Research On Inhibition Of Aβ₄₂ Aggregation And Reduction Of Aβ₄₂ Neurotoxicity By The Ethanol Extracts Of Achyranthes Bidentata Blume

Objectives: To study 3 -amyloid protein 42 (Aβ₄₂ aggregation and amyloid fibril formation induced by incubation in vitro, and observe the neurotoxictity of Aβ₄₂ to rat hippocampal neurons. To observe the effects of ethanol extracts of Achyranthes bidentata blume (Nx-E) inhibiting A 3 42 aggregation and reducing the neurotoxicittOf (Aβ₄₂.Methods: (1)(Aβ₄₂ alone and (Aβ₄₂ co-incubated with 1.25%, 2.5% or 5% Nx-E solutions were incubated in 37 , 5% CO2 incubator, then were monitored by thioflavine-T fluorescence and observed by transmission electron microscopy (TEM); (2) The newborn Sprague-Dawley rat hippocampal neurons were cultured and identified by NSE stain; (3) After incubation, the solutions of Aβ₄₂ or Aβ₄₂ co-incubated with 1.25%, 2.5%, 5.0% Nx-E were added to cell cultured medium.The numbers & length of neurites were measured with the convert phase microscope, and MTT & lactate dehydrogenase (LDH) assay were done to analyze the toxicity to hippocampal neurons.Results: (1) Thioflavine-T fluorometr y results showed that the fluorescence intensity increased with the time of Aβ₄₂ incubation going. The fluorescence intensity of (Aβ₄₂ non-incubated was near to that of the backgroud, and at the 7th day 0.25mmol L -1 Aβ₄₂ fluorescence intensity was significantly increased (P<0.01). Little amyloid fibril formed in non-incubated group but much did at the 7th day; (2) The fluorescence intensity in 2.5% Nx-E group reduced, and in 5.0% reduced remarkablely. Little fibril but many amorphous materials were observed; (3) Most of the newborn rat hippocampal cells became brown, suggesting them being neurons; (4) 25 mol L-1 Aβ₄₂ could reduce more numbers and the length of neurites than that of 12.5 mol L-1, so the former was used as the celltoxity concentration; (5) Compared with 25 mol L-1 Aβ₄₂, the solution of A 3 42 co-incubated with 2.5% or5.0% Nx-E could increase numbers and the length of neurites. The optical density(OD) of MTT assay increased and LDH decreased.Conclusions: Incubated up to 7 days alone, Aβ₄₂ aggregates and forms amyloid fibril.The neurotoxitityconcentration of Aβ₄₂ is 25 mol L-1. 2.5 % and 5 %Nx-E canprevent Aβ₄₂ from polymerizing and forming fibril, and reduce the neurotoxitity Themechanism may be Nx-E has anti-oxidative activity.