Biomedical subjects

A Liepins

Publications and source records attributed to A Liepins.

At least 19 recordsLinked to original sources

PubMed2001

Bax, Bcl-2, and NF-kappaB expression in sanguinarine induced bimodal cell death.

The apoptosis related proteins Bax, Bcl-2, and NF-kappaB were analyzed in sanguinarine induced apoptosis and blister cell death (BCD) of K562 erythroleukemia cells and in sanguinarine treated high Bcl-2 expressing JM1 pre-B lymphoblastic cells, utilizing immunofluorescence-flow cytometry. Sanguinarine induced apoptosis of K562 cells was found to have increased Bax expression and decreased NF-kappaB, whereas BCD showed a decrease in Bax expression and an increase in NF-kappaB. In contrast, high Bcl-2 expressing JM1 cells, when exposed to the same concentrations (and duration) of sanguinarine that induced PCD and BCD in K562 cells, failed to show the respective morphologies while showing a concomitant increase in Bcl-2. Results from studies with K562 cells suggest that Bax is pro-apoptotic and also that NF-kappaB activation may be associated with BCD. Results from studies with JM1 cells suggest that Bcl-2 is anti-apoptotic and anti-BCD. Results from JM1 cells strengthen the assumption in the literature of the central role Bcl-2 plays in chemoresistance by assuming an anti-PCD role. These results also suggest that, in JM1 cells, Bcl-2 may further complicate chemoresistance by being anti-BCD in nature, in addition to its anti-PCD role.

Alkaloids↗

PubMed2001

Role of Bcl-2 family proteins and caspase-3 in sanguinarine-induced bimodal cell death.

Sanguinarine, a benzophenanthridine alkaloid, has anticancer potential through induction of cell death. We previously demonstrated that sanguinarine treatment at a low level induced apoptosis or programmed cell death (PCD) in the Bcl-2 low-expressing K562 human erythroleukemia cells, and that a high level induced blister cell death (BCD); whereas Bcl-2 overexpressing, sanguinarine-treated JM1 pre-B lymphoblastic cells displayed neither apoptosis nor BCD morphologies. Here, we report that sanguinarine-treated K562 cells, when analyzed by western blot, showed significant increase in expression of the pro-apoptotic Bax protein in apoptosis, but not in BCD. cDNA expression array of PCD in K562 cells failed to reveal the presence of Bax at the gene transcript level, which suggests that this cell death process does not require de novo protein synthesis. Treated JM1 cells, on the other hand, showed an increase in the expression of Bcl-2 protein in both forms of cell death, but failed to show Bax expression. The role of other members of the Bcl-2 family remained negligible. Caspase-3 activation was observed in apoptosis of K562 cells but not in BCD or in sanguinarine-treated JM1 cells. These results suggest that sanguinarine in K562 cells induces apoptosis through increasing Bax and activating caspase-3, whereas sanguinarine-induced BCD involves neither. These results also suggest that in JM1 cells, Bcl-2 may play a role in susceptibility of cells to induction of apoptosis and BCD.

Alkaloids↗

PubMed2001

Sanguinarine induces bimodal cell death in K562 but not in high Bcl-2-expressing JM1 cells.

Our previous studies with low Bcl-2-expressing K562 cells have shown that, when treated with the putative anti-cancer drug sanguinarine, concentrations of 1.5 microg/ml induced the morphology of apoptosis or programmed cell death (PCD), while concentrations of 12.5 microg/ml induced a morphology of blister formation or blister cell death (BCD). To elucidate the possible role of Bcl-2 in this dual cell death modality induced by sanguinarine, K562 and the high Bcl-2-expressing JM1 cells were treated with sanguinarine concentrations of 1.5 microg/ml and 12.5 microg/ml respectively, and multiple parameters of their effects were studied using light and electron microscopy, terminal deoxynucleotidyl transferase (TdT) end-labeling, 51Cr release, trypan blue exclusion, propidium iodide exclusion, and annexin-V binding. In general, we found that, while K562 cells underwent PCD and BCD when treated with sanguinarine, JM1 cells failed to undergo either PCD or BCD under the same experimental conditions. Thus, the over-expression of anti-apoptotic Bcl-2 may have prevented sanguinarine from inducing PCD and BCD in JM1 cells. These results indicate that the resistance of JM1 cells to the alkaloid sanguinarine may have been due to an anti-BCD role played by Bcl-2, in addition to its widely reported anti-apoptotic role.

Alkaloids↗

PubMed1996

Induction of bimodal programmed cell death in malignant cells by the derivative Ukrain (NSC-631570).

Selective induction of malignant cell death is one of the major goals of effective and safe chemotherapy. Recent developments in the understanding of programmed cell death (PCD) or apoptosis are expected to provide new leads for a safer chemotherapy. The authors investigated whether the semisynthetic alkaloid thiophosphoric acid derivative Ukrain (NSC-631570) could induce PCD or apoptosis in human K562 leukaemia cells. Results showed that Ukrain induced two distinct modalities of cell death programmes. One modality corresponded morphologically to classical apoptosis or PCD characterized by blebbing and shedding of membrane vesicles with concomitant 51Cr release; however, the Ukrain-induced apoptosis was not associated with the characteristic nuclear DNA fragmentation. Higher concentrations of Ukrain induced a second cell death programme characterized by cell surface blister formation, high specific 51Cr release and extensive DNA polyploidy. These two cell death programmes are distinct from each other in that they are interphased by a silent period characterized by normal cell morphology and reduced specific 51Cr release.

Alkaloids↗

PubMed1996

Influence of Ukrain on DNA, RNA and protein synthesis in malignant cells.

3H labelled thymidine, uridine and leucine were used to evaluate the synthesis of DNA, RNA and proteins in malignant cells and normal cells incubated with Ukrain in different concentrations. Compared with the controls, the inhibiting effects of Ukrain are demonstrated in guinea pig hepatocytes, CIL hepatocytes, human tonsil cells, two murine lymphomas, murine myeloma, Yoshida cells, two HeLa strains, EsB- and EB- (murine) lymphomas. YAC-1, P815 and human WiDr cells. Ukrain inhibits the DNA, RNA and protein synthesis in malignant cell lines at relatively high concentrations and to a small extent in normal cells.

Alkaloids↗

PubMed1996

Influence of Ukrain on human xenografts in vitro.

Tumour cells were taken from human tumour xenografts (HTX) and serially transplanted into nude mice. These cells were used in a colony-forming assay in vitro. Tumour cells were incubated continuously for at least one week with several concentrations of the drug Ukrain. This was done with six different types and the colony formation was scored for each tumour. The drug effects were reported as percent T/C (Test/Control) for the numbers of colonies formed. Activity is considered to be present at T/C < 30%. A clear dose-response effect was found for Ukrain.

Alkaloids↗

PubMed1996

Mitogenic properties of Ukrain (NSC-6315170) on human peripheral blood monocytes: clinical implications.

Using a cell-proliferation assay, the authors examined and compared the mitogenic effects of Ukrain and phytohaemagglutinin (PHA) on human peripheral blood mononuclear cells (PBMCs), as well as their synergic effects. It was found that even a short period of pretreatment of the cell with Ukrain had a potent synergic effect on PHA mitogenesis resulting in significantly higher cell stimulation indices than those of PHA alone. Moreover, it was found that a short period of PHA treatment of the cells is almost imperative for Ukrain to exert its mitogenic effects. The mitogenic effect of Ukrain on human PBMCs is consistent with a previous clinical report which found that circulating lymphocytes were significantly increased in cancer patients treated with Ukrain. Thus the in vitro assay used in these studies may serve as a prognostic assay for potential patient responsiveness to Ukrain treatment, as well as a clinical parameter during Ukrain therapy.

Alkaloids↗

PubMed1996

Modulation of immune effector cell cytolytic activity and tumour growth inhibition in vivo by Ukrain (NSC 631570).

Ukrain is a semisynthetic compound consisting of alkaloids from Chelidonium majus L. conjugated to thiophosphoric acid, with immunomodulatory and therapeutic properties in cancer patients. The present in vitro studies demonstrate that Ukrain is an effective biological response modifier augmenting, by up to 48-fold, the lytic activity of splenic lymphocytes obtained from alloimmunized mice. The lytic activities of interleukin-2 (IL-2) treated spleen cells and peritoneal exudate lymphocytes were also significantly increased by the addition of Ukrain to the cell mediated lysis (CML) assay medium. The highest Ukrain-induced enhancement of splenic lymphocytolytic activity in vitro was found to occur at day 18 after alloimmunization was dose-dependent and specific for the immunizing P815 tumour cells. Since Ukrain was present only during the CML assays, its mode of action is thought to be via direct activation of the effector cells' lytic mechanism(s). The effect of Ukrain on the growth of Balb/c syngenic mammary adenocarcinoma was also evaluated. Intravenous, but not subcutaneous or intraperitoneal, administration of this drug was found to be effective in delaying tumour growth in an actual therapeutic protocol initiated five days after tumour implantation. No deleterious side-effects were observed using these in vivo treatment modalities. The role of macrophages in the observed retardation of tumour development was investigated, using peritoneal exudate macrophages (PEM) in cytotoxicity assays. Previous studies showed that PEM of mammary tumour-bearing mice lose their capacity to kill a variety of tumour target cells including the in vitro cultured homologous tumour cells (DA-3). Pretreatment of PEM from normal mice with 2.5 microM Ukrain for 24 h, followed by stimulation with either IFN-gamma or with lipopolysaccharide (LPS) plus IFN-gamma enhanced their cytotoxic activity. Treatment of PEM from tumour-bearing mice with 2.5 microM Ukrain and LPS results in a reversal of their defective cytotoxic response against DA-3 target cells. Furthermore, Ukrain alone, in the absence of a secondary signal, induced the activation of tumouricidal function of PEM from tumour-bearing, but not from normal, mice. These data indicate that Ukrain's in vivo effects against the development of mammary tumours may be due, at least in part, to its ability to restore macrophage cytolytic function.

Adjuvants, Immunologic↗

PubMed1996

Influence of Ukrain on immunological blood parameters in vitro and in vivo.

Immunological changes are often seen in subjects suffering from oncological disease. Decreased NK activity, alterations of the T4/T8 quotient, decreased phagocytic activity, low reactivity and decreased recognition of the "foreign" are common features seen in these patients. Cytostatic therapy (chemotherapy and radiation therapy) very often enhance these negative properties, thus limiting therapeutic possibilities by highly toxic sequels. Ukrain, being cytostatic and immune-stimulating and modulating, has no adverse effects on the organism.

Alkaloids↗

PubMed1996

Potential therapeutic efficacy of Ukrain (NSC 631570) in AIDS patients with Kaposi's sarcoma.

In this study two case reports are presented of therapy with Ukrain, a semi-synthetic thiophosphoric acid compound of alkaloids isolated from Chelidonium majus L, for the treatment of AIDS patients with Kaposi's sarcoma. Ukrain was injected i.v. in the dose of 5 mg every other day for a total of 10 injections. During treatment the Kaposi's sarcoma lesions diminished in size, showed decolouration and no lesion appeared in the 30-day interval after the beginning of treatment. Both patients tolerated Ukrain well and showed an improved immunohaematological status: an increase in total leukocytes, T-lymphocytes and T-suppressor numbers. In one case T-helper lymphocytes were also increased. Future investigations are necessary for the evaluation of Ukrain efficacy in the treatment of this type of patients.

Acquired Immunodeficiency Syndrome↗

PubMed1995

The ion channel behavior of the nuclear pore complex.

Macromolecule-conducting pores have been recently recognized as a distinct class of ion channels. The poor role of macromolecules as electrical charge carriers can be used to detect their movement along electrolyte-filled pores. Because of their negligible contribution to electrical ion currents, translocating macromolecules reduce the net conductivity of the medium inside the pore, thus decreasing the measured pore ion conductance. In the extreme case, a large translocating macromolecule can interrupt ion flow along the pore lumen, reflected as a negligible pore conductance. Therefore, ion conductance serves as a measurement of macromolecular transport, with lesser values indicating greater macromolecular translocation (in size and/or number). Such is the principle of operation of the widely used Coulter counter, an instrument for counting and sizing particles. It has long been known that macromolecules translocate across the central channel of nuclear pore complexes (NPCs). Recently, large conductance ion channel activity (100-1000 pS) was recorded from the nuclear envelope (NE) of various preparations and it was suggested that NPCs may be the source of this activity. Despite its significance to understanding the regulation of transcription, replication, mRNA export, and thus gene expression of normal and pathological states, no report has appeared demonstrating that this channel activity corresponds to ion flow along the central channel of the NPC. Here we present such a demonstration in adult mouse cardiac myocyte nuclei. In agreement with concepts introduced for macromolecule-conducting channels, our patch clamp experiments showed that ion conductance is reduced, and thus that ion flow is restricted during translocation of macromolecules containing nuclear targeting signals. Ion flow was blocked by mAb414, a monoclonal antibody raised against a major NPC glycoprotein and known to localize on the NPC channel where it blocks macromolecular transport. These results also establish patch clamp as a useful technique for the measurement of macromolecular translocation along the large central channel of the NPC and provide a basis for the design of future investigations of nuclear signaling for control of gene activity, mRNA export for gene expression, as well as other processes subservient to NPC-mediated nucleocytoplasmic exchange.

Animals↗

PubMed1995

Patch clamp detection of transcription factor translocation along the nuclear pore complex channel.

Transcription factors (TFs) are cytoplasmic proteins that play an essential role in gene expression. These proteins form multimers and this phenomenon is thought to be one of the mechanisms that regulate transcription. TF molecules reach their DNA binding sites through the large central channel of the nuclear pore complex (NPC). However, the NPC channel is known to restrict the translocation of molecules > or = 20-70 kD. Therefore, during their translocation, TF molecules and/or their multimers may plug the NPC channel and thus, interrupt ion flow through the channel, with a concomitant reduction in the ion conductance of the channel (gamma). Here we show with patch clamp that gamma is reduced during translocation of three major TFs: c-Jun (40 kD), NF-kappa B (approximately equal to 50 kD), and SP1 (approximately equal to 100 kD). Within a minute, femtomolar concentrations of these proteins reduced gamma suggesting a purely mechanical interaction between single TF molecules and the inner wall of the NPC channel. NPCs remained plugged for 0.5-3 hr in the absence of ATP but when ATP was added, channel plugging was shortened to < 5 min. After unplugging, channel closures were rarely observed and the number of functional channels increased. The transcription factors also stabilized the NPCs as shown by the extended duration of the preparations which allowed recordings for up to 72 hr. These observations are the first direct demonstration of the important role of NPCs in mediating nuclear translocation of TFs and, therefore, in forming part of the mechanisms regulating gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1995

Patch clamp and atomic force microscopy demonstrate TATA-binding protein (TBP) interactions with the nuclear pore complex.

The universal TATA-binding protein, TBP, is an essential component of the multiprotein complex known as transcription factor IID (TFIID). This complex, which consists of TBP and TBP-associated factors (TAFs), is essential for RNA polymerase II-mediated transcription. The molecular size of human TBP (37.7 kD) is close to the passive diffusion limit along the transport channel of the nuclear pore complex (NPC). Therefore, the possibility exists that NPCs restrict TBP translocation to the nuclear interior. Here we show for the first time, with patch-clamp and atomic force microscopy (AFM), that NPCs regulate TBP movement into the nucleus and that TBP (10(-15)-10(-10)M) is capable of modifying NPC structure and function. The translocation of TBP was ATP-dependent and could be detected as a transient plugging of the NPC channels, with a concomitant transient reduction in single NPC channel conductance, gamma, to a negligible value. NPC unplugging was accompanied by permanent channel opening at concentrations greater than 250 pM. AFM images demonstrated that the TBP molecules attached to and accumulated on the NPC cytosolic side. NPC channel activity could be recorded for more than 48 hr. These observations suggest that three novel functions of TBP are: to stabilize NPC, to force the NPC channels into an open state, and to increase the number of functional channels. Since TBP is a major component of transcription, our observations are relevant to the understanding of the gene expression mechanisms underlying normal and pathological cell structure and function.

Animals↗

PubMed1994

Cell injury and apoptosis.

Various forms of cellular injury, whether induced by immune effector cells, aberrant metabolic processes, chemotherapeutic drugs or temperature shifts, result in common morphological changes consisting of the formation and shedding of membrane vesicles from the injured cell surfaces, i.e., apoptosis. This dynamic cell surface membrane behavior appears to be dependent on the disruption of cytoplasmic microtubules. Concomitant with the altered cell surface morphology, certain physiological and biochemical events have been found to be associated with cell injury. These include changes in membrane permeability, elevated oxygen consumption rates and nuclear DNA fragmentation. However, it remains to be experimentally established which of these biological changes defines a state of irreparable cell injury and/or programmed cell death (PCD). Selective cell injury and death is the goal of many therapeutic modalities aimed at the destruction of malignant cells. On the other hand, prevention of cell injury is desirable in autoimmune diseases such as systemic lupus erythematosus, thyroiditis, insulin dependent diabetes and many others. Injury to the vascular endothelium may play a role not only in thrombosis, atherosclerosis and hypertension, but may also provide the avenues for the metastasis of malignant cells. The objective of the present review is to compare and evaluate the cell injury process induced by effector lymphocytes with that caused by low temperature. The latter mimics most, if not all, the currently known criteria of immune effector cell mediated PCD of target tumor cells.

Apoptosis↗

PubMed1992

Activation of spleen cell lytic activity by the alkaloid thiophosphoric acid derivative: Ukrain.

Alkaloids↗

PubMed1992

The effect of chronic and acute administration of deuterium oxide (D2O) on vascular smooth muscle contraction in spontaneously hypertensive and Wistar-Kyoto rats.

1. Oral administration of 25% D2O for 12 days reduced blood pressure of spontaneously hypertensive rats (SHR) to the level of Wistar-Kyoto (WKY) controls. 2. However, the chronic D2O treatment appeared to have little effect on the phenylephrine and potassium chloride induced dose-response curves of SHR and WKY rats, producing a decreased maximal contraction of the potassium chloride dose-response curve of SHR only. 3. Further acute studies revealed that desensitization results from chronic exposure to D2O such that 60% D2O produces a significant depression of contraction only in aortic rings obtained from SHR and WKY which had not been chronically treated with 25% D2O.

Animals↗

PubMed1992

Selective inhibition of in vitro cell growth by the anti-tumour drug Ukrain.

The inhibitory effect of Ukrain on malignant cells and on normal cells, in vitro, has been compared. To obtain a 50% inhibition of cell growth, a tenfold concentration had to be used with normal endothelial cells compared to a human osteosarcoma cell line. Hybrids of the two cell types showed nearly the same sensitivity as normal cells. A laser scanning microscope showed a high uptake of Ukrain in malignant cells, while the content in normal cells under the same experimental conditions was substantially lower.

Alkaloids↗

PubMed1992

Enhancement of macrophage tumouricidal activity by the alkaloid derivative Ukrain. In vitro and in vivo studies.

Ukrain is a semisynthetic drug with immunomodulatory properties, derived from Chelidonium majus L. alkaloids and thiophosphoric acid. The effect of this compound on the growth of Balb/c syngenic mammary adenocarcinoma was assessed. Intravenous, but not subcutaneous or intraperitoneal, administration of this drug was found to be effective in delaying tumour growth in an actual therapeutic protocol initiated five days after tumour implantation. No untoward side-effects were observed using these in vivo treatment modalities. The role of macrophages in the observed retardation of tumour development was investigated using peritoneal exudate macrophages (PEM) in cytotoxicity assays. In previous studies, the authors have found that PEM of mammary tumour bearing mice lose their capacity to kill a variety of tumour target cells including the in vitro cultured homologous tumour cells (DA-3). Pretreatment of PEM from normal mice with 2.5 microM Ukrain for 24 h followed by stimulation with either IFN-gamma or with LPS+IFN-gamma enhanced their cytotoxic activity. Treatment of PEM from tumour bearing mice with 2.5 microM Ukrain and LPS results in a reversal of their defective cytotoxic response against the DA-3 target cells. Furthermore, Ukrain alone, in the absence of a secondary signal, induced the activation of tumouricidal function of PEM from tumour bearing but not from normal mice. These data indicate that Ukrain's in vivo effects against the development of mammary tumours may be due, at least in part, to its ability to restore macrophage cytolytic function.

Adenocarcinoma↗