Diseases caused by immune inflammation, such as rheumatoid arthritis, multiple sclerosis, and Crohn’s disease, are intractable diseases to which novel therapeutics are highly demanded. Prostaglandin (PG) E₂ is the most ubiquitously produced PG with various actions. PGE₂ has been traditionally regarded as an immunosuppressant based on its inhibition of T cell activation in vitro. However, in vivo relevance of the immunosuppressant action of PGE₂ has remained obscure. Recently, several groups including ourselves have made unexpected findings that PGE₂ facilitates expansion of the Th17 subset of T helper cells of both human and mouse through elevation of cAMP via PGE receptors EP2 and EP4. We have further found that PGE₂ can induce and not suppress Th1 differentiation under certain conditions, again, through EP2 and EP4. Given the putative roles of these Th subsets in immune diseases such as the above, these findings suggest that, on the contrary to the traditional view, PGE₂ functions as a mediator of immune inflammation. Consistently, administration of an EP4 antagonist could suppress disease progression and development of antigen-specific Th17 cells in mice subjected to experimental allergic encephalomyelitis and contact hypersensitivity. In this perspective, we review these findings and discuss the prospect of EP4 antagonists as immunomodulatory drugs.

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The ability to perceive sweet compounds is important for animals to detect an external carbohydrate source of calories and has a critical role in the nutritional status of animals. In mice, a subset of sweet-sensitive taste cells possesses leptin receptors. Increase of plasma leptin with increasing internal energy storage in the adipose tissue suppresses sweet taste responses via this receptor. The data from recent studies indicate that leptin may also act as a modulator of sweet taste sensation in humans with a diurnal variation in sweet sensitivity. The plasma leptin level and sweet taste sensitivity are proposed to link with post-ingestive plasma glucose level. This leptin modulation of sweet taste sensitivity may influence an individual’s preference, ingestive behavior, and absorption of nutrients, thereby playing important roles in regulation of energy homeostasis.

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Dietary free glutamate is known to elicit umami, one of the five basic tastes percepted via the specific taste sensor cells on the tongue. Recent studies suggest the specific glutamate sensors exist in the gastric mucosa and contribute to the regulation of gastrointestinal functions, yet the precise mechanism remains still unknown. We established the method to enrich various cell fractions from the isolated rat gastric mucosa and characterized the expression of putative glutamate sensors using such cell fractions. The gastric mucosal cell fractions such as surface mucous, parietal, chief, and endocrine cells were successfully prepared by mucosal protease digestion, elutriation, and gradient centrifugation. The characteristics of these cells were confirmed by real-time RT-PCR using the respective cell-specific markers. Parietal cell fraction exclusively expressed putative umami receptor molecules such as T1R1 and mGluR1 compared to other fractions, although the degree of expression was low. In contrast, the representative taste cell specific markers such as PLCβ2 and TRPM5 were specifically expressed in the smaller endocrine cell fraction. Both parietal and smaller endocrine cell fractions also positively expressed some mGluR subtypes. The chief-cell fraction less expressed T1R1 and mGluR1. These results suggest that multiple glutamate sensors, probably different mechanisms from taste buds, contribute to the glutamate sensing in the gastric mucosa.

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Utilizing the human genome database, the recently developed G-protein–coupled receptors (GPCRs) deorphanizing strategy successfully identified multiple receptors of free fatty acids (FFAs). FFAs have been demonstrated to act as ligands of several GPCRs (FFAR1, FFAR2, FFAR3, and GPR120). These fatty acid receptors are proposed to play critical roles in various types of physiological homeostases. FFAR1 and GPR120 are activated by medium- and long-chain FFAs. In contrast, FFAR2 and FFAR3 are activated by short-chain FFAs. It has been elucidated that these four receptors are expressed in the gastrointestinal tract and have many essential roles as sensors of FFA. In this review, we summarize the physiological and pharmacological function of the receptors in the gastrointestinal tract.

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Ammonia is one of the important toxins produced by Helicobacter pylori (H. pylori), the major cause of peptic ulcer diseases. We examined whether glutamine or marzulene (a gastroprotective drug containing 1% sodium azulene and 99% glutamine) protects the gastric mucosa against H. pylori in vivo and investigated the mechanism underlying glutamine-induced mucosal protection against ammonia in gastric epithelial cells in vitro. Mongolian gerbils were fed for 3 months with a diet containing glutamine (2% – 20%) or marzulene (20%) starting from 2 weeks or 2 years after H. pylori infection. Then, gastric mucosal changes were evaluated both macro- and microscopically. Cultured gastric epithelial cells were incubated in the presence of ammonia, with or without glutamine; and cell viability, ammonia accumulation, and chemokine production were determined. Gerbils exhibited edema, congestion, and erosion after 3-month infection; and after 2-year infection, they showed cancer-like changes in the gastric mucosa. Glutamine and marzulene significantly suppressed these pathological changes caused in the gastric mucosa by H. pylori infection. Ammonia was accumulated in the cells, resulting in an increase in chemokine production and a decrease in cell viability. These pathological responses were prevented by glutamine. In addition, glutamine decreased chemokine production and cell death through inhibition of cellular accumulation of ammonia, resulting in the prevention of H. pylori–induced gastric diseases in vivo. These results suggest that glutamine/marzulene would be useful for prophylactic treatment of H. pylori–induced gastric diseases in patients.

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Functional dyspepsia is a clinical syndrome that features abdominal symptoms centered in the upper abdomen without an organic basis. Three possible mechanisms of gastric dysfunction could be related to functional dyspepsia: 1) delayed gastric emptying, 2) impaired gastric accommodation to food intake, and 3) hypersensitivity to gastric distention. Delayed gastric emptying has been suggested to lead to prolonged antral distension that causes dyspeptic symptoms. Delayed gastric emptying is therefore a focal point of debate about anorexia caused by dyspepsia, and prokinetic agents are often administered in Japan for its treatment. Recently, we found that addition of monosodium L-glutamate (MSG) to a high-energy liquid diet rich in casein promoted gastric emptying in healthy men. Therefore, another potential method to improve delayed gastric emptying could be enhancement of chemosensors that activate the autonomic nervous system innervating the gastrointestinal tract. In conclusion, enrichment with glutamate promoted gastric emptying after intake of a high-protein meal, suggesting that free glutamate is important for protein digestion and that MSG may be helpful for management of delayed gastric emptying in patients with functional dyspepsia.

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LYG-202 (C₂₅H₃₀N₂O₅) is a newly synthesized flavonoid that has been confirmed to possess an antitumor effect, but the mechanism is unclear. Our present study was performed to identify the anti-angiogenic activity of this novel compound in vitro and in vivo. LYG-202 inhibited vascular endothelial growth factor (VEGF) stimulated migration and tube formation of human umbilical vein endothelial cells and arrested microvessel outgrowth from rat aortic rings in vitro. Meanwhile, LYG-202 suppressed the neovascularization of Chicken Chorioallantoic Membrane in vivo. Mechanistic studies revealed that LYG-202 suppressed the VEGF-induced tyrosine phosphorylation of KDR/Flk-1 (VEGFR-2) as well as its downstream protein kinases activation, by decreasing phosphorylated forms of serine/threonine kinase Akt, extracellular signal-regulated kinase, and p38 mitogen-activated protein kinase. LYG-202 exerts anti-angiogenic activity both in vitro and in vivo, and these results suggest that it deserves further investigation as a promising anti–tumor angiogenesis compound.

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Glehnia littoralis (Umbelliferae) has been used traditionally in Korean, Japanese, and Chinese medicine for the treatment of immune-related diseases; however, its anti-inflammatory activity and underlying mechanism remain to be defined. We investigated the anti-inflammatory effect and inhibitory mechanism on inflammation by the methylene chloride fraction from Glehnia littoralis extract (MCF-GLE), which was more effective than Glehnia littoralis extract (GLE). MCF-GLE inhibited 12-O-Tetradecanoyl-phorbol-13-acetate (TPA)–induced inflammation in an inflammatory edema mouse model. Also, MCF-GLE strongly inhibited the releases of nitric oxide (NO), prostaglandin E₂ (PGE₂), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) and significantly suppressed the mRNA and protein expression of inducible nitric oxide synthase and cyclooxygenase-2 in lipopolysaccharide-stimulated RAW 264.7 macrophage cells in a dose-dependent manner. Furthermore, MCF-GLE suppressed NF-κB activation and IκB-α degradation. MCF-GLE also attenuated the activation of ERK and JNK in a dose-dependent manner. These results indicate that MCF-GLE has an inhibitory effect on the in vivo and in vitro inflammatory reaction and is a possible therapeutic agent. Our results suggest that the anti-inflammatory properties of MCF-GLE may result from the inhibition of pro-inflammatory mediators, such as NO, PGE₂, TNF-α, and IL-1β via suppression of NF-κB– and mitogen-activated protein kinases-dependent pathways.

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It was investigated whether the C3a-receptor antagonist (C3aRA) SB 290157 was involved in the suppression of anti-OVA pAb–induced arthritis because it is well known that anaphylatoxin C3a plays a crucial role in the development of an effective inflammatory response during complement activation. Anti-OVA pAb–induced arthritis was induced in DBA/1J mice by administration of anti-OVA pAb 0.5 h prior to intra-articular (i.a.) injection of OVA (0 h). Two peaks of joint swelling were observed at 0.5 and 3 h. The role of C3aRA in arthritis was investigated by injection of SB 290157 at concentrations of 10 and 30 mg/kg at 0 and 2 h. The antagonist was able to reduce joint swelling only at 3 h, and about 50% inhibition of joint swelling was observed with the concentration of 30 mg/kg. The C3 level was significantly decreased at 3 h compared with naïve mice showing complement consumption. Furthermore, the C3 activation was observed and increased corresponding to the graded concentration of anti-OVA pAb. The results also revealed that the C3aRA was able to reduce the expression of IL-1β in synovial tissue. Taken together, the results suggested that C3aRA may be effective in the inhibition of arthritis.

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We investigated the effects of YC-1, an activator of soluble guanylyl cyclase (sGC), on voltage-dependent K⁺ (Kv) channels in smooth muscle cells from freshly isolated rabbit coronary arteries by using the whole-cell patch clamp technique. YC-1 inhibited the Kv current in a dose-dependent fashion with an apparent K_d of 9.67 μM. It accelerated the decay rate of Kv channel inactivation without altering the kinetics of current activation. The rate constants of association and dissociation for YC-1 were 0.36 ± 0.01 μM⁻¹·s⁻¹ and 3.44 ± 0.22 s⁻¹, respectively. YC-1 did not have a significant effect on the steady-state activation and inactivation curves. The recovery time constant from inactivation was decreased in the presence of YC-1, and application of train pulses (1 or 2 Hz) caused a progressive increase in the YC-1 blockade, indicating that YC-1–induced inhibition of Kv currents is use-dependent. Pretreatment with Bay 41-2272 (also a sGC activator), ODQ (a sGC inhibitor), or Rp-8-Br-PET-cGMPs (a protein kinase G inhibitor) did not affect the basal Kv current and also did not significantly alter the inhibitory effect of YC-1. From these results, we suggest that YC-1 directly inhibits the Kv current independently of sGC activation and in a state-, time-, and use-dependent fashion.

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NS-126 (9-fluoro-11β,17,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione 21-cyclohexanecarboxylate 17-cyclopropanecarboxylate) is a novel, highly lipophilic anti-inflammatory corticosteroid. We compared NS-126 and the widely used intranasal corticosteroid fluticasone propionate (FP) in a guinea-pig model of allergic rhinitis and a rat model of airway eosinophilia. In the allergic rhinitis model, NS-126 and FP reduced sneezing and nasal obstruction to similar extents. In the airway eosinophilia model, both compounds inhibited the infiltration of eosinophils into the bronchoalveolar lavage fluid, but the effect of NS-126 was longer-lasting than that of FP. In vitro, NS-126 showed lower affinity than FP for the glucocorticoid receptor and was a weaker inhibitor of Th₂ cytokine and chemokine production and mast-cell secretory responses. We also investigated DX-17-CPC, a metabolite of NS-126 generated in nasal tissue by carboxylesterase-catalyzed hydrolysis at the 17-position. DX-17-CPC showed greater affinity than NS-126 for the glucocorticoid receptor and was a stronger inhibitor of Th₂ cytokine and chemokine production and mast-cell secretory responses. The long duration of the anti-allergic effects of NS-126 may be explained by its high lipophilicity, while the strength of its anti-allergic effects may be explained by the generation of the active metabolite DX-17-CPC. NS-126 is a long-acting intranasal corticosteroid and a promising therapeutic agent for allergic rhinitis.

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Matrix metalloproteinase-12 (MMP-12) has been suggested to play an important role in airway inflammatory diseases. Tumor necrosis factor-α (TNF-α) is known to cause an upregulation of MMP-12 via an activation of activator protein-1 (AP-1) in monocytes. In the present study, we investigated the effect of TNF-α on the expressions of MMP-12 in airway epithelial cells, one of the sources of MMP-12 in the airway, and its underlying mechanism. MMP-12 mRNA and protein expressions induced by TNF-α in the absence or presence of BMS-345541 (a selective IκB kinase inhibitor) or SP600125 [a selective c-Jun N-terminal kinase (JNK) inhibitor] were measured by quantitative real-time PCR and Western blotting, respectively. Furthermore, siRNAs for p65 and JNK2 were used to confirm the involvements of nuclear factor-κB (NF-κB) and AP-1 in the MMP-12 mRNA expression induced by TNF-α in A549 cells. Both MMP-12 mRNA and protein were upregulated by the treatment with TNF-α in time- and concentration-dependent manners. Both BMS-345541 and SP600125 inhibited the upregulation of MMP-12 induced by TNF-α. Furthermore, both the depletion of p65 and JNK2 by siRNAs significantly attenuated the upregulation of MMP-12 induced by TNF-α. These findings suggest that both NF-κB and JNK / AP-1 pathways are important for the MMP-12 upregulation induced by TNF-α in A549 cells.

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During random screening for chondrogenic differentiation inducers, we found that Compound-1, 4-[4-(2,3-dihydro-1,4-benzodioxin-6-yl)-1H-pyrazol-3-yl]benzene-1,3-diol, initiated chondrogenic differentiation of the chondroprogenitor cell line ATDC5. Compound-1 initiated chondrogenic differentiation of the mesenchymal stem cell line C3H10T1/2 in regions where cell aggregates formed and simultaneously inhibited adipogenic differentiation. In C3H10T1/2 cells, Compound-1 increased the expression of Sry-related high-mobility-group box transcription factors L-SOX5, SOX6, and SOX9 (SOX trio) more strongly than bone morphogenic protein (BMP)-2. cAMP-dependent protein kinase (PKA) inhibitors suppressed Compound-1–dependent L-SOX5 and SOX6 up-regulation. PKA inhibitors also suppressed the up-regulation of aggrecan mRNA induced by Compound-1, indicating that increases in L-SOX5 and SOX6 mRNA, in which the PKA pathway participates, are involved in the mechanisms behind the action of Compound-1. On the other hand, the SOX6 and aggrecan gene expression, which were up-regulated by BMP-2, were not affected by the PKA inhibitor. Compound-1 induced chondrogenic differentiation of bone marrow stromal cells and recovered cartilage matrix production by primary chondrocytes, which had been decreased by interleukin-1β. These results show the potential of Compound-1 to be a new cartilage repair agent for inducing chondrogenic differentiation via SOX trio up-regulation.

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Intestinal subepithelial myofibroblasts (ISMFs) are mesenchymal cells that exist under the epithelium of intestines. Primarily isolated ISMFs from rodents have been applied to experiments. However, due to the size of their intestines, the available cell number is limited. Thus, we attempted to isolate ISMFs from bovine colon as an alternative material. After detachment of smooth muscle and epithelial layers, colonic mucosa was explanted. After 2-week incubation, α-SMA (+) / vimentin (+) / desmin (−) ISMFs were harvested and applied for experiments. First we examined the effect of cell passage on morphology and proliferation activity of bovine ISMFs. Although 3rd and 7th passage bovine ISMFs did not exhibit any changes, 11th passage ISMFs showed rounded enlarged shape and lost proliferation potential. On the contrary, rat ISMFs displayed the above senescent changes at earlier passage (passage 4). In intracellular Ca²⁺ concentration measurement, bioactive substances (0.3 – 1 µM ATP, 0.1 – 1 µM serotonin, 10 – 100 nM endothelin-1, and 1 – 10 nM bradykinin) dose-dependently induced an increase in intracellular Ca²⁺ concentration in bovine ISMFs (passage 3 and 7). However, at passage 11, impairment in intracellular Ca²⁺ responses was observed. Thus, bovine ISMFs might be a novel useful tool with long life span and good cellular responses to investigate physiological/pathophysiological roles of ISMFs.

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Forsythiae Fructus is known to have diuretic, anti-bacterial, and anti-inflammatory activities. This study examined the hepatoprotective effects of pinoresinol, a lignan isolated from Forsythiae Fructus, against carbon tetrachloride (CCl₄)–induced liver injury. Mice were treated intraperitoneally with vehicle or pinoresinol (25, 50, 100, and 200 mg/kg) 30 min before and 2 h after CCl₄ (20 μl/kg) injection. In the vehicle-treated CCl₄ group, serum aminotransferase activities were significantly increased 24 h after CCl₄ injection, and these increases were attenuated by pinoresinol at all doses. Hepatic glutathione contents were significantly decreased and lipid peroxidation was increased after CCl₄ treatment. These changes were attenuated by 50 and 100 mg/kg of pinoresinol. The levels of protein and mRNA expression of inflammatory mediators, including tumor necrosis factor-α, inducible nitric oxide synthase, and cyclooxygenase-2, were significantly increased after CCl₄ injection; and these increases were attenuated by pinoresinol. Nuclear translocation of nuclear factor-κB (NF-κB) and phosphorylation of c-Jun, one of the components of activating protein 1 (AP-1), were inhibited by pinoresinol. Our results suggest that pinoresinol ameliorates CCl₄-induced acute liver injury, and this protection is likely due to anti-oxidative activity and down-regulation of inflammatory mediators through inhibition of NF-κB and AP-1.

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We investigated the effects of non-steroidal anti-inflammatory drugs on substrate-induced currents of L-glutamate (L-Glu) transporter EAAT1 expressed in Xenopus laevis oocytes. Niflumic acid (NFA) and diclofenac inhibited L-Glu-induced current through EAAT1 in a non-competitive manner. NFA produced a leftward shift in reversal potential (E_rev) of L-Glu-induced current and increased current amplitude at the potentials more negative than −100 mV. Diclofenac had no effects on E_rev and inhibited the current amplitude to the same extent at all negative potentials. These results indicate that NFA and diclofenac inhibit the L-Glu-induced EAAT1 current via different mechanisms. [Supplementary methods and Figure: available only at http://dx.doi.org/10.1254/jphs.09260SC]

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We investigated the involvement of substance P (SP) and the neurokinin-1 receptor (NK₁R) in the development of radiation-induced hair loss in mice. A dose of 40 Gy of gamma irradiation induced hair loss from the 10th to at least the 60th day after irradiation. A specific NK₁R antagonist, CP-99,994, significantly delayed radiation-induced hair loss and reduced its severity. Furthermore, gamma irradiation induced the expression of preprotachykinin-A, a precursor protein of SP, mRNA in irradiated murine skin on the 10th and 30th days after irradiation. These results indicated that gamma irradiation-induced hair loss was mediated by SP via NK₁R.

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