Effect Of Aβ_1-42 On Mitochondrial Structure And Function In SH-SY5Y Cell

Alzheimer’s disease (AD) is a primary neurodegenerative disease, characterized by persistent nerve dysfunction. It is investigated that Amyloid beta (A beta) deposits, which result in neuron apoptosis, play the main role in inducing AD. However, the pathogenesis of AD disease caused by Aβ is not very clear at present. At the same time, researchs proved that presenilin1and presenilin2mutation served as the main cause of the FAD. As PS act important functional parts of y-secretse,which participate in cleaving the amyloid precursor protein (β-APP), PS mutation will lead to abnormal cleavage of APP resulting in AP deposit, that meet the pathological hypothesis of gain of PS toxit function in FAD. But in the created PS1/PS2conditional double knockout mice model (PS cDKO), we saw the similar pathological characteristics with neurodegenerative disorder, such as ventricular enlargement and a large number of neuron apoptosis, but, interestingly, with no Aβ deposit in the PS cDKO, which unmatured with the pathological hypothesis of gain of PS toxit function in FAD. In addition, PS cDKO showed abundant abnormity of neuronal mitochondrial morphology, structure and function, such as the appearance of fragmented and abnormally distributed mitochondria as well as the change of size. Additionally, it was repoted that PS also contributed to mitochondrial biochemical function due to its existence in the mitochondrial. In our early trial, we found that Aβ treating SH-SY5Y cells leaded to obvious mitochondrial PS deficiency, suggesting that Aβ may express its toxit effect by inducing loss function of PS. What’s more, our previous experiments had investigated that loss function of PS could mediate its related protein-PARL (’presenilin-associated rhomboid-like’protein, in the inner notichondrial) to reduce the process on cleaveing the dynamin-related protein OPA1(in the inner mitochondrial). The cleavage of OPA1generates a pool of truncated OPA1that is soluble in the the mitochondrial intermembrane space (IMS), can regulate mitichondrial cristae remodeling, which lead to release of cytochrome c into the cytosol and trigger the cascade of reactions, finally, resulting in apoptosis. Futhermore, mitochondrial damage, energy shortage, DNA mutations are also early pathological phenomena of AD that Aβ is believed to participate in. And, the relationship between Aβ and mitochondrial dysfunction, which lead to apoptosis, has been studied largely in AD patients but being long to be uncovered. So, given all accumulating results, we hypothesize that Aβ may down regulate PS in the mitochondrial to induce the mitochondrial dependent "PS-PARL-OPA1" apoptotic pathway, which contributes to release of imtochondrial cytochrome C, dysfunction of mitochondrial, finally the apoptosis of neurons.In our trials, by treating SH-SY5Y cell with Aβ for24h (10μM and20μM Aβ1-42), we found Aβ damaged the normal mitochondrial structure and function with obvious decrease of mitochondrial membrane potential and significant down-regulation of mitochondrial fission and fusion related key genes Drpl and Mfn2expression. Meanwhile, expression of PS1, PARL and OPA1in the mitochondrial were inhibited by Aβ both in gene and protein level. It also showed remarkable increase of the release of mitochondrial cytochrome C as well as the number of apoptotic neurons. To figure out the hypothesis, PRAL-overexpression SHSY5Y cell was established by transfection. With the treatment of20μM Aβ1-42in the PARL overexpressed cells, we revealed significant reversion of PARL,OPA1, Drp1and Mfn2expression and cytochrome c release, along with the rate of decrease of mitochondrial membrane potential and apoptotic cells, compared with the20uM Aβ1-42treated wt-SH-SY5Y cells. In conclusion, these results indicate that Aβ142greatly upset the function of PS to induce mitochondrial "PS-PARL-OPA1" apoptotic pathway which suggests the release of mitochondrial cytochrome C as a apoptotic factor and mitochondrial structure impairment and function disorder, then is likely to lead to nueronal apoptosis.