Connexin 43 hemichannels mediate spatial and temporal disease spread in ALS

Abstract

Connexin 43 (Cx43) gap junctions and hemichannels mediate astrocyte intercellular communication in the central nervous system under normal conditions and may contribute to astrocyte-mediated neurotoxicity in amyotrophic lateral sclerosis (ALS). Here we show that astrocyte-specific knockout of Cx43 in a mouse model of ALS slows disease progression both spatially and temporally, provides motor neuron (MN) protection, and improves survival. In human ALS tissues and biofluids, we observe that higher levels of Cx43 correlate with accelerated disease progression. Using human iPSC-derived astrocytes (hiPSC-A) from both familial and sporadic ALS, we show that Cx43 is upregulated and that Cx43-hemichannels are enriched at the astrocyte membrane. We then demonstrate that the pharmacological blockade of Cx43-hemichannels in ALS astrocytes, during a specific temporal window, provides neuroprotection of hiPSC-MN and reduces ALS astrocyte-mediated neuronal hyperexcitability. Our data identify Cx43 hemichannels as novel conduits of astrocyte-mediated disease progression and a pharmacological target for disease-modifying ALS therapies.

Recovery of Depleted miR-146a in ALS Cortical Astrocytes Reverts Cell Aberrancies and Prevents Paracrine Pathogenicity on Microglia and Motor Neurons

“…As so, pre-miR-146a was able to reduce the number of [Ca + ]i transients in mSOD1 astrocytes and to downregulate Cx43 expression. Previous studies observed the reduction in Ca 2+ responses in the presence of a Cx43 blocker in ALS astrocytes (Almad et al, 2016(Almad et al, , 2020.…”

Electrophysiological In Vitro Study of Long‐Range Signal Transmission by Astrocytic Networks

“…Although seemingly small, a conceptual shift towards regarding astrocytic network information processing as valuable in its own right opens up interesting translational possibilities. Given that the abnormal calcium signals, as well as dysregulated expression and function, of proteins linking astrocytes in a syncytium and/or allowing for the release of chemical transmitters such as connexins, pannexins, and aquaporins are involved in brain disorders such as Parkinson's, [ 75 , 97 ] Alzheimer's, [ 98 , 99 ] epilepsy, [ 35 , 100 , 101 ] amyotrophic lateral sclerosis, [ 102 , 103 ] multiple sclerosis, [ 81 ] Down's syndrome, [ 104 ] and more, AstroMEA could provide an in vitro translational testing platform differentiating between astrocytic and neuronal network functions for the first time. For instance, disease‐associated mutations may be introduced in the bridging astrocytes to study how these may influence signal propagation, or small molecules targeting astrocytes could be tested, albeit their diffusion through a 3D matrix needs to be confirmed.…”

Mature iPSC-derived astrocytes of an ALS/FTD patient carrying the TDP43A90V mutation display a mild reactive state and release polyP toxic to motoneurons

“…Studies with human astrocytes generated from fibroblasts that have been reprogrammed to become induced pluripotent stem cells (iPSCs) or induced NPCs (iNPCs; termed also i-astrocytes) can help avoiding many of the problems observed with primary astrocytes and therefore have become valuable tools for disease modeling and therapeutic testing. Importantly, reduced MN survival has been found using human iPSC-or iNPC-derived astrocytes carrying mutations in SOD1 (Meyer et al, 2014;Almad et al, 2022;Gomes et al, 2022), C9ORF72 (Meyer et al, 2014;Birger et al, 2019;Varcianna et al, 2019), VCP (Hall et al, 2017) or using astrocytes derived from sALS patients (Meyer et al, 2014;Almad et al, 2022;Gomes et al, 2022). Additional studies using human iPSC-based models indicate that astrocytes harboring mutations in C9ORF72 (Zhao et al, 2020) or FUS caused a milder MN toxicity, characterized by MN pathophysiology (but not death), whereas astrocytes carrying a mutation in TARDBP (TDP43 M337V ) did not lead to detectable MN toxicity (Serio et al, 2013).…”

“…We also showed that polyP is excessively released by mouse and human ALS and ALS/FTD astrocytes and, importantly, demonstrated by gainand loss-of-function approaches, that polyP causes non-cell autonomous death of MNs (Arredondo et al, 2022). Recent analyses of iPSC cell-based models further suggest that toxic effects of human astrocytes on MN survival and neurite outgrowth may also be the result of an enhanced secretion of inflammatory cytokines from reactive FUS-ALS astrocytes (Stoklund Dittlau et al, 2022) as well as increased release of ATP released through the opening of Cx43 hemichannels that are upregulated in fALS SOD1 and sALS astrocytes (Almad et al, 2022). Conversely, loss of neuron-supportive mechanisms has also been proposed to contribute to MN death and impaired neurite network maintenance (Stoklund Dittlau and Van Den Bosch, 2023).…”