Abstract WP102: Interleukin-21 Promotes Neuronal Autophagy Following Cerebral Ischemia
Currently there is no treatment for the inflammatory responses that develop following cerebral ischemia. We have previously shown that the CD4+ T cell derived inflammatory cytokine IL-21 is highly upregulated in ischemic mouse brain following transient middle cerebral artery occlusion (tMCAO) and promotes neuronal tissue injury. We also found IL-21+ CD4+ cells in perivascular spaces of ischemic human brain tissue; however, the primary effects and cellular targets of IL-21 remain unknown. Thus, we compared genome-wide whole brain gene expression in wild-type (WT) and IL-21-/- mice following 1 hour tMCAO (n=3-5). RNA from whole brain was analyzed by Mouse Gene 1.0 ST microarray (Affymetrix) revealing that 2019 gene fragments representing 1505 genes had >3 fold higher expression in WT brain compared to IL-21-/- after 24 hours reperfusion. Gene score resampling of annotated probe scores identified biological process gene ontology (GO) terms with 3-8 member genes most significantly over-represented including: GO:0010507 Negative Regulation of Autophagy, GO:0090174 Organelle Membrane Fusion, GO:0000046 Autophagic vacuole fusion, and GO:0016242 Negative regulation of macroautophagy (p <0.001). These findings suggested a role for IL-21 in neuronal autophagy_consistent with our earlier reports of reduced expression of autophagy related gene 6 (ATG6) in infarcted brain tissue of IL-21-/- mouse compared to WT mice. Thus, we hypothesized that IL-21 could directly induce autophagy in hypoxic neuronal cells. IL-21 receptor was expressed on 10% of CD45- cells isolated from healthy mouse brain. Furthermore, using RT-PCR we detected Il21r mRNA expression on neuronal (Neura2A), astrocytic, and endothelial cell lines (MB114) with highest expression levels on Neuro2A cells. Surface expression on Neuro2A cells and primary neurons was confirmed by immunofluorescence. In preliminary experiments primary neurons treated with 256 ng/mL rIL-21 for 4 hours following 1-2 hour oxygen glucose deprivation showed increased expression of ATG6 compared to control treated cells (p<.05). In conclusion, these data suggest that IL-21 could directly promote neuronal autophagy following cerebral ischemia.
- © 2012 by American Heart Association, Inc.