Inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis by dietary olive oil and squalene

Epidemiological studies have suggested that frequent olive oil consumption may be a protective factor against lung cancer formation. Squalene, a characteristic compound in olive oil, is an inhibitor of 3- hydroxy-3-methylglutaryl coenzyme A reductase activity and has been proposed to inhibit the farnesylation of ras oncoproteins. The present study investigated the effect of dietary olive oil and squalene in a mouse lung tumorigenesis model. Female A/J mice were fed AIN-76A diets containing 5% corn oil (control), 19.6% olive oil, or 2% squalene starting at 3 weeks before a single dose of 4-(methylnitrosamino)-1-(3- pyridyl)-1-butanone (NNK) (103 mg/kg, i.p.). Animals were maintained on their respective diets throughout the study. At 16 weeks after NNK administration, 100% of the mice in the control group had lung tumors with a tumor multiplicity of 16 tumors per mouse. The olive oil and squalene diets significantly (P < 0.05) decreased the lung tumor multiplicity by 46 and 58%, respectively. The squalene diet significantly (P < 0.05) decreased lung hyperplasia by 70%. In mice fed a diet containing 2% squalene for 3 weeks, the activation of NNK was increased by 1.4- and 2.0-fold in lung and liver microsomes, respectively, but its relationship to the inhibition of carcinogenesis is not clear. These results demonstrate that dietary olive oil and squalene can effectively inhibit NNK-induced lung tumorigenesis.      

毛细管气相色谱法测定复方利福平片中异烟肼和吡嗪酰胺的含量

目的：建立复方利福平片中异烟肼和吡嗪酰胺的含量测定方法。方法：毛细管气相色谱法,以乙酰苯胺为内标,色谱柱为弹性石英毛细管柱２５ｍ ×０ ．３２ｍ ｍ ×０ ．５２μｍ （ＤＢ１） ;柱温１７０ ℃;气化室温度２５０ ℃;检测器温度２５０ ℃;载气为高纯氮。结果：异烟肼和吡嗪酰胺的线性范围分别是０ ．４２６ ～２ ．１３ｍｇｍｌ 和１ ．２３ ～６ ．１３ｍｇｍｌ;平均回收率分别为９９ ．８１ ％ 和９９ ．６３ ％ 。结论：方法简便,快速,准确,可作为该制剂的检测方法。     

长梗绞股蓝的化学成分研究

自长梗绞股蓝( Gynostemma longipes C.Y.Wu )的地上部分分得一个新的三萜皂甙,经化学方法和光谱分析确定其化学结构为19-氧化-3β,20(S),21-三羟基达玛烷-24-烯-3-O-｛[α-L-吡喃鼠李糖基(1→2)][β-D-吡喃木糖基(1→3)]｝α-L-阿拉伯糖甙,命名为长梗绞股蓝皂甙I(gylongiposideI)。     

Enzymes involved in the bioactivation of 4-(methylnitrosamino)-1-(3- pyridyl)-1-butanone in patas monkey lung and liver microsomes

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent tobacco-specific carcinogen in animals. Our previous studies indicated that there are differences between rodents and humans for the enzymes involved in the activation of NNK. To determine if the patas monkey is a better animal model for the activation of NNK in humans, we investigated the metabolism of NNK in patas monkey lung and liver microsomes and characterized the enzymes involved in the activation. In lung microsomes, the formation of 4-oxo-1-(3-pyridyl)-1-butanone (keto aldehyde), 4-(methylnitrosamino)-1-(3-pyridyl-N-oxide)-1-butanone (NNK- N-oxide), 4-hydroxy-1-(3-pyridyl)-1-butanone (keto alcohol), and 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) was observed, displaying apparent Km values of 10.3, 5.4, 4.9, and 902 microM, respectively. NNK metabolism in liver microsomes resulted in the formation of keto aldehyde, keto alcohol, and NNAL, displaying apparent Km values of 8.1, 8.2, and 474 microM, respectively. The low Km values for NNK oxidation in the patas monkey lung and liver microsomes are different from those in human lung and liver microsomes showing Km values of 400-653 microM, although loss of low Km forms from human tissue as a result of disease, surgery or anesthesia cannot be ruled out. Carbon monoxide (90%) significantly inhibited NNK metabolism in the patas monkey lung and liver microsomes by 38-66% and 82-91%, respectively. Nordihydroguaiaretic acid (a lipoxygenase inhibitor) and aspirin (a cyclooxygenase inhibitor) decreased the rate of formation of keto aldehyde and keto alcohol by 10-20 % in the monkey lung microsomes. Alpha-Napthoflavone and coumarin markedly decreased the oxidation of NNK in monkey lung and liver microsomes, suggesting the involvement of P450s 1A and 2A6. An antibody against human P450 2A6 decreased the oxidation of NNK by 12-16% and 22-24% in the patas monkey lung and liver microsomes, respectively. These results are comparable to that obtained with human lung and liver microsomes. Coumarin hydroxylation was observed in the patas monkey lung and liver microsomes at a rate of 16 and 4000 pmol/min/mg protein, respectively, which was 5-fold higher than human lung and liver microsomes, respectively. Immunoblot analysis demonstrated that the P450 2A level in the individual patas monkey liver microsomal sample was 6-fold greater than in an individual human liver microsomal sample. Phenethyl isothiocyanate, an inhibitor of NNK activation in rodents and humans, decreased NNK oxidation in the monkey lung and liver microsomes displaying inhibitor concentration resulting in 50% inhibition of the activity (IC50) values of 0.28-0.8 microM and 4.2-6.8 microM, respectively. The results demonstrate the similarities and differences between species in the metabolic activation of NNK. The patas monkey microsomes appear to more closely resemble human microsomes than mouse or rat enzymes and may better reflect the activation of NNK in humans.      

Correlations of knowledge and preference of medical students for a specialty career: a case-study of youth health care

Background  

Medical students develop interest in a specialty career during medical school based on knowledge and clinical experience of different specialties. How valid this knowledge is and how this knowledge relates to the development of preference for a specialty is not known. We studied their "subjective" knowledge of a specialty (students' reported knowledge) with "objective" knowledge of it (students actual knowledge as compared to reports of specialists) and their preference for this specialty at different stages of education, and used youth health care as a case study.     

A novel, orally active LPA1 receptor antagonist inhibits lung fibrosis in the mouse bleomycin model

Background and purpose:

The aim of this study was to assess the potential of an antagonist selective for the lysophosphatidic acid receptor, LPA₁, in treating lung fibrosis We evaluated the in vitro and in vivo pharmacological properties of the high affinity, selective, oral LPA₁-antagonist (4′-{4-[(R)-1-(2-chloro-phenyl)-ethoxycarbonylamino]-3-methyl-isoxazol-5-yl}-biphenyl-4-yl)-acetic acid (AM966).

Experimental approach:

The potency and selectivity of AM966 for LPA₁ receptors was determined in vitro by calcium flux and cell chemotaxis assays using recombinant and native cell cultures. The in vivo efficacy of AM966 to reduce tissue injury, vascular leakage, inflammation and fibrosis was assessed at several time points in the mouse bleomycin model.

Key results:

AM966 was a potent antagonist of LPA₁ receptors, with selectivity for this receptor over the other LPA receptors. In vitro, AM966 inhibited LPA-stimulated intracellular calcium release (IC₅₀ = 17 nM) from Chinese hamster ovary cells stably expressing human LPA₁ receptors and inhibited LPA-induced chemotaxis (IC₅₀ = 181 nM) of human IMR-90 lung fibroblasts expressing LPA₁ receptors. AM966 demonstrated a good pharmacokinetic profile following oral dosing in mice. In the mouse, AM966 reduced lung injury, vascular leakage, inflammation and fibrosis at multiple time points following intratracheal bleomycin instillation. AM966 also decreased lactate dehydrogenase activity and tissue inhibitor of metalloproteinase-1, transforming growth factor β1, hyaluronan and matrix metalloproteinase-7, in bronchoalveolar lavage fluid.

Conclusions and implications:

These findings demonstrate that AM966 is a potent, selective, orally bioavailable LPA₁ receptor antagonist that may be beneficial in treating lung injury and fibrosis, as well as other diseases that are characterized by pathological inflammation, oedema and fibrosis.     

Ets transcription factors cooperate with Sp1 to activate the human tenascin-C promoter

Tenascin-C (TN-C), an extracellular matrix glycoprotein is expressed during embryonic development, but is present only at low levels in normal adult tissues. TN-C is re-expressed during wound healing, fibrotic diseases and in cancer. To better understand the mechanisms that control TN-C gene expression, we examined the regulation of the human TN-C promoter in human fibroblasts. We demonstrate that a short segment of the TN-C promoter between bp -133 and -27 contains three evolutionarily conserved Ets binding sites (EBS). These three EBSs bind in vitro expressed Fli1 protein and mediate transactivation of the TN-C gene by Fli1. Furthermore, two proximal EBSs contribute significantly to basal activity of the TN-C promoter. GABP, which is present in human fibroblast nuclear extracts, interacts with the two proximal EBSs. In addition, several Sp1 and Sp3 binding sites have been located in close proximity to the EBSs within this promoter region. The studies performed in Drosophila cells demonstrate that either Fli1 or GABPalpha+beta1 functionally interact with Sp1 resulting in a synergistic stimulation of the TN-C promoter activity. In conclusion, this study shows for the first time that the TN-C gene is regulated by Ets proteins, which together with Sp1 act as potent activators of TN-C expression.     

Induction of matric metalloprotease-7 is common in mucinous ovarian tumors including early stage disease

Matrix metalloproteases are known to play an important role in tumor invasion by mediating degradation of the extracellular matrix. In this study, we have investigated the immunohistochemical expression of matrix metalloprotease-7 (MMP-7) in 44 mucinous ovarian tumors (9 adenomas, 13 low malignant potential tumors, 22 adenocarcinomas) and 6 normal ovaries. Positive staining of MMP-7 is observed in all mucinous ovarian tumors, whereas little or no staining was observed in surface epithelium as well as the epithelial cells of germinal inclusion cyst of the normal ovary. Positive immunostaining of MMP-7 is also observed in the secreted mucin in the tumor glands, which suggests the secretion of the MMP-7 protein from tumor cells. mRNA expression of MMP-7 was confirmed using RT-PCR. The MMP-7 gene was amplified in parallel with an internal control gene β-tubulin using a thermal cycler. mRNA expression levels of MMP-7 were significantly elevated in mucinous tumor samples compared with that in normal ovaries. Our results suggest that MMP-7 is frequently overexpressed in mucinous ovarian tumors and secreted with the mucin which is produced from the tumor cells. MMP-7 may therefore contribute to mucinous ovarian tumor development or enhanced growth capacity of mucinous ovarian tumors. MMP-7 may also serve as a target for therapeutic intervention in the down regulation of tumor progression.