MCP-1 and IL-8 as Pain Biomarkers in Fibromyalgia: A Pilot Study

Abstract

Although fibromyalgia (FM) is traditionally a non-inflammatory condition, emerging data also suggest that FM has an immunologic component. Previous studies have reported that peripheral blood concentrations of two chemokines (i.e., interleukin-8 [IL-8] and monocyte chemotactic protein-1 [MCP-1]) were elevated in FM patients compared with normal controls. We sought to determine the longitudinal relationships of changes in the levels (picogram/mL) of IL-8 and MCP-1 with changes in the severity of FM-related pain. Secondary data analysis of a cohort of 16 FM subjects who provided blood samples at two time points: week 1 and week 12. Setting. Urban rheumatology clinic practices. Individuals who met the American College of Rheumatology 1990 criteria for FM. Changes from week 1 to week 12 of the following variables: Brief Pain Inventory (BPI) pain severity and plasma concentrations of IL-8 and MCP-1. Change in BPI pain severity was significantly associated with changes in IL-8 and MCP-1 plasma concentrations. Specifically, for each unit increase in the change of BPI pain severity, IL-8 increased by 2.5 pg/mL (P = 0.03) and MCP-1 increased by 9.4 pg/mL (P = 0.006). None of the covariates (i.e., body mass index, medications, severity of depression, and overall FM burden) were significantly associated with either chemokines. Although preliminary, our findings raise the hypothesis that IL-8 and MCP-1 may be involved in the pathogenesis of FM. If replicated in a larger study, IL-8 and MCP-1 may assist in determining prognosis and in monitoring of treatment response.