Erythrocyte-neutrophil interactions: formation of leukotriene B4 by transcellular biosynthesis.

Abstract

Studies on the mechanism of leukotriene B4 biosynthesis in suspensions composed of neutrophils plus erythrocytes indicate that human erythrocytes convert neutrophil-derived leukotriene A4 into leukotriene B4. Leukotriene B4 formation by neutrophils in the presence of erythrocytes exceeded that from corresponding suspensions of neutrophils alone. The increase was proportional to the erythrocyte content of the suspension. The erythrocyte-dependent increase in leukotriene B4 biosynthesis did not equal the arithmetic sum of calcium ionophore-dependent biosynthesis by neutrophils plus calcium ionophore-dependent biosynthesis by erythrocytes, since erythrocytes produced no leukotriene B4 upon incubation with ionophore A23187. Erythrocytes did not stimulate 5-lipoxygenase activity within neutrophils, since the erythrocyte effect was confined to enzymatic hydration: leukotriene B4 increased coincident with decreased formation of 5,12-dihydroxyicosatetraenoic acids derived from nonenzymatic hydration. Biosynthesis of leukotriene B4 within the erythrocyte, from neutrophil-derived leukotriene A4, was established by comparing the effect of normal erythrocytes with erythrocytes containing a leukotriene A4 hydrolase that was inactivated by the substrate. In the latter case, leukotriene B4 formation increased by only 30-40%; in the former case, it increased by 100-200%. Transcellular biosynthesis of leukotriene B4 from erythrocyte-neutrophil interactions (i) explains the paradoxical presence of leukotriene A4 hydrolase within erythrocytes, a cell incapable of synthesizing leukotriene A4; (u) affords a mechanism to overcome rate limitations or "suicide inactivation" of leukotriene A4 hydrolase in neutrophils; (iii) exploits a cryptic capacity within erythrocytes, provisionally dormant cells in terms of icosanoid biosynthesis; (iv) indicates that the biosynthetic capacity of cell combinations is not necessarily equivalent to the sum of their separate capacities.Enzymatic cooperation between separate cell types may be a significant, but neglected, mechanism for the biosynthesis of certain prostaglandins or leukotrienes. This concept originated from studies on platelet-endothelial cell interactions, which showed that prostaglandin I2 (PGI2), an antithrombotic icosanoid, was produced by endothelial cells from plateletderived prostaglandin endoperoxide H2 (1-5). Analogous transcellular biosynthetic processes are conceivable for other cell combinations and for other arachidonic acid metabolites; however, few biologically relevant examples exist. Requirements for this process include "acceptor" cells with a constitutive enzymatic capacity for the formation of a biologically active icosanoid product but a deficient, or disabled, capacity for substrate generation, plus auxiliary "donor" cells that can fulfill that corresponding substrate requirement. In this context, neutrophil-erythrocyte interactions attracted our attention as potential sources for transcellular biosynthesis of leukotrienes (6).Ordinarily, biosynthesis of leu...

Human endothelial cells stimulate leukotriene synthesis and convert granulocyte released leukotriene A4 into leukotrienes B4, C4, D4 and E4

“…The amounts of LTB4 increased slowly with time and the synthesis had almost ceased after 30 rnin (Fig. 1 B), possibly reflecting a gradual inactivation of LTA4 hydrolase by its substrate [20]. Non-enzymatic hydrolysis products of LTA4 (i.e.…”

Leukotriene pathway genetics and pharmacogenetics in allergy

“…LTA 4 H is expressed ubiquitously in most tissues. In addition, the interaction between different cell types with cooperation of their enzymes can allow platelets (19) and vascular endothelial cells (20) or erythrocytes (21) to produce LTC 4 or LTB 4 , respectively, from LTA 4 transferred from neutrophils (transcellular metabolism). Subcellular localisation of the enzymes/proteins is important.…”

Coupling of recombinant 5‐lipoxygenase and leukotriene A4 hydrolase activities and transcellular metabolism of leukotriene A4 in Sf9 insect cells

“…Transcellular LTB, synthesis has been well described by measurement of LTB, in mixed neutrophil-erythrocyte incubations (McGee and Fitzpatrick, 1986). The present study examines this phenomenon in Sf9 cells infected with either rvH5LO or rvHLTA,h.…”

“…The conversion of LTA, to LTB, [(5S, 1 2R)-dihydroxy-6,14-cis-8, 10-trans-eicosatetraenoic acid) is catalyzed by the cytosolic enzyme LTA, hydrolase first purified from leukocytes (Radmark et a]., 1984). LTA, hydrolase undergoes suicide inactivation by its substrate LTA, and is therefore the rate-limiting step in production of LTB, and in accumulation and secretion of LTA, (Jakschik and Kuo, 1983;Evans et al, 1985, McGee andFitzpatrick, 1986;Orning et al, 1990).…”