Yong Huang

Porcine epidemic diarrhea virus N protein prolongs S-phase cell cycle, induces endoplasmic reticulum stress, and up-regulates interleukin-8 expression.

n Abstractn n Porcine epidemic diarrhea (PED) is an acute and highly contagious enteric disease of swine caused by porcine epidemic diarrhea virus (PEDV). The porcine intestinal epithelial cell is the PEDV target cell. In this study, we established a porcine intestinal epithelial cell (IEC) line which can stably express PEDV N protein. We also investigate the subcellular localization and function of PEDV N protein by examining its effects on cell growth, cycle progression, interleukin-8 (IL-8) expression, and survival. The results show that the PEDV N protein localizes in the endoplasmic reticulum (ER), inhibits the IEC growth and prolongs S-phase cell cycle. The S-phase is prolonged which is associated with a decrease of cyclin A transcription level and an increase of cyclin A degradation. The IEC expressing PEDV N protein can express higher levels of IL-8 than control cells. Further studies show that PEDV N protein induces ER stress and activates NF-κB, which is responsible for the up-regulation of IL-8 and Bcl-2 expression. This is the first report to demonstrate that PEDV N protein can induce cell cycle prolongation at the S-phase, ER stress and up-regulation interleukin-8 expression. These findings provide novel information on the function of the PEDV N protein and are likely to be very useful in understanding the molecular mechanisms responsible for PEDV pathogenesis.n n

Swainsonine Activates Mitochondria-mediated Apoptotic Pathway in Human Lung Cancer A549 Cells and Retards the Growth of Lung Cancer Xenografts

Swainsonine (1, 2, 8-trihyroxyindolizidine, SW), a natural alkaloid, has been reported to exhibit anti-cancer activity on several mouse models of human cancer and human cancers in vivo. However, the mechanisms of SW-mediated tumor regression are not clear. In this study, we investigated the effects of SW on several human lung cancer cell lines in vitro. The results showed that SW significantly inhibited these cells growth through induction of apoptosis in different extent in vitro. Further studies showed that SW treatment up-regulated Bax, down-regulated Bcl-2 expression, promoted Bax translocation to mitochondria, activated mitochondria-mediated apoptotic pathway, which in turn caused the release of cytochrome c, the activation of caspase-9 and caspase-3, and the cleavage of poly (ADP-ribose) polymerase (PARP), resulting in A549 cell apoptosis. However, the expression of Fas, Fas ligand (FasL) or caspase-8 activity did not appear significant changes in the process of SW-induced apoptosis. Moreover, SW treatment inhibited Bcl-2 expression, promoted Bax translocation, cytochrome c release and caspase-3 activity in xenograft tumor cells, resulting in a significant decrease of tumor volume and tumor weight in the SW-treated xenograft mice groups in comparison to the control group. Taken together, this study demonstrated for the first time that SW inhibited A549 cancer cells growth through a mitochondria-mediated, caspase-dependent apoptotic pathway in vitro and in vivo.

Development of multiplex PCR for simultaneous detection of six swine DNA and RNA viruses.

Uniplex and multiplex reverse transcription-polymerase chain reaction (RT-PCR) and PCR protocols were developed and evaluated subsequently for its effectiveness in detecting simultaneously single and mixed infections in swine. Specific primers for three DNA viruses and three RNA viruses, including classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), Japanese encephalitis virus (JEV), porcine circovirus type 2 (PCV2), porcine pseudorabies virus (PRV) and porcine parvovirus (PPV) were used for testing procedure. A single nucleic acid extraction protocol was adopted for the simultaneous extraction of both RNA and DNA viruses. The multiplex PCR consisted with two-step procedure which included reverse transcription of RNA virus and multiplex PCR of viral cDNA and DNA. The multiplex PCR assay was shown to be sensitive detecting at least 450pg of viral genomic DNA or RNA from a mixture of six viruses in a reaction. The assay was also highly specific in detecting one or more of the same viruses in various combinations in specimens. Thirty clinical samples and aborted fetuses collected from 4- to 12-week-old piglets were detected among 39 samples tested by both uniplex and multiplex PCR, showing highly identification. Because of the sensitivity and specificity, the multiplex PCR is a useful approach for clinical diagnosis of mixed infections of DNA and RNA viruses in swine.

Porcine epidemic diarrhea virus E protein causes endoplasmic reticulum stress and up-regulates interleukin-8 expression

BackgroundPorcine epidemic diarrhea virus (PEDV) is an important pathogen in swine and is responsible for substantial economic losses. Previous studies suggest that the PEDV E protein plays an important role in the viral assembly process. However, the subcellular localization and other functions of PEDV E protein still require more research.MethodsThe subcellular localization and function of PEDV E protein were investigated by examining its effects on cell growth, cell cycle progression, interleukin-8 (IL-8) expression and cell survival.ResultsThe results show that plenty of PEDV E protein is localized in the ER, with small quantities localized in the nucleus. The PEDV E protein has no effect on the intestinal epithelial cells (IEC) growth, cell cycle and cyclin A expression. The cells expressing PEDV E protein express higher levels of IL-8 than control cells. Further studies show that PEDV E protein induced endoplasmic reticulum (ER) stress and activated NF-κB which is responsible for the up-regulation of IL-8 and Bcl-2 expression.ConclusionsThis study shows that the PEDV E protein is localized in the ER and the nucleus and it can cause ER stress. The PEDV E protein had no effect on the IEC growth and cell cycle. In addition, the PEDV E protein is able to up-regulate IL-8 and Bcl-2 expression.

Transmissible gastroenteritis virus infection induces apoptosis through FasL- and mitochondria-mediated pathways

n Abstractn n Transmissible gastroenteritis virus (TGEV) has been reported to induce apoptosis in swine testis (ST) cells. However, the mechanisms underlying TGEV-induced apoptosis are still unclear. In this study we observed that TGEV infection induced apoptosis in porcine kidney (PK-15) cells in a time- and dose-dependent manner. TGEV infection up-regulated FasL, activated FasL-mediated apoptotic pathway, leading to activation of caspase-8 and cleavage of Bid. In addition, TGEV infection down-regulated Bcl-2, up-regulated Bax expression, promoted translocation of Bax to mitochondria, activated mitochondria-mediated apoptotic pathway, which in turn caused the release of cytochrome c and the activation of caspase-9. Both extrinsic and intrinsic pathways activated downstream effector caspase-3, followed by the cleavage of PARP, resulting in cell apoptosis. Moreover, TGEV infection did not induce significant DNA fragmentation in ammonium chloride (NH4Cl) pretreated PK-15 cells or cells infected with UV-inactivated TGEV. In turn, block of caspases activation also did not affect TGEV replication. Taken together, this study demonstrates that TGEV-induced apoptosis is dependent on viral replication in PK-15 cells and occurs through activation of FasL- and mitochondria-mediated apoptotic pathways.n n

TGEV nucleocapsid protein induces cell cycle arrest and apoptosis through activation of p53 signaling.

n Abstractn n Our previous studies showed that TGEV infection could induce cell cycle arrest and apoptosis via activation of p53 signaling in cultured host cells. However, it is unclear which viral gene causes these effects. In this study, we investigated the effects of TGEV nucleocapsid (N) protein on PK-15 cells. We found that TGEV N protein suppressed cell proliferation by causing cell cycle arrest at the S and G2/M phases and apoptosis. Characterization of various cellular proteins that are involved in regulating cell cycle progression demonstrated that the expression of N gene resulted in an accumulation of p53 and p21, which suppressed cyclin B1, cdc2 and cdk2 expression. Moreover, the expression of TGEV N gene promoted translocation of Bax to mitochondria, which in turn caused the release of cytochrome c, followed by activation of caspase-3, resulting in cell apoptosis in the transfected PK-15 cells following cell cycle arrest. Further studies showed that p53 inhibitor attenuated TGEV N protein induced cell cycle arrest at S and G2/M phases and apoptosis through reversing the expression changes of cdc2, cdk2 and cyclin B1 and the translocation changes of Bax and cytochrome c induced by TGEV N protein. Taken together, these results demonstrated that TGEV N protein might play an important role in TGEV infection-induced p53 activation and cell cycle arrest at the S and G2/M phases and apoptosis occurrence.n n

Evidence for different patterns of natural inter-genotype recombination between two PCV2 parental strains in the field

Co-infection with different virus strains is a precondition for genome recombination, which give rise to continuous evolution of porcine circovirus type 2 (PCV2). In the present study, 32 PCV2 positive clinical samples from the diseased and dead pigs were identified by classic PCR. 15 of 32 (46.8%) clinical samples were identified as infection with both PCV2a and PCV2b using genotype-specific PCR. 13/15 of PCV2 strains were identified as recombinants using sequencing analysis, phylogenetic analysis, recombination detection program and base-by-base comparison. Further analyses of the full-length sequences of these strains suggest that the natural recombination events occurred between strains DQ104423 (PCV2a) and AY579893 (PCV2b), yield two new recombinant clusters through different recombination patterns with crossover regions located in ORF2. Recombinant cluster 1 included 3 strains, and recombinant cluster 2 included 10 strains. These results demonstrate that recombination between PCV2a and PCV2b strains can occur in cap protein coding region through different patterns and yield different recombinants. Our study not only provided new evidences that PCV2 strains can undergo recombination through a variety of patterns, but also suggests that recombination events easily occur in the co-existence of different strains of PCV2.

Establishment and evaluation of a stable steroidogenic caprine luteal cell line

Many physiological, biological, pharmacologic, and toxicologic events and compounds affect the function of Saanen dairy goat luteal cells, resulting in implantation failure or early embryonic loss. Although primary luteal cell cultures have been used, their finite lifespan precludes assessment of long-term effects. In the present study, primary caprine luteal cells (CLCs) were immortalized through transfection of a plasmid containing the human telomerase reverse transcriptase (hTERT) gene. The expression of hTERT and telomerase activity were evaluated in transduced CLCs (hTERT-CLCs). In this study, these cells steadily expressed hTERT gene and exhibited higher telomerase activity at Passages 30 and 50. The hTERT-CLCs at Passages 30 and 50 expressed genes encoding key proteins, enzymes and receptors inherent to normal luteal cells, e.g., steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), 3β-hydroxysteroid dehydrogenase (3β-HSD), and LH-receptor (LH-R). In addition, immortalized caprine luteal cells produced detectable quantities of progesterone in response to 8-bromo-cAMP (8-Br-cAMP) or 22(R)-hydroxycholesterol (22R-HC) stimulation. Furthermore, this cell line appeared to proliferate more quickly than control cells, although no neoplastic transformation occurred either in vivo or in vitro. We concluded the immortalized CLCs by hTERT retained their original characteristics and may provide a useful model to study luteal cell functions.

Anti-proliferation of breast cancer cells with itraconazole: Hedgehog pathway inhibition induces apoptosis and autophagic cell death.

Itraconazole is a common antifungal which may have promise for treating various human cancers. We report that itraconazole was cytotoxic to MCF-7 and SKBR-3 breast cancer cell lines via apoptosis by altering mitochondria membrane potential, reducing BCL-2 expression and elevating caspase-3 activity. Itraconazole also induced autophagic cell death via LC3-II expression upregulation, P62/SQSTM1 degradation, autophagosome formation and increases in autophagic puncta. Itraconazole treatment inhibited hedgehog pathway key molecular expression, such as SHH and Gli1, resulting in promotion of apoptosis and autophagy. The anti-proliferation effect of itraconazole-induced apoptosis and autophagy via hedgehog pathway inhibition was confirmed with Gli1 inhibitor GANT61 and SHH siRNA, GANT61 and SHH siRNA synergistically enhanced cytotoxicity induced by itraconazole. A human xenograft nude mouse model corroborated the anti-breast cancer activity as evidenced by reduced tumor size, and increased tumor tissue apoptosis and autophagy. Thus, itraconazole has a potent anti-breast cancer activity that may be improved when combined with hedgehog pathway inhibitors.

Porcine circovirus type 2 activates PI3K/Akt and p38 MAPK pathways to promote interleukin-10 production in macrophages via Cap interaction of gC1qR

Porcine circovirus type 2 (PCV2) infection caused PCV2-associated diseases (PCVAD) is one of the major emerging immunosuppression diseases in pig industry. In this study, we investigated how PCV2 inoculation increases interleukin (IL)-10 expression in porcine alveolar macrophages (PAMs). PCV2 inoculation significantly upregulated IL-10 expression compared with PCV1. Upon initial PCV2 inoculation, PI3K/Akt cooperated with NF-κB pathways to promote IL-10 transcription via p50, CREB and Ap1 transcription factors, whereas inhibition of PI3K/Akt activation blocked Ap1 and CREB binding to the il10 promoter, and decreased the binding level of NF-κB1 p50 with il10 promoter, leading to great reduction in early IL-10 transcription. In the later phase of inoculation, PCV2 further activated p38 MAPK and ERK pathways to enhance IL-10 production by promoting Sp1 binding to the il10 promoter. For PCV2-induced IL-10 production in macrophages, PCV2 capsid protein Cap, but not the replicase Rep or ORF3, was the critical component. Cap activated PI3K/Akt, p38 MAPK, and ERK signaling pathways to enhance IL-10 expression. In the whole process, gC1qR mediated PCV2-induced PI3K/Akt and p38 MAPK activation to enhance IL-10 induction by interaction with Cap. Depletion of gC1qR blocked PI3K/Akt and p38 MAPK activation, resulting in significant decrease in IL-10 production in PCV2-inoculated cells. Thus, gC1qR might be a critical functional receptor for PCV2-induced IL-10 production. Taken together, these data demonstrated that Cap protein binding with host gC1qR induction of PI3K/Akt and p38 MAPK signalings activation is a critical process in enhancing PCV2-induced IL-10 production in porcine alveolar macrophages.