Anti-oxidative effects of silkworm storage protein 1 in HeLa cell

Silkworm hemolymph contains unique proteins that exhibit anti-apoptotic activity in mammalian cells. Among them, 30 K protein, which is one of the major anti-apoptotic molecules in silkworm hemolymph, has been well investigated. However, little is known about the biological functions of storage protein 1 (SP1), another main protein in silkworm hemolymph. In this study, the anti-apoptotic and anti-oxidative activities of SP1 were analyzed. A stable cell line expressing SP1 was constructed, which showed strong anti-apoptotic effect induced by staurosporine treatment. In addition, the cell line exhibited resistance to oxidative stress caused by hydrogen peroxide. For practical applications of SP1, recombinant SP1 was produced in Escherichia coli, and the supplementation of recombinant SP1 into culture medium exhibited anti-apoptotic and anti-oxidative activities. In addition, SP1 was found to be a cell-penetrating protein and localized in the cytosol as well as on the plasma membrane. The findings showed that SP1 itself is not an anti-oxidant; rather, it mediates intracellular anti-oxidative activity. In conclusion, the cellular resistance of SP1 to apoptosis and oxidative stress will provide a new strategy that could be utilized in the bio-industry for the production of biologics as well as for the development of anti-aging cosmetics.     

Down-regulation of Mcl-1 by inhibition of the PI3-K/Akt pathway is required for cell shrinkage-dependent cell death.

The anti-apoptotic effect of a chloride-bicarbonate exchange blocker has been previously examined in endothelial cells and cardiomyocytes. However, the anti-apoptotic effects of this blocker on epithelial cells and the mechanism of the anti-apoptotic effect remain unknown. We examined the anti-apoptotic effects of a chloride-bicarbonate exchange blocker in a renal epithelial cell line (MDCK cells). Changes in the expression of bcl-2 family proteins, which are known to have anti-apoptotic effects, were also examined. Staurosporine was used to induce apoptotic cell death in the MDCK cells. Staurosporine treatment was sufficient to induce apoptotic cell death, detected by propidium iodide and DNA ladder formation. A chloride-bicarbonate exchange blocker was added 24 h before the staurosporine treatment and during treatment. The chloride-bicarbonate exchange blocker inhibited the staurosporine-induced apoptosis in the MDCK cells in a dose-dependent manner. The expression of bcl-2 family gene products was detected by RT-PCR and Western blotting. No changes in the expression of Bax, Bid and Bik (pro-apoptotic proteins), or Bcl-2 (an anti-apoptotic protein) were detected. However, Mcl-1 expression was reduced by the staurosporine treatment, and this reduction was recovered when the chloride-bicarbonate exchange blocker was added. LY294002, a PI 3-kinase inhibitor, partially inhibited this anti-apoptotic effect. In conclusion, chloride-bicarbonate exchange blockers appear to offer cell-protective effects via Mcl-1 up-regulation.     

Protective effects of cynaroside against H₂O₂-induced apoptosis in H9c2 cardiomyoblasts

Flavonoids with potent anti-oxidative effects are the major effective components in traditional herbal medicine used in treating cardiovascular diseases. Cynaroside is a flavonoid compound that exhibits anti-oxidative capabilities. However, little is known about its effect on oxidative injury to cardiac myocytes and the underlying mechanisms. This study was designed to investigate the protective effects of cynaroside against H(2) O(2) -induced apoptosis in H9c2 cardiomyoblasts. H9c2 cells were pretreated with cynaroside for 4 h before exposure to 150 μM H(2) O(2) for 6 h. H(2) O(2) treatment caused severe injury to the H9c2 cells, which was accompanied by apoptosis, as revealed by analysis of cell nuclear morphology, through Annexin V FITC/PI staining and caspase proteases activation. Cynaroside pretreatment significantly reduced the apoptotic rate by enhancing the endogenous anti-oxidative activity of superoxide dismutase, glutathione peroxidase, and catalase, thereby inhibiting intracellular reactive oxygen species (ROS) generation. Moreover, cynaroside moderated H(2) O(2) -induced disruption of mitochondrial membrane potential, increased the expression of anti-apoptotic protein Bcl-2 while decreased the expression of pro-apoptotic protein Bax, and thereby inhibited the release of apoptogenic factors (cytochrome c and smac/Diablo) from mitochondria in H9c2 cells. Our data also demonstrated that cynaroside pretreatment showed an inhibitory effect on the H(2) O(2) -induced increase in c-Jun N-terminal kinase (JNK) and P53 protein expression. These results suggest that cynaroside prevents H(2) O(2) -induced apoptosis in H9c2 cell by reducing the endogenous production of ROS, maintaining mitochondrial function, and modulating the JNK and P53 pathways.     

Oleanolic acid initiates apoptosis in non-small cell lung cancer cell lines and reduces metastasis of a B16F10 melanoma model in vivo

Background

Drug resistance, a process mediated by multiple mechanisms, is a critical determinant for treating lung cancer. The aim of this study is to determine if oleanolic acid (OA), a pentacyclic triterpene present in several plants, is able to circumvent the mechanisms of drug resistance present in non-small cell lung cancer (NSCLC) cell lines and to induce their death.

Principal Findings

OA decreased the cell viability of the NSCLC cell lines A459 and H460 despite the presence of active, multidrug-resistant (MDR) MRP1/ABCC1 proteins and the anti-apoptotic proteins Bcl-2 and survivin. These effects are due to apoptosis, as evidenced by the capacity of OA to induce fragmentation of DNA and activate caspase 3. Induction of NSCLC cell death by OA cannot be explained by inhibition of the MDR proteins, since treatment with triterpene had little or no effect on the activity or expression of MRP1. Moreover, treatment with OA had no effect on the expression of the anti-apoptotic protein Bcl-2, but increased the expression of the pro-apoptotic protein Bax, altering the Bcl-2/Bax balance towards a pro-apoptotic profile. OA also decreased the expression of the anti-apoptotic protein survivin. Furthermore, OA decreased the expression of the angiogenic vascular endothelial growth factor (VEGF) and decreased the development of melanoma-induced lung metastasis.

Conclusion

Our data provide a significant insight into the antitumoral and antimetastatic activity of OA in NSCLC and suggest that including OA in the NSCLC regimens may help to decrease the number of relapses and reduce the development of metastases.     

Anti-apoptosis engineering

An increased understanding of apoptosis makes anti-apoptosis engineering possible, which is an approach used to inhibit apoptosis for the purpose of therapeutic, or industrial applications in the treatment of the diseases associated with increased apoptosis, or to improve the productivity of animal cell cultures, respectively. Some known anti-apoptotic proteins are the Bcl-2 family, IAP (inhibitor of apoptosis) and Hsps (heat shock proteins), with which anti-apoptosis engineering has progressed. This article reviews anti-apoptosis engineering using known anti-apoptotic compounds, and introduces a 30 K protein, isolated from silkworm hemolymph, as a novel anti-apoptotic protein, that shows no homology with other known anti-apoptotic proteins. The regulation of apoptosis, using anti-apoptotic proteins and genes originating from the silkworm,Bombyx mori, may provide a new strategy in this field.     

Serum withdrawal-induced apoptosis in ZrchI prion protein (PrP) gene-deficient neuronal cell line is suppressed by PrP, independent of Doppel

Previous studies have shown that cellular prion protein (PrP(C)) plays anti-apoptotic and antioxidative role against cell death induced by serum-deprivation (SDP) in an immortalized prion protein gene-deficient neuronal cell line derived from Rikn prion protein (PrP) gene-deficient (Prnp(-/-)) mice, which ectopically produce excess Doppel (Dpl) (PrP-like glycoprotein). To investigate whether PrP(C) inhibits apoptotic neuronal cell death without Dpl, an immortalized cell line was established from the brain of ZrchI Prnp(-/-) mice, which do not show ectopic expression of Dpl. The results using a ZrchI neuronal Prnp(-/-) cell line (NpL2) showed that PrP(C) potently inhibited SDP-induced apoptotic cell death. Furthermore, PrP(C) expression enhanced the superoxide dismutase (SOD) activity in NpL2 cells. These results indicate that Dpl production did not affect anti-apoptotic and anti-oxidative functions of PrP, suggesting that PrP(C) may be directly correlated with protection against oxidative stress.     

Loganin alleviates testicular damage and germ cell apoptosis induced by AGEs upon diabetes mellitus by suppressing the RAGE/p38MAPK/NF-κB pathway

Diabetes mellitus (DM) damages male reproduction at multiple levels, such as endocrine secretion, spermatogenesis and penile erection. We herein investigated the protective effects and mechanism of loganin targeting the advanced glycation end products (AGEs)/receptor for AGEs (RAGE)/p38 mitogen-activated protein kinase (p38MAPK)/NF-κB signalling pathway. Loganin relieved the general DM symptoms and decreased the blood glucose level of KK-Ay DM mice. Haematoxylin-eosin staining demonstrated that loganin ameliorated testicular histology and function and enhanced the activities of testis-specific markers lactate dehydrogenase (LDH), acid phosphatase (ACP) and gamma-glutamyl transferase (γ-GT). Loganin also showed evident anti-oxidative stress, anti-apoptotic and anti-inflammatory effects on DM-induced reproductive damage by restoring glutathione (GSH) level and superoxide dismutase (SOD) activity, as well as reducing reactive oxygen species (ROS) level and Bax/Bcl-2 ratio in vivo and in vitro. Western blotting exhibited that loganin significantly inhibited the AGEs/RAGE/p38MAPK/NF-κB signalling pathway. Acridine orange and ethidium bromide staining (AOEB) and Western blotting showed that loganin in combination with inhibitors of RAGE, p38MAPK and NF-κB exerted stronger anti-apoptotic effects on AGE-induced GC-2 cell damage compared with loganin alone. In conclusion, loganin can protect against DM-induced reproductive damage, probably by suppressing the AGEs/RAGE/p38MAPK/NF-κB pathway.     

Anti-apoptotic effects of the alpha-helix domain of silkworm storage protein 1

Apoptosis is a programmed cell death and a mechanism for the maintenance of multicellular organism homeostasis. In bioindustry, apoptosis during cell culture used to produce therapeutic proteins results in the reduction of productivity and quality. Thus, it is crucial to develop novel techniques and materials to inhibit apoptosis. Previous studies have found that storage protein 1 (SP1) has antiapoptotic effects on HeLa cells, but the part of SP1 responsible for the anti-apoptotic effects is unknown. Herein, the anti-apoptotic effects of the N-terminal, α-helix domain of SP1 (SPD1) were investigated by generating a cell line stably expressing SPD1. SPD1 expression conferred strong resistance to apoptosis induced by staurosporine (STS). SPD1 diminished the loss of the mitochondrial membrane potential and inhibited caspase-3 activation, suggesting that it acts as an upstream apoptosis inhibitor. SPD1 was also produced as a recombinant protein in E. coli and culture medium supplementation with recombinant SPD1 resulted in apoptosis inhibition in HeLa cells. The capability of SPD1 to penetrate cell membrane was also assessed, and the results show that it localized in the cytosol, as well as on the plasma membrane. This indicates that SPD1 is a cell-penetrating protein with high antiapoptotic activity. In conclusion, SPD1 is a novel protein responsible for the anti-apoptotic effect of SP1, and it can be considered as a new biomaterial that can minimize cell death and maximize productivity in biopharmaceutical industry. In addition, the miniaturization of SP1 in SPD1 can facilitate its practical usage as a culture medium supplement and cosmetic ingredient.     

MCL-1–dependent leukemia cells are more sensitive to chemotherapy than BCL-2–dependent counterparts

Myeloid cell leukemia sequence 1 (MCL-1) and B cell leukemia/lymphoma 2 (BCL-2) are anti-apoptotic proteins in the BCL-2 protein family often expressed in cancer. To compare the function of MCL-1 and BCL-2 in maintaining cancer survival, we constructed complementary mouse leukemia models based on Eμ-Myc expression in which either BCL-2 or MCL-1 are required for leukemia maintenance. We show that the principal anti-apoptotic mechanism of both BCL-2 and MCL-1 in these leukemias is to sequester pro-death BH3-only proteins rather than BAX and BAK. We find that the MCL-1–dependent leukemias are more sensitive to a wide range of chemotherapeutic agents acting by disparate mechanisms. In common across these varied treatments is that MCL-1 protein levels rapidly decrease in a proteosome-dependent fashion, whereas those of BCL-2 are stable. We demonstrate for the first time that two anti-apoptotic proteins can enable tumorigenesis equally well, but nonetheless differ in their influence on chemosensitivity.     

Synthesis and Biological Activity of Scyllatoxin-Based BH3 Domain Mimetics Containing Two Disulfide Linkages

The B cell lymphoma 2 (BCL2) proteins are a family of evolutionarily related proteins that act as positive or negative regulators of the intrinsic apoptosis pathway. Overexpression of anti-apoptotic BCL2 proteins in cells is associated with apoptotic resistance, which can result in cancerous phenotypes and pathogenic cell survival. Consequently, anti-apoptotic BCL2 proteins have attracted considerable interest as therapeutic targets. We recently reported the development of a novel class of synthetic protein based on scyllatoxin (ScTx) designed to mimic the helical BH3 interaction domain of the pro-apoptotic BCL2 protein Bax. These studies showed that the number and position of native disulfide linkages contained within the ScTx-Bax structure significantly influences the ability for these constructs to target anti-apoptotic BCL2 proteins in vitro. The goal of the present study is to investigate the contribution of two disulfide linkages in the folding and biological activity of ScTx-Bax proteins. Here, we report the full chemical synthesis of three ScTx-Bax sequence variants, each presenting two native disulfide linkages at different positions within the folded structure. It was observed that two disulfide linkages were sufficient to fold ScTx-Bax proteins into native-like architectures reminiscent of wild-type ScTx. Furthermore, we show that select (bis)disulfide ScTx-Bax variants can target Bcl-2 (proper) in vitro and that the position of the disulfide bonds significantly influences binding affinity. Despite exhibiting only modest binding to Bcl-2, the successful synthesis of ScTx-Bax proteins containing two disulfide linkages represents a viable route to ScTx-based BH3 domain mimetics that preserve native-like conformations. Finally, structural models of ScTx-Bax proteins in complex with Bcl-2 indicate that these helical mimetics bind in similar configurations as wild-type Bax BH3 domains. Taken together, these results suggest that ScTx-Bax proteins may serve as potent lead compounds that expand the repertoire of “druggable” protein–protein interactions.     

BimS-induced apoptosis requires mitochondrial localization but not interaction with anti-apoptotic Bcl-2 proteins

Release of apoptogenic proteins such as cytochrome c from mitochondria is regulated by pro- and anti-apoptotic Bcl-2 family proteins, with pro-apoptotic BH3-only proteins activating Bax and Bak. Current models assume that apoptosis induction occurs via the binding and inactivation of anti-apoptotic Bcl-2 proteins by BH3-only proteins or by direct binding to Bax. Here, we analyze apoptosis induction by the BH3-only protein Bim(S). Regulated expression of Bim(S) in epithelial cells was followed by its rapid mitochondrial translocation and mitochondrial membrane insertion in the absence of detectable binding to anti-apoptotic Bcl-2 proteins. This caused mitochondrial recruitment and activation of Bax and apoptosis. Mutational analysis of Bim(S) showed that mitochondrial targeting, but not binding to Bcl-2 or Mcl-1, was required for apoptosis induction. In yeast, Bim(S) enhanced the killing activity of Bax in the absence of anti-apoptotic Bcl-2 proteins. Thus, cell death induction by a BH3-only protein can occur through a process that is independent of anti-apoptotic Bcl-2 proteins but requires mitochondrial targeting.     

The anti-apoptotic effect of Notch-1 requires p56lck-dependent, Akt/PKB-mediated signaling in T cells

The Notch family of transmembrane receptors have been implicated in a variety of cellular decisions in different cell types. Here we investigate the mechanism underlying Notch-1-mediated anti-apoptotic function in T cells using model cell lines as the experimental system. Ectopic expression of the intracellular domain of Notch-1/activated Notch (AcN1) increases expression of anti-apoptotic proteins of the inhibitors of apoptosis (IAP) family, the Bcl-2 family, and the FLICE-like inhibitor protein (FLIP) and inhibits death triggered by multiple stimuli that activate intrinsic or extrinsic pathways of apoptosis in human and murine T cell lines. Numb inhibited the AcN1-dependent induction of anti-apoptotic proteins and anti-apoptotic function. Using pharmacological inhibitors and dominant-negative approaches, we describe a functional role for phosphatidylinositol 3-kinase (PI3K)-dependent activation of the serine-threonine kinase Akt/PKB in the regulation of AcN1-mediated anti-apoptotic function and the expression of FLIP and IAP family proteins. Using a cell line deficient for the T cell-specific, Src family protein, the tyrosine kinase p56(lck) and by reconstitution approaches we demonstrate that p56(lck) is required for the Notch-1-mediated activation of Akt/PKB function. Furthermore, the Src tyrosine kinase inhibitor, PP2, abrogated ectopically expressed AcN1-mediated anti-apoptotic function and phosphorylation of p56(lck). We present evidence that endogenous Notch-1 associates with p56(lck) and PI3K but that Akt/PKB does not co-immunoprecipitate with the Notch1.p56(lck).PI3K complex. Finally, we demonstrate that the Notch1.p56(lck).PI3K complex is present in primary T cells that have been activated in vitro and sustained in culture with the cytokine interleukin-2.     

Decreased expression of the Augmenter of Liver Regeneration results in increased apoptosis and oxidative damage in human-derived glioma cells

The mammalian growth factor erv1-like (GFER) gene encodes a sulfhydryl oxidase enzyme, named Augmenter of Liver Regeneration (ALR). Recently it has been demonstrated that ALR supports cell proliferation acting as an anti-apoptotic factor. This effect is determined by ALR ability to support the anti-apoptotic gene expression and to preserve cellular normoxic conditions. We recently demonstrated that the addition of recombinant ALR (rALR) in the culture medium of H₂O₂-treated neuroblastoma cells reduces the lethal effects induced by the hydrogen peroxide. Similar data have been reported in the regenerating liver tissue from partially hepatectomized rats treated with rALR. The purpose of the present study was to evaluate the effect of the GFER inhibition, via the degradation of the complementary mRNA by the specific siRNA, on the behaviour of the apoptosis (apoptotic gene and caspase expression and apoptotic cell number) and of the oxidative stress-induced parameters (reactive oxygen species (ROS), clusterin expression and mitochondrial integrity) in T98G glioma cells. The results revealed a reduction of (i) ALR, (ii) clusterin and (iii) bcl-2 and an increase of (iv) caspase-9, activated caspase-3, ROS, apoptotic cell number and mitochondrial degeneration. These data confirm the anti-apoptotic role of ALR and its anti-oxidative properties, and shed some light on the molecular pathways through which ALR modulates its biological effects.     

Interaction of Leukocyte Elastase Inhibitor/L-DNase II with BCL-2 and BAX

Leukocyte Elastase Inhibitor (LEI, also called serpin B1) is a protein involved in apoptosis among other physiological processes. We have previously shown that upon cleavage by its cognate protease, LEI is transformed into L-DNase II, a protein with a pro-apoptotic activity. The caspase independent apoptotic pathway, in which L-DNase II is the final effector, interacts with other pro-apoptotic molecules like Poly-ADP-Ribose polymerase (PARP) or Apoptosis Inducing Factor (AIF). The screening of LEI/L-DNase II interactions showed a possible interaction with several members of the BCL-2 family of proteins which are known to have a central role in the regulation of caspase dependent cell death. In this study, we investigated the regulation of LEI/L-DNase II pathway by two members of this family of proteins: BAX and BCL-2, which have opposite effects on cell survival. We show that, in both BHK and HeLa cells, LEI/L-DNase II can interact with BCL-2 and BAX in apoptotic and non-apoptotic conditions. These proteins which are usually thought to be anti-apoptotic and pro-apoptotic respectively, both inhibit the L-DNase II pro-apoptotic activity. These results give further insight in the regulation of caspase independent pathways and highlight the involvement of the intracellular environment of a given protein in the determinism of its function. They also add a link between caspase-dependent and independent pathways of apoptosis.     

Protection of hybridoma cells against apoptosis by a loop domain-deficient Bcl-xL protein

The ectopic expression of several members of the Bcl-2 family of anti-apoptotic proteins is a promising strategy to improve the viability of hybridoma cells in culture. However, the impact of post-translational modifications on the function of these proteins in murine hybridomas is unknown. To address this issue, the anti-apoptotic properties of a mutant of Bcl-xL devoid of the so-called “loop domain„ (Bcl-xL▵ 46-83) were investigated using the Sp2/ O-Ag14 hybridoma model. Clones of Sp2/ O-Ag14 cells expressing Bcl-xL▵ 46-83 exhibited resistance against L-glutamine deprivation to similar levels than cells expressing the wild type protein. In contrast, protection against the cytotoxic effects of cycloheximide (CHX) was highly dependent on the level of expression of the Bcl-xL▵ 46-83 mutant. Analysis of the growth behaviour of the transfected cells showed that Bcl-xL▵ 46-83 was superior to the wild type protein in prolonging Sp2/ O-Agl4 cell viability in stationary batch culture. Furthermore, the prolongation of cell viability in batch culture was directly proportional to the level of expression of the mutated protein. Our results indicate that removal of the loop domain improves the anti-apoptotic activity of Bcl-xL in hybridoma cells grown in stationary batch culture. This revised version was published online in August 2006 with corrections to the Cover Date.     

Transduction of anti-apoptotic proteins into chondrocytes in cartilage slice culture

Peptides of the protein transduction domain (PTD) mediate the introduction of passenger proteins into cells in vitro and in vivo, where the domains are positively charged. This unusual ability can be exploited for medical applications in protein therapeutics. Chondrocytes are embedded in a dense extracellular matrix, whose components are highly negatively charged. We examined whether PTD mediates the delivery of functional proteins into chondrocytes through the matrix using the super anti-apoptotic protein FNK fused with Tat/PTD peptide (PTD-FNK), the FNK protein being constructed from anti-apoptotic Bcl-xL to enhance its activity. The PTD-FNK protein labeled with a fluorescent dye was incorporated into chondrocytes through the matrix and immunostaining confirmed the transduction into the cells. The PTD-FNK protein protected chondrocytes from cell death induced by Fas antibody and nitrogen oxide (NO). Thus, the PTD peptide has the ability to deliver passenger proteins into chondrocytes by penetrating the extracellular matrix of cartilage.     

Influence of histidine tag attachment on picosecond protein dynamics

Polyhistidine affinity tags are routinely employed as a convenient means of purifying recombinantly expressed proteins. A tacit assumption is commonly made that His tags have little influence on protein structure and function. Attachment of a His tag to the N-terminus of the robust globular protein myoglobin leads to only minor changes to the electrostatic environment of the heme pocket, as evinced by the nearly unchanged Fourier transform infrared spectrum of CO bound to the heme of His-tagged myoglobin. Experiments employing two-dimensional infrared vibrational echo spectroscopy of the heme-bound CO, however, find that significant changes occur to the short time scale (picoseconds) dynamics of myoglobin as a result of His tag incorporation. The His tag mainly reduces the dynamics on the 1.4 ps time scale and also alters protein motions of myoglobin on the slower, >100 ps time scale, as demonstrated by the His tag's influence on the fluctuations of the CO vibrational frequency, which reports on protein structural dynamics. The results suggest that affinity tags may have effects on protein function and indicate that investigators of affinity-tagged proteins should take this into consideration when investigating the dynamics and other properties of such proteins.