Alsin and SOD1(G93A) proteins regulate endosomal reactive oxygen species production by glial cells and proinflammatory pathways responsible for neurotoxicity.
ABSTRACT Recent studies have implicated enhanced Nox2-mediated reactive oxygen species (ROS) by microglia in the pathogenesis of motor neuron death observed in familial amyotrophic lateral sclerosis (ALS). In this context, ALS mutant forms of SOD1 enhance Rac1 activation, leading to increased Nox2-dependent microglial ROS production and neuron cell death in mice. It remains unclear if other genetic mutations that cause ALS also function through similar Nox-dependent pathways to enhance ROS-mediate motor neuron death. In the present study, we sought to understand whether alsin, which is mutated in an inherited juvenile form of ALS, functionally converges on Rac1-dependent pathways acted upon by SOD1(G93A) to regulate Nox-dependent ROS production. Our studies demonstrate that glial cell expression of SOD1(G93A) or wild type alsin induces ROS production, Rac1 activation, secretion of TNFα, and activation of NFκB, leading to decreased motor neuron survival in co-culture. Interestingly, coexpression of alsin, or shRNA against Nox2, with SOD1(G93A) in glial cells attenuated these proinflammatory indicators and protected motor neurons in co-culture, although shRNAs against Nox1 and Nox4 had little effect. SOD1(G93A) expression dramatically enhanced TNFα-mediated endosomal ROS in glial cells in a Rac1-dependent manner and alsin overexpression inhibited SOD1(G93A)-induced endosomal ROS and Rac1 activation. SOD1(G93A) expression enhanced recruitment of alsin to the endomembrane compartment in glial cells, suggesting that these two proteins act to modulate Nox2-dependent endosomal ROS and proinflammatory signals that modulate NFκB. These studies suggest that glial proinflammatory signals regulated by endosomal ROS are influenced by two gene products known to cause ALS.
SourceAvailable from: Shinji Hadano
Dataset: ALS 2012NRI
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ABSTRACT: In recent years there has been an increasing awareness on the role of P2X7 receptor for extracellular ATP in modulating physiopathological mechanisms in the CNS. In particular, P2X7 was shown to be implicated in neuropsychiatry, chronic pain, neurodegeneration, neuroinflammation. Remarkably, P2X7 was shown to be a "gene modifier" in amyotrophic lateral sclerosis (ALS): the receptor is up-regulated in spinal cord microglia in human and rat at advanced stages of the disease; in vitro, activation of P2X7 exacerbates pro-inflammatory responses in ALS-microglia, as well as toxicity towards neuronal cells. Despite this detrimental in vitro role of P2X7, in P2X7(-/-)/SOD1-G93A mice the clinical onset of ALS was significantly accelerated and disease progression worsened, thus indicating that the receptor might have some beneficial effects at least at certain stages of disease. In order to clarify this dual action of P2X7 in ALS pathogenesis, in the present work we used the antagonist Brilliant Blue G (BBG), a blood-brain barrier permeable and safe drug already proven to reduce neuroinflammation in traumatic brain injury, cerebral ischemia/reperfusion, neuropathic pain and experimental autoimmune encephalitis. We tested BBG in SOD1-G93A ALS mouse model at asymptomatic, pre-symptomatic and late pre-symptomatic phases of disease. BBG at late pre-onset significantly enhances motoneuron survival and reduces microgliosis in lumbar spinal cord, modulating inflammatory markers such as NF-κB, NADPH oxidase 2, interleukin-1β, interleukin-10 and brain-derived neurotrophic factor. This is accompanied by delayed onset and improved general conditions and motor performance, in both male and female mice, although survival appears not affected. Our results prove the twofold role of P2X7 in the course of ALS, and establish that P2X7 modulation might represent a promising therapeutic strategy by interfering with the neuroinflammatory component of the disease.Disease Models and Mechanisms 07/2014; 7(9). DOI:10.1242/dmm.017038 · 5.54 Impact Factor
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ABSTRACT: Rac1 is a major player of the Rho family of small GTPases that controls multiple cell signaling pathways, such as the organization of cytoskeleton (including adhesion and motility), cell proliferation, apoptosis and activation of immune cells. In the nervous system, in particular, Rac1 GTPase plays a key regulatory function of both actin and microtubule cytoskeletal dynamics and thus it is central to axonal growth and stability, as well as dendrite and spine structural plasticity. Rac1 is also a crucial regulator of NADPH-dependent membrane oxidase (NOX), a prominent source of reactive oxygen species (ROS), thus having a central role in the inflammatory response and neurotoxicity mediated by microglia cells in the nervous system. As such, alterations in Rac1 activity might well be involved in the processes that give rise to Amyotrophic Lateral Sclerosis (ALS), a complex syndrome where cytoskeletal disturbances in motor neurons and redox alterations in the inflammatory compartment play pivotal and synergic roles in the final disease outcomes. Here we will discuss the genetic and mechanistic evidence indicating the relevance of Rac1 dysregulation in the pathogenesis of ALS.Frontiers in Cellular Neuroscience 09/2014; 8:279. DOI:10.3389/fncel.2014.00279 · 4.18 Impact Factor