Spinal cord pathology is ameliorated by P2X7 antagonism in SOD1-G93A mouse model of amyotrophic lateral sclerosis

Abstract

In recent years there has been an increasing awareness of the role of P2X7, a receptor for extracellular ATP, in modulating physiopathological mechanisms in the central nervous system. In particular, P2X7 has been shown to be implicated in neuropsychiatry, chronic pain, neurodegeneration and neuroinflammation. Remarkably, P2X7 has also been shown to be a ‘gene modifier’ in amyotrophic lateral sclerosis (ALS): the receptor is upregulated in spinal cord microglia in human and rat at advanced stages of the disease; in vitro, activation of P2X7 exacerbates pro-inflammatory responses in microglia that have an ALS phenotype, as well as toxicity towards neuronal cells. Despite this detrimental in vitro role of P2X7, in SOD1-G93A mice lacking P2X7, 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 that has already been proven to reduce neuroinflammation in traumatic brain injury, cerebral ischemia-reperfusion, neuropathic pain and experimental autoimmune encephalitis. We tested BBG in the SOD1-G93A ALS mouse model at asymptomatic, pre-symptomatic and late pre-symptomatic phases of disease. BBG at late pre-onset significantly enhanced motor neuron survival and reduced 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 was accompanied by delayed onset and improved general conditions and motor performance, in both male and female mice, although survival appeared unaffected. 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.

Clemastine Confers Neuroprotection and Induces an Anti-Inflammatory Phenotype in SOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis

“…This is consistent with our previous results showing that inhibition of P2X7 during a well-defined phase of ALS disease exerts neuroprotection and reduces neuroinflammation [40]. Given the wellrecognized role of P2X7 in the progression of inflammation [41], this also suggests that P2X7 might act as a M1 marker at least in ALS spinal cord at end stage.…”

“…Although NOX2 is an important mechanism in ALS pathogenesis [42], we have recently demonstrated that NOX2 blockade is not sufficient to prolong survival in SOD1 G93A mice [40]. This is consistent with the lack of beneficial therapeutic effects provided by NOX2 inhibitors [43] and in agreement with the present data showing that clemastine, while inhibiting NOX2, only slightly improved ALS pathological symptoms.…”

“…In this context, we also provided evidence that while eliciting beneficial effects, clemastine downregulated P2X7 in lumbar spinal cord, thus validating the concept that purinergic P2X7 receptor is a player in the pathogenesis of ALS in SOD1 G93A mice [21,40]. This is consistent with our previous results showing that inhibition of P2X7 during a well-defined phase of ALS disease exerts neuroprotection and reduces neuroinflammation [40].…”

Prophylactic Oral Administration of Magnesium Ameliorates Dextran Sulfate Sodium-Induced Colitis in Mice through a Decrease of Colonic Accumulation of P2X7 Receptor-Expressing Mast Cells

“…and i.p. administration following the reports of Marques et al 17) and Apolloni et al, 34) and its optimum dose was judged to be 250 mg/kg (p.o.) (data not shown).…”

Modulation of the neuronal network activity by P2X receptors and their involvement in neurological disorders

“…Furthermore there is a temporal effect in pre-symptomatic stages P2XR promotes survival of neurons but in symptomatic phase their activation is associated to increased cell death [93]. These differential effects of ATP and P2XR could be associated with different types of receptors, and in literature is reported that at least P2X4 and 7 are involved in the disease [92,94], and this could help to explain the dual effect of ATP in ALS.…”