Neuroprotection Effect Of Interleukin-17 In An Acute Autoimmune Disease-mediated Neuroinflammation

Object: This study aims to dissect the role of IL-17 in autoimmune diseasemediated acute neuroinflammation.Methods: Lewis rats were immunized with interphotoreceptor retinoid-binding protein(IRBP)to induce a monophasic EAU.Relative expression of the multiple effector T cell-associated molecules and neurotrophic factors was analyzed by real time RT-PCR;the production of IL-17 in retina was examined by immunohistochemisty and immunofluorescent microcopy.The antagonism of IL-17 at a late stage of diseases examined the production of IL-17 in retina and the disease resolution by immunohistochemisty.Neuronal apoptosis was measured by TUNEL assays.In vitro experiments,supernatant of peripheral blood monocyte cells from Wister rats stimulated by PMA/ ionomycin was used to mimic the high-level IL-17-containing cytokine milieu in vivo.Primary cultured cerebella neurons and/or astrocytes of Wister rats under IL-17-containing cytokine milieu stimulants were used to confirm neuroprotection of IL-17.Neuronal apoptosis was measured by TUNEL assays and necrosis by LDH assays.A laser scan confocal microscope was used to detect the change of intracellular concentration of calcium([Ca2+]i)in primary cultured neurons against acute pro-inflammatory stimulants with/out different concentrations of IL-17.The cellular signaling pathways in astrocytes under the acute pro-inflammatory stimulants were examined by western blotting.Levels of IL-17 and other cytokines in the acute pro-inflammatory stimuli medium and the supernatants of astrocytes were determined by ELISA.Results: The data were obtained in vivo in a monophasic experimental autoimmune uveitis(EAU)in Lewis rats;in this preparation,the high-level IL-17-containing cytokine milieu was demonstrated,along with IL-17 secretion by the resident neural cells.The antagonism of IL-17 at a late stage disturbed the disease resolution and resulted in significant neural apoptosis.Our data show a dynamic role of IL-17 in the maintenance of homeostasis and neuroprotection in active neuroinflammation.The application of the cytokine milieu containing elevated IL-17 only on primary cultured cerebellar granule neurons resulted in significant apoptosis,but the presence of astrocytes largely prevented the effect.The supernatants of the stimulated astrocytes,especially those that contained the highest level of IL-17,achieved the best protection,and this effect could be blocked by anti-IL-17 antibodies.The protein IL-17 inhibited intracellular calcium increase and protected the neurons under inflammatory attack from apoptosis.IL-17 but not IFN-? in the inflammatory media contributed to astrocyte secretion of IL-17,which depended on the JAK/STAT pathway activation.The astrocytes that were treated with IL-17 alone,or with prolonged treatment of the inflammatory media,failed to produce sufficient levels of IL-17.Conclusions: A dynamic role of IL-17 in the maintenance of homeostasis and neuroprotection in active neuroinflammation.