Clusterin expression during programmed and teratogen-induced cell death in the postimplantation rat embryo

Role of clusterin in the regulation of trophoblast development and preeclampsia

Preeclampsia (PE) threatens the safety of mothers and fetuses, and its pathogenesis is still unclear. Our previous study has found the relationship between PE and serum Clusterin (CLU). This study aimed to investigate the role of CLU on PE. Firstly, levels of CLU in serum and placental tissue from PE patients and healthy pregnancies were compared. Then, RNA sequencing, cell counting kit-8, matrigel invasion, cell apoptosis, and angiogenesis assay were performed to evaluate the role of CLU on primary isolation trophoblast cells. We found the expression of CLU was increased before the clinical syndrome occurred, whereas its level was positively related to the severity of PE. CLU significantly inhibited the expression of matrix metalloproteinase-9 and Vimentin and enhanced E-cadherin to inhibit epithelial-mesenchymal transition of trophoblast cells, further reducing its migration and invasion. Our results suggested that CLU may play a role in regulating trophoblast invasion and migration during placental development, which may be one of the risk factors for PE.

Increased levels of serum clusterin is associated with intrauterine growth restriction and adverse pregnancy outcomes in preeclampsia

AIM

Our aim was to investigate serum clusterin levels in preeclampsia and to determine whether any changes in clusterin levels are useful in distinguishing the presence of concomitant intrauterine growth restriction (IUGR) and in predicting adverse pregnancy outcomes.

METHODS

A prospective case-control study was carried out which included 86 pregnant women (47 patients with preeclampsia and 39 healthy controls). Maternal serum samples obtained from all participants and clusterin levels were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Compared with controls, women with preeclampsia had significantly higher clusterin levels (mean 83.8±23.6 vs. 119.2±40.5, P<0.01). Further analysis revealed the highest clusterin levels were in patients with preeclampsia and IUGR (P<0.001). According to the receiver operating characteristic (ROC) analysis performed for the predictive value of clusterin levels for adverse maternal outcomes, the area under the curve (AUC) was 0.738 (95% CI: 0.616-0.859). The best clusterin cut-off value in predicting adverse maternal outcomes was 102.6 pg/mL with 75% sensitivity and 66% specifity. Multivariable logistic regression analysis revealed serum clusterin levels of >102.6 pg/mL was independently associated with preeclampsia (OR: 6.18, 95% CI: 2.41-15.9) and maternal adverse outcomes (OR: 5.13, 95% CI: 2.01-13.1) and also clusterin levels higher than 117.4 pg/mL were associated with adverse neonatal outcomes (OR: 5.02, 95% CI: 1.04-24.3).

CONCLUSIONS

The current study suggests that increased levels of clusterin is associated with IUGR and probably predictive for adverse pregnancy outcomes in preeclampsia.

Expression of clusterin in normal and preeclamptic placentas

AIM

Clusterin is a multifunctional protein that is up-regulated during many different pathophysiological states. Clusterin may be related to a compensation mechanism involving aggregation of soluble proteins, inhibition of complement-mediated cell damage, adaptive regeneration or apoptosis. Clusterin may increase in response to cell damage that results from hypoxic stress in the preeclamptic placenta. The goal of this study was to measure clusterin expression and localization in normal and preeclamptic placental tissues.

METHODS

Immnunohistochemical and double immunofluorescent staining for clusterin was performed on eight normal and eight preeclamptic placental tissues, and clusterin expression was quantified by Western blotting.

RESULTS

Immunohistochemical analysis of clusterin in placental tissues obtained from normal pregnancies and those with preeclampsia showed localization of clusterin mainly in the syncytiotrophoblasts and villous endothelial cells. In the double immunofluorescent staining, clusterin was detected in the cytoplasm. The Western blot analysis showed that clusterin expression in the placental tissues of the preeclampsia group was significantly higher than in the normal pregnancy group.

CONCLUSIONS

Increased expression of clusterin in placental tissues might play an important role in the pathogenesis of preeclampsia.

Efficient suppression of secretory clusterin levels by polymer-siRNA nanocomplexes enhances ionizing radiation lethality in human MCF-7 breast cancer cells in vitro

Small interfering RNA molecules (siRNA) hold great promise to specifically target cytoprotective factors to enhance cancer therapy. Like antisense RNA strategies, however, the use of siRNA is limited because of in vivo instability. As a first step to overcome delivery issues, a series of graft copolymers of polyethylene glycol and polyethylenimine (PEI-g-PEG) were synthesized and investigated as nontoxic carriers for delivery of siRNA targeting the signaling peptide of secretory clusterin (sCLU), a prosurvival factor that protects cells from ionizing radiation (IR) injury, as well as chemotherapeutic agents. Three copolymers with different PEG grafting densities were tested for their abilities to bind and form nanocomplexes with siRNA. A copolymer composed of 10 PEG grafts (2 kDa each) per PEI polymer (2k10 copolymer) gave the highest binding affinity to siRNA by ethidium bromide exclusion assays, and had the smallest nanocomplex size (115 ± 13 nm diameter). In human breast cancer MCF-7 cells, 2k10–siRNA-sCLU nanocomplexes suppressed both basal as well as IR-induced sCLU protein expression, which led to an over 3-fold increase in IR-induced lethality over 2k10–siRNA scrambled controls. In summary, this study demonstrates the proof-of-principle in using nanoparticle-mediated delivery of specific siRNAs to enhance the lethality of IR exposure in vitro, opening the door for siRNA-mediated knockdown of specific cytoprotective factors, such as DNA repair, antiapoptotic, free radical scavenging, and many other proteins.

Conduction system abnormalities in rat embryos induced by maternal hyperthermia

Maternal hyperthermia induces severe malformations in the central nervous system (CNS) in both humans and laboratory animals. These phenomena are accompanied by apoptotic cell death, especially in the developing CNS. Cardiovascular malformations in conjunction with skeletal and CNS abnormalities have been reported in embryos of laboratory animals. In rats, hyperthermic treatment at 43 degrees C for 15 min at day 9 of pregnancy induced various severe external malformations in embryos, such as exencephaly, spina bifida, microphthalmia, anophthalmia, facial cleft or defect, generalized edema, and cardiovascular abnormalities. Examination of the embryonic heart revealed abnormal formation of the conduction system. Although hyperthermia causes marked hemodynamic defects, we could not obtain direct proof of a link between hemodynamic alteration by hyperthermia and malformations of the conduction system.

Ligands of peroxisome proliferator-activated receptor-gamma induce apoptosis in AR42J cells

INTRODUCTION

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a ligand-activated transcription factor that controls growth, differentiation, and inflammation in different tissues. Roles of PPAR-gamma activation in pancreatic acinar cells are poorly characterized.

AIMS

To examine the effects of PPAR-gamma activation on the induction of apoptosis in rat pancreatic AR42J cells.

METHODOLOGY

AR42J cells were treated with ligands of PPAR-gamma, and induction of apoptosis was evaluated by cell viability, DNA-fragmentation, and flow cytometry.

RESULTS

Treatment of the cells with ligands of PPAR-gamma (15-deoxy-open triangle12,14-prostaglandin J2 or troglitazone) induced apoptosis in a dose-dependent manner. Troglitazone-induced apoptosis was not blocked by inhibitors of caspases (acetyl-DEVD-aldehyde and benzoyloxycarbonyl-VAD-fluoromethylketone). Troglitazone induced the expression of pancreatitis-associated protein-1 and clusterin mRNAs. Troglitazone activated c-Jun NH2-terminal kinase/stress-activated protein kinase, but inhibited the activation of extracellular signal-regulated kinases 1/2. Troglitazone did not activate NF-kappaB, suggesting a role of NF-kappaB-independent pathways. In AR42J cells and isolated pancreatic acini, PPAR-gamma gene and protein were detected. In addition, troglitazone increased the PPAR-dependent transcriptional activity, suggesting that PPAR-gamma is functional in AR42J cells.

CONCLUSION

These results indicate that activation of PPAR-gamma induces apoptosis in AR42J cells and imply that PPAR-gamma may be a potential therapeutic target of pancreatic inflammation, because of its anti-inflammatory effects in addition to its proapoptotic effects.

Expression of clusterin in pancreatic acinar cell injuries in vivo and in vitro

Clusterin is a secretory glycoprotein that is highly induced in several tissues in response to injury. The pathophysiologic significance of clusterin in the pancreas remains largely unknown. The aim of this work was to examine whether clusterin is expressed in spontaneous chronic pancreatitis in the WBN/Kob rat and to investigate the relationship between clusterin and apoptosis in pancreatic acinar AR4-2J cells. In the in vivo study, 4-week-old male WBN/Kob rats developed chronic pancreatitis at 12 weeks. Clusterin mRNA was expressed after 12 weeks and then decreased. Immunohistochemistry showed clusterin expression in the acinar cells. In the in vitro study, clusterin mRNA and protein were strongly induced in AR4-2J cells treated either with arginine, menadione, tumor necrosis factor-alpha or transforming growth factor-beta1. In the time course study with arginine or menadione, clusterin mRNA was expressed after 4 hours and peaked at 8 and 24 hours, whereas DNA fragmentation peaked at 72 hours. Our results show that clusterin is overexpressed in the pancreas at the onset of chronic pancreatitis in vivo and in cultured acinar cells in response to various stimuli in vitro, suggesting that clusterin is a defense mechanism of the exocrine pancreas.

Lysophosphatidylcholine induces apoptosis in AR42J cells

Phospholipase A2 (PLA2) has been suggested to play an important role in the pathogenesis of acute pancreatitis, in part through the PLA2-generated phospholipid by-products, most notably lysophosphatidylcholine (lyso-PC). The effects of lyso-PC on pancreatic acinar cells, other than the induction of necrosis, are poorly characterized. Here we examined the effects of lyso-PC on the induction of apoptosis in rat pancreatic AR42J cells. Lyso-PC induced apoptosis in a dose-dependent manner at 10 and 25 microM, but induced cell lysis at > or = 50 microM. Lyso-PC-induced (at 25 microM) apoptosis was not blocked by a protein kinase C inhibitor (staurosporine) or by inhibitors of caspases (acetyl-DEVD-aldehyde and benzoyloxycarbonyl-VAD-fluoromethylketone). Lyso-PC at 10 and 25 microM induced the expression of clusterin mRNA and wild-type p53. Apoptosis induction by lyso-PC (at 25 microM) was not inhibited by a specific antagonist of platelet-activating factor (PAF) receptor, suggesting that the action was independent of th

Clusterin protects granulosa cells from apoptotic cell death during follicular atresia

Clusterin expression is associated with programmed cell death (apoptosis) in many cell types but its exact role has not yet been defined. This study was carried out to determine the cellular localization of clusterin in the ovary and its functional role in the apoptotic cell death of ovarian follicles. A homogenous population of healthy and atretic follicles was obtained by treating immature rats with pregnant mare serum gonadotropin (PMSG). Apoptotic cell death was evaluated by TUNEL. Clusterin expression in the healthy and atretic follicles was examined by immunohistochemical and Western blot analyses, and gene expression was examined by Northern blot analysis. Clusterin protein and its mRNA are only expressed in granulosa cells of atretic follicles obtained from PMSG-treated rats on day 5 of the treatment. Healthy follicles from PMSG-treated rats on day 2 of the treatment do not express clusterin. Theca and stroma cells of both healthy and atretic follicles showed no signs of apoptosis and did not express clusterin. Withdrawal of trophic support from granulosa cells in cultures to induce apoptosis resulted in a dramatic increase in the levels of clusterin and its mRNA compared to cells cultured in serum-supplemented medium. In an attempt to establish the functional role of clusterin in the apoptotic cell death of ovarian follicles, the biosynthesis of clusterin in granulosa cells of healthy follicles was blocked by treatment of cells with antisense oligonucleotide to its cDNA. Treatment of granulosa cells with the antisense oligonucleotide resulted in an increase in the apoptotic cell death compared to the control. These findings indicate that depletion of clusterin can lead to the programmed cell death in ovary, suggesting a functional role for this protein in follicular atresia.

Isolation of Ku70-binding proteins (KUBs)

DNA-dependent protein kinase (DNA-PK) plays a critical role in resealing DNA double-stand breaks by non-homologous end joining. Aside from DNA-PK, XRCC4 and DNA ligase IV, other proteins which play a role(s) in this repair pathway remain unknown; DNA-PK contains a catalytic subunit (DNA-PKcs) and a DNA binding subunit (Ku70 and Ku80). We isolated Ku70-binding proteins (KUB1-KUB4) using yeast two-hybrid analyses. Sequence analyses revealed KUB1 to be apolipoprotein J (apoJ), also known as X-ray-inducible transcript 8 (XIP8), testosterone-repressed prostate message-2 (TRPM-2) and clusterin. KUB2 is Ku80. KUB3 and KUB4 are unknown, >10 kb trans-cripts. Interactions of apoJ/XIP8 or KUB3 with Ku70 were confirmed by co-immunoprecipitation analyses in MCF-7:WS8 breast cancer or IMR-90 normal lung fibroblast cells, respectively. The interaction of apoJ/XIP8 with Ku70 was confirmed by far-western analyses. Stable over-expression of full-length apoJ/XIP8 in MCF-7:WS8 caused decreased Ku70/Ku80 DNA end binding that was restored by apoJ/XIP8 monoclonal antibodies. The role of apoJ/XIP8 in ionizing radiation resistance/sensitivity is under investigation.

Clusterin biogenesis is altered during apoptosis in the regressing rat ventral prostate

Clusterin was first characterized as an apoptosis-associated transcript after it was identified as testosterone-repressed prostate message (TRPM-2) that is expressed in the epithelial cells of the regressing rat ventral prostate. Increases in clusterin mRNA and protein have been consistently detected in apoptotic cell death paradigms, establishing clusterin gene expression as a prominent marker of apoptotic cell loss. However, enhanced protein expression has also been reported in surviving cells. This ambiguity makes it difficult to define the contribution of clusterin to apoptosis. To address this problem, a panel of polyclonal and monoclonal antibodies were raised against the clusterin alpha-chain, beta-chain, and mixed alpha/beta epitopes. These antibodies detect changes in the biogenesis of clusterin during apoptosis by Western analysis and immunohistochemistry. A 42-kDa glyco/isoform of clusterin appears to be up-regulated in dying epithelial cells. This glyco/isoform is apparently generated as a result of apoptosis-induced stimulation of a normal but under-utilized, synthetic pathway. These data demonstrate that clusterin synthesized by apoptotic cells can be immunologically distinguished from clusterin synthesized by surviving cells in damaged tissue.

Induction of thermotolerance in early postimplantation rat embryos is associated with increased resistance to hyperthermia-induced apoptosis

Previously we reported that hyperthermia (43 degrees C) induces cell death in neurulation stage rat embryos as part of the pathogenesis culminating in abnormal growth and development. We now show that hyperthermia-induced cell death occurs by a process termed apoptosis. DNA fragmentation, a hallmark of apoptosis, was noted as early as 2.5 hr after embryos were exposed to 43 degrees C. A smaller but significant increase in DNA fragmentation was also observed in embryos exposed to 42 degrees C, but only at the 5 hr time point. In control embryos, TUNEL-positive apoptotic bodies were consistently observed in the neuroepithelium at the point of neural tube closure and in the optic stalk. In embryos exposed to 43 degrees C, the number of TUNEL-positive apoptotic bodies was significantly increased. Using both gel electrophoresis and TUNEL, we also show that the induction of thermotolerance is associated with a significant reduction in DNA fragmentation. Together our results show that specific programmed cell death and hyperthermia-induced cell death correlate with internucleosomal DNA fragmentation characteristic of apoptosis. Finally, we show that the induction of thermotolerance in rat embryos is associated with a significant reduction in internucleosomal DNA fragmentation and associated apoptosis.

Simpson-Golabi-Behmel syndrome: genotype/phenotype analysis of 18 affected males from 7 unrelated families

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked overgrowth disorder recently shown to be caused by mutations in the heparan sulfate proteoglycan GPC3 [Pilia et al., Nat Genet; 12:241-247 1996]. We have used Southern blot analysis and polymerase chain reaction amplification of intra-exonic sequences to identify four new GPC3 mutations and further characterize three previously reported SGBS mutations. De novo GPC3 mutations were identified in 2 families. In general, the mutations were unique deletions ranging from less than 0.1 kb to more than 300 kb in length with no evidence of a mutational hot spot discerned. The lack of correlation between the phenotype of 18 affected males from these 7 families and the location and size of the GPC3 gene mutations suggest that SGBS is caused by a nonfunctional GPC3 protein.

Joint patterning defects caused by single and double mutations in members of the bone morphogenetic protein (BMP) family

The mouse brachypodism locus encodes a bone morphogenetic protein (BMP)-like molecule called growth/differentiation factor 5 (GDF5). Here we show that Gdf5 transcripts are expressed in a striking pattern of transverse stripes within many skeletal precursors in the developing limb. The number, location and time of appearance of these stripes corresponds to the sites where joints will later form between skeletal elements. Null mutations in Gdf5 disrupt the formation of more than 30% of the synovial joints in the limb, leading to complete or partial fusions between particular skeletal elements, and changes in the patterns of repeating structures in the digits, wrists and ankles. Mice carrying null mutations in both Gdf5 and another BMP family member, Bmp5, show additional abnormalities not observed in either of the single mutants. These defects include disruption of the sternebrae within the sternum and abnormal formation of the fibrocartilaginous joints between the sternebrae and ribs. Previous studies have shown that members of the BMP family are required for normal development of cartilage and bone. The current studies suggest that particular BMP family members may also play an essential role in the segmentation process that cleaves skeletal precursors into separate elements. This process helps determine the number of elements in repeating series in both limbs and sternum, and is required for normal generation of the functional articulations between many adjacent structures in the vertebrate skeleton.

Induction of heat shock protein 27 in rat embryos exposed to hyperthermia

Previously we reported that eight proteins were reproducibly induced in postimplantation rat embryos exposed to a brief heat shock (43 degrees C, 15 min). The major heat-inducible rat embryo protein has now been identified as heat shock protein 72 (Hsp 72). In addition, the induction of Hsp 72 is temporally correlated with induction of thermotolerance. One of the other rat embryo proteins previously shown to be induced by elevated temperature is a heat shock protein of approximately 27 kilodaltons (Hsp 27). In this report we show that this protein is recognized by an antibody directed against a conserved peptide sequence of Hsp 27. Unlike Hsp 72, Hsp 27 is constitutively expressed in the rat embryo in the absence of any thermal stress; however, the level of Hsp 27 is increased approximately 2-3-fold after thermal stress (43 degrees C, 10 min). Immunohistochemical analysis revealed that the constitutively expressed Hsp 27 is localized primarily to cells of the heart, cells that are uniquely resistant to the cytotoxic effects of hyperthermia. After thermal stress, Hsp 27 is expressed in all tissues of the embryo. Finally, our data show that Hsp 27 exists in the rat embryo as three major isoforms indicative of different phosphorylation states. Furthermore, most Hsp 27 in the heart is phosphorylated, whereas in the rest of the embryo, nonphosporylated Hsp 27 predominates. After thermal stress, levels of phosphorylated isoforms increase dramatically in nonheart tissues of the embryo. Together, these results suggest that Hsp 27 may play a role in the development of thermotolerance in the postimplantation mammalian embryo.