Neutrophil extracellular trap suppression in rheumatoid arthritis patients treated with biologic therapy: a prospective observational study

Abstract Background Rheumatoid arthritis (RA) is associated with increased cardiovascular risk, partly driven by chronic systemic inflammation. Neutrophil extracellular traps (NETs) have emerged as important mechanistic links between sustained immune activation and early vascular injury. Objective To evaluate changes in NET-associated activity following initiation of biologic therapy in patients with RA and to investigate the relationship between treatment- associated changes in NETs, lipid profile, and subclinical atherosclerosis. Methods In this prospective single-arm observational study, 36 patients with RA initiating biologic therapy were evaluated at baseline and after 6 months of treatment. Disease activity was assessed using DAS28-CRP, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR). Circulating citrullinated histone H3 (CitH3) levels were measured by ELISA as a robust marker of NETs. Carotid intima-media thickness (cIMT) was assessed using high-resolution B-mode ultrasonography. Linear regression analyses were performed to investigate the relationship between NETs activity, inflammatory burden, lipid profile, and subclinical atherosclerosis, both cross-sectionally and longitudinally following biologic therapy. Results Following initiation of biologic therapy, disease activity and inflammatory markers improved significantly. Circulating CitH3 levels decreased from a median 3.89 (0.11–32.78) to 2.56 (0.07–8.39; p -value 0.025) while cIMT decreased from a median 1 (0.7–1.6) mm to 0.75 (0.6–1.3 mm; p -value < 0.001) after 6 months of treatment. HDL cholesterol increased significantly from 56.36 ± 16.21 to 67.47 ± 17.56 mg/dL ( p < 0.001). At follow-up, CitH3 levels were independently associated with ESR (β = 0.448, p = 0.018), indicating a relationship between NETs and systemic inflammatory burden. Longitudinal analyses demonstrated that changes in HDL cholesterol were independently associated with changes in CitH3 (β = − 0.505, p = 0.003), whereas changes in DAS28, CRP, ESR, oxLDL, and cIMT were not independently associated with ΔCitH3. No significant differences in ΔCitH3 were observed between anti-TNF and non-anti-TNF therapies. Conclusions In this prospective observational cohort, initiation of biologic therapy was associated with reduced circulating CitH3 levels, alongside improvements in disease activity, inflammatory markers, HDL cholesterol, and cIMT. The longitudinal association between increases in HDL cholesterol and reductions in CitH3 was independent of changes in disease activity and cIMT, generating a hypothesis regarding a potential immunometabolic relationship between HDL cholesterol and NET-associated activity. These findings should be considered exploratory and require confirmation in larger, controlled prospective studies. Key Points • Biologic therapy was associated with a significant reduction in circulating CitH3 levels, consistent with reduced NET-associated activity in patients with RA. • Changes in HDL cholesterol independently predict changes in NETs, suggesting a possible HDL–NETs immunometabolic axis in RA patients under biologic treatment. • Concurrent improvement in NETs and subclinical atherosclerosis supports a potential role for NETs in RA-associated cardiovascular risk. • Similar reductions in CitH3 were observed across biologic treatment classes; however, the small and unequal subgroup sizes limit the ability to draw conclusions regarding class-specific effects.