Relaxant Effect of Chemotactic Peptides on Rabbit Vascular Strips: Evidence for Nitric Oxide Release from a Nonendothelial Source

Abstract

Two distinct peptides, C5a and f-Met-Leu-Phe (FMLP), that are chemotactic for phagocytic leukocytes affect profoundly the circulation in various in vivo systems. These peptides are known to relax strips of rabbit isolated blood vessels, the portal vein and pulmonary artery. In the present study, the effect of recombinant human C5a (2.5–25 nM) was examined and found to be qualitatively similar to that previously reported for FMLP. Indomethacin completely or partially inhibited the vasorelaxations induced by either peptide in the pulmonary artery and the portal vein, respectively. The relaxation induced by C5a was not abolished by removing the endothelial lining of the model vessels. The C5a or FMLP effects were more tachyphylactic in tissues continuously exposed to cycloheximide; this phenomenon was particularly pronounced for FMLP. A series of experiments were focused on the indomethacin-resistant component of the relaxation induced by either peptide on the portal vein. This component was not inhibited by capsaicin pretreatment or by endothelium removal, but was suppressed by treatment with N^G-nitro-L-arginine or reduced by LY-83583. These findings suggest that the chemotactic peptides elicit their mechanical effect on rabbit vascular smooth muscle through the release of secondary mediators not related to the endothelium; the mediators are tentatively identified as prostaglandins and nitric oxide. It is the coordinated combinations of the metabolic pathways that are involved in the final responses, with inherent differences between vessel sources and the agonists used.

C5a mediates secretion and activation of matrix metalloproteinase 9 from human eosinophils and neutrophils

“…This observation has implications apart from MMP-9 activation because nitric oxide can evoke relaxation of blood vessels resulting in increased tissue edema. Indeed it has been observed that C5a can induce relaxation of pulmonary arteries and portal veins even after the endothelial linings were removed suggesting that C5a can exert its effects through elaboration of secondary mediators, one of which could be nitric oxide [45].…”

Cloning and preliminary pharmacological characterization of the anaphylatoxin C5a receptor in the rabbit

“…The results of the competition binding assays with the cloned C5a rabbit receptor correlated well with the vasorelaxant effects of the C5a analogues on the rabbit pulmonary artery and portal vein, as the order of agonist potency was retained (C5a>Ac‐YSFKPMPLaR; Figure 4). The relaxant effect of C5a on the portal vein and pulmonary artery isolated from normal rabbits has been previously characterized, and is mainly prostaglandin‐dependent (Petitclerc & Marceau, 1991). The precise cell type responsive to the anaphylatoxin has not been determined, but, by analogy with muscular arteries of the rabbit, a low density subendothelial population of resident macrophages may be involved (Malinauskas et al ., 1995).…”

“…Rabbit vascular strips were prepared as described (Petitclerc & Marceau, 1991) and were suspended in 5 ml tissue baths containing Krebs solution (Petitclerc et al ., 1996). Their responses to agents were recorded using isometric transducers (model 52‐9545, Harvard Bioscience, South Natick, MA, U.S.A.).…”

“…Baseline (pre-injection) polymorphonuclear leukocyte and lymphocyte counts for all groups were, respectively, 3174+293 and 10074+1984 cells per ml of blood (n=17). responses in rabbit isolated portal veins and pulmonary arteries precontracted with phenylephrine; this type of reaction has been described and analysed previously (Hugli & Marceau, 1985;Petitclerc & Marceau, 1991;Drapeau et al, 1993). Only the prolonged relaxant response, expressed as a percentage of the contractile plateau, was used in the quantitative analysis of biological activity in the rabbit blood vessels (Figure 4).…”

Leukocyte-induced acute endothelial dysfunction in middle cerebral artery in rabbits. Response to aggregating platelets.

“…31 However, in some experiments using relatively high concentrations of the activators in vitro, fMLP produced vessel relaxation and nitric oxide release, and PMA has depressed endothelium-dependent reactions. 32 -* 3 Such phenomena are most unlikely to be significant in our experiments. Nevertheless, we performed a special investigation of PMA and fMLP effects on the MCA reactivity after intracarotid injection in leukocyte-depleted animals.…”