Cholesterol accumulation caused by low density lipoprotein receptor deficiency or a cholesterol-rich diet results in ectopic bone formation during experimental osteoarthritis

Introduction

Osteoarthritis (OA) is associated with the metabolic syndrome, however the underlying mechanisms remain unclear. We investigated whether low density lipoprotein (LDL) accumulation leads to increased LDL uptake by synovial macrophages and affects synovial activation, cartilage destruction and enthesophyte/osteophyte formation during experimental OA in mice.

Methods

LDL receptor deficient (LDLr^−/−) mice and wild type (WT) controls received a cholesterol-rich or control diet for 120 days. Experimental OA was induced by intra-articular injection of collagenase twelve weeks after start of the diet. OA knee joints and synovial wash-outs were analyzed for OA-related changes. Murine bone marrow derived macrophages were stimulated with oxidized LDL (oxLDL), whereupon growth factor presence and gene expression were analyzed.

Results

A cholesterol-rich diet increased apolipoprotein B (ApoB) accumulation in synovial macrophages. Although increased LDL levels did not enhance thickening of the synovial lining, S100A8 expression within macrophages was increased in WT mice after receiving a cholesterol-rich diet, reflecting an elevated activation status. Both a cholesterol-rich diet and LDLr deficiency had no effect on cartilage damage; in contrast, ectopic bone formation was increased within joint ligaments (fold increase 6.7 and 6.1, respectively). Moreover, increased osteophyte size was found at the margins of the tibial plateau (4.4 fold increase after a cholesterol-rich diet and 5.3 fold increase in LDLr^−/− mice). Synovial wash-outs of LDLr^−/− mice and supernatants of macrophages stimulated with oxLDL led to increased transforming growth factor-beta (TGF-β) signaling compared to controls.

Conclusions

LDL accumulation within synovial lining cells leads to increased activation of synovium and osteophyte formation in experimental OA. OxLDL uptake by macrophages activates growth factors of the TGF-superfamily.     

Caspase-1 deficiency in mice reduces intestinal triglyceride absorption and hepatic triglyceride secretion

Caspase-1 is known to activate the proinflammatory cytokines IL-1β and IL-18. Additionally, it can cleave other substrates, including proteins involved in metabolism. Recently, we showed that caspase-1 deficiency in mice strongly reduces high-fat diet-induced weight gain, at least partly caused by an increased energy production. Increased feces secretion by caspase-1-deficient mice suggests that lipid malabsorption possibly further reduces adipose tissue mass. In this study we investigated whether caspase-1 plays a role in triglyceride-(TG)-rich lipoprotein metabolism using caspase-1-deficient and wild-type mice. Caspase-1 deficiency reduced the postprandial TG response to an oral lipid load, whereas TG-derived fatty acid (FA) uptake by peripheral tissues was not affected, demonstrated by unaltered kinetics of [³H]TG-labeled very low-density lipoprotein (VLDL)-like emulsion particles. An oral gavage of [³H]TG-containing olive oil revealed that caspase-1 deficiency reduced TG absorption and subsequent uptake of TG-derived FA in liver, muscle, and adipose tissue. Similarly, despite an elevated hepatic TG content, caspase-1 deficiency reduced hepatic VLDL-TG production. Intestinal and hepatic gene expression analysis revealed that caspase-1 deficiency did not affect FA oxidation or FA uptake but rather reduced intracellular FA transport, thereby limiting lipid availability for the assembly and secretion of TG-rich lipoproteins. The current study reveals a novel function for caspase-1, or caspase-1-cleaved substrates, in controlling intestinal TG absorption and hepatic TG secretion.     

Effect of Metalaxyl on the incidence and severity of Pearl millet downy mildew disease in Northern Nigeria

Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight.     

Neutralizing Nanobodies Targeting Diverse Chemokines Effectively Inhibit Chemokine Function

Chemokine receptors and their ligands play a prominent role in immune regulation but many have also been implicated in inflammatory diseases such as multiple sclerosis, rheumatoid arthritis, allograft rejection after transplantation, and also in cancer metastasis. Most approaches to therapeutically target the chemokine system involve targeting of chemokine receptors with low molecular weight antagonists. Here we describe the selection and characterization of an unprecedented large and diverse panel of neutralizing Nanobodies (single domain camelid antibodies fragment) directed against several chemokines. We show that the Nanobodies directed against CCL2 (MCP-1), CCL5 (RANTES), CXCL11 (I-TAC), and CXCL12 (SDF-1α) bind the chemokines with high affinity (at nanomolar concentration), thereby blocking receptor binding, inhibiting chemokine-induced receptor activation as well as chemotaxis. Together, we show that neutralizing Nanobodies can be selected efficiently for effective and specific therapeutic treatment against a wide range of immune and inflammatory diseases.     

Rainfall,geology and landscape position generate large‐scale spatiotemporal fire pattern heterogeneity in an African savanna

Fire is considered a critical management tool in fire prone landscapes. Often studies and policies relating to fire focus on why and how the fire regime should be managed, often neglecting to subsequently evaluate management's ability to achieve these objectives over long temporal and large spatial scales. This study explores to what extent the long‐term spatio‐temporal fire patterns recorded in the Kruger National Park, South Africa has been influenced by management policies and to what extent it was dictated by underlying variability in the abiotic template. This was done using a spatially explicit fire‐scar database from 1941 to 2006 across the 2 million ha Park. Fire extent (ha burnt per annum) 1) is correlated with rainfall cycles 2) exhibits no long‐term trend and 3) is largely non‐responsive to prevailing fire management policies. Rainfall, geology and distance from the closest perennial river and the interactions between these variables influence large‐scale fire pattern heterogeneity: areas with higher rainfall, on basaltic substrates and far from rivers are more fire prone and have less heterogeneous fire regimes than areas with lower rainfall, on granitic substrates and closer to rivers. This study is the first to illustrate that under a range of rainfall and geological conditions, perennial rivers influence long‐term, landscape‐scale fire patterns well beyond the riparian zone (typically up to 15 km from the river). It was concluded that despite fire management policies which historically aimed for largely homogeneous fire return regimes, spatially and temporally heterogeneous patterns have emerged. This is primarily because of differences in rainfall, geology and distance from perennial rivers. We postulate that large‐scale spatio‐temporal fire pattern heterogeneity is implicit to heterogeneous savannas, even under largely homogenizing fire policies. Management should be informed by these patterns, embracing the natural heterogeneity‐producing template. We therefore suggest that management actions will be better directed when operating at appropriate scales, nested within the broader implicit landscape patterns, and when focusing on fire regime parameters over which they have more influence (e.g. fire season).     

Differences amongAGT1-encoded α-glucoside transporters and their ability to transport maltotriose inSaccharomyces yeasts

Improved fermentation of starch and its dextrin products would benefit the brewing and whiskey industries. Most strains ofSaccharomyces ferment glucose and maltose and partially ferment maltotriose, but are unable to utilise the larger dextrin products of starch. This utilisation pattern is partly attributed to the ability of yeast cells to transport the aforementioned mono-, di- and trisaccharides into the cytosol. The maltotriose transporting efficiency varies between differentSaccharomyces strains. In this study, severalSaccharomyces strains, including whiskey strains, were screened for growth on maltotriose. TheAGT1 genes, which encode a maltose transporter that show affinity for maltotriose uptake, were isolated from the strains that grew strongest in media with maltotriose as sole carbon source. The isolatedAGT1 alleles were sequenced and their chromosomal locations determined in the strains from which they were cloned. Nucleotide and deduced amino acid sequences of the isolated genes shared 95% and 98% identity, respectively. The efficiency of maltotriose transport was determined by expressing theAGT1 variants in an identical genetic background. TheK _m values obtained for all the permeases were very similar (≈3), but the permease with improved performance for maltotriose transport showed an approximately 30% higherV _max value than for the others. The data obtained suggest that the genetic variation among theAGT1-encoded transporters is reason for the variation in maltotriose transport efficiency among differentSaccharomyces strains. This study offers prospects for the development of yeast strains with improved maltose and maltotriose uptake capabilities that, in turn, could increase the overall fermentation efficiencies in the beer and whiskey industries.     

Increased permeability-oedema and atelectasis in pulmonary dysfunction after trauma and surgery: a prospective cohort study

We have developed a two-step procedure for preparing the skin before peripheral venous catheter (PVC) insertions. This procedure involves two successive swabbings with wipes soaked in alcoholic antiseptic. We investigated whether this two-step procedure was as effective and safe as the standard four-step procedure – washing with detergent, rinsing, drying, applying antiseptic – by carrying out a multicentre randomised equivalence study comparing the frequency of precursor signs of infection at the site of insertion for the two skin preparation procedures. The study was carried out over an eight-month period, and 248 PVC insertion sites were evaluated. The two-step procedure was used for 130 subjects and the standard procedure for 118. Taking into account all the confounding factors predisposing patients to the complications studied, the characteristics of the two groups of patients were found to be similar, with no significant differences noted. The incidence of precursor signs of infection was 11 % 24 hours after PVC insertion (27/248), 25 % at 48 hours (50/203) and at 29 % at 72 hours (34/119). Eleven patients had complications necessitating the withdrawal of the PVC: sensitivity of the insertion site, with redness and/or slight swelling and/or a palpable venous cord. No major complications were observed in this study. The frequency of local complications associated with PVCs reported in this study, whether simple or severe, was not affected by the skin preparation procedure used for PVC insertion (two-step or four-step procedure).     

Metabolic and chemical properties of basic proteins isolated from nuclei of rat liver and thymus gland

1. The effects of alkylating agents and disulphides on the thiol-containing proteins of nuclei from rat thymus and liver were studied. Three protein fractions were examined: histones extracted with 50mm- and 250mm-hydrochloric acid and the residual protein. None of the reagents selectively reacted with any one of the protein fractions. 2. Amino acid uptake in vitro into the histones of nuclei from rat thymus was analysed by preparative electrophoresis of the proteins extracted with 50mm- and 250mm-hydrochloric acid. After 1hr. at 37° the greater incorporation was into the proteins extracted with 50mm-hydrochloric acid. 3. Preparative electrophoresis was used to study the relative thiol contents of the proteins of the 50mm-hydrochloric acid extract from thymus nuclei by labelling the histones in vitro with ¹⁴C-labelled N-ethylmaleimide. 4. The capacity of the proteins extracted from rat thymus with 50mm- and 250mm-hydrochloric acid, and of the components from these extracts separated by preparative electrophoresis, to combine with DNA and to depress DNA-dependent RNA synthesis was studied. The histones extracted with 50mm-hydrochloric acid were more lysine-rich than those extracted with 250mm-hydrochloric acid. Wide variations were found in the abilities of the separated components to depress RNA synthesis.