Hepatoprotective effects of IL-22 on fulminant hepatic failure induced by d-galactosamine and lipopolysaccharide in mice

Interleukin-22 (IL-22), a member of the IL-10 cytokine family that is produced by activated Th22, Th1 and Th17 cells as well as natural killer cells, plays an important role in increase of innate immunity, protection from damage and enhancement of regeneration. Here, we examined the effects of IL-22 on acute liver failure model induced by d-galactosamine (GalN) and lipopolysaccharide (LPS). Administration of recombinant human IL-22 (rhIL-22) reduced the death rate markedly and prevented mice from severe hepatic injury, as evidenced by decreased serum alanine aminotransferase (ALT) and total bilirubin (T.Bil) activity as well as improved histological signs in liver. Furthermore, IL-22 treatment decreased the hepatic malondialdehyde (MDA) contents and increased the reduced glutathione levels. Serum tumor necrosis factor α (TNF-α) level and hepatic caspase-3 activity were significantly lower in mice administrated with IL-22. Moreover, IL-22 treatment significantly enhanced activation of STAT3 and up-regulated the expression of Bcl-xL, heme oxygenase-1 (HO-1) and redox factor-1 (Ref-1) in the liver injury induced by GalN/LPS. Collectively, these data indicate that IL-22 can provide critical protection against GalN/LPS-induced liver injury through anti-apoptotic, anti-oxidant and anti-inflammatory actions.     

Boron ameliorates fulminant hepatic failure by counteracting the changes associated with the oxidative stress

Boron has well-defined biological effects and may be of therapeutic benefit. In the current paper, the effect of boron in the form of borax was tested in experimental animal model of fulminant hepatic failure (FHF). The syndrome was induced in female Wistar rats by three consecutive daily intraperitoneal injections of thioacetamide (400 mg/kg). In the treatment groups, rats received borax (4.0 mg/kg) orally for three consecutive days followed by thioacetamide. The group administered with thioacetamide plus vehicle, and the borax alone treated rats served as controls. In all groups, rats were terminated 4 h after administering the last dose of thioacetamide, and the tissue/serum was used to measure hepatic levels of thiobarbituric acid reactive substances, reduced glutathione, and various enzymes associated with oxidative stress including peroxide metabolizing enzymes and xanthine oxidase. In thioacetamide treated group, many fold increase in the activity level of serum marker enzymes suggesting FHF was observed that could be brought down significantly in rats receiving boron. Modulation and a correlation in the activity level of oxidant generating enzyme and lipid peroxidation as well as hepatic glutathione level was also observed in rats receiving thioacetamide. In the group receiving boron followed by thioacetamide, these changes could be minimized moderately. The activity level of the peroxide metabolizing enzymes and the tripeptide glutathione, which decreased following thioacetamide treatment were moderately elevated in the group receiving boron followed by thioacetamide. The data clearly shows that borax partly normalizes the liver and offsets the deleterious effects observed in FHF by modulating the oxidative stress parameters.     

TNFR1 and TNFR2 regulate the extrinsic apoptotic pathway in myeloma cells by multiple mechanisms

The huge majority of myeloma cell lines express TNFR2 while a substantial subset of them failed to show TNFR1 expression. Stimulation of TNFR1 in the TNFR1-expressing subset of MM cell lines had no or only a very mild effect on cellular viability. Surprisingly, however, TNF stimulation enhanced cell death induction by CD95L and attenuated the apoptotic effect of TRAIL. The contrasting regulation of TRAIL- and CD95L-induced cell death by TNF could be traced back to the concomitant NFκB-mediated upregulation of CD95 and the antiapoptotic FLIP protein. It appeared that CD95 induction, due to its strength, overcompensated a rather moderate upregulation of FLIP so that the net effect of TNF-induced NFκB activation in the context of CD95 signaling is pro-apoptotic. TRAIL-induced cell death, however, was antagonized in response to TNF because in this context only the induction of FLIP is relevant. Stimulation of TNFR2 in myeloma cells leads to TRAF2 depletion. In line with this, we observed cell death induction in TNFR1-TNFR2-costimulated JJN3 cells. Our studies revealed that the TNF-TNF receptor system adjusts the responsiveness of the extrinsic apoptotic pathway in myeloma cells by multiple mechanisms that generate a highly context-dependent net effect on myeloma cell survival.     

Successful TRPV1 antagonist treatment for cardiac hypertrophy and heart failure in mice

Heart failure is becoming a global epidemic. It exerts a staggering toll on quality of life, and substantial medical and economic impact. In a pre-clinical model of cardiac hypertrophy and heart failure, we were able to overcome loss of heart function by administering the TRPV1 antagonist BCTC (4-(3-Chloro-2-pyridinyl)-N-[4-(1,1-dimethylethyl)phenyl]-1-piperazinecarboxamide). The results presented here identify TRPV1 antagonists as new treatment options for cardiac hypertrophy and heart failure.     

Deterioration of ischemia/reperfusion-induced acute renal failure in SOD1-deficient mice

Reactive oxygen species (ROS) are likely candidates for involvement in ischemia/reperfusion-induced acute renal failure (ARF). In this study, the issue of whether superoxide dismutase (SOD1)-deficiency exacerbates the ischemia/reperfusion-induced ARF was examined. At two weeks after a right nephrectomy of mice, the left renal vessels were clipped to induce renal ischemia and were then released after 45 min. The severe renal damage observed at one day was partially recovered at seven days after the induction of ischemia. SOD1^- / -  mice suffer from severe ARF compared with SOD1^+/ -  and SOD1^+/+ mice. The damage was more evident in aged animals (24-28 week old) than younger ones (10-12 week old). The expression of major antioxidative and redox enzymes, except for CuZnSOD, were substantially unchanged. Thus, the increased ARF in SOD1^- / -  mice appears to be mainly attributable to a deficiency in CuZnSOD. These data support the view that ROS are exacerbating factors in ischemia/reperfusion-induced ARF.     

NKT cells stimulated by long fatty acyl chain sulfatides significantly reduces the incidence of type 1 diabetes in nonobese diabetic mice

Sulfatide-reactive type II NKT cells have been shown to regulate autoimmunity and anti-tumor immunity. Although, two major isoforms of sulfatide, C16:0 and C24:0, are enriched in the pancreas, their relative role in autoimmune diabetes is not known. Here, we report that sulfatide/CD1d-tetramer(+) cells accumulate in the draining pancreatic lymph nodes, and that treatment of NOD mice with sulfatide or C24:0 was more efficient than C16:0 in stimulating the NKT cell-mediated transfer of a delay in onset from T1D into NOD.Scid recipients. Using NOD.CD1d(-/-) mice, we show that this delay of T1D is CD1d-dependent. Interestingly, the latter delay or protection from T1D is associated with the enhanced secretion of IL-10 rather than IFN-g by C24:0-treated CD4(+) T cells and the deviation of the islet-reactive diabetogenic T cell response. Both C16:0 and C24:0 sulfatide isoforms are unable to activate and expand type I iNKT cells. Collectively, these data suggest that C24:0 stimulated type II NKT cells may regulate protection from T1D by activating DCs to secrete IL-10 and suppress the activation and expansion of type I iNKT cells and diabetogenic T cells. Our results raise the possibility that C24:0 may be used therapeutically to delay the onset and protect from T1D in humans.     

病毒性心肌炎所致小鼠心力衰竭心肌组织内质网应激相关的凋亡关系的研究

目的：探讨病毒性心肌炎心力衰竭小鼠心肌组织内质网应激介导的凋亡途径。方法：40只雄性Balb／c小鼠分为病毒性心肌炎组和正常对照组（n=20）,病毒性心肌炎组应用柯萨奇B3病毒制作BALB／c小鼠病毒性心肌炎模型,观察小鼠的一般情况,7d行血流动力学检查后处死取心脏标本,用TUNEL法检测心肌细胞凋亡,RT-PCR检测心肌细胞内质网伴侣蛋白葡萄糖调节蛋白（GAP）78和GRP04的mRNA表达水平。结果：①与正常对照组相比,病毒性心肌炎组小鼠血流动力学指标明显降低（P〈0．01）;②TUNEL染色显示病毒性心肌炎心力衰竭小鼠心肌组织凋亡明显增多（P〈0．01）;③病毒性心肌炎组小鼠内质网伴侣蛋白GRP78和GRP94的mRNA表达水平均明显高于对照组（P〈0．01）。结论：病毒性心肌炎心力衰竭小鼠内质网应激可能介导了心肌细胞凋亡。     

CX3CL1/fractalkine shedding by human hepatic stellate cells: contribution to chronic inflammation in the liver

Chemokines are the inflammatory mediators that modulate liver fibrosis, a common feature of chronic inflammatory liver diseases. CX3CL1/fractalkine is a membrane-associated chemokine that requires step processing for chemotactic activity and has been recently implicated in liver disease. Here, we investigated the potential shedding activities involved in the release of the soluble chemotactic peptides from CX3CL1 in the injured liver. We showed an increased expression of the sheddases ADAM10 and ADAM17 in patients with chronic liver diseases that was associated with the severity of liver fibrosis. We demonstrated that hepatic stellate cells (HSC) were an important source of ADAM10 and ADAM17 and that treatment with the inflammatory cytokine inter-feron-γ induced the expression of CX3CL1 and release of soluble peptides. This release was inhibited by the metalloproteinase inhibitor batimastat; however, ADAM10/ADAM17 inhibitor GW280264X only partially affected shedding activity. By using selective tissue metalloprotease inhibitors and overexpression analyses, we showed that CX3CL1 was mainly processed by matrix metalloproteinase (MMP)-2, a metalloprotease highly expressed by HSC. We further demonstrated that the CX3CL1 soluble peptides released from stimulated HSC induced the activation of the CX3CR1-dependent signalling pathway and promoted chemoattraction of monocytes in vitro . We conclude that ADAM10, ADAM17 and MMP-2 synthesized by activated HSC mediate CX3CL1 shedding and release of chemotactic peptides, thereby facilitating recruitment of inflammatory cells and paracrine stimulation of HSC in chronic liver diseases.     

An inhibitor of c-Jun NH2-terminal kinase, SP600125, protects mice from D-galactosamine/lipopolysaccharide-induced hepatic failure by modulating BH3-only proteins

Fulminant hepatic failure (FHF) is a dramatic clinical syndrome characterized by massive hepatocyte apoptosis and very high mortality. The c-Jun-N-terminal kinase (JNK) pathway is an important stress-responsive kinase activated by several forms of liver injury. The aim of this study is to assess the role of JNK during D-galactosamine (GalN)/lipopolysaccharide (LPS)-induced liver injury, an experimental model of FHF, using SP600125, a small molecule JNK-specific inhibitor. Mice were given an intraperitoneal dose of GalN (800 microg/g body weight)/LPS (100 ng/g body weight) with and without subcutaneous SP600125 (50 mg/kg body weight) treatment (at 6 and 2 h before and 2 h after GalN/LPS administration). GalN/LPS treatment induced sustained JNK activation. Administration of SP600125 diminished JNK activity, suppressed lethality and the elevation of both serum alanine aminotransferase and aspartate aminotransferase, but had no effect on serum tumor necrosis factor-alpha, and reduced hepatocyte apoptosis after GalN/LPS administration. In support of the role of JNK in promoting the mitochondria-mediated apoptosis pathway, SP600125 prevented cytochrome c release, caspase-9 and caspase-3 activity. Moreover, SP600125 downregulated the mRNA and protein expression of Bad in the early periods following GalN/LPS injection and prevented Bid cleavage in the late periods. These results confirm the role of JNK as a critical apoptotic mediator in GalN/LPS-induced FHF. SP600125 has the potential to protect FHF by downregulating Bad and inhibiting Bid cleavage.     

Highly purified eicosapentaenoic acid prevents the progression of hepatic steatosis by repressing monounsaturated fatty acid synthesis in high-fat/high-sucrose diet-fed mice

Eicosapentaenoic acid (EPA) is a member of the family of n-3 polyunsaturated fatty acids (PUFAs) that are clinically used to treat hypertriglyceridemia. The triglyceride (TG) lowering effect is likely due to an alteration in lipid metabolism in the liver, but details have not been fully elucidated. To assess the effects of EPA on hepatic TG metabolism, mice were fed a high-fat and high-sucrose diet (HFHSD) for 2 weeks and were given highly purified EPA ethyl ester (EPA-E) daily by gavage. The HFHSD diet increased the hepatic TG content and the composition of monounsaturated fatty acids (MUFAs). EPA significantly suppressed the hepatic TG content that was increased by the HFHSD diet. EPA also altered the composition of fatty acids by lowering the MUFAs C16:1 and C18:1 and increasing n-3 PUFAs, including EPA and docosahexaenoic acid (DHA). Linear regression analysis revealed that hepatic TG content was significantly correlated with the ratios of C16:1/C16:0, C18:1/C18:0, and MUFA/n-3 PUFA, but was not correlated with the n-6/n-3 PUFA ratio. EPA also decreased the hepatic mRNA expression and nuclear protein level of sterol regulatory element binding protein-1c (SREBP-1c). This was reflected in the levels of lipogenic genes, such as acetyl-CoA carboxylase α (ACCα), fatty acid synthase, stearoyl-CoA desaturase 1 (SCD1), and glycerol-3-phosphate acyltransferase (GPAT), which are regulated by SREBP-1c. In conclusion, oral administration of EPA-E ameliorates hepatic fat accumulation by suppressing TG synthesis enzymes regulated by SREBP-1 and decreases hepatic MUFAs accumulation by SCD1.     

Yeast cells accumulate excess endogenous palmitate in phosphatidylcholine by acyl chain remodeling involving the phospholipase B Plb1p

In the yeast Saccharomyces cerevisiae, the molecular species profile of the major membrane glycerophospholipid phosphatidylcholine (PC) is determined by the molecular species-selectivity of the biosynthesis routes and by acyl chain remodeling. Overexpression of the glycerol-3-phosphate acyltransferase Sct1p was recently shown to induce a strong increase in the cellular content of palmitate (C16:0). Using stable isotope labeling and mass spectrometry, the present study shows that wild type yeast overexpressing Sct1p incorporates excess C16:0 into PC via the methylation of PE, the CDP-choline route, and post-synthetic acyl chain remodeling. Overexpression of Sct1p increased the extent of remodeling of PE-derived PC, providing a novel tool to perform mechanistic studies on PC acyl chain exchange. The exchange of acyl chains occurred at both the sn-1 and sn-2 positions of the glycerol backbone of PC, and required the phospholipase B Plb1p for optimal efficiency. Sct1p-catalyzed acyl chain exchange, the acyl-CoA binding protein Acb1p, the Plb1p homologue Plb2p, and the glycerophospholipid:triacylglycerol transacylase Lro1p were not required for PC remodeling. The results indicate that PC serves as a buffer for excess cellular C16:0.     

Chronic treatment with MIF-1 prevents the painful stimuli threshold elevation induced by neonatal handling in mice

Chronic postnatal stressful handling results in a hyposensitivity to thermal nociceptive stimuli. This phenomenon is strongly affected by manipulations of the opioid system. In the present experiment, we report that chronic treatment with MIF-1 during the neonatal period prevents the behavioral alterations induced by handling while it is completely ineffective if injected acutely before antinociceptive testing by the tail flick test at 45 days of life.     

Suppression of hepatic fat accumulation by highly purified eicosapentaenoic acid prevents the progression of d-galactosamine-induced hepatitis in mice fed with a high-fat/high-sucrose diet

The pathogenesis of non-alcoholic fatty liver disease (NAFLD) remains largely unknown. Here, we assessed the importance of hepatic fat accumulation on the progression of hepatitis. BALB/cA mice were fed with a standard diet (STD) or a high-fat and high-sucrose diet (HFHSD) for 14 days followed by intraperitoneal injection of d-galactosamine (DGalN) or vehicle. After 20–21 h, plasma and liver tissue were collected and analyzed. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in plasma were increased significantly in HFHSD-fed mice treated with DGalN compared to STD-fed mice treated with DGalN. This exacerbation by the HFHSD was also observed in the plasma soluble tumor necrosis factor receptor (sTNFR) levels, and hepatic levels of reactive oxygen species (ROS) and the fibrogenic gene expression, such as tissue inhibitor of matrix metalloproteinase 1 (TIMP-1), connective tissue growth factor (CTGF) and osteopontin (OPN) in HFHSD-fed mice treated with DGalN. The triglyceride contents of the liver were significantly increased by the HFHSD. When eicosapentaenoic acid (EPA), a suppressor of sterol regulatory element binding protein 1 (SREBP-1), was administered to HFHSD-fed mice, the sensitivity of DGalN, as a result of plasma ALT and AST levels, was suppressed accompanied by reduced plasma sTNFR2 level and hepatic levels of triglyceride, ROS, and fibrogenic parameters, and by increased plasma adiponectin levels. These data suggest that the progression of steatotic liver injury closely depends on the accumulation of fat in the liver and is prevented by EPA through the suppression of the fatty liver change.     

The regulation of hepatic stearoyl-coenzyme A desaturase in obese-hyperglycaemic (ob/ob) mice by food intake and the fatty acid composition of the diet.

1. The effects of food intake and the fatty acid composition of the diet on the hepatic stearoyl-CoA desaturase activity of obese-hyperglycaemic (ob/ob) mice were investigated. 2. Obese mice fed on a commercial mouse diet, ad libitum, had 6.5-fold more activity per liver cell than had lean mice. 3. On a diet containing 14% corn oil the activity was 65% less in obese mice and 62% less in lean mice compared with animals fed on the commercial diet. 4. Feeding with 14% saturated fat in the diet doubled the activity in lean mice compared with those on the commercial diet, but had no effect on the activity in obese mice. 5. Obese mice fed on the corn-oil diet contained a higher proportion of linoleic acid in the liver lipids than did lean mice fed on the commercial diet, but the acyl-CoA desaturase activity was 125% higher than in the lean mice. 6. Limiting the food intake of obese mice by pair-feeding with lean mice decreased their acyl-CoA desaturase activity when the animals were fed on the saturated-fat diet, but the activity remained 75% higher than in lean mice, whereas in obese mice pair-fed on the corn-oil diet the activity was the same as in lean mice. 7. During starvation the acyl-CoA desaturase activity in livers from obese mice decreased more slowly and proportionately less than in livers from lean mice. 8. It is concluded that increased substrate supply as a result of hyperphagia and not low concentration of linoleic acid is the main factor causing high acyl-CoA desaturase activity in obese mice.     

Diethylstilbestrol induces vaginal adenosis by disrupting SMAD/RUNX1-mediated cell fate decision in the Müllerian duct epithelium

Women exposed to diethylstilbestrol (DES) in utero frequently develop vaginal adenosis, from which clear cell adenocarcinoma can arise. Despite decades of extensive investigation, the molecular pathogenesis of DES-associated vaginal adenosis remains elusive. Here we report that DES induces vaginal adenosis by inhibiting the BMP4/Activin A-regulated vaginal cell fate decision through a downregulation of RUNX1. BMP4 and Activin A produced by vaginal mesenchyme synergistically activated the expression of ΔNp63, thus deciding vaginal epithelial cell fate in the Müllerian duct epithelial cells (MDECs) via direct binding of SMADs on the highly conserved 5′ sequence of ΔNp63. Therefore, mice in which Smad4 was deleted in MDECs failed to express ΔNp63 in vaginal epithelium and developed adenosis. This SMAD-dependent ΔNp63 activation required RUNX1, a binding partner of SMADs. Conditional deletion of Runx1 in the MDECs induced adenosis in the cranial portion of vagina, which mimicked the effect of developmental DES-exposure. Furthermore, neonatal DES exposure downregulated RUNX1 in the fornix of the vagina, where DES-associated adenosis is frequently found. This observation strongly suggests that the downregulation of RUNX1 is the cause of vaginal adenosis. However, once cell fate was determined, the BMP/Activin-SMAD/RUNX1 signaling pathway became dispensable for the maintenance of ΔNp63 expression in vaginal epithelium. Instead, the activity of the ΔNp63 locus in vaginal epithelium was maintained by a ΔNp63-dependent mechanism. This is the first demonstration of a molecular mechanism through which developmental chemical exposure causes precancerous lesions by altering cell fate.     

Altered availability of PD-1/PD ligands is associated with the failure to control autoimmunity in NOD mice

Costimulation via the PD-1 and B7-H1/B7-DC pathway regulates immunity. We investigated whether the PD-1/PD-L pathway is impaired in autoimmune diabetes. A progressive increase in the expression of PD-1 and B7-H1/B7-DC on T cells and APC, respectively, was observed in the pancreatic lymph nodes of female non-obese diabetic (NOD) mice as they developed diabetes. A significantly decreased expression of PD-1 and B7-H1/B7-DC on T cells and APC, respectively, was observed in the periphery of prediabetic NOD mice versus non-diabetic C57BL/6 strain. NOD islets also displayed a reduced capacity to upregulate B7-H1 following exposure to inflammatory cytokines. In vivo blocking studies in NOD/B7-2KONOD mice revealed that B7-H1 and B7-DC positively costimulate autoreactive CD4 and CD8 T cells and may co-operate with B7-2 to augment priming and expansion of naïve autoreactive T cells. In summary, these data suggest that diabetes susceptibility in NOD mice is associated with altered PD-1/PD-L availability.     

The role of AKT1 and autophagy in the protective effect of hydrogen sulphide against hepatic ischemia/reperfusion injury in mice

Hydrogen sulphide (H 2S) exerts a protective effect in hepatic ischemia-reperfusion (I/R) injury. However, the exact mechanism of H 2S action remains largely unknown. This study was designed to investigate the role of the PtdIns3K-AKT1 pathways and autophagy in the protective effect of H 2S against hepatic I/R injury. Primary cultured mouse hepatocytes and livers with or without NaHS (a donor of H 2S) preconditioning were exposed to anoxia/reoxygenation (A/R) and I/R, respectively. In certain groups, they were also pretreated with LY294002 (AKT1-specific inhibitor), 3-methyladenine (3MA, autophagy inhibitor) or rapamycin (autophagy enhancer), alone or simultaneously. Cell viability, expression of P-AKT1, T-AKT1, LC3 and BECN1 were examined. The severity of liver injury was measured by the levels of serum aminotransferase and inflammatory cytokine, apoptosis and histological examination. GFP-LC3 redistribution and transmission electron microscopy were used to test the activity of autophagy. H 2S preconditioning activated PtdIns3K-AKT1 signaling in hepatocytes. LY294002 could abolish the AKT1 activation and attenuate the protective effect of H 2S on hepatocytes A/R and hepatic I/R injuries. H 2S suppressed hepatic autophagy in vitro and in vivo. Further reducing autophagy by 3MA also diminished the protective effect of H 2S, while rapamycin could reverse the autophagy inhibitory effect and enhance the protective effect of H 2S against hepatocytes A/R and hepatic I/R injuries, consequently. Taken together, H 2S protects against hepatocytic A/R and hepatic I/R injuries, at least in part, through AKT1 activation but not autophagy. An autophagy agonist could be applied to potentiate this hepatoprotective effect by reversing the autophagy inhibition of H 2S.     

丹参单体IH764-3通过下调H2O2刺激的肝星状细胞FAK水平影响MMP-13和TIMP-1的表达

目的：研究丹参单体IH764—3对H2O2刺激的肝星状细胞（HSC）基质金属蛋白酶-13（MMP-13）、基质金属蛋白酶组织抑制因子-1（TIMP-1）表达的影响以及此过程中粘着斑激酶（FAK）的变化。方法：应用RT-PCR方法检测MMP-13及FAKmRNA表达,原位杂交方法检测TIMP-1mRNA水平,Western blotting技术检测FAK及TIMP-1蛋白表达。结果：IH764—3干预组的MMP-13mRNA在2h的表达强度明显上调,而TIMP-1mRNA表达明显受抑,FAKmRNA表达强度明显下调;IH764—3干预24h组FAK及TIMP-1蛋白表达受抑制。结论：丹参单体IH764—3可以诱导MMP-13表达,抑制TIMP-1表达,下调FAK表达是其中的机制之一。     

Control of FLIPL expression and TRAIL resistance by the extracellular signal-regulated kinase1/2 pathway in breast epithelial cells

Increased activation of the epidermal growth factor receptor (EGFR) is frequently observed in tumors, and inhibition of the signaling pathways originated in the EGFR normally renders tumor cells more sensitive to apoptotic stimuli. However, we show that inhibition of EGFR signaling in non-transformed breast epithelial cells by EGF deprivation or gefitinib, an inhibitor of EGFR tyrosine kinase, causes the upregulation of the long isoform of caspase-8 inhibitor FLICE-inhibitory protein (FLIP_L) and makes these cells more resistant to the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). We demonstrate that the extracellular signal-regulated kinase (ERK)1/2 pathway plays a pivotal role in the regulation of FLIP_L levels and sensitivity to TRAIL-induced apoptosis by EGF. Upregulation of FLIP_L upon EGF deprivation correlates with a decrease in c-Myc levels and c-Myc knockdown by siRNA induces FLIP_L expression. FLIP_L upregulation and resistance to TRAIL in EGF-deprived cells are reversed following activation of an estrogen activatable form of c-Myc (c-Myc-ER). Finally, constitutive activation of the ERK1/2 pathway in HER2/ERBB2-transformed cells prevents EGF deprivation-induced FLIP_L upregulation and TRAIL resistance. Collectively, our results suggest that a regulated ERK1/2 pathway is crucial to control FLIP_L levels and sensitivity to TRAIL in non-transformed cells, and this mechanism may explain the increased sensitivity of tumor cells to TRAIL, in which the ERK1/2 pathway is frequently deregulated.     

Uroporphyria and hepatic carcinogenesis induced by polychlorinated biphenyls-iron interaction: absence in the Cyp1a2(-/-) knockout mouse

Aryl hydrocarbon receptor ligands, such as polychlorinated biphenyls (PCBs), cause inhibition of the heme biosynthesis enzyme, uroporphyrinogen decarboxylase; this leads to uroporphyria and hepatic tumors, which are markedly enhanced by iron overload in C57BL/10 and C57BL/6 strains of mice. Cyp1a2(-/-) knockout mice were used to compare the effects of CYP1A2 expression on uroporphyria and liver carcinogenesis. PCBs in the diet (100ppm) of Cyp1a2(+/+) wild-type mice caused hepatic uroporphyria, which was strongly increased by iron-dextran (800mg Fe/kg). In contrast, uroporphyria was not detected in Cyp1a2(-/-) knockout mice, although expression of CYP1A1 and CYP2B10 was greatly induced. After 57 weeks on this diet, hepatic preneoplastic foci and tumors were seen in the Cyp1a2(+/+) mice; numbers and severity were enhanced by iron. No foci or tumors were detected in Cyp1a2(-/-) mice, although evidence for other forms of liver injury was observed. Our findings suggest a link not only between CYP1A2, iron metabolism, and the induction of uroporphyria by PCBs, but also with subsequent hepatocarcinogenesis.