LXR Pathway Activation by T0901317: A Novel Potential Experimental Strategy for ALS-Related Cognitive and Motor Impairments via Suppression of Necroptosis-associated RIPK1/RIPK3/MLKL Markers

To investigate the effects and mechanism of a synthetic LXR agonist, T0901317, on neuronal necroptosis-related signaling pathways in NSC-34 mouse neuronal cells transfected with the TDP-43-A315T plasmid, TDP-43-A315T transgenic mice of amyotrophic lateral sclerosis (ALS). SWATH proteinomics analysis was used to compare ALS patients with cognitive impairment (CI) and non-cognitive impairment (NOCI). TDP-43 abnormal aggregation and necroptosis-related protein expression were assessed with immunofluorescence and western blotting, while apoptosis and inflammatory cytokines were measured through TUNEL assay and ELISA, muscle and motor neuron degeneration were examined with H&E and Toluidine Blue staining. Additionally, the Y-maze and Rotarod tests were used to evaluate cognitive and motor functions. Our study indicates that the LXR pathway was more downregulated in the ALS patients with cognitive impairment. RIPK1, p-RIPK3, and p-MLKL protein levels were upregulated in the TDP-43-A315T plasmid-transfected neuron cells and the TDP-43-A315T transgenic mouse model. The LXR agonist T0901317 reduced the abnormal aggregation of TDP-43 protein and downregulated the protein levels of RIPK1, p-RIPK3, and p-MLKL in vivo and in vitro. Furthermore, T0901317 attenuated motor neuron death and ameliorated muscle degeneration in TDP-43-A315T mice. T0901317 significantly prolonged survival, ameliorated cognitive and motor deficits, and shifted microglial activation marker profiles. The beneficial effects of T0901317 were abolished by LXR antagonist GSK 2033, accompanied by upregulation of necroptotic signaling. The neuroprotective effects of activating LXR may involve the regulation of the RIPK1-RIPK3-MLKL axis and TDP-43 aggregation.