孕烷X受体在肾脏疾病中的研究进展

核受体是一类在机体内广泛分布的转录因子,在人体生理、病理过程中发挥重要作用。孕烷X受体（pregnane X receptor,PXR）为核受体家族成员之一,参与机体物质代谢,尤其在药物代谢中起关键作用。肾脏是药物代谢的主要器官之一,PXR参与肾脏药物代谢、转运等多种调节并参与多种肾脏疾病的病理生理过程。近年来多项研究关注PXR及其调控作用对肾脏及肾脏疾病的影响。本文将从PXR在肾脏与药物代谢和转运相关酶的相互作用以及PXR在肾脏疾病中的作用等方面进行综述。     

中草药对孕烷X受体和组成型雄烷受体等核受体通路影响的研究进展

孕烷X受体（pregnane X receptor,PXR）是核受体亚家族的成员之一,参与大量的外源性和内源性化学物质的生物转化,能被多种中草药激活,调节下游靶基因的表达,在药物代谢酶和转运体的调节中起重要作用。组成型雄烷受体（constitutive androstane receptor,CAR）和PXR一样能与外源性配体结合调节CYP2B6、CYP3A4、CYP2C19、UGT1A1的表达,共同参与CYP药物代谢酶的调节,成为药物作用的靶标。     

核受体作为炎症性肠疾病治疗靶点的研究进展

炎症性肠疾病是一种慢性肠道炎症疾病,其发病机制尚不明确,目前多认为与炎症和肠黏膜损伤有关。核受体是一种重要的转录调节因子,包括孕烷X受体(pregnane X receptor,PXR)、法尼酯X受体(farnesoid X receptor,FXR)和组成型雄甾烷受体(constitutive androstane receptor,CAR)等。近年深入研究发现,核受体可以通过抑制炎症信号通路、调节肠道紧密连接蛋白及代谢酶的表达减轻肠道炎症,并维持肠黏膜屏障功能,在炎症性肠疾病肠道保护方面发挥重要作用。因此,本文综述核受体PXR、FXR和CAR对炎症性肠疾病肠道的保护作用机制,为以核受体为靶点的炎症性肠疾病药物治疗提供新思路。     

孕烷X受体的研究进展及其在药物代谢中的作用

孕烷X受体(pregnane X receptor,PXR)是机体对有毒物质适应性防卫机制的一个重要组成部分,PXR被大量的外源性和内源性化学物质激活,这些物质包括类固醇、抗生素、抗真菌的物质和胆汁酸等.PXR配体结合区域三维结构显示它具有一个特殊球形配体结合腔,这种结构允许PXR与广泛的疏水性化学物质结合.PXR与9-顺式维甲酸受体(9-cis retinoic aid receptor,RXR)以异型二聚体的形式与细胞色素氧化酶P450 3A家族和其他参与药物代谢的Ⅱ相药物代谢酶以及药物转运蛋白的DNA响应元件结合,通过外源物刺激诱导多个基因的表达.分析PXR的结构与功能对药物设计和筛选具有重要的应用价值.     

孕烷X受体在药物性肝损伤中的研究进展

孕烷X受体（pregnane X receptor,PXR）是核受体家族中的一员,可调控多种药物代谢酶及转运体的表达,从而影响药物在肝脏的处置过程,增加药物性肝损伤发生的风险。深入了解PXR在药物性肝损伤中的作用,可预防或减少药物性肝损伤的发生,并有助于以PXR作为潜在靶点的新型药物的研发。     

共表达PXRLBD和SRC88以及PXR配体筛选的平衡透析模型的建立

孕烷X受体(pregnane X receptor,PXR),属核受体NR1I亚家族.PXR可由配体活化,当配体(如外源药物)与其配体结合域(ligand binding domain,LBD)结合后,PXR被活化,招募辅调控因子(如人甾体受体辅活化因子-1,steroid receptor eoactivator-1,SRC-1)形成复合物,通过其DNA结合域(DNA binding domain)结合到药物代谢酶基因启动子的特定DNA序列上,从而调控CYP3A4等药物代谢酶基因的转录[1,2].     

孕烷X受体和CYP3A相关性的研究进展

CYP3A是生物体内化学物代谢的关键酶 ,孕烷X受体 (PXR)是CYP3A基因表达的转录活化因子。PXR分子结构的不同导致CYP3A的种属差异。化学物通过PXR调节CYP3A的表达可能是影响化学物体内代谢的一条重要途径。研究PXR和CYP3A的相互作用对于新药设计、指导临床合理用药、预测药物相互作用、减少药物不良反应都具有重要意义。     

孕烷X受体(PXR)对药物代谢途径的调控

目的 从孕烷X受体（PXR）对药物代谢途径的调控入手,在代谢性药物相互作用、PXR在CYP3A4调控中的作用及其调控机制等方面作分析和阐述。方法 结合近年来国内外相关文献进行评述。结果 PXR是CYP3A4的主要转录调控因子,药物通过PXR介导的信号通路调节CYP3A4的表达是影响药物体内代谢变化的重要途径。结论 就临床药物而言,由PXR介导的CYP3A4酶蛋白表达的改变可造成合用药物药效的减弱甚至丧失,因此必须引起广大临床药师的足够重视。     

孕烷X受体：肝脏疾病的潜在药物靶标

孕烷X受体（PXR）属于配体依赖性调控靶基因的核受体亚家族,激活后可调控多种药物代谢酶和转运体的表达,影响临床药物的疗效和耐药性。PXR通过调控肝脏中脂质和糖类物质的代谢,影响肝脏疾病的发生发展进程,可作为肝脏疾病药物筛选与疾病治疗的潜在药物靶标。深入了解PXR及其调控机制对于预测药物-药物相互作用、避免或减轻药物不良反应以及设计和研发以PXR为靶点的新型药物均具有十分重要的意义。对PXR在肝脏疾病中的调控作用及药物通过PXR干预肝脏疾病进程的研究进展进行概述。

     

孕烷X受体介导的代谢酶和转运体转录调控及其在化疗药物耐药中的作用

孕烷X受体(PXR,NR1I2)是生物体内药物代谢酶和转运体基因表达的主要调控因子之一.近来研究发现,PXR介导的药物代谢酶和转运体的过表达,与化疗药物多药耐药的产生密切相关.鉴于PXR在药物代谢酶和转运体调控中的重要性和PXR转录调控的多样性,有必要对其导致的多药耐药形成机制进行更深入的研究.本文综述了PXR介导的代谢酶和转运体基因表达调控机制,及其引起化疗药物多药耐药的相关研究进展,为提高化疗药物敏感性、逆转化疗药物的多药耐药提供有效的治疗策略.     

New insights on the xenobiotic-sensing nuclear receptors in liver diseases--CAR and PXR--

The xenobiotic receptors CAR and PXR constitute two important members of the NR1I nuclear receptor family. They function as sensors of toxic byproducts derived from the endogenous metabolism and of exogenous chemicals, in order to enhance their elimination. They regulate numerous genes which are involved in drug and xenobiotic metabolism, including Phase I (cytochrome P450), Phase II (conjugation catalyzed by sulfotransferases, glucuronosyltransferases and glutathione S-transferases), and transporters (multidrug resistance proteins, multidrug resistance-associated proteins, and organic anion-transporting polypeptides). Although CAR and PXR were initially characterized as xenosensors, it is now evident that CAR and PXR also trigger pleiotropic effects on physiological or pathological functions. Recent studies have shown that the activation of CAR and PXR alters lipid metabolism, glucose homeostasis, and inflammation. Therefore, in addition to regulating drug elimination pathways, they also play important roles in regulating metabolic pathways. As a result, these receptors may be closely associated with the pathogenesis of many diseases. However, the pathophysiological roles of CAR and PXR are not fully understood. The purpose of this review is to discuss the physiological and pathological roles of CAR and PXR in liver diseases.     

Nuclear pregnane x receptor and constitutive androstane receptor regulate overlapping but distinct sets of genes involved in xenobiotic detoxification

The nuclear pregnane X receptor (PXR) and constitutive androstane receptor (CAR) play central roles in protecting the body against environmental chemicals (xenobiotics). PXR and CAR are activated by a wide range of xenobiotics and regulate cytochrome P450 and other genes whose products are involved in the detoxification of these chemicals. In this report, we have used receptor-selective agonists together with receptor-null mice to identify PXR and CAR target genes in the liver and small intestine. Our results demonstrate that PXR and CAR regulate overlapping but distinct sets of genes involved in all phases of xenobiotic metabolism, including oxidative metabolism, conjugation, and transport. Among the murine genes regulated by PXR were those encoding PXR and CAR. We provide evidence that PXR regulates a similar program of genes involved in xenobiotic metabolism in human liver. Among the genes regulated by PXR in primary human hepatocytes were the aryl hydrocarbon receptor and its target genes CYP1A1 and CYP1A2. These findings underscore the importance of these two nuclear receptors in defending the body against a broad array of potentially harmful xenobiotics.     

Coordinate regulation of human drug-metabolizing enzymes, and conjugate transporters by the Ah receptor, pregnane X receptor and constitutive androstane receptor

Coordinate regulation of Phase I and II drug-metabolizing enzymes and conjugate transporters by nuclear receptors suggests that these proteins evolved to an integrated biotransformation system. Two major groups of ligand-activated nuclear receptors/xenosensors evolved: the Ah receptor (activated by aryl hydrocarbons and drugs such as omeprazole) and type 2 steroid receptors such as PXR and CAR, activated by drugs such as rifampicin, carbamazepin and phenytoin. It is increasingly recognized that there is considerable cross-talk between these xenosensors. Therefore, an attempt was made to discuss biotransformation by the Ah receptor together with that of PXR and CAR. Due to considerable species differences the emphasis is on human biotransformation. Agonists coordinately induce biotransformation due to common xenosensor-binding response elements in the regulatory region of target genes. However, whereas different groups of xenobiotics appear to more selectively stimulate CYPs (Phase I), their regulatory control largely converged in modulating Phase II metabolism and transport. Biotransformation appears to be tightly controlled to achieve efficient homeostasis of endobiotics and detoxification of dietary phytochemicals, but nuclear receptor agonists may also lead to potentially harmful drug interactions.     

Modulation of constitutive androstane receptor (CAR) and pregnane X receptor (PXR) by 6-arylpyrrolo[2,1-d][1,5]benzothiazepine derivatives, ligands of peripheral benzodiazepine receptor (PBR)

Constitutive androstane receptor (CAR) and pregnane X receptor (PXR) regulate xenobiotic sensing and metabolism through interactions with multiple exogenous and endogenous chemicals. Compounds that activate CAR are often ligands of PXR; attention is therefore given to discovery of new, receptor-specific chemical entities that may be exploited for therapeutic and basic research purposes. Recently, ligands of the peripheral benzodiazepine receptor (PBR), PK11195 and FGIN-1-27, were shown to modulate both CAR and PXR. PBR is a mitochondrial transport protein responsible for multiple regulatory functions, including heme biosynthesis, a major component in cytochrome P450 (CYP) enzymes. To investigate possible new roles for PBR involvement in metabolic regulation, expression of the CAR and PXR target genes, CYP2B6 and CYP3A4, was measured in human hepatocytes following treatment with a targeted PBR ligand set. Luciferase reporter assays with transiently expressed wild-type CAR (CAR1), splice variant CAR3, or PXR in HuH-7 cells were used to further study activation of these receptors. Four structurally related PBR ligands (benzothiazepines) differentially modulate CAR1, CAR3 and PXR activity. Benzothiazepine NF49 is an agonist ligand of CAR3, a partial agonist of PXR, exhibits greater inverse agonist activity on CAR1 than does PK11195, and is a new tool for studying these closely related nuclear receptors.     

Regulatory cross-talk between drug metabolism and lipid homeostasis: constitutive androstane receptor and pregnane X receptor increase Insig-1 expression

Activation of pregnane X receptor (PXR) and constitutive androstane receptor (CAR) by xenobiotic inducers of cytochromes P450 is part of a pleiotropic response that includes liver hypertrophy, tumor promotion, effects on lipid homeostasis, and energy metabolism. Here, we describe an acute response to CAR and PXR activators that is associated with induction of Insig-1, a protein with antilipogenic properties. We first observed that activation of CAR and PXR in mouse liver results in activation of Insig-1 along with reduced protein levels of the active form of sterol regulatory element binding protein 1 (Srebp-1). Studies in mice deficient in CAR and PXR revealed that the effect on triglycerides involves these two nuclear receptors. Finally, we identified a functional binding site for CAR and PXR in the Insig-1 gene by in vivo, in vitro, and in silico genomic analysis. Our experiments suggest that activation Insig-1 by drugs leads to reduced levels of active Srebp-1 and consequently to reduced target gene expression including the genes responsible for triglyceride synthesis. The reduction nuclear Srebp-1 by drugs is not observed when Insig-1 expression is repressed by small interfering RNA. In addition, observed that Insig-1 is also a target of AMP-activated kinase, the hepatic activity of which is increased by activators of CAR and PXR and is known to cause a reduction of triglycerides. The fact that drugs that serve as CAR or PXR ligands induce Insig-1 might have clinical consequences and explains alterations lipid levels after drug therapy.