Effects of lysine deacetylation inhibition alone or in combination with arimoclomol on TDP-43 proteinopathy

Cytoplasmic inclusions containing TAR DNA-binding protein 43 kDa (TDP-43) are recognized as a major pathological feature of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Peptidyl-prolyl cis-trans isomerase A (PPIA) interacts with TDP-43 and influences its aggregation and function. This interaction is facilitated by PPIA lysine acetylation. Here, we investigated whether restoring lysine acetylation homeostasis exerts protective effects on TDP-43 proteinopathy in vitro and in vivo and how this relates with PPIA. We found that vorinostat/SAHA, a broad-spectrum histone deacetylase (HDAC) inhibitor that increases PPIA acetylation, is able to reverse TDP-43 mislocalization in a cellular model of TDP-43 proteinopathy. We confirmed its effects in peripheral blood mononuclear cells from ALS patients and explored its impact on TDP-43 proteinopathy and PPIA acetylation in the Thy1-hTDP-43 mouse model. Thy1-hTDP-43 mice treated with SAHA showed a delayed onset of TDP-43 pathology, associated with PPIA nucleus-cytoplasm redistribution, lower neurodegeneration and neuroinflammation, and improved neuromuscular function markers. However, these effects were transient. When combined with arimoclomol, a heat shock protein co-inducer, a mitigation of the neurodegeneration was sustained. A synergistic effect was observed in periphery, greatly enhancing tubulin acetylation and reducing phosphorylated TDP-43 accumulation in the sciatic nerve and acetylcholine receptor γ-subunit expression in gastrocnemius muscle. This study suggests that HDAC inhibition could be beneficial in restoring TDP-43 localization and function through multiple mechanisms, including modulation of PPIA acetylation. The combination of HDAC inhibition and arimoclomol shows a synergistic effect in vivo and has potential as a therapeutic approach for patients.