Genomic Instability, Defective Spermatogenesis, Immunodeficiency, and Cancer in a Mouse Model of the RIDDLE Syndrome

Eukaryotic cells have evolved to use complex pathways for DNA damage signaling and repair to maintain genomic integrity. RNF168 is a novel E3 ligase that functions downstream of ATM,γ-H2A.X, MDC1, and RNF8. It has been shown to ubiquitylate histone H2A and to facilitate the recruitment of other DNA damage response proteins, including 53BP1, to sites of DNA break. In addition, RNF168 mutations have been causally linked to the human RIDDLE syndrome. In this study, we report that Rnf168−/− mice are immunodeficient and exhibit increased radiosensitivity. Rnf168−/− males suffer from impaired spermatogenesis in an age-dependent manner. Interestingly, in contrast to H2a.x−/−, Mdc1−/−, and Rnf8−/− cells, transient recruitment of 53bp1 to DNA double-strand breaks was abolished in Rnf168−/− cells. Remarkably, similar to 53bp1 inactivation, but different from H2a.x deficiency, inactivation of Rnf168 impairs long-range V(D)J recombination in thymocytes and results in long insertions at the class-switch junctions of B-cells. Loss of Rnf168 increases genomic instability and synergizes with p53 inactivation in promoting tumorigenesis. Our data reveal the important physiological functions of Rnf168 and support its role in both γ-H2a.x-Mdc1-Rnf8-dependent and -independent signaling pathways of DNA double-strand breaks. These results highlight a central role for RNF168 in the hierarchical network of DNA break signaling that maintains genomic integrity and suppresses cancer development in mammals

Effect of combined treatment with bisphosphonate and vitamin D on atherosclerosis in patients with systemic lupus erythematosus : a propensity score-based analysis

Background: Premature atherosclerosis is one of the major complications of systemic lupus erythematosus (SLE). Recently, the biological linkage between atherosclerosis and osteoporosis has garnered much attention. The aim of this study is to explore correlation between the development of atherosclerosis and anti-osteoporotic treatment. Methods: Consecutive patients with SLE (n = 117) who underwent carotid ultrasonography were retrospectively analyzed using propensity scoring. Results: Of the 117 patients, 42 (36%), 27 (23%), and 30 (26%) were receiving bisphosphonates and vitamin D (BP + VD), bisphosphonates alone, or vitamin D alone, respectively. Low bone mineral density was more frequent, and carotid plaque was less prevalent in the BP + VD group compared with other treatment groups. Age (OR = 1.57) and BP + VD treatment (OR = 0.24) were shown by multivariate analysis to be associated with the presence of carotid plaque. In all strata divided using the propensity score, carotid plaque was statistically significantly less prevalent (p = 0.015, Mantel-Haenszel test) in the BP + VD group relative to the other treatment groups. Conclusion: Combined treatment with bisphosphonate and vitamin D may have a role in preventing atherosclerosis in patients with SLE

Anti-cyclic citrullinated peptide antibody titers decrease in rheumatoid arthritis patients treated with tocilizumab : A pilot study

Objectives: To analyze the effects of tocilizumab on peripheral B-cell subpopulation and its ability to produce anti-cyclic citrullinated peptide (CCP) antibody in patients with rheumatoid arthritis (RA). Methods: Thirteen consecutive RA patients initiated with tocilizumab were enrolled in our prospective study. Anti-CCP antibody titers and clinical parameters were evaluated during treatment. Peripheral blood B-cell subsets were analyzed using flow cytometry according to the Human Immunology Project. Results: Disease activity was significantly improved and anti-CCP antibody titers significantly decreased at week 24 compared to baseline. The percentages of post-switch memory B cells in CD19+ cells transiently increased at week 12, but there was no significant difference in any of the investigated B-cell subpopulations at week 24 compared to baseline. The ratios of post-switch memory to naive B cells (post-switch/naive) correlated negatively with anti-CCP antibody titers regardless of the time-points. Conclusion: Our study indicated that tocilizumab has a potential to reduce anti-CCP antibody production presumably by affecting post-switch/naive ratio, and that anti-CCP antibody titers reflect B-cell distribution/subpopulation. As anti-CCP antibodies are produced in lymph nodes or ectopic lymphoid structures in synovial tissues, not in circulation, transient increment of post-switch memory B cells after tocilizumab treatment may reflect the altered balance of B-cell distribution between circulation and arthritic joints, resulting in suppressed production of anti-CCP antibody in situ

Treatment of Vasodilator-resistant Mixed Connective Tissue Disease-associated Pulmonary Arterial Hypertension with Glucocorticoid and Cyclophosphamide

Pulmonary arterial hypertension (PAH) associated with systemic lupus erythematosus (SLE) or mixed connective tissue disease (MTCD), in contrast to other types of PAH, may respond to immunosuppressive therapy. Most PAH cases with an immunosuppressant response were in the early stages of the disease (WHO functional class III or less). The present case was a 34-year-old woman with MCTD-associated PAH (WHO functional class IV) who was resistant to a combination of three vasodilators. Afterwards, she was treated with glucocorticoid and cyclophosphamide. This case suggested the potential benefit of immunosuppressants in patients with severe MCTD-associated PAH