Irsogladine, an anti-ulcer drug, suppresses superoxide production by inhibiting phosphodiesterase type 4 in human neutrophils.

Neutrophil superoxide production is implicated in the pathogenesis of gastric mucosal damage induced by various ulcerative agents and Helicobacter pylori infection. We investigated here the effects of an anti-ulcer drug irsogladine [2, 4-diamino-6-(2, 5-dichlorophenyl)-s-triazine maleate] on cAMP formation in isolated human neutrophils. The cAMP level in human neutrophils was elevated by a phosphodiesterase (PDE) type 4 selective inhibitor rolipram, but not by any inhibitors of PDE1, PDE2 and PDE3. Irsogladine also increased cAMP formation in a concentration-dependent manner in neutrophils. A non-selective PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX) alone significantly increased cAMP level, whereas irsogladine was unable to further increase cAMP level in the presence of IBMX. Irsogladine inhibited concentration-dependently the superoxide (O(2)(-)) production induced by various stimuli including formyl-methionyl-leucyl-phenylalanine, opsonized zymosan, guanosine 5'-[gamma-thio] triphosphate, A23187 and phorbol 12-myristate 13-acetate. These effects of irsogladine were mimicked by rolipram, IBMX and dibutyryl cAMP. The inhibitory effects of irsogladine and rolipram on the O(2)(-) production were reversed by a protein kinase A inhibitor H-89. These results indicate that irsogladine inhibits the superoxide production in human neutrophils by the increase of cAMP content by PDE 4 inhibition, which in turn contributing to the anti-ulcer effects of irsogladine on gastric mucosal lesions associated with oxidative stress.

Phosphodiesterase inhibition by a gastroprotective agent irsogladine: preferential blockade of cAMP hydrolysis.

The effect of irsogladine [2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate], an antiulcer drug, on contents of cyclic nucleotides including cAMP and cGMP was investigated in rat stomachs. Irsogladine concentration-dependently increased cAMP content in rat glandula stomach. However, irsogladine at higher concentration (10(-5) M) was unable to further increase cAMP level in the presence of non-selective phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine, although 3-isobutyl-1-methylxanthine by itself increased cAMP level. On the other hand, irsogladine had no effect on the glandula cGMP content. Subsequently, the effect of irsogladine on the cyclic nucleotide degradation by purified bovine brain and heart PDEs was investigated. The cAMP degradation by purified bovine brain PDE was partially suppressed by PDE1 inhibitor vinpocetin, PDE2 inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride and PDE4 inhibitor rolipram but not by PDE3 inhibitor cilostamide, and completely inhibited by 3-isobutyl-1-methylxanthine, suggesting that is attributed almost exclusively to PDE1, PDE2 and PDE4. Meanwhile, cGMP degradation by purified bovine brain PDE was partially suppressed by erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride. Irsogladine preferentially inhibited the response to cAMP degradation compared with cGMP degradation by this brain PDE. The cAMP degradation by bovine heart PDE was almost completely inhibited by the combination with vinpocetine and cilostamide, indicating that is mediated almost exclusively by PDE1 and PDE3. Irsogladine suppressed this cAMP degradation measured in the presence of vinpocetine to almost the same extent as that determined in the presence of cilostamide. These results indicate that irsogladine produces the increase of intracellular cAMP content via non-selective inhibition of PDE isozymes, which may be a key mechanism involved in its gastroprotective actions.

Phosphodiesterase type IV inhibitors prevent ischemia-reperfusion-induced gastric injury in rats.

The effects of selective inhibitors of phosphodiesterase type IV (PDE4) on ischemia-reperfusion-induced gastric injuries were investigated in rats. Gastric ischemia was induced by applying a small clamp to the celiac artery, and reoxygenation was performed by removal of the clamp. Ischemia-reperfusion produced gastric hemorrhagic injuries and increased the content of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) and myeloperoxidase (MPO) activity in gastric mucosa. Rolipram (0.03-0.3 mg/kg, s.c.) and Ro-20-1724 (0.3-3 mg/kg, s.c.) prevented the development of gastric injury in a dose-dependent manner, and it also inhibited the increase in mucosal TNF-alpha content and MPO activity induced by ischemia-reperfusion. The anti-ulcer drug irsogladine (1-10 mg/kg, p.o.), which is known to possess a PDE4 inhibitory action, also inhibited the gastric injury produced by ischemia-reperfusion, as well as the increase in TNF-alpha levels and MPO activity. It is concluded that the ability of PDE4 inhibitors to inhibit cytokine TNF-alpha synthesis and the infiltration of polymorphonuclear leukocytes underlies their gastroprotective effects in ischemia-reperfusion-induced gastric injury. Our experiments suggest that drugs that inhibit PDE4 isoenzyme, such as the anti-ulcer drug irsogladine, may be a useful adjunct therapy for the treatment of the gastric damage that follows ischemia-reperfusion.

Irsogladine prevents monochloramine-induced gastric mucosal lesions by improving the decrease in mucosal blood flow due to the disturbance of nitric oxide synthesis in rats.

The inhibitory effect of an anti-ulcer drug irsogladine [2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate] on monochloramine (NH(2)Cl)-induced gastric mucosal lesions and its mechanisms of action were clarified in rats. Irsogladine dose-dependently prevented the formation of gastric mucosal lesions induced by 60 mM NH(2)Cl. The mucosal protective effect of irsogladine was not influenced by capsaicin-sensitive sensory defunctionalization. On the other hand, its protective effect was diminished by the inhibitor of nitric oxide synthase N(G)-nitro-L-arginine methylester (L-NAME), but not by the inducible nitric oxide synthase selective inhibitor aminoguanidine. Irsogladine restored the NH(2)Cl-induced decrease in the gastric cGMP formation as an index of nitric oxide synthesis, while it alone had no influence on the cGMP formation in intact tissues. Pretreatment with L-NAME abolished the recovery of cGMP by irsogladine. Furthermore, irsogladine ameliorated the NH(2)Cl-induced decrease in gastric mucosal blood flow, which was also reversed by pretreatment with L-NAME. These findings suggest that the improvement of the decrease in mucosal blood flow subsequent to the disturbance of gastric nitric oxide synthesis is involved in the protective effect of irsogladine on gastric mucosal lesions caused by NH(2)Cl.

[Regulation by autonomic nerves of bladder neck sphincter function--mainly on inhibitory NANC nerves].

This article describes current information concerning analyses of contraction and relaxation associated with electrical stimulation of efferent nerves in isolated mammalian sphincter muscles. Contractile responses of sphincters are mediated by alpha 1-adrenoceptors and muscarinic receptors stimulated by transmitters from adrenergic and cholinergic nerves, respectively, whereas those of the bladder body are almost exclusively mediated by transmitters from parasympathetic nerves. Relaxant responses to nerve stimulation are ascribed mainly to mechanisms that are sensitive and resistant to nitric oxide (NO) synthase inhibitors. Neurogenic calcitonin gene-related peptide and beta-adrenoceptor activation by neurogenic norepinephrine may also be involved in some mammals. Stimulus frequency is an important determinant to distinguish NO synthase-sensitive and -resistant components; responses at low frequencies are abolished by the enzyme inhibitors, whereas those at high frequencies are inhibited only partially. High and low frequency stimulation increases the cyclic GMP content in muscles, suggesting the involvement of neurogenic NO, although relaxation at high frequencies is only partially due to such a mechanism. From pharmacological studies so far analyzed, including ours performed with porcine urinary tract sphincters, it is concluded that NO synthase resistant-relaxation is not mediated by peptides nor compounds that open K+ channels in muscle cell membrane and stimulate beta-adrenoceptors. Contribution of NO and non-NO relaxing factor (s) in relaxant responses varies with animal species. Identification of this factor, determination of intracellular signaling processes and interaction with the NO/cyclic GMP system may give us a clue in developing new therapeutics to treat dysfunctions of the lower urinary tract sphincters.

Anti-inflammatory effect and low ulcerogenic activity of etodolac, a cyclooxygenase-2 selective non-steroidal anti-inflammatory drug, on adjuvant-induced arthritis in rats.

Adjuvant arthritic rats are known to be more susceptible to gastric damage induced by non-steroidal anti-inflammatory drugs (NSAIDs) than are normal rats. We compared the relative gastric safety profile of etodolac with those of meloxicam, diclofenac sodium and indometacin in adjuvant arthritic rats and normal rats or mice. As a measure of the safety profiles of NSAIDs, we used the safety index, the ratio of the dose that elicits gastric mucosal lesions to the effective dose as an anti-inflammatory or analgesic compound. The anti-inflammatory or analgesic effects of NSAIDs were assessed by paw swelling in adjuvant arthritic rats, and either carrageenin-induced paw edema or brewer's yeast-induced hyperalgesia, as well as acetic acid-induced writhing, in normal rats or mice. In addition, we also investigated the effects of these NSAIDs on human COX-1 and COX-2 activity. Etodolac and other NSAIDs inhibited paw swelling and caused gastric mucosal lesions in adjuvant arthritic rats in a dose-dependent manner. Etodolac showed the highest UD(50) value and safety index among these NSAIDs in arthritic rats. In normal rats, etodolac also showed the highest UD(50) value and safety index, except when its effects were assessed by acetic acid-induced writhing. Etodolac and meloxicam showed selectivity for human COX-2 over COX-1. In contrast, diclofenac sodium and indometacin were selective for COX-1. These results suggest that etodolac, a COX-2 selective NSAID, has anti-inflammatory effects with a better safety profile for the stomach than do non-selective NSAIDs, including diclofenac sodium and indometacin, in adjuvant arthritic as well as normal rats.

Functional role of inhibitory and excitatory nerves in the porcine lower urinary tract.

In the trigone (three portions) and proximal urethra isolated from castrated male pigs, transmural electrical stimulation (0.5-10 Hz) induced no or slight contractions followed by frequency-related relaxations. Atropine suppressed the contraction and potentiated the relaxation. N(G)-nitro-L-arginine methylester (L-NAME), a nitric oxide (NO) synthase inhibitor, depressed or abolished the relaxation induced by low frequency stimulation, but only slightly attenuated the response to high frequency stimulation. L-Arginine reversed the inhibitory effect. L-NAME-sensitive relaxation by 1 Hz stimulation was abolished by 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ), a guanylate cyclase inhibitor. Release of NO by nerve stimulation to trigonal strips was determined by increased formation of cyclic GMP in the incubation media containing guanylate cyclase and GTP. L-NAME-resistant relaxation by 10 Hz stimulation was not impaired by ODQ, capsaicin, chymotrypsin, K(+) channel inhibitors and beta-adrenoceptor antagonists. Similar results were obtained in the trigone and urethra from normal male and female pigs. Detrusor muscle responded to nerve stimulation with contraction followed by slight relaxation. Relaxations at 1 and 10 Hz stimulation under treatment with atropine and alpha,beta-methylene ATP were partially attenuated by L-NAME. It is concluded that there is no significant difference in the inhibitory responses, sensitive and resistant to L-NAME, to nerve stimulation in the trigone and proximal urethra from castrated and non-castrated male and female pigs. Relaxations to stimulation at 1 Hz seem to be mediated exclusively by neurogenic NO and cyclic GMP generation, whereas those to 10 Hz stimulation is mainly associated with non-NO relaxing factor(s), peptides, K(+) channel openers and beta-adrenoceptor agonist being unlikely involved.

[Current state on development of neuroprotective agents for cerebral ischemia].

The improvement of decreased cerebral blood flow using thrombolytic agents, anti-thrombin drugs, and antiplatelet drugs has been essential for acute ischemic stroke. Edaravone, a free radical scavenger, has been commercially available as a novel neuroprotective agent for ischemic stroke in Japan from 2001. The appearance of a neuroprotective agent implies that therapeutic strategy can be expanded through a combination with thrombolysis. In the previous development, several cases have reported that neuroprotective compounds failed in clinical trials. However, recent studies have clarified that the cerebral ischemia induced the neuronal cell death by mediating multiple mechanisms with necrosis and/or apoptosis. The cytotoxicity derived from the NO/peroxynitrite/free radical generating system, one of intracellular Ca2+ signaling, is a typical event in ischemic injury, which is protected by edaravone. Furthermore, it is suggested that suppression of excessively activated voltage-dependent Na+ and Ca2+ channels is effective as a strategy for neuroprotection, since abnormal excitatory stimuli in the neuronal network result in the cerebral infarction. The development of several compounds having different mechanisms of action for acute stroke is in progress. It is therefore prospected that the various novel neuroprotective agents will be provided for assuring the option of therapeutic strategy, since the reinforcement of medical stroke care including diagnosis contributes to the prolongation of the therapeutic time window.