title: Cross-talking between lymphocytes and platelets and its regulation by nitric oxide and peroxynitrite in physiological condition and endotoxemia.
abstract: OBJECTIVE
  Cross-talk between platelets and lymphocytes may play a role in different pathological conditions like sepsis. This study aimed to investigate the effect of lymphocytes on platelet aggregation in lipopolysaccharide (LPS)-stimulated and non-stimulated cells.
  
  
  METHODS
  Lymphocytes and platelet-rich plasma (PRP) were obtained from rat arterial blood. Platelets (1.2×108platelets/ml) were incubated with lymphocytes (0.8×106cells/ml) in the presence or not of LPS (100μg/ml), after which ADP (5μM)-induced platelet aggregation was carried out.
  
  
  RESULTS
  Lymphocytes inhibited by 51% the platelet aggregation, which was significantly prevented by the non-selective NO inhibitor l-NAME (300μM) or the selective iNOS inhibitor 1400W (100μM), as well as by the soluble guanylyl cyclase (sGC) inhibitor ODQ (10μM). The platelet inhibition by lymphocytes was accompanied by 2-fold increase of intraplatelet cGMP levels. Next, lymphocytes and platelets were co-incubated with LPS for 6h. In LPS-treated cells, lymphocytes produced a larger inhibition of platelet aggregation (62%), despite the same elevation of cGMP levels (2.2-fold increase). This inhibitory effect was prevented by l-NAME and 1400W, but rather unaffected by ODQ. The peroxynitrite (ONOO-) scavenger -(-)epigallocatechin gallate (ECG, 100μM) abolished the inhibition by lymphocytes on platelet aggregation in LPS-treated cells, but not in non-treated cells.
  
  
  CONCLUSIONS
  Our results show that lymphocytes act to inhibit platelet aggregation via iNOS-derived NO release and cGMP generation. In presence of LPS, ONOO-production accounts for the platelet inhibition.
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: Nádia J
authors.initials: NJ
authors.lastname: Almeida Cardelli
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Elisa Lopes-Pires
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: Pedro H L
authors.initials: PH
authors.lastname: Bonfitto
authors.affiliation: Laboratory of Inflammation Research, São Leopoldo Mandic Institute and Research Center, Campinas, Sao Paulo, Brazil.
authors.forename: Heloisa H
authors.initials: HH
authors.lastname: Ferreira
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: Edson
authors.initials: E
authors.lastname: Antunes
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas, SP, Brazil. Electronic address: sisimp@fcm.unicamp.br.
authors.forename: Sisi
authors.initials: S
authors.lastname: Marcondes
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000166:cytology*; D006152:Cyclic GMP / Q000378:metabolism; D019446:Endotoxemia / Q000378:metabolism*; D008214:Lymphocytes / Q000166:cytology*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D030421:Peroxynitrous Acid / Q000494:pharmacology*; D010974:Platelet Aggregation; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction
chemical_list: D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D006152:Cyclic GMP
keywords: Peroxynitrite; Soluble guanylyl cyclase; −(−)epigallocatechin gallate