Effects of IFN-B on TRAIL and Decoy Receptor Expression in Different Immune Cell Populations from MS Patients with Distinct Disease Subtypes

Abstract

Using quantitative RT-PCR, we compared mRNA levels for TRAIL [tumor necrosis factor (TNF)-related apoptosis-inducing ligand] and its receptors in various immune cell subsets derived from the peripheral blood of untreated normal subjects (NS) and patients with distinct subtypes of multiple sclerosis (MS): active relapsing-remitting MS (RRA), quiescent relapsing-remitting MS (RRQ), secondary-progressive MS (SPMS) or primary-progressive MS (PPMS). Consistent with a role for TRAIL in the mechanism of action of interferon-β (IFN-β), TRAIL mRNA levels were increased in monocytes from patients clinically responsive to IFN-β (RRQ) but not those unresponsive to this therapeutic (RRA). TRAIL-R3 (decoy receptor) expression was elevated in T cells from untreated RRMS patients while IFN-β therapy reversed this increase suggesting that IFN-β may promote the apoptotic elimination of autoreactive T cells by increasing the amount of TRAIL available to activate TRAIL death receptors. Serum concentrations of soluble TRAIL were increased to a similar extent by IFN-β therapy in RRQ, RRA and SPMS patients that had not generated neutralizing antibodies against this cytokine. Although our findings suggest altered TRAIL signaling may play a role in MS pathogenesis and IFN-β therapy, they do not support use of TRAIL as a surrogate marker for clinical responsiveness to this therapeutic.

Figure 1

Relative quantification of TRAIL mRNA expression in RNA extracted from whole blood, T cells, B cells, and monocytes employing qRT-PCR. (a) In whole blood, TRAIL gene expression was no different between the various groups. (b) In T cells, TRAIL gene expression was also no different among NS and the various patient groups. (c) In B cells, TRAIL gene expression was the same in the various groups examined. (d) In monocytes, TRAIL gene expression was increased in RRQ IFN and SPMS IFN patients relative to NS. TRAIL mRNA was also elevated in RRQ IFN relative to RRQ NO IFN. *P < .05,**P < .01 and ***P < .001, Dunn's post hoc test.

Figure 2

Relative quantification of TRAIL death (TRAIL-R1, TRAIL-R2) and decoy receptor (TRAIL-R3, TRAIL-R4) mRNAs in T cells. (a) In T cells, there were no differences in gene expression of TRAIL-R1 and (b) TRAIL-R2. (c) TRAIL-R3 gene expression was increased in RRMS NO IFN patients relative to the NS group while administration of IFN-β reversed this increase in RRMS patients (RRMS IFN). *P < .05 and *P < .01, Dunn's posthoc test.

Figure 3

Relative quantification of TRAIL death (TRAIL-R1, TRAIL-R2) and decoy receptor (TRAIL-R3, TRAIL-R4) mRNAs in B cells. (a) TRAIL-R1, (b) TRAIL-R3 and (d) TRAIL-R4 mRNA levels were not altered by IFN-β treatment or different between the various groups (NS group and MS subtypes). Insufficient amounts of B cell RNA were isolated to permit analysis of TRAIL-R4 levels for PPMS patients. (c) TRAIL-R3 gene expression was increased in SPMS patients irrespective of IFN-β treatment condition (SPMS NO IFN and SPMS IFN groups not different and therefore pooled) relative to the RRMS group. *P < .05, Dunn's post-hoc test.

Figure 4

Absolute quantification of soluble TRAIL protein in peripheral blood serum. (a) Levels of soluble TRAIL protein were increased in serum from IFN-β treated-patients irrespective of subgroup (RRMS, SPMS) or disease activity (RRQ, RRA) relative to NS and untreated MS patients. *P < .05, **P < .01, and ***P < .001, Dunn's post-hoc test. (b) Ten patients (RRQ IFN n = 4; RRA IFN n = 3; SPMS n = 3) that were NAB(+) showed attenuated sTRAIL levels relative to IFN-β NAB(−) MS patients. ***P < .001, Mann Whitney U test.