Bone morphogenetic protein 2 signaling in osteoclasts is negatively regulated by the BMP antagonist, twisted gastrulation

Bone morphogenetic proteins (BMPs) have been shown to regulate both osteoblasts and osteoclasts. We previously reported that BMP2 could directly enhance RANKL-mediated osteoclast differentiation by increasing the size and number of osteoclasts. Similarly, genetic deletion of the BMP antagonist Twisted gastrulation (TWSG1) in mice, resulted in an enhancement of osteoclast formation, activity and osteopenia. This was accompanied by increased levels of phosphorylated Smad (pSmad) 1/5/8 in Twsg1(-/-) osteoclasts in vitro. The purpose of this study was to develop an adenoviral vector overexpressing Twsg1 as a means of inhibiting osteoclast activity. We demonstrate that overexpressing TWSG1 in primary osteoclasts decreased the size and number of multinuclear TRAP-positive osteoclasts, expression of osteoclast genes, and resorption ability. Overexpression of TWSG1 did not affect osteoclast proliferation or apoptosis. However, overexpression of TWSG1 decreased the levels of pSmad 1/5/8 in osteoclasts. Addition of exogenous BMP2 to osteoclasts overexpressing TWSG1 rescued the size and levels of pSmad 1/5/8 compared to cultures infected with a control virus. Finally, TWSG1 overexpression in osteoclasts isolated from the Twsg1(-/-) mice rescued size of the osteoclasts while further addition of exogenous BMP2 reversed the effect of TWSG1 overexpression and increased the size of the osteoclasts similar to control virus infected cells. Taken together, we demonstrate that overexpressing TWSG1 in osteoclasts via an adenoviral vector results in inhibition of osteoclastogenesis and may provide a potential therapy for inhibiting osteoclast activity in a localized manner.

Abstract 306: Development of EC-DG as a molecular theranostic personalized medicine

Purpose: D-glucosamine has been reported to inhibit proliferation of cancer cells in culture and in vivo. We have then synthesized Tc-99m- ethylenedicysteine-glucosamine (EC-DG). We found Tc-99m-EC-DG was involved in cell proliferation in lung, breast and head and neck cultures and could assess breast cancer treatment outcome in vivo by planar scintigraphy. Tc-99m-EC-DG is a safe imaging agent in lung cancer patients. This study was amied to (1) assess a novel response to unlabeled rhenium-EC-DG (Re-EC-DG) involving the translation regulation of hypoxia inducible factor (HIF)-1alpha expression in lymphoma cells, and, (2) evaluate feasibility of using EC-DG for theranostic approaches in cancers.

Methods: For theranostic assessment studies, we synthesized cold Re-EC-DG. Re-EC-DG was synthesized via a two-step synthesis. The first step was to synthesize Re-EC by reacting rheniumoxo trichloride with EC. The second step was to react Re-EC with D-glucosamine tetraacetate, followed by de-acetylation. Twelve types of DLBCL cells were incubated with Re-EC-DG at various concentrations (0-10 mM) and TUNEL assays were used to determine cell apoptosis. To ascertain the mechanism of the anticancer properties for Re-EC-DG, DLBCL-LY10 cells were treated with Re-EC-DG (0-5 mM) for 48 hrs. Immunoblotting were then performed on nuclear extracts with 50 µg. For radiotheranostic assessment studies, 13762 breast tumor-bearing rats were imaged with In-111-EC-DG and tumor/muscle ratios were determined at 0.5-24 hrs. Radiation absorbed dose was estimated for the use of Y-90-EC-DG.

Results: There was a dose response relationship of Re-EC-DG inhibition in DLBCL cells. Extensive apoptosis was observed at 24 hrs in lymphoma cell cultures. Re-EC-DG showed significant tumorcidal activity compared to normal B-lymphocyte activity at doses >0.17 µmol. Re-EC-DG caused a decreased expression of HIF-1alpha under normoxic conditions in DLBCL-LY10 cells. Tumor-to-muscle ratios for In-111-EC-DG were 5.43±0.45 to 7.80±0.05 whereas In-111-EC had 3.24±0.32 to 4.64±0.16 at 0.5-24 hrs. Radiation exposure of In-111-EC-DG to whole body, blood-forming organs, gonads, and effective dose equivalent for a single dose at 5 mCi was below the limits of 3 rad annually and 5 rad total. The absorbed dose in all other organs was below the limits of 5 rad annually and 15 rad total.

Conclusion: EC-DG is a useful molecular theranostic compound. In-111-EC-DG has favorable dosimetry, providing a potential use of Y-90-EC-DG to treat cancers. Re-EC-DG inhibits HIF-1alpha expression and is an attractive anti-proliferation compound.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 306. doi:10.1158/1538-7445.AM2011-306

HDAC3 and HDAC7 have opposite effects on osteoclast differentiation

Histone deacetylases (HDACs) are negative regulators of transcription. Endochondral bone formation including chondrocyte and osteoblast maturation is regulated by HDACs. Very little is known about the role HDACs play in osteoclast differentiation. It has been previously reported that HDAC inhibitors, trichostatin A and sodium butyrate, suppress osteoclast differentiation through multiple mechanisms. In this study, we report that suppression of HDAC3 expression similar to HDAC inhibitors inhibits osteoclast differentiation, whereas osteoclasts suppressed for HDAC7 expression had accelerated differentiation when compared with control cells. Mitf, a transcription factor, is necessary for osteoclast differentiation. We demonstrate that Mitf and HDAC7 interact in RAW 264 cells and osteoclasts. The transcriptional activity of Mitf is repressed by HDAC7. Lastly, we show that either the amino or the carboxyl terminus of HDAC7 is sufficient for transcriptional repression and that the repression of HDAC7 is insensitive to trichostatin A, indicating that HDAC7 represses Mitf at least in part by deacetylation-independent mechanism.

Involvement of toll-like receptor 4 in alveolar bone loss and glucose homeostasis in experimental periodontitis

BACKGROUND AND OBJECTIVE

There is general agreement that certain fatty acids and lipopolysaccharides (LPS) promote inflammation through toll-like receptor 4 (TLR4), and that inflammation promotes insulin resistance. We therefore hypothesized that mice with periodontitis and a TLR4 loss-of-function (LOF) mutation fed a high-fat (HF) diet would develop improved glucose homeostasis compared with wild-type (WT) animals with periodontitis fed a HF diet.

MATERIAL AND METHODS

Wild-type and TLR4 mutant mice fed a HF diet were divided into four groups (n = 6/group): WT; WT with periodontitis (WT/P); mutant (Mut); and mutant with periodontitis (Mut/P). Periodontitis was induced by placing LPS soaked ligatures around maxillary second molars. Fasting insulin and glucose levels were measured weekly for 10 wk. Glucose tolerance was evaluated at baseline (week 1) and at 9 wk. Insulin signaling (phosphorylation of Akt) and tumor necrosis factor-α (TNF-α) mRNA levels in liver were determined when the mice were killed at week 10.

RESULTS

Mut/P mice developed less alveolar bone loss compared with WT/P mice (p < 0.05). Fasting glucose levels were improved after 8 wk of feeding a HF diet (weeks 9 and 10) in Mut/P mice compared with Mut, WT and WT/P mice (p < 0.05). Glucose tolerance was impaired in all groups compared with baseline (p < 0.05), except for the Mut/P group. Insulin signaling was improved (p < 0.05), and expression of TNF-α was decreased (p < 0.05) in the liver of Mut/P mice compared with the liver of WT/P mice.

CONCLUSION

The TLR4 LOF mutation partially protects against alveolar bone loss and improves glucose homeostasis in mice with periodontitis fed a HF diet.

Bone morphogenic protein 2 directly enhances differentiation of murine osteoclast precursors

Previous studies found that bone morphogenic proteins (BMPs) support osteoclast formation, but it is not clear whether this is a direct effect on osteoclasts or mediated indirectly through osteoblasts. We have shown that a mouse deficient for the BMP antagonist Twisted gastrulation suggested a direct positive role for BMPs on osteoclastogenesis. In this report, we further determine the significance of BMP signaling on osteoclast formation in vitro. We find that BMP2 synergizes with suboptimal levels of receptor activator of NF-kappaB ligand (RANKL) to enhance in vitro differentiation of osteoclast-like cells. The enhancement by BMP2 is not a result of changes in the rate of proliferation or survival of the bone marrow-derived cultures, but is accompanied by an increase in expression of genes involved in osteoclast differentiation and fusion. Treatment with BMP2 did not significantly alter expression of RANKL or OPG in our osteoclast cultures, suggesting that the enhancement of osteoclastogenesis is not mediated indirectly through osteoblasts or stromal cells. Consistent with this, we detected phosphorylated SMAD1,5,8 (p-SMAD) in the nuclei of mononuclear and multinucleated cells in osteoclast cultures. Levels of p-SMAD, BMP2, and BMP receptors increased during differentiation. RNAi suppression of Type II BMP receptor inhibited RANKL-stimulated formation of multinuclear TRAP-positive cells. The BMP antagonist noggin inhibited RANKL-mediated osteoclast differentiation when added prior to day 3, while addition of noggin on day 3 or later failed to inhibit their differentiation. Taken together, these data indicate that osteoclasts express BMP2 and BMP receptors, and that autocrine BMP signaling directly promotes the differentiation of osteoclasts-like cells.

Intracisternal administration of glibenclamide or 5-hydroxydecanoate does not reverse the neuroprotective effect of ketogenic diet against ischemic brain injury-induced neurodegeneration

PRIMARY OBJECTIVE

To investigate the role of ATP-sensitive potassium (K(ATP)) channels in the neuroprotective effects of a ketogenic diet against cardiac arrest-induced cerebral ischemic brain injury-induced neurodegeneration.

RESEARCH DESIGN

Male Sprague Dawley rats were randomly divided into three groups and were fed with a ketogenic diet for 25 days before being subjected to a cardiac arrest-induced cerebral ischemia for 8 minutes 30 seconds. Four hours before cardiac arrest-induced cerebral ischemia, one group was intracisternally injected with glibenclamide, a plasma membrane K(ATP) channel blocker. The second group was injected with 5-hydroxydecanoate, a mitochondrial K(ATP) channel blocker. The third group was without the pre-treatment with K(ATP) channel antagonist. Nine days after the cardiac arrest, rats were sacrificed. Fluoro-jade (FJ) staining was used to evaluate cerebral ischemic neurodegeneration in the rat brain sections.

MAIN OUTCOMES AND RESULTS

The number of FJ-positive degenerating neurons in the CA1 area of the hippocampus, the cerebellum and the thalamic reticular nucleus of the ketogenic diet-fed rats with or without glibenclamide or 5-hydroxydecanoate pre-treatment before cardiac arrest-induced cerebral ischemia is zero.

CONCLUSIONS

The results suggest that K(ATP) channels do not play a significant role in the neuroprotective effects of the ketogenic diet against cardiac arrest-induced cerebral ischemic injury-induced neurodegeneration.

Discovery and structure-activity relationship of 3-methoxy-N-(3-(1-methyl-1H-pyrazol-5-yl)-4-(2-morpholinoethoxy)phenyl)benzamide (APD791): a highly selective 5-hydroxytryptamine2A receptor inverse agonist for the treatment of arterial thrombosis

Serotonin, which is stored in platelets and is released during thrombosis, activates platelets via the 5-HT(2A) receptor. 5-HT(2A) receptor inverse agonists thus represent a potential new class of antithrombotic agents. Our medicinal program began with known compounds that displayed binding affinity for the recombinant 5-HT(2A) receptor, but which had poor activity when tested in human plasma platelet inhibition assays. We herein describe a series of phenyl pyrazole inverse agonists optimized for selectivity, aqueous solubility, antiplatelet activity, low hERG activity, and good pharmacokinetic properties, resulting in the discovery of 10k (APD791). 10k inhibited serotonin-amplified human platelet aggregation with an IC(50) = 8.7 nM and had negligible binding affinity for the closely related 5-HT(2B) and 5-HT(2C) receptors. 10k was orally bioavailable in rats, dogs, and monkeys and had an acceptable safety profile. As a result, 10k was selected further evaluation and advanced into clinical development as a potential treatment for arterial thrombosis.

Tenofovir treatment of primary osteoblasts alters gene expression profiles: implications for bone mineral density loss

There is strong clinical evidence that implicates tenofovir in the loss of bone mineral density during treatment of human immunodeficiency virus infection. In this study, we sought to test the hypothesis that tenofovir treatment of osteoblasts causes changes in the gene expression profile that would impact osteoblast function during bone formation. Primary osteoblasts were isolated and then treated with the tenofovir prodrug, tenofovir disoproxil fumarate (TDF). Total RNA from TDF-treated and untreated osteoblasts were extracted and used for microarray analysis to assess TDF-associated changes in the gene expression profile. Strikingly, the changes in gene expression profiles involved in cell signaling, cell cycle and amino acid metabolism, which would likely impact osteoblast function in bone formation. Our findings demonstrate for the first time that tenofovir treatment of primary osteoblasts results in gene expression changes that implicate loss of osteoblast function in tenofovir-associated bone mineral density loss.

Tenofovir-associated bone density loss

Clinical observations have revealed a strong correlation between loss of bone density in HIV-infected individuals, particularly in conjunction with the antiretroviral drug tenofovir, a nucleotide analog that inhibits HIV reverse transcriptase. The most compelling correlations have been observed in clinical studies involving young children and adolescents. These observations strongly suggest that bone density is being affected during active bone growth and development, implicating a role for tenofovir in bone loss. Here we discuss the literature and potential mechanisms for how tenofovir-associated bone loss may arise, which likely involves perturbation of cellular DNA synthesis and gene expression. Elucidation of the mechanism(s) involved in tenofovir-mediated bone loss will help in developing adjuvant therapies to reduce tenofovir-associated bone density loss.

Downregulation of Gnas, Got2 and Snord32a following tenofovir exposure of primary osteoclasts

Clinical observations have implicated the antiretroviral drug tenofovir with bone density loss during the management of HIV infection. The goal of this study was to investigate the in vitro effects of tenofovir exposure of primary osteoclasts in order to gain insights into the potential mechanisms for the drug-induced bone density loss. We hypothesized that tenofovir may alter the expression of key genes involved in osteoclast function. To test this, primary osteoclasts were exposed to physiologically relevant concentrations of the prodrug tenofovir disoproxil fumarate (TDF), then intensive microarray analysis was done to compare tenofovir-treated versus untreated cells. Specific downregulation of Gnas, Got2 and Snord32a were observed in the TDF-treated cells. The functions of these genes help to explain the basis for tenofovir-associated bone density loss. Our studies represent the first analysis of the effects of tenofovir on osteoclast gene expression and help to explain the basis of tenofovir-associated bone density loss in HIV-infected individuals.

Spinal cord injury causes rapid osteoclastic resorption and growth plate abnormalities in growing rats (SCI-induced bone loss in growing rats)

Spinal cord injury causes severe bone loss. We report osteoclast resorption with severe trabecular and cortical bone loss, decreased bone mineral apposition, and growth plate abnormalities in a rodent model of contusion spinal cord injury. These findings will help elucidate the mechanisms of osteoporosis following neurological trauma.

INTRODUCTION

Limited understanding of the mechanism(s) that underlie spinal cord injury (SCI)-induced bone loss has led to few treatment options. As SCI-induced osteoporosis carries significant morbidity and can worsen already profound disability, there is an urgency to advance knowledge regarding this pathophysiology.

METHODS

A clinically relevant contusion model of experimental spinal cord injury was used to generate severe lower thoracic SCI by weight-drop (10 g x 50 mm) in adolescent male Sprague-Dawley rats. Body weight and gender-matched naïve (no surgery) rats served as controls. Bone microarchitecture was determined by micro-computed tomographic imaging. Mature osteoclasts were identified by TRAP staining and bone apposition rate was determined by dynamic histomorphometry.

RESULTS

At 10 days post-injury we detected a marked 48% decrease in trabecular bone and a 35% decrease in cortical bone at the distal femoral metaphysis by micro-CT. A 330% increase in the number of mature osteoclasts was detected at the growth plate in the injured animals that corresponded with cellular disorganization at the chondro-osseous junction. Appositional growth studies demonstrated decreased new bone formation with a mineralization defect indicative of osteoblast dysfunction.

CONCLUSIONS

Contusion SCI results in a rapid bone loss that is the result of increased bone resorption and decreased bone formation.

Alcohol and malt liquor availability and promotion and homicide in inner cities

We investigated the role of the alcohol environment in explaining disparities in homicide rates among minorities in 10 cities in the United States using 2003 data from the Malt Liquor and Homicide study. We hypothesized that (a) higher concentrations of African Americans would be associated with higher homicide rates, as well as higher alcohol and malt liquor availability and promotion, and (b) the relationship between neighborhood racial/ethnic concentration and homicide would be attenuated by the greater alcohol and malt liquor availability and promotion in African American neighborhoods. Hypotheses were tested using separate Poisson, linear, and logistic regression models that corrected for spatial autocorrelation. Census block groups served as the unit of analysis (n = 450). We found that higher concentrations of African Americans were associated with higher homicide rates as well as greater alcohol availability, especially malt liquor availability. The promotion of malt liquor on storefronts was also significantly greater in African American than in other neighborhoods. However, none of the measures representing alcohol or malt liquor availability and promotion variables changed the effect of neighborhood racial/ethnic concentration on homicide. Limitations and implications of our findings are discussed.

NHA-oc/NHA2: a mitochondrial cation-proton antiporter selectively expressed in osteoclasts

Bone resorption is regulated by a complex system of hormones and cytokines that cause osteoblasts/stromal cells and lymphocytes to produce factors including RANKL, that ultimately result in the differentiation and activation of osteoclasts, the bone resorbing cells. We used a microarray approach to identify genes upregulated in RANKL-stimulated osteoclast precursor cells. Osteoclast expression was confirmed by multiple tissue Northern and in situ hybridization analysis. Gene function studies were carried out by siRNA analysis. We identified a novel gene, which we termed nha-oc/NHA2, which is strongly upregulated during RANKL-induced osteoclast differentiation in vitro and in vivo. nha-oc/NHA2 encodes a novel cation-proton antiporter (CPA) and is the mouse orthologue of a human gene identified in a database search: HsNHA2. nha-oc/NHA2 is selectively expressed in osteoclasts. NHA-oc/NHA2 protein localizes to the mitochondria, where it mediates Na(+)-dependent changes in mitochondrial pH and Na(+) acetate induced mitochondrial passive swelling. RNA silencing of nha-oc/nha2 reduces osteoclast differentiation and resorption, suggesting a role for NHA-oc/NHA2 in these processes. nha-oc/NHA2 therefore is a novel member of the CPA family and is the first mitochondrial NHA characterized to date. nha-oc/NHA2 is also unique in that it is the first eukaryotic and tissue-specific CPA2 characterized to date. NHA-oc/NHA2 displays the expected activities of a bona fide CPA and plays a key role(s) in normal osteoclast differentiation and function.

Prostanoids induce egr1 gene expression in cementoblastic OCCM cells

BACKGROUND AND OBJECTIVE

Prostanoids that activate protein kinase C signaling are potent anabolic stimulators of cementoblastic OCCM cells. Using cDNA subtractive hybridization, we identified early growth response gene-1 (egr1) as a prostanoid-induced gene. Egr1, a zinc-finger transcription factor expressed during tooth development, regulates cell growth and differentiation. We hypothesize that Egr1 may mediate part of the prostanoid-induced anabolic effect in cementoblasts. Our objective was to characterize prostanoid-induced egr1 gene expression in OCCM cells.

MATERIAL AND METHODS

Total RNA and proteins were assayed by northern blot and western immunoblot assays.

RESULTS

Prostaglandin E2-, prostaglandin F2alpha- and fluprostenol-induced egr1 mRNA levels peaked at 0.5 h and returned to baseline by 4 h. Prostaglandin F2alpha and fluprostenol more potently induced egr1 compared with prostaglandin E2. The phorbol ester, phorbol 12-myristate 13-acetate, which activates protein kinase C signaling, induced egr1 mRNA levels 66-fold over the control, whereas forskolin (a cAMP-protein kinase A activator) and ionomycin (a calcium activator) had no effect. Protein kinase C inhibition significantly inhibited prostaglandin E2-, prostaglandin F2alpha- and fluprostenol-induced egr1 mRNA levels. Finally, prostanoids maximally induced Egr1 protein at 1 h.

CONCLUSION

egr1 is a primary response gene induced by prostaglandin E2, prostaglandin F2alpha and fluprostenol in OCCM cells through protein kinase C signaling, suggesting that Egr1 may be a key mediator of anabolic responses in cementoblasts. Cementum is vital for periodontal organ maintenance and regeneration. Periodontal ligament fibers (Sharpey's fibers) insert into bone and cementum, thereby supporting the tooth in the alveolus (1). If the periodontal organ is lost, its regeneration requires cementoblast differentiation in order to form new cementum for periodontal ligament fiber insertion. Early attempts to regenerate cementum have proven difficult and rarely generate sufficient tissue (2). A better understanding of the molecular and cellular regulators that promote cementoblast differentiation is critical for developing targeted periodontal regeneration.

Expression analysis of nha-oc/NHA2: a novel gene selectively expressed in osteoclasts

Bone resorption by osteoclasts is required for normal bone remodeling and reshaping of growing bones. Excessive resorption is an important pathologic feature of many diseases, including osteoporosis, arthritis, and periodontitis [Abu-Amer, Y. (2005). Advances in osteoclast differentiation and function. Curr. Drug Targets. Immune. Endocr. Metabol. Disord. 5, 347-355]. On the other hand, deficient resorption leads to osteopetrosis which is characterized by increased bone mass and may lead to bone deformities or in severe cases to death [Blair, H.C., Athanasou, N.A. 2004. Recent advances in osteoclast biology and pathological bone ddresorption. Histol. Histopathol. 19, 189-199; Del Fattore, A., Peruzzi, B., Rucci, N., Recchia, I., Cappariello, A., Longo, M., Fortunati, D., Ballanti, P., Iacobini, M., Luciani, M., Devito, R., Pinto, R., Caniglia, M., Lanino, E., Messina, C., Cesaro, S., Letizia, C., Bianchini, G., Fryssira, H., Grabowski, P., Shaw, N., Bishop, N., Hughes, D., Kapur, R.P., Datta, H.K., Taranta, A., Fornari, R., Migliaccio, S., and Teti, A. 2006. Clinical, genetic, and cellular analysis of 49 osteopetrotic patients: implications for diagnosis and treatment. J. Med. Genet. 43, 315--325]. Recently, we identified a gene, nha-oc/NHA2, which is strongly up regulated during RANKL-induced osteoclast differentiation in vitro and in vivo. nha-oc/NHA2 encodes a novel cation/proton exchanger that is strongly expressed in osteoclasts. The purpose of this work was to further validate the restricted expression of nha-oc/NHA2 in osteoclasts by in situ hybridization. Our results showed that nha-oc is expressed predominantly in bone. In the head, expression was found in the supraoccipitale bone, calvarium, mandible, and maxilla. Furthermore, nha-oc positive cells co-express the osteoclast markers TRAP and cathepsin k, confirming nha-oc/NHA2 osteoclast localization. However, only a subset of cathepsin k-expressing cells is positive for nha-oc/NHA2, suggesting that nha-oc is expressed by terminally differentiated osteoclasts.

Roles for negative cell regulator 14-3-3sigma in control of MDM2 activities

The 14-3-3sigma, upregulated by p53 in response to DNA damage, can have a positive-feedback impact driving p53 activities and is a human cancer epithelial marker downregulated in various tumors. However, the precise roles of 14-3-3sigma during tumorigenesis are not well characterized. Here, we show that 14-3-3sigma is a critical regulator of murine double minute oncogene (MDM2). 14-3-3sigma interacts with MDM2 at the RING domain. The C-terminal region of 14-3-3sigma binds to MDM2 very efficiently. Importantly, 14-3-3sigma overexpression leads to destabilization of MDM2 through enhancing MDM2 self-ubiquitination and accelerating turnover rate. Conversely, loss of 14-3-3sigma results in a significant increase in MDM2 protein. Moreover, live-cell images indicated that 14-3-3sigma can affect the location of MDM2 from the nucleus to the cytoplasm, and that MDM2-mediated cytoplasmic localization of p53 can be reversed by the presence of 14-3-3sigma. Significantly, we further showed that 14-3-3sigma causes MDM2 downregulation, thereby stabilizing p53 and inhibiting tumor growth in animal tumors. Also, 14-3-3sigma blocks MDM2-mediated retinoblastoma degradation and p53 NEDDylation. Our results provide evidence that 14-3-3sigma is a pivotal MDM2 regulator involved in blocking a variety of activities of MDM2.

Tricritical phenomena at the gamma-->alpha transition in Ce0.9-xLaxTh0.1 alloys

The gamma-->alpha isostructural transition in the Ce0.9-xLaxTh0.1 system is measured as a function of La alloying using specific heat, magnetic susceptibility, resistivity, thermal expansivity or striction measurements. A line of discontinuous transitions, as indicated by the change in volume, decreases exponentially from 118 K to close to 0 K with increasing La doping, and the transition changes from being first-order to continuous at a critical concentration, x(c) approximately 0.14. At the tricritical point, the coefficient of the linear T term in the specific heat gamma and the magnetic susceptibility increase rapidly near x(c) and approach large values at x=0.35 signifying that a heavy Fermi-liquid state evolves at large doping. The Wilson ratio reaches a value above 2 for a narrow range of concentrations near x(c), where the specific heat and susceptibility vary most rapidly with the doping concentration.

Seroprevalence and risk factors of syphilis infection in pregnant women delivering at Harare Maternity Hospital, Zimbabwe

OBJECTIVE

To evaluate risk factors and outcomes of syphilis during pregnancy.

DESIGN

Hospital based, cross sectional study.

SETTING

Harare Maternity Hospital, Harare, Zimbabwe.

SUBJECTS

A random sample of 2 969 pregnant women.

MAIN OUTCOME MEASURES

Syphilis seroprevalence.

RESULTS

Of the 2 969 women who provided blood samples, 4.8% were RPR positive. Approximately 2.2% of study subjects were RPR positive and TPHA negative. Notably, 2.5% of the population was RPR and TPHA positive at the time of giving birth. Older women had a higher risk of having positive syphilis status (p = 0.057). Increases in parity and gravidity were significantly associated with increased risk of syphilis infection. Prior stillbirths were associated with an increased risk of syphilis infection (odds ratio [OR], 3.4; 95% CI, 1.61 to 7.37; p = 0.001). Syphilis positive mothers were significantly more likely to give birth to syphilis positive newborns (p < 0.0001).

CONCLUSIONS

Our results suggest that there should be more effective antenatal screening and treatment of syphilis in Harare. Syphilis affects many sub-Saharan countries where effective educational outreach, screening, and treatment should take place to prevent the transmission of this venereal disease, especially among reproductive age and pregnant women.

The proteasome inhibitor PS-341 inhibits growth and induces apoptosis in Bcr/Abl-positive cell lines sensitive and resistant to imatinib mesylate

BACKGROUND AND OBJECTIVES

Imatinib mesylate (IM) is the choice treatment for Bcr/Abl-positive malignancies. Emergence of resistance to IM warrants the exploration of novel well-tolerated anticancer agents. We intended to evaluate the effect of PS-341 on proliferation, survival, and cellular events in Bcr/Abl-positive cells sensitive and resistant to IM, and to investigate the effect of PS-341 and IM in conjunction.

DESIGN AND METHODS

Bcr/Abl-positive cell lines sensitive (p210Bcr/Abl KBM5, p210Bcr/Abl KBM7, and p190Bcr/Abl Z-119) or resistant (KBM5-R) to IM were treated with PS-341 alone or in combination with IM. The effect on cell growth was determined using the MTT assay. Cell-cycle analysis was performed by propidium iodide staining. Apoptosis was evaluated by measurement of sub-G1 DNA content, annexin V binding, and caspase 3 activity assays. Levels of apoptotic proteins, P-IkBalpha, Bcr/Abl, and phosphorylated Bcr/Abl were determined by western blotting. NF-kappaB activity was evaluated by electromobility gel shift assays.

RESULTS

PS-341 exerted growth inhibition effects in IM-sensitive and -resistant cells. This phenomenon correlated with accumulation of cells in the G2/M phase of cell cycle; transient downregulation of NFkappaB DNA binding activity; downregulation of Bcl-xL; activation of caspase 3, induction of apoptosis; inhibition of expression and phosphorylation of Bcr/Abl. Sequential combination of PS-341 followed by IM demonstrated a synergistic pro-apoptotic effect in IM-sensitive cells; concomitant exposure was antagonistic.

INTERPRETATION AND CONCLUSIONS

PS-341 suppresses growth and induces apoptosis in Bcr/Abl-positive cells sensitive and resistant to IM. The use of PS-341 should be explored in patients with chronic myelogenous leukemia resistant to IM. Trials of combinations of PS-341 and IM require cautious design.