Synergistic Protective Effects of Mitochondrial Division Inhibitor 1 and Mitochondria-Targeted Small Peptide SS31 in Alzheimer’s Disease

Abstract

The purpose our study was to determine the synergistic protective effects of mitochondria-targeted antioxidant SS31 and mitochondria division inhibitor 1 (Mdivi1) in Alzheimer’s disease (AD). Using biochemical methods, we assessed mitochondrial function by measuring the levels of hydrogen peroxide, lipid peroxidation, cytochrome c oxidase activity, mitochondrial ATP and GTPase Drp1 enzymatic activity in mutant AβPP cells. Using biochemical methods, we also measured cell survival and apoptotic cell death. Amyloid beta (Aβ) levels were measured using sandwich ELISA, and using real-time quantitative RT-PCR, we assessed mtDNA (mtDNA) copy number in relation to nuclear DNA (nDNA) in all groups of cells. We found significantly reduced levels of Aβ40 and Aβ42 in mutant AβPP cells treated with SS31, Mdivi1 and SS31+Mdivi1, and the reduction of Aβ42 levels were much higher in SS31+Mdivi1 treated cells than individual treatments of SS31 and Mdivi1. The levels of mtDNA copy number and cell survival were significantly increased in SS31, Mdivi1 and SS31+Mdivi1 treated mutant AβPP cells, however, the increased levels of mtDNA copy number and cell survival were much higher in SS31+Mdivi1 treated cells than individual treatments of SS31 and Mdivi1. Mitochondrial dysfunction is significantly reduced in SS31, Mdivi1 and SS31+Mdivi1 treated mutant AβPP cells, however the reduction is much higher in cells treated with both SS31+Mdvi1. Similarly, GTPase Drp1 activity is reduced in all treatments, but reduced much higher in SS31+Mdivi1 treated cells. These observations strongly suggest that combined treatment of SS31+Mdivi1 is effective than individual treatments of SS31 and Mdivi1. Therefore, we propose that combined treatment of SS31+Mdivi1 is a better therapeutic strategy for AD. Ours is the first study to investigate combined treatment of mitochondria-targeted antioxidant SS31 and mitochondrial division inhibitor 1 in AD neurons.

Mitochondrial division inhibitor 1 reduces dynamin-related protein 1 and mitochondrial fission activity

“…This reduction is mainly because of reduced Drp1 levels and GTPase Drp1 enzymatic activity. Our observations are strongly supported by earlier cell culture studies in AD (28,40) and HD (31). Another supporting evidence based on transmission electron microscopy (1) in N2a cells treated with Mdivi-1, (2) Drp1 overexpressed plus Mdivi-1 and (3) Drp1 RNA silenced plus Mdivi-1-treated is that significantly increased length of mitochondria and reduced mitochondrial number are likely because of reduced GTPase Drp1 enzymatic activity.…”

“…It has been well established that increased Drp1 activity produces excessively fragmented mitochondria in AD neurons (18,23,38–40). Excessive mitochondrial fragmentation is a major feature in neurodegenerative diseases (16–18,20,23,40–44). Reduction in GTPase Drp1 activity is considered as a therapeutic strategy in diseases that involve increased mitochondrial fragmentation and mitochondrial dysfunction (18,20,31).…”

Mitochondria as Potential Targets in Alzheimer Disease Therapy: An Update

“…In one of AD murine models, the SS31 reduced Aβ peptide production, mitochondrial dysfunction, and enhanced mitochondrial biogenesis and synaptic activity (Calkins et al, 2011; Reddy et al, 2017). Recently, a combination of SS31 and the mitochondrial division inhibitor 1 (Mdivi1) was tested in cultured AD cells with positive effects, suggesting that a combined treatment of mitochondria-targeted antioxidants could have higher effectiveness (Reddy et al, 2018).…”

Back to The Fusion: Mitofusin-2 in Alzheimer’s Disease

“…In this review, we have illustrated the fundamental role of Mfn2 in mitochondrial function in health and disease, in particular in AD. Recently, different authors have indicated how perturbations in mitochondrial dynamics, particularly in fission and fusion proteins, Drp1, Fis1, OPA1, and Mfn2, can contribute to neuropathology [54][55][56].…”