SARM1 Ablation Is Protective and Preserves Spatial Vision in an In Vivo Mouse Model of Retinal Ganglion Cell Degeneration

Abstract

The challenge of developing gene therapies for genetic forms of blindness is heightened by the heterogeneity of these conditions. However, mechanistic commonalities indicate key pathways that may be targeted in a gene-independent approach. Mitochondrial dysfunction and axon degeneration are common features of many neurodegenerative conditions including retinal degenerations. Here we explore the neuroprotective effect afforded by the absence of sterile alpha and Toll/interleukin-1 receptor motif-containing 1 (SARM1), a prodegenerative NADase, in a rotenone-induced mouse model of retinal ganglion cell loss and visual dysfunction. Sarm1 knockout mice retain visual function after rotenone insult, displaying preservation of photopic negative response following rotenone treatment in addition to significantly higher optokinetic response measurements than wild type mice following rotenone. Protection of spatial vision is sustained over time in both sexes and is accompanied by increased RGC survival and additionally preservation of axonal density in optic nerves of Sarm1−/− mice insulted with rotenone. Primary fibroblasts extracted from Sarm1−/− mice demonstrate an increased oxygen consumption rate relative to those from wild type mice, with significantly higher basal, maximal and spare respiratory capacity. Collectively, our data indicate that Sarm1 ablation increases mitochondrial bioenergetics and confers histological and functional protection in vivo in the mouse retina against mitochondrial dysfunction, a hallmark of many neurodegenerative conditions including a variety of ocular disorders.

Early loss of endogenous NAD+ following rotenone treatment leads to mitochondrial dysfunction and Sarm1 induction that is ameliorated by PARP inhibition

“…So, how does this mitochondrial dysfunction induced by rotenone correlates with cell death? Our previous study and a few recent studies have indicated that the TLR adaptor protein sterile alpha and TIR motif containing 1 (Sarm1) play a pivotal role in this process as knockdown of Sarm1 showed a significant reduction in rotenone-induced cell death in SH-SY5Y cells [10,11]. Furthermore, a study by Hughes et al [12] has revealed that Sarm1 inhibition can prevent axonal Abbreviations DMEM, Dulbecco's modified Eagle's medium; LC3, light-chain 3; NAD + , nicotinamide adenine dinucleotide + ; NR, nicotinamide riboside; PD, Parkinson's disease; RFP, red fluorescent protein; ROS, reactive oxygen species; SRB, sulforhodamine B.…”

“…So, how does this mitochondrial dysfunction induced by rotenone correlates with cell death? Our previous study and a few recent studies have indicated that the TLR adaptor protein sterile alpha and TIR motif containing 1 (Sarm1) play a pivotal role in this process as knockdown of Sarm1 showed a significant reduction in rotenone‐induced cell death in SH‐SY5Y cells [10,11]. Furthermore, a study by Hughes et al.…”

Optimisation of AAV-NDI1 Significantly Enhances Its Therapeutic Value for Correcting Retinal Mitochondrial Dysfunction

“…The ability of ophNdi1 and NDI1 to decrease ROS, a significant feature of mitochondrial dysfunction, and increase NADH oxidation activity, an indirect measure of complex I activity, was evaluated. To induce complex I deficiency and mitochondrial dysfunction, rotenone, a complex I inhibitor was utilised; an increase in ROS levels is typically a feature of rotenone-induced mitochondrial dysfunction [ 49 , 68 , 69 ]. Mitochondrial and cellular ROS levels were determined in ophNdi1 and NDI1 transfected HEK293 cells 24 h post-rotenone insult (5 nM) using MitoSOX™ and CellROX™ assays, respectively.…”

“…A mitochondrial stress test was performed 48 h later according to the manufacturer’s protocols (Seahorse XFe96 extracellular flux analyser, Agilent Technologies, CA, USA). Injection cycles were 5× for basal OCR, 5× following oligomycin (1 µM), 5× following FCCP (1 µM), 5× following rotenone (0.5 µM) and 5× following antimycin A (0.5 µM) injections [ 4 , 49 ]. Six replicas per group were analysed.…”

From Bench to Bed: The Current Genome Editing Therapies for Glaucoma

“…Overexpression of Nmnat1 in RGCs of D2 mice also prevented glaucomatous nerve damage in >70% of treated eyes ( Williams et al, 2017b ). On the other hand, suppression of SARM1 has been demonstrated to protect against mitochondrial dysfunction, leading to preservation of axon degeneration and retaining of visual function in an in vivo mouse model of RGC degeneration ( Finnegan et al, 2022 ).…”