Deoxycholic acid enhancement of lymphocyte migration through direct interaction with the intestinal vascular endothelium

BACKGROUND AND AIM

The small intestine plays a central role in gut immunity, and enhanced lymphocyte migration is involved in the pathophysiology of various enteropathy. Bile acid (BA) is closely related to lipid metabolism and gut microbiota and essential for gut homeostasis. However, the effects of BA on gut immunity have not been studied in detail, especially on the small intestine and lymphocyte migration. Therefore, we aimed to investigate the effect of BA on small intestinal lymphocyte microcirculation.

METHODS

The effect of deoxycholic acid (DCA), taurocholic acid (tCA), or cholic acid (CA) on the indomethacin (IND)-induced small intestinal enteropathy in mice was investigated. Lymphocyte movements were evaluated after exposure to BA using intravital microscopy. The effects of BA on surface expression of adhesion molecules on the vascular endothelium and lymphocytes through BA receptors were examined in vitro.

RESULTS

IND-induced small intestinal enteropathy was histologically aggravated by DCA treatment alone. The expression of adhesion molecules ICAM-1 and VCAM-1 was significantly enhanced by DCA. Exposure to DCA increased lymphocyte adhesion in the microvessels of the ileum, which was partially blocked by anti-α4β1 integrin antibody in vivo. The expression of ICAM-1 and VCAM-1 was significantly enhanced by DCA in vitro, which was partially suppressed by the sphingosine-1-phosphate receptor 2 (S1PR2) antagonist. The S1PR2 antagonist significantly ameliorated IND-induced and DCA-exaggerated small intestinal injury.

CONCLUSION

DCA exacerbated IND-induced small intestinal enteropathy. DCA directly acts on the vascular endothelium and enhances the expression levels of adhesion molecules partially via S1PR2, leading to enhanced small intestinal lymphocyte migration.

Microscopic Observation of Lymphocyte Dynamics in Rat Peyer's Patches

Naïve lymphocytes recirculate from the blood to the lymphoid tissues under physiological condition and it is commonly recognized as an important phenomenon in the gut immunity. The stroma of secondary lymphoid organs, such as Peyer's patches (PPs) or mesenteric lymph nodes, are where naïve lymphocytes sense antigens. Naïve lymphocytes circulate through the bloodstream to reach high endothelial venules, the portal of entry into PPs. Some immunomodulators are estimated to influence lymphocyte migration, but the precise evaluation of microcirculation dynamics is very difficult, and establishing a method to observe lymphocyte migration in vivo can contribute to the clarification of the precise mechanisms. We refined the method of collecting lymphocytes from the lymph duct and observing the detailed dynamics of gut-tropic lymphocytes in rat PPs. We chose confocal laser scanning microscopy to observe rat PPs in vivo and recorded it using time-lapse photography. We can now obtain clear images that can contribute to the analysis of lymphocyte dynamics.

Depression Promotes the Onset of Irritable Bowel Syndrome through Unique Dysbiosis in Rats

Background/Aims

Although studies using conventional animal models have shown that specific stressors cause irritable bowel syndrome (IBS), it is unclear whether depression itself causes IBS. Our aim was to establish a rat model to determine if depression itself promotes the onset of IBS and to elucidate the role of gut microbiota in brain-gut axis pathogenesis during coincident depression and IBS.

Methods

Rat models of depression were induced using our shuttle box method of learned helplessness. Visceral hypersensitivity was evaluated by colorectal distension (CRD) to diagnose IBS. Gut microbiota compositions were analyzed using high-throughput sequencing. In the subanalysis of rats without depression-like symptoms, rats with posttraumatic stress disorder (PTSD) were also examined.

Results

The threshold value of CRD in depressed rats was significantly lower than that in control rats. Microbial community analysis of cecal microbiota showed that the relative abundance of Clostridiales incertae sedis, the most prevalent microbe, was significantly lower in depressed rats than in control rats. The distribution pattern of the microbiota clearly differed between depressed rats and control rats. Neither visceral hypersensitivity nor the composition of gut microbiota was altered in rats with PTSD-like phenotypes.

Conclusions

Our rat model of depression is useful for clarifying the effect of depression on IBS and suggests that depression itself, rather than specific stressors, promotes the onset of IBS. Further, we provided evidence that various psychiatric diseases, viz., depression and PTSD, are associated with unique gut microbiota profiles, which could differentially affect the onset and progression of coincident IBS.

Crohn's Disease Accompanied with Small Intestinal Extramedullary Plasmacytoma

We herein present the case of an immunocompetent 63-year-old man who had previously undergone resection of Crohn's disease (CD)-related small intestinal obstruction more than 30 years ago. He had not been receiving any medication for many years, but had recently started to suffer from ileus. A stenosed site of ileo-cecal anastomosis was identified and therefore was surgically resected, which was diagnosed as CD with small intestinal extramedullary plasmacytoma (EMP). The subsequent progression of CD was successfully controlled by anti-TNFα agents without any recurrence of EMP for over 3 years, implying the clinical benefit and safety of the biological therapy. This was the first known case of a patient who received anti-TNFα agents after a resection of small intestinal EMP accompanied with CD.

Atypical Clinical Presentation of Crohn's Disease with Superior Mesenteric Vein Obstruction and Protein-losing Enteropathy

We herein report a 44-year-old man suffering from systemic edema due to protein-losing enteropathy (PLE) with superior mesenteric vein (SMV) obstruction and development of collateral veins, which subsequently proved to be a chronic result of thrombosis and a complication of Crohn's disease (CD). PLE was supposedly induced by both intestinal erosion and thrombosis-related lymphangiectasia, which was histologically proven in his surgically-resected ileal stenosis. Elemental diet and anti-TNFα agent improved his hypoalbuminemia after surgery. The rarity of the simultaneous coexistence of SMV obstruction and PLE and the precedence of these complications over typical abdominal symptoms of CD made the clinical course complex.

Nicotine treatment ameliorates DSS-induced colitis by suppressing MAdCAM-1 expression and leukocyte recruitment

The enhanced recruitment of leukocytes to the inflamed colon is a key feature of ulcerative colitis (UC). The gut-specific adhesion molecules involved in leukocyte recruitment have emerged as recent therapeutic targets. Nicotine absorbed from smoking has been reported to work protectively in UC patients. Our hypothesis is that nicotine may suppress the aberrant leukocyte recruitment and colonic inflammation via the suppression of the overexpressed gut-specific adhesion molecules in the inflamed colon. To test this hypothesis, the severity of colitis and the degree of leukocyte recruitment induced by gut-specific adhesion molecules were assessed in dextran sulfate sodium (DSS) colitis mice (C57BL/6J mice treated with 3% DSS) with or without nicotine treatment. We also studied the in vitro changes in the expression of adhesion molecules by using a vascular endothelial cell line. DSS-induced colitis was accompanied by increases in disease activity index (DAI), histological score, recruitment of leukocytes, and the expression of adhesion molecules, mucosal vascular addressin cell adhesion molecule-1 (MAdCAM-1) and VCAM-1. Nicotine treatment significantly attenuated MAdCAM-1 expression, leukocyte recruitment, DAI, and histological score. The expression of β7-integrin, the ligand for MAdCAM-1, on leukocytes was not affected by nicotine treatment. In vitro study, the TNF-α-enhanced mRNA expression of MAdCAM-1 was reduced by the coadministration of nicotine in a dose-dependent manner, possibly via nicotinic receptor activation. These results supported our hypothesis that nicotine treatment ameliorated colitis through the suppression of MAdCAM-1 expression on the microvessels in the inflamed colon. Further investigation is warranted on the role of nicotine in the treatment of UC.

Vitamin A-coupled liposome system targeting free cholesterol accumulation in hepatic stellate cells offers a beneficial therapeutic strategy for liver fibrosis

AIM

Liver fibrosis is a life-threatening disorder for which no approved therapy is available. Recently, we reported that mouse hepatic stellate cell (HSC) activation increased free cholesterol (FC) accumulation, partly by enhancing signaling through sterol regulatory element-binding protein 2 (SREBP2) and microRNA-33a (miR-33a), which resulted in HSC sensitization to transforming growth factor-β (TGFβ)-induced activation in a "vicious cycle" of liver fibrosis.

METHODS

Human HSCs were isolated from surgical liver specimens from control patients and patients with liver fibrosis. C57BL/6 mice were treated with carbon tetrachloride for 4 weeks and concurrently given SREBP2-siRNA- or anti-miR-33a-bearing vitamin A-coupled liposomes.

RESULTS

In human activated HSCs obtained from patients with liver fibrosis, FC accumulation was enhanced independently of serum cholesterol levels through increased signaling by both SREBP2 and miR-33a. This increased FC accumulation enhanced Toll-like receptor 4 (TLR4) protein levels and lowered the TGFβ-pseudoreceptor Bambi (bone morphogenetic protein and activin membrane-bound inhibitor) mRNA levels in HSCs. Notably, in a mouse liver fibrosis model, reduction of FC accumulation, specifically in activated HSCs by suppression of SREBP2 or miR-33a expression using SREBP2-siRNA- or anti-miR-33a-bearing vitamin A-coupled liposomes, downregulated TLR4 signaling, increased Bambi expression, and consequently ameliorated liver fibrosis.

CONCLUSIONS

Our results suggest that FC accumulation in HSCs, as an intracellular mediator promoting HSC activation, contributes to a vicious cycle of HSC activation in human and mouse liver fibrosis independent of serum cholesterol levels. Targeting FC accumulation-related molecules in HSCs through a vitamin A-coupled liposomal system represents a favorable therapeutic strategy for liver fibrosis.

Novel probiotics isolated from a Japanese traditional fermented food, Funazushi, attenuates DSS-induced colitis by increasing the induction of high integrin αv/β8-expressing dendritic cells

BACKGROUND

We isolated two novel probiotics strains (s193 and s292) from Funazushi, which is a traditional Japanese fermented food, and evaluated its effects on DSS-induced colitis to determine the possible underlying mechanisms.

METHODS

A single colony from homogenized Funazushi was isolated by its ability to suppress TNF-α in RAW 264.7. Effect of probiotics on colonic inflammation induced by DSS was evaluated. Effect of probiotics on Treg induction by CD11c⁺ dendritic cells (DCs) of MLNs were analyzed.

RESULTS

Two novel probiotics strains classified into the genus Lactobacillus were isolated (s193 and s292), and those strains showed stronger anti-inflammatory effects on DSS-induced colitis than those of L. gasseri isolated from the gut. mRNA expression β8 integrin in CD11c⁺DCs of MLNs and the number of Tregs in the large intestine were significantly increased by s193 and s292 administration compared with L. gasseri administration. Bone marrow DCs treated with s193 and s292 highly increased β8 integrin, and those cells strongly induced differentiation of CD4⁺ T cells into Tregs. Differentiation of Tregs was remarkably inhibited by anti-β8 integrin antibody treatment.

CONCLUSIONS

Strains s193 and s292 demonstrate strong anti-inflammatory effects on DSS-induced colitis through induction of β8 integrin expression on DCs. Our results suggested that Japanese traditional fermented foods are valuable sources for probiotics that are effective for IBD therapy and treatment.

Amelioration of colitis through blocking lymphocytes entry to Peyer's patches by sphingosine-1-phosphate lyase inhibitor

BACKGROUND AND AIM

Sphingosine-1-phosphate (S1P) receptor 1, a therapeutic target of the S1P1 agonist FTY720, plays a crucial role in lymphocyte migration and is expressed in several cells including naïve T lymphocytes and endothelial cells. 2-Acetyl-4-tetrahydroxybutyl imidazole (THI), an inhibitor of S1P lyase, exhibits immunomodulatory activity through increasing the S1P concentration in the secondary lymphoid organs, but its effects on colitis remain unclear. This study aimed to clarify how THI affects colitis and migration of naïve T lymphocytes in Peyer's patches (PPs).

METHODS

The effect of THI on gut immunity was investigated by analyzing the dextran sulfate sodium (DSS)-induced murine colitis model, lymphocyte components in thoracic duct lymphocytes (TDLs), and microscopic movement of TDLs in PPs.

RESULTS

2-Acetyl-4-tetrahydroxybutyl imidazole ameliorated DSS-induced colitis histologically by causing a significant decrease in colonic lymphocyte infiltration and expression of mucosal pro-inflammatory cytokines. THI suppressed the inflow of naïve T lymphocytes into the thoracic duct. Microscopic observation of PPs in control animals revealed that many TDLs egressed to the stroma and migrated to lymph capillaries after attaching to the high endothelial venules (HEVs). THI or FTY720 treatment in recipient animals blocked lymphocyte egression from the HEVs to the stroma.

CONCLUSIONS

This is the first study to clarify the ameliorating effects of THI on DSS-induced colitis. Microscopic observations demonstrated the involvement of HEVs in the egression of S1P-dependent gut-tropic T lymphocytes to lymph capillaries. This S1P lyase inhibitor might become a novel immunosuppressant for inflammatory bowel disease therapy by blocking infiltration of lymphocytes through HEVs into the stroma in PPs.

Evaluation by MR Enterocolonography of Lansoprazole-induced Collagenous Colitis Accompanied with Protein-losing Enteropathy

We herein describe a 69-year-old man suffering from chronic diarrhea caused by lansoprazole (LPZ)-induced collagenous colitis (CC) accompanied with protein-losing enteropathy (PLE), diagnosed by increased fecal alpha-1 antitrypsin clearance and the findings of leakage from the descending colon to the sigmoid colon on scintigraphy. MR enterocolonography (MREC) was also performed for differentiating digestive diseases, and inflamed findings were observed around the same portion as those on scintigraphy, suggesting that this region was responsible for protein loss in this case. The MREC findings improved after the cessation of LPZ, and hypoalbuminemia also improved simultaneously. This case suggests that MREC may be a new and useful diagnostic tool for CC with PLE.

Human intestinal spirochetosis mimicking ulcerative colitis

Human intestinal spirochetosis (HIS) is a colorectal infection caused by the Brachyspira species of intestinal spirochetes, whose pathogenicity in humans remains unclear owing to the lack of or mild symptoms. We monitored the 5-year clinical course of a woman diagnosed with HIS in whom ulcerative colitis (UC) had been suspected. Following a positive fecal occult blood test, she underwent a colonoscopic examination at a local clinic where she was diagnosed with "right-sided" UC concomitant with incidentally detected HIS, and was referred to our hospital. Colonoscopic, histopathological, and cytological examination revealed localized erosive colitis in the ascending and the right transverse colon concomitant with HIS resembling skip lesions of UC. Initially, we chose the wait-and-watch approach; however, she gradually developed bloody diarrhea. Metronidazole improved her abdominal symptoms, as well as her colonoscopic and histopathological findings, suggesting that HIS was responsible for her colorectal inflammation. This case reveals (1) a possible pro-inflammatory role of HIS, (2) difficulties in diagnosing HIS in chronic proctocolitis, and (3) a possible inclusion of some HIS cases in "UC". HIS could mimic UC and might be included in differential diagnoses for UC. Antibiotic administration is necessary following the detection of HIS, particularly in patients demonstrating an atypical presentation of UC.

Uric acid ameliorates indomethacin-induced enteropathy in mice through its antioxidant activity

BACKGROUND AND AIM

Uric acid is excreted from blood into the intestinal lumen, yet the roles of uric acid in intestinal diseases remain to be elucidated. The study aimed to determine whether uric acid could reduce end points associated with nonsteroidal anti-inflammatory drug (NSAID)-induced enteropathy.

METHODS

A mouse model of NSAID-induced enteropathy was generated by administering indomethacin intraperitoneally to 8-week-old male C57BL/6 mice, and then vehicle or uric acid was administered orally. A group of mice treated with indomethacin was also concurrently administered inosinic acid, a uric acid precursor, and potassium oxonate, an inhibitor of uric acid metabolism, intraperitoneally. For in vitro analysis, Caco-2 cells treated with indomethacin were incubated in the presence or absence of uric acid.

RESULTS

Oral administration of uric acid ameliorated NSAID-induced enteropathy in mice even though serum uric acid levels did not increase. Intraperitoneal administration of inosinic acid and potassium oxonate significantly elevated serum uric acid levels and ameliorated NSAID-induced enteropathy in mice. Both oral uric acid treatment and intraperitoneal treatment with inosinic acid and potassium oxonate significantly decreased lipid peroxidation in the ileum of mice with NSAID-induced enteropathy. Treatment with uric acid protected Caco-2 cells from indomethacin-induced oxidative stress, lipid peroxidation, and cytotoxicity.

CONCLUSIONS

Uric acid within the intestinal lumen and in serum had a protective effect against NSAID-induced enteropathy in mice, through its antioxidant activity. Uric acid could be a promising therapeutic target for NSAID-induced enteropathy.

Clinical features of inflammatory bowel disease of the elderly onset

The incidence and prevalence of inflammatory bowel disease (IBD) is increasing globally. IBD of the elderly is common with prevalence rates. Genetical background involve less in the pathophysiology older-onset of IBD. Response to drug therapies appears to be similar in elderly patients and younger patients. Corticosteroid treatment carries additional risk for elderly patients. In addition, poly-pharmacy and malignancies need to be taken into account. Pre-existing comorbidities and nutrition are important indicators of surgical outcomes. This article will review management of IBD in the elderly.

Regulation of the activity of the transcription factor Runx2 by two homeobox proteins, Msx2 and Dlx5

BACKGROUND

Runx2, formerly called PEBP2alphaA or Cbfa1, is a transcription factor whose deletion causes a complete lack of ossification. It directly regulates the expression of osteoblast-specific genes through the osteoblast-specific cis-acting element found in the promoter region of these genes.

RESULTS

In this study, we have found conditions in which induction of the expression of Runx2 is not accompanied by expression of an osteoblast-specific gene, osteocalcin in C2C12 cells. This finding suggests the existence of a repressor of the activity of Runx2. We have then found that the homeobox protein Msx2 is able to repress the transcription activity of Runx2 by interacting with it. Furthermore, our results have shown that the other homeobox protein Dlx5 has an activity which interferes with both abilities of Msx2 to interact with Runx2 and repress its transcription activity. It has previously been shown that a missense mutation of Msx2 (P148H) causes Boston-type craniosynostosis in humans. Interestingly, while this mutant form of Msx2 was able to bind to Runx2 and repress its activity, these abilities of Msx2 (P148H) were not subject to regulation by Dlx5.

CONCLUSION

These results suggest that regulation of the activity of Runx2 by Msx2 and Dlx5 plays an important role in the mammalian skull development.

Roles of Meltrin beta /ADAM19 in the processing of neuregulin

Meltrin beta/ADAM19 is a member of ADAMs (a disintegrin and metalloproteases), which are a family of membrane-anchored glycoproteins that play important roles in fertilization, myoblast fusion, neurogenesis, and proteolytic processing of several membrane-anchored proteins. The expression pattern of meltrin beta during mouse development coincided well with that of neuregulin-1 (NRG), a member of the epidermal growth factor family. Then we examined whether meltrin beta participates in the proteolytic processing of membrane-anchored NRGs. When NRG-beta1 was expressed in mouse L929 cells, its extracellular domain was constitutively processed and released into the culture medium. This basal processing activity was remarkably potentiated by overexpression of wild-type meltrin beta, which lead to the significant decrease in the cell surface exposure of extracellular domains of NRG-beta1. Furthermore, expression of protease-deficient mutants of meltrin beta exerted dominant negative effects on the basal processing of NRG-beta1. These results indicate that meltrin beta participates in the processing of NRG-beta1. Since meltrin beta affected the processing of NRG-beta4 but not that of NRG-alpha2, meltrin beta was considered to have a preference for beta-type NRGs as substrate. Furthermore, the effects of the secretory pathway inhibitors suggested that meltrin beta participates in the intracellular processing of NRGs rather than the cleavage on the cell surface.

TAK1 mediates the ceramide signaling to stress-activated protein kinase/c-Jun N-terminal kinase

Ceramide has been proposed as a second messenger molecule implicated in a variety of biological processes. It has recently been reported that ceramide activates stress-activated protein kinase (SAPK, also known as c-Jun NH2-terminal kinase JNK), a subfamily member of mitogen-activated protein kinase superfamily molecules and that the ceramide/SAPK/JNK signaling pathway is required for stress-induced apoptosis. However, the molecular mechanism by which ceramide induces SAPK/JNK activation is unknown. Here we show that TAK1, a member of the mitogen-activated protein kinase kinase kinase family, is activated by treatment of cells with agents and stresses that induce an increase in ceramide. Ceramide itself stimulated the kinase activity of TAK1. Expression of a constitutively active form of TAK1 resulted in activation of SAPK/JNK and SEK1/MKK4, a direct activator of SAPK/JNK. Furthermore, expression of a kinase-negative form of TAK1 interfered with the activation of SAPK/JNK induced by ceramide. These results indicate that TAK1 may function as a mediator of ceramide signaling to SAPK/JNK activation.

A novel kinase cascade mediated by mitogen-activated protein kinase kinase 6 and MKK3

A cDNA encoding a novel member of the mitogen-activated protein kinase kinase (MAPKK) family, MAPKK6, was isolated and found to encode a protein of 334 amino acids, with a calculated molecular mass of 37 kDa that is 79% identical to MKK3. MAPKK6 was shown to phosphorylate and specifically activate the p38/MPK2 subgroup of the mitogen-activated protein kinase superfamily and could be demonstrated to be phosphorylated and activated in vitro by TAK1, a recently identified MAPKK kinase. MKK3 was also shown to be a good substrate for TAK1 in vitro. Furthermore, when co-expressed with TAK1 in cells in culture, both MAPKK6 and MKK3 were strongly activated. In addition, co-expression of TAK1 and p38/MPK2 in cells resulted in activation of p38/MPK2. These results indicate the existence of a novel kinase cascade consisting of TAK1, MAPKK6/MKK3, and p38/MPK2.

TAB1: an activator of the TAK1 MAPKKK in TGF-beta signal transduction

Transforming growth factor-beta (TGF-beta) regulates many aspects of cellular function. A member of the mitogen-activated protein kinase kinase kinase (MAPKKK) family, TAK1, was previously identified as a mediator in the signaling pathway of TGF-beta superfamily members. The yeast two-hybrid system has now revealed two human proteins, termed TAB1 and TAB2 (for TAK1 binding protein), that interact with TAK1. TAB1 and TAK1 were co-immunoprecipitated from mammalian cells. Overproduction of TAB1 enhanced activity of the plasminogen activator inhibitor 1 gene promoter, which is regulated by TGF-beta, and increased the kinase activity of TAK1. TAB1 may function as an activator of the TAK1 MAPKKK in TGF-beta signal transduction.

Identification of a member of the MAPKKK family as a potential mediator of TGF-beta signal transduction

The mitogen-activated protein kinase (MAPK) pathway is a conserved eukaryotic signaling module that converts receptor signals into various outputs. MAPK is activated through phosphorylation by MAPK kinase (MAPKK), which is first activated by MAPKK kinase (MAPKKK). A genetic selection based on a MAPK pathway in yeast was used to identify a mouse protein kinase (TAK1) distinct from other members of the MAPKKK family. TAK1 was shown to participate in regulation of transcription by transforming growth factor-beta (TGF-beta). Furthermore, kinase activity of TAK1 was stimulated in response to TGF-beta and bone morphogenetic protein. These results suggest that TAK1 functions as a mediator in the signaling pathway of TGF-beta superfamily members.

Initiation of Xenopus oocyte maturation by activation of the mitogen-activated protein kinase cascade

Mitogen-activated protein kinase (MAPK) and MAPK kinase (MAPKK) are activated during Xenopus oocyte maturation concomitant with the activation of maturation promoting factor (MPF). We reported previously that an anti-MAPKK neutralizing antibody inhibited progesterone- or Mos- induced initiation of oocyte maturation. Here, we show that the injection of CL100 (also called MAPK phosphatase-1) into immature oocytes inhibited progesterone-induced oocyte maturation as well as MAPK activation and that injection of mRNA encoding a constitutively active MAPKK induced activation of histone H1 kinase and germinal vesicle breakdown in the absence of progesterone. Injection of recombinant STE11 protein (a yeast MAPKK kinase) also induced initiation of oocyte maturation. These data support the idea that the MAPKK/MAPK cascade plays an important role in oocyte maturation. Interestingly, injection of the active MAPKK mRNA or the STE11 protein resulted in induction and accumulation of Mos protein. Furthermore, in the presence of cycloheximide, the STE11-induced activation of MPF as well as the induction and accumulation of Mos was blocked, and the activation of MAPK was greatly reduced. The increase in Mos protein and the activation of MAPK by injecting cyclin A protein into immature oocytes were both blocked also by cycloheximide treatment. These results are consistent with an idea that there may exist a positive feedback loop consisting of Mos, the MAPKK/MAPK cascade, and MPF, which may be important for the initiation of oocyte maturation induced by progesterone.

Possible transsynaptic cholinergic neuromodulation by ATP released from ileal longitudinal muscles of guinea pigs

The effects of alpha, beta-methylene ATP (alpha, beta-mATP) and beta, gamma-methylene ATP (beta, gamma-mATP) on endogenous acetylcholine (ACh) release evoked by electrical nerve stimulation were evaluated in guinea-pig ileal longitudinal muscles. Release of ACh was measured with an HPLC-electrochemical detector system and release of ATP by luciferin-luciferase assay. Electrically evoked endogenous ACh release was reduced by both alpha, beta-mATP and beta, gamma-mATP at concentrations of 3 and 30 microM. The inhibitory effect of alpha, beta-mATP (30 microM) on ACh release was not detectable in the presence of theophylline (100 microM), a P1-purinoceptor antagonist, that itself enhanced ATP release. When exogenous ATP (0.1 microM) was added to the bath in which the ileal segment was suspended, it was rapidly metabolized, presumably by ecto-ATPase, and disappeared from the medium within 15 min. At 30 microM, alpha, beta-mATP induced ATP release in a suramin-sensitive but Ca(2+)- and atropine-insensitive manner, suggesting P2-receptor-mediated release of ATP from the smooth muscle. We conclude from these findings that alpha, beta-mATP and, probably, also beta, gamma-mATP, do not reduce ACh release by direct stimulation of presynaptic P1-purinoceptors, and that endogenous ATP released postjunctionally by these ATP analogs is decomposed metabolically to adenosine in the synapse and this adenosine triggers P1-purinoceptor sensitive neuromodulation of cholinergic transmission.

A mitogen-activated protein (MAP) kinase activating factor in mammalian mitogen-stimulated cells is homologous to Xenopus M phase MAP kinase activator

The mitogen-activated protein (MAP) kinases, a family of 40-45-kDa kinases whose activation requires both tyrosine and threonine/serine phosphorylations, are suggested to play key roles in various phosphorylation cascades. A previous study of Krebs and co-workers (Ahn, N. G., Seger, R., Bratlien, R. L., Diltz, C. D., Tonks, N. K., and Krebs, E. G. (1991) J. Biol. Chem. 266, 4220-4227) detected an activity in epidermal growth factor (EGF)-stimulated 3T3 cells that can stimulate inactive MAP kinases. We observed this activity in rat 3Y1 cells treated with various mitogenic factors and in PC12 cells treated with nerve growth factor (NGF). Its kinetics of activation and deactivation following EGF or NGF stimulation roughly paralleled that of MAP kinase. The MAP kinase activator required the presence of ATP and a divalent cation such as Mn2+ and Mg2+ and was inactivated by phosphatase 2A treatment in vitro. This activator has been isolated from EGF-stimulated 3Y1 cells by sequential chromatography and identified as a 45-kDa monomeric protein. It was able to activate mammalian and Xenopus MAP kinases in vitro and was very similar to Xenopus M phase MAP kinase activating factor, which was purified previously from mature oocytes (Matsuda, S., Kosako, H., Takenaka, K., Moriyama, K., Sakai, H., Akiyama, T., Gotoh, Y., and Nishida, E. (1992) EMBO J. 11, 973-982), in terms of its functional, immunological, and physicochemical properties. Thus, the same or a similar upstream activating factor may function in mitogen-induced and M phase-promoting factor-induced MAP kinase activation pathways.

Involvement of dihydropyridine-sensitive Ca2+ channels in adenosine-evoked inhibition of acetylcholine release from guinea pig ileal preparation

The effects of adenosine and nifedipine on endogenous acetylcholine (ACh) release evoked by electrical stimulation from guinea pig ileal longitudinal muscle preparations exposed to physostigmine were evaluated using an HPLC with electrochemical detection (ECD) system. Resting ACh release, which was sensitive to tetrodotoxin (0.3 microM), was enhanced by Bay K 8644 (0.5 microM; a Ca2+ antagonist) or 4-aminopyridine (30 microM; a K+ channel blocker) but not by theophylline (100 microM; a P1 purinoceptor antagonist) or atropine (0.3 microM). The enhancement of the resting ACh release by Bay K 8644 was virtually unaffected by atropine. Electrically evoked ACh release was enhanced by around two- to fourfold in the presence of theophylline, atropine, Bay K 8644, 4-aminopyridine, or atropine. On the other hand, the evoked ACh release was reduced by adenosine (10-30 microM), nifedipine (0.1-0.3 microM; a dihydropyridine Ca2+ channel antagonist), or bethanechol (1-3 microM) in a concentration-related fashion. The reduction induced by adenosine or nifedipine was almost abolished by either theophylline or Bay K 8644, whereas that induced by bethanechol was virtually unaffected by these drugs. The inhibition by adenosine of ACh release was not influenced in the presence of 4-aminopyridine or atropine. However, this inhibition by adenosine was considerably enhanced by halving the Ca2+ concentration in the Krebs solution and was diminished by doubling the Ca2+ concentration. These findings suggest that adenosine produces a cholinergic neuromodulation presumably via modifying dihydropyridine-sensitive Ca2+ channel activities in the cholinergic neurons, and thus L-type Ca2+ channels may exist on the nerve terminals.(ABSTRACT TRUNCATED AT 250 WORDS)

Antitumor activity of a benzaldehyde derivative

Benzaldehyde, in the form of 4,6-benzylidene-alpha-D-glucose (BG), was given iv at a daily dose of 720-1800 mg/m2 to 65 patients with inoperable carcinoma in the advanced stages. The overall objective response rate was 55%; seven patients achieved complete response, 29 achieved partial response, 24 remained stable, and five showed progressive disease. Response was seen in various cell types. Prolongation of survival was apparent for the patients. Toxic reactions were not observed during long-term injection with BG.