Characterization of apoptosis induced by sorbitol: a unique system for the detection of antiapoptotic activities of viruses

Metabonomic Study of Biochemical Changes in Human Hair of Heroin Abusers by Liquid Chromatography Coupled with Ion Trap-Time of Flight Mass Spectrometry

Hair analysis is with the advantage of non-invasive collection and long surveillance window. The present study employed a sensitive and reliable liquid chromatography coupled with ion trap-time of flight mass spectrometry method to study the metabonomic characters in the hair of 58 heroin abusers and 72 non-heroin abusers. Results indicated that certain endogenous metabolites, such as sorbitol and cortisol, were accelerated, and the level of arachidonic acid, glutathione, linoleic acid, and myristic acid was decreased in hair of heroin abusers. The metabonomic study is helpful for further understanding of heroin addiction and clinical diagnosis.

Reduction of bacterial adhesion on dental composite resins by silicon-oxygen thin film coatings

Adhesion of bacteria on dental materials can be reduced by modifying the physical and chemical characteristics of their surfaces, either through the application of specific surface treatments or by the deposition of thin film coatings. Since this approach does not rely on the use of drugs or antimicrobial agents embedded in the materials, its duration is not limited by their possible depletion. Moreover it avoids the risks related to possible cytotoxic effects elicited by antibacterial substances released from the surface and diffused in the surrounding tissues. In this work, the adhesion of Streptococcus mutans and Streptococcus mitis was studied on four composite resins, commonly used for manufacturing dental prostheses. The surfaces of dental materials were modified through the deposition of a-SiO(x) thin films by plasma enhanced chemical vapor deposition. The chemical bonding structure of the coatings was analyzed by Fourier-transform infrared spectroscopy. The morphology of the dental materials before and after the coating deposition was assessed by means of optical microscopy and high-resolution mechanical profilometry, while their wettability was investigated by contact angle measurements. The sample roughness was not altered after coating deposition, while a noticeable increase of wettability was detected for all the samples. Also, the adhesion of S. mitis decreased in a statistically significant way on the coated samples, when compared to the uncoated ones, which did not occur for S. mutans. Within the limitations of this study, a-SiO(x) coatings may affect the adhesion of bacteria such as S. mitis, possibly by changing the wettability of the composite resins investigated.

Ethanol influences on Bax associations with mitochondrial membrane proteins in neonatal rat cerebellum

These studies investigated interactions taking place at the mitochondrial membrane in neonatal rat cerebellum following ethanol exposure and focused on interactions between proapoptotic Bax and proteins of the permeability transition pore (PTP), voltage-dependent anion channel (VDAC) and adenine nucleotide translocator (ANT) of the outer and inner mitochondrial membranes, respectively. Cultured cerebellar granule cells were used to assess the role of these interactions in ethanol neurotoxicity. Analyses were made at the age of maximal cerebellar ethanol vulnerability (P4), compared to the later age of relative resistance (P7), to determine whether differential ethanol sensitivity was mirrored by differences in these molecular interactions. We found that, following ethanol exposure, Bax proapoptotic associations with both VDAC and ANT were increased, particularly at the age of greater ethanol sensitivity, and these interactions were sustained at this age for at least 2 h postexposure. Since Bax:VDAC interactions disrupt protective VDAC interactions with mitochondrial hexokinase (HXK), we also assessed VDAC:HXK associations following ethanol treatment and found such interactions were altered by ethanol treatment, but only at 2 h postexposure and only in the P4, ethanol-sensitive cerebellum. Ethanol neurotoxicity in cultured neuronal preparations was abolished by pharmacological inhibition of both VDAC and ANT interactions with Bax but not by a Bax channel blocker. Therefore, we conclude that, at this age, within the constraints of our experimental model, a primary mode of Bax-induced initiation of the apoptosis cascade following ethanol insult involves interactions with proteins of the PTP complex and not channel formation independent of PTP constituents.

Sorbitol-induced apoptosis of human leukemia is mediated by caspase activation and cytochrome c release

It has been reported that sorbitol induces apoptosis in several cancer cell lines. However, the molecular mechanism underlying the sorbitol-induced apoptotic process is not yet clearly understood. In the present study, the intracellular signaling pathways of sorbitol-induced apoptosis in human K562 cells were investigated using both morphological analysis and DNA fragmentation technique. In this study, we demonstrated that sorbitol-induced apoptosis in human K562 cells is a concentration- and time-dependent manner. This sorbitol-induced apoptosis in human K562 cells was also accompanied by the up-regulation of Bax, and down-regulation of p-Bcl-2, but no effect on the levels of Bcl-X(L). Moreover, the sorbitol treatment resulted in a significant reduction of mitochondria membrane potential, increase in the release of mitochondrial cytochrome c (cyt c), and activation of caspase 3. Furthermore, treatment with caspase 3 inhibitor (z-DEVD-fmk) was capable of preventing the sorbitol-induced caspase 3 activity and cell death. These results clearly demonstrate that the induction of apoptosis by sorbitol involves multiple cellular/molecular pathways and strongly suggest that pro- and anti-apoptotic Bcl-2 family proteins, mitochondrial membrane potential, mitochondrial cyt c, and caspase 3, they all participate in sorbitol-induced apoptotic process in human K562 cells.

Use of hyperosmolar stress to measure stress-activated protein kinase activation and function in human HTR cells and mouse trophoblast stem cells

Embryo growth is inversely correlated with hyperosmolar stress-induced stress-activated protein kinase/jun kinase (SAPK/JNK) induction. To examine whether stress has similar effects in stem cells derived from the embryo, the authors test trophoblast stem cells. The stress response of human placental and mouse trophoblast stem cell lines are tested here. Peak phosphorylated SAPK/JNK was induced by 400 mM sorbitol at 0.5 hours. At this dose, there is an SAPK/JNK-dependent decrease in mitogenic, phosphorylated cMyc at 0.5 hours preceding an SAPK/JNK-dependent decrease in cell cycle entrance at 24 hours. At 0.5 hours, SAPK/JNK decreases terminal deoxynucleotidyltransferase dUTP nick end labeling/apoptosis at sorbitol doses from 50 mM to 400 mM and induces phosphorylated cJun prior to an SAPK/JNK-dependent, approximate 8-fold increase in apoptosis by 24 hours at 400 mM. SAPK/JNK phosphorylation peaked at 0.5 to 4 hours and largely subsided by 12 hours. Thus, total SAPK/JNK exists before stress and mediates rapid, homeostatic molecular responses that become biologic consequences after phosphorylated SAPK/JNK ends. This suggests continuity in the homeostatic mechanisms and functions of SAPK/JNK in placental lineage cells during implantation, in which SAPK/JNK is completely responsible for cell cycle arrest and largely responsible for apoptosis.

In vitro models of acute and long-term continuous infection of human respiratory epithelial cells with Chlamydophila pneumoniae have opposing effects on host cell apoptosis

Persistent infection with the obligate intracellular pathogen Chlamydophila pneumoniae has been implicated in the pathogenesis of many chronic diseases, but its mechanism remains unclear. Many pathogens have been found to modulate cellular apoptosis in order to survive and multiply. Chlamydial species were shown to both induce and inhibit host cell apoptosis depending on the experimental conditions. We utilized in vitro models of acute and long-term continuous (LTC) infection with the same cell line (HEp-2) and chlamydial isolate (TW-183) used in both models. Host cell apoptosis in infected and uninfected cells was assessed by fluorescence microscopy and flow cytometry. While acute infection induced apoptosis 72 h post-infection, LTC-infected cells had low rates of apoptosis and showed resistance to different exogenous inducers of apoptosis (sorbitol, serum withdrawal, hydrogen peroxide) when compared to uninfected cells. Chronicity of infection appears to be a critical factor in the modulation of host cell apoptosis by C. pneumoniae. Induction of apoptosis may help to propagate the infection, while inhibition of apoptosis could help protect the organism in chronic infection.

Reactive oxygen and nitrogen species are involved in sorbitol-induced apoptosis of human erithroleukaemia cells K562

In this study, we found that production of both reactive oxygen (ROS) and nitrogen (RNS) species is a very early event related to treatment with hyperosmotic concentration of sorbitol. The production of nitric oxide (NO) was paralleled by the increase of the mRNA and protein level of the inducible form of the nitric oxide synthase (iNOS). ROS and RNS enhancement, process concomitant to the failure of mitochondrial trans-membrane potential (DeltaPsi), was necessary for the induction of apoptosis as demonstrated by the protection against sorbitol-mediated toxicity observed after treatment with ROS scavengers or NOS inhibitors. The synergistic action of ROS and RNS was finally demonstrated by pre-treatment with rosmarinic acid that, by powerfully buffering both these species, prevents impairment of DeltaPsi and cell death. Overall results suggest that the occurrence of apoptosis upon sorbitol treatment is an event mediated by oxidative/nitrosative stress rather than a canonical hyperosmotic shock.

The use of bacterial minicells to transfer plasmid DNA to eukaryotic cells

The delivery of DNA to mammalian cells is of critical importance to the development of genetic vaccines, gene replacement therapies and gene silencing. For these applications, targeting, effective DNA transfer and vector safety are the major roadblocks in furthering development. In this report, we present a novel DNA delivery vehicle that makes use of protoplasted, achromosomal bacterial minicells. Transfer of plasmid DNA as measured by green fluorescent protein expression was found to occur in as high as 25% of cultured Cos-7 cells when a novel chimeric protein containing the D2-D5 region of invasin was expressed and displayed on the surface of protoplasted minicells. Based on endoplasmic reticulum stress and other responses, protoplasted minicells were non-toxic to recipient eukaryotic cells as a consequence of the transfection process. Taken together, these results suggest that bacterial minicells may represent a novel and promising gene delivery vehicle.

Interference of bovine herpesvirus 1 (BHV-1) in sorbitol-Induced apoptosis

In order to determine the ability of bovine herpesvirus type 1 (BHV-1) to suppress apoptosis, we examined the effects of BHV-1 infection on sorbitol-induced apoptosis on Madin-Darby bovine kidney (MDBK) cells. BHV-1 suppresses sorbitol-induced apoptosis in a manner similar to that of herpes simplex virus type 1 (HSV-1), indicating that BHV-1 has one or more anti-apoptotic genes. To elucidate the molecular mechanisms of apoptosis, expression of some genes encoding apoptosis-inhibiting and -promoting factors were analyzed on BHV-1 infected cells during the process of sorbitol-induced apoptosis. Our results revealed that the expression of bcl-2 and bcl-x(L) decreased after 5 and 3 h p.i., respectively; while bax and procaspase-3 expression increased with respect to control as a function of p.i. times and at 7 h p.i. they were not observed. We further show that the expression of p53 gene was also enhanced, suggesting that this apoptotic mechanism is p53 dependent. From these results, we propose that BHV-1 has one or more genes encoding apoptosis-inhibiting factors which interfere with the involvement of bcl-2 gene family members and apoptotic pathway, depending upon caspase-3, triggered by sorbitol.

Herpes simplex virus type 2 US3 blocks apoptosis induced by sorbitol treatment

Previously, we established HEp2 cell lines which express the US3 protein kinase of herpes simplex virus type 2 upon induction with IPTG. Using these cells, we examined whether expression of US3 is sufficient to protect cells from apoptotic cell death induced by sorbitol. Cells expressing US3 showed significantly reduced nuclear fragmentation in the degree that DNA fragmentation and caspase-3 activation were suppressed. It is known that stressors such as osmotic shock and UV irradiation induce the activation of the JNK (c-Jun N-terminal kinase), which can lead to apoptotic cell death. Expression of US3 resulted in the suppression of sorbitol-induced phosphorylation of JNK and MKK4/SEK1, suggesting that the suppression of apoptotic cell death was due to the attenuation of JNK activity.

The PHD domain of MEKK1 acts as an E3 ubiquitin ligase and mediates ubiquitination and degradation of ERK1/2

ERK1/2 MAP kinases are important regulators in cellular signaling, whose activity is normally reversibly regulated by threonine-tyrosine phosphorylation. In contrast, we have found that stress-induced ERK1/2 activity is downregulated by ubiquitin/proteasome-mediated degradation of ERK1/2. The PHD domain of MEKK1, a RING finger-like structure, exhibited E3 ubiquitin ligase activity toward ERK2 in vitro and in vivo. Moreover, both MEKK1 kinase activity and the docking motif on ERK1/2 were involved in ERK1/2 ubiquitination. Significantly, cells expressing ERK2 with the docking motif mutation were resistant to sorbitol-induced apoptosis. Therefore, MEKK1 functions not only as an upstream activator of the ERK and JNK through its kinase domain, but also as an E3 ligase through its PHD domain, providing a negative regulatory mechanism for decreasing ERK1/2 activity.

Suppression of apoptotic and necrotic cell death by poliovirus

To determine an antiapoptotic activity of poliovirus type 1 (PV-1), we examined the effect of PV-1 infection on apoptosis that was induced in HEp-2 cells by the treatment with 1 M sorbitol. The virus did not induce apoptosis in the infected cells and could suppress both the fragmentation of chromosomal DNA and morphological cell and cell nuclei changes in the sorbitol-treated cells, indicating that PV-1 induces an antiapoptotic state. Comparison of the kinetics showed that this ability of the virus appeared in the infected cells at the time of progeny virus formation (maturation step of virus multiplication). Simultaneously with this antiapoptotic activity, PV-1 infection also suppressed non-apoptotic cell death induced by sodium chloride. Electron microscopic observation revealed that the cells killed by the sodium chloride treatment had undergone liquefactive necrosis, indicating that PV-1 can inhibit both apoptosis and necrosis. In addition, PV-1 can grow in the apoptotic cells, although the virus yield was reduced to a quarter of the yield in normal cells.

Lack of apoptosis in Sendai virus-infected HEp-2 cells without participation of viral antiapoptosis gene

Sendai virus (SeV) has been reported to induce apoptosis in many types of cells. In HEp-2 cells, however, it did not induce apoptosis in most of the infected cells under the conditions in which vesicular stomatitis virus induced massive apoptosis. The use of a novel technique, which allows the detection of viral antiapoptotic activity in the infected cells, showed that SeV does not have any antiapoptotic activity to interfere with the induction of apoptosis. Consistently, vesicular stomatitis virus-induced apoptosis was not interfered with by preinfection with SeV. These results indicate that the observed lack of apoptosis in these SeV-infected cells does not result from the suppression of apoptosis by viral antiapoptotic activity in the infected cells and suggest that, without activating a signaling pathway for the induction of apoptotic response in the infected cells, SeV can escape apoptosis of the cells, allowing long-term survival of the infected cells.

Physiological significance of apoptosis in animal virus infection

In contrast to insect viruses, animal viruses can produce considerable amounts of progeny virus in cells undergoing apoptosis. Nevertheless, viruses in general have acquired the ability to escape apoptosis of infected cells. These facts indicate that the role of apoptosis in virus infection is different in insect virus and animal virus, although both viruses need to avoid apoptosis of the infected cells for a viral life cycle in nature. In animal virus infection, the primary role of apoptosis is considered not to be a premature lysis of the infected cells (and the following abortion of virus multiplication) but to allow the dying cells to be phagocytosed by macrophages. This phagocytosis is able to prevent dysregulated inflammatory reactions at the site of virus infection and to initiate a specific immune response against the infected virus.