Early presymptomatic cholinergic dysfunction in a murine model of amyotrophic lateral sclerosis

Abstract

Sporadic and familiar amyotrophic lateral sclerosis (ALS) cases presented lower cholinergic activity than in healthy individuals in their still preserved spinal motoneurons (MNs) suggesting that cholinergic reduction might occur before MN death. To unravel how and when cholinergic function is compromised, we have analyzed the spatiotemporal expression of choline acetyltransferase (ChAT) from early presymptomatic stages of the SOD1G93A ALS mouse model by confocal immunohistochemistry. The analysis showed an early reduction in ChAT content in soma and presynaptic boutons apposed onto MNs (to 76%) as well as in cholinergic interneurons in the lumbar spinal cord of the 30-day-old SOD1G93A mice. Cholinergic synaptic stripping occurred simultaneously to the presence of abundant surrounding major histocompatibility complex II (MHC-II)-positive microglia and the accumulation of nuclear Tdp-43 and the appearance of mild oxidative stress within MNs. Besides, there was a loss of neuronal MHC-I expression, which is necessary for balanced synaptic stripping after axotomy. These events occurred before the selective raise of markers of denervation such as ATF3. By the same time, alterations in postsynaptic cholinergic-related structures were also revealed with a loss of the presence of sigma-1 receptor, a Ca2+ buffering chaperone in the postsynaptic cisternae. By 2 months of age, ChAT seemed to accumulate in the soma of MNs, and thus efferences toward Renshaw interneurons were drastically diminished. In conclusion, cholinergic dysfunction in the local circuitry of the spinal cord may be one of the earliest events in ALS etiopathogenesis.

Differential activation of neuronal and glial STAT3 in the spinal cord of the SOD1G93A mouse model of amyotrophic lateral sclerosis

“…Because the early dysfunction of cholinergic neurons has been reported in SOD1 G93A mice (Casas et al ., ), we examined the temporal changes in the ChAT immunoreactivity in the large (≥ 360 μm 2 ) YOYO‐1 + neurons, which can be presumptively defined as α‐motoneurons (Fig. H).…”

Neuromuscular Junction Impairment in Amyotrophic Lateral Sclerosis: Reassessing the Role of Acetylcholinesterase

“…Beyond these genes, a huge interested has been put on TARDBP gene, because its protein, TDP-43, is involved in multiple steps of RNA metabolism, including transcription, splicing, or transport of several mRNAs (Lagier-Tourenne et al, 2010; Lattante et al, 2013). Interestingly, ChAT mRNA is a target of TDP-43 (Buratti et al, 2010) and TDP-43 levels and localization in all the spinal MNs are severely affected early in the presymptomatic stage in hSOD1 G93A mice, and parallels the development of cholinergic dysfunctions (Casas et al, 2013). In this regard, we can speculate a possible implication for TDP-43 in the direct regulation and dysregulation of AChE or ColQ/PRiMA in ALS.…”

“…Recently, to unravel how and when cholinergic function is compromised, the spatiotemporal expression of ChAT from early presymptomatic stages of the hSOD1 G93A mouse model, has been analyzed by confocal immunohistochemistry. ChAT content was clearly reduced in MNs soma and cholinergic synaptic terminals very early, before MNs loss and NMJs detachment (Casas et al, 2013). Thus, ChAT reduction may contribute to distal degeneration.…”

Experimental Design and Data Analysis Issues Contribute to Inconsistent Results of C-Bouton Changes in Amyotrophic Lateral Sclerosis

“…Similar to the size of C-boutons, their number and density is another disputed topic in the ALS field in which inconsistent results of increase (Pullen and Athanasiou, 2009; Herron and Miles, 2012; Vinsant et al, 2013; Milan et al, 2015), decrease (Chang and Martin, 2009; Casas et al, 2013; Gallart-Palau et al, 2014; Milan et al, 2015; Vaughan et al, 2015), and no change (Chang and Martin, 2009; Pullen and Athanasiou, 2009; Herron and Miles, 2012; Casas et al, 2013; Gallart-Palau et al, 2014; Milan et al, 2015; Vaughan et al, 2015) have been reported at different disease stages, sometimes all in the same study. Importantly, postmortem data available from ALS patients show a decrease in C-bouton number at end stage (Nagao et al, 1998).…”