Modulation of Mast Cell Activity by a Peptide Agonist of the Thrombin Receptor: Role of Nitric Oxide

S. M. Strukova^1*, I. V. Chistov¹, B. A. Umarova¹, T. N. Dugina¹, T. P. Storozhevykh², V. G. Pinelis², and E. Glusa³

¹Department of Human and Animal Physiology, School of Biology, Lomonosov Moscow State University, Moscow, 119899 Russia; tel.: (095) 939-1416

²Laboratory of Membranology, Institute of Pediatrics, Russian Academy of Medical Sciences, Lomonosovsky pr. 2/62, Moscow, 117963 Russia; tel.: (095) 134-1445

³Center for Vascular Biology and Medicine, Friedrich Schiller Iena University, Erfurt, Germany

^* To whom correspondence should be addressed.

Received June 23, 1998; Revision received November 5, 1998

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The effect of a thrombin receptor agonist peptide (TRAP-6) on the release of nitric oxide (NO) and platelet activating factor (PAF) from resting and calcium-ionophore (A23187)-activated rat peritoneal mast cells (RPMC) was studied using a platelet aggregation bioassay. RPMC spontaneously released NO, which inhibited TRAP-6-, ADP-, and PAF-stimulated platelet aggregation. This effect of NO was abolished by the addition of an NO binding agent, oxyhemoglobin (oxyHb), to the platelet suspension. The RPMC-induced suppression of platelet aggregation was completely inhibited by the NO-synthase inhibitor L-NAME. TRAP-6 and its high affinity analog haTRAP stimulated the rapid release of NO from RPMC. The effect of TRAP-6 was inhibited by pretreatment of the RPMC with L-NAME or with the inhibitor of the constitutive NO-synthase isoform (cNOS) calmidazolium. TRAP-6 inhibited PAF release from A23187-activated RPMC via an NO-dependent mechanism. Platelet aggregation induced by PAF release from activated RPMC was also confirmed in experiments using the PAF receptor antagonist ginkgolide B. Thus, TRAP-6 is a rapidly acting modulator of mast cell reactivity; it stimulates NO release and inhibits PAF secretion.

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KEY WORDS: thrombin receptor agonist peptide, mast cells, nitric oxide, platelet activating factor

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