Background: Aberrations of monocyte/macrophage-associated cytokines are increasingly recognized in systemic lupus erythematosus (SLE). However, the combined expression of these cytokines has not been sufficiently studied in relation to either disease activity or renal involvement in SLE. Here, we explored clinical values of monocyte/macrophage-associated cytokines for monitoring of disease activity and renal involvement in SLE patients.
Methods: A total of 44 healthy people and 100 SLE patients were enrolled in this study. The serum levels of 8 monocyte/macrophage-associated cytokines [interferon gamma (IFN-γ), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), macrophage colony stimulating factor (M-CSF), interleukin-34 (IL-34), interleukin-10 (IL-10), and urokinase-type plasminogen activator receptor (uPAR)] were measured, and correlations between their levels and both SLE activity and renal involvement were analyzed using receiver operating characteristic (ROC) curves. Additionally, we analyzed the correlation between M-CSF level and laboratory or clinical data and used real time-polymerase chain reaction (RT-PCR) to assess M-CSF messenger RNA (mRNA) expression in sorted candidate cells.
Results: The levels of IL-6, IFN-γ, and TNF-α were significant for predicting SLE activity, while the M-CSF level was significant for predicting both SLE activity and renal involvement. Furthermore, the mRNA expression of M-CSF in monocytes from SLE patients was higher than that of healthy people, and the M-CSF level was positively correlated with monocyte numbers.
Conclusions: The cytokine M-CSF is a promising marker to evaluate both disease activity and renal involvement in SLE, and the high level of M-CSF in SLE patients was mainly derived from monocytes.
Keywords: Macrophage colony stimulating factor (M-CSF); disease activity; monocyte/macrophage; renal involvement; systemic lupus erythematosus (SLE).