Influence of extracellular matrix proteins on the development of cultured human dendritic cells

The development of dendritic cells (DC) is still only partly understood. Recently established culture systems using CD34+ cells or monocytes as precursor cells for the generation of DC indicate the necessity of pro-inflammatory cytokines for their development. In vivo the contact to other cells or to the proteins of the extracellular matrix might also be essential for their development. In our experiments we used granulocyte-macrophage colony-stimulating factor- and IL-4-treated human monocytes as precursor cells to investigate the interaction of DC at different maturation stages with the matrix proteins fibronectin, collagen type I and collagen type IV. We demonstrate a strong beta1-integrin-mediated adherence of immature DC to fibronectin that is lost completely during maturation. The binding to collagen type I was less strong but induced a maturation of the precursor cells. After 3 days of culture on this protein, the cells showed all features of fully matured DC such as expression of CD83 and an excellent allostimulatory capacity. The reason for this effect was shown to be the induction of TNF-alpha production by the DC themselves. In contrast to the adhesion to fibronectin, the maturation and the cytokine production of DC induced by collagen type I could not be inhibited by blocking of beta1-integrins. These results indicate that proteins of the extracellular matrix play an important role in the development and function of human DC.     

Decreased production and increased catabolism of apolipoprotein B-100 in apolipoprotein B-67/B-100 heterozygotes

Apolipoprotein (apo) B-67 is a truncated form of apoB-100 due to deletion of an adenine at cDNA 9327. Heterozygotes have one allele making apoB-100; therefore, plasma apoB levels would be predicted to be at least 50% of normal. However, apoB-67 heterozygotes have total plasma apoB levels that are 24% of normal. To determine the mechanisms responsible for the lower-than-expected levels of apoB, in vivo kinetics of apoB-100 were performed in three apoB-67/apoB-100 heterozygotes and compared with those of six control subjects by using a primed-constant infusion of [5,5,5-2H3]leucine in the fed state. Kinetic parameters were calculated by multicompartmental modeling of the data. The mean total apoB plasma concentration of the apoB-67 subjects was 21.8+/-6.1 mg/dL, or 24% of that of control subjects (89.6+/-24.1 mg/dL, P=.002). ApoB-67 subjects had lower mean VLDL apoB-100 production rates (3.6+/-1.2 versus 13.9+/-3.5 mg x kg(-1) x d(-1), P=.002) and lower mean transport rates of apoB-100 into LDL (3.5+/-1.4 versus 12.6+/-4.1 mg x kg(-1) x d(-1), P=.008) compared with control subjects. The transport rate into IDL was not significantly different (1.2+/-0.5 versus 6.2+/-4.0 mg x kg(-1) x d(-1), P=.07). The fractional catabolic rate of VLDL apoB-100 was significantly higher in apoB-67 subjects than in control subjects (18.1+/-8.6 versus 7.6+/-1.6 mg x kg(-1) x d(-1), P=.017). ApoB-100 IDL and LDL fractional catabolic rates were not significantly different. VLDL apoB-100 pool size in apoB-67 subjects was 11% of that of control subjects (15.8+/-7.7 versus 141.6+/-33.7 mg, P=.0004) due to a 74% lower production rate (26% of control values) and a 2.4-fold higher fractional catabolic rate. LDL apoB-100 pool size in apoB-67 subjects was 22% of that of control subjects (665.3+/-192.4 versus 2968.3+/-765.2 mg, P=.002) due primarily to a lower production rate (27% of control values). Thus, both decreased production of VLDL and LDL apoB-100 and increased catabolism of VLDL apoB-100 are responsible for the low levels of apoB-100 in apoB-67 subjects.     

Steroid receptor measurement in breast cancers: comparison between ligand binding and enzyme-immunoassay in cytosolic and nuclear extracts

We have analysed cytoplasmic and nuclear extracts of breast-cancer tissue from a total of 799 patients, measuring both oestrogen and progesterone receptors (ER, PR) using either the ligand binding assay (LBA) or the enzyme immunoassay technique (EIA). Mean and median receptor levels were much lower than those widely reported by others. For ER, this may in part be a consequence of the younger median age of the patient group. The frequency of positivity, using consensus cut-off values for clinical evaluation, was also lower than that reported by the EORTC Receptor Study Group. Although the measurements comparing the 2 methods were statistically correlated in terms of positivity, based on the above criteria for clinical assessment, concordance was considered to be relatively poor, particularly for ER when assayed in the same samples by the 2 methods. In cytosolic but not nuclear extracts, the LBA method gave a higher median value for ER than the EIA (except in the group that had EIA values greater than 15 fmol/mg protein); for PR, median values were higher with EIA in both cell fractions. There was an excellent correlation between receptor amounts in cytosolic and nuclear extracts for both ER and PR using the EIA; this was significantly better than with LBA. We also observed a correlation between ER and PR in both cytosolic and nuclear fractions which was most pronounced when the analysis was done by EIA. The amounts of ER in the cytosolic fraction were also correlated with the those of PR in the nuclear fraction and ER in the nuclear fraction with PR in the cytosolic fraction, but only when the EIA method was used. We conclude that the EIA method appears to be more sensitive and gives biologically more reliable results. However, the disagreement between the methods may be due to legitimate recognition of altered forms of the receptor and may be of biological significance. Although the presence of receptor in the cytosolic fraction is artifactual, its measurement by EIA does parallel the amounts of nuclear receptor, which may be a more relevant biological parameter.     

Serum ionic fluoride levels in haemodialysis and continuous ambulatory peritoneal dialysis patients

High serum fluoride (F-) in patients with chronic renal failure (CRF) and end-stage renal disease (ESRD) is associated with risk of renal osteodystrophy and other bone changes. This study was done to determine F- in normal healthy controls and patients with ESRD on haemodialysis (HD) or peritoneal dialysis (PD). Seventeen healthy controls (12 males, 5 females) and 39 ESRD patients on dialysis (17 males, 22 females) were recruited in the study in a community with 47.4 +/- 3.28 microM/l (range 44-51 microM/l) of F- content in drinking water. Control subjects showed a mean serum F- concentration of 1.08 +/- 0.350 microM/l. Males in control group showed slightly higher F- levels (1.15 +/- 0.334, range 0.55-1.9 microM/l) than females (0.92 +/- 0.370, range 0.6-1.5 microM/l). Mean serum F- concentration did not correlate significantly with age and sex among control subjects, whereas such correlation was observed in patients with ESRD on dialysis. Mean serum F- concentration was significantly higher in patients on dialysis (2.67 +/- 1.09, range 0.8-5.2 microM/l) than normal controls. When grouped according to sex, the mean serum F- concentration in males (3.05 +/- 1.04, range 1.8-5.2 microM/l) was significantly higher than females (2.38 +/- 1.08, range 0.8-5.2 microM/l). When patients were grouped according to age, it was observed that F- concentration was significantly higher in patients with age groups 21-70 (2.86 +/- 1.05) than those with age group 13-20 years (1.42 +/- 0.531). Thus F- concentration correlated with age and sex, being higher in males and above 20 years. Despite appreciable clearance of F- (39-90%) across the peritoneum, patients on CAPD showed higher serum F- concentration than those on HD (3.1 +/- 1.97 vs 2.5 +/- 1.137 microM/l). Of the total 39 patients on dialysis 39% had their serum F- concentration above 3.0 microM/l, posing the risk of renal osteodystrophy.     

BBB transport and P-glycoprotein functionality using MDR1A (-/-) and wild-type mice. Total brain versus microdialysis concentration profiles of rhodamine-123

PURPOSE: The effect of P-glycoprotein (Pgp) on brain distribution using mdr1a (-/-) mice was investigated. METHODS: Fluorescein (Flu) and FD-4 were used to check whether blood-brain barrier (BBB) integrity was maintained in mdr1a (-/-) mice. The Pgp substrate rhodamine-123 (R123) was infused and total brain, blood and brain microdialysate concentrations in mdr1a (-/-) mice and wild-type mice were compared. RESULTS: Maintenance of BBB integrity was indicated by equal total brain/blood ratios of Flu and FD-4 in both mice types. R123 concentrations in brain after i.v. infusion were about 4-fold higher in mdr1a (-/-) than in wild-type mice (P < 0.05), without changes in blood levels. After microdialysis experiments the same results were found, excluding artifacts in the interpretation of Pgp functionality by the use of this technique. However the 4-fold ratio in brain was not reflected in corresponding microdialysates. No local differences of R123 in the brain were found. By the no-net-flux method in vivo recovery appeared to 4.6-fold lower in mdrla (-/-) mice compared with wild-type mice. CONCLUSIONS: Pgp plays an important role in R123 distribution into the brain. Using intracerebral microdialysis, changes in in vivo recovery by the absence or inhibition of Pgp (or active efflux in general) need to be considered carefully.     

Nuclear protein import is decreased by engineered mutants of nuclear transport factor 2 (NTF2) that do not bind GDP-Ran

Nuclear transport factor 2 (NTF2) is associated with the translocation stage of nuclear protein import and binds both to nuclear pore proteins (nucleoporins) containing phenylalanine-rich repeats and to the Ras family GTPase Ran. In this study we probed the role of the NTF2-Ran interaction in nuclear protein import using site-directed mutants of NTF2 that interfere with its interaction with GDP-Ran. The design of these mutants was based on the X-ray crystal structure of NTF2 and was concentrated on conserved residues in and around the molecule's hydrophobic cavity. The mutant NTF2 cDNAs were expressed in Escherichia coli. Purified mutant proteins retained the interaction with FxFG-repeat nucleoporins, but several mutants in the negatively charged residues that surround the NTF2 cavity or in residues in the cavity itself were unable to bind GDP-Ran in vitro. The crystal structure of the E42K mutant protein showed significant structural changes only in this side-chain, indicating that it participated directly in the interaction with GDP-Ran. In permeabilised cell nuclear protein import assays, only wild-type NTF2 and mutants that bound GDP-Ran were functional. Furthermore, when the NTF2 E42K and D92N/D94N NTF2 mutants that failed to bind GDP-Ran in vitro were substituted for the chromosomal yeast NTF2, the yeast cells became non-viable, whereas yeast substituted with wild-type human NTF2 remained viable. We conclude that interaction between NTF2 and GDP-Ran is important for efficient nuclear protein import.