Gene expression profiling in peripheral blood cells of patients with rheumatoid arthritis in response to anti-TNF-alpha treatments

The efficacy of anti-TNF-α therapies highlights the role of TNF-α in the pathogenesis of rheumatoid arthritis (RA). However, the mechanism of action of these agents is poorly understood at the molecular level. The aim of this study was to characterize the effects of anti-TNF-α treatment on the global gene expression profile in peripheral blood mononuclear cells (PBMCs) of responder RA patients. Changes in gene expression were determined using oligonucleotide microarrays (25,341 genes) in PBMCs obtained before and after 12 wk of treatment with either etanercept or adalimumab from responder RA patients. Two hundred fifty-one genes displayed significant changes (false discovery rate < 0.1%) in expression level (178 upregulations with mean fold change = 1.5 and 73 downregulations with mean fold change = -1.50) after 12 wk of treatment. Importantly, the expression of several genes, including those coding for the calcium binding proteins S100A12 and A8, CD14 antigen, Selectin P, or ribosomal protein L39, reported to be upregulated in RA patients, were found to be decreased after anti-TNF-α treatment. Globally, inflammation, immune response, apoptosis, protein synthesis, and mitochondrial oxido-reduction were the most affected pathways in response to anti-TNF-α treatment. The obtained gene expression signature in PBMCs provides new information to better understand the mechanisms of action of anti-TNF-α treatment in RA patients.

Peripheral blood lymphocytes from patients with rheumatoid arthritis are differentially sensitive to apoptosis induced by anti-tumour necrosis factor-alpha therapy

OBJECTIVE

The efficacy of anti-tumour necrosis factor-alpha (TNF-alpha) therapies in rheumatoid arthritis (RA) has been mainly attributed to TNF-alpha neutralisation. Other mechanism as immune cell apoptosis, which is impaired in RA, may also be induced by anti-TNF-alpha therapies. The aim of our study was to investigate whether TNF-alpha inhibitors could induce apoptosis in vitro of the peripheral blood lymphocytes of RA patients.

METHODS

Peripheral blood mononuclear cells (PBMC) isolated from 24 patients with RA and 18 healthy donors were incubated with anti-TNF-alpha agents, infliximab or etanercept, in comparison with no agent and including an isotypic control, for 48 hours. Apoptosis was detected and quantified by annexin V labelling of phosphatidylserine externalization using cytofluorometric analysis and compared with PBMC production TNF-alpha in vitro.

RESULTS

In healthy donors, induced apoptosis was observed in 0.3% to 3.8% of lymphocytes with both therapies. In RA patients the treatment induced lymphocyte apoptosis in 17 of 24 patients with a percentage of annexin V-positive lymphocytes ranging from 0.1% to 25%. Among these 17 RA patients, a significant in vitro lymphocyte apoptosis (> 4%) was observed in 11 patients (46%) compared with healthy donors (p < 0.01). The variability of the response to anti-TNF-alpha within the RA population was not dependent on TNF-alpha synthesis or disease activity.

CONCLUSION

In vitro induction of lymphocyte apoptosis by anti-TNF-alpha was observed in a subgroup of RA patients. Based on these data, it would be of interest to further study the interindividual variations of sensitivity to apoptosis induced by TNF alpha inhibitors in relation to treatment efficacy or resistance observed in RA patients.