• neuroimmunology
• astrocytes
• interleukin-9
• neuroinflammation

Interleukin (IL)-9 is a cytokine mainly produced by immune cells. IL-9 is known to induce proliferation of mast cells, and it is involved in asthma, anaphylaxis, and resistance to nematode infection. In recent years the role of IL-9 is also emerging in central nervous system (CNS) related diseases. In particular, IL-9 has been found in post-mortem brain tissues of multiple sclerosis (MS) patients and in the cerebrospinal fluid (CSF) of MS patients. Interestingly, high levels of IL-9 in the CSF of MS patients are associated to a less severe disease, suggesting a protective role of IL-9 in MS. We hypothesized that IL-9 could have a beneficial effect on CNS resident cells and we investigated the potential role of IL-9 on astrocyte. Astrocytes play a crucial role in the maintenance of brain homeostasis through a structural and functional support of neuronal activity. During pathological conditions the inflammatory environment turns them into reactive cells, which actively contribute to the disease. However, they may also exert protective functions during diseases, such as release of anti-inflammatory factors, and trophic molecules for neurons. The aim of the study is to identify the effects of IL-9 on human inflammatory astrocytes. First, we used several stimuli to mimic the inflammatory environment and we analysed astrocytes’ activation from the molecular and functional point of view by flow cytometry, western blot and ELISA assays. In order to assess the effects of IL-9 on astrocytes’ activation, we stimulated activated astrocytes with recombinant IL-9, and we identified, by western blot and real time RT-PCR, the molecular mechanisms and the transcriptional signature modulated by IL-9 in human reactive astrocytes.