The hallmark of liver fibrosis is an increased extracellular matrix deposition, caused by an activation of hepatic stellate cells (HSC). Therefore, this cell type is an important target for pharmacotherapeutic intervention. Antifibrotic drugs are not efficiently taken up by HSC or may produce unwanted side-effects outside the liver. Cell-specific delivery can provide a solution to these problems, but a specific drug carrier for HSC has not been described until now. The mannose 6-phosphate/insulin-like growth factor II (M6P/ IGF-II) receptor, which is expressed in particular upon HSC during fibrosis, may serve as a target-receptor for a potential carrier. The aim of the present study was to examine if human serum albumin (HSA) modified with mannose 6-phosphate (M6P) is taken up by HSC in fibrotic livers. A series of M6P x -modified albumins were synthetized: x ‫؍‬ 2, 4, 10, and 28. Organ distribution studies were performed to determine total liver uptake. The hepatic uptake of M6P x -HSA increased with increasing M6P density. M6P x -HSA with a low degree of sugar loading (x ‫؍‬ 2-10) remained in the plasma and accumulated for 9% ؎ 0.5% or less in fibrotic rat livers. An increase in the molar ratio of M6P: HSA to 28:1 caused an increased liver accumulation to 59% ؎ 9% of the administered dose. Furthermore, we determined quantitatively the in vivo intrahepatic distribution of M6P x -HSA using double-immunostaining techniques. An increased substitution of M6P was associated with an increased accumulation in HSC; 70% ؎ 11% of the intrahepatic staining for M6P 28

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The pharmacokinetics of Indocyanine Green (ICG) has been studied in 15 patients given 0.5, 1.0 and 2.0 mg.kg-1. The plasma disappearance and biliary excretion rate were measured in patients with tightly fitting catheters under slight negative pressure in order to achieve complete collection of bile. Recovery of unchanged ICG in bile over 18 h after the i.v. injection was 80% of the dose in all three dose groups. Plasma disappearance in all 3 groups was biphasic, showing an initial phase with a t1/2 of 3-4 min and a secondary phase with a dose-dependent apparent t1/2 of 67.6, 72.5 and 88.7 min, respectively. After 0.5 and 1.0 mg.kg-1 the biliary excretion rate curves showed an ascending phase with a mean t1/2 of 5 min and a descending phase with a mean t1/2 of 72 min. It was inferred that the secondary component of the plasma-decay mainly reflected the biliary excretion rate. After 2.0 mg.kg-1 in some patients the biliary excretion curve showed features of saturation; the t1/2 of the descending phase ranged from 73 to 440 min, and the time of maximal excretion was increased from 1.3 to 2.7 h after injection, whilst the mean maximal excretion rate was in the same range as the excretion rate after the 1.0 mg.kg-1 dose. The non-linear pharmacokinetics was only moderately reflected in the measured plasma disappearance patterns. Two compartment analysis of the plasma levels indicated a clearance of 230-260 ml.min-1, whereas the clearance conventionally calculated from the initial t1/2 was 475 ml.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

In the mouse, both the mdr1a and the mdr1b gene encode drug-transporting P-glycoproteins. The mdr1a P-glycoprotein is expressed in epithelial cells of, among others, the liver and the intestine. Furthermore, the mdr1b gene product is found in the liver but is not detectable in the intestine. To establish the potential involvement of P-glycoprotein in the elimination of cationic amphiphilic drugs from the body, we investigated biliary, intestinal, and urinary excretion in mice with a homozygous disruption of the mdr1a gene (mdr1a(؊/؊) mice ). These mice are fully viable under laboratory conditions and have normal bile flow. Cumulative biliary excretion (expressed as percent of the intravenously administered dose excreted over a 1-hour period) of several cationic compounds was decreased as follows in mdr1a(؊/؊) mice compared with the wild-type animals: tri-n-butylmethylammonium (TBuMA), 0.7% versus 2.1%; azidoprocainamide methoiodide (APM), 3.8% versus 7.6%; and vecuronium, 22.7% versus 41.3%. The luminal secretion of both TBuMA and APM in the small intestine was profoundly decreased, respectively 4.6-fold (1.8% vs. 8.2% in the wild-type) and 7.9-fold (1.6% vs. 10.3% in the wild-type) in mdr1a(؊/؊) mice. Thus mdr1a P-glycoprotein contributes substantially to the removal of a wide variety of cationic agents from the body through intestinal and hepatobiliary secretion, but it evidently acts in concert with other transport system(s). These processes probably provide a protective mechanism limiting the overall rate of absorption as well as the bioavailability of potentially toxic organic

1 We have used mice with homozygously disrupted mdr1a and mdr1b genes (mdr1a/1b (7/7) mice) to study the role of the mdr1-type P-glycoprotein (P-gp) in the elimination of cationic amphiphilic compounds from the body. These mice lack drug-transporting P-gps, but show no physiological abnormalities under laboratory conditions and have normal bile¯ow. 2 3 H-labelled cationic drugs were administered intravenously (i.v.) to mice as a single bolus dose and the disposition of the studied cationic drugs was investigated by focusing on drug secretion into bile, intestinal lumen and urine. 3 Hepatobiliary secretion of the investigated cationic drugs was profoundly reduced in mice devoid of the mdr1-type P-gps. In fact, the cumulative biliary output, measured during 1 h, of the small type 1 compounds tri-butylmethyl ammonium (TBuMA) and azidoprocainamide methoiodide (APM), as well as of the more bulky type 2 cationic drug vecuronium, was reduced by at least 70% in the mdr1a/1b (7/7) mice compared to wild-type. 4 The intestinal secretion of TBuMA, APM and vecuronium was also profoundly reduced in mdr1a/1b (7/7) mice compared to wild-type mice. The absence of the mdr1-type P-gp resulted in virtual elimination of intestinal secretion of TBuMA and APM (490% reduced as compared to wild-type (P=0.0001 and 0.0022, respectively)). The intestinal secretion of the type 2 cation drug vecuronium was reduced by 58% (P=0.0004) compared to the wild-type mice. 5 Increased renal clearances of both the type 1 compounds TBuMA and APM and also of the type 2 cationic compound vecuronium in the mdr1a/1b (7/7) mice were observed. Furthermore, the balance between hepatic, intestinal and renal clearances of small type 1 organic cations clearly shifted towards a predominant role for renal clearance. Increased renal clearance may be explained by (over)expresion of additional mechanisms for renal organic cation secretion, alternatively they may also point to an as yet unde®ned role of P-glycoprotein in kidney physiology and renal secretory function. 6 We conclude that the elimination from the body of a broad spectrum of cationic amphiphilic drugs via liver and intestine, is largely dictated by the activity of mdr1-type P-glycoproteins.

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Dexa10-HSA has potent anti-inflammatory effects during BDL at extremely low doses, demonstrating the cell-specific targeting. However, the fibrotic process was not favourably affected. These results indicate a dual role for Dexa; besides blocking the release of pro-inflammatory cytokines it also reduces the release of antifibrotic mediators by SEC and KC.