Toxicokinetics, including saturable protein binding, of 4-chloro-2-methyl phenoxyacetic acid (MCPA) in patients with acute poisoning

Simultaneous determination of bromoxynil and MCPA in commercial samples and raw materials using reversed phase high performance liquid chromatography

This study encompasses a quick, efficient, repeatable and reproducible analytical method for simultaneous determination of Bromoxynil (3, 5-Dibromo-4-hydroxybenzonitrile) and MCPA (2-methyl-4-chlorophenoxyacetic acid) using RP-HPLC with UV-Detector. Bromoxynil + MCPA is one of the most selective post emergent herbicide formulations for the control of important broad leaf weeds infesting small grains (wheat, barley, oats, rye), conservation reserve program areas and grass grown for seed. Optimum weed control is achieved when Bromoxynil + MCPA is applied to actively growing weed seedlings. So, a simple, repeatable, reproducible and efficient simultaneous analytical method was developed for Bromoxynil + MCPA. The developed method was applied for the detection and quantitation of these pesticides in formulations and raw materials with excellent recoveries. It was validated according to ICH Guidelines with excellent linearity R2 = 0.992 for Bromoxynil and 0.998 for MCPA. For Bromoxynil, LOD = 1.57 mg/L and LOQ = 5.22 mg/L while for MCPA the LOD = 1.08 mg/L and LOQ = 3.62 mg/L was found. The proposed method has shown high precision (RSD %) 0.06% and 0.11% for Bromoxynil and MCPA respectively while the trueness has been calculated in terms of recovery percentage obtained as "mean value of Bromoxynil 99.53% and MCPA 100.10%" which is excellent under optimized conditions. For repeatability and reproducibility, five replicate readings of standard and sample were taken and had found within acceptable limits of relative standard deviation (RSD ≤  ± 2%). Finally, the robustness of the developed method was determined by changing flow rate and mobile phase ratios that has found within the permissible limits (% RSD NMT 1.5). So, the proposed analytical method has found to be more precise, valid and accurate at commercial scale.

Epidemiology and renal injury following 2-methyl-4-chlorophenoxyacetic acid (MCPA) poisoning

2-Methyl-4-chlorophenoxyacetic acid (MCPA) is a widely used chlorophenoxy herbicide. MCPA poisoning causes mitochondrial dysfunction, which can lead to kidney injury and death. The objective of this study is to describe the epidemiology, case fatality and extent of renal injury in a large cohort of MCPA self-poisonings. The study consists of two parts: (1) A report of epidemiological data and clinical outcomes in MCPA poisoned patients in Sri Lanka between 2002 and 2019; (2) Evaluation of acute kidney injury (AKI) using renal biomarkers in a subset from this cohort. Serum creatinine (sCr) and biomarkers were measured soon after hospitalization (2 [IQR 1-3] h) and at different time intervals. We measured serum biomarkers: sCr, cystatin C (sCysC), creatine kinase (CK), and urinary biomarkers: creatinine, kidney injury molecule-1 (KIM-1), clusterin, albumin, beta-2-microglobulin (β2M), cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), osteopontin (OPN), trefoil factor 3 (TFF3) and cytochrome C (CytoC). Kidney Disease Improving Global Outcomes (KDIGO) criteria was used to define acute kidney injury (AKI). There were 1653 patients; 65% were male. The median time from ingestion to examination was 3:54 (IQR 2:19-6:57) h. The overall case-fatality rate was 5.3%. Patients who died were older (42 [IQR 33.5-54] vs 27 [IQR 20-37] for survivors). The median estimated amount of MCPA ingested by patients who died was also greater (88 [IQR 34-200] vs. 30 [IQR 15-63] ml in survivors). Moderate to severe AKI (AKI2/3) was uncommon (6/59 patients in the biomarker study had KDIGO stage 2 or 3). Most patients in AKI2/3 group with increased sCr were older (median age 35 years [IQR 27-41]) compared to No AKI (23 years (19-29) years) or AKI1 (26 years (21-40) years) group who had no or mild increase in sCr. These patients had no pre-existing kidney diseases. In these patients, serum creatinine (maximum medium concentration; 1.12 [IQR 0.93-1.67] mg/dl) and CK (maximum medium concentration; 284 [IQR 94-428] U/l) were increased but sCysC (maximum medium concentration; 0.79 [IQR 0.68-0.81] mg/l) remained in the normal range within 72 h. All urinary biomarkers performed poorly in diagnosing AKI (area under the receiver operating characteristic curve < 0.68). The higher numbers of men with MCPA poisoning likely reflects greater occupational access to pesticides. Fatal outcome and higher ingested dose were more common in the elderly. Significant AKI with tubular injury biomarkers was uncommon. Most people with raised sCr were older and appeared to have no pre-existing kidney disease.

The chlorophenoxy herbicide MCPA: A mechanistic basis for the observed differences in toxicological profile in humans and rats versus dogs

1. Metabolism data for MCPA in rat, dog and human shows a single oral dose is quantitatively and rapidly absorbed with evidence of non-linear kinetics at >100 mg/kg bw. The extent of metabolism is low and consistent between rat and human, with substantially higher metabolic conversion in dog. Parent accounts for 50-67% dose in rat, ∼40% in human and 2-27% in dog. No dog specific metabolite is apparent.2. In rat and human, MCPA and metabolites are rapidly eliminated in urine (65-70% within 24 hours) but in dog, excretion is via urine and faeces (20-30% within 24 hours), with renal excretion saturating between 5 and 100 mg.kg bw.3. The species difference in excretion is reflected in pharmacokinetics. Terminal half-life is similar in rat and human (15-17 hour) but higher in dog (47 hour). Modelling shows species differences in single dose kinetics profoundly affect systemic exposure following repeat dosing.4. The difference in renal excretion and systemic exposure of MCPA between dogs and rats has been attributed to species differences in active transporters (OAT1/OAT3). A new in vitro flux study in renal proximal tubules supports this hypothesis with net secretion in rat and human of a similar magnitude but significantly less in dog.

Comparison of sample preparation approaches and validation of an extraction method for nitrosatable pesticides and metabolites in human serum and urine analyzed by liquid chromatography - Orbital ion trap mass spectrometry

In the acidic environment of the stomach, nitrosatable pesticide residues may react with nitrite to form potentially carcinogenic pesticide-associated N-nitroso compounds (PANOCs). The objective of this study was to develop a method for the analysis of 10 nitrosatable pesticides and breakdown products in human serum and urine. Three sample preparation methods were evaluated for extraction of target analytes from the biomatrices. Deproteinization by methanol for 300-μL aliquots of serum with a final extract volume of 225 μL resulted in excessive ion enhancement of some analytes and suppression of others. Three types of solid-phase extraction cartridges were tested for optimal analyte retention from 200-μL aliquots of serum with a final extract volume of 400 μL; this approach resulted in significant analyte loss for some compounds. The Quick, Easy, Cheap, Effective, Rugged, and Safe approach resulted in a suitable method for extraction of the analytes from each biomatrix. Biofluid samples (500 μL) were spiked to 100 μg L^-1 with analytical standards and extracted using 500 μL of acetonitrile (ACN) with 4% acetic acid (AcOH) for serum and 0.1% AcOH in ACN for urine. For extraction, 200 mg magnesium sulfate (MgSO₄) and 50 mg sodium acetate were added for serum and 200 mg MgSO₄ and 50 mg sodium chloride were added for urine. Final extract volumes for both biomatrices using the QuEChERS method was 400 μL after dilution. Samples were analyzed via ultra-high pressure liquid chromatography/high-resolution accurate mass orbital ion trap mass spectrometry. Mean recoveries for target analytes in serum and urine ranged between 74 and 120% (%RSD < 12) and 96 to 116% (%RSD ≤ 10), respectively. These methods may be used in large-scale biomonitoring studies to analyze PANNs and their parent compounds in human serum and urine.

Toxicological Effects of Traumatic Acid and Selected Herbicides on Human Breast Cancer Cells: In Vitro Cytotoxicity Assessment of Analyzed Compounds

The main consequence of herbicides use is the presence of their residues in food of plant origin. A growing body of evidence indicates that herbicides cause detrimental effects upon human health while demonstrating a direct link of pesticides exposure with the occurrence of human chronic diseases, including cancer. There is a pressing need to develop our knowledge regarding interactions of food contaminants and food components both in vitro and in vivo. Pesticides are highly undesirable food contaminants, and traumatic acid (TA) is a very beneficial food ingredient, therefore we decided to study if TA may act as a compound that delays the stimulatory effect of pesticides on breast cancer cells. To analyze the potential effects that selected herbicides (MCPA, mesotrione, bifenox and dichlobenil) may have upon cancerous cells, we conducted studies of the cytotoxicity of physiological concentrations of four pesticides and the mix of TA with tested herbicides in three different breast cancer cell lines (MCF-7, ZR-75-1 and MDA-MB-231) and one normal healthy breast cell line MCF-12A. Based on the obtained results we conclude that TA in a concentration-dependent manner might influence selected effects of the studied herbicides for particular cancer cells lines.

2-Methyl-4-chlorophenoxyacetic acid (MCPA) and bromoxynil herbicide ingestion

CONTEXT

Ingestion of bromoxynil and 2-methyl-4-chlorophenoxyacetic acid (MCPA) in combination is associated with high mortality. Toxicity is characterised by hyperthermia and metabolic acidosis. Dialysis is a proposed treatment, but little data exist regarding its effectiveness.

CASE DETAILS

Case 1: A 50-year-old female presented 18 h post-ingestion of 200  mL of bromoxynil(200 g/L) and MCPA(200 g/L). She was agitated, tachycardic and tachypnoeic. She was intubated and continuous venovenous haemodiafiltration (CVVHDF) was commenced. She deteriorated, becoming hypotensive, hyperthermic (39.5 °C) and hypercapnic (80 mmHg). She was cooled, paralysed, received CVVHDF for 2d and was extubated on day 4 making a full recovery. Case 2: A 60-year-old male presented 6 h post-ingestion of an unknown amount of bromoxynil (200 g/L) and MCPA (200 g/L). On arrival, he was tachycardic and tachypneic (pCO₂ 25 mmHg). At 8h post-ingestion he became hyperthermic, hypercapnic and acidotic (pH 7.15), and was intubated, paralysed, cooled and received CVVHDF for 36 h. He was extubated after 42 h and made a full recovery. Bromoxynil and MCPA serum and effluent concentrations were measured. Peak MCPA serum concentrations were 161 µg/ml and 259 µg/ml and peak bromoxynil concentrations were 119 µg/ml and 155 µg/ml in case 1 and 2, respectively. The estimated clearance of both herbicides by CVVHDF was low (<10 mL/min).

CONCLUSION

CVVHDF did not result in significant clearance of either herbicide but may have assisted with hyperthermia control. Both patients survived with vigorous cooling, paralysis and ventilatory support.

Role of biomarkers of nephrotoxic acute kidney injury in deliberate poisoning and envenomation in less developed countries

Acute kidney injury (AKI) has diverse causes and is associated with increased mortality and morbidity. In less developed countries (LDC), nephrotoxic AKI (ToxAKI) is common and mainly due to deliberate ingestion of nephrotoxic pesticides, toxic plants or to snake envenomation. ToxAKI shares some pathophysiological pathways with the much more intensively studied ischaemic AKI, but in contrast to ischaemic AKI, most victims are young, previously healthy adults. Diagnosis of AKI is currently based on a rise in serum creatinine. However this may delay diagnosis because of the kinetics of creatinine. Baseline creatinine values are also rarely available in LDC. Novel renal injury biomarkers offer a way forward because they usually increase more rapidly in AKI and are normally regarded as absent or very low in concentration, thereby reducing the need for a baseline estimate. This should increase sensitivity and speed of diagnosis. Specificity should also be increased for urine biomarkers since many originate from the renal tubular epithelium. Earlier diagnosis of ToxAKI should allow earlier initiation of appropriate therapy. However, translation of novel biomarkers of ToxAKI into clinical practice requires better understanding of non-renal factors in poisoning that alter biomarkers and the influence of dose of nephrotoxin on biomarker performance. Further issues are establishing LDC population-based normal ranges and assessing sampling and analytical parameters for low resource settings. The potential role of renal biomarkers in exploring ToxAKI aetiologies for chronic kidney disease of unknown origin (CKDu) is a high research priority in LDC. Therefore, developing more sensitive biomarkers for early diagnosis of nephrotoxicity is a critical step to making progress against AKI and CKDu in the developing world.

Toxicity assessment of 2,4-D and MCPA herbicides in primary culture of fish hepatic cells

In this study, we used primary cultures of fish hepatic cells as a tool for evaluating the effects of environmental contamination. Primary hepatic cell cultures derived from the subtropical fish Metynnis roosevelti were exposed to different concentrations (0.275, 2.75 and 27.5 μg L(-1)) of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA). Cellular respiratory activity was evaluated by polarography using three substrates: 0.5 M glucose, 0.5 M succinate and 0.5 M α-ketoglutarate. Significant changes were observed in cellular oxygen consumption with 0.5 M α-ketoglutarate. Even at low concentrations, 2,4-D and MCPA were potent uncouplers of oxidative phosphorylation. Primary cultures of M. roosevelti liver cells may provide a useful tool for the evaluation of environmental contaminant effects. A review of regulations regarding permitted concentrations of these herbicides is needed.

Surfactant toxicity in a case of (4-chloro-2-methylphenoxy) acetic acid herbicide intoxication

Objective:

Self-poisoning with (4-chloro-2-methylphenoxy) acetic acid (MCPA) is a common reason for presentation to hospitals, especially in some Asian countries. We encountered a case of a 76-year-old woman who experienced unconsciousness, shock and respiratory failure after ingesting 100 mL MCPA herbicide. We determined whether the surfactant in the formulation was the chemical responsible for the toxic symptom in this patient.

Design:

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability and lactate dehydrogenase (LDH) cytotoxicity assays were performed on human brain neuroblastoma SK-N-SH cells. The expressions of 84 genes in 9 categories that are implicated in cellular damage pathways were quantified using an RT2 Profiler™ PCR array on a human neuronal cell line challenged with polyoxyethylene tridecyl ether (PTE).

Setting:

Pesticide intoxication institute in university hospital.

Interventions:

Extracorporeal elimination with intravenous lipid emulsion.

Measurements:

Cell viability and gene expression.

Main Results:

In the MTT assay, MCPA only minimally decreased cell viability even at concentrations as high as 1 mM. Cells treated with 1-methoxy-2-propanol, dimethylamine and polypropylene glycol exhibited minimal decreases in viability, whilst the viability of cells challenged with PTE decreased dramatically; only 15.5% of cells survived after exposure to 1 µM PTE. Similarly, the results of the LDH cytotoxicity assay showed that MCPA had very low cytotoxicity, whilst cells treated with PTE showed incomparably higher LDH levels ( p < 0.0001). PTE up-regulated the expressions of genes implicated in various cell damage pathways, particularly genes involved in the inflammatory pathway.

Conclusions:

The surfactant PTE was likely the chemical responsible for the toxic symptom in our patient.

Hemoperfusion for the treatment of poisoning: technology, determinants of poison clearance, and application in clinical practice

Hemoperfusion is an extracorporeal treatment based on adsorption, historically reserved for the treatment of acute poisonings. Its use was popularized in the 1970s after several in vitro and animal experiments had demonstrated its efficacy, and was even preferred over hemodialysis in the management of overdosed patients. With the advent of new and more efficient dialytic modalities, hemoperfusion is now less frequently performed in the Western world. However, hemoperfusion still remains popular in developing countries. The present article reviews the technique of hemoperfusion, the factors influencing poison clearance through adsorption and its current applications.

A stepwise approach for the management of poisoning with extracorporeal treatments

The use of an extracorporeal treatment (ECTR) in a poisoned patient may be life-saving in a limited number of scenarios. The decision-processes surrounding the use of ECTR in poisoning is complex: most nephrologists are not trained to assess a poisoned patient while clinical toxicologists rarely prescribe ECTRs. Deciding on which ECTR is most appropriate for a poison requires a good understanding of the poison's physicochemical and pharmacokinetic properties. Further, a detailed understanding of the capabilities and limitations of the different ECTRs can be useful to select the most appropriate ECTR for a given clinical situation. This manuscript provides a stepwise approach to assess the usefulness of ECTRs in poisoning.

A Systematic Review of Carcinogenic Outcomes and Potential Mechanisms from Exposure to 2,4-D and MCPA in the Environment

Chlorophenoxy compounds, particularly 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxy)acetic acid (MCPA), are amongst the most widely used herbicides in the United States for both agricultural and residential applications. Epidemiologic studies suggest that exposure to 2,4-D and MCPA may be associated with increased risk non-Hodgkins lymphoma (NHL), Hodgkin's disease (HD), leukemia, and soft-tissue sarcoma (STS). Toxicological studies in rodents show no evidence of carcinogenicity, and regulatory agencies worldwide consider chlorophenoxies as not likely to be carcinogenic or unclassifiable as to carcinogenicity. This systematic review assembles the available data to evaluate epidemiologic, toxicological, pharmacokinetic, exposure, and biomonitoring studies with respect to key cellular events noted in disease etiology and how those relate to hypothesized modes of action for these constituents to determine the plausibility of an association between exposure to environmentally relevant concentrations of 2,4-D and MCPA and lymphohematopoietic cancers. The combined evidence does not support a genotoxic mode of action. Although plausible hypotheses for other carcinogenic modes of action exist, a comparison of biomonitoring data to oral equivalent doses calculated from bioassay data shows that environmental exposures are not sufficient to support a causal relationship. Genetic polymorphisms exist that are known to increase the risk of developing NHL. The potential interaction between these polymorphisms and exposures to chlorophenoxy compounds, particularly in occupational settings, is largely unknown.