Cell-based screen for altered nuclear phenotypes reveals senescence progression in polyploid cells after Aurora kinase B inhibition

Cellular senescence is a widespread stress response and is widely considered to be an alternative cancer therapeutic goal. Unlike apoptosis, senescence is composed of a diverse set of subphenotypes, depending on which of its associated effector programs are engaged. Here we establish a simple and sensitive cell-based prosenescence screen with detailed validation assays. We characterize the screen using a focused tool compound kinase inhibitor library. We identify a series of compounds that induce different types of senescence, including a unique phenotype associated with irregularly shaped nuclei and the progressive accumulation of G1 tetraploidy in human diploid fibroblasts. Downstream analyses show that all of the compounds that induce tetraploid senescence inhibit Aurora kinase B (AURKB). AURKB is the catalytic component of the chromosome passenger complex, which is involved in correct chromosome alignment and segregation, the spindle assembly checkpoint, and cytokinesis. Although aberrant mitosis and senescence have been linked, a specific characterization of AURKB in the context of senescence is still required. This proof-of-principle study suggests that our protocol is capable of amplifying tetraploid senescence, which can be observed in only a small population of oncogenic RAS-induced senescence, and provides additional justification for AURKB as a cancer therapeutic target.     

Indacaterol/glycopyrronium is cost-effective compared to salmeterol/fluticasone in COPD: FLAME-based modelling in a Swedish population

Background

This study assessed the cost-effectiveness of indacaterol/glycopyrronium (IND/GLY) versus salmeterol/fluticasone (SFC) in chronic obstructive pulmonary disease (COPD) patients with moderate to very severe airflow limitation and ≥1 exacerbation in the preceding year.

Methods

A previously published and validated patient-level simulation model was adapted using clinical data from the FLAME trial and real-world cost data from the ARCTIC study. Costs (total monetary costs comprising drug, maintenance, exacerbation, and pneumonia costs) and health outcomes (life-years (LYs), quality-adjusted life-years (QALYs)) were projected over various time horizons (1, 5, 10 years, and lifetime) from the Swedish payer’s perspective and were discounted at 3% annually. Uncertainty in model input values was studied through one-way and probabilistic sensitivity analyses. Subgroup analyses were also performed.

Results

IND/GLY was associated with lower costs and better outcomes compared with SFC over all the analysed time horizons. Use of IND/GLY resulted in additional 0.192 LYs and 0.134 QALYs with cost savings of €1211 compared with SFC over lifetime. The net monetary benefit (NMB) was estimated to be €8560 based on a willingness-to-pay threshold of €55,000/QALY. The NMB was higher in the following subgroups: severe (GOLD 3), high risk and more symptoms (GOLD D), females, and current smokers.

Conclusion

IND/GLY is a cost-effective treatment compared with SFC in COPD patients with mMRC dyspnea grade?≥?2, moderate to very severe airflow limitation, and ≥1 exacerbation in the preceding year.

     

Obesity and lipid stress inhibit carnitine acetyltransferase activity

Carnitine acetyltransferase (CrAT) is a mitochondrial matrix enzyme that catalyzes the interconversion of acetyl-CoA and acetylcarnitine. Emerging evidence suggests that this enzyme functions as a positive regulator of total body glucose tolerance and muscle activity of pyruvate dehydrogenase (PDH), a mitochondrial enzyme complex that promotes glucose oxidation and is feedback inhibited by acetyl-CoA. Here, we used tandem mass spectrometry-based metabolic profiling to identify a negative relationship between CrAT activity and muscle content of lipid intermediates. CrAT specific activity was diminished in muscles from obese and diabetic rodents despite increased protein abundance. This reduction in enzyme activity was accompanied by muscle accumulation of long-chain acylcarnitines (LCACs) and acyl-CoAs and a decline in the acetylcarnitine/acetyl-CoA ratio. In vitro assays demonstrated that palmitoyl-CoA acts as a direct mixed-model inhibitor of CrAT. Similarly, in primary human myocytes grown in culture, nutritional and genetic manipulations that promoted mitochondrial influx of fatty acids resulted in accumulation of LCACs but a pronounced decrease of CrAT-derived short-chain acylcarnitines. These results suggest that lipid-induced antagonism of CrAT might contribute to decreased PDH activity and glucose disposal in the context of obesity and diabetes.     

The risk of inter-specific competition in Australian short-necked turtles

Freshwater turtles are threatened globally; however, short-necked turtles in Eastern Australia have been particularly successful in exploiting natural and man-made permanent water bodies. The catchments of eastern Australia offer a unique opportunity to compare the diets of species in habitats where both genera co-exist, but only one genus is usually locally dominant. We compared the diets of species of Emydura and Myuchelys and Flaviemys in inland and coastal catchments in eastern Australia to determine the breadth of diets. We also conducted a more in depth study of the ecology and habitat preferences of the Bellinger River Emydura (Emydura macquarii macquarii) and Myuchelys georgesi. We found that diets of short-necked turtles on the east coast of Australia are separated by water conditions, and largely independent of species and location. Species of Myuchelys and Emydura are omnivorous. A high proportion of their food is from benthic macro-invertebrate communities in clear water. Terrestrial invertebrates and filamentous algae are present more in the diets of species inhabiting turbid water. Competition between species of Emydura and Myuchelys/Flaviemys is likely to occur when in sympatry, because species of Emydura can adapt their diets to various habitats and water quality. Myuchelys georgesi is restricted to, but common in, the Bellinger River. Interspecific competition may occur between E. m. macquarii and M. georgesi because of similar habitat preferences, diets and life histories. Emydura m. macquarii is not unique to the Bellinger River and hybridization with the endemic M. georgesi is a threatening process.     

Association of obesity and circulating adipose stromal cells among breast cancer survivors

A positive association of obesity with breast cancer incidence and mortality is well established. Recent reports indicate that adipose stromal cells (ASCs) play an important role in breast cancer development and progression by producing estrogens and tumor-promoting cytokines. Furthermore, circulating ASCs have been uniquely detected in obese individuals, which is likely due to increased tissue remodeling and cell mobilization. The number of circulating ASCs is even more prominent in obese patients with colon and prostate cancers, both of which are exacerbated by obesity. To determine whether a similar association exists for breast cancer, we collected blood samples from a cohort of breast cancer survivors and enumerated circulating ASCs by flow cytometry on the basis of the previously established ASC-associated immunophenotype (CD34⁺/CD31^?/CD45^?). We found significantly higher levels of circulating ASCs (p < 0.001) in breast cancer survivors with body mass index (BMI) ≥30 kg/m² than their non-obese counterparts (BMI < 30). We also compared circulating ASCs before and after exercise of only the obese subjects enrolled in a 6-month individualized exercise program, but found no statistically significant difference, likely due to limited number of subjects in the study. Our findings suggest that circulating ASCs can serve as a potential biomarker for future studies of the impacts of obesity and physical activity on breast cancer recurrence and survival.     

Stone Anvil Damage by Wild Bearded Capuchins (Sapajus libidinosus) during Pounding Tool Use: A Field Experiment

We recorded the damage that wild bearded capuchin monkeys (Sapajus libidinosus) caused to a sandstone anvil during pounding stone tool use, in an experimental setting. The anvil was undamaged when set up at the Fazenda Boa Vista (FBV) field laboratory in Piauí, Brazil, and subsequently the monkeys indirectly created a series of pits and destroyed the anvil surface by cracking palm nuts on it. We measured the size and rate of pit formation, and recorded when adult and immature monkeys removed loose material from the anvil surface. We found that new pits were formed with approximately every 10 nuts cracked, (corresponding to an average of 38 strikes with a stone tool), and that adult males were the primary initiators of new pit positions on the anvil. Whole nuts were preferentially placed within pits for cracking, and partially-broken nuts outside the established pits. Visible anvil damage was rapid, occurring within a day of the anvil''s introduction to the field laboratory. Destruction of the anvil through use has continued for three years since the experiment, resulting in both a pitted surface and a surrounding archaeological debris field that replicate features seen at natural FBV anvils.     

An Apparent Connection between Histidine, Recombination, and Repair in Neurospora

Two mutants of Neurospora crassa, uvs-3 and mei-3, share four properties--UV sensitivity, inhibition by histidine, meiotic blockage when homozygous, and increased duplication instability (due to mitotic crossing over, to deletions or to both). The present paper shows that a third nonallelic mutant, uvs-6, exhibits the same four properties.--Also, the instability of duplications in the absence of any UV-sensitive mutant is increased by the presence of histidine in the growth medium.     

Dyskerin is a component of the Arabidopsis telomerase RNP required for telomere maintenance

Dyskerin binds the H/ACA box of human telomerase RNA and is a core telomerase subunit required for RNP biogenesis and enzyme function in vivo. Missense mutations in dyskerin result in dyskeratosis congenita, a complex syndrome characterized by bone marrow failure, telomerase enzyme deficiency, and progressive telomere shortening. Here we demonstrate that dyskerin also contributes to telomere maintenance in Arabidopsis thaliana. We report that both AtNAP57, the Arabidopsis dyskerin homolog, and AtTERT, the telomerase catalytic subunit, accumulate in the plant nucleolus, and AtNAP57 associates with active telomerase RNP particles in an RNA-dependent manner. Furthermore, AtNAP57 interacts in vitro with AtPOT1a, a novel component of Arabidopsis telomerase. Although a null mutation in AtNAP57 is lethal, AtNAP57, like AtTERT, is not haploinsufficient for telomere maintenance in Arabidopsis. However, introduction of an AtNAP57 allele containing a T66A mutation decreased telomerase activity in vitro, disrupted telomere length regulation on individual chromosome ends in vivo, and established a new, shorter telomere length set point. These results imply that T66A NAP57 behaves as a dominant-negative inhibitor of telomerase. We conclude that dyskerin is a conserved component of the telomerase RNP complex in higher eukaryotes that is required for maximal enzyme activity in vivo.     

Parameters affecting telomere-mediated chromosomal truncation in Arabidopsis

Conversion of a double-strand break into a telomere is a dangerous, potentially lethal event. However, little is known about the mechanism and control of de novo telomere formation (DNTF). DNTF can be instigated by the insertion of a telomere repeat array (TRA) into the host genome, which seeds the formation of a new telomere, resulting in chromosome truncation. Such events are rare and concentrated at chromosome ends. Here, we introduce tetraploid Arabidopsis thaliana as a robust genetic model for DNTF. Transformation of a 2.6-kb TRA into tetraploid plants resulted in a DNTF efficiency of 56%, fivefold higher than in diploid plants and 50-fold higher than in human cells. DNTF events were recovered across the entire genome, indicating that genetic redundancy facilitates recovery of DNTF events. Although TRAs as short as 100 bp seeded new telomeres, these tracts were unstable unless they were extended above a 1-kb size threshold. Unexpectedly, DNTF efficiency increased in plants lacking telomerase, and DNTF rates were lower in plants null for Ku70 or Lig4, components of the nonhomologous end-joining repair pathway. We conclude that multiple competing pathways modulate DNTF, and that tetraploid Arabidopsis will be a powerful model for elucidating the molecular details of these processes.