Therapeutic targeting of vascular malformation in a zebrafish model of hereditary haemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia (HHT) causes arteriovenous malformations (AVMs) in multiple organs to cause bleeding, neurological and other complications. HHT is caused by mutations in the BMP co-receptor endoglin. We characterised a range of vascular phenotypes in embryonic and adult endoglin mutant zebrafish and the effect of inhibiting different pathways downstream of Vegf signalling. Adult endoglin mutant zebrafish developed skin AVMs, retinal vascular abnormalities and cardiac enlargement. Embryonic endoglin mutants developed an enlarged basilar artery (similar to the previously described enlarged aorta and cardinal vein) and larger numbers of endothelial membrane cysts (kugeln) on cerebral vessels. Vegf inhibition prevented these embryonic phenotypes, leading us to investigate specific Vegf signalling pathways. Inhibiting mTOR or MEK pathways prevented abnormal trunk and cerebral vasculature phenotypes, whereas inhibiting Nos or Mapk pathways had no effect. Combined subtherapeutic mTOR and MEK inhibition prevented vascular abnormalities, confirming synergy between these pathways in HHT. These results indicate that the HHT-like phenotype in zebrafish endoglin mutants can be mitigated through modulation of Vegf signalling. Combined low-dose MEK and mTOR pathway inhibition could represent a novel therapeutic strategy in HHT

Importance of exposure route for behavioural responses in Lumbriculus variegatus Müller (Oligochaeta: Lumbriculida) in short-term exposures to Pb

Abstract Goal, Scope and Background Lumbriculus variegatus Müller (Oligochaeta), a common freshwater sediment-dweller, has frequently been used in toxicokinetic studies, although has been less used in ecotoxicity tests. Methods For the first time the Multispecies Freshwater Biomonitor® (MFB) was applied in a short-term whole-sediment toxicity test. The MFB automatically and quantitatively recorded the spontaneous locomotory behaviour of Lumbriculus variegatus in exposures with two compartments, water and sediment. The study questioned, whether the animals altered their locomotion depending on the compartment which was spiked with lead (Pb). Results and Discussion As in the exposures to Pb-contaminated water/clean sediment, the animals exposed to Pb-contaminated sediment/clean water showed higher activities in intermediate Pb-concentrations. This indicates, that spontaneous locomotory activity is affected by Pb-concentrations at sublethal levels regardless of whether the Pb-concentration is found in the water or in the sediment, because these animals use both environmental compartments simultaneously. However, within the same Pb-levels, the animals showed higher locomotory activity in contaminated water compared with contaminated sediment. This indicates a possible tendency to withdraw from (‘avoidance’) contaminated water into the clean sediment compartment, whereas there was no withdrawal from contaminated sediment into clean water. The latter might be explained by the fact that withdrawal from sediment to water might increase the risk of predation and drift in nature, whereas retracting to sediment might provide shelter. Conclusions The study showed that spontaneous locomotory responses of L. variegatus to Pb depend on whether the water or sediment is contaminated. The study also concluded that the Multispecies Freshwater Biomonitor® can be applied effectively in sediment toxicity testing. Recommendations and Perspectives More emphasis should be given to the interactions of water/sediment in sediment ecotoxicity tests to better simulate field conditions and increase ecological realism in risk assessment, especially as quantitative recording methods exisit

Induced fit recognition of DNA by organometallic complexes with dynamic stereogenic centres

Organometallic chemistry offers novel concepts in structural diversity and molecular recognition that can be used in drug design. Here, we consider DNA recognition by η6-arene Ru(II) anticancer complexes by an induced-fit mechanism. The stereochemistry of the dinuclear complex [((η6-biphenyl)RuCl(en))2-(CH2)6]2 + (3, en = ethylenediamine) was elucidated by studies of the half unit [(η6-biphenyl)RuCl(Et-en)]+ (2, where Et-en is Et(H)NCH2CH2NH2). The structures of the separated and diastereomers of 2 were determined by x-ray crystallography; their slow interconversion in water (t½ ≈ 2 h, 298 K, pH 6.2) was observed by NMR spectroscopy. For 2 and 3 the configurations are more stable than (73:27). X-ray and NMR studies showed that reactions of 2 and 3 with 9-ethylguanine gave rise selectively to diastereomers. Dynamic chiral recognition of guanine can lead to high diastereoselectivity of DNA binding. The dinuclear complex 3 induced a large unwinding (31°) of plasmid DNA, twice that of mononuclear 2 (14°), and effectively inhibited DNA-directed RNA synthesis in vitro. This dinuclear complex gave rise to interstrand cross-links on a 213-bp plasmid fragment with efficiency similar to bifunctional cisplatin, and to 1,3-GG interstrand and 1,2-GG and 1,3-GTG intrastrand cross-links on site-specifically ruthenated 20-mers. Complex 3 blocked intercalation of ethidium considerably more than mononuclear 2. The concept of induced-fit recognition of DNA by organometallic complexes containing dynamic stereogenic centers via dynamic epimerization, intercalation, and cross-linking may be useful in the design of anticancer drugs

Facultative hemiepiphytism as a recruitment strategy in small‐seeded tree species

Aims: Shade-tolerant tree species often produce larger seeds with greater energetic resources to cope with light limitation. On the other hand, shade-intolerant species often produce smaller seeds with greater dispersal potential to colonise lighter, more disturbed areas of forest. We test the hypothesis that small-seeded species utilise an alternative recruitment strategy in a southern temperate rainforest by establishing epiphytically on the trunks of tree ferns. Location: Wellington region, North Island of New Zealand. Methods: To assess whether small-seeded tree species rely on tree fern epiphytism for recruitment we quantified relative abundances of both epiphytic and terrestrial subpopulations in 14 woody plant species across a range of seed sizes. We used a paired study design where we surveyed all 3,727 woody plants occurring on 322 tree ferns and in matching forest floor plots of equivalent area. Using a linear model, we then assessed the relationship between species’ seed size and their epiphytic tendency (arboreality). Results: Arboreality scores differed both between species and between life history stages. Seed size predicted arboreality regardless of life history stage, with small-seeded species more likely to occur arboreally than larger-seeded ones. However, the effect of seed size decreased predictably in later life history stages. Seed size also predicted arboreality when the model was rerun using subsets of data restricted to common understorey tree ferns. Conclusion: Interspecific differences in the epiphytic establishment of New Zealand tree species are pronounced, with only smaller-seeded species able to use this regeneration niche. Small-seeded species, especially Weinmannia racemosa, appear to be utilising an alternative recruitment strategy by establishing epiphytically on tree fern trunks