Stellate Cell Death Research Articles

Novel Therapeutic Targets in Liver Fibrosis.

Liver fibrosis is end-stage liver disease that can be rescued. If irritation continues due to viral infection, schistosomiasis and alcoholism, liver fibrosis can progress to liver cirrhosis and even cancer. The US Food and Drug Administration has not approved any drugs that act directly against liver fibrosis. The only treatments currently available are drugs that eliminate pathogenic factors, which show poor efficacy; and liver transplantation, which is expensive. This highlights the importance of clarifying the mechanism of liver fibrosis and searching for new treatments against it. This review summarizes how parenchymal, nonparenchymal cells, inflammatory cells and various processes (liver fibrosis, hepatic stellate cell activation, cell death and proliferation, deposition of extracellular matrix, cell metabolism, inflammation and epigenetics) contribute to liver fibrosis. We highlight discoveries of novel therapeutic targets, which may provide new insights into potential treatments for liver fibrosis.

Somatostatin Therapy Improves Stellate Cell Activation and Early Fibrogenesis in a Preclinical Model of Extended Major Hepatectomy.

Simple SummaryLiver resection is the best treatment for liver tumors; its clinical applicability, however, is limited by the mass and quality of the remnant liver. In this study, hepatic resections were performed in a pig model to define changes associated with sufficient and insufficient liver remnants. As well, somatostatin, a naturally occurring peptide hormone that exerts numerous largely inhibitory effects, was given in order to improve outcomes. We observed that extended major hepatectomy is associated with immediate changes in portal pressure leading to injury, stellate cell activation, collagen deposition, and cell death, all of which were improved with somatostatin therapy. This is one of few studies (potentially the first) describing collagen deposition as early as 24 h after extended major hepatectomy and implicating liver resection as potential cause for chronic liver injury.Liver resection treats primary and secondary liver tumors, though clinical applicability is limited by the remnant liver mass and quality. Herein, major hepatic resections were performed in pigs to define changes associated with sufficient and insufficient remnants and improve liver-specific outcomes with somatostatin therapy. Three experimental groups were performed: 75% hepatectomy (75H), 90% hepatectomy (90H), and 90% hepatectomy + somatostatin (90H + SST). Animals were followed for 24 h (N = 6) and 5 d (N = 6). After hepatectomy, portal pressure gradient was higher in 90H versus 75H and 90H + SST (8 (3–13) mmHg vs. 4 (2–6) mmHg and 4 (2–6) mmHg, respectively, p < 0.001). After 24 h, changes were observed in 90H associated with stellate cell activation and collapse of sinusoidal lumen. Collagen chain type 1 alpha 1 mRNA expression was higher, extracellular matrix width less, and percentage of collagen-staining areas greater at 24 h in 90H versus 75H and 90H + SST. After 5 d, remnant liver mass was higher in 75H and 90H + SST versus 90H, and Ki-67 immunostaining was higher in 90H + SST versus 75H and 90H. As well, more TUNEL-staining cells were observed in 90H versus 75H and 90H + SST at 5 d. Perioperative somatostatin modified portal pressure, injury, apoptosis, and stellate cell activation, stemming changes related to hepatic fibrogenesis seen in liver remnants not receiving treatment.

Suppression of Hepatic Stellate Cell Death by Toxic Advanced Glycation End-Products.

Advanced glycation end-products (AGEs) are produced by the non-enzymatic reaction of sugars with proteins. It has been revealed that glyceraldehyde-derived toxic AGEs (TAGE) are elevated in the serum of non-alcoholic steatohepatitis (NASH) patients. NASH causes liver fibrosis and progresses to cirrhosis and hepatocellular carcinoma. However, the impact of TAGE in liver fibrosis caused by extracellular matrix accumulation remains poorly understood. In this study, we examined the effect of TAGE on the activation of hepatic stellate cells that are involved in liver fibrosis. LX-2 cells treated with transforming growth factor-β1 (TGF-β1) significantly reduced cell viability by apoptosis. However, the decrease in cell viability with TGF-β1 treatment was significantly suppressed by TAGE co-treatment. The levels of α-smooth muscle actin (α-SMA) and platelet-derived growth factor (PDGF)-Rβ and its ligand PDGF-B were increased in LX-2 cells following TGF-β1 treatment, suggesting that these cells were activated; however, these increases were unaffected by TAGE co-treatment. Moreover, collagen I level was increased with TGF-β1 treatment, and this increase was further increased by TAGE co-treatment. These results suggested that the suppression of apoptosis in activated LX-2 cells by TGF-β1 and TAGE co-treatment is related to an increase in the production of the extracellular matrix such as collagen I. Therefore, it was suggested that TAGE might aggravate the liver fibrosis of chronic hepatitis, such as NASH.

216-LB: A Novel GPR119 Agonist, DA-1241, Reduces Hepatic Inflammation and Fibrosis in Preestablished Diet-Induced NASH Mice

There are no reports of the treatment effects of GPR119 agonists in pre-established NASH animal models yet. The aim of this study was to investigate the efficacy of DA-1241 monotherapy and to explore its combined effects with a dipeptidyl peptidase 4 (DPP-4) inhibitor in pre-established NASH mice. DA-1241 in the absence or presence of a DPP-4 inhibitor was given to biopsy-proven diet-induced NASH mice for 8 weeks. Plasma and liver tissue were tested for biochemical and/or histological analyses. Changes in gene expression profiles in the liver were evaluated by RNAseq method. Plasma profiles of a panel of cytokines were assessed. After 8-week administration, DA-1241 treatment significantly decreased hepatic lipid accumulation (-51.4%) and co-treatment of a DPP-4 inhibitor showed a further reduction (-60.6%). DA-1241 monotherapy and its combination reduced liver fibrosis score (-20.6% and -36.5%) with lower levels of hepatic type 1 collagen and plasma TIMP-1. Notably, DA-1241 alone and its combination significantly reduced the infiltration of immune cells into the liver (-25.0% and -49.1%) with drastically decreased the hepatic galectin-3 levels (-58.3% and -67.2%). Liver enzyme values decreased in both treatment groups. In line with these results, DA-1241 treatment alone prominently improved gene expression profiles associated with stellate cell activation, monocyte recruitment, inflammation signaling, and hepatocellular cell death. Moreover, plasma levels of clinically-related plasma cytokines such as CCL2, TNFα, and CXCL10 were also reduced in DA-1241-treated mice. All the effects augmented by its concomitant use with a DPP-4 inhibitor were supported by the increase of plasma active GLP-1 (6.6 folds vs. NASH control). To the best of our knowledge, this is the first report to comprehensively demonstrate the in vivo therapeutic efficacy of GPR119 agonist as monotherapy and combination therapy with DPP-4 inhibitors for the treatment of NASH. Disclosure H. Park: Employee; Self; Dong-A ST Co., Ltd. S. Lee: Employee; Self; Dong-A ST Co., LTD. M. Kim: Employee; Self; Dong-A ST Co., Ltd.

Hesperetin Mitigates Bile Duct Ligation-Induced Liver Fibrosis by Inhibiting Extracellular Matrix and Cell Apoptosis via the TGF-β1/Smad Pathway.

Hesperetin, a natural component of citrus fruits, is indicated to have beneficial anti-inflammatory effects on injury and various cancers as a transforming growth factor beta (TGF-β) inhibitor. However, little evidence associates hesperetin with liver fibrosis. Work from our laboratory aims at finding the mechanism by which hesperetin attenuates liver fibrosis. Bile duct ligation (BDL) was used to induce liver fibrosis in mice and the findings were determined using enzyme-linked immunosorbent assay, quantitative realtime polymerase chain reaction, western blotting and immunohistochemical staining. Data from Immunohistochemical staining and injury score indicated that pathological lesions were reduced by hesperetin treatment. Decreasing levels of several serum parameters including cytokines tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6), liver enzyme alanine aminotransferase (ALT) and aspartate aminotransferase (AST), fibrosis indicators laminin (LN), hyaluronic acid (HA) and hydroxylproline (Hyp) suggested similar results to the immunohistochemical. In addition, our data verified hesperetin could suppress the formation of extracellular matrix and hepatocyte apoptosis in vitro, together with promoting hepatic stellate cell death in vivo, which was considered to be associated with the inhibition of TGF-β1/Smad pathways. In the present study, the favorable role of hesperetin extracted from citrus peels was verified to prevent the progression of BDL-induced liver fibrosis via inhibiting TGF-β1/Smad pathway-mediated extracellular matrix progression and apoptosis.

Autophagy induced by purple pitanga (Eugenia uniflora L.) extract triggered a cooperative effect on inducing the hepatic stellate cell death

Activated hepatic stellate cells (HSC) are the major source of collagen I in liver fibrosis. Eugenia uniflora L. is a tree species that is widely distributed in South America. E. uniflora L. fruit-popularly known as pitanga-has been shown to exert beneficial properties. Autophagy contributes to the maintenance of cellular homeostasis and survival under stress situation, but it has also been suggested to be an alternative cell death pathway. Mitochondria play a pivotal role on signaling cell death. Mitophagy of damaged mitochondria is an important cell defense mechanism against organelle-mediated cell death signaling. We previously found that purple pitanga extract induced mitochondrial dysfunction, cell cycle arrest, and death by apoptosis and necrosis in GRX cells, a well-established activated HSC line. We evaluated the effects of 72-h treatment with crescent concentrations of purple pitanga extract (5 to 100μg/mL) on triggering autophagy in GRX cells, as this is an important mechanism to cells under cytotoxic conditions. We found that all treated cells presented an increase in the mRNA expression of autophagy-related protein 7 (ATG7). Concomitantly, flow cytometry and ultrastructural analysis of treated cells revealed an increase of autophagosomes/autolysosomes that consequentially led to an increased mitophagy. As purple pitanga extract was previously found to be broadly cytotoxic to GRX cells, we postulated that autophagy contributes to this scenario, where cell death seems to be an inevitable fate. Altogether, the effectiveness on inducing activated HSC death can make purple pitanga extract a good candidate on treating liver fibrosis.

Sorafenib induces autophagic cell death and apoptosis in hepatic stellate cell through the JNK and Akt signaling pathways.

Increasing hepatic stellate cell (HSC) death is an attractive approach for limiting liver fibrosis. We investigated the molecular mechanisms underlying the effects of sorafenib on HSCs. LX2 cells were incubated with sorafenib and a variety of inhibitors of apoptosis, autophagy, and necrosis. Electron microscopy was used to observe autophagosomes. Inhibitors and siRNA were used to examine the role of the Akt/mTOR/p70S6K and JNK pathways. Ultrastructural analysis revealed that rat HSCs treated with 5 μmol/l sorafenib accumulated residual digested material and empty or autophagic vacuoles. Incubating LX2 cells with lysosomal protease inhibitors increased the accumulation of LC3-II, indicating that sorafenib enhances autophagic flux in HSCs. Autophagy may precede apoptosis. Lower concentrations of sorafenib and a shorter treatment time resulted in the dominance of autophagic cell death over apoptosis. Further analysis showed that Beclin 1 is inactivated by the caspases induced by sorafenib during apoptosis. Inhibition of autophagy in LX2 cells using 3-methyladenine treatment or siRNA-mediated knockdown of Atg5 resulted in a marked increase in apoptosis. Finally, sorafenib induced programmed cell death by attenuation and activation of Akt/mTOR/p70S6K and JNK signaling. Sorafenib-induced cell death is mediated by both autophagy and apoptosis. Elucidation of the signaling pathways activated by sorafenib could potentially lead to novel antifibrosis therapies for chronic liver diseases.

Mesenchymal stem cells and their secreted molecules predominantly ameliorate fulminant hepatic failure and chronic liver fibrosis in mice respectively.

BackgroundOrthotopic liver transplantation is the only effective treatment for liver failure but limited with shortage of available donor organs. Recent studies show promising results of mesenchymal stem cells (MSCs)-based therapies.MethodsWe systematically investigate the therapeutic effects of MSCs or MSC-conditioned medium (MSC-CM) in ameliorating fulminant hepatic failure (FHF) and chronic liver fibrosis in mice. In addition, extensive flow cytometry analysis of spleens from vehicle and MSC- and MSC-CM-treated mice was applied to reveal the alteration of inflammatory state.ResultsIn FHF model, MSCs treatment reduced remarkably the death incidents; the analysis of gross histopathology showed that control livers were soft and shrunken with extensive extravasated blood, which was gradually reduced at later time points, while MSC–treated livers showed gross pathological changes, even 24 h after MSC infusion, and hematoxylin and eosin staining revealed dramatical hepatocellular death with cytoplasmic vacuolization suppressed by MSCs treatment; flow cytometry analysis of total lymphocytes showed that macrophages (F4/80) infiltrated into control livers more than MSC-treated livers; by contrast, MSC-CM partially ameliorates FHF. In chronic liver injury model, MSC and MSC-CM both suppressed fibrogenesis and necroinflammatory, and the later was better; activation of hepatic stellate cells (α-SMA) was inhibited; glycogen synthesis and storage (indicated by periodic acid-Schiff -staining) was improved; liver regeneration (Ki67) was promoted while liver apoptosis (TUNEL) was reduced. In the in vitro, MSCs promote macrophage line RAW264.7 apoptosis and MSC-CM promotes apoptosis and inhibits proliferation of HSC line LX-2. We also found that MSCs and MSC-CM could improve spleen; MSC-CM increased levels of Th2 and Treg cells, and reduced levels of Th17 cells, whereas levels of Th1 cells were unchanged; comparatively, MSC treatment did not affect Th17 and Treg cells and only slightly alters inflammatory state; MSC and MSC-CM treatment both substantially down-regulated macrophages in the spleens.ConclusionBoth MSCs and MSC-CM exert therapeutic effects by acting on various key cells during the pathogenesis of FHF and chronic fibrosis, stimulating hepatocyte proliferation and suppressing apoptosis, down-regulating infiltrating macrophages, converting CD4+ T lymphocyte system into an anti-inflammatory state, and facilitating hepatic stellate cell death.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-0792-1) contains supplementary material, which is available to authorized users.

Maternal separation on the ethanol-preferring adult rat liver structure

Background and rationale for the study. We designed to test whether there is interaction of maternal separation (MS) on the ethanol-preferring rats liver structure. The UCh rat pups were separated daily from their mothers during the stress hyporesponsive period (SHRP), between four and 14 days-old, always at the same time for four hours in a cage containing eight subdivisions, one for each pup. Subsequently, rats that presented the highest (UChB) and the lowest (UChA) ethanol (EtOH) consumption were selected to the study. Both UChB and UChA rats received 10% (v/v) EtOH and distilled water ad libitum until the end of the experiment (120 days-old). The liver was collected to histological routine for morphometric and stereological analyses, and immunohistochemistry.Results. There was an interaction of MS and EtOH on the liver: increased liver mass, peritubular vessels, stellate cell numbers, steatosis and cell death, decreased necrosis, sinusoidal capillary diameters and cell proliferation. While there was a decrease in FSH, testosterone and 5a-di-hidrotestosterone, and increasing corticosterone and cholesterol.Conclusions. There is interaction of MS and EtOH on the liver structure, dependent on the amount of EtOH intake. Furthermore, the interaction of stress and drugs can increase or decrease their effects on the liver or indirectly via hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes.

Blockage of TRPM7 channel induces hepatic stellate cell death through endoplasmic reticulum stress-mediated apoptosis

AimsProliferation is a ‘multiplier’ for extracellular matrix production and contraction of activated hepatic stellate cells (HSC) in fibrotic liver. Transient receptor potential melastatin-like 7 channels (TRPM7) are implicated in the survival and proliferation of several kinds of cells. This study was aimed to investigate the effect of TRPM7 blocker 2-APB on survival and proliferation of HSC and the underlying mechanisms. Main methodsRat HSC were stimulated by 2-APB for 24h and then collected for further use. Cell viability was detected by MTT, and apoptosis was determined by AnnexinV/PI staining and TUNEL assay. Gene expressions of TRPM7, α-SMA, bcl-2, bax, and endoplasmic reticulum (ER) stress key members CHOP, caspase-12, ATF4, ATF6, Xbp1, GRP78 and calnexin were evaluated with quantitative RT-PCR. Quantifications of α-SMA, TRPM7, CHOP and GRP78 proteins were carried out by Western blot. Transmission electron microscopy and Xbp1 mRNA splicing analysis were also used for detection of ER stress. Key findings2-APB decreased TRPM7 and α-SMA expressions in primary HSC, and inhibited proliferation of activated HSC in a dose-dependent manner. 2-APB also decreased total count of activated HSC and increased the number of apoptotic cells. 2-APB increased expressions of bax and ER stress key factors CHOP, caspase-12, ATF4, ATF6, Xbp1, GRP78 and calnexin. Meanwhile, ultra-structural ER changes and spliced Xbp1 mRNA were also observed in 2-APB treated HSC. SignificanceBlockage of TRPM7 could inhibit activation and proliferation of primary HSC and induce apoptotic death of activated cells, in which ER stress was identified as one of possible underlying molecular bases.

Nilotinib induces apoptosis and autophagic cell death of activated hepatic stellate cells via inhibition of histone deacetylases

Increasing hepatic stellate cell (HSC) death is a very attractive approach for limiting liver fibrosis. Tyrosine kinase inhibitors have been shown to have anti-fibrotic properties, but the mechanisms are poorly understood. Here, we identified the mechanism of action of the second-generation tyrosine kinase inhibitor nilotinib in inducing HSC death. Human HSC line (LX-2) and rat HSCs were treated with nilotinib and its predecessor, imatinib, in the absence or presence of various blockers, known to interfere with death signaling pathways. Nilotinib, but not imatinib, induced progressive cell death of activated, but not quiescent, HSCs in a dose-dependent manner. Activated HSCs died through apoptosis, as denoted by increased DNA fragmentation and caspase activation, and through autophagy, as indicated by the accumulation of autophagic markers, light chain (LC)3A-II and LC3B-II. Although inhibition of caspases with Z-VAD-FMK suppressed nilotinib-induced HSCs' apoptosis, there was no increase in HSCs' survival, because autophagy was exacerbated. However, blocking the mitochondrial permeability transition pore (mPTP) opening with cyclosporin A completely abolished both apoptosis and autophagy due to nilotinib. Moreover, nilotinib treatment decreased the protein expression of histone deacetylases 1, 2 and 4. Interestingly, pretreament with C646, a selective p300/CBP histone acetyl transferase inhibitor, resulted in diverting nilotinib-induced apoptosis and autophagy towards necrosis. In conclusion, the identification of mPTP as a target of nilotinib in activated HSCs suggests coordination with histone deacetylases inhibition to induce apoptosis and autophagy. Thus, our study provides novel insights into the anti-fibrotic effects of nilotinib.

N-Terminal Region of Gelsolin Induces Apoptosis of Activated Hepatic Stellate Cells by a Caspase-Dependent Mechanism

Activated hepatic stellate cells (HSCs) are the major source for alteration of extracellular matrix in fibrosis and cirrhosis. Conditioned medium (CM) collected from immortalized human hepatocytes (IHH) have earlier been shown to be responsible for apoptosis of HSCs. In this study, we have shown that antibodies raised against a peptide derived from a linear B-cell epitope in the N-terminal region of gelsolin identified a gelsolin fragment in IHH CM. Analysis of activated stellate cell death by CM collected from Huh7 cells transfected with plasmids encoding gelsolin deletion mutants suggested that the N-terminal half of gelsolin contained sequences which were responsible for stellate cell death. Further analysis determined that this activity was restricted to a region encompassing amino acids 1–70 in the gelsolin sequence; antibody directed to an epitope within this region was able to neutralize stellate cell death. Gelsolin modulation of cell death using this fragment involved upregulation of TRAIL-R1 and TRAIL-R2, and involved caspase 3 activation by extrinsic pathway. The apoptotic activity of N-terminal gelsolin fragments was restricted to activated but not quiescent stellate cells indicating its potential application in therapeutic use as an anti-fibrotic agent. Gelsolin fragments encompassing N-terminal regions in polypeptides of different molecular sizes were detected by N-terminal peptide specific antiserum in IHH CM immunoprecipitated with chronically HCV infected patient sera, suggesting the presence of autoantibodies generated against N-terminal gelsolin fragments in patients with chronic liver disease.

Cannabidiol causes activated hepatic stellate cell death through a mechanism of endoplasmic reticulum stress-induced apoptosis

The major cellular event in the development and progression of liver fibrosis is the activation of hepatic stellate cells (HSCs). Activated HSCs proliferate and produce excess collagen, leading to accumulation of scar matrix and fibrotic liver. As such, the induction of activated HSC death has been proposed as a means to achieve resolution of liver fibrosis. Here we demonstrate that cannabidiol (CBD), a major non-psychoactive component of the plant Cannabis sativa, induces apoptosis in activated HSCs through a cannabinoid receptor-independent mechanism. CBD elicits an endoplasmic reticulum (ER) stress response, characterized by changes in ER morphology and the initiation of RNA-dependent protein kinase-like ER kinase-, activating transcription factor-6-, and inositol-requiring ER-to-nucleus signal kinase-1 (IRE1)-mediated signaling cascades. Furthermore, CBD induces downstream activation of the pro-apoptotic IRE1/ASK1/c-Jun N-terminal kinase pathway, leading to HSC death. Importantly, we show that this mechanism of CBD-induced ER stress-mediated apoptosis is specific to activated HSCs, as it occurs in activated human and rat HSC lines, and in primary in vivo-activated mouse HSCs, but not in quiescent HSCs or primary hepatocytes from rat. Finally, we provide evidence that the elevated basal level of ER stress in activated HSCs has a role in their susceptibility to the pro-apoptotic effect of CBD. We propose that CBD, by selectively inducing death of activated HSCs, represents a potential therapeutic agent for the treatment of liver fibrosis.

Tocotrienols Induce Apoptosis and Autophagy in Rat Pancreatic Stellate Cells Through the Mitochondrial Death Pathway

Selective removal of activated pancreatic stellate cells (PSCs) through induction of their own programmed death is a goal of therapeutic interest in patients with chronic pancreatitis. Here, we investigated the effects of tocotrienols on PSC death outcomes. Activated and quiescent PSCs and acinar cells from rat pancreas were treated with vitamin E derivatives alpha-tocopherol; individual alpha-, beta-, gamma-, and delta-tocotrienols; and a tocotrienol rich fraction (TRF) from palm oil. TRF, but not alpha-tocopherol, reduced viability of activated PSC by setting up a full death program, independent of cell cycle regulation. Activated PSCs died both through apoptosis, as indicated by increased DNA fragmentation and caspase activation, and through autophagy, as denoted by the formation of autophagic vacuoles and LC3-II accumulation. In contrast to alpha-tocopherol, TRF caused an intense and sustained mitochondrial membrane depolarization and extensive cytochrome c release. Caspase inhibition with zVAD-fmk suppressed TRF-induced apoptosis but enhanced autophagy. However, mitochondrial permeability transition pore blockade with cyclosporin A completely abolished the deadly effects of TRF. beta-, gamma-, and delta-tocotrienol, but not alpha-tocotrienol nor alpha-tocopherol, reproduced TRF actions on activated PSCs. TRF death induction was restricted to activated PSCs because it did not cause apoptosis either in quiescent PSCs or in acinar cells. Tocotrienols selectively trigger activated pancreatic stellate cell death by targeting the mitochondrial permeability transition pore. Our findings unveil a novel potential for tocotrienols to ameliorate the fibrogenesis associated with chronic pancreatitis.

Apoptosis and Necrosis in the Liver: A Tale of Two Deaths?

Death of hepatocytes and other hepatic cell types is a characteristic feature of liver diseases as diverse as cholestasis, viral hepatitis, ischemia/reperfusion, liver preservation for transplantation and drug/toxicant-induced injury. Cell death typically follows one of two patterns: oncotic necrosis and apoptosis. Necrosis is typically the consequence of acute metabolic perturbation with ATP depletion as occurs in ischemia/reperfusion and acute drug-induced hepatotoxicity. Apoptosis, in contrast, represents the execution of an ATP-dependent death program often initiated by death ligand/death receptor interactions, such as Fas ligand with Fas, which leads to a caspase activation cascade. A common event leading to both apoptosis and necrosis is mitochondrial permeabilization and dysfunction, although the mechanistic basis of mitochondrial injury may vary in different settings. Prevention of these modes of cell death is an important target of therapy, but controversies still exist regarding which mode of cell death predominates in various forms of liver disease and injury. Resolution of these controversies may come with the recognition that apoptosis and necrosis frequently represent alternate outcomes of the same cellular pathways to cell death, especially for cell death mediated by mitochondrial permeabilization. An understanding of processes leading to liver cell death will be important for development of effective interventions to prevent hepatocellular death leading to liver failure and to promote cancer and stellate cell death in malignancy and fibrotic disease.

New mechanism of selective killing of activated hepatic stellate cells.

Background &amp; Aims: Hepatic stellate cells play an important role in liver fibrogenesis, and hepatic stellate cell death may be involved in the termination of this response. Methods: Molecular mechanisms of hepatic stellate cell killing were studied in hepatic stellate cell/Kupffer cell cocultures. Results: Lipopolysaccharide stimulation of hepatic stellate cell/Kupffer cell cocultures, but not of hepatic stellate cell monocultures, induced profound alterations of hepatic stellate cell morphology and hepatic stellate cell death. Kupffer cell–induced hepatic stellate cell killing required hepatic stellate cell/Kupffer cell contacts and was prevented by dexamethasone, prostaglandin E(2), tumor necrosis factor–related apoptosis–inducing ligand (TRAIL) receptor 2 antagonists, and down–regulation of receptor–interacting protein, but not by antioxidants, tumor necrosis factor receptor, or CD95 antagonists. Hepatic stellate cell death was characterized by activation of caspases 3, 8, and 9, terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick–end labeling negativity, lack of gross calcium overload, and TRAIL trafficking to the plasma membrane. Inhibition of caspase 9, but not of caspases 3, 8, or 10, prevented hepatic stellate cell death. Lipopolysaccharide induced a dexamethasone– and prostaglandin E(2)–sensitive expression of TRAIL in Kupffer cells. TRAIL receptors 1 and 2, FLIP (caspase 8–inhibitory protein), and receptor–interacting protein were up–regulated during hepatic stellate cell transformation; however, TRAIL addition did not induce hepatic stellate cell death. Hepatic stellate cell susceptibility toward Kupffer cell–induced death paralleled receptor–interacting protein and TRAIL–receptor expression levels. Conclusions: Activated Kupffer cell can effectively kill hepatic stellate cell by a caspase 9– and receptor–interacting protein–dependent mechanism, possibly involving TRAIL. The data may suggest a novel form of hepatic stellate cell death.

Caspase 9–dependent killing of hepatic stellate cells by activated Kupffer cells

Background & Aims: Hepatic stellate cells play an important role in liver fibrogenesis, and hepatic stellate cell death may be involved in the termination of this response. Methods: Molecular mechanisms of hepatic stellate cell killing were studied in hepatic stellate cell/Kupffer cell cocultures. Results: Lipopolysaccharide stimulation of hepatic stellate cell/Kupffer cell cocultures, but not of hepatic stellate cell monocultures, induced profound alterations of hepatic stellate cell morphology and hepatic stellate cell death. Kupffer cell–induced hepatic stellate cell killing required hepatic stellate cell/Kupffer cell contacts and was prevented by dexamethasone, prostaglandin E2, tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) receptor 2 antagonists, and down-regulation of receptor-interacting protein, but not by antioxidants, tumor necrosis factor receptor, or CD95 antagonists. Hepatic stellate cell death was characterized by activation of caspases 3, 8, and 9, terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling negativity, lack of gross calcium overload, and TRAIL trafficking to the plasma membrane. Inhibition of caspase 9, but not of caspases 3, 8, or 10, prevented hepatic stellate cell death. Lipopolysaccharide induced a dexamethasone- and prostaglandin E2–sensitive expression of TRAIL in Kupffer cells. TRAIL receptors 1 and 2, FLIP (caspase 8–inhibitory protein), and receptor-interacting protein were up-regulated during hepatic stellate cell transformation; however, TRAIL addition did not induce hepatic stellate cell death. Hepatic stellate cell susceptibility toward Kupffer cell–induced death paralleled receptor-interacting protein and TRAIL-receptor expression levels. Conclusions: Activated Kupffer cell can effectively kill hepatic stellate cell by a caspase 9– and receptor-interacting protein–dependent mechanism, possibly involving TRAIL. The data may suggest a novel form of hepatic stellate cell death.GASTROENTEROLOGY 2002;123:845-861