New insights into the pathogenesis of systemic lupus erythematosus (SLE): the role of apoptosis

Correlation of circulating CD27high plasma cells and disease activity in systemic lupus erythematosus

CD27 is a useful marker in assessing the number of circulating B cells and B cell subsets because it permits one step identification of the major B cell compartments, CD27- naïve and CD27+ memory B cells as well as CD27high plasma cells. Abnormalities in the distributionof CD27+ B cell subsets are useful in assessing disease activity in patients with systemic lupus erythematosus(SLE). In particular, the frequencyof CD27high plasma cells significantly correlates with lupus activity in both children and adults with SLE. Conventional immunosuppressive therapies affect the number of CD27- naive B cells and CD27high plasma cells, but do not target CD27+ memory B cells. These results suggest that disease flares may relate to the retention of CD27+ memory B cells after conventional immunosuppressive therapy and that new therapies that target these cells specifically may offer new opportunities to induce remission in SLE.

Expression of TLR-7, MyD88, NF-kB, and INF-α in B Lymphocytes of Mayan Women with Systemic Lupus Erythematosus in Mexico

Background

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease involving multiple organs. It is currently accepted that several genetic, environmental, and hormonal factors are contributing to its development. Innate immunity may have a great influence in autoimmunity through Toll-like receptors. TLR-7 recognizing single-strand RNA has been involved in SLE. Its activation induces intracellular signal with attraction of MyD88 and NF-kBp65, leading to IFN-α synthesis which correlate with disease activity.

Objective

To assess the expression of TLR-7, MyD88, and NF-kBp65 in B lymphocytes of Mayan women with SLE.

Methods

One hundred patients with SLE and 100 healthy controls, all of them Mayan women, were included. TLR-7 was analyzed on B and T lymphocytes, and MyD88 and NF-kB only in B lymphocytes. Serum INF-α level was evaluated by ELISA.

Results

Significant expression (p < 0.0001) of TLR-7 in B and T lymphocytes and serum IFN-α increased (p = 0.034) was observed in patients. MyD88 and NF-kBp65 were also increased in B lymphocytes of patients. TLR-7 and NF-kBp65 expression correlated, but no correlation with INF-α and disease activity was detected.

Conclusion

Data support the role of TLR-7 and signal proteins in the pathogenesis of SLE in the Mayan population of Yucatán.

Tumor necrosis factor-alpha single nucleotide polymorphisms in juvenile systemic lupus erythematosus

BACKGROUND

Juvenile systemic lupus erythematosus (JSLE) is a multi-system autoimmune disorder of unknown origin. Given the importance of the contribution of pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), towards the pathogenesis of JSLE, this study was performed to assess TNFA gene polymorphisms in a case-control study.

METHODS

Fifty nine patients with JSLE were enrolled in this study as case group and compared with healthy control subjects. The frequency of alleles, genotypes, and haplotypes of TNFA single-nucleotide polymorphisms (SNPs) at positions -308 and -238 were evaluated, using polymerase chain reaction with sequence-specific primers method.

RESULTS

The G allele at position -238 in TNFA promoter region was significantly more frequent in patients with JSLE than in the healthy controls (P value<0.001), while the frequency of A allele at the same position was significantly lower than controls. Furthermore, a significant positive association for G/G genotype at the same position was detected in patients' group compared with control subjects (P value<0.001). The GA haplotype of TNFA (positions -308, -238) was significantly less frequent in case group than in controls (P value<0.001), while GG was the most frequent haplotype for TNFA in the patient group, compared to controls (P value<0.01).

CONCLUSIONS

Pro-inflammatory cytokine gene polymorphisms may influence susceptibility to JSLE. Particular TNFA gene variants are associated with JSLE and could be used as a genetic marker for susceptibility to JSLE.

Expression of toll-like receptors 3, 7, and 9 in peripheral blood mononuclear cells from patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown aetiology. The results of experimental studies point to the involvement of innate immunity receptors-toll-like receptors (TLR)-in the pathogenesis of the disease. The aim of the study was to assess the expression of TLR3, 7, and 9 in the population of peripheral blood mononuclear cells (PBMC) and in B lymphocytes (CD19(+)), T lymphocytes (CD4(+) and CD8(+)) using flow cytometry. The study group included 35 patients with SLE and 15 healthy controls. The patient group presented a significantly higher percentage of TLR3- and TLR9-positive cells among all PBMCs and their subpopulations (CD3(+), CD4(+), CD8(+), and CD19(+) lymphocytes) as well as TLR7 in CD19(+) B-lymphocytes, compared to the control group. There was no correlation between the expression of all studied TLRs and the disease activity according to the SLAM scale, and the degree of organ damage according to the SLICC/ACR Damage Index. However, a correlation was observed between the percentage of various TLR-positive cells and some clinical (joint lesions) and laboratory (lymphopenia, hypogammaglobulinemia, anaemia, and higher ESR) features and menopause in women. The results of the study suggest that TLR3, 7, and 9 play a role in the pathogenesis of SLE and have an impact on organ involvement in SLE.

The complement cascade and renal disease

Serum complement cascade, a part of innate immunity required for host protection against invading pathogens, is also a mediator of various forms of disease and injury. It is activated by classical, lectin, and alternative pathways that lead to activation of C3 component by C3 convertases, release of C3b opsonin, C5 conversion and eventually membrane attack complex formation. The tightly regulated activation process yields also C3a and C5a anaphylatoxins, which target a broad spectrum of immune and non-immune cells. The review discusses the involvement of the complement cascade in kidney disease pathogenesis and injury. The role of the complement pathways in autoantibody-mediated forms of glomerulonephritis (lupus nephritis, anti-glomerular basement membrane disease, anti-neutrophil cytoplasmic autoantibody-induced or membranoproliferative glomerulonephritis, membranous nephropathy), C3 glomerulopathy, atypical forms of hemolytic uremic syndrome, ischemic-reperfusion injury of transplanted kidney, and antibody-mediated renal allograft rejection are discussed. The disturbances in complement activation and regulation with underlying genetics are presented and related to observed pathology. Also promising strategies targeting the complement system in complement-related disorders are mentioned.

Expression of Toll-like receptors and their detection of nuclear self-antigen leading to immune activation in JSLE

OBJECTIVES

Toll-like receptors (TLRs) essential in the functioning of the immune system have been implicated in the development of autoimmunity. TLR3, 7, 8 and 9 are capable of recognizing nucleic autoantigens typical of SLE. Their expression correlates positively with disease activity in adult-onset SLE. This study aimed to determine the role of TLRs in JSLE and whether apoptotic neutrophils are a source of nuclear autoantigen being detected through TLR3, 7, 8 and 9, leading to an inflammatory response.

METHODS

TLR3, 7, 8 and 9 mRNA and protein expression were measured in peripheral blood mononuclear cells (PBMCs) in JSLE patients compared with JIA and non-inflammatory controls. Activation of the TLRs by JSLE serum-induced apoptotic neutrophils was detected by measuring IFN-α mRNA and protein expression, and confirmed using myeloid differentiation factor 88 (MyD88) and TIR domain-containing adapter-inducing IFN-β (TRIF) inhibitors.

RESULTS

JSLE patients have increased TLR3, 8 and 9 mRNA and protein expression compared with controls (P < 0.05). Incubation of PBMCs with apoptotic neutrophils demonstrated a dose-response relationship for IFN-α mRNA expression. Inhibition of TLR signalling by blocking MyD88 and TRIF signalling decreased IFN-α mRNA expression in PBMCs incubated with apoptotic neutrophils (P < 0.05).

CONCLUSIONS

This study demonstrated significantly increased TLR expression in JSLE compared with controls. Our data indicate that apoptotic neutrophils trigger TLR activation through their presentation of autoantigens. The role of TLRs in this inflammatory response was demonstrated by a dose-response relationship to apoptotic neutrophil concentration and confirmed by a decrease in IFN-α production after inhibition of TLR signalling.

Cellular localization of nuclear antigen during neutrophil apoptosis: mechanism for autoantigen exposure?

Juvenile-onset systemic lupus erythematosus (JSLE) is a multisystem autoimmune disease characterized by hyperactive B-cells producing auto-antibodies directed against nuclear antigens. A potential source of these antigenic components is apoptotic cells. We have previously demonstrated increased dysregulated neutrophil apoptosis in JSLE patients. Here we investigate autoantigen expression on JSLE neutrophils during apoptosis. Neutrophils from non-inflammatory controls and JSLE patients were incubated with JSLE and control serum. Apoptosis and dsDNA expression was measured using flow cytometry and confocal microscopy. Increased neutrophil apoptosis and dsDNA expression was observed in JSLE and control neutrophils incubated with JSLE serum. During neutrophil apoptosis nuclear material was exposed on the cell surface rather than within the cell as seen with viable neutrophils. The increased neutrophil apoptosis induced by JSLE compared with control serum resulted in increased surface expression of nuclear antigens. This may provide an additional mechanism leading to the generation of autoantibodies in JSLE.

Differential expression of factors involved in the intrinsic and extrinsic apoptotic pathways in juvenile systemic lupus erythematosus

Dysregulated neutrophil apoptosis may result in the development of autoimmune disease by contributing to nuclear autoantigen exposure, leading to autoantibody generation and a breakdown in immune tolerance. It has previously been shown that neutrophil apoptosis is increased in juvenile-onset systemic lupus erythematosus (JSLE). This study aims to investigate the pathways involved in JSLE serum-induced apoptosis. Caspases 3, 7–9, IAP1/2, XIAP and FADD mRNA levels and TRAIL R2, BID/tBID, caspase 8 and 9 protein expression were measured in neutrophils from JSLE patients ( n = 14) and controls ( n = 10). The mRNA levels of caspases 7–9 were significantly higher in JSLE neutrophils than in controls, whereas the mRNA levels of IAP1, IAP2 and XIAP were decreased ( p < 0.05). A decrease in neutrophil apoptosis induced by JSLE serum was observed in the presence of caspase 8 and 9 inhibitors ( p < 0.05), and the activity of caspases 8 and 9 increased over time. tBID protein expression increased following incubation with JSLE serum. These data focus specifically on the expression and activity of the main caspases in the intrinsic and extrinsic apoptotic pathways. Increased expression of factors involved in the downstream signalling of the extrinsic apoptotic pathway indicates a prominent involvement of this pathway in JSLE serum-induced apoptosis.

The complement system in systemic autoimmune disease

Complement is part of the innate immune system. Its major function is recognition and elimination of pathogens via direct killing and/or stimulation of phagocytosis. Activation of the complement system is, however, also involved in the pathogenesis of the systemic autoimmune diseases. Activation via the classical pathway has long been recognized in immune complex-mediated diseases such as cryoglobulinemic vasculitis and systemic lupus erythematosus (SLE). In SLE, the role of complement is somewhat paradoxical. It is involved in autoantibody-initiated tissue damage on the one hand, but, on the other hand, it appears to have protective features as hereditary deficiencies of classical pathway components are associated with an increased risk for SLE. There is increasing evidence that the alternative pathway of complement, even more than the classical pathway, is involved in many systemic autoimmune diseases. This is true for IgA-dominant Henoch Schönlein Purpura, in which additional activation of the lectin pathway contributes to more severe disease. In anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis the complement system was considered not to be involved since immunoglobulin deposition is generally absent in the lesions. However, recent studies, both in human and animal models, demonstrated complement activation via the alternative pathway as a major pathogenic mechanism. Insight into the role of the various pathways of complement in the systemic autoimmune diseases including the vasculitides opens up new ways of treatment by blocking effector pathways of complement. This has been demonstrated for monoclonal antibodies to C5 or C5a in experimental anti-phospholipid antibody syndrome and ANCA-associated vasculitis.

Is disturbed clearance of apoptotic keratinocytes responsible for UVB-induced inflammatory skin lesions in systemic lupus erythematosus?

Apoptotic cells are thought to play an essential role in the pathogenesis of systemic lupus erythematosus (SLE). We hypothesise that delayed or altered clearance of apoptotic cells after UV irradiation will lead to inflammation in the skin of SLE patients. Fifteen SLE patients and 13 controls were irradiated with two minimal erythemal doses (MEDs) of ultraviolet B light (UVB). Subsequently, skin biopsies were analysed (immuno)histologically, over 10 days, for numbers of apoptotic cells, T cells, macrophages, and deposition of immunoglobulin and complement. Additionally, to compare results with cutaneous lesions of SLE patients, 20 biopsies of lupus erythematosus (LE) skin lesions were analysed morphologically for apoptotic cells and infiltrate. Clearance rate of apoptotic cells after irradiation did not differ between patients and controls. Influx of macrophages in dermal and epidermal layers was significantly increased in patients compared with controls. Five out of 15 patients developed a dermal infiltrate that was associated with increased epidermal influx of T cells and macrophages but not with numbers of apoptotic cells or epidermal deposition of immunoglobulins. Macrophages were ingesting multiple apoptotic bodies. Inflammatory lesions in these patients were localised near accumulations of apoptotic keratinocytes similar as was seen in the majority of LE skin lesions. In vivo clearance rate of apoptotic cells is comparable between SLE patients and controls. However, the presence of inflammatory lesions in the vicinity of apoptotic cells, as observed both in UVB-induced and in LE skin lesions in SLE patients, suggests that these lesions result from an inflammatory clearance of apoptotic cells.

Decreased expressions of the TNF-alpha signaling adapters in peripheral blood mononuclear cells (PBMCs) are correlated with disease activity in patients with systemic lupus erythematosus

Tumor necrosis factor (TNF)-alpha is a pleiotropic cytokine. Systemic lupus erythematosus (SLE) is an autoimmune and inflammatory disease. However, until now, the expression and pathophysiological role of TNF adapters in SLE have been poorly understood. This study aims to investigate the expression of mRNA for the TNF adapter proteins including TNF receptor-associated death domain (TRADD) protein, Fas-associated death domain (FADD) protein, receptor-interacting protein 1 (RIP-1), and TNF receptor-associated factor-2 (TRAF-2) in peripheral blood mononuclear cells (PBMCs) from patients with SLE and to explore the relationship between the expression of these adapters and the SLE disease activity. PBMCs were isolated from the venous blood of 51 SLE patients and 17 healthy subjects. The expression of mRNA for TNF adapter molecules such as TRADD, FADD, RIP-1, and TRAF-2 in PBMCs were analyzed by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR. There were constitutive expressions of mRNA for TRADD, FADD, RIP-1, and TRAF-2 in PBMCs from healthy subjects. The expression of mRNA for all the adapter molecules significantly decreased in PBMCs from patients with SLE, which were 0.38-, 0.69-, 0.59-, and 0.55-fold, respectively, compared to those of control subjects (P < 0.05). The expression of Caspase 3 was significantly increased in SLE patients (P < 0.01); however, the expression of IL-1beta was not significantly different between SLE and control subjects. The expression of TRADD, FADD, RIP-1, and TRAF-2 in PBMCs from patients with SLE were negatively correlated with SLEDAI, the correlation coefficient of which was -0.285, -0.280, -0.307, and -0.298, respectively (P < 0.05). The expression of mRNA for TNF adapter molecules TRADD, FADD, RIP-1, and TRAF-2 decreased significantly in PBMCs from patients with SLE, and the expression of these adapters were negatively correlated with the SLE activity index. These abnormalities may be involved in the immunopathogenic injury mediated by the aberration TNF-alpha signaling pathway in SLE.

UV hardening therapy: a novel intervention in patients with photosensitive cutaneous lupus erythematosus

BACKGROUND

Patients with cutaneous lupus erythematosus (LE) and a history of disease- related photoaggravation, confirmed by phototesting, may not respond to photoprotection and/or medical intervention. Ultraviolet B-hardening therapy may improve tolerance for environmental ultraviolet radiation (UVR) in photosensitive disorders.

OBJECTIVE

We studied the effect of UVB hardening on the cutaneous manifestations of patients with LE and their tolerance for UVR.

PATIENTS AND METHODS

A retrospective study of continuous, home-based, UVB-hardening therapy in 44 patients with cutaneous LE (systemic LE: 9 patients; chronic LE: 21 patients; subacute cutaneous LE: 10 patients; cutaneous LE not specified: 4 patients) who had confirmed photosensitivity. Exposure to the UVB source was performed year-round, 3 times weekly, with increasing doses to a maximum of 10 minutes per session. Tolerance for environmental UVR was established through questionnaires, phototesting, and assessment of disease activity by physician and patient.

RESULTS

Of 44 patients, 35 were able to gradually increase their monthly UVB doses. Nine patients dropped out because of insufficient efficacy or skin irritation, or were unable to adhere to the hardening regimen. Of the 35 patients who succeeded in hardening their skin with UVB, 28 patients reported an improved tolerance for environmental UVR. This outcome was confirmed by repeat phototesting in a subgroup. In only 5 patients, an improvement of cutaneous LE symptoms was noted by either physician or patient. No serious adverse events were encountered.

LIMITATIONS

This was a retrospective study and no control group was used.

CONCLUSION

This is the first report that describes UVB hardening as a potential therapy in patients with cutaneous LE and confirmed photosensitivity. This intervention may lead to improved tolerance for environmental UVR and, in a minority of patients, even to decreased cutaneous activity of LE.

Adolescent development and SLE

Adolescence is a time of profound biological and psychosocial change. The management of a complex chronic condition such as systemic lupus erythematosus (SLE) during this period is a challenging but rewarding task for the clinician. Early diagnosis and optimal disease control is essential in order to facilitate normal adolescent development and minimize long-term disease sequelae. Current treatment regimens are associated with significant toxicity in young people, and there is a need for new, less toxic regimens. There are currently no controlled therapeutic studies in adolescents with SLE. Those involved in the care of these young people must ensure that they have appropriate access to specialist medical services while ensuring that their specific needs as adolescents in the health-care system are addressed.

Partial construction of apoptotic pathway in PBMC obtained from active SLE patients and the significance of plasma TNF-α on this pathway

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder that affects various organs and systems. Increased apoptosis, together with defects in the uptake of apoptotic bodies, are thought to have a pathogenic role in SLE. By detection of chromatin condensation, 30% of apoptosis was detected in peripheral blood mononuclear cells (PBMC) from Thai patients with active SLE. Therefore, understanding of the molecular processes in PBMC apoptosis may allow us to gain insight into pathophysiology of SLE. Thus, genes involved in the apoptosis of PBMC from these patients were investigated ex vivo by cDNA array analysis. Seventeen apoptosis-related genes were stimulated in active SLE, more than twofold higher than in inactive SLE. These genes are classified into six groups, namely death receptors, death ligands, caspases, bcl-family, and neutral proteases and genes involved in endoplasmic reticulum stress-mediated apoptosis, such as caspase-4 and GADD153. Among those stimulated genes, tumor necrosis factor (TNF) and the TNF-receptor family were drastically up-regulated 60- and 19-fold higher than in healthy controls, respectively. Moreover, the degree of apoptosis correlated with the level of TNF-alpha in plasma, suggesting that the TNF family plays a role in the induction of apoptosis in SLE. To verify this hypothesis, PBMC from healthy individuals were treated with plasma from active SLE patients in the presence or absence of etanercept, a TNF inhibitor. In the presence of etanercept, active SLE plasma reduced the level of apoptosis to 26.43%. In conclusion, massive apoptotic death of PBMC occurred during the active stage of SLE. The molecular pathway of SLE-PBMC apoptosis was mediated at least via TNF/TNFR signaling pathway, which was confirmed by functional test of TNF-alpha in SLE patients' plasma.

Skin sensitivity to UVB irradiation in systemic lupus erythematosus is not related to the level of apoptosis induction in keratinocytes

OBJECTIVES

Accumulation of apoptotic cells has been suggested to be involved in the pathogenesis of systemic lupus erythematosus (SLE). As sunlight exposure is one of the factors that can trigger disease activity, we hypothesized that UV light may induce increased numbers of apoptotic cells in SLE.

METHODS

Fourteen SLE patients and 16 controls were irradiated with UVB to determine their minimal erythemal dose (MED). Subsequently, skin was irradiated with 1 MED and 2 MED, respectively, and after 24 h skin biopsies were analysed immunohistologically for the number of apoptotic cells and presence of pyknotic nuclear debris.

RESULTS

MED was significantly decreased in SLE patients and the presence of decreased MED was associated with a history of butterfly rash. Decreased MED was not related to other skin-related ACR criteria or to autoantibody specificities. No differences were detected in the numbers of apoptotic keratinocytes between patients and controls or in the amount of pyknotic nuclear debris following 1 and 2 MED irradiation, respectively. Absolute UVB doses were correlated with the number of apoptotic keratinocytes; dose-responses did not differ significantly between patients and controls.

CONCLUSIONS

Increased sensitivity of SLE patients to UVB, although associated with a history of malar rash, is not related to increased induction of apoptosis or increased levels of secondary necrosis in the skin. Thus, compared with controls, UVB-induced apoptosis is not increased in SLE patients under physiological conditions.

Apoptosis in Human Skin: Role in Pathogenesis of Various Diseases and Relevance for Therapy

Cell death by apoptosis is a physiological process that enables the elimination of cells without causing an inflammatory response. In self-renewing tissue like the epidermal layers of the skin, cell numbers are tightly regulated by a delicate balance between proliferation, differentiation, and cell death. Besides cell death by terminal differentiation in normal skin, cell death can also be induced by exposure to sunlight. This paper will review the different forms of cell death in the skin and discuss the role of apoptosis in diseases like skin cancer, psoriasis, and systemic lupus erythematosus.

Increase in activated CD8+ T lymphocytes expressing perforin and granzyme B correlates with disease activity in patients with systemic lupus erythematosus

OBJECTIVE

Cytotoxic T lymphocyte-mediated killing using granzyme B has recently been proposed to be a preferential and selective source of autoantigens in systemic autoimmune diseases, including systemic lupus erythematosus (SLE), while other reports have indicated that cytolytic activity in SLE patients was decreased. The aim of this study was to examine the phenotypic and functional status of the CD8+ T cells in SLE patients.

METHODS

Phenotype analysis of CD8+ T cells was carried out using flow cytometry. The cytotoxic potential of CD8+ T cells and its consequences were examined in redirected-killing experiments. SLE patients with quiescent disease (n = 41) were compared with SLE patients with active disease (n = 20), normal individuals (n = 36), and control patients with vasculitis (n = 14). Cytotoxic CD8+ T cell differentiation was examined by coculture with differentiated dendritic cells (DCs) in the presence of SLE patient sera.

RESULTS

Patients with disease flares were characterized by higher proportions of perforin- and/or granzyme B-positive lymphocytes with a differentiated effector phenotype (CCR7- and CD45RA+). The frequency of these cells in peripheral blood correlated with clinical disease activity as assessed by the SLE Disease Activity Index. These cells generated high amounts of soluble nucleosomes as well as granzyme B-dependent unique autoantigen fragments. Finally, the activation of DCs with serum from a patient with active lupus induced granzyme B expression in CD8+ T lymphocytes.

CONCLUSION

DCs generated in the presence of sera from SLE patients with active disease could promote the differentiation of CD8+ effector T lymphocytes that are fully functional and able to generate SLE autoantigens. Our data disclose a new and pivotal role of activated CD8+ T lymphocytes in SLE pathogenesis.

Why minocycline can cause systemic lupus - a hypothesis and suggestions for therapeutic interventions based on it

The tetracycline antibiotic minocycline is widely used in dermatology, but can sometimes cause systemic lupus erythematodes, a serious autoimmune disorder. It is not known how it does this. However, recent data suggest that minocycline can protect cells from apoptosis by inhibition of caspase-dependent and independent cell death pathways. Here, it is suggested that this ability of minocycline is responsible for the induction of lupus. This idea is based on the recent insight that incomplete or failed apoptosis of damaged cells, particularly keratinocytes, may be responsible for the development of auto-immunity. The protection against apoptosis as conferred by minocyclin may be incomplete, with failed apoptosis and development of autoimmunity as a result. Experimental confirmation of the theory may be obtained by in vitro experiments using induction of apoptosis in cell types known to be affected by lupus. Next, mice that are sensitive to apoptosis may be used for in vivo experiments. Novel therapeutic approaches to drug-induced lupus may be based on induction of apoptosis; DNA-damaging immunosuppressive agents appear particularly useful. Such treatments can be tested in apoptosis-deficient mice that develop autoimmune disease.

Programmed cell deaths. Apoptosis and alternative deathstyles

Programmed cell death is a major component of both normal development and disease. The roles of cell death during either embryogenesis or pathogenesis, the signals that modulate this event, and the mechanisms of cell demise are the major subjects that drive research in this field. Increasing evidence obtained both in vitro and in vivo supports the hypothesis that a variety of cell death programs may be triggered in distinct circumstances. Contrary to the view that caspase-mediated apoptosis represents the standard programmed cell death, recent studies indicate that an apoptotic morphology can be produced independent of caspases, that autophagic execution pathways of cell death may be engaged without either the involvement of caspases or morphological signs of apoptosis, and that even the necrotic morphology of cell death may be consistently produced in some cases, including certain plants. Alternative cell death programs may imply novel therapeutic targets, with important consequences for attempts to treat diseases associated with disregulated programmed cell death.

Ultraviolet B radiation-induced cell death: critical role of ultraviolet dose in inflammation and lupus autoantigen redistribution

The nuclear self-Ags targeted in systemic lupus erythematosus translocate to the cell membrane of UV-irradiated apoptotic keratinocytes and may represent an important source of self-immunization. It is hard to understand how the noninflammatory milieu accompanying most apoptosis might provoke an immunogenic response leading to autoantibodies. We have found that the precise amount of keratinocyte UV exposure is crucial in determining the rate of apoptosis, the amount of inflammatory cytokine production, and the degree of autoantigen translocation. Low doses of UVB (</=15 mJ/cm(2)) promptly induced a normal, caspase-dependent apoptosis, while intermediate doses of UV-B (35 mJ/cm(2)) caused apoptosis with altered morphology, slower DNA fragmentation, and poly(ADP-ribose) polymerase degradation accompanied by increased Bcl-2. High doses of UVB (80 mJ/cm(2)) induced instead necrosis. We observed IL-1 production upon intermediate and high UVB doses. Nuclear Ag redistribution was also markedly UV dose dependent: at low doses, Sm, Ku, and DNA translocated to the surfaces of early apoptotic cells. At intermediate doses, these Ags concentrated on the cell membrane when the nucleus was still visible. At high doses, these autoantigens diffused into the cytoplasm and were released into the supernatant. Taken together, the results show that low-dose UVB induces prompt noninflammatory apoptosis. In contrast, intermediate and high doses of UVB induce proinflammatory apoptosis and necrosis, where the production of inflammatory cytokines is accompanied by exposure and release of autoantigens. The key importance of the UV dose on the fate of apoptotic keratinocytes and on their potential immunogenicity should help clarify the role of UVB in inducing systemic lupus erythematosus autoimmunity.

Deformability-based flow cytometry

BACKGROUND

Elasticity of cells is determined by their cytoskeleton. Changes in cellular function are reflected in the amount of cytoskeletal proteins and their associated networks. Drastic examples are diseases such as cancer, in which the altered cytoskeleton is even diagnostic. This connection between cellular function and cytoskeletal mechanical properties suggests using the deformability of cells as a novel inherent cell marker.

METHODS

The optical stretcher is a new laser tool capable of measuring cellular deformability. A unique feature of this deformation technique is its potential for high throughput, with the incorporation of a microfluidic delivery of cells.

RESULTS

Rudimentary implementation of the microfluidic optical stretcher has been used to measure optical deformability of several normal and cancerous cell types. A drastic difference has been seen between the response of red blood cells and polymorphonuclear cells for a given optically induced stress. MCF-10, MCF-7, and modMCF-7 cells were also measured, showing that while cancer cells stretched significantly more (five times) than normal cells, optical deformability could even be used to distinguish metastatic cancer cells from nonmetastatic cancer cells. This trimodal distribution was apparent after measuring a mere 83 cells, which shows optical deformability to be a highly regulated cell marker.

CONCLUSIONS

Preliminary work suggests a deformability-based cell sorter similar to current fluorescence-based flow cytometry without the need for specific labeling. This could be used for the diagnosis of all diseases, and the investigation of all cellular processes, that affect the cytoskeleton.

Alternative programs of cell death in developing retinal tissue

We examined cell death in developing retinal tissue, following inhibition of protein synthesis, which kills undifferentiated post-mitotic cells. Ultrastructural features were found of both apoptosis and autophagy. Only approximately half of the degenerating cells were either terminal dUTP nick-end labeling (TUNEL)-positive or reacted with antibodies specific for activated caspases-3 or -9. Bongkrekic acid completely inhibited any appearance of cell death, whereas inhibitors of autophagy, caspases-9 or -3, prevented only TUNEL-positive cell death. Interestingly, inhibition of caspase-6 blocked TUNEL-negative cell death. Simultaneous inhibition of caspases-9 and -6 prevented cell death almost completely, but degeneration dependent on autophagy/caspase-9 still occurred under inhibition of both caspases-3 and -6. Thus, inhibition of protein synthesis induces in the developing retina various post-translational, mitochondria-dependent pathways of cell death. Autophagy precedes sequential activation of caspases-9 and -3, and DNA fragmentation, whereas, in parallel, caspase-6 leads to a TUNEL-negative form of cell death. Additional mechanisms of cell death may be engaged upon selective caspase inhibition.

Antinuclear antibodies recognize cellular autoantigens driven by apoptosis

OBJECTIVE

Present study addresses the issue whether cellular antigens recognised by antinuclear autoantibodies are driven by apoptosis.

MATERIALS AND METHODS

HEp-2 cells were committed to apoptosis by camptothecin; DNA fragmentation and FasL and Bax expression monitored apoptosis. Autoantigens were probed by indirect immunofluorescence and Western blot with autoantibodies or monoclonals against: DNA, Ro60, La, U1-RNP, CENP-B, DNA Topoisomerase I, Jo-1 and NuMA. A comparison of antinuclear antibody reactivity between living and apoptotic cells was performed by ELISA.

RESULTS

Apoptotic changes such as chromatin fragmentation, blebs and apoptotic bodies were induced with 20 mM camptothecin. Autoantigens were better detected in apoptotic cells. U1-RNP, Jo1, DNA-Topoisomerase I, CENP-B and NuMA exhibited fragmentation and redistribution as a consequence of apoptosis; in contrast, Ro60 and La ribonucleoproteins did not show proteolysis. Additionally the ELISA titers of antinuclear antibodies were higher in apoptotic cells than in normal cells.

CONCLUSION

Apoptosis induces molecular changes in different autoantigens, this modification increases the antigen-driven response of autoantibodies such as anti-RNP, anti-DNA Topoisomerase I, anti-CENP-B and anti-Jo1. Apoptotic changes would contribute to break down the tolerance in autoimmune connective tissue disease.

Correlation between circulating CD27high plasma cells and disease activity in patients with systemic lupus erythematosus

OBJECTIVE

Disease activity in systemic lupus erythematosus (SLE) is usually assessed with complex disease activity scores comprising a variety of different parameters. In order to determine whether SLE disease activity correlates with abnormal B lymphocyte activity, B cell subsets were analyzed, and their relationship to clinical and humoral measures of disease activity was assessed.

METHODS

The distribution of B cell subsets was determined by fluorescence-activated cell sorting analysis and assessed in relation to the autoantibody profile, disease activity measured by the SLE Disease Activity Index (SLEDAI) and the European Consensus Lupus Activity Measure scores, disease duration, and therapy.

RESULTS

The number and frequency of CD27(high) plasma cells were significantly correlated with the SLE disease activity indices and with the titer of anti-double-stranded DNA (anti-dsDNA) autoantibodies. Circulating B cell subsets were not influenced by age or sex, but appeared to relate to the duration of disease and the therapeutic regimen, with the number and frequency of CD27(high) plasma cells increasing and those of CD27- naive B cells decreasing over time. Patients were divided into those with a SLEDAI score of 0-8 (low disease activity) and those with SLEDAI score >8 (high disease activity). Patients with high disease activity had an increased frequency of both CD19+ B cells and CD27(high) plasma cells. By using a nonparametric data sieving algorithm, we observed that these B cell abnormalities provided predictive values for nonactive and active disease of 78.0% and 78.9%, respectively. The predictive value of the B cell abnormalities (78.9%) was greater than that of the humoral/clinical data pattern (71.4%), including anti-dsDNA antibody levels, circulating immune complexes, increased erythrocyte sedimentation rate, mucocutaneous involvement, and acute renal involvement.

CONCLUSION

Flow cytometric monitoring of B cell subsets in the peripheral blood provides new insights into abnormalities of B cell function in SLE and may also be a diagnostically valuable option for monitoring the activity of this autoimmune disease.

Oxygen free radicals and systemic autoimmunity

Reactive oxygen species generated during various metabolic and biochemical reactions have multifarious effects that include oxidative damage to DNA leading to various human degenerative and autoimmune diseases. The highly reactive hydroxy radical (*OH) can interact with chromatin and result in a wide range of sugar and base-derived products, DNA-protein cross-links and strand breaks. Studies from our laboratory have demonstrated that after modification the DNA becomes highly immunogenic and the induced antibodies exhibit variable antigen-binding characteristics. Systemic lupus erythematosus, a prototype autoimmune disease, is characterized by the presence of autoantibodies to multiple nuclear antigens. The detection of 8-hydroxyguanosine in the immune complex derived DNA of systemic lupus erythematosus patients reinforces the evidence that reactive oxygen species may be involved in its pathogenesis. Increased apoptosis and decreased clearance of apoptotic cells as observed in systemic lupus erythematosus (SLE) might well be a contributory factor in systemic autoimmunity. Clinically, titres of autoantibodies are closely related to the degree of renal inflammation. Anti-DNA antibodies may combine with circulating antigen and contribute to the deposition of immune complexes in renal glomeruli.