Therapeutic administration of etoposide coincides with reduced systemic HMGB1 levels in macrophage activation syndrome

Abstract

Background: Macrophage activation syndrome (MAS) is a potentially fatal complication of systemic inflammation. HMGB1 is a nuclear protein released extracellularly during proinflammatory lytic cell death or secreted by activated macrophages, NK cells, and additional cell types during infection or sterile injury. Extracellular HMGB1 orchestrates central events in inflammation as a prototype alarmin. TLR4 and the receptor for advanced glycation end products operate as key HMGB1 receptors to mediate inflammation.

Methods: Standard ELISA and cytometric bead array-based methods were used to examine the kinetic pattern for systemic release of HMGB1, ferritin, IL-18, IFN-γ, and MCP-1 before and during treatment of four children with critical MAS. Three of the patients with severe underlying systemic rheumatic diseases were treated with biologics including tocilizumab or anakinra when MAS developed. All patients required intensive care therapy due to life-threatening illness. Add-on etoposide therapy was administered due to insufficient clinical response with standard treatment. Etoposide promotes apoptotic rather than proinflammatory lytic cell death, conceivably ameliorating subsequent systemic inflammation.

Results: This therapeutic intervention brought disease control coinciding with a decline of the increased systemic HMGB1, IFN-γ, IL-18, and ferritin levels whereas MCP-1 levels evolved independently.

Conclusion: Systemic HMGB1 levels in MAS have not been reported before. Our results suggest that the molecule is not merely a biomarker of inflammation, but most likely also contributes to the pathogenesis of MAS. These observations encourage further studies of HMGB1 antagonists. They also advocate therapeutic etoposide administration in severe MAS and provide a possible biological explanation for its mode of action.

Keywords: FHL; HLH; HMGB1; Inflammation; Macrophage activation syndrome; Pathogenesis.

Fig. 1

High systemic HMGB1 levels in MAS patients. Plasma HMGB1 levels measured by ELISA were markedly increased during severe MAS as compared to children with uncomplicated JIA and healthy pediatric controls. The HMGB1 levels in the same cohort of JIA patients and healthy control children have been published previously in (Schierbeck et al. 2013). JIA juvenile idiopathic arthritis, MAS macrophage activation syndrome. *p < 0.05

Fig. 2

Longitudinal serum analyses before and after etoposide treatment in patient #1. High plasma levels of HMGB1 were observed during severe disease (a), and rapidly declined after initiation of etoposide treatment concomitantly with serum concentrations of ferritin (b), IFN-γ (c), and IL-18 (d). MCP-1 (e) levels peaked weeks later when the patient was recovering. CsA cyclosporine A; MP-pulses methylprednisolone pulses

Fig. 3

Serum analyses in patient #2 before and after treatment with etoposide. Two blood samples taken before and after etoposide therapy were analyzed when normalized levels of HMGB1 (a), ferritin (b) and IFN-γ (c) where documented after intervention with etoposide and subsequent clinical improvement. IL-18 declined but was still elevated (d) while MCP-1 increased (e). CsA cyclosporine A

Fig. 4

Longitudinal serum analyses before and after introduction of etoposide treatment in patient #4. The expression of plasma levels of HMGB1 (a), and serum levels of ferritin (b), IFN-γ (c), and IL-18 (d) corresponded very well to the clinical course of MAS with a rapid decline and clinical improvement after etoposide administration. MCP-1 levels were increased during the whole study period (e). CsA cyclosporine A; MP-pulses methylprednisolone pulses

Fig. 5

Longitudinal serum analyses before and after introduction of etoposide treatment in patient #3. The progression of plasma HMGB1 levels is illustrated in a. The first two plasma samples were collected at onset of sJIA without MAS manifestations. The HMGB1 levels increased at onset of MAS and declined promptly after treatment with etoposide infusions. Increased serum concentrations of ferritin (b) and IFN-γ (c) were documented during active MAS followed by a normalization post etoposide treatment. Serum IL-18 levels (d) were distinctly increased during the entire observation period with peak values during active phases of MAS. Serum MCP-1 levels did not reflect the clinical course (e). CsA: cyclosporine A; MP-pulses: methylprednisolone pulses

Fig. 6

Plasma HMGB1 levels in the four MAS patients before and after etoposide therapy. Plasma HMGB1 measured by ELISA was markedly increased in all patients during severe MAS before etoposide (Eto) treatment was added to ongoing therapy. Plasma HMGB1 concentration immediately before first dose of etoposide was compared to last available sample. HMGB1 levels were significantly reduced (*p < 0.05) post etoposide administration