Mouse hepatic oval cells require Met-dependent PI3K to impair TGF-β-induced oxidative stress and apoptosis

Uncovering a Novel Functional Interaction Between Adult Hepatic Progenitor Cells, Inflammation and EGFR Signaling During Bile Acids-Induced Injury

Chronic cholestatic damage is associated to both accumulation of cytotoxic levels of bile acids and expansion of adult hepatic progenitor cells (HPC) as part of the ductular reaction contributing to the regenerative response. Here, we report a bile acid-specific cytotoxic response in mouse HPC, which is partially impaired by EGF signaling. Additionally, we show that EGF synergizes with bile acids to trigger inflammatory signaling and NLRP3 inflammasome activation in HPC. Aiming at understanding the impact of this HPC specific response on the liver microenvironment we run a proteomic analysis of HPC secretome. Data show an enrichment in immune and TGF-β regulators, ECM components and remodeling proteins in HPC secretome. Consistently, HPC-derived conditioned medium promotes hepatic stellate cell (HSC) activation and macrophage M1-like polarization. Strikingly, EGF and bile acids co-treatment leads to profound changes in the secretome composition, illustrated by an abolishment of HSC activating effect and by promoting macrophage M2-like polarization. Collectively, we provide new specific mechanisms behind HPC regulatory action during cholestatic liver injury, with an active role in cellular interactome and inflammatory response regulation. Moreover, findings prove a key contribution for EGFR signaling jointly with bile acids in HPC-mediated actions.

Hypoxia preconditioning of human amniotic mesenchymal stem cells enhances proliferation and migration and promotes their homing via the HGF/C-MET signaling axis to augment the repair of acute liver failure

BACKGROUND

Transplantation of mesenchymal stem cells (MSCs) is a newly developed strategy for treating acute liver failure (ALF). Nonetheless, the low survival rate of MSCs after transplantation and their poor homing to damaged tissues limit the clinical application of MSCs. The research assessed whether hypoxic preconditioning (HPC) can improve the biological activity of human amniotic mesenchymal stem cells (hA-MSCs), promote their homing ability to the liver of mice with ALF, and influence liver tissue repair.

METHODS

Flow cytometry, CCK8, Transwell, and Western blotting assays were conducted to assess the effects of hypoxic preconditioning on the phenotype, proliferation, and migration of hA-MSCs and the changes in the c-Met and CXCR4 gene expression levels were studied. To evaluate the effects of the transplantation of hypoxic preconditioning of hA-MSCs on the homing and repair of D-galactosamine (D-GalN)/LPS-induced ALF, the mechanism was elucidated by adding c-Met, CXCR4-specific blockers (SU11274 and AMD3100).

RESULTS

After hypoxia pretreatment (1% oxygen volume fraction), hA-MSCs maintained the morphological characteristics of adherence and vortex colony growth and showed high CD44, CD90, and CD105 and low CD31, CD34, and CD45 expression levels. Hypoxic preconditioning of hA-MSCs significantly increased their proliferation and migration and highly expressed the c-Met and CXCR4 genes. In vivo and in vitro, this migration-promoting effect was suppressed by the c-Met specific blocker SU11274. In the acute liver failure mouse model, the HGF expression level was considerably elevated in the liver than that in the serum, lungs and kidneys. The transplantation of hypoxic preconditioned hA-MSCs introduced a remarkable improvement in the liver function and survival rate of mice with ALF and enhanced the anti-apoptosis ability of liver cells. The anti-apoptotic enhancing effect of hypoxic preconditioning was suppressed by the c-Met specific blocker SU11274. Hypoxic hA-MSCs administration was observed to have considerably increased the fluorescent cells in the liver than that recorded after administering normal oxygen-hA-MSCs. The number of hepatic fluorescent cells decreased remarkably after adding the c-Met inhibitor SU11274, compared to that recorded after hypoxic pretreatment, whereas the effect of c-Met inhibitor SU11274 on normal oxygen-hA-MSCs was not significant.

CONCLUSIONS

Hypoxic preconditioning depicted no impact on the morphology and phenotype features of the human amniotic mesenchymal stem cells, but it can promote their proliferation, migration, anti-apoptotic effect, and homing rate and improve the repair of acute liver failure, which might be mediated by the HGF/c-Met signaling axis.

C3G down-regulation enhances pro-migratory and stemness properties of oval cells by promoting an epithelial-mesenchymal-like process

Previous data indicate that C3G (RapGEF1) main isoform is highly expressed in liver progenitor cells (or oval cells) compared to adult mature hepatocytes, suggesting it may play an important role in oval cell biology. Hence, we have explored C3G function in the regulation of oval cell properties by permanent gene silencing using shRNAs. We found that C3G knock-down enhanced migratory and invasive ability of oval cells by promoting a partial epithelial to mesenchymal transition (EMT). This is likely mediated by upregulation of mRNA expression of the EMT-inducing transcription factors, Snail1, Zeb1 and Zeb2, induced in C3G-silenced oval cells. This EMT is associated to a higher expression of the stemness markers, CD133 and CD44. Moreover, C3G down-regulation increased oval cells clonogenic capacity by enhancing cell scattering. However, C3G knock-down did not impair oval cell differentiation into hepatocyte lineage. Mechanistic studies revealed that HGF/MET signaling and its pro-invasive activity was impaired in oval cells with low levels of C3G, while TGF-β signaling was increased. Altogether, these data suggest that C3G might be tightly regulated to ensure liver repair in chronic liver diseases such as non-alcoholic steatohepatitis. Hence, reduced C3G levels could facilitate oval cell expansion, after the proliferation peak, by enhancing migration.

Oncological transformation in vitro of hepatic progenitor cell lines isolated from adult mice

Colorectal cancer cells can transfer the oncogene KRAS to distant cells, predisposing them to malignant transformation (Genometastasis Theory). This process could contribute to liver metastasis; besides, hepatic progenitor cells (HPCs) have been found to be involved in liver malignant neoplasms. The objective of this study is to determine if mouse HPCs—Oval cells (OCs)—are susceptible to incorporate Kras GAT (G12D) mutation from mouse colorectal cancer cell line CT26.WT and if OCs with the incorporated mutation behave like malignant cells. To achieve this, three lines of OCs in different conditions were exposed to CT26.WT cells through transwell co-culture for a week. The presence of Kras^G12D and capacity to form tumors were analyzed in treated samples by droplet digital PCR and colony-forming assays, respectively. The results showed that the Kras^G12D mutation was detected in hepatic culture conditions of undifferentiated OCs and these cells were capable of forming tumors in vitro. Therefore, OCs are susceptible to malignant transformation by horizontal transfer of DNA with Kras^G12D mutation in an undifferentiated condition associated with the liver microenvironment. This study contributes to a new step in the understanding of the colorectal metastatic process.

BMP9 Promotes an Epithelial Phenotype and a Hepatocyte-like Gene Expression Profile in Adult Hepatic Progenitor Cells

Bone morphogenetic protein 9 (BMP9), a member of the TGF-β superfamily, has emerged as a new player in chronic liver diseases (CLDs). Its levels increase in the fibrotic liver where it promotes fibrogenesis. It also regulates hepatic progenitor cells (oval cells in rodents), a cell population that contributes to repopulate the liver and recover functionality upon severe damage, but it can also be pro-fibrogenic, depending upon the hepatic microenvironment. Here we analyze the effect of chronic exposure to BMP9 in oval cells. We show that cells chronically treated with BMP9 (B9T-OC) display a more epithelial and hepatocyte-like phenotype while acquiring proliferative and survival advantages. Since our previous studies had revealed a functional crosstalk between BMP9 and the HGF/c-Met signaling pathways in oval cells, we analyzed a possible role for HGF/c-Met in BMP9-induced long-term effects. Data evidence that active c-Met signaling is necessary to obtain maximum effects in terms of BMP9-triggered hepatocytic differentiation potential, further supporting functionally relevant cooperation between these pathways. In conclusion, our work reveals a novel action of BMP9 in liver cells and helps elucidate the mechanisms that serve to increase oval cell regenerative potential, which could be therapeutically modulated in CLD.

The TGF-β/NADPH Oxidases Axis in the Regulation of Liver Cell Biology in Health and Disease

The Transforming Growth Factor-beta (TGF-β) pathway plays essential roles in liver development and homeostasis and become a relevant factor involved in different liver pathologies, particularly fibrosis and cancer. The family of NADPH oxidases (NOXs) has emerged in recent years as targets of the TGF-β pathway mediating many of its effects on hepatocytes, stellate cells and macrophages. This review focuses on how the axis TGF-β/NOXs may regulate the biology of different liver cells and how this influences physiological situations, such as liver regeneration, and pathological circumstances, such as liver fibrosis and cancer. Finally, we discuss whether NOX inhibitors may be considered as potential therapeutic tools in liver diseases.

A Signaling Crosstalk between BMP9 and HGF/c-Met Regulates Mouse Adult Liver Progenitor Cell Survival

During chronic liver disease, hepatic progenitor cells (HPC, oval cells in rodents) become activated, proliferate, and differentiate into cholangiocytes and/or hepatocytes contributing to the final outcome of the regenerative process in a context-dependent fashion. Here, we analyze the crosstalk between the hepatocyte growth factor (HGF)/c-Met signaling axis, key for liver regeneration, and bone morphogenetic protein (BMP)9, a BMP family ligand that has emerged as a critical regulator of liver pathology. Our results show that HGF/c-Met signaling blocks BMP9-mediated apoptotic cell death, while it potentiates small mothers against decapentaplegic (SMAD)1 signaling triggered by BMP9 in oval cells. Interestingly, HGF-induced overactivation of SMAD1, -5, -8 requires the upregulation of TGF-β type receptor activin receptor-like kinase (ALK)1, and both ALK1 and SMAD1 are required for the counteracting effect of HGF on BMP9 apoptotic activity. On the other hand, we also prove that BMP9 triggers the activation of p38MAPK in oval cells, which drives BMP9-apoptotic cell death. Therefore, our data support a model in which BMP9 and HGF/c-Met signaling axes establish a signaling crosstalk via ALK1 that modulates the balance between the two pathways with opposing activities, SMAD1 (pro-survival) and p38 mitogen-activated protein kinases (p38MAPK; pro-apoptotic), which determines oval cell fate. These data help delineate the complex signaling network established during chronic liver injury and its impact on the oval cell regenerative response.

c-Met Signaling Is Essential for Mouse Adult Liver Progenitor Cells Expansion After Transforming Growth Factor-β-Induced Epithelial-Mesenchymal Transition and Regulates Cell Phenotypic Switch

Adult hepatic progenitor cells (HPCs)/oval cells are bipotential progenitors that participate in liver repair responses upon chronic injury. Recent findings highlight HPCs plasticity and importance of the HPCs niche signals to determine their fate during the regenerative process, favoring either fibrogenesis or damage resolution. Transforming growth factor-β (TGF-β) and hepatocyte growth factor (HGF) are among the key signals involved in liver regeneration and as component of HPCs niche regulates HPCs biology. Here, we characterize the TGF-β-triggered epithelial-mesenchymal transition (EMT) response in oval cells, its effects on cell fate in vivo, and the regulatory effect of the HGF/c-Met signaling. Our data show that chronic treatment with TGF-β triggers a partial EMT in oval cells based on coexpression of epithelial and mesenchymal markers. The phenotypic and functional profiling indicates that TGF-β-induced EMT is not associated with stemness but rather represents a step forward along hepatic lineage. This phenotypic transition confers advantageous traits to HPCs including survival, migratory/invasive and metabolic benefit, overall enhancing the regenerative potential of oval cells upon transplantation into a carbon tetrachloride-damaged liver. We further uncover a key contribution of the HGF/c-Met pathway to modulate the TGF-β-mediated EMT response. It allows oval cells expansion after EMT by controlling oxidative stress and apoptosis, likely via Twist regulation, and it counterbalances EMT by maintaining epithelial properties. Our work provides evidence that a coordinated and balanced action of TGF-β and HGF are critical for achievement of the optimal regenerative potential of HPCs, opening new therapeutic perspectives. Stem Cells 2019;37:1108-1118.

Protective Effects of Kaempferitrin on Advanced Glycation End Products Induce Mesangial Cell Apoptosis and Oxidative Stress

Advanced glycation end products (AGEs) and the receptor for AGEs (RAGE) both play important roles in diabetic nephropathy (DN). Previous studies have identified glomerular mesangial cells (GMCs) injury as a key early risk factor in the development of DN. Kaempferitrin (KM) is a potent antioxidant with hypoglycemic action. Although KM is known to protect against AGE-induced damage in GMCs, the effects and the mechanisms by which they occur are poorly understood. In this study, cultured rat GMCs were exposed to AGE-induced oxidative stress (OS) to model DN in vitro. Reactive oxygen species (ROS) was analyzed by 2',7'-dichlorofluorescin diacetate (DCFH-DA). Superoxide dismutase (SOD) and malondialdehyde (MDA) were studied using commercial kits. Mitochondrial membrane potential (Δψm) was measured by rhodamine 123. Hoechst 33258 and annexin V and propidium iodide (PI) double staining were performed to observe the apoptosis states in GMCs, whereas apoptosis and protective mechanism in AGE-induced GMCs were investigated by Western blot. The data revealed that KM effectively increased SOD activity, decreased MDA levels, suppressed ROS generation, and protected against OS in AGE-induced GMCs. Treatment with KM also inhibited the expression of collagen IV and transforming growth factor-β1 (TGF-β1), improved mitochondrial membrane potential recovery, and suppressed the mitochondrial/cytochrome c-mediated apoptosis pathway through the expression of anti-apoptotic factors in GMCs in vitro. These findings suggest that KM may be a new potential agent in the treatment of DN in future.

Delphinidin protects β2m-/Thy1+ bone marrow-derived hepatocyte stem cells against TGF-β1-induced oxidative stress and apoptosis through the PI3K/Akt pathway in vitro

β2m-/Thy1+ bone marrow-derived hepatocyte stem cells (BDHSCs) have a potential to be applied for cellular treatment in liver cirrhosis. However, the resultant tissue regeneration is restricted by transplanted cells' death. The accumulation of transforming growth factor beta 1 (TGF-β1) in liver fibrosis local microenvironment may play an essential role in the rapid cell death of implanted β2m-/Thy1+ BDHSCs. The main mechanism of poor survival of the target stem cells is still unknown. Delphinidin, an anthocyanidin, has potent antioxidant and anti-inflammatory activities. However, whether this bio-active ingredient can substantially contribute to β2m-/Thy1+ BDHSCs' protection from TGF-β1 induced apoptosis in vitro remains to be elucidated. In the present research, we determined whether delphinidin pretreatment can improve the survival of β2m-/Thy1+ BDHSCs during exposure to TGF-β1 and elucidated its underlying mechanisms. By using TGF-β1, we induced the apoptosis of β2m-/Thy1+ BDHSCs and assessed the apoptotic rates up to 24 h by flow cytometry. β2m-/Thy1+ BDHSC proliferation was gauged using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl- 2H-tetrazolium bromide (MTT) assay. The expression grades of Bcl-2, Akt, caspase-3, and Bax were observed through Western blot analysis. We found that delphinidin can significantly impede TGF-β1-induced apoptosis dose-dependently, scavenge reactive oxygen species (ROS), and inhibit the discharge of caspase-3 in β2m-/Thy1+ BDHSCs. We also demonstrated that delphinidin can activate the phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway. The suppression of ROS and succeeding apoptosis was achieved by pretreatment with LY294002, a PI3K/Akt pathway inhibitor. In summary, our findings revealed that delphinidin can protect β2m-/Thy1+ BDHSCs from apoptosis and ROS-dependent oxidative stress induced by the TGF-β1 via PI3K/Akt signaling pathway. On the basis of these data, delphinidin can be regarded as a promising anti-apoptotic agent for enhancing β2m-/Thy1+ BDHSC survival during cell transplantation in liver cirrhosis patients.

Bone morphogenetic protein 9 as a key regulator of liver progenitor cells in DDC-induced cholestatic liver injury

BACKGROUND & AIMS

Bone morphogenetic protein 9 (BMP9) interferes with liver regeneration upon acute injury, while promoting fibrosis upon carbon tetrachloride-induced chronic injury. We have now addressed the role of BMP9 in 3,5 diethoxicarbonyl-1,4 dihydrocollidine (DDC)-induced cholestatic liver injury, a model of liver regeneration mediated by hepatic progenitor cell (known as oval cell), exemplified as ductular reaction and oval cell expansion.

METHODS

WT and BMP9KO mice were submitted to DDC diet. Livers were examined for liver injury, fibrosis, inflammation and oval cell expansion by serum biochemistry, histology, RT-qPCR and western blot. BMP9 signalling and effects in oval cells were studied in vitro using western blot and transcriptional assays, plus functional assays of DNA synthesis, cell viability and apoptosis. Crosslinking assays and short hairpin RNA approaches were used to identify the receptors mediating BMP9 effects.

RESULTS

Deletion of BMP9 reduces liver damage and fibrosis, but enhances inflammation upon DDC feeding. Molecularly, absence of BMP9 results in overactivation of PI3K/AKT, ERK-MAPKs and c-Met signalling pathways, which together with an enhanced ductular reaction and oval cell expansion evidence an improved regenerative response and decreased damage in response to DDC feeding. Importantly, BMP9 directly targets oval cells, it activates SMAD1,5,8, decreases cell growth and promotes apoptosis, effects that are mediated by Activin Receptor-Like Kinase 2 (ALK2) type I receptor.

CONCLUSIONS

We identify BMP9 as a negative regulator of oval cell expansion in cholestatic injury, its deletion enhancing liver regeneration. Likewise, our work further supports BMP9 as an attractive therapeutic target for chronic liver diseases.

Targeting the vascular and perivascular niches as a regenerative therapy for lung and liver fibrosis

The regenerative capacity of lung and liver is sometimes impaired by chronic or overwhelming injury. Orthotopic transplantation of parenchymal stem cells to damaged organs might reinstate their self-repair ability. However, parenchymal cell engraftment is frequently hampered by the microenvironment in diseased recipient organs. We show that targeting both the vascular niche and perivascular fibroblasts establishes "hospitable soil" to foster the incorporation of "seed," in this case, the engraftment of parenchymal cells in injured organs. Specifically, ectopic induction of endothelial cell (EC)-expressed paracrine/angiocrine hepatocyte growth factor (HGF) and inhibition of perivascular NOX4 [NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase 4] synergistically enabled reconstitution of mouse and human parenchymal cells in damaged organs. Reciprocally, genetic knockout of Hgf in mouse ECs (Hgf^iΔEC/iΔEC) aberrantly up-regulated perivascular NOX4 during liver and lung regeneration. Dysregulated HGF and NOX4 pathways subverted the function of vascular and perivascular cells from an epithelially inductive niche to a microenvironment that inhibited parenchymal reconstitution. Perivascular NOX4 induction in Hgf^iΔEC/iΔEC mice recapitulated the phenotype of human and mouse liver and lung fibrosis. Consequently, EC-directed HGF and NOX4 inhibitor GKT137831 stimulated regenerative integration of mouse and human parenchymal cells in chronically injured lung and liver. Our data suggest that targeting dysfunctional perivascular and vascular cells in diseased organs can bypass fibrosis and enable reparative cell engraftment to reinstate lung and liver regeneration.

A novel bispecific c-MET/PD-1 antibody with therapeutic potential in solid cancer

The bispecific antibody is a novel antibody, which can target two different antigens and mediate specific killing effects by selectively redirecting effector cells to the target cells. Here, we designed and synthesized a bispecific antibody (BsAb) that can bind cellular-mesenchymal to epithelial transition factor (c-MET, overexpressed in several human solid tumor), and programmed death-1 (PD-1, involved in cancer cell immune evasion) with high affinity and specificity. We found that BsAb can induce the degradation of c-MET protein in cancer cells, including MKN45, a gastric cancer cell line, and A549, a lung cancer cell line. BsAb inhibited hepatocyte growth factor (HGF)-mediated proliferation, migration, and antiapoptosis, and downregulated HGF-stimulated phosphorylation of c-MET, protein kinase B (AKT), and extracellular signal-regulated kinase (ERK1/2). BsAb can also rescue T cell activation. Furthermore, xenograft analysis revealed that BsAb markedly inhibits the growth of subcutaneously implanted tumors and chronic inflammation. On the basis of these results, we have identified a potential bispecific drug, which can effectively target c-MET and PD-1 for the treatment of human solid cancers.

The Attenuation of Scutellariae radix Extract on Oxidative Stress for Colon Injury in Lipopolysaccharide-induced RAW264.7 Cell and 2,4,6-trinitrobenzene Sulfonic Acid-induced Ulcerative Colitis Rats

Background:

Oxidative stress (OS) has been regarded as one of the major pathogeneses of ulcerative colitis (UC) through damaging colon. It has been shown that Scutellariae radix (SR) extract has a beneficial effect for the prevention and treatment of UC.

Objective:

The aim of this study was to investigate whether SR had a potential capacity on oxidant damage for colon injury both in vivo and in vitro.

Materials and Methods:

The 2,4,6-trinitrobenzene sulfonic acid (TNBS) was used to induce UC rats model while 1 μg/ml lipopolysaccharide (LPS) was for RAW264.7 cell damage. Disease activity index (DAI) was determined to response the severity of colitis. The myeloperoxidase (MPO) activity in rat colon was also estimated. The 2,2’-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid assay was performed to evaluate the total antioxidant capacity of SR. Furthermore, the activity of glutathione peroxidase (GSH-PX), catalase (CAT), superoxide dismutase (SOD), and lipid peroxidation malondialdehyde (MDA) in cell supernatant and rat serum were detected by appropriate kits. In addition, an immunohistochemical assay was applied to examine transforming growth factor beta 1 (TGF-β1) protein expression in colon tissue.

Results:

The treatment with SR could significantly increase the activity of GSH-PX, CAT, and SOD associated with OS in LPS-induced RAW264.7 cell damage and TNBS-induced UC rats. However, the level of MDA was markedly reduced both in vitro and in vivo. Furthermore, SR significantly decreased DAI and reversed the increased MPO activity. Thus, SR could decrease the severity of acute TNBS-induced colitis in rats. Immunohistochemical assay showed that SR significantly downregulated TGF-β1 protein expression in colon tissue.

Conclusion:

Our data provided evidence to support this fact that SR attenuated OS in LPS-induced RAW264.7 cell and also in TNBS-induced UC rats. Thus, SR may be an interesting candidate drug for the management of UC.

SUMMARY

Scutellariae radix (SR) could significantly increase the activity of glutathione peroxidase, catalase, and superoxide dismutase associated with OS in lipopolysaccharide-induced RAW264.7 cell damage and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced ulcerative colitis rats

The level of malondialdehyde was markedly reduced by SR both in vitro and in vivo

SR could decrease the severity of acute TNBS-induced colitis in rats

SR could significantly downregulate the expression of transforming growth factor beta 1 protein in colon tissue.

Abbreviations used: OS: Oxidative stress, UC: Ulcerative colitis, SR: Scutellariae radix, TNBS: 2,4,6-trinitrobenzene sulfonic acid, DAI: Disease activity index, MPO: Myeloperoxidase, GSH-PX: Glutathione peroxidase, CAT: Catalase, SOD: Superoxide dismutase, MDA: Malondialdehyde, TGF-β1: Transforming growth factor beta 1, OD: Optical density, ROS: Reactive oxygen species.

Hepatocyte Growth Factor Reduces Free Cholesterol-Mediated Lipotoxicity in Primary Hepatocytes by Countering Oxidative Stress

Cholesterol overload in the liver has shown toxic effects by inducing the aggravation of nonalcoholic fatty liver disease to steatohepatitis and sensitizing to damage. Although the mechanism of damage is complex, it has been demonstrated that oxidative stress plays a prominent role in the process. In addition, we have proved that hepatocyte growth factor induces an antioxidant response in hepatic cells; in the present work we aimed to figure out the protective effect of this growth factor in hepatocytes overloaded with free cholesterol. Hepatocytes from mice fed with a high-cholesterol diet were treated or not with HGF, reactive oxygen species present in cholesterol overloaded hepatocytes significantly decreased, and this effect was particularly associated with the increase in glutathione and related enzymes, such as γ-gamma glutamyl cysteine synthetase, GSH peroxidase, and GSH-S-transferase. Our data clearly indicate that HGF displays an antioxidant response by inducing the glutathione-related protection system.

The Characteristics Variation of Hepatic Progenitors after TGF-β1-Induced Transition and EGF-Induced Reversion

Profibrogenesis cytokine, transforming growth factor- (TGF-) β1, induces hepatic progenitors experiencing epithelial to mesenchymal transition (EMT) to matrix synthesis cells, even tumor initiating cells. Our previous data found that epidermal growth factor (EGF) blocks and reverses TGF-β1-induced transition. The aim of this study is to determine the characteristic changes of hepatic progenitors after TGF-β1-induced transition and EGF-induced reversion. Hepatic oval cells, rat hepatic progenitors, were isolated from rats fed a choline-deficient diet supplemented with ethionine. TGF-β1-containing medium was used for inducing EMT, while EGF-containing medium was used for reversing EMT. During TGF-β1-induced transition and EGF-induced reversion, hepatic oval cells sustained their progenitor cell marker expression, including α-fetoprotein, albumin, and cytokeratin-19. The proliferation ability and differentiation potential of these cells were suppressed by TGF-β1, while EGF resumed these capacities to the level similar to the control cells. RNA microarray analysis showed that most of the genes with significant changes after TGF-β1 incubation were recovered by EGF. Signal pathway analysis revealed that TGF-β1 impaired the pathways of cell cycle and cytochrome P450 detoxification, and EGF reverted TGF-β1 effects through activating MAPK and PI3K-Akt pathway. EGF reverses the characteristics impaired by TGF-β1 in hepatic oval cells, serving as a protective cytokine to hepatic progenitors.

Combined effect of hydrogen sulphide donor and losartan in experimental diabetic nephropathy in rats

Background

Diabetic nephropathy (DN) is one of the complex complications of Diabetes Mellitus (DM). The present study has been designed to examine protective role of hydrogen Sulphide (H₂S) donor against streptozotocin (STZ) -induced behavioral, oxidative abnormalities and its DN like symptoms in rats.

Methods

For the induction of DN single intraperitoneal administration of STZ (45 mg/kg) was given till third week. Behavioral parameters were measured on 1st, 7th, 21st and 42nd days and biochemical parameters were performed on 42nd day. All the drug treatments [NaHS (10 & 30 μmol/kg i.p), DL-propargylglycine (10 mg/kg i.p), standard drug- Losartan (5 mg/kg p.o)] were given for 3 weeks staring from 21st day after the STZ injection.

Results

Three weeks treatment with sodium hydrosulphide (NaHS) (10 and 30 μmol/kg i.p,) significantly attenuated the behavioral and biochemical abnormalities in STZ-treated animals. DL-propargylglycine (10 mg/kg i.p) pretreatment with sub-effective dose of NaHS (30 μmol/kg i.p) significantly reversed the protective effect of NaHS. However, combination of both NaHS (30 μmol/kg i.p) and standard drug losartan (5 mg/kg p.o) potentiated their effects as compared to their effect alone.

Conclusion

The results of the present study suggest that H₂S treatment showed significant improvement in behavioral and biochemical abnormalities induced by STZ administration. Thus H₂S represents a target of treatment to prevent the progression of complications by DN.

HGF/c-Met signaling promotes liver progenitor cell migration and invasion by an epithelial-mesenchymal transition-independent, phosphatidyl inositol-3 kinase-dependent pathway in an in vitro model

Oval cells constitute an interesting hepatic cell population. They contribute to sustain liver regeneration during chronic liver damage, but in doing this they can be target of malignant conversion and become tumor-initiating cells and drive hepatocarcinogenesis. The molecular mechanisms beneath either their pro-regenerative or pro-tumorigenic potential are still poorly understood. In this study, we have investigated the role of the HGF/c-Met pathway in regulation of oval cell migratory and invasive properties. Our results show that HGF induces c-Met-dependent oval cell migration both in normal culture conditions and after in vitro wounding. HGF-triggered migration involves F-actin cytoskeleton reorganization, which is also evidenced by activation of Rac1. Furthermore, HGF causes ZO-1 translocation from cell-cell contact sites to cytoplasm and its concomitant activation by phosphorylation. However, no loss of expression of cell-cell adhesion proteins, including E-cadherin, ZO-1 and Occludin-1, is observed. Additionally, migration does not lead to cell dispersal but to a characteristic organized pattern in rows, in turn associated with Golgi compaction, providing strong evidence of a morphogenic collective migration. Besides migration, HGF increases oval cell invasion through extracellular matrix, a process that requires PI3K activation and is at least partly mediated by expression and activation of metalloproteases. Altogether, our findings provide novel insights into the cellular and molecular mechanisms mediating the essential role of HGF/c-Met signaling during oval cell-mediated mouse liver regeneration.

AST IV inhibits H₂O₂-induced human umbilical vein endothelial cell apoptosis by suppressing Nox4 expression through the TGF-β1/Smad2 pathway

Endothelial cell apoptosis plays an important role in the pathophysiological mechanisms of vascular complications in diabetes mellitus (DM). NADPH oxidase 4 (Nox4)-dependent reactive oxygen species (ROS) aggregation is the main cause of vascular endothelial cell apoptosis. The transforming growth factor-β1 (TGF-β1)/Smad2 signaling pathway is involved in the apoptosis of several types of cells. However, the association between vascular endothelial cell apoptosis and Nox4, and the involvement of the TGF-β1/Smad2 signaling pathway in vascular endothelial cell apoptosis remain unclear. In the present study, we aimed to investigate the role of Nox4-dependent ROS production and to determine the involvement of the TGF-β1/Smad2 signaling pathway in endothelial cell apoptosis induced by oxidative stress which causes vascular injury in DM. We demonstrated that hydrogen peroxide (H2O2) increased Nox4-dependent-ROS aggregation, as well as the expression of TGF-β1, Smad2, Bax and caspase-3, decreased Bcl-2 expression and increased the apoptosis of human umbilical vein endothelial cells (HUVECs). Treatment with diphenyliodonium (DPI), a specific inhibitor of Nox4 or astragaloside IV (AST IV), a monomer located in an extract of astragaloside, decreased Nox4 expression and the levels of ROS, decreased TGF-β1 and Smad2 expression, altered the expression of apoptosis-related genes and decreased the apoptosis of HUVECs. Treatment with LY2109761, a selective inhibitor of the TGF-β1/Smad2 pathway, produced results similar to those of DPI; however, LY2109761 had no effect on Nox4 expression and ROS levels. Taken together, the findings of the present study suggest that H2O2 contributes to HUVEC apoptosis by inducing Nox4-dependent ROS aggregation and activating the TGF-β1/Smad2 signaling pathway. Our data indicate that the protective effects of AST IV against vascular endothelial cell apoptosis in DM are mainly associated with the decrease in Nox4 expression through the TGF-β1/Smad2 signaling pathway. Furthermore, the inhibition of the activation of the TGF-β1/Smad2 signaling pathway may be another potential therapeutic strategy in the treatment of DM.

miR-133a enhances the protective capacity of cardiac progenitors cells after myocardial infarction

miR-133a and miR-1 are known as muscle-specific microRNAs that are involved in cardiac development and pathophysiology. We have shown that both miR-1 and miR-133a are early and progressively upregulated during in vitro cardiac differentiation of adult cardiac progenitor cells (CPCs), but only miR-133a expression was enhanced under in vitro oxidative stress. miR-1 was demonstrated to favor differentiation of CPCs, whereas miR-133a overexpression protected CPCs against cell death, targeting, among others, the proapoptotic genes Bim and Bmf. miR-133a-CPCs clearly improved cardiac function in a rat myocardial infarction model by reducing fibrosis and hypertrophy and increasing vascularization and cardiomyocyte proliferation. The beneficial effects of miR-133a-CPCs seem to correlate with the upregulated expression of several relevant paracrine factors and the plausible cooperative secretion of miR-133a via exosomal transport. Finally, an in vitro heart muscle model confirmed the antiapoptotic effects of miR-133a-CPCs, favoring the structuration and contractile functionality of the artificial tissue.

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miR-1 and miR-133a have a role in adult cardiac progenitor cells (CPCs)

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miR-133a-CPCs protect cardiac function

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miR-133a-CPCs increase vascularization and protect against hypertrophy

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miR-133a is enriched in CPCs-derived exosomes

Role of NF-κB in hepatic oval cell proliferation: Implications for mechanism underlying protective effects of baicalin against liver injury

AIM: To explore the role of nuclear factor kappa B (NF-κB) in hepatic oval cell proliferation and the possible mechanism underlying the therapeutic effect of baicalin against liver injury.

METHODS: 64 SD rats were randomly divided into 4 groups: a sham operation group, a model group, a low-dose baicalin group and a high-dose baicalin group. 2-acetylaminofluorene plus 2/3 partial hepatectomy (2-AAF+2/3PH) was used to establish the hepatic oval cell (HOC) proliferation model. The two baicalin groups were given 50 and 100 mg/kg of baicalin daily by lavage when modeling, respectively. The rats were killed on 1, 7, 14 and 21 d after PH in each group, and serum and liver tissue samples were collected. Hepatic pathological changes were observed by hematoxylin and eosin (HE) staining. Immunofluorescence, immunohistochemical staining, reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were used to evaluate the proliferation and differentiation of HOCs and the expression of NF-κB.

RESULTS: The HOC proliferation model was successfully established. HOC proliferation began to increase after PH, peaked on the 14^th day and decreased on the 21^st day. The expression pattern of NF-κB was consistent with the proliferation pattern of HOCs, and they were both reduced by baicalin intervention.

CONCLUSION: HOC proliferation is related to the activation of NF-κB. Baicalin could inhibit HOC proliferation possibly through the NF-κB signaling pathway, and this may be a possible mechanism for the therapeutic effect of baicalin against liver injury.

The attenuation of Moutan Cortex on oxidative stress for renal injury in AGEs-induced mesangial cell dysfunction and streptozotocin-induced diabetic nephropathy rats

Oxidative stress (OS) has been regarded as one of the major pathogeneses of diabetic nephropathy (DN) through damaging kidney which is associated with renal cells dysfunction. The aim of this study was to investigate whether Moutan Cortex (MC) could protect kidney function against oxidative stress in vitro or in vivo. The compounds in MC extract were analyzed by HPLC-ESI-MS. High-glucose-fat diet and STZ (30 mg kg⁻¹) were used to induce DN rats model, while 200 μg mL⁻¹ AGEs were for HBZY-1 mesangial cell damage. The treatment with MC could significantly increase the activity of SOD, glutathione peroxidase (GSH-PX), and catalase (CAT). However, lipid peroxidation malondialdehyde (MDA) was reduced markedly in vitro or in vivo. Furthermore, MC decreased markedly the levels of blood glucose, serum creatinine, and urine protein in DN rats. Immunohistochemical assay showed that MC downregulated significantly transforming growth factor beta 2 (TGF-β2) protein expression in renal tissue. Our data provided evidence to support this fact that MC attenuated OS in AGEs-induced mesangial cell dysfunction and also in high-glucose-fat diet and STZ-induced DN rats.

Role of c-Met/phosphatidylinositol 3-kinase (PI3k)/Akt signaling in hepatocyte growth factor (HGF)-mediated lamellipodia formation, reactive oxygen species (ROS) generation, and motility of lung endothelial cells

Hepatocyte growth factor (HGF) mediated signaling promotes cell proliferation and migration in a variety of cell types and plays a key role in tumorigenesis. As cell migration is important to angiogenesis, we characterized HGF-mediated effects on the formation of lamellipodia, a pre-requisite for migration using human lung microvascular endothelial cells (HLMVECs). HGF, in a dose-dependent manner, induced c-Met phosphorylation (Tyr-1234/1235, Tyr-1349, Ser-985, Tyr-1003, and Tyr-1313), activation of PI3k (phospho-Yp85) and Akt (phospho-Thr-308 and phospho-Ser-473) and potentiated lamellipodia formation and HLMVEC migration. Inhibition of c-Met kinase by SU11274 significantly attenuated c-Met, PI3k, and Akt phosphorylation, suppressed lamellipodia formation and endothelial cell migration. LY294002, an inhibitor of PI3k, abolished HGF-induced PI3k (Tyr-458), and Akt (Thr-308 and Ser-473) phosphorylation and suppressed lamellipodia formation. Furthermore, HGF stimulated p47(phox)/Cortactin/Rac1 translocation to lamellipodia and ROS generation. Moreover, inhibition of c-Met/PI3k/Akt signaling axis and NADPH oxidase attenuated HGF- induced lamellipodia formation, ROS generation and cell migration. Ex vivo experiments with mouse aortic rings revealed a role for c-Met signaling in HGF-induced sprouting and lamellipodia formation. Taken together, these data provide evidence in support of a significant role for HGF-induced c-Met/PI3k/Akt signaling and NADPH oxidase activation in lamellipodia formation and motility of lung endothelial cells.

Study on the apoptosis mechanism induced by T-2 toxin

T-2 toxin is known to induce apoptosis in mammalian cells. The mechanism of apoptosis induced by T-2 toxin has been proposed to be linked with oxidative stress and mitochondrial pathway. In the current study, the toxic effect of T-2 on Hela, Bel-7402, and Chang liver cells was examined in dose-dependent and time-dependent manner by MTT assay. Caspase-3 was found to be up-regulated under T-2 toxin stress, which suggested that T-2 toxin induced cell apoptosis. Endogenous GSH and MDA levels in all three cell lines were found down- and up-regulated respectively, which indicated the link between toxic effect of T-2 toxin and intracellular oxidative stress. It was also found by MTT assay that NAC, which maintained the level of GSH in cells, could protect cells from death. Western-blot result showed that the level of both activated Caspase-8 and Caspase-9 increased when cells were treated by T-2 toxin. Caspase-9 was found to be activated earlier than Caspase-8. It was also found that p53 was up-regulated under T-2 toxin stress in the study. These results implied that the effect of T-2 toxin on cells was apoptosis rather than necrosis, and it was probably induced through mitochondrial pathway. To the best of our knowledge, the present study is the first to show that JunD is down-regulated in T-2 toxin induced apoptosis. By construction of an over-expression vector for the JunD gene, we observed that the survival ratio of JunD over-expressed cells obviously increased under T-2 toxin stress. These results suggested that the mechanism of T-2 induced cell death was closely connected with oxidative stress, and that JunD plays an important role in the defensive process against T-2 toxin stress.