Role of neutrophil elastase in stress-induced gastric mucosal injury in rats

Dexmedetomidine postconditioning alleviates spinal cord ischemia-reperfusion injury in rats via inhibiting neutrophil infiltration, microglia activation, reactive gliosis and CXCL13/CXCR5 axis activation

PURPOSE

Spinal cord ischemia-reperfusion (I/R) injury is an unresolved complication and its mechanisms are still not completely understood. Here, we studied the neuroprotective effects of dexmedetomidine (DEX) postconditioning against spinal cord I/R injury in rats and explored the possible mechanisms.

MATERIALS AND METHODS

In the study, rats were randomly divided into five groups: sham group, I/R group, DEX0.5 group, DEX2.5 group, and DEX5 group. I/R injury was induced in experimental rats; 0.5 μg/kg, 2.5 μg/kg, 5 μg/kg DEX were intravenously injected upon reperfusion respectively. Neurological function, histological assessment, and the disruption of blood-spinal cord barrier (BSCB) were evaluated via the BBB scoring, hematoxylin and eosin staining, Evans Blue (EB) extravasation and spinal cord edema, respectively. Neutrophil infiltration was evaluated via Myeloperoxidase (MPO) activity. Microglia activation and reactive gliosis was evaluated via ionized calcium-binding adapter molecule-1(IBA-1) and glial fibrillary acidic protein (GFAP) immunofluorescence, respectively. The expression of C-X-C motif ligand 13 (CXCL13), C-X-C chemokine receptor type 5(CXCR5), caspase-3 was determined by western blotting. The expression levels of interleukin 6(IL-6), tumor necrosis factor-α(TNF-α), IL-1β were determined by ELISA assay.

RESULTS

DEX postconditioning preserved neurological assessment scores, improved histological assessment scores, attenuated BSCB leakage after spinal cord I/R injury. Neutrophil infiltration, microglia activation and reactive gliosis were also inhibited by DEX postconditioning. The expression of CXCL13, CXCR5, caspase-3, IL-6, TNF-α, IL-1β were reduced by DEX postconditioning.

CONCLUSIONS

DEX postconditioning alleviated spinal cord I/R injury, which might be mediated via inhibition of neutrophil infiltration, microglia activation, reactive gliosis and CXCL13/CXCR5 axis activation.

Bauhinia Protease Inhibitors Attenuate Gastric Ulcer by Blocking Neutrophil Enzymes

Proteases play a pivotal role in many signaling pathways; inhibitors of well-established proteases have shown a substantial therapeutic success. This study aimed to examine the in vivo effects of 3 protease inhibitors isolated from Bauhinia species: i) Bauhinia mollis elastase inhibitor, which blocks human neutrophil elastase (Ki_app 2.8 nM) and cathepsin G (Ki_app 1.0 nM) activities; ii) Bauhinia mollis trypsin inhibitor, a trypsin inhibitor (Ki_app 5.0 nM); and iii) Bauhinia bauhinioides cruzipain inhibitor, which inhibits elastase (Ki_app 2.6 nM), cathepsin G (Ki_app 160.0 nM), and the cysteine proteases cathepsin L (Ki_app 0.2 nM). Bauhinia bauhinioides cruzipain inhibitor, Bauhinia mollis elastase inhibitor, and Bauhinia mollis trypsin inhibitor were isolated using acetone and ammonium sulfate fractionations, DEAE-Sephadex, trypsin-Sepharose, and Resource-Q chromatographies. Mice and rats were treated intraperitoneally with 1 dose of inhibitor; gastric mucosal lesions were induced by cold-restraint stress. Oral pretreatment of mice with Bauhinia mollis elastase inhibitor or Bauhinia mollis trypsin inhibitor (1 - 10 mg/kg) did not show anti-ulcer effect, while Bauhinia bauhinioides cruzipain inhibitor (0.1 - 1.0 mg/kg) produced a similar reduction of the index of mucosal damage at all effective doses (30 to 33% < control). In rats at doses lower than those used in mice, Bauhinia mollis elastase inhibitor and Bauhinia bauhinioides cruzipain inhibitor reduced the index of mucosal damage by 66% and 54% of controls, respectively. The results indicate a protective effect against gastric mucosal lesions associated with elastase inhibition but not inhibition of trypsin activities. Moreover, the lack of Bauhinia mollis elastase inhibitor efficacy observed in mice may possibly be related to the reported structural differences of elastase in mice and rats.

MAGL inhibition modulates gastric secretion and motility following NSAID exposure in mice

Non-steroidal anti-inflammatory drugs (NSAIDs) are common analgesic drugs that also cause well-known, negative gastrointestinal (GI) side effects. The physiological mechanism(s) of NSAID-induced GI damage are unclear and are likely due to multiple causes. The most studied contributing mechanisms are increased gastric acid secretion and increased gastric motility. The present study was designed to determine which ulcerogenic effects of the NSAID diclofenac sodium are reversed by blocking the endocannabinoid catabolic enzyme monoacylglycerol lipase (MAGL). Both male and female mice were used to identify possible sex differences. We hypothesized that the MAGL inhibitor JZL184 would attenuate diclofenac-induced increases in both gastric acid secretion and gastric motility. Diclofenac dose-dependently induced gastric hemorrhages to a similar extent in both male and female mice. Gastric hemorrhage severity significantly correlated with gastric levels of myeloperoxidase, an objective measure of neutrophil infiltration. Similarly, JZL184 reduced gastric acidity, in controls as well as mice treated with pentagastrin, which stimulates gastric acid release. As hypothesized, JZL184 decreased gastric motility. Surprisingly, diclofenac also slowed gastric emptying, indicating that diclofenac-induced ulcers most likely occur through increased gastric acid secretion, and not increased gastric motility, as measured in the present study. Thus, MAGL inhibition may proffer gastroprotection through modulating the secretory pathway of gastric hemorrhage. These data underscore the importance of sampling multiple time points and using both sexes in research, in addition to multiple mechanistic targets, and contribute to the basic understanding of NSAID-induced gastric inflammation.

Gastroprotective and antielastase effects of protein inhibitors from Erythrina velutina seeds in an experimental ulcer model

Trypsin and chymotrypsin inhibitors from Erythrina velutina seeds have been previously isolated by our group. In previous studies using a sepsis model, we demonstrated the antitumor and anti-inflammatory action of these compounds. This study aimed to evaluate the gastroprotective and antielastase effects of protein inhibitors from E. velutina seeds in an experimental stress-induced ulcer model. Two protein isolates from E. velutina seeds, with antitrypsin (PIAT) and antichymotrypsin (PIAQ) activities, were tested. Both protein isolates showed a high affinity and inhibitory effect against human neutrophil elastase, with 84% and 85% inhibition, respectively. Gastric ulcer was induced using ethanol (99%) in 6 groups of animals (female Wistar rats, n = 6). Before ulcer induction, these animals were treated for 5 days with one of the following: (1) PIAT (0.2 mg·kg−1), (2) PIAT (0.4 mg·kg−1), (3) PIAQ (0.035 mg·kg−1), (4) ranitidine hydrochloride (50 mg·kg−1), (5) saline solution (0.9%), or (6) no intervention (sham). Both PIAT and PIAQ protected gastric mucosa, preventing hemorrhagic lesions, edema, and mucus loss. No histologic toxic effects of PIAT or PIAQ were seen in liver and pancreatic cells. Our results show that protein isolates from E. velutina seeds have potential gastroprotective effects, placing these compounds as natural candidates for gastric ulcer prevention.

Diacylglycerol lipase β inhibition reverses nociceptive behaviour in mouse models of inflammatory and neuropathic pain

BACKGROUND AND PURPOSE

Inhibition of diacylglycerol lipase (DGL)β prevents LPS-induced pro-inflammatory responses in mouse peritoneal macrophages. Thus, the present study tested whether DGLβ inhibition reverses allodynic responses of mice in the LPS model of inflammatory pain, as well as in neuropathic pain models.

EXPERIMENTAL APPROACH

Initial experiments examined the cellular expression of DGLβ and inflammatory mediators within the LPS-injected paw pad. DAGL-β (-/-) mice or wild-type mice treated with the DGLβ inhibitor KT109 were assessed in the LPS model of inflammatory pain. Additional studies examined the locus of action for KT109-induced antinociception, its efficacy in chronic constrictive injury (CCI) of sciatic nerve and chemotherapy-induced neuropathic pain (CINP) models.

KEY RESULTS

Intraplantar LPS evoked mechanical allodynia that was associated with increased expression of DGLβ, which was co-localized with increased TNF-α and prostaglandins in paws. DAGL-β (-/-) mice or KT109-treated wild-type mice displayed reductions in LPS-induced allodynia. Repeated KT109 administration prevented the expression of LPS-induced allodynia, without evidence of tolerance. Intraplantar injection of KT109 into the LPS-treated paw, but not the contralateral paw, reversed the allodynic responses. However, i.c.v. or i.t. administration of KT109 did not alter LPS-induced allodynia. Finally, KT109 also reversed allodynia in the CCI and CINP models and lacked discernible side effects (e.g. gross motor deficits, anxiogenic behaviour or gastric ulcers).

CONCLUSIONS AND IMPLICATIONS

These findings suggest that local inhibition of DGLβ at the site of inflammation represents a novel avenue to treat pathological pain, with no apparent untoward side effects.

The protective effect of apelin against water-immersion and restraint stress-induced gastric damage

The aim of the present study was to investigate the gastroprotective effect of apelin on water-immersion and restraint stress (WIRS)-induced gastric lesions. Male Wistar rats were divided into four groups: control, WIRS, F13A + WIRS and F13A. APJ receptor antagonist F13A was administered to rats to determine the influence of apelin on stress-induced gastric injury. WIRS administered for 6 h resulted in the development of gastric mucosal lesions accompanied by a significant increase in plasma corticosterone. WIRS increased the concentration of 4-hydroxynonenol (4-HNE) + malondialdehyde (MDA) and the expression of apelin and hypoxia inducible factor-1α (HIF-1α) in gastric mucosa. In addition, WIRS reduced the mucosal blood flow and gastric prostaglandin E(2) (PGE(2)) concentration. Plasma corticosterone, which was increased due to stress, was significantly decreased in the F13A + WIRS group. Gastric lesions and the 4-HNE + MDA concentration were also higher in the F13A + WIRS compared to the WIRS group. We conclude that apelin has a gastroprotective effect against stress-induced lesions possibly by reducing lipid peroxidation in gastric mucosa.

In vivo characterization of the highly selective monoacylglycerol lipase inhibitor KML29: antinociceptive activity without cannabimimetic side effects

BACKGROUND AND PURPOSE

Since monoacylglycerol lipase (MAGL) has been firmly established as the predominant catabolic enzyme of the endocannabinoid 2-arachidonoylglycerol (2-AG), a great need has emerged for the development of highly selective MAGL inhibitors. Here, we tested the in vivo effects of one such compound, KML29 (1,1,1,3,3,3-hexafluoropropan-2-yl 4-(bis(benzo[d][1,3]dioxol-5-yl)(hydroxy)methyl)piperidine-1-carboxylate).

EXPERIMENTAL APPROACH

In the present study, we tested KML29 in murine inflammatory (i.e. carrageenan) and sciatic nerve injury pain models, as well as the diclofenac-induced gastric haemorrhage model. KML29 was also evaluated for cannabimimetic effects, including measurements of locomotor activity, body temperature, catalepsy, and cannabinoid interoceptive effects in the drug discrimination paradigm.

KEY RESULTS

KML29 attenuated carrageenan-induced paw oedema and completely reversed carrageenan-induced mechanical allodynia. These effects underwent tolerance after repeated administration of high-dose KML29, which were accompanied by cannabinoid receptor 1 (CB1 ) receptor desensitization. Acute or repeated KML29 administration increased 2-AG levels and concomitantly reduced arachidonic acid levels, but without elevating anandamide (AEA) levels in the whole brain. Furthermore, KML29 partially reversed allodynia in the sciatic nerve injury model and completely prevented diclofenac-induced gastric haemorrhages. CB1 and CB2 receptors played differential roles in these pharmacological effects of KML29. In contrast, KML29 did not elicit cannabimimetic effects, including catalepsy, hypothermia and hypomotility. Although KML29 did not substitute for Δ(9) -tetrahydrocannabinol (THC) in C57BL/6J mice, it fully and dose-dependantly substituted for AEA in fatty acid amide hydrolase (FAAH) (-/-) mice, consistent with previous work showing that dual FAAH and MAGL inhibition produces THC-like subjective effects.

CONCLUSIONS AND IMPLICATIONS

These results indicate that KML29, a highly selective MAGL inhibitor, reduces inflammatory and neuropathic nociceptive behaviour without occurrence of cannabimimetic side effects.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6.

Repeated low-dose administration of the monoacylglycerol lipase inhibitor JZL184 retains cannabinoid receptor type 1-mediated antinociceptive and gastroprotective effects

The monoacylglycerol lipase (MAGL) inhibitor 4-nitrophenyl 4-(dibenzo[d][1,3]dioxol-5-yl(hydroxy)methyl)piperidine-1-carboxylate (JZL184) produces antinociceptive and anti-inflammatory effects. However, repeated administration of high-dose JZL184 (40 mg/kg) causes dependence, antinociceptive tolerance, cross-tolerance to the pharmacological effects of cannabinoid receptor agonists, and cannabinoid receptor type 1 (CB1) downregulation and desensitization. This functional CB1 receptor tolerance poses a hurdle in the development of MAGL inhibitors for therapeutic use. Consequently, the present study tested whether repeated administration of low-dose JZL184 maintains its antinociceptive actions in the chronic constriction injury of the sciatic nerve neuropathic pain model and protective effects in a model of nonsteroidal anti-inflammatory drug-induced gastric hemorrhages. Mice given daily injections of high-dose JZL184 (≥16 mg/kg) for 6 days displayed decreased CB1 receptor density and function in the brain, as assessed in [(3)H]SR141716A binding and CP55,940 [(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl) cyclohexanol]-stimulated guanosine 5'-O-(3-[(35)S]thio)triphosphate binding assays, respectively. In contrast, normal CB1 receptor expression and function were maintained following repeated administration of low-dose JZL184 (≤8 mg/kg). Likewise, the antinociceptive and gastroprotective effects of high-dose JZL184 underwent tolerance following repeated administration, but these effects were maintained following repeated low-dose JZL184 treatment. Consistent with these observations, repeated high-dose JZL184, but not repeated low-dose JZL184, elicited cross-tolerance to the common pharmacological effects of Δ(9)-tetrahydrocannabinol. This same pattern of effects was found in a rimonabant [(5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide)]-precipitated withdrawal model of cannabinoid dependence. Taken together, these results indicate that prolonged, partial MAGL inhibition maintains potentially beneficial antinociceptive and anti-inflammatory effects, without producing functional CB1 receptor tachyphylaxis/tolerance or cannabinoid dependence.

The protective of hydrogen on stress-induced gastric ulceration

Stress ulceration frequently occurs as a result of major stressful events and hydroxyl radical (⋅OH) is one of the major causative factors for it. Recently, it has been proved that hydrogen, a potent selectively ⋅OH scavenger, can effectively protect animals against ROS-induced tissue damage. In like manner, we hypothesize that hydrogen may have a protective effect against stress ulceration. Gastric ulceration was induced by the method of cold restraint stress. Rats in the hydrogen treatment group received hydrogen-rich saline (10 mL/kg body weight) 5 min before the stress. At 6h post-stress, gastric corpus mucosa was harvested for the measurement of malondialdehyde, protein carbonyl, 8-hydroxy-desoxyguanosine, glutathione, superoxide dismutase, myeloperoxidase, TNF-α, IL-1β and cytokine-induced neutrophils chemoattractant-1. In addition, western blotting was used to determine the expression of p38 MAPK, P-p38 MAPK, P-JNk, JNK, Bcl-xl, Bax and cleaved caspase-3. Nuclear translocation of NF-κB was assessed by electrophoretic mobility shift assay. Gastric mucosa structure and mucosal epithelial cells apoptosis were measured at 12h post-stress. Our present study showed that hydrogen treatment lessened the stress-induced lipid peroxidation, protein carbonyl and DNA oxidant and improved tissue antioxidant potential. In addition, hydrogen mitigated inflammatory response and neutrophils infiltration with suppressing the activity of P-p38 MAPK, P-JNk and NF-κB. Importantly, hydrogen ameliorated gastric mucosa damage with preventing cell apoptosis. Furthermore, the up-regulation of cleaved caspase-3, Bax and down-regulation of Bcl-xl expression were blocked by hydrogen treatment. In conclusion, hydrogen treatment effectively ameliorated stress-associated gastric mucosa damage via its anti-oxidant, anti-inflammatory and anti-apoptotic effects.

Endocannabinoid hydrolysis generates brain prostaglandins that promote neuroinflammation

Phospholipase A(2)(PLA(2)) enzymes are considered the primary source of arachidonic acid for cyclooxygenase (COX)-mediated biosynthesis of prostaglandins. Here, we show that a distinct pathway exists in brain, where monoacylglycerol lipase (MAGL) hydrolyzes the endocannabinoid 2-arachidonoylglycerol to generate a major arachidonate precursor pool for neuroinflammatory prostaglandins. MAGL-disrupted animals show neuroprotection in a parkinsonian mouse model. These animals are spared the hemorrhaging caused by COX inhibitors in the gut, where prostaglandins are instead regulated by cytosolic PLA(2). These findings identify MAGL as a distinct metabolic node that couples endocannabinoid to prostaglandin signaling networks in the nervous system and suggest that inhibition of this enzyme may be a new and potentially safer way to suppress the proinflammatory cascades that underlie neurodegenerative disorders.

Intragastrically administered lysophosphatidic acids protect against gastric ulcer in rats under water-immersion restraint stress

BACKGROUND AND AIM

Lysophosphatidic acid exerts important physiological effects on many types of animal cells through its specific binding to several G protein-coupled receptors. In particular, its potent wound-healing effect has attracted much attention. To determine whether lysophosphatidic acids in a foodstuff and Chinese medicine are effective in protecting against gastric ulcer, we subjected rats to water-immersion restraint stress.

METHODS AND RESULTS

Three direct administrations of a solution of lysophosphatidic acid with a C18 fatty acyl group to the rat stomach in a concentration range of 0.001-0.1 mM resulted in a significant reduction in the number of gastric ulcers induced during water-immersion restraint stress, and the potencies were as follows: linoleoyl species=α-linolenoyl species>oleoyl species. Intragastric administrations of a solution of highly purified lysophosphatidic acid from soybean lecithin significantly protected against the stress-induced gastric ulcers at lower concentrations than partially purified lysophosphatidic acid from soybean lecithin did. In addition, administration of a decocted solution of antyu-san, and lysophosphatidic acid-rich Chinese medicine, to the stomach was more effective in protecting against stress-induced ulcer than decoctations of antyu-san lacking the corydalis tuber component that is rich in lysophosphatidic acid.

CONCLUSIONS

These results clearly show that lysophosphatidic acid is the effective component of soybean lecithin and antyu-san in protection against stress-induced gastric ulcer in the rat model, and suggest that daily intake of lysophosphatidic acid-rich foods or Chinese medicines may be beneficial for prevention of stress-induced gastric ulcer in human subjects.

Inhibition of monoacylglycerol lipase attenuates nonsteroidal anti-inflammatory drug-induced gastric hemorrhages in mice

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used analgesics, but can cause gastric and esophageal hemorrhages, erosion, and ulceration. The endogenous cannabinoid (endocannabinoid; eCB) system possesses several potential targets to reduce gastric inflammatory states, including cannabinoid receptor type 1 (CB(1)), cannabinoid receptor type 2 (CB(2)), and enzymes that regulate the eCB ligands 2-arachidonoylglycerol (2-AG) and N-arachidonoyl ethanolamine (anandamide; AEA). In the presented study, we tested whether 4-nitrophenyl 4-(dibenzo[d][1,3]dioxol-5-yl(hydroxy)methyl)piperidine-1-carboxylate (JZL184), a selective inhibitor of the primary catabolic enzyme of 2-AG, monoacylglycerol lipase (MAGL), would protect against NSAID-induced gastric damage. Food-deprived mice administered the nonselective cyclooxygenase inhibitor diclofenac sodium displayed gastric hemorrhages and increases in proinflammatory cytokines. JZL184, the proton pump inhibitor omeprazole (positive control), or the primary constituent of marijuana, Δ(9)-tetrahydrocannabinol (THC), significantly prevented diclofenac-induced gastric hemorrhages. JZL184 also increased stomach levels of 2-AG, but had no effect on AEA, arachidonic acid, or the prostaglandins E(2) and D(2). MAGL inhibition fully blocked diclofenac-induced increases in gastric levels of proinflammatory cytokines interleukin (IL)-1β, IL-6, tumor necrosis factor α, and granulocyte colony-stimulating factor, as well as IL-10. Pharmacological inhibition or genetic deletion of CB(1) or CB(2) revealed that the gastroprotective effects of JZL184 and THC were mediated via CB(1). The antihemorrhagic effects of JZL184 persisted with repeated administration, indicating a lack of tolerance. These data indicate that increasing 2-AG protects against gastric damage induced by NSAIDs, and its primary catabolic enzyme MAGL offers a promising target for the development of analgesic therapeutics possessing gastroprotective properties.

Neutrophil elastase contributes to the development of ischemia/reperfusion-induced liver injury by decreasing the production of insulin-like growth factor-I in rats

Neutrophil elastase (NE) decreases the endothelial production of prostacyclin (PGI(2)) through the inhibition of endothelial nitric oxide synthase (NOS) activation and thereby contributes to the development of ischemia/reperfusion (I/R)-induced liver injury. We previously demonstrated that calcitonin gene-related peptide (CGRP) released from sensory neurons increases the insulin-like growth factor- I (IGF-I) production and thereby reduces I/R-induced liver injury. Because PGI(2) is capable of stimulating sensory neurons, we hypothesized that NE contributes to the development of I/R-induced liver injury by decreasing IGF-I production. In the present study, we examined this hypothesis in rats subjected to hepatic I/R. Ischemia/reperfusion-induced decreases of hepatic tissue levels of CGRP and IGF-I were prevented significantly by NE inhibitors, sivelestat, and L-658, 758, and these effects of NE inhibitors were reversed completely by the nonselective cyclooxygenase inhibitor indomethacin (IM) and the nonselective NOS inhibitor L-NAME but not by the selective inducible NOS inhibitor 1400W. I/R-induced increases of hepatic tissue levels of caspase-3, myeloperoxidase and the number of apoptotic cells were inhibited by NE inhibitors, and these effects of NE inhibitors were reversed by IM and L-NAME but not by 1400W. Administration of iloprost, a stable PGI(2) analog, produced effects similar to those induced by NE inhibitors. Taken together, these observations strongly suggest that NE may play a critical role in the development of I/R-induced liver injury by decreasing the IGF-I production through the inhibition of sensory neuron stimulation, which may lead to an increase of neutrophil accumulation and hepatic apoptosis through activation of caspase-3 in rats.

Bioactive caffeic acid esters from Glycyrrhiza glabra

Thin layer chromatography bioautography (using DPPH spray reagent) guided fractionation of Glycyrrhiza glabra led to the isolation of two caffeic acid derivative esters, viz. eicosanyl caffeate (1) and docosyl caffeate (2). The two compounds exhibited potent elastase inhibitory activity, with IC(50) values of 0.99 microg mL(-1) and 1.4 microg mL(-1) for 1 and 2, respectively. The compounds also showed moderate antioxidant activity in DPPH and ABTS scavenging assays. The results indicate a possible role of caffeic acid derivatives, in addition to flavonoids in the anti-ulcer properties of G. glabra.

Insulin-like growth factor-I reduces stress-induced gastric mucosal injury by inhibiting neutrophil activation in mice

OBJECTIVE

We previously reported that activated neutrophils are critically involved in the development of stress-induced gastric mucosal injury in mice. Caspase activation plays an important role in the pathogenesis of tissue injury by activating neutrophils through an increase in the expression of endothelial monocyte-activating polypeptide-II (EMAP-II), a chemoattractant for neutrophils. Since insulin-like growth factor-I (IGF-I) inhibits caspase activation, it is possible that IGF-I reduces gastric mucosal injury by inhibiting neutrophil activation. In the present study, we examined this possibility in mice subjected to water-immersion restraint stress (WIR).

DESIGN

Mice were intraperitoneally administered with IGF-I or vehicle before being subjected to WIR. Gastric mucosal injury, gastric myeloperoxidase (MPO) activity, the immunofluorescence intensity of MPO, caspase-3 activity, number of apoptotic cells, EMAP-II expression and activation of Akt and glycogen synthase kinase-3beta (GSK-3beta) in gastric mucosa were determined in mice subjected to WIR. Neutropenia was induced by administration of methotrexate (MTX).

RESULTS

Administration of IGF-I at dosages higher than 200 microg/kg significantly reduced gastric mucosal injury and inhibited increases in gastric MPO activities after 8h of WIR. Administration of MTX also reduced the gastric mucosal injury as well as inhibiting increases in both gastric mucosal MPO activities and circulating neutrophil number. IGF-I (500 microg/kg) inhibited the increases in both gastric MPO activity and the immunofluorescence intensity of MPO observed in the gastric mucosa, but had no effect on the increase in circulating neutrophil number after 8h of WIR. It also markedly blunted WIR-induced increases in caspase-3 activities and the number of apoptotic cells in the gastric mucosa after 8h of WIR. Gastric expression of EMAP-II was markedly increased at 8h after starting WIR and this increase was inhibited by IGF-I administration. Administration of IGF-I enhanced WIR-induced phosphorylation of Akt and GSK-3beta in the gastric mucosa.

CONCLUSION

These observations indicate that IGF-I reduces stress-induced gastric mucosal injury by inhibiting gastric accumulation of neutrophils through inhibition of caspase-3-mediated EMAP-II activation. Furthermore, IGF-I might inhibit caspase-3 activation through Akt/GSK-3beta signaling.

Activation of p38 MAPK by reactive oxygen species is essential in a rat model of stress-induced gastric mucosal injury

Stress ulceration is a common complication in critically ill patients and can result in significant upper gastrointestinal bleeding associated with a high morbidity and mortality. At present, little is known of the molecular mechanisms underlying the incidence of this type of gastric damage. In the present study, we investigated the temporal activation of the redox-sensitive p38 signaling transduction cascade and its roles in a well-defined experimental model of cold immobilization stress-induced gastric ulceration. Exposure of Sprague-Dawley rats to 6 h of cold immobilization stress led to a rapid activation of p38 in the gastric mucosa at as early as 15 min after stress, and this activation was maximal after 1.5 h of stress and still persisted until the end of stress. Selectively blocking p38 by pretreatment with SB 239063, a potent and selective p38 inhibitor, suppressed the stress-promoted TNF-alpha, IL-1beta, and CINC-1 production and then prevented the subsequent neutrophil infiltration, gastric mucosal epithelial necrosis and apoptosis, and the ulcerative lesions formation. Prior administration of the free radical scavengers, tempol and N-acetyl-L-cysteine, abolished the stress induction of p38 activation and the resulting mucosal inflammation and gastric injury. These results demonstrate that reactive oxygen species-mediated p38 activation plays an essential role in the pathogenesis of stress-induced gastric inflammatory damage in the rat model of cold immobilization stress. Our findings suggested that inhibition of p38 activation might be a potential strategy for the prophylaxis and treatment of stress ulceration.

Sustained activation of nuclear factor-kappaB by reactive oxygen species is involved in the pathogenesis of stress-induced gastric damage in rats

OBJECTIVE

Stress ulceration is a common complication in critically ill patients, but the mechanisms involved are poorly understood. In this study we investigated the temporal activation of the redox-sensitive transcription factor nuclear factor-kappaB and its roles in an experimental model of cold immobilization stress-induced gastric mucosal lesions.

DESIGN

Prospective, controlled, and randomized animal study.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

The rats were subjected to cold immobilization stress for a total of 6 hrs. The temporal profiles of nuclear factor-kappaB activation and expression of tumor necrosis factor-alpha, interleukin-1beta, cytokine-induced neutrophil chemoattractant-1 (CINC-1), intercellular adhesion molecule-1 (ICAM-1), and inducible nitric oxide synthase (iNOS) were determined in the gastric corpus mucosa of stressed rats. To study the roles of nuclear factor-kappaB activation, rats received an intravenous bolus of a specific nuclear factor-kappaB inhibitor Bay 11-7082 (20 mg/kg) 1 hr before stress. For antioxidant administration, rats were treated with intravenous injection of a free radical scavenger pyrrolidine dithiocarbamate (50, 100, and 200 mg/kg) 1 hr before stress.

MEASUREMENTS AND MAIN RESULTS

Exposure of rats to 6 hrs of stress led to a rapid and persistent activation of nuclear factor-kappaB, which was associated with transient degradation of inhibitory protein IkappaBalpha and slower but sustained degradation of IkappaBbeta. Nuclear factor-kappaB activation preceded the induction of tumor necrosis factor-alpha, interleukin-1beta, CINC-1, ICAM-1, and iNOS messenger RNAs, all of which were linearly increased with the duration of stress. Bay 11-7082 selectively blocked the stress-induced nuclear factor-kappaB activation and up-regulation of tumor necrosis factor-alpha, interleukin-1beta, CINC-1, ICAM-1, and iNOS messenger RNAs. Inhibition of expression of these proinflammatory genes prevented the increases in myeloperoxidase activity (an indicator of neutrophil infiltration) in gastric mucosa and the development of gastric damage. Pyrrolidine dithiocarbamate dose-dependently inhibited the stress-induced nuclear factor-kappaB pathway activation and consequential proinflammatory gene expression, neutrophil infiltration, and gastric damage, suggesting the involvement of reactive oxygen species in these processes.

CONCLUSIONS

Sustained activation of nuclear factor-kappaB by reactive oxygen species is an important in vivo mechanism mediating stress-induced gastric inflammatory damage in rats.

Inhibition of neutrophil activation by lafutidine, an H2-receptor antagonist, through enhancement of sensory neuron activation contributes to the reduction of stress-induced gastric mucosal injury in rats

Sensory neuron activation reduces water-immersion restraint stress (WIR)-induced gastric mucosal injury by inhibiting neutrophil activation through increase in endothelial production of prostacyclin. This study was designed to examine whether lafutidine, which is an H(2)-receptor antagonist and activates sensory neurons, inhibits neutrophil activation, thereby reducing WIR-induced gastric mucosal injury. Lafutidine enhanced WIR-induced increases in gastric tissue levels of calcitonin gene-related peptide (CGRP) and 6-keto-PGF(1alpha), a stable metabolite of prostacyclin, whereas famotidine, another H(2)-receptor antagonist, did not. Such lafutidine-induced increases in gastric tissue levels of 6-keto-PGF(1alpha) were reversed by pretreatment with capsazepine, an inhibitor of sensory neuron activation, CGRP(8-37), a CGRP antagonist, and indomethacin. Lafutidine inhibited acid-induced exacerbation of gastric mucosal injury in animals subjected to WIR by inhibiting neutrophil activation, whereas famotidine did not. Lafutidine synergistically increased CGRP release from isolated rat dorsal root ganglion neurons in the presence of anandamide, but famotidine did not. These observations suggest that lafutidine might reduce WIR-induced gastric mucosal injury not only by inhibiting acid secretion but also by inhibiting neutrophil activation through enhancement of sensory neuron activation.

Rebamipide decreases the susceptibility of gastric mucosa to acid-induced injury in rats by inhibiting neutrophil activation

We previously demonstrated that activated neutrophils increased the susceptibility of gastric mucosa to acid-induced injury in rats. As rebamipide, an anti-ulcer agent, inhibits neutrophil activation, we examined whether the rebamipide reduces stress-induced gastric mucosal injury by decreasing susceptibility to acid-induced gastric mucosal injury in rats. Increase in both gastric mucosal permeability and gastric microvascular permeability evaluated by (51)Cr-EDTA clearance and Evans blue leakage, respectively, at 6 hr after Water-Immersion Restraint Stress (WIR) were significantly lower in animals with leukocytopenia than those in controls. Pretreatment with neutrophil elastase (NE) inhibitors, an anti-P-selectin monoclonal antibody (MAb), and rebamipide significantly inhibited these increases at 6 hr after WIR. These treatments also inhibited decrease in gastric mucosal blood flow observed at 6 hr after WIR. Acid-induced exacerbation of gastric mucosal injury in rats at 6 hr after WIR was inhibited by NE inhibitors, anti-P-selectin MAb, and rebamipide. Rebamipide significantly inhibited WIR-induced increase in gastric MPO activity at 8 hr after WIR. Observations in the present study raised a possibility that rebamipide decreases the susceptibility of gastric mucosa to acid-induced injury by inhibiting neutrophil activation.

Anti-stress and anti-anxiety effects of centrally acting angiotensin II AT1 receptor antagonists

The brain and the peripheral (hormonal) angiotensin II systems are stimulated during stress. Activation of brain angiotensin II AT(1) receptors is required for the stress-induced hormone secretion, including CRH, ACTH, corticoids and vasopressin, and for stimulation of the central sympathetic activity. Long-term peripheral administration of the angiotensin II AT(1) antagonist candesartan blocks not only peripheral but also brain AT(1) receptors, prevents the hormonal and sympathoadrenal response to isolation stress and prevents the formation of stress-induced gastric ulcers. The mechanisms responsible for the prevention of stress-induced ulcers by the AT(1) receptor antagonist include protection from the stress-induced ischemia and inflammation (neutrophil infiltration and increase in ICAM-1 and TNF-alpha) in the gastric mucosa and a partial blockade of the stress-induced sympathoadrenal stimulation, while the protective effect of the glucocorticoid release during stress is maintained. AT(1) receptor antagonism prevents the stress-induced decrease in cortical CRH(1) and benzodiazepine binding and is anxiolytic. Blockade of brain angiotensin II AT(1) receptors offers a novel therapeutic opportunity for the treatment of anxiety and other stress-related disorders.

Menadione protects gastric mucosa against ethanol-induced ulcers

Previous studies have shown a definite role of mitogen activated protein kinase (MAPK) and epidermal growth factors (EGF) in the maintenance and repair of gastric mucosa. The aim of this study is to investigate the effect of menadione, an activator of MAPK pathway, on gastric acid secretion and experimentally induced gastric ulcer in rats. Acid secretion studies were undertaken using pylorus-ligated rats pretreated with menadione (5 - 45 mg/kg, i.p.). The effect of orally administered menadione on ethanol-induced gastric ulcers was also examined. The level of gastric wall mucus, non-protein sulfhydryls (NP-SH) and myeloperoxidase (MPO) was measured in the glandular stomach of rats following ethanol-induced gastric lesions. There was a significant inhibition of gastric acid secretion in the menadione treated rats. Pretreatment of rats with menadione significantly protected gastric mucosa against ethanol-induced gastric lesion. A significant attenuation of ethanol-induced reduction of gastric wall mucus, depletion of NP-SH and increase in gastric MPO activity was also observed in menadione treated rats. In conclusion, this study clearly showed acid antisecretory and antiulcer activity of menadione. Further studies are warranted to determine the mechanism of antiacid and gastroprotective effect of menadione.

Regulation of inflammatory responses by activated protein C: the molecular mechanism(s) and therapeutic implications

Activated protein C (APC), a natural anticoagulant, is formed from protein C by the action of the thrombin-thrombomodulin (TM) complex on the endothelial cell surface. Endothelial protein C receptor augments the activation of protein C by the thrombin/TM system. APC inactivates the activated form of coagulation factors V and VIII in the presence of protein S. Administration of APC reduced the pulmonary vascular injury and hypotension as well as the coagulation abnormalities by inhibiting production of the tumor necrosis factor-alpha (TNF-alpha) in rats given endotoxin (ET). These therapeutic effects of APC could not be attributed to its anticoagulant effects. APC inhibited ET-induced TNF-alpha production in human monocytes by inhibiting activation of nuclear factor K-B and activator protein-1 in vitro. Administration of the human plasma-derived APC ameliorated coagulation abnormalities without any adverse effects in patients with disseminated intravascular coagulation (DIC). Recombinant APC was reported to reduce the mortality of patients with severe sepsis, and the therapeutic effect was more marked in such patients with overt DIC than those without it. These observations strongly suggest that APC plays important roles in the regulation of inflammation as well as coagulation. Both anti-inflammatory and anticoagulant properties of APC might contribute to the therapeutic usefulness in patients with severe sepsis.

Angiotensin II AT1 receptor blockade prevents gastric ulcers during cold-restraint stress

Cold-restraint stress reduces gastric blood flow and produces acute gastric ulcers. We studied the role of Angiotensin II (Ang II) on gastric blood flow and gastric ulceration during stress. Spontaneously hypertensive rats, a stress-sensitive strain, were pretreated for 14 days with the AT(1) receptor antagonist candesartan before cold-restraint stress. AT(1) blockade increased gastric blood flow 40% to 50%; prevented gastric ulcer formation by 70% to 80%; reduced the increase in adrenomedullary epinephrine and TH mRNA without preventing the stress-induced increase in adrenal corticosterone; decreased the stress-induced expression of tumor necrosis factor alpha (TNF-alpha) and adhesion protein ICAM-1 in arterial endothelium, and neutrophil infiltration in the gastric mucosa; and decreased PGE(2) content. AT(1) receptor blockers prevent stress-induced ulcerations by a combination of gastric blood flow protection, decreased sympathoadrenal activation, anti-inflammatory effects with reduction in TNF-alpha, and ICAM-1 expression, leading to reduced neutrophil infiltration while maintaining the protective glucocorticoid effects and PGE(2) release. Ang II has a crucial role, through stimulation of AT(1) receptors, in the production and progression of stress-induced gastric injury, and AT(1) receptor antagonists could be of therapeutic benefit.

Computer-assisted visualization and quantitation of experimental gastric lesions in rats

INTRODUCTION

Photography is commonly used to evaluate macroscopic morphology of experimental gastric lesions. The conventional methods for quantitation of these lesions tend to be highly subjective, error-prone, and tedious. This study reports a simple and novel method for visualization of experimental gastric lesions by direct scanning of stomach samples and their quantitation by using computer-assisted image analysis.

METHODS

Gastric mucosal lesions were produced by indomethacin or ethanol in male Wistar rats. The stomachs were removed, opened along the greater curvature, and washed. The flattened stomach samples were sandwiched within a transparent plastic folder and scanned. The captured image was saved and subjected to lesion quantitation using a freely accessible image analysis program, Scion Image. A macro subroutine was optimized for automation of the entire procedure for ease in frequent applications.

RESULTS

The images obtained by direct scanning of stomach samples showed excellent morphologic visualization of gastric lesions. The standard spots having variable areas of same density, or same areas of variable densities, showed a direct relation with signal intensity (pixels). A linear correlation was observed between measured and actual values of the known standard areas. The representative samples of indomethacin- and ethanol-induced gastric ulcers showed the total lesion areas of 4.62+/-0.74 and 169.26+/-13.23 mm(2), respectively.

DISCUSSION

Direct scanning of stomach samples is a simple, cost-effective, rapid, and efficient procedure for morphologic evaluation of experimental gastric lesions. The output images of scanned stomach samples are superior to scanned photographs, and can be instantly used for quantitative assessment of mucosal injury using the image analysis program.

Activated protein C reduces stress-induced gastric mucosal injury in rats by inhibiting the endothelial cell injury

BACKGROUND AND OBJECTIVE

Activated protein C (APC) is a natural anticoagulant with anti-inflammatory activity. APC inhibits neutrophil activation through inhibition of tumor necrosis factor (TNF)-alpha production. Such anti-inflammatory activity of APC has recently been shown to be critical in the treatment of patients with severe sepsis. We previously demonstrated that activated neutrophils play a crucial role in the development of stress-induced gastric mucosal injury. Thus, inhibition of neutrophil activation by APC should reduce endothelial cell damage, maintain gastric blood flow, and lessen gastric mucosal injury. In the present study, we examined this possibility by using a rat model of water-immersion restraint stress (WIRS)-induced gastric mucosal injury.

METHODS AND RESULTS

Gastric mucosal injury was observed 4 h after WIRS, without increases in gastric mucosal levels of either myeloperoxidase activity or TNF-alpha, but with significant increases in plasma levels of TNF-alpha 1 h after WIRS. Intravenous administration of APC (100 micro g kg-1) significantly reduced WIRS-induced gastric mucosal injury by inhibiting decrease in gastric mucosal blood flow. Administration of APC also inhibited both the decrease in gastric tissue levels of 6-keto-prostaglandin F1alpha and the increase in gastric mucosal micorvascular permeability in animals subjected to WIRS. Furthermore, APC inhibited WIRS-induced increases in plasma levels of TNF-alpha. Neither active site-blocked factor Xa, which is a selective inhibitor of thrombin generation, nor active site-blocked APC had any effect on these events. Intraperitoneal administration of anti-rat TNF-alpha antibody produced effects similar to those of APC.

CONCLUSIONS

The observations in the present study strongly suggest that APC reduces stress-induced gastric mucosal injury by inhibiting the decrease in gastric mucosal blood flow through attenuation of the activated neutrophil-induced endothelial cell injury via inhibition of TNF-alpha production. In addition, we show that serine protease activity of APC, rather than its anticoagulant activity, is critical for the protective mechanism(s) by which TNF-alpha production could be inhibited.

Protective effect of coadministered superoxide dismutase and catalase against stress-induced gastric mucosal lesions

1. There are conflicting reports as to the protective effect of coadministered native superoxide dismutase (SOD) and catalase against gastric mucosal lesions in rats with water immersion restraint (WIR) stress. It is unclear how coadministered native SOD and catalase protect against WIR stress-induced gastric mucosal lesions. Therefore, in the present study, we re-examined the protective effect of coadministered native SOD and catalase against gastric mucosal lesions in rats with WIR stress. 2. Gastric mucosal lesions were induced in Wistar rats by 3 h WIR. Rats were injected subcutaneously with a mixture of purified bovine erythrocyte SOD and bovine liver catalase 1 h before the onset of WIR. Ulcer index, serum SOD, catalase and xanthine oxidase (XO), uric acid and gastric mucosal SOD, catalase, XO, myeloperoxidase (MPO; an index of tissue neutrophil infiltration), non-protein sulfhydryl (NP-SH) and thiobarbituric acid-reactive substances (TBARS; an index of lipid peroxidation) were assayed in all rats used. 3. Rats with 3 h WIR showed gastric mucosal lesions. Pre-administration of SOD plus catalase to rats with WIR prevented lesion formation. In the serum of rats with WIR alone, XO activity and uric acid concentration increased, whereas SOD and catalase activities did not change. Pre-administration of SOD plus catalase to rats with WIR did not affect increased serum XO activity and uric acid concentration, but did increase serum SOD and catalase activities. In the gastric mucosa of rats with WIR alone, increases in MPO activity and TBARS concentration and a decrease in NP-SH concentration occurred, whereas XO, SOD and catalase activities did not change. Pre-administration of SOD plus catalase to rats with WIR attenuated the changes in gastric mucosal MPO activity and TBARS and NP-SH concentrations, but did not affect gastric mucosal XO, SOD and catalase activities. Pre-administration of SOD plus catalase (in an inactivated form) to rats with WIR had no effect on gastric mucosal lesion formation and the levels of serum and gastric mucosal parameters studied. 4. These results indicate that coadministered native SOD and catalase protect against gastric mucosal lesions in rats with WIR stress and suggest that this protective effect of coadministered native SOD and catalase could be due to their activity to scavenge XO-derived active oxygen species that are increased in the blood.

Anti-inflammatory effects of angiotensin II AT1 receptor antagonism prevent stress-induced gastric injury

Stress reduces gastric blood flow and produces acute gastric mucosal lesions. We studied the role of angiotensin II in gastric blood flow and gastric ulceration during stress. Spontaneously hypertensive rats were pretreated for 14 days with the AT1 receptor antagonist candesartan before cold-restraint stress. AT1 receptors were localized in the endothelium of arteries in the gastric mucosa and in all gastric layers. AT1 blockade increased gastric blood flow by 40-50%, prevented gastric ulcer formation by 70-80% after cold-restraint stress, reduced the increase in adrenomedullary epinephrine and tyrosine hydroxylase mRNA without preventing the stress-induced increase in adrenal corticosterone, decreased the stress-induced expression of TNF-alpha and that of the adhesion protein ICAM-1 in arterial endothelium, decreased the neutrophil infiltration in the gastric mucosa, and decreased the gastric content of PGE2. AT1 receptor blockers prevent stress-induced ulcerations by a combination of gastric blood flow protection, decreased sympathoadrenal activation, and anti-inflammatory effects (with reduction in TNF-alpha and ICAM-1 expression leading to reduced neutrophil infiltration) while maintaining the protective glucocorticoid effects and PGE2 release. Angiotensin II has a crucial role, through stimulation of AT1 receptors, in the production and progression of stress-induced gastric injury, and AT1 receptor antagonists could be of therapeutic benefit.

Prostaglandin E1 reduces compression trauma-induced spinal cord injury in rats mainly by inhibiting neutrophil activation

Prostaglandin E1 (PGE1), a potent vasodilator, was recently reported to inhibit both neutrophil activation and monocytic production of tumor necrosis factor-alpha (TNF-alpha) in vitro. We previously reported that TNF-alpha was critically involved in the development of motor disturbances by increasing the accumulation of neutrophils at the site of injury in rats subjected to compression trauma-induced spinal cord injury. Therefore, it is possible that PGE1 reduces motor disturbances by inhibiting neutrophil activation in rats subjected to spinal cord injury. We examined this possibility in a rat model of spinal cord injury (SCI). Motor disturbances induced by spinal cord compression were evaluated using the inclined plane test, and footprint analysis. Accumulation of neutrophils at the site of trauma was evaluated by measuring tissue myeloperoxydase (MPO) activity. Tissue levels of TNF-alpha were determined using an enzyme-linked immunosorbent assay. Motor disturbances induced by spinal cord compression were significantly attenuated in rats administered PGE1. A histological examination revealed that intramedullary hemorrhages, observed 24 h after trauma, were markedly reduced in animals administered PGE1. Increases in the tissue levels of TNF-alpha and MPO activity in the damaged segment of spinal cord were significantly inhibited in animals that had received PGE1. These observations suggested that PGE1 reduces motor disturbances by inhibiting neutrophil activation directly or indirectly through the inhibition of TNF-alpha production at the site of injury. These effects of PGE1 might at least partly contribute to therapeutic effect on SCI in rats.

Glyproline peptide family: review on bioactivity and possible origins

Glyproline peptide family includes the simplest proline-containing linear peptides PG, GP, PGP, respective peptides with hydroxylated proline residues and (with some restriction) cyclic PG. Having close structural resemblance they display many similar bioactivities. The suppression of some reactions of blood coagulation and platelet aggregation and protection of gastric mucosa against various ulcerogenic factors are the most important glyproline effects. Glyprolines have two common putative sources: (1) collagen and elastin synthesis and catabolism, and (2) penetration of proline-containing di- and tripeptides from food protein hydrolysate from the intestine into bloodstream. Possible physiological and biochemical mechanisms of glyproline bioactivities are under discussion.

Inhibition of neutrophil activation by ranitidine contributes to prevent stress-induced gastric mucosal injury in rats

OBJECTIVE

Activated neutrophils play a critical role in stress-induced gastric mucosal injury. We investigated the effect of ranitidine, an H2-receptor antagonist, on neutrophil activation in vitro and in rats with stress-induced gastric mucosal injury.

DESIGN

Prospective, randomized, blinded, controlled study.

SETTING

Research laboratory at a university medical center.

INTERVENTIONS

Effects of ranitidine on neutrophil elastase release, production of O2-, intracellular calcium concentration and expression of adhesion molecules CD11b and CD18 were examined in human neutrophils in vitro. The effect of ranitidine (30 mg/kg iv) on the development of gastric mucosal injury, neutrophil accumulation, and lipid peroxidation was investigated in male Wistar rats subjected to water-immersion restraint stress.

MEASUREMENTS AND MAIN RESULTS

Ranitidine inhibited the release of neutrophil elastase as well as the production of O2-, the increase in the concentrations of intracellular calcium, a second messenger of neutrophil activation, and increases in CD11b and CD18 expression, in activated neutrophils. Ranitidine did not affect the expression of E-selectin on endothelial cells in vitro. Ranitidine significantly inhibited gastric accumulation of neutrophils and gastric mucosal lipid peroxidation in rats subjected to stress. Although oral administration of acid reversed the preventive effect of pirenzepine, an anti-cholinergic drug that inhibits gastric acid secretion, it did not affect the preventive effect of ranitidine. Leukocytopenia produced effects similar to those of ranitidine in animals subjected to stress.

CONCLUSIONS

Inhibition of neutrophil activation and gastric acid secretion by ranitidine might contribute to reduce stress-induced gastric mucosal injury.

Activated protein C reduces the ischemia/reperfusion-induced spinal cord injury in rats by inhibiting neutrophil activation

OBJECTIVE

To examine whether activated protein C (APC) reduces spinal cord injury in rats by inhibiting neutrophil activation after the transient ischemia.

SUMMARY BACKGROUND DATA

Ischemic spinal cord injury is an important pathologic mechanism leading to the paraplegia observed after surgery to repair aortic aneurysms. Activated neutrophils play a pivotal role in the development of ischemia/reperfusion-induced tissue injury. Recently, the authors have reported that APC, a physiologic anticoagulant, prevents lipopolysaccharide-induced pulmonary vascular injury by inhibiting neutrophil activation. These observations strongly suggest that APC reduces ischemia/reperfusion-induced spinal cord injury by inhibiting neutrophil activation.

METHODS

In rats, spinal cord ischemia was induced by using a balloon catheter placed into the aorta. After the transient ischemia, survival and motor function were evaluated, and histologic examination of the spinal cord was performed by using both hematoxylin-and-eosin staining and 2,3,5, -triphenyltetrazolium chloride (TTC) staining 24 hours after the ischemia. Tissue levels of myeloperoxidase and cytokines, including tumor necrosis factor-alpha (TNF-alpha) and rat interleukin-8, were measured in six experimental groups: sham-operated, control, APC (100 microg/kg, intravenous), dansyl glutamyl-glycyl-arginyl chloromethyl ketone-treated activated factor X (DEGR-F.Xa), a selective inhibitor of thrombin generation (1 mg/kg, intravenous), nitrogen mustard-induced leukocytopenia, and diisopropyl fluorophosphate-treated APC (DIP-APC), active site-blocked APC (100 microg/kg, intravenous). APC, DEGR-F.Xa, and DIP-APC were administered intravenously 30 minutes before aortic occlusion. Control and leukocytopenic rats received saline instead of other drugs.

RESULTS

Pretreatment with APC significantly reduced motor disturbances compared with those in control animals. In contrast, neither DEGR-F.Xa nor DIP-APC had any effect. Microinfarctions, evidenced by the absence of TTC staining and histologic change, were markedly reduced in animals given APC. The increases in the tissue levels of TNF-alpha, rat interleukin-8, and myeloperoxidase in the ischemic part of the spinal cord were significantly reduced in animals that received APC. These levels were not reduced in rats given DEGR-F.Xa or DIP-APC. Leukocytopenia produced effects similar to those of APC.

CONCLUSIONS

APC reduced the ischemia/reperfusion-induced spinal cord injury by inhibiting neutrophil activation. The therapeutic mechanisms of APC might depend on its inhibitory effect on the production of TNF-alpha, which is a potent activator of neutrophils. Although the anticoagulant effects of APC might not be related to its ability to inhibit TNF-alpha production, its serine protease activity appears to be essential in the therapeutic mechanism. APC appears to have potential as a therapeutic agent for prevention of spinal cord injury in patients undergoing aortic aneurysm repair.

Activated protein C reduces ischemia/reperfusion-induced renal injury in rats by inhibiting leukocyte activation

We examined whether activated protein C (APC) reduces ischemia/reperfusion (I/R)–induced renal injury by inhibiting leukocyte activation. In a rat model, intravenous administration of APC markedly reduced I/R-induced renal dysfunction and histological changes, whereas intravenous administration of dansyl glutamylglycylarginyl chloromethyl ketone–treated factor Xa (DEGR-FXa; active-site–blocked factor Xa), heparin or diisopropyl fluorophosphate–treated APC (DIP-APC; inactive derivative of ARC) had no effect. Furthermore, APC significantly inhibited the I/R-induced decrease in renal tissue blood flow and the increase in the vascular permeability, whereas neither DEGR-FXa, heparin, nor DIP-APC produced such effects. Renal I/R-induced increases in plasma levels of fibrin degradation products were significantly inhibited by APC, DEGR-FXa, and heparin. These observations suggest that APC reduces I/R-induced renal injury independently of its anticoagulant effects but in a manner dependent on its serine protease activity. Renal levels of tumor necrosis factor- (TNF-), rat interleukin-8, and myeloperoxidase were significantly increased after renal I/R. These increases were significantly inhibited by APC but not by DEGR-FXa, heparin, or DIP-APC. Leukocytopenia produced effects similar to those of APC. These findings strongly suggest that APC protects against I/R-induced renal injury not by inhibiting coagulation abnormalities but by inhibiting activation of leukocytes that play an important role in I/R-induced renal injury. Inhibition of leukocyte activation by APC could be explained by the inhibitory activity of TNF-.

Activated protein C reduces ischemia/reperfusion-induced renal injury in rats by inhibiting leukocyte activation

We examined whether activated protein C (APC) reduces ischemia/reperfusion (I/R)–induced renal injury by inhibiting leukocyte activation. In a rat model, intravenous administration of APC markedly reduced I/R-induced renal dysfunction and histological changes, whereas intravenous administration of dansyl glutamylglycylarginyl chloromethyl ketone–treated factor Xa (DEGR-FXa; active-site–blocked factor Xa), heparin or diisopropyl fluorophosphate–treated APC (DIP-APC; inactive derivative of ARC) had no effect. Furthermore, APC significantly inhibited the I/R-induced decrease in renal tissue blood flow and the increase in the vascular permeability, whereas neither DEGR-FXa, heparin, nor DIP-APC produced such effects. Renal I/R-induced increases in plasma levels of fibrin degradation products were significantly inhibited by APC, DEGR-FXa, and heparin. These observations suggest that APC reduces I/R-induced renal injury independently of its anticoagulant effects but in a manner dependent on its serine protease activity. Renal levels of tumor necrosis factor- (TNF-), rat interleukin-8, and myeloperoxidase were significantly increased after renal I/R. These increases were significantly inhibited by APC but not by DEGR-FXa, heparin, or DIP-APC. Leukocytopenia produced effects similar to those of APC. These findings strongly suggest that APC protects against I/R-induced renal injury not by inhibiting coagulation abnormalities but by inhibiting activation of leukocytes that play an important role in I/R-induced renal injury. Inhibition of leukocyte activation by APC could be explained by the inhibitory activity of TNF-.

Antithrombin prevents stress-induced gastric mucosal injury by increasing the gastric prostacyclin level in rats

The interaction of antithrombin (AT) with cell surface glycosaminoglycans has been shown to promote the endothelial release of prostacyclin (PGI2). Because PGI2 plays an important role in gastric cytoprotection, we examined whether AT prevents water-immersion restraint stress (WIR)-induced gastric mucosal injury in rats by promoting the endothelial release of PGI2. Intravenous administration of AT (250 U/kg) prevented WIR-induced gastric mucosal injury in rats. Gastric levels of 6-keto-prostaglandin F1alpha, a stable metabolite of PGI2, were significantly increased 0.5 and 1 hour after WIR in animals administered AT compared with control animals. The effects induced by AT in animals subjected to WIR were not observed in animals that were administered DEGR-Xa, a selective inhibitor of thrombin generation, or Trp49-modified AT, which lacks affinity for heparin. In animals subjected to WIR gastric mucosal blood flow was significantly reduced with a simultaneous increase in gastric mucosal microvascular permeability. Activated neutrophils have been implicated in the WIR-induced reduction of gastric mucosal blood flow by increasing microvascular permeability. Although AT prevented the reduction of gastric mucosal blood flow and the increase in gastric mucosal microvascular permeability in animals subjected to WIR, neither DEGR-Xa nor Trp49-modified AT had any effect. Pretreatment of animals with indomethacin completely inhibited the protective effects of AT against WIR-induced gastric mucosal injury and the AT-induced increase in post-WIR gastric 6-keto-prostaglandin F1alpha levels. These results strongly suggest that AT prevents stress-induced gastric mucosal injury by increasing the gastric levels of PGI2 through the interaction of AT with cell-surface glycosaminoglycans, thus increasing gastric mucosal blood flow both by vasodilation and by inhibiting neutrophil activation.

Plaunotol prevents indomethacin-induced gastric mucosal injury in rats by inhibiting neutrophil activation

BACKGROUND

Activated neutrophils play a critical role in indomethacin-induced gastric mucosal injury.

AIM

To investigate the effect of plaunotol, an anti-ulcer agent, on neutrophil activation in vitro and its effect on gastric mucosal injury and gastric accumulation of neutrophils in rats given indomethacin.

METHODS

Human monocytes and neutrophils were isolated from the peripheral blood of healthy volunteers. We examined the effect of plaunotol on neutrophil elastase release, production of O2-, intracellular calcium concentration and expression of adhesion molecules CD11b and CD18 in activated neutrophils in vitro. The effect of plaunotol on TNF-alpha production by monocytes stimulated with endotoxin also was investigated in vitro. The effect of plaunotol (100 mg/kg, p.o.) on gastric mucosal injury and neutrophil accumulation was investigated in male Wistar rats given indomethacin (30 mg/kg, p.o.).

RESULTS

Plaunotol inhibited the fMLP-induced release of neutrophil elastase from activated neutrophils, as well as the opsonized zymosan-induced production of O2- by neutrophils. Plaunotol significantly inhibited increased levels of intracellular calcium, a second messenger of neutrophil activation, in vitro. The fMLP-induced increases in CD11b and CD18 expression were also inhibited by plaunotol in vitro. Plaunotol inhibited monocytic production of TNF-alpha, a potent activator of neutrophils. Both gastric mucosal injury and gastric neutrophil infiltration in rats given indomethacin were significantly inhibited by the oral administration of plaunotol.

CONCLUSIONS

Plaunotol inhibits indomethacin-induced gastric mucosal injury, at least in part by inhibiting neutrophil activation.