Biomedical subjects

Barbara Malewicz

Publications and source records attributed to Barbara Malewicz.

6 recordsLinked to original sources

PubMed2006

Enhancement of mammary carcinogenesis in two rodent models by silymarin dietary supplements.

Silymarin is a mixture of polyphenolic flavonoids isolated from milk thistle (Silybum marianum) with anticancer activities reported for several organ sites. The present study tested the efficacy of dietary silymarin against mammary carcinogenesis in two rodent models. In the Sprague-Dawley rat model, female rats were fed a purified diet supplemented with none, 0.03, 0.1, 0.3 or 1% (w/w) of silymarin from 21 days of age (DOA) and carcinogenesis was initiated by a single i.p. injection of 1-methyl-1-nitrosourea (MNU) at 51 DOA. Mammary tumor (MT) development was followed till 110 days after carcinogen injection. In the MMTV-neu/HER2 transgenic mouse mammary carcinogenesis model, homozygous transgenic females were fed a purified diet supplemented with none or 0.3% silymarin, either from 28 or 120 DOA and MT development was followed to approximately 300 DOA. The results showed that dietary silymarin increased the plasma concentration of free and total silibinin, a major component of silymarin, in a dose-dependent manner in the rat, but did not decrease either MT incidence or number. Instead silymarin modestly increased the number of MNU-induced MTs in rats. Similarly, silymarin increased MT incidence and multiplicity and non-MTs in the neu-transgenic mice. In cell culture, treatment of human MCF-7 breast cancer cells with serum-achievable concentrations of silymarin in the rodent models stimulated their growth, in part through an estrogen-like activity. Because silymarin is being used in the treatment of liver cirrhosis and a variety of other human ailments, and is sold as a dietary supplement, our findings add a cautionary note to its application in breast cancer prevention.

Animals↗

PubMed2006

Potent antiandrogen and androgen receptor activities of an Angelica gigas-containing herbal formulation: identification of decursin as a novel and active compound with implications for prevention and treatment of prostate cancer.

Androgen and androgen receptor (AR)-mediated signaling are crucial for the development of prostate cancer. Identification of novel and naturally occurring phytochemicals that target androgen and AR signaling from Oriental medicinal herbs holds exciting promises for the chemoprevention of this disease. In this article, we report the discovery of strong and long-lasting antiandrogen and AR activities of the ethanol extract of a herbal formula (termed KMKKT) containing Korean Angelica gigas Nakai (AGN) root and nine other Oriental herbs in the androgen-dependent LNCaP human prostate cancer cell model. The functional biomarkers evaluated included a suppression of the expression of prostate-specific antigen (PSA) mRNA and protein (IC50, approximately 7 microg/mL, 48-hour exposure) and an inhibition of androgen-induced cell proliferation through G1 arrest and of the ability of androgen to suppress neuroendocrine differentiation at exposure concentrations that did not cause apoptosis. Through activity-guided fractionation, we identified decursin from AGN as a novel antiandrogen and AR compound with an IC50 of approximately 0.4 microg/mL (1.3 micromol/L, 48-hour exposure) for suppressing PSA expression. Decursin also recapitulated the neuroendocrine differentiation induction and G1 arrest actions of the AGN and KMKKT extracts. Mechanistically, decursin in its neat form or as a component of AGN or KMKKT extracts inhibited androgen-stimulated AR translocation to the nucleus and down-regulated AR protein abundance without affecting the AR mRNA level. The novel antiandrogen and AR activities of decursin and decursin-containing herbal extracts have significant implications for the chemoprevention and treatment of prostate cancer and other androgen-dependent diseases.

Androgen Antagonists↗

PubMed2005

The 3-hydroxy group and 4,5-trans double bond of sphingomyelin are essential for modulation of galactosylceramide transmembrane asymmetry.

The structural features of SPM that control the transbilayer distribution of beta-GalCer in POPC vesicles were investigated by (13)C- and (31)P-NMR spectroscopy using lipid analogs that share physical similarities with GalCer or SPM. The SPM analogs included N-palmitoyl-4,5-dihydro-SPM, 3-deoxy-SPM, 1-alkyl-2-amidophosphatidylcholine, and dipalmitoylphosphatidylcholine, a popular model "raft lipid". The transbilayer distributions of the SPM analogs and SPM in POPC vesicles were similar by (31)P-NMR. To observe the dramatic change in GalCer transbilayer distribution that occurs when SPM is included in POPC vesicles, the 3-OH group, 4,5-trans double bond, and amide linkage all were required in SPM. However, inclusion of 2 and 10 mol % dihydroSPM in SPM/POPC (1:1) vesicles mitigated and completely abrogated the effect of SPM on the transbilayer distribution of GalCer. Despite sharing some structural features with GalCer and localizing preferentially to the inner leaflet of POPC vesicles, dimyristoylphosphatidylethanolamine did not undergo a change in transbilayer distribution when SPM was incorporated into the vesicles. The results support the hypothesis that specific interactions may be favored among select sphingolipids in curvature-stressed membranes and emphasize the potential importance of the SPM-dihydroSPM ratio in membrane fission and fusion processes associated with vesicle biogenesis and trafficking.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2004

Methyl selenium metabolites decrease prostate-specific antigen expression by inducing protein degradation and suppressing androgen-stimulated transcription.

Prostate-specific antigen (PSA) is widely used clinically for prostate cancer diagnostics and as an indicator of therapeutic efficacy and recurrence. Several human chemoprevention trials are being conducted to validate the prostate cancer prevention efficacy of selenium and PSA is used in these trials as a biomarker of response. A better understanding of the effects of selenium metabolites on the kinetics of PSA turnover and secretion in prostate cancer cells treated with selenium at concentrations which are achievable physiologically will be important for interpreting the results of these trials. This study addresses whether the putative active anticancer selenium metabolite methylselenol or its precursor methylseleninic acid (MSeA) specifically inhibits PSA expression in the androgen-responsive LNCaP prostate cancer cell model. The results show that exposure to sub-apoptotic concentrations of MSeA and methylselenol inhibited PSA protein expression and secretion, whereas sodium selenite and selenomethionine lacked inhibitory effect. The inhibition was detectable at 3 h of exposure and required a threshold level of MSeA to sustain. Turnover experiments showed that MSeA caused rapid PSA degradation, which was partially blocked by lysosomal inhibitors, but not by a proteasomal inhibitor. Furthermore, MSeA treatment reduced PSA mRNA level, down-regulated androgen receptor protein expression, and inhibited androgen-stimulated PSA promoter transcription. In summary, methylselenol or MSeA specifically and rapidly inhibited PSA expression through two mechanisms of action: inducing PSA protein degradation and suppressing androgen-stimulated PSA transcription. These findings may have important mechanistic implications for the prostate specific cancer chemopreventive action of selenium.

Androgens↗

PubMed2004

Selenite-induced p53 Ser-15 phosphorylation and caspase-mediated apoptosis in LNCaP human prostate cancer cells.

The issue of p53 requirement for the caspase-mediated apoptosis induced by selenium in a cancer chemoprevention or chemotherapy context has not been critically addressed. We and others have shown that selenite induces apoptotic DNA laddering in the p53-mutant DU145 prostate cancer cells and the p53-null HL60 leukemia cells without the cleavage of poly(ADP-ribose) polymerase (PARP; i.e., caspase-independent apoptosis), whereas selenium compounds leading to the formation of methylselenol induce caspase-mediated apoptosis in these cells. Because selenite induces DNA single strand breaks, and because certain types of DNA damage activate p53, we investigated whether the human LNCaP prostate cancer cells, which contain a wild-type p53, execute selenite-induced apoptosis through caspase pathways. The results showed that exposure of LNCaP cells for 24 hours to lower micromolar concentrations of selenite led to DNA laddering, and to the cleavage of PARP and several pro-caspases. In contrast to this apoptosis sensitivity, LNCaP cells were rather resistant to similar concentrations of the methylselenol precursor methylseleninic acid. Selenite treatment led to a significant increase in p53 phosphorylation on Ser-15 (Ser15P). Time course experiments showed that p53 Ser15P occurred several hours before caspase activation and PARP cleavage. The general caspase inhibitor zVADfmk completely blocked PARP cleavage, and significantly decreased DNA laddering, but did not affect p53 Ser15P. An inhibitor for caspase-8 was equally as protective as that for caspase-9 against the selenite-induced apoptosis. Attenuating p53 by a chemical inhibitor pifithrin-alpha decreased the selenite-induced p53 Ser15P and led to concordant reductions of PARP cleavage and apoptosis. In summary, selenite-induced p53 Ser15P appeared to be important for activating the caspase-mediated apoptosis involving both the caspase-8 and the caspase-9 pathways in the LNCaP cells.

Amino Acid Chloromethyl Ketones↗

PubMed2002

Sphingomyelin modulates the transbilayer distribution of galactosylceramide in phospholipid membranes.

The interrelationships among sphingolipid structure, membrane curvature, and glycosphingolipid transmembrane distribution remain poorly defined despite the emerging importance of sphingolipids in curved regions and vesicle buds of biomembranes. Here, we describe a novel approach to investigate the transmembrane distribution of galactosylceramide in phospholipid small unilamellar vesicles by (13)C NMR spectroscopy. Quantitation of the transbilayer distribution of [6-(13)C]galactosylceramide (99.8% isotopic enrichment) was achieved by exposure of vesicles to the paramagnetic ion, Mn(2+). The data show that [6-(13)C]galactosylceramide prefers (70%) the inner leaflet of phosphatidylcholine vesicles. Increasing the sphingomyelin content of the 1-palmitoyl-2-oleoyl-phosphatidylcholine vesicles shifted galactosylceramide from the inner to the outer leaflet. The amount of galactosylceramide localized in the inner leaflet decreased from 70% in pure 1-palmitoyl-2-oleoyl-phosphatidylcholine vesicles to only 40% in 1-palmitoyl-2-oleoyl-phosphatidylcholine/sphingomyelin (1:2) vesicles. The present study demonstrates that sphingomyelin can dramatically alter the transbilayer distribution of a monohexosylceramide, such as galactosylceramide, in 1-palmitoyl-2-oleoyl-phosphatidylcholine/sphingomyelin vesicles. The results suggest that sphingolipid-sphingolipid interactions that occur even in the absence of cholesterol play a role in controlling the transmembrane distributions of cerebrosides.

Animals↗