Background/Purpose:

AS is a chronic inflammatory disease, of unknown aetiology, characterized by pathological ossification. We aimed: 1) To analyze the profile of inflammation, oxidative status and bone turnover in plasma and leukocyte subsets, as well as the endothelial function (EF) in AS patients. 2) To evaluate the relationship among those biomarkers and their correlation with disease activity.

Methods:

Thirty AS patients and 30 healthy donors were included in the study. Disease function and activity status were analyzed by BASFI and BASDAI indexes. EF was determined by the post occlusive hyperaemia test. Biomarkers of oxidative stress, inflammation, thrombosis and bone turnover were analyzed in lymphocytes, neutrophils and monocyte subsets (MON1: CD14⁺/CD16^–; MON2: CD14⁺/CD16⁺; MON3: CD14^dim/CD16⁺) by RT-PCR and flow cytometry. Antioxidant enzyme activities, nitric oxide (NO) and total antioxidant capacity (TAC) of plasma were measured by specific kits.

Results:

Compared to healthy donors, a significant EF alteration was observed in AS patients. The analysis of inflammatory markers showed increased expression of TNFα and signal transducter and activator of transcription 3 (STAT3) in neutrophils, and of IL6, IL23, IL2 and STAT3 in lymphocytes. The monocyte analysis demonstrated a reduction in %MON1, along with an increase in %MON2. MON1 showed a specific alteration of STAT3, I kappa B kinase (IKK), TNFα and IL6, whereas MON2+MON3 displayed elevated levels of IL23, macrophage inflammatory protein-1α, tissue factor and IKK. Osteogenic markers significantly elevated in neutrophils were ALP and dickkopf (DKK)-1. Lymphocytes displayed reduced levels of DKK1 and osteoprotegerin (OPG) whereas MON1 showed an alteration of BMP2, DKK1, OPG and TGFß1. Oxidative stress study showed that leukocyte subsets from patients display an increase in oxidative stress markers and mitochondrial dysfunction, along with an alteration of TAC and NO at plasma level. In vitro treatment of healthy leukocyte subsets with pooled serum from patients displaying structural damage and low inflammation status caused a significant increase in oxidative stress markers, as well as prominent changes in inflammatory and osteogenic gene expression.

Correlation studies showed that AS development was associated with endothelial dysfunction, inflammation and osteogenesis. Oxidative stress and mitochondrial dysfunction were associated with inflammatory and osteogenic markers. Endothelial dysfunction was correlated with inflammation and mitochondrial dysfunction. Osteogenesis was associated with inflammatory markers.

Conclusion:

1) AS patients show an endothelial dysfunction directly associated with the inflammatory profile and disease progression. 2) Circulating leukocyte subsets in AS patients seem to contribute to the inflammatory and bone turnover processes, so that neutrophils and MON1 seem to mediate both processes whereas lymphocytes and MON2+MON3 seem to be more associated with the inflammatory process. 3) The oxidative stress and, particularly, the mitochondrial dysfunction, might also mediate the inflammation and ossification processes present in AS

Funded by PI-0314-2012, SER

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/characterization-of-leukocyte-subsets-in-ankylosing-spondylitis-patients/