Study on the compounds containing 19F and 10B atoms in a single molecule for the application to MRI and BNCT

Magnetic resonance imaging (MRI) and boron-neutron capture therapy (BNCT) are quite attractive techniques for diagnosis and treatment of cancer, respectively. In order to progress the study on both MRI and BNCT, the novel compounds containing 19F and 10B atoms in a single molecule were designed and synthesized. In the present paper, the syntheses and the internalization rates into tumor cells of these compounds are elucidated.     

Mutated C-terminal fragments of Clostridium perfringens enterotoxin have increased affinity to claudin-4 and reversibly modulate tight junctions in vitro

Passage across epithelial cell sheets is the first step in drug absorption. Tight junctions (TJs) are located between adjacent epithelial cells and seal the intercellular space preventing leakage of solutes. Claudin, a tetra-transmembrane protein family, is a pivotal functional and structural component of the TJ barrier. Modulation of the claudin-based TJ seal is a strategy for mucosal drug absorption. We previously found that a claudin-4 binder, a C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE194), was a modulator of the TJ seal and a potent mucosal absorption enhancer. In the present study, we attempted to improve claudin-4 binders by modification of C-CPE194. Substitution of Asn at position 309 and Ser at position 313 with Ala increased the affinity to claudin-4 by 9.9-fold as compared to C-CPE194. Deletion of 10 amino acids in the N-terminal domain of the double-alanine-substituted mutant increased affinity to claudin-4 by 23.9-fold as compared to C-CPE194. These C-CPE194 mutants reversibly modulated the TJ seal in human intestinal epithelial cell sheets. The N-terminal-truncated mutant was the most potent modulator of the TJ seal. These findings indicate that the C-CPE mutant may be a promising lead for the development of a clinical TJ modulator.     

Cyclic lipopeptide antibiotics bind to the N-terminal domain of the prokaryotic Hsp90 to inhibit the chaperone activity

Chemical arrays were employed to screen ligands for HtpG, the prokaryotic homologue of Hsp (heat-shock protein) 90. We found that colistins and the closely related polymyxin B interact physically with HtpG. They bind to the N-terminal domain of HtpG specifically without affecting its ATPase activity. The interaction caused inhibition of chaperone function of HtpG that suppresses thermal aggregation of substrate proteins. Further studies were performed with one of these cyclic lipopeptide antibiotics, colistin sulfate salt. It inhibited the chaperone function of the N-terminal domain of HtpG. However, it inhibited neither the chaperone function of the middle domain of HtpG nor that of other molecular chaperones such as DnaK, the prokaryotic homologue of Hsp70, and small Hsp. The addition of colistin sulfate salt increased surface hydrophobicity of the N-terminal domain of HtpG and induced oligomerization of HtpG and its N-terminal domain. These structural changes are discussed in relation to the inhibition of the chaperone function.     

Mutations affecting retinotectal axonal pathfinding in Medaka, Oryzias latipes

We screened for mutations affecting retinotectal axonal projection in Medaka, Oryzias latipes. In wild-type Medaka embryos, all the axons of retinal ganglion cells (RGCs) project to the contralateral tectum, such that the topological relationship of the retinal field is maintained. We labeled RGC axons using DiI/DiO at the nasodorsal and temporoventral positions of the retina, and screened for mutations affecting the pattern of stereotypic projections to the tectum. By screening 184 mutagenized haploid genomes, seven mutations in five genes causing defects in axonal pathfinding were identified, whereas mutations affecting the topographic projection of RGC axons were not found. The mutants were grouped into two classes according to their phenotypes. In mutants of Class I, a subpopulation of the RGC axons branched out either immediately after leaving the eye or after reaching the midline, and this axonal subpopulation projected to the ipsilateral tectum. In mutants of Class II, subpopulations of RGC axons branched out after crossing the midline and projected aberrantly. These mutants will provide clues to understanding the functions of genes essential for axonal pathfinding, which may be conserved or partly divergent among vertebrates.     

Genetic dissection of the formation of the forebrain in Medaka, Oryzias latipes

The forebrain, consisting of the telencephalon and diencephalon, is essential for processing sensory information. To genetically dissect formation of the forebrain in vertebrates, we carried out a systematic screen for mutations affecting morphogenesis of the forebrain in Medaka. Thirty-three mutations defining 25 genes affecting the morphological development of the forebrain were grouped into two classes. Class 1 mutants commonly showing a decrease in forebrain size, were further divided into subclasses 1A to 1D. Class 1A mutation (1 gene) caused an early defect evidenced by the lack of bf1 expression, Class 1B mutations (6 genes) patterning defects revealed by the aberrant expression of regional marker genes, Class 1C mutation (1 gene) a defect in a later stage, and Class 1D (3 genes) a midline defect analogous to the zebrafish one-eyed pinhead mutation. Class 2 mutations caused morphological abnormalities in the forebrain without considerably affecting its size, Class 2A mutations (6 genes) caused abnormalities in the development of the ventricle, Class 2B mutations (2 genes) severely affected the anterior commissure, and Class 2C (6 genes) mutations resulted in a unique forebrain morphology. Many of these mutants showed the compromised sonic hedgehog expression in the zona-limitans-intrathalamica (zli), arguing for the importance of this structure as a secondary signaling center. These mutants should provide important clues to the elucidation of the molecular mechanisms underlying forebrain development, and shed new light on phylogenically conserved and divergent functions in the developmental process.     

Analysis of Wnt8 for neural posteriorizing factor by identifying Frizzled 8c and Frizzled 9 as functional receptors for Wnt8

The dorsal ectoderm of vertebrate gastrula is first specified into anterior fate by an activation signal and posteriorized by a graded transforming signal, leading to the formation of forebrain, midbrain, hindbrain and spinal cord along the anteroposterior (A-P) axis. Transplanted non-axial mesoderm rather than axial mesoderm has an ability to transform prospective anterior neural tissue into more posterior fates in zebrafish. Wnt8 is a secreted factor that is expressed in non-axial mesoderm. To investigate whether Wnt8 is the neural posteriorizing factor that acts upon neuroectoderm, we first assigned Frizzled 8c and Frizzled 9 to be functional receptors for Wnt8. We then, transplanted non-axial mesoderm into the embryos in which Wnt8 signaling is cell-autonomously blocked by the dominant-negative form of Wnt8 receptors. Non-axial mesodermal transplants in embryos in which Wnt8 signaling is cell-autonomously blocked induced the posterior neural markers as efficiently as in wild-type embryos, suggesting that Wnt8 signaling is not required in neuroectoderm for posteriorization by non-axial mesoderm. Furthermore, Wnt8 signaling, detected by nuclear localization of beta-catenin, was not activated in the posterior neuroectoderm but confined in marginal non-axial mesoderm. Finally, ubiquitous over-expression of Wnt8 does not expand neural ectoderm of posterior character in the absence of mesoderm or Nodal-dependent co-factors. We thus conclude that other factors from non-axial mesoderm may be required for patterning neuroectoderm along the A-P axis.     

Risk Factors for Cisplatin-Induced Nephrotoxicity and Potential of Magnesium Supplementation for Renal Protection

Background

Nephrotoxicity remains a problem for patients who receive cisplatin chemotherapy. We retrospectively evaluated potential risk factors for cisplatin-induced nephrotoxicity as well as the potential impact of intravenous magnesium supplementation on such toxicity.

Patients and Methods

We reviewed clinical data for 401 patients who underwent chemotherapy including a high dose (≥60 mg/m²) of cisplatin in the first-line setting. Nephrotoxicity was defined as an increase in the serum creatinine concentration of at least grade 2 during the first course of cisplatin chemotherapy, as assessed on the basis of National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. The severity of nephrotoxicity was evaluated on the basis of the mean change in the serum creatinine level. Magnesium was administered intravenously to 67 patients (17%).

Results

Cisplatin-induced nephrotoxicity was observed in 127 patients (32%). Multivariable analysis revealed that an Eastern Cooperative Oncology Group performance status of 2 (risk ratio, 1.876; P = 0.004) and the regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) (risk ratio, 1.357; P = 0.047) were significantly associated with an increased risk for cisplatin nephrotoxicity, whereas intravenous magnesium supplementation was associated with a significantly reduced risk for such toxicity (risk ratio, 0.175; P = 0.0004). The development of hypomagnesemia during cisplatin treatment was significantly associated with a greater increase in serum creatinine level (P = 0.0025). Magnesium supplementation therapy was also associated with a significantly reduced severity of renal toxicity (P = 0.012).

Conclusions

A relatively poor performance status and the regular use of NSAIDs were significantly associated with cisplatin-induced nephrotoxicity, although the latter association was marginal. Our findings also suggest that the ability of magnesium supplementation to protect against the renal toxicity of cisplatin warrants further investigation in a prospective trial.     

Galnt3 deficiency disrupts acrosome formation and leads to oligoasthenoteratozoospermia

Galnt3 belongs to the GalNAc transferase gene family involved in the initiation of mucin-type O-glycosylation. Male Galnt3-deficient (Galnt3 ^?/?) mice were infertile, as previously reported by Ichikawa et al. (2009). To investigate the involvement of Galnt3 in spermatogenesis, we examined the differentiation of germ cells in Galnt3 ^?/? mice. Galnt3 mRNA was most highly expressed in testis, and Galnt3 protein was localized in the cis-medial parts of the Golgi stacks of spermatocytes and spermatids in the seminiferous tubules. Spermatozoa in Galnt3 ^?/? mice were rare and immotile, and most of them had deformed round heads. They exhibited abnormal acrosome and disturbed mitochondria arrangement in the flagella. At the cap phase, proacrosomal vesicles of various sizes, which had not coalesced to form a single acrosomal vesicle, were attached to the nucleus in Galnt3 ^?/? mice. TUNEL-positive cells were increased in the seminiferous tubules. The binding of VVA lectin, which recognizes the Tn antigen (GalNAc-O-Ser/Thr), in the acrosomal regions of spermatids and spermatozoa in Galnt3 ^?/? mice was drastically reduced. Equatorin is a N, O-sialoglycoprotein localized in the acrosomal membrane and is suggested to be involved in sperm–egg interaction. Immunohistochemical and Western blot analyses showed a drastic reduction in the reactivity with MN9 antibody, which recognizes the O-glycosylated moiety of equatorin and inhibits sperm–egg interaction. These findings indicate that deficiency of Galnt3 results in a severe reduction of mucin-type O-glycans in spermatids and causes impaired acrosome formation, leading to oligoasthenoteratozoospermia, and suggest that Galnt3 may also be involved in the process of fertilization through the O-glycosylation of equatorin.     

Osteocyte network; a negative regulatory system for bone mass augmented by the induction of Rankl in osteoblasts and Sost in osteocytes at unloading

Reduced mechanical stress is a major cause of osteoporosis in the elderly, and the osteocyte network, which comprises a communication system through processes and canaliculi throughout bone, is thought to be a mechanosensor and mechanotransduction system; however, the functions of osteocytes are still controversial and remain to be clarified. Unexpectedly, we found that overexpression of BCL2 in osteoblasts eventually caused osteocyte apoptosis. Osteoblast and osteoclast differentiation were unaffected by BCL2 transgene in vitro. However, the cortical bone mass increased due to enhanced osteoblast function and suppressed osteoclastogenesis at 4 months of age, when the frequency of TUNEL-positive lacunae reached 75%. In the unloaded condition, the trabecular bone mass decreased in both wild-type and BCL2 transgenic mice at 6 weeks of age, while it decreased due to impaired osteoblast function and enhanced osteoclastogenesis in wild-type mice but not in BCL2 transgenic mice at 4 months of age. Rankl and Opg were highly expressed in osteocytes, but Rankl expression in osteoblasts but not in osteocytes was increased at unloading in wild-type mice but not in BCL2 transgenic mice at 4 months of age. Sost was locally induced at unloading in wild-type mice but not in BCL2 transgenic mice, and the dissemination of Sost was severely interrupted in BCL2 transgenic mice, showing the severely impaired osteocyte network. These findings indicate that the osteocyte network is required for the upregulation of Rankl in osteoblasts and Sost in osteocytes in the unloaded condition. These findings suggest that the osteocyte network negatively regulate bone mass by inhibiting osteoblast function and activating osteoclastogenesis, and these functions are augmented in the unloaded condition at least partly through the upregulation of Rankl expression in osteoblasts and that of Sost in osteocytes, although it cannot be excluded that low BCL2 transgene expression in osteoblasts contributed to the enhanced osteoblast function.