Probabilistic derivation of the interspecies assessment factor for skin sensitization

An interspecies sensitization assessment factor (SAF) is used in the quantitative risk assessment (QRA) for skin sensitization when a murine-based NESIL (No Expected Sensitization Induction Level) is taken as point of departure. Several studies showed that, on average, the murine sensitization threshold is in good correspondence with that determined in humans. However, on an individual level, the murine and human sensitization thresholds may differ considerably. In this study, the interspecies SAF was quantified by using a probabilistic approach, to be able to take these cases into account. As expected, the geometric means of the probability distributions of murine and human sensitization threshold ratios were close to one, but taking the 95 ^th percentile of these distributions resulted in an interspecies SAF of 15. By using this value, one is sure that with 95% probability, the sensitization threshold determined in mice does not underestimate the human threshold. It can be concluded that a murine-based NESIL requires the use of an interspecies SAF (of 15) in the QRA for skin sensitization, to correct for the differences between mice and humans. This empirically derived interspecies SAF contributes to refinement of the risk assessment methodology.     

Relationship Between the Heparin Management Test and the HemoTec Activated Clotting Time in Patients Undergoing Percutaneous Coronary Intervention

Point-of-care whole blood coagulation tests are critical in the management of patients who undergo percutaneous coronary intervention. The Hemochron and HemoTec devices have been traditionally used to measure the activated clotting time (ACT) in the cardiac catheterization laboratory. The heparin management test (HMT) was recently introduced into clinical practice as an alternative method to current ACT measurements that uses a different sample volume, contact activators and detection system to measure whole blood coagulation. We compared the HMT to the HemoTec ACT in 68 prospectively enrolled patients (127 blood samples) undergoing percutaneous coronary intervention. Measurements were performed 10 minutes after the initial heparin bolus and thereafter at the discretion of the attending physician. The mean HMT was 41 seconds higher (15%) than the HemoTec ACT (HMT 304±59 vs. ACT 263±52, P< 0.0001), but there was a significant correlation between the methods (r=0.77, P<0.0001). However, there was increasing disagreement between the two methods as the level of anticoagulation increased. The relationship between HMT and ACT was similar in patients in whom glycoprotein IIb/IIIa inhibitors were used. The HMT, therefore, appears to be more sensitive to heparin anticoagulation that the HemoTec ACT and correlates well with it in the range required for percutaneous coronary intervention.     

Cancer chemoprevention by dietary polyphenols: Promising role for epigenetics

Epigenetics refers to heritable changes that are not encoded in the DNA sequence itself, but play an important role in the control of gene expression. In mammals, epigenetic mechanisms include changes in DNA methylation, histone modifications and non-coding RNAs. Although epigenetic changes are heritable in somatic cells, these modifications are also potentially reversible, which makes them attractive and promising avenues for tailoring cancer preventive and therapeutic strategies. Burgeoning evidence in the last decade has provided unprecedented clues that diet and environmental factors directly influence epigenetic mechanisms in humans. Dietary polyphenols from green tea, turmeric, soybeans, broccoli and others have shown to possess multiple cell-regulatory activities within cancer cells. More recently, we have begun to understand that some of the dietary polyphenols may exert their chemopreventive effects in part by modulating various components of the epigenetic machinery in humans. In this article, we first discuss the contribution of diet and environmental factors on epigenetic alterations; subsequently, we provide a comprehensive review of literature on the role of various dietary polyphenols. In particular, we summarize the current knowledge on a large number of dietary agents and their effects on DNA methylation, histone modifications and regulation of expression of the non-coding miRNAs in various in vitro and in vivo models. We emphasize how increased understanding of the chemopreventive effects of dietary polyphenols on specific epigenetic alterations may provide unique and yet unexplored novel and highly effective chemopreventive strategies for reducing the health burden of cancer and other diseases in humans.     

Guiding principles for the implementation of non-animal safety assessment approaches for cosmetics: Skin sensitisation

Characterisation of skin sensitisation potential is a key endpoint for the safety assessment of cosmetic ingredients especially when significant dermal exposure to an ingredient is expected. At present the mouse local lymph node assay (LLNA) remains the ‘gold standard’ test method for this purpose however non-animal test methods are under development that aim to replace the need for new animal test data. COLIPA (the European Cosmetics Association) funds an extensive programme of skin sensitisation research, method development and method evaluation and helped coordinate the early evaluation of the three test methods currently undergoing pre-validation. In May 2010, a COLIPA scientific meeting was held to analyse to what extent skin sensitisation safety assessments for cosmetic ingredients can be made in the absence of animal data. In order to propose guiding principles for the application and further development of non-animal safety assessment strategies it was evaluated how and when non-animal test methods, predictions based on physico-chemical properties (including in silico tools), threshold concepts and weight-of-evidence based hazard characterisation could be used to enable safety decisions. Generation and assessment of potency information from alternative tools which at present is predominantly derived from the LLNA is considered the future key research area.     

Quantification of unfractionated heparin in human plasma and whole blood by means of novel fluorogenic anti-FXa assays

Novel and sensitive plate-based fluorogenic anti-factor Xa (FXa) assays were investigated to quantify unfractionated heparin (UFH) in human plasma and whole blood within the therapeutic ranges of 0-1.6 U/mL and 0-0.8 U/mL, respectively. Two fluorogenic anti-FXa assay methods were defined for low (0-0.6 U/mL) and high (0.6-1.2 U/mL) pharmacologically relevant UFH concentration ranges in pooled human plasma. In both cases significant differences were observed at intervals of 0.2 U/mL (P < 0.05). The semi-logarithmic plots of the calibration curves in the low and high UFH range were both fitted to linear regressions with correlation coefficients of 0.96 and >0.99, respectively. The assay was also optimized for whole blood which was capable of differentiating UFH concentrations at intervals of 0.2 U/mL (P < 0.05) in the range of 0-0.4 U/mL. The statistically different results were fitted to a linear regression with a correlation coefficient of >0.99. The results obtained in this study could assist diagnostic laboratories towards improved monitoring of UFH therapy.     

Neuronal histaminergic system in aging and age-related neurodegenerative disorders

The neuronal histaminergic system is involved in many physiological functions and is severely affected in age-related neurodegenerative diseases such as Parkinson's disease (PD) and Alzheimer's disease (AD). The properties of the neuronal histaminergic system in experimental animals and the alterations observed in postmortem brain material of PD or AD patients are reviewed. The production of neuronal histamine shows diurnal fluctuations in control subjects who had no neuropsychiatric disorders, while this fluctuation was strongly altered in patients with neurodegenerative diseases, including PD and AD. In addition, different alterations shown as expression levels of histidine decarboxylase (the key enzyme for histamine production), histamine-methyltransferase (the histamine deactivating enzyme), and histamine receptors (H_1–4R) were found in various neurodegenerative disorders. Discrepancies between results from animal models and postmortem human brain material studies have made clear that the validation of animal models is absolutely necessary and that studies on patients and human postmortem material are essential to understand the changes of neuronal histaminergic system occurring in neuropsychiatric disorders.     

Evidence for a less high acceptor substrate specificity of gastric histamine methyltransferase: methylation of imidazole compounds

The transmethylation catalysed by HMT (EC 2.1.1.8)¹ has been considered as absolutely specific for histamine as acceptor substrate. In this investigation N^α-MH, N^α,N^αDMH, spinaceamine and synthetically prepared 4-[(2-amino-ethylmercapto)-methyl]-imidazole could be identified as further methyl-group accepting substrates (optimum substrate concentration ~ 1 mM), but the yield of extractable ¹⁴C-labelled methylation products was never greater than 21 per cent of that of histamine. The 3 per cent methylation of N^α,N^α-DMH was considerably smaller than that of 33 per cent reported in the literature. This discrepancy was resolved and found to be ascribable to an inappropriate product extraction procedure used in the former experiments. When N^α-MH and N^α,N^α-DMH were the substrates, the corresponding products were isolated by t.1.c. in four different solvent systems and identified to be N^τ,N^α-DMH and N^τ,N^α,N^α-TMH. Thus HMT catalysed in all cases a uniform methyl of the N^α-nitrogen atom of the imidazole nucleus. The investigation of a series of various substituted imidazole compounds revealed that a methylation of the ring system had to be considered, if it was not substituted in the N^τ-, 2- or N^π-position and if it carried a 4-substituent with a strong basic aminogroup, whereas substitution in the ring 5-position seemed to be of minor importance. Furthermore H₁-receptor antagonists, H²-receptor antagonists, the non-imidazole H₂-receptor agonist dimaprit, as well as the enzyme inhibitors aminoguanidine, tranylcypromine, pargyline and nicolinamide, were not methylated under the catalysis of HMT. The evidence for a less high substrate specificity of HMT may influence the relevance of histamine determinations using this enzyme: caution seems necessary.     

HMT抗炎、镇痛作用实验研究

目的研究红毛七乙醇提取物(HMT)的抗炎、镇痛及对免疫系统的影响。方法观察MHT对大鼠足趾肿胀、小鼠扭体、热痛阈的抗炎、镇痛作用;通过小鼠碳粒廓清、鸡红细胞吞噬,评价HMT对非特异性免疫功能的影响;通过去除双侧肾上腺小鼠耳廓肿胀了解其抗炎的机制。结果受试药物口服给药,对大鼠足肿胀有明显抑制作用(P<0.05);能抑制醋酸所致的小鼠扭体次数(P<0.001);能延长小鼠热痛阈值;对二甲苯引起的耳廓肿胀有明显抑制作用(P<0.05);对小鼠网状内皮细胞吞噬功能有显著影响(P<0.001);能提高小鼠腹腔巨噬细胞吞噬功能;对切除双侧肾上腺的小鼠耳廓肿胀无明显抑制作用。结论HMT有抗炎、镇痛作用。     

Quantitative risk assessment for skin sensitisation: Consideration of a simplified approach for hair dye ingredients

With the availability of the local lymph node assay, and the ability to evaluate effectively the relative skin sensitizing potency of contact allergens, a model for quantitative-risk-assessment (QRA) has been developed. This QRA process comprises: (a) determination of a no-expected-sensitisation-induction-level (NESIL), (b) incorporation of sensitization-assessment-factors (SAFs) reflecting variations between subjects, product use patterns and matrices, and (c) estimation of consumer-exposure-level (CEL). Based on these elements an acceptable-exposure-level (AEL) can be calculated by dividing the NESIL of the product by individual SAFs. Finally, the AEL is compared with the CEL to judge about risks to human health.