Interaction of endostatin with integrins implicated in angiogenesis

Endostatin, a fragment of collagen XVIII, is a potent antagonist of angiogenesis and inhibitor of tumor growth in mouse models. At present, the mechanism of action of endostatin is unknown. We show here that recombinantly produced human endostatin interacts with alpha(5)- and alpha(v)-integrins on the surface of human endothelial cells. We further demonstrate that the endostatin-integrin interaction is of functional significance in vitro, as we found that immobilized endostatin supports endothelial cell survival and migration in an integrin-dependent manner. Soluble endostatin in turn inhibits integrin-dependent endothelial cell functions, such as cell migration. Taken together, these results implicate integrins as potential targets for endostatin function and support the importance of integrins in endothelial cell biology and angiogenesis.

Genetic variation in the amino-terminal part of apolipoprotein B: studies in hyperlipidemic patients

Hypertriglyceridemia is a heterogeneous lipid disorder often running in families. Variation in the apolipoprotein B (apo B) gene has been associated with serum triglyceride levels. Recently, a role of the amino-terminal end of apo B in binding with lipoprotein lipase (LPL) has been suggested. We screened the 5' end of the apo B gene in 76 Finnish severely hypertriglyceridemic (> 6 mmol/l) patients, using a single-strand conformation polymorphism (SSCP) screening method. We detected a previously unreported polymorphic C2316-->A change, causing a Val703-->Ile substitution. The minor 703 Ile allele frequency was 0.04 in hypercholesterolemic and normolipidemic population samples. This allele was associated with lower serum triglyceride levels in a normolipidemic population sample. Analysis of two previously reported polymorphisms also located in the amino-terminal domain of apo B (Thr71-->Ile and Val591-->Ala) revealed elevating effects on serum apo B concentrations in hypertriglyceridemic individuals. The 591 Ala allele was associated with elevated apo B (P=0.011), and individuals with both minor alleles (apo B 591 Ala + and apo B 71 Ile +) had higher apo B levels compared to subjects homozygous for both common alleles (P=0.004). Although no DNA sequence change seemed to be the cause of hypertriglyceridemia in our patients, genetic variation in the 5' end of the apo B gene may contribute to changes in serum apo B levels in hypertriglyceridemic patients.

Treatment of hypercholesterolemia and combined hyperlipidemia with simvastatin and gemfibrozil in patients with NIDDM. A multicenter comparison study

OBJECTIVE

To compare the lipid-lowering efficacies of simvastatin and gemfibrozil in NIDDM patients with combined (mixed) hyperlipidemia (CHL) or isolated hypercholesterolemia (IHC).

RESEARCH DESIGN AND METHODS

Patients with primary dyslipidemia and NIDDM were recruited for this double-blind, double-dummy comparison study from 10 Finnish centers. After a 4-week placebo run-in period, they were randomly assigned to simvastatin or gemfibrozil. The simvastatin group (n = 47) received 10 mg once nightly for 8 weeks, 20 mg for the next 8 weeks, and 40 mg for the third 8-week period. The gemfibrozil group (n = 49) received 600 mg twice daily throughout the 24 weeks. The lipid-lowering efficacies of both drugs were compared in all patients as well as separately in patients with CHL and IHC.

RESULTS

In all patients, simvastatin reduced LDL and total cholesterol and the LDL-to-HDL cholesterol ratio more effectively, whereas gemfibrozil was more effective in elevating HDL cholesterol and decreasing triglyceride levels. The drug effects differed according to lipid phenotype at baseline. Simvastatin decreased LDL cholesterol levels by 30-40% in both phenotypes. Gemfibrozil caused a 15% reduction in LDL cholesterol in IHC but no change in CHL patients. Simvastatin produced 15-30% reductions in triglyceride levels in CHL but no change in IHC patients. Gemfibrozil caused reductions in triglycerides in CHL (50% and more) and in IHC (40%) patients, with 12-18% increases in HDL cholesterol in these groups.

CONCLUSIONS

Simvastatin is useful in both CHL and IHC patients, whereas gemfibrozil can be used in patients with high triglyceride and low or normal LDL cholesterol levels.

Screening of the 3' two-thirds of the coding area of the apo B gene in Finnish hypercholesterolemic patients report of six new genetic variants

Hypercholesterolemia clustering in families not explained by either low density lipoprotein (LDL)-receptor mutations producing familial hypercholesterolemia (FH), or the apolipoprotein B (apo B) Arg3500-->Gln mutation with familial defective apo B (FDB), is common in the Finnish population. In search of previously unknown apo B mutations, we screened exons 26 to 29 of the apo B gene in 68 Finnish severely hypercholesterolemic (> or = 8 mmol/l) non-FH, non-FDB patients, using a single-strand conformation polymorphism analysis based screening method. Four rare and two polymorphic previously unreported DNA variations were detected. The rare variants were a three-nucleotide deletion, with the deletion of Asp2186, an A11961-->G change leading to a Thr3918-->Ala change, a T12922-->G change causing a Val4238-->Ala substitution, and a neutral T12935-->C change leading to a new RsaI cutting site. The polymorphic G12937-->C and G13569-->A changes leading to Arg4243-->Thr and Ala4454-->Thr substitutions, respectively, had minor allele frequencies of 0.03 and 0.02. None of these variants seemed to explain the hyperlipidemia in these patients. A major Finnish mutation causing severe hypercholesterolemia is unlikely to exist in the 3' two-thirds of the coding area of the apo B gene.

Analysis of novel apolipoprotein B mutations using a modified U937 cell line LDL binding assay

The U937 myelomonocyte proliferation assay can be used to detect patients with familial defective apolipoprotein B-100 (FDB). Previous studies have employed electronic cell counting to assess cell proliferation. We simplified the assay using 3H-thymidine incorporation DNA analysis to measure cell growth. We tested the modified method by analyzing the effects of different concentrations of native low density lipoproteins (LDL), methylated LDL, as well as LDLs obtained from patients with FDB on cell growth. Methylation of LDL to various degrees reduced cell proliferation correspondingly, and LDLs obtained from FDB patients decreased cell growth confirming that the modified method was able to detect binding defective species of LDL. We applied this method to analyze three novel apoB polymorphisms recently characterized in this laboratory (apoB His1896-->Arg, apoB Asn1887-->Ser, apoB Ala4454-->Thr), which did not significantly alter U937 cell proliferation. Our results show that this simplified assay can be used for screening for LDL variants with defective binding.

Two new immunogenetic polymorphisms of the apoB gene and their effect on serum lipid levels and responses to changes in dietary fat intake

In previous studies, apoB polymorphisms have been shown to modify serum lipid responses to changes in dietary fat intake. The functionally important apoB DNA change or changes underlying these effects have, however, remained unknown. Using a single-strand conformation polymorphism analysis-based screening method, we identified two previously unreported apoB polymorphisms located close to each other in the 5' region of apoB gene exon 26. This DNA segment corresponds to the binding site of monoclonal anti-apoB antibody D7.2. The two A-->G changes at apoB cDNA nucleotides 5869 and 5896 produced an Asn-->Ser change at amino acid 1887 and a His-->Arg change at amino acid 1896. In the Finnish population, allele frequencies of the rare alleles of the apoB 1887 (Asn-->Ser) and apoB 1896 (His-->Arg) polymorphisms were .02 and .11, respectively. Both polymorphisms were shown to have an independent effect on the binding affinity of LDL with monoclonal antibody D7.2. The effect of these polymorphisms on serum lipid levels and responses to changes in dietary fat intake in 102 healthy free-living subjects was assessed. The apoB 1896 Arg allele was associated with a higher serum LDL cholesterol level during a low-fat, low-cholesterol diet in men.

Screening for mutations in the exon 26 of the apolipoprotein B gene in hypercholesterolemic Finnish families by the single-strand conformation polymorphism method

To date, the only known apolipoprotein B (apo B) mutation causing hypercholesterolemia is the apo B 3500 Arg-->Gln or the familial defective apo B (FDB) mutation. This mutation has not been detected in the Finnish population. We have set up a systematic single-strand conformation polymorphism (SSCP) analysis-based screening method to search for other mutations in the exon 26 of the apo B gene in 21 Finnish hypercholesterolemic probands. The 7572-bp exon 26 covers half of the coding region of the gene including the DNA sequence coding for the putative low-density lipoprotein (LDL) receptor binding site on the apo B protein. Exon 26 was amplified as six 1190- to 1435-bp fragments, each of which was further split into three smaller 213- to 579-bp segments by restriction enzymes. These digestion products were run on nondenaturing polyacrylamide gels using at least three different electrophoretic conditions and autoradiographed. All previously known genetic variants in the exon 26 were detected by the SSCP method. A C-->T change at nucleotide 7064, in complete association with the XbaI site, was characterized by direct sequencing. This variant did not affect the amino acid sequence of the apo B protein. The SSCP-based procedure appears suitable for systematic screening for DNA sequence changes in large coding regions.

Initial healing of the posterior corneal surface following perforating trauma in guinea pig: a scanning electron microscope study

Using a scanning electron microscope, we have studied the healing of the posterior corneal surface after a small perforating trauma. Both corneas of adult guinea pigs were perforated with a needle and studied at various time intervals during recovery. Thirty minutes after the perforation the wound was sealed with a fibrous plug. Leukocytes adhered to the wounded area from the first day of healing on, but usually most of them disappeared after the third day. Fibroblast-like cells were present during the entire healing process from the first day on. Endothelial cells at the margin of the wound lost their hexagonal shape and began to slide over the plug. In 7 days the wound was completely covered by irregularly arranged endothelium. The endothelial cells did not reach their regular arrangement during the 14-day follow-up period.