大鼠处理普奈洛尔后改变α_1受体亚型介导的心功能(英文)

目的:研究普奈洛尔(Pro)作用后,大鼠心肌α_(1A)和α_(1B)受体亚型介导正性肌力和正性频率变化.方法:测定Pro大鼠和正常鼠左心室乳头状肌和右心房收缩力和心率.结果:给予Pro后,苯肾上腺素(Phe)使乳头状肌收缩力由53±17 mg增加到90±18 mg(P<0.05).Pro和对照组收缩力分别增加20±12和5±5 mg(P<0.05).氯乙基可乐定使两组收缩力变化无区别.5-甲基乌拉地尔存在时Phe使Pro组收缩力增加13±5mg,对照组无变化.正常和心率抑制时,Phe使两组动物α_(1B)介导心率增加无差别.结论:β受体阻断,α_1介导正性肌力增加主要由α_(1B)作用增强引起.     

老年大鼠心脏肾上腺素受体亚型的改变(英文)

目的:研究老年心脏肾上腺素受体亚型的改变.方法:制备3月龄与25月龄Wistar大鼠心脏膜标本,分别采用~(125)I-BE2254与~(125)I-Pindold作放射配基结合分析,测定α_1与β-肾上腺素受体.结果:老年大鼠心脏的α_1与β-肾上腺受体密度分别由年轻大鼠的119±4与45.9±1.9pmol/g下降至70±6与36.4±1.6 pmol/g(P<0.01),α_1-AR降低的幅度大于β-AR.此外α_(1A)与α_(1B)亚型之比由年轻大鼠的39:61下降至26:74(P<0.05).结论:老年大鼠心脏肾上腺素受体减少,且不同亚型减少的程度不同.     

α_(1A)-和α_(1B)-肾上腺素受体介导HEK293细胞增殖和Ca~(2 )-钙调蛋白依赖性蛋白激酶激活(英文)

目的:研究α_1-AR三种亚型对细胞增殖和Ca~(2 )-钙调蛋白依赖性蛋白激酶(CCDPK)的作用。方法:采用磷酸钙沉淀法进行转染,用放射配基结合实验测定α_1-AR表达量。用[~3H]胸腺嘧啶参入量测定细胞增殖,用免疫沉淀和髓鞘蛋白底物法测定CCDPK的活性。结果:三株表达α_(1A)-,α_(1B)-和α_(1D)-AR的细胞株表达受体密度约为0.6 nmol·g~(-1)。在普萘洛尔存在下,去甲肾上腺素(NE)作用24 h可浓度依赖地刺激HEK293/α_(1A)-AR和HEK293/α_(1B)-AR细胞DNA合成。NE 10 μmol·L~(-1)可促进HEK293/α_(1A)-AR和HEK293/α_(1B)-AR细胞DNA合成增加,刺激CCDPK活性的升高。NE不引起HEK293/α_(1D)-AR细胞DNA合成和CCDPK活性的显著改变。结论:在转染α_1-AR亚型的HEK293细胞中激动α_(1A)-或α_(1B)-AR可引起细胞增殖,激动α_(1D)-AR则无显著改变。     

α_1-肾上腺素受体三种亚型介导的HEK293细胞中环腺苷一磷酸蓄积的特点(英文)

目的:研究α_1-肾上腺素受体各亚型介导的HEK293细胞中环腺苷一磷酸蓄积反应的特点。方法:(1)用磷酸钙沉淀法将编码三种亚型α_1-肾上腺素受体的全长cDNA分别转染到HEK293细胞中。(2)采用放射配基结合实验测定各亚型α_1-肾上腺素受体在HEK293细胞的表达量。(3)用[~3H]腺嘌呤掺入法测定环腺苷一磷酸蓄积率。结果:(1)各亚型激活后均使HEK293细胞中环腺苷一磷酸蓄积率呈浓度依赖性增加,并被α_1-受体选择性拮抗剂哌唑嗪阻断。(2)比较各亚型的药理学特性发现,在三种亚型中,α_(1A)-肾上腺素受体介导的效应最强,而α_1-肾上腺素受体各亚型对去甲肾上腺素的敏感性最高。结论:三种亚型α_1-肾上腺素受体均能介导HEK293细胞中环腺苷一磷酸的生成,并且在介导的效应和敏感性的高低等方面存在差异。     

大鼠血管α_1肾上腺素受体两种亚型减敏与增敏过程的差别(英文)

研究α_1肾上腺素受体(α_1-AR)不同亚型之间激动剂诱导的减敏和利血平化诱导的增敏过程的差别.方法:采用大鼠离体血管收缩功能实验,观察主动脉、肾动脉和肠系膜动脉在CEC 100 μmol·L~(-1)温育30 min后,NE介导的累积浓度收缩曲线(CCRC)的变化,以观察不同血管的亚型差异;在观察减敏时,血管用NE 10 μmol·L~(-1)预温育1 h,洗出后做NE的CCRC;在观察增敏的差异时,大鼠用reserpine 4 mg·kg~(-1)ip 48 h后,观察NE诱导的CCRC的变化.本实验在灌流液中含yohimbine和propranolol以阻断α_2-和β-AR,这样NE仅激活α_1-AR.结果:CEC 100 μmol·L~(-1)温育30 min,使NE介导的主动脉,肠系膜动脉的最大收缩分别降低82.5±3.0％和54.2±9.5％,而对肾动脉则无影响,再次肯定主动脉主要含α_(1B)-AR,肾动脉主要含α_(1A)-AR,肠系膜动脉兼含两种亚型.NE 10 μmol·L~(-1)温育1 h后,NE介导的主动脉,肾动脉和肠系膜动脉收缩的敏感性降低,EC_(50)分别增加了14.4±5.9,1.8±0.8和7.3±1.8倍;而在利血平化大鼠NE介导肾动脉收缩反应增加了56％,主动脉则无变化.结论:α_(1B)-AR亚型介导的反应易发生减敏;a_(1A)-AR亚型介导的反应易发生增敏.     

普萘洛尔对大鼠心肌细胞膜α肾上腺素受体密度及α1A／α1B比例的影响

放射配基结合实验表明，大鼠ｉｐ普萘洛尔（ｐｒｏ）７ｄ后，心肌细胞膜α１肾上腺素受体密度由１３７±２５增加到１７８±３０ｆｍｏｌ／ｍｇｐｒｏｔｅｉｎ（Ｐ＜０．０５），ＫＤ值无显改变。５－ＭＵ竞争结合实验表明，使用Ｐｒｏ后α１Ａ亚型在α１受体总数中所占比例由１９±６％增加到３１±８％（Ｐ＜０．０５），但两种受体亚型的亲和力都未改变。说明β受体阻断后，α１Ａ亚型变化更为敏感。     

α_1-肾上腺素受体结构改变影响其生物学活性及生理功能的研究进展

α_1-肾上腺素受体(α_1-ARs)属于G蛋白偶联受体,包含α_1A、α_1B、α_(1D)3种亚型。α_1-ARs结构改变可导致其生理功能的改变。该文总结了α_1-ARs羧基端截短、二聚化、别构效应和点突变的结构改变,导致其内吞、磷酸化、脱敏以及对激动剂的亲和力等生理功能的变化。     

体外合成的鼠α_4和α_1干扰素的抗病毒活性

鼠α_4干扰素(Mu IFN-α_4)与其他MuIFN-α各亚型相比,主要是氨基酸序列中缺少了5个氨基酸(第103～107位),而其表达量极高。为比较MuIFN-α_4与其他各亚型之间的抗病毒活性,作者采用体外直接位点突变方法,改变MuIFN-α_4和MuIFN-α_1的编码基因,把MuIFN-α_1的15个核苷酸插入到MuIFN-α_4缺失的相应序列中,成为氨基酸替代的MuIFM-α_4(MuIFN-α_4AAR)。体外试验证明,MuIFN-α_1相应区已插入到MuIFN-α_4的第103～107位点中,并显示出了表达功     

α_1和α_2肾上腺素受体激动剂对大鼠左心房肌生理特性的影响

本文观察了选择性α_1肾上腺素受体激动剂苯福林和α_2肾上腺素受体激动剂B-HT933对大鼠左心房肌收缩性、兴奋性、自律性和功能性不应期的影响。苯福林在大鼠左心房肌标本上可致明显的正性肌力作用,同时可提高肾上腺素诱发的左房自律性、延长功能性不应期,这些作用可明显地被哌唑嗪所拮抗。但苯福林对大鼠左心房兴奋性无影响。B-HT933在同样实验条件下对大鼠左房收缩性、兴奋性、自律性和功能性不应期无影响。实验表明,突触后膜α受体兴奋所致的心脏作用由α_1亚型介导,但未能证实突触后膜α_2受体在大鼠左心房上具有功能性的作用。     

大鼠尾动脉平滑肌中α肾上腺素受体的分析

采用离体血管收缩功能实验方法分析大鼠尾动脉平滑肌中α肾上腺素受体(α受体)各种亚型的组成及各自的功能意义,结果表明:尾动脉平滑肌中α_1,受体在功能上占绝对支配地位,包含α_(1A)与α_(1B)两种亚型,它们与去甲肾上腺素的亲和性相同,α_(1A)受体具有较大的储备,而α_(1B)受体无储备,前者在α_1受体激动剂致血管收缩效应中发挥主导作用,α_(1A)与α_(1B)受体之间可能存在协同效应。     

Phenotype of the Cyp1a1/1a2/1b1-/- triple-knockout mouse

Crossing the Cyp1a1/1a2(-/-) double-knockout mouse with the Cyp1b1(-/-) single-knockout mouse, we generated the Cyp1a1/1a2/1b1(-/-) triple-knockout mouse. In this triple-knockout mouse, statistically significant phenotypes (with incomplete penetrance) included slower weight gain and greater risk of embryolethality before gestational day 11, hydrocephalus, hermaphroditism, and cystic ovaries. Oral benzo[a]pyrene (BaP) daily for 18 days in the Cyp1a1/1a2(-/-) produced the same degree of marked immunosuppression as seen in the Cyp1a1(-/-) mouse; we believe this reflects the absence of intestinal CYP1A1. Oral BaP-treated Cyp1a1/1a2/1b1(-/-) mice showed the same "rescued" response as that seen in the Cyp1a1/1b1(-/-) mouse; we believe this reflects the absence of CYP1B1 in immune tissues. Urinary metabolite profiles were dramatically different between untreated triple-knockout and wild-type; principal components analysis showed that the shifts in urinary metabolite patterns in oral BaP-treated triple-knockout and wild-type mice were also strikingly different. Liver microarray cDNA differential expression (comparing triple-knockout with wild-type) revealed at least 89 genes up- and 62 genes down-regulated (P-value < or = 0.00086). Gene Ontology "classes of genes" most perturbed in the untreated triple-knockout (compared with wild-type) include lipid, steroid, and cholesterol biosynthesis and metabolism; nucleosome and chromatin assembly; carboxylic and organic acid metabolism; metal-ion binding; and ion homeostasis. In the triple-knockout compared with the wild-type mice, response to zymosan-induced peritonitis was strikingly exaggerated, which may well reflect down-regulation of Socs2 expression. If a single common molecular pathway is responsible for all of these phenotypes, we suggest that functional effects of the loss of all three Cyp1 genes could be explained by perturbations in CYP1-mediated eicosanoid production, catabolism and activities.     

Dnmt1 regulates adipogenesis by Cdkn1a methylation

Obesity has recently become a major healthy concern in developed countries. This leads to intensive interest in the mechanism study of adipogenesis, in which epigenetic mechanisms are speculated to play an essential role. To explore the function of Dnmt1, its expression was first profiled during the course of adipocyte differentiation of 3T3-L1 cells. The results revealed a dynamic regulation of its expression at the initiation stage. Knockdown of Dnmt1 compromised the differentiation process and decreased lipid production within the cells. To the aspect of epigenetic regulation, promoter methylation of Cdkn1a was significantly increased at the initiation stage of the differentiation, accompanied by decreased Cdkn1a expression. Furthermore, knockdown of Dnmt1 led to an increased Cdkn1a expression, indicating that Dnmt1 inhibits Cdkn1a expression by promoter methylation. Furthermore, we found that knockdown of Cdkn1a up-regulated the expression of PPARγ and resulted in enhanced adipocyte differentiation. In summary, our results demonstrated that Dnmt1 regulated the process of adipogenesis by methylation of Cdkn1a promoter, suggesting that Cdkn1a played a fundamental role in the prevention of adipocyte hyperplasia.     

CYP1B1, a developmental gene with a potential role in glaucoma therapy

The association of CYP1B1 gene alterations in primary congenital glaucoma individuals has been known for about a decade. Recent evidence has shown the involvement of CYP1B1 mutations in a number of forms of glaucoma and anterior segment disorders. This suggests a wide role for CYP1B1 in ocular physiology. Histochemical studies of eyes from individuals with primary congenital glaucoma revealed abnormalities in the anterior chamber angle, the region between the cornea and the iris, containing the trabecular meshwork. The cells of the trabecular meshwork serve as a filter to allow drainage of the aqueous humour, the fluid formed by the ciliary body that fills the anterior chamber. Mutations in CYP1B1 that affect its activity have frequently been shown to influence development of the trabecular meshwork, and it is thought that CYP1B1, a monooxygenase, acts to form or degrade some endobiotic compound that is necessary for proper development of the filtering structures. The rapidly developing area of stem cell research suggests a potential therapeutic approach for glaucomas resulting from deleterious mutations in CYP1B1, that is, the transfer of stem cells, differentiated to a specific lineage, containing wild-type CYP1B1 to specific regions of the eye, where they will develop into normal cells of that region and rectify the defect.     

Role of P450 1A1 and P450 1A2 in bioactivation versus detoxication of the renal carcinogen aristolochic acid I: studies in Cyp1a1-/-, Cyp1a2-/-, and Cyp1a1/1a2-/- mice

Exposure to aristolochic acid I (AAI) is associated with aristolochic acid nephropathy, Balkan endemic nephropathy, and urothelial cancer. Individual differences in xenobiotic-metabolizing enzyme activities are likely to be a reason for interindividual susceptibility to AA-induced disease. We evaluated the reductive activation and oxidative detoxication of AAI by cytochrome P450 (P450) 1A1 and 1A2 using the Cyp1a1(-/-) and Cyp1a2(-/-) single-knockout and Cyp1a1/1a2(-/-) double-knockout mouse lines. Incubations with hepatic microsomes were also carried out in vitro. P450 1A1 and 1A2 were found to (i) activate AAI to form DNA adducts and (ii) detoxicate it to 8-hydroxyaristolochic acid I (AAIa). AAI-DNA adduct formation was significantly higher in all tissues of Cyp1a1/1a2(-/-) than Cyp1a(+/+) wild-type (WT) mice. AAI-DNA adduct levels were elevated only in selected tissues from Cyp1a1(-/-) versus Cyp1a2(-/-) mice, compared with those in WT mice. In hepatic microsomes, those from WT as well as Cyp1a1(-/-) and Cyp1a2(-/-) mice were able to detoxicate AAI to AAIa, whereas Cyp1a1/1a2(-/-) microsomes were less effective in catalyzing this reaction, confirming that both mouse P450 1A1 and 1A2 are both involved in AAI detoxication. Under hypoxic conditions, mouse P450 1A1 and 1A2 were capable of reducing AAI to form DNA adducts in hepatic microsomes; the major roles of P450 1A1 and 1A2 in AAI-DNA adduct formation were further confirmed using selective inhibitors. Our results suggest that, in addition to P450 1A1 and 1A2 expression levels in liver, in vivo oxygen concentration in specific tissues might affect the balance between AAI nitroreduction and demethylation, which in turn would influence tissue-specific toxicity or carcinogenicity.     

1-Hydroxy-1-norresistomycin, a new cytotoxic compound from a marine actinomycete, Streptomyces chibaensis AUBN1/7

In our systematic screening programme for marine actinomycetes, a bioactive streptomycete was isolated from marine sediment samples of the Bay of Bengal, India. The isolate yielded a new cytotoxic compound. This was obtained by solvent extraction followed by chromatographic purification. The pure compound was identified from spectroscopic data as a quinone-related antibiotic, 1-hydroxy-1-norresistomycin (1). It showed a potent cytotoxic activity against cell lines viz. HMO2 (gastric adenocarcinoma) and HePG2 (hepatic carcinoma) in vitro. It also exhibited antibacterial activities against Gram-positive and Gram-negative bacteria.