Traceable stimulus-dependent rapid molecular changes in dendritic spines in the brain.

Dendritic spines function as microcompartments that can modify the efficiency of their associated synapses. Here, we analyzed stimulus-dependent molecular changes in spines. The F-actin capping protein CapZ accumulates in parts of dendritic spines within regions where long-term potentiation has been induced. We produced a transgenic mouse line, AiCE-Tg, in which CapZ tagged with enhanced green fluorescence protein (EGFP-CapZ) is expressed. Twenty minutes after unilateral visual or somatosensory stimulation in AiCE-Tg mice, relative EGFP-CapZ signal intensification was seen in a subset of dendritic spines selectively in stimulated-side cortices; this right-left difference was abolished by NMDA receptor blockade. Immunolabeling of α-actinin, a PSD-95 binding protein that can recruit AMPA receptors, showed that the α-actinin signals colocalized more frequently in spines with the brightest EGFP-CapZ signals (top 100) than in spines with more typical EGFP-CapZ signal strength (top 1,000). This stimulus-dependent in vivo redistribution of EGFP-CapZ represents a novel molecular event with plasticity-like characteristics, and bright EGFP-CapZ in AiCE-Tg mice make high-CapZ spines traceable in vivo and ex vivo. This mouse line has the potential to be used to reveal sequential molecular events, including synaptic tagging, and to relate multiple types of plasticity in these spines, extending knowledge related to memory mechanisms.

Both selective COX-1 and COX-2 inhibitors aggravate gastric damage induced in rats by 2-deoxy-D-glucose. relation to gastric hypermotility and COX-2 expression.

BACKGROUND/AIM: 2-deoxy-D-glucose (2DG), despite causing gastric hypermotility via vagal stimulation, does not by itself induce damage in the stomach but produces gross lesions under prostaglandin (PG) deficiency induced by non-ulcerogenic dose of indomethacin. In this study, we examined the roles PG and cyclo-oxygenase (COX) isozymes play in the gastric ulcerogenic effect of 2DG in the rat stomach under PG deficiency caused by indomethacin. METHODS: The animals were given 2DG i.v. (200 mg/kg as a bolus injection followed by an infusion at 100 mg/kg), and the mucosa was examined for lesions 8 h later. SC-560 or/and rofecoxib was given p.o. 1 h before 2DG treatment. RESULTS: 2DG alone caused slight damage in the stomach despite causing acid hypersecretion and hypermotility. Neither SC-560 nor rofecoxib alone caused any damage in the stomach, yet these agents significantly aggravated 2DG-induced gastric lesions; the severity of damage was much greater when SC-560 was given together with 2DG. SC-560, but not rofecoxib, enhanced both acid secretion and gastric motility in response to 2DG, with a decrease in mucosal PGE2 content. Expression of COX-2 was up-regulated in the stomach as early as 2 h after 2DG treatment, and the PGE2 content was increased when determined 6 h later, in a COX-2-dependent/rofecoxib-sensitive manner. Both the expression of COX-2 and gastric hypermotility during 2DG treatment were inhibited by prior administration of atropine but not omeprazole, although 2DG-induced gastric lesions were prevented by both agents. CONCLUSION: These results suggest that potentiation by indomethacin of 2DG-induced gastric lesions is related to inhibition of both COX-1 and COX-2, and that 2DG up-regulates COX-2 in the gastric mucosa, the event occurring in association with gastric hypermotility and contributing to suppression of later extension of the damage.

Dopamine-induced protection against indomethacin-evoked intestinal lesions in rats--role of anti-intestinal motility mediated by D2 receptors.

BACKGROUND: Although it is known that dopamine prevents various gastrointestinal lesions, the underlying mechanism remains unclear. In the present study, we examined the protective effect of dopamine on indomethacin-induced small intestinal lesions, in relation to intestinal hypermotility. MATERIAL/METHODS: Male SD rats received indomethacin (10 mg/kg) subcutaneously (s.c.), and the small intestine was examined for lesions 24 hr later. Dopamine (1-10 mg/kg) or atropine (3 mg/kg) was administered s.c. twice, 30 min before and 8 hr after indomethacin, while sulpiride (3 mg/kg) and domperidone (3 mg/kg), the dopamine D2 receptor antagonists, or yohimbine (10 mg/kg), the alpha2-adrenoceptor antagonist, were administered s.c. twice, 30 min before each dosing of dopamine. Intestinal motility was measured using a balloon under urethane anesthesia. RESULTS: Indomethacin caused severe lesions in the small intestine, mainly both the jejunum and ileum. The intestinal ulcerogenic response to indomethacin was dose-dependently prevented by dopamine as well as atropine. The protective effect of dopamine was almost totally antagonized by domperidone and sulpiride but not by yohimbine. On the other hand, indomethacin markedly enhanced intestinal motility, and the hypermotility response was also prevented by dopamine as well as atropine. Both sulpiride and domperidone, but not yohimbine, also antagonized the inhibitory effect of dopamine on the indomethacin-induced intestinal hypermotility. CONCLUSIONS: These results suggest that dopamine protects the small intestine against indomethacin-induced damage, probably by inhibiting the intestinal hypermotility mediated by dopamine D2 receptors.

Role of cyclooxygenase (COX)-1 and COX-2 inhibition in nonsteroidal anti-inflammatory drug-induced intestinal damage in rats: relation to various pathogenic events.

We recently reported that cyclooxygenase (COX)-2 expression was up-regulated in the rat small intestine after administration of indomethacin, and this may be a key to nonsteroidal anti-inflammatory drug (NSAID)-induced intestinal damage. In the present study, we investigated the effect of inhibiting COX-1 or COX-2 on various intestinal events occurring in association with NSAID-induced intestinal damage. Rats without fasting were treated with indomethacin, SC-560 (a selective COX-1 inhibitor), rofecoxib (a selective COX-2 inhibitor), or SC-560 plus rofecoxib, and the following parameters were examined in the small intestine: the lesion score, the enterobacterial number, myeloperoxidase (MPO) and inducible nitric-oxide synthase (iNOS) activity, and intestinal motility. Indomethacin decreased mucosal prostaglandin (PG)E2 content and caused damage in the intestine within 24 h, accompanied by an increase in intestinal contractility, bacterial numbers, and MPO as well as iNOS activity, together with the up-regulation of COX-2 and iNOS mRNA expression. Neither SC-560 nor rofecoxib alone caused intestinal damage, but their combined administration produced lesions. SC-560, but not rofecoxib, caused intestinal hypermotility, bacterial invasion, and COX-2 as well as iNOS mRNA expression, yet the iNOS and MPO activity was increased only when rofecoxib was also administered. Although SC-560 inhibited the PG production, the level of PGE2 was restored 6 h later, in a rofecoxib-dependent manner. We conclude that inhibition of COX-1, despite causing intestinal hypermotility, bacterial invasion, and iNOS expression, up-regulates the expression of COX-2, and the PGE2 produced by COX-2 counteracts deleterious events, and maintains the mucosal integrity. This sequence of events explains why intestinal damage occurs only when both COX-1 and COX-2 are inhibited.

Mechanisms by which endogenous glucocorticoid protects against indomethacin-induced gastric injury in rats.

We investigated the mechanisms underlying the protective action of glucocorticoids against indomethacin-induced gastric lesions. One-week adrenalectomized rats with or without corticosterone replacement (4 mg/kg sc) were administered indomethacin (25 mg/kg sc), and gastric secretion (acid, pepsin, and mucus), motility, microvascular permeability, and blood glucose levels were examined. Indomethacin caused gastric lesions in sham-operated rats, with an increase in gastric motility and microvascular permeability as well as a decrease in mucus secretion. Adrenalectomy significantly worsened the lesions and potentiated these functional disorders. Glucose levels were lowered by indomethacin in sham-operated rats, and this response was enhanced by adrenalectomy. The changes observed in adrenalectomized rats were prevented by supplementations of corticosterone at a dose mimicking the indomethacin-induced rise in corticosterone, whereas the protective effect of corticosterone was attenuated by RU-38486, a glucocorticoid receptor antagonist. We conclude that the gastroprotective action of endogenous glucocorticoids may be provided by their support of glucose homeostasis and inhibitory effects on enhanced gastric motility and microvascular permeability as well as maintaining the production of mucus.

16,16-Dimethyl prostaglandin E2 inhibits indomethacin-induced small intestinal lesions through EP3 and EP4 receptors.

We evaluated the effect of various PGE analogs specific to EP receptor subtypes on indomethacin-induced small intestinal lesions in rats and investigated the relationship of EP receptor subtype with the PGE action using EP receptor knockout mice. Animals were administered indomethacin subcutaneously, and they were killed 24 hr later. 16,16-dimethyl prostaglandin E2 (dmPGE2) or various EP agonists were administered intravenously 10 min before indomethacin. Indomethacin caused hemorrhagic lesions in the rat small intestine, accompanied with an increase in intestinal motility and the number of enteric bacteria as well as iNOS and MPO activities. Prior administration of dmPGE2 dose-dependently prevented intestinal lesions, together with inhibition of those functional changes. These effects of dmPGE2 were mimicked by prostanoids (ONO-NT-012 and ONO-AE1-329), only specific to EP3 or EP4 receptors, although the intestinal motility was inhibited only by ONO-AE1-329. Intestinal mucus secretion and fluid accumulation were decreased by indomethacin but enhanced by dmPGE2, ONO-NT-012, and ONO-AE1-329 at the doses that prevented intestinal lesions. Indomethacin also caused intestinal lesions in both wild-type and knockout mice lacking EP1 or EP3 receptors, yet the protective action of dmPGE2 was observed in wild-type and EP1 receptor knockout mice but not the mice lacking EP3 receptors. These results suggest that the intestinal cytoprotective action of PGE2 against indomethacin is mediated by EP3/EP4 receptors and that this effect is functionally associated with an increase of mucus secretion and enteropooling as well as inhibition of intestinal hypermotility, the former two processes mediated by both EP3 and EP4 receptors, and the latter by EP4 receptors.

Protective effect of thiaton, an antispasmodic drug, against indomethacin-induced intestinal damage in rats.

The effect of thiaton [3-(di-2-thienylmethylene)-5-methyl-trans-quinolizidinium bromide], an antispasmodic drug, on indomethacin-induced intestinal damage was examined in rats. The animals were given indomethacin, s.c., and the intestinal mucosa was examined 24 h later. Thiaton or atropine was given s.c. twice, 30 min before and 8 h following indomethacin. Indomethacin caused intestinal damage, accompanied with increase in enterobacterial translocation as well as inducible nitric oxide synthase (iNOS) and myeloperoxidase (MPO) activities, and these changes were significantly prevented by supplementation with 16,16-dimethyl prostaglandin E2 (dmPGE2). Treatment of the animals with thiaton dose-dependently prevented the intestinal damage, together with the suppression of MPO and iNOS activities, and these effects were similarly observed by atropine. The increase of bacterial translocation was also significantly prevented by both thiaton and atropine, similar to dmPGE2. Indomethacin enhanced intestinal motility, and this effect was inhibited by either thiaton, atropine or dmPGE2. The intestinal mucus and fluid secretions were decreased by indomethacin but enhanced by dmPGE2. Both thiaton and atropine slightly decreased these secretions under basal conditions but significantly reversed the decrease in the secretions caused by indomethacin. These results suggest that thiaton protects the small intestine against indomethacin-induced damage and inflammatory changes, and this effect is related with prevention of enterobacterial translocation, the process being associated with inhibition of intestinal hypermotility caused by indomethacin, probably due to anti-muscarinic action.

Up-regulation of cyclooxygenase-2 by inhibition of cyclooxygenase-1: a key to nonsteroidal anti-inflammatory drug-induced intestinal damage.

Nonsteroidal anti-inflammatory drugs (NSAIDs) induce gastrointestinal ulceration as the adverse reaction. This effect of NSAIDs is attributable to endogenous prostaglandin (PG) deficiency caused by inhibition of cyclooxygenase (COX), yet the relation between COX inhibition and the gastrointestinal ulcerogenic property of NSAIDs remains controversial. Using selective COX inhibitors, we examined whether inhibition of COX-1 or COX-2 alone is sufficient for induction of intestinal damage in rats. Various COX inhibitors were administered p.o. in rats, and the animals were killed 24 h later. Mucosal PGE2 levels were determined by enzyme immunoassay, whereas the gene expression of COX isozymes was examined by reverse transcription-polymerase chain reaction. Nonselective COX inhibitors such as indomethacin inhibited PGE2 production and caused damage in the small intestine. Selective COX-2 inhibitors (rofecoxib or celecoxib) had no effect on the generation of PG, resulting in no damage. A selective COX-1 inhibitor (SC-560) did not cause damage, despite reducing PGE2 content. However, the combined administration of COX-1 and COX-2 inhibitors provoked intestinal damage with an incidence of 100%. COX-2 was up-regulated in the small intestine after administration of SC-560, and the PGE2 content was restored 6 h later, in a rofecoxib-dependent manner. The intestinal lesions induced by SC-560 plus rofecoxib were significantly prevented by later administration of 16,16-dimethyl PGE2. These results suggest that the intestinal ulcerogenic property of NSAID is not accounted for solely by inhibition of COX-1 and requires inhibition of COX-2 as well. The inhibition of COX-1 up-regulates COX-2 expression, and this may be a key to NSAID-induced intestinal damage.