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.     

Effect of experimental thyrotoxicosis on oxidative phosphorylation in rat liver, kidney and brain mitochondria

Coupled phosphorylation was examined in liver, kidney and brain mitochondria from rats made thyrotoxic by injecting repeated doses of triiodothyronine. Liver and kidney mitochondria were maximally affected under these conditions, whereas effects on brain mitochondria were marginal. State-3 respiration rates with succinate decreased considerably in all the tissues, whereas glutamate oxidation increased in liver, but decreased in kidney and brain mitochondria. Oxidation rates of beta-hydroxybutyrate decreased in kidney and brain mitochondria but were not significantly affected in liver mitochondria. Oxidation of ascorbate + TMPD was not affected. State-4 respiration rates increased in general with all the substrates resulting in lowering of the RCI. The ADP/O ratios decreased in a site-specific manner in the mitochondria from the three tissues. The content of cytochrome b decreased in all three tissues, whereas the content of cytochrome c + c1 increased in liver and kidney but decreased in brain. The content of cytochrome a, however, was not significantly affected. Basal and Mg2+-stimulated ATPase activities increased in mitochondria of liver and kidney but not in those of brain; total ATPase activities, however, were not altered. The results imply that excessive levels of thyroid hormones over normal in the serum can lead to impairment of mitochondrial energy metabolism in a tissue-specific manner.     

Effects of severe hemodynamic pressure overload on the properties of canine left ventricular myosin: mechanism by which myosin ATPase activity is lowered during chronic increased hemodynamic stress.

Left ventricular myosin ATPase activity, expressed as enzymatic V_max values, was analyzed in dogs subjected to severe left ventricular pressure overload (aortic stenosis). K⁺ and Ca²⁺ activated myosin ATPase activities in the left ventricle (LV) were significantly depressed (P < .01) in the experimental animals. For normal K⁺ activated myosin the V_max values in micromoles of Pi per mg per min were: right ventricle 2.10; left ventricle, 2.84. For Ca²⁺ activated myosin the V_max values were: right ventricle, 0.77; left ventricle 0.97, when assayed at 37°C. Myosin enzymatic activity in the left ventricle progressively declined following severe aortic banding, reaching a value similar to that observed for normal right ventricular myosin; NH₄⁺ activated left ventricular myosin ATPase activity remained unchanged (7.20 ± 0.4 μmol PO₄/mg.min). Left ventricular myosin from the hearts subject to severe stress simulated normal right ventricular myosin in ATPase activity, chain proportions and degree of calcium binding, Normal left ventricular myosin contained approximately 10% of the myosin protein concentration in the light chains; myosin from the left ventricles of the hemodynamically overloaded hearts contained 20% of the myosin protein concentration in the light chains (P < .001). With only one of the myosin light chains binding calcium left ventricular myosin from the stressed hypertrophied tissue bound approximately 2 mol Ca²⁺ mol^?1 myosin similar to myosin of the normal right ventricle; normal left ventricular myosin bound approximately 1 mol of Ca²⁺ mol^?1 myosin.     

浅析《症因脉治》中脾主运化理论

《症因脉治》是明代医家秦昌遇所撰的临床型医书。脾者,乃仓廪之本,气血生化之源。通过对脾主运化观点的阐释,说明脾主运化的重要性。根据本书特点并结合《症因脉治》中的症、因、脉、治4个方面对脾主运化理论进行探讨,同时结合诸贤附论与临床实践阐明对脾主运化的理解。     

心肾同治方对心力衰竭大鼠心功能的影响

目的：观察心肾同治方对心力衰竭大鼠心功能的影响。方法：60只大鼠制备为心力衰竭模型,随机平均分为心肾同治方低剂量组、中剂量、高剂量组,曲美他嗪组,模型组,假手术组。造模2周后对除假手术对照组之外的大鼠进行药物灌胃8周。分析两种ATP酶活性及浓度、琥珀酸脱氢酶（succinodehydrogenase,SDH）值以及血流动力学参数。结果：与模型组比较,假手术组心肌左室内压上升最大速率及左室收缩压值均有所上升,同时心肌左室内压下降最大速率及左室舒张压表现为显著下降。心肾同治方中剂量组、高剂量组的左室收缩压、左室舒张压、心肌左室内压上升最大速率、心肌左室内压下降最大速率相关指标均接近于曲美他嗪组和假手术组,其中以高剂量组的改善尤为明显。对大鼠中药干预治疗后,实验数据显示其心肌Na＋-K＋ATP酶及Ca2＋-Mg2＋ATP酶和SDH的活力指标低于假手术组相关指标,但较模型组大鼠的指标有明显的提升。随着中药心肾同治方剂量的增加,心肌Na＋-K＋ATP酶、Ca2＋-Mg2＋ATP酶、SDH活力也逐渐增强;心肾同治方高剂量与曲美他嗪干预大鼠后的指标数据基本趋同。结论：心肾同治方在改善大鼠心力衰竭及提高其心功能的过程中,主要机制为：增加心肌Na＋-K＋ATP酶及Ca2＋-Mg2＋ATP酶分泌,提升SDH活力,改善心力衰竭大鼠血流动力学参数。     

Toxic trace elements at gastrointestinal level

Many trace elements are considered essential [iron (Fe), zinc (Zn), copper (Cu)], whereas others may be harmful [lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As)], depending on their concentration and chemical form. In most cases, the diet is the main pathway by which they enter our organism. The presence of toxic trace elements in food has been known for a long time, and many of the food matrices that carry them have been identified. This has led to the appearance of legislation and recommendations concerning consumption. Given that the main route of exposure is oral, passage through the gastrointestinal tract plays a fundamental role in their entry into the organism, where they exert their toxic effect. Although the digestive system can be considered to be of crucial importance in their toxicity, in most cases we do not know the events that occur during the passage of these elements through the gastrointestinal tract and of ascertaining whether they may have some kind of toxic effect on it. The aim of this review is to summarize available information on this subject, concentrating on the toxic trace elements that are of greatest interest for organizations concerned with food safety and health: Pb, Cd, Hg and As.     

Imbalance of plasma membrane ion leak and pump relationship as a new aetiological basis of certain disease states

The basis for life is the ability of the cell to maintain ion gradients across biological membranes. Such gradients are created by specific membrane-bound ion pumps [adenosine triphosphatases (ATPases)]. According to physicochemical rules passive forces equilibrate (dissipate) ion gradients. The cholesterol/phospholipid ratio of the membrane and the degree of saturation of phospholipid fatty acids are important factors for membrane molecular order and herewith a determinant of the degree of non-specific membrane leakiness. Other operative principles, i.e. specific ion channels can be opened and closed according to mechanisms that are specific to the cell. Certain compounds called ionophores can be integrated in the plasma membrane and permit specific inorganic ions to pass. Irrespective of which mechanism ions leak across the plasma membrane the homeostasis may be kept by increasing ion pumping (ATPase activity) in an attempt to restore the physiological ion gradient. The energy source for this work seems to be glycolytically derived ATP formation. Thus an increase in ion pumping is reflected by increased ATP hydrolysis and rate of glycolysis. This can be measured as an accumulation of breakdown products of ATP and end-products of anaerobic glycolysis (lactate). In certain disease entities, the balance between ATP formation and ion pumping may be disordered resulting in a decrease in inter alia (i.a.) cellular energy charge, and an increase in lactate formation and catabolites of adenylates. Cardiac syndrome X is proposed to be due to an excessive leakage of potassium ions, leading to electrocardiographic (ECG) changes, abnormal Tl-scintigraphy of the heart and anginal pain (induced by adenosine). Cocksackie B3 infections, a common agent in myocarditis might also induce an ionophore-like effect. Moreover, Alzheimer's disease is characterized by the formation of extracellular amyloid deposits in the brain of patients. Perturbation of cellular membranes by the amyloid peptide during the development of Alzheimer's disease is one of several mechanisms proposed to account for the toxicity of this peptide on neuronal membranes. We have studied the effects of the peptide and fragments thereof on 45Ca2+-uptake in human erythrocytes and the energetic consequences. Treatment of erythrocytes with the beta 1-40 peptide, results in qualitatively similar nucleotide pattern and decrease of energy charge as the treatment with Ca2+-ionophore A23187. Finally, in recent studies we have revealed and published in this journal that a rare condition, Tarui's disease or glycogenosis type VII, primarily associated with a defect M-subunit of phosphofructokinase, demonstrates as a cophenomenon an increased leak of Ca2+ into erythrocytes.     

Comparative Mass Spectrometric Analyses of Enamel Matrix Proteins from Five Species Suggest a Common Pathway of Post-Secretory Proeteolytic Processing

A tartrate-resistant, iron-activated and vanadate-sensitive nucleotide tri- and diphosphatase has been purified from rat bone. The purified enzyme (1,400-fold, 45% yield) has an Mr on SDS-PAGE of 30,000 Da. Hydrodynamic properties include a Stokes radius of 24Å, a sedimentation coefficient of 3.2 S and a partial specific volume of 0.748 ml/g. The calculated Mr from hydrodynamic data is 32,000 and the enzyme binds 4 mol Triton X-100/mol enzyme. Substrate specificity studies demonstrate that the enzyme is active against nucleotide tri- and diphosphates and phosphotyrosine, but not against phosphoserine or phosphothreonine. Based on the purification profile and enzyme histochemistry, showing labelling of fewer mononuclear cells using ATP compared to conventional acid phosphatase substrates, it is suggested that the acid ATPase constitutes a unique form in the family of tartrate-resistant acid phosphatases and may thus have the potential as a marker for osteoclast ontogeny and function.