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Serum lysozyme: a potential marker of monocyte/macrophage activity in rheumatoid arthritis
I Torsteinsdóttir1, L Hâkansson, R Hällgren
1Department of Medical Sciences, Clinical Chemistry and Rheumatology, University Hospital, Uppsala, Sweden.
Objective:
Estimate the contribution of monocytes/macrophages to the disease process in rheumatoid arthritis (RA), by measuring the serum levels of the leucocyte-derived granular proteins: lysozyme, myeloperoxidase (MPO), lactoferrin and human neutrophil lipocalin (HNL).
Methods:
Serum levels of these granular proteins were measured in patients with RA (n=23) and in healthy controls (n=27), and in 10 patients with RA after treatment with low-dose prednisolone. The serum levels of the granular proteins were also measured before and after treatment with metyrapone, a substance that inhibits the synthesis of cortisol in the adrenals.
Results:
The serum levels of lysozyme and MPO were elevated in patients with RA, while the concentrations of lactoferrin and HNL were similar in both groups. Prednisolone treatment decreased the serum concentration of lysozyme and MPO. Metyrapone did not influence the level of the granular proteins measured.
Conclusions:
The increased serum levels of lysozyme and MPO, but not of HNL and lactoferrin in RA could indicate a stimulated secretory activity of mononuclear phagocytes. The measurement of serum lysozyme, as an indicator of monocyte/macrophage activity, might be used to study disease activity in RA.
Insights
Serum lysozyme and myeloperoxidase (MPO) levels are elevated in rheumatoid arthritis (RA) patients, indicating increased monocyte/macrophage activity. These markers may help monitor RA disease activity.
Area of Science:
- Immunology
- Rheumatology
- Biochemistry
Background:
- Rheumatoid arthritis (RA) involves complex immune dysregulation.
- Monocytes and macrophages are key cellular players in RA pathogenesis.
- Biomarkers reflecting mononuclear phagocyte activity are needed for RA assessment.
Purpose of the Study:
- To estimate the contribution of monocytes/macrophages to rheumatoid arthritis (RA).
- To measure serum levels of leucocyte-derived granular proteins: lysozyme, myeloperoxidase (MPO), lactoferrin, and human neutrophil lipocalin (HNL) in RA patients.
- To assess the impact of prednisolone and metyrapone on these markers.
Main Methods:
- Serum granular protein levels were quantified in 23 RA patients and 27 healthy controls.
- Measurements were repeated in 10 RA patients after prednisolone treatment.
- Serum levels were also assessed before and after metyrapone administration.
Main Results:
- Serum lysozyme and MPO concentrations were significantly elevated in RA patients compared to controls.
- Lactoferrin and HNL levels did not differ between groups.
- Prednisolone treatment led to a decrease in serum lysozyme and MPO levels.
Conclusions:
- Elevated serum lysozyme and MPO in RA suggest stimulated secretory activity of mononuclear phagocytes.
- Serum lysozyme may serve as a potential indicator of monocyte/macrophage activity in RA.
- Further research can explore these markers for monitoring RA disease activity.