calpain and tri-o-cresyl-phosphate

Tri-ortho-cresyl phosphate (TOCP) can cause toxic neuropathy known as organophosphate-induced delayed neuropathy (OPIDN), which is pathologically characterized by the swollen axon containing aggregations of neurofilaments, microtubules, and multivesicular vesicles. Autophagy is a self-degradative process which plays a housekeeping role in removing misfolded proteins and damaged organelles. The current study was designed to investigate the possible roles of autophagy in the pathogenesis of OPIDN. Adult hens were treated with a dose of 750mg/kg TOCP by gavage, or injected subcutaneously with 60mg/kg phenylmethanesulfonyl fluoride (PMSF) dissolved in DMSO 24h earlier and subsequently treated with TOCP, then sacrificed on the time-points of 0, 1, 5, 10, and 21 days after dosing of TOCP respectively. The levels of beclin-1 and μ-calpain in tibial nerves and spinal cords were determined by immunoblotting. The results showed that in both tissues TOCP increased the expression of μ-calpain while decreased that of beclin-1. When given before TOCP administration, PMSF pretreatment could protect hens against the delayed neuropathy. In the meantime, pretreatment with PMSF reduced calpain expression below basal and increased beclin-1 expression above basal in tibial nerve, whereas it simply returned calpain and beclin-1 expression to their basal levels in spinal cord. In conclusion, the intoxication of TOCP was associated with a significant change of beclin-1 in hen nervous tissues, which suggested that disruption of autophagy-regulated machinery in neurons might be involved in the pathogenesis of OPIDN.

Topics: Animals; Apoptosis Regulatory Proteins; Beclin-1; Calpain; Chickens; Female; Membrane Proteins; Neurotoxicity Syndromes; Phenylmethylsulfonyl Fluoride; Spinal Cord; Tibial Nerve; Tritolyl Phosphates

This work evaluated the potential of the isoforms of methamidophos to cause organophosphorus-induced delayed neuropathy (OPIDN) in hens. In addition to inhibition of neuropathy target esterase (NTE) and acetylcholinesterase (AChE), calpain activation, spinal cord lesions and clinical signs were assessed. The isoforms (+)-, (±)- and (-)-methamidophos were administered at 50mg/kg orally; tri-ortho-cresyl phosphate (TOCP) was administered (500mg/kg, po) as positive control for delayed neuropathy. The TOCP hens showed greater than 80% and approximately 20% inhibition of NTE and AChE in hen brain, respectively. Among the isoforms of methamidophos, only the (+)-methamidophos was capable of inhibiting NTE activity (approximately 60%) with statistically significant difference compared to the control group. Calpain activity in brain increased by 40% in TOCP hens compared to the control group when measured 24h after dosing and remained high (18% over control) 21 days after dosing. Hens that received (+)-methamidophos had calpain activity 12% greater than controls. The histopathological findings and clinical signs corroborated the biochemical results that indicated the potential of the (+)-methamidophos to be the isoform responsible for OPIDN induction. Protection against OPIDN was examined using a treatment of 2 doses of nimodipine (1mg/kg, i.m.) and one dose of calcium gluconate (5mg/kg, i.v.). The treatment decreased the effect of OPIDN-inducing TOCP and (+)-methamidophos on calpain activity, spinal cord lesions and clinical signs.

Topics: Acetylcholinesterase; Administration, Oral; Animals; Brain; Calcium; Calcium Gluconate; Calpain; Carboxylic Ester Hydrolases; Chickens; Female; Homeostasis; Insecticides; Neurotoxicity Syndromes; Nimodipine; Organothiophosphorus Compounds; Spinal Cord; Time Factors; Tritolyl Phosphates

Topics: Analysis of Variance; Animals; Biomarkers; Calcium; Calpain; Chickens; Esterases; Female; Insecticides; Muscles; Neurons; Neurotoxins; Organophosphorus Compounds; Sciatic Nerve; Tritolyl Phosphates; Verapamil

Activity of calcium-activated neutral protease (CANP or calpain), an enzyme responsible for degradation of axonal and muscle cytoskeletal elements, was determined in brain, sciatic nerve, and gastrocnemius muscle of hens given tri-ortho-tolyl phosphate (TOTP, 360 mg/kg po) or active congener phenyl saligenin phosphate (PSP, 2.5 mg/kg im) with and without a calcium channel blocker which ameliorated clinical signs of organophosphate-induced delayed neuropathy (nifedipine 1 mg/kg/day x 5). Calcium channel blocker administration was initiated 1 day prior to administration of organophosphate (OP). OP administration caused an increase in CANP activity in brain within 4 days and in sciatic nerve and gastrocnemius muscle within 2 days of administration. This increase did not occur if nifedipine was administered to PSP-treated hens. Total sciatic nerve calcium concentrations were also increased by PSP, but not until OP-treated hens were no longer being administered calcium blockers. This indicates that calcium channel blockers may contribute to amelioration of organophosphate-induced delayed neuropathy by attenuation of calcium-mediated disruption of axonal and muscle cytoskeletal homeostasis.

Topics: Animals; Brain; Calpain; Carboxylic Ester Hydrolases; Chickens; Cresols; Female; Muscles; Nifedipine; Peripheral Nerves; Peripheral Nervous System Diseases; Tritolyl Phosphates