Diphenyl ditelluride induces hypophosphorylation of intermediate filaments through modulation of DARPP-32-dependent pathways in cerebral cortex of young rats

作者：Heimfarth Luana; Loureiro Samanta Oliveira; Reis Karina Pires; de Lima Barbara Ortiz; Zamboni Fernanda; Lacerda Sabrina; Soska Angela Kronbauer; Wild Luisa; Teixeira da Rocha Joao Batista; Pessoa Pureur Regina^*

来源：Archives of Toxicology, 2012, 86(2): 217-230.

DOI：10.1007/s00204-011-0746-6

• Diphenyl ditelluride
• Cytoskeleton
• Calcium
• Protein phosphatase 1
• Protein kinase A
• DARPP-32

We studied the effect of different concentrations of diphenyl ditelluride (PhTe) 2 on the in vitro phosphorylation of glial fibrillary acidic protein (GFAP) and neurofilament (NF) subunits from cerebral cortex and hippocampus of rats during development. (PhTe) 2-induced hypophosphorylation of GFAP and NF subunits only in cerebral cortex of 9- and 15-day-old animals but not in hippocampus. Hypophosphorylation was dependent on ionotropic glutamate receptors, as demonstrated by the specific inhibitors 10 mu M DL-AP5 and 50 mu M MK801, 100 mu M CNQX and 100 mu M DNQX. Also, 10 mu M verapamil and 10 mu M nifedipine, two L-voltage-dependent Ca2+ channels (L-VDCC) blockers; 50 mu M dantrolene, a ryanodine channel blocker, and the intracellular Ca2+ chelator Bapta-AM (50 mu M) totally prevented this effect. Results obtained with 0.2 mu M calyculin A (PP1 and PP2A inhibitor), 1 mu M Fostriecin a potent protein phosphatase 2A (PP2A) inhibitor, 100 mu M FK-506 or 100 mu M cyclosporine A, specific protein phosphatase 2B inhibitors, pointed to PP1 as the protein phosphatase directly involved in the hypophosphorylating effect of (PhTe) 2. Finally, we examined the activity of DARPP-32, an important endogenous Ca2+-mediated inhibitor of PP1 activity. Western blot assay using anti-DARPP-32, anti-pThr34DARPP-32, and anti-pThr75DARPP-32 antibodies showed a decreased phosphorylation level of the inhibitor at Thr34, compatible with inactivation of protein kinase A (PKA) by pThr75 DARPP-32. Decreased cAMP and catalytic subunit of PKA support that (PhTe) 2 acted on neuron and astrocyte cytoskeletal proteins through PKAmediated inactivation of DARPP-32, promoting PP1 release and hypophosphorylation of IF proteins of those neural cells. Moreover, in the presence of Bapta, the level of the PKA catalytic subunit was not decreased by (PhTe) 2, suggesting that intracellular Ca2+ levels could be upstream the signaling pathway elicited by this neurotoxicant and targeting the cytoskeleton.

• 出版日期2012-2