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One of the pathways activated during liver fibrosis is the Rho kinase pathway, which regulates activation, migration, and contraction of hepatic stellate cells (HSC). Inhibition of this kinase by the Rho kinase inhibitor Y27632 [(+)-(R)-trans- 4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide dihydrochloride] has been shown to reduce fibrosis in animal models. However, kinase expression is ubiquitous, so any inhibitor may affect many cell types. We hypothesize that cell-specific delivery of a kinase inhibitor will be beneficial. Therefore, we conjugated Y27632 to the carrier mannose-6-phosphate (M6P) human serum albumin (HSA), which is taken up specifically in activated HSC through the M6P/insulin-like growth factor II receptor. This conjugate decreased protein expression of phosphorylated myosin light chain 2 (pMLC2) and vinculin, downstream of Rho kinase, in activated primary HSC and decreased the migration and contraction of HSC. In an ex vivo model, free Y27632 decreased contractility of rat aortas, whereas the Y27-conjugate did not, showing that the Y27-conjugate does not affect nontarget tissue. In chronic CCl(4)-induced liver fibrosis, both free drug and conjugate reduced HSC activation; however, only the Y27-conjugate significantly reduced collagen deposition. Treatment with the Y27-conjugate, but not with free drug, reduced pMLC2 expression in livers 24 h after injection, demonstrating prolonged inhibition of the Rho kinase pathway. The Rho kinase inhibitor Y27632 can be specifically targeted to HSC using M6PHSA, decreasing its effects in nontarget tissues. The targeted drug effectively reduced fibrotic parameters in vivo via the inhibition of the Rho kinase pathway.

Liver fibrosis is associated with proliferation of hepatic stellate cells (HSCs) and their transformation into myofibroblastic cells that synthesize scar tissue. Several studies indicate that induction of apoptosis in myofibroblastic cells may prevent fibrogenesis. Gliotoxin (GTX) was found to induce apoptosis of hepatic cells and caused regression of liver fibrosis. However, the use of apoptosis-inducing drugs may be limited due to lack of cell specificity, with a risk of severe adverse effects. In previous studies, we found that mannose-6-phosphate-modified human serum albumin (M6P-HSA) selectively accumulated in liver fibrogenic cells. The aim of this study therefore was to couple GTX to M6P-HSA and test its pharmacological effects in vitro and in rats with liver fibrosis. The conjugate GTX-M6P-HSA bound specifically to HSCs and reduced their viability. Apoptosis was induced in cultures of human hepatic myofibroblasts (hMFs) and in liver slices obtained from rats with liver fibrosis. In vivo treatment with GTX or GTX-M6P-HSA in bile duct ligated rats revealed a significant decrease in alpha-smooth muscle actin mRNA levels and a reduced staining for this HSC marker in fibrotic livers. In addition, although GTX also affected hepatocytes, GTX-M6P-HSA did not significantly affect other liver cells. In conclusion, we developed an HSC-specific compound that induced apoptosis in human hMFs, rat HSCs, and in fibrotic liver slices. In vivo, both GTX and GTX-M6P-HSA attenuated the number of activated HSCs, but GTX also affected hepatocytes. This study shows that cell-selective delivery of the apoptosis-inducing agent GTX is feasible in fibrotic livers.

The influence of pooled polyclonal immunoglobulin IgG interactions with both bacteria and model substrates in altering Pseudomonas aeruginosasurface adhesion is reported. Opsonization of this pathogen by polyclonal human IgG and preadsorption of IgG to glass surfaces both effectively reduce initial deposition rates and surface growth of P. aeruginosaIFO3455 from dilute nutrient broth in a parallel plate flow chamber. Polyclonal IgG depleted of P. aeruginosa–specific antibodies reduces the initial deposition rate or surface growth to levels intermediate between exposed and nonexposed IgG conditions. Bacterial surface properties are changed in the presence of opsonizing IgG. Plateau contact angle analysis via sessile drop technique shows a drop in P. aeruginosasurface hydrophobicity after IgG exposure consistent with a more hydrophilic IgG surface coat. Zeta potential values for opsonized versus nonopsonized bacteria exhibit little change. Xray photoelectron spectroscopy measurements provide surface compositional evidence for IgG attachment to bacterial surfaces. Surface elemental ratios attributed to IgG protein signals versus those attributed primarily to bacterial polysaccharide surface or lipid membrane change with IgG opsonization. Direct evidence for antibodymodified P. aeruginosasurface properties correlates both with reduction of bacterial adhesion to glass surfaces under flow in nutrient medium reported and previous reports of IgG efficacy against P. aeruginosamotility in vitroand infection in vivo. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 51, 224–232, 2000.

The key pathogenic event in liver fibrosis is the activation of hepatic stellate cells (HSC). Consequently, new antifibrotic therapies are directed toward an inhibition of HSC activities. The aim of the present study was to develop a drug carrier to HSC, which would allow cell-specific delivery of antifibrotic drugs thus enhancing their effectiveness in vivo. We modified human serum albumin (HSA) with 10 cyclic peptide moieties recognizing collagen type VI receptors (C*GRGDSPC*, in which C* denotes the cyclizing cysteine residues) yielding pCVI-HSA. In vivo experiments showed preferential distribution of pCVI-HSA to both fibrotic and normal rat livers (respectively, 62 +/- 6 and 75 +/- 16% of the dose at 10 min after intravenous injection). Immunohistochemical analysis demonstrated that pCVI-HSA predominantly bound to HSC in fibrotic livers (73 +/- 14%). In contrast, endothelial cells contributed mostly to the total liver accumulation in normal rats. In vitro studies showed that pCVI-HSA specifically bound to rat HSC, in particular to the activated cells, and showed internalization of pCVI-HSA by these cells. In conclusion, pCVI-HSA may be applied as a carrier to deliver antifibrotic agents to HSC, which may strongly enhance the effectiveness and tissue selectivity of these drugs. This approach has the additional benefit that such carriers may block receptors that play a putative role in the pathogenesis of liver fibrosis.

AbstractThe kinetic behaviour of a naproxen human serum albumin conjugate (Nap23-HSA) was investigated in rats and in isolated perfused rat livers (IPRL), as compared to its active metabolite naproxen-lysine (Nap-lysine) and free naproxen. Through covalently linking the antiinflammatory drug naproxen to HSA, this drug can be selectively delivered to non parenchymal cells of the liver. Liver endothelial and Kupffer cells play an important role in the pathogenesis of inflammatory liver diseases. Targeting naproxen to these cells might increase its efficacy and reduce the side effects.The altered kinetic properties of Nap23-HSA, after i.v. injection of 22 mg.kg−1, as compared to an equimolar amount of the uncoupled drug, were demonstrated in vivo by a decrease in the steady state volume of distribution (41 ± 5 vs. 134 ± 19 ml.kg−1), a decrease in its clearance (0.48 ± 0.05 vs. 0.63 ± 0.1 ml.min−1.kg−1), a shorter plasma half life (60 ± 11 vs. 152 ± 44 min) and a sustained biliary excretion.Liver targeting of Nap23-HSA was clearly demonstrated: drug content of the liver 180 min after injection was about 30 times higher for Nap23-HSA as compared to naproxen itself. The IPRL experiments showed that the Vmaxof hepatic removal of the conjugate was 40 μg.min−1.g liver−1. With doses below receptor saturation a rapid removal of the conjugate (t1/2= 6 min) from the perfusion medium was found.In conclusion, this study demonstrates the saturable uptake of Nap23-HSA and its lysosomal degradation in both in vivo and IPRL experiments. Covalently linked naproxen is released as Nap-lysine. This active metabolite accumulates in Kupffer and endothelial cells in which it reaches therapeutic concentrations. Release from these cells leads to rapid uptake by hepatocytes and carrier mediated excretion into bile. Levels of Nap-lysine in bile and plasma reflect the slowest step in its generation: the proteolytic release in endothelial and Kupffer cells.

AbstractNaproxen covalently linked to human serum albumin (NAP-HSA) is efficiently targeted to endothelial and Kupffer cells of the liver and may offer a new therapeutic approach in the treatment of liver disease associated with inflammatory processes. In the present investigation we explored the pharmacokinetic behaviour of targeted and non-targeted naproxen as well as the pharmacokinetic properties of the active metabolite, Naproxen-lysine (Nap-lysine), in rats rendered fibrotic by bile duct ligation (BDL) for 4 weeks. Furthermore, we studied the effect of endotoxemia, experimentally induced by intravenous injection of 800μg/kg lipopolysaccaride (LPS) upon the pharmacokinetics of these agents in order to investigate the feasibility of targeting naproxen to non-parenchymal cells in the inflamed and fibrotic liver. Our studies demonstrate that liver disease altered the pharmacokinetic behaviour of the different naproxen compounds. Thus, initial plasma concentrations of NAP-HSA and naproxen were markedly lower in BDL rats accompanied by an increase of the volume of distribution during the terminal elimination phase (VdβBDL vs control 114 ± 63 vs 50 ± 7 and 202 ± 24 vs 115 ± 11 ml/kg for naproxen and NAP-HSA, respectively). After injection of LPS, no significant change in the pharmacokinetics of NAP-HSA was found whereas the naproxen treated control animals showed an increase in the terminal volume of distribution (176 ±34 vs 115 ± 11 ml/kg) as well as an elevation of the plasma half-life (171 ± 27 vs 116 ± 14 min). The feasibility of targeting naproxen to the chronically diseased liver could be clearly demonstrated: 15 min after administration of the conjugate 46 and 55 of the administered dose was found in the liver of CTR and BDL rats, whereas after injection of free naproxen only 5 and 12 of the dose was detected in liver tissue, respectively.We conclude that targeting albumin-linked naproxen to non-parenchymal cells in the liver is still feasible under the pathological conditions induced in the present study. Liver fibrosis induced significant alterations in the pharmacokinetic behaviour of the studied compounds.

The early nephrotoxic effect of the antitumor drug adriamycin (ADR) is suggested to be related to the generation of oxygen free radicals. Therefore the O2 -dependence and the influence of free radical scavengers were studied in the model of the isolated perfused single glomerulus of Myxine glutinosa and by histochemi-cal demonstration of the glomerular ATP-ase. In Myxine, the glomerular ATP-ase activity was decreased after injection of ADR (5 mg/kg, i.v.).Both ADR-treated Myxine and controls were exposed for 48 h to an artificial atmosphere of 20% O2/80% N2 or 80% O2/20% N2, respectively. After 10 days a significant decrease of the hydraulic conductivity (k) was measured in the experimental group exposed to 80% O2 (k-values expressed as nl/s.mmHg.mm2: controls (7): 0.059 ± 0.017; ADR (7): 0.033 ± 0.026). The reduction of k following the administration of ADR (20 mg/kg) could be prevented by the sulphydryl donor N-acetylcysteine (NAC). The sieving coefficient for albumin (μ) was significantly increased in ADR-treated animals, showing no O2-dependence (μ × 10-2: controls (7) 1.3 ± 0.2; ADR 20% O2 (8): 8.1 ± 9.6; ADR 80% O2 (7): 6.9 ± 6.7). ω was not affected by NAC.The lipid peroxide levels in liver, kidney and heart of Myxine increased after the administration of ADR, peaking by day 2 to 5. The circulation disorders of ADR-treated Myxine were not due to an accumulation of the drug in the heart, but rather to a lack of the intracellular antioxidant glutathione.It is concluded that the early nephrotoxic effect of ADR, as reflected by a decreased glomerular ATP-ase activity, is mediated by free radical formation. Oxidative stress on membrane compounds seems to reduce the water permeability of the glomerular barrier, while the ADR-induced sieving defect may be due to oxygen independent pathological mechanisms.

We have demonstrated that reduced glomerular adenosine diphosphatase (ADPase) activity within the rat kidney is associated with an increased thrombotic tendency. To establish a possible causal relationship between these intraglomerular events, experiments were conducted to inhibit adenosine diphosphate (ADP) degradation without influencing other glomerular prothrombotic or antithrombotic mechanisms. Concurrently, we studied intraglomerular platelet aggregation. Two ways of selective inhibition of glomerular ADPase activity were applied: (1) by competitive substrates (ie, uridine diphosphate [UDP]), and (2) by the nondegradable ADP analogue ADP-beta-S. Both strategies were used during ex vivo alternate perfusion of kidneys with platelets and ADP (to test intraglomerular thrombotic tendency). Each group (n = 6) received different substrates or a combination of substrates. A significant increase in platelet aggregation was observed in kidneys after perfusion with platelets and ADP together with the competitive substrate UDP as compared to perfusions with platelets and ADP alone (78.5% +/- 9.8% v 27.9% +/- 11.4% glomeruli staining positive for platelets, P less than .005). In contrast, UDP alone had no effect on platelet aggregation. Other nucleoside polyphosphates (guanosine diphosphate and inosine triphosphate) were also effective as competitive substrates in the ex vivo perfusion model (n = 4). None of these substrates was capable of increasing ADP-induced aggregation when studied in vitro. In addition, ADP- beta-S also increased platelet aggregation in the perfusion model as compared with native ADP (P less than .005). These results show that selective reduction of ADP degradation in intact kidneys strongly promotes the intraglomerular proaggregatory condition. It can be concluded that glomerular ADPase exerts potent antithrombotic activity within the normal rat kidney.

Non-steroidal anti-inflammatory drugs (NSAID's) could be of value in the treatment of liver disease; however, their use in this situation is limited by renal side effects. Therefore, we explored whether naproxen covalently bound to human serum albumin (NAP-HSA) was able to reduce toxicity in an acute model of liver disease induced by endotoxin in rats pretreated with Corynebacterium parvum. In the isolated perfused liver of such animals endotoxin induced cholestasis (0.62 ± 0.05 vs. 0.24 ± 0.09 μl.min-1.g liver-1; p < 0.05), increased vascular resistance (11300 ± 400 vs. 311000 ± 2000 dyn.s.cm-5; p < 0.05) and alanine aminotransferase release (22 ± 9 vs. 149 ± 40 IU/l; p < 0.05). At the highest dose tested (22 mg/kg, corresponding to 6.0 μmoles naproxen), NAP-HSA normalized ALT release (21 ± 10 IU/l; p < 0.05) while an equimolar amount of non-targeted naproxen was only partially effective (56 ± 19 IU/l). A conventional dose of naproxen similarly prevented transaminase release. Cholestasis and increased vascular resistance were also prevented by NAP-HSA. Drug targeting by linking drugs to proteins is a potentially useful approach to maximizing drug effect while minimizing adverse events; this could be particularly useful for compounds with potentially serious adverse effects in patients with chronic liver disease such as the nonsteroidal anti-inflammatory agents used in the present study.

We studied glomerular ATPase activity, as detectable at the light microscopic (LM) level in cryostat sections of the rat kidney, after unilateral local X-irradiation. The biochemically detectable reduction in glomerular ATPase activity after X-irradiation could be demonstrated at the LM level by application of a modified cerium-based technique. Results show a clear reduction of reaction product in glomeruli in X-irradiated kidneys as compared with the contralateral control kidney. Technical parameters (i.e., tissue fixation, second thickness, cerium concentration of the incubation mixture, and percentage H2O2 added for the amplification step) were established for optimal reproducibility of the staining results. We show that this modified staining protocol allows detection of differences of ATPase activity in contrast to conventional histochemical methods. Inhibition studies with various phosphatase inhibitors and competitive substrate inhibition experiments revealed that the enzyme is specific for nucleoside di- and triphosphatases. Since reduced glomerular adenine nucleotidase activity has recently been recognized as an early event in (experimental) glomerulonephritis, we feel that the new staining protocol presented here may be highly relevant for routine tissue section screening in nephropathological research.

The extracellular presence of adenosine polyphosphatase was investigated in a number of rat tissues. The enzyme was demonstrated in basement membranes of epithelial cells of duodenum, urinary bladder, tongue, choroid plexus, submandibular salivary gland, lung and kidney, as well as in basement membranes of capillaries in these tissues. Furthermore adenosine polyphosphatase was demonstrated on collagen fibrils and in the cytoplasm of fibroblasts of all investigated tissues. It appears that the presence of adenosine polyphosphatase in basement membranes is a widespread phenomenon. Since extracellular ADP and ATP are known to promote respectively platelet aggregation and inflammation, the presence of extracellular ADP and ATP-hydrolyzing activity might contribute to inhibit these processes.

Liver fibrosis (LF) is among the top ten causes of death in the western world. The traditional method for diagnosis of LF is biopsy. We are seeking a non‐invasive imaging method for the diagnosis of LF and assessment of its onset and progression. Activation of hepatic stellate cells (HSC) is a key event in fibrosis and is characterized by upregulation of receptors for platelet derived growth factor (PDGF). We exploited this property to develop a ligand that will allow us to quantitate numbers of activated HSC based on their expression of PDGF receptor. Specifically we have explored the possibility of developing HSC‐selective radiopharmaceuticals by coupling bifunctional chelators to a cyclic peptide (C*SRNLIDC*)‐HSA conjugate1(pPB‐HSA) 1, which is a PDGF receptor recognizing compound.