Histopathologic and ultrastructural study of lupus-like skin lesions in a patient with Bloom syndrome

Increased DNA double-strand breaks and enhanced apoptosis in patients with lupus nephritis

OBJECTIVE

DNA double-strand breaks (DSBs) lead to mutations, genomic instability and apoptotic death, whereas accumulation of apoptotic cells results in excessive autoantigen presentation and autoantibody formation. We aimed to measure DSB levels in lupus nephritis, a severe complication of the prototypic systemic autoimmune disease.

METHODS

The intrinsic DNA damage and the apoptosis induction/DSB levels were evaluated in peripheral blood mononuclear cells of six patients and 10 healthy controls following exposure to genotoxic agents (melphalan, cisplatin) ex vivo. DSBs were assessed using immunofluorescence quantification of γH2AX foci and comet assay.

RESULTS

Intrinsic DNA damage was increased in lupus versus control cells in both assays (Olive Tail Moment units of 15.8 ± 2.3 versus 3.0 ± 1.4 in comet, p < 0.01; % γH2AX-positive cells: 13.6 ± 1.8 versus 4.6 ± 0.9, p < 0.01, respectively). Melphalan or cisplatin doses as low as 9.9 ± 4.8 or 29.8 ± 8.3 µg/ml, respectively, were sufficient to induce apoptosis in lupus cells; control cells required doses of 32.3 ± 7.7 and 67.7 ± 5.5 µg/ml, respectively. Drug-induced DSB levels were increased in lupus versus control cells, with the area under the curve (AUC) for melphalan-induced DSBs being 3050 ± 610 (% γH2AX-positive staining cells) × (drug dose) in patients and 1580 ± 350 in controls (p < 0.05); the corresponding values for cisplatin-induced AUC were 13900 ± 1800 for lupus and 4500 ± 750 for controls (p < 0.01). Interestingly, within either lupus patients or controls examined, the accumulation of DSBs correlated with apoptosis degrees (all p < 0.01). Results in lupus cells were not associated with individual disease activity level or treatment modalities at the time of the study.

CONCLUSION

These findings suggest a novel mechanism by which increased accumulation of DSBs may render cells more sensitive to apoptosis, thus contributing to the induction of systemic autoimmunity.

Patients with systemic sclerosis present increased DNA damage differentially associated with DNA repair gene polymorphisms

OBJECTIVE

Patients with systemic sclerosis (SSc) exhibit increased toxicity when exposed to genotoxic agents. In our study, we evaluated DNA damage and polymorphic sites in 2 DNA repair genes (XRCC1 Arg399Gln and XRCC4 Ile401Thr) in patients with SSc.

METHODS

A total of 177 patients were studied for DNA repair gene polymorphisms. Fifty-six of them were also evaluated for DNA damage in peripheral blood cells using the comet assay.

RESULTS

Compared to controls, the patients as a whole or stratified into major clinical variants (limited or diffuse skin involvement), irrespective of the underlying treatment schedule, exhibited increased DNA damage. XRCC1 (rs: 25487) and XRCC4 (rs: 28360135) allele and genotype frequencies observed in patients with SSc were not significantly different from those observed in controls; however, the XRCC1 Arg399Gln allele was associated with increased DNA damage only in healthy controls and the XRCC4 Ile401Thr allele was associated with increased DNA damage in both patients and controls. Further, the XRCC1 Arg399Gln allele was associated with the presence of antinuclear antibody and anticentromere antibody. No association was observed between these DNA repair gene polymorphic sites and clinical features of patients with SSc.

CONCLUSION

These results corroborate the presence of genomic instability in SSc peripheral blood cells, as evaluated by increased DNA damage, and show that polymorphic sites of the XRCC1 and XRCC4 DNA repair genes may differentially influence DNA damage and the development of autoantibodies.

Lupus-like histopathology in bloom syndrome: reexamining the clinical and histologic implications of photosensitivity

Bloom syndrome is a rare genodermatosis of autosomal recessive inheritance. Although lupus-like skin lesions characterize this disorder, mechanisms of photosensitivity are poorly understood. In this case presentation, the authors report a patient with Bloom syndrome whose lupus-like facial rash revealed striking histopathologic similarities to cutaneous lupus erythematosus.

Efficiency of the DNA repair and polymorphisms of the XRCC1, XRCC3 and XRCC4 DNA repair genes in systemic lupus erythematosus

Impaired DNA repair efficiency in systemic lupus erythematosus (SLE) patients has been reported in some studies, mainly regarding the repair of oxidative damage, but little is known about repair kinetics towards primarily single-stranded DNA breaks. In the present study, we aimed to investigate: (a) the efficiency of SLE peripheral blood leucocytes in repairing DNA damage induced by ionizing radiation and (b) the association of DNA repair gene (XRCC1 Arg399Gln, XRCC3 Thr241Met and XRCC4 Ile401Thr) polymorphisms in SLE patients, considering the whole group, or stratified sub-groups according to clinical and laboratory features. A total of 163 SLE patients and 125 healthy controls were studied. The kinetics of DNA strand break repair was evaluated by the comet assay, and genotyping for DNA repair genes was performed by PCR-RFLP. Compared with controls, SLE leucocytes exhibited decreased efficiency of DNA repair evaluated at 30 min following irradiation. A significant association with DNA repair gene polymorphisms was not observed for the whole group of SLE patients; however, the XRCC1Arg399Gln polymorphism was associated with the presence of anti-dsDNA antibody. The concomitance of two DNA repair polymorphic sites was associated with the presence of neuropsychiatric manifestations and antiphospholipid antibody syndrome. Taken together, these results indicated that SLE leucocytes repair less efficiently the radiation-induced DNA damage, and DNA repair polymorphic sites may predispose to the development of particular clinical and laboratory features.