Involvement of multidrug resistance-associated protein 2 (ABCC2/Mrp2) in biliary excretion of micafungin in rats

The drug transporter, multidrug resistance-associated protein 2 (ABCC2/Mrp2), is known to play important roles in excretion of various drugs. In the present study, we investigated whether Mrp2 is involved in the transport of micafungin, a newly developed antifungal agent. When Sprague-Dawley rats received an intravenous injection of micafungin (1 mg/kg) in combination with cyclosporine, the cyclosporine significantly delayed the disappearance of micafungin from plasma and decreased the systemic clearance and volume of distribution at steady-state of micafungin to 54% and 65% of the corresponding control values, respectively. When Sprague-Dawley rats received a constant-rate infusion of micafungin, cyclosporine significantly decreased the steady-state biliary clearance of micafungin (~80%). A significant decrease in the biliary clearance of micafungin (~60%) was observed in Eisai hyperbilirubinemic rats, which have a hereditary deficiency in Mrp2. The present findings at least suggest that Mrp2 is involved mainly in the hepatobiliary excretion of micafungin in rats.     

Role of Nrf2 in the pathogenesis of atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the vascular arterial walls. A number of studies have revealed the biological and genetic bases of atherosclerosis, and over 100 genes influence atherosclerosis development. Nrf2 plays an important role in oxidative stress response and drug metabolism, but the Nrf2 signaling pathway is closely associated with atherosclerosis development. During atherosclerosis progression, Nrf2 signaling modulates many physiological and pathophysiological processes, such as lipid homeostasis regulation, foam cell formation, macrophage polarization, redox regulation and inflammation. Interestingly, Nrf2 exhibits both pro- and anti-atherogenic effects in experimental animal models. These observations make the Nrf2 pathway a promising target to prevent atherosclerosis.     

Role of caspases in TNF-mediated regulation of cPLA(2)

A major part of the proinflammatory activity of tumor necrosis factor (TNF) is brought about by cytosolic phospholipase A(2) (cPLA(2)) that generates arachidonic acid, the precursor for the production of leukotrienes and prostaglandins. The activation of cPLA(2) and induction of proinflammatory lipid mediators is in striking contrast to the teleologic meaning of apoptosis, which is to avoid an inflammatory reaction. In this review we highlight the evidence for a caspase-mediated cleavage and inactivation of cPLA(2), which seems to be an important mechanism by which TNF downregulates cPLA(2) activity in cells undergoing apoptosis.     

Role of Y(2) receptors in the regulation of gastric tone in rats

We set out to determine the effect of peptide YY(3-36) (PYY(3-36)) on the gastric muscle tone in conscious rats by measuring intragastric pressure (IGP) during intragastric nutrient drink infusion. After an overnight fast, a chronically implanted gastric fistula was connected to a custom-made nutrient drink infusion system and a catheter to measure IGP. IGP was measured before and during the infusion of a nutrient drink (Nutridrink; 0.5 ml/min) until 10 ml was infused. Rats were treated with PYY(3-36) (0, 33, and 100 pmol·kg(-1)·min(-1)) in combination with a subcutaneous injection of the Y(2) receptor antagonists JNJ31020028 (10 mg/kg) or BIIE0246 (2 mg/kg). Experiments were also performed after subdiaphragmatic vagotomy and after pretreatment with 3 ml of nutrient drink (to mimic a fed state). IGP was compared as the average IGP during nutrient infusion, represented as means ± SE and compared using ANOVA. PYY(3-36) dose dependently increased the IGP during nutrient infusion (4.7 ± 0.3, 5.7 ± 0.5 and 7.3 ± 0.7 mmHg; P < 0.01) while JNJ31020028 and BIIE0246 could block this increase [4.4 ± 0.5 (P < 0.001) and 4.8 ± 0.4 (P < 0.05) mmHg, respectively]. Also in vagotomized rats, PYY(3-36) was able to significantly increase the IGP during, an effect attenuated by JNJ31020028. BIIE0246 and JNJ31020028 were not able to decrease the IGP when no PYY(3-36) was administered. PYY(3-36) increased gastric tone through an Y(2) receptor-mediated mechanism that does not involve the vagus nerve. Y(2) receptor antagonists were not able to decrease gastric tone without exogenous administration of PYY(3-36), indicating that Y(2) receptors do not play a crucial role in the determination of gastric tone in physiological conditions.     

转录因子Nrf2在肝脏疾病中的作用

NF-E2相关因子2(nuclear erythroid 2-related factor 2,Nrf2)是一种能调节肝脏中大量解毒和抗氧化防御基因表达的重要转录因子.氧化应激与各种形式的肝损伤有密切的关系.Nrf2由亲电体压力或氧化应激激活,并通过结合抗氧化反应元件(antioxidant response element,ARE)诱导其靶基因,从而对细胞产生保护作用.因此,Nrf2通路在肝脏疾病中的作用已被深入研究.多种动物模型研究结果表明,Nrf2通路通过靶基因表达,在对抗病毒性肝炎、药物性肝损伤、酒精性肝病、非酒精性脂肪肝及肝癌方面表现出了不同的生物功能.根据Nrf2及其信号通路在对抗肝损伤中产生保护作用的相关文献,本文综述并讨论了其作为治疗肝损伤的药物作用靶点方面可能的应用前景.     

核转录因子相关因子2的活化在肿瘤代谢中的作用

核转录因子(NF-E2)相关因子2（nuclear factor erythroid 2 related factor 2, Nrf2）是细胞应对外界应激的主要调控因子,通过调控多种靶基因的表达,在生理条件下减轻氧化应激,维持细胞稳态。其上游受多种因素调控,包括氧化与亲电应激、外界营养状态、细胞内代谢中间产物和能量状态等。在肿瘤细胞中,异常活跃的Nrf2使其抗氧化能力增强,并且通过介导代谢重编程（metabolic reprogramming）,促进肿瘤细胞增殖和生长。Keap1 (Kelch-like ECH-associated protein 1)是氧化和亲电应激感受器,通过募集泛素降解系统,对Nrf2的活性起主要调控作用。本文介绍Keap1依赖与非依赖条件下Nrf2的活化途径,着重介绍在肿瘤中Nrf2的异常活化,以及如何调控代谢重编程进而调节肿瘤细胞的合成代谢,最终促进肿瘤的进展。     

Role of protein phosphatases in the activation of CFTR (ABCC7) by genistein and bromotetramisole

Genistein and bromotetramisole(Br-t) strongly activate cystic fibrosis transmembrane conductanceregulator (CFTR; ABCC7) chloride channels on Chinese hamster ovarycells and human airway epithelial cells. We have examined the possiblerole of phosphatases in stimulation by these drugs using patch-clampand biochemical methods. Genistein inhibited the spontaneous rundown ofchannel activity that occurs after membrane patches are excised fromcAMP-stimulated cells but had no effect on purified protein phosphatasetype 1 (PP1), PP2A, PP2B, PP2C, or endogenous phosphatases when assayed as [³²P]PO₄ release from prelabeled casein,recombinant GST-R domain fusion protein, or immunoprecipitatedfull-length CFTR. Br-t also slowed rundown of CFTR channels, but, inmarked contrast to genistein, it did inhibit all four proteinphosphatases tested. Half-maximal inhibition of PP2A and PP2C wasobserved with 0.5 and 1.5 mM Br-t, respectively. Protein phosphataseswere also sensitive to (+)-p-Br-t, a stereoisomer of Br-tthat does not inhibit alkaline phosphatases. Br-t appeared to actexclusively through phosphatases since it did not affect CFTR channelsin patches that had low apparent endogenous phosphatase activity (i.e.,those lacking spontaneous rundown). We conclude that genistein and Br-tact through different mechanisms. Genistein stimulates CFTR withoutinhibiting phosphatases, whereas Br-t acts by inhibiting amembrane-associated protein phosphatase (probably PP2C) that presumablyallows basal phosphorylation to accumulate.

     

Role of nuclear receptors in the regulation of gene expression by dietary fatty acids (review)

Long chain fatty acids, derived either from endogenous metabolism or by nutritional sources play significant roles in important biological processes of membrane structure, production of biologically active compounds, and participation in cellular signaling processes. Recently, the structure of dietary fatty acids has become an important issue in human health because ingestion of saturated fats (containing triglycerides composed of saturated fatty acids) is considered harmful, while unsaturated fats are viewed as beneficial. It is important to note that the molecular reason for this dichotomy still remains elusive. Since fatty acids are important players in development of pathology of cardiovascular and endocrine system, understanding the key molecular targets of fatty acids, in particular those that discriminate between saturated and unsaturated fats, is much needed. Recently, insights have been gained on several fatty acid-activated nuclear receptors involved in gene expression. In other words, we can now envision long chain fatty acids as regulators of signal transduction processes and gene regulation, which in turn will dictate their roles in health and disease. In this review, we will discuss fatty acid-mediated regulation of nuclear receptors. We will focus on peroxisome proliferators-activated receptors (PPARs), liver X receptors (LXR), retinoid X receptors (RXRs), and Hepatocyte Nuclear Factor alpha (HNF-4alpha), all of which play pivotal roles in dietary fatty acid-mediated effects. Also, the regulation of gene expression by Conjugated Linoleic Acids (CLA), a family of dienoic fatty acids with a variety of beneficial effects, will be discussed.     

Role of iPLA(2) in the regulation of Src trafficking and microglia chemotaxis

Microglia are immune effector cells in the central nervous system (CNS) and their activation, migration and proliferation play crucial roles in brain injuries and diseases. We examined the role of intracellular Ca(2+) -independent phospholipase A(2) (iPLA(2)) in the regulation of microglia chemotaxis toward ADP. Inhibition of iPLA(2) by 4-bromoenol lactone (BEL) or iPLA(2) knockdown exerted a significant inhibition on phosphatidylinositol-3-kinase (PI3K) activation and chemotaxis. Further examination revealed that iPLA(2) knockdown abrogated Src activation, which is required for PI3K activation and chemotaxis. Colocalization studies showed that cSrc-GFP was retained in the endosomal recycling compartment (ERC) in iPLA(2) knockdown cells, but the addition of arachidonic acid (AA) could restore cSrc trafficking to the plasma membrane by allowing the formation/release of recycling endosomes associated with cSrc-GFP. Using BODIPY-AA, we showed that AA is selectively enriched in recycling endosomes. These results suggest that AA is required for the cSrc trafficking to the plasma membrane by controlling the formation/release of recycling endosomes from the ERC.     

核因子E2相关因子2在运动改善非酒精性脂肪性肝病中的作用

核因子E2相关因子2 (nuclear factor erythroid 2-related factor 2,Nrf2)信号通路在维持心血管疾病、神经系统退行性疾病以及慢性代谢性疾病中的细胞稳态方面起关键作用。研究表明,以氧化应激、炎症和线粒体功能失调为特征的慢性疾病可通过增加Nrf2表达来恢复机体氧化还原状态,治疗或预防疾病。非酒精性脂肪性肝病（nonalcoholic fatty liver disease,NAFLD）是一种由除酒精以外的其他多种因素导致的以肝脏脂肪变性为特征的慢性代谢性肝脏疾病,其患病率近年来在全球范围内逐渐增加。运动是防治NAFLD的有效手段,可通过运动方式、运动强度、运动环境和运动疲劳等因素影响Nrf2信号通路。本文通过阐述Nrf2信号通路的激活、其调控抗氧化的相关机制以及运动对Nrf2信号通路的影响,以NAFLD的发病机制为基础,探讨运动、Nrf2和NAFLD之间的关系,综述Nrf2在运动改善NAFLD中的作用及相关机制。为运动改善NAFLD的分子机制研究提供理论参考依据。     

Role of Ca(2+) fluctuations in L6 myotubes in the regulation of the hexokinase II gene.

Expression of the hexokinase (HK) II gene in skeletal muscle is upregulated by electrically stimulated muscle contraction and moderate-intensity exercise. However, the molecular mechanism by which this occurs is unknown. Alterations in intracellular Ca(2+) homeostasis accompany contraction and regulate gene expression in contracting skeletal muscle. Therefore, as a first step in understanding the exercise-induced increase in HK II, the ability of Ca(2+) to increase HK II mRNA was investigated in cultured skeletal muscle cells, namely L6 myotubes. Exposure of cells to the ionophore A-23187 resulted in an approximately threefold increase in HK II mRNA. Treatment of cells with the extracellular Ca(2+) chelator EGTA did not alter HK II mRNA, nor was it able to prevent the A-23187-induced increase. Treatment of cells with the intracellular Ca(2+) chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester (BAPTA-AM) also resulted in an approximately threefold increase in HK II mRNA in the absence of ionophore, which was similar to the increase in HK II mRNA induced by the combination of BAPTA-AM and A-23187. In summary, a rise in intracellular Ca(2+) is not necessary for the A-23187-induced increase in HK II mRNA, and increases in HK II mRNA occur in response to treatments that decrease intracellular Ca(2+) stores. Depletion of intracellular Ca(2+) stores may be one mechanism by which muscle contraction increases HK II mRNA.