Induction of NF-κB inflammatory pathway in monocytes by microparticles from patients with systemic lupus erythematosus

Abstract

Background: Elevated levels of circulating microparticles (MPs) and molecules of the complement system have been reported in patients with systemic lupus erythematosus (SLE). Moreover, microparticles isolated from patients with SLE (SLE-MPs) contain higher levels of damage-associated molecular patterns (DAMPs) than MPs from healthy controls (CMPs). We hypothesize that the uptake of MPs by monocytes could contribute to the chronic inflammatory processes observed in patients with SLE. Therefore, the aim of this study was to evaluate the expression of activation markers, production of proinflammatory mediators, and activation of the NF-κB signaling pathway in monocytes treated with CMPs and SLE-MPs. Methodology: Monocytes isolated from healthy individuals were pretreated or not with pyrrolidine dithiocarbamate (PDTC) and cultured with CMPs and SLE-MPs. The cell surface expression of CD69 and HLA-DR were evaluated by flow cytometry; cytokine and eicosanoid levels were quantified in culture supernatants by Cytokine Bead Array and ELISA, respectively; and the NF-κB activation was evaluated by Western blot and epifluorescence microscopy. Results: The cell surface expression of HLA-DR and CD69, and the supernatant levels of IL-6, IL-1β, PGE2, and LTB4 were higher in cultures of monocytes treated with SLE-MPs than CMPs. These responses were blocked in the presence of PDTC, a pharmacological inhibitor of the NF-κB pathway, with concomitant reduction of IκBα and cytoplasmic p65, and increased nuclear translocation of p65. Conclusions: The present findings indicate that significant uptake of SLE-MPs by monocytes results in activation, production of inflammatory mediators, and triggering of the NF-κB signaling pathway.

Modulation of B cell activation by extracellular vesicles and potential alteration of this pathway in patients with rheumatoid arthritis

“…Hence, it is worth proposing that m/lEVs can activate some regulatory pathways in B cells. Previously, our research group had reported that B cells can interact with and internalize m/lEVs [ 20 ], and therefore the regulatory effect of m/lEVs could be due to the recognition of surface or endosomal receptors present on the B cells. In support of this idea, it has been reported that exosomes, other m/lEVs of smaller sizes (30 − 100 nm) than m/lEVs, decreased the phospho-Btk expression in anti-BCR stimulated B cells from HD [ 45 ].…”

“…Differences between these past results and the present results can be explained by the type of cells used for culturing. The effect of m/lEVs in promoting the activation, rather than the inhibition, of B cells can be an indirect response because monocytes, which are present in the PBMCs, are the most efficient leukocytes to bind with and then internalize these vesicles [ 20 ]. Monocytes can produce high levels of proinflammatory cytokines (i.e., IL-1β, TNF-α, and IFN-α) after the treatment with m/lEVs and mainly when they form ICs [ 19 , 27 ].…”

“…However, the effect of m/lEVs on B cells in the context of RA and other autoimmune diseases remains unknown. Previously, it was described that B cells can interact and internalize m/lEVs [ 20 ]. Different components of m/lEVs can explain this interaction and can potentially tune B cell responses, such as nucleic acids (DNA, RNA, and miRNA [ 21 , 22 ]), phosphatidylserine (PS) [ 15 ], adhesion molecules (ICAM1, CD11b, and CD62L [ 23 , 24 ]), citrullinated peptides [ 13 , 15 ], ICs [ 6 , 15 ], and alarmins [ 13 , 15 ], among others [ 6 , 13 , 15 , 25 ].…”

Plasma microparticles from patients with systemic lupus erythematosus modulate the content of miRNAs in U937 cells

“…However, the IRF5 expression did not change in U937 cells exposed to any type of plasma microparticles here analysed. The transport of miRNA between cells is not the only way that MP could modulate immunological or inflammatory events; previously, evidence has shown that MP also could modulate the activation of NF-kB or the macrophage differentiation [43,44].…”

NF-κB in monocytes and macrophages – an inflammatory master regulator in multitalented immune cells

“…In a recent study, older age was associated with decreased LPS-mediated monocytic NF-kB activation and expression of HLA-DR molecules (57). On the contrary, induction of the NF-kB pathway was observed in monocytes from patients with systemic lupus erythematosus that was attributed to monocyte activation by microparticles which serve as damage-associated molecular patterns (DAMPs) during disease development (58).…”