calcimycin and Pain

Surfactin inhibits platelet and spleen cytosolic 100 kDa phospholipase A2 (PLA2). In contrast, this same compound enhances rat platelet group II PLA2 activity by approximately 2-fold and slightly increases group I PLA2 activity from porcine pancreas and Naja naja venom in vitro. Surfactin does not affect a Ca2+ -independent PLA2 partially purified from bovine brain. Thus, this compound inhibits selectively the cytosolic form of PLA2. Based on in vitro studies utilizing preincubation of surfactin with the enzyme, dialysis, and increased concentrations of substrates, the inhibitory effect of surfactin appears to be due to a direct interaction with the enzyme. Linear regression analysis of the linear portion of a concentration-response curve reveals an IC50 of 8.5 microM. To further determine the inhibitory pattern, a Dixon plot was constructed to show that the inhibition by surfactin is competitive, but not uncompetitive, with an inhibition constant of Ki = 4.7 microM in 50 mM Tris-HCl buffer, pH 8.0, at 37 degrees. Surfactin blocked non-stimulated and calcium ionophore A23187-stimulated release of arachidonic acid from monkey kidney CV-1 cells, which contain a cytosolic 100 kDa PLA2 as the major activity, as shown in an anionic exchange DEAE-5PW high performance liquid chromatography profile and western blotting analysis. Surfactin ameliorated inflammation induced by several chemicals. That is, it exhibited in vivo anti-inflammatory activity in several tested inflammatory reactions including 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema, carrageenan-induced rat paw edema, and acetic acid-induced mouse writhing. These results demonstrate that surfactin is a selective inhibitor for cytosolic PLA2 and a putative anti-inflammatory agent through the inhibitory effect produced by direct interaction with cytosolic PLA2, and that inhibition of cytosolic PLA2 activity may suppress inflammatory responses.

Topics: Acetic Acid; Animals; Anti-Inflammatory Agents, Non-Steroidal; Arachidonic Acid; Bacterial Proteins; Blood Platelets; Blotting, Western; Calcimycin; Cytosol; Edema; Enzyme Inhibitors; Haplorhini; Inflammation; Isoenzymes; Kidney; Lipopeptides; Male; Mice; Pain; Peptides, Cyclic; Phospholipases A; Phospholipases A2; Rats

Series of 6-aminoalkyloxazolo[4,5-b]pyridin-2(3H)-ones incorporating structural modifications both in the alkyl chain and basic amino moiety were tested for their analgesic efficacy and safety in mice and rats. Two of the synthesised compounds, 4a (3-methyl-6-[(4-phenyl-1-piperazinyl)methyl]oxazolo[4,5-b]pyridin-2(3H)-one) and 12a (3-methyl-6¿1-[2-(4-phenyl-1-piperazinyl)ethan-1-ol]¿oxazolo[4,5-b]pyridin- 2(3H)-one) were found to be more potent than aspirin with ED50 values of 26 (16.1-42.4) and 15.5 (11.4-21.2) mg/kg po (mouse, phenylquinone writhing test) respectively and 6 (3.1-9.8) and 5.5 (3.5-8.8) mg/kg po (rat, acetic acid writhing test). Compounds 4a and 12a proved to be potent nonopioid nonantiinflammatory analgesics but unfortunately have sedative properties at relatively low doses (respectively 64 and 16 mg/kg po, mice).

Topics: Analgesics; Animals; Arachidonate 5-Lipoxygenase; Brain; Calcimycin; Cell Membrane; Cyclooxygenase Inhibitors; Drug Design; Granulocytes; Guinea Pigs; Lipoxygenase Inhibitors; Male; Mice; Molecular Structure; Oxazoles; Pain; Prostaglandin-Endoperoxide Synthases; Pyridones; Rabbits; Rats; Rats, Wistar; Receptors, Cell Surface; Structure-Activity Relationship

1. In this study we used psychophysical experiments in humans and behavioral and electrophysiological studies in rats to evaluate nociceptive and C-fiber mechanoheat nociceptor (C-MH) responses to sustained mechanical stimuli that are initially nonpainful or nonnoxious. 2. In normal rat skin, sustained subthreshold mechanical stimuli activate C-MHs (n = 36) with a delayed onset that parallels the delayed pain sensation recorded in human psychophysical tests. 3. The subthreshold stimuli did not induce a decrease in mechanical threshold (n = 11), and the effect of the subthreshold stimulus on latency to firing of C-MHs (n = 6) persists for a very short time after the stimulus is removed (less than 10 s). 4. Intradermal injection of prostaglandin E2 (PGE2; 100 ng), which induced a significant decrease in the mechanical threshold of C-MHs (n = 7), had no effect on the latency of the delayed activation of C-MHs. Also, indomethacin, which inhibits the synthesis of prostaglandins, had no effect on the latency of the delayed paw-withdrawal response in the behavioral test. 5. Intradermal injection of the calcium ionophore A23187 significantly reduced the latency of the delayed activation of C-MHs (n = 6) the calcium chelator Quin 2 (n = 6) significantly increased the latency. A23187 and Quin 2 had similar effects on the latencies to paw withdrawal in behavioral tests. The sensitization of C-MHs (n = 9) by PGE2 was not, however, affected by Quin 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Aminoquinolines; Animals; Calcimycin; Electrophysiology; Humans; Indomethacin; Male; Nerve Fibers; Neurons, Afferent; Nociceptors; Pain; Physical Stimulation; Prostaglandins E; Rats; Rats, Inbred Strains; Reaction Time; Sensory Thresholds; Skin

There is evidence that 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) acts as an intracellular Ca++ antagonist producing decreases in free intracellular Ca++ and inhibiting many cellular processes dependent upon intracellular Ca++. Intracerebroventricularly administered TMB-8 was active in the mouse tail-flick test (ED50 = 50 micrograms), and this antinociceptive response was antagonized by naloxone (AD50 = 0.28 mg/kg s.c.), Ca++ (0.2-0.4 mumol i.c.v.) and, to a lesser degree, by ethylene glycol bis (beta-aminoethyl ether)N,N1-tetraacetic acid (0.02 and 0.06 mumol i.c.v.). TMB-8 (i.c.v.) was only marginally active in the p-phenylquinone test. The potency of TMB-8 (i.c.v.) was potentiated 10-fold in morphine-tolerant mice in the tail-flick test (ED50 = 2.5 micrograms). TMB-8 inhibited contraction of stimulated ilea (IC50 = 2.2 microM), an effect which was neither antagonized nor reversed by naloxone (1 microM). TMB-8 did not potentiate morphine, or was it potentiated by morphine, in the stimulated guinea pig ileum. Procaine, but not lidocaine showed dose-dependent activity in the tail-flick and p-phenylquinone tests (ED50 values, 136 and 83 micrograms, respectively, i.c.v.). The antinociception produced by procaine (i.c.v.) in the tail-flick test was antagonized by naloxone (AD50 = 0.4 mg/kg s.c.) Lidocaine (100 micrograms i.c.v.) produced only 30% maximum possible effect in the tail-flick tests, and was inactive in p-phenylquinone tests. Doses of lidocaine greater than 100 micrograms i.c.v. resulted in lethality of greater than 50% of the animals tested. Thus, the activity of TMB-8 resembles that of opiates in that both are antagonized by Ca++ or naloxone in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Analgesia; Anesthetics, Local; Animals; Atropine; Biological Assay; Brain; Calcimycin; Calcium; Dose-Response Relationship, Drug; Drug Interactions; Drug Tolerance; Electric Stimulation; Gallic Acid; Guinea Pigs; Injections, Intraventricular; Lidocaine; Male; Mice; Morphine; Naloxone; Nociceptors; Pain; Procaine

The antinociceptive effect of intracerebroventricularly administered acetylcholine as measured in the mouse tail-flick test was reduced by intracerebroventricularly injected calcium, magnesium and manganese. Maximum antagonism of acetylcholine-induced antinociception was observed with a 1-hour calcium pretreatment. Significant reduction existed at 2- but not 4-hour pretreatment. Barium and strontium were inactive. The antinociceptive effect of acetylcholine was potentiated by lanthanum and ethylene glycol tetraacetic acid but not by ethylenediamine tetraacetic acid. The ionophore A23187 was shown to increase greatly the antagonistic effect of a low dose of calcium. The ionophore alone did not significantly alter the effect of acetylcholine. Thus, it appears that calcium must penetrate cell membranes to reduce the effect of acetylcholine. In addition to acetylcholine, it was found that the antinociceptive effects of oxotremorine and physostigmine could also be reduced by calcium. These data indicate that alterations in intracellular calcium are involved in cholinergically induced antinociception.

Topics: Acetylcholine; Animals; Calcimycin; Calcium Chloride; Cations, Divalent; Chelating Agents; Drug Interactions; Lanthanum; Male; Mice; Mice, Inbred ICR; Oxotremorine; Pain; Physostigmine; Reaction Time; Time Factors