Inhibition of hydrogen sulfide generation contributes to gastric injury caused by anti-inflammatory nonsteroidal drugs

BACKGROUND & AIMS

Hydrogen sulfide (H(2)S), an endogenous gaseous mediator that causes vasodilation, is generated in mammalian tissues by cystathionine beta-synthase (CBS) and cystathionine-gamma-lyase (CSE). Here, we have investigated the role of H(2)S in a rodent model of nonsteroidal anti-inflammatory drug (NSAID) gastropathy.

METHODS

Rats were given acetyl salycilic acid (ASA) or an NSAID alone or in combination with NaHS, an H(2)S donor, and killed 3 hours later. Gastric blood flow was measured by laser-Doppler flowmetry, whereas intravital microscopy was used to quantify adhesion of leukocytes to mesenteric postcapillary endothelium.

RESULTS

At a dose of 100 micromol/kg, NaHS attenuated by 60%-70% the gastric mucosal injury, and tumor necrosis factor (TNF)-alpha, intercellular adhesion molecule (ICAM)-1, and lymphocyte function-associated antigen (LFA)-1 mRNA up-regulation induced by NSAIDs (P < .05) NaHS administration prevented the associated reduction of gastric mucosal blood flow (P < .05) and reduced ASA-induced leukocyte adherence in mesenteric venules. NaHS did not affect suppression of prostaglandin E(2) (PGE(2)) synthesis by NSAIDs. Glibenclamide, a K(ATP) channel inhibitor, and DL-propargylglycine, a CSE inhibitor, exacerbated, whereas pinacidil, a K(ATP) opener, attenuated gastric injury caused by ASA. Exposure to NSAIDs reduced H(2)S formation and CSE expression (mRNA and protein) and activity by 60%-70%. By promoter deletion and mutation analysis, an Sp1 consensus site was identified in the CSE promoter. Exposure to NSAIDs inhibits Sp1 binding to its promoter and abrogates CSE expression in HEK-293 cells transfected with a vector containing the core CSE promoter. Exposure to NSAIDs inhibits Sp1 and ERK phosphorylation.

CONCLUSIONS

These data establish a physiologic role for H(2)S in regulating the gastric microcirculation and identify CSE as a novel target for ASA/NSAIDs.

The third gas: H2S regulates perfusion pressure in both the isolated and perfused normal rat liver and in cirrhosis

The regulation of sinusoidal resistance is dependent on the contraction of hepatic stellate cells (HSC) around sinusoidal endothelial cell (SEC) through paracrine cross-talk of vasoconstrictor and vasodilator agents. Hydrogen sulfide (H2S), a recently discovered gas neurotransmitter, is a putative vasodilator whose role in hepatic vascular regulation and portal hypertension is unexplored. Four-week bile duct-ligated (BDL) rats with cirrhosis and control rats were treated daily with NaHS (56 micromol/kg) for 5 days. Isolated livers were perfused first with NaHS for 20 minutes and then with norepinephrine (NE) and the intrahepatic resistance studied. In normal rats and animals with cirrhosis, administration of NE resulted in a dose-dependent increase of portal pressure. This effect was attenuated by H2S treatment (P < .05). The H2S-induced relaxation of hepatic microcirculation was attenuated by glibenclamide, an adenosine triphosphate (ATP)-sensitive K+ channel inhibitor. L-Cysteine, a substrate of cystathionine-gamma-lyase (CSE), decreased vasoconstriction in normal rat livers (P < .05) but failed to do so in livers with cirrhosis. BDL resulted in a downregulation of CSE mRNA/protein levels and activity (P < .05). Our in vitro data demonstrate that CSE is expressed in hepatocytes, HSCs, but not in sinusoidal endothelial cells (SEC). HSC activation downregulates CSE mRNA expression, resulting in a defective production of H2S and abrogation of relaxation induced by L-cysteine. In conclusion, CSE-derived H2S is involved in the maintenance of portal venous pressure. The reduction of CSE expression in the liver with cirrhosis contributes to the development of increased intrahepatic resistance and portal hypertension.

Liver delivery of NO by NCX-1000 protects against acute liver failure and mitochondrial dysfunction induced by APAP in mice

1. NCX-1000, (3alpha, 5beta, 7beta)-3,7-dihydroxycholan-24oic acid[2-methoxy-4-[3-[4-(nitroxy)butoxy]-3-oxo-1-propenyl]phenyl ester, is a nitric oxide (NO)-derivative of ursodeoxyxholic acid (UDCA) that selectively release NO in the liver. 2. Here, we demonstrated that administering mice with 40 micromol kg(-1) NCX-1000, but not UDCA, improves liver histopathology and reduces mortality caused by 330 micromol kg(-1) APAP from 60 to 25% (P<0.01). Administration of NCX-1000, in a therapeutic manner, that is, 2 h after acetaminophen (APAP) intoxication reduced mortality, improved liver histopathology and prevented liver IFN-gamma, TNF-alpha, Fas/Fas ligand and inducible nitric oxide synthase (iNOS) mRNA accumulation caused by APAP. 3. In vitro exposure of primary cultures of mouse hepatocytes to APAP, 6.6 mm, resulted in apoptosis followed by necrosis. Loss of cell viability correlates with early mitochondrial membrane potential (Deltapsi(m)) hyperpolarization followed by depolarization and cytochrome c translocation from mitochondria to cytosol. APAP-induced apoptosis associated with procaspase-3 and -9 cleavage, appearance of truncated Bid and activation of poly(ADP-ribose) polymerase (PARP). 4. Treating primary culture of hepatocytes with 5 microm cyclosporine and 10 microm trifluoperazine for eight resulted in significant reduction of apoptosis induced by APAP suggesting that loss of Deltapsim was mechanistically involved in apoptosis induced by APAP in vitro. 5. NCX-1000, but not UDCA, concentration-dependently (ED(50)=16 microm) protected against Deltapsi(m) depolarization and reduced transition from apoptosis to necrosis caused by 6.6 mm APAP. 6. Treating primary cultures of hepatocytes with the NO-donor DETA-NO, 100 microm, reduced apoptosis induced by APAP and prevented caspase activation. 7. In conclusion, NCX-1000 is effective in protecting against APAP-induced hepatotoxicity when administered in a therapeutic manner. This protection may involve the inhibition of apoptosis and the maintenance of mitochondrial integrity.

A beta-oxidation-resistant lipoxin A4 analog treats hapten-induced colitis by attenuating inflammation and immune dysfunction

Lipoxins and aspirin-triggered 15-epi-lipoxins (ATL) are counter-regulatory eicosanoids with potent antiinflammatory actions. Oral efficacy and mechanism of action of ZK-192, a beta-oxidation-resistant 3-oxa-ATL analog, were examined in trinitrobenzenesulphonate (TNBS)-induced colitis. When dosed orally once daily, 300 and 1,000 mug/kg ZK-192 markedly attenuated TNBS colitis in rodents both in preventive and therapeutic regimens. ZK-192 attenuated weight loss, macroscopic and histologic colon injury, mucosal neutrophil infiltration, and colon wall thickening. ZK-192 was as effective as 3-10 mg/kg oral prednisolone. ZK-192 decreased mucosal mRNA levels for several inflammatory mediators: inducible nitric oxide synthase, cyclooxygenase 2, and macrophage inflammatory protein 2. ZK-192 also decreased mucosal mRNA and protein levels of T helper 1 effector cytokines: tumor necrosis factor alpha, IL-2, and IFN-gamma. Systemic levels of these cytokines were also dramatically attenuated. CD3/CD28-mediated costimulation of T helper 1 effector cytokine release in lamina propria mononuclear cells was markedly inhibited by ZK-192 ex vivo and in vitro. ZK-192 also prevented colitis in lymphocyte-deficient severe combined immunodeficient mice, with approximately 75% inhibition of mucosal tumor necrosis factor alpha and IL-2 levels. The results are further evidence that innate immune cells function as triggers for hapten-induced colitis. The combined antiinflammatory and immunomodulatory effects of ZK-192 in TNBS colitis suggest that ATL analogs may be an attractive oral treatment approach for inflammatory bowel diseases.

Nitric oxide regulates immune cell bioenergetic: a mechanism to understand immunomodulatory functions of nitric oxide-releasing anti-inflammatory drugs

The 2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester (NCX-4016) is a NO-releasing derivative of aspirin. In this study, we provide evidence that NCX-4016 delivered to PMBC-derived T lymphocytes and monocytes causes a transitory inhibition of cell respiration and approximately 50% reduction of cellular ATP, which translates in a time-reversible inhibition of cell proliferation and IL-2, IL-4, IL-5, and IFN-gamma secretion. Exposure of lymphocytes and monocytes to aspirin, 2-(acetyloxy)benzoic acid 3-(hydroxymethyl)phenyl ester (NCX-4017), a non-NO-releasing analog of NCX-4016, and cyclooxygenase inhibitors, reduced PG formation, but has no effect on cytokine/chemokine release. In contrast, delivering NO with (z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino] diazen-1-ium-1,2 diolate (DETA-NO) reproduced most of the metabolic and anti-cytokine activities of NCX-4016. Scavenging NO with hemoglobin or adding selective substrates of complex II, III, and IV of the mitochondrial respiratory chain reverses NCX-4016' inhibitory activities. Exposure to DETA-NO and NCX-4016 enhances glucose uptake, glycolytic rate, and lactate generation in CD3/CD28-costimulated lymphocytes, while reduced citric acid cycle intermediates. These effects were not reproduced by selective and nonselective cyclooxygenase 2 inhibitors. In summary, we demonstrated that exposure of lymphocytes to NCX-4016 causes a metabolic hypoxia that inhibits lymphocyte reactivity to costimulatory molecules, providing a potential counteregulatory mechanism to control activated immune system.

Cooperation between aspirin-triggered lipoxin and nitric oxide (NO) mediates antiadhesive properties of 2-(Acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester (NCX-4016) (NO-aspirin) on neutrophil-endothelial cell adherence

2-(Acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester (NCX-4016) is a nitric oxide (NO)-releasing derivative of aspirin that inhibits cyclooxygenase (COX) activity and releases NO. Acetylation of COX-2 by aspirin activates a transcellular biosynthetic pathway that switches eicosanoid biosynthesis from prostaglandin E(2) to 15-epi-lipoxin (LX)A(4) or aspirin-triggered lipoxin (ATL). Here, we demonstrate that exposure of neutrophil (PMN)/human umbilical vein endothelial cell (HUVEC) cocultures to aspirin and NCX-4016 triggers ATL formation and inhibits cell-to-cell adhesion induced by endotoxin (LPS) and interleukin (IL)-1beta by 70 to 90%. However, although selective and nonselective COX-2 inhibitors (celecoxib, rofecoxib, and naproxen) or N-t-butoxycarbonylmethionine-leucine-phenylalanine (Boc-1), an LXA(4) receptor antagonist, reduced the antiadhesive properties of aspirin by approximately 70%, antiadhesive effects of NCX-4016 were only marginally affected ( approximately 30%) by COX inhibitors and Boc-1, implying that COX-independent mechanisms mediate the antiadhesive properties of NCX-4016. Indeed, NCX-4016 causes a long-lasting (up to 12 h) release of NO and cGMP accumulation in HUVEC. Scavenging NO with 10 mM hemoglobin, in the presence of celecoxib, reduced the antiadhesive properties of NCX-4016 by approximately 80%. Confirming a role for NO, the NO donor diethylenetriamine-NO also inhibited PMN/HUVEC adhesion by approximately 80%. NCX-4016, but not aspirin, decreased DNA binding of nuclear factor-kappaB (NF-kappaB) on gel shift analysis and HUVEC's overexpression of CD54 and CD62E induced by LPS/IL-1beta. Reduction of binding of the two NF-kappaB subunits p50-p50 and p50-p65 was reversed by dithiothreitol, implying S-nitrosylation as mechanism of inhibition. In summary, our results support that ATL and NO are formed at the PMN/HUVEC interface after exposure to NCX-4016 and mediate the antiadhesive properties of this compound.

PAR1 antagonism protects against experimental liver fibrosis. Role of proteinase receptors in stellate cell activation

In fibroblasts, thrombin induces collagen deposition through activation of a G-protein-coupled receptor, proteinase-activated receptor 1 (PAR(1)). In the current study, we examined whether PAR(1) antagonism inhibits hepatic stellate cell (HSC) activation in vitro and whether it protects against fibrosis development in a rodent model of cirrhosis. A rat HSC line was used for in vitro studies whereas cirrhosis was induced by bile duct ligation (BDL). The current results demonstrated that HSCs express PAR(1), as well as proteinase-activated receptors 2 (PAR(2)) and 4 (PAR(4)), and that all three PARs were up-regulated in response to exposure to growth factor in vitro. Exposure to thrombin and to SFLLRN-(SF)-NH(2), a PAR(1) agonist, and GYPGKF (GY)-NH(2), a PAR(4) agonist, triggered HSC proliferation and contraction, as well as monocyte chemotactic protein-1 (MCP-1) production and collagen I synthesis and release. These effects were inhibited by the PAR(1) antagonist. Administration of this antagonist, 1.5 mg/kg/d, to BDL rats reduced liver type I collagen messenger RNA (mRNA) expression and surface collagen by 63%, as measured by quantitative morphometric analysis. Similarly, hepatic and urinary excretion of hydroxyproline was reduced significantly by the PAR(1) antagonist. In conclusion, PAR(s) regulates HSC activity; development of PAR antagonists might be a feasible therapeutic strategy for protecting against fibrosis in patients with chronic liver diseases.

Rectal function and bowel habit in irritable bowel syndrome

OBJECTIVES

Rectal compliance may influence rectal perception, but their functional implications remain incompletely understood. Our aim was to determine whether rectal function is related to bowel habit in the irritable bowel syndrome.

METHODS

The responses to fixed tension rectal distension applied by means of a tensostat were compared among constipation-predominant (n = 9), diarrhea-predominant (n = 7), alternating habit (n = 11) irritable syndrome subgroups, and healthy controls (n = 15).

RESULTS

Overall, patients had normal rectal compliance and increased perception, but compliance was lower in diarrhea-predominant as compared to constipation-predominant patients (6.7 +/- 0.7 ml/mmHg vs. 9.9 +/- 0.7 ml/mmHg, respectively; p < 0.05) and perception was higher (39 +/- 6 g vs. 64 +/- 9 g tolerance, respectively; p < 0.05).

CONCLUSION

Distinctive tensosensitivity and compliance characterize rectal function in irritable bowel syndrome subgroups with different bowel habit.

NCX-1000, a nitric oxide-releasing derivative of ursodeoxycholic acid, ameliorates portal hypertension and lowers norepinephrine-induced intrahepatic resistance in the isolated and perfused rat liver

BACKGROUND/AIMS

We studied whether acute administration of NCX-1000, a nitric oxide (NO)-releasing derivative of ursodeoxycholic acid (UDCA), to animals with established liver cirrhosis decreases intrahepatic resistance and modulates hepatic vascular hypereactivity to norepinephrine (NE).

METHODS

Four-week bile duct ligated (BDL) cirrhotic and control, sham-operated, rats were treated orally with 28 mg/kg per day NCX-1000 or 15 mg/kg per day UDCA for 5 days. Isolated normal and cirrhotic livers were perfused with NE, from 10 nM to 30 microM, in a recirculating system.

RESULTS

NCX-1000 administration to BDL cirrhotic rats decreased portal pressure (P<0.01) without affecting mean arterial pressure and heart rate. In the isolated perfused liver system, administration of NE resulted in a dose-dependent increase of intrahepatic resistance. Vasoconstriction caused by 30 microM NE was reduced by 60% in animals treated with NCX-1000 (P<0.001), while UDCA was uneffective. The same portal pressure lowering effect was documented in cirrhotic and sham operated rats. Administration of NCX-1000 to BDL and sham operated rats resulted in a similar increase of nitrite/nitrate and cGMP concentrations in the liver.

CONCLUSIONS

By selectively delivering NO to the liver, NCX-1000 increases cGMP concentrations and effectively counteracts the effect of endogenous vasoconstrictors on the hepatic vascular tone.

PAR-2 modulates pepsinogen secretion from gastric-isolated chief cells

In the present study, we investigated whether activation of protease-activated receptor type 2 (PAR-2) with SLIGRL (SL)NH2, a short mimetic agonistic peptide, directly stimulates pepsinogen secretion from gastric-isolated, pepsinogen-secreting (chief) cells. Immunostaining of gastric-dispersed chief cells with a specific anti-PAR-2 antibody demonstrated expression of PAR-2 receptors on membrane and cytoplasm. SL-NH2 and trypsin potently stimulated pepsinogen secretion (EC50 = 0.3 nM) and caused Ca2+ mobilization (EC50 = 0.6 nM). In contrast to SL-NH2, the scramble peptide LSIGRL-NH2 failed to stimulate pepsinogen release. Exposure to SL-NH2 also resulted in ERK1/2 phosphorylation and activation. Exposure of chief cells to phosphotyrosine kinase inhibitors and 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one, a selective MEK inhibitor, significantly reduced secretion induced by SL-NH2. Pepsinogen secretion induced by SL-NH2 was desensitized by pretreating the cells with the mimetic peptide and trypsin, and exposure to SL-NH2 abrogates pepsinogen secretion induced by carbachol and CCK-8, but not secretion induced by secretin and vasointestinal peptide. Exposure to Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2 (substance P) but not to calcitonin gene-related peptide increased pepsinogen release. The neurokinin-1 receptor antagonist, N-acetyl-l-tryptophan 3,5-bis(trifluoromethyl)benzyl ester, inhibited substance P-stimulated pepsinogen secretion, whereas it did not affect secretion induced by SL-NH2. Collectively, these data indicate that PAR-2 is expressed on gastric chief cells and that its activation causes a Ca2+-ERK-dependent stimulation of pepsinogen secretion.

Evidence that 5-lipoxygenase and acetylated cyclooxygenase 2-derived eicosanoids regulate leukocyte-endothelial adherence in response to aspirin

(1) Unlike other nonsteroidal anti-inflammatory drugs that inhibit formation of cyclooxygenase (COX)-dependent eicosanoids, acetylation of COX-2 by aspirin switches eicosanoid biosynthesis from prostaglandin E(2) (PGE(2)) to 15-epi-lipoxin A(4) (15-epi-LXA(4) or aspirin-triggered lipoxin, ATL). ATL formation by activated leukocytes (PMN) requires the intervention of 5-lipoxygenase (5-LOX), an enzyme that is involved in leukotriene B(4) (LTB(4)) formation. (2) In the present study, we have examined the role of acetylated COX-2 and 5-LOX in modulating antiadhesive effects of aspirin on adhesion of PMN to endotoxin (LPS)-primed human umbilical endothelial cells (HUVEC). (3) Treating PMN/HUVEC cocultures with aspirin resulted in a concentration-dependent inhibition of cell-to-cell adhesion induced by LPS. Treating HUVEC with selective COX-2 inhibitors, celecoxib and rofecoxib, caused an approximately 70% reversion of antiadhesive effect of aspirin. In contrast, inhibition of neutrophil's 5-LOX pathway with 1 micro M ZD2138, a selective 5-LOX inhibitor, 1 micro M BAY-X-1005, a FLAP inhibitor, or 100 micro M licofelone, a dual COX/5-LOX inhibitor, did not affect antiadhesive properties of aspirin. (4) Exposure to celecoxib (100 micro M) or rofecoxib (10 micro M) completely suppressed ATL formation caused by aspirin without affecting LTB(4) levels. ZD2138, licofelone and BAY-X-1005 inhibited ATL formation as well as LTB(4) generation. (5) Treatment with LXA(4) reduced PMN adhesion to HUVEC and counteracted the proadhesive effect of celecoxib. In contrast, exposure to Boc-1, an LXA(4) antagonist, counteracts the antiadhesive activities of aspirin. Exposure to U75302, an LTB(4) receptor antagonist, enhances the antiadesive effect of aspirin. (6) Reversal of antiadhesive activities of aspirin by celecoxib was associated with increased expression of LFA-1 on PMN and E-selectin on HUVEC. Addition of LXA(4), ZD2138 and U75302 inhibited these changes. (7) The present results support the notion that inhibition of ATL formation is mechanistically linked to the reversal of the antiadhesive activity of aspirin caused by selective COX-1 inhibitors and suggests that the LTB(4)/ATL balance modulates pro- and antiadhesive activity of nonsteroidal anti-inflammatory drugs at the leukocyte-endothelial cell interface.

Relative contribution of acetylated cyclo-oxygenase (COX)-2 and 5-lipooxygenase (LOX) in regulating gastric mucosal integrity and adaptation to aspirin

In addition to inhibiting formation of prothrombotic eicosanoids, aspirin causes the acetylation of cyclooxygenase (COX)-2. The acetylated COX-2 remains active, and upon cell activation, initiates the generation of 15R-HETE, a lipid substrate for 5-lipoxygenase (LOX) leading to the formation of 15-epi-LXA4 (also termed "aspirin-triggered lipoxin," or ATL). Because ATL potently inhibits polymorphonuclear cell (PMN) function, we assessed the relative contribution of this lipid mediator in conjunction with another 5-LOX product, the leukotriene (LT)B4, to the pathogenesis of acute damage and gastric adaptation to aspirin. Data presented herein indicate that acute injury and gastric adaptation to aspirin is associated with ATL generation. Administration of COX inhibitors (celecoxib, indomethacin, ketoprofen) to aspirin-treated rats exacerbated acute injury and abolished adaptation to aspirin. Moreover, it inhibited ATL formation and caused a four- to fivefold increase in LTB4 synthesis. In contrast, licofelone, a COX/5-LOX inhibitor, did not exacerbate acute gastric injury nor did it interfere with gastric adaptation to aspirin. Although licofelone blocked ATL and LTB4 formation in aspirin-treated rats, it attenuated aspirin-induced gastric PMN margination. These findings indicate that the balance between the production of LTB4 and ATL modulates PMN recruitment/function and gastric mucosal responses to aspirin.

Inhibition of intestinal bacterial translocation with rifaximin modulates lamina propria monocytic cells reactivity and protects against inflammation in a rodent model of colitis

BACKGROUND

A modification of the intestinal flora and an increased bacterial translocation is a common finding in patients with inflammatory bowel disease as well as in animal model of colitis. Rifaximin, a non-absorbable derivative of rifamycin, is an effective antibiotic that acts by inhibiting bacterial ribonucleic acid synthesis.

AIMS

In the present study, we investigated the effect of the administration of rifaximin (10, 30 and 50 mg/kg/day) or prednisolone (10 mg/kg/day) in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice.

METHODS

Colitis was induced in mice by intrarectal administration of TNBS (1.5 mg/mouse in 50% ethanol) and disease severity assessed clinically and by histologic scoring of colon damage, determination of interleukin (IL)-2, IL-12, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha (protein and mRNA and myeloperoxidase (MPO) activity in the colon. Cytokines production by the lamina propria mononuclear cells (LPMC) and luminal bacteria were also measured.

RESULTS

Rifaximin administration (30 or 50 mg/kg/day) increased survival rates of colitic mice and reduced colitis severity as demonstrated by improvement of wasting syndrome, histologic scores, decrease in colon IL-2, IL-12, IFN-gamma and TNF-alpha (protein and mRNA) levels, and diminished colon MPO activity. Rifaximin administration caused a significant reduction of colon bacterial translocation towards mesenteric lymph nodes. LPMC obtained from rifaximin-treated mice released significantly lower amount of IFN-gamma in response to ex vivo stimulation with agonistic anti-CD3 and anti-CD28 antibodies. Rifaximin (50 mg/kg/day) significantly accelerates recovery in mice with established colitis.

CONCLUSIONS

Luminal bacterial microflora plays a role in the pathogenesis of TNBS-induced colitis in mice. Rifaximin administration reduces the development of colitis and accelerates healing of established disease by preventing bacterial translocation.

Importance of innate immunity and collagen binding integrin alpha1beta1 in TNBS-induced colitis

Inflammation occurs in the context of integrin-mediated adhesive interactions of cells with their extracellular matrix environment. We investigated the role of the collagen binding integrin alpha1beta1 in a model of colitis. alpha1beta1 was expressed on lamina propria T cells and monocytes during disease. Both alpha1 deficiency and anti-alpha1 mAb treatment (prophylactic and therapeutic) protected against colitis. In vivo alpha1beta1 blockade improved macroscopic and histologic scores, decreased inflammatory cytokine production, and profoundly affected the ability of lamina propria mononuclear cells to proliferate and produce IFN-gamma in vitro. Development and alpha1-mediated inhibition of colitis can be lymphocyte independent, suggesting that activated monocytes also represent a key alpha1beta1-expressing cell type involved in colitis. These results underscore the importance of innate immunity and, specifically, of leukocyte/matrix interactions in regulating local inflammatory responses.

NCX-1015, a nitric-oxide derivative of prednisolone, enhances regulatory T cells in the lamina propria and protects against 2,4,6-trinitrobenzene sulfonic acid-induced colitis in mice

NCX-1015 is a nitric oxide (NO)-releasing derivative of prednisolone. In this study we show NCX-1015 protects mice against the S. A. development and induces healing of T helper cell type 1-mediated experimental colitis induced by intrarectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS). The beneficial effect of NCX-1015 was reflected in increased survival rates, improvement of macroscopic and histologic scores, a decrease in the mucosal content of T helper cell type 1 cytokines (protein and mRNA), and diminished myeloperoxidase activity in the colon. In contrast to its NO derivative, only very high doses of prednisolone were effective in reproducing these beneficial effects. NCX-1015 was 10- to 20-fold more potent than the parent compound in inhibiting IFN-gamma secretion by lamina propria mononuclear cells. Protection against developing colitis correlated with inhibition of nuclear translocation of p65Rel A in these cells. In vivo treatment with NCX-1015 potently stimulated IL-10 production, suggesting that the NO steroid induces a regulatory subset of T cells that negatively modulates intestinal inflammation.

Cyclooxygenase-2-derived lipoxin A4 increases gastric resistance to aspirin-induced damage

BACKGROUND & AIMS

Cyclooxygenase-2 (COX-2) has been implicated as contributing to mucosal defense. Acetylation of COX-2 by aspirin can result in production of an antiinflammatory substance, 15(R)-epi-LXA4. We determined whether aspirin-triggered lipoxin (LX) production via COX-2 diminishes aspirin-induced damage in the rat stomach.

METHODS

Rats were treated with aspirin plus or minus celecoxib or rofecoxib. Gastric generation of LXA4 was measured. Effect of exogenous LXA4 or an LXA4 receptor antagonist on gastric resistance to aspirin-induced damage was examined. Aspirin-induced leukocyte adherence in mesenteric venules, and the effects of LXA4, were examined by intravital microscopy.

RESULTS

Celecoxib and rofecoxib significantly increased the severity of aspirin-induced gastric damage. Aspirin rapidly up-regulated COX-2 expression in the stomach and caused a significant increase in gastric 15(R)-epi-LXA4 production, which was abolished by celecoxib. LXA4 dose dependently (0.25-2.5 microg/kg, intraperitoneally) reduced the severity of aspirin-induced gastric damage and suppressed aspirin-induced leukocyte adherence, whereas an LXA4 antagonist had the opposite effects.

CONCLUSIONS

Aspirin administration results in elevated production of 15(R)-epi-LXA4 via COX-2. LXA4 exerts very potent protective actions on the gastric mucosa. Co-administration of aspirin and a selective COX-2 inhibitor results in substantially more severe gastric injury than is produced with either agent alone.

NCX-4016, a nitric oxide-releasing aspirin, protects endothelial cells against apoptosis by modulating mitochondrial function

We investigated the effect of a nitric oxide (NO)-releasing derivative of aspirin (NCX-4016) on a mitochondria-dependent model of apoptosis in human umbilical endothelial cells (HUVEC). Exposure of HUVEC to staurosporine caused a progressive fall in mitochondrial membrane potential (DeltaPsi(m)) and apoptosis. Exposure to an NO donor, (z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA-NO), caused an early (1-3h) hyperpolarization of DeltaPsi(m) and reduction of apoptosis that was followed (at 4-8 h) by an accelerated collapse of DeltaPsi(m) and cell death. In contrast, treatment with NCX-4016, but not with aspirin or a non-NO-releasing analogue of NCX-4016, protected HUVEC against the apoptotic actions of staurosporine for up to 8 h. Confocal microscopy demonstrated that although NCX-4016 released NO in subcellular compartments, DETA-NO caused a generalized increase in cytosolic fluorescence. Exposure to DETA-NO resulted in a rapid and profound inhibition of cell respiration (78.3 +/- 6.4%), whereas NCX-4016 caused a less pronounced reduction in oxygen consumption (43.5 +/- 5.3%). Staurosporine caused a time-dependent activation of proapoptotic caspases. NCX-4016 prevented this activation, whereas DETA-NO failed to inhibit caspase activity. In contrast to DETA-NO, NCX-4016 did not increase mitochondrial oxidative stress. These data demonstrated that NCX-4016 conveys NO directly inside endothelial cells and modulates mitochondrial function.

Effect of acute and chronic levosulpiride administration on gastric tone and perception in functional dyspepsia

BACKGROUND

Altered visceral perception is common in functional dyspepsia (FD). Dopaminergic pathways control gastrointestinal motility, but whether they modulate visceral sensitivity is unknown.

AIM

To investigate whether levosulpiride, a D2 antagonist, modulates gastric sensitivity and compliance in dyspeptic patients.

METHODS

Eight healthy subjects and 16 dyspeptic patients underwent graded gastric distensions using a tensostat. In dyspeptic patients the same isotonic distensions were repeated during either levosulpiride or saline administration. Eight FD patients were evaluated after 4-week treatment with oral levosulpiride. Gastrointestinal symptoms were evaluated using a 100 mm visual analogue score. Perception was scored on a scale of 0 to 6.

RESULTS

Although healthy subjects and FD patients had similar gastric compliance, FD patients tolerated lower tension levels. At the same distending tension levels, levosulpiride decreased gastric compliance and perception score (14 +/- 6% and 38 +/- 10% change, respectively; P < 0.05 vs. saline) only in FD patients. Isotonic distensions exhibited very reproducible perception. Chronic levosulpiride administration significantly reduced dyspeptic symptoms and increased discomfort threshold.

CONCLUSIONS

Compared with healthy subjects, FD patients show marked gastric hypersensitivity. In FD patients levosulpiride decreased the perception of gastric distension with an action unrelated to change of gastric tone. Chronic levosulpiride administration significantly ameliorates gastrointestinal symptoms and increases the discomfort threshold.

Proteinase-activated receptor 2 is an anti-inflammatory signal for colonic lamina propria lymphocytes in a mouse model of colitis

The proteinase-activated receptor 2 (PAR-2) is a member of a family of G protein-coupled receptors for proteases. Proteases cleave PARs within the extracellular N-terminal domains to expose tethered ligands that bind to and activate the cleaved receptors. PAR-2 is highly expressed in colon in epithelial and neuronal elements. In this study we show that PAR-2 activation prevents the development and induces healing of T helper cell type 1-mediated experimental colitis induced by intrarectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) in mice. A role for PAR-2 in the protection against colon inflammation was explored by the use of SLIGRL-NH(2), a synthetic peptide that corresponds to the mouse tethered ligand exposed after PAR-2 cleavage. TNBS-induced colitis was dose-dependently reduced by the administration of SLIGRL-NH(2), whereas the scramble control peptide, LSIGRL-NH(2), was uneffective. This beneficial effect was reflected by increased survival rates, improvement of macroscopic and histologic scores, decrease in mucosal content of T helper cell type 1 cytokines, protein, and mRNA, and a diminished myeloperoxidase activity. SLIGRL-NH(2), but not the scramble peptide, directly inhibited IFN-gamma secretion and CD44 expression on lamina propria T lymphocytes. Protection exerted by PAR-2 in TNBS-treated mice was reverted by injecting mice with a truncated form of calcitonin gene-related peptide and by sensory neurons ablation with the neurotoxin capsaicin. Collectively, these studies show that PAR-2 is an anti-inflammatory receptor in the colon and suggest that PAR-2 ligands might be effective in the treatment of inflammatory bowel diseases.

NO-mesalamine protects colonic epithelial cells against apoptotic damage induced by proinflammatory cytokines

The activation of a self-amplifying cascade of caspases, of which caspase-8 is the apical protease, mediates Fas-, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-, and TNF-alpha-induced apoptosis in colon cell lines. Nitric oxide (NO) protects from apoptosis induced by Fas and TNF-alpha. We examined whether NCX-456, an NO-releasing derivative of mesalamine, protects colon epithelial cells from cytokine-induced apoptosis. Caco-2 and HT-29 cell lines express death factor receptors and are driven to apoptosis in response to incubation with Fas-agonistic antibody, TNF-alpha/interferon-gamma, and TRAIL. The two novel observations reported here are that 1) cotreatment of cells with NCX-456, but not mesalamine, resulted in concentration-dependent protection against death factor-induced apoptosis and inhibition of caspase activity, and 2) exposure to dithiothreitol, an agent that effectively removes NO from thiol groups, resulted in a 70% recovery of caspase activity, which is consistent with S-nitrosation as a major mechanism for caspase inactivation. These data suggest that caspase S-nitrosation represents a mechanism for protection of colonic mucosal epithelial cells from death factor-induced death.

NO-aspirin protects from T cell-mediated liver injury by inhibiting caspase-dependent processing of Th1-like cytokines

BACKGROUND & AIMS

Concanavalin A (con A)-induced hepatitis is an immunomediated disease in which assembly of CD4(+) T cells and T helper (Th)1-like cytokines causes Fas-mediated liver cell death. Nitric oxide (NO) modulates Th1 response in vitro. NCX-4016 is an NO-aspirin derivative that spares the gastrointestinal tract and shares molecular targets with NO. The aim of this study was to investigate whether this NO-aspirin modulates Th1-like response induced by con A.

METHODS

BALB/c mice were injected with 0.3 mg con A per mouse alone or in combination with NO-aspirin (18-100 mg/kg) or aspirin (10-55 mg/kg).

RESULTS

NO-aspirin, but not aspirin, caused a dose-dependent protection against liver damage induced by con A. At a dose of 100 mg/kg, NO-aspirin caused a 40%-80% reduction of interleukin (IL)-1beta, IL-12, IL-18, interferon (IFN)-gamma, and tumor necrosis factor alpha production without affecting cytokine messenger RNA expression. NO-aspirin prevented Fas, Fas ligand, and IL-2 receptor up-regulation on spleen lymphocytes and Fas ligand on hepatocytes and caused the S-nitrosylation/inhibition of IL-1beta-converting enzyme-like cysteine proteases (caspases) involved in the processing and maturation of IL-1beta and IL-18. IL-18 immunoneutralization prevented IFN-gamma release and protected from liver injury induced by con A. In contrast to a selective caspase 1 inhibitor, zVAD.FMK, a pancaspase inhibitor, prevented IFN-gamma release and protected the liver from injury.

CONCLUSIONS

Th1-like response induced by con A is mediated by IL-18 and requires activation of multiple caspases. NCX-4016 causes the S-nitrosylation/inhibition of caspases involved in cytokine production. Inhibition of Th1-like response is a new anti-inflammatory mechanism of action of NO-aspirin.