Quercetin inhibits heat shock protein induction but not heat shock factor DNA-binding in human breast carcinoma cells

Triptolide, an Inhibitor of the Human Heat Shock Response That Enhances Stress-induced Cell Death

Molecular chaperones, inducible by heat shock and a variety of other stresses, have critical roles in protein homeostasis, balancing cell stress with adaptation, survival, and cell death mechanisms. In transformed cells and tumors, chaperones are frequently overexpressed, with constitutive activation of the heat shock transcription factor HSF1 implicated in tumor formation. Here, we describe the activity of triptolide, a diterpene triepoxide from the plant Triptergium wilfordii, as an inhibitor of the human heat shock response. Triptolide treatment of human tissue culture cells prevented the inducible expression of heat shock genes, shown by suppression of an HSP70 promoter-reporter construct and by suppression of endogenous HSP70 gene expression. Upon examining the steps in the HSF1 activation pathway, we found that triptolide abrogates the transactivation function of HSF1 without interfering in the early events of trimer formation, hyperphosphorylation, and DNA binding. The ability of triptolide to inhibit the heat shock response renders these cells sensitive to stress-induced cell death, which may be of great relevance to cancer treatments.

Stimulatory effect of genistein and apigenin on the growth of breast cancer cells correlates with their ability to activate ER alpha

Genistein and apigenin are phytoestrogens present in commercial preparations used for the treatment of postmenopausal symptoms. In this study, we assessed the influence of these compounds on mammary tumor growth. Both compounds stimulate the proliferation of MCF-7 and T47D cells [estrogen receptor alpha (ERalpha-positive)], but do not stimulate the proliferation of an ERalpha-negative cell line (MDA-MB-435 cells). Genistein appeared more efficient in this regard due to its higher binding affinity for ERalpha, a property explained by a structural analysis of the binding of these compounds to the ERalpha's ligand binding domain. As previously described for estradiol (E(2)), genistein and apigenin down regulated ERalpha and enhanced estrogen response element (ERE)-dependent gene expression. The additional finding that genistein antagonizes the anti-proliferative effect of hydroxytamoxifen suggests phytoestrogens may be detrimental in women with breast cancer who are being treated with tamoxifen. In addition, because of their ability to stimulate breast cell growth, the widespread use of phytoestrogens in postmenopausal women could be detrimental.

Simvastatin promotes heat shock protein 27 expression and Akt activation in the rat retina and protects axotomized retinal ganglion cells in vivo

Heat shock proteins (Hsps) are stress proteins that mediate protein stabilization in various tissues and protect cells from environmental stress. Novel evidence suggests that overexpression of the small heat shock protein 27 (Hsp27) in neurons protects against neurotoxic stimuli and may act as an inhibitor of neurodegeneration. Overexpression of Hsps has been achieved by different means including pharmacological induction. Here, we show that intravitreal injection of the 3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitor simvastatin induces Hsp27 expression in axotomized retinal ganglion cells (RGCs) and enhances RGC survival 7 and 14 days after optic nerve (ON) axotomy by 90% and 19%, respectively. The flavonoid quercetin inhibited Hsp27 induction and abrogated simvastatin-mediated neuroprotection. Simvastatin increased Akt phosphorylation in vivo, indicating that the PI3K/Akt pathway contributes to central nervous system (CNS) protective effects achieved. We propose the use of statins as a feasible approach to reduce lesion-induced CNS neuronal degeneration in vivo.

Heat shock proteins protect both MPP+ and paraquat neurotoxicity

The exposure of immortalized rat neuroblast cells to MPP(+) and paraquat results in cell death. Heat shock pre-treatment prior to the addition of MPP(+) and paraquat significantly reduced cell death and led to an increase in the synthesis of Hsp 27 and Hsp70 proteins. Quercetin inhibits the synthesis of heat shock proteins (Hsp) and prevents their protective effect, which suggests that this protection was dependent on the Hsps synthesis. These data indicate that heat shock protects cells from the toxic effect of MPP(+) and paraquat. These results and the structural similarity between paraquat and MPP(+) support the role of paraquat as a putative risk factor in the etiology of Parkinson's disease.

Cactus pear: a natural product in cancer chemoprevention

BACKGROUND

Cancer chemoprevention is a new approach in cancer prevention, in which chemical agents are used to prevent cancer in normal and/or high-risk populations. Although chemoprevention has shown promise in some epithelial cancers, currently available preventive agents are limited and the agents are costly, generally with side effects. Natural products, such as grape seed, green tea, and certain herbs have demonstrated anti-cancer effects. To find a natural product that can be used in chemoprevention of cancer, we tested Arizona cactus fruit solution, the aqueous extracts of cactus pear, for its anti-cancer effects in cultured cells and in an animal model.

METHOD

Aqueous extracts of cactus pear were used to treat immortalized ovarian and cervical epithelial cells, as well as ovarian, cervical, and bladder cancer cells. Aqueous extracts of cactus pear were used at six concentrations (0, 0.5, 1, 5, 10 or 25%) to treat cells for 1, 3, or 5 days. Growth inhibition, apoptosis induction, and cell cycle changes were analyzed in the cultured cells; the suppression of tumor growth in nude mice was evaluated and compared with the effect of a synthetic retinoid N-(4-hydroxyphernyl) retinamide (4-HPR), which is currently used as a chemoprevention agent. Immunohistochemistry staining of tissue samples from animal tumors was performed to examine the gene expression.

RESULTS

Cells exposed to cactus pear extracts had a significant increase in apoptosis and growth inhibition in both immortalized epithelial cells and cancer cells in a dose- and time-dependent manner. It also affected cell cycle of cancer cells by increasing G1 and decreasing G2 and S phases. Both 4-HPR and cactus pear extracts significantly suppressed tumor growth in nude mice, increased annexin IV expression, and decreased VEGF expression.

CONCLUSION

Arizona cactus pear extracts effectively inhibited cell growth in several different immortalized and cancer cell cultures, suppressed tumor growth in nude mice, and modulated expression of tumor-related genes. These effects were comparable with those caused by a synthetic retinoid currently used in chemoprevention trials. The mechanism of the anti-cancer effects of cactus pear extracts needs to be further studied.

The effect of quercetin on pro-apoptotic activity of cisplatin in HeLa cells

It is well known that some tumour cells are very resistant to chemotherapy-induced cell death which indicate poor prognosis for patients. Thus the aim of the present study was to investigate the effect of quercetin on pro-apoptotic activity of cisplatin in human cervix carcinoma cells (HeLa). Three variants of experiments were performed. In the first one cells were incubated with studied drugs separately for 8 and 24h. In the second, drugs were added to the culture medium simultaneously. In third cisplatin or quercetin addition was followed by subsequent quercetin or cisplatin treatment, respectively. We observed different apoptotic effects, dependent on the drug succession. Preincubation of cells with quercetin followed by cisplatin treatment appeared to be the most effective and was correlated with strong activation of caspase-3 and inhibition of both heat shock proteins (Hsp72) and multi-drug resistance proteins (MRP) levels. Our results indicate that quercetin pretreatment sensitizes HeLa cells to cisplatin-induced apoptosis in HeLa cells.

Induction of cancer-specific cytotoxicity towards human prostate and skin cells using quercetin and ultrasound

Bioflavonoids, such as quercetin, have recently emerged as a new class of chemotherapeutic drugs for the treatment of various cancer types, but are marred by their low potency and poor selectivity. We report that a short application of low-frequency ultrasound selectively sensitises prostate and skin cancer cells against quercetin. Pretreatment of cells with ultrasound (20 kHz, 2 W cm⁻², 60 s) selectively induced cytotoxicity in skin and prostate cancer cells, while having minimal effect on corresponding normal cell lines. About 90% of the viable skin cancer cell population was lost within 48 h after ultrasound-quercetin (50 μM) treatment. Ultrasound reduced the LC₅₀ of quercetin for skin cancer cells by almost 80-fold, while showing no effect on LC₅₀ for nonmalignant skin cells.

Modulation of ΔF508 Cystic Fibrosis Transmembrane Regulator Trafficking and Function with 4-Phenylbutyrate and Flavonoids

Over 70% of patients with cystic fibrosis have the DeltaF508 mutation. This protein is a partially functional chloride (Cl-) channel that is prematurely degraded in the endoplasmic reticulum. Specific members of the flavonoid class of compounds have been shown to increase Cl- conductance of wild-type and DeltaF508 cystic fibrosis transmembrane regulator (CFTR). Although flavonoid effects on CFTR processing are unknown, evidence of effects on heat shock proteins, specifically those that have been shown to interact with CFTR, led us to believe that there would be an effect on CFTR processing through modulation of CFTR-chaperone interactions. We sought to determine (i) the effect of apigenin, genistein, kaempferol, and quercetin on CFTR processing in IB3-1 cells (F508/W1282X) and (ii) whether sequential treatment with 4-phenylbutyrate (4-PBA) to increase CFTR processing and flavonoid to directly stimulate CFTR would increase Cl- conductance. Our results show no significant effect on CFTR processing as measured by immunoblotting with 1 microM or 5 microM of apigenin, genistein, kaempferol, or quercetin. However, despite no effect on CFTR processing as determined by immunoblot, immunofluorescence demonstrated a favorable change in the intracellular distribution of CFTR with 24 h treatments of apigenin, kaempferol, and genistein. Furthermore, we observed an increase in Cl- conductance as measured by Cl- efflux in cells that were treated for 24 h with 4-PBA and then assayed with forskolin and 1 microM or 5 microM genistein, and also with cells treated for 24 h with either 4-PBA, 5 microM apigenin, or 1 microM quercetin. Thus, a combination of chronic treatment with 4-PBA or select flavonoids, followed by acute flavonoid exposure, may be beneficial in cystic fibrosis.

Decrease of heat shock protein levels and cell populations by wine phenolic extracts

The effect of red and white wine total extracts and phenolic fractions on heat shock protein (Hsp) levels in tumor cells and on tumor and endothelial cell populations in vitro has been investigated. Total extracts of red wines decreased Hsp70 and Hsp27 levels and the numbers of tumor and endothelial cells. Several red and white wine fractions significantly decreased Hsp27 levels, and some of them had also an effect on Hsp70 levels. A red wine fraction rich in polymeric flavanols and a white wine one rich in phenolic acids, flavonols, and tyrosol strongly lowered Hsp27 levels. Some red and white wine fractions strongly reduced tumor cell numbers, whereas most of them decreased endothelial cell numbers to variable extents. The present results indicate that wine phenolics decrease Hsp levels in tumor cells and tumor and endothelial cell populations. These properties may be important in the potent anticarcinogenic action of wine phenolics.

PTHrP [67-86] regulates the expression of stress proteins in breast cancer cells inducing modifications in urokinase-plasminogen activator and MMP-1 expression

It was previously reported that a midregion domain of parathyroid hormone-related protein (PTHrP), that is, [67-86]-amide, is able to restrain growth and promote matrigel penetration by the 8701-BC cell line, derived from a biopsy fragment of a primary ductal infiltrating carcinoma of the human breast, and that cell invasion in vitro is drastically impaired by inactivation of urokinase-plasminogen activator (uPa). In this study we started a more detailed investigation of the possible effects on gene expression arising from the interaction between PTHrP [67-86]-amide and 8701-BC breast cancer cells by a combination of conventional-, differential display-and semi-quantitative multiplex-polymerase chain reaction (PCR) assays. We present here the first evidence that the upregulation of some stress-related genes, most noticeably heat shock factor binding protein-1 (hsbp1) and heat shock protein 90 (hsp-90), is involved in the acquisition of an in vitro more invasive phenotype by cells treated with midregion PTHrP. This is conceivably accomplished by sequestering and inactivating heat shock factor-1 (hsf1) which is able to recognize Ets transcription-factor-binding sites present in some gene promoters, such as those of uPa and matrix metalloprotease-1 (MMP-1). In fact, our data show that incubation of PTHrP [67-86]-amide-treated cells with either antisense hsbp1-oligonucleotide or geldanamycin, an hsp90-inactivating antibiotic, results in downregulation of uPa and upregulation of MMP-1, and in a prominent inhibition of cell invasion in matrigel-containing Transwell chambers. Alternatively, incubation of untreated 8701-BC cells with quercetin, a flavonoid known to decrease the amount of free hsf1, is found to induce upregulation of uPa and downregulation of MMP-1, and an increase of matrigel invasion by cells, thus providing further supporting data of the involvement of hsf unavailability on the modulation of uPa and MMP-1 expression and on cell invasive behaviour. These studies confirm a previous postulate that over-secretion of uPa, rather than of other extracellular proteases, is a primary condition for the increase of invasive activity triggered by PTHrP [67-86]-amide in vitro, and support a role for midregion forms of PTHrP in potentially affecting pathological mammary growth and differentiation. They also identify two new key protagonists in the complex scenario of breast tumor cell invasiveness in vitro, that is, hsbp1 and hsp90, which deserve further and more extensive studies as potential and attractive molecular targets for anti-breast cancer treatments.

The immunophilin-ligands FK506 and V-10,367 mediate neuroprotection by the heat shock response

(1) The macrolid FK506 is widely used in transplantation to suppress allograft rejection. FK506 and its derivatives are powerful neuroprotective molecules, but the underlying mechanisms remain to be resolved. We have previously shown that the FK506 mediated neuroprotection against oxygen radicals is independent of the inhibition of calcineurin but depends on de novo protein synthesis. (2) Here, we have shown that FK506 mediates protection against H(2)O(2), UV-light or thapsigargin in neuronal cell lines, but not in non-neuronal cells such as R3T3 fibroblasts. We compared in detail the effect of FK506 on apoptotic features in PC12 cells after H(2)O(2) with V-10,367 which binds to FKBPs but does not inhibit calcineurin. Both molecules exert the same neuroprotective effect after H(2)O(2) stimulation. FK506, but not V-10,367, inhibited the cytochrome c release out of the mitochondria and the caspase 3 activation, while both molecules inhibited the cleavage of Poly-(ADP-ribose)-polymerase (Parp) and prevented the expression of p53. (3) FK506 and V-10,367 rapidly induced the expression of Hsp70 and Hsp27, but not Hsp90. Their neuroprotective actions could be completely blocked by quercetin, a functional inhibitor of the heat shock proteins. (4) We conclude that immunophilin-ligands such as FK506 and V-10,367 exert their neuroprotection independent of calcineurin through the induction of the heat shock response. The identification of the underlying signal transduction from application of immunophilin ligands to the expression of heat shock proteins represents a novel target cascade for neuroprotection.

Therapeutic approaches to repair defects in deltaF508 CFTR folding and cellular targeting

The deltaF508 mutation in the cystic fibrosis transmembrane regulator (CFTR) gene is the most common mutation in CF. The mutant CFTR protein is defective with respect to multiple functions including cAMP-regulated chloride conductance, nucleotide transport, and regulatory actions on other ion channels. Since the deltaF508 protein is also temperature-sensitive and unstable during translation and folding in the endoplasmic reticulum (ER), most of the nascent chains are targeted for premature proteolysis from the ER. This paper focuses on the events that occur in the ER during folding and reviews potential targets for therapeutic intervention.

Quercetin, apoptosis, heat shock

The present study was designed to investigate the correlation between the expression level of Hsp27 and Hsp72 and induction of apoptosis in HeLa cells in response to quercetin treatment. Treatment of HeLa cells with quercetin or with 1hr period of hyperthermia (42 degrees) increased the number of apoptotic cells. Inhibition of the expression of Hsp72 and Hsp27 in tumour cells by anti-sense oligonucleotides, enhanced the induction of apoptosis by quercetin. Heat shock itself had little effect on apoptotic cell death in these cells, but when combined with quercetin treatment, caused a significant increase in the number of apoptotic cells. These results suggest that the reduction of Hsps expression in the HeLa cell line promotes the induction of apoptosis by quercetin.

The mutant androgen receptor T877A mediates the proliferative but not the cytotoxic dose-dependent effects of genistein and quercetin on human LNCaP prostate cancer cells

High consumption of soybean products, such as phytoestrogens, has been hypothesized to contribute to a reduced incidence of prostate cancer in Southeast Asian people, although there have been inconsistent results among studies. Human LNCaP cells, extensively used as a model for androgen-dependent prostate tumor, express the androgen receptor (AR) mutant T877A promiscuously transactivated by estrogens and other ligands, which may further facilitate cancer progression. Here, for the first time to our knowledge, we demonstrate that genistein and quercetin, two phytoestrogens abundantly present in soybeans, activate either the AR mutant T877A in LNCaP or in transfected Chinese hamster ovary cells. This observation is supported by their capability to induce AR accumulation in the nuclear compartment of LNCaP together with mRNA down-regulation of the androgen target genes AR and PAP, and PSA up-regulation. Of interest, at concentrations eliciting transcriptional activity, both genistein and quercetin stimulate LNCaP cell growth, whereas at high levels, they become cytotoxic independently of AR expression, as ascertained in steroid receptor-negative Hela cells. The results of our study provide evidence that phytoestrogens may regulate several signaling processes in LNCaP cells; however, further studies are needed to assess their potential capability to restrain prostate tumor progression.

Estrogenic and antiproliferative activities of isoliquiritigenin in MCF7 breast cancer cells

Licorice root contains chemically diverse compounds that exhibit estrogenic effects in vitro and in vivo. The chalcone isoliquiritigenin (ISL) is a component of licorice extract exhibiting either antitumorigenic activity or estrogen receptor (ER) alpha-dependent growth promoting effects on breast cancer cells. In order to contribute to a better understanding of this apparent paradox, we synthesized and ascertained the estrogenic properties of ISL using, as model systems, the hormone-sensitive MCF7 breast cancer cells and the steroid-independent HeLa cells. Transfection experiments reveal that ISL is able to transactivate the endogenous ER alpha in MCF7 cells and this is supported by the capability to induce down-regulation of ER alpha protein levels and up-regulation of pS2 mRNA. Moreover, by using chimeric proteins consisting of the hormone binding domains of ER alpha and ER beta fused to the Gal4 DNA binding domain, we have determined that ISL is an estrogenic agonist of both ER isoforms. As a biological counterpart, low and intermediate ISL concentrations that induce substantial transcriptional activity stimulate the proliferation of MCF7 cells. However, high levels of ISL become cytotoxic even in steroid-receptor negative HeLa cells. Thus, the activity of ISL and the balance between risk or chemopreventive factor for estrogen-dependent breast cancer may depend on dietary intake.

Effects of quercetin on the heat-induced cytotoxicity of prostate cancer cells

BACKGROUND

It has been demonstrated that prostate cancer cells are relatively sensitive to heat stress. We have reported that heat treatment at 43 degrees C increases the expression of heat shock protein 70 (hsp70) in prostate cancer cells, leading to apoptosis. Hsp70 is a protein that protects cells against heat damage. Cells with lower levels of hsp70 have been shown to have a higher sensitivity to heat stress. Therefore, downregulation of hsp70 is expected to enhance heat-induced inhibitory effects on cell growth. Quercetin has been reported to be an agent that inhibits hsp70 expression. The present study was undertaken to investigate the effects of quercetin and/or heat on the growth of prostate cancer cells in vitro.

METHODS

Three human prostate cancer cell lines were used: Lncap; PC-3; and JCA-1. The cells were treated with quercetin and/or heat. Alterations in the cell cycle and hsp70 expression were examined by means of flow cytometry (FCM). The apoptotic cells were detected by FCM using fluorescein isothiocyanate (FITC) labeled annexin V.

RESULTS

Treatment with quercetin alone resulted in an apparent decrease of hsp70-positive cells and an increase of subG1 cells in JCA-1 and LNcap cells. Quercetin inhibited an increase of hsp70 expression after heat treatment and increased the number of subG1 cells with lower levels of hsp70 in JCA-1 and LNcap cells. Quercetin was found to enhance heat-induced inhibitory effects on cell growth and heat-induced apoptosis in both JCA-1 and LNcap cells.

CONCLUSION

These results suggest that quercetin may enhance heat-induced cytotoxicity in prostate cancer cell lines through the inhibition of hsp70 production.

Quercetin and tamoxifen sensitize human melanoma cells to hyperthermia

Hyperthermia produces regression of human cancer. Because hyperthermia has produced only limited results, attention has focused on searching for substances able to sensitize tumour cells to the effects of hyperthermia. The flavonoid quercetin has been reported to be a hyperthermic sensitizer in ovarian and uterine cervical tumours and in leukaemia. Quercetin and tamoxifen inhibit melanoma cell growth. We therefore investigated whether quercetin and tamoxifen can sensitize M10, M14 and MNT1 human melanoma cells to hyperthermia. We observed that both quercetin and tamoxifen synergize with hyperthermia (42.5 degrees C) in reducing the clonogenic activity of M14 and MNT1 and in inducing apoptotic cell death in all three cell lines. As revealed by flow cytometric and Northern blot analyses, quercetin and tamoxifen reduced heat shock protein-70 expression at both protein and mRNA levels. Our results suggest that quercetin and tamoxifen can be usefully combined with hyperthermia in the therapy of recurrent and/or metastatic melanoma.

Role of protein kinase Cdelta in transmitting hypoxia signal to HSF and HIF-1

An hypoxic microenvironment is an important modulator of gene expression in many pathophysiological conditions. In this study, we show a coordinate activation of heat shock transcription factor (HSF) and hypoxia-inducible factor-1 (HIF-1) in RIF tumor cells by hypoxia. Since heat shock protein (hsp) and angiogenic factor genes that are regulated by HSF and HIF-1 are thought to contribute to the malignant progression of hypoxic tumor cells, it was of our major interest to identify the components that are responsible for the activation of both HSF and HIF-1. Our finding that a bioflavonoid quercetin (QCT), a well known inhibitor of hsp gene expression, significantly inhibited the transcriptional activation of HSF and HIF-1 strongly suggests that QCT-sensitive molecule(s) is involved in the transcriptional activation of HSF and HIF-1 by hypoxia. Our results revealed that PCKalpha, delta and epsilon isoforms are expressed in RIF cells, but only PKCdelta was specifically translocated to the membrane by hypoxia. Our results also revealed that the translocation of PKCdelta was completely abrogated by QCT. Moreover, inhibiting the PKCdelta activation, either pharmacologically with phorbol 12-myristate 13-acetate or with bisindolymaleimide II or genetically by transient transfection of a dominant negative PKCdelta, significantly inhibited the transcriptional activation of HSF and HIF-1 by hypoxia. These results strongly substantiate a view that the PKCdelta isozyme is the QCT-sensitive molecule that plays an important role in transmitting hypoxia signals to both HSF and HIF-1. Here we show that the membrane translocation of PKCdelta is dependent on the activation of phosphoinositol 3-kinase (PI3K). Treatment with PI3K inhibitor, wortmannin or LY294002, abrogated not only PKCdelta translocation but the subsequent transcriptional activation of HSF and HIF-1 by hypoxia. Together, our study shows that the PKCdelta isozyme acts as a shared component in transmitting hypoxia-induced signals to both HSF and HIF-1, and that the upstream regulator of PKCdelta is PI3K.

Therapeutic strategies to correct malfunction of CFTR

Cystic fibrosis (CF) is a systemic autosomal recessive inherited disorder that results from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Although the gene was cloned 11 years ago, there still is no definitive treatment to correct the functional deficit. Current treatment strategies focus on pancreatic enzyme replacement and control of pulmonary inflammation and infection. This review examines novel strategies still in preclinical development or phase 1 clinical trials. Gene therapy is an evolving area of study that offers the potential for a cure for cystic fibrosis. CF lung disease is a significant barrier to effective gene delivery and transfer, but new vectors show promise in overcoming these limitations. There are also new pharmacological therapies aimed at correcting defects in CFTR processing and function. These are tailored to the specific class of mutation but may offer therapeutic benefit to many patients. They include phenylbutyrate, flavonoids, aminoglycosides and xanthines.

Human cyclophilin 40 is a heat shock protein that exhibits altered intracellular localization following heat shock

The unactivated steroid receptors are chaperoned into a conformation that is optimal for binding hormone by a number of heat shock proteins, including Hsp90, Hsp70, Hsp40, and the immunophilin, FKBP52 (Hsp56). Together with its partner cochaperones, cyclophilin 40 (CyP40) and FKBP51, FKBP52 belongs to a distinct group of structurally related immunophilins that modulate steroid receptor function through their association with Hsp90. Due to the structural similarity between the component immunophilins, FKBP52 and cyclophilin 40, we decided to investigate whether CyP40 is also a heat shock protein. Exposure of MCF-7 breast cancer cells to elevated temperatures (42 degrees C for 3 hours) resulted in a 75-fold increase in CyP40 mRNA levels, but no corresponding increase in CyP40 protein expression, even after 7 hours of heat stress. The use of cycloheximide to inhibit protein synthesis revealed that in comparison to MCF-7 cells cultured at 37 degrees C, those exposed to heat stress (42 degrees C for 3 hours) displayed an elevated rate of degradation of both CyP40 and FKBP52 proteins. Concomitantly, the half-life of the CyP40 protein was reduced from more than 24 hours to just over 8 hours following heat shock. As no alteration in CyP40 protein levels occurred in cells exposed to heat shock, an elevated rate of degradation would imply that CyP40 protein was synthesized at an increased rate, hence the designation of human CyP40 as a heat shock protein. Application of heat stress elicited a marked redistribution of CyP40 protein in MCF-7 cells from a predominantly nucleolar localization, with some nuclear and cytoplasmic staining, to a pattern characterized by a pronounced nuclear accumulation of CyP40, with no distinguishable nucleolar staining. This increase in nuclear CyP40 possibly resulted from a redistribution of cytoplasmic and nucleolar CyP40, as no net increase in CyP40 expression levels occurred in response to stress. Exposure of MCF-7 cells to actinomycin D for 4 hours resulted in the translocation of the nucleolar marker protein, B23, from the nucleolus, with only a small reduction in nucleolar CyP40 levels. Under normal growth conditions, MCF-7 cells exhibited an apparent colocalization of CyP40 and FKBP52 within the nucleolus.

Quercetin inhibits c-fos, heat shock protein, and glial fibrillary acidic protein expression in injured astrocytes

Quercetin, a bioflavonoid, is found widely in many kinds of fruits and vegetables. It is known to engage in many bioactivities, such as interfering with of the progress of stress responses to injury. In the present study, we investigated the effects of quercetin on some injury responses in primary cultures of astrocytes. These injury responses included the elevation of c-fos protein, heat shock protein (HSP70), and glial fibrillary acidic protein (GFAP). After heat shock insult, the levels of c-fos protein and HSP70 in astrocytes increased. With quercetin treatment, these proteins were significantly reduced. The inhibition of these injury responses by quercetin in astrocytes indicated a dose dependency, with the highest effect at 100 microM. We have previously established a scratch injury model in a primary culture of astrocytes. In that model, astrocytes responded to the scratch injury by an elevation in their GFAP level and formation of hypertrophic cell processes, which extend into the scratch areas. Quercetin treatment reduced the number of hypertrophic cell processes being extended into the scratch areas. With 100 microM of quercetin, there was a complete inhibition of the formation of the hypertrophic cell process. Western blot analysis for GFAP indicated that quercetin significantly reduced the induction of GFAP in the scratch model. At 100 microM, the total GFAP content in the injured cultures was reduced to a level lower than that of the control. This implied that quercetin might possess an antigliotic property.

Inhibition of Vpr-induced cell cycle abnormality by quercetin: a novel strategy for searching compounds targeting Vpr

Vpr, an accessory gene product of HIV-1 which induces cell cycle abnormality leading to the increased HIV replication, is supposed to be a possible target for anti-AIDS drugs. We recently established a cell line (MIT-23) in which Vpr-induced cell cycle perturbation could be manipulated by a tetracycline promoter. Here, we screened anti-Vpr activity in 27 kinds of herb drugs using MIT-23 cells. One of the extracts prepared from Houttuyniae herba showed an inhibitory activity. Quercetin (QCT), a compound of this crude drug, efficiently inhibited Vpr function without affecting its expression. Furthermore, data suggested that Vpr-induced transcription from HIV-LTR was considerably abrogated by QCT. These data indicate that QCT, a flavonoid previously reported to inhibit HIV replication, also targets Vpr, implicating that MIT-23 cell provides a novel strategy for screening compounds possessing anti-Vpr activity which would be in turn utilized for clarifying the mechanism of Vpr function.

Effects of quercetin and sunphenon on responses of cancer cells to heat shock damage

Quercetin is a flavonoid well known to inhibit growth and heat shock protein (HSP) synthesis of cancer cells. However, sunphenon has been scarcely reported concerning effects on cancer cells. We compared the effects of sunphenon with those of quercetin on the human cholangio-cellular carcinoma cell line (HuCC-T1). Both flavonoids inhibited HuCC-T1 growth in a concentration-dependent manner without reduction of HSP70 and HSP90 expression before heat shock damage. The heat shock reduced the cell viability of the quercetin-treated HuCC-T1, but not that of the sunphenon-treated cells. This inhibitory effect of quercetin on tolerance to heat shock is thought to be due to marked suppression of HSP72. Sunphenon conversely increased HSP72 expression after heat shock. Although neither flavonoid altered HSP90 protein levels before and after heat shock, quercetin delayed the reorganization of filamentous actin (F-actin) during the recovery period after heat shock. Since HSP90 could preserve F-actin structure during stresses, quercetin might affect the interaction between HSP90 and F-actin without influencing HSP90 expression. In conclusion, quercetin would be more useful than sunphenon in combined therapy with hyperthermia for cancer.