Heparan sulphate synthetic and editing enzymes in ovarian cancer

Several angiogenic growth factors including fibroblast growth factors 1 and 2 (FGF1 and FGF2) depend on heparan sulphate (HS) for biological activity. We previously showed that all cellular elements in ovarian tumour tissue synthesised HS but biologically active HS (i.e. HS capable of binding FGF2 and its receptor) was confined to ovarian tumour endothelium. In this study, we have sought to explain this observation. Heparan sulphate sulphotransferases 1 and 2 (HS6ST1 and HS6ST2) attach sulphate groups to C-6 of glucosamine residues in HS that are critical for FGF2 activation. These enzymes were strongly expressed by tumour cells, but only HS6ST1 was found in endothelial cells. Immunostaining with the 3G10 antibody of tissue sections pretreated with heparinases indicated that HS proteoglycans were produced by tumour and endothelial cells. These results indicated that, in contrast to the endothelium, HS produced by tumour cells may be modified by cell-surface heparanase (HPA1) or endosulphatase (SULF). Protein and RNA analysis revealed that HPA1 was strongly expressed by ovarian tumour cells in eight of ten specimens examined. HSULF-1, which removes specific 6-O-sulphate groups from HS, was abundant in tumour cells but weakly expressed in the endothelium. If this enzyme was responsible for the lack of biologically active HS on the tumour cell surface, we would expect exogenous FGF2 binding to be preserved; we showed previously that this was indeed the case although FGF2 binding was reduced compared to the endothelium and stroma. Thus, the combined effects of heparanase and HSULF could account for the lack of biologically active HS in tumour cells rather than deficiencies in the biosynthetic enzymes

In vivo clearance of surfactant lipids during acute pulmonary inflammation.

BACKGROUND: A decrease in pulmonary surfactant has been suggested to contribute to the lung dysfunction associated with pulmonary inflammation. A number of studies have implicated surfactant clearance as a possible mechanism for altered pool sizes. The objective of the current study was to specifically investigate the mechanisms of surfactant clearance in a rodent model of acute pulmonary inflammation. METHODS: Inflammation was induced by intrapulmonary instillation of lipopolysaccharide (LPS: 100 μg/kg). Lipid clearance was assessed at 18 and 72 hours post-LPS instillation by intratracheal administration of radiolabel surfactant-like liposomes 2 hours prior to isolation and analysis of inflammatory cells and type II cells. RESULTS: At both 18 and 72 hours after LPS instillation there was significantly less radioactivity recovered in the lavage fluid compared to respective control groups (p < 0.05). At both time points, the number of cells recovered by lavage and their associated radioactivity was greater compared to control groups (p < 0.01). There was no difference in recovery of radioactivity by isolated type II cells or other cells obtained from enzymatic digestion of lung tissue. CONCLUSION: These results show that increased clearance of surfactant lipids in our model of acute pulmonary inflammation is primarily due to the inflammatory cells recruited to the airspace and not increased uptake by alveolar type II cells

Methane bursts as a trigger for intermittent lake-forming climates on post-Noachian Mars

Lakes existed on Mars later than 3.6 billion years ago, according to sedimentary evidence for deltaic deposition. The observed fluviolacustrine deposits suggest that individual lake-forming climates persisted for at least several thousand years (assuming dilute flow). But the lake watersheds’ little-weathered soils indicate a largely dry climate history, with intermittent runoff events. Here we show that these observational constraints, although inconsistent with many previously proposed triggers for lake-forming climates, are consistent with a methane burst scenario. In this scenario, chaotic transitions in mean obliquity drive latitudinal shifts in temperature and ice loading that destabilize methane clathrate. Using numerical simulations, we find that outgassed methane can build up to atmospheric levels sufficient for lake-forming climates, if methane clathrate initially occupies more than 4% of the total volume in which it is thermodynamically stable. Such occupancy fractions are consistent with methane production by water–rock reactions due to hydrothermal circulation on early Mars. We further estimate that photochemical destruction of atmospheric methane curtails the duration of individual lake-forming climates to less than a million years, consistent with observations. We conclude that methane bursts represent a potential pathway for intermittent excursions to a warm, wet climate state on early Mars

Flow Chemistry Approaches Applied to the Synthesis of Saturated Heterocycles

Continuous-flow processing approaches are having a significant impact on the way we devise and perform chemical synthesis. Flow chemistry has repeatedly demonstrated numerous improvements with respect to synthesis efficiency, process safety and ease of reaction scale-up. In recent years flow chemistry has been applied with remarkable success to the generation of valuable target structures across a range of industries from basic bulk chemical manufacture and materials development to flavours, food and cosmetic applications. However, due to its earlier implementation, it has found so far many more advocates in areas of medicinal and agrochemical research and manufacture. In this review article, we summarise the key developments that continuous-flow synthesis has had in the area of saturated heterocycles, specifically focusing on approaches that generate these important entities from acyclic precursors

The "in and out" of glucosamine 6-O-sulfation: the 6th sense of heparan sulfate.

International audienceThe biological properties of Heparan sulfate (HS) polysaccharides essentially rely on their ability to bind and modulate a multitude of protein ligands. These interactions involve internal oligosaccharide sequences defined by their sulfation patterns. Amongst these, the 6-O-sulfation of HS contributes significantly to the polysaccharide structural diversity and is critically involved in the binding of many proteins. HS 6-O-sulfation is catalyzed by 6-O-sulfotransferases (6OSTs) during biosynthesis, and it is further modified by the post-synthetic action of 6-O-endosulfatases (Sulfs), two enzyme families that remain poorly characterized. The aim of the present review is to summarize the contribution of 6-O-sulfates in HS structure/function relationships and to discuss the present knowledge on the complex mechanisms regulating HS 6-O-sulfation