Effect of in vitro and in vivo anakinra on cytokines production in Schnitzler syndrome

Abstract

IL-1 receptor antagonist anakinra is usually highly efficient in Schnitzler syndrome (SS), a rare inflammatory condition associating urticaria, fever, and IgM monoclonal gammopathy. In this study, we aimed to assess lipopolysaccharide (LPS)-induced production of inflammatory cytokines by peripheral blood mononuclear cells (PBMCs) before and after 1 month of anakinra in patients with SS. LPS-induced production of IL-1β, IL-6 and TNFα was assessed by enzyme-linked immunosorbent assay with and without anakinra in vitro, and before and after 1 month (in vivo condition) of treatment in 2 patients with SS. Spontaneous production of IL-1β, IL-6 and TNF-α by PBMCs was similar in the patients and the healthy controls and was almost undetectable. Stimulation with LPS caused a higher release of cytokines from the patients than from the healthy controls. Before in vivo anakinra start, in vitro adjunction of anakinra reduced the high LPS-induced production of IL-1β and TNFα in both patients and of IL-6 in one patient. After 1 month of treatment with anakinra, while the patients had dramatically improved, there was also a marked reduction in LPS-induced cytokines production, which was almost normalized in one patient. This study shows an abnormal LPS-induced inflammatory cytokines production in SS, which can be decreased or even normalized by in vitro and in vivo anakinra.

Figure 1. Production of IL-1β, TNF-α and IL-6 by PBMCs of 2 Schnitzler syndrome (SS-1 for patient 1 and SS-2 for patient2) patients and 6 healthy subjects (HSs) in different conditions of culture.

(i) baseline: no stimulation condition of PBMCs; (ii) LPS stimulation (100 pg/ml); (iii) LPS stimulation (100 pg/ml) plus 500 ng/ml anakinra in vitro. Release of cytokine was evaluated in the supernatants collected at both 6 hours (middle gray histograms) and 16 hours (dark gray histograms) of culture conditions. Results are expressed as the mean of triplicate measures of cytokine concentration (± SD). In the SS patients, cytokine release was measured before and 1 month after in vivo anakinra treatment. In HSs, cytokine release is expressed as the mean of values (+/− SD) obtained in 6 independent evaluations.

Figure 2. Gene expression of IL-1β and IL-6 in unstimulated PBMCs by RNA quantitative real-time qPCR in the second patient with Schnitzler syndrome (SS-2) and healthy subjects (HS1 and HS2), at baseline (i.e. before the start of anakinra) and after 1 month of treatment with anakinra.