A final treatment with acetonitrile for 1min at RT was performed. miR-22, miR-155, miR-125b and miR-146b among the most highly modulated. We proved that miR-365 and miR-125b interfere, respectively, with the interleukin-6 and STAT3 pathway determining increased tumor necrosis factor alpha (TNF) transcription. As TNFdirectly upregulated miR-125b, and inhibitors of miR-365/miR-125b reduced TNFtranscription, we recognized the induction of miR-365 and miR-125b as a vicious gateway culminating in abnormal TNFrelease. These results strengthen the impact of miRNAs in modulating inflammatory genes linked to ALS and identify specific Rabbit polyclonal to Osteopontin miRNAs IDH-305 as pathogenetic mechanisms in the disease. Keywords:ALS, microglia, microRNAs, P2X7 receptor, TNFalpha Amyotrophic lateral sclerosis (ALS) is usually a widespread motor neuron disorder causing injury and death of lower and upper motor neurons.1Identification of superoxide dismutase 1 (SOD1) mutations accounting for about 20% of familiar ALS2allowed the production of transgenic mice overexpressing mutatedSOD1genes, with the SOD1-G93A strain being the most exploited. These mice develop loss of motor neurons together with symptoms resembling human ALS.3Moreover, clinical and electrophysiological data show that human SOD1-G93A phenotype resembles sporadic ALS in terms of disease progression, thus identifying the SOD1-G93A model as appropriate to investigate the molecular mechanisms of the sporadic disease.4 Mutated SOD1-mediated toxicity derives from both motor neurons and neighboring glia, with microgliosis highly contributing to neurodegeneration,5,6,7,8although far little attention has been paid to the study of how mutated SOD1 affects microglia features in particular.9,10Multiple mechanisms control the proper levels of protein expression during inflammation and, among these, microRNAs (miRNAs).11These small, non-coding RNAs are important regulators of protein synthesis under rapid environmental changes such as receptor activation.12Apart from their recognized role in cellular specification and physiopathological mechanisms, the recent discovery of circulating miRNAs also suggests that they provide novel means for paracrine and systemic communication.13,14Current findings demonstrate a correlation between miRNAs expression and microglia activation.15For instance, mutations of TDP43, a gene involved in miRNAs biogenesis, were lately found correlated to ALS.16Moreover, dysregulation IDH-305 of miRNAs in the best model for miRNAs ablation, the Dicer knockout mice, causes spinal motor neuron disease.17Finally, lack of miR-206 accelerates disease progression in ALS mouse.18All these findings strenghten the role of miRNAs in ALS pathology. Microglia activation can occurr through different means, among wich released tumor necrosis factor alpha (TNF) and extracellular ATP binding to ionotropic purinergic P2X7r.19In CNS, P2X7r is abuntantly expressed in microglia and involved in various pathologies.20In ALS, P2X7r is found upregulated in microglia of human spinal cord and in sections from mutated SOD1 rats.21,22In a previous work, we showed that ALS microglia exhibit P2X7r-dependent enhancement of TNF, COX-2, CD68, iNOS, NOX and pERK proteins, together with toxic effects exerted on neuronal cells.23,24However, despite a hypothesized role of P2X7r in ALS pathology, the full signaling and pathways involved are still unknown. The aim of this work was to define the miRNAs’ signature of microglia from non-transgenic (nt) and SOD1-G93A mice in both resting and P2X7r-activated conditions. We detected a specific subset of dysregulated inflammatory miRNAs that might contribute to ALS alterations. Our results strengthen the impact that miRNAs might have on post-transcriptional modulation of genes linked to inflammation and particularly to ALS. == Results == == Profiling of miRNA transcriptome of brain microglia from nt and SOD1-G93A mice == To examine the transcriptional profile and downstream regulation of individual miRNAs likely relevant to the ALS SOD1-G93A microglia phenotype, as appropriate model system we adopted primary microglia purified from newborn cerebral cortex of nt and SOD1-G93A mice. Of the total 627 mouse miRNAs included on the microarray chip employed, only a subset of about 130 miRNAs showed significant hybridization signal and this occurred in both nt and ALS microglia. We defined this novel subset as the miRNAs transcriptome of the brain microglia. As microglia share properties with both immune and nervous system cells (being the immune-competent cells of the brain), we compared the microglia miRNA transcriptome with the complete mouse miRNA profile of Landgrafet al.25(Supplementary Determine 1). The majority of miRNAs that we found significantly expressed in the brain microglia cultures were also present in the whole immune system and brain.25Of these,60% were immune system enriched,35% IDH-305 were shared by immune system and brain transcriptome, only5% belonged exclusively to the brain (Figure 1a). The transcriptional profile of the miRNA transcriptome of.