Hapten-induced colitis is associated with colonic patch hypertrophy and T helper cell 2-type responses

To investigate the potential involvement of T helper (Th)2-type responses in murine models of intestinal inflammation, we used trinitrobenzene sulfonic acid (TNBS)-hapten to induce inflammatory bowel disease in situations where Th1-type responses with interferon (IFN)-gamma synthesis are either diminished or do not occur. Intracolonic administration of TNBS to either normal (IFN-gamma+/+) or Th1-deficient IFN-gamma knockout (IFN-gamma-/-) BALB/c mice resulted in significant colitis. In IFN-gamma-/- mice, crypt inflammation was more severe than in IFN-gamma+/+ mice and was accompanied by hypertrophy of colonic patches with a lymphoepithelium containing M cells and distinct B and T cell zones resembling Peyer's patches. Hapten-specific, colonic patch T cells from both mouse groups exhibited a Th2 phenotype with interleukin (IL)-4 and IL-5 production. TNBS colitis in normal mice treated with anti-IL-4 antibodies or in IL-4(-/-) mice was less severe than in either IFN-gamma+/+ or IFN-gamma-/- mice. Our findings now show that the Th2-type responses in TNBS colitis are associated with colonic patch enlargement and inflammation of the mucosal layer and may represent a model for ulcerative colitis.

Peyer's patches are required for oral tolerance to proteins

To clarify the role of Peyer's patches in oral tolerance induction, BALB/c mice were treated in utero with lymphotoxin beta-receptor Ig fusion protein to generate mice lacking Peyer's patches. When these Peyer's patch-null mice were fed 25 mg of ovalbumin (OVA) before systemic immunization, OVA-specific IgG Ab responses in serum and spleen were seen, in marked contrast to low responses in OVA-fed normal mice. Further, high T-cell-proliferative- and delayed-type hypersensitivity responses were seen in Peyer's patch-null mice given oral OVA before systemic challenge. Higher levels of CD4(+) T-cell-derived IFN-gamma, IL-4, IL-5, and IL-10 syntheses were noted in Peyer's patch-null mice fed OVA, whereas OVA-fed normal mice had suppressed cytokine levels. In contrast, oral administration of trinitrobenzene sulfonic acid (TNBS) to Peyer's patch-null mice resulted in reduced TNBS-specific serum Abs and splenic B cell antitrinitrophenyl Ab-forming cell responses after skin painting with picryl chloride. Further, when delayed-type hypersensitivity and splenic T cell proliferative responses were examined, Peyer's patch-null mice fed TNBS were unresponsive to hapten. Peyer's patch-null mice fed trinitrophenyl-OVA failed to induce systemic unresponsiveness to hapten or protein. These findings show that organized Peyer's patches are required for oral tolerance to proteins, whereas haptens elicit systemic unresponsiveness via the intestinal epithelial cell barrier.

An ultrasound-driven needle-insertion robot for percutaneous cholecystostomy

A real-time ultrasound-guided needle-insertion medical robot for percutaneous cholecystostomy has been developed. Image-guided interventions have become widely accepted because they are consistent with minimal invasiveness. However, organ or abnormality displacement due to involuntary patient motion may undesirably affect the intervention. The proposed instrument uses intraoperative images and modifies the needle path in real time by using a novel ultrasonic image segmentation technique. In phantom and volunteer experiments, the needle path updating time was 130 and 301 ms per cycle, respectively. In animal experiments, the needle could be placed accurately in the target.

Alternate mucosal immune system: organized Peyer's patches are not required for IgA responses in the gastrointestinal tract

The progeny of mice treated with lymphotoxin (LT)-beta receptor (LTbetaR) and Ig (LTbetaR-Ig) lack Peyer's patches but not mesenteric lymph nodes (MLN). In this study, we used this approach to determine the importance of Peyer's patches for induction of mucosal IgA Ab responses in the murine gastrointestinal tract. Immunohistochemical analysis revealed that LTbetaR-Ig-treated, Peyer's patch null (PP null) mice possessed significant numbers of IgA-positive (IgA+) plasma cells in the intestinal lamina propria. Further, oral immunization of PP null mice with OVA plus cholera toxin as mucosal adjuvant resulted in Ag-specific mucosal IgA and serum IgG Ab responses. OVA-specific CD4+ T cells of the Th2 type were induced in MLN and spleen of PP null mice. In contrast, when TNF and LT-alpha double knockout (TNF/LT-alpha-/-) mice, which lack both Peyer's patches and MLN, were orally immunized with OVA plus cholera toxin, neither mucosal IgA nor serum IgG anti-OVA Abs were induced. On the other hand, LTbetaR-Ig- and TNF receptor 55-Ig-treated normal adult mice elicited OVA- and cholera toxin B subunit-specific mucosal IgA responses, indicating that both LT-alphabeta and TNF/LT-alpha pathways do not contribute for class switching for IgA Ab responses. These results show that the MLN plays a more important role than had been appreciated until now for the induction of both mucosal and systemic Ab responses after oral immunization. Further, organized Peyer's patches are not a strict requirement for induction of mucosal IgA Ab responses in the gastrointestinal tract.

Development of an MRI-compatible needle insertion manipulator for stereotactic neurosurgery

A variety of medical robots for stereotactic neurosurgery has been developed in recent years. Almost of all these robots use computed tomography (CT) to scan the brain of the patient before and during surgery. Currently, we are developing a needle insertion manipulator for magnetic resonance imaging (MRI)-guided neurosurgery. MRI techniques, including MRI angiography and functional MRI, are attractive for the development of interventional MRI therapies and operations. If a robot were available, these therapies would be minimally invasive, with more accurate guidance than is possible with current CT-guided systems. Actuation of a robot in an MRI environment is difficult because of the presence of strong magnetic fields. Therefore, the robot must be constructed of nonmagnetic materials. The system frame was manufactured using polyethylene terephthalate (PET) and was actuated using ultrasonic motors. Accuracy-evaluation procedures and phantom tests have been performed. The total accuracy of the system was approximately 3.0 mm. No artifacts caused by the manipulator were observed in the images.

Phorbol esters alter functions of the expressed dopamine transporter

Recent elucidation of the amino acid sequences of the neurotransmitter transporters reveals several consensus sequences for phosphorylation by kinases including protein kinase C. Protein kinase C activation did modulate the function of the rat dopamine transporter expressed in COS cells. Cell treatment with the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) reduced the affinity of binding of the radiolabeled cocaine analog [3H](-)-2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane (WIN 35,428) without affecting its Bmax. The uptake of [3H]dopamine was reduced by treatment with PMA in a staurosporine-sensitive manner. Kinetic analysis revealed that the inhibitory effect of PMA on [3H]dopamine uptake was due to reduced uptake velocity and a small reduction of affinity for Na+, without changed affinity for dopamine. 1-Oleoyl-2-acetyl-sn-glycerol (OAG) mimicked these actions of PMA. These results demonstrate that activation of protein kinase C alters dopamine transporter functions in both ligand recognition and substrate translocation. These phosphorylation phenomena in vitro suggest the possibility that phosphorylation could modulate the activity of this important dopaminergic synaptic regulator under physiological conditions.

Stimulation of cyclic ADP-ribose synthesis by acetylcholine and its role in catecholamine release in bovine adrenal chromaffin cells

Cyclic ADP-ribose (cADPR) is suggested to be a novel messenger of ryanodine receptors in various cellular systems. However, the regulation of its synthesis in response to cell stimulation and its functional roles are still unclear. We examined the physiological relevance of cADPR to the messenger role in stimulation-secretion coupling in cultured bovine adrenal chromaffin cells. Sensitization of Ca2+-induced Ca2+ release (CICR) and stimulation of catecholamine release by cADPR in permeabilized cells were demonstrated along with the contribution of CICR to intracellular Ca2+ dynamics and secretory response during stimulation of intact chromaffin cells. ADP-ribosyl cyclase was activated in the membrane preparation from chromaffin cells stimulated with acetylcholine (ACh), excess KCl depolarization, and 8-bromo-cyclic-AMP. ACh-induced activation of ADP-ribosyl cyclase was dependent on the influx of Ca2+ into cells and on the activation of cyclic AMP-dependent protein kinase. These and previous findings that ACh activates adenylate cyclase by Ca2+ influx in chromaffin cells suggested that ACh induces activation of ADP-ribosyl cyclase through Ca2+ influx and cyclic AMP-mediated pathways. These results provide evidence that the synthesis of cADPR is regulated by cell stimulation, and the cADPR/CICR pathway forms a significant signal transduction for secretion.

Elimination of colonic patches with lymphotoxin beta receptor-Ig prevents Th2 cell-type colitis

Past studies have shown that colonic patches, which are the gut-associated lymphoreticular tissues (GALT) in the colon, become much more pronounced in hapten-induced murine colitis, and this was associated with Th2-type T cell responses. To address the role of GALT in colonic inflammation, experimental colitis was induced in mice either lacking organized GALT or with altered GALT structures. Trinitrobenzene sulfonic acid was used to induce colitis in mice given lymphotoxin-beta receptor-Ig fusion protein (LTbetaR-Ig) in utero, a treatment that blocked the formation of both Peyer's and colonic patches. Mice deficient in colonic patches developed focal acute ulcers with Th1-type responses, whereas lesions in normal mice were of a diffuse mucosal type with both Th1- and Th2-type cytokine production. We next determined whether LTbetaR-Ig could be used to treat colitis in normal or Th2-dominant, IFN-gamma gene knockout (IFN-gamma(-/-)) mice. Four weekly treatments with LTbetaR-Ig resulted in deletion of Peyer's and colonic patches with significant decreases in numbers of dendritic cells. This pretreatment protected IFN-gamma(-/-) mice from trinitrobenzene sulfonic acid-induced colitis; however, in normal mice this weekly treatment was less protective. In these mice hypertrophy of colonic patches was seen after induction of colitis. We conclude that Th2-type colitis is dependent upon the presence of colonic patches. The effect of LTbetaR-Ig was mediated through prevention of colonic patch hypertrophy in the absence of IFN-gamma. Thus, LTbetaR-Ig may offer a possible treatment for the Th2-dominant form of colitis.

Mice deficient in Th1- and Th2-type cytokines develop distinct forms of hapten-induced colitis

BACKGROUND & AIMS

Most experimental models for inflammatory bowel disease in mice are associated with production of interferon (IFN)-gamma and other proinflammatory cytokines. We hypothesized that T-helper 2 (Th2)-type cells could also contribute to the colitis and cause inflammation different than that mediated by Th1-type cells.

METHODS

Trinitrobenzene sulfonic acid (TNBS)-induced colitis in C57BL/6 background mice genetically deficient in interleukin (IL)-12 p40 (IL-12(-/-)), IFN-gamma (IFN-gamma(-/-)), or IL-4 (IL-4(-/-)) was examined in comparison with control mice (C57BL/6(+/+)).

RESULTS

C57BL/6(+/+), IFN-gamma(-/-), and IL-12(-/-) mice developed patterns of colitis characterized by distortion of crypts, loss of goblet cells, and mononuclear cell infiltration with fibrosis of the mucosal layer. IL-4(-/-) mice had greater mortality than other groups because of penetrating ulcers; however, survivors developed milder lesions that were limited to focal acute ulceration. Colonic CD4(+) T cells from normal, IFN-gamma(-/-), or IL-12(-/- )mice produced both IL-4 and IL-5.

CONCLUSIONS

In TNBS colitis, Th1-like cytokine responses induce fatal, acute, transmural, and focal types of lesions, whereas Th2-like cytokine responses play a significant role in the diffuse atrophic changes in crypts and the mucosal layer that occur in the late stages of this disease.

gammadelta T cells regulate mucosally induced tolerance in a dose-dependent fashion

We used gammadelta TCR-deficient (TCRdelta(-/-)) mice to examine the role of gammadelta T cells for induction of mucosal responses and systemic tolerance to high versus low doses of oral antigen. When either TCRdelta(-/-) or TCRdelta(+/+) mice were immunized orally with a high dose of ovalbumin (OVA) prior to parenteral challenge, systemic IgG and IgE antibody responses were markedly reduced in both types of mice, while mucosal IgA responses were reduced only in the TCRdelta(-/-) mice. Reduced T cell proliferative responses and delayed-type hypersensitivity were seen in TCRdelta(-/-) and TCRdelta(+/+) mice given the high dose of OVA. Antigen-induced T(h)1 and T(h)2 cytokine production by splenic CD4(+) T cells was severely inhibited in orally tolerized TCRdelta(-/-) and TCRdelta(+/+) mice. In contrast, while oral tolerance associated with increased levels of IL-10 synthesis was induced by a low dose of OVA in TCRdelta(+/+) mice, the TCRdelta(-/-) mice were not tolerized and failed to produce IL-10. Our findings indicate that gammadelta T cells play a significant immunoregulatory role in IL-10-mediated, low-dose oral tolerance induction, but are not essential participants in the induction of systemic tolerance to orally introduced antigens given in larger doses.

Enhancement of stimulation-evoked catecholamine release from cultured bovine adrenal chromaffin cells by forskolin

Acetylcholine (ACh) increased cyclic AMP levels in cultured bovine chromaffin cells with a peak effect at 1 min after the addition. Pretreatment with forskolin (0.3 microM) enhanced the ACh-evoked cyclic AMP increase. The catecholamine (CA) release induced by ACh was enhanced by forskolin, but forskolin alone did not enhance the CA release. The effect of forskolin increased dose-dependently up to 1 microM, but decreased at higher concentrations. Dibutyryl cyclic AMP (DBcAMP) also enhanced ACh-evoked CA release, but the effect was less potent than that of forskolin. Forskolin enhanced both [3H]norepinephrine ([3H]NE) and endogenous CA release evoked by 30 mM K+ from cells that were preloaded with [3H]NE. The effects of forskolin were substantial when CA release was evoked with low concentrations of ACh or excess K+, but decreased with higher concentrations of the stimulants. Forskolin also enhanced the CA release induced by ionomycin and veratrine, or by caffeine in Ca2+-free medium. The potentiation by forskolin of the ACh-evoked CA release was manifest in low Ca2+ concentrations in the medium, but decreased when Ca2+ concentration was increased. These results suggest that cyclic AMP may play a role in the modulation of CA release from chromaffin cells.

Increased sialyl Lewis A expression and fucosyltransferase activity with acquisition of a high metastatic capacity in a colon cancer cell line

A human colon cancer cell line, OCUC-LM1(LM), was established from a liver metastasis in our laboratory. Intrasplenic injection of LM into nude mice was repeated three and five times, and the daughter cell lines were designated as LM-H3 and LM-H5 respectively. The level of sialyl Lewis A (SLA) in the supernatant of LM-H3 and LM-H5 was 3 and 4.5 times higher than that of LM respectively. Flow cytometric analysis of SLA expression showed that the peak channel for LM was 113; for LM-H3, 126; and for LM-H5, 146. The mean fluorescence intensity of LM was 102.3 +/- 43.5; for LM-H3, 126.2 +/- 28.4; and for LM-H5, 144.8 +/- 23.4. In endothelial cell adhesion assays, the percentages of adherent LM-H3 and LM-H5 cells were significantly higher than for LM. The activity of alpha1-->4 fucosyltransferase was higher in LM-H3 and LM-H5 than in LM, but there was no difference in alpha2-->3 sialyltransferase activities for type 1 chain among the cell lines. Our results suggest that SLA expression is associated with acquisition of a high capacity for liver metastasis of colon cancer; increased SLA expression is due mainly to increased fucosyltransferase activity.

Molecular cloning and characterization of rat trp homologues from brain

Identification of trp (transient receptor potential) gene from Drosophila photoreceptor and subsequent molecular cloning of the human cDNA homologues suggest its participation in capacitative calcium entry (CCE) or so called store-operated Ca2+ channel (SOC). We identified five different trp-related amplifications of reverse-transcription-polymerase chain reaction (RT-PCR) from rat brain; these corresponded to mouse trp homologues, mtrp1,3,4,5,6 and were distributed in various tissues with multiple expression levels. Two cDNAs, homologous to Drosophila trp from rat brain, designated rtrp3 and rtrp6, were isolated and characterized. By RT-PCR analysis, mRNAs of rtrp3 and rtrp6 were found to be expressed differently in brain and other tissues. In situ hybridization analysis revealed that rtrp6 mRNA was preferentially expressed in hippocampal dentate gyrus and cortical layers II and III. Expression of rat TRP3 and TRP6 in COS cells revealed an increase in CCE, as compared to that in the mock-transfected COS cells of the control. Isolation of cDNAs of rat trp gene family provides a useful model for studying mechanism of CCE.

Volumegraph (overlaid three-dimensional image-guided navigation). Clinical application of augmented reality in neurosurgery

OBJECTIVE

We have developed an overlaid three-dimensional image (Volumegraph)-guided navigation system that allows navigation during operative procedures. The three-dimensional image is superimposed on the patient's head and body via a semi-transparent mirror. The Volumegraph can display three-dimensional images in the air by a light beam which is based on CT/MRI.

METHOD

The system consists of a Volumegraph (thin plate of three-dimensional recorded medium), a Volumegraphscope and an original designed triangular-shaped marker system for registration. The three-dimensional data obtained from CT and MRI before the operation were processed by a computer. Such image data are applied for preoperative investigation to recognize the three-dimensional structure of organs and tumor. These reconstructed three-dimensional images were superimposed and registered at the patient's head according to a fiducial marker (registration). Then the operator can operate with this three-dimensional-image-guided navigation system.

RESULTS

Based on clinical application in 7 cases, the system was found to be advantageous because the surgical procedures could be navigated easily by augmented reality in the surgical field. Invisible parts of the surgical field were supplemented with the overlaid three-dimensional images (Volumegraph) as if it were the virtual operative field. At another time, spatial positioning and overlaid visualization by the Volumegraph was useful for identifying anatomical structures and functional location in the image.

CONCLUSION

This preliminary study of overlaid three-dimensional-image-guided navigation demonstrated its clinical usefulness. The application of augmented reality in the surgical field makes it possible to do a neurosurgical intervention easily and accurately.

Dominant negative isoform of rat norepinephrine transporter produced by alternative RNA splicing

We have cloned from rat brain a family of alternatively spliced cDNAs from a single gene, which encodes a norepinephrine transporter (NET) having variations at the 3'-region including both coding and noncoding regions. This produces two transporter isoforms, rNETa and rNETb, which differ at their COOH termini. The rNETa isoform reveals a COOH terminus homologous to human NET and transports norepinephrine. In contrast, rNETb revealed no detectable transport function but reduced functional expression of rNETa when both isoforms were expressed in the same cell. Thus, rNETb potentially functions as a dominant negative inhibitor of rNETa activity. Co-expression of rNETb with a gamma-aminobutyric acid transporter (rGAT1), a serotonin transporter (rSERT), and a dopamine transporter (rDAT) reduced their transport activity. No reduction was found with the glutamate/aspartate transporter (rGLAST). Alternative RNA splicing of NET suggests a novel mechanism for the regulation of synaptic transmission.

Nitric oxide synergistically potentiates interleukin-1 beta-induced increase of cyclooxygenase-2 mRNA levels, resulting in the facilitation of substance P release from primary afferent neurons: involvement of cGMP-independent mechanisms

We previously demonstrated that cultured rat dorsal root ganglion (DRG) cells respond to stimulation with interleukin-1 beta (IL-1 beta) by releasing substance P (SP), and this response is regulated via the cyclooxygenase (COX)-2 pathway. In this study, to ascertain the interaction between nitric oxide (NO) and prostaglandins in primary afferent neurons, we investigated the effect of NO on the IL-1 beta-induced release of SP in cultured DRG cells. An NO donor, S-nitroso-N-acetyl-DL-penicillamine (SNAP), did not in itself evoke SP release. However, it potentiated the IL-1 beta-induced release of SP. Similarly, while SNAP did not elicit the expression of COX-2 mRNA, it potentiated the expression induced by IL-1 beta in cultured DRG cells, and this potentiation was significantly suppressed by the NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (carboxy-PTIO). Moreover, SNAP also potentiated the expression of COX-2 protein induced by IL-1 beta in cultured DRG cells. The stimulatory effect of SNAP on the IL-1 beta-induced release of SP was completely inhibited on co-incubation with a selective COX-2 inhibitor, NS-398. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), a potent inhibitor of soluble guanylate cyclase, did not suppress, and a membrane-permeable cGMP analogue, 8-Br-cGMP, did not mimic the stimulatory effects of SNAP in DRG cells. These results suggest that in cultured DRG cells, NO potentiates the IL-1 beta-induced increase in COX-2 expression via a soluble guanylate cyclase-cGMP-independent pathway, resulting in facilitation of SP release. The interaction between NO and COX in primary afferent neurons might contribute to the change in nociceptive perception in inflammatory hyperalgesia.

Suppression of sialyl Lewis X expression and E-selectin-mediated cell adhesion in cultured human lymphoid cells by transfection of antisense cDNA of an alpha1-->3 fucosyltransferase (Fuc-T VII)

The antisense cDNA approach was used to identify the endogenous fucosyltransferase species responsible for synthesis of the sialyl Lewis X (NeuAcalpha2-->3 Galbeta1-->4[Fucalpha1-->3]GlcNAcbeta1-->R) determinant in human lymphoid cells. The cultured human adult T-cell leukemia cell line, ED40515-N, expressed the message of alpha1-->3 fucosyltransferase (Fuc-T) IV and VII, with a low level of the Fuc-T III and VI message, and manifested the sialyl Lewis X as well as Lewis X (Galbeta1-->4 [Fucalpha1-->3]GlcNAcbeta1-->R) determinant at the cell surface. Transfection of this cell line with the pRc/CMV vector containing an antisense human Fuc-T VII construct (pRc/CMV/5'FT7AS) resulted in a significant decrease of endogenous Fuc-T VII message and a marked reduction in the cell surface expression of sialyl Lewis X determinant as well as a reduction in the enzymatic activity of alpha1-->3 fucosyltransferase against sialylated type 2 chain substrate. This was accompanied by diminution of cell adhesive activity toward E-selectin on interleukin-1beta-treated endothelial cells. These results indicated that the synthesis of the sialyl Lewis X determinants that were functionally active as E-selectin ligands was mainly mediated by Fuc-T VII in these lymphoid cells. On the other hand, the message of Fuc-T IV showed no significant change in the transfectant clones, and the surface expression of the Lewis X antigen as well as the enzymatic activity of alpha1-->3 fucosyltransferase against non-sialylated type 2 chain substrate was well preserved. The clear contrast between the diminished expression of sialyl Lewis X and the conserved manifestation of Lewis X in the transfectant clones suggested that the synthesis of sialyl Lewis X and that of Lewis X are independently regulated by different fucosyltransferases in human lymphoid cells. Fuc-T VII must be involved in the synthesis of sialyl Lewis X, while the synthesis of Lewis X is mediated by an enzyme other than Fuc-T VII, most probably Fuc-T IV.

MPP+ toxicity and plasma membrane dopamine transporter: study using cell lines expressing the wild-type and mutant rat dopamine transporters

The Parkinsonism-inducing neurotoxin 1-methyl-4-phenylpyridinium (MPP+) causes specific cell death in dopaminergic neurons after accumulation by the dopamine transporter (DAT). COS cells, a non-neuronal cell line insensitive to high doses of MPP+, becomes sensitive to MPP+ when transfected with the rat DAT cDNA. We analyzed the bi-directional transport of MPP+ and its toxicity in several cell lines expressing wild or mutant DATs. Cell death in COS cells expressing wild DAT by exposure to MPP+ was concentration-dependent and cocaine-reversible. Increased wild DAT expression caused higher sensitivities to the toxin in HeLa cells. Although several mutant DATs demonstrated greater transport activity than the wild-type, they displayed similar or lower sensitivity to MPP+ toxicity. Reverse transport of preloaded [3H]MPP+ through DAT was facilitated in COS cells expressing certain mutant DATs, which consistently displayed less sensitivity to MPP+ toxicity. These results suggest that re-distribution of MPP+ due to influx/efflux turnover through the transporter is a key factor in MPP+ toxicity.

TWEAK/Fn14 pathway promotes a T helper 2-type chronic colitis with fibrosis in mice

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK), a TNF superfamily member, induces damage of the epithelial cells (ECs) and production of inflammatory mediaters through its receptor Fn14 in a model of acute colitis. In our current study of chronic colitis induced by repeated rectal injection of a hapten, we found that inflammation, fibrosis, and T helper 2 (Th2)-type immunity were significantly reduced in Fn14 gene knockout (KO) mice when compared with wild-type (WT) control mice. Expression of thymic stromal lymphopoietin (TSLP) was lower in Fn14 KO colon ECs than in WT ECs. TWEAK potentiates the induction of TSLP by interleukin-13 (IL-13) in colon explants from WT but not in Fn14 KO tissue. TSLP receptor KO mice exhibit milder chronic colitis, similar to that in Fn14 KO mice. TWEAK and IL-13 synergistically promote fibroblast proliferation. Thus we propose an IL-13-TWEAK/Fn14-TSLP axis as a key mechanism underlying chronic colitis with fibrosis.

Cellular and molecular aspects of monoamine neurotransmitter transporters

Neurotransmitter transporters terminate synaptic neurotransmission by accumulating neurotransmitters once again after release in a sodium- and chloride-dependent fashion. The availability of the cloned neurotransmitter transporters has allowed investigation into the roles of these transporters in neuronal function. Molecular biological and protein engineering studies including in vitro site-directed mutagenesis, chimera formation of several transporter clones, or epitope-tagging various regions of transporter proteins, have revealed the topology and functionally mapped the transporter proteins. Monoamine neurotransmitter transporters such as those for dopamine, norepinephrine and serotonin are of interest, since they are a target of drugs of abuse and are involved in neuronal disorders including Parkinson's disease and depression. Therefore, elucidating the molecular basis of these transporters may clarify these problems and help develop treatments with which to combat these disorders and drug abuse.

Inhibition of gamma-aminobutyric acid release from synaptosomes by local anesthetics

The effects of local anesthetics on the synthesis, release, and degradation of gamma-aminobutyric acid (GABA) in rat brains were investigated. The addition of procaine, lidocaine, cocaine, or tetracaine did not alter either glutamic acid decarboxylase (GAD) activity or GABA transaminase (GABA-T) activity in vitro. Neither did the enzyme activities in rats with local anesthetic-induced convulsions differ from control values. Tetracaine inhibited high K+-evoked [2,3-3H]GABA release from synaptosomes of rat brain in a dose-dependent manner with a minimal effective concentration of 10(-4) M. Cocaine, lidocaine, and procaine also reduced the release, although they were less potent than tetracaine. The GABA release inhibitors in order of potency are tetracaine, cocaine, lidocaine, and procaine which correlates well with their relative toxicity as convulsants. These results suggest that local anesthetics reduce GABAergic activities by inhibiting the release of the neurotransmitter from the nerve terminals, and that inhibition of the GABA system may be involved in the mechanism of local anesthetic-induced convulsions.

Stimulation-evoked Ca2+ fluxes in cultured bovine adrenal chromaffin cells are enhanced by forskolin

Forskolin, 1 microM, increased acetylcholine (ACh)-stimulated 45Ca uptake by chromaffin cells. The stimulatory effects of forskolin decreased with increasing concentration of ACh. The attenuation of the effect of forskolin on 45Ca uptake as a function of ACh concentration correlated well with changes in the forskolin effect on ACh-evoked catecholamine (CA) release. Forskolin increased excess KCl- and veratrine-evoked CA release and 45Ca uptake. Forskolin by itself stimulated 45Ca efflux and enhanced ACh-, excess KCl-, and veratrine-stimulated 45Ca efflux. High doses of forskolin inhibited both ACh-evoked 45Ca uptake and CA release. The inhibitory action of forskolin was specific to receptor-mediated response because excess KCl- and veratrine-stimulated 45Ca uptake and CA release were not inhibited. Forskolin, 0.3-30 microM, dose-dependently increased caffeine-stimulated CA release and 45Ca efflux in the absence of Ca2+ in the medium, and the effects were mimicked by dibutyryl cyclic AMP. These results suggest that cyclic AMP increases stimulation-induced CA release by enhancing calcium uptake across the plasma membrane and/or altering calcium flux in an intracellular calcium store.