The lysophospholipid mediator family is attracting increased attention for its role in the maintenance of human health and the prevention and treatment of human chronic diseases. This review focuses on recent findings about lysophosphatidic acid (LPA) and its potential precursor phospholipids present in the apical lumen of mammalian lower digestive tracts. In particular, information on the protective effect of LPA toward rat gastric mucosa allowed us to better understand the mechanisms of the gastric ulcer-protective effect of a Chinese medicine and the beneficial effects of intake of vegetables and/or soybean lecithin in foods. These findings may indicate that LPA-rich foodstuffs promote human health by regulating the integral and functional homeostasis of the gastrointestinal mucosa, although the safety of LPA supplementation should be intensively investigated further.
Methylmercury (MeHg) is an important environmental pollutant that causes severe disorders of the central nervous system, but the mechanism underlying its toxicity and the corresponding biological defense mechanisms remain largely unknown. Saccharomyces cerevisiae (S. cererisiae) yeast cells were used to elucidate the defense mechanisms against MeHg toxicity and to search for novel genes involved in MeHg resistance. S. cerevisiae is a eukaryotic organism that possesses many gene products that are functionally similar to those of mammals such as humans. We have previously reported that Cdc34 and Rad23 confer MeHg resistance to yeast cells. Interestingly, the both proteins are related to ubiquitin-proteasome system (UP system) that is involved in the intracellular degradation of proteins. In our detailed experiments, we found that the UP system might play an important role in lending protection against MeHg toxicity. This review summarizes the results of our studies on the role of the UP system as a defense mechanism against MeHg toxicity in yeast cells.
We investigated the estrogenic activity of commercial insecticides fenamiphos, fenthion, methiocarb, propaphos, sulprophos, and temephos as well as some phenolic compounds obtained as a result of their degradation. Using a yeast two-hybrid assay, the relative activities of 4-(methylthio)phenol, 3-methyl-4-(methylthio)phenol, 3,5-dimethyl-4-(methylthio)phenol, and 4,4'-thiodiphenol (TDP) were evaluated as 11, 10, 4, and 1000% (10 times) that of bisphenol-A. To reveal the binding abilities of the abovementioned phenolic compounds with respect to human estrogen receptor α (hERα), we carried out ER-ELISA and found that all compounds had significant abilities, particularly, TDP. From the viewpoint of bioisosterism, we discussed the similarity between a vinylene-group, -CH=CH-, and a thioether-group, -S-. We suggest that an alkylthio-group substituted at the “para”-position of a phenol ring plays a key role in the binding abilities of the investigated phenolic compounds.
We researched the preventive and therapeutic activities of the extract of Ramulus Mori (ERM) to observe its effects on collagen-induced arthritis (CIA) in mice and to explore the mechanisms of ERM in the treatment of rheumatoid arthritis (RA). We examined the in vitro levels of tumor necrosis factor α (TNF-α) released in macrophages and of interferon (IFN)-γ and interleukin (IL)-4 released in splenocytes. For in vivo experiments, we randomly divided 24 mice into four groups, after type II collagen (CII) injections and at euthanization. The levels of plasma cytokines (TNF-α, IL-6, IL-17), rheumatoid factor (RF; IgG, IgM), and anti-CII antibody were measured using ELISA kits. The number of immunocytes (CD4+ T cells, CD3+/CD69+ T cells, B220+/CD45+ B cells, CD11b+/Gr-1+ cells) relative to RA was calculated using flow cytometry (FACS). The articular index (AI) was recorded once a week for 4 weeks. Sections of tissues from the knee joints were stained with hematoxylin and eosin (H&E) and Masson trichrome (MT) after the mice with CIA were euthanized. ERM reduced the levels of TNF-α in macrophages and IFN-γ in spleen cells, decreased AI scores, and improved inflammation of paw joints (PJ). ERM also suppressed the number of immunocytes in peripheral blood mononuclear cells (PBMCs) and PJ, and reduced the levels of cytokines (TNF-α, IL-6, and IL-17), RF, and anti-CII antibody in the sera. TNF-α and Th1 cells play very important roles in the formation and development of RA. ERM and methotrexate notably decreased the induction of RA in the CIA mice model by reducing the levels of inflammatory cytokines and RF in the sera and suppressing the number of immunocytes among PBMCs and PJ.
It is generally known that many psychological factors, such as stress or insomnia, cause mental fatigue. However, the detailed mechanisms underlying mental fatigue have not been clarified. We speculated that mental fatigue may be caused by neuronal brain damage through the activation of N-methyl-D-aspartate (NMDA) receptors by quinolinic acid (QUIN), one of the metabolites of tryptophan in the kynurenine pathway. In the present study, we tested this hypothesis in mice using a home cage equipped with a running wheel; voluntary wheel-running reflected mental activity. In normal mice, wheel-running activity was not affected by intraperitoneal administration of QUIN, but it was significantly decreased by intracerebroventricular administration of QUIN. In restraint stress-loaded mice, whose blood-brain barriers were weakened, wheel-running activity was significantly decreased by intraperitoneal administration of QUIN, and this effect was inhibited by memantine hydrochloride (MEM), an NMDA receptor antagonist. Intraperitoneal administration of lipopolysaccharide (LPS) induced a decrease in wheel-running activity and a concomitant increase in blood and brain QUIN levels. MEM inhibited the LPS-induced decrease in wheel-running activity, but it did not affect the increase in blood and brain QUIN levels. The number of hippocampal neurons was significantly decreased by LPS treatment, and this effect was inhibited by MEM. These results suggest that QUIN, which is produced via tryptophan metabolism, decreases mental activity in mice by damaging brain neurons through the activation of NMDA receptors. This finding supports, at least in part, our hypothesis that the same mechanism contributes to causing human mental fatigue.
Cynomolgus monkeys [Macaca fascicularis (mf)] are widely used to determine pharmacokinetics and toxicological potential of many drug candidates as human models in the drug discovery and development. Cytochrome P450s (P450, CYP), one of the most important enzymes in drug metabolism, in monkey livers are generally similar to corresponding human P450s exhibiting high degrees of homologies in cDNAs and amino acid sequences. Species differences regarding important liver P450 3A and 2D function were examined between cynomolgus monkeys and humans using typical human P450 probe reactions using midazolam (a P450 3A marker), dextromethorphan and bufuralol (P450 2D markers). P450 3A-mediated midazolam 1'-hydroxylation activities in liver microsomes from individual monkey were highly correlated with midazolam 4'-hydroxylation activities but not correlated with dextromethorphan N-demethylation activities. Recombinant monkey CYP2D17 and CYP2D44 catalyzed dextromethorphan O- and N-demethylations as well as monkey mfCYP3A4 and mfCYP3A5 did. On the other hand, contributions of corresponding P450 2D6 and P450 3A4/5 to dextromethorphan N- and O-demethylations, in human liver microsomes were negligible under the present conditions. From these results, monkey P450 2D and 3A enzymes might have broader substrate specificity toward dextromethorphan oxidation than those in human livers. Special attention should be paid when enzymatic and pharmacokinetic data are extrapolated from monkeys to humans.
This study evaluated the antiinflammatory activities of an aqueous extract of Phellinus gilvus (PG) against carrageenan- and cotton pellet-induced acute and chronic inflammation in rats. Four acute and chronic inflammation groups included the vehicle control group, positive control group (aminopyrine, 100 mg/kg), PG10 group (PG, 10 mg/kg), and PG20 group (PG, 20 mg/kg). Oral administration of PG extract produced dose-dependent antiinflammatory effects in both the acute and chronic groups. In the carrageenan-induced paw edema, significant inhibitions were observed at 0.5 and 1 hr in the PG10 group and at 0.5, 1, 2, 4, 5, and 6 hr in the PG20 group. In the cotton pellet-induced granuolma formation, PG extract at 10 and 20 mg/kg per day also showed significant inhibition in the wet and dry weights of granuloma. The free radical scavenging assay indicated a dose-dependent scavenging activity of PG against 2,2-diphenyl-1-picrylhydrazyl free radicals. PG extract may be beneficial as an antiinflammatory agent by virtue of antioxidant action.
Toxicological and biomedical effects of nanoparticles to living subjects should be elucidated before use for safety. To address this point, we attended to proinflammatory cytokine release from macrophage-like RAW 264.7 cells as a measure of the impact of nanoscale particles to living subjects. We explored the specific impacts of TiO2 particles on the signaling cascades for proinflammatory cytokine and tumor necrosis factor-α (TNF-α release using a bioluminescent coculture system and an ELISA assay in the presence of various chemotherapeutic agents or biochemical inhibitors. This evaluation revealed that the proinflammatory cytokine release from the RAW 264.7 cells is synergically enhanced by the mixture of TiO2 particles and interferon-γ (IFN-γ), and TNF-α release is modulated by 40 nm TiO2 particles via a mitgen activated protein kinase (MAPK)/nuclear factor-kappa B (NF-κB) pathway. The TNF-α release is also affected by the agonist of glucocorticoid receptor in both basal and TiO2-particle-activated conditions. The present study evidences that nanoscale TiO2 particles exert a modulator to the initial steps of inflammation, called TNF-α release from RAW 264.7 cells.
Immunoglobulin E (IgE) plays an important role in allergic diseases. In this study, we found that a methanol extract of leaves of the camphor tree Cinnamomum camphora (C. camphora) reduced the amount of IgE secreted by human myeloma U266 cells. When the methanol extract was fractionated by extraction with organic solvents, the ethyl acetate fraction showed the highest activity. The fraction was further separated into several subfractions by preparative TLC. We identified the component of one of the active subfractions as dimethylmatairesinol. Authentic dimethylmatairesinol exhibited similar activity. Thus, the extract of C. camphora and its components including dimethylmatairesinol have potential as an anti-allergic agent.
Arsenic trioxide (As2O3) is known to promote liver and other cancers due to its ability to decrease the level of S-adenosyl-L-methionine (SAM), thus leading to the abnormal expression of oncogene c-myc. The present study investigated the effect of exogenous SAM on As2O3-induced c-myc expression in the normal human liver cells, HL-7702. c-myc expression increased approximately 50% after As2O3 treatments (0-20 μM) for 24 hr. However, this elevated c-myc expression is significantly inhibited by 0.2 μM SAM. Co-treatment of HL-7702 cells with 1.0 μM As2O3 and 0.2 μM SAM for 24 and 30 hr, caused prominent inhibitory effects on c-myc overexpression. The results indicate SAM could inhibit c-myc overexpression induced by As2O3 in HL-7702 cells. These findings may be of significance to the exploration of SAM in preventing arsenic carcinogenesis.
The administration of inorganic lead (Pb) ion to rats is well known to induce liver hyperplasia with liver enlargement and hypercholesterolemia. In the present study, the sensitivities of stroke-prone sponta-neously hypertensive rat (SHRSP) and its normoten-sive control strain, Wistar-Kyoto rat (WKY), to these effects of Pb ion were estimated. Lead nitrate (LN) dissolved in a distillated water for injection was administered to male SHRSP and WKY by a single intravenous injection at a dose of 100 μmol/kg body weight. In WKY, significant increases in the liver weight were observed at 24 and 48 hr after LN-administration, while in SHRSP, no such significant increases were observed up to 48 hr later. On the other hand, increased levels of serum total cholesterol after LN-administration were significantly higher in SHRSP than in WKY at each time, although the constitutive (control) level was the opposite. The present findings suggest that there is different susceptibility between SHRSP and WKY to LN-induced liver hyperplasia and hypercholesterolemia and further indicate that development of hypercholesterolemia is not necessarily correlated with that of liver hyperplasia.
The spatial contact of immune cells is predominant machinery for the modulation of local inflammatory sites as much as humoral regulation is for inflammation. In this study, we investigated the role of mast cells in the regulation of invariant natural killer T cells (iNKTs) functions. Co-cultivation of bone-marrow derived mouse mast cells (BMMCs) with purified and stimulated mouse iNKTs caused marked suppression of interleukin (IL)-4 but not interferon (IFN)-γ production in iNKTs. Suppression was accompanied by down-regulation of IL-4 mRNA expression. The Notch intracellular cytoplasmic domain in iNKTs was also completely diminished by co-cultivation with BMMCs. Suppressed IL-4 production was recovered when iNKTs were separately co-cultured with BMMCs using the transwell system. Furthermore, co-culture of iNKTs with activated BMMCs elicited partial suppression of IL-4 production. These findings suggest that mast cells modulate the function of iNKTs via the inhibition of Notch signaling.
Manganese (Mn) damages the central nervous system and causes Parkinson's disease (PD)-like syndrome called manganism. Abnormal accumulation of Mn and iron (Fe) is observed in the basal nuclei of patients with PD. Dopamine induces oxidative DNA damage in the presence of Fe or copper (Cu) in vitro. Therefore, an Mn-induced neural disorder may involve combined actions of Mn, Fe/Cu, and catecholamines. Here we investigated the combined effects of Mn(II) on the DNA damage induced by dopamine and either Fe(III) or Cu(II). Mn(II) enhanced the formation of 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG) induced by dopamine and Fe(III)/Cu(II), whereas Mn(II) did not induce 8-oxodG formation in the absence of Fe(III)/Cu(II). Mn(II) accelerated hydrogen peroxide (H2O2) production in the dopamine-Fe(III)/Cu(II) system. Furthermore, Mn(II) decreased superoxide anion radicals (O2•-) generated in the xanthine-xanthine oxidase system. These results indicate that Mn(II)-mediated enhancement of DNA damage is caused by facilitated conversion of O2•- to H2O2. In addition, Mn(II) accelerated the formation of aminochrome, an oxidized dopamine product, in the presence of Cu(II). This reaction may have involved Mn(III) accompanied by H2O2 production from O2•-, suggesting a mechanism for Mn-induced oxidative stress on dopaminergic neurons through the combined actions of Mn, Fe, Cu, and dopamine.
It is well known that oral calcium supplementation has inhibited the gastric carcinogenesis in animals treated with chemical carcinogen and sodium chloride. However, the therapeutic effects of calcium ion (Ca2+) for peritoneal dissemination of gastric carcinoma in vivo remain unknown. Here, we showed that Ca2+ could be effective for inhibiting the peritoneal metastasis of gastric carcinoma MKN-45 cells along with apoptosis in vivo. Significantly prolonged survival was obtained for the peritoneal dissemination mouse models of MKN-45 cells after the intraperitoneal injection (i.p.) of Ca2+. These results suggest that Ca2+ could be a new candidate i.p. drug against peritoneal dissemination of gastric cancer in human.