Modulation of inactivation by mutation N588K in KCNH2: A link to arrhythmogenesis in short QT syndrome

OBJECTIVE

Short QT syndrome (SQTS) is characterized by ventricular arrhythmias and sudden death. One form of SQTS is caused by mutation N588K in human ether-a-go-go-related gene (HERG). In this study we sought to determine the potential role of N588K in arrhythmias.

METHODS

We measured the characteristics of HERG current generated by wild-type (WT) KCNH2 and the N588K mutant channel expressed in mammalian TSA201 cells.

RESULTS

Whole-cell patch-clamp recordings of WT HERG currents showed the usual rapid onset of inactivation (rectification) at potentials more positive than +10 mV. In contrast, N588K currents rectified at potentials over +80 mV. Over the physiological range of potentials, N588K currents do not inactivate. During an action potential clamp, WT currents displayed a "hump" like waveform with slow activation kinetics and a rapid increase during phase 3 repolarization. In contrast, N588K currents were proportional to the amplitude of the action potential and displayed a dome-like configuration and a much larger current during the initial phases in the ventricle. Purkinje cell action potentials display a more negative phase 2 repolarization than the ventricle and elicited much smaller WT and N588K currents of similar amplitudes.

CONCLUSIONS

Physiologically the N588K mutation abolishes rectification of HERG currents and specifically increases I(Kr) in the ventricle with minimal effects on the Purkinje fiber action potential duration. Such preferential prolongation may explain the separation of the T and U waves observed in the ECG of SQTS patients and lead to re-excitation of the ventricle endocardium.

Emerging antibody-based HER2 (ErbB-2/neu) therapeutics

Targeting HER2(ErbB-2/neu) overexpressing tumor cells to selectively deliver anticancer agents and thereby reduce host toxicity represents a rational and emerging strategy for the treatment of breast and other epithelial cancers. The extracellular domain of the HER2 receptor tyrosine kinase is readily accessible to systemically administered antibody-based therapeutics, including growth-inhibiting monclonals such as rhuMAbHER2 (trastuzmab/Herceptin) as well as anti-HER2 immunotoxins, antibody-dependent enzyme prodrug therapy (ADEPT), and immune cell recruiting bispecific antibodies. In addition to summarizing recent advances in these antibody-based strategies, this review focuses on preclinical advances in the development of anti-HER2 immunoliposomes (ILs) as a platform technology for targeted drug delivery. Extensive in vitro and in vivo testing including efficacy and tumor uptake studies in multiple human tumor xenograft models now provide conclusive evidence for the superior therapeutic efficacy of anti-HER2 ILs-doxorubicin (dox) over free dox or liposomal (Ls)-dox, and even over combinations of dox and Ls-dox with rhuMAbHER2. As anti-HER2 ILs-dox approaches clinical testing in patients with advanced HER2 overexpressing breast cancer, future applications of this novel targeting strategy will also broaden to include intracellular delivery of other anticancer agents as well as therapeutic nucleic acids (oligonucleotides, genes).

Analysis of weight loss outcomes using VLCD in black and white overweight and obese women with and without metabolic syndrome

OBJECTIVE

To evaluate the efficacy of very low calorie diet (VLCD) in black and white obese women. Changes in weight, metabolic profile, and body composition are assessed.

METHOD

Patients are enrolled in a self-paid, university-based, outpatient weight loss program. All are prescribed VLCD (500-800 Cal/day), an exercise regimen, and group behavioral counseling. Black and white patients are matched for age, weight, body mass index, and by metabolic syndrome (MS) status.

RESULTS

A total of 304 black and white women (152 in each group) were included the analysis. Approximately 40% of patients had MS (white women: 39.5%; black women: 41.2%). Mean baseline weights were similar. After 12 weeks, weight reduction of 9.97% was seen in white women and 9.02% drop was seen in black women (both P<0.0001). However, the degree of weight change was not different between the groups (P = 0.244). Marked improvements in fasting glucose, total cholesterol, LDL, triglyceride, and blood pressures (BP) were observed (all P<0.01); however, no difference between cohorts were seen. Patients with MS had higher baseline weight, BP, glucose and triglyceride levels when compared to patients without MS (all P<0.01). Significant reductions in % body fat were seen in white and black patients, independent of MS status.

CONCLUSION

Obese patients, independent of race, were able to achieve significant weight loss when enrolled in a structured outpatient program. Weight loss significantly correlated with all aspects of MS. Our results suggest that differences seen in past studies may be influenced by socioeconomic and behavioral factors rather than differences in physiological response to dieting.

Long-term efficacy of soy-based meal replacements vs an individualized diet plan in obese type II DM patients: relative effects on weight loss, metabolic parameters, and C-reactive protein

BACKGROUND

Achieving significant weight loss and glycemic control in diabetic patients remains a challenging task.

OBJECTIVE

This study compared the effects of a soy-based meal replacement (MR) plan vs an individualized diet plan (IDP; as recommended by the American Diabetes Association) on weight loss and metabolic profile.

DESIGN/SUBJECTS

A total of 104 subjects were randomized prospectively to the two treatments for a total of 12 months.

RESULTS

In all, 77 of the 104 subjects completed the study. Percentage weight loss in MR group (4.57+/-0.81%) was significantly greater (P<0.05) than in IDP group (2.25+/-0.72%). Fasting plasma glucose was significantly reduced in MR group (126.4+/-4.9 mg/dl) compared with IDP group (152.5+/-6.6 mg/dl, P<0.0001) at 6 months but not at 12 months. Controlling for baseline levels, hemoglobin Alc level improved by 0.49+/-0.22% for those receiving MR when compared to IDP group (P<0.05). A greater number of subjects in MR group reduced their use of sulfonylureas (P<0.0001) and metformin (P<0.05) as compared to IDP group. High-sensitivity C-reactive protein (hs-CRP) decreased -26.3% (P = 0.019) in MR group compared to -7.06% (P = 0.338) in IDP group at 6 months. Similar changes were observed at 12 months with MR groups, with hs-CRP decreasing by -25.0% (P = 0.019) compared to -18.7% (P = 0.179) in IDP group.

CONCLUSION

This study demonstrates that MR is a viable strategy for weight reduction in diabetic patients, resulting in beneficial changes in measures of glycemic control and reduction of medications.

Expression and localization of the Epstein-Barr virus-encoded protein kinase

The protein kinase (PK) encoded by the Epstein-Barr Virus (EBV) BGLF4 gene is the only EBV protein kinase. The expression pattern of EBV PK during the reactivation of the viral lytic cycle and the subcellular localization of the protein were analyzed with a polyclonal antiserum raised against a peptide corresponding to the N terminus of EBV PK. Based on previously published data (E. Gershburg and J. S. Pagano, J. Virol. 76:998-1003, 2002) and the expression pattern described here, we conclude that EBV PK is an early protein that requires viral-DNA replication for maximum expression. By biochemical fractionation, the protein could be detected mainly in the nuclear fraction 4 h after viral reactivation in Akata cells. Nuclear localization could be visualized by indirect immunofluorescence in HeLa cells transiently expressing EBV BGLF4 in the absence of other viral products. Transient expression of 3'-terminal deletion mutants of EBV BGLF4 resulted in cytoplasmic localization, confirming the presence of a nuclear localization site in the C-terminal region of the protein. In contrast to the wild-type EBV PK, all of the mutants were unable to hyperphosphorylate EA-D during coexpression or to phosphorylate ganciclovir, as measured by an in-cell activity assay. Thus, the results demonstrate that the nuclear localization, as well as the kinase activity, of BGFL4 is dependent on an intact C-terminal region.

Comparing therapeutic and prophylactic protection against the lethal effect of paraoxon

Prophylactic and therapeutic efficacy against organophosphorus (OP) intoxication by pralidoxime (2-PAM) and atropine were studied and compared with sterically stabilized long-circulating liposomes encapsulating recombinant organophosphorus hydrolase (OPH), either alone or in various specific combinations, in paraoxon poisoning. Prophylactic and therapeutic properties of atropine and 2-PAM are diminished when they are used alone. However, their prophylactic effects are enhanced when they are used in combination. Present studies indicate that sterically stabilized liposomes (SL) encapsulating recombinant OPH (SL-OPH) alone can provide much better therapeutic and prophylactic protection than the classic 2-PAM + atropine combination. This protection was even more dramatic when SL-OPH was employed in combination with 2-PAM and/or atropine: the magnitude of prophylactic antidotal protection was an astounding 1022 LD(50) [920 mg/kg (LD(50) of paraoxon with antagonists)/ 0.95 mg/kg (LD(50) of control paraoxon)], and the therapeutic antidotal protection was 156 LD(50) [140 mg/kg (LD(50) of paraoxon with antagonists)/0.9 mg/kg (LD(50) of control paraoxon)]. The current study firmly establishes the value of using liposome encapsulating OPH.

Engineering therapeutic antibodies for improved function

The binding sites on human IgG1 for human Fc gamma receptor (Fc gamma R) I, Fc gamma RIIa, Fc gamma RIIb, Fc gamma RIIIa and neonatal FcR have been mapped. A common set of IgG1 residues is involved in binding to all Fc gamma Rs, while Fc gamma RII and Fc gamma RIII utilize distinct sites outside this common set. In addition to residues which abrogated binding to the Fc gamma R, several positions were found which improved binding only to specific Fc gamma Rs or simultaneously improved binding to one type of Fc gamma R and reduced binding to another type. Selected IgG1 variants with improved binding to Fc gamma RIIIa were then tested in an in vitro antibody-dependent cellular cytotoxicity (ADCC) assay and showed an enhancement in ADCC when either peripheral blood mononuclear cells or natural killer cells were used.

Solid-state fermentation of phytase from cassava dregs

Phytases produced by numerous microorganisms and plants degrade phytic acid that has chelated with metal ions in food and feed. It is important to study phytase for the role of metal ions in nutrition of animals and humans as well as in the reduction of organic phosphate content of aqueous environment. This article reports on solid-state fermentation of phytase from a new substrate of cassava dregs. Large quantities of cassava dregs are produced in tropical areas as a byproduct of cassava starch processing. Protein and inorganic salts were found to be low in cassava dregs. Cassava dregs could be employed for phytase synthesis after the addition of a nitrogen source and mineral salts. Ammonium nitrate was the best nitrogen source among the nitrogen sources investigated, including beef extract, yeast extract, urea, ammonium nitrate, sodium nitrate, and ammonium sulfate. Sodium dodecyl sulfate promoted phytase production from cassava dregs. A maximum phytase yield of 6.73 U/g of dry mass was obtained. The obtained phytase was stable at feed-processing temperature, since 70% of initial enzyme activity was maintained after 30 min of treatment at 75 degrees C.

Intracellular signaling molecules activated by Epstein-Barr virus for induction of interferon regulatory factor 7

Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) is the principal oncogenic protein in the EBV transformation process. LMP-1 induces the expression of interferon regulatory factor 7 (IRF-7) and activates IRF-7 protein by phosphorylation and nuclear translocation. LMP-1 is an integral membrane protein with two regions in its C terminus that initiate signaling processes, the C-terminal activator regions 1 (CTAR-1) and CTAR-2. Here, genetic analysis of LMP-1 has determined that the PXQXT motif that governs the interaction between LMP-1 CTAR-1 and tumor necrosis factor receptor-associated factors (TRAFs) is needed to induce the expression of IRF-7. Mutations in the PXQXT motif in CTAR-1 that disrupt the interaction between LMP-1 and TRAFs abolished the induction of IRF-7. Also, dominant-negative mutants of TRAFs inhibited the induction of IRF-7 by CTAR-1. The last three amino acids (YYD) of CTAR-2 are also important for the induction of IRF-7. When both PXQXT and YYD were mutated (LMP-DM), the LMP-1 mutant failed to induce IRF-7. Also, LMP-DM blocked the induction of IRF-7 by wild-type LMP-1. These data strongly suggest that both CTAR-1 and CTAR-2 of LMP-1 independently induce the expression of IRF-7. In addition, NF-kappaB is involved in the induction of IRF-7. A superrepressor of IkappaB (sr-IkappaB) could block the induction of IRF-7 by LMP-1, and overexpression of NF-kappaB (p65 plus p50) could induce the expression of IRF-7. In addition, we have found that human IRF-7 is a stable protein, and sodium butyrate, a modifier of chromatin structure, induces IRF-7.

Quantitative analysis of synthetic gene delivery vector design properties

As intracellular gene delivery pathways are highly complex combinations of multiple potentially rate-limiting cellular and molecular processes, approaches to the design of synthetic delivery vectors focusing on any single barrier individually will likely be suboptimal. We offer here an "integrative systems" approach to vector characterization and design, combining quantitative experiment and computational modeling studies of vector uptake and trafficking kinetics. This model is validated using data for delivery of a green fluorescent protein (GFP)-encoding plasmid by means of Lipofectamine, permitting specification of model parameter values. The model is then used to make a priori predictions on the effect of polymer length in polyplex vectors, with additional parameter values determined from previous independent experimental studies of plasmid release. Comparison with data on GFP expression via these polyplex vectors shows that the model successfully predicts an experimentally observed biphasic dependence of expression efficiency on polymer length and quantifies the contributions of competing effects yielding the optimal intermediate polymer length. Finally, we use the model to predict potential effects of incorporating nuclear localization sequences in these kinds of synthetic vectors, and find that the degree of benefit from these will depend on the values of other key system properties including the vector unpackaging rate constant. Thus, we demonstrate the usefulness of a bioengineering, integrative-systems modeling approach to improved vector design and analysis.

Methylation of episomal plasmids as a barrier to transient gene expression via a synthetic delivery vector

Efficient and sustained transgene expression are desirable features for many envisioned gene therapy applications, yet synthetic vectors tested to date are rarely successful in achieving these properties. Substantial research efforts have focused on protection of plasmid DNA from nuclease attack as well as increasing nuclear transport of plasmids, resulting in significant but still limited gains. We show here that a further barrier to efficient and sustained expression exists for synthetic vectors: plasmid DNA methylation. We have investigated this barrier for transient expression of a green fluorescent protein (GFP) transgene delivered via Lipofectamine, by testing the effects of culturing C3A human hepatoblastoma cells with 5-Azacytidine (AzaC), an irreversible inhibitor of DNA methyltransferase. To control for loss of plasmids by dilution during mitosis, transfected cells were growth-arrested for 1 week and their subsequent GFP expression quantified by FACS. In the presence of AzaC, a significantly greater fraction of transfected cells remained GFP-positive and possessed higher levels of GFP production relative to AzaC-untreated cells. Additionally, we have applied a Methyl-Assisted PCR (MAP) assay to quantify a subset of methylated CpG sites in the GFP gene. When MAP was performed on plasmids isolated from transfected cells, the extent of methylation was found to be inversely related to the level of GFP expression.

Dual role of the fringe connection gene in both heparan sulphate and fringe-dependent signalling events

The precise regulation of growth factor signalling is crucial to the molecular control of development in Drosophila. Post-translational modification of signalling molecules is one of the mechanisms that modulate developmental signalling specificity. We describe a new gene, fringe connection (frc), that encodes a nucleotide-sugar transporter that transfers UDP-glucuronic acid, UDP-N-acetylglucosamine and possibly UDP-xylose from the cytoplasm into the lumen of the endoplasmic reticulum/Golgi. Embryos with the frc mutation display defects in Wingless, Hedgehog and fibroblast growth factor signalling. Clonal analysis shows that fringe-dependent Notch signalling is disrupted in frc mutant tissue.

Carrier proteins determine local pharmacokinetics and arterial distribution of paclitaxel

The growing use of local drug delivery to vascular tissues has increased interest in hydrophobic compounds. The binding of these drugs to serum proteins raises their levels in solution, but hinders their distribution through tissues. Inside the arterial interstitium, viscous and steric forces and binding interactions impede drug motion. As such, this might be the ideal scenario for increasing the amount of drug delivered to, and residence time within, arterial tissues. We quantified carrier-mediated transport for paclitaxel, a model hydrophobic agent with potential use in proliferative vascular diseases, by determining, in the presence or absence of carrier proteins, the maximum concentration of drug in aqueous solution, the diffusivity in free solution, and the diffusivity in arterial tissues. Whereas solubility of paclitaxel was raised 8.1-, 21-, and 57-fold by physiologic levels of alpha(1)-acid glycoproteins, bovine serum albumin, and calf serum over that in protein-free solution, diffusivity of paclitaxel in free solution was reduced by 41, 49, and 74%, respectively. When paclitaxel mixed in these solutions was applied to arteries both in vitro and in vivo, drug was more abundant at the tissue interface, but protein carriers tended to retain drug in the lumen. Once within the tissue, these proteins did not affect the rate at which drug traverses the tissue because this hydrophobic drug interacted with the abundant fixed proteins and binding sites. The protein binding properties of hydrophobic compounds allow for beneficial effects on transvascular transport, deposition, and distribution, and may enable prolonged effect and rationally guide local and systemic strategies for their administration.

Immunobead RT-PCR versus regular RT-PCR amplification of CEA mRNA in peripheral blood

PURPOSE

The reverse transcription polymerase chain reaction (RT-PCR) amplification of tumor-specific mRNA has been used for the detection of cancer cells in peripheral blood. More recently, an immunomagnetic isolation and reverse transcription polymerase chain reaction (immunobead RT-PCR) was developed which has reportedly significant advantages over the previous RT-PCR analysis. In our study, we compared these two methods using a model set of peripheral blood containing tumor cells under standardized conditions.

MATERIAL AND METHODS

In order to compare the false positive rate, normal peripheral blood samples from five volunteers were analyzed by both methods. A model set of peripheral blood containing tumor cells was established by adding SNUC4 human colon cancer cells to peripheral blood collected from normal volunteers not showing any nonspecific bands upon electrophoresis of the PCR products. RT-PCR amplification of carcinoembryonic antigen (CEA) mRNA was done with total RNA and mRNA prepared from this model sample. In immunobead RT-PCR analysis, mRNA was prepared from the cells isolated with anti-CEA antibody-coated magnetic beads or anti-Ber-EP4 antibody-coated magnetic beads before the RT-PCR analysis.

RESULT

The immunobead RT-PCR yielded no non-specific band, while the regular RT-PCR using total RNA did show non-specific band formation in all five samples. When mRNA rather than total RNA was used, nonspecific bands were formed in three of the five samples. Immunobead RT-PCR allowed the detection of 10(1) tumor cells in 1 ml of peripheral blood. The regular RT-PCR analysis had a detection limit of 10(2) tumor cells in 1 ml of peripheral blood.

CONCLUSION

The immunobead RT-PCR proved to be more sensitive and specific than the regular RT-PCR at least in our model system.