α4β7研究进展

α４β７是一种整合素分子，主要介导淋巴细胞向粘膜部位的迁移和归巢，同时参与一些炎症反应，并对肠相关淋巴组织（ＧＡＬＴ）的发育，粘膜部位的免疫应答等有重要作用。     

Metabolism of 3α, 7α-dihydrexy-7β-methyl-5β-cholanoic acid and 3α,7β-dihydroxy-7α-methyi-5β-cholanoic acid in hamsters

The metabolic fate of the bile add analogs, 3α,7α-dihydroxy-7β-methyl-5β-cholanoic acid and 3α,7β-dihydroxy-7α-methyl-5β-cholanoic acid, was investigated and compared with that of chenodeoxycholic acid in hamsters. Both bile acid analogs were absorbed rapidly from the intestine and excreted into bile at similar to that of chenodeoxycholic acid. In the strain of hamster studied, the biliary bile were conjugated with both glycine and taurine. After continuous intravenous infusion, chenodeoxycholic acid the analogs became the major bile acid constituents in bile. After oral administration of a single dose of these compounds, fecal analysis revealed the existence of unchanged material (25–35%) as well as considerable amounts of metabolites (65–75%). The major metabolites excreted into feces were more polar than the starting material and were tentatively identified as trifaydroxy-7-methyl compounds by radioactive thin-layer chromatography. However, monohydroxy compounds were also found in the fecal extracts. These results show that chenodeoxycholic acid and ursodeoxycholic acid with a methyl group at the 7-position are resistant to bacterial 7-dehydroxylation than the normally occurring bile acids and that a certain proportion of these analogs is hydroxylated to give the corespondiag trihydroxy compound(s), In a control experiment, about 5% of administered chenodeoxychoulic acid was metabolized to a trihydroxy feile acid, but most of the compound (95%) was transformed into lithocholic acid.     

整合素α4β7研究进展

α4β7是一种整合素分子 ,主要介导淋巴细胞向粘膜部位的迁移和归巢 ,同时参与一些炎症反应 ,并对肠相关淋巴组织 (GAL T)的发育、粘膜部位的免疫应答等有重要作用     

7α-Hydroxy-sesquiterpene lactones from Decachaeta ovatifolia

In addition to the known sesquiterpene lactone pinnatifidin, and the flavones 6-methoxyacacetin and 6-methoxyapigenin, the dichloromethane extract of the aerial parts of Decachaeta ovatifolia afforded four new sesquiterpene lactones: a germacranolide 7α-hydroxycostunolide, a guaianolide 4α,15-dihydro-7α-hydroxy-3-desoxyzaluzanin C and two eudesmanolides, 7α-hydroxysantamarine and 7α-hydroxyreynosin. The structure of 7α-hydroxycostunolide was confirmed by X-ray analysis.     

7-Oxo-, 7α-hydroxy- and 7β-hydroxysterols from Euphorbia fischeriana

7-Oxo, 7α-hydroxy- and 7β-hydroxysterols (campesterol, stigmasterol and sitosterol derivatives) were isolated from the roots of Euphorbia fischeriana, a drug used for its antitumour properties in traditional Chinese medicine. Some of these steroids show antitumour activity and might be related to the presumed activity of the drug.     

Structural characterization of human cholesterol 7α-hydroxylase

Hepatic conversion to bile acids is a major elimination route for cholesterol in mammals. CYP7A1 catalyzes the first and rate-limiting step in classic bile acid biosynthesis, converting cholesterol to 7α-hydroxycholesterol. To identify the structural determinants that govern the stereospecific hydroxylation of cholesterol, we solved the crystal structure of CYP7A1 in the ligand-free state. The structure-based mutation T104L in the B′ helix, corresponding to the nonpolar residue of CYP7B1, was used to obtain crystals of complexes with cholest-4-en-3-one and with cholesterol oxidation product 7-ketocholesterol (7KCh). The structures reveal a motif of residues that promote cholest-4-en-3-one binding parallel to the heme, thus positioning the C7 atom for hydroxylation. Additional regions of the binding cavity (most distant from the access channel) are involved to accommodate the elongated conformation of the aliphatic side chain. Structural complex with 7KCh shows an active site rigidity and provides an explanation for its inhibitory effect. Based on our previously published data, we proposed a model of cholesterol abstraction from the membrane by CYP7A1 for metabolism. CYP7A1 structural data provide a molecular basis for understanding of the diversity of 7α-hydroxylases, on the one hand, and cholesterol-metabolizing enzymes adapted for their specific activity, on the other hand.     

Synthesis of 3α,7α-dihydroxy-5β-androstan-17-one

A short and efficient method for the stereospecific synthesis of 3α,7α-dihydroxy-5β-androstan-17-one was accomplished from the readily available 4-androstene-3,17-dione. Key steps are the stereospecific and selective epoxidation of 4,6-androstadiene-3,17-dione, followed by hydrogenations with carefully selected reagents, solvents and reaction conditions.     

人KAT7基因促进雌激素受体α表达

目的:构建带有Myc标签的赖氨酸乙酰基转移酶(KAT7)的真核表达载体,获得Myc-KAT7融合蛋白,并检测其对雌激素受体α(ERα)表达的影响。方法:以本实验室保存的乳腺文库为模板,采用PCR技术从中扩增出人KAT7基因的编码序列,插入p XJ-40-Myc载体;将重组质粒与空载体分别转染人胚肾293T细胞,通过Western印迹检测转染细胞的表达情况,并提取总RNA采用q RT-PCR检测ERα的表达。结果:双酶切和测序结果表明Myc-KAT7真核表达质粒构建成功,转染293T细胞后Western印迹鉴定表明融合蛋白得到表达,q RT-PCR表明KAT7在转录水平能够促进ERα表达。结论:构建了带Myc标签的人KAT7真核表达载体,并发现KAT7对ERα的表达具有促进作用。     

Cholesterol 7α-hydroxylase in rat liver microsomal preparations

Subcellular fractions containing microsomes prepared from rat livers homogenized in the absence of EDTA catalysed the oxidation of cholesterol to 7alpha-hydroxycholesterol, 7-oxocholesterol, 7beta-hydroxycholesterol and 5alpha-cholestane-3beta,5,6beta-triol. These reactions required native protein, molecular oxygen and NADPH. It is suggested that these compounds are formed by a peroxidation analogous to the peroxidation of fatty acids catalysed by liver microsomal preparations. Incubations of [4-(14)C]cholesterol with microsomal preparations from rat liver homogenized in the presence of EDTA gave 7alpha-hydroxy[(14)C]cholesterol as the main product. This reaction required molecular oxygen and NADPH, and was inhibited by CO. The mass of 7alpha-hydroxycholesterol formed during the incubation was measured by a double-isotope-derivative dilution procedure. This procedure was used to assay the activity of cholesterol 7alpha-hydroxylase and to measure low concentrations of endogenous 7alpha-hydroxycholesterol in liver.     

Screening of mycelial fungi for 7α- and 7β-hydroxylase activity towards dehydroepiandrosterone

In total, 481 fungal strains were screened for the ability to carry out 7(α/β)-hydroxylation of dehydroepiandrosterone (DHEA, 3β-hydroxy-5-androsten-17-one). Representatives of 31 genera of 15 families and nine orders of ascomycetes, 17 genera of nine families and two orders of zygomycetes, two genera of two families and two orders of basidiomycetes, and 14 genera of mitosporic fungi expressed 7(α/β)-hydroxylase activity. The majority of strains were able to introduce a hydroxyl group to position 7α. Active strains selectively producing 3β,7α-dihydroxy-5-androsten-17-one were found among Actinomucor, Backusella, Benjaminiella, Epicoccum, Fusarium, Phycomyces and Trichothecium, with the highest yield of 1.25 and 1.9 g L^?1 from 2 and 5 g L^?1 DHEA, respectively, reached with F. oxysporum. Representatives of Acremonium, Bipolaris, Conidiobolus and Curvularia formed 3β,7β-dihydroxy-5-androsten-17-one as a major product from DHEA. The structures of the major steroid products were confirmed by TLC, gas chromatography (GC), mass spectra (MS), and ¹H-NMR analyses.     

The involvement of cytochrome b5 in 5β-cholestane-3α,7α,12α-triol 25-hydroxylation and taurodeoxycholate 7α-hydroxylation of rat liver

Role of cytochrome b₅ in NADPH-supported 5β-cholestane-3α,7α,12α-triol 25-hydroxylation and taurodeoxycholate 7α-hydroxylation of rat liver microsomes was investigated using highly purified antibodies against cytochrome b₅. Anti-b₅ antibody strongly inhibited both hydroxylation reactions indicating that cytochrome b₅ is a functional component in these steroid hydroxylation systems. It was shown that the involvement of cytochrome b₅ in these systems could be altered by the conditions of the reaction systems.     

α7烟碱型乙酰胆碱受体与炎症调节

由促炎因子介导的炎症反应是机体对感染和损伤的一种防御机制。适量的促炎因子有利于激活免疫系统清除病原体,并可促进组织修复;而过量产生的促炎因子则可造成组织损伤,因此维持炎症反应的平衡十分重要。以往认为体液机制是炎症反应的唯一调节因素,新近发现的胆碱能神经抗炎通路对炎症反应的调节越来越受到人们的重视,而α7烟碱型乙酰胆碱受体（α7nAChR）是介导神经抗炎通路的关键分子。本文主要介绍α7nAChR的结构、分布及其介导的抗炎作用机制,并对α7nAChR激动剂及其临床应用研究和尚待解决的问题予以综述。     

α7-cholinergic receptor mediates vagal induction of splenic norepinephrine

Classically, sympathetic and parasympathetic systems act in opposition to maintain the physiological homeostasis. In this article, we report that both systems work together to restrain systemic inflammation in life-threatening conditions such as sepsis. This study indicates that vagus nerve and cholinergic agonists activate the sympathetic noradrenergic splenic nerve to control systemic inflammation. Unlike adrenalectomy, splenectomy and splenic neurectomy prevent the anti-inflammatory potential of both the vagus nerve and cholinergic agonists, and abrogate their potential to induce splenic and plasma norepinephrine. Splenic nerve stimulation mimics vagal and cholinergic induction of norepinephrine and re-establishes neuromodulation in α7 nicotinic acetylcholine receptor (α7nAChR)-deficient animals. Thus, vagus nerve and cholinergic agonists inhibit systemic inflammation by activating the noradrenergic splenic nerve via the α7nAChR nicotinic receptors. α7nAChR represents a unique molecular link between the parasympathetic and sympathetic system to control inflammation.     

Biotransformation of 7α-hydroxy- and 7-oxo-ent-atis-16-ene derivatives by the fungus Gibberella fujikuroi

The microbiological transformation of 7α,19-dihydroxy-ent-atis-16-ene by the fungus Gibberella fujikuroi gave 19-hydroxy-7-oxo-ent-atis-16-ene, 13(R),19-dihydroxy-7-oxo-ent-atis-16-ene, 7α,11β,19-trihydroxy-ent-atis-16-ene and 7α,16β,19-trihydroxy-ent-atis-16-ene, while the incubation of 19-hydroxy-7-oxo-ent-atis-16-ene afforded 13(R),19-dihydroxy-7-oxo-ent-atis-16-ene and 16β,17-dihydroxy-7-oxo-ent-atisan-19-al. The biotransformation of 7-oxo-ent-atis-16-en-19-oic acid gave 6β-hydroxy-7-oxo-ent-atis-16-en-19-oic acid, 6β,16β,17-trihydroxy-7-oxo-19-nor-ent-atis-4(18)-ene and 3β,7α-dihydroxy-6-oxo-ent-atis-16-en-19-oic acid.     

Improved synthesis of 3α,7α,12α,24ξ -tetrahydroxy-5 β -cholestan-26-oic acid

This paper describes three simple and short methods for the conversion of cholic acid into cholylaldehyde with protected hydroxyl groups. The first method involves lithium aluminum hydride reduction of the tetrahydropyranyl ether of methyl cholate and oxidation of the resulting primary alcohol with pyridinium chlorochromate. The second method employs diborane for the reduction of the -COOH group to the -CH₂OH group, while the third method involves the reduction of 3α, 7α, 12α -triformyloxy-5β -cholan-24-oic acid (as the acid chloride) directly into 3α, 7α, 12α -triformyloxy-5β -cholan-24-al with TMA-ferride (tetramethylammonium hydridoirontetracarbonyl). The aldehyde obtained by any of the above methods underwent smooth Reformatsky reaction with ethyl α -bromopropionate to yield 3α, 7α, 12α, 24ξ -tetrahydroxy-5β -cholestan-26-oic acid.     

Photochemical action spectrum of the co-inhibited 5β-cholestane-3α, 7α, 12α-triol 26-hydroxylase system

The inhibition of the mitochondrial hydroxylation of 5β-cholestane-3α, 7α, 12α-triol at the 26 position by a CO:O₂ gas mixture was maximally reversed by monochromatic light at the wavelength of 450 nm. This establishes the involvement of a cytochrome P450 dependent monooxygenase in the 26-hydroxylation of 5β-cholestane-3α, 7α, 12α-triol in rat liver mitochondria.     

ELIC-α7 Nicotinic Acetylcholine Receptor (α7nAChR) Chimeras Reveal a Prominent Role of the Extracellular-Transmembrane Domain Interface in Allosteric Modulation

The native α7 nicotinic acetylcholine receptor (α7nAChR) is a homopentameric ligand-gated ion channel mediating fast synaptic transmission and is of pharmaceutical interest for treatment of numerous disorders. The transmembrane domain (TMD) of α7nAChR has been identified as a target for positive allosteric modulators (PAMs), but it is unclear whether modulation occurs through changes entirely within the TMD or changes involving both the TMD and the extracellular domain (ECD)-TMD interface. In this study, we constructed multiple chimeras using the TMD of human α7nAChR and the ECD of a prokaryotic homolog, ELIC, which is not sensitive to these modulators, and for which a high resolution structure has been solved. Functional ELIC-α7nAChR (EA) chimeras were obtained when their ECD-TMD interfaces were modified to resemble either the ELIC interface (EA_ELIC) or α7nAChR interface (EA_α7). Both EA_α7 and EA_ELIC show similar activation response and desensitization characteristics, but only EA_α7 retained the unique pharmacology of α7nAChR evoked by PAMs, including potentiation by ivermectin, PNU-120596, and TQS, as well as activation by 4BP-TQS. This study suggests that PAM modulation through the TMD has a more stringent requirement at the ECD-TMD interface than agonist activation.     

Bile acids. LXIV. Synthesis of 5α-cholestane-3α,7α,25-triol and esters of new 5α-bile acids

Interest in the structural requirements of a sterol or bile acid for maximal activity by an hepatic microsomal steroid 12α-hydroxylase prompted the preparation of 5α-cholestane-3α, 7α, 25-triol and 5α-analogs of 3α, 7α-dihydroxy-5β-cholane-24-carboxylic acid. Methyl 3α, 7α-dihydroxy-5β-cholane-24-carboxylate derived from methyl chenodeoxycholate via the Arndt-Eistert reaction was allomerized with Raney nickel in boiling p-cymene to provide a number of products of which methyl 3,7-dioxo-5β- and 5α-cholane-24-carboxylates, methyl 3-oxo-7α-hydroxy-5β-and 5α-cholane-24-carboxylates, were identified. Reduction with K-Selectride of methyl 3-oxo-7α-hydroxy-5β-cholane-24-carboxylate, provided a high yield of methyl 3α, 7α-dihydroxy-5α-cholane-24-carboxylate. Treatment of this ester with an excess of methyl magnesium iodide afforded 5α-cholestane-3α, 7α, 25-triol. The products were characterized by thin-layer and gas liquid chromatography, proton resonance, infrared and mass spectrometry.     

α7 nAChR在上皮组织的表达及其功能的研究进展

α7 nAChR是配体门控离子通道蛋白超家族的典型代表,烟碱型乙酰胆碱受体的一个重要亚型,是复杂的五聚体跨膜蛋白,介导Na+、Ca2+流入,K+流出,尤以对Ca2+通透性高。α7 nAChR分布广泛且功能多样,不仅分布于中枢和外周神经系统,介导神经元的快速突触传递,其在许多非神经元细胞和组织中亦有表达,包括内皮细胞,支气管上皮细胞,皮肤角蛋白细胞,膀胱上皮细胞,血管平滑肌等,并参与其功能调节及功能障碍相关疾病的病理生理过程,如可调节细胞质运动和细胞间黏附,细胞增殖,血管生成以及肿瘤的侵袭和迁移。本文主要介绍烟碱型乙酰胆碱受体α7亚型在不同胚层来源的上皮组织细胞中的表达及其功能特征,以期通过激活或抑制α7 nAChR的表达来降低与其密切相关疾病的发生率。     

α7nAChR在上皮组织的表达及其功能的研究进展

α7 nAChR是配体门控离子通道蛋白超家族的典型代表,烟碱型乙酰胆碱受体的一个重要亚型,是复杂的五聚体跨膜蛋白,介导Na^＋、Ca^2＋流入,K^＋流出,尤以对Ca^2＋通透性高。α7 nAChR分布广泛且功能多样,不仅分布于中枢和外周神经系统,介导神经元的快速突触传递,其在许多非神经元细胞和组织中亦有表达,包括内皮细胞,支气管上皮细胞,皮肤角蛋白细胞,膀胱上皮细胞,血管平滑肌等,并参与其功能调节及功能障碍相关疾病的病理生理过程,如可调节细胞质运动和细胞间黏附,细胞增殖,血管生成以及肿瘤的侵袭和迁移。本文主要介绍烟碱型乙酰胆碱受体α7 亚型在不同胚层来源的上皮组织细胞中的表达及其功能特征,以期通过激活或抑制α7 nAChR的表达来降低与其密切相关疾病的发生率。