Genetic ablation of IP(3) receptor 2 increases cytokines and decreases survival of SOD1(G93A) mice

Amyotrophic lateral sclerosis (ALS) is a devastating progressive neurodegenerative disease characterized by the selective death of motor neurons. Disease pathophysiology is complex and not yet fully understood. Higher gene expression of the inositol 1,4,5-trisphosphate receptor 2 gene (ITPR2), encoding the IP(3) receptor 2 (IP(3)R2), was detected in sporadic ALS patients. Here, we demonstrate that IP(3)R2 gene expression was also increased in spinal cords of ALS mice. Moreover, an increase of IP(3)R2 expression was observed in other models of chronic and acute neurodegeneration. Upregulation of IP(3)R2 gene expression could be induced by lipopolysaccharide (LPS) in murine astrocytes, murine macrophages and human fibroblasts indicating that it may be a compensatory response to inflammation. Preventing this response by genetic deletion of ITPR2 from SOD1(G93A) mice had a dose-dependent effect on disease duration, resulting in a significantly shorter lifespan of these mice. In addition, the absence of IP(3)R2 led to increased innate immunity, which may contribute to the decreased survival of the SOD1(G93A) mice. Besides systemic inflammation, IP(3)R2 knockout mice also had increased IFNγ, IL-6 and IL1α expression. Altogether, our data indicate that IP(3)R2 protects against the negative effects of inflammation, suggesting that the increase in IP(3)R2 expression in ALS patients is a protective response.