Incomplete oxidation of palmitate and leakage of intermediary products during anoxia

Surviving isolated rat hearts were perfused utilizing the Langendorff technique with [1-¹⁴C]palmitate or [16-¹⁴C]palmitate. During anoxia it was possible to isolate shorter-chain fatty acids and hydroxylated intermediates in the perfusate. When the heart was well oxygenated this was not the case. During oxygenation most of the palmitate was utilized and some of its labeled fragments were used for elongation of other fatty acids. During anoxia this was not observed. The fatty acid composition of the heart did not show a statistically significant change during anoxia, but the perfusate was enriched with some metabolites. It is suggested that changes in permeability in the cell membrane which occur during anoxia may cause leakage or transport of lipids, including short fatty acids and hydroxy intermediates.     

Arsenic Inhibits Autophagic Flux,Activating the Nrf2-Keap1 Pathway in a p62-Dependent Manner

The Nrf2-Keap1 signaling pathway is a protective mechanism promoting cell survival. Activation of the Nrf2 pathway by natural compounds has been proven to be an effective strategy for chemoprevention. Interestingly, a cancer-promoting function of Nrf2 has recently been observed in many types of tumors due to deregulation of the Nrf2-Keap1 axis, which leads to constitutive activation of Nrf2. Here, we report a novel mechanism of Nrf2 activation by arsenic that is distinct from that of chemopreventive compounds. Arsenic deregulates the autophagic pathway through blockage of autophagic flux, resulting in accumulation of autophagosomes and sequestration of p62, Keap1, and LC3. Thus, arsenic activates Nrf2 through a noncanonical mechanism (p62 dependent), leading to a chronic, sustained activation of Nrf2. In contrast, activation of Nrf2 by sulforaphane (SF) and tert-butylhydroquinone (tBHQ) depends upon Keap1-C151 and not p62 (the canonical mechanism). More importantly, SF and tBHQ do not have any effect on autophagy. In fact, SF and tBHQ alleviate arsenic-mediated deregulation of autophagy. Collectively, these findings provide evidence that arsenic causes prolonged activation of Nrf2 through autophagy dysfunction, possibly providing a scenario similar to that of constitutive activation of Nrf2 found in certain human cancers. This may represent a previously unrecognized mechanism underlying arsenic toxicity and carcinogenicity in humans.     

Race-ethnicity,nativity, neighbourhood context and reports of unfair treatment by police

This research describes how race-ethnicity, nativity and neighbourhood characteristics are associated with reports of unfair treatment by police in the previous five years by residentially stable men. Data are from waves 1 and 2 of the Los Angeles Family and Neighborhood Survey. Results suggest that foreign-born Latinos are less likely than African Americans and US-born whites to report unfair treatment. After accounting for tract percentage Latino, US-born Latinos were less likely to report unfair treatment than African Americans, which partially supports a gradient model. Neighbourhood affluence was negatively associated with reports, but poverty, percentage Latino and immigrant concentration were not. The importance of neighbourhood privilege is highlighted, as is the need to better understand Latino immigrants' experiences with police. Future work should examine immigrants' interpretation of interactions with police and their willingness to report unfair treatment.     

The BRCA1-binding protein BRAP2 can act as a cytoplasmic retention factor for nuclear and nuclear envelope-localizing testicular proteins

Regulation of nuclear protein import is central to many cellular processes such as development, with a key mechanism being factors that retain cargoes in the cytoplasm that normally localize in the nucleus. The breast cancer antigen BRCA1-binding protein BRAP2 has been reported as a novel negative regulator of nuclear import of various nuclear localization signal (NLS)-containing viral and cellular proteins, but although implicated in differentiation pathways and highly expressed in tissues including testis, the gamut of targets for BRAP2 action in a developmental context is unknown. As a first step towards defining the BRAP2 interactome, we performed a yeast-2-hybrid screen to identify binding partners of BRAP2 in human testis. Here we report characterization for the first time of three of these: the high mobility group (HMG)-box-domain-containing chromatin component HMG20A, nuclear mitotic apparatus protein NuMA1 and synaptic nuclear envelope protein SYNE2. Co-immunoprecipitation experiments indicate association of BRAP2 with HMG20A, NuMA1, and SYNE2 in testis, underlining the physiological relevance of the interactions, with immunohistochemistry showing that where BRAP2 is co-expressed with HMG20A and NuMA1, both are present in the cytoplasm, in contrast to their nuclear localization in other testicular cell types. Importantly, quantitative confocal microscopic analysis of cultured cells indicates that ectopic expression of BRAP2 inhibits nuclear localization of HMG20A and NuMA1, and prevents nuclear envelope accumulation of SYNE2, the first report of BRAP2 altering localization of a non-nuclear protein. These results imply for the first time that BRAP2 may have an important role in modulating subcellular localization during testicular development.     

Targeting the Microbiota to Address Diet-Induced Obesity: A Time Dependent Challenge

Links between the gut microbiota and host metabolism have provided new perspectives on obesity. We previously showed that the link between the microbiota and fat deposition is age- and time-dependent subject to microbial adaptation to diet over time. We also demonstrated reduced weight gain in diet-induced obese (DIO) mice through manipulation of the gut microbiota with vancomycin or with the bacteriocin-producing probiotic Lactobacillus salivarius UCC118 (Bac⁺), with metabolic improvement achieved in DIO mice in receipt of vancomycin. However, two phases of weight gain were observed with effects most marked early in the intervention phase. Here, we compare the gut microbial populations at the early relative to the late stages of intervention using a high throughput sequencing-based analysis to understand the temporal relationship between the gut microbiota and obesity. This reveals several differences in microbiota composition over the intervening period. Vancomycin dramatically altered the gut microbiota composition, relative to controls, at the early stages of intervention after which time some recovery was evident. It was also revealed that Bac⁺ treatment initially resulted in the presence of significantly higher proportions of Peptococcaceae and significantly lower proportions of Rikenellaceae and Porphyromonadaceae relative to the gut microbiota of L. salivarius UCC118 bacteriocin negative (Bac^-) administered controls. These differences were no longer evident at the later time. The results highlight the resilience of the gut microbiota and suggest that interventions may need to be monitored and continually adjusted to ensure sustained modification of the gut microbiota.     

Katanin Localization Requires Triplet Microtubules in Chlamydomonas reinhardtii

Centrioles and basal bodies are essential for a variety of cellular processes that include the recruitment of proteins to these structures for both centrosomal and ciliary function. This recruitment is compromised when centriole/basal body assembly is defective. Mutations that cause basal body assembly defects confer supersensitivity to Taxol. These include bld2, bld10, bld12, uni3, vfl1, vfl2, and vfl3. Flagellar motility mutants do not confer sensitivity with the exception of mutations in the p60 (pf19) and p80 (pf15) subunits of the microtubule severing protein katanin. We have identified additional pf15 and bld2 (ε-tubulin) alleles in screens for Taxol sensitivity. Null pf15 and bld2 alleles are viable and are not essential genes in Chlamydomonas. Analysis of double mutant strains with the pf15-3 and bld2-6 null alleles suggests that basal bodies in Chlamydomonas may recruit additional proteins beyond katanin that affect spindle microtubule stability. The bld2-5 allele is a hypomorphic allele and its phenotype is modulated by nutritional cues. Basal bodies in bld2-5 cells are missing proximal ends. The basal body mutants show aberrant localization of an epitope-tagged p80 subunit of katanin. Unlike IFT proteins, katanin p80 does not localize to the transition fibers of the basal bodies based on an analysis of the uni1 mutant as well as the lack of colocalization of katanin p80 with IFT74. We suggest that the triplet microtubules are likely to play a key role in katanin p80 recruitment to the basal body of Chlamydomonas rather than the transition fibers that are needed for IFT localization.     

Glutamine‐driven oxidative phosphorylation is a major ATP source in transformed mammalian cells in both normoxia and hypoxia

Mammalian cells can generate ATP via glycolysis or mitochondrial respiration. Oncogene activation and hypoxia promote glycolysis and lactate secretion. The significance of these metabolic changes to ATP production remains however ill defined. Here, we integrate LC‐MS‐based isotope tracer studies with oxygen uptake measurements in a quantitative redox‐balanced metabolic flux model of mammalian cellular metabolism. We then apply this approach to assess the impact of Ras and Akt activation and hypoxia on energy metabolism. Both oncogene activation and hypoxia induce roughly a twofold increase in glycolytic flux. Ras activation and hypoxia also strongly decrease glucose oxidation. Oxidative phosphorylation, powered substantially by glutamine‐driven TCA turning, however, persists and accounts for the majority of ATP production. Consistent with this, in all cases, pharmacological inhibition of oxidative phosphorylation markedly reduces energy charge, and glutamine but not glucose removal markedly lowers oxygen uptake. Thus, glutamine‐driven oxidative phosphorylation is a major means of ATP production even in hypoxic cancer cells.     

EPS8 Inhibition Increases Cisplatin Sensitivity in Lung Cancer Cells

Cisplatin, a commonly used chemotherapeutic, is associated with ototoxicity, renal toxicity and neurotoxicity, thus identifying means to increase the therapeutic index of cisplatin may allow for improved outcomes. A SNP (rs4343077) within EPS8, discovered through a genome wide association study of cisplatin-induced cytotoxicity and apoptosis in lymphoblastoid cell lines (LCLs), provided impetus to further study this gene. The purpose of this work was to evaluate the role of EPS8 in cellular susceptibility to cisplatin in cancerous and non-cancerous cells. We used EPS8 RNA interference to determine the effect of decreased EPS8 expression on LCL and A549 lung cancer cell sensitivity to cisplatin. EPS8 knockdown in LCLs resulted in a 7.9% increase in cisplatin-induced survival (P = 1.98×10⁻⁷) and an 8.7% decrease in apoptosis (P = 0.004) compared to control. In contrast, reduced EPS8 expression in lung cancer cells resulted in a 20.6% decrease in cisplatin-induced survival (P = 5.08×10⁻⁵). We then investigated an EPS8 inhibitor, mithramycin A, as a potential agent to increase the therapeutic index of cisplatin. Mithramycin A decreased EPS8 expression in LCLs resulting in decreased cellular sensitivity to cisplatin as evidenced by lower caspase 3/7 activation following cisplatin treatment (42.7%±6.8% relative to control P = 0.0002). In 5 non-small-cell lung carcinoma (NSCLC) cell lines, mithramycin A also resulted in decreased EPS8 expression. Adding mithramycin to 4 NSCLC cell lines and a bladder cancer cell line, resulted in increased sensitivity to cisplatin that was significantly more pronounced in tumor cell lines than in LCL lines (p<0.0001). An EGFR mutant NSCLC cell line (H1975) showed no significant change in sensitivity to cisplatin with the addition of mithramycin treatment. Therefore, an inhibitor of EPS8, such as mithramycin A, could improve cisplatin treatment by increasing sensitivity of tumor relative to normal cells.     

Purification of Plasma Membrane of Guinea Pig Peritoneal Macrophages

A method using sucrose density gradient centrifugation is described for the purification of plasma membrane of guinea pig peritoneal exudate macrophages. Assays for composition and for marker enzyme activities have been modified for use with the small amounts of subcellular macrophage material. The plasma membrane was obtained in 57% yield and contained 7% of the protein. The purified plasma membrane fraction is five-fold enriched in phospholipid to protein ratio and contains no contaminating DNA, none of the cytoplasmic marker lactate dehydrogenase, no detectable mitochondrial contamination and a low contamination with lysosomal enzymes (7%). Purified plasma membrane containing 4 mg of protein can be prepared from 1 ml of pelleted macrophages in a one-day operation.     

Design,structure–activity relationship and in vivo efficacy of piperazine analogues of fenarimol as inhibitors of Trypanosoma cruzi

A scaffold hopping exercise undertaken to expand the structural diversity of the fenarimol series of anti-Trypanosoma cruzi (T. cruzi) compounds led to preparation of simple 1-[phenyl(pyridin-3-yl)methyl]piperazinyl analogues of fenarimol which were investigated for their ability to inhibit T. cruzi in vitro in a whole organism assay. A range of compounds bearing amide, sulfonamide, carbamate/carbonate and aryl moieties exhibited low nM activities and two analogues were further studied for in vivo efficacy in a mouse model of T. cruzi infection. One compound, the citrate salt of 37, was efficacious in a mouse model of acute T. cruzi infection after once daily oral dosing at 20, 50 and 100 mg/kg for 5 days.