Excretion time courses of lambda-cyhalothrin metabolites in the urine of strawberry farmworkers and effect of coexposure with captan

There are limited literature data on the impact of coexposure on the toxicokinetics of pesticides in agricultural workers. Using the largely employed pyrethroid lambda-cyhalothrin (LCT) and fungicide captan as sentinel pesticides, we compared individual temporal profiles of biomarkers of exposure to LCT in strawberry field workers following an application episode of LCT alone or in coexposure with captan. Participants provided all urine voided over a 3-day period after an application of a pesticide formulation containing LCT alone (E1) or LCT mixed with captan (E2), and in some cases following re-entry in treated field (E3). Pyrethroid metabolites were measured in all urine samples, in particular 3-(2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethyl-cyclopropanecarboxylic acid (CFMP), 3-phenoxybenzoic acid (3-PBA), and 4-hydroxy-3-phenoxybenzoic acid (4-OH3PBA). There were no obvious differences in individual concentration-time profiles and cumulative excretion of metabolites (CFMP, 3-PBA, 4-OH3BPA) after exposure to LCT alone or in combination with captan. For most workers and exposure scenarios, CFMP was the main metabolite excreted, but time courses of CFMP in urine did not always follow that of 3-PBA and 4-OH3BPA. Given that the latter metabolites are common to other pyrethroids, this suggests that some workers were coexposed to pyrethroids other than LCT. For several workers and exposure scenarios E1 and E2, values of CFMP increased in the hours following spraying. However, for many pesticide operators, other peaks of CFMP were observed at later times, indicating that tasks other than spraying of LCT-containing formulations contributed to this increased exposure. These tasks were mainly handling/cleaning of equipment used for spraying (tractor or sprayer) or work/inspection in LCT-treated field according to questionnaire responses. Overall, this study provided novel excretion time course data for LCT metabolites valuable for interpretation of biomonitoring data in workers, but also showed that coexposure was not a major determinant of variability in exposure biomarker levels. Our analysis also pointed out the importance of measuring specific metabolites.

Impact of pesticide coexposure: an experimental study with binary mixtures of lambda-cyhalothrin (LCT) and captan and its impact on the toxicokinetics of LCT biomarkers of exposure

This study aimed at gaining more insights into the impact of pesticide coexposure on the toxicokinetics of biomarkers of exposure. This was done by conducting an in vivo experimental case-study with binary mixtures of lambda-cyhalothrin (LCT) and captan and by assessing its impact on the kinetic profiles of LCT biomarkers of exposure. Groups of male Sprague-Dawley rats were exposed orally by gavage to LCT alone (2.5 or 12.5 mg/kg bw) or to a binary mixture of LCT and captan (2.5/2.5 or 2.5/12.5 or 12.5/12.5 mg/kg bw). In order to establish the temporal profiles of the main metabolites of LCT, serial blood samples were taken, and excreta (urine and feces) were collected at predetermined intervals up to 48 h post-dosing. Major LCT metabolites were quantified in these matrices: 3-(2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-dimethyl-cyclopropane carboxylic (CFMP), 3-phenoxybenzoic acid (3-PBA), 4-hydroxy-3-phenoxybenzoic acid (4-OH3PBA). There was no clear effect of coexposure at the low LCT dose on the kinetics of CFMP and 3-PBA metabolites, based on the combined assessment of temporal profiles of these metabolites in plasma, urine and feces; however, plasma levels of 3-PBA were diminished in the coexposed high-dose groups. A significant effect of coexposure on the urinary excretion of 4-OH3PBA was also observed while fecal excretion was not affected. The temporal profiles of metabolites in plasma and in excreta were further influenced by the LCT dose. In addition, the study revealed kinetic differences between metabolites with a faster elimination of 3-PBA and 4-OH3BPA compared to CFMP. These results suggest that the pyrethroid metabolites CFMP and 3-PBA, mostly measured in biomonitoring studies, remain useful as biomarkers of exposure in mixtures, when pesticide exposure levels are below the reference values. However, the trend of coexposure effect observed in the benzyl metabolite pathway (in particular 4-OH3BPA) prompts further investigation.

Toxicokinetics of bisphenol-S and its glucuronide in plasma and urine following oral and dermal exposure in volunteers for the interpretation of biomonitoring data

The measurement of bisphenol-S (BPS) and its glucurono-conjugate (BPSG) in urine may be used for the biomonitoring of exposure in populations. However, this requires a thorough knowledge of their toxicokinetics. The time courses of BPS and BPSG were assessed in accessible biological matrices of orally and dermally exposed volunteers. Under the approval of the Research Ethics Committee of the University of Montreal, six volunteers were orally exposed to a BPS-d8 deuterated dose of 0.1 mg/kg body weight (bw). One month later, 1 mg/kg bw of BPS-d8 were applied on 40 cm² of the forearm and then washed 6 h after application. Blood samples were taken prior to dosing and at fixed time periods over 48 h after treatment; complete urine voids were collected pre-exposure and at pre-established intervals over 72 h postdosing. Following oral exposure, the plasma concentration-time courses of BPS-d8 and BPSG-d8 over 48 h evolved in parallel, and showed a rapid appearance and elimination. Average peak values (±SD) were reached at 0.7 ± 0.1 and 1.1 ± 0.4 h postdosing and mean (±SD) apparent elimination half-lives (t_½) of 7.9 ± 1.1 and 9.3 ± 7.0 h were calculated from the terminal phase of BPS-d8 and BPSG-d8 in plasma, respectively. The fraction of BPS-d8 reaching the systemic circulation unchanged (i.e. bioavailability) was further estimated at 62 ± 5% on average (±SD) and the systemic plasma clearance at 0.57 ± 0.07 L/kg bw/h. Plasma concentration-time courses and urinary excretion rate profiles roughly evolved in parallel for both substances, as expected. The average percent (±SD) of the administered dose recovered in urine as BPS-d8 and BPSG-d8 over the 0-72 h period postdosing was 1.72 ± 1.3 and 54 ± 10%. Following dermal application, plasma levels were under the lower limit of quantification (LLOQ) at most time points. However, peak values were reached between 5 and 8 h depending on individuals, suggesting a slower absorption rate compared to oral exposure. Similarly, limited amounts of BPS-d8 and its conjugate were recovered in urine and peak excretion rates were reached between 5 and 11 h postdosing. The average percent (±SD) of the administered dose recovered in urine as BPS-d8 and BPSG-d8 was about 0.004 ± 0.003 and 0.09 ± 0.07%, respectively. This study provided greater precision on the kinetics of this contaminant in humans and, in particular, evidenced major differences between BPA and BPS kinetics with much higher systemic levels of active BPS than BPA, an observation explained by a higher oral bioavailability of BPS than BPA. These data should also be useful in developing a toxicokinetic model for a better interpretation of biomonitoring data.

Goodpasture disease as a consequence of melioidosis

We describe a case of anti-glomerular basement membrane (GBM) antibody-mediated disease in association with concomitant Burkholderia pseudomallei (melioidosis) bacteraemia. The temporal profile of the illness and initial absence of circulating anti-GBM antibodies, in light of the subsequent definitive histological diagnosis of anti-GBM disease, makes this case interesting and unusual. Additionally, there have been no prior case reports suggesting melioidosis as a cause of biopsy-proven glomerulonephritis.

Predictions of bisphenol A hepatic clearance in the isolated perfused rat liver (IPRL): impact of albumin binding and of co-administration with naproxen

1. This study aimed (i) to characterise hepatic clearance (CL) of bisphenol A (BPA) and naproxen (NAP) administered alone or in binary mixtures to highlight the influence of a binding to albumin (ALB) using an isolated perfused rat liver (IPRL) system; and (ii) to compare results of prediction algorithms with measured clearance rates. 2. The IPRL system and liver microsomes were used to determine the metabolic constants of BPA and NAP either in the presence or absence of ALB. In this study, the IPRL was used as proxy for the in vivo situation. Accordingly, diverse in vitro-to-in vivo and in vivo-to-in vivo extrapolations (IVIVEs) were made to predict CL of BPA determined in situ/in vivo with ALB from metabolic data determined without ALB by using different binding correction methods (i.e., direct and conventional scaling as well as a novel scaling considering an ALB-facilitated uptake mechanism). 3. The addition of ALB significantly influenced the liver kinetics of BPA and NAP either administered alone or in binary mixtures, which was reflected in the Michaelis-Menten constants. Analysis of concomitant exposures of BPA and NAP gave a fully competitive inhibition. Furthermore, the IVIVE method based on the ALB-facilitated uptake mechanism provided the most accurate predictions of CL_{in vivo} as compared with the other IVIVE methods when the impact of ALB is considered. 4. Our findings support the notion that high binding to ALB reduces the biotransformation of BPA and NAP when administered alone or in mixtures in the IPRL system. However, the free drug concentration in liver in vivo is probably higher than expected since the IVIVE method based on a potential ALB-facilitated uptake mechanism is the most robust prediction method. Overall, this study should improve the physiologically-based pharmacokinetic (PBPK) modelling of chemical-drug interactions.

Involvement of transient receptor potential melastatin-related 7 (TRPM7) channels in cadmium uptake and cytotoxicity in MC3T3-E1 osteoblasts

Exposure to cadmium (Cd) disrupts bone metabolism, causing osteoporosis. Impaired vitamin D metabolism was initially proposed as the underlying mechanism, yet recent studies argue for the direct effect of Cd on bone cells. This study aimed at characterizing (109)Cd uptake and cytotoxicity in MC3T3-E1 osteoblasts. Time-dependent accumulation of (109)Cd was observed with a 50% lethal concentration (LC(50)) of 9.6 ± 1.2 μM at 24-h. Reducing extracellular calcium (Ca) or magnesium (Mg) increased Cd cytotoxicity. The presence of Ca, Mg, zinc or gadolinium decreased (109)Cd uptake suggesting the involvement of non-selective cationic channels. The Mg-sensitive part of (109)Cd uptake increased at acidic pH, a condition known to stimulate TRPM7 channel activity. Stimulating TRPM7 channel activity by cellular Mg starvation enhanced (109)Cd uptake. Silencing TRPM7 channel expression abolished the Mg-sensitive and the Mg starvation-induced uptake indicating that TRPM7 is involved in Cd transport in osteoblasts.

Cadmium-induced hormetic effect in differentiated Caco-2 cells: ERK and p38 activation without cell proliferation stimulation

Cadmium (Cd) is a toxic metal that enters the food chain. Following oral ingestion, the intestinal epithelium may in part protect against Cd toxicity but is also a target tissue. Using human enterocytic-like Caco-2 cells, we have previously shown differences in sensitivity to Cd according to the differentiation status. The present study focuses on Cd effects on differentiated cells. Concentration and time-dependent increases in MTT (3-[4,5-dimethyl-2-thiazol-2-yl]-2,5-diphenyltetrazolium bromide assay) activity were observed in post-confluent cultures exclusively, with a twofold maximal stimulation in 21-day-old cells exposed to 10 microM Cd for 24 h. No concomitant increase in [methyl-(3)H] thymidine incorporation was noted and Cd did not modify cell distribution in the cell-cycle phases. However, Cd-induced increase in MTT activity was inhibited by cycloheximine as well as by inhibitors of ERK1/2 and p38, but not by that of JNK. Consistently, Cd increased the levels of ERK1/2 and p38 phosphorylation. Inhibition of Ras-GTP or PI3K enhanced the stimulatory effect of Cd, whereas mTOR inhibition had no effect. Inhibition of G protein-phospholipase and PKC decreased MTT stimulation. These results show a hormesis-like stimulation of Cd on MTT activity in differentiated intestinal cells exclusively. This effect is not related to cell proliferation but more likely to increased protein synthesis which involves ERK1/2 and p38 cascades and possibly PLC-beta signaling pathways. Because growth-related differentiation of intestinal cells is linked to the selective and sequential activation of MAPKs, the impacts that these Cd-induced perturbations in signaling pathways may have on intestinal functions clearly deserve to be investigated.

Living related renal transplantation: the Christchurch experience

AIM

To determine the outcome of renal transplants from living related donors.

METHODS

Retrospective analysis of 33 living related donor renal transplants done between March 1976 and 31 December 1994 at Christchurch Hospital.

RESULTS

One of the 33 renal transplants patients received an ABO incompatible kidney and was excluded from the statistical analysis. Twenty-one (66%) of 32 grafts continue to function. The 1, 5 and 10 year graft survival rates were 82%, 73% and 48%, respectively. The estimated 1 and 10 year patient survival rates were 96% and 94%, respectively. With the introduction of cyclosporin the 1 and 5 year graft survival rates increased to 90% and 80%, respectively. Three patients received donor specific transfusion preconditioning and one patient a skin graft from the prospective donor. Four patients (12.5%) had current and/or peak panel reactive antibody titres of more than 25%. Three of these grafts failed after 2, 95 and 463 days. Two grafts were lost due to catastrophic vascular complications.

CONCLUSION

The overall outcome for patients who were not highly sensitised was excellent. The degree of sensitisation of the recipient, and the extent of atherosclerotic vascular disease in the recipient, were major predisposing factors for the graft loss due to rejection and vascular complications during the early post transplant period.