Clinical association of circulating VEGF-B levels with hyperlipidemia and target organ damage in type 2 diabetic patients

Vascular endothelial growth factor-B (VEGF-B is an important member of the VEGF protein family. Recent animal studies indicated that VEGF-B signaling had determinant roles in insulin resistance, lipid distribution and metabolism in type 2 diabetes. The clinical significance of VEGF-B in type 2 diabetes is still not clear. This study aimed to correlate VEGF-B levels with biochemistry characteristics and target organ damage in type 2 diabetic patients. Serum VEGF-B levels were measured using ELISA. A crosssectional control study, which included 180 type 2 diabetic patients and 62 healthy subjects, was carried out. Diabetic patients who were undergoing insulin therapy were not included. This results showed that serum VEGF-B levels did not differ between the type 2 diabetic patients and the healthy controls (169.2∓118.8 vs 163.5∓115.2 pg/mL; P=0.734). VEGF-B levels in type 2 diabetic patients were significantly associated with the levels of c-peptide, total cholesterol and triglyceride. T-test analysis showed that the associations of serum VEGF-B levels with insulin resistance, pancreatic reserve, HDL and LDL were not significant. Regression analysis showed that VEGF-B levels were significantly correlated with diabetic retinopathy and nephropathy. No significant association between VEGF-B and macro-vasculopathy was found. In conclusion, our study findings suggested that VEGF-B levels did not differ between the type 2 diabetic patients and the normal controls. High VEGF-B levels might correlate with the presence of hyperlipidemia and target organ damage in type 2 diabetic patients.

Impact of the basic amine on the biological activity and intracellular distribution of an aza-anthrapyrazole: BBR 3422

The anthrapyrazoles have entered clinical trials and show significant activity against breast cancer. However, these drugs are cardiotoxic and ineffective in multidrug-resistant (MDR) tumor cells. We have reported previously on the synthesis and antitumor characteristics of the 9-aza-anthrapyrazoles and their lack of cardiotoxicity; unfortunately, the leading candidates are cross-resistant in MDR-expressing cells. The results also indicated that the side arm structures of 9-aza-anthrapyrazole play a critical role in determining the drug resistance in MDR-expressing cells-only compounds that have a tertiary amine on both side arms are not cross-resistant. To further elucidate the biochemical and pharmacological impact of the side arm structures, one of the 9-aza-anthrapyrazole compounds, BBR 3422 [2-(2-aminoethyl)-5-(2-methylaminoethyl)indazolo[4,3-g,h]isoquinoline-6(2H)-one], was selected to be photolabeled with N-hydroxysuccinimidyl-4-azidosalicylic acid (NHS-ASA). In comparison to the parental compound, the photolabeled BBR 3422 was not as cytotoxic or DNA active, but it competed better than the parental compound against azidopine on P-glycoprotein labeling. In addition, confocal microscopic studies showed that BBR 3422 was clustered mainly in the cell nucleus, but its photolabeled analogue was located in the cytoplasm of the human breast cancer cell line MCF-7. Only a trace amount of both compounds was detected in the doxorubicin-derived resistant cell line MCF-7/ADR. The treatment of MCF-7/ADR cells with verapamil increased the intracellular amounts of both compounds.

A novel action of human apurinic/apyrimidinic endonuclease: excision of L-configuration deoxyribonucleoside analogs from the 3' termini of DNA

beta-l-Dioxolane-cytidine (l-OddC, BCH-4556, Troxacitabine) is a novel unnatural stereochemical nucleoside analog that is under phase II clinical study for cancer treatment. This nucleoside analog could be phosphorylated and subsequently incorporated into the 3' terminus of DNA. The cytotoxicity of l-OddC was correlated with the amount of l-OddCMP in DNA, which depends on the incorporation by DNA polymerases and the removal by exonucleases. Here we reported the purification and identification of the major enzyme that could preferentially remove l-OddCMP compared with dCMP from the 3' termini of DNA in human cells. Surprisingly, this enzyme was found to be apurinic/apyrimidinic endonuclease (APE1) (), a well characterized DNA base excision repair protein. APE1 preferred to remove l- over d-configuration nucleosides from 3' termini of DNA. The efficiency of removal of these deoxycytidine analogs were as follows: l-OddC > beta-l-2',3'-dideoxy-2', 3'-didehydro-5-fluorocytidine > beta-l-2',3'-dideoxycytidine > beta-l-2',3'-dideoxy-3'-thiocytidine > beta-d-2',3'-dideoxycytidine > beta-d-2',2'-difluorodeoxycytidine > beta-d-2'-deoxycytidine >/= beta-d-arabinofuranosylcytosine. This report is the first demonstration that an exonuclease can preferentially excise l-configuration nucleoside analogs. This discovery suggests that APE1 could be critical for the activity of l-OddC or other l-nucleoside analogs and may play additional important roles in cells that were not previously known.

Characterization of an amino-terminal fragment of the bacteriophage T4 uvsY recombination protein

The uvsY protein plays essential roles in homologous genetic recombination processes in the bacteriophage T4. In vitro, uvsY promotes the formation of presynaptic filaments containing stoichiometric amounts of the T4 uvsX recombinase bound to single-stranded DNA. uvsY protein has intrinsic binding activities towards ssDNA, uvsX, and gp32, the T4-encoded SSB, however, it has not been directly determined which of these activities are essential for uvsY's role in presynapsis. We have therefore sought to generate altered forms of uvsY deficient in uvsX- and/or gp32-binding, in order to assess whether these specific protein-protein interactions are essential for uvsY recombination functions. Limited chymotrypsinolysis of the 16 kDa uvsY protein generates two major fragments: an 11.5 kDa fragment containing the N-terminus of uvsY, and a 4.5 kDa C-terminal fragment. We have expressed and purified the large fragment as a fusion protein containing the N-terminal 101 amino acids of uvsY. We show that this truncated uvsY species, which we call uvsYNT, retains ssDNA-binding activity, but is devoid of both uvsX- and gp32-binding activities. Like native uvsY, uvsYNT stimulates the ssDNA-dependent ATPase activity of the uvsX protein, however, the synergistic effects observed between uvsY, uvsX, and gp32 are not observed with uvsYNT. In addition, uvsYNT weakly stimulates uvsX-catalyzed DNA strand exchange reactions. The latter result is surprising since it suggests that specific interactions with uvsX and/or gp32 are not absolutely essential for uvsY recombination functions. Taken together, the data are consistent with a model in which uvsY-ssDNA interactions alone are capable of promoting the assembly of functional uvsX-ssDNA complexes, while uvsY-protein interactions stabilize uvsX-ssDNA complexes.