Organophosphorus induced delayed neurotoxicity (OPIDN) has occurred in factory workers exposed in production of organophosphorus chemicals, which are used as plasticizers, lubricants, fire-retardants, or pesticides. Certain animal species (i.e., cats, dogs, cows, and chickens) are also susceptible, while others (rodents and some primates) are not. Although the chicken is the animal of choice to study this effect, it has many drawbacks. Our previous studies suggest the cat may be a better animal model to study the mechanisms of OPIDN. Although the mechanisms of OPIDN are not known, it is generally believed that the initial event is the phosphorylation of a protein (e.g. neurotoxic esterase, NTE) at the neurotoxicity target. We have postulated that subsequent changes in cellular Ca++ content leads to either enhanced phosphorylation of tubulin or a dissolution of neurofilaments. Both consequences lead to a disruption of axoplasmic transport and larger accumulations of Ca++ resulting in focal internodal swelling and Ca++ dependent proteolysis. Our preliminary studies have shown that in the cat brain, proteins relevant to OPIDN are concentrated in the synaptosomal fraction. Also, phosphorylation of brain synaptosomal protein with Gamma 32p-ATP was altered in cats as a result of TOCP treatment. We propose to study the effect of the neurotoxic organophosphorus esters (OP), TOCP, EPN, and DFP in comparison with the non-neurotoxic parathion on the normal phosphorylating mechanisms of neuronal proteins and on Ca++ concentrations of the axoplasm of neuronal organelles, as well as the isolation and characterization of tubulin and neurofilaments. In the beginning, we will examine the [Gamma 32p]ATP phosphorylatable proteins in brain and spinal cord synaptosomal cytosol and membrane fractions of normal cats. Optimum phosphorylating conditions will be established including the effect of calcium ions and calmodulin. The effect of in vivo protein phosphorylation will be determined. The effect of TOCP, EPN, DFP and parathion on slow and fast axoplasmic transport of radiolabeled proteins as well as NTE will be investigated. The characterization of tubulin and neurofilaments using electron microscopy as well as SDS-PAGE in TOCP treated cats will be studied. Electron microscopy will also be used to study cellular Ca++ levels in various organelles using x-ray energy spectrometry for the demonstration of calcium ions in swollen and degenerating axons. Finally, cats administered glucocorticoids in combination with OP's will be used to examine the reported benefit of glucocorticoid therapy in relation to the postulated mechanisms.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
9R01ES005154-04
Application #
3253388
Study Section
Safety and Occupational Health Study Section (SOH)
Project Start
1988-09-01
Project End
1992-08-31
Budget Start
1988-09-01
Budget End
1989-08-31
Support Year
4
Fiscal Year
1988
Total Cost
Indirect Cost
Name
Duke University
Department
Type
Schools of Medicine
DUNS #
071723621
City
Durham
State
NC
Country
United States
Zip Code
27705
Damodaran, T V; Attia, M K; Abou-Donia, M B (2011) Early differential cell death and survival mechanisms initiate and contribute to the development of OPIDN: a study of molecular, cellular, and anatomical parameters. Toxicol Appl Pharmacol 256:348-59
Damodaran, Tirupapuliyur V; Gupta, Ram P; Attia, Moustafa K et al. (2009) DFP initiated early alterations of PKA/p-CREB pathway and differential persistence of beta-tubulin subtypes in the CNS of hens contributes to OPIDN. Toxicol Appl Pharmacol 240:132-42
Damodaran, T V; Rahman, A A; Abou-Donia, M B (2000) Early differential induction of C-jun in the central nervous system of hens treated with diisopropylphosphorofluoridate (DFP). Neurochem Res 25:1579-86
Gupta, R P; Abou-Donia, M B (1999) Tau phosphorylation by diisopropyl phosphorofluoridate (DFP)-treated hen brain supernatant inhibits its binding with microtubules: role of Ca2+/Calmodulin-dependent protein kinase II in tau phosphorylation. Arch Biochem Biophys 365:268-78
Gupta, R P; Abou-Donia, M B (1998) Tau proteins-enhanced Ca2+/calmodulin (CaM)-dependent phosphorylation by the brain supernatant of diisopropyl phosphorofluoridate (DFP)-treated hen: tau mutants indicate phosphorylation of more amino acids in tau by CaM kinase II. Brain Res 813:32-43
Knoth-Anderson, J; Abou-Donia, M B (1993) Differential effects of triphenylphosphite and diisopropyl phosphorofluoridate on catecholamine secretion from bovine adrenomedullary chromaffin cells. J Toxicol Environ Health 38:103-14
Abou-Donia, M B; Viana, M E; Gupta, R P et al. (1993) Enhanced calmodulin binding concurrent with increased kinase-dependent phosphorylation of cytoskeletal proteins following a single subcutaneous injection of diisopropyl phosphorofluoridate in hens. Neurochem Int 22:165-73
Gupta, R P; Lapadula, D M; Abou-Donia, M B (1992) Ca2+/calmodulin-dependent protein kinase II from hen brain. Purification and characterization. Biochem Pharmacol 43:1975-88
Jensen, K F; Lapadula, D M; Anderson, J K et al. (1992) Anomalous phosphorylated neurofilament aggregations in central and peripheral axons of hens treated with tri-ortho-cresyl phosphate (TOCP). J Neurosci Res 33:455-60
Lapadula, E S; Lapadula, D M; Abou-Donia, M B (1992) Biochemical changes in sciatic nerve of hens treated with tri-o-cresyl phosphate: increased phosphorylation of cytoskeletal proteins. Neurochem Int 20:247-55

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