Identification of human autoantibodies to the DNA ligase IV/XRCC4 complex and mapping of an autoimmune epitope to a potential regulatory region

The nonhomologous end-joining pathway is the principal mechanism for repair of ionizing radiation-induced, double-strand breaks in mammalian cells. Three polypeptides in this pathway, including the two subunits of Ku protein and the catalytic subunit of the DNA-dependent protein kinase, are known targets of autoantibodies in systemic rheumatic diseases. Here we show that two additional polypeptides in the pathway, DNA ligase IV and XRCC4, are also targets of autoantibodies. These Abs were present in 20% of patients with systemic lupus erythematosus and overlap syndrome. Previous work has shown that XRCC4 is subject to radiation-induced post-translational modification, including phosphorylation by DNA-dependent protein kinase and cleavage by caspase 3. We mapped a major autoimmune epitope in XRCC4 and found that it encompassed a DNA-dependent protein kinase phosphorylation site, which is located at serine 260; that it was adjacent to a site for caspase 3, which cleaves after residue 265; and that it also spanned a site for the inflammatory protease, granzyme B, which cleaves after residue 254. The finding that five different polypeptides in the nonhomologous end-joining pathway are potential targets of autoantibodies together with the observation that one of the autoimmune epitopes in XRCC4 coincides with a sequence that is a nexus for radiation-induced regulatory events suggest that exposure to agents that introduce DNA double-strand breaks may be one of the factors that influences the development of an autoimmune response in susceptible individuals.     

羊肚菌免疫调节作用研究

观察DNFB诱导小鼠迟发型变态反应、血清溶血素测定（血凝法）、小鼠腹腔巨噬细胞吞噬鸡红细胞试验,结果表明,羊肚菌可以促进小鼠细胞免疫功能提高液免疫功能,促进小鼠体内抗体的产生,具有增强小鼠腹巨噬功能,是一种比较有效的免疫调节剂。     

Association of socioeconomic status and receipt of colorectal cancer investigations: a population- based retrospective cohort study

Background

Although the Canadian health care system was designed to ensure equal access, inequities persist. It is not known if inequities exist for receipt of investigations used to screen for colorectal cancer (CRC). We examined the association between socioeconomic status and receipt of colorectal investigation in Ontario.

Methods

People aged 50 to 70 years living in Ontario on Jan. 1, 1997, who did not have a history of CRC, inflammatory bowel disease or colorectal investigation within the previous 5 years were followed until death or Dec. 31, 2001. Receipt of any colorectal investigation between 1997 and 2001 inclusive was determined by means of linked administrative databases. Income was imputed as the mean household income of the person''s census enumeration area. Multivariate analysis was performed to evaluate the relationship between the receipt of any colorectal investigation and income.

Results

Of the study cohort of 1 664 188 people, 21.2% received a colorectal investigation in 1997–2001. Multivariate analysis demonstrated a significant association between receipt of any colorectal investigation and income (p < 0.001); people in the highest-income quintile had higher odds of receiving any colorectal investigation (adjusted odds ratio [OR] 1.38; 95% confidence interval [CI] 1.36–1.40) and of receiving colonoscopy (adjusted OR 1.50; 95% CI 1.48–1.53).

Interpretation

Socioeconomic status is associated with receipt of colorectal investigations in Ontario. Only one-fifth of people in the screening-eligible age group received any colorectal investigation. Further work is needed to determine the reason for this low rate and to explore whether it affects CRC mortality.Colorectal cancer (CRC) is the most common cause of cancer-related death among nonsmokers in North America. In 2004 an estimated 19 200 Canadians will receive a diagnosis of CRC and 8400 will die from the disease.¹ Although the age-standardized incidence and mortality of CRC have been decreasing, the number of new cases is increasing because of the growing size of the elderly population.CRC screening reduces the incidence and disease-specific mortality,^2,3,4,5,6 is cost-effective^7,8 and is endorsed by many professional societies.^{9,10,11,12,13,14,15} In 1994 the Canadian Task Force on the Periodic Health Examination (now the Canadian Task Force on Preventive Health Care) concluded that there was insufficient evidence to support CRC screening in asymptomatic people over the age of 40 years.¹⁶ In the 2001 update of these guidelines⁹ fecal occult blood testing (FOBT) every 1 or 2 years or flexible sigmoidoscopy every 5 years was recommended for screening average-risk people 50 years of age or older; there was judged to be insufficient evidence to support colonoscopy as the initial screening test. Despite these endorsements the use of CRC screening remains suboptimal.^17,18,19The Canadian health care system covers all medically necessary services without user fees. Although equity has been achieved in certain areas,^20,21 low socioeconomic status (SES) is associated with a lower rate of use of cardiovascular procedures^22,23 and screening tests for breast and cervical cancer.^24,25,26 It is unknown whether SES affects the receipt of CRC screening investigations. This study assessed the association of neighbourhood income (a marker of SES) with the receipt of colorectal investigations in people eligible for screening who lived in Ontario.     

飞机草浸提液对斜纹夜蛾生长发育及种群参数的影响

[目的]明确飞机草浸提液对斜纹夜蛾生长发育和繁殖的影响。[方法]在实验室内利用不同浓度的飞机草水浸提液处理香蕉叶后喂养斜纹夜蛾幼虫,并观察记录斜纹夜蛾的生长发育情况。[结果]随着飞机草浸提液浓度的升高,斜纹夜蛾幼虫和蛹的发育历期逐渐延长,蛹重逐渐降低;母液处理下的幼虫和蛹发育历期最长,分别比对照处理延长了7.92和2.88 d,母液处理下的蛹重最轻,较对照降低了25.4%;飞机草浸提液处理降低了斜纹夜蛾低龄幼虫的存活率,对高龄幼虫和蛹的存活率影响不显著。随着飞机草浸提液浓度的升高,斜纹夜蛾种群净增值率R₀、内禀增长率r_m和周限增长率λ均逐渐降低,种群平均世代周期T和种群加倍时间t逐渐延长。[结论]飞机草对斜纹夜蛾具有一定的生防潜力,可应用于斜纹夜蛾的生物源农药开发研究。     

Pirh2 mediates the sensitivity of myeloma cells to bortezomib via canonical NF-κB signaling pathway

Clinical success of the proteasome inhibitor established bortezomib as one of the most effective drugs in treatment of multiple myeloma (MM). While survival benefit of bortezomib generated new treatment strategies, the primary and secondary resistance of MM cells to bortezomib remains a clinical concern. This study aimed to highlight the role of p53-induced RING-H2 (Pirh2) in the acquisition of bortezomib resistance in MM and to clarify the function and mechanism of action of Pirh2 in MM cell growth and resistance, thereby providing the basis for new therapeutic targets for MM. The proteasome inhibitor bortezomib has been established as one of the most effective drugs for treating MM. We demonstrated that bortezomib resistance in MM cells resulted from a reduction in Pirh2 protein levels. Pirh2 overexpression overcame bortezomib resistance and restored the sensitivity of myeloma cells to bortezomib, while a reduction in Pirh2 levels was correlated with bortezomib resistance. The levels of nuclear factorkappaB (NF-κB) p65, pp65, pIKBa, and IKKa were higher in bortezomib-resistant cells than those in parental cells. Pirh2 overexpression reduced the levels of pIKBa and IKKa, while the knockdown of Pirh2 via short hairpin RNAs increased the expression of NF-κB p65, pIKBa, and IKKa. Therefore, Pirh2 suppressed the canonical NF-κB signaling pathway by inhibiting the phosphorylation and subsequent degradation of IKBa to overcome acquired bortezomib resistance in MM cells.     

Paradoxical buffering of calcium by calsequestrin demonstrated for the calcium store of skeletal muscle

Contractile activation in striated muscles requires a Ca²⁺ reservoir of large capacity inside the sarcoplasmic reticulum (SR), presumably the protein calsequestrin. The buffering power of calsequestrin in vitro has a paradoxical dependence on [Ca²⁺] that should be valuable for function. Here, we demonstrate that this dependence is present in living cells. Ca²⁺ signals elicited by membrane depolarization under voltage clamp were compared in single skeletal fibers of wild-type (WT) and double (d) Casq-null mice, which lack both calsequestrin isoforms. In nulls, Ca²⁺ release started normally, but the store depleted much more rapidly than in the WT. This deficit was reflected in the evolution of SR evacuability, E, which is directly proportional to SR Ca²⁺ permeability and inversely to its Ca²⁺ buffering power, B. In WT mice E starts low and increases progressively as the SR is depleted. In dCasq-nulls, E started high and decreased upon Ca²⁺ depletion. An elevated E in nulls is consistent with the decrease in B expected upon deletion of calsequestrin. The different value and time course of E in cells without calsequestrin indicate that the normal evolution of E reflects loss of B upon SR Ca²⁺ depletion. Decrement of B upon SR depletion was supported further. When SR calcium was reduced by exposure to low extracellular [Ca²⁺], release kinetics in the WT became similar to that in the dCasq-null. E became much higher, similar to that of null cells. These results indicate that calsequestrin not only stores Ca²⁺, but also varies its affinity in ways that progressively increase the ability of the store to deliver Ca²⁺ as it becomes depleted, a novel feedback mechanism of potentially valuable functional implications. The study revealed a surprisingly modest loss of Ca²⁺ storage capacity in null cells, which may reflect concurrent changes, rather than detract from the physiological importance of calsequestrin.     

Imaging superoxide flash and metabolism-coupled mitochondrial permeability transition in living animals

The mitochondrion is essential for energy metabolism and production of reactive oxygen species (ROS). In intact cells, respiratory mitochondria exhibit spontaneous "superoxide flashes", the quantal ROS-producing events consequential to transient mitochondrial permeability transition (tMPT). Here we perform the first in vivo imaging of mitochondrial superoxide flashes and tMPT activity in living mice expressing the superoxide biosensor mt-cpYFP, and demonstrate their coupling to whole-body glucose metabolism. Robust tMPT/superoxide flash activity occurred in skeletal muscle and sciatic nerve of anesthetized transgenic mice. In skeletal muscle, imaging tMPT/superoxide flashes revealed labyrinthine three-dimensional networks of mitochondria that operate synchronously. The tMPT/superoxide flash activity surged in response to systemic glucose challenge or insulin stimulation, in an apparently frequency-modulated manner and involving also a shift in the gating mode of tMPT. Thus, in vivo imaging of tMPT-dependent mitochondrial ROS signals and the discovery of the metabolism-tMPT-superoxide flash coupling mark important technological and conceptual advances for the study of mitochondrial function and ROS signaling in health and disease.