A new unifying hypothesis for lathyrism, konzo and tropical ataxic neuropathy: nitriles are the causative agents

Cyanide and Cyanogenic Compounds-Toxicity, Molecular Targets, and Therapeutic Agents

Cyanide (CN) is a well-known mitochondrial poison. CN poisoning may result from acute or long-term exposure to a number of CN compounds. Recent insight into the chemical affinities of the CN anion has increased our understanding of its toxicity and the mechanisms of antidotal actions, which, together with information on various exposure sources, are reviewed in the present article. A literature search in Scopus, Embase, Web of Science, PubMed, and Google Scholar for the period 2001-2024 revealed that the CN anion after exposure or degradation of CN compounds is distributed to vulnerable copper and iron-containing targets, especially in mitochondria, thus blocking the electron transport chain. Intake of cyanogenic compounds may exert subacute or chronic toxic effects, also because of the interaction with cobalt in vitamin B12. Antidotal agents exert their effects through the affinity of CN for cobalt- or iron-containing compounds. Research on CN interactions with metalloproteins may increase our insight into CN toxicity and efficient antidotal regimens.

Scenario on Production, Processing, and Utilization of Grasspea (Lathyrus sativus L.) in Agromarginal Geographies and Its Future Prospects

Grasspeas are environmentally successful and robust legumes with major traits of interest for food and nutrition security. It is a critical crop in areas prone to drought, overmoisture stress, and famine, hence, regarded as an "insurance crop" because of its inherent resilience of climatic calamities. The current status and prospects of grasspea, as well as various breeding and food processing approaches to improve this crop for integration in diverse and sustainable agrifood systems, are discussed in this review. Grasspeas are often the source of important micronutrients and proteins (18%-34%), saving peoples' lives during famine. Grasspea consumption is increasing in some countries; however, uninterrupted consumption of grasspea should be avoided, especially when they are green or unripe and when they are raw. Effective food processing techniques are essential to reduce the neurotoxic hazards associated with eating grasspea. Several effective processing steps can be used to reduce toxicity in addition to the development of toxin-free varieties for production and consumption. With advances in the scientific investigation of the grasspea, integration of genetics, processing, and behavioral components has been suggested.

Toxic Damage to Motor Neurons

Abstract—Amyotrophic lateral sclerosis (ALS) is a multifactor disease in the development of which both genetic and environmental factors play a role. Specifically, the effects of organic and inorganic toxic substances can result in an increased risk of ALS development and the acceleration of disease progression. It was described that some toxins can induce potentially curable ALS-like syndromes. In this case, the specific treatment for the prevention of the effects of the toxic factor may result in positive clinical dynamics. In this article, we review the main types of toxins that can damage motor neurons in the brain and spinal cord leading to the development of the clinical manifestation of ALS, briefly present historical data on studies on the role of toxic substances, and describe the main mechanisms of the pathogenesis of motor neuron disease associated with their action.

Two fatal cases of acetone cyanohydrin poisoning: case report and literature review

Acetone cyanohydrin (ACH), an organic cyanide, is mainly used in the production of methyl methacrylate (MMA), and it also exists in cassava roots, the main calorie source in some tropical countries. ACH can decompose spontaneously or enzymatically into acetone and highly toxic hydrogen cyanide (HCN) and be potentially toxic to its contacts. Given that limited forensic studies and case reports on fatal ACH poisoning are available, herein, we present a report of two fatal cases of ACH poisoning in which the two victims, with postmortem cyanide blood concentrations of 4.22 μg/ml and 4.07 μg/ml, suffered from acute poisoning of ACH due to a traffic accident. Furthermore, a literature review of cyanide poisoning case reports from 2000 to 2020 was carried out, and 28 subjects with cyanide poisoning were presented, including the age, sex, cause of poisoning, autopsy findings and the cyanide concentration in the blood. ACH poisoning lacks specific and reliable autopsy findings for diagnosis, and relevant toxicological studies are necessary. Due to the chemical properties of ACH that allow it to easily decompose, the toxicological analysis of acetone and cyanide in biological samples is essential for the diagnosis of ACH poisoning.

Bitter taste receptors: Genes, evolution and health

Bitter taste perception plays vital roles in animal behavior and fitness. By signaling the presence of toxins in foods, particularly noxious defense compounds found in plants, it enables animals to avoid exposure. In vertebrates, bitter perception is initiated by TAS2Rs, a family of G protein-coupled receptors expressed on the surface of taste buds. There, oriented toward the interior of the mouth, they monitor the contents of foods, drinks and other substances as they are ingested. When bitter compounds are encountered, TAS2Rs respond by triggering neural pathways leading to sensation. The importance of this role placed TAS2Rs under selective pressures in the course of their evolution, leaving signatures in patterns of gene gain and loss, sequence polymorphism, and population structure consistent with vertebrates' diverse feeding ecologies. The protective value of bitter taste is reduced in modern humans because contemporary food supplies are safe and abundant. However, this is not always the case. Some crops, particularly in the developing world, retain surprisingly high toxicity and bitterness remains an important measure of safety. Bitter perception also shapes health through its influence on preference driven behaviors such as diet choice, alcohol intake and tobacco use. Further, allelic variation in TAS2Rs is extensive, leading to individual differences in taste sensitivity that drive these behaviors, shaping susceptibility to disease. Thus, bitter taste perception occupies a critical intersection between ancient evolutionary processes and modern human health.

Atoh1 Directs Regeneration and Functional Recovery of the Mature Mouse Vestibular System

Utricular hair cells (HCs) are mechanoreceptors required for vestibular function. After damage, regeneration of mammalian utricular HCs is limited and regenerated HCs appear immature. Thus, loss of vestibular function is presumed irreversible. Here, we found partial HC replacement and functional recovery in the mature mouse utricle, both enhanced by overexpressing the transcription factor Atoh1. Following damage, long-term fate mapping revealed that support cells non-mitotically and modestly regenerated HCs displaying no or immature bundles. By contrast, Atoh1 overexpression stimulated proliferation and widespread regeneration of HCs exhibiting elongated bundles, patent mechanotransduction channels, and synaptic connections. Finally, although damage without Atoh1 overexpression failed to initiate or sustain a spontaneous functional recovery, Atoh1 overexpression significantly enhanced both the degree and percentage of animals exhibiting sustained functional recovery. Therefore, the mature, damaged utricle has an Atoh1-responsive regenerative program leading to functional recovery, underscoring the potential of a reprogramming approach to sensory regeneration.

The mature mouse utricle, which detects linear acceleration, displays limited regeneration, but whether function returns is unknown. Sayyid et al. show that regenerated hair cells appear and mature over months, resulting in a limited, unsustained functional recovery. Atoh1 overexpression enhances regeneration and leads to a sustained recovery of vestibular function.

Chronic consumption of cassava juice induces cellular stress in rat substantia nigra

OBJECTIVES

Cassava (Manihot esculenta Crantz) contains cyanogenic glycosides (linamarin and lotaustralin) that have been associated with neurological disorders in humans and rats. In basal ganglia, the dopaminergic neurons of substantia nigra pars compacta (SNpc) show high cytotoxic susceptibility; therefore, the chronic consumption of cassava (CCC) could induce neurodegeneration in SNpc. In this study we examine the impact of CCC on the integrity of the nigrostriatal system, including apoptosis and microgliosis.

MATERIALS AND METHODS

Male Wistar rats were administered cassava juice daily (3.57 g/kg and 28.56 g/kg, per os) or linamarin (0.15 mg/ml, IP), and its effects were evaluated in rota-rod and swim tests at days 7, 14, 21, 28, and 35 of administration. In SNpc, oxidative/nitrosative stress was determined by malondialdehyde/4-hydroxyalkenals (MDA-4-HAD) and nitrite contents. Tyrosine hydroxylase immunoreactivity (TH-IR) was evaluated in SNpc, neostriatum (NE), and nucleus accumbens (NA). Apoptosis and microgliosis were determined by active-caspase-3 (C3) and CD11b/c (OX42) expression in the medial region of SNpc.

RESULTS

Chronic administration of cassava juice, or linamarin, increased motor impairment. The rats that received 28.56 g/kg cassava showed increased MDA-4-HAD content in SNpc and nitrite levels in NE with respect to controls. Significant loss of TH-IR in SNpc, NE, and NA was not found. The 28.56 g/kg cassava administration produced dopaminergic atrophy and microgliosis, whereas linamarin induced hypertrophy and C3-related apoptosis in SNpc.

CONCLUSION

CCC induces cellular stress on dopaminergic neurons, which could contribute to motor impairment in the rat.

Preclinical and clinical research on the toxic and neurological effects of cassava (Manihot esculenta Crantz) consumption

Cassava (Manihot esculenta Crantz) is a tropical plant that is used as fresh food, processed food, or raw material for the preparation of flours with high nutritional value. However, cassava contains cyanogenic glycosides, such as linamarin and lotaustralin, that can trigger severe toxic effects and some neurological disorders, including motor impairment, cognitive deterioration, and symptoms that characterize tropical ataxic neuropathy and spastic epidemic paraparesis (Konzo). These alterations that are associated with the consumption of cassava or its derivatives have been reported in both humans and experimental animals. The present review discusses and integrates preclinical and clinical evidence that indicates the toxic and neurological effects of cassava and its derivatives by affecting metabolic processes and the central nervous system. An exhaustive review of the literature was performed using specialized databases that focused on the toxic and neurological effects of the consumption of cassava and its derivatives. We sought to provide structured information that will contribute to understanding the undesirable effects of some foods and preventing health problems in vulnerable populations who consume these vegetables. Cassava contains cyanogenic glycosides that contribute to the development of neurological disorders when they are ingested inappropriately or for prolonged periods of time. Such high consumption can affect neurochemical and neurophysiological processes in particular brain structures and affect peripheral metabolic processes that impact wellness. Although some vegetables have high nutritional value and ameliorate food deficits in vulnerable populations, they can also predispose individuals to the development of neurological diseases.

Historical setting and neuropathology of lathyrism: Insights from the neglected 1944 report by Oliveras de la Riva

Lathyrism is a central motor system disorder recognized since antiquity resulting from prolonged dietary dependence on the grasspea (Lathyrus sativus). The neuropathology underlying the characteristic spastic paraparesis of lathyrism is sketchy. Described here is a landmark but little-known Spanish-language neuropathological study of two patients with lathyrism of recent onset. Due to erroneous interpretations of Filimonov's influential work in 1926, it was assumed that spastic paraparesis of lathyrism was explained by destruction of Betz's pyramidal cells in the motor cortex. Contrary to present understanding, Betz cells and anterior horn cells were preserved, and pathological findings dominated by myelin loss were largely limited to pyramidal tracts in the lumbar cord. Thickening of the adventitia of capillaries and arterioles, together with proliferation of perivascular astrocytes, was found along the length of the spinal cord. Oliveras de la Riva proposed that the segmental spinal pathology arose because distal regions of elongate pyramidal tract axons are distant from their trophic center in the motor cortex, a view not far from the current distal axonopathy concept of lathyrism. In addition, we review the historical circumstances of Filimonov's work in Russia, a summary of the epidemic of lathyrism in Spain following its Civil War (1936-1939), and some historical aspects of the Cajal Institute in Madrid, where Oliveras de la Riva's work was carried out under the supervision of Fernando de Castro, one of Cajal's favorite students.

Tropical ataxic neuropathy: Findings of a neuroepidemiological survey of Odeda, southwest Nigeria

BACKGROUND

Tropical ataxic neuropathy seems to have dwindled in public health importance in Nigeria despite the high consumption of cassava-based meals by a huge proportion of people in local Nigerian communities. Yet a recent report suggest its persistence in the same ethnogeographic setting where it was first reported in Nigeria. Our objective was to investigate the prevalence of tropical ataxic neuropathy in Odeda, Ogun state, southwest Nigeria inhabited by a different ethnic group compared to Epe where the disease was first described.

METHODS

A two-stage, cross-sectional survey of Odeda local government area for the prevalence and profile of toxiconutritional neurological disorders was carried out between May and June 2015. A screening instrument was applied by trained non - medical interviewers with positive responders further evaluated by a neurologist.

RESULTS

2392 individuals aged 18 years or older were screened and had a mean age of 37.2 ± 16.1 years, were predominantly of Egba Yoruba ethnicity. Thirty nine cases of tropical ataxic neuropathy were diagnosed and crude prevalence rate was 16.3/1000 (95% CI 11.2-21.4/1000). Older age and rural residence were associated with higher prevalence. Distal sensory polyneuropathy was the most common feature whereas sensorineural deafness was the least common finding.

CONCLUSION

This report provides evidence that tropical ataxic neuropathy persists and in a wider geographic spread. Thus tropical ataxic neuropathy still remains a significant public health importance and concerted efforts are required to mitigate or eradicate tropical ataxic neuropathy in southwest Nigeria and other regions of Africa affected by cassava- related toxiconutritional disorders.

Evaluation of the health risks related to the presence of cyanogenic glycosides in foods other than raw apricot kernels

In 2016, the EFSA Panel on Contaminants in the Food Chain (CONTAM) published a scientific opinion on the acute health risks related to the presence of cyanogenic glycosides (CNGs) in raw apricot kernels in which an acute reference dose (ARfD) of 20 μg/kg body weight (bw) was established for cyanide (CN). In the present opinion, the CONTAM Panel concluded that this ARfD is applicable for acute effects of CN regardless the dietary source. To account for differences in cyanide bioavailability after ingestion of certain food items, specific factors were used. Estimated mean acute dietary exposures to cyanide from foods containing CNGs did not exceed the ARfD in any age group. At the 95th percentile, the ARfD was exceeded up to about 2.5-fold in some surveys for children and adolescent age groups. The main contributors to exposures were biscuits, juice or nectar and pastries and cakes that could potentially contain CNGs. Taking into account the conservatism in the exposure assessment and in derivation of the ARfD, it is unlikely that this estimated exceedance would result in adverse effects. The limited data from animal and human studies do not allow the derivation of a chronic health-based guidance value (HBGV) for cyanide, and thus, chronic risks could not be assessed.

Current scenario of consumption of Lathyrus sativus and lathyrism in three districts of Chhattisgarh State, India

Lathyrism is a disease caused by excessive consumption of grass pea, Lathyrus sativus especially under conditions of severe drought. Grass pea contains 3-N-oxalyl-L-2, 3-diaminopropanoic acid (β-ODAP) a putative neurotoxin which acts through excitatory mechanism causing Neurolathyrism. Due to awareness of the disease, availability of food and levels of consumption of L. sativus there is reduction in lathyrism cases where higher consumption of L. sativus is reported in India. The present study was undertaken with the objective to assess the current scenario of consumption of L. sativus, incidence of cases of lathyrism, β-ODAP, protein and amino acids content in L. sativus pulse collected from three districts (Bilaspur, Durg and Raipur) of Chattisgarh state. For this purpose, a total of 17,755 (13,129 rural and 4626 urban) individuals from 151 villages and 60 wards from urban area were covered for clinical examination. Out of total 5769 households (HHs) covered during the survey, 1602 HHs were cultivators, 1791 HHs non-cultivators and 2376 agricultural and other labourers. A one day 24-hour re-call diet survey was carried out in 5758 HHs (4549 rural and 1209 urban). A total of 360 split grass pea (SGP) samples were collected to estimate β-ODAP, protein and amino acids content. Results of the study revealed that an average consumption of SGP was 20.9 gm/CU/day in Bilaspur and no consumption was reported among urban population of Raipur. Only nine old cases of lathyrism were found during the study. The mean β-ODAP content in SGP was 0.63 ± 0.14, 0.65 ± 0.13 and 0.65 ± 0.14 gm/100 gm, whereas the protein content was 27.0 ± 2.39, 27.0 ± 1.99 and 26.7 ± 1.90 gm/100 gm in samples collected from Bilaspur, Durg and Raipur districts respectively. Arginine content was high in SGP and sulphur containing amino acids (cysteine and methionine) were less than other amino acids. In conclusion, the consumption of SGP was lower in these three districts with lower β-ODAP content than earlier reports, thus the lower prevalence of lathyrism in the districts surveyed.

β-N-Oxalyl-l-α,β-diaminopropionic Acid (β-ODAP) Content in Lathyrus sativus: The Integration of Nitrogen and Sulfur Metabolism through β-Cyanoalanine Synthase

Grass pea (Lathyrus sativus L.) is an important legume crop grown mainly in South Asia and Sub-Saharan Africa. This underutilized legume can withstand harsh environmental conditions including drought and flooding. During drought-induced famines, this protein-rich legume serves as a food source for poor farmers when other crops fail under harsh environmental conditions; however, its use is limited because of the presence of an endogenous neurotoxic nonprotein amino acid β-N-oxalyl-l-α,β-diaminopropionic acid (β-ODAP). Long-term consumption of Lathyrus and β-ODAP is linked to lathyrism, which is a degenerative motor neuron syndrome. Pharmacological studies indicate that nutritional deficiencies in methionine and cysteine may aggravate the neurotoxicity of β-ODAP. The biosynthetic pathway leading to the production of β-ODAP is poorly understood, but is linked to sulfur metabolism. To date, only a limited number of studies have been conducted in grass pea on the sulfur assimilatory enzymes and how these enzymes regulate the biosynthesis of β-ODAP. Here, we review the current knowledge on the role of sulfur metabolism in grass pea and its contribution to β-ODAP biosynthesis. Unraveling the fundamental steps and regulation of β-ODAP biosynthesis in grass pea will be vital for the development of improved varieties of this underutilized legume.

A Stochastic Multiscale Model That Explains the Segregation of Axonal Microtubules and Neurofilaments in Neurological Diseases

The organization of the axonal cytoskeleton is a key determinant of the normal function of an axon, which is a long thin projection of a neuron. Under normal conditions two axonal cytoskeletal polymers, microtubules and neurofilaments, align longitudinally in axons and are interspersed in axonal cross-sections. However, in many neurotoxic and neurodegenerative disorders, microtubules and neurofilaments segregate apart from each other, with microtubules and membranous organelles clustered centrally and neurofilaments displaced to the periphery. This striking segregation precedes the abnormal and excessive neurofilament accumulation in these diseases, which in turn leads to focal axonal swellings. While neurofilament accumulation suggests an impairment of neurofilament transport along axons, the underlying mechanism of their segregation from microtubules remains poorly understood for over 30 years. To address this question, we developed a stochastic multiscale model for the cross-sectional distribution of microtubules and neurofilaments in axons. The model describes microtubules, neurofilaments and organelles as interacting particles in a 2D cross-section, and is built upon molecular processes that occur on a time scale of seconds or shorter. It incorporates the longitudinal transport of neurofilaments and organelles through this domain by allowing stochastic arrival and departure of these cargoes, and integrates the dynamic interactions of these cargoes with microtubules mediated by molecular motors. Simulations of the model demonstrate that organelles can pull nearby microtubules together, and in the absence of neurofilament transport, this mechanism gradually segregates microtubules from neurofilaments on a time scale of hours, similar to that observed in toxic neuropathies. This suggests that the microtubule-neurofilament segregation can be a consequence of the selective impairment of neurofilament transport. The model generates the experimentally testable prediction that the rate and extent of segregation will be dependent on the sizes of the moving organelles as well as the density of their traffic.

The shape and function of axons is dependent on a dynamic system of microscopic intracellular protein polymers (microtubules, neurofilaments and microfilaments) that comprise the axonal cytoskeleton. Neurofilaments are cargoes of intracellular transport that move along microtubule tracks, and they accumulate abnormally in axons in many neurotoxic and neurodegenerative disorders. Intriguingly, it has been reported that neurofilaments and microtubules, which are normally interspersed in axonal cross-sections, often segregate apart from each other in these disorders, which is something that is never observed in healthy axons. Here we describe a stochastic multiscale computational model that explains the mechanism of this striking segregation and offers insights into the mechanism of neurofilament accumulation in disease.

Lathyrus diversity: available resources with relevance to crop improvement--L. sativus and L. cicera as case studies

BACKGROUND

The Lathyrus genus includes 160 species, some of which have economic importance as food, fodder and ornamental crops (mainly L. sativus, L. cicera and L. odoratus, respectively) and are cultivated in >1·5 Mha worldwide. However, in spite of their well-recognized robustness and potential as a source of calories and protein for populations in drought-prone and marginal areas, cultivation is in decline and there is a high risk of genetic erosion.

SCOPE

In this review, current and past taxonomic treatments of the Lathyrus genus are assessed and its current status is examined together with future prospects for germplasm conservation, characterization and utilization. A particular emphasis is placed on the importance of diversity analysis for breeding of L. sativus and L. cicera.

CONCLUSIONS

Efforts for improvement of L. sativus and L. cicera should concentrate on the development of publicly available joint core collections, and on high-resolution genotyping. This will be critical for permitting decentralized phenotyping. Such a co-ordinated international effort should result in more efficient and faster breeding approaches, which are particularly needed for these neglected, underutilized Lathyrus species.

Cross-species and tissue variations in cyanide detoxification rates in rodents and non-human primates on protein-restricted diet

We sought to elucidate the impact of diet, cyanide or cyanate exposure on mammalian cyanide detoxification capabilities (CDC). Male rats (~8 weeks old) (N=52) on 75% sulfur amino acid (SAA)-deficient diet were treated with NaCN (2.5mg/kg bw) or NaOCN (50mg/kg bw) for 6 weeks. Macaca fascicularis monkeys (~12 years old) (N=12) were exclusively fed cassava for 5 weeks. CDC was assessed in plasma, or spinal cord, or brain. In rats, NaCN induced seizures under SAA-restricted diet whereas NaOCN induced motor deficits. No deficits were observed in non-human primates. Under normal diet, the CDC were up to ~80× faster in the nervous system (14 ms to produce one μmol of thiocyanate from the detoxification of cyanide) relative to plasma. Spinal cord CDC was impaired by NaCN, NaOCN, or SAA deficiency. In M. fascicularis, plasma CDC changed proportionally to total proteins (r=0.43; p<0.001). The plasma CDC was ~2× relative to that of rodents. The nervous system susceptibility to cyanide may result from a "multiple hit" by the toxicity of cyanide or its cyanate metabolite, the influences of dietary deficiencies, and the tissue variations in CDC. Chronic dietary reliance on cassava may cause metabolic derangement including poor CDC.

Vestibulotoxic properties of potential metabolites of allylnitrile

This study addressed the hypothesis that epoxidation of the double bond in allylnitrile mediates its vestibular toxicity, directly or after subsequent metabolism by epoxide hydrolases. The potential metabolites 3,4-epoxybutyronitrile and 3,4-dihydroxybutyronitrile were synthesized and characterized. In aqueous solutions containing sodium or potassium ions, 3,4-epoxybutyronitrile rearranged to 4-hydroxybut-2-enenitrile, and this compound was also isolated for study. Male adult Long-Evans rats were exposed to allylnitrile or 3,4-epoxybutyronitrile by bilateral transtympanic injection, and vestibular toxicity was assessed using a behavioral test battery and scanning electron microscopy (SEM) observation of the sensory epithelia. Overt vestibular toxicity was caused by 3,4-epoxybutyronitrile at 0.125 mmol/ear and by allylnitrile in some animals at 0.25 mmol/ear. Additional rats were exposed by unilateral transtympanic injection. In these studies, behavioral evidences and SEM observations demonstrated unilateral vestibular toxicity after 0.125 mmol of 3,4-epoxybutyronitrile and bilateral vestibular toxicity after 0.50 mmol of allylnitrile. However, 0.25 mmol of allylnitrile did not cause vestibular toxicity. Unilateral administration of 0.50 mmol of 3,4-dihydroxybutyronitrile or 4-hydroxybut-2-enenitrile caused no vestibular toxicity. The four compounds were also evaluated in the mouse utricle explant culture model. In 8-h exposure experiments, hair cells completely disappeared after 3,4-epoxybutyronitrile at concentrations of 325 or 450μM but not at concentrations of 150μM or lower. In contrast, no difference from controls was recorded in utricles exposed to 450μM or 1.5mM of allylnitrile, 3,4-dihydroxybutyronitrile, or 4-hydroxybut-2-enenitrile. Taken together, the present data support the hypothesis that 3,4-epoxybutyronitrile is the active metabolite of allylnitrile for vestibular toxicity.

Vestibular toxicity of cis-2-pentenenitrile in the rat

cis-2-Pentenenitrile, an intermediate in the synthesis of nylon and other products, causes permanent behavioral deficits in rodents. Other low molecular weight nitriles cause degeneration either of the vestibular sensory hair cells or of selected neuronal populations in the brain. Adult male Long-Evans rats were exposed to cis-2-pentenenitrile (0, 1.25, 1.50, 1.75, or 2.0mmol/kg, oral, in corn oil) and assessed for changes in open field activity and rating scores in a test battery for vestibular dysfunction. Surface preparations of the vestibular sensory epithelia were observed for hair cell loss using scanning electron microscopy. A separate experiment examined the impact of pre-treatment with the universal CYP inhibitor,1-aminobenzotriazole, on the effect of cis-2-pentenenitrile on vestibular rating scores. The occurrence of degenerating neurons in the central nervous system was assessed by Fluoro-Jade C staining. cis-2-Pentenenitrile had a dose-dependent effect on body weight. Rats receiving 1.50mmol/kg or more of cis-2-pentenenitrile displayed reduced rearing activity in the open field and increased rating scores on the vestibular dysfunction test battery. Hair cell loss was observed in the vestibular sensory epithelia and correlated well with the behavioral deficits. Pre-treatment with 1-aminobenzotriazole blocked the behavioral effect. Fluoro-Jade C staining did not reveal significant neuronal degeneration in the central nervous system apart from neurite labeling in the olfactory glomeruli. We conclude that cis-2-pentenenitrile causes vestibular toxicity in a similar way to allylnitrile, cis-crotononitrile and 3,3'-iminodipropionitrile (IDPN), and also shares other targets such as the olfactory system with these other nitriles. The present data also suggest that CYP-mediated bioactivation is involved in cis-2-pentenenitrile toxicity.

Role of CYP2E1-mediated metabolism in the acute and vestibular toxicities of nineteen nitriles in the mouse

Allylnitrile, cis-crotononitrile, and 3,3'-iminodipropionitrile are known to cause vestibular toxicity in rodents, and evidence is available indicating that cis-2-pentenenitrile shares this effect. We evaluated nineteen nitriles for vestibular toxicity in wild type (129S1) and CYP2E1-null mice, including all the above, several neurotoxic nitriles, and structurally similar nitriles. A new acute toxicity test protocol was developed to facilitate evaluation of the vestibular toxicity by a specific behavioral test battery at doses up to sub-lethal levels while using a limited number of animals. A mean number of 8.5±0.3 animals per nitrile, strain and sex was necessary to obtain evidence of vestibular toxicity and optionally an estimation of the lethal dose. For several but not all nitriles, lethal doses significantly increased in CYP2E1-null mice. The protocol revealed the vestibular toxicity of five nitriles, including previously identified ototoxic compounds and one nitrile (trans-crotononitrile) known to have a different profile of neurotoxic effects in the rat. In all five cases, both sexes were affected and no decrease in susceptibility was apparent in CYP2E1-null mice respect to 129S1 mice. Fourteen nitriles caused no vestibular toxicity, including six nitriles tested in CYP2E1-null mice at doses significantly larger than the maximal doses that can be tested in wild type animals. We conclude that only a subset of low molecular weight nitriles is toxic to the vestibular system, that species-dependent differences exist in this vestibular toxicity, and that CYP2E1-mediated metabolism is not involved in this effect of nitriles although it has a role in the acute lethality of some of these compounds.

Konzo: from poverty, cassava, and cyanogen intake to toxico-nutritional neurological disease

Konzo is a distinct neurological entity with selective upper motor neuron damage, characterized by an abrupt onset of an irreversible, non-progressive, and symmetrical spastic para/tetraparesis. Despite its severity, konzo remains a neglected disease. The disease is associated with high dietary cyanogen consumption from insufficiently processed roots of bitter cassava combined with a protein-deficient diet. Epidemics occur when these conditions coincide at times of severe food shortage. Up to 1993, outbreaks in poor rural areas in Africa contributed to more than 3,700 cases of konzo. The number of affected people is underestimated. From unofficial reports, the number of cases was estimated to be at least 100,000 in 2000, in contrast to the 6,788 cases reported up to 2009 from published papers.

Neurological disorders associated with cassava diet: a review of putative etiological mechanisms

Tropical ataxic neuropathy (TAN) and epidemic spastic paraparesis (konzo) are two neurological disorders associated with the consumption of cassava (Manihot esculenta) in several African countries. TAN is characterized by sensory polyneuropathy, sensory ataxia, bilateral optic atrophy and bilateral sensori-neural deafness. It occurs in elderly individuals subsisting on a monotonous cassava diet with minimal protein supplementation. Konzo is a syndrome of symmetrical spastic paraparesis with a predilection for children and young women and invariably associated with consumption of inadequately processed bitter cassava roots with minimal protein supplementation. Despite numerous epidemiological, clinical and biochemical studies aimed at elucidating the etiological mechanisms of these disorders, their etiologies remain unknown, and there is no known treatment. The diseases continue to be prevalent in endemic areas, causing significant disability and increased mortality. A fresh appraisal of the putative etiologic mechanisms proposed for these intriguing and enigmatic syndromes is presented in this paper. Evidences against a causal role for cyanide intoxication are discussed, and evidences implicating thiamine deficiency as a unifying etiological mechanism for these neurological syndromes are presented. It is concluded that urgent research is needed to evaluate thiamine status and implement a therapeutic trial of thiamine in these debilitating neurological disorders.