Myelin basic protein-primed T cells induce Neurotrophins in glial cells via α5β3 integrin

Increasing the level of neurotrophins within the central nervous system may have therapeutic efficacy in patients with various neurological diseases. Earlier we have demonstrated that myelin basic protein ( MBP)-primed T cells induce the expression of various proinflammatory molecules in glial cells via cell-to-cell contact. Here we describe that after Th2 polarization by gemfibrozil or other drugs, MBP-primed T cells induced the expression of neurotrophic molecules such as brain-derived neurotrophic factor ( BDNF) and neurotrophin-3 ( NT-3), but not proinflammatory molecules in microglia and astroglia via cell-to-cell contact. MBP-primed Th2 cells expressed alpha 5 and beta 3 integrins and functional blocking antibodies against both alpha 5 and beta 3 integrins inhibited the ability of MBP-primed Th2 cells to induce glial neurotrophins. On the other hand, glial cells expressed PDGF-R beta and neutralization of this glial receptor abrogated the ability of Th2 cells to induce neurotrophins in glia. Activation of glial cAMP response element-binding protein ( CREB) by MBP-primed Th2 cell contact and inhibition of contact-mediated expression of neurotrophins by antisense knockdown of glial CREB suggest that MBP-primed Th2 cell-glia contact induces the expression of neurotrophins through glial activation of CREB. Accordingly, blocking of either alpha 5 beta 3 integrins on T cells or PDGF-R beta on glial cells impaired the ability of MBP-primed Th2 cells to induce glial activation of CREB. Furthermore, we demonstrate that these MBP-primed Th2 cells entered into the central nervous system and increased the expression of neurotrophins in vivo in the brain. This study illuminates the importance of alpha 5 beta 3 and PDGF-R beta in guiding the novel neurotrophic property of neuroantigen-primed T cells via activation of CREB that may be of therapeutic importance in various neurological disorders.