Acat1 Knockdown Gene Therapy Decreases Amyloid-β in a Mouse Model of Alzheimer's Disease

Abstract

Both genetic inactivation and pharmacological inhibition of the cholesteryl ester synthetic enzyme acyl-CoA:cholesterol acyltransferase 1 (ACAT1) have shown benefit in mouse models of Alzheimer's disease (AD). In this study, we aimed to test the potential therapeutic applications of adeno-associated virus (AAV)-mediated Acat1 gene knockdown in AD mice. We constructed recombinant AAVs expressing artificial microRNA (miRNA) sequences, which targeted Acat1 for knockdown. We demonstrated that our AAVs could infect cultured mouse neurons and glia and effectively knockdown ACAT activity in vitro. We next delivered the AAVs to mouse brains neurosurgically, and demonstrated that Acat1-targeting AAVs could express viral proteins and effectively diminish ACAT activity in vivo, without inducing appreciable inflammation. We delivered the AAVs to the brains of 10-month-old AD mice and analyzed the effects on the AD phenotype at 12 months of age. Acat1-targeting AAV delivered to the brains of AD mice decreased the levels of brain amyloid-β and full-length human amyloid precursor protein (hAPP), to levels similar to complete genetic ablation of Acat1. This study provides support for the potential therapeutic use of Acat1 knockdown gene therapy in AD.

ACAT1/SOAT1 as a Therapeutic Target for Alzheimer's Disease

“…In addition, Acat1 KD significantly diminished the oligomeric Aβ content in the brains of the 3XTg-AD mice [91]. These observations implicate that, in addition to its effect on reducing Aβ production, ACAT1 blockage may also promote the clearance of oligomeric Aβ.…”

“…These data are consistent with our earlier findings made in the Acat1 KO/3XTg-AD mice [77], supporting the conclusion that blocking ACAT1 is sufficient to benefit AD. The result of Murphy et al [91] also demonstrated that after the AD onset, partial inactivation of ACAT1 (~40%) in the brain was sufficient to cause a decrease in the levels of Aβ1-42 in the 3XTg-AD mice.…”

“…The 3XTg-AD mouse model displays memory dysfunction by 9 months of age and starts to develop significant Aβ1-42 accumulation approximately at 10 months of age [86]. The results by Murphy et al [91] showed that Acat1 gene KD reduced the levels of full-length human APP protein and Aβ1-42 in the brains of the 3XTg-AD. These data are consistent with our earlier findings made in the Acat1 KO/3XTg-AD mice [77], supporting the conclusion that blocking ACAT1 is sufficient to benefit AD.…”

“…It is important to know whether blocking ACAT1 benefits AD in vivo, especially after the disease onset. Thus, Murphy et al from this laboratory tested whether ACAT1 inhibition can still elicit beneficial effects in the 3XTg-AD mice at the postsymptomatic stage [91]. To inhibit ACAT1 specifically, we chose to inject Acat1 gene KD construct to the brains of 10-month-old 3XTg-AD mice, using a recombinant adeno-associated virus vector to express the anti-Acat1 siRNA.…”

Analysis of acyl coenzyme A: cholesterol acyltransferase (ACAT) expression in human tissues

“…Cholesterol turnover and biology has been linked to AD based on circumstantial evidence (summarized from Chang et al, 2010;Bryleva et al 2010;Murphy et al, 2013), including observations that inhibition or knockdown of ACAT-1 in mice can result in reduced accumulation of amyloid peptides accompanied by ameliorated cognitive defects. However the mechanism and role of ACAT-1 in this process is a matter for speculation and ongoing research.…”