Modulation of the gene expression pattern in peripheral blood mononuclear cells by biologicals in rheumatoid arthritis

Tumor necrosis factor (TNF)-α and IL-1β belong to the key mediators in the pathogenesis of rheumatoid arthritis (RA). Neutralization of these cytokines with biologicals like anti-TNF (etanercept) and IL-1 receptor antagonist (IL-1ra) (anakinra) induces a rapid and sustained decline in disease activity in RA patients. However, about 30% of patients receiving these therapies are nonresponders.

Here we report the application of DNA array technology (Affymetrix) in monitoring the modulation of gene expression of cells from peripheral blood under anti-TNF (etanercept) and IL-1ra (anakinra) treatment. Blood samples were taken from 14 RA patients before and 72 hours after initiation of etanercept (n = 10) or anakinra (n = 4) therapy. Total RNA from mononuclear cells (peripheral blood mononuclear cells) was prepared with the RNeasy kit (Qiagen). Affymetrix chip technology was used to analyse the expression levels. The therapy response was determined by changes in the disease activity score (DAS28) 3 months after the start of treatment.

Under anti-TNF therapy, the expression of genes for cytokines such as TNF-α, IL-1β, IL-1ra and PBEF, and for chemokines like IL-8, MIP-1α and MIP-1β, as well as for other disease-associated proteins like cyclooxygenase-2, intracellular adhesion molecule-1 and manganese superoxide dismutase, changed differentially. Interestingly, changes in the expression profile detected 3 days after the start of treatment were found to be closely associated with the outcome of therapy as reflected 3 months later by the disease activity score. Using real-time PCR, Affymetrix data were confirmed and expression of low abundant transcripts, which were not detected on microarrays such as IL-6, were observed. The application of anakinra influenced the expression levels of L-1β, IL-8, and cyclooxygenase-2 in a similar fashion, this being in contrast to anti-TNF treatment expression levels of TNF-α, MIP-1α and MIP-1β, which remained unchanged.

Our data give new insights into the effects of biologicals used in RA treatment on the transcriptional level. Early expression profiling of biological treatment can be a useful tool for monitoring changes at the mRNA level after neutralization of TNF-α and IL-1β, and thus for the predicting the outcome of therapy at an early stage of treatment. The data indicate the presence of genetic heterogeneities within the group of RA patients, suggesting the presence of genetic polymorphisms in the identified genes.