Increased apoptotic neutrophils and macrophages and impaired macrophage phagocytic clearance of apoptotic neutrophils in systemic lupus erythematosus

Abstract

Objective. To evaluate whether patients with systemic lupus erythematosus (SLE) have a higher rate of apoptosis in and secondary necrosis of polymorphonuclear neutrophils (PMNs) and macrophages compared with controls; to compare the rate of macrophage phagocytic clearance of apoptotic PMNs in patients with SLE and healthy controls; to evaluate whether in vitro PMN and macrophage apoptosis and secondary necrosis, and the ability of macrophages to phagocytose apoptotic bodies, are correlated with lupus disease activity; and to determine whether macrophage clearance of apoptotic bodies in patients with SLE and normal controls is related to certain serum factors.Methods. Thirty-six patients with SLE and 18 healthy, nonsmoking volunteers were studied. PMNs and monocytes were isolated from fresh blood and cultured in the presence of different sources of serum. Apoptotic PMNs and macrophages were examined by annexin V binding and morphology on May-Giemsastained cytopreparations, at different time points. The presence of secondary necrotic PMNs and macrophages was verified by staining with trypan blue. Macrophage phagocytosis of apoptotic PMNs was measured using a coded, observer-blinded, microscopically quantified phagocytosis assay. Cells were cultured in the presence of serum obtained from healthy subjects or from patients with SLE.Results. At 5 and 24 hours, the percentage of apoptotic PMNs from patients with SLE was significantly higher than that of PMNs from healthy subjects. At 24 and 48 hours, the percentage of secondary necrotic PMNs from patients with SLE was also significantly higher than the percentage of necrotic PMNs from controls. Serum from patients with SLE accelerated the rate of apoptosis in and secondary necrosis of PMNs from healthy subjects. Macrophages from SLE patients were less capable of phagocytosing apoptotic PMNs compared with macrophages obtained from controls. Macrophages from patients with active SLE were less capable of phagocytosing apoptotic PMNs than were macrophages from patients with inactive SLE, but the difference was not statistically significant. The percentage of phagocytosis of apoptotic PMNs by macrophages from SLE patients correlated negatively with the SLE Disease Activity Index, serum levels of anti-doublestranded DNA, and the erythrocyte sedimentation rate, and correlated positively with serum levels of C3, C4, and albumin, the hemoglobin level, and the leukocyte count. Serum from SLE patients not only significantly increased macrophage apoptosis in cells from healthy subjects but also remarkably down-regulated the clearance of apoptotic PMNs by macrophages from healthy subjects. In contrast, serum from healthy subjects significantly increased phagocytosis of apoptotic PMNs by macrophages from SLE patients.Conclusion. The observed increase of apoptotic PMNs and macrophages and the poor ability of macrophages from patients with SLE to phagocytose apoptotic bodies may indicate an impaired clearance mechanism, which may be mediated by factors in a patient's serum.Systemic lu...

The −844C/T polymorphism in the Fas ligand promoter associates with Taiwanese SLE

“…20,30 The excess of lymphocyte apoptosis and deficient phagocyte-mediated clearance of apoptotic cells could contribute to B-cell hyperactivity and subsequent autoantibodies overproduction. [9][10]12 Taken together, these findings suggest that molecular mechanisms regulating FasL gene expression are crucial to SLE autoimmunity. The inducible regions of the human FasL promoter have been mapped by deletion and mutational analysis and include the basic regulatory region between À273 and the transcription start site, a region between À431 and À273 responsible for enhanced regulatory transcription, a negative regulatory region between À473 and À900, and another region from À900 to À1200 possibly responsible for enhanced regulatory transcription.…”

“…Furthermore, altered monocyte phenotypes and neutropenia lead to impaired recognition and clearance of apoptotic cells, and correlate with anti-dsDNA and disease activity. 6,[9][10][11] Fas ligand (FasL), a trimeric type II membrane protein, belongs to the TNF receptor family that induces apoptosis of cells bearing Fas receptor. 12 Observations in mouse models of SLE demonstrated that mice with Fas (MRL/lpr) or FasL (gld) mutations developed lymphadenopathy with accumulation of CD4ÀCD8À double negative lymphocytes.…”

Sialic acid–binding Ig‐like lectin 1 expression in inflammatory and resident monocytes is a potential biomarker for monitoring disease activity and success of therapy in systemic lupus erythematosus

“…All SLE patients had active disease, and their mean score on the SLE Disease Activity Index (SLEDAI) (32) was 17 (range [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. SLE patients had a mean C-reactive protein (CRP) level of 5.7 mg/liter, and a mean erythrocyte sedimentation rate (ESR) of 40 mm/hour.…”

“…Moreover, this accelerated apoptosis of monocytes is associated with the formation of autoantibodies and with organ damage (18,19). Second, a clearance deficiency of monocytes and macrophages causes accumulation of apoptotic bodies in different tissue types (20,21). Third, some monocytes become professional antigen-presenting cells upon stimulation with IFN␣ and may present processed antigens of ingested apoptotic cells and nucleosomes to CD4ϩ T cells that subsequently become activated (22).…”

Apoptosis in health and disease and modulation of apoptosis for therapy: An overview

“…Immune homeostasis and maintenance of immune tolerance are dependent on apoptosis induction and rapid clearance of apoptotic cells in peripheral and central lymphoid organs (40). Autoimmune disease arise from either defective elimination of autoreactive T or B cells, resulting in tissue destruction, or from defective clearance of apoptotic cells displaying autoantigen on their cell surface as in the case of Systemic Lupus Erythematosis (SLE) subjects (41). The BH-3 only protein Bim dependent apoptosis constitutes a critical barrier to autoimmunity.…”