Regulation of Pro-Apoptotic Bax and Trail Gene Expressions by H5N1 in Madin-Darby Canine Kidney (Mdck) Cell Line

Avian influenza virus (AIV) A H5N1 is able to cause zoonosis with high morbidity and mortality. Several studies suggested the regulation of cellular apoptosis for virus survival by influenza viruses. This sheds light on the development of antivirals that can improve cellular apoptosis to fight influenza infections. This study aimed to investigate the regulation of pro-apoptotic gene expressions by H5N1 in MDCK cells. The H5N1 infection (102.67TCID50/ml) was performed for 8, 24, 48, 72, 96 and 120 hours. Upon incubation, the percentage of cell death, DNA fragmentation and pro-apoptotic gene expressions i.e. Bax, TRAIL, Caspase 3 (Cas3) and 8 (Cas8), and Fas-ligand (FasL) were determined. The degree of DNA laddering and pro-apoptotic gene expressions were determined on agarose gels. The results indicated that severe cytopathic effects (CPE) caused by H5N1 appeared as early as 24 hour post-infection (hpi) meanwhile a significant cell death was observed starting at 48 hpi. However, DNA laddering was not observed in both of the control and infected DNA samples. Downregulation of Bax gene expression was recorded at 24 -72 hpi and a total suppression was observed at 96 and 120 hpi. Similarly, a significant decrease in the TRAIL gene expression was observed at 48-120 hpi. On the contrary, the expressions of Cas3, Cas8 and FasL genes were not detected in the mock and infected samples. Conclusively, this study suggested that H5N1 might downregulate cellular apoptosis prematurely for viral survival which can be a target cellular mechanism for newly developed antivirals to combat H5N1 infections

ALTERNATIVE SPLICING OF mRNA TRAIL REGULATES APOPTOSIS IN THE GLIOBLASTOMA MULTIFORME T-98G CELL LINE

Objective: This is an in vitro experimental study designed to analyze the role of alternative splicing of mRNA in the apoptotic process of the cancer cells. Here we induced apoptosis in the glioblastoma multiforme (GBM) T-98G cell line to obtain a better understanding in the regulation of mRNA expression of the soluble Tumor Necrosis factor-related Apoptosis-Inducing Ligand (sTRAIL) gene. Methods: Cells were induced to undergo apoptosis by treatment with rotenone at 10, 20 and 40 µM for 6 h. Dimethylsulphoxide (DMSO) was used to dissolve rotenone and as a negative control. The morphology of the GBM-T98G cells was viewed with an inverted microscope. DNA, RNA and protein extractions were performed to analyse apoptotic DNA fragmentation by a DNA laddering assay, a quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) for TRAIL mRNA expression and ELISA for caspase-9 protein expression. Electrophoresis was also performed on TRAIL complementary DNA (cDNA) produced from TRAIL qRT-PCR mRNA. Results: Nucleosomal DNA degradation was confirmed by DNA laddering, whereas the TRAIL melting curve and the cDNA electrophoresis showed a shift in the balance of the TRAIL mRNA isoform to the pro-apoptotic mRNA isoform, in conjunction with a significant increase in expression of TRAIL mRNA and caspase-9 protein. Conclusion: These findings indicate the regulation of apoptotic events at the level of TRAIL mRNA expression, as indicated by the shift in the balance of mRNA expression of the TRAIL isoform towards the pro-apoptotic isoform.

Sensitization of breast cancer cells to doxorubicin via stable cell line generation and overexpression of DFF40

There are a number of reports demonstrating a relationship between the alterations in DFF40 expression and development of some cancers. Here, increased DFF40 expression in T-47D cells in the presence of doxorubicin was envisaged for therapeutic usage. The T-47D cells were transfected with an eukaryotic expression vector encoding the DFF40 cDNA. Following incubation with doxorubicin, propidium iodide (PI) staining was used for cell cycle distribution analysis. The rates of apoptosis were determined by annexin V/PI staining. Apoptosis was also evaluated using the DNA laddering analysis. The viability of DFF40-transfected cells incubated with doxorubicin was significantly decreased compared with control cells. However, there were no substantial changes in the cell cycle distribution of pIRES2-DFF40 cells incubated with doxorubicin compared to control cells. The expression of DFF40, without doxorubicin incubation, had also no significant effect on the cell cycle distribution. There was no DNA laddering in cells transfected with the empty pIRES2 vector when incubated with doxorubicin. In contrast, DNA laddering was observed in DFF40 transfected cells in the presence of doxorubicin after 48 h. Also, the expression of DFF40 and DFF45 was increased in DFF40 transfected cells in the presence of doxorubicin enhancing cell death. Collectively our results indicated that co-treatment of DFF40-transfected cells with doxorubicin can enhance the killing of these tumor cells via apoptosis. Thus, modulation of DFF40 level may be a beneficial strategy for treatment of chemo-resistant cancers.

Engineered cellular gene-replacement platform for selective and inducible proteolytic profiling

Cellular demolition during apoptosis is completed by executioner caspases, that selectively cleave more than 1,500 proteins but whose individual roles are challenging to assess. Here, we used an optimized site-specific and inducible protease to examine the role of a classic apoptotic node, the caspase-activated DNase (CAD). CAD is activated when caspases cleave its endogenous inhibitor ICAD, resulting in the characteristic DNA laddering of apoptosis. We describe a posttranscriptional gene replacement (PTGR) approach where endogenous biallelic ICAD is knocked down and simultaneously replaced with an engineered allele that is susceptible to inducible cleavage by tobacco etch virus protease. Remarkably, selective activation of CAD alone does not induce cell death, although hallmarks of DNA damage are detected in human cancer cell lines. Our data strongly support that the highly cooperative action of CAD and inhibition of DNA repair systems are critical for the DNA laddering phenotype in apoptosis. Furthermore, the PTGR approach provides a general means for replacing wild-type protein function with a precisely engineered mutant at the transcriptional level that should be useful for cell engineering studies.

Baicalein Protects Cardiomyocytes Against Mitochondrial Oxidant Injury Associated with JNK Inhibition and Mitochondrial Akt Activation

Baicalein, a flavonoid derived from Scutellaria baicalensis Georgi, possesses cardioprotection against oxidant injury by scavenging reactive oxygen species (ROS). Few studies investigate whether baicalein protection is mediated by attenuating mitochondrial ROS and modulating the prosurvival and proapoptotic signaling. Primary cultured chick cardiomyocytes were used to study the role of baicalein in mitochondrial superoxide [Formula: see text] generation and signaling of Akt and JNK. Cells were exposed to H 2 O 2 for 2 h and baicalein was given 2 h prior to and during 2 h of H 2 O 2 exposure. Cell viability was assessed by propidium iodide and DNA fragmentation. H 2 O 2 (500 μM) significantly induced 45.3 ± 6.2% of cell death compared to the control (p < 0.001) and resulted in DNA laddering. Baicalein (10, 25 or 50 μM) dose-dependently reduced the cell death to 38.7 ± 5.6% (p = 0.226); 31.2 ± 3.9% (p < 0.01); 30.3 ± 5.3% (p < 0.01), respectively. It also attenuated DNA laddering. Further, baicalein decreased intracellular ROS and mitochondrial [Formula: see text] generation that was confirmed by superoxide dismutase PEG-SOD and mitochondria electron transport chain complex III inhibitor stigmatellin. In addition, baicalein increased Akt phosphorylation and decreased JNK phosphorylation in H 2 O 2-exposed cells. Moreover, baicalein augmented mitochondrial phosphorylation of Akt Thr308 and GSK3β Ser9, and prevented mitochondrial cytochrome c release assessed by cellular fractionation. Our results suggest that baicalein cardioprotection may involve an attenuation of mitochondrial [Formula: see text] and an increase in mitochondrial phosphorylation of Akt and GSK3β while decreasing JNK activation.

Synthesis and Cytotoxic Activity of Methyl Glycyrrhetinate Esterified with Amino Acids

Methyl glycyrrhetinate was esterified at position C3 of ring A using different amino acids. A short, unbranched chain of four carbon atoms with two amino groups in positions 2 and 4 was shown to be the most active compound of this series (IC50 = 0:8 M on liposarcoma Lipo cells). These compounds trigger apoptosis as shown by an acridine orange/ethidium bromide assay, trypan blue tests and DNA laddering experiments.

Mitochondrial-Mediated Apoptosis by the Sesquiterpene Oil α-Bisabolol and Its Synergism with Imatinib and Nilotinib In BCR-ABL+ Cells

Abstract 4456 Background. The plant-derived agent α-bisabolol is a small oily sesquiterpene alcohol that has been demonstrated to be cytotoxic against human malignant non-hematological and leukemic cells (Bonifacio M et al, Blood, 2009 ASH annual meeting abstracts;114:4800). Here we tested its activity against BCR-ABL+ cell lines and primary cells from patients, alone or in combination with the Tyrosine-Kinase Inhibitors (TKIs) Imatinib and Nilotinib. Also, the mechanism of α-bisabolol cytotoxicity in BCR-ABL+ cells was assessed. Methods. We used the BCR-ABL+ K562, LAMA-84 and CML-T1 cell lines and primary leukemic cells from 14 patients with BCR-ABL+ Acute Lymphoblastic Leukemia at diagnosis. First, the citotoxicity of single-agent α-bisabolol was determined by MTT. Then, mitochondrial membrane potential of treated cells was evaluated by the JC-1 dye in flow cytometry and fluorescence microscopy. Permeabilized leukemic cells were assayed for oxygen consumption by measuring mitochondrial state 3 and uncoupled respiration. Reactive oxygen species (ROS) production in α-bisabolol treated cells were quantified in flow cytometry by oxidation of CM-H2DCFDA, measuring the fluorescence intensity of the DCF products. Apoptosis was studied by the poly(ADP-ribose) polymerase (PARP) cleavage and internucleosomal DNA laddering analysis. Finally, the combination effects between α-bisabolol and Imatinib or Nilotinib (kindly provided by Novartis) were analyzed according to the median-effect method of Chou and Talalay using the CalcuSyn software. Results. α-bisabolol reduced the viability of BCR-ABL+ cells in a dose-dependent manner. The mean IC50 values of α-bisabolol were 46±11 μ M for primary leukemic cells and ranged from 62 to 115 μ M in the cell lines. JC-1 staining of BCR-ABL+ primary leukemic cells treated with 40 μ M α-bisabolol for 3 to 5 hours demonstrated a dissipation of the mitochondrial transmembrane potential (ΔΨm), thus indicating the start of the apoptotic process. Moreover, NADH-supported state 3 respiration in α-bisabolol treated leukemic cells was significantly decreased in comparison with untreated leukemic controls (140.0±70.5 vs 280.7±11.9 pmol O2/min/106 cells; p<.05). Finally, PARP cleavage and DNA laddering followed α-bisabolol exposure of leukemic BCR-ABL+ blasts. The apoptosis induction was accompanied by ROS production. When tested in combination at constant ratio with Imatinib or Nilotinib, α-bisabolol showed overall slight to strong synergistic effects, without evidence for antagonism across a range of doses (Table 1). In 3 patients with mutation of BCR-ABL (T315I, E255V and Y253H, respectively) we observed full activity of α-bisabolol as single agent and confirmed the synergism between α-bisabolol and Imatinib. Conclusion. This study indicates that α-bisabolol is an effective pro-apoptotic agent for human acute BCR-ABL+ leukemia cells via induction of mitochondrial membrane damage. The combination of α-bisabolol with Imatinib or Nilotinib allows a dose reduction up to 90% of each drug to obtain the same cytotoxic effect, so indicating a clear synergism. α-bisabolol may be a potential candidate for the treatment of BCR-ABL+ leukemias and the effective dose of TKIs could be reduced in a combined treatment with α-bisabolol. Disclosures: No relevant conflicts of interest to declare.