The elevation of endocannabinoid levels through inhibiting their degradation afforded neuroprotection in CaMKIIα-TDP-43 mice, a conditional transgenic model of frontotemporal dementia. However, which cannabinoid receptors are mediating these benefits is still pending to be elucidated. We have investigated the involvement of the CB₁ and the CB₂ receptor using chronic treatments with selective ligands in CaMKIIα-TDP-43 mice, analysis of their cognitive deterioration with the Novel Object Recognition test, and immunostaining for neuronal and glial markers in two areas of interest in frontotemporal dementia. Our results confirmed the therapeutic value of activating either the CB₁ or the CB₂ receptor, with improvements in the animal performance in the Novel Object Recognition test, preservation of pyramidal neurons, in particular in the medial prefrontal cortex, and attenuation of glial reactivity, in particular in the hippocampus. In addition, the activation of both CB₁ and CB₂ receptors reduced the elevated levels of TDP-43 in the medial prefrontal cortex of CaMKIIα-TDP-43 mice, an effect exerted by mechanisms that are currently under investigation. These data reinforce the notion that the activation of CB₁ and CB₂ receptors may represent a promising therapy against TDP-43-induced neuropathology in frontotemporal dementia. Future studies will have to confirm these benefits, in particular with one of the selective CB₂ agonists used here, which has been thoroughly characterized for clinical development.

Frontotemporal dementia (FTD) causes progressive neurodegeneration in the frontal and temporal lobes, leading to behavioral, cognitive, and language impairments. With no effective treatment available, exploring new therapeutic approaches is critical. Recent research highlights the transcription factor Nuclear Factor erythroid-derived 2-like 2 (NRF2) as vital in limiting neurodegeneration, with its activation shown to mitigate FTD-related processes like inflammation. Dimethyl fumarate (DMF), an NRF2 activator, has demonstrated neuroprotective effects in a TAU-dependent FTD mouse model, reducing neurodegeneration and inflammation. This suggests DMF repositioning potential for FTD treatment. Until now, no trial had been conducted to analyze the effect of DMF on TDP-43-dependent FTD. In this study, we aimed to determine the potential therapeutic efficacy of DMF in a TDP-43-related FTD mouse model that exhibits early cognitive impairment. Mice received oral DMF treatment every other day from presymptomatic to symptomatic stages. By post-natal day (PND) 60, an improvement in cognitive function is already evident, becoming even more pronounced by PND90. This cognitive enhancement correlates with the neuroprotection observed in the dentate gyrus and a reduction in astrogliosis in the stratum lacunosum-moleculare zone. At the prefrontal cortex (PFC) level, a neuroprotective effect of DMF is also observed, accompanied by a reduction in astrogliosis. Collectively, our results suggest a potential therapeutic application of DMF for patients with TDP-43-dependent FTD.

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disease for which no effective treatments currently exist. The FDA and EMA have approved only riluzole, a drug that modestly extends patient survival by 3-18 months. In our research, we have identified a novel CK1δ inhibitor, IGS2.7, which modulates TDP-43 proteinopathy, the main ALS pathological hallmark, in both patient-derived cellular models and TgTDP-43 mice. To assess the potential of IGS2.7 as a therapeutic candidate and considering riluzole remains the standard care for ALS patients, we evaluated its effects in combination with riluzole. Our results demonstrate that co-administration of IGS2.7 and riluzole at effective doses does not cause adverse effects. However, no additional therapeutic benefit was observed beyond that of IGS2.7 monotherapy, suggesting that IGS2.7 may be viable as either a stand-alone treatment or as an adjunct to riluzole. Notably, when suboptimal doses of both drugs were administered, a combined effect was observed. This suggests that, once IGS2.7 reaches clinical testing, its use together with lower doses of riluzole may enhance therapeutic efficacy while potentially minimizing side effects. Additional in vivo pre-clinical studies will be required to further evaluate this possibility, although only clinical trials will ultimately determine its clinical relevance.