Ethidium bromide-induced demyelination in the sciatic nerve of diabetic rats

Abstract

-This study aims to observe the process of myelin loss and repair following the injection of the gliotoxic agent ethidium bromide (EB) in the sciatic nerve of rats previously induced to diabetes mellitus by streptozotocin. Injection of EB was also done in non-diabetic rats. The animals were euthanatized from 3 to 31 days after intraneural injection and nerve sections were collected for ultrastructural study. In nondiabetic rats, Schwann cells (CS) showed signs of intoxication 3 days after, with cytoplasmic vacuolization and rejection of their myelin sheaths. Myelin debris were removed by macrophages in the endoneurium and mast cells were abundant in the lesions. From 14 days following EB injection, supernumerary CS were seen in the expanded endoneurium as well as thin myelin sheaths indicating remyelination. Diabetic rats presented a more extensive myelin vesiculation and segmentar demyelination, with delayed activities from both macrophages and remyelinating SC. No mast cells were noted.KEY WORDS: demyelination, diabetes mellitus, ethidium bromide, peripheral nervous system, remyelination, Schwann cells.desmielinização induzida pelo brometo de etídio no nervo ciático de ratos diabéticos resumo -O estudo visa à observação do processo de perda e reparo mielínico pós-injeção do gliotóxico brometo de etídio (BE) no nervo ciático de ratos previamente induzidos a diabetes mellitus pela estreptozotocina. Injeção de BE foi igualmente realizada em ratos não-diabéticos. Os animais foram eutanasiados dos 3 aos 31 dias pós-injeção intraneural, com colheita de amostras neurais para estudo ultraestrutural. Nos animais não-diabéticos, as células de Schwann (CS) mostraram sinais de intoxicação a partir dos 3 dias pós-gliotóxico, com vacuolização citoplasmática e rejeição de suas bainhas de mielina. Restos mielínicos eram removidos por macrófagos no interior do endoneuro e mastócitos eram abundantes nas lesões. A partir dos 14 dias, CS supranumerárias foram encontradas no endoneuro expandido, além de finas bainhas de mielina indicativas de remielinização. Os ratos diabéticos apresentaram vesiculação mielínica e desmielinização segmentar mais extensas, bem como ausência de mastócitos e atraso na atividade macrofágica e na função remielinizante das CS. PALAVRAS-CHAVE: brometo de estídio, células de Schwann, desmielinização, diabetes mellitus, remielinização, sistema nervoso periférico.

Internode length is reduced during myelination and remyelination by neurofilament medium phosphorylation in motor axons

“…Therefore, we hypothesized, that much like myelin thickness, axons might contribute to establishing internode length and that this could be altered during remyelination resulting in reduced internode length. As an initial approach, we used ethidium bromide (EtBr) injection as an established model for inducing demyelination in the sciatic nerve (Bondan et al, 2009. EtBr injections into sciatic nerves of 1-month-old wild type mice induced demyelination in an ~7mm long region along the injected nerve (Supplementary Figs.…”

“…1). Sciatic nerves were collected for analysis at three different time points; maximal demyelination point, at 7 days post-injection; beginning of remyelination, 14 days post-injection; and complete remyelination point, 30 days post-injection (Bondan et al, 2009; Bondan and Monteiro Martins Mde, 2013; Riet-Correa et al, 2002). For detailed analysis of nerves after ethidium bromide injection, Swiss Webster mice were treated as described above.…”