Release of TNF-alpha from lipopolysaccharide (LPS)-stimulated Kupffer cells in serum- and nutrient-free medium

In monocytes/macrophages LPS stimulation occurs by the binding of LPS and the serum component LPS-binding protein (LBP) to CD14. This study was conducted to investigate whether this mechanism also occurs in Kupffer cells. Rat Kupffer cells were stimulated for up to 8 h by LPS (0, 100 ng/ml, 10 microg/ml) in RPMI medium or in nutrient-free Krebs-Henseleit (KH) buffer. Some incubations were performed without serum, while in others serum was provided. TNF-alpha concentrations of the supernatants were measured by ELISA. LPS stimulation of Kupffer cells yielded the following results. In KH without any additives a considerable amount of TNF-alpha was released. Incubation in RPMI without serum caused twice as much TNF-alpha to be released as when KH was used. The addition of autologous serum to RPMI did not increase TNF-alpha response. These results provide evidence that a substantial part of TNF-alpha release by LPS-stimulated Kupffer cells occurs in a serum- and thus LBP-independent way.

The quality of a liver graft

Because transplantation success is influenced by the quality of the graft, the objective of this study was to find parameters to evaluate transplant livers in the recipient centre. In 64 liver grafts, the venous effluates of a portal back-table flush were investigated for various parameters. Amongst them, glutathione S-transferase (GST), glutamate dehydrogenase (GLDH) and the leucocyte count were found superior in predicting graft survival. Using the combination of these parameters, 100-day graft survival of between 95% (all parameters positive) and 0% (all parameters negative) was predicted. We concluded that good liver grafts are characterized by a low width of injury (cytosolic component: GST), a low depth of injury (mitochondrial component: GLDH), as well as by a potential to induce tolerance (passenger leucocytes). Perfusate analysis seems to be a valuable tool to recognize problematic grafts in advance and to quantify the "graft factor" in considerations concerning quality control.

Influence of perioperative sHLA I concentrations on the histological development of the liver graft

Soluble HLA I (sHLA I) in human serum are ascribed an immunoregulatory role in the context of organ transplantation. Based on histological findings, the objective of the current study was to evaluate the protective influence of sHLA I in liver transplantation from the time point of reperfusion. The sHLA I concentrations in serum samples derived from the liver vein immediately after reperfusion (flush catheter) of 38 patients with liver transplantations were determined by ELISA. The postoperative histological findings of the transplant biopsies were categorized according to rejection, endothelialitis, cholestasis, and necrosis, as well as fatty degeneration. An evaluation according to Kaplan-Meier showed a lower incidence for all of these factors in liver grafts with high sHLA concentrations (P < 0.05). We conclude that low sHLA I concentrations during reperfusion correlate with later complications, thus indicating that sHLA I may have protective potential in liver transplantation.

RANTES in the postoperative course after liver transplantation

RANTES (regulated upon activation, normal T-cell expressed and secreted), an inflammatory cytokine, promotes accumulation and activation of leukocytes. In 67 liver transplantations, systemic concentrations of RANTES were correlated to graft survival and incidence of rejection. RANTES levels either increased to highly elevated levels at day 14 (84 +/- 64 ng/ml; group 1; n = 43) or remained within the limit of healthy controls (19 +/- 11 ng/ml at day 14; group 2; n = 24). The 100-day graft function rate was 0.91 in group 1 and 0.63 in group 2 (P = 0.002). The risk ratio for rejection during the first 100 days was increased 2.2-fold in group 2 compared to group 1 (P = 0.02). High postoperative release of RANTES after liver transplantation, a beneficial factor, may reflect a general systemic immunological activation. It can be concluded that high early systemic RANTES levels may play a role in immunological recognition leading to a tolerance of the liver graft.

Endotoxemia in organ donors: graft function following liver transplantation

Translocation of endotoxin (LPS) to the portal-venous system is produced by multiple factors. In the case of normal liver function, LPS is rapidly cleared from the portal blood by Kupffer cells; in impaired liver function, LPS can reach the systemic circulation. The objective of this study was to investigate whether elevated donor endotoxin levels affect graft function in the recipient. LPS levels in donor plasma were measured in 14 consecutive liver transplantations. Grafts with donor LPS levels < or = 12 pg/ml had a function probability of 100% after 600 days (n = 10). LPS concentrations of > 12 pg/ml in donor plasma led to loss of function in 75% of the liver grafts (n = 4; P = 0.003; Wilcoxon). Elevated LPS values in donor plasma seem to impair the prognosis of the grafts and could predict poor graft function as early as at the time of brain death.

MHC antigen presentation on the surface of hepatocytes: modulation during and after hypoxic stress

Presentation and recognition of MHC antigen on the surface of cells is the basic process of initiating rejection and distinguishing "self and not self". This is considered to begin when a transplanted organ is reperfused with the blood of the recipient. In this study, the modulation of MHC I antigen presentation during preservation was investigated in a cell culture model using primary hepatocyte cultures of male Wistar rats. By incubation with different preservation solutions used in clinical transplantation, expression of the MHC antigen was observed during cold hypoxia. Primary hepatocyte cultures were isolated from male Wistar rats by a modified Seglen technique and seeded to glass slides, thus obtaining monolayer cultures. After 1 day of resting the cultures were incubated under different conditions using Krebs Henseleit solution (KH), Euro-Collins solution (EC), HTK solution of Bretschneider (HTK) and University of Wisconsin solution (UW) as incubation media. The conditions of incubation were warm normoxia (37 degrees C, pO2 100 mm Hg) and cold hypoxia (4 degrees C, pO2 < 0.1 mm Hg), which is the main condition of organ preservation. Incubation time was 6 h. Before starting the incubation reference cultures were fixed and every 60 min several cultures were withdrawn from the experiment and fixed also. MHC expression was studied by staining the cultures with monoclonal antibodies against rat MHC class I and class II. As expected, MHC class II was not present on the surface of hepatocytes, while MHC class I was demonstrated on the controls as well as on the cultures that were incubated using KH and EC independent of temperature and hypoxia or normoxia. At the end of the incubation they were still positive but not as strong as in the beginning. During incubation using HTK and UW, MHC I was not detectable at all phases of the experiment. In conclusion, hypoxic stress did not completely eradicate MHC I expression in rat hepatocytes, while the composition of the preservation medium may result in a hepatocyte surface negative for MHC I. Hydroxyethylstarch may be the substance in UW that covers the MHC antigen, while in HTK, mannitol or the histidine complex may play the same role. MHC negativity of the cells of a preserved transplant is another reason for the benefit of UW or HTK.

Preservation studies using acinar cell cultures of the pancreas: stimulation of amylase/lipase release before and after hypoxic stress

In clinical pancreas transplantation, postischemic (i. e. postpreservation) transplant pancreatitis is a major problem in some cases but also an interesting model of pancreatitis. In this study, the effect of simulated organ preservation of isolated acinar cells was evaluated as regards enzyme release (basic and cerulein-stimulated), using common preservation solutions as the incubation media. Primary pancreas acinar cell cultures were isolated from the pancreas of male Wistar rats using the modified method of Amsterdam and Jamieson. After resting the cells in culture flasks for 1 week, monolayer cultures were obtained. The basic enzyme release of amylase and lipase was measured as well as the effect of stimulation with cerulein (10(-8) M) and the effect of replacing the medium (without changing the consistence or temperature of the medium). In a second step, the cultures were incubated under conditions of cold hypoxia for 6 h (4 degrees C, P O2 < 0.1 mm Hg) using Krebs-Henseleit solution (KH), Euro-Collins solution (EC), HTK solution of Bretschneider (HTK) or University of Wisconsin solution (UW) as the incubation solution. After 6 h, the media were changed to warm normoxic KH, and a second stimulation test with cerulein was performed. The native microstructure of the cultures was observed as well. Enzyme release was elevated by a factor of 5 by stimulating the acinar cells with cerulein as well as by changing the medium in the experiments prior to the hypoxic incubation. After hypoxic incubation and change to KH, the morphology of the cultures was excellent, while the basic enzyme release was on a very low level, no matter which preservation solution was used during cold hypoxia. Stimulation with cerulein caused only minimal elevation of enzyme release during an observation period of 60 min. These observations show that cold storage in preservation solution provides maintenance of the cell morphology and sufficient down-regulation of enzyme release of pancreatic acinar cells. Thus, acinar cells alone do not seem to be the pacemaker of pancreatitis after organ preservation. The presented experimental model will be the subject of extended evaluation in the future.

Loss of cyclin A and G1-cell cycle arrest are a prerequisite of ceramide-induced toxicity in human arterial endothelial cells

BACKGROUND

Ceramide is an important messenger of TNF- and lipid-induced apoptosis. We previously demonstrated the adverse effect of TNF in the process of reendothelialization as well as the dependence of its effect on cell-cycle regulation. The current study was designed to investigate the linkage between ceramide induced toxicity and growth arrest in human endothelial cells.

METHODS AND RESULTS

Cultured human arterial endothelial cells (HAEC) served as an in-vitro model to test the cellular effects of C2-ceramide (C2). C2-induced cell death in HAECs occurred time- and dose-dependently. The LD(50) in subconfluent cells was three times lower than in confluent cell layers (25 vs. 75 microM). C2 caused up to 70% inhibition of BrdU and [3H]thymidine incorporation at non-toxic concentrations as a result of G1 cell-cycle arrest. Downregulation of cyclin A and p21(Cip1/Waf1) protein expression was observed independently of C2-toxicity, while expression of other cell-cycle regulatory genes was not affected. Inhibition of cyclin A protein expression by sequence-specific antisense-oligonucleotides was paralleled by significant growth-inhibition. The protein phosphatase inhibitor okadaic acid induced endothelial cell proliferation, which was completely abrogated by C2. In contrast, aphidicolin-synchronized endothelial cells demonstrated elevated cyclin A levels along with 30% higher BrdU-incorporation and 70% less C2-toxicity. G1-arrested cells, however, showed significantly enhanced C2-toxicity, lack of cyclin A expression and induction of uncleaved caspase-3 (CPP32).

CONCLUSIONS

Ceramide abrogates endothelial cell proliferation independently of apoptosis or necrosis at low concentrations (<or=10 microM) through loss of cyclin A expression with subsequent G1 cell-cycle arrest. Synchronization of HAECs in S-phase with aphidicolin overcomes C2-induced G1-arrest and partially blocks ceramide toxicity. These findings demonstrate the dependence of ceramide toxicity on cell cycle regulation, suggesting a strong bidirectional relationship between cell-cycle control and cell death in vessel biology.

All-trans retinoic acid regulates proliferation, migration, differentiation, and extracellular matrix turnover of human arterial smooth muscle cells

OBJECTIVE

The vitamin-A derivative all-trans retinoic acid (atRA) is a potent regulator of cell growth, differentiation, and matrix formation of various cell types and plays an important role in embryogenesis. However, sparse data are available about its effects on human vessel diseases. Thus, we studied the effects of atRA on human arterial smooth muscle cell (haSMC) and endothelial cell (haEC) proliferation, migration, differentiation and extracellular matrix (ECM) turnover in mono- and transfilter cocultures.

METHODS

Effects of atRA on human arterial cells in monocultures were determined using cell counting assays, BrdU-ELISA and MTT-tests. In transfilter cocultures haSMC-growth was studied under the stimulatory effect of proliferating haEC. Using Northern blot analysis, effects of atRA on mRNA expression of ECM-proteins were examined while protein expression and activity of matrix metalloproteinases were determined by Western blotting and zymography.

RESULTS

atRA caused a dose dependent inhibition of haSMC-growth in monocultures (IC(50) at 0.022 microM) whereas haEC-growth was inhibited less potently (IC(50) at 97 microM). In addition, proliferation and migration of haSMC through a porous membrane were inhibited dose dependently by micromolar atRA-doses after non-stop and single dose application of atRA on the endothelial side of the complex transfilter coculture system. Immunostainings and Northern blotting demonstrated an enhanced alpha-smooth muscle actin and heavy chain myosin expression in haSMC after atRA-treatment. Whereas mRNA-expression of the glycoproteins thrombospondin-1 and fibronectin were decreased, collagen-1 mRNA expression was even slightly stimulated. Transcription of biglycan and TGF-beta1 were not influenced in a specific manner. Finally, protein expression and activity of the matrix metalloproteinases MMP-2 and MMP-9 were inhibited significantly by atRA.

CONCLUSIONS

atRA was found to be a potent inhibitor of both haSMC-proliferation and -migration, even in coculture with haEC releasing growth factors. In addition, redifferentiation, ECM synthesis and ECM degradation were regulated by atRA which also influence haSMC migration and intima formation. Thus, atRA-treatment seems to be a promising strategy for the inhibition of processes involved both in atherosclerosis and restenosis.

TNF-alpha and its receptors mediate graft rejection and loss after liver transplantation

Tumour necrosis factor-alpha (TNF-alpha) plays a pivotal role in the immune response and mediates inflammation by its receptors (TNF-RI and TNF-RII), as observed during rejection episodes and impaired graft function after liver transplantation. TNF-alpha and its receptors were analysed by an ELISA technique in serum samples from 77 consecutive liver transplantations in 63 patients. Samples were collected preoperatively from donors and recipients and then daily in the first two postoperative weeks. Peak levels of TNF-alpha and its soluble receptors (sTNF-RI and sTNF-RII) in the first and second postoperative week correlated with the extent of reperfusion injury. Impaired graft functions correlated with high sTNF-RI levels preoperatively (> 5 ng/ml, p = 0.01) and in the postoperative period (> 16 ng/ml, p = 0.02). Significantly increased TNF-alpha (> 25 pg/ml, p = 0.009) and sTNF-RI levels (> 5 ng/ml, p = 0.05) were found in donors of grafts with a high rejection risk. Elevated levels of TNF-alpha in the postoperative period correlated with an increased rejection risk (> 90 pg/ml, p = 0.02). The activity of the immune system with high concentrations of TNF-alpha and its receptors both in the recipient and the transplant donor seems to play an essential role in allograft development.

The postoperative course of gamma-glutamyl transpeptidase--a marker of cytomegalovirus (CMV) replication risk?

Cytomegalovirus (CMV) infection is a common complication in the postoperative course of liver transplantation. In order to start early prophylactic therapy, but to avoid unnecessary treatment, or expensive screening, a desirable goal in post-transplant monitoring is to find appropriate markers in standard laboratory diagnostics. In the present study, the results of a 6-week CMV replication monitoring schedule by the pp65 antigenemia assay in 100 liver graft recipients were included. The activities of transaminases, glutamate dehydrogenase and gamma-glutamyl transpeptidase (gamma-GT) were measured by routine laboratory methods. In contrast to the transaminases, the serum activity of gamma-GT increased during the first postoperative week. The maximum levels were 246 +/- 211 U/l in patients without (n = 46) and 140 +/- 89 U/l in patients with early CMV replication (n = 54; p = 0.02). Patients with gamma-GT levels below 200 U/l on the 5th postoperative day (n = 72) had a CMV replication risk of 65%, whereas those patients with gamma-GT levels above this threshold had a risk of 30% (n = 28; p = 0.0007; relative risk = 2.9). These findings provide a routinely usable marker for the identification of patients at an increased risk of CMV replication. It can be considered that these phenomena may be caused by an additional immunosuppressive effect of the CMV virus.

MR imaging and (1)H spectroscopy of brain metabolites in hepatic encephalopathy: time-course of renormalization after liver transplantation

PURPOSE

To evaluate changes in hydrogen 1 magnetic resonance (MR) spectroscopic findings in overt or subclinical hepatic encephalopathy (HE) after liver transplantation and to compare these changes with clinical outcomes and basal ganglia high signal intensity (BGH).

MATERIALS AND METHODS

Twenty-two patients scheduled for liver transplantation and 17 healthy control subjects were examined with (1)H MR spectroscopy and standard nonenhanced MR imaging. Eight patients underwent complete MR imaging and (1)H spectroscopic examinations before liver transplantation and at 3-4-week, 12-28-week, and 10-12-month follow-up after liver transplantation.

RESULTS

Before liver transplantation, typical (1)H spectroscopic changes-decreased myo-inositol (mI)/creatine (Cr) and choline (Cho)/Cr ratios and an elevated glutamine and glutamate (Glx)/Cr ratio-were found in 21 patients. Eighteen patients had BGH at T1-weighted imaging. Three to 7 months after liver transplantation, the mI/Cr and Glx/Cr ratios were within the normal range in five of eight and eight of eight patients, respectively, without any residual signs of subclinical or overt HE; however, at MR imaging, seven patients still had BGH.

CONCLUSION

After successful liver transplantation, renormalization of HE-specific brain metabolite changes is detected at (1)H spectroscopy and precedes the disappearance of BGH. The neuropsychologic signs of subclinical or overt HE follow the changes seen at (1)H spectroscopy rather than those seen at MR imaging.

Toxicity, uptake kinetics and efficacy of new transfection reagents: increase of oligonucleotide uptake

Human arterial smooth muscle cell (haSMC) proliferation is stimulated by platelet-derived growth factor (PDGF) release of human arterial endothelial cells (haEC) whereas transforming growth factor-beta(1) (TGF-beta(1)) secretion by haSMC promotes extracellular matrix formation. Inhibitory concepts with antisense oligonucleotides (ASO) against those growth factors might be promising, requiring, however, sufficient transfection efficacy. Thus, toxicity and efficacy of new transfection reagents were examined. MTT tests showed that high doses >1.6 microg/ml of the liposome Cytofectin GSV((R)) (CF) and the dendrimer SuperFect (SF) reduced mitochondrial activity of haEC after > or =4 h transfection whereas viability of haSMC was not influenced. DAC-30((R)) showed significant toxic effects on haEC and haSMC at each dose after > or =4 h and Lipofectin((R)) (LF) caused complete detachment of haEC and haSMC in medium containing 10% serum. Uptake studies demonstrated that 'naked' ASO were not incorporated intracellularly whereas transfection within CF or SF resulted in a strong cytoplasmic and nuclear labeling after 2-5 h. With DAC-30, only a slight cytoplasmic fluorescence was found. SF caused an unexpected stimulation of endothelial PDGF-AB synthesis. Thus, CF was favored for inhibition studies. ELISA, Western and Northern blotting showed a significant inhibition of endothelial PDGF-B and smooth muscle TGF-beta(1) mRNA expression and synthesis after transfection for 3-5 h using 0.1-1.0 microM ASO versus control oligonucleotides. We conclude that Cytofectin GSV is superior to the other transfection reagents, predominantly at haEC, showing an improved efficacy and less toxicity than the classical liposome Lipofectin. Cytofectin GSV might offer a promising tool for antisense strategies in the treatment of vascular disorders.

Effects of cerivastatin on human arterial smooth muscle cell proliferation and migration in transfilter cocultures

Statins competitively inhibit 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity reducing mevalonate synthesis. In this study, antiproliferative and antimigratory effects of the new compound cerivastatin were analyzed and compared with classic statins of the first and second generation using mono- and cocultures of human arterial smooth muscle (haSMC) and endothelial (haEC) cells. Effects on the mitotic index and mitochondrial activity of haEC and haSMC monocultures were tested using BrdU enzyme-linked immunosorbent assay (ELISA) and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) tests, respectively. In lactate dehydrogenase (LDH) assays, cytotoxicity of statins was studied. Transfilter cocultures were performed for 14 days to evaluate haSMC growth under the stimulatory effect of proliferating haEC, which release growth factors [e.g., platelet-derived growth factor (PDGF)]. The hydrophobic statins simvastatin, lovastatin, and atorvastatin significantly inhibited haSMC and haEC growth in monocultures at 0.5-50 microM. However, most potent effects were exerted by cerivastatin in 10- to 30-fold lower doses without any significant cytotoxicity. More important, cerivastatin showed also significant effects on haSMC proliferation and migration in transfilter cocultures at extremely low doses (IC50, 0.04-0.06 microM), even when applied exclusively to the endothelial side and in the presence of low-density lipoprotein (LDL). Addition of mevalonate abolished the effects of cerivastatin completely. Even in the presence of growth-stimulating haEC and LDL, cerivastatin was found to be the most potent inhibitor of haSMC proliferation and migration in doses that also can be reached in human serum after oral drug administration. The results support the concept that statins seems to influence additional cellular mechanisms beyond cholesterol reduction, which might also have a relevance for the prevention of restenosis.

Hepatocytes are permissive for human cytomegalovirus infection in human liver cell culture and In vivo

The cytopathic potential of human cytomegalovirus (HCMV) in human liver cells was analyzed in cell culture and in tissue sections from patients with HCMV hepatitis. Liver cell cultures, consisting of hepatocytes, bile duct epithelial cells, and stromal cells were infected by various HCMV strains. Cytopathic effects, viral gene expression, and virus production were detected. Infected cell types were identified by immunocytochemical double labeling. Hepatocytes were the predominant target cells of HCMV infection in liver tissues and in cell culture. Late-stage infected cultured hepatocytes produced infectious progeny virus, and infectious virus was propagated from liver tissue specimens. HCMV infection in cultured liver cells closely resembled in vivo infection of the liver with regard to the target cell spectrum and the permissive course of infection. It is concluded that HCMV can cause direct liver parenchyma damage by efficient cytolytic infection of hepatocytes.

[Contrast-enhanced MR cholangiography in percutaneous bile duct drainage]

PURPOSE

To evaluate MR-cholangiography after instillation of contrast media via indwelling biliary tubes.

METHODS

In 8 patients with stenoses of the central bile ducts, physiological saline solution and diluted contrast media (Gd-DTPA, 5 mmol/l) were consecutively administered via an indwelling biliary tube. MR cholangiograms were obtained before and after saline injection using a HASTE-sequence and after administration of Gd-DTPA using a T1-weighted gradient echo sequence.

RESULTS

Peripheral bile ducts were better visualised in the water-sensitive approach than after Gd-DTPA enhancement. In patients with short-time drainage bile duct definition was poor due to periportal oedema. Visualisation of peripheral bile ducts could be improved by injection of saline solution in these patients. After administration of Gd-DTPA via the biliary tube contrast enhancement of the central bile ducts was achieved in all patients except for one patient on long-term drainage with an indwelling Yamakawa tube.

CONCLUSION

T1-weighted visualisation of the central bile ducts can be achieved by means of injection of Gd-DTPA via indwelling biliary tubes.