Calorimetric study of the interaction of binary DMTAP/DOTAP cationic liposomes with plasmid DNA.

Cationic liposomes have been suggested as possible agents for nonviral gene transfer. The interaction of plasmid DNA (pDNA) with dispersions of stable unilamellar cationic liposomes based on the binary lipid system 1,2-dimyristoyl-3-trimethyl-ammonium-propane (DMTAP):1,2-dioleoyl-3-trimethyl-ammonium-propane (DOTAP) has been studied by using isothermal titration calorimetry (ITC), high-precision differential scanning calorimetry (DSC), dynamic light scattering (DLS), and circular dichroism (CD). Systematic calorimetric and DLS exploration of the DMTAP:DOTAP binary system reveals that single-bilayer liposomes are stable at the 4:1 molar ratio, exhibiting the main lipid-phase transition temperature at approximately 25.3 degrees C, and a total enthalpy change deltaH = 8.5 +/- 0.4 kcal/mol. The interaction of pDNA with unilamellar DMTAP:DOTAP vesicles was investigated by ITC experiments, which clearly distinguished endothermic binding between the phosphate and the ammonium groups from exothermic processes, driven by slow kinetics, corresponding to interliposomal, DNA-triggered aggregation that leads to the formation of large multilamellar liposome/pDNA assemblies. Lipid-added-to-pDNA and pDNA-added-to-lipid experiments have been carried out in order to systematically explore the interaction mechanisms. Complex ITC profiles are revealed, which may be linked to packing rearrangements of the pDNA molecules bound at the outer liposomal surface, possibly due to binding to more than one liposome or due to p-DNA-enhanced heterogeneity in the local lipid concentration. DNA-mediated aggregation effects are detected at high [ammonium]/[phosphate] molar ratios in the case of lipid-added-to-pDNA interactions and at relatively low [phosphate]/[ammonium] molar ratios in the case of pDNA-added-to-lipid.

Apoptosis and hepatitis C virus infection in renal transplant recipients.

Hepatocellular injury in renal transplant recipients with hepatitis C virus (HCV) infection remains unclear. The suppressed immune response, in combination with increased viremia levels, provides a unique setting for the study of a potential HCV-induced apoptotic process. Liver biopsy specimens from 59 HCV-infected renal transplant recipients were examined histologically. DNA fragmentation was detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-nick end labeling assay, and the CD8 T-cell count was assessed immunohistochemically.A low apoptotic index (0-2.5) was observed in 31 cases, a moderate index (2.6-5) in 16, and a high index (>5) in 12. Apoptotic cell death correlated significantly with viremia because it was demonstrated by higher HCV-RNA levels in cases with a high number of apoptotic cells (odds ratio, 2.96; 95% confidence interval, 1.0-8.5; P = .04). No correlation was found between the apoptotic index and hepatitis necroinflammatory activity, CD8 cell count, fibrosis stage, immunosuppressive therapy, or genotype. In HCV-infected renal transplant recipients, apoptotic cell death seems to be associated with high viral load, thus providing indications of viral interference in the pathogenetic process.

Greek BRCA1 and BRCA2 mutation spectrum: two BRCA1 mutations account for half the carriers found among high-risk breast/ovarian cancer patients.

127 Greek breast/ovarian cancer families were screened for germline BRCA1/2 mutations by dHPLC followed by direct sequencing. Our results indicated 16 and 5 breast/ovarian cancer families bearing deleterious mutations in the BRCA1 and BRCA2 genes, respectively. Two novel BRCA2 germline mutations (G4X and 3783del10) are reported here for the first time. Subsequent compilation of our present findings with previously reported mutation data reveals that in a total of 287 Greek breast/ovarian cancer families, 46 and 13 carry a deleterious mutation in BRCA1 and BRCA2, respectively. It should be noted that two BRCA1 mutations, 5382insC and G1738R, both located in exon 20, account for 46% of the families found to carry a mutation. Based on our mutation analysis results, we propose here a hierarchical, cost-effective BRCA1/2 mutation screening protocol for individuals of Greek ethnic origin. The suggested protocol can impact on the clinical management of breast-ovarian cancer families on a national healthcare system level.

Thermal unfolding of human BRCA1 BRCT-domain variants.

Missense mutations at the BRCT domain of human BRCA1 protein have been associated with an elevated risk for hereditary breast/ovarian cancer. They have been shown to affect the binding site and they have also been proposed to affect domain stability, severely hampering the protein's tumor suppressor function. In order to assess the impact of various such mutations upon the stability and the function of the BRCT domain, heat-induced denaturation has been employed to study the thermal unfolding of variants M1775R and R1699W, which have been linked with the disease, as well as of V1833M, which has been reported for patients with a family history. Calorimetric and circular dichroism results reveal that in pH 9.0, 5 mM borate buffer, 200 mM NaCl, analogously to wild type BRCT, all three variants undergo partial thermal unfolding to a denatured state, which retains most of the native's structural characteristics. With respect to wild-type BRCT, the mutation M1775R induces the most severe effects especially upon the thermostability, while R1699W also has a strong impact. On the other hand, the thermal unfolding of variant V1833M is only moderately affected relative to wild-type BRCT. Moreover, isothermal titration calorimetric measurements reveal that contrary to M1775R and R1699W variants, V1833M binds to BACH1 and CtIP phosphopeptides.

Correlation between increased serum sFas levels and microalbuminuria in type 1 diabetic patients.

OBJECTIVE: The aim of this study was to elucidate if apoptosis dysregulation is present in type 1 diabetic patients with microalbuminuria. SUBJECTS AND METHODS: The following variables were determined in 29 type 1 diabetic patients: the duration of diabetes, soluble Fas (sFas), Bcl-2, hemoglobin A(1c) levels, glomerular filtration rate (GFR) and microalbuminuria, using the urine albumin to urine creatinine ratio (ACR). Age and gender were assessed and patients were categorized into two groups, according to their ACR: the microalbuminuric (MA) group with an ACR > or =30 mg/g, and the normoalbuminuric (NA) group with an ACR <30 mg/g. RESULTS: The differences between the two groups regarding sFas, Bcl-2 and GFR were not statistically significant. However, in the MA group, a significant positive relationship between sFas and ACR was observed (r = 0.736, p = 0.015). Dividing patients into two subgroups--mild versus severe (ACR > or =150 mg/g) microalbuminuric patients--significant differences in sFas (60.4 vs. 87.2 pg/ml; p = 0.047) and GFR (113 vs. 69.5 ml min(-1) 1.73 m(-2); p = 0.021) were observed, whereas in Bcl-2, the difference was not significant (77.96 vs. 71.13 ng/ml). CONCLUSIONS: At the early stages of diabetic nephropathy in type 1 diabetic patients, there seems to be a dysregulation of apoptosis, as expressed by enhanced sFas levels, leading to the speculation that the prevalence of antiapoptotic mechanisms (sFas) may promote mesangial proliferation.