Tamoxifen induces ultrastructural alterations in membranes of Bacillus Stearothermophilus

Tamoxifen (TAM), a non-steroid antiestrogen, is the mostly used drug for chemotherapy and chemoprevention of breast cancer. However, the mechanisms by which TAM inhibits cell proliferation in breast cancer are not fully understood. TAM strongly incorporates in biomembranes and a variety of effects have been assigned to biophysical and biochemical interactions with membranes. Therefore, a better understanding of the physicochemical basis of interaction of TAM with biomembranes is essential to elucidate the molecular mechanisms of action. A strain of Bacillus stearothermophilus has been used as a model to clarify the interaction of TAM with the cell membrane. TAM effects on the ultrastructure of membranes of this bacterium were evaluated by electron microscopy. Important ultrastructural alterations were observed in B. stearothermophilus treated with TAM, namely change in the geometry of the membrane profile from asymmetric to symmetric, disaggregation of ribosomes, coagulation of the cytoplasmic matrix, occurrence of mesossomes, appearance of fractures in membranes and the alteration of the ultrastructure of cell wall. These ultrastructural alterations confirm that TAM is a membrane-active drug and that membrane damage may be involved in molecular mechanisms of cell death induced by this drug.     

Molecular mechanisms of the metabolite 4-hydroxytamoxifen of the anticancer drug tamoxifen: use of a model microorganism

A strain of the thermophilic eubacterium Bacillus stearothermophilus was used as a model system to identify membrane mediated cytotoxic effects of 4-hydroxytamoxifen, following previous studies with tamoxifen. With this experimental approach we attempted to further clarify tamoxifen and 4-hydroxytamoxifen membrane interactions often evoked as responsible for their multiple cellular effects. Bacterial growth and the oxygen consumption rate provided quantitative data of the cytotoxic action of hydroxytamoxifen. The effects of hydroxytamoxifen on the physical properties of bacterial lipid membrane preparations were also evaluated by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. Cultures of B. stearothermophilus grown in a complex medium containing hydroxytamoxifen in the concentration range of 1 to 7 μ exhibited progressively longer lag adapting periods, decreased specific growth rates and lower growth yields, as compared to control cultures. Hydroxytamoxifen also affected the electron redox flow of B. stearothermophilus protoplasts and induced significant perturbation of the structural order of bacterial lipid dispersions. We concluded that the bacterial model provides useful information about the nature and repercussion of membrane physical interactions of this lipophilic drug, on the basis of an easy and economic methodology.     

Use of the microorganism Bacillus stearothermophilus as a model to evaluate toxicity of the lipophilic environmental pollutant endosulfan.

Microorganisms are very powerful tools for the supply of information about the toxic effects of lipophilic compounds, since an impairment of cell growth usually occurs as a result of perturbations related, in most cases, with the partition of toxicants in membranes. The thermophilic eubacterium Bacillus stearothermophilus has been used as a model system to identify - and β-endosulfan interactions with the membrane possibly related with the insecticide toxicity. Two approaches have been pursued: (a) bacterial growth is followed and the effects of endosulfan isomers determined; (b) biophysical studies with the fluorescent fluidity probe 1,6-diphenyl-1,3,5-hexatriene (DPH) were performed to assess the effects of - and β-endosulfan on the organization of the membrane lipid bilayer. The effects on growth were quantitatively evaluated by determination of growth parameters, namely the lag phase, the specific growth rate and the cell density reached by cultures in the stationary phase. Growth inhibition by and β-endosulfan dependent on the concentration is diminished or removed by the addition of 2.5 m Ca²⁺ to bacterial cultures. Fluorescence DPH polarization consistently showed opposite effects of Ca²⁺ and - and β-endosulfan on the physical state of bacterial polar lipid dispersions.     

Tamoxifen induces hepatocellular carcinoma in rat liver: A 1-year study with two antiestrogens

The effects of equimolar doses of the triphenylethylene antiestrogens tamoxifen and toremifene on female Sprague-Dawley rat liver were studied in a 52-week toxicity study which included a 13-week recovery period. Liver tumors were found in four out of five rats at the highest dose level of tamoxifen (45 mg/kg per day) after 52 weeks of dosing, and these appeared to be hepatocellular carcinomas in three rats. After the 13-week recovery period all surviving rats in the highest tamoxifen dose group had large liver tumors (diameter up to 2 cm) which appeared to be hepatocellular carcinomas in five out of six rats. No tumor was observed in the toremifene-treated rats (48 mg/kg per day) either after 52 weeks of dosing or after the recovery period. Electron microscopic morphometric analysis after 52 weeks of dosing revealed that at the tamoxifen high dose level, the volume densities of the peroxisomes, mitochondria, and residual bodies were elevated in the nonneoplastic hepatocytes of the rats. In the neoplastic hepatocytes of the tamoxifen-treated rats the volume density of nuclei was slightly elevated. The slight proliferation of peroxisomes and mitochondria might be related to tumor development in the tamoxifen treated rats.     

嗜热脂肪芽胞杆菌生产1，6—二磷酸果糖的研究

研究了嗜热脂肪芽胞杆菌发酵生产1，6-二磷酸果糖（FDP）的工艺条件和工艺特点，采用活化培养工艺，改变菌体细胞透性和生理状态，获得高产率的FDP发酵液（产量为60mg/ml)。本法生产FDP具有副产物少，转化率高，发酵稳定的优点。     

Enzymatically active subunits of Bacillus stearothermophilus enolase bound to Sepharose

The octameric enolase from Bacillus stearothermophilus was immobilized onto Sepharose 4B activated by the cyanogen bromide reaction under conditions for achieving essentially a single-point attachment. The immobilized enzyme was dissociated with guanidine hydrochloride to yield bound monomeric enolase. The Sepharose-bound subunit regained activity upon removal of the denaturant. It was also possible to rehybridize immobilized monomers to native octamers. Of note, the thermal stability of the immobilized enolase subunit does not appreciably differ from that of the parent soluble octameric enzyme. Thus, these results indicate that single subunits of thermophilic enolase are active and that oligomerization is not a prerequisite for the enzymic activity as well as for thermal stability.     

固定化嗜热脂肪芽孢杆菌生产1,6-二磷酸果糖的研究

采用卡拉胶包埋嗜热脂肪芽孢杆菌，制成块状固定化细胞，对固定化细胞包埋方法及其用于生产1，6－二磷酸果糖（FDP）的工艺条件作了探索，在固定化细胞包埋前，包埋后及用于生产FDP 10批次后采用活化培养工艺，均可提高固定化细胞生产FDP的能力，转化培养液中的FDP产量达到40－65mg/ml，固定化细胞用于生产FDP的批次可达到20次左右。     

三苯氧胺对晚期大肠癌多药耐药逆转作用研究

目的 探讨三苯氧胺对多药耐药大肠癌患者外周血淋巴细胞膜P-糖蛋白含量的影响及对FOLFOX4方案化疗效果的影响.方法 选择淋巴细胞膜 P-gp表达阳性大肠癌患者62 例,随机分为三苯氧胺组 (33 例) 和单纯化疗组 (29 例).应用流式细胞免疫学方法对两组患者治疗前后淋巴细胞膜 P-gp含量进行定量研究,观察化疗效果.结果 三苯氧胺能显著降低外周血淋巴细胞膜P-gp 含量(P< 0.01),提高P -g p 转阴率(P< 0.01),显著提高化疗总有效率(P< 0.01)、中位生存期(P< 0.05)和1年生存率(P< 0.01).结论 三苯氧胺能有效逆转晚期大肠癌多药耐药,提高化疗效果.     

The Distribution and Metabolism of 14C-Labelled Tamoxifen in Spayed Female Mice

Abstract: The distribution and metabolism of ¹⁴C-tamoxifen (a non-steroidal triaryl ethylene anti-oestrogen) have been investigated in ovarieectomized mice. The autoradiograms showed accumulation of radioactivity in the liver and the bile as an indication of an excretory pathway, but a rapid and high accumulation was also seen in the lung and the adrenals, organs normally not considered as target organs for tamoxifen. The liver and sebaceous glands could be detected on the autoradiograms up to fourteen days after a single intravenous dose. However, in most organs the amount of retained radioactivity was very low after 24 hours. By using the autoradiograms as a guideline a metabolic study was performed. High concentrations of unmetabolized tamoxifen was detected in the lung and the adrenals as well as in the pancreas. Relatively high amounts of a compound tentatively identified as 4-hydroxy-tamoxifen were present in the pancreas and the liver and there were also indications for the presence of N-desmethyl-tamoxifen in these tissues. These metabolites are considered to possess anti-oestrogenic activity.     

他莫昔芬与托瑞米芬治疗乳腺癌的经济学分析

目的:评估2种内分泌治疗乳腺癌药的经济学价值。方法:130例乳腺癌患者按照不同的治疗方案分为他莫昔芬组(TAM组)80例,托瑞米芬组(TOR组)50例,观察2组治疗方案的疗效及安全性,运用药物经济学的成本-效果分析方法进行评价。结果:TAM、TOR组治疗药品成本分别为90.30、809.52元,有效率分别为88.75%、94%。结论:从药物经济学角度评估,TAM方案优于TOR方案。     

三苯氧胺逆转卵巢癌细胞株多药耐药性的研究

目的探讨三苯氧胺(TAM)逆转卵巢癌细胞株的耐药性和逆转机制。方法应用ATP-TCA法检测细胞株的耐药性及TAM的逆转效果,应用流式细胞仪检测TAM对罗丹明123(Rh123)在细胞内积聚和外排的影响,应用免疫荧光技术定量测定TAM对P糖蛋白表达的影响。结果TAM能增加阿霉素对耐药株的细胞毒性作用,能增加耐药株细胞内Rh123的积聚,减少其外排,而对P糖蛋白的表达没有影响。结论TAM能部分逆转卵巢癌细胞株的耐药性,其强度与维拉帕米相当,其作用机理是抑制P糖蛋白的功能,而对其表达水平没有影响。     

Ultrastructural alterations in Trypanosoma (Schizotrypanum) cruzi induced by Delta(24(25)) sterol methyl transferase inhibitors and their combinations with ketoconazole

We report the ultrastructural alterations induced on the proliferative stages of Trypanosoma cruzi, the causative agent of Chagas' disease, by two Δ²⁴⁽²⁵⁾ sterol methyl transferase (24(25)-SMT) inhibitors, 22,26-azasterol and 24(R,S),25-epiminolanosterol. Both compounds are sterol biosynthesis inhibitors which had previously been shown to be potent growth inhibitors and whose effects are potentiated by the C14a demethylase inhibitor, ketoconazole. Epimastigotes treated with the minimal growth inhibitory concentration of 22,26-azasterol (10 μM) for 144 h, which were completely depleted of endogenous 4-desmethyl sterols and accumulated 24-desalkyl sterols, showed the appearance of electron-dense granules, mitochondrial swelling and intense vacuolization. At high concentration (≥ 30 μM) the sterol analog induced gross alterations in the organization of chromatin and rapid cell lysis. The treatment of epimastigotes with 24-(R,S),25-epiminolanosterol induced, at low concentrations, (1 μM) alterations similar to those observed with 22,26-azasterol but additionally, modifications of the kinetoplast were observed. Higher concentrations (≥ 3 μM) induced total lysis. The combination of both sterol analogs with ketoconazole, at sub-optimal concentrations, induced the same alterations as 22,26-azasterol 10 μM or epiminolanosterol 1 μM. The results confirm the conclusions of previous studies which indicated that one important cytotoxic effects of sterol biosynthesis inhibitors in this organism is the alteration of the parasite's mitochondrial system.     

毛细管气相色谱法测定枸橼酸他莫昔芬原料药中有机溶剂的残留量

目的：建立毛细管气相色谱法测定枸橼酸他莫昔芬原料药中有机溶剂残留量的方法。方法：色谱柱：DB-624（30m&#215;0．53mm&#215;3μm）弹性石英毛细管柱；柱温采用程序升温：起始40℃，保持13min，20℃／min升至230℃，保持15min；氢火焰离子化检测器，载气：氮气，流速：3．0ml&#183;min-1，进样口温度：140℃；检测器温度：250℃；分流比为5：1。结果：甲醇、丙酮、乙酸乙酯、四氢呋喃及甲苯浓度的线性均在各自浓度范围内，线性关系良好。平均回收率为：95．1％～98．1％。结论：方法操作简便、结果准确可靠，可以用于枸橼酸他莫昔芬原料药中有机溶剂残留的测定。     

他莫昔芬对高血压脑出血模型大鼠早期脑损伤的神经保护作用研究

目的:研究他莫昔芬对高血压脑出血模型大鼠早期脑损伤的神经保护作用。方法:取大鼠随机分为假手术组、模型组和高、中、低剂量实验(他莫昔芬10、5、2.5 mg/kg)组,每组48只,除假手术组外其余各组大鼠建立高血压脑出血模型,建模后分别腹腔注射相应药物,每24 h给药1次。考察给药后4、8、12、24、72 h和7 d时各组大鼠血肿周围脑组织中Fas相关死亡域蛋白(FADD)的阳性细胞数、凋亡细胞数、脑水肿情况以及脑组织形态学变化情况。结果:与假手术组比较,其余各组大鼠不同时间的脑组织中FADD阳性细胞数、凋亡细胞数、脑水肿比例均明显增加(P<0.05);与模型组比较,低剂量实验组大鼠的FADD阳性细胞数(给药后24、72 h)、凋亡细胞数(给药后24、72 h和7 d)和脑组织含水量(给药后72 h)均明显减少(P<0.05),中、高剂量实验组大鼠的FADD阳性细胞数(给药后8、12、24、72 h)、凋亡细胞数(给药后12、24、72 h和7 d)和脑组织含水量(给药后12、24、72 h和7 d)均明显减少(P<0.05),各剂量实验组大鼠血肿周围组织水肿范围变小、程度减轻,炎症细胞的浸润减轻,固缩细胞减少,肿胀细胞增多,细胞周围间隙变小,且均呈剂量依赖性。结论:他莫昔芬能够呈剂量依赖性地抑制高血压脑出血模型大鼠的FADD阳性细胞表达,减少脑组织细胞的凋亡,同时减轻脑出血后的脑水肿,发挥显著的神经保护作用。     

Comparison of cytopathological changes induced by mercury chloride exposure in renal cell lines (VERO and BGM)

The response to mercury chloride was assessed in two cell lines of renal origin, determining the range of toxic concentrations by Neutral Red assay after 24-h of exposure. Morphological changes in the Buffalo Green Monkey (BGM) and VERO cell lines after exposure to subcytotoxic doses (0.045 and 0.038 mM, respectively) equivalent to EC10 (effective concentrations 10%) of mercury chloride were evaluated at the structural and ultrastructural level by optic, transmission and scanning microscopy. Using transmission electron microscopy, the most notable findings in treated cells were the presence of intracytoplasmic inclusion bodies and apoptotic bodies. Scanning microscopy pointed to a cell with a disrupted perinuclear region and a decreased number of surface microvilli. Similar alterations in both in vivo and in vitro experiments have been described by other authors. We conclude that BGM and VERO renal cell lines can be considered as useful tools for toxicological studies involving mercury chloride.     

The Role of Flavin-Containing Monooxygenase (FMO) in the Metabolism of Tamoxifen and Other Tertiary Amines

Tamoxifen is utilized in breast cancer therapy and in chemoprevention. Tamoxifen may enhance risk for other neoplasias, especially endometrial cancer. The risk:benefit depends on the rate of metabolic activation versus detoxication. Cytochrome P450-dependent α-hydroxylation, followed by sulfonation, represents a metabolic activation pathway, producing products capable of covalent DNA adduction. In contrast, tamoxifen N-oxygenation represents a detoxication pathway, with the caveat that N-oxides can be reduced back to the parent amines. The N-oxygenation pathway will be the focus for this review. Dr. David Kupfer pioneered studies on cytochrome P450 and flavin-containing monooxygenase (FMO) tamoxifen metabolism. We collaborated with Dr. Kupfer's laboratory and recently determined that the low level of tamoxifen N-oxide production in human liver microsomes may be explained by the kinetics of FMO1 versus FMO3.     

Indomethacin induces free radical-mediated changes in renal brush border membranes

Nonsteroidal anti-inflammatory drugs (NSAIDs) are used extensively in clinical medicine. One disadvantage of their use, however, is the occurrence of adverse effects in the kidneys. The side effects produced in this organ have been classically attributed to the inhibitory effect of these drugs on the activity of cyclooxygenase, a key enzyme in prostaglandin synthesis. Our earlier work with indomethacin, a commonly used NSAID, has shown that oxidative stress and mitochondrial dysfunction occur in the kidney in response to the drug. In view of this, this study looked into the effect of indomethacin on brush border membranes (BBM) from the kidney, as these biomembranes are prime targets of oxygen free radicals. Rats, fasted overnight, were dosed with indomethacin (20 mg/kg) by gavage and sacrificed 24 h later. BBM were isolated from the kidneys by polyethylene glycol precipitation. It was found that there was an increase in levels of products of peroxidation and a fall in the level of alpha-tocopherol in the BBM from indomethacin-dosed rats. These BBM also exhibited impaired glucose transport. The lipid composition of the membranes was also found to be altered. Alterations in lipids were associated with up-regulation of phospholipase A₂. Pretreatment with L-arginine, a nitric oxide donor, protected against these effects of indomethacin. Thus, this study suggests that indomethacin induces impairment in structure and function of BBM in the kidney, with these effects possibly mediated by free radicals and activation of phospholipases. We postulate that such alterations may be important in the pathogenesis of NSAID-induced nephropathy.     

Tamoxifen effects on respiratory chain complexes and creatine kinase activities in an animal model of mania

The present study aimed to investigate the effects of tamoxifen (TMX) on locomotor behavior and on the activities of mitochondrial respiratory chain complexes and creatine kinase (CK) in the brain of rats subjected to an animal model of mania induced by d-amphetamine (d-AMPH)—reversion and prevention protocols. The d-AMPH administration increased locomotor activity in saline-treated rats under prevention and reversion treatment; furthermore, there was evident reduction in the locomotion in the d-amphetamine group treated with TMX. d-AMPH significantly decreased the activity of mitochondrial respiratory chain complexes in saline-treated rats in prefrontal cortex, hippocampus, striatum and amygdala in both prevention and reversion treatment. Depending on the cerebral area and evaluated complex, TMX was able to prevent and reverse this impairment. A decrease in CK activity was also verified in the brain of rats when d-AMPH was administrated in both experiments; the administration of TMX reversed but not prevented the decrease in CK activity induced by d-AMPH. The present study demonstrated that TMX reversed and prevented the alterations in behavioral and energy metabolism induced by d-AMPH (alterations were also observed in bipolar disorder), reinforcing the need for more studies about inhibitors of PKC as possible targets for new medications in the treatment of bipolar disorder.     

Dapsone hydroxylamine induces premature removal of human erythrocytes by membrane reorganization and antibody binding

BACKGROUND AND PURPOSE

N-hydroxylation of dapsone leads to the formation of the toxic hydroxylamines responsible for the clinical methaemoglobinaemia associated with dapsone therapy. Dapsone has been associated with decreased lifespan of erythrocytes, with consequences such as anaemia and morbidity in patients treated with dapsone for malaria. Here, we investigated how dapsone and/or its hydroxylamine derivative (DDS-NHOH) induced erythrocyte membrane alterations that could lead to premature cell removal.

EXPERIMENTAL APPROACH

Erythrocytes from healthy donors were subjected to incubation with dapsone and DDS-NHOH for varying times and the band 3 protein tyrosine-phosphorylation process, band 3 aggregation, membrane alteration and IgG binding were all examined and compared with erythrocytes from two patients receiving dapsone therapy.

KEY RESULTS

The hydroxylamine derivative, but not dapsone (the parent sulphone) altered membrane protein interactions, leading both to aggregation of band 3 protein and to circulating autologous antibody binding, shown in erythrocytes from patients receiving dapsone therapy. The band 3 tyrosine-phosphorylation process can be used as a diagnostic system to monitor membrane alterations both in vitro, assessing concentration and time-dependent effects of DDS-NHOH treatment, and in vivo, evaluating erythrocytes from dapsone-treated patients, in resting or oxidatively stimulated conditions.

CONCLUSIONS AND IMPLICATIONS

DDS-NHOH-induced alterations of human erythrocytes can be directly monitored in vitro by tyrosine-phosphorylation level and formation of band 3 protein aggregates. The latter, together with antibody-mediated labelling of erythrocytes, also observed after clinical use of dapsone, may lead to shortening of erythrocyte lifespan.     

Vegetative Insecticidal Protein Vip3Aa Is Transported via Membrane Vesicles in Bacillus thuringiensis BMB171

Vegetative insecticidal protein Vip3Aa, secreted by many Bacillus thuringiensis (Bt) strains during the vegetative growth stage, represents the second-generation insecticidal toxin. In recent years, significant progress has been made on its structure and action mechanism. However, how it is translocated across the cytoplasmic membrane into the environment remains a mystery. This work demonstrates that Vip3Aa is not secreted by the General Secretion (Sec) System. To reveal the secretory pathway of Vip3A, we purified the membrane vesicles (MVs) of B. thuringiensis BMB171 and observed by TEM. The size of MVs was determined by the dynamic light scattering method, and their diameter was approximately 40–200 nm, which is consistent with the vesicles in Gram-negative bacteria. Moreover, Vip3A could be detected in the purified MVs by Western blot, and immunoelectron microscopy reveals Vip3A antibody-coated gold particles located in the MVs. After deleting its signal peptide, chitinase B (ChiB) failed to be secreted. However, the recombinant ChiB, whose signal peptide was substituted with the N-terminal 39 amino acids from Vip3A, was secreted successfully through MVs. Thus, this sequence is proposed as the signal region responsible for vesicle transport. Together, our results revealed for the first time that Vip3Aa is transported to the medium via MVs.