Bip overexpression, but not CHOP inhibition, attenuates fatty-acid-induced endoplasmic reticulum stress and apoptosis in HepG2 liver cells

AIMS

In this study we investigated whether attenuation of endoplasmic reticulum stress (ER stress) could protect HepG2 cells from free fatty acid (FFA)-induced apoptosis.

MAIN METHODS

Human liver cell line HepG2 cells were exposed to Sodium Palmitate (Pa) or Sodium Oleate (Ol). Apoptosis and ER stress of HepG2 cells were analyzed with flow cytometry, real-time RT-PCR and Western Blotting. An expression plasmid encoding for the ER chaperone immunoglobulin heavy chain-binding protein (Bip) was transfected into HepG2 cells to attenuate ER stress. Small interfering RNA siCHOP was used to knockdown the expression of C/EBP Homologous Protein (CHOP) in HepG2.

KEY FINDINGS

Pa led to cytotoxicity and apoptosis in HepG2 cells in a dose-dependent pattern and also induced ER stress indicated by increased phosphorylation of eIF2α, upregulation of IRE1α and CHOP. Bip expression levels were slightly down regulated after Pa treatment. The unsaturated fatty acid, Ol, induced neither apoptosis nor ER stress in HepG2 cells. Overexpression of Bip attenuated Pa-induced ER stress and led to a significant reduction in Pa-mediated apoptosis, indicating a requirement of ER stress for lipotoxicity in liver cells. siRNA-mediated reduction of CHOP did not protect against Pa-induced apoptosis.

SIGNIFICANCE

While ER stress makes a necessary contribution to palmitate cytotoxicity, inhibition of CHOP alone is not sufficient to prevent palmitate-induced apoptosis. Our findings could advance the detailed understanding on the mechanism of high fatty acid (FFA)-induced apoptosis.

Engineering a novel self-powering electrochemical biosensor

This paper records the efforts of a multi-disciplinary team of undergraduate students from Glasgow University to collectively design and carry out a 10 week project in Synthetic Biology as part of the international Genetic Engineered Machine competition (iGEM). The aim of the project was to design and build a self-powering electrochemical biosensor called ‘ElectrEcoBlu’. The novelty of this engineered machine lies in coupling a biosensor with a microbial fuel cell to transduce a pollution input into an easily measurable electrical output signal. The device consists of two components; the sensor element which is modular, allowing for customisation to detect a range of input signals as required, and the universal reporter element which is responsible for generating an electrical signal as an output. The genetic components produce pyocyanin, a competitive electron mediator for microbial fuel cells, thus enabling the generation of an electrical current in the presence of target chemical pollutants. The pollutants tested in our implementation were toluene and salicylate. ElectrEcoBlu is expected to drive forward the development of a new generation of biosensors. Our approach exploited a range of state-of-the-art modelling techniques in a unified framework of qualitative, stochastic and continuous approaches to support the design and guide the construction of this novel biological machine. This work shows that integrating engineering techniques with scientific methodologies can provide new insights into genetic regulation and can be considered as a reference framework for the development of biochemical systems in synthetic biology.

Exendin-4 protects pancreatic beta cells from human islet amyloid polypeptide-induced cell damage: potential involvement of AKT and mitochondria biogenesis

AIM

Glucagon-like peptide-1 (GLP-1) stimulates beta-cell proliferation and enhances beta-cell survival, whereas oligomerization of human islet amyloid polypeptide (hIAPP) may induce beta-cell apoptosis and reduce beta-cell mass. Type 2 diabetes is associated with increased expression of IAPP. As GLP-1-based therapy is currently developed as a novel antidiabetic therapy, we examined the potential protective action of the GLP-1 receptor agonist exendin-4 on hIAPP-induced beta-cell apoptosis.

METHODS

The study was performed in clonal insulinoma (INS-1E) cells. Both method of transcriptional and translational and sulphorhodamine B (SRB) assays were used to evaluate cell viability and cell mass. Western blot analysis was applied to detect protein expression. Transfection of constitutively active protein kinase B (PKB/AKT) was performed to examine the role of AKT. Mitochondrial biogenesis was quantified by mitogreen staining and RT-PCR.

RESULTS

First, we confirmed that hIAPP induced cell apoptosis and growth inhibition in INS-1E cells. These effects were partially protected by exendin-4 in association with partial recovery of the hIAPP-mediated AKT inhibition. Furthermore, AKT constitutive activation attenuated hIAPP-induced apoptosis, whereas PI3K/AKT inhibition abrogated exendin-4-mediated effects. These findings suggest that the antiapoptotic and proliferative effects of exendin-4 in hIAPP-treated INS-1E cells were partially mediated through AKT pathway. Moreover, hIAPP induced FOXO1 but inhibited pdx-1 nucleus translocation. These effects were restored by exendin-4. Finally, mitogreen staining and RT-PCR revealed enhanced mitochondrial biogenesis by exendin-4 treatment.

CONCLUSIONS

Collectively, these results suggest that GLP-1 receptor agonist protects beta cells from hIAPP-induced cell death partially through the activation of AKT pathway and improved mitochondrial function.

Site- and branch-specific sialylation of recombinant human interferon-gamma in Chinese hamster ovary cell culture

Since sialic acid content is known to be a critical determinant of the biological properties of glycoproteins, it is essential to characterize and monitor sialylation patterns of recombinant glycoproteins intended for therapeutic use. This study reports site- and branch-specific differences in sialylation of human interferon-gamma (IFN-gamma) derived from Chinese hamster ovary (CHO) cell culture. Sialylation profiles were quantitated by reversed-phase HPLC separations of the site-specific pools of tryptic glycopeptides representing IFN-gamma's two potential N-linked glycosylation sites (i.e., Asn(25) and Asn(97)). Although sialylation at each glycosylation site was found to be incomplete, glycans of Asn(25) were more heavily sialylated than those of Asn(97). Furthermore, Man(alpha1-3) arms of the predominant complex biantennary structures were more favorably sialylated than Man(alpha1-6) branches at each glycosylation site. When the sialylation profile was analyzed throughout a suspension batch culture, sialic acid content at each site and branch was found to be relatively constant until a steady decrease in sialylation was observed coincident with loss of cell viability. The introduction of a competitive inhibitor of sialidase into the culture supernatant prevented the loss of sialic acid after the onset of cell death but did not affect sialylation prior to cell death. This finding indicated that incomplete sialylation prior to loss of cell viability could be attributed to incomplete intracellular sialylation while the reduction in sialylation following loss of cell viability was due to extracellular sialidase activity resulting from cell lysis. Thus, both intracellular and extracellular processes defined the sialic acid content of the final product. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 390-398, 1977.

Influence of Primatone RL supplementation on sialylation of recombinant human interferon-gamma produced by Chinese hamster ovary cell culture using serum-free media

Although serum-free media have been widely used in mammalian cell culture for therapeutic protein production, the effects of serum-substitutes on product quality have not been extensively examined. This study observed an adverse effect of Primatone RL, an animal tissue hydrolysate commonly used as a serum-substitute to promote cell growth, on sialylation of interferon-gamma (IFN-gamma) derived from Chinese hamster ovary (CHO) cell culture in both batch and fed-batch modes. In batch cultures, decreased sialylation was observed at each of the glycosylation sites (i.e., Asn(25) and Asn(97)) of IFN-gamma with the use of elevated concentrations of the peptone. Although poorest sialylation was obtained with the use of a growth-inhibiting concentration of Primatone RL, diminished sialylation was observed at the optimal peptone concentration for cell growth and product yield. Since incubation of the product in Primatone RL-supplemented acellular medium did not result in decreased sialylation, the negative effect of Primatone RL could not be attributed to extracellular desialylation of IFN-gamma by components of the peptone. In the fed-batch mode, a culture utilizing a serum-free feeding medium supplemented with Primatone RL demonstrated poorer sialylation than a similar culture not fed the peptone. The results of both the batch and fed-batch experiments indicate that the adverse effect of the peptone was not due solely to ammonia accumulation. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 353-360, 1997.

Coexpression and Synergistic Role of Multiple Atypical Chemokine Binders in Breast Cancer

Background: The expression and role of Duffy antigen receptor for chemokine (DARC), D6 and ChemoCentryx chemokine receptor (CCX-CKR) in breast cancer have already been studied independently in the past several years. However, the relationship and importance of these atypical chemokine binders (ACB) are still unclear. In this large scale clinical study, we invastigated the characteristics of multiple ACB simultaneously. Material and Methods: The protein levels of DARC, D6 and CCX-CKR were analyzed by immunohistochemistry in 517 patients with invasive breast cancer, 29 patients with noninvasive breast cancer. All of these cases come from the Cancer Hospital of Fudan University during 2001-2006, with complete clinicopathological data and follow-up data, including survival information. Results: In the invasive breast cancer patients, triple, double and single positive expression of these ACB were 135 cases (26.1%), 154 cases (29.8%) and 121 cases (23.4%), respectively. On the other hand, 107 cases (20.7%) were complete negative. The triple positive staining was significantly conversely correlated with lymph node metastasis, disease stage, relapse-free survival (RFS) as well as overall survival (OS). DARC, D6, and CCX-CKR were independent factors that influenced lymph node metastasis and their coexpression was favorable prognostic factor for RFS and OS. Discussion: Our results confirmed that DARC, D6, and CCX-CKR play a negative role in breast cancer. Furthermore, their triple or double high coexpression is more favorable for the patients, suggesting that multiple ACB may provide better protection against metastasis and relapse by synergistically regulating chemokine network in breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4166.

Construction of antisense RNA expression vectors and correction of splicing defect in human beta-globin gene (IVS-2-654 C-->T mutant) in HeLa cells

The antisense fragments, which were available in in vitro system, were cloned into the mammalian expression vector pcDNA3, and were transfected into H654 cells, a mammalian cell line stably expressing the thalassaemic (IVS-2-654 C-->T) human beta-globin gene. In these transfected cells, the level of correctly spliced beta-globin mRNA in total beta-globin mRNA (beta/(beta + beta*)) was improved from 0.07 (0 d) to 0.22 (3 d), and this effect persisted for up to 15 d post transfection. All the results demonstrated that antisense RNAs were able to be transcribed from the antisense fragment expression vectors stably and effectively suppressed aberrant splicing pattern of the mutated beta-globin gene (IVS-2-654 C-->T) and restored correct splicing pathway. This work provided a novel approach with potential clinical significance to gene therapy of this kind of splicing mutants including beta-thalassaemia (IVS-2-654 C-->T) by antisense RNAs.

Infertility and venereal disease in cattle inseminated with semen containing bovine herpesvirus type 5

A group of 20 cows and heifers experienced poor conception rates and probable ovarian dysfunction after being artificially inseminated. When first examined, some showed signs of vulvovaginitis, with pustular, ulcerative lesions consistent with a herpesvirus infection. They had had no contact with bulls during the current breeding season. Bovine herpesvirus type 5 (BHV-5) was isolated from samples of frozen semen from the batch that had been used for the artificial insemination programme. BHV-5 was also isolated from the semen of a second apparently healthy bull during routine screening of its semen.