Reactive oxygen species trigger motoneuron death in non-cell-autonomous models of ALS through activation of c-Abl signaling

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease in which pathogenesis and death of motor neurons are triggered by non-cell-autonomous mechanisms. We showed earlier that exposing primary rat spinal cord cultures to conditioned media derived from primary mouse astrocyte conditioned media (ACM) that express human SOD1G93A (ACM-hSOD1G93A) quickly enhances Nav channel-mediated excitability and calcium influx, generates intracellular reactive oxygen species (ROS), and leads to death of motoneurons within days. Here we examined the role of mitochondrial structure and physiology and of the activation of c-Abl, a tyrosine kinase that induces apoptosis. We show that ACM-hSOD1G93A, but not ACM-hSOD1WT, increases c-Abl activity in motoneurons, interneurons and glial cells, starting at 60 min; the c-Abl inhibitor STI571 (imatinib) prevents this ACM-hSOD1G93A-mediated motoneuron death. Interestingly, similar results were obtained with ACM derived from astrocytes expressing SOD1G86R or TDP43A315T. We further find that co-application of ACM-SOD1G93A with blockers of Nav channels (spermidine, mexiletine, or riluzole) or anti-oxidants (Trolox, esculetin, or tiron) effectively prevent c-Abl activation and motoneuron death. In addition, ACM-SOD1G93A induces alterations in the morphology of neuronal mitochondria that are related with their membrane depolarization. Finally, we find that blocking the opening of the mitochondrial permeability transition pore with cyclosporine A, or inhibiting mitochondrial calcium uptake with Ru360, reduces ROS production and c-Abl activation. Together, our data point to a sequence of events in which a toxic factor(s) released by ALS-expressing astrocytes rapidly induces hyper-excitability, which in turn increases calcium influx and affects mitochondrial structure and physiology. ROS production, mediated at least in part through mitochondrial alterations, trigger c-Abl signaling and lead to motoneuron death.

Astroglia acquires a toxic neuroinflammatory role in response to the cerebrospinal fluid from amyotrophic lateral sclerosis patients

“…Recently, Rojas and colleagues demonstrated that the astroglial-conditioned media from mSOD1 model brought about mitochondrial dysfunction, ROS elevation, and Ca 2+ influx in normal glial cells, as well as neurons [60]. The ability of the conditioned media from these cultures to exert toxicity to neurons, as well as propagating pathology to glial cells, provides further proof to our own model of the propagation of pathology through the circulating fluid (ALS-CSF).…”

Mitochondria Initiate and Regulate Sarcopenia

“…This occurs through p66Shc which generates H 2 O 2 that in turn, reacts with cytochrome c and induces oxidation of the mPTP and mitochondrial swelling (126). This mechanism is similar to neural degenerative diseases where induction of ROS (80, 113) contributes to motor neuron death (116). Thus, mitochondrial susceptibility to mPTP opening is a common point which triggers downstream cell destruction in both neuron and muscle cells.…”

Chronic infusion of SOD1G93A astrocyte‐secreted factors induces spinal motoneuron degeneration and neuromuscular dysfunction in healthy rats

“…Controls included ACM derived from transgenic mice expressing hSOD1 WT (ACM-hWT) or non-transgenic mouse SOD1 WT (ACM-WT) astrocytes. Thus, mutant SOD1-expressing astrocytes derived from mice (Castillo et al, 2013;Di Giorgio et al, 2007;Fritz et al, 2013;Nagai et al, 2007;Rojas, Cortes, Abarzua, Dyrda, & van Zundert, 2014;Rojas et al, 2015), rats (Cassina et al, 2008;Vargas, Pehar, Cassina, Beckman, & Barbeito, 2006), and humans (Marchetto et al, 2008) cause motoneuron pathology and death. Additionally, immunohistochemical analyses at day 16 revealed reactive astrogliosis and significant loss of motoneurons in the ventral horn of the infused region.…”