Characterization of proliferative effects of insulin, insulin analogues and insulin-like growth factor-1 (IGF-1) in human lung fibroblasts

Insulin has been approved for inhaled application, but safety concerns remain, because of un-physiologically high insulin concentrations in the lung. Since insulin may act as growth factor, possible proliferative effects of insulin, insulin analogues and insulin-like growth factor-1 (IGF-1) on human lung fibroblasts were studied. As measure of proliferation [(3)H]-thymidine incorporation was studied in HEL-299, MRC-5, IMR-90 and primary human lung fibroblasts. In all cells, mRNA encoding IGF-1 receptors and two variants of insulin receptors was detected. Insulin and IGF-1 stimulated [(3)H]-thymidine incorporation in all cells. Comparison of the concentration-dependent effects in HEL-299 cells showed that IGF-1 and insulin glargine were more potent (EC(50), 3 and 6 nM) and more effective (maximum increase, by 135-150%) than insulin and insulin detemir (EC(50), 22 and 110 nM; maximum increase: by 80%). Proliferative effects of IGF-1 and insulin were inhibited to the same extent by an antibody (1H7) directed against the IGF-1 receptor α-subunit. Insulin-induced stimulation of [(3)H]-thymidine incorporation was reduced by 83% after siRNA-mediated down-regulation of IGF-1 receptor by about 75%, but not affected by a similar down-regulation of the insulin receptor. Insulin and IGF-1 caused rapid up-regulation of the early genes FOS, EGR-1 and EGR-2 as well as of the gene coding for IGF-1. In conclusion, in human lung fibroblasts insulin exerts marked proliferative effects and the pharmacological profile of this response as well as specific receptor knock-down experiments suggest mediation via IGF-1 receptors. The risk of unwanted structural lung alterations by long-term inhalative application of insulin should be considered.

Real-time imaging reveals the single steps of brain metastasis formation

Brain metastasis frequently occurs in individuals with cancer and is often fatal. We used multiphoton laser scanning microscopy to image the single steps of metastasis formation in real time. Thus, it was possible to track the fate of individual metastasizing cancer cells in vivo in relation to blood vessels deep in the mouse brain over minutes to months. The essential steps in this model were arrest at vascular branch points, early extravasation, persistent close contacts to microvessels and perivascular growth by vessel cooption (melanoma) or early angiogenesis (lung cancer). Inefficient steps differed between the tumor types. Long-term dormancy was only observed for single perivascular cancer cells, some of which moved continuously. Vascular endothelial growth factor-A (VEGF-A) inhibition induced long-term dormancy of lung cancer micrometastases by preventing angiogenic growth to macrometastases. The ability to image the establishment of brain metastases in vivo provides new insights into their evolution and response to therapies.

Imaging glioma cell invasion in vivo reveals mechanisms of dissemination and peritumoral angiogenesis

Infiltration of cancer cells into normal tissue is a hallmark of malignant gliomas and compromises treatment options. A lack of appropriate models limits the study of this invasion in vivo, which makes it difficult to fully understand its anatomy and the role of dynamic interactions with structures of the normal brain. We developed a novel methodology by utilizing multiphoton laser scanning microscopy (MPLSM) to image the movement of glioma cells deep within the normal brain of live mice in real time. This allowed us to track the invasion of individual RFP-expressing GL261 cells in relation to perfused vasculature or GFP-labeled endothelial cells repetitively over days, up to a depth of 0.5 mm. Glioma cells moved faster and more efficiently when the abluminal site of a blood vessel was utilized for invasion. Cells that invaded perivascularly were frequently found next to (a) multiple capillary structures where microvessels run parallel to each other, (b) capillary loops or glomeruloid-like bodies, and (c) dilated capillaries. Dynamic MPLSM for more than 48 h revealed that single invasive glioma cells induced intussusceptive microvascular growth and capillary loop formation, specifically at the microvascular site with which they had contact. As the main tumor grew by cooption of existing brain vessels, these peritumoral vascular changes may create a beneficial environment for glioma growth. In conclusion, our study revealed new mechanisms of peritumoral angiogenesis and invasion in gliomas, providing an explanation for their interdependence.

Dendritic pathology in prion disease starts at the synaptic spine

Spine loss represents a common hallmark of neurodegenerative diseases. However, little is known about the underlying mechanisms, especially the relationship between spine elimination and neuritic destruction. We imaged cortical dendrites throughout a neurodegenerative disease using scrapie in mice as a model. Two-photon in vivo imaging over 2 months revealed a linear decrease of spine density. Interestingly, only persistent spines (lifetime > or = 8 d) disappeared, whereas the density of transient spines (lifetime < or = 4 d) was unaffected. Before spine loss, dendritic varicosities emerged preferentially at sites where spines protrude from the dendrite. These results implicate that the location where the spine protrudes from the dendrite may be particularly vulnerable and that dendritic varicosities may actually cause spine loss.

Loss of the cellular prion protein affects the Ca2+ homeostasis in hippocampal CA1 neurons

Previous neurophysiological studies on prion protein deficient (Prnp(-/-)) mice have revealed a significant reduction of slow afterhyperpolarization currents (sI(AHP)) in hippocampal CA1 pyramidal cells. Here we aim to determine whether loss of PrP(C.) directly affects the potassium channels underlying sI(AHP) or if sI(AHP) is indirectly disturbed by altered intracellular Ca(2+) fluxes. Patch-clamp measurements and confocal Ca(2+) imaging in acute hippocampal slice preparations of Prnp(-/-) mice compared to littermate control mice revealed a reduced Ca(2+) rise in CA1 neurons lacking PrP(C) following a depolarization protocol known to induce sI(AHP). Moreover, we observed a reduced Ca(2+) influx via l-type voltage gated calcium channels (VGCCs). No differences were observed in the protein expression of the pore forming alpha1 subunit of VGCCs Prnp(-/-) mice. Surprisingly, the beta2 subunit, critically involved in the transport of the alpha1 subunit to the plasma membrane, was found to be up-regulated in knock out hippocampal tissue. On mRNA level however, no differences could be detected for the alpha1C, D and beta2-4 subunits. In conclusion our data support the notion that lack of PrP(C.) does not directly affect the potassium channels underlying sI(AHP), but modulates these channels due to its effect on the intracellular free Ca(2+) concentration via a reduced Ca(2+) influx through l-type VGCCs.

Cortical dysplasia resembling human type 2 lissencephaly in mice lacking all three APP family members

The Alzheimer's disease beta-amyloid precursor protein (APP) is a member of a larger gene family that includes the amyloid precursor-like proteins, termed APLP1 and APLP2. We previously documented that APLP2-/-APLP1-/- and APLP2-/-APP-/- mice die postnatally, while APLP1-/-APP-/- mice and single mutants were viable. We now report that mice lacking all three APP/APLP family members survive through embryonic development, and die shortly after birth. In contrast to double-mutant animals with perinatal lethality, 81% of triple mutants showed cranial abnormalities. In 68% of triple mutants, we observed cortical dysplasias characterized by focal ectopic neuroblasts that had migrated through the basal lamina and pial membrane, a phenotype that resembles human type II lissencephaly. Moreover, at E18.5 triple mutants showed a partial loss of cortical Cajal Retzius (CR) cells, suggesting that APP/APLPs play a crucial role in the survival of CR cells and neuronal adhesion. Collectively, our data reveal an essential role for APP family members in normal brain development and early postnatal survival.

Hyperpermeability of pulmonary endothelial monolayer: protective role of phosphodiesterase isoenzymes 3 and 4

The regulation of endothelial permeability is poorly understood. An increase in endothelial permeability in the pulmonary microvasculature, however, is critical in noncardiogenic pulmonary edema and other diffuse inflammatory reactions. In the present study thrombin and Escherichia coli hemolysin (HlyA), a membrane-perturbing bacterial exotoxin, were used to alter hydraulic permeability of porcine pulmonary artery and human endothelial cell monolayers. We also investigated the pharmacological approach of adenylyl cyclase activation/phosphodiesterase (PDE) inhibition to block endothelial hyperpermeability. Thrombin (1-5 units/ml) and HlyA (0.5-3 hemolytic units/ml) dose and time dependently (> 15 min) increased endothelial permeability. Forskolin, cholera toxin, and prostaglandin E1, which all stimulate adenylyl cyclase activity, abrogated this effect. One mM dibutyryl cAMP, a cell membrane-permeable cAMP analogue, was similarly active. Endothelial hyperpermeability was also reduced dose dependently by inhibitors of different PDE isoenzymes (motapizone, rolipram, and zardaverine, which block PDE3 and/or PDE4). The effectiveness of PDE inhibitors was increased in the presence of adenylyl cyclase activators. Analysis of cyclic nucleotide hydrolyzing PDE activity in lysates of human umbilical vein endothelial cells showed high activities of PDE isoenzymes 2, 3, and 4. Consistent with the functional data PDE3 and PDE4 were the major cAMP hydrolysis enzymes in intact endothelial cells. We conclude that the hyperpermeability of pulmonary endothelial monolayers, evoked by thrombin or HlyA, can be blocked by the simultaneous activation of adenylyl cyclase and inhibition of PDEs, especially of PDE3 and PDE4. The demonstration of PDE isoenzymes 2-4 in human endothelial cells will help optimize this therapeutic approach.

Spectroscopic characterization of flavin mononucleotide bound to the LOV1 domain of Phot1 from Chlamydomonas reinhardtii

The absorption and emission behavior of flavin mononucleotide (FMN) in the light-, oxygen- and voltage-sensitive (LOV) domain LOV1 of the photoreceptor Phot1 from the green alga Chlamydomonas reinhardtii was studied. The results from the wild-type (LOV1-WT) were compared with those from a mutant in which cysteine 57 was replaced by serine (LOV1-C57S), and with free FMN in aqueous solution. A fluorescence quantum yield of phi(F) = 0.30 and a fluorescence lifetime of tau(F) = 4.6 ns were determined for FMN in the mutant LOV1-C57S, whereas these quantities are reduced to about phi(F) = 0.17 and tau(F) = 2.9 ns for LOV1-WT, indicating an enhanced intersystem crossing in LOV1-WT because of the adjacent sulfur of C57. A single-exponential fluorescence decay was observed in picosecond laser time-resolved fluorescence measurements for both LOV1-WT and LOV1-C57S as expected for excited singlet state relaxation by intersystem crossing and internal conversion. An excitation intensity dependent fluorescence signal saturation was observed in steady-state fluorescence measurements for LOV1-WT, which is thought to be because of the formation of a long-lived intermediate flavin-C(4a)-cysteinyl adduct in the triplet state (few microseconds triplet lifetime, adduct lifetime around 150 s). No photobleaching was observed for LOV1-C57S, because no thiol group is present in the vicinity of FMN for an adduct formation.

Sulfur polymer solidification/stabilization of elemental mercury waste

Elemental mercury, contaminated with radionuclides, presents a waste disposal problem throughout the Department of Energy complex. In this paper we describe a new process to immobilize elemental mercury wastes, including those contaminated with radionuclides, in a form that is non-dispersible, will meet EPA leaching criteria, and has low mercury vapor pressure. In this stabilization and solidification process, elemental mercury is combined with an excess of powdered sulfur polymer cement (SPC) and sulfide additives in a mixing vessel and heated to approximately 40 degrees C for several hours, until all of the mercury is converted into mercuric sulfide (HgS). Additional SPC is then added and the temperature of the mixture raised to 135 degrees C, resulting in a molten liquid which is poured into a mold where it cools and solidifies. The final treated waste was characterized by powder X-ray diffraction and found to be a mixture of the hexagonal and orthorhombic forms of mercuric sulfide. The Toxicity Characteristic Leaching Procedure was used to assess mercury releases, which for the optimized process averaged 25.8 microg/l, with some samples being well below the new EPA Universal Treatment Standard of 25 microg/l. Longer term leach tests were also conducted, indicating that the leaching process was dominated by diffusion. Values for the effective diffusion coefficient averaged 7.6x10(-18) cm2/s. Concentrations of mercury vapor from treated waste in equilibrium static headspace tests averaged 0.6 mg/m3.

The abundant retinal protein of the Chlamydomonas eye is not the photoreceptor for phototaxis and photophobic responses

The chlamyopsin gene (cop) encodes the most abundant eyespot protein in the unicellular green alga Chlamydomonas reinhardtii. This opsin-related protein (COP) binds retinal and was thought to be the photoreceptor controlling photomovement responses via a set of photoreceptor currents. Unfortunately, opsin-deficient mutants are not available and targeted disruption of non-selectable nuclear genes is not yet possible in any green alga. Here we show that intron-containing gene fragments directly linked to their intron-less antisense counterpart provide efficient post-transcriptional gene silencing (PTGS) in C. reinhardtii, thus allowing an efficient reduction of a specific gene product in a green alga. In opsin-deprived transformants, flash-induced photoreceptor currents (PC) are left unchanged. Moreover, photophobic responses as studied by motion analysis and phototaxis tested in a light-scattering assay were indistinguishable from the responses of untransformed wild-type cells. We conclude that phototaxis and photophobic responses in C. reinhardtii are triggered by an as yet unidentified rhodopsin species.

Human and rat alveolar macrophages express multiple EDG receptors

Endothelial differentiation gene (EDG) receptors are a new family of eight G protein-coupled receptors for the lysophospholipids lysophosphatitic acid and sphingosine-1-phosphate. In the present experiments, the expression of EDG receptors in rat and human alveolar macrophages was studied by reverse transcription-polymerase chain reaction (RT-PCR). In alveolar macrophages of both species, mRNA for multiple EDG receptors could be detected, but the pattern of expression was different in both species. In human alveolar macrophages, mRNA for EDG1, EDG2, EDG4, EDG7 receptors and, to a lesser extent, for the EDG7 receptor was detected, whereas in rat macrophages, mRNA for EDG2, EDG5 receptors and, to a lesser extent, for the EDG6 receptor was found. In functional experiments, it was observed that lysophosphatitic acid and sphingosine-1-phosphate can stimulate O(2)(-) generation in rat and human alveolar macrophages suggesting that lysophosphatitic acid and sphingosine-1-phosphate possibly acting via EDG receptors may play a role in controlling the activation of macrophages.

A Streptomyces rimosus aphVIII gene coding for a new type phosphotransferase provides stable antibiotic resistance to Chlamydomonas reinhardtii

Although Chlamydomonas reinhardtii serves as the most popular algal model system, no efficient enzymatic selection marker for the nuclear transformation of wild-type cells is available. We sequenced an aminoglycoside 3'-phosphotransferase gene (aph) from Streptomyces rimosus. Though the derived protein sequence is homologous to members of APH type V, it constitutes a new type, named APHVIII. Since the aphVIII gene has a codon bias similar to that of the nuclear genome of green algae, the aphVIII coding sequence was fused to the 5'- and 3'-untranslated regions of the C. reinhardtii rbcS2 gene. C. reinhardtii transformants were capable of inactivating the antibiotics paromomycin, kanamycin, and neomycin, to which wild-type cells are sensitive. After addition of the 5'-region of hsp70A as a second promoter and insertion of the rbcS2 intron I, the transformation rate increased to two transformants per 1 x 10(5) cells, which is close to the efficiency of transforming auxotrophic strains with the homologous marker arg7. Transformation with the promoter-less aphVIII led to random gene fusion at high frequency. In an aphVIII-based reporter gene assay we have found a so far unknown promoter activity of the 3'-untranslated region of rbcS2, that may promote antisense RNA synthesis from the rbcS2 gene in vivo. We conclude that the aphVIII gene is a useful marker for nuclear transformation and promoter tagging of C. reinhardtii wild-type and probably other green algae.