Apoptotic Pathways: Ten Minutes to Dead

Sirt3 protects cortical neurons against oxidative stress via regulating mitochondrial Ca2+ and mitochondrial biogenesis

Oxidative stress is a well-established event in the pathology of several neurobiological diseases. Sirt3 is a nicotinamide adenine nucleotide (NAD+)-dependent protein deacetylase that regulates mitochondrial function and metabolism in response to caloric restriction and stress. This study aims to investigate the role of Sirt3 in H2O2 induced oxidative neuronal injury in primary cultured rat cortical neurons. We found that H2O2 treatment significantly increased the expression of Sirt3 in a time-dependent manner at both mRNA and protein levels. Knockdown of Sirt3 with a specific small interfering RNA (siRNA) exacerbated H2O2-induced neuronal injury, whereas overexpression of Sirt3 by lentivirus transfection inhibited H2O2-induced neuronal damage reduced the generation of reactive oxygen species (ROS), and increased the activities of endogenous antioxidant enzymes. In addition, the intra-mitochondrial Ca2+ overload, but not cytosolic Ca2+ increase after H2O2 treatment, was strongly attenuated after Sirt3 overexpression. Overexpression of Sirt3 also increased the content of mitochondrial DNA (mtDNA) and the expression of mitochondrial biogenesis related transcription factors. All these results suggest that Sirt3 acts as a prosurvival factor playing an essential role to protect cortical neurons under H2O2 induced oxidative stress, possibly through regulating mitochondrial Ca2+ homeostasis and mitochondrial biogenesis.

NG as a novel nitric oxide donor induces apoptosis by increasing reactive oxygen species and inhibiting mitochondrial function in MGC803 cells

NG, O(2)-(2,4-dinitro-5-{[2-(12-en-28-β-D-galactopyranosyl-oleanolate-3-yl)-oxy-2-oxoethyl] amino} phenyl) 1-(N-hydroxyethylmethylamino) diazen-1-ium-1,2-diolate, was identified in our laboratory as a novel nitric oxide-releasing prodrug with antitumor effects. A previous study showed that NG inhibited cell growth, and induced apoptosis in HepG2 cells. In this study, the inhibitory effects of NG on the viability of MGC803 cells were examined using methylthiazolyl tetrazolium biomide (MTT) assay, neutral red assay and trypan blue exclusion test. The results showed that NG had strong cytotoxicity to induce apoptosis, which was characterized by a significant externalization of phosphatidylserine, nuclear morphological changes and enhanced Bax-to-Bcl-2 ratio. Moreover, the release of cytochrome c (Cyt c) from mitochondria and the activation of caspase-9/3 were also detected, indicating that NG may induce apoptosis through a mitochondrial-mediated pathway. NG induced mitochondrial dysfunction in MGC803 cells by altering membrane potential (△Ψm), the inhibition of complexes I, II and IV consequently decreasing ATP level. Furthermore, the treatment of MGC803 cells with NG caused a marked rise in oxidative stress as characterized by accumulation of reactive oxygen species (ROS), excessive malondialdehyde (MDA) production and a reduction in glutathione hormone (GSH) level and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity. In addition, pretreatment with N-acetylcysteine (NAC), a GSH synthesis precursor, was partially protective against the NG-induced ROS generation and cell apoptosis. In contrast, pretreatment of MGC803 cells with L-buthionine-S, R-sulfoximine (BSO), a GSH synthesis inhibitor, increased the ROS levels, and aggravated cell apoptosis by NG. These results suggest that NG-induced apoptosis in MGC803 cells is mediated, at least in part, by the increase in ROS production, oxidative stress and mitochondrial dysfunction.

Oxygen free radicals and mitochondrial signaling in oligospermia and asthenospermia

The aim of this study was to investigate the roles of oxygen free radicals and mitochondrial signaling in semen disorders, in particular, how this induces low concentrations and reduced motility of sperm. Ejaculate samples were obtained from 120 young adult males (mean age, 28.7±5.3 years) with normal semen (n=30), oligospermia (n=30), asthenospermia (n=30) and oligoasthenozoospermia (n=30). The malondialdehyde (MDA) content, total superoxide dismutase (T‑SOD) activity and glutathione peroxidase (GSH‑Px) activity of the sperm samples were determined by enzymatic assays. Mitochondrial membrane potential (MMP) was determined by flow cytometric detection of accumulated membrane‑permeable JC‑1 fluorescent dye. The mRNA and protein expression levels of apoptosis-associated genes [Bcl‑2, Bax, cytochrome c (Cyt C) and caspase-3] were measured by quantitative polymerase chain reaction and western blotting. Intergroup differences were evaluated by Student's t‑test. The sperm samples from all semen disorder groups exhibited significantly lower T‑SOD content and GSH‑Px activity (all P<0.05 versus normal sperm), and the extent of reduction revealed a disorder-associated trend (asthenospermia < oligospermia ≈ oligoasthenozoospermia). By contrast, the semen disorder groups had significantly higher MDA content (all P<0.05 versus normal sperm); the extent of this increase also revealed a disorder-associated trend (asthenospermia > oligospermia ≈ oligoasthenozoospermia). The sperm from patients with semen disorders also exhibited significantly lower MMP than normal sperm, as evidenced by lower mean ratios of JC‑1+ sperm per group. The semen disorder groups had significantly higher Bax, Cyt C and caspase-3 mRNA and protein expression levels in the sperm samples, but significantly lower levels of Bcl‑2 (all P<0.05 versus normal sperm). However, only the extent of increases in Cyt C and caspase-3 exhibited a disorder-associated trend (oligospermia > asthenospermia). In conclusion, oxygen free radicals may be involved in reduced sperm concentration and motility, possibly through effects on the mitochondrial apoptotic signaling pathway. Perturbed mitochondrial release of Cyt C may be the distinguishing molecular feature between oligospermia and asthenospermia.

Detection of DNA damage in peripheral blood mononuclear cells from pancreatic cancer patients

DNA repair is a key mechanism in maintaining genomic stability: repair deficiencies increase DNA damage and mutations that lead to several diseases, including cancer. We extracted DNA from peripheral blood mononuclear cells (PBMCs) of 48 pancreatic adenocarcinoma cases and 48 healthy controls to determine relative levels of nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) damage by QPCR. All participants were never smokers and between the ages of 60 and 69. Average levels among cases were compared to controls using a rank sum test, and logistic regression adjusted for potential confounding factors (age, sex, and diabetes mellitus). Cases had less DNA damage, with a significant decrease in mtDNA damage (P-value = 0.03) and a borderline significant decrease in nDNA damage (P = 0.08). Across samples, we found mtDNA abundance was higher among non-diabetics compared to diabetics (P = 0.04). Our results suggest that patients with pancreatic adenocarcinoma have less DNA damage in their PBMCs, and that having diabetes, a known pancreatic cancer risk factor, is associated with lower levels of mtDNA abundance.

Chemical glycosylation of cytochrome c improves physical and chemical protein stability

Background

Cytochrome c (Cyt c) is an apoptosis-initiating protein when released into the cytoplasm of eukaryotic cells and therefore a possible cancer drug candidate. Although proteins have been increasingly important as pharmaceutical agents, their chemical and physical instability during production, storage, and delivery remains a problem. Chemical glycosylation has been devised as a method to increase protein stability and thus enhance their long-lasting bioavailability.

Results

Three different molecular weight glycans (lactose and two dextrans with 1 kD and 10 kD) were chemically coupled to surface exposed Cyt c lysine (Lys) residues using succinimidyl chemistry via amide bonds. Five neo-glycoconjugates were synthesized, Lac₄-Cyt-c, Lac₉-Cyt-c, Dex₅(10kD)-Cyt-c, Dex₈(10kD)-Cyt-c, and Dex₃(1kD)-Cyt-c. Subsequently, we investigated glycoconjugate structure, activity, and stability. Circular dichroism (CD) spectra demonstrated that Cyt c glycosylation did not cause significant changes to the secondary structure, while high glycosylation levels caused some minor tertiary structure perturbations. Functionality of the Cyt c glycoconjugates was determined by performing cell-free caspase 3 and caspase 9 induction assays and by measuring the peroxidase-like pseudo enzyme activity. The glycoconjugates showed ≥94% residual enzyme activity and 86 ± 3 to 95 ± 1% relative caspase 3 activation compared to non-modified Cyt c. Caspase 9 activation by the glycoconjugates was with 92 ± 7% to 96 ± 4% within the error the same as the caspase 3 activation. There were no major changes in Cyt c activity upon glycosylation. Incubation of Dex₃(1 kD)-Cyt c with mercaptoethanol caused significant loss in the tertiary structure and a drop in caspase 3 and 9 activation to only 24 ± 8% and 26 ± 6%, respectively. This demonstrates that tertiary structure intactness of Cyt c was essential for apoptosis induction. Furthermore, glycosylation protected Cyt c from detrimental effects by some stresses (i.e., elevated temperature and humidity) and from proteolytic degradation. In addition, non-modified Cyt c was more susceptible to denaturation by a water-organic solvent interface than its glycoconjugates, important for the formulation in polymers.

Conclusion

The results demonstrate that chemical glycosylation is a potentially valuable method to increase Cyt c stability during formulation and storage and potentially during its application after administration.

Altered antioxidant system stimulates dielectric barrier discharge plasma-induced cell death for solid tumor cell treatment

This study reports the experimental findings and plasma delivery approach developed at the Plasma Bioscience Research Center, Korea for the assessment of antitumor activity of dielectric barrier discharge (DBD) for cancer treatment. Detailed investigation of biological effects occurring after atmospheric pressure non-thermal (APNT) plasma application during in vitro experiments revealed the role of reactive oxygen species (ROS) in modulation of the antioxidant defense system, cellular metabolic activity, and apoptosis induction in cancer cells. To understand basic cellular mechanisms, we investigated the effects of APNT DBD plasma on antioxidant defense against oxidative stress in various malignant cells as well as normal cells. T98G glioblastoma, SNU80 thyroid carcinoma, KB oral carcinoma and a non-malignant HEK293 embryonic human cell lines were treated with APNT DBD plasma and cellular effects due to reactive oxygen species were observed. Plasma significantly decreased the metabolic viability and clonogenicity of T98G, SNU80, KB and HEK293 cell lines. Enhanced ROS in the cells led to death via alteration of total antioxidant activity, and NADP+/NADPH and GSH/GSSG ratios 24 hours (h) post plasma treatment. This effect was confirmed by annexin V-FITC and propidium iodide staining. These consequences suggested that the failure of antioxidant defense machinery, with compromised redox status, might have led to sensitization of the malignant cells. These findings suggest a promising approach for solid tumor therapy by delivering a lethal dose of APNT plasma to tumor cells while sparing normal healthy tissues.

ROS-dependent antiproliferative effect of brassinin derivative homobrassinin in human colorectal cancer Caco2 cells

This study was designed to examine the in vitro antiproliferative effect of brassinin and its derivatives on human cancer cell lines. Among seven tested compounds, homobrassinin (K1; N-[2-(indol-3-yl)ethyl]-S-methyldithiocarbamate) exhibited the most potent activity with IC₅₀ = 8.0 μM in human colorectal Caco2 cells and was selected for further studies. The flow cytometric analysis revealed a K1-induced increase in the G₂/M phase associated with dysregulation of α-tubulin, α₁-tubulin and β₅-tubulin expression. These findings suggest that the inhibitory effect of K1 can be mediated via inhibition of microtubule formation. Furthermore, simultaneously with G₂/M arrest, K1 also increased population of cells with sub-G₁ DNA content which is considered to be a marker of apoptotic cell death. Apoptosis was also confirmed by annexin V/PI double staining, DNA fragmentation assay and chromatin condensation assay. The apoptosis was associated with the loss of mitochondrial membrane potential (MMP), caspase-3 activation as well as intracellular reactive oxygen species (ROS) production. Moreover, the antioxidant Trolox blocked ROS production, changes in MMP and decreased K1 cytotoxicity, which confirmed the important role of ROS in cell apoptosis. Taken together, our data demonstrate that K1 induces ROS-dependent apoptosis in Caco2 cells and provide the rationale for further in vivo anticancer investigation.

Dioscin induced activation of p38 MAPK and JNK via mitochondrial pathway in HL-60 cell line

Saponins have shown promise in cancer prevention and therapy; however, little is known about the detailed signaling pathways underlying their anticancer activities. In the present study, we examined the mechanisms of action of dioscin, a glucosides saponin isolated from Polygonatum zanlanscianense pump, in human myeloblast leukemia HL-60 cells. Dioscin suppressed HL-60 cell growth in a dose-dependent manner. This inhibition was due to the induction of apoptosis as revealed by the externalization of phosphatidylserine, and cleavages of lamin A/C and PARP-1. Treatment with dioscin induced apoptosis through activation of caspases 3, 7, 8, 9, and 10. Phosphorylation of p38 MAPK and JNK contributed to dioscin-induced apoptosis upstream of caspase activation. Using various inhibitors and antioxidant agents, we found that mitochondrial derived reactive oxygen species and depletion of mitochondrial transmembrane potential lead to the phosphorylation of p38 MAPK and JNK. Taken together, our results demonstrated that dioscin induces apoptosis by activation of p38 MAPK and JNK through the caspase-dependent mitochondrial death pathway. This work suggests that dioscin may be used as a drug lead for the treatment of myeloblast leukemia.

Caspase 3 inactivation protects against hepatic cell death and ameliorates fibrogenesis in a diet-induced NASH model

BACKGROUND/AIMS

Hepatocyte cell death is a key feature of nonalcoholic steatohepatitis (NASH). As the contribution of specific caspases remains unclear, our aim was to ascertain the effect of caspase 3 suppression on liver injury and fibrogenesis.

METHODS

C57BL/6 wild-type (WT) and caspase 3 knock out (Casp3 (-/-)) mice were placed on a methionine- and choline-deficient (MCD) diet for 6 weeks to induce steatohepatitis and liver fibrosis. Thereafter, liver injury, liver fibrosis and hepatocellular apoptosis were quantified in liver sections. Additionally, expression of proteins associated with liver inflammation and fibrogenesis was analyzed.

RESULTS

WT mice fed MCD diet showed marked activation of caspase 3 in hepatocytes, in conjunction with steatohepatitis and increased hepatic triglyceride levels, hepatocyte ballooning, inflammation and fibrosis. Casp3 (-/-) mice fed the MCD diet showed similar serum aminotransferase levels and NAFLD activity scores (NAS) compared with WT MCD-fed mice. However, Casp3 (-/-) mice on the MCD diet showed a marked reduction in expression of transcripts for profibrogenic genes, which translated into reduced hepatic collagen deposition. These changes were associated with decreased levels of apoptosis, and a significant reduction in the expression of cytokines involved in inflammatory signaling. Casp3 (-/-) mice on the MCD showed a reduction in expression of chemokine receptor 2 (CCR2) leading to ameliorated infiltration of inflammatory lymphocyte antigen 6 complex, locus C1 (Ly6c) positive monocytes.

CONCLUSION

These findings support a prominent role for hepatocyte caspase 3 activation in NASH-related apoptosis, fibrogenesis and fibrosis which in part is mediated via CCR2-dependent infiltration of Ly6c positive monocytes.

Receptor-interacting protein kinases modulate noise-induced sensory hair cell death

Receptor-interacting protein (RIP) kinases promote the induction of necrotic cell death pathways. Here we investigated signaling pathways in outer hair cells (OHCs) of adult male CBA/J mice exposed to noise that causes permanent threshold shifts, with a particular focus on RIP kinase-regulated necroptosis. One hour after noise exposure, nuclei of OHCs in the basal region of the cochlea displayed both apoptotic and necrotic features. RIP1 and RIP3 protein levels increased and caspase-8 was activated. Treatment with pan-caspase inhibitor ZVAD blocked the activation of caspase-8 and reduced the number of apoptotic nuclei, while increasing levels of RIP1, RIP3, and necrotic OHCs. Conversely, treatment with necrosis inhibitor necrostatin-1 (Nec-1) or RIP3 siRNA (siRIP3) diminished noise-induced increases in RIP1 and RIP3, and decreased necrotic OHC nuclei. This treatment also increased the number of apoptotic nuclei without increasing activation of caspase-8. Consistent with the elevation of levels of RIP1 and RIP3, noise-induced active AMPKα levels increased with ZVAD treatment, but decreased with Nec-1 and siRIP3 treatment. Furthermore, treatment with siRIP3 did not alter the activation of caspase-8, but instead increased activation of caspase-9 and promoted endonuclease G translocation into OHC nuclei. Finally, auditory brainstem response functional measurements and morphological assessment of OHCs showed that ZVAD treatment reduces noise-induced deficits. This protective function is potentiated when combined with siRIP3 treatment. In conclusion, noise-induced OHC apoptosis and necrosis are modulated by caspases and RIP kinases, respectively. Inhibition of either pathway shifts the prevalence of OHC death to the alternative pathway.

Insights into regulatory molecules of intestinal epithelial cell turnover during experimental infection by Heterophyes heterophyes

Heterophyiasis is an intestinal disease that remains endemic in many parts of the world, particularly the Nile Delta of Egypt and Southeast Asia, yet the populations at risk of infection expand throughout the world. The main histopathological feature of infection is villous atrophy, but the underlying factors are not well understood. Apoptosis of the villous epithelial cells was previously reported to be enhanced during intestinal parasitic infections; however, the role of Heterophyes heterophyes on enterocyte apoptosis was to be explored. Therefore, intestinal sections from mice experimentally infected with H. heterophyes were studied histopathologically and immunohistochemically for caspase-3 and NF-κB and compared to non-infected control mice. Atrophic villi covered by poorly differentiated epithelial cells were observed in the 2nd week post-infection. Also, we noted marked hyperplasia of the intestinal crypts with abundant inflammatory cellular infiltrate in the lamina propria, as well as apoptosis of cells lining the intestinal villi. Both caspase-3 and NF-κB showed positive staining in the intestinal epithelial cells with varying grades of intensity over the length of infection. Caspase-3 expression rose at the 2nd week p.i. then decreased over time, whereas NF-κB expression showed progressive increase throughout the weeks of infection. In conclusion, caspase-3 activation may be an important factor in the apoptotic pathway in early heterophyiasis, and, on the other hand, NF-κB seems to play a role in protecting the intestinal cells from excessive apoptosis. These observations may help open new avenues for tissue protective therapies that avoid or control the deleterious processes of apoptosis in various inflammatory conditions.

Microarray analysis of serum mRNA in patients with head and neck squamous cell carcinoma at whole-genome scale

With the increasing demand for noninvasive approaches in monitoring head and neck cancer, circulating nucleic acids have been shown to be a promising tool. We focused on the global transcriptome of serum samples of head and neck squamous cell carcinoma (HNSCC) patients in comparison with healthy individuals. We compared gene expression patterns of 36 samples. Twenty-four participants including 16 HNSCC patients (from 12 patients we obtained blood samples 1 year posttreatment) and 8 control subjects were recruited. The Illumina HumanWG-6 v3 Expression BeadChip was used to profile and identify the differences in serum mRNA transcriptomes. We found 159 genes to be significantly changed (Storey's P value <0.05) between normal and cancer serum specimens regardless of factors including p53 and B-cell lymphoma family members (Bcl-2, Bcl-XL). In contrast, there was no difference in gene expression between samples obtained before and after surgery in cancer patients. We suggest that microarray analysis of serum cRNA in patients with HNSCC should be suitable for refinement of early stage diagnosis of disease that can be important for development of new personalized strategies in diagnosis and treatment of tumours but is not suitable for monitoring further development of disease.

Necrosis-driven systemic immune response alters SAM metabolism through the FOXO-GNMT axis

Sterile inflammation triggered by endogenous factors is thought to contribute to the pathogenesis of acute and chronic inflammatory diseases. Here, we demonstrate that apoptosis-deficient mutants spontaneously develop a necrosis-driven systemic immune response in Drosophila and provide an in vivo model for studying the organismal response to sterile inflammation. Metabolomic analysis of hemolymph from apoptosis-deficient mutants revealed increased sarcosine and reduced S-adenosyl-methionine (SAM) levels due to glycine N-methyltransferase (Gnmt) upregulation. We showed that Gnmt was elevated in response to Toll activation induced by the local necrosis of wing epidermal cells. Necrosis-driven inflammatory conditions induced dFoxO hyperactivation, leading to an energy-wasting phenotype. Gnmt was cell-autonomously upregulated by dFoxO in the fat body as a possible rheostat for controlling energy loss, which functioned during fasting as well as inflammatory conditions. We propose that the dFoxO-Gnmt axis is essential for the maintenance of organismal SAM metabolism and energy homeostasis.

Nonthermal plasma induces head and neck cancer cell death: the potential involvement of mitogen-activated protein kinase-dependent mitochondrial reactive oxygen species

Nonthermal plasma (NTP) is generated by ionization of neutral gas molecules, which results in a mixture of energy particles including electrons and ions. Recent progress in the understanding of NTP has led to its application in the treatment of various diseases, including cancer. However, the molecular mechanisms of NTP-induced cell death are unclear. The purpose of this study was to evaluate the molecular mechanism of NTP in the induction of apoptosis of head and neck cancer (HNC) cells. The effects of NTP on apoptosis were investigated using MTT, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling, Annexin V assays, and western blot analysis. The cells were examined for production of reactive oxygen species (ROS) using DCFCA or MitoSOX staining, intracellular signaling, and an animal model. NTP reduced HNC cell viability in a dose-dependent manner and induced apoptosis. NTP resulted in alteration of mitochondrial membrane potential and accumulation of intracellular ROS generated from the mitochondria in HNC cells. Blockade of ROS production by N-acetyl-L-cysteine inhibited NTP-induced apoptosis. NTP led to the phosphorylation of c-JUN N-terminal kinase (JNK) and p38, but not extracellular-regulated kinase. Treatment with JNK and p38 inhibitors alleviated NTP-induced apoptosis via ROS generation. Taken together, these results show that NTP induced apoptosis of HNC cells by a mechanism involving MAPK-dependent mitochondrial ROS. NTP inhibited the growth of pre-established FaDu tumors in a nude mouse xenograft model and resulted in accumulation of intracellular ROS. In conclusion, NTP induced apoptosis in HNC cells through a novel mechanism involving MAPK-mediated mitochondrial ROS. These findings show the therapeutic potential of NTP in HNC.

PI3K/Akt pathway involving into apoptosis and invasion in human colon cancer cells LoVo

In this study we determined the effects of Curcumin on human colon cancer cells line LoVo. We found that Curcumin significantly inhibited the proliferation, migration and invasion, and clone formation of LoVo cells in a dose-dependent manner. Curcumin also dose-dependently reduced the phosphorylation of proteins Akt and increased expression levels of the genes caspase-3, cytochrome-c, Bax mRNA in LoVo cells. In addition, Curcumin dose-dependently decreased gene Bcl-2 mRNA expression. Similar results were observed in LoVo cells treated with LY294002. These in vitro studies suggest that Curcumin may play its anti-cancer actions partly via suppressing PI3K/Akt signal pathway in LoVo cells.

Many players in BCL-2 family affairs

During apoptotic cell death, cellular stress signals converge at the mitochondria to induce mitochondrial outer-membrane permeabilization (MOMP) through B cell lymphoma-2 (BCL-2) family proteins and their effectors. BCL-2 proteins function through protein-protein interactions, the mechanisms and structural aspects of which are only now being uncovered. Recently, the elucidation of the dynamic features underlying their function has highlighted their structural plasticity and the consequent complex thermodynamic landscape governing their protein-protein interactions. These studies show that canonical interactions involve a conserved, hydrophobic groove, whereas non-canonical interactions function allosterically outside the groove. We review the latest structural advances in understanding the interactions and functions of mammalian BCL-2 family members, and discuss new opportunities to modulate these proteins in health and disease.

E93 predominantly transduces 20-hydroxyecdysone signaling to induce autophagy and caspase activity in Drosophila fat body

During the larval-prepupal transition in Drosophila, a balancing crosstalk occurs between autophagy and caspase activity in the remodeling fat body: the inhibition of autophagy induces caspase activity and the inhibition of caspases induces autophagy. Both autophagy and caspase activity are induced by a pulse of molting hormone (20-hydroxyecdysone, 20E) via the 20E nuclear receptor complex, EcR-USP. We here demonstrate that E93, a 20E primary-response gene encoding an HTH transcription factor, predominantly transduces 20E signaling to induce autophagy and caspase activity in the remodeling fat body. RNAi knockdown or mutation of E93 blocks autophagy and caspase activity, E93 overexpression induces them both, while E93 overexpression has a better rescuing effect on the inhibition of autophagy than caspase activity caused by EcR(DN) overexpression. At the transcriptional level, E93 not only greatly impacts the 20E-triggered transcriptional cascade, but also upregulates essential autophagy and apoptosis genes. Meanwhile, at the phosphorylational level, E93 blocks the PI3K-TORC1 signaling to initiate autophagy. Taken together, we conclude that autophagy and caspase activity are induced by 20E and predominantly transduced by E93 in the remodeling fat body of Drosophila.

Molecular mechanisms of exopolysaccharide from Aphanothece halaphytica (EPSAH) induced apoptosis in HeLa cells

The present study aims to investigate the pharmacological effect of the exopolysaccharides from Aphanothece halophytica GR02 (EPSAH) on the HeLa human cervical cancer cell line. HeLa cells were cultured in RPMI-1640-10% FBS medium containing with or without different concentrations of EPSAH. Cell viability was assessed by methylthiazol tetrazolium (MTT) assay. Cell apoptosis was elevated with Wright-Giemsa staining, AO/EB double staining, and DNA fragmentation assay. Apoptosis-associated molecules from cultured HeLa cells were quantified using Western blot analysis. Our results suggest that EPASH induces apoptosis in HeLa cells by targeting a master unfolded protein response (UPR) regulator Grp78. Grp78 further promotes the expression of CHOP and downregulates expression of survivin, which leads to activate mitochondria-mediated downstream molecules and p53-survivin pathway, resulting in caspase-3 activation and causing apoptosis. These findings provide important clues for further evaluating the potential potency of EPSAH for use in cancer therapy.

The molecular basis for the pharmacokinetics and pharmacodynamics of curcumin and its metabolites in relation to cancer

This review addresses the oncopharmacological properties of curcumin at the molecular level. First, the interactions between curcumin and its molecular targets are addressed on the basis of curcumin's distinct chemical properties, which include H-bond donating and accepting capacity of the β-dicarbonyl moiety and the phenylic hydroxyl groups, H-bond accepting capacity of the methoxy ethers, multivalent metal and nonmetal cation binding properties, high partition coefficient, rotamerization around multiple C-C bonds, and the ability to act as a Michael acceptor. Next, the in vitro chemical stability of curcumin is elaborated in the context of its susceptibility to photochemical and chemical modification and degradation (e.g., alkaline hydrolysis). Specific modification and degradatory pathways are provided, which mainly entail radical-based intermediates, and the in vitro catabolites are identified. The implications of curcumin's (photo)chemical instability are addressed in light of pharmaceutical curcumin preparations, the use of curcumin analogues, and implementation of nanoparticulate drug delivery systems. Furthermore, the pharmacokinetics of curcumin and its most important degradation products are detailed in light of curcumin's poor bioavailability. Particular emphasis is placed on xenobiotic phase I and II metabolism as well as excretion of curcumin in the intestines (first pass), the liver (second pass), and other organs in addition to the pharmacokinetics of curcumin metabolites and their systemic clearance. Lastly, a summary is provided of the clinical pharmacodynamics of curcumin followed by a detailed account of curcumin's direct molecular targets, whereby the phenotypical/biological changes induced in cancer cells upon completion of the curcumin-triggered signaling cascade(s) are addressed in the framework of the hallmarks of cancer. The direct molecular targets include the ErbB family of receptors, protein kinase C, enzymes involved in prostaglandin synthesis, vitamin D receptor, and DNA.

Orphan nuclear receptor TR3 acts in autophagic cell death via mitochondrial signaling pathway

Autophagy is linked to cell death, yet the associated mechanisms are largely undercharacterized. We discovered that melanoma, which is generally resistant to drug-induced apoptosis, can undergo autophagic cell death with the participation of orphan nuclear receptor TR3. A sequence of molecular events leading to cellular demise is launched by a specific chemical compound, 1-(3,4,5-trihydroxyphenyl)nonan-1-one, newly acquired from screening a library of TR3-targeting compounds. The autophagic cascade comprises TR3 translocation to mitochondria through interaction with the mitochondrial outer membrane protein Nix, crossing into the mitochondrial inner membrane through Tom40 and Tom70 channel proteins, dissipation of mitochondrial membrane potential by the permeability transition pore complex ANT1-VDAC1 and induction of autophagy. This process leads to excessive mitochondria clearance and irreversible cell death. It implicates a new approach to melanoma therapy through activation of a mitochondrial signaling pathway that integrates a nuclear receptor with autophagy for cell death.

Cooperative inhibitory effect of sinomenine combined with 5-fluorouracil on esophageal carcinoma

AIM: To investigate the inhibitory effects of sinomenine (SIN) combined with 5-fluorouracil (5-FU) on esophageal carcinoma in vitro and in vivo.

METHODS: Esophageal carcinoma (Eca-109) cells were cultured in DMEM. The single or combined growth inhibition effects of SIN and 5-FU on the Eca-109 cells were examined by measuring the absorbance of CCK-8 dye in living cells. Hoechst 33258 staining and an Annexin V/PI apoptosis kit were used to detect the percentage of cells undergoing apoptosis. Western blotting was used to investigate the essential mechanism underlying SIN and 5-FU-induced apoptosis. SIN at 25 mg/kg and 5-FU at 12 mg/kg every 3 d, either combined or alone, was injected into nude mice and tumor growth inhibition and side effects of the drug treatment were observed.

RESULTS: SIN and 5-FU, both in combination and individually, significantly inhibited the proliferation of Eca-109 cells and induced obvious apoptosis. Furthermore, the combined effects were greater than those of the individual agents (P < 0.05). Annexin V/PI staining and Hoechst 33258 staining both indicated that the percentage of apoptotic cells induced by SIN and 5-FU combined or alone were significantly different from the control (P < 0.05). The up-regulation of Bax and down-regulation of Bcl-2 showed that the essential mechanism of apoptosis induced by SIN and 5-FU occurs via the mitochondrial pathway. SIN and 5-FU alone significantly inhibited the growth of tumor xenografts in vivo, and the combined inhibition rate was even higher (P < 0.05). During the course of chemotherapy, no obvious side effects were observed in the liver or kidneys.

CONCLUSION: The combined effects of SIN and 5-FU on esophageal carcinoma were superior to those of the individual compounds, and the drug combination did not increase the side effects of chemotherapy.

Fengycin inhibits the growth of the human lung cancer cell line 95D through reactive oxygen species production and mitochondria-dependent apoptosis

To investigate the antitumor activity and action mechanism of fengycin using the human lung cancer cell line 95D. The antitumor activity of fengycin was tested in vitro and in vivo. Reactive oxygen species production, Ca(2+) uptake, and mitochondrial membrane potential loss induced by fengycin in 95D cells were measured by flow cytometry and a laser confocal microscope. Lactate dehydrogenase release and caspase activity in fengycin-treated 95D cells were assayed using cytotoxicity detection kits. Apoptosis triggered by fengycin was identified by 4,6-diamidino-2-phenylindole (DAPI) staining and flow cytometry. The effects of fengycin on cell-cycle and apoptosis-related proteins were evaluated by quantitative reverse-transcription PCR and western blot. Treatment with fengycin not only significantly decreased cell proliferation in various cancer cell lines including 95D but inhibited the growth of xenografted 95D cells in nude mice. Fengycin also induced reactive oxygen species production and Ca(2+) uptake, as well as lactate dehydrogenase release and mitochondrial membrane potential loss. Further experiments showed that fengycin could trigger apoptosis in 95D cells and cause cell-cycle arrest at the G0/G1 stage by downregulating cyclin D1 and cyclin-dependent kinase 4 (CDK4). While investigating caspase activity and the expression of apoptosis-related proteins, fengycin was found to induce apoptosis in 95D cells through the mitochondrial pathway, evidenced by increased caspase activity, Bax expression, and cytochrome c release into the cytoplasm, as well as decreased Bcl-2 levels. Fengycin can inhibit the growth of the cancer cell line 95D by regulating the cell cycle and promoting apoptosis, suggesting that it may have potential as an anticancer treatment.

Balancing crosstalk between 20-hydroxyecdysone-induced autophagy and caspase activity in the fat body during Drosophila larval-prepupal transition

In the fruitfly, Drosophila melanogaster, autophagy and caspase activity function in parallel in the salivary gland during metamorphosis and in a common regulatory hierarchy during oogenesis. Both autophagy and caspase activity progressively increase in the remodeling fat body, and they are induced by a pulse of the molting hormone (20-hydroxyecdysone, 20E) during the larval-prepupal transition. Inhibition of autophagy and/or caspase activity in the remodeling fat body results in 25-40% pupal lethality, depending on the genotypes. Interestingly, a balancing crosstalk occurs between autophagy and caspase activity in this tissue: the inhibition of autophagy induces caspase activity and the inhibition of caspases induces autophagy. The Drosophila remodeling fat body provides an in vivo model for understanding the molecular mechanism of the balancing crosstalk between autophagy and caspase activity, which oppose with each other and are induced by the common stimulus 20E, and blockage of either path reinforces the other path.

Lipocalin-2 induces apoptosis in human hepatocellular carcinoma cells through activation of mitochondria pathways

Lipocalin 2 (LCN2) is a secreted, iron-binding glycoprotein that is abnormally expressed in some malignant human cancers. However, the roles of LCN2 in hepatocellular carcinoma (HCC) cells are unknown. In this study, we suggested the LCN2 and LCN2R were weak detected in the HCC cell lines, LCN2 and LCN2R were found to be down-regulated in tumor tissues in 16 HCC patients. MTT, DAPI, TUNEL, and flow cytometry analyses revealed that LCN2 overexpression dramatically inhibited cell viability, induced apoptosis features of cell-cycle arrest in sub-G1 phase, in DNA fragmentation, and in condensation of chromatin in Huh-7 and SK-Hep-1 cells. Western blots were used to detect the activation of caspase, pro-apoptosis, and anti-apoptosis protein expression in overexpress-LCN2 HCC cells. LCN2-induced apoptosis was characterized by cleavage of caspase-9, -8, -3, and PARP protein, and a reduction in the mitochondrial membrane potential (MMP). Furthermore, LCN2 also enhanced the down-regulated Bcl-2 and up-regulated the expression of Bax. In addition, our experiments with caspase inhibitors LEHD-FMK and IETD-FMK prevent LCN2-induced apoptosis. We also demonstrated that treatment of overexpress-LCN2 HCC cells with the LCN2 neutralized antibody also significantly attenuated LCN2-induced cell apoptosis. These findings indicate that LCN2 overexpression can effectively induce apoptosis of HCC cells and may be used as a potent therapy against human HCC.

Strong anticancer potential of nano-triterpenoid from Phytolacca decandra against A549 adenocarcinoma via a Ca(2+)-dependent mitochondrial apoptotic pathway

We isolated a triterpenoid from an ethanolic extract of Phytolacca decandra and nanoencapsulated it with biodegradable nontoxic polymers of poly(lactide-co-glycolide) to examine if the nanoform of this hitherto unexplored betulinic-acid derivative (NdBA) could produce a stronger anticancer effect by rendering better drug bioavailability and targeted delivery than the nonencapsulated betulinic-acid derivative (dBA). The nanoparticles were characterized with the help of physicochemical and morphological studies involving dynamic light scattering and atomic force microscopy. A549 cancer cells were exposed to NdBA and dBA at the IC50 doses of 50 μg/mL and 100 μg/mL, respectively. Mitochondrial dysfunction-mediated apoptosis was determined by examining the changes in the intracellular calcium content, the reactive oxygen species accumulation, the cytochrome c release, the upregulation of Bcl-2-associated-X protein (Bax) and caspase 3, the downregulation of B cell lymphoma 2, and the mitochondrial membrane potential (ΔΨm) depolarization. Apoptosis was also verified by acridine orange staining observed under fluorescence microscopy and annexin V-fluorescein isothiocyanate/propidium iodide staining through flow cytometric studies. The levels of intracellular adenosine triphosphate/adenosine diphosphate ratio decreased, and the ATPase activity increased more strikingly in A549 cells exposed to NdBA than in A549 cells exposed to dBA. Overall results showed that both drugs directly target the mitochondrial oxidative phosphorylation system, with NdBA having a stronger effect, indicating NdBA to be a better candidate for the development of an anticancer drug for use against lung adenocarcinomas.

Silencing of Pokemon enhances caspase-dependent apoptosis via fas- and mitochondria-mediated pathways in hepatocellular carcinoma cells

The role of Pokemon (POK erythroid myeloid ontogenic actor), a recently identified POK transcription factor with proto-oncogenic activity, in hepatocellular carcinogenesis has only been assessed by a few studies. Our previous study revealed that Pokemon is overexpressed in hepatocellular carcinomas (HCC) and promotes HCC cell proliferation and migration via an AKT- and ERK- dependent manner. In the present study, we used the TUNEL assay and FACS analysis to demonstrate that oxaliplatin induced apoptosis was significantly increased in cells with silenced Pokemon. Western blots showed that p53 expression and phosphorylation were significantly increased in Pokemon defective cells, thereby initiating the mitochondria-mediated and death receptor-mediated apoptotic pathways. In the mitochondria-mediated pathway, expression of pro-apoptotic Bcl-2 family members (including Bad, Bid, Bim and Puma) as well as AIF was increased and decreasing the mitochondrial membrane potential resulted in cytochrome C released from mitochondrial in HepG2 si-Pokemon cells. In addition, upon oxaliplatin treatment of Pokemon-silenced cells, the FAS receptor, FADD and their downstream targets caspase-10 and caspase-8 were activated, causing increased release of caspase-8 active fragments p18 and p10. Increased activated caspase-8-mediated cleavage and activation of downstream effector caspases such as caspase-9 and caspase-3 was observed in HepG2 si-Pokemon cells as compared to control. Therefore, Pokemon might serve as an important mediator of crosstalk between intrinsic and extrinsic apoptotic pathways in HCC cells. Moreover, our findings suggest that Pokemon could be an attractive therapeutic target gene for human cancer therapy.

Mechanisms of immune privilege in the posterior eye

Immune privilege protects vital organs and their functions from the destructive interference of inflammation. Because the eye is easily accessible for surgical manipulation and for assessing and imaging the outcomes, the eye has been a major tissue for the study of immune privilege. Here, we focus on the immune regulatory mechanisms in the posterior eye, in part, because loss of immune privilege may contribute to development of certain retinal diseases in the aging population. We begin with a background in immune privilege and then focus on the select regulatory mechanisms that have been studied in the posterior eye. The review includes a description of the immunosuppressive environment, regulatory surface molecules expressed by cells in the eye, types of cells that participate in immune regulation and finally, discusses animal models of retinal laser injury in the context of mechanisms that overcome immune privilege.

Role of ceramide in diabetes mellitus: evidence and mechanisms

Diabetes mellitus is a metabolic disease with multiple complications that causes serious diseases over the years. The condition leads to severe economic consequences and is reaching pandemic level globally. Much research is being carried out to address this disease and its underlying molecular mechanism. This review focuses on the diverse role and mechanism of ceramide, a prime sphingolipid signaling molecule, in the pathogenesis of type 1 and type 2 diabetes and its complications. Studies using cultured cells, animal models, and human subjects demonstrate that ceramide is a key player in the induction of β-cell apoptosis, insulin resistance, and reduction of insulin gene expression. Ceramide induces β-cell apoptosis by multiple mechanisms namely; activation of extrinsic apoptotic pathway, increasing cytochrome c release, free radical generation, induction of endoplasmic reticulum stress and inhibition of Akt. Ceramide also modulates many of the insulin signaling intermediates such as insulin receptor substrate, Akt, Glut-4, and it causes insulin resistance. Ceramide reduces the synthesis of insulin hormone by attenuation of insulin gene expression. Better understanding of this area will increase our understanding of the contribution of ceramide to the pathogenesis of diabetes, and further help in identifying potential therapeutic targets for the management of diabetes mellitus and its complications.

Crosstalk between apoptosis, necrosis and autophagy

Apoptosis and necrosis are the two major modes of cell death, the molecular mechanisms of which have been extensively studied. Although initially thought to constitute mutually exclusive cellular states, recent findings reveal cellular contexts that require a balanced interplay between these two modes of cellular demise. Several death initiator and effector molecules, signaling pathways and subcellular sites have been identified as key mediators in both processes, either by constituting common modules or alternatively by functioning as a switch allowing cells to decide which route to take, depending on the specific situation. Importantly, autophagy, which is a predominantly cytoprotective process, has been linked to both types of cell death, serving either a pro-survival or pro-death function. Here we review the recent literature that highlights the intricate interplay between apoptosis, necrosis and autophagy, focusing on the relevance and impact of this crosstalk in normal development and in pathology. This article is part of a Special Section entitled: Cell Death Pathways.

p53-dependent release of Alarmin HMGB1 is a central mediator of senescent phenotypes

Cellular senescence irreversibly arrests proliferation in response to potentially oncogenic stress. Senescent cells also secrete inflammatory cytokines such as IL-6, which promote age-associated inflammation and pathology. HMGB1 (high mobility group box 1) modulates gene expression in the nucleus, but certain immune cells secrete HMGB1 as an extracellular Alarmin to signal tissue damage. We show that nuclear HMGB1 relocalized to the extracellular milieu in senescent human and mouse cells in culture and in vivo. In contrast to cytokine secretion, HMGB1 redistribution required the p53 tumor suppressor, but not its activator ATM. Moreover, altered HMGB1 expression induced a p53-dependent senescent growth arrest. Senescent fibroblasts secreted oxidized HMGB1, which stimulated cytokine secretion through TLR-4 signaling. HMGB1 depletion, HMGB1 blocking antibody, or TLR-4 inhibition attenuated senescence-associated IL-6 secretion, and exogenous HMGB1 stimulated NF-κB activity and restored IL-6 secretion to HMGB1-depleted cells. Our findings identify senescence as a novel biological setting in which HMGB1 functions and link HMGB1 redistribution to p53 activity and senescence-associated inflammation.

BID-induced structural changes in BAK promote apoptosis

The BCL-2 family protein BAK is responsible for mitochondrial outer membrane permeabilization (MOMP), which leads to apoptosis. The BCL-2 homology (BH) 3-only protein BID activates BAK to perform this function. We report the NMR solution structure of the human BID BH3–BAK complex, which identified the activation site at the canonical BH3-binding groove of BAK. Mutating the BAK BH1 in the groove prevented activation and MOMP but not the binding of BID. BAK BH3 mutations allowed BID binding and activation but blunted function by blocking BAK oligomerization. BAK activation follows a “hit-and-run” mechanism whereby BID dissociates from the trigger site allowing BAK oligomerization at an overlapping interface. In contrast, the BH3-only proteins NOXA and BAD are predicted to clash with the trigger site, and are not activators of BAK. These findings provide insights into the early stages of BAK activation.

TW01001, a novel piperazinedione compound, induces mitotic arrest and autophagy in non-small cell lung cancer A549 cells

Here, we report that TW01001, a novel piperazinedione compound, could be a new mitotic inhibitor for the treatment of non-small cell lung cancer by the following observations in A549 cells: (1) induction of cells to accumulate at G2/M phase, which ultimately led to cell apoptotic death, (2) accumulation of p53 and inhibition of survival signalings, and (3) induction of p53-independent autophagy. Taken together, our data suggested that TW01001 induces autophagy-p53-signaling pathway to cause mitotic arrest and cell growth inhibition in A549 cells and provides the framework for further development as a novel therapeutic agent for lung cancer treatment.

TNF-induced death signaling triggers alveolar epithelial dysfunction in acute lung injury

The ability of the alveolar epithelium to prevent and resolve pulmonary edema is a crucial determinant of morbidity and mortality in acute lung injury (ALI). TNF has been implicated in ALI pathogenesis, but the precise mechanisms remain undetermined. We evaluated the role of TNF signaling in pulmonary edema formation in a clinically relevant mouse model of ALI induced by acid aspiration and investigated the effects of TNF p55 receptor deletion, caspase-8 inhibition, and alveolar macrophage depletion on alveolar epithelial function. We found that TNF plays a central role in the development of pulmonary edema in ALI through activation of p55-mediated death signaling, rather than through previously well-characterized p55-mediated proinflammatory signaling. Acid aspiration produced pulmonary edema with significant alveolar epithelial dysfunction, as determined by alveolar fluid clearance (AFC) and intra-alveolar levels of the receptor for advanced glycation end-products. The impairment of AFC was strongly correlated with lung caspase-8 activation, which was localized to type 1 alveolar epithelial cells by flow cytometric analysis. p55-deficient mice displayed markedly attenuated injury, with improved AFC and reduced caspase-8 activity but no differences in downstream cytokine/chemokine production and neutrophil recruitment. Caspase-8 inhibition significantly improved AFC and oxygenation, whereas depletion of alveolar macrophages attenuated epithelial dysfunction with reduced TNF production and caspase-8 activity. These results provide in vivo evidence for a novel role for TNF p55 receptor-mediated caspase-8 signaling, without substantial apoptotic cell death, in triggering alveolar epithelial dysfunction and determining the early pathophysiology of ALI. Blockade of TNF-induced death signaling may provide an effective early-phase strategy for ALI.

Dual functions for cytosolic α-mannosidase (Man2C1): its down-regulation causes mitochondria-dependent apoptosis independently of its α-mannosidase activity

Cytosolic α-mannosidase (Man2C1) trims free oligosaccharides in mammalian cells, and its down-regulation reportedly delays cancer growth by inducing mitotic arrest or apoptosis. However, the mechanism by which Man2C1 down-regulation induces apoptosis is unknown. Here, we demonstrated that silencing of Man2C1 via small hairpin RNAs induced mitochondria-dependent apoptosis in HeLa cells. Expression of CHOP (C/EBP homologous protein), a transcription factor critical to endoplasmic reticulum stress-induced apoptosis, was significantly up-regulated in Man2C1 knockdown cells. However, this enhanced CHOP expression was not caused by endoplasmic reticulum stress. Interestingly, Man2C1 catalytic activity was not required for this regulation of apoptosis; introduction of mutant, enzymatically inactive Man2C1 rescued apoptotic phenotypes of Man2C1 knockdown cells. These results show that Man2C1 has dual functions: one in glycan catabolism and another in apoptotic signaling.

Multivariate analysis of apoptotic markers versus cell cycle phase in living human cancer cells by microfluidic cytometry

Measurement of apoptotic markers in tumors can be directly correlated with the cell cycle phase using flow cytometry (FCM). The conventional DNA content analysis requires cell permeabilization to stain nuclei with fluorescent probes such as propidium iodide or use of a costly UV-excitation line for Hoechst 33342 probe. The access to FCM is also still limited to centralized core facilities due to its inherent high costs and complex operation. This work describes development and proof-of-concept validation of a portable and user-friendly microfluidic flow cytometer (μFCM) that can perform multivariate real time analysis on live cells using sampling volumes as small as 10 microliters. The μFCM system employs disposable microfluidic cartridges fabricated using injection molding in poly(methylmethacrylate) transparent thermoplastic. Furthermore, the dedicated and miniaturized electronic hardware interface enables up to six parameter detection using a combination of spatially separated solid-state 473 (10 mW) and 640 nm (20 mW) lasers and x-y stage for rapid laser alignment adjustment. We provide new evidence that a simple 2D flow focusing on a chip is sufficient to measure cellular DNA content in live tumor cells using a far-red DNA probe DRAQ5. The feasibility of using the μFCM system for a dose-response profiling of investigational anti-cancer agents on human hematopoietic cancer cells is also demonstrated. The data show that μFCM can provide a viable novel alternative to conventional FCM for multiparameter detection of caspase activation and dissipation of mitochondrial inner membrane potential (ΔΨm) in relation to DNA content (cell cycle phase) in live tumor cells.

Stromal cell-derived factor-1β mediates cell survival through enhancing autophagy in bone marrow-derived mesenchymal stem cells

Bone marrow-derived mesenchymal stem/stromal cells (BMSCs) hold great potential for cell-based therapy, yet the therapeutic efficacy remains uncertain. Transplanted BMSCs often fail to engraft within the bone marrow (BM), in part due to the poor survival of donor cells in response to inflammatory reactions, hypoxia, oxidative stress, or nutrient starvation. Two basic cell processes, apoptosis and autophagy, could potentially be responsible for the impaired survival of transplanted BMSCs. However, the functional relationship between apoptosis and autophagy in BMSC homeostasis is complex and not well understood. The stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4) signaling axis appears to be critical in maintaining proliferation and survival of BM stem cell populations through improving cell proliferation and survival in response to stress; however, the exact mechanisms remain unclear. We recently described novel genetically engineered Tet-Off-SDF-1β BMSCs, which over-express SDF-1β under tight doxycycline-control, thus providing an ideal model system to investigate the isolated effects of SDF-1β. In this study we tested the hypothesis that SDF-1β can mediate cell survival of BMSCs in vitro through increasing autophagy. We found that SDF-1β had no effect on BMSC proliferation; however, SDF-1β significantly protected genetically engineered BMSCs from H2O2-induced cell death through increasing autophagy and decreasing caspase-3-dependent apoptosis. Taken together, we provide novel evidence that the SDF-1/CXCR4 axis, specifically activated by the SDF-1β isoform, plays a critical role in regulating BMSC survival under oxidative stress through increasing autophagy.

Growth inhibition effect of peptide P110 plus cisplatin on various cancer cells and xenotransplanted tumors in mice

The combined use of currently used anticancer genotoxins with other drugs is a therapeutic tool for potentially increasing the efficacy of the genotoxins. In the present study, the effects of a RasGAP-derived peptide, P110 (RasGAP301-316), designed to target Ras-GTPase activating protein SH3 domain-binding proteins (G3BPs), on the chemotherapeutic agent, cisplatin (DDP), were examined. P110 was demonstrated to enhance the effect of DPP in vitro and in vivo. The results indicate that P110 significantly increased the DDP-induced apoptosis in SGC-7901, HCT-116, HeLa and A-549 cells. Furthermore, P110 combined with DDP significantly suppressed the growth of C26 xenograft tumors in a dose-dependent manner. This synergistic effect may be associated with DDP-induced apoptosis, involving the downregulation of Bcl-2 and the upregulation of Bax, cytochrome c and caspase-3. The results of the present study indicate that P110, in combination with chemotherapeutics, is likely to represent a potential therapeutic strategy for cancer.

Inhibition of dendritic cell apoptosis by Leishmania mexicana amastigotes

Macrophages (Mφ) and dendritic cells are the major target cell populations of the obligate intracellular parasite Leishmania. Inhibition of host cell apoptosis is a strategy employed by multiple pathogens to ensure their survival in the infected cell. Leishmania promastigotes have been shown to protect Mφ, neutrophils, and dendritic cells from both natural and induced apoptosis. Nevertheless, the effect of the infection with Leishmania amastigotes in the apoptosis of these cell populations has not been established, which results are very important since amastigotes persist in cells for many days and are responsible for sustaining infection in the host. As shown in this study, apoptosis of monocyte-derived dendritic cells (moDC) induced by treatment with camptothecin was downregulated by infection with L. mexicana amastigotes from 42.48 to 36.92% as detected by Annexin-V binding to phosphatidylserine. Also, the infection of moDC with L. mexicana amastigotes diminished the fragmentation of DNA as detected by terminal deoxynucleotidyl transferase-mediated fluorescein-dUTP nick end labeling assay, and changes in cell morphology were analyzed by electron microscopy. The observed antiapoptotic effect was found to be associated with an 80% reduction in the presence of active caspase-3 in infected moDC. The capacity of L. mexicana amastigotes to delay apoptosis induction in the infected moDC may have implications for Leishmania pathogenesis by favoring the invasion of its host and the persistence of the parasite in the infected cells.

Bcl-2 family proteins and cytoskeleton changes involved in DM-1 cytotoxic effect on melanoma cells

Melanoma is one of the most aggressive types of skin cancer and its incidence rate is still increasing. All existing treatments are minimally effective. Consequently, new therapeutic agents for melanoma treatment should be developed. The DM-1 compound is a curcumin analog that possesses several curcumin characteristics, such as antiproliferative, antitumor, and anti-metastatic properties. The aim of this study was to evaluate the different signaling pathways involved in the cytotoxic effect of DM-1 on melanoma cells. The apoptotic process and cytoskeletal changes were evaluated by immunoblotting and immunofluorescence, respectively, in melanoma cells. After DM-1 treatment, SK-MEL-5 melanoma cells showed actin filament disorganization with spicule formation throughout the cytoskeleton and significant reduction of focal adhesion as well as they were present only at cell extremities, conferring a poor connection between the cell and the substrate. Besides this, there was significant filopodium retraction and loss of typical cytoskeleton scaffold. These modifications contributed to cell detachment followed by cell death. Furthermore, DM-1-induced apoptosis was triggered by multiple Bcl-2 proteins involved in both the extrinsic and the intrinsic apoptotic pathways. SK-MEL-5 cells showed a death mechanism mainly by Bcl-2/Bax ratio decrease, whereas A375 cells presented apoptosis induction by Mcl-1 and Bcl-xL downregulation. In SK-MEL-5 and A375 melanoma cells, there was a significant increase in the active form of caspase 9, and the inactive form of the effector caspase 3 was decreased in both cell lines. Expression of cleaved poly ADP ribose polymerase was increased after DM-1 treatment in these melanoma cell lines, demonstrating that the apoptotic process occurred. Altogether, these data elucidate the cellular and molecular mechanisms involved in the cytotoxicity induced by the antitumor agent DM-1 in melanoma cells.

Prima-1 induces apoptosis in bladder cancer cell lines by activating p53

OBJECTIVES

Bladder cancer represents 3% of all carcinomas in the Brazilian population and ranks second in incidence among urological tumors, after prostate cancer. The loss of p53 function is the main genetic alteration related to the development of high-grade muscle-invasive disease. Prima-1 is a small molecule that restores tumor suppressor function to mutant p53 and induces cancer cell death in various cancer types. Our aim was to investigate the ability of Prima-1 to induce apoptosis after DNA damage in bladder cancer cell lines.

METHOD

The therapeutic effect of Prima-1 was studied in two bladder cancer cell lines: T24, which is characterized by a p53 mutation, and RT4, which is the wild-type for the p53 gene. Morphological features of apoptosis induced by p53, including mitochondrial membrane potential changes and the expression of thirteen genes involved in apoptosis, were assessed by microscopic observation and quantitative real-time PCR (qRT-PCR).

RESULTS

Prima-1 was able to reactivate p53 function in the T24 (p53 mt) bladder cancer cell line and promote apoptosis via the induction of Bax and Puma expression, activation of the caspase cascade and disruption of the mitochondrial membrane in a BAK-independent manner.

CONCLUSION

Prima-1 is able to restore the transcriptional activity of p53. Experimental studies in vivo may be conducted to test this molecule as a new therapeutic agent for urothelial carcinomas of the bladder, which characteristically harbor p53 mutations.

Small-molecule activation of the TRAIL receptor DR5 in human cancer cells

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) activates apoptosis through the death receptors DR4 and DR5. Because of its superior safety profile and high tumor specificity compared to other TNF family members, recombinant soluble TRAIL and agonistic antibodies against its receptors are actively being developed for clinical cancer therapy. Here, we describe the identification and characterization of the small molecules that directly target DR5 to initiate apoptosis in human cancer cells. The activity was initially discovered through a high-throughput chemical screen for compounds that promote cell death in synergy with a small-molecule mimetic of Smac, the antagonist for inhibitor of apoptosis protein. Structure-activity relationship studies yielded a more potent analog called bioymifi, which can act as a single agent to induce DR5 clustering and aggregation, leading to apoptosis. Thus, this study identified potential lead compounds for the development of small-molecule TRAIL mimics targeting DR5 for cancer therapy.