Chronic neuropsychological sequelae of cholinesterase inhibitors in the absence of structural brain damage: two cases of acute poisoning

Isocyanate induces cytotoxicity via activation of phosphorylated alpha synuclein protein, nitrosative stress, and apoptotic pathway in Parkinson's Disease model-SHSY-5Y cells

BACKGROUND

Neurotoxic disorders account for a significant portion of the diseases that influence the worldwide disease burden. Parkinson's disease is one such disease that is linked with environmental toxin exposure. Isocyanates are a highly reactive industrial intermediate used widely in manufacturing plastic products, paints, etc. This study aims to delineate the neurotoxic potential of isocyanate in Parkinson's cell model-SHSY-5Y cells.

METHODOLOGY

SHSY-5Y cells were treated with isocyanate analogue (N succinimidyl N methyl carbamate) in time and dose dependant manner. Different parameters were assessed like protein expression, nitrosative stress level, antioxidant enzymes level and apoptosis.

RESULTS

Our findings demonstrate that dose- and time-dependent isocyanate exposure increases reactive nitrogen species and decreases the glutathione, SOD, and catalase levels. Further, increased phosphorylated alpha-synuclein protein and activation of caspase 3 exert cytotoxicity in SHSY-5Y cells.

CONCLUSION

Our research reveals that widely used isocyanate induces cytotoxicity, apoptosis, nitrosative stress, and protein dysfunction, which might constitute a potential mechanism of neurodegeneration in Parkinsonism.

Hydrolase CehA and a Novel Two-Component 1-Naphthol Hydroxylase CehC1C2 are Responsible for the Two Initial Steps of Carbaryl Degradation in Rhizobium sp. X9

Carbaryl is a widely used carbamate pesticide in agriculture. The strain Rhizobium sp. X9 possesses the typical carbaryl degradation pathway in which carbaryl is mineralized via 1-naphthol, salicylate, and gentisate. In this study, we cloned a carbaryl hydrolase gene cehA and a novel two-component 1-naphthol hydroxylase gene cehC1C2. CehA mediates carbaryl hydrolysis to 1-naphthol and CehC1, an FMNH₂ or FADH₂-dependent monooxygenase belonging to the HpaB superfamily, and hydroxylates 1-naphthol in the presence of reduced nicotinamide-adenine dinucleotide (FMN)/flavin adenine dinucleotide (FAD), and the reductase CehC2. CehC1 has the highest amino acid similarity (58%) with the oxygenase component of a two-component 4-nitrophenol 2-monooxygenase, while CehC2 has the highest amino acid similarity (46%) with its reductase component. CehC1C2 could utilize both FAD and FMN as the cofactor during the hydroxylation, although higher catalytic activity was observed with FAD as the cofactor. The optimal molar ratio of CehC1 to CehC2 was 2:1. The K_m and K_cat/K_m values of CehC1 for 1-naphthol were 74.71 ± 16.07 μM and (8.29 ± 2.44) × 10^-4 s^-1·μM^-1, respectively. Moreover, the enzyme activities and substrate spectrum between CehC1C2 and previously reported 1-naphthol hydroxylase McbC were compared. The results suggested that McbC had a higher 1-naphthol hydroxylation activity, while CehC1C2 had a broader substrate spectrum.

Cloning and expression of the carbaryl hydrolase gene mcbA and the identification of a key amino acid necessary for carbaryl hydrolysis

Carbamate hydrolase is the initial and key enzyme for degradation of carbamate pesticides. In the present study, we report the isolation of a carbaryl-degrading strain Pseudomonas sp. XWY-1, the cloning of its carbaryl hydrolase gene (mcbA) and the characterization of McbA. Strain XWY-1 was able to utilize carbaryl as a sole carbon source and degrade it using 1-naphthol as an intermediate. Transposon mutagenesis identified a mutant of XWY-1M that was unable to hydrolyze carbaryl. The transposon-disrupted gene mcbA was cloned by self-formed adaptor PCR, then expressed in Escherichia coli BL21(DE3) and purified. McbA was able to hydrolyze carbamate pesticides including carbaryl, isoprocarb, fenobucarb, carbofuran efficiently, while it hydrolyzed aldicarb, and propoxur poorly. The optimal pH of McbA was 7.0 and the optimal temperature was 40°C. The apparent K_m and k_cat values of McbA for carbaryl were 77.67±12.31μM and 2.12±0.10s^-1, respectively. Three amino acid residues (His467, His477 and His504) in the predicted polymerase/histidinol phosphatase-like domain were shown to be closely related to the activity of McbA, with His504 being the most important, as a replacement of His504 led to the complete loss of activity. This is the first study to identify key amino acids in McbA.

Associations between the self-reported frequency of hearing chemical alarms in theater and regional brain volume in Gulf War Veterans

BACKGROUND

We previously reported evidence of reduced cortical gray matter (GM), white matter (WM), and hippocampal volume in Gulf War (GW) veterans with predicted exposure to low-levels of nerve agent according to the 2000 Khamisiyah plume model analysis. Because there is suggestive evidence that other nerve agent exposures may have occurred during the Gulf War, we examined the association between the self-reported frequency of hearing chemical alarms sound during deployment in the Gulf War and regional brain volume in GW veterans.

METHODS

Ninety consecutive GW veterans (15 female, mean age: 52±8years) participating in a VA-funded study underwent structural magnetic resonance imaging (MRI) on a 3T scanner. Freesurfer (version 5.1) was used to obtain regional measures of cortical GM, WM, hippocampal, and insula volume. Multiple linear regression was used to determine the association between the self-reported frequencies of hearing chemical alarms during the Gulf War and regional brain volume.

RESULTS

There was an inverse association between the self-reported frequency of hearing chemical alarms sound and total cortical GM (adjusted p=0.007), even after accounting for potentially confounding demographic and clinical variables, the veterans' current health status, and other concurrent deployment-related exposures that were correlated with hearing chemical alarms. Post-hoc analyses extended the inverse relationship between the frequency of hearing chemical alarms to GM volume in the frontal (adjusted p=0.02), parietal (adjusted p=0.01), and occipital (adjusted p=0.001) lobes. In contrast, regional brain volumes were not significantly associated with predicted exposure to the Khamisiyah plume or with Gulf War Illness status defined by the Kansas or Centers for Disease Control and Prevention criteria.

CONCLUSIONS

Many veterans reported hearing chemical alarms sound during the Gulf War. The current findings suggest that exposure to substances that triggered those chemical alarms during the Gulf War likely had adverse neuroanatomical effects.

Assessing biomarkers and neuropsychological outcomes in rural populations exposed to organophosphate pesticides in Chile--study design and protocol

Background

Health effects of pesticides are easily diagnosed when acute poisonings occurs, nevertheless, consequences from chronic exposure can only be observed when neuropsychiatric, neurodegenerative or oncologic pathologies appear. Therefore, early monitoring of this type of exposure is especially relevant to avoid the consequences of pathologies previously described; especially concerning workers exposed to pesticides on the job. For acute organophosphate pesticides (OPP) exposure, two biomarkers have been validated: plasma cholinesterase (ChE) and acetylcholinesterase (AChE) from erythrocytes. These enzymes become inhibited when people are exposed to high doses of organophosphate pesticides, along with clear signs and symptoms of acute poisoning; therefore, they do not serve to identify risk from chronic exposure. This study aims to assess a novel biomarker that could reflect neuropsychological deterioration associated with long-term exposure to organophosphate pesticides via the enzyme acylpeptide-hydrolase (ACPH), which has been recently identified as a direct target of action for some organophosphate compounds.

Methods/Design

Three population groups were recruited during three years (2011–2013): Group I having no exposure to pesticides, which included people living in Chilean coastal areas far from farms (external control); Group II included those individuals living within the rural and farming area (internal control) but not occupationally exposed to pesticides; and Group III living in rural areas, employed in agricultural labour and having had direct contact with pesticides for more than five years. Blood samples to assess biomarkers were taken and neuropsychological evaluations carried out seasonally; in three time frames for the occupationally exposed group (before, during and after fumigation period); in two time frames for internal control group (before and during fumigation), and only once for the external controls. Neuropsychological evaluations considered cognitive functions, affectivity and psychomotor activity. The biomarkers measured included ChE, AChE and ACPH. Statistical analysis and mathematical modelling used both laboratory results and neuropsychological testing outcomes in order to assess whether ACPH would be acceptable as biomarker for chronic exposure to OPP.

Discussion

This study protocol has been implemented successfully during the time frames mentioned above for seasons 2011, 2012 and 2013–2014.

Evaluation of genome damage in subjects occupationally exposed to possible carcinogens

In occupational exposures, populations are simultaneously exposed to a mixture of chemicals. We aimed to evaluate DNA damage due to possible carcinogen exposure (phenylhydrazine, ethylene oxide, dichloromethane, and 1,2-dichloroethane) in lymphocytes of pharmaceutical industry workers from the same production line. Population comprised 16 subjects (9 females and 7 males) who were exposed to multiple chemicals for 8 months. Genome damage was assessed using alkaline comet assay, micronucleus assay, and comet assay coupled with fluorescent in situ hybridization (comet-FISH). After 8 months of exposure, the issue of irregular use of all available personal protective equipment (PPE) came into light. To decrease the risk of exposure, strict use of PPE was enforced. After 8 months of strict PPE use, micronuclei frequency and comet assay parameters in lymphocytes of pharmaceutical workers significantly decreased compared with prior period of irregular PPE use. Comet-FISH results indicated a significant shift in distribution of signals for the TP 53 gene toward a more frequent occurrence in the comet tail. Prolonged exposure to possible carcinogens may hinder DNA repair mechanisms and affect structural integrity of TP 53 Two indicators of loss of TP 53 gene integrity have risen, namely, TP 53 fragmentation rate in lymphocytes with persistently elevated primary damage and incidence of TP 53 deletions in undamaged lymphocytes.

Assessment of Health Care and Economic Costs Due to Episodes of Acute Pesticide Intoxication in Workers of Rural Areas of the Coquimbo Region, Chile

BACKGROUND

The increase in agricultural activity that Chile experienced in the past 20 years resulted in a boost in the use of pesticides. Despite pesticides' productivity benefits, they caused health problems such as the increased frequency of episodes of acute poisoning, which constitutes a relevant problem in terms of occupational health. The Chilean authorities require several preventive measures at workplaces, which are not always implemented, increasing the risk of intoxications in farmers. So far in Chile, there are no studies concerning the public health care expenses associated with acute work-related pesticide intoxications. From the societal perspective, there are costs involved if the worker needs to take sick leave and families incur costs to take care of their sick members.

OBJECTIVES

This study aimed to determine the costs associated with health care services used by people who suffered from work-related acute pesticide poisoning, as well as the economic costs for the families of the workers involved, and finally the costs of these episodes for the employer/industrial sector.

METHODS

This study considered a 3-year period (January 2009 to December 2011). Three sources of data were reviewed: reported cases at the Regional Health Authority, for the profile of the intoxications; registers of patients attended in public hospitals, for data on costs of health care services; and public information of living conditions nationwide.

RESULTS

The overall costs of a single case depend on the severity of intoxication, days of sick leave, and type of health care needed. Most cases (77%) would be ambulatory and would be assisted at an emergency room, with an average cost of US $330 per case. Those cases that might need hospitalization (23%) and, therefore, more days off work have an average cost of US $1158 per case. Taking into account the number of patients reported each year in the country, the cost per annum would be about US $185,000, but considering the underreporting of intoxications and underestimation of costs at the public insurance system fees, this amount could be six to eight times higher (US $1.1 million to US $1.4 million a year).

CONCLUSIONS

This study is the first attempt to estimate costs related to this occupational and public health problem. There is an opportunity to further improve the cost-benefit balance of preventive measures that relate not only to acute poisonings but also to health problems originating from chronic and low-dose exposure to pesticides (e.g., neuropsychological impairment).

Effect of occupational exposure to multiple pesticides on translocation yield and chromosomal aberrations in lymphocytes of plant workers

Employees handling pesticides are simultaneously exposed to different active substances. Occurring multiple chemical exposures may pose a higher risk than it could be deduced from studies evaluating the effect of a single substance. This study comprised 32 pesticide plantworkers exposed to carbofuran, chlorpyrifos, metalaxyl, and dodine and an equal number of control subjects. Groups were matched by age (43.8 +/- 10.16 vs 41.8 +/- 7.42, respectively), sex (14 females; 18 males), and smoking (11 smokers; 21 nonsmokers). Chromosome aberration and translocation frequencies were determined using a standard aberration assay and fluorescent in situ hybridization (FISH) by applying painting probes for chromosomes 1, 2, and 4. Although significant, an observed increase in chromatid breaks (5.2 +/- 2.49) compared to controls (2.1 +/- 0.87), p(PostHoc) = 0.000001 is biologically irrelevant. Genomic frequency of translocations was also significantly elevated (exposed 0.0165 +/- 0.0070; control 0.0051 +/- 0.0023, P(PostHoc) = 0.000004). The distribution of translocations among chromosomes 1, 2, and 4 did not differ from control subjects. It corresponded to the distribution of DNA content among selected chromosomes indicating randomness of DNA damage. A good translocation yield correlation within years spent in pesticide production indicates that multiple pesticide exposure may pose a risk to genome integrity. However, for more accurate health risk assessments, the use of probes for some other groups of chromosomes should be considered.

Potential developmental neurotoxicity of pesticides used in Europe

Pesticides used in agriculture are designed to protect crops against unwanted species, such as weeds, insects, and fungus. Many compounds target the nervous system of insect pests. Because of the similarity in brain biochemistry, such pesticides may also be neurotoxic to humans. Concerns have been raised that the developing brain may be particularly vulnerable to adverse effects of neurotoxic pesticides. Current requirements for safety testing do not include developmental neurotoxicity. We therefore undertook a systematic evaluation of published evidence on neurotoxicity of pesticides in current use, with specific emphasis on risks during early development. Epidemiologic studies show associations with neurodevelopmental deficits, but mainly deal with mixed exposures to pesticides. Laboratory experimental studies using model compounds suggest that many pesticides currently used in Europe--including organophosphates, carbamates, pyrethroids, ethylenebisdithiocarbamates, and chlorophenoxy herbicides--can cause neurodevelopmental toxicity. Adverse effects on brain development can be severe and irreversible. Prevention should therefore be a public health priority. The occurrence of residues in food and other types of human exposures should be prevented with regard to the pesticide groups that are known to be neurotoxic. For other substances, given their widespread use and the unique vulnerability of the developing brain, the general lack of data on developmental neurotoxicity calls for investment in targeted research. While awaiting more definite evidence, existing uncertainties should be considered in light of the need for precautionary action to protect brain development.

Clinical observation of 12 farmers who believe themselves to have suffered from chronic pesticide intoxication

BACKGROUND/AIM

We assessed twelve cases of suspected chronic pesticide intoxication, with medically unexplained physical symptoms.

METHODS

Complete blood cell count (CBC), blood chemistry, routine urinalysis, chest X-ray, ECG, gastrofiberscopy, abdominal ultrasonography, neuroselective sensory nerve conduction threshold, and psychological assessment were performed on 12 farmers who believe themselves to have suffered from chronic pesticide intoxication.

RESULTS

No specific abnormalities were observed on CBC, routine urinalysis, chest X-ray, ECG, gastroscopy, abdominal ultrasonography, or peripheral nerve conduction velocity test. They persistently manifested helplessness, depression, and anxiety. The results of both psychological assessment and general physical examination revealed the following clinical features: depression (8 cases), multiple chemical hypersensitivity syndrome (2 cases), alcoholism (1 case), and religious preoccupation (1 case).

CONCLUSION

In those living in the western rural area of South Korea, depression is a prominent ongoing presentation in pesticide-exposed farmers, in addition to unexplainable physical symptoms.

Pupil reaction to light in Alzheimer's disease: evaluation of pupil size changes and mobility

AIMS

The aim of the study is to assess pupil size changes and mobility evaluation as a diagnostic marker in patients with probable Alzheimer's disease (AD).

MATERIAL AND METHODS

Twenty-three control subjects and 23 patients with probable AD entered the study. The latter patients had been under observation for 2 years and had undergone all necessary examinations to verify their initial diagnosis. A full record of the pupil's reaction to light was registered. Ten parameters from these data were measured, reported and then compared in both group of subjects.

RESULTS

Patients with probable AD had abnormal pupillary function compared with such function in healthy aging. All pupillary light reflex (PLR) variables differed significantly between the two groups (p<0.005) except baseline pupil diameter (D1) and minimum pupil diameter (D2). Maximum constriction acceleration (ACmax) was the best predictor in classifying a subject as normal or as AD with perfect classification ability (area under the curve =1, p<0.001). In addition, the correlation between the percentage recovery-redilatation (%D1) and ACmax was highly negative in the group of AD patients (r = -0.808, p<0.005).

CONCLUSIONS

Pupil size changes and mobility examination may be a fast, non-invasive and efficient additional diagnostic marker in AD diagnosis.

Age related effects of pesticide exposure on neurobehavioral performance of adolescent farm workers in Brazil

Adolescents (10 to 18 years old) from a rural area in the state of Rio de Janeiro, Brazil were tested using the Behavioral Assessment and Research System (BARS) to evaluate their performance. Participants were drawn from two areas--a school serving farm children (rural N=38) and a school serving children from a city within this area (urban N=28). These children were drawn from an ongoing study being carried out by Fundação Oswaldo Cruz where rural and urban participants were matched for age, sex, and level in school. For this ongoing study, the participants had been interviewed to determine their occupational history, especially their activities that might involve exposure to pesticides. Interview responses were used to assign an exposure index to each participant. While a few BARS performance measures suggested behavioral impairments for the rural versus the urban participants, a stronger and more consistent association between BARS measures (especially impairment of tapping, digit span, and selective attention) and level of exposure to pesticides was noted when the exposure index was entered into a multiple linear regression analysis. Exposure appeared to be especially strong for the youngest participants (10-11 years old). The relationship between these behaviors and the exposure index was stronger than the relationship between behaviors and either age or sex.