Gastric ulcer disease remains widespread; a stressful lifestyle and nonsteroidal antiinflammatory drugs (NSAIDs) make significant contributions to this pathological situation. The findings overviewed here support the idea that glucocorticoid hormones released in response to acute stress or NSAIDs act as gastroprotective substances and exert many of the same actions in the stomach as prostaglandins (PGs) and nitric oxide (NO) as well as capsaicin-sensitive afferent neurons. Glucocorticoids exert a gastroprotective effect by both maintaining local defensive factors (mucosal blood flow and mucus production) and inhibiting pathogenic elements (gastric motility and microvascular permeability). Furthermore, they exert gastroprotective actions in co-operation with PGs, NO, and the afferent neurons; and their compensatory action is observed when the protective mechanism provided by either of these factors is impaired. The gastroprotective action of glucocorticoids is also associated with maintenance of general body homeostasis, including blood glucose levels and systemic blood pressure. In conclusion, glucocorticoids released in response to acute stress or NSAIDs are naturally occurring protective factors that play an important role in maintenance of the gastric mucosal integrity. This led us to re-evaluate the traditional paradigm that glucocorticoid hormones produced during activation of the hypothalamic-pituitary-adrenocortical axis are ulcerogenic in the stomach.

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Recently, we have reported that purified Salvia miltiorrhiza extract (PSME) could prevent myocardial infarction in vivo and myocardial ischemia/reperfusion injury in isolated rat hearts (ex vivo). The aim of this project is to determine whether PSME exerts any cardioprotective effects in vitro. The vascular smooth muscle cell line was used and the effects of the drugs were determined after inducing hypoxia. Gene expression levels of the pro-apoptotic genes Asp53, Bax, and Fas were significantly down-regulated by 0.78-, 0.82-, and 0.87-fold, respectively, and Bcl-2 was up-regulated by 0.82-fold in the PSME-treated groups as compared to the hypoxic group (P<0.05). Significant reduction in immunoreactivity of the protein products of these genes as well as least nuclear green fluorescence observed in TUNEL staining indicate the therapeutic potential of this drug. Furthermore, cardiac antioxidant enzymes assay confirmed this deduction as PSME had slight preserving effects on superoxide dismutase and catalase (0.25 ± 0.01 vs 0.488 ± 0.02 units/mg protein and 0.026 ± 0.012 vs 0.076 ± 0.01 μmol per min per mg protein, respectively; each P<0.05). No significant results were obtained with glutathione S-transferase and GSH peroxidase antioxidant tests. Our results demonstrated that PSME exerts antioxidant effects in vitro, indicating the therapeutic potential of this drug.

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To clarify the role of NO in mouse anaphylactic hypotension, effects of a nitric oxide (NO) synthase inhibitor, N^G-nitro-L-arginine methyl ester (L-NAME), on antigen-induced hypotension and portal hypertension were determined in anesthetized BALB/c mice. Systemic arterial pressure (Psa), central venous pressure (Pcv), and portal venous pressure (Ppv) were directly and simultaneously measured. Mice were first sensitized with ovalbumin, and then the injection of antigen was used to decrease Psa and increase Ppv. Pretreatment with L-NAME (1 mg/kg) attenuated this antigen-induced systemic hypotension, but not the increase in Ppv. The effect of inhibitors of soluble guanylate cyclase on anaphylactic hypotension were studied with either methylene blue (3.0 mg/kg) or 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (10 mg/kg). Neither modulated any antigen-induced changes. Furthermore, methylene blue did not improve systemic hypotension induced by Compound 48/80 (4.5 mg/kg), a mast cell degranulator, which can produce non-immunological anaphylactoid reactions. These data show in anesthetized BALB/c mice that L-NAME attenuated anaphylactic hypotension without affecting portal hypertension. This beneficial effect of L-NAME appears not to depend on the soluble guanylate cyclase pathway.

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In the present study, we investigated whether the peripherally acting μ-opioid receptor agonist loperamide would inhibit allodynia in the non-inflamed dermatome of mice with herpetic pain. Subcutaneous (s.c.) injection of loperamide (1 and 3 mg/kg) inhibited allodynia. Local (intraplantar) injection of loperamide (1 and 5 μg/site) also produced an anti-allodynic effect. The peripheral opioid receptor antagonist naloxone methiodide (0.1 mg/kg, s.c.) and the μ-opioid receptor-selective antagonist β-funaltrexamine (40 nmol/site, intraplantar and 20 mg /kg, s.c.) antagonized the anti-allodynic effects of systemic and local loperamide. Local injection of loperamide into the contralateral hind paw was without effect, suggesting that the effect is mediated through local action, not systemic action. Acute and subacute tolerance did not develop to the anti-allodynic effect of loperamide. In addition, there were no cross-tolerance between local opioids (morphine and loperamide) and systemic morphine. These results suggest that stimulation of peripheral μ-opioid receptors suppresses herpetic allodynia without tolerance development. The non-narcotic μ-opioid receptor agonist loperamide may relieve acute herpetic pain in patients with herpes zoster.

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Second-hand smoke is associated with increased risk of cardiovascular diseases. So far, little is known about the signaling mechanisms of second-hand smoke-induced vascular dysfunction. Endothelial junctions are fundamental structures important for maintaining endothelial barrier function. Our study showed that sidestream cigarette smoke (SCS), a major component of second-hand smoke, was able to disrupt endothelial junctions and increase endothelial permeability. Sidestream cigarette smoke stimulated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and myosin light chain (MLC). A selective inhibitor of p38 MAPK (SB203580) prevented SCS-induced loss of endothelial barrier integrity as evidenced by transendothelial resistance measurements. Resveratrol, an antioxidant that was able to inhibit SCS-induced p38 MAPK and MLC phosphorylation, also protected endothelial cells from the damage. Thus, p38 MAPK mediates SCS-induced endothelial permeability. Inhibition of p38 MAPK may have therapeutic potential for second-hand smoke-induced vascular injury.

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The topoisomerase I inhibitor irinotecan is widely used in anticancer therapy, although the detailed mechanism is still unclear. We investigated the apoptotic mechanisms of irinotecan in human hepatocellular carcinoma (HCC) cell lines (Huh7). SN-38 caused a significant decrease in cell proliferation and induced apoptosis in Huh7 cells and HepG2 cells. SN-38 significantly increased the expression of p53 protein and its phosphorylation at Ser¹⁵ in the nucleus and apoptosis-inducing proteins Bax, caspase-9, and caspase-3, while it significantly decreased the antiapoptosis protein Bcl-xL of Huh7 cells. SN-38-induced apoptosis was recovered after p53 antisense oligodeoxynucleotide (AS ODN) pretreatment, while Huh7 cells were precultured with p53 AS ODN, followed by the addition of SN-38 for 24 h. Furthermore, increases in p53 DNA-binding activity were observed in the nuclei of Huh7 cells after SN-38 treatment as shown by electrophoretic mobility shift analysis. SN-38 binding motifs were detected in the proximal promoter of p53 (bases −433 to −317 and −814 to −711). These results suggest that the p53-mediated apoptosis pathway is important in the anticancer effects of irinotecan in hepatocellular carcinoma.

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Itching is the most important symptom in atopic dermatitis because the persistent scratching in response to itching aggravates the disease. However, the etiologic mechanisms of itching in atopic dermatitis remain uncertain. HR-1 hairless mice fed a special diet, HR-AD, develop atopic dermatitis-like symptoms with prolonged scratching episodes. The purpose of this study was to examine whether skin nerve fiber changes were involved in the prolonged scratching seen in this mouse model. On day 56 after the start of feeding, prolonged scratching, as well as atopic dermatitis-like skin changes, were clearly observed in HR-AD-fed mice, while no abnormal changes were observed in mice fed a normal diet. Immunohistochemical analyses of the skin using antibody to protein gene product 9.5 showed the development of numerous immunoreactive nerve fibers in the epidermis of HR-AD-fed mice. Furthermore, after cessation of HR-AD feeding, the reduction in intraepidermal nerve fibers coincided with decreased scratching. Neither the prolongation of scratching nor the increase in intraepidermal nerve fibers was affected by dexamethasone treatment. Thus, the increased number of intraepidermal nerve fibers could be involved in the aggravation of itch-related scratching observed in this model.

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We investigated the participation of γ-aminobutyric acid (GABA) neurons of the medial septal area in eight-arm radial maze performance in rats. The intra-septal injection of muscimol, a GABA_A agonist, caused an increase in total error and working memory error. On the other hand, no significant effect was observed with reference memory error. Donepezil and tacrine (cholinesterase inhibitors) antagonized the muscimol-induced spatial memory deficits. Histidine (1500 mg/kg, i.p.) also improved the total error and working memory error induced by muscimol. At this dose, histidine caused a significant increase in the histamine content of the cortex, hippocampus, and hypothalamus in rats. In addition, the intra-hippocampal injection of histamine also antagonized muscimol-induced spatial memory deficits. The practical conclusion is that the GABA_A receptor of the medial septal area plays an important role in working memory, and also, the disturbance of working memory induced by muscimol is mediated not only by cholinergic but also by histaminergic systems in the spatial memory of rats.

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Hyperglycemia, which occurs under the diabetic condition, induces serious diabetic complications. Diabetic neuropathies, affecting the autonomic, sensory, and motor peripheral nervous system, are among the most frequent complications of diabetes. Little is known about the direct toxic effect of high glucose concentrations on neuronal cells. Therefore in the present study, glucose-induced toxicity was studied in PC12 cells as an in vitro cellular model for diabetic neuropathy using the MTT assay. The possible role of apoptosis was also investigated in this toxicity. The result showed that a 3-fold increase in optimum glucose concentration for PC12 cells (13.5 mg/ml) significantly reduced cell viability after 48 h. In Western blot analysis, the ratio of Bax/Bcl-2 protein expression in cells treated with high glucose was significantly increased compared to controls. Additionally high glucose could induce a DNA ladder pattern in PC12 cells, a hallmark of apoptosis indicating nuclear fragmentation. From our present results, it may be concluded that high glucose can cause PC12 cell death, in which apoptosis plays an important role possibly by the mitochondrial pathway through higher expression of Bax pro-apoptotic protein.

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We examined the pharmacological profile of ramosetron, a 5-HT₃-receptor antagonist for irritable bowel syndrome with diarrhea, comparing it with those of other 5-HT₃-receptor antagonists, alosetron and cilansetron, and the anti-diarrheal agent loperamide. Ramosetron showed high affinity for cloned human and rat 5-HT₃ receptors, with K_i values of 0.091 ± 0.014 and 0.22 ± 0.051 nmol/L, respectively, while its affinities for other receptors, transporters, ion channels, and enzymes were negligible. Dissociation of ramosetron from the human 5-HT₃ receptor was extremely slow (t_1/2 = 560 min), while alosetron (t_1/2 = 180 min) and cilansetron (t_1/2 = 88 min) dissociated relatively rapidly. Ramosetron competitively inhibited 5-HT-induced contraction of isolated guinea-pig colon, with pA₂ values of 8.6 (8.5 – 9.0). Ramosetron given orally also dose-dependently inhibited the von Bezold-Jarisch reflex in rats, with an ED₅₀ value of 1.2 (0.93 – 1.6) μg/kg. In addition, oral ramosetron dose-dependently inhibited restraint stress-induced defecation in rats, with an ED₅₀ value of 0.62 (0.17 – 1.2) μg/kg. In all of these experiments, the potencies of ramosetron were greater than those of alosetron, cilansetron, or loperamide. These results indicate that ramosetron is a highly potent and selective 5-HT₃-receptor antagonist, with beneficial effects against stress-induced abnormal defecation in rats.

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Based on radio-ligand binding and molecular modeling studies, sarpogrelate shows a moderate selectivity for 5-HT_2B versus 5-HT_2A receptors. To confirm the modeling data of sarpogrelate to 5-HT_2B receptors predicting interaction of sarpogrelate towards Asp135 in helix 3 of 5-HT_2B receptors, we constructed and characterized the mutation of this residue by site-directed mutagenesis. The Asp135Ala mutant did not exhibit any affinity for [³H]rauwolscine. Therefore, it was not possible to find sarpogrelate affinity to the mutant using [³H]rauwolscine. The mutation also abolished agonist-stimulated inositol phosphates formation. These results provide evidence that Asp135 is important for the interaction between 5-HT_2B receptors and sarpogrelate.

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We examined the effect of trimidox (3,4,5-trihydroxybenzamidoxime) on the production of nitric oxide (NO) by lipopolysaccharide (LPS) in mouse RAW 264.7 macrophages. Trimidox (50 – 300 μM) concentration-dependently inhibited NO production by LPS (0.01, 0.1, or 1 μg/ml) after incubation for 24 h. LPS-induced expression of inducible NO synthase (iNOS) and degradation of IκBα were prevented by trimidox. The protective effect against NO production by LPS was not only observed in prior incubation but also later incubation with trimidox until iNOS was activated by LPS. These results suggest that trimidox has a predominantly protective effect against LPS-induced production of NO via iNOS expression.

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Wrong:This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD) (The Regional Research Universities Program/Chungbuk BIT Research-Oriented University Consortium).
Right:This work was supported by a research grant of the Chungbuk National University in 2006.

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