Alexandra Schmid-Kotsas

Platelet-Derived Growth Factors Stimulate Proliferation and Extracellular Matrix Synthesis of Pancreatic Stellate Cells: Implications in Pathogenesis of Pancreas Fibrosis

At present, the cell-cell interactions and molecular mechanisms of pancreas fibrogenesis are largely unknown. The purpose of this study was to investigate paracrine stimulatory loops between platelets and pancreatic stellate cells (PSC). Human PSC were obtained by outgrowth from fibrotic human pancreas. Native platelet lysate (nPL) and transiently acidified platelet lysate (aPL) were added to cultured PSC (passage 4 to 7) in the absence of serum. The synthesis of collagen types I and III and c-fibronectin (cFN) was demonstrated on protein (immunofluorescence and quantitative immunoassay) and mRNA (Northern blot) level. Using sections of human pancreas with acute pancreatitis, platelet aggregates in capillaries were demonstrated by transmission electron microscopy. nPL, and to an even greater extent aPL, significantly increased the synthesis of collagen types I and III and of c-FN (120 μl/ml aPL increased collagen type I concentration in PSC supernatants by 1.99 ± 0.17 times and c-FN of 2.49 ± 0.28 times, mean ± sd, n = 3). nPL and aPL also significantly stimulated cell proliferation (increased bromodeoxyuridine (BrdU) incorporation by 6.4 ± 0.78 times and 10 ± 0.29 times, respectively). By preincubating aPL with transforming growth factor β (TGFβ)- and platelet-derived growth factor (PDGF)-neutralizing antibodies and the TGFβ-latency associated peptide, respectively, TGFβ1 was identified as the main mediator stimulating matrix synthesis and PDGF as the responsible mitogen. Our data demonstrate that platelets contain fibrogenic mediators that stimulate proliferation (PDGF) and matrix synthesis (TGFβ1) of cultured PSC. We suggest that platelets and PSC cooperate in the development of pancreas fibrosis.

Lipopolysaccharide-Activated Macrophages Stimulate the Synthesis of Collagen Type I and C-Fibronectin in Cultured Pancreatic Stellate Cells

We have recently identified and characterized pancreatic stellate cells (PSC) in rats and humans (Gastroenterology 1998, 15:421-435). PSC are suggested to represent the main cellular source of extracellular matrix in chronic pancreatitis. Now we describe a paracrine stimulatory loop between human macrophages and PSC (rat and human) that results in an increased extracellular matrix synthesis. Native and transiently acidified supernatants of cultured macrophages were added to cultured PSC in the presence of 0.1% fetal calf serum. Native supernatants of lipopolysaccharide-activated macrophages stimulated the synthesis of collagen type I 1.38 +/- 0.09-fold of control and c-fibronectin 1.89 +/- 0.18-fold of control. Transiently acidified supernatants stimulated collagen type I and c-fibronectin 2.10 +/- 0.2-fold and 2.80 +/- 0.05-fold of control, respectively. Northern blot demonstrated an increased expression of the collagen-I-(alpha-1)-mRNA and fibronectin-mRNA in PSC 10 hours after addition of the acidified macrophage supernatants. Cell proliferation measured by bromodeoxyuridine incorporation was not influenced by the macrophage supernatants. Unstimulated macrophages released 1.97 pg TGFbeta1/microgram of DNA over 24 hours and lipopolysaccharide-activated macrophages released 6.61pg TGFbeta1/microgram of DNA over 24 hours. These data together with the results that, in particular, transiently acidified macrophage supernatants increased matrix synthesis, identify TGFbeta as the responsible mediator. In conclusion, our data demonstrate a paracrine stimulation of matrix synthesis of pancreatic stellate cells via TGFbeta1 released by activated macrophages. We suggest that macrophages might play a pivotal role in the development of pancreas fibrosis.

Depending on their concentration oxidized low density lipoproteins stimulate extracellular matrix synthesis or induce apoptosis in human coronary artery smooth muscle cells.

Abstract Various lines of evidence indicate that oxidative stress resulting in lipid peroxidation and protein modification is involved in the pathogenesis of atherosclerosis and coronary heart disease. We have investigated the effect of modified (oxidized) low-density lipoproteins (oxLDL) on collagen and fibronectin synthesis in cultured human coronary artery smooth muscle cells (HCA-SMC). As shown by immunofluorescence microscopy and time-resolved fluorescence immunoassay, oxLDL dose-dependently stimulated collagen type I and fibronectin synthesis in cultured HCA-SMC. The effect on matrix synthesis was biphasic, with a maximum effect at concentrations between 1 and 10 μg/ml oxLDL. Higher oxLDL concentrations (>25 μg/ml) were cytotoxic. Beside oxLDL, malondialdehyde-modified LDL also stimulated extracellular matrix synthesis. In the presence of 100 μg/ml ascorbic acid, 25, 50 and 100 μg/ml oxLDL induced apoptosis within 6–8 hours (demonstrated by TUNEL-reaction, annexin-V binding and APO-2.7-expression). Apoptosis was not induced by normal (unmodified) LDL and malondialdehyde-modified LDL. The radical scavengers and antioxidants TROLOX and probucol and the hydrogen peroxide eliminator catalase significantly reduced oxLDL-induced apoptosis. Our results demonstrate that low concentrations of oxLDL are profibrogenic by stimulating extracellular matrix synthesis, whereas higher oxLDL concentrations induce oxidative stress and apoptosis in coronary artery smooth muscle cells. The profibrogenic effect might be relevant in the formation of atherosclerotic plaques, and the proapoptotic effect might contribute to an increased plaque vulnerability.

Triplex-forming oligodeoxynucleotides targeting survivin inhibit proliferation and induce apoptosis of human lung carcinoma cells

Survivin is expressed in most cancers but is undetectable in differentiated adult cells, and plays an important role both in the suppression of apoptosis and mitotic spindle checkpoint; thus it has attracted great interest as a potential drug target. In this study, we investigated the antigene and antiproliferative effects of triplex-forming oligodeoxynucleotides (TFO) targeting survivin in human lung carcinoma A549 cells. Survivin-specific TFOs form stable triplexes under physiological conditions as tested by electrophoretic mobility shift assays. Treatment of A549 cells with survivin-specific but not control TFOs at a concentration of 400 nM in the presence of uptake-enhancing liposome significantly reduced survivin protein level, inhibited cell proliferation, and induced cell apoptosis as demonstrated by immunoblot, cell number counting, and Annexin V-staining. Moreover, we found that the triplex-forming potential of TFOs measured in vitro does not necessarily correlate with the ability of TFOs to affect expression of a targeted gene in vivo. Our results indicate that targeting survivin is a promising alternative strategy for the development of novel anticancer therapeutics.

The immunosuppressive drug mycophenolic acid reduces endothelin-1 synthesis in endothelial cells and renal epithelial cells.

Several studies have demonstrated that endothelin-1 (ET-1) plays an important pathophysiological role in ischaemic renal failure and drug-induced renal injury, such as cyclosporine A (CsA)- and tacrolimus-associated nephrotoxicity. This study aimed to investigate whether the new immunosuppressive drug mycophenolic acid (MPA), which in contrast with CsA and tacrolimus lacks nephrotoxic side effects, modulates ET-1 synthesis in endothelial cells and renal epithelial cells. ET-1 release by cultured human umbilical vein endothelial cells (HUVEC), human renal artery endothelial cells (RAEC) and rabbit proximal tubule cells was measured with a specific ELISA. ET-1 mRNA expression was investigated by reverse transcription-PCR. MPA (2.5-50 microg/ml) induced a significant decrease in ET-1 mRNA expression (minimum 51.8+/-3.8% of control; P<0.001) in HUVEC and RAEC. After a 48 h incubation with MPA (1-50 microg/ml), a significant decrease in ET-1 release per culture well (minimum 56.8+/-1.7%; P<0.001) and DNA content per culture well (minimum 58.7+/-1.9%; P<0.001) was observed with HUVEC and RAEC, whereas ET-1 release referred to the DNA content in the corresponding culture well did not differ significantly from controls. In rabbit proximal tubule cells, ET-1 release referred to the cell number in the corresponding culture well was also reduced after incubation with MPA (minimum 86.2+/-2.4%; P<0.05). This study provides evidence that, in contrast with CsA and tacrolimus, MPA does not stimulate ET-1 synthesis. The present results might explain the clinical observation that renal function often improves when CsA or tacrolimus is replaced by mycophenolate mofetil.

Characterization of modified low density lipoprotein subfractions by capillary isotachophoresis

Oxidative modification of low density lipoproteins (LDLs) is an important pathogenetic factor in atherosclerosis. The various steps in oxidative modifications of LDL can be monitored using different methodologies with varying degrees of complexity. In this study, we propose capillary isotachophoresis (CITP) as a suitable tool to detect and measure the degree of oxidation of LDL. LDL was isolated from pooled plasma of healthy volunteers by sequential ultracentrifugation, and oxidation was performed in vitro as well as in cell culture experiments. Native LDL and oxidatively modified LDL were characterized by apo B‐100 fluorescence and conjugated diene formation. Samples were separated by CITP combined with sudan black B staining. To underline the inherent advantages of this approach, CITP was compared with classical lipoprotein electrophoresis using agarose gel. We demonstrate the CITP method to be highly sensitive, as changes in peak area of the separated LDL subfractions were detected after only 2 h of oxidation. The leading LDL peaks increased, while the terminating LDL peaks decreased in parallel throughout the duration of oxidation. The LDL samples, oxidized for 4–24 h, also exhibited an increased migration velocity of the fractions. In summary, we present the first study investigating LDL‐subfractions separated by CITP and the alterations of these LDL‐subfractions after gradual in vitro oxidation and after oxidative modification by monocyte‐derived macrophages and vascular smooth muscle cells.

Liposomal delivery of antisense oligonucleotides for efficient downregulation of Bcl-2 and induction of apoptosis.

AIM The aim of this study was to enhance the delivery and thus anti-tumoral efficiency of antisense bcl-2 oligonucleotides (ODNs). METHODS Bcl-2 overexpressing DoHH2 lymphoma and HeLa-cells were transfected with ODNs using a polycationic liposome preparation. Specific hybridization of antisense ODNs was demonstrated by gel-shift assays and in vitro transcription/translation studies. Cellular uptake of oligonucleotides was evaluated by fluorescence microscopy. Inhibition of bcl-2 translation was demonstrated by quantitative RT-PCR and Western Blot. TUNEL assay, ANNEXIN V-binding and Apo-2.7 expression were performed to evaluate induction of apoptosis. RESULTS Using polycationic liposomes, a ODN transfection rate of 95% in HeLa and 45% in DoHH2 cells were demonstrated by fluorescence microscopy. 24 hours after transfection quantitative RT-PCR detected a 56% decrease of bcl-2 mRNA in antisense and a 7% decrease in sense transfected DoHH2 cells (p < 0.05). In HeLa-cells, bcl-2 expression was almost completely inhibited 72 hours after antisense ODN transfection. Antisense treated cells also showed significant induction of apoptosis. CONCLUSIONS Polycationic liposome-mediated transfection of bcl-2 antisense ODNs causes enhanced cellular uptake and efficient bcl-2 downregulation in bcl-2 overexpressing cell lines. This delivery strategy may explain why significant induction of apoptosis was achieved at low oligonucleotide concentrations (approximately 200 pmol/5 x 10(5) tumor cells).

Inhibitory effect of epidermal growth factor and hepatocyte growth factor on endothelin-1 release by rabbit proximal tubule cells

Several studies have demonstrated an upregulation of endothelin-1 (ET-1) synthesis in acute and chronic renal failure. Epidermal growth factor (EGF) and hepatocyte growth factor (HGF) have been shown to stimulate renal tubular cell proliferation and to accelerate renal regeneration after drug-induced and ischemia-induced renal injury. This study aimed to investigate the effect of EGF and HGF on ET-1 release, and whether the effect of EGF and HGF is antagonized by the tyrosine kinase inhibitor lavendustin A. Rabbit proximal tubule cells were incubated for 48 h with EGF or HGF (0.1-10.0 nM), lavendustin A (0.1-10.0 microM) or co-incubated with EGF or HGF (1 nM) and lavendustin A. ET-1 concentrations in the culture medium were measured with a specific enzyme-linked immunosorbent assay (ELISA). EGF and HGF exerted a significant (p < 0.001) dose-dependent inhibitory effect on ET-1 release. Lavendustin A induced a dose-dependent stimulation of ET-1 release and antagonized the inhibitory effect of EGF and HGF on ET-1 release. The inhibition of EGF and HGF receptor tyrosine kinase activity by lavendustin A was confirmed by Western blotting. These data suggest that EGF and HGF reduce ET-1 release via EGF and HGF receptor tyrosine kinase activity. The inhibitory action of EGF and HGF on ET-1 release might be involved in mediating the protective effects of EGF and HGF in renal injury.

Pancreatic Stellate Cells and Their Role in Fibrogenesis

Pancreas fibrosis is a result of an increased deposition and a reduced degradation of extracellular matrix.1,2 Until recently the molecular mechanisms and cell-cell interactions resulting in pancreas fibrosis were largely unknown. Years ago the presence of retinoid containing fat-storing cells was demonstrated in panceas of mice,3 rats and humans.4 While a potential role of these cells in pancreas remodelling and fibrosis was already discussed by Ikejiri et al.,4 it took another 8 years to isolate and characterize these cells.5,6 In 1998 we reoprted the isolation of retinoidcontaining fat-storing cells from pancreas of humans, rats, and mice.6 Because these cells show similarities in their retinoid metabolism and morphology to hepatic stellate cells e.g. numerous retinoid-containing perinuclear fat droplets, cytoplasmic extensions, stellate shape morphology, expression of the cytoskeletal filaments vimentin, desmin, and α-smooth muscle actin, we named them pancreatic stellate cells (PSC).6