Intrinsic Apoptotic Signaling Pathway Research Articles

Uterine endoplasmic reticulum stress and its unfolded protein response may regulate caspase 3 activation in the pregnant mouse uterus.

We have previously proposed that uterine caspase-3 may modulate uterine contractility in a gestationally regulated fashion. The objective of this study was to determine the mechanism by which uterine caspase-3 is activated and consequently controlled in the pregnant uterus across gestation. Utilizing the mouse uterus as our gestational model we examined the intrinsic and extrinsic apoptotic signaling pathways and the endoplasmic reticulum stress response as potential activators of uterine caspase-3 at the transcriptional and translational level. Our study revealed robust activation of the uterine myocyte endoplasmic reticulum stress response and its adaptive unfolded protein response during pregnancy coinciding respectively with increased uterine caspase-3 activity and its withdrawal to term. In contrast the intrinsic and extrinsic apoptotic signaling pathways remained inactive across gestation. We speculate that physiological stimuli experienced by the pregnant uterus likely potentiates the uterine myocyte endoplasmic reticulum stress response resulting in elevated caspase-3 activation, which is isolated to the pregnant mouse myometrium. However as term approaches, activation of an elevated adaptive unfolded protein response acts to limit the endoplasmic reticulum stress response inhibiting caspase-3 resulting in its decline towards term. We speculate that these events have the capacity to regulate gestational length in a caspase-3 dependent manner.

Pravastatin slows the progression of heart failure by inhibiting the c-Jun N-terminal kinase-mediated intrinsic apoptotic signaling pathway

Tumor necrosis factor‑α (TNF-α) and c‑Jun N‑terminal kinases (JNKs) are known to be associated with apoptosis and are important in cardiac remodeling. It remains to be determined whether statins inhibit cardiac remodeling through interfering with TNF‑α‑JNK‑related signaling pathways. This study was designed to investigate the effect of pravastatin on the progression of hypertrophy to heart failure in transverse aortic constriction (TAC) and the associations with TNF‑α‑JNK signaling. Either pravastatin (5 or 20 mg/kg/day) or vehicle was orally administered to male C57BL/6J mice with TAC. Cardiac remodeling and left ventricular hemodynamics, as well as JNK-dependent apoptotic signals were analyzed 4 weeks following TAC. Neonatal rat cardiomyocytes were cultured to investigate the effect of pravastatin on TNF‑α‑induced JNK‑related apoptotic signals. Notably, pravastatin reduced the heart/body weight and lung/body weight ratios. In addition, a decrease of left ventricular (LV) echocardiographic dimensions, an increase of LV fractional shortening and diastolic index, a reduction of JNK activity, caspase‑12 and Bax were observed in the pravastatin‑treated groups. The TNF‑α‑induced phosphorylation of JNK and upregulation of caspase‑12 and Bax in cultured cardiomyocytes was inhibited by pravastatin. These results indicated that pravastatin attenuates cardiac remodeling by inhibiting JNK‑dependent pro‑apoptotic signaling.

Equine arteritis virus induced cell death is associated with activation of the intrinsic apoptotic signalling pathway

Equine arteritis virus (EAV) causes a respiratory and reproductive disease in horses, equine viral arteritis. Though cell death in infection with EAV is considered to occur by apoptosis, the underlying molecular mechanism has not been extensively elucidated. We investigated the expression of mRNA of pro-apoptotic and caspase genes during EAV infection in BHK21 cells, a well-established cell type for EAV replication. Using a SYBR Green real-time PCR, mRNA of p53, Bax, caspase 3 and caspase 9 were found up-regulated in a time dependent manner in EAV infected cells. Western blot analysis for caspase 3 and caspase 9 showed expression of cleaved forms of these proteins during EAV infection. In addition, a luminescence-based cell assay for caspase 3/7 activation as a hallmark in apoptosis confirmed apoptotic cell death. The findings demonstrate that cell death in EAV infected BHK21 cells results from apoptosis mediated through the intrinsic signalling pathway.

Overexpression of angiopoietin-1 reduces doxorubicin-induced apoptosis in cardiomyocytes

Doxorubicin (Dox) is a major anticancer chemotherapeutic agent. However, it causes cardiomyopathy due to the side effect of cardiomyocyte apoptosis. We have previously reported that angiopoietin-1 significantly reduced myocardial infarction after ischemic injury and protected cardiomyocytes from oxidative stress-induced apoptosis. It is hypothesized that angiopoietin-1 may protect cardiomyocytes from Dox-induced apoptosis. Cardiomyocytes H9C2 were transfected with adenovirus expressing angiopoietin-1 (Ad5-Ang-1) 24 h before the cells were challenged with Dox at a concentration of 2 μmol/L. Ad5-GFP served as the vector control. Cardiomyocyte apoptosis was evaluated using Annexin V-FITC staining and caspase-3 and caspase-8 activity was determined by Western blotting. The results showed that Dox treatment significantly induced cardiomyocyte apoptosis as evidenced by the greater number of Annexin V-FITC stained cells and increases in caspase-3 and caspase-8 activity. In contrast, overexpression of angiopoietin-1 significantly prevented Dox-induced cardiomyocyte apoptosis. To elucidate the mechanisms by which angiopoietin-1 protected cells from Dox-induced apoptosis, we analyzed both extrinsic and intrinsic apoptotic signaling pathways. We observed that angiopoietin-1 prevented Dox-induced activation of both extrinsic and intrinsic apoptotic signaling pathways. Specifically, angiopoietin-1 prevented DOX-induced in-creases in FasL and Bax levels and cleaved caspase-3 and caspase-8 levels in H9C2 cells. In addition, overexpression of angiopoietin-1 also activated the pro-survival phosphoinositide-3 kinase (PI3K)/Akt signaling pathway and decreased Dox-induced nuclear factor-kappaB (NF-κB) activation. Our data suggest that promoting the expression of angiopoietin-1 could be a potential approach for reducing Dox-induced cardiomyocyte cytoxicity.

A Sparse Update Method for Solving Underdetermined Systems of Nonlinear Equations Applied to the Manipulation of Biological Signaling Pathways

We are interested in sparse solutions of underdetermined systems of nonlinear equations and present an iterative method that updates the current iterate by a sparse vector defined as the solution of a constrained $\ell_1$-minimization problem. Local quadratic convergence of the iterates toward a solution of the underdetermined system of nonlinear equations is guaranteed under standard differentiability assumptions. Our work is motivated by the pharmaceutical modulation of defective biological signaling pathways as linked to various pathological conditions. Based on differential equation models of signal transduction networks the inverse problem of correcting qualitative biological behavior such as bistability or oscillation typically leads to an underdetermined system of nonlinear equations. In this context sparse solutions point to a low number of network intervention sites that may serve as manageable drug target candidates. The practicability of our method is demonstrated by means of a defective biological switch associated to the intrinsic apoptotic signaling pathway.

Tanshinone�IIA induces growth inhibition and apoptosis in gastric cancer in vitro and in vivo

As a phytochemical derived from the roots of Salvia miltiorrhiza Bunge, TanshinoneIIA has been reported to possess anti-inflammatory and antioxidant activity. Studies in breast, colon, prostate and lung cancer indicate that TanshinoneIIA may exhibit a promising antitumor activity. However, systemic studies of the cytotoxic effects of TanshinoneIIA on gastric cancer have not been described. The present study offers a comprehensive evaluation of the antitumor effects of TanshinoneIIA in gastric cancer cells invitro and in a mouse xenograft model. Cell viability and apoptosis invitro were evaluated through the MTT assay and flow cytometry analysis. The results indicate that TanshinoneIIA can induce gastric cancer cell growth inhibition and apoptosis in a time- and concentration-dependent manner. Furthermore, we investigated the mechanism of the apoptotic effects induced by TanshinoneIIA. We found that TanshinoneIIA can not only cause cell cycle arrest in the G2/M phase, but also trigger the intrinsic apoptotic signaling pathway. The results suggest that TanshinoneIIA may serve as an effective adjunctive reagent in the treatment of gastric cancer.

Glycoprotein secreted by Absidia corymbifera is associated with apoptosis of human umbilical vein endothelial cells

Objective To partially purify the toxic factor secreted by A. corymbifera and to analyze the mechanism of A. corymbifera-induced human umbilical vein endothelial cell (HUVEC) apoptosis. Methods Glycoprotein secreted by A. corymbifera was purified by Con A Lectin chromatography. The influence of different protein fractions on HUVEC apoptosis was determined by flow eytometer. Both denaturing and nondenaturing deglycosylation of purified glycoprotein was performed and the ability of the protein moiety and carbohydrate moiety to induce HUVEC apoptosis was evaluated respectively. Activation of related caspases during A. corymbifera-induced apoptosis was analyzed by Western blot. The role of caspase-8 and -9 in HUVEC apoptosis was investigated using caspase inhibitors. Caspase inhibitors were used to stop the suppression of HUVEC viability by XTT assay. Results Flow cytometric analysis shows the total protein as well as the glycoprotein fraction of A. corymbifera may induce HUVEC apoptosis in a dose dependent manner. In contrast, similar activity was not observed in the non-glycoprotein fraction. Neither deglycosylated protein nor carbohydrate moiety is able to induce HUVEC apoptosis alone. In the apoptotic signaling pathway, caspase9, caspase-3 and cytochrome C were activated significantly, except caspase-8. Moreover, caspase-9 inhibitor, instead of caspase-8 inhibitor, completely abrogates A. corymbifera-induced HUVEC apoptosis. Caspase9 and caspase-3 inhibitors completely waived the suppression of HUVEC viability by A. corymbifera. Conclusion Glycoprotein secreted by A. corymbifera is associated with HUVEC apoptosis. Intact glycoprotein is essential for the apoptotic progress. Intrinsic apoptotic signaling pathway mediates A. corymbifera-induced HUVEC apoptosis. Key words: Mucorales; Absidia corymbifera; Glycoprotein; Human umbilical vein endothelial cell; Apoptosis

Parthenolide, a Sesquiterpene Lactone, Expresses Multiple Anti-cancer and Anti-inflammatory Activities

Parthenolide, a naturally occurring sesquiterpene lactone derived from feverfew (Tanacetum parthenium), exhibits exceptional anti-cancer and anti-inflammatory properties, making it a prominent candidate for further studies and drug development. In this review, we briefly investigate molecular events and cell-specific activities of this chemical in relation to cytochrome c, nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), signal transduction and activation of transcription (STAT), reactive oxygen species (ROS), TCP, HDACs, microtubules, and inflammasomes. This paper reports that parthenolide shows strong NF-κB- and STAT-inhibition-mediated transcriptional suppression of pro-apoptotic genes. This compound acts both at the transcriptional level and by direct inhibition of associated kinases (IKK-β). Similarly, this review discusses parthenolide-induced ROS-mediated apoptosis of tumor cells via the intrinsic apoptotic signaling pathway. The unique ability of this compound to not harm normal cells but at the same time induce sensitization to extrinsic as well as intrinsic apoptosis signaling in cancer cells provides an important, novel therapeutic strategy for treatment of cancer and inflammation-related disorders.

Sulforaphane blocks hypoxia-mediated resistance to TRAIL-induced tumor cell death

Hypoxia occurs frequently in various solid tumors and elicits a cellular response designed to improve cell survival through adaptive processes, thereby accelerating cancer progression and the development of chemotherapy resistance. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily, leads to tumor cell death via both intrinsic and extrinsic apoptotic signaling pathways. Hypoxia inhibits TRAIL-mediated apoptosis and attenuates the therapeutic activity of TRAIL in cancer management. Hypoxia-inducible factor-1α (HIF-1α) plays a central role in tumor hypoxia by up-regulating gene expression related to angiogenesis, cancer invasion and anti-apoptosis. Sulforaphane (SFN), a phenethyl isothiocyanate, elicits HIF-1α inactivation under hypoxia. This study investigated whether hypoxic inhibition of TRAIL-mediated tumor cell death is increased by SFN-mediated HIF-1α instability. SFN induced cell death in various tumor cells, including SK-N-SH, SNU-638, HeLa and A549 cells, and showed cell cytotoxicity in hypoxia-exposed tumor cells. Western blot analysis showed that SFN treatment increased p53 and activated caspase-3 proteins, and decreased HIF-1α activation under hypoxia. Under low-oxygen conditions, TRAIL-treated cells displayed inhibited apoptosis, while SFN-pre-treated cells exhibited stronger sensitization to TRAIL under the hypoxic conditions. SFN treatment enhanced TRAIL-induced activation of proteins, including caspase-3 and p53. SFN dose-dependently decreased HIF-1α protein levels in cancer cells, which was mediated by decreased protein stability. This study demonstrated that SFN recovered hypoxia-mediated resistance to TRAIL via instability of HIF-1α, and also suggests that combination therapy with SFN and TRAIL may provide a novel strategy for treating hypoxic solid tumors.

Interruption of cenph Causes Mitotic Failure and Embryonic Death, and Its Haploinsufficiency Suppresses Cancer in Zebrafish

Kinetochore proteins associate with centromeric DNA and spindle microtubules and play essential roles in chromosome segregation during mitosis. In this study, we uncovered a zebrafish mutant, stagnant and curly (stac), that carries the Tol2 transposon element inserted at the kinetochore protein H (cenph) locus. Mutant embryos exhibit discernible cell death as early as 20 hours postfertilization, extensive apoptosis, and upward curly tail during the pharyngula period and deform around 5 days postfertilization. The stac mutant phenotype can be rescued by cenph mRNA overexpression and mimicked by cenph knockdown with antisense morpholinos, suggesting the responsibility of cenph deficiency for stac mutants. We demonstrate that the intrinsic apoptosis pathway is hyperactivated in stac mutants and that p53 knockdown partially blocks excess apoptosis in stac mutants. Mitotic cells in stac mutants show chromosome missegregation and are usually arrested in G(2)/M phase. Furthermore, compared with wild type siblings, heterozygous stac fish develop invasive tumors at a dramatically reduced rate, suggesting a reduced cancer risk. Taken together, our findings uncover an essential role of cenph in mitosis and embryonic development and its association with tumor development.

Mitochondria in cell death

Apoptosis can be thought of as a signalling cascade that results in the death of the cell. Properly executed apoptosis is critically important for both development and homoeostasis of most animals. Accordingly, defects in apoptosis can contribute to the development of autoimmune disorders, neurological diseases and cancer. Broadly speaking, there are two main pathways by which a cell can engage apoptosis: the extrinsic apoptotic pathway and the intrinsic apoptotic pathway. At the centre of the intrinsic apoptotic signalling pathway lies the mitochondrion, which, in addition to its role as the bioenergetic centre of the cell, is also the cell's reservoir of pro-death factors which reside in the mitochondrial IMS (intermembrane space). During intrinsic apoptosis, pores are formed in the OMM (outer mitochondrial membrane) of the mitochondria in a process termed MOMP (mitochondrial outer membrane permeabilization). This allows for the release of IMS proteins; once released during MOMP, some IMS proteins, notably cytochrome c and Smac/DIABLO (Second mitochondria-derived activator of caspase/direct inhibitor of apoptosis-binding protein with low pI), promote caspase activation and subsequent cleavage of structural and regulatory proteins in the cytoplasm and the nucleus, leading to the demise of the cell. MOMP is achieved through the co-ordinated actions of pro-apoptotic members and inhibited by anti-apoptotic members of the Bcl-2 family of proteins. Other aspects of mitochondrial physiology, such as mitochondrial bioenergetics and dynamics, are also involved in processes of cell death that proceed through the mitochondria. Proper regulation of these mitochondrial functions is vitally important for the life and death of the cell and for the organism as a whole.

Abstract 1280: Inhibition of cellular FLICE-inhibitory protein and induction of Death Receptor 5 expression is a major component of δ- tocotrienol-induced apoptosis in pancreatic cancer cells

Abstract Background: Previous pre-clinical studies have demonstrated that δ-tocotrienol, is the most bioactive natural vitamin E compound against pancreatic cancer. δ-Tocotrienol induces growth arrest and apoptosis in several human pancreatic cancer cell lines; however, the underlying mechanism remains unknown. In this study, we evaluated the role of the extrinsic and intrinsic apoptotic signaling pathways in δ-tocotrienol-induced apoptosis. Also, we investigated the modulation of cellular FLICE-inhibitory protein (c-FLIP) and death receptor 5 (DR5) by δ-tocotrienol, and the involvement of c-FLIP down-regulation and DR5 up-regulation in δ-tocotrienol-induced apoptosis. Methods: We examined δ-tocotrienol induced apoptosis in human pancreatic cancer cell lines in vitro and in vivo. We used western blot and immunohistochemistry to determine the expression of DR4, DR5, Caspase 8, Caspase 9, Caspase 3, c-FLIP, and PARP. The effect of combination treatment with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and δ-tocotrienol was also determined. We examined the cellular effects of DR5 knockdown using small interfering RNA oligonucleotides, and c-FLIP overexpression using c-FLIP cDNA, on δ-tocotrienol-induced apoptosis using various assays. Results: Delta-tocotrienol activated caspase-8 and its downstream caspases but not caspase-9. Caspase-8 specific inhibitor abrogated δ-tocotrienol-induced apoptosis whereas caspase-9 specific inhibitor did not, indicating that δ-tocotrienol induces caspase-8 -dependent apoptosis. c-FLIP was rapidly down-regulated by δ-tocotrienol in all of the tested cell lines. Delta-tocotrienol up-regulated DR4 and DR5 significantly and enhanced TRAIL-induced apoptosis. Enforced expression of ectopic c-FLIP, and DR5 knockdown partially abolished δ-tocotrienol-induced apoptosis. δ-Tocotrienol inhibition of pancreatic tumor growth in SCID mice was associated with significant induction of apoptosis, activation of caspase 8, and down-regulation of c-FLIP expression. Conclusion: We conclude that DR5 up-regulation and c-FLIP down-regulation contributes to δ-tocotrienol-induced apoptosis in pancreatic cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1280.

Abstract 222: Inhibition of cellular FLICE-inhibitory protein and induction of death receptor 5 expression is a major component of δ-tocotrienol-induced apoptosis in pancreatic cancer cells

Abstract Background: Previous pre-clinical studies have demonstrated that δ-tocotrienol, is the most bioactive natural vitamin E compound against pancreatic cancer. δ-Tocotrienol induces growth arrest and apoptosis in several human pancreatic cancer cell lines; however, the underlying mechanism remains unknown. In this study, we evaluated the role of the extrinsic and intrinsic apoptotic signaling pathways in δ-tocotrienol induced apoptosis and investigated the modulation of cellular FLICE-inhibitory protein (c-FLIP) and death receptor 5 (DR5) by δ-tocotrienol and the involvement of c-FLIP down-regulation and DR5 up-regulation in δ-tocotrienol-induced apoptosis. Methods: We examined δ-tocotrienol induced apoptosis in human pancreatic cancer cell lines in vitro and in vivo. We used western blot and immunohistochemistry to determine the expression of DR4, DR5, Caspase 8, Caspase 9, Caspase 3, C-FLIPs and PARP. The effect of combination treatment with TRAIL and δ-tocotrienol was also determined. We examined the cellular effects of DR5 knockdown using small interfering RNA oligonucleotides, and c-FLIP overexpression using cDNA, on δ-tocotrienol-induced apoptosis using various assays. Results: Delta-tocotrienol activated caspase-8 and its downstream caspases but not caspase-9, whereas caspase-8 specific inhibitor abrogated δ-tocotrienol-induced apoptosis indicating that δ-tocotrienol induces caspase-8-dependent apoptosis. c-FLIP was rapidly down-regulated by δ-tocotrienol in all of the tested cell lines. δ-Tocotrienol up-regulated DR4 and DR5 significantly and enhanced tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis. Enforced expression of ectopic c-FLIP, and DR5 knockdown partially abolished δ-tocotrienol-induced apoptosis. δ-Tocotrienol inhibition of pancreatic tumor growth in SCID mice was associated with significant induction of apoptosis, activation of caspase 8, and down-regulation of c-FLIP expression. Conclusion: We conclude that DR5 up-regulation and c-FLIP down-regulation contributes to δ-tocotrienol-induced apoptosis in pancreatic cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 222.

The intrinsic apoptotic signaling pathway in gastric adenocarcinomas of Brazilian patients: Immunoexpression of the Bcl-2 family (Bcl-2, Bcl-x, Bak, Bax, Bad) determined by tissue microarray analysis

This study was undertaken to investigate the immunoexpression of Bcl-2 family proteins (Bcl-2, Bcl-x, Bax, Bak and Bad) and to evaluate the correlation between the immunoexpression of these proteins and that of cleaved caspase 3, Ki-67 and p53. A tissue microarray (TMA) paraffin block was constructed using gastric carcinoma tissue (test group) and adjacent normal gastric mucosa (control group) from 87 patients who had not previously undergone radiotherapy or chemotherapy. Sections from the TMA block (4 µm) were subjected to immunohistochemistry for Bcl-2, Bcl-x, Bax, Bak, Bad, p53, Ki-67 and cleaved caspase-3. The slides were evaluated by the semi-quantitative method, and the scores obtained (intensity vs. percentage of staining) were correlated with one another and with the apoptotic index, cellular proliferation and data regarding patient survival. The studied proteins were present in the tumor tissue and in the normal gastric mucosa, but at different intensities and with differences in the number of positive cells. There was an association between tumor size and p53 expression, and intestinal type adenocarcinoma was positively correlated with the expression of Bax, Bad and Ki-67. The immunoexpression of Bcl-x, Bak, Bad, p53 and Ki-67 showed statistically significant differences between the tumor tissue and the adjacent normal gastric mucosa. There was an association between the expression of Bax, Bak and Bad in the normal gastric mucosa. No correlation between patient survival and the expression of these proteins was observed. Overexpression of the Bcl-x protein in the adenocarcinomas and the difference in Bcl-x expression between the test and the control group may be related to the anti-apoptotic effect of this protein. The reduced expression of Bak and Bad and the increased expression of p53 and Ki-67 in the adenocarcinomas demonstrate the imbalance between apoptosis and cellular proliferation, which results in uncontrolled tumor cell proliferation.

The intrinsic apoptotic signaling pathway in gastric adenocarcinomas of Brazilian patients: Immunoexpression of the Bcl-2 family (Bcl-2, Bcl-x, Bak, Bax, Bad) determined by tissue microarray analysis

This study was undertaken to investigate the immunoexpression of Bcl-2 family proteins (Bcl-2, Bcl-x, Bax, Bak and Bad) and to evaluate the correlation between the immunoexpression of these proteins and that of cleaved caspase 3, Ki-67 and p53. A tissue microarray (TMA) paraffin block was constructed using gastric carcinoma tissue (test group) and adjacent normal gastric mucosa (control group) from 87 patients who had not previously undergone radiotherapy or chemotherapy. Sections from the TMA block (4 µm) were subjected to immunohistochemistry for Bcl-2, Bcl-x, Bax, Bak, Bad, p53, Ki-67 and cleaved caspase-3. The slides were evaluated by the semi-quantitative method, and the scores obtained (intensity vs. percentage of staining) were correlated with one another and with the apoptotic index, cellular proliferation and data regarding patient survival. The studied proteins were present in the tumor tissue and in the normal gastric mucosa, but at different intensities and with differences in the number of positive cells. There was an association between tumor size and p53 expression, and intestinal type adenocarcinoma was positively correlated with the expression of Bax, Bad and Ki-67. The immunoexpression of Bcl-x, Bak, Bad, p53 and Ki-67 showed statistically significant differences between the tumor tissue and the adjacent normal gastric mucosa. There was an association between the expression of Bax, Bak and Bad in the normal gastric mucosa. No correlation between patient survival and the expression of these proteins was observed. Overexpression of the Bcl-x protein in the adenocarcinomas and the difference in Bcl-x expression between the test and the control group may be related to the anti-apoptotic effect of this protein. The reduced expression of Bak and Bad and the increased expression of p53 and Ki-67 in the adenocarcinomas demonstrate the imbalance between apoptosis and cellular proliferation, which results in uncontrolled tumor cell proliferation.

Investigation of anti-leukemia molecular mechanism of ITR-284, a carboxamide analog, in leukemia cells and its effects in WEHI-3 leukemia mice

ITR-284, a potent anti-leukemia agent of carboxamide derivative, has been shown to inhibit the proliferation of leukemia cells. In this study, the underlying molecular mechanisms in vitro and anti-leukemia activity in vivo of ITR-284 were investigated. ITR-284 reduced the cell viability and induced apoptosis in HL-60 and WEHI-3 leukemia cells. Following exposure of cells to 30nM of ITR-284, there is a time-dependent decrease in the mitochondrial membrane potential (ΔΨm) and an increase in the reactive oxygen species (ROS). ITR-284 treatment also caused a time-dependent increase of Fas/CD95, cytosolic cytochrome c, cytosolic active form of caspase-8/-9/-3, cytosolic Apaf-1 and Bax, and the decrease of Bcl-2. However, the ITR-284-induced caspase-8/-9 and -3 activities can be blocked by pan-caspase inhibitor (Z-VAD-FMK). In addition, the anti-leukemia effects of ITR-284 in vivo were further evaluated in BALB/c mice inoculated with WEHI-3 cells. Orally treatment with ITR-284 (2 and 10mg/kg/alternate day for 7 times) increased the survival rate and prevented the loss of body weight in leukemia mice. The enlargement of spleen and infiltration of immature myeloblastic cells into spleen red pulp were significantly reduced in ITR-284-treated mice compared with control mice. Moreover, ITR-284 application can enhance the anti-leukemia effect of all-trans retinoic acid (ATRA). These results revealed that ITR-284 acted against both HL-60 and WEHI-3 in vitrovia both intrinsic and extrinsic apoptotic signaling pathways, and exhibited an anti-leukemic effect in a WEHI-3 orthotopic mice model of leukemia.

Lipid raft connection between extrinsic and intrinsic apoptotic pathways

Apoptosis in mammalian cells is modulated by extrinsic and intrinsic signaling pathways through the formation of death receptor-mediated death-inducing signaling complex (DISC) and mitochondrial-derived apoptosome, respectively. We found by ultrastructural approaches that the antitumor drug edelfosine induced aggregates of lipid rafts containing Fas/CD95 receptor and Fas-associated death domain-containing protein in leukemic cells. Death receptors together with DISC and apoptosome constituents were recruited in rafts during edelfosine treatment in multiple myeloma cells. This apoptotic response involved caspases-8/-9/-10 that were translocated to rafts. Lipid raft disruption by cholesterol depletion inhibited loss of mitochondrial transmembrane potential, caspase activation and apoptosis, whereas cholesterol replenishment restored these responses. Our data indicate that rafts act as scaffolds where extrinsic and intrinsic apoptotic signaling pathways concentrate, forming clusters of apoptotic signaling molecule-enriched rafts (CASMER), which function as novel supramolecular entities in the triggering of apoptosis, and play an important role in edelfosine-induced apoptosis in blood cancer cells.

α-LIPOIC ACID ATTENUATES HEMORRHAGIC SHOCK-INDUCED APOPTOTIC SIGNALING AND VASCULAR HYPERPERMEABILITY

Hemorrhagic shock (HS) is associated with the disruption of endothelial cell barrier leading to vascular hyperpermeability. Previous studies from our laboratory implicate reactive oxygen species (ROS) and the intrinsic apoptotic signaling cascades as mediators of vascular hyperpermeability after HS. Here we report the protective effects of alpha-lipoic acid, a natural antioxidant with antiapoptotic properties, against vascular hyperpermeability after HS. Hemorrhagic shock was induced in Sprague-Dawley rats by withdrawing blood to reduce the MAP to 40 mmHg for 60 min followed by resuscitation for 60 min. The rats were given fluorescein isothiocyanate-albumin (50 mg/kg) i.v., and the mesenteric postcapillary venules were examined for change in hyperpermeability using intravital microscopy. Mitochondrial ROS formation and change in mitochondrial transmembrane potential were measured using dihydrorhodamine 123 and the cationic dye JC-1, respectively. The mitochondrial release of cytochrome c and activation of caspase 3 were measured using enzyme-linked immunosorbent assay and fluorometric assay, respectively. Hemorrhagic shock resulted in vascular hyperpermeability and mitochondrial ROS formation. The activation of mitochondrial intrinsic apoptotic signaling pathway was evidenced from mitochondrial depolarization, an increase in cytochrome c release, and activation of caspase 3. alpha-Lipoic acid (100 mg/kg) given before the shock period attenuated vascular hyperpermeability, mitochondrial ROS formation, mitochondrial depolarization, cytochrome c release, and activation of caspase 3 (P < 0.05). Together, these results demonstrate that alpha-lipoic acid provides protection against vascular hyperpermeability by modulating the mitochondrial "intrinsic" apoptotic signaling.

Tumor Necrosis Factor-α Induces Intrinsic Apoptotic Signaling During Renal Obstruction Through Truncated Bid Activation

Tumor necrosis factor-alpha has a significant role in renal tubular cell apoptosis during obstruction induced renal injury. While we have previously reported the role of tumor necrosis factor-alpha in extrinsic pathway apoptotic signaling during renal obstruction, to our knowledge its effect on intrinsic pathway signaling and mitochondrial release of cytochrome C has not previously been evaluated. Male Sprague-Dawley rats were anesthetized and underwent unilateral ureteral obstruction vs sham operation. At 24 hours before surgery and every 84 hours thereafter the animals received vehicle or a pegylated form of soluble tumor necrosis factor receptor type 1. The kidneys were harvested 1 week postoperatively. The renal cortex was analyzed for tumor necrosis factor-alpha production (enzyme-linked immunosorbent assay), apoptosis (TUNEL and enzyme-linked immunosorbent assay), Bcl-2, Bcl-x(L), Bax, caspase 8 and truncated Bid expression (Western blot), and mitochondrial cytochrome C release (immunohistochemistry). Renal obstruction induced increased tumor necrosis factor-alpha production, apoptotic renal tubular death, the expression of Bax, caspase 8 and truncated BID, and mitochondrial release of cytochrome C, while simultaneously stimulating decreased Bcl-2 and Bcl-x(L) expression. Treatment with the pegylated form of soluble tumor necrosis factor receptor type 1 significantly decreased obstruction induced tumor necrosis factor-alpha production, apoptosis, Bax, caspase 8, truncated Bid expression and mitochondrial cytochrome C release, and increased Bcl-2 and Bcl-x(L) expression. These results demonstrate that tumor necrosis factor-alpha stimulates Bid and subsequent intrinsic apoptotic signaling pathway activation during unilateral ureteral obstruction, resulting in mitochondrial cytochrome C release and apoptotic cell death. We identified tumor necrosis factor-alpha neutralization as a potential therapeutic option for ameliorating obstruction induced renal injury.

Farnesol, a Fungal Quorum-Sensing Molecule Triggers Apoptosis in Human Oral Squamous Carcinoma Cells

Farnesol is a catabolite within the isoprenoid/cholesterol pathway that has exhibited significant antitumor activity. Farnesol was recently identified as a quorum-sensing molecule produced by the fungal pathogen Candida albicans. In this study, we hypothesize that synthetic and Candida-produced farnesol can induce apoptosis in vitro in oral squamous cell carcinoma (OSCC) lines. Cell proliferation, apoptosis, mitochondrial degradation, and survivin and caspase expressions were examined. In addition, global protein expression profiles were analyzed using proteomic analysis. Results demonstrated significant decrease in proliferation and increase in apoptosis in cells exposed to farnesol and C. albicans culture media. Concurrently, protein expression analysis demonstrated a significant decrease in survivin and an increase in cleaved-caspase expression, whereas fluorescent microscopy revealed the presence of active caspases with mitochondrial degradation in exposed cells. A total of 36 differentially expressed proteins were identified by proteomic analysis. Among the 26 up-regulated proteins were those involved in the inhibition of carcinogenesis, proliferation suppression, and aging. Most notable among the 10 down-regulated proteins were those involved in the inhibition of apoptosis and proteins overexpressed in epithelial carcinomas. This study demonstrates that farnesol significantly inhibits the proliferation of OSCCs and promotes apoptosis in vitro through both the intrinsic and extrinsic apoptotic signaling pathways. In addition, we report for the first time the ability of Candida-produced farnesol to induce a similar apoptotic response through the same pathways. The capability of farnesol to trigger apoptosis in cancer cells makes it a potential tool for studying tumor progression and an attractive candidate as a therapeutic agent.