Hiroaki Furuta

Cytolytic action of Vibrio vulnificus haemolysin on mast cells from rat peritoneal cavity

The mode of action of Vibrio vulnificus haemolysin (VVH) on mast cells from the peritoneal cavity of the rat was examined. VVH induced histamine release, and damage to the mast cells, in a dose-dependent fashion. When 1 microgram of VVH was added to c. 10(5) mast cells at 37 degrees C, histamine release was observed after a lag period of 5-10 s, and was complete within 5 min. The action was temperature-dependent, and was not induced at 4 degrees C. Disodium cromoglycate, a membrane stabiliser for mast cells, inhibited the histamine release significantly, but the effect was not dose-dependent. Moreover, leakage of lactate dehydrogenase from VVH-treated mast cells was observed. These results suggest that VVH acts on the cell membrane of mast cells and is cytolytic.

Histamine-release induced by 7s nervegrowth factor of mouse submandibular salivary glands

The 7S nerve-growth factor (7S NGF) purified from mouse submandibular glands induced histamine release from rat-isolated mast cells in the presence of lysophosphatidyl-serine. When 7S NGF was injected intradermally into the rat skin, the vascular permeability increased. This response was abolished by the antihistamine, diphenhydramine. These results show that 7S NGF acts as a potent histamine releaser.

Isolation and characterization of histamine-releasing peptides from human parotid saliva

Peptides responsible for releasing histamine were purified from human parotid saliva. The amino acid composition of the peptides showed a high proportion of histidine, lysine and arginine. Molecular weights of these peptides were between 3000 and 5000 as determined by SDS-acrylamide gel electrophoresis. These peptides induced histamine release from rat-isolated mast cells accompanied with degranulation in a dose-dependent manner over the concentration range 5-50 micrograms/ml.

Stimulatory effects of 4-methylcatechol, dopamine and levodopa on the expression of metallothionein-III (GIF) mRNA in immortalized mouse brain glial cells (VR-2g)

Metallothionein (MT)-III, originally discovered as a growth inhibitory factor (GIF), is a brain specific isomer of MTs and is markedly reduced in the brain of Alzheimers disease patients (AD) and in several other neurodegenerative diseases. We analyzed the level and regulation of mRNA expression of MT-III in immortalized fetal mouse brain glial cells (VR-2g) by reverse transcriptase-polymerase chain reaction (RT-PCR). The basal expression level of MT-III mRNA is very low in VR-2g cells. 4-Methylcatechol, dopamine (DA) and levodopa (l-3, 4-dihydroxyphenylalanine), which stimulate the synthesis of nerve growth factor (NGF), further increased the expression of MT-III mRNA in VR-2g cells.

Metallothionein expression and localization in rat bone tissue after cadmium injection

We investigated the induction of metallothionein (MT) by cadmium (Cd) in the bone tissue of rats. To clarify the cell response to Cd in bone, the isoform-specific expression of MT mRNAs (MT-I and MT-II) was examined by reverse transcriptase-polymerase chain reaction (RT-PCR). Both MT-I and MT-II mRNA levels were increased within 3 h by Cd administration. MT (MT-I/MT-II) localization after single Cd injection were also confirmed by immunohistochemical studies. Notably, MT-positive cells were time-dependently increased, and the positive cells were mainly localized in osteocytes. The cell-specific induction of MT may be associated with Cd accumulation and Cd-induced bone injury in vivo. Furthermore, we also found that MT was consecutively expressed in some osteoclasts of control rats. This finding suggested a new role of osteoclasts in bone metabolism.

Stimulation of guinea pig neutrophil superoxide anion-producing system with thymol

Thymol stimulated O2− production in guinea pig neutrophils. O2− production occurred about 30 sec after the addition of thymol, and its rate was independent of extracellular Ca2 +. Thymol-induced activity was inhibited by trifluoperazine (TFP), an inhibitor of protein kinase c, and its IC50 was less than that for 12-O-tetradecanoyl phorbol 13-acetate (TPA) induced activity. After complete activation, O2− production was reversed by addition of TFP or by washing out and resuspending in a stimuli-free medium. The responsiveness of the thymol-pulsed cells to another stimulus, TPA, was somewhat more than resting cells, but the responsiveness of the former cells to thymol was about half that of the latter cells. The ATP level of cells was reduced to one half its initial value during activation by thymol. These data suggest that the magnitude of thymol-induced O2− production in neutrophils is dependent on the initial density of the binding sites of the cells with thymol and the initial intracellular ATP concentration.

Differences of superoxide production in blood leukocytes stimulated with thymol between human and non-human primates.

Thymol induced superoxide production (O2-) by blood leukocytes was examined in various primates including man. Leukocytes of chimpanzee and hamadryas baboon cells showed only 35% of the maximal O2- production rate obtained in human cells, and those of the Japanese monkey and orang-utan failed to respond. In contrast, when cells were stimulated with 12-O-tetradecanoyl phorbol acetate, no significant difference in the O2- production rate was observed between human and monkey cells except for chimpanzee. These results showed that human leukocytes are the most sensitive to thymol among the primates tested. The responsiveness of non-human primate leukocytes could be classified into two types, African-type(chimpanzee and baboon) and Asian-type(orang-utan and macaque).

Antioxidants protect against dopamine-induced metallothionein-III (GIF) mRNA expression in mouse glial cell line (VR-2g).

Metallothionein (MT)-III, originally discovered as a growth inhibitory factor (GIF), is a brain specific isomer of MTs and is markedly reduced in the brain of patients with Alzheimers disease (AD) or other neurodegenerative diseases. We analyzed the level and regulation of mRNA expression of MT-III in immortalized fetal mouse brain glial cells (VR-2g) by reverse transcriptase-polymerase chain reaction (RT-PCR). We have recently reported that dopamine (DA) increases the expression of MT-III mRNA in vitro. In this study, we investigated the mechanism of such increase by examining the effects of DA agonists (SKF38393 or bromocriptine) and DA antagonists (SCH23390 or sulpiride) on the expression of MT-III mRNA. MT-III mRNA did not change by either agonist and DA-increased MT-III mRNA was not inhibited by either antagonist. These results suggested that the induction of MT-III mRNA by DA was not mediated by stimulation of DA receptors. On the other hand, DA-induced MT-III mRNA expression was strongly inhibited by the addition of antioxidants (glutathione, vitamin E or ascorbic acid), indicating that DA-enhanced MT-III mRNA was mediated by reactive oxygen species. Our results suggest that oxidative stress may be one of the principle factors that modulate MT-III mRNA expression.

Opposing pharmacological actions of cepharanthin on lipopolysaccharide-induced histidine decarboxylase activity in mice spleens

A biscoclaurin alkaloid preparation, cepharanthin (Ceph), is reported to have opposing pharmacological effects, enhancement or depression, on several cells and tissues, although detailed mechanisms remain unclear. Previously, we reported that Ceph enhanced lipopolysaccharide (LPS)-induced histidine decarboxylase (HDC) activity in mice spleens by consecutive pre-administration. In this study, we examined the pharmacological effects on HDC activity of a single Ceph pre-administration to test the influence of the administration method. Consequently, HDC activities were decreased by a single administration 15 minutes before LPS challenge in ddY and ICR mice spleens. Moreover, to further examine this suppressing effect, we employed genetically mast cell-deficient WBB6F1 W/Wv (W/Wv) mice to avoid the influence of mast cells. In W/Wv mice, HDC activity was enhanced, but not in the congenic WBB6F1 +/+ mice. These findings suggest that mast cells influence the depressant effect on HDC activity by a Ceph single administration in mast cell sufficient mice.