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Articles by L Liu
Total Records ( 42 ) for L Liu
  H Tang , F Chen , Q Tan , S Tan , L Liu and F. Zhang
 

Polycomb repressive complex 2 (PRC2), which mediates trimethylation of lysine 27 on histone H3 (K27me3), plays an important role in many types of stem cell differentiation. Here, we try to reveal how PRC2, PRC2-mediated repressive histone marker H3K27me3, and active histone marker histone H4 acetylation (acH4) regulate the CD11b transcription during all-trans retinoic acid (ATRA)-induced HL-60 leukemia cell differentiation. By using quantitative real-time polymerase chain reaction (qPCR) and western blot analysis, we found that the mRNA and protein expression levels of two members of PRC2 were decreased during ATRA-induced HL-60 differentiation, respectively. When treated with ATRA for 72 h, the EZH2 and SUZ12 mRNA levels were decreased to 35% and 38% of the control group, respectively. At the same time, the granulocytic mature surface marker CD11b expression was increased significantly at mRNA level detected by qPCR and protein level detected by flow cytometry. By using chromatin immunoprecipitation assay, we compared the local changes in SUZ12 binding and PRC2-mediated H3K27me3 at the promoter of CD11b during ATRA-induced HL-60 differentiation. Both the levels of SUZ12 binding and PRC2-mediated H3K27me3 at the promoter of CD11b were decreased for 4.1 and 3.8 folds, respectively. And we also found the increase in the acH4 level up to 4 folds after 72 h of ATRA treatment. These results suggested that the histone modification including PRC2-mediated repressive histone marker H3K27me3 and active histone marker acH4 may involve in CD11b transcription during HL-60 leukemia cells reprogramming to terminal differentiation.

  Q Liu , Z Dai , Z Liu , X Liu , C Tang , Z Wang , G Yi , L Liu , Z Jiang , Y Yang and Z. Yuan
 

It has been reported that oxidized low-density lipoprotein (Ox-LDL) can increase the expression of adipophilin. However, the detailed mechanisms are not fully understood. The aim of this study was to investigate the mechanism of Ox-LDL on adipophilin expression and the intracellular lipid droplet accumulation. A mouse macrophage-like cell line, RAW264.7, was used throughout, and it was found that Ox-LDL induced adipophilin expression in a dose-dependent manner. Moreover, Ox-LDL induced peroxisome proliferator-activated receptor- (PPAR) expression and PPAR-specific inhibitor T0070907 abrogated Ox-LDL-induced adipophilin expression, but specific agonist GW1929 not. Furthermore, Ox-LDL induced phosphorylation of ERK1/2, and ERK1/2-specific inhibition by PD98059 suppressed the Ox-LDL-induced PPAR and adipophilin expression. The results showed that ERK1/2 or PPAR-specific inhibition decreased the amounts of intracellular lipid droplets. Meanwhile, the PPAR-specific agonist increased intracellular lipid droplets. These results suggested that Ox-LDL-induced increase in adipophilin level via ERK1/2 activation is one of the mechanisms of inducing greater amounts of intracellular lipid droplets in RAW264.7 cells, which indicated that adipophilin is involved in atherosclerotic progression.

  R Peters , N Beckett , L Burch , M. C de Vernejoul , L Liu , J Duggan , C Swift , B Gil Extremera , A Fletcher and C. Bulpitt
 

Background: fractures may have serious implications in an elderly individual, and fracture prevention may include a careful choice of medications.

Design: the Hypertension in the Very Elderly Trial (HYVET) was a double-blind placebo-controlled trial of a thiazide-like diuretic (indapamide 1.5 mg SR) with the optional addition of the angiotensin-converting enzyme (ACE) inhibitor (perindopril 2–4 mg). Fracture was a secondary end point of the trial.

Setting: HYVET recruited participants from Eastern and Western Europe, China, Australasia, and Tunisia.

Subjects: all participants were ≥80 years of age and hypertensive.

Methods: participants were randomised to receive a thiazide-like diuretic (indapamide 1.5 mg SR) ± ACE inhibitor (perindopril 2–4 mg) or matching placebos. Incident fractures were validated and analysed based on time to first fracture.

Results: there were 3,845 participants in HYVET and a total 102 reported fractures (42 in the active and 60 in the placebo group). When taking only validated first fractures, 90 were included in the analyses (38 in the active and 52 in the placebo group). Cox proportional hazard regression, adjusted for key baseline risk factors, resulted in a point estimate of 0.58 (95% CI 0.33–1.00, P = 0.0498).

Conclusions: despite the lowering of blood pressure, treatment with a thiazide-like diuretic and an ACE inhibitor does not increase and may decrease fracture rate.

  L Liu , B. J Duke , B Malik , Q Yue and D. C. Eaton
 

The epithelial sodium channel (ENaC) is regulated by epidermal growth factor (EGF). We investigate whether ENaC is regulated by another EGF receptor (EGFR) ligand, transforming growth factor- (TGF-). We show that chronic (24 h) treatment with TGF- inhibits ENaC in Xenopus laevis kidney cells 20 times more strongly than EGF. By using single-channel measurements, we show that TGF- significantly reduces the number of ENaC per patch. The open probability (Po) is unchanged by 24-h treatment with TGF-. -, β-, and -ENaC mRNA levels are significantly reduced by TGF- or EGF. TGF- or EGF reduces - and -ENaC proteins in the membrane; however, β-ENaC is unchanged. TGF- or EGF inhibits ENaC by activating EGFR since the EGFR inhibitor AG1478 blocks the effects of both. The MAPK 1/2 inhibitor U0126 also blocks the effect of TGF- or EGF on ENaC, indicating that the MAPK1/2 pathway is involved in the TGF-- or EGF-induced inhibition of ENaC. Interestingly, acute treatment (<1 h) with TGF- or EGF does not inhibit ENaC current; it enhances ENaC activity by increasing Po. Pretreatment of the cells with U0126 potentiates the acute TGF-- or EGF-induced stimulation of ENaC. This TGF-- or EGF-induced increase in sodium current is abolished by a phosphatidylinositol 3-kinase (PI-3 kinase) inhibitor, LY294002, suggesting that PI-3 kinase is involved in the activation of sodium transport. In conclusion, chronic treatment with TGF- or EGF inhibits ENaC by decreasing the number of channels in the membrane transcriptionally through MAPK1/2 pathways, but acute treatment with TGF- or EGF activates ENaC by increasing Po via PI-3 kinase.

  P Yao , L Hao , N Nussler , A Lehmann , F Song , J Zhao , P Neuhaus , L Liu and A. Nussler
 

It has been reported that naturally occurring quercetin exerts hepatoprotective effects through heme oxygenase-1 (HO-1) induction. However, the precise mechanism of how ethanol-associated liver damage is counteracted by quercetin-enhanced HO-1 metabolism still remains unclear. To further decipher the protective role of quercetin on ethanol-induced liver damage, we treated human hepatocytes with quercetin and various (end) products of the HO-1 pathway. Our data clearly showed that quercetin treatment attenuated ethanol-induced damage, whereas hemoglobin and zinc protoporphyrin 9 (ZnPP) abolished such effects. Iron-II aggravated ethanol toxicity and was only partially reduced by quercetin. In contrast, carbon monoxide (CO) dose dependently inhibited ethanol-induced cytochrome P450 2E1 (CYP 2E1) activity and hepatotoxicity but had no influence on CYP 2E1 protein expression. Similarly, hemoglobin dramatically stimulated CYP 2E1 activity but not the protein expression in quercetin- and ethanol-cotreated hepatocytes. ZnPP significantly promoted CYP 2E1 protein expression in the presence and absence of CO treatment but inhibited ethanol-induced CYP 2E1 activation following CO incubation in quercetin- and ethanol-cotreated hepatocytes. These results suggested that quercetin virtually attenuated ethanol-derived oxidative damage via HO-1 induction. Heme degradation and CO release may mediate the protective effects through inhibiting ethanol-induced CYP 2E1 synthesis and enzymatic activity, respectively.

  X Zhang , X Wei , L Liu , G. P Marti , M. S Ghanamah , M. J Arshad , L Strom , R Spence , J Jeng , S Milner , J. W Harmon and G. L. Semenza
 

Objective  To perform a systematic exploration of the phenomenon of mobilization of circulating angiogenic cells (CACs) in an animal model. This phenomenon has been observed in patients with cutaneous burn wounds and may be an important mechanism for vasculogenesis in burn wound healing.

Design  We used a murine model, in which burn depth can be varied precisely, and a validated culture method for quantifying circulating CACs.

Setting  Michael D. Hendrix Burn Research Center, Baltimore, Maryland.

Participants  Male 129S1/SvImJ mice, aged 8 weeks, and 31 patients aged 19-59 years with burn injury on 1% to 64% of the body surface area and evidence of hemodynamic stability.

Main Outcome Measures  Burn wound histological features, including immunohistochemistry for blood vessels with CD31 and -smooth muscle actin antibodies, blood flow measured with laser Doppler perfusion imaging, and mobilization of CACs into circulating blood measured with a validated culture technique.

Results  Increasing burn depth resulted in a progressive delay in the time to mobilization of circulating CACs and reduced mobilization of CACs. This delay and reduction in CAC mobilization was associated with reduced perfusion and vascularization of the burn wound tissue. Analysis of CACs in the peripheral blood of the human patients, using a similar culture assay, confirmed results previously obtained by flow cytometry, that CAC levels peak early after the burn wound.

Conclusion  If CAC mobilization and wound perfusion are important determinants of clinical outcome, then strategies designed to augment angiogenic responses may improve outcome in patients with severe burn wounds.

Trial Registration  clinicaltrials.gov Identifier: NCT00796627

  W Chen , Y Luo , L Liu , H Zhou , B Xu , X Han , T Shen , Z Liu , Y Lu and S. Huang
 

Cryptotanshinone (CPT), a natural compound isolated from the plant Salvia miltiorrhiza Bunge, is a potential anticancer agent. However, little is known about its anticancer mechanism. Here, we show that CPT inhibited cancer cell proliferation by arresting cells in G1-G0 phase of the cell cycle. This is associated with the inhibition of cyclin D1 expression and retinoblastoma (Rb) protein phosphorylation. Furthermore, we found that CPT inhibited the signaling pathway of the mammalian target of rapamycin (mTOR), a central regulator of cell proliferation. This is evidenced by the findings that CPT inhibited type I insulin-like growth factor I– or 10% fetal bovine serum–stimulated phosphorylation of mTOR, p70 S6 kinase 1, and eukaryotic initiation factor 4E binding protein 1 in a concentration- and time-dependent manner. Expression of constitutively active mTOR conferred resistance to CPT inhibition of cyclin D1 expression and Rb phosphorylation, as well as cell growth. The results suggest that CPT is a novel antiproliferative agent. Cancer Prev Res; 3(8); 1015–25. ©2010 AACR.

  B Liu , D Chen , L Yang , Y Li , X Ling , L Liu , W Ji , Y Wei , J Wang , Q Wei , L Wang and J. Lu
 

Mitogen-activated protein kinase kinase 4 (MKK4) is a critical mediator of stress-activated protein kinase signals that regulate apoptosis, inflammations and tumorigenesis. Several polymorphisms have been identified in the MKK4 gene. We hypothesized that genetic variants in the MKK4 promoter may alter its expression and thus cancer risk. In a case–control study of 1056 lung cancer cases and 1056 sex and age frequency-matched cancer-free controls, we genotyped two common polymorphisms in the MKK4 promoter region (–1304T>G and –1044A>T) with the Taqman assay, and we found that compared with the most common –1304TT genotype, carriers of –1304G variant genotypes had a decreased risk of lung cancer [odds ratio (OR) = 0.74; 95% confidence interval (CI) = 0.61–0.90 for TG, and OR = 0.62; 95% CI = 0.41–0.94 for GG] in an allele dose–response manner (adjusted Ptrend = 0.0005). Further stratification analysis showed that the protective role of the –1304G variant allele was more evident in low or normal body mass index (BMI) but restrained in the overweighters and that the –1304G variant genotypes interacted with BMI in reducing cancer risk (adjusted Pinteraction = 0.003). Moreover, the luciferase assay showed that the G allele in the promoter significantly increased the transcription activity of the MKK4 gene in vitro and that the MKK4 protein expression levels of the G variant carriers was significantly higher in tumor tissues than those of the –1304TT genotype. However, no significant association was observed between the –1044A>T polymorphism and risk of lung cancer. Our data suggest that the functional –1304G variant in the MKK4 promoter contributes to a decreased risk of lung cancer by increasing the promoter activity and that the G variant may be a marker for susceptibility to lung cancer.

  L Liu , Y. H Li , Y. B Niu , Y Sun , Z. J Guo , Q Li , C Li , J Feng , S. S Cao and Q. B. Mei
 

Evidence strongly supported a link between inflammation and cancer. Patients with colitis have high risk for development of colon cancer. Nuclear factor-kappa B (NF-B), partially induced by lipopolysaccharide (LPS) binding to Toll-like receptor (TLR) 4, is a vital molecule in supervising the transformation of colitis to colon cancer. It could be a good strategy to prevent colitis carcinogenesis for targeting LPS/TLR4/NF-B pathway. In the present study, we obtained an oligogalactan composed of five galacturonic acids from apple pectin and evaluated its protective efficacy on intestinal toxicities and carcinogenesis in a mouse model of colitis-associated colon cancer induced by 1,2-dimethylhydrazine and dextran sodium sulfate (DSS). The apple oligogalactan (AOG) was highly effective against intestinal toxicities and carcinogenesis and decreased the elevated levels of TLR4 and tumor necrosis factor- (TNF-) induced by inflammation in vivo in this model system. In vitro studies, AOG alone only slightly increased the levels of protein expression and messenger RNA of TLR4, phosphorylation of IB and production of TNF- in HT-29 cells. However, AOG significantly decreased the elevation of all the biomarkers induced by LPS when it was combined with LPS. The effect of AOG may be related to membrane internalization and redistribution of TLR4 from cell membrane to cytoplasm. AOG is active against inflammation and carcinogenesis through targeting LPS/TLR4/NF-B pathway. Both AOG and LPS are agonists of TLR4 for sharing the same ligand but AOG has a much lower intrinsic activity than that of LPS. AOG may be useful for treatment of colitis and prevention of carcinogenesis in the clinics.

  A Goyal , S. R Mehta , R Diaz , H. C Gerstein , R Afzal , D Xavier , L Liu , P Pais and S. Yusuf
 

Background— In patients with acute myocardial infarction (AMI), hyperglycemia predicts death, but the prognostic significance of hypoglycemia is controversial.

Methods and Results— We evaluated the prognostic significance of hypoglycemia and hyperglycemia in 30 536 AMI patients in a post hoc analysis of 2 large trials of glucose-insulin-potassium therapy in AMI. Glucose levels on admission and at 6 and 24 hours after admission, as well as 30-day mortality, were documented. In separate multivariable Cox models for admission and postadmission glucose, we compared the prognostic value of hypoglycemia (≤70 mg/dL) and hyperglycemia (≥140 mg/dL) with normoglycemia (>70 and <140 mg/dL). Analyses were repeated with hypoglycemia defined as glucose ≤60 mg/dL and in key subgroups based on diabetes or insulin (glucose-insulin-potassium) allocation status. Both high and low percentiles of admission glucose predicted increased 30-day mortality. However, for postadmission glucose, this U-shaped relationship was attenuated so that only high and not low glucose levels remained prognostic. Hyperglycemia (≥140 mg/dL), both on admission (adjusted hazard ratio 1.43, 95% confidence interval 1.32 to 1.56, P<0.0001) and after admission (adjusted hazard ratio 1.47, 95% confidence interval 1.31 to 1.66, P<0.0001), predicted death compared with normoglycemia. In contrast, hypoglycemia (glucose ≤70 mg/dL) on admission was not prognostic (adjusted hazard ratio 1.16, 95% confidence interval 0.84 to 1.62, P=0.37), nor was postadmission hypoglycemia (adjusted hazard ratio 0.96, 95% confidence interval 0.72 to 1.26, P=0.75). Exploratory analyses that redefined hypoglycemia as glucose ≤60 mg/dL showed consistent results, as did analyses restricted to diabetic patients (18% of the study population). Postadmission hypoglycemia was more common in insulin (glucose-insulin-potassium)–treated patients (6.9%) than in untreated patients (3.4%) but did not predict mortality in either subgroup.

Conclusions— Both admission and postadmission hyperglycemia predict 30-day death in AMI patients. In contrast, only hypoglycemia on admission predicted death, and this relationship dissipated after admission. These data suggest hypoglycemia may not be a direct mediator of adverse outcomes in AMI patients.

  M Bohm , M Baumhakel , K Teo , P Sleight , J Probstfield , P Gao , J. F Mann , R Diaz , G. R Dagenais , G. L. R Jennings , L Liu , P Jansky , S Yusuf and for the ONTARGET/TRANSCEND Erectile Dysfunction Substudy Investigators
 

Background— Although erectile dysfunction (ED) is associated with cardiovascular risk factors and atherosclerosis, it is not known whether the presence of ED is predictive of future events in individuals with cardiovascular disease. We evaluated whether ED is predictive of mortality and cardiovascular outcomes, and because inhibition of the renin-angiotensin system in high-risk patients reduces cardiovascular events, we also tested the effects on ED of randomized treatments with telmisartan, ramipril, and the combination of the 2 drugs (ONTARGET), as well as with telmisartan or placebo in patients who were intolerant of angiotensin-converting enzyme inhibitors (TRANSCEND).

Methods and Results— In a prespecified substudy, 1549 patients underwent double-blind randomization, with 400 participants assigned to receive ramipril, 395 telmisartan, and 381 the combination thereof (ONTARGET), as well as 171 participants assigned to receive telmisartan and 202 placebo (TRANSCEND). ED was evaluated at baseline, at 2-year follow-up, and at the penultimate visit before closeout. ED was predictive of all-cause death (hazard ratio [HR] 1.84, 95% confidence interval [CI] 1.21 to 2.81, P=0.005) and the composite primary outcome (HR 1.42, 95% CI 1.04 to 1.94, P=0.029), which consisted of cardiovascular death (HR 1.93, 95% CI 1.13 to 3.29, P=0.016), myocardial infarction (HR 2.02, 95% CI 1.13 to 3.58, P=0.017), hospitalization for heart failure (HR 1.2, 95% CI 0.64 to 2.26, P=0.563), and stroke (HR 1.1, 95% CI 0.64 to 1.9, P=0.742). The study medications did not influence the course or development of ED.

Conclusions— ED is a potent predictor of all-cause death and the composite of cardiovascular death, myocardial infarction, stroke, and heart failure in men with cardiovascular disease. Trial treatment did not significantly improve or worsen ED.

Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT 00153101.

  Z Fu , M Wang , M Gucek , J Zhang , J Wu , L Jiang , R. E Monticone , B Khazan , R Telljohann , J Mattison , S Sheng , R. N Cole , G Spinetti , G Pintus , L Liu , F. D Kolodgie , R Virmani , H Spurgeon , D. K Ingram , A. D Everett , E. G Lakatta and J. E. Van Eyk
 

Advancing age induces aortic wall thickening that results from the concerted effects of numerous signaling proteins, many of which have yet to be identified. To search for novel proteins associated with aortic wall thickening, we have performed a comprehensive quantitative proteomic study to analyze aortic proteins from young (8 months) and old (30 months) rats and identified 50 proteins that significantly change in abundance with aging. One novel protein, the milk fat globule protein epidermal growth factor 8 (MFG-E8), increases 2.3-fold in abundance in old aorta. Transcription and translation analysis demonstrated that aortic MFG-E8 mRNA and protein levels increase with aging in several mammalian species including humans. Dual immunolabeling shows that MFG-E8 colocalizes with both angiotensin II and monocyte chemoattractant protein (MCP)-1 within vascular smooth muscle cells (VSMCs) of the thickened aged aortic wall. Exposure of early passage VSMCs from young aorta to angiotensin II markedly increases MFG-E8 and enhances invasive capacity to levels observed in VSMCs from old rats. Treatment of VSMCs with MFG-E8 increases MCP-1 expression and VSMCs invasion that are inhibited by the MCP-1 receptor blocker vCCI. Silencing MFG-E8 RNA substantially reduces MFG-E8 expression and VSMCs invasion capacity. The data indicate that arterial MFG-E8 significantly increases with aging and is a pivotal relay element within the angiotensin II/MCP-1/VSMC invasion signaling cascade. Thus, targeting of MFG-E8 within this signaling axis pathway is a potential novel therapy for the prevention and treatment of the age-associated vascular diseases such as atherosclerosis.

  W. T Wong , X. Y Tian , Y Chen , F. P Leung , L Liu , H. K Lee , C. F Ng , A Xu , X Yao , P. M Vanhoutte , G. L Tipoe and Y. Huang
  Rationale:

Bone morphogenic protein (BMP)4 can stimulate superoxide production and exert proinflammatory effects on the endothelium. The underlying mechanisms of how BMP4 mediates endothelial dysfunction and hypertension remain elusive.

Objective:

To elucidate the cellular pathways by which BMP4-induced endothelial dysfunction is mediated through oxidative stress–dependent upregulation of cyclooxygenase (COX)-2.

Methods and Results:

Impaired endothelium-dependent relaxations, exaggerated endothelium-dependent contractions, and reactive oxygen species (ROS) production were observed in BMP4-treated mouse aortae, which were prevented by the BMP4 antagonist noggin. Pharmacological inhibition with thromboxane prostanoid receptor antagonist or COX-2 but not COX-1 inhibitor prevented BMP4-induced endothelial dysfunction, which was further confirmed with the use of COX-1–/– or COX-2–/– mice. Noggin and knockdown of BMP receptor 1A abolished endothelium-dependent contractions and COX-2 upregulation in BMP4-treated aortae. Apocynin and tempol treatment were effective in restoring endothelium-dependent relaxations, preventing endothelium-dependent contractions and eliminating ROS overproduction and COX-2 overexpression in BMP4-treated aortae. BMP4 increased p38 mitogen-activated protein kinase (MAPK) activity through a ROS-sensitive mechanism and p38 MAPK inhibitor prevented BMP4-induced endothelial dysfunction. COX-2 inhibition blocked the effect of BMP4 without affecting BMP4-induced ROS overproduction and COX-2 upregulation. Importantly, renal arteries from hypertensive rats and humans showed higher levels of COX-2 and BMP4 accompanied by endothelial dysfunction.

Conclusions:

We show for the first time that ROS serve as a pathological link between BMP4 stimulation and the downstream COX-2 upregulation in endothelial cells, leading to endothelial dysfunction through ROS-dependent p38 MAPK activation. This BMP4/ROS/COX-2 cascade is important in the maintenance of endothelial dysfunction in hypertension.

  L Liu , J Wang , L Zhao , J Nilsen , K McClure , K Wong and R. D. Brinton
 

Progesterone receptor (PR) expression and regulation of neural progenitor cell (NPC) proliferation was investigated using NPC derived from adult rat brain. RT-PCR revealed that PRA mRNA was not detected in rat NPCs, whereas membrane-associated PRs, PR membrane components (PGRMCs) 1 and 2, mRNA were expressed. Progesterone-induced increase in 5-bromo-2-deoxyuridine incorporation was confirmed by fluorescent-activated cell sorting analysis, which indicated that progesterone promoted rat NPC exit of G0/G1 phase at 5 h, followed by an increase in S-phase at 6 h and M-phase at 8 h, respectively. Microarray analysis of cell-cycle genes, real-time PCR, and Western blot validation revealed that progesterone increased expression of genes that promote mitosis and decreased expression of genes that repress cell proliferation. Progesterone-induced proliferation was not dependent on conversion to metabolites and was antagonized by the ERK1/2 inhibitor UO126. Progesterone-induced proliferation was isomer and steroid specific. PGRMC1 small interfering RNA treatment, together with computational structural analysis of progesterone and its isomers, indicated that the proliferative effect of progesterone is mediated by PGRMC1/2. Progesterone mediated NPC proliferation and concomitant regulation of mitotic cell cycle genes via a PGRMC/ERK pathway mechanism is a potential novel therapeutic target for promoting neurogenesis in the mammalian brain.

  K. S Sandhu , C Shi , M Sjolinder , Z Zhao , A Gondor , L Liu , V. K Tiwari , S Guibert , L Emilsson , M. P Imreh and R. Ohlsson
 

Recent observations highlight that the mammalian genome extensively communicates with itself via long-range chromatin interactions. The causal link between such chromatin cross-talk and epigenetic states is, however, poorly understood. We identify here a network of physically juxtaposed regions from the entire genome with the common denominator of being genomically imprinted. Moreover, CTCF-binding sites within the H19 imprinting control region (ICR) not only determine the physical proximity among imprinted domains, but also transvect allele-specific epigenetic states, identified by replication timing patterns, to interacting, nonallelic imprinted regions during germline development. We conclude that one locus can directly or indirectly pleiotropically influence epigenetic states of multiple regions on other chromosomes with which it interacts.

  D Xie , H Bai , L Liu , X Xie , J Ayello , X Ma and J. Zhang
 

Influenza affects most of the world's population annually, often causing a secondary infection, but pathological mechanisms of influenza virus infection remain unclear. We have found that influenza viruses have a selective preference for infecting monocytes and mature immune effector cells. This paper provides evidence that influenza virus infection increases the expression of granzyme B (GrB) in monocytes, activated T and B cells. All GrB+ cells had cytolytic function. GrB+CD62Lhigh central memory (TCM) cells were fast response population to virus infection when compared with GrB+CD62Llow population. The influenza virus-infected PBMC could be killed by GrB+ cells. We propose the following mechanism for influenza: (i) influenza virus within the respiratory tract overcomes humoral defenses; (ii) free virus is directly engulfed by the immune system effector cells and free virus also infects epithelial cells; (iii) virus-infected epithelial cells and the immune system cells are killed by cytotoxic cells. These indicated that an immune system that was combating a virus infection needs to sacrifice some of its immune system cells. Therefore, influenza viruses might temporally destroy the human immune system's line of defense, resulting in susceptibility to a secondary infection. This might be a prevalent mechanism existing in cell-mediated immune responses.

  C Vogel , A Chan , B Gril , S. B Kim , J Kurebayashi , L Liu , Y. S Lu and H. Moon
 

The management of human epidermal growth factor receptor 2-positive (ErbB2+) breast cancer is challenging; patients with ErbB2+ breast tumors have more aggressive disease and a poor prognosis. The increasing incidence of breast cancer in Asia and the limitations of existing treatments pose additional challenges. In this review, we summarize the preclinical and clinical evidence that indicates how lapatinib, a novel inhibitor that targets the human epidermal growth factor receptor (ErbB1) and ErbB2 may help clinicians address four particularly challenging issues in the management of ErbB2+ breast cancer. These issues are: (i) trastuzumab therapy failure, (ii) development of central nervous system metastases, (iii) minimizing toxicity and (iv) selecting the most appropriate partners (chemotherapy and non-chemotherapy) for combination therapy with lapatinib. Lapatinib, in combination with chemotherapeutic agents, such as capecitabine, provides clinical benefits to patients with ErbB2+ breast cancer, including patients who develop progressive disease on trastuzumab. Lapatinib, in combination with non-chemotherapeutic agents, such as letrozole, may also provide a chemotherapy-free treatment option for postmenopausal patients with estrogen receptor-positive/ErbB2+ metastatic breast cancer. Encouraging results have also emerged regarding the synergistic effects of lapatinib in combination with other agents for the treatment of ErbB2+ breast cancer. Promising findings have also been reported for the use of lapatinib to prevent and treat central nervous system metastases. Collectively, these results indicate that the judicious use of lapatinib, an effective oral therapy with a manageable toxicity profile, can enhance the management of patients with ErbB2+ breast cancer.

  P Gao , K Liu , L Liu , Z Wang , Z Liao , Z Xu , W Wang , X Bai , E Wang and Y. Li
 

The higher-order harmonic resonances, including second and third harmonic modes, were induced by applying alternative current signals inside a high-resolution transmission electron microscope (HRTEM), which have been used to study the mechanical properties of individual cadmium sulphide (CdS) nanowires. Young's moduli (E) and mechanical quality factors (Q) of individual CdS nanowires with diameters in the range of 50–350 nm were measured with the assistance of the mechanical resonances. The results indicate that the smooth nanowires have larger E and Q in comparison with the rough nanowires, and for the rough nanowires, E and Q increase with increasing diameters. The morphology- and size-dependent mechanical properties of CdS nanowires are directly correlated with their structure, as imaged by in situ TEM.

  J Ai , Y Wang , J. A Dar , J Liu , L Liu , J. B Nelson and Z. Wang
 

The development of castration-resistant prostate cancer (PCa) requires that under castration conditions, the androgen receptor (AR) remains active and thus nuclear. Heat shock protein 90 (Hsp90) plays a key role in androgen-induced and -independent nuclear localization and activation of AR. Histone deacetylase 6 (HDAC6) is implicated, but has not been proven, in regulating AR activity via modulating Hsp90 acetylation. Here, we report that knockdown of HDAC6 in C4-2 cells using short hairpin RNA impaired ligand-independent nuclear localization of endogenous AR and inhibited PSA expression and cell growth in the absence or presence of dihydrotestosterone (DHT). The dose-response curve of DHT-stimulated C4-2 colony formation was shifted by shHDAC6 such that approximately 10-fold higher concentration of DHT is required, indicating a requirement for HDAC6 in AR hypersensitivity. HDAC6 knockdown also inhibited C4-2 xenograft tumor establishment in castrated, but not in testes-intact, nude mice. Studies using HDAC6-deficient mouse embryonic fibroblasts cells showed that inhibition of AR nuclear localization by HDAC6 knockdown can be largely alleviated by expressing a deacetylation mimic Hsp90 mutant. Taken together, our studies suggest that HDAC6 regulates AR hypersensitivity and nuclear localization, mainly via modulating HSP90 acetylation. Targeting HDAC6 alone or in combination with other therapeutic approaches is a promising new strategy for prevention and/or treatment of castration-resistant PCa.

  G Yao , M Yin , J Lian , H Tian , L Liu , X Li and F. Sun
 

Many members of the TGF-β superfamily are indicated to play important roles in ovarian follicular development, such as affecting granulosa cell function and oocyte maturation. Abnormalities associated with TGF-β1 signaling transduction could result in female infertility. MicroRNAs (miRNAs), as small noncoding RNAs, were recently found to regulate gene expression at posttranscriptional levels. However, little is known about the role of miRNAs in TGF-β-mediated granulosa cell proliferation and granulosa cell function. In this study, the miRNA expression profiling was identified from TGF-β1-treated mouse preantral granulosa cells (GCs), and three miRNAs were found to be significantly up-regulated and 13 miRNAs were down-regulated. Among up-regulated miRNAs, miR-224 was the second most significantly elevated miRNA. This up-regulation was attenuated by treatment of GCs with SB431542 (an inhibitor of TGFβ superfamily type I receptors, thus blocking phosphorylation of the downstream effectors Smad2/3), indicating that miR-224 expression was regulated by TGF-β1/Smads pathway. The ectopic expression of miR-224 can enhance TGF-β1-induced GC proliferation through targeting Smad4. Inhibition of endogenous miR-224 partially suppressed GC proliferation induced by TGF-β1. In addition, both miR-224 and TGF-β1 can promote estradiol release from GC, at least in part, through increasing CYP19A1 mRNA levels. This is the first demonstration that miRNAs can control reproductive functions resulting in promoting TGF-β1-induced GC proliferation and ovarian estrogen release. Such miRNA-mediated effects could be potentially used for regulation of reproductive processes or for treatment of reproductive disorders.

  Z Meng , Y Wang , L Wang , W Jin , N Liu , H Pan , L Liu , L Wagman , B. M Forman and W. Huang
 

Liver repair is key to resuming homeostasis and preventing fibrogenesis as well as other liver diseases. Farnesoid X receptor (FXR, NR1H4) is an emerging liver metabolic regulator and cell protector. Here we show that FXR is essential to promote liver repair after carbon tetrachloride (CCl4)-induced injury. Expression of hepatic FXR in wild-type mice was strongly suppressed by CCl4 treatment, and bile acid homeostasis was disrupted. Liver injury was induced in both wild-type and FXR–/– mice by CCl4, but FXR–/– mice had more severe defects in liver repair than wild-type mice. FXR–/– livers had a decreased peak of regenerative DNA synthesis and reduced induction of genes involved in liver regeneration. Moreover, FXR–/– mice displayed increased mortality and enhanced hepatocyte deaths. During the early stages of liver repair after CCl4 treatment, we observed overproduction of TNF and a strong decrease of phosphorylation and DNA-binding activity of signal transducer and activator of transcription 3 in livers from FXR–/– mice. Exogenous expression of a constitutively active signal transducer and activator of transcription 3 protein in FXR–/– liver effectively reduced hepatocyte death and liver injury after CCl4 treatment. These results suggest that FXR is required to regulate normal liver repair by promoting regeneration and preventing cell death.

  L Liu , J Hou , J Du , R. S Chumanov , Q Xu , Y Ge , J. A Johnson and R. M. Murphy
 

Tg2576 mice produce high levels of beta-amyloid (Aβ) and develop amyloid deposits, but lack neurofibrillary tangles and do not suffer the extensive neuronal cell loss characteristic of Alzheimer's disease. Protection from Aβ toxicity has been attributed to up-regulation of transthyretin (TTR), a normal component of plasma and cerebrospinal fluid. We compared the effect of TTR purified from human plasma (pTTR) with that produced recombinantly (rTTR) on Aβ aggregation and toxicity. pTTR slowed Aβ aggregation but failed to protect primary cortical neurons from Aβ toxicity. In contrast, rTTR accelerated aggregation, while effectively protecting neurons. This inverse correlation between Aβ aggregation kinetics and toxicity is consistent with the hypothesis that soluble intermediates rather than insoluble fibrils are the most toxic Aβ species. We carried out a detailed comparison of pTTR with rTTR to ascertain the probable cause of these different effects. No differences in secondary, tertiary or quaternary structure were detected. However, pTTR differed from rTTR in the extent and nature of modification at Cys10. We hypothesize that differential modification at Cys10 regulates TTR's effect on Aβ aggregation and toxicity.

  M. Q Zheng , K Tang , M. C Zimmerman , L Liu , B Xie and G. J. Rozanski
 

-Glutamyl transpeptidase (-GT) is a key enzyme in GSH metabolism that regulates intracellular GSH levels in response to extracellular GSH (GSHo). The objective of this study was to identify the role of -GT in reversing pathogenic K+ channel remodeling in the diseased heart. Chronic ventricular dysfunction was induced in rats by myocardial infarction (MI), and studies were done after 6–8 wk. Biochemical assays of tissue extracts from post-MI hearts revealed significant increases in -GT activity in left ventricle (47%) and septum (28%) compared with sham hearts, which paralleled increases in protein abundance and mRNA. Voltage-clamp studies of isolated left ventricular myocytes from post-MI hearts showed that downregulation of transient outward K+ current (Ito) was reversed after 4–5 h by 10 mmol/l GSHo or N-acetylcysteine (NACo), and that the effect of GSHo but not NACo was blocked by the -GT inhibitors, acivicin or S-hexyl-GSH. Inhibition of -glutamylcysteine synthetase by buthionine sulfoximine did not prevent upregulation of Ito by GSHo, suggesting that intracellular synthesis of GSH was not directly involved. However, pretreatment of post-MI myocytes with an SOD mimetic [manganese (III) tetrapyridylporphyrin] and catalase completely blocked recovery of Ito by GSHo. Confocal microscopy using the fluorogenic dye 2',7'-dichlorodihydrofluorescein diacetate confirmed that GSHo increased reactive oxygen species (ROS) generation by post-MI myocytes and to a lesser extent in myocytes from sham hearts. Furthermore, GSHo-mediated upregulation of Ito was blocked by inhibitors of tyrosine kinase (genistein, lavendustin A, and AG1024) and thioredoxin reductase (auranofin and 13-cis-retinoic acid). These data suggest that GSHo elicits -GT- and ROS-dependent transactivation of tyrosine kinase signaling that upregulates K+ channel activity or expression via redox-mediated mechanisms. The signaling events stimulated by -GT catalysis of GSHo may be a therapeutic target to reverse pathogenic electrical remodeling of the failing heart.

  L Xiao , J. N Rao , T Zou , L Liu , T. X Yu , X. Y Zhu , J. M Donahue and J. Y. Wang
 

Intestinal epithelium is a rapidly self-renewing tissue in the body, and its homeostasis is tightly regulated by numerous factors including polyamines. Decreased levels of cellular polyamines increase activating transcription factor (ATF)-2, but the exact role and mechanism of induced ATF-2 in the regulation of intestinal epithelial cell (IEC) growth remain elusive. Cyclin-dependent kinase (CDK) 4 is necessary for the G1-to-S phase transition during the cell cycle, and its expression is predominantly controlled at the transcription level. Here, we reported that induced ATF-2 following polyamine depletion repressed CDK4 gene transcription in IECs by increasing formation of the ATF-2/JunD heterodimers. ATF-2 formed complexes with JunD as measured by immunoprecipitation using the ATF-2 and JunD antibodies and by glutathione S-transferase (GST) pull-down assays using GST-ATF-2 fusion proteins. Studies using various mutants of GST-ATF-2 revealed that formation of the ATF-2/JunD dimers depended on the COOH-terminal basic region-leucine zipper domain of ATF-2. Polyamine depletion increased ATF-2/JunD complex and inhibited CDK4 transcription as indicated by a decrease in the levels of CDK4-promoter activity and its mRNA. ATF-2 silencing not only prevented inhibition of CDK4 transcription in polyamine-deficient cells but also abolished repression of CDK4 expression induced by ectopic JunD overexpression. ATF-2 silencing also promoted IEC growth in polyamine-depleted cells. These results indicate that induced ATF-2/JunD association following polyamine depletion represses CDK4 transcription, thus contributing to the inhibition of IEC growth.

  M. T Howes , M Kirkham , J Riches , K Cortese , P. J Walser , F Simpson , M. M Hill , A Jones , R Lundmark , M. R Lindsay , D. J Hernandez Deviez , G Hadzic , A McCluskey , R Bashir , L Liu , P Pilch , H McMahon , P. J Robinson , J. F Hancock , S Mayor and R. G. Parton
 

Quantitative ultrastructural analysis and proteomics detail CLIC structure, composition, and function.

  J. F Heneghan , T Mitra Ganguli , L. F Stanish , L Liu , R Zhao and A. R. Rittenhouse
 

In superior cervical ganglion (SCG) neurons, stimulation of M1 receptors (M1Rs) produces a distinct pattern of modulation of N-type calcium (N-) channel activity, enhancing currents elicited with negative test potentials and inhibiting currents elicited with positive test potentials. Exogenously applied arachidonic acid (AA) reproduces this profile of modulation, suggesting AA functions as a downstream messenger of M1Rs. In addition, techniques that diminish AA's concentration during M1R stimulation minimize N-current modulation. However, other studies suggest depletion of phosphatidylinositol-4,5-bisphosphate during M1R stimulation suffices to elicit modulation. In this study, we used an expression system to examine the physiological mechanisms regulating modulation. We found the β subunit (CaVβ) acts as a molecular switch regulating whether modulation results in enhancement or inhibition. In human embryonic kidney 293 cells, stimulation of M1Rs or neurokinin-1 receptors (NK-1Rs) inhibited activity of N channels formed by CaV2.2 and coexpressed with CaVβ1b, CaVβ3, or CaVβ4 but enhanced activity of N channels containing CaVβ2a. Exogenously applied AA produced the same pattern of modulation. Coexpression of CaVβ2a, CaVβ3, and CaVβ4 recapitulated the modulatory response previously seen in SCG neurons, implying heterogeneous association of CaVβ with CaV2.2. Further experiments with mutated, chimeric CaVβ subunits and free palmitic acid revealed that palmitoylation of CaVβ2a is essential for loss of inhibition. The data presented here fit a model in which CaVβ2a blocks inhibition, thus unmasking enhancement. Our discovery that the presence or absence of palmitoylated CaVβ2a toggles M1R- or NK-1R–mediated modulation of N current between enhancement and inhibition identifies a novel role for palmitoylation. Moreover, these findings predict that at synapses, modulation of N-channel activity by M1Rs or NK-1Rs will fluctuate between enhancement and inhibition based on the presence of palmitoylated CaVβ2a.

 
 
 
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