Islet Stellate Cells Isolated from Fibrotic Islet of Goto-Kakizaki Rats Affect Biological Behavior of Beta-Cell

We previously isolated islet stellate cells (ISCs) from healthy Wistar rat islets. In the present study, we isolated "already primed by diabetic environment" ISCs from islets of Goto-Kakizaki rats, determined the gene profile of these cells, and assessed the effects of these ISCs on beta-cell function and survival. We detected gene expression of ISCs by digital gene expression. INS-1 cell proliferation, apoptosis, and insulin production were measured after being treated with ISCs supernatant (SN). We observed the similar expression pattern of ISCs and PSCs, but 1067 differentially expressed genes. Insulin production in INS-1 cells cultured with ISC-SN was significantly reduced. The 5-ethynyl-2'-deoxyuridine-positive INS-1 cells treated with ISC-SN were decreased. Propidium iodide- (PI-) positive INS-1 cells were 2.6-fold higher than those in control groups. Caspase-3 activity was increased. In conclusion, ISCs presented in fibrotic islet of GK rats might be special PSCs, which impaired beta-cell function and proliferation and increased beta-cell apoptosis.

Molecular determinants of the profibrogenic effects of endothelin-1 in pancreatic stellate cells

AIM: To gain molecular insights into the expression and functions of endothelin-1 (ET-1) in pancreatic stellate cells (PSC).

METHODS: PSCs were isolated from rat pancreas tissue, cultured, and stimulated with ET-1 or other extracellular mediators. Cell proliferation was assessed by measuring the incorporation of 5-bromo-2’-deoxyuridine into DNA and cell migration was studied in a transwell chamber assay. Gene expression at the level of mRNA was quantified by real-time polymerase chain reaction. Expression and phosphorylation of proteins were monitored by immunoblotting, applying an infrared imaging technology. ET-1 levels in cell culture supernatants were determined by an enzyme immunometric assay. To study DNA binding of individual transcription factors, electrophoretic mobility shift assays were performed.

RESULTS: Among several mediators tested, transforming growth factor-β1 and tumour necrosis factor-α displayed the strongest stimulatory effects on ET-1 secretion. The cytokines induced binding of Smad3 and NF-κB, respectively, to oligonucleotides derived from the ET-1 promoter, implicating both transcription factors in the induction of ET-1 gene expression. In accordance with previous studies, ET-1 was found to stimulate migration but not proliferation of PSC. Stimulation of ET-1 receptors led to the activation of two distinct mitogen-activated protein kinases, p38 and extracellular signal-regulated kinases (ERK)1/2, as well as the transcription factor activator protein-1. At the mRNA level, enhanced expression of the PSC activation marker, α-smooth muscle actin and two proinflammatory cytokines, interleukin (IL)-1β and IL-6, was observed.

CONCLUSION: This study provides novel lines of evidence for profibrogenic and proinflammatory actions of ET-1 in the pancreas, encouraging further studies with ET-1 inhibitors in chronic pancreatitis.

Influence of somatostatin to biochemical parameters in patients with primary hyperparathyroidism

Somatostatin (SRIF) is effective in the nonoperative management of a variety endocrine tumors. A potential role of SRIF for treatment of patients with primary hyperparathyroidism (pHPT) has been suggested. In a controlled, prospective, triple-blinded, randomized clinical trial, the somatostatin analogue octreotide (SMS 201-995, Sandostatin) was evaluated in 40 patients with well documented pHPT. Amongst other biochemical parameters, serum calcium and-phosphate and levels of parathyroid hormone, calcitonin, and osteocalcin as well as octreotide were assessed before and for 4 hours after a single iv. application of 200 micrograms ocreotide or placebo. SRIF-receptor autoradiography was performed in parathyroid tissue samples. Baseline values revealed a constellation of biochemical parameters typically found in pHPT. Following 200 micrograms octreotide, no significant changes in any of the biochemical parameters investigated for were observed. Multivariate analysis was performed to identify patient subpopulations in which any given combination of laboratory parameters changed in response to either drug or placebo. However, no 'responders' to octreotide were identified. 45% of patients receiving octreotide, reported side effects. Parathyroid tissue samples were negative for SRIF-receptor expression. It is concluded that a single dose iv. application of octreotide does not result in appreciable changes of biochemical parameters relevant in pHPT and carries a high rate of side effects. Furthermore, absence of SRIF-receptors in parathyroid tissue from patients with pHPT, together with lack of octreotide effects, suggests that somatostatin-analogues may not be effective in the non-operative therapy of pHPT.

Identification of a novel switch in the dominant forms of cell adhesion-mediated drug resistance in glioblastoma cells

The failure of malignant cells to undergo apoptosis is a major obstacle in cancer therapy, and thus identifying the underlining molecules involved therein is imperative for improving patient survival. An important mechanism of drug resistance is cell adhesion-mediated drug resistance (CAM-DR). In this study we identify a novel switch by which glioblastoma multiforme (GBM) cells alter the mode of CAM-DR. In the absence of a microenvironmental cue provided by components of the extracellular matrix (ECM), GBM cells are able to employ an alternative, but equally effective, mode of CAM-DR by forming spheres via cell-cell interactions. Intriguingly, when inhibiting cell-cell interactions in the absence of ECM components, either by low cell density or by inhibition of gap junctions (intercellular connexin tunnels) through chemical inhibition with carbenoxyolone or co-incubation with the connexin-mimicking Gap 27 Cx37,43 peptide, GBM cells were sensitized to tumor necrosis factor-related apoptosis-inducing ligand- and CD95-induced apoptosis. By demonstrating that GBM cells can alternate from one form of CAM-DR (cell-substrate tethering) to another (homocellular cell-cell adhesion) and that inhibition of both forms is necessary for apoptosis sensitization, our findings not only have important implications for novel approaches to restore defective apoptosis programs, but also reveal a novel role of gap junctions in GBM.

Oxidized low density lipoproteins induce apoptosis in human lymphocytes: involvement of mitogen-activated protein kinases

Oxidized low density lipoproteins (oxLDL), macrophages and T-lymphocytes are present in atherosclerotic lesions. We and others have shown that oxLDL is cytotoxic for macrophages, endothelial, smooth muscle and activated T-lymphocytes and induce apoptosis. Here we demonstrate that (i) oxidized LDL (oxLDL), oxidized VLDL (oxVLDL) and hydrogen peroxide (H2O2) induce apoptosis in human T-lymphocytes and (ii) mitogen-activated protein kinases are involved in this process. Apoptosis was monitored by immunofluorescence microscopy and flow cytometry for annexin V binding, Apo 2.7 expression, the TUNEL reaction and caspase 3 activity. In the presence of oxLDL (100 microg/ml), oxVLDL (50 microg/ml) and H2O2 (5 mM), the fraction of apoptotic cells increased within 6 hours to more than 70%. Preincubation of lymphocytes with the MAPKK inhibitor PD-98059 and the p38MAPK inhibitor SB-203580 almost completely abolished these effects. Furthermore, oxLDL and H2O2 but not native LDL strongly enhanced phosphorylation of JNK, p38MAPK and p42/44MAPK. The results suggest that in the resting lymphocyte apoptosis triggered by oxidized lipoproteins and oxidative stress depends on the activation of p44/42MAPK and p38MAPK cascades.

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.

Influence of hepatocyte growth factor, epidermal growth factor, and mycophenolic acid on endothelin-1 synthesis in human endothelial cells

BACKGROUND

Endothelin-1 (ET-1) is a potent vasoconstrictive peptide which plays an important pathophysiological role in ischaemic renal failure and drug-induced renal injury such as cyclosporin A (CsA)- and tacrolimus-associated nephrotoxicity. In contrast, hepatocyte growth factor (HGF) and epidermal growth factor (EGF) seem to accelerate renal regeneration after ischaemic and drug-induced renal injury. This study aimed to investigate the influence of HGF and EGF on ET-1 synthesis in cultured human umbilical vein endothelial cells (HUVEC) and renal artery endothelial cells (RAEC). In addition, we have investigated whether mycophenolic acid (MPA), a new immunosuppressive drug, which in contrast to CsA and tacrolimus lacks nephrotoxic side effects, modulates ET-1 synthesis in endothelial cells.

METHODS

ET-1 release was measured with a specific enzyme-linked immunosorbent assay. ET-1 mRNA expression was investigated by reverse transcription polymerase chain reaction.

RESULTS

HGF and EGF (0.001-10 nM) exerted a significant concentration-dependent inhibitory effect on ET-1 release by HUVEC and RAEC (minimum 56.1+/-4.3% of control, n=6, mean+/-SE). The suppressive effect of HGF and EGF on ET-1 synthesis was dose-dependently antagonized by the tyrosine kinase inhibitors tyrphostin AG1478, lavendustin A and methyl 2,5-dihydroxycinnamate. Incubation of HUVEC and RAEC with MPA (2.5, 10, 25, and 50 microg/ml) for 3-5 h induced a significant reduction of ET-1 mRNA expression. After 48 h incubation with MPA (1-50 microg/ml) a significant decrease of ET-1 release and DNA content per culture well was observed, whereas ET-1 release referred to the DNA content in the corresponding culture well did not differ significantly from controls.

CONCLUSIONS

The present findings demonstrate that HGF and EGF reduce ET-1 synthesis in endothelial cells via their receptor tyrosine kinase activity and suggest that the renoprotective effects of HGF and EGF might be linked to their inhibitory action on ET-1 synthesis. This study also provides evidence that, in contrast to CsA and tacrolimus, MPA does not stimulate ET-1 synthesis. This might explain the clinical observation that renal function often improves when CsA or tacrolimus is replaced by mycophenolate mofetil.

Oxidized low-density lipoproteins bind to the scavenger receptor, CD36, of hepatic stellate cells and stimulate extracellular matrix synthesis

Cumulating evidence suggests that oxidative stress resulting in lipid peroxidation and protein modification is involved in the pathogenesis of chronic liver injury and fibrogenesis. We investigated the effects of oxidized low-density lipoproteins (oxLDL) on collagen and fibronectin synthesis of cultured human and rat hepatic stellate cells (HSC). As shown on protein and mRNA levels, oxLDL dose-dependently stimulated the synthesis of collagen types I and III and fibronectin of cultured HSC. The effect was biphasic, with a maximum between 5 and 25 microg/mL oxLDL (c-fibronectin concentration in HSC supernatants increased 3.9-fold; collagen type I increased 4-fold). Higher oxLDL concentrations were cytotoxic. LDL modified with malondialdehyde (MDA) was not toxic, but stimulated extracellular matrix synthesis as well. As demonstrated by immunofluorescence microscopy (double staining of CD36 and iso-alpha-smooth muscle actin [iso-alpha-sm actin]), immunoblot, and reverse-transcription polymerase chain reaction (RT-PCR), respectively, cultured human HSC express the oxLDL receptor, CD36 (glycoprotein IIIb). Colocalization of CD36 and iso-alpha-sm actin on sinusoidal lining cells was further demonstrated using sections of human fibrotic liver. Preincubation of cultured human HSC with the monoclonal antibody, OKM5, known to block CD36-mediated oxLDL uptake, resulted in a reduction of the oxLDL-stimulated collagen type I synthesis by 56%. In summary, our results demonstrate that low concentrations of modified lipoproteins (oxLDL and MDA-LDL) represent fibrogenic mediators that bind to CD36 and stimulate matrix synthesis of HSC.

Endothelin-1 synthesis and endothelin B receptor expression in human coronary artery smooth muscle cells and monocyte-derived macrophages is up-regulated by low density lipoproteins

Endothelin-1 (ET-1) is a potent vasoconstrictive peptide exerting its effects predominantly by paracrine and autocrine mechanisms. ET-1 acts as a mitogen and co-mitogen on vascular smooth muscle cells, and accumulating evidence suggests that ET-1 is involved in the pathogenesis of atherosclerosis. Deposition of low density lipoproteins (LDL) in the vessel wall is known to play a crucial role in the development of atherosclerotic lesions. In the present study, we have investigated the effect of native LDL (nLDL) and oxidatively modified LDL (oxLDL) on ET-1 synthesis and endothelin receptor expression in cultured human coronary artery smooth muscle cells and human monocyte-derived macrophages. Native LDL and oxLDL induced a significant stimulation of ET-1 release and ET-1 mRNA expression in human coronary artery smooth muscle cells and monocyte-derived macrophages. Antibodies against the scavenger receptor CD36 significantly reduced the oxLDL-induced stimulation of ET-1 synthesis. The antioxidants trolox and probucol did not significantly inhibit the LDL-induced rise of ET-1 release. Endothelin B receptor expression was up-regulated in both cell types after incubation with nLDL and oxLDL. In coronary smooth muscle cells, endothelin A receptor expression was slightly increased by LDL, whereas endothelin A receptor was not detectable in monocyte-derived macrophages. Coronary artery smooth muscle cells secreted a more than 150-fold higher amount of immunoreactive ET-1 into the cell culture medium than monocyte-derived macrophages. In summary, the present data, demonstrating a LDL-induced up-regulation of the endothelin system in coronary smooth muscle cells and in monocyte-derived macrophages, provide further support for a pathophysiological role of endothelin in coronary atherosclerosis and suggest that ET-1 might be involved in mediating the atherogenic effects of LDL.

Identification of mediators stimulating proliferation and matrix synthesis of rat pancreatic stellate cells

The aim of this study was to identify fibrogenic mediators stimulating activation, proliferation, and/or matrix synthesis of rat pancreatic stellate cells (PSC). PSC were isolated from the pancreas of normal Wistar rats and from rats with cerulein pancreatitis. Cell activation was demonstrated by immunofluorescence microscopy of smooth muscle alpha-actin (SMA) and real-time quantitative RT-PCR of SMA, fibronectin, and transforming growth factor (TGF)-beta(1). Proliferation was measured by bromodeoxyuridine incorporation. Matrix synthesis was demonstrated on the protein and mRNA level. Within a few days in primary culture, PSC changed their phenotype from fat-storing to SMA-positive myofibroblast-like cells expressing platelet-derived growth factor (PDGF) alpha- and PDGF beta-receptors. TGF-beta(1) and tumor necrosis factor (TNF)-alpha accelerated the change in the cells' phenotype. Addition of 50 ng/ml PDGF and 5 ng/ml basic fibroblast growth factor (bFGF) to cultured PSC significantly stimulated cell proliferation (4.37 +/- 0.49- and 2.96 +/- 0.39-fold of control). Fibronectin synthesis calculated on the basis of DNA was stimulated by 5 ng/ml bFGF (3.44 +/- 1.13-fold), 5 ng/ml TGF-beta(1) (2.46 +/- 0.89-fold), 20 ng/ml PDGF (2.27 +/- 0.68-fold), and 50 ng/ml TGF-alpha (1.87 +/- 0.19-fold). As shown by RT-PCR, PSC express predominantly the splice variant EIII-A of fibronectin. Immunofluorescence microscopy and Northern blot confirmed that in particular bFGF and TGF-beta(1) stimulated the synthesis of fibronectin and collagens type I and III. In conclusion, our data demonstrate that 1) TGF-beta(1) and TNF-alpha accelerate the change in the cell phenotype, 2) PDGF represents the most effective mitogen, and 3) bFGF, TGF-beta(1), PDGF, and, to a lesser extent, TGF-alpha stimulate extracellular matrix synthesis of cultured rat PSC.

Hepatocyte growth factor is upregulated by low-density lipoproteins and inhibits endothelin-1 release

Low-density lipoproteins (LDL) are known to cause endothelial injury and to promote the development of atherosclerotic lesions. This study demonstrates a significant concentration-dependent stimulatory effect of LDL on hepatocyte growth factor (HGF) synthesis (maximum release: 423 +/- 16% of control) and HGF receptor mRNA expression in cultured human coronary artery endothelial cells (HCAEC). HGF is a potent mitogen for endothelial cells but does not affect smooth muscle cell proliferation. In contrast, endothelin-1 (ET-1) acts as a mitogen on vascular smooth muscle cells and seems to be upregulated in coronary atherosclerosis. In this study, the basal ET-1 synthesis in HCAEC was concentration-dependently reduced by HGF (minimum: 54 +/- 3% of control). This inhibitory effect seems to be mediated via the tyrosine kinase activity of the HGF receptor c-met, since it was antagonized by the tyrosine kinase inhibitor lavendustin A. In addition, HGF also significantly reduced the LDL-stimulated ET-1 release. The LDL-induced upregulation of HGF synthesis in HCAEC and the inhibitory effect of HGF on ET-1 synthesis suggest a protective role of HGF in coronary atherosclerosis.

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 microl/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 beta (TGFbeta)- and platelet-derived growth factor (PDGF)-neutralizing antibodies and the TGFbeta-latency associated peptide, respectively, TGFbeta1 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 (TGFbeta1) 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.

Separation of lipoproteins by capillary isotachophoresis combined with enzymatic derivatization of cholesterol and triglycerides

Combining specific enzymatic derivatization of cholesterol or triglycerides with capillary isotachophoresis (CITP), human serum lipoproteins are separated into 14 lipoprotein subfractions, monitored and quantitated by direct capillary UV detection. By comparing the separation patterns of human serum with the patterns of lipoprotein particles isolated by sequential ultracentrifugation it became evident that peaks 1-5 represent lipoproteins of the high density lipoprotein (HDL) fraction, peaks 6-8 embody the very low density lipoprotein (VLDL) fraction and chylomicrons, and peaks 7-14 represent the low density lipoprotein (LDL) fraction. Peaks 7 and 8 were found in the VLDL as well as in the LDL fraction. Using triglyceride-specific staining peaks 6-8 occurred prominently; and with cholesterol-specific staining, peaks 1-5 and 7-14 were prominent. The coefficient of variation, for the sum of the peak heights of a pooled serum, was 3.94 for triglyceride-specific staining and 2.32 for cholesterol-specific staining. A linearity range between 0.23 and 2.29 mM/L was found for triglyceride-specific staining and between 0.043 and 4.33 mM/L for cholesterol-specific staining. The practicability of the method was evaluated (i) using blood of humans before and 45 min after an oral fat load. Triglyceride-specific staining revealed a prominent increase in the VLDL fraction and chylomicrones containing peaks 6 and 7, and a minor increase in the HDL fraction containing peaks 3 and 4, and (ii) in patients with manifest hypothyroidism before and after thyroxine therapy. Cholesterol-specific staining demonstrated a massive decrease in the first peak of the HDL fraction and in peaks 9 and 11 of the LDL fraction regarding the hypo versus hyperthyroid state.

Alpha2-macroglobulin reduces paracrine- and autocrine-stimulated matrix synthesis of cultured rat hepatic stellate cells

BACKGROUND

Transforming growth factor beta1 (TGF-beta1) is considered to represent a major fibrogenic mediator in the liver. The aim of the present study was to investigate whether alpha2-macroglobulin (alpha2M) might reduce paracrine- and autocrine-stimulated matrix synthesis of cultured rat hepatic stellate cells (HSCs) by scavenging TGF-beta.

METHODS AND RESULTS

Using native agarose electrophoresis, we demonstrated that alpha2M binds [125I]-TGF-beta1 within minutes. Preincubation of transiently acidified supernatants of cultured Kupffer cells, secondary cultured (activated) HSC and platelet lysate with, respectively, 500 and 2000 microg mL-1 alpha2M significantly reduced the concentration of active TGF-beta1 in these media. As a consequence of TGF-beta scavenging by alpha2M, paracrine-stimulated proteoglycan synthesis of primary cultured HSCs was reduced significantly. Furthermore, addition of 200 microg mL-1 alpha2M to passaged (activated) HSCs resulted in (a) a reduction in autocrine-stimulated extracellular matrix synthesis (proteoglycan -52%, fibronectin -55%) and (b) increased cell proliferation. A similar reduction in matrix synthesis was observed after the addition of 5 micromol L-1 TGF-beta1 antisense oligonucleotide to activated HSCs.

CONCLUSION

We conclude that alpha2M reduces paracrine-and autocrine-stimulated extracellular matrix synthesis of cultured HSCs by scavenging TGF-beta. These mechanisms might restrict liver fibrogenesis.

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

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 microg/ml oxLDL. Higher oxLDL concentrations (>25 microg/ml) were cytotoxic. Beside oxLDL, malondialdehyde-modified LDL also stimulated extracellular matrix synthesis. In the presence of 100 microg/ml ascorbic acid, 25, 50 and 100 microg/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.

Identification, culture, and characterization of pancreatic stellate cells in rats and humans

BACKGROUND & AIMS

Until now, the basic matrix-producing cell type responsible for pancreas fibrosis has not been identified. In this report, retinoid-containing pancreatic stellate cells (PSCs) in rat and human pancreas are described, and morphological and biochemical similarities to hepatic stellate cells are shown.

METHODS

Electron and immunofluorescence microscopy (collagen types I and III, fibronectin, laminin, alpha-actin, and desmin) was performed using pancreatic tissue and cultured PSCs. Extracellular matrix synthesis was shown using quantitative immunoassay and Northern blot analysis.

RESULTS

PSCs are located in interlobular areas and in interacinar regions. Early primary cultured PSCs contain retinol and fatty acid retinyl-esters. Addition of retinol to passaged cells resulted in retinol uptake and esterification. During primary culture, the cells changed from a quiescent fat-storing phenotype to a highly synthetic myofibroblast-like cell expressing iso-alpha-smooth muscle actin (>90%) and desmin (20%-40%) and showing strong positive staining with antibodies to collagen types I and III, fibronectin, and laminin. As determined on protein and messenger RNA level, serum growth factors stimulated the synthesis of collagen type I and fibronectin.

CONCLUSIONS

The identification of PSCs, particularly in fibrotic areas, and the similarities of these cells to hepatic stellate cells suggest that PSCs participate in the development of pancreas fibrosis.

Immediate metabolic effects of different nutritional regimens in critically ill medical patients

OBJECTIVE

Metabolic effects of different caloric regimens were investigated in nonsurgical, medical patients with multiple-organ failure (MOF).

DESIGN

Seven total parenteral nutrition (TPN) regimens were administered, differing in amount (14, 28, and 56 kcal/kg per day, i.e., hypo-, iso-, and hypercaloric nutrition, respectively) and distribution [carbohydrates (COH), amino acids (AA), long-chain and medium-chain triglycerides (LCT/MCT)] of calories. Each regimen was administered over 12 h. Metabolism was monitored by energy expenditure (EE), body temperature (BT), protein breakdown (PB), and blood glucose and serum lactate levels. Measurements were started within 2 days of MOF onset.

SETTING

The study was conducted in a medical intensive care unit.

PATIENTS

Twenty patients with MOF on mechanical ventilation (mean Apache II score x = 26) were investigated.

MEASUREMENTS AND RESULTS

The mean values of the EE (x = 31 kcal/kg per day), BT (x = 38 degrees C), PB (x = 1.5 g/kg per day), and lactate (x = 2.0 mmol/l) and glucose level (x = 222 mg/dl) parameters were elevated. EE, BT, and lactate and glucose levels were significantly lower under hypocaloric nutrition than during iso- and hypercaloric nutrition (p < 0.01). Differences in the metabolic effects of LCT and MCT were not significant. PB was significantly elevated under hypercaloric nutrition (p < 0.01). Protein balance was positive under hypercaloric nutrition, and negative under iso- and hypocaloric nutrition.

CONCLUSIONS

In nonsurgical, medical patients neither hypercaloric nor isocaloric nutritional support prevented protein catabolism; in contrast, they enhanced the metabolic burden measured by EE, thermogenesis, urea production rate, and glucose and lactate levels. A hypocaloric regimen is therefore recommended for these patients during the early phase of MOF.

Molecular mechanisms of liver fibrogenesis--a homage to the role of activated fat-storing cells

During the last few years, considerable progress has been made in the dissection of cellular and molecular mechanisms of hepatic fibrogenesis. The disease, initiated by hepatocellular damage and perpetuated by inflammatory reactions, results not only in an overall increase in extracellular matrix (ECM) but also in molecular and histological rearrangement of virtually all matrix molecules including collagens, structural glycoproteins, proteoglycans and hyaluronan. These alterations of ECM cause severe clinical (e.g. hemodynamic) complications and further metabolic changes in the whole organ. Perisinusoidal fat (retinoid)-storing cells have been identified as the (precursor) cell type mainly responsible for matrix production in the diseased liver. However, these cells have to be activated, i.e. stimulated to proliferate, to transform phenotypically to myofibroblasts and to express matrix genes before full competency for fibrogenesis is reached. Multiple cell interactions with Kupffer cells, platelets, endothelial cells and hepatocytes mediated by various cytokines and growth factors (e.g. TGF-beta 1, TGF-alpha, PDGF, FGF, IGF-1) are involved in the mechanism of fat-storing cell activation which is the common and central pathogenetic mechanism in fibrogenesis. A three-step cascade model of fat-storing cell activation is proposed, which offers target mechanisms for possible anti-fibrotic interventions.

Regulation of proteoglycan expression in fibrotic liver and cultured fat-storing cells

Considerable progress has been made in recent years with the molecular dissection of proteoglycans in normal and fibrotic human and rat liver. Proteoglycans constitute a major fraction of extracellular, pericellular and intracellular glycoconjugates. In former times, proteoglycans were classified nearly exclusively on the basis of the composition of their carbohydrate chain (glycosaminoglycan, GAG) attached to the core protein. Accordingly, three main types are discerned in liver, which are in order of decreasing concentrations heparan sulfate (HS, more than 60% of total GAG), dermatan sulfate and chondroitin-4,6-sulfate isomers. Keratan sulfate has not been detected in rat and human liver. Recently, proteoglycans have been characterized by sequencing and cloning of the core proteins to which a number of specific glycosaminoglycan side chains are covalently linked. Accordingly, decorin and biglycan have been identified as major chondroitin sulfate/dermatan sulfate proteoglycans in the extracellular space. In addition, evidence was obtained recently for the expression of aggrecan and lumican, both keratan sulfate bearing proteoglycans, and of syndecan in liver. Using in situ hybridization techniques the temporal and spatial pattern of expression of biglycan, decorin and aggrecan has been assessed. These studies together with Northern blot hybridizations performed with isolated parenchymal and nonparenchymal liver cells confirm that fat-storing cells (Ito cells, perisinusoidal lipocytes), are the most important, principal cellular site of proteoglycan production in diseased liver. The level of expression is regulated by a number of cytokines among which TGF beta, TNF alpha and TGF alpha play significant roles. The effects of these cytokines on proteoglycan expression are dependent on the stage of phenotypic transition of fat storing cells to the activated myofibroblast. Taken together, these data point to the potentially significant role which proteoglycans might fulfil in the regulation of cellular functions and in the maintenance of the supramolecular organization of the extracellular matrix in normal and in diseased liver during the process of fibrogenesis.

Tumor necrosis factor alpha (TNF alpha) and transforming growth factor beta 1 (TGF beta 1) stimulate fibronectin synthesis and the transdifferentiation of fat-storing cells in the rat liver into myofibroblasts

Transforming growth factor-beta (TGF beta 1) and tumor necrosis factor alpha (TNF alpha) stimulate the transdifferentiation of fat-storing cells (FSC) in the rat liver into highly active and "synthetic" myofibroblast-like cells (MFBIC). This activation has been documented by differential-interference contrast and light microscopy using morphologic criteria (a reduction in the number and size of fat droplets, cell flattening and the development of long cytoplasmic extensions), by the loss of retinyl-palmitate (measured by HPLC) and by the enhanced expression of iso-alpha smooth muscle actin (demonstrated by immunofluorescence microscopy). Furthermore, while cell growth measured by the cell count and DNA content is slightly inhibited by TGF beta 1 (0.81 of the control), the combination of TGF beta 1 with TNF alpha stimulates cell proliferation to 1.44 times of the control. In addition the combination of TGF beta and TNF alpha potentiated the stimulatory effect on fibronectin synthesis (TGF beta alone: 1.4 times control; TNF alpha alone: 2.2 times control; TGF beta plus TNF alpha: 4.7 times control). The total protein synthesis was not altered by TGF beta or TNF alpha. In summary the results obtained identify TGF beta and TNF alpha as mediators stimulating key events in liver fibrogenesis (i.e. FSC proliferation, FSC transdifferentiation into MFBIC, and fibronectin synthesis).

The response of rat liver perisinusoidal lipocytes to polypeptide growth regulator changes with their transdifferentiation into myofibroblast-like cells in culture

During culture on uncoated plastic wells rat liver perisinusoidal lipocytes change their differentiated phenotype (transdifferentiate) within 1-2 weeks and obtain a myofibroblast-like phenotype (myofibroblast-like cells). This transdifferentiation was documented by morphologic (loss of fat droplets, flat cell shape, cytoplasmic extensions, expression of iso-alpha smooth muscle actin) and biochemical criteria (loss of retinyl-palmitate, enhanced matrix synthesis). Whereas transforming growth factor alpha (TGF alpha) stimulated and transforming growth factor beta (TGF beta 1) inhibited the proliferation of perisinusoidal lipocytes (early culture) these cytokines did not effect the growth of the myofibroblast-like cells. Opposite effects were obtained with platelet-derived growth factor (PDGF) which stimulated the growth of myofibroblast-like cells only. Insulin-like growth factor (IGF1) was mitogenic in both perisinusoidal lipocytes and myofibroblast-like cells, respectively. Furthermore, whereas the expression of the mRNAs of decorin and biglycan was stimulated by TGF beta 1 in perisinusoidal lipocytes, the synthesis of these mRNAs was stimulated in myofibroblast-like cells predominantly by TGF alpha. Similar effects of TGF alpha and TGF beta 1 have been observed on the glycosaminoglycan-([35S]sulfate incorporation) and proteoglycan level ([3H]leucin incorporation into decorin and biglycan). Neither IGF1 and PDGF stimulated glycosaminoglycan synthesis in perisinusoidal lipocytes or in myofibroblast-like cells. The results demonstrate that the effects of the polypeptide growth regulators TGF alpha, TGF beta 1 and PDGF depend on the cell phenotype (stage of cell activation/transdifferentiation) and may be completely different in perisinusoidal lipocytes and its transformed counterpart the myofibroblast-like cells.

Serum iron, ferritin, and vitamin B12 during prolonged omeprazole therapy

Since gastric acid plays an important role in the absorption process of iron and vitamin B12, we determined levels of iron, ferritin, vitamin B12, and folic acid in 75 serum samples obtained during continuous omeprazole therapy (6-48 months after start of therapy) from 34 patients with peptic diseases (primarily reflux esophagitis). Serum iron and ferritin levels were decreased in two and three patients, respectively, but there is little evidence that omeprazole administration was causally related to these findings. Serum vitamin B12 and folic acid levels were normal in all cases. We conclude that iron, vitamin B12, and folic acid malabsorption is unlikely to occur, at least within the initial 3-4 years of continuous omeprazole therapy.

Activation of rat liver perisinusoidal lipocytes by transforming growth factors derived from myofibroblastlike cells. A potential mechanism of self perpetuation in liver fibrogenesis

Rat liver perisinusoidal lipocytes (PL) cultured on uncoated plastic transform spontaneously within 6-10 d to myofibroblastlike cells (MFBlC). Parallel to the transformation the TGF alpha- and TGF beta 1-mRNA expression increased and was highest in MFBlC. Competitive radioligand binding assays demonstrated that in contrast to untransformed PL the MFBlC synthesize and secrete transforming growth factor (TGF)-alpha (15 fmol/cell per 24 h) and predominantly the latent form of TGF beta 1 (0.2 fmol/cell per 24 h). Medium conditioned by MFBlC (MFBcM) significantly stimulated PL proliferation with little effect on PL proteoglycan synthesis. By transient acidification of the MFBcM, known to activate the latent form of TGF beta 1, the stimulatory effect on PL proteoglycan synthesis was enhanced and furthermore PL transformation (measured by expression of iso-alpha smooth muscle actin and loss of retinylpalmitate) was accelerated. Preincubation of this medium with neutralizing antibodies to TGF beta resulted in (a) the growth inhibitory effect was converted to a growth stimulation and (b) the stimulatory effect on proteoglycan synthesis was abolished. In summary our data indicate that progressive activation of PL on plastic (transformation to MFBlC) leads to an enhanced expression of the TGF alpha- and TGF beta 1-mRNAs and secretion of the corresponding proteins. Medium conditioned by MFBIC stimulates proliferation, transformation, and PG synthesis of untransformed PL. These mechanisms are suggested to be relevant in self perpetuation of liver fibrogenesis.

Bidirectional effects of Kupffer cells on hepatocyte proliferation in vitro

The control of rat hepatocyte DNA synthesis in vitro by Kupffer cells and transformed perisinusoidal lipocytes, i.e. myofibroblast-like cells was studied. Conditioned media from Kupffer cells inhibit the replicative (hydroxyurea-sensitive) DNA synthesis dose-dependently in primary cultures of hepatocytes stimulated by epidermal growth factor (EGF). The cytokine responsible for the inhibition was identified as transforming growth factor beta (TGF beta). After neutralization of activated TGF beta in these media, DNA synthesis is stimulated in quiescent hepatocytes via transforming growth factor alpha (TGF alpha) demonstrated by competitive TGF alpha/EGF-receptor blocking on hepatocytes. Results similar to those obtained with Kupffer cells were found with conditioned media of myofibroblast-like cells. Northern blot hybridization confirms the expression of both TGF beta and TGF alpha in Kupffer cells and myofibroblast-like cells, respectively. These findings support the notion that Kupffer cells and myofibroblast-like cells might regulate in both directions liver regeneration depending on the proportion of secreted TGF alpha and TGF beta and on the activation status of TGF beta, of which a significant fraction is secreted in the latent form.

Modulation of hepatic lipocyte proteoglycan synthesis and proliferation by Kupffer cell-derived transforming growth factors type beta 1 and type alpha

Soluble mediators elaborated by activated Kupffer cells have been implicated in the activation of liver fat-storing cells. In the present study some of these factors were identified as TGF beta and TGF alpha affecting disparate reactions in the activation process. TGF beta is secreted in an inactive, latent form by Kupffer cells. It is activated after addition to primary FSC cultures and stimulates dose-dependently sulfated proteoglycan synthesis especially that of chondroitin sulfate, whereas the incorporation of [3H] thymidine is reduced significantly. These effects were neutralized completely by anti-TGF beta antibodies which ultimately converted the proliferation inhibitory effect of Kupffer cell medium in a proliferation stimulatory action. The latter is at least partially due to TGF alpha. Both cytokines are preferentially expressed in activated Kupffer cells. We conclude that Kupffer cells modulate the mitogenic activity of FSC in culture depending on the ratio of activated TGF beta and TGF alpha and affect chondroitin sulfate synthesis mainly by TGF beta. The results suggest a paracrine activation of FSC in injured liver by both transforming growth factors secreted by activated Kupffer cells.

Transformed fat storing cells inhibit the proliferation of cultured hepatocytes by secretion of transforming growth factor beta

Conditioned medium from secondary cultures of fat storing cells (transformed fat storing cells) inhibits replicative (hydroxyurea-sensitive) DNA synthesis dose-dependently in primary cultures of hepatocytes stimulated in vitro by transforming growth factor (TGF) alpha. Similarly, [3H]thymidine incorporation into the DNA of hepatocytes from the regenerating rat liver is reduced by about 70% by fat storing, cell conditioned medium. Medium which had been transiently acidified was more potent than native medium. It displaced [125I]TGF-beta from binding sites on the hepatocyte surface and the inhibitory activity was completely blocked by anti-TGF-beta antibodies. From binding studies, a TGF-beta concentration of 1.8 +/- 0.4 ng/ml conditioned medium produced by 2 X 10(5) cells per 24 h was estimated. Transformed, but not primary, cultures of fat storing cells at an early state produce and secrete TGF-beta, which reduces hepatocellular proliferation significantly.

Cellular sources of noncollagenous matrix proteins: role of fat-storing cells in fibrogenesis

The main types of noncollagenous ECM proteins in liver are FN, laminin, PGs and elastin. Also present is a pure carbohydrate polymer, hyaluronic acid. Their concentrations increase during fibrogenesis in a specific sequence and spatial distribution. FN is among the first to appear. The accumulation of matrix proteins in the space of Disse (perisinusoidal fibrosis) is most important for some clinical consequences of fibrosis. Perisinusoidal FSC are the cell type responsible for exaggerated ECM formation at sites of tissue injury, since these cells synthesize at a high rate in vitro all the noncollagenous matrix components occurring in fibrotic liver matrix (FN, laminin, dermatan sulfate, chondroitin sulfate, hyaluronic acid) and since FSC proliferate and transform into myofibroblast-like cells with an enhanced matrix protein synthesis rate. Recent experimental data suggest strong cellular cooperation of these cells with activated liver macrophages or Kupffer cells, platelets, and regenerating hepatocytes, which leads via a paracrine mechanism involving TGF beta, TGF alpha/EGF, PDGF, and probably other cytokines to stimulated proteoglycan synthesis, proliferation, and transformation into myofibroblast-like cells. The latter cell type has the potential of auto-stimulation (by an autocrine process) involving secretion of TGF beta and TGF alpha/EGF. Based on these findings, a model of FSC activation is proposed (Fig. 10).

Transforming growth factors (TGF alpha and TGF beta 1) stimulate chondroitin sulfate and hyaluronate synthesis in cultured rat liver fat storing cells

The synthesis of total sulfated glycosaminoglycans (GAG) was stimulated by transforming growth factors (TGF alpha 1.4-fold at 5 ng/ml, and TGF beta 1 2.05-fold at 2.5 ng/ml) in primary cultures of rat liver fat storing cells (FSC). The combination of both TGFs resulted in an additively stimulated synthesis of total sulfated GAG (more than 3-fold), chondroitin sulfate (more than 15-fold) and hyaluronate (3.8-fold), respectively, whereas the formation of dermatan sulfate was unchanged and that of heparan sulfate was slightly reduced. In summary, TGFs were identified as important mediators of stimulated GAG synthesis in those cells of the liver (FSC), which are the primary site of matrix glycoconjugate production.

The role of thrombocytes in liver fibrogenesis: effects of platelet lysate and thrombocyte-derived growth factors on the mitogenic activity and glycosaminoglycan synthesis of cultured rat liver fat storing cells

A central problem in the study of the pathogenesis of liver fibrosis (fibrogenesis) is the identification of the cellular sources of the extracellular matrix and the dissection of the molecular mediators stimulating connective tissue synthesis in certain hepatic target cells. In the present study the role of platelets and of some platelet-derived polypeptide growth factors in the proliferation and proteoglycan synthesis of rat liver fat storing cells in culture (the principle connective tissue-producing cell type in liver) was determined. Fat storing cell proliferation was determined by measurement of the DNA-content, and [3H]thymidine- and bromodeoxyuridine-incorporation. Glycosaminoglycan synthesis was determined by the measurement of [35S]sulphate incorporation. Human platelet lysate (0.3 to 2.6 g protein per litre medium) stimulated, in a dose-dependent manner, both the proliferation and glycosaminoglycan synthesis of rat liver fat storing cells kept as a primary culture in Dulbecco's modification of Eagle's medium in the absence of foetal calf serum. More than 70% of the newly synthesized glycosaminoglycans were found in the medium. Among the various thrombocyte-derived polypeptides tested as candidate mediators of the platelet-derived fibrogenic activity, platelet derived growth factor was not effective in enhancing glycosaminoglycan synthesis, and it stimulated the proliferation of fat storing cells only about 2 fold. On the other hand, epidermal growth factor proved to be a stimulus of both processes. Transforming growth factor beta (greater than 10 pmol/l) inhibited foetal calf serum (Dulbecco's modification of Eagle's medium with a fraction of foetal calf serum of 0.1) and epidermal growth factor stimulated proliferation but enhanced the synthesis of sulphated glycosaminoglycans about 2-fold. These results suggest the possible role of transforming growth factor beta as a negative modulator for fat storing cells proliferation but a positive modulator for fat storing cell transformation and extracellular glycosaminoglycan matrix synthesis. Furthermore, our results indicate a cooperation between different hepatic and extrahepatic cell types by paracrine stimulation of fat storing cells. Transforming growth factor beta in combination with epidermal growth factor appear to be candidate mediators of the platelet-derived fibrogenic activity, which stimulates fat storing cells in culture, and might also be effective in vivo during hepatic repair processes following liver injury.

Liver fat storing cell proliferation is stimulated by epidermal growth factor/transforming growth factor alpha and inhibited by transforming growth factor beta

Human epidermal growth factor (EGF) and rat recombinant transforming growth factor alpha (TGFa) stimulated in a dose dependent manner the proliferation of rat liver fat storing cells (FSC) grown as primary culture in Dulbecco's modification of Eagles medium (DMEM) with 0.5% fetal calf serum (FCS). Cell proliferation was measured by DNA-content, [3H]thymidine- and bromodeoxyuridine-incorporation, respectively. Half maximal stimulation of [3H]thymidine incorporation was seen with 8ng/ml EGF and 7 ng/ml TGFa, respectively. In a radioreceptor assay using [125I]EGF as ligand TFGa binds with the same affinity as EGF to EGF-cell surface receptors on FSC. Eight ng/ml TGFa was required to produce half-maximal inhibition of [125I]EGF binding. If transforming growth factor beta (TGF beta) was added simultaneously with EGF or TGFa, FSC proliferation was inhibited strongly.

[Myoglobin-latex test. A new rapid test for the improvement of the early diagnosis of acute myocardial infarct]

Myoglobin concentrations were determined radioimmunologically and with a semiquantitative rapid latex test in 684 serum samples. There was a good correlation of both tests. The latex test becomes positive above 90 micrograms/l, i.e. the diagnostically relevant range. Myoglobin was determined in 27 patients with acute myocardial infarction at the same time as serum values of enzymes CK, CK-MB, LDH and GOT. This was done during three days every two hours. Diagnostically useful myoglobin increases were found on average already 2.6 +/- 0.9 hours after onset of pain, i.e. 3-4 hours before the first increase of enzymes CK-MB and CK. Out of 85 patients with acute myocardial infarction already 70% had a positive myoglobin latex test at the time of admission. In contrast, only 30% had increased enzyme activities (CK and CK-MB). Non-infarct-associated increases of myoglobin in serum were seen in patients with terminal renal failure, severe shock, muscle trauma, muscle diseases, alcohol intoxication and after reanimation.

[Correlations between lipoproteins and glycosylated hemoglobins in juvenile diabetes mellitus (author's transl)]

Based upon a 3-week observation at a summer camp for diabetic children whose medical therapy, metabolic rate, diet, physical exercise and special training could be closely monitored, the following parameters were measured at the beginning and at the end: In whole blood and young erythrocytes HbA1, in serum triglycerides, cholesterol, HDL-cholesterol, as well as apolipoprotein A and B. From these data, the LDL-cholesterol and the atherosclerosis indices (LDL-cholesterol/HDL-cholesterol and apolipoprotein B/apolipoprotein A) were determined. The following results were obtained: the parameters of lipid-metabolism recognized as risk factors for vascular complications such as triglycerides, cholesterol, LDL-cholesterol and apolipoprotein B, were the same as those obtained from a control group of healthy children in the same age. Using HbA1 as the basis for the observations, the risk factors were reduced by normalisation of glucose metabolism. On the other hand, the apolipoprotein A and HDL-cholesterol, well known as protective factors against atherosclerosis, are higher than in the control group and show a further increase with metabolic normalisation. The conclusion is: If medical therapy, metabolic rate, diet, physical exercise and special training are better controlled, the risk of diabetes developing macroangiopathy can be diminished.