1,720,969 research outputs found
Hypoxia response in glioblastoma cells: effect of trehalose on macropinocytosis, autophagy and cell survival
Full text linkIn glioblastoma multiforme, the most malignant brain tumor in adults, the hypoxic milieu is believed to contribute to tumor aggressiveness and resistance to therapy. Here, human glioblastoma U373-MG and T98G cells were exposed to hypoxia (1 % oxygen) or normoxia (18 % oxygen), and treated with trehalose, a natural disaccharide increasingly studied for its therapeutic potential in cancer. In all samples under hypoxia, HIF-1 alpha stabilization was accompanied by a decrease in Nrf2 and p62/SQSTM1 proteins; redox imbalance also occurred, as documented by increased levels of ROS and parallel lowering of glutathione. Trehalose treatment increased Nrf2 and p62 proteins under normoxia, an effect lost or downsized under hypoxia. Differently, under both oxygen concentrations, trehalose increased glutathione content, consistently with its antioxidant role. In U373-MG cells, trehalose induced remarkable macropinocytosis under hypoxia, albeit less than under normoxia; on the contrary, in autophagy-proficient T98G cells, trehalose further increased the autophagic process under hypoxia compared to normoxia. As regards long-term cell fate (evaluated as colony-forming capacity), hypoxia only proved to be a favorable condition for T98G cells. However, in both cell lines, trehalose treatment significantly and dose-dependently decreased clonogenic capacity under normoxia and hypoxia; in particular, the long-lasting stimulation of macropinocytosis in U373-MG cells induced extensive cell death by methuosis. Overall, our findings suggest that trehalose-induced macropinocytosis or autophagy could also play a tumour-suppressive role in the hypoxic tumor milieu that characterizes glioblastoma, making its synergy with conventional chemotherapy and radiotherapy worth exploring
Lipid peroxidation and antioxidant systems in the liver injury produced by glutathione depleting agents
No full textThe mechanisms of the liver damage produced by three glutathione (GSH) depleting agents, bromobenzene, allyl alcohol and diethylmaleate, was investigated. The change in the antioxidant systems represented by α-tocopherol (vitamin E) and ascorbic acid were studied under conditions of severe GSH depletion. With each toxin liver necrosis was accompanied by lipid peroxidation that developed only after severe depletion of GSH. The hepatic level of vitamin E was decreased whenever extensive lipid peroxidation developed. In the case of bromobenzene intoxication, vitamin E decreased before the onset of lipid peroxidation. Changes in levels of the ascorbic and dehydroascorbic acid indicated a redox cycling of vitamin C with the oxidative stress induced by all the three agents. Such a change of the redox state of vitamin C (increase of the oxidized over the reduced form) may be an index of oxidative stress preceding lipid peroxidation in the case of bromobenzene. In the other cases, such a change is likely to be a consequence of lipid peroxidation. Experiments carried out with vitamin E deficient or supplemented diets indicated that the pathological phenomena occurring as a consequence of GSH depletion depend on hepatic levels of vitamin E. In vitamin E deficient animals, lipid peroxidation and liver necrosis appeared earlier than in animals fed the control diet. Animals fed a vitamin E supplemented diet had an hepatic vitamin E level double that obtained with a commercial pellet diet. In such animals, bromobenzene and allyl alcohol had only limited toxicity and diethylmaleate none in spite of comparable hepatic GSH depletion. Thus, vitamin E may largely modulate the expression of the toxicity by GSH depleting agents. © 1990
The autophagy inducer trehalose stimulates macropinocytosis in NF1-deficient glioblastoma cells
Full text linkBACKGROUND: Glioblastoma is a highly aggressive brain tumor. A big effort is required to find novel molecules which can cross the blood–brain barrier and efficiently kill these tumor cells. In this perspective, trehalose (α-glucopyranosyl‐[1→1]‐α‐d‐glucopyranoside), found in various dietary sources and used as a safe nutrient supplement, attracted our attention for its pleiotropic effects against tumor cells. METHODS: Human glioblastoma cell lines U373-MG and T98G were exposed to trehalose and analyzed at different time points. Cell proliferation was evaluated at medium term, and clonogenic capacity and cell morphology were evaluated at long term. Western blot was used to evaluate biochemical markers of autophagy (also measured in cells co-treated with EIPA or chloroquine), and mTOR, AMPK and ERK 1/2 signalling. Macropinocytosis was evaluated morphologically by bright-field microscopy; in cells loaded with the fluorescein-conjugated fluid-phase tracer dextran, macropinocytic vacuoles were also visualized by fluorescence microscopy, and the extent of macropinocytosis was quantified by flow cytometry. RESULTS: The long-term effect of trehalose on U373-MG and T98G cell lines was impressive, as indicated by a dramatic reduction in clonogenic efficiency. Mechanistically, trehalose proved to be an efficient autophagy inducer in macropinocytosis-deficient T98G cells and an efficient inducer of macropinocytosis and eventual cell death by methuosis in U373-MG glioblastoma cells, proved to be poorly responsive to induction of autophagy. These two processes appeared to act in a mutually exclusive manner; indeed, co-treatment of U373-MG cells with the macropinocytosis inhibitor, EIPA, significantly increased the autophagic response. mTOR activation and AMPK inhibition occurred in a similar way in the two trehalose-treated cell lines. Interestingly, ERK 1/2 was activated only in macropinocytosis-proficient U373-MG cells harbouring loss-of-function mutations in the negative RAS regulator, NF1, suggesting a key role of RAS signalling. CONCLUSIONS: Our results indicate that trehalose is worthy of further study as a candidate molecule for glioblastoma therapy, due to its capacity to induce a sustained autophagic response, ultimately leading to loss of clonogenic potential, and more interestingly, to force macropinocytosis, eventually leading to cell death by methuosis, particularly in tumor cells with RAS hyperactivity. As a further anticancer strategy, stimulation of macropinocytosis may be exploited to increase intracellular delivery of anticancer drugs
Cross-talk between calpain and caspase-3/-7 in cisplatin-induced apoptosis of melanoma cells: a major role of calpain inhibition in cell death protection and p53 status
No full textThe contribution of different proteolytic systems, in particular calpains and effector caspases, in apoptotic cell death is still controversial. In this paper, we show that during cisplatin-induced apoptosis of human metastatic melanoma cells, calpain activation, as measured in intact cells by two different fluorescent substrates, is an early event, taking place well before caspase-3/-7 activation, and progressively increasing during 48 h of treatment. Such activation appears to be independent from any intracellular calcium imbalance; in fact, an increase of cytosolic calcium along with emptying of the reticular stores occur only at very late stages, uniquely in frankly apoptotic, detached cells. Calpain activation proves to be an early and crucial event in the apoptotic machinery, as demonstrated by the significant protection of cell death in samples co-treated with the calpain inhibitors, MDL 28170, calpeptin and PD 150606, where a variable but significant reduction of both caspase-3/-7 activity and cell detachment is observed. Consistently, such a protective effect can be at least partially due to the impairment of cisplatin-induced p53 activation, occurring early in committed, preapoptotic cells. Furthermore, in late apoptotic cells, calpain activity is also responsible for the formation of a novel p53 proteolytic fragment (approximate to 26 kDa), whose function is so far to be elucidated
Autophagy is upregulated in ovarian endometriosis: A possible interplay with p53 and heme oxygenase-1
No full textOBJECTIVE:
To evaluate the occurrence of the autophagic process in ovarian endometriomas compared with eutopic endometrium of affected women and with normal endometrium of healthy women.
DESIGN:
Biochemical and molecular study in tissue extracts.
SETTING:
University cellular pathology laboratory and university hospital.
PATIENT(S):
Patients with ovarian endometriosis (n = 13) and healthy women (n = 18).
INTERVENTION(S):
Specimens of endometrium were obtained by hysteroscopy from patients with endometriosis and from healthy control subjects; specimens of ovarian endometriomas were collected by laparoscopy. All patients underwent surgery after the end of menstrual bleeding, resulting in most of our patients (approximately 80% in each group) being in the proliferative phase.
MAIN OUTCOME MEASURE(S):
Autophagy was evaluated by Western blot analysis of biochemical markers (LC3-II, LC3-II/LC3-I ratio and p62) and by quantitative real-time polymerase chain reaction of autophagy-related genes (ATG14, BECN1, ATG7, and LC3B); apoptosis-related (p53 and Bcl-2) and oxidative stress-related (heme oxygenase-1) proteins were also evaluated by Western blot analysis.
RESULT(S):
All tested biochemical markers and messenger RNA levels of autophagy-related genes showed a significant up-regulation of autophagy in ovarian endometriomas compared with eutopic endometria of affected or healthy women. Moreover, a significant decrease of p53 protein and a significant increase of heme oxygenase-1 protein was also evident in endometriomas.
CONCLUSION(S):
The upregulated autophagic process observed in ovarian endometriomas can be regarded as an integral part of endometriosis pathogenesis, possibly contributing to survival of endometriotic cells in ectopic sites and to lesion maintenance. The decreased susceptibility to apoptosis and the persistent oxidative stress experienced by endometriotic cells could favor autophagy stimulation
Long-Term Doxorubicin Release From Multiple Stimuli-Responsive Hydrogels Based on -Amino-Acid Residues
No full textWe have developed a series of pH- and temperature- stimuli-sensitive vinyl hydrogels, bearing -amino acid residues (L-phenylalanine, L-valine) and incorporating magnetic nanoparticles of different chemical compositions (CoFe2O4 and Fe3O4). The goal was to study the potential applications of these nanocomposites in the controlled release of doxorubicin (DOXO), a potent anticancer drug. The strength of the electrostatic interaction between the protonated nitrogen of the DOXO molecule and the ionized carboxylic groups of the hydrogel allowed effective control of the drug release rate in saline solutions. The embedded magnetic nanoparticles were an additional remote control of the drug release under the stimulus of an appropriate external alternating magnetic field (AMF). Data showed that the controlled release of DOXO proceeded for months and followed a diffusion-controlled release mechanism, while maintaining the amount of released drug within acceptable therapeutic windows. The amount of the released DOXO was found in all cases substantially higher than the “control” because the application of the AMF augments in stimulating the nanoparticles within the DOXO-loaded hydrogel. In vitro experiments have shown that the released DOXO is able to induce cell death to cervix adenocarcinoma cells (HeLa cells)
Early mitochondrial disfunction in bromobenzene treated mice: A possible factor of liver injury
No full textThe membrane potential of liver mitochondria isolated from bromobenzene treated mice was studied. Specifically, the efficiency of the energy-transducing mitochondrial membrane was measured during the phase between the occurrence of a massive loss of hepatic GSH, after 2-3 hr of bromobenzene intoxication, and the appearance of lipid peroxidation and cell death (12-15 hr after treatment). Partial uncoupling of oxidative phosphorylation was observed in mitochondria during the early period of intoxication (3-9 hr). These anomalies in oxidative metabolism did not result in irreversible damage to the mitochondrial inner membrane. The possibility that phenolic metabolites of bromobenzene are responsible for the uncoupling effects was examined. Orto- and especially para-bromphenol reproduced the alterations of mitochondrial function when added to normal mitochondira at concentrations comparable to those found in the livers of the intoxicated animals. Since the concentration of the bromophenols (especially p-bromophenol) largely increases after the intoxidation times as tested here, mitochondrial uncoupling may represent a mechanism of liver damage acting synergistically with or even independently of other factors such as oxidative stress and lipid peroxidation. © 1990
Cisplatin/Hydrogel Complex in Cancer Therapy
No full textHydrogels containing R-amino acid residues (L-phenylalanine, L-histidine) were used to complex the chemotherapeutic
agent cisplatin. The release of the drug in phosphate buffer solution showed an initial burst effect,
followed by a near zero-order release phase over the seven days of reported period. Unlike the nonreleasing
pattern of the hydrogel poly(N-acryloyl-L-phenylalanine-co-N-isopropylacrylamide) (CP2), the homopolymer
poly(N-acryloyl-L-phenylalanine) (P9) hydrogel showed a released amount of cisplatin loaded from a water/
DMSO mixture that was three times greater than that loaded from simple water. The hydrogel P9 formed with
cisplatinum(II) complex species of well-defined stoichiometry; the drug species was released by a chemically
controlled process. The Pt(II)/L (L is the monomeric unit of the polymer) stoichiometric molar ratio of 0.5,
corresponding to two close carboxylate groups per Pt(II), was found by the viscometric data on the soluble polymer
analogue. The platinum species released from cisplatin-loaded (from water) hydrogel retained its cytotoxic activity
toward Me665/2/21 human melanoma cell line, in the same manner shown by the native cisplatin. On the contrary,
the platinum species released from cisplatin-loaded (from water/DMSO) hydrogel was devoid of any cytotoxic
effect
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
