Cancer cell death by programmed necrosis?

A recent paper by Zong et al. describes how alkylating agents kill cells by a process they term "programmed necrosis," induced by excessive activation of PARP resulting in degradation of cytosolic NAD(+) and inhibition of glycolysis. We argue that it is not obvious whether chemotherapy in patients can induce sufficient NAD(+) loss to affect glycolysis; that the "programmed" nature of the necrosis requires more evidence; and that there are mechanisms making cancer cells hypersensitive to DNA damage other than their high rate of aerobic glycolysis.     

Is cell death induced by nematocysts extract of medusa pelagia noctiluca related to oxidative stress?

Pelagia noctiluca, a jellyfish widely distributed in the Mediterranean waters, especially in coastal areas of Tunisia, has garnered attention because of its stinging capacity and the resulting public health hazard. Crude extracts of P. noctiluca nematocysts have been tested for their cytotoxicity on Vero cells. Our results clearly showed that nematocysts induced cell mortality in a dose‐ and time‐dependent manner. A cytoprotective effect against cell mortality was obtained when Vero cells were treated with Vitamin E. This process was further confirmed by the generation of reactive oxygen species (ROS) and the induction of Hsp 70 and 27 protein expressions. Thus, our findings suggested that oxidative stress is involved in the toxicity of pelagia nematocysts and may therefore constitute the major mechanism of this medusa nematocysts toxicity. © 2011 Wiley Periodicals, Inc. Environ Toxicol 28: 498–506, 2013.     

Is apoptosis cause of pre-eclampsia?

Pre-eclampsia is the main cause of fetal and maternal morbidity and death associated with hypertension during complicating pregnancy. During physiological pregnancy, the immunological system undergoes secondary modifications, with an "exchange" between mother and fetus. Cytokines play an important role in the complex condition of partial fetal "rejection". It has suggested that the condition depend on immunological factors. In line with this hypothesis, apoptosis appear to play a key role in the pathophysiology of placental ischemia and the mechanism underlying this condition may be influenced by substances such as Bcl-2 which inhibits apoptosis. Neither aspirin nor calcium appear to improve maternal hypertension and proteinuria, although late ongoing trials may alter this view. At present, the condition can be resolved only by the end of pregnancy. Further studies are required in order to improve our understanding of these immunological mechanisms underlying hypertension during pregnancy, as the key to effective therapy may be their ability to "manipulate" them in an appropriate way.     

Is endogenously released DOPA itself an upstream factor for increase in glutamate release and delayed neuronal cell death induced by transient ischemia in rats?

DOPA itself is a neuromodulator in striata. In rat striata, DOPA by itself released neuronal glutamate in slices and caused cell death via glutamate release in cultured fetal neurons, suggesting involvement of DOPA in an upstream process of mechanisms for in vivo neuronal cell death. We attempted to clarify whether or not this idea is truly the case in conscious Wistar rats. Four vessels were occluded for 10 min during microdialysis of striata. DOPA, dopamine and glutamate in perfusates collected every 10 min were measured by HPLC-ECD and spectrophotometer. Delayed neuronal cell death in striata and hippocampus was evaluated 96 hr after ischemia. DOPA was indeed evoked with dopamine and glutamate during and after ischemia, and peak increases by respective 6-, 210- and 8-fold of a basal level were seen at the fraction immediately after ischemia. Delayed neuronal cell death was slight to moderate in striata and severe in hippocampus. Intrastriatal perfusion of NSD-1015, a central DOPA decarboxylase inhibitor, at 30 microM 10 min before ischemia, markedly increased DOPA and glutamate release by ischemia with slight inhibition of dopamine release and exaggerated delayed neuronal cell death in striata. Meanwhile, intrastriatal perfusion of DOPA cyclohexyl ester (DOPA CHE) at 10-100 nM, a novel stable potent competitive DOPA antagonist, antagonized dose-dependently increases in glutamate release by ischemia without modification of dopamine release. DOPA CHE at 100 nM protected striatal neurons from delayed cell death. Hippocampal neuronal cell death was neither affected by NSD-1015 nor by DOPA CHE. Endogenously released DOPA itself seems to act on its recognition site and to be a causal factor for increase in glutamate release and resultant delayed neuronal cell death by transient ischemia in rats.     

Does atorvastatin induce aortic smooth muscle cell apoptosis in vivo?

It has been reported that HMG-CoA reductase inhibitors such as atorvastatin induce vascular smooth muscle cell (SMC) apoptosis in vitro. However, this effect remains to be demonstrated in vivo. The present studies were designed to test the ability of atorvastatin to induce SMC apoptosis in vivo, using the spontaneously hypertensive rat (SHR) as a well-known reference model of SMC apoptosis induction in vivo by cardiovascular drugs including the calcium channel blocker amlodipine. Atorvastatin was administered to SHR for 3 or 6 weeks either alone or together with amlodipine, a drug combination clinically available to patients. Primary endpoints included aortic medial hypertrophy and aortic SMC hyperplasia, internucleosomal DNA fragmentation and expression of the apoptosis regulatory proteins Bax and Bcl-2. The SHR aorta showed no evidence of SMC apoptosis induction by atorvastatin, even at the high dose of 50 mg kg(-1) day(-1), although the statin significantly reduced oxidative stress after 3 weeks and blood pressure after 6 weeks of administration. Amlodipine-induced regression of aortic hypertophy and aortic SMC hyperplasia were dose- and time-dependent, but there was no interaction between atorvastatin and amlodipine in modulating the primary endpoints. These results do not support the notion that atorvastatin induces SMC apoptosis in the aortic media in vivo.     

Dioxin toxicity,aryl hydrocarbon receptor signaling,and apoptosis—Persistent pollutants affect programmed cell death

Exogenous ligands of the aryl hydrocarbon receptor (AhR) such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related substances are highly toxic pollutants ubiquitously present in the environment. They cause a variety of toxic effects to different organs and tissues. Among other effects, TCDD exposure to laboratory animals leads to thymus atrophy and immunosuppression on the one hand, and to tumor formation on the other. Apoptosis appears to be involved in both these toxic effects: AhR activation by TCDD was discussed to induce apoptosis of immune cells, leading to the depletion of thymocytes and ultimately immunosuppression. This mechanism could help to explain the highly immunotoxic actions of TCDD but it is nevertheless under debate whether this is the mode of action for immunosuppression by this class of chemical substances. In other cell types, especially liver cells, TCDD inhibits apoptosis induced by genotoxic treatment. In initiation-promotion studies, TCDD was shown to be a potent liver tumor promoter. Among other theories it was hypothesized that TCDD acts as a tumor promoter by preventing initiated cells from undergoing apoptosis. The exact mechanisms of apoptosis inhibition by TCDD are not fully understood, but both in vivo and in vitro studies consistently showed an involvement of the tumor suppressor p53 in this effect. Various strings of evidence have been established linking apoptosis to the detrimental effects of exogenous activation of the AhR. Within this article, studies elucidating the effects of TCDD and related substances on apoptosis signaling, be it inducing or repressing, is to be reviewed.     

Function of HeLa cell cytoplasm in apoptosis induced by cisplatin in a cell-free system

在构建Ｂｃｌ－２高表达及其对照细胞株基础上，用非细胞体系研究了顺铂诱导的ＨｅＬａ细胞凋亡中细胞质的作用．实验结果显示凋亡细胞胞质提取物可引起正常细胞核的固缩及染色质边缘化，类似完整细胞凋亡的改变，而Ｂｃｌ－２高表达株的胞质提取物具有抗凋亡能力．说明引起凋亡的物质及对抗凋亡的物质在细胞质中都存在，细胞质在顺铂诱导的ＨｅＬａ细胞凋亡中起着较重要的作用．     

Is digitalis compound-induced cardiotoxicity, mediated through guinea-pig cardiomyocytes apoptosis?

Our aim in performing this study was to analyze in vivo the cell death mechanism induced by toxic doses of digitalis compounds on guinea-pig cardiomyocytes. We analyzed three study groups of five male guinea pigs each. Guinea pigs were intoxicated under anesthesia with ouabain or digoxin (at a 50-60% lethal dose); the control group did not receive digitalis. A 5-hours period elapsed before guinea pig hearts were extracted to obtain left ventricle tissue. We carried out isolation of mitochondria and cytosol, cytochrome c and caspase-3 and -9 determination, and electrophoretic analysis of nuclear DNA. TdT-mediated DUTP-X nick end labeling (TUNEL) reaction was performed in histologic preparations to identify in situ apoptotic cell death. Ultrastructural analysis was performed by electron microscopy. Electrophoretic analysis of DNA showed degradation into fragments of 200-400 base pairs in digitalis-treated groups. TUNEL reaction demonstrated the following: in the control group, <10 positive nuclei per field; in the digoxin-treated group, 2-14 positive nuclei per field, while in the ouabain-treated group counts ranged from 9-30 positive nuclei per field. Extracts from ouabain-treated hearts had an elevation of cytochrome c in cytosol and a corresponding decrease in mitochondria; this release of cytochrome c provoked activation of caspase-9 and -3. Electron microscopy revealed presence of autophagic vesicles in cytoplasm of treated hearts. Toxic dosages of digitalis at 50-60% of the lethal dose are capable of inducing cytochrome c release from mitochondria, processing of procaspase-9 and -3, and DNA fragmentation; these observations are mainly indicative of apoptosis, although a mixed mechanism of cell death cannot be ruled out.     

Why is particulate matter produced by wildfires toxic to lung macrophages?

The mechanistic basis of the high toxicity to lung macrophages of coarse PM from the California wildfires of 2008 was examined in cell culture experiments with mouse macrophages. Wildfire PM directly killed macrophages very rapidly in cell culture at relatively low doses. The wildfire coarse PM is about four times more toxic to macrophages on an equal weight basis than the same sized PM collected from normal ambient air (no wildfires) from the same region and season. There was a good correlation between the extent of cytotoxicity and the amount of oxidative stress observed at a given dose of wildfire PM in vitro. Our data implicate NF-κB signaling in the response of macrophages to wildfire PM, and suggest that most, if not all, of the cytotoxicity of wildfire PM to lung macrophages is the result of oxidative stress. The relative ratio of toxicity and of expression of biomarkers of oxidant stress between wildfire PM and “normal” PM collected from ambient air is consistent with our previous results in mice in vivo, also suggesting that most, if not all, of the cytotoxicity of wildfire PM to lung macrophages is the result of oxidative stress. Our findings from this and earlier studies suggest that the active components of coarse PM from the wildfire are heat-labile organic compounds. While we cannot rule out a minor role for endotoxin in coarse PM preparations from the collected wildfire PM in our observed results both in vitro and in vivo, based on experiments using the inhibitor Polymyxin B most of the oxidant stress and pro-inflammatory activity observed was not due to endotoxin.     

Is maintenance therapy always necessary for patients with ulcerative colitis in remission?

BACKGROUND: The efficacy of sulphasalazine and mesalazine in preventing relapse in patients with ulcerative colitis is well known. It is less clear how long such maintenance should be continued, and if the duration of disease remission is a factor that affects the risk of recurrence. AIM: To determine whether the duration of disease remission affects the relapse rate, by comparing the efficacy of a delayed-release mesalazine (Asacol, Bracco S.p.A., Milan, Italy) against placebo in patients with ulcerative colitis with short- and long-duration of disease remission. METHODS: 112 patients (66 male, 46 female, mean age 35 years), with intermittent chronic ulcerative colitis in clinical, endoscopic and histological remission with sulphasalazine or mesalazine for at least 1 year, were included in the study. Assuming that a lower duration of remission might be associated with a higher relapse rate, the patients were stratified according to the length of their disease remission, prior to randomization into Group A (Asacol 26, placebo 35) in remission from 1 to 2 years, or Group B (Asacol 28, placebo 23) in remission for over 2 years, median 4 years. Patients were treated daily with oral Asacol 1.2 g vs. placebo, for a follow-up period of 1 year. RESULTS: We employed an intention-to-treat analysis. In Group A, whilst no difference was found between the two treatments after 6 months, mesalazine was significantly more effective than placebo in preventing relapse at 12 months [Asacol 6/26 (23%), placebo 17/35 (49%), P = 0.035, 95% Cl: 48-2.3%]. In contrast, in Group B no statistically significant difference was observed between the two treatments, either at 6 or 12 months [Asacol 5/28 (18%), placebo 6/23 (26%), P = 0.35, 95% Cl: 31-14%] of follow-up. Patients in group B were older, and had the disease and remission duration for longer, than those in Group A. CONCLUSIONS: Mesalazine prophylaxis is necessary for the prevention of relapse by patients with ulcerative colitis in remission for less than 2 years, but this study casts doubt over whether continuous maintenance treatment is necessary in patients with prolonged clinical, endoscopic and histological remission, who are at very low risk of relapse.     

Is CYP1A1 induction always related to AHR signaling pathway?

Humans are daily subjected to ever increasing amounts of exogenous compounds. Some of them are capable of inducing cytochrome P450s, a process that allows the cell to adapt to changes in its chemical environment. One of the most widely CYP studied is CYP1A1 because it metabolises a large number of xenobiotics to cytotoxic and/or mutagenic derivatives. To date, results from the literature indicate that induction of CYP1A1 does not only involve the classical activation cascade of the Ah receptor, e.g. binding of the ligand to the AhR, heterodimerisation with Arnt protein, constitution of a complex with XRE responsive element and subsequent gene activation. Indeed, some xenobiotics do activate CYP1A1 gene expression in spite of their inability to compete with TCDD for binding to the AhR. Other signaling pathways must therefore also be considered. Firstly, the CYP1A1 inducer compounds could be very weak AhR ligands or may be metabolized into a form which is in turn capable of binding to the Ah receptor. A second hypothesis would be that these molecules could act through other signaling cascades. At this time, two of them seem to be implicated. One concerns the RARs signal transduction pathway, as already described for retinoic acid. The second may involve tyrosine kinase activation, but the precise relationship between this activation and CYPA1 induction remains yet to be established. For the moment there is still a black box which needs to be investigated.     

Echinacoside stimulates cell proliferation and prevents cell apoptosis in intestinal epithelial MODE-K cells by up-regulation of transforming growth factor-β1 expression

Cistanche deserticola MA (C. deserticola) has been widely used as a laxative herbal in herbal medicine for the treatment of irritable bowel syndrome or constipation, and echinacoside (ECH) is one of the major bioactive ingredients in this herbal. Our aim was to investigate the effect of ECH on intestinal epithelial cell growth and death. MODE-K, an intestinal epithelial cell line, was used as an in vitro model of the intestine. Cell proliferation was measured by methylthiazol tetrazolium (MTT) assay. Cell apoptosis was determined with Annexin-V staining. Here we showed that in cultured MODE-K cells, ECH significantly stimulated cell proliferation and enhanced cell survival by reducing cell apoptosis in the presence of H(2)O(2) or the mixture of pro-inflammatory cytokines, while transforming growth factor (TGF)-β1 expression was up-regulated in a dose-dependent manner. Knockdown of TGF-β1 expression disrupted both the proliferative and cytoprotective activities of ECH, which was further confirmed by neutralization of TGF-β1 activity using anti-TGF-β1 antibody. These data suggest that ECH as one of bioactive ingredients in herbal C. deserticola and others may improve mucosal tissue repair by stimulating intestinal epithelial cell proliferation and preventing cell death via up-regulation of TGF-β.     

Hydrogen sulphide protects mouse pancreatic β-cells from cell death induced by oxidative stress, but not by endoplasmic reticulum stress

BACKGROUND AND PURPOSE

Hydrogen sulphide (H₂S), a potentially toxic gas, is also involved in the neuroprotection, neuromodulation, cardioprotection, vasodilatation and the regulation of inflammatory response and insulin secretion. We have recently reported that H₂S suppresses pancreatic β-cell apoptosis induced by long-term exposure to high glucose. Here we examined the protective effects of sodium hydrosulphide (NaHS), an H₂S donor, on various types of β-cell damage.

EXPERIMENTAL APPROACH

Isolated islets from mice or the mouse insulinoma MIN6 cells were cultured with palmitate, cytokines (a mixture of tumour necrosis factor-α, interferon-γ and interleukin-1β), hydrogen peroxide, thapsigargin or tunicamycin with or without NaHS. We examined DNA fragmentation, caspase-3 and -7 activities and reactive oxygen species (ROS) production in the treated cells thereafter. Apoptotic cell death in isolated islets was also assessed by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) method.

KEY RESULTS

NaHS suppressed DNA fragmentation and the activities of caspase-3 and -7 induced by palmitate, the cytokines or hydrogen peroxide. In contrast, NaHS failed to protect islets and MIN6 cells from apoptosis induced by thapsigargin and tunicamycin, both of which cause endoplasmic reticulum stress. NaHS suppressed ROS production induced by cytokines or hydrogen peroxide but it had no effect on ROS production in thapsigargin-treated cells. NaHS increased Akt phosphorylation in MIN6 cells treated with cytokines but not in cells treated with thapsigargin. Treatment with NaHS decreased TUNEL-positive cells in cytokine-exposed islets.

CONCLUSIONS AND IMPLICATIONS

H₂S may prevent pancreatic β-cells from cell apoptosis via an anti-oxidative mechanism and the activation of Akt signalling.     

NFκB inhibitors induce cell death in glioblastomas

Identification of novel target pathways in glioblastoma (GBM) remains critical due to poor prognosis, inefficient therapies and recurrence associated with these tumors. In this work, we evaluated the role of nuclear-factor-kappa-B (NFκB) in the growth of GBM cells, and the potential of NFκB inhibitors as antiglioma agents. NFκB pathway was found overstimulated in GBM cell lines and in tumor specimens compared to normal astrocytes and healthy brain tissues, respectively. Treatment of a panel of established GBM cell lines (U138MG, U87, U373 and C6) with pharmacological NFκB inhibitors (BAY117082, parthenolide, MG132, curcumin and arsenic trioxide) and NFκB-p65 siRNA markedly decreased the viability of GBMs as compared to inhibitors of other signaling pathways such as MAPKs (ERK, JNK and p38), PKC, EGFR and PI3K/Akt. In addition, NFκB inhibitors presented a low toxicity to normal astrocytes, indicating selectivity to cancerous cells. In GBMs, mitochondrial dysfunction (membrane depolarization, bcl-xL downregulation and cytochrome c release) and arrest in the G2/M phase were observed at the early steps of NFκB inhibitors treatment. These events preceded sub-G1 detection, apoptotic body formation and caspase-3 activation. Also, NFκB was found overstimulated in cisplatin-resistant C6 cells, and treatment of GBMs with NFκB inhibitors overcame cisplatin resistance besides potentiating the effects of the chemotherapeutics, cisplatin and doxorubicin. These findings support NFκB as a potential target to cell death induction in GBMs, and that the NFκB inhibitors may be considered for in vivo testing on animal models and possibly on GBM therapy.     

Human heart failure: Is cell therapy a valid option?

The concept of the heart as a terminally differentiated organ incapable of replacing damaged myocytes has been at the center of cardiovascular research and therapeutic development for the past 50 years. The progressive decline in myocyte number with aging and the formation of scarred tissue following myocardial infarction have been interpreted as irrefutable proofs of the post-mitotic characteristics of the adult heart. However, emerging evidence supports a more dynamic view of the myocardium in which cell death and cell restoration are vital components of the remodeling process that governs organ homeostasis, aging and disease. The identification of dividing myocytes throughout the life span of the organisms and the recognition that undifferentiated primitive cells regulate myocyte turnover and tissue regeneration indicate that the heart is a self-renewing organ controlled by a compartment of resident stem cells. Moreover, exogenous progenitors of bone marrow origin transdifferentiate and acquire the cardiomyocyte and vascular lineages. This new reality constitutes the foundation of the numerous cell-based clinical trials that have been conducted in the last decade for the treatment of ischemic and non-ischemic cardiomyopathies.     

Is it true that ozone is always toxic? The end of a dogma

There are a number of good experimental studies showing that exposure by inhalation to prolonged tropospheric ozone damages the respiratory system and extrapulmonary organs. The skin, if extensively exposed, may also contribute to the damage. The undoubtful strong reactivity of ozone has contributed to establish the dogma that ozone is always toxic and its medical application must be proscribed. Although it is less known, judiciously practiced ozonetherapy is becoming very useful either on its own or applied in combination with orthodox medicine in a broad range of pathologies. The opponents of ozonetherapy base their judgment on the ozone chemistry, and physicians, without any knowledge of the problem, are often skeptical. During the last 15 years, a clear understanding of the action of ozone in biology and medicine has been gained, allowing today to argue if it is true that ozone is always toxic. The fundamental points that are discussed in this paper are: the topography, anatomical and biochemical characteristics of the organs daily exposed to ozone versus the potent antioxidant capacity of blood exposed to a small and precisely calculated dose of ozone only for a few minutes. It is becoming clear how the respiratory system undergoing a chronic oxidative stress can release slowly, but steadily, a huge amount of toxic compounds able to enter the circulation and cause serious damage. The aim of this paper is to objectively evaluate this controversial issue.