Tri-ortho-cresyl phosphate (TOCP) decreases the levels of cytoskeletal proteins in hen sciatic nerve

In Vitro Immunotoxicity of Organophosphate Flame Retardants in Human THP-1-Derived Macrophages

Scarce attention has been paid to the immunotoxicity of organophosphate flame retardants (PFRs), which poses a challenge to the systematic assessment of their health risks. In this study, a battery of in vitro immunotoxicity screening assays, including adhesion, phagocytosis, and 48 cytokine/chemokine production, was measured after exposing THP-1-derived macrophages to six selected common PFRs (TPHP, TDCPP, TNBP, TOCP, TCEP, and TBOEP) at a noncytotoxic concentration (≤50 μM). Our results showed that TPHP and TBOEP partially attenuated the adhesion and phagocytosis of the THP-1 mφs and that TDCPP caused a functional loss of phagocytosis, implying the potential immunosuppression. In contrast, TNBP and TOCP may cause an immunostimulation by significantly promoting cell adhesion and enhancing phagocytic efficiency. Additionally, the results from a cytokine/chemokine secretion analysis revealed the proinflammatory properties of TDCPP, TPHP, and TBOEP. TOCP was thought to disrupt the inflammatory balance by inhibiting both proinflammatory and antiinflammatory cytokines. TCEP showed no effect on adhesion or phagocytosis and little modulation of cytokine release at this experimental concentration. Overall, this study supports that PFRs can be immunotoxic to macrophages in different ways and provides evidence for developing more sensitive in vitro immunotoxicity bioassay methods.

TRPA1 channel mediates organophosphate-induced delayed neuropathy

The organophosphate-induced delayed neuropathy (OPIDN), often leads to paresthesias, ataxia and paralysis, occurs in the late-stage of acute poisoning or after repeated exposures to organophosphate (OP) insecticides or nerve agents, and may contribute to the Gulf War Syndrome. The acute phase of OP poisoning is often attributed to acetylcholinesterase inhibition. However, the underlying mechanism for the delayed neuropathy remains unknown and no treatment is available. Here we demonstrate that TRPA1 channel (Transient receptor potential cation channel, member A1) mediates OPIDN. A variety of OPs, exemplified by malathion, activates TRPA1 but not other neuronal TRP channels. Malathion increases the intracellular calcium levels and upregulates the excitability of mouse dorsal root ganglion neurons in vitro. Mice with repeated exposures to malathion also develop local tissue nerve injuries and pain-related behaviors, which resembles OPIDN. Both the neuropathological changes and the nocifensive behaviors can be attenuated by treatment of TRPA1 antagonist HC030031 or abolished by knockout of Trpa1 gene. In the classic hens OPIDN model, malathion causes nerve injuries and ataxia to a similar level as the positive inducer tri-ortho-cresyl phosphate (TOCP), which also activates TRPA1 channel. Treatment with HC030031 reduces the damages caused by malathion or tri-ortho-cresyl phosphate. Duloxetine and Ketotifen, two commercially available drugs exhibiting TRPA1 inhibitory activity, show neuroprotective effects against OPIDN and might be used in emergency situations. The current study suggests TRPA1 is the major mediator of OPIDN and targeting TRPA1 is an effective way for the treatment of OPIDN.

Acrylamide alters cytoskeletal protein level in rat sciatic nerves

Occupational exposure and experimental intoxication with acrylamide (ACR) produce neuropathy characterized by nerve degeneration. To investigate the mechanism of ACR-induced neuropathy, male adult Wistar rats were given ACR (20, 40 mg/kg i.p. 3 days/week) for 8 weeks. Sciatic nerves were Triton-extracted and centrifuged at a high speed (100,000 x g) to yield pellet and supernatant fractions. The contents of six cytoskeletal proteins (NF-L, NF-M, NF-H, alpha-tubulin, beta-tubulin, and beta-actin) in both fractions were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Results showed that the three neurofilament (NF) subunits (NF-L, NF-M, NF-H) in both the pellet and the supernatant fraction decreased significantly (P < 0.01) in the high-dosing group, except for NF-M in the pellet. alpha-tubulin, beta-tubulin, and beta-actin increased significantly in the supernatant (P < 0.01), whereas both alpha-tubulin and beta-tubulin decreased significantly in the pellet (P < 0.01). However, beta-actin was not altered significantly in the sciatic nerves pellet. These findings suggest that ACR altered the cytoskeletal protein level in sciatic nerve, which may be one of the molecular mechanisms of ACR-induced peripheral neuropathy.