Objective: To compare the toxicity of mechanism beta amyloid peptide (Abeta) 25-35 and 31-35 to cultured rat cortical neurons.
Methods: The primary rat cerebral cortical neurons of rat were cultured 48 hours and randomly divided into control, Abeta25-35 (25 micromol/L)and Abeta31-35 (25 micromol/L) treated groups. After twenty four hours culturing, the cells were collected MTT assay was performed to measure the viability of cultured neurons. The mitochondrial membrane potential was determined to investigate the alteration of mitochondrial structure and function of neurons by laser scanning confocal microscope. The DNA damage of neurons was measured by single cell gel electrophoresis. The expressions of Bcl-2, Bax and p53 gene were measured by reverse transcriptase polymerase chain reaction (RT-PCR). Each experiment was repeated three times.
Results: The absorbance (0.746 +/- 0.071, 0.811 +/- 0.083) and fluorescence intensity (3.050 +/- 0.240, 2.806 +/- 0.203) of neurons in Abeta25-35 and 31-35 treated group were significantly lower (t(A) were 4.023 and 5.401, t(fluorescence intensity) were 9.524 and 7.589 respectively, P < 0.01) than those in control group (1.038 +/- 0.125 and 4.280 +/- 0.358 respectively). The percentage of comet cells (59.0%, 48.5%) and tail length (57.3 +/- 4.7, 54.2 +/- 6.8) microm in Abeta25-35 and 31-35 treated group were significantly higher (chi(2)(comet cell) were 99.397 and 137.071, t(tail length) were 19.058 and 29.173 respectively, P < 0.01) than those in control group (4.5% and (5.2 +/- 1.1) microm respectively). Compared with control group (Bax/Bcl-2 ratio 0.2090 +/- 0.0991, p53/beta-actin ratio 1.6560 +/- 0.0853), the Bax/Bcl-2 ratio (t value were 2.429 and 2.356 respectively, P < 0.05) and expressions of p53 (t value were 2.366 and 2.503 respectively, P < 0.05) gene were significantly increased (P < 0.05) in Abeta25-35 (Bax/Bcl-2 ratio 1.2774 +/- 0.0762, p53/beta-actin ratio 2.0284 +/- 0.2223) and Abeta31-35 (Bax/Bcl-2 ratio 1.0330 +/- 0.0683, p53/beta-actin ratio 1.9505 +/- 0.2725) treated group.
Conclusions: Neurotoxicity-induced by Abeta31-35 in cortical neurons is similar to that induced by Abeta25-35, which is possibly related to its direct neurotoxic and apoptotic effects to neurons.