Antibodies to neural proteins in organophosphorus-induced delayed neuropathy (OPIDN) and its amelioration

Effects of endocrine disrupting chemicals on myelin development and diseases

In the central and peripheral nervous systems, myelin is essential for efficient conduction of action potentials. During development, oligodendrocytes and Schwann cells differentiate and ensure axon myelination, and disruption of these processes can contribute to neurodevelopmental disorders. In adults, demyelination can lead to important disabilities, and recovery capacities by remyelination often decrease with disease progression. Among environmental chemical pollutants, endocrine disrupting chemicals (EDCs) are of major concern for human health and are notably suspected to participate in neurodevelopmental and neurodegenerative diseases. In this review, we have combined the current knowledge on EDCs impacts on myelin including several persistent organic pollutants, bisphenol A, triclosan, heavy metals, pesticides, and nicotine. Besides, we presented several other endocrine modulators, including pharmaceuticals and the phytoestrogen genistein, some of which are candidates for treating demyelinating conditions but could also be deleterious as contaminants. The direct impacts of EDCs on myelinating cells were considered as well as their indirect consequences on myelin, particularly on immune mechanisms associated with demyelinating conditions. More studies are needed to describe the effects of these compounds and to further understand the underlying mechanisms in relation to the potential for endocrine disruption.

Novel Approach for Detecting the Neurological or Behavioral Impact of Physiological Episodes (PEs) in Military Aircraft Crews

Introduction

Military and civil aviation have documented physiological episodes among aircrews. Therefore, continued efforts are being made to improve the internal environment. Studies have shown that exposures to many organic compounds present in emissions are known to cause a variety of physiological symptoms. We hypothesize that these compounds may reversibly inhibit acetylcholinesterase, which may disrupt synaptic signaling. As a result, neural proteins leak through the damaged blood-brain barrier into the blood and in some, elicit an autoimmune response.

Materials and Methods

Neural-specific autoantibodies of immunoglobulin-G (IgG) class were estimated by the Western blotting technique in the sera of 26 aircrew members and compared with the sera of 19 normal healthy nonaircrew members, used as controls.

Results

We found significantly elevated levels of circulating IgG-class autoantibodies to neurofilament triplet proteins, tubulin, microtubule-associated tau proteins (Tau), microtubule-associated protein-2, myelin basic protein, and glial fibrillary acidic protein, but not S100 calcium-binding protein B compared to healthy controls.

Conclusion

Repetitive physiological episodes may initiate cellular injury, leading to neuronal degeneration in selected individuals. Diagnosis and intervention should occur at early postinjury periods. Use of blood-based biomarkers to assess subclinical brain injury would help in both diagnosis and treatment.

Tubulin and Tau: Possible targets for diagnosis of Parkinson's and Alzheimer's diseases

Neurodegenerative diseases including Alzheimer’s disease (AD) and Parkinson’s disease (PD) are characterized by progressive neuronal loss and pathological accumulation of some proteins. Developing new biomarkers for both diseases is highly important for the early diagnosis and possible development of neuro-protective strategies. Serum antibodies (AIAs) against neuronal proteins are potential biomarkers for AD and PD that may be formed in response to their release into systemic circulation after brain damage. In the present study, two AIAs (tubulin and tau) were measured in sera of patients of PD and AD, compared to healthy controls. Results showed that both antibodies were elevated in patients with PD and AD compared to match controls. Curiously, the profile of elevation of antibodies was different in both diseases. In PD cases, tubulin and tau AIAs levels were similar. On the other hand, AD patients showed more elevation of tau AIAs compared to tubulin. Our current results suggested that AIAs panel could be able to identify cases with neuro-degeneration when compared with healthy subjects. More interestingly, it is possible to differentiate between PD and AD cases through identifying specific AIAs profile for each neurodegenerative states.

A Panel of Autoantibodies Against Neural Proteins as Peripheral Biomarker for Pesticide-Induced Neurotoxicity

In the present study, we screened the sera of subjects chronically exposed to mixtures of pesticides (composed mainly of organophosphorus compounds (OPs) and others) and developed neurological symptoms for the presence of autoantibodies against cytoskeletal neural proteins. OPs have a well-characterized clinical profile resulting from acute cholinergic crisis. However, some of these compounds cause neuronal degeneration and demyelination known as organophosphorus compound-induced delayed neurotoxicity (OPIDN) and/or organophosphorus compound-induced chronic neurotoxicity (OPICN). Studies from our group have demonstrated the presence of autoantibodies to essential neuronal and glial proteins against cytoskeletal neural proteins in patients with chemical-induced brain injury. In this study, we screened the serum of 50 pesticide-exposed subjects and 25 non-exposed controls, using Western blot analysis against the following proteins: neurofilament triplet proteins (NFPs), tubulin, microtubule-associated tau proteins (Tau), microtubule-associated protein-2 (MAP-2), myelin basic protein (MBP), myelin-associated glycoprotein (MAG), glial fibrillary acidic protein (GFAP), calcium-calmodulin kinase II (CaMKII), glial S100-B protein, and alpha-synuclein (SNCA). Serum reactivity was measured as arbitrary chemiluminescence units. As a group, exposed subjects had significantly higher levels of autoantibody reactivity in all cases examined. The folds of increase in of autoantibodies against neural proteins of the subjects compared to healthy humans in descending order were as follows: MBP, 7.67, MAG 5.89, CaMKII 5.50, GFAP 5.1, TAU 4.96, MAP2 4.83, SNCA 4.55, NFP 4.55, S-100B 2.43, and tubulin 1.78. This study has demonstrated the presence of serum autoantibodies to central nervous system-specific proteins in a group of farmers chronically exposed to pesticides who developed neurological signs and symptoms of neural injury. These autoantibodies can be used as future diagnostic/therapeutic target for OP-induced neurotoxicity.

Autoantibodies associated with prenatal and childhood exposure to environmental chemicals in Faroese children

Methylmercury, polychlorinated biphenyls (PCBs), and perfluorinated compounds (PFCs) are ubiquitous and persistent environmental chemicals with known or suspected toxic effects on the nervous system and the immune system. Animal studies have shown that tissue damage can elicit production of autoantibodies. However, it is not known if autoantibodies similarly will be generated and detectable in humans following toxicant exposures. Therefore, we conducted a pilot study to investigate if autoantibodies specific for neural and non-neural antigens could be detected in children at age 7 years who have been exposed to environmental chemicals. Both prenatal and age-7 exposures to mercury, PCBs, and PFCs were measured in 38 children in the Faroe Islands who were exposed to widely different levels of these chemicals due to their seafood-based diet. Concentrations of IgM and IgG autoantibodies specific to both neural (neurofilaments, cholineacetyltransferase, astrocyte glial fibrillary acidic protein, and myelin basic protein) and non-neural (actin, desmin, and keratin) antigens were measured and the associations of these autoantibody concentrations with chemical exposures were assessed using linear regression. Age-7 blood-mercury concentrations were positively associated with titers of multiple neural- and non-neural-specific antibodies, mostly of the IgM isotype. Additionally, prenatal blood-mercury and -PCBs were negatively associated with anti-keratin IgG and prenatal PFOS was negatively associated with anti-actin IgG. These exploratory findings demonstrate that autoantibodies can be detected in the peripheral blood following exposure to environmental chemicals. The unexpected association of exposures with antibodies specific for non-neural antigens suggests that these chemicals may have toxicities that have not yet been recognized.

Neuroantibody biomarkers: links and challenges in environmental neurodegeneration and autoimmunity

The majority of neurodegenerative (ND) and autoimmune diseases (AID) remain idiopathic. The contribution of environmental chemicals to the development of these disorders has become of great interest in recent years. A convergence of mechanism between of ND and AID development has also emerged. In the case of ND, including neurotoxicity, the focus of this review, work over the last two decade in the realm of biomarker development, indicates that the immune response provides a venue whereby humoral immunity, in the form of autoantibodies to nervous system specific proteins, or neuroantibodies (NAb), may provide, once validated, a sensitive high throughput surrogate biomarker of effect with the potential of predicting outcome in absence of overt neurotoxicity/neurodegeneration. In addition, NAb may prove to be a contributor to the progression of the nervous system pathology, as well as biomarker of stage and therapeutic efficacy. There is a compelling need for biomarkers of effect in light of the introduction of new chemicals, such as nanoengineered material, where potential neurotoxicity remains to be defined. Furthermore, the convergence of mechanisms associated with ND and AID draws attention to the neglected arena of angiogenesis in defining the link between environment, ND, and AID.

Nervous system autoantibodies and vitamin D receptor gene polymorphisms in hemodialysis patients

Cognitive deficits are prevalent in hemodialysis (HD) patients. Vitamin D deficiency and vitamin D receptor (VDR) gene single nucleotide polymorphism (SNPs) have been linked to both neurodegeneration (ND) and neuroprotection, respectively. Autoantibodies (Ab) to myelin basic protein (MBP), glial fibrillary acidic protein (GFAP), and neurofilament (NF) triplet proteins arise secondary to nervous system (NS) damage providing a means to assess neurological injury. Characterization of Ab biomarkers of NS damage in HD patients, their association with VDR SNPs, and nutritional vitamin D (NVD) therapy was performed. VDR genotypes, cytokines, and Ab biomarkers to NS proteins in HD subjects receiving ergocalciferol (n = 40) were compared with nonusers (n = 71). Interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and immunoglobulin G (IgG) titers against NFs, GFAP, and MBP were measured by immunoassay. Subjects were genotyped for VDR SNPs BsmI (rs1544410) and FokI (rs2228570). Subjects (age 63.3 ± 16.1 years, 66% male) who were C allele carriers of BsmI had higher values of NF-68 antibody titers (p = 0.027). Ergocalciferol users (n = 40) compared with nonusers (n = 71) had lower Ab titers to NS proteins; however, only anti-NF-160 and anti-MBP titers were significantly (p < 0.05) higher. IgG against NS proteins in HD patients suggests neuronal and glial insult and a relationship with VDR alleles. NVD may provide some neuroprotection, indicated by anti-NF-160 and anti-MBP, which was markedly lowered in ergocalciferol patients. This preliminary study suggests that Ab detection may be useful in monitoring ND and the potential of NVD for neuroprotection in HD patients.

Mechanisms for consideration for intervention in the development of organophosphorus-induced delayed neuropathy

Organophosphorus-induced delayed neuropathy (OPIDN) is a neurodegenerative disorder characterised by ataxia progressing to paralysis with concomitant central and peripheral distal axonopathy. Symptoms of OPIDN in people include tingling of the hands and feet. This tingling is followed by sensory loss, progressive muscle weakness and flaccidity of the distal skeletal muscles of the lower and upper extremities and ataxia, which appear about 8-14 days after exposure. Some organophosphorus compounds (OPs) that are still used in worldwide agriculture have potential to induce OPIDN, including methamidophos, trichlorfon, dichlorvos and chorpyrifos. This review summarizes experimental attempts to prevent and/or treat OPIDN and the different mechanisms involved in each approach. The initial mechanism associated with development of OPIDN is phosphorylation and inhibition of neuropathy target esterase (NTE). The phosphorylated enzyme undergoes a second reaction known as "aging" that results in the loss of one of the "R" groups bound to the phosphorus of the OP. A second mechanism involved in OPIDN is an imbalance in calcium homeostasis. This can lead to the activation of calcium-activated neutral protease and increases in calcium/calmodulin-dependent protein kinases. These events contribute to aberrant phosphorylation of cytoskeletal proteins and protein digestion in the terminal axon that can proceed similarly to Wallerian-type degeneration. Several experimental studies demonstrated alleviation of the signs and symptoms of OPIDN by restoring calcium balance. Other studies have used preadministration of NTE inhibitors, such as carbamates, thiocarbamates, sulfonyl fluorides and phosphinate to prevent OPIDN. Progress is being made, but there is yet no single specific treatment available for use in clinical practice to prevent or alleviate the severe effects of OPIDN.