Short interfering RNA against the PDCD5 attenuates cell apoptosis and caspase-3 activity induced by Bax overexpression

Human Amniotic Fluid Mesenchymal Stem Cell-Derived Exosomes Inhibit Apoptosis in Ovarian Granulosa Cell via miR-369-3p/YAF2/PDCD5/p53 Pathway

Human amniotic fluid stem cell-derived exosome (HuAFSC-exosome) transplantation is considered a promising treatment for premature ovarian failure (POF). However, its mechanism remains unclear. In this study, exosomes were isolated and enriched from HuAFSC subsets of CD44+/CD105+, and the exosomes were transplanted into a POF model in vitro and in vivo. Our results confirmed that the exosomes produced by CD44+/CD105+ HuAFSCs could achieve therapeutic effects in a mouse POF model. Our research also showed that CD44+/CD105+ HuAFSC-exosomes carrying miR-369-3p could specifically downregulate the expression of YAF2, inhibit the stability of PDCD5/p53, and reduce the apoptosis of ovarian granulosa cells (OGCs), thereby exerting therapeutic effects on POF. Knowledge of these mechanisms demonstrates that miRNAs carried by CD44+/CD105+ HuAFSC-exosomes are critical to the therapy of POF. This will be useful for the clinical application of stem cells.

Suboptimal folic acid exposure rewires oncogenic metabolism and proteomics signatures to mediate human breast cancer malignancy

Whether treatment with folic acid (FA) affects human breast cancer positively or negatively remains unclear. We subjected human MCF-7 cells, a human breast cancer cell line, to suboptimal FA at low levels (10 nM; LF) and high levels (50 μM; HF) and investigated the molecular mechanisms underlying their effects through metabolic flux and systematic proteomics analyses. The data indicated that LF induced and HF aggravated 2-fold higher mitochondrial toxicity in terms of suppressed oxidative respiration, increased fermented glycolysis, and enhanced anchorage-independent oncospheroid formation. Quantitative proteomics and Gene Ontology enrichment analysis were used to profile LF- and HF-altered proteins involved in metabolism, apoptosis, and malignancy pathways. Through STRING analysis, we identified a connection network between LF- and HF-altered proteins with mTOR. Rapamycin-induced blockage of mTOR complex 1 (mTORC1) signaling, which regulates metabolism, differentially inhibited LF- and HF-modulated protein signatures of mitochondrial NADH dehydrogenase ubiquinone flavoprotein 2, mitochondrial glutathione peroxidase 4, kynureninase, and alpha-crystallin B chain as well as programmed cell death 5 in transcript levels; it subsequently diminished apoptosis and oncospheroid formation in LF/HF-exposed cells. Taken together, our data indicate that suboptimal FA treatment rewired oncogenic metabolism and mTORC1-mediated proteomics signatures to promote breast cancer development.

Ca2+ participates in programmed cell death by modulating ROS during pollen cryopreservation

After cryopreservation, the Ca²⁺ content increased, which affected the intracellular ROS content, then participated in the occurrence of programmed cell death in pollen. Programmed cell death (PCD) is one of the reasons for the decline in pollen viability after cryopreservation. However, the role of calcium ions (Ca²⁺) in PCD during pollen cryopreservation has not been revealed in the existing studies. In this study, Paeonia lactiflora 'Fen Yu Nu' pollen was used as the research material for investigating the effects of Ca²⁺ changes on PCD indices and reactive oxygen species (ROS) during pollen cryopreservation. The results showed that after cryopreservation, with the decrease of pollen viability, the Ca²⁺ content significantly increased. The regulation of Ca²⁺ content had a significant effect on PCD indices, which showed that the Ca²⁺ carrier A23187 accelerated the decrease of mitochondrial membrane potential level and increased the activity of caspase-3-like and caspase-9-like proteases and the apoptosis rate. The expression levels of partial pro-PCD genes were upregulated, the anti-PCD gene BI-1 was downregulated, and the addition of Ca²⁺-chelating agent EGTA had the opposite effect. The addition of the Ca²⁺ carrier A23187 after cryopreservation significantly increased the ROS content of pollen, the addition of the Ca²⁺-chelating agent EGTA had the opposite effect, and Ca²⁺ regulators also had significant effects on the contents of ROS production and clearance-related substances. Ca²⁺ affected intracellular ROS content by acting on the ROS production and clearance system during the cryopreservation of pollen and is thus involved in the occurrence of PCD.

Cryopreserved-pollen viability is regulated by NO-induced programmed cell death

After cryopreservation, the NO content in pollen increased, inducing programmed cell death as a key reason for reduced viability. Low recovery of biomaterials after cryopreservation is a bottleneck that limits the application of this technology. At present, the mechanism of viability decline after cryopreservation is not fully understood. In this study, the effects of nitric oxide (NO) on programmed cell death (PCD) and its relationship with viability were investigated, using Paeonia lactiflora 'Fen Yu Nu' pollen with significantly decreased viability after cryopreservation. The results showed that: the activity of caspase-3-like and caspase-9-like protease and the apoptosis rate of pollen cells were significantly increased, the expression level of the promoting PCD (pro-PCD) genes was up-regulated, while the expression level of the inhibiting PCD (anti-PCD) genes was down-regulated after preservation in liquid nitrogen (LN); the NO content in pollen cells increased significantly after LN exposure. The correlation analysis showed that NO was significantly correlated with pollen viability and all indicators of PCD. The addition of a NO carrier SNP after LN storage reduced pollen viability, increased endogenous NO content, decreased mitochondrial membrane potential level, activated caspase-3-like and caspase-9-like protease in pollen cells, and increased cell apoptosis rate. The expression levels of pro-PCD genes PDCD2 and ATG8CL were significantly up-regulated, while the expression levels of anti-PCD genes DAD1, BI-1 and LSD1 were significantly down-regulated. The addition of NO scavenger c-PTIO improved pollen viability, and produced the opposite effect of sodium nitroferricyanide (III) dihydrate (SNP), but did not change the mitochondrial membrane potential. These results suggest that NO induced PCD during the cryopreservation of pollen, which was one of the reasons for the significant decrease of pollen viability after cryopreservation.

The Effect of Global DNA Methylation on PDCD5 Expression in the PBMC of Occupational Chromate Exposed Workers

OBJECTIVES

To evaluate the alteration of protein of programmed cell death 5 (PDCD5) in peripheral blood mononuclear cells (PBMC) and DNA methylation caused by hexavalent chromium exposure.

METHODS

There were 112 workers and 56 controls in this study. The chromium in RBC and urine, PBMC with PDCD5+, DNA methylation, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and score of DNA damage were measured.

RESULTS

In chromate exposed workers, the percent of PBMC with PDCD5+, urine 8-OHdG, and score of DNA damage were significantly higher, whereas global DNA methylation was significantly lower. The binary logistic regression and generalized linear mixed model analysis showed that the percent of PBMC with PDCD5+ was significantly associated with global DNA hypomethylation.

CONCLUSIONS

The aberrant DNA hypomethylation plays an important role in PBMC apoptosis of occupational hexavalent chromium exposure.

The Molecular Evolution and Functional Divergence of Lamprey Programmed Cell Death Genes

The programmed cell death (PDCD) family plays a significant role in the regulation of cell survival and apoptotic cell death. However, the evolution, distribution and role of the PDCD family in lampreys have not been revealed. Thus, we identified the PDCD gene family in the lamprey genome and classified the genes into five subfamilies based on orthologs of the genes, conserved synteny, functional domains, phylogenetic tree, and conserved motifs. The distribution of the lamprey PDCD family and the immune response of the PDCD family in lampreys stimulated by different pathogens were also demonstrated. In addition, we investigated the molecular function of lamprey PDCD2, PDCD5, and PDCD10. Our studies showed that the recombinant lamprey PDCD5 protein and transfection of the L-PDCD5 gene induced cell apoptosis, upregulated the expression of the associated X protein (BAX) and TP53 and downregulated the expression of B cell lymphoma 2 (BCL-2) independent of Caspase 3. In contrast, lamprey PDCD10 suppressed apoptosis in response to cis-diaminedichloro-platinum (II) stimuli. Our phylogenetic and functional data not only provide a better understanding of the evolution of lamprey PDCD genes but also reveal the conservation of PDCD genes in apoptosis. Overall, our results provide a novel perspective on lamprey immune regulation mediated by the PDCD family.

Chronic sun exposure is associated with distinct histone acetylation changes in human skin

BACKGROUND

Photoageing is attributed to continuous sunlight or artificial ultraviolet exposure and manifests as clinical and histological changes in skin. Epigenetic changes have been found to be involved in the pathogenesis of photoageing. However, the underlying mechanisms are unclear.

OBJECTIVES

To analyse histone modification patterns in sun-exposed and nonexposed skin, and to identify the abnormally histone-modified genes related to photoageing.

METHODS

Skin biopsies were collected from both the outer forearm (sun-exposed area) and the buttock (sun-protected area) in 20 healthy middle-aged female volunteers. Global histone H3/H4 acetylation and H3K4/H3K9 methylation statuses were assessed by enzyme-linked immunosorbent assay. Expression levels of histone acetyltransferases and histone deacetylases were measured by reverse-transcriptase quantitative polymerase chain reaction (qPCR) and Western blot. Chromatin immunoprecipitation combined with DNA microarray (ChIP-chip) assay with anti-acetyl-histone H3 antibody in a sun-exposed pool (combining six sun-exposed skin samples) and a nonexposed pool (combining six nonexposed skin samples) was conducted to explore the abnormally acetylated histone H3 genes related to photoageing; ChIP-qPCR was then used to verify the results of ChIP-chip.

RESULTS

We observed higher global histone H3 acetylation levels increased EP300 and decreased HDAC1 and SIRT1 expression in sun-exposed skin compared with matched nonexposed skin. Furthermore, the ChIP-chip assay showed that 227 genes displayed significant hyperacetylation of histone H3, and 81 genes displayed significant hypoacetylation of histone H3 between the two groups. Histone H3 acetylation levels on the promoters of PDCD5, ITIH5, MMP1 and AHR were positively correlated with the mRNA expression of the corresponding gene.

CONCLUSIONS

Chronic sun exposure-induced histone H3 hyperacetylation may play a critical role in the pathogenesis of skin photoageing.

PDCD5 regulates cell proliferation, cell cycle progression and apoptosis

Programmed cell death (PDCD)5 is cloned from human leukemia cell line TF-1. PDCD5 is one of the members of the programmed cell death protein family that is frequently involved in tumor growth and apoptosis. To investigate the molecular and cellular functions of PDCD5, the present study established a PDCD5 stably overexpressing A431 cell line and examined the role of PDCD5 in cell proliferation, cell cycle progression and apoptosis. The data demonstrated that overexpression of PDCD5 significantly inhibited cell proliferation, induced cell cycle arrest at G2/M phase and apoptosis in A431 cells. The expression profiles of certain key regulators of these cellular events were further investigated, including P53, B cell lymphoma (BCL)-2, BCL-2 associated X protein (BAX) and caspase (CASP)3. The data demonstrated that at the transcript and protein levels, P53, BAX and CASP3 were all upregulated in the PDCD5 stably overexpressing A431 cells whereas BCL-2 was downregulated, indicating that PDCD5 acts as an important upstream regulator of P53, BCL-2, BAX and CASP3. The data suggest that PDCD5 regulates cell proliferation, cell cycle progression and apoptosis in A431 cells. PDCD5 may be a novel tumor suppressor gene, and may be potentially used for cancer treatment in the future.

Protein serine/threonine phosphatase PPEF-1 suppresses genotoxic stress response via dephosphorylation of PDCD5

Programmed cell death 5 (PDCD5) is believed to play a crucial role in p53 activation; however, the underlying mechanism of how PDCD5 function is regulated during apoptosis remains obscure. Here, we report that the serine/threonine phosphatase PPEF-1 interacts with and dephosphorylates PDCD5 at Ser-119, which leads to PDCD5 destabilization. Overexpression of wild-type PPEF-1, but not inactive PPEF-1^D172N, efficiently suppressed CK2α-mediated stabilization of PDCD5 and p53-mediated apoptosis in response to etoposide (ET). Conversely, PPEF-1 knockdown further enhanced genotoxic stress responses. Notably, PPEF-1 suppressed p53-mediated genotoxic stress response via negative regulation of PDCD5. We also determined that overexpression of wild-type PPEF-1, but not inactive PPEF-1^D172N, significantly increased tumorigenic growth and chemoresistance of A549 human lung carcinoma cells. Collectively, these data demonstrate that PPEF-1 plays a pivotal role in tumorigenesis of lung cancer cells by reducing PDCD5-mediated genotoxic stress responses.

Roles of programmed cell death protein 5 in inflammation and cancer (Review)

PDCD5 (programmed cell death 5) is an apoptosis related gene cloned in 1999 from a human leukemic cell line. PDCD5 protein containing 125 amino acid (aa) residues sharing significant homology to the corresponding proteins of species. Decreased expression of PDCD5 has been found in many human tumors, including breast, gastric cancer, astrocytic glioma, chronic myelogenous leukemia and hepatocellular carcinoma. In recent years, increased number of studies have shown the functions and mechanisms of PDCD5 protein in cancer cells, such as paraptosis, cell cycle and immunoregulation. In the present review, we provide a comprehensive review on the role of PDCD5 in cancer tissues and cells. This review summarizes the recent studies of the roles of PDCD5 in inflammation and cancer. We mainly focus on discoveries related to molecular mechanisms of PDCD5 protein. We also discuss some discrepancies between the current studies. Overall, the current available data will open new perspectives for a better understanding of PDCD5 in cancer.

Low dose perfluorooctanoate exposure promotes cell proliferation in a human non-tumor liver cell line

Perfluorooctanoate (PFOA) is a well-known persistent organic pollutant widely found in the environment, wildlife and humans. Medical surveillance and experimental studies have investigated the potential effects of PFOA on human livers, but the hepatotoxicity of PFOA on humans and its underlying mechanism remain to be clarified. We exposed a human liver cell line (HL-7702) to 50μM PFOA for 48h and 96h, and identified 111 significantly differentially expressed proteins by iTRAQ analysis. A total of 46 proteins were related to cell proliferation and apoptosis. Through further analysis of the cell cycle, apoptosis and their related proteins, we found that low doses of PFOA (50-100μM) promoted cell proliferation and numbers by promoting cells from the G1 to S phases, whereas high doses of PFOA (200-400μM) led to reduced HL-7702 cell numbers compared with that of the control mainly due to cell cycle arrest in the G0/G1 phase. To our knowledge, this is the first report on the promotion of cell cycle progression in human cells following PFOA exposure.

AtPDCD5 plays a role during dark-senescence in Arabidopsis

In this work, we investigated the role of an Arabidopsis protein, AtPDCD5, during senescence after a 24h-dark period. Previously, we demonstrated that AtPDCD5 participates in programmed cell death (PCD) after UV-B exposure and in age-induced senescence. The results presented here, together with previous data, demonstrate that AtPDCD5 not only plays an important role during DNA damage responses induced by UV-B radiation, but also takes part in PCD programs such as dark-induced senescence in Arabidopsis.

Cellular functions of programmed cell death 5

Programmed cell death 5 (PDCD5) was originally identified as an apoptosis-accelerating protein that is widely expressed and has been well conserved during the process of evolution. PDCD5 has complex biological functions, including programmed cell death and immune regulation. It can accelerate apoptosis in different type of cells in response to different stimuli. During this process, PDCD5 rapidly translocates from the cytoplasm to the nucleus. PDCD5 regulates the activities of TIP60, HDAC3, MDM2 and TP53 transcription factors. These proteins form part of a signaling network that is disrupted in most, if not all, cancer cells. Recent evidence suggests that PDCD5 participates in immune regulation by promoting regulatory T cell function via the PDCD5-TIP60-FOXP3 pathway. The stability and expression of PDCD5 are finely regulated by other molecules, such as NF-κB p65, OTUD5, YAF2 and DNAJB1. PDCD5 is phosphorylated by CK2 at Ser119, which is required for nuclear translocation in response to genotoxic stress. In this review, we describe what is known about PDCD5 and its cellular functions.

Establishment of a specific cell death induction system in Bombyx mori by a transgene with the conserved apoptotic regulator, mouse Bcl-2-associated X protein (mouse Bax)

The induction of apoptosis in vivo is a useful tool for investigating the functions and importance of particular tissues. B-cell leukaemia/lymphoma 2-associated X protein (Bax) functions as a pro-apoptotic factor and induces apoptosis in several organisms. The Bax-mediated apoptotic system is widely conserved from Caenorhabditis elegans to humans. In order to establish a tissue-specific cell death system in the domestic silkworm, Bombyx mori, we constructed a transgenic silkworm that overexpressed mouse Bax (mBax) in particular tissues by the Gal4-upstream activation sequence system. We found that the expression of mBax induced specific cell death in the silk gland, fat body and sensory cells. Fragmentation of genomic DNA was observed in the fat body, which expressed mBax, thereby supporting apoptotic cell death in this tissue. Using this system, we also demonstrated that specific cell death in sensory cells attenuated the response to the sex pheromone bombykol. These results show that we successfully established a tissue-specific cell death system in vivo that enabled specific deficiencies in particular tissues. The inducible cell death system may provide useful means for industrial applications of the silkworm and possible utilization for other species.

Bifurcation analysis and potential landscapes of the p53-Mdm2 module regulated by the co-activator programmed cell death 5

The dynamics of p53 play important roles in the regulation of cell fate decisions in response to various stresses, and programmed cell death 5 (PDCD5) functions as a co-activator of p53 that modulates p53 dynamics. In the present paper, we investigated how p53 dynamics are modulated by PDCD5 during the deoxyribose nucleic acid damage response using methods of bifurcation analysis and potential landscape. Our results revealed that p53 activities display rich dynamics under different PDCD5 levels, including monostability, bistability with two stable steady states, oscillations, and the coexistence of a stable steady state (or two states) and an oscillatory state. The physical properties of the p53 oscillations were further demonstrated by the potential landscape in which the potential force attracts the system state to the limit cycle attractor, and the curl flux force drives coherent oscillation along the cyclic trajectory. We also investigated the efficiency with which PDCD5 induced p53 oscillations. We show that Hopf bifurcation can be induced by increasing the PDCD5 efficiency and that the system dynamics exhibited clear transition features in both barrier height and energy dissipation when the efficiency was close to the bifurcation point.

In silico identification of genetically attenuated vaccine candidate genes for Plasmodium liver stage

Genetically attenuated parasites (GAPs) that lack genes essential for the liver stage of the malaria parasite, and therefore cause developmental arrest, have been developed as live vaccines in rodent malaria models and recently been tested in humans. The genes targeted for deletion were often identified by trial and error. Here we present a systematic gene - protein and transcript - expression analyses of several Plasmodium species with the aim to identify candidate genes for the generation of novel GAPs. With a lack of liver stage expression data for human malaria parasites, we used data available for liver stage development of Plasmodium yoelii, a rodent malaria model, to identify proteins expressed in the liver stage but absent from blood stage parasites. An orthology-based search was then employed to identify orthologous proteins in the human malaria parasite Plasmodium falciparum resulting in a total of 310 genes expressed in the liver stage but lacking evidence of protein expression in blood stage parasites. Among these 310 possible GAP candidates, we further studied Plasmodium liver stage proteins by phyletic distribution and functional domain analyses and shortlisted twenty GAP-candidates; these are: fabB/F, fabI, arp, 3 genes encoding subunits of the PDH complex, dnaJ, urm1, rS5, ancp, mcp, arh, gk, lisp2, valS, palm, and four conserved Plasmodium proteins of unknown function. Parasites lacking one or several of these genes might yield new attenuated malaria parasites for experimental vaccination studies.

Recombinant human PDCD5 (rhPDCD5) protein is protective in a mouse model of multiple sclerosis

Background

In multiple sclerosis (MS) and its widely used animal model, experimental autoimmune encephalomyelitis (EAE), autoreactive T cells contribute importantly to central nervous system (CNS) tissue damage and disease progression. Promoting apoptosis of autoreactive T cells may help eliminate cells responsible for inflammation and may delay disease progression and decrease the frequency and severity of relapse. Programmed cell death 5 (PDCD5) is a protein known to accelerate apoptosis in response to various stimuli. However, the effects of recombinant human PDCD5 (rhPDCD5) on encephalitogenic T cell-mediated inflammation remain unknown.

Methods

We examined the effects of intraperitoneal injection of rhPDCD5 (10 mg/kg) on EAE both prophylactically (started on day 0 post-EAE induction) and therapeutically (started on the onset of EAE disease at day 8), with both of the treatment paradigms being given every other day until day 25. Repeated measures two-way analysis of variance was used for statistical analysis.

Results

We showed that the anti-inflammatory effects of rhPDCD5 were due to a decrease in Th1/Th17 cell frequency, accompanied by a reduction of proinflammatory cytokines, including IFN-γ and IL-17A, and were observed in both prophylactic and therapeutic regimens of rhPDCD5 treatment in EAE mice. Moreover, rhPDCD5-induced apoptosis of myelin-reactive CD4⁺ T cells, along with the upregulation of Bax and downregulation of Bcl-2, and with activated caspase 3.

Conclusions

Our data demonstrate that rhPDCD5 ameliorates the autoimmune CNS disease by inhibiting Th1/Th17 differentiation and inducing apoptosis of predominantly pathogenic T cells. This study provides a novel mechanism to explain the effects of rhPDCD5 on neural inflammation. The work represents a translational demonstration that rhPDCD5 has prophylactic and therapeutic properties in a model of multiple sclerosis.

The p53 binding protein PDCD5 is not rate-limiting in DNA damage induced cell death

The tumour suppressor p53 is an important mediator of cell cycle arrest and apoptosis in response to DNA damage, acting mainly by transcriptional regulation of specific target genes. The exact details how p53 modulates this decision on a molecular basis is still incompletely understood. One mechanism of regulation is acetylation of p53 on lysine K120 by the histone-acetyltransferase Tip60, resulting in preferential transcription of proapoptotic target genes. PDCD5, a protein with reported pro-apoptotic function, has recently been identified as regulator of Tip60-dependent p53-acetylation. In an effort to clarify the role of PDCD5 upon DNA damage, we generated cell lines in which PDCD5 expression was conditionally ablated by shRNAs and investigated their response to genotoxic stress. Surprisingly, we failed to note a rate-limiting role of PDCD5 in the DNA damage response. PDCD5 was dispensable for DNA damage induced apoptosis and cell cycle arrest and we observed no significant changes in p53 target gene transcription. While we were able to confirm interaction of PDCD5 with p53, we failed to do so for Tip60. Altogether, our results suggest a role of PDCD5 in the regulation of p53 function but unrelated to cell cycle arrest or apoptosis, at least in the cell types investigated.

Transmembrane protein 106A is silenced by promoter region hypermethylation and suppresses gastric cancer growth by inducing apoptosis

Inactivation of tumour suppressor genes by promoter methylation plays an important role in the initiation and progression of gastric cancer (GC). Transmembrane 106A gene (TMEM106A) encodes a novel protein of previously unknown function. This study analysed the biological functions, epigenetic changes and the clinical significance of TMEM106A in GC. Data from experiments indicate that TMEM106A is a type II membrane protein, which is localized to mitochondria and the plasma membrane. TMEM106A was down-regulated or silenced by promoter region hypermethylation in GC cell lines, but expressed in normal gastric tissues. Overexpression of TMEM106A suppressed cell growth and induced apoptosis in GC cell lines, and retarded the growth of xenografts in nude mice. These effects were associated with the activation of caspase-2, caspase-9, and caspase-3, cleavage of BID and inactivation of poly (ADP-ribose) polymerase (PARP). In primary GC samples, loss or reduction of TMEM106A expression was associated with promoter region hypermethylation. TMEM106A was methylated in 88.6% (93/105) of primary GC and 18.1% (2/11) in cancer adjacent normal tissue samples. Further analysis suggested that TMEM106A methylation in primary GCs was significantly correlated with smoking and tumour metastasis. In conclusion, TMEM106A is frequently methylated in human GC. The expression of TMEM106A is regulated by promoter hypermethylation. TMEM106A is a novel functional tumour suppressor in gastric carcinogenesis.

Pretreatment of mice with oligonucleotide prop5 protects them from influenza virus infections

Influenza A virus is a successful parasite and requires host factors to complete its life cycle. Prop5 is an antisense oligonucleotide, targeting programmed cell death protein 5 (PDCD5). In this study, we tested the antiviral activity of prop5 against mouse-adapted A/FM/1/47 strain of influenza A virus in a mouse model. Prop5 intranasally administered the mice at dosages of 10 and 20 mg/kg/d at 24 h and 30 min before infection, provided 80% and 100% survival rates and prolonged mean survival days in comparison with influenza virus-infected mice (both p < 0.01). Moreover, viral titres in mice pretreated with prop5, at dose of 10 and 20 mg/kg/d, had declined significantly on day two, four, and six post-infection compared with the yields in infected mice (p < 0.05 or p < 0.01); lung index in mice pretreated with prop5 (20 mg/kg/d) had been inhibited on day six post-infection (p < 0.05). Western blotting and immunohistochemistry showed that prop5 could down-regulate the PDCD5 protein expression levels in lung tissues of infected mice. These data indicate that antisense oligonucleotide prop5 is a promising drug for prophylaxis and control influenza virus infections and provides an insight into the host-pathogen interaction.

The von Hippel-Lindau tumor suppressor regulates programmed cell death 5-mediated degradation of Mdm2

Functional loss of the von Hippel-Lindau (VHL) tumor suppressor protein (pVHL), which is part of an E3-ubiquitin ligase complex, initiates most inherited and sporadic clear-cell renal cell carcinomas (ccRCC). Genetic inactivation of the TP53 gene in ccRCC is rare, suggesting that an alternate mechanism alleviates the selective pressure for TP53 mutations in ccRCC. Here we use a zebrafish model to describe the functional consequences of pVHL loss on the p53/Mdm2 pathway. We show that p53 is stabilized in the absence of pVHL and becomes hyperstabilized upon DNA damage, which we propose is because of a novel in vivo interaction revealed between human pVHL and a negative regulator of Mdm2, the programmed cell death 5 (PDCD5) protein. PDCD5 is normally localized at the plasma membrane and in the cytoplasm. However, upon hypoxia or loss of pVHL, PDCD5 relocalizes to the nucleus, an event that is coupled to the degradation of Mdm2. Despite the subsequent hyperstabilization and normal transcriptional activity of p53, we find that zebrafish vhl(-/-) cells are still as highly resistant to DNA damage-induced cell cycle arrest and apoptosis as human ccRCC cells. We suggest this is because of a marked increase in expression of birc5a, the zebrafish homolog of Survivin. Accordingly, when we knock down Survivin in human ccRCC cells we are able to restore caspase activity in response to DNA damage. Taken together, our study describes a new mechanism for p53 stabilization through PDCD5 upon hypoxia or pVHL loss, and reveals new clinical potential for the treatment of pathobiological disorders linked to hypoxic stress.

Serum programmed cell death protein 5 (PDCD5) levels is upregulated in liver diseases

Intracellular protein molecules are detected in the blood following release from damaged cells. PDCD5 is widely expressed in most types of normal human tissue and is unregulated in cells undergoing apoptosis. It is therefore hypothesized that release of PDCD5 into the circulation might be a specific marker of apoptosis. In this study, a sandwich ELISA was developed for quantification of soluble PDCD5 protein and used to investigate serum PDCD5 levels in liver diseases. The highest levels of PDCD5 were detected in acute icteric hepatitis (AIH) patients compared with normal subjects and other detected liver diseases, such as chronic active hepatitis B (CAHB), chronic persistent hepatitis B (CPHB) and and liver cirrhosis (LC). Increased PDCD5 levels correlated well with ALT and AST in AIH and CAHB patients. In patients with CPHB, increased PDCD5 levels correlated well with AST, TBI, DBIL, and IBIL. In LC patients, PDCD5 levels correlated well with AST/ALT and DBIL. More importantly, increased PDCD5 levels were also observed in patients with normal ALT or AST levels. These data demonstrate a correlation between increased levels of PDCD5 in serum and liver disease progression and indicate the potential utility of serum PDCD5 as a biomarker for monitoring liver injury.

PDCD5 negatively regulates autoimmunity by upregulating FOXP3(+) regulatory T cells and suppressing Th17 and Th1 responses

Maintenance of FOXP3 protein expression is crucial for differentiation and maturation of regulatory T (Treg) cells, which play important roles in immune homeostasis and immune tolerance. We demonstrate here that PDCD5 interacts with FOXP3, increases acetylation of FOXP3 in synergy with Tip60 and enhances the repressive function of FOXP3. In PDCD5 transgenic (PDCD5tg) mice, overexpression of PDCD5 enhanced the level of FOXP3 protein and percentage of CD4(+)CD25(+)FOXP3(+) cells. Naïve CD4(+) T cells from PDCD5tg mice were more sensitive to TGF-β-induced Treg polarization and expansion. These induced Tregs retained normal suppressive function in vitro. Severity of experimentally-induced autoimmune encephalomyelitis (EAE) in PDCD5tg mice was significantly reduced relative to that of wild-type mice. The beneficial effect of PDCD5 likely resulted from increases of Treg cell frequency, accompanied by a reduction of the predominant pathogenic Th17/Th1 response. Activation-induced cell death enhanced by PDCD5 was also linked to this process. This is the first report revealing that PDCD5 activity in T cells suppresses autoimmunity by modulating Tregs. This study suggests that PDCD5 serves as a guardian of immunological functions and that the PDCD5-FOXP3-Treg axis may be a therapeutic target for autoimmunity.

The involvement of programmed cell death 5 (PDCD5) in the regulation of apoptosis in cerebral ischemia/reperfusion injury

AIMS

Programmed Cell Death 5 (PDCD5) is a protein that accelerates apoptosis in different types of cells in response to various stimuli and is down-regulated in many cancer tissues. We hypothesized in this study that down-regulating PDCD5 can protect the brain from ischemic damage by inhibiting PDCD5-induced apoptotic pathway.

METHODS

One hundred and sixty male Sprague-Dawley rats were randomly assigned to five groups: Sham surgery (n = 25), MCAO (n = 45), MCAO+rhPDCD5 (RhPDCD5) (n = 30), MCAO+control siRNA (n = 30), and MCAO+PDCD5 siRNA (n = 30). At 24 h following MCAO, immunohistochemistry and Western blot were performed.

RESULTS

PDCD5 siRNA reduced the infarct volume, improved neurological deficits, improved cerebral blood flow (CBF), and reduced Evans blue extravasation. Meanwhile, over-expression of PDCD5 protein with recombinant human PDCD5 (rhPDCD5) had an opposite effect. Immunohistochemistry and Western blot demonstrated PDCD5 siRNA decreased the expressions of key proapoptotic proteins such as p53, Bax/Bcl-2, and cleaved caspase-3 in the penumbra areas, whereas rhPDCD5 increased cell apoptosis. Double fluorescence labeling showed the positive immunoreactive materials of PDCD5 were partly colocalized with MAP2, GFAP, CD34, p53, and caspase-3 in the penumbra areas in brain.

CONCLUSIONS

PDCD5-induced apoptosis and over-expression of PDCD5 are harmful to the ischemic neurons in vivo. Meanwhile, the inhibition of PDCD5 may be protective via reducing the apoptotic-related protein such as p53, Bax, and caspase-3. This observation may have potential for the treatment of ischemic cerebral stroke.

Determination of PDCD5 in Peripheral Blood Serum of Cancer Patients

OBJECTIVE

Programmed cell death 5 (PDCD5) is an apoptosis related gene and plays an important role in the pathogenesis and development of cancer. Whether PDCD5 is present in peripheral blood serum has not been reported. The aim of this study is to determine the contents of PDCD5 protein in peripheral blood serum of cancer patients, as well as normal subjects.

METHODS

ELISA was used to detect the serum PDCD5 concentrations in 100 normal persons, 83 patients with breast cancer, 74 patients with gastrointestinal tract cancer and 41 patients with lung cancer. The results were statistically analyzed and discussed.

RESULTS

PDCD5 could be detected in peripheral blood serum in both normal subjects and cancer patients. The serum PDCD5 contents in normal persons ranged from 3.8 to 6.1 ng/ml with a median of 4.70±0.68 ng/ml. For cancer patients the PDCD5 levels were 4.59±0.90, 4.79±1.14 and 10.43±22.34 ng/ml for breast cancer, gastrointestinal cancer and lung cancer patients respectively. There was no statistically significant difference between the serum PDCD5 concentrations of normal persons and cancer patients.

CONCLUSION

PDCD5 is present in peripheral blood. The PDCD5 levels in cancer patients are not statistically different from that of normal persons, though decreased expression of PDCD5 in malignant tissues has been found.

PDCD5 promotes cisplatin-induced apoptosis of glioma cells via activating mitochondrial apoptotic pathway

Glioma is one of the most common primary brain tumors. Despite surgical resection, radiotherapy, and chemotherapy, the prognosis of patients with malignant glioma remains poor. Programmed cell death 5 (PDCD5) is a newly described pro-apoptotic protein. Our previous study showed that PDCD5 downregulation in gliomas was associated with higher pathological grade. Here, we investigated the effect of PDCD5 on chemosensitivity of glioma cells and its mechanism. We demonstrated that overexpression or knockdown of PDCD5 had no significant effect on the proliferation of glioma cell lines (U87, U251, and T98G) in the absence of chemotherapeutic agents. However, PDCD5 overexpression effectively sensitized U87 cells to chemotherapeutic drugs (cisplatin, carboplatin, and vincristine) in a concentration-dependent manner, while its knockdown resulted in decreased chemosensitivity in U251, T98G, and U87 cells. Importantly, expression of PDCD5 also markedly inhibited tumor cell proliferation and colony formation in the presence of low doses of cisplatin. Furthermore, we found that PDCD5 expression promoted cisplatin-induced apoptosis, increased markedly the activation of caspase-3 and caspase-9, and decreased significantly the ratio of Bcl-2/Bax proteins, but had no effect on the activation of caspase-8. Taken together, our findings indicate that PDCD5 promotes chemosensitivity by activating mitochondria-related apoptotic pathway, and that the combination of PDCD5 and chemotherapeutic drugs such as cisplatin, is expected to be an effective therapeutic strategy for the malignant glioma.

PDCD5-regulated cell fate decision after ultraviolet-irradiation-induced DNA damage

Programmed cell death 5 (PDCD5) is a human apoptosis-related molecule that is involved in both the cytoplasmic caspase-3 activity pathway (by regulating Bax translocation from cytoplasm to mitochondria) and the nuclear pathway (by interacting with Tip60). In this study, we developed a mathematical model of the PDCD5-regulated switching of the cell response from DNA repair to apoptosis after ultraviolet irradiation-induced DNA damage. We established the model by combining several hypotheses with experimental observations. Our simulations indicate that the ultimate cell response to DNA damage is dependent on a signal threshold mechanism, and the PDCD5 promotion of Bax translocation plays an essential role in PDCD5-regulated cell apoptosis. Furthermore, the model simulations revealed that PDCD5 nuclear translocation can attenuate cell apoptosis, and PDCD5 interactions with Tip60 can accelerate DNA damage-induced apoptosis, but the final cell fate decision is insensitive to the PDCD5-Tip60 interaction. These results are consistent with experimental observations. The effect of recombinant human PDCD5 was also investigated and shown to sensitize cells to DNA damage by promoting caspase-3 activity.

The anti-tumor role and mechanism of integrated and truncated PDCD5 proteins in osteosarcoma cells

Osteosarcoma (OS) is a high-grade malignant bone tumor. In these studies, the cell apoptosis-related gene, programmed cell death 5 gene (PDCD5), and various fragments of it, were overexpressed in the OS cell line, MG-63. The effects of PDCD5 on MG-63 cells both in vivo and in vitro were then identified. Our results indicate that PDCD5 can induce apoptosis and G(2) phase arrest in MG-63 cells. Moreover, expression of PDCD5 in established xenografted tumors was associated with a decrease in tumor size and weight. Accordingly, the survival rate of these mice was significantly higher than that of mice bearing tumors that did not express PDCD5. To analyze the signaling pathway involved, western blotting was performed. In these assays, PDCD5 was found to inhibit the Ras/Raf/MEK/ERK signaling pathway, leading to inhibition of cyclin B and CDK1. In addition, down-regulation of ERK resulted in activation of caspase 3 and caspase 9. These results are consistent with the G(2) phase arrest observed with overexpression of PDCD5. However, a G(1) phase arrest was not observed. Therefore, proteins associated with the G(1) phase of the cell cycle were overexpressed in combination with PDCD5 overexpression. Overall, these studies demonstrate the anti-tumor activity of PDCD5 in the OS cell line, MG-63, and provide insight into relevant mechanisms that may lead to novel treatments for OS.

Correlation of PDCD5 and apoptosis in hair cells and spiral ganglion neurons of different age of C57BL/6J mice

This study examined the expression pattern of programmed cell death 5 (PDCD5) in cochlear hair cells and spiral ganglion neurons (SGNs) and its association with age-related hearing loss in mice. Sixty C57BL/6J (C57) mice at different ages were divided into four groups (3, 6, 9 or 12 months). PDCD5 expression was detected by using immunohistochemistry, real-time PCR and Western blot. Morphological change of the cochleae was also evaluated by using immunoassay. The results showed that the expression of PDCD5 had a gradual increase with ageing in both protein and RNA levels in C57 mice, as well as gradually increased apoptosis of cochlear hair cells and SGNs. In addition, we also found that caspase-3 activity was enhanced and its expression was enhanced with ageing. It is implied that overexpression of PDCD5 causes the increase in caspase-3 activity and the subsequent increase of apoptosis in cochlear hair cells and SGNs, and thereby plays a role in the pathogenesis of presbycusis. Thus, PDCD5 may be a new target site for the treatment and prevention of age-related hearing loss.

Dissection of DEN-induced platelet proteome changes reveals the progressively dys-regulated pathways indicative of hepatocarcinogenesis

Due to the lack of precise markers indicative of its occurrence, progression, and malignant stages, hepatocellular carcinoma (HCC) is currently associated with high mortality. Given the fact that thrombocytopenia is associated with chronic liver diseases, and the multifunctional nature of platelets we reason that phenotype-specific platelets could be the systemic barometer for hepato-carcinogenesis. The mass spectrometry (MS)-based proteomic efforts to discover novel biomarkers in plasma or serum are largely compromised by a few of the overwhelmingly abundant proteins that comprise over 95% of the total protein mass of plasma or sera. Platelets however are free of these MS signal-suppressing proteins. On the basis of a HCC animal model where diethyl nitrosamine (DEN) administration on male rats specifically induces HCC, by using a multiplex quantitative proteomic approach, we profiled the phase-to-phase proteome changes in a series of viable phenotype-specific platelets along with the DEN-induced progressive liver transformation. The platelet proteome was found highly responsive to each physiological stage of liver inflammation or pathogenesis. Using data-dependent bioinformatics network analysis, we found that certain pathway modules involved in immune response, tissue wound repair, apoptosis, cell proliferation, and catabolism and metabolism were differentially regulated, which were uncovered by the DEN-induced differential expression of the corresponding pathway components. The phase-specific presentations of these pathways suggested that the DEN-induced progression of immune suppression and apoptosis resistance is dynamically coordinated in the platelets. These novel platelet signatures are interconnected in the dynamic networks along with HCC progression and could be identified noninvasively for HCC prognosis and early diagnosis.

Recombinant human PDCD5 sensitizes chondrosarcomas to cisplatin chemotherapy in vitro and in vivo

Clinical management of chondrosarcoma remains a challenging problem, largely due to the toxicity and resistance of this tumor to conventional chemotherapy. Programmed Cell Death 5 (PDCD5) is a protein that accelerates apoptosis in different cell types in response to various stimuli, and has been shown to be down-regulated in many cancer tissues. In this study, mRNA and protein levels of PDCD5 were found to be up-regulated in cisplatin-treated SW1353 chondrosarcoma cells compared with untreated cells. Recombinant human PDCD5 (rhPDCD5) was also shown to sensitize chondrosarcoma cells to cisplatin-based chemotherapy, with inhibition of cell growth and apoptosis detected both in vitro and in vivo. Increased expression of Bax and decreased expression of Bcl-2 were also observed, along with release of cytochrome c from mitochondria into the cytosol. Additionally, cleavage of caspase-9 and caspase-3, as well as the cleavage of poly (ADP-ribose) polymerase (PARP), were detected, suggesting that sensitization of chondrosarcoma cells involves the intrinsic mitochondrial apoptosis pathway. In vivo, the treatment of a xenograft model of chondrosarcoma with rhPDCD5 and cisplatin significantly inhibited tumor cell proliferation and induced apoptosis compared to treatment with cisplatin alone. Overall, these data provide a theoretical basis for the administration of rhPDCD5 and cisplatin for the treatment of patients with chondrosarcoma.

PDCD5 interacts with Tip60 and functions as a cooperator in acetyltransferase activity and DNA damage-induced apoptosis

Tip60 is a histone acetyltransferase (HAT) involved in the acetyltransferase activity and the cellular response to DNA damage. Here, we show that programmed cell death 5 (PDCD5), a human apoptosis-related protein, binds to Tip60 and enhances the stability of Tip60 protein in unstressed conditions. The binding amount of PDCD5 and Tip60 is significantly increased after UV irradiation. Further, PDCD5 enhances HAT activity of Tip60 and Tip60-dependent histone acetylation in both basal and UV-induced levels. We also find that PDCD5 increases Tip60-dependent K120 acetylation of p53 and participates in the p53-dependent expression of apoptosis-related genes, such as Bax. Moreover, we demonstrate the biological significance of the PDCD5-Tip60 interaction; that is, they function in cooperation to accelerate DNA damage-induced apoptosis and knockdown of PDCD5 or Tip60 impairs their apoptosis-accelerating activity, mutually. Consistent with this, PDCD5 levels increase significantly on DNA damage in U2OS cells, as does Tip60. Together, our findings indicate that PDCD5 may play a dual role in the Tip60 pathway. Specifically, under normal growth conditions, PDCD5 contributes to maintaining a basal pool of Tip60 and its HAT activity. After DNA damage, PDCD5 functions as a Tip60 coactivator to promote apoptosis.

Involvement of PDCD5 in the regulation of apoptosis in fibroblast-like synoviocytes of rheumatoid arthritis

Apoptosis is reduced in the synovial tissue of patients with rheumatoid arthritis (RA), possibly due to decreased expression of pro-apoptotic genes. Programmed Cell Death 5 (PDCD5) has been recently identified as a protein that mediates apoptosis. Although PDCD5 is down-regulated in many human tumors, the role of PDCD5 in RA has not been investigated. Here we report that reduced levels of PDCD5 mRNA and protein are detected in RA synovial tissue (ST) and fibroblast-like synoviocytes (FLS) than in tissue and cells from patients with osteoarthritis (OA). We also report differences in the PDCD5 expression pattern in tissues from patients with these two types of arthritis. PDCD5 showed a scattered pattern in rheumatoid synovium compared with OA, in which the protein labeling was stronger in the synovial lining layer than in the sublining. We also observed increased expression and nuclear translocation of PDCD5 in RA patient-derived FLS undergoing apoptosis. Finally, overexpression of PDCD5 led to enhanced apoptosis and activation of caspase-3 in triptolide-treated FLS. We propose that PDCD5 may be involved in the pathogenesis of RA. These data also suggest that PDCD5 may serve as a therapeutic target to enhance sensitivity to antirheumatic drug-induced apoptosis in RA.

Analysis of the bovine neutrophil transcriptome during glucocorticoid treatment

The objective of this study was to characterize a large portion of the bovine neutrophil transcriptome following treatment with the anti-inflammatory glucocorticoid dexamethasone (Dex). Total RNA was isolated from blood neutrophils of healthy cattle (5 castrated male Holsteins) immediately following cell purification (0 h) or after ex vivo aging for 4 h with or without added Dex. Additional neutrophils were cotreated with a glucocorticoid receptor (GR) antagonist (RU486) and Dex for 4 h. RNA was amplified, dye labeled (Cy3 or Cy5), and hybridized to a series of National Bovine Functional Genomics Consortium (NBFGC) microarrays. LOWESS data normalization followed by mixture model analyses showed that 11.15% of the spotted NBFGC cDNAs (2,036/18,263) were expressed in 4-h (untreated) neutrophils. Subsequent two-step mixed-model analysis detected ( P ≤ 0.05) 1,109 differentially expressed genes, of which contrast analysis indicated those that were independently responsive to aging (1,064), Dex (502), RU486 + Dex (141), or RU486 (357). In silico analysis revealed that 416 of the differentially expressed genes are unknown, 59 did not cluster well based on known function, and 634 clustered into 20 ontological categories. Independent validation of differential expression was done for 14 of the putatively Dex-responsive genes across these categories. Results showed that Dex induced rapid translocation of GR into the neutrophil nucleus and signaled dramatic alterations in expression of genes that delay apoptosis, enhance bactericidal activity, and promote tissue remodeling without inflammation or fibrosis. Thus these findings revealed hitherto unappreciated plasticity of blood neutrophils and potentially novel anti-inflammatory/wound-healing actions of glucocorticoids.

Anticancer effects of amooranin in human colon carcinoma cell line in vitro and in nude mice xenografts

Amooranin (AMR), a natural triterpenoid drug isolated and characterized from Amoora rohituka stem bark, is cytotoxic to SW620 human colon carcinoma cell line with an IC(50) value of 2.9 microg/ml. This novel compound caused depolarization of mitochondrial membrane and decrease of membrane potential, indicating initial signal of apoptosis induction. The percentage of cells with decreased mitochondrial potential ranged from 7.4% at 1 microg/ml to 60.5% at 100 microg/ml AMR. Flow cytometric analysis of apoptosis using Annexin-V-FITC staining showed that the percentage of apoptotic cells ranged from 7.5% at 1 microg/ml to 59.2% at 100 microg/ml AMR. AMR-induced apoptosis was accompanied by redistribution of cytochrome c from mitochondria to cytosol as well as down regulation of Bcl-2 and Bcl-X(L) proteins in a dose-dependent manner. SW620 human colon carcinoma xenograft mice treated with AMR showed significant reduction in tumor growth rates compared to saline- and doxorubicin-treated groups. The reduction in tumor growth rate was better in xenografts treated with 2 mg/kg AMR than 5 and 10 mg/kg treated mice. The analysis of global gene expression changes induced by AMR in xenograft tumors by microarray hybridization revealed that several genes involved in energy pathways, transport, apoptosis, immune response, nucleic acid metabolism, protein metabolism, cell growth and/or maintenance, signal transduction and cell communication, were affected by this natural cancer drug. These results suggest that the anticancer properties of AMR in SW620 human colon carcinoma cell line are mediated through its effects on functional genomics, targeting the apoptotic process.