Effect of quaternary benzo[c]phenanthridine alkaloids sanguilutine and chelilutine on normal and cancer cells.

Sanguilutine and chelilutine, quaternary benzo[c]phenanthridine alkaloids, were studied for their antiproliferative activities with regard to their ability to induce oxidative stress. We observed potent antiproliferative activities for both alkaloids against three tumour (HeLa; HL-60; A-2780) and two normal (V-79; LEP) cell lines. Both alkaloids were efficient inductors of apoptosis. Statistical analysis revealed higher toxicity for sanguilutine compared to chelilutine and unequal sensitivity with regard to individual cell lines, although independent of the character of the cell line (i.e. tumour vs. normal). Dihydrofluorescein diacetate staining was used to measure intracellular ROS accumulation after treatment with sanguilutine, chelilutine, sanguinarine, and chelerythrine. In addition, anti-oxidative effects were studied. The effects of the alkaloids were compared with the effects of commonly used anti-oxidants, such as trolox, caffeine acid, and chlorogenic acid. None of the tested alkaloids (0.1 and 1 microg/ml) increased ROS production. Pre-incubation of sanguinarine and chelilutine (at all tested concentrations) and sanguilutine and chelerythrine (1 microg/ml) decreased oxidative stress caused by H(2)O(2). These findings indicate high antiproliferative and pro-apoptotic effects of sanguilutine and chelilutine that are not accompanied by oxidative stress induction, to the contrary, both alkaloids showed anti-oxidative effects.

Dibenzocyclooctadiene lignans overcome drug resistance in lung cancer cells--study of structure-activity relationship.

A panel of nine dibenzo[a,c]cyclooctadiene lignans, schizandrin, gomisin A, gomisin N, gomisin J, angeloylgomisin H, tigloylgomisin P, deoxyschizandrin, gamma-schizandrin and wuweizisu C was examined for their effect on multidrug resistance, as well as their anti-proliferative activities. COR-L23/R, a multidrug resistant sub-line, which has been reported to over-express multidrug resistance-associated protein (MRP1), was used for the experiments together with its parent cell line COR-L23 (human lung cell carcinoma). We found that lignans deoxyschizandrin and gamma-schizandrin at relatively non-toxic concentrations restored the cytotoxic action of doxorubicin to COR-L23/R cells. Deoxyschizandrin and gamma-schizandrin also significantly enhanced the accumulation of doxorubicin in drug resistant cells. Both lignans alone had no effect on the cell cycle; however, when combined with sub-toxic doses of doxorubicin, they induced cell cycle arrest in the G2/M phase, which is typical for toxic doses of doxorubicin. Our results suggest that deoxyschizandrin and gamma-schizandrin potentiate the cytotoxic effect of doxorubicin in doxorubicin resistant lung cancer cells COR-L23/R by increasing the accumulation of doxorubicin inside the cells. The common structural feature of both active lignans is the R-biaryl configuration and the absence of a hydroxy group at C-8. Unlike the reversal effect, the cytotoxicity of lignans with the R-biaryl configuration was similar to that observed for lignans with the S-biaryl configuration.

Differences in osmotolerant and cell-wall properties of two Zygosaccharomyces rouxii strains.

The osmotolerant and cell wall properties of the two most studied wild-type Zygosaccharomyces rouxii strains (CBS 732 and ATCC 42981) were examined. Differences in their (1) tolerance to high salt content in the medium, (2) resistance to the lysing enzymes Lyticase and Zymolyase, (3) cell-wall polymer content and (4) cell wall micromorphology suggested that the less osmotolerant CBS 732 strain possesses a more rigid cell wall than the more osmotolerant ATCC 42981, whose cell wall seems to be more flexible and elastic.

Interaction of benzo[c]phenanthridine and protoberberine alkaloids with animal and yeast cells.

We compared the effects of four quaternary benzo[c]phenanthridine alkaloids--chelerythrine, chelilutine, sanguinarine, and sanguilutine--and two quaternary protoberberine alkaloids-berberine and coptisine--on the human cell line HeLa (cervix carcinoma cells) and the yeasts Saccharomyces cerevisiae and Schizosaccharomyces japonicus var. versatilis. The ability of alkaloids to display primary fluorescence, allowed us to record their dynamics and localization in cells. Cytotoxic, anti-microtubular, and anti-actin effects in living cells were studied. In the yeasts, neither microtubules nor cell growth was seriously affected even at the alkaloid concentration of 100 microg/ml. The HeLa cells, however, responded to the toxic effect of alkaloids at concentrations ranging from 1 to 50 microg/ml. IC50 values for individual alkaloids were: sanguinarine IC50 = 0.8 microg/ml, sanguilutine IC50 = 8.3 microg/ml, chelerythrine IC50 = 6.2 microg/ml, chelilutine IC50 = 5.2 microg/ml, coptisine IC50 = 2.6 microg/ml and berberine IC50 > 10.0 microg/ml. In living cells, sanguinarine produced a decrease in microtubule numbers, particularly at the cell periphery, at a concentration of 0.1 microg/ml. The other alkaloids showed a similar effect but at higher concentrations (5-50 microg/ml). The strongest effects of sanguinarine were explained as a consequence of its easy penetration through the cell membrane owing to nonpolar pseudobase formation and to a high degree of molecular planarity.

Cytoskeleton in regenerating protoplasts and restoration of cell polarity in the yeast Saccharomyces cerevisiae.

The actin cables and microtubules were disrupted during protoplasting in Saccharomyces cerevisiae cells. In the process of protoplast regeneration, the cytoplasmic microtubules were the first to be restored; the actin patches remained regularly distributed under the surface of the growing protoplast. After the cell wall had been regenerated in a gelatine medium, the actin patches aggregated into clusters, which marked the site of bud development. An incomplete cell wall was the apparent cause for uncoupling between karyokinesis and cytokinesis. The presence of several nuclei in the cell gave rise to several buds emerging simultaneously and was probably related to their random positions. In haploids, however, the axial type of budding was also obvious in the reverting protoplasts. These observations suggest that actin is a structure involved in the restoration of polar growth during protoplast regeneration, and that the cell wall plays an important role in this process: in its absence, actin fails to polarise.

Cell wall and cytoskeleton reorganization as the response to hyperosmotic shock in Saccharomyces cerevisiae.

Transfer of exponentially growing cells of the yeast Saccharomyces cerevisiae to hyperosmotic growth medium containing 0.7-1 M KCl, 1 M mannitol, and/or 1 M glycerol caused cessation of yeast growth for about 2 h; thereafter, growth resumed at almost the original rate. During this time, formation of fluorescent patches on the inner surface of cell walls stained with Primulin or Calcofluor white was observed. The fluorescent patches also formed in solutions of KCl or when synthesis of the cell wall was blocked with cycloheximide and/or 2-deoxyglucose. The patches gradually disappeared as the cells resumed growth, and the new buds had smooth cell walls. Electron microscopy of freeze-etched replicas of osmotically stressed cells revealed deep plasma membrane invaginations filled from the periplasmic side with an amorphous cell wall material that appeared to correspond to the fluorescent patches on the cell surface. The rate of incorporation of D-[U-14C]glucose from the growth medium into the individual cell wall polysaccharides during osmotic shock followed the growth kinetics. No differences in cell wall composition between osmotically stressed yeast and control cells were found. Hyperosmotic shock caused changes in cytoskeletal elements, as demonstrated by the disappearance of microtubules and actin microfilaments. After 2-3 h in hyperosmotic medium, both microtubules and microfilaments regenerated to their original polarized forms and the actin patches resumed their positions at the apices of growing buds. The response of S. cerevisiae strains with mutations in the osmosensing pathway genes hog1 and pbs2 to hyperosmotic shock was similar to that of the wild-type strain. We conclude that, besides causing a temporary disassembling of the cytoskeleton, hyperosmotic shock induces a change in the organization of the cell wall, apparently resulting from the displacement of periplasmic and cell wall matrix material into invaginations of the plasma membrane created by the plasmolysis.

Topology of microtubules and actin in the life cycle of Xanthophyllomyces dendrorhous (Phaffia rhodozyma).

The morphology of budding and conjugating cells and associated changes in microtubules and actin distribution were studied in the yeast Xanthophyllomyces dendrorhous (Phaffia rhodozyma) by phase-contrast and fluorescence microscopy. The non-budding interphase cell showed a nucleus situated in the central position and bundles of cytoplasmic microtubules either stretching parallel to the longitudinal cell axis or randomly distributed in the cell; none of these, however, had a character of astral microtubules. During mitosis, the nucleus divided in the daughter cell, cytoplasmic microtubules disappeared and were replaced by a spindle. The cytoplasmic microtubules reappeared after mitosis had finished. Actin patches were present both in the bud and the mother cell. Cells were induced to mate by transfer to ribitol-containing medium without nitrogen. Partner cells fused by conjugation projections where actin patches had been accumulated. Cell fusion resulted in a zygote that produced a basidium with parallel bundles of microtubules extended along its axis and with actin patches concentrated at the apex. The fused nucleus moved towards the tip of the basidium. During this movement, nuclear division was taking place; the nuclei were eventually distributed to basidiospores. Mitochondria appeared as vesicles of various sizes; their large amounts were found, often lying adjacent to microtubules, in the subcortical cytoplasm of both vegetative cells and zygotes.

Colocalization of microtubules and mitochondria in the yeast Schizosaccharomyces japonicus var. versatilis.

Both living and fixed cells of Schizosaccharomyces japonicus var. versatilis showed thread-like mitochondria when studied by phase-contrast and fluorescence microscopy. In the interphase cells, mitochondria extended from pole to pole and converged towards the growing tips. The mitochondrial threads did not disrupt but persisted during mitosis and, subsequently, their bundle was split between the two daughter cells by a concentrically growing septum. Mitochondria in the interphase cells were accompanied by cytoplasmic microtubules. These disappeared during mitosis and, instead, spindle microtubules were formed in the nucleus. The cytoplasmic microtubules reappeared after anaphase B, again in coaligment with mitochondria. Protoplasting as well as the action of microtubule inhibitors methyl-1-(butylcarbamoyl)-2-benzimidazolecarbamate (benomyl) and 2-methylbenzimidazole (MBC) resulted in rapid disintegration of microtubules and, suprisingly, also in disruption of mitochondria into small bodies. Removal of the inhibitors or a short regeneration of protoplasts allowed both the cytoplasmic microtubules and the thread-like mitochondria to reaggregate into the original pattern. Cytochalasin D treatment caused a complete disintegration of actin filaments, while the cytoplasmic microtubules and mitochondria remained intact. These findings of a transient close association of mitochondria and microtubules and their relative independence of the arrangement of actin filaments suggest that microtubules, but not actin cables, form supports for positioning or movement of mitochondria along the cylindrical cells. The persistence of mitochondria in the cell centre during mitosis may be accounted for by the fact that disrupted microtubules fail to provide support for mitochondrial movement towards the cell poles.