Formation of sulphidopeptide‐leukotrienes by cell‐cell interaction causes coronary vasoconstriction in isolated, cell‐perfused heart of rabbit

Abstract

We have studied the transcellular biosynthesis of bioactive leukotrienes (LTs), generated upon blood cell-vascular wall interactions and their functional consequences, in the spontaneously beating, cellperfused, heart of the rabbit. Rabbit isolated hearts were perfused under recirculating conditions (50 ml) with 5 x 106 cells of unpurified (buffy coat) or purified human neutrophils (PMNL), and challenged with 0.5 pM A23187 for 30 min. Coronary perfusion pressure (CPP), heart rate (HR), left ventricular end-diastolic pressure (LVEDP) and left ventricular pressure (LVP) were monitored continuously. Leukotriene formation was measured by specific enzyme-immunoassay and confirmed by reversed phase h.p.l.c. and u.v. spectral analysis. 2 Basal CPP values averaged 44 ± 1.4 mmHg; A23187 triggered a marked increase in CPP both in the presence of buffy coat cells (+ 100% above basal) and PMNL (+ 270% above basal); the latter change in CPP was accompanied by a rise in LVEDP (+ 138% above basal). 3 The increase in CPP was preceded by a statistically significant rise in iLTC4-D4 concentration in the circulating buffer. Pretreatment with two structurally unrelated LTD4 receptor antagonists, LY171883and SKF104353 (10 fM), fully prevented the increase in CPP and LVEDP. A similar protection was also observed when the rabbit heart was perfused with PMNL that had been pretreated with MK886 (1 JLM), a potent inhibitor of leukotriene biosynthesis. 4 The increased coronary tone was accompanied by a marked release of lactate dehydrogenase (LDH), a marker of ischaemic damage; pretreatment of the heart with the LTD4 receptor antagonists as well as of the PMNL with MK886 resulted in a complete suppression of LDH activity release. 5 Positive identification of LTC4-D4 in the perfusates was obtained and a significant correlation observed between the CPP values and iLTC4-D4 concentrations. 6 This study suggests that challenge of PMNL present within the coronary vasculature, causes a LTD4-dependent coronary vasoconstriction, favoured by an efficient uptake of PMNL-derived LTA4 by endothelial cells. The activation of the 5-lipoxygenase pathway in the context of tight interactions between blood cells and coronary vasculature, is suggested to have an important outcome in the alterations of coronary flow and cardiac contractility.

Staphylococcal α-toxin provokes neutrophil-dependent cardiac dysfunction: role of ICAM-1 and cys-leukotrienes

“…Third, the functional abnormalities were fully prevented when the 5-LO metabolism was blocked by the specific inhibitor MK-886. These findings are in line with previous studies demonstrating corresponding physiological effects (i.e., rise in CPP, impairment of contractile function) on infusion or generation of cys-LTs in the coronary vasculature of isolated hearts (36)(37)(38), and in models of cardiac ischemia and reperfusion a significant cardioprotection was demonstrated when LT bioactivity was blocked (28,36).…”

Leukotriene A4, and not leukotriene B4, is the main 5‐lipoxygenase metabolite released by bovine leukocytes

“…In fact, inhibition of LTC4 formation arising from the interaction of human PMNL and glomerular endothelial cells, by antibodies against CD18 and L-selectin, has recently been reported [30]. It has previously been shown that challenge of PMNL while perfusing isolated lung or heart of the rabbit resulted in a shift from LTB4, observed after challenge of isolated PMNL, to cysteinyl leukotrienes, representing the main 5-LO product observed in the perfusion media [9][10][11]. The data obtained in this work support the hypothesis that a diversion from LTA4 hydrolase to LTC4 synthase metabolites could indeed take place when PMNL are activated in the context of tight interactions with cells (i.e.…”

“…Recent studies using organ systems perfused with PMNL [9][10][11] have indicated the pathophysiological relevance of the transcellular metabolism of LTA4, in particular when tight cell-cell interactions occur, such as during adhesion and diapedesis of PMNL through the microvascular endothelium.…”

Inhibition of 5-lipoxygenase-activating protein (FLAP) reduces pulmonary vascular reactivity and pulmonary hypertension in hypoxic rats.

“…Confounding aspects of earlier studies were that the agents used to treat pulmonary hypertension were not specific, and little is known about the pathophysiological role of lung 5-LO. The consensus is that inflammatory cells, neutrophils, and macrophages are the source of 5-LO in the lung and that these cells can generate LT directly or via transcellular metabolism (11)(12)(13)(14)(15). Both chronic hypoxia and intravascular inflammation activate cytokine production in the lung (4,16,17).…”