Extracellular Release of Annexin A2 is Enhanced upon Oxidative Stress Response via the p38 MAPK Pathway after Low-Dose X-Ray Irradiation.

The extracellular microenvironment affects cellular responses to various stressors including radiation. Annexin A2, which was initially identified as an intracellular molecule, is also released into the extracellular environment and is known to regulate diverse cell surface events, however, the molecular mechanisms underlying its release are not well known. In this study, we found that in cultured human cancer and non-cancerous cells an extracellular release of annexin A2 was greatly enhanced 1-4 h after a single 20 cGy X-ray dose, but not after exposure to ultraviolet C (UVC) radiation. Extracellular release of annexin A2 was also enhanced after H2O2 and nicotine treatments, which was suppressed by pretreatment with the antioxidant, N-acetyl cysteine. Among the oxidative stress pathway molecules examined in HeLa cells, AMP-activated protein kinase α (AMPKα) and p38 mitogen-activated protein kinase (MAPK) were mostly activated by low-dose X-ray radiation, and the p38 MAPK inhibitor, SB203580, but not compound C (an AMPKα inhibitor), suppressed the enhancement of the annexin A2 extracellular release after low-dose X irradiation. In addition, the enhancement was suppressed in the cells in which p38α MAPK was downregulated by siRNA. HeLa cells and human cultured cells preirradiated with 20 cGy or precultured in media from low-dose X-irradiated cells showed an increase in resistance to radiation-induced cell death, and the increase was suppressed by treatment of the irradiated cell-derived media with anti-annexin A2 antibodies. In addition, extracellularly added recombinant annexin A2 conferred cellular radiation resistance. These results indicate that an oxidative stress-activated pathway via p38 MAPK was involved in the extracellular release of annexin A2, and this pathway was stimulated by low-dose X-ray irradiation. Furthermore, released annexin A2 may function in low-dose ionizing radiation-induced responses, such as radioresistance.

Protein kinase Cα-mediated cytotoxic activity of ineupatorolide B from Inula cappa DC. in HeLa cells.

There is an ongoing search for plant-derived sesquiterpenes, particularly for those with anticancer activity against human cancer cells. The sesquiterpene ineupatorolide B (InB), isolated from the Inula cappa, showed potent growth-inhibitory activity against HeLa cells but less activity against MM1-CB melanoma cells. Staining by terminal deoxynucleotidyl transferase dUTP nick-end labeling method revealed that this activity was, at least in part, due to the induction of apoptosis. The activities of major transcription factors were examined by using a luciferase reporter assay. The results showed that the transactivation ability of nuclear factor of activated T-cell (NFAT) was enhanced. The activation of NFAT by InB was largely suppressed by preincubation with protein kinase C (PKC) inhibitors such as staurosporine and K252a. Western blot analysis revealed that the the levels of phosphorylated PKCα, but not other subtypes, increased after treatment with InB. Knockdown of PKCα using siRNA attenuated the cytotoxic activity of InB. Thus, InB may exhibit growth-inhibitory activity through the activation of PKCα, followed by an increase in NFAT transactivation ability.

Downregulation of microRNA-431 by human interferon-ß inhibits viability of medulloblastoma and glioblastoma cells via upregulation of SOCS6.

miRNAs are small non-coding RNAs that inhibit gene expression by cleaving or hindering the translation of target mRNAs. In this study, we focused on miR-431, which mediated inhibition of cell viability by human interferon-ß (HuIFN-ß). We aimed to demonstrate an antineoplastic effect of HuIFN-ß via miR-431 expression against medulloblastoma and glioblastoma, because HuIFN-ß is frequently used in adjuvant therapy of these tumors. Addition of HuIFN-ß to medulloblastoma and glioblastoma cells reduced viability, significantly decreased miR-431 expression, upregulated expression of SOCS6 (putative miR-431 target genes) and inhibited Janus kinase (JAK) 1 and signal transducer and activator of transcription (STAT) 2. The mitogen-activated protein kinase (MAPK) pathway, but not the phosphoinositide 3-kinase (PI3K)-Akt pathway, was downregulated in medulloblastoma cells, whereas the PI3K-Akt pathway, but not the MAPK pathway, was downregulated in glioblastoma cells. Addition of HuIFN-ß and transient transfection with miR-431 to medulloblastoma and glioblastoma cells did not reduce viability, downregulated expression of SOCS6, and concomitantly activated the JAK1 and STAT2. We propose that, in medulloblastoma and glioblastoma cells, HuIFN-ß decreases miR-431 expression and upregulates SOCS6 expression, and consequently inhibit cell proliferation by suppressing the JAK-STAT signaling pathway.

Expression level of sonic hedgehog correlated with the speed of gastric mucosa regeneration in artificial gastric ulcers.

BACKGROUND AND AIM: Gastric ulcer healing is a complex process involving cell proliferation and tissue remodeling. Sonic hedgehog (Shh) activates the Shh signaling pathway, which plays a key role in processes such as tissue repair. Shh and interleukin 1ß (IL1ß) have been reported to influence the proliferation of gastric mucosa. We evaluated the relationships between the speed of gastric ulcer healing and the levels of expression of Shh and IL1ß. METHODS: The study included 45 patients (mean age 71.9 ± 9.0 years; M/F, 30/15) who underwent endoscopic submucosal dissection (ESD) for gastric cancer, followed by standard dose of oral proton-pump inhibitor for 4 weeks. Subsequently, the size of ESD-induced artificial ulcers were measured to determine the speed of gastric ulcer healing, and regenerating mucosa around the ulcers and appropriately matched controls were collected from patients by endoscopic biopsy. Polymerase chain reaction (PCR) array analysis of genes in the Shh signaling pathway was performed, and quantitative reverse transcription (RT)-PCR was used to measure IL1ß mRNA. RESULTS: The levels of Shh and IL1ß mRNA were 3.0 ± 2.7-fold and 2.5 ± 2.5-fold higher, respectively, in regenerating mucosa of artificial ulcers than in appropriately matched controls, with the two being positively correlated (r = 0.9, P < 0.001). Shh (r = 0.8, P < 0.001) and IL1ß (r = 0.7, P < 0.005) expression was each positively correlated with the speed of gastric ulcer healing, but multivariate analysis showed that Shh expression was the only significant parameter (P = 0.045). CONCLUSIONS: Expression of Shh was correlated with the speed of gastric ulcer healing, promoting the regeneration of gastric mucosa.

Involvement of heat shock protein 27 in the susceptibility of KT human breast cancer cells to UVC and interferon lethality.

Revealing the key molecules regulating the stress-response pathways in human cells is an intriguing problem. Chaperones, such as glucose-regulated protein 78 (GRP78) and heat shock protein 27 (HSP27), are important molecules for protecting the viability of human cells; however, it remains to be further clarified whether the molecules differentially modulate cellular responses to various types of stressors, such as DNA-damaging ultraviolet ray C (principally 254-nm wavelength, UVC) and cytocidal cytokine interferons. In the present study, the human breast cancer cell lines KT and MCF-7 were examined for GRP78 and HSP27 expression following exposure to UVC and human interferon-ß (HuIFN-ß). The KT cells demonstrated a higher sensitivity to both UVC and HuIFN-ß lethality than MCF-7 cells. The cellular expression levels of GRP78 in KT cells, assessed by western blot analysis, were approximately 2-fold higher than that in MCF-7 cells, while the expression of HSP27 in the KT cells was 20% of the expression in the MCF-7 cells. Decreased resistance to UVC lethality was observed in GRP78 siRNA-transfected KT cells. In addition, HSP27 cDNA transfection of KT cells resulted in an increased resistance to UVC lethality. The cDNA-transfected KT cells showed an increased viability against HuIFN-ß, compared with that of empty vector-transfected cells. By contrast, KT cells pretreated with HuIFN-ß and irradiated with UVC demonstrated an increased resistance to UVC lethality, in association with increased levels of HSP27 expression. Thus, HSP27 may control the survival response pathways to both UVC and HuIFN-ß in the human cells examined.

Extracellular release of annexin II from pancreatic cancer cells and resistance to anticancer drug-induced apoptosis by supplementation of recombinant annexin II.

OBJECTIVES: Extracellular microenvironment plays crucial roles in the development of cancers and chemoresistance. Pancreatic carcinoma is resistant to almost all chemotherapeutic agents. In this study, we identified annexin II in the medium from pancreatic cancer cells as a protein released into the extracellular environment. METHODS: Medium from 5-hour cultures of various cancer cells was collected. Proteins in the medium were detected by molecular mass analysis and immunoblotting. Anticancer drug sensitivity of cells preincubated with or without recombinant annexin II (rANX II) was measured using crystal violet assay and colony survival assay. Apoptosis-related molecules were analyzed by immunoblotting. RESULTS: Recombinant ANX II supplementation in the medium confers resistance to anticancer drugs, including cisplatin, 5-fluorouracil, and gemcitabine, in MiaPaCa-2 and AsPC-1 cells. In MiaPaCa-2 cells, rANX II supplementation resulted in suppression of caspase-3 activation associated with increased Bcl-2/Bax ratios. Suppression of cisplatin-induced cell death by rANX II supplementation was canceled by inhibitors of phosphatidylinositol 3-kinase and mitogen-activated protein kinase kinase signal pathways. CONCLUSIONS: The current study is the first report to demonstrate that supplementation of rANX II in the medium increased resistance to anticancer drugs in pancreatic cancer cells. Recombinant ANX II exerts cell death-suppressive function by antagonizing cisplatin-induced apoptosis.

Inhibition of cell viability by human IFN-ß is mediated by microRNA-431.

MicroRNAs (miRNAs) are small non-coding RNAs that inhibit gene expression by cleaving or hindering the translation of target mRNAs. We used microarray-based comparative transcriptome analysis to identify changes in miRNA expression and function between a human cell line, RSa, which is highly sensitive to HuIFN-ß-mediated inhibition of cell viability, and its variant, the F-IFr cell line, which is relatively resistant to the cytokine. miR-431 expression was significantly higher in RSa cells compared with F-IFr cells. The addition of HuIFN-ß to RSa cultures reduced cell viability, down-regulated expression of IGF1R and IRS2 (putative miR-431 target genes), and inhibited the PI3K-Akt and MAPK pathways. The survival of F-IFr cells was not reduced by HuIFN-ß, but transient transfection with miR-431 precursors significantly decreased viability and concomitantly down-regulated IGF1R and IRS2 expression. In addition, the MAPK pathway, but not the PI3K-Akt pathway, was suppressed in F-IFr cells. Based on these results, we propose that, in RSa cells, HuIFN-ß-induced miR-431 expression may down-regulate IGF1R and IRS2 expression, and consequently inhibit cell proliferation by suppressing the MAPK pathway.

Extracellular recombinant annexin II confers UVC-radiation resistance and increases the Bcl-xL to Bax protein ratios in human UVC-radiation-sensitive cells.

In this study, we found that refractoriness to ultraviolet (UVC) light-induced cell death was increased in UVC-radiation-sensitive cells derived from Cockayne syndrome patients when the cells were precultured in medium supplemented with recombinant annexin II (rANX II). In CS3BES cells, an immortal cell line derived from Cockayne syndrome patients, the rANX II supplementation-induced UVC-radiation resistance was suppressed by treatment with an anti-annexin II antibody and EGTA. The amount of biotinylated annexin II on the cell surface increased in the rANX II-supplemented cells but did not increase in the cells that were cotreated with rANX II and EGTA. The capacity to remove UVC-radiation-damaged DNA, (6-4) photoproducts and cyclobutane pyrimidine dimers, was the same in cells that were precultured with rANX II and in control cells that did not receive rANX II supplementation. The rANX II supplementation-induced UVC-radiation resistance was also observed in nucleotide excision repair-deficient cells and xeroderma pigmentosum group A-downregulated cells. The Bcl-xL to Bax protein ratios, an index of survival activity in cells exposed to lethal stresses, were increased in the cells that had been precultured in rANX II for 24 h prior to UVC irradiation. Treatment with a phosphatidylinositol 3-kinase inhibitor suppressed the increased UVC-radiation resistance and Bcl-xL to Bax ratios in the cells with rANX II supplementation. Furthermore, downregulation of Bcl-xL by siRNA transfection also suppressed the UVC-radiation resistance that was induced by rANX II supplementation. These results suggest that the increase in the Bcl-xL to Bax ratios may be associated with enhanced resistance to UVC-radiation-induced cell death.

UVC mutagenicity is suppressed in Japanese miso-treated human RSa cells, possibly via GRP78 expression.

Little is known about the ability of miso, to modulate mutability in human cells. We have observed increased levels of glucose-regulated protein 78 (GRP78) expression in association with suppression of mutation in human RSa cells irradiated with ultraviolet C (UVC). Here we examined to determine whether miso treatment results in increased GRP78 expression and suppression of UVC mutagenicity in RSa cells. Supernatants of water extracts of miso products and their components were tested. In the sample-treated cells, the amount of GRP78, as estimated by RT-PCR and immunoblotting analysis, increased, and the UVC-induced ouabain resistant mutation (Oua(R)) and the K-ras codon 12-base substitution mutation frequency decreased. This decrease was not observed in cells with downregulation of GRP78 by GRP78 siRNA transfection. The results suggest that miso suppresses UVC mutagenicity by increasing GRP78 expression in human cells.

Anti-proliferative and apoptosis-inducible activity of labdane and abietane diterpenoids from the pulp of Torreya nucifera in HeLa cells.

Two abietane and one labdane type diterpenoids were isolated from the methanol extracts of Torreya nucifera pulp and investigated for their ability to inhibit the growth of human cancer cells. Among the three compounds, the labdane compound kayadiol was found to have the most effective inhibitory effect against a wide variety of human cancer cells. Using the MTT assay, kayadiol was determined to have an IC50 (50% inhibition concentration) of 30 µM in HeLa cells, and also to exhibit anti-proliferative effects towards six other human cancer cell lines, with IC50 values of 30-50 µM. Kayadiol treatment of HeLa cells resulted in a dose-dependent generation of apoptotic events, including DNA laddering (≤100 µM). Moreover, kayadiol-treated HeLa cells showed activation of caspases-3 and -9, as well as an increase in the depolarization of mitochondrial membrane potential and the Bax/Bcl-2 ratio. These results indicate that a mitochondria-related apoptotic pathway is involved in the kayadiol-induced death of HeLa cells. Kayadiol is therefore a promising novel anti-proliferative agent and merits further investigation.

Nm23-H1 is responsible for SUMO-2-involved DNA synthesis induction after X-ray irradiation in human cells.

Human cells derived from nevoid basal carcinoma syndrome (NBCCS) patients show increased levels of DNA synthesis activity after X-ray irradiation which is suggested to be casually related to reduction in cellular amounts of small ubiquitin-like protein modifier (SUMO-2/SMT-3A). In the present study, an increased level of DNA synthesis activity was found 8h after X-ray irradiation in HeLa cells with reduction in SUMO-2 amounts by siRNA treatment for SUMO-2. When comparative proteomic analysis was performed between the siRNA and mimic control siRNA treated cells using two-dimensional (2D) electrophoresis and mass spectrometry, three proteins were identified as candidates. Our research focused on Nm23-H1, a nucleoside diphosphate kinase, whose amounts decreased after X-ray irradiation in HeLa cells treated with siRNA for SUMO-2. In the Nm23-H1 siRNA treated cells, induction of DNA synthesis was also detected. Furthermore, in synchronized HeLa cells, DNA synthesis was confirmed in the S phase. Moreover, increased expression of proliferating cell nuclear antigen (PCNA) was observed in Nm23-H1 siRNA treated HeLa cells after X-ray irradiation. In addition, Nm23-H1 was modified with SUMO-2 after X-ray irradiation. The present findings suggest that the reduction of Nm23-H1 is related to the decrease in sumoylation, which in turn, is involved in the induction of DNA synthesis via the regulation of PCNA expression after X-ray irradiation.

Anti-proliferative and apoptosis-inducible activity of Sarcodonin G from Sarcodon scabrosus in HeLa cells.

There is an ongoing search for plant-derived diterpenes, especially for diterpenes with anti-inflammatory activity that also have anti-proliferative effects on human cancer cells. A cyathane-type diterpene, Sarcodonin G (SG), isolated from the mushroom Sarcodon scabrosus and already reported to have anti-inflammatory activity, inhibited proliferation of HeLa cells to the greatest extent among 4 cyathane diterpenes tested. SG showed an IC50 (50% inhibition concentration) of 20 microM, estimated by MTT assay 2 days after culture of cells with the chemical. SG treatment of HeLa cells resulted in dose-dependent generation of apoptotic events such as DNA-laddering (< or =100 microM). Moreover, SG-treated HeLa cells showed activation of caspase-3 and caspase-9 and increase of Bax/Bcl-2 ratios, as analyzed by Western blot analysis. The anti-proliferative effects of SG treatment on HeLa cells were lessened by a caspase inhibitor, Z-VAD-FMK. SG also showed anti-proliferative effects toward 5 other human cancer cell lines with IC50 values of 20-40 microM. Because of these anti-proliferative effects via possible caspase activation, SG holds promise of being a novel anti-proliferative agent deserving further investigation.

Annexin II, a novel HSP27-interacted protein, is involved in resistance to UVC-induced cell death in human APr-1 cells.

Heat shock protein 27 (HSP27) is implicated in diverse biologic functions as a molecular chaperone. We found that HSP27 is involved in the protection of human cells against UVC lethality. To elucidate the molecular mechanisms underlying UVC resistance, we searched for HSP27-interacted proteins related to resistance in UVC-resistant human cells, APr-1. Three candidates for HSP27-interacted proteins were found from cell lysates using an affinity column coupled with GST-fused HSP27 protein. Interaction between HSP27 and two candidates, annexin II and HSP70, was confirmed by immunoprecipitation analysis. After UVC irradiation, the amount of the complex of HSP27 and annexin II decreased in the postnuclear fraction, while it increased in the nuclear fraction. Cells transfected with annexin II-siRNA were more susceptible to UVC lethality. These results suggest that annexin II is a novel HSP27-interacted protein which is involved in UVC resistance in human cells, at least those tested here.

Down-regulation of molecular chaperone 78-kd glucose-regulated protein/immunoglobulin-binding protein expression involved in enhancement of human RS cell mutability.

OBJECTIVES: Enhancement of cell mutability via extracellular materials of cancer cells is a crucial event leading to the development of cancers; however, the activation process of mutability is still not well understood. In this study, to identify the regulatory mechanism of cell mutability, we investigated mutability modulated in response to human pancreatic cancer cell-conditioned medium and identified the candidates for cellular molecules involved in the mutability modulation. METHODS: To test the mutation-modulating effects of the conditioned medium, human RS cells were cultured with medium derived by culturing human pancreatic cancer KP-4 cells, followed by irradiation with UV (mainly 254 nm in wavelength). Mutations were detected by phenotypic ouabain resistance and genetic base substitution of K-ras codon 12. Messenger RNA differential display was used to identify genes that were differentially expressed between conditioned medium-treated and mock-treated RSa cells. The influence of 78-kd glucose-regulated protein/immunoglobulin-binding protein (GRP78/BiP) expression on mutability was assessed by the down-regulation of GRP78/BiP using antisense oligonucleotides or antisense complementary DNA. RESULTS: The UV-induced mutagenicity in RS cells was strengthened by preculture with KP-4 cell-conditioned medium. Messenger RNA differential display revealed that GRP78/BiP expression was suppressed in RS cells after treatment of the conditioned medium. Furthermore, the level of UV-induced mutations was elevated significantly in GRP78/BiP down-regulated cells. CONCLUSIONS: Culture of human RS cells with pancreatic cancer KP-4 cell-conditioned medium resulted in increased UV mutagenicity, possibly via the down-regulation of GRP78/BiP.

Odorant-binding proteins OBP57d and OBP57e affect taste perception and host-plant preference in Drosophila sechellia.

Despite its morphological similarity to the other species in the Drosophila melanogaster species complex, D. sechellia has evolved distinct physiological and behavioral adaptations to its host plant Morinda citrifolia, commonly known as Tahitian Noni. The odor of the ripe fruit of M. citrifolia originates from hexanoic and octanoic acid. D. sechellia is attracted to these two fatty acids, whereas the other species in the complex are repelled. Here, using interspecies hybrids between D. melanogaster deficiency mutants and D. sechellia, we showed that the Odorant-binding protein 57e (Obp57e) gene is involved in the behavioral difference between the species. D. melanogaster knock-out flies for Obp57e and Obp57d showed altered behavioral responses to hexanoic acid and octanoic acid. Furthermore, the introduction of Obp57d and Obp57e from D. simulans and D. sechellia shifted the oviposition site preference of D. melanogaster Obp57d/e(KO) flies to that of the original species, confirming the contribution of these genes to D. sechellia's specialization to M. citrifolia. Our finding of the genes involved in host-plant determination may lead to further understanding of mechanisms underlying taste perception, evolution of plant-herbivore interactions, and speciation.

Down-regulation of SMT3A gene expression in association with DNA synthesis induction after X-ray irradiation in nevoid basal cell carcinoma syndrome (NBCCS) cells.

Fibroblast cells derived from nevoid basal carcinoma syndrome (NBCCS) patients show increased levels of DNA synthesis after X-ray irradiation. Genes, whose expression is modulated in association with the DNA synthesis induction, were searched by using PCR-based mRNA differential display analysis in one of the NBCCS cell lines, NBCCS1 cells. Decreased levels of SMT3A gene expression were found in X-ray-irradiated NBCCS1 cells. This decrease was also shown by RT-PCR analysis in another cell line, NBCCS3 cells. In addition to NBCCS cells, normal fibroblast cells showed the DNA synthesis induction after X-ray irradiation when they were treated with antisense oligonucleotides (AO) for SMT3A. However, treatment of normal fibroblasts with the random oligonucleotides (RO) resulted in decreased levels of DNA synthesis after X-ray irradiation. Thus, down-regulation of SMT3A gene expression may be involved in the DNA synthesis induction after X-ray irradiation in the NBCCS cells at least tested.

Leupeptin-sensitive proteases involved in cell survival after X-ray irradiation in human RSa cells.

Proteases have received attention as important cellular components responsible for stress response in human cells. However, little is known about the role of proteases in the early steps of cell response after X-ray irradiation. In the present study, we first searched for proteases whose activity levels are changed soon after X-ray irradiation in human RSa cells with a high sensitivity to X-ray cell-killing. RSa cells showed an increased level of fibrinolytic protease activity within 10 min after irradiation with X-ray (up to 3 Gy). The induced protease activity was proved to be inhibited by leupeptin. We next examined whether this protease inducibility is related to the X-ray susceptibility of cells. Treatment of RSa cells with leupeptin prior to X-ray irradiation resulted in lowered colony survival and an increased ratio of G(2)/M-arrested cells and apoptotic cells. These results suggest that leupeptin-sensitive proteases are involved in the resistance of human RSa cells to X-ray cell-killing.

Decreased cell survival and DNA repair capacity after UVC irradiation in association with down-regulation of GRP78/BiP in human RSa cells.

In contrast to extensive studies on the roles of molecular chaperones, such as heat shock proteins, there are only a few reports about the roles of GRP78/BiP, an endoplasmic reticulum (ER) stress-induced molecular chaperone, in mammalian cell responses to DNA-damaging stresses. To investigate whether GRP78/BiP is involved in resistance to a DNA-damaging agent, UVC (principally 254 nm in wavelength), we established human cells with down-regulation of GRP78/BiP by transfection of human RSa cells with antisense cDNA for GRP78/BiP. We found that the transfected cells showed higher sensitivity to UVC-induced cell death than control cells transfected with the vector alone. In the antisense-cDNA transfected cells, the removal capacities of the two major types of UVC-damaged DNA (thymine dimers and (6-4) photoproducts) in vivo and DNA synthesis activity of whole cell extracts to repair UVC-irradiated plasmids in vitro were remarkably decreased compared with those in the control cells. Furthermore, the antisense-cDNA transfected cells also showed slightly higher sensitivity to cisplatin-induced cell death than the control cells. Cisplatin-induced DNA damage is primarily repaired by nucleotide excision repair, like UVC-induced DNA damage. The present results suggest that GRP78/BiP plays a protective role against UVC-induced cell death possibly via nucleotide excision repair, at least in the human RSa cells tested.

Protective role of HSP27 against UVC-induced cell death in human cells.

It is an intriguing problem whether heat shock proteins (HSPs) play a protective role in UVC-induced cell death in human cells, and the problem has not been solved. To search for the HSPs involved in UVC resistance, gene expression profiles using cDNA array were compared between UVC-sensitive human RSa cells and their UVC-resistant variant AP(r)-1 cells. The expression levels of heat shock protein 27 (HSP27) were lower in RSa cells than in AP(r)-1 cells. RSa cells transfected with sense HSP27 cDNA showed slightly lower sensitivity to UVC-induced cell death than the control cells transfected with a vector alone and much lower sensitivity than RSa cells transfected with the antisense HSP27 cDNA. Furthermore, the removal capacities of the two major types of UVC-damaged DNA (thymine dimers and (6-4)photoproducts) in the cells with the up-regulation of HSP27 were moderately elevated compared with those in the control cells, while those in the cells with down-regulation were remarkably suppressed. These results suggest that HSP27 is involved in the UVC-resistance of human cells, at least those tested, possibly via functioning in nucleotide excision repair.

Modulation of cell mutability by serum factors from volunteers who experienced head-down-tilt bed rest.

Head-down-tilt bed rest (BR) is utilized to mimic a microgravity environment. In this study, we examined whether the modulating activity of serum factors on cell mutability was changed in seventeen volunteers subjected to BR. For comparison, serum was comparatively obtained from seven volunteers who experienced the parabolic flight (PF). Cultured human cells were treated with serum and then irradiated with UV or X-ray. Mutagenicity was estimated by identification of K-ras codon 12 base substitution mutation, following PCR and differential dot-blot hybridization. Modulating activity was detected in one sample from each of post-BR and post-PF serum.