Dysregulated autotaxin expression by T cells in multiple sclerosis.

Multiple sclerosis (MS) is a demyelinating disease characterized by infiltration of autoreactive T cells into the central nervous system (CNS). In order to understand how activated, autoreactive T cells are able to cross the blood brain barrier, the unique molecular characteristics of pathogenic T cells need to be more thoroughly examined. In previous work, our laboratory found autotaxin (ATX) to be upregulated by activated autoreactive T cells in the mouse model of MS. ATX is a secreted glycoprotein that promotes T cell chemokinesis and transmigration through catalysis of lysophoshphatidic acid (LPA). ATX is elevated in the serum of MS patients during active disease phases, and we previously found that inhibiting ATX decreases severity of neurological deficits in the mouse model. In this study, ATX expression was found to be lower in MS patient immune cells during rest, but significantly increased during early activation in a manner not seen in healthy controls. The ribosomal binding protein HuR, which stabilizes ATX mRNA, was also increased in MS patients in a similar pattern to that of ATX, suggesting it may be helping regulate ATX levels after activation. The proinflammatory cytokine interleukin-23 (IL-23) was shown to induce prolonged ATX expression in MS patient Th1 and Th17 cells. Finally, through ChIP, re-ChIP analysis, we show that IL-23 may be signaling through pSTAT3/pSTAT4 heterodimers to induce expression of ATX. Taken together, these findings elucidate cell types that may be contributing to elevated serum ATX levels in MS patients and identify potential drivers of sustained expression in encephalitogenic T cells.