Biomedical subjects

Koichi Kato

Publications and source records attributed to Koichi Kato.

76 records · Page 5Linked to original sources

PubMedDate not supplied

Polyol pathway and protein kinase C activity of rat Schwannoma cells.

BACKGROUND: Polyol pathway hyperactivity-induced decreases in protein kinase C (PKC) activities have been proposed as a pathogenic mechanism of diabetic neuropathy. Increased PKC activities have recently been invoked in the pathogenesis of other diabetic complications, especially retinopathy, nephropathy, and macroangiopathy. However, it remains unclear whether PKC activities in neural cells such as Schwann cells are increased, decreased, or unchanged. This study investigated the effects of high glucose and increased polyol pathway activity on neural cell growth and PKC activities. METHODS: Rat Schwannoma cells were cultured in 5.5 or 20 mM glucose in the presence or absence of an aldose reductase inhibitor, epalrestat (1 microM) for 14 days. Proliferation activities, PKC activities, and the protein expression of PKC isoforms were measured. RESULTS: Proliferation and PKC activities under the 20 mM glucose condition were significantly decreased compared to those under the 5.5 mM glucose condition and were prevented by epalrestat. Among PKC isoforms, the protein expression of PKC-alpha under the 20 mM glucose condition was significantly reduced compared to that under the 5.5 mM glucose condition. Epalrestat significantly inhibited the decreased expression of PKC-alpha protein. There were no significant changes in the protein expression of PKC-beta. CONCLUSIONS: These results suggest that PKC, especially PKC-alpha activity, is decreased in Schwann cells exposed to high glucose and that this deficit is mediated through polyol pathway hyperactivity.

Aldehyde Reductase↗

PubMedDate not supplied

Fabrication of cell-based arrays using micropatterned alkanethiol monolayers for the parallel silencing of specific genes by small interfering RNA.

The emergence of small interfering RNA (siRNA) opened a new opportunity to study gene functions in a genome. However, large-scale loss-of-function analyses further require cell-based high-throughput methods that allow simultaneous silencing of the huge number of genes by siRNA. In this study, we aim at fabricating the cell-based siRNA arrays that facilitate parallel introduction of multiple siRNAs into cultured mammalian cells. The siRNA arrays were prepared using surface chemical processes including the micropatterning of a self-assembled monolayer and the layer-by-layer assembly of siRNA and cationic lipid. We examined the feasibility of the siRNA array for the sequence-specific gene silencing in an array format. Furthermore, the effects of siRNA loading and culture period after transfection were studied to optimize cell-based assays on the siRNA arrays. The results obtained in this study demonstrated that our method provides the siRNA arrays with spatial specificity in gene silencing, which will serve to obtain a quantitative data set from the cell-based screens on siRNA arrays.

Base Sequence↗

PubMedDate not supplied

Rapid protein anchoring into the membranes of Mammalian cells using oleyl chain and poly(ethylene glycol) derivatives.

The cell membrane is an important interface for communication with extracellular events, and incorporation of bioactive substances, such as antibodies and receptors, into the cell membrane may enhance the potential abilities of cells. Gene manipulation, chemical modification of membrane proteins, and cell surface painting using a GPI anchor have been performed to introduce substances into cell membranes. Furthermore, many lipid anchors have also been used to modify lipid membranes such as liposomes. In this study, we have focused on developing an easy and rapid method for anchoring of substances including macromolecular proteins into the membranes of living mammalian cells. We employed a single oleyl chain derivative coupled with hydrophilic poly(ethylene glycol) (PEG90, the ethyleneoxide (EO) unit is 90) to facilitate solubilization in water. This water-soluble derivative was designated Biocompatible Anchor for Membrane (BAM). Some proteins (streptavidin, EGFP and an antibody) were coupled with BAM90 at the distal terminal of PEG and rapidly (within a few minutes) anchored into the membranes of various cells (NIH3T3, 32D, Ba/F3, hybridoma 9E10). However, the anchored BAM90 disappeared from the cell membranes within 4-5 h in serum-free culture media, and moreover, the retention time of anchoring was shortened (1-2 h) in culture medium containing 10% FBS. We further prepared a dioleylphosphatidylethanolamine (DOPE)-PEG derivative (DOPE-BAM80, the EO unit is 80) as a double oleyl chain derivative for comparison with the single oleyl chain derivative, BAM90. The retention time of anchored DOPE-BAM80 was longer than that of BAM90 and more than 8 h in culture media with and without 10% serum. Furthermore, the treatment time of DOPE-BAM80 for anchoring was nearly as short (within a few minutes) as that of BAM90. In addition, both types of BAMs, BAM90 and DOPE-BAM80, showed no cytotoxicity. Therefore, DOPE-BAM80 is useful for protein anchoring to cells. Although the utilization of BAM90 is considered to be limited, it is expected to useful in restricted environments, for example, in tissues such as the cornea, peritoneum, bladder, and various mucosae, which are less exposed to serum. Thus, we suggest the possibility that both types of BAM can be applied to cell surface engineering.

Adsorption↗

PubMedDate not supplied

Modulating the actions of NK cell-mediated cytotoxicity using lipid-PEG (n) and inhibitory receptor-specific antagonistic peptide conjugates.

Regulating the cell surface modulates the actions of the biological cell response, derives practical applications, and is of scientific interest. On the basis of our previous study using dioleylphosphatidylethanolamine poly(ethylene glycol) with multiple units of ethyleneoxide (DOPE-PEG (n)), we demonstrated the potency of DOPE-PEG (80) as a cell surface modulator. We prepared conjugates of DOPE-PEG (80) and two antagonistic peptides (C1, SGGGCLFNLPWLCG; C26, SGGGCPFSFLPWCG), specifically designed for the inhibitory receptor of natural killer (NK) cells. We confirmed that NK cells exhibited cytotoxicity against DOPE-PEG (80)-peptides-incorporated target cells. We further investigated whether the DOPE-PEG (80)-peptides could affect the cytotoxicity of NK cells in a concentration-dependent manner. C1 peptide showed down-regulation of cytotoxicity at higher concentration, whereas C26 peptide exhibited the saturated cytotoxicity of NK cells at the same concentration. These results suggest that DOPE-PEG (80) can achieve the role of a cell surface modulator without inhibiting the action of conjugated molecules, despite their relatively small size.

Animals↗