Abstract
Purpose: :
T cells are essential for the development of autoimmune uveitis. Our previous study showed that OX40, a key co-stimulatory molecule, plays a pivotal role in enhancing T cell response and ocular inflammation. However, the molecular mechanism by which OX40 regulates uveitogenic T cells remains to be fully elucidated. Recently, cyclin dependent kinase 5 (CdK5), a unique serine/threonine kinase, has been implicated in T cell activation. Furthermore, CdK5 exerts several key downstream effects in common with OX40. Thus, we sought to determine whether CdK5 is a critical intermediary of OX40 signaling, leading to exacerbation of uveitis.
Methods: :
The splenocytes of DO11.10 mice were activated by cognate antigen ovalbumin (OVA) for up to 72 hours. Flow cytometry was performed to compare intracellular CdK5 expression between CD4+OX40+ and OX40- T cells. In addition, these cells were treated with CdK5 inhibitor Roscovitine, and T cell apoptosis was measured by Annexin V staining and MitoCapture assay. Lastly, experimental autoimmune uveitis (EAU) was induced by immunization of B10.RIII mice with interphotoreceptor binding protein. Some mice were further treated with OX40 activating antibody, and EAU score was determined on day 21 to assess the effect of Roscovitine on OX40-enhanced uveitis.
Results: :
To explore the relationship of OX40 with CdK5, we categorized DO11.10 CD4+ cells to 2 distinct populations based on surface OX40 expression. After OVA activation, OX40+ cells expressed more intracellular CdK5 than OX40- lymphocytes. In addition, blocking phosphatidylinositol 3-kinases, which mediates OX40 signaling pathway, reduced the expression of CdK5. Moreover, inhibition of CdK5 by Roscovitine led to the decrease of activated CD4+CD44+ lymphocyte number, which coincided with increased T cell apoptosis. Finally, weekly treatment of Roscovitine attenuated the severity of OX40-enhanced EAU.
Conclusions: :
These results implicated CdK5 in OX40-augmented T cell response and suggest that targeting CdK5 may be a novel therapeutic strategy for treating T cell-mediated uveitis.
Keywords: autoimmune disease • uveitis-clinical/animal model • inflammation