Enhanced activation of dendritic cells by autologous apoptotic microvesicles in MRL/lpr mice

Abstract

IntroductionSystemic lupus erythematosus is associated with a persistent circulation of modified autoantigen-containing apoptotic debris that might be capable of breaking tolerance. We aimed to evaluate apoptotic microvesicles obtained from lupus or control mice for the presence of apoptosis-associated chromatin modifications and for their capacity to stimulate dendritic cells (DC) from lupus and control mice.MethodApoptotic microvesicles were in vitro generated from splenocytes, and ex vivo isolated from plasma of both MRL/lpr lupus mice and normal BALB/c mice. Microvesicles were analyzed using flow cytometry. Bone marrow-derived (BM)-DC cultured from MRL/lpr or BALB/c mice were incubated with microvesicles and CD40 expression and cytokine production were determined as measure of activation.ResultsMicrovesicles derived from apoptotic splenocytes or plasma of MRL/lpr mice contained more modified chromatin compared to microvesicles of BALB/c mice, and showed enhanced activation of DC, either from MRL/lpr or BALB/c mice, and consecutively an enhanced DC-mediated activation of splenocytes. The content of apoptosis-modified chromatin in microvesicles of apoptotic splenocytes correlated with their potency to induce interleukin-6 (IL-6) production by DC. Microvesicle-activated MRL/lpr DC showed a significant higher production of IL-6 and tumor growth factor-β (TGF-β) compared to BALB/c DC, and were more potent in the activation of splenocytes.ConclusionApoptotic microvesicles from MRL/lpr mice are more potent activators of DC, and DC from MRL/lpr mice appear relatively more sensitive to activation by apoptotic microvesicles. Our findings indicate that aberrations at the level of apoptotic microvesicles and possibly DC contribute to the autoimmune response against chromatin in MRL/lpr mice.

Cell death in the pathogenesis of systemic lupus erythematosus and lupus nephritis

“…Bone marrow-derived DCs exposed to acetylated nucleosomes undergo maturation and activate syngenic T cells. Apoptotic microparticles, which expose modified nucleosomes at the cell surface (123-125), are found in both SLE patients and mice (125-127). Apoptotic microparticles from MRL/ lpr mice express elevated levels of modified chromatin and induce enhanced maturation of DCs than BALB/c mice (125).…”

“…Apoptotic microparticles, which expose modified nucleosomes at the cell surface (123-125), are found in both SLE patients and mice (125-127). Apoptotic microparticles from MRL/ lpr mice express elevated levels of modified chromatin and induce enhanced maturation of DCs than BALB/c mice (125). DNASE1L3 is a serum enzyme that is critical for the degradation of chromatin in microparticles precluding autoantibody recognition of microparticle DNA and humans and mice lacking DNASE1L3 develop SLE-like disease (127-131).…”

Role of syndecan-1 in the interaction between dendritic cells and T cells

“…DC were cultured from bone marrow obtained from wild-type (WT) C57Bl6, Sdc-1 -/- and Balb/c mice according to a method adopted from Lutz et al (24, 25). In short, femora and tibiae were harvested after cervical dislocation and bone marrow was flushed with medium (RPMI-1640 Dutch modification (Invitrogen, USA), supplemented with 50 µM β-mercaptoethanol (Sigma-Aldrich, St Louise, USA), 1% glutamax (Invitrogen), 1% pyruvate (Invitrogen) and 10,000 U/ml penicillin-streptomycin (Invitrogen).…”

“…Proliferation of cells was analyzed by dilution of the CFSE signal using flow cytometry. Apoptosis of splenocytes was induced by incubation with 4-nitroquinoline 1-oxide (4-NQO, Sigma) for 18 hours as we described previously (25), and the degree of apoptosis was analyzed by annexin-V and propidium iodide staining using flow cytometry.…”

A review of studies of the proteomes of circulating microparticles: key roles for galectin-3-binding protein-expressing microparticles in vascular diseases and systemic lupus erythematosus

“…Development of SLE is linked to defective clearance of apoptotic cells leading to an excess of highly auto-immunogenic cellular debris (apoptotic bodies and MPs) triggering anti-nuclear autoimmunity [8, 78–82]. An early important pathological feature is the occurrence of immune complex deposits in the glomerular basement membrane (GBM) that activate the complement system and incite inflammation [76, 83, 84].…”