Systemic Inflammation Induced by microRNAs: Endometriosis-Derived Alterations in Circulating microRNA 125b-5p and Let-7b-5p Regulate Macrophage Cytokine Production.

Context: Endometriosis is characterized by aberrant inflammation. We previously reported increased levels of microRNA (miRNA) 125b-5p and decreased levels of miRNA Let-7b-5p in serum of patients with endometriosis.

Objective: Determine the regulatory function of miRNAs 125b-5p and Let-7b-5p on production of proinflammatory cytokines in endometriosis.

Design: Case-control study.

Setting: University hospital.

Patients: Women with (20) and without (26) endometriosis; human U937 macrophage cell line.

Intervention: Sera were collected from surgically diagnosed patients and differentiated U937 cells that were transfected with miRNAs 125b-5p and Let-7b-5p mimics and inhibitor.

Main Outcome Measures: Enzyme-linked immunosorbent assay for tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-8, and IL-1β levels and quantitative real-time polymerase chain reaction for expression of miRNAs 125b-5p and Let-7b-5p in sera of patients with and without endometriosis. Transfected macrophages were evaluated for expression of inflammatory cytokines, intracellular production, and secretion of these cytokines.

Results: We noted substantial elevation of TNF-α, IL-1β, and IL-6, marked upregulation of miRNA 125b, and considerable downregulation of Let-7b in sera of patients with endometriosis vs control. There was a positive correlation between miRNA 125b levels and TNF-α, IL-1β, and IL-6 and a negative correlation between miRNA Let-7b levels and TNF-α in sera of patients with endometriosis. Transfection experiments showed a noteworthy upregulation of TNF-α, IL-1β, IL-6, and IL-8 in macrophages transfected with miRNA 125b mimic or Let-7b inhibitor. The secreted cytokine protein levels and intracellular imaging studies closely correlate with the messenger RNA changes.

Conclusions: Endometriosis-derived miRNAs regulate macrophage cytokine production that contributes to inflammation associated with this condition.