Proximal discrepancies in intrinsic atomic interaction determines comparative in vivo biotoxicity of Chlorpyrifos and 3,5,6-trichloro-2-pyridinol in embryonic zebrafish

Bioaccumulation of Chlorpyrifos (CP) as pesticides due to their aggrandized use in agriculture has raised serious concern on the health of ecosystem and human beings. Moreover, their degraded products like 3,5,6-trichloro-2-pyridinol (TCP) has enhanced the distress due to their unpredictable biotoxicity. This study evaluates and deduce the comparative in vivo mechanistic biotoxicity of CP and TCP with zebrafish embryos through experimental and computational approach. Experimental cellular and molecular analysis showed higher induction of morphological abnormalities, oxidative stress and apoptosis in TCP exposed embryos compared to CP exposure due to upregulation of metabolic enzymes like Zhe1a, Sod1 and p53. Computational analysis excavated the differential discrepancies in intrinsic atomic interaction as a reason of disparity in biotoxicity of CP and TCP. The mechanistic differences were deduced due to the differential accumulation and internalisation leading to variable interaction with metabolic enzymes for oxidative stress and apoptosis causing physiological and morphological abnormalities. The study unravelled the information of in vivo toxicity at cellular and molecular level to advocate the attention of taking measures for management of CP as well as TCP for environmental and human health.

MITOGEN-ACTIVATED PROTEIN INHIBITORS: FULL-FIELD ELECTRORETINOGRAM DEMONSTRATING GENERALIZED RETINAL DYSFUNCTION

PURPOSE

To report a patient with generalized retinal toxicity to mitogen-activated protein inhibitors.

METHODS

Retrospective case report.

RESULTS

Full-field electroretinogram findings indicate a generalized toxicity to the use of the mitogen-activated protein inhibitor trametinib. There was an improved response and resolution of serous detachments after decreasing the dose.

CONCLUSION

Mitogen-activated protein inhibitors may affect global retinal function, as opposed to the serous detachments that are concentrated in the posterior pole. This may be of importance in further understanding the underlying pathologic mechanisms.

Real-Life Impact of Drug Toxicity on Dolutegravir Tolerability: Clinical Practice Data from a Multicenter Italian Cohort

Dolutegravir (DTG) is currently one of the most used Integrase inhibitors (INI) in antiretroviral therapies (ARV) in both naïve and experienced people living with HIV (PLWHIV). We analyzed a multicenter cohort of PLWHIV, both naïve and experienced, starting an ARV including DTG. We enrolled 3775 PLWHIV: 2763 (73.2%) were males, with a median age of 50 years. During 9890.7 PYFU, we observed 930 discontinuations (9.4 per 100 PYFU). Estimated probabilities of maintaining DTG at three and five years were 75.1% and 67.2%, respectively. Treatment-naïve pts showed a lower probability of maintaining DTG at three and five years compared to treatment-experienced PLWHIV (log-rank p < 0.001). At a multivariate analysis, a longer time of virological suppression (aHR 0.994, p < 0.001) and having experienced a previous virological failure (aHR 0.788, p = 0.016) resulted protective against DTG discontinuation. Most discontinuations (84.0%) happened within the first 12 months of DTG initiation, in particular, 92.2% of discontinuations due to neuropsychiatric toxicity were observed in the first year. Our data confirm the overall good tolerability of DTG in clinical practice, with a low rate of discontinuations. CNS toxicity resulted the main reason for DTG discontinuation, with most related interruptions happening in the first year from DTG introduction.

Dabrafenib- and trametinib-associated glomerular toxicity: A case report

RATIONALE

Combined treatment with dabrafenib, a B-RAF inhibitor, and trametinib, a mitogen-activated protein kinase inhibitor, is an effective option for patients with metastatic melanoma. A few cases of acute kidney injury associated with tubulointerstitial nephritis and 1 case of nephrotic syndrome have been reported in patients on this drug combination; however, progressive renal injury has not been reported. In this case study, we report a patient with metastatic melanoma who developed glomerular capillary endothelial toxicity and progressive glomerular sclerosis during combination therapy.

PATIENT CONCERN

Our patient was an 80-year-old woman with a history of type 2 diabetes and chronic kidney disease.

DIAGNOSIS AND INTERVENTION

She was diagnosed with metastatic melanoma and commenced combination therapy with dabrafenib and trametinib.

OUTCOMES

Her renal function progressively deteriorated; by month 20 after treatment commencement, her serum creatinine level had increased from 1.59 to 3.74 mg/dL. The first kidney biopsy revealed marked glomerular and endothelial cell damage. Her medication was stopped, but no improvement was evident. At 5 months after the first biopsy, her serum creatinine level had increased to 5.46 mg/dL; a second kidney biopsy revealed focal segmental glomerular sclerosis and marked tubulointerstitial fibrosis. She was started on hemodialysis.

LESSONS

We describe a patient with a metastatic melanoma who developed progressive kidney failure during treatment with dabrafenib and trametinib. The most prominent microscopy findings were glomerular endothelial damage in the initial kidney biopsy and accelerated glomerular sclerosis and tubulointerstitial fibrosis in the follow-up biopsy. We hypothesize that a decreased renal reserve and impairment of kidney repair capacity caused by inhibition of B-RAF, a downstream mediator of vascular endothelial growth factor, may explain the progressive kidney injury.

Evaluation of toxicological effects of organophosphorus pesticide metabolites on human HepG2 cells

Trichloropyridinol (TCP); 3, 5, 6-trichloro-2-pyridinol is the primary metabolites of the organophosphorus pesticide chlorpyrifos. It is more highly persistent than parent compounds in the environment and might represent serious risks to human health. In this study, we investigated the toxicological effects and mechanism of TCP on HepG2 cells. The results revealed that TCP induced DNA damage and apoptosis on HepG2 cells. Besides, up-regulating the expression level of Bax /Bcl-2, a reduction in mitochondrial membrane potential, caspase-9/-3 activation and the release of cytochrome-c are contributed to the toxicological effects of TCP on HepG2 cells. These data indicated that the cytotoxic effects of TCP might be associated with the activity of mitochondrial apoptotic pathways. In conclusion, the results demonstrated that TCP poses a potential threat to human health by inducing toxicological effects in the liver.

Cytotoxic and estrogenic activity of chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol. Study of marine yeasts as potential toxicity indicators

Chlorpyrifos (CP) is one of the organophosphate insecticides most used worldwide today. Although the main target organ for CP is the nervous system triggering predominantly neurotoxic effects, it has suggested other mechanisms of action as cytotoxicity and endocrine disruption. The risk posed by the pesticide metabolites on non-target organisms is increasingly recognized by regulatory agencies and natural resource managers. In the present study, cytotoxicity and estrogenic activity of CP, and its principal metabolite 3,5,6-trichloro-2-pyridinol (TCP) have been evaluated by in vitro assays, using two mammalian cell lines (HEK293 and N2a), and a recombinant yeast. Results indicate that TCP is more toxic than CP for the two cell lines assayed, being N2a cells more sensitive to both compounds. Both compounds show a similar estrogenic activity being between 2500 and 3000 times less estrogenic than 17β-estradiol. In order to find new toxicity measurement models, yeasts isolated from marine sediments containing CP residues have been tested against CP and TCP by cell viability assay. Of the 12 yeast strains tested, 6 of them showed certain sensitivity, and a concentration-dependent response to the tested compounds, so they could be considered as future models for toxicity tests, although further investigations and proves are necessary.

A year-long extended release nanoformulated cabotegravir prodrug

Long-acting cabotegravir (CAB) extends antiretroviral drug administration from daily to monthly. However, dosing volumes, injection site reactions and health-care oversight are obstacles towards a broad usage. The creation of poloxamer-coated hydrophobic and lipophilic CAB prodrugs with controlled hydrolysis and tissue penetrance can overcome these obstacles. To such ends, fatty acid ester CAB nanocrystal prodrugs with 14, 18 and 22 added carbon chains were encased in biocompatible surfactants named NMCAB, NM2CAB and NM3CAB and tested for drug release, activation, cytotoxicity, antiretroviral activities, pharmacokinetics and biodistribution. Pharmacokinetics studies, performed in mice and rhesus macaques, with the lead 18-carbon ester chain NM2CAB, showed plasma CAB levels above the protein-adjusted 90% inhibitory concentration for up to a year. NM2CAB, compared with NMCAB and NM3CAB, demonstrated a prolonged drug release, plasma circulation time and tissue drug concentrations after a single 45 mg per kg body weight intramuscular injection. These prodrug modifications could substantially improve CAB's effectiveness.

Toxic effects of fluridone on early developmental stages of Japanese Medaka (Oryzias latipes)

The herbicide fluridone is intensively applied to control invasive aquatic plants globally, including in the Sacramento and San Joaquin Delta (the Delta), California, USA. Our previous study revealed that the adult stage of Delta Smelt showed acute and sub-lethal adverse effects following 6 h of exposure to environmentally relevant concentrations of fluridone. To further investigate mechanisms of toxicity of fluridone and to assess its toxicity to early life stages of fish, we performed additional exposures using the fish model Japanese Medaka (Oryzias latipes). Male and female Medaka embryos were exposed to concentrations of fluridone for 14 d and showed reduced hatching success in a dose dependent manner. The half maximal effective concentration for the hatching success was 2.3 mg L^-1. In addition, male and female Medaka larvae were acute exposed to fluridone for 6 h to assess their swimming behavior and gene expression patterns. Fish exposed to fluridone at 4.2 mg L^-1 or higher became lethargic and showed abnormal swimming behavior. The response to the stimuli was significantly impaired by fluridone at 21 mg L^-1 and above in males, and at 104 mg L^-1 in females. Transcriptome analysis identified a total of 799 genes that were significantly differentially expressed, comprising 555 up-regulated and 244 down-regulated genes in males exposed to 21 mg L^-1 of fluridone. The gene set enrichment analysis indicated a number of biological processes altered by fluridone. Among the genes involved in those biological processes, the expression of the genes, acetylcholinesterase, retinoic acid receptor, insulin receptor substrate, glutathione reductase, and glutathione S transferase, exhibited dose- and sex-dependent responses to fluridone. The study indicated that fluridone exposure led to detrimental toxic effects at early developmental stages of fish, by disturbing the biological processes of growth and development, and the nervous system, inducing oxidative stress and endocrine disruption.

Sub-lethal effects of herbicides penoxsulam, imazamox, fluridone and glyphosate on Delta Smelt (Hypomesus transpacificus)

Concerns regarding non-target toxicity of new herbicides used to control invasive aquatic weeds in the San Francisco Estuary led us to compare sub-lethal toxicity of four herbicides (penoxsulam, imazamox, fluridone, and glyphosate) on an endangered fish species Delta Smelt (Hypomesus transpacificus). We measured 17β-estradiol (E2) and glutathione (GSH) concentrations in liver, and acetylcholinesterase (AChE) activity in brain of female and male fish after 6 h of exposure to each of the four herbicides. Our results indicate that fluridone and glyphosate disrupted the E2 concentration and decreased glutathione concentration in liver, whereas penoxsulam, imazamox, and fluridone inhibited brain AChE activity. E2 concentrations were significantly increased in female and male fish exposed to 0.21 μM of fluridone and in male fish exposed to 0.46, 4.2, and 5300 μM of glyphosate. GSH concentrations decreased in males exposed to fluridone at 2.8 μM and higher, and glyphosate at 4.2 μM. AChE activity was significantly inhibited in both sexes exposed to penoxsulam, imazamox, and fluridone, and more pronounced inhibition was observed in females. The present study demonstrates the potential detrimental effects of these commonly used herbicides on Delta Smelt.

Effects of chlorpyrifos and trichloropyridinol on HEK 293 human embryonic kidney cells

Chlorpyrifos (CPF) [O, O-diethyl -O-3, 5, 6-trichloro-2-pyridyl phosphorothioate] is an organophosphate insecticide widely used for agricultural and urban pest control. Trichloropyridinol (TCP; 3,5,6-trichloro-2-pyridinol), the primary metabolite of CPF, is often used as a generic biomarker of exposure for CPF and related compounds. Human embryonic kidney 293 (HEK 293) cells were exposed to CPF and TCP with varying concentrations and exposure periods. Cell cultures enable the cost-effective study of specific biomarkers to help determine toxicity pathways to predict the effects of chemical exposures without relying on whole animals. Both CPF and TCP were found to induce cytotoxic effects with CPF being more toxic than TCP with EC₅₀ values of 68.82 μg/mL and 146.87 μg·ml^-1 respectively. Cell flow cytometric analyses revealed that exposure to either CPF or TCP leads to an initial burst of apoptotic induction followed by a slow recruitment of cells leading towards further apoptosis. CPF produced a strong induction of IL6, while TCP exposure resulted in a strong induction of IL1α. Importantly, the concentrations of CPF and TCP required for these cytokine inductions were higher than those required to induce apoptosis. These data suggest CPF and TCP are cytotoxic to HEK 293 cells but that the mechanism may not be related to an inflammatory response. CPF and TCP also varied in their effects on the HEK 293 proteome with 5 unique proteins detected after exposure to CPF and 31 unique proteins after TCP exposure.

IQGAP1 is an oncogenic target in canine melanoma

Canine oral mucosal melanoma is an aggressive malignant neoplasm and is characterized by local infiltration and a high metastatic potential. The disease progression is similar to that of human oral melanomas. Whereas human cutaneous melanoma is primarily driven by activating mutations in Braf (60%) or Nras (20%), human mucosal melanoma harbors these mutations much less frequently. This makes therapeutic targeting and research modeling of the oral form potentially different from that of the cutaneous form in humans. Similarly, research has found only rare Nras mutations and no activating Braf mutations in canine oral melanomas, but they are still reliant on MAPK signaling. IQGAP1 is a signaling scaffold that regulates oncogenic ERK1/2 MAPK signaling in human Ras- and Raf- driven cancers, including melanomas. To investigate whether IQGAP1 is a potential target in canine melanoma, we examined the expression and localization of IQGAP1 in primary canine melanomas and canine oral melanoma cell lines obtained from the University of California-Davis. Using CRISPR/Cas9 knockout of IQGAP1, we examined effects on downstream ERK1/2 pathway activity and assayed proliferation of cell lines when treated with a peptide that blocks the interaction between IQGAP1 and ERK1/2. We observed that canine IQGAP1 is expressed and localizes to a similar extent in both human and canine melanoma by qPCR, Western blot, and immunofluorescence. Deletion of IQGAP1 reduces MAPK pathway activation in cell lines, similar to effects seen in human Braf^V600E cell lines. Additionally, we demonstrated reduced proliferation when these cells are treated with a blocking peptide in vitro.

Re-examining HSPC1 inhibitors

HSPC1 is a critical protein in cancer development and progression, including colorectal cancer (CRC). However, clinical trial data reporting the effectiveness of HSPC1 inhibitors on several cancer types has not been as successful as predicted. Furthermore, some N-terminal inhibitors appear to be much more successful than others despite similar underlying mechanisms. This study involved the application of three N-terminal HSPC1 inhibitors, 17-DMAG, NVP-AUY922 and NVP-HSP990 on CRC cells. The effects on client protein levels over time were examined. HSPC1 inhibitors were also applied in combination with chemotherapeutic agents commonly used in CRC treatment (5-fluorouracil, oxaliplatin and irinotecan). As HSPA1A and HSPB1 have anti-apoptotic activity, gene-silencing techniques were employed to investigate the significance of these proteins in HSPC1 inhibitor and chemotherapeutic agent resistance. When comparing the action of the three HSPC1 inhibitors, there are distinct differences in the time course of important client protein degradation events. The differences between HSPC1 inhibitors were also reflected in combination treatment-17-DMAG was more effective compared with NVP-AUY922 in potentiating the cytotoxic effects of 5-fluorouracil, oxaliplatin and irinotecan. This study concludes that there are distinct differences between N-terminal HSPC1 inhibitors, despite their common mode of action. Although treatment with each of the inhibitors results in significant induction of the anti-apoptotic proteins HSPA1A and HSPB1, sensitivity to HSPC1 inhibitors is not improved by gene silencing of HSPA1A or HSPB1. HSPC1 inhibitors potentiate the cytotoxic effects of chemotherapeutic agents in CRC, and this approach is readily available to enter clinical trials. From a translational point of view, there may be great variability in sensitivity to the inhibitors between individual patients.

Toxicity of 3,5,6-trichloro-2-pyridinol tested at multiple stages of zebrafish (Danio rerio) development

Organophosphate compounds (OP) are widely used throughout the world for pest control. 3,5,6-Trichloro-2-pyridinol (TCP) is a primary metabolite of two OP compounds namely CP and triclopyr. This study is carried out to know whether a metabolite of parent compound is doing well or harm to biota. The potential effect of TCP was evaluated on development as destabilization of any events transpiring during embryogenesis could be deleterious. To determine this, 4-hpf zebrafish embryos were exposed to five concentrations of TCP (200, 400, 600, 800, 1000 μg/L) or 99.5 % acetone (solvent control). Different early life-stage parameters were observed at four different developmental stages, 24, 48, 72 and 96 hpf. TCP-treated embryo/larvae showed increased mortality, delay in hatching time and decrease in percentage of hatched embryos. Reduction in heartbeat rate, blood flow and body and eye pigmentation was noticed in a dose-dependent manner. Pericardial and yolk sac edema were most severe malformations caused by TCP. Along with this crooked spine/notochord, tail deformation was noticed in hatched and unhatched embryos. The malformations observed provide a good starting point for examination of the molecular mechanisms that are affected during development by TCP. Results gain significance as TCP, which is a breakdown product, appears to be more toxic during development compared to parent compound, CP (our earlier publication).

Chlorpyrifos exposure in farmers and urban adults: Metabolic characteristic, exposure estimation, and potential effect of oxidative damage

Chlorpyrifos is a widely used organophosphorus pesticide that efficiently protects crops against pests. However, recent studies suggest that severe exposure to chlorpyrifos may present adverse health effects in human. To analyze the exposure level and metabolic characteristics of chlorpyrifos pesticide in urban adults and farmers with/without occupation pesticide contact, the occurrence of urinary chlorpyrifos and methyl chlorpyrifos (CP-me), as well as their metabolite, 3,5,6-trichloro-2-pyridinol (TCPy), was determined in farmers of an agricultural village in China, and in urban adults of a nearby town. The geometric mean (GM) concentrations of TCPy, which is the major marker of chlorpyrifos exposure, were 4.29 and 7.57μg/g-creatinine in urban adults and farmers before pesticide application, respectively. Chlorpyrifos spraying significantly increased the concentrations of urinary TCPy. In the first day after spraying, a GM concentration of 43.7μg/g-creatinine was detected in the urine specimens from farmers, which decreased to 38.1 and 22.8μg/g-creatinine in the second and third day after chlorpyrifos spraying. The ratio of TCPy and its parent compounds, i.e. chlorpyrifos and CP-me, was positively associated with the sum concentration of urinary chlorpyrifos, CP-me, and TCPy, suggesting the increasing metabolic efficiency of chlorpyrifos to TCPy at higher chlorpyrifos exposure levels. To estimate the farmers' occupational exposure to chlorpyrifos pesticide, a new model based on the fitted first-order elimination kinetics of TCPy was established. Occupational chlorpyrifos exposure in a farmer was estimated to be 3.70μg/kg-bw/day (GM), which is an exposure level that is higher than the recommended guideline levels. Significant increase of urinary 8-hydroxydeoxyguanosine (8-OHdG) was observed on the first day after chlorpyrifos spraying, which indicates a potential oxidative damage in farmers. However, urinary 8-OHdG returned to its baseline level within two days.

Ecological impacts of fluridone and copper sulphate in catfish aquaculture ponds

Fluridone and copper sulphate are often used for controlling macrophytes and algae in aquaculture ponds. The present study examined the ecological effects of these chemicals on macrophyte, phytoplankton, and zooplankton biomass; plankton community structure; water quality parameters; and fish survival and yield in catfish culture ponds using a randomized complete block design. The estimated half-life of fluridone in the individual ponds ranged from 1.6 d to 10.8 d. Free copper ion activity in ponds treated with copper sulphate was dynamic, ranging from pCu of 7.7 to 8.9 after each application and decreasing to approximately 12 (1 × 10(-12)  M) within 1 wk after each application, approaching observed values in control ponds (pCu = 12.3-13.4). No difference in macrophyte biomass was observed among treatments. Fluridone and copper treatments elicited different responses within the phytoplankton community. Copper treatments reduced Cyanophyta biomass but increased biomass of more tolerant taxa among the Chlorophyta and Chrysophyta. Fluridone treatments reduced total phytoplankton biomass including Cyanophyta and increased the sensitivity of Chlorophyta and Chrysophyta to copper. Copper also affected zooplankton community composition as a result of direct toxic effects on sensitive zooplankton taxa (e.g., Cladocera), whereas Copepoda biomass in copper-treated ponds exceeded that in controls. Catfish survival and yield were not significantly different among treatments. The results of the present study suggest that fluridone and copper interact at realistic application rates, increasing the ability to control algae compared with treatments where they are applied alone.

Hepatotoxicity and nephrotoxicity induced by the chlorpyrifos and chlorpyrifos-methyl metabolite, 3,5,6-trichloro-2-pyridinol, in orally exposed mice

3,5,6-Trichloro-2-pyridinol (TCP) is a primary degradation product of chlorpyrifos and chlorpyrifos-methyl. TCP has longer half-life in soil and greater solubility in water than its parent compound, and cause wide contamination in environments. However, studies about the toxic effects of TCP are limited and outdate. In this study, 5 mg/kg/day, 50 mg/kg/day, and 150 mg/kg/day TCP were given to male mice through gavage for four weeks. As a result, the final body weights of TCP treated groups were significantly lower than control, and the relative organ weights of the liver and kidney were significantly higher than that of control. In addition, NMR-based metabolomics was used to investigate the toxic effects of TCP. It was found that a total of 39 serum metabolites were significantly changed in the TCP-treated groups, and these metabolites are related to hepatotoxicity and nephrotoxicity. These results were also confirmed by histopathology, serum biochemical, and oxidative stress analysis. In addition, metabolic disturbances due to TCP exposure were also observed based on altered metabolites. As far as we know, these results are the first to show the metabolomic toxicity of TCP, which warrants further research.

Targeting vascular endothelial growth factor receptor 2 and protein kinase D1 related pathways by a multiple kinase inhibitor in angiogenesis and inflammation related processes in vitro

Emerging evidence suggests that the vascular endothelial growth factor receptor 2 (VEGFR2) and protein kinase D1 (PKD1) signaling axis plays a critical role in normal and pathological angiogenesis and inflammation related processes. Despite all efforts, the currently available therapeutic interventions are limited. Prior studies have also proved that a multiple target inhibitor can be more efficient compared to a single target one. Therefore, development of novel inflammatory pathway-specific inhibitors would be of great value. To test this possibility, we screened our molecular library using recombinant kinase assays and identified the previously described compound VCC251801 with strong inhibitory effect on both VEGFR2 and PKD1. We further analyzed the effect of VCC251801 in the endothelium-derived EA.hy926 cell line and in different inflammatory cell types. In EA.hy926 cells, VCC251801 potently inhibited the intracellular activation and signaling of VEGFR2 and PKD1 which inhibition eventually resulted in diminished cell proliferation. In this model, our compound was also an efficient inhibitor of in vitro angiogenesis by interfering with endothelial cell migration and tube formation processes. Our results from functional assays in inflammatory cellular models such as neutrophils and mast cells suggested an anti-inflammatory effect of VCC251801. The neutrophil study showed that VCC251801 specifically blocked the immobilized immune-complex and the adhesion dependent TNF-α -fibrinogen stimulated neutrophil activation. Furthermore, similar results were found in mast cell degranulation assay where VCC251801 caused significant reduction of mast cell response. In summary, we described a novel function of a multiple kinase inhibitor which strongly inhibits the VEGFR2-PKD1 signaling and might be a novel inhibitor of pathological inflammatory pathways.

Multimodal assessment of non-specific hemostatic agents for apixaban reversal

BACKGROUND

Non-specific hemostatic agents, namely activated prothrombin complex concentrate (aPCC), PCC and recombinant activated factor (F) VII (rFVIIa), can be used, off-label, to reverse the effects of FXa inhibitors in the rare cases of severe hemorrhages, as no approved specific antidote is available. We have evaluated the ability of aPCC, PCC and rFVIIa to reverse apixaban.

METHODS

Healthy volunteer whole blood was spiked with therapeutic or supra-therapeutic apixaban concentrations and two doses of aPCC, PCC or rFVIIa. Tests performed included a turbidimetry assay for fibrin polymerization kinetics analysis, scanning electron microscopy for fibrin network structure observation, thrombin generation assay (TGA), thromboelastometry, prothrombin time and activated partial thromboplastin time.

RESULTS

aPCC generated a dense clot constituting thin and branched fibers similar to those of a control without apixaban, increased fibrin polymerization velocity and improved quantitative (endogenous thrombin potential and peak height) as well as latency (clotting and lag times) parameters. Adding PCC also improved the fibrin and increased quantitative parameters, but fibrin polymerization kinetics and latency parameters were not corrected. Finally, rFVIIa improved latency parameters but failed to restore the fibrin network structure, fibrin polymerization velocity and quantitative parameters.

CONCLUSION

aPCC was more effective than PCC or rFVIIa in reversing in vitro the effects of apixaban. aPCC rapidly triggered the development of an apparently normal fibrin network and corrected latency and quantitative parameters, whereas PCC or rFVIIa had only a partial effect.

Fluridone: a combination germination stimulant and herbicide for problem fields?

BACKGROUND

Problem weeds in agriculture, such as Lolium rigidum Gaud., owe some of their success to their large and dormant seed banks, which permit germination throughout a crop-growing season. Dormant weed seed banks could be greatly depleted by application of a chemical that stimulates early-season germination and then kills the young seedlings. Fluridone, a phytoene desaturase-inhibiting herbicide that can also break seed dormancy, was assessed for its efficacy in this regard.

RESULTS

The germination of fluridone-treated Lolium rigidum seeds was stimulated on soils with low organic matter, and almost 100% seedling mortality was observed, while the treatment was only moderately effective on a high-organic-matter potting mix. Seedlings from wheat, canola, common bean and chickpea seeds sown on fluridone-treated sandy loam were bleached and did not survive, but lupins and field peas grew normally.

CONCLUSION

This proof-of-concept study with fluridone suggests that it may be possible to design safe and effective molecules that act as germination stimulants plus herbicides in a range of crop and soil types: a potentially novel way of utilising herbicides to stimulate seed bank germination and a valuable addition to an integrated weed management system.

Health risk characterization of chlorpyrifos using epidemiological dose-response data and probabilistic techniques: a case study with rice farmers in Vietnam

Various methods for risk characterization have been developed using probabilistic approaches. Data on Vietnamese farmers are available for the comparison of outcomes for risk characterization using different probabilistic methods. This article addresses the health risk characterization of chlorpyrifos using epidemiological dose-response data and probabilistic techniques obtained from a case study with rice farmers in Vietnam. Urine samples were collected from farmers and analyzed for trichloropyridinol (TCP), which was converted into absorbed daily dose of chlorpyrifos. Adverse health response doses due to chlorpyrifos exposure were collected from epidemiological studies to develop dose-adverse health response relationships. The health risk of chlorpyrifos was quantified using hazard quotient (HQ), Monte Carlo simulation (MCS), and overall risk probability (ORP) methods. With baseline (prior to pesticide spraying) and lifetime exposure levels (over a lifetime of pesticide spraying events), the HQ ranged from 0.06 to 7.1. The MCS method indicated less than 0.05% of the population would be affected while the ORP method indicated that less than 1.5% of the population would be adversely affected. With postapplication exposure levels, the HQ ranged from 1 to 32.5. The risk calculated by the MCS method was that 29% of the population would be affected, and the risk calculated by ORP method was 33%. The MCS and ORP methods have advantages in risk characterization due to use of the full distribution of data exposure as well as dose response, whereas HQ methods only used the exposure data distribution. These evaluations indicated that single-event spraying is likely to have adverse effects on Vietnamese rice farmers.

Peripheral nerve and skin damage associated with working in a STCP factory: report of four cases

Sodium 3,5,6-trichloropyridin-2-ol (STCP) is a widely used intermediate for the production of chlorpyrifos. However, its effect on the health of workers in STCP factories has become increasingly problematic. This article reports four workers who worked in a STCP factory developed peripheral neuropathy in the lower extremities and chloracne-like skin lesions on the whole body. Patches of follicular skin eruptions (mainly blackheads, accompanied by follicular orifice cornification occasionally accompanied by milia-like skin eruptions) were found on the head and face, around the auricle, chest and back, abdomen and scrotum. In one patient, the activity of serum cholinesterase was decreased and recovered slowly, but there were no muscarinic, nicotinic, or central nervous system symptoms. The concentrations of urine STCP detected in four patients were 0.266, 0.066, 0.044, and 0.033 μg/mL.

Induction of micronuclei by 2-hydroxypyridine in water and elimination of solution genotoxicity by UVC (254 nm) photolysis

2-Hydroxypyridine (2-HPY) is a major first-stage product formed upon the photolytic destruction of 2-halogenated pyridines. Genotoxicity of 2-HPY in water was studied as a function of concentration. Aqueous solutions of 2-HPY were irradiated by ultraviolet (UV) at 254 nm. 2-HPY concentration, solution total organic carbon (TOC) concentration and solution genotoxicity were measured as a function of treatment time and their profile as a function of time is presented in this work. 2-HPY was found to be genotoxic at all concentrations in the range of 5-400 μg ml(-1). 2-HPY mineralises completely upon prolonged UV irradiation. All untreated and irradiated solution samples, taken at different photo-treatment times, were tested in cultured human lymphocytes applying the cytokinesis block micronucleus (CBMN) assay. The genotoxicity of the solution was reduced near to the control level after prolonged UV irradiation.

In vitro effects of pirfenidone on cardiac fibroblasts: proliferation, myofibroblast differentiation, migration and cytokine secretion

Cardiac fibroblasts (CFs) are the primary cell type responsible for cardiac fibrosis during pathological myocardial remodeling. Several studies have illustrated that pirfenidone (5-methyl-1-phenyl-2-[1H]-pyridone) attenuates cardiac fibrosis in different animal models. However, the effects of pirfenidone on cardiac fibroblast behavior have not been examined. In this study, we investigated whether pirfenidone directly modulates cardiac fibroblast behavior that is important in myocardial remodeling such as proliferation, myofibroblast differentiation, migration and cytokine secretion. Fibroblasts were isolated from neonatal rat hearts and bioassays were performed to determine the effects of pirfenidone on fibroblast function. We demonstrated that treatment of CFs with pirfenidone resulted in decreased proliferation, and attenuated fibroblast α-smooth muscle actin expression and collagen contractility. Boyden chamber assay illustrated that pirfenidone inhibited fibroblast migration ability, probably by decreasing the ratio of matrix metalloproteinase-9 to tissue inhibitor of metalloproteinase-1. Furthermore, pirfenidone attenuated the synthesis and secretion of transforming growth factor-β1 but elevated that of interleukin-10. These direct and pleiotropic effects of pirfenidone on cardiac fibroblasts point to its potential use in the treatment of adverse myocardial remodeling.

Ricinus communis intoxications in human and veterinary medicine-a summary of real cases

Accidental and intended Ricinus communis intoxications in humans and animals have been known for centuries but the causative agent remained elusive until 1888 when Stillmark attributed the toxicity to the lectin ricin. Ricinus communis is grown worldwide on an industrial scale for the production of castor oil. As by-product in castor oil production ricin is mass produced above 1 million tons per year. On the basis of its availability, toxicity, ease of preparation and the current lack of medical countermeasures, ricin has gained attention as potential biological warfare agent. The seeds also contain the less toxic, but highly homologous Ricinus communis agglutinin and the alkaloid ricinine, and especially the latter can be used to track intoxications. After oil extraction and detoxification, the defatted press cake is used as organic fertilizer and as low-value feed. In this context there have been sporadic reports from different countries describing animal intoxications after uptake of obviously insufficiently detoxified fertilizer. Observations in Germany over several years, however, have led us to speculate that the detoxification process is not always performed thoroughly and controlled, calling for international regulations which clearly state a ricin threshold in fertilizer. In this review we summarize knowledge on intended and unintended poisoning with ricin or castor seeds both in humans and animals, with a particular emphasis on intoxications due to improperly detoxified castor bean meal and forensic analysis.

Toxicological effects of the aquatic herbicide, fluridone, on male water mites (Hydrachnidiae: Arrenurus: Megaluracarus)

The acute toxicities for technical grade fluridone (Sonar™) and the commercial formulation of fluridone (Sonar®AS) were assessed for male water mites (Hydrachnidiae: Arrenurus: Megaluracarus). Signs of toxicity were evaluated by detection of locomotor dysfunction or death after exposure to concentrations of 100,000, 10,000, 1,000, and 100 μg/L of Sonar™ and 10,000, 5,000, 1,000, 100, and 10 μg/L of Sonar®AS in US EPA, moderately hard reconstituted water (MHRW). The median effective concentration (EC50) was 891 and 631 μg/L for Sonar™ at 48 and 96 h and less than 10 μg/L for Sonar®AS at 96 h. Increased duration of exposure to Sonar®AS from 48 to 96 h had a significant effect on increasing the rate of combined morbidity and mortality. At the lowest concentration of Sonar®AS tested, which is half the concentration allowed within 400 m of any functioning potable water intake for human usage, 40% of the mites were adversely affected at 48 h and 70% were affected after 96 h of exposure. This study demonstrates that Sonar®AS is 60-fold more toxic to water mites than the active ingredient alone. At currently acceptable application rates of 90-150 μg/L fluridone, the addition of ingredients classified as inert, as in Sonar®AS, result in an increased risk of adverse effects on populations of male water mites (Arrenurus: Megaluracarus) in aquatic ecosystems.

Penicidones A-C, three cytotoxic alkaloidal metabolites of an endophytic Penicillium sp

Along with the known secondary metabolites lumichrome, physcion, and emodin-1,6-dimethyl ether, three alkaloids named penicidones A-C (1-3) were isolated from the culture of Penicillium sp. IFB-E022, an endophytic fungal strain residing in the stem of Quercus variabilis (Fagaceae). The structures of penicidones A-C were established by a correlative interpretation of spectroscopic data including IR, UV and HR-ESI-MS, as well as by analysis of a set of 1D and 2D NMR experiments. The stereochemistry of compounds 1 and 2 was obtained by comparison of the optical rotation with those of vermistatin and its analogues. Penicidones A-C were the first group of natural products possessing a penicidone framework. Compounds 1-3 exhibited moderate cytotoxicity against four cancer cell lines.

Toxicity of chlorpyrifos and TCP alone and in combination to Daphnia carinata: the influence of microbial degradation in natural water

The acute toxicity of chlorpyrifos and its principal metabolite 3,5,6-trichloropyridinol (TCP) alone and in combination to a cladoceran, Daphnia carinata, was studied in both cladoceran culture medium and natural water collected from a local suburban stream. TCP was found to be more toxic than its parent chemical chlorpyrifos to Daphnia survival in cladoceran culture medium. However, TCP in natural water was not toxic to D. carinata up to 2 microgL(-1). The LC(50) values for chlorpyrifos, TCP and chlorpyrifos+TCP were 0.24, 0.20 and 0.08 microgL(-1), respectively, in cladoceran culture medium. Although the parent chemicals and their degradation products co-exist in natural waters, the existing guidelines for water quality are based on individual chemicals. The results of this investigation suggest that chlorpyrifos and TCP can interact synergistically, additively or antagonistically, resulting in an increase or decrease in the overall toxicity of the mixture compared to individual compounds. The indigenous microorganisms in natural water could play a significant role in degradation of these compounds thereby influencing their toxicity in receiving waters. This study clearly suggests that the joint action of pesticides and their degradation products should be considered in the development of water quality guidelines. To our knowledge, this is the first study on the interactive effect of chlorpyrifos and TCP to a cladoceran and suggests that these two compounds are non-toxic when present together at concentrations up to 0.12 microgL(-1). However, these compounds together act additively at and above 0.5 microgL(-1) to fresh water invertebrates and therefore pollution with these compounds may adversely affect natural ecosystems.

Expression of Th1/Th2 cytokines in human blood after in vitro treatment with chlorpyrifos, and its metabolites, in combination with endotoxin LPS and allergen Der p1

Exposure to organophosphate (OP) pesticides has been associated with respiratory symptoms and may be related to asthma; however, few studies have examined the molecular basis for these associations. Asthma and allergic disorders are characterized by elevated Th2 cytokines (IL-4, IL-5, IL-13), whereas the chronic inflammatory response in asthmatic airways is maintained by Th1 cytokine IFN-gamma. The goal of this in vitro study was to examine the effects of OP chlorpyrifos (CPF), and its metabolites chlorpyrifos-oxon (CPO) and 3,5,6-trichloro-2-pyridinol (TCP), singly, and in combination with endotoxin lipopolysaccharide (LPS) or house dust mite Dermatophagoides pteronyssinus (Der p1) allergen, on expression of IFN-gamma and IL-4, Th1 and Th2 signature cytokines, respectively. Cytokine expression was measured by ELISA and flow cytometry. Human blood cultures were treated with CPF/CPO/TCP (1-1000 microg ml(-1)) and LPS (1.5-2.5 microg ml(-1)) or Der p1 (200 AU ml(-1)) and supernatants were collected at 48 h. Pesticides CPF, CPO and TCP did not induce cytokine expression in vitro, while LPS and Der p1 induced IFN-gamma and IL-4 expression, respectively. Whole blood cultures treated with low doses of CPO (1 and 10 microg ml(-1)), in combination with LPS, expressed higher levels of IFN-gamma than LPS alone (P < 0.05). While CPO increased LPS-dependent induction of IFN-gamma, CPO treatment did not alter Der p1 induction of IL-4. The interaction between CPO and LPS, which results in an increased type 1 immune response, should be investigated further, particularly since the combination of OP pesticides and endotoxin is common in rural, agricultural communities.

Effects of kava alkaloid, pipermethystine, and kavalactones on oxidative stress and cytochrome P450 in F-344 rats

Kava-containing products remain popular in the United States and continue to be sold in health food stores and ethnic markets regardless of the fact that it was banned in Western countries such as Germany, France, Switzerland, Australia, and Canada, following reports of alleged hepatotoxicity. It is therefore critical to establish efficacy and verify adverse effects and/or herb-drug interactions for kava-kava (Piper methysticum). We have previously demonstrated that kava alkaloid, pipermethystine (PM), abundant in leaves and stem peelings, induces mitochondrial toxicity in human hepatoma cells, HepG2, as compared with the bioactive components, kavalactones (KL), abundant in the rhizome. The current study compared short-term toxic effects of PM in Fischer-344 (F-344) rats to acetone-water extracts of kava rhizome (KRE). Treatment of F-344 rats with PM (10 mg/kg) and KRE (100 mg/kg) for 2 weeks failed to elicit any significant changes in liver function tests or cause severe hepatic toxicity as measured by lipid peroxidation and apoptosis markers such as malondialdehyde, Bax, and Bcl-2. However, PM-treated rats demonstrated a significant increase in hepatic glutathione, cytosolic superoxide dismutase (Cu/ZnSOD), tumor necrosis factor alpha mRNA expression, and cytochrome P450 (CYP) 2E1 and 1A2, suggesting adaptation to oxidative stress and possible drug-drug interactions.

Aquatic herbicides and herbicide contaminants: In vitro cytotoxicity and cell-cycle analysis

Concerns have arisen about the possible effects of herbicide contamination in aquatic ecosystems. Crop herbicides are introduced into the aquatic environment both inadvertently through runoff events and intentionally through the use of those registered for use in waterways. Acetochlor and atrazine are two agricultural crop herbicides that have often been reported to contaminate waters. Diquat and fluridone are both registered aquatic management herbicides. In this study, a mammalian in vitro cell cytotoxicity assay was used to evaluate the cytotoxicity of these four commonly used herbicides. The ranked order of the cytotoxicity was: diquat (C(1/2) = 0.036 mM +/- 0.011) > acetochlor (C(1/2) = 0.060 mM +/- 0.010) > fluridone (C(1/2) = 0.172 mM +/- 0.029) atrazine (C(1/2) = 0.581 mM +/- 0.050). In addition, flow cytometric analysis was conducted on CHO cells to investigate the potential impact of these four herbicides on the cell cycle. Acetochlor and diquat had the greatest impact on the cell cycle. Acetochor exposure resulted in a decreased number of cells in the G1 phase of the cell cycle, whereas diquat exposure resulted in a decreased number of cells in both the G1 and G2 phases. Both atrazine and fluridone resulted in a decrease in cells in the G2 phase. The agricultural crop herbicides and aquatic management herbicides gave similar results in cytotoxicity and in the cell-cycle assay at the end points tested.

Determination of biological reference values for chlorpyrifos metabolites in human urine using a toxicokinetic approach

Urinary biomarkers of chlorpyrifos (CPF) exposure are often measured in field studies, although biological reference values (BRVs) are not yet available to assess health risks. This study aimed at proposing BRVs for CPF metabolites in workers' urine based on a toxicokinetic approach. As a first step, a toxicokinetic model was developed, using published human kinetic data, to link the absorbed dose of CPF under a variety of exposure routes and temporal scenarios to the urinary excretion of its major metabolites, 3,5,6-trichloro-2-pyridinol (3,5,6-TCP) and alkyl phosphates (AP). The model was then used to propose BRVs for CPF metabolites in urine below which workers should not experience adverse health effects. This was achieved by linking (1) a literature-reported, repeated CPF no-observed-effect level (NOEL) daily exposure dose for the inhibition of red-blood-cell acetylcholinesterase activity to a corresponding absorbed daily dose, and (2) this absorbed daily dose to the urinary excretion of CPF metabolites. Model simulations under a variety of exposure scenarios showed that the safest BRVs are obtained from a dermal exposure scenario with the slowest absorption rate compatible with available literature data rather than from respiratory or oral exposure scenarios. Also, model simulations showed that, for a given total absorbed dose, absorption over 8 hours results in smaller 3,5,6-TCP and AP urinary excretion rates than those obtained from the same dose absorbed over shorter durations. From these considerations, BRVs were derived by simulating an 8-hour dermal CPF exposure such that the total absorbed daily dose corresponds to the absorbed NOEL. The reference values are proposed in the form of total amounts of 3,5,6-TCP and AP metabolites excreted in urine over chosen time periods (24 and 48 hours).

Iron chelation therapy

Although iron chelation therapy with deferoxamine (DFO) has changed life expectancy in thalassemic patients, compliance with the rigorous requirements of long-term subcutaneous DFO infusions is unsatisfactory. This problem underlines the current efforts for developing alternative, orally effective chelators to improve compliance and treatment results. For the patient with transfusional iron overload in whom results of DFO treatment are unsatisfactory, several orally effective agents are now available. The most important of the new generation of oral chelators are deferiprone and ICL670. Total iron excretion with deferiprone is less than with DFO, but deferiprone has a better ability to penetrate cell membranes and may have a better cardioprotective effect than DFO. Current studies of the clinical efficacy and tolerability of ICL670 indicate that at a single oral dose of 20 mg/kg daily, it may be as effective as parenteral DFO used at the standard dose of 40 mg/kg daily. Combined chelation treatment, employing a weak chelator that penetrates cells better, and a stronger chelator with efficient urinary excretion, may result in improved therapeutic effect through iron shuttling between the two compounds. The efficacy of combined chelation treatment is additive and offers an increased likelihood of success in patients previously failing DFO or deferiprone monotherapy.

Activity of Ricinus communis (Euphorbiaceae) and ricinine against the leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae) and the symbiotic fungus Leucoagaricus gongylophorus

The focus of this study was the identification of compounds from plant extracts for use in crop protection. This paper reports on the toxic activity of fractions of leaf extracts of Ricinus communis L (Euphorbiaceae) and isolated active compounds in the leaf-cutting ant Atta sexdens rubropilosa Forel and its symbiotic fungus Leucoagaricus gongylophorus (Singer) Möller. The main compounds responsible for activity against the fungus and ant in leaf extracts of R communis were found to be fatty acids for the former and ricinine for the ants.

Genotoxic activity of newly synthesized derivatives of cyano-pyridone in murine cells in vivo and in vitro

Possible genotoxic activity of two newly synthesized cyanopyridone compounds [4-(N-methyl-phalimidyl-3)-3-cyano-4-methyl-pyridone-2 (MPhCMP) and 1-(4-hydroxyphenyl)-3-cyano-4-methyl-pyridone-2 (HCMP)] with in vitro antitumor activity was studied both in in vitro and in vivo murine test systems. In L5178Y mouse lymphoma cells, HCMP did not induce micronuclei (MN) at the highest available (because of toxicity) concentration (100 microg/ml), while MPhCMP at dose of 50 microg/ml induced 2.6-fold, and at dose of 100 microg/ml 3.95-fold increase of number of the cells with MN. The concentration of 100 microg/ml is a threshold of toxicity of MPhCMP. In experiments on possible DNA damaging activity (the comet assay) of both substances using the same doses as in in vitro mutagenesis assay, we did not reveal any evidence of DNA damage. The acute toxicity of compounds was studied on male Swiss albino mice. LD50 values of MPhCMP and HCMP were 177.5 and 288 mg/kg, respectively. MPhCMP was more potent MN inductor than HCMP (2.5-fold at doses equivalent to 1/2 of LD50). Both substances possessing in vitro antitumor activity along with weak genotoxicity have a good chance for successful in vivo antitumor studies in rodents.

CLINICAL EVALUATION OF THE ORAL IRON CHELATOR DEFERIPRONE FOR THE POTENTIAL TREATMENT OF IRON OVERLOAD IN BIRD SPECIES

The clinical use of oral Fe chelators for the treatment of Fe-storage disease in birds requires evaluation. In this study, the efficacy of the Fe chelator deferiprone in reducing hepatic Fe stores, its effects on hematologic, biochemical, and plasma Fe parameters, and its potential toxicity during a 30-day treatment period were investigated in a controlled setting using two model species, the white leghorn chicken (Gallus gallus f. domestica) and the domestic pigeon (Columba livia). A second phase of the study investigated deferiprone-related Fe elimination in the excreta. Deferiprone, administered orally at a dosage of 50 mg/kg twice daily to birds that had been experimentally Fe loaded, significantly reduced hepatic Fe concentrations compared with levels in Fe-loaded and non-Fe-loaded controls. There were no significant alterations in routine clinical hematologic or biochemical parameters, although decreased transferrin saturation was noted in both species. Side effects associated with deferiprone administration were decreased weight gain and significant decreases in plasma Zn concentrations. No mortalities occurred in the pigeons, but there were three deaths in the deferiprone-treated group of Fe-loaded chickens, most likely associated with acute reduction of Fe required for normal enzymatic processes. Histologic changes associated with deferiprone treatment were not noted. Deferiprone caused a dose-dependent increase of Fe in the excreta at oral dosages of 50 and 75 mg/kg once daily in both species. Deferiprone is a promising, orally active Fe chelator for the treatment of Fe overload in birds, although its potential side effects need to be considered.

In vitro toxicity of kava alkaloid, pipermethystine, in HepG2 cells compared to kavalactones

Kava herbal supplements have been recently associated with acute hepatotoxicity, leading to the ban of kava products in approximately a dozen countries around the world. It is suspected that some alkaloids from aerial kava may have contributed to the problem. Traditionally, Pacific Islanders use primarily the underground parts of the shrub to prepare the kava beverage. However, some kava herbal supplements may contain ingredients from aerial stem peelings. The aim of this study was to test the in vitro effects of a major kava alkaloid, pipermethystine (PM), found mostly in leaves and stem peelings, and kavalactones such as 7,8-dihydromethysticin (DHM) and desmethoxyyangonin (DMY), which are abundant in the roots. Exposure of human hepatoma cells, HepG2, to 100 microM PM caused 90% loss in cell viability within 24 h, while 50 microM caused 65% cell death. Similar concentrations of kavalactones did not affect cell viability for up to 8 days of treatment. Mechanistic studies indicate that, in contrast to kavalactones, PM significantly decreased cellular ATP levels, mitochondrial membrane potential, and induced apoptosis as measured by the release of caspase-3 after 24 h of treatment. These observations suggest that PM, rather than kavalactones, is capable of causing cell death, probably in part by disrupting mitochondrial function. Thus, PM may contribute to rare but severe hepatotoxic reactions to kava.

Chlorpyrifos induces apoptosis in rat cortical neurons that is regulated by a balance between p38 and ERK/JNK MAP kinases

Chlorpyrifos, an acetylcholinesterase (AChE) inhibitor, is a widely used organophosphate pesticide. Recent concern has focused on its neurotoxicity that is not attributable to AChE inhibition. Here, we report that chlorpyrifos and chlorpyrifos-oxon, but not 3,5,6-trichloro-2-pyridinol (TCP; the breakdown product of chlorpyrifos and chlorpyrifos-oxon), induce apoptosis in primary cortical neurons cultured from embryonic day 17 or newborn rats. It is generally agreed that chlorpyrifos-oxon is approximately three orders of magnitude more potent than chlorpyrifos in inhibition of brain acetylcholinesterase activity. However, our data demonstrate that chlorpyrifos-oxon is only slightly more potent than chlorpyrifos in inducing apoptosis. This indicates that chlorpyrifos-induced apoptosis may occur independently of AChE inhibition, although AChE activity was not measured in this study. Furthermore, chlorpyrifos activates the ERK1/2 and p38 MAP kinases. Surprisingly, blocking ERK1/2 activation by the MEK inhibitor SL327 caused a small but statistically significant inhibition of apoptosis, while blocking p38 with SB202190 significantly accelerated apoptosis induced by chlorpyrifos. This suggests a pro- and anti-apoptotic role for ERK1/2 and p38, respectively. Although chlorpyrifos did not stimulate total JNK activity, it caused a sustained activation of a sub-pool of JNK in the nucleus and stimulated phosphorylation of c-Jun, a downstream target of JNK. Transient expression of a dominant negative c-Jun mutant inhibited chlorpyrifos-induced apoptosis, suggesting a role for JNK and JNK-mediated transcription in this cell death. Together, our data suggest apoptosis as a novel toxic endpoint of chlorpyrifos neurotoxicity in the brain that may be independent of AChE inhibition. Furthermore, activation of the ERK1/2 and JNK MAP kinases contributes to, while activation of the p38 MAP kinase counteracts chlorpyrifos-induced apoptosis in cortical neurons.

Safety monitoring of cardiac and hepatic systems in beta-thalassemia patients with chelating treatment in Taiwan

We conducted a prospective 3-yr clinical study comparing deferiprone (L1) with desferrioxamine (DFX). The therapeutic efficacy and potential side-effects on cardiac and/or hepatic systems of thalassemia patients were assessed by left ventricular ejection fraction, T2-weighted magnetic resonance imaging, and biochemical parameters. In both groups, levels of serum ferritin decreased significantly, and the hepatic function improved notably. Besides decrement of iron, no marked pathohistological changes were observed in the liver biopsies. These results indicated that for patients who failed to respond to DFX treatment, the use of L1 to remove excess iron deposition is recommended.

Multidentate pyridinones inhibit the metabolism of nontransferrin-bound iron by hepatocytes and hepatoma cells

The therapeutic effect of iron (Fe) chelators on the potentially toxic plasma pool of nontransferrin-bound iron (NTBI), often present in Fe overload diseases and in some cancer patients during chemotherapy, is of considerable interest. In the present investigation, several multidentate pyridinones were synthesized and compared with their bidentate analogue, deferiprone (DFP; L1, orally active) and desferrioxamine (DFO; hexadentate; orally inactive) for their effect on the metabolism of NTBI in the rat hepatocyte and a hepatoma cell line (McArdle 7777, Q7). Hepatoma cells took up much less NTBI than the hepatocytes (< 10%). All the chelators inhibited NTBI uptake (80-98%) much more than they increased mobilization of Fe from cells prelabelled with NTBI (5-20%). The hexadentate pyridinone, N,N,N-tris(3-hydroxy-1-methyl-2(1H)-pyridinone-4-carboxaminoethyl)amine showed comparable activity to DFO and DFP. There was no apparent correlation between Fe status, Fe uptake and chelator activity in hepatocytes, suggesting that NTBI transport is not regulated by cellular Fe levels. The intracellular distribution of iron taken up as NTBI changed in the presence of chelators suggesting that the chelators may act intracellularly as well as at the cell membrane. In conclusion (a) rat hepatocytes have a much greater capacity to take up NTBI than the rat hepatoma cell line (Q7), (b) all chelators bind NTBI much more effectively during the uptake phase than in the mobilization of Fe which has been stored from NTBI and (c) while DFP is the most active chelator, other multidentate pyridinones have potential in the treatment of Fe overload, particularly at lower, more readily clinically available concentrations, and during cancer chemotherapy, by removing plasma NTBI.

Phototoxicity and photogenotoxicity of nine pyridone derivatives

Nine structurally related pyridone derivatives were assayed for photogenotoxicity and phototoxicity in the Ames test, the chromosomal aberration test in V79 cells and the neutral red uptake (NRU) test in 3T3 cells. All nine compounds absorb light to a comparable degree at wavelengths between 380 and 430 nm. Seven of the nine compounds were found to produce high quantities of singlet oxygen (1O(2)) upon irradiation in the presence of oxygen. These seven compounds were highly phototoxic in the NRU test, three were clearly and two were marginally photomutagenic in the Ames test, five were assessed as clearly and two as equivocally photoclastogenic in the chromosomal aberration test. Two compounds showed substantially lower 1O(2) yields. The pyridone ring of these two compounds is attached to a non-aromatic ring, while for the seven other compounds the chromophore system including the pyridone ring consists of two or three aromatic rings. One of the two compounds with low 1O(2) yields was distinctly less phototoxic and did not induce photogenotoxic effects. The other, structurally an indolo derivative and not the common thieno derivative, was, however, similarly phototoxic as the seven compounds with high 1O(2) quantum yield and was also clearly photogenotoxic indicating that different action pathways, not involving singlet oxygen, have to be considered at least for this compound.

Effect of imipramine on 1-methyl-4-phenylpyridinium ion-induced hydroxyl radical generation in rat striatum

We examined the effect of imipramine (a tricyclic antidepressant drug) on hydroxyl radical (.OH) generation induced by 1-methyl-4-phenylpyridinium ion (MPP(+)) in extracellular fluid of rat striatum, using a microdialysis technique. Imipramine enhanced the formation of.OH trapped as 2,3-dihydroxybenzoic acid (DHBA) induced by MPP(+) (5 mM). Introduction of imipramine (0.1, 0.5 and 1.0 mM) dose-dependently increased the level of dopamine (DA) release. Concomitantly, imipramine enhanced DA efflux and the level of DHBA induced by MPP(+), as compared with MPP(+)-treated control. When corresponding experiments were performed with reserpinized rats, there were small increases in the levels of DA and nonsignificant increase in the formation of DHBA. When iron (II) was administered to imipramine (1 mM)-treated animals, a marked elevation of DHBA was observed, compared with MPP(+)-only treated animals. A positive linear correlation was observed between iron (II) and DHBA (R(2)=0.985) in the dialysate. These results indicate that imipramine enhances generation of.OH induced by MPP(+) during enhanced DA overflow.

Effects on Mycobacterium avium replication in normal human macrophages by deferiprone (L1) and other iron chelators. Possible implications on toxicity

Mycobacterium avium growth in cultured human macrophages is influenced by serum lipids, transferrin and iron levels. Iron-saturated transferrin enhances M. avium growth, whereas apotransferrin inhibits mycobacterial replication. The ability of iron chelators to mimic the effects of transferrin on intracellular and extracellular M. avium growth was examined. Smooth, transparent, AIDS patient derived M. avium 7497 scrovar 4 was used to infect 7-day cultured human macrophages. Growth was measured by determining the colony-forming units (CFU) after infected macrophages were lysed 0 to 7 days after infection. The new iron chelating drug deferiprone (1,2-dimethyl-3-hydroxypyrid-4-one or L1, CAS 30652-11-0), 1-ethyl-2-methyl-3-hydroxypyrid-4-one (L1NEt), 1-propyl-2-methyl-3-hydroxypyrid-4-one (L1NPr), 1-allyl-2-methyl-3-hyproxypyrid-4-one (L1NAll), and 3,4-dihydroxycinnamic acid enhanced intracellular and extracellular mycobacterial replication at concentrations of 0.1-2.5 micrograms/ml. 2-Pyridinecarboxaldehyde-2-quinolylhydrazone (PCQH) inhibited intracellular replication from 0.1-1.0 microgram/ml. Most, but not all of the PCQH-induced intracellular inhibition could be eliminated using iron at concentrations greater than 1.0 microgram/ml. Iron also suppressed the effects of PCQH on extracellular M. avium replication. These results indicate that iron chelators may have variable effects at different concentrations and can significantly alter both intracellular and extracellular M. avium replication. It is suggested that at low concentrations deferiprone and other aketohydroxypyridine chelators could enhance the growth of M. avium but at high concentrations may function as adjunct therapy with other antimicrobials against infections with M. avium. These findings are important for therapeutic considerations and dose protocol design in relation to the new iron chelating drug deferiprone, which is currently used in thalassaemia and other iron loaded patients, some of whom are suffering from AIDS.

Deferiprone versus deferoxamine in patients with thalassemia major: a randomized clinical trial

Deferiprone has been suggested as an effective oral chelation therapy for thalassemia major. To assess its clinical efficacy, we compared deferiprone with deferoxamine in a large multicenter randomized clinical trial. One-hundred forty-four consecutive patients with thalassemia major and serum ferritin between 1500 and 3000 ng/ml were randomly assigned to deferiprone (75 mg/kg/day) (n = 71) or deferoxamine (50 mg/kg/day) (n = 73) for 1 year. The main measure of efficacy was the reduction of serum ferritin. Liver and heart iron contents were assessed by magnetic resonance. Liver iron content and fibrosis stage variations were assessed on liver biopsy by the Ishak score in all patients willing to undergo liver biopsy before and after treatment. The mean serum ferritin reduction was 222 +/- 783 ng/ml in the deferiprone and 232 +/- 619 ng/ml in the deferoxamine group (P = 0.81). No difference in the reduction of liver and heart iron content was found by magnetic resonance between the two groups. Thirty-six patients accepted to undergo repeat liver biopsy: 21 in the deferiprone and 15 in the deferoxamine group. Their mean reduction of liver iron content was 1022 +/- 3511 microg/g of dry liver and 350 +/- 524, respectively (P = 0.4). No difference in variation of the Ishak fibrosis stage was observed between the two groups. Treatment was discontinued because of reversible side effects in 5 patients in the deferiprone group (3 hypertransamin/asemia and 2 leukocytopenia) and in none in the deferoxamine group. These findings suggest that deferiprone may be as effective as deferoxamine in the treatment of thalassemia major with few mild and reversible side effects.

Genotoxicity of iron chelators in L5178Y mouse lymphoma cells

To further study the mechanism of observed iron mutagenicity and cellular toxicity, a number of different iron chelators were evaluated to select a compound that was not mutagenic and had limited toxicity to mouse lymphoma cells. A series of iron chelators including those used clinically, those under development for clinical applications, and those used in nonclinical applications were evaluated. The mutagenic activity of the iron chelators was assessed in L5178Y mouse lymphoma cells. Eight of the 12 iron chelators that were tested induced mutagenic responses both with and without the addition of S9. Among those chelators used clinically or developed for clinical use, the only compound that did not induce a mutagenic response was the starch deferoxamine conjugate. In contrast, deferoxamine mesylate showed the highest toxicity in this group of chemicals and the concentrations leading to toxicity and mutagenicity between the activated and nonactivated assays were not significantly different. The other three chelators that were not mutagenic were Na2EDTA, phytic acid, and ferrozine.

Chelating agents for uranium(VI): 2. Efficacy and toxicity of tetradentate catecholate and hydroxypyridinonate ligands in mice

Uranium(VI) (UO2(2+), uranyl) is nephrotoxic. Depending on isotopic composition and dosage, U(VI) is also chemically toxic and carcinogenic in bone. Several ligands containing two, three, or four bidentate catecholate or hydroxypyridinonate metal binding groups, developed for in vivo chelation of other actinides, were found, on evaluation in mice, to be effective for in vivo chelation of U(VI). The most promising ligands contained two bidentate groups per chelator molecule (tetradentate) attached to linear 4- or 5-carbon backbones (4-LI, butylene; 5-LI, pentylene; 5-LIO, diethyl ether). New ligands were then prepared to optimize ligand affinity for U(VI) in vivo and low acute toxicity. Five bidentate binding groups--sulfocatechol [CAM(S)], carboxycatechol [CAM(C)], methylterephthalamide (MeTAM), 1,2-hydroxypyridinone (1,2-HOPO), or 3,2-hydroxypyridinone (Me-3,2-HOPO)--were each attached to two linear backbones (4-LI and 5-LI or 5-LIO). Those ten tetradentate ligands and octadentate 3,4,3-LI(1,2-HOPO), an effective actinide chelator, were evaluated in mice for in vivo chelation of 233U(VI) (injection at 3 min, 1 h, or 24 h or oral administration at 3 min after intravenous injection of 233UO2Cl2) and for acute toxicity (100 micromol kg(-1) injected daily for 10 d). The combined efficacy and toxicity screening identified 5-LIO(Me-3,2-HOPO) and 5-LICAM(S) as the most effective low-toxicity agents. They chelate circulating U(VI) efficiently at ligand:uranium molar ratios > or = 20, remove useful amounts of newly deposited U(VI) from kidney and bone at molar ratios > or = 100, and reduce kidney U(VI) levels significantly when given orally at molar ratios > or = 100. 5-LIO(Me-3,2-HOPO) has greater affinity for kidney U(VI) while 5-LICAM(S) has greater affinity for bone U(VI), and a 1:1 mixture (total molar ratio = 91) reduced kidney and bone U(VI) to 15 and 58% of control, respectively--more than an equimolar amount of either ligand alone.

Multidentate hydroxypyridinonate ligands for Pu(IV) chelation in vivo: comparative efficacy and toxicity in mouse of ligands containing 1,2-HOPO or Me-3,2-HOPO

PURPOSE

To identify the most effective multidentate 1,2-HOPO and Me-3,2-HOPO ligands for chelation of Pu(IV) in vivo.

MATERIALS AND METHODS

Two sets of ligands with four identical backbones were prepared containing two, three or four bidentate 1,2-HOPO or Me-3,2-HOPO groups, and 3,4,3-LI(1,2-HOPO) was resynthesized in a higher yielding procedure. They were evaluated in mouse for acute toxicity and reduction of tissue 238Pu, in comparison with CaNa3-DTPA (30 micromol kg(-1)).

RESULTS

Nine HOPO ligands, promptly injected or given orally or injected at low dosage, are superior to CaNa3-DTPA for reducing 238Pu retention in mouse. Five, given by delayed injection or promptly injected or orally administered as ferric complexes, are superior to CaNa3-DTPA or FeNa2-DTPA respectively. The Me-3,2-HOPO ligands are more effective than their structural 1,2-HOPO analogues, demonstrating the greater affinity of Me-3,2-HOPO for Pu(IV) in vivo.

CONCLUSIONS

The most efficacious ligand, 3,4,3-LI(1,2-HOPO), contains the less stably binding 1,2-HOPO group; therefore, its linear spermine backbone must confer advantages for Pu(IV) binding (greater solubility, more favorable arrangement of ligating groups, more flexible backbone). Effective low toxicity tetradentate 5-LIO(Me-3,2-HOPO) and hexadentate TREN-(Me-3,2-HOPO) and highly effective but moderately toxic 3,4,3-LI(1,2-HOPO) (LD50 approximately 300 micromol kg(-1) in mouse) are recommended for further investigation.

Developmental toxicity studies in rats and rabbits with 3,5,6-trichloro-2-pyridinol, the major metabolite of chlorpyrifos

3,5,6-Trichloro-2-pyridinol (TCP), the primary metabolite of chlorpyrifos and chlorpyrifos-methyl, was evaluated for potential developmental toxicity. Groups of 32-34 bred female Fischer 344 rats were given 0, 50, 100, or 150 mg TCP/kg/day by gavage on gestation days 6-15; the fetuses were evaluated on gestation day 21. Similarly, groups of 16 inseminated female New Zealand White rabbits were given 0, 25, 100, or 250 mg TCP/kg/day by gavage on gestation days 7-19, and fetuses were evaluated on gestation day 28. No clinical signs of toxicity attributed to TCP were noted in either species. In rats, at 150 mg/kg/day, maternal effects included slight decreases in feed consumption, significantly depressed body weight gain (25% relative to controls) resulting in significantly lower maternal terminal body weights, and increased relative liver weight. At 100 mg/kg/day, maternal body weight gain in rats was depressed approximately 22%. Among rabbits, maternal effects were limited to the group given 250 mg/kg/day, which lost an average of approximately 70 g during the treatment period (vs. 140 g in the controls). There were no effects on fetal weight or viability, nor were there significant increases in any fetal alteration in either species. A slightly higher (not statistically significant) than usual incidence of central nervous system anomalies occurred in rabbits, but these anomalies were found in both treated and control groups in this study as well as contemporaneous studies of unrelated compounds. This, and the fact that these anomalies were not seen with the parent compound, chlorpyrifos, suggest that their origin was spontaneous. Thus, TCP was not considered fetotoxic or teratogenic in either rats or rabbits, even at dose levels that produced maternal toxicity.

Neuronal differentiation in PC12 cells is inhibited by chlorpyrifos and its metabolites: is acetylcholinesterase inhibition the site of action?

Developmental expression of AChE has been associated with neuronal differentiation (P. G. Layer and E. Willbold, Prog. Histochem. Cytochem. 29, 1-94, 1995). In this study we used pheochromocytoma (PC12) cells, a noncholinergic cell line, rich in acetylcholinesterase (AChE) activity, to examine the effects of cholinesterase-inhibiting pesticides on neural differentiation. The experimental paradigm was focused on whether alterations in cholinesterase (ChE) activity by a pesticide or its metabolites would affect neurite outgrowth, a morphological marker of neuronal differentiation. Results indicated that (1) in controls, both total ChE and AChE activities were significantly increased in NGF-primed PC12 cells compared to NGF-unprimed cells, while the basal expression of butyrylcholinesterase (BuChE) activity was much lower (1.3-7% of total ChE activity) in either the presence or the absence of NGF; (2) an increase in AChE activity was highly correlated (r(2) = 0.99) with the extension of neurite outgrowth, suggesting a link between the expression of AChE activity and the elaboration of neurite outgrowth; (3) NGF increased neurite outgrowth in a time- and concentration-dependent manner; and (4) either chlorpyrifos (CPF) or its metabolites (CPF oxon and TCP) inhibited NGF-induced neurite outgrowth (branches per cell, fragments per cell, total neurite outgrowth per cell) in PC12 cells. These data suggest that the expression of AChE activity is associated with the extension of neurite outgrowth. Both enzyme activity and neurite branching were disrupted by CPF oxon; however, CPF and its other metabolite TCP (1 microgram/ml) caused inhibition of neurite outgrowth in the absence of ChE inhibition, suggesting an alternative mechanism(s) may be involved in pesticide-induced inhibition of differentiation.