Session Title: Vasculitis III
Session Type: Abstract Submissions (ACR)
Background/Purpose: : Increased neutrophil activation has been previously shown in Behçet’s disease (BD) patients and it is unclear whether neutrophil activation occurs constitutively or if it is secondary to a yet unknown stimulus or some serum or tissue soluble factor. NF-kB seems to modulate the immune response in BD and has been associated to apoptosis-related factors leading to apoptosis resistance in T cell subsets. The present study investigated the NF-kB pathway and its activation induced by TLR.
Methods: Neutrophils and peripheral blood mononuclear cells (PBMC) were obtained from patients with active BD (aBD; n=30), inactive BD (iBD; n=31), septic patients (SP; n=25), and healthy controls (HC; n=30). BD activity was established as Behçet’s Disease Current Activity Form simplified (BDCAFs) score≥2. The functional analysis of the NF-kB pathway was performed by: 1) determining CD62L shedding after stimulation with specific ligands for TLR-2, -3, -4, -5, -7, and with Streptococcus pneumoniae, Streptococcus sanguinis, and Candida albicans; 2) the intracellular expression of phosphorylated NF-kB-p65 before and after stimulation with PMA, TLR-3, TLR-7, plasma from HC, aBD or iBD; 3) the intracellular expression of STAT3 before and after stimulation with PMA, IL-10, or plasma from HC or aBD.
Results: BD patients homogeneously presented very low CD62L shedding with all forms of stimulus, in contrast to the large dispersion observed in the other groups. The percent increase in CD62L shedding was more evident after activation by TLR3 in iBD (31±28%: p=0.022) and aBD (27±20%; p=0.029) than in SP (3.4±25%). In contrast, the activation by TLR7 was lower in iBD (27±23%; p=0.022) and aBD (32±27%; p=0.029) than in SP (74±39%). Neutrophils from aDB presented higher expression of phosphorylated NF-kB-p65 before stimuli (mean of intensity of fluorescence [MFI]=123.54±47.63 versus HC=69.43±39.29, p=0.050) and after PMA (MFI=194.10±97.18 versus HC=92.24±42.34, p=0.030) and TLR7 (MFI=135.76±45.92 versus HC=77.51±42.34, p=0.050). Monocytes from aDB also presented higher expression of phosphorylated NF-kB-p65 before stimuli (MFI=313.40±110.81 versus HC=135.98±87.61, p=0.018) and after PMA (MFI=372.80±145.01 versus HC=175.51±98.35, p=0.030) and TLR3 (MFI=320.40±117.39 versus HC=162.15±74.47, p=0.030). Phosphorylated NF-kB-p65 expression and CD62L shedding after human plasma and microbial stimuli, respectively, was equivalent for phagocytes from aBD, iBD, and HC. STAT3 expression in neutrophils and monocytes showed no difference among the aBD, iBD, and HC. There was no difference in medication use between aBD and iBD.
Conclusion: We originally showed that the NF-kB pathway of phagocytes is constitutively activated in BD patients and that there is additional increment after TLR stimuli. The low CD62L shedding of BD phagocytes may be due to exhaustion of the NF-kB pathway. These findings may underlie the characteristic hyperactivity of neutrophils in BD, represented by activation of the final pathway for several stimuli, like cytokines, chemoattractants and microorganisms, potentially involved in the pathophysiology of this disease.
S. F. Perazzio,
P. V. S. Pereira,
A. W. S. Souza,
L. E. C. Andrade,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/nf-%ce%bab-pathway-is-depleted-in-phagocytes-from-behcets-disease-patients-secondarily-to-constitutive-phosphorylation-of-the-p65-subunit/