calcimycin and tolfenamic-acid

Fenamates, a subgroup of nonsteroidal anti-inflammatory drugs, inhibit several functions of human polymorphonuclear leukocytes (PMNs) in vitro, by a thus far unknown mechanism. To determine the mechanism behind this action, we studied the effects of two fenamates (flufenamic and tolfenamic acids) on Ca2+ metabolism in human PMNs. The two fenamates inhibited the increases in intracellular free calcium concentration induced by either the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine or the calcium ionophore A23187 in fura-2-labeled PMNs. This inhibition was concluded to be due to blocking of the cation influx, as evidenced by measurement of Mn2+ influx and the influx of radioactive calcium. In addition, the actions of flufenamic and tolfenamic acids were similar to those of an experimental blocker of nonselective cation channels (SK&F 96365). The two other control compounds, an antagonist of voltage-dependent calcium channels (nifedipine) and an inhibitor of prostanoid synthesis (ketoprofen), were ineffective. In conclusion, inhibition of calcium influx in PMNs is introduced as a novel prostanoid-independent mode of action of two nonsteroidal anti-inflammatory drugs with fenamate structure, flufenamic and tolfenamic acids, which could explain their earlier documented inhibitory effects on PMN functions.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Calcimycin; Calcium; Calcium Channel Blockers; Diphenylamine; Flufenamic Acid; Humans; Imidazoles; In Vitro Techniques; Intracellular Fluid; Ion Transport; Ketoprofen; Manganese; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Nifedipine; ortho-Aminobenzoates

The present work was designed to study the pharmacological control of the receptor-mediated activation of human neutrophils by tolfenamic acid (2(-)[(3-chloro-2-methylphenyl)-amino]benzoic acid). Tolfenamic acid inhibited in a concentration-dependent manner the degranulation response and Ca2+ influx in neutrophils activated either by the chemotactic peptide fMLP (N-formyl-methionyl-leucylphenylalanine) or Ca2+ ionophore A23187 (calcimycin). When fMLP was used to activate neutrophils, tolfenamic acid (30 microM) reduced Ca2+ influx by 50% and degranulation by 20%. A23187-triggered Ca2+ influx and degranulation were inhibited by 60% and 40%, respectively, by 30 microM tolfenamic acid. Tolfenamic acid did not inhibit the release of Ca2+ from intracellular stores induced either by fMLP or A23187. To confirm the inhibition of receptor-mediated cation influx by tolfenamic acid, the agonist induced Mn2+ influx was studied in Ca2+ free medium. Tolfenamic acid (10-30 microM) reduced fMLP-stimulated Mn2+ influx in neutrophils in a concentration-dependent manner. The simultaneous Ca2+ release from intracellular stores was not affected. Protein kinase C activity in sonicated human neutrophils and the purified enzyme from rat brain were inhibited by the protein kinase inhibitor H-7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine) but not by tolfenamic acid. Both failed to inhibit neutrophil degranulation induced by phorbol myristate acetate, a protein kinase C activator. Tolfenamic acid (100 microM) increased the cellular cAMP levels up to 1.3-fold in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. No effects on cellular cGMP levels were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acid Sequence; Calcimycin; Calcium; Calcium Channel Blockers; Cell Degranulation; Cyclic AMP; Cyclic GMP; Depression, Chemical; Glucuronidase; Humans; In Vitro Techniques; Ionophores; Manganese; Molecular Sequence Data; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; ortho-Aminobenzoates; Protein Kinase C

Special interest has been focused on the development of dual inhibitors of the cyclo-oxygenase and lipoxygenase pathways of arachidonic acid metabolism. In contrast to other classic NSAIDs, some fenamates in clinically achievable concentrations have been shown to inhibit synthesis of 5-lipoxygenase products in vitro. In the present work, we studied the effect of orally administered tolfenamic acid (600 mg) on Ca ionophore A 23187 -induced leukotriene synthesis in isolated human polymorphonuclear leukocytes. Leukotriene production was reduced in all 14 subjects studied, the mean inhibition of LTB4 synthesis being 16 +/- 3% and that of LTC4 33 +/ 7%. The inhibition correlated positively with serum acid concentrations. We suggest that inhibition of leukotriene synthesis is an additional mechanism of the anti-inflammatory, antimigraine and antidysmenorrhoeic effects of tolfenamic acid, and a possible explanation for its rare gastric and bronchoconstrictive side-effects.

Topics: Adult; Anti-Inflammatory Agents, Non-Steroidal; Calcimycin; Female; Humans; Leukotriene B4; Male; Neutrophils; ortho-Aminobenzoates; SRS-A; Thromboxane B2