A site-specific analysis of the implications of a changing ozone profile and climate for stomatal ozone fluxes in Europe

In this study, we used eight sites from across Europe to investigate the implications of a future climate (2 °C warmer and 20% drier) and a changing ozone profile (increased background concentrations and reduced peaks) on stomatal ozone fluxes of three widely occurring plant species. A changing ozone profile with small increases in background ozone concentrations over the course of a growing season could have significant impacts on the annual accumulated stomatal ozone uptake, even if peak concentrations of ozone are reduced. Predicted increases in stomatal ozone uptake showed a strong relationship with latitude and were larger at sites from northern and mid-Europe than those from southern Europe. At the sites from central and northern regions of Europe, including the UK and Sweden, climatic conditions were highly conducive to stomatal ozone uptake by vegetation during the summer months and therefore an increase in daily mean ozone concentration of 3–16% during this time of year (from increased background concentrations, reduced peaks) would have a large impact on stomatal ozone uptake. In contrast, during spring and autumn, the climatic conditions can limit ozone uptake for many species. Although small increases in ozone concentration during these seasons could cause a modest increase in ozone uptake, for those species that are active at low temperatures, a 2 °C increase in temperature would increase stomatal ozone uptake even in the absence of further increases in ozone concentration. Predicted changes in climate could alter ozone uptake even with no change in ozone profile. For some southern regions of Europe, where temperatures are close to or above optimum for stomatal opening, an increase in temperature of 2 °C could limit stomatal ozone uptake by enhancing stomatal closure during the summer months, whereas during the spring, when many plants are actively growing, a small increase in temperature would increase stomatal ozone uptake

Ozone critical levels for (semi-)natural vegetation dominated by perennial grassland species

New critical levels for ozone based on accumulated flux through stomata (phytotoxic ozone dose, POD), for temperate perennial grassland (semi-)natural vegetation, have been agreed for use within the Convention on Long-Range Transboundary Air Pollution. These were based on data from several experiments conducted under naturally fluctuating environmental conditions that were combined and analysed to give linear dose-response relationships. Dose-response functions and flux-based critical levels were derived based on biomass and flower number. These parameters showed a statistically significant decline with increasing accumulated stomatal ozone flux. The functions and critical levels derived are based on sensitive species and can be used for risk assessments of the damaging effect of ozone on temperate vegetation communities dominated by perennial grassland species. The critical level based on flower number was lower than that for biomass, representing the greater sensitivity of flower number to ozone pollution

Updated stomatal flux and flux-effect models for wheat for quantifying effects of ozone on grain yield, grain mass and protein yield

Field measurements and open-top chamber experiments using nine current European winter wheat cultivars provided a data set that was used to revise and improve the parameterisation of a stomatal conductance model for wheat, including a revised value for maximum stomatal conductance and new functions for phenology and soil moisture. For the calculation of stomatal conductance for ozone a diffusivity ratio between O3 and H2O in air of 0.663 was applied, based on a critical review of the literature. By applying the improved parameterisation for stomatal conductance, new flux-effect relationships for grain yield, grain mass and protein yield were developed for use in ozone risk assessments including effects on food security. An example of application of the flux model at the local scale in Germany shows that negative effects of ozone on wheat grain yield were likely each year and on protein yield in most years since the mid 1980s

Influence of the CXCL1 rs4074 A allele on alcohol induced cirrhosis and HCC in patients of European descent

BACKGROUND AND AIMS: CXCL1 (CXC chemokine-ligand-1) is a ligand for CXC chemokine receptor 2 expressed on hepatic stellate cells (HSC). Thus, CXCL1 might contribute to HSC activation and fibrogenesis. In the present study, we investigated the influence of the CXCL1 rs4074 polymorphism on the occurrence of alcohol induced liver cirrhosis and hepatocellular carcinoma (HCC). METHODS: The study involved 458 patients with alcoholic cirrhosis (170 with HCC), 115 alcoholics without liver disease and 342 healthy controls. All subjects were genotyped for the CXCL1 rs4074 polymorphism and CXCL1 serum levels of 132 patients were measured. In vitro CXCL1 secretion in TLR-transfected cell lines were studied by ELISA. RESULTS: Distribution of the CXCL1 genotypes (GG/GA/AA) was 159/219/80 in patients with alcoholic cirrhosis, 52/44/19 in alcoholic controls and 158/140/44 in healthy controls. Patients with alcohol-induced cirrhosis were significantly more often carriers of the CXCL1 rs4074 A allele (65.3%) than alcoholics without liver disease (54.8%, OR=1.55; 95%CI=1.025-2.350; p=0.04) and healthy controls (53.8%, OR=1.62; 95%CI=1.212-2.151; p=0.001). Accordingly, the frequency of the CXCL1 rs4074 A allele was significantly higher in the cirrhotic patients than in the subjects without cirrhosis (41.4% vs. 33.9%, OR=1.38, 95% CI:1.14-1.66, p=0.001). Furthermore cirrhotic carriers of the CXCL1 rs4074 A allele had significantly higher CXCL1 serum levels than carriers of the GG genotype. In contrast to sera from healthy controls, sera from patients with alcoholic cirrhosis induced CXCL1 secretion in TLR2- (p=0.016) and TLR4- (p=0.008) transfected HEK293 cells. This finding indicates that sera from patients with alcoholic cirrhosis contain soluble ligands that can induce CXCL1 production via stimulation of TLRs. CONCLUSION: The enhanced CXCL1 serum levels in carriers of the rs4074 A allele together with their increased frequency in patients with alcohol induced cirrhosis suggest the CXCL1 rs4074 A allele as a genetic risk factor for alcoholic cirrhosis

CXCL1 serum levels in patients with alcoholic cirrhosis and healthy controls with distinct <i>CXCL1</i>

<div><p><b>rs4074 genotypes</b>. </p> <p>This figure shows CXCL1 serum concentrations in 66 healthy controls (grey columns) and in 66 patients with alcoholic cirrhosis (black columns) stratified with respect to rs4074 variants G/G, G/A and A/A. Results are shown as means ± standard errors. Groups were compared with the Mann-Whitney U test. </p></div

In Vitro CXCL1 induction in TLR2- and TLR4-transfected HEK293 cells.

<p>HEK293 cells stably transfected with human TLR2 (HEK/TLR2) and human TLR4 (HEK/TLR4) as well as untransfected HEK293 cells (HEK -) were incubated with sera from patients with alcoholic cirrhosis (box plots on the right side) and sera from healthy controls (box plots on the left side). Stimulation with sera from cirrhotic patients showed significantly enhanced CXCL1 secretion in the TLR2- and TLR4-transfected cells but not in the un-transfected control cells. In contrast, sera from healthy controls did not up-regulate CXCL1 secretion in the TLR2- and TLR4-transfected HEK293 cells. P values were calculated using Mann-Whitney U test.</p

Frequency of the rs4074 A allele in the study groups.

<p>This figure illustrates that carriers of the <i>CXCL1 </i><i>rs4074</i> A allele were equally frequent in patients with alcohol related cirrhosis without and with HCC, but overrepresented in comparison to patients with alcohol abuse without liver damage and to healthy controls. Statistical significances refer to Fisher´s exact test.</p

Upregulation of fibrosis markers in human HSC after stimulation with CXCL1.

<p>After incubation with and without 250pg/ml recombinant CXCL1 for 16 hours, human HSC were stained for α-SMA and Collagen type I and analysed by flow cytometry. This representative set of histograms shows that α-SMA and Collagen type I expression increases after CXCL1 stimulation (solid lines) as compared to the unstimlated controls (dotted line).</p