Transglutaminase 2 expression in the salivary myoepithelial cells of mouse embryo

Earlier a strong transient expression of transglutaminase 2 (TGase 2) localized at the anchoring sites of muscle bundles in human embryo was observed. In this study, we report a similar transient expression of the TGase 2 in the salivary myoepithelial cells of mouse embryo by immunohistochemistry, RNA in situ hybridisation, and RT-PCR. From 35 submandibular glands of mouse embryos and postnatal mice, a consistent expression of TGase 2 in the myoepithelial cells via a stage-specific manner was identified by mono-clonal antibody to TGase 2 immunostaining. A similar expression pattern of TGase 2 in the myoepithelial cells was also observed by RNA in situ hybridisation analysis. The expression of TGase 2 in the salivary epithelium and mesenchyme during the prenatal 14.5-15.5 days was found minimally diffusely spread and became intensely focalised in the myoepithelial cells of salivary acini and ducts during the prenatal 16.5-18.5 days but thereafter gradually decreased until postnatal 7 days and remained weak in postnatal 3 weeks. Such transient rise and fall expressions of TGase 2 were also found with the sequential amount of RT-PCR products during the same period. The alpha-smooth muscle actin (alpha-SMA) as a positive control in the myoepithelial cells of mouse submandibular glands was consistently expressed during the prenatal and postnatal period. These results of transient expression of TGase 2 in the myoepithelial cells coincided with the formation of the dendritic basket structure in the periphery of acini and ducts, suggest a possible catalytic role of transglutaminase in a newly formed cellular matrixes during the cytodifferentiating stage of mouse prenatal and neonatal submandibular glands.

Subacute toxicity evaluation of a new camptothecin anticancer agent CKD-602 administered by intravenous injection to rats

The subacute toxicity of a new camptothecin anticancer agent, CKD-602, was investigated after 4-week repeated intravenous administration of the chemical in Sprague-Dawley rats. The test chemical was administered intravenously to rats at dose levels of 0, 0.003, 0.013, or 0.067 mg/kg/day for males and 0, 0.004, 0.018, or 0.089 mg/kg/day for females. At the end of the treatment period, 10 rats/sex/group were sacrificed. The remaining 5 rats/sex in the vehicle control and high dose groups continued the study without treatment for 2 weeks (recovery period). During the test period, clinical signs, mortality, body weights, food and water consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weights, and histopathology were examined. In both sexes of the high dose group, an increase in the incidence of abnormal clinical signs and paleness of the eyes, a reduction in the body weight gain, food consumption and urine protein, and an increase in the water consumption were observed. Hematological investigations revealed a decrease in the red blood cells, hemoglobin and hematocrit and an increase in the mean corpuscular volume, mean corpuscular hemoglobin, platelets, and reticulocytes in a dose-dependent manner. Serum total cholesterol and total protein values were lower in females than those of controls, but not in males. An increase in the heart and liver weights and a decrease in the thymus weight were also found. Histopathological alterations included an increase in the incidence of atrophy of the sternal marrow, atrophy, fibrosis and mast cell hyperplasia of the femoral marrow, atrophy of the white pulp and extramedullary hematopoiesis of the spleen, atrophy of the thymus, auricular hypertrophy of the heart, extramedullary hematopoiesis and centriacinar telangiectasis of the liver, follicular degeneration of the ovary, and inflammation of the tail. The major treatment-related effects were not recovered at the end of 2-week recovery period. There were no adverse effects in the low and middle dose groups of both genders. In the present experimental conditions, the target organs were determined to be bone marrow, blood cells, spleen, liver, thymus, and heart. The no-observed-adverse-effect level was considered to be 0.013 mg/kg/day for males and 0.018 mg/kg/day for females.

Orphan nuclear receptor small heterodimer partner represses hepatocyte nuclear factor 3/Foxa transactivation via inhibition of its DNA binding

Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor and acts as a coregulator of various nuclear receptors. Herein, we examined a novel cross talk between SHP and a forkhead transcription factor HNF3 (hepatocyte nuclear factor 3/Foxa. Transient transfection assay demonstrated that SHP inhibited the transcriptional activity of all three isoforms of HNF3, HNF3alpha, beta, and gamma. In vivo and in vitro protein interaction studies showed that SHP physically interacted with HNF3. Adenovirus-mediated overexpression of SHP significantly decreased the mRNA levels of glucose-6-phosphase (G6Pase), cholesterol 7-alpha-hydroxylase (CYP7A1), and phosphoenolpyruvate carboxykinase (PEPCK) in HepG2 cells and rat primary hepatocytes. Moreover, the mRNA level of G6Pase was notably increased by down-regulation of SHP with small interfering RNA. Interestingly, HNF3 transactivity was still repressed by SHPDelta128-139 that fails to repress nuclear receptors. Mapping of interaction domain revealed that SHP interacted with forkhead DNA binding domain of HNF3alpha. Gel mobility shift and chromatin immunoprecipitation assays demonstrated that SHP inhibits DNA binding of HNF3. These results suggest that SHP is involved in the regulation of G6Pase, CYP7A1, and PEPCK gene expression via novel mechanism of inhibition of HNF3 activity and expand the role of SHP as a coregulator of other family of transcription factors in addition to nuclear receptors.

Functional efficiency of the senescent cells: replace or restore?

It is generally accepted that aging is a phenomenon of irreversibility, inevitability, and universality with parenchymal loss and functional decline. Consequently, the major goals of aging research are focused on the development of a replace strategy of the aged organs or cells, based on immortalizing tools, stem cells, or artificial substitutes. Recently, however, a new concept of functional recovery has been introduced on the basis of the functional restoration of the responsiveness of the senescent cells toward a variety of agonists, including growth factors. The aging phenotypes of hyporesponsiveness and morphological alteration are shown to be readily adjusted by modulation of the several membrane-associated molecules, named gatekeeper molecules, among which caveolin is one of the major determinants. Caveolin is the essential component of the caveolae, responsible for regulation of signal transduction, endocytosis and trancytosis, and cytoskeletal arrangement via its scaffolding domain. The caveolin status is associated strictly with cellular transformation, if depleted, and with senescent phenotype, if overexpressed. Therefore, simple reduction of caveolin status in senescent cells leads to restoration of the functional responsiveness to mitogenic stimuli and even of the cellular shape. These data strongly suggest that the gatekeeper molecules, represented by caveolin, may play the prime role in determination of the senescent phenotypes. From these results, it can be summarized that the replace principle would not necessarily be the essential one, but the restore principle can be somehow substituted for the betterment of the aged cells and organisms.

Morphological adjustment of senescent cells by modulating caveolin-1 status

Morphological change is one of the cardinal features of the senescent phenotype; for example, senescent human diploid cells have a flat large shape. However, the mechanisms underlying such senescence-related morphological alterations have not been well studied. To investigate this situation, we characterized the senescence-dependent changes of cellular structural determinants in terms of their levels and activities. These determinants included integrins, focal adhesion complexes, and small Rho GTPases, and special emphasis was placed on their relationships with caveolin-1 status. We observed that the expression integrin beta(1) and focal adhesion kinase (FAK) were increased and that the phosphorylations of FAK and paxillin, hallmarks of focal adhesion formation, were also increased in senescent human diploid fibroblast cells. Moreover, the Rho GTPases Rac1 and Cdc42 were found to be highly activated in senescent cells. In addition, focal adhesion complexes and Rho GTPases were up-regulated in the caveolin-rich membrane domain in the senescent cells. Activated Rac1 and Cdc42 directly interacted with caveolin-1 in senescent cells. Interestingly, caveolin-1 knock-out senescent cells, achieved by using small interfering RNA and antisense oligonucleotide, showed disrupted focal adhesion formation and actin stress fibers via the inactivation of FAK, which resulted in morphological adjustment to the young cell-like small spindle shape. Based on the results obtained, we propose that caveolin-1 plays an important role in senescence-associated morphological changes by regulating focal adhesion kinase activity and actin stress fiber formation in the senescent cells.

Nur77 activated by hypoxia-inducible factor-1alpha overproduces proopiomelanocortin in von Hippel-Lindau-mutated renal cell carcinoma

Mutation in the von Hippel-Lindau (VHL) protein associated with renal cell carcinoma causes hypoxia-inducible factor (HIF) to stabilize and consequently to induce various HIF-targeting proteins. In this study, we found that proopiomelanocortin (POMC), an adrenocorticotropic hormone precursor, is up-regulated constitutively in VHL-mutated renal cell carcinoma. A critical transcription factor responsible for POMC overproduction was identified as Nur77, a member of the orphan steroid receptor superfamily. Little is known about how VHL mutation leads to activation of Nur77. We report that Nur77 is directly regulated by HIF. We show that HIF-1alpha, but not HIF-2alpha, binds to a putative HIF responsive element in the Nur77 promoter, activating the expression of Nur77. Mutation or deletion of the HIF binding site in the Nur77 promoter abrogates activation of a luciferase reporter gene under the control of Nur77 promoter by HIF-1alpha. The treatment of Nur77 antisense oligonucleotide reduces POMC transcription under hypoxic conditions. We confirmed that Nur77 and POMC are up-regulated in VHL-mutated renal cell carcinoma. In this study, we provide the first molecular evidence that Nur77 activated by HIF under hypoxic conditions regulates production of the peptide hormone precursor POMC.

Aging-associated increase of gelsolin for apoptosis resistance

Gelsolin, a Ca(2+)-dependent actin regulatory protein, was recently suggested to participate in apoptosis regulation. In this study, we found that the level of gelsolin is elevated in senescent human diploid fibroblasts (HDFs) and also in the tissues of old rats, i.e., in the liver, kidney, heart, spleen, stomach, and brain, etc. The ubiquitous increase of gelsolin in the aged organs and cells led us to assume that it might be related with one of the cardinal senescent phenotypes, aging-associated apoptosis resistency. Thus, we tested the sensitivity of senescent cells to apoptosis by menadione, an apoptosis-inducing agent, before and after the down-regulation of gelsolin. The down-regulation of gelsolin in senescent HDFs, independently of Bcl-2 family expression, resulted in an increased sensitivity to menadione-induced apoptotic cell death. The observed ubiquitous increase of gelsolin in the senescent states of cells and tissues, and the increased sensitivity to apoptosis-induction by gelsolin down-regulation, suggests that gelsolin would be partly responsible for age-related apoptosis resistance.

Molecular cloning, chromosomal mapping, and characteristic expression in tooth organ of rat and mouse Krox-25

A novel member of the Krox family of proteins, designated Krox-25, was identified by screening clones from the cDNA libraries of a rat incisor and mouse embryo craniofacial tissue. Rat and mouse Krox-25 mRNAs are about 2.4 kb long, encoding 225 and 224 amino acids, respectively. Krox-25 consists of five zinc finger motifs homologous to the Drosophila Krüppel segmentation gene and also contains several consensus amino acid sequences for a protein kinase C binding domain. Northern blot analysis revealed an intense expression of Krox-25 mRNA in rat and mouse teeth, although it was expressed weakly in other tissues, including calvaria, brain, lung, thymus, kidney, and submandibular gland of mouse. In situ hybridization showed that Krox-25 mRNA began to be expressed weakly in the early odontogenic mesenchyme and primitive enamel epithelium located at the apical end of the rat incisor, and Krox-25 expression increased in the presecretory ameloblasts and became intense in the secretory ameloblasts. This expression was also similar to the results of immunohistochemistry and Western blot, especially the Krox-25 localization in the nuclei of enamel epithelial cells. These results suggest that Krox-25 plays an important role as a transcription factor for the cytodifferentiation and amelogenesis of enamel epithelium.

Muscle fibre size and capillarity in Korean diving women

AIM

Effects of prolonged habitual cold-water immersion on fibre size and capillarity in vastus lateralis muscle were studied in human beings. The hypothesis tested in the present study was that cold acclimatized human skeletal muscle would have reduced muscle fibre size and higher capillarity, favouring the idea of efficacy of recruitment under cold environment.

METHODS

Ten women breath-hold divers (BHDs) and 10 active women (controls CONs) participated in this study. Muscle biopsy was obtained from vastus lateralis and determined fibre type composition and capillary density.

RESULTS

A major finding was that all BHDs revealed a markedly smaller cross-sectional area (CSA) in all fibre types than the CONs, or even than any other morphological data reported in previous investigations. Furthermore, mean CSA of type II fibre (range 1205-2766 microm2) was much smaller than type I fibre (2343-4327 microm2). The number of capillaries per fibre in different fibre types in the BHDs was higher than in the CONs (P < 0.001), and diffusional area was smaller in type II fibres than in type I fibres (P < 0.001). The BHDs and the CONs have similarity in the percentage of type I fibres, but type II fibre was predominant in both groups. Interestingly the proportion of type IIx fibre in the BHDs was higher (31%) than in the CONs (22%). No significant difference was found in the thigh circumference between the groups.

CONCLUSION

The present study demonstrates that prolonged habitual cold-water immersion may induce a decrease in fibre size and an increase in capillarity in human skeletal muscle.

Analysis of the effect of aging on the response to hypoxia by cDNA microarray

Little is known about the detail of hypoxia-responsive gene expression patterns in advanced age, even though aging is thought to be partially associated with a decreased response to hypoxia. In the present study, we identified several hypoxia-inducible genes and investigated the effect of aging on hypoxic gene expression profiles using cDNA microarray analysis of young/old human diploid fibroblasts. Of 7458 genes in the microarray, we found that genes involved in angiogenesis, defense against oxidative stress, and transcription regulation are severely impaired in senescent cell, which is consistent with the fact that aged cells have attenuated responses to various stimuli.

The in vitro effects of dehydroepiandrosterone on human osteoarthritic chondrocytes

OBJECTIVE

To investigate the in vitro effects of dehydroepiandrosterone (DHEA) on human osteoarthritic chondrocytes.

DESIGN

Chondrocytes isolated from human osteoarthritic knee cartilage were three-dimensionally cultured in alginate beads, except for cell proliferation experiment. Cells were treated with DHEA in the presence or absence of IL-1beta. The effects on chondrocytes were analyzed using a 3-(4,5-dimethylthiazol-2yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS) assay (for chondrocyte proliferation), a dimethylmethylene blue (DMB) assay (for glycosaminoglycan (GAG) synthesis), and an indole assay (for DNA amount). Gene expressions of type I and II collagen, metalloproteinase-1 and -3 (MMP-1 and -3), and tissue inhibitor of metalloproteinase-1 (TIMP-1) as well as the IL-1beta-induced gene expressions of MMP-1 and -3 were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). The protein synthesis of MMP-1 and -3 and TIMP-1 was determined by Western blotting.

RESULTS

The treatment of chondrocytes with DHEA did not affect chondrocyte proliferation or GAG synthesis up to 100 micro M of concentration. The gene expression of type II collagen increased in a dose-dependent manner, while that of type I decreased. DHEA suppressed the expression of MMP-1 significantly at concentrations exceeding 50 micro M. The gene expression of MMP-3 was also suppressed, but this was without statistical significance. The expression of TIMP-1 was significantly increased by DHEA at concentrations exceeding 10 micro M. The effects of DHEA on the gene expressions of MMP-1 and -3 were more prominent in the presence of IL-1beta, in which DHEA suppressed not only MMP-1, but also MMP-3 at the lower concentrations, 10 and 50 micro M, respectively. Western blotting results were in agreement with RT-PCR, which indicates that DHEA acts at the gene transcription level.

CONCLUSIONS

Our study demonstrates that DHEA has no toxic effect on chondrocytes up to 100 micro M of concentration and has an ability to modulate the imbalance between MMPs and TIMP-1 during OA at the transcription level, which suggest that it has a protective role against articular cartilage loss.

Immunocytochemical evidence that amyloid beta (1-42) impairs endogenous antioxidant systems in vivo

Amyloid beta, the major constituent of the senile plaques in the brains of patients with Alzheimer's disease, is cytotoxic to neurons and has a central role in the pathogenesis of the disease. We have previously demonstrated that potent antioxidants idebenone and alpha-tocopherol prevent learning and memory impairment in rats which received a continuous intracerebroventricular infusion of amyloid beta, suggesting a role for oxidative stress in amyloid beta-induced learning and memory impairment. To test the hypothesis, in the present study, we investigated alterations in the immunoreactivity of endogenous antioxidant systems such as mitochondrial Mn-superoxide dismutase, glutathione, glutathione peroxidase and glutathione-S-transferase following the continuous intracerebroventricular infusion of amyloid beta for 2 weeks. The infusion of amyloid beta (1-42) resulted in a significant reduction of the immunoreactivity of these antioxidant substances in such brain areas as the hippocampus, parietal cortex, piriform cortex, substantia nigra and thalamus although the same treatment with amyloid beta (40-1) had little effect. The alterations induced by amyloid beta (1-42) were not uniform, but rather specific for each immunoreactive substance in a brain region-dependent manner. These results demonstrate a cytological effect of oxidative stress induced by amyloid beta (1-42) infusion. Furthermore, our findings may indicate a heterogeneous susceptibility to the oxidative stress produced by amyloid beta.

Senescent phenotype can be reversed by reduction of caveolin status

Hyporesponsiveness to growth factors is one of the fundamental characteristics of senescent cells. We previously reported that the up-regulation of caveolin attenuates the growth factor response and the subsequent downstream signal cascades in senescent human diploid fibroblasts. Therefore, in the present experiment, we investigated the modulation of caveolin status in senescent cells to determine the effect of caveolin on mitogenic signaling efficiency and cell cycling. We reduced the level of caveolin-1 in senescent human diploid fibroblasts using its antisense oligonucleotides and small interfering RNA, and this resulted in the restoration of normal growth factor responses such as the increased phosphorylation of Erk, the nuclear translocation of p-Erk, and the subsequent activation of p-Elk upon epidermal growth factor stimulation. Moreover, DNA synthesis and the re-entry of senescent cells into cell cycle were resumed upon epidermal growth factor stimulation concomitantly with decreases in p53 and p21. Taken together, we conclude that the loss of mitogenic signaling in senescent cells is strongly related to their elevated levels of caveolin-1 and that the functional recovery of senescent cells at least in the terms of growth factor responsiveness and cell cycle entry might be achieved simply by lowering the caveolin level.

Distributions of ACE and APOE polymorphisms and their relations with dementia status in Korean centenarians

BACKGROUND

Genetic polymorphisms of angiotensin-converting enzyme (ACE) and apolipoprotein E (APOE) have been reported to be associated with human longevity and dementia in the elderly. However, whether such putative longevity genes exert the same effects on different ethnic groups living in different environments is not well known.

METHODS

We investigated the distributions of the ACE and APOE genotypes and their relations with dementia status in Korean centenarians by cross-sectional study. A total of 103 centenarians (13 men and 90 women, mean age 102.4 +/- 2.6 years) were included in this study. The allele frequencies of the genes were compared with those of two control groups: 7232 apparently healthy adults (4100 men and 3132 women) of mean age 48.5 +/- 9.6 years for the ACE genotyping, and 6435 adults (5008 men and 1427 women) of mean age 50.7 +/- 7.9 years for the APOE genotyping. The dementia status of the centenarians was assessed by clinical psychologist using the Clinical Dementia Rating (CDR) score.

RESULTS

The frequencies of genotypes and alleles of the ACE and APOE genes of the centenarians were not significantly different from those of the control groups. There was a lack of association between presence of the D allele on the ACE gene and dementia status. However, the frequency of the epsilon4 allele of the APOE gene was significantly higher in centenarians with dementia than in centenarians without definitive dementia (9.1% versus 1.5%, p <.05).

CONCLUSIONS

These results suggest that neither the ACE nor the APOE gene is significantly associated with longevity in the Korean population, but that the APOE epsilon4 allele is still related with dementia even at age 100 and older.

Solubilization of waste activated sludge by alkaline pretreatment and biochemical methane potential (BMP) tests for anaerobic co-digestion of municipal organic waste

Biochemical methane potential (BMP) tests have been carried out to determine the anaerobic digestibility of the waste activated sludge (WAS) and the sludge pretreated by NaOH (PWAS). The optimal NaOH dosage was determined to be 45 meq NaOH/L. The maximum SCOD solubilization was 27.7, 31.4 and 38.3% at the temperatures of 25, 35 and 55 degrees C respectively after 4 hours reaction. The final methane yield of simulated food waste (SFW) was 430 ml CH4/g VS(added), and those of PWAS (25 degrees C), PWAS (35 degrees C) and PWAS (55 degrees C) was 274, 286 and 310 ml CH4/g VS(added) respectively after 20 days. The figures were 66%, 73% and 88% higher than that of WAS. The methane production in anaerobic co-digestion is considerably affected by the fraction of SFW and PWAS in the feed. The anaerobic digestibility of the feed mixture (SFW with PWAS) is higher than that of the feed mixture (SFW with WAS). Anaerobic co-digestion of food waste with the PWAS is found to be an attractive option to reduce the solid waste volume with improved methane recovery.

Biological conversion of wood hydrolysate to succinic acid by Anaerobiospirillum succiniciproducens

Anaerobiospirillum succiniciproducens grew on a minimal salts medium containing wood hydrolysate (equivalent to 27 g glucose l(-1)) and, when supplemented with 10 g corn steep liquor l(-1) as a complex nitrogen source, succinic acid at 24 g l(-1) was obtained (yield = 88% w/w glucose). This may therefore be an economical method to produce succinic acid.

Age-dependent agonist-specific dysregulation of membrane-mediated signal transduction: emergence of the gate theory of aging

Although a general mechanism for the limited responsiveness of senescent cells has yet to be established, reduced responsiveness may in part be ascribed to deficits in the apparatus required for cell surface receptor-mediated signal transduction. Age-related changes of receptor-mediated signal transduction occur at many levels, and are known to include quantitative and qualitative changes in growth factor receptors, G-protein coupled receptors, and many other downstream signaling molecules. Here, we emphasize the prime role of the cellular surface in the perception and transmission of external stimuli in response to the aging process. As major means of cellular signal transduction, the receptor tyrosine kinase (RTK) system and the G protein-coupled receptor (GPCR) system of senescent cells were investigated. We observed that the RTK system was severely damaged, while the GPCR system was only partially inactivated by aging. These results suggest that the agonist-dependent dysregulation of and imbalance of signal transduction pathways might be responsible for the functional deterioration of senescent cells, and indicate a possibility of the functional recovery of senescent cells through agonist-specific signal system activation. Moreover, those data evoke the emerging concept that the senescent phenotype may be modulated by the membrance-associated signal system, implying the gate theory of aging.