In patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), pentraxin-3 (PTX3) may play a key role as a potential new inflammatory biomarker, according to findings from a longitudinal, prospective Swedish study published in the Scandinavian Journal of Rheumatology.

The pathogenesis of AAV is intricate and remains to be elucidated. In individuals with the disease, the formation of neutrophil extracellular traps, along with the release of reactive oxygen species from activated neutrophils, is associated with endothelial damage. These neutrophil extracellular traps activate the alternative pathway, thereby generating the C5a protein fragment, which is thought to play a role in the priming of neutrophils. This process, in turn, creates an inflammatory amplification loop involved in the pathogenesis of AAV.

In response to various inflammatory stimuli, the protein PTX3 is produced extensively by a number of cells, such as macrophages, vascular endothelial cells, kidney endothelial cells, and dendritic cells. The researchers of the current study sought to describe the evolution and potential role of PTX3 as a biomarker of inflammatory activity in patients with AAV.   

Seventy-nine individuals with active AAV comprised the study cohort, along with 23 healthy controls. Disease activity was evaluated via use of the Birmingham Vasculitis Activity Score (BVAS) 2003 at baseline and at 6-month follow-up. Plasma PTX3 concentrations were measured in all participants; urinary PTX3 levels were measured in 34 of the patients. In all participants, C-reactive protein (CRP), albuminuria, and creatinine were measured. The cumulative glucocorticoid dose at study inclusion was computed as well.

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Of the 79 patients, 43 were men and 36 were women. The median patient age was 58 years (range, 19-86 years). Overall, 70 individuals had newly diagnosed disease and 9 experienced an AAV relapse. Fifty-four patients were diagnosed with granulomatosis with polyangiitis, 21 with microscopic polyangiitis, and 4 with eosinophilic granulomatosis with polyangiitis.

Plasma PTX3 levels in patients were significantly higher at baseline compared with follow-up (median, 2.85 vs 1.23 ng/mL, respectively; P <.001). In addition, PTX3 concentrations were significantly higher at baseline and at 6 months in patients with AAV than in controls (P <.001).

Plasma PTX3 levels and urinary PTX3 levels were significantly associated with BVAS at baseline (P <.001 and P =.008, respectively). Further, plasma PTX3 concentrations were correlated significantly with the cumulative glucocorticoid dose administered at baseline (P <.001). A significant association was also observed between the glucocorticoid dose administered at baseline and plasma PTX3 levels (P <.0001). No association was reported, however, between plasma PTX3 levels and urinary PTX3 levels.

There was also a significant association observed between plasma PTX3 levels/urinary PTX3 levels and albuminuria/ estimated glomerular rate. Plasma and urinary PTX3 concentrations were significantly higher among individuals with renal involvement. No association was observed between PTX3 levels and CRP, nor between CRP levels and BVAS at baseline.

“Plasma and urinary PTX3 seem to reflect disease activity in AAV better than the commonly used CRP,” the researchers explained. “PTX3 may have a potential role as a biomarker in monitoring disease activity in patients with AAV, particularly in those with kidney involvement,” they concluded.

Reference

Jonasdottir AD, Antovic A, Qureshi AR, et al. Pentraxin-3 – a potential biomarker in ANCA-associated vasculitis. Scand J Rheumatol. Published online April 6, 2023. doi:10.1080/03009742.2022.2045790