The purpose of this study was to evaluate urine monocyte chemoattractant protein-1 (MCP-1) and IL-8 as biomarkers of SLE flare. Urine was collected every 2 mo from patients who were followed prospectively in the Ohio SLE Study. Renal and nonrenal flares were identified and MCP-1 and IL-8 were measured by specific ELISA in samples that were collected at flare. When available, MCP-1 and IL-8 were also measured in urine samples before and after flare. For comparison, MCP-1 and IL-8 were measured in the urine of healthy individuals and in renal and nonrenal SLE patients with stable disease activity (disease controls). Most patients were receiving maintenance immunosuppressive therapy before flare. At renal flare, mean urine MCP-1 (uMCP-1) was significantly greater than uMCP-1 at nonrenal flare and from healthy volunteers and renal disease controls. The level of uMCP-1 correlated with the increase in proteinuria at flare and was higher in patients with proliferative glomerulonephritis and in patients with impaired renal function. Urine MCP-1 was increased beginning 2 to 4 mo before flare. Patients who responded to therapy showed a slow decline in uMCP-1 over several months, whereas nonresponders had persistently high uMCP-1. In contrast, uIL-8 did not change with disease activity and was not elevated at renal or nonrenal flare compared with disease controls. In conclusion, uMCP-1 but not uIL-8 is a sensitive and specific biomarker of renal SLE flare and its severity, even in patients who receive significant immunosuppressive therapy. Persistently elevated uMCP-1 after treatment may indicate ongoing kidney injury that may adversely affect renal prognosis. S ubstantial animal and human evidence suggests that chemokines, in particular monocyte chemoattractant protein-1 (MCP-1) and IL-8, contribute to kidney injury in the glomerulonephritis (GN) of SLE (reviewed in 1,2). In murine models of SLE GN, genetic deletion or pharmacologic blockade of MCP-1 attenuates glomerular and interstitial inflammation and reduces kidney damage (3-5). In humans with SLE GN, MCP-1 and IL-8 are expressed in the kidneys, and their transcripts can be detected by in situ hybridization, confirming intrarenal chemokine production (6 -8). Furthermore, urine MCP-1 and IL-8 (uMCP-1, uIL-8) levels are increased in SLE patients during active renal disease and in some reports decrease with treatment-induced disease remission (6,7,9 -11). Thus, uMCP-1, uIL-8, or both may be clinically relevant biomarkers of SLE GN. To date, however, the association of urine chemokines with renal and nonrenal SLE activity has not been examined rigorously through serial measurement of chemokine levels before, during, and after disease flares. This study was undertaken to investigate the relationship of uMCP-1 and uIL-8 to the onset, severity, and resolution of SLE flare in a cohort of well-characterized patients who were followed in the Ohio SLE Study (OSS), a prospective longitudinal investigation of risk factors for SLE flare in patients with renal or nonrenal SLE.
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