DNA Ladder Formation Research Articles

Induction of apoptosis in human leukemia U937 cells by anthocyanins through down-regulation of Bcl-2 and activation of caspases

Anthocyanins are a class of flavonoids, widely spread throughout the plant kingdom, that exhibit important anti-oxidant and anti-inflammatory actions as well as chemotherapeutic effects. However, little is known concerning the molecular mechanisms by which these activities are exerted. In this study, we investigated the anthocyanins isolated from Vitis coignetiae Pulliat for their potential anti-proliferative and apoptotic effects on human leukemia U937 cells. It was found that these anthocyanins inhibit cell viability and induce apoptotic cell death of U937 cells in a dose-dependent manner, as measured by hemocytometer counts, by alteration in the mitochondrial membrane potential, by increases in sub-G1 populations and by DNA ladder formation. Apoptosis of U937 cells by anthocyanins was associated with modulation of expression of Bcl-2 and IAP family members. Consequently, anthocyanin treatment induced proteolytic activation of caspase-3, -8 and -9, and a concomitant degradation of poly(ADP-ribose) polymerase. However, anthocyanin-induced growth inhibition and apoptosis were significantly attenuated in Bcl-2 overexpressing U937 cells. Furthermore, z-DEVD-fmk, a caspase-3 specific inhibitor, blocked apoptosis and increased the survival of anthocyanin-treated U937 cells. Taken together, these results show that Bcl-2 and caspases are key regulators of apoptosis in response to anthocyanins in human leukemia U937 cells.

3-Oxoolean-12-en-27-oic Acid Isolated from Aceriphyllum rossii Induces Caspase-8-Dependent Apoptosis in Human Promyelocytic Leukemia HL-60 Cells

In the present study, we investigated the effects of 3-oxoolean-12-en-27-oic acid (3-OA) isolated from the underground parts of Aceriphyllum rossii (Saxifragaceae) on the viability and apoptosis of HL-60 human promyelocytic leukemia cells, and the mechanisms underlying its action. 3-OA-treated HL-60 cells and HeLa human cervix adenocarcinoma cells displayed several apoptotic features, such as, DNA fragmentation, DNA laddering by agarose gel electrophoresis, and hypodiploid DNA contents by flow cytometry, and 3-OA also caused the activations of caspase-8, -9 and -3. Pretreatment with z-VAD-fmk (a broad-caspase inhibitor) almost completely suppressed 3-OA-induced DNA ladder formation and hypodiploid DNA contents, thereby implicating the caspase cascade in the apoptotic process. In addition, z-IETD-fmk (a caspase-8 inhibitor) and z-DEVD-fmk (a caspase-3 inhibitor) also completely neutralized the apoptotic effect of 3-OA in HL-60 cells. Furthermore, 3-OA increased Fas-related protein contents and the mRNA expressions of Fas ligand (FasL), Fas, and Fas-associated death domain (FADD). Preincubation with anti-Fas or anti-FasL blocking antibodies completely prevented 3-OA-induced apoptosis. Taken together, these results suggest that 3-oxoolean-12-en-27-oic acid induces apoptosis by activating caspase-8 via FasL-stimulated death receptor signaling.

Simvastatin treatment induces morphology alterations and apoptosis in murine cochlear neuronal cells

Conclusion. Simvastatin presented neurodegenerative morphological changes and cell death via its specific inhibition of mevalonate pathway induced apoptosis in cultured cochlear neuronal cells. These findings might contribute to understanding the auditory neurobiological effects of HMG-CoA reductase inhibitors. Objectives. The statins are 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors that are widely used as anti-hypercholesterol drugs because of their beneficial cardiovascular effects. However, the effects of statins in neuronal cells are controversial, and no studies have examined the effect of statins in cochlear neuronal cells. The objective of this study was to evaluate the direct effect of simvastatin on cochlear neuronal cells and examine the mechanisms underlying these effects. Materials and methods. Cultured mouse cochlear neuroblasts (VOT-33) and primary rat cochlear explants containing spiral ganglion neurons were treated with simvastatin in the absence or presence of mevalonate. Results. Simvastatin caused a loss of the cytoplasmic projections in VOT-33. In primary rat cochlear nerve cells, simvastatin decreased staining for NF200, a neuro-cytoskeletal protein. We also found that simvastatin-induced VOT-33 apoptosis, as indicated by accumulation of the sub G0/G1 fraction, DNA-ladder formation, and caspase-3 activation. The above-mentioned effects were abolished by mevalonate treatment.

Mechanism of docetaxel-induced apoptosis in human hepatocellular carcinoma cells

Objective To investigate the effect of docetaxel on the proliferation and apoptosis of human hepatocellular carcinoma cells and explore the mechanism of docetaxel-induced apoptosis. Methods Human hepatoma cells HepG2 and Huh7 were treated with different concentrations of do-cetaxel for different times, and the proliferation of these cells were examined by WST-1 proliferation assay. Hoechst 33342 staining and DNA ladder were used to detect cell apoptosis. The activities of caspase-3 and caspase-9 were investigated by Western blotting. Results Docetaxel inhibited prolifera-tion of hepatoma cells in a dose-and time-dependent manner. Furthermore, DNA ladder formation and fragmented nuclei were showed in hepatoma cells after docetaxel treatment, indicating that docetaxel induced apoptosis in these cells. Moreover, docetaxel induced caspase-3 and easpase-9 activation. And a caspase-3 inhibitor, Z-VAD-FMK, significantly inhibited docetaxel-induced apoptosis in these hepa-toma cells. Conclusions DocetaxeI suppresses the proliferation of hepatoma cells through inducing ap-optosis and the activated caspase-3 might play an important role in this process. Key words: Carcinoma hepatocellular; Docetaxel; Apoptosis

Bacterial reduction in genotoxicity of Direct Red 28 dye

Direct Red 28 (DR28) is a benzidine-based azo dye widely used in several countries. It has also been a subject of intense research for its anti-prion activity. Like other benzidine-based azo dyes, it is also carcinogenic and toxic. However, there are very few studies addressing its detoxification. In the present study, a Bacillus velezensis strain was used for detoxification of DR28. Toxicity was checked by a battery of highly sensitive genotoxicity assays like comet assay, DNA ladder formation, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and flow cytometric Annexin V binding assay. HL-60 cell line was used as the test system. All the assays showed an initial increase in toxicity upon biodegradation due to release of mutagenic products, like benzidine and 4-aminobiphenyl, from the dye. These intermediates caused significant DNA damage and induced apoptosis in HL-60 cells. Then the culture degraded these mutagenic intermediates, due to which the toxicity was reduced gradually, finally resulting in nearly complete detoxification.

The synthesis of ursolic acid derivatives with cytotoxic activity and the investigation of their preliminary mechanism of action

Nineteen ursolic acid derivatives (15 novel compounds) modified at the C-3 and the C-28 positions were synthesized. The cytotoxic activity of the derivatives was evaluated against HeLa, BGC-823 and SKOV3 cells by MTT assay. Inducing apoptosis and affecting cell cycle distribution by the derivatives in HeLa cells were assessed by flow cytometry and DNA fragmentation. Compounds 10b and 11b were particularly active to inhibit HeLa cells growth through inducing apoptosis and arresting cell cycle progression. The typical ‘sub-G1 peak’ and DNA ladder formation were checked and cell cycle was arrested at the S phase in a dose-dependent manner.

Possible involvement of caspase-6 and -7 but not caspase-3 in the regulation of hypoxia-induced apoptosis in tube-forming endothelial cells

We recently reported that a broad-spectrum caspase inhibitor zVAD-fmk failed, while p38 inhibitor SB203580 succeeded, to prevent chromatin condensation and nuclear fragmentation induced by hypoxia in tube-forming HUVECs. In this study, we investigated the reasons for zVAD-fmk's inability to inhibit these morphological changes at the molecular level. The inhibitor effectively inhibited DNA ladder formation and activation of caspase-3 and -6, but it surprisingly failed to inhibit caspase-7 activation. On the other hand, SB203580 successfully inhibited all of these molecular events. When zLEHD-fmk, which specifically inhibits initiator caspase-9 upstream of caspase-3, was used, it inhibited caspase-3 activation but failed to inhibit caspase-6 and -7 activation. It also failed to inhibit hypoxia-induced chromatin condensation, nuclear fragmentation and DNA ladder formation. Taken together, our results indicate that, during hypoxia, caspase-7 is responsible for chromatin condensation and nuclear fragmentation while caspase-6 is responsible for DNA ladder formation.

As2O3 toxicity in rat hepatocytes: manifestation of caspase-mediated apoptosis

In India, arsenic contamination in ground water is of immediate environmental concern affecting a large number of inhabitants in Kolkata. Arsenic is known to be one of the most toxic metalloids naturally occurring in the environment giving rise to severe toxic manifestations including cancer. Because arsenic is also used in chemotherapy of leukemia, it was considered worthwhile to concentrate on the mechanism of toxic action in normal hepatocytes which has not been addressed earlier. Rat hepatocytes were isolated and incubated in As(2)O(3) at concentrations of 10, 20, and 40 microM in a time-dependent manner (0, 15, 30 min and 1, 2, and 4 h). The expression of the common stress proteins HSP 70 and 90 throughout the experimental duration confirmed the magnitude of toxic effect imposed by arsenic. Microscopic observations showed clear apoptotic changes in hepatocytes, which were further characterized by DNA ladder formation in time- and concentration-dependent manners. Apoptosis was triggered by caspase activation and over expression of bax at 10 microM As(2)O(3) and at 20 and 40 microM concentrations of As(2)O(3), MAP kinases were found to mediate the apoptotic pathway. Co-treatment of cells with arsenic and caspase inhibitor (Ac-DEVD-Cho) led to over expression of bcl-2, suppression of bax, and cytosolic sequestration of Bid and Bad. It is therefore concluded that caspase activation has a direct role in arsenic-induced apoptosis mediated by mitochondrial factors at 10 microM As(2)O(3), and JUN N-terminal kinase (JNK) and P38 activation are the major mediators of apoptosis at the higher test concentrations (20 and 40 microM) of As(2)O(3).

Cytotoxicity and apoptosis induction of weisiensin B isolated from Rabdosia weisiensis C.Y. Wu in human hepatoma cells

Weisiensin B, a new ent-kaurane diterpenoid, was isolated from traditional Chinese herb Rabdosia weisiensis C.Y. Wu. In this study, cytotoxicity of weisiensin B was tested on four different tumor cell lines and the effect of growth inhibition and apoptosis in BEL-7402 cell line were investigated in vitro. The results indicated that weisiensin B had significant antiproliferation activity on the four cell lines. Further study on BEL-7402 cells involving Hoechst 33258 stain and DNA fragmentation assay revealed the characteristic apoptotic features of nuclear and DNA ladder formation. Flow cytometric (FCM) analysis with propidium iodide (PI) staining demonstrated that BEL-7402 cells treated with weisiensin B were arrested in G2/M phase. The results demonstrated that a significant fraction of weisiensin B-treated cells died by an apoptotic pathway in BEL-7402 cells.

Mechanism of patulin-induced apoptosis in human leukemia cells (HL-60)

Patulin (PAT) is a fungal secondary metabolite that exhibits potential cellular and animal toxicities. In this study, human promyelocytic leukemia (HL-60) cells were used to elucidate the mechanism and death mode associated with PAT. Morphological evidence of apoptosis, including membrane blebbing, nuclei fragmentation and DNA laddering formation was clearly observed 6 h after exposure to PAT. The results of Western blotting indicated that PAT activated various processed caspases, and cleaved DFF45 and poly (ADP-ribose) polymerase (PARP) in a dose-dependent manner; it also induced a time-dependent increase in caspase 3 and 9 catalytic activities. The apoptosis mediated by PAT in HL-60 was accompanied with cytochrome c release from mitochondria and Bcl-2 expression decrease. The presence of thiol-containing compounds with PAT dramatically reduced the caspase 3 activity that was triggered by PAT; the addition of antioxidants, including mannitol and Tiron, had a similar effect. However, the suppression of p53 protein expression by RNA interference (RNAi) in human embryonic kidney (HEK293) cells did not significantly modify PAT-elicited caspase 3 activity. These findings suggest that PAT-induced apoptosis is mediated through the mitochondrial pathway without the involvement of p53; the interaction with sulfhydryl groups of macromolecules by PAT and the subsequent generation of reactive oxygen species (ROS) plays a primary role in the apoptotic process.

Actinobacillus pleuropneumoniae serotype 10 derived ApxI induces apoptosis in porcine alveolar macrophages

Actinobacillus pleuropneumoniae (AP) is the causative agent of swine pleuropneumonia, a fibrinous, exudative, hemorrhagic, necrotizing pleuropneumonia affecting all ages of pigs. Actinobacillus pleuropneumoniae exotoxins (Apx) are one of the major virulence factors of AP. Due to the complex nature of Apx toxins produced by AP, little is known regarding the interactions of individual species of Apx toxin with target cells. The objective of this study was to examine whether AP serotype 10-derived exotoxin, ApxI, caused apoptosis in porcine alveolar macrophages (PAMs) and to delineate the underlying signaling pathways. Isolated PAMs were stimulated with different concentrations of native ApxI and monitored for apoptosis using Hoechst staining, TUNEL, and DNA laddering assays. The ApxI-stimulated PAMs exhibited typical morphological features of apoptosis, including condensation of chromatin, formation of apoptotic bodies and DNA laddering. ApxI-induced apoptosis in a concentration- and time-dependent manner. Furthermore, to delineate the signaling events involved in ApxI-induced apoptosis, it was observed that caspase 3 was activated in ApxI-stimulated PAMs. Ablation of caspase 3 activity via specific inhibitors protected PAMs from apoptosis by ApxI. This study is the first to demonstrate that native ApxI causes apoptosis in PAMs at low concentrations and that these apoptotic events are mediated via a caspase 3-dependent pathway. These findings suggest a role of ApxI in AP infection as it might impair the host defense system through the induction of apoptosis in PAMs.

Cytochrome P450 ω-hydroxylase inhibition reduces cardiomyocyte apoptosis via activation of ERK1/2 signaling in rat myocardial ischemia-reperfusion

Cytochrome P450 (CYP) ω-hydroxylases and their arachidonic acid metabolites play important roles in myocardial ischemia-reperfusion injury. In this study we investigated the effects of several selective CYP ω-hydroxylase inhibitors on myocardial ischemia/reperfusion-induced myocardial apoptosis. Rats were subjected 30 min of ischemia and 2 h of reperfusion. Groups received either 17-octadecynoic acid (17-ODYA, 0.3 or 3 mg/kg), N-methylsulfonyl-12, 12-dibromododec-11-enamide (DDMS, 0.4 or 0.8 mg/kg), N-hydroxy- N'-(4-butyl-2-methylphenyl) formamidine (HET0016, 0.1 or 1 mg/kg) or vehicle 10 min prior to ischemia. To further assess the role of mitogen-activated protein kinases (MAPKs) in the CYP ω-hydroxylase inhibitor-induced anti-apoptotic effect, rats also received PD98059 (1 mg/kg), SB203580 (1 mg/kg) or SP600125 (6 mg/kg) 15 min prior to ischemia, with subsets of rats also receiving HET0016 10 min prior to ischemia. Compared with vehicle group, 17-ODYA, DDMS and HET0016 significantly inhibited myocardial apoptosis as evidenced by decreased DNA ladder formation, terminal dUTP deoxynucleotidyltransferase nick end-labeling (TUNEL) positive nuclear staining. They also decreased caspase-3 activity and Bax protein expression but up-regulated the expression of Bcl-2. Conversely, exogenous 20-HETE administration exerted opposite effects. Moreover, HET0016 increased the activity of extracellular signal-related protein kinases 1 and 2 (ERK1/2) but had no significant effect on p38 MAPK or c-Jun N-terminal kinase (JNK) during ischemia/reperfusion. Pretreatment with PD98059, the inhibitor of ERK1/2, but not SB203580 or SP600125, almost completely blocked the effect exerted by HET0016. Taken together, these data suggest that CYP ω-hydroxylase inhibition exerts significant anti-apoptosis effects, at least in part, by activation of ERK1/2 in ischemia/reperfusion heart.

Arsenic trioxide and lead acetate induce apoptosis in adult rat hepatic stem cells

In the present study, the toxicity of arsenic trioxide and lead acetate was assessed in adult hepatic stem cells induced in the 2-acetyl-aminofluorene/partial hepatectomy rat model. Isolated oval cells were incubated separately for 6 h with 40 muM each of arsenic trioxide and lead acetate. 3-(4,5-Dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide assay denoted significant time-dependent cell death in arsenic and lead treated oval cells. The degree of stress imposed by these metals was evidenced by induction of heat shock protein (HSP) 70 and HSP 90. Arsenic and lead were found to trigger apoptosis as revealed by DNA ladder formation, Western blots of apoptotic factors, and reverse transcriptase polymerase chain reaction analyses of bax and bcl-2. Results clearly indicate that both arsenic and lead induced apoptosis is caspase-mediated and accompanied by extracellular signal-regulated kinase (ERK) dephosphorylation. Full-length BH3-interacting-domain death agonist expression in presence of caspase 3 inhibitor unravels a direct involvement of caspase in As and Pb induced apoptosis. Expression patterns of apoptosis inducing factor, B cell lymphoma-2 (Bcl-2) antagonist of cell death, Bcl-2-associated X protein, and Bcl2 also signify mitochondrial regulation of apoptosis effected by lead and arsenic. It is concluded that stimulation of caspase cascade and simultaneous ERK dephosphorylation are the most significant operative pathways directly associated with apoptotic signals triggered by arsenic and lead in the oval cells.

Synthetic chenodeoxycholic acid derivative, HS-1200, induces apoptosis of human hepatoma cells via a mitochondrial pathway

We investigated whether HS-1200 has anti-proliferation effects on human hepatoma cells in vitro. Here, chromatin condensation, DNA ladder formation and proteolytic cleavage of poly (ADP-ribose) polymerase (PARP) were observed after treatment of HS-1200, indicating the occurrence of apoptotic cell death, which was associated with up-regulation of Bax, cleaved-caspase-3 and cleaved-caspase-9. Inhibition of caspase-9 rescued HS-1200-induced apoptosis. Furthermore, cells treated with HS-1200 showed a reduction in mitochondrial membrane potential (Δ ψ m) and caused cytochrome c release into the cytosol. The results indicated that synthetic chenodeoxycholic acid HS-1200 could induce cell apoptosis in BEL7402 human hepatoma cell line, via a Bax/cytochrome c/caspase-9 independent pathway. This study suggested that HS-1200 is potentially useful as an apoptosis inducer for the treatment of hepatocellular carcinoma.

사람 두경부 편평세포암종 HEp2 세포에서 BCH에 의한 세포성장 억제기전

Amino acid transporters are essential for the growth and proliferation in all living cells. Among the amino acid transporters, the system L amino acid transporters are the major nutrient transport system responsible for the Na + -independent transport of neutral amino acids including several essential amino acids. The L-type amino acid transporter 1 (LAT1), an isoform of system L amino acid transporter, is highly expressed in cancer cells to support their continuous growth and proliferation. 2-Aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) is a model compound for the study of amino acid transporter as a system L selective inhibitor. We have examined the effect and mechanism of BCH on cell growth suppression in HEp2 human head and neck squamous cell carcinoma. The BCH inhibited the L-leucine transport in a concentration-dependent manner with a IC50 value of 51.2±3.8 μM in HEp2 cells. The growth of HEp2 cells was inhibited by BCH in the timeand concentration-dependent manners. The formation of DNA ladder was not observed with BCH treatment in the cells. Furthermore, the proteolytic processing of caspase-3 and caspase-7 in the cells were not detected by BCH treatment. These results suggest that the BCH inhibits the growth of HEp2 human head and neck squamous cell carcinoma through the intracellular depletion of neutral amino acids for cell growth without apoptotic processing.

ERK-like MAPK signaling and cytochrome c response to oleic acid in two-liquid-phase suspension cultures of Taxus cuspidata

To elucidate the underlying signal mechanisms of Taxus cuspidata in response to oleic acid (OA) in two-liquid-phase suspension cultures (TLPSCs), the mitogen-activated protein kinase (MAPK) activation and release of cytochrome c (CytC) from mitochondria in TLPSC T. cuspidata were investigated with Western blot. The results showed that a long-term treatment with 4% (v/v) OA caused apoptosis and release of CytC from mitochondria and inhibited the activation of extracellular signal-regulated kinase-like (ERK-like) MAPK (approximately 46 kDa) in TLPSC of T. cuspidata, but a short-term treatment significantly increased the ERK-like MAPK activity. These findings suggest that the coordinate expression of p-ERK and CytC is fundamentally involved in cell survival or death in TLPSC T. cuspidata. Further investigation confirmed that anthracene-9-carboxylate (an ion-channel blocker) and suramin (a G-protein inhibitor) markedly blocked the ERK-like MAPK activity, inhibited DNA ladder formation and O 2 − burst and reduced Taxol production. Although diphenyliodonium (an inhibitor of O 2 − formation) successfully blocked DNA ladder formation and decreased Taxol production, it did not significantly affect the ERK-like MAPK activity, indicating that the ERK-like MAPK activation should depend on the OA-stimulated G-protein and ion-channel activity, but not on the oxidative burst during the apoptosis and Taxol production in TLPSC T. cuspidata cells.

Knockdown of SMYD3 by RNA interference inhibits cervical carcinoma cell growth and invasion in vitro

Elevated expression of SMYD3 is a frequent genetic abnormality in several malignancies. Few studies knocking down SMYD3 expression in cervical carcinoma cells have been performed to date. In this paper, we established an inducible short hairpin RNA expression system to examine its role in maintaining the malignant phenotype of HeLa cells. After being induced by doxycycline, SMYD3 mRNA and protein expression were both reduced, and significant reductions in cell proliferation, colony formation and migration/invasion activity were observed in the SMYD3-silenced HeLa cells. The percentage of cells in sub-G1 was elevated and DNA ladder formation could be detected, indicating potent induction of apoptosis by SMYD3 knockdown. These findings imply that SMYD3 plays crucial roles in HeLa cell proliferation and migration/invasion, and that it may be a useful therapeutic target in human cervical carcinomas.

Chenopodium album seed extract-induced sperm cell death: exploration of a plausible pathway

BackgroundThis study was conducted for to explore the plausible pathway of Chenopodium album seed extract (CAE)-mediated sperm cell death. Study DesignThe role of CAE for its spermicidal action was assessed by (a) measuring lipid peroxidation, protein carbonyl content and intracellular glutathione content in CAE exposed sperm cells; (b) assaying antioxidant enzymes like catalase and superoxide dismutase (SOD); (c) analyzing protein expressions by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis; (d) fluorimetric measurement of intracellular H2O2 level and generation of reactive oxygen species (ROS) in CAE-treated sperm cells; and (e) DNA ladder formation study. ResultsCAE-induced sperm death is due to (a) lipid peroxidation of the sperm cell membrane, oxidation of some critical cellular proteins and depletion of intracellular reduced gluthathione, indicating production of ROS; (b) activation of Mn-SOD and inactivation of catalase favoring endogenous accumulation of H2O2; (c) generation of O2− at an enhanced rate during oxidative stress as evidenced by increased Mn-SOD activity and protein expression; (d) accumulation of ROS in spermatozoa reflected in the fluorimetric experiments; and (e) increased production of O2− and H2O2 induced apoptosis-like death in sperm cells as observed by DNA ladder formation. ConclusionThe sperm death mediated by CAE is due to oxidative damage of cellular macromolecules by in situ generation of ROS.

Novel sugar-cholestanols as anticancer agents against peritoneal dissemination of tumor cells

Chemically synthesized sugar-cholestanols with mono-, di-, and tri-saccharides attached to cholestanol showed strong inhibiting activity against the proliferation of colorectal and gastric cancer cells. In contrast, cholestanol without sugar moieties was totally ineffective. Furthermore, when cancer cells were exposed to GlcNAcRbetacholestanol (R=(-) or beta1-3Gal), the compound was rapidly taken up via the lipid rafts/microdomains on the cell surface. The uptake of sugar-cholestanol in mitochondria increased gradually and was followed by the release of cytochrome c from mitochondria and the activation of apoptotic signals through the mitochondrial pathway and the caspase cascade, leading to apoptotic cell death, characterized by DNA ladder formation and nuclear fragmentation. Additionally, the examination of GlcNAcRbetacholestanol in a mouse model of peritoneal dissemination showed a dramatic reduction of tumor growth (P < 0.003) and prolonged mouse survival time (P<0.0001). Based on these observations, we believe that the sugar-cholestanols described here have clinical potential as novel anticancer agents.

Delayed rectifier potassium channels are involved in SO2 derivative-induced hippocampal neuronal injury

Recent studies implicate the possible neurotoxicity of SO2, however, its mechanisms remain unclear. In the present study, we investigated SO2 derivative-induced effect on delayed rectifier potassium channels (IK) and cellular death/apoptosis in primary cultured hippocampal neurons. The results demonstrate that SO2 derivatives (NaHSO3 and Na2SO3, 3:1M/M) effectively augmented IK and promoted the activation of delayed rectifier potassium channels. Also, SO2 derivatives increased neuronal death percentage and contributed to the formation of DNA ladder in concentration-dependent manners. Interestingly, the neuronal death and DNA ladder formation, caused by SO2 derivatives, could be attenuated by the delayed rectifier potassium channel blocker (tetraethylammonium, TEA), but not by the transient outward potassium channel blocker (4-aminopyridine, 4-AP). It implies that stimulating delayed rectifier potassium channels were involved in SO2 derivative-caused hippocampal neuronal insults, and blocking these channels might be one of the possibly clinical treatment for SO2-caused neuronal dysfunction.