Per Hedqvist

Heparin-binding protein (HBP/CAP37): a missing link in neutrophil-evoked alteration of vascular permeability.

Polymorphonuclear leukocyte infiltration into tissues in host defense and inflammatory disease causes increased vascular permeability and edema formation through unknown mechanisms. Here, we report the involvement of a paracrine mechanism in neutrophil-evoked alteration in endothelial barrier function. We show that upon neutrophil adhesion to the endothelial lining, leukocytic β2 integrin signaling triggers the release of neutrophil-borne heparin-binding protein (HBP), also known as CAP37/azurocidin, a member of the serprocidin family of neutrophil cationic proteins. HBP induced Ca++-dependent cytoskeletal rearrangement and intercellular gap formation in endothelial-cell monolayers in vitro, and increased macromolecular efflux in microvessels in vivo. Moreover, selective inactivation of HBP prevented the neutrophils from inducing endothelial hyperpermeability. Our data suggest a fundamental role of neutrophil-derived HBP in the vascular response to neutrophil trafficking in inflammation. Targeting this molecule in inflammatory disease conditions offers a new strategy for prevention of endothelial barrier dysfunction caused by misdirected leukocyte activation.

Effects of adenosine on adrenergic neurotransmission; prejunctional inhibition and postjunctional enhancement.

SummaryThe action of adenosine on adrenergic neuroeffector transmission was studied in the rabbit kidney in vitro and in situ, in the canine subcutaneous adipose tissue in situ and in the guinea-pig vas deferens in vitro. In the kidney, adenosine (0.1–10 μM) caused a concentration-dependent increase in vascular resistance and in vasoconstrictor responses to nerve stimulation and administered noradrenaline. In the adipose tissue, adenosine also increased the vasoconstrictor responses but it decreased vascular resistance.In all three tissues studied adenosine significantly and reversibly depressed noradrenaline release evoked by nerve stimulation in a concentration-dependent manner. This effect of adenosine was not altered by phenoxybenzamine which blocked all vasoconstrictor responses and diminished the rise in vascular resistance by adenosine in the kidney. It is concluded that adenosine affects adrenergic neuroeffector transmission by two discrete mechanisms, prejunctional inhibition and postjunctional enhancement.

Identification and biological activity of novel ω-oxidized metabolites of leukotriene B4 from human leukocytes

The leukotrienes constitute a new group of biologically active compounds derived from polyunsaturated fatty acids [ 11. Thus, arachidonic acid can be oxygenated by a lipoxygenase to SS-hydroperoxyeicosatetraenoic acid [2], which is further converted to an unstable epoxide, 5,6-oxido-7,9,11,14-eicosatetraenoic acid (leukotriene Aq, LTA4) [3,4]. This intermediate is transformed enzymatically by addition of glutathione into a ‘slow-reacting substance of anaphylaxis’ (SRS-A), LTC4 [5,6]. The biological activity of most SRS-A preparations is due to LTC4 and the two metabolites LTD4 and LTE4 [7-91. LTA4 can also be hydrolyzed enzymatically to 5S,12R-dihydroxy-6-cis,8,1O-trans,l4-cis-eicosatetraenoic acid (LTB4) [ 1 O-l 2] or non-enzymatically to isomeric 5,12and 5,6-dihydroxy-eicosatetraenoic acids [ 131. We have reported the formation of a novel dihydroxy-acid, 5S,12S-dihydroxy-6-trans,8-cis,lOtrans,l4-cis-eicosatetraenoic acid (SS,12SDHETE), in preparations of human leukocytes [ 14). This dihydroxy-acid was not formed via an epoxide intermediate, but by a double oxygenation of arachidonic acid. In addition, an w-hydroxylated metabolite, 5S,12S,20trihydroxy-6-trans,8-cis,lO-trarzs,lLF-cis-eicosatetraenoic acid (5S,12S,20-THETE), was identified. This report describes the formation of an w-hydroxylated metabolite of LTB4, 5S,12R,20-trihydroxy-6cis

Increase in vascular permeability induced by leukotriene b4 and the role of polymorphonuclear leukocytes

,lO-trans,l4&s-eicosatetraenoic acid (20-OHLTB4) in human leukocyte preparations and further conversion of this trihydroxy acid to a dicarboxylic acid (20-COOH-LTB4). In addition, the biological activity of LTB4, 20-OH-LTB4 and 20-COOH-LTB4, on guinea pig lung strips is reported.

Prostaglandin endoperoxides IV. Effects on smooth muscle

Leukotriene B4 (LTB4), a metabolite of arachidonic acid, is known to be a potent chemotactic and chemokinetic substance. We have used the hamster cheek pouch microcirculation model to study the effect of LTB4 on vascular permeability and the involvement of neutrophil granulocytes in this response. Intravascular fluorescein-labeled dextran (mol wt 150,000) was used as a tracer of macromolecular permeability. Topical application of LTB4 (150 nM-5 μM) to the hamster cheek pouch resulted in an immediate increase in adhering leukocytes in postcapillary venules and later larger venules. Leukocyte accumulation was reversible, but continued longer the higher the dose of LTB4 used. Subsequently, a dose-dependent increase in vascular permeability was seen at postcapillary and larger venules, with a maximum 10–20 min after application; the maximum occurred later the higher the dose of LTB4. Depletion of neutrophil granulocytes by pretreatment of the animals with antineutrophil serum obtained from immunized rabbits significantly decreased the permeability response to LTB4, whereas the response to histamine was unaffected. These results suggest that neutrophil granulocytes play a role in LTB4-mediated permeability increase. LTB4 may be of importance both for the leukocyte accumulation and for the edema formation seen in inflammatory reactions.

Leukotrienes C4, D4 and E4 cause widespread and extensive plasma extravasation in the guinea pig

Abstract The effect on smooth muscle of the endoperoxides PGG2 and PGH2, which are intermediates in prostaglandin biosynthesis, was studied in different systems in vitro and in vivo . On gastrointestinal smooth muscle (gerbil colon, rat stomach) PGG2 and PGH2 produced contractions comparable to those of PGE2 and PGF2a whereas contractions elicited on vascular (rabbit aorta) and airway (guinea-pig trachea) smooth muscle were considerably greater than those of PGE2 and PGF2a respectively. On intravenous injection into guinea-pigs PGG2 and PGH2 caused a triphasic change in blood pressure and were 8–10 times more effective than PGF2a in producing an increase in tracheal insufflation pressure. When given as aerosols the unstable endoperoxides were less effective than PGF2a. It is concluded that the endoperoxides are potent smooth muscle stimulants and that they are more effective than their degradation products (PGD2, PGE2, PGF2a) in some systems.

Control by prostaglandin E2 of sympathetic neurotransmission in the spleen

Summary1.Intravenous injection of leukotriene C4 (1 nmol × kg−1) caused substantial plasma exudation in anesthetized guinea pigs, as evidenced by marked hemoconcentration 15% in 5 min) and significant extravasation of Evans blue.2.Fluorometric quantitation of Evans blue content in 38 selected tissues documented that leukotriene C4 caused significant plasma extravasation throughout the body, except for the brain, stomach, duodenum, colon and gonads.3.In particular, the respiratory and the uro-genital tracts, but also the conjunctiva, the esophagus, the bile ducts and the umbilical ligaments, were very sensitive to the edemapromoting effect of leukotriene C4.4.Intravenous injection of leukotriene D4 (1 nmol × kg −1) or E4 (5 nmol × kg−1) evoked plasma extravasation with a distribution and magnitude that was similar to that induced by leukotriene C4.5.It is concluded that the three major constituents of slow reacting substance of anaphylaxis (SRS-A), leukotrienes C4, D4 and E4, cause a generalized and extensive plasma exudation that is consistent with the proposal that these leukotrienes are important mediators of inflammation.

Antagonistic effects of theophylline and adenosine on adrenergic neuroeffector transmission in the rabbit kidney.

The effect of graded doses of prostaglandin E2 (PGE2) on release of noradrenaline (NA) and on smooth muscle contraction in response to nerve stimulation in cat spleen was studied. PGE2 markedly depressed the outflow of NA from isolated spleen in response to nerve stimulation; the inhibition progressively increases with the concentration of PGE2. It is concluded that the PGE2 depressed the release of NA from nerve terminals. There was an absence of effect of PGE2 on resting outflow of NA which indicated that the spontaneous leakage of NA from sympathetic neurons occurred by a mechanism that differs from that of nerve stimulation-induced release of NA. On the basis of its natural occurrence and of the demonstrated effects of exogenous PGE2 it seems likely that the endogenous PGE2 plays a physiologically significant role in the sympathetic neuro-effector system of the cat spleen.

Endogenous nitric oxide as a modulator of rabbit skeletal muscle microcirculation in vivo

The actions of adenosine and theophylline on adrenergic neuroeffector transmission were studied in the rabbit kidney perfused with Tyrodes solution in which the norepinephrine stores had been labeled with (-)-norepinephrine[3H] {(-)-NE[3H]}. We found that adenosine inhibited (-)-NE[3H] release induced by nerve stimulation, increased basal perfusion pressure, and enhanced the vasoconstrictor response to nerve stimulation and norepinephrine in a dose-dependent manner. Theophylline per se had effects on neuroeffector transmission opposite to those of adenosine. All effects of adenosine were antagonized effectively or annulled by theophylline in concentrations having little or no effect on rabbit kidney phosphodiesterase activities. Two other compounds, Ro 20-1724 and ZK 62.711, being equally potent or more potent than theophylline as phosphodiesterase inhibitors, failed to antagonize adenosine-mediated inhibition of (-)-NE[3H] release by nerve stimulation. Ro 20-1724 in high concentration (10∼4 M) inhibited the vasoconstrictor response to nerve stimulation, but it had little additional effect on the enhancement by adenosine. These findings suggest that theophylline specifically antagonizes the effects of adenosine on pre- and postjunctional transmission in the kidney. The results also are consistent with the view that endogenous adenosine may play a role as modulator of adrenergic neuroeffector transmission.

Aspects of Prostaglandin Function in the Lung

1 Intravital microscopy of rabbit tenuissimus muscle microvasculature was used for in vivo studies of the role of endogenous nitric oxide (NO) in local vascular control. Derivatives of arginine were applied topically in order to modulate the formation of NO from l‐arginine. 2 l‐NG‐monomethylarginine (l‐NMMA) (10–100 μm), but not d‐NG‐monomethylarginine (d‐NMMA), dose‐dependently reduced microvascular diameters. The vasoconstriction induced by l‐NMMA (100 μm) was prevented by pretreatment with l‐arginine (1 mm) but not with d‐arginine (1 mm). Intravenous infusions of l‐arginine (300 mg kg−1) reversed the effect of l‐NMMA (100 μm). l‐Arginine or d‐arginine applied topically at 1 mm per se had no effect on microvascular diameters. 3 Vasodilatation by acetylcholine (0.03‐3 μm) was significantly inhibited by l‐NMMA (100 μm), whereas vasodilatation by adenosine (0.1–100 μm) or sodium nitroprusside (100 nm) was not affected. 4 The hyperaemic response after tenuissimus muscle contractions induced by motor nerve stimulation was unaffected by the presence of l‐NMMA (100 μm). 5 Aggregates of platelets and white blood cells were seen in venules during superfusion with l‐NMMA (100 μm), but not with d‐NMMA (100 μm). 6 Our results suggest that endogenous NO formed from l‐arginine is a modulator of microvascular tone and platelet and white cell‐vessel wall interaction in vivo. Nitric oxide does not, however, appear to play a role in the mediation of functional hyperaemia in this tissue.