Effects of LPS analysed in mouse models harboring disease-mutations in the ±2- or ±3Na+/K+-ATPase, respectively

Abstract

The enzyme Na+,K+-ATPase (Sodium Potassium Adenosine Trisfosfatase) is an integral membrane ion pump, essential to maintain the osmotic balance of cells, by its energy-driven ability to export Na+ and import K+. Its functions are vital to all cells. Of the four ±1-4 subunit isoforms, ±1-3 are expressed in the central nervous system. The ±2 isoform is highly enriched in atrocytes and the ±3 isoform is neuron-specific. Mutations in the genes encoding ±2 and ±3 isoforms can cause different neurological disorders, such as familial hemiplegic migraine type-2 (FHM2) (ATP1A2 mutations), or Rapid-onset Dystonia pakinsonims and Alternating Hemiplegia of Childhood (RDP/AHC, repesctively, for a3 mutations). Interestingly, recent findings showed that knockdown of the a2Na+/K+-ATPase in mutant superoxide dismutase 1 (SOD1) astrocytes were able to protect motor neurons from degeneration in co-cultured primary motor neurons, and showed that mitochondrial respiration and inflammatory gene expressions were induced in astrocytes from the SOD1 mutant mice, suggesting that the upregulation of the a2Na+/K+-ATPase stimulated mRNAs encoding mitochondrial respiration and expression of secreted inflammatory factors. Moreover, previous studies showed that ouabain, an inhibitor of the Na+,K+-ATPase, presented an important anti-inflammatory and anti-apoptotic action in the brain. The overall goal of this project is to test the effect of Na+,K+-ATPase in neuroinflammation. Towards this purpose, we will use heterozygous mice harboring disease mutations in the a2 (a2+/G301R mice) and a3 (a3+/D801Y mice) isoforms, respectively. Lipopolysaccharide (LPS) is a major bacterial TLR4 ligand that activates the innate immune response, and systemic administration of LPS can cause neuroinflammation in animal models by mechanisms involving expression of pro-inflammatory cytokines, activation of NF-ºB and inhibition of neurotrophic factor production. Accumulating evidence suggests a relationship between neurodegenerative diseases and neuroinflammation. For this purpose, we propose to examine how ±2 and ±3-containing Na+,K+-ATPase are associated with neuroinflammation in a2+/G301R and a3+/D801Y mice. Therefore, the project is important as it will contribute to a better understanding of the pathophysiology of the diseases associated with neuroinflammaiton.