Doxorubicin induces apoptosis and CD95 gene expression in human primary endothelial cells through a p53-dependent mechanism.

Regulation of the homeostasis of vascular endothelium is critical for the processes of vascular remodeling and angiogenesis under physiological and pathological conditions. Here we show that doxorubicin (Dox), a drug used in antitumor therapy, triggered a marked accumulation of p53 and induced CD95 gene expression and apoptosis in proliferating human umbilical vein endothelial cells (HUVECs). Transfection and site-directed mutagenesis experiments using the CD95 promoter fused to an intronic enhancer indicated the requirement for a p53 site for Dox-induced promoter activation. Furthermore, the p53 inhibitor pifithrin-alpha (PFT-alpha) blocked both promoter inducibility and protein up-regulation of CD95 in response to Dox. Up-regulated CD95 in Dox-treated cells was functional in eliciting apoptosis upon incubation of the cells with an agonistic CD95 antibody. However, Dox-mediated apoptosis was independent of CD95/CD95L interaction. The analysis of apoptosis in the presence of PFT-alpha and benzyloxycarbonyl-Val-Ala-dl-Asp-fluoromethylketone revealed that both p53 and caspase activation are required for Dox-mediated apoptosis of HUVECs. Finally, Dox triggered Bcl-2 down-regulation, cytochrome c release from mitochondria, and the activation of caspases 9 and 3, suggesting the involvement of a mitochondrially operated pathway of apoptosis. These results highlight the role of p53 in the response of primary endothelial cells to genotoxic drugs and may reveal a novel mechanism underlying the antitumoral properties of Dox, related to its ability to induce apoptosis in proliferating endothelial cells.     

Hydrogen peroxide induces apoptosis in HeLa cells through mitochondrial pathway

Cervical cancer is the most common cancer amongst females in India and is associated with high risk HPVs, reactive oxygen species (ROS), and excessive inflammation in most cases. ROS in turn affects the expression of pro- and anti-apoptotic proteins. The objective of the present study was to elucidate the effect of hydrogen peroxide (H(2)O(2)) on apoptotic signaling molecules in vitro. HeLa cell line expresses the Human papilloma virus - 18, E6 oncoprotein which causes the ubiquitin mediated degradation of p53 protein and is thus p53 deficient. p53 is known to act as a cellular stress sensor and triggers apoptosis. p73, a member of the p53 family also induces apoptosis in response to DNA damaging agents but unlike p53, it is infrequently mutated in human tumors. We demonstrate here, that in HeLa cells, apoptosis is triggered by H(2)O(2) via the mitochondrial pathway involving upregulation of p73, and its downstream target Bax. This was accompanied by upregulation of ERK, JNK, c-Myc, Hsp-70 and down regulation of anti-apoptotic Bcl-XL, release of cytochrome c from mitochondria and activation of caspases-9 and -3.     

ERKs/p53 signal transduction pathway is involved in doxorubicin-induced apoptosis in H9c2 cells and cardiomyocytes

The cardiotoxic effects of doxorubicin, a potent chemotherapeutic agent, have been linked to DNA damage, oxidative mitochondrial damage, and nuclear translocation of p53, but the exact molecular mechanisms causing p53 transactivation and doxorubicin-induced cardiomyopathy are not clear. The present study was carried out to determine whether extracellular signal-regulated kinases (ERKs), which are known to be activated by DNA damaging agents, are responsible for doxorubicin-induced p53 activation and oxidative mitochondrial damage in H9c2 cells. Cell death was measured by terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling, annexin V-fluorescein isothiocyanate, activation of caspase-9 and -3, and cleavage of poly(ADP-ribose) polymerase (PARP). We found that doxorubicin produced cell death in H9c2 cells in a time-dependent manner, beginning at 6 h, and these changes are associated decreased expression of Bcl-2, increases in Bax and p53 upregulated modulator of apoptosis-alpha expression, and collapse of mitochondria membrane potential. The changes in cell death and Bcl-2 family proteins, however, were preceded by earlier activation and nuclear translocation of ERKs, followed by increased phosphorylation at Ser15 and nuclear translocation of the phosphorylated p53. The functional importance of ERK1/2 and p53 in doxorubicin-induced toxicity was further demonstrated by the specific ERK inhibitor U-0126 and p53 inhibitor pifithrin (PFT)-alpha, which abrogated the changes in Bcl-2 family proteins and cell death produced by doxorubicin. U-0126 blocked the phosphorylation and nuclear translocation of both ERK1/2 and p53, whereas PFT-alpha blocked only the changes in p53. Doxorubicin and ERK inhibitors produced similar changes in ERK1/2-p53, PARP, and caspase-3 in neonatal rat cultured cardiomyocytes. Thus we conclude that ERK1/2 are functionally linked to p53 and that the ERK1/2-p53 cascade is the upstream signaling pathway responsible for doxorubicin-induced cardiac cell apoptosis. ERKs and p53 may be considered as novel therapeutic targets for the treatment of doxorubicin-induced cardiotoxicity.     

A 43 kD protein from the leaves of the herb Cajanus indicus L. modulates doxorubicin induced nephrotoxicity via MAPKs and both mitochondria dependent and independent pathways

Doxorubicin (Dox), a chemotherapeutic drug, is used for the treatment of different types of cancers. Application of this drug has now been made limited because of its several acute and chronic side effects. The aim of this work is to investigate the nephroprotecive role of a 43 kD protein (CI protein) isolated from the leaves of Cajanus indicus L, against Dox-induced oxidative impairment and kidney tissue damage. Administration of Dox (20 mg/kg body weight, once) significantly enhanced levels of blood urea nitrogen (BUN), creatinine, uric acid, TNF-α, urinary γ-glutamyl transpeptidase (γ-GT) activity, total urinary protein and urinary glucose level. Moreover, Dox exposure increased intracellular ROS production, lipid peroxidation, protein carbonylation and ATPases (like Na⁺/K⁺, Mg²⁺.) activities. On the other hand, the same exposure decreased GSH level and the activities of antioxidant enzymes; indicating that Dox-induced renal damage was mediated via oxidative stress. Signal transduction studies showed that Dox markedly decreased mitochondrial membrane potential, disturbed Bcl-2 family protein balance, enhanced cytochrome c release in the cytosol, increased levels of Apaf1, caspase-9/3/8, FAS, cleaved PARP protein and ultimately led to apoptotic cell death. In addition, Dox distinctly increased the phosphorylation of p38, JNK and ERK MAPKs. Post treatment with CI protein (3 mg/kg body weight, once daily for 4 days), however, reduced Dox-induced oxidative stress and suppressed all these apoptotic events. Histological studies also support the beneficial role of the CI protein in this organ pathophysiology. Combining, results suggest that CI protein might act as a beneficial agent in Dox-induced renal dysfunctions.     

Induction of apoptosis in the lung tissue from rats exposed to cigarette smoke involves p38/JNK MAPK pathway

Smoking is a major cause of human lung cancer. Past studies suggest that apoptosis might influence the malignant phenotype, but little is known about the association between apoptosis and cigarette smoke (CS)-induced lung pathogenesis. Using an in situ cell death detection kit (TA300), the association of CS with apoptosis was determined in a concentration-dependent manner. Furthermore, the expression of related proteins were investigated in the terminal bronchiole areas of the lung tissue from rats exposed to CS. Results showed that the expression of phosphotyrosine proteins was increased significantly in lung tissue of rats exposed to CS from 5 to 15 cigarettes. Using Western blotting and immunoprecipitation assay, Fas, a death receptor, was proved just be one of these phosphotyrosine proteins. CS triggered activation of MAP kinase (p38/JNK or ERK2) pathway, which led to Jun or p53 phosphorylation and FasL induction links Fas phosphorylation. Further, smoke treatment produced an increase in the level of proapoptotic proteins (Bax, t-Bid, cytochrome c and caspase-3), but a decline in Bcl-2, procaspase-8 and procaspase-9 proteins. Thus, CS-induced apoptosis may result from two main mechanisms, one is the activation of p38/JNK-Jun-FasL signaling, and the other is stimulated by the stabilization of p53, increase in the ratio of Bax/Bcl-2, release of cytochrome c; thus, leading to activation of caspase cascade.     

Human papillomaviruses type 16+ and 18+ cervical carcinoma cells are sensitive to staurosporine-mediated apoptosis

We have recently shown that staurosporine (ST) can trigger apoptosis of CaSki and HeLa cervical tumor cells from G2/M checkpoint, though the mechanism remains elusive. In this study, we reported that ST induced the inhibition of E6 and E7 viral oncogene and MDM2 expression, while it led to increased levels of p53, which was transiently located to mitochondria. Additionally, the proteins of the p53-regulated genes, p21(WAF1) and Bax, were increased with a similar time, while Bcl-2 and Bcl-X(L) expression was lowered. Upon ST treatment, the cytochrome c was released into the cytosol and, then, activation of caspases-9 and -3 led to Poly(ADP)RibosePolymerase (PARP) cleavage. Finally, characteristic morphological signs confirmed the apoptosis execution. Thus, taken together, all these observations suggest that apoptosis can be reactivated in HPV-positive human carcinoma cells and highlight that ST could be used as a potently chemotherapy agent to enhance the sensitivity of tumor cells to apoptosis.     

The role of mitogen-activated protein kinase in cadmium-induced primary rat cerebral cortical neurons apoptosis via a mitochondrial apoptotic pathway

Cadmium (Cd) is an extremely toxic metal capable of severely damaging several organs, including the brain. Studies have shown that Cd induces neuronal apoptosis partially by activating the mitogen-activated protein kinase (MAPK) pathways. However, the underlying mechanism of MAPK involving the mitochondrial apoptotic pathway in neurons remains unclear. In this study, primary rat cerebral cortical neurons were exposed to Cd, which significantly decreased cell viability and the B-cell lymphoma 2/Bcl-2 associate X protein (Bcl-2/Bax) ratio and increased the percentage of apoptotic cells, release of cytochrome c, cleavages of caspase-3 and poly (ADP-ribose) polymerase (PARP), and nuclear translocation of apoptosis-inducing factor (AIF). In addition, Cd induced phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 MAPK. Inhibition of ERK and JNK, but not p38 MAPK, partially protected the cells from Cd-induced apoptosis. ERK and JNK inhibition also blocked alteration of the Bcl-2/Bax ratio, release of cytochrome c, cleavages of caspase-3 and PARP, and nuclear translocation of AIF. Taken together, these data suggest that the ERK- and JNK-mediated mitochondrial apoptotic pathways play important roles in Cd-induced neuronal apoptosis.     

Doxorubicin-induced neurotoxicity is attenuated by a 43-kD protein from the leaves of Cajanus indicus L. via NF-κB and mitochondria dependent pathways

Doxorubicin (Dox) is an effective anthracycline antitumour drug although its clinical efficacy is restricted because of several acute and chronic side effects. It has been suggested that Dox-induced anticancer effect and neurotoxicity do not follow identical mechanism. The present study has been carried out to investigate the neuroprotecive role of a 43-kD protein (Cajanus indicus (CI) protein) against Dox-induced oxidative impairment and brain tissue damage. Administration of Dox (25 mg/kg body weight) increased reactive oxygen species (ROS) production, altered neuro antioxidant status, activities of brain specific coenzymes (like acetyl coenzyme, monoamine oxidase, etc.), ATPases (like Na(+)/K(+), Ca(2+), etc.) and brain biogenic amines levels. Signal transduction studies showed that Dox markedly decreased mitochondrial membrane potential, disturbed Bcl-2 family protein balance, enhanced cytochrome c release in the cytosol, increased levels of Apaf1, caspase-9/3, cleaved PARP protein and ultimately led to apoptotic cell death. In addition, Dox markedly increased nuclear factor kappa B (NF-κB) nuclear translocation in association with IKKα/β phosphorylation and IκBα degradation. Post-treatment with CI protein (3 mg/kg body weight, once daily for next 4 days), however, reduced Dox-induced oxidative stress, attenuated the nuclear translocation of NF-κB and protected the brain tissue from Dox-induced apoptotic death. Histological studies also support these experimental findings. Results suggest that CI protein might act as a beneficial agent against Dox-induced neuronal dysfunctions.     

A novel agent attenuates cardiotoxicity and improves antitumor activity of doxorubicin in breast cancer cells

Doxorubicin (Dox) is a well-known chemotherapeutic agent used in the treatment of various cancers. However, Dox-induced cardiotoxicity limits its further clinical use. We have previously reported a small molecular named biotin-conjugated ADTM analog (BAA) that exhibits cytoprotective effects against oxidative stress–induced cell injury in cardiomyoblast H9c2 cells. Here, the protective effects of BAA, indexed by attenuation of the cardiotoxicity induced by Dox as well as synergistic antitumor activity that increases the chemotherapeutic efficacy of Dox were investigated. Our results demonstrated that BAA significantly ameliorated Dox-induced toxicity in the H9c2 cells and zebrafish models. In addition, BAA attenuated Dox-induced endoplasmic reticulum (ER) stress in H9c2 cells. An ER stress inhibitor, 4-phenylbutyric acid, reversed the protective effect of BAA in H9c2 cells. In contrast, in human breast tumor MDA-MB-231 cells, BAA significantly enhanced Dox-induced cytotoxicity through upregulating Dox-induced ER stress response. Taken together, our findings indicate that Dox combined with BAA can significantly enhance its antitumor activity in breast cancer cells and reduce its cardiotoxicity, at least in part, by mediating ER stress activation.     

Jun kinase delays caspase-9 activation by interaction with the apoptosome

Activation of c-Jun N-terminal kinase 1/2 (JNK) can delay oxidant-induced cell death, but the mechanism is unknown. We found that oxidant stress of cardiac myocytes activated both JNK and mitochondria-dependent apoptosis and that expression of JNK inhibitory mutants accelerated multiple steps in this pathway, including the cleavage and activation of caspases-3 and -9 and DNA internucleosomal cleavage, without affecting the rate of cytochrome c release; JNK inhibition also increased caspase-3 and -9 cleavage in a cell-free system. On activation by GSNO or H(2)O(2), JNK formed a stable association with oligomeric Apaf-1 in a approximately 1.4-2.0 mDa pre-apoptosome complex. Formation of this complex could be triggered by addition of cytochrome c and ATP to the cell-free cytosol. JNK inhibition abrogated JNK-Apaf-1 association and accelerated the association of procaspase-9 and Apaf-1 in both intact cells and cell-free extracts. We conclude that oxidant-activated JNK associates with Apaf-1 and cytochrome c in a catalytically inactive complex. We propose that this interaction delays formation of the active apoptosome, promoting cell survival during short bursts of oxidative stress.     

Hispolon from Phellinus linteus possesses mediate caspases activation and induces human nasopharyngeal carcinomas cells apoptosis through ERK1/2, JNK1/2 and p38 MAPK pathway

Hispolon, a phenol compound isolated from Phellinus linteus (PL), possesses anti-inflammatory, antiproliferative, and antioxidant effects. However, the effects of hispolon on human nasopharyngeal carcinomas have yet to be evaluated. Here, the molecular mechanism by which hispolon anticancer effects in human nasopharyngeal carcinomas cells was investigated. The results showed that hispolon significantly inhibited cell proliferation of HONE-1 and NP-039 cell lines. Furthermore, hispolon induced apoptosis through caspases-3, -8, and -9 activations and PARP cleavage in dose- and time-dependent manner in HONE-1 and NP-039 cells. Moreover, hispolon also showed that increase phosphorylation of ERK1/2, p38 MAPK and JNK1/2 in dose- and time-dependent manner by western blot analysis. However, hispolon-induced activation of the caspase-3, -8 and -9 significantly abolished by inhibition of p38 MAPK and JNK1/2 specific inhibitors. In this study, we determine that the effects of hispolon on the apoptosis and related regulation mechanism in HONE-1 and NPC-039 cells takes place. Our findings revealed that hispolon may be a useful candidate as a chemotherapeutic agent for NPC therapy.     

Subcellular basis of vitamin C protection against doxorubicin-induced changes in rat cardiomyocytes

Understanding the molecular basis of doxorubicin (Dox)-induced cardiomyopathy is crucial to finding cardioprotective strategies. Oxidative stress-mediated pathways are known to contribute to cardiomyocyte apoptosis due to Dox. Improving the antioxidant defenses of cardiomyocytes could be one strategy for cardiac protection. We tested the effects of vitamin C (Vit C), a potent antioxidant, on Dox-induced cardiomyocyte apoptosis. Adult rat cardiomyocytes were incubated for 24 h with Dox (0.01-10 μM), with and without different concentrations of Vit C (5-100 μM). Exposure to Dox (10 μM) resulted in a 98% increase in the production of reactive oxygen species (ROS) and creatine kinase (CK) release, 70% increase in p53 as well as ASK-1 activation, 40% increase in p38 activation, 30% increase in pro-apoptotic Bax over anti-apoptotic Bcl-xl ratio and caspase activation, and about 20% reduction in cell viability. Vit C (25 μM) was able to mitigate Dox-induced changes by decreasing ROS and CK release by 50%, reducing p53 activation by 40%. The increase in ASK-1 and p38 was also significantly mitigated, and apoptosis was reduced while cardiomyocytes viability was improved. This study shows that Dox-induced cardiomyocyte death is mediated by a direct membrane effect as well as intracytoplasmic changes promoting the cardiomyocyte apoptosis. These findings suggest a nutritional approach of using Vit C for preventing Dox-induced cardiotoxicity and better management of cancer patients.     

Helicobacter pylori lipopolysaccharide induces apoptosis of cultured guinea pig gastric mucosal cells

Helicobacter pylori lipopolysaccharide (LPS) is generally accepted as a low-toxicity virulence. Primary cultures of guinea pig gastric mucosal cells expressed the Toll-like receptor 4 and were sensitive to H. pylori LPS as well as Escherichia coli LPS. H. pylori LPS stimulated phosphorylation of transforming growth factor-beta-activated kinase 1 (TAK1), TAK1-binding protein 1 (TAB1), and c-Jun NH(2)-terminal kinase (JNK) 2. H. pylori LPS at >2.1 endotoxin unit/ml (>1 ng/ml) activated caspase-8, stimulated cytochrome c release from mitochondria, and subsequently activated caspases-9 and -3, leading to apoptosis. Epidermal growth factor blocked all of these apoptotic processes and inhibited apoptosis, whereas it did not modify the phosphorylation of TAK1, TAB1, and JNK2. A comparatively specific inhibitor of caspase-8 or -9 blocked apoptosis, whereas cytochrome c release was prevented only with a caspase-8-like inhibitor. Our results suggest that caspase-8 and mitochondria may play crucial roles in H. pylori LPS-induced apoptosis and that this accelerated apoptosis may be involved in abnormal cell turnover of H. pylori-infected gastric mucosa.     

The hierarchical relationship between MAPK signaling and ROS generation in human leukemia cells undergoing apoptosis in response to the proteasome inhibitor Bortezomib

The hierarchy of events accompanying induction of apoptosis by the proteasome inhibitor Bortezomib was investigated in Jurkat lymphoblastic and U937 myelomonocytic leukemia cells. Treatment of Jurkat or U937 cells with Bortezomib resulted in activation of c-Jun-N-terminal kinase (JNK) and p38 MAPK (mitogen-activated protein kinase), inactivation of extracellular signal-regulating kinase 1/2 (ERK1/2), cytochrome c release, caspase-9, -3, and -8 activation, and apoptosis. Bortezomib-mediated cytochrome c release and caspase activation were blocked by the pharmacologic JNK inhibitor SP600125, but lethality was not diminished by the p38 MAPK inhibitor SB203580. Inducible expression of a constitutively active MEK1 construct blocked Bortezomib-mediated ERK1/2 inactivation, significantly attenuated Bortezomib lethality, and unexpectedly prevented JNK activation. Conversely, pharmacologic MEK/ERK1/2 inhibition promoted Bortezomib-mediated JNK activation and apoptosis. Lastly, the antioxidant N-acetyl-l-cysteine (LNAC) attenuated Bortezomib-mediated reactive oxygen species (ROS) generation, ERK inactivation, JNK activation, mitochondrial dysfunction, and apoptosis. In contrast, enforced MEK1 and ERK1/2 activation or JNK inhibition did not modify Bortezomib-induced ROS production. Together, these findings suggest that in human leukemia cells, Bortezomib-induced oxidative injury operates at a proximal point in the cell death cascade to antagonize cytoprotective ERK1/2 signaling, promote activation of the stress-related JNK pathway, and to trigger mitochondrial dysfunction, caspase activation, and apoptosis. They also suggest the presence of a feedback loop wherein Bortezomib-mediated ERK1/2 inactivation contributes to JNK activation, thereby amplifying the cell death process.     

Schisandrin B elicits a glutathione antioxidant response and protects against apoptosis via the redox-sensitive ERK/Nrf2 pathway in H9c2 cells

This study investigated the signal transduction pathway involved in the cytoprotective action of (-)schisandrin B [(-)Sch B, a stereoisomer of Sch B]. Using H9c2 cells, the authors examined the effects of (-)Sch B on MAPK and Nrf2 activation, as well as the subsequent eliciting of glutathione response and protection against apoptosis. Pharmacological tools, such as cytochrome P-450 (CYP) inhibitor, antioxidant, MAPK inhibitor, and Nrf2 RNAi, were used to delineate the signaling pathway. (-)Sch B caused a time-dependent activation of MAPK in H9c2 cells, with the degree of ERK activation being much larger than that of p38 or JNK. The MAPK activation was followed by an increase in the level of nuclear Nrf2, an indirect measure of Nrf2 activation, and the eliciting of a glutathione antioxidant response. The activation of MAPK and Nrf2 seemed to involve oxidants generated from a CYP-catalyzed reaction with (-)Sch B. Both ERK inhibition by U0126 and Nrf2 suppression by Nrf2 RNAi transfection largely abolished the cytoprotection against hypoxia/reoxygenation-induced apoptosis in (-)Sch B-pretreated cells. (-)Sch B pretreatment potentiated the reoxygenation-induced ERK activation, whereas both p38 and JNK activations were suppressed. Under the condition of ERK inhibition, Sch B treatment did not protect against ischemia/reperfusion injury in an ex vivo rat heart model. The results indicate that (-)Sch B triggers a redox-sensitive ERK/Nrf2 signaling, which then elicits a cellular glutathione antioxidant response and protects against hypoxia/reoxygenation-induced apoptosis in H9c2 cells. The ERK-mediated signaling is also likely involved in the cardioprotection afforded by Sch B in vivo.     

Opposing effects of ERK and p38 MAP kinases on HeLa cell apoptosis induced by dipyrithione

Dipyrithione (2, 2'-dithiobispyridine-1, 1'-dioxide, PTS2), a pyrithione derivate, is highly bactericidal and fungicidal. In this study we examined its apoptotic effect on HeLa cells. PTS2 induced HeLa cell death in a dose and time dependent manner. ERK1/2 and p38 were markedly activated, but little JNK1/2 activation was detected. Suppression of p38 activation by SB203580 reduced the extent of apoptosis of the HeLa cells and also prevented induction of p21, release of cytochrome c, and cleavage of caspase-3 and PARP. Inhibition of ERK1/2 with PD98059 increased apoptosis, indicating that ERK1/2 activation has an anti-apoptotic effect on PTS2-induced HeLa cell apoptosis. PTS2 also inhibited murine sarcoma 180 and hepatoma 22 tumor growth in an animal tumor model. Our findings indicate that PTS2 possesses anti-tumor activity, that caspase-3 and poly (ADP-ribose) polymerase (PARP) are involved in PTS2-induced HeLa cell apoptosis and that ERK1/2 and p38 have opposing effects on this apoptosis.     

α-TEA inhibits survival and enhances death pathways in cisplatin sensitive and resistant human ovarian cancer cells

RRR-α-tocopherol ether linked acetic acid analog (α-TEA), is a potential chemotherapeutic agent for ovarian cancer. Pro-death and pro-life signaling pathways were studied to understand the anti-cancer actions of α-TEA on cisplatin-sensitive (A2780S) and -resistant (A2780/cp70R) human ovarian cancer cells. Both cell lines were refractory to Fas; whereas, α-TEA sensitized them to Fas signaling. α-TEA increased levels of Fas message, protein and membrane-associated Fas. Neutralizing antibodies to Fas or Fas L partially blocked α-TEA-induced apoptosis. α-TEA induced prolonged activation of c-Jun N-terminal kinase (JNK) and its substrate c-Jun; Bax conformational change; and cleavage of Bid and caspases-8, -9 and -3. Chemical inhibitors of JNK, and caspases blocked α-TEA-induced apoptosis. α-TEA decreased phosphorylation of protein kinase B (Akt/PKB) and extracellular signal-regulated kinase (ERK1/2), as well as cellular FLICE-like inhibitory protein (c-FLIP) and Survivin protein levels. Knockdown of Akt and ERK activity using phosphoinositide- 3-kinase (PI3K) and mitogen-activated protein kinase kinase (MKK1) inhibitors enhanced α-TEA-induced apoptosis. Over-expression of constitutively active Akt2 and MKK1 blocked α-TEA-induced apoptosis. Collectively, data show α-TEA to be a potent apoptotic inducer of both cisplatin-sensitive and -resistant human ovarian cancer cells via activating death receptor Fas signaling and suppressing anti-apoptotic AKT and ERK targets.     

Induction of apoptosis by shikonin through a ROS/JNK-mediated process in Bcr/Abl-positive chronic myelogenous leukemia （CML） cells

This study examined the signaling events induced by shikonin that lead to the induction of apoptosis in Bcr/ Abl-positive chronic myelogenous leukemia （CML） cells （e.g., K562, LAMA84）. Treatment of K562 cells with shikonin （e.g., 0.5 pM） resulted in profound induction of apoptosis accompanied by rapid generation of reactive oxygen species （ROS）, striking activation of c-Jun-N-terminal kinase （JNK） and p38, marked release of the mitochondrial proteins cytochrome c and Smac/DIABLO, activation of caspase-9 and -3, and cleavage of PARP. Scavenging of ROS completely blocked all of the above-mentioned events （i.e., JNK and p38 phosphorylation, cytochrome c and Smac/DIABLO release, caspase and PARP cleavage, as well as the induction of apoptosis） following shikonin treatment. Inhibition of JNK and knock-down of JNK1 significantly attenuated cytochrome c release, caspase cleavage and apoptosis, but did not affect shikonin-mediated ROS production. Additionally, inhibition of caspase activation completely blocked shikonin-induced apoptosis, but did not appreciably modify shikonin-mediated cytochrome c release or ROS generation. Altogether, these findings demonstrate that shikonin-induced oxidative injury operates at a proximal point in apoptotic signaling cascades, and subsequently activates the stress-related JNK pathway, triggers mitochondrial dysfunction, cytochrome c release, and caspase activation, and leads to apoptosis. Our data also suggest that shikonin may be a promising agent for the treatment of CML, as a generator of ROS.