Is plasma beta-glucuronidase a novel human biomarker for monitoring anticholinesterase pesticides exposure? A Malaysian experience

A cross-sectional study was conducted to investigate the effects of acute and chronic pesticide exposure on the plasma beta-glucuronidase enzyme activity among five patients of acute pesticide poisoning in Tengku Ampuan Rahimah Hospital, Klang, 230 farmers in the MADA area, Kedah and 49 fishermen in Setiu, Terengganu. The duration of pesticide exposure among the patients was unknown, but the plasma samples from patients were collected on day one in the hospital. The duration of pesticide exposure among the farmers was between 1 and 45 years. The beta-glucuronidase activity was compared with plasma cholinesterase activity in the same individual. The plasma cholinesterase activity was measured using Cholinesterase (PTC) Reagent set kit (Teco Diagnostics, UK) based on colorimetric method, while the plasma beta-glucuronidase activity was measured fluorometrically based on beta-glucuronidase assay. The plasma cholinesterase activity was significantly reduced (p<0.05) among the patients (1386.786+/-791.291 U/L/min) but the inhibition in plasma cholinesterase activity among the farmers (7346.5+/-1860.786 U/L/min) was not significant (p>0.05). The plasma beta-glucuronidase activity among the farmers was significantly elevated (p<0.05) (0.737+/-0.425 microM/h) but not significant among the patients (p>0.05). The plasma cholinesterase activity was positively correlated with the plasma beta-glucuronidase activity among the farmers (r=0.205, p<0.01) but not among the patients (r=0.79, p>0.05). Thus, plasma beta-glucuronidase enzyme activity can be measured as a biomarker for the chronic exposure of pesticide. However, further studies need to be performed to confirm whether plasma beta-glucuronidase can be a sensitive biomarker for anticholinesterase pesticide poisoning.     

Is beta-glucuronidase a clinical useful biomarker for an acute organophosphorus poisoning?

beta-glucuronidase is considered a sensitive biomarker for acute organophosphorus poisoning. In this well-documented study, multiple plasma samples over time were collected. A decrease in plasma concentration of beta-glucuronidase was surprisingly observed, even within normal range. These findings do not support the hypothesis that beta-glucuronidase is a useful biomarker for acute organophosphorus poisoning in humans.     

Is the forced swimming test a suitable model for revealing antidepressant activity?

The forced swimming test is reviewed. This test appears to be suitable for detecting antidepressant activity in rats but not in mice. Difference in experimental procedure may account for the different sensitivity to drugs of the two animal species. Offprint requests to: F. Borsini     

Is there a need for emerging drugs for the acute respiratory distress syndrome?

The acute respiratory distress syndrome (ARDS) is a common and devastating syndrome of acute respiratory failure for which little effective pharmacotherapy exists. The authors describe some interventions that show promise as potential therapies for this condition, with particular reference to clinically relevant human models of ARDS. Aspirin, mesenchymal stromal (stem) cells, keratinocyte growth factor, IFN-β and oncostatin M inhibition are discussed.     

Is inhalation exposure to formaldehyde a biologically plausible cause of lymphohematopoietic malignancies?

The United States Environmental Protection Agency (EPA) recently proposed a hypothetical mode of action (MOA) to explain how inhaled formaldehyde (FA) might induce leukemia, lymphoma and a variety of other lymphohematopoietic (LHP) malignancies in occupationally exposed workers. The central hypothesis requires that B lymphocytes or hematopoietic progenitor cells (HPC) present at the "portal of entry (POE)" undergo sustained mutagenic change as a result of direct FA exposure. These modified cells would then migrate back to the bone marrow or primary lymphatic tissue and subsequently develop into specific LHP disease states. Chemical interaction at the POE is an absolute requirement for the hypothesized MOA as there is no convincing evidence that inhaled FA causes distant site (e.g., bone marrow) toxicity. The purpose of this review is to critically evaluate this proposed MOA within the context of the existing data concerning the toxicokinetic and biological properties of FA, the current understanding of the induction of chemically-induced leukemias and lymphomas, as well as within EPA's specific guidelines for evaluating the MOA of chemically-induced cancers. Specifically, we examine the scientific support for the hypothesis that FA exposure may induce carcinogenic transformation of localized lymphocytes or peripheral hematopoietic progenitor cells (HPC) in the absence of discernable systemic hematopoietic toxicity (i.e., peripheral transformation). While little or no empirical evidence exists upon which to fully evaluate the proposed hypothesis, available data does not support the proposed concept of "peripheral transformation" at the chemical entry site. Numerous animal bioassays evaluating chronic inhalation of FA clearly do not support this hypothesis since no properly conducted study as ever shown an increase in any LHP malignancy. Moreover, the notion that FA can cause any LHP malignancy is not supported with either epidemiologic data or current understanding of differing etiologies and risk factors for the various hematopoietic and lymphoproliferative malignancies. It is therefore concluded that existing science does not support the proposed MOA as a logical explanation for proposing that FA is a realistic etiological factor for any LHP malignancy.     

Is exposure to formaldehyde in air causally associated with leukemia?--A hypothesis-based weight-of-evidence analysis

Recent scientific debate has focused on the potential for inhaled formaldehyde to cause lymphohematopoietic cancers, particularly leukemias, in humans. The concern stems from certain epidemiology studies reporting an association, although particulars of endpoints and dosimetry are inconsistent across studies and several other studies show no such effects. Animal studies generally report neither hematotoxicity nor leukemia associated with formaldehyde inhalation, and hematotoxicity studies in humans are inconsistent. Formaldehyde's reactivity has been thought to preclude systemic exposure following inhalation, and its apparent inability to reach and affect the target tissues attacked by known leukemogens has, heretofore, led to skepticism regarding its potential to cause human lymphohematopoietic cancers. Recently, however, potential modes of action for formaldehyde leukemogenesis have been hypothesized, and it has been suggested that formaldehyde be identified as a known human leukemogen. In this article, we apply our hypothesis-based weight-of-evidence (HBWoE) approach to evaluate the large body of evidence regarding formaldehyde and leukemogenesis, attending to how human, animal, and mode-of-action results inform one another. We trace the logic of inference within and across all studies, and articulate how one could account for the suite of available observations under the various proposed hypotheses. Upon comparison of alternative proposals regarding what causal processes may have led to the array of observations as we see them, we conclude that the case for a causal association is weak and strains biological plausibility. Instead, apparent association between formaldehyde inhalation and leukemia in some human studies is better interpreted as due to chance or confounding.     

Is there a causal relationship between exposure to diesel exhaust and multiple myeloma?

This article presents a comprehensive critical review of the epidemiology of multiple myeloma in relation to occupational diesel exhaust exposure. The review includes cohort and proportional mortality studies of workers exposed to diesel exhaust, and population-based case-control studies of multiple myeloma. None of the cohort or proportional mortality studies reported a significant increase of multiple myeloma in relation to diesel exhaust, with the exception of a study of Danish truck drivers. Several limitations in this Danish study (such as inadequate cohort identification, small number of multiple myeloma deaths and inappropriate analytical method) made the result unreliable. Furthermore, the data in this study of Danish truck drivers were part of and, hence, superseded by a large study in Denmark, which did not find any increased risk of multiple myeloma. Similarly, none of the case-control studies reported a significant increase of multiple myeloma in relation to diesel exhaust, with the exception of the smallest case-control study based on multiple myeloma patients in central and southeast Sweden. The result of this small Swedish study was not reliable because of incomplete case ascertainment, inappropriate controls and confounding. Furthermore, the data in this small Swedish study were part of and, hence, superseded by a large national study of workers exposed to diesel exhaust in Sweden, which did not find any increased risk of multiple myeloma. Other than the study of Danish truck drivers and the small case-control study of multiple myeloma patients in central and southeast Sweden, all other epidemiological investigations consistently reported no increase of multiple myeloma in relation to occupational diesel exhaust exposure. Furthermore, none of the studies reported a positive exposure-response relationship between diesel exhaust and multiple myeloma. Several studies that analysed data by jobs or occupations according to level of exposure and by duration of exposure did not find any upward trend. In addition to the review, a formal causation analysis based on an application of the Hill criteria confirms that there is no causal relationship between diesel exhaust and multiple myeloma.     

Is quinine a suitable probe to assess the hepatic drug-metabolizing enzyme CYP3A4?

AIMS: To evaluate the antimalarial agent quinine as a potential in vivo probe for hepatic cytochrome P450 (CYP) 3A4 activity. METHODS: Ten healthy adult volunteers received, by randomized crossover design, either a single oral dose of quinine sulphate (600 mg) alone, or quinine sulphate (600 mg) plus the CYP3A4 inhibitor troleandomycin (TAO; 500 mg every 8 h). Plasma and urine samples were collected before quinine administration, and up to 48 h thereafter, then analysed by h.p.l.c. for both quinine and its CYP3A4-generated metabolite, 3-hydroxyquinine. During both phases, the erythromycin breath test (ERMBT) was administered at specific times to assess hepatic CYP3A4 activity. RESULTS: Compared with control, TAO treatment significantly decreased the mean time-averaged ERMBT result by 77% (95% CI, 68, 85%), the mean apparent oral clearance of quinine (CL/F ) by 45% (95% CI, 39, 52%), and the mean apparent formation clearance of 3-hydroxyquinine (CL3-OH) by 81% (95% CI, 76, 87%). There was no correlation between the TAO-mediated percent decrease in the time-averaged ERMBT result and the percent decrease in CL/F or in CL3-OH. When TAO and control treatments were analysed separately, there were no significant correlations between the time-averaged ERMBT result and CL/F, CL3-OH, or single plasma quinine concentration at 12, 24, and 48 h. CONCLUSIONS: Quinine may be a useful probe to detect inhibition of liver CYP3A4 activity within an individual. Further studies are needed to determine whether it can provide a quantitative measure of CYP3A4 activity suitable for intersubject comparison.     

Is level of exposure to a 12-step facilitation therapy associated with treatment outcome?

This study examined whether level of exposure to Stimulant Abuser Groups to Engage in 12-Step (STAGE-12), a 12-Step facilitative therapy, is related to treatment outcome. Data were from a large National Drug Abuse Treatment Clinical Trials Network (CTN) study comparing STAGE-12 combined with treatment-as-usual (TAU) to TAU alone. These analyses include only those randomized to STAGE-12 (n = 234). Assessments occurred at baseline and 30, 60, 90, and 180 days following randomization. High-exposure patients (n = 158; attended at least 2 of 3 individual, and 3 of 5 group, sessions), compared to those with less exposure (n = 76), demonstrated: (1) higher odds of self-reported abstinence from, and lower rates of, stimulant and non-stimulant drug use; (2) lower probabilities of stimulant-positive urines; (3) more days of attending and lower odds of not attending 12-Step meetings; (4) greater likelihood of reporting no drug problems; (5) more days of duties at meetings; and (6) more types of 12-Step activities. Many of these differences declined over time, but several were still significant by the last follow-up. Treatment and research implications are discussed.     

Is prenatal tobacco exposure a risk factor for early adolescent smoking? A follow-up study

Recent reports indicate a relation between prenatal tobacco exposure (PTE) and offspring smoking. Many of these reports have been retrospective or have not included important variables such as other prenatal substance exposures, maternal and child psycho-social characteristics, mother's current smoking, and friends' smoking. No prior study has examined the timing of PTE. In this prospective study of a birth cohort of 567 14-year-olds, we examined the relation between trimester-specific PTE, offspring smoking, and other correlates of adolescent smoking. Average age of the adolescents was 14.8 years (range: 13.9-16.6 years), 51% were female, 54% were African-American. Data on maternal tobacco and other substance use were collected both prenatally and postnatally, 51% of the mothers were prenatal smokers and 53% smoked when their children were 14 years. PTE in the third trimester significantly predicted offspring smoking (ever/never, smoking level, age of onset) when demographic and other prenatal substances were included in the analyses. PTE remained a significant predictor of the level of adolescent smoking when maternal and child psychological characteristics were added to the model. When more proximal measures of the child's smoking were included in the model, including mother's current smoking and friends' smoking, PTE was no longer significant. Significant predictors of adolescent smoking at age 14 were female gender, Caucasian race, child externalizing behavior, maternal anxiety, and child depressive symptoms. Although direct effects of PTE on offspring smoking behavior have previously been reported from this study and by others, by early-adolescence, this association is not significant after controlling for the more proximal covariates of adolescent smoking such as mother's current smoking and peer smoking.     

Is the use of a 200 ml vessel suitable for dissolution of low dose drug products?

This work evaluated the use of a commercially available 200 ml vessel for dissolution of five drug products with various solubilities. Each of the five drug products (four with USP monographs and one proprietary tablet formulation) was run at four different conditions (USP 25 monograph, six dosage units in single 1l vessel, 200 ml at the USP Monograph speed, and 200 ml at calculated paddle speed which matches the hydrodynamics of the USP vessel). Six dosage units in a single vessel were used as a comparison to increase the drug concentration for dissolution testing. Due to the different dissolution hydrodynamics, drug dissolution from the dosage forms was slower using the 200 ml conversion kit than when the USP method with a 1l vessel was used. However, use of the 200 ml vessel at higher paddle speeds calculated by the power/volume equation, yielded similar results as the monograph method. Thus, it appears that using the power/volume ratio calculation to obtain comparable hydrodynamics lends utility to the 200 ml vessel as a means for characterizing the dissolution profile of low dose solid oral drug products. The results of the multiple dosage units per vessel also gave similar results to that of the USP monograph method.     

Unveiling the nexus between parental exposure to toxicants and heritable spermiotoxicity - Is life history a shield or a shadow?

The knowledge on parental experiences is critical to predict how organisms react to environmental challenges. So, the DNA integrity of Procambarus clarkii spermatozoa exposed ex vivo to the herbicide penoxsulam (Px) or ethyl methanesulfonate (EMS; model genotoxicant) was assessed with and without the influence of in vivo parental exposure to the same agents. The parental exposure alone did not affect the DNA of unexposed spermatozoa. However, the history of Px exposure increased the vulnerability to oxidative lesions in Px-exposed offspring. Otherwise, parental exposure to EMS allowed the development of protection mechanisms expressed when F₁ was also exposed to EMS, unveiling life history as a shield. The parental exposure to a different agent adverse and decisively affected Px spermiotoxic potential, pointing out life history as a shadow to progeny. Given the complexity of the aquatic contamination scenarios, involving mixtures, the spermiotoxicity of Px to wild P. clarkii populations emerged as probable.     

Sublethal effects of exposure to chemical compounds: a cause for the decline in Atlantic eels?

Because of their unusual life cycle, American and European eels (Anguilla rostrata Lesueur and A. anguilla L.), are particularly exposed to pollutant effects. Because silver eels fast when they leave the freshwater system, the transoceanic migration forces them to constitute energy reserves in the form of muscle lipids, that are needed for successful spawning. Using species biological data, toxicological and ecotoxicological information, hypotheses are given to assess the contribution of pollution from freshwater sources to the recorded decline in the American and European eels fisheries since the 1980s. This paper first describes the lipid storage problems and the relative migratory capacities. Then several studies on the accumulation of xenobiotics in various anatomical compartments, on the biological half-lives of these compounds, and on their sublethal toxicity, are reviewed. During migration, lipid mobilization returns persistent lipophilic pollutants back into circulation, these being concentrated particularly in gonads at the crucial time of gametogenesis. Extrapolation of toxicological analysis (individual physiology) to the population level (spawning success) suggests that the quality of future spawners leaving freshwaters is one of the prime factors for the conservation of this threatened species.     

Is a positive history of non-anaesthetic drug allergy a predictive factor for positive allergy tests to anaesthetics?

AIMS

International recommendations stipulate not performing screening skin tests to a drug in the absence of a clinical history consistent with that specific drug allergy. Nevertheless, two publications showed that a positive history of non-anaesthetic drug allergy was the only predictive factor for a positive skin test when screening for allergy to anaesthetic drugs was done. We selected from a surgical population 40 volunteers with a prior history of allergy to non-anaesthetic drugs in order to analyse the prevalence of positive allergy tests to anaesthetics.

METHODS

The selected adult patients were tested for 11 anaesthetic drugs using in vivo tests: skin prick (SPT) and intradermal (IDT) tests and in vitro tests: the basophil activation test (BAT) and detection of drug-specific immunoglobulin E (IgE).

RESULTS

The prevalence for the positive SPT and IDT was 1.6% and 5.8% respectively. The result of flow cytometry agreed with the SPT in five out of seven positive SPT (71%). IgEs confirmed two positive SPT with corresponding positive BAT. Ten per cent of the patients had a positive prick test to neuromuscular blocking agents (NMBA). For midazolam none of the SPT was positive, but 11 patients had positive IDT nonconfirmed by BAT.

CONCLUSION

The prevalence of positive in vivo and in vitro allergy tests to NMBAs is higher in our study population. This could be an argument for pre-operative SPT to NMBAs for the surgical population with reported non-anaesthetic drug allergies. A larger prospective study is needed to validate changes in clinical practice.     

Is toxicogenomics a more reliable and sensitive biomarker than conventional indicators from rats to predict drug-induced liver injury in humans?

Around 40% of drug-induced liver injury (DILI) cases are not detected in preclinical studies using the conventional indicators. It has been hypothesized that genomic biomarkers will be more sensitive than conventional markers in detecting human hepatotoxicity signals in preclinical studies. For example, it has been hypothesized and demonstrated in some cases that (1) genomic biomarkers from the rat liver can discriminate drug candidates that have a greater or lesser potential to cause DILI in susceptible patients despite no conventional indicators of liver toxicity being observed in preclinical studies, and (2) more sensitive biomarkers for early detection of DILI can be derived from a "subtoxic dose" at which the injury in the liver occurs at the molecular but not the phenotypic level. With a public TGx data set derived from short-term in vivo studies using rats, we divided drugs exhibiting human hepatotoxicity into three groups according to whether elevated alanine aminotransferase (ALT) or total bilirubin (TBL) were observed in the treated rats: (A) The elevation was observed in the treated rats, (B) no elevation was observed for all of the treated rats, and (C) no elevation could be observed at a lower dose and shorter duration but occur when a higher or longer treatment was applied. A control group (D) was comprised of drugs known not to cause human hepatotoxicity and for which no rats exhibited elevated ALT or TBL. We developed classifiers for groups A, B, and C against group D and found that the gene signature from scenario A could achieve 83% accuracy for human hepatotoxicity potential of drugs in a leave-one-compound-out cross-validation process, much higher than scenarios B (average 45%) and C (61%). Furthermore, the signature derived from scenario A exhibited relevance to hepatotoxicity in a pathway-based analysis and performed well on two independent public TGx data sets using different chemical treatments and profiled with different microarray platforms. Our study implied that the human hepatotoxicity potential of a drug can be reasonably assessed using TGx analysis of short-term in vivo studies only if it produces significant elevation of ALT or TBL in the treated rats. The study further revealed that the value of "sensitive" biomarkers derived from scenario C was not promising as expected for DILI assessment using the reported TGx design. The study will facilitate further research to understand the role of genomic biomarkers from rats for assessing human hepatotoxicity.