Migration of neutrophils from blood to tissue: alteration of modulatory effects of prostanoid on superoxide generation in rabbits and humans.

Alteration of neutrophil function is associated with their migration from blood into tissue. We evaluated this alteration in both human and rabbit neutrophils, by comparing the inhibitory effects of prostanoids on formylmethionyl-leucyl-phenylalanine (fMLP)-stimulated superoxide generation in human circulating blood neutrophils with those in saliva, and also comparing rabbit circulating blood neutrophils with those exudated into peritoneal cavity. We showed that EP-receptor agonists (PGE1) EP2/EP3 agonist (misoprostol), EP2-receptor agonist (butaprost) and DP-receptor agonist (PGD2) inhibited fMLP-stimulated superoxide production from human blood neutrophils in a concentration-dependent manner. In contrast, these prostanoids produced a significantly smaller maximum inhibition of fMLP-stimulated superoxide production in salivary neutrophils compared to those in blood neutrophils. Similar differences were observed for rabbit blood and peritoneal neutrophils. The inhibitory effect of EP2 agonist (butaprost) on the fMLP-stimulated superoxide generation in human blood neutrophils was significantly higher than that of EP3 agonist (ONO-AP-324). The EP1 antagonist (SC-51322) and EP4 antagonist (AH23848B) employed in this study could not antagonize the inhibitory effect of PGE2. TP agonist (U-46619) failed to show any inhibitory effect in either blood or salivary neutrophils. These results indicated that EP2 and DP receptors are the primary receptors mediating the prostanoids inhibition of fMLP-stimulated superoxide generation from neutrophils. Furthermore, it can be concluded that neutrophils become less responsive to prostanoids in terms of fMLP-stimulated superoxide production in association with their migration from blood to tissue.

Ibudilast, an anti-allergic and cerebral vasodilator, modulates superoxide production in human neutrophils.

We evaluated the effect of ibudilast on superoxide generation in human neutrophils by chemiluminescence development using luciferine analog, FCLA. By incubating neutrophils with ibudilast (2-200 microM) for more than 10 minutes, fMLP- or PMA-induced chemiluminescence was enhanced. However, the fMLP-induced chemiluminescence was suppressed by incubation for less than 10 minutes. This suppressed effect was missing with PMA-induced chemiluminescence. On the both fMLP- and PMA-induced chemiluminescence, the priming effect of ibudilast was further enhanced by the treatment with H-7, a protein kinase C inhibitor. In contrast, the priming effect of ibudilast on the fMLP-induced chemiluminescence was abolished by the treatment with ST-638, a selective inhibitor of tyrosine kinase. Ibudilast showed a transient stimulatory effect on cyclic AMP accumulation which continued for only a few minutes. Ibudilast showed no significant effect on phospholipase D dependent chemiluminescence, 1,4,5 trisphosphate level, or protein kinase C activity. Ibudilast inhibited extracellular calcium influx. These results suggest that ibudilast acts on or through tyrosine kinase to achieved its priming effect on the fMLP-induced chemiluminescence. The early and transient increase in cyclic AMP level may explain the inhibitory effect of ibudilast on the fMLP-induced chemiluminescence after short time of incubation.

Heterogeneity of circulating and exudated polymorphonuclear leukocytes in superoxide-generating response to cyclic AMP and cyclic AMP-elevating agents. Investigation of the underlying mechanism.

It has been found that cyclic AMP and cyclic AMP-elevating agents inhibit formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated superoxide production from polymorphonuclear leukocytes (PMNs). The quantitative differences of this inhibitory effect on human and rabbit blood versus human salivary and rabbit peritoneal (tissue) PMNs were investigated. PMNs from all sources showed the same pattern of fMLP-stimulated superoxide generation, although it was slightly higher in tissue PMNs. However, treatment with salbutamol differentially blunted fMLP-stimulated superoxide production from blood PMNs compared with tissue PMNs in both human and rabbit. While it could inhibit production from blood PMNs by 30-60%, it had only a negligible effect on generation from tissue PMNs. Similarly, forskolin, phosphodiesterase IV inhibitor Ro-201724, and dibutryl cyclic AMP showed significantly higher inhibitory effects on superoxide generation from blood PMNs than tissue PMNs in both species. beta-Adrenergic receptors, cyclic AMP accumulation, and protein kinase A activity were investigated in blood versus tissue PMNs to clarify the mechanism underlying the above-mentioned differences. At the beta-adrenergic receptor level, no significant changes were detected in the number or the binding affinity of the receptors in tissue versus blood PMNs of human and rabbit. On the other hand, cyclic AMP accumulation was significantly higher in response to salbutamol and Ro-201724 in fMLP-stimulated blood versus tissue PMNs in human and rabbit. At the same time, blood PMNs showed significantly higher cyclic AMP-dependent protein kinase A activity than tissue PMNs in human and rabbit. We concluded that tissue PMNs are less responsive to the effect of cyclic AMP-elevating agents in terms of fMLP-stimulated superoxide inhibition. This is due to differences, at least, at two levels. The first is lower accumulation of cyclic AMP and the second is lower protein kinase A activity in tissue versus blood PMNs.

Opioid receptor interaction and adenylyl cyclase inhibition of dihydroetorphine: direct comparison with etorphine.

To find out the reason of weak addiction property of dihydroetorphine, we compared the affinities of dihydroetorphine to the type selective opioid receptor and inhibition effect on the adenylyl cyclase activity with those of etorphine. Dihydroetorphine and etorphine have almost the same binding affinities to all types (mu, delta, and kappa) of opioid receptors and antagonist binding sites, and have similar inhibition activities to forskolin stimulated adenylyl cyclase. However, dihydroetorphine showed significantly smaller value of DTNB-index compared with that of etorphine. This differentiation may explain partly the high analgesic with low dependence properties of dihydroetorphine.

Effect of some drugs acting at the central-type benzodiazepine receptors on blood glucose in mice.

1. The effects of some drugs acting at the central-type benzodiazepines receptors on blood glucose levels in mice were studied. 2. Clonazepam, injected intraperitoneally in doses of 0.625-5 mg, produced a dose-dependent increase in blood glucose 30 min after administration. 3. The hyperglycaemic effect of clonazepam (2.5 mg/kg, i.p.) was dose-dependently reduced by Ro 15-1788 (10-40 mg/kg, i.v.), a benzodiazepine antagonist. 4. Ro 5-3663, a GABA antagonist which may act at the picrotoxinin site, produced a significant increase in blood glucose (5 or 10 mg/kg, i.p.); however, when given together with clonazepam (2.5 mg/kg, i.p.) attenuation of the hyperglycaemic effect was observed. 5. Pk 8165, a partial agonist, lacked an effect on blood glucose over the dose range of 5-20 mg/kg, i.p. but caused a slight increase in blood glucose in a dose of 40 mg/kg, i.p.