Uracil in DNA: consequences for carcinogenesis and chemotherapy

The synthesis of thymidylate (TMP) occupies a convergence of two critical metabolic pathways: folate metabolism and pyrimidine biosynthesis. Thymidylate is formed from deoxyuridylate (dUMP) using N(5),N(10)-methylene tetrahydrofolate. The metabolic relationship between dUMP, TMP, and folate has been the subject of cancer research from prevention to chemotherapy. Thymidylate stress is induced by nutritional deficiency of folic acid, defects in folate metabolism, and by antifolate and fluoropyrimidine chemotherapeutics. Both classes of chemotherapeutics remain mainstay treatments against solid tumors. Because of the close relationship between dUMP and TMP, thymidylate stress is associated with increased incorporation of uracil into DNA. Genomic uracil is removed by uracil DNA glycosylases of base excision repair (BER). Unfortunately, BER is apparently problematic during thymidylate stress. Because BER requires a DNA resynthesis step, elevated dUTP causes reintroduction of genomic uracil. BER strand break intermediates are clastogenic if not repaired. Thus, BER during thymidylate stress appears to cause genome instability, yet might also contribute to the mechanism of action for antifolates and fluoropyrimidines. However, the precise roles of BER and its components during thymidylate stress remain unclear. In particular, links between BER and downstream events remain poorly defined, including damage signaling pathways and homologous recombination (HR). Evidence is growing that HR responds to persistent BER strand break intermediates and DNA damage signaling pathways mediate cross talk between BER and HR. Examination of crosstalk among BER, HR, and damage signaling may shed light on decades of investigation and provide insight for development of novel chemopreventive and chemotherapeutic approaches.     

Toxicity evaluation of some traditional African spices on breast cancer cells and isolated rat hepatic mitochondria

Background

Fagara leprieuri (FL), Fagara xanthoxyloïdes (FX), Mondia whitei (MW) and Xylopia aethiopica (XA) are used in many African countries as food spices or in traditional medicine to treat several maladies. In this work, we (a) investigate whether the crude spice extracts present selective cytotoxicity for breast cancer cell lines and (b) investigate whether the same extracts affect the bioenergetics and calcium susceptibility of isolated liver mitochondrial fractions.

Results

All extracts were cytotoxic to the cell lines studied, with the exception of MW, which was less toxic for a normal cell line. Interestingly, some of the extracts did not depolarize mitochondria in intact breast cancer MCF-7 cells, although this effect was observed in a normal breast cancer cell line (MCF-12A). All extracts increased hepatic mitochondrial state 2/4 respiration and decreased the respiratory control ratio and the transmembrane electric potential. Also, the extracts induced the mitochondrial permeability transition (MPT).

Conclusions

Mitochondrial toxicity may be part of the mechanism by which the spices tested cause inhibition of proliferation and death in the cell lines tested. This study also warrants caution in the excessive use of these spices for human consumption.     

脊柱侧弯患者椎旁肌组织单体的放射性核素衍射研究和肌短缩蛋白的生物化学特性观察

目的采用椎旁肌组织单体的放射性核素衍射和肌短缩蛋白的生化特性分析法研究KingⅡ～Ⅲ型脊柱侧凸患者椎旁肌纤维组织结构畸形变的程度以及形变机制。方法12例KingⅡ～Ⅲ型脊柱侧凸患者,男3例,女9例：年龄13岁～15岁：畸形顶点的凸侧和凹侧椎旁肌标本离体后立即被固定在其在体内的延展状态（长度）。将标本平均分成两组：一组标本采用不同投照时间放射性同位素衍射成像观察,另一组标本采用OPHCKa法测定磷含量,和双次放射线折光法观察肌球蛋白和肌动蛋白。常规标本烘干,固定,胸椎脊柱的楔形截骨和椎体截骨或髓核挖出术中通过开放的路径获得的标本,每个凸侧和凹侧顶点各3个节段,每个节段3～4个标本,每一个标本获得连贯性的6块切片,12例患者,共972张切片。结果采用放射性同位素衍射法观察在11份椎旁肌标本显示出肌初原纤维结构的稀疏PMYa衍射区,只在其中的一份标本中没有观察到初纤维结构成像区：大角度放射性观察,能够区分不同放射制剂的折光力强度的不同,以及它们在多肽键上的定位特点。由于酶的缺乏,而表现出不同强度放射制剂折光范围的增宽（在角度范围内）,椎旁肌脱水模式实验显示,其中一束分散射线的反射长度为9．8A。受损的椎旁肌组织中三磷酸腺苷氮化肌球蛋白的活性明显下降,凸侧和凹侧椎旁肌的三磷酸腺苷一氮化受抑制现象存在明显差别。凸侧的三磷酸腺苷一氮化的活性较凹侧低25％～30％。结论成对取材的凸凹侧椎旁肌标本中没有系统性的差别,而是受到脊柱畸形的牵拉或压迫的影响而改变的特征,短缩越明显的肌肉组织,它的定向力障碍角的特征越明显,说明脊柱侧凸疾病导致患者椎旁肌发生深度的营养不良性改变,并整个过程伴随蛋白质的化学活性的破坏。这些病理变化提示脊柱侧凸疾病能够引起椎旁肌继发病变。     

Animal models to test drugs with potential antidiabetic activity

Although medicinal plants have been historically used for diabetes treatment throughout the world, few of them have been validated by scientific criteria. Recently, a large diversity of animal models has been developed to better understand the pathogenesis of diabetes mellitus and new drugs have been introduced in the market to treat this disease. The aim of this work was to review the available animal models of diabetes and some in vitro models which have been used as tools to investigate the mechanism of action of drugs with potential antidiabetic properties. In addition, a MEDLINE/PUBMED search for articles on natural products, pancreatectomy and diabetes mellitus treatment published between 1996 and 2006 was done. In the majority of the studies, natural products mainly derived from plants have been tested in diabetes models induced by chemical agents. This review contributes to the researcher in the ethnopharmacology field to designs new strategies for the development of novel drugs to treat this serious condition that constitutes a global public health.     

Understanding peroral absorption: regulatory aspects and contemporary approaches to tackling solubility and permeability hurdles

Oral drug absorption is a process influenced by the physicochemical and biopharmaceutical properties of the drug and its inter-relationship with the gastrointestinal tract. Drug solubility, dissolution and permeability across intestinal barrier are the key parameters controlling absorption. This review provides an overview of the factors that affect drug absorption and the classification of a drug on the basis of solubility and permeability. The biopharmaceutical classification system (BCS) was introduced in early 90׳s and is a regulatory tool used to predict bioavailability problems associated with a new entity, thereby helping in the development of a drug product. Strategies to combat solubility and permeability issues are also discussed.     

注射用辅酶A、三磷酸腺苷二钠及肌苷注射液配伍稳定性考察

摘 要 目的：考察注射用辅酶A、三磷酸腺苷二钠注射液及肌苷注射液在5%葡萄糖注射液中的配伍稳定性。 方法: 在室温条件下,模拟临床用药方法,配制3种药物与5%葡萄糖注射液的配伍溶液,采用HPLC法测定辅酶A、三磷酸腺苷二钠和肌苷的含量及有关物质变化情况,同时考察配伍溶液的外观、pH和不溶性微粒的变化情况。结果: 室温下4 h内,配伍溶液的外观、pH、不溶性微粒、各药物含量及有关物质均无明显变化;24 h后,配伍溶液出现浑浊絮状物,pH、不溶性微粒、含量及有关物质均明显发生变化。结论:在室温条件下,注射用辅酶A、三磷酸腺苷二钠注射液及肌苷注射液在5%葡萄糖注射液中的配伍溶液应于4 h内使用完。     

Cardioprotective effects of sinomenine in myocardial ischemia/reperfusion injury in a rat model

BackgroundIschemia reperfusion (I/R) play an imperative role in the expansion of cardiovascular disease. Sinomenine (SM) has been exhibited to possess antioxidant, anticancer, anti-inflammatory, antiviral and anticarcinogenic properties. The aim of the study was scrutinized the cardioprotective effect of SM against I/R injury in rat.MethodsRat were randomly divided into normal control (NC), I/R control and I/R + SM (5, 10 and 20 mg/kg), respectively. Ventricular arrhythmias, body weight and heart weight were estimated. Antioxidant, inflammatory cytokines, inflammatory mediators and plasmin system indicator were accessed.ResultsPre-treated SM group rats exhibited the reduction in the duration and incidence of ventricular fibrillation, ventricular ectopic beat (VEB) and ventricular tachycardia along with suppression of arrhythmia score during the ischemia (30 and 120 min). SM treated rats significantly (P < 0.001) altered the level of antioxidant parameters. SM treatment significantly (P < 0.001) repressed the level of creatine kinase MB (CK-MB), creatine kinase (CK) and troponin I (Tnl). SM treated rats significantly (P < 0.001) repressed the tissue factor (TF), thromboxane B2 (TXB2), plasminogen activator inhibitor 1 (PAI-1) and plasma fibrinogen (Fbg) and inflammatory cytokines and inflammatory mediators.ConclusionOur result clearly indicated that SM plays anti-arrhythmia effect in I/R injury in the rats via alteration of oxidative stress and inflammatory reaction.     

ATP通过P2受体调节大鼠近端结肠纵行肌的舒张与收缩反应(英文)

目的腺苷三磷酸(ATP)对大鼠离体远端结肠纵行肌运动的影响已明确,对近端结肠纵行肌的影响可能不同,但未有报告,为此对此进行观察并探讨其受体机制。方法观察静息张力时或预收缩时0.1μmol·L-1～1mmol·L-1ATP和1～100μmol·L-1腺苷对大鼠近端结肠纵行肌的抑制和兴奋作用。结果在静息张力下,1μmol·L-1～1mmol·L-1ATP对大鼠近端结肠纵行肌产生3种效应,即抑制自发性收缩反应,一过性轻度降低基础张力(0.05～0.08g),随后产生浓度依赖性收缩反应(0.04～0.44g)。0.1μmol·L-1河豚毒素不影响ATP的上述作用。在静息张力下,1～100μmol·L-1腺苷对近端结肠纵行肌未产生明显的收缩反应。应用5羟色胺(5HT)或乙酰胆碱(ACh)预收缩标本时,1μmol·L-1～1mmol·L-1ATP产生明显的浓度依赖性舒张反应(23.2%～94.6%,5HT预收缩;24.8%～92.4%,ACh预收缩),而腺苷引起的舒张反应明显小于ATP。结论在大鼠离体近端结肠纵行肌,ATP主要通过嘌呤嘧啶(P)2受体介导收缩反应,部分通过P1受体介导舒张反应。     

Rociletinib (CO-1686) enhanced the efficacy of chemotherapeutic agents in ABCG2-overexpressing cancer cells in vitro and in vivo

Overexpression of adenosine triphosphate (ATP)-binding cassette subfamily G member 2 (ABCG2) in cancer cells is known to cause multidrug resistance (MDR), which severely limits the clinical efficacy of chemotherapy. Currently, there is no FDA-approved MDR modulator for clinical use. In this study, rociletinib (CO-1686), a mutant-selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), was found to significantly improve the efficacy of ABCG2 substrate chemotherapeutic agents in the transporter-overexpressing cancer cells in vitro and in MDR tumor xenografts in nude mice, without incurring additional toxicity. Mechanistic studies revealed that in ABCG2-overexpressing cancer cells, rociletinib inhibited ABCG2-mediated drug efflux and increased intracellular accumulation of ABCG2 probe substrates. Moreover, rociletinib, inhibited the ATPase activity, and competed with [¹²⁵I] iodoarylazidoprazosin (IAAP) photolabeling of ABCG2. However, ABCG2 expression at mRNA and protein levels was not altered in the ABCG2-overexpressing cells after treatment with rociletinib. In addition, rociletinib did not inhibit EGFR downstream signaling and phosphorylation of protein kinase B (AKT) and extracellular signal-regulated kinase (ERK). Our results collectively showed that rociletinib reversed ABCG2-mediated MDR by inhibiting ABCG2 efflux function, thus increasing the cellular accumulation of the transporter substrate anticancer drugs. The findings advocated the combination use of rociletinib and other chemotherapeutic drugs in cancer patients with ABCG2-overexpressing MDR tumors.     

腺苷三磷酸-氯化镁对大鼠肾脏缺血再灌注损伤的保护作用

[目的 ]通过观察肾脏组织中钠钾 腺苷三磷酸酶和钙 腺苷三磷酸酶活性和病理组织学变化 ,探讨腺苷三磷酸 氯化镁对肾脏缺血再灌注损伤的保护作用机理 .[方法 ]将大鼠随机分为 3组 ,分别用生物化学方法观察再灌注 0h ,2h ,6h的钠钾 腺苷三磷酸酶和钙 腺苷三磷酸酶活性的变化以及组织病理学变化 .[结果 ]腺苷三磷酸 氯化镁组和对照组肾小管上皮细胞变性、坏死数低于缺血再灌注组 ,而腺苷三磷酸 氯化镁组和对照组之间无显著性差异 .钠钾 腺苷三磷酸酶和钙 腺苷三磷酸酶的活性在腺苷三磷酸 氯化镁组和对照组之间无显著性差异 ,但两组均高于缺血再灌注组 .[结论 ]腺苷三磷酸 氯化镁对大鼠肾脏缺血再灌注损伤有保护作用 .