Activation of the JAK-STAT Signaling Pathway after In Vitro Stimulation with IFNß in Multiple Sclerosis Patients According to the Therapeutic Response to IFNß

Abstract

Interferon beta (IFNß) is a common treatment used for multiple sclerosis (MS) which acts through the activation of the JAK-STAT pathway. However, this therapy is not always effective and currently there are no reliable biomarkers to predict therapeutic response. We postulate that the heterogeneity in the response to IFNß therapy could be related to differential activation patterns of the JAK-STAT signaling pathway. Our aim was to evaluate the basal levels and the short term activation of this pathway after IFNß stimulation in untreated and IFNß treated patients, as well as according to therapeutic response. Therefore, cell surface levels of IFNAR subunits (IFNAR1 and IFNAR2) and the activated forms of STAT1 and STAT2 were assessed in peripheral blood mononuclear cells from MS patients by flow cytometry. Basal levels of each of the markers strongly correlated with the expression of the others in untreated patients, but many of these correlations lost significance in treated patients and after short term activation with IFNß. Patients who had undergone IFNß treatment showed higher basal levels of IFNAR1 and pSTAT1, but a reduced response to in vitro exposure to IFNß. Conversely, untreated patients, with lower basal levels, showed a greater ability of short term activation of this pathway. Monocytes from responder patients had lower IFNAR1 levels (p = 0.039) and higher IFNAR2 levels (p = 0.035) than non-responders just after IFNß stimulation. A cluster analysis showed that levels of IFNAR1, IFNAR2 and pSTAT1-2 in monocytes grouped 13 out of 19 responder patients with a similar expression pattern, showing an association of this pattern with the phenotype of good response to IFNß (p = 0.013). Our findings suggest that an activation pattern of the IFNß signaling pathway in monocytes could be associated with a clinical phenotype of good response to IFNß treatment and that a differential modulation of the IFNAR subunits in monocytes could be related with treatment effectiveness.

Differential Responsiveness of Monocyte and Macrophage Subsets to Interferon

“…The anti‐IFNAR monoclonal antibody might compete with IFNα2 for binding to IFNAR‐1, as is true of other anti–IFNAR‐1 monoclonal antibodies . Alternatively, since type I IFN binding induces IFNAR‐1 internalization , receptor expression could be modulated by endogenous type I IFN (SLE patients) or exogenous IFNα2b (in vitro). The latter explanation may be more likely, since a 1‐hour preincubation with IFNα2b prior to staining with anti‐IFNAR antibodies did not cause a dose‐dependent reduction in IFNAR staining (data not shown).…”

Autoreactive B cells in SLE, villains or innocent bystanders?

“…90 In addition, a positive correlation between serum IFNα and various disease parameters has also been established. 94 Several studies have demonstrated that IFNβ induces endocytosis and degradation of IFNAR1 to regulate the cell signaling. The relative lack of detectable IFNβ in serum is consistent with its much higher affinity for cell-surface bound IFNAR1 and IFNAR2, as well as a lower absolute abundance.…”

“…92 Functionally, the higher affinity of IFNβ for IFNAR1 and IFNAR2 increases the efficiency of ternary complex formation and stability, especially at low receptor surface concentrations. 94 94 Several studies have demonstrated that IFNβ induces endocytosis and degradation of IFNAR1 to regulate the cell signaling.…”

“…92,93 Indeed, the regulation of IFNAR1 and IFNAR2 expression levels is a major mechanism controlling the potency of cell responsiveness to IFNβ. 94 Several studies have demonstrated that IFNβ induces endocytosis and degradation of IFNAR1 to regulate the cell signaling. 92,95,96 Downregulation of IFNAR1 appears to occur rapidly in a tunable fashion, while IFNAR2 expression displays a slower basal turnover.…”

“…97 Additionally, both IFNAR2 and IFNAR1 can interact with IFNβ leading to signal transduction and changes in gene expression (IFNβ/IFNAR1 and IFNβ/IFNAR2), 98 a property that may explain differences in the response to IFNβ treatment. 94…”