RESUMEN
Rat gastric mucosal damage was induced by ischemia-reperfusion. The 5-lipoxygenase inhibitors MK886 and A63162, the 12-lipoxygenase inhibitor baicalein, the 15-lipoxygenase inhibitor PD146176 and the lipoxin (LX) A(4)/annexin 1 antagonist Boc1 increased mucosal damage in a dose-dependent manner. Low doses of these compounds, which have no effects on mucosal integrity, cause severe damage when combined with low doses of indomethacin, celecoxib or dexamethasone. 16,16-Dimethylprostaglandin (PG) E(2) and LXA(4) can replace each other in preventing mucosal injury induced by either cyclooxygenase or lipoxygenase inhibitors. The results suggest that not only cyclooxygenases, but also lipoxygenases have a role in limiting gastric mucosal damage during ischemia-reperfusion.
Asunto(s)
Anexinas/metabolismo , Mucosa Gástrica/efectos de los fármacos , Lipooxigenasa/fisiología , Receptores de Formil Péptido/fisiología , Receptores de Lipoxina/fisiología , Daño por Reperfusión/tratamiento farmacológico , 16,16-Dimetilprostaglandina E2/farmacología , Acetamidas/farmacología , Animales , Antiulcerosos/farmacología , Celecoxib , Inhibidores de la Ciclooxigenasa/farmacología , Dexametasona/farmacología , Sinergismo Farmacológico , Flavanonas/farmacología , Fluorenos/farmacología , Mucosa Gástrica/irrigación sanguínea , Mucosa Gástrica/patología , Glucocorticoides/farmacología , Indoles/farmacología , Indometacina/farmacología , Inhibidores de la Lipooxigenasa/farmacología , Masculino , Oligopéptidos/farmacología , Éteres Fenílicos , Antagonistas de Prostaglandina/farmacología , Pirazoles/farmacología , Ratas , Ratas Wistar , Receptores de Lipoxina/antagonistas & inhibidores , Daño por Reperfusión/metabolismo , Daño por Reperfusión/patología , Sulfonamidas/farmacologíaRESUMEN
The role of cyclooxygenases and prostaglandins in experimental models of gastroprotection is well established. We investigated the effects of the 5-lipoxygenase inhibitor A63162, the 12-lipoxygenase inhibitor baicalein and the 15-lipoxygenase inhibitor PD146176 as well as the nonspecific lipoxin A(4)/annexin-1 antagonist Boc1 on adaptive protection induced by 20% ethanol against 70% ethanol, and on protection induced by sodium salicylate against the mucosal-damage-aggravating effects of celecoxib and dexamethasone during local ischemia-reperfusion in rats. It was found that both types of gastroprotection were antagonized by the lipoxygenase inhibitors and the lipoxin A(4)/annexin-1 antagonist in doses that have no direct damaging effect on gastric mucosa. The results suggest that not only cyclooxygenases, but also active lipoxygenases and, possibly, annexin-1 are required for these types of gastroprotection to occur.
Asunto(s)
Anexinas/metabolismo , Inhibidores de la Ciclooxigenasa/farmacología , Etanol/farmacología , Mucosa Gástrica/efectos de los fármacos , Lipooxigenasa/fisiología , Receptores de Formil Péptido/fisiología , Receptores de Lipoxina/antagonistas & inhibidores , Salicilato de Sodio/farmacología , Acetamidas/farmacología , Animales , Celecoxib , Inhibidores de la Ciclooxigenasa 2/farmacología , Dexametasona/farmacología , Interacciones Farmacológicas , Flavanonas/farmacología , Fluorenos/farmacología , Mucosa Gástrica/irrigación sanguínea , Mucosa Gástrica/patología , Glucocorticoides/farmacología , Inhibidores de la Lipooxigenasa/farmacología , Masculino , Oligopéptidos/farmacología , Éteres Fenílicos , Antagonistas de Prostaglandina/farmacología , Pirazoles/farmacología , Ratas , Ratas Wistar , Daño por Reperfusión/metabolismo , Daño por Reperfusión/patología , Daño por Reperfusión/prevención & control , Sulfonamidas/farmacologíaRESUMEN
In rats, neither the cyclooxygenase-1 inhibitor SC-560 nor the cyclooxygenase-2 inhibitor rofecoxib damages the gastric mucosa. Coadministration of dexamethasone induced injury in SC-560- but not in rofecoxib-treated rats. High levels of cyclooxygenase-1 protein occurred in the gastric mucosa of control rats, with no change after administration of SC-560. In contrast, the gastric cyclooxygenase-2 protein levels were low in control rats, but increased in a time-dependent manner after administration of SC-560. Dexamethasone prevented the increase in cyclooxygenase-2 protein levels. Our findings show that inhibition of cyclooxygenase-1 upregulates cyclooxygenase-2. When the upregulation is prevented by dexamethasone, gastric damage develops, suggesting that induction of cyclooxygenase-2 represents a compensatory mechanism that counteracts the injurious effect of cyclooxygenase-1 inhibition.
Asunto(s)
Antiinflamatorios/efectos adversos , Inhibidores de la Ciclooxigenasa/efectos adversos , Dexametasona/efectos adversos , Mucosa Gástrica/efectos de los fármacos , Animales , Ciclooxigenasa 1/biosíntesis , Ciclooxigenasa 2/biosíntesis , Inhibidores de la Ciclooxigenasa 2/efectos adversos , Interacciones Farmacológicas , Quimioterapia Combinada , Mucosa Gástrica/enzimología , Mucosa Gástrica/patología , Lactonas/efectos adversos , Masculino , Pirazoles/efectos adversos , Ratas , Ratas Wistar , Sulfonas/efectos adversos , Factores de TiempoRESUMEN
Traditional NSAIDs, selective cyclooxygenase (COX)-2 inhibitors, and inhibitors of nitric oxide synthase (NOS) impair the healing of preexisting gastric ulcers. However, the role of COX-1 (with or without impairment of COX-2) and the interaction between COX and NOS isoforms during healing are less clear. Thus we investigated healing and regulation of COX and NOS isoforms during ulcer healing in COX-1 and COX-2 deficiency and inhibition mouse models. In this study, female wild-type COX-1(-/-) and COX-2(-/-) mice with gastric ulcers induced by cryoprobe were treated intragastrically with vehicle, selective COX-1 (SC-560), COX-2 (celecoxib, rofecoxib, and valdedoxib), and unselective COX (piroxicam) inhibitors. Ulcer healing parameters, mRNA expression, and activity of COX and NOS were quantified. Gene disruption or inhibition of COX-1 did not impair ulcer healing. In contrast, COX-2 gene disruption and COX-2 inhibitors moderately impaired wound healing. More severe healing impairment was found in dual (SC-560 + rofecoxib) and unselective (piroxicam) COX inhibition and combined COX impairment (in COX-1(-/-) mice with COX-2 inhibition and COX-2(-/-) mice with COX-1 inhibition). In the ulcerated repair tissue, COX-2 mRNA in COX-1(-/-) mice, COX-1 mRNA in COX-2(-/-) mice, and, remarkably, NOS-2 and NOS-3 mRNA in COX-impaired mice were more upregulated than in wild-type mice. This study demonstrates that COX-2 is a key mediator in gastric wound healing. In contrast, COX-1 has no significant role in healing when COX-2 is unimpaired but becomes important when COX-2 is impaired. As counterregulatory mechanisms, mRNA of COX and NOS isoforms were increased during healing in COX-impaired mice.
Asunto(s)
Ciclooxigenasa 1/deficiencia , Ciclooxigenasa 2/deficiencia , Óxido Nítrico Sintasa/metabolismo , Úlcera Gástrica/enzimología , Úlcera Gástrica/patología , Cicatrización de Heridas/fisiología , Animales , Isoenzimas/metabolismo , Ratones , Ratones NoqueadosRESUMEN
The rationale for the development of selective inhibitors of cyclooxygenase-2 (COX-2) was the proposal that this enzyme plays an important role in inflammation but does not contribute to the resistance of the gastrointestinal mucosa against injury. However, studies from several groups have established that both COX-1 and COX-2 have important functions in the maintenance of gastrointestinal mucosal integrity. Thus, in the normal rat stomach lesions only develop when both COX-1 and COX-2 are inhibited. On the other hand, in specific pathophysiological situations the isolated inhibition of either COX-1 or COX-2 without simultaneous suppression of the other COX isoenzyme is ulcerogenic. Furthermore, COX-2 plays an important role in the healing of gastric ulcers and inhibition of COX-2 delays ulcer healing. From these findings the initial concept that only inhibition of COX-1 interferes with gastrointestinal defense has to be re-evaluated.
Asunto(s)
Ciclooxigenasa 1/metabolismo , Ciclooxigenasa 2/metabolismo , Mucosa Gástrica/fisiopatología , Úlcera Gástrica/fisiopatología , Animales , Ciclooxigenasa 1/fisiología , Ciclooxigenasa 2/fisiología , Inhibidores de la Ciclooxigenasa/farmacología , Mucosa Gástrica/efectos de los fármacos , Mucosa Gástrica/enzimología , Úlcera Gástrica/enzimología , Cicatrización de Heridas/efectos de los fármacos , Cicatrización de Heridas/fisiologíaRESUMEN
The cyclooxygenase (COX)-2 inhibitors 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5II)-furanone (DFU) (0.02-2 mg/kg) and N-[2-(cyclohexyloxy)-4-nitrofenyl]-methanesulfonamide (NS-398) (0.01-1 mg/kg), the COX-1 inhibitor 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC-560) (0.05-5 mg/kg), and dexamethasone (1 mg/kg) were studied in rats challenged with intragastric acid (300 mM HCl). All compounds induced severe gastric damage when rats were treated concurrently with the inhibitor of constitutive and inducible nitric-oxide (NO) synthase N(G)-monomethyl-L-arginine methyl ester (L-NAME) (3 or 40 mg/kg). DFU and NS-398 caused significantly less damage in rats receiving the selective inhibitor of inducible NO synthase N-(3-(aminomethyl)benzyl)acetamidine (1400W) (0.3 mg/kg). The COX-1 inhibitor SC-560 induced moderate damage in the acid-challenged stomach even without suppression of NO, but damage was aggravated by L-NAME. The COX-3 inhibitor phenacetin (400 mg/kg) did not injure the gastric mucosa despite suppression of NO. Furthermore, DFU, NS-398, SC-560, and dexamethasone caused severe injury in the acid-challenged stomach of rats pretreated with capsaicin to ablate afferent neurons. The mucosal damage induced by the COX-1 inhibitor, the COX-2 inhibitors, and dexamethasone in L-NAME- or capsaicin-treated rats was reversed by coadministration of 16,16-dimethyl-prostaglandin E2 (2 x 8 ng/kg). Gross mucosal damage was paralleled by histology. Our results support the concept that endogenous NO, prostaglandins, and afferent neurons act in concert in the regulation of gastric mucosal integrity. The prostaglandins necessary for mucosal defense in the face of NO suppression, and afferent nerve ablation can be derived either from COX-1 or COX-2. The data do not propose a protective role for a phenacetin-sensitive COX-3. Our findings suggest that not only COX-1 but also COX-2 has important functions in the maintenance of gastric integrity.
Asunto(s)
Mucosa Gástrica/enzimología , Isoenzimas/metabolismo , Neuronas Aferentes/metabolismo , Óxido Nítrico/metabolismo , Prostaglandina-Endoperóxido Sintasas/metabolismo , Animales , Inhibidores de la Ciclooxigenasa/farmacología , Mucosa Gástrica/citología , Masculino , Degeneración Nerviosa/metabolismo , Neuronas Aferentes/efectos de los fármacos , Prostaglandinas/metabolismo , Ratas , Ratas WistarRESUMEN
Oral administration of the nonselective cyclooxygenase (COX) inhibitor indomethacin (20 mg/kg), the COX-1 inhibitor 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC-560) (20 mg/kg), or the COX-2 inhibitor rofecoxib (1-20 mg/kg) antagonized the gastroprotective effects of 16,16-dimethyl-prostaglandin (PG) E2 (75 ng/kg p.o.) and 20% ethanol in rats. The effects of the COX inhibitors were reversed by the activator of ATP-sensitive potassium (KATP) channels cromakalim (0.3-0.5 mg/kg p.o.). The protective effects of 16,16-dimethyl-PGE2 and 20% ethanol were counteracted by the phospholipase C inhibitor 1-(6-((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U-73122), but not its inactive analog 1-(6-((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-2,5-pyrrolidine-dione (U-73343) (1 mg/kg each i.v.). Likewise, the protein kinase C inhibitors chelerythrine (0.7 mg/kg i.v.) and staurosporine (3 microg/kg i.v.) inhibited gastroprotection. Effects of these enzyme inhibitors were not reversed by cromakalim. Submaximally effective doses of SC-560 (0.2 mg/kg p.o.) and rofecoxib (0.02 mg/kg p.o.) were additive and abolished the protection induced by 20% ethanol. The findings show that inhibition of COX-1 or COX-2 antagonizes not only adaptive gastroprotection by 20% ethanol but also the protective effect of exogenous PG in a cromakalimsensitive manner. Endogenous PG obviously add to the protective activity of exogenous PG. Gastroprotection by PG involves phospholipase C, protein kinase C, and KATP channels. Activation of KATP channels does not exert protection when the activity of phospholipase C or protein kinase C is suppressed.
Asunto(s)
Fenómenos Fisiológicos del Sistema Digestivo , Dinoprost/análogos & derivados , Isoenzimas/fisiología , Prostaglandina-Endoperóxido Sintasas/fisiología , Prostaglandinas/fisiología , Proteína Quinasa C/fisiología , Fosfolipasas de Tipo C/fisiología , Animales , Cromakalim/farmacología , Ciclooxigenasa 1 , Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa/farmacología , Dinoprost/farmacología , Inhibidores Enzimáticos/farmacología , Estrenos/farmacología , Etanol/farmacología , Isoenzimas/efectos de los fármacos , Masculino , Proteínas de la Membrana , Prostaglandina-Endoperóxido Sintasas/efectos de los fármacos , Proteína Quinasa C/efectos de los fármacos , Pirrolidinonas/farmacología , Ratas , Ratas Wistar , Fosfolipasas de Tipo C/efectos de los fármacosRESUMEN
This study compares the involvement of ATP-sensitive potassium (K(ATP)) channels and prostaglandins in various forms of gastroprotection in the rat. Instillation of 1 ml of 70% ethanol induced severe gastric mucosal damage (lesion index 39 +/- 0.8), which was substantially but not maximally reduced by oral pretreatment with 16,16-dimethyl-prostaglandin (PG) E(2) (75 ng/kg), 20% ethanol (1 ml), sodium salicylate (15 mg/kg), the metal salt lithium chloride (7 mg/kg), the sulfhydryl-blocking agent diethylmaleate (5 mg/kg), and the thiol dimercaprol (10 mg/kg). Administration of indomethacin (20 mg/kg) increased gastric mucosal damage induced by 70% ethanol (lesion index 45 +/- 0.8) and significantly reduced the protective effect of 20% ethanol, sodium salicylate, lithium chloride, diethylmaleate, and dimercaprol. The blocker of K(ATP) channels glibenclamide (5-10 mg/kg) significantly antagonized the protective effect of 16,16-dimethyl-PGE(2), 20% ethanol, sodium salicylate, lithium chloride, diethylmaleate, and dimercaprol. The inhibition of protection induced by glibenclamide was reversed by pretreatment with the K(ATP) channel activator cromakalim (0.3-0.5 mg/kg). In conclusion, our results indicate a role of K(ATP) channels in the gastroprotective effect of 16,16-dimethyl-PGE(2) and of the other agents tested. Since the protection afforded by these agents is additionally indomethacin-sensitive, it is suggested that under these conditions endogenous prostaglandins act as activators of K(ATP) channels, and this mechanism, at least in part, mediates gastroprotection.
Asunto(s)
Adenosina Trifosfato/fisiología , Mucosa Gástrica/fisiología , Canales de Potasio/fisiología , Prostaglandinas/fisiología , Úlcera Gástrica/prevención & control , 16,16-Dimetilprostaglandina E2/administración & dosificación , Transportadoras de Casetes de Unión a ATP , Adaptación Fisiológica/efectos de los fármacos , Adaptación Fisiológica/fisiología , Administración Oral , Animales , Dimercaprol/uso terapéutico , Relación Dosis-Respuesta a Droga , Etanol/administración & dosificación , Etanol/uso terapéutico , Etanol/toxicidad , Mucosa Gástrica/efectos de los fármacos , Mucosa Gástrica/metabolismo , Gliburida/administración & dosificación , Canales KATP , Cloruro de Litio/uso terapéutico , Masculino , Maleatos/uso terapéutico , Bloqueadores de los Canales de Potasio , Canales de Potasio de Rectificación Interna , Ratas , Ratas Wistar , Salicilato de Sodio/uso terapéutico , Úlcera Gástrica/inducido químicamente , Úlcera Gástrica/tratamiento farmacológicoRESUMEN
The interactions of sodium salicylate and the selective cyclooxygenase-2 inhibitors N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide (NS-398) and 5.5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5II)-furanone (DFU), dexamethasone and the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine methylester (L-NAME) were examined in ischaemia-reperfusion damage and adaptive protection in the rat stomach. Ischaemia-reperfusion damage was substantially aggravated by pretreatment with NS-398 (4 mg/kg), DFU (2 mg/kg), dexamethasone (1 mg/kg) or L-NAME (3 and 10 mg/kg). Salicylate (0.01-0.05 mg/kg) reversed the aggravating effect of NS-398, DFU and dexamethasone, while the effect of L-NAME was counteracted by L-arginine (twice 400 mg/kg) but not salicylate (0.05 or 10 mg/kg). Instillation of 20% ethanol prevented mucosal damage induced by 70% ethanol. This adaptive gastroprotection was abolished by pretreatment with NS-398 (1 mg/kg), DFU (0.2 mg/kg) or L-NAME (10 mg/kg). Salicylate (0.01-0.05 mg/kg) reversed the inhibition of protection by NS-398 and DFU, while the effect of L-NAME (10 mg/kg) was antagonized by L-arginine (100 mg/kg) but not salicylate (0.05 mg/kg). The precise mechanism of the functional antagonism between extremely low doses of salicylate and selective cyclooxygenase-2 inhibitors remains to be investigated.