Search

Apoptosis induced in primary cultures of rat hepatocytes by transforming growth factor beta 1 (TGF-beta 1) was greatly attenuated by inhibitors (5 microM) of calpain I and calpain II, respectively. Both inhibitors prevented the TGF-beta-elicited increase of nucleosomal DNA fragments and the occurrence of DNA-breaks in the TUNEL reaction. The detrimental effect of TGF-beta on cell viability measured by the WST-1 test was strongly reduced by calpain inhibitors. Calpain II > I inhibitors suppressed spontaneous DNA cleavage in hepatocytes during culture and prevented the appearance of immunocytochemically visible TGF-beta (APAAP staining), which occurs in untreated parenchymal cell cultures. The data show that inactivation of calpains attenuates both the TGF-beta-elicited and the spontaneous apoptosis of cultured hepatocytes; the latter effect is likely due to the suppression of endogenous TGF-beta activation. It is suggested that calpains participate in these processes.

This article has been retracted at the request of the Editor-in-Chief. Reason: The above Letter to the Editor was a report in reference to a previous work published in the Journal of Hepatology (OA Gressner et al., Pharmacological application of caffeine inhibits TGF-B stimulated connective tissue growth factor expression in hepatocytes via PPAR gamma and Smad2/3-dependent pathways. J Hepatol 2008; 49: 758–767). It appears that in this Letter to the Editor, the manuscript submitted referred to 4 groups of 5 rats studied. This Letter to the Editor was accepted without any modifications. However, after acceptance of this letter by the Editors, the authors made major modifications at the stage of the galley proofs without informing the Editor or the Associate Editor. The changes introduced were major scientific changes because: 1.The number of rats per group was reduced from 5 to 1; therefore, instead of a total of 20 rats being studied, a total of only 4 rats were studied. 2.Throughout the manuscript sentences have been changed from "rats" to "rat". 3.The standard deviation values were removed at the proof stage and more importantly some results were completely altered. 4.A full paragraph was added at the end of the paper, which was not present in the original version submitted to the Journal. In light of the above reasons, the Editors have concluded that the authors have presented falsified results which misled the Editors. As a consequence to the aforementioned breaches, we have decided to retract this Letter to the Editor from the Journal of Hepatology.

The molecular and cellular mechanisms of activation of fat-storing cells (Ito cells or parasinusoidal lipocytes), a prerequisite of the fibrogenic response of injured liver, were studied by analysis in vitro of some aspects of the intercellular communication between parenchymal liver cells and fat-storing cells. Conditioned medium harvested from early serum-free monolayer cultures of hepatocytes isolated from normal rat liver stimulated strongly, reproducibly and dose-dependently the proliferation of nonconfluent fat-storing cells maintained under serum-reduced conditions. During exposure of fat-storing cells for 48 hr to the conditioned medium, the incorporation of [3H]thymidine into DNA was stimulated four to six times over control values, the DNA content per culture well was elevated by 40% above control values and the immunocytochemical detection of bromodeoxyuridine-labeled cell nuclei was increased from 13% stained nuclei in controls to 70% stained nuclei in treated fat-storing cells. The mitogenic effects of hepatocyte-conditioned medium were similar to or even higher than those of 10% fetal calf serum. No mitoinhibitory activity could be detected in the hepatocyte-conditioned medium when arginase, as a potential inhibitor, was excluded. Rat skin fibroblasts could not be stimulated under conditions where the proliferation activity of fat-storing cells was greatly enhanced. The occurrence of the mitogenic activity in the medium is not dependent on de novo synthesis or secretion because the media of hepatocytes cultured under anoxic conditions in the presence of cycloheximide, brefeldin A or ethylenediaminetetraacetate were highly active in promoting fat-storing cell proliferation, although hepatocyte viability was greatly reduced under some of these conditions. A significant positive correlation (r = 0.95, p < 0.01) was found between lactate dehydrogenase activity and the mitogenic potency of the conditioned medium. The proliferation factor for fat-storing cells could also be demonstrated in the lysate of freshly isolated hepatocytes from normal liver. The stimulatory activity in the medium was partially enriched by a combination of gel permeation and anion exchange fast protein liquid chromatography and characterized as a protein with an apparent molecular weight of about 60 kD that is heat and pH sensitive but insensitive to reducing agents. It does not bind to immobilized heparin; nor does soluble heparin or proteinase inhibitor affect the mitogenic activity of the factor.(ABSTRACT TRUNCATED AT 400 WORDS)

The induction of apoptosis of rat liver parenchymal cells (PC) by transforming growth factor beta (TGF-beta)-expressing transforming fat-storing cells (FSC), i.e., myofibroblasts (MFB), was studied under culture conditions and compared with the apoptotic effect of human recombinant TGF-beta1. MFB were obtained by subculture of FSC. The TGF-beta concentration in the conditioned medium of myofibroblast (MFBcM) determined with the Mink cell proliferation inhibition assay was