Elevated levels of soluble fractalkine and increased expression of CX3CR1 in neuropsychiatric systemic lupus erythematosus.

The aim of the present study was to determine the levels of soluble fractalkine (sFKN) and expression of CX3CR1 in neuropsychiatric systemic lupus erythematosus (NPSLE). Disease activity of SLE was assessed using the SLE Disease Activity Index (SLEDAI). The mRNA expression levels of CX3CR1 and FKN were quantified using reverse transcription-quantitative polymerase chain reaction. Levels of sFKN in the serum and cerebrospinal fluid (CSF) were measured using enzyme-linked immunosorbent assays. The mRNA expression levels of CX3CR1 in peripheral blood mononuclear cells from patients with NPSLE, non-NPSLE and Behcet's disease were significantly higher than that of rheumatoid arthritis and healthy persons. Levels of sFKN in the serum and CSF of cells with diffuse NPSLE (DNPSLE) were significantly higher than those of focal NPSLE (FNPSLE) cells. Serum levels of sFKN were higher in patients with NPSLE or non-NPSLE than heathy persons. sFKN in CSF were significantly higher in DNPSLE than non-NPSLE cells, but there were no significant difference between FNPSLE and control. Treatment reduced sFKN in serum and CSF in patients with NPSLE. There was significant correlation between sFKN in the serum of patients with SLE and the SLEDAI. sFKN levels were correlated with IgG in CSF from patients with NPSLE. The mRNA expression levels of CX3CR1 in the brain tissue of lupus mice were significantly higher than normal mice; however, the mRNA expression of FKN was lower than normal mice. These results suggest that sFKN and CX3CR1 may be involved in vasculitis and SLE, particularly in DNPSLE, which may occur by damaging the blood-brain barrier or recruiting expression microglial cells of CX3CR1. Additionally, sFKN appears to be a serological marker in patients with SLE, and may be useful for the diagnosis and treatment of NPSLE.