Synthesis of pH-responsive N-acetyl-cysteine modified starch derivatives for oral delivery

In this study, a novel type of pH-responsive polymer PyHES-NAC (2-hydroxy-3-(2-propynyloxy) propyl hydroxyethyl starch (PyHES)) – (N-acetyl-cysteine (NAC)) was synthesized. First, PyHES was prepared via hydrophobic modification of hydroxyl groups in hydroxyethyl starch (HES) with propynylglycidyl ether (PGE), and then pH-responsive carboxylic acid group was connected to propynyl group via thiol-yne click reaction with NAC. Aqueous PyHES-NAC solutions exhibited a good transference between hydrophobic (or self-assembly) and hydrophilic static along with the change of pH value and protective properties of drugs under acidic conditions. 10.0% DOX was released under artificial gastric fluid after 2 h, whereas an immediate release (above 80%) was observed under artificial intestinal fluid. Drug loading capacity of PyHES-NAC was increased by the increase of degree of substitution (DS) of hydrophobic propynyl groups in PyHES, and 41 wt% DOX Loading capacity was the highest value in our study area.     

N-乙酰半胱氨酸防治脓毒症的研究进展

脓毒症是临床常见危重症,病死率高,其发病机制复杂,目前认为氧化应激参与其发病过程,N-乙酰半胱氨酸作为一种巯基供给体,具有抗氧化损伤,抗炎等作用,日益受到重视。现就脓毒症的发病机制、N-乙酰半胱氨酸防治脓毒症的机制及其在动物实验和临床应用中的情况作一介绍。     

N-乙酰半胱氨酸和维生素C抗大鼠急性肺损伤作用的比较研究

目的比较研究N-乙酰半胱氨酸（NAC）和维生素C（Vc）抗大鼠急性肺损伤（ALI）作用。方法采用大鼠油酸（OA）所致急性肺损伤模型，随机分为正常对照组（NS组）、AU模型组（OA组）、维生素C干预组（Vc组）、NAC干预组（NAC组）。观察NAC和vc对大鼠急性肺损伤时MDA，SOD和GSH—PX水平，病理改变，肺系数，免疫组化iNOS等的影响。结果NAC组和Vc组可明显降低损伤所致肺系数、iNOS表达、组织MDA等水平的升高；同时，又能显著升高肺组织SOD、GSH—PX水平，且Vc组和NAC组之间无显著性差别（P〉0．05）。结论抗氧化剂NAC和Vc可通过抑制MDA、iNOS表达，改善SOD、GSH—Px等方式减少氧自由基的产生，减轻肺损伤程度，对油酸所致急性肺损伤后的肺纤维化有一定防护作用。     

Inhibition of cathepsin S induces autophagy and apoptosis in human glioblastoma cell lines through ROS-mediated PI3K/AKT/mTOR/p70S6K and JNK signaling pathways

Cathepsin S is a lysosomal cysteine protease that is overexpressed in various cancer models and plays important role in tumorigenesis, however the mechanisms are unclear. In the present study, we found that inhibition of cathepsin S induced autophagy and mitochondrial apoptosis in human glioblastoma cells. Blockade of autophagy by either a chemical inhibitor or RNA interference attenuated cathespin S inhibition-induced apoptosis. Furthermore, autophagy and apoptosis induction was dependent on the suppression of phosphatidylinositide 3-kinases/protein kinase B/mammalian target of rapamycin/p70S6 kinase (PI3K/AKT/mTOR/p70S6K) signaling pathway and activation of c-Jun N-terminal kinase (JNK) signaling pathway. In addition, reactive oxygen species (ROS) served as an upstream of PI3K/AKT/mTOR/p70S6K and JNK signaling pathways. In conclusion, the current study revealed that cathepsin S played an important role in the regulation of autophagy and apoptosis in human glioblastoma cells.     

Intracellular ATP levels determine cell death fate of cancer cells exposed to both standard and redox chemotherapeutic agents

Cancer cells generally exhibit high levels of reactive oxygen species (ROS) that stimulate cell proliferation and promote genetic instability. Since this biochemical difference between normal and cancer cells represents a specific vulnerability that can be selectively targeted for cancer therapy, various ROS-generating agents are currently in clinical trials, either as single agents or in combination with standard therapy. However, little is known about the potential consequences of an increased oxidative stress for the efficacy of standard chemotherapeutic agents. In this context, we have assessed the influence of an oxidative stress generated by the combination of ascorbate and the redox-active quinone menadione on the capacity of melphalan, a common alkylating agent, to induce apoptosis in a chronic myelogenous leukemia cell line. Our data show that oxidative stress did not inhibit but rather promoted cancer cell killing by melphalan. Interestingly, we observed that, in the presence of oxidative stress, the type of cell death shifted from a caspase-3 dependent apoptosis to necrosis because of an ATP depletion which prevented caspase activation. Taken together, these data suggest that ROS-generating agents could be useful in combination with standard chemotherapy, even if all the molecular consequences of such an addition remain to be determined.     

CHIP E3 ligase regulates mammalian senescence by modulating the levels of oxidized proteins

Senescence can be induced by various stressors including oxidative stress. It has been reported that CHIP (C-terminus of Hsp70-interacting protein) ligase is induced during senescence while CHIP^−/− mice exhibit accelerated aging. Here, we explore the effects of modulating CHIP expression on mammalian senescence. We demonstrate that CHIP silencing induces premature senescence that is accompanied by elevated levels of oxidized proteins. On the contrary, ectopic expression of CHIP leads to oxidized proteins levels reduction. Moreover, we reveal that CHIP^−/− mouse fibroblasts have an impaired ubiquitin proteasome system. Taken together, we propose that CHIP influences cellular senescence by modulating the oxidative load.     

DNA damage in organs of mice treated acutely with patulin, a known mycotoxin

Patulin, a known mycotoxin, is considered a significant contaminant in apples, apple-derived products and feeds. This study investigated the genotoxic effects of patulin in multiple organs (brain, kidney, liver and urinary bladder) of mice using an in vivo comet assay. We assessed the mechanism underlying this genotoxicity by measuring the GSH content and the thiobarbituric acid-reactive species (TBARS) level. Male CF-1 mice were given 1.0-3.75mg/kg patulin intraperitoneally. The effect of patulin was dose-dependent and the highest patulin dose induced DNA strand breaks in the brain (damage index, DI, in hippocampus increased from 36.2 in control animals to 127.5), liver (44.3-138.4) and kidneys (31.5-99); decreased levels of GSH (hippocampus - from 46.9 to 18.4nmol/mg protein); and an increase in lipid peroxidation (hippocampus - from 5.8 to 20.3 MDA equivalents/mg protein). This finding establishes an interrelationship between the pro-oxidant and genotoxic effects of patulin. Pre-treatment administration of N-acetyl-cysteine reduced patulin-induced DNA damage (hippocampus - DI from 127.5 to 39.8) and lipid peroxidation (hippocampus - 20.3 to 12.8 MDA equivalents/mg protein) by restoring cellular GSH levels, reinforcing the positive relationship between patulin-induced GSH depletion and DNA damage caused by systemic administration of this mycotoxin.     

Inhibition of the OCTN2 carnitine transporter by HgCl2 and methylmercury in the proteoliposome experimental model: insights in the mechanism of toxicity

Mercury causes toxic effects in many tissues interacting with protein cysteine (Cys) thiols. Transport systems represent critical targets of mercurials. Indeed, the majority of transport systems of higher eukaryotes contain several Cys residues. One of the most up to date method of studying transport is the reconstitution of transporters in proteoliposomes. This method has been used as a useful approach to test the effect of HgCl₂ and methylmercury (MeHg) on the carnitine (OCTN2) transporter. OCTN2, extracted from kidney brush border membranes with 3% octaethylene glycol monododecyl ether (C₁₂E₈), was reconstituted in liposomes by removing the detergent with hydrophobic chromatography columns. Transport was measured as [³H]carnitine uptake into proteoliposomes containing carnitine (antiport reaction). Mercurials strongly inhibited the antiport. Inhibition was reversed by 1,4-dithioerythritol, L-cysteine (Cys), and N-acetyl-L-cysteine (NAC) indicating that it was caused by covalent reaction of mercurials with Cys residue(s). The IC₅₀ for HgCl₂, and MeHg were 2.5 and 7.4 µM, respectively. Kinetic studies showed non competitive or mixed inhibition for HgCl₂ or MeHg with Ki of 4.2 and 13 µM, respectively. The presence of substrate prevented the inhibition indicating that the mercurial binding residue (Cys) is in the substrate binding site. Efflux of carnitine from proteoliposomes was trans-stimulated, not inhibited, by higher concentrations (500 µM) of extraliposomal MeHg and HgCl₂. Differently, no effects on uptake of carnitine were exerted by mercurials present in the internal compartment of the proteoliposomes. The results allowed gaining new insights in the molecular mechanism of inhibition and of mercurial toxicity.     

金属铬离子及抗氧化剂N-乙酰半胱氨酸对人成骨样细胞MG63形态学的影响

目的 研究金属铬离子(Cr6 )对人成骨样细胞MG63形态学的影响以及抗氧化剂N-乙酰半胱氨酸(NAC)对Cr6 作用的拮抗效应.方法 分别用含5μmol/L Cr6 、10μmol/L Cr6 、20μmol/L Cr6 、2mmol/L NAC以及2mmol/L NAC 10μmol/L Cr6 的F12培养基培养人成骨样细胞MG63 24h.其中,2mmol/L NAC 10μmol/L Cr6 组为2mmol/L NAC预处理细胞30min后再用含10μmol/L Cr6 的F12培养基继续培养24 h.另设空白对照组,即用不含Cr6 和NAC的F12培养基培养MG63细胞.倒置相差显微镜和透射电镜分别观察各组细胞形态和细胞超微结构的改变.结果 低浓度Cr6 处理组(5μmol/L Cr6 )MG63细胞伪足回缩,细胞间隙增大,细胞线粒体肿胀,粗面内质网扩张,胞浆出现少量空泡;随着Cr6 浓度的增高(10μmol/L Cr6 ),细胞逐渐变圆,脱壁,细胞内出现大量空泡,细胞核异形性大,染色质固缩,出现假包涵体;高浓度Cr6 处理组(20μmol/L Cr6 )MG63细胞大部分脱壁,细胞超微结构改变更明显,胞膜不完整,细胞出现崩解,可见细胞碎片;NAC单独处理组与NAC Cr6 处理组细胞形态结构与对照组相比均无明显改变.结论 Cr6 对人成骨样细胞MG63形态结构有明显的破坏,且随着Cr6 浓度的增高,破坏程度加剧;NAC可抑制Cr6 引起的MG63细胞形态学改变.