Up-regulation of PI3K/Akt signaling by 17beta-estradiol through activation of estrogen receptor-alpha, but not estrogen receptor-beta, and stimulates cell growth in breast cancer cells

Estrogen stimulates cell proliferation in breast cancer. The biological effects of estrogen are mediated through two intracellular receptors, estrogen receptor-alpha (ERalpha) and estrogen receptor-beta (ERbeta). However, the role of ERs in the proliferative action of estrogen is not well established. Recently, it has been known that ER activates phosphatidylinositol-3-OH kinase (PI3K) through binding with the p85 regulatory subunit of PI3K. Therefore, possible mechanisms may include ER-mediated phosphoinositide metabolism with subsequent formation of phosphatidylinositol-3,4,5-trisphosphate (PIP(3)), which is generated from phosphatidylinositol 4,5-bisphosphate via PI3K activation. The present study demonstrates that 17beta-estradiol (E2) up-regulates PI3K in an ERalpha-dependent manner, but not ERbeta, and stimulates cell growth in breast cancer cells. In order to study this phenomenon, we have treated ERalpha-positive MCF-7 cells and ERalpha-negative MDA-MB-231 cells with 10nM E2. Treatment of MCF-7 cells with E2 resulted in a marked increase in PI3K (p85) expression, which paralleled an increase in phospho-Akt (Ser-473) and PIP(3) level. These observations also correlated with an increased activity to E2-induced cell proliferation. However, these effects of E2 on breast cancer cells were not observed in the MDA-MB-231 cell line, indicating that the E2-mediated up-regulation of PI3K/Akt pathway is ERalpha-dependent. These results suggest that estrogen activates PI3K/Akt signaling through ERalpha-dependent mechanism in MCF-7 cells.     

Curcumin suppresses phorbol ester-induced matrix metalloproteinase-9 expression by inhibiting the PKC to MAPK signaling pathways in human astroglioma cells

The aberrant expression of matrix metalloproteinase-9 (MMP-9) is implicated in the invasion and angiogenesis process of brain tumor. This study has investigated the effects of curcumin on MMP-9 expression in human astroglioma cell lines. Curcumin significantly inhibited the MMP-9 enzymatic activity and protein expression that was induced by PMA. The inhibitory effect of curcumin on MMP-9 expression correlates with the decreased MMP-9 mRNA level and the suppression of MMP-9 promoter activity. The curcumin-mediated inhibition of MMP-9 gene expression appears to occur via NF-kappaB and AP-1 because their DNA binding activities were suppressed by curcumin. Furthermore, curcumin strongly repressed the PMA-induced phosphorylation of ERK, JNK, and p38 MAP kinase, which were dependent on the PKC pathway. Therefore, the inhibition of MMP-9 expression by curcumin might have therapeutic potential for controlling the growth and invasiveness of brain tumor.     

TNF-alpha activates death pathway in human aorta smooth muscle cell in the presence of 7-ketocholesterol

This study was undertaken to investigate whether a physiologically compatible concentration of 7-ketocholesterol had any effect on human vascular smooth muscle cells (HVSMCs). We found that 7-ketocholesterol changed the viability of human aorta smooth muscle cells (HAoSMC) not by cytotoxicity but by activation of tumor necrosis factor-alpha receptor (TNFR)-mediated death. Whereas TNF-alpha did not affect the viability in the presence of 7alpha-hydroxycholesterol or cholesterol, the cytokine induced HAoSMC death in the presence of 7-ketocholesterol as detected by morphology, viability, and fragmentation of chromosomal DNA. The HAoSMC death was inhibited by a neutralizing anti-TNF receptor 1 (TNFR1) antibody and by the caspase inhibitors of z-VAD and z-DEVD. Activations of caspase-8 and -3 were detected from dying HAoSMCs. 7-Ketocholesterol inhibited translocation of the nuclear factor kappaB (NF-kappaB) subunits of p65 and p50 from the cytosol into the nucleus, increase of NF-kappaB activity, and expression of caspase-8 homolog Fas ligand interleukin-1-converting enzyme inhibitory protein by TNF-alpha. We also found that X-chromosome-linked inhibitor of apoptosis protein was degraded in dying HAoSMC. The present study proposes that 7-ketocholesterol would contribute to the disappearance of HVSMC in the atherosclerotic lesions by enhancing receptor-mediated death. This is the first report demonstrating induction of TNF-alpha-mediated death by oxysterol in cells.     

Cellular differentiation-induced attenuation of LPS response in HT-29 cells is related to the down-regulation of TLR4 expression

Intestinal epithelial cells not only present a physical barrier to bacteria but also participate actively in immune and inflammatory responses. The migration of epithelial cells from the crypt base to the surface is accompanied by a cellular differentiation that leads to important morphological and functional changes. It has been reported that the differentiation of colonic epithelial cells is associated with reduced interleukin (IL)-8 responses to IL-1beta. Although toll-like receptor 4 (TLR4) has been previously identified to be an important component of mucosal immunity to lipopolysaccharide (LPS) in the colon, little is known about the regulation of TLR4 in colonic epithelial cells during cellular differentiation. We investigated the effects of differentiation on LPS-induced IL-8 secretion and on the expression of TLR4. Differentiation was induced in colon cancer cell line HT-29 cells by butyrate treatment or by post-confluence culture and assessed by measuring alkaline phosphatase (AP) activity. IL-8 secretion was measured by ELISA, and TLR4 protein and mRNA expressions were followed by Western blot and RT-PCR, respectively. HT-29 cells were found to be dose-dependently responsive to LPS. AP activity increased in HT-29 cells by differentiation induced by treatment with butyrate or post-confluence culture. We found that IL-8 secretion induced by LPS was strongly attenuated in differentiated cells versus undifferentiated cells, and that cellular differentiation also attenuated TLR4 mRNA and protein expressions. Pretreating HT-29 cells with tumor necrosis factor (TNF)-alpha or interferon (INF)-gamma augmented LPS-induced IL-8 secretion and TLR4 expression. These TNF-alpha- or INF-gamma-induced augmentations of LPS response and TLR4 expression were all down-regulated by differentiation. Collectively, we conclude that cellular differentiation attenuates IL-8 secretion induced by LPS in HT-29 cells, and this attenuation is related with the down-regulation of TLR4 expression.     

Co-culture of human CD34+ cells with mesenchymal stem cells increases the survival of CD34+ cells against the 5-aza-deoxycytidine- or trichostatin A-induced cell death

It has been suggested that epigenetic regulation plays an important role in maintaining the stemness and lineage differentiation of hematopoietic stem cells (HSCs), 5-aza-deoxycytidine (aza-D) and Trichostatin A (TSA) being candidate additives for HSC ex vivo expansion. Although they have potent activity to maintain the stemness, they can also cause serious cell death. This study examined the effects of mesenchymal stem cells (MSCs) on the maintenance of CD34+ cells driven by aza-D and TSA in culture with the combined cytokines of thrombopoietin, flt-3 ligand, stem cell factor, interleukin-3, and interleukin-6. In cultures without MSCs, although aza-D and TSA retained the CD34 frequency 4 to 8 times more than in the cytokines alone, a large portion of cells underwent apoptotic cell death. Consequently, CD34+ cell expansion could not be achieved in any condition without MSCs. In cultures with MSCs, the total cell number was higher in aza-D or TSA than in any conditions in the cultures without MSCs. The CD34 frequency was also similar to the level in the cultures in aza-D or TSA without the MSCs. These results suggest that a co-culture of CD34+ cells with the MSCs might not simply deliver the proliferation signals but also stemness and survival signals, and overlap the action of epigenetic regulators.     

Oxalomalate, a competitive inhibitor of NADP+-dependent isocitrate dehydrogenase, regulates heat shock-induced apoptosis

Heat shock may increase oxidative stress due to increased production of reactive oxygen species and/or the promotion of cellular oxidation events. Recently, we demonstrated that the control of cytosolic and mitochondrial redox balance and the cellular defense against oxidative damage is one of the primary functions of NADP(+)-dependent isocitrate dehydrogenase (ICDH) by supplying NADPH for antioxidant systems. The protective role of ICDH against heat shock-induced apoptosis in U937 cells was investigated in the control and the cells pre-treated with oxalomalate, a competitive inhibitor of ICDH. Upon exposure to heat shock, there was a distinct difference between the control cells and the cells pre-treated with 3mM oxalomalate for 3h in regard to apoptotic parameters, cellular redox status, and mitochondrial function. The oxalomalate pre-treated cells showed significant enhancement of apoptotic features such as activation of caspase-3, up-regulation of Bax, and down-regulation of Bcl-2 compared to the control cells upon exposure to heat shock. This study indicates that ICDH may play an important role in regulating the apoptosis induced by heat shock presumably through maintaining the cellular redox status.     

ADAM22 plays an important role in cell adhesion and spreading with the assistance of 14-3-3

Cellular adhesion plays important roles in a variety of biological processes. The ADAM family contains disintegrin-like and metalloproteinase-like domains which potentially have cell adhesion and protease activities. Recent studies suggest that the interaction between 14-3-3zeta and ADAM22cyt can regulate cell adhesion and spreading, therefore it has a potential role in neural development and function. 14-3-3 family has seven highly conserved members that regulate various cellular functions. Using yeast two-hybrid method, we identified that ADAM22cyt bound some other 14-3-3 family members. The interaction was further confirmed by in vitro protein pull-down assay and co-immunoprecipitation. We also found that the overexpression of exogenous ADAM22 in HEK293 cells could significantly enhance cell adhesion and spreading, compared with the truncated ADAM22 lack of 14-3-3 binding motifs. These results strongly demonstrated a functional role for ADAM22/14-3-3 in cell adhesion and spreading.     

Hepatocyte adhesion on a poly[N-p-vinylbenzyl-4-O-beta-D-galactopyranosyl-D-glucoamide]-coated poly(L-lactic acid) surface

A surface of poly(l-lactic acid) (PLLA) was modified by coating with poly[N-p-vinylbenzyl-4-O-beta-d-galactopyranosyl-d-glucoamide] (PVLA), which was employed to improve the hepatocyte adhesion owing to its amphiphilic property and the presence of a hepatocyte recognition motif. We characterized the surface properties through water contact angle, electron spectroscopy for chemical analysis (ESCA), and scanning probe microscopy (SPM). The effect of PVLA coating on the efficiency of hepatocyte adhesion was evaluated by protein assay and optical microscopy. The surface morphology was under the influence of the concentration of PVLA coating solution and it played a critical role in hepatocyte adhesion. It was confirmed that galactose moieties in PVLA, which can bind to the asialoglycoprotein receptor (ASGPR) on hepatocytes, have a more dominant effect on hepatocyte adhesion than enhanced hydrophilicity. We suggest that the PVLA-PLLA system will be a useful method to improve hepatocyte cell seeding and adhesion onto scaffold matrices.     

Structure-activity relationship of 5'-substituted fluoro-neplanocin a analogues as potent inhibitors of S-adenosylhomocysteine hydrolase

Four 5'-substituted fluoro-neplanocin A analogues la-d were designed and synthesized, and the inhibitory activity against SAH was in the following order: NH2 > SH > F, N3, indicating a hydrogen bonding donor is essential for inhibitory activity.