ORP-3, a human oxysterol-binding protein gene differentially expressed in hematopoietic cells

Using differential display polymerase chain reaction, a gene was identified in CD34+-enriched populations that had with low or absent expression in CD34- populations. The full coding sequence of this transcript was obtained, and the predicted protein has a high degree of homology to oxysterol-binding protein. This gene has been designated OSBP-related protein 3 (ORP-3). Expression of ORP-3 was found to be 3- to 4-fold higher in CD34+ cells than in CD34- cells. Additionally, expression of this gene was 2-fold higher in the more primitive subfraction of hematopoietic cells defined by the CD34+38- phenotype and was down-regulated with the proliferation and differentiation of CD34+ cells. The ORP-3 predicted protein contains an oxysterol-binding domain. Well-characterized proteins expressing this domain bind oxysterols in a dose-dependent fashion. Biologic activities of oxysterols include inhibition of cholesterol biosynthesis and cell proliferation in a variety of cell types, among them hematopoietic cells. Characterization and differential expression of ORP-3 implicates a possible role in the mediation of oxysterol effects on hematopoiesis.

Role of the ATP-binding cassette drug transporters in the intestinal absorption of tanshinone IIB, one of the major active diterpenoids from the root of Salvia miltiorrhiza

There is an increasing use of herbal medicines worldwide, and the extracts from the root of Salvia miltiorrhiza are widely used in the treatment of angina and stroke. In this study, we investigated the mechanism for the intestinal absorption of tanshinone IIB (TSB), a major constituent of S. miltiorrhiza. The oral bioavailability of TSB was about 3% in rats with less proportional increase in its maximum plasma concentration (C_max) and area under the plasma concentration-time curve (AUC) with increasing dosage. The time to C_max (T_max) was prolonged at higher oral dosage. In a single pass rat intestinal perfusion model, the permeability coefficients (P_app) based on TSB disappearance from the lumen (P_lumen) were 6.2- to 7.2-fold higher (p < 0.01) than those based on drug appearance in mesenteric venous blood (P_blood). The uptake and efflux of TSB in Caco-2 cells were also significantly altered in the presence of an inhibitor for P-glycoprotein (PgP) or for multi-drug resistance associated protein (MRP1/2). TSB transport from the apical (AP) to basolateral (BL) side in Caco-2 monolayers was 3.3- to 5.7-fold lower than that from BL to AP side, but this polarized transport was attenuated by co-incubation of PgP or MRP1/2 inhibitors. The P_app values of TSB in the BL-AP direction were significantly higher in MDCKII cells over-expressing MDR1 or MRP1, but not in cells over-expressing MRP2-5, as compared with the wild-type cells. The plasma AUC_0-24hr in mdr1a and mrp1 gene-deficient mice was 10.2- to 1.7-fold higher than that in the wild-type mice. Furthermore, TSB significantly inhibited the uptake of digoxin and vinblastine in membrane vesicles containing PgP or MRP1. TSB also moderately stimulated PgP ATPase activity. Taken collectively, our findings indicate that TSB is a substrate for PgP and MRP1 and that drug resistance to TSB therapy and drug interactions may occur through PgP and MRP1 modulation.

Bovine muc1 inhibits binding of enteric bacteria to caco-2 cells

Inhibition of bacterial adhesion to intestinal epithelial receptors by the consumption of natural food components is an attractive strategy for the prevention of microbial related gastrointestinal illness. We hypothesised that Muc1, a highly glycosylated mucin present in cows’ milk, may be one such food component. Purified bovine Muc1 was tested for its ability to inhibit binding of common enteric bacterial pathogens to Caco-2 cells grown in vitro. Muc1 caused dose-dependent binding inhibition of Escherichia coli, Salmonella enterica serovar Typhimurium (S. Typhimurium), Staphylococcus aureus and Bacillus subtilis. This inhibition was more pronounced for the Gram negative compared with Gram positive bacteria. It was also demonstrated that Muc1, immobilised on a membrane, bound all these bacterial species in a dose-dependent manner, although there was greater interaction with the Gram negative bacteria. A range of monosaccharides, representative of the Muc1 oligosaccharide composition, were tested for their ability to prevent binding of E. coli and S. Typhimurium to Caco-2 cells. Inhibition was structure dependent with sialic acid, L(-) fucose and D(+) mannose significantly inhibiting binding of both Gram negative species. N-acetylglucosamine and N-acetylgalactosamine significantly inhibited binding of E. coli whilst galactose, one of the most abundant Muc1 monosaccharides, showed the strongest inhibition against S. Typhimurium. Treatment with sialidase significantly decreased the inhibitory properties of Muc1, demonstrating the importance of sialic acid in adhesion inhibition. It is concluded that bovine Muc1 prevents binding of bacteria to human intestinal cells and may have a role in preventing the binding of common enteropathogenic bacteria to human intestinal epithelial surfaces.

Polymorphisms affecting vitamin D-binding protein modify the relationship between serum vitamin D (25[OH]D3) and food allergy

BACKGROUND: There is evolving evidence that vitamin D insufficiency may contribute to food allergy, but findings vary between populations. Lower vitamin D-binding protein (DBP) levels increase the biological availability of serum vitamin D. Genetic polymorphisms explain almost 80% of the variation in binding protein levels. OBJECTIVE: We sought to investigate whether polymorphisms that lower the DBP could compensate for adverse effects of low serum vitamin D on food allergy risk. METHODS: From a population-based cohort study (n = 5276) we investigated the association between serum 25-hydroxyvitamin D3 (25[OH]D3) levels and food allergy at age 1 year (338 challenge-proven food-allergic and 269 control participants) and age 2 years (55 participants with persistent and 50 participants with resolved food allergy). 25(OH)D3 levels were measured using liquid chromatography-tandem mass spectrometry and adjusted for season of blood draw. Analyses were stratified by genotype at rs7041 as a proxy marker of DBP levels (low, the GT/TT genotype; high, the GG genotype). RESULTS: Low serum 25(OH)D3 level (≤50 nM/L) at age 1 years was associated with food allergy, particularly among infants with the GG genotype (odds ratio [OR], 6.0; 95% CI, 0.9-38.9) but not in those with GT/TT genotypes (OR, 0.7; 95% CI, 0.2-2.0; P interaction = .014). Maternal antenatal vitamin D supplementation was associated with less food allergy, particularly in infants with the GT/TT genotype (OR, 0.10; 95% CI, 0.03-0.41). Persistent vitamin D insufficiency increased the likelihood of persistent food allergy (OR, 12.6; 95% CI, 1.5-106.6), particularly in those with the GG genotype. CONCLUSIONS: Polymorphisms associated with lower DBP level attenuated the association between low serum 25(OH)D3 level and food allergy, consistent with greater vitamin D bioavailability in those with a lower DBP level. This increases the biological plausibility of a role for vitamin D in the development of food allergy.

Amoebiasis vaccine development: a snapshot on E. histolytica with emphasis on perspectives of Gal/GalNAc lectin

Amoebiasis/amebiasis is a gastrointestinal infection caused by an enteric dwelling protozoan, Entamoeba histolytica. The disease is endemic in the developing world and is transmitted mainly via the faecal-oral route (e.g., in water or food) and may or may not be symptomatic. This disease of socio-economic importance worldwide involves parasite adherence and cytolysis of human cells followed by invasion that is mediated by galactose-binding (Gal/GalNAc) surface lectin. Disruption of the mucus layer leads to invasive intestinal and extraintestinal infection. Gal-lectin based vaccinations have conferred protection in various animal models against E. histolytica infections. Keeping in view the pivotal role of Gal/GalNAc lectin in amoebiasis vaccine development, its regulation, genomic view of the parasite involving gene conversion in lectin gene families, current knowledge about involvement of Gal/GalNAc lectin in adherence, pathogenicity, signalling, encystment, generating host immune response, and in turn protozoa escape strategies, and finally its role as effective vaccine candidate has been described. This review will help researchers to explore pathogenesis mechanism along with genomic studies and will also provide a framework for future amoebiasis vaccine development studies.

Protozoa lectins and their role in host-pathogen interactions

Lectins are proteins/glycoproteins of non-immune origin that agglutinate red blood cells, lymphocytes, fibroblasts, etc., and bind reversibly to carbohydrates present on the apposing cells. They have at least two carbohydrate binding sites and their binding can be inhibited by one or more carbohydrates. Owing to carbohydrate binding specificity of lectins, they mediate cell-cell interactions and play role in protozoan adhesion and host cell cytotoxicity, thus are central to the pathogenic property of the parasite. Several parasitic protozoa possess lectins which mediate parasite adherence to host cells based on their carbohydrate specificities. These interactions could be exploited for development of novel therapeutics, targeting the adherence and thus helpful in eradicating wide spread of protozoan diseases. The current review highlights the present state knowledge with regard to protozoal lectins with an emphasis on their haemagglutination activity, carbohydrate specificity, characteristics and also their role in pathogenesis notably as adhesion molecules, thereby aiding the pathogen in disease establishment.