Biomedical subjects

Hiroshi Kogo

Publications and source records attributed to Hiroshi Kogo.

At least 19 recordsLinked to original sources

PubMed2006

Palindrome-mediated chromosomal translocations in humans.

Recently, it has emerged that palindrome-mediated genomic instability contributes to a diverse group of genomic rearrangements including translocations, deletions, and amplifications. One of the best studied examples is the recurrent t(11;22) constitutional translocation in humans that has been well documented to be mediated by palindromic AT-rich repeats (PATRRs) on chromosomes 11q23 and 22q11. De novo examples of the translocation are detected at a high frequency in sperm samples from normal healthy males, but not in lymphoblasts or fibroblasts. Cloned breakpoint sequences preferentially form a cruciform configuration in vitro. Analysis of the junction fragments implicates frequent double-strand-breaks (DSBs) at the center of both palindromic regions, followed by repair through the non-homologous end joining (NHEJ) pathway. We propose that the PATRR adopts a cruciform structure in male meiotic cells, creating genomic instability that leads to the recurrent translocation.

AT Rich Sequence↗

PubMed2006

Chromosomal translocations mediated by palindromic DNA.

There is evidence accumulating to suggest that non-B DNA structures have a potential for genomic instability that induces genomic rearrangements including translocations and deletions. One of the best studied examples is the recurrent t(11;22) constitutional translocation in humans that is mediated by palindromic AT-rich repeats (PATRRs) on chromosomes 11q23 and 22q11. Cloned breakpoint sequences favor adopting a cruciform configuration in vitro. Analysis of the junction fragments implicates frequent double-strand-breaks at the center of both palindromic regions, followed by repair through the nonhomologous end joining pathway. De novo examples of the translocation are detected at a substantial frequency in sperm samples from normal healthy males, but not in other normal somatic tissues or cell lines derived from humans. Further our recent findings indicate that polymorphism of the PATRR affects the frequency of de novo translocation events and symmetrical alleles preferentially generate the translocation. We propose that the symmetric PATRR is likely to adopt a cruciform structure in male meiotic cells, creating genomic instability that leads to the recurrent translocation.

Animals↗

PubMed2006

Relationship between prostaglandin E2 and vascular endothelial growth factor (VEGF) in angiogenesis in human vascular endothelial cells.

To address the role of prostaglandin E2 (PGE2) in tube formation of endothelial cells and the relationships between the action of PGE2 and vascular endothelial growth factor (VEGF), cultured human umbilical vein endothelial cells (HUVECs) were used to evaluate tube formation on Matrigel and the expression of angiogenesis-related genes. PGE2 treatment stimulated the tube-like formation of HUVECs. Whereas VEGF-induced tube formation was significantly suppressed by ETYA, an inhibitor of arachidonic acid metabolism, or SU5614, an inhibitor of VEGF-receptor tyrosine kinase, the stimulatory effect of PGE2 was observed in the presence of ETYA or SU5614. Thus, PGE2 counteracted both ETYA- and SU5614-induced blockage of angiogenesis in the presence of VEGF. VEGF induced cyclooxygenase (COX) -2 mRNA expression in HUVECs and increased the PGE2 concentration in the medium. PGE2 treatment enhanced the expression of VEGF mRNA. These findings suggest that PGE2 directly stimulates angiogenesis, apart from VEGF signaling, and further induces VEGF expression in HUVECs. In addition, the effect of VEGF on angiogenesis may be mediated, in part, by PGE2 secretion.

5,8,11,14-Eicosatetraynoic Acid↗

PubMed2006

Genetic variation affects de novo translocation frequency.

Translocation is one of the most frequently occurring human chromosomal aberrations. The constitutional t(11;22)(q23;q11), which is the only known recurrent non-Robertsonian translocation, represents a good model for studying translocations in humans. Here we demonstrate polymorphisms of the palindromic sequence at the t(11;22) breakpoint that affect the frequency of de novo translocations in sperm from normal males. A typical allele consists of a perfect palindrome, producing ~10-5 de novo t(11;22) translocations. Alleles with an asymmetric center do not form the t(11;22). Our data show the importance of genome sequence on chromosomal rearrangements, a class of human mutation that is thought to be random.

AT Rich Sequence↗

PubMed2006

Differential expression of caveolin-3 in mouse smooth muscle cells in vivo.

Expression of caveolin-1 and -3 in mouse smooth muscle cells in vivo was examined by immunohistochemistry. Caveolin-1 was detected in almost all smooth muscles examined, except for the pupillary dilator muscle, whereas caveolin-3 was present only in smooth muscles of some specific tissues. In the eye, the pupillary sphincter muscle was intensely positive for caveolin-3, whereas the ciliary muscle and pupillary dilator muscle were negative. In the gastrointestinal tract, caveolin-3 was detected in the inner circular layer, but not in the outer longitudinal layer. Vascular smooth muscle cells of the resistance-sized artery in the uterus and corpus cavernosum were intensely positive for caveolin-3, whereas those of the aorta were only weakly positive and those of the vena cava were negative. Caveolin-3 was also detected in smooth muscle cells of the urinary bladder, ureter, prostatic vas deferens, and seminal vesicle. The different levels of caveolin-3 expression among various smooth muscle tissues were confirmed by Western blot analysis. Even within the same muscle, the relative expression levels of caveolin-1 and -3 were variable among neighboring cells, suggesting distinct fine regulation of expression of these two caveolins. Moreover, even in the same cell, caveolin-1 and -3 showed different distributions. These results indicate that the two caveolins form distinct caveolae in smooth muscles, and that caveolin-1 and -3 serve different functions. Their differential expression may therefore be related to the functional diversity of smooth muscles.

Animals↗

PubMed2006

Expression of stathmin family genes in the murine uterus during early pregnancy.

Stathmin, a cytosolic phosphoprotein that regulates microtubule dynamics during cell-cycle progression, is abundantly expressed at embryo implantation sites in rats. Here, we characterized the expression of stathmin and its family genes in the murine uterus during the peri-implantation period. Stathmin protein was expressed in the glandular and luminal epithelium, blood vessels, and stromal cells on day 3 of pregnancy. On the day of implantation (day 5), stathmin was mainly localized in blood vessels in the endometrium. On day 7, intense stathmin expression was limited to capillary vessels and secondary decidual cells. Stathmin expression was higher at implantation sites than at uterine segments between implantation sites and increased during oil-induced decidualization. Although the artificially-induced deciduoma weights and number of implantation sites were similar between stathmin-knockout (KO) and wild-type (WT) mice, the stathmin-KO mice had fewer newborn pups (reduced by 30%). The expression of alkaline phosphatase, desmin, and cyclin D3 was attenuated in decidual zones of stathmin-KO mice. Messenger RNA level of the stathmin family gene, SCG10, was high at the time of decidualization in WT and stathmin-KO mice. In contrast, the others of stathmin family members, SCLIP and RB3 were highly expressed in stathmin-KO mice compared to WT mice. These results suggest that stathmin and stathmin family genes are expressed in the murine endometrium with enhanced expression in the implantation or the decidualization process.

Animals↗

PubMed2006

Capillary morphogenesis gene (CMG)-1 is among the genes differentially expressed in mouse male germ line stem cells and embryonic stem cells.

We recently established a technique to expand male germ line stem (GS) cells in long-term culture without losing their spermatogenic capacity. To gain insight into the genetic program of these cells, we compared the mRNA expression profile of GS cells with that of embryonic stem (ES) cells using DNA microarrays. We found 79 genes that were upregulated in GS cells compared to ES cells, including synaptonemal complex protein-1, deleted in azoospermia-like, ubiquitin-conjugating enzyme E2B, and ubiquitin carboxy-terminal hydrolase L1, all of which are functionally important for spermatogenesis. In addition, we identified a cDNA encoding the mouse ortholog of capillary morphogenesis gene (CMG)-1. CMG-1 transcripts were predominantly produced in spermatogonia and spermatocytes in mouse testis. When CMG-1 expression was attenuated in a mouse spermatocyte-derived cell line, GC-2spd(ts), by a target-specific short interfering RNA, the morphology of the cells was changed and the expression of cyclin D2 was abrogated. A reporter assay using a genomic region upstream of the mouse cyclin D2 gene revealed that this downmodulation occurs at the transcriptional level. We detected FLAG-tagged CMG-1 protein in the nuclei of transfected COS7 cells, suggesting that CMG-1 may play a unique role in the transcriptional regulation of the cyclin D2 gene. The upregulated GS genes identified in this study will provide useful information for the future investigation of spermatogonial stem cells and the early phase of male germ cell differentiation.

Animals↗

PubMed2006

Inhibition of the progression of aortic calcification by etidronate treatment in hemodialysis patients: long-term effects.

To confirm the inhibitory effect of etidronate on the progression of vascular calcification (VC), 21 patients were randomly enrolled. All 21 patients had end-stage renal disease and were undergoing hemodialysis (HD) three times per week. Patients were observed clinically for 12 months before etidronate treatment and then etidronate was given orally just prior to sleep on the days of dialysis for 23 months. The aortic calcification area (ACA) increased significantly during the 12 months before etidronate treatment. While the ACA of the drug-treated group did not change 12 and 23 months after the initiation of etidronate treatment, the ACA in the control group was significantly elevated 23 months later. These results strongly indicate that etidronate inhibits the progression of VC. Bone mineral density did not change during etidronate treatment. Our findings suggest that etidronate might effectively protect against progressive VC in HD patients.

Aortic Diseases↗

PubMed2006

Expression of stathmin in human uterus and decidualizing endometrial stromal cells.

The cytosolic phosphoprotein stathmin is upregulated at the site of embryo implantation in the rodents. However, stathmin expression in the human uterus has not yet been investigated. The distribution of uterine and placental stathmin was analyzed by immunohistochemistry, while stathmin mRNA expression was detected in endometrial tissues by the reverse transcriptase-PCR. Cultured endometrial stromal cells were used to investigate whether stathmin plays a role in decidualization. Stathmin is expressed specifically in the glandular epithelium and the stromal cells of human endometrial tissue. It is also expressed by cytotrophoblasts and extravillous trophoblasts, but not by syncytiotrophoblasts or decidual tissues during the first trimester of pregnancy. When stromal cells isolated from normal endometrial tissues were cultured and stimulated to decidualize by progesterone (P4) plus estrogen or dibutyryl cyclic 3',5'-AMP, their total and phosphorylated stathmin levels decreased. Knocking down stathmin expression in the cultured stromal cells using small interfering RNA, before the cells were exposed to the decidualizing agents, significantly suppressed decidualization, as indicated by the decreased expression of IGF-binding protein-1 and prolactin. Stathmin is differently expressed in human endometrial and placental cells and may participate in the decidualization of endometrial stromal cells.

Blotting, Western↗

PubMed2005

Spermatogonial cell-mediated activation of an IkappaBzeta-independent nuclear factor-kappaB pathway in Sertoli cells induces transcription of the lipocalin-2 gene.

In spermatogenesis, Sertoli cells serve as supporting cells for the proliferation and differentiation of germ cells. However, it appears that Sertoli cell function is regulated by adjacent spermatogonial cells in the testis because expression of lipocalin-2 mRNA, which encodes an iron-siderophore-binding protein, is barely detectable in Sertoli cells of germ cell-deficient W/Wv mice, and more abundantly expressed in jsd/jsd mice. By employing a coculture system comprising immortalized Sertoli cells (designated as Sertoli-B) and c-Kit(+) spermatogonial cells from 7-d-old mouse testis, we found that lipocalin-2 gene transcription in Sertoli cells is induced by a factor secreted from spermatogonial cells. Transfection of Sertoli-B cells with a series of reporter constructs encompassing an upstream region of the mouse lipocalin-2 gene revealed that a nuclear factor (NF)-kappaB binding consensus sequence in the proximal region of lipocalin-2 gene is responsible for transcriptional activation. A major NF-kappaB component, p65, bound to this region and translocated from the cytoplasm to the nucleus upon stimulation with spermatogonial cell-conditioned medium. Moreover, short interference RNA directed to p65 or a dominant-negative form of IkappaBalpha suppressed the spermatogonial cell factor-mediated transcription of lipocalin-2. However, NF-kappaB-activating inflammatory molecules, such as IL-1beta and lipopolysaccharide, did not induce lipocalin-2 mRNA in Sertoli-B cells and the expression of lipocalin-2 was unaffected in the testis of IkappaBzeta-deficient mice. These results demonstrate that spermatogonial cells regulate lipocalin-2 gene expression in Sertoli cells in a manner distinct from that employed by immune cells.

Acute-Phase Proteins↗

PubMed2005

Crucial transcription factors in endoderm and embryonic gut development are expressed in gut-like structures from mouse ES cells.

Mouse embryonic stem (ES) cells are pluripotent and retain the potential to form an organ similar to the gut showing spontaneous contractions in vitro. The morphological features of these structures and their formation, as assessed using the hanging drop method to produce embryoid bodies (EBs), seem to be similar to those in vivo. To determine whether the same molecular mechanisms are involved in the formation process, the expression pattern of transcription factors regulating endoderm and gut development in the mouse embryo was examined by in situ hybridization and compared with in vivo expression. Expression of gene products was also examined by immunohistochemistry, and expression colocalization was analyzed with double staining. The results showed that all factors examined, that is, Sox17, Id2, HNF3beta/Foxa2, and GATA4, were expressed in both EBs and gut-like structures. Moreover, their expression patterns were similar to those in the mouse embryo. EBs after the hanging drop period and before outgrowth already expressed all factors that were colocalized with each other in EB epithelial structures. These findings suggest that the origin of the gut-like structure is determined during the hanging drop period and that the gut-like structure is formed as the epithelial structure in EBs during the hanging drop period. They also indicate that the in vitro system using mouse ES cells mimics in vivo development and should prove useful in the study of molecular mechanisms for endoderm and gut development.

Animals↗

PubMed2005

Effect of etidronate on aortic calcification and bone metabolism in calcitriol-treated rats with subtotal nephrectomy.

The present study was undertaken to determine the effects of etidronate (ED) on calcitriol-induced aortic calcification and bone metabolism in rats with renal failure. Severe aortic calcification was induced by treatment with calcitriol for 3 weeks in rats in which 5/6 of the kidneys were removed (SNx group). Treatment of ED (10 mg/kg) together with calcitriol after subtotal nephrectomy (SNx) significantly inhibited thoracic and abdominal aortic calcification 3 weeks after the operation; however, ED (2 mg/kg) was ineffective. The serum levels of osteocalcin and pyridinoline decreased in ED (10 mg/kg) treated-renal failure rats compared with SNx rats. Total bone mineral density (BMD) in the SNx group was lower than that in the sham group, in which animals were treated with calcitriol after a sham operation. The total BMD value in the ED (10 mg/kg)-treated group was similar to that in the SNx group, whereas the levels of cancellous BMD were low in the ED (10 mg/kg)-treated rats. Our data show that ED at a dosage that suppresses bone metabolism markedly inhibits vascular calcification in rats with renal failure.

Amino Acids↗

PubMed2005

Stimulatory effects of eicosanoids on ovarian angiogenesis in early luteal phase in cyclooxygenase-2 inhibitor-treated rats.

Our previous study demonstrated that impaired ovarian vasculature is responsible for the decrease in serum progesterone observed in cyclooxygenase (COX)-2 inhibitor-treated rats. To explore the role of arachidonic acid metabolites in the formation of the corpus luteum, we determined in the present study the effects of prostaglandin (PG) and thromboxane (TX) receptor agonists together with vascular endothelial growth factor (VEGF) on progesterone secretion and angiogenesis in the newly formed corpus luteum in NS-398 (a selective inhibitor of COX-2)-treated rats. Uterine injection of PGE2 or U-46619 (TXA2 receptor agonist) prevented decreased levels of serum progesterone and ovarian hemoglobin, an indicator of amounts of vasculature in NS-398-treated rats. Luteal capillary vessel establishment was inhibited by NS-398, as determined by histological examination of ovarian vascular plexuses, while administration of PGE2 reversed the effect. VEGF enhanced the levels of serum progesterone and ovarian hemoglobin, and increased the density of ovarian capillaries. However, VEGF-induced angiogenesis was inhibited by NS-398 treatment. These results suggest that PGE2 and TXA2 stimulate angiogenesis in the newly formed corpus luteum and that there is a possibility that these eicosanoids are involved in VEGF-induced progesterone production and the increase in luteal blood flow.

Animals↗

PubMed2005

Changes in ovarian steroidogenesis in insulin-resistant, type 2 diabetic Goto-Kakizaki rats after thyroidectomy and gonadotropin treatment.

The present study used thyroidectomized insulin-resistant, type 2 diabetic Goto-Kakizaki (GK) rats to assess whether insulin resistance and hypothyroidism modulate ovarian physiology. Animals were treated with daily injections of 5 IU equine chorionic gonadotropin for 5 days starting 1 week after thyroidectomy. Control groups included rats of GK and control (Wistar) strains treated only with equine chorionic gonadotropin or thyroidectomy, or with no treatment (intact). In Wistar rats, equine chorionic gonadotropin injections tended to increase the serum concentrations of luteinizing hormone (LH) and testosterone more in the thyroidectomy group than in intact rats. Similar changes in LH and testosterone were observed in the thyroidectomy + equine chorionic gonadotropin and equine chorionic gonadotropin groups of GK rats, but the LH and testosterone levels in the thyroidectomy + equine chorionic gonadotropin group were significantly higher in GK rats. Expression of ovarian LH receptor messenger RNA (mRNA) was enhanced by thyroidectomy. The LH receptor mRNA levels were significantly higher in the thyroidectomy+equine chorionic gonadotropin group of GK rats than in the corresponding group of control rats. These results indicate that hypothyroidism in animals with insulin resistance and type 2 diabetes promotes LH and testosterone secretions, and suggests that the enhanced-testosterone levels is partially mediated by the enhancement of LH receptor expression and an increase in the serum level of LH.

Animals↗

PubMed2005

Palindromic AT-rich repeat in the NF1 gene is hypervariable in humans and evolutionarily conserved in primates.

Palindromic sequences are dispersed in the human genome and may cause chromosomal translocations in humans. They constitute unsequenced gaps in the human genome because of their resistance to PCR amplification, cloning into vectors, and sequencing. We have overcome these difficulties by using a combination of optimized PCR conditions, cloning in a recombination-deficient E. coli strain, and RNA polymerases in sequencing. Using these methods, we analyzed a palindromic AT-rich repeat (PATRR) in the neurofibromatosis type 1 (NF1) gene on chromosome 17 (17PATRR). The 17PATRR manifests a size polymorphism due to a highly variable length of (AT)(n) dinucleotide repeats within the PATRR. 17PATRRs can be categorized into two types: a longer one that comprises a nearly or completely perfect palindrome, and a shorter one that represents its deleted asymmetric derivative. In vitro analysis shows that the longer 17PATRR is more likely to form a cruciform structure than the shorter one. Two reported t(17;22)(q11;q11) patients with NF1, whose breakpoints were identified within the 17PATRR, have translocations that are derived from perfect or nearly perfect palindromic alleles. This implies that the symmetric structure of a PATRR can induce a translocation. We identified conserved PATRRs within the NF1 gene in great apes and similar inverted repeats in two Old World monkeys, but not in New World monkeys or other mammals. This indicates that the palindromic region appeared approximately 25 million years ago and elongated during primate evolution. Although such palindromic regions are usually unstable and disappear rapidly due to deletion, the 17PATRR in the NF1 gene was stably conserved during evolution for reasons that are still unknown.

AT Rich Sequence↗

PubMed2005

Effect of troglitazone on the excess testosterone and LH secretion in thyroidectomized, insulin-resistant, type 2 diabetic Goto-Kakizaki rats.

Our previous study suggested that hypothyroidism in Goto-Kakizaki (GK) rats with insulin resistance and type 2 diabetes elevates their serum testosterone and luteinizing hormone (LH) levels and ovarian LH receptor messenger RNA (mRNA) expression. The present study assessed the effects of troglitazone (Tro), an insulin-sensitizing agent, on these hypothyroidism-induced hormonal changes in GK rats. GK and normal (Wistar strain) female rats were thyroidectomized (Tx) and then injected with 5 IU of equine chorionic gonadotropin (eCG) for 5 d starting 1 wk after thyroidectomy (the control groups). In the test groups, Tx GK and Wistar rats were injected with both eCG and Tro (100 mg kg-1) po for 5 d. Tro treatment had no effect on the elevated LH serum levels in eCG-treated Tx GK rats but suppressed their enhanced serum testosterone levels as well as significantly decreasing their LH receptor mRNA expression. Tro lowered testosterone and LH receptor mRNA levels in cultured theca cells. These results indicate that Tro lowers the elevated testosterone secretion and ovarian LH receptor mRNA expression that is induced in GK rats by Tx and gonadotropin treatment, which suggests that insulin resistance may be involved in enhancing testosterone production and LH receptor expression in the ovary.

Animals↗

PubMed2004

ADRP is dissociated from lipid droplets by ARF1-dependent mechanism.

Adipocyte differentiation-related protein (ADRP) is a member of PAT proteins existing in lipid droplets (LDs). By yeast two-hybrid screening, we identified ADP-ribosylation factor 1 (ARF1) as a binding partner of ADRP. The interaction of ADRP and ARF1 was verified by GST pull-down and co-immunoprecipitation experiments. Interestingly, ADRP precipitated the GDP-bound ARF1 preferentially to the GTP-bound ARF1. Consistent with this, either brefeldin A (BFA), a fungal metabolite to inhibit ARF-GEF, or a dominant-negative mutant of ARF1 caused dissociation of ADRP from LD. On the other hand, overexpression of wild-type ARF1 did not promote the ADRP dissociation or new LD formation. By using deletion mutants, a central domain of ADRP, which is dispensable for LD binding, was shown to bind to ARF1. The present study showed that the GDP-bound ARF1 induces dissociation of ADRP from the LD surface, and that LD is a target of BFA action.

3T3 Cells↗

PubMed2004

Characterization of endothelium-dependent relaxation and modulation by treatment with pioglitazone in the hypercholesterolemic rabbit renal artery.

The present study was undertaken to investigate vascular function in hypercholesterolemic rabbits and also to characterize the effects of pioglitazone on it. Rabbits were fed normal, 0.5% cholesterol chow, or 0.5% cholesterol chow plus 300 ppm pioglitazone for 5 or 10 weeks. The tension of isolated renal artery rings was measured isometrically, and morphometric analysis was performed. The cholesterol chow diet administered for 5 weeks did not affect acetylcholine-induced relaxation in the renal artery but that for 10 weeks decreased it. The N(G)-nitro-L-arginine (L-NOARG)- and indomethacin-resistant endothelium-dependent relaxation induced by acetylcholine in the renal artery was enhanced in rabbits receiving the cholesterol chow for 5 or 10 weeks, as compared to rabbits receiving the control diet, and the percentage of plaque area formation was increased in the renal artery by the cholesterol chow for 10 weeks. Pioglitazone normalized them without lowering serum lipid levels. The resistant parts of acetylcholine-induced relaxation was significantly inhibited when the renal artery was treated with charybdotoxin, an inhibitor of large and intermediate conductance Ca(2+)-activated K(+) channels, or N,N-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF 525a), a cytochrome P-450 monooxygenase inhibitor. Results indicate that hypercholesterolemia enhances endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation in the rabbit renal artery and pioglitazon normalizes it without lowering serum lipid levels, and suggest that the maintenance of endothelial function by pioglitazon is related to the mechanisms for its anti-atheromatous activity.

Animals↗