱和脂肪酸含量显著减低．本研究通过自我剪切2A肽介导Δ-12和ω-3脂肪酸脱氢酶(FAT-2和FAT-1)以及人过氧化氢酶(human catalase,hCAT)在小鼠的肌肉同时表达．结果表明,转基因小鼠肌肉中长链n-3多不饱和脂肪酸含量提高2.6倍,长链n-6多不饱和脂肪酸含量没有显著变化,而n-6/n-3比例显著降低(P < 0.01)．同时蛋白质印迹检测到人过氧化氢酶hCAT在小鼠的肌肉组织中表达,且过氧化氢酶活性比野生型小鼠显著提高(P < 0.01)．     

Quantitative Structure-Activity Relationship Study on Some 5-Lipoxygenase Inhibitors

Abstract

A quantitative structure-activity relationship (QSAR) study has been made on some lipoxygenase inhibitors belonging to the series of ω-phenylalkyl hydroxamic acids, ω-naphthylalkyl hydroxamic acids, eicosatetraenoic acids, and 1H.benzimidazole-4-ols. It was found that the hydrophobic character of the molecules and the size of their substituents selectively govern their lipoxygenase inhibitory activity. The enzyme active site possesses a non-heme ferric ion, a hydrophobic domain, and a carboxylic acid binding site. It was found that while the functional group of inhibitors must interact with the ferric ion, the substituent on one side of it would be involved in hydrophobic interaction and that on the other side in van der Waals interaction with the enzyme so leading to an enhancement in the inhibitory activity of the inhibitors.     

Computational Selection,Identification and Structural Analysis of ω-Aminotransferases with Various Substrate Specificities from the Genome Sequence of Mesorhizobium loti MAFF303099

ω-Aminotransferase (ω-AT) is an important class of enzymes for the synthesis of chiral amines or β-amino acids. Family profile analysis was applied to screen putative ω-ATs from Mesorhizobium loti MAFF303099, a nitrogen fixation bacterium that has a larger number of ATs than other microorganisms. By family profile analysis, we selected 10 putative ω-ATs according to E-value. The functions of the putative ω-ATs were investigated by examining activities towards amines and/or β-amino acids. 10 putative proteins were found to have ω-AT activity with narrow or broad substrate specificity. Structure analysis using crystal structure of mll7127 and homology models of mll1632 and mll3663 indicated that the structures of active sites of the enzymes were very similar and highly conserved, but their substrate specificities appreared to be determined by residues positioned at the entrance region of the active site binding pockets.     

ω-Hydroxyundec-9-enoic acid induces apoptosis through ROS-mediated endoplasmic reticulum stress in non-small cell lung cancer cells

ω-Hydroxyundec-9-enoic acid (ω-HUA), a hydroxyl unsaturated fatty acid derivative, is involved in the antifungal activity of wild rice (Oryza officinalis). Here, we investigated the anti-cancer activity of ω-HUA on a non-small cell lung cancer (NSCLC) cell line. ω-HUA increased apoptosis and induced cleavages of caspase-6, caspase-9, and poly (ADP-ribose) polymerase (PARP). ω-HUA treatment significantly induced endoplasmic reticulum (ER) stress response. Suppression of CHOP expression and inhibiting ER stress by 4-phenylbutyrate (4-PBA) significantly attenuated the ω-HUA treatment-induced activation of caspase-6, caspase-9, and PARP, and subsequent apoptotic cell death, indicating a role for ER stress in ω-HUA-induced apoptosis. In addition, cells subjected to ω-HUA exhibited significantly increased quantity of reactive oxygen species (ROS), and the ROS scavenger N-acetyl-l-cysteine (NAC) inhibited ω-HUA-induced apoptotic cell death and ER stress signals, indicating a role for ROS in ER stress-mediated apoptosis in ω-HUA-treated cells. Taken together, these results suggest that sequential ROS generation and ER stress activation are critical in ω-HUA treatment-induced apoptosis and that ω-HUA represents a promising candidate for NSCLC treatment.     

Structure, evolution and action of vitamin B6-dependent enzymes

The number of known three-dimensional structures of vitamin B₆-dependent enzymes has doubled in the past two years. A fourth type of fold for B₆-dependent enzymes, involving a TIM-barrel domain, has been discovered. Alanine racemase is the first known representative of this new fold. Significant progress has been made in understanding the allosteric effects in the tryptophan synthase reaction.     

Liposomal membranes XI. A suggestion to structural characteristics of acido-thermophilic bacterial membranes

To understand the role of ω-cyclohexyl fatty acid residue of lipids in acido-thermophilic bacterial membranes, three unusual phosphatidylcholines, 1,2-di-11-cyclohexylundecanoyl-l-α-phosphatidylcholine (11_CYPC), 1,2-di-13-cyclohexyltridecanoyl-l-α-phosphatidylcholine (13_CYPC), and 1–13-cyclohexyltridecanoyl-2–11-cyclohexylundecanoyl-l-α-phosphatidylcholine (1–13_CY-2–11_CYPC) were prepared and the steady-state fluorescence anisotropy of 1,6-diphenylhexatriene (DPH) in the hydrophobic domain of these liposomal bilayers was determined. Compared with the case of dipalmitoyl (DPPC) or dimyristoyl phosphatidylcholine (DMPC), introducing the ω-cyclohexyl moiety onto lecithins makes the bilayers fluid below the phase transition temperature, while immobilizes them above the phase transition temperatures. The properties of the unusual phosphatidylcholine liposomes suggested by the steady-state fluorescence anisotropy investigation were in good agreement with those obtained from the thermotropic and permeability investigations. Results obtained are discussed from the view point of the role and function of lipid membranes of acido-thermophilic bacteria which contain unusual fatty acids.     

Tetronic acid and diarylpropanes from Iryanthera elliptica

The trunk wood of Iryanthera elliptica Ducke (Myristicaceae) contains, besides 2-(ω-piperonyltridecyl) -4-methylidenetetronic acid (iryelliptin), three biogenetically related compounds: (±)-7,4′-dihydroxy-3′-methoxyflavan, 1-(4′-hydroxy-2′-methoxyphenyl)- 3-(4″-hydroxy-3″-methoxyphenyl)-propane and spiro-[3-methoxy-2,5-cyclohexadien-1.1′-6′,7′- dihydroxy-5′-methoxy-1′,2′,3′,4′-tetrahydronaphthalen]-4-one-(spiroelliptin). Spiroelliptin rearranges upon methylation to 2,2′-trimethylene-3,4,5,4′,5′-penta-methoxybiphenyl.     

Specificity effects in the biosynthesis of fatty acids in Bacillus acidocaldarius

Addition to Bacillus acidocaldarius of acids which can act as primers for fatty acid synthesis promote the synthesis of corresponding fatty acids competitively. The effective acids are n?C₅ to -?₇ (not C₄ or C₈), iso- and anteiso-C, and ?C, (not C4), and a range of cyclic acids from cyclobutylacetic and cyclopentanecarboxylic to cycloheptylacetic. New non-natural ω-cyclobutyl-, ω-cyclopentyl-, and ω-cycloheptyl-fatty acids are obtainable. The range of acceptable primers and the range of fatty acids produced therefrom indicate, respectively, the substrate specificities of the transacylase which introduces acyl species into fatty acids synthesis and the one which removes them. The specificity of the primer transacylase may be similar to that in some rumen anaerobes.     

The contributions of aspirin and microbial oxygenase to the biosynthesis of anti-inflammatory resolvins: novel oxygenase products from omega-3 polyunsaturated fatty acids

Resolvins (Rvs) are oxygenated products derived from omega-3 polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid that carry potent protective bioactions present in resolving inflammatory exudates. Resolvin E1 (RvE1) is biosynthesized in vivo from EPA via transcellular biosynthetic routes during cell-cell interactions, and thus RvE1 is formed in vivo during multicellular responses such as inflammation and microbial infections. RvE1 protects tissues from leukocyte-mediated injury and counterregulates proinflammatory gene expression. These newly identified Rvs may underlie the beneficial actions of omega-3 PUFAs especially in chronic disorders where unresolved inflammation is a key mechanism of pathogenesis. Here, we present an overview of the biosynthesis of RvE1, with a focus on the aspirin-triggered and microbial P450-initiated pathways. The generation of RvE1 and its actions appear to dampen acute leukocyte responses and facilitate the resolution of inflammation.