Adaptive growth changes in the liver remnant are affected by the size of hepatectomy in rats

In this study we investigated the dynamics of hepatocyte hyperplasia and hypertrophy in rats subjected to increasing sizes of partial hepatectomy (PH). A total of 104 rats were randomized according to the size of PH. On postoperative days (PODs) 1, 3 and 5, blood was drawn and the remnant liver removed for stereological analysis. Liver parameters and regeneration rate were significantly affected by size of PH. On POD 1, hepatocyte volumes had increased significantly in all PH groups. On POD 3, all groups showed hepatocyte volumes approximating baseline. On POD 5, hepatocyte volumes were significantly lower in PH (90) than in baseline, sham and PH (30) rats. Increasing hepatocyte proliferation was not observed following PH (30). Following PH (70), cell proliferation was significantly elevated on PODs 1 and 3, and following PH (90) on PODs 3 and 5. In conclusion, general hypertrophy of hepatocytes after different size of PH was followed by hepatocyte proliferation only in the liver remnant of PH (70) and PH (90).     

Defective hepatic regeneration after partial hepatectomy in leptin-deficient mice is not rescued by exogenous leptin

Liver regeneration after partial hepatectomy (PH) is impaired in leptin-deficient ob/ob mice. Here, we tested whether exogenous leptin and/or correction of the obese phenotype (by food restriction or long-term leptin administration) would rescue hepatocyte proliferation and whether the hepatic progenitor cell compartment was activated in leptin-deficient ob/ob livers after PH. Because of the high mortality following 70% PH to ob/ob mice, we performed a less extensive (55%) resection. Compared to lean mice, liver regeneration after 55% PH was deeply impaired and delayed in ob/ob mice. Administration of exogenous leptin to ob/ob mice at doses that restored circulating leptin levels during the surgery and postsurgery period or for 3 weeks prior to the surgical procedure did not rescue defective liver regeneration. Moreover, correction of obesity, metabolic syndrome and hepatic steatosis by prolonged administration of leptin or food restriction (with or without leptin replacement at the time of PH) did not improve liver regeneration in ob/ob mice. The hepatic progenitor cell compartment was increased in ob/ob mice. However, after PH, the number of progenitor cells decreased and signs of proliferation were absent from this cell compartment. In this study, we have conclusively shown that neither leptin replacement nor amelioration of the metabolic syndrome, obese phenotype and hepatic steatosis, with or without restitution of normal circulating levels of leptin, was able to restore replicative competence to ob/ob livers after PH. Thus, leptin does not directly signal to liver cells to promote hepatocyte proliferation, and the obese phenotype is not solely responsible for impaired regeneration.     

雌激素对大鼠肝细胞再生的影响及其作用机理的研究

Liver regeneration model following partial hepatectomy was used to study the effect and mechanism of estrogen on hepatocyte regeneration of rats. Each animal in the experimental groups received a single injection of diethylstilbestrol (DES) subcutaneously. Results showed that estrogen had a remarkable promoting effect on hepatocyte regeneration. Both 3H-TdR labelling and mitosis indices of hepatocytes in the experimental groups increased markedly. In DES-treated rats, synthesis of estrogen receptor of hepatocyte increased gradually and the translocation of ER from cytoplasm to nucleus was also enhanced at the same time, indicating that the mechanism of DES on hepatocyte regeneration consisted promoting of the interaction of ER and nucleus. There was no statistically significant difference (P greater than 0.05) found in the number of Kupffer cells between all the experimental and their corresponding control groups. But in ultrastructure, Kupffer cells of animals in the experimental groups presented increase of cell size with abundant cytoplasm; longer and more pseudopodia as well as phagolysosomes, suggesting that DES could activate Kupffer cell and promote its function. The relationship between Kupffer cells and liver regeneration is discussed.     

G protein-coupled receptor 30-dependent protein kinase A pathway is critical in nongenomic effects of estrogen in attenuating liver injury after trauma-hemorrhage

Although nongenomic effects of 17beta-estradiol (E2) are mediated via the estrogen receptor alpha (ER-alpha), the existence of another novel ER, G protein-coupled receptor 30 (GPR30), has been suggested as a candidate for triggering a broad range of E2-mediated signaling. GPR30 also acts independently of the ER to promote activation of the protein kinase A (PKA) pathway, which protects cells from apoptosis through Bcl-2. In this study, we examined whether the salutary effects of E2 in attenuating hepatic injury after trauma-hemorrhage are mediated via GPR30- or ER-alpha-regulated activation of PKA-dependent signaling. At 2 hours after trauma-hemorrhage, administration of E2-conjugated to bovine serum albumin (E2-BSA, membrane impermeable) or E2 induced the up-regulation of ER-alpha and GPR30 and attenuated hepatic injury. This was accompanied by increases in PKA activity and Bcl-2 expression. Inhibition of PKA in E2-BSA-treated trauma-hemorrhage rats by PKA inhibitor H89 prevented the E2-BSA attenuation of hepatic injury. Isolated hepatocytes were transfected with small interfering RNA to suppress GPR30 or ER. We found that suppression of GPR30 but not ER-alpha prevented E2-BSA- or E2-induced PKA activation and Bcl-2 expression. These results suggest that the nongenomic salutary effect of E2 in reducing hepatic injury after trauma-hemorrhage is mediated through the PKA-dependent pathway via GPR30 but not ER-alpha.     

Caspase信号通路调控大鼠再生肝肝细胞的凋亡

目的 从基因转录水平了解Caspase信号通路各途径对大鼠再生肝肝细胞凋亡的调节作用。方法 将114只大鼠随机分为19组,包括9个部分肝切除组,9个假手术组和1个正常对照组。于手术后10个不同时间点用常规的两步灌流法和Percoll密度梯度离心法分离大鼠肝细胞,用大鼠Genome 230 2.0芯片检测在大鼠肝再生（LR）中Caspase信号通路相关基因表达变化,用荧光定量PCR确定芯片结果的可靠性,用生物信息学和系统生物学等方法分析基因表达变化预示的Caspase信号通路在调控大鼠再生肝肝细胞凋亡中的作用。结果Caspase信号通路涉及38条途径和123个基因,大鼠Genome 230 2.0芯片含其中的106个基因,38个基因在大鼠肝再生中与肝细胞相关。Caspase信号通路抑制细胞凋亡的21条途径中,途径1、2和11在大鼠部分肝切除（PH）后的30h,途径27、29和31在72h,途径15和16在2h和30h,途径3和4在30h和72h抑制肝细胞凋亡。促进细胞凋亡的17条途径中,途径14在2h,途径34在6h,途径7在30h,途径13在2h和30h,途径36在6h和30h促进肝细胞凋亡。同时,尚未发现其他途径参与肝细胞增殖和（或）凋亡调控。结论 Caspase信号通路的15条途径和38个基因调控大鼠再生肝的肝细胞凋亡。     

Methylseleninic acid (MSA) inhibits 17β-estradiol-induced cell growth in breast cancer T47D cells via enhancement of the antioxidative thioredoxin/ thioredoxin reductase system

The purpose of this study was to clarify the cell growth inhibitory mechanism of human breast cancer cells caused by selenium (Se) compounds. In the presence of 17β-estradiol (E(2)) at physiological concentrations, growth of estrogen receptor α (ERα)-positive T47D cells was markedly inhibited by 1 × 10(-6) mol/L methylseleninic acid (MSA) with no Se related toxicity.Under conditions where cell growth was inhibited, MSA decreased ERα mRNA levels and subsequent protein levels; further decreasing expression of estrogen-responsive finger protein (Efp) which is a target gene product of ERα and promotes G2/M progression of the cell cycle. Therefore, the decline in Efp expression is presumed to be involved in G2 arrest. Coincidentally, the antioxidative thioredoxin/ thioredoxin reductase (Trx/TrxR) system in cells was enhanced by the synergistic action of E(2) and MSA. It has been reported that ROS-induced oxidative stress enhanced ERα expression. E(2) increased production of intracellular ROS in T47D cells. Meanwhile, MSA significantly decreased E(2)-induced ROS accumulation. From these results, activation of the Trx/TrxR system induced by the coexistence of MSA and E(2) suppresses oxidative stress and decreases expression of ERα, and finally induces the growth arrest of T47D cells through disruption of ERα signaling.     

STAT-3 overexpression and p21 up-regulation accompany impaired regeneration of fatty livers

Fatty liver is an important cause of morbidity in humans and is linked to impaired liver regeneration after liver injury, but the mechanisms for impaired liver regeneration remain unknown. In the normal liver, the interleukin (IL)-6/STAT-3 pathway is thought to play a central role in regeneration because this pathway is disrupted in IL-6-deficient mice that exhibit impaired liver regeneration after 70% partial hepatectomy (PH). To determine whether inhibition of STAT-3 is involved in fatty liver-related mitoinhibition, regenerative induction of STAT-3 was compared in normal mice and leptin-deficient ob/ob mice that have fatty livers and markedly impaired liver regeneration after PH. In both groups, two waves of STAT-3 activation were observed, the first in endothelia and the second in hepatocytes. Before PH, a significantly higher percentage of ob/ob endothelial and hepatocyte nuclei expressed phosphorylated (activated) STAT-3. After PH, phospho-STAT-3 accumulated in liver nuclei of lean mice and this response was markedly exaggerated in ob/ob mice. Moreover, a striking inverse correlation was noted between hepatocyte nuclear accumulation of phospho-STAT-3 and DNA synthesis (as assessed by bromodeoxyuridine labeling), as well as cyclin D1 mRNA induction and protein expression. In contrast, STAT-3 activation was positively correlated with p21 protein expression in both groups of mice. Because these results link exaggerated STAT-3 activation with impaired hepatocyte proliferation, STAT-3 inhibition cannot be a growth-arrest mechanism in ob/ob fatty livers. Rather, hyperinduction of this factor may promote mitoinhibition by up-regulating mechanisms that impede cell cycle progression.     

In vivo hepatic endoplasmic reticulum stress in patients with chronic hepatitis C

In hepatocytes, the accumulation of unfolded proteins in the endoplasmic reticulum (ER) causes ER stress and the unfolded protein response (UPR), mediated by the ER‐resident stress sensors ATF‐6, IRE1, and PERK. UPR‐responsive genes are involved in the fate of ER‐stressed cells. Cells carrying hepatitis C virus (HCV) subgenomic replicons exhibit in vitro ER stress and suggest that HCV inhibits the UPR. Since in vivo ER homeostasis is unknown in livers with chronic HCV infection, we investigated ER stress and the UPR in liver samples from untreated patients with chronic hepatitis C (CHC), in comparison with normal livers. Electron microscopy, western blotting, and real‐time RT‐PCR were used in liver biopsy specimens. Electron microscopy identified features showing ER stress in hepatocyte samples from patients with CHC; however, ‘ER‐stressed’ hepatocytes were found in clusters (3‐5 cells) that were scattered in the liver parenchyma. Western blot analysis confirmed the existence of hepatic ER stress by showing activation of the three ER stress sensors ATF‐6, IRE1, and PERK in CHC. Real‐time RT‐PCR showed no significant induction of UPR‐responsive genes in CHC. In contrast, genes involved in the control of diffuse processes such as liver proliferation, inflammation, and apoptosis were significantly induced in CHC. In conclusion, livers from patients with untreated CHC exhibit in vivo hepatocyte ER stress and activation of the three UPR sensors without apparent induction of UPR‐responsive genes. This lack of gene induction may be explained by the inhibiting action of HCV per se (as suggested by in vitro studies) and/or by our finding of the localized nature of hepatocyte ER stress. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Roles of estrogen receptor α and β in the regulation of proliferation in endometrial carcinoma

Endometrial carcinoma (EC), an estrogen-dependent gynecological malignancy, is prevalent worldwide. Estrogen receptor α (ERα) and estrogen receptor β (ERβ) are two main estrogen receptor isoforms, which mediate estrogen-induced proliferation in EC. However, the dynamic changes of ERα and ERβ subtype expression and their functions on proliferation in EC remain elusive. In this study, we aimed to investigate the expression of ERα and ERβ in para-tumor eutopic endometrium, endometrial atypical hyperplasia and EC by immunohistochemistry and then analyse their clinical significance. Subsequently, Ishikawa cells with ERα or ERβ knockdown by lentivirus transfection were used to explore the relationship between ERα/ERβ and cell proliferation, and preliminarily evaluate whether metformin’s inhibitory effect on estrogen-induced cell proliferation was mediated by ERα and ERβ. We found that the expression of ERα and ERβ were markedly changed in endometrial hyperplasia and EC compared with that in para-tumor eutopic endometrium and exhibited different expression trends. Through further analysis, we discovered that ERα presented higher expression in endometrial atypical hyperplasia and early stage of EC than that in para-tumor eutopic endometrium, while the expression of ERβ gradually decreased from para-tumor eutopic endometrium to EC. Additionally, the cell cycle-related protein, CyclinD1 was gradually increased but p21 decreased. Furthermore, knockdown of ERα and ERβ severally in Ishikawa cells either inhibited or promoted estrogen-induced cell proliferation through regulating CyclinD1 and p21 expression. Meanwhile, the inhibitory effect of metformin on estrogen-induced cell proliferation was respectively blunted or partly reversed by knockdown of ERα or ERβ. Altogether, ERα and ERβ have different expression patterns in the progression of EC either facilitating or suppressing cell proliferation through regulating the expression of CyclinD1 and p21 in EC cells, and may also mediate the inhibitory effect of metformin on estrogen-induced EC cells proliferation.     

雌激素与IL-6、IL-8在卵巢癌细胞中的调节作用

目的 探讨雌激素与IL-6、IL-8在卵巢癌细胞中的交互调节作用及作用机制.方法 选择兼有雌激素受体(estrogen receptor,ER)及IL-6、IL-8受体表达的卵巢癌细胞系CAOV-3和OVCAR-3作为研究模型,分别探讨17B-雌二醇(estradiol,E2)对IL-6、IL-8及其受体表达的作用以及IL-6、IL-8对EB表达及ER转录活性的作用.结果 一方面E2不仅可经NF-κB途径促进卵巢癌细胞IL-6、IL-8分泌,而且还对二者受体的表达具有一定的调节作用.E2诱导的促IL-6、IL-8分泌作用可被其受体阻断剂他莫昔芬(tamoxifen,Txf)完全阻断.另一方面在无雌激素的条件下,IL-6、IL-8能上调卵巢癌细胞Erα表达及下调ERB表达,且还能分别通过丝裂原活化蛋白激酶(MAPK)信号通路和Src活化增强卵巢癌细胞ER的转录活性,该作用可被Txf完全封闭.结论 雌激素与IL-6、IL-8两种细胞因子在卵巢癌细胞中交互调节,由此通过产生的放大信号通路促进卵巢癌的生长和发展.     

Estrogen and its receptor enhance mechanobiological effects in compressed bone mesenchymal stem cells

Mechanical stimulation and estrogen have been proven to be two important factors in promoting mesenchymal stem cell activity, which is closely associated with bone formation, mass maintenance and remodeling. However, the superposition effects of mechanical stimulation and estrogen on stem cells remain unknown. It is also unclear if the estrogen receptor (ER) plays only a key role in estrogen signaling or if it is also involved in the mechanotransduction of stem cells. To investigate the role of estrogen and its receptors in the mechanobiological effects in bone mesenchymal stem cells (BMSCs), isolated mesenchymal stem cells from bone marrow were exposed to mechanical pressure under additional estrogen treatment or ER blockade. Cell proliferation was examined using an MTT assay and alkaline phosphatase (ALP) activity was determined by a modified enzyme kinetic method. Alignment of the cytoskeleton was observed by Coomassie brilliant blue staining and F-actin fluorescent staining. Cellular ultrastructure was observed under transmission electron microscope. Expression of ERα was investigated using Western blot analysis. Results indicated that mechanical pressure promoted cell proliferation, ALP activity, ERα expression and F-actin stress fiber formation. Overall, this effect was enhanced by the addition of estrogen and inhibited by ER blockade. We concluded that pressure stimulated proliferation and differentiation capability via F-actin transduction in BMSCs. The effects were enhanced by the addition of estrogen, and the ER plays an important role in regulating mechanobiological effects and the mechanotransduction processes of BMSCs.     

High-Throughput Analysis of Tumor Necrosis Factor Signaling Pathways in Eight Cell Types during Rat Hepatic Regeneration

This study aims to clarify the relevance of tumor necrosis factor (TNFs) signaling pathways and liver regeneration (LR) at the cellular level. Eight liver cell types were isolated using Percoll density gradient centrifugation and immunomagnetic beads methods. Expressions of TNF signaling pathway-involved genes in each cell type after 2/3 hepatectomy (PH) were detected using gene chip. Results show the following: gene TNFα was upregulated in most cell types, especially in Kupffer cells (KC); TNFβ expression was insignificantly changed in eight liver cell types; the majority of genes involved in four TNFα signaling pathways showed increased expression during LR in hepatocytes (HC); TNFα-induced NFκB pathway-involved genes were upregulated preferentially between 2 and 24 h during LR in biliary epithelial cells (BECs); and TNFα-induced apoptotic pathway genes were downregulated preferentially at progressing phase of LR in dendritic cells (DCs). Referring to the above results, TNFα-mediated signaling pathways, in contrast to TNFβ, play the more proactive role in LR, and four TNFα-mediated signaling pathways seem helpful to regulate biological events in HC; BEC proliferation was partly controlled by TNFα-mediated NFκB pathway; and the impaired TNFα-mediated apoptotic pathway in DCs might contribute to the restoration of DC mass after PH. Briefly, the comparative analysis of genomewide expression profiles of TNF signaling pathways between different cell types is helpful in understanding the implication of TNF signaling in LR at the cellular level.     

肝细胞生长和分化相关基因在大鼠肝再生中的表达方式及作用分析

目的在基因转录水平了解肝再生中肝细胞的生长和分化情况。方法用搜集网站资料和查阅相关论文等方法获得参与肝细胞生长和分化基因,用大鼠基因组230 2.0芯片检测它们在大鼠肝再生(LR)中的表达情况,通过比较手术组和假手术组中基因表达差异性以确定上述基因中的肝再生相关基因。结果初步证实上述基因中110个基因与肝再生相关。肝再生启动(PH后0.5~4h)、G0/G1过渡(PH后4~6h)、细胞增殖(PH后6~66h)、细胞分化和组织结构功能重建(PH后72~168h)等4个阶段起始表达的基因数为63、11、43和3,基因总表达的次数为63、43、101和80,表明相关基因主要在肝再生启动阶段起始表达,在不同阶段发挥作用。它们共表达上调488次,下调248次,分为6种表达方式,表明肝再生中细胞生理生化活动的多样性和复杂性。结论肝细胞生长和分化贯穿于整个肝再生中。     

Insulin-like growth factor-2 (IGF-2) activates estrogen receptor-α and -β via the IGF-1 and the insulin receptors in breast cancer cells

The estrogen receptor (ER) is a primary target for breast cancer (BC) treatment. As BC progresses to estrogen-independent growth, the insulin-like growth factor-1 receptor (IGF-1R) and the ER interact in synergistic cross-talk mechanisms, which result in enhanced activation of both receptors' signaling cascades. Insulin-like growth factor-2 (IGF-2) is critical in BC progression and its actions are mediated by the IGF-1R. Our previous studies showed that IGF-2 regulates survival genes that protect the mitochondria and promote chemoresistance. In this study, we analyzed BC cells by subcellular fractionation, Western-Blot, qRT-PCR, and siRNA analysis. Our results demonstrate that IGF-2 activates ER-α and ER-β, and modulates their translocation to the nucleus, membrane organelles, and the mitochondria. IGF-2 actions are mediated by the IGF-1R and the insulin receptor. This novel mechanism of IGF-2 synergistic cross-talk signaling with ER-α and ER-β can promote estrogen-independent BC progression and provide new therapeutic targets for the treatment of BC patients.