Serologic evidence that ascaris and toxoplasma infections impact inflammatory responses to Helicobacter pylori in Colombians

Background: Helicobacter pylori‐infected children from coastal Tumaco, Colombia, have more parasitism, and adults have lower gastric cancer risk compared with high‐altitude Pasto/Tuquerres residents. Because helminth and Toxoplasma gondii infections alter helicobacter gastritis in rodent models, we determined whether seropositivity to Ascaris lumbricoides or T. gondii was associated with Th2‐IgG1 or Th1‐IgG2 responses to H. pylori. Methods: Sera (240) from the two populations were evaluated for A. lumbricoides and T. gondii seropositivity and results correlated with IgE and IgG isotype responses to H. pylori. Results: Most Tumaco children and adults were seropositive for A. lumbricoides (89%, 66%), T. gondii (59%, 98%), or both (45%, 66%). In contrast, seropositivity among Pasto/Tuquerres children was much lower (9%A. lumbricoides, 11%T. gondii, and 2% dual positive) but increased in adults (58%A. lumbricoides, 82%T. gondii, and 41% dual positive). A. lumbricoides seropositivity correlated with elevated IgE and anti‐inflammatory Th2‐IgG1 responses to H. pylori, while T. gondiigondii seropositivity was linked to elevated IgE, pro‐inflammatory Th1‐IgG2, IgG3, and IgG4 responses to H. pylori. Individuals with high T. gondii titers had reduced Th1‐IgG2, IgG3, and IgG4 responses to H. pylori. Conclusions: Results support regional differences for childhood parasitism and indicate A. lumbricoides and T. gondii infections may impact inflammatory responses to H. pylori and partially explain differences in gastric cancer risk in Colombia.     

Mechanistic and Structural Understanding of Uncompetitive Inhibitors of Caspase-6

Inhibition of caspase-6 is a potential therapeutic strategy for some neurodegenerative diseases, but it has been difficult to develop selective inhibitors against caspases. We report the discovery and characterization of a potent inhibitor of caspase-6 that acts by an uncompetitive binding mode that is an unprecedented mechanism of inhibition against this target class. Biochemical assays demonstrate that, while exquisitely selective for caspase-6 over caspase-3 and -7, the compound’s inhibitory activity is also dependent on the amino acid sequence and P1’ character of the peptide substrate. The crystal structure of the ternary complex of caspase-6, substrate-mimetic and an 11 nM inhibitor reveals the molecular basis of inhibition. The general strategy to develop uncompetitive inhibitors together with the unique mechanism described herein provides a rationale for engineering caspase selectivity.     

An ancient history of gene duplications, fusions and losses in the evolution of APOBEC3 mutators in mammals

ABSTRACT: BACKGROUND: The APOBEC3 (A3) genes play a key role in innate antiviral defense in mammals by introducing directed mutations in the DNA. The human genome encodes for seven A3 genes, with multiple splice alternatives. Different A3 proteins display different substrate specificity, but the very basic question on how discerning self from non-self still remains unresolved. Further, the expression of A3 activity/ies shapes the way both viral and host genomes evolve. RESULTS: We present here a detailed temporal analysis of the origin and expansion of the A3 repertoire in mammals. Our data support an evolutionary scenario where the genome of the mammalian ancestor encoded for at least one ancestral A3 gene, and where the genome of the ancestor of placental mammals (and possibly of the ancestor of all mammals) already encoded for an A3Z1-A3Z2-A3Z3 arrangement. Duplication events of the A3 genes have occurred independently in different lineages: humans, cats and horses. In all of them, gene duplication has resulted in changes in enzyme activity and/or substrate specificity, in a paradigmatic example of convergent adaptive evolution at the genomic level. Finally, our results show that evolutionary rates for the three A3Z1, A3Z2 and A3Z3 motifs have significantly decreased in the last 100 Mya. The analysis constitutes a textbook example of the evolution of a gene locus by duplication and sub/neofunctionalization in the context of virus-host arms race. CONCLUSIONS: Our results provide a time framework for identifying ancestral and derived genomic arrangements in the APOBEC loci, and to date the expansion of this gene family for different lineages through time, as a response to changes in viral/retroviral/retrotransposon pressure.     

DNA damage in peripheral blood lymphocytes in patients during combined chemotherapy for breast cancer

Combined chemotherapy is used for the treatment of a number of malignancies such as breast cancer. The target of these antineoplastic agents is nuclear DNA, although it is not restricted to malignant cells. The aim of the present study was to assess DNA damage in peripheral blood lymphocytes (PBLs) of breast cancer patients subjected to combined adjuvant chemotherapy (5-fluorouracil, epirubicin and cyclophosphamide, FEC), using a modified comet assay to detect DNA single-strand breaks (SSB) and double-strand breaks (DSB).

Forty-one female patients with advanced breast cancer before and after chemotherapy and 60 healthy females participated in the study. Alkaline and neutral comet assays were performed in PBLs according to a standard protocol, and DNA tail moment was measured by a computer-based image analysis system.

Breast cancer patients before treatment had higher increased background levels of SSB and DSB as compared to healthy women. During treatment, a significant increase in DNA damage was observed after the 2nd cycle, which persisted until the end of treatment. Eighty days after the end of treatment the percentage of PBLs with SSB and DSB remained elevated, but the magnitude of DNA damage (tail moment) returned to baseline levels. There was no correlation between PBL DNA damage and response to chemotherapy.

DNA-SSB and DSB in PBLs are present in cancer patients before treatment and increase significantly after combined chemotherapy. No correlation with response to adjuvant chemotherapy was found. Biomonitoring DNA damage in PBLs of cancer patients could help prevent secondary effects and the potential risks of developing secondary cancers.     

Sulfated polysaccharides promote the assembly of amyloid beta(1-42) peptide into stable fibrils of reduced cytotoxicity

The histopathological hallmarks of Alzheimer disease are the self-aggregation of the amyloid beta peptide (Abeta) in extracellular amyloid fibrils and the formation of intraneuronal Tau filaments, but a convincing mechanism connecting both processes has yet to be provided. Here we show that the endogenous polysaccharide chondroitin sulfate B (CSB) promotes the formation of fibrillar structures of the 42-residue fragment, Abeta(1-42). Atomic force microscopy visualization, thioflavin T fluorescence, CD measurements, and cell viability assays indicate that CSB-induced fibrils are highly stable entities with abundant beta-sheet structure that have little toxicity for neuroblastoma cells. We propose a wedged cylinder model for Abeta(1-42) fibrils that is consistent with the majority of available data, it is an energetically favorable assembly that minimizes the exposure of hydrophobic areas, and it explains why fibrils do not grow in thickness. Fluorescence measurements of the effect of different Abeta(1-42) species on Ca(2+) homeostasis show that weakly structured nodular fibrils, but not CSB-induced smooth fibrils, trigger a rise in cytosolic Ca(2+) that depends on the presence of both extracellular and intracellular stocks. In vitro assays indicate that such transient, local Ca(2+) increases can have a direct effect in promoting the formation of Tau filaments similar to those isolated from Alzheimer disease brains.     

Collpas: Activity Hotspots for Frugivorous Bats (Phyllostomidae) in the Peruvian Amazon

In the SE Peruvian Amazon, large numbers of frugivorous bats regularly visit natural forest clearings known locally as collpas (which are also referred to as clay licks or mineral licks). Bats arrive at collpas to drink water that has accumulated in depressions created by larger geophagous mammals that consume exposed soil. Although collpa visitation is common, little is known about its causes and its ecological implications for the bat community. We compared patterns of use of collpas and non- collpa forest sites by bats in SE Peru. We mist netted bats at collpas and non- collpa sites during the dry season and compared abundance, species richness, species composition, sex ratio, and reproductive condition. More species were captured at collpas than at non- collpa sites, and collpas were visited almost exclusively by frugivores. Overall, bat-capture frequency and combined frugivorous bat-capture frequency were higher at collpas than at non- collpa sites, although some species of frugivorous bats were captured more frequently at non- collpa sites than at collpas ( e.g ., Carollia spp.). Irrespective of capture site, more female bats were pregnant or lactating than not, but there was a distinct female sex bias in bats that visited collpas : 70 percent of bats captured at collpas were female, whereas 44 percent of bats captured away from collpas were female. These patterns suggest that collpas may provide important resources for frugivorous bats in SE Peru, just as they are thought to provide important resources to the vertebrates that consume collpa soils. Accordingly, collpas are important conservation targets in the region.     

Binding of sulphonated indigo derivatives to RepA-WH1 inhibits DNA-induced protein amyloidogenesis

The quest for inducers and inhibitors of protein amyloidogenesis is of utmost interest, since they are key tools to understand the molecular bases of proteinopathies such as Alzheimer, Parkinson, Huntington and Creutzfeldt–Jakob diseases. It is also expected that such molecules could lead to valid therapeutic agents. In common with the mammalian prion protein (PrP), the N-terminal Winged-Helix (WH1) domain of the pPS10 plasmid replication protein (RepA) assembles in vitro into a variety of amyloid nanostructures upon binding to different specific dsDNA sequences. Here we show that di- (S2) and tetra-sulphonated (S4) derivatives of indigo stain dock at the DNA recognition interface in the RepA-WH1 dimer. They compete binding of RepA to its natural target dsDNA repeats, found at the repA operator and at the origin of replication of the plasmid. Calorimetry points to the existence of a major site, with micromolar affinity, for S4-indigo in RepA-WH1 dimers. As revealed by electron microscopy, in the presence of inducer dsDNA, both S2/S4 stains inhibit the assembly of RepA-WH1 into fibres. These results validate the concept that DNA can promote protein assembly into amyloids and reveal that the binding sites of effector molecules can be targeted to inhibit amyloidogenesis.