University of Marburg

About: University of Marburg is a education organization based out in Marburg, Germany. It is known for research contribution in the topics: Population & Gene. The organization has 23195 authors who have published 42907 publications receiving 1506069 citations. The organization is also known as: Philipps University of Marburg & Philipps-Universität.

Reactive oxygen species mediate thymoquinone-induced apoptosis and activate ERK and JNK signaling

Abstract: Thymoquinone (TQ), a component of black seed essential oil, is known to induce apoptotic cell death and oxidative stress, however, the direct involvement of oxidants in TQ-induced cell death has not been established yet. Here, we show that TQ inhibited the proliferation of a panel of human colon cancer cells (Caco-2, HCT-116, LoVo, DLD-1 and HT-29), without exhibiting cytotoxicity to normal human intestinal FHs74Int cells. Further investigation in DLD-1 revealed that apoptotic cell death is the mechanism for TQ-induced growth inhibition as confirmed by flow cytometry, M30 cytodeath and caspase-3/7 activation. Apoptosis was induced via the generation of reactive oxygen species (ROS) as evidenced by the abrogation of TQ apoptotic effect in cells preincubated with the strong antioxidant N-acetyl cysteine (NAC). TQ increased the phosphorylation states of the mitogen-activated protein kinases (MAPK) JNK and ERK, but not of p38. Their activation was completely abolished in the presence of NAC. Using PD98059 and SP600125, specific ERK and JNK inhibitors, the two kinases were found to possess pro-survival activities in TQ-induced cell death. These data present evidence linking the pro-oxidant effects of TQ with its apoptotic effects in colon cancer and prove a protective role of MAPK.

Design of Estradiol Loaded PLGA Nanoparticulate Formulations: A Potential Oral Delivery System for Hormone Therapy

Abstract: Estradiol (E2), a highly lipophilic molecule with good oral absorption but poor oral bioavailability, was incorporated into poly(lactide-co-glycolide) (PLGA) nanoparticles to improve its oral bioavailability. Nanoparticles were prepared by using polyvinyl alcohol (PVA) or didodecyldimethylammonium bromide (DMAB) as stabilizer, leading to negatively (size 410.9 ± 39.4 nm) and positively (size 148.3 ± 10.7 nm) charged particles, respectively. Both preparations showed near zero order release in vitro with about 95% drug being released within 45 and 31 days for PVA and DMAB, respectively. In situ intestinal uptake studies in male Sprague–Dawley (SD) rats showed higher uptake of DMAB stabilized nanoparticles. Following oral administration to male SD rats, E2 could be detected in blood for 7 and 2 days from DMAB and PVA stabilized nanoparticles, respectively. Histopathological examination and blood counts indicated the absence of inflammatory response. These data suggest that DMAB stabilized PLGA nanoparticles have great potential as carriers for oral delivery of estradiol.

Integrin targeting using RGD-PEI conjugates for in vitro gene transfer.

Abstract: Background Targeting to integrin receptor ανβ3 by RGD peptides seems to be a promising approach for gene delivery to proliferating endothelial cells of tumor metastases. PEGylation of cationic polymers offers a reduction of non-specific binding to cell surfaces. However, little knowledge exists on the influence of charge shielding by PEGylation on targeted gene delivery. Therefore, a variety of RGD peptide-polyethylenimine (PEI) conjugates with different degrees of substitution, with or without poly(ethylene glycol) (PEG) spacer, were synthesized. Influence of degree of substitution and PEG spacer on physicochemical properties as well as on integrin targeting of DNA/polymer complexes was evaluated. Methods The tetrapeptide RGDC was coupled to PEI with or without a PEG spacer. Complex formation with DNA was monitored by ethidium bromide (EtBr) fluorescence quenching. Hydrodynamic diameters of complexes and zeta-potential were assessed using a Zetasizer. Fluorescence correlation spectroscopy (FCS) was used to determine peptide binding to living cells. Transfection efficiency was evaluated employing a luciferase reporter gene. Binding of complexes to Mewo cells was monitored by flow cytometry. Results Polyplexes of RGD-PEI or RGD-PEG-PEI and DNA showed reduced quenching of EtBr fluorescence compared with PEI. All RGD conjugates formed small polyplexes (approximately 100 nm in diameter at a nitrogen/phosphate (N/P) ratio of 6.7). At N/P = 6.7, the zeta-potentials of RGD-PEI complexes were similar to PEI complexes (25–30 mV), while RGD-PEG-PEI formed neutral complexes. FCS showed saturable binding of RGD peptide to Mewo human melanoma cells and only low binding to A549 human lung carcinoma cells. A degree of substitution of 4.6% with SPDP as coupling reagent yielded a conjugate showing 50 times higher luciferase expression in Mewo cells than unmodified PEI at low N/P ratios around 3.3, while a degree of substitution of 1.6% only led to a moderately increased transfection efficiency. Flow cytometry experiments suggest that this effect is partly caused by increased attachment of complexes to cell surfaces. No improvement in transfection efficiency was found in ανβ3-negative A549 cells. RGD-PEG-PEI complexes showed reasonable transfection efficiencies at high N/P ratios; however, no targeting effect could be found. Conclusions Coupling of the tetrapeptide RGDC without a PEG spacer improved transfection efficiency of PEI in integrin-expressing Mewo cells by 1–2 orders of magnitude, especially at low N/P ratios. The use of a PEG spacer seems to impair targeting, possibly by not only shielding PEI, but also the RGD ligand. Copyright © 2003 John Wiley & Sons, Ltd.