Cerliponase Alfa Decreases Aβ Load And Alters Autophagy- Related Pathways In Mouse Hippocampal Neurons Exposed To Faβ1-42

Abstract

Extracellular aggregation of amyloid-beta (A beta) in the brain plays a central role in the onset and progression of Alzheimer's disease (AD). Moreover, intraneuronal accumulation of A beta via oligomer internalization might play an important role in the progression of AD. Deficient autophagy, which is a lysosomal degradation process, occurs during the early stages of AD. Tripeptidyl peptidase-1 (TPP1) functions as a lysosomal enzyme, and TPP1 gene mutations are associated with type 2 late infantile neuronal ceroid lipofuscinosis (LINCL). Nevertheless, there is little information about the role of TPP1 in the pathogenesis of AD; therefore, the present study aimed to measure the decrease in intraneuronal A beta accumulation by a recombinant analog of the TPP1 enzyme, cerliponase alfa (CER) (Brineura (R)), and to determine whether autophagy pathways play a role in this decrease. In this study, endogenous A beta accumulation was induced by fA beta(1-42) (a toxic fragment of full-length A beta) exposure, and mouse hippocampal neuronal cells (HT-22) were treated with CER (human recombinant rhTPP1 1 mg mL-1). Soluble A beta, TPP1, and the proteins involved in autophagy, including mammalian target of rapamycin (p-mTOR/ mTOR), p62/sequestosome-1 (p62/SQSTM1), and microtubule-associated protein 1 A/1B-light chain 3 (LC3), were evaluated using western blotting. The sirtuin-1, beclin-1, and Atg5 genes were also studied using RT-PCR. A beta and TPP1 localizations were observed via immunocytochemistry. CER reduced the A beta load in HT-22 cells by inducing TPP1 expression and converting pro-TPP1 into the mature form. Furthermore, exposure to CER and fA beta(1-42) induced the autophagy-regulatory/related pathways in HT-22 cells and exposure to CER alone increased sirtuin-1 activity. Based on the present findings, we suggest that augmentation of TPP1 with enzyme replacement therapy may be a potential therapeutic option for the treatment of AD.