Abstract
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 α-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.
Footnotes
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This study was supported by a grant from the Innovational Research Incentives Scheme of the Netherlands Organisation for Scientific Research and by a grant from the Dutch Technology Foundation STW.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.107.132290.
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ABBREVIATIONS: HSC, hepatic stellate cell; GTX, gliotoxin; M6P-HSA, mannose-6-phosphate-modified human serum albumin; PBS, phosphate-buffered saline; MF, myofibroblast; hMF, hepatic myofibroblast; FCS, fetal calf serum; SMA, smooth muscle actin; DAPI, 4,6-diamidino-2-phenylindole; BDL, bile duct ligation; PAS, periodic acid-Schiff; PCR, polymerase chain reaction; Ct, threshold cycle; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; ALT, alanine aminotransferase; AST, aspartate aminotransferase; ANOVA, analysis of variance; eNOS, endothelial nitric-oxide synthase; KC, Kupffer cell; EC, endothelial cell; IDN-6556, 3-(2-[(2-tert-butyl-phenylaminooxalyl)-amino]-propionylamino)-4-oxo-5-(2,3,5,6-tetrafluoro-phenoxy)-pentanoic acid; FU, fluorescence units.
- Received September 28, 2007.
- Accepted December 10, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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